Doutorado em Engenharia Elétrica

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A brain-computer interface architecture based on motor mental tasks and music imagery
(Universidade Federal do Espírito Santo, 2013-08-30) Benevides, Alessandro Botti; Bastos Filho, Teodiano Freire; Sarcinelli Filho, Mário; Ferreira, André; Frizera Neto, Anselmo; Conci, Aura; Tierra Criollo, Carlos Julio
This present research proposes a Brain-Computer Interface (BCI) architecture adapted to motor mental tasks and music imagery. For that purpose the statistical properties of the electroencephalographic signal (EEG) were studied, such as its probability distribution function, stationarity, correlation and signal-to-noise ratio (SNR), in order to obtain a minimal empirical and well-founded parameter system for online classification. Stationarity tests were used to estimate the length of the time windows and a minimum length of 1.28 s was obtained. Four algorithms for artifact reduction were tested: threshold analysis, EEG filtering and two Independent Component Analysis (ICA) algorithms. This analysis concluded that the algorithm fastICA is suitable for online artifact removal. The feature extraction used the Power Spectral Density (PSD) and three methods were tested for automatic selection of features in order to have a training step independent of the mental task paradigm, with the best performance obtained with the Kullback-Leibler symmetric divergence method. For the classification, the Linear Discriminant Analysis (LDA) was used and a step of reclassification is suggested. A study of four motor mental tasks and a non-motor related mental task is performed by comparing their periodograms, Event-Related desynchronization/synchronization (ERD/ERS) and SNR. The mental tasks are the imagination of either movement of right and left hands, both feet, rotation of a cube and sound imagery. The EEG SNR was estimated by a comparison with the correlation between the ongoing average and the final ERD/ERS curve, in which we concluded that the mental task of sound imagery would need approximately five times more epochs than the motor-related mental tasks. The ERD/ERS could be measured even for frequencies near 100 Hz, but in absolute amplitudes, the energy variation at 100 Hz was one thousand times smaller than for 10 Hz, which implies that there is a small probability of online detection for BCI applications in high frequency. Thus, most of the usable information for online processing and BCIs corresponds to the α/µ band (low frequency). Finally, the ERD/ERS scalp maps show that the main difference between the sound imagery task and the motor-related mentaltasks is the absence of ERD at the µ band, in the central electrodes, and the presence of ERD at the αband in the temporal and lateral-frontal electrodes, which correspond tothe auditory cortex, the Wernickes area and the Brocas area.
A Estabilidade Transiente de Sistemas Elétricos na Presença de Geradores Síncronos Virtuais: Metodologias de Análise e Controles Adaptativos
(Universidade Federal do Espírito Santo, 2020-11-16) Carletti, Daniel; Encarnacao, Lucas Frizera; https://orcid.org/0000000261627697; http://lattes.cnpq.br/5578918284508758; https://orcid.org/000000027903200X; http://lattes.cnpq.br/; Simonetti, Domingos Savio Lyrio; https://orcid.org/0000000159202932; http://lattes.cnpq.br/1107005171102255; Aredes, Mauricio; https://orcid.org/; http://lattes.cnpq.br/; Medina, Augusto Cesar Rueda; https://orcid.org/0000000242913153; http://lattes.cnpq.br/7397584412509839; Santos, Walbermark Marques dos; https://orcid.org/0000000298716028; http://lattes.cnpq.br/5558697161842579
The dynamic stability assessment of electrical power systems is an activity of utmost importance to guarantee the energy delivery to consumers in a safe and stable way. The study of transient stability, which deals with maintaining the generation plants i
A fairness-focused spectrum assignment algorithm for elastic optical networks
(Universidade Federal do Espírito Santo, 2016-09-27) Tessinari, Rodrigo Stange; Garcia, Anilton Salles; Waldman, Hélio; Martins, Joberto Sérgio Barbosa; Resendo, Leandro Colombi; Segatto, Marcelo Eduardo Vieira; Paiva, Marcia Helena Moreira
In the past few years, Elastic Optical Networking (EON) emerged as the next generation core network technology, intended to surpass Wavelength-Division Multiplexing (WDM) weaknesses and limitations. WDM is the most successful and widely used technology in the backbone of the optical networks. However, in recent years Internet traffic in the core network has been doubling almost every two years, and predictions indicate that it will continue to exhibit exponential growth due to emerging applications such as high-definition and real-time video communications. To keep pace with the always greater demand for bandwidth, EON relies on Optical Orthogonal Frequency Division Multiplexing (OOFDM) and advanced modulation technologies which enhance spectral efficiency and flexibility. OOFDM allows the aggregation of multiple sub-carriers to form super-channels, thus changing the paradigm of the network from fixed-size WDM channels to variable-sized EON channels that can reduce spectrum waste up to 60%. EON presents several other benefits such as high spectral and energy efficiency and flexible bandwidth adaptation over time. Despite all benefits, no technology is perfect, and the added EON efficiency and flexibility comes at the price of increased complexity and new problems, such as spectrum fragmentation and service unfairness. A considerable amount of work has been done on both fragmentation and unfairness problems, introducing a broad range of solutions, which raises the following question: "how to compare existent solutions and how to identify which one is better suited for the required scenario?" In this context, it is presented the first contribution of this Doctoral Thesis, ElasticO++, an Elastic Optical Network Simulation Framework for OMNeT++. ElasticO++ is a framework created to enable testing a whole range of routing, modulation, spectrum assignment, defragmentation algorithms, parameters, and topologies. At present, the proposed framework is the first software available capable of working with fragmentation and defragmentation in dynamic network scenarios. The flexibility offered on the proposed tool allows both academia and industry to develop new algorithms and techniques for Elastic Optical Networks. The second contribution of this Doctoral Thesis is the Zone-Based Spectrum Assignment Algorithm. The proposed algorithm is an attempt to solve the unfairness and fragmentation problems, taking advantage of the spectrum management concept. In this Doctoral Thesis, it is presented two versions of the technique: the static version and the dynamic version. The static version is intended to be used in cases where the information regarding the nature of the network traffic is known beforehand, whereas the dynamic version was developed as a solution in cases in which absolutely no information is known.
