VELOCITY ESTIMATION FOR ELECTRIC POWER STEERING SYSTEMS

• US 20180148087A1
• Filed: 11/30/2016
• Published: 05/31/2018
• Est. Priority Date: 11/30/2016
• 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: Wang, Qi, Pramod, Prerit, Champagne, Anthony J.
• Granted Patent: US 10,322,746 B2
• Time in Patent Office: Days
• CPC Class Codes: B62D 15/021 Determination of steering angle
• CPC Class Codes: B62D 5/0409 Electric motor acting on the steering column
• CPC Class Codes: B62D 5/046 Controlling the motor
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 5/0472 for damping vibrations
• CPC Class Codes: B62D 5/0481 monitoring the steering system, e.g. failures

Abstract

Technical solutions are described for facilitating a steering system to determine a motor velocity estimate for a motor of the steering system. For example, the steering system may include a state observer module that computes a base motor velocity estimate of the motor based on a plant model of the steering system. The steering system may further include a delay compensation module that computes a delay compensated velocity estimate based on the base motor velocity estimate and an acceleration of the motor. The steering system may further include a standstill detection module that modifies the delay compensated velocity estimate in response to a handwheel of the steering system being in standstill mode.

Claims

1. A steering system that can determine a motor velocity estimate for a motor of the steering system, the steering system comprising:

a state observer module configured to compute a base motor velocity estimate of the motor based on a plant model of the steering system; and

a standstill detection module configured to modify a delay compensated velocity estimate in response to a handwheel of the steering system being in standstill mode, the delay compensated velocity estimate being computed based on the base motor velocity.

2. The steering system of claim 1, wherein the delay compensated velocity estimate is used for at least one of damping, inertia compensation, and hysteresis compensation, by the steering system.

3. The steering system of claim 1, wherein the state observer module computes the base motor velocity estimate based on:

an assist torque generated by the steering system as a current input to the plant model of the steering system, and

a handwheel torque measured by a handwheel sensor as a measured output of the plant model of the steering system.

4. The steering system of claim 3, wherein the state observer module computes the base motor velocity estimate further based on a handwheel position as a measured state of the plant model of the steering system.

5. The steering system of claim 1, further comprising a delay compensation module configured to compute the delay compensated velocity estimate based on the base motor velocity estimate and an acceleration of the motor.

6. The steering system of claim 5, wherein the delay compensation module computes the acceleration of the motor by computing a derivative of the motor velocity estimate.

7. The steering system of claim 1, wherein the standstill detection module determines that the handwheel is in standstill mode based on a derivative of a handwheel position.

8. The steering system of claim 7, wherein the standstill detection module determines that the handwheel is in standstill mode in response to the derivative of the handwheel position being in a predetermined range for a predetermined duration of time.

9. The steering system of claim 1, wherein the standstill detection module modifies the delay compensated velocity estimate to zero in response to the handwheel being in standstill mode.

10. The steering system of claim 1, wherein the motor is a brushless motor.

11. The steering system of claim 1, wherein the motor is a brushed motor.

12. A method for determining a motor velocity estimate for a motor of a steering system, the method implemented by a control module of the steering system, the method comprising:

computing a base motor velocity estimate of the motor based on a plant model of the steering system;

computing a delay compensated velocity estimate based on the base motor velocity estimate and an acceleration of the motor; and

modifying the delay compensated velocity estimate in response to a handwheel of the steering system being in standstill mode.

13. The method of claim 12, wherein the steering system uses the delay compensated velocity estimate for at least one of damping, inertia compensation, and hysteresis compensation.

14. The method of claim 12, wherein computing the base motor velocity estimate is based on:

an assist torque generated by the steering system as a current input to the plant model of the steering system, and

a handwheel torque measured by a handwheel sensor as a measured output of the plant model of the steering system.

15. The method of claim 14, wherein computing the base motor velocity estimate is further based on a handwheel position as a measured state of the plant model of the steering system.

16. The method of claim 12, wherein determining that the handwheel is in standstill mode is based on a derivative of a handwheel position.

17. The method of claim 16, wherein the handwheel is determined to be in standstill mode in response to the derivative of the handwheel position being in a predetermined range for a predetermined duration of time.

18. The method of claim 12, wherein modifying the delay compensated velocity estimate comprises setting the delay compensated velocity estimate to zero in response to the handwheel being in standstill mode.

19. An electric power steering (EPS) system comprising:

a state observer module configured to compute a base motor velocity estimate of a motor based on a plant model of the steering system;

a delay compensation module configured to compute a delay compensated velocity estimate based on the base motor velocity estimate and an acceleration of the motor; and

a standstill detection module configured to modify the delay compensated velocity estimate in response to a handwheel of the EPS system being in standstill mode.

20. The electric power steering system of claim 19, wherein the state observer module computes the base motor velocity estimate based on:

an assist torque generated by the steering system as a current input to the plant model of the EPS system, and

a handwheel torque measured by a handwheel sensor as a measured output of the plant model of the EPS system.