Robust Gust Load Alleviation of Flexible Aircraft Equipped with Lidar

Abstract

This work concerns the problem of gust load alleviation of a flexible aircraft by focusing on Airbus’s XRF1 aircraft concept, with a fully actuated wing. The aircraft is equipped with a lidar sensor, which measures the wind velocity ahead of it, together with standard sensors. Based on the available measurements, controllers are then designed by $H_{\infty }$ and $\mu$ syntheses, with emphasis put on the multiple-input multiple-output robustness in order to reduce a selected set of loads due to the wind, hence potentially saving mass in the aircraft design. A state-space model of the flexible aircraft is obtained by means of an aeroelastic computation and system identification from frequency data. The controllers’ performance is evaluated through their capability to reduce shear force, bending, and torsion moments on different locations of the aircraft in response to different types of discrete gusts and continuous turbulence; the constraints of the sensors and the actuators are taken into account. The gain in performance due to the use of lidar is assessed, and a tradeoff is discussed concerning the optimal measurement distance. Finally, the closed-loop robustness is assessed by simulations where different types of uncertainties are applied to the system.