Lane centering fail-safe control using differential braking

• US 8,670,903 B2
• Filed: 05/05/2011
• Issued: 03/11/2014
• Est. Priority Date: 05/05/2011
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Lee, Jin-Woo, Moshchuk, Nikolai K., Chen, Shih-Ken
• Primary Examiner(s): MANCHO, RONNIE M
• Application Number:
  US13/101,397
• Publication Number:
  US 20120283907A1
• Time in Patent Office: 1,041 Days
• Field of Search: 701/41, 701/42, 701/28, 701/57, 701/58, 701/59, 701/60, 180/446, 180/167, 180/168, 180/400, 702/151, 702/127, 702/109
• US Class Current: 701/41
• CPC Class Codes: B60T 2201/08 Lane monitoring; Lane Keeping Systems
• CPC Class Codes: B60T 2260/02 Active Steering, Steer-by-Wire
• CPC Class Codes: B60T 2270/402 Back-up
• CPC Class Codes: B60T 8/17557 specially adapted for lane departure prevention road vehicle drive control systems for lane keeping otherwise than by controlling a particular sub-unit B60W30/12
• CPC Class Codes: B60W 2050/0025 Transfer function weighting factor
• CPC Class Codes: B60W 2710/182 Brake pressure, e.g. of fluid or between pad and disc
• CPC Class Codes: B60W 2720/14 Yaw
• CPC Class Codes: B60W 30/12 Lane keeping
• CPC Class Codes: B60W 50/029 Adapting to failures or work around with other constraints, e.g. circumvention by avoiding use of failed parts
• CPC Class Codes: B62D 15/025 Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation B62D1/28 takes precedence
• CPC Class Codes: B62D 9/005 Emergency systems using brakes for steering

Abstract

Method, system and non-transitory computer-readable medium for fail-safe performance of a lane centering system. An electrical power steering (EPS) system of a vehicle is monitored for a failure and operation of the lane centering system is switched to a differential braking controller to output differential braking commands to a differential breaking system upon determining that a failure of the EPS system has occurred, where the output braking commands direct the differential braking system to apply force a brake for a wheel of vehicle, such by the applied braking force the vehicle follows a desired path determined for a lane centering operation.

Claims

1. A method for fail-safe performance of a lane centering system, the method comprising:

using a computer processor,

monitoring an electrical power steering system of a vehicle for a failure; and

switching operation of the lane centering system to a differential braking controller to output differential braking commands to a differential breaking system, upon determining that a failure of the electrical power steering system has occurred,

wherein the output braking commands direct the differential braking system to apply force a brake for a wheel of vehicle, such by the applied braking force the vehicle follows a desired path determined for a lane centering operation.

2. The method of claim 1, comprising determining a differential braking command by determining a yaw moment.

3. The method of claim 2, wherein the yaw moment is determined according a cost function that minimizes the difference between the desired path and a predicted path of the vehicle.

4. The method of claim 3, wherein the yaw moment is the value for (Δ

τ

) found in minimizing lateral offset error (y_err) and heading angle error (φ

_err) in the cost function;

5. The method of claim 4, wherein at least one of Q(x) and R(t) comprises a pre-determined value determined through vehicle dynamics simulation or vehicle testing.

6. The method of claim 2, comprising determining a total force value based on the yaw moment.

7. The method of claim 6, wherein the total force value represents a total force to be allocated to a front and a rear wheel of the vehicle.

8. The method of claim 7, wherein the front and rear wheel is on either the right-hand side or left-hand side of the vehicle.

9. The method of claim 8, wherein the total force value is allocated to the front and rear wheels of either the right-hand side or the left-hand side according to the sign of the yaw moment.

10. The method of claim 7, wherein the total force is determined for the front and rear wheels of the vehicle according to the formula:

F_total=Δ

τ

*2/w,

wherein Δ

τ

is the yaw moment and w is a value representing the wheelbase size of the vehicle.

11. The method of claim 7, comprising determining a distribution ratio to allocate portions of the total force value between the determined front and rear wheels based on a load value for the vehicle and a value representing lateral acceleration, wherein the ratio is a value between zero and one.

12. The method of claim 11, wherein distribution of the total force value for the front and real wheel is determined according to formulas:

F<sub>front—

wheel</sub>=α

Δ

τ

*2/w, for the front wheel, and

F<sub>rear—

wheel</sub>=(1−

α

)Δ

τ

*2/w, for the rear wheel,

wherein α

is the distribution ratio, Δ

τ

is the yaw moment and w is a value representing the wheelbase size of the vehicle.

13. The method of claim 12, comprising:

determining if the distribution of the total force value for the front wheel is within a friction ellipse for a tire of the front wheel;

determining if the distribution of the total force value for the rear wheel is within a friction ellipse for a tire of the rear wheel;

modifying the yaw moment value if the distribution of the total force values for both the front and rear wheels are not within the friction ellipses for the tires of the front and rear wheels.

14. The method of claim 13, comprising:

modifying the distribution of the total force values for both the front and rear wheels if the distribution of the total force value for at least one of the front and rear wheels is within the friction ellipses for tire of the wheel.

15. A system for fail-safe performance of a lane centering system, the system for fail-safe performance comprising:

a differential braking controller coupled to a differential braking system; and

a supervisory element coupled to the differential braking controller and a lane centering system, the supervisory element configured to monitor an electrical power steering system of a vehicle for a failure and, upon determining that a failure has occurred, switch an output of the lane centering system to an output of the differential braking controller,

wherein the output of the differential braking controller provides a braking command to the differential braking system for an application of a braking force to a wheel of the vehicle, wherein by the applied braking force the vehicle follows a desired path determined for a lane centering operation.

16. The system of claim 15, comprising:

a desired path estimation unit to provide data for a desired path of the vehicle;

a predicted path estimation unit to provide data for a predicted path of the vehicle; and

a yaw moment determination unit to determine a yaw moment based on the data for the desired path and the data for the predicted path.

17. The system of claim 16 wherein the yaw moment determination unit is located in either differential braking controller or a steering controller of the lane centering system.

18. The system of claim 15, wherein the supervisory function controls an output of the lane centering system to the electrical power steering system and the differential braking system.

19. A non-transitory computer-readable medium having stored thereon instructions, which when executed by a processor cause the processor to perform the method of:

monitoring an electrical power steering system of a vehicle for a failure; and

switching operation of the lane centering system to a differential braking controller, to output differential braking commands to a differential breaking system, upon determining that a failure of the electrical power steering system has occurred,

wherein the output braking commands direct the differential braking system to apply force a brake for a wheel of vehicle, such by the applied braking force the vehicle follows a desired path determined for a lane centering operation.

20. A non-transitory computer-readable medium of claim 19, wherein the stored instructions are downloaded for execution by a computer processor of a vehicle.