U.S. patent application number 14/029269 was filed with the patent office on 2015-03-19 for hill rollback speed control.
The applicant listed for this patent is Robert Bosch GmbH. Invention is credited to Ravikumar Bhadange, Qingyuan Li, George Thomas.
Application Number | 20150081182 14/029269 |
Document ID | / |
Family ID | 51398878 |
Filed Date | 2015-03-19 |
United States Patent
Application |
20150081182 |
Kind Code |
A1 |
Li; Qingyuan ; et
al. |
March 19, 2015 |
HILL ROLLBACK SPEED CONTROL
Abstract
A hill rollback control system and method for controlling a
rollback speed of a motor vehicle with wheel brakes. Upon
ascertaining that the vehicle is rolling back, the system and
method determine, based on a grade angle of the terrain that the
vehicle is traveling on and a temperature of a transmission, a
target rollback speed for the vehicle. The target rollback speed is
lower when the grade of the terrain is above a threshold value.
Also, the target rollback speed is lower when the temperature of
the transmission is above a threshold value. The actual rollback
speed of the vehicle is set and maintained at the target rollback
speed by applying the vehicle's wheel brakes.
Inventors: |
Li; Qingyuan; (Ann Arbor,
MI) ; Thomas; George; (Westland, MI) ;
Bhadange; Ravikumar; (Farmington, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Robert Bosch GmbH |
Stuttgart |
|
DE |
|
|
Family ID: |
51398878 |
Appl. No.: |
14/029269 |
Filed: |
September 17, 2013 |
Current U.S.
Class: |
701/53 ;
477/92 |
Current CPC
Class: |
B60W 10/184 20130101;
Y10T 477/644 20150115; B60T 7/122 20130101; B60W 10/11 20130101;
B60T 2201/06 20130101 |
Class at
Publication: |
701/53 ;
477/92 |
International
Class: |
B60W 10/184 20060101
B60W010/184; B60W 10/11 20060101 B60W010/11 |
Claims
1. A system for controlling a rollback speed of a motor vehicle
having wheel brakes, the system comprising: a driving direction
arbitration module configured to receive a first signal and output
an actual direction signal; a start/stop arbitration module
configured to receive the actual direction signal and a gear shift
signal, and generate a hill rollback control enable signal; a
vehicle speed limit module configured to a receive a terrain grade
angle signal, the vehicle speed limit module configured to set a
target rollback speed signal to a first predetermined value if a
value of the terrain grade angle signal is equal to or below a
grade threshold, and a second predetermined value if the value of
the terrain grade angle signal is above the grade threshold, a
vehicle brake control module configured to receive the hill
rollback control enable signal, the target rollback speed signal,
and a vehicle speed signal, and determine a brake control signal to
apply the wheel brakes to maintain the rollback speed of the
vehicle at a value of the target rollback speed signal.
2. The system of claim 1, wherein the second predetermined value is
less than the first predetermined value.
3. The system of claim 2, wherein the vehicle speed limit module is
configured to receive a transmission temperature signal.
4. The system of claim 3, where the vehicle speed limit module is
configured to set the target rollback speed signal to a third
predetermined value if the value of the terrain grade angle signal
is equal to or below the grade threshold and a value of the
transmission temperature signal is above a temperature threshold,
and a forth predetermined value if and the value of the terrain
grade angle signal is above the grade threshold and the value of
the transmission temperature signal is equal above the temperature
threshold.
5. The system of claim 4, wherein the third predetermined value is
less than the first predetermined value, the fourth predetermined
value is less than the second predetermined value, and the fourth
predetermined value is less than the third predetermined value.
6. The system of claim 1, wherein the first predetermined value and
the second predetermined value are based on an exact value of the
terrain grade angle signal.
7. The system of claim 1, wherein the first signal is at least one
of a wheel direction signal and a transmission output shaft sensor
direction signal.
8. The system of claim 1, wherein the start/stop arbitration module
receives a driver brake request signal.
