Feedback Linearization and Control of NASA SCOLE System by Output Feedback

We treat the question of large rotational maneuver and vibration stabilization of NASA Spacecraft Control Laboratory Experiment system (SCOLE). The mathematical model of SCOLE system includes the dynamical equations for rigid body slew maneuver and three-dimensional vibration of the rigid shuttle, the flexible beam and the reflector with an offset mass. The design approach taken here is to decompose the rigid mode control from vibration stabilization. Feedback input (Shuttle torque)-output (attitude angles) map linearization technique is used for designing attitude control system for large-angle slewing. Linearization of input-output (i-o) map is accomplished by nonlinear inversion theory. It is shown that attitude control system asymptotically decouples the flexible dynamics and linear feedback law is easily designed for vibration suppression. For the synthesis of the control law an observer is designed. Simulation results are presented to show in the closed-loop system large angle maneuver can be accomplished using only the measured state variables.