A Human-Machine Interface Based on Eye Tracking for Controlling and Monitoring a Smart Home Using the Internet of Things
(Universidade Federal do Espírito Santo, 2019-02-20) Bissoli, Alexandre Luís Cardoso; Encarnação, Lucas Frizera; Bastos Filho, Teodiano Freire; Adams, Kimberly; Krishnan, Sridhar; Villa Parra, Ana Cecilia; Ferreira, André
People with severe disabilities may have difficulties when interacting with their home devices, due to the limitations inherent to their disability. Simple home activities may be even impossible for this group of people. Although many works have been devoted to proposing new assistive technologies to improve the lives of people with disabilities, some studies have found that the abandonment of such technologies is quite high. In this sense, this work presents a new and useful assistive system based on eye tracking for controlling and monitoring a smart home based on internet of things, which was developed following concepts of user-centered design and usability. With this system, a person with severe disabilities was able to control everyday equipment of her residence, such as lamps, television, fan and radio. In addition, her caregiver was able to monitor remotely, by internet, her use of the system in real time. Additionally, the user interface developed here has some functionalities that allowed improving the usability of the system as a whole. The experiments were divided into two steps. In the first step, the assistive system was assembled in an actual home, where tests were conducted with 29 participants without disabilities (group of able-bodied participants). In the second step, the system was tested with online monitoring, for seven days, by a person with severe disability (end-user), in her own home, not only to increase convenience and comfort, but also so that the system could be tested where it would in fact be used. At the end of both steps, all the participants answered the SUS questionnaire, which showed that both the group of able-bodied participants and the person with severe disabilities evaluated the assistive system with a mean of 89.9 and 92.5, respectively.Keywords:Human-Machine Interface (HMI); Human-Computer Interaction (HCI); Smart Home; Eye Tracking; Assistive Technology; Usability Evaluation; User-Centered Design (UCD); Home Automation; Internet of Things (IoT).
A methodology for cloud robotics implementation based on open-source software : from human-robot interaction to autonomous applications
(Universidade Federal do Espírito Santo, 2020-11-26) Mello, Ricardo Carminati de; Neto, Anselmo Frizera; https://orcid.org/0000000206873967; http://lattes.cnpq.br/8928890008799265; https://orcid.org/0000000304204273; http://lattes.cnpq.br/; Ribeiro, Moises Renato Nunes; https://orcid.org/0000000291492391; http://lattes.cnpq.br/1005553714687743; Siqueira, Adriano Almeida Goncalves; https://orcid.org/; http://lattes.cnpq.br/; Garcia, Carlos Andres Cifuentes; https://orcid.org/; http://lattes.cnpq.br/; Diaz, Camilo Arturo Rodriguez; https://orcid.org/0000000196575076; http://lattes.cnpq.br/2410092083336272; Lima, Eduardo Rocon de; http://lattes.cnpq.br/6623746131086816
The advent of the cloud robotics paradigm has the potential to unleash a whole new generation of smart robotic devices by allowing robots to communicate with each other and with remote computing platforms to share experiences, sensor data, and to offload
A novel approach of independent brain-computer interface based on SSVEP
(Universidade Federal do Espírito Santo, 2016-09-01) Tello, Richard Junior Manuel Godinez; Ferreira, André; Müller, Sandra Mara Torres; Bastos Filho, Teodiano Freire; Ciarelli, Patrick Marques; Lima, Eduardo Roncon de; Sá, Antônio Maurício Miranda de
Over the past ten years, Brain Computer Interfaces (BCIs) based on Steady- State Visual Evoked Potentials (SSVEP) have attracted the attention of many researchers due to the promissory results and the high accuracy rates achieved. This type of BCI provides to people with severe neuromotor difficulties the possibility to communicate with the world around them using visual attention modulation to blinking lights at a given frequency. This thesis aiming at developing a new approach of Independent BCI, in which users are not required to perform neuromuscular tasks to select visual targets, a feature that distinguishes it from traditional SSVEP-BCIs. Thus, people with severe motor disabilities as Amyotrophic Lateral Sclerosis (ALS) have a new alternative channel to communicate with the world around them using brain signals. Several contributions were done in this thesis, such as: improvement of the feature extractor called Multivariate Synchronization Index (MSI) for detecting evoked potentials; development of a new method for detecting evoked potentials through correlating multidimensional models (tensors); a first study on the influence of colored stimuli in SSVEPs detection using LEDs; the development of the concept of Compressive sensing applied to SSVEPs; and, finally, the development of a novel independent BCI under an approach named Figure-Ground Perception (FGP)
