Robust sensing and control of the weld pool surface

Gas tungsten arc welding is the primary process for precision joining. To develop a control system for this process, a novel sensor is proposed to measure the depth of the weld pool surface using a non-transferred arc. A flat surface is periodically established to provide a real-time reference. The main-arc-on period is selected as the system's input. Because of possible large variations/ranges in manufacturing conditions, an interval model control algorithm with updated intervals is adopted. To demonstrate the use of the proposed sensor and control algorithm, closed-loop experiments under different variations have been conducted. Circumferential butt welding of steel pipe has also been included as an application example.