DECAT - Departamento de Controle e Automação

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/490

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2005 - 200972010 - 201916

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Autor: search.filters.author.Monteiro, Paulo Marcos de Barros

Resultados da Pesquisa

Agora exibindo 1 - 10 de 23
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    Capacitive impedance measurement : dual-frequency approach.
    (2019) Rêgo Segundo, Alan Kardek; Pinto, Érica Silva; Santos, Gabriel Almeida; Monteiro, Paulo Marcos de Barros
    The most widely used technique for measuring capacitive impedances (or complex electrical permittivity) is to apply a frequency signal to the sensor and measure the amplitude and phase of the output signal. The technique, although efficient, involves high-speed circuits for phase measurement, especially when the medium under test has high conductivity. This paper presents a sensor to measure complex electrical permittivity based on an alternative approach to amplitude and phase measurement: The application of two distinct frequencies using a current-to-voltage converter circuit based in a transimpedance amplifier, and an 8-bit microcontroller. Since there is no need for phase measurement and the applied frequency is lower compared to the standard method, the circuit presents less complexity and cost than the traditional technique. The main advance presented in this work is the use of mathematical modeling of the frequency response of the circuit to make it possible for measuring the dielectric constant using a lower frequency than the higher cut-off frequency of the system, even when the medium under test has high conductivity (tested up to 1220 µS/cm). The proposed system caused a maximum error of 0.6% for the measurement of electrical conductivity and 2% for the relative dielectric constant, considering measurement ranges from 0 to 1220 µS/cm and from 1 to 80, respectively.
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    Capacitive impedance measurement : dual-frequency approach.
    (2019) Rêgo Segundo, Alan Kardek; Pinto, Érica Silva; Santos, Gabriel Almeida; Monteiro, Paulo Marcos de Barros
    The most widely used technique for measuring capacitive impedances (or complex electrical permittivity) is to apply a frequency signal to the sensor and measure the amplitude and phase of the output signal. The technique, although efficient, involves high-speed circuits for phase measurement, especially when the medium under test has high conductivity. This paper presents a sensor to measure complex electrical permittivity based on an alternative approach to amplitude and phase measurement: The application of two distinct frequencies using a current-to-voltage converter circuit based in a transimpedance amplifier, and an 8-bit microcontroller. Since there is no need for phase measurement and the applied frequency is lower compared to the standard method, the circuit presents less complexity and cost than the traditional technique. The main advance presented in this work is the use of mathematical modeling of the frequency response of the circuit to make it possible for measuring the dielectric constant using a lower frequency than the higher cut-off frequency of the system, even when the medium under test has high conductivity (tested up to 1220 μS/cm). The proposed system caused a maximum error of 0.6% for the measurement of electrical conductivity and 2% for the relative dielectric constant, considering measurement ranges from 0 to 1220 μS/cm and from 1 to 80, respectively.
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    Application of methodology for the adequacy of the electrical motor's power sizing : permanent and transient analysis.
    (2018) Rêgo Segundo, Alan Kardek; Oliveira Filho, Delly; Queiroz, Josué Morgan; Martins, José Helvecio; Monteiro, Paulo Marcos de Barros
    The suitability of the motive force contributes to the efficient use of electrical energy. On the other hand, the inadequate size of electric motors is directly connected to increased investment and running costs. This article presents the theory and mainly the application of a methodology for the adequacy of the motive power. The research was conducted at the Federal University of Viçosa dairy factory. This methodology consists in measuring motor rotation, acquiring technical information from the manufacturer’s manual, and identifying the type of motor load. In addition, it uses the linearization method to estimate the resistance torque in steady state. This step is achieved without the need for using additional equipment or sending the motor to a laboratory for measuring the torque. In this sense, the studies can be made during the production process. Thus, this relevant methodology has the advantage of allowing the studies to be carried out at the agro-industry facilities. After getting all the information described above, it was possible to determine whether each motor at the factory was oversized. Then, the suitable motor was selected according to the load type. The application of the methodology described herein could provide around 50.6% savings in the monthly electricity costs at the dairy factory, and an attractive internal return rate.
