FE analysis and experimental characterization of a high torque travelling wave ultrasonic motor

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 three pairs of Bolted Langevin Transducers opportunely shifted both in space and time. Each transducer is designed to excite in the ring radial nonaxisymmetric modes. The motor has been clamped to the housing by using two flanges passing through the middle plane of two transducers. The effective excitation of the travelling wave in the stator, has been simulated with FEM. Experimental measurements were carried out on a manufactured prototype in order to validate numerical results and to evaluate motor performances. Main characteristics of the motor are summarized as follow: weight 0.67 Kg, working frequency 23.5 kHz, max rotational speed 116 rpm, static torque 0.94 Nm.