Constant amplitude control of high-power ultrasonic drive system

In precision ultrasonic process, the amplitude of the transducer will change while the load changes. which causes the unstable process and the decline of the process quality and efficiency. To solve these problems, the theoretical model of controlling ultrasonic amplitude output is established by feedbacked current. The theory is based on Kirchhoff´s circuit laws. And then a method of constant amplitude control is proposed by controlling buck converter´s output voltage. By MATLAB/Simulink, the simulation shows that the current is constant though the load changed. The result proved the scheme of constant amplitude control was feasible. Finally, the PID algorithm has been completed in the ultrasonic drive system based on ARM chips. The amplitude of the transducer was measured by a laser Doppler vibrometer and compared with the constant voltage control and the constant power.