Dynamic Property Estimation and Control of Large Space Structures During In-Space Assembly

Assembling a large space structure (LSS) in space using numerous small parts requires various types of joints and fasteners, which can pose challenges to the structure's dynamic properties. Large space structures are typically designed based on predefined dynamic characteristics- such as natural frequencies, damping ratios, and mode shapes- according to their operational conditions. However, achieving these intended dynamic properties in the final assembled structure is often difficult due to the complex mechanisms involved in joint contact interfaces. In other words, the presence of joints alters the structure's dynamic properties, causing deviations from the design-phase assumptions. The more joints a structure has, the greater the deviation from the originally anticipated dynamic properties. Due to the complexity of joint interfaces, numerical simulations often fail to accurately predict the final dynamic properties of an assembled structure- especially when it contains many joints. To address this issue, current state-of-the-art methods rely on measurement techniques, such as experimental modal analysis, to estimate the actual dynamic properties. Conducting modal testing on a fully assembled structure in space presents two main challenges. First, comprehensive modal testing requires attaching numerous sensors at different points on the structure, which is impractical in space. Second, even if feasible, joint dynamics and contact uncertainties may cause measured dynamic properties to differ from as-designed values. A new approach is needed to measure the dynamic properties of the structure at various assembly stages with minimal effort. This would enable forecasting the final dynamic properties of the fully assembled structure, detecting any deviations from the pre-set design properties, and finding mitigations during assembly to ensure the final structure matches the design specifications.