Robust feedforward/feedback control synthesis for uncertain dynamical systems

A robust {dollar}Hsbinfty{dollar} control design method for dynamical systems with structured parametric uncertainty is developed. The proposed design methodology incorporates the internal model principle for persistent-disturbance rejection. A non-colocated control problem of flexible space structures subject to parameter variations is used to illustrate the design methodology and to address some important issues arising in robust control design. The {dollar}infty{dollar}-norm parameter margin as well as the conventional gain/phase margins are employed as a stability robustness measure of a closed-loop system with structured multi-parameter variations. A proper implementation of a robust non-minimum-phase compensator for a non-zero set-point control problem is also proposed. The proposed robust control design methodology has been successfully applied to the Hubble Space Telescope and the Space Station, resulting in significant improvement in system performance and stability robustness.; Two approaches to robustified open-loop control of uncertain flexible systems are developed with the objective of achieving fast maneuvering and reduction of residual vibration. In the first approach, robust time-optimal control inputs are obtained by solving a parameter optimization problem subject to robustness constraints. In the second approach, a time-optimal control input is preshaped using a tapped-delay filter. It is shown that new approaches provide near-minimum-time maneuvering and robust suppression of residual structural vibrations in the presence of model parameter variations. On-off reaction jet control logic for uncertain flexible spacecraft are also investigated from the viewpoint of minimizing the maneuver time, fuel consumption, and structural mode excitation.