CASCADED POSITION CONTROL ARCHITECTURE FOR STEERING SYSTEMS

• US 20190308664A1
• Filed: 04/05/2019
• Published: 10/10/2019
• Est. Priority Date: 04/05/2018
• 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: PRAMOD, PRERIT, ZHENG, KAI, GEORGE, MARIAM SWETHA
• Granted Patent: US 11,203,379 B2
• Time in Patent Office: Days
• CPC Class Codes: B62D 15/0225 by measuring on a steering gear element, e.g. on a rack bar
• CPC Class Codes: B62D 15/025 Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation B62D1/28 takes precedence
• CPC Class Codes: B62D 6/002 computing target steering angles for front or rear wheels B62D7/159 takes precedence
• 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
• CPC Class Codes: G01L 5/22 for measuring the force applied to control members, e.g. control members of vehicles, triggers

Abstract

Technical solutions are described for disturbance feedforward compensation technique for improving the disturbance rejection properties of a closed loop position control system using a cascaded control structure with an inner velocity and outer position control loops. According to one or more embodiments, a system includes a position controller that receives an input rack-position command, and a measured rack-position, and computes a velocity command based on a difference in the input rack-position command and the measured rack-position. The system further includes a velocity controller that receives the velocity command, and a measured motor velocity, and computes an input torque command based on a difference in the velocity command and the measured motor velocity. The system adjusts a position of a rack by generating an amount of torque corresponding to the applying the input torque command to a motor.

Claims

1. A system comprising:

a position controller configured to;

receive an input rack-position command, and a measured rack-position; and

compute a velocity command based on a difference in the input rack-position command and the measured rack-position;

a velocity controller configured to;

receive the velocity command, and a measured motor velocity; and

compute an input torque command based on a difference in the velocity command and the measured motor velocity; and

wherein, the system adjusts a position of a rack by generating an amount of torque corresponding to the applying the input torque command to a motor.

2. The system of claim 1, wherein the position controller and the velocity controller are arranged to form a cascaded control loop comprising a position feedback loop and a velocity feedback loop respectively, the cascaded control loop provides rack position tracking.

3. The system of claim 1, further comprising a damping controller that is configured to:

compute a first torque command by scaling the measured motor velocity using a damping term; and

modify the input torque command by adding the first torque command into the input torque command for rack position tracking.

4. The system of claim 1, further comprising a disturbance controller configured to:

estimate a rack force acting on the rack; and

modify the input torque command using the rack force that is estimated.

5. The system of claim 4, wherein the rack force that is estimated is scaled using a configurable parameter.

6. The system of claim 1, wherein the velocity command is computed based on a configurable parameter of the position controller.

7. The system of claim 6, wherein the position controller is a proportional controller.

8. The system of claim 1, wherein the input torque command is computed based on a configurable parameter of the velocity controller.

9. The system of claim 8, wherein the velocity controller is a proportional-integral controller.

10. A method comprising:

computing, by a position controller, a velocity command based on a difference in an input rack-position command and a measured rack-position that is provided as a first feedback term;

computing, by a velocity controller, an input torque command based on a difference in the velocity command and a measured motor velocity that is provided as a second feedback term, the velocity controller forming a cascaded control loop with the position controller for providing rack position tracking; and

adjusting, by a motor, a position of a rack by generating an amount of torque corresponding to the input torque command.

11. The method of claim 10, further comprising:

computing, by a damping controller, a first torque command by scaling the measured motor velocity using a damping term; and

modifying the input torque command by adding the first torque command into the input torque command for rack position tracking.

12. The method of claim 10, wherein the velocity command is computed based on a configurable parameter of the position controller.

13. The method of claim 10, wherein the position controller is a proportional controller.

14. The method of claim 10, wherein the input torque command is computed based on a configurable parameter of the velocity controller.

15. The method of claim 10, wherein the velocity controller is a proportional-integral controller.

16. A steering system comprising:

a motor;

a rack; and

a plurality of controllers that comprises a position controller and a velocity controller, the controllers perform a method for providing a rack position tracking using a cascaded control loop comprising a velocity feedback loop and a position feedback loop, the method comprising;

computing, by the position controller, a velocity command based on a difference in an input rack-position command and a measured rack-position that is provided as a first feedback term;

computing, by the velocity controller, an input torque command based on a difference in the velocity command and a measured motor velocity that is provided as a second feedback term; and

adjusting, using the motor, a position of the rack by generating an amount of torque corresponding to the input torque command.

17. The steering system of claim 16, wherein the steering system is a steer by wire system.

18. The steering system of claim 16, wherein the plurality of controllers further comprises a damping controller, and the method further comprising:

computing, by the damping controller, a first torque command by scaling the measured motor velocity using a damping term; and

modifying the input torque command by adding the first torque command into the input torque command for rack position tracking.

19. The steering system of claim 16, wherein the position controller is a proportional controller and wherein the velocity command is computed based on a configurable parameter of the proportional controller.

20. The steering system of claim 16, wherein the velocity controller is a proportional-integral controller, and wherein the input torque command is computed based on a configurable parameter of the velocity controller.