Rotary position encoding using non-maximal-length pseudo-random codes
AssigneeNovanta Corporation
InventorChia-Pin Liang
Life of this patent
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Abstract
A rotary position encoder includes a detection unit and a scale co-configured and co-operative to detect a relative rotational position and to generate a position output accordingly. The scale has a scale pattern according to a linear-feedback shift register (LFSR) pseudo-random code, which is a non-maximal length code having a seed value, tap positions, and modified least-significant bit position(s) of code words that satisfy rotary constraint by which each code word follows in sequence from the adjacent code word.
Claims15
A rotary position encoder, comprising:
- a detection unit;
- and
- a scale,
- wherein the detection unit and scale are co-configured and co-operative to detect a relative rotational position therebetween and to generate a position output indicative thereof,
- and wherein the scale has a scale pattern thereon according to a linear-feedback shift register (LFSR) pseudo-random code, the LFSR code being a non-maximal-length (non-ML) code having a seed value, tap positions, and modified least-significant bit positions of code words that satisfy a rotary constraint by which each code word follows in sequence from the adjacent code word,
- and wherein, based on the seed value, tap positions, and sequence length, the number of modified least-significant bit positions is a minimal number that makes the LFSR code satisfy the relaxed rotary constraint and have no duplication of any code words.
A scale for a rotary position encoder having a detection unit co-configured with the scale to detect a relative rotational position therebetween and to generate a position output indicative thereof, the scale having a scale pattern thereon according to a linear-feedback shift register (LFSR) pseudo-random code, the LFSR code being a non-maximal-length (non-ML) code having a seed value, tap positions, and modified least-significant bit positions of code words that satisfy a rotary constraint by which each code word follows in sequence from the adjacent code word,
- wherein, based on the seed value, tap positions, and sequence length, the number of modified least-significant bit positions is a minimal number that makes the LFSR code satisfy the relaxed rotary constraint and have no duplication of any code words.
A detection unit for use in a rotary position encoder having a scale co-configured with the detection unit to detect a relative rotational position therebetween and to generate a position output indicative thereof, the scale having a scale pattern thereon with scale elements arranged according to respective a linear-feedback shift register (LFSR) pseudo-random code, the LFSR code being a non-maximal-length (non-ML) code having a seed value, tap positions, and modified least-significant bit positions of code words that satisfy a rotary constraint by which each code word follows in sequence from the adjacent code word, the detection unit being able to detect the scale elements of the scale and to identify scale position based on detection of the LFSR code according to a configuration of the detection unit when used with the scale,
- wherein, based on the seed value, tap positions, and sequence length, the number of modified least-significant bit positions is a minimal number that makes the LFSR code satisfy the rotary constraint and have no duplication of any code words.
Dependencies are inferred from the claim text.