Adaptive demagnetization compensation for a motor in an electric or partially electric motor vehicle

• US 20030051929A1
• Filed: 03/27/2002
• Published: 03/20/2003
• Est. Priority Date: 09/17/2001
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Curran, Patrick J., Raftari, Abbas, Garg, Vijay K.
• Granted Patent: US 6,679,346 B2
• Time in Patent Office: Days
• US Class Current: 180/65.3
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60L 50/15 with additional electric power supply with capacitors charged by engine-driven generators B60L50/40; with batteries charged by engine-driven generators B60L50/61
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors

Abstract

In an electric or hybrid electric vehicle, a voltage monitor (102) is directly coupled to a traction motor (38) and/or generator motor (30) to detect a permanent magnet induced voltage within the motor at a predetermined speed and no load condition (300). A controller (100) compares the detected permanent magnet induced voltage with an expected reference voltage that represents an expected permanent magnet induced voltage at full magnetization and the predetermined speed (302). The controller produces an indication of magnetization based on the reference voltage, the detected permanent magnet induced voltage, and the predetermined speed. If the indication of magnetism reaches a predetermined threshold, the motor is made inoperable and/or a current to the motor is limited to prevent damage to components (306, 308, 310, 312, 314). Preferably, a user of the vehicle is made aware of these actions by an audible and/or visual indicator (308, 314). If available, another source of motive power is substituted for the motor that is made inoperable (316).

Claims

1. A device for adapting to magnet degradation in a motor of a vehicle comprising:

a permanent magnet induced voltage monitor that measures a detected permanent magnet induced voltage of the motor at a predetermined speed; and

a processor that;

compares the detected permanent magnet induced voltage with a reference voltage that reflects a permanent magnet induced voltage of the motor with a fully magnetized permanent magnet at the predetermined speed;

determines an indication of magnetization based on the detected permanent magnet induced voltage and the reference voltage; and

limits an amount of current supplied to the motor based on the indication of magnetization.

2. The device of claim 1 wherein the permanent magnet induced voltage monitor comprises coils on a stator of the motor and a voltmeter coupled to the coils to detect the detected permanent magnet induced voltage.

3. The device of claim 1 wherein the permanent magnet induced voltage monitor measures the detected permanent magnet induced voltage under a no load condition.

4. The device of claim 1 wherein the processor limits the amount of current supplied to the motor after the indication of magnetism reaches a predetermined threshold.

5. The device of claim 3 wherein the detected permanent magnet induced voltage is measured when contacts to an inverter supplying a current to the motor are opened.

6. The device of claim 3 wherein the amount of current supplied to the motor is limited to an amount of current that is safe for components of the vehicle.

7. The device of claim 1 wherein the motor is one of a traction motor coupled to wheels of the vehicle or a generator motor coupled to planetary gears and to wheels of the vehicle.

8. A method for compensating for permanent magnet degradation in a motor of a vehicle, the method comprising the steps of:

detecting a permanent magnet induced voltage of the motor running at a predetermined speed;

comparing the permanent magnet induced voltage with a reference voltage that represents an expected permanent magnet induced voltage for the motor where a permanent magnet in the motor is fully magnetized;

determining a state of magnetism based on the permanent magnet induced voltage, the reference voltage and the predetermined speed; and

limiting an amount of current supplied to the motor based on the state of magnetism.

9. The method of claim 8 further comprising the step of:

storing the state of magnetism for future reference.

10. The method of claim 8 wherein the step of detecting the permanent magnet induced voltage further comprises inducing a voltage in a coil located adjacent a stator of the motor.

11. The method of claim 10 wherein the step of detecting the permanent magnet induced voltage further comprises detecting the permanent magnet induced voltage at a no load condition.

12. The method of claim 9 wherein the step of limiting the amount of current to the motor includes limiting the amount of current to the motor after the state of magnetism reaches a predetermined threshold.

13. The method of claim 9 further comprising the step of generating an audible or visual indication if the state of magnetism is below a predetermined threshold.

14. The method of claim 11 wherein the step of detecting the permanent magnet induced voltage further comprises detecting the permanent magnet induced voltage when the vehicle is idle or running at a steady state.