Analysis and design of high performance multiphase electric drives for vehicle and aircraft applications

The first part of this thesis has focused on the construction of a twelve-phase asynchronous machine for More Electric Aircraft (MEA) applications. In fact, the aerospace world has found in electrification the way to improve the efficiency, reliability and maintainability of an aircraft. This idea leads to the aircraft a new management and distribution of electrical services. In this way is possible to remove or to reduce the hydraulic, mechanical and pneumatic systems inside the aircraft. The second part of this dissertation is dedicated on the enhancement of the control range of matrix converters (MCs) operating with non-unity input power factor and, at the same time, on the reduction of the switching power losses. The analysis leads to the determination in closed form of a modulation strategy that features a control range, in terms of output voltage and input power factor, that is greater than that of the traditional strategies under the same operating conditions, and a reduction in the switching power losses.

Development of an Elevated Temperature Loop Heat Pipe for Space Applications and Investigation of Non Condensable Gas Impact on its Performance

Un caloducto en bucle cerrado o Loop Heat Pipe (LHP) es un dispositivo de transferencia de calor cuyo principio de operación se basa en la evaporación/condensación de un fluido de trabajo, que es bombeado a través de un circuito cerrado gracias a fuerzas de capilaridad. Gracias a su flexibilidad, su baja masa y su mínimo (incluso nulo) consumo de potencia, su principal aplicación ha sido identificada como parte del subsistema de control térmico de vehículos espaciales. En el presente trabajo se ha desarrollado un LHP capaz de funcionar eficientemente a temperaturas de hasta 125 oC, siguiendo la actual tendencia de los equipos a bordo de satélites de incrementar su temperatura de operación. En la selección del diseño optimo para dicho LHP, la compatibilidad entre materiales y fluido de trabajo se identificó como uno de los puntos clave. Para seleccionar la mejor combinación, se llevó a cabo una exhaustiva revisión del estado del arte, además de un estudio especifico que incluía el desarrollo de un banco de ensayos de compatibilidad. Como conclusión, la combinación seleccionada como la candidata idónea para ser integrada en el LHP capaz de operar hasta 125 oC fue un evaporador de acero inoxidable, líneas de titanio y amoniaco como fluido de trabajo. En esa línea se diseñó y fabricó un prototipo para ensayos y se desarrolló un modelo de simulación con EcosimPro para evaluar sus prestaciones. Se concluyó que el diseño era adecuado para el rango de operación definido. La incompatibilidad entre el fluido de trabajo y los materiales del LHP está ligada a la generación de gases no condensables. Para un estudio más detallado de los efectos de dichos gases en el funcionamiento del LHP se analizó su comportamiento con diferentes cantidades de nitrógeno inyectadas en su cámara de compensación, simulando un gas no condensable formado en el interior del dispositivo. El estudio se basó en el análisis de las temperaturas medidas experimentalmente a distintos niveles de potencia y temperatura de sumidero o fuente fría. Adicionalmente, dichos resultados se compararon con las predicciones obtenidas por medio del modelo en EcosimPro. Las principales conclusiones obtenidas fueron dos. La primera indica que una cantidad de gas no condensable más de dos veces mayor que la cantidad generada al final de la vida de un satélite típico de telecomunicaciones (15 años) tiene efectos casi despreciables en el funcionamiento del LHP. La segunda es que el principal efecto del gas no condensable es una disminución de la conductancia térmica, especialmente a bajas potencias y temperaturas de sumidero. El efecto es más significativo cuanto mayor es la cantidad de gas añadida. Asimismo, durante la campaña de ensayos se observó un fenómeno no esperado para grandes cantidades de gas no condensable. Dicho fenómeno consiste en un comportamiento oscilatorio, detectado tanto en los ensayos como en la simulación. Este efecto es susceptible de una investigación más profunda y los resultados obtenidos pueden constituir la base para dicha tarea. ABSTRACT Loop Heat Pipes (LHPs) are heat transfer devices whose operating principle is based on the evaporation/condensation of a working fluid, and which use capillary pumping forces to ensure the fluid circulation. Thanks to their flexibility, low mass and minimum (even null) power consumption, their main application has been identified as part of the thermal control subsystem in spacecraft. In the present work, an LHP able to operate efficiently up to 125 oC has been developed, which is in line with the current tendency of satellite on-board equipment to increase their operating temperatures. In selecting the optimal LHP design for the elevated temperature application, the compatibility between the materials and working fluid has been identified as one of the main drivers. An extensive literature review and a dedicated trade-off were performed, in order to select the optimal combination of fluids and materials for the LHP. The trade-off included the development of a dedicated compatibility test stand. In conclusion, the combination of stainless steel evaporator, titanium piping and ammonia as working fluid was selected as the best candidate to operate up to 125 oC. An LHP prototype was designed and manufactured and a simulation model in EcosimPro was developed to evaluate its performance. The first conclusion was that the defined LHP was suitable for the defined operational range. Incompatibility between the working fluid and LHP materials is linked to Non Condensable Gas (NCG) generation. Therefore, the behaviour of the LHP developed with different amounts of nitrogen injected in its compensation chamber to simulate NCG generation, was analyzed. The LHP performance was studied by analysis of the test results at different temperatures and power levels. The test results were also compared to simulations in EcosimPro. Two additional conclusions can be drawn: (i) the effects of an amount of more than two times the expected NCG at the end of life of a typical telecommunications satellite (15 years) is almost negligible on the LHP operation, and (ii) the main effect of the NCG is a decrease in the LHP thermal conductance, especially at low temperatures and low power levels. This decrease is more significant with the progressive addition of NCG. An unexpected phenomenon was observed in the LHP operation with large NCG amounts. Namely, an oscillatory behaviour, which was observed both in the tests and the simulation. This effect provides the basis for further studies concerning oscillations in LHPs.

