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Hoy en día con el desarrollo de sensores inerciales basados en Sistemas Micro\-electromecánicos (MEMS), podemos encontrar acelerómetros y giróscopos embebidos en diferentes dispositivos y plataformas, teniéndolos en relojes, teléfonos inteligentes, consolas de video juego hasta sistemas de navegación terrestre y vehículos aéreos no tripulados (UAVs), {\em etc}. A pesar del amplio rango de aplicaciones donde están siendo utilizados, los sensores inerciales de bajo costo (grado MEMs) son afectados por errores aleatorios y determinísticos que degradan el rendimiento de los sistemas, en especial, los sistemas de navegación, un ejemplo de ello es la integración del Sistema de Posicionamiento Global (GPS) y el Sistema de Navegación Inercial (INS). Aunque diferentes investigaciones se han realizado para minimizar y modelar el error estocástico de los sensores inerciales MEMS, la estimación de los parámetros de este error y su eliminación sigue siendo una tarea poco fácil de realizar. Por este motivo, en esta tesis planteamos soluciones para facilitar la estimación de los parámetros y la compensación del error estocástico, específicamente, para el bias-drift, con el propósito de mejorar el rendimiento del sistema integrado GPS/INS basado en MEMS. Adicionalmente, el sistema de navegación es implementado en un Arreglo de Compuertas Programables en Campo (FPGA), donde se exploran las posibilidades que este tipo de plataformas puede ofrecer y como recursos hardware dedicados podrían ser utilizados para acelerar el filtro de navegación que es donde se presenta el mayor costo computacional. Finalmente, con el fin de evaluar la compensación del error estocástico, el Filtro de Kalman Extendido (EKF) de la estrategia de integración loosely-coupled GPS/INS es aumentado con diferentes modelos del error. Los resultados muestran el rendimiento del sistema de navegación cuando se realiza la compensación del bias-drift bajo bloqueos de la señal del GPS, utilizando datos reales recolectados en un vehículo terrestre en varias campañas. / Nowadays with the development of inertial sensors based on Micro-Electrome\-chanical Systems (MEMS), embedded accelerometers and gyroscopes can be found in several devices and platforms ranging from watches, smart phones, video game consoles up to terrestrial navigation systems and unmanned aerial vehicles (UAVs), {\em etc}. Despite the wide range of applications where such sensors are being used, low cost inertial sensors (MEMS grade) are affected by random and deterministic errors that degrade the systems performance, especially, in navigation systems like the Global Positioning System (GPS)/Inertial Navigation System (INS) integration. Albeit different researches have been conducted to minimize and model the stochastic error of MEMS inertial sensors, the estimation of the random noise parameters and its attenuation is still a non-trivial task. Therefore, in this thesis we propose solutions to facilitate the estimation of the parameters or the stochastic error and its compensation, specifically, for the bias-drift, with the aim of enhancing the performance of MEMS based INS/GPS integrated systems. Additionally, we implement the navigation system on a Field Programmable Gate Array (FPGA), where we explore the possibilities that this sort of platforms could offer and how dedicated hardware resources could be used to accelerate the navigation filter, that presents the highest computational burned. Eventually, in order to assess the compensation of the stochastic error, the Extended Kalman Filter (EKF) of the loosely-coupled GPS/INS integration strategy is augmented with different error models. Results show the performance of the navigation system during the compensation of the bias-drift under GPS signal blockages using real data collected in a land vehicle during several campaigns.

In this thesis we present a novel approach to sensor-based motion planning developed using the mathematical tools provided by the field of nonsmooth analysis. The work is based on a broad body of background material developed using the tools of differential topology (smooth analysis), that is limited to simple cases like a point or circular robot. Nonsmooth analysis is required to extend this background work to the case of a polygonal robot moving amidst polygonal obstacles. We present a detailed nonsmooth analysis of the distance function for arbitrary configuration spaces and use this analysis to develop a planner for a rotating and translating polygonal mobile robot. Using the tools of nonsmooth analysis, we then describe a one-dimensional nonsmooth roadmap of the robot's freespace called the Nonsmooth Critical Set + Nonsmooth Generalised Voronoi Graph (NC_RIT+NGVG) where the robot is equidistant to a number of obstacles, in a critical configuration or passing between two obstacles. We then use the related field of nonsmooth control theory to develop several provably stable control laws for following and exploring the nonsmooth roadmap. Finally, we implement a motion planner in simulation and for a real polygonal mobile robot, thus verifying the utility and practicality of the nonsmooth roadmap.

