超声波电机自激振荡驱动电路的变频控制特性

针对单相超声波电机的自激振荡驱动电路，重点分析了电路选频网络中不同元件参数对电路自激选频特性的影响，建立了电机动态阻抗变化特征、电路自激信号频率和电路参数之间的一个方程组，得出在超声波电机的工作频率范围内，电路自激频率随选频网络中下端电阻的增大而增大，随电感的增大而减小，实验结果与理论推导基本相符。电路中选择不同的电阻和电感值可以实现调频，即对超声波电机的变频控制。在电机稳定工作点的一定频带范围内电路可以实现自动频率跟踪功能。

Characteristic of Variable Frequency Control of Self-oscillating Driving Circuit for Ultrasonic Motor

This paper presents characteristics of frequency- selected circuit that is affected by different parameters in self-oscillating driving circuit for single phase ultrasonic motor (USM). An equation group is established among characteristic of dynamic impedance, frequency of self-oscillating signal and circuit parameters. Through academic analysis and emulation it is suggested that frequency of circuit will increase when resistance increases, and decrease when inductance increases, which is proved by experimental results. When selecting different resistance and inductance, variable frequency control of USM can be realized. At steady working point, circuit can follow up resonant point of the motor.