A digital-twin-enabled precision pre-welding assembly method for complex pipelines

Complex bent pipes and tees are key connection components in aerospace fluid delivery systems, and their pre-welding assembly quality directly affects system reliability and service safety. To address the limitations of conventional assembly methods in complex pipeline docking, including missing measurement references, deformation-prone thin-walled structures, inaccurate alignment in geometrically discontinuous regions, and low reconfiguration efficiency due to dedicated fixtures, this paper proposes a digital-twin-enabled multi-robot collaborative precision pre-welding assembly method for complex pipelines. To solve the problem of weak physical measurement references, a reconfigurable multi-robot assembly platform equipped with an optical tracking system and PTF with reflective markers is developed. To establish an accurate virtual representation of complex pipe components, a high-fidelity digital twin modeling module is constructed based on measured point-cloud data and geometric constraints. To achieve consistent pose interaction between the physical and virtual spaces, a visual tracking and pose-mapping method based on distributed reflective markers on PTF is introduced. On this basis, trajectory planning with collision-risk screening and closed-loop pose compensation are integrated to realize virtual-real coupled assembly control. Experimental results show that the proposed method achieves high-precision pre-welding docking of complex pipelines, with final docking position error within 0.13 mm and docking angle error within 0.24°. Compared with conventional mold-dependent methods, the proposed reconfigurable assembly mode supports direct adaptation to different product types without extra fixture redesign and manufacturing, significantly reducing preparation and changeover time while improving flexibility and engineering efficiency.