Missile longitudinal autopilot design using a generalized extended state observer-based mixed H 2 / H ∞ control method

Abstract

This work presents a novel robust control design approach for missile longitudinal autopilot under multiple disturbances and uncertainties. The uncertainties and disturbances of the missile dynamics are treated as a lumped disturbance based on the concept of equivalent input disturbance. Then a generalized extended state observer is employed to estimate the system states and the equivalent input disturbance in an integrated manner. These estimates are used to construct the state-feedback controller as well as to attenuate the effect of the exogenous disturbances and endogenous uncertainties. The state-feedback controller is obtained by solving the linear matrix inequalities of mixed $H_2$ / $H_{\infty }$ control problem, which provides an impressive flexibility to tune the controller to compromise between $H_2$ performance and $H_{\infty }$ performance. Closed-loop stability of the system under the presented controller-observer structure is also established. The proposed design tactfully circumvents the engineering implementation problems encountered by mixed $H_2$ / $H_{\infty }$ control, achieves strong robustness against disturbances and uncertainties, and does not involve any complicated nonlinear control methodologies. Numerical simulation results of nominal and perturbed performance comparisons with classic methods sufficiently demonstrate the feasibility and robustness of the proposed method.