Les réseaux véhiculaires sont passés du stade de simple curiosité pour revêtir aujourd'hui un intérêt certain aussi bien du point de vue de l'industrie automobile que des opérateurs de réseaux et services. Ces réseaux sont en effet une classe émergente de réseaux sans fil permettant des échanges de données entre véhicules ou encore entre véhicules et infrastructure. Ils suscitent un intérêt certain aussi bien en Europe qu’au Japon et en Amérique du Nord, dans le but de fournir de nouvelles technologies capables d'améliorer la sécurité et l'efficacité des transports routiers. Suivant cette même vision, nous nous intéressons dans cette thèse aux communications inter-véhicules dans un environnement urbain. Notre objectif est de proposer des solutions de routage ad hoc et de dissémination géolocalisée, adaptées à un environnement ville, répondant à la fois aux exigences et besoins technologiques des cas d'utilisation envisagés (principalement des services d'information et de confort), mais aussi et surtout aux contraintes des communications inter-véhiculaires ad hoc (fragmentation fréquente du réseau, connectivité intermittente, etc…). Notre démarche consiste à prendre en compte un paramètre clé qui influence le bon fonctionnement du réseau ad hoc de véhicules, à savoir la densité du réseau. Dans un premier temps, nous proposons un mécanisme distribué qui permet de caractériser de manière plus fine la densité de trafic d'un tronçon de route entre deux intersections, en fournissant une distribution spatiale des véhicules mobiles sur la voie de circulation. Ensuite, nous proposons un nouveau protocole de routage géographique, qui tire partie des caractéristiques des voies urbaines et qui intègre le mécanisme d'estimation de densité de trafic pour le routage des paquets. Pour finir, et afin de compléter les mécanismes de communication véhiculaire ad hoc (couche réseau) proposés, nous nous intéressons à la dissémination des données. Nous proposons un nouveau mécanisme distribué et ad hoc qui permet d'émuler le fonctionnement d'une infrastructure classique destinée à diffuser localement (au niveau d'une intersection) des paquets de données de manière périodique. Certains aspects de nos solutions sont évalués analytiquement alors que leurs performances sont évaluées par simulation à l'aide de l'outil QNAP, du simulateur QualNet et du modèle de mobilité réaliste VanetMobiSim. / Inter-Vehicle Communication (IVC) is attracting considerable attention from the research community and the automotive industry, where it is beneficial in providing Intelligent Transportation System (ITS) as well as assistant services for drivers and passengers. In this context, Vehicular Networks are emerging as a novel category of wireless networks, spontaneously formed between moving vehicles equipped with wireless interfaces that could have similar or different radio interface technologies, employing short-range to medium-range communication systems. The distinguished characteristics of vehicular networks such as high mobility, potentially large scale, and network partitioning introduce several challenges, which can greatly impact the future deployment of these networks. In this thesis, we focus on inter-vehicle communication in urban environments. Our main goal is to propose new routing and dissemination algorithms, which efficiently adapts to the vehicular networks characteristics and applications. Temporary disconnection in vehicular network is unavoidable. It is thereby of imminent practical interest to consider the vehicular traffic density. Therefore, at first, we propose a completely distributed and infrastructure–free mechanism for city road density estimation. Then, and based on such traffic information system, we propose a novel intersection-based geographical routing protocol, capable to find robust and optimal routes within urban environments. Finally, in order to help the efficient support of dissemination-based applications, a self-organizing mechanism to emulate a geo-localized virtual infrastructure is proposed, which can be deployed in intersections with an acceptable level of vehicular density. The advocated techniques are evaluated by a combination of network simulation and a microscopic vehicular traffic model.

