Abstract
A miniature ultrasonic motor fabricated from a LiNbO3 rectangular plate was studied to improve its rotation characteristics. In this motor, the coupling modes of in-plane longitudinal and flexural modes caused by crystal anisotropy are used to realize a single-phase drive motor. The mode coupling vibrator is designed to have crystal cut angles and the width-to-length ratio W/L of the vibrator shape. In this study, we noted the new coupling condition of W/L≈0.84 compared with the conventional ratio of W/L=0.255. We considered the mechanism of the mode coupling and the design of the stator vibrator by finite element method analysis and experiments. From the results, we fabricated and investigated prototype motors of the vibrator with dimensions of 10×2.55×0.5 and 4.10×3.48×0.5 mm3. The newly designed motor with the vibrator of W/L=0.849 improved the motor characteristics for the equalization of rotation in both directions.