Research On Rod Type Linear Travelling Wave Ultrasonic Motor

This project is supported by the National Natural Science Foundation of China(No.51375225). Major work for this project was finished in the Institute of Dynamics and Vibration Research at Leibniz University Hannover and State Key Laboratory of Mechanics and Control of Mechanical Structures at Nanjing University of Aeronautics and Astronautics.In this paper, the research situation of linear ultrasonic motors was simply reviewed, and based on the development of the linear travelling waves ultrasonic motors in the domestic and overseas and its issues existed in the reseach, a novel rod type linaer ultrasonic motor utilizing longitudinal travelling waves is proposed. The longitudinal vibrations generated by piezoelectric transducer excite longitudinal travelling waves in the waveguide. In the mean time, the passive damper is adopted to eliminate the reflections of the longitudinal travelling waves in the waveguide, which will achieve a pure longitudinal travelling wave in the waveguide. Due to the longitudinal travelling waves propagate along the waveguide, the surface particles will move as elliptical trajectory, which will drive the slider to move as linear motion by friction force.The modelings of longitudinal vibration velocity/displacement for the surface particles of the stator system are established based on the applicability of the transfer matrix method used in the rod elements. According to the definition of the Poisson’s effect, the modelings of radial vibration velocity/displacement for the surface particles of the stator system are derived.In order to verify the validity of the design of the motor, the testing system is established. The longitudinal and radial vibration velocities of the surface particles for the stator system are conducted to measure, which verified the feasibility of the motor’s design. To improve the performance of the motor, the geometry of the passive damper is optimized by experiments and simulation, which obtained the optimized geometry.The vibration characterisitic and the performance tests for the motor are conducted based on the optimized geometry of the passive damper. Firstly, the elliptical trajectories on the surface of the waveguide are obtained. Secondly, the standing wave ratio on the surface of the waveguide is obtained when the longitudinal vibration velocity of the surface particles on the stator system after optimization is measured, which reduced 29.7% compared with before optimization. At last, the preliminary motion behavior test for the assembled motor is conducted. The slider can reach 120mm/s when the sin voltage is applied with 200 V.