CONTINUOUS ESTIMATION OF SURFACE FRICTION COEFFICIENT BASED ON EPS AND VEHICLE MODELS

• US 20160280251A1
• Filed: 03/22/2016
• Published: 09/29/2016
• Est. Priority Date: 03/25/2015
• Status: Active Grant

• Current Assignee: Steering Solutions IP Holding Corporation (Nexteer Automotive Group Ltd.)
• Original Assignee: Steering Solutions IP Holding Corporation (Nexteer Automotive Group Ltd.)
• Inventors: George, Mariam Swetha, Shah, Shrenik P., Bolourchi, Farhad, Varunjikar, Tejas M.
• Granted Patent: US 9,845,109 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B62D 6/006 using a measured or estimated road friction coefficient

Abstract

A system and a method of controlling a power steering system of a vehicle are provided. A control system includes a control module operable to determine a rack force of the vehicle based on at least one of a motor velocity, a driver torque and a motor torque, determine a plurality of modeled rack forces based on a roadwheel angle and a vehicle speed, compare the rack force to the plurality of modeled rack forces to generate a friction level included in a control signal, and send the control signal to the power steering system.

Claims

1. A control system for a power steering system of a vehicle, comprising:

a control module operable to receive sensor data and control the power steering system, the control module configured to;

determine a rack force of the vehicle based on at least one of a motor velocity, a driver torque and a motor torque;

determine a plurality of modeled rack forces based on a roadwheel angle and a vehicle speed;

compare the rack force to the plurality of modeled rack forces to generate a friction level included in a control signal; and

send the control signal to the power steering system.

2. The control system of claim 1, wherein the control module is further configured to determine the rack force of the vehicle based on an estimate obtained by an electric power steering system observer.

3. The control system of claim 1, wherein the control module is further configured to check magnitudes of the rack force and the plurality of modeled rack forces to determine whether to update the friction level.

4. The control system of claim 1, wherein the plurality of estimated rack forces include a snow rack force, a dry rack force, and an ice rack force, wherein when the rack force falls between the snow rack force and dry rack force, the friction level is determined based on the snow rack force subtracted from at least the dry rack force.

5. The control system of claim 1, wherein the plurality of estimated rack forces include a snow rack force, a dry rack force, and an ice rack force, wherein when the rack force falls between the snow rack force and ice rack force, the friction level is determined based on the snow rack force subtracted from at least the ice rack force.

6. The control system of claim 1, wherein the friction level can be wirelessly broadcast to a second vehicle over a dedicated short-range communications (DSRC) architecture.

7. A method of controlling a power steering system of a vehicle, the method comprising:

determining a rack force of the vehicle based on at least one of a motor velocity, a driver torque and a motor torque;

determining a plurality of modeled rack forces based on a roadwheel angle and a vehicle speed;

comparing the rack force to the plurality of modeled rack forces to generate a friction level included in a control signal; and

sending the control signal to the power steering system.

8. The method of claim 7, further comprising determining the rack force of the vehicle based on an estimate obtained by an electric power steering system observer.

9. The method of claim 7, further comprising checking magnitudes of the rack force and the plurality of modeled rack forces to determine whether to update the friction level.

10. The method of claim 7, wherein the plurality of estimated rack forces include a snow rack force, a dry rack force, and an ice rack force, wherein when the rack force falls between the snow rack force and dry rack force, the friction level is determined based on the snow rack force subtracted from at least the dry rack force.

11. The method of claim 7, wherein the plurality of estimated rack forces include a snow rack force, a dry rack force, and an ice rack force, wherein when the rack force falls between the snow rack force and ice rack force, the friction level is determined based on the snow rack force subtracted from at least the ice rack force.

12. The method of claim 7, wherein the friction level can be wirelessly broadcast to a second vehicle over a dedicated short-range communications (DSRC) architecture.

13. A computer readable medium having stored thereon instructions for executing a method of controlling a power steering system of a vehicle, the method comprising:

determining a rack force of the vehicle based on at least one of a motor velocity, a driver torque and a motor torque;

determining a plurality of modeled rack forces based on a roadwheel angle and a vehicle speed;

comparing the rack force to the plurality of modeled rack forces to generate a friction level included in a control signal; and

sending the control signal to the power steering system.

14. The computer readable medium of claim 13, further comprising determining the rack force of the vehicle based on an estimate obtained by an electric power steering system observer.

15. The computer readable medium of claim 13, further comprising checking magnitudes of the rack force and the plurality of modeled rack forces to determine whether to update the friction level.

16. The computer readable medium of claim 13, wherein the plurality of estimated rack forces include a snow rack force, a dry rack force, and an ice rack force, wherein when the rack force falls between the snow rack force and dry rack force, the friction level is determined based on the snow rack force subtracted from at least the dry rack force.

17. The computer readable medium of claim 13, wherein the plurality of estimated rack forces include a snow rack force, a dry rack force, and an ice rack force, wherein when the rack force falls between the snow rack force and ice rack force, the friction level is determined based on the snow rack force subtracted from at least the ice rack force.

18. The computer readable medium of claim 13, wherein the friction level can be wirelessly broadcast to a second vehicle over a dedicated short-range communications (DSRC) architecture.