U.S. patent application number 09/836732 was filed with the patent office on 2002-01-31 for apparatus and method for determining vehicle operating and dynamic parameters.
Invention is credited to Schanzenbach, Matthias, Weiberle, Reinhard.
Application Number | 20020013651 09/836732 |
Document ID | / |
Family ID | 8168452 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020013651 |
Kind Code |
A1 |
Weiberle, Reinhard ; et
al. |
January 31, 2002 |
Apparatus and method for determining vehicle operating and dynamic
parameters
Abstract
The invention describes an apparatus and method for determining
at least one wheel slip of a vehicle and at least one of a pitch
angle, a road angle, a roll angle for use in at least one vehicle
control system. The method and apparatus are characterized in that
at least three deflection displacements are determined, and then at
least one wheel slip of the vehicle and at least one of the pitch
angle, the road angle, the roll angle of the vehicle are determined
based on the at least three deflection displacements. The wheel
slip(s) of the vehicle and at least one of the pitch angle, the
road angle, and the roll angle of the vehicle may be provided or
otherwise made available to the at least one vehicle control
system.
Inventors: |
Weiberle, Reinhard;
(Vaihingen/enz, DE) ; Schanzenbach, Matthias;
(Eberstadt, DE) |
Correspondence
Address: |
KENYON & KENYON
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
8168452 |
Appl. No.: |
09/836732 |
Filed: |
April 17, 2001 |
Current U.S.
Class: |
701/71 ; 180/197;
701/82 |
Current CPC
Class: |
B60G 2400/0512 20130101;
B60G 2800/70 20130101; B60G 2400/252 20130101; B60G 2800/21
20130101; B60G 2400/61 20130101; B60G 2800/22 20130101; B60T 8/172
20130101; B60G 2400/104 20130101; B60G 2800/0192 20130101; B60G
2400/63 20130101; B60G 17/0195 20130101; B60G 2800/215 20130101;
B60G 2400/106 20130101; B60G 2400/102 20130101; B60G 2400/208
20130101; B60G 2400/822 20130101; B60G 2400/0511 20130101; B60G
2800/92 20130101; B60G 17/018 20130101; B60G 2400/204 20130101;
B60G 2800/93 20130101 |
Class at
Publication: |
701/71 ; 701/82;
180/197 |
International
Class: |
B60T 008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 17, 2000 |
EP |
00 107 952.4 |
Claims
1. An apparatus for determining at least one wheel slip (s) of a
vehicle (10) and at least one of a pitch angle (.PHI.), a road
angle and a roll angle (.chi.) of the vehicle for use in at least
one vehicle control system (1), characterized in that the apparatus
includes: at least three deflection displacement sensing devices
that are adapted for sensing a first parameter that corresponds to
a first deflection displacement, a second parameter that
corresponds to a second deflection displacement, and at least a
third parameter that corresponds to a third deflection
displacement; and a processor (P.sub.B) for determining the at
least one wheel slip (s) of the vehicle and the at least one of the
pitch angle, the road angle and the roll angle based on the first
deflection displacement, the second deflection displacement, and
the third deflection displacement.
2. The apparatus as defined in claim 1, characterized in that the
at least one vehicle control system (1) is at least one of an
active-handling control system, an anti-lock brake control system,
an acceleration control system, a deceleration control system, a
drive-train control system, a roll-stability control system, a
traction control system, a vehicle stability control system and a
vehicle dynamics control system.
3. The apparatus as defined in claim 1 or 2, characterized in that
the at least one vehicle control system (1) includes an anti-lock
brake control system that controls a brake system based on at least
one of a vehicle velocity (.nu..sub.fzg) and the at least one wheel
slip (s), and further characterized in that the processor (P.sub.B)
determines the at least one wheel slip (s) and determines a vehicle
velocity (84 .sub.fzg) based on the at least one wheel slip
(s).
4. The apparatus as defined in claim 1, 2, or 3, characterized in
that the apparatus includes a sensing device that is adapted to
sense a first parameter that corresponds to a transverse
acceleration of the vehicle (10), and further characterized in that
the processor determines the at least one wheel slip (s) of the
vehicle (10) and the at least one of the pitch angle (.PHI.), the
road angle and the roll angle (.chi.) based on the transverse
acceleration.
5. The apparatus as defined in claim 4, characterized in that the
sensing device is a transverse acceleration sensor.
6. The apparatus as defined in claim 1, 2, 3, 4, or 5,
characterized in that the at least one vehicle control system (1)
includes a deceleration control system, having a braking
characteristic curve, that controls a brake system based on at
least one of the braking characteristic curve and an unbraked wheel
acceleration, and further characterized in that the processor
(P.sub.B) determines an unbraked wheel acceleration during a
braking operation, and adds the unbraked wheel acceleration as an
offset to the braking characteristic curve.
7. The apparatus as defined in claim 6, characterized in that the
processor (P.sub.B) determines the road angle and determines the
unbraked wheel acceleration based on at least a vehicle velocity
(.nu..sub.fzg) and the road angle.
8. The apparatus as defined in claim 7, characterized in that the
processor (P.sub.B) determines the vehicle velocity (.nu..sub.fzg)
based on the at least one wheel slip,(s).
9. The apparatus as defined in claim 1, 2, 3, 4, 5, 6, 7, or 8,
characterized in that the processor provides the at least one wheel
slip (s) of the vehicle (10) and the at least one of the pitch
angle (.PHI.), the road angle, and the roll angle (.chi.) of the
vehicle (10) to the at least one vehicle control system (1).
10. An apparatus for determining at least one wheel slip (s) of a
vehicle (10) and at least one of a pitch angle (.PHI.), a road
angle and a roll angle (.chi.) of the vehicle (10) for use in at
least one vehicle control system(1), including a deceleration
control system, which has a braking characteristic curve, that
controls a brake system based on at least one of the braking
characteristic curve and an unbraked wheel acceleration,
characterized in that the apparatus includes: means for sensing a
first parameter that corresponds to a first deflection
displacement, a second parameter that corresponds to a second
deflection displacement, and at least a third parameter that
corresponds to at least a third deflection displacement; means for
determining the at least one wheel slip (s) based on at least one
of first deflection displacement, the second deflection
displacement, and the third deflection displacement; means for
determining the at least one wheel slip (s) based on at least one
of first deflection displacement, the second deflection
displacement, and the third deflection displacement; means for
determining the road angle and at least one of the pitch angle and
the roll angle (.chi.) based on at least one of first deflection
displacement, the second deflection displacement, and the third
deflection displacement; and means for determining an unbraked
wheel acceleration during a braking operation and adding the
unbraked wheel acceleration as an offset to the braking
characteristic curve.
11. The apparatus as defined in claim 10, characterized in that the
apparatus includes means for providing the at least one wheel slip
(s) of the vehicle (10) and the at least one of the pitch angle
(.PHI.), the road angle, and the roll angle of the vehicle (10) to
the at least one vehicle control system.
12. The apparatus as defined in claim 10 or 11, characterized in
that the means for determining the unbraked wheel acceleration
determines the unbraked wheel acceleration based on at least a
vehicle velocity (.nu..sub.fxg) and the road angle.
13. The apparatus as defined in claim 12, characterized in that the
apparatus includes means for determining the vehicle velocity
(.nu..sub.fzg) based on the at least one wheel slip (s).
14. The apparatus as defined in one of the foregoing claims,
characterized in that the processor (P.sub.B) determines at least
one wheel normal force and a vehicle mass (m) based on the at least
one wheel normal force.
15. A method for determining at least one wheel slip (s) of a
vehicle (10) and at least one of a pitch angle(.PHI.), a road angle
and a roll angle (.chi.) for use in at least one vehicle control
system (1), characterized in that the method includes the steps of:
determining a first deflection displacement; determining a second
deflection displacement; determining a third deflection
displacement; and determining the at least one wheel slip (s) of
the vehicle (10) and the at least one of the pitch angle (.PHI.),
the road angle and the roll angle (.chi.) based on the first
deflection displacement, the second deflection displacement, and
the third deflection displacement.
16. The method as defined in claim 15, characterized in that the at
least one vehicle control system (1) is at least one of an
active-handling control system, an anti-lock brake control system,
an acceleration control system, a deceleration control system, a
drive-train control system, a roll-stability control system, a
traction control system, a vehicle stability control system and a
vehicle dynamics control system.
17. The method as defined in claim 15 or 16, characterized in that
the at least one vehicle control system (1) includes an anti-lock
brake control system that controls a brake system based on at least
one of a vehicle velocity (.nu..sub.fzg) and the at least one wheel
slip (s), and further characterized in that the method includes the
steps of: determining the at least one wheel slip (s); and
determining a vehicle velocity (.nu..sub.fzg) based on the at least
one wheel slip (s).
18. The method as defined in claim 15, 16, or 17, characterized in
that the at least one vehicle control system (1) includes a
deceleration control system, having a braking characteristic curve,
that controls a brake system based on at least one of the braking
characteristic curve and an unbraked wheel acceleration, and
further characterized in that the method includes the steps of:
determining an unbraked wheel acceleration during a braking
operation; and adding the unbraked wheel acceleration as an offset
to the braking characteristic curve.
19. The method as defined in claim 18, characterized in that the
method includes the steps of: determining the road angle; and
determining the unbraked wheel acceleration based on at least a
vehicle velocity (.nu..sub.fzg) and the road angle.
