618 research outputs found

    Kinematic GNSS Shadow Matching Using Particle Filters

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    Student Paper Award Winner. The poor performance of GNSS user equipment in urban canyons is a well-known problem and is particularly inaccurate in the cross-street direction. However, the accuracy in this direction greatly affects many applications, including vehicle lane identification and high-accuracy pedestrian navigation. Shadow matching was proposed to help solve this problem by using information derived from 3D models of buildings. Though users of GNSS positioning typically move, previous research has focused on static shadow-matching positioning. In this paper, for the first time, kinematic shadow-matching positioning is tackled. Kalman filter based shadow matching is proposed and also, in order to overcome some of its predicted limitations, a particle filter is proposed to better solve the problem

    Robust GNSS Carrier Phase-based Position and Attitude Estimation Theory and Applications

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    Mención Internacional en el título de doctorNavigation information is an essential element for the functioning of robotic platforms and intelligent transportation systems. Among the existing technologies, Global Navigation Satellite Systems (GNSS) have established as the cornerstone for outdoor navigation, allowing for all-weather, all-time positioning and timing at a worldwide scale. GNSS is the generic term for referring to a constellation of satellites which transmit radio signals used primarily for ranging information. Therefore, the successful operation and deployment of prospective autonomous systems is subject to our capabilities to support GNSS in the provision of robust and precise navigational estimates. GNSS signals enable two types of ranging observations: –code pseudorange, which is a measure of the time difference between the signal’s emission and reception at the satellite and receiver, respectively, scaled by the speed of light; –carrier phase pseudorange, which measures the beat of the carrier signal and the number of accumulated full carrier cycles. While code pseudoranges provides an unambiguous measure of the distance between satellites and receiver, with a dm-level precision when disregarding atmospheric delays and clock offsets, carrier phase measurements present a much higher precision, at the cost of being ambiguous by an unknown number of integer cycles, commonly denoted as ambiguities. Thus, the maximum potential of GNSS, in terms of navigational precision, can be reach by the use of carrier phase observations which, in turn, lead to complicated estimation problems. This thesis deals with the estimation theory behind the provision of carrier phase-based precise navigation for vehicles traversing scenarios with harsh signal propagation conditions. Contributions to such a broad topic are made in three directions. First, the ultimate positioning performance is addressed, by proposing lower bounds on the signal processing realized at the receiver level and for the mixed real- and integer-valued problem related to carrier phase-based positioning. Second, multi-antenna configurations are considered for the computation of a vehicle’s orientation, introducing a new model for the joint position and attitude estimation problems and proposing new deterministic and recursive estimators based on Lie Theory. Finally, the framework of robust statistics is explored to propose new solutions to code- and carrier phase-based navigation, able to deal with outlying impulsive noises.La información de navegación es un elemental fundamental para el funcionamiento de sistemas de transporte inteligentes y plataformas robóticas. Entre las tecnologías existentes, los Sistemas Globales de Navegación por Satélite (GNSS) se han consolidado como la piedra angular para la navegación en exteriores, dando acceso a localización y sincronización temporal a una escala global, irrespectivamente de la condición meteorológica. GNSS es el término genérico que define una constelación de satélites que transmiten señales de radio, usadas primordinalmente para proporcionar información de distancia. Por lo tanto, la operatibilidad y funcionamiento de los futuros sistemas autónomos pende de nuestra capacidad para explotar GNSS y estimar soluciones de navegación robustas y precisas. Las señales GNSS permiten dos tipos de observaciones de alcance: –pseudorangos de código, que miden el tiempo transcurrido entre la emisión de las señales en los satélites y su acquisición en la tierra por parte de un receptor; –pseudorangos de fase de portadora, que miden la fase de la onda sinusoide que portan dichas señales y el número acumulado de ciclos completos. Los pseudorangos de código proporcionan una medida inequívoca de la distancia entre los satélites y el receptor, con una precisión de decímetros cuando no se tienen en cuenta los retrasos atmosféricos y los desfases del reloj. En contraposición, las observaciones de la portadora son super precisas, alcanzando el milímetro de exactidud, a expensas de ser ambiguas por un número entero y desconocido de ciclos. Por ende, el alcanzar la máxima precisión con GNSS queda condicionado al uso de las medidas de fase de la portadora, lo cual implica unos problemas de estimación de elevada complejidad. Esta tesis versa sobre la teoría de estimación relacionada con la provisión de navegación precisa basada en la fase de la portadora, especialmente para vehículos que transitan escenarios donde las señales no se propagan fácilmente, como es el caso de las ciudades. Para ello, primero se aborda la máxima efectividad del problema de localización, proponiendo cotas inferiores para el procesamiento de la señal en el receptor y para el problema de estimación mixto (es decir, cuando las incógnitas pertenecen al espacio de números reales y enteros). En segundo lugar, se consideran las configuraciones multiantena para el cálculo de la orientación de un vehículo, presentando un nuevo modelo para la estimación conjunta de posición y rumbo, y proponiendo estimadores deterministas y recursivos basados en la teoría de Lie. Por último, se explora el marco de la estadística robusta para proporcionar nuevas soluciones de navegación precisa, capaces de hacer frente a los ruidos atípicos.Programa de Doctorado en Ciencia y Tecnología Informática por la Universidad Carlos III de MadridPresidente: José Manuel Molina López.- Secretario: Giorgi Gabriele.- Vocal: Fabio Dovi

