Doutorado em Engenharia Elétrica e da Computação (EMC)

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Acústica aplicada no desenvolvimento de equipamentos para agricultura de precisão
(Universidade Federal de Goiás, 2022-07-08) Furriel, Geovanne Pereira; Calixto, Wesley Pacheco; http://lattes.cnpq.br/9073478192027867; Calixto, Wesley Pacheco; Silva, José Geraldo da; Araújo, Wanderson Rainer Hilário de; Jakelaitis, Adriano; Cruz Junior, Gelson da
This work presents methodology for development of precision agriculture equipment based on acoustic and vibration techniques. The proposed methodology uses the scale reduction method to simulate the induced vibration and the direction of sound pressure fields. After analyzing the scale-down model, the prototype is built in real dimensions to validate the proposed system. Two acoustic induction systems are designed and evaluated, one for applying phytosanitary products and the other for selective fruit harvesting. When applying the phytosanitary product, there is a reduction in drift and an increase in leaf coverage by approximately 45%. In the selective harvest, the proposed method is analyzed, and approximately 40% of the fruits were harvested at the appropriate maturation stage. The acoustic techniques presented applied to agriculture are promising for developing equipment for handling and harvesting in precision coffee farming. The results indicate that using acoustic techniques promotes the reduction of the inherent wear of the harvest in the plants.
Aferição de usabilidade de interfaces assistivas sob o prisma da computação afetiva
(Universidade Federal de Goiás, 2022-04-07) Mezencio, Rovilson; Lemos, Rodrigo Pinto; http://lattes.cnpq.br/3333000136853156; Lemos, Rodrigo Pinto; Gomide, Renato Sousa; Alves, Ricardo Henrique Fonseca; Guedes, Leonardo Guerra de Rezende; Vasques, Thiago Lara
The usability of interfaces is connected to the perception and emotion of each user. The way each individual feels the world around them is their own. Assess or test an interface from a cognitive point of view and measure with a simple note whether or not it can be improved in a generic way without discovering if groups of individuals need special attention or if they react in a similar way, it is already an ancient science. Affective computing arises to study whether these perceptions, emotions, attitudes and behaviors can be measured and how this can improve interfaces so that there is greater personalization in the use of interfaces. Assistive Software interfaces need to be more personalized than interfaces are general-purpose. Each user has their specific difficulty and different personalities. Psychometric tests in their variety and scientificity have been used to classify sets of users and verify if their needs can be grouped. The idea now is to find out if people within groups with similar skills, competences, personalities, way of acting and thinking may have similar technological needs when using some technology. This work raised the techniques and methodologies for usability assessment of assistive or non-assisted interfaces. Then, a bibliographic research was carried out to understand which would be the best personality classifier available in Portuguese. Furthermore, methodologies were sought in Affective Computing to assess emotions activated in the use of an available and free assistive tool. Then, an attempt was made to assess the quality of an interface, as well as the grade or level it reached Also, the perceptions caused by its use were verified and if there is a way to make a grouping based on the personalities mapped by an inventory based on the Big Five. A survey was carried out with 96 (ninety-six) participants who were grouped into four different personalities in order to verify if different personalities have similar cognitive and emotional perceptions when performing a task in an assistive tool. Compiling the data and using specific statistical techniques for the correlation study, it is concluded that there are indications that people with the same personality, classified using the Personality Characteristics Inventory-ICP, a national method based on the Big Five , may have similar cognitive and emotional perceptions.
Análise de viabilidade técnica, econômica e ambiental de um projeto de eficiência energética associado com geração distribuída
(Universidade Federal de Goiás, 2022-04-25) Faria, Adriano Ferreira de; Marra, Enes Gonçalves; http://lattes.cnpq.br/8463332056679918; Alvarenga, Bernardo Pinheiro de; http://lattes.cnpq.br/9850449311607643; Alvarenga, Bernardo Pinheiro de; Marra, Enes Gonçalves; Belchior, Fernando Nunes; Viajante, Ghunter Paulo; Domingos, José Luis
This study focused on developing a sustainability project carried out in 11 Federal Institute of Education, Science, and Technology of Goiás (IFG) campuses, combining energy efficiency and distributed generation actions to optimize energy consumption by through the retrofit of the lighting system, installation of a photovoltaic generation system, energy monitoring, and qualification and training of teachers, students and employees, in compliance with the guidelines established by the National Electric Energy Agency (ANEEL) within the scope of the Public Call for Priority Projects for EE and Strategic R&D nº 01/2016 – “Energy Efficiency and Mini Generation in Public Institutions of Higher Education”. In the lighting system, 18,377 inefficient lamps were replaced by lamps with more efficient technology, with an energy saving of 867.9 MWh/year and a peak demand reduction of 309.6 kW. The proposed generation system aimed to install 3076 PV modules on the rooftops of selected campus buildings, totaling 1 MWp of installed power with an average annual power generation of 1736.9 MWh/year. The total project investment was USD 1,348,768.50 and the global cost–benefit ratio of the project was 0.68, which will result in annual savings of approximately USD 197,321.85. This corresponded to a 58% reduction in energy bills. The project proposed in this work was considered technically and economically viable within the scope of the Brazilian Energy. The estimate of avoided carbon emissions is also carried out, considering the methodologies used by the United Nations Framework Climate Change Convention (UNFCCC) for Clean Development Mechanism (CDM) projects that include energy efficiency activities and grid-connected renewable energy generation, resulting in an avoided emission of 983.36 tCO2 eq.
