U.S. patent application number 13/924679 was filed with the patent office on 2014-09-18 for vehicle speed control system and method.
The applicant listed for this patent is Zachary C Rogalski, Ivan Roman, Jason Trombley, Loren M Trotter. Invention is credited to Zachary C Rogalski, Ivan Roman, Jason Trombley, Loren M Trotter.
Application Number | 20140277987 13/924679 |
Document ID | / |
Family ID | 51531573 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140277987 |
Kind Code |
A1 |
Rogalski; Zachary C ; et
al. |
September 18, 2014 |
VEHICLE SPEED CONTROL SYSTEM AND METHOD
Abstract
A system and method of operating a vehicle at a driver selected
target speed. The system and method configured to identify a target
speed based on a position of a gear shift selector and control
engine torque and brake pressure to control the vehicle to operate
at the target speed. The system and method is further provides
manipulating the engine torque and brake pressure of the vehicle in
response to a driver's throttle and brake commands to operate at a
speed desired by the driver.
Inventors: |
Rogalski; Zachary C;
(Rochester Hills, MI) ; Roman; Ivan; (Commerce
Township, MI) ; Trotter; Loren M; (Linden, MI)
; Trombley; Jason; (Metamora, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rogalski; Zachary C
Roman; Ivan
Trotter; Loren M
Trombley; Jason |
Rochester Hills
Commerce Township
Linden
Metamora |
MI
MI
MI
MI |
US
US
US
US |
|
|
Family ID: |
51531573 |
Appl. No.: |
13/924679 |
Filed: |
June 24, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61784801 |
Mar 14, 2013 |
|
|
|
Current U.S.
Class: |
701/93 |
Current CPC
Class: |
B60W 2540/12 20130101;
B60W 2540/16 20130101; B60W 10/18 20130101; B60W 30/143 20130101;
B60K 31/042 20130101; B60W 2540/10 20130101; B60W 2720/10 20130101;
B60W 10/06 20130101 |
Class at
Publication: |
701/93 |
International
Class: |
B60W 30/14 20060101
B60W030/14; B60W 10/18 20060101 B60W010/18; B60W 10/06 20060101
B60W010/06 |
Claims
1. A system of controlling vehicle speed, comprising: a gear shift
selector operable by a user of the vehicle to be set in one of a
plurality of positions; an electronic memory configured to store a
plurality of vehicle target speeds that correspond to the plurality
of positions of the gear shift selector, respectively; and a
controller communicatively coupled to the electronic memory and
configured to: receive a signal from the gear shift selector
indicating a set position of the plurality of positions, identify
the vehicle target speed of the plurality of target speeds that
corresponds to the set position of the gear shift selector, and
generate at least one of an engine torque request and a brake
torque request to control the vehicle speed to equal the target
speed.
2. The system of controlling vehicle speed according to claim 1,
wherein the electronic memory is further configured to store a
plurality of additional vehicle target speeds that correspond to
the plurality of positions of the gear shift selector,
respectively, and to a plurality of incline positions of the
vehicle.
3. The system of controlling vehicle speed according to claim 2,
wherein the controller is further configured to identify the
vehicle target speed of the plurality of target speeds that
corresponds to the set position of the gear shift selector and to
an incline position of the vehicle.
4. The system of controlling vehicle speed according to claim 1,
wherein the controller is further configured to output a signal
corresponding to the engine torque request to an engine of the
vehicle to increase torque provided by the engine to increase the
vehicle speed.
5. The system of controlling vehicle speed according to claim 1,
wherein the controller is further configured to output a signal
corresponding to the brake torque request to a braking system of
the vehicle to increase brake pressure provided by the braking
system to decrease the vehicle speed.
6. The system of controlling vehicle speed according to claim 1,
wherein the controller is further configured to receive a signal
indicative of a relative position of at least one of an accelerator
pedal and a brake pedal of the vehicle.
7. The system of controlling vehicle speed according to claim 6,
wherein the controller is further configured to generate a second
engine torque request based on the relative position of the
accelerator pedal.
8. The system of controlling vehicle speed according to claim 6,
wherein the controller is further configured to generate a second
brake torque request based on the relative position of the brake
pedal.
9. The system of controlling vehicle speed according to claim 1,
wherein at least one of the plurality of vehicle target speeds is
adjusted downward in direct relation to a grade upon which the
vehicle is travelling.
10. The system of controlling vehicle speed according to claim 1,
wherein the controller is further configured to stop generating the
at least one of the engine torque request and the brake torque
request if a fault is detected.
11. A method of controlling vehicle speed, comprising: Storing, in
an electronic memory, a plurality of vehicle target speeds that
correspond to a plurality of respective positions of a gear shift
selector of the vehicle; receiving by, an electronic controller, a
signal indicating a positing of the gear shift selector;
identifying, by the electronic controller, the vehicle target speed
of the plurality of target speeds that corresponds to the set
position of the gear shift selector; and generating, by the
electronic controller, at least one of an engine torque request and
a brake torque request to control the vehicle speed to equal the
target speed.
