Anti-spin control for a separately excited motor drive system

• US 6,611,116 B2
• Filed: 05/10/2001
• Issued: 08/26/2003
• Est. Priority Date: 05/10/2000
• Status: Expired due to Term

• Current Assignee: Curtis Instruments Incorporated
• Original Assignee: Curtis Instruments Incorporated
• Inventors: May, Bill, Nahapetian, Gevorg, Bachman, Michael
• Primary Examiner(s): Dang, Khanh
• Application Number:
  US09/853,404
• Publication Number:
  US 20020005304A1
• Time in Patent Office: 838 Days
• Field of Search: 318/34, 318/51, 318/52, 318/63, 318/79, 318/88, 318/109, 318/111, 318/139, 388/801, 388/802, 388/803, 388/804
• US Class Current: 318/139
• CPC Class Codes: B60L 3/102 of individual wheels
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility

Abstract

Methods and apparatus for controlling performance of electric motors in a system having two or more electric motors, the motors adapted for being coupled to two or more wheels of an electric vehicle, each of the electric motors having armature and field coils which are independently excited by a source of voltage to generate armature and field currents, the armatures being connected in series to the voltage source include detecting a condition in the system indicating that one of the wheels is slipping, reducing power delivered to one of the motors that is associated with the slipping wheel in response to the detection of the condition, providing power to the one or more motors that are not associated with the slipping wheel after the power delivered to the motor associated with the slipping wheel is reduced, and restoring the power delivered to the one of the motors associated with the slipping wheel in response to a recovery event.

Claims

1. In a system having two or more electric motors, the motors adapted for being coupled to two or more wheels of an electric vehicle, each of the electric motors having armature and field coils which are independently excited by a source of voltage to generate armature and field currents, the armatures being connected in series to the voltage source, a method of controlling performance of the electric motors, comprising:

detecting a condition in the system indicating that one of the wheels is slipping;

reducing power delivered to one of the motors that is associated with the slipping wheel in response to the detection of the condition;

providing power to the one or more motors that are not associated with the slipping wheel after the power delivered to the motor associated with the slipping wheel is reduced; and

restoring the power delivered to the one of the motors associated with the slipping wheel in response to a recovery event, wherein the recovery event is ascertained from at least one of a detection of movement of the vehicle for a specified period of time, detection of movement of the vehicle for a specified distance, and detection of movement of the vehicle in a desired direction.

2. In a system having two or more electric motors, the electric motors adapted for being coupled to two or more wheels of an electric vehicle, each of the electric motors having armature and field coils which are independently excited by a source of voltage to generate armature and field currents, the armatures being connected in series to the voltage source, a method of controlling performance of the electric motors, comprising:

detecting a condition in the system to ascertain when to deactivate one of the electric motors;

identifying one of the electric motors to deactivate when the condition is detected;

eliminating current in the identified one of the electric motors, the current being armature current or field current;

providing armature current and field current to the one or more electric motors that are not identified as one of the electric motors to deactivate after the current is eliminated in the identified one of the electric motors; and

automatically restoring the current in the identified one of the electric motors in response to a recovery event.

3. The method as recited in claim 2, wherein the current is field current.

4. The method as recited in claim 2, wherein the current is armature current.

5. The method as recited in claim 2, wherein eliminating current in the identified motor comprises:

shunting the current around the identified motor with a relay.

6. The method as recited in claim 5, wherein the relay is around the field coils of the identified motor.

7. The method as recited in claim 2, wherein the field coils of the motors are connected in series.

8. The method as recited in claim 7, wherein the current is field current and eliminating current in the identified motor comprises:

ascertaining a value of the field current flowing through the field coils of the motors;

setting a field current command to zero, the field current command indicating a desired field current flowing through the field coils of the motors;

detecting that the field current is substantially zero;

closing a relay around the field coils of the identified motor; and

setting the field current command back to the value of the field current that was previously ascertained.

