Traction system for electrically powered vehicles

• US 8,903,577 B2
• Filed: 10/30/2009
• Issued: 12/02/2014
• Est. Priority Date: 10/30/2009
• Status: Active Grant

• Current Assignee: Greenvision Group Technologies Corporation
• Original Assignee: LSI Industries Incorporated
• Inventors: Jalbout, Bassam D., Wong, Brian
• Primary Examiner(s): RODDEN, JOSHUA E
• Application Number:
  US12/609,545
• Publication Number:
  US 20110106350A1
• Time in Patent Office: 1,859 Days
• Field of Search: 701/22, 701/82, 701/89, 180/65.1, 180/65.275, 180/65.285, 318/1, 318/101, 318/98, 318/606
• US Class Current: 701/22
• CPC Class Codes: B60K 28/16 responsive to, or preventing, skidding of wheels brake control systems for vehicle drive stability B60T8/1755; arrangements responsive to a speed condition for adjusting wheel braking force B60T8/32; control of vehicle driving stability otherwise than by controlling the propulsion unit only B60W30/02; preventing wheel slippage by reducing power in rail vehicles B61C15/00
• CPC Class Codes: B60L 15/08 using pulses
• CPC Class Codes: B60L 15/2045 for optimising the use of energy
• CPC Class Codes: B60L 15/2072 for drive off
• CPC Class Codes: B60L 2200/26 Rail vehicles
• CPC Class Codes: B60L 50/00 Electric propulsion with power supplied within the vehicle with power supply from force of nature, e.g. sun or wind, B60L8/00; for monorail vehicles, suspension vehicles or rack railways B60L13/00
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 2520/26 Wheel slip
• CPC Class Codes: B60W 2552/40 Coefficient of friction
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

Fixed frequency, fixed duration pulse streams are used to control power switches for one or more electrical motors of electrically powered vehicles or hybrid vehicles having one or more electric motors. The advantages of a pulse system are increased power efficiency and system simplicity over analog systems. The capability of system calibration with a single pulse allows the system to be used under any conditions, and real time adaptation to changes in conditions. Such system and methods provide much improved acceleration over other electrical systems, by making the best use of the coefficient of starting or static friction. The systems and methods provide a non slip traction control system, and the use of an off state in the pulse stream is superior to the use of braking systems for the same purpose, which waste power and cause mechanical wear. In addition, related computer program products are described.

Claims

1. A system for controlling power applied to one or more drive wheels of a vehicle, the system comprising:

an electric motor configured and arranged to supply power for driving a wheel;

the wheel configured and arranged to receive power from the electric motor;

a controller operative to (i) receive acceleration commands and wheel slip information for the wheel as inputs, wherein the wheel slip information comprises a measurement of a time from an application of a maximum torque until slippage of the wheel starts, and (ii) produce as an output a control signal for the electric motor driving the wheel, wherein the control signal includes a timing cycle with a series of pulses having fixed frequency and fixed duration within the timing cycle to cause current to flow to the electric motor during an ON state of the timing cycle, wherein a first pulse of the series of pulses with wheel slip is measured by monitoring and recording a first time duration of the first pulse comprising the time from the application of the maximum torque until slippage of the wheel starts and a second recovery time duration of the first pulse, and using the first and second recovery time durations to generate subsequent pulses of the series of pulses in the timing cycle; and

a current switch connected to the electric motor including an input to receive the control signal to place the switch in one of the ON state and an OFF state according to the timing cycle.

2. The system of claim 1, wherein the controller is configured and arranged to adjust the timing cycle of the pulses of fixed frequency and fixed duration.

3. The system of claim 2, wherein the controller is configured and arranged to adjust the timing cycle based on a sensed coefficient of friction of the wheel.

4. The system of claim 1, wherein the controller is configured and arranged to provide real-time adjustment of the power supplied to the wheel, wherein changing traction conditions can be accommodated.

5. The system of claim 1, wherein the system is configured and arranged for automatic measurement, storage, and use of a pulse length for the first time duration.

6. The system of claim 1, wherein the system is configured and arranged for automatic measurement, storage, and use of a pulse length for the second recovery time furation.

7. The system of claim 1, wherein the wheel slip information comprises a coefficient of starting friction or a coefficient of sliding friction.

8. The system of claim 1, further comprising a second electric motor, a second wheel, and a second current switch, wherein the controller is configured and arranged to (i) receive acceleration commands and wheel slip information for the second wheel as inputs, and (ii) produce as an output a control signal for the second electric motor driving the second wheel, wherein the control signal includes a timing cycle with a series of pulses of fixed frequency and fixed duration within the timing cycle to cause current to flow to the second electric motor during the ON state of the timing cycle, and wherein the second current switch is connected to the second electric motor and includes an input to receive the control signal to place the second current switch in one of the ON state and the OFF state according to the timing cycle.

9. The system of claim 8, wherein the controller is configured and arranged to detect which wheels have a minimum acceptable traction for inclusion in a synchronized power pulse provided to the wheels.

