A new ultrasonic motor utilizing longitudinal vibration of sandwich type transducers

This study presents and verifies a new idea for simplifying the frequency matching process of ultrasonic motor by constructing a new sandwich type ultrasonic motor, which utilizes the combination of the symmetrical and antisymmetrical longitudinal modes of mirror symmetrical structure. Two Langevin transducers in combination with two isosceles triangular beams are used to construct the stator. The superior point of the stator is that the frequency matching process can be neglected, because the resonance frequency difference of the two operation modes is very small, which is the characteristic of the symmetrical structure motor. The influence of the triangular beam structure on the vibration amplitude of the driving foot was analyzed. Driven by AC signals with the driving frequency of 55 kHz and voltage 400 Vp-p, the no-load speed and the maximal output torque of the prototype motor were 24.41 rpm and 7.84 N·cm, respectively. The motor is simple in structure, low cost in fabrication and feasible to implement linear or rotary movement of moveable body.