Note: Descriptions are shown in the official language in which they were submitted.
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Regenerative Braking for Electric and Hybrid Vehicles
CROSS REFERENCE TO RELATED APPLICATIONS
[001] This disclosure claims the benefit of priority to US Patent
Application Serial No.
16/177,070 filed October 31, 2018 entitled "Regenerative Braking for Electric
and Hybrid
Vehicles" and US Provisional Application Serial No. 62/662,826, filed April
26, 2018 entitled
"Architecture and Systems for Electric and Hybrid All-Terrain Vehicles," the
contents of which
are both hereby incorporated by reference in their entirety for all purposes.
FIELD OF THE DISCLOSURE
[002] The present disclosure relates generally to electric or hybrid
electric vehicles, such as
industrial and/or all-terrain vehicles and more particularly to control
systems for use therein.
BACKGROUND
[003] Vehicles, such as hybrid-electric and all-electric vehicles may
include energy
recapture systems. Such energy recapture systems may include regenerative
braking systems, as
one possible implementation.
SUMMARY
I. Overview
[004] Various embodiments will be described that provide various advantages
for electric
and hybrid vehicles. It is appreciated that features of these various
embodiments may be
combined with each other in accordance with the desired system requirements.
It should be
understood that these embodiments may be combined with each other in various
combinations.
[005] Additionally, many of the examples and embodiments described herein
make
reference motor controllers that perform various functions and provide various
functionality.
According to various implementations and examples, reference is made to a
motor controller
available from Curtis Instruments of Mt. Kisco, New York. The Curtis manual
for Enhanced
AC Controllers for Induction Motors and Surface Permanent Magnet Motors,
Software Version
OS 30.0, is incorporated herein by reference. An overview of various
implementations will now
be described at various levels of detail.
Al. Regenerative Braking Control
[006] A first embodiment of this disclosure relates to regenerative braking
systems and
more particularly to controlling regenerative braking systems in various
contexts.
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[007] Increasingly, vehicles, such as fully electric and hybrid-electric
("hybrid") vehicles,
that utilize energy recovery systems are being employed for various
applications. Vehicles that
implement energy recovery systems may have several benefits as compared to
vehicles that lack
such energy recovery systems.
[008] Vehicular energy recovery systems take various forms, one of which is
a regenerative
braking system, which may take various forms. One form of a regenerative
braking system
utilizes a motor that is configured to act as a generator that converts
mechanical energy
generated from the braking process to electrical energy which may be stored in
various forms.
Examples of such energy storage forms may include mechanical forms, such as a
flywheel,
electrical forms, such as capacitors, or chemical forms, such as a battery.
[009] Regenerative braking systems may provide benefits to owners and
operators of
electric or hybrid vehicles. One such benefit may take the form of extending
the overall range
of the vehicle. Various other advantages result from using a regenerative
braking system as
well.
[0010] Regenerative braking systems may be used in various different
scenarios. For
instance, a vehicle may utilize a regenerative braking system to slow a
vehicle. However,
current regenerative braking systems suffer from the drawback that
regenerative braking systems
may not apply torque from the regenerative braking system to slow the vehicle
in a manner that
is consistent with a driver's expectations regarding the application of the
regenerative torque.
[0011] As a specific example of such a drawback, in many vehicles, a driver
may have to
manually select an amount of regenerative torque that the regenerative braking
system should
apply when slowing a vehicle. In many instances, the manually selected torque
amount may not
produce the maximum amount of energy that could theoretically be recaptured.
[0012] As another example, when a vehicle is going downhill, a driver of a
vehicle may
apply the service brakes to slow the vehicle and/or to bring the vehicle to a
constant speed when
neutral braking torque could instead be applied to slow the vehicle. When the
driver applies
service brakes to slow a vehicle going downhill, not only do the service
brakes undergo
unnecessary wear and heating of the service brakes that could be avoided by
the application of
neutral braking torque, but also energy that could be recaptured by the
regenerative braking
system is lost.
[0013] One embodiment is directed to solving problems related to optimizing
the behavior of
regenerative braking in various scenarios. More particularly, an embodiment is
directed to
determining amounts of torque to apply during regenerative braking, to
maintaining a desired
speed and thereby vehicle stability while performing regenerative braking
without depression of
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the brake pedal, and to limiting use of service brakes in vehicles undergoing
regenerative
braking.
[0014] This embodiment may have particular application to a vehicle that
has certain
components. One such component may include a battery pack, which may act as
the vehicle's
energy source. Another component may take the form of one or more a drive
motors, which may
provide torque to drive the vehicle's axle(s). In the case that the vehicle is
equipped with a
regenerative braking system, the drive motor may also be configured to apply
regenerative
braking torque in response to a received voltage phase and magnitude, which
causes the drive
motor to produce a regenerative current, which may in turn be supplied to the
battery pack for
storage. Yet another component may take the form of a motor controller. At a
high level, the
motor controller may comprise a configurable computing device that may be
configured to
periodically obtain inputs, execute a control loop and other functions based
on the obtained
inputs, and finally generate one or more outputs based on the output of the
executed functions.
[0015] The motor controller may receive inputs from, may control, and/or
may otherwise be
coupled to various components and systems of the vehicle. As examples, the
motor controller
may be coupled to and/or may control the drive motor, battery, and a set
driver controls, as some
non-limiting examples. The motor controller may be coupled to various other
components of
the vehicle as well.
[0016] This implementation may apply to scenarios in which a vehicle is
engaged in a
particular mode, such as a neutral braking mode, which occurs when a driver
removes his/her
foot from the accelerator, and more particularly to a downhill neutral braking
mode in which the
vehicle undergoes neutral braking and the motor controller of the vehicle is
configured to
automatically determine an amount of neutral braking torque to apply to slow
the vehicle to a
more or less constant speed. Further, while in the engaged mode, the vehicle
may be configured
to perform the functions of optimizing the amount of energy recaptured during
the process of
neutral braking and avoiding operation of the service brakes during the
engaged mode. The
process of applying a determined amount of regenerative braking torque during
neutral braking
and performing various other functions related to braking may take various
forms.
[0017] In general, the techniques of this embodiment may apply to a hybrid
or electric
vehicle having a motor controller that is configured to determine different
amounts of neutral
braking torque to maximize energy recapture and to maintain an approximately
constant vehicle
speed when the vehicle is engaged in a particular braking mode, such as a
neutral braking mode
and more particularly, a downhill neutral braking mode.
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[0018] One such input that the motor controller may receive may indicate a
mode in which
the vehicle is engaged. For instance, the motor controller may receive a value
from a
component coupled to the motor controller indicating the vehicle is engaged in
a regenerative
braking mode such as a neutral braking mode, also referred to as a downhill
neutral braking
mode. After determining that the motor controller is engaged in a neutral
braking mode, the
motor controller may execute one or more subroutines associated with the given
neutral braking
mode.
[0019] More particularly, after determining that the vehicle is engaged in
a given neutral
braking mode, such as a neutral braking mode or a downhill neutral braking
mode, the motor
controller may be configured to execute (e.g., periodically) a "neutral
braking subroutine," that
may comprise one or more subroutines dedicated to managing the vehicle while
in the given
regenerative braking mode. For instance, while in the neutral braking mode,
the neutral braking
mode subroutine may cause the motor controller to manage various components of
the vehicle,
such as the drive motor, etc.
[0020] At a high level, a neutral braking mode subroutine may be configured
to repeatedly
(e.g., periodically) determine an amount of regenerative braking torque to
apply to the drive
motor and apply the determined amount of neutral braking torque to the drive
motor to generate
a regenerative braking current. In some implementations, motor controller may
be configured to
determine an amount of torque to apply to the drive motor to cause the vehicle
to maintain an
approximately constant speed and such that the regenerative current supplied
by the drive motor
to the vehicle's battery is maximized. The motor controller may determine an
amount of torque
to apply to the drive motor when the vehicle is engaged in a neutral braking
mode in various
manners.
[0021] In a particular implementation, the motor controller may be
configured to access a set
of neutral braking torque curves and used the curves to determine and apply
the determined
regenerative braking torque to the drive motor when the vehicle is engaged in
a neutral braking
mode, such as a downhill neutral braking mode. A neutral braking mode occurs
when a vehicle
undergoes neutral braking. Neutral braking occurs when the vehicle is moving
and the throttle
(e.g., the accelerator pedal) is reduced towards the neutral position. In a
more particular case of
neutral braking, such as the downhill neutral braking mode, the vehicle is
both moving downhill
and is undergoing neutral braking.
[0022] In a particular implementation, the set of one or more neutral
braking torque curves
may have been predefined or may be determined and defined dynamically by the
motor
controller. Each curve (also be referred to as a "map") may consist of a set
of points, and each
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given point of the curve may specify an amount (e.g., a percentage) of
regenerative braking
torque to apply to the drive motor based on a parameter of the vehicle, such
as the vehicle's
speed, a rotational velocity of the drive motor, etc. The conditions
associated with selecting a
given neutral braking torque curve and with determining the amount of
regenerative braking
torque to apply to the drive motor may take various forms.
[0023] In one implementation, the motor controller may select a
regenerative torque curve
based on a gear in which the vehicle is engaged. For example, the motor
controller may select a
first regenerative torque curve if the vehicle is in a first gear (e.g., a
high gear) and may select a
second regenerative torque curve if the vehicle is engaged in a second,
different gear (e.g., a
lower gear relative to the first gear).
[0024] According to another implementation, the motor controller may be
configured to
select a neutral braking torque curve depending on a mode in which the vehicle
is engaged. For
example, the motor controller may be configured to select a first regenerative
braking curve if
the vehicle is engaged in a downhill neutral braking mode, a second
regenerative braking mode
if the vehicle is engaged in a different mode, such as a maximum range mode or
a maximum
performance mode. A vehicle may be equipped with other driving modes and may
be
configured to select regenerative torque curves in various other manners as
well.
[0025] The motor controller may be configured to determine that the vehicle
is engaged in
the neutral braking mode based on a signal received from a component coupled
to the motor
controller. As an example, the motor controller may be coupled to a set of
driver controls that
may be operable by a driver of the vehicle, such as switches, pedals, knobs,
etc. The driver may
activate a control, such as a switch, to engage the neutral braking mode, such
as the downhill
neutral braking mode. The neutral braking mode may be activated in various
other manners as
well.
[0026] Additional detail regarding an example neutral braking mode
subroutine will now be
described. To begin execution of the neutral braking mode subroutine, the
motor controller may
obtain any input values that are relative to the neutral braking mode
subroutine. Such input
values may take the form of a vehicle speed value, or a rotational velocity of
n motor, as some
examples. If necessary, after obtaining any input values for the neutral
braking mode
subroutine, the motor controller may preprocess or convert the input values to
a different format.
For example, the motor controller may obtain an input value corresponding to a
speed of the
vehicle and may convert the speed value to a value indicative of a rotational
velocity of the drive
motor or vice versa. The motor controller may obtain various other additional
input values and
may convert various other values as well.
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[0027] After obtaining or converting the form of any inputs, the neutral
braking mode
subroutine may then determine an amount of regenerative braking torque to
apply to the drive
motor. The neutral braking mode subroutine may then cause the motor controller
to apply the
determined amount of regenerative braking torque to the drive motor, which
results in the drive
motor producing a regenerative current.
[0028] Once a regenerative current is generated, a second subroutine,
referred to as a "drive
current limit handling subroutine" subroutine may then cause the motor
controller to control the
regenerative current supplied to the battery pack to at least partially
recharge the battery pack.
The functions of determining an amount of regenerative braking torque to apply
to the drive
motor, causing the drive motor to apply the determined amount of regenerative
torque to the
drive motor, and supplying regenerative current to the battery pack may take
various forms.
[0029] The motor controller may determine the amount of regenerative
braking torque to
apply to the drive motor based on the selected neutral braking torque curve.
According to an
implementation, the motor controller may determine the amount of regenerative
braking torque
to apply to the drive motor based on the selected neutral braking torque curve
by using the
selected neutral braking torque curve to map an input value to the curve to an
output amount of
regenerative braking torque as that is specified by the selected neutral
braking torque curve.
[0030] According to an implementation, the input to the input to the
neutral braking torque
curve may be a rotational velocity, such as a number of RPMs or the speed of
the vehicle, which
may be expressed in terms of kilometers or miles per hour, as some examples.
The output of the
neutral braking torque curve may be expressed in terms of a percentage of
regenerative braking
torque to apply to the drive motor.
[0031] To map an input value to an output value based on the selected
neutral braking torque
curve, the motor controller may execute call one or more mapping functions,
which run
continuously and in parallel with the neutral braking mode subroutine. Such a
mapping
functions may perform the task of constantly mapping input value such as a
rotational velocity
to the selected curve and generating an output in the form an amount of
regenerative braking
torque based on the selected neutral braking torque curve. In some examples,
the amount of
regenerative braking torque that the motor controller may apply to the drive
motor may be
expressed as a percentage of a maximum amount of regenerative braking torque
that motor
controller may apply to drive motor during regenerative braking. The amount of
regenerative
braking torque may be expressed in various other forms as well.
[0032] After the neutral braking mode subroutine causes the motor
controller to determine an
amount of regenerative braking torque to apply to the drive motor, the neutral
braking mode
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subroutine may then cause the motor controller to apply the determined amount
of regenerative
braking torque to the drive motor.
[0033] As a result of the drive motor applying the determined amount of
regenerative torque
to the drive motor, a regenerative braking current is generated by the drive
motor. The drive
current limit handling subroutine may cause the motor controller to in turn
supply the
regenerative braking current to the battery pack of the vehicle. The functions
involving the
motor controller supplying the regenerative braking current to the battery
pack as part of
executing the neutral braking mode subroutine may take various forms.
[0034] At a high level, the drive current limit handling subroutine may
cause the motor
controller to supply the regenerative braking current to the battery back
based on an amount of
charge that the battery pack can accept. A battery management system (BMS),
which may be in
communication with the motor controller and the battery pack via a suitable
communications
protocol such as a CANbus, may provide various data to the motor controller
related to the
operation of the battery pack, which may include an amount of current that the
battery pack can
accept or provide at a given time. The amount of current that the battery pack
can accept or
provide at a given time is but one example of data that the battery management
system may
provide to the motor controller. The battery management system may provide
other data related
to the operation of the battery pack to the motor controller as is well known
by those normally
skilled in that art.
[0035] More particularly, the battery management system may determine a
charge level of
the battery pack, and based on the determined charge level, may determine an
amount of
regenerative current that the battery pack can accept. If the battery
management system
determines that the battery pack is near a full charge level, the battery
management system
determines that the battery is able to accept a lower amount of regenerative
current. If the
battery management system determines that the battery pack has a low charge
level, the battery
management system may determine that the battery pack can accept a higher
amount of
regenerative current. In any case, the battery management system may
periodically provide to
the motor controller an amount of current that the battery pack can accept at
a given time.
[0036] If the motor controller determines that the amount of regenerative
braking current
exceeds a regenerative current limit that may be based on the maximum current
the battery pack
can accept, the drive current limit handling subroutine may cause the drive
motor to reduce the
amount of regenerative current supplied to the battery pack to regenerate the
battery charge level
to the regenerative current limit. The motor controller may reduce the amount
of regenerative
current supplied to the battery pack in various manners. For instance, the
motor controller may
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reduce the amount of regenerative current supplied to the battery pack by
reducing an amount of
root mean squared (RMS) AC current allowed during regeneration, which in turn
reduces the
amount of regenerative current supplied to the battery pack during
regeneration. The motor
controller may reduce the amount of regenerative current supplied to the
battery pack in various
other manners as well.
[0037] Various functions and examples with respect the regenerative braking
embodiment
have been described and will be described in greater detail herein.
[0038] An example apparatus implemented in accordance with the present
disclosure
includes a motor controller coupled to a drive motor and a battery pack of a
vehicle, wherein the
motor controller comprises a processor that is configured to: determine that
the vehicle is
engaged in a neutral braking mode, and after determining that the vehicle is
engaged in the
neutral braking mode: select a neutral braking torque curve; determine a
rotational velocity of
the drive motor; based on the determined rotational velocity of the drive
motor, determine an
amount of regenerative braking torque to apply to the drive motor based on the
selected neutral
braking torque curve; apply the determined amount of regenerative braking
torque to the drive
motor, wherein applying the determined amount of regenerative braking torque
to the drive
motor results in a regenerative current generated by the drive motor; and
supply the regenerative
current to the battery pack to at least partially recharge the battery pack.
[0039] Another example method implemented in accordance with the present
disclosure
includes determining that the vehicle is engaged in a neutral braking mode,
and after
determining that the vehicle is engaged in the neutral braking mode: selecting
a neutral braking
torque curve; determining a rotational velocity of a drive motor of the
vehicle; based on the
determined rotational velocity of the drive motor, determining an amount of
regenerative
braking torque to apply to the drive motor based on the selected neutral
braking torque curve;
applying the determined amount of regenerative braking torque to the drive
motor, wherein
applying the determined amount of regenerative braking torque to the drive
motor results in a
regenerative current generated by the drive motor; and supplying the
regenerative current to the
battery pack to at least partially recharge the battery pack.
[0040] An example tangible machine-readable medium has instructions stored
thereon
implemented in accordance with the present disclosure that when executed,
cause at least one
processor to determine that a vehicle is engaged in a neutral braking mode;
and after
determining that the vehicle is engaged in the neutral braking mode: select a
neutral braking
torque curve; determine a rotational velocity of a drive motor of the vehicle,
based on the
determined rotational velocity of the drive motor; determine an amount of
regenerative braking
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torque to apply to the drive motor based on the selected neutral braking
torque curve; apply the
determined amount of regenerative braking torque to the drive motor wherein
applying the
determined amount of regenerative braking torque to the drive motor results in
a regenerative
current generated by the drive motor; and supply the regenerative current to
the battery pack to
at least partially recharge the battery pack.
1. Traction Control of Dual Motor All-Wheel Drive Electric Vehicles
[0041] Another embodiment is related to traction control of dual motor, all-
wheel drive
electric vehicles. The traction control system of the present embodiment is
intended for dual
motor all-wheel drive off-road electric drive vehicles and improves traction
at low speeds under
difficult road conditions of high grades and unfavorable terrain. According to
various
implementations, the traction control system may be used in battery-only
vehicles and hybrid
electric vehicles.
[0042] The traction control embodiment may present various advantages
including, for
example: (1) maximizing traction between front and rear axles on conditions of
high grade and
poor terrain, (2) minimizing spin and energy loss of spinning wheels, (3)
automatically adjusting
for forward and reverse drive on uphill grades, (4) preventing of digging-in
of spinning wheels
on loose sand or snow, (5) allowing untrained drivers to maneuver effectively
over the most
difficult terrain, (6) providing driver-selectable means to cancel the
traction control, (7)
providing a controllable differential, (8) providing a minimum speed for
activation of traction
control, and (9) utilizing a comparison between Front RMS Current and Rear RMS
Current to
detect cases when one wheel of the vehicle is in the air. The traction control
embodiment may
provide various other advantages as well.
2. Performance Optimization for Dual Motor All-Wheel Drive Electric and
Hybrid
Vehicles
[0043] Another embodiment is related to performance optimization of dual
motor, all-wheel
drive electric and hybrid vehicles.
[0044] This embodiment described herein relates to means for controlling
the division of
torque between the front axle and the rear axle to accommodate different
vehicle speed ranges
and varying terrain conditions.
[0045] At low vehicle speeds and difficult terrain both front and rear
motors can operate at
full torque for maximum traction. At higher vehicle speeds, maximum traction
is no longer
required and it is beneficial to reduce the torque generated by the front
motor. At still higher
vehicle speeds it may be desirable to reduce the front motor torque
contribution to zero.
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[0046] The torque division means may also comprise driver selected means
for propelling the
vehicle by the front drive motor only. These driver-selected means may also be
operable to
propel the vehicle by the rear drive motor only.
[0047] These driver-selected means may also be operable to allow the driver
to select the
desired torque division between front and rear axles at will, even when the
vehicle is moving at
high speed. The torque division means may also comprise means for
automatically limiting the
current drawn from the battery to safe levels commensurate with the state of
the battery.
3. Regeneration and Braking Control
[0048] This disclosure also describes a regeneration and braking control
embodiment. The
braking and regeneration control embodiment optimizes and simplifies control
of electric and
parallel hybrid vehicles during extended downhill and braking operation.
[0049] Some example advantages of the regeneration and braking control
embodiment
comprise switch-selectable regeneration means for extended downhill operation
so vehicle speed
can be maintained without depression of brake pedal. The switch-selectable
regeneration means
eliminates heating of service brakes and maximizes recovery of energy, allows
optimized
regeneration of energy during braking between front and rear wheels while
maintaining vehicle
stability, and controls rate of response of the brake pedal in front and or
rear controller to
respond rapidly at high vehicle speeds and more slowly at lower vehicle
speeds. Thus, the
regeneration and braking control embodiment prevents instability in the
controller at very low
speeds while providing required rapid response at high speeds. Additional
detail of this
embodiment will be described in greater detail herein.
4. Optimizing Performance of 4WD Electric Drive Vehicles by Equalizing
Component
Temperatures
[0050] Another embodiment disclosed herein relates to optimizing
performance of 4WD
electric drive vehicles by equalizing component temperatures. More
particularly, in an all-wheel
electric drive system, one of the drive axles inevitably assumes more of the
load than the other
axle. For example, while climbing a steep grade for extended periods, the rear
drive motor and
controller may tend to overheat thereby limiting vehicle performance.