12. The method of controlling vehicle speed according to claim 11,
further comprising storing, in the electronic memory, a plurality
of additional vehicle target speeds that correspond to the
plurality of respective positions of the gear shift selector and to
a plurality of incline positions of the vehicle.
13. The method of controlling vehicle speed according to claim 12,
further comprising identifying, by the electronic controller, the
vehicle target speed of the plurality of target speeds that
corresponds to the set position of the gear shift selector and to
an incline position of the vehicle.
14. The method of controlling vehicle speed according to claim 11,
further comprising outputting, by the electronic controller, a
signal corresponding to the engine torque request to an engine of
the vehicle to request the engine to increase engine torque.
15. The method of controlling vehicle speed according to claim 11,
further comprising outputting, by the electronic controller, a
signal corresponding to the brake torque request to a braking
system of the vehicle to request the braking system to increase
brake pressure.
16. The method of controlling vehicle speed according to claim 11,
further comprising receiving, by the electronic controller, a
signal indicative of a relative position of at least one of an
accelerator pedal and a brake pedal of the vehicle.
17. The method of controlling vehicle speed according to claim 16,
further comprising generating, by the electronic controller, a
second engine torque request based on the relative position of the
accelerator pedal to operate the vehicle at a driver input
speed.
18. The method of controlling vehicle speed according to claim 17,
further comprising operating the vehicle at the target speed once
the accelerator position returns to an original position.
19. The method of controlling vehicle speed according to claim 16,
further comprising generating, by the electronic controller, a
second brake torque request based on the relative position of the
brake pedal.
20. The method of controlling vehicle speed according to claim 20,
further comprising operating the vehicle at the target speed once
the brake position returns to an original position.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority to U.S. Provisional
Patent Application No. 61/784,801, filed Mar. 14, 2013, the entire
contents of which are incorporated herein by reference.
FIELD
[0002] The present disclosure relates to a speed control system and
method for a vehicle, more particularly, to a speed control system
and method for a vehicle operating at a slow or crawl speed
selected by a driver.
BACKGROUND
[0003] When driving a vehicle, particularly in an off-road
scenario, it is important for the vehicle's driver to be able to
precisely and constantly control the vehicle's speed. This may be
difficult to do in some operating circumstances. For example, in an
off-road context, additional engine torque is required as the
vehicle is often climbing a rock or other obstacle. However,
immediately after the vehicle summits the obstacle, substantially
less torque is required to maintain an approximately constant
vehicle speed. In fact, an increase of brake pressure may be
required to maintain a constant speed when descending the obstacle.
This transition from increased torque to reduced torque and braking
can happen very rapidly, making it difficult for the driver to
maintain an approximately constant speed. Manual transmission
vehicles typically combat this problem by employing low gears that
enable the vehicle to climb the obstacle with little or no throttle
application by the driver. Likewise, inherent engine braking in a
low gear ratio manual transmission means that little to no
conventional brake application is necessary to maintain the
constant speed when descending the obstacle.
[0004] A typical automatic transmission, however, does not have as
low a gear ratio as a typical manual transmission. Thus, both
throttle and braking by the driver are necessary to maintain an
approximately constant speed when driving over obstacles. Some
prior art automatic transmissions have accomplished this type of
control with the use of a driver operated dial that allows the
driver to select from several preset speeds at which the vehicle
may be instructed to travel. The vehicle's electronic control unit
typically manipulates engine torque and braking to cause the
vehicle to move at one of the preset speeds. However, in these
designs, the driver is unable to control the speed of the vehicle
using the throttle and brake pedal. Instead, the vehicle must
travel at one of the preset speeds.
[0005] What is needed, therefore, is a method of operating a
vehicle transmission to smoothly and accurately control vehicle
speed during off-road driving. What is further needed is a method
of manipulating the engine torque and brake pressure of a vehicle
in response to driver throttle and brake commands to allow driver
override if the driver wishes to increase or decrease the vehicle
speed during operation.
SUMMARY
[0006] In one form, the present disclosure provides a system and
method of operating a vehicle having an automatic transmission
including determining a target speed and operating the vehicle at
the target speed, detecting a throttle or brake input from a driver
wherein the throttle or brake input establishes a driver input
speed. The method also includes operating the vehicle at the driver
input speed until the driver terminates the throttle or brake
input, and operating the vehicle at the target speed once the
throttle or brake input is terminated.
[0007] In another form, the present disclosure provides a system
and method of operating a vehicle including activating the speed
control system and method upon a driver request if enable
conditions are satisfied, and determining a target speed
corresponding to a driver selected speed and incline of the vehicle
and operating the vehicle at the determined target speed. The
system and method also includes detecting a throttle or brake input
from the driver wherein the throttle or brake input establishes a
driver input speed, and operating the vehicle at the driver input
speed until the driver terminates the throttle or brake input. The
system and method further includes operating the vehicle at the
target speed once the throttle or brake input is terminated, and
deactivating the method upon a request by the driver if disable
conditions are satisfied.