Análise e otimização da rede de distribuição de energia utilizando conceitos de redes inteligentes
(Universidade Federal de Goiás, 2021-10-21) Caetano Neto, João; Calixto, Wesley Pacheco; http://lattes.cnpq.br/9073478192027867; Calixto, Wesley Pacheco; Reis, Márcio Rodrigues da Cunha; Lemos, Rodrigo Pinto; Marques, Leonardo Garcia; Magalhães, Alana da Silva
The main objective of this work is to develop a methodology for analyzing the quality of the voltage level in the distribution power grid to identify and re-duce the violations of voltage limits through the proposition of optimal points for the allocation of photovoltaic distributed generation. The methodology uses the geographic location of the power grid and its consumers to perform the grouping and classification in spatial grids of 100×100 m using the average annual consumption profile. The generated profiles, including the grid infor-mation, are sent to the photovoltaic distributed generation allocation algo-rithm, which, using an optimization process, identifies the geographic location, the required installed capacity, and the minimum number of photovoltaic gen-eration units that must be inserted to minimize the violations of voltage limits, respecting the necessary restrictions. The entire proposal is applied in a real feeder with thousands of bars, whose model is validated with measurements carried out in the field. Different violations of voltage limits scenarios are used to validate the methodology, obtaining grids with better voltage quality after the optimized allocation of photovoltaic distributed generation. The proposal presents itself as a new tool in the work of adapting the voltage of the distri-bution power grid using photovoltaic distributed generation.
Aplicação da inteligência artificial, ontologia e mineração de dados para classificação de sentenças judiciais
(Universidade Federal de Goiás, 2021-12-20) Castro Junior, Antonio Pires de; Calixto, Wesley Pacheco; http://lattes.cnpq.br/9073478192027867; Peretta, Igor Santos; Araújo, Wanderson Rainer Hilário de; Soares, Fabrizzio Alphonsus Alves de Melo Nunes; Gomes, Viviane Margarida; Calixto, Wesley Pacheco
The objective of this work is to apply together ontology with bag-of-words models, similarity learning, and document classification in texts with uttered decisions. The objective is to improve the results of data mining in a database of court decisions. An automatic method of searching sentences in judicial processes related to the one under judgment is developed using the frequency term-inverse of frequency in documents model together with the Jaccard similarity coefficient, establishing weights on the co-occurrence of terms in legal texts of the same category. A dataset with document vectorization is used for supervised training of machine learning algorithms, aiming to classify new justice processes. The proposed methodology provides flexibility to the Judiciary, simulating the role of legal advisors in preparing court decisions with less time and efficiency in the search for jurisprudential standards. The results obtained show that, through accuracy metrics, the proposed model is effective and efficient, and can be applied in the process of identification of court decisions. Thus, the application of artificial intelligence, ontology, and data mining is indicated for information retrieval in court decisions.
Aplicação da transformada de Hilbert-Huang e da seleção paraconsistente de características no campo da entomologia agrícola: uma abordagem para identificação e estimativa de densidade de cigarras em lavouras cafeeiras
(Universidade Federal de Goiás, 2023-12-01) Souza, Uender Barbosa de; Escola, João Paulo Lemos; http://lattes.cnpq.br/5894769490673984; Brito, Leonardo da Cunha; http://lattes.cnpq.br/6660680440182900; Brito, Leonardo da Cunha; Vieira, Flávio Henrique Teles; Lemos, Rodrigo Pinto; Escola, João Paulo Lemos; Maccagnan, Douglas Henrique Bottura
The sounds emitted by various insect species carry specific and reliable acoustic characteristics. For this reason, acoustic identification of insects has been widely investigated by the scientific community in the field of pattern recognition. In Brazil, the cicada species Quesada gigas is considered a pest in coffee crops due to its sap-feeding habits, which can cause losses to farmers during intense attacks. Given this scenario, and considering the fact that the most striking characteristic of cicadas is sound emission for reproductive purposes, this work proposes a system designed to assist in the management of pest insects in coffee crops. Specifically, this system aims to detect the presence of cicadas or estimate their density through acoustic signals. The approach innovatively combines the extraction and analysis/selection of sound features through the Hilbert-Huang Transform (HHT) and Paraconsistent Feature Engineering, two emerging methods of growing interest in the scientific community. A detailed study was conducted on the influence of eight stopping criteria for the Empirical Mode Decomposition, the first step of HHT, considering variations of parameters, temporality, signal sampling, and also the encoding of these signals in two formats. The first defines vectors by the energies of the Intrinsic Mode Functions (IMFs) in order of extraction, while the second distributes the energies of the IMFs according to the 25 frequency bands of the Bark Scale. Additionally, the dimensional variation of the vectors was analyzed. The experiments allowed determining low computational cost configurations, showcasing the efficacy of the proposed system, with models based on Support Vector Machines achieving accuracies above 98% in both identification and density estimation of cicadas. Thus, this document details the theoretical foundations, design, development of the system, discussions about possibilities for its practical application, and an initial analysis of a developed application for smartphones. This proposal has the potential to encourage the reuse of old electronic equipment, promoting sustainable and economically viable practices.
Complexidade natural de sistemas com base em análise de sensibilidade
(Universidade Federal de Goiás, 2020-09-30) Gomes, Viviane Margarida; Calixto, Wesley Pacheco; http://lattes.cnpq.br/9073478192027867; Calixto, Wesley Pacheco; Wainer, Gabriel Andres; Peretta, Igor Santos; Pinheiro Neto, Daywes; Martins, Weber
This work proposes a methodology for analyzing systems based on a particular measure of complexity, called the natural complexity of the system. This measure corresponds to the proper level of complexity of each system, characterized by the region of optimized configurations. Given the optimal or optimized solution, the sensitivity analysis is performed to define the impact generated at the output of the system due to variations in the input parameters. The proposed methodology comprises: i) sensitivity analysis metrics, ii) system complexity metrics based on weighted connections, iii) analysis of the system using natural complexity as a reference and iv) development of models for application of the methodology. The complexity metric uses the sensitivity indices of the parameters to define the relevance values of the connections, in order to establish a relationship between the parties and the whole. The results point to the complexity metric as a mechanism for synthesizing the configuration, arrangement, performance and workload of the system in a single measure. Regarding the measure of natural complexity, it may be used as a reference of the desired level of complexity, since it was significantly different from the measures obtained under overload or idle conditions. Thus the natural complexity may correspond to the minimum complexity value of the system in regular activity. The proposed complexity metric strengthened the assertion that every system exhibits some level of complexity. Thus, it may be said that complexity is the totality of the system in interaction, with its own internal dynamics and its own environmental flows.
Contribuições à modelagem, controle e integração de dispositivos fotovoltaicos a sistemas elétricos de potência
(Universidade Federal de Goiás, 2023-11-03) Corrêa, Henrique Pires; Vieira, Flávio Henrique Teles; http://lattes.cnpq.br/0920629723928382; Vieira, Flávio Henrique Teles; Palhares, Reinaldo Martinez; Kopcak, Igor; Negrete, Lina Paola Garcés; Belchior , Fernando Nunes
The prominence attained by photovoltaic (PV) power generation among the various available renewable energy resources has led to the need of analyzing and engineering such technology at a wide range of implementation scales, beginning from the electrical characteristics of PV cells, passing through the local control of PV generation systems, up to the massive integration of PV resources to wider electrical power systems, such as the distribution grid. This thesis is divided into three parts, each of which presents novel contributions to the study of PV systems in the three aforementioned scales of analysis. In the first part, analytical modeling of PV cell current-voltage (I-V) characteristics by means of explicit closed-form equations is addressed. A new piecewise quadratic model is proposed, which is shown to perform either better or comparably, for different solar cells, to state-of-the-art models in terms of accuracy. Two methods are established for computing the model parameters: the first one is analytical and only requires datasheet information, whereas the second one uses linear-complexity optimization with respect to I-V samples in order to further improve accuracy. In the second part, the problem of maximum power point tracking (MPPT) in two-stage PV systems is considered. First, a new hybrid MPPT method which uses direct duty cycle control for enhanced tracking efficiency is developed for grid-tied systems. Then, an analytical MPPT approach for single-phase off-grid variable-voltage systems is presented and subsequently generalized to consider current harmonics and three-phase loads. Both proposed MPPT methods are shown, by means of simulation, to perform better than existing methods with similar implementation complexities. In the third part, voltage control of distribution systems with photovoltaic penetration by means of PV inverter reactive power support is studied. Three novel decentralized methods for controlling the inverter reactive power setpoints are proposed. The first method considers voltage measurements are available at each PV inverter and consists in the heuristic specification of a cooperative decentralized Markov decision process (MDP), whose offline solution yields voltage control policies to be carried out by the grid zone controllers. On the other hand, the second method assumes voltage measurement and computational resources are scarce and establishes a decentralized strategy which only uses two voltage measurements per control zone and is directly compatible with droop-type controls usually found in PV inverters. At last, a third method is presented which combines cooperative MDP, droop control and a switching mechanism for achieving a compromise between voltage regulation and reduction of active power losses. All methods are compared to similar existing approaches, via simulations with real irradiance profiles in a large distribution grid, yielding favorable performances.
Controle adaptativo de fluxos de tráfego de redes baseado em modelagem multifractal e sistemas fuzzy
(Universidade Federal de Goiás, 2019-08-13) Cardoso, Alisson Assis; Vieira, Flávio Henrique Teles; http://lattes.cnpq.br/0920629723928382; Vieira, Flávio Henrique Teles; Sousa, Marcos Antônio de; Lemos, Rodrigo Pinto; Vieira, Robson Domingos; Dantas, Maria José Pereira
The network traffic flows that arrive at the base station to be transmitted to the mobile users, in a 5G network system, enter the queuing process until transmission rates are provided. In order to minimize the delay, this work proposes the use of flow control algorithms based on the prediction of user queue behavior. Thus, the more accurate the data prediction, the greater the accuracy and control of flow control algorithms. To improve accuracy, models describing the behavior of network traffic are employed. In this work, two adaptive modeling algorithms based on the Lognormal Beta and BetaMWM models are proposed to model the network traffic and allow its use in real-time applications, such as the 5G network. Simulations are performed in comparisons to multifractal models found in the literature to validate the proposed algorithms, where results in terms of expected value, variance, moments of 2º to 4º order, mean squared errors of autocorrelation and distribution function prove the adaptively use of the algorithms. To perform the flow control, an equation is also proposed to obtain the optimal prediction-based control rate, where generalized ortonormal functions and fuzzy modeling are employed. Simulations of the Downlink 5G link are also performed to validate the proposed flow control algorithms. For this, results in terms of Flow, Utilization, Loss Rate, Delay and Average Waiting Queue are presented, proving the efficiency in the use of multifractal models, orthonormal basis functions, and fuzzy modeling in flow control algorithms for Downlink 5G systems. Taking advantage of the proposed multifractal modeling, an equation is also proposed to estimate the delay limitation for the first recommendations of the 5G network using the network calculation theory. For this, it is proposed a stochastic envelope process for network traffic based on the Adaptive Beta Lognormal model where comparisons with envelope processes known in the literature are performed.
Controle de potência reativa para adequação de valores de tensão e redução de perdas em redes elétricas com geração distribuída fotovoltaica
(Universidade Federal de Goiás, 2024-05-06) Lopes Filho, Gilberto; Vieira, Flávio Henrique Teles; http://lattes.cnpq.br/0920629723928382; Vieira, Flávio Henrique Teles; Negrete, Lina Paola Garces; Corrêa, Henrique Pires; Franco, Ricardo Augusto Pereira; Souza, Gustavo Souto de Sá e
This work presents contributions aimed at improving the electrical voltage profile in compliance with regulatory standards and reducing or minimizing losses in a radial electrical network with distributed photovoltaic generation. By injecting reactive power in a controlled manner through inverters connecting their respective photovoltaic generators to the distribution network buses, it is possible to control network voltages and losses. This work proposes three distinct approaches. The first algorithm, based on observations of the electrical network’s behavior, determines generated reactive power values capable of reducing electrical losses and regulating voltage for various levels of distributed generation penetration and load power factor. The allocation of photovoltaic generators and power values is randomly generated, and through a Monte Carlo simulation, the performance of the proposal can be analyzed. The second proposal uses heuristic algorithms (Genetic Algorithm and Firefly Algorithm) to estimate optimal reactive power values at the buses, aiming at voltage regulation, minimization of electrical losses, or minimization of losses with constraints on voltage magnitude values. The third proposal employs analytical relationships between reactive power, power loss, and voltage deviation to control reactive power injections into the electrical network. These analytical relationships, derived from the equations in this work, ensure computational simplicity while optimizing loss reduction and voltage deviation. This proposal includes the Loss Reduction Algorithm (LRA) and the Voltage Regulation Algorithm (VRA) and introduces an approach to efficiently switch between them called the Combined Control Strategy (CCS). The CCS seeks to provide a balance between voltage regulation and the reduction of electrical losses. Computational simulations are conducted to validate and analyze the performance of each proposal, varying various parameters of the algorithms and the network. All such Proposals are compared with other methods described in the literature, highlighting the superiority of the contributions presented in this work