10. The system of claim 9, wherein the detection of the minimum acceptable traction is based on a minimum time before a slide starts to occur.

11. The system of claim 10, wherein the minimum time is 15 milliseconds.

12. The system of claim 8, further comprising a third electric motor, a third wheel, and a third current switch, wherein the controller is configured and arranged to (i) receive acceleration commands and wheel slip information for the third wheel as inputs, and (ii) produce as an output a control signal for the third electric motor driving the third wheel, wherein the control signal includes a timing cycle with a series of pulses of fixed frequency and fixed duration within the timing cycle to cause current to flow to the third electric motor during the ON state of the timing cycle, and wherein the third current switch is connected to the third electric motor and includes an input to receive the control signal to place the third current switch in one of the ON state and the OFF state according to the timing cycle.

13. The system of claim 12, further comprising a fourth electric motor, a fourth wheel, and a fourth current switch, wherein the controller is configured and arranged to (i) receive acceleration commands and wheel slip information for the fourth wheel as inputs, and (ii) produce as an output a control signal for the fourth electric motor driving the fourth wheel, wherein the control signal includes a timing cycle with a series of pulses of fixed frequency and fixed duration within the timing cycle to cause current to flow to the fourth electric motor during the ON state of the timing cycle, and wherein the fourth current switch is connected to the fourth electric motor and includes an input to receive the control signal to place the fourth current switch in one of the ON state and the OFF state according to the timing cycle.

14. The system of claim 13, wherein the controller is configured and arranged to provide synchronization of the series of pulses provided to the four electric motors for synchronized four-wheel drive operation.

15. The system of claim 13, wherein the controller is configured and arranged to detect which wheels have a minimum acceptable traction for inclusion in a synchronized power pulse provided to the wheels.

16. The system of claim 15, wherein the detection of the minimum acceptable traction is based on a minimum time before a slide starts to occur.

17. The system of claim 16, wherein the minimum time is 15 milliseconds.

18. The system of claim 1, wherein the duration of each pulse of the control signal is equal to a period of time between pulses in the timing cycle.

19. The system of claim 1, wherein the duration of each pulse of the control signal is less than or equal to a period of time between pulses in the timing cycle.

20. The system of claim 1, wherein the number of pulses in the timing cycle varies from zero to a maximum number corresponding to an acceleration level of the electric motor from zero to a maximum acceleration level.

21. The system of claim 1, further comprising a processing system to generate the control signal supplied to the current switch and to time the start and end of each of the series of pulses within the timing cycle.

22. The system of claim 1, wherein a length of the timing cycle is constant and an acceleration of the vehicle is varied by changing the number of pulses from the timing cycle to another timing cycle.

23. The system of claim 1, wherein the wheel slip information comprises a coefficient of starting friction and a coefficient of sliding friction.

24. A method for controlling the power applied to one or more electric motors coupled to one or more wheels of an electrically powered vehicle, the method comprising:

providing a timing cycle;

determining a desired acceleration rate for a vehicle powered by one or more electrically driven wheels;

based on receiving acceleration commands and wheel slip information for the one or more wheels, wherein the wheel slip information comprises a measurement of a time from an application of a maximum torque until slippage of one of the wheels starts, generating a control signal for each of the one or more wheels including a series of pulses having fixed frequency and fixed duration within the timing cycle corresponding to the desired acceleration rate, wherein a first pulse of the series of the pules with wheel slip is measured by monitoring and recording a first time duration of the first pulse comprising the time from the application of the maximum torque until slippage of one of the wheels starts and a second recovery time duration of the first pulse, and using the first and second recovery time durations to generate subsequent pulses of the series of pulses in the timing cycle; and

supplying the control signal to a respective input of each of one or more current switches, each current switch being connected to an electric motor, each electric motor being connected to a respective one of the wheels, to place the respective switch in one of an ON state during each of the series of pulses and an OFF state after each of the series of pulses to cause current to flow to the respective electric motor connected to each electrically driven wheel during the ON state and cause the respective electric motor to supply a desired power to each electrically driven wheel over the timing cycle.

25. The method of claim 24, wherein the one or more electrically driven wheels comprises two wheels.

26. The method of claim 25 wherein the duration of each pulse of the control signal is equal to a period of time between pulses in the timing cycle.

27. The method of claim 25 wherein the duration of each pulse of the control signal is less than or equal to a period of time between pulses in the timing cycle.

28. The method of claim 25 wherein the number of pulses in the timing cycle varies from zero to a maximum number corresponding to a power level of an electric motor from zero to a maximum power level.

29. The method of claim 24, wherein the one or more electrically driven wheels comprises four wheels.

30. The method of claim 24, wherein providing the timing cycle includes establishing a timing cycle of a constant length and the power applied to each wheel is varied by changing the number of generated pulses from one timing cycle to another timing cycle.

31. The method of claim 24, further comprising adjusting the timing cycle of the pulses of fixed frequency and fixed duration.

