Programa de Pós-Graduação em Engenharia Elétrica e de Computação
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Master Thesis Utilização de substratos heterogêneos e planos de terra inclinados no desenvolvimento de antenas e filtros de microfita sintonizáveis(Universidade Federal do Rio Grande do Norte, 2012) Vieira, Antônio José Ferreira; D’Assunção, Adaildo Gomes; Silva, Sandro Gonçalves da; http://lattes.cnpq.br/6122570451445215; Barbin, Silvio Ernesto; http://lattes.cnpq.br/8233811412819096; http://lattes.cnpq.br/4159638862269940; http://lattes.cnpq.br/4743930013220286; Melo, Marcos Tavares de; http://lattes.cnpq.br/4933635747860906; Mendonça, Laércio Martins de; http://lattes.cnpq.br/1853488415531363This work aims to present tunable microstrip filters and antennas for applications in wireless communication systems, allowing variations in their resonant frequencies and bandwidths. Thus, in systems that present a high-intensity noise, changes in the operating frequency and bandwidth can provide higher reliability traffic of Information and improve the signal to noise ratio ofthe system. A technique was proposed to tune these devices, which consists in tilting the ground plane ofthese devices and vary the corresponding inclination angle as needed to meet the desired performances. Filters and antennas were designed using both circuit and transmission line theories combined with the tilted ground plane technique. Thereafter simulation was performed using the commercial software Ansoft-HFSS in order to validate the theoretical results. Furthermore several prototypes were built and measured using a vector network analyzer. A good agreement between measured and simulated results was observed. The obtained results showed an increase of up to 140% in the bandwidth ofthe filters and a range of up to 31% in resonant frequency of the studied antennas. Consequently by analyzing the performances of the considered microstrip devices it was observed that the application ofthe technique of tilted ground plane provides a considerable increase in the filters bandwidths and a signifícant percentage change in the resonant frequency value ofthe antennas. Therefore this technique is adequate for adjusting the response of microstrip devices with applications in filtering and electromagnetic radiation.Master Thesis Utilização de ressonadores metamateriais na melhoria de desempenho de filtros planares(Universidade Federal do Rio Grande do Norte, 2019-12-26) Silva Neto, João Alexandre da; Campos, Antônio Luiz Pereira de Siqueira; ; ; http://lattes.cnpq.br/8099257962727975; Costa, Iradilson Ferreira da; ; Rodrigues, Márcio Eduardo da Costa;This work proposes the insertion of Complementary Split-Ring Resonators (CSRR) in the planar filter ground. The intention is to improve some filter parameters found in the literature that have practical application, considering the growing demand for higher performance, smaller size, lower weight and cost of the devices that integrate the communication systems. The filters chosen were: a bandpass filter that uses Matrioska geometry for applications in the 2.45 GHz Industrial Scientific and Medical (ISM) band; and a low pass filter for digital TV applications. The idea is to insert the CSRR into the structure ground plane to increase the free attenuation of the Matrioska band-reject filter and to reduce the size of the low-pass filter. In the work the numerical and experimental results are presented, for the purpose of validation of the proposed technique. A good agreement between the results is observed, showing that the proposals presented were achieved. In the Matrioska band-reject filter, a significant improvement was obtained in the free attenuation in the filter rejection range, whereas in the low-pass filter a significant reduction in its dimensions was obtained.Doctoral Thesis Formulações explícitas para controladores preditivos generalizados: uma abordagem multiparamétrica(Universidade Federal do Rio Grande do Norte, 2019-10-30) Fonseca, Daniel Guerra Vale da; Maitelli, André Laurindo; ; ; Cavalcanti, Anderson Luiz de Oliveira; ; Dantas, André Felipe Oliveira de Azevedo; ; Dorea, Carlos Eduardo Trabuco; ; Barros, Péricles Rezende;Generalized Predictive Control (GPC) is one of the most traditional and popular Modelbased Predictive Control (MPC) techniques in industry and academia and has been applied over decades in several systems to improve the control performance. This type of controller uses process model information to predict future system behavior. In addition, GPC can deal directly with both MIMO systems and process constraints. However, when considering the constraint set, the controller needs to solve a Quadratic Programming (QP) (or a Linear Programming – LP) in real time, which can be prohibitive in certain cases, such as for embedded systems. This work uses multiparametric programming (mp) to generate an Explicit Piece-wise Affine (PWA) control law for GPC (mp-GPC) which holds the same control performance without the need to keep solving the optimization problem at each sample time. Hence, initially, the proposed formulation is compared with GPC based on online QP. The results show that the performance is maintained, reducing the computational time to calculate the control action. Then, a new format is proposed, which differs from the last one by the number of parameters needed in the mp formulation. Both propositions are applied in three different situations: a MIMO system, a process with input-output delays and a underactuated