Structure design method of bar-structure linear ultrasonic motors

Since the transmission efficiency of vibration wave is decreased in a bar with sudden variable cross-sections, a new design method based on continuous variable cross-section for Langevin vibrators was proposed. Firstly, the relationship between the cross-section shape of the bar and transmission efficiency of longitudinal wave was discussed. Then the longitudinal vibration of bars with continuous variable cross-section was derived as well as its profile function. Meanwhile its acoustic characteristics were also discussed. Finally an improved linear motor was designed by using the Langevin vibrators with continuous variable cross-section. Its maximum thrust is increased to 21.4 N, the maximum speed is up to 235 mm/s, and thrust weight ratio of 25 under condition of 200 Vrms. The speed-frequency relation, the speed-phase difference relation, speed-voltage relation of the motor was obtained by testing. The experiment results indicate that the motor has better output performance.