An innovative method to increase the resolution of optical encoders in motion servo systems

Presently, most high performance motion servo systems rely on optical encoders for position and velocity feedback. Optical encoders with higher resolutions will increase the performance and accuracy of these motion systems. One method to increase the resolution of optical encoders without the need to increase their optical resolution is to use sine-cosine interpolation. There are a few existing methods to accomplish this task. However, all of them have limitations or disadvantages. This paper provides a general overview of these existing methods, highlights their features and limitations. Then, a novel and simple method to realise sine-cosine interpolation of optical encoders is proposed. The proposed method can be implemented by using very few logic gates and comparators. Construction of a 16 times interpolation circuit show that the proposed interpolation circuit can be built with very few components, and its accuracy will not decrease when the travelling speed of the encoder is increased