Discrete-time Sliding Mode Control of GMAW Systems using Infrequent Output Measurements

Gas metal arc welding (GMAW) is the most popular industrial welding process today, preferred for its versatility, speed and relative ease of adapting to robotic automation. This process has been used extensively by many industrial environments especially, the automobile industry. The advantages of automated welding process with feedback controllers include increased productivity, consistency in welding quality, as well as health and safety benefits for the welder. This paper proposes a discrete time sliding mode controller, a highly robust controller, to control the welding current and arc voltage of a GMAW system using output feedback. The concept of multirate output feedback technique, with infrequent output measurements has been employed to design the robust controller. A linear multi input multi output (MIMO) system model has been considered here for the design. Since the proposed algorithm is based on output feedback, it is more practical in comparison to any state feedback based control algorithms. The performance of the controller is analyzed in the presence of model parameter uncertainties and the simulation results prove the efficiency of the controller proposed.