Abstract: Aiming at the shortcomings of traditional pipeline welding robots such as long start-up time, slow speed response, insensitive speed change, and slow climbing speed, and the problem of variable parameters and multiple disturbances during the orbital motion of the welding robot, an improved FSMC ( Fuzzy Sliding Mode Control) is proposed. The discontinuous intelligent control method combined with fuzzy PI(Proportional Integral) realizes double closed loop control. The inner loop is the current loop control based on fuzzy PI, and the outer loop is the speed loop control based on the improved fuzzy sliding mode algorithm. This kind of control effectively reduces the external disturbance of the orbital motion system, and increases the response speed and robustness of the system. For the speed setting and excessive speed change under variable load, variable speed, and variable welding mode, a follow-up is proposed. The system adopts a tracking and setting system of subregional fine target speed, which effectively divides the range of different welding methods of the welding robot and the precise feedback mechanism. After simulation and experimental testing, the entire control system has the functions of parameter self-tuning and self-adjustment during the welding process. The walking robot has smooth speed transition, fast speed response, good robustness, and stable and reliable pipeline all-position welding.

Key words: all-position welding robot, orbital motion, fuzzy sliding mode control (FSMC), fuzzy proportional integral(PI), follow-up system