Controle e estabilização de aeronaves não tripuladas submetidas a falhas nos motores
(Universidade Federal de Goiás, 2024-06-07) Bulhões, Júnio Santos; Magalhães, Alana da Silva; http://lattes.cnpq.br/4812531916179139; Calixto, Wesley Pacheco; http://lattes.cnpq.br/9073478192027867; Calixto, Wesley Pacheco; Magalhães, Alana da Silva; Coimbra, Antonio Paulo; Araújo, Wanderson Rainer Hilário de; Martins, Marcella Scoczynski Ribeiro
The objective of this work was to develop a methodology that utilizes control techniques to stabilize unmanned aerial vehicles subjected to engine failures. The methodology includes the creation of a test bench that allows independent rotational movements of ϕ and θ, eliminating translational movements and reducing its interference with the aircraft’s inertia matrix. Control techniques are implemented to stabilize the aircraft in situations of propulsor failure. The experiments demonstrate an improvement in the aircraft’s stability, with a reduction of more than 80% in the effects produced by the failure in the initial moments and the maintenance of stability in scenarios with up to 30% propulsor performance degradation. The proposed method surpasses other approaches in terms of efficiency and preservation of the aircraft’s autonomy. Both the developed test bench and the simulator are validated, and the auxiliary control that operates post-failure is tested in simulation and on the test bench, demonstrating its ability to stabilize the aircraft during failures in one of its propulsors, providing a viable and efficient solution for real-world situations.
Desenvolvimento de métrica de avaliação bilíngue por estrutura frasal aplicada à tradução automática
(Universidade Federal de Goiás, 2021-10-08) Silva, Alan Henrique Ferreira; Wainer, Gabriel Andres; Calixto, Wesley Pacheco; http://lattes.cnpq.br/9073478192027867; Calixto, Wesley Pacheco; Wainer, Gabriel Andres; Reis, Márcio Rodrigues da Cunha; Marques, Leonardo Garcia; Araújo, Wanderson Rainer Hilário de
This work proposes a metric capable of evaluating automatic bilingual translations, through the use of phrasal structures between the source and target languages. Existing methods currently provide a dependent assessment of large amounts of data as texts examples. The proposed methodology uses as a database the association of generic phrasal structures between the source and target language to assess the text quality, resulting given by an automatic translation machine. The method validation is performed using comparative studies between the evaluations generated by the proposed metric and the BLEU and METEOR metrics. The results obtained shows greater accuracy of evaluation of the proposed metric compared to the other metrics, with an improvement of approximately $5\%$ compared to the results of the evaluation of human translators. The results obtained in the tests validate the capability of the metric as an auxiliary tool in the evaluation of machine translations.
Detecção de imagens falsificadas baseada em descritores locais de textura e rede neural convolucional
(Universidade Federal de Goiás, 2020-06-30) Ferreira, William Divino; Soares, Fabrizzio Alphonsus Alves de Melo Nunes; http://lattes.cnpq.br/7206645857721831; Cruz Júnior, Gélson da; http://lattes.cnpq.br/4370555454162131; Cruz Júnior, Gélson da; Pedrini, Hélio; Salvini, Rogério Lopes; Costa, Ronaldo Martins da; Lemos, Rodrigo Pinto
Nowadays, digital image transformation has become a widespread activity. Hence, image copying, cloning, and resizing are easily performed, making it challenging to check image integrity and authenticity. Moreover, a criminal investigation from digital images becomes extremely hard, because using those images as proof demands to ensure its legitimately,under a risk to implicate the whole legal process.In this sense, this work develops a model for forged images based on local texture descriptors with convolutional neural networks. Henceforth, in this work, firstly, we evaluated fourteen local texture descriptors in five public image texture datasets, and then we selected descriptors with the best efficacy. Second, the selected descriptors are applied to four public datasets to extract texture features from forged and legit images. Finally, those features are used to train a residual convolutional neural network, and then, classifying images as authentic or forged with a Support Vector Machine Classifier. A result of the proposed model provides enthusiasm, mainly when applied to a dataset with a small number of images.
