U.S. patent application number 09/795575 was filed with the patent office on 2002-08-29 for modification of pedal progression with acceleration feedback using electronic throttle control.
Invention is credited to Jess, Richard B., Mehta, Vivek, Royer, James R., Stiles, Steven D..
Application Number | 20020120385 09/795575 |
Document ID | / |
Family ID | 25165874 |
Filed Date | 2002-08-29 |
United States Patent
Application |
20020120385 |
Kind Code |
A1 |
Mehta, Vivek ; et
al. |
August 29, 2002 |
MODIFICATION OF PEDAL PROGRESSION WITH ACCELERATION FEEDBACK USING
ELECTRONIC THROTTLE CONTROL
Abstract
A method and apparatus for controlling the throttle position of
a vehicle by modifying the pedal to throttle progression typically
used by the electronic throttle controller to a throttle
progression based on the driver's target acceleration and vehicle
speed. Target acceleration is determined using a lookup table with
inputs current vehicle speed and accelerator pedal displacement.
Another lookup determines the end vehicle speed the driver will
attain if the pedal displacement does not change. A signal
indicating the new throttle position is the output of a controller
whose input is the difference between end vehicle speed and current
vehicle speed and whose gain is based on the target acceleration.
Changes in throttle position can be limited based on an arbitration
incorporating information received from other vehicle control
systems. Preferably, control of the throttle will revert to the
idle control system whenever the accelerator pedal is not
displaced.
Inventors: |
Mehta, Vivek; (Bloomfield
Hills, MI) ; Stiles, Steven D.; (Clarkston, MI)
; Jess, Richard B.; (Haslett, MI) ; Royer, James
R.; (Flushing, MI) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
25165874 |
Appl. No.: |
09/795575 |
Filed: |
February 28, 2001 |
Current U.S.
Class: |
701/110 ;
123/350; 180/179 |
Current CPC
Class: |
F02D 2041/1409 20130101;
F02D 31/002 20130101; B60W 2720/106 20130101; F02D 2041/1422
20130101; F02D 2200/501 20130101; B60W 2540/10 20130101; F02D
11/105 20130101 |
Class at
Publication: |
701/110 ;
123/350; 180/179 |
International
Class: |
F02D 041/14 |
Claims
What is claimed is:
1. A method of controlling a throttle actuator to a throttle
position in an internal combustion engine in a vehicle, comprising
the steps of: measuring an accelerator pedal displacement;
measuring a current vehicle speed; using a first table lookup
function to determine a target acceleration based on the
accelerator pedal displacement and the current vehicle speed; using
a second table lookup function to determine an end vehicle speed
based on the accelerator pedal displacement; determining a desired
throttle position using the current vehicle speed, the end vehicle
speed and a gain based on the target acceleration; and signaling
the throttle actuator to the desired throttle position.
2. The method according to claim 1, further comprising the steps
of: checking at least one other control system in the vehicle for a
limitation to changes in the throttle position; and blocking the
step of signaling the throttle actuator when the checking step
indicates a limitation to increases in throttle position.
3. The method according to claim 1, wherein the step of determining
the desired throttle position comprises the steps of: inputting the
difference between the current vehicle speed and the end vehicle
speed into a controller; and using a gain for the controller based
on the target acceleration.
4. The method according to claim 3, wherein the controller is a PID
controller.
5. An apparatus for a throttle actuator to a throttle position in
an internal combustion engine in a vehicle, comprising: means for
measuring an accelerator pedal displacement; means for measuring a
current vehicle speed; a lookup table to determine one of a target
acceleration based on the accelerator pedal displacement and the
current vehicle speed and an end vehicle speed based on the
accelerator pedal displacement; means for determining a desired
throttle position using the current vehicle speed, the end vehicle
speed and a gain based on the target acceleration; and means for
signaling the throttle actuator to the desired throttle
position.
6. The apparatus according to claim 5, further comprising: means
for checking at least one other control system in the vehicle for a
limitation to changes in the throttle position; and blocking the
step of signaling the throttle actuator when the checking step
indicates increases in throttle limit changes in the desired
throttle position.
7. The apparatus according to claim 5, wherein determining the
desired throttle position comprises: means for inputting the
difference between the current vehicle speed and the end vehicle
speed into a controller; and means for using a gain for the
controller based on the target acceleration.
