Accommodation of kinematic disturbances during minimum-time maneuvers of flexible spacecraft

Abstract

This paper is concerned with control of the perturbations experienced by a flexible spacecraft during a minimum-time maneuver. The spacecraft is modeled as a rigid hub with a flexible appendage. The perturbations consist of deviations from a rigid-body maneuver and elastic vibration. The vibration is described by a linear, time-varying set of ordinary differential equations subjected to piecewise-constant disturbances caused by inertia! forces resulting from the maneuver. The control is carried out during the maneuver period, which is relatively short, and it uses an observer to estimate the controlled state and part of the disturbance vector. The controller is divided into an optimal finite-time linear quadratic regulator for the reduced-order model and a disturbance-accommodation control that minimizes a weighted norm spanning the constant part of the full-modeled state. The controller is designed to mitigate the effects of control and observation spillover, as well as of modeling errors. The developments are illustrated by means of a numerical example.