[0051] The present embodiment provides temperature equalization methods
that are
operative to automatically adjust the division of power between front and rear
axles depending
on component temperatures.
[0052] This embodiment provides numerous advantages. The advantages of this
embodiment include: (1) improving vehicle performance by reducing effects of
automatic
cutbacks of motor load, and (2) extension of vehicle component life by
reducing load on higher
temperature components, as some non-limiting examples.
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5. Optimizing Electric Vehicle Performance While Preserving Required Range
[0053] Another embodiment of this disclosure relates to optimizing electric
vehicle
performance while preserving a required range.
[0054] More particularly, for any electric vehicle, the expected operating
range depends on
the amount of stored energy remaining in the vehicle energy storage system,
the road and terrain
conditions that the vehicle must traverse, and the required route including
range for a safe return
if desired. Electric vehicles are particularly sensitive to this issue because
of the limited energy
stored in the vehicle energy storage system; however, the functions related to
this embodiment
are applicable to hybrid-electric vehicles as well.
[0055] The purpose of the present invention is to provide a predictive or
look-ahead method
that takes into account details of the remainder of the route, including the
return if desired, and
advises the vehicle operator accordingly.
[0056] In a preferred implementation of the present embodiment, means are
provided for
operating with the Curtis Instruments controllers and a computationally
intensive computer
(Vehicle Management Unit or VMU) in a co-processor mode. Detailed computations
are carried
out in the co-processor and the results of these computations are communicated
to the Curtis
controllers which control the current supplied to the vehicle motors.
[0057] In an alternative implementation of the present embodiment, the
predictive functions
will also comprise means for automatically reducing the current or power drawn
from the energy
storage system to preserve the amount of energy required to return (e.g.,
return-to-base in
military operations). Similarly, the allowed maximum performance or the
vehicle may be
enhanced if substantially more energy than expected remains in the battery.
[0058] In another alternative implementation of the present embodiment,
override means are
provided to allow the vehicle operator or a remote-controlled operator to
apply maximum
vehicle propulsion power to escape an unexpected predicament. As soon as the
emergency
condition is over, the override means can be operative to recalculate the
remaining portion of the
mission.
[0059] In another alternative implementation of the present embodiment,
that is applicable to
an electric-hybrid vehicle, predictive means are provided for unscheduled
charging of the battery
if a long uphill region is expected in the near future. Similarly, the battery
could be partially
depleted if a long downhill region is expected thereby improving overall fuel
consumption and
remaining range.
[0060] This embodiment addresses two problems: (1) the mission profile
mapped according
to this embodiment has been carefully mapped so the terrain and road
conditions of the
remaining mission are known or estimated in advance, and (2) details of the
terrain and road
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conditions are not known in advance but the return-to-base location is known.
This algorithm
may use map-based GPS data of the geography and terrain conditions.
[0061] The system provides various advantages in that the embodiment (1)
automatically
provides for maximum instantaneous vehicle performance while ensuring return-
to-base
capability, and (2) reduces the training level required of the vehicle
operator.
6. Optimizing Range of 4WD Electric Vehicles and Hybrid-Electric Vehicles
Based on
Control Tables
[0062] This disclosure also describes an embodiment that is related to
optimizing range of
vehicles, such as 4WD electric vehicles, and hybrid-electric vehicles based on
control tables.
[0063] The performance of complex electric and hybrid-electric drive
systems may be
optimized by preparing control tables based on, for example, detailed
simulation analysis of
typical vehicle duty cycles. These control tables may then be downloaded to
the Vehicle
Management Unit computer (VMU) so that operation of the various power sources
(e.g., battery
power, engine and battery power) can be optimized to obtain, for example,
maximum range or
minimum fuel consumption.
[0064] These algorithms often require a VMU with extensive computational
capabilities
which may be in excess of the capability of the control computers, such as
Curtis control
computer, used in the vehicles of the present disclosure. As described
elsewhere herein, motor
controllers (e.g., Curtis controllers) communicate vehicle, battery and motor
component data to
the VMU. The VMU may also carry out the numerically intensive computation
based on the
various control tables stored therein and communicate the best solution to the
(e.g., Curtis)
controller(s). The controller(s) may then issue appropriate commands to the
motors to provide
the required power in the most efficient way possible.
[0065] This embodiment provides several advantages. For example, this
embodiment
enables use of advanced vehicle control techniques while retaining the
advantages of the unique
functionality of the (e.g., Curtis) motor control unit(s), and (2) reduces the
training level of
vehicle operators. This embodiment may provide various other advantages as
well.
7. Series Hybrid Range Extender for All-Wheel Drive Electric Vehicles
[0066] Another embodiment according to this disclosure is related to a
series hybrid range
extender for all-wheel drive electric vehicles. According to the present
embodiment, the all-
wheel drive electric vehicle may also comprise an engine, an engine driven
generator and a
generator controller in a series hybrid architecture to substantially increase
the range of the
vehicle, as shown in various figures herein.
[0067] In an alternative embodiment of the present invention, the series
hybrid also
comprises engine control means operable to take advantage of the drivability
and energy
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management features described herein for an all-wheel drive electric vehicle.
It is a particular
feature of this embodiment that the engine control means can be seamlessly
integrated into the
control software for the all-wheel drive electric vehicle.
8. Parallel Hybrid Output Power Assist with Improved Performance and Silent
Capability
[0068] Another embodiment of this disclosure related to parallel hybrid
output power assist
with improved performance and silent capability. This embodiment may comprise
sub-
embodiments 8.1 and 8.2.
8.1 Improved Shift Gradeability in Output Power Split Hybrid Mode
[0069] This sub-embodiment relates to a hybrid-electric vehicle driven by a
conventional
combustion engine and an electric drive motor. In such a vehicle, the drive
train may be a post-
transmission hybrid powertrain wherein the electric motor is located after the
multi-speed
transmission. The multi-speed transmission may be a manual shifted
transmission and where a
2-speed reduction gear is located between the transmission output and the
vehicle drive axles.
[0070] Various problems are associated with the example type of powertrain
described with
respect to this sub-embodiment. One of the problems associated with such a
powertrain occurs
during the 1-2 shift on difficult terrain at low vehicle speeds. In such
cases, the interruption of
torque transfer from the engine to the vehicle may prevent engagement in the
2nd gear without
the engine stalling.
[0071] The transfer case may use a dog-clutch to engage a "Hi Gear" and a
dog-clutch to
engage a "Lo Gear." When neither dog clutch is engaged, the transfer case is
in neutral. This
neutral state of the transfer case allows the engine to charge the battery at
vehicle standstill in
any desired gear and allows the engine to rotate rapidly at standstill to
recharge the battery.
[0072] One benefit of this embodiment is to provide functions for using the
electric motor
torque during the gear shift to prevent the vehicle from decelerating during
the power
interruption of the gear shift. The invention may also be used to allow the
engine to recharge the
battery during standstill in the most efficient transmission gear.
8.2 Output Power Assist with Combustion Engine and Automatic Transmission
[0073] Another sub-embodiment related to power assist applies to a hybrid
electric vehicle
driven by a conventional combustion engine and an electric drive motor. The
drive train may be
a post-transmission hybrid powertrain wherein the electric motor is located
after the multi-speed
transmission. The multi-speed transmission may be a conventional automatic
transmission with
a torque converter and a 2-speed reduction gear that is located between the
transmission output
and the vehicle drive axles. A 3-dimensional representation of the powertrain
of the present
invention is shown in FIG. 30.
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[0074] Various flows may be used in various circumstances such as, for
example, rough
terrain, silent operation, use with a hybrid mode that involves battery
charging, operation in a
"charge in park" mode, and/or various other modes.
[0075] FIG. 31 shows some of the major drive line components of the Output
Power Assist
hybrid powertrain that may be used with the present invention.
[0076] FIG. 32 shows an example flow of power in a Standard Drive operating
mode. In
such a mode: (1) power is provided by the internal combustion engine, and (2)
the electric motor
rotates freely without affecting the output.
[0077] The flow of power in a Fuel Saver operating mode of the present
embodiment is
shown in FIG. 33. The Fuel Save operating mode may provide several advantages
in that the
Fuel Saver configuration may: (1) achieve maximum or near-maximum fuel
efficiency and
range, (2) provide power by the internal combustion engine, and (3) facilitate
the electric motor
to add power at high vehicle load and absorb power during periods of low
driving load to
improve efficiency of the engine.
[0078] A flow of power in a Hybrid Combined Drive operating mode is shown
in FIG. 34.
The Hybrid Combined Drive mode may: (1) be used when extra power is required
for rough
terrain, (2) provide power by the internal combustion engine and the electric
motor
simultaneously, (3) control the electric motor output torque with the motor
controller. The
electric motor torque output may be adjusted according to the demand for
driving power by the
vehicle operator. The flow of power in a Silent Mode of operation in shown in
the FIG. 35. The
Silent Mode is used to achieve silent operation with minimal engine exhaust
[0079] In yet another embodiment disclosed herein, the Output Power Assist
hybrid
powertrain of the present invention, wherein the powertrain also comprises a
second drive motor
and second motor controller, may be configured to provide enhanced performance
in the hybrid
and silent modes of operation.
[0080] Also in accordance with an preferred implementation of the present
embodiment, the
hybrid vehicle powertrain also comprises a Vehicle Management Unit (VMU) which
coordinates operation of aspects of the conventional drive components.
[0081] Also in accordance with an implementation of the present embodiment,
the hybrid
vehicle powertrain also comprises an Energy Storage system with sufficient
energy storage and
power capacity to propel the vehicle with electrical energy in a battery only
or silent mode of
operation and to assist the power delivered by the engine to enhance the
maximum performance
capability of the vehicle.
[0082] In accordance with yet another preferred embodiment of the
invention, the Energy
Storage system may comprise a battery and supercapacitor.
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[0083] Various control means of the present embodiment are also described
herein. The
control means may: (1) provide full torque from both motors at low motor
speeds until the peak
discharge current limit (DCL) from the BMS is reached, (2) reduce the torque
from both motors
to prevent excessive battery discharge current, (3) control the current
provided by each of the
drive motors so as to minimize the overall losses of each motor thereby
reducing the current
provided by the batteries. Additionally, the control means may comprise:
(1)first override means
to reduce the motor torque by limiting motor speeds and field weakening in the
event of a
message from the BMS and (2) second override means to ignore all warnings and
messages and
to record each event and length of time of occurrence in the memory of the
controllers. The
control means may control the torque provided by both motors to favorably
affect the
transmission shift schedule and the torque converter clutch lock up schedule.
[0084] In yet another preferred implementation of the present embodiment,
the transmission
and torque converter clutch sensor means comprises vehicle communication
(e.g., CANbus
reading) means operable to read the transmission gear ratio and torque
converter clutch status.
[0085] In still another preferred implementation of the present embodiment,
the transmission
and torque converter clutch sensor means comprises pressure switch means
operable to provide
information to the transmission control means regarding the operating state of
the transmission
gear and the torque converter clutch status.
[0086] In yet another preferred implementation of the present embodiment,
mode control
means are provided that are operable to favor high vehicle performance at the
expense of fuel
consumption by judiciously providing short bursts of power from the energy
storage system to
cause the VMU to unlock the torque converter lockup clutch and/or downshift
the transmission
to a lower gear.
9.
Generalized Control for Electric or Hybrid Vehicles With Multiple Sources of
Energy
[0087] Additional embodiments relate to a generalized energy management
system for an
electric vehicle drive train with a range extender. The range extender may
comprise a
multiplicity of energy sources in addition to the vehicle's main battery.
[0088] The present embodiment may apply, for example, to a 2-Motor 4WD
electric vehicle.
The energy supply system (ESS) of this embodiment comprises a conventional
battery and a
conventional BMS.
[0089] The present embodiment relates to the method used to integrate
operation of an
energy supply system comprising multiple sources of energy.
[0090] According to the present embodiment, the vehicle system
controller(s) receive
information from an ES S Computer. It will be appreciated by those skilled in
the art that the
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functionality of the ESS Computer can be integrated into the power controller
of the generator
which may be, for example, a conventional Curtis AC Motor Controller.
[0091] The vehicle system controller(s) may be configured with the required
functionality to
compute the power (e.g., PowerWeNeed) to meet the required driver commands and
transmit
this power requirement to the ESS computer. The ESS computer may be programmed
with the
functionality to decide how best to provide the power from the available
sources of energy (i.e.
the battery and/or the heat engine). If the power cannot be provided by any
combination of the
available power sources, the ESS Computer may transmit the maximum allowed
discharge
current in the value of ESS DCL.
[0092] It will be appreciated that as far as the vehicle controller(s) are
concerned, it does not
matter if the allowed discharge current is limited by the battery discharge
limit (e.g., PackDCL)
or by ESS DCL (in the present invention). The vehicle system controller(s)
will react to the
numerical value of the discharge current limit (e.g., PackDCL or ESS DCL).
[0093] It will be appreciated therefore that the investment and time spent
in developing and
debugging the intricate vehicle controls will operate without change. (In a
certain sense it is like
a plug-and-play system).
[0094] The ESS computer may be programmed with knowledge of, for example,
the battery,
fuel cell, super cap, etc. to decide on the best division of power. The
vehicle system controller
software does not have to know anything about how the ESS Computer makes its
decisions.
10. Dealing with Under-Performing Battery Modules
[0095] This embodiment relates to dealing with under-performing battery
modules.
[0096] As background, the importance of balancing the state of charge (SOC)
of a multi-cell
Lithium based battery is well known in the literature. Similarly, the
importance of preventing
even one of the cells of a multi-cell battery from exceeding prescribed limits
is also well known.
See for example XP Power System User Manual Rev. 4.8 published by Valence
Technology of
Austin Texas. Ideally, the SOC of each of the cells in a battery is
substantially the same and
intricate procedures have been developed for ensuring that Lithium based
batteries are properly
charge and balanced.
[0097] Safe operation of Lithium based batteries (particularly large
batteries used in electric
vehicles) may be supervised by a BMS. A BMS may monitor the state of each of
the cells in a
multi-cell battery and report on the state of the battery as a whole and also
on the worst-case
cell(s) of the battery. Thus, a BMS may report the voltage of lowest voltage
cell in the battery
pack, the lowest temperature cell, the highest temperature cell, the cell with
the lowest SOC, the
highest SOC, etc. The system may need to respond to the messages sent by the
BMS and
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decrease the load on the battery pack if required. In extreme cases, it may
even be required to
shut the vehicle down completely to prevent a dangerous situation from
occurring.
[0098] For various reasons that are well known in the literature, one or
more of the battery
modules may be at a lower SOC than the other modules. For maximum safety, the
BMS may be
programmed to base its calculations for the maximum recommended discharge
current limit
(e.g., PackDCL) on the battery module with the lowest SOC. The value of the
module with the
lowest SO C may also be reported to the driver as a measure of the charge
remaining in the
battery.
[0099] The present embodiment may be used to prevent this anomalous
situation from
interfering with the driver's concentration and providing meaningful feedback
to the vehicle
operator, and yet protecting the battery as required. The battery state
display may also comprise
means which are operative, when an SO C mismatch warning is issued by the BMS,
to display
the average value of the SO C as calculated by the vehicle controller(s).
Using the SO C of the
weakest module will continue to protect the battery.
[00100] In an alternative implementation of the present embodiment, the
average value of the
SOC may be reported to the vehicle operator and the SO C of the weakest cell
may be used to
protect the battery.
11. Preserving Residual Energy Level in Energy Storage System
[00101] Another embodiment relates to preserving residual energy levels in
energy storage
systems. As background, battery-only electric vehicle drive systems often
require a low voltage
energy source for operating relays, warning and indicator lights, and other
low power devices
typically associated with on- and off-road vehicles. Similarly, a hybrid-
electric vehicle may also
require a low voltage energy source for operating a starter motor to start the
combustion engine.
These auxiliary devices are often powered by a low voltage (e.g., 12V or 24V)
conventional
battery.
[00102] As is well known by one normally skilled in the art, the vehicle
cannot even be started
if the low voltage battery is completely discharged. To prevent this from
occurring, DC-DC
Converter means may be provided to keep the low voltage battery in a charged
state. The energy
required for this may come from the main high voltage energy storage device of
the vehicle. It
will be apparent that if the main high voltage energy storage device is
completely discharged,
the low voltage battery will become completely discharged and the vehicle will
be completely
unresponsive and may not even be capable of issuing an error state message
indicating what the
problem is. Such a case may occur if the vehicle is left completely unattended
for a long period
of time without the conventional vehicle ignition switch being turned off.
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[00103] The present embodiment provides residual energy control means to
preserve a
minimum amount of energy in the low voltage system and in the high voltage
energy storage
device of the vehicle.
[00104] In another embodiment, the residual energy control means also
comprises SOC
display means operative to transform the battery pack state of charge (e.g.,
PackSOC) as
reported by the BMS to a displayed SOC, wherein the displayed SO C may report
a higher
numerical value than the actual battery pack state of charge.
[00105] In another embodiment, the residual energy control means may also
comprise as
conventional serial display unit (e.g., Curtis Model 840 or similar device)
for displaying
numerical values to the vehicle operator.
[00106] It will be apparent to one normally skilled in the art of using motor
controllers (e.g.,
controllers manufactured by Curtis Instruments) that numerical values may be
stored in
EEPROM memory by a fleet manager and that these values cannot be changed by a
user of the
vehicle.
12. Controllable Differential System for 4WD Electric Vehicles
[00107] Another embodiment of this disclosure relates to a controllable
differential system for
4WD electric vehicles.
[00108] As background, the importance of being able to lock a differential to
maximize
traction is well known in the literature and various mechanisms for
implementing this are well
known to one normally skilled in the art. In most cases, a driver-selectable
differential-lock
mechanism is provided in both the front axle drive and the rear-axle drive
system. These
differential lock mechanisms prevent loss of traction when one of the drive
wheels slips but at
the cost of losses in the drive train on uneven terrain.
[00109] A serious problem often associated with a front-differential lock
system is the
susceptibility of the front axle drive system to heavy shocks when operating
in a rough rock-
strewn terrain. These shocks often lead to premature damage to the front axle.
[00110] The present embodiment can be used to minimize shocks encountered by
the front
axle by providing a rapid means for temporarily applying a varying torque on
the faster of the
drive wheels, thereby increasing traction to the front axle. This varying
friction torque may be
selectively applied only when desired by the operator.
[00111] The present embodiment comprises at least one shaft speed sensor
arranged to
monitor the rotational speed of at least one of the front wheels. The speed of
the differential
input shaft may be known from the speed sensor located on the front axle drive
motor. The
speed of the second front wheel therefore may be calculated from the known
speed of the front
axle drive motor, the known gear ratios, and speed measured by said shaft
speed sensor.
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[00112] The present embodiment also comprises friction disks and friction
control means on
both sides of the differential and operative to provide a varying friction
torque to one of the
drive wheels when desired. In one embodiment of the invention, the friction
disks are the front
wheel disk brakes.
[00113] Thus, if the speed of one of the front wheels is substantially higher
than the speed of
the second front wheel, the friction control means will operate to apply a
friction torque to the
faster brake disk, thereby forcing the slower wheel to provide a driving
torque proportional to
the torque applied to the faster wheel.
[00114] It will be apparent to one normally skilled in the art that the
traction of the front axle
will be increased when one of the brakes disks are activated. This embodiment
may take various
other forms as well.
13. Parallel Hybrid with CVT
[00115] Another embodiment of this disclosure relates to a Parallel Hybrid
vehicle having a
continuously variable transmission (CVT). This embodiment utilizes the 4WD
electric vehicle
drive technology and software components for battery only vehicles as part of
a hybrid
powertrain. In accordance with an embodiment of the present invention, an
internal combustion
engine is drivingly connected to the rear drive motor via a continuously
variable transmission
(CVT) and clutch.
[00116] The present embodiment provides numerous advantages and features. For
example,
the present embodiment may provide: (1) silent operation with front wheel
drive (FWD), rear
wheel drive (RWD) and all wheel drive (AWD) vehicles, (2) means for FWD, RWD
and AWD
when the engine operates, (3) an engine to drive a rear axle while providing
electrical power to
recharge the battery and/or power the front drive motor, (4) stop-start
operation of the engine,
(5)redundant controls to front and rear drive components, (6), redundant
digital and analog
controls for the system, (7), vehicle operation that continues if the
communication system (e.g.,
a CANbus) fails, (8) vehicle operation in the event of catastrophic failure in
electrical system,
(9) 4WD operation if battery fails or is empty, (10) a vehicle range that is
limited only by the
vehicle's fuel supply, and/or (11) operation at high vehicle speed in excess
of the maximum
speeds allowed by the vehicle's electric motors. The present embodiment may
provide various
other advantages as well.
14. Safety Measure for Remote Control of Electric and Hybrid Vehicles
[00117] Yet another embodiment may provide safety measure for remote control
of electric
and hybrid vehicles. This aspect of the invention deals with control means for
enhancing the
safety of remote controlled electric and hybrid vehicles and in particular a
means for bringing
the vehicle to a safe stop when remote control is lost.
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[00118] Such control means may comprise a combination of mechanical and
software control
features, such as: (1) release of spring-loaded brake responsive to detection
of loss of control of
the vehicle, and/or (2) electrically disabling drive controller(s) responsive
to detection of loss of
control of the vehicle. The present embodiment may provide various other
advantages as well.
