Research On Control System And Self-Adjusting Pulse Power Supply Of Connecting Rod Cutting Machine

The machining of engine connecting rod cracking groove is a key process in connecting rod cracking process.The research group proposed a bidirectional synchronous WEDM machining method and developed a connecting rod cutting groove machine.Aiming at the problems of low machining efficiency,large electrode wire loss and low integration of the machine tool,this thesis improves and optimizes the structure of the machine tool,and puts forward the control strategy of combining STM32 motion control system with FPGA selfadjusting pulse power supply.STM32 with superior performance is selected as the main control for motion control.The modular design method is used to complete the hardware circuit design.Free RTOS is used to manipulate the task scheduling mechanism of the system in software to improve the flexibility and real-time performance of each function task function.The self-tuning pulse power supply uses FPGA with high computing power as the main control.According to the current spark discharge state,FPGA dynamically adjusts the pulse width length to realize constant energy processing.At the same time,it inhibits the mutation of pulse discharge current and reduces the loss of electrode wire caused by instantaneous electrical stress.The main research contents are as follows :（1）Machine tool structure optimization.In view of the serious jitter of electrode wire and the short effective stroke of wire storage drum in the current machining process of machine tools,the structure optimization of wire walking tension mechanism and wire storage circulation mechanism was carried out,and the working fluid circulation system was rebuilt to ensure the good working condition of machine tools.（2）Motion control system design.The motion control board is designed based on STM32,which is mainly composed of auxiliary power supply module,minimum system module,input and output module and motor drive module.The Free RTOS real-time control system is transplanted to the software,and the task allocation and scheduling of each task function are carried out,so as to realize the communication with the touch screen of the host computer,the state control of the wire storage drum and the water supply pump,the drive control of the machining motor and the centering motor,and the development of the application function of the machine tool.（3）Design of self-adjusting pulse power supply.The self-tuning pulse power supply is developed based on FPGA.The pulse discharge state is detected in real time based on pulse width detection method.According to different spark discharge states,FPGA automatically adjusts pulse width and pulse length.Pulse power supply can realize open circuit automatic reduction of pulse frequency,equal energy discharge processing,inhibition of harmful pulse generation,short circuit burping protection and other functions.At the same time,the inductance with appropriate inductance is connected in series in the main circuit of the power supply to suppress the current mutation after discharge breakdown,and the rectangular current wave is transformed into a triangular wave to reduce the loss of the electrode wire caused by the discharge breakdown moment.（4）Process experiment verification.The safety and stability of machine tool control system are verified through process experiments.The feasibility and processing effect of selfadjusting pulse power supply are verified by using the factors of cracking groove width,processing efficiency and workpiece heat affected zone size as evaluation indexes.The optimal processing parameters are determined by orthogonal experiment,and the experimental analysis of wire loss is carried out under this parameter.