20. The method as defined in claim 19, characterized in that the
method includes the step of determining the vehicle velocity
(.nu..sub.fzg) based on the at least one wheel slip (s).
21. The method as defined in claim 10, characterized in that the
method includes the step of providing the at least one wheel slip
(s) of a vehicle (10) and the at least one of the pitch angle
(.PHI.), the road angle, and the roll angle (.chi.) of the vehicle
(10) to the at least one vehicle control system.
22. The method as defined in claim 15, 16, 17, 18, 19, 20, or 21,
characterized in that the method includes the steps of: determining
at least one wheel normal force; and determining a vehicle mass (m)
based on the at least one wheel normal force.
Description
[0001] The present invention concerns, in part, an apparatus as
defined in the preambles of claims 1 and 10, and a method as
defined in the preamble of claim 15.
[0002] Each of commonly assigned patent references DE 40 39 629 C2
(which has a corresponding PCT reference WO 92/10377) and DE 42 28
414 A1 relate to devices and methods in the field of regulating
vehicle dynamics or movements. According to an abstract of DE 40 39
629 C2, it concerns a system for generating signals for adjusting
or controlling a vehicle body. To reduce certain movements of the
vehicle, speed sensor signals and suspension deflection sensor
signals are involved in determining the vehicle speed and the
longitudinal and transverse vehicle accelerations. Vehicle
movements, which may include "proper" swinging, pitching or rolling
movements and "proper" vertical displacements of the front and rear
of the vehicle, are involved in compensating or controlling the
vehicle suspension systems. Additionally, according to an abstract
of DE 42 28 414 A1, a signal processing system detects a first set
of signals that represent the movement of the vehicle relative to a
fixed reference system, and uses these signals to provide a
corresponding set of corrected signals for a travel path of the
vehicle. In particular, the sensor signals may represent the
transverse velocity and the longitudinal, transverse and vertical
accelerations of the vehicle. As discussed in the abstract, the
system may be used to control or regulate an active vehicle
suspension system, and may correct for certain vehicle movements
relative to an inclined path that may be associated with the
gravitational acceleration components of the measured signals.
[0003] Vehicle brake-by-wire systems, such as, for example,
electromechanical brake systems or electro-hydraulic brake systems,
may be equipped with wheel braking force control, wheel braking
torque control or other anti-lock brake control systems, and may
also be provided with a deceleration control system. In a
deceleration control system of a brake-by-wire system, there may be
no fixed setpoint value for a wheel deceleration that may be
associated or correlated with a particular level of brake-pedal
travel or brake-pedal force that corresponds with the experience or
experiential frame of reference of a driver. Accordingly, a
deceleration control system may present certain problems in
determining or obtaining an expected or setpoint deceleration value
for a particular point on a "driver" or a "brake pedal operation"
characteristic curve. It is believed that this is because in such a
deceleration control system or "deceleration pedal" braking system,
an unpressed brake pedal may correspond to a wheel deceleration of
zero (0) and an actuated or depressed brake pedal may correspond to
a wheel acceleration that is less than zero (0). In particular, one
problem that may occur, for example, is when a driver is driving
down a hill. In such a case, the driver may achieve wheel
acceleration even while depressing the brake pedal. Any such wheel
acceleration, of course, should be less than the wheel acceleration
that might result if the driver did not actuate or depress the
brake pedal. That is, when driving down a hill, the vehicle may
accelerate more if the brake pedal is not actuated or depressed. If
the driver increases the force on the brake pedal, this should
reduce wheel acceleration to zero (0) and eventually make it
negative so that there is wheel deceleration, rather than wheel
acceleration.
[0004] This braking behavior may be simulated by determining an
instantaneous unbraked wheel acceleration and adding it as an
offset to a characteristic curve of the "brake pedal operation" for
a driver. If the unbraked wheel acceleration offset is not
determined during actual braking conditions, however, then the
characteristic curve of the "brake pedal operation" may depart (in
a possibly dangerous manner or way) from the experience or
experiential frame of reference of the driver. For example, when
driving off of a car transporter ramp, for example, or down some
other incline, a driver may brake on the ramp or other inclined
surface to adjust the deceleration to zero (0). The offset that is
determined or obtained, however, may be for an accelerating
vehicle. Accordingly, if the same operation of the brake pedal is
used to adjust the deceleration to zero (0) after the vehicle moves
to a relatively level surface, then the brakes may open or
otherwise become ineffective. Since the driver may not decelerate
by depressing the brake pedal while on a level road, this result
may be inconsistent with the experiential frame of reference of the
driver.
[0005] As further regards the implementation of a wheel
deceleration control systems and/or an anti-lock brake system
control system, such an implementation may be problematic since the
controlled deceleration of the wheels may make it impractical for
the wheel speed sensors to measure the wheel speeds when the wheel
speeds are dropping relatively sharply because of relatively high
wheel decelerations. In this regard, FIG. 1 shows a graph of wheel
deceleration control at low friction values (.mu.), in which
V.sub.jahrzueg corresponds to a vehicle speed or velocity
V.sub.vehicles V.sub.Rad, soll corresponds to a desired wheel speed
V.sub.wheel-desired and V.sub.Rad, ist corresponds to an actual
wheel speed V.sub.wheel-actual. In particular, FIG. 1 shows
deceleration control at low friction values (.mu.), in which the
actual wheel speed conforms to the desired wheel speed, and in
which the wheel slip becomes increasingly greater until the wheel
locks when a vehicle speed is not zero (0).
[0006] In certain anti-lock brake control systems, wheel locking
may be detected by comparing the vehicle speed with the wheel
speeds. As a practical matter, however, wheel slip and other
factors may complicate the process of detecting or determining the
actual vehicle speed or velocity. Accordingly, in certain anti-lock
brake control systems, vehicle speed may be determined
approximately based on each of the wheel speeds. Thus, for example,
the output of a wheel speed sensor on each wheel may be provided to
a processor for an anti-lock brake control system, in which the
wheel speeds are compared to determine an estimated vehicle speed.
The estimated vehicle speed may, of course, be differentiated to
determine the vehicle acceleration or deceleration. If any wheel
(or set of wheels) exceeds or drops below some predetermined
velocity rate and/or acceleration rate, a correcting control signal
may be applied to the braking system to compensate for any locking
or slipping of a wheel. Accordingly, if a more accurate vehicle
velocity--which depends on the wheel slip(s), could be determined,
it is believed that a more accurate or efficient anti-lock braking
control system may be provided.
[0007] The method and apparatus of some exemplary embodiments of
the present invention are characterized in that a plurality of
deflection displacements are determined, and then at least one
wheel slip of a vehicle and at least one of a pitch angle, a road
angle, and a roll angle of the vehicle are determined based on the
plurality of deflection displacements. Also, at least one wheel
slip of a vehicle and at least one of the pitch angle, the road
angle, and the roll angle of the vehicle may be provided or
otherwise made available to at least one vehicle control
system.
[0008] In view of the above needs and problems, one embodiment of
the present invention is directed to an apparatus for determining
at least one wheel slip of a vehicle and at least one of a pitch
angle, a road angle and a roll angle of the vehicle for use in at
least one vehicle control system, characterized in that the
apparatus includes: at least three sensing devices that are adapted
for sensing a first parameter that corresponds to a longitudinal
acceleration, a second parameter that corresponds to a transverse
acceleration, and a third parameter that corresponds to a vertical
acceleration; and a processor that determines the at least one
wheel slip of the vehicle and the at least one of the pitch angle,
the road angle and the roll angle based on the longitudinal
acceleration, the transverse acceleration and the vertical
acceleration. The at least one wheel slip of the vehicle and the at
least one of the pitch angle, the road angle, and the roll angle of
the vehicle may be provided to the at least one vehicle control
system.
[0009] Another embodiment of the present invention is directed to a
method for determining at least one wheel slip of a vehicle and at
least one of a pitch angle, a road angle and a roll angle for use
in at least one vehicle control system, characterized in that the
method includes the steps of: determining a longitudinal
acceleration; determining a transverse acceleration; determining a
vertical acceleration; and determining the at least one wheel slip
of the vehicle and the at least one of the pitch angle, the road
angle and the roll angle based on the longitudinal acceleration,
the transverse acceleration and the vertical acceleration. The at
least one wheel slip of the vehicle and the at least one of the
pitch angle, the road angle, and the roll angle of the vehicle may
be provided to the at least one vehicle control system.
[0010] Still another embodiment of the present invention is
directed to an apparatus for determining at least one wheel slip of
a vehicle and at least one of a pitch angle, a road angle and a
roll angle of the vehicle for use in at least one vehicle control
system, including a deceleration control system, which has a
braking characteristic curve, that controls a brake system based on
at least one of the braking characteristic curve and an unbraked
wheel acceleration, characterized in that the apparatus includes:
means for sensing a first parameter that corresponds to a
longitudinal acceleration, a second parameter that corresponds to a
transverse acceleration, and a third parameter that corresponds to
a vertical acceleration; means for determining the at least one
wheel slip based on at least one of the longitudinal acceleration,
the transverse acceleration and the vertical acceleration; means
for determining the road angle and at least one of the pitch angle
and the roll angle based on at least one of the longitudinal
acceleration, the transverse acceleration and the vertical
acceleration; and means for determining the unbraked wheel
acceleration during a braking operation and adding the unbraked
wheel acceleration as an offset to the braking characteristic
curve.
