Active Gust Load Alleviation of High-Aspect Ratio Flexible Wing Aircraft

Abstract

This paper presents a novel active gust load alleviation approach within a multi-objective flight control framework developed by NASA for a flexible wing aircraft. The aircraft model is based on the NASA Generic Transport Model (GTM). The wing structures incorporate an aerodynamic control surface known as the Variable Camber Continuous Trailing Edge Flap (VCCTEF). Previous work already showed the ability of the VCCTEF to perform aeroelastic mode suppression, drag minimization and maneuver load alleviation in a multi-objective flight control framework. In this paper, the multi-objective flight control framework is extended to include active gust load alleviation. A Linear-Quadratic Gaussian (LQG) controller is augmented with Model Reference Adaptive Control (MRAC) to provide active gust load alleviation. Disturbance estimation is done using an Extended State Observer (ESO) to support the design of the active gust load alleviation controller. The results demonstrate the potential of active gust load alleviation within a multi-objective flight control framework for a high-aspect ratio flexible wing aircraft embodied with the VCCTEF.

Multi-Objective Flight Control for Ride Quality Improvement for Flexible Aircraft

“…A multi-objective flight control system has been previously developed to simultaneously gain aerodynamic efficiency, ASE mode suppression, and gust/maneuver load alleviation while maintaining traditional pilot command-tracking tasks for guidance and navigation. [4][5][6][7][8]17 This study continues to build upon the previous studies to address ride quality in the multi-objective flight control framework.…”

“…The load transmission into the passenger cabin can create discomfort. The unsteady load response can be modeled by P = P x x + P u u + P w w (6) where P is a load vector which can be normalized by the aircraft weight for forces and by suitable moment references for moments.…”

“…All of these constraints while seeking the optimal aerodynamic performance present themselves as a multi-objective flight control problem. 17 A multi-objective flight control framework [4][5][6][7][8]17 has been developed to address these operational constraints and the efficiency goal simultaneously in order to arrive at optimal solutions that can provide good compromise between the efficiency goal and operational constraints. These optimal solutions take advantage of a distributed multi-functional flight control actuation concept developed by NASA called the Variable Camber Continuous Trailing Edge Flap (VC-CTEF) 9,10,12,13 which can be used to simultaneously achieve multiple flight control objectives.…”

Progress on Gust Load Alleviation Wind Tunnel Experiment and Aeroservoelastic Model Validation for a Flexible Wing with Variable Camber Continuous Trailing Edge Flap System

“…by ignoring u 0 since the steady-state lift is not changing. This control law requires estimatingŵ which can be through an extended-state implementation, 24 adaptive estimation, 18 or a transfer function which requires a physical insight into the disturbance. Alternatively, the disturbance feedforward could be ignored but the load alleviation and drag minimization objectives are still met through the feedback term due to the optimal control formulation.…”

Recent researches on morphing aircraft technologies in Japan and other countries

“…Although there are many concepts integrating smart materials and structures to realize morphing aircraft/wings, there are also approaches for morphing to extend traditional designs. The VCCTEF system may be one of representative recent designs to accommodate traditional commercial aircraft taking advantage of the morphing wing concept (Ferrier et al, 2018;Hashemi et al, 2018;Nguyen et al, 2018). The VCCTEF system achieved the circular wing camber by implementing three chordwise control surface segments of equal chord length, which resulted in a smooth chordwise Tsushima and Tamayama, Mechanical Engineering Reviews, Vol.6, No.2 (2019) [DOI: 10.1299/mer.19-00197] pressure distribution.…”