joao edgar chaves filho - Academia.edu (original) (raw)

Papers by joao edgar chaves filho

We describe and evaluate a novel optimization-based off-line path planning algorithm for mobile r... more We describe and evaluate a novel optimization-based off-line path planning algorithm for mobile robots based on the Counterexample-Guided Inductive Optimization (CEGIO) technique. CEGIO iteratively employs counterexamples generated from Boolean Satisfiability (SAT) and Satisfiability Modulo Theories (SMT) solvers, in order to guide the optimization process and to ensure global optimization. This paper marks the first application of CEGIO for planning mobile robot path. In particular, CEGIO has been successfully applied to obtain optimal two-dimensional paths for autonomous mobile robots using off-the-shelf SAT and SMT solvers. Index Terms-optimization, satisfiability modulo theory, path planning, mobile robots.

Nowadays, the use of converters is attracting increasing attention due to diversification of elec... more Nowadays, the use of converters is attracting increasing attention due to diversification of electric power sources. In particular, DC-DC converters are used to ensure the stability in the DC supply responsible for feeding a DC microgrid with constant voltage. Thus, classical and modern controls methodologies are used to ensure the stability of the feed system when connected to a constant power load (CPL). This paper compares control methodologies for pole allocation using Diophantine equation, root locus, linear-quadratic regulator and the Lyapunov equation by using performance indices as integral of square error (ISE), integral of square weighted by time (ISET) and integral of square of control (ISSC).

This work presents the development of an Automatic Voltage Regulator (AVR) applied to a low-volta... more This work presents the development of an Automatic Voltage Regulator (AVR) applied to a low-voltage power energy system, for the realization of this, digital control concepts and techniques were used. The control and regulation system was developed and embedded in the Arduino Due development platform, a microcontroller considered of high performance. The signal sent by the controller is used in a DC-DC power converter Buck topology to control its average voltage value which is used to power the field coil of the synchronous generator, thus providing the electrical excitation required for the creation of a magnetic field. This control is done by varying the working cycle of the static switch, which allows a variation of the average voltage of the DC-DC power converter element of the Buck type, this information is the result of the calculation in the microcontroller, and with this it is used the pulse width modulation (PWM) technique to perform the static key switch.. The results show that the controlled system was successful in presenting the desired performance by means of simulation and experimental tests. Resumo: Neste trabalho é apresentado o desenvolvimento de um Regulador Automático de Tensão (RAT) aplicado a um sistema de microgeração de energia. O sistema de controle e regulação foi desenvolvido e embarcado de controle e regulação foi desenvolvida e embarcada na plataforma de desenvolvimento do Arduino Due, um microcontrolador considerado de alto desempenho. O sinal enviado pelo controlador é utilizado em um conversor de potência CC-CC de topologia Buck, para controlar o seu valor médio de tensão que é utilizado para alimentar a bobina de campo do gerador síncrono, fornecendo, assim, a excitação elétrica necessária para a criação de um campo magnético. Esse controle é feito através da variação do ciclo de trabalho da chave estática, o que permite uma variação da tensão média do elemento conversor de potência CC-CC do tipo Buck, tal informação é resultado do cálculo no microcontrolador, e com isso utiliza-se a técnica de modulação por largura de pulsos (PWM), para realizar o chaveamento da chave estática. Os resultados mostram que o sistema controlado, obteve êxito com relação a apresentar o desempenho desejado por meio da realização de testes de simulação e experimentais.

Mobile robotics has applications in many different areas, such as in industries, homes and milita... more Mobile robotics has applications in many different areas, such as in industries, homes and military. For the development of navigation system for mobile robotics, localization is one of the main tasks, since this parameter is necessary to assist decisions making and plan how the robot will achieve the desired points. Several approaches to this problem are used, with odometry widely applied. However, odometry often do not present good precision results when applied to indoor environments. In this context, this work presents the development of a navigation system considering localization and position control based on computer vision applied to mobile robots in indoor environments. It is presented a comparison between the location system based on odometry and the proposed system based on computer vision. The experimental results demonstrates the efficiency of the proposed localization system and compares it to an odometrybased method. Resumo: A robótica móvel possui aplicações nas mais diversasáreas, como em indústrias, residências e até militar. Para o desenvolvimento de um sistema de navegação para sistemas robóticos, a localizaçãoé uma tarefa primordial, uma vez que este parâmetroé necessário para planejar como robô chegará aos pontos desejados e auxiliar na tomada de decisões. São utilizadas diversas abordagens para este problema, sendo a odometria amplamente aplicada. Entretanto, a odometria costuma não apresentar bons resultados relacionadosà precisão quando aplicada a ambientes internos. Neste contexto, este trabalho apresenta o desenvolvimento de um sistema de navegação (englobando localização e controle de posição) baseado em visão computacional, aplicado a robôs móveis em ambientes internos.É apresentado ainda um comparativo entre o sistema de localização baseado em odometria e o sistema proposto baseado em visão computacional. Ao fim do trabalho,é demonstrada (por meio de resultados experimentais) a eficiência do sistema de localização baseado em visão computacional em comparação com a localização por odometria.