    Advanced Integration of GNSS and External Sensors for Autonomous Mobility Applications

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    L'abstract è presente nell'allegato / the abstract is in the attachmen

    New on-board multipurpose architecture integrating modern estimation techniques for generalized GNSS based autonomous orbit navigation

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    This dissertation investigates a novel Multipurpose Earth Orbit Navigation System (MEONS) architecture aiming at providing a generalized GNSS based spacecraft orbit estimation kernel matching the modern navigation instance of enhanced flexibility with respect to multiple Space Service Volume (SSV) applications (Precise Orbit Determination for Earth Observation satellite, Low Thrust Low to High Autonomous Orbit Rising, formation flying relative navigation, Small Satellite Autonomous Orbit Acquisition). The possibility to address theoretical and operational solutions within a unified framework is a foundamental step for the implementation of a reusable and configurable high performance navigation capability on next generation platforms

    Contributions to high accuracy snapshot GNSS positioning

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    (English) Snapshot positioning is the technique to determine the position of a Global Navigation Satellite System (GNSS) receiver using only a very brief interval of the received satellite signal. In recent years, this technique has received a great amount of attention thanks to its unique advantages in power efficiency, Time To First Fix (TTFF) and economic costs for deployment. However, the state of the art algorithms regarding snapshot positioning were based on code measurements only, which unavoidably limited the positioning accuracy to meter level. The present PhD research aims at achieving high-accuracy (centimetre level) snapshot positioning by properly utilizing carrier phase measurements. Two technical challenges should be tackled before such level of accuracy can be achieved, namely, satellite transmission time inaccuracy and the so-called Data Bit Ambiguity (DBA) issue. The first challenge is essentially originated from the lack of absolute timing accuracy in the receiver, as only the coarse time information is available from an external assistance module and its error can be up to a few seconds. Applying a conventional Coarse Time Filter (CTF) can increase this timing accuracy to millisecond level. However, this is still not enough for carrier-phase based positioning since the satellite position errors introduced by such timing errors range up to one meter, which certainly impedes the carrier phase Integer Ambiguity Resolution (IAR). A method is proposed to set a global time tag and correspondingly construct the pseudoranges with full period corrections. The second challenge is caused by the fact that snapshot measurements are generated based on the results of the correlation between the received signal and the local replicas. Multiple replicas are typically produced in snapshot positioning following the Multi Hypothesis (MH) acquisition architecture. It may happen that more than one local replica (i.e. hypothesis) result in the maximum correlation energy. Hence, we need to identify the actual secondary codes or data bit symbols encoded in the received signal, i.e. to resolve the DBA. Particularly, when the local replica is generated with exactly opposite symbols to the actual ones, the resulting carrier phase measurement contains a Half Cycle Error (HCE) and impedes also the IAR step. A method has been proposed in this PhD to resolve the DBA issue for pilot signals with encoded secondary codes. This method attempts to form a consensus among all satellites regarding their secondary codes under the assistance of their flight time differences. A different approach has been developed for data signals. It amends the carrier phase HCEs one after another by an iterative satellite inclusion procedure. This approach uses the Real Time Kinematics (RTK) LAMBDA Ratio Factor (LRF) as an indicator to evaluate the potential existence of the HCEs. The present PhD focuses on implementing the so-called Snapshot RTK (SRTK) technique. As in the classic RTK technique, SRTK cancels most of the measurement errors through the Double-Differenced (DD) process. The workflow details of SRTK are explained incorporating the aforementioned new algorithms. Several experiments were performed based on real world signal recordings and the results confirm the feasibility of obtaining SRTK fix solutions. The performance of SRTK is numerically demonstrated under different parameters of signal bandwidth, integration time and baseline distance. The SRTK fix rates can reach more than 90% in most of the scenarios, with centimetre-level positioning errors observed in the fixed solutions. It can be concluded that upon the implementation of the global time tag method, high accuracy snapshot positioning becomes feasible with the SRTK technique and its performance varies depending on the SRTK configuration. The algorithms developed for the DBA issue and carrier phase HCEs also prove to effectively improve the performance of SRTK.