Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
1998-03-20
2001-05-01
Zanelli, Michael J. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C180S422000
Reexamination Certificate
active
06226579
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method and an apparatus for operating a steering system for a motor vehicle.
A prior art steering system is disclosed by DE-OS 40 31 316 (corresponding to U.S. Pat. No. 5,205,371) and to the extent it is relevant to understanding this invention, will be described with reference to
FIGS. 1 and 2
. In such a steering system the motions of the actuator
13
or
23
, the motor angle &dgr;
M
, are superimposed in the auxiliary drive
12
or
22
on the steering motions imparted by the driver through the steering wheel
11
or
21
, the steering wheel angle &dgr;
L
detected by the sensor
28
. The total motion &dgr;
L
′ thus obtained is transmitted through the steering mechanism
14
and the steering linkage
16
to the steerable wheels
15
a
and
15
b
to set the steering angle &dgr;
V
. The actuator
13
or
23
can be an electric motor. The operating principle of such a steering system consists of determining the motor angle &dgr;
M
dependent on the steering wheel angle &dgr;
L
and dependent on signals Sm to control the dynamic behavior of the vehicle, with the steering wheel angle &dgr;
L
being determined through the sensor
28
and with the signals Sm representing vehicle motions detected by the sensors
26
. The total steering angle is obtained according to the equation
&dgr;
L
′=&dgr;
L
/i
ü
+&dgr;
M
,
in which the transmission ratio can be i
ü
=1 or i
ü
≈1.
DE-OS 40 38 079 (corresponding to U.S. Pat. No 5,316,379) shows the superimposition of a steering component (compensating steering angle) on the front wheel and/or the rear wheel. The compensating steering angle, which depends on the differences between brake pressures, compensates for the yawing motion in the case of so-called ì-split braking, i.e. braking in which the coefficients of roadway friction are significantly different on the right and left sides of the vehicle.
DE 196 01 825.0, not a prior art publication, shows a steering system that is similar to DE-OS 40 31 316 described above (corresponding to U.S. Pat. No. 5,205,371). In this case two steering components are superimposed to obtain a desired output rotational motion for the servomotor, with a first steering component serving for steering assistance, while a second steering component depends on the angular yaw rate, transverse acceleration, and/or the vehicle's longitudinal speed.
DE A1 36 25 392 shows the generation of a correction signal to a servomotor that controls the front wheel steering angle. The correction signal in this case depends on a desired-actual yaw rate difference.
GB-PS 1,414,206 shows compensation of crosswind effects by a superimposed steering angle intervention.
The purpose of this invention is to combine various control and regulation functions relating to a steering system in a suitable fashion.
SUMMARY OF THE INVENTION
As already mentioned hereinabove, this invention relates to a steering system for a motor vehicle with at least one steerable wheel, an actuator, and an auxiliary drive. The steering motion initiated by the driver of the vehicle and the motion initiated by the actuator are superimposed by the auxiliary drive to generate the steering motion of the steerable wheel. At least two steering components are computed and a control signal is generated by superimposing the computed steering components to control the actuator. The core of the invention consists of computing the steering components in parallel and independently of one another.
The invention makes it possible to combine several functions beneficially to control road behavior. This provides an improvement of running dynamics by means of steering interventions.
The individual steering components are advantageously computed by providing that each of the steering components is computed to achieve a predetermined control or regulation objective. It is provided in particular that the control or regulation objectives for the individual steering components are stated differently. The steering components in this case can be computed at the same time, or in each sensing step when accomplished in a digital processor.
Thus, different individual functions of steering intervention are combined with one another.
The combination of individual steering components pursuant to the invention produces all of the advantages that the steering system permits, and thus exhausts the entire possible potential of steering interventions. The different individual functions supplement and assist one another mutually. Furthermore, the invention guarantees ease of application since the individual functions affect only some running dynamics characteristics of the vehicle and can be individually fine-tuned. For this reason there are few objective conflicts in application since the different functions provide adequate degrees of freedom for the selective control of individual characteristics and to produce definite benefits. The individual functions can be combined freely as needed or desired.
An especially beneficial refinement of the invention provides that the steering components are computed by
regulating the yawing motion of the motor vehicle, particularly the angular yaw rate, to a definite desired value (yaw rate control), and/or
counteracting a yawing motion caused by a motor vehicle braking process (yaw moment compensation), and/or
counteracting crosswind effects (crosswind compensation), and/or
a steering component dependent on the speed of rotation of the steering wheel) (corrective steering).
It can be provided in particular that
in the case of yaw rate control, the instantaneous angular yaw rate is detected, the desired value is determined at least dependent on the detected rotation of the steering wheel and the detected vehicle speed, and a steering component is computed dependent on the difference between the instantaneous angular yaw rate and the desired value, and/or
in the case of yaw moment compensation, a steering component is computed that is dependent on the detected brake pressures applied to the vehicle's brakes on different sides of the vehicle, and/or
in the case of crosswind compensation, a steering component is computed dependent on air pressures detected at various positions on the vehicle body.
It can also be provided pursuant to the invention that the computed steering components be coordinated differently, in particular weighted, dependent on the instantaneous running conditions. The underlying idea for this refinement is to control some or all of the prevailing individual steering functions through a priority coordinator.
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Hackl Matthias
Kraemer Wolfgang
Baker & Daniels
Gibson Eric M
Robert & Bosch GmbH
Zanelli Michael J.
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