system. A comparison is made by checking the computational time spent to calculate the control signal, as well as the time required for mp resolution. Finally, studies involving a Hybrid Multiparametric GPC formulation were done , which makes use of the resolution of a multiparametric Mixed-Integer Linear Programming (mp-MILP). A nonlinear valve is used as a case study, in which its nonlinear characteristics are treated as a set of inequalities for the optimization problem, in order to minimize its effects.Doctoral Thesis Realimentação de estados baseada em regras fuzzy tipo-2 para servocontrole de sistemas não lineares(2019-12-09) Farias, Missilene da Silva; Araújo, Fábio Meneghetti Ugulino de; ; ; Maitelli, André Laurindo; ; Menezes Filho, José Bezerra de; ; Gabriel Filho, Oscar; ; Bessa, Wallace Moreira;Many researches use Takagi-Sugeno fuzzy models to accurately represent nonlinear dynamic systems. However, Takagi-Sugeno fuzzy makes the implementation of fuzzy controller more complex as system order and nonlinearities increase. Thus, the present work is aimed to overcome these limitations by using an interval type-2 fuzzy rule-based system in which the membership functions and the number of rules can be freely chosen simplifying the implementation of the technique. To this end, it is established a direct state feedback servo control to generate the nonlinear control action using parallel distributed compensation techniques with no need to include fuzzy models to describe the dynamic system. The proposed strategy is applied to a synchronous generator and also to a magnetic levitation system. From the results, it was verified that the proposed fuzzy servo control is able to stabilize the systems analyzed at different equilibrium points with higher performance and less settling times compared to the other servo controllers analyzed, given the uncertainties in the linearized model. In fact, the developed fuzzy control proved to be a proper way to accomplish this task, because fuzzy logic control itself does not depend on an accurate model.Master Thesis Análise e design de estruturas 2,5D de superfícies seletivas de frequência para aplicações em sistemas modernos de comunicações sem fio(2019-12-12) Duarte, Mychael Jales; Silva Neto, Valdemir Praxedes da; ; ; D'Assunção, Adaildo Gomes; ; D'Assunção Júnior, Adaildo Gomes; ; Vasconcelos, Cristhianne de Fátima Linhares de; ; Brito Filho, Francisco de Assis;This work presents a study on 2.5D Frequency Selective Surfaces (FSS) for applications in modern wireless communications systems. Initially, simple 2.5D patch structures are analyzed. The simple FSS are formed by square loop and Minkowski fractal-based loop. The use of the fractal curve caused a circuit miniaturization, the appearance of a new transmission band and a decrease in the bandwidth in the analyzed frequency band. The FSS 2.5D are formed from the simple structures which, for the formation of their elements, the turns were sectioned into parts, where they were printed on the upper and lower face of the dielectric and interconnected with 0.5 mm diameter cylindrical copper conductor wires. The 2.5D surfaces provided circuit miniaturization compared to fractal, without the appearance of new transmission bands in the analyzed band and without decreasing the relative bandwidth. Proving the efficiency of this miniaturization technique, three ultra-miniaturized structures for SMP (in the 1900 MHz and 2300MHz bands), Wi-Fi Halow (in the 900 MHz band) and Wi-Fi 6 (dual-band 2.45 GHz and 5.00 GHz) systems have been proposed, all three with dimensions of 10 mm x 10 mm unit cell. All FSS were stable with respect to the angle of incidence of the flat wave on the circuit surface. The simulated numerical results for the designed prototypes were obtained by the ANSYS HFSS software. The prototypes were constructed and the experimental characterization of the transmission coefficients, bandwidth and resonance frequency was performed, values obtained were compared and discussed with the results of the simulations, which showed good agreement.Master Thesis Implementação de um estimador neural de velocidade em um motor de indução trifásico(2019-12-16) Silva, Carlos Yuri Ferreira; Salazar, Andres Ortiz; ; ; Lock, Alberto Soto; ; Araújo, Fábio Meneghetti Ugulino de; ; Paiva, José Álvaro de;This work proposes to perform the speed control of an induction motor (1 cv, 2 poles, 220/380 V) without the use of a mechanical sensor attached to the rotor, avoiding some inconveniences such as a periodic maintenance and increased complexity and number of equipment are always part of the engine running. The three phase induction motor is the most used type of machine for electric drives. Low cost, construction simplicity and reliability are the motives that explains this statement. For the induction motor control was applied the control strategy known as Field Oriented Control and for the estimation of the motor rotor speed was used an artificial neural network, which observer electrical and mechanical system variables. The practical results were satisfatory, since the neural network worked for the measeured and estimated velocity, being possible to perform the control os the motor with the estimated speed in the range of 100 to 170 rad/s.Doctoral Thesis Sistema de geração automática de audiodescrição a partir de análise de conteúdo de vídeo(2019-11-28) Campos, Virginia Pinto; Gonçalves, Luiz Marcos Garcia; ; ; Gomes, Rafael Beserra; ; Silva, Bruno Marques Ferreira da; ; Reis, Ney Robinson Salvi