U.S. patent application number 16/549081 was filed with the patent office on 2021-02-25 for method and system for controlling a vehicle.
The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Zhengyu DAI, Sanghyun HONG, Jianbo LU, Jonathan SULLIVAN.
Application Number | 20210053584 16/549081 |
Document ID | / |
Family ID | 1000005381741 |
Filed Date | 2021-02-25 |
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United States Patent
Application |
20210053584 |
Kind Code |
A1 |
SULLIVAN; Jonathan ; et
al. |
February 25, 2021 |
METHOD AND SYSTEM FOR CONTROLLING A VEHICLE
Abstract
A vehicle has an accelerator pedal in communication with a prime
mover, a transmission, and a controller. The controller is
configured to, in response to receiving a first input indicative of
a vehicle state and a second input indicative of a curve along a
vehicle path within a predetermined time interval, downshift the
transmission and modify a driver torque request map associated with
the accelerator pedal to reduce a percentage of pedal travel
associated with positive drive torque. A method of controlling a
vehicle includes downshifting a transmission and modifying a driver
torque request map associated with an accelerator pedal to reduce a
percentage of pedal travel associated with positive drive torque
when a vehicle state and a curve from an electronic horizon system
predict a vehicle lateral acceleration in the curve being above a
first threshold value.
Inventors: |
SULLIVAN; Jonathan;
(Ferndale, MI) ; LU; Jianbo; (Northville, MI)
; HONG; Sanghyun; (Ann Arbor, MI) ; DAI;
Zhengyu; (Canton, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Family ID: |
1000005381741 |
Appl. No.: |
16/549081 |
Filed: |
August 23, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60W 40/109 20130101;
B60W 30/045 20130101; B60W 50/085 20130101; B60W 30/18145 20130101;
B60W 2540/10 20130101; B60W 2050/0026 20130101; B60W 2710/1005
20130101; B60W 50/14 20130101; B60W 2520/125 20130101 |
International
Class: |
B60W 50/08 20060101
B60W050/08; B60W 30/18 20060101 B60W030/18; B60W 40/109 20060101
B60W040/109; B60W 50/14 20060101 B60W050/14; B60W 30/045 20060101
B60W030/045 |
Claims
1. A vehicle comprising: an accelerator pedal in communication with
a prime mover; a transmission; an electronic horizon system; and a
controller in communication with the prime mover and the
accelerator pedal, the transmission, and the electronic horizon
system, the controller configured to, in response to receiving a
first input indicative of a vehicle state and a second input
indicative of a curve along a vehicle path within a predetermined
time interval from the electronic horizon system, downshift the
transmission and modify a driver torque request map associated with
the accelerator pedal to reduce a percentage of pedal travel
associated with positive drive torque when the first and second
inputs predict a vehicle lateral acceleration in the curve above a
first threshold value.
2. The vehicle of claim 1 wherein the controller is further
configured to, in response to receiving the first input and the
second input, downshift the transmission without modifying the
driver torque request map when the first and second inputs predict
the vehicle lateral acceleration in the curve below the first
threshold value and above a second threshold value, wherein the
second threshold value is less than the first threshold value.
3. The vehicle of claim 1 wherein the electronic horizon system
further comprises a navigation system; and wherein the prime mover
further comprises an engine.
4. The vehicle of claim 1 wherein the vehicle state associated with
the first input is a vehicle speed.
5. The vehicle of claim 1 wherein the controller is further
configured to modify a transmission shift schedule such that the
transmission is downshifted.
6. A method of controlling a vehicle comprising: receiving a first
signal indicative of a vehicle state; receiving a second signal
from an electronic horizon system indicative of a curve along a
vehicle path within a predetermined time interval; and downshifting
a transmission and modifying a driver torque request map associated
with an accelerator pedal to reduce a percentage of pedal travel
associated with positive drive torque when the vehicle state and
the curve predict a vehicle lateral acceleration in the curve being
above a first threshold value.
7. The method of claim 6 further comprising downshifting the
transmission without modifying the driver torque request map when
the vehicle state and the curve predict the vehicle lateral
acceleration in the curve being below the first threshold value and
above a second threshold value, wherein the second threshold value
is less than the first threshold value.
