Note: Descriptions are shown in the official language in which they were submitted.
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VEHICLE CLOCK TAMPERING DETECTOR
BACKGROUND OF THE INVENTION
1. Field of the Invention
This application relates to a system and method for controlling an
engine to provide a vehicle operator with enhanced vehicle capabilities (e.g.,
the
ability to manually exceed an established maximum vehicle speed normally
imposed
by the vehicles engine control) for a selected period of time, and a system
for
determining whether the engine control clock has been tampered with to prolong
or
extend any such enhanced capabilities.
2. Background Art
Vehicle engines, and particularly truck engines, are typically
controlled by electronic engine control modules which implement various
methods
of controlling the vehicle engine to optimize the operation of the vehicle.
For
example, U.S. Patent No. 5,477,827, assigned to Detroit Diesel Corporation,
also
the assignee of the present invention, discloses a system and method for
controlling
an engine including the capability of establishing a normal maximum speed and
adding to that maximum speed for a selected time period as a driver
performance
incentive whenever the' driver operates the vehicle within certain established
performance goals, such as minimization of idle time, selection of the optimal
transmission gear, maint;~ining a steady throttle, or reducing the use of
engine driven
accessory loads.
The capability of establishing a normal speed limit provides fleet
managers and individual truck owners with the capability of insuring that
their truck
operators drive safely and meet desired fuel efficiency and other vehicle and
engine
operation goals. However, programming electronic engine control modules to
establish vehicle speed limits which may, for example, maximize fuel
efficiency, may
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otherwise limit the operator's ability to operate the vehicle in an optimal
fashion in
an atypical situation, such as an emergency, or when it is desirable to safely
pass
other vehicles at a speed in excess of the establi shed normal speed limit for
the
vehicle.
Because the goals of the vehicle owner or fleet manager (c:.g, fuel
efficiency, economy of operation) may at times conflict with the goals of the,
vehicle
operator (e.g., minimizing time on the road), the operator may have incentive
to
defeat or tamper with the electronic engine control, such as by disconnecting
or
tampering with sensors. or changing the engine control's clock.
;SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a system
and method for controlling an engine which allows the manufacturer, fleet
manager,
or vehicle owner to estahlish a normal vehicle speedl limit, but which also
allows the
vehicle operator to exceed that established speed limit to allow the operator
1;o safely
pass other vehicles, or otherwise operate the vehicle at a higher speed in an
emergency.
It is also an object of the present invention to provide a system and
method for controlling a vehicle engine which provides the operator the
capability
of manually operating the vehicle to exceed the established normal speed limit
of the
vehicle for a preselected time period, including warning the operator when the
period
during which the operator can manually override the vehicle speed limit is
about to
lapse.
It is also an object of the present invention to provide a system and
method for controlling .a vehicle engine which detects tampering with the
engine
control clock, and records any such tampering, and/or alters the engine
control to
reduce or eliminate the possibility of defeating programmed engine control
restrictions.
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It is also an object of the present invention to provide a system and
method for controlling a vehicle engine which provides the operator the
capability
of manually operating i:he vehicle to exceed the normally established
operational
limits of the vehicle for a preselected time period, and for automatically re-
establishing the preselected time period of enhanced operation at established
intervals
(e.g., every 24 hours), ;provided that no clock tampering has been detected.
In carrying out the above and other objects, the computer readable
storage medium, control, and method of the present invention includes
providing the
operator with a particular operating capability for a time period which is re-
established at a predefiined reset interval, periodically determining whether
the
system clock has been clanged to a time which would prompt reinitialization of
the
time period during which the operator may utilize the particular capability
and, if
such a change has occurred logging a record of the tampering event and/or
suspending any steps which would provide the capability to the operator for
any
additional time. In one embodiment, the present invention includes
establishing a
normal vehicle speed limit, establishing a passing duration period, estabh
ping a
passing override reset irnterval, and controlling the engine in response to
operator
input to provide a vehicle speed exceeding the normal vehicle speed limit for
a
cumulative passing period not greater than the passing duration period at any
time
during the passing override reset interval. If no system clock tampering has
been
detected, the passing duration period is re-established at the beginning of
each reset
interval (i.e., the operator is automatically provided with, for example, 30
minutes
of speed limit override time during each 24 hour period) . If clock tampering
is
detected, the system records the occurrence of the clock tampering. .And, if
tampering is detected, the system may also disable or delay the
reinitialization of the
passing duration period., so as to prevent the operator from obtaining
additional
enhanced driving capabilities by tapering with the clock.
