Study On Arc Stability Of Double-pulsed MIG Welding And Arc Length Intelligent Control

Arc stability plays crucial role in welding technology,which reflects in resistance to arc interruption and short-circuiting.However,the welding process involves complex physical and chemical changes,which will bring up strong interference and produce signal fluctuation and influence welding quality.It is significant to apply the arc-control algorithm to maintain the stability of the arc in the welding process for improving the welding quality and efficiency.This subject conducts research on arc stability and arc length intelligent control aiming on the problem that arc stability is easy to be interfered by external factors.Melt inert-gas welding(MIG)is a kind of wide-used welding technology,which has great advantages in improving welding efficiency,energy efficiency and weld bead formation.The proposal of double-pulsed MIG welding further improves heat input distribution and weld bead quality.Arc-control algorithm of this subject was established on the theory of pulsed MIG welding.The experimental platform was established with full-bridge inverter as the main circuit,with digital signal processer(DSP)as control center,following with auxiliary circuit including driving circuit,sampling circuit and fault-protection circuit.The welding performance of aluminum alloy was analyzed,and the experimental plan was planned preliminarily according to the characteristics of pulsed MIG welding.To verify the feasibility and effectiveness of control program,dynamic model of arc length was established to simulate the change of arc in the welding process.The real-time feedback of arc voltage would reduce the stability of the system and cause fluctuation,therefore the mean voltage was carried out as feedback to achieve arc length closed-loop control comparing with giving voltage.PID model was established taking average voltage and given voltage as input and wire feed speed(WFS)as output to conduct the arc length closed-loop control simulation.It is shown that giving voltage has significant impact on control effect.To predict appropriate giving voltage,support vector machine(SVM)model was analyzed and established.The experiments of arc length control algorithm were conduct on experimental platform,including pulsed MIG welding,double-pulsed MIG welding and pulsed MIG stepped welding.The influence of arc-control algorithm on weld bead formation was analyzed.The parameters of PID were tuned according experiment results.The error sources of the voltage and current signals collected in the test process were analyzed and eliminated.Arc stability was analyzed quantitatively and the impact of this control program on arc stability was revealed,which could be used to optimize the control model.SVM model was established based on existing experimental data,which could achieve intelligent arc length control.