Phase plane based transitional damping for electric power steering

• US 9,540,040 B2
• Filed: 06/26/2014
• Issued: 01/10/2017
• Est. Priority Date: 06/26/2014
• 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: Varunjikar, Tejas M., Champagne, Anthony J.
• Primary Examiner(s): Do, Truc M
• Assistant Examiner(s): WHITTINGTON, JESS G
• Application Number:
  US14/315,612
• Publication Number:
  US 20150375779A1
• Time in Patent Office: 929 Days
• Field of Search: None
• US Class Current: 1/1
• 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 5/0484 for reaction to failures, e.g. limp home
• CPC Class Codes: B62D 6/008 Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications
• CPC Class Codes: B62D 6/10 characterised by means for sensing or determining torque

Abstract

A method for controlling a motor in an electrical power steering system is provided. The method generates a damping torque command for reducing an undesired torque to be generated by the motor. The method generates an assist torque command that specifies a desired torque to be generated by the motor. The method determines whether to send the damping torque command to the motor as a function of a hand wheel velocity and a hand wheel angle. The method combines the assist torque command and the damping torque command to send to the motor when it is determined that the damping torque command is to be sent to the motor.

Claims

1. A method for controlling a motor in an electrical power steering system, comprising:

generating a damping torque command to send to the motor for reducing an undesired torque;

generating an assist torque command that specifies a desired torque to be generated by the motor;

determining whether to send the damping torque command to the motor as a function of a hand wheel velocity and a hand wheel angle; and

combining the assist torque command and the damping torque command to send to the motor only when it is determined that the damping torque command is to be sent to the motor.

2. The method of claim 1, wherein the determining comprises:

determining to send the damping torque command when the hand wheel velocity is less than a velocity threshold and the hand wheel angle is greater than an angle threshold; and

determining to send the damping torque command when the hand wheel velocity is greater than a negative of the velocity threshold and the hand wheel angle is less than a negative of the angle threshold.

3. The method of claim 1, wherein the determining comprises, when the hand wheel velocity is greater than a velocity threshold and the hand wheel angle is greater than an angle threshold, or when the hand wheel velocity is less than a negative of the velocity threshold and the hand wheel angle is less than a negative of the angle threshold:

scaling the damping torque command based on a vehicle velocity of a vehicle that includes the electronic power steering system; and

determining to send the damping torque command to the motor.

4. The method of claim 1, further comprising:

determining a current assist mode from a plurality different assist modes that correspond to different operational statuses of a vehicle that includes the electric power steering system;

identifying a change in the current assist mode from one of the plurality of different assist modes to another; and

scaling the damping torque command based on a duration of time that has elapsed since the change is identified.

5. The method of claim 4, wherein the scaling comprises:

maintaining a whole of damping torque command when the duration of time is less than a first duration threshold;

scaling down the damping torque command when the duration of time is greater than or equal to the first duration threshold and is less than a second duration threshold; and

scaling down the damping torque command such that no damping torque is generated by the motor when the duration of time is greater than or equal to the second duration threshold.

6. The method of claim 1, wherein the combining the assist torque command and the damping torque command comprises adding the assist torque command and the damping torque command.

7. The method of claim 1, further comprising:

determining a current assist mode from a plurality different assist modes that correspond to different operational statuses of a vehicle that includes the electric power steering system;

identifying a change in the current assist mode from a first assist mode of the plurality of different assist modes to a second assist mode of the plurality of different assist modes; and

determining to send the damping torque command to the motor when a transition from the first assist mode to the second assist mode is deemed incomplete when an assist mode duration is less than a first duration threshold or has reached an upper limit and when the current assist mode corresponds to an operational status that indicates an abnormality in the vehicle.

8. A system of a vehicle comprising:

an electrical power steering system that includes a motor;

a control module configured to;

generate a damping torque command to send to the motor for reducing an undesired torque;

generate an assist torque command that specifies a desired torque to be generated by the motor;

determine whether to send the damping torque command to the motor as a function of a hand wheel velocity and a hand wheel angle; and

combine the assist torque command and the damping torque command to send to the motor only when it is determined that the damping torque command is to be sent to the motor.

9. The system of claim 8, wherein the control module is configured to determine whether to send the damping torque command to the motor by:

determining to send the damping torque command when the hand wheel velocity is less than a velocity threshold and the hand wheel angle is greater than an angle threshold; and

determining to send the damping torque command when the hand wheel velocity is greater than a negative of the velocity threshold and the hand wheel angle is less than a negative angle threshold.

10. The system of claim 8, wherein when the hand wheel velocity is greater than a velocity threshold and the hand wheel angle is greater than an angle threshold, or when the hand wheel velocity is less than a negative of the velocity threshold and the hand wheel angle is less than a negative of the angle threshold, wherein the control module is configured to determine whether to send the damping torque command to the motor by:

scaling the damping torque command based on a vehicle velocity of a vehicle that includes the electronic power steering system; and

determining to send the damping torque command to the motor.

11. The system of claim 8, wherein the control module is further configured to:

determine a current assist mode from a plurality different assist modes that correspond to different operational statuses of a vehicle that includes the electric power steering system;

identify a change in the current assist mode from one of the plurality of different assist modes to another; and

scaling the damping torque command based on a duration of time that has elapsed since the change is identified.

