Control method analysis based on welding process

The fundamental difficulty of realizing pulsed GTAW automation and intellectualization is to detect and control the weld pool´s dynamic behavior, such as weld pool´s geometry parameters, weld penetration and weld beam forming. Arc welding is a complex process which involves interactions of materials, metallurgy and physical chemistry. Weld quality (weld beam forming, microstructures and properties of joint) is related to the multiple parameters of welding technology, these parameters are related, coupled in the dynamic process and overlapped in the static process. The dynamic process of the weld pool is a high complex object with strong nonlinearity, multi-variable coupling and a mount of stochastic and uncertain factors, and this makes it very difficult to control the weld pool´s dynamic changes, and to control the weld pool´s width, penetration and weld beam forming. To solve the problem by using of classic and modern control theory will face the challenges both on the theory and application. In this paper, the PID control law is designed for the two-order welding pool model obtained by identification and the Smith predictor is adopted to compensate time-delay at the start of welding. Tuning method of PID controler based on optimal transfer function is presented as well. Test shows that the Smith predictor can compensate time-delay well.