8. The method of claim 7 further comprising: outputting a first
user notification to a user interface in response to the predicted
vehicle lateral acceleration being above the first threshold value;
outputting a second user notification to the user interface in
response to the predicted vehicle lateral acceleration being below
the first threshold value and above the second threshold value; and
overriding the transmission downshift and the driver torque request
map modification in response to receiving a user input from the
user interface.
9. The method of claim 6 further comprising modifying at least one
of a transmission shift schedule and the driver torque request map
by calculating a three-dimensional map plotting a fuel usage, a
target velocity, and a vehicle lateral acceleration in the
curve.
10. The method of claim 9 wherein a local minimum for the target
velocity in the three-dimensional map is used to modify the at
least one of the transmission shift schedule and the driver torque
request map.
11. The method of claim 6 further comprising receiving a third
signal indicative of an environmental state; wherein the
transmission is downshifted and the driver torque request map is
modified when the vehicle state, the curve, and the environmental
state predict the vehicle lateral acceleration in the curve being
above the first threshold value.
12. A vehicle comprising: an accelerator pedal in communication
with a prime mover; a transmission; and a controller configured to,
in response to receiving a first input indicative of a vehicle
state and a second input indicative of a curve along a vehicle path
within a predetermined time interval, downshift the transmission
and modify a driver torque request map associated with the
accelerator pedal to reduce a percentage of pedal travel associated
with positive drive torque.
13. The vehicle of claim 12 wherein the controller is further
configured to modify a transmission shift schedule in response to
receiving the first and second inputs thereby causing the
transmission to downshift.
14. The vehicle of claim 12 wherein the transmission is downshifted
and the driver torque request map is modified prior to the vehicle
entering the curve.
15. The vehicle of claim 12 further comprising a user notification
system in communication with the controller; wherein the controller
is further configured to output a notification to the user
notification system prior to downshifting the transmission and
modifying the driver torque request map.
16. The vehicle of claim 15 further comprising a user interface;
wherein the controller is configured to receive a user input
overriding the transmission downshift and the driver torque request
map modification.
17. The vehicle of claim 12 wherein the vehicle state for the first
input includes at least one of a present vehicle speed and a
predicted vehicle speed in the curve.
18. The vehicle of claim 12 further comprising an electronic
horizon system with a global positioning system in communication
with the controller, wherein the electronic horizon system is
configured to provide data indicative of the second input to the
controller.
19. The vehicle of claim 12 wherein the second input is also
indicative of a grade along the vehicle path.
20. The vehicle of claim 12 wherein the prime mover is an internal
combustion engine.
Description
TECHNICAL FIELD
[0001] Various embodiments relate to a vehicle with an electronic
horizon system, and a method of controlling the vehicle, to limit
lateral acceleration of the vehicle in a curve.
BACKGROUND
[0002] When a vehicle is traveling along a roadway or path, the
vehicle may encounter a curve such as a blind curve. A blind curve
is a curve where the apex or minimum radius of the turn is
obstructed by objects in the driver's field of view. As such, it is
difficult for the driver to gauge an appropriate entry speed for
the curve. As the vehicle speed increases in a curve, the lateral
acceleration on the vehicle likewise increases. Currently, yaw
control methods may be employed by the vehicle, for example, with
the vehicle in a curve and experiencing a lateral acceleration
above a threshold value. Alternatively, a shift schedule of the
vehicle may be modified as described in U.S. Patent Publication No.
2014/0142822 or PCT Publication No. WO 2017/177110 A1.
SUMMARY
[0003] In an embodiment, a vehicle is provided with an accelerator
pedal in communication with a prime mover, a transmission, an
electronic horizon system, and a controller in communication with
the prime mover and the accelerator pedal, the transmission, and
the electronic horizon system. The controller is configured to, in
response to receiving a first input indicative of a vehicle state
and a second input indicative of a curve along a vehicle path
within a predetermined time interval from the electronic horizon
system, downshift the transmission and modify a driver torque
request map associated with the accelerator pedal to reduce a
percentage of pedal travel associated with positive drive torque
when the first and second inputs predict a vehicle lateral
acceleration in the curve above a first threshold value.
[0004] In another embodiment, a method of controlling a vehicle is
provided. A first signal indicative of a vehicle state is received.
