Fast and Precise Control for the Vibration Amplitude of an Ultrasonic Transducer Based on Fuzzy PID Control

Abstract

This work presents a novel constant frequency ultrasonicamplitude control (CFUAC) method based on fuzzy proportional-integral-derivative (FPID) and amplitude direct feedback. The frequency shift and amplitude nonlinearity of the piezoelectric transducer (PT) are measured to determine the optimal constant control frequency of 19.2 kHz. The FPID controller is designed to adapt to the nonlinear changes in different target amplitudes and loads. A direct PT amplitude feedback method is used to improve the signal’s anti-interference ability and accuracy. The 5% settling time and steady-state error of FPID can reach 92.22 ms and <inline-formula> <tex-math notation= LaTeX >$\\pm 0.18~\\mu \\text{m}$ </tex-math></inline-formula> at the step response under 24 <inline-formula> <tex-math notation= LaTeX >$\\mu \\text{m}$ </tex-math></inline-formula>. The 5% settling time and steady-state error of FPID are less than 131.44 ms and <inline-formula> <tex-math notation= LaTeX >$\\pm 0.26~\\mu \\text{m}$ </tex-math></inline-formula> at 10 <inline-formula> <tex-math notation= LaTeX >$\\mu \\text{m}$ </tex-math></inline-formula> under 150 N. The results confirmthat fast and precise control of the vibration amplitude of an ultrasonic transducer can be realized by the proposed method. The new CFUAC method lays a foundation for revealing the ultrasonic welding and metal processing (UWMP) mechanism and helps to expand the application of ultrasonic vibration in the fields of precision machining and high dynamic ultrasonicmedical equipment.