Method and system controlling an electrical motor with temperature compensation

• US 8,547,045 B2
• Filed: 06/27/2011
• Issued: 10/01/2013
• Est. Priority Date: 02/23/2011
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Wu, Long, Shaw, Robert
• Primary Examiner(s): Masih, Karen
• Application Number:
  US13/169,407
• Publication Number:
  US 20120212169A1
• Time in Patent Office: 827 Days
• Field of Search: 318/432, 318/400.02, 318/400.23, 318/805, 318/803, 318/807
• US Class Current: 318/432
• CPC Class Codes: H02P 21/141 Flux estimation
• CPC Class Codes: H02P 29/662 the rotor having permanent magnets H02P29/67 takes precedence
• CPC Class Codes: H02P 7/285 controlling armature supply only

Abstract

A temperature estimation module estimates a change in temperature of the magnets associated with the rotor of the motor based on an operational magnetic flux strength that is compared to a reference magnetic flux strength determined at a known ambient temperature and for a predetermined operating range of the motor The temperature estimation module or the system establishes a relationship between the estimated change in the temperature and a magnetic torque component of a target output torque of the motor consistent with the predetermined operating range. The current adjustment module or the system adjusts a command (e.g., quadrature-axis current command) for the motor to compensate for shaft torque variation associated with the estimated change in the temperature in conformance with the established relationship.

Claims

1. A method for controlling an electrical motor comprising a rotor with associated magnets and a stator, the method comprising:

estimating a change in temperature of the magnets associated with the rotor of the motor based on an operational magnetic flux strength that is compared to a reference magnetic flux strength determined at a known ambient temperature and for a predetermined operating range of the motor;

establishing a relationship between the estimated change in the temperature and a magnetic torque component of a target output torque of the motor consistent with the predetermined operating range; and

adjusting a command for the motor to compensate for shaft torque variation associated with the estimated change in the temperature in conformance with the established relationship.

2. The method according to claim 1 wherein the operational magnetic flux strength is derived from an operational quadrature-axis voltage command and wherein the reference magnetic flex strength is derived from a reference quadrature-axis voltage command.

3. The method according to claim 1 wherein the establishing of the relationship comprises determining the magnetic torque component of the target output torque as a function of the reference magnetic flux strength, a direct-axis current command, a quadrature-axis current command, direct-axis inductance and quadrature-axis inductance.

4. The method according to claim 1 wherein the adjusting of the command further comprises adjusting a quadrature-axis current command.

5. The method according to claim 1 wherein the adjusting of the command further comprises increasing a quadrature-axis current command in response to an increase in the temperature.

6. The method according to claim 1 wherein the adjusting of the command further comprises adjusting a quadrature-axis current command based on the estimated change in the temperature and a magnetic torque component of the target output torque.

7. The method according to claim 6 wherein the change in the estimated change in the temperature is determined in accordance with the following equation:

8. The method according to claim 6 wherein the magnetic torque component is determined in accordance with the following equation:

9. The method according to claim 1 wherein the relationship is determined in accordance with the following equation:

10. The method according to claim 1 wherein the command is determined in accordance with the following equations:

11. A system for controlling an electrical motor, where the motor comprises a rotor with associated magnets and a stator, the system comprising:

a data processor for estimating a change in temperature of the magnets associated with the rotor of the motor based on an operational magnetic flux strength that is compared to a reference magnetic flux strength determined at a known ambient temperature and for a predetermined operating range of the motor;

a temperature estimation module for establishing a relationship between the estimated change in the temperature and a magnetic torque component of a target output torque of the motor consistent with the predetermined operating range; and

a current adjustment module for adjusting a command for the motor to compensate for shaft torque variation associated with the estimated change in the temperature in conformance with the established relationship.

12. The system according to claim 11 wherein the data processor is arranged to derive the operational magnetic flux strength from an operational quadrature-axis voltage command and wherein the data processor is arranged to derive the reference magnetic flex strength from a reference quadrature-axis voltage command.

13. The system according to claim 11 wherein the data processor is adapted to execute software instructions of the temperature estimation module to establish the relationship, where the relationship comprises the magnetic torque component of the target output torque as a function of the reference magnetic flux strength, a direct-axis current command, a quadrature-axis current command, direct-axis inductance and quadrature-axis inductance.

14. The system according to claim 11 wherein the command comprises a quadrature-axis current command.

15. The system according to claim 11 wherein the command comprises a respective increase in a quadrature-axis current command in response to a corresponding increase in the temperature.

16. The system according to claim 11 wherein the command comprises an adjustment to a quadrature-axis current command based on the estimated change in the temperature and a magnetic torque component of the target output torque.

17. The system according to claim 16 wherein the change in the estimated change in the temperature is determined by the data processor in accordance with the following equation:

18. The system according to claim 16 wherein the magnetic torque component is determined by the data processor in accordance with the following equation:

19. The system according to claim 11 wherein the relationship is determined by the data processor in accordance with the following equation:

20. The system according to claim 11 wherein the command is determined by the data processor in accordance with the following equations: