U.S. patent application number 10/604464 was filed with the patent office on 2005-01-27 for hill holding brake system for hybrid electric vehicles.
This patent application is currently assigned to FORD GLOBAL TECHNOLOGIES, LLC.. Invention is credited to Cikanek, Susan Rebecca, Sureshbabu, Natarajan.
Application Number | 20050017580 10/604464 |
Document ID | / |
Family ID | 32825607 |
Filed Date | 2005-01-27 |
United States Patent
Application |
20050017580 |
Kind Code |
A1 |
Cikanek, Susan Rebecca ; et
al. |
January 27, 2005 |
HILL HOLDING BRAKE SYSTEM FOR HYBRID ELECTRIC VEHICLES
Abstract
A hill holding function of a hybrid electric vehicle is
initiated when the powertrain control module determines that a hill
holding condition exists. In the hill holding condition, the
electro-hydraulic brakes will provide brake torque to each wheel
and the powertrain control module will turn off the internal
combustion engine. The system can also detect a two footer
condition where the vehicle operator requests both acceleration
torque and brake torque simultaneously. The hill holding function
of the hybrid electric vehicle in a two footer situation will apply
the electro-hydraulic brakes and turn off the internal combustion
engine. When the operator requests acceleration in either the hill
holding or the two footer condition, the electric brake controller
will transition the release of the electro-hydraulic brakes and the
powertrain control module will turn on the internal combustion
engine.
Inventors: |
Cikanek, Susan Rebecca;
(Wixom, MI) ; Sureshbabu, Natarajan; (Canton,
MI) |
Correspondence
Address: |
BROOKS KUSHMAN P.C./FGTL
1000 TOWN CENTER
22ND FLOOR
SOUTHFIELD
MI
48075-1238
US
|
Assignee: |
FORD GLOBAL TECHNOLOGIES,
LLC.
One Parklane Blvd. Suite 600 Parklane Towers East
Dearborn
MI
48126
|
Family ID: |
32825607 |
Appl. No.: |
10/604464 |
Filed: |
July 23, 2003 |
Current U.S.
Class: |
303/191 ;
903/947 |
Current CPC
Class: |
B60L 7/26 20130101; B60L
15/2063 20130101; B60K 6/46 20130101; B60L 2240/486 20130101; B60L
2240/36 20130101; B60W 2510/0283 20130101; Y02T 10/7072 20130101;
Y02T 10/72 20130101; B60L 2240/463 20130101; B60L 3/106 20130101;
B60L 2260/26 20130101; B60L 3/0076 20130101; B60W 2510/0291
20130101; B60W 2540/10 20130101; B60L 2240/507 20130101; B60L
2240/465 20130101; B60W 2520/10 20130101; B60W 2552/15 20200201;
B60L 50/61 20190201; B60L 2260/22 20130101; B60L 2240/32 20130101;
B60L 2240/461 20130101; B60L 2240/642 20130101; B60W 10/18
20130101; B60L 2240/12 20130101; B60W 2540/16 20130101; B60W 10/06
20130101; Y02T 90/16 20130101; Y02T 10/70 20130101; B60W 20/00
20130101; B60L 2240/423 20130101; B60L 2240/443 20130101; B60W
10/08 20130101; B60L 2250/26 20130101; B60W 2540/12 20130101; Y02T
10/62 20130101; B60W 20/12 20160101; B60W 2510/1015 20130101; Y02T
10/64 20130101 |
Class at
Publication: |
303/191 |
International
Class: |
B60T 008/32 |
Claims
1. A hybrid electric vehicle comprising: an internal combustion
engine configured to rotate in a single direction to selectively
drive a drive wheel and provide engine compression braking torque
to the drive wheel; an integrated starter generator motor connected
to the internal combustion engine that rotates in a same direction
as the internal combustion engine, the integrated starter generator
motor adapted to selectively start the internal combustion engine;
a powertrain control module that controls the operating parameters
of the internal combustion engine and the integrated starter
generator motor, the powertrain control module being selectively
actuated by a vehicle operator by actuating an accelerator pedal to
request an accelerator torque; an electro-hydraulic brake system
for vehicle braking, the electro-hydraulic brake system being
selectively actuated by the vehicle operator by actuating a vehicle
brake pedal to request a brake torque; an electronic brake
controller for controlling the brake torque applied to the drive
wheel by the electro-hydraulic brake system; and a vehicle rollback
sensor for determining a vehicle rollback state; wherein the
electronic brake controller actuates the electro-hydraulic, brake
system in a hill holding condition, when vehicle rollback is
detected, the requested brake torque is less than a first
predetermined level, the requested accelerator torque is less than
a second predetermined level, and the internal combustion engine is
running.
2. The hybrid electric vehicle of claim 1 wherein the powertrain
control module turns off the internal combustion engine in the hill
holding condition.
3. The hybrid electric vehicle of claim 1 wherein, the internal
combustion engine is started to provide torque to the drive wheel
and an adaptive filter is applied to decrease the brake torque
exerted by the electro-hydraulic braking system when the
accelerator pedal is actuated and the hybrid electric vehicle is in
a hill holding condition in which the hybrid electric vehicle is
stationary on an inclined surface.
