A novel control algorithm for weld pool control

Purpose – Quality control of arc welding process is the key component in robotic welding system. The purpose of this paper is to address vision‐sensing technology and model‐free adaptive control (MFC) of weld pool size during automatic arc welding system. Design/methodology/approach – The shape and size parameters for the weld pool are used to describe the weld pool geometry, which is specified by the backside weld width. The welding current and wire‐feeding speed are selected as the control variable, and the backside width of weld pool is selected as the controlled variable. To achieve the goal of full penetration and fine weld seam formation, a multiple input single output (MISO) MFC is designed for control of the backside pool width. Findings – The research findings show that it is feasible to develop such a MISO MFC of weld pool size, which is independent on mathematic model of weld pool dynamics. And the control algorithm is simple to use and has a minimal computational burden. Research limitations/implications – This is a work in progress. The controlled process results are mainly influenced by the period of competing control algorithm and image processing, which could be improved by the hardware and enhancing computation speed. The closed‐loop control is a two inputs‐one output system. Thus, the means by which the multiple input multiple output (MIMO) control method is applied to weld pool dynamics is work for the future. Practical implications – The control system is applicable to automatic gas tungsten arc welding (GTAW). Originality/value – The MISO MFC has been set up for automatic GTAW to overcome the nonlinear and uncertainty of GTAW process, in which two welding parameters can be adjusted simultaneously. In addition, this controller is independent on welding pool dynamic model.