Arc Sensor Based Real-time Monitoring For Robotic CO₂ Welding

There are many kinds of disturbing factors during robotic CO₂ welding, for example, the machining and fitting errors of the workpiece, the thermal distortion of the workpiece and the change of arc length during welding process and so on. These factors have important effects on the weld quality. If the disturbing factors are detected in real time, on-line monitoring of weld quality can be realized through adjusting the welding process parameters in order to avoid the defective welds and assure high weld quality. Thus, it has big economic benefit and engineering practicality.Arc welding process is a very complicated process with many interacting factors mixed together, so the transient state of welding process is related to many parameters. However, when the welding conditions change, some parameters change clearly while other parameters do not. So how to extract obvious feature information from the process parameters, which describes different welding conditions, is very important to realize the real-time monitoring. The weld quality under different welding conditions is related to the welding parameters which are inherent electrical parameters in the welding process itself, i.e. welding current, welding voltage, arc sound, short-circuiting frequency and so on. It is well known that using arc sensors to detect the electrical parameters (welding voltage and welding current) is very economical, practical and reliable. In this study, robotic CO2 welding experiments for butt joint and T joint are carried out. Arc sensor is used to measure and process the electrical parameters during the welding process. At the middle part of the welding seam, a notch is intentionally machined. This sudden increased gap along the welding seam is used to simulate the fitting errors of the joint in practical production. The real-time acquiring and processing system of the measured signals are developed based on...