Influence of the Number of Driving Transducers on the Performance of a High Power Travelling Wave Ultrasonic Motor

Ultrasonic motors have been exploited mainly in low power and low duty cycle applications. In aerospace applications, there is also the need for motors able to provide high torque but employed at very low duty cycle. In this work numerical simulations and experimental measurements carried out on a high power ultrasonic motor are presented. The proposed motor is composed of a annular shaped stator and two cone shaped rotors. The rotors are pressed in contact to the borders of the inner surface of the stator by means of an opportune pre-stress system. A travelling rotating wave is generated in the stator by at least two Bolted Langevin Transducers. Each transducer is designed to excite in the ring radial nonaxisymmetric modes. The effective excitation of the travelling wave in the stator, with both two and four driving transducers, has been simulated with FEM. Experimental results have shown that revolution speed, torque and mechanical power are improved by increasing the number of driving transducers from two to four