Application of fuzzy logic to spatial thermal control in fusion welding

For constant current arc welding processes, the arc voltage signal variations that occur as a function of changes in the contact-tube-to-work distance (CTWD) can be used to automatically control a welding system with respect to bead placement and proper sidewall fusion. However, the arc voltage signals are uncertain and noisy because of many external disturbances. In this work, the theory of fuzzy sets was used as a general framework to interpret the uncertain are signals and provide logic for control. The fuzzy logic controller weld joint tracking system was implemented and tested with pulsed gas metal arc welds (P-GMAW) under a variety of conditions. The goal was to obtain quick and accurate response to tracking errors in the presence of disturbances. A series of experiments were conducted to evaluate the performance of the fuzzy logic controller. The experimental results show that the fuzzy logic controller was found to be suitable for these purposes and better than methods based on signal averaging and bipolar decision levels under these criteria.