9. The system of claim 1, wherein the start/stop arbitration module
receives a plurality of vehicle state signals.
10. The system of claim 9, wherein the plurality of vehicle state
signals includes a brake overheat warning signal.
11. The system of claim 9, wherein the plurality of vehicle state
signals includes a hill-hold control brake request signal.
12. The system of claim 1, wherein the vehicle brake control module
receives a driver acceleration request signal.
13. A method for controlling a rollback speed of a vehicle having
wheel brakes, the method comprising: ascertaining, with a first
sensor, the direction that the vehicle is moving; determining,
using a module, if the vehicle is traveling in a direction opposite
from a direction associated with a current state of a gear shift
lever; ascertaining, with a terrain grade angle sensor, a grade
angle of the terrain; setting, using the module, a target rollback
speed to a first predetermined value if the grade angle of the
terrain is equal to or below a grade threshold, or a second
predetermined value if the grade angle of the terrain is above the
grade threshold, generating, using the module, a braking signal to
cause the vehicle to apply a value of pressure to the vehicle
brakes ascertaining, with the first sensor, the speed of the
vehicle; and adjusting, using the module, the braking signal if the
speed of the vehicle is not equal to the target rollback speed.
14. The method of claim 13, wherein the second predetermined value
is less than the first predetermined value.
15. The method of claim 14, wherein the method ascertains, with a
second sensor, a temperature of a transmission in the vehicle.
16. The method of claim 15, wherein the method sets, using the
module, the target rollback speed to a third predetermined value if
the grade angle of the terrain is equal to or below the grade
threshold and the temperature of the transmission is above a
temperature threshold; or a fourth predetermined value if the grade
angle of the terrain is above the grade threshold and the
temperature of the transmission is above the temperature
threshold.
17. The method of claim 16, wherein the third predetermined value
is less than the first predetermined value, the fourth
predetermined value is less than the second predetermined value,
and the fourth predetermined value is less than the third
predetermined value.
18. The method of claim 13, wherein the first predetermined value
and the second predetermined value are based on an exact value of
the grade angle of the terrain.
19. The method of claim 13, wherein the first sensor is at least
one of a plurality of wheel sensors and a transmission output shaft
sensor.
20. The method of claim 15, wherein the second sensor is a
temperature sensor.
Description
BACKGROUND
[0001] The present invention relates to vehicle control. More
particularly, embodiments of the invention relate to systems and
methods to control a rollback speed of a vehicle.
[0002] Passenger and other vehicles may be equipped with systems
that prevent the vehicle from rolling backward when the vehicle is
located on a hill. For example, a vehicle may travel up a hill or
an upward slope and come to stop at an intersection. At the
intersection, the driver presses a brake pedal to keep the vehicle
stopped. However, when continuing to travel, the brake pedal must
be momentarily released. Because the vehicle is positioned on an
incline, the vehicle may travel backwards.
[0003] In vehicles equipped with manual transmissions, it is known
to equip the vehicle with a device that holds the vehicle brakes
(for example, drum or disc brakes on the vehicle's wheels) until
the clutch is at a friction point. Such a device is an example of a
hill-hold control mechanism.
SUMMARY
[0004] While hill hold control is known generally, with the advent
of more sophisticated transmissions, for example, dual dry-clutch
transmission, more sophisticated mechanisms not just for hill-hold
control, but hill rollback control would be useful. The invention
provides, among other things, a module and method for controlling
the rollback speed of a motor vehicle having wheel brakes based on
the grade of the terrain and the temperature of the
transmission.
