Cette thèse propose des modèles multi-agents réactifs fondés sur un cadre formel pour la vérification de propriétés et les valider par la simulation et l'expérimentation en considérant la navigation multi-véhicules comme domaine d'application. La navigation multi-véhicules soulève plusieurs problématiques : perception de l'environnement, communication inter-véhicule, évitement d'obstacle, ... Dans ce contexte, nous avons abordé plus particulièrement les aspects suivants : - Concernant la navigation multi-véhicules nous avons abordé deux problèmes spécifiques : la conduite en convoi ou platooning et la navigation autonome. En ce qui concerne la navigation autonome, nous avons mis l'accent sur l'évitement d'obstacles. - Concernant l'approche proposée : nous adoptons les systèmes multi-agents réactifs, dont les interac- tions sont inspirée de la physique. Pour la conduite en convoi, nous proposons un modèle d'interaction basé sur la physique classique. En ce qui concerne l'évitement d'obstacles, nous adoptant un modèle inspiré de la physique statistique. - Nous plaçons les systèmes multi-agents réactifs dans un cadre formel pour la vérification des pro- priétés, compte-tenu des contraintes de sécurité imposées par la classe d'applications cible. Pour faire face à la complexité des modèles, nous proposons une règle et une méthode de vérification compositionnelle. Cela nous a permis de vérifier la satisfaction d'une propriété de sûreté essentielle : la non-collision entre véhicules lors de la conduite en convoi. - Nous abordons également la question de la validation du système multi-agents par la simulation et l'expérimentation : nous avons contribué au développement d'un simulateur de la conduite en convoi et la navigation autonome. Le simulateur prend en compte les caractéristiques physiques des véhicules et est couplé à un outil de visualisation 3D. Nous avons aussi expérimenté nos modèles sur des véhicules tels que le Cycab et le GEM Car.

Structures and material combinations, tailored for multiple purposes, are within the reach of vehicle manufacturers. Besides reducing the environmental impact of the transportation sector these multi-functional structures can reduce costs, such as development, manufacturing and maintenance, and at the same time offer improved comfort to the passengers. This thesis sets out to develop multi-functional design algorithms and evaluate concepts for future composite high speed train car bodies with the objective of optimising the amount of mass needed to fulfil all functions of the structure. In a first step complete composite car bodies were developed, optimised and evaluated based on global stiffness requirements and load cases. The knowledge gained in this step was used as requirements for the strength and stiffness of panels during the continued development of the multi-functional optimisation which, besides strength and stiffness, later also considers sound transmission, thermal insulation, geometric restrictions, manufacturability and fire safety. To be able to include fire safety in the analysis, a method for simulating the high temperature response of layered composite structures was needed, and developed. Significant weight reductions are proven when utilising carbon fibre in the load carrying structure of the vehicle, on component level as high as 60%. Structures can be made significantly thinner when using the algorithms developed in this thesis and wall thickness is reduced by 5-6 cm. Analysis carried out and extensive literature surveys also suggest significant cost savings in manufacturing, maintenance and use-phase, even thou the raw material cost can be significantly higher as compared to the conventional steel or aluminium alternatives. Results from drive cycle simulations showed that the benefit, with respect to reduced energy consumption, is in the range of 0.5-0.8% per reduced weight percentage, comparable to both automotive and air applications. The algorithms and methods established in this thesis can be directly applied for the development and analysis of future high speed train car bodies. / <p>QC 20130521</p>

A distributed variant of multi-objective particle swarm optimization (MOPSO) called multi-objective parallel asynchronous particle swarm optimization (MOPAPSO) is presented, and the effects of distribution of objective function calculations to slave processors on the results and performance are investigated and employed for the synthesis of Grashof mechanisms. By using a formal multi-objective handling scheme based on Pareto dominance criteria, the need to pre-weight competing systemic objective functions is removed and the optimal solution for a design problem can be selected from a front of candidates after the parameter optimization has been completed. MOPAPSO's ability to match MOPSO's results using parallelization for improved performance is presented. Results for both four and ve bar mechanism synthesis examples are shown. / UOIT

No description available.

