Implementation of an Internet-based remote controller with guaranteed exponential stabilization

International audienceAn Internet-based remote control system is designed and implemented. The communication is based on the Master-Slave structure. The Master PC communicates with the Slave from about 40km away by UDP protocol. In order to guarantee the Master and Slave clocks to be synchronized, the NTP (Network Time Protocol) is used in both sides. The packets are sent together with time-stamps. The controller design (Master) relies on a remote observer that achieves a state prediction of the application (Slave), despite the variable communication delays. The Slave comprises a PC and a robot Miabot of Merlin company. Internet-based remote systems are subject to variable time delays (including communication and data-sampling delays). We have continuously tested the RTT (round-triptime) between the two PCs in the day-time and night-time by the protocol ICMP (Internet Control Message). From these tests, an evaluation of the maximal time delay is obtained. The structure allows one to guarantee an exponential stabilization performance, which is proven via a Lyapunov-Krassovski functional technique and involves the estimated delay upperbound. This means that the guaranteed decay rate is computed (via some LMI optimization) in relation to some maximal value of the communication delays. Of course, for greater delay values, the performance cannot be guaranteed anymore and an alternative solution has to be considered. In our system, we give a command for the robot to stop until the communication comes back to a sufficient quality

Performance Evaluation of Distributed Systems: a Component-Based Modeling Approach Based on Object Oriented Petri Nets

Non

Networked control and observation for Master-Slave systems

2009, 350 p. 110 illus., Hardcover. ISBN: 978-0-387-85594-3This chapter concerns the design of a remote control loop constituted by a Slave system (with computing and energy limitations) and a Master computer, communicating via an Internet connection. In such a situation, the communication cost is reduced but the Quality of Service of the Internet connection is not guaranteed. In particular, when the Slave dynamics are expected to be fast enough, the network induces perturbations (delays, jitters, packet dropouts and sampling) that may damage the performance. Here, the proposed solution relies on a delay-dependent, state-feedback control, computed by the Master on the basis of an observer. This last estimates the present Slave's state from its past sampled outputs, despite the various delays. Then, the computing task is concentrated in the Master. The theoretical results are based on the Lyapunov-Krasovskii functional and the approach of LMI, which guarantee the stabilization performance with respect to the expected maximum delay of the connection. Two strategies are applied: one is a constant controller/observer gain strategy, which takes into account a fixed upperbound for the communication delay. The second strategy aims at improving the performance by adapting the gains to the available network QoS (here, with two possible upperbounds)

A gain scheduling strategy for the control and estimation of a remote robot via Internet

International audienceA gain scheduling strategy for the controller of a remote robot based on Internet and Bluetooth networks is designed and implemented. The Internet communication is based on the Master-Slave structure, UDP protocol. The Slave comprises a PC and a mobile robot, interconnected through the protocol Bluetooth. The Master is a second PC which realizes the remote control, the design of which is based on a remote observer achieving a state prediction of the robot (Slave), despite the variable communication delays, sampling and packets losses. The detected variable time delays serve as the switching signals. The gain scheduling state feedback controller is based on Lyapunov-Krasovskii functional and the approach of LMI, which guarantee the uniform stabilization performance

Output control with Internet-in-the-loop : An event-driven realization

International audienceThis work is devoted to the remote feedback control of a linear process with "Internet in the loop". In such a networked control situation, variable and unpredictable delays arise, which may decrease the global performance or destabilize the system. Our aim is to obtain the best performance despite the variation of the network QoS (quality of service). The considered application is based on a Master-Slave structure. The Slave is a light mobile robot, that receives the control data and sends its sampled position via a UDP protocol. A Master computer realizes the remote control, based on a remote observer and a state feedback. The global strategy is without buffers. The packets are time-stamped so the Master detects the variable time delays (the network QoS). This information is used to adapt its observer/controller gains and guarantee the best possible performances. The design of this gain scheduling strategy relies on Lyapunov-Krasovskii functionals with an LMI optimization which guarantees the stability even with packet losses. Experimental results are provided

Synthèse de contrôleurs Réseaux de Petri pour le routage dynamique des trains dans un noeud ferroviaire

International audienceCet article présente une méthode de prévention des collisions et des blocages pour le routage automatique des trains dans les noeuds ferroviaires. La méthode de contrôle proposée doit permettre d'optimiser le nombre de trains traversant simultanément le noeud ferroviaire. Le routage des trains est fait de manière dynamique, les trains ne suivent pas un itinéraire mais s'adaptent aux aléas du réseaux. Cette approche permet d'avoir une flexibilité et une densité de trains accrue dans les noeuds ferroviaire. Mais elle doit garantir la sécurité du système et notamment l'absence de collisions entre trains dans le noeud. Pour cela, nous proposons la construction par synthèse d'un Réseau de Petri initial permettant à chaque train d'utiliser et de libérer les ressources au fur et à mesure de sa progression dans le noeud ferroviaire. Mais ce modèle initial peut entrainer un contrôle bloquant. Ainsi nous proposons une méthode de résolution des blocages potentiels permettant de garantir la vivacité du modèle final

