Load-Adaptive Frequency Tracking Control Implementation of Two-Phase Resonant Inverter for Ultrasonic Motor

Abstract

This paper describes the operating principles of newly developed ultrasonic motors (USM's) that are attractive as compact and high-torque actuators. These USM's have recently begun to be used for certain unique practical utilizations in the fields of industrial, medical, consumer, and automotive applications. A two-phase high-frequency resonant inverter for driving the USM is presented. The unique operating characteristics of the USM are examined using this inverter. Two principles of resonant frequency tracking control strategy, one concerned with a sensor interface scheme mounted on the USM and a second sensorless interface scheme based on electromechanical conversion theory, are described. These control methods are realized by analog-oriented signal processing and the PLL technique. The revolving speed control obtained by this inverter-fed USM system with two types of resonant frequency tracking control methods is illustrated and discussed using an experimental breadboard. © 1992 IEEE