Diseño y ensayos en tierra de paneles solares para un satélite de órbita baja = Design and testing procedures of a Low Earth Orbit (LEO) satellite solar panels

Debido al reciente incremento de conflictos en el mundo árabe y dado el interés nacional de España en dicha zona, se propone en este proyecto un estudio inicial para el diseño y desarrollo de un microsatélite que ayude al gobierno de España a mantener esa zona bajo observación constante. En el presente trabajo se abarcan todos los subsistemas del satélite, haciéndose un estudio más detallado del subsistema de potencia

Diseño y ensayos en tierra de las baterías para un satélite de órbita baja = Design and testing procedures of a Low Earth Orbit (LEO) satellite battery

Este proyecto consiste en el estudio y dimensionado inicial del sistema de potencia de un satélite de observación, que sirva de ayuda a otros sistemas de mayor precisión a la hora de detectar posibles terremotos y actividad volcánica mediante el análisis de señales electromagnéticas presentes en la ionosfera. Para ello el satélite incorpora, entre otros elementos sensores eléctricos, un analizador de plasma, y un detector de partículas. Con esta instrumentación se pretenden detectar los cambios que se producen en el campo electromagnético terrestre como consecuencia del movimiento de las placas tectónicas, y descubrir así las posibles anomalías que preceden a un seísmo. Para no sobrepasar el presupuesto con el que se ha ideado el proyecto se utilizarán sistemas que permitan la lectura de datos de la forma más simple, pudiendo ocurrir que los datos recogidos no se transmitan al control de Tierra en tiempo real, impidiendo a los científicos analizar los datos recogidos hasta unos días después, de ahí que este satélite experimental deba emplearse, en principio, como apoyo a programas de detención de terremotos más sofisticados y con mayores medios técnicos. Evidentemente, con este sistema también se podrán recoger datos tras los seísmos y examinarlos posteriormente. La órbita del satélite será una órbita LEO (Low Earth Orbit) de una altitud aproximada de 670 Km, estimándose el tiempo de vida del satélite en 5 años. Intentando emplear la mayor parte de los recursos económicos en el equipamiento científico, la estructura será la más simple posible, esto es, un paralelepípedo de dimensiones compactas con un peso aproximado de 185 kg, contando con paneles solares desplegables y en su interior con baterías que proporcionarán potencia al satélite durante la fase de lanzamiento y en momentos concretos.

Diseño y ensayos en tierra de paneles solares y baterías para un satélite de órbita baja = Design and testing procedures of a Low Earth Orbit (LEO) satellite power subsystem (solar panels and battery)

Las principal conclusión que se puede obtener tras el estudio es que el satélite, tal y como se ha tenido en cuenta, es perfectamente funcional desde el punto de vista eléctrico. Por la parte de la generación de potencia, los paneles son capaces de ofreces una cantidad tal como para que aproximadamente la mitad (en el caso de funcionamiento normal) de esta potencia sea destinada a la carga útil. Además, incluso en los modos de fallo definidos, el valor de potencia dedicada a la carga útil, es suficientemente alta como para que merezca la pena mantener el satélite operativo. Respecto de las baterías, se puede observar por su comportamiento que están, sobredimensionadas y por ello actúan como un elemento regulador del sistema completo, ya que tiene un amplio margen de trabajo por el cual se puede modificar el funcionamiento general. Y esto se demuestra no sólo en cuanto al estado de carga, que para el perfil de consumo constante y el de cuatro pulsos de 120 W por día se mantiene siempre por encima del 99%, si no también en términos de charging rate, el cual se está siempre dentro de los límites establecidos por el fabricante, asegurando una vida operativa acorde con la nominal. Por último, sobre el propio método de simulación se puede extraer que aun no siendo la mejor plataforma donde estudiar estos comportamientos. Presenta el inconveniente de que, en ciertas partes, restringe la flexibilidad a la hora de cambiar múltiples condiciones al mismo tiempo, pero a cambio permite un estudio bastante amplio con un requisito de conocimientos y de complejidad bajo, de manera que habilita a cualquier estudiante a llevar a cabo estudios similares.

