Cotutela Universitat Politècnica de Catalunya i Universität Stuttgart, Institut für Raumfahrtsysteme (IRS) / Manned missions carried out in the last decades were either close to Earth or short missions. In contrast, Space Agencies future plans include manned exploration missions to asteroids, the Moon and finally Mars. The expected mission durations rise significantly and the greater distance from Earth makes a resupply or rescue mission almost impossible. These future plans make it necessary to develop a new Environmental Control and Life Support System (ECLSS), which ensures the survival of the astronauts for such missions. These frame conditions will impose a high degree of closure and a high reliability for the ECLSS. In this thesis, firstly, the different ECLSS technology/component options are presented, and its suitability for a long duration human spaceflight is analyzed. From all technologies the most promising, regenerative systems for atmosphere, water and waste management are selected in order to examine them as part of a complete ECLSS. Different approaches to evaluate the reliability of complex systems are analyzed. Since the failure of a component within the system does not necessarily lead a failure of the entire ECLSS, as the system is able to compensate for some failures, the Stochastic Dynamic Discrete Simulation (SDDS) method is selected. To carry out an SDDS, a robust and adaptable ECLSS model simulation is required. A new software is developed, based on the simulation tool Environment for Life-Support Systems Simulation and Analysis (ELISSA) from the Institute of Space Systems - University of Stuttgart. As a result of a stochastic simulation a list of failure times is obtained, which can be treated using the Maximum Likelihood Estimation (for parametric models) or the Kaplan-Meier method (for non-parametric models), to define the reliability of the system. The input data required to apply the SDDS are the reliabilities of each possible component of the ECLSS. The reliability of each component is defined by the failure rate or its parts. It can be seen, that the use of redundancies (spare parts) is essential for long duration missions, as the reliability of the system without them after 60 days is lower than 50%. The analysis of all components, including their spare parts, is carried out with the Multi-Opbjective Optimization Problem to achieve a high reliability with the lowest possible mass. Both methodologies, SDDS and MOOP have been implemented creating the user-friendly new software RELISSA. Finally, as an example, RELISSA is used to analyze a manned Mars mission. With this analysis, technologies currently in use (on board ISS) are compared with new technologies (currently under development), with the potential to reduce the system mass. The results clearly show that the new technologies can significantly reduce the mass of the system, for results of similar reliability. With these results, the need of development efforts of ECLSS technologies for manned missions beyond Low Earth Orbit is corroborated. / Les missions tripulades realitzades en les últimes dècades, van ser missions properes a la Terra o de curta durada. Per contra, els plans futurs de les Agències Espacials inclouen missions d'exploració tripulades a asteroides, la Lluna o Mart. La durada esperada d'aquestes missions s'incrementa significament i la major distància de la Terra fa que una missió d’abastiment o rescat sigui pràcticament impossible. Aquests futurs plans fan necessari el desenvolupament d'un nou Sistema de Control Ambiental i Suport a la Vida (ECLSS - Environmental Control and Life Support System), que asseguri la supervivència dels astronautes per a aquestes missions . Aquestes condicions imposen un alt nivell de tancament del sistema i una alta fiabilitat per al ECLSS. En aquesta tesi, es presenten les diferents opcions tecnològiques, components i s’analitza la seva viabilitat per a missions tripulades de llarga durada. De totes les tecnologies, se seleccionen els sistemes regeneratius més prometedors per a la gestió de l’atmosfera, l'aigua i els residus, per tal d'analitzar-los com a part de l'ECLSS. S'analitzen diferents mètodes per tal d'avaluar la fiabilitat de sistemes complexos . Com que la fallada d'un component del sistema no implica necessàriament una fallada de tot l'ECLSS, ja que el sistema és capaç de compensar algunes fallades, se selecciona el mètode de simulació dinàmica- estocàstica (SDDS - Stochastic Dynamic Discrete Simulation). Per a dur a terme l'SDDS, es necessita un model de simulació ECLSS robust i adaptable. Es desenvolupa un nou software, basat en l'eina de Simulació de l'Institut de Sistemes Espacials - Universitat de Stuttgart, Environm ent for Life-Support Systems Simulation and Analysis (ELISSA). Com a resultat de la simulació estocàstica, s'obté una llista de temps de fallada, a partir de la qual, amb el mètode de Màxima Versemblança (per a models paramètrics ) o de Kaplan-Meier (per a models no paramètrics ) es defineix la fiabilitat del sistema. Les dades d'entrada necessàries per aplicar l'SDDS són les fiabilitats de cada un dels possibles com ponents de l'ECLSS. La fiabilitat de cada component es defineix a partir de la taxa de fallada de les seves parts. Es pot observar que l'ús de redundàncies (peces de recanvi) és essencial per a missions de llarga durada, ja que la fiabilitat del sistema sense recanvis disminueix més del 50% passats 60 dies. L'anàlisi de tots els components, incloent-hi les peces de recanvi, es realitza a partir del problema d'optimització d'objectius múltiples (MOOP - Multi-Opbjective Optimization Problem ), per tal d'obtenir una altra fiabilitat amb la menor massa possible. Les dues metodologies , SDDS i MOOP, s'han implementat creant un nou software, user-friendly, RELISSA. Finalment, com exemple, s'ha utilitzar RELISSA per analitzar una missió tripulada a Mart. Amb aquesta anàlisi es comparen tecnologies actualment en ús (a l'Estació Espacial Internacional) i noves tecnologies (actualment en desenvolupament) amb el potencial de reduir la massa del sistema. Els resultats mostren clarament que les noves tecnologies poden reduir significament la massa dels sistema, per a resultats similars de fiabilitat. Amb aquests resultats, es corrobora la necessitat de dedicar esforços de desenvolupament en tecnologies ECLSS per a missions tripulades més enllà de l'òrbita baixa terrestre (LEO - Low Earth Orbit).

