A model-based error propagation and tolerance-aware framework for the on-orbit assembly of modular space trusses

Model-based systems engineering bridges the gap between terrestrial verification and on-orbit operational uncertainty for future ultra-large space infrastructures. On-Orbit Assembly (OOA) effectively overcomes traditional launch volume constraints. However, the inability of ground experiments to fully replicate stochastic in-orbit perturbations necessitates rigorous kinematic error modeling to guarantee assembly precision for modular space trusses. This paper proposes a tolerance-aware mechanism synthesis strategy to mitigate OOA errors directly at the hardware level. First, a quasi-static stochastic error propagation model is constructed as the theoretical foundation, explicitly quantifying the evolution from local geometric uncertainties to the global spatial error envelope. Then, guided by sensitivity analysis identifying angular deviation as the dominant factor, a boundary-driven compliance design strategy is developed for OOA. This strategy parameterizes the physical interface to intercept recursive error transmission, effectively offloading the burden of real-time correction to optimized mechanical compliance. Finally, full-scale OOA prototype experiments validate this theoretical-to-physical mapping. Results demonstrate that the OOA system achieves deterministic high-precision assembly (global straightness error ≤ 1 mm/m) under stochastic disturbances without high-bandwidth sensor feedback. By translating theoretical kinematic bounds into physical compliance, this study reduces the dependence on feedback-intensive active compensation under the modeled assembly conditions. Ultimately, it offers a deterministic and highly robust hardware solution for future space infrastructures.