A Comparison of Optimal LQR Controller and Robust H∞ Controller for RLV

Reusable Launch Vehicles (RLV) are a new generation of space vehicles capable of delivering payload at significantly lower cost. Classical approaches to feedback design have provided reliable methodologies for many years for designing controllers and are predominantly used in the aerospace industry for the design and analysis of automatic flight control systems. These techniques cannot be applied directly to RLV as it is a complex multi-input multi-output system which has high uncertainty on aerodynamic coefficients during atmospheric re-entry phase and are subjected to various disturbances during flight regimes. Hence, a robust controller is at most necessary for any new aerodynamic configuration of RLV. This paper proposes a LQR as well as H-infinity controller for a rigid model of RLV. Robustness of the proposed controllers under various plant parameter perturbations is demonstrated using simulations.