Development and analysis of mathematical methods for estimating statistical parameters in sensor array-based systems
(Universidade Federal de Goiás, 2020-02-07) Kunzler, Jonas Augusto; Sander, Oliver; Lemos, Rodrigo Pinto; lattes.cnpq.br/3333000136853156; Lemos, Rodrigo Pinto; Sander, Oliver; Fleury, Claudio Afonso; Vieira, Robson Domingos; Castro, Marcelo Stehling de
A estimação da direção de chegada e a estimação de pulsos de energia na espectroscopia de raios-x são baseadas no mesmo parâmetro, o deslocamento de fase de sinais em relação a uma referência. Neste trabalho é demonstrada a possibilidade de aplicar técnicas já estabelecidas para a estimação da direção de chegada ao problema de espectroscopia. Os dois temas são correlacionados em uma parte introdutória e em seguida eles são discutidos separadamente dando ênfase nas características intrínsecas de cada um. No problema de estimação da direção de chegada, inicialmente apresenta-se o modelo de sinal para o arranjo de sensores e alguns métodos baseados no estimador de máxima verossimilhança. Considerando um arranjo de sensores linearmente distribuídos e com espaçamento uniforme entre os elementos, os sinais induzidos em cada circuito serão cópias defasadas de um sinal de referência. O defasamento está intimamente relacionado com a direção de chegada. No domínio espacial, as direções de chegada representam frequências de funções exponenciais complexas, as quais deverão ser estimadas. Os principais métodos de estimação são o MODE, MODEX, o MODEX modificado, e o SEAD. Atenção especial é dispensada ao método SEAD que é baseado na decomposição em autovalores da matriz de correlação espacial modificada. A diferença entre os dois maiores autovalores gera uma curva com picos proeminentes indicando as direções de chegada de ondas planas. A esta curva dá-se o nome de espectro diferencial. Uma análise matemática do espectro diferencial, denominada de espectro diferencial total, é desenvolvida e demonstra-se que a norma matricial induzida pela norma-2 vetorial é a principal componente do cálculo. Portanto, propõe-se uma abordagem baseada em normas matriciais para a estimação das direções de chegada. Uma descrição matemática geral foi desenvolvida, a qual explicita a relação entre os verdadeiros ângulos de chegada e um ângulo sintético usado para varrer todo o espectro, a correlação entre as fontes, o número de fontes e o número de sensores. Demonstra-se que a diferença entre os ângulos determina a amplitude do pico gerado. A formulação matemática do espectro angular constitui em uma das principais contribuições deste trabalho, porém, outros aprimoramentos foram alcançados através da proposta de uso de normas matriciais. A utilização da abordagem baseada em normas evita a necessidade de realização da decomposição da matriz em autovalores e, consequentemente, o tempo de execução total do método é reduzido e o erro quadrático médio é reduzido para situação de fontes afastadas. Comparando as propostas com os métodos estabelecidos na literatura, a abordagem de normas supera o método MODE e seus derivados com relação ao erro quadrático médio. Porém, com relação ao tempo de execução os métodos baseados no SEAD são mais custosos computacionalmente para um número de fontes menor do que 4. A estimação de pulsos de energia na espectroscopia de raios-x não é um tema novo, porém, o multiplexador SQUID de micro-ondas é uma abordagem relativamente nova e, atualmente, ele consiste em um tema de pesquisa pujante. O objetivo do sistema é estimar a energia de partículas energéticas que incidem em detectores, os quais podem ser do tipo transition edge sensor ou metallic magnetic calorimeters. Os calorímetros metálicos são sensores paramagnéticos que estão situados em um campo magnético fraco, eles traduzem variação de temperatura em variação de fluxo magnético. Para realizar a leitura das variação de fluxo magnético decorrente da incidência de partículas emprega-se um componente supercondutor denominado de superconducting quantum interference device (SQUID). O SQUID é um interferômetro de extrema sensibilidade e se comporta como um indutor variável. O SQUID é acoplado a uma terminação de uma linha de transmissão supercondutora e produz alterações na frequência de ressonância do circuito. Portanto, a energia de partículas pode ser lida eletronicamente através da demodulação de uma onda de rádio que percorre o ressonador. A modulação ocorre na amplitude e fase de uma portadora complexa. Após a exclusão de frequências intermediárias, resultado do processo de mixagem da portadora, obtem-se uma portadora complexa de frequência baixa sobre a qual métodos de estimação de fase são aplicados. Pela semelhança com o problema de estimação da direção de chegada, propõe-se uma abordagem baseada em arranjo de sensores e decomposição da matriz de correlação espacial em autovalores. Desta forma, estabelece-se uma analogia entre os dois problemas. Para a obtenção da matriz de correlação, considera-se a existência de um vetor de referência cuja fase não depende da incidência de partículas, i.e., quando o sistema está em repouso. Este vetor de referência é comparado por meio da função de correlação com os dados que são recebidos a cada instante. Define-se um comprimento do vetor de dados que seja conveniente e, desta forma, obtem-se uma matriz de snapshots com dois sensores e uma matriz de correlação de dimensões 2 × 2. A decomposição em autovalores pode ser resolvida explicitamente em função das entradas da matriz, de tal maneira, que uma formulação geral para o método é apresentada. Além disso, simplificações podem ser impostas com o objetivo de implementação em hardware dedicado. O erro de estimação é analisado para o método proposto e o método de máxima verossimilhança. O método de autovalores apresentou maior robustez ao ruído e em algumas circunstâncias consegue resolver o problema de estimação sem artifícios externos, algo que não ocorre para o método de máxima verossimilhança.