8. The apparatus according to claim 5, wherein the controller is a
PID controller.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates in general to internal
combustion engine control systems and, specifically, to an internal
combustion engine control system for modifying pedal progression
with acceleration feedback.
[0003] 2. Description of the Art
[0004] The accelerator pedal in an automobile must read the intent
of the driver to: (1) accelerate the vehicle; (2) maintain vehicle
speed (i.e., neither accelerate nor decelerate the vehicle); and
(3) decelerate the vehicle. Moreover, the pedal must provide
position feedback to the driver. Currently, these functions are
performed through an electronic throttle control, which uses a
simple pedal to throttle position progression table. When the
accelerator pedal is displaced, the angle of the throttle is
increased by a throttle actuator. This allows more air into the
engine and thereby increases engine power. The spring load of the
pedal changes at each pedal position, providing feedback to the
driver.
[0005] Current electronic throttle control produces excessive
variations in throttle position and speed for a given pedal
displacement as terrain, altitude, gear, axle or vehicle load
change. Further, the current method cannot predict the vehicle
speed intended by the driver. Cruise control systems can also be
used to accelerate or decelerate the vehicle or to maintain vehicle
speed. However, such systems require hardware beyond that needed by
the electronic throttle control.
SUMMARY OF THE INVENTION
[0006] The present invention is a method and apparatus for
controlling the throttle position of an engine by modifying the
current electronic throttle control. The invention makes changes to
the throttle position using the driver's intended acceleration and
speed, instead of using the current pedal progression that directly
changes throttle position based on accelerator pedal
displacement.
[0007] Specifically, the method starts by measuring the
displacement of an accelerator pedal and the current speed of the
vehicle. Using a table lookup function incorporating pedal
displacement and the current vehicle speed, the driver's target
acceleration is determined. A second table lookup function is used
to determine the driver's intended end vehicle speed, which is the
speed the driver would reach if the accelerator pedal remained at
its measured displacement. Then, a desired throttle position is
calculated using an acceleration-based rate of change. Preferably,
a standard arbitration is performed with signals from other engine
control systems. If the other systems do not indicate a need to
limit changes to the throttle position, the throttle is adjusted to
the desired throttle position.
[0008] The apparatus of the present invention comprises means for
measuring the displacement of an accelerator pedal and the current
speed of the vehicle. It also comprises a table lookup function
incorporating pedal displacement and the current vehicle speed to
determine the driver's target acceleration. A second table lookup
function determines the driver's intended end vehicle speed. The
apparatus also includes means for calculating a desired throttle
position using an acceleration-based rate of change and means for
performing a standard arbitration using signals from other engine
control systems. Finally, the apparatus contains means for
adjusting the throttle to the desired throttle position, which
adjustment will occur if the other systems do not indicate a need
to limit changes to the throttle position.
[0009] In one aspect of the invention, the desired throttle
position is the output of a PID controller using as its input the
difference between current vehicle speed and the end vehicle speed
and a gain using the acceleration-based rate of change.
[0010] In one aspect of the invention, the acceleration-based rate
of change is the driver's target acceleration. In another aspect of
the invention, the acceleration-based rate of change is another
engine parameter calculated from the driver's target acceleration,
such as torque.
[0011] The present invention automatically regulates acceleration,
and thus vehicle speed. This allows tracking to a target
acceleration and maintaining vehicle speed at points of zero
acceleration using a simple and direct interface to determine
driver intent. The invention allows the driver to maintain a
desired vehicle speed at a comfortable pedal position regardless of
terrain, altitude or vehicle loading conditions without requiring a
cruise control system. Finally, the invention accurately determines
the end vehicle speed, which can be used as an input into other
engine control systems such as for future enhancements in
transmission shift scheduling.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The various features, advantages and other uses of the
present invention will become more apparent by referring to the
following detailed description and drawings in which:
[0013] FIG. 1 is a pictorial diagram of an engine and engine
control hardware involved in carrying out the present
invention;
[0014] FIG. 2 is a block diagram illustrating a flow of operations
for carrying out the method of this invention using the hardware of
FIG. 1;
[0015] FIG. 3 is a partial lookup table of acceleration as a
function of accelerator pedal displacement and vehicle speed;
and
[0016] FIG. 4 is a block diagram representing the inputs and
outputs of the controller used in the present invention.
