Multi-agent framework based on smart sensors/actuators for machine tools control and monitoring

Throughout the history, the evolutions of the requirements for manufacturing equipments have depended on the changes in the customers' demands. Among the present trends in the requirements for new manufacturing equipments, there are more flexible and more reactive machines. In order to satisfy those requirements, this paper proposes a control and monitoring framework for machine tools based on smart sensor, on smart actuator and on agent concepts. The proposed control and monitoring framework achieves machine monitoring, process monitoring and adapting functions that are not usually provided by machine tool control systems. The proposed control and monitoring framework has been evaluated by the means of a simulated operative part of a machine tool. The communication between the agents is achieved thanks to an Ethernet network and CORBA protocol. The experiments (with and without cooperation between agents for accommodating) give encouraging results for implementing the proposed control framework to operational machines. Also, the cooperation between the agents of control and monitoring framework contributes to the improvement of reactivity by adapting cutting parameters to the machine and process states and to increase productivity

Data validation: a case study for a feed-drive monitoring

The monitoring of machine-tools implicated in the metal cutting process is the subject of increasing developments because of requests on control, reliability, availability of machine-tools and on work-piece quality. The use of computers contributes to a better machine and process monitoring by enabling the implementation of complex algorithms for control, monitoring, … The improvement of monitoring of the main machine-tools devices, the feed-drives and the spindles that drive the cutting process, can be realised by estimating their fault sensitive physical parameters from their continuous-time model. We have chosen to use a continuous-time ARX model. We particularly focus on slow time varying phenomena. This estimation should run while there is no machining process to avoid false detection of faults on the machine due to the cutting process. High speed motions, that occur at least for each tool exchange, are exploited. Some functional constraints require the use of an off-line estimation method, we have chosen an ordinary least squares method. Estimating the physical parameters is insufficient to obtain an efficient monitoring. A measurement analysis and validation are necessary as the validation of the estimated physical parameters. An approach of the measurement and physical parameter estimation validation for a NC machine-tool feed-drive is proposed

Design methodology for smart actuator services for machine tool and machining control and monitoring

This paper presents a methodology to design the services of smart actuators for machine tools. The smart actuators aim at replacing the traditional drives (spindles and feed-drives) and enable to add data processing abilities to implement monitoring and control tasks. Their data processing abilities are also exploited in order to create a new decision level at the machine level. The aim of this decision level is to react to disturbances that the monitoring tasks detect. The cooperation between the computational objects (the smart spindle, the smart feed-drives and the CNC unit) enables to carry out functions for accommodating or adapting to the disturbances. This leads to the extension of the notion of smart actuator with the notion of agent. In order to implement the services of the smart drives, a general design is presented describing the services as well as the behavior of the smart drive according to the object oriented approach. Requirements about the CNC unit are detailed. Eventually, an implementation of the smart drive services that involves a virtual lathe and a virtual turning operation is described. This description is part of the design methodology. Experimental results obtained thanks to the virtual machine are then presented

A distributed architecture to implement a prognostic function for complex systems

The proactivity in maintenance management is improved by the implementation of CBM (Condition-Based Maintenance) principles and of PHM (Prognostic and Health Management). These implementations use data about the health status of the systems. Among them, prognostic data make it possible to evaluate the future health of the systems. The Remaining Useful Lifetimes (RULs) of the components is frequently required to prognose systems. However, the availability of complex systems for productive tasks is often expressed in terms of RULs of functions and/or subsystems; those RULs have to bring information about the components. Indeed, the maintenance operators must know what components need maintenance actions in order to increase the RULs of the functions or subsystems, and consequently the availability of the complex systems for longer tasks or more productive tasks. This paper aims at defining a generic prognostic function of complex systems aiming at prognosing its functions and at enabling the isolation of components that needs maintenance actions. The proposed function requires knowledge about the system to be prognosed. The corresponding models are detailed. The proposed prognostic function contains graph traversal so its distribution is proposed to speed it up. It is carried out by generic agents