[0008] Thus, a system and method of operating an automatic
transmission that controls the driving experience in an off-road
setting is provided. The system and method controls the engine
torque and brakes of a vehicle in response to a driver's throttle
and brake commands to maintain an approximately constant speed
desired by the vehicle operator.
[0009] Further areas of applicability of the present disclosure
will become apparent from the detailed description provided
hereinafter. It should be understood that the detailed description,
including disclosed embodiments and drawings, are merely exemplary
in nature intended for purposes of illustration only and are not
intended to limit the scope of the invention, its application or
use. Thus, variations that do not depart from the gist of the
invention are intended to be within the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a block diagram depicting components of the
selec-speed control system according to an embodiment disclosed
herein;
[0011] FIG. 2 illustrates a block diagram depicting the functional
components for the SSC system in accordance with an exemplary
embodiment of the present disclosure.
[0012] FIG. 3 is a flowchart depicting the activation and
deactivation of the selec-speed control system according to an
embodiment disclosed herein;
[0013] FIG. 4A is an exemplary table listing target speeds of the
selec-speed control system for an exemplary transmission in a
vehicle operated on a variety of grades;
[0014] FIG. 4B is another exemplary table listing target speeds of
the speed control system; and
[0015] FIG. 5 illustrates an exemplary flowchart of SSC system
operation during driver override in accordance with an exemplary
embodiment of the present invention.
DETAILED DESCRIPTION
[0016] Before describing the disclosed embodiments of the
technology in detail, it is to be understood that the technology is
not limited in its application to the details of the particular
arrangement shown herein since the technology is capable of other
embodiments. Also, the terminology used herein is for the purpose
of description and not of limitation.
[0017] The system and method described herein provides for
selec-speed control ("SSC"). SSC is a feature of an electronic
brake control system that allows a vehicle to travel at a slow
speed (i.e., a crawl speed) selected by the driver. The system
controls the vehicle speed on level ground, uphill or downhill. The
selec-speed control system ("SSC system") is provided to enable a
vehicle to travel over rough off-road terrain without driver input
for throttle or brakes. To control vehicle speed, SSC can apply the
vehicle brakes and request torque, above driver request, from the
engine controller. SSC function is to be very smooth, acceleration
or deceleration is, in most cases, to be very slow.
[0018] FIG. 1 illustrates a block diagram depicting the vehicle
components for implementing the SSC system in accordance with an
exemplary embodiment of the present disclosure. The SSC system
includes a SSC controller 100. The SSC controller includes a
non-volatile memory that stores the instructions for carrying out
the control process of the SSC system and a processor configured to
execute the instructions accordingly. As will be discussed in more
detail below, the SSC controller 100 receives a driver selected
target speed based on input received from the user-selected gear
position of the gear shift selector.
[0019] During SSC control, the SSC controller 100 receives data
from an accelerator pedal sensor 10 and a brake pedal sensor 11,
which serves as a user override as will be discussed in more detail
below. The SSC controller 100 also receives data from one or more
additional sensors 30. The additional sensors 30 may include, but
are not limited to, a vehicle inclination sensor (grade), one or
more speed sensors, a transmission state sensor, and an SSC switch.
The SSC controller 100 is also in communication with an engine 50
and brake system 60 of the vehicle in which the SSC controller 100
is located. Essentially, the SSC controller 100 comprises two
separate and concurrent running controllers to modulate brake
pressure and engine torque separately to maintain the driver
selected target speed. Furthermore, in one embodiment the SSC
controller 100 can be in further communication with a warning
system 40 that communicates a visual, audible or physical warning
to the driver when an error has occurred in the SSC system.
[0020] FIG. 2 illustrates a block diagram depicting the functional
components for the SSC system in accordance with an exemplary
embodiment of the present disclosure. In the exemplary embodiment,
the SSC controller 100 is comprised in an electronic brake control
module ("EBC module") 210. As shown, the EBC module 210, which
includes the SSC controller 100 of FIG. 1, is communicatively
coupled with four slave modules: (1) a central body control module
("CBC module") 215, (2) a drivetrain control module ("DTC module")
220, (3) a powertrain control module ("PC module") 225, and (4) a
transmission control module ("TC module") 230. As shown, the EBC
module 210 is configured to output signals to and receive signals
from each of the four modules. More particularly, it is
contemplated that the EBC module 210 serves as the driver of the
SSC system and is configured to output control signals to the CBC
module 215, DTC module 220, the PC module 225, and the TC module
230 to modulate engine torque, transmission gear, lamp handling,
and the front, center and/or rear differential to maintain the
vehicle at the driver selected target speed in a smooth manner
while optimizing performance based on the driver selected terrain.
It should also be appreciated that in alternative embodiments,
additional or fewer of these respective modules can be used to
implement the SSC system and/or the respective functionalities of
these systems could be combined in one or more of the various
modules.