A novel cascaded multilevel converter topology based on three-phase cells
(Universidade Federal do Espírito Santo, 2021-08-24) Camargo, Renner Sartorio; Encarnacao, Lucas Frizera; https://orcid.org/0000000261627697; http://lattes.cnpq.br/5578918284508758; https://orcid.org/; http://lattes.cnpq.br/; Rolim, Luis Guilherme Barbosa; https://orcid.org/; http://lattes.cnpq.br/; Simonetti, Domingos Savio Lyrio; https://orcid.org/0000000159202932; http://lattes.cnpq.br/1107005171102255; Aredes, Mauricio; https://orcid.org/; http://lattes.cnpq.br/; Nunes, Weder Totola; Santos, Walbermark Marques dos; https://orcid.org/0000000298716028; http://lattes.cnpq.br/5558697161842579; Peña, Emilio José Bueno
Due to the structural characteristics of modern electrical grids, composed mainly of an energy matrix that is very diverse and sparse, and by electrical loads that demand high power levels, maintaining electrical energy within the quality standards define
A novel stimulation paradigm for a brain-computer interface based on SSVEP
(Universidade Federal do Espírito Santo, 2015-11-30) Atencio, Anibal Cotrina; Ferreira, André; Bastos Filho,Teodiano Freire; Frizera Neto, Anselmo; Sarcinelli Filho, Mario; Krohling, Renato Antônio; Sá, Antonio Mauricio Ferreira Leite Miranda de
Brain-computer interfaces (BCIs) are systems that provide a direct connection between users’ brain signals and a computer, generating an alternative channel of communication that does not involve the traditional way as muscles and nerves. They help to restore or replace useful functions of people with paralysis. For instance, BCI systems based on SSVEP (SSVEP-BCI) present a set of stimuli flickering at different frequencies to the users, detect which stimulus is being gazed and associate this information to commands that can be used to control a robotic wheelchair, an exoskeleton, or a speller. Nowadays, SSVEP-BCIs are being widely used due to the high SNR of their response that is achieved when the target stimulus is brought to the center of the user’s field of view. Paradoxically, it is their main disadvantage because bringing a stimulus to the center of the field of view demands muscular activity making them not suitably for paralyzed people who cannot control their head, neck and/or eyeball movements for redirecting their gaze. In optical systems, the range of distance near the point of focus where objects are perceived sharp is referred as Depth-of-field; objects outside this region are defocused and blurred. The mechanism of the visual system that adjusts the eye focal length for focusing does not demand neck, head and/or eyeball movements. Furthermore, ophthalmology studies state that the amplitude and the latency of visual evoked potentials are affected by defocusing. In this context, this Thesis proposes a novel SSVEP-BCI paradigm, in which two stimuli are presented together in the center of the user’s field of view but at different distances from him, ensuring that if one stimulus is focused on, the other one is non-focused, and vice versa; with the aim of providing an alternative way of sending commands through a stimuli selection by a focusing mechanism. In this sense, first, a model of VEP generation for two stimuli is introduced and the hypothesis that distinguishable SSVEP can be elicited by the focused stimulus, regardless of the non-focused stimulus is also present, is tested by employing the SFT-based ORD. Next, a demodulation method based in LPF and HPF is proposed for the case in that two stimuli are present in the field of view; and spatial-temporal retinal response for flickering stimuli is described by using PSF and NPSF functions. Finally, CCA, PSDA, LASSO with EEG signals re-referenced at Pz and CAR are employed to detect the SSVEP pattern. Accuracy rate, Kappa coefficient, AUC, and ITR are used to evaluate the detection performance. As a result of the hypothesis test, the absence of evoked potentials due to a focused stimulus, when a non-focused stimulus is also present was rejected in most of the cases. In SSVEP detection experiments, an average accuracy rate of 0.93 was achieved for a time window of 7s and for eight healthy subjects who were asked to focus on just one stimulus at a time.
