Control and Pointing of Very Flexible Large Space Structures

The extreme flexibility of proposed ultra-lightweight spacecraft, such as the Air Force's PowerSail, will require a new generation of attitude control systems (ACS) that can accommodate low-frequency flexible dynamics within the pointing control bandwidth.In addition, as spacecraft designs continue to reduce mass density, it will become increasingly difficult to construct and validate dynamic models on the ground that are of sufficient fidelity to use for traditional fixed-gain control design. To meetthese challenges, we will show the feasibility of (Phase I) and demonstrate (Phase II) an adaptive attitude control design approach that works during flight to autonomously identify the system dynamics affecting the control bandwidth, then design feedbackcontrol laws to achieve predefined performance and stability criteria. Our technical approach is based on our Frequency Domain Expert (FDE) control algorithm, which has been demonstrated on the Space Station Freedom as part of the Middeck Active ControlExperiment (MACE-II).