Diagnóstico otimizado de transformadores de potência mediante a integração de técnicas preditivas
(Universidade Federal de Goiás, 2018-02-22) Marques, André Pereira; Brito, Leonardo da Cunha; http://lattes.cnpq.br/6660680440182900; Ribeiro, Cacilda de Jesus; http://lattes.cnpq.br/8998911644222586; Ribeiro, Cacilda de Jesus; Brito, Leonardo da Cunha; Domingues, Elder Geraldo; Rocha, Adson Silva; Arruda, Colemar
The effective application of predictive maintenance techniques for power transformers is essential for the early detection of defects and failures, and in order to trigger scheduled preventive or corrective actions. This precludes the need for urgent and/or emergency interventions, aiming to reduce unscheduled power outages, which are usually more costly and cause great inconvenience to consumers and the electric power system. In this context, this work focuses on the development of an optimized diagnostic methodology for power transformers, by integrating eleven predictive techniques (with 27 quantities). These techniques are analyzed with respect to voltage level, type of electrical connection and age of the transformers – when applicable –, based on the experience of specialists/analysts, on standards and technical guidelines, and on statistical analyses of a database of actual field and laboratory tests. The analyses of the validation of the results are significant and presented through a specialized system, demonstrating their practical application. The novelty of this thesis consists in the development of an original classification method, called Normalized Doubly Weighted Sum (NDWS), and in the detailed description of the predictive techniques that are integrated, their functionalities, the creation of equations, the definition of criteria and parameters, with their weights and scores for the classification of “A” (excellent) to “E” (very poor), and recommended actions aimed at underpinning decision- making, thereby contributing to the body of studies in this field. Hence, it can be concluded that this work offers a comprehensive and efficient tool to aid in the optimized diagnosis of power transformers, insulated with kraft paper and immersed in mineral insulating oil, providing effective diagnostics and maintenance of these devices, and thus increasing the reliability of electric power systems.
Efeitos da operação do gerador de indução no comportamento do gerador síncrono operando em um sistema isolado alimentando cargas não lineares
(Universidade Federal de Goiás, 2018-07-13) Oliveira, José Mário Menescal de; http://lattes.cnpq.br/2672882686688933; Alves, Antônio César Baleeiro; http://lattes.cnpq.br/1188328474646154; Alves, Antônio César Baleeiro; Rodrigues, Kleiber David; Salerno, Carlos Henrique; Santos, Euler Bueno dos; Nerys, José Wilson Lima
This thesis demonstrates the effects of harmonic pollution in a salient pole synchronous generator and an induction generator operating in parallel on an isolated system, supplying a non-linear load. The main contributions of this research-study consist of identifying and quantifying the oscillations that non-linear load cause on the electric variables of synchronous and induction generators, such as, the electromagnetic conjugate that presents oscillations of sixth harmonic due to the distorted currents.
Equações estruturais aplicadas à avaliação da satisfação dos consumidores residenciais de energia elétrica
(Universidade Federal de Goiás, 2022-07-19) Santos Neto, Agenor Sousa; Reis, Márcio Rodrigues da Cunha; http://lattes.cnpq.br/1167385371830496; Calixto, Wesley Pacheco; http://lattes.cnpq.br/9073478192027867; Calixto, Wesley Pacheco; Reis, Márcio Rodrigues da Cunha; Magalhães, Alana da Silva; Marques, Leonardo Garcia; Lemos, Rodrigo Pinto
The main objective of this work is to apply structural equation modeling with partial least squares, and based on covariance, to evaluate the satisfaction of residential consumers of electricity. The model used commends the results of both structural equation modeling to indicate which best suits the measurement of the satisfaction of residential consumers who make use of electricity from utilities and licensees. The constructs evaluated are satisfaction, quality, value, loyalty and trust, whose analysis of the confidence interval shows that all weights are significant, demonstrating the importance of these indicators in the representation of constructs. The constructs trust, quality and value explain 74.4% of the variability of the satisfaction construct, so that the explanatory capacity of this relationship is considered satisfactory. The model developed allows utilities/licensees to maintain the monitoring of indicators measured by the proposed methodology and evaluate the evolution of consumer satisfaction in the face of suggestions for improvement strategies.