DETAILED DESCRIPTION
[0017] Referring now to FIG. 1, air flows into an internal
combustion engine 10 through an intake throttle blade 12, which
throttle blade 12 is controlled by a throttle actuator 13. The air
is combined into fuel air mixtures and burned in the engine
cylinders (not shown). After the air is burned in the cylinders,
the exhaust gas flows through an exhaust gas conduit 16 and a
catalytic device 18, finally releasing into the atmosphere through
a tail pipe 20. An accelerator pedal 14 is displaced in response to
operator demand for engine output power. The accelerator pedal 14
could also take the form of a stick, such as that present in a
vehicle equipped for operation by the handicapped.
[0018] Associated with the engine are various conventional sensors
known in the art, which provide typical signals related to engine
control. Coupled to the throttle 12 is a throttle position sensor
(TPS) 22. Vehicle speed is determined from a sensor 24, coupled
through a flexible cable (not shown) to the driveshaft 26, which
rotates at an angular speed proportional to vehicle speed. The
degree to which the accelerator pedal 14 is displaced in response
to operator demand for engine output power is indicated by a pedal
position sensor 28.
[0019] The engine controller 30 is a conventional digital computer
used by those in the art for engine control, and includes the
standard elements of the central processing unit (CPU), random
access memory, read-only memory, analog to digital convertor(s),
input/output circuitry, and clock circuitry. The controller 30 is
activated upon application of ignition power to an engine 10. When
activated, the controller 30 carries out a series of operations
stored in an instruction-by-instruction format in memory for
providing engine control, diagnostic and maintenance operations.
Signals from the previously mentioned sensors flow over the paths
indicated in FIG. 1 and serve as inputs to the controller 30. Using
these inputs, the controller 30 performs appropriate computations
and outputs various signals. For example, the controller 30 uses
the pedal position sensor 28 in an electronic throttle control
algorithm to produce a signal, labeled "ETC", to control the
throttle actuator 13. When the accelerator pedal 14 is displaced,
the ETC signal directs the throttle actuator 13 to increase the
angle of the throttle 12, allowing more air into the engine and
thereby increasing engine power.
[0020] FIG. 2 shows a flow of operations to control the throttle
position of the vehicle by modifying the direct relationship
between the accelerator pedal 14 and engine power to a relationship
based on vehicle acceleration. Specifically, such a procedure
begins at step 40, and proceeds to step 42. In step 42, the
accelerator pedal displacement is determined according to current
methods. Hysteresis and dead band are applied to accommodate sensor
noise and slight fluctuations in driver positioning of the
accelerator pedal. In step 44, the current vehicle speed is
measured and stored.
[0021] In a preferred aspect of the invention, the accelerator
pedal displacement determined in step 42 is checked in step 46 to
see if it is equal to 0%, which means that the driver is not
displacing the accelerator pedal. If the accelerator pedal
displacement is 0%, then the procedure ends at step 48. In this
aspect, another engine control system will determine throttle
position, preferably the engine's idle control algorithm. If,
however, the accelerator pedal displacement is not 0%, the
procedure advances to step 50. In another aspect of the invention,
the procedure advances from step 46 to step 50 even if the
accelerator pedal displacement determined in step 42 is equal to 0%
because the present invention will determine throttle position even
if the driver is not displacing the accelerator pedal.
[0022] In step 50, a table lookup function is used to provide a
target acceleration based on the accelerator pedal displacement
from step 42 and the current vehicle speed from step 44. A sample
lookup table used for this table lookup function is illustrated in
FIG. 3, which lookup table shows accelerator pedal displacement as
a function of vehicle speed. By example, accelerator pedal
displacement is shown as percent of displacement. Alternatively,
accelerator pedal displacement could be an absolute value, such as
millimeters. Similarly, vehicle speed is in miles per hour and
acceleration is in m/sec.sup.2 by example only. The table of FIG. 3
does not include values for the situation where the accelerator
pedal displacement measured in step 42 is 0% because, in a
preferred aspect of the invention, other engine control systems
determine throttle position when the driver is not displacing the
accelerator pedal. In another aspect of the invention, however,
values can be included in the table for the condition where
accelerator pedal displacement is 0%.
[0023] The table shown in FIG. 3 as an example of a lookup table
for use in the present invention is only a partial lookup table
developed based on a vehicle's desired accelerator response
profile. Each vehicle model can have a different response profile,
and thus a different lookup table than another vehicle model.
