AUTOMATED UPPER/LOWER HEAD CROSS DIRECTION ALIGNMENT BASED ON MEASUREMENT OF SENSOR SENSITIVITY
A method includes moving a first sensor assembly to a plurality of cross direction positions relative to a second sensor assembly, where the first and second sensor assemblies are configured to move in the cross direction relative to a web of material. The method also includes, for each of the plurality of cross direction positions, determining a sensor value associated with a sensor source disposed at the second sensor assembly as measured by a sensor receiver disposed at the first sensor assembly. The method further includes determining a starting alignment position of the first sensor assembly to be a first cross direction position where a difference between the sensor value at the first cross direction position and a corresponding sensor value at one or more adjacent cross direction positions is a minimum.
1 . A method comprising:
moving a first sensor assembly to a plurality of cross direction positions relative to a second sensor assembly, the first and second sensor assemblies configured to move in the cross direction relative to a web of material;
for each of the plurality of cross direction positions, determining a sensor value associated with a sensor source disposed at the second sensor assembly as measured by a sensor receiver disposed at the first sensor assembly; and
determining a starting alignment position of the first sensor assembly to be a first cross direction position where a difference between the sensor value at the first cross direction position and a corresponding sensor value at one or more adjacent cross direction positions is a minimum.
2 . The method of claim 1 , wherein each sensor value comprises a sensor reading or a magnitude of a sensor voltage signal.
3 . The method of claim 1 , wherein:
the sensor source comprises a source element configured to generate an emission; and
the sensor receiver comprises a receiving element configured to measure the emission.
4 . The method of claim 3 , wherein:
the source element is configured to emit at least one of: nuclear radiation, infrared light, visible light, and a magnetic field; and
the receiving element is configured to measure the at least one of: nuclear radiation, infrared light, visible light, and a magnetic field.
5 . The method of claim 1 , further comprising:
correlating the sensor values and the corresponding cross direction positions to determine a sensor value versus position profile curve.
6 . The method of claim 5 , wherein the first cross direction position coincides with a zero slope or minimum slope of the profile curve.
7 . The method of claim 1 , wherein determining the sensor value for each cross direction position comprises activating the sensor source and measuring a received signal at the sensor receiver.
8 . The method of claim 1 , wherein the cross direction positions span a range covering opposite sides of an estimated position of a center line of the sensor source.
9 . The method of claim 8 , wherein the cross direction positions are evenly spaced.
10 . The method of claim 1 , wherein the method is performed off-web during a maintenance period.
11 . An apparatus comprising:
a first sensor assembly configured to move in a cross direction relative to a web of material, the first sensor assembly comprising:
a sensor receiver configured to receive and measure emissions from a sensor source disposed at a second sensor assembly; and
at least one controller configured to:
control a motor configured to move the first sensor assembly to a plurality of cross direction positions relative to the second sensor assembly;
determine, for each of the plurality of cross direction positions, a sensor value associated with the sensor source as measured by the sensor receiver; and
determine a starting alignment position of the first sensor assembly to be a first cross direction position where a difference between the sensor value at the first cross direction position and a corresponding sensor value at one or more adjacent cross direction positions is a minimum.
12 . The apparatus of claim 11 , wherein each sensor value comprises a sensor reading or a magnitude of a sensor voltage signal.
13 . The apparatus of claim 11 , wherein:
the sensor source comprises a source element configured to generate the emissions; and
the sensor receiver comprises a receiving element configured to measure the emissions.
14 . The apparatus of claim 13 , wherein:
the source element is configured to emit at least one of: nuclear radiation, infrared light, visible light, and a magnetic field; and
the receiving element is configured to measure the at least one of: nuclear radiation, infrared light, visible light, and a magnetic field.
15 . The apparatus of claim 11 , wherein the controller is further configured to correlate the sensor values and the corresponding cross direction positions to determine a sensor value versus position profile curve.
16 . The apparatus of claim 15 , wherein the first cross direction position coincides with a zero slope or minimum slope of the profile curve.
17 . The apparatus of claim 11 , wherein the cross direction positions span a range covering opposite sides of an estimated position of a center line of the sensor source.
18 . The apparatus of claim 17 , wherein the cross direction positions are evenly spaced.
19 . A system comprising:
a first sensor assembly and a second sensor assembly, the first sensor assembly configured to be disposed on a first side of a web of material and to move in a cross direction relative to the web, the second sensor head configured to be disposed on a second side of the web opposite the first side and to move in the cross direction;
the first sensor assembly further configured to:
move to a plurality of cross direction positions relative to the second sensor assembly;
for each of the plurality of cross direction positions, determine a sensor value associated with a sensor source disposed at the second sensor assembly as measured by a sensor receiver disposed at the first sensor assembly; and
determine a starting alignment position of the first sensor assembly to be a first cross direction position where a difference between the sensor value at the first cross direction position and a corresponding sensor value at one or more adjacent cross direction positions is a minimum.
20 . A non-transitory computer readable medium embodying a computer program, the computer program comprising computer readable program code for:
moving a first sensor assembly to a plurality of cross direction positions relative to a second sensor assembly, the first and second sensor assemblies configured to move in the cross direction relative to a web of material;
for each of the plurality of cross direction positions, determining a sensor value associated with a sensor source disposed at the second sensor assembly as measured by a sensor receiver disposed at the first sensor assembly; and
determining a starting alignment position of the first sensor assembly to be a first cross direction position where a difference between the sensor value at the first cross direction position and a corresponding sensor value at one or more adjacent cross direction positions is a minimum.