[0011] Yet another embodiment of the present invention is directed
to an apparatus for determining at least one wheel slip of a
vehicle and at least one of a pitch angle, a road angle and a roll
angle of the vehicle for use in at least one vehicle control
system, characterized in that the apparatus includes: at least
three deflection displacement sensing devices that are adapted for
sensing a first parameter that corresponds to a first deflection
displacement, a second parameter that corresponds to a second
deflection displacement, and at least a third parameter that
corresponds to a third deflection displacement; and a processor for
determining the at least one wheel slip of the vehicle and the at
least one of the pitch angle, the road angle and the roll angle
based on the first deflection displacement, the second deflection
displacement, and the third deflection displacement. The at least
one wheel slip of the vehicle and the at least one of the pitch
angle, the road angle, and the roll angle of the vehicle may be
provided to the at least one vehicle control system.
[0012] Still another embodiment of the present invention is
directed to a method for determining at least one wheel slip of a
vehicle and at least one of a pitch angle, a road angle and a roll
angle for use in at least one vehicle control system, characterized
in that the method includes the steps of: determining a first
deflection displacement; determining a second deflection
displacement; determining a third deflection displacement; and
determining the at least one wheel slip of the vehicle and the at
least one of the pitch angle, the road angle and the roll angle
based on the first deflection displacement, the second deflection
displacement, and the third deflection displacement. The at least
one wheel slip of the vehicle and the at least one of the pitch
angle, the road angle, and the roll angle of the vehicle may be
provided to the at least one vehicle control system.
[0013] Yet another embodiment of the present invention is directed
to an apparatus for determining at least one wheel slip of a
vehicle and at least one of a pitch angle, a road angle and a roll
angle of the vehicle for use in at least one vehicle control
system, including a deceleration control system, which has a
braking characteristic curve, that controls a brake system based on
at least one of the braking characteristic curve and an unbraked
wheel acceleration, characterized in that the apparatus includes:
means for sensing a first parameter that corresponds to a first
deflection displacement, a second parameter that corresponds to a
second deflection displacement, and at least a third parameter that
corresponds to at least a third deflection displacement; means for
determining the at least one wheel slip based on at least one of
first deflection displacement, the second deflection displacement,
and the third deflection displacement; means for determining the at
least one wheel slip based on at least one of first deflection
displacement, the second deflection displacement, and the third
deflection displacement; means for determining the road angle and
at least one of the pitch angle and the roll angle based on at
least one of first deflection displacement, the second deflection
displacement, and the third deflection displacement; and means for
determining an unbraked wheel acceleration during a braking
operation and adding the unbraked wheel acceleration as an offset
to the braking characteristic curve.
[0014] Further advantages of the present invention(s) are also
evidenced by the claims, including the dependent claims, and the
present description, including the referenced Figures.
[0015] The present invention(s) are described and explained in
detail with respect to the exemplary embodiments and to the
referenced Figures.
[0016] FIG. 1 shows a graph of wheel deceleration control at low
friction values (.mu.), in which V.sub.fahrzeug corresponds to a
vehicle speed or velocity V.sub.vehicles V.sub.Rad, soll
corresponds to a desired wheel speed V.sub.wheel-desired and
V.sub.rad, ist corresponds to an actual wheel speed
V.sub.wheel-actual.
[0017] FIG. 2 shows a two (2) dimensional schematic of a vehicle
10, which has a center of gravity "SP", and which has front wheels
20, rear wheels 30 and rear wheel springs 31 (the front wheel
springs are not shown).
[0018] FIG. 3 shows a schematic representation of the wheel load
distribution of the vehicle 10 of FIG. 2.
[0019] FIG. 4 shows a total vehicle control system 1 that may
include a number of vehicle control subsystems or Systems
VCS.sub.A, VCS.sub.B, . . . , VCS.sub.H, . . . , VCS.sub.R, . . . ,
VCS.sub.Z(100a, 100b, . . . , 100h, . . . , 100r, . . . , 100z)
that may be used to implement the methods of FIG. 5, FIG. 6, FIG. 7
and/or FIG. 8.
[0020] FIG. 5 shows an acceleration sensor method for determining
the vehicle wheel slip(s) and other vehicle dynamic parameters,
including the road angle.
[0021] FIG. 6 shows a deflection displacement sensor method for
determining vehicle wheel slip(s) and other vehicle dynamic
parameters, including the wheel normal forces and the vehicle
mass.
[0022] FIG. 7 shows a deceleration control method that uses either
the acceleration sensor method of FIG. 5 or the deflection
displacement sensor method of FIG. 6 for determining the unbraked
wheel acceleration, as well as other vehicle dynamic parameters,
including the vehicle wheel slip(s) and the road angle.
[0023] FIG. 8 shows a wheel slip braking control method that uses
either the acceleration sensor method of FIG. 5 or the deflection
displacement sensor method of FIG. 6 for determining the vehicle
wheel slip(s), as well as other vehicle dynamic parameters,
including the road angle.
[0024] To discuss the apparatus and method of the present
invention, some of the definitions or parameters that are used are
as follows:
[0025] l=wheelbase length;
[0026] S.sub.spur=track width;
[0027] h=height of center of gravity;
[0028] m=vehicle mass;
[0029] .alpha..sub.laengs ({tilde over
(.alpha.)}.sub.laengs)=longitudinal acceleration (adjusted
longitudinal acceleration);
[0030] .alpha..sub.quer=transverse acceleration;
[0031] .alpha..sub.vert=vertical acceleration;
[0032] g=gravitational acceleration;
[0033] .gamma.=angle of the vertical axis to the direction in which
the gravitational acceleration acts;
[0034] .alpha..sub.laengs=road angle in the vehicle's longitudinal
direction (where up corresponds to a negative value, and down
corresponds to a positive value);
[0035] .alpha..sub.quer=road angle in the vehicle's transverse
direction;
[0036] .chi.=roll angle;
[0037] .PHI.=pitch angle;
[0038] .PSI.=yaw angle;
[0039] .delta..sub.lenkung (.delta..sub.l)=steering angle; and
[0040] .beta.=attitude angle.
[0041] Additionally, some further definitions and parameters are as
follows:
[0042] .alpha..sub.zentripetal=centripetal acceleration;
[0043] .alpha..sub.stoer=interference acceleration associated with
the air resistance (negative in the direction of .nu..sub.fzg);
[0044] .iota..sub..nu.=distance from the front axle to the center
of gravity of the vehicle;
[0045] .iota..sub.h=distance from the rear axle to the center of
gravity of the vehicle;
[0046] F.sub.Nk=wheel normal force (normal force on k-th
wheel);
[0047] .nu..sub.fzg=relative speed of the vehicle;
[0048] .chi..sub.f=deflection displacement associated with a wheel
spring(s) of the vehicle;
[0049]
.DELTA..chi..sub..function..sub..sub.--.sub..sup.nick=difference
between the deflection displacement of the wheel springs of the
front and rear axles of the vehicle; and
[0050] .DELTA.x.sub.f.sub..sub.--.sub..sup.wank=difference between
the deflection displacement of the wheel springs of the left and
right sides of the vehicle.
[0051] In one approach or method, at least three acceleration
sensors, which may be mounted perpendicularly to one another, may
be used to determine the braking slip at each of the vehicle wheels
and the road angle, as well as other dynamic parameters, such as
the pitch angle and the road angle. Preferably, the acceleration
sensors should be positioned as close as is practical to the
vehicle's center of gravity to reduce or at least limit certain
dynamic acceleration effects. In this regard, FIG. 2 shows a two
(2) dimensional schematic of a vehicle 10, which has a center of
gravity "SP", and which has front wheels 20, rear wheels 30 and
rear wheel springs 31 (the front wheel springs are not shown).
[0052] As discussed below, if used with an electronic stability
(program) control system (ESP, FDR or other suitably appropriate
vehicle control system) that has a transverse acceleration sensor,
then only two additional acceleration sensors may be required.
While the apparatus and method described below may, of course, make
use of certain electronic stability (program) control (ESP, FDR or
other vehicle control system) sensor signals (which may exclude the
pre-control pressure sensor) so that only two additional
acceleration sensors are required, the apparatus and method may, of
course, be implemented without using such systems by providing at
least three acceleration sensors or some other suitably appropriate
sensor arrangement.
[0053] For the longitudinal acceleration sensor, which is oriented
or positioned in the vehicle's longitudinal direction:
.sup..alpha.laengs_sensor=g.cndot.sin(.PHI.+.alpha..sub.laengs)+.alpha..su-
b.laengs .cndot.cos(.PHI.)+.alpha..sub.vert.cndot.sin(.PHI.)
(1).
[0054] Thus, the longitudinal acceleration sensor signal depends on
the pitch angle .PHI. and the road angle .alpha., and not on the
vehicle's roll angle .chi.. This is because the rolling motion
occurs in a plane that is perpendicular to the direction in which
the longitudinal acceleration .alpha..sub.laengs is sensed.
[0055] For the transverse acceleration sensor, which is oriented or
positioned in the vehicle's transverse direction:
.sup.60quer_sensor=g.cndot.sin(.chi.+.alpha..sub.quer)+.alpha..sub.quer.cn-
dot.cos(.chi.)+.alpha..sub.vert.cndot.sin(.chi.) (2).
