On current control method for single-phase AC resistance spot welding

The paper deals with the constant current control for single-phase AC resistance spot welding (RSW), which is the most commonly used control strategy in modern welding industry. The process of RSW is nonlinear and time-varying. After analyzing the working principle and nonlinear properties of RSW, a mathematical relation between input and output variables for constant current control is developed. A PI controller, which is used to regulate the desired current used in the mathematical relation, is employed to improve the performance. The final experimental results showed the performance obtained by new controller was better than that by a fine-tuned PID controller.