This thesis aims to dissert about air transport network design taking into consideration the current needs about efficiency in a very competitive industry. The main focus for this work is the airline's point of view and for this reason is going to be common to talk about profitability. A methodology is proposed to analyse current networks and to introduce modifications. First, an analytical approach is proposed with the aim to understand better the interaction of key parameters in network design at strategical level. Analyitical models demonstrate to be very useful because with a few parameters it is possible to decide if point to point or hub and spoke configuration suits better for an airline, given a set of supply conditions. Furthermore, the performance of networks with stopover configuration is tested, basically because for long routes with low demand this newtorks work well, how it was demonstrated by public transport systems. The differenciation of this research, compared against previous studies, is to include the performance of new entrant airlines in the industry. This aspect is carried out evaluating accurately the impact of fixed costs in the evaluation of cost operators. Despite airlines tend to consider aircraft ownership costs and labor costs as variable ones, they are not. They had an important impact in profit and loss account. A bad utilitzation factor of airplane or crew staff is very undesirable for operator and it can consider do not operate new routes if the resources are not well used. Secondly, analytical models are powerful but it is not possible to evaluate accurately the daily operational aspects for real networks with real flight schedules because these models take into consideration average values of some parameters. For this reason, this thesis develops a Tabu search algorithm to carry out airline network planning, based on linear models of each different planning problem. To do this contribution, these models are developed before for linear programming and they are solved with a combination of complete enumeration algorithm and exhaustive search algorithm. Both algorithms provide exact solution or global optimum for any problem statement. Later, Tabu search algorithm improves performance of searching with lower computational cost. The main conclusion is that Tabu developed is a better tool for airline planning than exact techniques because of lower times of computation. This performs better for large networks that, finally, are real networks. However, exact techniques could be interesting for small airlines that can be start-ups. Third, one of main reasons to develop a quantification of costs for managing airlines is due to the problem of complexity in networks. With the growth of air transportation and congestion at airports, primary or reactionary delays become higher day after day. Reactiveness of network depends of configuration and planning. Airlines manages it with extra reources, one way is allocating buffer times in flight schedule and other is having aircrafts at ground at main bases to enter in service and recover flight plans. Airline network design, planning and efficient algorithms are key assets to provide robustness for airlines. Finally, driving airlines in high competitive environments are difficult. Running low costs is the main decision for managers. However, analysing the problem from theory game point of view, allows finding key reasons to support this argument. First, a Stakelberg model is defined for two competing airlines. This model demonstrates that a war on frequencies or fares damages both competitors. Furthermore, a Cournot model it is shown and it proposes a navigation fee attending to correct utilization of capacity. Both models are a theoretical framework but demonstrate consistency and encourage further investigations. / El diseño de redes de transporte aéreo es un factor clave de eficiencia en una industria altamente competitiva. A pesar de que la rentabilidad es de suma importancia, el sistema considera la experiencia del usuario y los beneficios sociales para obtener un óptimo global. Un enfoque analítico permite derivar principios de diseño de redes de transporte aéreo: la tesis muestra cómo unas pocas variables y sus interacciones explican los factores clave del diseño de la red a nivel estratégico. Los servicios punto-a-punto muestran supremacía en las redes simples y para demandas altas y compensadas, una configuración con escalas es adecuada para rutas lejanas con poca demanda, y las operaciones hub and spoke mejoran las dos estrategias anteriores para redes grandes, cuando la demanda es baja o cuando las frecuencias son altas, pero son más sensibles a la propagación de demoras. El enfoque analítico permite prever el comportamiento de nuevas compañías aéreas entrando en el sector. El modelo incluye costes fijos de propiedad del avión y laborales (al contrario de las hipótesis habituales de la industria, que trabaja con costes variables), puesto que tienen un impacto importante en la cuenta de resultados. Una vez se han derivado guías de diseño, la tesis formula un planteamiento más realista del diseño de redes de transporte aéreo basado en programación matemática lineal, que se resuelve con una combinación del Algoritmo de Enumeración Completa y el Algoritmo de Búsqueda Exhaustiva (ambos proporcionan la solución exacta o un óptimo global para cualquier planteamiento del problema). El modelo incluye asignación de flotas, rutas de aeronaves y programación de tripulaciones. Mientras que los algoritmos exactos son apropiados para aerolíneas pequeñas, los problemas más grandes necesitan Búsqueda Tabú. El crecimiento del transporte aéreo y la congestión en los aeropuertos (a veces propiciada por las operaciones hub&spoke) pueden afectar las demoras con un efecto de bola de nieve o látigo; sin embargo el análisis de la complejidad de la red aérea puede incrementar la resiliencia de las operaciones. Un buen diseño de la red aérea, una buena planificación y unos algoritmos eficientes, son aspectos clave para proporcionar fiabilidad a las aerolíneas y así reducir los recursos inactivos asociados a “colchones de tiempo” (en los horarios de los vuelos) y/o en aviones “de reserva” en la plataforma para recuperar planes de vuelo. El “acolchado” mejora la percepción de la calidad por parte del pasajero, pero con un control activo del horario de vuelos puede conseguirse la misma percepción con costes menores. El entorno competitivo de las aerolíneas se analiza con teoría de juegos: un modelo de Stakelberg para dos aerolíneas competidoras muestra que una guerra de frecuencias o tarifas es perjudicial para ambas aerolíneas. Un modelo Cournot propone una tasa de navegación y de congestión según la correcta utilización de la capacidad. Vuelos (de la misma alianza) a lo largo del mundo con escalas en los hubs principales se proponen como investigación futura