Escalonamento de recursos em redes LTE utilizando processo envelope de tráfego multifractal e curva de serviço mínima
(Universidade Federal de Goiás, 2018-12-14) Abrahão, Diego Cruz; Vieira, Flávio Henrique Teles; http://lattes.cnpq.br/0920629723928382; Vieira, Flávio Henrique Teles; Sousa, Marcos Antônio de; Lemos, Rodrigo Pinto; Lima, Marcos Antônio Cardoso de; Cardoso, Kleber Vieira
In this work, a variation of the MWM (Multifractal Wavelet Model) model is proposed for network traffic flows, in such a way that its parameters are estimated adaptively. Next, it proposes an envelope process of network traffic based on the parameters' adaptive estimation of this model, whose final objective is to provide quality of service (QoS) in real time. The proposed envelope is compared to the main envelopes processes known in the literature, that are based on traffic models, such as: Brownian Motion (Bm), Fractional Brownian Motion (fBm) and Multifractal Brownian Motion (mBm). This work investigates the use of F-OFDM multi-carrier modulation, which is one of the candidates for 5G networks. It is known that the LTE / LTE-A (Long-Term Evolution) network uses Adaptive Modulation and Coding (AMC) technique that have the function of adjusting the modulation order and code rate based on the user's channel state information, in order to achieve a Block Error Rate (BLER) lesser than 10%. In this work, simulations of the LTE downlink are carried out using OFDM and F-OFDM multicarrier modulation, with the objective of mapping the BLER as a function of SNR (Signal-to-Noise Ratio). This mapping is necessary for the network to adjust the modulation and code scheme appropriate to each user. It's also proposed an adaptive algorithm for resource allocation in the LTE/LTE-A downlink, with admission control of the users. This algorithm aims to improve the performance of some network parameters and to guarantee maximum delay, through of following information: backlog, channel condition and user’s traffic behavior. In order to control the admission of users and to estimate the maximum delay of the network, a minimum adaptive service curve of the LTE / LTE-A network is proposed. The proposed algorithm for resource allocation is compared with several scheduling schemes known in the literature through computational simulations of different LTE network scenarios using OFDM and F-OFDM multi-carrier modulation.
Estudo, implementação e otimização de técnicas de controle avançado
(Universidade Federal de Goiás, 2022-10-06) Ganzaroli, Cleber Asmar; Calixto, Wesley Pacheco; http://lattes.cnpq.br/9073478192027867; Magalhães, Alana da Silva; Calixto, Wesley Pacheco; Gomide, Renato de Sousa; Lemos, Rodrigo Pinto; Araújo, Wanderson Rainer Hilário de
This work proposes the tuning, implementation, analysis and comparison of different control strategies applied to the same system. The controllers studied are: Proportional, Integral and Derivative, Nonlinear Predictive, Fuzzy Control and Sliding Mode Control. These techniques are applied to the speed control of an independently excited DC motor driven by a fully controlled three-phase rectifier. The methodology proposes the bench design, the modeling of the real system by the system identification method, the sensitivity analysis and the adjustments of the controllers parameters using an optimization process. Comparisons are made between the techniques, highlighting their characteristics and performance considering similar conditions of execution. The robustness of each control when acting on a non-linear system is investigated. All control techniques are applied in three different tests: i) step-type reference signal, without load application, ii) reference signal with amplitude variation, without load application and iii) step-type reference signal, with load application. The techniques present satisfactory performance in the execution of the proposed control, depending, therefore, on the analysis of the system to be implemented to determine the appropriate method.
Geometria de malha de aterramento elétrico otimizada
(Universidade Federal de Goiás, 2022-09-30) Silva, Carlos Leandro Borges da; Calixto, Wesley Pacheco; http://lattes.cnpq.br/9073478192027867; Calixto, Wesley Pacheco; Reis, Márcio Rodrigues da Cunha; Magalhães, Alana da Silva; Lemos, Rodrigo Pinto; Nerys, José Wilson Lima
This work presents a methodology for calculating earth resistance, grid potential elevation, soil surface potential, touch voltage and step voltage in ground grids with optimized geometry in two-layer stratified soils. The values of the potential and touch and step voltages are obtained at any point on the grid. The proposed equation uses the methods of images and an average potential. The main characteristic of this model in relation to the others is the possibility of calculating grounding grids containing horizontal and vertical electrodes positioned at any distance and at any angle. The results obtained with the proposed methodology are presented and discussed. The results show a reduction of approximately 60% in the amount of horizontal conductors and approximately 30% in the amount of vertical rods in electrical grounding grids. The optimization of the grounding grids geometry presented in this work allows the creation of electrical grounding grids that meet the safety criteria with lower cost compared to traditional methods, in addition to allowing the reduction of the inductive effect due to a smaller amount of conductors in the grounding grids.

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