摘要：AbstractThis paper presents a new approach to include thrust and mass uncertainties in the worst case loads analysis of launch vehicles during the atmospheric ascend. The analysis is based on recent results on the worst case gain computation of uncertain, finite time horizon linear time varying (LTV) systems. Representing the uncertainties as integral quadratic constraints, the worst case gain condition can be formulated as a parameterized Riccati differential equation (RDE). While this framework allows including certain parametric uncertainties, e.g., aerodynamic uncertainties, it is not straightforward to include thrust uncertainty in the launcher analysis. The reason being that there is an inherent coupling between the thrust and the mass of the launcher, such that any uncertainty in the thrust also effects the mass of the launcher. Further, both thrust and mass have a direct effect on the launch trajectory, whereas the LTV model is obtained via linearization along the nominal trajectory. Hence, it is no longer valid, for large perturbations of the launch trajectory. The former issue is resolved in the paper by including a mass state in the launcher model and treating the thrust uncertainty as an external disturbance. For the latter problem it is proposed to cover a set of launch trajectories with a dynamic uncertainty. Using the robust LTV framework, a worst case aerodynamic loads analysis under thrust uncertainty and wind disturbances is performed in this paper. The results are compared to a Monte Carlo simulation on a high fidelity nonlinear launcher model.
关键词：KeywordsRobustness AnalysisUncertain Linear SystemsSpace Vehicles
