Dynamic structure identification of Bayesian network model for fault diagnosis of FMS

International audienceThis paper proposes an approach to accurately localize the origin of product quality drifts, in a flexible manufacturing system (FMS). The logical diagnosis model is used to reduce the search space of suspected equipment in the production flow; however, it does not help in accurately localizing the faulty equipment. In the proposed approach, we model this reduced search space as a Bayesian network that uses historical data to compute conditional probabilities for each suspected equipment. This approach helps in making accurate decisions on localizing the cause for product quality drifts as either one of the equipment in production flow or product itself

Diagnosis in complex system with multiple failure sources

International audienceThis paper proposes an approach to accurately localize the origin of product quality drifts, in a flexible manufacturing system (FMS). The failure propagation mechanism in a production process is proposed based on the relationships between failure sources to explain the failure propagation following production flow. The logical diagnosis model is used to reduce the search space of suspected equipment in the production flow; however, it does not help in accurately localizing the faulty equipment. In the proposed approach, we model this reduced search space as a Bayesian network that uses historical data to compute conditional probabilities for each suspected equipment. This approach helps in making accurate decisions on localizing the cause for product quality drifts as either one of the equipment in production flow or product itself

Architecture de surveillance-commande pour les systèmes à événements discrets complexes

The work presented deals with the supervision of flexible manufacturing systems. It presents the integration of real-time monitoring of process failures. The originality of this approach is to consider the control and the monitoring on the same level and not the monitoring as a palliative for the control. A structure of a monitoring-control module is proposed. This module is made up of two cooperating models based on the activity concept. The first one, the reference model for monitoring and control, gives all the functionalities of the monitoring system. The second one, the strategy model for monitoring and control, models the constraints imposed by the objectives of the firm and the users. The execution of a monitoring treatment is not limited to the strict sequence ¿ detection, diagnosis, decision and recovery ¿. Other elaborated sequences are allowed and can be executed by the module. Taking the executed activity into account, a supervisor integrated in each module of the hierarchy manages the information by directing each one to the suitable monitoring or control functions: detection, follow, control, diagnosis, decision, recovery or emergency. An example based on a manufacturing process illustrates the main benefits of the approach: monitoring flexibility, reactivity to the process evolutions, respect of the monitoring constraints imposed by the factory.Le travail présenté dans ce mémoire s'inscrit dans le contexte de la supervision des ateliers flexibles de production manufacturière. Il traite plus particulièrement de l'intégration de la surveillance temps réel des défaillances du procédé. L'approche se distingue en considérant la commande et la surveillance sur un même plan et non la surveillance comme un palliatif à la commande. Une structure d'un module de surveillance-commande est proposée. Le module est constitué de deux modèles coopérants basés sur le concept d'activités : l'un, appelé modèle de référence pour la surveillance-commande, modélise toutes les fonctionnalités mises en ¿uvre par le système de surveillance, l'autre, appelé modèle de la stratégie de surveillance-commande, modélise les contraintes imposées par les objectifs propres de l'entreprise et des utilisateurs. L'exécution d'un traitement de surveillance (séquence d'activités) n'est pas limitée au strict enchaînement des fonctions détection, diagnostic, décision puis reprise. D'autres séquences mettant en ¿uvre des activités de surveillance-commande plus élaborées (par exemple, activation de plusieurs fonctions de surveillance-commande du module simultanément) sont autorisées et réalisables par le module. En fonction des activités en cours d'exécution, un superviseur implanté dans chacun des modules gère l'ensemble des informations qui transitent par le module en les orientant vers la ou les fonctions de surveillance-commande aptes à les prendre en compte : détection, diagnostic, décision, reprise, urgence, suivi, commande. Un exemple d'application basé sur un processus manufacturier réel, la cellule flexible de l'Ecole Nationale d'Ingénieur de Tarbes (ENIT), illustre les apports de notre approche. Ils se traduisent en terme de flexibilité de surveillance, de réactivité aux diverses évolutions du procédé, de prise en compte et de respect des contraintes imposées par l'entreprise d'un point de vue surveillance

Diagnosis for control system reconfiguration

International audienceThe objective of the Automated Manufacturing System reconfiguration is to react to failures such as breakdowns of actuators or sensors. Following such events, the control laws run by the control system are often blocked and thus become inadequate. Thus, it is therefore necessary to reconfigure the control system. This reconfiguration process is inevitably based on the capacities still offered by the operating part to achieve the production objectives. In this context, the paper proposes an on-line function diagnosis able to provide the required information on the capacities of the operating part. It is based on a model of the operating part in normal operation, and generic rules to obtain the possible origins and consequences of a detected symptom of failure