4. The hybrid electric vehicle of claim 1 further comprising a
transmission having a plurality of gear ratios and wherein the
electronic brake controller does not actuate the electro-hydraulic
brake system during a vehicle creep condition, in which the
accelerator and brake pedals are not actuated, a gear ratio of the
transmission is engaged and the powertrain control module
determines whether vehicle creep will be powered by the internal
combustion engine, the integrated starter generator motor or
both;
5. The hybrid electric vehicle as set forth in claim 1 further
comprising a transmission having a plurality of gear ratios and
wherein the electronic brake controller actuates the
electro-hydraulic brake system during a predetermined two footer
condition in which, the hybrid electric vehicle is on a grade, the
transmission is in gear, the accelerator pedal and the brake pedal
are actuated, and the brake torque requested is greater than the
accelerator torque requested.
6. The hybrid electric vehicle as set forth in claim 5, wherein the
powertrain control module turns off the internal combustion engine
in the predetermined two footer condition.
7. A method of hill holding a hybrid electric vehicle comprising:
measuring a vehicle rollback state based on a first signal from a
vehicle rollback sensor; measuring a brake torque request based on
a second signal from a brake pedal sensor; measuring an accelerator
torque request based on a third signal from an accelerator pedal
sensor determining a running state of an internal combustion engine
based on a fourth signal from an engine sensor determining a
vehicle creep output by comparing a fifth signal from a vehicle
speed sensor to a predetermined vehicle creep speed: determining
whether hill holding condition exists based on the first, second,
third, and fourth signals and the vehicle creep output; actuating a
set of electro-hydraulic brakes in the hill holding condition.
8. The method as set forth in claim 7 further comprising turning
off the internal combustion engine while in the hill holding
condition.
9. The method as set forth in claim 8 further comprising,
de-actuating the electro-hydraulic brakes turning on the internal
combustion engine and accelerating the hybrid electric vehicle
using the internal combustion engine when the vehicle operator
actuates the accelerator pedal
10. The method as set forth in claim 7 further comprising detecting
a vehicle gear selection using a gear selection sensor calculating
presence of a two footer condition when second signal is greater
than the third signal, and actuating the electro-hydraulic brakes
while in the two footer condition.
11. The method as set forth in claim 10 further comprising turning
off the internal combustion engine in the two footer condition.
12. The method as set forth in claim 10 further comprising sensing
a vehicle acceleration request using the accelerator pedal sensor,
de-actuating the electro-hydraulic brakes turning on the internal
combustion engine and accelerating the hybrid electric vehicle
using the internal combustion engine.
Description
BACKGROUND OF INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to a braking system
for a hybrid electric vehicle and, more particularly, to a hill
holding brake system for a hybrid electric vehicle.
[0003] 2. Background Art
[0004] A conventional wheeled automotive vehicle includes an
internal combustion engine powered by fossil fuels. The desire to
reduce emissions and consumption of fossil fuels in an internal
combustion engine vehicle is well established.
[0005] An electric vehicle comprises a battery and an electrical
generator motor powerplant system to provide torque to a set of
wheels. However, electric vehicles have limited range, limited
power capabilities, and require a substantial amount of time to
recharge the battery. Additionally, electric vehicles require the
development of an extensive infrastructure to recharge the battery
and service the electric vehicles.
[0006] A hybrid electric vehicle includes a conventional internal
combustion engine powertrain and an electrical generator motor
powerplant. Hybrid electric vehicles reduce emissions and
consumption of fossil fuels. Hybrid electric vehicles address the
limitations of the electric vehicle relating to battery life,
vehicle range, vehicle performance, and vehicle infrastructure
development requirements.
[0007] Hybrid electric vehicles can have many different
configurations. A limited storage requirement hybrid electric
vehicle is one configuration having an internal combustion engine,
providing tractive power to the wheels, in combination with an
integrated starter generator motor powerplant, providing a small
amount of tractive torque to the wheels. The integrated starter
generator motor powerplant tractive torque is provided mainly as a
boost. The integrated starter generator motor starts the internal
combustion engine and charges the battery.
[0008] Vehicle operators prefer hybrid electric vehicles that have
braking and acceleration characteristics that are similar to a
conventional internal combustion engine vehicle with an automatic
transmission. Holding a vehicle on a hill when an operator's foot
is taken off of the brake pedal, called hill holding, is a
characteristic desired by vehicle operators. Hill holding in a
conventional vehicle occurs when the vehicle is on a hill, the
brake pedal and accelerator pedal are not actuated, and the
automatic transmission is engaged. The vehicle powertrain delivers
enough torque at idle from the internal combustion engine through
the transmission to the wheels to hold the vehicle on a hill. The
internal combustion engine in a hybrid electric vehicles wastes
fuel and produces undesirable emissions to hold the vehicle on a
hill because the internal combustion engine must continue to
operate while the vehicle is stopped.
[0009] The integrated starter generator motor in a hybrid electric
vehicle is capable of delivering enough torque to hill hold.