dos; ; Araújo, Tiago Maritan Ugulino de;Audio description is an accessibility feature designed to make visual information accessible to blind or low vision people. To increase the range of audio description tracks in digital video applications, we propose a system for automatic audio description generation of videos. The system can use as source of information about the film the original script or the video itself. As a proof of concept, we developed a prototype that automatically generates audio description based on actions taken from the script and objects recognized in the video. The experiments contemplated the application of the solution in fiction films and surveillance videos. For fiction films, an evaluation was made with blind people. The results indicated that through the automatic audio description generated by the solution, it was possible to provide contextual information that can help the user in the general understanding of the story. For surveillance videos, a performance evaluation was made using the delay time of each component. Results indicate that a solution has the potential to be used in contexts that require real-time AD.Doctoral Thesis Correntropia complexa: definição, propriedades e aplicações(2019-09-30) Guimarães, João Paulo Ferreira; Martins, Allan de Medeiros; ; ; Dória Neto, Adrião Duarte; ; Silveira, Luiz Felipe de Queiroz; ; Borries, Ricardo Von; ; Fontes, Aluisio Igor Rego;Recent studies have demonstrated that correntropy is an efficient tool for analyzing higher-order statistical moments in non-Gaussian noise environments. Although correntropy has been used with complex-valued data, no theoretical study was pursued to elucidate its properties, nor how to best use it for optimization. By using a probabilistic interpretation, this work presents a novel similarity measure between two complex-valued random variables, which is defined as complex correntropy. Its properties are studied as well as a new recursive solution for the Maximum Complex Correntropy Criterion (MCCC) and two algorithms are derived, one based on the ascendent gradient and a second one on a fixed-point solution. Simulations were made in order to evaluate how robust this new measure is to impulsive noise in different problems: liner system identification, channel equalization and in a compressive sensing problem. It is also shown the application of complex correntropy as a tool to analyse the similarity between angles. The results demonstrate prominent advantages of the proposed method when compared with the classical algorithms in the literature.Doctoral Thesis Modelo analítico para avaliação da estabilidade de links em redes industriais sem fio(2019-12-09) Florêncio, Heitor Medeiros; Dória Neto, Adrião Duarte; ; ; Salazar, Andres Ortiz; ; Martins, Daniel Lopes; ; Brandão, Dennis; ; Melo, Jorge Dantas de;Wireless Sensor Networks (WSN) have emerged in the industrial environment with the purpose of increasing flexibility and deploying measurement and actuation elements in hard to reach areas. However, due to the peculiarities of wireless communication in the industrial environment, the use of metrics to evaluate the performance of communication links is crucial. An essential property for assessing network behavior is the stability of links. Several studies define metrics for evaluating link stability using different parameters. This thesis presents an analytical model for evaluating link stability based on received signal strength and packet delivery rate. The results obtained through tests performed with different scenarios showed that the analytical model can identify link installability situations when it comes to high variation in received signal strength and low packet delivery. Then, an ISA 100.11a network control system was developed to validate the model proposed in this work. The results obtained with the application of the model in the level control system presented steady state error values below the predetermined maximum limit, while in the control tests that did not consider the link stability factor the error exceeded the limit.Doctoral Thesis Sistema para auxílio em instalação e manutenção de redes industriais sem fio voltado para aplicação de controle(2019-12-27) Santos, Anderson Costa Silva dos; Dória Neto, Adrião Duarte; ; ; Maitelli, André Laurindo; ; Martins, Daniel Lopes; ; Casillo, Danielle Simone da Silva; ; Melo, Jorge Dantas de;Nowadays, wireless communication has aroused interest and is a tendency in industry environments. In part this interest is due to the ease of deployment and maintenance of this network, which dispenses sophisticated designs and execution of works of deploying cables, which in industrial environment often prohibitively expensive, and enabling the addition of new applications when compared to their wired counterparts. Despite its high degree of applicability, a wireless network faces some technical (reliability, energy consumption, environment interference) and cultural challenges present as the main negative points for the deployment of large-scale industrial wireless networks in the industry. To reduce some these problems, this work presents a system with multiobjective modeling to aid installation and maintenance (real time) of devices - sensors and actuators - in industrial wireless networks, allowing the use of controllers in these networks whose packet exchange within the sampling time, with emphasis on WirelessHART and ISA100.11a standards, which presents themselves as the most promising solution for industrial wireless networks.