Navegando por Autor "Rocha, Ronilson"

Agora exibindo 1 - 17 de 17

An inductor-free realization of the Chua’s circuit based on electronic analogy.
(2009) Rocha, Ronilson; Torricos, Rene Orlando Medrano
Although literature presents several alternatives, an approach based on the electronic analogy was still not considered for the implementation of an inductor-free realization of the double scroll Chua’s circuit. This paper presents a new inductor-free configuration of the Chua’s circuit based on the electronic analogy. This proposal results in a versatile and functional inductorless implementation of the Chua’s circuit that offers new and interesting features for several applications. The analogous circuit is implemented and used to perform an experimental mapping of a large variety of attractors.
Analogia eletrônica no ensino de Física.
(2005) Rocha, Ronilson; Martins Filho, Luiz de Siqueira; Machado, Romuel Figueiredo
Este artigo introduz um procedimento para o projeto de circuitos eletrônicos analógicos simples que emulam o comportamento dinâmico de sistemas físicos e matemáticos. Tais circuitos podem ser utilizados como uma aproximação experimental para desenvolvimento de atividades experimentais de ensino, sendo facilmente aplicáveis em qualquer laboratório. Como exemplo, as versões eletrônicas dos sistemas caóticos de Duffing e Rossler são projetadas e implementadas, resultando em protótipos simples, baratos, robustos, versáteis e funcionais.
Automação de uma máquina de torção visando sua aplicação na realização de ensaios a frio e a quente.
(2017) Oliveira Filho, Wagner Rossi de; Faria, Geraldo Lúcio de; Rocha, Ronilson; Faria, Geraldo Lúcio de; Vilela, Jefferson José; Godefroid, Leonardo Barbosa; Rocha, Ronilson
Experimentos em escala real no setor metalúrgico possuem baixa viabilidade econômica para sua realização. Ainda sim, existe a necessidade contínua de aperfeiçoamento de processos de produção em busca de eficiência e qualidade nos produtos. Entre eles o processo de laminação a quente, que tem sido objeto de muitas pesquisas na ultimas décadas. Os fenômenos que ocorrem neste processo podem ser estudados em pequena escala por meio de ensaios de torção a quente, simulando condições semelhantes ao processo metalúrgico industrial. Neste trabalho foi realizada a automação e adaptação de uma máquina de torção de carregamento por pendulo da fabricante Amsler, desde a etapa de seleção de materiais e dispositivos, com o objetivo de permitir a realização de ensaios automatizados a frio e a quente, possibilitando assim que, no futuro, estudos possam ser desenvolvidos no intuito de simular o comportamento mecânico de aços em processos de laminação a quente. Um algoritmo para desenvolvimento de um software de controle e aquisição de dados da máquina foi proposto e executado utilizando a ferramenta LABVIEW. A execução do projeto de automação se mostrou viável e eficiente. Obteve-se uma máquina de torção automatizada completamente funcional e capaz de realizar ensaios a quente em temperaturas máximas de até 1150oC, incluindo a possibilidade de realização de ensaios por passes. Foi constatado um erro máximo de 0,7% para o fundo de escala do momento de torção e até 0,72o para o ângulo de torção. Foram realizados ensaios de torção a frio e a quente que comprovaram a eficiência do sistema e permitiram a visualização de fenômenos como o encruamento e recuperação por meio das curvas de tensão-deformação.
Chua circuit based on the exponential characteristics of semiconductor devices.
(2022) Rocha, Ronilson; Torricos, Rene Orlando Medrano
The use of non-ideal features of semiconductor devices is an interesting option for implementations of nonlinear electronic systems. This paper analyzes the Chua circuit with nonlinearity based on the expo- nential hyperbolic characteristics of semiconductor devices. The stability analysis using describing func- tions predicts the dynamics of this nonlinear system, which is corroborated by numerical investigations and experimental results. The dynamic behaviors and bifurcations of this nonlinear system are mapped in parameter space in order to create a base for studies, analyses, and designs. The dynamic behavior of the experimental high speed implementation of this version of Chua circuit differs from the expected dynamics for a conventional Chua circuit due to effects of unmodelled non-idealities of the real semicon- ductor devices, displaying that new and different dynamics for the Chua circuit can be obtained exploring different nonlinearities.
