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Disertaciones |
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1
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WILSON ROCHA LACERDA JUNIOR
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Meta Model Structure Selection: An Algorithm For Building Polynomial NARX Models For Regression And Classification
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Líder : SAMIR ANGELO MILANI MARTINS
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MIEMBROS DE LA BANCA :
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EDUARDO MAZONI ANDRADE MARCAL MENDES
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ERIVELTON GERALDO NEPOMUCENO
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MARCIO JUNIOR LACERDA
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SAMIR ANGELO MILANI MARTINS
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Data: 17-feb-2020
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Resumen Espectáculo
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The polynomial Nonlinear Autoregressive with eXogenous inputs (NARX) model family has been extensively studied over the last three decades, and several techniques have been proposed in this respect. The traditional work has mainly focused on methods based on a stepwise procedure known as Forward-Regression Orthogonal Least Squares (FROLS) algorithm. Extensions to model with multiples input and output have been stated as well as developing multi-objective approaches. Recently, the identification framework has been carried out in a probabilistic pattern, and contemporary techniques have been proposed consisting of evolutionary algorithms. These methods incorporate the knowledge about the probability distribution of possible model structures into the search process. An especially exciting class of new algorithm is the one based on metaheuristic. In this dissertation, a variant meta-heuristic method based on Hybrid Binary Particle Swarm Optimization and Gravitational Search Algorithm is presented for a single objective and multi-objective model structure selection. It takes into account the complexity of the model and the contribution of each term to build parsimonious models by proposing a new cost function formulation. In addition, the proposed method is adapted to obtain models in situations where the output is represented by a dichotomous variable, resulting in a classification model. The robustness of the new algorithm is tested on several simulated and experimental system with different nonlinear characteristics. The obtained results show that the proposed algorithm is capable of identifying the correct model, for cases where the model structure is known, and determine parsimonious models for experimental data even for those systems for which traditional and contemporary methods habitually fails. The new algorithm is validated over classical methods such as the FROLS and recent approaches based on meta-heuristic.
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2
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3
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DEIVITY DO CARMO SANTOS
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Líder : PAULO CEZAR MONTEIRO LAMIM FILHO
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MIEMBROS DE LA BANCA :
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FABIANO BIANCHINI BATISTA
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LANE MARIA RABELO
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PAULO CEZAR MONTEIRO LAMIM FILHO
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WALMIR MATOS CAMINHAS
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Data: 06-mar-2020
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Resumen Espectáculo
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Three-phase induction motors are responsible for a large part of the conversion of electrical energy into mechanical energy in several types of applications. In the industrial sector, for example, the performance and operating conditions of these electric machines have a significant impact on the entire production process and, consequently, on profit margins. Given the important role played, it is highly relevant to seek ways to anticipate eventual failures, thus avoiding unexpected stopeges in the production line. Amoung the main techniques used in the diagnosis of electrical machine failures, the Motor Current Signature Analysis is quite widespread and consolidated. However, this has some limitations associated with the load and the constructive characteristics of the motor. In this context, it is desired alternatives that are able to word around the deficiencies in traditional methods and detect anomalies even in the early stages, ensuring more freedom and efficiency in maintenance planning. Stray flux monitoring for this purpose has been shown to be prominent due to the high sensitivity of the signals to small variations in operating conditions. In this work, the stages of design and implementation of a stray flux sensor are presented, as well as a methodology for processing the device signals, in order to assess the viability of these signals for fault diagnosis. From signals of electromotive force, induced in the sensor by the stray flux, orbits are built whose characteristics reflect the motor’s operating conditions. Five faulty conditions were analyzed and the results demonstrated the effectiveness of the proposed technique.