15. Predicting Remaining Battery Life Based on Analysis of Total Energy
Consumption
[00119] Still another embodiment of the present disclosure is related to
predicting remaining
battery life of a vehicle based on the analysis of the total energy
consumption.
[00120] As background to this embodiment, the state-of-health of a secondary
battery when
subject to variations in charge and discharge rates, battery cell temperature,
unequal cell
balancing, depth of discharge, etc. are important factors in fleet management
of electric and
hybrid electric vehicles. This is especially critical in applications which
require a guaranteed
return-to-base capability.
[00121] The current embodiment deals with techniques for predicting the
remaining useful life
of a battery based on the total amount of energy delivered by the battery
cells over the
operational life of the battery.
[00122] In an alternate implementation of the present embodiment, the
techniques also
comprise means for predicting the remaining useful life of a battery based on
manufacturer
supplied data of battery life as a function of temperature and battery life as
a function of depth of
discharge.
[00123] As some implementations of the present embodiment, data reported by
the BMS may
be used to compute the total amp-hr (ampere-hour) throughput of the entire
battery pack and/or
the total amp-hr throughput of each battery cell and compare it with
manufacture-supplied
predictions of battery life as a function of the depth of discharge of the
battery.
[00124] Various embodiments and implementations and embodiments of the present
disclosure have been described. Additional detail regarding these
implementations and
embodiments will be described in greater detail below.
[00125] Although the following discloses example methods, apparatus, systems,
and articles
of manufacture including, among other components, firmware and/or software
executed on
hardware, it should be noted that such methods, apparatus, systems, and/or
articles of
manufacture are merely illustrative and should not be considered as limiting.
For example, it is
contemplated that any or all of these firmware, hardware, and/or software
components could be
embodied exclusively in hardware, exclusively in software, exclusively in
firmware, or in any
combination of hardware, software, and/or firmware. Accordingly, while the
following describes
example methods, apparatus, systems, and/or articles of manufacture, the
examples provided are
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not the only way(s) to implement such methods, apparatus, systems, and/or
articles of
manufacture.
[00126] When any of the appended claims are read to cover a purely software
and/or firmware
implementation, at least one of the elements in at least one example is hereby
expressly defined
to include a tangible medium such as a memory, DVD, CD, Blu-ray, etc., storing
the software
and/or firmware.
[00127] These embodiments and many additional embodiments are described more
below.
Further, the detailed description is presented largely in terms of
illustrative environments,
systems, procedures, steps, logic blocks, processing, and other symbolic
representations that
directly or indirectly resemble the operations of data processing devices
coupled to networks.
These process descriptions and representations are typically used by those
skilled in the art to
most effectively convey the substance of their work to others skilled in the
art. Numerous
specific details are set forth to provide a thorough understanding of the
present disclosure.
However, it is understood to those skilled in the art that certain embodiments
of the present
disclosure may be practiced without certain, specific details. In other
instances, well known
methods, procedures, components, and circuitry have not been described in
detail to avoid
unnecessarily obscuring aspects of the embodiments.
[00128] Reference herein to "embodiment" means that a particular feature,
structure, or
characteristic described in connection with the embodiment can be included in
at least one
example embodiment of the invention. The appearances of this phrase in various
places in the
specification are not necessarily all referring to the same embodiment, nor
are separate or
alternative embodiments mutually exclusive of other embodiments. As such, the
embodiments
described herein, explicitly and implicitly understood by one skilled in the
art, may be combined
with other embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[00129] Features, aspects, and advantages of the presently disclosed
technology are better
understood with regard to the following description, appended claims, and
accompanying
drawings where:
[00130] FIG. 1 is a conceptual diagram of a vehicle configuration;
[00131] FIG. 2 is a conceptual diagram of a motor controller;
[00132] FIG. 3 is a conceptual diagram of a vehicle configuration;
[00133] FIG. 4 is a conceptual diagram of two motor controllers;
[00134] FIG. 5 is a conceptual diagram of a vehicle configuration;
[00135] FIG. 6 is a conceptual diagram of a main control loop and a
subroutine;
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[00136] FIG. 7 is a conceptual diagram of a neutral braking torque curve;
[00137] FIG. 8 is a conceptual diagram of a neutral braking torque curve;
[00138] FIG. 9 is a conceptual diagram of a charge current limit map;
[00139] FIG. 10 is a conceptual diagram of a drive current limit handling
subroutine;
[00140] FIGS. 11A¨B are graphs of a deceleration event;
[00141] FIGS. 12A-12C are graphs of a deceleration event;
[00142] FIG. 13 is a flowchart of a method for performing regenerative braking
during a
neutral braking mode;
[00143] FIG. 14 is a conceptual diagram of a vehicle configuration;
[00144] FIG. 15 is a conceptual diagram of a vehicle configuration configured
to implement
traction control;
[00145] FIG. 16 is a graph of peak DC current as a function of vehicle speed;
[00146] FIG. 17 is a graph of motor speeds;
[00147] FIG. 18 is a conceptual diagram of a front only mode of vehicle
operation;
[00148] FIG. 19 is a conceptual diagram of a code listing for handling
regenerative braking
torque and regenerative current limits;
[00149] FIG. 20 is a graph of an example relationship between a neutral
braking torque
variable and vehicle speed;
[00150] FIG. 21 is a diagram of a code listing for controlling vehicle
braking;
[00151] FIG. 22 is a conceptual diagram that summarizes techniques for
limiting regenerative
braking in a rear motor controller;
[00152] FIG. 23 is a graph related to limiting regenerative braking in a rear
motor controller;
[00153] FIG. 24 is a graph related to limiting regenerative braking in a rear
motor controller;
[00154] FIG. 25 is a is a graph related to limiting regenerative braking in a
rear motor
controller;
[00155] FIG. 26 is a is a graph related to limiting regenerative braking in a
rear motor
controller;
[00156] FIG. 27 is a conceptual diagram illustrating adjusting neutral braking
torque based on
vehicle speed;
[00157] FIG. 28 is a conceptual diagram of a vehicle configuration;
[00158] FIG. 29 is a conceptual diagram of a post-transmission hybrid
powertrain;
[00159] FIG. 30 is a 3-dimensional representation of a powertrain;
[00160] FIG. 31 is a 3-dimensional representation of a powertrain;
[00161] FIG. 32 is a conceptual diagram illustrating an example flow of power
in a standard
drive operating mode;
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[00162] FIG. 33 is a conceptual diagram illustrating an example flow of power
in a fuel saver
operating mode;
[00163] FIG. 34 is a conceptual diagram illustrating an example flow of power
in a hybrid
combine drive operating mode;
[00164] FIG. 35 is a conceptual diagram illustrating an example flow of power
in a silent
operation mode;
[00165] FIG. 36 is a conceptual diagram illustrating an example flow of power
in a hybrid
mode;
[00166] FIG. 37 is a conceptual diagram illustrating an example flow of power
in a charge in
park operating mode;
[00167] FIG. 38 is a conceptual diagram of an output power assist hybrid
powertrain;
[00168] FIG. 39 is a conceptual diagram of performance curves of a
motor/generator;
[00169] FIG. 40 is a conceptual diagram of a fuel map;
[00170] FIG. 41 is a conceptual diagram of an example torque converter clutch
lockup
schedule;
[00171] FIG. 42 is a conceptual diagram of an example transmission gear shift
schedule;
[00172] FIG. 43 is a conceptual diagram of a vehicle configuration;
[00173] FIG. 44 is a conceptual diagram of an example flow between an energy
supply system
and vehicle system controllers;
[00174] FIG. 45 is a conceptual diagram of an example flow between an energy
supply system
and vehicle system controllers;
[00175] FIG. 46 is a conceptual diagram of an example flow between an energy
supply system
and vehicle system controllers;
[00176] FIG. 47 is a conceptual diagram illustrating an example charge state
of battery
modules in a battery pack;
[00177] FIG. 48 is a conceptual diagram illustrating example states of charge
of battery
modules in a battery pack;
[00178] FIG. 49 is a conceptual diagram illustrating example states of charge
of battery
modules in a battery pack;
[00179] FIG. 50 is a conceptual diagram illustrating a relationship between a
real and display
state of charge of battery modules in a battery pack;
[00180] FIG. 51 is a conceptual diagram illustrating an example of power on
logic;
[00181] FIG. 52 is a conceptual diagram illustrating an example of shutdown
logic;
[00182] FIG. 53 is a conceptual diagram illustrating an example of operating
mode
restrictions;
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[00183] FIG. 54 is a conceptual diagram illustrating an example vehicle
configuration;
[00184] FIG. 55 is a conceptual diagram of components in a parallel hybrid
vehicle having a
continuously variable transmission;
[00185] FIG. 56 is a conceptual diagram of dual motor controllers;
[00186] FIG. 57 is a conceptual diagram of electrical connections and driver
controls;
[00187] FIG. 58 is a conceptual diagram of a state diagram that illustrates
transitions between
different system operating modes;
[00188] FIG. 59 is a conceptual diagram illustrating transitions between
operating modes;
[00189] FIG. 60 is a conceptual diagram of an example main loop that may allow
a vehicle to
run in reverse;
[00190] FIG. 61 is a flow diagram of an example method for operating a gear
change
mechanism;
[00191] FIG. 62 is a flow diagram of an example method to activate and
deactivate an engine
ignition relay;
[00192] FIG. 63 is a conceptual diagram illustrating an example operation of
an interlock
control;
[00193] FIG. 64 is a conceptual diagram illustrating an example operation of
an interlock
control means;
[00194] FIG. 65 is a conceptual diagram illustrating example techniques for
determining
amounts of regenerative torque;
[00195] FIG. 66 is a conceptual diagram illustrating example maps for
determining
regenerative braking torque;
[00196] FIG. 67 illustrates example code of a regenerative current handling
subroutine;
[00197] FIG. 68 illustrates example code for controlling recharging of
battery;
[00198] FIG. 69 illustrates graphs for determining torque rollback drive
current limits;
[00199] FIG. 70 is a conceptual diagram illustrating techniques for bringing a
remote-
controlled vehicle to a safe stop in the event of a system failure;
[00200] FIG. 71 is a conceptual diagram illustrating techniques for bringing a
remote-
controlled vehicle to a safe stop in the event of a system failure; and
[00201] FIGS. 72A¨B are conceptual diagrams illustrating the operation of a
torque rollback
means.
[00202] In addition, the drawings are for the purpose of illustrating example
embodiments, but
it is understood that the present disclosure is not limited to the
arrangements and instrumentality
shown in the drawings.
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DETAILED DESCRIPTION
Example Configurations
[00203] Referring now to the drawings, in which like numerals may refer to
like parts
throughout the figures. In general, the figures in this section depict example
configurations of
vehicles and their components with which the embodiments, implementations, and
examples of
this disclosure may be implemented.
[00204] Turning now to FIG 1, FIG. 1 is a conceptual architectural diagram of
a single-axle
drive vehicle configuration 100 having a single-drive motor. Vehicle
configuration 100 includes
front wheels, a conventional steering mechanism coupled to the front wheels, a
motor controller
102 that is coupled to a drive motor 104 and a battery management system (BMS)
108 that is in
turn coupled to a battery pack 106.
[00205] Battery pack 106 is electrically connected to the DC power inputs of
motor controller
102 which converts the DC power from battery pack 106 to a three-phase AC
power accepted by
drive motor 104. According to an implementation, motor controller 102 may be a
Curtis 1238E
AC Induction Motor Controller but may generally comprise any suitable AC
controller or Curtis
AC controller.
[00206] Battery pack 106 is also connected to battery management system (BMS)
108 which
monitors each of the battery modules of battery pack 106 and provides
appropriate signals to
motor controller 102 to limit the amount of power allocated to drive motor
104, thereby
protecting the battery pack 106 from damage. According to a preferred
implementation, BMS
108 may comprise an Orion BMS-2 but may take various other forms as well.
[00207] Motor controller 102 may be in communication with the battery
management system
(BMS) 108 and/or additional devices connected through a shared communication
medium such
as, for example, CAN devices via a CANbus. Motor controller 102 is also
coupled to driver
controls 110 and to drive motor 104.
[00208] The conventional steering mechanism may provide steering capability
for vehicle
configuration 100. The operator may also use driver controls 110 to control
various functions
and/or modes or operation of vehicle configuration 100.
[00209] Motor controller 102 comprises a programmable computing device such as
a central
processing unit (CPU), application-specific integrated circuit (ASIC),
programmable logic
controller (PLC), field-programmable gate array (FPGA), digital signal
processor (DSP), system
on a chip (SoC), or another type of computing device. Motor controller 102 may
also comprise
power electronics that may be used to power the drive motor 104. Alternately,
the power
electronics may be provided in a separate power controller as is known in the
art. Motor
controller 102 may generally be configured control the operation of various
components coupled
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to motor controller 102 such as, for example, the CAN devices, battery pack
106 (via BMS 108),
and drive motor 104.
[00210] In vehicle configuration 100, drive motor 104 may comprise an electric
drive motor,
and may preferably comprise a three-phase AC induction motor or surface
permanent magnet
electric motor. Drive motor 104 may be drivingly connected via a fixed gear
reduction to a
conventional two-speed axle and a differential unit. The two-speed gear and
differential may
preferably comprise a driver-selectable high gear ratio and a driver-
selectable low gear ratio.
The fixed gear reduction may comprise a fixed ratio belt reduction. The output
shafts of the
differential are preferably connected via a fixed ratio chain drive to the
rear drive wheels of the
elective vehicle. It will also be appreciated that the two-speed gear and
differential may also
comprise a multiplicity of driver-selectable gear ratios.
[00211] Conventional service brakes are provided for the front wheels and the
rear wheels as
is known in the art. The service brakes are not shown in FIG. 1.
[00212] Vehicle configuration 100 may be powered by an energy storage system
with
sufficient energy and power capacity to propel a vehicle having vehicle
configuration 100. In a
preferred embodiment, the energy storage system may be a battery pack
comprising a number of
lithium ion battery modules arranged in series and parallel that may provide a
suitable voltage
for effective operation of motor controller 102 and drive motor 104.
[00213] According to various examples, motor controller 102 may control the
operation of
vehicle configuration 100 and more particularly drive motor 104 in response to
receiving control
signals, inputs, etc. (e.g. from driver controls 110, drive motor 102, BMS
108, and/or various
other components of vehicle configuration 100).
[00214] According to an implementation, motor controller 102 may control the
speed or
torque of drive motor 104 by applying energy from battery pack 106 to drive
motor 104. In
response to receiving the applied energy, drive motor 104 may, in turn, apply
force in the form
of torque to a selected gear, which causes the axle connected to the selected
gear and in turn a
chain drive to rotate, which causes the rear wheels of vehicle configuration
100 to rotate.
[00215] As mentioned above, motor controller 102 may generally control the
operation of
various components of vehicle configuration 100. FIG. 2 is conceptual diagram
of various
inputs and outputs that may be coupled to motor controller 102. According to
various
embodiments the motor controller illustrated in FIG. 2 may correspond to a
Curtis Motor
controller. However, motor controller 102 may take various other forms as
well.
[00216] As illustrated in FIG. 2, motor controller 102 may be coupled to
various switches,
denoted as "SW x," where x is some number, potentiometers, ("Pot's"), pedals,
etc. As
examples illustrated in FIG. 2, motor controller 102 may be coupled to an
accelerator pedal,
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brake pedal, low gear switch, forward and reverse gear switches, a downhill
neutral braking
mode switch, a maximum performance mode switch, maximum range switch, and a
"dead man
switch," as some examples. Motor controller 102 may also output various
signals, such as a
precharge signal, buzzer signal, auxiliary signal, etc.
[00217] Some or all of connections to motor controller 102 may comprise driver
controls 110.
More particularly, driver controls 110 may comprise a throttle pot wiper means
operative to
indicate the position of an accelerator pedal, which provides information to
the motor controller
102 regarding the amount of driving torque desired by the vehicle operator to
propel the vehicle.
[00218] The driver controls 110 connected to motor controller 102 may also
comprise brake
pot wiper means operative to indicate the position of a brake pedal that
provides information to
motor controller 102 regarding the amount of decelerating torque desired by
the vehicle
operator.
[00219] As will be understood by those normally skilled in the art, the brake
pedal may also
be mechanically connected to the service brakes of the vehicle so that
mechanical pressure on
the brake pedal will also provide hydraulic pressure to the service brakes
operative to decelerate
the vehicle.
[00220] The driver controls 110 also comprise an InLowGear SW 16 switch. If
the
InLowGearSwitch 5W16 is ON, Motor Controller is configured to determine that
the two-
speed gear is arranged for operation in the low gear. Similarly, if the
InLowGear 5W16 switch
is OFF, motor controller 102 is configured to determine that the two-speed
gear is arranged for
operation in the high gear.
[00221] Driver controls 110 may also comprise a Downhill 5W6 switch input
thereby
allowing the vehicle operator to implement a downhill control mode if the
Downhill SW _6
switch is in the ON position.
[00222] It will be apparent to one normally skilled in the art that the
various switch inputs
shown in 2 may be replaced by switches such as that provided Blink S.r.l. of
Milan, Italy. The
Blink device transmits the status of a number of switches to the Motor
Controller via CANbus.
Motor controller 102 may be coupled to various other inputs and outputs as
well.
[00223] FIG. 3 illustrates a second vehicle configuration 300. Vehicle
configuration 300 may
be generally similar to vehicle configuration 100 in that vehicle
configuration 300 may be an
electrical vehicle. However, vehicle configuration 300 may differ from vehicle
configuration
100 due to inclusion of two drive motors rather than the single drive motor
104 of vehicle
configuration 100. Vehicle configuration 300 may further differ from vehicle
configuration 100
of FIG. 1 in that the dual motors of vehicle configuration 300 drive not just
a single rear axle as
illustrated in FIG. 1, but two axles (a front axle and a rear axle).
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[00224] As mentioned with respect to FIG. 3, vehicle configuration 300 may
include two
motor controllers and two motors. Further, vehicle configuration 300 is a dual
axle drive vehicle
configuration rather than a single axle drive vehicle configuration. These
dual motor controllers
of FIG. 3 may generally be configured to control the operation of various
components of vehicle
configuration 300. Each motor controller of the dual motor controllers may be
configured in a
manner similar to motor controller 102 but each motor controller may control a
respective
motor.
[00225] In vehicle configuration 300, dual-in-line AC Motors, motor 1 and
motor 2, are
preferably drivingly connected via a fixed ratio belt drive to a hi low
transfer case. The high low
Transfer case preferably comprises a driver selected high gear ratio and
driver-selected low gear
ratio. The dual In-line AC motors, motor 1 and motor 2 may be identical in
mechanical and
electrical properties and are drivingly connected to rotate around a common
shaft.
[00226] The hi low transfer case is drivingly-connected to an input shaft of
an offset transfer
case. The offset transfer case is operable to rotate output shaft 1 and output
shaft 2 of the offset
transfer case thereby dividing the mechanical power coming to or from drive
motor 1 and drive
motor 2. Output shaft 1 in turn is drivingly-connected to a rear axle via a
rear differential and
thence to the final drives and wheels on the rear axle.
[00227] Similarly, output shaft 2 in turn is drivingly connected to the front
axle via the front
differential and thence to the wheels on the front axle.
[00228] The rear differential and the front differential may be equipped with
conventional
lock-up differential clutches as is done in conventional four-wheel drive
vehicles.
[00229] It is a feature of the present embodiment of the invention that the
first control method
described with reference to 1 for operation in the High Gear and the second
control method for
operation in the Low Gear described with reference to FIG. 1 are operable to
control
deceleration and downhill operation of the Dual Axle Drive of Fig. 3.
[00230] It will be apparent that the numerical values used to establish the
neutral braking
torque curves 700 and 800 of FIGS. 7 and 8 will be different for the AWD
vehicle configuration
of FIG. 3.
[00231] Turning now to FIG. 4, FIG. 4 illustrates is conceptual diagram of
various inputs and
outputs of the dual motor controllers of vehicle configuration 300. It should
be understood that
according to various embodiments the motor controllers illustrated in FIG. 4
may comprise
Curtis Motor controllers. However, the motor controllers of FIG. 4 may take
various other
forms as well.
[00232] The accelerator pedal and the brake pedal of the driver controls of
Fig. 4 may also be
electrically connected to the throttle pot and brake pot inputs of Curtis
Drive Controller 2 for
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purposes of redundancy. Alternately, the values of the throttle pot and brake
pot may be
transmitted to the drive controller 2 over the CANbus. Note that the CANbus is
not shown in
Fig. 4.
[00233] It is also noted that the On/Off status of all of the switches
connected to Curtis drive
controller 1 are transmitted to Curtis Drive Controller 2 via the CANbus. It
will be apparent
therefore that drive motor 1 and drive motor 2 may provide propulsion power to
all four drive
wheels.
[00234] FIG. 5 illustrates a third vehicle configuration 500. Vehicle
configuration 500 may be
generally similar to vehicle configuration 100 in that vehicle configuration
500 may be a single
axle-drive vehicle that include a motor controller. However, vehicle
configuration 500 may
differ from vehicle configuration 100 in that vehicle configuration 500 is a
hybrid-vehicle that
includes an engine, a generator and a generator controller and a drive motor
rather than solely an
electric drive motor as described with respect to vehicle configuration 100 of
FIG. 1.
[00235] Vehicle configuration 500 also comprises a range extender comprising a
thermal
engine, an electric generator and a generator controller. It is a feature of
the embodiment of
vehicle configuration 500 that the first control method described with
reference to 1 for
operation in the High Gear and the second control method for operation in the
Low Gear are
operable for controlling vehicle deceleration and downhill operation of
vehicle configuration
500.
