Method and system for determining an inertially-adjusted vehicle reference speed

• US 6,600,979 B1
• Filed: 02/26/2002
• Issued: 07/29/2003
• Est. Priority Date: 02/26/2002
• Status: Active Grant

• Current Assignee: Westinghouse Air Brake Technologies Corporation
• Original Assignee: General Electric Company
• Inventors: Donajkowski, Roland Paul, Worden, Bret Dwayne, Kumar, Ajith K.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Hernandez, Olga
• Application Number:
  US09/683,874
• Time in Patent Office: 518 Days
• Field of Search: 701/20, 701/1, 701/74, 701/69, 180/197, 734/88, 734/89
• US Class Current: 701/20
• CPC Class Codes: B60T 13/665 the systems being specially adapted for transferring two or more command signals, e.g. railway systems B60T13/662 takes precedence
• CPC Class Codes: B60T 17/228 for railway vehicles
• CPC Class Codes: B60T 2250/04 Vehicle reference speed; Vehicle body speed
• CPC Class Codes: B60T 8/172 Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence

Abstract

Method and system for determining a reference speed indicative of true ground speed of a vehicle having a plurality of axles are provided. The reference speed for a designated one of the axles is dynamically adjusted to account for changes in vehicular acceleration that may occur while determination of the reference speed is being performed. The method allows collecting a stream of samples over respective sampling intervals of at least one motion-indication parameter corresponding to a respective axle of the vehicle. In one aspect thereof, one may use a torque reduction rulebase configured to avoid high torque reduction, and inaccuracies in the motion-indication parameter due to high levels of creep, if any, in a wheel of the respective axle. The method further allows estimating an inertia value for the vehicle based on respective changes in tractive effort and acceleration over each sampling interval. The collected motion parameter samples may be adjusted for changes in acceleration over each sampling interval using the estimated inertial value. A signal indicative of axle speed may be limited to at least one respective limit value of rate and magnitude based on the inertially-adjusted parameter samples to, for example, provide accurate slip control.

Claims

1. A method for determining a reference speed indicative of true ground speed of a vehicle having a plurality of axles, the reference speed for a designated one of the axles being dynamically adjusted to account for changes in vehicular acceleration that may occur while determination of the reference speed is being performed, the method comprising:

collecting a stream of samples over respective sampling intervals of at least one motion-indication parameter corresponding to a respective axle using a torque reduction rulebase configured to avoid high torque reduction, and inaccuracies in the motion-indication parameter due to high levels of creep, if any, in a wheel of the respective axle;

estimating an inertia value for the vehicle based on respective changes in tractive effort and acceleration over each sampling interval;

adjusting the collected motion parameter samples for changes in acceleration over each sampling interval using the estimated inertial value; and

limiting a signal indicative of axle speed to at least one respective limit value of rate and magnitude based on the inertially-adjusted parameter samples, the limited signal indicative of axle speed comprising the reference speed for the designated axle.

2. The method of claim 1 wherein the at least one motion-indication parameter corresponding to the respective axle is selected from the group consisting of speed and acceleration.

3. The method of claim 1 wherein the torque reduction rulebase comprises a first stage for reducing torque level applied to the respective axle to a first torque value, and determining whether or not the level of creep at said first torque value exceeds a creep threshold value.

4. The method of claim 3 wherein, in the event the level of creep at said first torque value is below the creep threshold value, obtaining a respective sample for the at least one motion-indication parameter corresponding to the respective axle.

5. The method of claim 4 wherein, in the event the level of creep at said first torque value exceeds the creep threshold value, transitioning to a second stage for reducing torque level applied to the respective axle to a second torque value lesser than the first torque value, and obtaining a respective sample for the at least one motion-indication parameter corresponding to the respective axle.