However, the use of the integrated starter generator motor in a
hybrid electric vehicle wastes battery power and requires
additional cooling during hill holding conditions.
[0010] U.S. Pat. No. 6,321,144 to Crombez, for example, discloses a
method and system for preventing roll back in an electric vehicle
and a hybrid electric vehicle. The rotary electric traction motor
disclosed in Crombez is capable of bi-directional operation and is
not directly connected to the internal combustion engine.
[0011] The present invention is directed to providing a robust hill
holding system that reduces emissions, increases battery range, and
reduces fuel consumption in a hybrid electric vehicle with an
integrated starter generator motor.
SUMMARY OF INVENTION
[0012] The present invention relates to a hill holding control
method and system for a hybrid vehicle having an internal
combustion engine, an integrated starter generator motor, and a
electro-hydraulic brake system that provides hydraulic brake torque
during a hill holding condition. The present invention improves the
operating efficiency and driveability of the hybrid electric
vehicle.
[0013] According to one aspect of the invention, a hybrid electric
vehicle is provided that includes an internal combustion engine
that rotates in a single direction and is connected to an
integrated starter generator motor. The integrated starter
generator motor is provided for starting the internal combustion
engine. The internal combustion engine and the integrated starter
generator motor may selectively drive a set of wheels and provide
brake torque at each driven wheel. A vehicle operator can
selectively actuate the electro-hydraulic brake system. An
electronic brake control system also controls the electro-hydraulic
brake system and controls the level of electro-hydraulic brake
torque applied to the wheels by the electro-hydraulic brake system.
The electronic brake control system actuates the electro-hydraulic
brake to hold the vehicle on a hill instead of using engine
compression braking torque or integrated starter generator motor
braking torque. A powertrain control module turns off the internal
combustion engine while the electro-hydraulic brakes are applied
during hill holding conditions.
[0014] When a vehicle operator requests acceleration during the
hill holding condition, the electronic brake control system reduces
electro-hydraulic brake torque at the wheels and the powertrain
control module turns on the internal combustion engine. A vehicle
transmission is engaged for seamless acceleration following the
hill holding brake application.
[0015] Another aspect of the invention relates to the method of
holding a hybrid electric vehicle on a hill. A vehicle roll-back
state, a vehicle brake pedal actuation measurement, a powertrain
pedal actuation measurement, and an internal combustion engine
running state are monitored by the powertrain control module to
determine if the hybrid electric vehicle is in a hill holding
condition. In a hill holding condition the electronic brake
controller actuates the electro-hydraulic brakes and the powertrain
control module turns off the internal combustion engine.
[0016] There are numerous benefits accruing to the method and
system of the present invention. For example, the method and
system:
[0017] 1) improves the operating efficiency of the hybrid electric
vehicle by not using the integrated starter generator motor to
provide this function and eliminates the need for additional
cooling for the integrated starter generator motor;
[0018] 2) improves the drive-ability of the hybrid electric
vehicle;
[0019] 3) is capable of holding the hybrid electric vehicle on a
hill of greater grade than present transmissions;
[0020] 4) allows a manual transmission vehicle to emulate the hill
holding function of a automatic transmission vehicle;
[0021] 5) allows automatic transmissions a more efficient method of
hill holding since the clutch pressure does not have to be
maintained to provide hill holding; and
[0022] 6) allows hill holding to be performed more efficiently than
present day transmission hill holding systems by not using the
transmission to provide this function saving energy by not keeping
the clutch pressure on and eliminating the need for additional
cooling for the transmission.
[0023] These and other aspects of the invention will be apparent to
one of ordinary skill in the art in view of the attached drawings
and following detailed description of the preferred embodiment.
BRIEF DESCRIPTION OF DRAWINGS
[0024] FIG. 1 is a schematic diagram illustrating a preferred
hybrid electric vehicle configuration on which the method of the
present invention can be implemented;
[0025] FIG. 2 is a schematic diagram illustrating a representative
torque controller for the hybrid electric vehicle's dual
powerplants;
[0026] FIG. 3 is a table of hybrid electric vehicle conditions
which dictate hill holding strategies;
[0027] FIG. 4 is a flowchart of vehicle transition when the engine
is on and the operator desires to creep the vehicle forward;
[0028] FIG. 5 is a flowchart of vehicle transition when the engine
is off and the operator desires to creep the vehicle forward;
[0029] FIG. 6 is a flowchart of vehicle transition for when the
engine is off;
[0030] FIG. 7 is a flowchart of vehicle transition for when the
engine is on;
[0031] FIG. 8 is a flowchart of vehicle transition for when the
engine is on with no electro-hydraulic brakes and the operator
desires to creep the vehicle forward;
[0032] FIG. 9 is a flowchart of vehicle transition for when the
engine is off with no electro-hydraulic brakes and the operator
desires to creep the vehicle forward;
[0033] FIG. 10 is a flowchart of vehicle transition for when the
engine is off with no electro-hydraulic brakes; and
[0034] FIG. 11 is a flowchart of vehicle transition for when the
engine is on with no electro-hydraulic brakes.
