Interval model based control of gas metal arc welding

A control system is developed to control pulsed gas metal arc welding process. To guarantee the desired metal transfer mode, i.e., one drop per pulse, the welding current is switched from the peak level to the background level so that an oscillation of the droplet is excited up. When the droplet moves downwards, the welding current is switched back to the peak level. The combination of the downward momentum of the oscillating droplet and the increased electromagnetic force guarantees that the droplet be detached. Instead of the duration of the background current, the waveform of the welding current is adjusted to control the melting rate of the electrode wire so that the metal transfer frequency can keep constant during welding. To simplify the control system, the ranges of the welding operational parameters are used to quantify the uncertainty in the dynamic model of the welding process. Based on the uncertainty range of the dynamic model, a single control algorithm has been developed to handle different operational parameters. Experiments confirmed effectiveness of the developed system