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4
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LUAN PASCOAL DA COSTA ANDRADE
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Líder : SAMIR ANGELO MILANI MARTINS
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MIEMBROS DE LA BANCA :
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ALIPIO MONTEIRO BARBOSA
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ERIVELTON GERALDO NEPOMUCENO
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GLEISON FRANSOARES VASCONCELOS AMARAL
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SAMIR ANGELO MILANI MARTINS
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Data: 09-mar-2020
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Resumen Espectáculo
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Systems identification is the area of science responsible for obtaining mathematical models for systems of any nature from observed data. It is not always possible to obtain an adequate representation due to the high complexity of the system, difficulties in data collection, problems due to noise or due to the precision required by the application. There are alternatives to circumvent these situations and among them is to consider forecasts of multiple models for the same event. The combination of models tends to reduce the risk inherent in the classic paradigm of modeling to represent a process by a single model. Despite being used in other machine learning contexts, the combination of models was not observed being applied to system identification, especially to polynomial NARMAX models. This work proposes the combinatorial network of non-linear models, characterized by combining polynomial NARMAX models. The network can be used to obtain models with better representativeness of the system from representations of worse quality. The method also applies when a single model must be chosen from a set, as in the case of multiobjective identification, bypassing the decision criterion. The developed methodology was applied in the context of multiobjective identification to a simulated system, an electric heater and a pH neutralization plant. The technique was also implemented in the context of systems identification through interval arithmetic using an electromechanical system composed of a motor and a generator. In all cases, a set of representations was available, and the proposed methodology not only avoided the choice of a single model, but also performed better than the combined submodels.
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5
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MARCELO MOREIRA DE CARVALHO
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Líder : LANE MARIA RABELO
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MIEMBROS DE LA BANCA :
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LANE MARIA RABELO
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LEONARDO ADOLPHO RODRIGUES DA SILVA
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LEONARDO ANTONIO BORGES TORRES
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MARCIO FALCAO SANTOS BARROSO
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Data: 13-mar-2020
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Resumen Espectáculo
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The current master thesis presents the modeling of the laying head system focusing on the characterization of the forces acting inside the pipe and the movement dynamics considering the laying head pipe with three degrees of freedom, operating at the lamination speed of 110 textrm m/s. The forces coming from the contact and kinetic friction of the wire rod with the inner wall of the laying pipe are very important inputs for understanding and classifying the main loop formation problems: premature wear of laying pipe and non-uniformity of the turn radius. With the characterization of these forces, it became possible to evaluate the distribution profile of forces acting on the laying head pipe , which are very sensitive to movement kinematics and to the kinetic friction coefficient, the main parameter responsible for causing internal pipe wear. It was also possible to evaluate the correlated effects the lack of synchronism between the translation speed of the wire and the rotation speed of laying head pipe, a parameter that stands out as critical for a good uniformity. lightning. The dynamic modeling of the laying head pipe with three degrees of freedom made it possible to evaluate its movement dynamics by characterizing the movements of its center of mass. In this approach it is noteworthy that the pipe exit hole of the pipe can perform unwanted movements with rotations about the axis of the pipe support bearing, key parameter for a good turn formation at high speeds. Moreover, it is presented by the torque equations dynamic coupling between the torques acting on the three axes of rotation, a phenomenon that can be explored as a proposal to control the correction of such unwanted movements.
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6
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EDUARDO PINTO MAGALHÃES
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Líder : MARCIO FALCAO SANTOS BARROSO
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MIEMBROS DE LA BANCA :
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EDUARDO BENTO PEREIRA
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EDUARDO MAZONI ANDRADE MARCAL MENDES
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ERIVELTON GERALDO NEPOMUCENO
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MARCIO FALCAO SANTOS BARROSO
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Data: 05-may-2020
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Resumen Espectáculo
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The friction-loaded cycle ergometer is a device created in the mid-18th century and has now
been the most common instrument concerning the necessity of characterize diseases of the neu- romuscular system and muscle functions. Its use stands out in several areas of science, assisting
in the recovery of injuries, in the association of increased strength and muscle functional capac- ity and in the ability to generate power. In addition to power, the results from the combinations
of force-speed relations support to understand the limits of the human body, especially that of a physically disabled person, whose capacity is limited, as well as that of a high-performance athlete. In addition to the large numbers of applications to promote physical well-being, the cycle ergometer plays an important role in strengthening social well-being. In the last census presented by the IBGE, the motor disability presented the second-highest index among the other disabilities investigated. According to the OMS, physical disabilities are understood to be both the limitations of body functions and the influence of social and environmental factors. Besides
that, OMS requests that Member States create devices for rehabilitation and assistance. Al- though there is a strong desire from the academic community to make this device remarkable,
the cost of producing it is high, the accuracy and reliability of its measurement system are low and data monitoring is not integrated into the device. Facing the number of people who can
benefit from the use of this device, regarding the diagnosis and treatment of multiple patholo- gies and social inclusion, this work presents the design and implementation of an automation
system in an friction-loaded cycle ergometer to measure and monitor the total strength of the disabled person. According with the results of this work, an accurate system of measurement, control and analysis of the total force was obtained, given by the sum of the frictional load plus the load corresponding to the force produced against the inertia of the wheel.
