Motor control anti-windup and voltage saturation design for electric power steering

1. A system for preventing controller windup in an electric motor, the system comprising:

a limiting module that determines a limited voltage command in response to a commanded voltage exceeding an available voltage of a motor power source, the limited voltage command is applied to an electric motor;

a saturation parameter module that determines a saturation parameter based on the limited voltage command, the saturation parameter indicates a magnitude of the commanded voltage exceeding the available voltage, the saturation parameter is a reciprocal of a ratio of the commanded voltage to the limited voltage command;

a processing module that processes the saturation parameter to generate a processed saturation parameter; and

a reference current modifier module that generates a modified current command based on the processed saturation parameter, the modified current command is applied to the control system to improve the current command tracking.

2. The system of claim 1 , wherein the modified current command retains a proportion of the direct axis (d-axis) current and a quadrature axis (q-axis) current provided by the commanded voltage.

3. The system of claim 1 , wherein the limiting module determines the limited voltage command by preserving a vector direction of the commanded voltage.

4. The system of claim 1 , wherein the modified current command comprises a d-axis correction provided by the following equation:

I dT =(1−γ d ) I dmax +γ d I dR ,

I dT is a d-axis component of the modified current command, γ d is a d-axis component of the saturation parameter, I dR is a reference current command, and I dmax is a maximum value of the d-axis current.

5. The system of claim 1 , wherein the modified current command comprises a q-axis correction provided by the following equation:

I qT=γ q I qR ,

I qT is a q-axis component of the modified current command, γ q is a q-axis component of the saturation parameter, and I qR is a q-axis component of a reference current command.

6. The system of claim 1 , wherein the saturation parameter is based on a difference of the commanded voltage and the available voltage.

7. The system of claim 1 , wherein the processed saturation parameter is represented by a square root of an inverse of the saturation parameter.

8. The system of claim 1 , wherein the saturation parameter is an inverse of an amount of saturation.

9. The system of claim 1 , wherein the saturation parameter retains a direction of a limited voltage command.

10. A method for preventing controller windup in an electric motor, the method comprising:

determining a limited voltage command in response to a commanded voltage exceeding an available voltage of a motor power source, the limited voltage command is applied to an electric motor;

determining a saturation parameter based on the limited voltage command, the saturation parameter indicates a magnitude of the commanded voltage exceeding the available voltage, the saturation parameter is an inverse ratio of the commanded voltage to the limited voltage command;

processing the saturation parameter to generate a processed saturation parameter while retaining a nonlinear state; and

generating a modified current command based on the processed saturation parameter, the modified current command is applied to the electric motor to improve current command tracking.

11. The method of claim 10 , wherein the modified current command retains a proportion of the direct axis (d-axis) current and a quadrature axis (q-axis) current provided by the commanded voltage.

12. The method of claim 10 , wherein the limited voltage command is determined by preserving a vector direction of the commanded voltage.

13. The method of claim 10 , wherein the modified current command comprises a d-axis correction provided by the following equation:

I dT =(1−γ d ) I dmax +γ d I dR ,

I dT is a d-axis component of the modified current command, γ d is a d-axis component of the saturation parameter, I dR is a reference current command, and I dmax is a maximum value of the d-axis current.

14. The method of claim 10 , wherein the modified current command comprises a q-axis correction provided by the following equation:

I qT =γ q I qR ,

I qT is a q-axis component of the modified current command, γ q is a q-axis component of the saturation parameter, and I qR is a q-axis component of a reference current command.

15. The method of claim 10 , wherein the saturation parameter is based on a difference of the commanded voltage and the available voltage.

16. The method of claim 10 , wherein the processed saturation parameter is represented by a square root of an inverse of the saturation parameter.

17. The method of claim 10 , wherein the saturation parameter is an inverse of an amount of saturation.

18. The method of claim 10 , wherein the saturation parameter retains a direction of a limited voltage command.