When implemented on an electronic engine control module, the
system, medium, and method of the present invention thus allows an opeo~ator
to
override the normal vehicle operation limits (such as the speed limit)
imposed, for
example, by the vehicle fleet manager, for a limited period of time to allow
the
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vehicle operator to safely pass other vehicles. P~loreover, if clock tampering
is
detected, the system and method of the present invention will record any such
tampering on an event log, and may also eliminate the reinitialization of any
enhanced driving capabilities to prevent the operator to benefit from such
tampering.
These arid other objects, features and advantages of the present
invention are readily apparent from the following detailed description of the
best
mode for carrying out the invention when taken in connection with the
accompanying
drawings .
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a block diagram illustrating a system including an
electronic control module which may be programmed to employ the method of the
present invention;
FIGURE 2 is a flow chart generally illustrating one embodiment of
time-based enhanced engine operation capabilities which could employ the
engine
control including the method of the present invention;
FIGURE 3 is a flow chart illustrating a particular embodiment of the
method of Figure 2;
FIGURE 4 is a flow chart illustrating another particular embodiment
of the method of Figure 2;
FIGURE 5 is a flow chart illustrating yet another particular
embodiment of the method of Figure 2;
FIGURE 6 is a flow chart generally illustrating the clock tampering
detection feature which may be implemented with engine controls, such a.s
those
embodiments shown in Figures 1-5, to prevent personnel from altering or
defeating
the programmed engine operation limitations of the control systems;
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FIGURE 7 is a flow chart illustrating one particular embodiment of
the method of Figure 6;
FIGURE 8 is a flow chart illustrating another particular embodiment
of the method of Figure 6; and
FIGURE 9 is a flow chart illustrating yet another particular
embodiment of the method of Figure 6.
DETAILED DESC'.RIPTION OF THE PREFERRED EMBODIMENTS
Referring now to Figure 1, a block diagram illustrating a system
including a vehicle passing speed timer with clock tamperialg detection
according to
the present invention is shown. The system is particularly suited for use in a
vehicle,
indicated generally by rf;ference numeral 10, which typically includes an
engine 12
coupled to a transmission 14 via a master friction clutch 16. In one
embodiment,
engine 12 is a compression-ignition internal combustion engine, such as a
four, six,
eight, or more cylinder diesel engine. Transmission 14 is typically a multiple
gear
ratio transmission which is manually or semi-automatically actuated to select
one of
the available gear ratios. Master friction clutch 16 may be manually or
automatically
controlled by a clutch actuator (not specifically illustrated) as is well
known in the
art.
Vehicle 10 may also include various sensors 18 for generating signals
indicative of corresponding operational conditions or parameters of engine 12,
transmission 14, clutch 7.6, and the like. Sensors 18 are in electrical
communication
with a controller 20 vi.a input ports 22. Controller 20 preferably includes a
microprocessor 24 in communication with various computer readable storage
media
26 via data and control hus 28. Computer readable storage media 26 may include
any of a number of known devices which function as a read-only memory (RCPM)
30,
random access memory (RAM) 32, keep-alive memory (IMAM) 34, and the like. The
computer readable storage media may be implemented by any of a number of known
physical devices capable of storing data representing instructions executable
via a
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computer such as controller 20. Known devices may include but are not limited
to
PROMS, EPROMs, EEPROMs, flash memory, and the like in addition to magnetic,
optical and combination media capable of temporary or permanent data storage.
