No description available.

Large enterprises are often interested in tracking objects and people within buildings to improve resource allocation and occupant experience. Infrastructure-based indoor positioning systems (IIPS) can provide this service at low-cost by leveraging already deployed Wi-Fi infrastructure. Typically, IIPS perform localization and tracking of devices by measuring only Wi-Fi signals at wireless access points and do not rely on inertial sensor data at mobile devices (e.g., smartphones), which would require explicit user consent and sensing capabilities of the devices. Despite these advantages, building an economically viable cost-effective IIPS that can accurately and simultaneously track many devices over very large buildings is difficult due to three main challenges. First, Wi-Fi signal measurements are extremely noisy due to unpredictable multipath propagation and signal attenuation. Second, as the IIPS obtain measurements in a best effort manner without requiring any applications installed on a tracked device, the measurements are temporally sparse and non-periodic, which makes it difficult to exploit historical measurements. Third, the cost-effective IIPS have limited computational resources, in turn limiting scalability in terms of the number of simultaneously tracked devices. Prior approaches have narrowly focused on either improving the accuracy or reducing the complexity of localization algorithms. To compute the location at the current time step, they typically use only the latest explicit Wi-Fi measurements (e.g., signal strengths). The novelty of our approach lies in considering contexts of a device that can provide useful indications of the device's location. One such example of context is device motion. It indicates whether or not the device's location has changed. For a stationary device, the IIPS can either skip expensive device localization or aggregate noisy, temporally sparse location estimates to improve localization accuracy. Another example of context applicable to a moving device is a floor map that consists of pre-defined path segments that a user can take. The map can be leveraged to constrain noisy, temporally sparse location estimates on the paths. The thesis of this dissertation is that embedding context-aware capabilities in the IIPS enhances its performance in tracking many devices simultaneously and accurately. Specifically, we develop motion detection and map matching to show the benefits of leveraging two critical contexts: device motion and floor map. Providing motion detection and map matching is non-trivial in the IIPS where we must rely only on data from the Wi-Fi infrastructure. This thesis makes two contributions. First, we develop feature-based and deep learning-based motion detection models that exploit temporal patterns in Wi-Fi measurements across different access points to classify device motion in real time. Our extensive evaluations on datasets from real Wi-Fi deployments show that our motion detection models can detect device motion accurately. This, in turn, allows the IIPS to skip repeated location computation for stationary devices or improve the accuracy of localizing these devices. Second, we develop graph-based and image-based map matching models to exploit floor maps. The novelty of the graph-based approach lies in applying geometric and topological constraints to select which path segment to align the current location estimate. Our graph-based map matching can align a location estimate of a user device on the path taken by the user and close to the user's current location. The novelty of the image-based approach lies in representing for the first time, input data including location estimates and the floor map as 2D images. This novel representation enables the design, development, and application of encoder-decoder neural networks to exploit spatial relationships in input images to potentially improve location accuracy. In our evaluation, we show that the image-based approach can improve location accuracy with large simulated datasets, compared to the graph-based approach. Together, these contributions enable improvement of the IIPS in its ability to accurately and simultaneously track many devices over large buildings.

Global navigation satellite systems (GNSS), such as the Global Positioning System (GPS) have been increasingly used in navigation and tracking of vehicles. Using GPS, certain positioning errors and limitations, such as multipath effects and the geometric position of the satellites (DOP) or signal obstructions by high buildings, trees and terrain, have to be considered. Generally travel on road or footpath, map-matching algorithms can be used to correlate the computed system location with a digital map network. Map Matched GPS (MMGPS) is a test-bed simulator for researching algorithms and techniques to reduce the error in position provided by a low cost stand-alone GPS receiver. In order to correctly map-match the GPS positions, a decision about the correct road can be difficult, especially at road junctions, slip roads or almost parallel roads. Investigations into the use of artificial neural networks (ANNs) for reliability and accuracy improvement of map-matched GPS positioning was initiated in previous research [Winter, 2002]. However, there are generally strong interference effects that lead to slow learning and poor generalization when a single ANN is trained to perform different subtasks on different occasions [Jacobs et al., 1991], e.g. correct transport network (TN) segment selection considering different TN geometry. Interference can be reduced by training a system composed of several different "expert" ANNs using a TN geometry indicator to decide which of the experts should be used for each training case. An aim of this research was the design, development and implementation of such a modular neural network (MNN). This work uses a new measure for indicating TN geometry, directly derived from GPS positions in MMGPS. An improvement of more than 50% to traditional map-matching techniques was achieved using the proposed MNN approach, when the correct road could not be uniquely identified by map-matching.

No description available.

