Design Of Power Supply System For Electron Beam Welding Machine And Research On Control Optimization

Electron beam welding is a welding method with high efficiency and high energy density,which has been continuously developed and improved in recent years.At present,it has played an important role in aerospace and other industries.Especially in the processing of large and complex components,it shows its own advantages compared with other welding methods.The deformation zone produced by electron beam welding in the welding process is small,and the operation process is easy to control.It not only has strong penetration,but also is suitable for the welding of refractory metals and dissimilar metals.As a key part of electron beam welding machine,the working performance of power supply system will directly affect the quality of electron beam welding.The in-depth study of the power supply system can not only improve its stability and efficiency,but also further promote and develop the electron beam welding technology.This dissertation researches and designs a set of electron beam welding machine power supply system based on DSP control.The power supply system includes the main circuit and the control circuit.The main circuit is divided into two parts: high-voltage power supply and filament power supply.The high-voltage power supply provides 10 k V high voltage during the working process to form a high-voltage electric field,and the filament power supply outputs20 A current to heat the filament and overflow electrons to form an electron beam in the high-voltage electric field.This dissertation designs the main circuit topologies of high-voltage power supply and filament power supply,and mainly studies the high-voltage power supply.The main circuit includes low-voltage inverter circuit,high-voltage boost circuit and silicon stack rectifier and filter circuit.The low-voltage inverter circuit adjusts and inverts the 100 V DC power through the step-down conversion circuit and the LCC full-bridge inverter circuit,and outputs the AC power that can be quickly adjusted,then boosts the voltage through the high-voltage booster circuit,and finally supplies 10 k V DC high voltage to the electron gun through the silicon stack rectifier filter circuit.In this dissertation,the parameters of the main circuit of high voltage power supply and filament power supply are calculated and the models of required components are selected based on the actual situation.The power supply control system takes DSP as the control core,adopts BUCK slow loop control and LCC inverter fast loop control,and adjusts the voltage by changing duty cycle and phase shift control respectively.In order to study the loop response optimization problem,the simulation model is established on the MATLAB Simulink platform.According to the characteristics of fuzzy control,PID control and fuzzy PID control,the three control modes are designed respectively.On this basis,the PID controller,fuzzy controller and fuzzy PID controller are continuously debugged.The results show the effectiveness of the three control algorithms.Finally,fuzzy PID control is adopted to achieve smaller voltage overshoot and faster response speed,with good dynamic performance.In the control system,the hardware circuits such as drive circuit,signal acquisition circuit and protection circuit are mainly designed and made into the board.The control logic and signal acquisition,fuzzy PID control,PWM drive are analyzed in detail connecting with the control strategy and control technology,and completed the preparation of the main control program and subprogram.The combined test results of software and hardware prove that the control system has good performance and meets the functional requirements of the system.After the simulation verification,the main circuit,control circuit and protection circuit of the power supply system are built according to the design,and a physical prototype of the principle is completed.The power supply system has carried out no-load test,connection simulation load test and connection electron gun test.After analyzing the feedback data measured in the test process and the collected voltage and current waveform,the results show that the designed power supply system and control optimization scheme of electron beam welding machine have reached the expected design indexes and meet the working requirements of electron beam welding machine.