Contact mode and force transferring model of cylindrical ultrasonic motors with bending vibration modes

Cylindrical ultrasonic motors can be widely used in many fields such as zoom and focus system of cameras, electric curtain and micro-driver of MEMS.This work concentrates on single-point and double-point contact modes between the stator and the rotor,which are proved by the theory and the experiment,then put forward a conception of the critical pre-pressure and the force transferring relation in two different contact modes mentioned above,moreover analyze the mechanical characteristics and the efficiency of the motors.Simulated results are confirmed by experimental ones.The proposed model is useful to analyze the relation between the motor characteristics and the pre-pressure. Finally theφ14 mm prototype was fabricated.Its maximum torque is 0.11 Nm,the no-load speed is about 300 r/min.