Mathematical models of regulatory networks become more difficult to construct and understand as they grow in size and complexity. Large regulatory network models can be built up from smaller models, representing subsets of reactions within the larger network. This dissertation focuses on novel model construction techniques that extend the ability of biological modelers to construct larger models by supplying them with tools for decomposing models and using the resulting components to construct larger models. Over the last 20 years, molecular biologists have amassed a great deal of information about the genes and proteins that carry out fundamental biological processes within living cells --- processes such as growth and reproduction, movement, signal reception and response, and programmed cell death. The full complexity of these macromolecular regulatory networks is too great to tackle mathematically at the present time. Nonetheless, modelers have had success building dynamical models of restricted parts of the network. Systems biologists need tools now to support composing "submodels" into more comprehensive models of integrated regulatory networks. We have identified and developed four novel processes (fusion, composition, flattening, and aggregation) whose purpose is to support the construction of larger models. Model Fusion combines two or more models in an irreversible manner. In fusion, the identities of the original (sub)models are lost. Beyond some size, fused models will become too complex to grasp and manage as single entities. In this case, it may be more useful to represent large models as compositions of distinct components. In Model Composition one thinks of models not as monolithic entities but rather as collections of smaller components (submodels) joined together. A composed model is built from two or more submodels by describing their redundancies and interactions. While it is appealing in the short term to build larger models from pre-existing models, each developed independently for their own purposes, we believe that ultimately it will become necessary to build large models from components that have been designed for the purpose of combining them. We define Model Aggregation as a restricted form of composition that represents a collection of model elements as a single entity (a "module"). A module contains a definition of pre-determined input and output ports. The process of aggregation (connecting modules via their interface ports) allows modelers to create larger models in a controlled manner. Model Flattening converts a composed or aggregated model with some hierarchy or connections to one without such connections. The relationships used to describe the interactions among the submodels are lost, as the composed or aggregated model is converted into a single large (flat) model. Flattening allows us to use existing simulation tools, which have no support for composition or aggregation. / Ph. D.

The present thesis deals with the analysis of Environmental Control System (ECS) as a part of the aircraft conceptual design. The research focuses on developing methods for modelling, simulation and optimization of current and future cooling technologies suitable for aircraft applications. The work started with a pre-study in order to establish the suitability of different cooling technologies for ECS application. Therefore, five technologies namely, Bootstrap (BS), Reverse-Bootstrap (RBS), vapour cycle system (VCS), magnetic cooling (MC) and thermo-electric cooling (EC), were assessed from a theoretical point of view by the method of benchmarking. This resulted into the selection of three most suitable technologies that were further modelled and simulated in Dymola. In order to compare the optimum designs for each technology, the models were optimized using the modeFRONTIER software. The comparison was performed based on the optimum ratio of maximum power of cooling and minimum fuel penalty. The results showed that VCS has the “best” performances compared to BS and RBS. In addition to the active technologies, passive cooling methods such as liquid cooling by means of jet-fuel and poly-alpha-olefin were considered to address high heat transfer rates. In order to apply the cooling technologies in the ECS, concept system architectures were formulated using the functional analysis. This led to the identification of basic functions, components and sub-systems interaction. Based on the comparison carried out previously and the functional analysis, two ECS architectures were developed. Design optimization procedure was applied further in order to assess each concept and also to study the differences between the two concept architectures. The results depict the complex interaction of different key parameters of the architectures and their influence on the outcome. The study culminated with a proposed methodology for formulation of systems architecture using information from the optimization results and a robust functional analysis method. To sum up, the thesis proposes a simulation-based optimization method that allows inclusion of ECS system in aircraft conceptual design phase. The study also proves the complexity of the conceptual design stage for ECS architectures which highly influences the design of the combat aircraft.

