Automatic landing system design using multiobjective robust control

Wind disturbance is one of the major factors that could jeopardize a safe landing. To improve the safety of automatic landing, in this paper, a linear model of the aircraft in longitudinal motion is established first and further augmented by introducing the tracking error integral equations to achieve a desirable tracking performance. Then, two different design methods are proposed to obtain robust controllers in the presence of parametric uncertainties, external disturbances, and input constraints. One of the methods uses the H∞ state-feedback and regional pole placement technique, and the corresponding controller is designed via a Lyapunov approach. The other method develops the robust exact pole placement technique subject to the input constraints, under which framework the controller is designed through minimizing the condition number of the solution of a Sylvester-like equation. The existence conditions for both admissible controllers are formulated as linear matrix inequalities. Finally, the Boeing 747 airplane and the windshear model are employed to show the effectiveness and robustness of the proposed design techniques.