Programa de Pós-Graduação em Engenharia Elétrica e de Computação
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Doctoral Thesis Estrutura neuro-fuzzy tipo-2 modificada para identificação e predição de comportamento de sistemas não lineares(Universidade Federal do Rio Grande do Norte, 2023-12-11) Cavalcante, Mário Sérgio Freitas Ferreira; Araújo, Fabio Meneghetti Ugulino de; http://lattes.cnpq.br/5473196176458886; http://lattes.cnpq.br/3876176661625657; Rocha, Thiago de Souza; http://lattes.cnpq.br/2541078732974933; Martins, Allan de Medeiros; https://orcid.org/0000-0002-9486-4509; http://lattes.cnpq.br/4402694969508077; Lima, Jean Mario Moreira de; http://lattes.cnpq.br/7467476735834560; Araújo, Ícaro Bezerra Queiroz de; https://orcid.org/0000-0002-6769-4946; http://lattes.cnpq.br/5668210125232252System identification is a crucial sphere of engineering dedicated to finding economical yet accurate models for fully understanding how systems behave. In effectuating this aim, these models predict future behavior while enabling simulations for optimization purposes inclusive of parameter adjustments where necessary for enhanced performance levels.However, what makes identifying systems challenging is the selection process regarding model structure choice and the estimation method used when making predictions concerning non-linearities present in complex phenomena affecting multiple variables. Nonetheless, experts have devised viable options toward precise modelling solutions by employing sophisticated techniques such as artificial intelligence algorithms or polynomial multi-model frameworks. he proposed thesis offers an approach that fuses interval type-2 fuzzy logic together with neural network training skills towards producing a generalized structure that enables both local model selection combined modeling which permits approximating or forecasting the behavior of any given system. The results were obtained using three case studies: the chaotic Mackey-Glass time equation, a furnace system, and a multisection tank system. The results of the pro- posed network for the approximation and prediction of these systems were compared with techniques from the literature, and the modified type-2 neuro-fuzzy interval network (MIT2FNN) showed lower mean squared error (MSE) values than the other techniques.Doctoral Thesis Simulação e projeto de antenas MIMO para aplicações nas tecnologias UWB, 5G e em smartphones(Universidade Federal do Rio Grande do Norte, 2023-05-23) Paiva, Samuel Belarmino de; D’Assunção, Adaildo Gomes; Silva Neto , Valdemir Praxedes da; https://orcid.org/0000-0003-3867-3297; http://lattes.cnpq.br/4160231554601828; http://lattes.cnpq.br/4159638862269940; https://orcid.org/0000-0002-4914-1803; http://lattes.cnpq.br/6498243690382060; Mendonça., Laércio Martins de; https://orcid.org/0000-0001-7861-3761; http://lattes.cnpq.br/1853488415531363; D’Assunção Junior, Adaildo Gomes; http://lattes.cnpq.br/7359899329008024; Serres, Alexandre Jean René; https://orcid.org/0000-0002-2912-5769; http://lattes.cnpq.br/5988817460788034; Peixeiro, Custódio José de Oliveira; http://lattes.cnpq.br/7635975069148170This work presents three MIMO (multiple-input multiple-output) antennas for applications in modern wireless communication systems. The first proposed MIMO antenna has compact dimensions, high isolation between ports and can be used for wireless local area network (WLAN) applications; the second proposed MIMO antenna is a miniaturized MIMO antenna, with high isolation between the ports and which can be used in ultra-wideband (UWB) applications; the proposed third MIMO antenna can be used for smartphone applications and covers the WLAN and 5G bands. Among the advantages that 5G offers, we can highlight ultra-fast speeds, low latency, large channel capacity, high spectral efficiency and massive connection density. Then, MIMO antennas have been extensively studied for applications in this technology, because they can considerably increase the data rate and the channel capacity, due to the channel capacity being proportional to the number of antennas used in transmission and reception, as well they can also improve the link reliability of wireless communications systems through multi-path data transmission and reception. The proposed MIMO antennas were designed using ANSYS HFSS software for numerical characterization, and the prototypes were manufactured with FR-4 dielectric and measured, showing good agreement between simulated and measured results. A key performance parameter of MIMO antennas, the envelope correlation coefficient (ECC), is analyzed and presents good results for the three proposed MIMO antennas. Furthermore, for the proposed antenna for smartphone applications, the effects caused by the user's hands are investigated, which is an extremely important performance parameterDoctoral Thesis Soluções de multi-conectividade para Redes LTE e NR(Universidade Federal do Rio Grande do Norte, 2023-10-27) Guerra, Tarciana Cabral de Brito; Sousa Júnior, Vicente Angelo de; https://orcid.org/0000-0003-2859-6136; http://lattes.cnpq.br/6358312955522220; http://lattes.cnpq.br/3014434468963722; Abinader Júnior, Fuad