Low speed control of traveling-wave ultrasonic motor

There are three methods in speed control of traveling-wave ultrasonic motor (TUSM), including driving frequency, voltage and phase difference. Through the finite element method, the vibration model can be analyzed in different driving frequency. As a result of the non-work model's influence, the movement of TUSM is chopping in low speed when the driving frequency is far away from the resonance frequency of the work model. The stator stress is centralized in the excessively low phase difference. That affects the life of TUSM. In low speed control, the above question can be avoided through the voltage regulation. A 60mm-diameter TUSM was used in this research. Using DSP (digital signal processor) chip TMS320F2812, a control system of USM (ultrasonic motor) was built. The system realizes the low speed control of TUSM by voltage regulation. The result confirms this method.