[0021] In the exemplary embodiment, the EBC module 210 is
configured to transmit a selec-speed status signal ("SSC_Sts") to
both the CBC module 215 and the TC module 230 that indicates
whether the SSC system is "OFF" (e.g., indicated by a "0") or "ON"
(e.g., indicated by a "1") or "INHIBIT" for manual override (e.g.,
indicated by a "2"). The EBC module 210 also transmits a
selec-speed lamp signal ("SSC_Lmp") to the CBC module 215 as
instructions to indicate whether the selec-speed lamp on the
instrument cluster and the selec-speed switch is "ON" or "OFF" or
unavailable or the like.
[0022] The EBC module 210 is further configured to transmit a
signal indicating an upper gear limit ("Gr_Max") to the TC module
230 when the vehicle is operating in SSC operation. The upper gear
limit is provided to control proper engine braking and aid in
maintaining speed during SSC operation. Preferably, the upper gear
limit is predetermined by the system design to control the proper
engine braking and aid in maintaining proper vehicle speed during
SSC operation. Accordingly, the transmission must honor the upper
gear limit request during SSC operation. In the exemplary
embodiment, the upper gear limit signal ("Gr_Max") is in a passive
state when SSC is not enabled, SSC is enabled but the vehicle is
not in a forward driven gear, SSC is enable but the system is in
driver override (discussed below), and following driver throttle
override and while the vehicle is above the speed threshold defined
by SSC operation. Further, during normal SSC operation (i.e.,
engine control without driver override) or following driver
override and the vehicle is below the speed threshold, the upper
gear limit will be first gear in the exemplary embodiment. Further,
if the vehicle is traveling at a slope less than threshold for
activation of the SSC engine controller component, the upper gear
limit will be second gear in the exemplary embodiment. In addition,
in one embodiment, the EBC module 210 is also configured to
transmit a signal indicating a lower gear limit ("Gr_Min") to the
TC module 230 when the vehicle is operating in SSC operation.
[0023] Furthermore, the CBC module 215 is configured to provide
status signals to the EBC module 210, which include whether the
vehicle has Hill Descent Control ("HDC") functionality
("HDC_Prsnt"), whether the vehicle supports an SSC system
("SSC_Prsnt"), whether the driver has enabled the SSC system
("SSC_En"), whether any of the doors are ajar ("Dr_Ajar"), and
whether the parking brake is engaged ("PBr_Eng"). As should be
appreciated to one skilled in the art, the EBC module 210
interprets each of these signals received from the CBC module 215
when generating its instruction signals for the various modules to
operate the SSC system. In one embodiment, the CBC module 215 is
further configured to provide a signal to the EBC module 210
indicating whether forward, center and/or rear differential on the
vehicle is present an active (signal not shown in FIG. 2). It is
contemplated for certain vehicles, the signal serves as a
robustness check since the SSC system cannot function on such
vehicles without at least a functional rear differential that is
active and present.
[0024] Furthermore, during SSC operation, the TC module 230 is a
slave to the EBC module 210 in order to maintain the proper gearing
to optimize the off road performance and smoothness of the SSC
controller. The TC module 230 is configured to provide a signal to
the EBC module 210 indicating the PRNDL position ("PRNDL"), which
in turn can be provided to the driver on the instrument cluster.
Furthermore, the TC module 230 generates signals indicating the
current gear ("Gr") and target gear ("Gr_Targ") of the
transmission.
[0025] As discussed above the EBC module 210 is also
communicatively coupled to the PC module 225. Generally speaking,
the PC module 225 is the electronics system for controlling the
powertrain of the vehicle, i.e., the group of components that
generate power and deliver it to the road surface, water, or air,
including the engine, transmission, drive shafts, differentials,
final drive and the like. In the exemplary embodiment, the EBC
module 210 provides an engine torque request signal ("EngTrq_Rq")
or brake torque request signal (not shown or, alternatively, with
"EngTrq_Rq" signal) to the PC module 225 to request engine
torque/brake torque to keep the vehicle traveling at the driver set
target speed as discussed above. In one embodiment, the EBC module
210 does not output engine torque requests if the vehicle is
traveling down a slope steeper than a threshold. This is because
the gravity and idle torque forces are sufficient for the vehicle
to maintain the target speed. In a refinement of this embodiment,
the EBC module 210 provides an engine torque maximum request signal
("EngTrq_Max_Rq") and an engine torque minimum request signal
("EngTrq_Min_Rq") to the PC module 225, which serve as
control/override signals to correctly control when the engine
torque request ("EngTrq_Rq") should be honored by the system.
