Absolute incremental position encoder and method
First Claim
1. A position encoder comprising:
- a track encoded with a pattern comprised of a plurality of unique subsequences;
sensors to detect the pattern as the track moves; and
a processing element to detect a portion of at least one of the unique subsequences from the signals provided by the sensors for use in determining either an absolute or incremental position of the track.
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Accused Products
Abstract
A position encoder uses a track encoded with a pattern of bit-widths in accordance with a sequence. The sequence may be any sequence having unique subsequences, and may be a pseudo-random noise (PRN) sequence such that each N-bit subsequence occurs only once on the track. Sensors detect transitions between the bits and bit-widths as the track moves with respect to the sensors to provide in-phase and quadrature-phase pick-off signals. The pickoff signals are summed and absolute value thresholded. The absolute value thresholded sum signal is sampled when the quadrature pairs are in the “00” or “11” quadrants, and latched when the sum signal goes high to distinguish between wide and narrow bit widths. The latch is shifted into a shift data register for use in determining the position of the encoder track. In the case of a PRN sequence having a length of 2N bits, the position may be an absolute position when the number of valid bits in the shift data register is at least N. The position may be an incremental position when the number of transitions detected is less than N.
21 Citations
27 Claims
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1. A position encoder comprising:
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a track encoded with a pattern comprised of a plurality of unique subsequences;
sensors to detect the pattern as the track moves; and
a processing element to detect a portion of at least one of the unique subsequences from the signals provided by the sensors for use in determining either an absolute or incremental position of the track. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of determining a position of a track encoded with a pattern comprised of a plurality of unique subsequences, the method comprising:
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detecting transitions as the track moves with sensors;
combining outputs of the sensors to generate a least a portion of the unique subsequences; and
comparing the generated portion with the pattern to determine either an absolute or incremental position of the track. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. A system comprising:
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first and second nested gimbals;
a first position encoder to determine an angular position of the first gimbal with respect to a base; and
a second position encoder to determine an angular position of the second gimbal with respect to the first gimbal, wherein the position encoders have tracks encoded with a pattern of bit-widths in accordance with sequence comprised of a plurality of subsequences, have sensors to detect the pattern as the tracks move, and have a processing element to determine the positions of the tracks from sensor signals. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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Specification