A Bonded Type Ultrasonic Motor Using the Bending of a Crossbeam

This paper proposed a new crossbeam ultrasonic motor, which was made of a cross-shaped metal frame and eight pieces of lead zirconate titanate ceramic plates with a size of 10 mm × 3 mm × 1 mm. Two cross-cone-shaped horns were machined at two ends of the crossbeam, and the tips of the horns served as the driving feet. Ellipse trajectories of the two driving feet were generated by superimposing two orthogonal first bending vibrations with the same resonance frequency but a temporal shift of 90°. A Symmetric structure of the proposed ultrasonic motor solved the problem of mode frequencies degeneracy. A new method to excite these two bending vibrations was proposed. Finite-element method simulation was developed to obtain the vibration characteristics of the crossbeam motor. The new excitation method was compared with the traditional one, and it was found that the vibration amplitudes of the driving feet under the new excitation method were about three times that of the traditional one. At last, experiments were accomplished on a fabricated prototype. The two tested first bending resonance frequencies agreed well with each other at ~ 40.5 kHz. Mechanical output performance of the prototype was tested; the maximum speed was ~ 64 r/min, and the maximum output torque was ~ 10.4 mN · m. This paper provides a new idea for an ultrasonic motor with a miniature structure and also a new excitation method for bending vibration.