Process for controlling the yaw relationship of vehicles

• US 6,648,426 B1
• Filed: 03/22/1999
• Issued: 11/18/2003
• Est. Priority Date: 03/20/1998
• Status: Expired due to Fees

• Current Assignee: Daimler Chrysler Company LLC (Stellantis NV)
• Original Assignee: Daimler Chrysler Company LLC (Stellantis NV)
• Inventors: Suissa, Avshalom, Boettiger, Friedrich
• Primary Examiner(s): Lavinder, Jack
• Assistant Examiner(s): KING, BRADLEY T
• Application Number:
  US09/273,759
• Time in Patent Office: 1,702 Days
• Field of Search: 303/140, 303/146, 303/147, 303/155, 303/165, 303/177, 303/168
• US Class Current: 303/146
• CPC Class Codes: B60T 2260/02 Active Steering, Steer-by-Wire
• CPC Class Codes: B60T 8/1755 Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve road vehicle drive control systems for control of driving stability otherwise than by controlling a particular sub-unit B60W30/02

Abstract

To control the yaw behavior of a vehicle, a setpoint for the yaw rate of the vehicle is determined from the steering angle specified by the driver and a vehicle speed that has been determined. An actual value of the yaw rate is also determined. A controlling deviation is then determined from the difference between the actual value and the setpoint of the yaw rate, and is then supplied to controllers operating independently of one another. In one controller, the steering controller, the setpoint is determined for the wheel steering angle of the steered wheels, while in the other controller, the braking controller, a setpoint is determined for the change in the braking pressure of the brake wheels. Taking this value into account, a specified braking pressure is then determined. By means of the braking pressure control elements, the corresponding specified braking pressure is produced in the wheel brake cylinders and the corresponding wheel steering angle is supplied to the steered wheels by steering control members.

Claims

1. Method for controlling yaw behavior of a vehicle having steered wheels on at least one axle and having a plurality of braked wheels, said method comprising:

determining a setpoint for a vehicle yaw rate, using a desired value for a steering angle of the vehicle, specified by a driver of the vehicle, and a determined value of the vehicle speed;

determining an actual value of the vehicle yaw rate; and

determining a controlling deviation from a difference between the actual value and the setpoint for the yaw rate;

wherein

the controlling deviation is supplied to a steering controller and to a braking controller, which steering controller and braking controller respond to the controlling deviation independently of each other, with at least one steering setpoint for a steering angle of the steered wheels being determined in the steering controller as a function of the controlling deviation, independently of the braking controller, and respective braking setpoints for change in braking pressure being determined in the braking controller as a function of the controlling deviation for respective ones of the braked wheels, independently of the steering controller;

a specified braking pressure is determined for respective ones of the braked wheels as a function of the respective braking setpoints for the change in braking pressure;

a braking pressure corresponding to the specified braking pressure is produced by braking pressure adjusting members in wheel brake cylinders of respective braked wheels;

a wheel steering angle corresponding to said steering setpoint is produced by steering adjustment members at the steered wheels;

the influence of the braking controller on the vehicle can be adjusted by an amplification factor that is variable in response to operation of the vehicle; and

the amplification factor influences behavior of the braking controller, while the behavior of the steering controller remains unchanged.

2. Method according to claim 1 wherein said specified braking pressure for respective ones of the braked wheels is determined in such fashion that exceeding of at least one specified slip limit is prevented.

3. Method according to claim 1 wherein:

the wheel brake cylinders are combined into groups;

each group is composed of at least one wheel brake cylinder; and

said specified braking pressure for respective ones of the braked wheels is determined for said braked wheels according to said groups.

4. Method according to claim 3 wherein a setpoint is obtained for each group of wheel brake cylinders for a change in braking pressure.

5. Method according to claim 1 wherein said at least one steering setpoint includes a steering setpoint determined for the wheels of each of said at least one axle having steered wheels.

6. Method according to claim 1 wherein when determining the setpoint for the wheel steering angles, it is assumed that circumferential forces transmitted to the road are the same on both sides of the vehicle.

7. Method according to claim 1 wherein in determining the setpoint for the change in braking pressure it is assumed that no lateral forces are transmitted to the road.

8. Method according to claim 1 wherein:

a deviation of the setpoint for wheel steering angle of steered wheels that results from a desired steering angle entered by a driver of the vehicle is limited to a value between 5° and

10°

.

9. Method according to claim 1 wherein a deviation of wheel steering angle from a wheel steering angle that is necessary in order, at an adhesion coefficient m=1, to reach the specified yaw rate which results from the steering angle specified by the driver, is limited to a value between 5°

and 10°

.

10. Method according to claim 1 wherein a setpoint of the wheel steering angle is limited to a value which is determined in such fashion that a side slip angle of the steered wheels does not exceed a limiting value.

11. Method according to claim 2 wherein the specified braking pressure is determined as follows:

initially braking pressure specified by the driver for each wheel is limited to a value that is determined so that wheel slip at this braking pressure would not exceed a first slip threshold value;

at least one setpoint for change in braking pressure is added to this threshold value; and

a result obtained by such addition is limited to a value that is determined so that the wheel slip does not exceed a second slip threshold value that is greater than the first slip threshold value.

12. Method according to claim 11 wherein for each axle of the vehicle, respectively independent first and second slip threshold values are specified.

13. Method according to claim 2 wherein:

in the braking controller, in addition to at least one setpoint for the change in braking pressure, a slip threshold adjustment is also determined for the change in braking pressure, with an admissible wheel slip being determined from at least one specified slip limit and respective slip threshold adjustment; and

the specified braking pressure is limited to a value such that the respective admissible wheel slip is not exceeded.