DETAILED DESCRIPTION
[0035] Referring now to the drawings figures, there is illustrated
in FIG. 1 a representative configuration of a hybrid electric
vehicle 10 having a internal combustion engine 12 coupled to an
integrated starter generator motor 14. The two powerplants are
coupled by a clutch 16 to a transmission 18, and a differential 20
to provide torque to a set of vehicle wheels 22. A powertrain
control module 24 controls the operating parameters of the internal
combustion engine 12 and the integrated starter generator motor 14.
An electronic brake control system 26 controls a set of
electro-hydraulic brakes 28. Both controllers are shown as logical
units, and can be embodied in one or more separate controller or
computer-controlled devices. A vehicle communication data network
30 enables communications between the hybrid electric vehicle
components, the electronic brake controller 26 and the powertrain
control module 24 at suitable update rates.
[0036] The powertrain control module 24 provides adaptive filtering
that activates when the clutch 16 is engaged as the vehicle
accelerates from a hill holding condition. The adaptive filtering
could be continuously variable or could be provided by a sequence
of individual filters.
[0037] Referring now to FIG. 2, a diagram of the hybrid electric
vehicle torque control system is provided. The system coordinates
the powertrain control module 24 with the electronic brake
controller 26 to provide hill holding in the hybrid electric
vehicle.
[0038] Inputs to the powertrain control module 24 include a gear
selector switch 42 that provides the powertrain control module 24
with information relating to the position of the gear selector
switch 42. A powertrain torque sensor provides information relating
to the amount of torque delivered by the powertrain 44 to the
powertrain control module 24. An accelerator pedal sensor 46
provides the powertrain control module 24 with information
corresponding to the position of an accelerator pedal. A vehicle
speed sensor 48 provides a value corresponding to the speed of the
vehicle to the powertrain control module 24. Values corresponding
to a torque limit of the powertrain are obtained at 50 from a
lookup tables and provided to the powertrain control module 24.
[0039] Inputs to the powertrain control module 24 from the
electronic brake control system 26 include a master cylinder
pressure 52 measured by a master cylinder pressure sensor. The
electronic brake control system 26 sends a torque modification
request at 54 to the powertrain control module 24.
[0040] Inputs to the electronic brake control system 26 from the
powertrain control module 24 include the powertrain negative torque
limit from a powertrain torque sensor at 56. The powertrain control
module 24 provides information from an accelerator position sensor
at 58 to the electronic brake controller 26. The vehicle speed
sensors 48 and the gear selector switch 42 are analyzed by the
powertrain control module to provide a vehicle direction at 60. The
powertrain control module 24 provides the electronic brake
controller 26 with data representative of the powertrain torque
request at 62, the torque delivered at 64, the final torque request
at 66, and the engine on/off state 68.
[0041] The powertrain control module, using inputs from the gear
selector switch 42 and vehicle speed 48, provides the electronic
brake controller 26 with the PRDNE direction 70.
[0042] Inputs to the electronic brake controller 26 also include
the wheel speed data at 72 from the wheel speed sensors. Brake
pedal position sensors provide information relating to a brake
pedal request at 74. Brake pressure sensors provide an input for
brake pressures at 76.
[0043] The electronic brake controller 26 provides a brake pressure
required output at 78 that controls the electro-hydraulic brakes 28
of the vehicle.
[0044] The data inputs and outputs of the powertrain control module
24 and the electronic brake controller 26 process in a vehicle
level algorithm and a brake algorithm. The hybrid electric vehicle
using the vehicle level algorithm and brake algorithm provides
electro-hydraulic brake torque reduction by the electronic brake
control system during driver commanded vehicle acceleration from a
vehicle stopped on a hill.
[0045] When the vehicle begins to accelerate under normal driving
conditions, the vehicle algorithm reduces the electro-hydraulic
brake torque using an adaptive filter that allows the powertrain
system to start and provide the traction torque at the same rate.
The adaptive filtering can be continuously variable or a sequence
of individual filters. The different filters and control logic are
determined by vehicle conditions, including environmental
conditions, and conditions of vehicle components such as: the
clutch, the transmission, the brakes, the engine, the motor, and
the battery. Clutch filters may be dependent upon the clutch
status, clutch wear, clutch temperature, clutch pressure, and
clutch input and output speeds. Transmission filters may be
dependent upon transmission current gear, transmission next gear,
and transmission configuration. Brake filters may be dependent upon
the driver brake pedal command, brake system fault conditions,
brake fade/temperature conditions, and the ABS status. Engine and
motor filters may be dependent upon master cylinder pressure,
throttle angle, engine friction, engine speed, motor speed, motor
efficiency, engine brake torque, engine emissions and engine fuel
rate. Other miscellaneous filters and control logic may include
such factors as the battery state of charge, energy storage device
fault conditions, wheel slip conditions, driveline resonance and
road surface conditions.
[0046] When the acceleration is complete and the vehicle engages
the clutch, the vehicle algorithm decreases the powertrain negative
torque limit 62 with an adaptive filter such that the
electro-hydraulic brake torque goes off at the same rate and the
traction torque is increased. This method of control provides
optimal drive-ability and energy savings allowing a seamless
handoff between the electro-hydraulic brake torque and the
powertrain torque.
