One of the best known forms of feeding back a system is through a three-term control law called PID (Proportional-Integral-Derivative) controller. PID controllers are sufficient for many control problems, particularly when process dynamics are not highly nonlinear and the performance requirements are modest. Besides, because of its simple structure, the PID controller is the most adopted control scheme by industry and practitioners. Since, the PI(D) tuning methods are based on the linearization, commissioning a PI(D) to operate around a single operating point is relatively easy, however, the performance will be below par in wide operating regimes. To overcome this drawback the current practice is to re-tune the gains of the controllers based on a linear model of the plant evaluated at various operating points, a procedure known as gain-scheduling. There are several disadvantages of gain-scheduling including the need to switch (or interpolate) the controller gains and the non-trivial definition of the regions in the plants state space where the switching takes place --both problems are exacerbated if the dynamics of the plant is highly nonlinear. This makes impossible to guarantee the system stability. In this context, the current thesis work is aimed at the designing of PI controllers, based on the passivity theory, such that the stability of the nonlinear model is guarantied in closed-loop. The approach here presented is constructive and motivated by the applicaton to physical systems.

Membres du jury :

M. Stanislav ARANOVSKIY, Maître de conférence, ITMO University, examinateur.

M. Robert GRIÑÓ, Professeur, Polytechnic University of Catalonia, rapporteur.

M. Hugues MOUNIER, Professeur, Laboratoire de Signaux et Systèmes, examinateur.

M. Romeo ORTEGA, Directeur de recherche au CNRS, directeur de thèse.

M. Jacquelien SCHERPEN, Professeur, University of Groningen, rapporteur.