[0056] Finally, for the vertical acceleration sensor, which is
oriented or positioned in the direction of the vehicle's vertical
axis:
.sup..alpha.vert_sensor=g.cndot.cos(.gamma.)-.alpha..sub.quer.cndot.sin(.c-
hi.)-.alpha..sub.laengs.cndot.sin(.PHI.)+.alpha..sub.vert.cndot.cos(.delta-
.) (3) ,
[0057] where .delta..sub.i represents the angle of the vehicle's
vertical axis to a normal line of the driving plane and .gamma.
represents the angle of the vertical axis to the direction in which
the gravitational acceleration "g" acts. The longitudinal
acceleration .alpha..sub.laengs may be determined as follows:
.alpha..sub.laengs=.alpha..sub.brems.cndot.cos(.beta.)+.alpha..sub.stoer.c-
ndot.cos(.beta.)+.alpha..sub.zentripetal.cndot.sin(.beta.) (4)
.
[0058] Since .alpha..sub.laengs is in the direction of the
vehicle's longitudinal axis, the adjusted longitudinal acceleration
{tilde over (.alpha.)}.sub.laengs and the transverse acceleration
.alpha..sub.quer may be determined as follows:
{tilde over
(.alpha.)}laengs=.alpha..sub.brems.cndot.cos(.beta.)+.alpha..s-
ub.zentripetal.cndot.sin(.beta.) (4a);
.alpha..sub.quer=.alpha..sub.brems.cndot.sin(.beta.)+.alpha..sub.stoer.cnd-
ot.sin(.beta.)+.alpha..sub.zentripetal.cndot.cos(.beta.) (5).
[0059] Using, for example, the methods in an electronic stability
program control system (such as ESP, FDR or some other suitably
appropriate vehicle control system), the attitude angle .beta. may
be determined as is known, for example, from van A. Zanten, R.
Erhardt, G. Pfaff, F. Kost, T. Ehret, U. Hartmann, Control Aspects
of the Bosch-VDC, AVEC '96, International Symposium on Advanced
Vehicle Control at Aachen University of Technology, 1996 ("the AVC
reference"), and is therefore not discussed any further.
[0060] As to determining the angle .gamma., it may be determined as
follows:
[0061] The sum of the pitch angle V and the longitudinal road angle
.alpha..sub.laengs represents the projection of a sensor position
in the x-z plane, and the sum of the roll angle .chi. and the
transverse road angle .alpha..sub.quer represents the projection of
the sensor position onto the y-z plane. Accordingly, the resulting
position of the sensor may be obtained by the intersection of two
planes. A first plane E1 runs parallel to the y-axis and has the
slope of the projection onto the x-z plan, and a second plane E2
runs parallel to the x-axis and has the slope of the projection in
the y-z plane. The result is a line that describes the direction of
action on the vertical sensor and a resulting angle .gamma. of the
vertical axis to the direction in which the gravitational
acceleration acts.
[0062] The first plane E1 is composed of two directions and one
point P1, as follows: 1 P1 = ( 0 0 0 ) a _ = ( 0 1 0 ) a _ = ( z
tan ( laengs + ) 0 z ) , and E1 : x _ = ( 0 t 1 0 ) + s 1 ( z tan (
laengs + ) 0 z ) .
[0063] The second plane E2 is also composed of two directions and
one point P2, as follows: 2 P2 = ( 0 0 0 ) a _ = ( 1 0 0 ) a _ = (
0 z tan ( quer + ) z ) , and E3 : x _ = ( t 2 0 0 ) + s 2 ( 0 z tan
( quer + ) z ) .
[0064] The intersection of the two planes, namely planes E1 and E2,
provides the following:
S.sub.1.cndot.z tan(.alpha..sub.laengs+.PHI.)=t.sub.2;
t.sub.1=S.sub.2.cndot.z .cndot.tan(.alpha..sub.quer+.chi.); and
S.sub.1.cndot.z=S.sub.2.cndot.z.
[0065] It therefore follows that: t.sub.1=S.sub.1.cndot.z.cndot.tan
(.alpha..sub.quer+.chi.), and substitution into the plane equation
provides the following: 3 G : x _ = s ( tan ( laengs + ) tan ( quer
+ ) 1 ) .
[0066] Additionally, the angle ("winkel") between the direction in
which the gravitational acceleration acts and the direction of
action on the sensor may be determined as follows: 4 x _ n _ z = x
_ n _ z cos ( winkel ( x _ , n _ z ) ) winkel ( x _ , n _ z ) = =
arccos ( s ( tan ( laengs + ) tan ( quer + ) 1 ) ( 0 0 1 ) S ( tan
2 ( laengs + ) + tan 2 ( a quer + ) - 1 ) )
[0067] Thus, the angle .gamma. may be determined as follows: 5 =
arccos ( 1 tan 2 ( laengs + ) + tan 2 ( quer + ) + 1 ) . ( 6 )
[0068] The steering angle .delta..sub.1 is determined, in a
corresponding way, as follows: 6 l = arccos ( 1 tan 2 ( ) + tan 2 (
) + 1 ) . ( 7 )
[0069] Furthermore, the centripetal acceleration, based on the
instantaneous speed and the radius of curvature that is traveled,
may be determined as follows: 7 a zentripetal = v fzg 2 r kurve . (
8 )
[0070] Based on the wheel speeds and the wheel slip(s), the wheel
hub speed may be determined as follows: 8 v nabe , i = 1 1 - i v
rad , i . (9a)
[0071] The vehicle speed may be determined based on the wheel
speeds, the braking slip(s), and the yaw speed. Accordingly, the
vehicle speed at the center of gravity of the vehicle may be
determined as follows: 9 v fzg = 1 1 - i v rad , i S spur 2 . . ( 9
)
[0072] The radius of curvature may be determined based on the
vehicle speed .nu..sub.fzg, the steering angle .delta..sub.lenkung,
the wheelbase 1, the steering ratio i.sub.L, and the characteristic
speed .nu..sub.char (see the following reference: Mitschke, M.
Dynamik der Kraftfahrzeuge ("motor vehicle dynamics"),, vol. C:
Fahrverhalten ("driving behavior"), Springer-Verlag, 2nd edn.
(1990) ("the Mitschke reference"), equations 9.5 and 9.6 at page
34), as follows: 10 r kurve = i L l lenkung + i L l v fzg 2 v char
2 lenkung . ( 10 )
[0073] As regards the roll angle, it includes a static roll angle,
which is caused by or at least related to unsymmetrical loading,
and a dynamic roll angle, which is caused by or at least related to
the transverse acceleration and the transverse road angle.
Depending on the particular application, it is believed that the
static roll angle may be assumed to be zero without introducing
unacceptable error, since the stabilizers may help maintain the
vehicle in a relatively level orientation. The dynamic roll angle
may be determined based on the track width and the vehicle's
deflection displacement, which may be measured using deflection
displacement sensors at the front and rear axles, and may be
determined as follows: 11 = arctan ( X feder S spur ) , ( 11 a
)
[0074] where .DELTA.X.sub.feder represents the difference in the
deflection displacement between the two (2) wheels of one (1) axle
of the vehicle. Since the vehicle may be "compressed" because of an
increased wheel load on one side and may be "extended" because of a
reduced wheel load on the other side, the overall "compression and
extension" may be determined as follows: 12 X feder = 1 C f - wank
2 F N , ( 11 b )
[0075] where .DELTA.F.sub.N represents the load change associated
with a wheel(s). In the foregoing equation,
C.sub..function..sub..sub.--.sub..su- p.wank describes or
corresponds to the spring constant which acts in the direction of
the rolling motion (including the torsional rigidity of any
stabilizer). The additional or differential wheel load, which is
associated with a transverse force F.sub.quers may be determined as
follows: 13 F N = 1 2 h S spur F quer . ( 11 c )
[0076] Additionally, the transverse force F.sub.quer may be
determined, based on the transverse acceleration and the vehicle
mass, as follows:
F.sub.quer=m.cndot..alpha..sub.quer (11d).
[0077] Based on the transverse road angle, it follows that: 14 X
feder = 1 C f - wank h S spur m g tan ( quer ) cos ( quer ) . ( 11
e )
[0078] By making the appropriate substitutions in the above
equations of 11a, 11b, 11c, 11d and 11e, the total roll angle .chi.
may be determined as follows: 15 = arctan ( h m C f - wank S spur 2
( a quer + g sin ( quer ) ) ) . ( 11 )
[0079] The pitch angle .PHI. includes a static component
.PHI..sub.stat and a dynamic component .PHI..sub.d.
.PHI.=.PHI..sub.stat+.PHI..sub.d (12).
[0080] In particular, the static component .PHI..sub.stat of the
pitch angle .PHI. describes or corresponds to the nature of the
load, and the dynamic component .PHI..sub.d of the pitch angle
.PHI. describes or corresponds to the longitudinal acceleration and
the road angle. Corresponding to the procedure used for the roll
angle, the components of the dynamic pitch angle are the deflection
(or compression) displacement associated with the front axle, the
extension travel associated with the rear axle and the wheel base
length .iota.. Accordingly, the dynamic pitch angle .PHI..sub.d may
be determined as follows: 16 d = arctan ( 2 S feder 1 ) = arctan (
( ( l v l + l h l ) m h l C feder l ( - a ~ laengs + g sin ( laengs
) ) ) . ( 13 )
[0081] If there is no wind, the deceleration .alpha..sub.stoer
associated with the vehicle's air resistance may be determined as
follows: 17 a stoer = - F Lx m = - 1 m C w A 2 V 2 fzg ( 14 )
[0082] (see the Mitschke reference, equation 25. 6), where "A"
corresponds to the vehicle's cross-sectional area, C.sub.W
corresponds to the drag coefficient, and .rho. corresponds to the
air density.