[0047] Referring now to FIG. 3, a table 90 of hybrid electric
vehicle conditions that dictate the hill holding strategy is
provided.
[0048] The powertrain control module compares the vehicle speed 48
from the wheel speed sensor with a calibratable vehicle creep speed
in column 92. The vehicle creep speed is typically set at 6 miles
per hour on a zero percent grade. The application of both the brake
pedal and the accelerator pedal determines the existence of a two
footer condition. During a two footer condition the vehicle can be
on a grade in a forward or a reverse gear, the vehicle operator
actuates both the accelerator pedal for a accelerator torque
request and the brake pedal for a brake torque request, and the
magnitude of the brake torque request is greater than the
accelerator torque request.
[0049] The results of the vehicle rollback determination is
displayed in column 94. Vehicle rollback occurs when the driver
releases both the accelerator and brake pedals with the vehicle at
a rest condition on a grade, while the vehicle is in a forward gear
82 and starts rolling backwards, or when the vehicle is in a
reverse gear 82 and starts rolling forward. Column 96 displays the
results of electronic brake controller comparison of the brake
pedal actuation received by a brake pedal sensor with a
calibratable predetermined force X, measured in pounds per square
inch. Column 98 displays the powertrain control module comparison
of an accelerator pedal actuation, measured by an accelerator pedal
sensor, with a calibratable predetermined percentage value Z.
Column 100 displays the internal combustion engine's running state
from an engine sensor.
[0050] Rows 102 and 134 result in the vehicle in a two footer
condition with the engine on and the electro-hydraulic brakes
applying at grade hold torque. The electro-hydraulic brakes applies
at the wheel cylinders and is mechanically summed with the total
torque request, which is applied additionally. The hill holding
strategy maintains electro-hydraulic brakes at the grade hold
torque amount, for example, the amount of torque needed to hold the
vehicle on approximately 3% grade. The hill holding strategy
calculates the total torque request by summing the accelerator
pedal torque request and brake pedal torque request.
[0051] When the total torque request is greater than zero, the
accelerator pedal torque request at the total torque request amount
is added if the magnitude of total torque request is greater than
the magnitude of grade hold torque. The hill holding strategy
proceeds to the FIG. 4 flowchart of the vehicle transition when the
engine is on and operator desires to creep vehicle forward.
[0052] When the total torque request is less than zero, additional
vehicle friction brake torque is applied as follows.
[0053] If the magnitude of brake pedal torque request is greater
than the magnitude of grade hold torque, then the brake torque
request applies at the brake pedal torque request minus the grade
hold torque.
[0054] If the magnitude of brake pedal torque request is less than
the magnitude of grade hold torque, then no additional friction
brake torque is applied and the hill holding strategy proceeds to
the FIG. 7 flowchart of the transition for when the engine is
on.
[0055] If total torque request equals zero, then the hill holding
strategy proceeds to the FIG. 7 flowchart of the transition for
when the engine is on.
[0056] Rows 104 and 136 result in the vehicle in a two footer
condition with the engine off and the electro-hydraulic brakes
applying at grade hold torque. The hill holding strategy continues
to apply electro-hydraulic brakes at the grade hold torque amount
and adds total torque request as follows.
[0057] When the total torque request is greater than zero, the
vehicle acceleration pedal at total torque request amount is added
if the magnitude of total torque request is greater than the
magnitude of grade hold torque. The hill holding strategy proceeds
to the FIG. 5 flowchart of vehicle transition when the engine is
off and the operator desires to creep the vehicle forward.
[0058] When the total torque request is less than zero, the vehicle
brake torque is added as follows.
[0059] If the magnitude of the brake pedal torque request is
greater than magnitude of grade hold torque, brake pedal torque
request applies at brake pedal torque request minus the grade hold
torque.
[0060] If the magnitude of the brake pedal torque request is less
than the magnitude of grade hold torque, no additional friction
brake torque is applied. The hill holding strategy proceeds to the
FIG. 6 flowchart of the vehicle transition for when the engine is
off.
[0061] If the total torque request equals zero, the hill holding
strategy proceeds to the FIG. 6 flowchart of the transition for
when the engine is off.
[0062] Rows 106 and 138 result in the engine on with a brake pedal
torque request, and the electro-hydraulic brakes applying at grade
hold torque. Additional brake pedal torque request is added as
follows.
[0063] When the magnitude of the brake pedal torque request is
greater than magnitude of the grade hold torque, electro-hydraulic
brakes apply at the grade hold torque adding the difference between
the brake pedal torque request and grade hold torque.
[0064] When the magnitude of the brake pedal torque request is less
than the magnitude of grade hold torque, electro-hydraulic brakes
apply at grade hold torque.
[0065] Rows 108 and 140 result in the engine off with a brake pedal
torque request, and electro-hydraulic brakes applying at the grade
hold torque.
[0066] The strategy continues with the electro-hydraulic brakes
applying at the grade hold torque plus additional brake pedal
torque request is added as follows.
