Neurofuzzy model-based predictive control of weld fusion zone geometry

A closed-loop system is developed to control the weld fusion which is specified by the topside and back-side bead widths of the weld pool. Because in many applications only a top-side sensor is allowed which is attached to and moves with the welding torch, an image processing algorithm and neurofuzzy model have been incorporated to measure and estimate the top-side and back-side bead widths based on an advanced top-side vision sensor. The welding current and speed are selected as the control variables. It is found that the correlation between any output and input depends on the value of another input. This cross-coupling implies that a non-linearity exists in the process being controlled. A neurofuzzy model is used to model this non-linear dynamic process. Based on the dynamic fuzzy model, a predictive control system has been developed to control the welding process. Experiments confirmed that the developed control system is effective in achieving the desired fusion state despite the different disturbances.