6. The method of claim 5 wherein the transitioning to the second stage comprises a step-wise transitioning.

7. The method of claim 5 wherein the transitioning to the second stage comprises a ramp-wise transitioning.

8. The method of claim 1 wherein the estimating of the inertia value for the vehicle comprises accumulating tractive effort over a present sampling interval and further comprises calculating the difference in accumulated tractive effort between the present sampling interval and the preceding sampling interval, the calculated difference corresponding to changes in tractive effort over said sampling intervals.

9. The method of claim 8 wherein the estimating of the inertia value for the vehicle further comprises calculating the difference between an acceleration sample obtained in the present sampling interval and an acceleration sample obtained in the preceding sampling interval, the calculated difference corresponding to changes in acceleration over said sampling intervals.

10. The method of claim 9 wherein the estimating of the inertia value for the vehicle further comprises determining whether the calculated changes in tractive effort and acceleration meet respective threshold values and polarities.

11. The method of claim 10 wherein the estimating of the inertia value of the vehicle comprises calculating the ratio of the changes in tractive effort over the changes in acceleration.

12. The method of claim 10 wherein the estimating of the inertia value for the vehicle further comprises storing a value of the estimated inertial value based upon whether the calculated changes in tractive effort and acceleration meet the respective threshold values and polarities.

13. The method of claim 12 wherein the estimating of the inertia value for the vehicle further comprises calculating an average of a predefined number of the stored inertial values.

14. The method of claim 13 further comprising calculating the difference in tractive effort accumulated over a preceding sampling interval and a value of present tractive effort command, and multiplying the calculated difference with the calculated average of vehicle inertia to generate an adjustment to each corresponding axel acceleration sample.

15. The method of claim 14 further comprising generating an adjustment to each corresponding axle speed sample based on the generated adjustment to the respective acceleration sample.

16. A method for determining inertial estimates of a vehicle during dynamic operation thereof, the method comprising:

collecting a stream of samples over respective sampling intervals of at least one motion-indication parameter corresponding to a respective axle of the vehicle; and

estimating an inertia value for the vehicle based on respective changes in tractive effort and acceleration over each sampling interval, wherein the estimating of the inertial value for the vehicle comprises accumulating a signal indicative of tractive effort over a present sampling interval and further comprises calculating the difference in accumulated tractive effort between the present sampling interval and the preceding sampling interval, the calculated difference corresponding to changes in tractive effort over said sampling intervals.

17. The method of claim 16 wherein the estimating of the inertia value for the vehicle further comprises calculating the difference between an acceleration sample obtained in the present sampling interval and an acceleration sample obtained in the preceding sampling interval, the calculated difference corresponding to changes in acceleration over said sampling intervals.

18. The method of claim 17 wherein the estimating of the inertia value for the vehicle further comprises determining whether the calculated changes in tractive effort and acceleration meet respective threshold values and polarities.

19. The method of claim 18 wherein the estimating of the inertia value of the vehicle comprises calculating the ratio of the changes in tractive effort over the changes in acceleration.

20. The method of claim 18 wherein the estimating of the inertia value for the vehicle further comprises storing a value of the estimated inertial value based upon whether the calculated changes in tractive effort and acceleration meet the respective threshold values and polarities.

21. The method of claim 20 wherein the estimating of the inertia value for the vehicle further comprises calculating an average of a predefined number of the stored inertial values.

22. A method for controlling torque applied to an axle of a vehicle while performing sampling of motion-indication parameters of said axle, the method comprising:

collecting a stream of samples over respective sampling intervals of at least one motion-indication parameter corresponding to a respective axle using a multi-stage torque reduction rulebase; and

configuring the multi-stage torque reduction rulebase to avoid high torque reduction, and inaccuracies in the motion-indication parameter due to high levels of creep, if any, in a wheel of the respective axle.

23. The method of claim 22 wherein the at least one motion-indication parameter corresponding to the respective axle is selected from the group consisting of speed and acceleration.

