Application of the genetic optimizaton method to the design of ultrasonic motors

Ultrasonic motors often use a combination of structural modes to generate the desired elliptical vibration field that ultimately results in the linear or rotary motion of an object. Designing an ultrasonic device that combines structural modes of vibration represents a non-trivial exercise, especially when it is desired to maximize the electromechanical coupling coefficient of the piezoelectric elements, the amplitude of vibration, and the force factor of the device. Other parameters may also be combined and render the exercise even more difficult: targeting a specific frequency, constraining dimensions, electrical constraints, etc. To help designing such ultrasonic structures, we propose to use the genetic optimization method in combination to the finite element method. Although evolutionary methods are not new and have been successfully applied to a variety of problems (including smart devices), they have never been applied, to the best of our knowledge, to the design of ultrasonic motors. In this paper, we review the general aspects of the method utilized, and provide several examples, including experimental verification.