[0005] In one embodiment, the invention provides a system for
controlling a non-zero rollback speed of a motor vehicle with wheel
brakes. The system includes a driving direction arbitration module
that is configured to receive at least one of a wheel direction
signal and a transmission output shaft sensor direction signal. The
driving direction arbitration module outputs an actual direction
driving signal. The system further includes a start/stop
arbitration module configured to receive the actual direction
signal and a gear shift signal. The start/stop arbitration module
outputs a hill rollback control enable signal. The system further
includes a vehicle speed limit module that is configured to receive
a terrain grade angel signal. The vehicle speed limit module
generates a target rollback speed signal of a first predetermined
value if the value of the terrain grade angle signal is equal to or
below a grade threshold. The vehicle speed limit module further
generates a target rollback speed signal of a second predetermined
value if the value of the terrain grade angle signal is above the
grade threshold. The system further includes a vehicle brake
control module that is configured to receive the hill rollback
control enable signal, the target rollback speed signal, and a
vehicle speed signal. The vehicle brake control module determines a
brake control signal to apply the wheel brakes to maintain the
rollback speed of the vehicle at a value of the target rollback
speed signal.
[0006] In another embodiment, the invention provides a method of
controlling a non-zero rollback speed of a vehicle having wheel
brakes. A first sensor ascertains the direction that the vehicle is
moving. A module determines if the vehicle is traveling in a
direction opposite from a direction associated with a current state
of a gear shift lever. A terrain grade angle sensor ascertains a
grade angle of the terrain. The module sets a target rollback speed
to a first predetermined value if the grade angle of the terrain is
equal to or below a grade threshold. The module further sets the
target rollback speed to a second predetermined value if the grade
angle of the terrain is above the grade threshold. The method
generates a braking signal to cause the vehicle to apply a value of
pressure to the vehicle brakes. The first sensor ascertains the
speed of the vehicle. The module adjusts the braking signal is the
speed of the vehicle is not equal to the target rollback speed.
[0007] In yet another embodiment, the invention provides a system
for controlling a non-zero rollback speed of a motor vehicle with
wheel brakes. The system includes a driving direction arbitration
module that is configured to receive at least one of a wheel
direction signal and a transmission output shaft sensor direction
signal. The driving direction arbitration module outputs an actual
direction driving signal. The system further includes a start/stop
arbitration module configured to receive the actual direction
signal and a gear shift signal. The start/stop arbitration module
outputs a hill rollback control enable signal. The system further
includes a vehicle speed limit module that is configured to receive
a terrain grade angel signal and a transmission temperature signal.
The vehicle speed limit module generates a target rollback speed
signal of a first predetermined value if the value of the terrain
grade angle signal is equal to or below a grade threshold and the
value of the transmission temperature signal is below a temperature
threshold. The vehicle speed limit module further generates a
target rollback speed signal of a second predetermined value if the
value of the terrain grade angle signal is above the grade
threshold and the value of the transmission temperature signal is
below a temperature threshold. The vehicle speed limit module
further generates a target rollback speed signal of a third
predetermined value if the value of the terrain grade angle signal
is equal to or below the grade threshold and the value of the
transmission temperature signal is above a temperature threshold.
The vehicle speed limit module further generates a target rollback
speed signal of a forth predetermined value if the value of the
terrain grade angle signal is above the grade threshold and the
value of the transmission temperature signal is equal above the
temperature threshold. The system further includes a vehicle brake
control module that is configured to receive the hill rollback
control enable signal, the target rollback speed signal, and a
vehicle speed signal. The vehicle brake control module determines a
brake control signal to apply the wheel brakes to maintain the
rollback speed of the vehicle at a value of the target rollback
speed signal.
[0008] In yet another embodiment, the invention provides a method
of controlling a non-zero rollback speed of a vehicle having wheel
brakes. A first sensor ascertains the direction that the vehicle is
moving. A module determines if the vehicle is traveling in a
direction opposite from a direction associated with a current state
of a gear shift lever. A terrain grade angle sensor ascertains a
grade angle of the terrain. A second sensor ascertains a
temperature of a transmission in the vehicle. The module sets a
target rollback speed to a first predetermined value if the grade
angle of the terrain is equal to or below a grade threshold and the
temperature of the transmission is equal to or below a temperature
threshold. The module further sets the target rollback speed to a
second predetermined value if the grade angle of the terrain is
above the grade threshold and the temperature of the transmission
is equal to or below the temperature threshold. The module sets a
target rollback speed to a third predetermined value if the grade
angle of the terrain is equal to or below the grade threshold and
the temperature of the transmission is above the temperature
threshold. The module further sets the target rollback speed to a
fourth predetermined value if the grade angle of the terrain is
above the grade threshold and the temperature of the transmission
is above the temperature threshold. The method generates a braking
signal to cause the vehicle to apply a value of pressure to the
vehicle brakes. The first sensor ascertains the speed of the
vehicle. The module adjusts the braking signal is the speed of the
vehicle is not equal to the target rollback speed.