Computer readable storage media 26 include data representing various
program instructions, software, and control logic to effect control of various
systems
and sub-systems of vehicle 10, such as engine 12, transmission 14, and the
like.
Controller 20 receives signals from sensors 18 via input ports 22 and
generates
output signals which may be provided to various actuators and/or components
via
output ports 36. Signals may also be provided to a display device 40 which
includes
various indicators such as lights 38 to communicate information relative to
system
operation to the operator of the vehicle. Preferably, display 40 includes at
least one
illuminated indicator such as a check engine light to alert the operator to a
malfunction or error. Display 40 may also include an alphanumeric portion or
other
suitable operator interface to provide more specific status information to a
vehicle
operator or technician. As such, display 40 represents one or more displays or
indicators which may bc: located throughout the vehicle interior and exterior
but is
preferably located in the cab or interior of the vehicle.
A data, diagnostics, and programming interface 42 may also be
selectively connected to controller 20 via a plug 44 to exchange various
information
therebetween. Interface 42 may be used to change values within the computer
readable storage media 26, such as configuration settings, calibration
variables,
control logic and the like. Interface 42 may also be used to retrieve engine
historical
information logged as a result of diagnostic or malfunction codes, including
information which is us~°d to assist personnel performing routine
maintenance, or
troubleshooting malfunctions, as well as engine and vehicle operation data,
including
data specifically associated with the vehicle's passing speed timer feature of
the
present invention, which may be analyzed to evaluate vehicle operator
performance
in addition to vehicle performance.
Sensors 22 preferably include an engine speed sensor 46. Engine
speed may be detected using any of a number of known sensors which provide
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signals indicative of rotational speed for flywheel 18, or various internal
engine
components such as ~:he crankshaft, camshaft, or the like. In a preferred
embodiment, engine speed is determined using a timing reference signal
generated
by a multi-tooth wheel coupled to the camshaft. A clutch sensor 48 may be
provided
to determine the clutch slip or engagement position of master friction clutch
16. An
input shaft speed sensor 50 may be provided to determine the input speed of
transmission 14. An output shaft sensor 52 may be: provided to detect the
rotational
speed of output shaft 54~. Wheel speed sensors, such as sensor 56, may be used
to
provide an indication of the current wheel speed of one or more vehicle
wheels.
Such sensors are comrr.~only used in traction control systems (TCS) and anti-
lock
braking systems (ABS). Of course, one or more sensors may provide signals to
various other controllers, which are eventually communicated to controller 20
rather
than being directly connected via input ports 22 as illustrated in Figure 1.
As will be appreciated by one of ordinary skill in the art, most vehicle
applications will neither require nor utilize all of the sensors illustrated
in Figure 1.
As such, it will be appreciated that the objects, features, and advantages of
the
present invention are independent of the particular manner in which the
selected
operating parameters are sensed.
In operation, controller 20 receives signals from sensors 18 and
executes control logic embedded in hardware and/or software to implement the
vehicle passing speed control feature of the present invention. In a preferred
embodiment, controller 20 is the DDEC controller available from Detroin Diesel
Corporation in Detroit, Michigan. Various other features of this controller
are
described in detail in U.:~. Patent Nos. 5,477,827 and 5,445,128, the
disclosures of
which are hereby incorporated by reference in their entirety.
Referring now to Figures 2 and 3, flow charts illustrating
representative control logic 100 of a system and method according to the
present
invention are shown. As will be appreciated by one of ordinary skill in the
art, the
control logic may be implemented or effected in hardware, software, or a
combination of hardware and software. The various functions are preferably
effected
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by a programmed microprocessor, such as the DDEC controller, but may include
one
or more functions implemented by dedicated electric, electronic, and
integrated
circuits. As will also be appreciated, the control logic may be implemented
using
any of a number of known programming and processing techniques or strategies
and
is not limited to the order or sequence illustrated here for convenience only.
For
example, interrupt or event driven processing is typically employed in real-
time
control applications, such as control of a vehicle engine or transmission.
