Robust attitude control of a spacecraft with flexible dynamics

Abstract: The employment of Electrical Propulsion, to reduce the cost of satellites, has also increasedthe use of large solar arrays. Such solar panels are associated with low-frequency resonantmodes, and to ensure fine pointing of the satellite, the attitude control should not excitethese modes. This is a difficult task in such complex systems, whose exact a prioriknowledge is largely unavailable during the early design phase.The primary scope of this thesis is to synthesize a robust algorithm for attitude controlthat deals with modeling errors.The first part is dedicated to understanding the principal causes of uncertainty thatwill inevitably limit the design. Once a description of the uncertainty has been obtained,two different approaches to robust control algorithms have been investigated. The outcomeis the syntheses of two multivariable controllers with different performance and stabilitymargins. Since this project has been carried out during the development of a new fullelectric spacecraft concept by OHB, it has been possible to validate the two controllersin the on-board software simulator of the spacecraft. The results confirm the robustcontrollers as possible alternatives to the current design.