[0067] When the magnitude of the brake pedal torque request is
greater than the magnitude of grade hold torque, electro-hydraulic
brakes apply at grade hold torque amount adding the difference
between the brake pedal torque request and the grade hold
torque.
[0068] When the magnitude of the brake pedal torque request is less
than the magnitude of grade hold torque, the electro-hydraulic
brakes apply at grade hold torque.
[0069] When the magnitude of the brake pedal torque request is less
than X psi, where X is predetermined and calibratable pressure
measured in psi, the hill holding strategy proceeds to the FIG. 6
flowchart of the vehicle transition for when the engine is off.
[0070] Row 110 results in the engine on with an accelerator pedal
torque request, and electro-hydraulic brakes applying at grade hold
torque. The electro-hydraulic brakes applies at the grade hold
torque amount with the additional accelerator pedal torque request
is added as follows.
[0071] When the magnitude of the accelerator pedal torque request
is greater than the magnitude of grade hold torque, the hill
holding strategy proceeds to the FIG. 4 flowchart of the vehicle
transition when the engine is on and operator desires to creep
vehicle forward.
[0072] When the magnitude of the accelerator pedal torque request
is less than magnitude of grade hold torque, the hill holding
strategy proceeds to the FIG. 7 flowchart of the vehicle transition
for when the engine is on.
[0073] Row 112 results in engine off with an accelerator pedal
torque request, and electro-hydraulic brakes applying at grade hold
torque. Additional accelerator pedal torque request is added as
follows.
[0074] When the magnitude of the accelerator pedal torque request
is greater than the magnitude of grade hold torque, the hill
holding strategy proceeds to the FIG. 5 flowchart of the vehicle
transition when the engine is off and the operator desires to creep
the vehicle forward.
[0075] When the magnitude of the accelerator pedal torque request
is less than the magnitude of grade hold torque, the hill holding
strategy proceeds to the FIG. 6 flowchart of the vehicle transition
for when the engine is off.
[0076] Row 114 results in the engine on and the electro-hydraulic
brakes applying at grade hold torque. The hill holding strategy
proceeds to the FIG. 6 flowchart of the vehicle transition for when
the engine is off.
[0077] Row 116 results in the engine off and the electro-hydraulic
brakes applying at grade hold torque with the hill holding strategy
waiting for a vehicle condition change.
[0078] Rows 118 and 150 result in the vehicle engine on in the two
footer condition. The total torque request applies as follows.
[0079] When the total torque request is greater than zero, vehicle
acceleration pedal applies at the total torque request amount. The
hill holding strategy proceeds to the FIG. 8 flowchart of the
vehicle transition for when the engine is on with no
electro-hydraulic brakes and the operator desires to creep the
vehicle forward.
[0080] When the total torque request is less than zero, vehicle
brake torque applies at the total torque request amount, the hill
holding strategy proceeds to the FIG. 11 flowchart of the vehicle
transition for when the engine is on with no electro-hydraulic
brakes.
[0081] When the total torque request equals zero, apply nothing.
The hill holding strategy proceeds to the FIG. 11 flowchart of the
vehicle transition for when the engine is on with no
electro-hydraulic brakes.
[0082] Row 120 results in the engine off in a two footer condition.
The total torque request applies according to the following.
[0083] When the total torque request is greater than zero, the
vehicle acceleration applies at total torque request amount. The
hill holding strategy proceeds to the FIG. 9 flowchart of the
vehicle transition for when the engine is off with no
electro-hydraulic brakes and the operator desires to creep the
vehicle forward.
[0084] When the total torque request is less than zero, the vehicle
brake torque applies at total torque request amount. The hill
holding strategy proceeds to the FIG. 10 flowchart of the vehicle
transition for when the engine is off with no electro-hydraulic
brakes.
[0085] When the total torque request equals zero, apply nothing.
The hill holding strategy proceeds to the FIG. 10 flowchart of the
vehicle transition for when the engine is off with no
electro-hydraulic brakes.
[0086] Rows 122 and 154 result in engine on and applying the brake
pedal torque request.
[0087] Rows 124 and 156 result in engine off and applying the brake
pedal torque request. If the magnitude of brake pedal torque
request is less than X psi, the hill holding strategy proceeds to
the FIG. 6 flowchart of the vehicle transition for when the engine
is off.
[0088] Rows 126 and 158 results in engine on and applying the
accelerator pedal torque request. If the vehicle speed is less than
or equal to the creep speed then the hill holding strategy proceeds
to the FIG. 8 flowchart of the vehicle transition for when the
engine is on with no electro-hydraulic brakes and the operator
desires to creep the vehicle forward. If the vehicle speed is not
less than the creep speed then the hill holding strategy proceeds
to FIG. 11 flowchart of the vehicle transition for when the engine
is on with no electro-hydraulic brakes.
[0089] Rows 128 and 160 result in the engine off and applying the
accelerator pedal torque request. The hill holding strategy
proceeds to the FIG. 9 flowchart of the vehicle transition for when
the engine is off with no electro-hydraulic brakes and the operator
desires to creep the vehicle forward.
[0090] Rows 130 and 162 results in the engine on and applying
nothing.
