A Sandwich Rotary Traveling Wave Ultrasonic Motor using Wedges for Adjustable Preload:Design and Performance Evaluation

In this paper, a sandwich-type rotating traveling wave ultrasonic motor is proposed and investigated. This motor uses the TE vibration mode of piezoelectric ceramics to excite the B(0, 9) working mode of the annular stator to achieve large torque output characteristics. The modal analysis and harmonic response analysis are first conducted using the finite element software, to obtain the optimization geometrical sizes of the motor stator. Then the prototype of the motor is processed and assembled for vibration measurements to confirm the simulation results. Finally, output performance experiments of the motor prototype are carried out to evaluate the motor performances. The results show that the motor prototype can be normally driven by synthesizing traveling waves. Under the driving conditions of 180 N preload, 500Vpp voltage, and 18.4KHz excited frequency, the no-load speed of the motor prototype is 16.64 RPM, and the stall torque is 1Nꞏm. In this paper, a structure design method of the sandwich motor stator is proposed, in which this method can excite two-phase standing waves of the same frequency and orthogonality while ensuring the uniform circumferential stiffness of the motor stator, and can perfectly synthesize traveling waves for driving. Also pioneering the use of wedges to apply adjustable preload to the piezoelectric ceramic sheets.