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1. WO2018148014 - APPARATUS AND METHODS FOR MEASURING BELTS

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

WHAT IS CLAIMED IS:

1. Apparatus for measuring belts, comprising:

a first rangefinder making first distance measurements from the first rangefinder to a belt having a regularly spaced topographical feature and advancing at a belt speed in a direction of belt travel transverse to the distance between the first rangefinder and the belt;

a processor receiving the first distance measurements from the first rangefinder and producing a first profile record of a predetermined number of sequential first distance measurements and determining the occurrences of the regularly spaced topographical feature in the first profile record.

2. Apparatus as in claim 1 wherein the processor determines the distance between

consecutive positions of the regularly spaced topographical feature on the belt from consecutive occurrences of the regularly spaced topographical feature in the first profile record and the belt speed.

3. Apparatus as in claim 1 wherein the processor produces an auto-correlation of the first profile record and determines the distance between consecutive positions of the regularly spaced topographical feature on the belt from consecutive occurrences of the regularly spaced topographical feature in the auto-correlation of the first profile record and the belt speed.

4. Apparatus as in claim 1 further comprising:

a second rangefinder making second distance measurements from the second

rangefinder to the belt, wherein the second rangefinder is offset from the first rangefinder in the direction of belt travel by a separation distance;

wherein the processor receives the second distance measurements, produces a second profile record of a predetermined number of sequential second distance

measurements, and determines the occurrences of the regularly spaced

topographical features in the second profile record.

5. Apparatus as in claim 4 wherein the processor computes the belt speed as the ratio of the separation distance to the time delay between the occurrence of the regularly spaced topographical feature in the first profile record and the occurrence of the same regularly spaced topographical feature in the second profile record.

6. Apparatus as in claim 4 wherein the processor produces a cross-correlation of the first profile record and the second profile record to determine a cross-correlation time delay between the occurrence of the regularly spaced topographical feature in the first profile record and the occurrence of the same regularly spaced topographical feature in the second profile record.

7. Apparatus as in claim 6 wherein the processor computes the belt speed as the ratio of the separation distance to the cross-correlation time delay.

8. Apparatus as in claim 6 wherein the processor produces a first auto-correlation of the first profile record to determine a first auto-correlation time delay between consecutive occurrences of the regularly spaced topographical feature in the first profile record.

9. Apparatus as in claim 8 wherein the processor computes belt pitch as the product of the separation distance and the ratio of the first auto-correlation time delay to the cross- correlation time delay.

10. Apparatus as in claim 8 wherein the processor produces a second auto-correlation of the second profile record to determine a second auto-correlation time delay between consecutive occurrences of the regularly spaced topographical feature in the second profile record.

11. Apparatus as in claim 10 wherein the processor computes belt pitch as the product of the separation distance and ratio of the average of the first and second auto-correlation time delays to the cross-correlation time delay.

12. Apparatus as in claim 8 wherein the processor assigns the time delay between the

highest peak in the first auto-correlation and the highest peak in a predetermined later region of interest of the first auto-correlation as the first auto-correlation time delay.

13. Apparatus as in claim 12 wherein the predetermined later region of interest of the first auto-correlation spans an expected range of first auto-correlation time delays that depends on belt speed and pitch of the belt.

14. Apparatus as in claim 6 wherein the processor determines the rms value of the cross- correlation and sets a peak threshold as a function of the rms value and selects only peaks in the cross-correlation above the peak threshold as indicating possible occurrences of the topographical feature.

15. Apparatus as in claim 4 wherein the first and second profile records each span at least two occurrences of the regularly spaced topographical feature of the belt advancing past the first and second rangefinders.

16. Apparatus for measuring belts, comprising:

a first rangefinder making first distance measurements from the first rangefinder to a belt having a regularly spaced topographical feature and advancing in a direction of belt travel transverse to the distance between the first rangefinder and the belt;

a second rangefinder making second distance measurements from the second

rangefinder to the belt, wherein the second rangefinder is offset from the first rangefinder in the direction of belt travel by a separation distance;

a processor receiving the first and second distance measurements, producing

corresponding first and second records of a predetermined number of sequential first and second distance measurements, and producing a cross-correlation of the first record and the second record to determine a cross-correlation time delay between the occurrence of the topographical feature in the first record and the occurrence of the topographical feature in the second record.

17. Apparatus as in claim 16 wherein the processor computes the speed of the belt as the ratio of the separation distance to the cross-correlation time delay.

18. Apparatus as in claim 17 wherein the processor computes a running average of the

speed of the belt from the speeds computed from consecutive cross-correlations.

19. Apparatus as in claim 16 wherein the processor produces a first auto-correlation of the first record to determine a first auto-correlation time delay between consecutive occurrences of the regularly spaced topographical feature in the first record.

20. Apparatus as in claim 19 wherein the processor computes belt pitch as the product of the separation distance and ratio of the first auto-correlation time delay to the cross- correlation time delay.