A-2. Regenerative Braking Control
[00236] A first embodiment of this disclosure relates to regenerative braking
systems and
more particularly to controlling regenerative braking systems in various
contexts. According to
various implementations, the techniques of the present embodiment may be
applicable to various
vehicle configurations such as vehicle configurations 100, 300, and 500.
[00237] Such fully electric and hybrid-electric ("hybrid") vehicle
configurations 100, 300 and
500, utilize energy recovery systems are being employed for various
applications. Vehicles that
implement energy recovery systems may have several benefits as compared to
vehicles that lack
such energy recovery systems.
[00238] Vehicular energy recovery systems take various forms, one of which is
a regenerative
braking system, which may also take various forms. One form of a regenerative
braking system
utilizes a motor and motor controller that are configured to act as a
generator that converts
mechanical energy generated from the braking process to electrical energy
which may be stored
in various forms. In the context of vehicle configurations 100, 300, and 500,
the braking process
may store energy in a chemical form, such as in a battery pack.
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[00239] This embodiment is directed to solving problems related to optimizing
the behavior of
regenerative braking in various scenarios. More particularly, this embodiment
is directed to: (1)
determining amounts of torque to apply during a neutral braking mode; (2)
maintaining a desired
speed and thereby maintaining vehicle stability while performing regenerative
braking; (3)
allowing regenerative braking of a vehicle to occur without requiring a driver
of a vehicle to
depress the brake pedal; and (4) limiting use of service brakes in vehicles
undergoing
regenerative braking.
[00240] Referring back now to vehicle configuration 100, drive motor 104 is
equipped with a
regenerative braking system. Drive motor 104 may cause the regenerative
braking system to
apply regenerative braking torque, which may cause drive motor 104 to produce
a regenerative
braking current, which may in turn be supplied to battery pack 106 to
regenerate the charge
stored in battery pack 106.
[00241] Motor controller 102 may be in charge of various functions related to
the operation of
vehicle configuration 100 including functions related to regenerative braking.
At a high level,
motor controller 102 may comprise a configurable computing device that may be
configured to
(e.g., periodically) obtain inputs, execute a control loop and other functions
based on the
obtained inputs, and finally generate one or more outputs based on the output
of the executed
functions.
[00242] FIG. 6 illustrates, pseudocode 600 for an example control loop and a
subroutine 640
for controlling regenerative braking torque. At a high level, the control loop
is an outermost or
top-level loop that executes repeatedly, for instance approximately 250-250
times per second.
The example control loop of FIG. 6 may be written in VCL (vehicle control
language) that is
executable by a motor controller 102 such as, for example, a Curtis motor
controller such as
motor controller 102 according to a preferred implementation.
[00243] It should be noted that all of the CANbus communications, function
evaluations, map
computations, etc. are executed in the background and run continuously. All
functions that deal
with processing information sent over the CANbus from the BMS are handled in a
BMS Control module. This includes handling and processing of fault messages
and exception
states as well as dealing with other performance limits that may be imposed.
The BMS Control
module is also responsible for setting up the BMS Charge Current Limiting Map
as described
hereinabove with reference to Fig. 600.
[00244] At a high level, the main control loop calls three subroutines: (1) a
battery
management system control subroutine (BMS Control), (2) a vehicle control
subroutine
(VehicleControl T4), and (3) a drive current limit handling subroutine
(Handle Drive Current Limit), which is discussed in greater detail with
respect to FIG. 11.
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The main control loop 600 is but one example and may include more or fewer
function calls or
take various other forms as well.
[00245] The VehicleControl T4 subroutine handles functions that deal with
processing
information from the vehicle and driver controls 110. Among the functions
carried out in this
module deal with handling of the Curtis VCL Throttle and VCL Brake commands
that control
the actual torque provided or absorbed by drive motor, various safety
functions, forward and
reverse handling and other functions normally required to operate a vehicle
safely.
[00246] As part of executing the main control loop, motor controller 102 may
receive inputs
from, and may control various components and systems of a vehicle
configuration, such as
vehicle configuration 100, 300, 500, etc. As examples, motor controller 102
may be
communicatively coupled to control drive motor 104, battery pack 106, and
driver controls 110,
as some non-limiting examples.
[00247] This embodiment may apply to scenarios in which a vehicle is engaged
in a particular
mode, such as a neutral braking mode, and even more particularly a downhill
neutral braking
mode, as some examples. In the particular mode, motor controller 102 may be
configured to
automatically determine an amount of neutral braking torque to apply to slow
the vehicle to a
more or less constant speed. Also while in the engaged neutral braking mode,
motor controller
102 may be configured to perform the functions of optimizing the amount of
energy recaptured
during the process of regenerative braking and avoiding operation of the
service brakes during
the engaged mode. The process of applying a determined amount of regenerative
braking torque
and performing various other functions related to braking may take various
forms.
[00248] One such input that the motor controller may receive may indicate a
mode in which
the vehicle is engaged. For instance, the motor controller may receive a value
from a
component coupled to the motor controller indicating the vehicle is engaged in
a neutral braking
mode. After the motor controller determines that the vehicle is engaged in a
given neutral
braking mode, the motor controller may execute various subroutines associated
with the given
neutral braking mode.
[00249] More particularly, after determining that the vehicle is engaged in a
given neutral
braking mode, the motor controller may be configured to execute (e.g.,
periodically) the neutral
braking subroutine, which may comprise one or more subroutines, that are
dedicated to
managing the vehicle while in the neutral braking mode. For instance, while in
the neutral
braking mode, the neutral braking mode subroutine may cause the motor
controller to manage
various components of the vehicle, such as a drive motor, battery pack, etc.
[00250] At a high level, the one or more neutral braking subroutines may be
configured to
repeatedly (e.g., periodically) determine and apply an amount of regenerative
braking torque to
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apply to the drive motor 104 to generate a regenerative braking current. In
some
implementations, motor controller 102 may be configured to determine an amount
of torque to
apply to the motor 104 to cause the vehicle to maintain an approximately
constant speed and
such that the regenerative current supplied by drive motor 104 to battery pack
106 is maximized.
Motor controller 102 may determine an amount of torque to apply to drive motor
104 when the
vehicle is engaged in a regenerative braking mode in various manners.
[00251] In a particular implementation, motor controller 102 may be configured
to access a set
of neutral braking torque curves and use the curves to determine and apply
regenerative braking
torque to drive motor 104 when the vehicle is engaged in a neutral
regenerative braking mode,
such as a downhill neutral braking mode. A neutral braking mode occurs when a
vehicle
undergoes neutral braking. Neutral braking occurs when the vehicle is moving
and the throttle
(e.g., the accelerator pedal) is reduced towards the neutral position. In a
more particular case of
neutral braking, such as the downhill neutral braking mode, the vehicle is
both moving downhill
and is undergoing neutral braking.
[00252] The neutral braking torque curves of the neutral braking mode may have
been
predefined or may be determined and defined dynamically by motor controller
102. Each curve
(also be referred to as a "map") may consist of a set of points, and each
given point of the curve
may specify an amount (e.g., a percentage) of regenerative braking torque to
apply to drive
motor 104 based on a parameter of the vehicle, such as the vehicle's speed, a
rotational velocity
of drive motor 104, etc. The conditions associated with selecting a given
neutral braking torque
curve and with determining the amount of torque to apply to the drive motor
may take various
forms.
[00253] In one implementation, motor controller 102 may select a regenerative
torque curve
based on a gear in which the vehicle is engaged. For example, motor controller
102 may select a
first regenerative torque curve if the vehicle is in a first gear (e.g., a
high gear) and may select a
second regenerative torque curve if the vehicle is engaged in a second,
different gear (e.g., a
lower gear relative to the first gear).
[00254] According to another implementation, motor controller 102 may be
configured to
select a neutral braking torque curve depending on a mode in which the vehicle
is engaged. For
example, motor controller 102 may be configured to select a first neutral
braking curve if the
vehicle is engaged in a downhill neutral braking mode, a second neutral
braking mode if the
vehicle is engaged in a different mode, such as a maximum range mode or a
maximum
performance mode. A vehicle may be equipped with other driving modes and may
be
configured to select regenerative torque curves in various other manners as
well.
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[00255] Motor controller 102 may be configured to determine that the vehicle
is engaged in a
neutral braking mode based on a signal received from a component coupled to
motor controller
102. As an example, driver controls 110 that may comprise switches, pedals,
knobs, etc. The
driver may activate a control such as a switch to engage the neutral braking
mode. The neutral
braking mode may be activated in various other manners as well.
[00256] Motor controller 102 may be configured to determine an amount of
neutral braking
torque to apply to the drive motor of the vehicle based on a variety of
factors. Such factors may
include a speed of the vehicle, a rotational velocity of a drive motor, or
various other factors.
[00257] FIG. 6 also includes an example of code 640. The example code 640
comprises a
subroutine of the one or more neutral braking subroutines that may be executed
by motor
controller 102. More particularly, code 640 is a neutral braking torque
handling subroutine that
handles some of the functions of determining and applying neutral braking
torque to drive motor
104. At high level, the neutral brake torque handling subroutine determines
whether the vehicle
is engaged in a high gear or a low gear, and whether the vehicle is engaged in
a downhill neutral
braking mode.
[00258] A Curtis variable, EnableDownhill Strategy, may be set if it becomes
necessary to
cancel operation of the mode. If EnableDownHillStrategy is OFF, a value of 5%
is assigned to
the My Neutral Braking TrqM, which specifies the maximum amount of
regenerative braking
torque that motor controller 102 should supply to drive motor 104. Specifying
a low value such
as 5% regenerative braking torque substantially prevents any charging current
from entering the
battery and the vehicle can only be stopped through application of the
vehicle's service brakes.
[00259] If the vehicle has the high gear engaged and the downhill neutral
braking mode is
engaged (as indicated by switch 16 being off and switch 6 being on,
respectively), then motor
controller 102 determines and applies regenerative braking torque for the
downhill neutral
braking mode in the high gear based on a neutral braking torque curve for the
high gear in the
downhill neutral braking mode. If the vehicle has the low gear engaged and the
downhill neutral
braking mode is engaged (as indicated by switch 16 being on and switch 6 being
on,
respectively), then the motor controller determines neutral braking torque for
the downhill
neutral braking mode in the low gear based on a neutral braking torque curve
for the low gear.
[00260] According to some other implementations, motor controller 102 may
select a given
neutral braking torque curve based on a type of the vehicle, which motor
controller 102 may be
programmed to determine or may determine dynamically (e.g., at run-time).
Motor controller
102 may select a neutral braking torque curve in various other manners as
well.
[00261] Referring back to pseudocode 640, after determining that the vehicle
is engaged in a
particular mode and determining an engaged gear of the vehicle, the neutral
braking torque
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handling subroutine executed by motor controller 102 may determine and apply
amount of
regenerative braking to drive motor 104. In turn, applying the determined
amount of
regenerative torque to drive motor 104, results in a regenerative current
being generated by drive
motor 104.
[00262] After selecting a regenerative torque curve, motor controller 102 may
use the selected
neutral braking torque curve to determine an amount of regenerative braking
torque to apply to
the drive motor. According to an implementation, motor controller 102 may
determine the
amount of regenerative braking torque to apply to drive motor 104 based on the
selected neutral
braking torque curve by using the selected neutral braking torque curve to map
an input value to
the curve to determine an output amount of regenerative braking torque as that
is specified by
the selected neutral braking torque curve.
[00263] According to an implementation, the input to the input to the neutral
braking torque
curve may be a rotational velocity, such as a number of RPMs or the speed of
the vehicle, which
may be expressed in terms of kilometers or miles per hour, as some examples.
The output of the
neutral braking torque curve may be expressed in terms of a percentage of
regenerative braking
torque to apply to the drive motor or in various other manners as well.
[00264] To map an input value to an output value based on the selected neutral
braking torque
curve, the neutral braking torque handling subroutine may utilize one or more
mapping
functions. Such a mapping function may perform the task of mapping input value
such as a
rotational velocity to the selected curve and generating an output in the form
an amount of
regenerative braking torque based on the selected neutral braking torque
curve. In some
examples, the amount of regenerative braking torque that drive motor 104 may
apply may be
expressed as a percentage of a maximum amount of regenerative braking torque
that the drive
motor may apply. The amount of regenerative braking torque may be expressed in
various other
forms as well.
[00265] Turning now to FIG. 7, a neutral braking torque curve and
corresponding functions
and definitions related to the torque curve are illustrated. FIG. 7 includes a
neutral braking
torque curve 700, code blocks 720 and 740 for defining neutral braking torque
curve 700 and
includes a listing 760 of inputs corresponding outputs used to define neutral
braking torque
curve 700.
[00266] At a high level, neutral braking torque curve 700 comprises a series
of points. The x-
axis value of each point on neutral braking torque curve 700 corresponds to a
rotational velocity
of drive motor 104. Each input rotational velocity that neutral braking torque
curve 700 is a
variable beginning with the prefix "P User3x," where "x" is some number. Each
of the
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"P User" variables are stored may be stored non-volatile memory such that
their values persist
even when motor controller 102 is not powered.
[00267] The y-axis value of each point on neutral braking torque curve 700 is
an amount of
regenerative braking torque that is determined based on the "P User13x,"
variables, where "x"
is some number, that define neutral braking torque curve 700. Each of these "P
User" variables
stored in non-volatile memory that may be set by a programmer offline (i.e.,
while motor
controller 102 is not executing) using a programming tool as described in
greater detail herein
with respect to programming interface 760.
[00268] In some examples, the output amount of regenerative braking torque
that drive motor
104 may apply based on neutral braking torque curve 700 may be expressed as a
percentage of a
maximum amount of regenerative braking torque that motor controller 102 may
apply to drive
motor 104. The amount of regenerative braking torque may be expressed in
various other forms
as well.
[00269] Turning now to code block 720, code block 720 may be executed once
during
initialization of motor controller 102 to convert speed values to RPM values
that may be used to
define neutral braking torque curve 700. At a high level, each line of code
block 720 takes a
speed variable stored in a variable (in this case 10, 20, 30, and 40 kilometer
per hour
respectively) and converts the speed of a given the variable into an RPM value
based on the
constant Speed to RPM (equal to 66), which may be predefined by motor
controller 102 and in
particular a Curtis motor controller.
[00270] More particularly, each line of code block 720 inputs a speed in
kilometer per hour
stored in a given P Userx variable, multiplies the speed in kilometers per
hour by the
Speed to RPM constant (equal to 66 in FIG. 7), and then divides the result by
10, all of which
is accomplished using a multiply and divide function, which in turn multiplies
two inputs to the
function and divides the resulting product by the third input to the function.
[00271] According to the illustrated implementation in FIG. 7, the VCL Get
Muldiv function
may comprise such a multiply and divide function that motor controller 102 may
use to perform
the multiplication and division operations. According to the example of FIG.
7, the output
values of these multiply and divide operations take the form of variables
named AutoUser3x,
where xis some number. Each AutoUser3x variable represents a number of RPMs of
drive
motor 104 that corresponds to the speed stored in a given P User3x variable.
For instance, the
value of the AutoUser3x variable represents the number of RPMs of drive motor
104 that
corresponds to the speed in kilometers per hour stored in the P User34
variable. It should be
understood that other functions or code, which may be expressed in other
programming
languages may produce a similar result.
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[00272] More particularly, motor controller 102 may execute code block 720 to
convert the
speed of drive motor 104 into RPMs thereby avoiding having to determine RPM
values that
correspond to vehicle speeds during execution of the main control loop. After
determining the
RPMs corresponding to a set of vehicle speeds, the programmer may then use the
RPMs in
conjunction with functions of code block 740 to define neutral braking torque
curve 700.
[00273] Once RPM values corresponding to respective vehicle speeds have been
determined,
for instance using code block 720, code block 740 may be used to create a map
that conforms to
neutral braking torque curve 700.
[00274] At a high level, code block 740 takes a set of input values and maps
them to a set of
output values. In the example of FIG. 7, the input values are each RPM values
contained in the
AutoUser3x variables, and the corresponding output values are amounts of
regenerative braking
torque stored in the P User13x variables.
[00275] The implementation illustrated with respect to code block 740 uses a
Setup MAP
function provided by a VCL library to create the mapping between the input and
output values.
However, any function in any programming language may be used to construct
such a mapping
between vehicle speed (in this instance RPM) and an amount regenerative
braking torque.
[00276] After defining map, code block 740 finally automates the indexing into
the map by
calling the VCL Automate MAP function, which periodically, and separately from
the main
control loop, inputs the built-in motor controller 102 variable (Motor RPM)
value as an index
into the curve to determine an amount of neutral braking torque to apply to
the drive motor. The
Automate MAP function continuously and in the background: (1) takes the RPM
value stored in
the variable Motor RPM as input, (2) determines the two closest points on the
curve to the
Motor RPM value, (3) interpolates between the two closest points, and (4)
outputs the
interpolated value two closest points as an amount of torque, which is stored
in the
Donwhill Regen Map6 Output variable While the Automate MAP function is used in
the
example of code block 740, other functions in other languages could be used to
accomplish a
similar purpose.
[00277] As an example, at a given point in time, the input rotational velocity
stored in the
variable Motor RPM may be 15 kph, which may correspond to 99 rpm, and which
falls halfway
between points P User134 and P User135. In such a case, Automate MAP map
function first
determines the two closest points, to the 99rpm value, which in this case are
P User134, which
corresponds to 90% regenerative braking torque, and P User135, which
corresponds to 100%
regenerative braking torque. The Automate MAP function then linearly
interpolate between the
two closest points: (1) P User134, which corresponds to 90% regenerative
braking torque, and
(2) P User135, which corresponds to 100% regenerative braking torque, to
arrive at a final
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output value of 95% regenerative braking torque that should be applied to
drive motor 104,
which is stored in the Downhill Regen Map6 Output variable. It should be
understood that
motor controller 102 may be configured to determine output values that fall
within two points
used that are used to define a neutral braking torque curve in various other
manner as well.
[00278] Motor controller 102 may generally execute code blocks 720 and 740
once, as part of
the startup routine of motor controller 102 that occurs before the main
control loop begins
executing. However, the Automate MAP function continues to occur continuously
and in the
background (e.g., in parallel with the main control loop) once it is called.
By executing code
blocks 720 and 740 only once at startup and not during the main control loop,
motor controller
102 avoids the overhead of repeatedly defining neutral braking torque curve
700 during each
main control loop iteration. Avoiding repeated definition of the neutral
braking torque curve in
turn reduces execution time of each main control loop, which improves the
execution
performance of the main control loop.
[00279] FIG. 7 also includes a conceptual diagram 760 of a programming
interface that a
programmer may use to set the values of variables, such as the P User13x
variables of motor
that are used to define amounts of regenerative braking torque, and P User3x
variables that
define a speed of the vehicle.
[00280] To summarize, conceptual diagram 760 of the programming interface
specifies that
the neutral braking torque curve 700 only applies if the downhill neutral
braking mode is
engaged and the vehicle is engaged in its high gear. For the downhill neutral
braking mode,
from 0 km/h to 10km/h non-inclusive, 90% regenerative braking torque is to be
applied; from
10km/h to 20km/h (non-inclusive), 90% regenerative braking torque that is to
be applied; from
30km/h to 50km/h (non-inclusive), 70% regenerative braking torque that is to
be applied, and
from 50 km/h and above, 40% regenerative braking torque that is to be applied.
[00281] Conceptual diagram 760 further specifies that each of the P User3x
variables store
each x-axis point that defines neutral braking torque curve 700 and that the P
User13x variables
store each of the y-axis regenerative torque values that define neutral
braking torque curve 700.
[00282] It further should be understood that the points that define the ranges
of neutral braking
torque curve 700 may have been determined using trial and error methods based
on a particular
vehicle on which the neutral braking mode is implemented. It should also
further be understood
that applying neutral braking torque curve 700 may result in the vehicle
maintaining
approximately constant speed during operation on a downgrade, assuming there
is no wheel
slippage.
[00283] Turning now to FIG. 8, a neutral braking torque curve and
corresponding functions
and definitions related to the torque curve are illustrated. FIG. 8
illustrates a neutral braking
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torque curve 800 and includes a conceptual diagram 860 of an interface for
programming
variables used to define neutral braking torque curve 800.
[00284] At a high level, neutral braking torque curve 820 comprises a series
of points that
each correspond to an amount of regenerative braking torque to apply to drive
motor 104 while
the vehicle is engaged in a low gear and in a downhill neutral braking mode
while undergoing
neutral braking.
[00285] In the example of FIG. 8, the input to the neutral braking torque
curve 800 is a
rotational velocity of drive motor 104 expressed as the variable Motor RPM,
which may be
expressed in RPMs or various other forms. The output of neutral braking curve
800 is an
amount of regenerative braking torque that is stored in the Downhill Regen
Map7 Output
variable.
[00286] Neutral braking torque curve 800 is defined by a series of input
points and output
points. The input points of neutral braking curve 800 are stored in the
variables P User5x,
where x is some number and which represent RPM values. The output values of
neutral braking
torque curve 800 are defined by variables "P User14x," where "x" is some
number that
represent regenerative braking torque values.
[00287] In some examples, the amount of regenerative braking torque that motor
controller
102 may cause drive motor 104 to apply may be expressed as a percentage of a
maximum
amount of regenerative braking torque that motor controller 102 can apply to
drive motor 104.
The amount of regenerative braking torque may be expressed in various other
forms as well.