Science of Computer Programming, Nov 1, 2018

This paper describes three variants of a counterexample guided inductive optimization (CEGIO) app... more This paper describes three variants of a counterexample guided inductive optimization (CEGIO) approach based on Satisfiability Modulo Theories (SMT) solvers. In particular, CEGIO relies on iterative executions to constrain a verification procedure, in order to perform inductive generalization, based on counterexamples extracted from SMT solvers. CEGIO is able to successfully optimize a wide range of functions, including non-linear and non-convex optimization problems based on SMT solvers, in which data provided by counterexamples are employed to guide the verification engine, thus reducing the optimization domain. The present algorithms are evaluated using a large set of benchmarks typically employed for evaluating optimization techniques. Experimental results show the efficiency and effectiveness of the proposed algorithms, which find the optimal solution in all evaluated benchmarks, while traditional techniques are usually trapped by local minima.

Springer eBooks, 2015

This work presents the Digital-System Verifier (DSVerifier), which is a verification tool develop... more This work presents the Digital-System Verifier (DSVerifier), which is a verification tool developed for digital systems. In particular, DSVerifier employs the bounded model checking technique based on satisfiability modulo theories (SMT) solvers, which allows engineers to verify the occurrence of design errors, due to the finite word-length approach employed in fixed-point digital filters and controllers. This tool consists in an additional module for the efficient SMT-based context-bounded model checker and presents command-line and graphical user interface (GUI) versions. Indeed, the GUI version is essential for reporting property violations, together with associated counterexamples. It is worth noticing that DSVerifier is implemented in C/C++ and uses JavaFX for providing GUI support.

Design Automation for Embedded Systems, Mar 10, 2016

The extensive use of fixed-point digital controllers demands a growing effort to prevent design e... more The extensive use of fixed-point digital controllers demands a growing effort to prevent design errors that appear in the discrete-time domain. The present article describes a novel verification methodology, which employs Bounded Model Checking (BMC) based on Satisfiability Modulo Theories (SMT) to verify the occurrence of the design errors, because of the finite word-length (FWL) format, in fixed-point digital controllers. Here, the performance realizations of the digital controllers realizations that use delta operators are compared to those that use traditional direct forms. The experimental results show that the delta-form realization substantially reduces the digital controllers' fragility when compared to the direct-form realization. Additionally, the proposed methodology can be very effective and efficient to verify real-world digital controllers, where conclusive results are obtained in nearly 98% of the benchmarks.

Renewable Energy, Mar 1, 2016

This paper investigates a new scheme for fault detection and isolation based on time series and d... more This paper investigates a new scheme for fault detection and isolation based on time series and data analysis. This scheme is applied in wind turbines which are used to tap the potential of renewable energy. The proposed scheme is performed in two steps and it is based on process data without using any kind of physical modeling. The first step, the fault detection, is based on an alternative method based on the Gibbs sampling algorithm in which the occurrence of a sensor fault is modeled as a change point detection in a time series. The second step, the fault isolation, is handled via a Fuzzy/Bayesian network scheme classifying the kind of fault. The proposed fault detection and isolation (FDI) strategy offers as main contribution the independence from any kind of dynamical modeling and the unprecedented usage of the Gibbs sampling. Furthermore, this work offers a novel data driven FDI approach based on Fuzzy-Bayesian inference and suitable for the wind turbines systems. This approach presents a good performance for detection and diagnostics of sensor faults in a standard wind turbine benchmark.

Digital controllers have several advantages with respect to their flexibility and design's simpli... more Digital controllers have several advantages with respect to their flexibility and design's simplicity. However, they are subject to problems that are not faced by analog controllers. In particular, these problems are related to the finite word-length implementation that might lead to overflows, limit cycles, and time constraints in fixed-point processors. This paper proposes a new method to detect design's errors in digital controllers using a state-of-the art bounded model checker based on satisfiability modulo theories. The experiments with digital controllers for a ball and beam plant demonstrate that the proposed method can be very effective in finding errors in digital controllers than other existing approaches based on traditional simulations tools.

