Adaptive voltage control in fusion arc welding

Automatic voltage control (AVC) systems are commonly used in gas tungsten arc welding (GTAW) to maintain constant arc length. Although AVCs usually perform adequately in most operating circumstances, there are conditions during which the traditional systems cause problems because the arc voltage-to-arc length gain, K_arc, a feedforward gain, is not constant but varies with the nominal values of the arc current and voltage. Thus, an AVC that has a fixed voltage set point will not maintain a fixed arc length if the arc current changes. In this paper an adaptive controller is introduced that is capable of “identifying” the arc sensitivity characteristic and adjusting the controller in real time for optimum response without any a priori knowledge of the current/gain relationship