Ultrasonic Motors Using Longitudinal and Bending Multimode Vibrators with Mode Coupling by Externally Additional Asymmetry or Internal Nonlinearity

Abstract

The present paper deals with some ultrasonic motors using longitudinal and bending multimode vibrators with their mode couplings caused by externally additional asymmetry or internal nonlinearity. A rectangular plate vibrator with two corners on one diagonal line cut to make its resonance modes couple with each other was used, along with a rectangular plate vibrator under the condition that two resonance frequencies are obtained, for example, as f _L/f _B=2.0, because internal nonlinear coupling of parametric vibration between two resonance modes is generated under this condition. Using these vibrators with mode couplings, it was found that some ultrasonic motors of simple form can be constructed. The ultrasonic motor using the phenomenon of mode-coupling vibrations dealt with here is not completely new, and a few trial constructions have already been reported [Jpn. J. Appl. Phys. 24 (1985) Suppl. 24-2, p. 739]. However, their motions were not reversible in ordinary driving with an electrical signal of a constant frequency. In contrast, the motors that the authors proposed in this paper can be expected to have a reversible motion.