Robust Roll Autopilot Design for Tactical Missiles

Abstract

In this paper, a robust roll autopilot based on the extended state observer technique is proposed. The autopilot is robust to uncertainties, external disturbances, the airframe flexibility, and fast unmodeled sensor lags. The external disturbances and the parametric uncertainties in the roll loop are treated as a composite disturbance and the extended state observer is used to estimate the composite disturbance and the states of the system in an integrated manner. The estimated disturbance and the estimated states are used to robustify linear quadratic regulator autopilots designed for nominal systems. The closed-loop stability of the observer-controller combination is proved. Simulation results are presented to demonstrate the efficacy of the extended state observer in estimation of the uncertainties and the states, and in meeting the objectives of the design. Lastly, the proposed design is compared with some well-known designs reported in the literature.