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

An ultrasonic motor (USM) drive using a two-phase current-source parallel-resonant inverter is proposed in this study. A single-phase equivalent model of the USM is first described. Then, a detailed theory for the newly designed driving circuit for the USM, in which the inherent parasitic capacitances formed by the polarized piezoelectric ceramic of the USM are parts of the two parallel-resonant tanks, is introduced. Since the dynamic characteristics of the USM are greatly influenced by the variation in the quality factors of the parallel-resonant tanks, two transformers are added to feed the stored energy in the resonant tanks back to the DC source to reduce the quality factors. Detailed experimental results are provided to demonstrate the effectiveness of the proposed driving circuit