A second signal is received from an electronic horizon system
indicative of a curve along a vehicle path within a predetermined
time interval. A transmission is downshifted and a driver torque
request map associated with an accelerator pedal is modified to
reduce a percentage of pedal travel associated with positive drive
torque when the vehicle state and the curve predict a vehicle
lateral acceleration in the curve being above a first threshold
value.
[0005] In yet another embodiment, a vehicle is provided with an
accelerator pedal in communication with a prime mover, a
transmission, and a controller. The controller is configured to, in
response to receiving a first input indicative of a vehicle state
and a second input indicative of a curve along a vehicle path
within a predetermined time interval, downshift the transmission
and modify a driver torque request map associated with the
accelerator pedal to reduce a percentage of pedal travel associated
with positive drive torque.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 illustrates a schematic of a vehicle according to an
embodiment;
[0007] FIG. 2 illustrates a schematic of a vehicle along a path
with a curve;
[0008] FIG. 3 illustrates a flow chart for a method of controlling
the vehicle of FIG. 1 in the scenario of FIG. 2 according to an
embodiment; and
[0009] FIG. 4 illustrates a simplified modified torque request map
according to an embodiment and resulting from the method of FIG.
3.
DETAILED DESCRIPTION
[0010] As required, detailed embodiments of the present disclosure
are provided herein; however, it is to be understood that the
disclosed embodiments are merely exemplary and may be embodied in
various and alternative forms. The figures are not necessarily to
scale; some features may be exaggerated or minimized to show
details of particular components. Therefore, specific structural
and functional details disclosed herein are not to be interpreted
as limiting, but merely as a representative basis for teaching one
skilled in the art to variously employ the present disclosure.
[0011] FIG. 1 illustrates a schematic of a vehicle 10 configured to
implement the present disclosure. The vehicle 10 has one or more
prime movers 12. In the present example, the vehicle has an
internal combustion engine 14 that is used to propel the vehicle.
In further examples, the vehicle 10 may additionally be provided
with another prime mover, such as an electric machine 16 connected
to a traction battery, such that the vehicle may be propelled using
torque from the engine, the electric machine, or a combination
thereof. In a further example, the vehicle 10 may be a fully
electrified vehicle, such that the vehicle may be propelled solely
using electric power from one or more electric machines. In various
examples, the vehicle 10 may be provided as a hybrid vehicle, such
as a parallel, power split, or series hybrid electric vehicle, a
battery electric vehicle, start-stop vehicle, a micro-hybrid
vehicle, a battery electric vehicle, a plug-in hybrid electric
vehicle, or other vehicle system architectures with electric
propulsion.
[0012] The prime mover(s) 12 for the vehicle output mechanical
power to propel the vehicle. The prime mover(s) are connected to
the driveline. The driveline includes the transmission 18,
differential, and vehicle wheels 20, and their interconnecting
components.
[0013] In some embodiments, the transmission 18 is an automatic
transmission and connected to the drive wheels in a conventional
manner, and may include a differential. The transmission may be a
geared transmission, and may be a step ratio transmission or a
continuously variable transmission. The vehicle 10 is also provided
with a pair of non-driven wheels, however, in alternative
embodiments, a transfer case and a second differential can be
utilized to positively drive all of the vehicle wheels. The
transmission 18 has a gear box to provide various gearing ratios
for the vehicle 10. The transmission gearbox may include clutches
and planetary gearsets, or other arrangements of clutches and gear
trains as are known in the art. In alternative embodiments, the
transmission 18 is a continuously variable transmission or
automated mechanical transmission. The transmission may be an
automatic six speed transmission, other speed automatic
transmission, or other gearbox as is known in the art. Furthermore,
the transmission 18 may be a semi-automatic transmission such as a
manumatic that allows the driver to opt out of an automatic
transmission mode, and manually and electronically control the
transmission shifting via shift paddles or the like.
[0014] The transmission gearbox 18 may include gear sets (not
shown) that are selectively placed in different gear ratios by
selective engagement of friction elements such as clutches and
brakes to establish the desired multiple discrete or step drive
ratios. The friction elements are controllable through a shift
schedule that connects and disconnects certain elements of the gear
sets to control the ratio between a transmission output shaft and
the transmission input shaft. The gearbox is automatically shifted
from one ratio to another based on various vehicle and ambient
operating conditions by an associated controller, such as a
transmission control unit (TCU). The gearbox then provides
powertrain output torque to output shaft.