[0091] Row 132 results in engine off and the hill holding strategy
proceeds to the FIG. 6 flowchart of the vehicle transition for when
the engine is off.
[0092] Row 142 results in engine on with an accelerator pedal
torque request and the electro-hydraulic brakes applying at the
grade hold torque. The accelerator pedal torque request is added as
follows.
[0093] When the magnitude of the accelerator pedal torque request
is greater than or less than the magnitude of grade hold torque,
the hill holding strategy proceeds to the FIG. 4 flowchart of the
vehicle transition when the engine is on and operator desires to
creep vehicle forward.
[0094] Row 144 results in engine off and electro-hydraulic brakes
applying at the grade hold torque plus the accelerator pedal torque
request.
[0095] When the magnitude of the accelerator pedal torque request
is greater than or less than the magnitude of grade hold torque,
the hill holding strategy proceeds to the FIG. 5 flowchart of
vehicle transition when the engine is off and the operator desires
to creep the vehicle forward.
[0096] Row 146 results in the engine on and the electro-hydraulic
brakes applying at grade hold torque.
[0097] Row 148 results in engine off, electro-hydraulic brakes
applying at grade hold torque, the hill holding strategy proceeds
to the FIG. 6 flowchart of the vehicle transition for when the
engine is off.
[0098] Row 152 results in engine off in the two footer condition.
The total torque request applies according to the following.
[0099] When the total torque request is greater than or less than
zero, vehicle acceleration applies at the total torque request
amount. The hill holding strategy proceeds to the FIG. 9 flowchart
of the vehicle transition for when the engine is off with no
electro-hydraulic brakes and the operator desires to creep the
vehicle forward.
[0100] When the total torque request equals zero, apply nothing.
The hill holding strategy proceeds to the FIG. 9 flowchart of
transition for when the engine is off with no electro-hydraulic
brakes and the operator desires to creep the vehicle forward.
[0101] Row 164 results in the engine off and nothing applied. The
hill holding strategy proceeds to the FIG. 6 flowchart of the
vehicle transition for when the engine is off.
[0102] Referring to FIG. 4, flowchart of the vehicle transition
when the engine is on and operator desires to creep vehicle forward
is provided.
[0103] In step 170, during each frame interval the following events
occur. The forward clutch is applied. Next, a crankshaft torque
sensor computes a traction torque at the crankshaft. The crankshaft
torque can also be determined by sensing various engine factors
such as speed, throttle angle, and fuel rate. Corrections to these
input factors should be made if these factors were modified to
perform additional functions that do not normally translate to drag
on the drivetrain, for example some of the load of the engine may
be diverted to supply the auxiliary load or charge or discharge the
energy storage subsystem and may reflect as a higher throttle
angle. The engagement factor is determined by sensing various
clutch factors, such as pressure, to obtain the knowledge of what
percentage of the torque applied to the clutch can be obtained at
the clutch output. The gear ratio from the engine to the wheel is
computed by knowledge of the present gear. The traction torque at
the crankshaft computation, the engagement factor computation and
the gear ratio from the engine to the wheel computation are a
function of the driver accelerator pedal command and may be
preprogrammed in an accelerator pedal map. The traction torque at
the crankshaft computation, the engagement factor computation and
the gear ratio from the engine to the wheel computation compute the
desired traction torque at each wheel.
[0104] Next in step 172, wheel traction torque desired is summed
with the wheel brake torque desired to compute the total wheel
torque delivered.
[0105] In decision step 174, the total wheel torque delivered is
compared to zero.
[0106] If the total wheel torque delivered is greater then zero,
then the flowchart continues to step 176. In step 176, the
electro-hydraulic brakes torque is computed as the difference
between the grade hold torque and the total wheel torque
delivered.
[0107] If the total wheel torque delivered is less than or equal to
zero, then the flowchart continues to decision step 178. In step
178, the magnitude of the brake pedal torque request is compared
with the magnitude of the grade hold torque.
[0108] When the magnitude of the brake pedal torque request is
greater than the magnitude of the grade hold torque, the flowchart
proceeds to step 180 where wheel brake torque desired is calculated
by summing the electro-hydraulic brakes torque at grade hold torque
and the brake pedal torque request minus the grade hold torque.
[0109] When the magnitude of the brake pedal torque request is less
than or equal to the magnitude of the grade hold torque, the
flowchart proceeds to step 182 where wheel brake torque desired is
set to the electro-hydraulic brakes torque at grade hold
torque.
[0110] Steps 176, 180 and 182 then proceed to step 184 where the
total wheel torque delivered is computed as the difference between
the wheel traction torque desired and the wheel brake torque
desired.
[0111] Next in step 186 the electro-hydraulic brake torque is
compared to zero. If the electro-hydraulic brake torque is equal to
zero, then the hill holding strategy returns to the analysis in
table of FIG. 3. If the electro-hydraulic brake torque is not equal
to zero the analysis returns to the top of the flowchart to step
170.
