To realize applications involving low speed and high torque in the high-performance actuator industry, especially in the aerospace field, we propose a novel 70H traveling wave rotary ultrasonic motor (TRUM) with an outer diameter of 70 mm and an aperture ratio of 53% (the ratio between the aperture and outer diameter). The power transmission mechanism between the stator and the rotor is analyzed, and a method for realizing low-speed–high-torque characteristics of TRUMs is proposed. ANSYS software is used to simulate the modal parameters of the stator, and the ratio β between the normal amplitude and the tangential vibration velocity of the stator is proposed. The larger the value of β, the lower the speed and the higher the torque. Furthermore, two prototype motors are fabricated, namely, 70HA and 70HB. Compared with 70HA, the maximum no-load speed of the improved 70HB (50 rpm) is decreased by 23.1% and the maximum stall torque (2.4 N∙m) is increased by 100%. Besides this, with a smaller mass of 210 g and a higher torque density of 11.43 N∙m/kg, 70HB has fundamentally different mechanical characteristics.

For application in control moment gyros, we considered a hollow traveling wave ultrasonic motor with a diameter of 70 mm. The effective electromechanical coupling coefficient (EMCC) of the stator was determined. The influence of the vibration mode of the stator and the structural dimensions of the metal elastomer and piezoelectric ceramic ring on the effective EMCC was investigated. According to the FEM simulation results, four different stators were manufactured and tested. The EMCC obtained through the simulations was greater than the measured values, with the lowest simulated and measured values being 17.202% and 16.431%, respectively, and the highest simulated and measured values being 28.452% and 26.780%, respectively. The relative errors between the simulated and measured values were all less than 10%. This work will help us to improve the output efficiency of the motor.

In order to achieve the application of ultra-sonic motors in small pan/tilt/zoom (PTZ), this study designed a light arc-shaped ultrasonic motor where the first-order longitudinal vibration mode and the second-order bending vibration mode were superimposed in the stator plane, in order to drive the rotation of the rotor. The stator was fabricated by phosphorous bronze and piezoelectric ceramic. ANSYS was used to simulate the motor performance in order to optimize its size and determine its operating mode. The motion trail of the end surface of the driving feet was also simulated. The frequency and amplitude of the motor prototype were measured using a three-dimensional (3D) laser vibration meter. The results, which were in good agreement with the simulation results, demonstrated that the prototype exhibited favorable vibration characteristics. The mechanical characteristics of the prototype were also tested. At an operating frequency of 126.5 kHz and an excitation signal of 350V_pp, the maximum rotating speed of the motor reached up to 230 rpm. Finally, the output torque of the motor configurations with single-stator and double-stator were proposed respectively was investigated. The output torque of the motor under the single-stator configuration reached up to 2.6×10^-2 N·m, The double-stator which was 1.5 times greater than that under of single stator configuration. Conclusively, the designed motor is characterized by its light weight, high torque, and favorable output performances.