A novel hollow type of traveling wave rotary ultrasonic motor is proposed, optimized, fabricated, and tested in this study. Unlike conventional ultrasonic motors, this novel ultrasonic motor adopts a bran-new preloading method that preload is applied from the bottom of the stator through a wave spring, which can not only enhance the anti-overload ability but also extend the working life of the motor. According to this motor, a three-dimensional finite element model has been built by the commercial finite element software ADINA. In terms of the friction material and the preload, a detailed further optimization procedure is given after the initial design. Finally, the appropriate size and location of the friction layer and a proper preload for this motor have been determined. Almost all of the motor’s mechanical capacities, such as rotational speed, torque, and deformation, can be obtained by simulations in ADINA, which have good agreement with experimental results.

Existing rotary ultrasonic motors operating in extreme environments cannot meet the requirements of good environmental adaptability and compact structure at same time, and existing ultrasonic motors with Langevin transducers show better environmental adaptability, but size of these motors are usually big due to the radial arrangement of the Langevin transducers. A novel dual driving face rotary ultrasonic motor is proposed, and its working principle is experimentally verified. The working principle of the novel ultrasonic motor is firstly proposed. The 5th in-plane flexural vibration travelling wave, excited by the Langevin transducers around the stator ring, is used to drive the rotors. Then the finite element method is used in the determination of dimensions of the prototype motor, and the confirmation of its working principle. After that, a laser Doppler vibrometer system is used for measuring the resonance frequency and vibration amplitude of the stator. At last, output characteristics of the prototype motor are measured, environmental adaptability is tested and performance for driving a metal ball is also investigated. At room temperature and 200 V(zero to peak) driving voltage, the motor’s no-load speed is 80 r/min, the stalling torque is 0.35 N·m and the maximum output power is 0.85 W. The response time of this motor is 0.96 ms at the room temperature, and it decreases or increases little in cold environment. A metal ball driven by the motor can rotate at 210 r/min with the driving voltage 300 V(zero to peak). Results indicate that the prototype motor has a large output torque and good environmental adaptability. A rotary ultrasonic motor owning compact structure and good environmental adaptability is proposed, and lays the foundations of ultrasonic motors’ applications in extreme environments.

The application of ultrasonic motor (USM) has been seriously restricted by its relatively low efficiency. The energy loss caused by the radial sliding on the contact surface of the motor is considered as one of the major reasons for the low efficiency of USM. In this report, the solution is proposed to reduce the radial sliding by optimizing the stator comb-teeth of the traveling wave rotary ultrasonic motor (TWUSM). Theoretical analysis, simulation, and experiments were conducted in PMR60 type TWUSM (motor model) to verify the optimized method. The results indicate that the friction angle $\alpha$ , which represents the degree of radial sliding, can be efficiently reduced by chamfering the teeth on the stator of motor. The maximum efficiency of 44.3% is obtained in the modified motor of which the stator chamfer size is 1.0 mm × 45°, which is nearly two times higher than that of the nonmodified motor (25%). Therefore, it is a feasible and simple pathway to improve the efficiency of the USM.