A novel multi-mode differential ultrasonic motor based on variable mode excitation

•We propose a novel multi-mode differential ultrasonic motor.•The motor can work at three different operation modes and provide three different speed-thrust characteristics based on a unique variable mode excitation method.•The three-step speed regulation can be realized with the motor based on variable mode control.•The motor can drive two rotors or sliders moving with same or contrary direction.

A novel multi-mode differential ultrasonic motor (USM) with two sandwich-type transducers has been developed. The salient feature of this motor is that it can work at three operation modes and provide three different output characteristics by changing the excitation method. Then, the motor can realize three-step speed regulation by switching the operation mode, and drive two rotors rotating or two sliders moving with same or contrary direction. The stator contains two sandwich-type transducers which are connected by two metal isosceles triangular beams. Four AC voltage signals are needed to excite eight piezoelectric ceramic pairs of the stator. By changing the connection way and frequency of the applied AC voltage signals, the longitudinal and bending vibration modes of the stator can be excited and degenerated. The variable mode excitation method and the working principle of the motor are analyzed. A prototype of the motor was designed and fabricated. The no-load speed and maximal thrust force of the prototype motor at three operation modes are tested.