Combined finite element analysis - Genetic algorithm method for the design of ultrasonic motors

The operation of a linear or rotary ultrasonic motor relies on the production of an elliptical vibration at the surface of the stator. To achieve a suitable vibration state, many ultrasonic motors use a combination of structural modes of the stator. Because these modes may be different in nature, designing a viable stator is not trivial. In addition, the design may be complicated by other considerations, such as the electromechanical coupling coefficient of the piezoelectric elements, the amplitude of the vibrations, and the force factor of the device. Similarly, it may also be desired to incorporate parameters such as the operation frequency, geometrical dimensions and weight, electrical current and so on, which may render the design problem extremely difficult to solve. To help in designing such ultrasonic structures, it is proposed to use the genetic optimization method in combination with the finite element method. The combination of these two design tools is innovative and provides a unique approach to the complex problem of ultrasonic motor design. In this paper, the general aspects of the method utilized are reviewed and an application example that includes experimental verification data is provided.