Driving Circuit Design of a Circular Ridge-wave Ultrasonic Motor

This study aimed to develop a novel driving circuit for a circular cylindrical ridge-wave ultrasonic motor. The driving circuit framework of a piezoelectric actuator consisted of three major levels, which were phase, power, and resonance. Previously, analogous phase shifters were used in the split-phase circuit; in this study, a digital circuit was used instead. Bridge inverters are mainly used in power stage circuits and include half-bridge inverters and full-bridge inverters. In this study, a half-bridge inverter was used in a power stage amplification circuit. With regard to the resonance level, an LC series resonant and parallel load circuit was applied due to its structural simplicity, low cost, low electromagnetic interference, control signal feedback, and quick response. The measurements of motor performances indicated that under the maximum driving voltage amplitude of 200 Vp-p, driving frequency of 35.04 KHz, and pre-load of 1 Nt, a maximum torque of 22.6 mN-m and maximum revolution speed of 334 rpm could be reached, while electromechanical conversion efficiency was improved by 25%.