[0015] The vehicle 10 has a control system 22 (or controller) with
one or more controllers or control modules for the various vehicle
components and systems. The control system 22 for the vehicle may
include any number of controllers, and may be integrated into a
single controller, or have various modules. Some or all of the
controllers may be connected by a controller area network (CAN) or
other system. It is recognized that any controller, circuit or
other electrical device disclosed herein may include any number of
microprocessors, integrated circuits, memory devices (e.g., FLASH,
random access memory (RAM), read only memory (ROM), electrically
programmable read only memory (EPROM), electrically erasable
programmable read only memory (EEPROM), or other suitable variants
thereof) and software which co-act with one another to perform
operation(s) disclosed herein. In addition, any one or more of the
electrical devices as disclosed herein may be configured to execute
a computer-program that is embodied in a non-transitory computer
readable medium that is programmed to perform any number of the
functions as disclosed herein.
[0016] The vehicle is provided with a user interface 24, such as a
human machine interface (HMI). The user interface 24 may provide a
user notification system. The user interface 24 may be provided
with a display screen, and may have buttons or other inputs for a
vehicle occupant. The user interface 24 may additionally be
provided with indicator lights, audible alerts, and the like.
Furthermore, the user interface 24 may be provided with a
microphone such that the vehicle occupant may provide an input to
the user interface via a voice command.
[0017] The transmission 18 is controlled using the transmission
control unit (TCU) 26 or the like to operate on a shift schedule,
such as a production shift schedule, that connects and disconnects
elements within the gear box to control the gear ratio between the
transmission output and transmission input.
[0018] The vehicle 10 is provided with a control unit for the prime
movers (ECU) 28. The prime mover control unit 28 may be provided by
more than one controller for the case of a vehicle with both an
engine and an electric machine. The prime mover control unit 28 may
have an accelerator pedal map as well as an engine map or electric
machine map stored in memory.
[0019] A vehicle system controller (VSC) 30 transfers data between
the TCU 26 and ECU 28 and is also in communication with various
vehicle sensors and the user interface 24. The control system 22
for the vehicle 10 may include any number of controllers, and may
be integrated into a single controller, or have various modules.
Some or all of the controllers may be connected by a controller
area network (CAN) or other system. The control system may be
configured to control operation of the various components of the
transmission, and the prime mover(s) under any of a number of
different conditions, including according to a method as described
below.
[0020] The VSC 30 receives signals indicative of driver demand. An
accelerator pedal position sensor (APPS) is in communication with
the VSC, and provides information related to the accelerator pedal
position, or tip in and tip out of the accelerator pedal. Tip in
may be used in relation to a request from the driver for more
speed, power, and/or torque, while tip out may be used in relation
to a request from the driver for less speed, power, and/or torque.
The brake pedal position sensor (BPPS) and gear selection (PRNDL)
are also in communication with the VSC to provide information
related to driver demand.
[0021] Under normal powertrain conditions, the VSC 30 interprets
the driver's demands (e.g. PRNDL and acceleration or braking
requests via the accelerator and brake pedal inputs), and then
determines the wheel torque command based on the driver demand and
powertrain limits. In addition, the VSC 30 determines when and how
much torque each prime mover 12 needs to provide in order to meet
the driver's torque demand and to achieve the operating points
(torque and speed) of the prime mover(s). The VSC 30 additionally
determine the gear selection or gear ratio for the transmission 18
based on the production shift schedule.
[0022] The vehicle 10 may have speed sensors positioned at various
locations of the powertrain and driveline. The speed sensors
provide information to the control system 22 regarding the
rotational speed of a shaft in approximately real time, although
there may be some lag due to response time, and signal and data
processing. In the embodiment shown in FIG. 1, there is a speed
sensor that measures the speed of the prime mover(s) output
shaft(s), the speed of the transmission input shaft, the speed of
the transmission output shaft, and the speed of one or both of the
axles connected to the wheels.
[0023] The vehicle has an electronic horizon system 32 that
provides an indication of the surroundings of the vehicle 10 to the
control system 22. The electronic horizon system 32 may include a
navigation system for the vehicle with a global positioning system,
to provide both a vehicle position and a map database. The map
database may include detailed mapping information, such as that
used with autonomous vehicles. The navigation system may include
global positioning satellite data. The electronic horizon system 32
may additionally include sensors on the vehicle, such as cameras,
radar, LIDAR, and the like. The electronic horizon system may be
provided as a part of an advanced driver assistance system (ADAS),
and the ADAS may be provided with adaptive cruise control. In some
examples, the electronic horizon system 32 may be connected to a
cloud, for example, using a connected-vehicle-to-everything
communication (V2X) system.