Further, economy, normal and performance modes for a single vehicle
could be incorporated through the use of multiple lookup tables or
by multipliers. For example, given the same accelerator pedal
displacement and current vehicle speed, the lookup table for the
performance mode would provide a target acceleration greater than
that provided by the lookup table for the economy mode.
[0024] Some examples using FIG. 3 will illustrate the use of the
table lookup function to determine target acceleration in step 50
of FIG. 2. If the accelerator pedal displacement measured in step
42 is 10%, and the current vehicle speed measured in step 44 is 40
mph, then the target acceleration indicated by the driver is 0.1
m/sec.sup.2. If the accelerator pedal displacement measured in step
42 is 4%, and the current vehicle speed measured in step 44 is 30
mph, then the target acceleration indicated by the driver is -0.3
m/sec.sup.2, i.e., a target deceleration of 0.3 m/sec.sup.2.
[0025] Returning now to FIG. 2, another table lookup function is
used in step 52 to determine the end vehicle speed for a given
accelerator pedal displacement. The end vehicle speed is the speed
at which the vehicle would eventually settle if the accelerator
pedal displacement remained constant. The same lookup table of FIG.
3 illustrates the operation of this table lookup function. Because
zero acceleration indicates a driver's desire to maintain current
vehicle speed, step 52 is performed by advancing down the column of
the accelerator pedal displacement as measured in step 42 until a
row indicating zero acceleration is reached. The speed
corresponding to zero acceleration is the end vehicle speed. By
example, if the accelerator pedal displacement is 10%, then the end
vehicle speed is 50 mph. Also by example, if the accelerator pedal
displacement is 4%, then the end vehicle speed is 10 mph.
[0026] Returning now to FIG. 2, a standard controller, preferably a
feed forward proportional, integral and derivative (PID)
controller, is used in step 54 to determine a desired vehicle speed
and thus a desired throttle position. A block diagram illustrating
the inputs and outputs for the controller is illustrated in FIG. 4.
Current vehicle speed measured in step 44 is the feedback variable.
The difference (error) between the end vehicle speed from step 52
and the current vehicle speed from step 44 is fed into the
controller, which calculates a desired vehicle speed using a gain
based on the target acceleration from step 50. The target
acceleration from step 50 itself can be used in the controller to
determine the gain or, as is easily seen by one skilled in the art,
the gain can be determined from another acceleration-based engine
parameter such as torque or horsepower if, for example, a mass
sensor is located on the vehicle. The output of the controller is
the signal ETC, which is intended to control the throttle actuator
13 of the vehicle to a desired throttle position corresponding to
the desired vehicle speed.
[0027] Returning now to FIG. 2, the desired throttle position is
determined in step 54. In step 56, the procedure checks other
engine control systems to determine whether these systems detect a
problem limiting changes in the throttle position. Such systems
include brake torque, driveline protection, traction control, and
powertrain protection, to name a few. In step 58, this arbitration
is performed. If any of these systems indicate a need to limit
increases in the throttle position, and the desired throttle
position requires an increase over the current throttle position,
the procedure ends at step 48 without changing throttle position.
For example, if the traction control system detects icy conditions,
the result of the arbitration will be to close down the throttle,
i.e., no increases in throttle position will be allowed, preventing
acceleration. If, however, the other systems do not indicate a need
to limit increases in the throttle position, then the procedure
advances to step 60, where the signal ETC directs the throttle
actuator 13 to increase, reduce or maintain the angle of the
throttle 12 to the desired throttle position determined in step 54.
The procedure then ends at step 48. The procedure runs at
predetermined intervals from start up of the engine to shut down.
Pedal displacement and speed are sampled at predetermined
intervals, preferably at 12.5 ms intervals.
[0028] Thus, the present invention controls the throttle position
of an engine by incorporating the driver's intentions as to target
acceleration and end vehicle speed, instead of using the current
pedal progression of the electronic throttle control that directly
changes throttle position based on accelerator pedal displacement.
In this manner, the driver can maintain a constant vehicle speed
through the application of a consistent pedal displacement
regardless of terrain, altitude or vehicle loading conditions
without activating a cruise control system. The driver can also
accelerate or decelerate the vehicle to an end vehicle speed
through application of a consistent pedal displacement.
* * * * *