arXiv (Cornell University), Aug 14, 2017

We describe and evaluate a novel optimization-based off-line path planning algorithm for mobile r... more We describe and evaluate a novel optimization-based off-line path planning algorithm for mobile robots based on the Counterexample-Guided Inductive Optimization (CEGIO) technique. CEGIO iteratively employs counterexamples generated from Boolean Satisfiability (SAT) and Satisfiability Modulo Theories (SMT) solvers, in order to guide the optimization process and to ensure global optimization. This paper marks the first application of those solvers for planning mobile robot path. In particular, CEGIO has been successfully applied to obtain optimal two-dimensional paths for autonomous mobile robots using off-the-shelf SAT and SMT solvers. Index Terms-optimization, satisfiability modulo theory, path planning, mobile robots.

arXiv (Cornell University), Apr 11, 2017

This paper describes three variants of a counterexample guided inductive optimization (CEGIO) app... more This paper describes three variants of a counterexample guided inductive optimization (CEGIO) approach based on Satisfiability Modulo Theories (SMT) solvers. In particular, CEGIO relies on iterative executions to constrain a verification procedure, in order to perform inductive generalization, based on counterexamples extracted from SMT solvers. CEGIO is able to successfully optimize a wide range of functions, including non-linear and non-convex optimization problems based on SMT solvers, in which data provided by counterexamples are employed to guide the verification engine, thus reducing the optimization domain. The present algorithms are evaluated using a large set of benchmarks typically employed for evaluating optimization techniques. Experimental results show the efficiency and effectiveness of the proposed algorithms, which find the optimal solution in all evaluated benchmarks, while traditional techniques are usually trapped by local minima.

2022 IEEE 27th International Conference on Emerging Technologies and Factory Automation (ETFA), Sep 6, 2022

Fault detection and repair of the components of photovoltaic (PV) systems are essential to avoid ... more Fault detection and repair of the components of photovoltaic (PV) systems are essential to avoid economic losses and facility accidents, thereby ensuring reliable and safe systems. This article presents a method to detect faults in a PV system based on power ratio (PR), voltage ratio (VR), and current ratio (IR). The lower control limit (LCL) and upper control limit (UCL) of each ratio were defined using the data of a test site system under normal operating conditions. If PR exceeded the set range, the algorithm considered a fault. Subsequently, PR and IR were examined via the algorithm to diagnose faults in the system as series, parallel, or total faults. The results showed that PR exceeded the designated range between LCL (0.93) and UCL (1.02) by dropping to 0.91-0.68, 0.88-0.62, and 0.66-0.33 for series, total, and parallel faults, respectively. Moreover, VR exceeded the LCL (0.99) and UCL (1.01) by 0.95-0.69 and 0.91-0.62 for series and total faults, respectively, but not under parallel faults condition. IR did not change in series and total faults but exceeded the range of LCL (0.93) and UCL (1.05) by dropping to 0.66-0.33. Thus, faults in PV systems can be detected and diagnosed by analyzing quantitative output values.

Isa Transactions, Feb 1, 2018

This paper describes a novel robust decentralized control design methodology for a single inducto... more This paper describes a novel robust decentralized control design methodology for a single inductor multiple output (SIMO) DC-DC converter. Based on a nominal multiple input multiple output (MIMO) plant model and performance requirements, a pairing input-output analysis is performed to select the suitable input to control each output aiming to attenuate the loop coupling. Thus, the plant uncertainty limits are selected and expressed in interval form with parameter values of the plant model. A single inductor dual output (SIDO) DC-DC buck converter board is developed for experimental tests. The experimental results show that the proposed methodology can maintain a desirable performance even in the presence of parametric uncertainties. Furthermore, the performance indexes calculated from experimental data show that the proposed methodology outperforms classical MIMO control techniques.

ISA Transactions, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Energies, 2020

The DC microgrid system is composed by converters that operate like feeders and loads. Among thes... more The DC microgrid system is composed by converters that operate like feeders and loads. Among these loads, we highlight the constant power loads (CPLs) that may cause instability in the microgrid, observed in the form of undesired oscillations due to its negative impedance behavior. Therefore, this work proposes to use performance indices and stability margins to evaluate state and output feedback control strategies for stabilization of DC microgrids. In particular, it is proposed to evaluate the stability margin of the proposed methodologies by means of the impedance relations in the microgrid based on the Middlebrook criterion. Our simulations and tests showed the relation between the performance and stability degradation and the microgrid impedances variation.

