Research on adaptive control of medium frequency DC resistance spot welding

The electrode wear and spot area change in the continuous welding process of medium frequency DC resistance spot welding lead to unstable welding current, spatter and nugget diameter reduction. A fuzzy PI adaptive control scheme is studied and designed. In each control cycle, the dynamic resistance change rate and the instantaneous maximum welding power are used as the inputs of the fuzzy controller. Through the current closed-loop feedback control, the output of the fuzzy PI controller is used to control the switch on and off of the full bridge inverter, so as to maintain the constant welding current. Simulation and experimental results show that the scheme has the advantages of small ripple, small overshoot, high control precision, fast response speed and better welding quality than the traditional PID control.