Finite element modeling and optimization of tube-shaped ultrasonic motors

Recent developments in ultrasonic motor design have demonstrated that small size tube-shaped motors could be fabricated at low cost. Motors with diameters between 15 and 2.5mm have been fabricated and tested. The performance evaluation of these motors is still in progress, but have already shown promising results: the smallest ones exhibit no-load speeds in the range of 70rad/s and blocked torques close to 0.9mN•m. In this paper, we review the operating principle of these devices and several implementation examples. Then, we show how the finite element method (ATILA) can be used, in combination with genetic optimization procedures, to design tube-shaped motors in various dimensions and for different performance objectives. Several design examples are presented and discussed.