<p>Using more than just on antenna can significantly speed up the data rate in a wireless communication system. These systems are commonly referred to as Diversity- and MIMO-systems. Due to tight volume restriction for the antennas, e.g. in a mobile phone, electromagnetic coupling between the antennas will degrade the capacity of the wireless system and lower the coverage.</p><p><p>In the proposed thesis, a thorough study of Ethertronics’ standard antennas will be established in which the antennas will be used in a multiport system, e.g. MIMO. The thesis will be strongly related to Ethertronics’ engagement in Chase and therefore also dependent on the latest progresses on MPA (Multiport Analyzer) developed in Chase. The thesis will result in a working methodology how to use MPA plus design-, location- and orientation rules for the standard antennas used in a multiport system.</p></p>

Using more than just on antenna can significantly speed up the data rate in a wireless communication system. These systems are commonly referred to as Diversity- and MIMO-systems. Due to tight volume restriction for the antennas, e.g. in a mobile phone, electromagnetic coupling between the antennas will degrade the capacity of the wireless system and lower the coverage. In the proposed thesis, a thorough study of Ethertronics’ standard antennas will be established in which the antennas will be used in a multiport system, e.g. MIMO. The thesis will be strongly related to Ethertronics’ engagement in Chase and therefore also dependent on the latest progresses on MPA (Multiport Analyzer) developed in Chase. The thesis will result in a working methodology how to use MPA plus design-, location- and orientation rules for the standard antennas used in a multiport system.

Multi-spacecraft interferometry imaging is an innovative concept intended to apply formations of satellites to obtain high resolution images allowing for the synthesis of a large size aperture through the combination of the signal from several sub-apertures. The design of such systems requires the design of trajectories that cover a specified region of the observation plane to obtain appropriate information to reconstruct an image of the source. A proposed configuration consists of symmetrical formations which use control thrust to actively follow spiral trajectories that would appropriately cover the specified regions. An optimization problem has to be solved to design the optimal trajectories with minimum fuel consumption. The present work introduces an algorithm to obtain near optimal maneuvers for multi-spacecraft interferometric imaging systems. Solutions to the optimization problem are obtained assuming the optimality of spiral coverage of the spatial frequency plane. The relationship between the error in the frequency content and the reliability of the image is studied to make a connection to the dynamics of the maneuver and define the parameters of the optimization problem. The solution to the problem under deep space dynamics is shown to be convex and is solved by discretization into a non-linear programing problem. Further, the problem is extended to include the effects of dynamical constraints and the effect of time varying relative position from the imaging system to the target. For the calculation of the optimal trajectories, a two-stage hierarchical controller is proposed that obtains acceleration requirements of near minimum fuel maneuvers for different target-system configurations. Several cases are simulated to apply the algorithm. From the obtained results some conclusions about the feasibility and dynamical requirements of these systems are described.