9. The method as recited in claim 8, wherein restoring the current in the identified motor in response to a recovery event comprises:

setting the field current command to zero, the field current command indicating a desired field current flowing through the field coils of the motors;

detecting that the field current is substantially zero;

opening the relay around the field coils of the identified motor; and

setting the field current command back to the value of the field current that was previously ascertained.

10. The method as recited in claim 7, wherein the current is field current and eliminating current in the identified motor comprises:

ascertaining a value of the field current flowing through the field coils of the motors;

reducing the field current flowing through the field coils of the motors to substantially zero;

closing a relay around the field coils of the identified motor; and

setting the field current flowing through the field coils of the unidentified motors to the value of the field current that was previously ascertained.

11. The method as recited in claim 10, wherein restoring the current in the identified motor in response to a recovery event comprises:

reducing the field current flowing through the field coils of the motors to substantially zero;

opening the relay around the field coils of the identified motor; and

setting the field current flowing through the field coils of the unidentified motors to the value of the field current that was previously ascertained.

12. The method as recited in claim 2, wherein the field coils of the motors are connected in parallel.

13. The method as recited in claim 12, wherein the current is field current and eliminating current in the identified motor comprises:

ascertaining a value of the field current flowing through the field coils of the motors;

setting a field current command to zero, the field current command indicating a desired field current flowing through the field coils of the motors;

detecting that the field current is substantially zero;

opening a relay around the field coils of the identified motor; and

setting the field current command to one half the value of the field current that was previously ascertained.

14. The method as recited in claim 13, wherein restoring the current in the identified motor in response to a recovery event comprises:

closing the relay around the field coils of the identified motor; and

setting the field current command back to the value of the field current that was previously ascertained.

15. The method as recited in claim 12, wherein the current is field current and eliminating current in the identified motor comprises:

ascertaining a value of the field current flowing through the field coils of the motors;

ascertaining a number of the electric motors in the system;

reducing the field current flowing through the field coils of the motors to substantially zero;

opening a relay around the field coils of the identified motor; and

setting the field current flowing through the field coils of the unidentified motors to (1-1/the number of the electric motors in the system) the value of the field current that was previously ascertained.

16. The method as recited in claim 15, wherein restoring the current in the identified motor in response to a recovery event comprises:

closing the relay around the field coils of the identified motor; and

setting the field current flowing through the field coils of the unidentified motors to the value of the field current that was previously ascertained.

17. The method as recited in claim 2, wherein the field coils of the motors are connected in parallel and each of the motors has a separate associated field amplifier.

18. The method as recited in claim 17, wherein the current is field current, the method further comprising:

pulsing the field coils of the identified motor;

detecting a first speed of the identified motor via the pulsed field coils;

detecting a second speed of another one of the motors; and

determining whether the first speed and the second speed are substantially equivalent;

wherein the recovery event is triggered when it is determined that the first speed and the second speed are substantially equivalent.

19. The method as recited in claim 18, wherein detecting the speed of the identified motor comprises detecting a back EMF of the identified motor.

20. The method as recited in claim 17, wherein eliminating current in the identified motor comprises:

reducing the field current in the identified motor to substantially zero.

21. The method as recited in claim 20, further comprising:

ascertaining a value of the field current flowing through the field coils of the identified motor prior to reducing the field current in the identified motor to substantially zero;

wherein restoring the current in the identified motor in response to a recovery event comprises restoring the field current in the identified motor to the value of the field current that was previously ascertained.

22. The method as recited in claim 2, wherein detecting a condition in the system to ascertain when to deactivate one of the motors comprises:

ascertaining a first voltage across the motors;

sensing a second voltage across the one of the motors;

dividing the first voltage across the motors by a number of the motors in the system to ascertain an ideal second voltage;

obtaining a voltage range within which the second voltage is to be from the ideal second voltage when the condition in the system is not detected; and

determining whether the sensed second voltage is within the obtained voltage range from the ideal second voltage, wherein the condition is detected when the sensed second voltage is determined not to be within the obtained voltage range from the ideal second voltage.

