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Shaft Encoder Using Debruijn Sequence

IP.com Disclosure Number: IPCOM000086738D
Original Publication Date: 1976-Oct-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Martino, MJ: AUTHOR

Abstract

The drawing shows a track 2 that is formed on the circumferential surface of a rotatable shaft or on the face of a disk that is carried by a rotatable shaft. The track is divided into eight sectors that are distinctively marked to each represent a binary 1 or 0, represented by shading or the absence of shading. Sensors 3, 4 and 5 are positioned to each read one of three adjacent sectors of track 2, and are connected to provide binary signals at the input of a code translator 6, which produces the translated three-bit code at its output. This shaft encoder has the advantage that the single track is encoded to produce a multibit code.

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Shaft Encoder Using Debruijn Sequence

The drawing shows a track 2 that is formed on the circumferential surface of a rotatable shaft or on the face of a disk that is carried by a rotatable shaft. The track is divided into eight sectors that are distinctively marked to each represent a binary 1 or 0, represented by shading or the absence of shading. Sensors 3, 4 and 5 are positioned to each read one of three adjacent sectors of track 2, and are connected to provide binary signals at the input of a code translator 6, which produces the translated three-bit code at its output. This shaft encoder has the advantage that the single track is encoded to produce a multibit code.

The track is encoded in a deBruijn sequence. In the example of the drawing where the track has eight sectors, the sequence is 00010111, any window of three consecutive bits produces a unique three-bit code.

Codes appear as the three-bit window is shifted from one position to the next along the numerical sequence and the corresponding codes appear at the outputs of the sensors as the track moves past the sensors, as the following table shows. Position Code

0 0 0 0

1 0 0 1

2 0 1 0

3 1 0 1

4 0 1 1

5 1 1 1

6 1 1 0

7 1 0 0. Code translator 6 operates conventionally to translate the code to the binary shown in the table or to another desired counterpart of the position number.

DeBruiin codes of any length can be constructed for providing a desired degree of resolution for the shaft encoder. Each n-bit code in a sequence is followed by one of two possible successor codes (which differ only in the rightmost bit position) and all possible sequences of the n bits can be presented as a tree in which the branch points re...