Mousse; https://orcid.org/0000-0001-8533-2300; http://lattes.cnpq.br/8583462151923968; Aguayo, Leonardo; https://orcid.org/0000-0001-5316-6344; http://lattes.cnpq.br/4815464320872808; Rodrigues, Marcio Eduardo da Costa; http://lattes.cnpq.br/2116993138825543; Silva Neto, Valdemir Praxedes da; https://orcid.org/0000-0003-3867-3297; http://lattes.cnpq.br/4160231554601828; Freitas Júnior, Walter da Cruz; https://orcid.org/0000-0002-0821-3460; http://lattes.cnpq.br/0694425837735193The Dual Connectivity (DC) technology is an essential feature of New Radio (NR), the access network of the 3rd Generation Partnership Project (3GPP) to 5G, as it is the basis for some architectural options of this generation of communication systems since the beginning of its implementation. Furthermore, because this technology can enhance throughput, reliability, and mobility management, among other factors, it is expected to be relevant even in 6G. With DC, users can connect to multiple access networks in the user plane, allowing the same user to receive data from Long Term Evolution (LTE) and NR, for example. However, this technology brings additional challenges to the network regarding its configurations, as it might reduce the system performance if not appropriately chosen. Thus, this work aims to conceive DC NR-LTE strategies that can extract the advantages of this technology to the 5G applications, particularly extended reality services (XR), that belong to the enhanced Mobile Broadband (eMBB) e Ultra-Reliable Low-Latency Commmunications (URLLC) use cases. The conceived strategies can work with a fixed or intelligent configuration (via machine learning). The latter has the advantages of being more flexible and easier to implement. Using a touristic scenario, we developed and tested the strategies in the MmWave module of the Network Software 3 (ns-3), allowing internet navigation and interaction with virtual content using LTE and/or NR mmWave connections. The results show that both strategies (fixed or via machine learning) have the potential to improve user satisfaction in the tested scenarios when compared to the situation when only one system is responsible for the user data planeDoctoral Thesis Aplicação de modelos de sequências quase periódicas em guias de onda ópticos(Universidade Federal do Rio Grande do Norte, 2023-12-22) Bezerra Segundo, Marcos Tulio Antunes; Silva, José Patrocínio da; https://orcid.org/0000-0003-1843-7879; http://lattes.cnpq.br/5753289728835624; 09205304433; Souza Júnior, Vicente Angelo de; Mendonça, Laercio Martins de; https://orcid.org/0000-0001-7861-3761; http://lattes.cnpq.br/1853488415531363; Andrade, Humberto Dionisio de; https://orcid.org/0000-0003-0746-7183; http://lattes.cnpq.br/1253785596446469; Araújo, Magno Medeiros de; https://orcid.org/0000-0003-1520-0569; http://lattes.cnpq.br/0572539368449081One of the most traditional segmentation models applied in optical waveguides is the Bragg Grating, also known as Fiber Bragg Grating (FBG), where the sequencing in the propagation region follows a periodic pattern. More recently, some models of quasiperiodic sequences have been applied in photonic crystals, especially considering devices with onedimensional stratifi cation. In this work, waveguides based on directing light through media with refractive index sequenced in the propagation direction are proposed. The core guiding model of these structures is based on quasiperiodic sequencing of the refractive index that forms the signal propagation region. In this context, wellknown optical fiber models are modified to fit the segmentation structures of the signalguiding regions. Core fracturing structures of waveguide models were investigated by applying quasiperiodic models such as Fibonacci, Thue Morse, Double Period, and Octonacci sequences with the aim of comparing their performance with guides using Bragg Grating as a segmentation strategy. For this study, COMSOL® software was used to simulate various types of segmentation. Transmission and reflection parameters at the interfaces between the different media making up the applied sequences were analyzed. The results obtained show similarities between the transmission response of the proposed guides and quasiphotonic crys tals they were based on, but with the addition of absorptance, a phenomenon not previously observed. Another factor observed in the results was the applicability of these segmented waveguides as thermal sensors, even showing better responses than their periodic counterparts.Doctoral Thesis Um novo método para sintonia de controladores PID não lineares sob restrições usando modelo Fuzzy Takagi-Sugeno(Universidade Federal do Rio Grande do Norte, 2023-06-26) Martins, Jose Kleiton Ewerton da Costa; Dórea, Carlos Eduardo Trabuco; Araújo, Fábio Meneghetti Ugulino de; https://orcid.org/0009-0002-5019-0140; http://lattes.cnpq.br/5473196176458886; https://orcid.org/0000-0002-3999-2874; http://lattes.cnpq.br/0143490577842914; https://orcid.org/0000-0001-5968-2729; http://lattes.cnpq.br/1867570379475142; Dantas , André Felipe Oliveira de Azevedo; https://orcid.org/0000-0002-4172-3913; http://lattes.cnpq.br/8684342148910073; Bessa , Wallace