A fuzzy neural network controller for parallel-resonant ultrasonic motor drive

A newly designed driving circuit for the traveling-wave-type ultrasonic mot or (USM), which consists of a push-pull dc-dc power converter and a current -source two-phase parallel-resonant inverter, is presented in this study. M oreover, since the dynamic characteristics of the USM are difficult to obta in and the motor parameters are time varying, a fuzzy neural network (NN) c ontroller is proposed to control the USM drive system. In the proposed cont roller, a fuzzy model-following controller is implemented to control the ro tor position of the USM, and an on-line trained NN with variable learning r ates is implemented to tune the output scaling factor of the fuzzy controll er. To guarantee the convergence of tracking error, analytical methods base d on a discrete-type Lyapunov function are proposed to determine the desire d variable learning rates. From the experimental results, accurate tracking response can be obtained by the proposed controller, and the influences of parameter variations and external disturbances on the USM drive also can b e reduced effectively.