[0083] The braking deceleration .alpha..sub.brems may be determined
as follows: 18 a brems = - 1 m k = 1 4 F Br k = - 1 m k = 1 4 F N k
k . ( 15 a )
[0084] In the linear operating range of a tire characteristic
curve, the coefficient of friction, .mu..sub.k, depends on the
wheel slip, .lambda..sub.k, and the tire's slip rigidity,
k.sub.Relfen, which is a tire-specific characteristic value that
depends on or varies with the slip angle .alpha..sub.k and the
wheel normal force F.sub.Nk. During partial linear braking, in
which the tires are in the linear operating range of the tire
characteristic curve, the braking deceleration may be determined as
follows: 19 a brems = - 1 m k = l 4 F N k k k Reifen ( k , F N k )
, ( 15 )
[0085] in which the slip angle .alpha..sub.k depends on or is a
function of .nu..sub.fzg and .GAMMA..sub.kurve (see the Mitschke
reference, equations 9.20 and 9.21 at page 37). Also,
.lambda..sub.k is the slip of the k-th wheel and F.sub.Nk is the
associated wheel load, which includes a static wheel load
distribution component and an acceleration-dependent component. The
dynamic changes in a wheel load for a wheel(s) may be determined as
follows: 20 F N d y n = l v / h l h l m a ~ laengs 1 2 h S spur m a
quer . ( 16 a )
[0086] FIG. 3 shows a schematic representation of the wheel load
distribution of the vehicle 10 of FIG. 2. In this regard, if the
vehicle 10 is mapped onto a plane that has a normal line running in
the direction of the vehicle's transverse axle, the static wheel
load distribution component may be determined as follows: 21 F stat
- V A / HA = l h / v h tan ( laengs ) l m g cos ( laengs ) . ( 16 b
)
[0087] For each wheel, the static wheel load may be determined by
projecting the vehicle onto the plane in the travel direction of
the vehicle. To simplify the equation of 16b, it may be assumed
that the center of gravity is located in the middle of the vehicle,
which provides the following: 22 F stat = S spur 2 h tan ( quer ) S
spur F stat - V A / HA cos ( quer ) . ( 16 c )
[0088] It therefore follows that: 23 F N = S spur 2 h tan ( quer )
S spur l h / v h tan ( laengs ) l m g cos ( laengs ) cos ( quer ) l
v / h l h l m a ~ laengs 1 2 h S spur m a quer . ( 16 )
[0089] The braking slip .lambda. may be determined as follows: 24 =
1 - V Rad V nabe . ( 17 a )
[0090] Now, the wheel hub speed V.sub.nabe may be determined by
integrating the longitudinal acceleration of the associated wheel
hub. Since integration adds up any errors, the braking or wheel
slip at a constant deceleration (which may be determined using the
wheel speeds), may be determined as follows: 25 = 1 - a Rad a nabe
, ( 17 )
[0091] where the accelerations may be determined as follows: 26 a
nabe = a fzg S spur 2 ; ( 17 b )
.alpha..sub.fzg=.alpha..sub.brems+.alpha..sub.stoer+g.cndot.sin(.alpha..su-
b.laengs).cndot.cos(.beta.) (17c).
[0092] Also, the parameter {tilde over (.alpha.)}.sub.fzg may be
determined as follows:
{tilde over
(.alpha.)}.sub.fzg=.alpha..sub.stoer+g.cndot.sin(.alpha..sub.l-
aengs).cndot.cos(.beta.) (17d),
[0093] where {tilde over (.alpha.)}.sub.fzg represents the
difference between .alpha..sub.fzg and .alpha..sub.brems.
[0094] Thus, the wheel slip .lambda..sub.k for each wheel may be
determined based on the determined decelerations for each wheel
using equation 17, as shown above.
[0095] Thus, a total of seventeen (17) equations are available for
eighteen (18) unknown parameters, which include the longitudinal
road angle .alpha..sub.laengs, the pitch angle .PHI., the
longitudinal acceleration .alpha..sub.laengs, the vertical
acceleration .alpha..sub.vert, the roll angle .chi., the transverse
road angle .alpha..sub.quer, the transverse acceleration
.alpha..sub.quer, the centripetal acceleration
.alpha..sub.zentripetal, the angle .gamma. of the vehicle's
vertical axis to the direction in which the gravitational
acceleration acts, the angle .delta..sub.1 of the vehicle's
vertical axis to the normal line of the driving plane, the radius
of curvature .GAMMA..sub.kurve, the vehicle speed .nu..sub.fzg, the
static pitch angle .PHI..sub.stat, the dynamic pitch angle
.PHI..sub.d, the braking deceleration .alpha..sub.brems, the wheel
normal force F.sub.Nk, the braking slip .lambda..sub.k, and the
interference acceleration .alpha..sub.stoer. So that there are only
seventeen (17) unknowns to be identified, the static pitch angle
.PHI..sub.stat may be considered a constant when driving, and is
determined when a longitudinal deceleration .alpha..sub.laengs is
zero (0) (that is, for no braking, the wheel rotational speed is
considered to be a constant, and a shift in the center of gravity
(for example, due to a load shift) during a braking operation is
not recognized).
[0096] Using this approach or method, the wheel slip(s), the road
angle, the pitch angle and the roll angle may be determined using
three acceleration sensors to implement a deceleration control
system, which may, for example, use ESP (FDR) sensor technology
(excluding the pressure sensor), especially a wheel deceleration
control system for brake-by-wire systems or a brake control
system.
[0097] Another approach uses a transverse acceleration sensor and a
plurality of deflection displacement sensors (such as, for example,
three or four spring deflection displacement sensors)--rather than
the longitudinal and vertical acceleration sensors--to determine
the wheel normal forces. In this case, the vehicle mass (which is
not assumed to be constant as above), the wheel slip(s), the road
angle, the pitch angle and the roll angle are determined based on
the wheel normal forces. If a vehicle has, for example, a vehicle
control system (ESP, FDR, or some other vehicle control system)
having a transverse acceleration sensor and/or a vehicle headlight
control system, which includes vertical aim control and two
corresponding spring deflection displacement sensors, then no
additional transverse acceleration sensor and only two additional
deflection displacement sensors may be necessary. Additionally, if
the deflection displacement associated with all four wheels may be
determined, for example, with only three deflection displacement
sensors, then only one (rather than two) additional spring
deflection displacement sensor may be required. Thus, deflection
displacement sensors may be used for all four wheels--or for only
three wheels if practical, together with a transverse acceleration
sensor to determine the braking or wheel slip of each of the
vehicle wheels and the road angle, as well as other dynamic
parameters, such as the roll angle and the pitch angle.
[0098] In particular, in this "deflection displacement sensor"
approach or method, a suitably appropriate deflection displacement
sensor arrangement, which may include three or four spring
deflection displacement sensors, may be used to determine or
measure the deflection displacement .chi..sub..function.,i
associated with each wheel (where i corresponds to .nu..iota. (left
front), .nu..GAMMA. (right front), h.iota. (left rear), and
h.GAMMA. (right rear)). The deflection displacement values
.chi..sub..function.,i may be used to determine the wheel normal
forces F.sub.N,i as follows:
F.sub.N,l=c.sub..function.,l.cndot..chi..sub..function.,l (21),
[0099] where c.sub..function.,i corresponds to or designates the
rigidity of the suspension of each wheel. As a practical matter,
however, the relationship between the deflection displacement
.chi..sub..function. and the wheel normal force F.sub.N,i may not
be linear (that is, c.sub..function. may be constant in one
operating range and may depend on .chi..sub..function. in another
operating range). In such a case, the relationship between the
deflection displacement and the wheel normal force may need to be
experimentally determined for each type of vehicle. This
information may then be stored as an appropriate characteristic
curve. It is noted that the mathematical relationships discussed
apply to a steady state system.
[0100] As mentioned, assuming that the vehicle body is sufficiently
torsion-resistant, three (rather than four) deflection displacement
sensors may be sufficient to determine the deflection displacement
for each of the four vehicle wheels. In particular, in a
torsion-resistant vehicle body, the difference in deflection
displacement between the left and the right wheels is about the
same on both axles (that is,
.DELTA..chi..sub..function..sub..sub.--.sub..sup.wank,.nu..about..DELTA..-
chi..sub..function..sub..sub.--.sub..sup.wank,n). Accordingly, if
the deflection displacement is determined or measured for each of
three wheels, for example, .nu..iota. (left front), .nu..GAMMA.
(right front), and h.iota. (left rear), then the deflection
displacement of h.GAMMA. (right rear) may be determined as
follows:
.chi..sub..function.,h.nu.=.chi..sub..function.,h.iota.-.DELTA..chi..sub..-
function..sub..sub.--.sub..sup.wank,h=.chi..sub..function.,h.iota.-(.chi..-
sub..function.,.nu..iota.-.chi..sub..function.,.nu..GAMMA.)
(21a).