21. Apparatus as in claim 19 wherein the processor produces a second auto-correlation of the second record to determine a second auto-correlation time delay between

consecutive occurrences of the regularly spaced topographical feature in the second record.

22. Apparatus as in claim 21 wherein the processor computes belt pitch as the product of the separation distance and ratio of the average of the first and second auto-correlation time delays to the cross-correlation time delay.

23. Apparatus as in claim 19 wherein the processor assigns the time delay between the

highest peak in the first auto-correlation and the highest peak in a predetermined later region of interest of the first auto-correlation as the first auto-correlation time delay.

24. Apparatus as in claim 23 wherein the predetermined later region of interest of the first auto-correlation spans an expected range of first auto-correlation time delays that depends on belt speed and pitch of the belt.

25. Apparatus as in claim 16 wherein the processor determines the rms value of the cross- correlation and sets a peak threshold as a function of the rms value and selects only peaks in the cross-correlation above the peak threshold as indicating possible occurrences of the same topographical feature.

26. Apparatus as in claim 16 wherein the first and second records each span at least two occurrences of the regularly spaced topographical features of the belt advancing past the first and second rangefinders.

27. A method for measuring a belt having a regularly spaced topographical feature, the method comprising:

advancing a belt having a regularly spaced topographical feature in a direction of belt travel at a belt speed;

making first measurements constituting a profile of the belt along its length;

producing a first profile record of a predetermined number of sequential first

measurements; and

determining the occurrences of the regularly spaced topographical feature in the first profile record.

28. The method of claim 27 further comprising producing a first auto-correlation of the first profile record to determine a first auto-correlation time delay between consecutive occurrences of the regularly spaced topographical feature in the first profile record, wherein the first auto-correlation time delay is proportional to belt pitch.

29. The method of claim 28 further comprising assigning the time delay between the highest peak in the first auto-correlation and the highest peak in a predetermined later region of interest of the first auto-correlation as the first auto-correlation time delay.

30. The method of claim 29 further comprising centering the predetermined later region of interest of the first auto-correlation on an expected first auto-correlation time delay that depends on belt speed and pitch of the belt.

31. The method of claim 27 further comprising:

making second measurements offset along the length of the belt from the first

measurements by a separation distance, wherein the second measurements constitute the profile of the belt;

producing a second profile record of a predetermined number of sequential second

measurements; and

determining the occurrences of the regularly spaced topographical feature in the second profile record.

32. The method of claim 31 further comprising computing the speed of the belt as the ratio of the separation distance to the time delay between the occurrence of the regularly spaced topographical feature in the first profile record and the occurrence of the same regularly spaced topographical feature in the second profile record.

33. The method of claim 31 further comprising:

defining an acceptable range of values for the first and second distance measurements; discarding the first and second profile records if any one of the first or second distance measurements is outside the acceptable range of values.

34. The method of claim 31 further comprising producing a cross-correlation of the first profile record and the second profile record to determine a cross-correlation time delay between the occurrence of the regularly spaced topographical feature in the first profile record and the occurrence of the same regularly spaced topographical feature in the second profile record, wherein the cross-correlation time delay is inversely proportional to the belt speed.

35. The method of claim 34 further comprising computing the speed of the belt as the ratio of the separation distance to the cross-correlation time delay.

36. The method of claim 35 further comprising computing a running average of the speed of the belt.

37. The method of claim 34 further comprising:

determining the rms value of the cross-correlation;

setting a peak threshold as a function of the rms value; and

selecting only peaks in the cross-correlation above the peak threshold as indicating possible occurrences of the topographical feature.

38. The method of claim 34 further comprising:

computing a first mean of the first distance measurements in the first profile record; computing a second mean of the second distance measurements in the second profile record;

subtracting the first mean from each of the first distance measurements to produce a zero-mean first profile record;

subtracting the second mean from each of the second distance measurements to produce a zero-mean second profile record;

using the zero-mean first and second profile records to produce the cross-correlation.

39. The method of claim 34 further comprising producing a first auto-correlation of the first profile record to determine a first auto-correlation time delay between consecutive occurrences of the regularly spaced topographical feature in the first profile record and computing belt pitch as the product of the separation distance and the ratio of the first auto-correlation time delay to the cross-correlation time delay.

40. The method of claim 39 further comprising computing a running average of the belt pitch.

41. The method of claim 39 further comprising producing a second auto-correlation of the second profile record to determine a second auto-correlation time delay between consecutive occurrences of the topographical feature in the second profile record, wherein the second auto-correlation time delay is proportional to belt pitch.

42. The method of claim 41 further comprising computing belt pitch as the product of the separation distance and ratio of the average of the first and second auto-correlation time delays to the cross-correlation time delay.

43. The method of claim 27 wherein the regularly spaced topographical feature is an

inherent feature of the belt having a main function other than having its occurrences in the first belt profile determined.