Design Of Ultrasonic Power Supply For Ultrasonic Vibration Assisted Grinding And Research On Automatic Identification Of Resonant Frequency

With the rapid development of new technology in aviation,electronics,optics and communication industry,the needs of hard and brittle materials and hard to process materials is increasing day by day,which puts forward higher requirements for the processing efficiency,processing quality and processing accuracy of key parts.How to improve the machining efficiency,machining quality and machining accuracy of key parts is an urgent problem in the field of machining.Ultrasonic vibration assisted grinding is a kind of compound machining method which combines ultrasonic machining and grinding.Compared with traditional grinding,it has great advantages in machining efficiency,machining quality and machining accuracy.The function of ultrasonic power supply is to produce stable ultrasonic signal for exciting vibration of piezoelectric transducer,Therefore,the performance of ultrasonic power directly determines the machining quality of ultrasonic vibration assisted grinding.In ultrasonic vibration assisted grinding,the ultrasonic power supply needs to automatically identify the resonant frequency of the ultrasonic tool holder after changing the tool and can stably output the corresponding frequency;in addition,the ultrasonic power supply needs to have the function of power adjustment to adapt to different processing materials.For this reason,this paper has carried out the following research work:(1)According to the design indicators of the ultrasonic power supply,the overall scheme of the ultrasonic power supply was determined.By comparing the commonly used rectifier circuits,voltage regulator circuits and inverter circuits,the main circuit topology of the ultrasonic power supply was determined.A DC step-down chopper circuit and a half-bridge inverter circuit composed of an IGBT constitute the main circuit of the ultrasonic power supply.Through calculation,the parameters of the key components of the main circuit are selected.In Multisim Simulation software,the influence of the parameters of the key components on the output voltage waveform of the circuit is simulated,and the parameters of the components were optimized based on the simulation results.(2)The impedance of the equivalent circuit model of the ultrasonic tool holder piezoelectric transducer was analyzed in detail.The relationship between the loop current of the transducer and the frequency of the excitation signal was studied,and the series resonance frequency of the piezoelectric transducer was selected as the resonance frequency to be recognized by the ultrasonic power supply.The impedance characteristics of the piezoelectric transducer in the two matching modes of series inductance matching and parallel inductance matching were compared,and the tuning matching method of the piezoelectric transducer was determined.According to the equivalent impedance of piezoelectric transducer and the equivalent internal resistance of ultrasonic power supply,the impedance matching of piezoelectric transducer was completed,and the parameters and models of high frequency transformer are determined by area product method.(3)Through the current and voltage sampling circuit,signal processing circuit,current RMS detection circuit and phase difference detection circuit,the topological structure of the feedback control circuit of the ultrasonic power supply was determined.The selected devices were simulated in Multisim Simulation software,and the simulation results are compared with the theoretical calculation.The control idea and software flow of the ultrasonic power supply control system were described in detail.The program of automatic identification of resonance frequency and power control of ultrasonic power supply was compiled.(4)Based on the designed circuit diagram,an ultrasonic power source prototype was produced and the ultrasonic power source resonance frequency automatic identification performance test was carried out.The comparison test with the impedance analyzer and the repeated test of the prototype of the ultrasonic power source verify the stability of the automatic identification of the resonant frequency of the ultrasonic power source.The accuracy of the automatic identification of the frequency resonance of the ultrasonic power source was verified by the tool end face amplitude verification test.