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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Design and Reconfiguration of Manufacturing Systems in Agile Manufacturing Environments

Daghestani, Shamil F. 20 April 1999 (has links)
Agile manufacturing has become a topic of great interest over the past several years. The entire domain of modeling and analyzing different types of agile manufacturing environments and systems, however, remain largely unexplored. The objective of this research is to provide fundamental insight into how manufacturing systems should be designed and reconfigured over time in order to cope with different agile manufacturing environments. To achieve this objective, three approaches are developed and integrated into one simulation-based model. The first approach is used to model different agile manufacturing environments. The second approach is used to define various ways in which manufacturing systems can be designed and reconfigured (i.e., design/reconfiguration strategies). The third comprises the cost and objective functions used to measure system performance when different design/reconfiguration strategies are used in different agile manufacturing environments. Based upon the assumptions adopted during this thesis, the experimental work performed suggests that despite the fact that agility incurs high costs, agile manufacturing systems are indeed necessary for certain manufacturing environments in which product life cycles are short yet demand per product type is high. Therefore, it is important in certain manufacturing environments to focus on reconfiguration in short periods of time, even at the expense of higher reconfiguration costs. / Master of Science
2

Contribution à l'analyse de sûreté de fonctionnement basée sur les modèles des systèmes dynamiques, réparables et reconfigurables / Contribution to model Based Safety Analysis for dynamic repairable reconfigurable systems

Piriou, Pierre-Yves 27 November 2015 (has links)
Dans les travaux existants, les analyses basées sur les modèles de la Sûreté de Fonctionnement (SdF) d'un système automatisé sont généralement focalisées uniquement sur la partie procédé. Aussi, les stratégies de reconfiguration du procédé - réalisées par le contrôle-commande - ne sont souvent pas modélisées, sinon de manière imprécises et sans échec possible. Pourtant, ces stratégies ont un impact certain sur la SdF du système bouclé, qui doit être pris en compte dans les modèles afin d'améliorer la pertinence des analyses. Le travail dont rend compte cette thèse contribue à la modélisation et à l'analyse de la SdF des systèmes dynamiques, réparables et reconfigurables. Premièrement, un nouveau formalisme de modélisation est proposé pour prendre en compte avec précision les différentes stratégies de reconfiguration du système avec leurs possibles échecs. Ce formalisme développe et généralise le principe des BDMP (Boolean logic Driven Markov Processes en anglais), auxquels il associe des machines de Moore afin de spécifier formellement les stratégies de reconfiguration. Dans un second temps, deux techniques d'analyse basées sur un modèle GBDMP (BDMP Généralisé) sont décrites. Ces techniques permettent d'obtenir un résultat qualitatif : l'ensemble des plus courtes Séquences de Coupe Minimales (SCM), ainsi qu'un résultat quantitatif : indicateur probabiliste de la disponibilité du système. Finalement, la modélisation GBDMP et l'analyse de SdF basée sur un modèle GBDMP sont expérimentées sur un cas d'étude représentatif de plusieurs problématiques industrielles liées au secteur de la production d'énergie électrique. / Existing works on Model Based Safety Analysis of an automated system generally focus on the process part. Process reconfiguration strategies that are driven by the control are often modeled without failure and with a lack of accuracy. However these strategies have a real impact on the safety of the closed-loop system. In order to improve the relevance of analysis, this impact has to be captured in models. This thesis contributes to modeling and analysis of dynamic repairable reconfigurable systems. Firstly a new modeling formalism is proposed to relevantly take into account different reconfiguration strategies that can fail. This formalism develops and generalizes the principle of Boolean logic Driven Markov Processes (BDMP), and enriches it with Moore machine for formally specifying reconfiguration strategies. In a second stage, two analysis techniques based on a Generalized BDMP (GBDMP) model are described. These techniques allow to obtain a qualitative result: the set of shortest Minimal Cut Sequences (MCS), and a quantitative result: probabilistic indicator of system availability. Finally, a case study coming from the electric power production field is addressed. This case study shows how several industrial problems can be solved in GBDMP framework.

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