Research On Arc Length Control And Simulation Of Digital Pulsed MIG Welding Power Source

Pulsed MIG welding as one kind of GMAW(Gas Metal Arc Welding) is with its welding current changes periodically, which can control pulsed energy effectively through adjusting peak current and peak time. It is developed widely for its good direction transition, less splashed material and nice figure. So research on the Pulsed MIG welding power source becomes more and more important.In the paper,Pulsed MIG welding power source system is designed based on DSP. The system control the welding process based on TMS320F240 of high performance with high integrated level special chip, and use many anti-interference and protection measures. So the system has high control accuracy and high stabilization accuracy in base current and peak current. Meanwhile the system is with high flexibility and high superiority of digital control through modifying the software. And based on traditional arc length control means, the paper put forward to the double closed loop control: inner loop is current loop which controls peak current and base current precisely to assure stable droplet transform; outer loop is voltage loop which controls base time to assure arc length adjustment quickly in external disturbance through welding voltage feedback to reach arc length stable.The present models of Pulsed MIG welding system based on input signals of peak current, peak time, base current and base time with fixed frequency and magnitude, not taking into account real-time control in welding voltage, so the simulation results is not consistent well with the experimental one. The paper established the dynamic simulation model of Pulsed MIG welding power source-arc system based on S-function of Matlab/Simulink extension tool. The results of simulation display good dynamic performance in step change.