(Español) El posicionamiento instantáneo es la técnica para determinar la posición de un receptor del Sistema Global de Navegación por Satélite (GNSS) utilizando solo un intervalo muy breve de la señal recibida. En los últimos años, esta técnica ha recibido una gran atención gracias a sus ventajas únicas en eficiencia energética, tiempo hasta la primera posición (TTFF) y reducidos costes económicos para la implementación. Sin embargo, el estado del arte de los algoritmos relacionados con el posicionamiento de señales instantáneas utilizaron solo medidas de código, lo que inevitablemente limitó la precisión del posicionamiento a al nivel del metro. La presente Tesis Doctoral tiene como objetivo lograr un posicionamiento instantáneo de alta precisión (nivel centimétrico) mediante las medidas de fase de la portadora. Para ello, deben abordarse dos desafíos técnicos antes de que se pueda alcanzar ese nivel de precisión: resolver la inexactitud del tiempo de transmisión del satélite y el llamado problema de ambigüedad de bit de datos (DBA). El primer desafío se origina esencialmente por la falta de precisión de tiempo absoluto en el receptor, ya que solo está disponible la información del tiempo aproximado desde un módulo de asistencia externo y su error puede ser de hasta unos segundos. Así, se propone un método para establecer una etiqueta de tiempo global y construir correspondientemente los pseudorangos con correcciones de período completo. El segundo desafío se debe al hecho de que las mediciones instantáneas se generan en función de los resultados de la correlación entre la señal recibida y las réplicas locales. Las múltiples réplicas generalmente se producen en el posicionamiento de instantáneas siguiendo la arquitectura de de adquisición de el Múltiples Hipótesis (MH). Por lo tanto, se necesita identificar los códigos secundarios reales o los símbolos de bits de datos codificados en la señal recibida, para resolver el DBA. En particular, cuando la réplica local se genera con símbolos exactamente opuestos a los reales, el resultado de la medición de la fase de la portadora contiene un error de medio ciclo (HCE) e impide también la resolución de ambigüedad entera (IAR). Se ha propuesto un método en esta Tesis Doctoral para resolver el problema de DBA para señales piloto con códigos secundarios. Este método intenta formar un consenso entre todos los satélites con respecto a sus códigos secundarios bajo la asistencia de sus diferencias de tiempo de vuelo. Un enfoque diferente ha sido desarrollado para señales que contienen datos del mensaje de navegación. Se modifica los HCE de la fase de portadora uno tras otro mediante un procedimiento iterativo de inclusión de satélites. Este método utiliza el factor de relación LAMBDA (LRF) utilizado en posicionamiento relativo en tiempo real (RTK) como indicador para evaluar la existencia potencial de los HCE. La presente tesis doctoral se centra en implementar la técnica denominada Snapshot RTK (SRTK). Se realizaron varios experimentos basados ?en ?señales del mundo real. Las grabaciones y los resultados confirman la viabilidad de obtener soluciones SRTK con IAR. El rendimiento de SRTK es numéricamente demostrado bajo diferentes parámetros tales como el ancho de banda de señal, tiempo de integración y distancia de línea de base. Las tasas de fijación IAR de SRTK pueden alcanzar más del 90% en la mayoría de los escenarios, observándose errores de posicionamiento centimétricos en las soluciones fijas. Se puede concluir que tras la implementación del método de etiqueta de tiempo global, que el posicionamiento de instantáneas de alta precisión se vuelve factible con la técnica SRTK y las prestaciones varían dependiendo de la configuración. Los algoritmos desarrollados para la resolución de DBA y los HCE de fase portadora también demuestran que mejoran efectivamente el rendimientoCiència i tecnologies aeroespacial

