Piezoelectric actuator using ultrasonic traveling wave of screw form

A piezoelectric actuator, which is composed of a piezoelectrically driven stator and a rotor, is made and the characteristics are investigated experimentally. If an ultrasonic wave is excited to propagate in the stator, particles on the internal surface move elliptically. Since the internal surface is machined as an internal thread and an external thread (rotor) is put into the stator, the external thread is rotated through the friction force and moved in the axial direction. The traveling wave is excited by a piezoelectric element bonded to the stator. This idea was first proposed by S. Ueha et al. in 1987. However, efficiency of their actuator was less than 3%. In this paper, in order to improve the characteristics of this type of actuator, several kinds of materials have been used for the rotor, and the performance of the actuator has been measured. It is confirmed that the efficiency could be improved when fiber reinforced plastics are used for the rotor