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7
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RAYANE RAINER LEAL
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AMORTECIMENTO DE OSCILAÇÕES ELETROMECÂNICAS EM SISTEMAS COM ELOS DE TRANSMISSÃO HVDC
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Líder : WESLEY PERES
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MIEMBROS DE LA BANCA :
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ERIVELTON GERALDO NEPOMUCENO
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JOAO ALBERTO PASSOS FILHO
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RENAN SOUZA MOURA
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WESLEY PERES
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Data: 17-jul-2020
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Resumen Espectáculo
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This dissertation addresses the study of the problem of damping low-frequency electromechanical oscillations in power systems through the use of High Voltage Direct Current (HVDC) transmission links. Initially, the HVDC link model was included in an optimal power flow (OPF) to obtain the power system steady-state aiming at minimizing the generation cost. In a second stage, the HVDC link was modelled by a nonlinear differential–algebraic system of equations. These equations, together with the ones that describe the operation of the system in alternating current, are numerically linearized at the initial operating condition provided by the OPF. Further, the modal analysis is carried out, with the main objective of evaluating whether the low-frequency electromechanical oscillations are adequately damped. To increase the damping of these oscillations, damping controllers are included at generators and the HVDC link. For generators, conventional power system stabilizers (PSS) are considered. For the HVDC link, either conventional or multiband stabilizers (PSS4B) are considered. The damping controllers have been simultaneously designed by an optimization approach for maximizing the minimum damping coefficient of the system. The proposed methodology has been applied to the two-area four-generator power system and the New England system. The results show that only HVDC link (even with damping controller) is not able to ensure the power system stability. However, when damper controllers for HVDC link and synchronous generators are designed together, the system has a significant damping gain, thus guaranteeing its small-signal stability.
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8
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ALEXANDRE DE OLIVEIRA MIELI
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ANALYZE STATISTICS OF THE OUTDOOR-INDOOR SIGN AND COMPARISON BETWEEN PREDICTION METHODS COST231 E MIURA ET AL. IN INDOOR COVERAGE
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Líder : GLAUCIO LOPES RAMOS
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MIEMBROS DE LA BANCA :
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GLAUCIO LOPES RAMOS
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LENI JOAQUIM DE MATOS
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PEDRO VLADIMIR GONZALEZ CASTELLANOS
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SANDRO TRINDADE MORDENTE GONÇALVES
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Data: 28-ago-2020
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Resumen Espectáculo
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This work consists of two analyzes carried out from a measurement campaign in a narrow band, at the frequency of 768 MHz, with outdoor transmission and indoor reception at an initial distance of approximately 112 m. The first analysis verifies the behavior of mobile radio signal in confined environments (the building corridors). With the data obtained in the measurements, it is possible to observe the probability density function (PDF) that best fits the small-scale variability of the signal. Following this study, through signal attenuation, the path loss is compared to two signal prediction models specific to outdoor-indoor environments: COST231 and another proposed by Miura et al., concluding on the best fit for the indoor signal coverage.
