Optimal Open Loop and Nonlinear Feedback Control for Remote Orbital Capture (multi-Body Dynamics, Recovery, Satellite Servicing, Payload Handling)

113 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.Optimal open loop and nonlinear feedback control histories are presented for the problem of detumbling (passivating) a target satellite by a remotely operated robot spacecraft. Detumbling is required so that the robot spacecraft, sometimes called a teleoperator or orbital maneuvering vehicle (OMV), can return the target satellite to low-Earth orbit for servicing and repair. The dynamics of the coupled two-body system are described with equations of motion derived from an Eulerian formulation (the Hooker-Margulies equations). Two degrees of rotational freedom are allowed at the joint which connects the OMV and target spacecraft, and the joint is allowed to translate on the surface of the OMV. The initial condition of the axially symmetric target satellite is free spin and precession. Representative masses and inertias are assumed for each body. The detumbling controls, which are the external (thruster) and internal (joint) torques applied by the OMV, are found from optimal control theory and Liapunov stability theory. Applying optimal control theory yields a nonsingular two-point-boundary-value-problem which is solved numerically for the open loop controls over a specified time interval. Control constraints on the thrusters and one of the joint torques are also considered. Liapunov stability theory is used to derive a nonlinear feedback control law which results in the asymptotic stability of a set of equilibria for the two-body system. This control law is analyzed numerically and compared to the results of optimum open loop control. Also presented is an example in which open loop controls nearly detumble the target satellite and feedback controls complete detumbling. In all cases the constraint force and torque at the joint are determined. Detumbling is shown to be a very benign process requiring only very small control torques and producing only small constraint loads.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD