A novel on-orbit assembly system of truss units and lightweight design of MTUA robot based on topological approximation

The growing construction of space solar power stations increases demand for truss unit assembly systems, but current systems using collaborative robots for both individual truss building and multi unit on orbit assembly face challenges. These include unclear component sources that hamper tracking and replication, robots moving back and forth that reduces efficiency, and inconsistent component robot interactions that raise control needs while lowering reliability. To address these issues, this paper proposes a new on-orbit assembly system of truss units. It separates individual truss construction from multi unit assembly, assigns each task to dedicated robots for a pipeline process, adopts plug in locking for rods and joints with standardized robot end effector interaction, and designs two new robots with preliminary qualitative function and performance evaluation. Meanwhile, to solve low efficiency in robot lightweight design caused by frequent topological optimization and poor manufacturability when building stiffness weight mapping models, a lightweight method based on boundary specification and topological approximation is proposed. It enables one time rapid generation of the same component’s topological structure under identical mass retention ratio and stress conditions, eliminating repeated iterations in traditional topological optimization and manufacturability post processing. Verified via MTUA (multiple truss unit assembly) robot case study, results show only three topological optimizations are needed per robot connecting rod type to build stiffness mass mapping models, the structural material distribution is more reasonable and free of burrs, and the robot mass is reduced by 17.4% while meeting stiffness requirements. This research provides references for truss unit on orbit assembly robot configuration design and a foundation for similar robots’ lightweight design.