PROVIDING ASSIST TORQUE WITHOUT HAND WHEEL TORQUE SENSOR FOR ZERO TO LOW VEHICLE SPEEDS

• US 20160075371A1
• Filed: 09/15/2014
• Published: 03/17/2016
• Est. Priority Date: 09/15/2014
• 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: Kaufmann, Timothy W., Varunjikar, Tejas M., Champagne, Anthony J.
• Granted Patent: US 9,409,595 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B62D 5/04 electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 5/0484 for reaction to failures, e.g. limp home
• CPC Class Codes: B62D 5/049 detecting sensor failures

Abstract

A method of controlling an electric power steering system of a vehicle is provided. The method estimates steering rack force to be caused by a tire of the vehicle and a surface of a ground with which the tire is in contact in response to determining that one or more hand wheel torque sensors of the vehicle are not enabled. The method generates a steering assist torque command based on the estimated steering rack force. The method controls the electric power steering system using the steering assist torque command.

Claims

1. A method of controlling an electric power steering system of a vehicle, the method comprising:

filtering a hand wheel angle with a low-pass filter;

flittering a hand wheel velocity with a low-pass filter;

determining that one or more hand wheel torque sensors of the vehicle are not enabled;

estimating steering rack force caused by a tire of the vehicle and a surface of a ground with which the tire is in contact with the filtered hand wheel angle and the filtered hand wheel velocity;

generating a steering assist torque command based on the estimated steering rack force; and

controlling the electric power steering system using the steering assist torque command.

3. The method of claim 1, further comprising:

scaling down a maximum value of torque, which the tire is capable of generating, based on a vehicle velocity; and

using the scaled down maximum value of torque to estimate the steering rack force.

4. The method of claim 1, further comprising:

generating a scale factor using the steering assist torque command and a hand wheel velocity; and

scaling the estimated steering rack force with the scale factor.

5. The method of claim 1, further comprising:

generating a scale factor using the steering assist torque command, a vehicle velocity and a hand wheel angle; and

scaling the estimated steering rack force with the scale factor.

6. The method of claim 1, further comprising:

generating a scale factor using a hand wheel angle and a hand wheel velocity; and

scaling the estimated steering rack force with the scale factor.

7. The method of claim 1, further comprising:

generating a scale factor using the steering assist torque command, a vehicle velocity and a hand wheel angle; and

scaling the estimated steering rack force with the scale factor.

8. The method of claim 1, further comprising:

generating a scale factor using a vehicle velocity; and

scaling the estimated steering rack force with the scale factor.

9. The method of claim 1, further comprising:

generating a first scale factor using the steering assist torque command, a vehicle velocity and a hand wheel angle;

generating a second scale factor using a hand wheel angle and a hand wheel velocity;

generating a third scale factor using the steering assist torque command, a vehicle velocity and a hand wheel angle;

generating a fourth scale factor using a vehicle velocity;

generating a product of the first, second, third and fourth scale factors; and

scaling the estimated steering rack force with the product.

10. The method of claim 1, further comprising:

generating an assist torque command by;

estimating a lateral acceleration of the vehicle based on a hand wheel angle; and

determining an amount of assist torque based on the estimated lateral acceleration; and

blending the two assist torque commands to control the electric power steering system using the blend of the two steering assist torque commands.

2. (canceled)

11. A system of a vehicle comprising:

a power steering system that includes one or more hand wheel torque sensors; and

a control module configured to;

filter a hand wheel angle with a low-pass filter;

filter a hand wheel velocity with a low-pass filter;

estimate, using the filtered hand wheel angle and the filtered hand wheel velocity, a steering rack force caused by a tire of the vehicle and a surface of a ground with which the tire is in contact in response to determining that one or more hand wheel torque sensors of the vehicle are not enabled;

generate a steering assist torque command based on the estimated steering rack force; and

control the electric power steering system using the steering assist torque command.

13. The system of claim 11, wherein the control module is further configured to:

scale down a maximum value of torque, which the tire is capable of generating, based on a vehicle velocity; and

use the scaled down maximum value of torque to estimate the steering rack force.

14. The system of claim 11, wherein the control module is further configured to:

generate a scale factor using the steering assist torque command and a hand wheel velocity; and

scale the estimated steering rack force with the scale factor.

15. The system of claim 11, wherein the control module is further configured to:

generate a scale factor using the steering assist torque command, a vehicle velocity and a hand wheel angle; and

scale the estimated steering rack force with the scale factor.

16. The system of claim 11, wherein the control module is further configured to:

generate a scale factor using a hand wheel angle and a hand wheel velocity; and

scale the estimated steering rack force with the scale factor.

17. The system of claim 11, wherein the control module is further configured to:

generate a scale factor using the steering assist torque command, a vehicle velocity and a hand wheel angle; and

scale the estimated steering rack force with the scale factor.

18. The system of claim 11, wherein the control module is further configured to:

generate a scale factor using a vehicle velocity; and

scale the estimated steering rack force with the scale factor.

19. The system of claim 11, wherein the control module is further configured to:

generate a first scale factor using the steering assist torque command, a vehicle velocity and a hand wheel angle;

generate a second scale factor using a hand wheel angle and a hand wheel velocity;

generate a third scale factor using the steering assist torque command, a vehicle velocity and a hand wheel angle;

generate a fourth scale factor using a vehicle velocity;

generate a product of the first, second, third and fourth scale factors; and

scale the estimated steering rack force with the product.

20. The system of claim 11, wherein the control module is further configured to:

generate an assist torque command by;

estimating a lateral acceleration of the vehicle based on a hand wheel angle; and

determining an amount of assist torque based on the estimated lateral acceleration; and

blending the two assist torque commands to control the electric power steering system using the blend of the two steering assist torque commands.

12. (canceled)