[pt] O uso de códigos corretores de erro tem sido a alternativa convencional utilizada em sistemas de comunicação digitais para melhorar o desempenho em termos de probabilidade de erro de bit dos sistemas com limitação de potência. A melhoria do desempenho quando se emprega estes códigos convencionais é alcançada com um aumento na faixa de freqüências utilizada pelo sistema ou uma redução na taxa de transmissão de informação. Técnicas que realizam a modulação e a codificação de forma integradas permitem obter desempenho superior ao de sistemas sem codificação, sem acarretar aumento de faixa. O presente trabalho analisa, através de simulação em computador digital, o desempenho de sistemas de comunicações digitais que empregam a modulação Multi-h, uma modulação codificada que faz uso eficiente da faixa. A simulação realizada considera um ambiente com não- linearidade, limitação de faixa e perturbação por um ruído aditivo branco Gaussiano. A técnica de simulação emprega utiliza o sinal em banda básica representado por suas amostras tomadas no domínio do tempo a intervalos constantes. As filtragens necessárias para simular o efeito da limitação de faixa foram realizadas com filtros de Butterworth digitais. O desempenho de códigos com número pequeno de estados ( = < 16) e probabilidade de erros maiores do que 10-4 foi analisado. Um programa para cálculo de distância Euclideana mínima normalizada, d min, de códigos Multi-h foi desenvolvido. A distância d min, é utilizada para estabelecer um limitante da probabilidade de erro por bit em sistemas cuja única perturbação é o ruído aditivo branco Gaussiano. Códigos com d min maiores possuem melhor desempenho e portanto este parâmetro é utilizado para escolher bons códigos. Um programa para cálculo da densidade espectral de potência de códigos Multi-h foi também desenvolvido. Para reduzir a complexidade do decodificador o número de estados da treliça correspondente ao código utilizado deve ser pequeno. Escolhendo-se um conjunto adequado de índices obtem-se códigos de complexidade reduzida com bom desempenho e boas características espectrais. Uma das restrições impostas ao conjunto de índices para reduzir a complexidade do decodificador é que os mesmos sejam razões nk/q entre números inteiros. Outros aspectos relacionados à redução da complexidade são discutidos neste trabalho. Em particular, uma propriedade que o conjunto de índices de modulação deve obedecer para que o número de estados da treliça seja q é estabelecida. Uma discussão sobre características da estrutura da treliça é também apresentada. / [en] Error correcting codes have been used in power limited digital communication systems to improve the system error probability performance. This performance improvement is obtained at the price of an expanded occupied bandwidth or a lower rate of information transmission. Integrated coding and modulation techniques allow an increased performance without this bandwitdt expansion. In this thesis, a digital computer simulation analysis of the performance of communication systems which incorporates Multi-h codes, a bandwidth efficient modulation, is carried out. The simulated system consider a band-limited non-linear channel perturbed by additive, white Gaussian noise. The simulation technique selected uses a base-band signal represented by it´s time domain samples equally spaced. The band limiting effect is obtained with Butterworth digital filters. The performance of codes with small number of states ( = < 16) and error probability range greater than 10 exp(-4) is analised. A computer program to calculate the normalized mínimum Euclidean distance, d min, of Multi-h codes was developped. The distance d min is used to establish an upper bound on the bit error probability for transmission over additive, white Gaussian noise channels. Codes with larger dmin have a better performance, been dmin, thus, an indication of good codes. A program developped to calculate power spectrum density of Multi-h codes is also presented. To reduce decoder complexity the number of trellis states should be small. By properly selecting a set of modulation indices codes with good performance, reduced complexity and small spectral occupation is obtained. A restriction on the set of indices to get a reduce complexity decoder is to have indices d which are integer ratios nk/q. Other related aspects are discussed in this work. In particular, a condition to get a number of trellis state equal to q is proposed. A discussion on the structed of the trellis is also presented.

L'analyse et la compréhension des mécanismes d'érosion en présence d'un environnement critique au niveau de pression et de température des produits de combustion d'un propergol solide au sein d'une tuyère de moteur fusée, constituent l'objectif principal de ce présent mémoire. Les principaux paramètres, le pourcentage d'aluminium dans l'écoulement, la température adiabatique de flamme.le flux de chaleur en face de la géométrie de l' insert et ses propriétés thermochimiques, sont plus particulièrement étudiés à travers une approche numérique et expérimentale. Le phénomène d'ablation qui se produit au niveau de l' insert d'une tuyère pendant le fonctionnement du moteur propergol solide est ainsi étudié et des résultats d'essais des moteurs à échelle réduite et pleine sont présentés puis simulés numériquement. En effet, les essais mis en place, riches en résultats sur les conditions du matériau de l'insert avant et après le tir, ne permettent pas une analyse complète du développement des mécanismes en jeu au cours du temps de fonctionnement des moteurs. Pour introduire ces phénomènes physiques plutôt complexes, une stratégie de développement progressive est mise en place. Au départ, un modèle 1D a traité les équations de transfert de chaleur utilisant une technique de discrétisation numérique multi-blocs. A partir de la méthode 1D, des expressions simples pour représenter l'évolution des fronts d'ablation et de pyrolyse sont définies.Ces expressions sont alors utilisées de façon directe sur le traitement des problèmes axisymétriques et confrontées avec les simulations du moteur test. Finalement, la méthode aux frontières immergées est appliquée pour traiter du couplage entre l'écoulement et l'insert, mettant en évidence le phénomène d'ablation. Les simulations numériques reproduisent les résultats expérimentaux et montrent une méthodologie numérique robuste, correspondant à des attentes en ce qui concerne l'évaluation du phénomène d'ablation au sein d'une tuyère de moteur fusée. / The main objective of this study is understand the ablation mechanisms in the presence of a critical environment in pressure and temperature within a solid propellant rocket motor. The well-known parameters, aluminum percentage in the flow, adiabatic flame temperature and the consequent heat flux in front of the geometry of the insert and its thermochemical properties are studied from anumerical and experimental strategy. The ablation phenomenon, which occurs at the nozzle insert during the operation of the solid propellant rocket motor, is th us studied and results of tests of the small and full-scale motors are presented as well as numerically simulated. Indeed, tests carried-out provide results on the conditions of the material of the insert before and after firing tests, do not allow is to provide a complete analysis of the development of the mechanisms involved during the running time of the engines. To introduce these rather complex physical phenomena a strategy of progressive development is followed. Initially, a 1D model treated the heat transfer equations using a multi-block numerical discretization technique. From the 1D method, simple expressions to represent the evolution of the ablation and pyrolysis fronts are defined. These expressions are then used directly on the treatment of axisymmetric problems and confronted with simulations of the scale motor. Finally, the immersed boundary method is applied to tackle coupling between flow and heat transfer on the insert, highlighting the phenomenon of ablation. The numerical simulations reproduce the experimental results and show a robust numerical methodology, corresponding to expectations in what concerns the evaluation of the ablation phenomenon within a solid propellant rocket motor nozzle.

