Note: Descriptions are shown in the official language in which they were submitted.
CA 02510649 2006-10-13
MOTOR CONT120L SYSTEM A1~T0 METHOD WITH ADAPTIVE C't~RR~ PROFTLS
Related A»plications
This application contains subject matter related to U.S. Patent No. 6,492,756
of
.Maslov et al., issued on December 10, 2002, U.S. publication number US 2003-
0193263
of Maslov et al., published on October 16, 2003, U.S. publication number
US 2003-0193250 of Maslov et aL, published on October 16, 2003, U.S.
publication
number US 2003-0193264 of Pyntikov et aL, published on October I6, 2003 and
International PCT publication number WO 2004/0Q1953 of Maslov et aL,
.published on
December 3I, 2003,
IS
»eld of the Invention
The present invention relates to control of electric motors, more particularly
to
implanentation, individually, of a pluralit~r of motor cormrol s~emes to elect
associated
stator current waveform praf~les.
Background
The above-identified copending patent appiicatians desaibe the challenges of
developing efficient electric motor drives. Elerxronic~ily controlled pulsed
ion of
2S motor windings offers the prospect of more ~Tex~'ble management of motor
characteristics.
By control of pulse width, duty cycle, and switched application of an energy
source to
appropriate stator windings, greater functional versatility can be achieved:
The use of
permanent magnets in conjunction with such windings is advantageous in
limiting current
consumption. . .
In a vehicle drive environment, wherein power availability for a traction
motor is
limited to an on-board supply, it is highly desirable to attain a high torque
output
capability at minimum power consumption while maintaining high efficiency in
all
conditions of traction motor operation. Motor structural arrangements
described in the
copending applications contribute to these objectives. As described in those
applications,
elecdromagnet core segments may be configured as isolated magnetically
permeable
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CA 02510649 2006-04-07
structures in an annular ring to provide increased flux concentration.
Isolation of the
electromagnet core segments permits individual concentration of flux in the
magnetic
cores, with a minimum of flux loss or deleterious transformer interference
effects
occurring from interaction other electromagnet members.
The above-identified PCT Publication No. WO 2004/001953 describes a control
system for a multiphase motor that compensates for variations in individual
phase circuit
elements. A high degree of precision controllability is obtained with each
phase control
loop closely matched with its corresponding winding and structure. Successive
switched
energization of each phase winding is governed by a controller that generates
signals in
accordance with parameters associated with the respective stator phase
components and
selected driving algorithms. The phase windings are energized with current of
sinusoidal
waveform for high efficiency operation. The control system varies the output
current to
respond to, and accurately track, the user's torque command input.
The sinusoidal current waveform profile obtained with this commutation
strategy
can extend battery life through efficient operation. However, in vehicle
driving operation
there may be a need fox torque capability in excess of that available from the
most
efficient control scheme. Typically, the power supply is rated for a maximum
current
discharge rate, for example, 10.0 amps. If the user of the system requests a
torque
command that correlates to this maximum current draw, then the motor torque
output for a
sinusoidal current waveforrn profile is limited, for example, to approximately
54.0 Nm in
a motor with a configuration such as described above. In vehicle drive
applications,
torque input commands are associated by users with commands for change of
speed. In
typical driving operation, user torque requests are subject to wide
variability with little, if
any, long term predictability. A driver may demand higher acceleration or
greater speed
than the system can accommodate at maximum torque with a sinusoidal current
waveform.
Driving conditions, such as steep uphill grade or heavy vehicle load or the
like, may
impose other limitations on available speed and acceleration. Other non-
vehicular
applications may have similar high torque requirements.
The need thus exists for a vehicle motor control system that is capable of
performing with high efficiency yet can deliver increased torque output when
required by
the user. This need is addressed by making
available a plurality of motor control schemes for a motor drive, each of
which can provide
a unique current waveform profile. One of the motor control schemes may be
selected by
the user to obtain a current waveform profile that has the greatest capability
to meet
operating objectives. For example, a control scheme may be selected that
yields high
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CA 02510649 2006-04-07
efficiency operation, such as a sinusoidal waveform, while another control
scheme may be
selected that provides higher torque, albeit with less operating effciency.
Selection
among motor control schemes may be made in accordance with the user's needs or
objectives with respect to torque and efficiency, or other factors, e.g., low
torque ripple
and noise, etc., at any particular time. A selected motor control scheme will
be
implemented to generate control signals to produce motor energization current
having the
associated waveform profile.
