Process for controlling driving dynamics of a street vehicle

Details Process for controlling driving dynamics of a street vehicle Process for controlling driving dynamics of a street vehicle

1999-03-22

2001-04-24

Cuchlinski, Jr., William A. (Department: 3661)

Data processing: vehicles, navigation, and relative location

Vehicle control, guidance, operation, or indication

Indication or control of braking, acceleration, or deceleration

C701S001000, C701S036000, C701S041000, C701S072000, C701S050000, C701S053000, C701S055000, C701S079000

Reexamination Certificate

active

06223114

ABSTRACT:

BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of Germany patent document 198 12 237.3, filed Mar. 20, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method and apparatus for regulating the driving dynamics of a road vehicle.
In such method and apparatus reference values are generated by means of a simulation computer of an electronic control unit, under clock control in successive cycles of a predeterminable duration T
K
(5 to 10 ms, for example). The control unit implements an automatic regulation process based on a model that represents the vehicle in terms of parameters which depend on its design and its load state as well as its operating data, using measured current values of the vehicle steering angle &dgr;, vehicle speed v
X
and possibly the transverse acceleration a
q
for at least the yaw rate {dot over (&PSgr;)} and the float angle &bgr; of the vehicle. Control signals are generated based on a comparison of a setpoint {dot over (&PSgr;)}
SO
of the yaw rate of the vehicle with actual values {dot over (&PSgr;)}
I
of the yaw rate which are continuously recorded by means of a yaw rate sensor device. The result is used to activate at least one wheel brake of the vehicle and/or reduce the engine driving torque to compensate for deviations in the actual value of each critical setpoint.
A driving dynamics regulating method (FDR) of this kind is known from ATZ Automobiltechnische Zeitschrift, Vol. 96 (1994), No. 11, pages 674 to 689. In this known method, based on the so-called one-track model of a vehicle, a setpoint {dot over (&PSgr;)}
SO
is generated according to the relationship
Ψ
.
so
=
v
x
·
δ
(
a
+
c
)
⁢
(
1
+
v
x
2
v
CH
2
)
in which v
CH
represents the so-called characteristic speed of the vehicle; a is the distance of the front axle from the center of gravity of the vehicle; and c is the distance of the rear axle from the center of gravity of the vehicle.
The “characteristic speed” v
CH
refers to the vehicle-specific speed that corresponds to a maximum of the quotient {dot over (&PSgr;)}/&dgr;, which is valid for low transverse accelerations &agr;
q
≦3 ms
−2
. Driving dynamics regulation in this case takes the form of state regulation of float angle &bgr; and the yaw rate. Float angle &bgr;, which expresses the difference between the direction of travel and the direction of the lengthwise axis of the vehicle, must not exceed a specified limiting value.
In the driving dynamics regulation explained thus far, because of the manner of generation of the setpoint for the yaw rate of the vehicle, especially when the driver produces a rapid change in the steering angle as the result of an “abrupt” steering maneuver, the actual value of the yaw rate {dot over (&PSgr;)} of the vehicle deviates drastically from the setpoint. Because of the above-mentioned dependence of the steering angle, such deviation leads the actual value of the yaw rate of the vehicle, which changes more slowly as a result of the inertia of the vehicle, in every case. If the regulation responds in this case, it decreases the lateral guiding force at the rear axle of the vehicle, which in the above situation is undesirable because it causes an oversteering tendency in the wrong direction. At a later point in time such oversteering must be corrected by another regulating intervention. Such a “regulating play”, which results from the establishment of an unrealistic setpoint, represents a potential danger that should be avoided.