24. The method of claim 22 wherein the multi-stage torque reduction rulebase comprises a first stage for reducing torque level applied to the respective axle to a first torque value, and determining whether or not the level of creep at said first torque value exceeds a creep threshold value.

25. The method of claim 24 wherein, in the event the level of creep at said first torque value is below the creep threshold value, obtaining a respective sample for the at least one motion-indication parameter corresponding to the respective axle.

26. The method of claim 25 wherein, in the event the level of creep at said first torque value exceeds the creep threshold value, transitioning to a second stage for reducing torque level applied to the respective axle to a second torque value lesser than the first torque value, and obtaining a respective sample for the at least one motion-indication parameter corresponding to the respective axle.

27. The method of claim 26 wherein the transitioning to the second stage comprises a step-wise transitioning.

28. The method of claim 26 wherein the transitioning to the second stage comprises a ramp-wise transitioning.

29. A method for using an inertial estimate of a vehicle for adjusting at least one parameter indicative of vehicle motion, the method comprising:

collecting a stream of samples over respective sampling intervals of at least one motion-indication parameter corresponding to a respective axle of the vehicle;

estimating an inertia value for the vehicle; and

adjusting the collected motion-indication parameter samples for changes in acceleration over each sampling interval based on the estimated inertial value of the vehicle to generate an adjustment to each corresponding axle acceleration sample.

30. The method of claim 29 further comprising limiting a signal indicative of axle speed to at least one respective limit value of rate and/or magnitude based on the inertially-adjusted parameter samples.

31. The method of claim 29 further comprising calculating the difference in tractive effort accumulated over a preceding sampling interval and a value of present tractive effort command, and multiplying the calculated difference with a calculated average of vehicle inertia to generate the adjustment to each corresponding axle acceleration sample.

32. The method of claim 31 further comprising generating an adjustment to each corresponding axle speed sample based on the generated adjustment to the respective acceleration sample.

33. The method of claim 29 wherein the inertially-adjusted parameter samples bound a signal indicative of ground speed of the vehicle.

34. The method of claim 29 wherein the inertially-adjusted parameter samples comprise a signal indicative of ground speed of the vehicle.

35. The method of claim 29 wherein the inertially-adjusted parameter samples allow determining creep detection in the respective axle of the vehicle.

36. The method of claim 29 wherein the vehicle comprises a train made up of a locomotive coupled to one or more cars and the inertially-adjusted parameter samples are used to make a determination of the number of cars hauled by the locomotive.

37. The method of claim 36 wherein the inertially-adjusted parameter samples are used to make an estimation of total blended braking effort for stopping the train.

38. A system for determining a reference speed indicative of true ground speed of a vehicle having a plurality of axles, the reference speed for a designated one of the axles being dynamically adjusted to account for changes in vehicular acceleration that may occur while determination of the reference speed is being performed, the system comprising:

a module configured to collect a stream of samples over respective sampling intervals of at least one motion-indication parameter corresponding to a respective axle using a torque reduction rulebase configured to avoid high torque reduction, and inaccuracies in the motion-indication parameter due to high levels of creep, if any, in a wheel of the respective axle;

an inertia estimator configured to estimate an inertia value for the vehicle based on respective changes in tractive effort and acceleration over each sampling interval;

a module configured to adjust the collected motion parameter samples for changes in acceleration over each sampling interval using the estimated inertial value; and

a limiter configured to limit a signal indicative of axle speed to at least one respective limit value of rate and magnitude based on the inertially-adjusted parameter samples, the limited signal indicative of axle speed comprising the reference speed for the designated axle.

39. The system of claim 38 wherein the at least one motion-indication parameter corresponding to the respective axle is selected from the group consisting of speed and acceleration.

40. The system of claim 38 wherein the torque reduction rulebase comprises a first stage for reducing torque level applied to the respective axle to a first torque value, and determining whether or not the level of creep at said first torque value exceeds a creep threshold value.