Les systèmes industriels (automobile, aérospatial, etc.) sont de plus en plus complexes à cause des contraintes économiques et écologiques. Cette complexité croissante impose des nouvelles contraintes au niveau du développement. La question de la maitrise de la capacité d’analyse de leurs architectures est alors posée. Pour résoudre cette question, les outils de modélisation et de simulation sont devenus une pratique courante dans les milieux industriels afin de comparer les multiples architectures candidates. Ces outils de simulations sont devenus incontournables pour conforter les décisions. Pourtant, la mise en œuvre des modèles physiques est de plus en plus complexe et nécessite une compréhension spécifique de chaque phénomène simulé ainsi qu’une description approfondie de l’architecture du système, de ses composants et des liaisons entre composants. L’objectif de cette thèse est double. Le premier concerne le développement d’une méthodologie et des outils nécessaires pour construire avec précision les modèles de simulation des architectures de systèmes qu’on désire étudier. Le deuxième s’intéresse à l’introduction d’une approche innovante pour la conception, la production et l’intégration des modèles de simulations en mode « plug and play » afin de garantir la conformité des résultats aux attentes, notamment aux niveaux de la qualité et de la maturité. Pour accomplir ces objectifs, des méthodologies et des processus d’ingénierie des systèmes basés sur les modèles (MBSE) ainsi que les systèmes d’information ont été utilisés. Ce travail de thèse propose pour la première fois un processus détaillé et un outil pour la conception des modèles de simulation. Un référentiel commun nommé « Modèle de carte d'identité (MIC) » a été développé pour standardiser et renforcer les interfaces entre les métiers et les fournisseurs sur les plans organisationnels et techniques. MIC garantit l’évolution et la gestion de la cohérence de l’ensemble des règles et les spécifications des connaissances des domaines métiers dont la sémantique est multiple. MIC renforce également la cohérence du modèle et réduit les anomalies qui peuvent interférer pendant la phase dite IVVQ pour Intégration, Vérification, Validation, Qualification. Finalement, afin de structurer les processus de conception des modèles de simulation, le travail s’est inspiré des cadres de l’Architecture d’Entreprise en reflétant les exigences d’intégration et de standardisation du modèle opératoire de l’entreprise. Pour valider les concepts introduits dans le cadre de cette thèse, des études de cas tirés des domaines automobile et aérospatiale ont été réalisées. L'objectif de cette validation est d'observer l'amélioration significative du processus actuel en termes d'efficacité, de réduction de l'ambiguïté et des malentendus dans la modélisation et la simulation du système à concevoir. / Simulation models are widely used by industries as an aid for decision making to explore and optimize a broad range of complex industrial systems’ architectures. The increased complexity of industrial systems (cars, airplanes, etc.), ecological and economic concerns implies a need for exploring and analysing innovative system architectures efficiently and effectively by using simulation models. However, simulations designers currently suffer from limitations which make simulation models difficult to design and develop in a collaborative, multidisciplinary design environment. The multidisciplinary nature of simulation models requires a specific understanding of each phenomenon to simulate and a thorough description of the system architecture, its components and connections between components. To accomplish these objectives, the Model-Based Systems Engineering (MBSE) and Information Systems’ (IS) methodologies were used to support the simulation designer’s analysing capabilities in terms of methods, processes and design tool solutions. The objective of this thesis is twofold. The first concerns the development of a methodology and tools to build accurate simulation models. The second focuses on the introduction of an innovative approach to design, product and integrate the simulation models in a “plug and play" manner by ensuring the expected model fidelity. However, today, one of the major challenges in full-vehicle simulation model creation is to get domain level simulation models from different domain experts while detecting any potential inconsistency problem before the IVVQ (Integration, Verification, Validation, and Qualification) phase. In the current simulation model development process, most of the defects such as interface mismatch and interoperability problems are discovered late, during the IVVQ phase. This may create multiple wastes, including rework and, may-be the most harmful, incorrect simulation models, which are subsequently used as basis for design decisions. In order to address this problem, this work aims to reduce late inconsistency detection by ensuring early stage collaborations between the different suppliers and OEM. Thus, this work integrates first a Detailed Model Design Phase to the current model development process and, second, the roles have been re-organized and delegated between design actors. Finally an alternative architecture design tool is supported by an ontology-based DSL (Domain Specific Language) called Model Identity Card (MIC). The design tools and mentioned activities perspectives (e.g. decisions, views and viewpoints) are structured by inspiration from Enterprise Architecture Frameworks. To demonstrate the applicability of our proposed solution, engine-after treatment, hybrid parallel propulsion and electric transmission models are tested across automotive and aeronautic industries.

