Spatial feature tracking impedence sensor using multiple electric fields
First Claim
1. Apparatus for tracking a feature on a workpiece comprising:
- at least two pairs of electrodes disposed on a planar mount oriented parallel to the axis of the feature and above the workpiece with one electrode in each pair operating as a transmitter of an electric field and the other electrode in each pair operating as a receiver of the field;
means to drive each of the transmitting electrodes at a separate frequency;
means to combine the signals from the receiver electrodes to provide information indicative of the position of the mount relative to the feature; and
means to drive the mount in response to the position information.
4 Assignments
0 Petitions
Accused Products
Abstract
Linear and other features on a workpiece are tracked by measuring the fields generated between electrodes arrayed in pairs. One electrode in each pair operates as a transmitter and the other as a receiver, and both electrodes in a pair are arrayed on a carrier. By combining and subtracting fields between electrodes in one pair and between a transmitting electrode in one pair and a receiving electrode in another pair, information describing the location and orientation of the sensor relative to the workpiece in up to six degrees of freedom may be obtained. Typical applications will measure capacitance, but other impedance components may be measured as well. The sensor is designed to track a linear feature axis or a protrusion or pocket in a workpiece. Seams and ridges can be tracked by this non-contact sensor. The sensor output is useful for robotic applications.
26 Citations
19 Claims
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1. Apparatus for tracking a feature on a workpiece comprising:
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at least two pairs of electrodes disposed on a planar mount oriented parallel to the axis of the feature and above the workpiece with one electrode in each pair operating as a transmitter of an electric field and the other electrode in each pair operating as a receiver of the field; means to drive each of the transmitting electrodes at a separate frequency; means to combine the signals from the receiver electrodes to provide information indicative of the position of the mount relative to the feature; and means to drive the mount in response to the position information. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. Apparatus for tracking a feature on a workpiece comprising:
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at least two pairs of electrodes disposed on a planar mount oriented parallel to the axis of the feature and above the workpiece with one electrode in each pair operating as a transmitter and the other electrode in each pair operating as a receiver; means to drive each of the transmitting electrodes at a separate frequency; inverting charge amplifier means to initially buffer the signal output from each receiver electrode; means for cancelling signals due to undesired impedances at the frequency of a transmitting electrode comprising variable amplifier means which separately amplify each of the outputs of the means to drive each transmitting electrode to a level sufficient to null the output of the inverting charge amplifier means when the planar mount is in a predefined position relative to the workpiece; means to combine the signals from the receiver electrodes after undesired impedance signal cancellation to provide information indicative of the location of the mount relative to the feature; and means to drive the mount in response to the location information. - View Dependent Claims (11, 12)
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13. Apparatus for tracking a feature on a workpiece comprising:
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mount means having a relatively thin planar region oriented generally perpendicular to the surface (z-axis) of the workpiece and parallel to the longitudinal axis of the feature (x-axis); first, second, third, and fourth electrode means wherein the first and second electrode means are located on one side of the lowermost extension of the planar region and third and fourth electrode means are located on the opposite side of the planar region and directly behind the first and second electrode means respectively; means to create an oscillating electric potential at one of the electrode means at each side of the planar region and means to sense the oscillating electric potential at the other of the electrode means at each side; means to create a first combined signal indicative of deviations of the mount means in a direction perpendicular (z-axis) to the surface of the workpiece comprising means to determine the sum of the electric field between the transmitting electrode means on the one side and the sensing electrode means on the opposite side and the electric field between the transmitting electrode means on the opposite side and the sensing electrode means on the one side; and means to drive the mount means such that a predetermined value for the first combined signal is maintained. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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Specification