In a vehicle traction application, for example, user profile selection
provides a
vehicle driver flexibility to adjust operation to meet objectives. For
example, if the user
seeks to reach the destination in minimum time, a high torque profile can be
selected and
maintained throughout a trip to provide maximum speed and acceleration
capability. If,
however, a greater concern is to conserve an on-board energy source for a
relatively long
trip, the high efficiency profile can be selected throughout, possibly with
the user's
selection of the high torque profile at various points on a limited basis.
More detailed
descriptions of exemplified waveforms, particularly high efficiency,
sinusoidal
waveforms, and high torque, square wave shaped waveforms can be found in the
art.
The variable conditions and changing requirements of vehicle operation,
however,
may call for a change in profile more frequently or rapidly than the driver
can, or would
desire to, keep pace with. A driver's torque requests may be adequately met
with selection
of the high efficiency profile mode except for relatively transient instances
such as passing
situations, uphill grades, etc. In those instances, the driver may not be
sufficiently
responsive to the changing conditions to obtain optimum advantage of a change
in
selection from a high efficiency profile to a high torque profile. When the
high torque
requirement conditions diminish, return to the high efficiency profile may be
delayed until
the user realizes that the high torque profile is no longer necessary, thus
drawing
unnecessary current from the battery. Thus, it would be desirable to use the
high torque
mode only when torque greater than that available from the high efficiency
mode is
required.
Described in the art is a system in which a motor control scheme is
automatically
selected on a dynamic basis to provide an appropriate energization current
waveform
profile. The system is responsive to a user input signal that represents a
torque request.
The user input signal is continually sensed and the ability of the system to
meet the torque
request is monitored to select the appropriate motor control scheme
accordingly. The
ability of the
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CA 02510649 2005-07-29
WO 2004/070934 PCT/US2004/002377
system to meet torque request is a function of motor speed, which is also
continuously
sensed to facilitate the torque demand monitoring function. The high
efficiency motor
control scheme is implemented unless the corresponding current waveform
profile is
unable to meet the torque demand. The high torque motor control scheme is
implemented
only when increased torque demand is needed.
While such a system is adaptive to provide appropriate stator current
waveforms to
meet system torque demands, other conditions, of which the driver may not be
aware, may
mitigate against implementation of the high torque motor control scheme.
Events not
directly related to torque production capability may occur that would indicate
that the high
efficiency mode is appropriate even during periods of high torque demand. For
example,
the battery supply voltage may reach a low threshold level that represents an
impending
need for battery recharge or a replacement. The high efficiency profile mode
would delay
these requirements. As another example, the motor may be operating at severe
load
conditions, thereby developing increased heating. Motor temperature may reach
a level
indicative of the need for low current draw and thus an overriding preference
for
implementation of the high efficiency profile mode of operation. Other
external
conditions may also factor into a preference for one or more of a plurality of
different
stator current waveform profiles.
The need thus remains for a more adaptive system in which a motor control
scheme is automatically selected based on a plurality of conditions to provide
an
appropriate energization current waveform profile.
Disclosure of the Invention
The present invention fulfills this need by providing a plurality of motor
control
schemes for a motor drive, each of which can produce a unique motor
energization current
waveform profile. One or more conditions extrinsic to the motor are sensed
continuously
throughout motor operation. Such conditions are related to motor operation
other than
directly sensed motor functions such as position, speed and current feedback
parameters.
One of the motor control schemes is automatically selected on a dynamic basis
to provide
motor stator current energization with an appropriate current waveform
profile. Selection
of a motor control scheme is made in accordance with criteria associated with
the
monitored conditions as well as with torque requirements. The present
invention thus
provides additional advantages in motors having ferromagnetically autonomous
stator
electromagnets.
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WO 2004/070934 PCT/US2004/002377
The motor control schemes may comprise a high efficiency motor control scheme
that provides a current waveform profile for relatively optimum operating
efficiency and a
high torque motor control scheme that provides a current waveform profile for
relative
high operating torque response. The system is responsive to a user signal that
sets a torque
command request. The torque request and the ability of the system to meet the
torque
demand are monitored and the appropriate motor control scheme is selected
accordingly.
The high efficiency motor control scheme is implemented unless the
corresponding
current waveform profile is unable to meet the torque demand. If the torque
demand
exceeds the torque capability of the system when operating in the high
efficiency mode,
the high torque motor scheme is implemented in the absence of contrary signals
generated
from the sensing of extrinsic conditions.