Implementation of an Internet-controlled system under variable delays

International audienceThis work deals with the control and the observation of a remote system using Internet as a communication line. The process consists in a Slave part S, with poor computing capacity, connected to a Master M through the Internet. The internal times of both M and S are synchronized thanks to a common GPS clock. The global system must ensure some speed performance whatever the delay variations. The main technical restriction is that the delays are less than some known bound, even if the framework we consider takes into account the perturbations generated by the Internet communication delays, by the packet losses and by the sampling phenomenon as well. In what concerns the design of the observer and controller, most of the theorems to be used here refer to proofs given in [14], and this will allow for focussing on the implementation aspects

Contribution à la Spécification et à la Vérification des Exigences Temporelles (Proposition d'une extension des SRS d'ERTMS niveau 2)

Les travaux développés dans cette thèse visent à assister le processus d ingénierie des exigences temporelles pour les systèmes complexes à contraintes de temps. Nos contributions portent sur trois volets : la spécification des exigences, la modélisation du comportement et la vérification. Pour le volet spécification, une nouvelle classification des exigences temporelles les plus communément utilisées a été proposée. Ensuite, afin de cadrer l utilisateur durant l expression des exigences, une grammaire de spécification à base de motifs prédéfinis en langage naturel est développée. Les exigences générées sont syntaxiquement précises et correctes quand elles sont prises individuellement, néanmoins cela ne garantie pas la cohérence de l ensemble des exigences exprimées. Ainsi, nous avons développé des mécanismes capables de détecter certains types d incohérences entre les exigences temporelles. Pour le volet modélisation du comportement, nous avons proposé un algorithme de transformation des state-machine avec des annotations temporelles en des automates temporisés. L idée étant de manipuler une notation assez intuitive et de générer automatiquement des modèles formels qui se prêtent à la vérification. Finalement, pour le volet vérification, nous avons adopté une technique de vérification à base d observateurs et qui repose sur le model-checking. Concrètement, nous avons élaboré une base de patterns d observation (ou observateurs) ; chacun des patterns développés est relatif à un type d exigence temporelle dans la nouvelle classification. Ainsi, la vérification est réduite à une analyse d accessibilité des états correspondants à la violation de l exigence associéeThe work developed in this thesis aims to assist the engineering process of temporal requirements for time-constrained complex systems. Our contributions concern three phases: the specification, the behaviour modelling and the verification. For the specification of temporal requirements, a new temporal properties typology taking into account all the common requirements one may meet when dealing with requirements specification, is introduced. Then, to facilitate the expression, we have proposed a structured English grammar. Nevertheless, even if each requirement taken individually is correct, we have no guarantee that a set of temporal properties one may express is consistent. Here we have proposed an algorithm based on graph theory techniques to check the consistency of temporal requirements sets. For the behaviour modelling, we have proposed an algorithm for transforming UML State Machine with time annotations into Timed Automata (TA). The idea is to allow the user manipulating a quite intuitive notation (UML SM diagramsduring the modelling phase and thereby, automatically generate formal models (TA) that could be used directly by the verification process. Finally, for the verification phase, we have adopted an observer-based technique. Actually, we have developed a repository of observation patterns where each pattern is relative to a particular temporal requirement class in our classification. Thereby, the verification process is reduced to a reachability analysis of the observers KO states relatives to the requirements violationVILLENEUVE D'ASCQ-ECLI (590092307) / SudocSudocFranceF

A switched system approach to exponential stabilization through communication network

International audienceThe paper considers a networked control loop, where the plant is a "slave" part, and the remote controller and observer constitute the "master". Since the performance of Networked Control Systems (NCS) depends on the Quality of Service (QoS) available from the network, it is worth to design a controller that takes into account qualitative information on the QoS in realtime. The goal of the design is to provide a controller that guarantees two things: 1) high performances (here expressed by exponential decay rates) when the QoS remains globally the same; 2) global stability when the QoS changes. In order to guarantee the global stability, the controller will switch by respecting a dwell time constraint. The dwell time parameters are obtained by using the switched system theories and the obtained conditions are Linear Matrix Inequalities (LMI). An experiment illustrates how the controller can be implemented for a control over Internet application (remote control of a small robot)

MODELISATION DE CONTROLEURS DISCRETS POUR L'INDUSTRIE 4.0

International audienceCe papier présente une étude relative au développement de systèmes de production intelligents dans le contexte de l'industrie manufacturière. Nous montrons que de tels systèmes doivent être agile, c'est-à-dire capable de s'adapter rapidement à des contextes changeant comme une production particulière ou une panne. Dans cette étude nous modélisons le système de commande de ces systèmes par une approche en couches et générique. Nous distinguons plusieurs classes de modèles permettant de gérer chacun différentes catégories de flexibilité. L'objectif essentiel de l'étude est de fournir une méthode rigoureuse et systématique permettant de modéliser et de vérifier de manière efficace ce type de système