Mixed H ₂/H _∞ output feedback attitude control for flexible spacecraft

The H ₂/H _∞ output feedback attitude control problem of the flexible spacecraft composed of a central rigid body and some attached appendages is researched in this paper. The attitude control problem of such flexible spacecrafts is always difficult because the vibration of the elastic appendages can affect the central rigid motion and the measurement of the vibration modes is not easy in practice. A dynamic output feedback H ₂/H _∞ controller is designed here to perform attitude control in the presence of flexible vibration, model uncertainties and space environmental disturbances. The proposed algorithm with H _∞ output controller can implement the attitude control and the elastic mode stabilization at the same time. The system dynamics is also improved via the H ₂ design. Simulation shows the effectiveness of the presented algorithm.