A novel dual stator-ring rotary ultrasonic motor

In this work, a novel dual stator-ring rotary ultrasonic motor is proposed, designed, fabricated and characterized for raising driving torque of the rotary ultrasonic motor operating in the flexural vibration mode. It uses four bending mode Langevin transducers, which are evenly distributed between its two identical stator rings, to excite the ninth order flexural mode traveling waves in the two stator-rings and drive its two rotors. Driving bars assembled at the center of the Langevin transducers are employed to excite two ninth order flexural standing waves spatially and temporally orthogonal to each other in each stator-ring, and form the traveling wave. Results of vibration measurement are used to confirm the operating principle, and the finite element method is used to design the motor size in order that the motor can operate in resonance. The appearance size of the motor is 80 mm × 80 mm × 53 mm, stator outer diameter is 60 mm, and operating frequency is around 39 kHz. The major mechanical and thermal characteristics of the motor have been measured. At the room temperature and 250 V0-p operating voltage, its stalling torque is 1.6 Nm, no-load speed is 120 rpm, and output power reaches the maximum (=5.5 W) with a driving torque of 0.9 Nm and speed of 54 rpm. At ambient temperature of 100 °C, the motor still has stalling torque of 0.9 Nm and no-load speed of 79 rpm for a operating voltage of 250 V0-p, which means that this motor can operate in relatively high temperature environment.