Study on arc sensor algorithm for weld seam tracking in gas metal arc welding of butt joints

The positional accuracy requirement of the welding torch with respect to the weld seam is the major impediment in arc welding robot applications. The weld seam tracking sensor is essential to improve the flexibility of arc welding robot applications. In this study, an arc sensor which utilizes the electrical signal obtained from the welding arc itself was developed for gas metal arc welding of butt joints. In order to overcome the fluctuation in the welding current signal, the current signal was fitted to a curve which is inversely proportional to the trace of the tip-to-workpiece distance by using the quadratic curve-fitting method. The availability of the curve-fitted welding current signal was investigated and the seam tracking results of the system that uses the curve-fitting method were compared with the ones of another system that controls the moving speed of the welding torch in the height direction.