[0009] Other aspects of the invention will become apparent by
consideration of the detailed description and accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates a vehicle on an incline and movement of
the vehicle in a direction that is opposite to the direction
associated with a forward gear selection.
[0011] FIG. 2 illustrates a schematic of a hill rollback speed
control system or module according to one embodiment of the
invention.
[0012] FIG. 3 illustrates the internal structure of a hill rollback
speed control system or module according to one embodiment of the
invention.
[0013] FIG. 4 illustrates an embodiment of the operation of the
hill rollback speed control system or module as shown in FIG.
2.
[0014] FIG. 5 is a graphical illustration of how a hill rollback
speed control system or module operates in cooperation with a hill
hold control module.
DETAILED DESCRIPTION
[0015] Before any embodiments of the invention are explained in
detail, it is to be understood that the invention is not limited in
its application to the details of construction and the arrangement
of components set forth in the following description or illustrated
in the following drawings. The invention is capable of other
embodiments and of being practiced or of being carried out in
various ways.
[0016] Also, it is to be understood that the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting. The use of "including,"
"comprising" or "having" and variations thereof herein is meant to
encompass the items listed thereafter and equivalents thereof as
well as additional items. The terms "mounted," "connected" and
"coupled" are used broadly and encompass both direct and indirect
mounting, connecting and coupling. Further, "connected" and
"coupled" are not restricted to physical or mechanical connections
or couplings, and can include electrical connections or couplings,
whether direct or indirect. Also, electronic communications and
notifications may be performed using other known means including
direct connections, wireless connections, etc.
[0017] It should also be noted that a plurality of hardware and
software based devices, as well as a plurality of different
structural components may be utilized to implement the invention.
Furthermore, and as described in subsequent paragraphs, the
specific configurations illustrated in the drawings are intended to
exemplify embodiments of the invention. Alternative configurations
are possible.
[0018] FIG. 1 illustrates a vehicle 100 having a front 102 and a
rear 104 on a terrain 105. In this embodiment, the terrain is an
incline. The vehicle 100 includes four wheels 110, 112, 114, and
116. Each wheel is equipped with a brake (such as a disc brake or
drum brake) 120, 122, 124, and 126, and four wheel sensors 130,
132, 134, and 136. A typical vehicle brake system is hydraulic.
However, embodiments of the invention could be implemented with
electrically-actuated brakes or other types of braking systems. The
vehicle includes other components including a controller 140, a
transmission 142, and an engine 144. In one embodiment, the
controller 140 is part of vehicle brake and electronic stability
control system such as the ESP.RTM. control system from Robert
Bosch GmbH. A driver of the vehicle generates control inputs using
a steering wheel 150, a gear shift lever 152, a brake pedal 154,
and an accelerator pedal 156. Shifting of the gear shift lever
generates a driver gear shift request signal (discussed below).
Actuation of the brake pedal generates a driver brake request
signal (also discussed below). Actuation of the accelerator pedal
generates a driver acceleration signal (also discussed below).