Moreira; https://orcid.org/0000-0002-0935-7730; http://lattes.cnpq.br/3256782908311485; Linhares ., Leandro Luttiane da Silva; http://lattes.cnpq.br/2692012987625830Most of the existing controllers in industries are from the PID family (Proportional-Integral-Derivative) developed for linear systems, although the processes are non-linear. Therefore, they present a significant loss of performance when operating outside the operating point for which they were designed. An alternative controller is the so-called PDC (Distributed Parallel Compensator) which, based on a Fuzzy Takagi-Sugeno model, results in a non-linear controller. The Fuzzy Takagi-Sugeno model is intrinsically non-linear, due to the membership functions that make up its structure. Thus, this model can represent nonlinear systems in such a way that, from the physical model of the system, it is possible to obtain a Fuzzy Takagi-Sugeno model that represents it exactly, which contributes to obtaining the PDC. The Fuzzy Takagi-Sugeno model can be represented by the composition of local models. In the PDC controller methodology, local controllers are designed, which can be a PID, for each local model, thus presenting the same rules structure as the Fuzzy Takagi-Sugeno model, that is, the controller shares the same membership functions. Normally, the PDC stability guarantee considers a quadratic Lyapunov function as a candidate, thus allowing it to be tested for linear matrix inequalities (LMIs) that are solvable using efficient convex optimization algorithms. However, polyhedral Lyapunov functions have shown advantages over the quadratic function, especially with regard to satisfying constraints on state, input and output variables, showing their potential to be used to guarantee stability and performance of a PDC-controlled system. In view of this, this work proposes an optimization-based method for tuning Proportional-Integral (PI) controllers for nonlinear systems subject to constraints on the controlled variable and actuator saturation. Conditions are presented for a polyhedron contained in the set of constraints to be invariant with respect to a closed-loop system with a controller subject to saturation. These conditions are used in the formulation of a bilinear programming problem whose solution provides the controller parameters that satisfy the constraints and an associated invariant set. Throughout the development of the work, several variations of the main technique were explored and their advantages and disadvantages were shown through the results. The results are presented in numerical examples. Starting with linear systems and testing I-P controllers and a traditional PI controller with a filter for the reference, we explore case studies with: saturation allowance, state constraints, time-delay, high order systems, servo and regulator problem. Then we explore nonlinear systems testing systems with and without the affine term and controllers with and without the feedfoward term, exploring case studies with: saturation permission, state constraints and servo problem. The results show that the developed method obtains a tuning for the controller that does not violate any state constraint and allows saturation, thus illustrating its efficiencyDoctoral Thesis High-level subsumption-based control architecture for sail-powered autonomous surface vehicles(Universidade Federal do Rio Grande do Norte, 2023-08-04) Negreiros, Álvaro Pinto Fernandes de; Gonçalves, Luiz Marcos Garcia; https://orcid.org/0000-0002-7735-5630; http://lattes.cnpq.br/1562357566810393; https://orcid.org/0000-0001-8162-7144; http://lattes.cnpq.br/1359449865610489; Vasconcelos, Eduardo Charles; http://lattes.cnpq.br/9622415604083776; Santos, Davi Henrique dos; https://orcid.org/0000-0002-4286-235X; http://lattes.cnpq.br/5492310878477548; https://orcid.org/0000-0001-5650-1718; http://lattes.cnpq.br/4791589931798048; Silva, João Moreno Vilas Boas de Souza; https://orcid.org/0000-0002-3200-6605; http://lattes.cnpq.br/8722766030280997; Alsina, Pablo Javier; https://orcid.org/0000-0002-2882-5237; http://lattes.cnpq.br/3653597363789712This work proposes a high-level control architecture for an Autonomous Surface Vessel (ASV) designed to overcome the challenges associated with executing missions under varying weather conditions and with energy autonomy. The project is built on the understanding that while a number of low-level control techniques are readily available as open source, there remains a need for a high-level control architecture. This architecture would facilitate the creation of a resilient, versatile sailing vessel capable of handling any mission without requiring the user to master navigation specifics, naval procedures, or corner cases. The proposed solution involves developing a control architecture inspired by sub- sumption, and centered on hierarchical behaviors. This structure incorporates a variety of specialized behaviors adapted to different contexts, each of which is established using reinforcement learning techniques (PPO). A combination of Gazebo simulation environment with the ROS framework for training was used to validate the proposed architecture. This simulation enables