Extended state observer-based robust pitch autopilot design for tactical missiles

Abstract

In this article, a new design based on the extended state observer (ESO) technique for the pitch autopilot of a tail-controlled, skid-to-turn missile is proposed. The pitch-plane dynamics with the angle of attack as output is significantly uncertain. The ESO simultaneously estimates the state and the uncertainty. The estimated uncertainty is used to robustify the input–output–linearization-based controller designed for the nominal system. Closed-loop stability of the observer–controller combination is proved. The notable feature of the proposed design is that it neither requires accurate plant model nor any information about the uncertainty. The effectiveness of the ESO in estimation of the uncertainties and states and in meeting the specified tracking performance in the presence of significant uncertainties is illustrated by simulation. Finally, to demonstrate the efficacy of the proposed design, comparison of its performance with some of the well-known existing controllers is presented.