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    An analysis of the economic viability and greenhouse gas emissions reductions resulting from the use of solar water heaters in a typical Brazilian dwelling.
    (2017) Altoé, Leandra; Oliveira Filho, Delly; Carlo, Joyce Correna; Monteiro, Paulo Marcos de Barros; Martins, Isabella Theresa de Almeida
    Several countries have reduced their energy consumption and greenhouse gas emissions levels in buildings by promulgating laws, formulating standards and instituting certification programs. In this context, Brazil launched an energy efficiency certification for buildings in 2009. This study aimed to analyze the economic viability and potential greenhouse gas emissions reductions associated with the use of solar water heaters in a typical Brazilian dwelling. Solar thermal systems were simulated at different energy efficiency levels and shower water flow rates. It was found that the use of solar water heater, as compared with electric heater without a hot water storage, presented internal return rate of approximately 26% per year, simple payback around 4.5 years; net present value about US$ 2,194.00 and cost of conserved energy around US$ 0.12 kWh-1. This study also verified that solar water heater use in a typical Brazilian dwelling reduced emissions compared with electric and gas heating by approximately 95 and 256 kgCO2equivalentyear-1, respectively. The total reduction potential of greenhouse gas emissions by use solar water heaters for the Brazilian residential sector was substantial, around 5.75 million tCO2equivalentyear-1.
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    Simulation of distributed generation with photovoltaic microgrids - case study in Brazil.
    (2015) Xavier, Gustavo Azevedo; Oliveira Filho, Delly; Martins, José Helvecio; Monteiro, Paulo Marcos de Barros; Diniz, Antônia Sônia Alves Cardoso
    Elevated prices and lack of proper legislation and government incentives have been the main barriers in the development of the photovoltaic market in Brazil. In an attempt to overcome those barriers, a microgrid model was proposed and simulated. In the proposed microgrids, residential consumers are connected to each other to maximize the investment return by trading the surplus of generated energy among them. Different topologies and scenarios were studied from electrical energy and economic standpoints. Stochastic data of solar radiation were simulated for the city of Viçosa, Minas Gerais, Brazil, for the period of one year, considering the statistical behavior of a series over 20 years. The system output power and energy balance were calculated considering a model for photovoltaic generators and the radiation simulated data. By determining the generated energy and electrical needs of the microgrid members, the cash flow and economic feasibility were calculated. Sensitivity analyses were performed by varying economic parameters to determine situations where investment becomes feasible. This paper shows that microgrid contributes to improve the economics and the initial investments. The number of participants in a microgrid, the electricity and the equipment costs are important parameters to speed up the economic and technical feasibility process.
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    Computer programs for analysis of solar domestic hot water systems : RETScreen case study.
    (2015) Altoé, Leandra; Oliveira Filho, Delly; Martinez, Francisco Javier Rey; Carlo, Joyce Correna; Monteiro, Paulo Marcos de Barros
    The simulation programs are important tools for analyzing different energetic options, including the use of energy efficiency measures and renewable energies. The objective of this study was to analyze comparatively the different computer tools available for modeling of solar domestic hot water systems in buildings. Among the main simulation software in use for this purpose, there are RETScreen International, EnergyPlus, TRNSYS, SolDesigner, SolarPro, e T*SOL. Among the tools mentioned, only EnergyPlus and RETScreen International are free, but they allow obtaining interesting results. In the presented case study can be seen the versatility of the RETScreen program, which allows for analysis of energy production, economic viability and carbon dioxide emissions. Within the range of computer solar water heaters simulators currently available, it is necessary that the user knows the tool specifications, such as programming language and capabilities so one may choose the program that is most suitable to produce the expected results for one's knowledge and modeling skills.
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    Viabilidade técnico-econômica da geração de energia elétrica em barragens de perímetros irrigados.
    (2016) Ribeiro, Marcos Caldeira; Oliveira Filho, Delly; Mantovani, Everardo Chartuni; Costa, José Márcio; Martins, José Helvecio; Monteiro, Paulo Marcos de Barros; Altoé, Leandra
