An H∞ Preview Approach to Active Load Alleviation Design for Flexible Aircraft

Abstract

Turbulence and gusts are causing variations of the aerodynamic forces and moments that are applied to the aircraft structure, resulting in passenger discomfort and dynamic loads that the structure should be designed to support. Designing Gust Load Alleviation (GLA) systems allows achieving higher passenger comfort and reducing the dynamic structural loads. In this thesis a methodology for designing combined feedback/feedforward GLA systems, which relies on the availability of a measured wind profile ahead of the aircraft (e.g. by a Doppler LIDAR sensor), is proposed. It is based on H_∞ optimal control techniques and a discrete-time preview-control problem formulation. Moreover, to allow making design trade-offs between different objectives, and also to allow the specification of robustness criteria, a formulation of the problem using multi-channel H_∞ optimal control techniques is followed. The developed methodology is intended to be applied to large airplanes (e.g. transport airplanes or business jets). The simulation results show the effectiveness of the proposed design methodology in accounting for the measured wind profile in order to achieve higher passenger comfort and less dynamic structural loads, while ensuring both controller optimality and design flexibility.