[0024] The electronic horizon system 32 may contain or receive
information related to conditions of the roadways, e.g. curvature,
grade, and the like. The electronic horizon system 32 may
additionally contain or receive additional information related to
the roadways, such as designated speed limits or recommended speeds
for the roadway, the road surface condition, e.g. rough versus
smooth, and the like. Furthermore, the electronic horizon system 32
may receive information related to environmental conditions, such
as weather conditions. For example, the electronic horizon system
32 may receive a signal from windshield wipers to indicate
precipitation, from a temperature sensor to indicate possible ice
or snow formation on the roadway, or from a remote signal with
weather condition and forecasting data.
[0025] According to various embodiments, the control system 22
controls the vehicle 10 while the vehicle is experiencing a lateral
load or force, this lateral force may be caused by the vehicle
driving through a turn or a curve in a roadway. Often times roads
have turns or curves where the apex or minimum radius of the turn
is unpredictable by the driver or is obstructed by objects in the
driver's field of view. This makes it difficult for a driver to
gauge an entry speed for the vehicle into and through the turn. As
the speed of the vehicle increases, the lateral force on the
vehicle and its occupants also increases, and may be greater than
is desired by the occupants. When a turn or curve is obstructed,
the driver has a reduced reaction time to provide an input to the
vehicle, such as by applying a braking force or reducing the
accelerator pedal input, to slow the vehicle. Even when a curve or
a turn is unobstructed and in clear view of the driver, it may be
difficult to gauge the appropriate speed for the vehicle, and the
vehicle may enter or be in the curve at a speed that is higher than
desired, for example, based on current road conditions. For
example, in a curve or turn with a decreasing radius, or with the
apex of the turn being obstructed, it is difficult for a driver to
appropriately gauge an the speed of the vehicle to a desired entry
speed for the turn, and as a result, the entry speed may be greater
than desired by the driver, resulting in higher lateral loads on
the vehicle than intended by the driver.
[0026] According to the present disclosure, the control system 22
controls the vehicle 10 to intervene in a situation where the
vehicle speed as requested by the driver is greater than a desired
entrance speed to a turn or curve such that a higher lateral load
would be imparted on the vehicle than desired without intervention
by the control system. The electronic horizon system 32 provides an
indication of the desired entrance speed or target speed for the
vehicle.
[0027] Furthermore, the control system 22 controls the vehicle 10
without being apparant to the driver to maintain a connected
driving feeling, and in a manner that maintains or increases fuel
economy for the vehicle. The control method alerts the driver to
the forthcoming curve and situation, and controls the vehicle 10 as
described below to reduce vehicle speed through the curve, while
still allowing the driver to override the control system and
control the vehicle as the driver sees fit. Additionally, the
control method controls the vehicle 10 such that the vehicle is
capable to react quickly during and after these turning events,
which may require high torque reserves and already being in a gear
that is configured to provide a desired torque ratio.
[0028] According to the present disclosure, the control system 22
includes a model predictive controller, for example, integrated
into the VSC 30, that accesses the electronic horizon system or
other information related to future road preview to perform shift
scheduling and pedal map modification based on a state estimation
of the vehicle in a future corner. The future corner or curve may
be the immediate next curve for the vehicle, and may be on the
order of ten to fifteen seconds ahead of the vehicle based on the
vehicle's present speed. Additionally, the control system 22
provides an alert to the driver, e.g. via the user interface, that
the vehicle may be approaching a lateral load threshold. The alert
may include an audible signal such as a chime, a visual indicator
such as a dash , or a haptic signal or feedback to the driver. The
alert using haptic feedback may be provided via the accelerator
pedal, via the steering wheel, or the like.
