Driving characteristics of a hexadecagon-shaped ultrasonic motor

A novel hexadecagon-shaped ultrasonic motor is proposed. The stator is easy to fabricate because of its simple structure. The stator of the hexadecagon ultrasonic motor is composed of an elastic ring and ceramics. The elastic ring has sixteen sides and angles. The eight ceramics are attached on the outer surfaces of the eight sides of the ring. When rotor of the cylindrical shaft is inserted inside the ring stator, the central lines of the sixteen sides of the stator hold the shaft with slight pressures. This slight pressure is the preload of the motor and it can be controlled by the radius and the thickness of the ring. When two AC voltages that have a 90-degree phase difference are applied to the eight ceramics, elliptical displacements of the inner surface of the ring are obtained. These elliptical displacements of the inner surface rotate the shaft rotor through friction. The proposed hexadecagon ultrasonic motor was designed and analyzed by using a finite element analysis (ATILA), depending on the number of piezoelectric ceramics and hexadecagon modes. As a result, the stator was optimally designed by defining the output displacement characteristics, which depend on changes in the chosen parameters.