Longitudinal - torsional type piezoelectric actuator for the high speed rotational motor

Abstract

A new ultrasonic compound type piezoelectric actuator for high speed unidirectional rotational type motor has been developed. Longitudinal-torsional hybrid vibrations are excited in the actuator in order to achieve large vibration velocities of the contacting points. Piezoelectric actuator consists of two metal hollow cylinders with different cross-section area, two piezoceramic rings and a special star type waveguide that is located at the node of longitudinal vibrations of the actuator. Single channel harmonic signal is used to excite the first longitudinal mode of the actuator. The second mode of torsional vibrations is obtained by employing curvilinear radial vibrations of the star type waveguide that operates as longitudinal vibration mode converter. First longitudinal mode of the star rods is induced by transverse deformations of the cylindrical parts of the actuator. Numerical investigation of the piezoelectric actuator was performed to analyse natural frequencies, modal shapes and actuator response to the harmonic excitation. Experimental prototype of the actuator was fabricated and operating principle of the actuator was validated.