The goal of the invention therefore is to provide an improved method of the type described above which achieves a setpoint specification for the dynamic state values of the vehicle that corresponds to a realistic movement behavior of the vehicle.
Another object of the invention is to provide a device that is suitable for implementing the method.
These and other objects and advantages are achieved by the control arrangement according to the invention, which generates setpoints for the yaw rate {dot over (&PSgr;)}
S
and the float angle &bgr;
S
, corresponding to a dynamically stable behavior of a two-axle vehicle, by means of a clock-controlled evaluation of the following relationships:
m
z
·
v
·
β
+
1
v
⁢
(
m
z
·
v
2
+
C
v
·
1
v
-
C
H
·
1
H
)
·
Ψ
.
+
(
C
v
+
C
H
)
·
β
-
C
v
·
δ
=
0
and
J
Z
·
Ψ
¨
+
1
v
⁢
(
C
v
·
1
v
2
+
C
H
·
1
H
2
)
·
Ψ
.
-
(
C
H
·
1
H
-
C
v
·
1
v
)
·
β
-
C
v
·
1
v
·
δ
=
0
Under the conditions selected according to the invention as stability criteria (namely that the transverse forces produced by rounding a curve as well as the lateral guiding forces that develop as a result of the change in the steering angle &bgr;(t) must be compensated, and also that the rotating and yaw moments acting on the vehicle must be compensated) this relationship represents a more realistic model for the dynamic behavior of the real vehicle than the known method for establishing the setpoint of the yaw rate, since the inertial behavior of the vehicle must also be taken adequately into account by the vehicle model used according to the invention.
These relationships can be expressed as a matrix equation in the form
[
P
]·(
{overscore ({dot over (X)})}
)=[
Q]
·(
{overscore (X)}
)+(
{overscore (C)}
)·&dgr;(
t
)  (I)
in which [P] represents a 4×4 matrix with the elements p
ij
(p
ij
=0,m
Z
v,0,0; 0,0,0, J
Z
; 0,0,0,0; 0,−1,0,0), [Q] represents a 4×4 matrix with elements q
ij
(q
ij
=0, −C
V
−C
H
, 0, −m
Z
·v−(C
V
l
V
−C
H
l
H
)/v; 0, C
H
l
H
−C
V
l
V
, 0, (−1
v
2
C
v
−1
H
2
C
H
)/v; 0,0,0,0; 0,0,0,1), {overscore (C)} represents a four-component column vector with the components c
i
(c
i
=C
V
,C
V
l
V
,0,0), {overscore (X)} represents a four-component column vector formed of the state values &bgr;
Z
and {dot over (&PSgr;)}
Z
with components x
i
(x
i
=0,&bgr;
Z
,0,{dot over (&PSgr;)}
z
) and {overscore ({dot over (X)})} represents the time derivative d{overscore (X)}/dt. Evaluation of this relationship takes the form of an updating of the driving dynamic state values &bgr;
Z
(k−1) that have been determined at a point in time t(k−1), to the point in time t(k) that is later by the clock time length T
k
, by evaluation of the relationship
X
_
⁡
(
k
)
=
{
P
T
k
-
[
Q
]
}
-
1
·
{
P
T
k
·
X
_
⁡
(
k
-
1
)
+
C
_
·
δ
⁡
(
k
)
}
with values of the matrix elements p
ij
and q
ij
that have been updated to the point t(k) (i.e., determined at that point in time).
The coefficient matrix [P] (associated with the time rates of change, {umlaut over (&PSgr;)} and {dot over (&bgr;)}, of the state values {dot over (&PSgr;)} and &bgr; which are to be controlled) of the matrix equation (I) that represents the vehicle reference model, contains only matrix elements that are “absolutely” constant independently of the vehicle data or are vehicle-specifically constant. That is, either they do not change during travel, or they are vehicle-specific constants that are multiplied by the lengthwise speed of the vehicle or are divided by the latter (i.e., values that, with a supportable knowledge of the vehicle-specific values, can be determined at any time from measurements of the lengthwise speed of the vehicle with corresponding accuracy).
The same is also true of the matrix elements of the matrix [Q] associated with the state values {dot over (&PSgr;)} and &bgr; to be regulated, the “state vector,” provided they contain terms that are proportional and/or inversely proportional to the lengthwise speed of the vehicle and contain these terms as factors in other vehicle-specific constants.
The diagonal operating stiffness values C
V
and C
H
in t

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