Optimal Formation Flight Control Using Coupled Inter-Spacecraft Dynamics

Abstract

The increasing number of formation ight space missions proposed by the scienti c community for the near future has led many researchers to the study, development and implementation of optimal control systems applied to a multi-spacecraft system. The approaches taken may vary among authors, but it is generally agreed upon that having independent controllers at each spacecraft leads to a non-optimal solution in a global or formation-wide sense, even when independent controllers are implemented using any of the locally optimal techniques known from the theory of control. Most of the future formation ight missions have been designed with an interferometric purpose, such as performing a space-based distributed telescope structure that would y into deep space with an observational objective. In that case, where global positioning systems such as GPS are no longer available, relative positioning not only becomes necessary to achieve control of the multi-spacecraft system, but it also becomes a crucial factor that would determine the performance of the system with regards to the optical science output. In fact, if we rede ne the state vector of the plant and use the relative states that need to be tracked instead of independent global positions, we get to a de nition with coupled dynamics of the whole multi-agent system. This research focuses on the control performance obtained when the controller is designed using coupled inter-spacecraft dynamics and how this approach can lead to an optimal solution in a global sense, both in optical performance and overall fuel usage. The rst part of the thesis will address the theoretical advantages that may arise within the coupled dynamics architecture and the second part analyses the performance of the results obtained when testing the real implementation of the controller on hardware. This study, concerning implementation and performance of formation ight controllers in a real case scenario such as deep space interferometer missions, will lead towards increasing mission lifetime, performance improvement and a step forward in the eld.