Baseline Flight Control System for High Altitude Long Endurance Aircraft

Abstract

High Altitude Long Endurance (HALE) aircraft consist of extremely light-weight structuresin combination with a high wingspan and high aspect ratio. The coupling of these propertiesresults in a dynamic behavior of the aircraft system which is different to classical transport orunmanned aircraft configurations. The key finding in the analysis of the dynamic behavior ofthe aeroelasticHALEaircraft is a strong interaction of structural and rigid body eigenmodes.This leads to challenges in the design of a robust flight control algorithm for the full flightenvelope with state-of-the-art techniques. This work addresses these difficulties and proposes ageneric design process which can be used to develop flight control algorithms forHALEaircraft.The design process starts with the definition of specific performance and robustness criteriaforHALEflight control laws which emerge from the combination of general aircraft designstandards with the limitations and capabilities of theHALEconfiguration. Subsequently, again-scheduled, fixed structure control design architecture is proposed. The inner loop controldesign is enriched with envelope protection functionalities. The design process concludes withan extensive validation and verification process to clear the baseline flight control system forflight testing. The proposed design process is applied to the German Aerospace Center’s newlydeveloped HALE platform.