[0112] Referring to FIG. 5, a flowchart of vehicle transition when
the engine is off and the operator desires to creep the vehicle
forward is provided. During each frame interval the powertrain
control module starts the engine in step 200. Step 202 shows that
the hill holding strategy proceeds to the FIG. 4 flowchart of the
vehicle transition when the engine is on and the operator desires
to creep the vehicle forward.
[0113] Referring to FIG. 6, a flowchart of the vehicle transition
for when the engine is off is provided. During each frame interval
the powertrain control module starts the engine in step 204. Step
206 shows that the hill holding strategy proceeds to the FIG. 7
flowchart of the vehicle transition for when the engine is on.
[0114] Referring to FIG. 7, a flowchart of the vehicle transition
for when the engine is on is provided. In step 210, the desired
traction torque at each wheel is zero. The wheel brake torque
desired is equal to the electro-hydraulic brakes torque. The
flowchart continues to decision step 212 where the magnitude of the
brake pedal torque request and the magnitude of the grade hold
torque are compared to each other. The comparison is used to
compute the amount of electro-hydraulic brake torque to be
delivered at each wheel by the hydraulic system.
[0115] When the magnitude of the brake pedal torque request is
greater than magnitude of grade hold torque, the flowchart goes to
step 214. In step 214, the wheel brake torque desired equals
electro-hydraulic brake torque at grade hold torque plus the
difference between the brake pedal torque request and the grade
hold torque.
[0116] When the magnitude of the brake pedal torque request is less
than or equal to the magnitude of grade hold torque, the flowchart
goes to step 216. No additional friction brake torque is applied.
The wheel brake torque desired equals electro-hydraulic brake
torque at grade hold torque.
[0117] Steps 214 and 216 continue to step 218 where the total wheel
torque delivered is computed by adding the wheel traction torque
desired with the wheel brake torque desired.
[0118] The flowchart continues with decision step 220 where the
electro-hydraulic brake torque is compared to zero. If the
electro-hydraulic brake torque is equal to zero the flowchart goes
back to the initial analysis in FIG. 3 table as shown in step 222.
If the electro-hydraulic brake torque is not equal to zero the
system returns to step 210 of the FIG. 7 flowchart.
[0119] Referring to FIG. 8 flowchart of the vehicle transition when
the engine is on with no electro-hydraulic brakes and operator
desires to creep vehicle forward.
[0120] In step 230, during each frame interval the following events
occur. The forward clutch applies. Next, a crankshaft torque
sensor, or other sensing methods enable the computation of the
traction torque at the crankshaft. Clutch sensors enable
computation of the engagement factor. Knowledge of present gear
enables computation of the gear ratio from the engine to the wheel.
The traction torque at the crankshaft computation, the engagement
factor computation and the gear ratio from the engine to the wheel
computation are a function of the accelerator pedal command and may
be preprogrammed in an accelerator pedal map. The traction torque
at the crankshaft computation, the engagement factor computation
and the gear ratio from the engine to the wheel computation are
used to compute the desired traction torque at each wheel.
[0121] Next in step 232, wheel traction torque desired is summed
with the wheel brake torque desire to compute the total wheel
torque delivered.
[0122] Next in step 234, the clutch is determined to be fully
engaged or not. If the clutch is determined to be fully engaged,
then the flowchart strategy returns to the analysis in table 90 of
FIG. 3. If the electro-hydraulic brake torque is not equal to zero
the analysis returns to step 230 of the flowchart of the vehicle
transition when the engine is on with no electro hydraulic brakes
and operator desires to creep vehicle forward.
[0123] Referring to FIG. 9, a flowchart of transition for when the
engine is off with no electro-hydraulic brakes and the operator
desires to creep the vehicle forward is provided.
[0124] In step 240, the powertrain control module turns the engine
on. The flowchart continues to step 242, where the hill holding
strategy proceeds to the FIG. 8 flowchart of the vehicle transition
when the engine is on with no electro-hydraulic brakes and the
operator desires to creep the vehicle forward.
[0125] FIG. 10 flowchart of transition for when the engine is off
with no electro-hydraulic brakes. In step 244, the powertrain
control module turns the engine on. The flowchart continues to step
246, where the hill holding strategy proceeds to the FIG. 11
flowchart of the vehicle transition when the engine is on with no
electro-hydraulic brakes.
[0126] Referring to FIG. 11, a flowchart of transition when the
engine is on with no electro-hydraulic brakes is provided.
[0127] In step 260, the wheel traction torque desired at each wheel
is zero.
[0128] In step 262, the amount of electro-hydraulic brake torque to
be delivered at each wheel by the hydraulic system is zero and
wheel brake torque desired equals brake pedal torque request.
[0129] In step 264, the total wheel torque delivered equals wheel
traction torque desired plus the wheel brake torque desired.
[0130] The flowchart continues with decision step 266 where the
decision on clutch engagement is made. If the clutch is engaged the
flowchart goes back to the initial analysis in FIG. 3 table 90. If
the clutch is not fully engaged the flowchart proceeds to step 260
of the FIG. 11 flowchart.
[0131] While the best mode for carrying out the invention has been
described in detail, those familiar with the art to which this
invention relates will recognize various alternative designs and
embodiments for practicing the invention as defined by the
following claims.
* * * * *