Speed control of ultrasonic motors by auto-tuning fuzzy PI control

In this paper, an auto-tuning fuzzy PI control scheme is presented for speed control systems with ultrasonic motors produced by the Shinsei Corporation in Japan. The properties of ultrasonic motors vary in a large range with the temperature and load torque, therefore, it is necessary to adjust the control gains of the PI controller for fine control performance. The proposed scheme can compensate the property uncertainties of the motors by optimizing the fuzzy control rules, which determine the proportional gain and integral gain of the PI controller, by means of the on-line auto-tuning factors. The effectiveness of the proposed control scheme is examined by experiments. Furthermore, the control scheme is simple and general, and it is based on the commercial products, so it can be applied in many practical cases.