A socially assistive robot as a therapeutic tool for applied behavior analysis therapy in children with autism spectrum disorder through dynamically modulated serious games
(Universidade Federal do Espírito Santo, 2024-10-07) Freitas, Éberte Valter da Silva; Bastos Filho, Teodiano Freire; https://orcid.org/0000-0002-1185-2773; Caldeira, Eliete Maria; Cuadros, Marco Antonio de Souza Leite; Valadão, Carlos Torturella; Vasquez, Luiz Fernando Guerrero
This work presents the programming/adaptation of the Socially Assistive Robot (SAR) called Mobile Autonomous Robot for Interaction with Autistics and Trisomy 21 (MARIA T21) to be able to carry out interventions, according to the Applied Behavior Analysis (ABA) therapy, applied to Children with Autism Spectrum Disorder (ASD), Serious Games (SGs), which are projected by MARIA T21, with difficulty modulation dynamics, are used as part of this therapy thus creating a motivating and facilitating effect for children and therapists. The SGs were developed in Unity 3D, using C Sharp language (C#), and modulated according to the child’s performance, eye attention level, and user’s facial emotion, being integrated into the robot through the Robot Operating System (ROS). The child-Robot Interaction (CRI) protocol followed in this research was carried out in a child’s psychotherapy room at the APAE (Association of Parents and Friends of Excepcional People for the acronym in Portuguese) of Vitoria in Espirito Santo state (Brazil), which was instrumented with four video cameras and supervised by a group of researchers. The sample consisted of 18 children with a conclusive diagnosis of ASD, 3 girls and 15 boys, aged 5 to 9 years and presence of stereotyped movements of eyes and/or hands and/or feet. The experiments were separated into three modules for which SGs or specific therapeutic dynamics were applied, namely: Cognitive Module, Physical Module and Functional Module. The first one brings together the games and dynamics applied by MARIA T21 focused on the development and improvement of cognitive learning skills, whereas the physical module brings SGs for motor evaluation and correction, that can be used for physical and postural strengthening by a physiotherapist. Finally, the functional module has applications of SGs and Occupational Therapy dynamics in order to work on the so-called Activities of Daily Living (ADLs) and encourage autonomy in those assisted. In addition to the data recorded by MARIA T21, two evaluation scales– Pediatric Evaluation of Disability Inventory Computer Adaptive Test (PEDI-CAT) and System Usability Scale (SUS)– were applied for each module, and another for the degree of acceptance of the robot in therapy by the child. The results obtained so far enable the use MARIA T21 as an ABA therapeutic tool. In addition, the SGs are capable of dynamically modulating their difficulty, providing greater user adherence and continued attention in the optimal learning zone of the ABA bibliography while carrying out the activities. The technology embedded in the robot has also enabled the identification and quantification of characteristics and parameters, such as the presence and recurrence of stereotypies and postural dysregulations, placing the robot as an innovative and promising tool to assist health professionals in the early diagnosis, conduction and follow-up of therapies.
Adaptive x-ray tomography image reconstruction
(Universidade Federal do Espírito Santo, 2019-08-08) Wirtti, Tiago Tadeu; Salles, Evandro Ottoni Teatini; https://orcid.org/0000000282873045; http://lattes.cnpq.br/5893731382102675; https://orcid.org/ 0000-0003-0731-6326 ; http://lattes.cnpq.br/3414259707581590; Filho, Mario Sarcinelli; https://orcid.org/0000000276968996; http://lattes.cnpq.br/3459331011913021; Andreao, Rodrigo Varejao; https://orcid.org/0000000268005700; http://lattes.cnpq.br/5589662366089944; Pinto, Luiz Alberto; https://orcid.org/; http://lattes.cnpq.br/; Kim, Hae Yong
In X-ray tomography image reconstruction, one of the most successful approaches involves a statistical modeling with l2 norm function for fidelity regularized by a functional with lp norm, 1 < p < 2, with p ∈ R. Among them stands out, for its results and computational performance, a technique that reconstructs an image by alternating minimization for (i) solving the l2 norm fidelity term by Simultaneous Algebraic Reconstruction Technique (SART) and (ii) constraining the regularization term, defined by a Discrete Gradient Transform (DGT) sparse transformation, using Total Variation (TV) minimization. This work proposes an improvement to the reconstruction process by adding a Bilateral Edge preserving (BEP) regularization term to the objective function, resulting in a three-step method. BEP is a noise reduction framework and has the purpose of adaptively eliminating noise in the initial phase of reconstruction process. BEP improves optimization of the f idelity term and, as a consequence, improves the result of DGT minimization by total variation. Regular dosage experiments shown favorable results compared to classical methods, such as Filtred Backprojection (FBP), and more modern ones, such as l2 norm optimization by using SART, and the l2 norm SART solution regularized by l1 norm TV optimization of DGT (SART+DGT), especially with the Structural Similarity Index Measurement (SSIM) metric. Although not so prominent in the case of regular dosing reconstruction, Peak Signal-to-noise Ratio (PSNR) results are consistent with those of SSIM. For low dosage, the quality of the reconstruction worsens for all methods, but is markedly lower for the FBP and SART methods. In this context of limited number of projections (low dosage), the reconstructions with the method here proposed presents better defined edges, in addition to better contrast and less artifacts in surfaces of regular intensity (low intensity variation). These results are generally obtained with a smaller number of steps compared to the other iterative methods implemented in this Thesis. However, this behavior (of the proposed method) depends on the parameterization of the lp norm, 1 ≤ p ≤ 2, used in the BEP stage. It is experimentally shown that by varying the norm during the reconstruction process it is possible to keep the proposed method stable over a sufficiently large number of iteractions. It is also graphically shown that the method converge, meaning that the SSIM and PSNR metrics can be continuously improved by a sufficiently large number of iteractions. For reconstructions with a limited number of projections (low-dose reconstruction), the proposed method can achieve higher PSNR and SSIM results because it can better control the noise in the initial processing phase.
