Diagnostic strategy for an electric motor using sensorless control and a position sensor

• US 20040046519A1
• Filed: 09/11/2002
• Published: 03/11/2004
• Est. Priority Date: 09/11/2002
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Miller, John Michael, Leonardi, Franco, Degner, Michael W., Huang, Henry Heping
• Granted Patent: US 6,750,626 B2
• Time in Patent Office: Days
• US Class Current: 318/432
• CPC Class Codes: B60K 1/02 comprising more than one electric motor
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60L 2220/18 Reluctance machines
• CPC Class Codes: B60L 2240/421 Speed
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 3/0023 Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 50/61 by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
• CPC Class Codes: B60L 7/14 for vehicles propelled by ac motors
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 2510/0685 Engine crank angle
• CPC Class Codes: B60W 2510/081 Speed
• CPC Class Codes: B60W 2710/083 Torque
• CPC Class Codes: B60W 50/00 Details of control systems for road vehicle drive control not related to the control of a particular sub-unit , e.g. process diagnostic or vehicle driver interfaces
• CPC Class Codes: H02P 23/03 specially adapted for very low speeds
• CPC Class Codes: H02P 6/16 Circuit arrangements for detecting position
• CPC Class Codes: H02P 6/18 without separate position detecting elements
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/64 : Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 : Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors

Abstract

A strategy to control and diagnose the operation of an electric motor using a sensorless control system augmented by feedback from a position and speed sensor is disclosed. The strategy can improve the robustness of operation and diagnose potential faults in electric motors. The present invention includes a method for diagnosing operation of an electric motor and a method and system for controlling an electric motor. In the diagnostic method, a sensorless system and a sensor based system are checked against each other to determine if either of the systems is faulted. In the control method, the sensor based control system is used when the motor speed is below a predetermined threshold and the sensorless system is used when the motor speed is above the predetermined threshold. The position sensor can be a low resolution position sensor, an engine crankshaft sensor, an engine camshaft sensor, or a transmission sensor.

Claims

1. A method for diagnosing operation of an electric motor, comprising:

determining a first shaft position using a sensorless control system;

determining a second shaft position using a position sensor; and

evaluating operation of said electric motor based at least in part on comparison of said first shaft position to said second shaft position.

2. The method according to claim 1, further comprising evaluating operation of said sensorless control scheme based on said second shaft position.

3. The method according to claim 1, further comprising evaluating operation of said position sensor based on said first shaft position.

4. The method according to claim 1, further comprising determining a modified shaft position based on said first shaft position and said second shaft position.

5. The method according to claim 4, further comprising:

transmitting said modified shaft position to a torque controller; and

transmitting a voltage command from said torque controller to an inverter.

6. A method for controlling an electric motor, comprising:

determining an electric motor rotational speed;

operating said electric motor using a sensorless control system if said electric motor rotational speed is above a predetermined threshold; and

operating said electric motor using a sensor based control system if said electric motor rotational speed is below said predetermined threshold.

7. The method according to claim 6, further comprising correcting said sensorless control system with said sensor based control system.

8. The method according to claim 6, further comprising correcting said sensor based control system with said sensorless control system.

9. The method of claim 6, wherein the step of operating said electric motor using a sensorless control system if said electric motor rotational speed is above a predetermined threshold comprises the steps of:

determining motor speed and position from a plurality of phase current and phase voltage signals;

determining an inverter voltage command from said motor speed and position; and

determining the plurality of phase current and phase voltage signals from said inverter voltage command.

10. The method of claim 9, further comprising:

determining motor speed and position from a position sensor; and

correcting said phase current and phase voltage signal determined motor speed and position with said position sensor determined motor speed and position.

11. The method of claim 6, wherein the step of operating said electric motor using a sensor based control system if said electric motor rotational speed is below said predetermined threshold step comprises the steps of:

determining motor speed and position from a position sensor;

determining an inverter voltage command from said motor speed and position; and

determining a plurality of phase current and phase voltage signals from said inverter voltage command.

12. The method of claim 11, further comprising:

determining motor speed and position from a plurality of phase current and phase voltage signals; and

correcting said position sensor determined motor speed and position with said phase current and phase voltage signal determined motor speed and position.

13. The method of claim 6, wherein said predetermined threshold is about 50 rpm.

14. The method of claim 6, wherein said predetermined threshold is in the range of about 10 rpm to about 100 rpm.

15. A system to control an electric motor comprising:

an inverter operatively connected to said electric motor;

a position estimator operatively connected to said electric motor and said inverter;

a torque controller operatively connected to said position estimator and said inverter;

a position sensor operatively connected to said electric motor and said position estimator;

a processor for determining a first electric motor shaft position based on an output from said inverter;

said processor ordered to determine a second electric motor shaft position based on an output from said position sensor; and

said processor programmed to correct said first electric motor shaft position by using data related to said second electric motor shaft position.

16. The system according to claim 15 wherein said processor is programmed to correct said second electric motor shaft position using data related to said first electric motor shaft position.

17. The system according to claim 15, wherein said position sensor is a low resolution position sensor.

18. The system according to claim 15, wherein said position sensor is an engine crankshaft position sensor.

19. The system according to claim 15, wherein said position sensor is an engine camshaft position sensor.

20. The system according to claim 115, wherein said position sensor is a transmission sensor.

21. An vehicle comprising:

an electric motor;

an inverter operatively connected to said motor;

a position estimator operatively connected to said motor and said inverter;

a torque controller operatively connected to said position estimator and said inverter;

a position sensor operatively connected to said motor and said position estimator;

means for determining a first electric motor shaft position based on an output from said inverter;

means for determining a second electric motor shaft position based on an output from said position sensor; and

means for correcting said first electric motor shaft position by said second electric motor shaft position output.

22. The vehicle according to claim 21, further comprising means for correcting said second electric motor shaft position by said first electric motor shaft position output.

23. The vehicle according to claim 21, wherein said position sensor is a low resolution position sensor.

24. The vehicle according to claim 21, wherein said position sensor is an engine crankshaft position sensor.

25. The vehicle according to claim 21, wherein said position sensor is an engine camshaft position sensor.

26. The vehicle according to claim 21, wherein said position sensor is a transmission sensor.

27. An article of manufacture for controlling an electric motor, comprising:

a computer readable storage device; and

a control strategy embodied in said computer readable storage device for directing a computer to control the steps of determining an electric motor rotational speed, operating said electric motor using a sensorless control system if said electric motor rotational speed is above a predetermined threshold, and operating said electric motor using a sensor based control system if said electric motor rotational speed is below said predetermined threshold.

28. The article of manufacture according to claim 27, wherein said predetermined threshold is about 50 rpm.

29. The article of manufacture according to claim 27, wherein said predetermined threshold is in the range of about 10 rpm to about 100 rpm.