Real-time Detection And Discrimination Of Discharging States In Micro Electrical Discharge Machining

Micro electrical discharge machining (micro-EDM), as one important branch of EDM, has found its wide applications in industry for its untouched machining process. More and more attentions are paid to micro-EDM because of eliminating mechanical stresses, chatter and vibration between electrode and work piece during machining process. Discriminating the states of micro-electrical discharge machining is the precondition of reaching a stable control, whereas the discharging states is quite complex and changeful, which counteracts its further development. Based on the theory of micro-EDM, the physical laws and rules during micro-EDM discharging process were discussed firstly in this thesis. Investigating the features of the measured gap voltage and gap current and studying the affect of pulse energy on machining parameters are performed to provide the necessary theory base for discriminating of discharging states and control.Dividing and estimating the sparkle states exactly is one of key techniques to improve EDM control quality. High frequency and low electrical power of micro-EDM causes the waveforms of voltage and current highly distorted, thus indistinguishable by the conventional EDM discrimination systems due to the low ration of signal to noise. Such uncertainty of signals in discrimination of discharging states really brought a new challenge in micro-EDM field. According to the characters of micro-EDM and in order to avoid the limitation of a single sensor, the technology of data fusion is applied to distinguish the discharging states. A special real-time and high-speed data acquisition system is developed to harmonize the signal acquisition and processing. High-speed collection and transmitting of signal is realized with high-speed data acquisition card as the hardware. At the same time, subregional data cyclic processing is researched which provides fine data base for the signal disposal. The fuzzy logic rules are used to combine the complementary signals from the gap voltage and current which are taken as the two inputs to the fuzzy system and deduce a value in a range representing the discharging state of the sampling point. Different statistical ways are designed to account points except for the off state in a pulse according to different micro--energy pulse power sets. The ratio is adopted to analyze the pulse discharging states. Finally, the proportion of different pulse discharging states will be regarded as the criterion to control the machining process. The system is base on the multimedia timer technique, the real-time discriminating program is finished in the platform of Window 2000 operating system. The main program and management interface programs are written with the VC++ integrated development tools, which realized the functions of data acquisition, analysis and management. The experimental results show that the system is real-time, precise and ensures the realization of reliable control for Micro-EDM.The discriminating system for micro-EDM designed in this thesis also can be used in conventional electrical discharge machining. On the other hand, it is a good use for reference for other real-time detecting system whose signals are anamorphic.