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9
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JESSICA CRISTINE BONOTO DE OLIVEIRA
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Líder : GLAUCIO LOPES RAMOS
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MIEMBROS DE LA BANCA :
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GLAUCIO LOPES RAMOS
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HUMBERTO XAVIER DE ARAUJO
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PAULO TIBURCIO PEREIRA
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SANDRO TRINDADE MORDENTE GONÇALVES
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Data: 18-sep-2020
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Resumen Espectáculo
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With the emergence and advancement of technologies, wireless communication systems for connecting objects to the Internet (Internet of Things), where devices exchange information in real time has been the subject of many studies. These systems use frequencies below 1 GHz in order to increase coverage, have high performance and thus ensure high information rates. In this work is presented the study of a propagation channel for application in Internet of Things in the frequency fixed in 903 MHz. With this, it is made the characterization of the fast fading of the signal and the effect of the presence of people in this channel from measures captured in indoor and outdoor environments. Different cases are used for the study and when evaluating the effects on the small-scale variation of the received signal level, a greater variability of the channel with the presence of people can be observed, and some statistical probability models are the key for the study, behavior and results found.
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10
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VINÍCIUS DA SILVA BORGES
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Líder : ERIVELTON GERALDO NEPOMUCENO
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MIEMBROS DE LA BANCA :
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CARLOS AUGUSTO DUQUE
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ERIVELTON GERALDO NEPOMUCENO
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MARCIO EISENCRAFT
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MÁRCIO MATIAS AFONSO
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Data: 18-sep-2020
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Resumen Espectáculo
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The finite numerical resolution of digital number representation has an impact on the properties of filters. Much effort has been done to develop efficient digital filters investigating the effects in the frequency response. However, it seems that there is less attention to the influence in the entropy by digital filtered signals due to the finite precision. To contribute in such a direction, this manuscript presents some remarks about the entropy of filtered signals. Three types of filters are investigated: Butterworth, Chebyshev, and elliptic. Using a boundary technique, the parameters of the filters are evaluated according to the word length of 16 or 32 bits. It has been shown that filtered signals have their entropy increased even if the filters are linear. A significant positive correlation (p < 0.05) was observed between order and Shannon entropy of the filtered signal using the elliptic filter. Comparing to signal-to-noise ratio, entropy seems more efficient at detecting the increasing of noise in a filtered signal. Such knowledge can be used as an additional condition for designing digital filters.
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11
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Pedro Henrique Nascimento Vieira
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Líder : MARCO AURELIO DE OLIVEIRA SCHROEDER
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MIEMBROS DE LA BANCA :
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ALBERTO RESENDE DE CONTI
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ANTONIO CARLOS SIQUEIRA DE LIMA
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MARCO AURELIO DE OLIVEIRA SCHROEDER
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MARIA CRISTINA DIAS TAVARES
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RAFAEL SILVA ALIPIO
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RODOLFO ANTONIO RIBEIRO DE MOURA
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Data: 18-sep-2020
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Resumen Espectáculo
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Lightning strikes pose a risk to people and equipment. For safety, electrical grounding systems are projected. However, it is necessary to be able to make a quantitative analysis of the project and the quantities of interest, such as step voltage. This often requires computer simulations. A mathematical model that can be used for such simulations is the Hybrid Electromagnetic Model (HEM). This work presents the HEM deducted from both T and Π equivalent circuits, using both a Global Immitance and Nodal Admittance formulation. There are also a number of simplifications that are presented that can be used with HEM, such as modified HEM (mHEM) or power series (sHEM). The main objective is to develop a high performance and open source computer program that implements HEM and its variants for use by industry and academia. To this end, good programming practices are followed. The program was created with the C programming language, with interfaces for Julia and MATLAB for easy use by the end user. The user must understand the algorithmic model t wants to implement, as the program is a numeric library (set of functions). The impedance matrices depend only on the medium and the geometry of the conductors. Taking advantage of geometric symmetry avoids redoing unnecessary calculations. An algorithm that uses the symmetry of uniform rectangular grids has been developed. The computational gain it offers is less pronounced the greater the number of segments in the system. For testing the program, simulations of a buried horizontal conductor and a rectangular grid are made, both results compared with those that have been published. Ground potential rise (GPR), electric field and step voltage are calculated. The step voltage is obtained both by the difference in scalar electric potential and by the line integral of the electric field. The results show that step voltage is not equal to potential difference.