Another advantage of the present invention is that one or more system
operating
conditions can be monitored and compared with criteria that call for use of
particular
wavefonn profiles. Motor temperature may be monitored and compared with a
particular
heat threshold above which the high efficiency motor control scheme is
selected for
implementation. The power supply voltage may be monitored and compared with a
supply voltage threshold level. If the monitored voltage is below this
threshold, the high
efficiency motor control scheme is selected for implementation. If either of
these
thresholds is met, the high torque motor control scheme is not selected,
regardless of the
monitored torque conditions.
An additional advantage of the invention is that the user may be given the
option to
disengage the automatic profile selection by inputting a manual selection. For
example, in
a vehicle application a driver may elect to employ the high torque mode
throughout
operation so that the destination can be achieved as soon as possible.
The present invention may be manifested in a control system for a multiphase
motor having a plurality of stator phase components, each stator phase
component
comprising a phase winding formed on a core element, and a permanent magnet
rotor.
Preferably, each of the stator core elements comprises ferromagnetic material
separated
from direct contact with the other core elements, each stator phase component
thereby
forming an autonomous electromagnet unit. Stator energization current is
provided by a
direct current power supply through circuitry coupled to a controller. The
controller can
access data from profile memory storage for any of a plurality of motor
control schemes to
implement stator energization current having a corresponding waveform profile.
Using
the accessed data, the controller generates control signals that are applied
to energization
circuitry for supplying current to the phase windings with a particular
current waveform
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CA 02510649 2006-04-07
profile in accordance with the selected motor control scheme. Each motor
control scheme
provides motor driving current that corresponds to torque command signals
received at the
controller input terminal. The energization circuitry may comprise a plurality
of
controllable switches having control terminals coupled to the controller via
pulse width
modulation .
The controller .is dynamically responsive to one or more monitored conditions
to
effect selection of the motor control schemes. The stored motor control
schemes are
determinative of the current waveform profiles and, when accessed, are
incorporated into
controller operation. A user input, coupled to the controller, provides a
torque command
signal, the controller deriving therefrom a torque demand. The controller
preferably is
provided with additional inputs, including motor operational feedback signals
such as
speed, rotor position, stator current and the like, and signals indicative of
extrinsic
conditions such as temperature and supply voltage level. If the sensed motor
temperature
exceeds a temperature threshold or if the sensed power supply voltage level is
below a
voltage level threshold, data for the high efficiency motor control scheme is
accessed from
storage for motor control implementation.
In the absence of these conditions, data for the torque motor control scheme
is
accessed when the torque demand exceeds a torque threshold and data for the
high
efficiency motor control scheme is accessed when the torque demand does not
exceed the
torque threshold. The torque threshold is set in dependence on the torque
output capacity
of the motor for high efficiency motor control operation. As torque output
capacity is
dependent on speed, the torque threshold is variable. Based on received input
signals, the
controller can derive the motor torque demands and the control voltages
necessary to meet
the torque demands on a real time basis. If the voltage required to sustain
sinusoidal
waveform profile mode exceeds the power supply voltage, then the controller
selects the
high torque profile mode operation, accessing the data therefor from the
profile memory.
As an alternative to repeated real time calculation for profile selection, a
lookup table that
correlates profile selection with torque request input and monitored speed may
be stored in
memory.
Additional advantages of the present invention will become readily apparent to
those
skilled in this art from the following detailed description, wherein only the
preferred
embodiment of the invention is shown and described, simply by way of
illustration of the
best mode contemplated of carrying out the invention. As will be realized, the
invention is
capable of other and different embodiments, and its several details are
capable of
modifications in various obvious respects, all without departing from the
invention.
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CA 02510649 2006-04-07
Accordingly, the drawings and description are to be regarded as illustrative
in nature, and not
as restrictive.
Brief Description of Drawings
The present invention is illustrated by way of example, and not by way of
limitation, in the figures of the accompanying drawing and in which like
reference
numerals refer to similar elements and in which:
Fig. 1 is an exemplary view showing rotor and stator elements in a
configuration
that may be employed in the present invention.
Fig. 2 is a block diagram of a motor control system in accordance with the
present
invention.
Fig. 3 is a block diagram that illustrates torque controller methodology for
use in
the control system of Fig. 2.
Fig. 4 is a flow chart for operation of the profile selection functionality in
accordance with the present invention.
Detailed Description of the Invention
The present invention is applicable in a motor such as disclosed in U.S.
