| Abstract: | In recent years, ultrasonic motors (USM) as new actuators have attracted special interest. Several kinds 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 in the 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 changed largely 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 proposes mainly a new sensorless high-performance control scheme of an inverter-fed ultrasonic motor, which is based on a control system technology with two feedbacks incorporating automatic resonant frequency tracking and constant velocity amplitude control strategies. This control system is realized in terms of a high-frequency chopper and a two-phase series/parallel resonant inverter. The experimental results are demonstrated and discussed compared with the theoretical ones. |
