Abstract：[Objective] Accurate weld seam recognition and automatic tracking control are crucial for ensuring the welding quality and operational efficiency of crawling robots. To achieve the efficient and automatic tracking of curved surface welds on large structural components, this work proposes a crawling robot bidirectional automatic tracking technology based on a single laser sensor and an adaptive weight welding gun cascade control method. [Methods] A kinematic model was established for a crawling robot. The methods for estimating distance deviation between the laser system and the weld seam and correcting the angle between the robot and the weld seam were analyzed. By dynamically adjusting the position of the crawling robot with respect to the weld seam, the robot achieved bidirectional automatic tracking along the weld seam. Based on the welding process parameters and weld position information, the welding gun posture and end position were determined. The motion displacement value of the welding gun transmission joint was obtained by solving the inverse kinematics model of the actuator, and the joint motor was adjusted based on the motion displacement value for real-time welding gun calibration. [Results] The influence of the distance between the laser system and the center of the robot on the straight weld path tracking was simulated and analyzed. Distances between 35 and 50 cm enabled rapid tracking of the weld seam by the laser system and center of the robot. The initial distance deviation had a small impact on the deviation between the laser system and the weld seam but has a significant impact on the angle correction between the robot and the weld seam. The stability conditions of the cascade control system were analyzed, and the bidirectional tracking performance of the robot along the weld seam was tested at the 5G and 6G welding positions. The distance deviation curve between the laser system and the weld seam during the tracking process and the angle correction curve between the robot and the weld seam were obtained. The distance deviation between the laser system and the weld seam was less than 2 cm, and the angle correction between the robot and the weld seam was approximately 1°. [Conclusions] To ensure the stability of the cascade control system, the distance deviation between the laser system and the weld seam should be converted to the distance deviation of the robot tail for proportion integration differentiation (PID) input. The crawling robot motion control system satisfies the bidirectional automatic tracking along the weld seam in the 5G and 6G test scenarios, and the system has accurate welding gun positioning capability. Prealignment of the weld should be done before the welding operation of the crawling robot to further ensure operating stability.
冯消冰, 郑军, 杨尚贤, 潘百蛙. 面向大型结构件焊接的爬行机器人视觉跟踪控制[J]. 清华大学学报（自然科学版）, 2025, 65(5): 867-881.
FENG Xiaobing, ZHENG Jun, YANG Shangxian, PAN Baiwa. Visual tracking control of a crawling robot for welding large structural components. Journal of Tsinghua University(Science and Technology), 2025, 65(5): 867-881.
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2025, Vol. 65 