Actualment existeix un interès creixent en desenvolupar vehicles que permetin la seva mobilitat en terrenys abruptes. Els vehicles de rodes són els que presenten una millor relació entre la capacitat de superació d’obstacles i eficiència energètica. En aquesta tesi s’analitza l’eficiència energètica i les prestacions de les transmissions hidrostàtiques de vehicles de múltiples eixos amb configuracions complexes destinats a operar en terrenys irregulars. Els objectius són desenvolupar una metodologia per al disseny de transmissions hidrostàtiques d’aquest tipus de vehicles i analitzar els rendiments dels components principals d’una transmissió hidrostàtica i del seu conjunt. Els resultats posen de manifest que el disseny de transmissions hidrostàtiques en aquests vehicles és un procés complex amb múltiples solucions tècnicament factibles. A més, es quantifica l’afectació de les restriccions imposades per la transmissió en la capacitat de tracció del vehicle i es posa de manifest la influència de la interacció entre components de la transmissió i de les condicions d’operació en el seu rendiment global. Finalment es mostra la variabilitat dels rendiments, tant del conjunt de la transmissió com el funcional del vehicle, en aquestes condicions d’operació. / Actualmente existe un interés creciente en desarrollar vehículos que permitan su movilidad en terrenos abruptos. Los vehículos de ruedas son los que presentan una mejor relación entre la capacidad de superación de obstáculos y eficiencia energética. En esta tesis se analiza la eficiencia energética y las prestaciones de las transmisiones hidrostáticas de vehículos de múltiples ejes con configuraciones complejas destinados a operar en terrenos irregulares. Los objetivos son desarrollar una metodología para el diseño de transmisiones hidrostáticas de este tipo de vehículos y analizar los rendimientos de los componentes principales de una transmisión hidrostática y de su conjunto. Los resultados ponen de manifiesto que el diseño de transmisiones hidrostáticas en estos vehículos es un proceso complejo con múltiples soluciones técnicamente factibles. Además, se cuantifica la afectación de las restricciones impuestas por la transmisión en la capacidad de tracción del vehículo y se pone de manifiesto la influencia de la interacción entre componentes de la transmisión y de las condiciones de operación en su rendimiento global. Finalmente se muestra la variabilidad de los rendimientos, tanto del conjunto de la transmisión como el funcional del vehículo, en estas condiciones de operación. / Nowadays there is a growing interest in developing vehicles that enable its mobility in rough terrain. The wheeled vehicles are those that have a better relationship between the ability to overcome obstacles and efficiency. This thesis evaluates the efficiency and performance of hydrostatic transmissions for multiple axle vehicles with complex configurations designed to operate in rough terrain. The objectives are to develop a methodology for the design of hydrostatic transmissions for these vehicles and analyze the efficiency of the main components of a hydrostatic transmission and the efficiency of the transmission as a whole. The results show that the design of hydrostatic transmissions in these vehicles is a complex process with multiple solutions technically feasible. It also quantifies the effect of the restrictions imposed by the transmission over the vehicle traction capacity and it is demonstrated the influence of the interaction between components of the transmission and the operating conditions on the overall performance. Finally it is shown the variability of the transmission efficiency and the functional efficiency in these operating conditions.

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LISA (Laser Interferometer Space Antenna) is a joint mission of ESA and NASA, which aims to be the first space-borne gravitational wave observatory. LISA will consist in a constellation of three spacecraft at the vertexes of an equilateral triangle of side 5 million kilometers. The constellation will orbit around the Sun trailing the Earth by some 20 degrees. Each of the spacecraft harbors two proof masses, carefully protected against external disturbances such as solar radiation pressure and charged particles, which ensures they are in nominal free-fall in the interplanetary gravitational field. Gravitational waves will show as differential accelerations between pairs of proof masses, and the main aim of LISA is to measure such acceleration using laser interferometry. The technologies required for the LISA mission are many and challenging. This, coupled with the fact that some flight hardware cannot be tested on ground, led ESA to define a technology demonstrator to test in flight the required critical technologies. This precursor mission is called LISA Pathfinder (LPF). The payload of LISA Pathfinder is the LISA Technology Package (LTP), and will be the highest sensitivity geodesic explorer flown to date. The LISA Technology Package is designed to measure relative accelerations between two test masses in nominal free fall placed in a single spacecraft, since one LISA arm is squeezed from 5 million kilometer to 35 cm. Its success will prove the maturity of the necessary technologies for LISA such as the Optical Metrology System and the Drag Free concept. The differential acceleration reading will be perturbed by identified disturbances, such as thermal fluctuations or magnetic effects. These disturbances are monitored by the Diagnostics Subsystem. The Magnetic Diagnostics System is one of its modules and is a critical subsystem, since magnetic noise is apportioned to 40% of the total noise budget. In this respect, to estimate the magnetic noise contribution, the Magnetic Diagnostics Subsystem will