Anais do 14º Simpósio Brasileiro de Automação Inteligente, 2019

In this work, automatic control techniques are investigated in order to improve the performance o... more In this work, automatic control techniques are investigated in order to improve the performance of power system stabilizers (ESP) applying FOPSS method based on Newton-Raphson method to obtain the fractional order controller parameters. A small scale electric power system model was used, with the purpose of comparing the dynamic behavior of the fractional controller, with a PSS controller tuned by methodology based on classical frequency response. Seven simulational tests, applying a 0.05 impulse variation at the system voltage reference, were carried out with the insertion of both controllers. The obtained results were corroborated by integral indices obtained related to the active power deviation, and to the control effort of the controllers for those seven operating points. Resumo: Neste trabalho, técnicas de controle automático são investigadas para melhorar o desempenho dos estabilizadores do sistema de potência (ESP) aplicando o método FOPSS baseado no método de Newton-Raphson, para obtenção dos parâmetros do controlador de ordem fracionária. Um modelo de sistema de energia elétrica em escala reduzida foi utilizado, com o objetivo de comparar o comportamento dinâmico do controlador fracionário, com um controlador PSS sintonizado por metodologia baseada na resposta de frequência clássica. Sete testes simulacionais, aplicando uma variação de impulso de 0,05 na referência de tensão do sistema, foram realizados com a inserção de ambos os controladores. Os resultados obtidos foram corroborados pelos índices integrais obtidos relacionados ao desvio de potência ativa e pelo esforço de controle dos controladores para esses sete pontos de operação.

IEEE Transactions on Computers, 2017

A verification methodology is described and evaluated to formally determine uncertain linear syst... more A verification methodology is described and evaluated to formally determine uncertain linear systems stability in digital controllers with considerations to the implementation aspects. In particular, this methodology is combined with the digital-system verifier (DSVerifier), which is a verification tool that employs Bounded Model Checking based on Satisfiability Modulo Theories to check the stability of digital control systems with uncertainty. DSVerifier determines the control system stability, considering all the plant interval variation set, together with the Finite Word-length (FWL) effects in the digital controller implementation; DSVerifier checks the robust non-fragile stability of a given closed-loop system. The proposed methodology and respective tool are evaluated considering non-fragile control examples from literature. Experimental results show that the approach used in this study is able to foresee fragility problems in robust controllers, which could be overlooked by other existing approaches due to underestimating of FWL effects.

IEEE Transactions on Consumer Electronics, 2013

Software Product Lines (SPL) is an efficient software engineering approach for dealing with reusa... more Software Product Lines (SPL) is an efficient software engineering approach for dealing with reusable components in products that not only share common features, but also support specific functionalities that satisfy a particular market segment. This approach is interesting for the consumer electronics industry, particularly for mobile device applications. Despite having a significant common core, software applications developed for that domain have to be frequently adapted to different device features, such as operating systems and screen resolution. Thus, developers need to select proper software components to suitably compose the applications for each new device in a family of devices. In this paper, an approach that is able to customize consumer electronics software applications for different devices, in a dynamic and automated way, is presented. It results in a tool called AppSpotter that composes applications by selecting software components according to the features of each target device. To check the tool's performance, a set of experiments were realized in order to simulate different scenarios with up to 10,000 components 1 .

IEEE Transactions on Consumer Electronics, 2012

This paper presents the implementation process for an API that integrates interactive digital TV ... more This paper presents the implementation process for an API that integrates interactive digital TV (iDTV) applications and home network (HN) services, mainly concerning issues of the Brazilian iDTV model. The research in this field is important because it represents current trends on the use of iDTV opening many business opportunities. With the convergence of service providers, modern communication technologies and consumer electronics devices at home, new iDTV applications have emerged, particularly those that use the set-top-boxes (or digital TV sets) processing power to provide additional services, which extends the possibilities of interaction between the user and the connected home. To implement this platform, a known model, which considers aspects of the Ginga middleware and the Open Services Gateway Initiative (OSGi) framework, was used. The idea behind the API model is to export service objects from one side to another, allowing the development of two types of applications: the first one on the Ginga-J machine and the last one on the Ginga-NCL machine. The main goals of this paper are (i) presenting the use of free tolls to perform such integration and (ii) showing the most relevant aspects in the core of the two models. Finally, a basic step-by-step process is shown in order to build integrated iDTV-HN real applications using this platform. 1 .

2016 VI Brazilian Symposium on Computing Systems Engineering (SBESC), 2016

This paper presents a novel, complete, and flexible optimization algorithm, which relies on recur... more This paper presents a novel, complete, and flexible optimization algorithm, which relies on recursive executions that re-constrains a model-checking procedure based on Satisfiability Modulo Theories (SMT). This SMT-based optimization technique is able to optimize a wide range of functions, including non-linear and non-convex problems using fixed-point arithmetic. Although SMT-based optimization is not a new technique, this work is the pioneer in solving non-linear and non-convex problems based on SMT; previous applications are only able to solve integer and rational linear problems. The proposed SMT-based optimization algorithm is compared to other traditional optimization techniques. Experimental results show the efficiency and effectiveness of the proposed algorithm, which finds the optimal solution in all evaluated benchmarks, while traditional techniques are usually trapped by local minima.

