Design issues in the control of large flexible spacecraft slew maneuvers

Linearized dynamical models of slew maneuvers of a large flexible spacecraft are utilized to design state feedback control systems to perform arbitrary slew maneuvers and to achieve total vibration suppression of flexible appendages. The control system designs are based on linear quadratic Gaussian loop transfer recovery (LQG/LTR) design methodology. The linearized slew maneuver equations used are derived from a nonlinear model developed for large-angle nonlinear arbitrary slew maneuvers and include 10-mode truncation for the vibrations of the flexible appendage. The slew maneuver control systems are developed for the combined problem of the slew maneuver of the entire assembly and the total vibration suppression of the appendage. The designs incorporate both the structured and the unstructured model uncertainties. The controller designs are further analyzed in terms of singular values and transmission zeros of the closed-loop transfer function matrix of the multivariable system. These singular values are utilized in studying the system sensitivity due to modal frequencies of the truncated model of the elastic member and the structural damping. The sensitivity study is further interpreted in terms of the robustness issues