Practical SOSM Controller Design for Short-Circuit Mode of Transfer in GMAW using Two Sliding Surfaces

Abstract

Abstract GMAW is a complete arc welding process of creating all types of metal joints of desirable quality involving virtually all metals of any thickness in any position. However, in doing so, there is continuous shift in operating point of arc and/or in arc characteristics leading to wide range parametric variations and disturbances injected into the system. Moreover, the process involves multiple dynamical events such as in arc characteristics, melting rate, dynamics of arc length and droplet transfer mechanism etc. for creating eventual welding joints where each event suffers from non-linearity as well as parametric variations. Control of such process optimally, though complex, but is essentially required as welding joints are made through indirect control of operating point of arc where for certain events feedback signals are difficult to get. Sliding mode control (SMC) concepts are considered as robust and have the ability to reject external disturbances and generate parametric insensitive response characteristics. This article, using already established control laws, explores the ability of SOSM in GMAW with robust performance characteristics. Implementation along with results of popular short-circuit mode of transfer is presented here.