Speed tracking servo control system incorporating traveling-wave-type ultrasonic motor and feasible evaluations

In recent years, a variety or ultrasonic motors (USM's) hare attracted special interest as a new type of actuator in servo motion control systems, for practical applications, the speed servo control system incorporating the ultrasonic motor developed in Japan has same special unique features, However, tit system has several significant problems, such as the inherent speed ripple characteristics, the speed regulation characteristics under the condition of applied disturbance load torque, and the speed tracking characteristics. In order to solve these practical problems, some control schemes of ultrasonic-actuated motor systems have been proposed and discussed theoretically, which include fuzzy reasoning control, adaptive control, repetitive learning control, and neural-network-based learning control, However, it is considered that these control strategies mentioned above have not been sufficiently substantiated from a feasible experimental point of view. This paper presents a newly proposed precise speed tracking serum control system using the compact traveling-wave-type ultrasonic motor, ifs proposed control scheme is composed of both the driving frequency control loop with thf variable-gain strategy and the applied voltage control loop with the speed ripple reduction strategy of the USM, The improved speed characteristics realized by this proposed control system are demonstrated and evaluated in experiments.