Output-feedback control of arc length for manual gas metal arc welding with higher order sliding modes

This paper explores the design of a non-linear output-feedback control technique based on the higher order sliding mode approach for an uncertain manual gas metal arc welding (GMAW) system. To cope with the large uncertainties affecting the dynamics of the system and the rapid changes in contact tip to workpiece distance (CT) caused by the uneven movement of the welding gun by the operator, an output-feedback control system has been developed with an observer-controller that combines the second order sliding mode (SOSM) controllers and an SOSM differentiator. A non-linear single input single output (SISO) system model has been considered here for the design. Thus, the robust output feedback controller with observer is proposed here, which has been compared with an earlier proposed classical feedback linearisation approach. Simulation results are presented and discussed in order to establish a framework for comparison.