A simple approach to design a binary coded absolute shaft encoder

Abstract

In this paper, an optical type absolute shaft encoder coding pattern is presented. Compared with the conventional binary or gray code pattern resolution (2n), the proposed code exhibits two times more resolution (2n2). Even, to represent high density positional information of rotating object, it is required very less number of tracks. This pattern sequence is based on n-by-2 matrices of binary codes where consecutive two columns of each code represented as high-low order bits. To retrieve the encoded position from these coding patterns, an extra pulse track was added at the outside of coded tracks. Moreover, it was used for providing a synchronized clock pulse into a simple photodetector-based sequential logic circuitry; it is the decoding unit of this encoder. Thus, depending on these synchronized pulses, the proposed encoder is able to provide error free positional information for a high-speed rotating object. Eventually, in order to prove this concept, a prototype is designed and tested, where a satisfactory performance was achieved.