Controle ótimo H2 para coluna de flotação.
(Programa de Pós-Graduação em Engenharia Mineral. Departamento de Engenharia de Minas, Escola de Minas, Universidade Federal de Ouro Preto., 2008) Lima, Luciana Batista de; Rocha, Ronilson
Devido ao aumento na demanda de recursos naturais não renováveis e a inevitável exaustão das jazidas minerais de alto teor, o desafio de efetuar o beneficiamento de minérios mais complexos, atendendo a especificações cada vez mais rígidas, tem proporcionado um maior destaque ao processo de flotação em coluna no contexto da indústria mineral. Na flotação em coluna, partículas hidrofóbicas, de um fluxo descendente de material alimentado a uma altura de aproximadamente ⅔ da coluna, medidos a partir de sua base, são arrastadas para uma zona de espuma por um fluxo ascendente de bolhas de ar em contracorrente, sendo que as partículas hidrofílicas são levadas para a região de limpeza por um fluxo de água de lavagem. Esta técnica de beneficiamento de minério têm se consolidado por permitir melhorias dos concentrados na aplicação a diferentes tipos de minérios, incluindo os de granulometrias de liberação mais fina, e economia no investimento e manutenção de projeto. Neste trabalho é apresentado um sistema de controle multivariável robusto para o processo de flotação em coluna utilizando um controlador ótimo H2. A utilização desta técnica de controle é bastante pertinente, considerando a sua grande capacidade em manter a estabilidade do processo e rejeitar perturbações. Este sistema de controle no processo de flotação em coluna atua de forma direta sobre as variáveis manipuladas (vazão de água de lavagem, ar e não flotado) de modo a afetar adequadamente as variáveis controladas (nível da camada de espuma, bias e holdup do ar) acompanhando as variações em seus valores de referência e minimizando a interação entre as variáveis, mesmo com a ocorrência de perturbações. É apresentado o desenvolvimento e avaliação do projeto do controlador multivariável H2 para a operação de coluna de flotação visando melhoria no desempenho final do processo. Ferramentas de software são utilizadas para simular diversas condições operacionais sendo que a avaliação da eficiência do controlador proposto é realizada verificando as respostas obtidas das simulações.
Desenvolvimento de ferramenta computacional para auxílio ao projeto de gemas lapidadas.
(2005) Martins Filho, Luiz de Siqueira; Mol, Adriano Aguiar; Rocha, Ronilson
Efficiency parameters estimation in gemstones cut design using artificial neural networks.
(2007) Mol, Adriano Aguiar; Martins Filho, Luiz de Siqueira; Silva, José Demisio Simões da; Rocha, Ronilson
This paper deals with the problem of estimating cut results for faceted gemstones. The proposed approach applies artificial neural networks for a faceted gemstones analysis tool that could be further developed for incorporation in a computer-aided-design (CAD) context. Basic concepts concerning gemstone processing are introduced and the design of computational tools using neural networks is discussed. The model presented proposes two criteria to assess the efficiency of lapidary designs for rock crystal quartz: brilliance and yield. Closing the article, 62 different lapidary models were used to train and test the neural network tool.
Experimental characterization of nonlinear systems : a real-time evaluation of the analogous Chua’s circuit behavior.
(2010) Rocha, Ronilson; Andrucioli, Guilherme Lucio Damião; Torricos, Rene Orlando Medrano
This paper presents an experimental characterization of the behavior of an analogous version of the Chua’s circuit. The electronic circuit signals are captured using a data acquisition board (DAQ) and processed using LabVIEW environment. The following aspects of the time series analysis are analyzed: time waveforms, phase portraits, frequency spectra, Poincaré sections, and bifurcation diagram. The circuit behavior is experimentally mapped with the parameter variations, where are identified equilibrium points, periodic and chaotic attractors, and bifurcations. These analysis techniques are performed in real-time and can be applied to characterize, with precision, several nonlinear systems.