La multiplication des environnements logiciels pour la Modélisation & Simulation DEVS pose un problème de collaboration à la communauté scientifique. En effet, l'utilisation d'outils disparates rend l'échange, la réutilisation et la comparaison de modèles très difficiles, empêchant les scientifiques de s'appuyer sur des travaux précédents pour construire leurs modèles. L'interopérabilité des outils n'est pas le seul problème soulevé par le besoin de modèles toujours plus complexes. Au fur et à mesure que les modèles grossissent, leur développement devient plus difficile, notamment en termes de détection des erreurs de conception. D'autre part, la simulation de ces modèles demande de plus en plus de ressources. Par conséquent, il est nécessaire de concevoir des techniques pour améliorer la performance des simulateurs et pour fournir des fonctionnalités de vérification de modèle afin d'assister les scientifiques dans la conception de leurs modèles. Dans cette thèse, nous proposons deux approches innovantes pour la M&S DEVS qui s'attaquent aux problèmes susmentionnés. La première contribution décrite dans ce document est un environnement basé sur les modèles pour modéliser des systèmes avec le formalisme DEVS, intitulé SimStudio. Cet environnement repose sur l'Ingénierie Dirigée par les Modèles pour fournir un cadriciel de haut niveau dans lequel les scientifiques peuvent créer, éditer et visualiser des modèles, et générer automatiquement un ensemble d’artefacts, notamment des spécifications de modèles compatibles avec différents simulateurs DEVS. Le noyau de SimStudio est un métamodèle de DEVS, indépendant de toute plateforme, qui fournit un format pivot pour la représentation des modèles DEVS. En se basant sur ce métamodèle, nous avons développé plusieurs fonctionnalités de vérification de modèle ainsi que plusieurs transformations de modèle pouvant être utilisées pour générer automatiquement de la documentation, des diagrammes ou du code ciblant diverses plateformes DEVS. Ainsi, SimStudio fournit une preuve de concept des capacités d’intégration qu’un standard DEVS pourrait fournir ; en fait, le métamodèle présenté dans cette thèse pourrait potentiellement servir de base de réflexion pour un tel standard. La seconde contribution de cette thèse est DEVS-MetaSimulateur (DEVS-MS), une bibliothèque DEVS qui utilise la métaprogrammation pour générer des exécutables de simulation spécialisés et optimisés pour le modèle qu’ils traitent. Pour ce faire, la bibliothèque effectue un grand nombre d’opérations durant la compilation, résultant en un code de simulation où une grande partie de l’overhead de simulation a été éliminé. Les tests que nous avons effectués ont montré que les programmes générés étaient très efficaces, mais le gain de performance n’est pas la seule caractéristique intéressante de DEVS-MS. En effet, grâce à la métaprogrammation, DEVS-MS peut également partiellement vérifier à la compilation que les modèles sont corrects, c’est-à-dire que leurs caractéristiques sont bien conformes au formalisme DEVS. Les erreurs de modélisation sont ainsi détectées et signalées très tôt dans le cycle de développement, et avec un taux de détection bien meilleur que ne le permettrait des tests classiques. / The multiplication of software environments supporting DEVS Modeling & Simulation is becoming a hindrance to scientific collaboration. Indeed, the use of disparate tools in the community makes the exchange, reuse and comparison of models very difficult, preventing practitioners from building on previous works to devise models of ever-increasing complexity. Tool interoperability is not the only issue raised by the need for models of higher and higher complexity. As models grow, their development becomes more error-prone, and their simulation becomes more resource-consuming. Consequently, it is necessary to devise techniques for improving simulators performance and for providing thorough model verification to assist the practitioner during model design. In this thesis, we propose two innovative approaches for DEVS Modeling & Simulation that tackle the aforementioned issues. The first contribution described in this document is a model-driven environment for modeling systems with the DEVS formalism, named SimStudio. This environment relies on Model-Driven Engineering to provide a high-level framework where practitioners can create, edit and visualize models, and automatically generate multiple artifacts, most notably model specifications compatible with various DEVS simulators. The core of SimStudio is a platform-independent metamodel of the DEVS formalism, which provides a pivot format for DEVS models. Based on this metamodel, we developed several model verification features as well as many model transformations that can be used to automatically generate documentation, diagrams or code targeting various DEVS platforms. Thus, SimStudio gives a proof of concept of the integration capabilities that a DEVS standard would provide; as