[0101] In this case, the mass of the vehicle is not assumed to be a
constant, as was assumed above, but is instead determined based on
the sum of the wheel normal forces, which are based on the measured
deflection displacements: 27 m = 1 g i = 1 4 F N , i . ( 22 )
[0102] The pitch angle .PHI. and the roll angle X may be determined
based on the deflection displacement values as follows: 28 = arctan
( x f , v - x f , h l ) , ( 23 )
[0103] where 29 x f , v = 1 2 ( x f , vl + x f , vr ) , and x f , h
= 1 2 ( x f , hl + x f , hr ) ;
[0104] and 30 = arctan ( x f , l - x f , r S spur ) , ( 24 )
[0105] where 31 x f , l = 1 2 ( x f , vl + x f , hl ) , and x f , r
= 1 2 ( x f , vr + x f , hr ) .
[0106] As before, for the transverse acceleration sensor, which is
oriented in the vehicle's transverse direction:
.sup..alpha.quer_sensor=g.cndot.sin(.chi.+.alpha..sub.quer)+.alpha..sub.qu-
er.cndot.cos(.chi.)+.alpha..sub.vert.cndot.sin(.chi.) (25a).
[0107] By rearranging and simplifying this equation, the transverse
acceleration .alpha..sub.quer may be determined as follows: 32 a
quer = quer - sensor - g sin ( + quer ) cos ( ) . ( 25 )
[0108] The accelerations {tilde over (.alpha.)}.sub.laengs and
.alpha..sub.quer may be determined as follows:
{tilde over
(.alpha.)}.sub.laengs=.alpha..sub.brems.cndot.cos(.beta.)+.alp-
ha..sub.zentripetal.cndot.sin(.beta.) (26);
.alpha..sub.quer=.alpha..sub.brems.cndot.sin(.beta.)+.alpha..sub.stoer.cnd-
ot.sin(.beta.)+.alpha..sub.zentripetal.cndot.cos(.beta.) (27) .
[0109] The attitude angle .beta. may be determined as was discussed
above.
[0110] Also, as discussed above, the centripetal acceleration,
based on the instantaneous speed and the radius of curvature that
is traveled, may be determined as follows: 33 a zentripetal = v fzg
2 r kurve . ( 28 )
[0111] As above, the wheel hub speed may be determined, based on
the wheel speeds and the wheel slip(s), as follows: 34 v nabe = 1 1
- v rad = 1 - v rad v nabe . ( 29 a )
[0112] The vehicle speed may be determined based on the wheel
speeds, the braking slip(s), and the yaw speed. Accordingly, the
vehicle speed at the center of gravity of the vehicle may be
determined as follows: 35 v fzg = 1 1 - i v rad , i S spur 2 . i =
1 - v rad , i v fzg S spur 2 . . ( 29 )
[0113] As before, the radius of curvature may be determined based
on the vehicle speed .nu..sub.fzg, the steering angle
.delta..sub.1, the wheelbase .iota., the steering ratio i.sub.L,
and the characteristic speed .nu..sub.chars as discussed above (see
the Mitschke reference, equations 9.5 and 9.6 at page 34), as
follows: 36 r kurve = i L l l + i L l v fzg 2 v char 2 l = i L l l
( 1 + v fzg 2 v char 2 ) . ( 30 )
[0114] Also, as before, the braking deceleration .alpha..sub.brems
may be determined as follows: 37 a brems = - 1 m k = 1 4 F Br k = -
1 m k = 1 4 F N k k ( 31 a )
[0115] As discussed, in the linear range of the tire characteristic
curve, the coefficient of friction .mu. depends on the wheel slip
.lambda..sub.k and the tire's slip rigidity k.sub.Relfens which is
a tire-specific characteristic value that may vary based on the
slip angle .alpha. and the wheel normal force F.sub.N. Accordingly,
during partial linear braking, in which the tires are in the linear
operating range of the tire characteristic curve, the braking
deceleration .alpha..sub.brems may be determined as follows: 38 a
brems = - 1 m k = 1 4 F N k k Reifen ( k , F N ) , ( 31 )
[0116] in which the slip angle .alpha..sub.k depends on v.sub.fzg
and .GAMMA..sub.kurve (see the Mitschke reference at page 37
(equations 9.20 and 9.21)), .lambda..sub.k is the slip of the k-th
wheel and F.sub.Nk is the associated wheel load.
[0117] The difference in deflection displacement in the vehicle's
transverse direction
.DELTA..chi..sub..function..sub..sub.--.sub..sup.wan-
k=.chi..sub..function.,.iota.-.chi..sub..function.,.GAMMA. may be
separated into a static component
.DELTA..chi..sub..function..sub..sub.---
.sub..sup.wank.sub..sub.--.sub..sup.stat, which is associated with
loading on one side, and a dynamic component
.DELTA..chi..sub..function..sub..sub-
.--.sub..sup.wank.sub..sub.--.sub..sup.d, which is associated with
the transverse road angle .alpha..sub.quer and with the transverse
acceleration .alpha..sub.quer that is exerted at the vehicle's
center of gravity "SP":
.DELTA..chi..sub..function..sub..sub.--.sub..sup.wank=.DELTA..chi..sub..fu-
nction..sub..sub.--.sub..sup.wank.sub..sub.--.sub..sup.stat+.DELTA..chi..s-
ub..function..sub..sub.--.sub..sup.wank.sub..sub.--.sub..sup.d
(32a).
[0118] Since the static component
.DELTA..chi..sub..function..sub..sub.--.-
sub..sup.wank.sub..sub.--.sub..sup.stat may be relatively small, it
may be assumed to be zero to simplify the equation, which provides
the following: 39 x f - wank = x f - wank - d = 2 ( F N , quer + F
N , neig ) C f - wank . ( 32 b )
[0119] The variable C.sub..function..sub..sub.--.sub..sup.wank
corresponds to or describes the spring force constant acting in a
rolling motion (including the torsional rigidity of the vehicle
stabilizer). As a practical matter, if
C.sub..function..sub..sub.--.sub..sup.wank is not essentially a
constant, then it may need to be experimentally determined and
stored as a characteristic curve.
[0120] The change in wheel load .DELTA.F.sub.N,quer that is
associated with the transverse acceleration may be determined as
follows: 40 F N , quer = 1 2 h S spur m a quer . ( 32 c )
[0121] A transverse road angle may be associated with a change in a
wheel load .DELTA.F.sub.N,neig, which may be determined as follows:
41 F N , neig = 1 2 h S spur m g tan ( quer ) cos ( quer ) .
(32d)
[0122] Accordingly, the difference in deflection displacement in
the vehicle's transverse direction .DELTA.F.sub.N,wank may be
determined as follows: 42 x f _ wank = h m a quer + h m g sin (
quer ) C f _ wank S spur . (32e)
[0123] By rearranging this equation, the transverse road angle
.alpha..sub.quer may be determined as follows: 43 quer = arcsin ( 1
g ( X f , wank C f _ wank S spur h m - a quer ) ) ( 32 )
[0124] The difference in deflection displacement in the vehicle's
longitudinal direction
.DELTA..chi..sub..function..sub..sub.--.sub..sup.n- ick, which
includes a static component .DELTA..chi..sub..function..sub..su-
b.--.sub..sup.nick.sub..sub.--.sub..sup.stat and a dynamic
component
.DELTA..chi..sub..function..sub..sub.--.sub..sup.nick.sub..sub.--.sub..su-
p.d, may be determined as follows:
.DELTA..chi..sub..function..sub..sub.--.sub..sup.nick=.DELTA..chi..sub..fu-
nction..sub..sub.--.sub..sup.nick.sub..sub.--.sub..sup.stat+.DELTA..chi..s-
ub..function..sub..sub.--.sub..sup.nick.sub..sub.--.sub..sup.d
(33).
[0125] The dynamic difference in deflection displacement in the
vehicle's longitudinal direction
.DELTA..chi..sub..function..sub..sub.--.sub..sup.n-
ick.sub..sub.--.sub..sup.d is associated with the longitudinal
acceleration {tilde over (.alpha.)}.sub.laengs and the longitudinal
road angle .alpha..sub.laengs.
[0126] Like the method that was used to determine the difference in
deflection displacement in the vehicle's transverse direction, the
dynamic component of the difference in deflection displacement in
the vehicle's longitudinal direction
.DELTA..chi..sub..function..sub..sub.--.-
sub..sup.nick.sub..sub.--.sub..sup.d may be similarly determined as
follows: 44 X f _ nick _ d = ( l v l C f _ v + l h l C f _ h ) m h
l ( - a ~ laengs + g sin ( laengs ) ) (34a)
[0127] By rearranging this equation, the longitudinal road angle
.alpha..sub.laengs may be determined as follows: 45 laengs = arcsin
( 1 g ( X f _ nick _ d C f _ v C f _ h l v C f _ h + l h C f _ v l
2 m h + a ~ laengs ) ) . ( 34 )
[0128] By differentiating equation 29 with respect to time and
assuming that the wheel slip .lambda..sub.k is constant for a
relevant period of time, the vehicle acceleration .alpha..sub.fzg
may be determined as follows: 46 a fzg = v . fzg = 1 1 - i v . rad
, i S spur 2 , (35a)
[0129] and the vehicle deceleration .alpha..sub.fzg may be
determined as follows:
.alpha..sub.fzg=.alpha..sub.brems+.alpha..sub.stoer+g.cndot.sin(.alpha..su-
b.laengs).cndot.cos(.beta.) (35b).
