Method and Apparatus for Controlling Active Rear Steering

• US 20120065842A1
• Filed: 02/09/2010
• Published: 03/15/2012
• Est. Priority Date: 02/12/2009
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: O'Dea, Kevin A., Ghoneim, Youssef A., Feller, Ross, Argalas, Edward J.
• Granted Patent: US 8,494,719 B2
• Time in Patent Office: Days
• US Class Current: 701/42
• CPC Class Codes: B62D 6/002 computing target steering angles for front or rear wheels B62D7/159 takes precedence
• CPC Class Codes: B62D 6/003 in order to control vehicle yaw movement, i.e. around a vertical axis B62D6/007 takes precedence
• CPC Class Codes: B62D 7/159 characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

A controller of an active rear steering (ARS) control system includes a processor and a software module. The software module includes instructions that, when executed by the processor, cause the processor to determine rear steering angles, determine a vehicle state, determine shaping functions, and determine a rear steering command.

Claims

1. An active rear steering control system for a vehicle, comprising:

a front steering angle sensor configured to measure a front steering angle of the vehicle;

a yaw rate sensor configured to measure a yaw rate of the vehicle;

a speed sensor configured to measure a speed of the vehicle; and

a controller comprising instructions that, when executed by a processor, cause the processor to;

determine a first rear steering angle as a function of the front steering angle;

determine a second rear steering angle as a function of the yaw rate;

determine a vehicle state as a function of the speed;

determine a first shaping function associated with the first rear steering angle as a function of the vehicle state;

determine a second shaping function associated with the second rear steering angle as a function of vehicle state; and

determine a rear steering command as a function of the first rear steering angle, the second rear steering angle, the first shaping function, and the second shaping function.

2. The active rear steering control system of claim 1, wherein determining the vehicle state comprises selecting from an enumerated list of vehicle states.

3. The active rear steering control system of claim 1, wherein determining the vehicle state comprises determining the magnitude of a vehicle state signal.

4. The active rear steering control system of claim 1, wherein the vehicle state is further a function of the front steering angle.

5. The active rear steering control system of claim 4, wherein the vehicle state is a function of the rate of change of the front steering angle.

6. The active rear steering control system of claim 1, wherein the vehicle state is further a function of the yaw rate.

7. The active rear steering control system of claim 6, wherein the vehicle state is a function of the rate of change of the yaw rate.

8. The active rear steering control system of claim 1, wherein the vehicle state is further a function of the front steering angle and the yaw rate.

9. The active rear steering control system of claim 1, wherein the rear steering command is the sum of the first rear steering angle multiplied by the first shaping function and the second rear steering angle multiplied by the second shaping function.

10. The active rear steering control system of claim 1, wherein each of the first shaping function and the second shaping function is selected from a plurality of gains.

11. The active rear steering control system of claim 10, wherein the gains are determined as a function of the front steering angle.

12. The active rear steering control system of claim 1, wherein each of the first shaping function and the second shaping function is further a function of an associated one of the first rear steering angle and the second rear steering angle.

13. The active rear steering control system of claim 1, further comprising an actuator that is configured to control a rear steering angle of rear wheels of the vehicle according to the rear steering command.

14. The active rear steering control system of claim 1, wherein the first rear steering angle is further a function of a front wheel stiffness and a rear wheel stiffness.

15. The active rear steering control system of claim 1, wherein the second rear steering angle is further a function of the speed, a vehicle mass, a front wheel stiffness, a rear wheel stiffness, a distance from a front axle to a center of gravity of the vehicle, and a distance from a rear axle to the center of gravity.

16. A controller of an active rear steering control system, comprising:

a processor; and

at least one software module comprising instructions that, when executed by the processor, cause the processor to;

determine a first rear steering angle as a function of a front steering angle measured by a steering angle sensor of the active rear steering control system;

determine a second rear steering angle as a function of a yaw rate measured by a yaw rate sensor of the active rear steering control system;

determine a vehicle state as a function of a speed measured by a speed sensor of the active rear steering control system;

determine a first shaping function associated with the first rear steering angle as a function of the vehicle state;

determine a second shaping function associated with the second rear steering angle as a function of vehicle state; and

determine a rear steering command as a function of the first rear steering angle, the second rear steering angle, the first shaping function, and the second shaping function.

17. The controller of claim 16, wherein the vehicle state is further a function of the front steering angle.

18. The controller of claim 16, wherein the vehicle state is further a function of the yaw rate.

19. The controller of claim 16, wherein the rear steering command is the sum of the first rear steering angle multiplied by the first shaping function and the second rear steering angle multiplied by the second shaping function.