Likewise,
parallel processing or mufti-tasking systems and methods may be used to
accomplish
the objects, features, and advantages of the present invention. The present
invention
is independent of the particular programming language, operating system, or
processor used to implement the control logic illustrated.
Block 10a? of Figure 2 represents initialization of various programming
variables and thresholds, one or more of which may be determined during
initialization or reprogramming of the system. Other values may be retrieved
from
a non-volatile memory or computer readable storage media upon engine start-up
or
other event such as detection of a fault or error. The: reference values are
determined
and stored in memory, and preferably include vehicle speed, normal maximum
speed, passing duration., and reset interval. Vehicle speed may be sensed
directly
and/or derived from the gear ratio andlor one or more of sensors 18. The gear
ratio
rnay be communicated by a transmission controller but is preferably a virtual
gear
ratio (VGR) which may .be determined using the ratio of transmission input to
output
speed. One of ordinary skill in the art will recognize a number of methods to
determine transmission input and output speeds which may be directly sensed or
indirectly inferred from various other sensed parameters.
The passing duration and reset interval values, as well as the tl~.ireshold
values for other operating parameters described hereinafter, are typically
programmed into the computer readable storage media 26 via interface 42 during
the
initial configuration of the engine control, or subsequently by the truck
owner or
fleet service personnel.. The reference values determined by block 1.02 are
periodically reset or captured (and stored) based on occurrence of one ar more
predetermined events .
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The normal maximum road (vehicle) speed limit is typically sca by the
vehicle owner or fleet manager at a value which maximizes fuel efficiency,
and/or
otherwise maximizes th~° economical operation of the vehicle.
The passing duration is the time period during which the driver is
allowed to manually request vehicle speed in excess of the normal maximum
vehicle
speed. In one embodiment, this time period may be programmed to be between 0
and 255 minutes, and is typically of about 30 minutes duration. It should be
noted,
however, that the system of the present invention can be configured to
acconunodate
a passing duration period of greater than 255 minutes, if so desired.
The reset: interval is the period of time after which the electronic
control module 20 reestablishes the passing duration, to enable operatioai of
the
vehicle at passing speed in excess of the programmed vehicle speed limit for a
period
of time up to the passing duration period during the next interval. The reset
interval
is preferably 24 hours, hut it can be any desired time period. In one
embodiment,
the reset interval is reestablished (l. e. , a new 24 hour period begins) upon
the lapse
of the previous reset interval, regardless of the real time. In an
altE;rnative
embodiment, the reset interval may be reestablished at midnight, based upon
the real-
time clock in the controller 20 in lieu of, or in addition to, reestablishing
the interval
period at the lapse of thf: current interval.
The threshold values for other operating parameters utilized in the
method of the present invention, such as the passing speed increment
th~° upper
activation throttle position, the lower activation throttle position, the
throttle
sequence activation period, the warning period, and/or the ramp-down time are
also
preferably initialized at 102 as described above.
As indicated at 104, if the passing speed timer is enabled, the system
periodically determines whether the operator has made a manual speed request,
such
as by moving the foot pedal. It should be noted that it is contemplated that
the
passing speed timer of the present invention will be enabled to provide speed
in
excess of the vehicle speed limit to the operator only upon manual input by
the
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operator, since it is anticipated that this excess speed will be utilized only
for passing
or other unanticipated emergencies. Thus, if the operator has not made a
manual
request for speed (e.g. , cruise control or another automatic speed control is
in
effect), the system exits the passing speed logic I00. If the driver has made
a manual
speed request, the system checks, at 106 to determine whether the requestE;d
speed
is greater than the normal vehicle speed limit. If the requested speed is
within the
normal vehicle speed limit, the system exits logic 100.
In one embodiment, the passing speed adder of the present invention
is activated by a specific positioning sequence of the throttle. In this
embodiment the
driver must press the ~:hrottle pedal above an upper activation throttle
position
(preferably between 60 and 99 % of full throttle, and most preferably about 95
% of
full throttle), then release the throttle to a position below the lower
activation throttle
position (preferably between 1 and 50 % of full throttle, and most preferably
about
5 % of full throttle), then above the upper limit again, then below the lower
limit, and
then above the upper iinnit for a third time, all within a specified
activation period.