Distributed machining control and monitoring using smart sensors/actuators

The study of smart sensors and actuators led, during the past few years, to the development of facilities which improve traditional sensors and actuators in a necessary way to automate production systems. In an other context, many studies are carried out aiming at defining a decisional structure for production activity control and the increasing need of reactivity leads to the autonomization of decisional levels close to the operational system. We suggest in this paper to study the natural convergence between these two approaches and we propose an integration architecture dealing with machine tool and machining control that enables the exploitation of distributed smart sensors and actuators in the decisional system

Burdekin's utopian visions : a study of four interwar texts

This thesis is an exploration of four of Katharine Burdekin’s utopian texts from the interwar period. Each text offers a unique perspective on the genre. The earliest text considered is The Rebel Passion (1929), Burdekin’s first utopian text and the only one that shows the representation of a truly positive society. In contrast, her later novel Swastika Night (1937), written on the cusp of the Second World War, is a dystopian nightmare set hundreds of years in the future, envisioning a society under the rule of a Nazi Empire. The third novel explored is The End of this Day’s Business (written in 1935 but published for the first time in 1989) a sex-role reversal utopia that explores gender inequality through the reversal of traditional gender roles: women rule and men are subservient. Finally, Proud Man (1934) is an intriguing tale of an androgynous character from a utopian reality who visits England in the 1930s

Etude de la contagion sur les marchés actions

Ce travail a pour but de mettre en évidence la nécessité de l’analyse en continu des coefficients de corrélation dans le but de prévenir le risque systémique. Dans un premier temps, on verra les fondements théoriques qui ont articulé la réflexion constituant la genèse de ce travail. Dans un deuxième temps, grâce à deux exemples, on verra comment l’étude des co-mouvements peut permettre d’observer l’effet de contagion sur les marchés actions. Finalement, des potentielles applications de l’analyse des coefficients de corrélation seront mises en avant. Par cette démarche, on constatera que l’observation des mouvements joints par le biais de l’analyse technique, peut permettre de déceler des opportunités d’investissements

Tesla, changement de paradigme ou feu de paille ?

Tesla, le constructeur de voitures entièrement électriques, vous connaissez ? On en croise de plus en plus souvent sur la route et malgré l’absence de publicité, la marque parvient à créer un réel intérêt chez les individus. Le but de ce travail est d’analyser les chances que Tesla devienne un leader mondial du véhicule électrique et celles de voir cette société disparaître aux oubliettes comme d’autres premiers entrants dans des secteurs économiques différents. L’analyse des trois différentes strates de l’environnement (Macroenvironnement – Industrie – Concurrents et marchés) nous a permis de relever les éléments qui possèdent un impact, positif ou négatif, sur Tesla. Premièrement, l’analyse PESTEL nous a permis de découvrir divers facteurs d’influence qui peuvent être des opportunités telles que la tendance écologique, la baisse du prix des batteries de type lithium-ion ou encore le réchauffement climatique. En revanche, le développement des voitures à hydrogène, ainsi que le durcissement de la loi sur l’environnement sont deux exemples de menaces que Tesla doit surveiller. Deuxièmement, les deux variables pivots ayant le plus d’impact et étant les plus incertaines ont permis de réaliser quatre scénarios à l’horizon 2030. L’évolution du prix du pétrole et l’intervention des politiques par rapport aux voitures propres ont été croisés. Le scénario 1 « Changement de paradigme » est celui qui est le plus favorable pour Tesla et postule pour un monde dans lequel le prix du pétrole est haut et l’intervention des politiques est favorable aux voitures propres. Le scénario 3 « Statu quo » est beaucoup plus menaçant pour la marque qui se verra mettre plusieurs barrières au travers de son chemin à cause du bas prix du pétrole et de l’intervention politique pas ou peu avantageuse pour les voitures propres, ce qui exigera des moyens financiers plus importants avant de réaliser le premier profit. Dans l’industrie, les 5(+1) forces de Porter, puis la dynamique de la concurrence nous ont démontrés que malgré le calme au niveau concurrentiel qui règne actuellement, il n’en sera pas autant à l’avenir. En effet, Tesla est menacée par une forte augmentation de l’intensité concurrentielle, étant donné que tous les plus grands constructeurs automobiles actuels s’y mettent et proposent déjà souvent un modèle hybride, électrique, voir à hydrogène pour certaines marques