US 4,730,110 A · Shaft position encoder

Abstract

A multi-turn shaft position encoder employs a plurality of encoder discs with successive speed reductions of 1:2.sup.n and the generation of n+1 bits of binary data representative of the angular position of the respective discs as the input shaft rotates. Specifically, a high-speed disc is coupled to an input shaft and low-speed disc means is coupled to the input shaft with a speed reduction of 1:2.sup.n relative to the high-speed disc. At least one group of n+1 bits of binary data representative of the angular position of the high-speed disc are generated as the input shaft rotates. A group of n+1 bits of data representative of the angular position of the low-speed disc means is generated as the input shaft rotates. Thus, the low-speed disc is divided in to 2.sup.n units per revolution but produces 2.sup.n+1 bits of data. The data is generated by the encoder in unit distance code and is then converted into fewer bits of data in natural binary code. The encoder has a high-speed disc in connection with which two groups of data bits are generated, one being shifted relative to the other. In addition, there is cumulative bit shifting from disc to disc. The n+1.sup.st bit is generated on the same track of each encoder disc as the n.sup.th bit by placing the corresponding data bit-generating sensors at angularly spaced apart positions relative to the same track.

Claims25

Dependent claims

A shaft position encoder comprising:

an input shaft;
a high-speed disc coupled to the input shaft;
at least one group of n concentric tracks on the high-speed disc, n being greater than one, each track comprising slotted openings that form alternating transparent and opaque sectors;
n+1 pairs of light sources and light sensors associated with each group of tracks, the light sources and light sensors being disposed on opposite sides of the high-speed disc in alignment with respective tracks such that two pairs are aligned with one of the tracks;
a low-speed disc means coupled to the input shaft with a speed reduction of 1:2.sup.n relative to the high-speed disc;
a group of n concentric tracks on the low-speed disc means, each track comprising slotted openings that form alternating transparent and opaque sectors;
and
n+1 pairs of light sources and light sensors associated with the group of tracks on the low-speed disc means, the sources and sensors being disposed on opposite sides of the low-speed disc means in alignment with the respective tracks such that two pairs are aligned with one of the tracks thereon.

5 more elements

Dependencies are inferred from the claim text.

Shaft position encoder

Life of this patent

Shaft position encoder

Life of this patent

Abstract

Claims25