Admittance control of a robotic knee orthosis based on motion intention through sEMG of trunk muscles
(Universidade Federal do Espírito Santo, 2017-12-04) Parra, Ana Cecilia Villa; Frizera Neto, Anselmo; Bastos Filho, Teodiano Freire; Ferreira, Andre; Caldeira, Eliete Maria de Oliveira; Rocon, Eduardo; Bó, Antonio Padilha Lanari
The population that requires devices for motion improvement has increased considerably, due to aging and neurological impairments. Robotic devices, such as robotic orthosis, have greatly advanced with the objective of improving both the mobility and quality of life of people. Clinical researches remark that these devices, working in constant interaction with the neuromuscular and skeletal human system, improves functional compensation and rehabilitation. Hence, the users become an active part of the training/rehabilitation, facilitating their involvement and improving their neural plasticity. For this purpose, control approaches based on motion intention have been presented as a novel control framework for robotic devices. This work presents the development of a novel robotic knee exoskeleton controlled by motion intention based on sEMG, which uses admittance modulation to assist people with reduced mobility and improve their locomotion. For recognition of the lower-limb motion intention, sEMG signals from trunk are used, which implies a new approach to control robotic assistive devices. The control system developed here includes a stage for human-motion intention recognition (HMIR) system, which is based on techniques to classify motion classes related to knee joint. The motion classes that are taken into account are: stand-up, sit-down, knee flexionextension, walking, rest in stand-up position and rest sit-down position. For translation of the users intention to a desired state for the robotic knee exoskeleton, the system includes a finite state machine, in addition to admittance, velocity and trajectory controllers, which has also the function of stopping the movement according to the users intention. This work also proposes a method for on-line knee impedance modulation, which generates variable gains through the gait cycle for stance control during gait. The proposed HMIR system showed, in off-line analysis, an accuracy between 76% to 83% to recognize motion intention of lower-limb muscles, and 71% to 77% for trunk. Experimental on-line results of the controller showed that the admittance controller proposed here offers knee support in 50% of the gait cycle, and assists correctly the motion classes. A positive effect of the controller on users regarding safety during gait was also found, with a score of 4 in a scale of 5. Thus the robotic knee exoskeleton introduced here is an alternative method to empower knee movements using motion intention based on sEMG signals from lower limb and trunk muscles.
Alternativas de topologias retificadoras para aerogeradores síncronos a ímã permanente de baixa potência
(Universidade Federal do Espírito Santo, 2015-12-11) Freitas, Tiara Rodrigues Smarssaro de; Menegáz, Paulo José Mello; Simonetti, Domingos Sávio Lyrio; Antunes, Fernando Luiz Marcelo; Fardin, Jussara Farias; Encarnação, Lucas Frizera; Pinto Filho, Wilson Aragão Correia
Two controlled rectifier topologies applied to low power wind energy conversion system with permanent magnet synchronous generator are presented. For low power or stand-alone operation systems, where the energy from wind generation is a significant part of the total power system, generators and converters have the role of maintaining the grid’s voltage and frequency constant, despite the fluctuations of the wind turbine. In variable speed permanent magnet synchronous generator (PMSG), the preferred solution has been a conversion on two stages: AC-DC-AC. Several converter topologies have been explored, but kind of this conversion has many controlled elements, most of them with 6 controlled switches in AC-DC conversion, making it difficult and more expensive its control; each new topology introduces new aspects and always looking for a converter that best suits the system with minimally influence to the quality of power generation. The topologies presented in the literature are effective for the high power levels, but when it comes to systems with lower power levels, simpler converters (single or three controlled switches) can serve the purpose of rectification with a lower cost and without the conversion quality been reduced. The contribution of this thesis is the development of a new SEPIC rectifier topology using three controlled switches, and the analysis and new application of an existing resonant buck topology, with a single controlled switch, to wind energy system. They are simpler rectifying solutions, applied to low power wind generation based on permanent magnet synchronous generator, offering simplicity and control facility. The converter’s project, the equations that define them, the simulation and experimental results for each converter are presented. It was verified that both topologies could achieve high power-factor and low harmonic distortion employing only one single gate signal, on a wide range of wind speed with no current’s generator closed loop control.
