Load-adaptive frequency tracking control implementation of two-phase resonant inverter for ultrasonic motor

The operating principles of newly developed ultrasonic motors (USMs) that are attractive as compact and high-torque actuators are described. A two-phase high-frequency resonant inverter for driving the USM is presented. The unique operating characteristics of the USM are examined using the 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.>