[0026] When additional engine/brake torque is not required, the EBC
module 210 will provide a static signal (not shown) to the PC
module 225. In turn, the PC module 225 is configured to output a
signal ("EngTrq_Stat") to the EBC module 210 indicating the
instantaneous torque output by the engine. The PC module 225 also
transmits a signal (quantified by a percentage) ("ActAccPed %") of
the position of the pedal. In one embodiment, a brake pedal is
directly wired to the EBC module 210 or, alternatively, the brake
switch is wired to the PC module 225. In either case, when the user
presses the accelerator or brake pedal for additional torque during
selec-speed operation, a signal ("ActAccPed %") is transmitted to
the EBC module 210 indicating the position of the accelerator
and/or brake pedal. In one refinement, the PC module 225 transmits
a signal (quantified by a percentage) ("VirAccPed %") of the
virtual position of the pedal. The EBC module 210 then processes
this signal to generate a corresponding torque request signal back
to the PC module 225, which causes the engine to generate
appropriate torque or, alternatively, modulate brake pressure to
effectuate the driver's override request. It should be appreciated
that during driver override in the exemplary embodiment, the EBC
module 210 should not continue sending additional torque request
above that requested by the driver based on the position of the
accelerator and/or brake pedal.
[0027] In an additional embodiment, the PC module 225 is configured
to transmit signals to the EBC module 210 including a driver engine
torque signal ("EngTrqD") that outputs the driver demanded
propulsion torque, an engine torque enable request ("EngTrqEn_Rq"),
engine torque maximum ("EngTrq_Max") and engine torque minimum
("EngTrq_Min") signals, and an engine displacement ("Eng_Disp")
signal. It should be appreciated to one skilled in the art that
these signals are interpreted by the EBC module 210 during SSC
operation when generating its control signals.
[0028] Finally, the EBC module 210 is configured to transmit a
front, center and/or rear differential coupling request to the DTC
module 220. In one embodiment, during SSC control, the front,
center and/or rear differential is desired to be coupled as a
function of steering, inclination, and terrain select mode. The
value should therefore be calibrated to optimize performance during
selec-speed control. The signals transmitted from the EBC module
210 to the DTC module 220 can include a differential torque request
signal ("Diff_Trq_Rq"), which is a torque request across front,
center and/or rear differentials, and can also include a
differential control request ("Diff_Cntrl_Rq"), which serves as a
control signal to dictate how the DTC module 220 should respond to
the differential torque request signal ("Diff_Trq_Rq"). For
example, in some configurations, it may not be necessary for the
DTC module to respond to a differential torque request signal
("Diff_Trq_Rq").
[0029] The DTC module 220 is also configured to transmit multiple
signals to the EBC module 210. First, the DTC module 220 outputs
the status of the transfer case ("TCase_Sts") and communicates
whether the drivetrain is in the 4Low state, as required for SSC
control. Second, the DTC module 220 is configured to transmit a
terrain mode status signal ("TerMd_Sts") to specify the terrain
mode for the SSC system, as will be discussed in more detail below.
Third, in the exemplary embodiment, the DTC module 220 and the EBC
module 210 communicate as a feedback loop. In other words, the DTC
module 220 is configured to transmit a desired differential torque
signal ("Des_Diff_Trq") and an actual differential torque signal
("Act_Diff_Trq"). This signals can be for any one or all three of
the front, center and/or rear differentials. In response to these
signals, the EBC module 210 can transmit further differential
torque request signals ("Diff_Trq_Rq") to adjust the differential
torque accordingly, as would be skilled to one skilled in the
art.
[0030] Finally, as noted above the CBC module 215 is configured to
output whether the front, center and/or rear differential is
present on the vehicle and active. However, in an alternative
embodiment, the DTC module 220 is configured to transmit this
signal to the EBC module 210.
[0031] It should be understood that the four slave modules 215-230
communicate with and are controlled by the EBC module 210 of
selec-speed control using, inter alia, the data
signals/communication discussed above. However, it is reiterated
that different vehicles may have varying configurations of these
modules. For example, the functionality of any of the four slave
modules 215-230 can be combined to one or more modules, or,
alternatively, be divided into separate modules.
[0032] FIG. 3 is an example flowchart 100 depicting the activation
and deactivation of the selec-speed control system in accordance
with the present disclosure. Initially, the SSC system is activated
by a driver operable switch at Step 105. Once the driver presses
the SSC switch (Step 310), the SSC controller 100 determines
whether the enable conditions required to allow the SSC system to
be activated are satisfied (Step 315). The enable conditions can
include, but are not limited to, detecting that no existing faults
that prevent normal operation of the vehicle's electronic stability
control system ("ESC"), the transfer case is in its low range
operating configuration, the driver is applying the brakes, the
driver is not applying the throttle, the park brake is not applied,
the vehicle is not moving, and the SSC switch has been pressed for
a predetermined amount of time (in one embodiment 5 seconds). In
one embodiment, the enable conditions are one or several of those
listed above, but necessarily all conditions are required. For
example, it is contemplated that in one embodiment, SSC operation
can be enabled while the vehicle is moving. Furthermore, other
enable conditions may be utilized independently or in combination
with those above. In one embodiment, the SSC system may be
activated if the transfer case is in a four wheel high range. In
the event the enable conditions are satisfied (Step 315), the SSC
system is enabled (Step 325). In the event the enable conditions
are not satisfied (Step 315), the SSC system is not enabled and a
visual, audible or physical warning is sent to the driver (Step
320).
