Research on an Assembly Method for Large Irregular Thin-Walled Components Based on a Six-Axis Industrial Robot

Abstract

To address the challenges of low stiffness, high deformability, weak positioning references, and the coexistence of multiple constraint bases during the assembly of large and complex thin-walled components, an automated assembly method based on a six-axis industrial robot integrated with binocular vision is proposed, enabling high-precision and coordinated docking in the assembly process of large irregular thin-walled parts. First, an error propagation analysis is conducted for the irregular thin-walled components, and the maximum allowable deviation domain in both translational and rotational spaces that ensures successful assembly is derived. On this basis, a staged assembly strategy following the principle of “initial positioning, primary docking, and secondary constraint” is proposed. The robot first uses binocular vision to estimate the pose deviation of thin-walled part 1 with respect to the locating pins on the fixed base and plans the target TCP pose to achieve pin–hole alignment. Subsequently, the tongue-and-groove (rabbet) mating between thin-walled parts 1 and 2 is performed. Finally, thin-walled part 2 is guided by vision to align with the locating pins on the movable base, completing secondary positioning and constraint, thereby realizing a multi-datum closed-loop assembly. An adaptive pose-error compensation mechanism is incorporated into the assembly process, enabling the robot to satisfy geometric assembly constraints even in the presence of initial fixturing errors and elastic deformations of the thin-walled components. The experimental results demonstrate that, under the combined constraints of binocular reconstruction errors and the robot’s repeatability, the proposed method can reliably achieve multi-datum automatic assembly of large-scale irregular thin-walled components. It significantly reduces the reliance on manual alignment and improves both the assembly success rate and consistency, providing an effective technical pathway for the robotic assembly of large flexible structures.