[00288] In general, a programmer may define a neutral braking torque curve
such as neutral
braking torque curve 800 using VCL code similar to code blocks 720 and 740
described with
respect to FIG. 7 with some small changes. Generally, the VCL code used to
define neutral
braking torque curve 800 may use a different constant, Speed to RPM Lo (equal
to 160.2) in
the example of FIG. 8, instead of Speed to RPM (equal to 66), to convert the
vehicle's speed to
RPMs but may otherwise be similar with the exception of using differently-
named variables
(e.g., using P User143 instead of P User133) and using P User50 instead of P
User30, etc.)
[00289] Finally, FIG. 8 also includes a conceptual diagram 860 of a
programming interface for
motor controller 102 that allows a programmer to set the values of the input
variables and
corresponding output variables used to define neutral braking torque curve
800. To summarize
the conceptual diagram 860 of the programming interface, neutral braking
torque curve 800 only
applies if the downhill neutral braking mode is engaged and the vehicle is
engaged in its low
gear.
[00290] For the downhill neutral braking mode, from 0 km/h to 5km/h (non-
inclusive), motor
controller 102 is configured to apply 50% regenerative braking torque to drive
motor 104. From
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5km/h to 10km/h (non-inclusive), motor controller 102 is configured to apply
60% regenerative
braking torque to drive motor 104. From 10km/h to 15km/h (non-inclusive),
motor controller
102 configured to apply 55% regenerative braking torque to drive motor 104.
From 15km/h to
20km/h (non-inclusive), motor controller 102 is configured to apply 30%
regenerative braking
torque to drive motor 104, and from 20 km/h and above, motor controller 102 is
configured to
apply 20% regenerative braking torque to drive motor 104. Conceptual diagram
860 further
specifies that each of the P User5x variables store each x-axis point that
defines neutral braking
torque curve 800 and that the P User14x variables store each of the y-axis
regenerative torque
values that define neutral braking torque curve 800.
[00291] While FIGS. 7 and 8 illustrate respective neutral braking torque
curves that output an
amount of regenerative torque that motor controller 102 may apply to a drive
motor such as
drive motor 104 based on an input RPM, it should be understood that such
neutral braking
torque curves may take various other forms, which may include different range
bounds and
different amounts of torque to be applied.
[00292] After determining the amount of regenerative torque to apply to drive
motor 104,
motor controller 102 may apply the determined amount of regenerative braking
torque to drive
motor 104. Motor controller 102 may apply the determined amount of
regenerative braking
torque in various manners.
[00293] According to an implementation, to apply neutral braking torque, motor
controller
102 may execute a braking command, such as the Curtis Brake Command, which
controls
regenerative braking of drive motor 104 by controlling the phase voltage and
phase current
generated by motor controller 102 and thereby the phase current generated by
drive motor 104.
As a more particular example, the Brake Command may generate the determined
amount of
phase current such that phase difference between the phase voltage and the
phase current
generates a phase current equal to Drive Current Limit * Neutral Braking TrqM.
As an
example, if the value of Drive Current Limit * Neutral Braking TrqM is 50%,
motor
controller 102 will absorb 50% of the maximum rating of the controller.
[00294] As a result of motor controller 102 applying the determined amount of
phase current
and phase voltage, a regenerative braking current is generated by drive motor
104. A drive
current limit handling subroutine (such as the Handle Drive Current Limit
subroutine
illustrated in FIG. 10) may cause motor controller 102 to in turn supply the
regenerative braking
current to battery pack 106 of the vehicle. The functions involving motor
controller 102
supplying the regenerative braking current to battery pack 106.
[00295] At a high level, the drive current limit handling subroutine may cause
motor controller
102 to supply the regenerative braking current to battery pack 106 based on an
amount of charge
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that battery pack 106 can accept. Battery management system 108, which may be
in
communication with the motor controller 102 and battery pack 106 via a
suitable
communications protocol, such as a CANbus, may provide various data to motor
controller 102
related to the operation of battery pack 106, which may include an amount of
charge that battery
pack 106 can accept at a given time. The amount of charge that battery pack
106 can accept at a
given time is but one example of data that BMS 108 may provide to motor
controller 102. BMS
108 may provide other data related to the operation of the battery pack 106
and to the motor
controller 102 as is well known by those normally skilled in the art.
[00296] As described in the above-mentioned Curtis manual incorporated by
reference, the
value of the Regen Control Limit variable determines the maximum value of the
RMS
regenerative current that motor controller 102 can absorb from the drive motor
104. As will be
understood by those normally skilled in the art, the regenerative torque
applied to the output
shaft of the drive motor 104 depends on the motor magnetic characteristics,
motor speed, motor
efficiency and the phase difference between a phase voltage and a phase
current that is actually
applied by motor controller 102. The actual values of the phase current and
phase voltage are
calculated by motor controller 102 to optimize motor performance over the
entire motor
operating range.
[00297] During regeneration, the regenerative torque is in the direction
opposite to that of the
rotational direction of drive motor 104. Consequently, during regeneration,
drive motor 104
operates as a generator thereby absorbing kinetic energy from the vehicle and
causing the
vehicle to decelerate. If the vehicle is on a downgrade the regenerative
torque may be operable
to maintain the vehicle speed at a substantially constant value.
[00298] By way of example, if the value of the variable Regen Current Limit is
100%, and a
Curtis controller, such as, for example, the Curtis 1238E-76 controller is
used, the maximum
RMS phase current that motor controller 102 can absorb is approximately 650
amperes, which
represents the rated short-term RMS current motor controller 102 can provide
or absorb to or
from drive motor 104. Similarly, if the value of Regen Current Limit is 75%,
the controller
will absorb about 487 Amps phase current, thereby reducing the regenerative
torque by three
quarters.
[00299] Further as described in the above-mentioned Curtis manual, the value
assigned to the
Neutral Braking TrqM variable may further reduce the regenerative torque that
motor
controller 102 applies to drive motor 104 when the accelerator pedal is
reduced toward the
neutral position. Thus, if the vehicle is moving forward, and the vehicle
operator removes his
foot from the accelerator pedal, the vehicle enters the neutral braking mode
and the RMS
regenerative current will be reduced to Regen Current Limit * Neutral Braking
TrqM.
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[00300] Turning now to FIG. 9, a graph 900 illustrates a relationship between
a DC current
that battery pack 106 can accept (denoted as OrionPackCCL) at any given time,
and a variable,
BMS Regen Current Limit, that represents a maximum percentage of RMS current
that may be
generated by drive motor 104 during regeneration.
[00301] According to an implementation, BMS 108 continuously calculates a
value for
OrionPackCCL in amperes, which represents the maximum DC current battery pack
106 can
accept at any given time. The numerical value for OrionPackCCL is transmitted
to motor
controller 102 over the CANbus. In some implementations, the. BMS Regen
Current Limit
variable may comprise a Curtis variable to which a programmer may assign a
value. After the
BMS Regen Current Limit Curtis variable is assigned a value, motor controller
102 may
automatically limit any RMS current during regeneration to the percentage
specified by
BMS Regen Limit Current.
[00302] In general, the BMS Regen Current Limt variable may be based on the
value of the
OrionPackCCL variable. According to the exemplary values shown in Fig. 9, when
the value of
OrionPackCCL is 400 amperes or higher, the value of BMS Regen Current Limit
may be fixed
to the value of 75% of the rated short-term RMS current limit of motor
controller 102, thereby
limiting the maximum DC regenerative current supplied to battery pack 106
during regeneration
to 75% of the rated short-term RMS current. Limiting the maximum DC
regenerative current
that may be supplied to battery pack 106 may prevent supplying extremely high
regenerative
currents to battery pack 106 and may thereby avoid damaging battery pack 106.
[00303] At lower values of OrionPackCCL, which may occur for example if
battery pack 106
is in a high state of charge, the value of BMS Regen Current Limit will
decrease, thereby
reducing the chance of overcharging the battery pack 106. In an
implementation, if battery pack
106 is close to a full charge, the OrionPackCCL variable will decrease towards
zero and the
value assigned to BMS Regen Current Limit will be reduced to 5% of the rated
short-term
RMS current, thereby protecting battery pack 106 from receiving any
substantial current. It will
be apparent to one normally skilled in the art that these predefined values
may be adjusted to
conform to the capacity of battery pack 106.
[00304] The techniques referenced with respect to Fig. 9 for limiting the
maximum RMS
current during regen is well known to users of Curtis motor controllers and
may be implemented
by using a VCL Map function which may be setup to run in the background and
continuously
provide a value for BMS Regen Current Limit as the values of OrionPackCCL
changes.
[00305] Referring now to graph 900 of FIG. 9, while the charge level of
battery pack 106 is
higher, (represent as being near the origin on the x-axis), the BMS REGEN
CURRENT LIMIT
and OrionPackCCL variables have lower values. When the maximum amount of DC
current
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acceptable by battery pack 106 represented by the OrionPackCCL variable is at
or near zero,
BMS Regen Current Limit may be equal to 5%. The BMS Regen Current Limit may be
set
to a relatively low percentage, such as 5%, to protect battery pack 106 from
receiving substantial
amounts of current.
[00306] As the battery pack has less charge (i.e. moving to the right along
the x-axis of graph
900), and OrionPackCCL indicates that battery pack 106 can accept more
current,
BMS Regen Current Limit increases up until the point at which battery pack 106
can accept
400 amps of regenerative current, at which point BMS Regen Current Limit
reaches a
maximum of 75% of the rated short-term RMS regenerative current of motor
controller 102.
[00307] As another potential implementation relating to limiting regenerative
current supplied
to battery pack 106, the drive current limit handling subroutine executed by
motor controller 102
may compare the amount of regenerative current battery pack 106 can accept
with the amount of
regenerative current produced by the neutral braking torque that motor
controller 102 may apply
to drive motor 104. If motor controller 102 determines that the amount of
regenerative braking
current is less than or equal to the amount of regenerative current battery
pack 106 can accept,
the drive current limit handling subroutine may cause motor controller 102 to
supply the
regenerative current to battery pack 106 by converting the regenerative
current, which is an
alternating (AC) current, to a direct current (DC) form and then supplying the
converted DC
current to regenerate the charge level of battery pack 106.
[00308] Alternatively, if motor controller 102 determines that the amount of
regenerative
braking current exceeds the current the battery pack 106 can accept, the drive
current limit
handling subroutine may cause drive motor 104 to reduce the amount of
regenerative current
supplied to the battery pack 106 regenerate the charge level of battery pack
106. Motor
controller 102 may reduce the amount of regenerative current supplied to
battery pack 106 in
various manners. For instance, the motor controller may reduce an amount of
regenerative
current supplied to battery pack 106 by reducing an amount of root mean
squared (RMS) AC
current allowed during regeneration, thereby reducing the amount of DC
regenerative current
supplied to the battery pack 106. The motor controller 102 may reduce the
amount of
regenerative current supplied to battery pack 106 in various other manners as
well.
[00309] Turning now to FIG. 10, an example code block 1000 of a drive current
limit handling
subroutine is illustrated.
[00310] At a high level, the example code block of FIG. 10 is a drive current
limit handling
subroutine "Handle Drive Current Limit," which is executed by the main control
loop 600 that
was described with respect to FIG. 6.
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[00311] To begin, at line 2 of the Handle Drive Current Limit subroutine first
determines the
RMS regenerative current limit from BMS 108 as described with respect to FIG.
10 and assigns
the determined RMS regenerative current limit to the Regen Current Limit
variable, which is a
Curtis variable that causes motor controller 102 to generate the specified
percentage amount of
maximum RMS regenerative current.
[00312] After assigning the value of Regen Current Limit, the Handle Drive
Current Limit
subroutine sets the Brake Current Limit variable, which sets the maximum
amount of RMS
current during a braking command (i.e. when the brake pedal is depressed)
equal to the
Regen Current limit variable. Finally, the Handle Drive Current Limit
subroutine sets the
Curtis variable Neutral Braking TrqM, which determines an amount of
regenerative braking
torque from a neutral braking curve as described with respect to FIGS. 7 and 8
and causes motor
controller 102 to apply the percentage of maximum regenerative braking torque
determined
from the neutral braking torque curve to drive motor 104.
[00313] Finally, after applying the specified amount of regenerative braking
torque, the
subroutine of code block 1000 calls a return statement, which causes motor
controller 102 to exit
the subroutine.
[00314] Turning now to FIGS. 11A-11B and FIGS. 12A-12E, a first graph 1110, a
second
graph 1120, a third graph 1230, a fourth graph 1240, and a fifth graph 1250
are illustrated. First
graph 1100 illustrates the application of neutral braking torque resulting
using a given neutral
braking torque curve as described above. The data in FIGS. 11A-11B and 12A-12E
represent a
single deceleration event from a relatively high vehicle speed, as shown in
Point 1 of graph
1230.
[00315] Turning to graph 1110 of FIG. 11A, during the deceleration event, a
peak amount of
100% neutral braking torque is reached at 83.6 seconds when the vehicle has a
speed of
approximately 20 km/hr as shown in point 4 of graph 1110. Graph 1110 also
illustrates that the
Regen Current Limit corresponds to roughly 75% of maximum regenerative braking
torque,
which is constant throughout the deceleration event.
[00316] Turning now to second graph 1120, second graph 1120 illustrates the
RMS current
resulting from applying the Neutral Braking Torque of 100% illustrated at
Point 4 in first graph
1100 and the corresponding battery pack current (referred to in second graph
1120 as "Orion
Pack Current") that is supplied to battery pack 106 by motor controller 102.
[00317] Turning now to graph 1230 of FIG. 12A, graph 1230 illustrates the
motor RPM of a
vehicle during the deceleration event. The vehicle's motor RPMs decrease over
time as a result
of the application of regenerative braking torque to drive motor 104.
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[00318] Turning now to graph 1240 of FIG. 12B, graph 1240 illustrates the
transition between
releasing a throttle command (which ends at point 1) and engaging the neutral
braking mode
(which begins at point 2). More particularly, at about t = 72 sec
(corresponding to Point 2), the
throttle command is reduced to the neutral position of zero percent as the
vehicle operator
removes all pressure from the accelerator pedal. At or after Point 2, all of
the conditions are now
satisfied for beginning neutral braking.
[00319] Turning now to graph 1250 of FIG. 12C, graph 1250 illustrates
application of service
brakes, which occurs at point 5 when the vehicle has reached substantially
zero speed and at
which point the driver has activated the brake pedal. It should be noted that
the brake command
is zero during the entire deceleration process until the vehicle reaches zero
speed at Point 5.
[00320] There are a number of notable occurrences illustrated in graphs 1110,
1120, 1230,
1240, and 1250. For instance, in graph 1120, it should be noted that while a
peak RMS current
of 445 amps is reached at 83.6 seconds as a result of applying the peak value
of 100% neutral
braking torque, the Orion Pack Current illustrated in graph 1120 decreases at
this time due in
part to the application of the Regen Current Limit and also due to the
decreasing speed of the
vehicle, which in turn results in a lower efficiency of conversion of the RMS
current to the
Orion Pack Current. Additionally, as vehicle speed decreases so too does the
voltage produced
by drive motor 104. This lower voltage is converted to a higher voltage that
is acceptable by
batter pack 106, and the conversion from lower to higher voltage further
reduces the amount of
DC current supplied to battery pack 106.
[00321] It will be also be appreciated by one normally skilled in vehicle
mechanics that the
deceleration profile of the Motor RPM of FIGS. 11A¨B and 12A¨C is generated by
inertia of
the vehicle and the rotational inertia of the drive line components. The
particular shape of the
Motor RPM profile depends on friction losses and inefficiencies of all drive
line components
and the torque absorbed by drive motor 104. It will also be apparent that the
torque absorbed by
the drive motor may also be used to maintain a substantially constant vehicle
speed on
downgrades.
[00322] FIGS. 11A¨B and 12A-12C are illustrative of but one example of a
deceleration
event that involves regenerative braking. It should be understood that the
various currents,
speeds, braking torques, etc., involved in neutral braking in accordance with
this disclosure may
take various other forms as well.
[00323] Turning now to FIG. 13, a flowchart illustrating a method 1300
corresponding to the
regenerative braking embodiment is illustrated.
[00324] The method of FIG. 13 begins as block 1302 at which point motor
controller 102 may
determine that a vehicle is engaged in a neutral braking mode.
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[00325] At block 1304, after determining that the vehicle is engaged in a
neutral braking
mode, motor controller 102 may select a neutral braking torque curve.
[00326] At block 1306, motor controller 102 may determine a rotational
velocity of the drive
motor, such as drive motor 104.
[00327] At block 1308, motor controller 102 may, based on the determined
rotational velocity,
determine an amount of regenerative braking torque to apply to drive motor 104
based on the
selected neutral braking torque curve.
[00328] At block 1310, motor controller may apply the determined amount of
regenerative
braking torque to drive motor 104, wherein applying the determined amount of
regenerative
braking torque to the drive motor results in a regenerative current generated
by drive motor 104.
[00329] At block 1312, motor controller 102 may supply the regenerative
current to a battery
pack (e.g., battery pack 106) of the vehicle to at least partially recharge
the battery pack.
[00330] According to some examples, motor controller 102 may apply the
determined amount
of regenerative braking torque to drive motor 104 and may supply the
regenerative current to the
battery pack by setting the values of variables that cause motor controller
102, and/or drive
motor 104 to perform the functions described with respect to method 1300, such
as the functions
of blocks 1310, 1312, etc.
[00331] As an example, to apply the determined regenerative braking torque to
drive motor
104, motor controller 102 may set the value of the Neutral Braking TrqM
variable equal to the
determined amount of regenerative braking torque. As another example, motor
controller 102
may update the Regen Current Limit variable and the BMS Regen Current Limit
variable.
[00332] It may generally be understood that motor controller 102 may execute
method 1300
repeatedly for instance in a loop. It should further be understood that method
1300 may include
more or fewer blocks, which may occur in orders other than those specified
with respect to FIG.
13.
[00333] Various implementations and examples associated with the present
embodiment
related to regenerative braking have been described. However, it should be
understood that the
present embodiment may take various other forms as well.
1. Traction Control of Dual Motor All-Wheel Drive Electric Vehicles
[00334] A second embodiment is related to traction control of dual motor, all-
wheel drive
electric vehicles. The traction control system of the present embodiment is
intended for dual
motor all-wheel drive off-road electric drive vehicles and improves traction
at low speeds under
difficult road conditions of high grades and unfavorable terrain. According to
various
implementations, the traction control system may be used in battery-only
vehicles and hybrid
electric vehicles.
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[00335] An exemplary powertrain of a dual motor all-wheel drive electric
vehicle is shown in
block-diagram form FIG. 14, which shows the electrical connections and driver
controls for the
front controller and rear controller of the dual motor all-wheel drive
electric vehicle of the
present invention.
[00336] The traction control embodiment may present various advantages.
Examples of some
such advantages may include: (1) maximizing traction between front and rear
axles on
conditions of high grade and poor terrain, (2) minimizing spin and energy loss
of spinning
wheels, (3) automatically adjusting for forward and reverse drive on uphill
grades, (4)
preventing of digging-in of spinning wheels on loose sand or snow, (5)
allowing untrained
drivers to maneuver effectively over the most difficult terrain, (6) providing
driver-selectable
means to cancel the traction control, (7) providing a controllable
differential, (8)providing a
minimum speed for activation of traction control, and (9) utilizing a
comparison between
Front RMS Current and Rear RMS Current to detect cases when one wheel of the
vehicle is in
the air. The traction control embodiment may provide various other advantages
as well. The
traction control embodiment will now be described in greater detail.
[00337] At a high level, the traction control embodiment may be relevant to a
4-wheel electric
drive vehicle implementation, comprising a front drive motor and a rear drive
motor, a front
controller and rear controller. In one implementation, the front drive motor
is connected via a
fixed ratio gear to a differential for driving the front axle. The rear drive
motor drives are
connected via a fixed ratio belt and a 2-speed gear and differential box. The
differential box
drives a left trailing arm and a right trailing arm via the axle, and each of
the trailing arms is a
construction including a chain for driving the rotation of the wheel based on
the rotation of the
axle. The trailing arm itself is a movable and pivotable well-known
construction in the
mechanical art. The trailing arm suspension is a known construction and
provides the electric
vehicle with a very large travel of the rear wheels with respect to the body,
with respect to the
frame, and this travel is useful in off-road conditions and gives the vehicle
tremendous
maneuverability.
[00338] The system according to this traction control system embodiment also
includes a
battery compartment and battery management system, the battery compartment
delivers the
electric power for the drive motors. The front controller and the rear
controller obtain their
power from the battery compartment by direct connection. The battery
management system is
connected to various individual battery cells to monitor their individual
capacities and storage
and can provide information to the front and rear controllers about which
cells are usable for
drawing power.
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[00339] The front and rear controllers are power controllers, generally known
as inverters, for
converting DC power to AC power to drive the front and rear drive motors which
are AC 3-
phase motors. In addition to the power conversion function of the power
controllers, they are
computerized, therefore programmable, to enable them to control the torque on
the AC drive
motors, through techniques including voltage, current and phase control.
[00340] An example of a front and rear controller is an AC induction motor
controller, by
Curtis Instruments, the controller features an indirect field orientation
(IFO) vector control,
which enables controlling the torque and efficiency across the entire speed
range. The
controllers are adapted for receiving inputs such as temperature and speed at
the motor shaft,
and for integrating this information and enabling control of the drive motor.