23. The method as recited in claim 22, wherein sensing a second voltage across the one of the motors comprises:

monitoring a voltage between two of the armatures with respect to ground.

24. The method as recited in claim 22, wherein the motors are adapted for being coupled to one or more wheels of a vehicle and wherein obtaining a voltage range within which the second voltage is to be from the ideal second voltage when the condition in the system is not detected comprises:

ascertaining a relative turning radius of two of the wheels of the vehicle; and

applying the ascertained relative turning radius of two of the wheels of the vehicle to the first voltage to ascertain the voltage range, wherein the voltage range is proportional to the relative turning radius of the wheels.

25. The method as recited in claim 22, wherein the motors are adapted for being coupled to one or more wheels of a vehicle and wherein obtaining a voltage range within which the second voltage is to be from the ideal second voltage when the condition in the system is not detected comprises:

ascertaining a relative angle of rotation of two of the wheels of the vehicle using one or more angle sensors; and

applying the relative angle of rotation of the two wheels of the vehicle to the first voltage to ascertain the voltage range, wherein the voltage range is proportional to the relative angle of rotation of the wheels.

26. The method as recited in claim 2, wherein detecting a condition in the system to ascertain when to deactivate one of the motors comprises:

determining whether an acceleration rate of the one of the motors exceeds a maximum allowed acceleration rate.

27. The method as recited in claim 2, wherein the motors are adapted for being coupled to one or more wheels of a vehicle and wherein detecting a condition in the system to ascertain when to deactivate one of the motors comprises:

ascertaining a first speed of the one of the motors.

28. The method as recited in claim 27, wherein ascertaining the first speed of the one of the motors comprises:

sensing the first speed of the motor via a speed sensor coupled to the associated one of the wheels.

29. The method as recited in claim 27, further comprising:

ascertaining a second speed of another one or more of the motors; and

comparing the first speed of the one of the motors with the second speed.

30. The method as recited in claim 29, wherein ascertaining the first speed and the second speeds comprises:

inputting armature current, applied voltage, and field current associated with each motor into a motor model; and

applying the motor model to determine the first speed and the second speed.

31. The method as recited in claim 2, wherein the recovery event is a detection of movement of the vehicle in a desired direction after identifying one of the motors to deactivate, eliminating current in the identified motor, and providing armature current and field current to the one or more motors that are not identified as one of the motors to deactivate.

32. The method as recited in claim 2, wherein the recovery event is a detection of movement of the vehicle for a specified period of time after identifying one of the motors to deactivate, eliminating current in the identified motor, and providing armature current and field current to the one or more motors that are not identified as one of the motors to deactivate.

33. The method as recited in claim 2, wherein the recovery event is a detection of movement of the vehicle for a specified distance after identifying one of the motors to deactivate, eliminating current in the identified motor, and providing armature current and field current to the one or more motors that are not identified as one of the motors to deactivate.

34. The method as recited in claim 31, wherein the current is field current, the method further comprising:

detecting a reduction in armature current in one of the motors to detect the movement of the vehicle.

35. The method as recited in claim 31, further comprising:

inputting voltage data and current data into a motor model; and

applying the motor model to detect a speed of the identified motor.

36. The method as recited in claim 31, further comprising:

detecting a difference between the speed of the identified motor and another one of the motors via one or more speed sensors; and

determining whether the difference is within a specified amount;

wherein the movement of the vehicle is detected when the difference is determined to be within the specified amount.

37. The method as recited in claim 2, wherein the recovery event is a lapse of a predetermined period of time after identifying one of the motors to deactivate, eliminating current in the identified motor, and providing armature current and field current to the one or more motors that are not identified as one of the motors to deactivate.

38. The method as recited in claim 2, wherein the recovery event is a non-automatic user-initiated event that is performed by a user of the vehicle.

39. The method as recited in claim 38, wherein the user-initiated event is a return of a throttle in the vehicle to neutral.

