H Infinity Robust Control for Gust Load Alleviation of Geometrically Nonlinear Flexible Aircraft

2026-03-18

AI Summary

This study addresses the challenge of simultaneously mitigating excessive structural loads and maintaining trajectory stability in geometrically nonlinear flexible aircraft subjected to gust disturbances. By constructing a low-dimensional system via nonlinear model order reduction, the work presents the first successful application of an H∞ robust controller—designed on this reduced-order model—to a high-dimensional aeroelastic system. The control strategy treats wingtip displacement as the performance output and trailing-edge control surfaces as actuators, incorporating input-shaping weighting functions to jointly optimize load alleviation and rigid-body trajectory tracking. Numerical simulations on Global Hawk–like unmanned aerial vehicles and flexible flying-wing configurations demonstrate that the proposed approach significantly reduces gust-induced structural loads while preserving excellent flight path stability, exhibiting strong robustness and practical engineering applicability.

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Abstract

H Infinity robust control synthesis for gust load alleviation of very flexible aircraft is presented. The controller is synthesised on a compact reduced-order model comprising 8 degrees of freedom for the UAV configuration and 9 for the flying-wing, obtained through nonlinear model order reduction of the coupled fluid-structure-flight dynamics system, and validated on the full nonlinear model. The control architecture employs trailing-edge flap deflection as the actuator and wing-tip displacement as the performance output, with an input-shaping weighting function Kc that governs the trade-off between structural load alleviation and rigid-body trajectory deviation. Results are presented for a Global Hawk-like UAV and a very flexible flying-wing configuration. The methodology demonstrates that H infinity controllers designed on low-order ROMs can robustly alleviate gust loads when applied to high-dimensional nonlinear aeroelastic systems.

Problem

• gust load alleviation
• geometrically nonlinear
• flexible aircraft
• aeroelastic systems
• H infinity control

Innovation

• H-infinity control
• model order reduction
• gust load alleviation
• geometrically nonlinear flexible aircraft
• aeroelasticity