The Modeling And Control For Micro-arc Plasma Machining Process Of Monocrystalline Silicon

In the curting of semiconductor materials such as monocrystalline silicon,the conventional wire saw cutting process often resul ts in poor quality of the machined surface and problems such as fracture and chipping of the silicon wafer due to its contact processing.Therefore,consider non-contact discharge machining.However,due to the influence of semiconductor material bulk resistance,and conductor-semiconductor contact barriers,the conventional EDM discharge gap of single-crstal silicon materials is not easily broken down.Therefore,by adjusting the discharge gap,the researchers can maintain the discharge state spark discharge,avoid arc discharge,resulting in the formation of micro-arc plasma cutting.This paper comprehensively analyzes the discharge gap state detection and discharge gap control problem in micro-arc plasma cutting.The gap impedance characteristics of micro-arc plasma cutting discharge of single-crystal silicon materials are studied.Through the system identification and adaptive control theory,a generalized predictive control sy stem for single cry stal silicon micro-arc plasma cutting discharge gaps based on LabVIEW is designed.The experimental parameters of the process parameters were studied.The results show that the theoretical model can be applied to the process control of the single-cn stal silicon micro-arc plasma cutting gap discharge state.The specific work is as follows:(1)According to the volt-ampere characteristic and discharge form of the gas breakdown process,it is determined that the discharge of the micro-arc plasma cutting based on the single-crystal silicon should be maintained between the defective glow discharge and the arc discharge.By studying the impedance characteristics of micro-arc plasma cutting discharge gaps of semiconductor materials such as single crystal silicon,and performing related numerical analysis,a micro-arc plasma dynamic resistance model based on discharge gaps is proposed.At the same time,the function fitting relationship between the plasma dynamic model and the discharge gap is established to facilitate the subsequent estimation of the inter-electrode discharge gap.(2)Establish a single-input single-output model with micro arc plasma cutting feedrate as input and the average dynamic resistance between poles as output.Under the environment of MATLAB,the order of the single crystal silicon micro-arc plasma cutting system model was identified by the F-test of model residual variance.A recursive least squares algorithm with a forgetting factor of 0.97 was used as the on-line parameter estimation method of the model and the parameters of the control system model were obtained,thereby establishing a difference equation of the average dynamic resistance and feed rate of the discharge gap.(3)Design a generalized predictive controller for monocrystalline silicon micro-arc plasma cutting discharge state control.Write related controller algorithms,test and simulate different types of reference signals(such as straight line,square wave,sine wave,sawtooth wave,etc.)in MATLAB environment to check the control performance of the control system such as rapidity,stability,accuracy,etc.To meet the working requirements for monocrystalline silicon micro-arc plasma cutting.(4)Set up the hardware and software platform of the generalized predictive control system for micro-arc plasma cutting.Through the experimental verification of the controller's control performance,different types of target reference signals(such as straight line,square wave,sine wave,sawtooth wave,etc.)are tracked.The experimental results show that the servo control of micro-arc plasma cutting discharge state under different reference signals can be realized.Compared with the constant feed process,the generalized predictive machining process is more stable,which can avoid the occurrence of short-circuit open circuit and avoid arc discharge.In this way,micro-arc plasma cutting of semiconductor materials such as single crystal silicon is realized,which improves the surface quality of the processed material.