Apparatus and methods for measuring belts

Patent metadata

Field	Value
Publication number	US-10794686-B2
Application number	US-201816480052-A
Country	US
Kind code	B2
Filing date	Jan 24, 2018
Priority date	Feb 9, 2017
Publication date	Oct 6, 2020
Grant date	Oct 6, 2020

Abstract

Apparatus and methods for determining belt speed and pitch using correlation techniques. The apparatus includes a pair of rangefinders separated by a predetermined distance. The rangefinders each measure the distance to the belt at two positions separated from each other in the direction of belt travel. The apparatus creates at least one time-series profile record corresponding to the profile of a belt. The time delays between occurrences of a regularly spaced topographical feature in the belt's profile are used by a processor to compute belt pitch and speed. Correlation techniques are used for robust results.

First claim

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;
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.

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 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.

5. Apparatus as in claim 1 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.

6. Apparatus as in claim 5 wherein the processor computes the belt speed as the ratio of the separation distance to the cross-correlation time delay.

7. Apparatus as in claim 5 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.

8. Apparatus as in claim 7 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.

9. Apparatus as in claim 7 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.

10. Apparatus as in claim 9 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.

11. Apparatus as in claim 7 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.

12. Apparatus as in claim 11 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.

13. Apparatus as in claim 5 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.

14. Apparatus as in claim 1 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.

15. 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;
determining the occurrences of the regularly spaced topographical feature in the first profile record;
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.

16. The method of claim 15 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.

17. The method of claim 16 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.

18. The method of claim 17 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.

19. The method of claim 15 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.

20. The method of claim 15 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.

21. The method of claim 15 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.

22. The method of claim 21 further comprising computing the speed of the belt as the ratio of the separa

Assignees

• Laitram Llc

Inventors

• Murray William S
• Lagneaux Jason

Classifications

• G01B11/043

  for measuring length · CPC title

• G01B11/14 Primary

  for measuring distance or clearance between spaced objects or spaced apertures (G01B11/26 takes precedence; rangefinders G01C3/00) · CPC title

• G01P3/68

  using optical means, i.e. using infrared, visible, or ultraviolet light (G01P3/80 takes precedence {; by reflection of waves G01S17/58}) · CPC title

• G01B7/042

  for measuring length · CPC title

• B65G15/30

  Belts or like endless load-carriers (co-operating with rails or the like B65G21/22; {co-operating} with rollers B65G39/20) · CPC title