Memristive oscillator based on Chua’s circuit : stability analysis and hidden dynamics.
(2017) Rocha, Ronilson; Ruthiramoorthy, Jothimurugan; Kathamuthu, Thamilmaran
This paper presents a theoretical stability analysis of amemristive oscillator derived from Chua’s circuit in order to identify its different dynamics, which are mapped in parameter spaces. Since this oscillator can be represented as a nonlinear feedback system, its stability is analyzed using the method based on describing functions, which allows to predict fixed points, periodic orbits, hidden dynamics, routes to chaos, and unstable states. Bifurcation diagrams and attractors obtained from numerical simulations corroborate theoretical predictions, confirming the coexistence of multiple dynamics in the operation of this oscillator.
Multivariable H2 and H∞ control for a wind energy conversion system – a comparison.
(2010) Rocha, Ronilson; Coutinho, Gilmar Alves; Ferreira, Alexandre José; Torga, Flávio Allison
The Wind Energy Conversion System (WECS) is a nonlinear system, highly dependent on a stochastic variable characterized by sudden variations, and subjected to cyclical disturbances caused by operational phenomena. Thus, the quality of a WECS controller is measured by its capacity to deal with unmodeled dynamics, stochastic signals, and periodic, as well as non-periodic disturbances. Since the WECS' objectives can be easily specified in terms of maximum allowable gain in the disturbance-to-output transfer functions, H2 and H∞ methodologies can be good options for designing a WECS stabilizing controller, combining specifications such as: disturbance attenuation, asymptotic tracking, bandwidth limitation, robust stability, and trade-off between performance and control effort. Designs for WECS multivariable feedback controllers based on H2 and H∞ methodologies are presented in this paper. The performances of both controllers are computationally simulated, analyzed and compared in order to identify the advantages and drawbacks of each controller design.
Photovoltaic panels as attitude sensors for artificial satellites.
(2016) Rocha, Ronilson; Rodrigues, Luis
The main contribution of this paper is to present a formal analysis of the use of PV panels as attitude sensors in order to determine the orientation of a satellite relative to the sun and the satellite's angular rates. Four artificial satellite configurations are considered: parallelepiped, hexagonal, octagonal prismatic, and winged satellites. Since the short-circuit currents of PV panels are fundamental variables for the determination of the orientation relative to the sun, this paper also shows methods for measuring them using power converters that condition and regulate the generated electric power. Furthermore, some aspects of the use of PV panels as sensors are experimentally verified. The results show that the accuracy of the measurements with PV panels can be acceptable for applications involving low-cost small, micro-, nano-, and picoartificial satellites, thus increasing the sensing options for future spacecraft missions.
Procedimento experimental para a determinação de atitude de satélites artificiais.
(2008) Ferreira, Alexandre José; Castro, João Carlos Vilela de; Martins Filho, Luiz de Siqueira; Duarte, Ricardo de Oliveira; Prado, Ricardo Sérgio; Rocha, Ronilson
Este artigo apresenta uma metodologia experimental desenvolvida no âmbito do projeto de um dispositivo de determinação de atitude de satélites artificiais. O dispositivo é baseado na utilização de um magnetômetro de estado sólido como sensor principal, um sensor virtual de sol, e um microcontrolador da família 8051. Os testes experimentais e o desenvolvimento da metodologia baseiam-se inicialmente na utilização do software LabView para os cálculos, e da geração de campo magnético através de uma bobina de Helmholtz. O algoritmo adotado para a estimação da atitude do satélite utiliza uma representação através de quatérnions, e um princípio de otimização denominado Método q. Resultados obtidos através do microcontrolador e do LabView são apresentados e analisados. Conclusões e perspectivas sobre as próximas etapas do projeto fecham o artigo.
A rotor flux and speed observer for sensorless single-phase : induction motor applications.