the digital replication of the vessel’s behaviors, which simplifies the implementation process and mitigates the challenges and costs tied to real-world sailing operations. The simulation results of this study indicate that the high-level control architecture of the virtual sailing vessel was successful in passing both perimeter scanning and long-distance tests. This suggests that the ASV is equipped to navigate the several situations it might encounter in real-world missionsDoctoral Thesis Observer-based output feedback control using invariant polyhedral sets for fuzzy T-S models under constraints(Universidade Federal do Rio Grande do Norte, 2023-08-07) Isidório, Isaac Dantas; Dorea, Carlos Eduardo Trabuco; https://orcid.org/0000-0002-3999-2874; http://lattes.cnpq.br/0143490577842914; https://orcid.org/0000-0003-2230-9749; http://lattes.cnpq.br/0096743305286980; Castelan Neto, Eugênio de Bona; https://orcid.org/0000-0002-8079-3738; http://lattes.cnpq.br/5680858790581538; Araújo, Fábio Meneghetti Ugulino de; https://orcid.org/0009-0002-5019-0140; http://lattes.cnpq.br/5473196176458886; Queiroz, Kurios Iuri Pinheiro de Melo; https://orcid.org/0000-0002-6085-613X; http://lattes.cnpq.br/7489022506091803; Oliveira, Vilma Alves de; https://orcid.org/0000-0001-6078-9515; http://lattes.cnpq.br/6430129533142328In this work, is proposed a numerical method for the computation of state observer-based output feedback controllers for fuzzy Takagi-Sugeno (T-S) systems subject to con-straints based on invariant set theory. In this regard, Positively Invariant (PI) polyhedral sets are used to ensure that state and input control constraints are satisfied at all times. Sufficient conditions are established for a polyhedron defined in the augmented state- space (state + estimation error) to be PI. The problem of tracking a constant reference signal is also considered, for which the concept of robust positive invariance is used along with a stabilizing Integral-Proportional (I-P) controller. Sufficient conditions are estab- lished for a polyhedron defined in the augmented state-space (state + estimation error + tracking error integral state) to be PI in the presence of a constant reference signal, which can be interpreted as a bounded disturbance. From the invariance conditions, a bilinear optimization problem is formulated to simultaneously compute the controller’s gains and the positively invariant polyhedron, guaranteeing the satisfaction of the constraints. The two types of observer found in the literature of fuzzy T-S systems are considered: the first considers the membership functions dependent only on the system output; the sec- ond, in turn, refers to the general case, where these functions can be associated with any state variables. In the simplest case, although the membership functions depend only on the output, the estimated state feedback results, in general, in controllers with better per- formance and with larger sets of admissible states associated with them than the output static feedback control. For the general case, as membership functions depend on non-accessible states, an estimation mechanism is needed to calculate these variables. In both cases, this role is played by the fuzzy T-S observerDoctoral Thesis Projeto e análise de um biosensor plasmônico para medição de glicerol em aplicações point-of-care(Universidade Federal do Rio Grande do Norte, 2023-07-27) Araújo, Magno Medeiros de; Silva, José Patrocínio da; https://orcid.org/0000-0003-1843-7879; http://lattes.cnpq.br/5753289728835624; https://orcid.org/0000-0003-1520-0569; http://lattes.cnpq.br/0572539368449081; Mendonça, Laercio Martins de; https://orcid.org/0000-0001-7861-3761; http://lattes.cnpq.br/1853488415531363; Silva Neto, Valdemir Praxedes da; https://orcid.org/0000-0003-3867-3297; http://lattes.cnpq.br/4160231554601828; Fonseca, Iguatemi Eduardo da; https://orcid.org/0000-0002-5457-7601; http://lattes.cnpq.br/4519016123693631; Esquerre, Vitaly Félix Rodriguez; https://orcid.org/0000-0003-3884-7162; http://lattes.cnpq.br/9324813375750858The manufacturing processes advancement in silicon wafers has enabled integration between electronics and photonics. Data will no longer be processed with electrons for the technology sectors but with photons, providing higher processing and transmission rates. In this context, the health and well-being sectors, for example, will have new equipment, allowing remote and individual monitoring and diagnosis, enhancing the prevention and treatment of diseases. Thus, this research proposes a photonic device with graphene applied and a surface plasmon resonance structure for sensing applications. Initially, they are concepts related to photonic devices and their different applications. Photonic crystals, plasmonic devices, graphene, and their use in optical guides are also presented. Then, the methodology used in the research development is explained, dealing with modeling and simulation. The results are presented and analyzed as the structure’s spectral behavior for different glycerol concentrations, which reinforces the potential for point-of-care applications considering its compactness and simplicity of construction