Amplificadores óticos a fibra sob um ambiente dinâmico
(Universidade Federal do Espírito Santo, 2006-08-18) Freitas, Márcio; Calmon, Luiz de Calazans; Barbero, Andrés Pablo López; Ribeiro, Moisés Renato Nunes; Pontes,Maria José; Segatto, Marcelo Eduardo Vieira; Frasson, Antônio Manoel Ferreira
The recent advance in WDM technologies with the ability of add, drop and in effect construct wavelength-switched and wavelength-routed networks has brought a new dynamic-reconfigurable WDM network. This dynamic environment brings, besides the already well-known transmission impairments (such as chromatic dispersion, nonlinear effects, PMD, ASE, etc), a new set of impairments related to the add-drop possibilities that could severely degrade the system performance. Furthermore, the development of new optical amplifiers that could reach high output power values has also brought an increasing impact of nonlinear effects in the signal propagation at different applications. The optical fiber amplifiers presented in the study are the erbium-doped fiber, the ytterbiumdoped fiber amplifier, the erbium-ytterbium codoped fiber amplifier and the Raman fiber amplifiers. For this study, appropriate numeric models for each amplifier were implemented. This work investigates by numerical simulation how the optical fiber amplifiers and consequently the system performance are affected by the dynamic-reconfigurable traffic. Some contributions about the study of the power transient evolution generated by the optical amplifiers in different transmission bandwidths, under different amplifier configurations and in different applications are presented. It is also presented a contribution for the optimization of control methods to minimize the power transients generated by the optical amplifiers due the add-drop of channels in the system. Moreover, this work also analyzes the impact of high powers generated in the amplification process, and presents some contributions for the study of the nonlinear effects in the signals propagation through the amplifier.
Análise de vulnerabilidade em smart grid utilizando métricas de centralidade em grafos
(Universidade Federal do Espírito Santo, 2019-02-18) Coelho, Elizandra Pereira Roque; Segatto, Marcelo Eduardo Vieira; https://orcid.org/000000034083992X; http://lattes.cnpq.br/2379169013108798; https://orcid.org/0000-0003-3713-3563; http://lattes.cnpq.br/2204128834479828; Medina, Augusto Cesar Rueda; https://orcid.org/0000000242913153; http://lattes.cnpq.br/7397584412509839; Santos, Walbermark Marques dos; https://orcid.org/0000000298716028; http://lattes.cnpq.br/5558697161842579; Freitas Filho, Walmir de ; https://orcid.org/0000-0002-2042-6741; http://lattes.cnpq.br/0356536062945134; Lourenco, Elizete Maria
Contingency analysis of power systems represents a critical part of the security monitoring required to maintain the reliability of the power system and identify areas of operational vulnerability of the power grid. In general, the traditional methods of N − 1 contingency analysis simulate some interruptions, due to the high computational costs involved. Thus, they may fail to identify some critical contingencies that can lead to cascading failures. Considering also that with the advances of the technologies inserted to the system in order to provide Smart Grids, it is realized that the complexity of the energy system is constantly increasing. Such increased complexity requires new methods that permit the analysis of multiple contingencies be developed. The present work proposes a new exhaustive search approach for simple and multiple contingency analysis in electric power transmission systems. Such an approach is based on centrality measures of network. First, the proposed method evaluates all possible N − 1 transmission line interruptions in a very short computational time, and only requires topological information from the network. The results are presented for two electric power systems: ITAIPU 11 bus and IEEE 39 bus. The methodology applied to the analysis of multiple contingencies is evaluated for the ITAIPU 11, IEEE 39, IEEE 57 IEEE 118 systems. Finally, in order to cover the applicability of the method to networks with more complex interconnections, a proposal based on algorithm of Di erential Evolution and centrality measures. The proposed methodology is evaluated for the aforementioned systems, with the addition of the Polish system 2383 bus. Comparisons between the results obtained by the proposed method and the traditional ones are performed. The proposed method works even when traditional system measurements are not available
Análise, projeto e implementação de um inversor trifásico baseado no conversor CC-CC Buck-Boost
(Universidade Federal do Espírito Santo, 2020-08-27) Melo, Vinicius Secchin de; Santos, Walbermark Marques dos; https://orcid.org/0000000298716028; http://lattes.cnpq.br/5558697161842579; https://orcid.org/; http://lattes.cnpq.br/; Rech, Cassiano; https://orcid.org/; http://lattes.cnpq.br/; Vieira, Jose Luiz de Freitas; https://orcid.org/; http://lattes.cnpq.br/; Martins, Denizar Cruz; https://orcid.org/; http://lattes.cnpq.br/; Simonetti, Domingos Savio Lyrio; https://orcid.org/0000000159202932; http://lattes.cnpq.br/1107005171102255; Fardin, Jussara Farias; https://orcid.org/000000034785556X; http://lattes.cnpq.br/1912113095988528; Sousa, Gilberto Costa Drumond
In the current power scenario it has becoming increasingly important to use alternative energy sources in order to contribute to the electrical system. Research and improvement of new power inverters topologies are essential to ensure the viability of ren
AProSiMA - ambiente de resolução cooperativa de problemas baseado em simulação multiagente
(Universidade Federal do Espírito Santo, 2007-12-21) Azevedo, Lívia Lopes; Menezes, Crediné Silva de; Cury, Davidson; Boeres, Maria Claudia Silva; Tavares, Orivaldo de Lira; Castro Junior, Alberto Nogueira de
The complex systems studies has caught researchers ́ attention in several knowledge areas lately, because of increasing interest in the way of systems ́ organization. Examples of complex systems are presented in a variety of situation which we live and they have been largely studied through model of multiagent simulation. However, there is a gap between environments for complex systems studies and their users. This thesis shows a proposal to an environment named AProSiMA, which allows no experts users in program planning, build up their own model of multiagent simulation. The environment still presents like a general proposal to propose a process of cooperative problem solving. By the way it ́s available to the users: acess to information recover and mechanisms to locate experts who may be geographically distributed and invite them to work in a cooperative system looking for a solution to the problem, shared place to discuss and formalize the problems ́ resolution strategies; mechanisms to direct questions and answers to the experts, cooperated groups formation and communication mechanisms which may support up the cooperative work.