have two main tasks: (1) estimate the magnetic properties of the test masses, i.e., their remanent magnetic moment and susceptibility, and (2) infer the magnetic field and its gradient at the location of the test masses. To this end, the Magnetic Diagnostics Subsystem includes two coils which generate controlled magnetic fields at the locations of the test masses. These magnetic fields will excite the dynamical response of both test masses. Thus, by adequate processing of the kinematic excursions delivered by the interferometer, the magnetic characteristics of the test masses can be estimated within 1% accuracy level. Additionally, the Magnetic Diagnostic Subsystem includes a set of four tri-axial fluxgate magnetometers. However, the magnetic field and its gradient need to be measured at the positions of the test masses and the readouts of the magnetometers do not provide a direct measurement of the magnetic field at these positions. Thus, an interpolation method must be implemented to calculate them. This is a difficult problem, mostly because the magnetometers are too distant from the locations of the test masses (more than 20 cm away) and because there are not sufficient magnetic channels to go beyond a classical linear interpolation method, which yields extremely poor interpolation results. Consequently, in this thesis we present and validate an alternative interpolation method based on neural networks. We put forward its robustness and accuracy in several mission scenarios and we stress the importance of an extensive magnetic testing campaign. Under these assumptions, we deliver magnetic field and gradient estimates with 10% accuracy. Finally, the estimate of the magnetic noise contribution to the total acceleration between the two LPF’s test masses is determined with an accuracy of 15%. This result represents an enhancement of the estimation quality in one order of magnitude with respect to former studies. / LISA (Laser Interferometer Space Antenna) és un missió espacial conjunta de l’ESA i la NASA, que serà el primer detector d’ones gravitacionals a l’espai. LISA consisteix en una constel·lació de tres satèl·lits situats als vèrtexs d’un triangle equilàter de 5 milions de quilòmetres de costat. La constel·lació orbitarà al voltant del Sol seguint la Terra a uns 20 graus. Cada un dels satèl·lits contindrà dues masses de prova, curosament protegides de pertorbacions externes com la pressió de la radiació solar, assegurant que estiguin en una caiguda lliure nominal en el camp gravitacional interplanetari. Les ones gravitacionals creen acceleracions diferencials entre el parell de masses de prova. Així doncs el principal objectiu de LISA és mesurar l’esmentada acceleració utilitzant interferometria làser. Les tecnologies necessàries per LISA són molt exigents. A més, la majoria d’elles no poden ser testejades a la Terra. Per tant, l’ESA va determinar la necessitat de llançar una missió precursora que actués com a demostrador tecnològic, aquesta missió és LISA Pathfinder (LPF). La seva càrrega útil és el LISA Technology Package (LTP) i serà el sensor geodèsic de més alta sensitivitat a l’espai. El LISA Technology Package està dissenyat per mesurar acceleracions diferencials entre dues masses de prova en caiguda lliure situades en un sol satèl·lit, reduint un dels braços de LISA des de 5 milions de quilòmetres fins a 35 cm. L’èxit de la missió suposaria la demostració de la maduresa de les tecnologies necessàries per LISA, com són el Optical Metrology System i el concepte Drag Free. La mesura de l’acceleració diferencial estarà afectada per certes pertorbacions com podrien ser les fluctuacions tèrmiques o els efectes magnètics a l’interior del satèl·lit. Aquestes pertorbacions són monitoritzades pel Subsistema de Diagnòstic. El Subsistema de Diagnòstic Magnètic és un dels seus mòduls i és un sistema crític, perquè el soroll magnètic representa un 40% del soroll total. Amb la finalitat d’estimar la contribució del soroll magnètic, el Subsistema de Diagnostic Magnètic ha de (1) estimar les propietats magnètiques de les masses de prova, i.e., el seu moment magnètic remanent i la seva susceptibilitat, i (2) estimar el camp magnètic i el seu gradient a la posició de les masses de prova. Així doncs, aquest subsistema integra dues bobines per generar camps magnètics a la posició de les masses. Aquests camps magnètics exciten la resposta dinàmica de les dues masses. Finalment, amb el processament de les excursions cinemàtiques proporcionades per l’interferòmetre podem estimar les característiques magnètiques amb una precisió de l’1%. D’altra banda, el Subsistema de Diagnòstic Magnètic també integra 4 magnetòmetres triaxials. No obstant, el camp magnètic i el seu gradient ha de ser mesurat a la posició de les masses de prova i les lectures dels magnetòmetres no estan situades en aquestes posicions. Per tant, cal implementar un sistema d’interpolació. Aquest problema presenta una dificultat especial perquè els magnetòmetres estan situats lluny de les masses de prova (més de 20 cm) i perquè només hi ha mesures magnètiques per realitzar una interpolació de primer ordre. Aquest mètode dóna resultats inacceptables, per tant en aquesta tesi presentem i validem un mètode d’interpolació alternatiu basat en xarxes neuronals. En demostrem la seva robustesa i exactitud en diferents casos i remarquem la importància de disposar d’una extensa campanya de tests magnètics. Sota aquests supòsits, estimem el camp magnètic i el seu gradient amb un error inferior al 10%. Finalment, l’estimat de la contribució del soroll magnètic en la mesura de l’acceleració diferencial de les dues masses de prova es pot determinar amb una exactitud del 15%. Aquest resultat suposa una millora de la qualitat d’estimació en un ordre de magnitud en comparació a estudis previs.

