A novel high-speed rotary ultrasonic motor applied to micro air vehicles

In this paper, a novel ultrasonic motor based on the out-of plane flexural vibration mode is designed. The motor consists of a hollow carbon cylinder and a disc-type coplanar piezoelectric trimorph actuator. The cylinder is glued in the center of the metal disc. The electrodes of the piezoelectric layers of the actuator are divided into the four equal sections. There are four piezoelectric plates bonded to the bottom face of the metal disk for exciting the stator's out-of-plane flexural vibration mode. The shaft is used to amplify the vibration amplitude of the metal disk. The rotor pressed on the conical surface of the shaft can be driven to rotate by the traveling wave induced friction force. The preload between the stator and rotor is applied by one nut screwed to the solid shaft. A prototype of the proposed motor is fabricated and characterized. The vibration amplitude of the stator's metal disk is measured by the PSV laser Doppler vibrometer. The prototype's rotational speed can reach 5000 r/min and the amplitude of the disk can reach 0.3μm when the driven frequency is 33.186 kHz and the driven voltage is 350 Vp-p.