An ultrasonic motor drive using a current-source parallel-resonant inverter with energy feedback

An ultrasonic motor (USM) drive using a two-phase current-source parallel-r esonant inverter is proposed in this study. A single-phase equivalent model of the USM is first described. Then, a detailed theory for the newly desig ned driving circuit for the USM, in which the inherent parasitic capacitanc es formed by the polarized piezoelectric ceramic of the USM are parts of th e two parallel-resonant tanks, is introduced. Since the dynamic characteris tics of the USM are greatly influenced by the variation in the quality fact ors of the parallel-resonant tanks, two transformers are added to feed the stored energy in the resonant tanks back to the de source to reduce the qua lity factors. Detailed experimental results are provided to demonstrate the effectiveness of the proposed driving circuit.