Stability analysis of a general class of singularly perturbed linear hybrid systems

Motivated by a real problem in steel production, we introduce and analyze a general class of singularly perturbed linear hybrid systems with both switches and impulses, in which the slow or fast nature of the variables can be mode-dependent. This means that, at switching instants, some of the slow variables can become fast and vice-versa. Firstly, we show that using a mode-dependent variable reordering we can rewrite this class of systems in a form in which the variables preserve their nature over time. Secondly, we establish, through singular perturbation techniques, an upper bound on the minimum dwell-time ensuring the overall system's stability. Remarkably, this bound is the sum of two terms. The first term corresponds to an upper bound on the minimum dwell-time ensuring the stability of the reduced order linear hybrid system describing the slow dynamics. The order of magnitude of the second term is determined by that of the parameter defining the ratio between the two time-scales of the singularly perturbed system. We show that the proposed framework can also take into account the change of dimension of the state vector at switching instants. Numerical illustrations complete our study

Optimistic minimax search for noncooperative switched control with or without dwell time

International audienceWe consider adversarial problems in which two agents control two switching signals, the first agent aiming to maximize a discounted sum of rewards, and the second aiming to minimize it. Both signals may be subject to constraints on the dwell time after a switch. We search the tree of possible mode sequences with an algorithm called optimistic minimax search with dwell time (OMSd), showing that it obtains a solution close to the minimax-optimal one, and we characterize the rate at which the suboptimality goes to zero. The analysis is driven by a novel measure of problem complexity, and it is first given in the general dwell-time case, after which it is specialized to the unconstrained case. We exemplify the framework for networked control systems where the minimizer signal is a discrete time delay on the control channel, and we provide extensive simulations and a real-time experiment for nonlinear systems of this type

Analyse de stabilité et synchronisation des systèmes singulièrement perturbés

This PhD thesis is dedicated to the study of stability and control design for singularly perturbed systems. In the first part, we introduce and analyze a general class of singularly perturbed linear hybrid systems, in which the slow or fast nature of the variables is mode-dependent. Our stability analysis is based on classical results of Lyapunov’s theory for singularly perturbed systems. A second part of this work presents the design of a decentralized control strategy that allows singularly perturbed multi-agent systems to achieve synchronization with global performance guarantees. To avoid the use of centralized information related to the interconnection network structure, the problem is solved by rewriting the synchronization problem in terms of stabilization of a singularly perturbed uncertain linear systemaThis PhD thesis is dedicated to the study of stability and control design for singularly perturbed systems. In the first part, we introduce and analyze a general class of singularly perturbed linear hybrid systems, in which the slow or fast nature of the variables is mode-dependent. Our stability analysis is based on classical results of Lyapunov’s theory for singularly perturbed systems. A second part of this work presents the design of a decentralized control strategy that allows singularly perturbed multi-agent systems to achieve synchronization with global performance guarantees. To avoid the use of centralized information related to the interconnection network structure, the problem is solved by rewriting the synchronization problem in terms of stabilization of a singularly perturbed uncertain linear systemLes travaux de cette thèse portent sur l’analyse de stabilité et la synthèse de commande pour les systèmes singulièrement perturbés. Dans une première partie, nous présentons et analysons une classe générale de systèmes linéaires hybrides singulièrement perturbés dans lesquels la nature lente et rapide des variables d’état dépend du mode de fonctionnement. L’analyse de stabilité est fondée sur des résultats classiques de la théorie de Lyapunov pour les systèmes singulièrement perturbés. Une deuxième partie de ce travail présente la conception d’une loi de commande décentralisée qui garantit la synchronisation des systèmes multi-agents singulièrement perturbés avec un coût global garanti. Afin de contourner l’utilisation d’informations centralisées liées à la structure du réseau d’interconnexion, le problème est résolu en reformulant le problème de synchronisation comme un problème de stabilisation d’un système linéaire incertain singulièrement perturb

