Kalman filter based calibration of precision motion control

A method is described and validated for the automatic calibration of analog sine-wave quadrature sensors, such as optical encoders, embedded in a functioning system. The algorithm uses a Kalman filter to estimate the true position of the direct-drive actuator joint using a model of it's dynamics, an applied actuator command and measurements from the uncalibrated sensor. From the estimated true position, a lookup table is constructed which corrects sensor errors. Our results indicate that this method achieves accuracies typical of interferometric calibration, without requiring an external measurement device. The accuracy is surprisingly robust to modeling errors.