Publication
No. 2003-0193263, although the invention can be used with various
other permanent magnet motors. Fig. 1 thus is an exemplary view showing rotor
and
stator elements as described in that application, the disclosure of which has
been
incorporated herein. Rotor member 20 is an annular ring structure having
permanent
magnets 21 substantially evenly distributed along cylindrical back plate 25.
The
permanent magnets are rotor poles that alternate in magnetic polarity along
the inner
periphery of the annular ring. The rotor surrounds a stator member 30, the
rotor and stator
members being separated by an annular radial air gap. Stator 30 comprises a
plurality of
electromagnet core segments of uniform construction that are evenly
distributed along the
air gap. Each core segment comprises a generally U-shaped magnetic structure
36 that
forms two poles having surfaces 32 facing the air gap. The legs of the pole
pairs are
wound with windings 38, although the core segment may be constructed to
accommodate
a single winding formed on a portion linking the pole pair. Each stator
electromagnet core
structure is separate, and magnetically isolated, from adjacent stator core
elements. The
stator elements 36 are secured to a non-magnetically permeable support
structure, thereby
forming an annular ring configuration. This configuration eliminates emanation
of stray
transformer flux effects from adjacent stator pole groups. The stator
electromagnets are
7
CA 02510649 2006-04-07
thus autonomous units comprising respective stator phases. The concepts of the
invention,
more fully described below, are also applicable to other permanent magnet
motor
structures, including a unitary stator core that supports all of the phase
windings.
Fig. 2 is a block diagram of a motor control system in accordance with the
present
invention. A plurality of multiphase motor stator phase windings 38 are
switchably
energized by driving current supplied from d-c power source 40, such as a
battery, via
hybrid power block 42. The power block may comprise electronic switch sets
that are
coupled to controller 44 via a pulse width modulation converter and gate
drivers. Each
phase winding is connected to a switching bridge having control terminals
connected to
receive pulse modulated output voltages from the controller. Alternatively,
the switching
bridges and gate driver components may be replaced by amplifiers linked to the
controller
output voltages. A more detailed description of the winding power circuitry
can be found
in the art.
Current in each phase winding is sensed by a respective one of a plurality of
current sensors 45 whose outputs are provided to controller 44. The controller
may have a
plurality of inputs for this purpose or, in the alternative, signals from the
current sensors
may be multiplexed and connected to a single controller input. Rotor position
and speed
sensor 46 provides rotor position and speed feedback signals to the
controller. The sensor
may comprise a well known resolver, encoder or their equivalents and a speed
approximator that converts the position signals to speed signals in a well
known manner.
The controller is connected to the supply 40 by a primary power supply bus.
The
controller is also provided with user inputs, including a torque request input
47 and a
profile selection input 48, and other inputs 49 received from sensed extrinsic
conditions
such as motor temperature and battery voltage.
Coupled to the controller are program RAM memory 50, program ROM 52,
DATA RAM 54 and profile memory 56. These illustrated units are merely
representative
of any well known storage arrangements by which the controller may access
stored
random data and program data. Profile memory 56 is shown separately in the
drawing for
purposes of illustration of the inventive concepts. The profile memory may
comprise a
ROM in which are stored the portions of the motor control scheme programs that
dictate
the motor current waveform profiles obtained with implementation of the
associated
control schemes. The profile memory data may be stored in the form of a
profile functions
library and lookup tables. The profile memory data structure can be in a form
of real-time
calculations and optimization routines. As an alternative, or in addition, to
ROM, a unit
can be provided that calculates values during real-time motor operation.
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CA 02510649 2006-04-07
In the vehicle drive application example, the torque request input 47
represents
torque required by the driver's throttle. An increase in throttle is
indicative of a command
to increase speed, which can be realized by an increase in torque.
Alternatively, it may be
indicative of a command to increase torque in order to maintain the same speed
of a
vehicle under heavy load conditions, such as uphill driving. In operation, the
control
system torque tracking functionality should maintain steady state torque
operation for any
given torque request input through varying external conditions, such as
changes in driving
conditions, load gradient, terrain, etc., and should be responsive to changes
at the torque
request input to accommodate the driver's throttle commands. The manner in
which the
control system responds to torque input requests is dependent upon the
particular motor
control scheme implemented. A plurality of motor control schemes are available
to obtain
an appropriate response. Each control scheme effects a particular motor
current waveform
profile having unique characteristics with respect to efficiency, torque
capacity, response
capability, power losses, etc.
