WEB LONGITUDINAL POSITION SENSOR

• US 20100097462A1
• Filed: 12/19/2007
• Published: 04/22/2010
• Est. Priority Date: 01/11/2007
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Biyikli, Levent, Carlson, Daniel H., Nelson, Brian K., Strand, John T., Wertz, Daniel S.
• Granted Patent: US 9,440,812 B2
• Time in Patent Office: Days
• US Class Current: 348/143
• CPC Class Codes: B65H 23/0216 with an element utilising photoelectric effect
• CPC Class Codes: B65H 23/032 Controlling transverse register of web
• CPC Class Codes: B65H 23/1882 and controlling longitudinal register of web
• CPC Class Codes: B65H 2511/512 Marks, e.g. invisible to the human eye; Patterns
• CPC Class Codes: B65H 2557/10 for signal transmission
• CPC Class Codes: G03F 9/00 Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically G03F7/22 takes precedence; preparation of photographic masks G03F1/00; within photographic printing apparatus for making copies G03B27/00
• CPC Class Codes: G06T 2207/30124 Fabrics; Textile; Paper
• CPC Class Codes: G06T 2207/30204 Marker
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80

Abstract

Methods and systems for determining longitudinal position of an elongated web are described. Sensors are used to detect one or more substantially continuous fiducial marks disposed longitudinally on the web. The sensors generate signals associated with the fiducial marks. A position detector receives the signals and determines a longitudinal position of the web using the sensor signals. The fiducial marks may be periodic fiducial marks, such as sine and/or cosine marks on the web and/or may be piecewise continuous marks. The coarse longitudinal position of the web can be determined based on periodically recurring features of the fiducial marks. The fine longitudinal position can be determined based on continuous portions of the fiducial marks between the periodically recurring features.

Claims

1. A method to determine the position of an elongated web, comprising:

sensing one or more substantially continuous fiducial marks disposed longitudinally on the web; and

determining a longitudinal position of the web based on the fiducial marks.

2. The method of claim 1, further comprising compensating for lateral movement of the web.

3. The method of claim 1, wherein sensing the one or more fiducial marks comprises sensing one or more substantially continuous periodic fiducial marks disposed longitudinally on the web.

4. The method of claim 1, wherein sensing the one or more fiducial marks comprises sensing one or more sinusoidal fiducial marks disposed longitudinally on the web.

5. The method of claim 1, wherein sensing the one or more fiducial marks comprises sensing a fiducial mark having a region with a finite, non-zero slope.

6. The method of claim 1, wherein sensing the one or more fiducial marks comprises sensing a sine fiducial mark and a cosine fiducial mark disposed longitudinally on the web.

7. The method of claim 1, wherein sensing the one or more fiducial marks comprises sensing one or more piecewise continuous fiducial marks disposed longitudinally on the web.

8. The method of claim 1, wherein:

sensing the one or more fiducial marks comprises sensing one or more periodic fiducial marks; and

determining the longitudinal position of the web comprises determining the longitudinal position based on periodically recurring features of the one or more periodic fiducial marks.

9. The method of claim 1, wherein:

sensing the one or more fiducial marks comprises sensing one or more periodic fiducial marks; and

determining the longitudinal position of the web comprises;

determining a coarse longitudinal position based on periodically recurring features of the one or more periodic fiducial marks; and

determining a fine longitudinal position based on portions of the one or more fiducial marks between the periodically recurring features.

10. The method of claim 9, wherein:

the one or more periodic fiducial marks comprise sine and cosine fiducial marks; and

the periodically recurring features comprise zero crossings of the sine or cosine fiducial marks.

11. The method of claim 9, wherein:

the one or more periodic fiducial marks comprise sine and cosine fiducial marks; and

the periodically recurring features comprise peaks of the sine or cosine fiducial marks.

12. The method of claim 1, further comprising determining a lateral position of the web based on the longitudinal fiducial marks or a lateral position reference.

13. The method of claim 12, wherein the lateral position reference comprises a lateral fiducial mark disposed on the web.

14. The method of claim 12, wherein the lateral position reference comprises a web edge.

15. The method of claim 1, wherein:

sensing the one or more fiducial marks comprises;

generating signals corresponding to the fiducial marks; and

filtering the signals; and

determining the longitudinal position of the web based on the fiducial marks comprises determining the longitudinal position of the web using the filtered signals.

16. The method of claim 1, wherein:

sensing the one or more fiducial marks comprises;

sensing a sine fiducial mark and a cosine fiducial mark; and

generating signals corresponding to the sine fiducial mark and the cosine fiducial mark; and

determining the longitudinal position of the web comprises calculating an arctan 2 function of the sine and cosine signals.

17. The method of claim 1, further comprising controlling longitudinal movement of the web based on the longitudinal position.

18. An apparatus for determining a position of an elongated web, comprising:

one or more sensors configured to sense one or more substantially continuous fiducial marks disposed in a longitudinal direction on the web, the one or more sensors configured to generate signals corresponding to the fiducial marks; and

a position detector configured to receive the sensor signals and to determine a longitudinal position of the web using the sensor signals.

19. The apparatus of claim 18, wherein the web comprises a flexible web.

20. The apparatus of claim 18, wherein the web comprises a polymeric web.

21. The apparatus of claim 18, wherein the web comprises a paper, fiber, woven or nonwoven material.

22. The apparatus of claim 18, wherein the one or more fiducial marks comprise one or more sinusoidal fiducial marks.

23. The apparatus of claim 18, wherein the one or more fiducial marks comprise one or more fiducial marks deposited along with a layer of elements on the web.

24. The apparatus of claim 18, wherein the one or more sensors comprise one or more optical sensors.

25. The apparatus of claim 18, wherein the one or more sensors comprise one or more cameras.

26. The apparatus of claim 18, wherein:

the fiducial marks comprise periodic fiducial marks; and

the position detector is configured to determine a coarse longitudinal position of the web based on periodically recurring features of the periodic fiducial marks and to determine a fine longitudinal position of the web based on portions of the fiducial marks between the periodically recurring features.

27. The apparatus of claim 18, further comprising a filter configured to filter the sensor signals.

28. The apparatus of claim 27, wherein the filter comprises a recursive filter.

29. The apparatus of claim 27, wherein the filter comprises a Kalman filter.

30. The apparatus of claim 18, further comprising a control unit configured to control longitudinal movement of the web based on the longitudinal position.

31. The apparatus of claim 18, further comprising a control unit configured to control longitudinal movement of the web based on the longitudinal position.

32. The apparatus of claim 18, wherein the position detector is further configured to compensate for lateral web position shifts in determining the longitudinal position.

33. The apparatus of claim 18, further comprising:

a lateral position sensor configured to sense a lateral position reference; and

a lateral position detector configured to determine a lateral web position based on the lateral position reference

34. The apparatus of claim 33, further comprising a control unit configured to control lateral and longitudinal movement of the web based on the lateral position and the longitudinal position of the web, respectively.

35. The apparatus of claim 18, wherein the fiducial marks comprise printed marks on the web.

36. The apparatus of claim 18, wherein the fiducial marks comprise laser ablated marks on the web.

37. The apparatus of claim 18, wherein the fiducial marks comprise cuts or voids in the web.

38. The apparatus of claim 18, wherein the fiducial marks are embossed, cast or coated on the web.