Low-Impact Contact between Electrodes of Pneumatic Servo Welding Gun Using Segmented Sliding-Mode Control

In automobile manufacturing, improving the quality and efficiency of resistance spot welding and avoiding the damage caused by excessive impact force are of significance. This paper proposes a low-impact contact evaluation method for the pneumatic servo welding gun and the concept of optimal cushioning distance. A segmented sliding-mode control method is used. By analyzing the electrode contact mechanism, the gradual progress of spot welding is controlled by the method proposed in this paper. The cushioning effects of PID control, sliding-mode variable structure control, and segmented sliding-mode variable structure control are compared by experiments. The results show that the contact force during the 0.05 s after the electrode contact is not more than 10% of the welding force using sliding-mode control, approximately 0.2 kN, which satisfies the proposed low-impact contact requirements.