The programming
language for this controller is known as VCL, which is a vehicle control
language, and is a
programming language for Curtis controllers.
[00341] One of the problems which needs to be addressed in the design of an
off-road
electrical vehicle, is the possibility that the vehicle is travelling on a
steep incline and climbing
in its direction of movement. The accelerator pedal for the vehicle, which
will be monitored,
outputs an electrical signal that may be used for controlling the controller's
outputs to the
wheels. On a level road, these controls would comprise a certain torque
command, but once the
vehicle is moving not on a level road, but is instead climbing, there may a
weight shift to the
rear wheels. In such a case involving a non-level road, the torque command
must be modified in
order to achieve proper torque distribution. Otherwise, there may be slippage
of the wheels
during this movement.
[00342] Depending on the motion of the vehicle, this slippage can occur either
on the front
wheels or the rear wheels, if the vehicle is climbing in its normal direction
where the front
wheels are going to slip, or if it is backing out of a ditch where the rear
wheels are pulling the
vehicle. Since most of the weight is on the front wheels of the vehicle the
rear wheels will slip
because the front wheels do not have enough torque to push the vehicle up the
slope on reverse
motion. Once the rear wheels are slipping, even depressing the accelerator
pedal for introducing
more torque wastes energy. This problem of wasting energy and loss of traction
is also
experienced in the case where the vehicle is traveling on loose sand, in which
case both axles
may slip, and without the necessary intervention through the control system,
the vehicle will not
make progress, and therefore the control system must provide some sort of
control to overcome
these loose ground or slipping conditions.
[00343] A solution to this problem as described in this embodiment involves
monitoring the
speed of the front and rear motors. A differential is provided for enabling
the wheels to turn at
different speeds upon turning of the vehicle. In the case of a locked
differential, the speed of
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rotation of the wheels is the same. However, in the locked differential case,
the torque on the
individual wheels can be different while the speeds are identical. The present
embodiment
provides traction control, and when the vehicle is moving forward, the
traction control system
applies traction control to the front axle to maximize traction on the front
axle. In a climbing
situation, using the traction control system of the present invention, the
front wheel torque is
adjusted by a PID(Proportional Integral Differential) controller, so as to
control the slippage and
thereby maximize the torque delivered by the front axle. When reversing the
vehicle motion, by
backing up a hill, the traction control system operates in reverse, which
provides the rear wheels
with a controlled range of slippage.
[00344] Reference is now made to Fig. 15 wherein the vehicle is moving forward
and
attempting to climb an uphill grade. In this example, both rear wheels are in
contact with the
ground and there is no slippage between either of the rear tires and the
ground. In this example,
the vehicle is operating in the All-Wheel Drive (AWD) mode wherein driving
traction is
provided by both the Front Motor and the Rear Motor.
[00345] If the Two Speed Gear is set for operation in the HiRatio,
rrontDif f Ratio*FixedRed RtRear
NFrontSynchHi = NRear,
RtFront ChainRatio*RearDif fRatio*HiRatio
where NFrontSynchHi is the no-slip speed of the front motor when the Two Speed
Gear is in the
HiRatio and NRear is the speed of the rear motor in rpm, as reported over the
CANbus from the
Rear Motor controller and RtRear and RtFront are the effective rolling radii
of the rear and from
tires respectively in meters. Also, according to the above equation,
FrontDiffRatio and
RearDiffRatio are the speed ratios of the front and rear differentials;
FixedRed is the speed ratio
of the fixed gear reduction between the Front Motor and the Front
Differential; ChainRatio is the
speed ratio of the chain drive drivingly connected between Rear Diff and the
rear tire; BeltRatio
is the speed ratio between the Rear Motor output shaft and the input shaft of
the two-speed
transfer case. As used herein, speed ratios represent the input shaft speed
divided by the output
shaft speed for each component.
[00346] In an implementation of the present embodiment, the Front Motor and
the Rear Motor
are controlled by Torque Control wherein the respective motors are given a
Throttle Command
which causes the respective motors to generate an RMS current which is
proportional to the
Throttle Command. Thus, in an exemplary embodiment of the present invention, a
Throttle
Command of 100% will cause the RMS current in both Front Motor and Rear Motor
to develop
650 amps RMS. This is the maximum torque the motors can generate in this
example.
[00347] It is well known in the art that when motor torque is specified by the
controller, the
rotational speed of the motor is dependent on the load on the motor.
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[00348] Referring again to Fig. 15, operation of the traction control system
is now described
for a number of different terrain conditions. These examples are intended for
descriptive
purposes only. For the sake of clarity, the 2Speed Gear is in the HiGear ratio
and the Throttle
Command from the vehicle operator is 100%.
Example 1 ¨ The Front Wheels Do Not Slip
[00349] The Front Controller is operative to generate maximum torque by the
Front Motor.
The terrain conditions are such that the front wheels do not slip and the
maximum possible
tractive effort is generated on all wheels. Since there is no slippage, the
speed of the front motor
is NFrontSynchHi rpm.
Example 2 ¨ Traction Control When Front Wheels Slip
[00350] Irregular terrain conditions and acceleration of the vehicle may cause
weight transfer
from the front wheels to the rear wheels. If the tractive effort developed by
the front motor
exceeds the traction limit between the front wheels and the ground, the speed
of the front motor
will increase, and the front wheels will slip.
[00351] It is well known in the art that maximum traction between a tire and
the ground is
achieved when a certain amount of slip is present. Typical values for maximum
friction between
the tire and road is about 10% slip for dry road surfaces and about 5% for wet
road surfaces. If
the wheel slip is higher than these values, the friction actually decreases,
thereby reducing the
traction of the vehicle.
[00352] The Traction Control system of the present invention is operative to
limit the speed of
the Front Motor according to the following equation:
MaxSpeedTrqM = AllowedSlip * NFrontSynchHi,
where AllowedSlip is a parameter that may be adjusted by the operator of the
vehicle. In a
preferred embodiment of the invention, this maximum speed of the Front Motor
is limited by a
conventional PID feedback control loop wherein the Throttle Command to the
Front Motor is
reduced thereby decreasing the torque developed by the Front Motor.
[00353] As used herein, a parameter refers to a value that may be set in the
motor controllers
by various means provided by the manufacturers of the controller. A parameter
may be changed
only when the vehicle is at rest and the parameter change does not take effect
until the controller
is reset.
[00354] Values of AllowedSlip are preferably greater than 1.02 and less than
1.2 and more
preferably 1.1, depending on the terrain and weather conditions. In an
alternative
implementation, the value of AllowedSlip may be set by switch means activated
by the vehicle
operator to adjust to changing conditions. In yet another additional
implementation of the
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present embodiment, the value of AllowedSlip may be set by potentiometer means
activated by
the vehicle operator.
[00355] In an implementation, a lower bound may be placed on the value of
MaxSpeedTrqM.
Thus, if the calculated value of MaxSpdTrqM, which depends on the value of the
speed of the
Rear Motor NRear, is less than a parameter TractCtrlMinMtrSpeed, the value of
MaxSpeedTrqM may be set equal to TractCtrlMinMtrSpeed. In some examples,
values of
TractCtrlMinMtrSpeed are preferably greater than 100 rpm and less than 1200
rpm and more
preferably 750 rpm.
Example 3: Canceling Traction Control at Driver Request
[00356] Under certain terrain conditions wherein the traction coefficient
between the driving
wheels and the ground are unusually low, it may become advantageous to
override the traction
control system and allow both front and rear wheels to slip. A typical example
of such
conditions may occur when the vehicle is traversing very loosely packed sand
dunes.
[00357] If the driving wheels are allowed to slip, some of the sand is flung
rearwards and at
least some vehicle traction is generated by both front and rear wheels.
[00358] Driver-selectable switch means are therefore provided which are
operative to cancel
the traction control algorithm and allow the Front Motor to reach speeds above
MaxSpdTrqM.
[00359] It will be apparent that this type of driving is wasteful of energy
and should be used
for very short periods of time.
Example 4: Preventing Front Wheel Slip Completely
[00360] As described hereinabove, the traction control system of the present
invention
typically limits the speed of the front motor so that the speed of the front
wheels do not exceed
the speed of the rear wheels by more than typically 10% - 15%.
[00361] Under certain terrain conditions, even this 10% - 15% slip may be
excessive. A
typical example of such terrain conditions occur in very rocky conditions
wherein one of the
front wheels for example is in not in contact with the ground. As is well
known to one skilled in
the art, a typical open differential always applies the same amount of torque
to each wheel.
Since one of the front wheels is in the air and thereby unloaded,
substantially zero torque will be
provided to the loaded front wheel that is in contact with the ground. The
speed of the loaded
wheel will be zero, but the speed of the unloaded wheel will be double the
value when the
vehicle is moving straight ahead.
[00362] Free-wheeling of the unloaded wheel is normally not a problem unless
someone is
walking close to the unloaded spinning wheel. Any rocks or dirt thrown up by
intermittent
contact of the unloaded rapidly spinning wheel with the ground may cause
injury.
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[00363] It will be apparent to one normally skilled in the art that if one of
front wheels is
freely rotating, the total torque required by the front drive motor will be
very low and hence the
RMS current provided by the front drive motor will very low.
[00364] The RMS current provided by the rear drive motor, which will be
providing all of the
torque propelling the vehicle, will be substantially higher than the RMS
current of the front
drive motor.
[00365] It is a purpose of this alternate embodiment of the present invention
to monitor the
Rear Motor RMS current and the Front Motor RMS current. When there is a larger
than
expected difference between the RMS Motor Torques the traction control system
will be
operative to limit the Front Motor RMS torque to almost zero, thereby
preventing the unloaded
motor from spinning rapidly.
[00366] Operation of the traction control system described herein when the
TwoSpdGear is in
the LoGearRatio is identical to operation in the HiGearRatio except that the
Front Motor speed
is controlled by the value of NFrontSynchLo as defined by the following
rrontDif f Ratio*FixedRed
equation:NFrontSynchLo =
RtFront
RtRear
NRear.
ChainRatio*RearDif f Ratio*LoRatio
[00367] It will be apparent to one normally skilled in the art that the
traction control method
described hereinabove will be operative to control vehicle traction if the
vehicle is moving in
reverse while climbing a grade. In this case, the maximum speed of the Rear
Motor is calculated
as a function of the speed of the Front Motor.
[00368] In an alternate embodiment of the present invention, the traction
control means are
operative to run in a front Wheel Only mode of operation. Operation of the
Front Wheel Only
mode is identical to operation in the AWD Mode except that the torque command
of the rear
motor controller is limited to small values which are sufficient to overcome
the spin loss of the
Rear Motor and associated drive line components.
[00369] In another alternate embodiment of the present invention, the traction
control means
are operative to run in a Rear Only mode of operation. Operation of the Rear
Only mode is
identical to operation in the AWD Mode except that the Torque Command of the
Front Motor
Controller is limited to small values which are sufficient to overcome the
spin loss of the Front
Motor and associated drive line components.
[00370] It is well known in the art that the motor controllers used to control
operation of the
vehicle comprise a number of manufacturer-provided safety features which are
required to
assure safe operation of the vehicle. A description of these safety features
may be found in the
Troubleshooting chart of the relevant Curtis Instruments Manuals.
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[00371] In accordance with another implementation of the present embodiment,
the Front
motor controller and the rear motor controller also comprise at least one
error override means for
overriding faults detected by the motor controllers and allowing reduced
performance of the
vehicle.
[00372] It should be understood that this embodiment may take various other
forms as well.
2. Performance Optimization for Dual Motor All-Wheel Drive Electric and
Hybrid
Vehicles
[00373] Another embodiment is related to performance optimization of dual
motor, all-wheel
drive electric and hybrid vehicles.
[00374] As an introduction, driver-selectable mode changing means for limiting
the
performance of an electric vehicle are known in the prior art. Typical modes
include high
performance, normal performance, and limp home modes. These methods typically
restrict the
maximum current drawn by the drive motor(s) and/or limit maximum vehicle
speeds.
[00375] The embodiment relates to means for controlling the division of torque
between the
front axle and the rear axle to accommodate different vehicle speed ranges and
varying terrain
conditions. Reference is now made to FIG. 14.
[00376] At low vehicle speeds and difficult terrain both front and rear motors
can operate at
full torque for maximum traction. At higher vehicle speeds, maximum traction
is no longer
required and it is beneficial to reduce the torque generated by the front
motor. At still higher
vehicle speeds it may be desirable to reduce the front motor contribution to
zero.
[00377] The torque division means may also comprise driver selected means for
propelling the
vehicle by the Front Drive Motor only. These driver-selected means may also be
operable to
propel the vehicle by the Rear Drive Motor only.
[00378] These driver-selected means may also be operable to allow the driver
to select the
desired torque division between front and rear axles at will, even when the
vehicle is moving at
high speed.
[00379] The torque division means may also comprise means for automatically
limiting the
current drawn from the battery to safe levels commensurate with the state of
the battery.
[00380] Reference is now made to Fig. 16 which shows the peak battery current
as a function
of vehicle velocity.
[00381] The Rear Motor and the Front Motor curves represent the peak battery
current that
may be drawn from each of the motors at a driver command requesting full
torque as a function
of vehicle velocity.
[00382] It will be apparent that if both motors are allowed to operate at
maximum torque, the
battery current may reach excessive levels as shown by the curve. Total DC
Current if Both
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Motors at Max Current. If this continues for more than a few tens of seconds
overheating and
damage to the battery may result.
[00383] To prevent possible damage to the battery and preserve the battery
capacity, front
torque rollback means are provided to reduce the torque provided by the Front
Motor as a
function of vehicle speed. As illustrated in Fig. 72A¨B. the front torque
rollback means are
operable to limit the battery current drawn by the front controller to the
values shown generally
by the curve Front Trq Rollback.
[00384] Preferred values of the parameter Rollback BEGINS at is greater than
10 kph and less
than 50 kph and more preferably about 20 km/hr.
[00385] Preferred values of the parameter Rollback END at is at least 15 kph
and less than 60
kph and more preferably about 35 km/hr.
[00386] Preferred values of the parameter TrqAtEndAt is at least 5% and less
than 100% and
more preferably about 20%.
[00387] Preferred values of the parameter TrqAtMaxSpd is at least 5% and less
than 100%
and more preferable about 19%.
[00388] The percentage values for the torque rollback function represents the
percentage of
the maximum rated RMS current of the front controller.
[00389] It will be appreciated that if the values of TrqAtEndAt and
TrqAtMaxSpd are set to
100%, the both motors will provide the maximum possible torque at all vehicle
speeds.
[00390] It will further be appreciated that the Front Torque Rollback Function
has the
tendency to provide full torque from both front and rear controllers at low
vehicle speeds and
gradually reduce the contribution of the front controller as the vehicle speed
increases.
[00391] In an alternate implementation of the present embodiment, the torque
rollback method
is operative to vary as a function of the battery SOC.
[00392] In an alternate implementation of the present embodiment, the torque
division means
is operable to transfer torque in a continuous manner between the front motor
and rear motor to
equalize the temperature of the respective motor and/or controllers.
[00393] In another implementation of the present embodiment, the torque
division means is
operable to issue an alarm to the vehicle operator if one or both of the
motors or controllers are
approaching dangerous temperature levels. This allows the vehicle operator to
reduce the
demand for power or activate the driver selected means and remove the load
completely from
the higher temperature device.
[00394] In an alternate implementation of the present embodiment, the torque
division means
may also be operable to take advantage of different torque-multiplications
provided by the front
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motor, rear motor in high gear and rear motor in low gear. This is analogous
to having three
different transmission ratios in a conventional vehicle.
[00395] Referring now to Fig. 17, the curve Rear Mtr Spd Lo Gear shows the
rear motor speed
as a function of vehicle speed when the 2 Speed Gear is in a Low Gear ratio.
This is analogous
to a first gear ratio in a conventional vehicle transmission wherein maximum
driving torque is
required.
[00396] The curve Rear Motor Spd HiGear shows the rear motor speed as a
function of
vehicle speed when the 2 Speed Gear is in a High Gear ratio. This is analogous
to the 2nd gear
of a conventional vehicle transmission wherein an intermediate level of
driving torque is
required but a higher vehicle speed is desired.
[00397] The curve Front Motor Spd shows the speed of the Front Motor as a
function of
vehicle speed. This is analogous to the 3rd gear of a conventional
transmission wherein a high
vehicle speed is required but less driving torque is required.
[00398] In an alternative implementation of the present embodiment, range
control means are
provided to allow the vehicle operator to select between Front Wheel Only
(FrontOnly), Rear
Wheel Only (RWD) and All Wheel Drive (AWD) modes of operation while the
vehicle is in
motion. The range control means override the vehicle operator requests if an
inappropriate range
is selected and allow the selected range to be operative when the motor speed
reaches an
appropriate level.
[00399] Reference is now made to Fig. 18 which shows an exemplary method used
in the Rear
Controller to send a message to the Front Controller that the Rear Motor has
reached a high-
speed range. This message forces the Front Controller to operate in the Front
Only mode of
operation whereby the Front Controller provides substantially all of the
driving torque to propel
the vehicle.
[00400] In another alternative embodiment of the present invention, the range
control means
are operative to reduce the maximum armature current to low values at high
motor speeds.
[00401] As described in the publications of Curtis Instruments, the maximum
possible
operating speed of the motors is less than 8000 rpm and it is advisable to
operate at speeds
substantially lower than this to avoid operation at very low efficiency of the
motors and
controllers.
[00402] In an alternative embodiment of the present invention, the range
control means are
operative to electrically disconnect the power transistors of the Rear Motor
Controller at
rotational speeds above about 7000 rpm thereby allowing the front motor to
propel the vehicle to
very high speeds.
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[00403] This alternative embodiment of the ranges control means also comprises
means for
electrically reconnecting the power transistors of the rear motor controller
at a rotational speed
of the rear motor substantially below 7000 rpm thereby providing adequate
hysteresis and
preventing rapid transitions of connecting and reconnecting the power
transistors.
[00404] In yet another alternative embodiment of the present invention, the
range control
means also comprise means for electrically disconnecting the power transistors
of the Rear
Motor Controller and the Front Motor Controller at high rotational speeds.
This range control
method is particularly suitable for parallel hybrid electric vehicles which
are provided with an
additional source of mechanical power such as a heat engine.
[00405]
3. Regeneration and Braking Control
[00406] This disclosure also describes a regeneration and braking control
embodiment. The
braking and regeneration control embodiment optimizes and simplifies control
of electric and
parallel hybrid vehicles during extended downhill and braking operation.
[00407] Some example advantages of the regeneration and braking control
embodiment
comprise switch-selectable regeneration means for extended downhill operation
so vehicle speed
can be maintained without depression of brake pedal. The switch-selectable
regeneration means
eliminates heating of service brakes and maximizes recovery of energy, allows
optimized
regeneration of energy during braking between front and rear wheels while
maintaining vehicle
stability, and controls rate of response of the brake pedal in front and or
rear controller to
respond rapidly at high vehicle speeds and more slowly at lower vehicle
speeds. Thus, the
regeneration and braking control embodiment prevents instability in the
controller at very low
speeds while providing required rapid response at high speeds.
[00408] To assure vehicle stability under all road conditions, separate
controls are provided
for the Front Controller and the Rear Controller.
[00409] Reference is now made to Fig. 19 which shows how regenerative braking
is limited in
the Front Controller by assigning values to the Curtis variables Neutral
Braking Torque and
Regen Current Limit.
[00410] Reference is also made to Fig. 20 which shows an exemplary functional
relationship
between a My Neutral Braking TrqM variable and the vehicle speed as
represented by the
speed of the front motor.
[00411] Reference is also made to Fig. 21 which shows an exemplary method
operative to
control vehicle braking for normal driving when there is no request for
application of the vehicle
service brakes, when there is a low request for braking, and when the request
for application of
the service brakes is high enough generate hydraulic pressure in the service
brakes.
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[00412] Reference is now made to Fig. 22 which summarizes an exemplary method
operative
to limit regenerative braking in the Rear Controller. Five separate cases are
considered:
[00413] Reference is also made to Fig. 23 which shows an exemplary method
operative to
limit regenerative braking in the Rear Controller when the vehicle is
operating in an All-Wheel
Drive Mode and the 2 Spd Gear is in the High Gear ratio.
[00414] Reference is also made to Fig. 24 which shows an exemplary method
operative to
limit regenerative braking in the Rear Controller when the vehicle is
operating in an All-Wheel
Drive Mode and the 2 Spd Gear is in the Low Gear ratio.
[00415] Reference is also made to Fig. 25 which shows an exemplary method
operative to
limit regenerative braking in the Rear Controller when the vehicle is
operating in a Rear Wheel
Drive Mode and the 2 Spd Gear is in the High Gear ratio.
[00416] Reference is also made to Fig. 26 which shows an exemplary method
operative to
limit regenerative braking in the Rear Controller when the vehicle is
operating in a Rear Wheel
Drive Mode and the 2 Spd Gear is in the Low Gear ratio.
[00417] In each case, the Neutral Braking Torque of the Curtis Vehicle Control
Language is
dynamically adjusted as a function of vehicle speed as represented by the
speed of the Front
Motor.
[00418] It will be apparent that the techniques described with respect to
FIGS. 19-26 are
applicable to the Series Hybrid Range Extender for All-Wheel Drive Electric
Vehicles and the
Parallel Hybrid with CVT vehicles described herein below.
[00419] Reference is now made to Fig. 27 which shows a method operable to
change the
maximum rate of increase of regenerative torque in the Front Controller as a
function of vehicle
speed. This method allows rapid buildup of regenerative braking at moderate
and high vehicle
speeds while preventing instability at low vehicle speeds.
