Arc stability estimation and fuzzy control for arc stabilisation in short circuit transfer mode of CO2 arc welding

Abstract

The purpose of the present work is to evaluate and control the arc stability in the short circuit transfer mode of CO₂ arc welding. The arc stability was investigated under different welding conditions, using the arc stability index developed by Mita et al., and a fuzzy control algorithm was developed. The correct parameters for the subset of fuzzy input/output variables were determined from the experimental results using a regression model. Simulations using the fuzzy controller with the selected parameters were performed. Application of the arc stability control in real welding showed convergent performance, similar to the result of the simulations. Also, when a step change in contact tip to work distance (CTWD) was introduced, the arc was initially unstable; however, it became stable within 6 s. Furthermore, when the CTWD was varied continuously, a stable arc was maintained even under conditions where the CTWD increased.