A Composite Unknown Input Observer and H∞ Control Strategy for Flexible Spacecraft with Time Delay

This paper considers the problem of the attitude control for flexible spacecraft with disturbances, actuator fault and time delay. The disturbances include the bounded environmental disturbances and the disturbance caused by the vibration of the flexible appendages. A composite control structure, which includes unknown input observer control (UIO) and delay dependent H∞ control, is proposed to achieve a stable control of the attitude angle and attitude angular velocity, and a decomposition coefficient of delay integral inequality is introduced to reduce the design algorithm conservatism. Finally, simulation results are given to show the effectiveness of the proposed method.