Back Lane Marking Registry: uma abordagem de localização e seguimento de caminho por veículos autônomos em via sinalizada
(Universidade Federal do Espírito Santo, 2017-11-23) Vivacqua, Rafael Peixoto Derenzi; Martins, Felipe Nascimento; Vassallo, Raquel Frizera; Wolf, Denis Fernando; Samatelo, Jorge Leonid Aching; Komati, Karin Satie; Amaral, Paulo Faria Santos
This thesis aimed to contribute with the development of autonomous driving technology. More specifically, the aim of this work was to design, build and test all the hardware and software needed to adapt a commercial vehicle so that it is able to successfully perform a predetermined transport mission repeatedly, as if it was a train traveling on a virtual railway. The issue of dynamic obstacles was not addressed in this research. Three approaches widely used in the literature were studied: (i) direct path tracking by detection of lane markings, (ii) global localization tracking (GNSS), and (iii) path tracking by lane marking maps. A prototype vehicle was built, respecting the low cost philosophy of the project, to carry out the experimental tests. The first two approaches served as the basis for the development of the final approach, based on visual track marker maps. This approach has produced the most positive results of the work and represents the greatest contribution of this thesis: the method called Back Lane Marking Registry or BLMR. The BLMR allows the construction of accurate, reliable and extensive perception of lane markings in the vicinity of the vehicle from low-cost sensors. This extensive perception combined with a fast filtering algorithm and map matching techniques led to localization accuracy which is high enough for autonomous application, as demonstrated in tests conducted in Italy.
Base de dados e benchmarks para prognóstico de anomalias em sistemas de elevação de petróleo
(Universidade Federal do Espírito Santo, 2019-08-27) Vargas, Ricardo Emanuel Vaz; Salles, Evandro Ottoni Teatini; https://orcid.org/0000000282873045; http://lattes.cnpq.br/5893731382102675; https://orcid.org/0000-0001-6243-4590; http://lattes.cnpq.br/1658300192778908; Schnitman, Leizer; https://orcid.org/0000-0002-0399-6689; http://lattes.cnpq.br/0473342349140026; Campos, Mario Cesar Mello Massa de; https://orcid.org/0000-0002-5746-6915; http://lattes.cnpq.br/6108445696913310; Rauber, Thomas Walter; https://orcid.org/0000000263806584; http://lattes.cnpq.br/0462549482032704; Orosa, Luis Marti
The oil industry considers that prognosis of anomalies in oil-producing wells can help to reduce production losses, environmental accidents, and human casualties and reduce maintenance costs. An oil well refers to a set of sensors and mechanical, pneumatic, and hydraulic systems. As in virtually any industrial process, several types of anomalies also occur in the process of oil lifting and flow assurance. This thesis formulates and evaluates the hypothesis that anomalies in naturally flowing wells can be detected with Machine Learning and that the use of expert hand-drawn and simulated instances is a feasible solution for the training of rare actual anomalies' detectors. The scarcity of measurements in such processes is a drawback due to the low reliability of instrumentation in such hostile environments. Another issue is the absence of anomalies' data – in quantity, quality, and adequately structured – in naturally flowing wells. To contribute to Machine Learning-based approaches to the prognosis of this type of anomaly, this work prepared and made public an original and realistic dataset with instances of eight types of anomalies characterized by eight process variables. Many hours of working together with experts from Petróleo Brasileiro S.A. were required to validate historical instances and to produce simulated and hand-drawn instances. The methodology developed and used in this preparation is detailed. Specific challenges that researchers can explore with the published dataset are defined. Experimental results related to these challenges suggest that the formulated hypotheses are true. This work has resulted in two relevant contributions. A challenging public dataset that can be used as a benchmark for the development of (i) machine learning techniques related to inherent difficulties of actual data, and (ii) methods for specific tasks associated with anomalies' classification in naturally flowing wells. The other contribution is the proposal of the defined benchmarks.