La Tarification à l’Activité (T2A) contraint les services d’urgences hospitalières à développer différentes stratégies d’'allocation efficiente des ressources. L'optimisation de la prise en charge est centrale à cette problématique et vise des coûts de production couverts par les revenus induits par la T2A. Aussi, l'objectif de la thèse est d’identifier l’apport d’un Système d’Aide à la Décision (SAD) basé sur les Systèmes Multi-Agents (SMA) utilisant une modélisation basée sur un algorithme d'ordonnancement des moyens de production des soins en trois phases (OR-3P). Cette modélisation formalise l'organisation de ces services autour de cinq types d'agents. L’Agent Ordonnanceur y chargé d’affecter les personnels de l’équipe médicale et de gérer les flux de patients. Il joue un rôle prépondérant dans la recherche d’optimisation. Les résultats obtenus de l’application simulée de l’OR-3P, montrent l’optimisation des délais d’attente et de passage global, une augmentation de la productivité et une indication qualitative du bon fonctionnement de la prise en charge. Ces résultats incitent à réaliser des expérimentations dans des établissements français. / The activity-based payment, which is known in France as T2A requires hospital emergency departments, faced with a very strong growth in their activities since 1990, to develop strategies of an efficient allocation of resources. The optimization of medical treatment is central to this issue and should allow obtaining production costs covered by funding induced T2A. The main objective of the thesis was to identify the contribution of a System Decision Support (DSS) based on Multi-Agent Systems (MAS), using multi-agent modelling of care means production, using a three-phase scheduling algorithm, so called OR-3P. This modelling formalizes the organization of emergency departments around five types of agent. The scheduler Officer is responsible for assigning personnel to the medical team in an efficient framework for managing patient flow, plays the leading role in the search of optimized management. Results from the application of OR-3P, show an optimizing of the delays and the overall passage, an increase in productivity, a qualitative indication of proper functioning. These results lead to tests in French institutions.

