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The work presented in this PhD thesis report is situated within the framework of the nonlinear and robust control of transport aircrafts. The purpose of this thesis is to couple the properties of nonlinear controllers (adaptation to the aircraft nonlinearities, explicit controllers synthesis, easy and decoupled setting once the synthesis is achieved, genericity of the obtained control laws) with essential robustness properties. Indeed, to guarantee the flight safety, both in manual handling and in automatic control, the control laws have to present strong robust stability and performances properties. After an introduction to the industrial and research context, a "techniques, methods and tools" part allows us to point out the thesis contributions in the nonlinear robust control and automatic modelling domains. The nonlinear robust control technique presented, called RMI control (for "Robust Multi-Inversion") is based on the now classical Nonlinear Dynamic Inversion (NDI) technique, notably studied at Airbus for some years (Fabrice VILLAUME, Jean DUPREZ), and is robustified by adding a complementary observation loop. We also present an automatic tool creating nonlinear, multivariable and embeddable models, as well as neural networks correlated methods. This tool is mandatory for the industrialization of our model-based flight control laws. Then the applicative part of the thesis underlines the specificities of the "aircraft" system and proposes flight control laws architectures, associated reference trajectories, and the advanced validation of the whole system by simulations performed on Airbus' certified simulator. Finally, after a conclusion on the main results and perspectives linked to the thesis, we propose annexes allowing to go further into the details of certain parts of our study.; Le travail présenté dans ce mémoire de thèse s'inscrit dans le cadre de la commande non-linéaire et robuste des avions de transport. Le but de cette thèse est de coupler les propriétés de la commande non-linéaire (adaptation aux non-linéarités de l'avion, synthèse de correcteurs explicites, facilité de réglage une fois la synthèse réalisée, généricité des lois de commande obtenues) à des propriétés de robustesse indispensables à l'activité aéronautique. En effet, pour garantir la sécurité des vols tant en pilotage manuel qu'en pilotage automatique, les lois de commande doivent présenter des propriétés fortes de stabilité et de performances robustes. Après une introduction au contexte industriel et de recherche du sujet de thèse, une partie "techniques, méthodes et outils" nous permet de mettre en avant les contributions du travail de thèse dans les domaines de la commande non-linéaire robuste et de la modélisation automatique. La technique de commande non-linéaire robuste présentée, appelée commande RMI (Robust Multi-Inversion) s'appuie sur la technique désormais classique d'inversion de la dynamique, notamment étudiée à Airbus depuis quelques années (Fabrice VILLAUME, Jean DUPREZ) et qu'elle robustifie par l'adjonction d'une boucle supplémentaire d'observation. Nous présentons aussi un outil de génération automatique de modèles non-linéaires, multivariables et embarquables, ainsi que les méthodes afférentes basées sur les réseaux de neurones. Cet outil est nécessaire à l'industrialisation des lois de commandes non-linéaires basées modèles. La partie applicative de la thèse souligne ensuite les particularités du système "avion" et propose des architectures de lois de commande, des trajectoires de référence associées, et la validation avancée de l'ensemble par simulations sur simulateur certifié. Enfin, après une conclusion sur le bilan de la thèse et les perspectives envisageables, nous proposons des annexes permettant d'approfondir certains aspects de notre ét ude.

The characteristics of the thrust-vectored X-31A aircraft with reduced vertical tail were investigated as one of the key research objectives within the German-American VECTOR program. This paper describes the design of the flight control laws for this modified configuration of the X-31A using Nonlinear Dynamic Inversion (NDI), as well as the subsequent handling qualities evaluation in the flight simulator. NDI is based on the inversion of model equations, so that control laws are easily adapted to varying aircraft configurations and, as will be shown in this paper, may be generated automatically with the help of advanced modeling tools. Initially, the NDI control laws for the original X-31A aircraft configuration with full vertical stabilizer were developed in an off-line design phase. Next, the aerodynamic database of the simulator model was supplemented with data from wind tunnel measurements with 30 % and 50 % of the vertical tail removed. Based on the updated simulation model, the control laws were automatically re-generated and implemented in the VECTOR fixed-base flight simulator facility. Six experienced pilots assessed and compared flying qualities (for conventional as well as post-stall flight conditions) for full and 50% tail configurations. In general, Level 1 flying qualities were achieved for both configurations. However, with the tail (including rudder) reduced, controllability limits were reached at lower thrust levels due to the deteriorating thrust vectoring control effectiveness

The application of Nonlinear Dynamic Inversion for the design of a robust attitude controller for a civil aircraft is discussed. The main function of the controller is to improve the flying qualities, including stability, of the aircraft dynamics. For parameter synthesis multi-objective optimisation is used. The required robustness is achieved via a multi-model approach and local robustness criteria. In addition to the feedback gains, physical parameters in the inverse model that are considered uncertain in the design model, are used as synthesis parameters. The control laws are automatically generated from a symbolic aircraft model in the modeling language Modelica. The design was used as a stability and command augmentation function in an automatic Fly-by-Wire landing system and was successfully flight tested.

This paper deals with the development of a flight control scheme based on the Nonlinear Dynamic Inversion technique (NDI). Such a scheme has been implemented on the Flight Control System (FCS) of a trirotors prototype model used to simulate tilt rotor air vehicles dynamics during all those phases when aerodynamic surfaces are less effective or not effective at all. An adaptive flight control scheme has been developed based on Radial Basis Function Neural Network (RBFNN) and NDI making both attitude and trajectory tracking control system less sensitive to modelling errors. To demonstrate the effectiveness of the proposed control technique both numerical simulations and experimental tests have been performed. To this end a scaled multi-rotor test bed has been built simulating a tilt rotor unmanned air vehicle (UAV) in hovering and low speed flight conditions. The control system has been implemented on an embedded board based on an ARM Cortex M4 processor and a low cost Inertial Measurement Unit with triaxial MEMS accelerometer, gyroscope and magnetometer sensors. As accuracy of NDI control system can be affected by model uncertainties and sharp transients due to the RBFNN adaptation transients, a model calibration phase is needed. To this end preliminary flight tests have been performed for UAV dynamic model identification and control parameters tuning.