    Bidirectional UWB Localization: A Review on an Elastic Positioning Scheme for GNSS-deprived Zones

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    A bidirectional Ultra-Wideband (UWB) localization scheme is one of the three widely deployed design integration processes ordinarily destined for time-based UWB positioning systems. The key property of the bidirectional UWB localization is its ability to serve both the navigation and tracking assignments on-demand within a single localization scheme. Conventionally, the perspective of navigation and tracking in wireless localization systems is viewed distinctly as an individual system because different methodologies were required for the implementation process. The ability to flexibly or elastically combine two unique positioning perspectives (i.e., navigation and tracking) within a single scheme is a paradigm shift in the way location-based services are observed. Thus, this article addresses and pinpoints the potential of a bidirectional UWB localization scheme. Regarding this, the complete system model of the bidirectional UWB localization scheme was comprehensively described based on modular processes in this article. The demonstrative evaluation results based on two system integration processes as well as a SWOT (strengths, weaknesses, opportunities, and threats) analysis of the scheme were also discussed. Moreover, we argued that the presented bidirectional scheme can also be used as a prospective topology for the realization of precise location estimation processes in 5G/6G wireless mobile networks, as well as Wi-Fi fine-time measurement-based positioning systems in this article.Comment: 30 pages, 12 figure

    A Systematic Survey of Control Techniques and Applications: From Autonomous Vehicles to Connected and Automated Vehicles

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    Vehicle control is one of the most critical challenges in autonomous vehicles (AVs) and connected and automated vehicles (CAVs), and it is paramount in vehicle safety, passenger comfort, transportation efficiency, and energy saving. This survey attempts to provide a comprehensive and thorough overview of the current state of vehicle control technology, focusing on the evolution from vehicle state estimation and trajectory tracking control in AVs at the microscopic level to collaborative control in CAVs at the macroscopic level. First, this review starts with vehicle key state estimation, specifically vehicle sideslip angle, which is the most pivotal state for vehicle trajectory control, to discuss representative approaches. Then, we present symbolic vehicle trajectory tracking control approaches for AVs. On top of that, we further review the collaborative control frameworks for CAVs and corresponding applications. Finally, this survey concludes with a discussion of future research directions and the challenges. This survey aims to provide a contextualized and in-depth look at state of the art in vehicle control for AVs and CAVs, identifying critical areas of focus and pointing out the potential areas for further exploration

    Multisensor navigation systems: a remedy for GNSS vulnerabilities?

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    Space-based positioning, navigation, and timing (PNT) technologies, such as the global navigation satellite systems (GNSS) provide position, velocity, and timing information to an unlimited number of users around the world. In recent years, PNT information has become increasingly critical to the security, safety, and prosperity of the World's population, and is now widely recognized as an essential element of the global information infrastructure. Due to its vulnerabilities and line-of-sight requirements, GNSS alone is unable to provide PNT with the required levels of integrity, accuracy, continuity, and reliability. A multisensor navigation approach offers an effective augmentation in GNSS-challenged environments that holds a promise of delivering robust and resilient PNT. Traditionally, sensors such as inertial measurement units (IMUs), barometers, magnetometers, odometers, and digital compasses, have been used. However, recent trends have largely focused on image-based, terrain-based and collaborative navigation to recover the user location. This paper offers a review of the technological advances that have taken place in PNT over the last two decades, and discusses various hybridizations of multisensory systems, building upon the fundamental GNSS/IMU integration. The most important conclusion of this study is that in order to meet the challenging goals of delivering continuous, accurate and robust PNT to the ever-growing numbers of users, the hybridization of a suite of different PNT solutions is required