12. The system of claim 11, wherein the scaling comprises:

maintaining a whole of damping torque command when the duration of time is less than a first duration threshold;

scaling down the damping torque command when the duration of time is greater than or equal to the first duration threshold and is less than a second duration threshold; and

scaling down the damping torque command such that no damping torque is generated by the motor when the duration of time is greater than or equal to the second duration threshold.

13. The system of claim 8, wherein the control module is configured to combine the assist torque command and the damping torque command by adding the assist torque command and the damping torque command.

14. The system of claim 8, wherein the control module is further configured to:

determine a current assist mode from a plurality different assist modes that correspond to different operational statuses of a vehicle that includes the electric power steering system;

identify a change in the current assist mode from a first assist mode of the plurality of different assist modes to a second assist mode of the plurality of different assist modes; and

determine to send the damping torque command to the motor when a transition from the first assist mode to the second assist mode is deemed incomplete when an assist mode duration is less than a first duration threshold or has reached an upper limit and when the current assist mode corresponds to an operational status that indicates an abnormality in the vehicle.

15. A method for controlling a motor in an electrical power steering system, comprising:

generating a damping torque command to send to the motor for reducing an undesired torque;

generating an assist torque command that specifies a desired torque to be generated by the motor;

determining whether to send the damping torque command to the motor as a function of a hand wheel velocity and a hand wheel angle; and

combining the assist torque command and the damping torque command to send to the motor when it is determined that the damping torque command is to be sent to the motor, and wherein the determining comprises;

determining to send the damping torque command when the hand wheel velocity is less than the hand wheel angle multiplied by a tangent of a phase plane angle and when the hand wheel angle is greater than zero; and

determining to send the damping torque command when the hand wheel velocity is greater than the hand wheel angle multiplied by the tangent of the phase plane angle and the hand wheel angle is less than zero.

16. A method for controlling a motor in an electrical power steering system, comprising:

generating a damping torque command to send to the motor for reducing an undesired torque;

generating an assist torque command that specifies a desired torque to be generated by the motor;

determining whether to send the damping torque command to the motor as a function of a hand wheel velocity and a hand wheel angle; and

combining the assist torque command and the damping torque command to send to the motor when it is determined that the damping torque command is to be sent to the motor, and wherein the determining comprises, when the hand wheel velocity is greater than the hand wheel angle multiplied by a tangent of a phase plane angle and the hand wheel angle is greater than zero, or when the hand wheel velocity is less than the hand wheel angle multiplied by the tangent of the phase plane angle and the hand wheel angle is less than zero;

scaling the damping torque command based on a vehicle velocity of a vehicle that includes the electronic power steering system, determining to send the damping torque command to the motor.

17. The method of claim 16, wherein the scaling comprises:

maintaining a whole of the damping torque command when the vehicle velocity is less than a first velocity threshold;

scaling down the damping torque command when the vehicle velocity is greater than or equal to the first velocity threshold and is less than a second velocity threshold; and

scaling down the damping torque command such that no damping torque is generated by the motor when the vehicle velocity is greater than or equal to the second velocity threshold.

18. A system of a vehicle comprising:

an electrical power steering system that includes a motor;

a control module configured to;

generate a damping torque command to send to the motor for reducing an undesired torque;

generate an assist torque command that specifies a desired torque to be generated by the motor;

determine whether to send the damping torque command to the motor as a function of a hand wheel velocity and a hand wheel angle; and

combine the assist torque command and the damping torque command to send to the motor when it is determined that the damping torque command is to be sent to the motor; and

wherein the control module is configured to determine whether to send the damping torque command to the motor by;

determining to send the damping torque command when the hand wheel velocity is less than the hand wheel angle multiplied by a tangent of a phase plane angle and the hand wheel angle is greater than zero; and

determining to send the damping torque command when the hand wheel velocity is greater than the hand wheel angle multiplied by the tangent of the phase plane angle and the hand wheel angle is less than zero.

19. A system of a vehicle comprising:

an electrical power steering system that includes a motor;

a control module configured to;

generate a damping torque command to send to the motor for reducing an undesired torque;

generate an assist torque command that specifies a desired torque to be generated by the motor;

determine whether to send the damping torque command to the motor as a function of a hand wheel velocity and a hand wheel angle; and

combine the assist torque command and the damping torque command to send to the motor when it is determined that the damping torque command is to be sent to the motor; and

wherein when the hand wheel velocity is greater than the hand wheel angle multiplied by a tangent of a phase plane angle and the hand wheel angle is greater than zero, or when the hand wheel velocity is less than the hand wheel angle multiplied by the tangent of the phase plane angle and the hand wheel angle is less than zero, the control module is configured to determine whether to send the damping torque command to the motor by;

scaling the damping torque command based on a vehicle velocity of a vehicle that includes the electronic power steering system; and

determining to send the damping torque command to the motor.

20. The system of claim 19, wherein the scaling comprises:

maintaining a whole of the damping torque command when the vehicle velocity is less than a first velocity threshold;

scaling down the damping torque command when the vehicle velocity is greater than or equal to the first velocity threshold and is less than a second velocity threshold; and

scaling down the damping torque command such that no damping torque is generated by the motor when the vehicle velocity is greater than or equal to the second velocity threshold.