    implantação de perímetros irrigados requer a construção de barragens em cursos d’água para suprir a necessidade hídrica das culturas. Geralmente, estas estruturas são utilizadas apenas para abastecer o sistema de irrigação, sendo seu potencial hidroelétrico desprezado. O objetivo deste trabalho foi avaliar a viabilidade técnico-econômica da geração de energia elétrica em barragens de perímetros irrigados. Foi realizado um estudo de base para a barragem de Manoel Novaes que atende o perímetro de Mirorós, na Bahia. Uma Pequena Central Hidrelétrica poderia gerar 29% do consumo e 12% da demanda de energia elétrica do sistema de irrigação do perímetro. O investimento apresentaria os seguintes indicadores de viabilidade: Valor Presente Líquido de R$ 1.425.616,54, Taxa Interna de Retorno igual a 44%, Relação Benefício/Custo de 2,76 e Tempo de Retorno de Capital igual a 5 anos e 8 meses. O estudo realizado para o perímetro irrigado de Mirorós pode servir de referência para análise de outros perímetros, de modo a incentivar o melhor aproveitamento deste tipo de barragem no Brasil.
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    Utilização de conversores analógico-digitais endereçáveis para medições de variáveis climáticas.
    (2006) Martins, José Helvecio; Pinto, Paulo Raimundo; Lopes, Daniela de Carvalho; Monteiro, Paulo Marcos de Barros; Monte, José Eduardo Carvalho
    A utilização de dispositivos eletrônicos endereçáveis em sistemas de automação vem aumentando consideravelmente, assim como o desenvolvimento e a aplicação de sistemas automáticos, para o setor agrícola, têm sido bastante incentivados. Devido à complexidade destes sistemas e à necessidade de maior confiabilidade e simplicidade em suas estruturas, novas formas de transmissão de dados têm sido propostas e estudadas. Neste trabalho, instrumentos digitais para medições de temperatura do ar, umidade relativa do ar, radiação solar e velocidade do ar foram desenvolvidos com base em conversores analógico-digitais endereçáveis. A utilização dos dispositivos propostos possibilita a implantação de sistemas de monitoramento e controle com apenas três fios, conectados diretamente a um computador, responsável pelo gerenciamento da transmissão e pelo tratamento dos dados. Calibrações e validações preliminares foram realizadas com os instrumentos digitais endereçáveis desenvolvidos, resultando em medidas com exatidão e precisão elevadas.
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    Experiência de aprendizagem baseada em projetos no ensino de robótica.
    (2014) Cocota Júnior, José Alberto Naves; D'Angelo, Thiago; Monteiro, Paulo Marcos de Barros
    With the teaching of robotics it is possible to explore the multidisciplinary formation of the engineering student. The use of an appropriate learning methodology enables the development of transversal skills in this educational formation. In this paper we discuss a new experience with Project-Based Learning (PBL) involving the design and development of a low-cost robot manipulator with six degrees of freedom, to motivate the undergraduate students studying Robotics Elements discipline in Control and Automation Engineering and Mechanical Engineering courses of the Escola de Minas at the Universidade Federal de Ouro Preto, carried out during two years (from 2012 to 2014). The key learning objectives and the tools used to implement this project will be detailed. Evaluation results show that this project was effective in engaging the students.
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    A novel low-cost instrumentation system for measuring the water content and apparent electrical conductivity of soils.
    (2015) Rêgo Segundo, Alan Kardek; Martins, José Helvecio; Monteiro, Paulo Marcos de Barros; Oliveira, Rubens Alves de; Freitas, Gustavo Medeiros
    The scarcity of drinking water affects various regions of the planet. Although climate change is responsible for the water availability, humanity plays an important role in preserving this precious natural resource. In case of negligence, the likely trend is to increase the demand and the depletion of water resources due to the increasing world population. This paper addresses the development, design and construction of a low cost system for measuring soil volumetric water content (θ), electrical conductivity (σ) and temperature (T), in order to optimize the use of water, energy and fertilizer in food production. Different from the existing measurement instruments commonly deployed in these applications, the proposed system uses an auto-balancing bridge circuit as measurement method. The proposed models to estimate θ and σ and correct them in function of T are compared to the ones reported in literature. The final prototype corresponds to a simple circuit connected to a pair of electrode probes, and presents high accuracy, high signal to noise ratio, fast response, and immunity to stray capacitance. The instrument calibration is based on salt solutions with known dielectric constant and electrical conductivity as reference. Experiments measuring clay and sandy soils demonstrate the satisfactory performance of the instrument.