We describe and evaluate a novel optimization-based off-line path planning algorithm for mobile r... more We describe and evaluate a novel optimization-based off-line path planning algorithm for mobile robots based on the Counterexample-Guided Inductive Optimization (CEGIO) technique. CEGIO iteratively employs counterexamples generated from Boolean Satisfiability (SAT) and Satisfiability Modulo Theories (SMT) solvers, in order to guide the optimization process and to ensure global optimization. This paper marks the first application of CEGIO for planning mobile robot path. In particular, CEGIO has been successfully applied to obtain optimal two-dimensional paths for autonomous mobile robots using off-the-shelf SAT and SMT solvers. Index Terms-optimization, satisfiability modulo theory, path planning, mobile robots.

Nowadays, the use of converters is attracting increasing attention due to diversification of elec... more Nowadays, the use of converters is attracting increasing attention due to diversification of electric power sources. In particular, DC-DC converters are used to ensure the stability in the DC supply responsible for feeding a DC microgrid with constant voltage. Thus, classical and modern controls methodologies are used to ensure the stability of the feed system when connected to a constant power load (CPL). This paper compares control methodologies for pole allocation using Diophantine equation, root locus, linear-quadratic regulator and the Lyapunov equation by using performance indices as integral of square error (ISE), integral of square weighted by time (ISET) and integral of square of control (ISSC).

This work presents the development of an Automatic Voltage Regulator (AVR) applied to a low-volta... more This work presents the development of an Automatic Voltage Regulator (AVR) applied to a low-voltage power energy system, for the realization of this, digital control concepts and techniques were used. The control and regulation system was developed and embedded in the Arduino Due development platform, a microcontroller considered of high performance. The signal sent by the controller is used in a DC-DC power converter Buck topology to control its average voltage value which is used to power the field coil of the synchronous generator, thus providing the electrical excitation required for the creation of a magnetic field. This control is done by varying the working cycle of the static switch, which allows a variation of the average voltage of the DC-DC power converter element of the Buck type, this information is the result of the calculation in the microcontroller, and with this it is used the pulse width modulation (PWM) technique to perform the static key switch.. The results show that the controlled system was successful in presenting the desired performance by means of simulation and experimental tests. Resumo: Neste trabalho é apresentado o desenvolvimento de um Regulador Automático de Tensão (RAT) aplicado a um sistema de microgeração de energia. O sistema de controle e regulação foi desenvolvido e embarcado de controle e regulação foi desenvolvida e embarcada na plataforma de desenvolvimento do Arduino Due, um microcontrolador considerado de alto desempenho. O sinal enviado pelo controlador é utilizado em um conversor de potência CC-CC de topologia Buck, para controlar o seu valor médio de tensão que é utilizado para alimentar a bobina de campo do gerador síncrono, fornecendo, assim, a excitação elétrica necessária para a criação de um campo magnético. Esse controle é feito através da variação do ciclo de trabalho da chave estática, o que permite uma variação da tensão média do elemento conversor de potência CC-CC do tipo Buck, tal informação é resultado do cálculo no microcontrolador, e com isso utiliza-se a técnica de modulação por largura de pulsos (PWM), para realizar o chaveamento da chave estática. Os resultados mostram que o sistema controlado, obteve êxito com relação a apresentar o desempenho desejado por meio da realização de testes de simulação e experimentais.

Mobile robotics has applications in many different areas, such as in industries, homes and milita... more Mobile robotics has applications in many different areas, such as in industries, homes and military. For the development of navigation system for mobile robotics, localization is one of the main tasks, since this parameter is necessary to assist decisions making and plan how the robot will achieve the desired points. Several approaches to this problem are used, with odometry widely applied. However, odometry often do not present good precision results when applied to indoor environments. In this context, this work presents the development of a navigation system considering localization and position control based on computer vision applied to mobile robots in indoor environments. It is presented a comparison between the location system based on odometry and the proposed system based on computer vision. The experimental results demonstrates the efficiency of the proposed localization system and compares it to an odometrybased method. Resumo: A robótica móvel possui aplicações nas mais diversasáreas, como em indústrias, residências e até militar. Para o desenvolvimento de um sistema de navegação para sistemas robóticos, a localizaçãoé uma tarefa primordial, uma vez que este parâmetroé necessário para planejar como robô chegará aos pontos desejados e auxiliar na tomada de decisões. São utilizadas diversas abordagens para este problema, sendo a odometria amplamente aplicada. Entretanto, a odometria costuma não apresentar bons resultados relacionadosà precisão quando aplicada a ambientes internos. Neste contexto, este trabalho apresenta o desenvolvimento de um sistema de navegação (englobando localização e controle de posição) baseado em visão computacional, aplicado a robôs móveis em ambientes internos.É apresentado ainda um comparativo entre o sistema de localização baseado em odometria e o sistema proposto baseado em visão computacional. Ao fim do trabalho,é demonstrada (por meio de resultados experimentais) a eficiência do sistema de localização baseado em visão computacional em comparação com a localização por odometria.

