The Identification Method Of EDM Discharge States Based On Fast Digital Signal Processing

EDM is widely used because it is suitable for any hard-to-cut conductive material and it has no obvious macroscopic force.However,the EDM frequency is high and the process is random,which seriously affect the identification accuracy of the discharge states.The servo control Servo system in EDM process is based on the results of the discharge state identification,so accurate and efficient discharge state identification system is the basis for realizing high precision and high efficiency machining of EDM.Therefore,it is very important to study the identification method of EDM.A high-speed acquisition system is established,which is based on a data acquisition card and a computer.The data acquisition card and computer is interacted through Labview software in order to achieve synchronization acquisition of voltage signal and current signal,which lay the foundation for the identification of EDM discharge states.Aiming at the instability of EDM signal,a method of EDM state identification based on wavelet transform is proposed.First,the optimal decomposition layer is determined by comparing the test method.And then by analyzing the factors that affect the results of wavelet transform,the threshold of the wavelet transform is determined by pulse width to distinguish the EDM discharge states.The threshold is used to distinguish the open state,the spark discharge state,the stable arc state,and the short circuit state.Finally,the rate of four discharge states in a statistical period is obtained.Combined with high-speed acquisition system,the real-time identification method of discharge states is achieved.The discharge characteristics of EDM are studied,and the differences of voltammetric characteristics and frequency characteristics of each discharge state are analyzed.At the same time,the formation and maintenance of the sustaining voltage are researched.Besides,the spark discharge state is compared with the arc discharge state,so as to provide the basis for the discharge state identification.As the test conditions will affect the discharge state characteristics,so the EDM characteristics under the different test parameters are studied.By changing the open circuit voltage,pulse width,workpiece material and electrode material,the parameters that affect the discharge state characteristics are deter mined.By setting the inter-electrode voltage threshold,the inter-electrode current threshold and the spectral threshold,the accurate and effective identification of the no-load state,the spark discharge state,the stable arc state and the pulse interva l is realized.Combined with high-speed acquisition system,the feasibility of this discharge state identification method is verified by experiment.