<p> Cooperative teleoperation combines two traditional areas of robotics, i.e. teleoperation and collaborative manipulation. Cooperative telerobotic systems consist of multiple pairs of master I slave robotic manipulators operating in a shared environment. Due to dynamic interaction among slave manipulators as well as communication latency, control of such systems is particularly challenging and the application of standard teleoperation controller may result in instability. </p> <p> In this thesis a multilateral control framework is proposed for cooperative teleoperation systems that allows for transmission of position and force information between all master and slave robots rather than merely between corresponding units. Two different control approaches are introduced that establish kinematic correspondence among masters and slaves. The operators are presented with a virtual intervening tool in order to collaboratively interact with the environment. Models of operators, master and slave robots, tool, and environment are incorporated in the design. </p> <p> A multilateral adaptive nonlinear control architecture is proposed. Performance and stability of cooperative teleoperation systems are addressed under dynamic interactions between slave robots in the presence of model uncertainty. The robustness of the controller with respect to communication latency is also analyzed. Simulation and experimental studies demonstrate that the proposed approach is highly effective in all phases of a teleoperation task, i.e. in free motion and in contact with both flexible and rigid environments. </p> <p> The second approach involves finite-dimensional state-space models that incorporate the delay for free motion/ soft contact as well as rigid contact modes of operation. Local dynamic linearization control laws are employed to linearize robotic manipulators' dynamics. Model-based discrete-time Linear Quadratic Gaussian (LQG) controllers are proposed that can deliver a stable transparent response for each phase of operation. The robustness of these controllers with respect to parameter uncertainty is examined via the Nyquist analysis. Simulation results demonstrate the effectiveness of the proposed approach. </p> / Thesis / Master of Applied Science (MASc)

<p> Cooperative teleoperation combines two traditional areas of robotics, i.e. teleoperation and collaborative manipulation. Cooperative telerobotic systems consist of multiple pairs of master I slave robotic manipulators operating in a shared environment. Due to dynamic interaction among slave manipulators as well as communication latency, control of such systems is particularly challenging and the application of standard teleoperation controller may result in instability. </p> <p> In this thesis a multilateral control framework is proposed for cooperative teleoperation systems that allows for transmission of position and force information between all master and slave robots rather than merely between corresponding units. Two different control approaches are introduced that establish kinematic correspondence among masters and slaves. The operators are presented with a virtual intervening tool in order to collaboratively interact with the environment. Models of operators, master and slave robots, tool, and environment are incorporated in the design. </p> <p> A multilateral adaptive nonlinear control architecture is proposed. Performance and stability of cooperative teleoperation systems are addressed under dynamic interactions between slave robots in the presence of model uncertainty. The robustness of the controller with respect to communication latency is also analyzed. </p> <p> Simulation and experimental studies demonstrate that the proposed approach is highly effective in all phases of a teleoperation task, i.e. in free motion and in contact with both flexible and rigid environments. </p> <p> The second approach involves finite-dimensional state-space models that incorporate the delay for free motion/ soft contact as well as rigid contact modes of operation. Local dynamic linearization control laws are employed to linearize robotic manipulators' dynamics. Model-based discrete-time Linear Quadratic Gaussian (LQG) controllers are proposed that can deliver a stable transparent response for each phase of operation. The robustness of these controllers with respect to parameter uncertainty is examined via the Nyquist analysis. Simulation results demonstrate the effectiveness of the proposed approach. </p> / Thesis / Master of Applied Science (MASc)

Virtual Software Corporations (VSCs) are a novel and important organisational form for large-scale software development. The increased complexity of this development environment requires the use of tools to support human actors in undertaking their tasks, which in turn require modelling solutions able to capture the VSC specific issues. One of the key aspects identified for software development in a VSC setting is the need to support co-ordination. One approach in the development of support for coordination in heterogeneous environments in respect to processes and support tools, such as VSCs, is the use of commitment management. The purpose of this thesis is to define a formalism suitable for capturing and managing commitments, as a means to support co-ordination. This is done by first analysing existing VSCs, and determining the requirements for co-ordination support. Consequently a formalism is defined to address the requirements. The formalism is based on a commitment modelling approach and deontic logic, a modal logic, which is used to manage the commitments. The defined formalism is the basis of a prototype support system, which is used for testing and evaluating. The evaluation has focused on identifying the level of support provided for the initial requirements. To this end three process examples have been used: the initial case study, the study of an independent VSC and the example of a desired process for software configuration management.The results indicate that the formalism, through the use of the prototype system, is able to represent and to manage commitments, as the most important issues in coordinating VSC software development. Thus it has a significant contribution as a modelling approach and it was shown to be applicable to realistic process scenarios.