[0130] Accordingly, since the vehicle's deceleration is known,
rearranging equation 35a provides that the wheel slip
.lambda..sub.k for each wheel may be determined as follows: 47 i =
1 - v . rad , i a fzg S spur 2 . ( 35 )
[0131] Thus, a total of fifteen (15) equations provide the wheel
normal force F.sub.N, the vehicle mass m, the pitch angle .PHI.,
the roll angle .chi., the longitudinal acceleration {tilde over
(.alpha.)}.sub.laengs, the transverse acceleration
.alpha..sub.quer, the interference acceleration .alpha..sub.stoer,
the centripetal acceleration .alpha..sub.zentripetal, the radius of
curvature .GAMMA..sub.kurve, the vehicle speed .nu..sub.fzg, the
transverse road angle .alpha..sub.quer, the longitudinal road angle
.alpha..sub.laengs, the static difference in deflection
displacement .DELTA..chi..sub..function..sub..sub.--.sub..sup.-
nick.sub..sub.--.sub..sup.stat, the dynamic difference in
deflection displacement
.DELTA..chi..sub..function..sub..sub.--.sub..sup.nick.sub..s-
ub.--.sub..sup.d, the braking deceleration .alpha..sub.brems, and
the braking or wheel slip .lambda..sub.k. So that there are fifteen
(15) unknowns to be determined, the static difference in deflection
displacement
.DELTA.x.sub.f.sub..sub.--.sub..sup.nick.sub..sub.--.sub..su-
p.stat during a braking operation may be considered a constant. In
particular, the static difference in deflection displacement
.DELTA..chi..sub..function..sub..sub.--.sub..sup.nick.sub..sub.--.sub..su-
p.stat is determined for when the longitudinal deceleration {tilde
over (.alpha.)}.sub.laengs is zero (0) (that is, for no braking,
the wheel rotational speed is a constant, and a shift in the center
of gravity (for example, due to a shifting vehicle load) during a
braking operation is not considered).
[0132] Using this approach or method, the wheel normal forces, the
vehicle mass, the wheel slip(s), the road angle, the pitch angle
and the roll angle may be determined using a transverse
acceleration sensor and three or four deflection displacement
sensors to implement a deceleration control system, which may, for
example, use ESP (FDR) sensor technology (excluding the pressure
sensor), especially a wheel deceleration control system for
brake-by-wire systems. In such a case, the vehicle mass is not
assumed to be constant, but may be determined using the deflection
displacement sensors so that the wheel normal forces are not
estimated based on a constant vehicle mass, but are instead
determined based on the deflection displacement measurements. It is
believed that this should provide a more accurate system.
[0133] As regards the "acceleration sensor" method and the
"deflection displacement sensor" method described above, one
embodiment of a total vehicle control system 1, which may use these
methods to determine the wheel slip, the road angle and/or other
dynamic parameters, is shown in FIG. 4. In particular, FIG. 4 shows
a total vehicle control system 1 that may include a number of
vehicle control subsystem s or systems VCS.sub.A, VCS.sub.B, . . .
, VCS.sub.H, . . . , VCS.sub.R, . . . , VCS.sub.Z (100a, 100b, . .
. , 100h, . . . , 100r, . . . , 100z). The vehicle control system
VCS.sub.A (100a) may, for example, correspond to an active vehicle
control system, which may include a vehicle stability program
control system (ESP, FDR or some other vehicle control system) and
various sensors, including a transverse acceleration sensor, for
maintaining the stability of a vehicle during certain driving
conditions by controlling certain vehicle driving systems 50, which
may include, for example, acceleration, braking, suspension and
steering systems. The vehicle control system VCS.sub.H(100h) may,
for example, correspond to a vehicle headlamp control system for
controlling a vehicle headlight system 60, and if it includes
vertical aim control, it may-determine the displacement of the
front and rear of the vehicle, as measured, for example, by two (2)
deflection displacement sensors. The vehicle control system
VCS.sub.R (100r) may, for example, correspond to a vehicle
roll-stability control system (such as EAS) for maintaining the
roll stability of a vehicle during certain driving conditions,
which may also provide various control signals to control certain
vehicle operations 50 that affect the roll stability of a vehicle.
The vehicle control system VCS.sub.Z (100z) may be some other
vehicle control system, such as an active-handling control system,
an electronic drive train control system (such as ACC), a traction
control system or some other vehicle control system, which may
provide various control signals for controlling acceleration,
braking, steering, suspension and other vehicle driving systems 50.
Finally, the vehicle control system VCS.sub.B (100b) may be a brake
control system, which, for example, include a brake force or torque
control system VCS.sub.B1 (100b1) and a deceleration control system
VCS.sub.B2 (100b2), which may be used to control a brake-by wire
system 70. The brake-by wire system 70 may, for example, be an
electromechanical brake system or an electro-hydraulic brake
system.
[0134] Additionally, each of the vehicle control systems VCS.sub.A,
VCS.sub.B, . . . , VCS.sub.H, . . . , VCS.sub.R, . . . , VCS.sub.Z
(100a, 100b, . . . , 100h, . . . , 100r, . . . , 100z) may have its
own processor or may share a processor with one of the other
vehicle control systems. The processor may be any suitably
appropriate processor, and may, for example, be a micro-controller,
a microprocessor, an ASIC processor or some other processor.
Processors P.sub.A, P.sub.B, . . . , P.sub.H, . . . , P.sub.R, . .
. , P.sub.Z(110a, 110b, . . . , 110h, . . . 110r, . . . , 110z) are
shown in each of the vehicle control systems VCS.sub.A, VCS.sub.B,
. . . , VCS.sub.H, . . . , VCS.sub.R, . . . , VCS.sub.Z(100a, 100b,
. . . , 100h, . . . , 100r, . . . , 100z). In particular, the
processor P.sub.B may be a processor P.sub.B1 (110b1) and a
processor P.sub.B2 (110b2) as shown in FIG. 4. In particular, the
processor P.sub.B may be a processor P.sub.B1 (110b1) and a
processor P.sub.B2 (110b2) that are used to implement or program,
respectively, the slip control method and/or the deceleration
control method discussed below for either the "acceleration sensor"
embodiment or the "deflection displacement sensor" embodiment, as
discussed above.
[0135] Additionally, each of the vehicle control systems VCS.sub.A,
VCS.sub.B, . . . , VCS.sub.H, . . . , VCS.sub.R, . . . , VCS.sub.Z
(100a, 100b, . . . , 100h, . . . , 100r, . . . , 100z) may include
a corresponding sensor arrangement. These sensor arrangements may
include, for example, a sensor arrangement S.sub.A (120a) having
sensors S.sub.A1, S.sub.A2, . . . , S.sub.An (120a1, 120a2, . . . ,
120an), a sensor set S.sub.B (120b) having sensors S.sub.B1,
S.sub.B2, . . . , S.sub.Bn (120b1, 120b2, . . . , 120bn), a sensor
set S.sub.H (120h) having sensors S.sub.H1, S.sub.H2, . . . ,
S.sub.Hn (120h1, 120h2, . . . , 120hn), and a sensor set S.sub.Z
(1230n) having sensors S.sub.Z1, S.sub.Z2, . . . , S.sub.Zn (120z1,
120z2, . . . , 120zn). Additionally, depending on the particular
application and the various cost and design considerations of the
vehicle control systems, some of the sensors may be shared so that
there is no unnecessary duplication of sensors that are used to
measure the same parameters for different vehicle control systems.
Thus, sensor S.sub.A1 (120a1) may, for example, correspond to or be
the same sensor as sensor S.sub.B1 (120b1). Also, for example, the
active vehicle control system VCS.sub.A(100a) may have a sensor set
S.sub.A (120a) that includes a transverse acceleration sensor, such
as S.sub.A1 (120a1), which may also be used by the deceleration
control system VCS.sub.B2 (100b2) (or a wheel slip brake control
system, as discussed below) of the vehicle brake control system
VCS.sub.B (100b). Additionally, as mentioned above, the vehicle
headlamp control system VCS.sub.H (100h) may have a sensor set
S.sub.H (120h) that includes two deflection displacement sensors
S.sub.H1 (120h1) and S.sub.H2 (120h2), such as spring deflection
displacement sensors, which may also be used by the deceleration
control system VCS.sub.B2 (100b2) of the vehicle brake control
system VCS.sub.B (100b).
[0136] In the logic flowchart of FIG. 5, an "acceleration sensor"
method 200 is shown for determining the vehicle wheel slip(s) and
other vehicle dynamic parameters, including the road angle. In the
case of the acceleration sensor method 200 of FIG. 5, the braking
system sensors S.sub.B1 (120b1), S.sub.B2 (120b2) and S.sub.B3
(120b3) may be a longitudinal acceleration sensor, a transverse
acceleration sensor and a vertical acceleration sensor, or some
other suitably appropriate acceleration sensor arrangement, to
implement the slip control braking method and/or the deceleration
control method in the vehicle control braking system VCS.sub.B
(100b).
[0137] As regards FIG. 5, the processor P.sub.B (110b) (which may
be the processor P.sub.B1 (110b1) and/or the processor P.sub.B2
(110b2)) may be used to implement or program the acceleration
sensor embodiment or method 200 of FIG. 5, which may then be used,
for example, for the deceleration control method 400 of FIG. 7
and/or the slip control method 500 of FIG. 8 (as discussed below).
First, in step 210, the processor determines the longitudinal
acceleration. In step 220, the processor determines the transverse
acceleration. In step 230, the processor determines the vertical
acceleration. Steps 210 to 230 may, of course, be done
concurrently. Next, in step 240, the processor determines the wheel
slip(s), the pitch angle, the road angle and the roll angle, as
well as other vehicle dynamic parameters, as discussed above.
