Scanner belt load and stretch compensation control system

• US 8,564,851 B2
• Filed: 10/25/2011
• Issued: 10/22/2013
• Est. Priority Date: 10/25/2011
• Status: Active Grant

• Current Assignee: Honeywell ASCA Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell ASCA Incorporated (Honeywell International Inc.)
• Inventors: Beselt, Ron
• Primary Examiner(s): Worku, Negussie
• Application Number:
  US13/281,120
• Publication Number:
  US 20130100503A1
• Time in Patent Office: 728 Days
• Field of Search: 358/474, 358/486, 358/497, 358/496, 358/475, 356/328, 356/429, 162/263, 162/198, 162/193, 162/302, 324/229, 324/226, 104/95, 104/89, 702/117, 702/500
• US Class Current: 358/474
• CPC Class Codes: G01B 2210/44 with detectors on both sides of the object to be measured
• CPC Class Codes: H04N 1/053 in main scanning direction, e.g. synchronisation of line start or picture elements in a line
• CPC Class Codes: H04N 1/128 using a scanning head arranged for linear reciprocating motion
• CPC Class Codes: H04N 1/203 Simultaneous scanning of two or more separate pictures , e.g. two sides of the same sheet refeeding a sheet for double-sided scanning H04N1/00572
• CPC Class Codes: H04N 2201/0471 using dedicated detectors
• CPC Class Codes: H04N 2201/04734 Detecting at frequent intervals, e.g. once per line for sub-scan control
• CPC Class Codes: H04N 2201/04753 Control or error compensation of scanning position or velocity
• CPC Class Codes: H04N 2201/04755 by controlling the position or movement of a scanning element or carriage, e.g. of a polygonal mirror, of a drive motor
• CPC Class Codes: H04N 2201/04794 Varying the control or compensation during the scan, e.g. using continuous feedback or from line to line

Abstract

Upper to lower assembly analog position sensors in a dual scanning system measure alignment offsets. A controller uses error signals from the position sensors to calculate actuator error profiles that are used in the next scan in the same direction, with different error profiles being used for forward and reverse scans. Since the alignment error profiles are repeatable for a given set of scanner conditions, the actuator controller anticipates what the error signal will be before each scanning assembly reaches a given position. An optimized error correction can be calculated based on the error profiles and actuator bandwidth without concerns regarding feedback loop speed, overshoot, and unstable control oscillations. An actuation system driven from error profiles can correct for alignment offsets by actively changing belt tensions at the offsetting drive pulleys and/or changing the position of sensor assemblies relative to the drive belt systems.

Claims

1. A scanning system having dual mounting heads that define a measurement gap, which has a web entry end and a web exit end that is downstream from the web entry end, and which is configured to accommodate a continuous web that has a first side and a second side and that travels in a downstream direction, which comprises:

(a) a first elongated member that extends along a first direction wherein the first elongated member supports a first mobile mounting head that is disposed adjacent to the first side of the web, the first mobile mounting head including a first operative surface facing the first side of the web;

(b) means for driving the first mobile mounting head;

(c) a second elongated member that extends along a second direction that is parallel to the first direction wherein the second elongated member supports a second mobile mounting head that is disposed adjacent to the second side of the web, the second mobile mounting head including a second operative surface facing the second side of the web, wherein the first operative surface and the second operative surface define the measurement gap through which the continuous web travels;

(d) means for driving the second mobile mounting head such that movement of the first mobile mounting head is synchronized with movement of the second mobile mounting head;

(e) an alignment error generating means for generating error signals representing a difference in alignment between the first and second mobile mounting heads as the first and second mobile mounting heads scan back and forth along a translation axis; and

(f) actuator means for regulating relative positions of the first mobile mounting head and/or the second mobile mounting head, wherein the actuator means is controlled by the error signals.

2. The scanning system of claim 1 wherein the means for driving the first mobile mounting head includes a first belt system, wherein the means for driving the second mobile mounting head includes a second belt system and wherein the actuator means for regulating relative positions adjusts tension in the first belt system and/or tension in the second belt system.

3. The scanning system of claim 2 wherein the actuator means for regulating relative positions comprises one or more belt tension actuators that are coupled to the first belt system, the second belt system or to both belt systems and that adjusts tension in either or both the first and second belt systems.

4. The scanning system of claim 3 wherein the one or more belt tension actuators comprise one or more linear actuators.

5. The scanning system of claim 1 wherein the actuator means for regulating relative positions comprises one or more head-movement actuators that maneuvers the first mobile mounting head, the second mobile mounting head, or both the first and second mobile mounting heads.

6. The scanning system of claim 5 wherein the one or more head-movement actuators comprise a first linear actuator that is operatively connected to the first mobile mounting head and/or a second linear actuator that is operatively connected to the second mobile mounting head.