Fig. 3 is a block diagram that illustrates a motor control scheme utilized in
the
PCT Publication WO 2004/001953 identified above. Reference is made to that
publication for detailed description of operation. In order to develop the
desired phase
currents the following per-phase voltage control expression is applied to the
driver for the
phase windings:
Yi(t)=Lidld=ldt+R;If+E,+ksef
Fig. 3 represents the methodology, generally indicated by reference numeral
60, by
which the controller derives the components of this voltage expression in real
time,
utilizing the torque request input and the signals received from phase current
sensors,
position sensor and speed detector. Functional block 70 represents the
formulation and
addition of the components of the above expression to obtain the control
voltage in real
time. Each of the functional blocks 62, 64, 66, 68, 72, 74 and 76, shown as
inputs to block
70, represents the generation of the various elements of the components
obtained from real
time inputs received by the controller or parameter constants. Block 62
represents a
precision torque tracking functionality, the per-phase desired current
trajectories being
selected according to the following expression:
Id, Z~d sin ~N,9, J
~ CNsKrI
where 1~ denotes per-phase desired current trajectory, id denotes the user's
requested
torque command, NS represents the total number of phase windings, K~; denotes
a per-
phase torque transmission coefficient and 8 t represents rotor position for
the a''h phase.
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CA 02510649 2006-04-07
The per-phase current magnitude is dependent upon the per-phase value of the
torque
transmission coefficient K.~;.
In operation, controller 44 successively outputs control signals V; (t) to the
hybrid
power block for individual energization of respective phase windings in a
sequence
S established in the controller. Each successive control signal VI (t) is
related to the
particular current sensed in the corresponding phase winding, the immediately
sensed
rotor position and speed, and also to model parameters, Ke; and K.~, that have
been
predetermined specifically for the respective phases. The computations
illustrated in Fig.
3 are performed successively in real time. The expression shown in block 62 in
this motor
control scheme provides the desired current component for the tracking torque
output
control signal V; (t) with a sinusoidal waveform profile. The sine wave
current trajectory
Is;n (t) is generated from the following equation
Isin = Ini Sm (Nr B)
where In, denotes the phase current magnitude, Nr denotes the number of
permanent
1 S magnet pairs and 9; denotes the measured per phase rotor position signal.
As described in
the art, this sinusoidal current waveform profile provides efficient motor
operation.
Different expressions for block 62 can be used for the torque tracking
functionality
of Fig. 3 to obtain different current waveform profiles for manifesting other
operational
aspects, although sacrificing some of the efficiency achieved with the
sinusoidal
waveform profile. For higher torque operation, the expression of block 62
shown in Fig. 3
can be replaced with an expression yielding a square wave current waveform
trajectory I~q
(t), such as
Isq = In= S~ (Sln (Nr e~~)
where sgn (x) denotes the standard signum function and is defined as 1 if x >
0, 0 if x = 0,
and -1 if x < 0. A more detailed description comparing the efficiency and
torque features
of the two different current waveform profiles obtained from the motor control
schemes
discussed above can be found in the art.
Profile memory S6 stores data that are used by the controller to obtain the
current
values that satisfy the expressions exemplified above. For the square wave
profile, the
expression L;dld;ldt may be prestored. The data may be stored as lookup tables
in a profile
functions library, each motor control scheme having a corresponding lookup
table. Each
entry in a lookup table represents a value of current, shown as the output of
block 62 in
3S Fig. 3, for a particular combination of torque request value and rotor
position for the
CA 02510649 2005-07-29
WO 2004/070934 PCT/US2004/002377
corresponding motor control scheme. If a control scheme is selected for which
the
sinusoidal waveform is produced, the corresponding profile memory data is
accessed.
Square wave profile memory data would be accessed if the corresponding control
scheme
is selected. Alternatively, the profile memory may store data for each profile
with which
the desired current value Idt is repeatedly computed by the controller in real
time. While
expressions for sinusoidal and square wave waveforms have been set forth above
for
purposes of illustration, other waveform profiles, such as sawtooth, etc., may
be utilized
for different operational purposes.
Selection of profile data can be made by the controller automatically as
appropriate
during motor operation. Alternatively, a user can select an operational mode
corresponding to one of the profiles by inputting a profile selection signal
at controller
input 48. Profile selection operation is described with reference to the flow
chart shown in
Fig. 4. The description peuains to a specific example in which the profile
memory
contains data for implementing a high efficiency profile motor control scheme,
such as a
control scheme for producing a sinusoidal motor current waveform and for
implementing
a high torque profile, such as a control scheme for producing a square wave
motor current
waveform. This example is merely illustrative, as data for other profiles may
be stored in
the profile memory and accessed under operating conditions for which different
current
waveforms are appropriate.