Science of Computer Programming, Nov 1, 2018

This paper describes three variants of a counterexample guided inductive optimization (CEGIO) app... more This paper describes three variants of a counterexample guided inductive optimization (CEGIO) approach based on Satisfiability Modulo Theories (SMT) solvers. In particular, CEGIO relies on iterative executions to constrain a verification procedure, in order to perform inductive generalization, based on counterexamples extracted from SMT solvers. CEGIO is able to successfully optimize a wide range of functions, including non-linear and non-convex optimization problems based on SMT solvers, in which data provided by counterexamples are employed to guide the verification engine, thus reducing the optimization domain. The present algorithms are evaluated using a large set of benchmarks typically employed for evaluating optimization techniques. Experimental results show the efficiency and effectiveness of the proposed algorithms, which find the optimal solution in all evaluated benchmarks, while traditional techniques are usually trapped by local minima.

Springer eBooks, 2015

This work presents the Digital-System Verifier (DSVerifier), which is a verification tool develop... more This work presents the Digital-System Verifier (DSVerifier), which is a verification tool developed for digital systems. In particular, DSVerifier employs the bounded model checking technique based on satisfiability modulo theories (SMT) solvers, which allows engineers to verify the occurrence of design errors, due to the finite word-length approach employed in fixed-point digital filters and controllers. This tool consists in an additional module for the efficient SMT-based context-bounded model checker and presents command-line and graphical user interface (GUI) versions. Indeed, the GUI version is essential for reporting property violations, together with associated counterexamples. It is worth noticing that DSVerifier is implemented in C/C++ and uses JavaFX for providing GUI support.

Design Automation for Embedded Systems, Mar 10, 2016

The extensive use of fixed-point digital controllers demands a growing effort to prevent design e... more The extensive use of fixed-point digital controllers demands a growing effort to prevent design errors that appear in the discrete-time domain. The present article describes a novel verification methodology, which employs Bounded Model Checking (BMC) based on Satisfiability Modulo Theories (SMT) to verify the occurrence of the design errors, because of the finite word-length (FWL) format, in fixed-point digital controllers. Here, the performance realizations of the digital controllers realizations that use delta operators are compared to those that use traditional direct forms. The experimental results show that the delta-form realization substantially reduces the digital controllers' fragility when compared to the direct-form realization. Additionally, the proposed methodology can be very effective and efficient to verify real-world digital controllers, where conclusive results are obtained in nearly 98% of the benchmarks.

Renewable Energy, Mar 1, 2016

This paper investigates a new scheme for fault detection and isolation based on time series and d... more This paper investigates a new scheme for fault detection and isolation based on time series and data analysis. This scheme is applied in wind turbines which are used to tap the potential of renewable energy. The proposed scheme is performed in two steps and it is based on process data without using any kind of physical modeling. The first step, the fault detection, is based on an alternative method based on the Gibbs sampling algorithm in which the occurrence of a sensor fault is modeled as a change point detection in a time series. The second step, the fault isolation, is handled via a Fuzzy/Bayesian network scheme classifying the kind of fault. The proposed fault detection and isolation (FDI) strategy offers as main contribution the independence from any kind of dynamical modeling and the unprecedented usage of the Gibbs sampling. Furthermore, this work offers a novel data driven FDI approach based on Fuzzy-Bayesian inference and suitable for the wind turbines systems. This approach presents a good performance for detection and diagnostics of sensor faults in a standard wind turbine benchmark.

Digital controllers have several advantages with respect to their flexibility and design's simpli... more Digital controllers have several advantages with respect to their flexibility and design's simplicity. However, they are subject to problems that are not faced by analog controllers. In particular, these problems are related to the finite word-length implementation that might lead to overflows, limit cycles, and time constraints in fixed-point processors. This paper proposes a new method to detect design's errors in digital controllers using a state-of-the art bounded model checker based on satisfiability modulo theories. The experiments with digital controllers for a ball and beam plant demonstrate that the proposed method can be very effective in finding errors in digital controllers than other existing approaches based on traditional simulations tools.