    Fly by data link: feasibility of a relative navigation solution for aviation relying on a future L-band data link

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    Trabalho final de Mestrado para obtenção do grau de Mestre em Engenharia de Electrónica e TelecomunicaçõesO presente trabalho estuda uma solução alternativa de navegação aeronáutica que contribua para a racionalização da infrastrutura terrestre de ajudas-rádio de navegação na Europa. O conceito designado de “Performance Based Navigation (PBN)” emerge actualmente ao nível da Organização Internacional de Aviação Civil, visando o aperfeiçoamento do sistema de gestão do tráfego aéreo ao nível da eficiência, segurançae capacidade. O conceito PBN promove a modernização da infrastrutura aeronáutica com base na utilização preferencial de sistemas de navegação por satélite, designadamente mediante o recurso a sinais disponibilizados pelas constelações “Global Navigation Satellite System (GNSS)”. Face às vulnerabilidades dos sistemas GNSS a interferências RF, “jamming” deliberado ou fenómenos solares, foi decidido manter uma infrastrutura de recurso/”backup”, para mitigar falhas GNSS, baseada numa redede rádio-ajudas terrestres “Distance Measuring Equipment (DME)”. Visto que estes DMEs não facultam uma boa cobertura, especialmente a baixa altitude, e tratando-se de equipamentos próximos da obsolescência tecnológica e pouco eficientes em termos de espectro rádioeléctrico, a sua racionalização requer uma tecnologia alternativa. O presente trabalho explora o recurso a novas tecnologias aeronáuticas de comunicações dados ar-solo, designadamente o futuro “data link” OFDM/TDMA de banda L (LDACS), verificando a sua adequação para suportarem as funções de navegação descritas substituindo os DMEs. Pretende-se confirmar a viabilidade com base no conceito de Navegação Relativa (RELNAV) usado em contexto militar recorrendo a filtros Kalman. As características da tecnologia LDACS são descritas e são apresentados resultados de testes do seu desempenho em termos de medição de distâncias (“ranging”). Com base nas capacidades RELNAV militares são propostos melhoramentos baseadosem filtros Kalman, simulando para demonstrar que o LDACS pode ser usado para funçãode navegação. Demonstrada a viabilidade, fica em aberto a oportunidade para sinergias que poderão viabilizar a racionalização da infrastrutura terrestre de navegação e aviónicos.Abstract: The main purpose of this work is to study an alternative solution for aeronautical aircraft navigation contributing to the rationalization of the existing European ground navigation infrastructure. The emerging Performance Based Navigation (PBN) concept, described in the document 9613 of the International Civil Aviation Organization (ICAO), calls for increased reliance on Global Navigation Satellite Systems (GNSS) (and its augmentation/differential correction systems1) but retaining ground beacons such as the Distance Measuring Equipments (DME) to cope with Global Positioning System (GPS) and GALILEO outages (e.g. jamming/solar storms). The present work will focus on demonstrating the feasibility of an alternative technology to allow the decommissioning of such DME beacons based on the re-use offuture L-Band Air Ground Data Link (LDACS) communication solutions being subject of research studies. Such data links may support the required levels of positioning, navigation and timing required to complement GNSS when the aircraft fly in an area navigation environment. This work will describe the LDACS data link technologies2 and will explain how such communications enablers would be able to support a “relative navigation” function similar to the one available in military data link technologies usinga geodetic grid. The feasibility of the proposed solution will be demonstrated on the basis of lessons learnt from military relative navigation and simulations which will evidence the technical performance/error parameters of the system in terms of ranging, bearing and horizontal positioning and other relevant QoS aspects. In addition, the multipath and co-site interference effects will be also discussed. Should the proposed solution be demonstrated as viable, it may open the door, not only for synergies leading to a more seamless aircraft equipage but also to the rationalization of aeronautical systems in the spectrum band 960-1215 MHz, which is highly congested and subject of stringent non-interference basis operational limitations
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