Commande des Systèmes Aérospatiaux non Linéaires à Dimensions Finie et Infinie

RESUME La synthese de lois de commande pour les systemes aerospatiaux demeure un probleme complexe soumis a de multiples contraintes d’architecture, de performance et de certification. La recherche d’un rapport performance-poids minimal offrant une autonomie de fonctionnement maximisee est une problematique majeure amenant a employer des structures dont la flexibilite est sans cesse accrue. Une telle tendance amene a devoir developper des solutions de commande active des phenomenes aeroelastiques. Dans ce contexte global, cette these s’articule autour de deux themes majeurs, a savoir la commande des systemes aerospatiaux non lineaires par la methode du sequencement des gains et la commande des ailes d’avions flexibles modelisees par des systemes a parametres distribues. Dans la premiere partie portant sur la methode du sequencement des gains, on s’attarde plus specifiquement sur la problematique des termes de couplage caches (TCC). Ces termes tirent leur origine de la variation du parametre de sequencement dans le temps. En effet, alors que la synthese des gains du controleur est effectuee en un point de fonctionnement donne suppose invariant dans le temps, l’implementation finale voit le parametre de sequencement varier. Cette difference de nature du point de fonctionnement entre la phase de synthese et l’implementation finale est la source meme des TCC. Lorsque negliges ou non consideres adequatement, ils sont a meme de degrader les performances du systeme boucle, voire le destabiliser. La premiere solution developpee dans cette these pour gerer les TCC reside dans leur incorporation dans le processus de synthese. La difficulte majeure d’une telle approche reside dans le fait que les TCC ne dependent pas uniquement de la valeur des gains au point d’operation courant mais egalement de leur evolution dans un voisinage de ce dernier. Des lors, les methodes de synthese classiques de controleurs sequences ne permettent par leur inclusion de maniere directe. La solution proposee dans cette these consiste a tirer profit de methodes d’autosequencement des gains, i.e., des methodes de synthese de controleurs sequences dont les formules de sequencement sont fixees a priori. Trois approches sont investiguees : la synthese H1 structuree, le placement de structure propre et une approche iterative pouvant se baser sur une methode de synthese quelconque. La seconde solution developpee vise a s’affranchir de la problematique des TCC lors de la phase de synthese afin de la traiter au niveau de la strategie d’implementation du controleur sequence. La strategie employee tire avantage de composantes de filtrage localisees en entree et en sortie du controleur sequence. ----------ABSTRACT Control system development for aerospace systems remains a complex issue due to multiple architectural constraints, stringent performance requirements, and strict certification processes. As the autonomy of such systems is critical, the balance between weight and performance pushes toward structures exhibiting increased flexibility. Such a trend forces the development of active control strategies for aeroelastic phenomenon. In this context, this thesis investigates two main themes: gain-scheduling control of nonlinear aerospace systems and control of flexible aircraft wings modeled by distributed parameter systems. The first part of the thesis deals with gain-scheduling control design. The investigations are devoted to the issue of hidden coupling terms (HCTs). The occurrence of HCTs is due to the time-varying nature of the scheduling parameter. Indeed, the operating points that are supposed to be constant in the synthesis phase are time-varying in final implementation, which induces the HCTs. If not considered properly, they can result in a severe performance degradation, and even the destabilization of the closed-loop system. The first solution developed in this thesis for handling HCTs consists in the explicit inclusion of HCTs in the synthesis process. The main difficulty of such an approach comes from the fact that HCTs do not only depend on the controller gains at the current operating point, but also on their evolution around this point. Thus, classic gain-scheduled control design methods cannot include the effect of HCTs in a straightforward manner. The solution proposed in this thesis takes advantage of self-scheduling methods, i.e., gain-scheduled control synthesis methods allowing to impose a priori the scheduling functions. Three approaches are investigated: structured H1 design, eigenstructure assignment, and an iterative approach employing an arbitrary synthesis method. The second solution developed aims at avoiding the occurrence of the HCTs at the implementation level. Such a solution allows proceeding to the synthesis of the gain-scheduled controller while not considering the impact of the HCTs, as their occurrence can be avoided by an appropriate implementation. The employed strategy takes advantage of filtering components located at both input and output of the gain-scheduled controller. The validity of this scheme is confirmed by theoretical analyses ensuring that the implementation preserves the input-output behavior of the local controllers, while not affecting the internal stability properties corresponding to the uncontrollable and unobservable modes.