4. Optimizing Performance of 4WD Electric Drive Vehicles by Equalizing
Component
Temperatures
[00420] Another embodiment disclosed herein relates to optimizing performance
of 4WD
electric drive vehicles by equalizing component temperatures. More
particularly, in an all-wheel
electric drive system, one of the drive axles inevitably assumes more of the
load than the other
axle. For example, while climbing a steep grade for extended periods, the rear
drive motor and
controller may tend to overheat thereby limiting vehicle performance.
[00421] The present embodiment provides temperature equalization methods that
are
operative to automatically adjust the division of power between front and rear
axles depending
on component temperatures.
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[00422] This embodiment provides numerous advantages. The advantages of this
embodiment include: (1) improving vehicle performance by reducing effects of
automatic
cutbacks of motor load, and (2) extension of vehicle component life by
reducing load on higher
temperature components, as some non-limiting examples.
5. Optimizing Electric Vehicle Performance While Preserving Required Range
[00423] Another embodiment of this disclosure relates to optimizing electric
vehicle
performance while preserving a required range.
[00424] More particularly, for any electric vehicle, the expected operating
range depends on
the amount of stored energy remaining in the vehicle energy storage system,
the road and terrain
conditions that the vehicle must traverse, and the required route including
and range for a safe
return if desired. Electric vehicles are particularly sensitive to this issue
because of the limited
energy stored in the vehicle energy storage system; however, but the functions
related to this
embodiment are applicable to hybrid-electric vehicles as well.
[00425] The purpose of the present embodiment is to provide a predictive or
look-ahead
method that takes into account details of the remainder of the route,
including the return if
desired, and advises the vehicle operator accordingly.
[00426] In a preferred implementation of the present embodiment, means are
provided for
operating with the Curtis Instruments controllers and a computationally
intensive computer
(Vehicle Management Unit or VMU) in a co-processor mode. Detailed computations
are carried
out in the co-processor and the results of these computations are communicated
to the Curtis
controllers which control the current supplied to the vehicle motors.
[00427] In an alternative implementation of the present embodiment, the
predictive functions
will also comprise means for automatically reducing the current or power drawn
from the energy
storage system to preserve the amount of energy required to return (e.g.,
return-to-base in
military operations). Similarly, the allowed maximum performance or the
vehicle may be
enhanced if substantially more energy than expected remains in the battery.
[00428] In another alternative implementation of the present embodiment,
override means are
provided to allow the vehicle operator or a remote controlled operator to
apply maximum
vehicle propulsion power to escape an unexpected predicament. As soon as the
emergency
condition is over, the override means can be operative to recalculate the
remaining portion of the
mission.
[00429] In another alternative implementation of the present embodiment, that
is applicable to
an electric-hybrid vehicle, predictive means are provided for unscheduled
charging of the battery
if a long uphill region is expected in the near future. Similarly, the battery
could be partially
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depleted if a long downhill region is expected thereby improving overall fuel
consumption and
remaining range.
[00430] This embodiment addresses two problems: (1) the mission profile mapped
according
to this embodiment has been carefully mapped so the terrain and road
conditions of the
remaining mission are known or estimated in advance, and (2) details of the
terrain and road
conditions are not known in advance but the return-to-base location is known.
This algorithm
requires may use map-based GPS data of the geography and terrain conditions.
[00431] The system provides various advantages in that the embodiment (1)
automatically
provides for maximum instantaneous vehicle performance while ensuring return-
to- base
capability, and (2) reduces the training level required of the vehicle
operator.
6. Optimizing Range of 4WD Electric Vehicles and Hybrid-Electric Vehicles
Based on
Control Tables
[00432] This disclosure also describes an embodiment is related to optimizing
range of
vehicles, such as 4WD electric vehicles, and hybrid-electric vehicles based on
control tables.
[00433] The performance of complex electric and hybrid-electric drive systems
may be
optimized by preparing control tables based on, for example, detailed
simulation analysis of
typical vehicle duty cycles. These control tables may then be downloaded to
the Vehicle
Management Unit computer (VMU) so that operation of the various power sources
(e.g., battery
power, or engine and battery power) can be optimized to obtain, for example,
maximum range
or minimum fuel consumption.
[00434] These algorithms often require a VMU with extensive computational
capabilities
which may be in excess of the capability of the control computers, such as
Curtis control
computer, used in the vehicles of the present disclosure. As described
elsewhere herein, motor
controllers (e.g., Curtis controllers) communicate vehicle, battery and motor
component data to
the VMU. The VMU may also carry out the numerically intensive computation
based on the
various control tables stored therein and then communicate the best solution
to the (e.g., Curtis)
controller(s). The controller(s) may then issue appropriate commands to the
motors to provide
the required power in the most efficient way possible.
[00435] This embodiment provides several advantages. As examples, this
embodiment
enables use of advanced vehicle control techniques while retaining the
advantages of the unique
functionality of the (e.g., Curtis) motor control unit(s), and (2) reduces the
training level of
vehicle operators. This embodiment may provide various other advantages as
well.
7. Series Hybrid Range Extender for All-Wheel Drive Electric Vehicles
[00436] Another embodiment according to this disclosure is related to a series
hybrid range
extender for all-wheel drive electric vehicles. According to the present
embodiment, the all-
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wheel drive electric vehicle may also comprise an engine, an engine driven
generator and a
generator controller in a series hybrid architecture to substantially increase
the range of the
vehicle, as shown in FIG. 28.
[00437] In an alternative embodiment of the present invention, the series
hybrid also
comprises engine control means operable to take advantage of the drivability
and energy
management features described herein for an all-wheel drive electric vehicle.
It is a particular
feature of this embodiment that the engine control means can be seamlessly
integrated into the
control software for the all-wheel drive electric vehicle.
8. Parallel Hybrid Output Power Assist with Improved Performance and Silent
Capability
[00438] Another embodiment of this disclosure related to parallel hybrid
output power assist
with improved performance and silent capability. This embodiment may comprise
sub-
embodiments 8.1 and 8.2
8.1 Improved Shift Gradeability in Output Power Split Hybrid Mode
[00439] This sub-embodiment relates to a hybrid-electric vehicle driven by a
conventional
combustion engine and an electric drive motor. In such a vehicle, the drive
train is may be a
post-transmission hybrid powertrain wherein the electric motor is located
after the multi-speed
transmission. Such a post-transmission hybrid powertrain is illustrated in
FIG. 29. The multi-
speed transmission may be a manual shifted transmission and where a 2-speed
reduction gear is
located between the transmission output and the vehicle drive axles.
[00440] Various problems are associated with the type of powertrain described
with respect to
this sub-embodiment. One of the problems associated with such a powertrain
occurs during the
1-2 shift on difficult terrain at low vehicle speeds. In such cases, the
interruption of torque
transfer from the engine to the vehicle may prevent engagement in the 2nd gear
without the
engine stalling.
[00441] The transfer case may use a dog-clutch to engage a "Hi Gear" and a dog-
clutch to
engage a "Lo Gear." When neither dog clutch is engaged the transfer case is in
neutral. This
neutral state of the transfer case allows the engine to charge the battery at
vehicle standstill in
any desired gear and allows the engine to rotate rapidly at standstill to
recharge the battery.
[00442] One benefit of this embodiment is to provide functions for using the
electric motor
torque during the gear shift to prevent the vehicle from decelerating during
the power
interruption of the gear shift. The invention may also be used to allow the
engine to recharge the
battery during standstill in the most efficient transmission gear.
8.2 Output Power Assist with Combustion Engine and Automatic Transmission
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[00443] Another sub-embodiment relates to a hybrid electric vehicle driven by
a conventional
combustion engine and an electric drive motor. The drive train may be a post-
transmission
hybrid powertrain wherein the electric motor is located after the multi-speed
transmission. The
multi-speed transmission may be a conventional automatic transmission with a
torque converter
and a 2-speed reduction gear that is located between the transmission output
and the vehicle
drive axles. Various flows may be used in various circumstances such as, for
example, rough
terrain, for silent operation, for use with a hybrid mode that involves
battery charging, operation
in a "charge in park" mode, and/or various other modes.
[00444] In yet another embodiment disclosed herein, the Output Power Assist
hybrid
powertrain of the present invention wherein the powertrain also comprises a
second drive motor
and second motor controller may be configured to provide enhanced performance
in the hybrid
and silent modes of operation.
[00445] The FIG. 31 shows more clearly the major drive line components of the
Output Power
Assist hybrid powertrain of the present invention.
[00446] FIG. 32 shows the flow of power in a Standard Drive operating mode. In
such a
mode: (1) power is provided by the internal combustion engine, and (2) the
electric motor
rotates freely without affecting the output.
[00447] The flow of power in a Fuel Saver operating mode of the present
embodiment is
shown in FIG. 33. The Fuel Save operating mode may provide several advantages
in that the
Fuel Saver configuration may: (1) achieve maximum fuel efficiency and range,
(2) provide
power by the internal combustion engine, and (3) the electric motor adds power
at high vehicle
load and absorbs power during periods of low driving load to improve
efficiency of the engine.
[00448] A flow of power in a Hybrid Combined Drive operating mode is shown in
the FIG.
34. The Hybrid Combined Drive Mode may: (1) be used when extra power is
required for rough
terrain, (2) provided power by the internal combustion engine and the electric
motor
simultaneously, (3) control the electric motor output torque with the motor
controller. The
electric motor torque output may be adjusted according to the demand for
driving power by the
vehicle operator. The flow of power in a Silent Mode of operation in shown in
the FIG. 35. The
Silent Mode is used to achieve silent operation with minimal engine exhaust.
Additionally, in
while the vehicle is engaged in the Silent Mode, power is provided only by the
electric motor
and battery. It should be understood that the transmission must be in neutral
in the Silent Mode.
[00449] The flow of power in a Hybrid Mode w/Battery Charging operating mode
is shown in
FIG. 36. The Hybrid Mode is used to charge the vehicle's batteries while
driving. In the Hybrid
Mode, power is provided by the internal combustion engine to drive the vehicle
and the electric
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motor. Further, in the Hybrid mode, the electric motor acts as a generator and
charges the
battery pack.
[00450] The flow of power in a Charge in Park operating mode is shown in FIG.
37. This
mode is used to charge the batteries while vehicle is stationary. In the
Charge in Park mode,
power is provided by the internal combustion engine to drive the electric
motor. The Electric
Motor acts as a generator and charges the battery pack while the vehicle is in
the Charge in Park
mode. It should be understood that the transfer case must be in neural and the
transmission
engaged in the Charge in Park mode.
[00451] Reference is now made to Fig. 38 which shows a preferred embodiment of
the Output
Power Assist hybrid powertrain of the present invention wherein the powertrain
also comprises a
second drive motor and second motor controller to provide enhanced performance
in the hybrid
and silent modes of operation.
[00452] Also in accordance with an implementation of the present embodiment,
the hybrid
vehicle powertrain also comprises a Vehicle Management Unit (VMU) which
coordinates
operation of all aspects of the conventional drive components.
[00453] Also in accordance with an implementation of the present embodiment,
the hybrid
vehicle powertrain also comprises an Energy Storage system with sufficient
energy storage and
power capacity to propel the vehicle with electrical energy only in a battery
only or silent mode
of operation and to assist the power delivered by the engine to enhance the
maximum
performance capability of the vehicle.
[00454] In accordance with yet another preferred embodiment of the invention,
the Energy
Storage system may comprise a battery and supercapacitor.
[00455] The performance curves of a typical motor/generator are shown in the
drawing below,
corresponding to Fig. 39. The performance characteristics shown are for a
single unit of the
motor. It will be understood that the Dual Motor system is capable of
providing twice the torque
and power and consume twice the battery DC as shown in Fig. 39.
[00456] Various control means of the present embodiment are also described
herein. The
control means may: (1) provide full torque from both motors at low motor
speeds until the peak
discharge current limit (DCL) from the BMS is reached, (2) Reduce the torque
from both motors
to prevent excessive battery discharge current, (3) control the current
provided by each of the
drive motors so as to minimize the overall losses of each motor thereby
reducing the current
provided by the batteries. Additionally, the control means may comprise:
(1)first override means
to reduce the motor torque by limiting motor speeds and field weakening in the
event of a
message from the BMS and (2) second override means to ignore all warnings and
messages and
to record each event and length of time of occurrence in the memory of the
controllers. The
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control means may control the torque provided by both motors to favorably
affect the
transmission shift schedule and the torque converter clutch lock up schedule.
[00457] Referring now to Fig. 40, there is shown a fuel map of a typical
gasoline engine. The
vertical axis shows engine shaft torque and the horizontal axis represents the
speed of the
engine. The dashed lines represent curves of constant power and the contour
curves show loci
of constant engine efficiency.
[00458] Assume for the purpose of example that the current road load and
driver commands
are such that 25 kw at the transmission output shaft are required to propel
the vehicle. Assume
further that the vehicle is equipped with a 5-speed transmission so that 5
different engine
operating points may be selected at each vehicle speed. For the sake of
clarity in this description,
it is assumed that the transmission efficiency and vehicle accessory loads are
the same in each
transmission gear.
[00459] The 25 kw of power required by the vehicle may be provided at a
relatively high
engine speed at point G2 representing 2nd gear. At this point the efficiency
of the engine is
about 25%. The required 25 kw can also be provided if the transmission is in
3rd gear (G3)
wherein the engine operates at a more favorable operating point with an
efficiency is about
29.5%.
[00460] It will be apparent that the best operating point of the engine will
be in 4th gear (G4)
wherein the engine efficiency is about 32.5%. This represents the highest
engine efficiency that
can provide 25 kw to the transmission output shaft.
[00461] If, however, the load (torque) on the engine were increased for
example to about 120
N-m, the engine efficiency would increase to about 35%. The engine loading can
be increased
without affecting the vehicle speed by causing the motor to act as a
generator. The electrical
output generator is used to recharge the battery. The extra energy that is
stored in the battery
may be used at a later time to allow the engine to provide less power than
would normally be
used to propel the vehicle thereby saving fuel.
[00462] This type of operation is often termed Opportunity Charging because
advantage is
taken of the opportunity to improve the overall operating efficiency of the
vehicle. Opportunity
Charging is a well-known method of improving fuel consumption and requires a
relatively
sophisticated vehicle control computer.
[00463] In a preferred implementation of the present embodiment, indirect
engine control
means are provided to favorably affect the transmission shift schedule and
torque converter
lock-up clutch schedule by controlling the armature current of at least one of
the electric drive
motors.
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[00464] It is also purpose of the present invention to provide advanced fuel
saving techniques
that are implemented using the relatively limited computing capability of
Curtis Motor
Controllers.
[00465] Referring again to Fig. 38 which shows the main powertrain components
of the hybrid
vehicle powertrain.
[00466] The TCC Lockup Schedule, the Transmission Gear Shift Schedule and all
of the
electronic and software controls required to operate the engine are
implemented in the Vehicle
Management Unit (VMU) which is operative to control all aspects of vehicle
operation.
[00467] Reference is also made to Fig. 41 which shows an exemplary torque
converter clutch
(TCC) lockup schedule.
[00468] The region below and to the right of the solid curve in Fig. 41
represents the Lockup
Region, a region of relatively low engine load, wherein the vehicle
requirements can be met with
the TCC locked, thereby avoiding the losses associated with hydrodynamic
operation of the
torque converter. Similarly, the region above the dashed curve represents the
Unlocked Region,
a region of relatively high engine load, wherein higher available engine
torque and torque
multiplication of the torque converter allows the instantaneous vehicle
performance requirement
to be met. It will also be apparent to one normally skilled in the art that
the region between the
solid Lockup curve and the dashed Unlock curve is provided for hysteresis
between the locked
and unlocked torque converter clutch state.
[00469] As is well known by one normally skilled in the art, the lockup
schedule is calibrated
by the vehicle manufacturer to achieve a compromise between vehicle
performance and fuel
consumption in all gears and different lockup schedules are provided for each
transmission gear.
[00470] The lockup schedule is often calibrated in terms of vehicle speed and
the Throttle Pct.
The percent throttle in turn is substantially proportional to the position of
the accelerator pedal.
As used herein, if the Pct (percent) Throttle is 0%, the engine generates
substantially zero useful
torque. If the Pct Throttle is 100%, the engine produces maximum torque at the
current speed of
the engine.
[00471] Continuing with the example of Fig. 41, the vehicle is operating in
transmission gear
4 at Point 1 at 75 km/hr with the TCC open. The terrain conditions are such
the engine is
operating at a throttle of about 35% and the vehicle operator desires to
maintain the vehicle
speed at a constant 75 kph. The TCC is operating in the hydrodynamic range and
the efficiency
of the torque converter may typically be in the range of 75% to 85%.
[00472] In an implementation of the present embodiment, TCC control means are
provided
which are operable to increase the RMS Current of at least one of the drive
motors to provide
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sufficient electrical torque so that the vehicle can be maintained at 75 kph
with an engine throttle
pct of about 25% (Point 2).
[00473] It will be apparent that the engine throttle pct is now below the
solid Lockup Region
curve for Gear 4, and the VMU will be operative to command the TCC to lock
establishing
thereby a mechanical connection between the engine output shaft and the
transmission range
pack. The efficiency of the torque converter will now be substantially 100%.
[00474] It will also be apparent that the power required to provide the
increased RMS current
comes from the energy storage system.
[00475] Reference is now made to the Fig. 42 showing an exemplary transmission
gear shift
schedule of the Automatic Transmission Gearbox of the Hybrid Vehicle
Powertrain of Fig. 38
wherein the gear shift schedule in Fig. 42 is implemented when the Automatic
Transmission
Gearbox is operating in Gear 3.
[00476] The region below and to the right of the solid curve in Fig. 42
represents a region of
relatively light engine loading wherein the automatic transmission gearbox can
operate in the 4th
gear ratio in the indicated vehicle velocity range above about 38 km/hr
thereby allowing the
engine to operate in a favorable region at high efficiency.
[00477] The region above the dashed curve represents a region of heavy engine
loading
characterized by high accelerator pedal depression and consequent high engine
torque. This
region is commonly called the 'kickdown' region which results in a downshift
to Gear 2 to
provide a rapid increase in engine power and vehicle performance.
[00478] It will be apparent to one normally skilled in the art that the region
between the 3-4
Upshift Region and the 2-3 Downshift Region is provided for hysteresis between
the gear shifts
to prevent rapid and frequent gear shifts.
[00479] Continuing with the example of Fig. 42, the vehicle is operating at
Point 3 at 70
km/hr. The terrain conditions are such that the engine operates at a throttle
of 40% and the
vehicle operator desires to maintain the vehicle speed at a constant value of
70 km/hr.
[00480] In an embodiment of the present invention, transmission control means
are provided
that are operable to increase the RMS current of at least one of the motor
controllers to provide
sufficient torque from at least one of the drive motors so that the vehicle
can be maintained at 70
kph with an engine throttle of only 25% (Point 4).
[00481] It will be apparent that the engine throttle pct is now below the
solid 3-4 Upshift curve
and the VMU will be operative to command a shift from Gear 3 to Gear 4,
thereby improving
engine efficiency.
[00482] It will also be apparent that the power required to provide the
increased RMS current
comes from the energy storage system.
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[00483] It will also be apparent to one normally skilled in the art that once
the transmission
has shifted into Gear 4, the VMU will keep the transmission in Gear 4 until
there is a substantial
increase in the demand for additional propulsion power.
[00484] In yet another implementation of the present embodiment, the
transmission and torque
converter clutch sensor means comprises vehicle CANbus reading means operable
to read the
transmission gear ratio and torque converter clutch status.
[00485] In still another implementation of the present embodiment, the
transmission and
torque converter clutch sensor means comprises pressure switch means operable
to provide
information to the transmission control means regarding the operating state of
the transmission
gear and the torque converter clutch status.
[00486] In yet another implementation of the present embodiment, mode control
means are
provided that are operable to favor high vehicle performance at the expense of
fuel consumption
by judiciously providing short bursts of power from the energy storage system
to cause the
VMU to unlock the torque converter lockup clutch and/or downshift the
transmission to a lower
gear.
9. Generalized Control for Electric or Hybrid Vehicles with Multiple
Sources of
Energy
[00487] Additional embodiments relate to a generalized Energy Management
System for an
electric vehicle drive train with a Range Extender. The Range Extender may
comprise a
multiplicity of energy sources in addition to the vehicle's main battery.
[00488] FIG. 43 shows in block diagram form the main physical components of a
2-Motor
4WD electric vehicle to which the present embodiment may apply. It is
appreciated that this
block diagram is exemplary only and that various modifications may be made.
The Energy
Supply System of this embodiment comprises a conventional battery and a
conventional Battery
Management System.
[00489] The Front and Rear Controllers are computers and 3(i) AC Induction
Motor
Controllers. These controllers are programmed with proprietary software that
allows the vehicle
to be driven in response to driver commands and thermal and electrical
limitations of electric
components. The software implements traction control, divides the front/rear
power for optimum
performance, and responds to restrictions suggested by the BMS.
[00490] FIG. 44 represents the electric vehicle drive system from the point of
view of the flow
of energy and control information between the Energy Supply System (the
Battery and BMS)
and the Vehicle System Controllers.
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[00491] In addition to warnings and alarm messages sent by the BMS, values for
the
maximum instantaneous discharge current (PackDCL) and the maximum
instantaneous charge
current (PackCCL) are transmitted by the BMS.
