Reduction of encoder measurement errors in UKIRT telescope control system using a Kalman filter

The tracking performance of the United Kingdom InfraRed Telescope (UKIRT) is directly related to the accuracy of the position measurement which is given by an encoder. It is found that the encoder has some deterministic and random measurement errors which cause consistent "wobbling" of the telescope. Therefore, a Kalman filter with deterministic error input model is adopted in this embedded real-time control system to reduce both deterministic and random measurement error effects. Our extensive test shows that the system tracking performance is improved. Astronomers' report confirms our result.