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 an adaptive, attitude control design approach that works during flight to autonomously identify the system dynamics affecting the control bandwidth, then design feedback control laws to achieve predefinedperformance and stability criteria. This approach is an extension of our Frequency Domain Expert (FDE) control algorithm, which is currently being demonstrated on the Space Station Freedom as part of the Middeck Active Control Experiment (MACE-II).Weintend to partner with the Air Force Research Laboratory (AFRL) to inject this technology into future Air Force programs, beginning with the PowerSail technology demonstration program. Once the technology has been demonstrated successfully on a flightexperiment, operational uses both for the integrated, deployable PowerSail technology and for the adaptive attitude control system technology will be exploited. In parallel with this DOD-related effort, a smaller effort will be launched in the area ofindustrial servo-controllers in Phase II. The unique capabilities of the proposed technologies will enable the implementation of an automatic, coordinated, multi-axis servo control system embodied in a stand-alone control computer.