Absolute digital position encoder
First Claim
1. A method of manufacturing an absolute Gray coded position encoder that has n sensors, each sensor having k states so that an output code of the encoder is of order k, the method comprising the steps of:
- (a) generating all n-digit, k-order necklaces that do not have a sub-period;
(b) ordering a plurality of the necklaces generated in step (a) to obtain an ordered set of necklaces such that a Gray code condition is met between adjacent necklaces of said ordered set;
(c) encoding a track of said encoder using said ordered set of necklaces generated in step (b); and
(d) providing n sensors along said track, each sensor detecting one respective digit of the output code.
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Abstract
A method and apparatus to convert absolute angular or linear position to digital information utilizes a ternary coding scheme. The code is arranged along a single track. Sensors placed at essentially equal intervals distinguish three states per position. The sensor outputs are converted from ternary to binary data by combinatorial logic. The sensors may be mechanical contacts, optical detectors, magnetic detectors, or capacitive detectors. Such an encoder may be used as a potentiometer, multiposition switch replacement, shaft encoder, or length measurement device.
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Citations
29 Claims
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1. A method of manufacturing an absolute Gray coded position encoder that has n sensors, each sensor having k states so that an output code of the encoder is of order k, the method comprising the steps of:
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(a) generating all n-digit, k-order necklaces that do not have a sub-period; (b) ordering a plurality of the necklaces generated in step (a) to obtain an ordered set of necklaces such that a Gray code condition is met between adjacent necklaces of said ordered set; (c) encoding a track of said encoder using said ordered set of necklaces generated in step (b); and (d) providing n sensors along said track, each sensor detecting one respective digit of the output code. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of manufacturing an absolute Gray coded position encoder that has n sensors, each sensor having k states so that an output code of the encoder is of order k, the method comprising the steps of:
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(a) identifying all n-digit, k-order bi-necklaces that do not repeat when rotated by less than 2n positions, each bi-necklace including, respectively, a necklace and a complement of the necklace; (b) ordering a plurality of the bi-necklaces generated in step (a) to obtain an ordered set of bi-necklaces such that the respective necklaces of adjacent bi-necklaces of said plurality satisfy a Gray code condition; (c) encoding a track of the encoder using said ordered set of bi-necklaces generated in step (b); and (d) providing n sensors along said track, each sensor detecting one respective digit of the output code. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A quaternary, Gray-coded, absolute digital position encoder, comprising:
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a first member having first and second circular tracks thereon, said first and second tracks positioned in concentric relation to one another, said first track having a first binary code formed thereon and said second track having a second binary code formed thereon, said first and second binary codes forming a quaternary code, and said first and second tracks forming a quaternary track; and a second member movably mounted with respect to said first member, said second member having a plurality of quaternary sensors which sense said quaternary code, each quaternary sensor comprising, respectively, a first binary sensor which senses said first binary code and a second binary sensor which senses said second binary code, said first and second binary sensors being angularly aligned with one another, each quaternary sensor generating a respective quaternary digit of a code word; wherein said quaternary sensors are positioned relative to said first and second tracks such that individual values of the code word correspond uniquely to respective relative positions of said first and second members, and such that only one quaternary digit of the code word can change at-a-time during relative movement of said first and second members. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A ternary, absolute digital position encoder, comprising:
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a first member having thereon a single circular track with a plurality of ternary code elements extending therealong to form a ternary code; and a second member supported for relative movement with respect to the first member, the second member having thereon a plurality of ternary sensors which are positioned adjacent to the track and configured to read the ternary code, each of the ternary sensors corresponding to a respective ternary digit of a code word; wherein the ternary code and the sensors are arranged such that each value of the code word corresponds uniquely to a relative position of the first and second members. - View Dependent Claims (20, 21, 22, 23, 24)
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25. A quaternary, absolute digital position encoder, comprising:
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a first member having thereon a circular track with a quaternary code extending therealong; and a second member supported for relative movement with respect to the first member, the second member having thereon a plurality of quaternary sensors which are positioned adjacent to the track and configured to read the quaternary code, each of the quaternary sensors comprising a pair of angularly-aligned photodetectors that are illuminated by a common light source, each quaternary sensor corresponding to a respective quaternary digit of a code word; wherein the quaternary code and the sensors are arranged such that each value of the code word corresponds uniquely to a relative position of the first and second members. - View Dependent Claims (26, 27, 28, 29)
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Specification