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12
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LUIS FERNANDO FREIRE
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Líder : MARCIO FALCAO SANTOS BARROSO
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MIEMBROS DE LA BANCA :
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EDUARDO MAZONI ANDRADE MARCAL MENDES
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ERIKA LORENA FONSECA COSTA DE ALVARENGA
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MARCIO FALCAO SANTOS BARROSO
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Data: 23-oct-2020
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Resumen Espectáculo
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13
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LEANDRO DA CONCEIÇÃO MEDEIROS
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Líder : ERIVELTON GERALDO NEPOMUCENO
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MIEMBROS DE LA BANCA :
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ERIVELTON GERALDO NEPOMUCENO
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EDUARDO BENTO PEREIRA
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VALTER JUNIOR DE SOUZA LEITE
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LILIANA FAJARDO OLIVEIRA
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Data: 16-nov-2020
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Resumen Espectáculo
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Preliminary techniques for estimating muscle fiber conduction velocity was consolidated in the early 80s, but due to recent technological progress in electronics and computing, only in the last few decades studies have been published demonstrating more accessible and more practicable applications. This project aims to provide information about muscle fatigue through muscle fiber conduction velocity (MFCV) estimation upon the use of surface electromyography (sEMG), studying and improving bitstream modulation techniques and cross-correlation. The modulation technique discussed in this study presents an assessment based on a set of data generated by gain variation, providing an average of MFCV. The estimated results reveal a decrease in the MFCV correlated with the fatigue condition of the observed muscle. The main contribution of this work is the use of bitstream modulation for MFCV estimation, allowing distinguishing the decrease of MFCV statistically in different modulation representations on sEMG signals. The method was evaluated upon experimental study and supplied estimates of MFCV similar to those obtained by the literature, providing more conservative values when taking in account the average of a set of velocities every second.
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14
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TATIANE MARTINS OLIVEIRA
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QUADRATIC ĆUK CC-CC CONVERTER FOR WIDE CONVERSION RANGE APPLICATIONS
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Líder : FERNANDO LESSA TOFOLI
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MIEMBROS DE LA BANCA :
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RENÉ PASTOR TORRICO BASCOPÉ
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ANIEL SILVA DE MORAIS
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FERNANDO LESSA TOFOLI
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HEVERTON AUGUSTO PEREIRA
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Data: 11-dic-2020
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Resumen Espectáculo
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Non-isolated DC-DC converters with a wide conversion range are considered a viable solution for applications in which galvanic isolation is not mandatory. Several aspects must be taken into account for developing new topologies, e.g., the number of components, stresses on semiconductors, efficiency, and voltage again. Using the graft scheme technique, this work presents a quadratic Ćuk converter operating in continuous conduction mode with a single active switch. The advantages of this converter include high-voltage step-up or step-down without requiring extreme duty ratios. In addition, the input current and the current through the output stage are non-pulsating, thus implying reduced electromagnetic interference (EMI) levels. This work presents the qualitative and quantitative analyzes of the proposed topology, as well as simulation and experimental results obtained from a laboratory prototype to validate the theoretical assumptions. The developed prototype has the following specifications: input voltage of 30 V, output voltage of 150 V, output power of 100 W, and switching frequency of 50 kHz.
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15
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GABRIEL OLIVEIRA FERREIRA
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State feedback control for linear and state polynomial continuous-time LPV systems under constraints
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Líder : MARCIO JUNIOR LACERDA
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MIEMBROS DE LA BANCA :
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FABRÍCIO GONZALEZ NOGUEIRA
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MARCIO JUNIOR LACERDA
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SAMIR ANGELO MILANI MARTINS
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VALTER JUNIOR DE SOUZA LEITE
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Data: 18-dic-2020
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Resumen Espectáculo
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This work investigates new convex conditions to design robust and Linear Parameter Varying (LPV) gains for continuous time-varying systems subject to saturating actuator and energy bounded disturbances. The input-to-state stability conditions are used to design controllers ensuring the minimization of the L2-gain between the disturbance input and the controlled output. Furthermore, optimization procedures to maximize the estimate of the region of attraction, and the bound to the control signal as well, are formulated. By means of sum of squares (SOS) decomposition, this work is also concerned with the design of state-feedback controllers for LPV polynomial continuous-time systems. The vector field presents polynomial dependence on states. For both cases, the state-feedback gains designed depend on the filtered time-varying parameter. When designing time-varying controllers for time-varying systems in practical situations, the noise on the parameter measures may induce abrupt changes in the gain values and, consequently, in the control signal. Therefore, one may expect early damages on the actuator due to wear and fatigue. Hence, filtering the time-varying parameter and guaranteeing that the closed-loop filtered system is stable may produce state-feedback gains with smaller variance over time. The methods proposed consider the filtered parameter on the stabilization problems and, as an advantage over the existing literature, there is no need to know the bounds of the time-derivative of the parameter and such function does not need to be continuous. Convex conditions are also developed for the case when LPV polynomial continuous-time systems present input constraints. Hence, this work deals singly with three kinds of systems: • input-to-state stabilization for continuous-time varying systems with saturating actuators; • design of state-feedback controllers for continuous-time varying systems with state polynomial dependency. • design of state-feedback controllers for continuous-time varying systems with state polynomial dependency and input constraints. For all cases, the efficacy of the proposed methods is illustrated with numerical examples. Key-words: Saturating actuators. Filtered parameter. Input-to-state. Region of attraction. Sum of squares. Polynomial continuous-time varying systems.
