abstract: Global Positioning System (GPS) is a navigation system widely used in civilian and military application, but its accuracy is highly impacted with consequential fading, and possible loss of communication due to multipath propagation and high power interferences. This dissertation proposes alternatives to improve the performance of the GPS receivers to obtain a system that can be reliable in critical situations. The basic performance of the GPS receiver consists of receiving the signal with an antenna array, delaying the signal at each antenna element, weighting the delayed replicas, and finally, combining the weighted replicas to estimate the desired signal. Based on these, three modifications are proposed to improve the performance of the system. The first proposed modification is the use of the Least Mean Squares (LMS) algorithm with two variations to decrease the convergence time of the classic LMS while achieving good system stability. The results obtained by the proposed LMS demonstrate that the algorithm can achieve the same stability as the classic LMS using a small step size, and its convergence rate is better than the classic LMS using a large step size. The second proposed modification is to replace the uniform distribution of the time delays (or taps) by an exponential distribution that decreases the bit-error rate (BER) of the system without impacting the computational efficiency of the uniform taps. The results show that, for a BER of 0.001, the system can operate with a 1 to 2 dB lower signal-to-noise ratio (SNR) when an exponential distribution is used rather than a uniform distribution. Finally, the third modification is implemented in the design of the antenna array. In this case, the gain of each microstrip element is enhanced by embedding ferrite rings in the substrate, creating a hybrid substrate. The ferrite rings generates constructive interference between the incident and reflected fields; consequently, the gain of a single microstrip element is enhanced by up to 4 dB. When hybrid substrates are used in microstrip element arrays, a significant enhancement in angle range is achieved for a given reflection coefficient compared to using a conventional substrate. / Dissertation/Thesis / Ph.D. Electrical Engineering 2013

O presente trabalho discorre sobre os principais fatores que influenciam o projeto do sistema de posicionamento dinâmico (SPD) de um navio aliviador. Os fatores discutidos estão relacionados às questões de confiabilidade de sistemas e às características dos atuadores tipicamente utilizados em embarcações com SPD, tais como, dutos e azimutais. Em relação à confiabilidade de sistemas, os métodos de avaliação por diagramas de blocos e análise de modos de falha e efeitos (FMEA) são discutidos com a aplicação direcionada aos navios aliviadores com SPD. O uso de banco de dados de incidentes de operações com sistemas flutuantes com SPD também é comentado. As alternativas mais utilizadas de arranjo propulsivo para navios aliviadores são apresentadas e analisadas. As interações hidrodinâmicas entre casco-atuador, atuador-atuador e atuador-corrente são apresentadas e comentadas. Ensaios realizados em tanque de provas com propulsores em duto e azimutais instalados em modelos em escala reduzida são apresentados. O texto apresenta a execução de um projeto de dimensionamento propulsivo de um navio aliviador com SPD que opera em águas brasileiras. Para tanto, um procedimento de projeto é sugerido com as seguintes etapas: estudo dos pontos de operação, definição de requisitos de projeto, cálculo de estimativas iniciais, tomada de decisão para a escolha do arranjo propulsivo pelo método de análise hierárquica (AHP), análise de confiabilidade do SPD por FMEA e, por fim, avaliação de desempenho. A avaliação do desempenho do sistema propulsivo projetado é realizada por diagramas de capacidade e simulações dinâmicas. Uma breve comparação entre navios aliviadores com classificações diferentes é realizada e comentada. / This work discusses the main factors that influence the design of dynamic positioning system (DPS) of a shuttle tanker. The factors discussed are related to issues of reliability of systems and the characteristics of the thrusters typically used on DPS vessels, such as ducts and azimuth. Regarding the reliability of systems, methods of reliability evaluation by block diagrams and analysis of failure modes and effects (FMEA) are discussed in the application on DPS shuttle tankers. The utilization of incidents database of offshore vessels with DPS are discussed. The most used alternatives of propulsive arrangement for shuttle tankers are presented and analyzed. Hydrodynamic interactions between hull-thruster, thruster-thruster and thruster-current are presented and commented. Tests with duct and azimuth propellers installed in scale models are presented. This work presents the design of the propulsive subsystem of a DPS shuttle tanker which operates in Brazilian waters. Thus, a design procedure is suggested with the following steps: a study of the operation points, definition of the design requirement, initial estimates, choice the propulsive arrangement by Analytic Hierarchy Process (AHP), reliability analysis of DPS by FMEA and performance evaluation. The performance evaluation of propulsive subsystem is evaluated by wind and current capability plots and dynamical simulations. A brief comparison of shuttle tankers with different classifications is performed and discussed.

