Small size disc type piezoelectric actuator for rotary ultrasonic motor

Abstract

A new design concept of disc type piezoelectric actuator used for small size rotary type ultrasonic motor is proposed in the paper. Radial-bending type hybrid vibrations of the special disc is employed to drive a rotor. Stator of the actuator has special waveguides in the center that are aligned to the tangential direction of the contacting surface of the rotor. The waveguides are used to transform radial vibrations of the disc into rotational vibrations of the contacting ring. Bending vibrations of the disc is employed to obtain axial vibrations of the contacting surface. Elliptical motion of the contact points is obtained by superposition of the both vibration modes. Two actuators with regular beam waveguides and quadrilateral shape waveguides were analyzed. Both piezoelectric actuator are bimorph type and consist of a steel disc with threaded waveguides and two piezoceramic rings. Numerical and experimental investigation of the piezoelectric actuators was performed to validate operating principle and to analyze vibrations of the contact points. Electrical and mechanical output characteristics of the piezoelectric actuators were measured. Results of investigation were analyzed and discussed.