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

No description available.

Over the last forty years, the use of electronic controls within the automotive industry has grown considerably. In-vehicle network technologies such as the Controller Area Network (CAN) and Local Interconnect Network (LIN) are used to connect Electronic Control Units (ECU) together, mainly to reduce the amount of wiring that would be required if hardwired integration were used. Modern passenger cars contain many networks, which means that for the architecture designer, there is an almost overwhelming number of choices on how to design/partition the system depending on factors such as cost, weight, availability of ECUs, safety, Electro-Magnetic Compatibility (EMC) etc. Despite the increasing role played by in-vehicle networks in automotive electrical architectures, its design could currently be described as a “black art”. Not only is there an almost overwhelming number of choices facing the designer, but there is currently a lack of a quantifiable process to aid decision making and there is a dearth of published literature available. NetGen is a software tool used to design CAN/J1939, LIN and FlexRay networks. For the product to remain competitive, it is desirable to have novel features over the competition. This report describes a body of work, the aim of which was to research in-vehicle network design processes, and to provide an improvement to such processes. The opportunities of customer projects and availability of customer information resulted in the scope of the research focusing on the adoption of LIN technology and whether the adoption of it could reduce the cost and weight of the target architecture. The research can therefore be seen to address two issues: firstly the general problem of network designers needing to design in-vehicle network based architectures balancing the needs of many design targets such as cost, weight etc, and secondly the commercial motivation to find novel features for the design tool, NetGen. The outcome of the research described in this report was the development of design processes that can be used for the selection of low cost and weight automotive electrical architectures using coarse information, such as that which would be easily available at the very beginning of a vehicle design programme. The key benefit of this is that a number of candidate networked architectures can be easily assessed for their ability to reduce cost and weight of the electrical architecture.