[00492] It is the task of the software of the present invention in the Vehicle
System
Controllers to incorporate all of this information and issue appropriate
commands to the front
and rear drive motors to optimize system performance while protecting the
battery and all
electrical components.
[00493] It is generally understood by those skilled in the art that the amount
of energy
contained in the battery may not be sufficient for all types of mission
profiles. To extend the
range of application of the vehicle, a Range Extender may be added to the
vehicle drive system.
Such a Range Extender may comprise a small conventional internal combustion
heat engine
which can supplement the energy provided by the battery.
[00494] The Heat Engine provides for the long-term average power requirement
of the
vehicle, which can be surprisingly low, while the battery provides for the
peak power required to
overcome obstacles.
[00495] The theory and operation of a Range Extender are well known in the
literature and is
not the subject of the present invention.
[00496] The present embodiment relates to the method used to integrate
operation of an
Energy Supply System comprising multiple sources of energy.
[00497] According to FIG. 45, the Vehicle System Controllers receive
information from an
ESS Computer. It will be appreciated by those skilled in the art that the
functionality of the ESS
Computer can be integrated into the Power Controller of the Generator which
may be a
conventional Curtis AC Motor Controller.
[00498] The Vehicle System Controllers are configured switch the required
functionality to
compute the PowerWeNeed to meet the required driver commands and transmit this
power
requirement to the ESS computer. The ESS Computer will be programmed with the
functionality to decide how best to provide the PowerWeNeed from the available
sources of
energy (i.e. the Battery and/or the Heat Engine). If the PowerWeNeed cannot be
provided by
any combination of the available power sources, the ESS Computer will transmit
the maximum
allowed discharge current in the value of ESS DCL.
[00499] It will be appreciated that as far as the Vehicle Controllers are
concerned, it does not
matter if the allowed discharge current is limited by the battery PackDCL or
by ESS DCL (in the
present invention). The Vehicle System Controllers react to the numerical
value (PackDCL or
ESS DCL).
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[00500] It will be appreciated therefore that the investment and time spent in
developing and
debugging the intricate vehicle controls will operate without change. (In a
certain sense it is like
a plug-and-play system).
[00501] The ESS Computer will be programmed with all the knowledge of the
Battery, Fuel
Cell and SuperCap to decide on the best division of power. The Vehicle System
Controller
software does not have to know anything about how the ESS Computer makes its
decisions.
[00502] In the FIG. 46, the Energy Supply System comprises a battery, a fuel
cell and a
SuperCap.
[00503] The Vehicle System Controller Software may be exactly the as in the
above-
mentioned embodiment with the Heat Engine.
[00504] The ESS Computer will be programmed with all the knowledge of the
Battery, Fuel
Cell and SuperCap to decide on the best division of power. The Vehicle System
Controller
software does not have to know anything about how the ESS Computer makes its
decisions.
10. Dealing with Under-Performing Battery Modules
[00505] This embodiment relates to dealing with under-performing battery
modules.
[00506] As background, the importance of balancing the State of Charge (SOC)
of a multi-cell
Lithium based battery is well known in the literature. Similarly, the
importance of preventing
even one of the cells of a multi-cell battery from exceeding prescribed limits
is also well known.
See for example XP Power System User Manual Rev. 4.8 published by Valence
Technology of
Austin Texas. Ideally, the SOC of each of the cells in a battery is
substantially the same and
intricate procedures have been developed for ensuring that Lithium based
batteries are properly
charge and balanced.
[00507] Safe operation of Lithium based batteries (particularly large
batteries used in electric
vehicles) may be supervised by a BMS. A BMS may monitor the state of each of
the cells in a
multi-cell battery and reports on the state of the battery as a whole and also
on the worst-case
cell(s) of the battery. Thus, a BMS may report the voltage of lowest voltage
cell in the battery
pack, the lowest temperature cell, the highest temperature cell, the cell with
the lowest SOC, the
highest SOC, etc. The system may need to respond to the messages sent by the
BMS and
decrease the load on the battery pack if required. In extreme cases, it may
even be required to
shut the vehicle down completely to prevent a dangerous situation from
occurring.
[00508] For various reasons that are well known in the literature, one or more
of the battery
modules may be at a lower SOC than the other modules.
[00509] Reference is now made to Fig. 47 which shows the charge state of each
of the battery
modules in the battery pack at the start of a run. As may be seen in Fig. 47,
most of the modules
are above 90% SOC but Module No. 7 is at 62%.
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[00510] For maximum safety, the BMS is programmed to base its calculations for
the
maximum recommended Discharge Current Limit (PackDCL) on the battery module
with the
lowest SOC. The value of the Lowest Module SOC is also reported to the driver
as a measure of
the charge remaining in the battery.
[00511] Reference is now made to Fig. 48 which shows the Average SOC of all
the modules
and the SOC of the weakest module as reported by the BMS. As may be seen in
Fig. 48 as the
battery is discharged, all of the modules experience a substantially uniform
decrease in the
reported value of the SOC.
[00512] Hence, as the weakest cell (lower curve) is discharged, this value is
reported to the
driver. This is the safest procedure because the BMS has to protect the
weakest cell and the
driver has to be notified about the decrease in the remaining battery energy.
[00513] Another example of a misbalanced battery pack is shown in Fig. 49. The
upper curve
in Fig. 49 shows the average value of the SOC of all the modules. This average
value is
calculated by the Vehicle Controller based on information for each module
broadcast by the
BMS. Note that the weakest module starts at about 35%. As the vehicle travels,
the weakest
cell SOC (lower curve) drops to about 33% and remains at this SOC for an
extended period of
time.
[00514] This behavior is unexpected. The battery is surely being discharged,
as shown in the
upper curve and by the fact that the vehicle is moving a not-inconsiderable
distance. However,
the SOC of the weakest cell remains unchanged at about 33%.
[00515] As far as the battery safety is concerned, the battery is protected
because the BMS
uses the data for the weakest module.
[00516] The vehicle operator however notices that something is wrong because
he continues
driving and the SOC is not decreasing as expected.
[00517] The present embodiment may be used to prevent this anomalous situation
from
interfering with the driver's concentration and providing meaningful feedback
to the vehicle
operator, and yet protecting the battery as required. The battery state
display means may also
comprise means which are operative, when an SOC Mismatch warning is issued by
the BMS, to
display the Average Value of the SOC as calculated by the Vehicle Controller.
The SOC of the
weakest module will continue to protect the battery.
[00518] In an alternative implementation of the present embodiment, the
average value of the
SOC may be reported to the vehicle operator and the SOC of the weakest cell
will always be
used to protect the battery.
12. Preserving Residual Energy Level in Energy Storage System
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[00519] Another embodiment relates to preserving residual energy levels in
energy storage
systems. As background, battery-only electric vehicle drive systems often
require a low voltage
energy source for operating relays, warning and indicator lights, and other
low power devices
typically associated with on and off-road vehicles. Similarly, a hybrid-
electric vehicle may also
require a low voltage energy source for operating a starter motor to start the
combustion engine.
These auxiliary devices are often powered by a low voltage 12V or 24V
conventional battery.
[00520] As is well known by one normally skilled in the art, the vehicle
cannot even be started
if the low voltage battery is completely discharged. To prevent this from
occurring, DC-DC
Converter means may be provided to keep the low voltage battery in a charged
state. The energy
required for this may come from the main high voltage energy storage device of
the vehicle. It
will be apparent that if the main high voltage energy storage device is
completely discharged,
the low voltage battery will become completely discharged and the vehicle will
be completely
unresponsive and not even be capable of issuing an error state message
indicating what the
problem is. Such a case may occur if the vehicle is left completely unattended
for a long period
of time without the conventional vehicle ignition switch being turned off.
[00521] The present embodiment provides residual energy control means to
preserve a
minimum amount of energy in the low voltage system and in the high voltage
energy storage
device of the vehicle.
[00522] In another embodiment, the residual energy control means also
comprises SOC
display means operative to transform the battery pack State of Charge
(PackSOC) as reported by
the Battery Management System to a Displayed SOC wherein the Displayed SOC
reports a
higher numerical value than the actual PackSOC.
[00523] In another preferred embodiment of the present invention, the residual
energy control
means also comprises as conventional serial display unit (e.g., Curtis Model
840 or similar
device) for displaying numerical values to the vehicle operator.
[00524] Referring now to Fig. 50 an exemplary functional relationship between
the PackSOC
and the Displayed SOC is shown.
[00525] It will be apparent to one normally skilled in the art of using motor
controllers (e.g.,
controllers manufactured by Curtis Instruments) that numerical values may be
stored in
EEPROM parameter memory by a fleet manager and that these values cannot be
changed by a
user of the vehicle.
[00526] In the example of Fig. 50, a linear relationship may be established by
entering the
value of P User31 of 20%. Thus, if the Pack SOC is 100% the Displayed SOC will
be reported
as 100% and if the PackSOC is 20%, the Displayed SOC will be reported as zero
but 20% of the
battery energy still remains.
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[00527] It will be apparent that the functional relationship between the
PackSOC and the
Displayed SOC may be given almost any desired characteristic.
[00528] In yet another preferred implementation of the present embodiment, the
LED warning
lights associated with serial display units may be activated by using the
Displayed SO C values.
[00529] In yet another implementation of the present embodiment, the residual
energy control
means also comprises Power ON Logic means operable to control the vehicle
electrical systems
when the vehicle is first turned ON. The Power ON logic is described in in
Fig. 51.
[00530] In yet another preferred embodiment of the present invention, the
residual energy
control means also comprises Shutdown Control Logic means operable to control
the shutdown
of the vehicle if the PackSOC falls below a prescribed value.
[00531] The Shutdown Control Logic is described in exemplary form in Fig. 52.
[00532] In yet another preferred embodiment of the present invention, the
residual energy
control means also comprises Operating Mode Restriction means operable to
limit the maximum
power that can be taken from the high voltage battery as energy level changes.
[00533] The Operating Mode Restriction means are described in exemplary form
in Fig. 53.
[00534] In still another implementation of the present embodiment, the
operating mode
restriction means may be activated automatically by the value of the
DisplayedSOC and by
manual switch means on the driver control panel and wherein the automatic
setting of the mode
restriction means overrides the manual switch settings.
12. Controllable Differential System for 4WD Electric Vehicles
[00535] Another embodiment of this disclosure relates to a controllable
differential system for
4WD electric vehicles.
[00536] As background, the importance of being able to lock a differential to
maximize
traction is well known in the literature and various mechanisms for
implementing this are well
known to one normally skilled in the art. In most cases, a driver-selectable
differential-lock
mechanism is provided in both the front axle drive and the rear-axle drive
system. These
differential lock mechanisms prevent loss of traction when one of the drive
wheels slips but at
the cost of losses in the drive train on uneven terrain.
[00537] A serious problem often associated with a front-differential lock
system is the
susceptibility of the front axle drive system to heavy shocks when operating
in a rough rock-
strewn terrain. These shocks often lead to premature damage to the front axle.
[00538] It is the purpose of the present embodiment to minimize shocks
encountered by the
front axle by providing a rapid means for temporarily applying a varying
torque on the faster of
the drive wheels, thereby increasing traction to the front axle. This varying
friction torque will
be selectively applied only when desired by the operator.
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[00539] The present invention comprises at least one shaft speed sensor
arranged to monitor
the rotational speed of at least one of the front wheels. The speed of the
differential input shaft is
known from the speed sensor located on the front axle drive motor. The speed
of the second
front wheel therefore may be calculated from the known speed of the front axle
drive motor, the
known gear ratios, and speed measured by said shaft speed sensor.
[00540] The present invention also comprises friction disks and friction
control means on both
sides of the differential and operative to provide a varying friction torque
to one of the drive
wheels when desired. In a preferred embodiment of the invention, the friction
disks are the front
wheel disk brakes.
[00541] Thus, if the speed of one of the front wheels is substantially higher
than the speed of
the second front wheel, the friction control means will operate to apply a
friction torque to the
faster brake disk, thereby forcing the slower wheel to provide a driving
torque proportional to
the torque applied to the faster wheel.
[00542] It will be apparent to one normally skilled in the art that the
traction of the front axle
will be increased when one of the brakes disks are activated. This embodiment
may take various
other forms as well.
13. Parallel Hybrid with CVT
[00543] Another embodiment of this disclosure relates to a Parallel Hybrid
vehicle having a
continuously variable transmission (CVT). This embodiment utilizes the 4WD
electric vehicle
drive technology and software components for battery only vehicles as part of
a hybrid
powertrain. In accordance with a preferred embodiment of the present
invention, an internal
combustion engine is drivingly connected to the Rear Drive Motor via a
continuously variable
transmission (CVT) and clutch as show in FIG. 54.
[00544] It is appreciated that the above block diagram is exemplary only and
that various
modifications may be made. By way of example an intermediate shaft may be
placed between
the CVT output pulley and the rear drive motor, as shown in Fig. 55.
[00545] Reference is now made to Fig. 56 which shows the electrical
connections and driver
controls for the front controller and rear controller of the dual motor all-
wheel drive hybrid
vehicle of the present invention.
[00546] Reference is also made to Fig. 57, which shows the electrical
connections and driver
controls for the engine control functions of the present invention.
[00547] The present embodiment provides numerous advantages and features. As
some
examples, the present embodiment may provide: (1) Silent operation with Front
WD, Rear WD
and All Wheel Drive, (2) FrontWD, RWD and AWD available when the engine
operates, (3)
may allow an engine to drive a rear axle while providing electrical power to
recharge the battery
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and or power the Front Drive motor, (4) stop-start operation of Engine, (5)
redundant controls to
front and rear, (6), redundant digital and analog controls, (7) vehicle
operation that continues if a
CANbus fails, (8) vehicle operation in the event of catastrophic failure in
electrical system, (9)
4WD operation if battery fails or is empty, (10) a vehicle range that is
limited only by the
vehicle's fuel supply, and/or (12) operation at high vehicle speed in excess
of the maximum
speeds allowed by the vehicle's the electric motors. The present embodiment
may provide
various other advantages as well.
[00548] Reference is now made to Fig. 58 which shows the different operating
modes and
transitions between the operating modes for the parallel hybrid powertrain of
the present
invention.
[00549] This powertrain has the following operating modes:
[00550] EVOnly - The engine is disconnected and off. All of the performance
characteristics
of the dual motor all-wheel drive electric vehicle are inherited.
[00551] ICEOnly ¨ The high voltage electrical system is shut down and the
vehicle operates as
a conventional vehicle with rear wheel drive.
[00552] Hybrid ¨ The front wheels may be driven electrically and the rear
wheels are driven
by the engine. The rear motor may be used to charge the battery under
conditions of low vehicle
load thereby allowing the engine to operate more efficiently. Under high load
conditions, the
battery and rear motor may assist the engine thereby enhancing vehicle
performance.
[00553] Charge In Park - the battery is charged by the engine and the rear
controller with the
vehicle at standstill.
[00554] Reference is now made to Fig. 59 which shows some details of the
conditions
required to make a transition between the operating modes.
[00555] Reference is also made to Fig. 60 which shows some details of methods
operative to
run the vehicle in the reverse direction.
[00556] Reference is now made to Fig. 61 which shows some details of methods
operative to
shift the 2 Spd Gear between the LoRatio, HiRatio and Neutral positions
thereby preventing
inadvertent operation of the gear change mechanism of the 2 Spd Gear.
[00557] Reference is also made to Fig. 62 which shows some details of methods
operative to
activate and deactivate an engine ignition relay thereby preventing
inadvertent operation of the
engine ignition relay if the vehicle is moving or the engine is rotating.
[00558] It will be appreciated that when the engine is operating in the Hybrid
Mode, the
vehicle will be capable of substantially higher speeds than in the EV Only
mode.
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[00559] Reference is now made to Fig. 63, which shows an interlock control
means operable
to disconnect and reconnect the power electronics in each of the front and
rear controllers at
high motor speeds.
[00560] As is known by those normally skilled in the art of using Curtis motor
controllers,
clearing the Interlock disables the motor bridge which effectively disconnects
the power
electronics. Similarly, setting the Interlock effectively connects the power
electronics.
[00561] As is known by those skilled in the art of using Curtis motor
controllers, changing the
state of the Interlock while the motor controller is delivering power will
generate a system fault
thereby preventing motor control functions until the fault is cleared.
[00562] This system fault can be prevented by setting the Curtis parameter HRD
SRO Type
to 0 but this effectively disables the critical safety feature that prevents
Uncommanded Powered
Motion.
[00563] Reference is now made to Fig. 64 which shows a Sequencing Error at
Startup method
operative to implement essential safety features preventing Uncommanded
Powered Motion.
[00564] It will be apprecitaed that the Sequencing Error at Startup method
described above is
also applicable to the Dual Motor All-Wheel Drive Electric Vehicle.
[00565] Reference is now made to Fig. 65 which shows a Hybrid Regen Trq method
operative
to control the amount of regenerative torque requested by the Rear Controller
while operating in
the Hybrid Mode.
[00566] In the exemplary diagram of Fig. 65, the amount of regenerative torque
is determined
separately as a function of the system variables battery state (MAP1), speed
of the engine in the
Low Gear Ratio (MAP2), speed of the engine in the High Gear Ratio (MAP3)
temperature of the
Rear Controller (MAP4), speed of the vehicle (MAP5) and a throttle command of
the driver
controls (MAP6). The Hybrid Regen Trq calculations are carried out in the
Engine Controller
and the Lowest Value of the different functions is reported in the variable
RearHybridRegenCmdFrom1310 and transmitted to the Rear Controller.
[00567] Reference is now made to Fig. 66 which shows exemplary values that may
be used to
determine the numerical values for each of the MAP1 ¨ MAP6 functions.
[00568] Reference is now made to Fig. 67 which shows how the
RearHybridRegenCmdFrom1310 variable is implemented in the rear motor
controller by
assigning it to the Regen Current Limit variable.
[00569] Reference is now made to Fig. 68, which shows a Regen and Engine
Throttle Control
Method for Charge in Park method operative to control recharging of the
battery using engine
power when the vehicle is in the Charge in Park mode of operation.
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[00570] It will be appreciated that the battery can also be charged to full
capacity by using a
conventional battery charger under control of the Battery Management System
(BMS).
[00571] In an alternative embodiment of the Regen and Engine Throttle Control
Method for
Charge in Park method, the amount of battery charging is reduced if the
temperature of the
hottest battery cell triggers an Over Temperature Warning Value issued by the
Battery
Management System.
[00572] In an alternate embodiment of the present invention, the Front Torque
Rollback
means is operative to use one schedule for the EV Only Mode and another
schedule when
operating in the Hybrid Mode, as seen in the functions displayed in Fig. 69A
and Fig. 69B.
[00573] It will be appreciated that the Front Torque Rollback schedule for the
Hybrid Mode
allows more power to be provided by the Front Motor at higher vehicle speeds.
[00574] It will be apparent that the control methods described hereinabove
with respect to
Traction Control for Dual All-Wheel Drive Electric Vehicles are operative in
the Parallel Hybrid
with CVT.
[00575] It will also be apparent that the methods described hereinabove for
Optimizing
Vehicle Performance with Under-performing Battery Modules are operative in the
Parallel
Hybrid with CVT.
[00576] It will also be apparent that all of the driveability features
described hereinabove for
the Dual Motor All Wheel Drive Vehicles are operative in the Parallel Hybrid
with CVT.
[00577] It will also be apparent that the interlock control method described
hereinabove for
the Parallel Hybrid with CVT are operative in the Dual All-Wheel Drive
Electric vehicle.
[00578]
14. Safety Measure for Remote Control of Electric and Hybrid Vehicles
[00579] Yet another embodiment may provide safety measure for remote control
of electric
and hybrid vehicles. This aspect of the invention deals with control means for
enhancing the
safety of remote controlled electric and hybrid vehicles and in particular
means for bringing the
vehicle to a safe stop when remote control is lost.
[00580] Reference is made to Figs. 70 and 71, which show a preferred method
for bringing a
remote-controlled vehicle to a safe stop in the event of a failure in the
system.
[00581] Such control means may comprise a combination of mechanical and
software control
features, such as: (1) release of spring-loaded brake responsive to detection
of loss of control of
the vehicle, and/or (2) electrically disabling drive controllers responsive to
detection of loss of
control of the vehicle. The present embodiment may provide various other
advantages as well.
15. Predicting Remaining Battery Life Based on Analysis of Total Energy
Consumption
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[00582] Still another embodiment of the present disclosure is related to
predicting remaining
battery life of a vehicle based on Analysis of Total Energy Consumption.
[00583] As background to this embodiment, the state-of-health of a secondary
battery when
subject to variations in charge and discharge rates, battery cell temperature,
unequal cell
balancing, depth of discharge, etc. is an important factor in fleet management
of electric and
hybrid electric vehicles. This is especially critical in applications which
require a guaranteed
return-to-base capability.
III. Conclusion
[00584] Various inventions have been described in sufficient detail with a
certain degree of
particularity. It is understood to those skilled in the art that the present
disclosure of
embodiments has been made by way of examples only and that numerous changes in
the
arrangement and combination of parts may be resorted without departing from
the spirit and
scope of the present disclosure as claimed. While the embodiments discussed
herein may appear
to include some limitations as to the presentation of the information units,
in terms of the format
and arrangement, the embodiments have applicability well beyond such
embodiment, which can
be appreciated by those skilled in the art. Accordingly, the scope of the
present disclosure is
defined by the appended claims rather than the forgoing description of
embodiments.