32. The method of claim 31, wherein adjusting the timing cycle is based on a sensed coefficient of friction of the driven wheel.

33. The method of claim 32, wherein adjusting the timing cycle comprises real-time adjustment, wherein changing traction conditions can be accommodated.

34. The method of claim 24, further comprising automatic measurement, storage, and use of a pulse length for the first duration.

35. The method of claim 24, further comprising automatic measurement, storage, and use of a pulse length for the second recovery time duration.

36. The method of claim 24, further comprising sensing wheel slip information, wherein the wheel slip information comprises a coefficient of starting friction or a coefficient of sliding friction.

37. The method of claim 24, wherein supplying the control signal comprises providing synchronization of pulses provided to two or more electric motors for synchronized two-wheel drive or four-wheel drive operation.

38. The method of claim 24, further comprising detecting which of the wheels have a minimum acceptable traction for inclusion in a synchronized power pulse provided to the wheels.

39. The method of claim 38, wherein detecting the minimum acceptable traction is based on a minimum time before a slide starts to occur.

40. The method of claim 39, wherein the minimum time is 15 milliseconds.

41. The method of claim 24, further comprising sensing the wheel slip information, wherein the wheel slip information comprises a coefficient of starting friction and a coefficient of sliding friction.

42. A computer program product residing on a non-transitory computer-readable storage medium having a plurality of instructions stored thereon, which when executed by a processing system, cause the processing system to:

provide a timing cycle;

determine a desired acceleration rate for a vehicle powered by one or more electrically driven wheels;

based on acceleration commands and wheel slip information for the one or more wheels, wherein the wheel slip information comprises a measurement of a time from an application of a maximum torque until slippage of one of the wheels starts, generate a control signal for each of the one or more wheels including a series of pulses having fixed frequency and fixed duration within the timing cycle corresponding to the desired acceleration rate, wherein a first pulse of the series of pulses with wheel slip is measured by monitoring and recording a first time duration of the first pulse comprising the time from the application of the maximum torque until slippage of one of the wheels starts and a second recovery time duration of the first pulse, and using the first and second recovery time durations to generate subsequent pulses in the timing cycle; and

supply the control signal to a respective input of one or more current switches, each current switch being connected to an electric motor, each electric motor being connected to a respective one of the wheels, to place the respective switch in one of an ON state during each pulse of the series of pulses and an OFF state after each pulse to cause of the series of pulses current to flow to the respective electric motor connected to each electrically driven wheel during the ON state and cause the respective electric motor to supply a desired power to each electrically driven wheel over the timing cycle.

43. The computer program product of claim 42, wherein the computer-readable storage medium comprises flash memory.

44. The computer program product of claim 42, wherein the computer-readable storage medium comprises ROM memory.

45. The computer program product of claim 42, wherein the one or more electrically driven wheels comprises two wheels.

46. The computer program product of claim 42, wherein the one or more electrically driven wheels comprises four wheels.

47. The computer program product of claim 42, wherein providing the timing cycle includes establishing a timing cycle of a constant length and the power applied to each wheel is varied by changing the number of generated pulses from the timing cycle to another timing cycle.

48. The computer program product of claim 42, wherein the duration of each pulse of the control signal is equal to a period of time between pulses in the timing cycle.

49. The computer program product of claim 42, wherein the duration of each pulse of the control signal is less than or equal to a period of time between pulses in the timing cycle.

50. The computer program product of claim 42, wherein the number of pulses in the timing cycle varies from zero to a maximum number corresponding to a power level of an electric motor from zero to a maximum power level.

51. The computer program product of claim 42, further comprising an instruction to adjust the timing cycle of the pulses of fixed frequency and fixed duration.

52. The computer program product of claim 42, further comprising an instruction to adjust the timing cycle based on a sensed coefficient of friction of the driving wheel.

53. The computer program product of claim 42, further comprising an instruction to adjust the timing cycle for real-time adjustment, wherein changing traction conditions can be accommodated.

54. The computer program product of claim 42, further comprising an instruction for automatic measurement, storage, and use of a pulse length for the first time duration.

55. The computer program product of claim 42, further comprising an instruction for automatic measurement, storage, and use of a pulse length for the second recovery time duration.

56. The computer program product of claim 42, wherein the wheel slip information comprises a coefficient of starting friction or a coefficient of sliding friction.

57. The computer program product of claim 42, further comprising an instruction for providing synchronization of pulses provided to two or more of the electric motors for synchronized two-wheel drive or four-wheel drive operation.

58. The computer program product of claim 42, further comprising an instruction for detecting which of the wheels have a minimum acceptable traction for inclusion in a synchronized power pulse provided to the wheels.

59. The computer program product of claim 58, wherein detecting the minimum acceptable traction is based on a minimum time before a slide starts to occur.

60. The computer program product of claim 59, wherein the minimum time is 15 milliseconds.

61. The computer program product of claim 42, wherein the wheel slip information comprises a coefficient of starting friction and a coefficient of sliding friction.