14. Method according to claim 13 wherein a slip threshold adjustment is determined for each specified slip limit.

15. Method according to claim 13 wherein a slip threshold adjustment is assigned to each setpoint for change in the braking pressure.

16. Method according to claim 15 wherein assignment of the slip threshold adjustment is based on a relationship between slip and braking pressure, with the amount of the slip threshold adjustment corresponding to a change in the slip which results when braking pressure is changed by the setpoint and when the sign of the slip threshold adjustment corresponds to a sign of the setpoint of the change in the braking pressure.

17. Method according to claim 16 wherein a straight positive rise is assumed as a relationship between slip and braking pressure.

18. Method according to claim 14 wherein an admissible slip is limited to a maximum value that is between 100% and 150% of a specified slip limit.

19. Method according to claim 1 wherein a slip limit is specified for each axle of the vehicle.

20. Method for controlling yaw behavior of a vehicle having steered wheels on at least one axle and having a plurality of braked wheels, said method comprising;

determining a setpoint for a vehicle yaw rate, using a desired value for a steering angle of the vehicle, specified by a driver of the vehicle, and a determined value of the vehicle speed;

determining an actual value of the vehicle yaw rate; and

determining a controlling deviation from a difference between the actual value and the setpoint for the yaw rate;

wherein

the controlling deviation is supplied to a steering controller and to a braking controller, which steering controller and braking controller respond to the controlling deviation independently of each other, with at least one steering setpoint for a steering angle of the steered wheels being determined in the steering controller as a function of the controlling deviation, independently of the braking controller, and respective braking setpoints for change in braking pressure being determined in the braking controller as a function of the controlling deviation for respective ones of the braked wheels, independently of the steering controller;

a specified braking pressure is determined for respective ones of the braked wheels as a function of the respective braking setpoints for the change in braking pressure;

a braking pressure corresponding to the specified braking pressure is produced by braking pressure adjusting members in wheel brake cylinders of respective braked wheels;

a wheel steering angle corresponding to said steering setpoint is produced by steering adjustment members at the steered wheels; and

the influence of the braking controller on the vehicle can be adjusted by a presettable amplification factor, while the behavior of the steering controller remains unchanged;

wherein the amplification factor is determined as a function of values specified by the driver.

21. Method according to claim 20, wherein

values of steering angle and braking pressure are specified by the driver;

a desired lateral force is derived from the steering angle;

a desired circumferential force is derived from the braking pressure;

the amplification factor is determined so that as a desired lateral force rises, the amplification factor and hence the influence of the braking controller, both decrease; and

as a desired circumferential force increases, the amplification factor, and hence the influence on the braking controller, increases.

22. A device for controlling yaw behavior of a vehicle having steered vehicle wheels and braked vehicle wheels, comprising:

a steering input device for a vehicle operator to input a desired value for a steering angle of the vehicle;

a braking input device operable by the vehicle operator to input a braking pressure;

a unit which generates a setpoint for a vehicle yaw rate based on said desired value for the steering angle of the vehicle;

a unit which provides a signal indicative of an actual value of the vehicle yaw rate;

a comparison unit which determines a controlling deviation from a difference between the actual value and the setpoint for the vehicle yaw rate;

a steering controller which determines at least one steering setpoint for a steering angle of the steered wheels, as a function of the controlling deviation, for causing a steering actuator to set a wheel steering angle corresponding to said steering setpoint; and

a braking controller which determines respective braking setpoints for change in braking pressure for respective ones of the braked wheels, as a function of the controlling deviation, for causing braking actuators to adjust braking pressure for the respective braked wheels as a function of said braking setpoint and of said braking pressure input by the vehicle operator;

wherein,

said steering controller and said braking controller respond to said controlling deviation independently of each other to generate respective steering and braking setpoints, with at least one steering setpoint for a steering angle of the steered wheels being determined in the steering controller as a function of the controlling deviation, independently of the braking controller, and respective braking setpoints for change in braking pressure being determined in the braking controller as a function of the controlling deviation for respective ones of the braked wheels, independently of the steering controller, whether or not the vehicle operator has operated the braking input device, to provide vehicle yaw behavior control.

23. Method for controlling yaw behavior of a vehicle having steered wheels on at least one axle and having a plurality of braked wheels, said method comprising:

determining a setpoint for a vehicle yaw rate, using a desired value for a steering angle of the vehicle, specified by a driver of the vehicle, and a determined value of the vehicle speed;

determining an actual value of the vehicle yaw rate; and

determining a controlling deviation from a difference between the actual value and the setpoint for the yaw rate;

wherein

the controlling deviation is supplied to a steering controller and to a braking controller, which steering controller and braking controller respond to the controlling deviation independently of each other, with at least one steering setpoint for a steering angle of the steered wheels being determined in the steering controller as a function of the controlling deviation, independently of the braking controller, and respective braking setpoints for change in braking pressure being determined in the braking controller as a function of the controlling deviation for respective ones of the braked wheels, independently of the steering controller;

a specified braking pressure is determined for respective ones of the braked wheels as a function of the respective braking setpoints for the change in braking pressure;

a braking pressure corresponding to the specified braking pressure is produced by braking pressure adjusting members in wheel brake cylinders of respective braked wheels;

a wheel steering angle corresponding to said steering setpoint is produced by steering adjustment members at the steered wheels; and

the influence of the braking controller on the vehicle can be adjusted by a presettable amplification factor determined as a function of values specified by the driver.