arXiv (Cornell University), Aug 14, 2017

We describe and evaluate a novel optimization-based off-line path planning algorithm for mobile r... more We describe and evaluate a novel optimization-based off-line path planning algorithm for mobile robots based on the Counterexample-Guided Inductive Optimization (CEGIO) technique. CEGIO iteratively employs counterexamples generated from Boolean Satisfiability (SAT) and Satisfiability Modulo Theories (SMT) solvers, in order to guide the optimization process and to ensure global optimization. This paper marks the first application of those solvers for planning mobile robot path. In particular, CEGIO has been successfully applied to obtain optimal two-dimensional paths for autonomous mobile robots using off-the-shelf SAT and SMT solvers. Index Terms-optimization, satisfiability modulo theory, path planning, mobile robots.

arXiv (Cornell University), Apr 11, 2017

This paper describes three variants of a counterexample guided inductive optimization (CEGIO) app... more This paper describes three variants of a counterexample guided inductive optimization (CEGIO) approach based on Satisfiability Modulo Theories (SMT) solvers. In particular, CEGIO relies on iterative executions to constrain a verification procedure, in order to perform inductive generalization, based on counterexamples extracted from SMT solvers. CEGIO is able to successfully optimize a wide range of functions, including non-linear and non-convex optimization problems based on SMT solvers, in which data provided by counterexamples are employed to guide the verification engine, thus reducing the optimization domain. The present algorithms are evaluated using a large set of benchmarks typically employed for evaluating optimization techniques. Experimental results show the efficiency and effectiveness of the proposed algorithms, which find the optimal solution in all evaluated benchmarks, while traditional techniques are usually trapped by local minima.

2022 IEEE 27th International Conference on Emerging Technologies and Factory Automation (ETFA), Sep 6, 2022

Fault detection and repair of the components of photovoltaic (PV) systems are essential to avoid ... more Fault detection and repair of the components of photovoltaic (PV) systems are essential to avoid economic losses and facility accidents, thereby ensuring reliable and safe systems. This article presents a method to detect faults in a PV system based on power ratio (PR), voltage ratio (VR), and current ratio (IR). The lower control limit (LCL) and upper control limit (UCL) of each ratio were defined using the data of a test site system under normal operating conditions. If PR exceeded the set range, the algorithm considered a fault. Subsequently, PR and IR were examined via the algorithm to diagnose faults in the system as series, parallel, or total faults. The results showed that PR exceeded the designated range between LCL (0.93) and UCL (1.02) by dropping to 0.91-0.68, 0.88-0.62, and 0.66-0.33 for series, total, and parallel faults, respectively. Moreover, VR exceeded the LCL (0.99) and UCL (1.01) by 0.95-0.69 and 0.91-0.62 for series and total faults, respectively, but not under parallel faults condition. IR did not change in series and total faults but exceeded the range of LCL (0.93) and UCL (1.05) by dropping to 0.66-0.33. Thus, faults in PV systems can be detected and diagnosed by analyzing quantitative output values.

Isa Transactions, Feb 1, 2018

This paper describes a novel robust decentralized control design methodology for a single inducto... more This paper describes a novel robust decentralized control design methodology for a single inductor multiple output (SIMO) DC-DC converter. Based on a nominal multiple input multiple output (MIMO) plant model and performance requirements, a pairing input-output analysis is performed to select the suitable input to control each output aiming to attenuate the loop coupling. Thus, the plant uncertainty limits are selected and expressed in interval form with parameter values of the plant model. A single inductor dual output (SIDO) DC-DC buck converter board is developed for experimental tests. The experimental results show that the proposed methodology can maintain a desirable performance even in the presence of parametric uncertainties. Furthermore, the performance indexes calculated from experimental data show that the proposed methodology outperforms classical MIMO control techniques.

ISA Transactions, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Energies, 2020

The DC microgrid system is composed by converters that operate like feeders and loads. Among thes... more The DC microgrid system is composed by converters that operate like feeders and loads. Among these loads, we highlight the constant power loads (CPLs) that may cause instability in the microgrid, observed in the form of undesired oscillations due to its negative impedance behavior. Therefore, this work proposes to use performance indices and stability margins to evaluate state and output feedback control strategies for stabilization of DC microgrids. In particular, it is proposed to evaluate the stability margin of the proposed methodologies by means of the impedance relations in the microgrid based on the Middlebrook criterion. Our simulations and tests showed the relation between the performance and stability degradation and the microgrid impedances variation.