A multi-domain homogenization method is proposed and developed in this thesis based on a two-scale technique. The method is capable of analyzing composite structures with several periodic distributions by partitioning the entire domain of the composite into substructures making use of the classical homogenization theory following a first-order standard continuum mechanics formulation. The need to develop the multi-domain homogenization method arose because current homogenization methods are based on the assumption that the entire domain of the composite is represented by one periodic or quasi-periodic distribution. However, in some cases the structure or composite may be formed by more than one type of periodic domain distribution, making the existing homogenization techniques not suitable to analyze this type of cases in which more than one recurrent configuration appears. The theoretical principles used in the multi-domain homogenization method were applied to assemble a computational tool based on two nested boundary value problems represented by a finite element code in two scales: a) one global scale, which treats the composite as an homogeneous material and deals with the boundary conditions, the loads applied and the different periodic (or quasi-periodic) subdomains that may exist in the composite; and b) one local scale, which obtains the homogenized response of the representative volume element or unit cell, that deals with the geometry distribution and with the material properties of the constituents. The method is based on the local periodicity hypothesis arising from the periodicity of the internal structure of the composite. The numerical implementation of the restrictions on the displacements and forces corresponding to the degrees of freedom of the domain's boundary derived from the periodicity was performed by means of the Lagrange multipliers method. The formulation included a method to compute the homogenized non-linear tangent constitutive tensor once the threshold of nonlinearity of any of the unit cells has been surpassed. The procedure is based in performing a numerical derivation applying a perturbation technique. The tangent constitutive tensor is computed for each load increment and for each iteration of the analysis once the structure has entered in the non-linear range. The perturbation method was applied at the global and local scales in order to analyze the performance of the method at both scales. A simple average method of the constitutive tensors of the elements of the cell was also explored for comparison purposes. A parallelization process was implemented on the multi-domain homogenization method in order to speed-up the computational process due to the huge computational cost that the nested incremental-iterative solution embraces. The effect of softening in two-scale homogenization was investigated following a smeared cracked approach. Mesh objectivity was discussed first within the classical one-scale FE formulation and then the concepts exposed were extrapolated into the two-scale homogenization framework. The importance of the element characteristic length in a multi-scale analysis was highlighted in the computation of the specific dissipated energy when strain-softening occurs. Various examples were presented to evaluate and explore the capabilities of the computational approach developed in this research. Several aspects were studied, such as analyzing different composite arrangements that include different types of materials, composites that present softening after the yield point is reached (e.g. damage and plasticity) and composites with zones that present high strain gradients. The examples were carried out in composites with one and with several periodic domains using different unit cell configurations. The examples are compared to benchmark solutions obtained with the classical one-scale FE method. / En esta tesis se propone y desarrolla un método de homogeneización multi-dominio basado en una técnica en dos escalas. El método es capaz de analizar estructuras de materiales compuestos con varias distribuciones periódicas dentro de un mismo continuo mediante la partición de todo el dominio del material compuesto en subestructuras utilizando la teoría clásica de homogeneización a través de una formulación estándar de mecánica de medios continuos de primer orden. La necesidad de desarrollar este método multi-dominio surgió porque los métodos actuales de homogeneización se basan en el supuesto de que todo el dominio del material está representado por solo una distribución periódica o cuasi-periódica. Sin embargo, en algunos casos, la estructura puede estar formada por más de un tipo de distribución de dominio periódico. Los principios teóricos desarrollados en el método de homogeneización multi-dominio se aplicaron para ensamblar una herramienta computacional basada en dos problemas de valores de contorno anidados, los cuales son representados por un código de elementos finitos (FE) en dos escalas: a) una escala global, que trata el material compuesto como un material homogéneo. Esta escala se ocupa de las condiciones de contorno, las cargas aplicadas y los diferentes subdominios periódicos (o cuasi-periódicos) que puedan existir en el material compuesto; y b) una escala local, que obtiene la respuesta homogenizada de un volumen representativo o celda unitaria. Esta escala se ocupa de la geometría, y de la distribución espacial de los constituyentes del compuesto así como de sus propiedades constitutivas. El método se basa en la hipótesis de periodicidad local derivada de la periodicidad de la estructura interna del material. La implementación numérica de las restricciones de los desplazamientos y las fuerzas derivadas de la periodicidad se realizaron por medio del método de multiplicadores de Lagrange. La formulación incluye un método para calcular el tensor constitutivo tangente no-lineal homogeneizado una vez que el umbral de la no-linealidad de cualquiera de las celdas unitarias ha sido superado. El procedimiento se basa en llevar a cabo una derivación numérica aplicando una técnica de perturbación. El tensor constitutivo tangente se calcula para cada incremento de carga y para cada iteración del análisis una vez que la estructura ha entrado en el rango no-lineal. El método de perturbación se aplicó tanto en la escala global como en la local con el fin de analizar la efectividad del método en ambas escalas. Se lleva a cabo un proceso de paralelización en el método con el fin de acelerar el proceso de cómputo debido al enorme coste computacional que requiere la solución iterativa incremental anidada. Se investiga el efecto de ablandamiento por deformación en el material usando el método de homogeneización en dos escalas a través de un enfoque de fractura discreta. Se estudió la objetividad en el mallado dentro de la formulación clásica de FE en una escala y luego los conceptos expuestos se extrapolaron en el marco de la homogeneización de dos escalas. Se enfatiza la importancia de la longitud característica del elemento en un análisis multi-escala en el cálculo de la energía específica disipada cuando se produce el efecto de ablandamiento. Se presentan varios ejemplos para evaluar la propuesta computacional desarrollada en esta investigación. Se estudiaron diferentes configuraciones de compuestos que incluyen diferentes tipos de materiales, así como compuestos que presentan ablandamiento después de que el punto de fluencia del material se alcanza (usando daño y plasticidad) y compuestos con zonas que presentan altos gradientes de deformación. Los ejemplos se llevaron a cabo en materiales compuestos con uno y con varios dominios periódicos utilizando diferentes configuraciones de células unitarias. Los ejemplos se comparan con soluciones de referencia obtenidas con el método clásico de elementos finitos en una escala.

