Controlled Dynamics of Flexible Orbiting Tethered Systems: Analysis and Experiments

Abstract

The equations of motion for a class of tethered satellite systems (TSS) undergoing planar motion in a Keplerian orbit are derived using the Lagrangian procedure. The system consists of a rigid platform from which a point mass subsatellite can be deployed or retrieved by a flexible tether. The model incorporates an offset of the tethered attachment point from the platform center of mass and its time dependent variation. The feedback linearization technique (FLT) is used to design the attitude regulator. A hybrid strategy, using thruster and offset schemes, is used for regulating the tether swing, and momentum gyros are employed for the platform control. The offset strategy is also used for active control of the tether flexibility during stationkeeping in conjunction with the thruster-based attitude controller. Finally, effectiveness of the offset- based attitude controller is demonstrated through ground-based experiments, thus substantiating the trends predicted by the numerical simulations.