[0019] When the vehicle 100 is on the terrain 105, gravitational
forces act on the vehicle in such a manner that the vehicle will
travel in the direction indicated by the arrow Al, unless an
opposing force, such as torque generated by the engine 144 and
transmitted to the wheels 110, 112, 114, and 116 of the vehicle or
a braking force generated by the brakes 120, 122, 124, and 126,
acts on the vehicle to, for example, maintain the vehicle in a
stationary position or cause the vehicle to move in a forward
direction, indicated by arrow A2. It should be understood that an
uphill driving scenario or situation occurs when the front 102 of
the vehicle is facing the crest of the incline and the vehicle is
moving toward the crest. A downhill driving scenario or situation
occurs when the back 104 of the vehicle is facing the crest of the
incline and the vehicle is moving away from the crest. In an uphill
driving scenario, where the vehicle is travelling in the direction
of arrow A2, stops on the incline and remains stationary for some
period of time, and thereafter resumes travel in the direction of
arrow A2, there is a short period of time where it is possible for
the vehicle to move in the direction of arrow A1, or rollback. This
rollback is possible because there is a lag between the time when a
driver releases the brakes (removes his or her foot from the brake
pedal 154) to stop requesting actuation of the brakes (for example,
a zero brake request signal) and the time that the driver uses the
accelerator pedal 156 to make a torque request (for example, a
non-zero driver acceleration signal) in which the actual torque
generated in response to that request is sufficient to overcome the
gravitational forces acting on the vehicle and move it forward in
the direction of A2.
[0020] FIG. 2 is a schematic illustration of a hill-rollback
control ("HRC") module 200 according to one embodiment of the
invention. In general terms, the HRC module maintains the rollback
speed (i.e., a non-zero speed) of a vehicle 100 in uphill driving
scenarios. The HRC module is located in the controller 140. The
controller also includes a hill-hold control ("HHC") module 202, an
electronic processing unit 204, a memory 206, and an input/output
interface 208. The input/output interface connects the controller
to external devices such as sensors. In one embodiment, the
input/output interface is connected to a controller area network
("CAN") bus 210. A CAN bus is a known vehicle network through which
various vehicle systems can transmit and receive information. The
controller receives signals from a plurality of sensors. In one
embodiment, communications between the controller and the sensors
occur over the CAN bus. However, it is possible to connect the
sensors (via wired or wireless connection) directly to the
controller.
[0021] The plurality of sensors include: a terrain grade angle
sensor 214, four wheel sensors 130, 132, 134, and 136, a
transmission temperature sensor 242, a gear shift sensor 252, a
brake pedal sensor 254, and an accelerator pedal sensor 256. The
terrain grade angle sensor determines the grade angle of the
terrain 105 that the vehicle 100 is traveling on. The wheel sensors
determine the direction and speed that the wheels 110, 112, 114,
and 116 are turning. The transmission temperature sensor is located
in the transmission 142 and determines the temperature of the
transmission. The gear shift sensor determines the position of the
gear shift lever 152 (e.g., park (P), reverse (R), neutral (N), and
drive (D) in an automatic transmission). The brake pedal sensor
determines if the driver is actuating the brake pedal 154. The
accelerator pedal sensor determines if the driver is actuating the
accelerator pedal 156.
[0022] FIG. 3 illustrates the internal structure of a HRC module
200 according to one embodiment of the invention. The HRC module
contains four sub-modules including a Driving Direction Arbitration
Module ("DDAM") 310, a Start/Stop Arbitration Module ("SSAM") 320,
a Vehicle Speed Limit Module ("VSLM") 340, and a Vehicle Brake
Control Module ("VBCM") 350. The DDAM determines the actual
direction that the vehicle 100 is moving. In one embodiment, the
DDAM makes this determination using wheel direction signals 312,
313, 314, and 315 received from each of the wheel sensors 130, 132,
134, and 136. The wheel direction signals indicate the direction
that each of the wheels 120, 122, 124, and 126 are turning. In
another embodiment, the DDAM makes this determination using a
transmission output shaft sensor ("TOSS") direction signal 318
received from a sensor in the transmission 142. The TOSS direction
signal is an electrical signal that represents the direction of
transmission output shaft rotation. In another embodiment, the DDAM
receives and compares both the wheel direction signals and the TOSS
direction signal to determine the direction that the vehicle is
moving. The DDAM generates an actual direction signal 322 which
represents the actual direction that the vehicle is moving.
