Adaptive Control-based High-Performance Drive System Implementation of Traveling-Wave Type Ultrasonic Motor

In recent years, ultrasonic motors (USM) as new actuators have attracted special interest. Some sorts of constructions and characteristics of USMs have been reported so far. Of these USMs, a traveling-wave type USM has many characteristics such as high torque at low speed range, large holding torque based upon frictional force, flexible free forms, compactness in size and low magnetic noise. In practice, an inherent mechanical resonant frequency and a velocity amplitude of USM are largely changed according to operating temperature due to frictional drive, load disturbance torque, and applied voltage levels. Therefore, it is necessary to develop a new control system which solves these items and always supplies the required power with high-efficiency and high-performance in the practical applications. This paper is mainly a newly-proposed sensorless high-performance control scheme of inverter-fed ultrasonic motor, which is based upon a control system technology with two feedbacks incorporating an automatic resonant frequency tracking and a constant velocity amplitude control strategies. This control system is realized in terms of high-frequency chopper and two-phase series/parallel resonant inverter. The experimental results are demonstrated and discussed as compared with the theoretical ones.