[0033] In one embodiment, the SSC system is disabled if a fault is
detected (Step 330). Thus, the SSC system checks to determine
whether an SSC fault has occurred (Step 330). SSC faults include,
but are not limited to, a fault in the ESC system or a vehicle
speed over a predetermined speed (e.g., 20 mph). In one embodiment,
the faults include one or several of those listed above, however,
other faults may exist. In the event no faults exist (Step 330),
the method continues SSC operation (Step 345). In the event a fault
exists (Step 330), the SSC system is disabled (Step 335) and a
warning is sent to the driver (Step 340).
[0034] To manually exit SSC operation, the driver presses the SSC
switch (Step 350). In the event the driver does not press the SSC
switch (Step 350), the SSC system continues operation (Step 355)
and returns to the step of checking for SSC system faults (Step
330). Once the driver presses the SSC switch to deactivate the SSC
(Step 350), the SSC system determines whether the disable
conditions required to allow the SSC system to be deactivated are
satisfied (Step 360). The disable conditions include, but are not
limited to, detecting that the driver is applying the brakes, the
vehicle is not moving, and/or the SSC switch has been pressed for a
predetermined amount of time (in one embodiment 5 seconds). In one
embodiment, the SSC may be disabled if the vehicle is moving at any
speed and the SSC switch has been pressed for a predetermined
amount of time (in one embodiment 5 seconds). In one embodiment,
the disable conditions include one or several of those listed
above, however, additional disable conditions may exist. In the
event the disable conditions are satisfied (Step 360), the SSC
system is disabled (Step 375). In the event the disable conditions
are not satisfied (Step 360), the SSC system continues operation
(Step 365), a warning is sent to the driver (Step 370), and the SSC
system then returns to the step of checking for SSC system faults
(Step 330).
[0035] In operation, the SSC system attempts to achieve a target
speed defined by the driver. Specifically, using the gear shift
selector, the driver can set the target speed by moving the gear
shift to a desired position (e.g., P, R, N, D, L, or any numerical
value indicated thereon). Once the target speed is defined by the
user based on the gear shift position, during SSC control, the SSC
system manipulates the torque produced by the vehicle's engine 50
and the brake pressure produced by the vehicle's brake system 60.
As will be discussed in more detail below with respect to FIGS. 4A
and 4B, the exemplary SSC system features a target speed for each
gear ratio provided in the automatic transmission and the target
speeds are stored in the SSC controller 100. Furthermore, the
target speed for each gear ratio is set for operation on level
ground, but the SSC system is further configured to adjust the gear
ratio based on the grade the vehicle is traveling on. In the
exemplary embodiment, the target speed will be adjusted downward
whenever the vehicle is on a graded slope traveling downhill. The
downward adjustment is a factor of the steepness of the graded
slope.
[0036] It should be understood that in order to adjust the target
speed during SSC control, the user can adjust the gear shift
selector, which controls the target speed. In one refinement of the
inventive system, the driver can also adjust the target speed by
manipulating the "+" and "-" buttons of the cruise control
mechanism. It should also be appreciated that while the target
speed corresponds to the user selected gear position of the gear
shift selector, the transmission is not necessarily in the same
gear as the user selected gear position. For example, even if the
gear shift selector is in 3rd gear, the transmission may be in 1st,
2nd or 3rd based on the engine torque requirements necessary to
ensure the vehicle is traveling at the target speed. In other
words, the gear shift selector serves as designation for the
maximum or highest gear during SSC control, but the SSC controller
100 controls the gear ratio independently of the gear designated by
the gear shift selector.
[0037] FIG. 4A is an exemplary table listing target speeds of the
SSC system for an exemplary transmission in a vehicle operated on a
variety of grades. The target speeds of FIG. 4A are for exemplary
purposes only, however, it should be appreciated that the target
speed will increase as the indicated gear increases. As shown, the
target speed for 1st gear is 1.3 mph, the target speed for 2nd gear
is 2.7 mph, and so forth. In other words, once the user instructs
the vehicle to operate in SSC, the user can position the gear shift
selector to designate the specific target speed for SSC operation.
When the vehicle is traveling on level ground or uphill (or only
slightly downhill), the SSC controller 100 will request engine
torque as necessary (as described in detail above) to ensure the
vehicle travels at the corresponding target speed. If the vehicle
is traveling downhill, sensors 30 will provide a signal indicative
of the grade (see the left column of FIG. 4A) and the SSC
controller 100 will determine the corresponding target speed based
on both the position of the gear shift selector and the grade. For
example, when the gear shift selector is in third gear and the
vehicle is traveling at a 30% downhill grade, the target speed is
3.0 mph. Accordingly, the SSC controller 100 will output signals
accordingly to the braking system to manipulate brake pressure to
maintain the target speed. It is reiterated that the actual speed
values shown in FIG. 4A are for illustrative purposes only and that
the invention is in no way intended to be limited by these speed
values. Further, as shown in FIG. 4A, the grade % is in five
percent increments. Accordingly, in the exemplary embodiment, it is
contemplated that if the actual vehicle incline is between two
grades, the SSC controller 100 will round up or down accordingly.
