Speed tracking servocontrol system with speed ripple reduction scheme for traveling-wave-type ultrasonic motor

Abstract

Recently, as an area of application of ultrasonic waves to the energy-related subject, technical development of ultrasonic motors is expected. To date, the principles and characteristics of several types of ultrasonic motors have been reported. Components taking advantage of the characteristic features of the ultrasonic motor have been in part reduced to practice. Further, several methods have been reported on the driving control method for the ultrasonic motor. In the speed tracking servocontrol system using the ultrasonic motor, the effect of the load torque and the control characteristics of the speed tracking are only partly reported and are insufficient for practical applications. Further, the fluctuation of the speed, or the speed ripple, caused by the manufacturing process of the ultrasonic motor has not been studied carefully. In this paper, a new speed servocontrol system is proposed in which the speed ripple reduction, load torque characteristics, and speed tracking are taken into consideration. The proposed system uses two control loops. A speed control loop using a variable gain is constructed in the driving frequency control section. Further, only the speed ripple is extracted from the revolving speed detection signal and is used for feedback compensation to the constant voltage control loop in the applied voltage control section. A test experiment is carried out and the experimental results are used to determine the effectiveness of the proposed speed servocontrol system. © 1998 Scripta Technica, Electron Comm Jpn Pt 3, 81(9): 1–9, 1998