A technique is proposed to improve the accuracy of indoor positioning systems based on WIFI radio-frequency signals by using dynamic access points and fingerprints (DAFs). Moreover, an indoor position system that relies solely in DAFs is proposed. The walking pattern of indoor users is classified as dynamic or static for indoor positioning purposes. I demonstrate that the performance of a conventional indoor positioning system that uses static fingerprints can be enhanced by considering dynamic fingerprints and access points. The accuracy of the system is evaluated using four positioning algorithms and two random access point selection strategies. The system facilitates the location of people where there is no wireless local area network (WLAN) infrastructure deployed or where the WLAN infrastructure has been drastically affected, for example by natural disasters. The system can be used for search and rescue operations and for expanding the coverage of an indoor positioning system.

I detta arbete utforskas cybersäkerhetsaspekter av positionssystem inom sjöfartssektorn. Syftet är att identifiera åtgärder för att hantera och förebygga säkerhetshot samt utforska implementering av övningar för att bygga kompetens i detektering och hantering av dessa hot. Genom en systematisk litteraturstudie granskades befintlig forskning. Resultaten visar på vikten av anpassade utbildningsprogram, en förändrad inställning till cybersäkerhet, behovet av starka säkerhetskulturer samt effektiva förebyggande strategier och beredskapsplaner. Studien utreder även den kollektiva ansträngningen mellan rederier, tillverkare och andra maritima aktörer för att förbättra systemens motståndskraft mot cyberhot.  Slutligen uppmanar avhandlingen till vidare forskning för att utveckla mer detaljerade implementeringsstrategier. / In this work, cybersecurity aspects are explored within positioning systems in the maritime sector. The purpose is to identify means for handling and preventing security threats and explore the implementations of drills to build competency in detecting and handling these threats through a systematic literature review that looks at existing research. The results show the need for education courses, a changed outlook on cybersecurity, a strong security culture, effective prevention strategies, and contingencies. The study also investigates the collective effort between shipping companies, manufacturers, and maritime actors to improve the systems' resilience to cyber threats. Finally, the work encourages further research to develop more detailed implementation strategies.

As automation in the construction site of the future becomes a reality, position location systems are necessary to provide real-time data to an operator. This thesis addresses problems associated with development of a real time automated position location system using a method similar to hyperbolic navigation methods. The Automated Position and Control (APAC) project is a joint effort between the Civil and Electrical Engineering departments at Virginia Polytechnic and State University and Bechtel Eastern Power Corporation. / Master of Science

Este trabalho aborda o estudo de um sistema de referência inercial de posição e atitude e um sistema de controle para um helicóptero autônomo utilizando, como base para formulação e testes, o modelo linearizado da aeronave Yamaha R-MAX. Um sistema de referência inercial (INS) e um sistema de referência de atitude e orientação (AHRS) são utilizados para estimar a posição e atitude da aeronave, e estimadores robustos baseados no filtro de Kalman são empregados para minimizar os efeitos de incertezas paramétricas. É utilizada uma estratégia de controle em cascata com três malhas consistindo de uma malha interna para garantir a estabilidade do helicóptero (são utilizadas as técnicas LQR e H \'INFINITO\', separadamente), uma malha intermediária baseada em linearização por realimentação (FLC) para desacoplar os pares entrada/saída e uma malha externa baseada em um controlador proporcional-derivativo (PD) para permitir o rastreamento da trajetória. Resultados de simulação são apresentados para avaliar o desempenho de cada abordagem. / This work concerns the study of an inertial reference system and a control system for an autonomous helicopter using, as basis for the formulation and testing, the linearized mo del of the aircraft Yamaha R-MAX. An inertial navigation system (INS) and an attitude and orientation reference system (AHRS) are used to estimate the position and attitude of the aircraft and robust estimators based on Kalman filter are employed to minimize the effects of parametric uncertainties. A cascaded control architecture with three control methodologies is used, consisting of an inner-loop to ensure stability of the helicopter (the LQR and H \'INFINITE\' techniques are used, separately), a mid-loop based on linearization feedback (FLC) to decouple the dynamics ofthe lateral, longitudinal, vertical and heading axes and an outer-loop based on a proportional-derivative (PD) controller to enable trajectory tracking. Simulation results are presented to evaluate the performance of each approach.