40. The method as recited in claim 38, wherein the user-initiated event is an initiation of braking of the vehicle.

41. The method as recited in claim 2, further comprising:

providing an indicator of the detected condition, the indicator being a visual or auditory indicator; and

performing the eliminating, providing, and re-establishing steps in response to a user-initiated event.

42. Apparatus for controlling performance of two or more DC motors used for driving an electric vehicle, each of the electric motors having armature and field coils which are independently excited by a source of voltage to generate armature and field currents, comprising:

a source of DC voltage;

two or more motor armatures connected in series to the voltage source through an armature control circuit to provide independent control of the motor armatures;

two or more motor field windings coupled to the two or more motor armatures and connected to the source of voltage through a field winding control circuit to provide control of the two or more motor field windings independent of the armatures;

a detection mechanism for detecting a condition in one of the motors, the condition when in a first state indicating that one of the motors is to be deactivated and when in a second state indicating that none of the motors are to be deactivated;

an identification mechanism coupled to the detection mechanism, the identification mechanism adapted for identifying one of the motors to deactivate when the condition is in the first state;

a motor controller coupled to the armatures and the field windings, the motor controller being adapted for eliminating current in the identified motor when the condition is in the first state and for restoring current in the identified motor in response to a recovery event, the current being armature current or field current;

a drive mechanism for providing armature current and field current to the motors that are not identified by the sensing mechanism as one of the motors to deactivate after the motor controller has eliminated the current in the identified motor; and

a recovery mechanism coupled to the motor controller, the recovery mechanism being adapted for restoring current in the identified motor in response to a recovery event that is a user-initiated event performed by a user of the vehicle.

43. The apparatus as recited in claim 42, wherein the current is armature current.

44. The apparatus as recited in claim 42, wherein the current is field current.

45. The apparatus as recited in claim 42, wherein the motor controller includes a shunting mechanism and a recovery mechanism, the shunting mechanism being adapted for eliminating field current in the identified motor and the recovery mechanism being adapted for restoring the field current in the identified motor in response to a recovery event.

46. The apparatus as recited in claim 45, wherein the field windings are connected in series, each of the field windings having an associated relay, wherein the shunting mechanism is adapted for closing the relay around the field windings of the identified motor, and wherein the recovery mechanism is adapted for opening the relay around the field windings of the identified motor in response to the recovery event.

47. The apparatus as recited in claim 45, wherein the field windings are connected in parallel, each of the field windings having an associated relay, wherein the shunting mechanism is adapted for opening the relay around the field windings of the identified motor, and wherein the recovery mechanism is adapted for closing the relay around the field windings of the identified motor in response to the recovery event.

48. The apparatus as recited in claim 45, wherein the field windings are connected in parallel, each of the field windings having an associated field amplifier, wherein the shunting mechanism is adapted for reducing the field current in the identified motor to substantially zero, and wherein the recovery mechanism is adapted for restoring the field current in the identified motor to its previous value in response to the recovery event.

49. Apparatus for controlling performance of two or more DC motors used for driving an electric vehicle, each of the electric motors having armature and field coils which are independently excited by a source of voltage to generate armature and field currents, comprising:

a source of DC voltage;

two or more motor armatures connected in series to the voltage source through an armature controller to provide independent control of the motor armatures;

two or more motor field windings coupled to the two or more motor armatures and connected to the source of voltage through a field winding controller to provide control of the two or more motor field windings independent of the armatures;

a detection mechanism for identifying one of the motors to deactivate;

a shunting mechanism coupled to the detection mechanism and to the field windings for eliminating field current in the identified motor;

a drive mechanism for providing armature current and field current to the motors that are not identified by the detection mechanism as one of the motors to deactivate after the shunting mechanism has eliminated field current in the identified motor; and

a recovery mechanism adapted for restoring field current in the identified motor in response to a recovery event, wherein the recovery event is ascertained from at least one of a detection of movement of the vehicle for a specified period of time, detection of movement of the vehicle for a specified distance, and detection of movement of the vehicle in a desired direction.