Intelligent Thermal Control of Resistance Welding of Fiberglass Laminates for Automated Manufacturing

A novel approach to automate large-scale resistance welding of thermoplastic composite materials, based on real-time temperature control, is presented in this paper. Resistance welding, a kind of fusion bonding, is a widespread alternative process to mechanical fastening and adhesive bonding in joining thermoplastic composites. A second-order linear observer was identified to estimate the online temperature at the weld interface. A fuzzy logic controller (FLC) was designed to control the weld temperature using both process voltage and linear weld speed as the control inputs and using the temperature estimate as the feedback signal. The FLC was implemented in real time with the experimental setup using an industrial robot—KUKA KR 210. The closed-loop controller was capable of successfully controlling the weld temperature within 10% of the desired temperature, resulting in superior weld quality when compared to open-loop results. The results thus affirm the suitability of the control strategy for large-scale automated welding.