Search

International audience; The PHYLOG project aims at offering a model-based software-aided certification framework for aeronautical systems based on multi/many-core architectures. Certifying such platforms will entail fulfilling the high level objectives of the MCP-CRI / CAST-32A position paper. To reach this general objective, we have defined a certification framework based on patterns to express any argumentation; as well as formal and automatic analyses to support the proof of the argumentation. In this paper, we will introduce the certification methodology and apply it on the KEYSTONE platform.

In this paper, a Lyapunov-like approach ables to characterize the stability of a dynamical system with both stochastic uncertainties and saturating inputs is developed. The behaviour of the system considered is described using the Polynomial Chaos Theory (PCT) which allows to represent it by using a deterministic modeling in a higher dimensional state space. A constructive algorithm is then proposed in order to estimate a robust stability domain, as large as possible, for the probabilistic saturated system. Such conditions are built by exploiting properties of a quadratic Lyapunov function and of standard saturation function.

Hybrid controllers are flexible tools for achieving system stabilization and/or performance improvement tasks. More particularly, hybrid controllers enrich the spectrum of achievable trade-offs. Indeed, the interaction of continuous- and discrete-time dynamics in a hybrid controller leads to rich dynamical behavior and phenomena not encountered in purely continuous-time system. Reset control systems are a class of hybrid controllers whose states are reset depending on an algebraic condition. In this thesis, we propose constructive conditions (Linear Matrix Inequalities) to analyze stability and performance level of a closed-loop system including a reset element. More particularly, we consider a magnitude saturation which could be the source of undesirable effects on these performances, including instability. Proposed results estimate the stability domain and a performance level of such a system, by using Lyapunov-like approaches. Constructive algorithms are obtained by exploiting properties of quadratic - or piecewise quadratic - Lyapunov functions. Beyond analysis results, we propose design methods to obtain a stability domain as large as possible. Design methods are based on both continuous-time approaches (anti-windup compensator) and hybrid-time approaches (design of adapted reset rules).; Les contrôleurs à réinitialisation sont une classe de systèmes hybrides dont la valeur de tout ou partie des états peut être instantannément modifiée sous certaines conditions algébriques. Cette interaction entre dynamique temps-continu et temps-discret de ces contrôleurs permet souvent de dépasser les limites des contrôleurs temps- continu. Dans cette thèse, nous proposons des conditions constructives (sous forme d'Inégalités Matricielles Linéaires) pour analyser la stabilité et les performances de boucle de commande incluant un contrôleur à réinitialisation. En particulier, nous prenons en compte la présence de saturation en amplitude des actionneurs du système. Ces non- linéarités sont souvent source d'une dégradation des performances voir d'instabilité. Les résultats proposés permettent d'estimer le domaine de stabilité et un niveau de performance pour ces systèmes, en s'appuyant sur des fonctions de Lyapunov quadratiques ou quadratiques par morceaux. Au delà de l'aspect analyse, nous exposons deux approches pour améliorer la région de stabilité (nouvelle loi de réinitialisation et stratégie "anti- windup").

Hybrid controllers are flexible tools for achieving system stabilization and/or performance improvement tasks. More particularly, hybrid controllers enrich the spectrum of achievable trade-offs. Indeed, the interaction of continuous- and discrete-time dynamics in a hybrid controller leads to rich dynamical behavior and phenomena not encountered in purely continuous-time system. Reset control systems are a class of hybrid controllers whose states are reset depending on an algebraic condition. In this thesis, we propose constructive conditions (Linear Matrix Inequalities) to analyze stability and performance level of a closed-loop system including a reset element. More particularly, we consider a magnitude saturation which could be the source of undesirable effects on these performances, including instability. Proposed results estimate the stability domain and a performance level of such a system, by using Lyapunov-like approaches. Constructive algorithms are obtained by exploiting properties of quadratic - or piecewise quadratic - Lyapunov functions. Beyond analysis results, we propose design methods to obtain a stability domain as large as possible. Design methods are based on both continuous-time approaches (anti-windup compensator) and hybrid-time approaches (design of adapted reset rules).

In this PhD thesis, the integrated control/structure design of a large flexible spacecraft is addressed using structured H ∞ synthesis. The problem is endeavored by developing a modeling technique forflexible multibody systems, called the Two Input Two Output Port (TITOP) model. This general framework allows the assembly of a flexible multibody system in chain-like or star-like structure, using finite element models as input data. Additionally, the TITOP modeling technique allows the consideration of parametric variations inside the system, a necessary characteristic in order to perform integrated control/structure design.In contrast to another widely used method, the assumed modes method, the TITOP modelling technique is robust against changes in the boundary conditions which link the flexible bodies. Furthermore, the TITOP modeling technique can be used as an accurate approximation even when kinematic nonlinearities can be large. The TITOP modeling technique is extended to the modeling of piezoelectric actuators and sensors for the control of flexible structures and revolute joints.Different control strategies, either for controlling rigid body and flexible body motion, are tested withthe developed models for obtaining the best controller’s architecture in terms of perturbation rejection and vibration damping. The implementation of the integrated control/structure design in the structured H ∞ scheme is developed considering the different system’s specifications, such as system’s bandwidth or modes damping, in the form of H ∞ weighting functions. The integrated attitude control/structure design of a flexible satellite is performed using all the developed techniques and the optimization of the control law and several structural parameters is achieved.; Dans cette étude de thèse, le problème du co-design mécanique/contrôle d’attitude avec méthodes de la commande robuste structurée est considéré. Le problème est abordé en développant une technique pour la modélisation de systèmes flexibles multi-corps, appelé modèle Two-Input Two-Output Port (TITOP).En utilisant des modèles d’éléments finis comme données d’entrée, ce cadre général permet de déterminer, sous certaines hypothèses, un modèle linéaire d’un système de corps flexibles enchaînés. De plus, cette modélisation TITOP permet de considérer des variations paramétriques dans le système, une caractéristique nécessaire pour réaliser des études de co-design contrôle/structure. La technique de modélisation TITOP est aussi étendue pour la prise en compte des actionneurs piézoélectriques et des joints pivots qui peuvent apparaître dans les sous- structures.Différentes stratégies de contrôle des modes rigides et flexibles sont étudiées avec les modèles obtenus afin de trouver la meilleure architecture de contrôle pour la réjection des perturbations basse fréquence et l’amortissement des vibrations. En exploitant les propriétés d’outils de synthèse H ∞ structurée, la mise en œuvre d’un schéma de co-design est expliquée, en considérant les spécifications du système (bande passante du système et amortissement des modes) sous forme de contraintes H ∞ . L’étude d’un tel co-design contrôle d’attitude/mécanique d’un satellite flexible est illustré en utilisant toutes les techniques développées, optimisant simultanément une loi de contrôle optimisée et certains paramètres structuraux.