Diseño y ensayos en tierra de paneles solares para un satélite de órbita baja = Design and testing procedures of a Low Earth (LEO)satellite solar panels

El Proyecto Fin De Carrera presentado a continuación contiene una descripción del prediseño del microsatélite de observación terrestre Gaia, particularizando ésta especialmente en el sistema de potencia del mismo. En el presente capítulo se describen los objetivos de la misión expuesta y los requerimientos del satélite objeto de este proyecto.

Design, development and testing of Calspan/Chrysler research safety vehicle - phase II. Volume I. Final technical report.

National Highway Traffic Safety Administration, Washington, D.C.

Space vehicle displays design criteria.

"Prepared under the direction of an advisory committee chaired by Dr. Jerome I. Elkind...Preparation of the monograph was directed by Dr. Thomas J. Triggs at Bolt Beranek and Newman, Inc."

Design of underground installations in rock; space layouts and excavation methods.

Mode of access: Internet.

Dynamic Simulation Methods for Evaluating Motor Vehicle and Roadway Design and Resolving Policy Issues, 1990

This study had three objectives: (1) to develop a comprehensive truck simulation that executes rapidly, has a modular program construction to allow variation of vehicle characteristics, and is able to realistically predict vehicle motion and the tire-road surface interaction forces; (2) to develop a model of doweled portland cement concrete pavement that can be used to determine slab deflection and stress at predetermined nodes, and that allows for the variation of traditional thickness design factors; and (3) to implement these two models on a work station with suitable menu driven modules so that both existing and proposed pavements can be evaluated with respect to design life, given specific characteristics of the heavy vehicles that will be using the facility. This report summarizes the work that has been performed during the first year of the study. Briefly, the following has been accomplished: A two dimensional model of a typical 3-S2 tractor-trailer combination was created. A finite element structural analysis program, ANSYS, was used to model the pavement. Computer runs have been performed varying the parameters defining both vehicle and road elements. The resulting time specific displacements for each node are plotted, and the displacement basin is generated for defined vehicles. Relative damage to the pavement can then be estimated. A damage function resulting from load replications must be assumed that will be reflected by further pavement deterioration. Comparison with actual damage on Interstate 80 will eventually allow verification of these procedures.

The design and testing of a daylighting device : optimising the energy and optical performance of Australian commercial buildings

The effective daylighting of multistorey commercial building interiors poses an interesting problem for designers in Australia’s tropical and subtropical context. Given that a building exterior receives adequate sun and skylight as dictated by location-specific factors such as weather, siting and external obstructions; then the availability of daylight throughout its interior is dependant on certain building characteristics: the distance from a window façade (room depth), ceiling or window head height, window size and the visible transmittance of daylighting apertures. The daylighting of general stock, multistorey commercial buildings is made difficult by their design limitations with respect to some of these characteristics. The admission of daylight to these interiors is usually exclusively by vertical windows. Using conventional glazing, such windows can only admit sun and skylight to a depth of approximately 2 times the window height. This penetration depth is typically much less than the depth of the office interiors, so that core areas of these buildings receive little or no daylight. This issue is particularly relevant where deep, open plan office layouts prevail. The resulting interior daylight pattern is a relatively narrow perimeter zone bathed in (sometimes too intense) light, contrasted with a poorly daylit core zone. The broad luminance range this may present to a building occupant’s visual field can be a source of discomfort glare. Furthermore, the need in most tropical and subtropical regions to restrict solar heat gains to building interiors for much of the year has resulted in the widespread use of heavily tinted or reflective glazing on commercial building façades. This strategy reduces the amount of solar radiation admitted to the interior, thereby decreasing daylight levels proportionately throughout. However this technique does little to improve the way light is distributed throughout the office space. Where clear skies dominate weather conditions, at different times of day or year direct sunlight may pass unobstructed through vertical windows causing disability or discomfort glare for building occupants and as such, its admission to an interior must be appropriately controlled. Any daylighting system to be applied to multistorey commercial buildings must consider these design obstacles, and attempt to improve the distribution of daylight throughout these deep, sidelit office spaces without causing glare conditions. The research described in this thesis delineates first the design optimisation and then the actual prototyping and manufacture process of a daylighting device to be applied to such multistorey buildings in tropical and subtropical environments.