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16
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DANYENE GUIMARÃES ALVARENGA
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SENSITIVITY ANALYSIS OF ELECTROMAGNETIC WAVE PROPAGATION PARAMETERS IN UNDERGROUND CABLES
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Líder : MARCO AURELIO DE OLIVEIRA SCHROEDER
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MIEMBROS DE LA BANCA :
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JOAO AMIM MOOR NETO
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MARCO AURELIO DE OLIVEIRA SCHROEDER
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RODOLFO ANTONIO RIBEIRO DE MOURA
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URSULA DO CARMO RESENDE
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Data: 21-dic-2020
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Resumen Espectáculo
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The use of underground transmission line has grown all over the world. In this sense, the calculation of the electromagnetic parameters of underground cables is extremely important for various types of simulations in energy systems. In this work, a formulation is used to calculate the longitudinal and transversal parameters of an underground electrical system, as well as a formulation of ground return impedance to model the underground cable system. Thus, the behaviors of the attenuation and speed parameters of the system's earth mode of propagation are analyzed face of the influence of several factors, considering frequencies from 10 Hz up to 100 kHz. For the frequency range considered, the effect of displacement currents is neglected in the formulations, since it has no influence on the results. Several sensitivity analyzes are performed, considering: different soil resistivities, different thicknesses and permissivities of the last cable insulation layer and different spacing between the system cables. The results illustrate the physical consistency of the electromagnetic modeling of the parameters considered and the importance of studying soil effects and other factors in the performance of an underground transmission system.
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17
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LOURENÇO MODESTO DOS ANJOS
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Líder : LEONIDAS CHAVES DE RESENDE
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MIEMBROS DE LA BANCA :
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ANSELMO BARBOSA RODRIGUES
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LEONIDAS CHAVES DE RESENDE
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MARCO AURELIO DE OLIVEIRA SCHROEDER
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MÁRCIO MATIAS AFONSO
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Data: 23-dic-2020
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Resumen Espectáculo
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Due to the increasing use of automation in industrial processes, critical load equipment, personal computers and electronically controlled devices in residential installations, there is currently a greater interest in relation to Power Quality (QEE) problems. An important aspect related to QEE is the voltage compliance of power system. That is, the product delivered within the limits specified by Organs regulatory agencies. Due to the problems caused by voltage disturbances, which can be mentioned, disconnection of sensitive equipment, damage from voltage swell, increased losses in transformers and low efficiency operations of electrical equipment, there is this concern with voltage compliance. This work aims to contribute to the studies of voltage sags and swells (VTCD), seeking to demonstrate the real impact they cause on industrial consumers, even with full compliance with the standards determined in norms and resolutions. Initially, the main national and international standards applicable to VTCD are presented, characterization of events and verification of impact on loads, analyzing their similarities and peculiarities. The study on the implantation of a semiconductor factory in Brazil, aims to evaluate the impacts of low power quality from the phase of studies of the electrical system to the final operation / production. Finally, a proposal for a more detailed assessment of VTCD impacts is presented, within the normative scope
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