[0029] Following the driver alert, the control system 22 may cause
or induce a downshift in the transmission 18 (as opposed to a
downshift commanded by the driver, or otherwise scheduled in the
shift scheduler) to take advantage of engine braking to reduce the
vehicle speed and alert the driver to slow down further. According
to one example, the transmission downshifts commanded by the
control system are equal torque shifts, but as the future vehicle
speed predicted through the curve provides an indication of higher
and higher lateral loads, a driver torque request map (such as an
accelerator pedal map) may be modified by the control system 22 to
reduce the amount of area in the pedal map that leads to positive
torque, and further reduce the vehicle speed. For example, the
accelerator pedal would need to travel a greater distance, or
farther tip in, to result in a positive torque at the wheels. The
accelerator pedal map modification favors a negative torque output
at the wheels, corresponding to engine braking and reduced vehicle
speed. The pedal map may be modified further for high predicted
vehicle speeds and lateral loads through the curve. For example,
for a given accelerator pedal position or percentage tip in, the
torque request may be continuously decreased as the predicted
lateral load increases while still ensuring that the pedal map
includes the max torque available in the gear so that the driver
can reach full tip in or open throttle and override the control
system and modification if desired. Essentially the accelerator
pedal map modification results in an accelerator pedal that feels
more and more "dead" to the driver as the predicted lateral load
through the curve increases.
[0030] The control system 22 includes, for example stored in
memory, a model or algorithm for the lateral capability and loads
for the vehicle during operation. The model may include a road
performance index, e.g. coefficient of friction, to assess
reasonable expectations of tire grip in future corners where the
future curvature and target velocity are used to predict lateral
acceleration and forces. The road performance index may be updated
using environmental conditions and the like.
[0031] The control system 22 includes a method to determine how to
control the vehicle 10 according to the present disclosure, and in
a future curve or turn. The method may be provided with a cost
function that applies cost weights to different vehicle states as
inputs. In one example, the method applies cost weights to brake
pressure, fuel rate, error from velocity target, and lateral
acceleration beyond a threshold value. The control system 22 uses
the cost function to determine an optimal coast down strategy for
the vehicle based on the future physical limits of the curve ahead,
e.g. curvature, radius, grade, and the like. The control system 22
modifies the shift schedule and the accelerator pedal map for the
vehicle based on the optimal trajectory of the vehicle through the
curve, and manipulated variables found by the method. The control
system 22 modifies the shift schedule and selects an optimized gear
to allow for torque reserve and engine braking potential. The
control system 22 modifies the accelerator pedal map to bias the
driver into reducing the vehicle speed with an upcoming curve,
while alerting the driver of the future road condition. By alerting
the driver of the upcoming curve, and then modifying the shift
schedule and accelerator pedal map, the control system provides for
reduced lateral acceleration and forces on the vehicle through the
curve while maintaining drivability and rideability through the
curve.
[0032] The method applied by the control system 22 uses road
preview information and data provided by the electronic horizon
system 32 to perform shift scheduling for the transmission 18 and
accelerator pedal map modification based on state estimation of the
vehicle 10 in an upcoming, future corner.
[0033] The control system 22 provides an alert to the driver that
the lateral acceleration of the vehicle 10 will exceed a threshold
value, and the alert may be provided by a chime, dash icon, haptic
feedback, or the like. Then, the control system 22 induces and
commands a transmission 18 downshift to utilize engine braking to
slow the vehicle, and also provide an alert to the driver to
further slow the vehicle speed if needed.
[0034] The control system 22 may preemptively modify the
accelerator pedal map to reduce the amount of pedal travel that is
associated with positive torque output at the wheels in order to
favor engine braking as the predicted lateral acceleration of the
vehicle increases. The accelerator pedal map still provides maximum
torque from the prime mover(s) 12 within a smaller section or range
of the pedal travel to allow the driver to override the system if
they so choose.
[0035] Conventional vehicle control systems are dependent on
intervention at the time of increased lateral vehicle acceleration,
such as roll attenuation and other electronic stability control
systems, or are completely autonomous and allow no driver control
or input during the control event. The method according to the
present disclosure provides for an automatic control of the vehicle
10 through a curve or during increased vehicle lateral
acceleration, while providing for a connected driving feel,
maintaining or increasing fuel economy, and overall driver and
occupant satisfaction. Additionally since the method may be
configured to gradually introduce and increase the control inputs
in advance of the curve, fuel economy and vehicle control and
stability are higher than when using a conventional reactionary
control method.