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This thesis presents laboratory and field studies into the effects of solar radiation on the thermal comfort of vehicle occupants. Whilst, thermal comfort has been widely studied in built environments, there have been relatively few studies into thermal comfort in vehicles. Those studies that have been conducted have noted that the effect of solar radiation is considerable in these confined microclimates. The aim of this thesis was to provide baseline data for the effects of solar radiation on thermal sensation and determine how this information can be integrated to provide a method for the assessment of vehicle thermal comfort. This was achieved using a specially constructed whole body solar chamber in a series of four laboratory studies looking at different aspects of solar radiation on human thermal comfort and an extensive field trial conducted in Seville, Spain. The laboratory studies were as follows:- 1, The effect of the intensity of direct simulated solar radiation on human thermal responses. Eight male subjects were exposed to 4 different intensity solar radiation conditions. Physiological and psychological measurements were taken. It was established that a mean response to 200 Wm"2 of direct simulated solar radiation will give a thermal sensation shift of one positive scale point. 2, The effect of the spectral content of simulated solar radiation on human thermal responses. Eight male subjects were exposed to 4 different spectral radiation conditions, with the same total radiation intensity, 400 wm·2 • There was found to be no significant difference in the thermal sensation responses due to spectra. 3, The effects of glazing type on human thermal comfort responses. Eight male subjects were exposed to 4 different automotive glazings, with a fixed external solar radiation level of 1000 wm·2 • The spectral qualities of glazing can significantly effect human thermal comfort. The lower the transmission of visible radiation through the glazing, the lower the thermal sensation felt by subject in a neutral environment. 4, The effect of direct short wavelength and long wavelength radiation on human thermal comfort. Nine male subjects were exposed to short wavelength, long wavelength and combined short and long wavelength radiation. For the conditions investigated it was established that the addition of reradiation from internal components has an effect on thermal sensation when combined with direct solar radiation. However, it is not considered that it will be a major factor in a real world situation, as dashboards generally do not maintain high surface temperatures in vehicles without high air temperatures. Using the data collected in the laboratory studies a predictive model, PMV sotu, was developed which integrated directed solar radiation into an existing thermal comfort model (PMV) in the form of a factor, Rsolar· Rsolar is a correction factor for the addition of short wavelength radiation which converts actual measured solar radiation to a thermal sensation scale adjustment The PMV solar model was validated with other models in field trials conducted in Seville, Spain. Four male subjects, undertook a series of 32, one hour long experiments over 8 days, whilst travelling on a Spanish highway. Environmental, physiological and psychological measurements were taken throughout the experiments to provide data for validation of THE PMV solar model. The assessment of human thermal comfort in vehicles is complex. Variation in environmental parameters in terms of both spatial and temporal changes, make accurate prediction of thermal comfort difficult. However, the PMV solar model provides an improved level of prediction of the state of thermal comfort of the vehicle occupants, in environments which have a high solar radiation level over existing thermal indices.

This study investigates rapid changes in contact resistance, termed intermittences or short duration discontinuities, on tin-plated electrical contacts that are undergoing fretting tests. Voltage and current levels are comparable to the levels found in automotive systems. The thesis begins with an overview of the theory of mechanical and electrical contact, factors that determine the performance of an electrical contact and previous work on intermittences. Building upon this background information a low frequency fretting apparatus and a high¬speed data acquisition system are developed, capable of monitoring the voltage-drop across and current through the contact with a sample rate of up to 1 gigasamples per second. During the fretting experiments the build-up of debris is observed. As expected in this type of experiment the contact resistance rises with increasing number of fretting cycles. An increase in current accelerates the contact degradation. The contact surface is analysed using SEM and SEM/EDX. Several features are found in the recorded signals. These include plateaus, slopes of several tens of kilovolts per second, voltage-drops across the contact interface of above the melting voltage of tin and intermittences that can occur, when no forced relative motion between the contact partners is present. The observations are combined to a set of requirements of a model to explain intermittency phenomena. Previously proposed models are evaluated on the basis of these findings. Finally the asperity model is extended to incorporate the results of the experiments. It is proposed that melting of asperiti.es causes short-duration discontinuities and events that occur when no forced relative motion is present. Both could not be explained within the asperity model before. The thesis concludes with a definition of the term 'intermittence' as the temporary disruption of metallic conduction in a closed electrical contact. This definition is an improvement over the previous definition, because it allows setting a specific resistance threshold to detect intermittences in fretting experiments. Future work is suggested.

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