a matter of fact, the metamodel presented in this thesis could possibly serve as a basis for such a standard. The second contribution of this thesis is DEVS-MetaSimulator (DEVS-MS), a DEVS library relying on metaprogramming to generate simulation executables that are specialized and optimized for the model they handle. To do so, the library performs many computations during compilation, resulting in a simulation code where most overhead have been eliminated. The tests we conducted showed that the generated programs were very efficient, but the performance gain is not the only feature of DEVS-MS. Indeed, through metaprogramming, DEVS-MS can also assert the correctness of models by verifying model characteristics at compile-time, detecting and reporting modeling errors very early in the development cycle and with better confidence than what could be achieved with classical testing.

La simulation multi-disciplinaire et multi-physique représente un enjeu scientifique et industriel majeur. La simulation a été essentiellement traitée par les physiciens (mécanique, électromagnétique, ...) comme un problème numérique sur des cas d'étude très précis mais n'a jamais été abordée d'un point de vue système. La problématique générale posée par la simulation de systèmes complexes inclut la composition des modèles, l'optimisation multi-objectifs, la sémantique et la vérification formelle des compositions et le cadre offert par l'ingénierie système. Cette thèse propose une démarche originale établissant les fondements théoriques et méthodologiques pour un processus sans rupture entre ingénierie système, optimisation multi-objectif et simulation multi-physique. Des cas d'études issus de l'automobile démontrent la validité de cette approche expérimentée sur la base du langage Modelica. / Multi-disciplinary and multi-physics simulation represents a major scientific and industrial challenge. The simulation has essentially been considered by physicists (mechanic domain, electromagnetic domain, ...) as a numerical problem on specific case studies but has never been adressed from a system perspective. The general problem induced by the numerical simulation of complex systems include model composition, multi-objective optimization, the semantics and formal verification of compositions and the frame of systems engineering. This thesis proposes an original approach establishing the theoretical and methodological foundations for a seamless process between systems engineering, multi-objective optimization and multi-physics simulation. Automotive case studies show the validity of such an approach based on Modelica langage.

Early in the process of developing or upgrading new weapon systems, Department of Defense (DoD) system and technology developers are faced with decisions regarding which technologies are appropriate for inclusion into the conceptual design. To reduce risk and improve decision making, system and technology developers need a capability to assess the impact of technology reliability on the attributable Operating and Support (O&S) cost of the system. Early understanding of the reliability implications of potential technologies on system O&S cost will help make better informed decisions early in the system development timeline, prior to points of design lock-in. Using a Marine Corps case study and a system dynamics simulation model, this thesis examines the nature of the relationship between component reliability and attributable changes in O&S cost. This thesis also develops a potential analysis methodology repeatable for future use. The modeling results indicate that this relationship is best described as exponential decay, meaning that the savings in O&S cost per system mile is proportional for any fixed incremental change in component reliability. We find these results to be insensitive to changes in preventative maintenance policies, maintenance deferment ratios, and component replacement cost. We completed verification and validation using the case study and existing Marine Corps systems, finding good association between the modeling results and the actual system. This analysis is valuable to the system and technology developer by helping to answer the question: "how reliable is reliable enough in terms of O&S cost" when considering technologies with uncertainties in long-term performance. / Master of Science