[0036] The control system 22 and method according to the present
disclosure includes accelerator pedal and brake pedal inputs into
the cost function for the future horizon to plan transmission
shifts or alter accelerator pedal/driver demand maps. The future
horizon is based on an upcoming curvature in the roadway, e.g.
within ten to fifteen seconds of the vehicle location at the
present vehicle speed, and the present speed of the vehicle. The
control system and method may provide an alert to the driver that a
future speed of the vehicle (e.g. within the future horizon) will
cause the lateral vehicle acceleration to exceed a threshold, or
that an obstructed curve or corner is ahead, e.g. a blind apex.
[0037] FIG. 2 illustrates a schematic of a vehicle 10 along a path
50 on a roadway. The vehicle 10 is driving along a roadway on a
vehicle path. Based on the vehicle path, the vehicle is approaching
a curve 52 or turn in the roadway. As shown in the Figure, the
curve 52 be a decreasing radius curve, although other types of
curves are also contemplated. The curve 52 may additionally be a
blind corner, e.g. based on one or more obstructions to the driver.
Furthermore, the curve 52 on the roadway may have an associated
grade or changing grade, and the environmental conditions, e.g.
weather and roadway condition, may affect the traction surface of
the roadway. The roadway condition may refer to whether the road is
a paved or unpaved surface, and the like.
[0038] The control system 22 and electronic horizon system 32
determine that the upcoming curve 52 is within a predetermined time
(At) of vehicle 10 travel or position to implement the control
strategy for the vehicle as described herein. In one example, the
control system 22 and electronic horizon system 32 are monitoring
the roadway, and initiate the control strategy when the curve is
ten to fifteen seconds ahead of the present vehicle position. In
other examples, other times, e.g. less than ten seconds or more
than fifteen seconds are also contemplated.
[0039] FIG. 3 illustrates a flow chart for a method 200 according
to the present disclosure. The method may be used to control the
vehicle 10 of FIG. 1 according to various embodiments. The method
200 may be implemented by a controller such as the controller and
control system 22 in FIG. 1. In other examples, various steps may
be omitted, added, rearranged into another order, or performed
sequentially or simultaneously. Although the method 200 is
described with respect to use with a vehicle 10 as shown in FIG. 1,
the method may likewise be applied for use with a vehicle with
another architecture as described above with respect to FIG. 1. At
step 202, the method 200 starts.
[0040] At step 204, the controller 22 receives inputs, such as the
first, second, and third inputs. The controller 22 is configured to
receive a first input indicative of a vehicle state. The vehicle
state may include a present vehicle speed. The first input may
additionally or alternatively include a predicted vehicle speed in
a curve along a vehicle path within a predetermined time interval
of the present vehicle position based on data from the electronic
horizon system.
[0041] The controller 22 is also configured to receive a second
input indicative of a curve along a vehicle path within a
predetermined time interval of the present vehicle position from
the electronic horizon system 32. The predetermined time interval
may be on the order of five seconds, ten seconds, fifteen seconds,
twenty seconds, or more. The second input may additionally include
information related to the grade of the vehicle path within the
predetermined time interval.
[0042] The controller 22 may additionally receive other data as a
third input indicative of an environmental state, and this data may
be representative of a grade of the vehicle path within the
predetermined time interval such as grade, a speed limit set for
the vehicle path, an environmental condition such as precipitation
or ambient temperature, a road condition indicative of the roadway
surface, and the like.
[0043] The controller 22 is configured to predict a vehicle lateral
acceleration in the curve ahead, and compare the predicted vehicle
lateral acceleration to first and second threshold values. The
first threshold value is higher than the second threshold value,
and the comparison of the vehicle lateral acceleration in relation
to the first and second threshold values trigger differing vehicle
control strategies.
[0044] At step 206, the controller 22 uses a cost optimizer
function to determine an operating point or state for the vehicle
based on the inputs and the expected or predicted vehicle state in
the curve or roadway ahead. The controller 22 may perform a
separate cost optimizer function for each gear in the transmission,
with only the function block for the first and second gears of the
transmission shown in FIG. 3. The method 200 and controller 22 may
use a hybrid model predictive cost function. In one example, the
controller 22 performs an iterative process using one or more of
the following as inputs: fuel, brake, weight, lateral acceleration,
target velocity, and change in velocity from actual to target, with
each input assigned an associated cost. The costs associated with
each input may be based on a weighted function with the cost
weights being same as one another or may vary depending on the
input. Alternatively, the costs may be based on an exponential
function. The controller 22 creates a three-dimensional surface or
map for each gear that plots a fuel usage, a target velocity, and a
vehicle lateral acceleration in the curve. The controller 22 then
determines a local minimum for the three-dimensional map, and
proceeds to block 208 when the minimum cumulative cost is
found.