The impact of orbital errors on the estimation of satellite clock errors and PPP

Precise satellite orbit and clocks are essential for providing high accuracy real-time PPP (Precise Point Positioning) service. However, by treating the predicted orbits as fixed, the orbital errors may be partially assimilated by the estimated satellite clock and hence impact the positioning solutions. This paper presents the impact analysis of errors in radial and tangential orbital components on the estimation of satellite clocks and PPP through theoretical study and experimental evaluation. The relationship between the compensation of the orbital errors by the satellite clocks and the satellite-station geometry is discussed in details. Based on the satellite clocks estimated with regional station networks of different sizes (∼100, ∼300, ∼500 and ∼700 km in radius), results indicated that the orbital errors compensated by the satellite clock estimates reduce as the size of the network increases. An interesting regional PPP mode based on the broadcast ephemeris and the corresponding estimated satellite clocks is proposed and evaluated through the numerical study. The impact of orbital errors in the broadcast ephemeris has shown to be negligible for PPP users in a regional network of a radius of ∼300 km, with positioning RMS of about 1.4, 1.4 and 3.7 cm for east, north and up component in the post-mission kinematic mode, comparable with 1.3, 1.3 and 3.6 cm using the precise orbits and the corresponding estimated clocks. Compared with the DGPS and RTK positioning, only the estimated satellite clocks are needed to be disseminated to PPP users for this approach. It can significantly alleviate the communication burdens and therefore can be beneficial to the real time applications.

Res Communis? A critical legal geography of outer space, Antarctica, and the deep seabed

This chapter provides a critical legal geography of outer Space, charting the topography of the debates and struggles around its definition, management, and possession. As the emerging field of critical legal geography demonstrates, law is not a neutral organiser of space, but is instead a powerful cultural technology of spatial production. Drawing on legal documents such as the Outer Space Treaty and the Moon Treaty, as well as on the analogous and precedent-setting legal geographies of Antarctica and the deep seabed, the chapter addresses key questions about the legal geography of outer Space, questions which are of growing importance as Space’s available satellite spaces in the geostationary orbit diminish, Space weapons and mining become increasingly viable, Space colonisation and tourism emerge, and questions about Space’s legal status grow in intensity. Who owns outer Space? Who, and whose rules, govern what may or may not (literally) take place there? Is the geostationary orbit the sovereign property of the equatorial states it supertends, as these states argued in the 1970s? Or is it a part of the res communis, or common property of humanity, which currently legally characterises outer Space? Does Space belong to no one, or to everyone? As challenges to the existing legal spatiality of outer Space emerge from spacefaring states, companies, and non-spacefaring states, it is particularly critical that the current spatiality of Space is understood and considered.

Half-bridge SIC inverter for hybrid electric vehicles: Design, development and testing at higher operating temperature

In recent years, Silicon Carbide (SiC) semiconductor devices have shown promise for high density power electronic applications, due to their electrical and thermal properties. In this paper, the performance of SiC JFETs for hybrid electric vehicle (HEV) applications is investigated at heatsink temperatures of 100 °C. The thermal runaway characteristics, maximum current density and packaging temperature limitations of the devices are considered and the efficiency implications discussed. To quantify the power density capabilities of power transistors, a novel 'expression of rating' (EoR) is proposed. A prototype single phase, half-bridge voltage source inverter using SiC JFETs is also tested and its performance at 25 °C and 100 °C investigated.

Space, Time and Learning in the Hippocampus: How Fine Spatial and Temporal Scales Are Expanded into Population Codes for Behavioral Control

The hippocampus participates in multiple functions, including spatial navigation, adaptive timing, and declarative (notably, episodic) memory. How does it carry out these particular functions? The present article proposes that hippocampal spatial and temporal processing are carried out by parallel circuits within entorhinal cortex, dentate gyrus, and CA3 that are variations of the same circuit design. In particular, interactions between these brain regions transform fine spatial and temporal scales into population codes that are capable of representing the much larger spatial and temporal scales that are needed to control adaptive behaviors. Previous models of adaptively timed learning propose how a spectrum of cells tuned to brief but different delays are combined and modulated by learning to create a population code for controlling goal-oriented behaviors that span hundreds of milliseconds or even seconds. Here it is proposed how projections from entorhinal grid cells can undergo a similar learning process to create hippocampal place cells that can cover a space of many meters that are needed to control navigational behaviors. The suggested homology between spatial and temporal processing may clarify how spatial and temporal information may be integrated into an episodic memory.