The activation time ma:y be any preselected time which is adequate to allow
the
driver to move the throttle through the sequence of positions required to
activate the
feature. This time period is preferably set to between 1 and 20 seconds, and
most
preferably about 5 seconds.
It will be appreciated that other predefined throttle positioning
sequences may be utiliized to activate the passing speed timer of the present
invention. The sequence should preferably be simple, relatively quick to
perform,
and preferably not a sequence of throttle positions which might be encountered
in the
course of normal driving. Alternatively, a separate switch, or other operator
signaling device, may be utilized to activate the passing speed adder without
departing from the spirit of the present invention.
It should he noted that it is contemplated that the method and system
of the present invention will be implemented in conjunction with other systems
and
methods which automatically adjust the vehicle speed. limit, such as the fuel
economy
speed limit adder disclosed in U.S. Patent No. 5,477,827, or other speed-based
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incentive engine control;. When the method of the present invention is
implemented
with, for example, a fuf:l economy speed adder, it is contemplated that the
passing
speed increments, the iuel economy incentive speed adder, and any other speed
adders will be cumulatively added to the vehicle°s normal speed limit
when
appropriate. Of course, if desired, a programmable optimal vehicle speed limit
may
be provided to limit the cumulative total of the normal maximum vehicle speed
and
any cumulative total speed adders .
If ( as shown at 108) the requested speed is greater than the normal
maximum vehicle speed ;and any other speed adders) within a selected threshold
time
period (preferably about 20 seconds), the system will allow the vehicle to
operate at
a higher speed until the speed requested by the operator drops or until the
passing
duration time expires (as shown at 110). If the speed requested by the
operator is
now below the normal :limit (at 112), the system thereafter limits the speed
to its
normal maximum (at 111). If the vehicle speed is above the normal maximum, the
system checks to determiine whether the passing duration interval has lapsed
(at 113).
If not, the system continues to monitor the vehicle speed and the amount of
time left
in the passing duration interval. If the passing duration interval has lapsed
(at 113)
the system restores the speed limit to the normal maximum (plus any other
vehicle
speed adders supported by the system) until such time as the passing speed
timer is
again activated (as determined at 104).
Figure 3 illustrates generally a clock tampering detection function
which may be employed in the systems of Figures 1-2 to prevent personnel from
defeating the engine performance limits established in the engine control
module.
The system periodically determines (at 150) whether the clock has been
changed.
If not, the system exits this logic and returns to implementing normal control
functions. If the clock I~as been changed, the system may be programmed (at
152)
to take one or more actions to prevent personnel from avoiding normal engine
control limitations by tampering with the clock. For example, the system may
alter
or limit the control to prevent the operator from obtaining any enhanced
operational
capabilities which would otherwise have been provided when clock tampering is
detected.
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In addition, or in the alternative, the system may simply log the fact
and time of the tampering in an events log which can be downloaded from the
electronic control module, or transmitted from the control module to a remote
receiver to the fleet owner or manager responsible for monitoring the
operation of
the vehicles. It should be noted that as used herein, ''clock" or "system
clock" may
be any of a number of time keeping devices which are either part of the
microprocessor 24 and its associated memory 26, or a separate time keeping
device
connected to the control her 20 via one of the input ports 22. The clock is
preferably
set to keep real time, and it is utilized by the engine control in connection
with
various of its control functions.
As will b~: appreciated by those skilled in the art, while it is desirable
to allow personnel, including vehicle operators, th.e capability to reset the
engine
control clock, various control functions, such as the vehicle passing speed
timer
disclosed herein, may reward the vehicle operator with enhanced vehicle
control
capabilities for selected :periods of time, or at certain selected times of
the day. As
such, certain or all clock changes must be monitored to assure that personnel
do not
reset the clock in order to obtain greater than desired access to enhanced
engine
operating capabilities and, thereby defeat the normal performance limitations
implemented by the engine controller.