Finally, in step 250, the processor provides or otherwise makes
available (for example, providing the information to a memory) the
determined parameters to one or more vehicle control systems
VCS.sub.A, VCS.sub.B, . . . , VCS.sub.B, . . . , VCS.sub.H, . . . ,
VCS.sub.Z(100a, 100b, . . . , 100h, . . . , 100r, . . . ,
100z).
[0138] In the logic flowchart of FIG. 6, a "deflection
displacement" sensor method 300 is shown for determining vehicle
wheel slip(s) and other vehicle dynamic parameters, including the
wheel normal forces and the vehicle mass. In the case of the
deflection displacement sensor method 300 of FIG. 6, the braking
system sensors S.sub.B1 (120b1), S.sub.B2 (120b2), S.sub.B3 (120b3)
and S.sub.B4 (120b4) may be one or more (at least up to four)
spring deflection displacement sensors for each vehicle wheel, as
discussed above, or some other suitably appropriate deflection
displacement sensor arrangement, to implement the slip control
braking method and/or the deceleration control method in the
vehicle control braking system VCS.sub.B (100b).
[0139] As regards FIG. 6, the processor P.sub.B (which may be the
processor P.sub.B1 (110b1) and/or the processor P.sub.B2 (110b2))
may be used to implement or program the acceleration sensor
embodiment or method 300 of FIG. 6, which may then be used, for
example, for the deceleration control method 400 of FIG. 7 and/or
the slip control method 500 of FIG. 8 (as discussed below). First,
in step 310, the processor determines the transverse acceleration.
In step 320, the processor determines a plurality of vehicle
deflection displacements. Next, in step 330, the processor
determines the wheel normal forces and the vehicle mass, as
described above. In step 340, the processor determines the wheel
slip(s), the pitch angle, the road angle and the roll angle, as
well as other vehicle dynamic parameters, as discussed above.
Finally, in step 350, the processor provides or otherwise makes
available (for example, providing the information to a memory) the
determined parameters to one or more vehicle control systems
VCS.sub.A, VCS.sub.B, . . . , VCS.sub.H, . . . , VCS.sub.R, . . . ,
VCS.sub.Z(100a, 100b, . . . , 100h, . . . , 100r, . . . ,
100z).
[0140] Thus, the above apparatuses, methods and systems may be used
to determine the braking slip value(s) or factor(s) and the road
angle, as well as the pitch angle, the roll angle, as well as other
vehicle dynamic parameters, by using either a suitably appropriate
acceleration sensor arrangement, which may be three (or two)
additional acceleration sensors (each of which sense a parameter
corresponding to an acceleration), or a suitably appropriate
deflection displacement sensor arrangement, which may be four (or
which, for example, may be as few as three, two or even one)
additional deflection displacement sensors. In either case, the
actual number of sensors used or the number of additional sensors
required (whether acceleration sensors or deflection displacement
sensors) will depend on the particular vehicle control systems that
are available to share such sensors, as discussed above.
[0141] As discussed, when working with a deceleration control
system for a brake-by-wire system, whether an electromechanical
braking system or an electro-hydraulic braking system, it is
believed that a fixed value corresponding to a wheel deceleration
setpoint may not correspond to a particular level of brake-pedal
travel or brake-pedal force that corresponds with the experience or
experiential frame of reference of the driver. For example, when a
driver is driving down a hill, the driver may also achieve wheel
acceleration even while depressing the brake pedal. Of course, such
wheel acceleration is still less than the wheel acceleration that
may result without actuating or depressing the brake pedal. By
increasing pressure on the brake pedal, this should reduce wheel
acceleration down to zero (0) and eventually make it negative so
that there is wheel deceleration, rather than wheel acceleration.
By using the above apparatuses, methods and/or systems, this
braking behavior may be simulated by determining an unbraked wheel
acceleration during a braking operation, and adding it as an offset
to a characteristic curve of a brake pedal for a driver, including
during a braking operation. In particular, during braking, the
processor P.sub.B2 (110b2) may be used to determine the unbraked
wheel acceleration based on the wheel slip and the road angle
relative to a horizontal level, as well as the other dynamic
parameters, that may be determined as discussed above. For example,
the processor P.sub.B2 (110b2) may be used to determine the vehicle
speed based on the wheel speed(s) and the determined wheel slip(s)
(as determined above).
[0142] In the logic flowchart of FIG. 7, a braking deceleration
method 400 is shown for determining the unbraked wheel
deceleration, which may be based on either of the methods or
systems of FIG. 5 and FIG. 6. In particular, the processor P.sub.B2
(110b2) may, for example, be used to implement or program the
deceleration control method 400 of FIG. 7. First, in step 410, the
processor determines the braking deceleration. In step 420, the
processor determines the interference deceleration. In step 440,
the processor determines the unbraked wheel acceleration based on
steps 410 to 430. In step 450, the processor either adds the
unbraked wheel acceleration as an offset to a "deceleration pedal"
or brake-pedal characteristic curve or provides (or otherwise makes
available (for example, providing the information to a memory)) the
determined parameters, including the unbraked wheel deceleration
offset, to the vehicle control system VCS.sub.B2 (100b2) for
controlling wheel deceleration and the vehicle brake system 70
based on the adjusted "deceleration pedal" characteristic curve
and/or the unbraked wheel deceleration in step 460.
[0143] Additionally, the processor P.sub.B1 (110b1) may be used to
implement an anti-lock braking apparatus or system that determines
the braking or wheel slip(s) that wheel lock or slip may be
appropriately controlled, and it may do this by comparing the
determined vehicle speed and the determined wheel speeds, which the
processor determines based on the methods discussed above. As
discussed, the determined vehicle speed may also be differentiated
to obtain vehicle acceleration or deceleration, and if any wheel(s)
exceeds or drops below some predetermined velocity rate and/or
acceleration rate, the processor P.sub.B1 (110b1) may apply a
correcting control signal to the braking system 70 so as to
compensate for any wheel locking or slipping. Accordingly, by using
the present apparatuses, methods or system, a more accurate vehicle
speed or velocity may be determined based on the wheel slip(s), and
it is believed that this should provide a more accurate or
efficient anti-lock braking control system. The acceleration
sensors should, of course be selected so that they are sufficiently
accurate to implement the foregoing slip control method in the
partial linear braking range, as discussed.
[0144] In the logic flowchart of FIG. 8, a wheel slip brake control
method 500 is shown for controlling the vehicle brake system 70 by
determining the wheel slip(s) and the wheel speed(s), which may be
based on either of the methods or systems of FIG. 5 and FIG. 6, as
discussed above. In particular, the processor P.sub.B1 (110b1) may,
for example, be used to implement or program the slip control
method 500 of FIG. 8. First, in step 520, the processor determines
or otherwise obtains the wheel slip(s) from either of the methods
or systems of FIG. 5 or FIG. 6. In step 540, the processor
determines the vehicle speed based on the wheel slip(s) and the
wheel speed(s). In step 560, the processor provides the vehicle
speed and/or the wheel slip(s) to an "ABS" processor or system,
such as VCS.sub.B1 (100b1), which may then be used to control any
wheel brake lock and/or wheel slip(s) based on the vehicle speed
and/or the wheel slip(s) in step 580.
[0145] Also, of course, the additional information, such as the
pitch angle, the roll angle, the longitudinal acceleration, the
transverse acceleration, and the road angle to horizontal may be
provided or otherwise made available to other vehicle control
systems, such as, for example, an active-handling control system,
an electronic drive train control system (such as ACC), a roll
stabilization control system (such as EAS), a traction control
system or some other vehicle dynamics control system (such as ESP
or FDR).
[0146] In summary, a transverse (yaw) acceleration (or velocity)
and either the longitudinal and vertical accelerations or the
determined deflection displacements the vehicle wheel(s) may be
used to determine the following:
[0147] The unbraked wheel acceleration/deceleration .alpha..sub.fzg
may be determined and added to a brake-pedal characteristic curve
as an offset to obtain the "normal" brake system behavior for a
particular driver. In particular, the vehicle deceleration
.alpha..sub.fzg may be determined based on a braking deceleration
.alpha..sub.brems, an interference deceleration .alpha..sub.stoer
(corresponding to an aerodynamic drag and a tire rolling
resistance) and a downgrade force) as follows:
.alpha..sub.fzg=.alpha..sub.brems+.alpha..sub.stoer+g.cndot.sin(.alpha..su-
b.laengs).cndot.cos(.beta.).
[0148] Additionally, the unbraked wheel acceleration
.alpha..sub.nabe (based on the unbraked vehicle acceleration
.alpha..sub.fzg and the yaw acceleration) may be determined as
follows: 48 a nabe = a fzg S spur 2 ,
[0149] where the unbraked vehicle acceleration .alpha..sub.fzg may
correspond to {tilde over (.alpha.)}.sub.fzg that represents the
difference between .alpha..sub.fzg and .alpha..sub.brems, which may
be determined as follows: 49 a brems = - 1 m k = 1 4 F N k k k
Reifen ( k , F N k ) .
[0150] Also, in the "deflection displacement sensor" approach or
method, the wheel contact forces may be based on a vehicle mass
that is determined based on the measured deflection
displacements--rather than being based on an assumed vehicle mass,
as with the "acceleration sensor" method. Finally, the brake or
wheel slip(s), which may be based on the wheel deceleration and the
vehicle deceleration, may be used to provide slip control for an
anti-lock braking system.
* * * * *