Stability Control of Weld Formation in Variable Polarity Plasma Arc Welding

本项目将研究一种新的方法来调节施加到工件上的热量和电弧力，作为变极性等离子弧焊中锁孔稳定性闭环控制的基础。机器视觉系统将用于从工件正面捕获清晰的锁孔图像，并将这些图像与焊缝形成的动态相关联。建立了基于神经网络模型的锁孔尺寸与送丝速度、焊接电流等控制变量的闭环控制系统，并进行了试验。变极性等离子弧焊是一种理想的铝合金电弧焊工艺。它的特点是无气孔，在3mm至25mm厚段的单道中进行全透焊，成本相对较低。目前，焊缝成形的稳定性仍然依赖于开环控制。由于存在意想不到的干扰，该过程的关键特性可能会丢失。对于关键产品的制造来说，这是不可接受的，因为焊接精度必须在第一次试验中达到。预计该项目将推动等离子弧焊技术的发展，并对国防、航空、汽车、船舶等行业的高质量关键铝合金产品的生产产生重大影响。

This project will investigate a novel approach in regulating the heat and arc force applied to the workpiece as a basis for closed-loop control of the keyhole stability in variable polarity plasma arc welding. A machine vision system will be used to capture clear keyhole images from the front side of a workpiece and correlate these images with the dynamics of weld formation. A closed-loop control system based on a neural network model that relates the keyhole size with control variables such as wire feeding speed and welding current was established and tested. Variable polarity plasma arc welding is an ideal arc welding process for aluminum alloys. It features gas pore-free, full-penetration weld in a single pass of thick sections ranging from 3 mm to 25 mm, and relatively low cost. Currently, the stability of weld formation is still dependent on open-loop control. The critical features of this process can be lost due to the existence of unexpected interference. This is unacceptable for the fabrication of key products where welding accuracy must be achieved in the first trail. The project is expected to advance the plasma arc welding technology and result in significant impact on the production of high-quality key aluminum alloy products in the defense, avioanics, automobile, and shipbuilding industries.