In the embodiment of Figure 4, the system determines (at 160)
whether a particular time change obtained by resetting the clock would prompt
reinitialization of any enhanced operating capabilities. If not, system does
not
recognize the clock resetting as a tampering event. If the time change would
prompt
reinitialization of any enhanced operating capabilities, however, the system
treats the
clock resetting as tampering and (at 162) alters the engine control to delay
or ~~revent
further enhanced operating capabilities (such as additional passing speed time
) which
might have otherwise resulted from resetting the clock. Thus, the clock
tampering
logic employed in the present invention could vary from simply determining
vrhether
the clock had been changE:d within a preselected recent time frame to
determining the
frequency and nature of the time changes in a preselected recent time frame to
determine whether "tampering" has occurred. Similarly, the logic of the
present
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invention may, upon determining that clock tampering has occurred, take a
variety
of actions from merely logging the fact and time of the tampering in an events
log
to delaying or completely suspending particular engine operation capabilities
in
response to detecting tampering.
To reduce the risk of tampering, it may be required that the time of
the next reset interval, along with the current remaining duration value be
periodically stored in memory. whenever the system clock is changed to a time
which prompts reinitialization of the reset interval, the then current value
of the
duration interval could be maintained until completion of the next reset
interval. For
example, assume the system establishes the reset interval at four hours and
the
passing duration interval at 30 minutes. If the vehicle has been operated so
that there
is one hour remaining in the current reset interval and there is six minutes
of passing
speed duration time remaining, and the system clock is moved ahead two hours,
a
new four hour reset interval is initiated, but only six minutes of passing
duration time
is allocated for the next four hour interval. Thereafter, the passing speed
duration
will be reestablished to 30 minutes at the beginning of each subsequent reset
interval.
In this manner, an operator cannot easily obtain a full passing speed duration
of 30
minutes by simply resetting the clock to the next four hour interval.
Again, it will be appreciated that the clock tampering logic of the
present invention may be implemented to insure the proper use of other speed-
based
incentive engine controls, as well as other operating capabilities which are
provided
by the engine control and are based upon, or are limited by, time, including,
fox
example, calendar and/or time based control of engine start-up (e.g.,
automotive
warm up in winter) or shutdown (e.g., time limited idling during summer
months),
or speed limiting (e.g., road speed limits are lower during evening hours than
during
daytime hours). The anti-clock tampering feature of the present invention may
also
be employed to insure that the engine control clock has not been altered to
sabotage
accident reconstruction (or other engine performance) data that would
otherwise be
available from the engin° control log. Other known calendar based and
time teased
features will similarly benefit from implementation of the anti-clock
tampering logic
of the present invention.
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Referring now to Figure 5, one embodiment of the clock tampering
feature of the present invention first determines (at 170) whether the clock:
has been
changed. If so, the system determines (at 172) whether the clock was turned
back
in time. If the clock was turned back in time, the system (at 174) limits the
control
to maintain the current time allocation for time-based capabilities yet begin
a new
time interval. Thus, for example, if the enhanced capability is the allocation
of 15
minutes of vehicle passing speed (i.e., the capability of manually operating
the
vehicle in excess of the normal vehicle speed limit) for a cumulative period
of up to
minutes per day, and the clock was tampered with to reset the clock to an
earlier
10 time (for example, to 11:59 p.m. the previous day, so that a new time
interval would
begin at midnight, onf: minute after the clock has been reset), the system
could
maintain the current passing speed duration at its current accumulated lame
(for
example, three remaining minutes are maintained); and a new time interval is
begun
immediately.
