Robust flight control design for the HIRM based on linear quadratic control

In this paper the application of Linear Quadratic Optimal Control based techniques to the HIRM (High Incidence Research Model) Robust Flight Control design problem is considered. The structure of the proposed controller is basically a Proportional Integral action, both for the longitudinal and for the lateral-directional parts, designed with optimality criteria in order to achieve the performance and robustness requirements. Moreover, the control scheme is completed by the compensation of some physical non linearities, some demand shaping filters and a switching logic based on the angle of attack and on the Mach number. Most of the design requirements are easily satisfied; some others need a heavier tuning of the controller design parameters. A procedure to tune such parameters, formulated in terms of an optimization problem, is proposed. Simulation results, from the HIRM automated evaluation procedure are also provided at the end of the paper, from which it is shown that the proposed controller meets the requirements.