7. The scanning system of claim 1 wherein the alignment error generating means comprises an alignment sensor that determines misalignment between the first mobile mounting head and the second mobile mounting head.

8. The scanning system of claim 1 comprising a common drive mechanism that is coupled to both the first and the second mobile mounting heads.

9. The scanning system of claim 1 wherein the first mobile mounting head is secured on a first carriage that is supported on the first elongated member and the second mobile mounting head is secured on a second carriage that is supported on the second elongated member.

10. A scanning system, that detects characteristics of a sheet of material during linear translation along a translation axis of a bi-directionally driven mobile detector device, and that comprises:

(a) a scanning apparatus which comprises;

(i) a first elongated member that extends along a first direction wherein the first elongated member supports a first carriage on which a first sensor head is mounted;

(ii) a second elongated member that extends along a second direction that is parallel to the first direction wherein the second elongated member supports a second carriage on which a second sensor head is mounted; and

(iii) a common drive mechanism that moves the first carriage along a main scanning direction and moves the second carriage along a second direction that is parallel to the first direction, wherein the first sensor head and second sensor head move in a synchronized fashion, and wherein the common drive mechanism includes a first pulley assembly that guides a first belt that is coupled to the first carriage and a second pulley assembly that guides a second belt that is coupled to the second carriage;

(b) an alignment sensor configured to continuously measure offset between the first sensor head and the second sensor head as the mobile detector device is translated back and forth along the translation axis and to generate misalignment error signals in relation to a position of the mobile detector device and its direction of movement;

(c) actuator means for manipulating the common drive mechanism to alter tension in the first belt and/or second belt or for regulating relative positions of the first sensor head to the second sensor head;

(d) computing means in communication with the alignment sensor to process the misalignment error signals to generate alignment correction profiles and storing the alignment correction profiles; and

(e) control means in communication with the computing means for correcting misalignment offsets by actuating the actuator means to maintain the offset between the first sensor head and the second sensor head within a specified level.

11. The scanning system of claim 10 wherein the actuator means for manipulating the common drive mechanism adjusts the tension in the first belt system and/or tension in the second belt system.

12. The scanning system of claim 10 wherein the actuator means for manipulating the common drive mechanism comprises one or more belt tension actuators that are coupled to the first pulley assembly, the second pulley assembly or to both the first and second pulley assemblies and that adjusts tension in either or both the first and second pulley assemblies.

13. The scanning system of claim 12 wherein the one or more tension actuators comprise one or more linear actuators.

14. The scanning system of claim 10 wherein the actuator means for manipulating the common drive mechanism comprises one or more head-movement actuators that maneuvers the first sensor head, the second sensor head, or both the first and second sensor heads.

15. A method of controlling the synchronized movement of dual scanner heads in a scanning system that detects characteristics of a sheet of material during linear translation along a translation axis of a bi-directionally driven mobile detector device, wherein the scanning system includes (i) a first elongated member that extends along a first direction wherein the first elongated member supports a first carriage on which a first sensor head is mounted, wherein the first mounting head including a first operative surface facing a first side of a continuous web;

(ii) a second elongated member that extends along a second direction that is parallel to the first direction wherein the second elongated member supports a second carriage on which a second sensor head is mounted, wherein the second mounting head including a second operative surface facing a second side of the web and wherein the first operative surface and the second operative surface define the measurement gap through which the continuous web travels; and

(iii) a common drive mechanism that moves the first carriage along a main scanning direction and moves the second carriage along a second direction that is parallel to the first direction, wherein the first sensor head and second sensor head moves in a synchronized fashion, and wherein the common drive mechanism includes a first pulley assembly that guides a first belt that is coupled to the first carriage and a second pulley assembly that guides a second belt that is coupled to the second carriage;

said method comprising the steps of;

(a) measuring misalignment between the first sensor head and the second sensor head as the mobile detector device is translated back and forth along the translation axis;

(b) generating misalignment error signals in relation to positions of the mobile detector device and its direction of movement; and

(c) correcting misalignment offsets by actuating one or more actuators to maintain the misalignment within a specified level.

16. The method of claim 15 further comprising the step of:

(d) recording the misalignment error signals as a function of direction and position of the mobile detector device and wherein step (c) comprises using the recorded misalignment error signals to regulate relative positions of the first and second mounting heads.

17. The method of claim 16 wherein step (c) comprises using the recorded misalignment error signals measured at a location along the translation axis to regulate the relative positions of the first and second mounting heads at the same location in subsequent movements of the first and second carriages along the main scanning direction.

18. The method of claim 15 wherein step (c) comprises activating one or more actuators to adjust tension in the first pulley assembly and/or the second pulley assembly.

19. The method of claim 15 wherein the one or more actuators comprise one or more linear actuators.

20. The method of claim 15 wherein step (c) comprises activating one or more actuators to maneuver the first sensor head and/or the second sensor head in a translation axis direction.