(2012) Caruso, Massimo; Cecconi, Vittorio; Tommaso, Antonino Oscar Di; Rocha, Ronilson
It is usual to find single-phase induction motor (SPIM) in several house, office, shopping, farm, and industry applications, which are become each time more sophisticated and requiring the development of efficient alternatives to improve the operational performance of this machine. Although the rotor flux and rotational speed are essential variables in order to optimize the operation of a SPIM, the use of conventional sensors to measure them is not a viable option. Thus, the adoption of sensorless strategies is the more reasonable proposal for these cases. This paper presents a rotor flux and rotational speed observer for sensorless applications involving SPIMs. Computer simulations and the experimental results are used to verify the performance of the proposed observer.
A sensorless control for a variable speed wind turbine operating at partial load.
(2011) Rocha, Ronilson
This paper presents a sensorless control for a variable speed wind turbine (WT) operating at partial load in order to eliminate the direct measurement of the wind speed. In this proposal, the estimated aerodynamic torque is used to determine the optimal reference of the speed control for maximum energy conversion. The maximization of the efficiency on energy conversion and the minimization of detrimental dynamical loads are control trade-offs considered in the design of an optimal discrete-time feedback LQG/LTR controller for the Wind Energy Conversion System (WECS), which is based on the optimization of a quadratic cost function. The performance of the proposed control when the WT is submitted to a gust or step variation on wind speed is evaluated from computational simulations. It is also presented some proposals for sensorless control of the electrical generator.
Stability analysis and mapping of multiple dynamics of Chua’s circuit in full four-parameter SpacesV.
(2015) Rocha, Ronilson; Torricos, Rene Orlando Medrano
The stability analysis is used in order to identify and to map different dynamics of Chua’s circuit in full four-parameter spaces. The study is performed using describing functions that allow to identify fixed point, periodic orbit, and unstable states with relative accuracy, as well as to predict route to chaos and hidden dynamics that conventional computational methods do not detect. Numerical investigations based on the computation of eigenvalues and Lyapunov exponents partially support the predictions obtained from the theoretical analysis since they do not capture the multiple dynamics that can coexist in the operation of Chua’s circuit. Attractors obtained from initial conditions outside of neighborhoods of the equilibrium points confirm the multiplicity of dynamics in the operation of Chua’s circuit and corroborate the theoretical analysis.
Stability analysis for the Chua circuit with cubic polynomial nonlinearity based on root locus technique and describing function method.
(2020) Rocha, Ronilson; Medrano Torricos, Rene Orlando
This work investigates the dynamics of the Chua circuit with cubic polynomial nonlinearity using methods for stability analysis based on linearization and frequency response. Root locus technique maps eigenvalues of the linearized system in order to analyze the local stability, which allows to verify dynamic features, motion patterns, and attractor topologies. The method based on describing functions allows analyze effects of the cubic nonlinearity in the system, as well as predict equilibrium and fixed points, periodic and chaotic orbits, limit cycles, multistability and hidden dynamics, unstable states, and bifurcations. The stability of the Chua circuit with cubic polynomial nonlinearity is analyzed using both approaches in order to identify and map dynamics in parameter spaces. Numerical investigations based on computational simulations corroborate the theoretical results obtained using this stability analysis. This theoretical analysis and the numerical investigations present interesting insights about the dynamics of the Chua circuit with cubic polynomial nonlinearity and provides a design tool for electroelectronic implementations.
The negative side of Chua’s circuit parameter space : stability analysis, period-adding, basin of attraction metamorphoses, and experimental investigation.
(2014) Torricos, Rene Orlando Medrano; Rocha, Ronilson
Although Chua’s circuit is one of the most studied nonlinear dynamical systems, its version with negative parameters remains practically untouched. This work reports an interesting and rich dynamic scenery that was hidden in this almost unexplored region. The study is focused on 2D parameter space and presents an analysis of stability based on describing functions. Numerical investigations present a gallery of period-adding cascades and a strong presence of basin boundary metamorphoses. The key to this new scenario is that for negative parameters, Chua’s system does not satisfy the Shilnikov condition and it is shown that the homoclinic orbit organizes the parameter space completely different from as known. The obtained experimental results corroborate with the numerical and theoretical investigations.