Semiclosed-loop motion control with robust weld bead tracking for a spiral seam weld beads grinding robot

Abstract

• A novel two-DOF platform for the seam weld beads grinding is designed. • A semiclosed-loop motion control method is proposed for accurate grinding. • Robust weld bead tracking improved the detection and grinding accuracy of welds. Grinding robots have been widely used in industrial manufacturing, but not in the production of large steel pipes. In this paper, a grinding robot is developed for the removal of the external and internal seam weld beads at the end of a spiral welded pipe. A two-degree-of-freedom linear motion platform is added to the end of a six-degree-of-freedom industrial robot to achieve high-precision grinding and to decouple the motions. A semiclosed-loop motion control method is proposed to control the position of the grinding mechanism under the spark spatter during grinding. Based on the identification method of weld bead feature points and the closed-loop control of position, the tracking method of seam weld beads is proposed to realize robust detection and grind planning. Two sets of experiments including tracking and grinding were carried out on both external and internal seam weld beads. The results show that the developed structure and proposed methods are effective and perform well. The grinding robot with the two-degree-of-freedom linear motion component makes the robot trajectory planning and decoupling control greatly convenient.