Vehicle-to-grid uses vehicles with on-board electricity storage as an energy storage system for the electricity grid. Vehicles not only take power from the grid when charging, but can supply power back to the grid. This storage mechanism can then be used in various applications, for example, providing balancing services and helping the introduction of renewable energy sources. Research into vehicle-to-grid suggests that it is feasible in certain applications. Indeed, the component technology required for vehicle-to-grid has been successfully demonstrated. Gaps in the analysis of vehicle-to-grid feasibility remain. Notably, the behaviour of individuals in a vehicle-to-home context is not well understood. A vehicle-to-home simulation tool was developed to address these gaps. The tool incorporates a use case methodology and a Matlab Simulink model. Application of the use case methodology identifies the inputs and constraints determined by users in a vehicle-to-home system. Feeding these inputs into the model facilitates the sensitivity analysis of vehicle-to-home operation to these user dependent variables. The use of the simulation tool is demonstrated in two case studies: Using an electric vehicle as back-up power supply; and using an electric vehicle to support small-scale distributed generation. The operation of a vehicle-to-home system in these case studies is presented, along with the sensitivity of operation to input parameters including: battery storage capacity, vehicle usage and vehicle charging. Both case studies demonstrated that, given the correct conditions|notably cooperation of the vehicle user|vehicle-to-home can operate successfully in storage applications. It was shown that an electric vehicle could provide back-up storage to households for a useful amount of time|between 20 hours and several days. It was shown that an electric vehicle can be used to store energy from a small-scale wind turbine such that the generation is better utilised than if no storage is available. The developed simulation tool enables analysis of novel vehicle-to-home applications not possible with previous models of vehicle-to-grid. The use of the tool highlighted the importance of including individual variation in behaviour when studying vehicle-to-home systems.

Club motorsport, a low cost, amateur form of motorsport, forms a significant part of the motorsport industry in the United Kingdom. If efforts are not made to move towards more environmentally friendly technologies, then this form of motorsport is at risk of becoming irrelevant. One approach taken by other motorsport sectors has been to implement hybrid electric vehicle technology, which can result in improved vehicle performance on the race track. However, the companies that operate in the club motorsport sector do not typically have the resources and experience necessary to develop these technologies. An innovative process was used to guide the design of a new hybrid electric vehicle drivetrain for use in club motorsport. This process made use of the ability for vehicle manufacturers to set the vehicle specifications in club motorsport. A conjoint analysis of customer requirements was carried out, a first for the industry, and led to the development of a market simulation tool. A vehicle simulation tool was then developed to assist in the evaluation of the hybrid electric drivetrain design options. The result of following this process was a new and innovative hybrid electric drivetrain installed in a Westfield Sportscars Sport Turbo, reducing 0-60mph acceleration time from 5.4 seconds to 3.8 seconds. An innovative type of system control was implemented, by where the driver is given a finite amount of boost energy for use throughout the race. The drivetrain can also be easily transferred to other vehicle platforms, as the first shelf engineered hybrid drivetrain for motorsport, allowing its use by multiple manufacturers across the club motorsport and niche vehicle sectors. This project has shown that it is possible to implement environmentally friendly technologies, such as hybrid electric vehicle technology, into club motorsport and be able to meet customer, technical and cost requirements. The process that has been developed enables innovation in hybrid electric race car design. This has been shown in the development of a hybrid electric vehicle suitable for use, and sale, in the club motorsport industry.

No description available.

wo dimensions. Pseudo-GPS was integrated into the testbed to allow for independent verification and validation of a vehicle's performance. The docking simulator was developed by integrating computer hardware and attitude sensors into a newly-designed vehicle architecture to support its navigation and control needs. A position and attitude estimator was created to fuse the vehicle's sensor inputs. A control system was designed to allow for position control through eight thrusters and attitude control through the use of a reaction wheel. Finally, experiments of proximity navigation were conducted. One experiment established the versatility of the vehicle's control system by performing a closed loop maneuver. A second experiment successfully demonstrated a complete docking scenario.