It should be understood, however, grade percentages should not be
limited to five percent increments and that in an alternative
embodiment, a target speed could be provided in one percent
increments, etc.
[0038] As discussed in detail above, once the target speed is
determined by the SSC controller 100, to maintain the target speed,
the SSC system selectively requests engine torque from the
vehicle's engine or increases brake pressure of the vehicle's
brakes. In one embodiment, the SSC system may request torque from
the vehicle's engine when travelling down a grade of 3% or more. In
one embodiment, the SSC system may request a maximum of 160 Nm of
torque ("SSC torque limit") from the vehicle's engine. Furthermore,
the SSC system can request a maximum of more or less than 160 Nm of
torque from the vehicle's engine. In one embodiment, the maximum
torque requested by the SSC system from the engine requested may
vary in accordance with the grade on which the vehicle is
travelling. For example, the maximum permissible torque may
increase in relation to an increase in the grade upon which the
vehicle is travelling. In one embodiment, the maximum permissible
torque decreases in relation to an increase in a grade that the
vehicle is travelling. In one embodiment, the SSC system may
request maximum torque for a constant duration of less than 10
seconds, when the vehicle is moving, and less than 10 seconds when
the vehicle is stationary. In one embodiment, the SSC system may
only request maximum torque for a constant duration of more or less
than 10 seconds when the vehicle is moving and more or less than 10
seconds when the vehicle is stationary. In one embodiment, the
maximum permissible torque is higher when the vehicle is operated a
low range mode than in a four wheel high mode. While FIG. 4A
establishes a target speed for each gear position and grade, the
driver may override the target speed using the vehicle's
accelerator and/or brake.
[0039] It is reiterated that FIG. 4A provides one exemplary design
implementation for the SSC control system and method described
herein. It is contemplated that the settings illustrated in FIG. 4A
are set during manufacture of the SSC control system and/or set by
modifying/updating the software for the system accordingly. The
control speed settings of FIG. 4A are provided for exemplary
purposes.
[0040] FIG. 4B illustrates an alternative exemplary table listing
target speeds of the SSC system. In this embodiment, the ratio
between gear and target speed for a 0% grade is on a linear scale.
For example, the target speed for 1st gear is 1 kph, the target
speed for 2nd gear is 2 kph, the target speed for 3rd gear is 3
kph, and so forth. As further shown in FIG. 5, the target speed of
the vehicle will be adjusted based on grade. As shown, the right
column illustrates the target speed at 100% to be 1 kph for all
gears, although it should be appreciated that the exemplary 100%
grade if theoretical and simply shown to illustrate that the target
speed will decrease between 0% and 100% grade (except for
"reverse", "neutral" and "drive" gears that always operated at 1
kph in this embodiment). In one embodiment, the SSC system is
configured to interpolate interim speeds when the grade is changing
and can consider hysteresis to avoid highly dynamic speed
targets.
[0041] FIG. 5 illustrates an exemplary flowchart of SSC system
operation during driver override in accordance with an exemplary
embodiment of the present invention. Initially, at Step 510 the SSC
controller 100 calculates a target speed based on the position of
the gear shift selector and the grade of ground being traversed by
the vehicle, as discussed in detail above. Next, at Steps 515A and
515B, the SSC controller 100 calculates control errors for the SSC
brake controller component and SSC engine controller component of
the SSC controller 100. At Step 520A and 520B, the SSC controller
100 then applies any necessary brake torque requests (Step 520A)
and torque requests (Step 520B) to ensure the vehicle is operating
at the target speed. It should be understood that these request
take into account error values, if any, calculated at Steps 515A
and 515B, respectively.
[0042] Steps 525A and 525B are illustrative of driver override.
Specifically, if the driver depresses the accelerator and/or brake
pedal, the PC module 225 transmits a signal (quantified by a
percentage) of the position of the respective pedals to the EBC
module 210. The EBC module 210 (i.e., the SSC controller 100)
performs a comparison at each of Steps 525A and 525B to determine
whether an override is required.
[0043] At Step 525A, if the brake request is greater than "0", the
SSC controller 100 will generate a brake torque request because the
system has determined that the driver wishes to go slower than the
operating target speed (Step 530A). If the brake request is "0"
then the SSC controller 100 will take no further action regarding
brake torque request at that time (Step 535A). It should be
appreciated that in an alternative embodiment, the comparison value
"0" can be some other value greater than 0.
[0044] Similar, at Step 525B, the SSC controller 100 will compare
the driver requested torque with the current value of engine torque
being requested by the SSC system to maintain the target speed. If
the SSC engine torque is greater than the driver torque request,
the SSC controller 100 will continue to output the SSC engine
torque request (Step 535B). However, if the driver torque request
is greater than the engine torque request, the SSC controller 100
will generate an additional torque request to mirror the driver's
request (Step 530B).
[0045] It should be appreciated that in the exemplary embodiment,
the two parallel legs of the process illustrated in FIG. 5 (for
brake torque and engine torque) are being performed concurrently.
