Design Of Servo Control System For Spindle Rotating Ultrasonic Vibration Assisted EDM Platform

Electrical Discharge Machining(EDM)is a method of machining a workpiece by a pulsed discharge between the tool electrode and the workpiece electrode in a certain medium.Spindle rotating ultrasonic vibration has a great effect on improving the discharge stability of EDM,increasing the discharge gap,improving the material removal rate,and promoting the discharge of electrical corrosion products,thereby improving the processing speed and processing quality.Because the composite machining process of rotation,ultrasonic vibration and electrical discharge machining is relatively complicated,this paper mainly studies the servo control system of the spindle rotating ultrasonic vibration assisted EDM.First,the mechanism of EDM was studied,mainly from three aspects: the formation and expansion of discharge channels,the removal mechanism of materials,and the deionization of the inter-electrode medium.Then the influence of rotating ultrasonic vibration on EDM is analyzed,mainly from the aspects of discharge gap,particle energy,ejection and material removal.In order to improve the machining accuracy,on the basis of the EDM machine tool currently developed by the research group,according to the structural characteristics of the machine tool,the errors generated by the main moving parts of the machine tool are analyzed,and the structural relationship is described by the multi-body system theory to homogeneous coordinates The transformation method derives the geometric error model.Under the requirement of ensuring the overall accuracy,an optimization function is established to minimize the geometric error-cost and maximize the geometric error-reliability.The ISGA and MATLAB integration method using NSGA-II algorithm was used for optimization analysis,which showed that the model can reduce costs and improve reliability on the premise of ensuring accuracy.In order to design an efficient servo control system,a mathematical model of the control system position loop,speed loop,current loop,machining gap and other links was established,and simulation was performed using Simulink in MATLAB.The classic PID control algorithm is difficult to deal with the complex changes of the machining gap.Therefore,this paper designs a PID adaptive adjustment controller based on BP neural network,and uses Simulink in MATLAB for simulation analysis.Using C ++ as the development language,IMAC400 motion control card is developed for the second time.The human-computer interaction interface is designed,and the four modules of status monitoring module,motion control module,program management module and online instruction module are mainly developed.A BP-PID controller is designed to control the EDM gap in real time,the average gap voltage detected by the gap voltage detection circuit is used as an input parameter,and the discharge gap is controlled by the established EDM gap model.The simulation results show that the designed BP-PID controller has good rapidity and stability,and the servo control system has ideal self-adjustment and self-adaptation capability.