Brain-computer interface based on compressive sensing and steady-state visual evoked potentials applied to command a robotic wheelchair
(Universidade Federal do Espírito Santo, 2023-09-21) Flor, Hamilton Rivera; Bastos Filho, Teodiano Freire; https://orcid.org/0000000211852773; http://lattes.cnpq.br/3761585497791105; https://orcid.org/0000-0001-7401-899X; http://lattes.cnpq.br/7555679246370907; Naves, Eduardo Lazaro Martins; Sa, Antonio Mauricio Ferreira Leite Miranda de; Floriano, Alan Silva da Paz; Krishnan, Sridar; Slawinski, Emanuel
People with severe physical disabilities are unable to use standard robotic wheelchairs, which generally demands some motor skills, and therefore total usage of associate muscles. Robotic wheelchairs commanded by Brain-Computer Interfaces (BCIs) based on Electroencephalography (EEG) have demonstrated to be an alternative for these end-users, as such systems translate brain patterns ongoing EEG signals into control commands. However, BCIs relying on local processing encounter limitations in power, scalability, and real-time. In general, existing robotic wheelchairs commanded by BCIs require powerful hardware for high speed signal processing. On the other hand, end-users need a long training process for safely driving these devices. As a solution, cloud-based BCIs and cloud robotics have emerged, leveraging cloud computing for high-performance data processing, storage, and analysis. This integration empowers advanced and adaptive robotic assistance, transforming tele-rehabilitation and e-health applications for people with disabilities. However, integrating cloud computing with BCIs introduces its own set of challenges. These include an efficient and reliable transmission of large volumes of data and stable communication between the brain signal sensor, cloud infrastructure, and robotic wheelchair. To address these challenges, this thesis proposes a novel cloud-BCI system for conveying wheelchair commands through the use of Steady-State Visual Evoked Potential (SSVEP), Compressive Sensing (CS), and a communication framework. The system enhances Information Transfer Rate (ITR), ensuring stable communication among the BCI, cloud infrastructure, and robotic wheelchair. Leveraging cloud Service-Oriented architecture and Robotic Operating System (ROS), the system allows for easy integration of diverse robotic platforms, and provides flexibility to integrate various protocols, classifiers, metrics, and command techniques. In conclusion, the cloud-BCI system developed here demonstrates to be an efficient and flexible solution for commanding a robotic wheelchair, making it a valuable tool for researchers and developers in the field of assistive technologies, tele-rehabilitation, and training scenarios.
Brain-Computer Interface Based on High-Frequency Steady-State Visual Evoked Potentials from Below-the-Hairline Areas Thesis
(Universidade Federal do Espírito Santo, 2019-06-19) Floriano, Alan Silva da Paz; Filho, Teodiano Freire Bastos; https://orcid.org/0000000211852773; http://lattes.cnpq.br/3761585497791105; https://orcid.org/; http://lattes.cnpq.br/; Ferreira, Andre; https://orcid.org/; http://lattes.cnpq.br/; Muller, Sandra Mara Torres; https://orcid.org/; http://lattes.cnpq.br/; Sa, Antonio Mauricio Ferreira Leite Miranda de; https://orcid.org/; http://lattes.cnpq.br/; Diez, Pablo F.
Steady-State Visual Evoked Potentials (SSVEPs) are brain responses that present the same frequency (and/or harmonics) of the visual stimulation. Applications, such as BrainComputer Interfaces, can be derived of their properties. SSVEP response is often maximal on the visual cortex area, consequently, most of the existing SSVEP-based BCIs use electrodes located at occipital and parietal regions. However, these areas are generally covered by hair, which cause complications in the electrode contact with the skin. On the other hand, currently, researchers are looking at how to transfer BCIs from the lab to the patient’s home. Recent studies have reported the use of below-the-hairline areas, such as behind-the-ears (temporal area), with stimuli in low/medium frequency bands, to control BCI systems, which suggests that measuring the EEG from hairless areas presents key advantages for technology transfer. However, the visual stimuli in low/medium frequencies used in these studies can produce visual fatigue and other problems to users. This thesis presents studies about characterization of SSVEP response from below-the-hairline areas in high-frequency, with the aim of developing a practical BCI without generating discomfort to users. First, results of our research indicate that SSVEP response from hairless areas are influenced by the reference electrode position, and that the best configuration to measure this response is temporal-frontal montage (TP9-Fpz and TP10-Fpz). The second important result found in our research was that chromatic and luminance stimuli elicit strong SSVEP on the hairless areas, and that the SSVEP response is related to frequency and stimuli color. Results indicate that green-red stimulus elicits the highest SSVEP response in the medium-frequency range (15-25 Hz). On the other hand, green-blue stimulus elicits the highest SSVEP at high-frequencies (30-40 Hz). In addiction, results show that a combination of colors and luminance enhance the SSVEP detection accuracy. Another important contribution of our research was the combination of high-frequency SSVEP (from below-the-hairline areas) with eye focusing mechanism (Depth-of-Field) to command a robot in a virtual environment. In online tests, the volunteers achieved an success rate of 96%. These findings contribute to state of the art, and the development of more practical and comfortable BCIs.

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