Closed-loop control of thin plate TIG butt welding with reserved gap based on fusion hole

In the reserved gap TIG welding process for thin plates, the morphology of the fusion hole is closely related to the weld penetration. To ensure penetration and obtain excellent welded joints, it is essential to control the size of the fusion hole during the welding process to develop reliable welding automation. In this paper, an active disturbance rejection control (ADRC) algorithm is designed for real-time welding process control. Based on the clear fusion hole images, an image processing algorithm effectively extracts the topside fusion hole width (FWt). By analyzing the dynamic behavior of the fusion hole under different welding parameters, it is found that the topside fusion hole width is most sensitive to wire feeding speed. Wire feeding speed is selected as the control variable for the closed-loop control system. The system identification of the welding system is carried out by giving a step signal of wire feeding speed. At the same time, the effect of the ADRC algorithm and the PID algorithm for controlling the topside fusion hole width with a reserved gap is compared. Experimental results show that ADRC can better control the topside fusion hole width and achieve good weld penetration than the PID algorithm. The ADRC can control the topside fusion hole width to within 2.5 mm ± 0.53 mm.