Stability analysis and synchronisation of singularly perturbed systems

Les travaux de cette thèse portent sur l’analyse de stabilité et la synthèse de commande pour les systèmes singulièrement perturbés. Dans une première partie, nous présentons et analysons une classe générale de systèmes linéaires hybrides singulièrement perturbés dans lesquels la nature lente et rapide des variables d’état dépend du mode de fonctionnement. L’analyse de stabilité est fondée sur des résultats classiques de la théorie de Lyapunov pour les systèmes singulièrement perturbés. Une deuxième partie de ce travail présente la conception d’une loi de commande décentralisée qui garantit la synchronisation des systèmes multi-agents singulièrement perturbés avec un coût global garanti. Afin de contourner l’utilisation d’informations centralisées liées à la structure du réseau d’interconnexion, le problème est résolu en reformulant le problème de synchronisation comme un problème de stabilisation d’un système linéaire incertain singulièrement perturbéThis PhD thesis is dedicated to the study of stability and control design for singularly perturbed systems. In the first part, we introduce and analyze a general class of singularly perturbed linear hybrid systems, in which the slow or fast nature of the variables is mode-dependent. Our stability analysis is based on classical results of Lyapunov’s theory for singularly perturbed systems. A second part of this work presents the design of a decentralized control strategy that allows singularly perturbed multi-agent systems to achieve synchronization with global performance guarantees. To avoid the use of centralized information related to the interconnection network structure, the problem is solved by rewriting the synchronization problem in terms of stabilization of a singularly perturbed uncertain linear syste

Event triggering strategies for consensus in clustered networks

International audienceThis paper focuses on consensus in networks partitioned in several clusters. It uses the multi-agent framework in which the network is seen as a sum of interconnected subsystems called agents. We assume that each agent updates its state continuously by taking into account the states of some other agents belonging to the same cluster. This protocol allows reaching only local agreements in the network. In order to get consensus we endow an agent per cluster with the capacity to discretely interact outside its own cluster. The discrete interaction of one agent with agents from other clusters is modeled as a state jump or reset. The inter-clusters interactions are activated by using event dependent rules. The goal of the paper is to design event triggering reset strategies that guarantee the consensus is achieved. No global dwell time separating the reset instants is imposed but we show that a dwell time per cluster is ensured by the proposed reset strategies

Synchronization in networks of linear singularly perturbed systems

International audienceThis work is motivated by the fact that many real systems are characterized by two features. The first one is that they are obtained by interconnecting a bunch of simpler subsystems that have to synchronize in order to reach a global goal. The second one is that each subsystem presents dynamics that evolves on different time-scales. Taking into account the two features leads to the problem of synchronization in networks of singularly perturbed systems. In this work we are providing a preliminary study that considers the problem where each subsystem is linear and the network topology is represented by a connected undirected graph that is fixed in time. We show that we can proceed to a time-scale separation of the overall network dynamics and design the controls that synchronize the slow dynamics and the fast ones. Applying the joint control actions to the network of singularly perturbed systems we obtain an approximation of the synchronization behavior imposed for each scale. The methodology requires a variable transformation to overcome the fact that we are dealing with non-standard singularly perturbed systems. One example illustrates the synchronization behavior of linear singularly perturbed systems

Stability analysis of singularly perturbed switched linear systems

International audienceThis chapter proposes a methodology for stability analysis of singularly perturbed switched linear systems. We emphasize that, besides the stability of each subsystem, we need a dwell-time condition to guarantee the overall system stability. The main results of this study provide a characterization of an upper bound on the dwell time ensuring the overall system’s stability. Remarkably, this bound is the sum of two terms. The first one is an upper bound on the dwell time ensuring stability of the reduced-order linear switched system, which is zero if all the reduced modes share a common Lyapunov function. The magnitude of the second term is of order of the parameter defining the ratio between the two timescales of the singularly perturbed system

Stability analysis of singularly perturbed switched and impulsive linear systems

International audienceThis paper proposes a new methodology for stability analysis of singularly perturbed linear systems whose dynamics is affected by switches and state jumps. The overall problem is formulated in the framework of hybrid singularly perturbed systems and we use Lyapunov-based techniques to investigate its stability. We emphasize that, beside the stability of slow and fast dynamics, we need a dwell-time condition to guarantee the overall singularly perturbed system is globally asymptotically stable. Furthermore, we characterize this dwell-time as the sum of one term related to the stabilization of systems evolving on one timescale (slow dynamics) and one term of the order of the parameter defining the ratio between the timescales. As highlighted in the paper the second term is required to compensate the effect of the jumps introduced in the state of the boundary layer system by the switches and impulses affecting the overall dynamics. Some numerical examples illustrates our results

Design of O(ε) dwell-time graph for stability of singularly perturbed hybrid linear systems

International audienceThe paper deals with singularly perturbed hybrid systems. It proposes a methodology for building a graph defining all the rules that ensure the origin is a stable equilibrium in presence of a dwell-time of order of the parameter defining the ratio between the two timescales of the system. In this framework one can also treat the corresponding problem for interesting particular cases such as: singularly perturbed switched linear systems without impulses, one scale hybrid systems or one scale switched systems. A numerical example illustrates the theoretical results completing the paper