However, in an alternative embodiment, these checks can be
performed in sequence or the like. Furthermore, it should be
appreciated that this process is being performed continuously and
that the brake torque request and engine torque requests are
constantly being adjusted to ensure that the vehicle is traveling
at a smooth and consistent speed (except when driver override
dictates that the vehicle travels faster or slower than the target
speed.
[0046] Further, it is noted that in the exemplary embodiment,
during acceleration or deceleration due to driver override, the SSC
system is not turned off or disabled. Rather, the SSC system
maintains the driver input speed based on the accelerator or brake
pedal position instead of the target speed. When the accelerator is
depressed and the torque requested by the driver is less than the
SSC torque limit (160 Nm in the example above), the SSC torque
limit will remain in effect even though the driver has depressed
the accelerator. However, if the torque requested by the driver
exceeds the SSC torque limit, the SSC system will permit the engine
to produce the torque requested by the driver for the duration of
the driver's command. Once the driver releases the accelerator, the
SSC system will gradually return to the target speed of FIG. 3 in a
smooth manner. In one embodiment, this operation depends on the
vehicle speed. Thus, it is contemplated that the SSC system will
not reduce from a high rate a speed, rather, once the driver gets
below a configurable parameter speed the SSC system will become
active and begin controlling the PC module 225, the TC module 230
and brakes to operate at the target speed.
[0047] As stated above, the driver may also depress the brake pedal
and, thereby, cause the vehicle to move slower than the target
speeds of FIG. 4A or 4B. This new speed becomes the driver input
speed and is maintained by the SSC system. Again, it is noted that
during this braking, the SSC system is not turned off or disabled,
even if the vehicle is brought to a complete stop. Once the driver
releases the brake pedal, the SSC system will gradually return to
the target speed of FIG. 4A or FIG. 4B in a smooth manner.
[0048] The SSC system smoothly transitions from the target speed to
the driver input speed and, conversely, from the driver input speed
to the target speed. In one embodiment, the rate at which the SSC
system transitions from the target speed to the driver input speed
or vice versa is dependent upon the difference in the engine torque
or braking force called for by the target speed and the driver
input speed. In one embodiment, the grade upon which the vehicle is
operating may also be taken into account.
[0049] The gear in which the transmission is operated is determined
by the SSC system. In one embodiment, the default gear in which the
transmission is operated is first gear (i.e., the lowest gear ratio
in the automatic transmission). In one embodiment, the transmission
is shifted out of first gear and into decreasing gear ratios (i.e.,
second gear, third gear, etc.) when a higher target speed is
selected by the driver of the vehicle. For example, a higher gear
may be selected at higher vehicle speeds. In one embodiment, other
factors such as the grade upon which the vehicle is travelling may
be taken into account when selecting the gear that the transmission
is operated in. In one embodiment, the SSC system changes through
gear ratios sequentially and, for example, does not jump from the
lowest gear ratio directly to the third lowest gear ratio. In one
embodiment, the SSC system allows a driver to operate the vehicle
while applying both the accelerator and the brakes at the same
time.
[0050] Thus, a method of operating an automatic transmission that
simulates the driving experience of a manual transmission in an
off-road setting is provided. The method manipulates the engine
torque and brakes of the vehicle in response to driver throttle and
brake commands to maintain an approximately constant speed desired
by the driver.
[0051] In addition, for the SSC system and method discussed above,
it is contemplated that in one embodiment, the vehicle can be
provided with a Select Terrain dial/switch in which the vehicle is
configured to customize/tailor the SSC operation according to the
driving terrain (e.g., rock, mud, sand, snow, etc.). In one
embodiment, the device is configured to identify the driving
terrain according to appropriate sensors as would be understood to
one skilled in the art and provided by the DTC module discussed
above as a terrain mode status signal ("TerMd_Sts"). Alternatively,
the SSC system includes a driver operable dial/switch that enables
the driver to select the driving condition/terrain.
[0052] In the exemplary embodiments, based on the selected terrain
of the Select Terrain switch, the SSC system operates according to
the following calibrations/modifications: (1) "rock" mode--slower
engine builds, more active braking, emulate two foot driver
operation, possible grade dependent engine builds, differential
(e-Locker or ELSD) more aggressively coupled; (2) "auto"
mode--control is geared more toward driver comfort and smoothness,
no two foot driving emulation (less brake interventions), less
aggressive ELSD coupling; (3) "mud" mode--similar characteristics
to the "auto" terrain mode, but this mode controls the engine to
build faster to dig into the surface better; (4) "sand"
mode--similar characteristics to the "auto" terrain mode, but this
mode controls the engine to build faster to dig into the surface
better; and (5) "snow" mode--similar characteristics to the "auto"
terrain mode. It should be appreciated that these modes and
respective calibrations are provided as examples to indicate that
the SSC system can be configured to operate according to driving
terrain and condition. To achieve the appropriate response
according to the selected terrain mode, the SSC controller 100
while operate the SSC engine controller component as discussed
above and as would be understood to one skilled in the art.
* * * * *