Cylindrical traveling wave ultrasonic motor using longitudinal sandwich transducers

This paper proposed a cylindrical traveling wave ultrasonic motor using longitudinal sandwich transducers. The stator components of the proposed motor contained a cylinder and four longitudinal sandwich transducers. The cylinder and the horns of the transducers were manufactured from a piece of duralumin alloy. The longitudinal vibration of transducer was excited by the longitudinal vibration of PZT (piezoelectric ceramic material). Two bending vibrations were generated in the cylinder by the transducers. When the amplitude of two bending vibrations was equal, and their phase difference on time and space was half of the circumference ratio and a flexural traveling wave was formed in the cylinder. Thus, an elliptical motion was achieved at the particle on the tooth. And the driving force was the frictional force between the rotor and the stator. The cylinder and longitudinal sandwich transducer were designed with finite element method (FEM). The longitudinal resonance frequency of the transducer and the bending resonance frequency of cylinder were degenerated. The test results show that, typical output of the prototype reaches a no-load speed of 110 r/min and maximum moment of 0.5 N·m.