15 Thus, b:y turning back the clock, the operator maintains three
remaining minutes of vehicle passing speed time for the period beginning at
the
newly set time of 11:59 p.m. until 11:59 p.m. the next day (assuming that the
reset
interval is 24 hours). ~Chus, this embodiment assumes that any time change to
an
earlier time is tampering and, as a result, delays reinitialization of any
enhanced
capabilities for a full time interval. If the clock has been changed but was
not turned
back in time, the system determines (at 176) whether the clock has been reset
forward in time past the end of the current interval if it has, the system
treats this
event as tampering and takes the same actions (at 174) as if the clock had
been turned
back in time.
If the clock has been changed to move the time ahead but still within
the current interval, (as at 178) the system may maintain the current
allocation for
the enhanced capability (for example, leave the current accumulated passim
speed
duration at it is) and simply adjust the end of the time interval
commensurately with
the amount of the time change. For example, if the current internal is due to
end at
midnight and the current time is changed from 8:00 p.m. to 11:30 p.m., system
(at
178) would simple move the end of the current interval ahead in time by 3 1/2
hours,
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to 3:30 a.m. In this manner, the time interval cannot be effectively shortened
by
moving the clock ahead within the current interval.
Figure 6 illustrates an alternative embodiment of the present invention
which employs logic for determining the number of time changes during a
particular
time period and/or the aggregate time gained/lost from such time changes as
indices
of tampering. The system determines (at 180) whether the clock has been
changed.
If it has, the system determines (at 182) whether the last time change was
within the
same time interval as the just determined time change. If not, system
variables
corresponding to the number of time changes and the aggregate amount of time
gainedllost from those changes are reset to zero (at 184 and 186). If the
latest clock
change and previous clock changes) have occurred within the same time
interval,
the system increments l:he number of time changes (at 188).
The system then determines (at 1900 if the number of changes with
this time interval is greater than a preselected maximum. If so, the system
treats the
multiple changes as a tampering event and alters the engine control and/or
logs the
occurrence of the tampering (at 192) as previously described herein. In this
manner,
the system may ignore less than a maximum number of time changes during any
particular time interval. If the number of time changes in the current
interval is less
than the maximum number, the system then determines (at 194) whether the
aggregate time from all tame changes made during the current interval is
greater than
a preselected maximum aggregate amount of tune (delta time). If the current
aggregate is greater than the maximum aggregate delta time, the system treats
the
time changes as tampering and alters the control functions and/or logs a
tampering
event (at 192). If not, no action is taken unless and until another clock
change occurs
during this time interval.
In this manner, it will be appreciated that multiple number of small
time changes which aggregate to, for example, move the clock ahead in time a
significant portion of the time interval (for example, four time changes, each
:moving
the clock one hour ahead) will be regarded as tampering since they effectively
materially shorten the time interval. Again, if tampering is occurred any one
or
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more actions may be taken. In one embodiment, the end point of the time
interval
may be moved forward commensurate with the aggregate amount of time change.
In another embodiment, a new time interval may be initiated without
reallocation of
any additional time for any time based operational enhancements during the
next
interval. Alternatively, selected types of tampering, or any detected
tampering, may
result in suspension of any enhanced operational capabilities which would
otherwise
have been provided by the controller 20, until the vehicle is returned for
<,>ervice.
Figure 7 illustrates one embodiment of the passing speed adder feature
wherein the logic at 112 of Figure 1 includes the additional capability of
providing
speed in excess of the normal vehicle speed limit up to an amount equal to an
established passing speed increment. The passing speed increment variable in
this
embodiment would be established at 102 (in Figure 1 ) as a threshold operating
parameter at the time t:he system is configured, or at the time the vehicle:
passing
speed feature of the present invention is enabled. A passing speed increment
of
between one and 20 miles per hour is preferably allowed. More preferably, the
passing speed increment is ten miles per hour. Thus, in this embodiment, the
logic
at 112 determines whether the requested speed is greater than the sum of the
normal
maximum vehicle speed and the passing speed increment, at 114. If so, the
system
limits the vehicle speed to the sum of the maximum vehicle speed and the
passing
speed increment for the duration of the request, or for the remainder of the
passing
duration, whichever is less. If the requested speed is not greater than the
sum of the
vehicle speed limit and the established passing speed increment, the system
allows
the requested speed, at 118 for the duration of t1 a request, or until the
passing
duration period has expired, whichever is sooner.
