Method and apparatus for controlling active rear steering

• US 8,494,719 B2
• Filed: 02/09/2010
• Issued: 07/23/2013
• 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 LLC (General Motors Company)
• Inventors: Feller, Ross, O'Dea, Kevin A., Ghoneim, Youssef A., Argalas, Edward J
• Primary Examiner(s): Trammell, James
• Assistant Examiner(s): MELTON, TODD M
• Application Number:
  US12/702,652
• Publication Number:
  US 20120065842A1
• Time in Patent Office: 1,260 Days
• Field of Search: 701/36, 701/41, 701/42, 188/408, 188/409, 188/410, 188/417, 188/443, 188/447
• 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 at least;

calculate a first rear steering angle based on the front steering angle;

calculate a second rear steering angle based on the yaw rate;

select a marker indicative of a vehicle state, yielding a vehicle state marker, selecting the vehicle state marker including;

comparing a steering angle velocity to a steering angle velocity threshold, comparing a yaw acceleration to a yaw acceleration threshold, and comparing vehicle speed to a speed threshold;

wherein the steering angle velocity is the rate of change of the steering angle and the yaw acceleration is the rate of change of the yaw rate;

select a first shaping function associated with the first rear steering angle based on the vehicle state marker and the first rear steering angle;

select a second shaping function associated with the second rear steering angle based on the vehicle state marker and the second rear steering angle; and

calculate a rear steering command based on 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 selecting the vehicle state marker comprises selecting from an enumerated list of vehicle state markers.

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

4. The active rear steering control system of claim 1, wherein the calculation of the rear steering command includes a 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.

5. The active rear steering control system of claim 4, wherein each of the first shaping function and the second shaping function is selected from a plurality of gains.

6. The active rear steering control system of claim 5, wherein the gains are calculated based on the front steering angle.

7. 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.

8. The active rear steering control system of claim 1, wherein the first rear steering angle is further calculated based on a front wheel stiffness and a rear wheel stiffness.

9. The active rear steering control system of claim 1, wherein the second rear steering angle is further calculated based on 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.

10. The active rear steering control system of claim 1, wherein:

the first rear steering angle is based on the front steering angle and further includes;

11. The active rear steering control system of claim 10, wherein:

the second rear steering angle is based on the yaw rate and a longitudinal speed and further includes;

12. The active rear steering control system of claim 1, wherein the second rear steering angle is based on the yaw rate and a longitudinal speed and further includes:

13. 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 at least;

calculate a first rear steering angle based on a front steering angle measured by a steering angle sensor of the active rear steering control system;

calculate a second rear steering angle based on a yaw rate measured by a yaw rate sensor of the active rear steering control system;

select a marker indicative of a vehicle state, yielding a vehicle state marker;

select a first shaping function associated with the first rear steering angle based on the vehicle state marker and the first rear steering angle;

select a second shaping function associated with the second rear steering angle based on the vehicle state marker and the second rear steering angle; and

calculate a rear steering command wherein the calculation of the rear steering angle includes a 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.

14. The controller of claim 13, wherein the vehicle state is based on the front steering angle.

15. The controller of claim 13, wherein the vehicle state marker is based on the yaw rate.

16. The controller of an active rear steering control system of claim 13, wherein selecting the marker indicative of the vehicle state includes:

comparing a front steering angle velocity to a steering angle velocity threshold;

comparing a yaw acceleration to a yaw acceleration threshold; and

comparing vehicle speed to a speed threshold;

wherein the steering angle velocity is a rate of change of the front steering angle and the yaw acceleration is a rate of change of the yaw rate.