Robust and Gain-Scheduled Flight Control of Fixed-Wing UAVs in Wind and Icing Conditions

Abstract

Simulations of a fixed-wing unmanned aerial vehicle with varying degrees of icing, both symmetric and asymmetric, and both ice accretion and ice shedding, show the applicability of robust $H_{\infty}$ inner-loop control for both the lateral and the longitudinal axes to extend the flight envelope. A gain-scheduled extension of the controller compares favourably in performance, at the cost of complexity and needing to know current the icing level. The results also show that higher airspeeds reduces the disturbance related to instantaneous removal of ice. A simple analysis of the open-loop dynamics of the aerodynamic model show that only the spiral-mode eigenvalue moves into the right hand plane with increased icing levels.