Motor control current sensor loss of assist mitigation for electric power steering

• US 9,809,247 B2
• Filed: 01/26/2016
• Issued: 11/07/2017
• Est. Priority Date: 01/30/2015
• 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: Kleinau, Julie A., Pramod, Prerit, Skellenger, Dennis B., Sengottaiyan, Selva Kumar
• Primary Examiner(s): MELTON, TODD M
• Application Number:
  US15/006,901
• Publication Number:
  US 20160229449A1
• Time in Patent Office: 651 Days
• 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
• CPC Class Codes: H02P 23/0004 Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control

Abstract

A power steering system includes a torque modifier module that generates a modified torque command in response to a current sensor fault, a magnitude of the modified torque command changes over a time period. The power steering system also includes a feedforward selection module that applies a dynamic feedforward compensation to a motor current command, thereby generating a motor voltage that is applied to a motor of the power steering system, the dynamic feedforward compensation modifies a frequency response of the power steering system.

Claims

1. A power steering system comprising:

a torque modifier module that generates a modified torque command in response to a current sensor fault, a magnitude of the modified torque command changes over a time period; and

a feedforward selection module that applies a dynamic feedforward compensation to a motor current command, the dynamic feedforward compensation based on motor inductance and motor-circuit resistance, thereby generating a motor voltage that is applied to a motor of the power steering system, the dynamic feedforward compensation modifies a frequency response of the power steering system, the motor current command is based on the modified torque command.

2. The power steering system of claim 1, further comprising a stability compensator selector module that selects a stability compensator of a steering torque control loop of the power steering system when a current sensor fault is detected, the stability compensator selector module generates a compensated torque command sent to the torque modifier module.

3. The power steering system of claim 2, the modified torque command is based at least in part on the compensated torque command.

4. The power steering system of claim 2, the dynamic feedforward compensation is based on a transfer function defined by an approximation of a true derivative.

5. The power steering system of claim 4, the approximation of the true derivative is represented by

6. The power steering system of claim 1, the modified torque command is reduced to a magnitude of zero when the current sensor fault is detected, the modified torque command is increased from a magnitude of zero over a time period.

7. The power steering system of claim 6, the modified torque command has a steady state value defined by a scale factor applied to the modified torque command during the time period.

8. A power steering system comprising:

a stability compensator selector module that selects a stability compensator of a steering torque control loop of the power steering system when a current sensor fault is detected, the stability compensator generates a compensated torque command based on frequency response of a motor control system of a motor of the power steering system; and

a torque modifier module that generates a modified torque command from the compensated torque command in response to a current sensor fault, a magnitude of the modified torque command changes over a time period, a motor voltage that is applied to the motor of the power steering system is based on the modified torque command.

9. The power steering system of claim 8, further comprising a feedforward selection module that applies a dynamic feedforward compensation to a motor current command, thereby generating the motor voltage that is applied to a motor of the power steering system, the dynamic feedforward compensation modifies a frequency response of the power steering system, the motor current command is based on the modified torque command.

10. The power steering system of claim 9, the dynamic feedforward compensation is based on a transfer function defined by an approximation of a true derivative.

11. The power steering system of claim 10, the approximation of the true derivative is represented by

12. The power steering system of claim 8, the modified torque command is increased from a magnitude of zero when the current sensor fault is detected.

13. The power steering system of claim 12, the modified torque command has a steady state value defined by a scale factor applied to the modified torque command during a time period.

14. A method for controlling a power steering system comprising:

generating a modified torque command in response to a current sensor fault, a magnitude of the modified torque command changes over a time period; and

applying a dynamic feedforward compensation to a motor current command, the dynamic feedforward compensation based on motor inductance and motor-circuit resistance, thereby generating a motor voltage that is applied to a motor of the power steering system, the dynamic feedforward compensation modifies a frequency response of the power steering system, the motor current command is based on the modified torque command.

15. The method of claim 14, further comprising selecting a stability compensator of a steering torque control loop of the power steering system when a current sensor fault is detected, the stability compensator selector module generates a compensated torque command.

16. The method of claim 14, the modified torque command is increased from a magnitude of zero when the current sensor fault is detected.

17. The method of claim 16, the modified torque command has a steady state value defined by a scale factor applied to the modified torque command during a time period.

18. The method of claim 14, the dynamic feedforward compensation is based on a transfer function defined by an approximation of a true derivative.

19. The method of claim 18, the approximation of the true derivative is represented by