Robust Controller Design For Flexible Space SystemUsing A Combination Of LQG/LTR And PRLQGMethods

Abstract

In this paper an asymptotic Linear Quadratic Gaussian (LQG) design procedure based on a modification of the Parameter Robust Linear Quadratic Gaussian (PRLQG) approach is developed for designing a robust controller that accounts for unmodelled dynamics and parameter uncertainty for multi-input multioutput systems. The unmodelled dynamics are assumed to be characterized as a single block dynamic uncertainty at a point in the closed-loop system. Plant parameter variations are represented as an internal feedback loop via the inputoutput decomposition. A direct structural relationship between parameter uncertainties and the weighting matrices in the design of the LQG controller is exploited. This procedure is then applied to design a robust controller for attitude control and vibration suppression of the MB-1 Space Station configuration taking into account this mixed uncertainty model. This technique yields considerable improvement in robustness with respect to parameter variation without affecting the level of nominal performance and robustness with respect to unmodelled dynamics achieved during the design. Simulations have shown that when the system is submitted to unit impulse the controller was able to impose quick convergence to the system.