[0023] The SSAM 320 determines if the HRC module 200 should be
enabled. In one embodiment, the SSAM receives the actual direction
signal 322 from the DDAM 310 and a gear shift signal 324 from the
gear shift sensor 252. The SSAM uses the gear shift signal to
determine the direction which the driver intends the vehicle 100 to
move. For example, if the gear shift signal is set to DRIVE, then
the direction that the driver intends the vehicle to move is
forward (i.e., in the direction of arrow A2). If the actual
direction signal indicates that vehicle is moving backward (i.e.,
in the direction of arrow A1) and the gear shift signal is set to
DRIVE, the SSAM identifies that the vehicle is rolling back and the
HRC module 200 should be enabled. The SSAM enables the HRC module
by generating a HRC enable signal 326.
[0024] In another embodiment, the SSAM 320 additionally receives a
driver brake request signal 328 from the brake pedal sensor 254. If
the driver brake request signal indicates that the brake pedal 154
is actuated, the SSAM will not generate the HRC enable signal 326.
In another embodiment, the SSAM 320 additionally receives a
plurality of vehicle state signals 330. In one embodiment, the
vehicle state signals include a brake overheat warning signal. In
another embedment, the vehicle state signals include a HHC brake
request signal. If the SSAM receives the brake overheat warning
signal or the HHC brake request signal, the SSAM will not generate
the HRC enable signal 326.
[0025] The VSLM 340 determines a target rollback speed of the
vehicle 100 for the HRC module 200 to maintain. In one embodiment,
the VSLM receives a terrain grade angle signal 344 from the terrain
grade angle sensor 214. If the grade angle of the terrain,
represented by the terrain grade angle signal, is less than or
equal to a grade threshold value, the VSLM sets the target rollback
speed signal 348 to a first predetermined value, for example 6
kilometers per hour ("KPH"). Alternatively, if the grade angle of
the terrain is greater than the grade threshold value, the VSLM
sets the target rollback speed signal to a second predetermined
value, for example 4 KPH. In some embodiments, the second
predetermined value is less than the first predetermined value. In
some embodiments, the second predetermined value is based on the
exact value of grade angle.
[0026] In another embodiment, the VSLM 340 additionally receives a
transmission temperature signal 342 from the transmission
temperature sensor 242. If the grade angle of the terrain is less
than or equal to the grade threshold value and the temperature of
the transmission, represented by the transmission temperature
signal, is greater than a temperature threshold value, the VSLM
sets the target rollback speed signal 348 to a third predetermined
value, for example 5 KPH. Alternatively, if the grade angle of the
terrain is greater than the grade threshold value and the
temperature of the transmission is greater than the temperature
threshold value, the VSLM sets the target rollback speed signal to
a fourth predetermined value, for example 3 KPH. In some
embodiments, the third predetermined value is less than the first
predetermined value and the fourth predetermined value is less than
the first predetermined value.
[0027] The VBCM 350 determines the necessary pressure to apply the
brakes 120, 122, 124, and 126 of the wheels 110, 112, 114, and 116
in order to maintain the rollback speed of the vehicle 100 at the
value specified by the target rollback speed signal 348. The VBCM
receives the HRC enable signal 326 from the SSAM 320, the target
rollback speed signal from the VSLM 340, a driver acceleration
request signal 352 from the accelerator pedal sensor 256, and a
vehicle speed signal 354 from at least one of the wheel sensors
130, 132, 134, and 136. When the VBCM receives the HRC enable
signal, it compares the vehicle speed signal to the target rollback
speed signal. If the vehicle speed signal is not equal to the
target rollback speed signal (i.e. the vehicle is rolling back
faster or slower than the target rollback speed), the VBCM
calculates the necessary force for the brakes to apply to the
wheels in order to set the vehicle speed at the target speed,
indicated by the target rollback speed signal. The VBCM causes the
calculated force to be applied to the brakes by generating and
transmitting a brake control signal 356 to the brakes.