The multiplication of software environments supporting DEVS Modeling & Simulation is becoming a hindrance to scientific collaboration. Indeed, the use of disparate tools in the community makes the exchange, reuse and comparison of models very difficult, preventing practitioners from building on previous works to devise models of ever-increasing complexity. Tool interoperability is not the only issue raised by the need for models of higher and higher complexity. As models grow, their development becomes more error-prone, and their simulation becomes more resource-consuming. Consequently, it is necessary to devise techniques for improving simulators performance and for providing thorough model verification to assist the practitioner during model design. In this thesis, we propose two innovative approaches for DEVS Modeling & Simulation that tackle the aforementioned issues. The first contribution described in this document is a model-driven environment for modeling systems with the DEVS formalism, named SimStudio. This environment relies on Model-Driven Engineering to provide a high-level framework where practitioners can create, edit and visualize models, and automatically generate multiple artifacts, most notably model specifications compatible with various DEVS simulators. The core of SimStudio is a platform-independent metamodel of the DEVS formalism, which provides a pivot format for DEVS models. Based on this metamodel, we developed several model verification features as well as many model transformations that can be used to automatically generate documentation, diagrams or code targeting various DEVS platforms. Thus, SimStudio gives a proof of concept of the integration capabilities that a DEVS standard would provide; as a matter of fact, the metamodel presented in this thesis could possibly serve as a basis for such a standard. The second contribution of this thesis is DEVS-MetaSimulator (DEVS-MS), a DEVS library relying on metaprogramming to generate simulation executables that are specialized and optimized for the model they handle. To do so, the library performs many computations during compilation, resulting in a simulation code where most overhead have been eliminated. The tests we conducted showed that the generated programs were very efficient, but the performance gain is not the only feature of DEVS-MS. Indeed, through metaprogramming, DEVS-MS can also assert the correctness of models by verifying model characteristics at compile-time, detecting and reporting modeling errors very early in the development cycle and with better confidence than what could be achieved with classical testing.

On-orbit satellite servicing is critical to maximizing space utilization and sustainability and is of growing interest for commercial, civil, and defense applications. Reliance on astronauts or anchored robotic arms for the servicing of next-generation large, complex space structures operating beyond Low Earth Orbit is impractical. Substantial literature has investigated the mission design and analysis of robotic servicing missions that utilize a single servicing satellite to approach and service a single target satellite. This motivates the present research to investigate a fleet of servicing satellites performing several operations for a large, central space structure. This research leverages a distributed control approach, implemented using the Horizon Simulation Framework (HSF), to develop a tool capable of integrated mission modeling and task scheduling for a servicing satellite fleet. HSF is a modeling and simulation framework for verification of system level requirements with an emphasis on state representations, modularity, and event scheduling. HSF consists of two major modules: the main scheduling algorithm and the system model. The distributed control architecture allocates processing and decision making for this multi-agent cooperative control problem across multiple subsystem models and the main HSF scheduling algorithm itself. Models were implemented with a special emphasis on the dynamics, control, trajectory constraints, and trajectory optimization for the servicing satellite fleet. The integrated mission modeling and scheduling tool was applied to a sample scenario in which a fleet of 3 servicing assets is tasked with performing 12 servicing activities for a large satellite in Geostationary Orbit. The tool was able to successfully determine a schedule in which all 12 servicing activities were completed in under 32 hours, subject to the fuel and trajectory constraints of the servicing assets.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / Current changes in the way that large flight test systems are utilized have affected the industry’s methodology in both the early design phases and in the implementation of nextgeneration hardware and software. The reduction of available RF spectrum, the implementation of packet telemetry methods and systems, and a desire to implement commercial-off-the-shelf (COTS) hardware are only some of the considerations that telemetry systems integrators and product houses have to face. This paper describes how test methodology changes affect current large systems design at both government test ranges and at airframe/missile manufacturer test facilities. In addition, consideration is given to the area of increased processing power as it affects hardware and software design, the leveraging of such current and future telecommunications technology as network switch technology and compression, cross utilization, standardized technology, and the movement toward platform-independent software.