Graphical models for prognostics integration of complex discrete event systems

International audienc

Equipment Health Factor prediction for complex semiconductor manufacturing facility

International audienceThis work takes place within the IMPROVE European project aimed at increasing the availability of manufacturing equipment and to avoid rejection of the products in the semiconductor field. The thermal furnaces are one of the important production equipment. They are composed of two processing reactors for the gas deposition on silicon wafers at low pressure and high temperature. Due to the occurrence and the severity of registered drifts, this equipment requires special attention. In this context, we propose a probabilistic model to predict failures based on Bayesian belief networks. The sequential data are strongly present on the extracted databases and their modeling is important. For their simplicity and flexibility, the dynamic Bayesian networks are used for this. They allow predict the future failures according to their causes and in a dynamic way

Analyse des risques des systèmes complexes : vers une approche Bayésienne

National audienc

Logic control law design for automated manufacturing systems

International audienceTo respond rapidly to the highly volatile market, the reconfigurable manufacturing systems (RMS) have brought forward challenging issues. First of all there is a need to build a formal model of a manufacturing configuration. Second it has to be rather easy to derive the models associated to the manufacturing configuration changes (reconfiguration) from such an initial model. An off-line method of rapid design of an optimal logic control law (configuration) based on Petri net (PN) is presented in this paper. From a controlled system modeling point of view, the main characteristics of the level 1 of the CIM architecture are depicted. Subsequently, the formal tool used in the automated planning field is extended to provide a controlled system model. The concept of operation is structured in order to introduce the behavioral properties of the operations. A four-step method is then proposed to design a logic control law that satisfies several goals: reduction of the lead time, satisfaction of the work orders objectives, minimization of the time cycle. Finally, the proposed design method is illustrated on a manufacturing cell

Logic control law design for automated manufacturing systems

International audienceTo respond rapidly to the highly volatile market, the reconfigurable manufacturing systems (RMS) have brought forward challenging issues. First of all there is a need to build a formal model of a manufacturing configuration. Second it has to be rather easy to derive the models associated to the manufacturing configuration changes (reconfiguration) from such an initial model. An off-line method of rapid design of an optimal logic control law (configuration) based on Petri net (PN) is presented in this paper. From a controlled system modeling point of view, the main characteristics of the level 1 of the CIM architecture are depicted. Subsequently, the formal tool used in the automated planning field is extended to provide a controlled system model. The concept of operation is structured in order to introduce the behavioral properties of the operations. A four-step method is then proposed to design a logic control law that satisfies several goals: reduction of the lead time, satisfaction of the work orders objectives, minimization of the time cycle. Finally, the proposed design method is illustrated on a manufacturing cell

Filters Based Approach with Temporal and Combinational Constraints for Cybersecurity of Industrial Control Systems

International audienceIndustrial Control Systems (ICS) are increasingly deployed in critical infrastructures. Originally designed to increase the productivity of ICS as well as safety and reliability, nowadays these systems are becoming the target of hackers. Several attacks highlighted vulnerabilities, the most relevant one, Stuxnet, stroke in 2010. Protection of ICS against cyberattacks has to be considered. Security of these systems is different from IT security solutions because exchanged data have physical consequences. For that, a new approach for Intrusion Detection System (IDS) in ICS was presented based on filters monitoring orders and reports. Methodology to obtain these filters and their locations in the ICS architecture were introduced. In this paper, we present major improvements in detection mechanisms of these filters. Distance concept, introduced in previous paper (Sicard et al., 2017), is developed and combined to trajectory concept that allows filters to detect deviations from expected behavior. Distance from optimal or forbidden states is essential to compute order sequence bringing back the system into safe states. Trajectory, which is the evolution of distance during state evolution, improves detection mechanism by analyzing sequences sent to the system and received by Programmable Logic Controller (PLC). This combinational security prevents damages against goods and people. Implementation of time based intrusion detection is a step forward for improving filters. Temporal windows indicate when actions have to be done and if received reports correspond to executed orders. Thus, our filter approach secures ICS against combinational and temporal attacks affecting security of goods and people or quality