Gain scheduled flight control law for a flexible aircraft : A practical approach

Abstract: This paper presents a gain-scheduling method applied to flight control law design. The method is a stabilitypreservinginterpolation technique ofexisting controllers under observer-state feedback form. Application is made on a flexible civil aircraft example considering multiple scheduling parameters. Although the interpolation technique gives powerful a priori stability guarantees, the sufficient condition to satisfy leads to conservative results in practice. We thus use a fixed observer model and check stability andperformance thanks to μ-analysis. Provided results are really satisfactory for a final controller of little complexity

Conception multi-objectifs de lois de pilotage pour un avion de transport civil

ABSTRACT. Due to modern day aircrafts evolution, requirements for flight control laws are more and more numerous and varied. For that reason, control laws designers need now to use multiobjectives synthesis techniques. We then choose to develop to solve today aircraft issue. The whole designed procedure use: first H1 to compute an initial stabilizing controller, then Q- parametrization to introduce the design shapping, convex synthesis to optimize the controller with respect to the requirements set, robust modal control to produce a performing and reduced order controller, and last observer state feedback controller interpolation for gain scheduling

Commande adaptative pour avion de transport tolérante aux erreurs de modèle et aux pannes

Cette thèse s'intéresse à l'adaptation des lois de pilotage d'un avion de transport civil aux différentes incertitudes qui peuvent affecter sa dynamique. Le procédé de pilotage adaptatif est censé fonctionner en temps réel à bord de l'avion afin d'optimiser la performance boucle fermée en fonction des conditions dans lesquelles il évolue. Les incertitudes peuvent être liées à la méconnaissance des conditions de vol (par exemple la vitesse et l'altitude), à des non-linéarités aérodynamiques inconnues ou encore à la méconnaissance du pilote aux commandes. Les procédés adaptatifs qui répondent à ces problèmes se doivent d'être performants sur l'ensemble du domaine opérationnel de l'avion en présence de perturbations réalistes. D'autres contraintes spécifiques peuvent être ajoutées en fonction du contexte (par exemple des charges limites, la stabilité aéroélastique, etc.). Plusieurs méthodes adaptatives sont testées afin d'adapter le système aux larges incertitudes qui le composent. Elles associent en général un estimateur en ligne (aussi appelé loi de mise-à-jour) à une loi de commande structurée. La synthèse de ces deux éléments peut être réalisée simultanément pour les méthodes adaptatives dites " directes ", comme par exemple le Model Reference Adaptative Control qui utilise la stabilité au sens de Lyapounov. Mais cette synthèse peut aussi être découplée pour les méthodes adaptatives dites "indirectes", ce qui offre un large choix de techniques pour chaque élément (comme les Moindres Carrés pour l'estimation de paramètres physiques incertains et la synthèse sous forme LFR pour le correcteur). Le choix de la méthode dépend fortement du contexte applicatif et des nombreuses contraintes associées. Trois applications sont au cœur de ce mémoire. Elles traitent de l'ajustement de lois de guidage à un modèle pilote inconnu, du contrôle longitudinal de non-linéarités de l'avion, et de la mise au point de lois longitudinale et latérale de pilotage manuel qui s'adaptent à des conditions de vol inconnues. Des méthodes avancées d'analyse linéaire et non-linéaire (dérivées de la -analyse et d'algorithmes d'optimisation) sont aussi mises en place pour valider ces systèmes sophistiqués adaptatifs en temps réel. D'une façon générale, les méthodes adaptatives indirectes ont donné le plus de satisfaction. Leur performance est aussi bonne que celle des méthodes directes, mais le fait qu'elles estiment en ligne des paramètres physiques facilite la surveillance temps réel du procédé adaptatif et sa validation.This thesis deals with adapting flight control laws of a civil transport aircraft to various incertainties which can affect its behaviour. The adaptive flight control system is supposed to run in real time onboard the airplane so that its closed-loop performance is optimized with respect to the current conditions. These incertainties may be linked to unknown flight conditions (e.g. unknown airspeed and altitude), or unknown aerodynamics non-linearities or even unknown behaviour of the pilot in command. The adaptive schemes that are derived to answer these problems must be valid on the whole flight envelope with realistic disturbances but other additional contraints may exist depending on the context (e.g. loads limits, aeroelastic stability, etc.). To accommodate for large uncertainties on the system, adaptive methods are investigated. They usually combine an online estimator (also called an update law) with a structured flight control law. The synthesis of both elements may be simultaneous on 'direct' adaptive methods, e.g. on Model Reference Adaptive Control, using Lyapunov's stability theory. But it can also be decoupled on 'indirect' adaptive methods, giving a full spectrum of techniques for both elements (such as Least-Squares for estimating unknown physical parameters and the LFR framework for designing controllers). The choice of a specific method really depends on the application context and the related constraints.Three applications are the core of this report. They deal with adjusting guidance law to the pilot's unknown behaviour, controlling a longitudinal non-linearity, and providing manual longitudinal and lateral flight control laws which adapt to unknown flight conditions. Advanced linear and non-linear analysis techniques (based on -analysis or on optimization algorithms) are also applied to validated these sophisticated real-time adaptive systems. Results showed that indirect adaptive schemes were generally the most satisfactory. Their performance is similar to the one of direct schemes but as indirect methods provide physical parameter estimates, real-time monitoring and offline validation seem quite easier.TOULOUSE-ISAE (315552318) / SudocSudocFranceF

Optimization Based Clearance of Flight Control Laws: A Civil Aircraft Application

This book summarizes the main achievements of the EC funded 6th Framework Program project COFCLUO – Clearance of Flight Control Laws Using Optimization. This project successfully contributed to the achievement of a top-level objective to meet society’s needs for a more efficient, safer and environmentally friendly air transport by providing new techniques and tools for the clearance of flight control laws. This is an important part of the certification and qualification process of an aircraft – a costly and time-consuming process for the aeronautical industry.   The overall objective of the COFCLUO project was to develop and apply optimization techniques to the clearance of flight control laws in order to improve efficiency and reliability. In the book, the new techniques are explained and benchmarked against traditional techniques currently used by the industry. The new techniques build on mathematical criteria derived from the certification and qualification requirements together with suitable models of the aircraft.  The development of these criteria and models are also presented in the book.   Because of wider applicability, the optimization-based clearance of flight control laws will open up the possibility to design innovative aircraft that today are out of the scope using classical clearance tools.  Optimization-based clearance will not only increase safety but it will also simplify the whole certification and qualification process, thus significantly reduce cost. The achieved speedup will also support rapid modeling and prototyping and reduce “time to market”

Gain scheduling using multimodel eigenstructure assigment : a new application

This article presents a study on the improvement of an existing longitudinal control law for in-use flexible aircraft using a powerful gain-scheduling technique that is multimodel eigenstructure assignement with self-scheduled dynamic feedback. The main objective is to desensitize the aircraft structural response with respect to the frequency variations of the first bending mode for an extended flight domain in order to ensure handling qualities specifications and passengers’ comfort in turbulence

Optimization Based Clearance of Flight Control LawsA Civil Aircraft Application /

XXIV, 452p. 206 illus., 124 illus. in color.onlin

Adaptive Retuning of Feedforward Controller – Application to the Airbrake Compensation of an Aircraft

International audienc