Travelling Wave Ultrasonic Motor for Aerospace Applications

In the present work a travelling wave ultrasonic motor (TWUSM) is proposed. It is composed of an annular shaped stator and of two cone–shaped rotors that are pressed in contact to the borders of the inner surface of the stator. A rotating travelling wave has been generated in stator by using as vibration generators two Bolted Langevin Transducers (BLT) oppurtunely shifted in space and in time. The vibrational behaviour of the stator as well as the travelling wave generation have been simulated with a finite element method (FEM) software. A prototype of the motor has been manufactured and experimentally characterized. It exibits a static torque of about 0.8 N·m and a maximum angular speed of about 300 rpm. Possible variations of the present design aimed to increase output torque or minimize encumbrance are described and discussed