Stability Analysis And Control Of MIG Welding Process With Double Arc Pulses

With the enactment of the national " the thirteenth Five-Year Plan ",and raise the concept of “industrial 4.0”,“Made in China 2025”,the concept of green development is increasingly mentioned, the research and application of lightweight alloy material in the industrial field more and more widely, so there is an increasingly welding demand between the light alloys. Due to the special properties of the alloy plate, solving the contradiction between the heat input and welding process stability has become more meaningful. Dual-arc pulsed MIG welding because of its low heat input and high welding efficiency has been widely used in the welding field. This welding method will produce the problems of coupling arc instability due its pulse constant current power supply, so the stability of dual-arc pulsed MIG welding was studied in this paper, and the main research contents include the following aspects.Modeling and simulating for welding arc length and droplet transfer process by MATLAB/Simulink, analyzing of the effect of welding process stability in the case of sudden external disturbance, and the influence of different sizes of current parameters for droplet transition rule. The results showed that, under external disturbance, the controller can quickly adjust the wire feeding speed make arc in a stable state, when the main circuit current and bypass current is too small to make stable droplet transfer proceeds, you can adjust the pulse current parameters like the peak current is increased while reducing the base current,or decreasing the duty cycle while increasing the peak current, geting more stable droplet transfer process in the case of the average current and the bypass average current of the main road is constant.The signal collection and data storage system was built based on LabVIEW, and the test platform was designed for dual-arc pulsed MIG welding, the welding electrical signals, video signal in the process of welding can be collected, stored and displayed,and displayed and output of analog signals, digital signals.By using the probability density method, approximate entropy analysis method to judge the stability of welding process based on electrical signal acquired from the welding process and an evaluation system for stability of welding process was established. By analyzing the data obtained from the test process, the test results showed that the welding process more stable, approximate entropy of arc voltage signal is smaller, the ratio of probability density peak is smaller. On the contrary, the welding process more unstable, approximate entropy of arc voltage signal is larger, the ratio of probability density peak is larger too.On the basis of the simulation results, this paper proposed control scheme based on the arc voltage and the visual feedback, using the arc voltage feedback and visual feedback to control the wire feeding speed in real time, to achieve the purpose of controling arc stability indirectly.In the meanwhile, this paper designed an incremental PID controller. Then the stability test was carried out based on control scheme and controller, and the control results are analyzed. The test results showed that the controller can eliminate the influence caused by outside interference, and the dual-arc pulsed MIG welding process is always in a stable state. The welding test can get good welding appearances show that the control scheme has got a good performance.