Orientador: Luiz Carlos Kretly / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T21:22:28Z (GMT). No. of bitstreams: 1 VerreJunior_Carlos_M.pdf: 3988779 bytes, checksum: e142d23f246ba59d81a08d0b96595a87 (MD5) Previous issue date: 2011 / Resumo: O uso de dispositivos GPS/GSM em sistemas de monitoramento de veículos, para transmitir informações como posição e direção do veículo para centros de controle através de comunicação sem fio sobre redes GPRS tem se aprimorado rapidamente. Estes dispositivos tem se mostrado bastante eficientes garantindo uma maior segurança ao usuário que pode bloquear e localizar o seu veículo segundos depois de ter seu veículo furtado. Além das informações de posição e direção, também se faz viável a obtenção antecipada de informações de acidentes na rodovia em que o condutor esta trafegando, além de emissões de alertas em casos de acidente acionando assim o serviço de resgate de maneira imediata, passando de maneira precisa a localização correta do veículo. Além dessas vantagens, o condutor também pode contar com o suporte direto das montadoras que transmitem e recebem informações do veículo mantendo assim o usuário atualizado sobre as necessidades de manutenção em seu veículo. Todos os sistemas de segurança do veículo, como por exemplo, o AirBag e o cinto de segurança, são projetados para evitar que após uma colisão os tripulantes do veículo sofram lesões, no entanto não são desenvolvidos para que o acidente seja evitado como é o caso da tecnologia de comunicação R2V. Em busca de solucionar o problema, e antes mesmo que o acidente ocorra o motorista seja avisado, muitas tecnologias estão atualmente à prova pelas montadoras de veículos. Este trabalho apresenta metodologias de projeto e simulações que representam de maneira qualitativa as dificuldades envolvidas em um projeto de rastreamento veicular utilizando as tecnologias de GPS/GSM, estudando o desenvolvimento e otimização de uma antena de GPS (ponto crítico) até a influência sofrida pela antena das partes metálicas do veículo quando a antena é localizada na parte interna do veículo (painel de instrumento), levando como base o teto do veículo (ponto ideal) para a solução e base de comparação da solução / Abstract: The use of GPS / GSM vehicle tracking systems to transmit information such as position and direction of the vehicle to control centers through wireless networks over GPRS has improved rapidly. These devices have been quite effective by ensuring greater security to the user who can block and locate your vehicle seconds after the vehicle has been stolen. Besides the position information and direction, it is also feasible to obtain advance information of accidents on the highway when the driver is traveling, in addition to emissions of alert in case of an accident triggering rescue services in a prompt manner, and allowing for the correct location of the vehicle. Besides these advantages, the driver can also rely on the direct support of the makers that transmit and receive information from the vehicle thus keeping the user updated about the maintenance needs on the vehicle. All current security systems of the vehicle, such as the airbag and seat belts, are designed to keep the passengers of the vehicle from suffering injuries, but are not developed to avoid an accident , as is the case of R2V communication technology. In seeking to solve this problem, by warning the driver even before the accident occurs, many technologies are currently on trial for automakers. This work presents design methodologies and simulations that represent a qualitative way of detecting the difficulties involved in a project vehicle tracking by using the technologies of GPS / GSM, studying the development and optimization of a GPS antenna (critical point) to the effect experienced by the antenna metal parts of the vehicle when the antenna is located inside the vehicle (instrument panel), taking as basis the roof of the vehicle (ideal point) to the solution and the basis for comparison of the solution / Mestrado / Eletrônica / Mestre em Engenharia Automobilistica

The localization of wireless devices, e.g. mobile phones, laptops, and handheld GPS receivers, has gained much interest due to the benefits it provides, including quicker emergency personnel dispatch, location-aided routing, as well as commercial revenue opportunities through location based services.  GPS is the dominant position location system in operation, with 31 operational satellites producing eight line of sight satellites available to users at all times making it very favorable for system implementation in all wireless networks.  Unfortunately when a GPS receiver is in a challenging environment, such as an urban or indoor scenario, the signal quality often degrades causing poor accuracy in the position estimate or failure to localize altogether due to satellite availability. Our goal is to introduce a new solution that has the ability to overcome this limitation by improving the accuracy and availability of a GPS receiver when in a challenging environment.  To test this theory we created a simulated GPS receiver using a MATLAB simulation to mimic a standard GPS receiver with all 31 operational satellites.  Here we are able to alter the environment of the user and examine the errors that occur due to noise and limited satellite availability.  Then we introduce additional user(s) to the GPS solution with the knowledge (or estimate) of the distances between the users.  The new solutions use inter-receiver distances along with pseudoranges to cooperatively determine all receiver location estimates simultaneously, resulting in improvement in both the accuracy of the position estimate and availability. / Master of Science

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