Anais do 14º Simpósio Brasileiro de Automação Inteligente, 2019

In this work, automatic control techniques are investigated in order to improve the performance o... more In this work, automatic control techniques are investigated in order to improve the performance of power system stabilizers (ESP) applying FOPSS method based on Newton-Raphson method to obtain the fractional order controller parameters. A small scale electric power system model was used, with the purpose of comparing the dynamic behavior of the fractional controller, with a PSS controller tuned by methodology based on classical frequency response. Seven simulational tests, applying a 0.05 impulse variation at the system voltage reference, were carried out with the insertion of both controllers. The obtained results were corroborated by integral indices obtained related to the active power deviation, and to the control effort of the controllers for those seven operating points. Resumo: Neste trabalho, técnicas de controle automático são investigadas para melhorar o desempenho dos estabilizadores do sistema de potência (ESP) aplicando o método FOPSS baseado no método de Newton-Raphson, para obtenção dos parâmetros do controlador de ordem fracionária. Um modelo de sistema de energia elétrica em escala reduzida foi utilizado, com o objetivo de comparar o comportamento dinâmico do controlador fracionário, com um controlador PSS sintonizado por metodologia baseada na resposta de frequência clássica. Sete testes simulacionais, aplicando uma variação de impulso de 0,05 na referência de tensão do sistema, foram realizados com a inserção de ambos os controladores. Os resultados obtidos foram corroborados pelos índices integrais obtidos relacionados ao desvio de potência ativa e pelo esforço de controle dos controladores para esses sete pontos de operação.

IEEE Transactions on Computers, 2017

A verification methodology is described and evaluated to formally determine uncertain linear syst... more A verification methodology is described and evaluated to formally determine uncertain linear systems stability in digital controllers with considerations to the implementation aspects. In particular, this methodology is combined with the digital-system verifier (DSVerifier), which is a verification tool that employs Bounded Model Checking based on Satisfiability Modulo Theories to check the stability of digital control systems with uncertainty. DSVerifier determines the control system stability, considering all the plant interval variation set, together with the Finite Word-length (FWL) effects in the digital controller implementation; DSVerifier checks the robust non-fragile stability of a given closed-loop system. The proposed methodology and respective tool are evaluated considering non-fragile control examples from literature. Experimental results show that the approach used in this study is able to foresee fragility problems in robust controllers, which could be overlooked by other existing approaches due to underestimating of FWL effects.

IEEE Transactions on Consumer Electronics, 2013

Software Product Lines (SPL) is an efficient software engineering approach for dealing with reusa... more Software Product Lines (SPL) is an efficient software engineering approach for dealing with reusable components in products that not only share common features, but also support specific functionalities that satisfy a particular market segment. This approach is interesting for the consumer electronics industry, particularly for mobile device applications. Despite having a significant common core, software applications developed for that domain have to be frequently adapted to different device features, such as operating systems and screen resolution. Thus, developers need to select proper software components to suitably compose the applications for each new device in a family of devices. In this paper, an approach that is able to customize consumer electronics software applications for different devices, in a dynamic and automated way, is presented. It results in a tool called AppSpotter that composes applications by selecting software components according to the features of each target device. To check the tool's performance, a set of experiments were realized in order to simulate different scenarios with up to 10,000 components 1 .

IEEE Transactions on Consumer Electronics, 2012

This paper presents the implementation process for an API that integrates interactive digital TV ... more This paper presents the implementation process for an API that integrates interactive digital TV (iDTV) applications and home network (HN) services, mainly concerning issues of the Brazilian iDTV model. The research in this field is important because it represents current trends on the use of iDTV opening many business opportunities. With the convergence of service providers, modern communication technologies and consumer electronics devices at home, new iDTV applications have emerged, particularly those that use the set-top-boxes (or digital TV sets) processing power to provide additional services, which extends the possibilities of interaction between the user and the connected home. To implement this platform, a known model, which considers aspects of the Ginga middleware and the Open Services Gateway Initiative (OSGi) framework, was used. The idea behind the API model is to export service objects from one side to another, allowing the development of two types of applications: the first one on the Ginga-J machine and the last one on the Ginga-NCL machine. The main goals of this paper are (i) presenting the use of free tolls to perform such integration and (ii) showing the most relevant aspects in the core of the two models. Finally, a basic step-by-step process is shown in order to build integrated iDTV-HN real applications using this platform. 1 .

2016 VI Brazilian Symposium on Computing Systems Engineering (SBESC), 2016

This paper presents a novel, complete, and flexible optimization algorithm, which relies on recur... more This paper presents a novel, complete, and flexible optimization algorithm, which relies on recursive executions that re-constrains a model-checking procedure based on Satisfiability Modulo Theories (SMT). This SMT-based optimization technique is able to optimize a wide range of functions, including non-linear and non-convex problems using fixed-point arithmetic. Although SMT-based optimization is not a new technique, this work is the pioneer in solving non-linear and non-convex problems based on SMT; previous applications are only able to solve integer and rational linear problems. The proposed SMT-based optimization algorithm is compared to other traditional optimization techniques. Experimental results show the efficiency and effectiveness of the proposed algorithm, which finds the optimal solution in all evaluated benchmarks, while traditional techniques are usually trapped by local minima.