[0045] For each gear at step 206, the controller 22 may estimate
the likely costs and the target velocity, calculate the actual
costs, and perform these steps as an iterative process until the
costs to reach a minimum cost or minimum target velocity are
reached.
[0046] At block 208, the controller 22 compares the local minimums
from each of the gears from blocks 206, and selects the one with
the lowest cumulative cost that also meets specified criteria for
the vehicle 10 such as a lateral vehicle acceleration that is below
a threshold value, a vehicle speed through the curve that is less
than a specified speed, or the like. The controller 22 may use a
cost optimizer function at block 208 as well, with a cost
associated with each gear to determine the result.
[0047] At step 210, the controller 22 modifies the shift schedule
for the transmission 18 based on the results from block 208. The
controller 22 may modify the shift schedule by identifying the
desired downshift based on the inputs and the cost optimizer
function results. The controller 22 may further modify the shift
schedule by blocking one or more shifts within the event or curve
horizon, e.g. within the predetermined time interval.
[0048] At step 212, the controller 22 modifies the torque request
map, or accelerator pedal map, based on the results from block 208.
An example of a modification of an accelerator pedal map is shown
in FIG. 4. FIG. 4 illustrates torque request from the prime
mover(s) 12 as a function of the accelerator pedal position as
measured by the APPS. The production or unmodified torque request
map 300 is shown with a broken line, while the modified torque
request map 302 is shown with a solid line. As can be seen from the
Figure, the modified map provides engine braking through a first
range 304 of pedal travel, and also provides the same torque as the
unmodified map through another range 306 of pedal travel.
[0049] Referring back to FIG. 3, at step 214, the controller 22
provides an alert to the user. The controller 22 is configured to
output a first user notification to the user interface 24 in
response to the predicted vehicle lateral acceleration being above
the first threshold value.
[0050] The controller 22 is also configured to output a second user
notification to the user interface 24 in response to the predicted
vehicle lateral acceleration being below the first threshold value
and above the second threshold value.
[0051] At step 216, the controller 22 determines if the occupant or
user has overridden the control strategy. The vehicle occupant or
driver may override the transmission 18 downshift and/or the driver
torque request map modification by providing a user input to the
user interface 24.
[0052] If the occupant has overridden the control strategy, the
method 200 proceeds to block 218 and ends. If the occupant has not
overridden the control strategy, the method 200 proceeds to block
220.
[0053] At step 220, the controller 22 controls the vehicle 10
through the event or curve by downshifting the transmission 18 when
the first and second inputs predict a vehicle lateral acceleration
in the curve above a first threshold value, and modifying the
driver torque request map associated with the accelerator pedal to
reduce a percentage of pedal travel associated with positive drive
torque when the first and second inputs predict a vehicle lateral
acceleration in the curve above the first threshold value. In
response to the predicted vehicle lateral acceleration, the
controller 22 may modify the transmission shift schedule in order
to cause the downshift. The controller 22 may be further configured
to downshift the transmission 18 and modify the accelerator pedal
map when the first input indicative of the vehicle state, second
input indicative of the curve, and the third input indicative of
the environmental state predict the vehicle lateral acceleration in
the curve being above the first threshold value.
[0054] At step 222, the controller 22 is further configured to
downshift the transmission 18 without modifying the driver torque
request map when the first and second inputs predict the vehicle
lateral acceleration in the curve below the first threshold value
and above the second threshold value.
[0055] The transmission 18 is downshifted and/or the driver torque
request map is modified prior to the vehicle 10 entering the curve
52.
[0056] The method then ends at block 222.
[0057] While exemplary embodiments are described above, it is not
intended that these embodiments describe all possible forms of the
disclosure. Rather, the words used in the specification are words
of description rather than limitation, and it is understood that
various changes may be made without departing from the spirit and
scope of the disclosure. Additionally, the features of various
implementing embodiments may be combined to form further
embodiments of the disclosure.
* * * * *