41. The system of claim 40 wherein, in the event the level of creep at said first torque value is below the creep threshold value, obtaining a respective sample for the at least one motion-indication parameter corresponding to the respective axle.

42. The system of claim 41 wherein, in the event the level of creep at said first torque value exceeds the creep threshold value, transitioning to a second stage for reducing torque level applied to the respective axle to a second torque value lesser than the first torque value, and obtaining a respective sample for the at least one motion-indication parameter corresponding to the respective axle.

43. The system of claim 42 wherein the transitioning to the second stage comprises a step-wise transitioning.

44. The system of claim 42 wherein the transitioning to the second stage comprises a ramp-wise transitioning.

45. The system of claim 38 wherein the inertia estimator comprises an integrator configured to integrate tractive effort over a present sampling interval and further comprises a subtractor for calculating the difference in accumulated tractive effort between the present sampling interval and the preceding sampling interval, the calculated difference corresponding to changes in tractive effort over said sampling intervals.

46. The system of claim 45 wherein the inertia estimator further comprises a subtractor for calculating the difference between an acceleration sample obtained in the present sampling interval and an acceleration sample obtained in the preceding sampling interval, the calculated difference corresponding to changes in acceleration over said sampling intervals.

47. The system of claim 46 wherein the inertia estimator further comprises logic for determining whether the calculated changes in tractive effort and acceleration meet respective threshold values and polarities.

48. The system of claim 47 wherein the inertia estimator comprises a module for calculating the ratio of the changes in tractive effort over the changes in acceleration.

49. The system of claim 48 wherein the inertia estimator comprises memory for storing a value of the estimated inertial value based upon whether the calculated changes in tractive effort and acceleration meet the respective threshold values and polarities.

50. The system of claim 49 wherein the inertia estimator further comprises an averaging module configured to calculate an average of a predefined number of the stored inertial values.

51. The system of claim 50 further comprising a subtractor configured to calculate the difference in tractive effort accumulated over a preceding sampling interval and a value of present tractive effort command, and a multiplier configured to multiply the calculated difference with the calculated average of vehicle inertia to generate an adjustment to each corresponding axel acceleration sample.

52. The system of claim 51 further comprising an extrapolator configured to generate an adjustment to each corresponding axle speed sample based on the generated adjustment to the respective acceleration sample.

53. A method for using an inertial estimate of a vehicle for adjusting at least one parameter indicative of vehicle motion, the method comprising:

collecting a stream of samples over respective sampling intervals of at least one motion-indication parameter corresponding to a respective axle of the vehicle;

estimating an inertia value for the vehicle;

adjusting the collected motion-indication parameter samples for changes in acceleration over each sampling interval based on the estimated inertial value of the vehicle; and

limiting a signal indicative of axle speed to at least one respective limit value of rate and/or magnitude based on the inertially-adjusted parameter samples.

54. The method of claim 53 further comprising calculating the difference in tractive effort accumulated over a preceding sampling interval and a value of present tractive effort command, and multiplying the calculated difference with a calculated average of vehicle inertia to generate an adjustment to each corresponding axle acceleration sample.

55. The method of claim 54 further comprising generating an adjustment to each corresponding axle speed sample based on the generated adjustment to the respective acceleration sample.

56. The method of claim 53 wherein the inertially-adjusted parameter samples bound a signal indicative of ground speed of the vehicle.

57. The method of claim 53 wherein the inertially-adjusted parameter samples comprise a signal indicative of ground speed of the vehicle.

58. The method of claim 53 wherein the inertially-adjusted parameter samples allow determining creep detection in the respective axle of the vehicle.

59. The method of claim 53 wherein the vehicle comprises a train made up of a locomotive coupled to one or more cars and the inertially-adjusted parameter samples are used to make a determination of the number of cars hauled by the locomotive.

60. The method of claim 59 wherein the inertially-adjusted parameter samples are used to make an estimation of total blended braking effort for stopping the train.