US 2013/0100503 A1 · Scanner Belt Load and Stretch Compensation Control System

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.

Claims20

Dependent claims

A system for controlling the movement of a scanning system having dual mounting heads that define a measurement gap adapted 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 a first side of the web, the first 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 a second side of the web, the second 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, and wherein the measurement gap has a web entry end and a web exit end that is downstream from the web entry end, and wherein movement of the first mobile carriage is synchronized with movement of the second mobile mounting head;
(d) means for driving the second mobile mounting head;
(e) an alignment error generating means for generating error signals representing the difference in alignment between the first and second mobile heads as the first and second mobile heads scan back and forth along a translation axis;
and
(f) actuator means for regulating the relative position of the first mobile mounting head and/or the second mobile mounting head, wherein the actuator means is controlled by the error signals.

4 more elements

A system for monitoring 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, the system comprising:

(a) the scanning system being monitored 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 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;
(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 the position of the moving mobile detector device and its direction of movement;
(c) actuator means for manipulating the common drive mechanism to alter the tension in the first belt and/or second belt or for regulating the relative position 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 misalignments offsets by actuating the actuator means to maintain the misalignment error within a specified level.

7 more elements

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 the 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 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 the 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 the position of the moving mobile detector device and its direction of movement;
and
(c) correcting misalignment offsets by actuating one or more actuators to maintain the misalignment error within a specified level.

4 more elements

Dependencies are inferred from the claim text.

Scanner Belt Load and Stretch Compensation Control System

Life of this patent

Scanner Belt Load and Stretch Compensation Control System

Life of this patent

Abstract

Claims20