DECAT - Departamento de Controle e Automação
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/490
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12 resultados
Resultados da Pesquisa
Item Stability analysis and mapping of multiple dynamics of Chua’s circuit in full four-parameter SpacesV.(2015) Rocha, Ronilson; Torricos, Rene Orlando MedranoThe 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.Item Photovoltaic panels as attitude sensors for artificial satellites.(2016) Rocha, Ronilson; Rodrigues, LuisThe 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.Item Memristive oscillator based on Chua’s circuit : stability analysis and hidden dynamics.(2017) Rocha, Ronilson; Ruthiramoorthy, Jothimurugan; Kathamuthu, ThamilmaranThis 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.Item An inductor-free realization of the Chua’s circuit based on electronic analogy.(2009) Rocha, Ronilson; Torricos, Rene Orlando MedranoAlthough 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.Item 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 MedranoThis 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.Item 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, RonilsonAlthough 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.Item A sensorless control for a variable speed wind turbine operating at partial load.(2011) Rocha, RonilsonThis 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.Item 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, RonilsonThis 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.Item Desenvolvimento de ferramenta computacional para auxílio ao projeto de gemas lapidadas.(2005) Martins Filho, Luiz de Siqueira; Mol, Adriano Aguiar; Rocha, RonilsonItem 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, RonilsonEste 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.