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listelement.badge.dso-type Item , LMI-based robust PID controller with measurement filter for arbitrary-order SISO systems(Universidade Federal de Minas Gerais, 2026-03-13) Elder Pereira FeniliEsta tese apresenta uma nova metodologia para o projeto de controladores PID baseada em desigualdades matriciais lineares (LMI). O método proposto pode ser aplicado a sistemas de ordem arbitrária com ou sem retardo no tempo. A estrutura central da abordagem consiste em uma arquitetura inovadora de controle, desenvolvida no espaço de estados, que possibilita a combinação de sistemas de ordem arbitrária com controladores PI/PID associados a diferentes filtros para ruído de medição ou, ainda, com um controlador PI sem filtro. Além disso, a metodologia permite considerar múltiplos objetivos de projeto, tais como rejeição de perturbações, seguimento de referência, atenuação de ruído de medição, alocação de polos para sistemas livres de atraso, definição da taxa de decaimento exponencial para sistemas com retardo no tempo, garantia de ganhos positivos para o controlador PID e margens de robustez no domínio da frequência, por meio da imposição de limites superiores para a norma $\mathscr{H}_{\infty}$ das principais funções de sensibilidade. A abordagem também contempla a presença de incertezas paramétricas. Na etapa de validação, realizamos exemplos numéricos e um experimento prático em um protótipo Twin Rotor MIMO System (TRMS), contemplando uma ampla gama de sistemas, desde modelos de baixa ordem até modelos de ordem superior. Nessas análises, combinamos diferentes tipos de controladores e múltiplos objetivos de forma simultânea. Os resultados obtidos foram comparados com métodos recentes e relevantes da literatura, evidenciando a eficácia e a superioridade da metodologia proposta.listelement.badge.dso-type Item , Multiscale analysis of pressurized fractures - an approach based on phase-field models and adaptive FEM-SPIM coupling(Universidade Federal de Minas Gerais, 2026-04-27) Eduarda Marques FerreiraO fraturamento hidráulico envolve padrões complexos de trincas, frequentemente intensificados pela ação da pressão do fluido nas superfícies de fratura, levando à ocorrência de fenômenos como nucleação, ramificação e coalescência de trincas. A representação adequada desses mecanismos requer modelos robustos, capazes de descrever tanto a evolução das trincas quanto as não linearidades do material. Nesse contexto, os modelos de phase-field têm se destacado como uma abordagem promissora, permitindo o tratamento automático do início e propagação de trincas através da sua formulação variacional. Entretanto, a maioria dos materiais envolvidos em fraturamento hidráulico apresenta heterogeneidade intrínseca, e a ampla faixa de escalas espaciais envolvidas aumenta ainda mais a complexidade do problema. Esse cenário motiva o desenvolvimento de abordagens multiescala capazes de relacionar os processos de fratura na microescala ao comportamento estrutural. Esta tese apresenta uma investigação abrangente de um modelo de phase-field para fraturas pressurizadas, considerando análises em escala única e multiescala. No nível de escala única, é desenvolvida uma estratégia de acoplamento entre o Método dos Elementos Finitos (MEF) e o método sem malha Smoothed Point Interpolation Method (SPIM). A abordagem evolui de um acoplamento prescrito para uma estratégia adaptativa e automatizada, na qual o SPIM é empregado em regiões de fratura ativa, onde refinamento adaptativo é conduzido, guiado por critérios associados à variável de phase-field. Com base nesses resultados, propõe-se um framework multiescala baseado no esquema FE2. A formulação incorpora procedimentos de homogeneização e transferência de informações entre escalas, visando equilibrar custo computacional e precisão, com a modelagem por phase-field restrita à escala inferior e a homogeneização aplicada sobre uma região ativa de fratura. O framework também permite o uso de acoplamento adaptativo MEF–SPIM na microescala. Simulações numéricas são apresentadas para avaliar as estratégias propostas, demonstrando resultados consistentes. De modo geral, os resultados indicam que as abordagens desenvolvidas constituem uma estrutura eficaz para a modelagem de fraturas pressurizadas, com potencial aplicação em problemas complexos de engenharia envolvendo fraturamento hidráulico.listelement.badge.dso-type Item , Task planning and motion control with temporal logic specifications(Universidade Federal de Minas Gerais, 2026-03-27) Marcos da Silva PereiraThis work proposes three task planning and motion control frameworks that generates task plans for a given linear temporal logic specification (LTL), which are then executed using a constrained motion controller. In the first framework, we propose a new encoding for task specifications, directly in the task-space, as constraints of a mixed-integer linear program that can be used with off-the-shelf LTL linear encoding. We apply our framework to plan and execute trajectories for a free-flying robot and show that the task plan is accomplished without collisions, even in the presence of unexpected obstacles that are not considered in the planning phase, while control signal constraints are satisfied. Next, we propose a pick-and-place task planning and motion control framework that generates a optimized sequence of moves for objects while treating rearrangements. The third framework integrates a vehicle routing problem technique from the literature with the first framework to plan and execute inspection tasks motivated by the oil and gas industry challenges. In all the frameworks, the system can get trapped into local minima because of the local constrained controller, but we provide ways to escape from them by using the task planner and an adaptive random walk technique. We compared the frameworks with sampling-based planners from the literature. The frameworks were evaluated in simulation and the results show speed gains in planning and execution with higher success rates. Our frameworks main contribution to the state of the art is the generation of task plans with correctness guarantees and their execution in a closed-loop manner such that the system is reactive to changes in the workspace.listelement.badge.dso-type Item , Desempenho térmico e óptico de policarbonato com adição