In the absence of a profile select signal detected by the controller, an
automatic
profile selection mode is involved. At step 100, the controller detects
whether a user
profile selection signal has been received at input 48 to determine whether
the automatic
mode is to be invoked. If the determination in step 100 is negative, the
controller
determines at step 102 whether the received profile select signal is a high
torque profile
selection. If not, the controller, after any appropriate delay, accesses the
profile memory
to retrieve data from the high efficiency profile lookup table at step 104.
The retrieved
data yields the desired current value Id, for the instantaneous values of the
torque request
and the sensed rotor position levels. If, instead, the high torque profile has
been selected,
as determined in step 102, the corresponding lookup table is accessed at step
106 and the
appropriate value of Id, for this table is obtained. The process flow from
both steps 104
and 106 returns to step 100 for determination of whether there is still a user
profile
selection received and the nature of such selection to continue in the above
described
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CA 02510649 2006-04-07
manner. Operation at steps 104 and 106 occurs after the. selection in step 102
for a period
sufficiently long to overcome transient effects in profile changeover. Thus,
an appropriate
delay for return of the process flow to step 100 may extend for a number of
successive
feedback samplings.
If no user profile selection input signal is present and the system has not
been
switched off, the controller determines at step 100 that the waveform profile
is to be
automatically selected. At step 108, the controller compares the sensed
battery voltage,
received as a signal at input 49, and compares the voltage level with a
predetermined
voltage threshold level. If the battery voltage is lower than the threshold
level, after any
appropriate delay the controller selects the high efficiency mode and accesses
the profile
memory to retrieve data from the high efficiency profile lookup table at step
110. A delay
would be appropriate if it is required to switch between motor control
schemes. While
operating in this mode, process flow at regular intervals returns to step 108
to continue
comparison of a sampled battery voltage with the voltage threshold level. If
the battery
voltage is determined at step 108 to be above the threshold level, the
controller compares
the sensed motor temperature, received as a signal at input 49, and determines
whether it
exceeds a predetermined temperature level at step 112. If the temperature is
determined to
be high in step 112, the high efficiency mode is indicated and the process
flow returns to
step 110. If the motor temperature is within an acceptable level, the flow
proceeds to step
114 wherein it is determined by the controller whether the torque capacity of
the motor, in
the high efficiency mode implementation, is sufficient to meet the demand
imposed by the
user's torque input request for the current motor speed. As more fully
described in the
art, the motor torque capacity can be determined
by comparing the required controller output voltage with the power supply
voltage. The
torque demands can be met if the derived control voltages, made with reference
to the
value of the controller V (t) from the output of block 70, do not exceed the
voltage level
of the power supply. The computation of the required voltage, as well as the
comparison,
can be performed on a real time basis by the controller for each input
sampling.
Alternatively, a lookup table can be accessed that correlates torque capacity
with torque
request and motor speed.
If it is determined in step 114 that the torque capacity is sufficient, flow
proceeds
to step 110, either to continue operation with the high efficiency profile or,
with
appropriate delay, switch from another control scheme to select the high
efficiency motor
control scheme and access the corresponding data from the profile memory for
implementation. If the controller determines at step 114 that the high
efficiency motor
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WO 2004/070934 PCT/US2004/002377
control scheme cannot meet the torque demand, then after any appropriate delay
the
controller the high torque motor control scheme is selected and data therefor
retrieved
from the profile memory. During operation in the high torque mode, the
process, at
regular intervals returns to step 100 to continue determination of profile
selection.
It is apparent from the above description that the motor control system of the
present invention is adaptive to the demands of the user as well as to
extrinsic conditions
of which the user may not be aware. The system provides operation with highest
torque
capacity only when necessary to address extreme demands and then only when
external
motor conditions are favorable.
In this disclosure there is shown and described only preferred embodiments of
the
invention and but a few examples of its versatility. It is to be understood
that the invention is
capable of use in various other combinations and environments and is capable
of changes or
modifications within the scope of the inventive concept as expressed herein.
For example,
various other current waveform profiles may be utilized. The profile memory
thus may store
a plurality of profiles accessible by the controller in response to receipt of
specific profile
selection commands. In another modification, the determination of torque
capability
determination can be made with respect to the actual supply voltage, rather
than nominal
supply voltage, with each controller input sampling.
13
