Study On Ultrasonic Motor Drives

Ultrasonic motor (USM) is a novel motor with special materials and completely new driving principle. The inverse piezoelectric effect of the ceramics causes the ultrasonic vibration of stator to obtain a frictional driving force, which then drives the rotor, pressed against the stator. Compared with the conventional electric motor, USM has many features, such as compact in size, high-torque at low speed, high holding torque when power off, no magnetic interactive effect, quick response and quiet operation. Therefore, it is expected to be used in the field of small power level applications, such as aeronautics and space, robots, precise positioning devices, medical devices, miniaturized machines, and so on. Consequently, scientists home and abroad have paid more and more attentions to the research and applications. The thesis mainly investigates the speed control system, and precise servo system on USM, aimed to build an experimental platform for further research and industrialization. The contents are summarized as follows: The development and applications of ultrasonic motor are systematically reviewed. Subsequently, a review for driving and control techniques is outlined. The inverse piezoelectric effect of the ceramics and the ultrasonic vibrator are described. Meanwhile, the principle of the ring traveling wave ultrasonic motor is introduced. An experimental system for ultrasonic motor drives based on DSP is equipped. It looks a good platform to the experimental investigation. To the motor's speed stability, a frequency-tracking scheme with the feedback of rotor's speed is investigated. Based on high precision position detection, a DSP based precise servo system is developed. Furthermore, a precise position control scheme using P controller with dead-zone compensation to the phase difference is investigated theoretically and experimentally.