Microcontroller based digitally controlled ultrasonic motor drive system

Abstract

Piezoelectric driven ultrasonic motors have been attracted as considerable actuators for the servo speed and position applications in recent years. These motors have important features and advantages to be preferred in the special movement applications. Ultrasonic motors have different operating principles and different drive and control systems than the electromagnetic motors. In this study, microcontroller based digitally controlled drive system has been proposed for a travelling-wave ultrasonic motor. Drive system includes power circuit, interface electronics circuits and microcontroller parts. Power circuit is combined from half-bridge serial-resonance inverter to provide highfrequency two-phase voltages. Interface circuits include gate drive, direction control, opto-coupler and filter circuits. Microcontroller is programmed to generate required digital control signals for overall control of the motor. Related to the reference speed, the microcontroller generates control signal resulting proper driving frequency. Consequently, the actual motor speed tracks the reference speed precisely. The speed feedback is taken from optical encoder and transmitted to the controller as digital speed and position signals. The developed drive system has been tested experimentally. The obtained results show the effectiveness and reliability of the proposed system. The microcontroller based drive system can be applied easily and successfully to the ultrasonic motor.