No description available.

Controlling systems with multiple robots is quickly becoming the next large hurdle that must be overcome for groups of robots to successfully function as a team. An agent oriented approach for this problem is presented in this thesis. By using an agent oriented method, the robots can act independently yet still work together. To be able to establish communities of robots, a basic agent oriented control system for each robot must first be implemented. This thesis introduces a novel method to create Physical Robot Agents, promoting a separation of cognitive and reactive behaviours into a two layer system. These layers are further abstracted into key subsections that are required for the Physical Robot Agents to function. To test this architecture, experiments are performed with physical robots to determine the feasibility of this approach. <br /><br /> A real-time implementation of a Physical Robot Agent would greatly expand its field of use. The speed of internal communication is analyzed to validate the application of this architecture to real-time tasks. <br /><br /> It is concluded that the Physical Robot Agents are well suited for multiple robot systems and that real-time applications are feasible.

Controlling systems with multiple robots is quickly becoming the next large hurdle that must be overcome for groups of robots to successfully function as a team. An agent oriented approach for this problem is presented in this thesis. By using an agent oriented method, the robots can act independently yet still work together. To be able to establish communities of robots, a basic agent oriented control system for each robot must first be implemented. This thesis introduces a novel method to create Physical Robot Agents, promoting a separation of cognitive and reactive behaviours into a two layer system. These layers are further abstracted into key subsections that are required for the Physical Robot Agents to function. To test this architecture, experiments are performed with physical robots to determine the feasibility of this approach. <br /><br /> A real-time implementation of a Physical Robot Agent would greatly expand its field of use. The speed of internal communication is analyzed to validate the application of this architecture to real-time tasks. <br /><br /> It is concluded that the Physical Robot Agents are well suited for multiple robot systems and that real-time applications are feasible.

The objective of the proposed research is to develop novel, fully-packaged voltage controlled oscillators (VCOs), concurrent oscillators, and multi-mode filters using Liquid Crystalline Polymer (LCP) dielectric material that are directly applicable to simultaneous multi-band radio communication. Integrated wireless devices of the near-future will serve more diverse range of applications (computing, voice/video/data communication) and hence, will require more functionality. This research is focused on providing cost-effective and area-efficient solutions for multi-band/multi-mode oscillators and filters using system-on-package (SOP) design methodology. Silicon-based integrated circuits (ICs) provide an economical method of miniaturizing modules and hence, are attractive for multi-band applications. However, fully monolithic solutions are limited, by its high substrate losses, and marginal quality factors (Qs) of the passives, to low profile applications. Furthermore, the VCOs made on conventional packaging technologies are not very cost-effective. This thesis is directed towards developing highly optimized VCOs and filters using LCP substrate for use in multi-mode radio systems. The thesis investigates and characterizes lumped passive components on new LCP based technology feasible for VCO and filter design. The dissertation then investigates design techniques for optimizing both power consumption and the phase noise of the VCOs to be employed in commercial wireless systems. This work then investigates the temperature performance of LCP-based VCOs satisfying military standards. Another aspect of the thesis is the development of dual-band (multi-mode) oscillators. The approach is to employ existing multi-band theories to demonstrate one of the first prototypes of the oscillator. Finally, the design of multi-mode, lumped-element type filters was investigated.

With the ever-growing developments of sustainable energy sources such as fuel cells, photovoltaics, and other distributed generation, the need for a reliable power conversion system that interfaces these sources is in great demand. In order to provide the highest degree of flexibility in a truly distributed network, it is desired to not only interface multiple sources, but to also interface multiple loads. Modern multi-port converters use high frequency transformers to deliver the different power levels, which add to the size and complexity of the system. The different topological variations of the proposed multi-port dc-dc converter have the potential to solve these problems. This thesis proposes a unique dc-dc current source converter for multi-port power conversion. The presented work will explain the proposed multi-port dc-dc converter's operating characteristics, control algorithms, design and a proof of application. The converter will be evaluated to determine its functionality and applicability. Also, it will be shown that our converter has advantages over modern multi-port converters in its ease of scalability from kW to MW, low cost, high power density and adaption to countless combinations of multiple sources. Finally we will present modeling and simulation of the proposed converter using the PSIM software. This research will show that this new converter topology is unstable without feedback control. If the operating point is moved, one of the source ports of the multiport converter becomes unstable and dies off supplying very little or no power to the load while the remaining source port supplies all of the power the load demands. In order to prevent this and add stability to the converter a simple yet unique control method was implemented. This control method allowed for the load power demanded to be shared between the two sources as well as regulate the load voltage about its desired value.