Additionally, the VBCM will not generate the brake control signal
to apply pressure to the brakes if the driver acceleration request
signal indicates that the driver is requesting enough torque for
the vehicle to move in the forward direction of arrow A2.
[0028] FIG. 4 illustrates an embodiment of the operation of the HRC
module 200 as shown in FIG. 2. First, the HRC module ascertains the
direction that the vehicle 100 is moving in (S400). Then, the HRC
module determines if the vehicle is rolling back (S405). If the
vehicle is rolling back, the HRC module ascertains the grade angle
of the terrain (S410). In some embodiments, the HRC module
additionally ascertains the temperature of the transmission 142
(S415). Then the HRC module determines if the grade angle of the
terrain is above than a grade threshold (S420). In some embodiment,
the HRC module additionally determines if the temperature of the
transmission is above than a temperature threshold (S425, S430). If
the grade angle of the terrain is equal to or below the grade
threshold and the temperature of the transmission is equal to or
below the temperature threshold, the HRC module sets the target
rollback speed to a first predetermined value (e.g., 6 KPH) (S435).
Alternatively, if the grade angle of the terrain is above the grade
threshold and the temperature of the transmission is equal to or
below the temperature threshold, the HRC module sets the target
rollback speed to a second predetermined value (e.g., 4 KPH)
(S440). Alternatively, if the grade angle of the terrain is equal
to or below the grade threshold and the temperature of the
transmission is above the temperature threshold, the HRC module
sets the target rollback speed to a third predetermined value
(e.g., 5 KPH) (S445). Alternatively, if the grade angle of the
terrain is above the grade threshold and the temperature of the
transmission is above the temperature threshold, the HRC module
sets the target rollback speed to a fourth predetermined value
(e.g., 3 KPH) (S450). Next, in the some embodiments, the HRC module
applies an initial pressure to the brakes 120, 122, 124, and 126 of
the vehicle (S455). Then, the HRC module ascertains the speed of
the vehicle (S460). Next, the HRC module determines if the speed of
the vehicle is equal to the target rollback speed (S465). If the
speed of the vehicle is equal to the target rollback speed, the HRC
module maintains the pressure applied to the brakes of the vehicle
(S470). If the speed of the vehicle is not equal to target rollback
speed, the HRC module adjusts the pressure applied to the brakes of
the vehicle (S475). It is to be understood that the HRC module
increases the pressure applied to the brakes if the speed of the
vehicle is above the target rollback speed and decreases the
pressure applied to the brakes of the vehicle of the speed of the
vehicle is below the target rollback speed.
[0029] FIG. 5 graphically illustrates how the HRC module 200
operates in cooperation with the HHC module 202. The horizontal
axis of the graph 500 represents time with units in seconds. The
vertical axis of the graphs represents both brake caliper pressure
with units in bars and the speed of the vehicle 100 with units in
KPH. The driver releases the brake pedal 154 and the pressure
applied to the brakes 120, 122, 124, and 126 as a result of the
driver input decreases as shown in graph (T502). Even though the
driver is not pressing on the brake pedal, the vehicle does not
move because the HHC module is applying pressure to the brakes.
When the pressure applied to the brakes as a result of the driver
pressing on the brake pedal reaches a minimum value of 5 bar, the
HHC module ascertains that the driver has released the brake pedal
(T504). After a set delay period, the HHC module releases the
pressure applied to the brakes in two phases (T506). The pressure
applied to the brakes by the HHC module reaches a minimum value
when it is insufficient to overcome the force of gravity and the
vehicle begins to rollback (T508). The pressure applied to the
brakes by the HHC module reaches a minimum value at which time the
HRC module detects that the vehicle is rolling back. The HRC module
then starts to apply pressure to the brakes in order to maintain
the vehicle at a target speed of 6 KPH (T510).
[0030] Thus, the invention provides, among other things, a hill
rollback control mechanism that controls a rollback speed of a
vehicle based on a grade angle of a terrain and a temperature of a
transmission. Various features and advantages of the invention are
set forth in the following claims.
* * * * *