Control of Large Space Structures Using Reduced-order Models

Abstract

Simulation of space structures forms a critical part of the space station design process. The distributed parameter system is discretized by suitable approximation techniques such as Rayleigh-Ritz or finite element methods and is represented by a finite set of ordinary differential equations. From the control engineer\u27s perspective, this finite set of equations is often too large for control computations and reduced-order models are synthesized and used for controller design. The current work addresses the finite element modeling, reduced-order model synthesis and the design and validation of suboptimal controllers for a realistic model of a space station. The balanced realization technique and the Routh approximation method are used to develop meaningful lower-order models for controller design. If the state variables are not available for feedback, then an appropriate state estimator has to be designed. This aspect of the design is not considered in the paper. Extensive simulations for the control tasks of vibration suppression, attitude control and minimization of line-of-sight errors demonstrate that any performance degradation incurred by using suboptimal controllers is minimal

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