Research On Radial Bengding Mode Ultrasonic Motor Using Embedded Piezoelectric Elements

Ultrasonic motors (USM) which offer several advantages with respect to electromagnetic ones, including high energy density, light quality, electromagnetic compatibility, have broad application prospects in many traveling fields, but the low driving power, short lifetime and poor stability have blocked the process of its industrialization. The circle traveling wave USM with embedded piezoelectric ceramic-like structure has a great advantage in terms of configuration, which integrates the advantages of the traditional bonded-type USM of compact and the sandwiched type USM of high electromechanical coupling efficiency mode. For this kind of configuration, USM with nested piezoelectric elements using axial bending mode has been developed out, but the axial amplitude of particles on driving teeth is inconsistent, and energy utilization rate is very low. In order to improve the electromechanical coupling efficiency and the consistency of the driving particles'vibration trajectories, this paper proposes a new type of traveling wave USM which uses embedded piezoelectric elements and radial bending mode. The radial amplitude along the axis has a very good consistency, and it's beneficial to improve the utilization of the stator's vibration.In this paper, the motor structure and the principle of traveling wave excitation were introduced in detail. The vibration trajectories of particles on driving teeth were derived, and the factors that influence the electromechanical coupling efficiency were analyzed from the perspective of the electrical model. By using ANSYS software, a parameterized model of the stator was established. We got the vibration frequency and working mode by modal analysis, and obtained the optimal parameters by sensitivity analysis. The electromechanical coupling efficiency was qualitative analyzed through the study of admittance, the elliptical motion trajectory was verified by transient analysis, and the quality of the traveling wave was analyzed. Based on the theoretical study and simulation results, a prototype motor was fabricated and experimentally characterized. Typical output of the motor is no-load speed of 146r/min and maximum torque of 1N·m.