Figure 8 illustrates another embodiment of the present system and
method including the spf;ed adder feature wherein the logic of block 112
(shown in
Figure 2) also includes logic for determining whether the passing duration
period has
diminished to a period of time less than an established warning period (at
120). If
so, the system issues a warning, at 122, either in the form of a message on a
graphic
display, illuminating a Iight, activating an alarm, or other method of
indicating to the
operator that the passing; speed timer is about to lapse and he/she will
shortly be
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limited to the normal maximum vehicle speed. In one embodiment the system will
cause the check engine lamp (CEL) to flash rapidly as a warning that the
passing
speed duration time is about to lapse. The established warning period is an
adequate
amount of time to allow the driver to complete a typical passing maneuver. In
one
embodiment this period may be set at 0-255 seconds, and is most preferably
about
one minute prior to the end of the passing duration.
Figure 9~ illustrates additional logic which may be included in the logic
at 112 of Figure 2 which allows speed in excess of the normal maximum, but
gradually reduces the vehicle speed once the passing duration period has
lapsed, in
order to allow the vehicle to gradually slow to th.e normal maximum speed
limit.
The system determines, at 124, whether the passing duration period is now
equal to
zero. If so, the system, at 126 allows the requested speed in excess of
maximum (or,
if the embodiment of Figure 3 is implemented, the system allows the speed np
to the
maximum plus any other speed adders, plus the passing speed increment). The
speed
is, however, gradually reduced following expiration of the passing duration
period,
preferably at a rate adequate to slow the vehicle to the normal maximum speed
within
a preselected speed reduction time interval. In once embodiment, this ramp-
down
time is five seconds. The engine control can, of course, use any of a variety
of
methods to slow the vehicle to its normal maximum speed including controlling
the
fuel supply, andlor other engine breaking and speed control techniques such as
are
disclosed in U.S. Patent No. 5,477,827.
If the pas sing duration period has not lapsed, the system allows speed
in excess of the normal maximum as described above. As with the other
threshold
values, the ramp-down tune is preferably established when the engine control
module
is calibrated, or during a subsequent programming by authorized personnel,
such as
a fleet manager. In one embodiment, the ramp-down time may be specified to be
between 0 to 255 seconds.
It will also be appreciated that the various different embodiments of
Figures 7-9 may be implemented alone or in conjunction with each other so
that, for
example, the system may limit requested speed to the normal maximum plus an
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established passing speed increment, issue a warning to the driver when the
passing
duration period is less than an established warning period, and/or gradually
reduce
the requested additional speed when the passing duration has lapsed.
It will also be appreciated that the system of the present invention may
record various data associated with the use of this feature for later review
by the
operator, fleet manager, vehicle owners, or service personnel. For example,
the
system may record cumulative time spent in "passing speed", cumulative
distance
traveled in "passing speed" , and the time and frequency of any incidents of
clock
tampering or other warnings issued. This information may be downloaded with
other
engine historical W formation using interface 42 or other known methods and
apparatus .
Again, the particular order of operations illustrated is for convenience
only. Preferably, one or more of the computations/decisions illustrated are
made
essentially concurrently and do not depend on the result of other operations
except
where necessary as will be recognized by one of ordinary skill in the art.
Thus, the present invention provides a system and method for allowing
a vehicle operator the flexibility to operate his/her vehicle at a speed
exceeding the
normal vehicle speed limit to allow the driver to perform normal passing., and
to
provide additional speed in limited emergencies, while limiting or eliminating
this
2Q capability if clock tampering is detected, so as not to allow personnel to
defeat
vehicle operation and safety goals attained by normally established vehicle
speed
limits.
While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and describe
all
possible forms of the invention. Rather, the words used in the specification
are
words of description rather than limitation, and it is understood that various
changes
may be made without departing from the spirit and scope of the invention.
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