Servoposicionadores pneumáticos são sistemas com tecnologia limpa, pois utiliza o ar comprimido como fluido de trabalho, leves, baratos e apresentam boa relação entre a capacidade de carga e a potência fornecida. Contudo, eles apresentam não-linearidades inerentes ao sistema pneumático, como efeitos devidos à compressibilidade do ar, ao atrito e vazamentos. Por estes motivos os controladores lineares mostram-se ineficientes para estes sistemas e é necessário utilizar estratégias de controle mais elaboradas, como, por exemplo, controle por redes neurais, controle com estrutura variável, controle adaptativo ou baseado em linearização por realimentação. Neste trabalho, foi estudada a aplicação do método de linearização por realimentação aliada ao método de controle por realimentação de estados e projeto por alocação de pólos ao controle de um servoposicionador pneumático. A estratégia de linearização por realimentação utiliza as estimativas das não-linearidades do modelo pneumático para linearizar o comportamento do servoposicionador pneumático e permitir o uso tanto de controladores lineares como não-lineares. A análise e prova das características de estabilidade completa do sistema em malha fechada com parâmetros conhecidos foi realizada, obtendo-se a garantia da convergência dos erros de seguimento para zero. Também foi realizada a análise de robustez, com a análise do comportamento do sistema frente às incertezas dos parâmetros estimados. Simulações e ensaios experimentais foram realizados para avaliar o comportamento e a eficiência do controlador proposto. Os resultados do controlador mostram-se promissores, com uma redução de aproximadamente 50% no erro de posição no seguimento de trajetória e na parada precisa com relação às técnicas lineares usualmente aplicadas a estes sistemas. Entretanto, no posicionamento percebe-se a influência do atrito, indicando que a sua compensação deve ser considerada em futuros desenvolvimentos. / Pneumatic positioning systems are clean, lightweight, cheap and present a good rate between the payload and supply power. However, this system shows a highly non-linear behavior, caused mainly by the compression of the air and the friction force. Linear strategies do not present an efficiently control in this kind of system and an improved design technique of control is needed, as neural network control, adaptive control, variable structure control or feedback linearization. In this work, it is developed the application of a feedback linearization control scheme integrated with the state feedback and pole placement method to a pneumatic positioning system. The feedback linearization strategy uses the non-linearities estimation of the pneumatic model to linearize the pneumatic positioning system and allow the use of linear or non-linear controls technique to control the behavior of the servopositioner. In this work, an analysis of the convergence properties of the closed-loop errors of the system when the proposed controller is employed is provided. It is shown that if the parameters are known than the system presents asymptotic convergence of the tracking errors to zero. The robustness properties analysis of the controller is also presented and the system behavior with the uncertainty parameters is analysed. Simulation and experimental tests were performed to assess the behavior and the efficiency of the feedback linearization control. The result of the proposed control shows to be promising on the reduction of position errors in trajectory tracking and in steadystate behavior. The tests show the presence of a strong influence of the friction force and that the friction comparation in techniques must be studied in futher developments.

Durante o desenvolvimento dessa dissertação foi criado um novo controlador de navios para aproamento automático de mínima energia (weathervane), de acordo com condições ambientais incidentes, mantendo o posicionamento de um ponto de controle arbitrário. O controlador proposto utiliza a metodologia ZPC (Zero Power Control), empregando o método da integral de realimentação, originalmente proposto para aplicação em sistemas de levitação magnética. Além da análise de estabilidade, também foi utilizado o simulador numérico de sistemas oceânicos TPN (Tanque de Provas Numérico), atestando o funcionamento do controlador sob a influência de diversas condições. Foram simulados casos com agentes ambientais (onda, vento e correnteza) desalinhados, ondas irregulares, posicionamento da popa no navio, dentre outros. O desempenho do controlador desenvolvido foi comparado, através de análise estática, com o desempenho de outras lógicas de controle weathervane, apresentando desempenho igual ou superior. Finalmente, um navio em escala reduzida foi submetido a testes em um tanque físico. Os resultados experimentais foram bastante satisfatórios, validando os resultados numéricos obtidos. Com isto, conclui-se que o controlador projetado atende os propósitos para o qual foi concebido com sucesso, sendo viável e possuindo diversas aplicações práticas imediatas. / A new controller was developed during this thesis, intended to automatically calculate the optimum heading (weathervane) for any given environmental condition. The vessel positioning is kept while this controller adapts the heading. The proposed controller utilizes the Zero Power Control (ZPC) methodology, generally applied to magnetic levitation systems. The chosen ZPC strategy is the integral feedback. A stability analysis was carried, in addition to simulations at the oceanic systems numerical simulator TPN (Numerical Offshore Tank), proving the controller availability under the influence of several environmental conditions. Cases with misaligned environmental agents (wind, waves and current), irregular waves, stern control, among others were simulated. In order to prove its performance, the final controller was compared with existing weathervane controllers through a static analysis, showing that it was equal or superior. Finally, a scale model ship was undergone to tests on a physical tank. The experimental results were pretty good, validating the obtained numerical results. In conclusion, the designed controller attends its design requirements successfully, being viable and having several immediate practical applications.