Research On Frequency Tracking Model And Performance Optimization Of Ultrasonic Machining

With the development of all kinds of hard brittle materials and composite materials,it is difficult for traditional processing methods to process these materials.In recent years,the research at home and abroad shows that the ultrasonic machining of ultrasonic transducer is an effective method to process these materials.But when working in the ultrasonic processing system,the resonant frequency of the ultrasonic transducer will drift.To make the ultrasonic machining process effective,we must ensure that the frequency of the output ultrasonic signal of the ultrasonic machining system is always near the resonance frequency point of the ultrasonic transducer,otherwise it will reduce or even lose the ultrasonic machining ability.The purpose of this paper is to study the frequency tracking model and performance optimization of ultrasonic machining,in order to track the resonant frequency of ultrasonic transducer in real-time,fast and accurately.An electrical impedance model of an ultrasonic transducer is established for the equivalent electrical circuit of the transducer near the resonant frequency.On this basis,the relationship between the resonant frequency of the ultrasonic transducer and the parameters of the transducer is analyzed.The effect of different driving frequencies on the phase difference between the two ends of an ultrasonic transducer and the flow over current is analyzed by using the electrical impedance model.At the same time,we use PLL phase-locked method to track the system frequency.The control methods are divided into two kinds: PID control and fuzzy adaptive PID control.They are analyzed and compared respectively,and two control methods are experimentally verified.Aiming at the problem of ultrasonic frequency shift in ultrasonic machining system when machining,the impedance model of transducer and tool holder is established by studying the equivalent circuit of transducer at resonance frequency,and the relationship between each parameter and impedance model is deduced.On this basis,the frequency tracking controller is designed to get the frequency tracking control system of ultrasonic machining to meet the requirements of processing.Taking the ultrasonic machining tool holder as the research object,in order to achieve the ultrasonic generator tracking the resonant frequency of the hilt,the electrical modeling and phase characteristics of the ultrasonic machining tool holder are studied,and the controller is designed.The results are: the precise model of ultrasonic transducer and ultrasonic knife,the relationship between the resonantfrequency and the variables,wideband frequency sweep method is improved,the fuzzy adaptive PID controller for ultrasonic machining system frequency tracking PID controller and a better control effect.Optimizing the performance of the frequency tracking of the ultrasonic machining system makes the system tracking the resonant frequency of the ultrasonic transducer more fast and accurate.