Search

This paper focuses on a tool to estimate lost data on network control systems. The tool is also able to detect loss of data integrity and estimate the correct value. A new formulation of the Finite Memory Observer using a finite collection of measurements and input is proposed to achieve these goals. First, the realisation of this tool is based on a Markov chain used to implement an event triggering mechanism applied to models of lost network measurement packets. The Finite Memory Observer (FMO) is based on a continuous time system model which corresponds better to time management in further works. The new formulation, dealing with loss of measurement packets, uses timestamping of data received to adjust the data estimation-predictions generated. The propagation of data loss in the observer's window and its effect on the estimate is presented. Finally, on a simple packet loss scenario, the accuracy of this prediction-estimation observer is presented. Secondly, the FMO is used to detect modification of data. Given the packet strategy, when a data modification is detected , the associated measurement will be not used for its estimation/prediction.

The works described in this thesis deal with the integrity and availability of networked control systems information. The importance of this has been highlighted by the growing number of cyber-attacks. A finite memory observer is proposed as a tool to answer this problem. This tool provides an answer to the problems of packet loss on the network as well as to static and dynamic cyber-attacks using bias injection. Combined with a detection-decision-correction strategy, the reliability of system information during cyber-attacks is ensured. The uncertainties of the models of some systems are also taken into account in the development of the finite memory observer. More specifically, two categories of uncertainties are addressed (uncertain systems and correlated noise systems). All case studies are illustrated by numerical simulations confirming the qualities of this tool. Finally, we will apply this tool to teleoperated systems subjected to new types of attacks called “smart attacks”., Les travaux décrits dans cette thèse concernent l’intégrité et la disponibilité des informations de systèmes commandés en réseau. L’importance de celles-ci a été mise en exergue face au nombre de plus en plus important de cyber-attaques. Nous proposons comme outil pour répondre à cette problématique un observateur à mémoire finie. Cet outil apporte une réponse aux problèmes de pertes de paquets sur le réseau ainsi qu’aux cyber-attaques statiques et dynamiques par injection de biais. Associé à une stratégie de détection-décision-correction, la fiabilité des informations de systèmes lors de cyber-attaques est assurée. Les incertitudes du modèle pour certains systèmes sont également prises en compte dans le développement de l’observateur à mémoire finie. Plus particulièrement, deux catégories d’incertitudes sont traitées (systèmes incertains et systèmes à bruits corrélés). Tous les cas d’études sont illustrés par des simulations numériques confirmant les qualités de cet outil. Enfin, nous appliquerons cet outil aux systèmes télé-opérés soumis à de nouveaux types d’attaques appelés attaques intelligentes".