de TiO2 em refletores automotivos por termografia(Universidade Federal de Minas Gerais, 2025-12-05) Isabella Luísa Vieira Aquino CassimiroReflectors used in automotive lights are typically made of polycarbonate. However, this polymer exhibits low light reflectivity. To enhance its reflective properties, it is typically metallized an additional process that significantly increases production costs. Therefore, developing polymers that do not require metallization is of interest. In this context, the use of polycarbonate reinforced with titanium dioxide nanoparticles presents a promising alternative. Studies have shown that such incorporation can improve the degradation temperature and mechanical properties of the composites. For automotive reflectors, in addition to thermal degradation, it is essential to understand the thermal diffusivity and emissivity of these composites to ensure the component's thermal performance. Current studies on such properties in polycarbonate with titanium dioxide nanoparticles are mostly limited to hardness and optical characteristics, evaluated with spectroscopy. This study investigated the thermal and luminous performance of polycarbonate (PC) samples with 10 wt% titanium dioxide nanoparticles (PC-10%TiO₂), as well as automotive reflectors made from the same composite. The influence of 10% TiO₂ addition to PC was evaluated through structural analysis using X-ray diffraction (DRX) and scanning electron microscopy (MEV), while thermal stability was analyzed using thermogravimetric analysis (TGA). The reflectivity efficiency of the materials was assessed under ultraviolet (UV) radiation exposure. Radiometric properties were evaluated using active infrared thermography. Spectral thermography in the mid- and long-wave infrared ranges was used to determine emissivity and provided relevant insights into the thermal behavior of the materials under use conditions up to 70 °C. Lighting tests were also conducted on PC-10%TiO₂ reflectors, using commercial metallized polymer reflectors as reference. The integrated analysis of DRX, TGA, and MEV confirmed that TiO₂ was properly incorporated into the polycarbonate without compromising its structural integrity. TGA results showed that the addition of 10 wt% TiO₂ increased the degradation temperature from 167 °C to 495 °C. After UV radiation exposure, no changes in the reflectivity of PC-10%TiO₂ were observed in the visible light range. The long-wave infrared emissivity of PC-10%TiO₂ (average 0.96) was 3% lower than that of pure PC. PC-10%TiO₂ showed a thermal diffusivity of 0.20 mm²/s, which is 28.6% lower than that of pure PC, indicating greater thermal inertia due to the presence of nanoparticles. The luminous performance of the PC-10%TiO₂ reflector was, on average, 4% lower than that of a commercial metallized polycarbonate reflector. However, for vehicle reflectors, this illuminance level meets current industry standards. These results indicate that PC-10%TiO₂ has potential for use in the production of interior vehicle lamp reflectors, without significantly compromising light reflectivity and offering the added benefits of improved thermal resistance and reduced heat buildup around the reflector. The economic analysis indicated that this composite may represent a viable and cost-effective solution for automotive reflector manufacturing.listelement.badge.dso-type Item , “Desfazer uma imagem do passado : a escrevivência como construção futura(Universidade Federal de Minas Gerais, 2025-02-07) Arleam Francislene Martins DiasABSTRACT This research aims to analyze the paths for empowerment of black women through the “Writing Experience” (Escrevivência) and black female authors’ writing. To understand the references of writing and writers that are part of the repertory and that provoked the desire to write in these women, considering that black women are crossed by social issues that are common to all of us, each one lives their experience in their own way and time. The experience, thought of as a theoretical concept in this research, is collective, as well as individual. To hear from black female writers what the construction of their writings goes through, is to allow them to name themselves. From a methodological point of view, the research relied on conversations in the format of face-to-face interviews, based on a script. In addition, letters were exchanged between the researcher and the participants, inspired by the methodology of cartography and the idea of the carbon effect, as in the marks that writings produce. Thus, this research explores the stories of black female writers, based on the sharing of experiences, with the commitment to “undo an image of the past”, build new epistemes and disobey an order and model of writing that promotes the erasure of the ancient knowledge of black women. The interviews made it possible to analyze the following issues: the deeper relationship between the subjects and the writers Carolina Maria de Jesus and Conceição Evaristo, in which they declared the direct influence of the writers on their reading and writing repertories; the influence of other writing references that make up their repertories; the self-recognition of the subjects as writers, revealing that the nomination of a writer does not necessarily require publishing. “Writing Experience” (Escrevivência) has established itself as a future construct, as the sharing of experiences amongst black women can contribute to the construction of new epistemes, highlighting a marker of this transformation as the age of publishment of the subjects in comparison to the references Carolina Maria de Jesus and Conceição Evaristo, who published much younger. The analyzed interviews reinforce the clues regarding the hypothesis presented by this research, Carbon Effect, which is understood as the means of transmission and construction of the knowledge that passes through the writing marks left by the references of black women, creating new stories and paths of empowerment. We will seek to research this specific area further. We hope that this research, its data and positions are accessed and shared as a way of fighting the epistemicide, racism, sexism and classicism faced by black women, so that, increasingly, their writings and epistemes are registered in the world. For there are many of us, countless. We are beginning, middle, beginning.