Books
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A. S. Bazanella, L. Campestrini, and D. Eckhard, Data-driven Controller Design: The ${H}_2$ Approach, Netherlands: Springer, 2012.
[Bibtex]@BOOK{Bazanella:Campestrini:Eckhard:2012, title = {Data-driven Controller Design: The ${H}_2$ Approach}, publisher = {Springer}, year = {2012}, author = {A. S. Bazanella and L. Campestrini and D. Eckhard}, address = {Netherlands}, doi = {10.1007/978-94-007-2300-9}, abstract = {Data-driven methodologies have recently emerged as an important paradigm alternative to model-based controller design and several such methodologies are formulated as an H2 performance optimization. This book presents a comprehensive theoretical treatment of the H2 approach to data-driven control design. The fundamental properties implied by the H2 problem formulation are analyzed in detail, so that common features to all solutions are identified. Direct methods (VRFT) and iterative methods (IFT, DFT, CbT) are put under a common theoretical framework. The choice of the reference model, the experimental conditions, the optimization method to be used, and several other designer?s choices are crucial to the quality of the final outcome, and firm guidelines for all these choices are derived from the theoretical analysis presented. The practical application of the concepts in the book is illustrated with a large number of practical designs performed for different classes of processes: thermal, fluid processing and electromechanical.} } -
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A. S. Bazanella and J. M. Gomes da Silva Jr., Sistemas de controle: princípios e métodos de projeto, Brasil: UFRGS Editora, 2006.
[Bibtex]@BOOK{Bazanella:GomesdaSilva:2006, title = {Sistemas de controle: princ{\'i}pios e m{\'e}todos de projeto}, publisher = {UFRGS Editora}, year = {2006}, author = {A. S. Bazanella and J.M. {Gomes da Silva Jr.}}, address = {Brasil} }
Thesis
- E. C. Boeira, “Sintonia de controladores multivariáveis pelo método da referência virtual com regularização Bayesiana,” Master Thesis, Porto Alegre, 2018.
[Bibtex]@mastersthesis{Boeira:2018, author = {E. C. Boeira}, title = {Sintonia de controladores multivari\'{a}veis pelo m\'{e}todo da refer\^{e}ncia virtual com regulariza\c{c}\~{a}o Bayesiana}, school = {Universidade Federal do Rio Grande do Sul}, year = {2018}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/185245}, abstract = {This work proposes a new extension for the multivariable formulation of the datadriven control method known as Virtual Reference Feedback Tuning. When the process to be controlled contains a significant amount of noise, the standard VRFT approach, that uses either the least squares method or the instrumental variable technique, yield estimates with very poor statistical properties, that may lead the control system to undesirible closed loop performances. Aiming to enhance these statistical properties and hence, the system’s closed loop performance, this work proposes the use of regularization on the multivariable formulation of the VRFT method. Regularization is a feature that has been widely used and researched on the System Identification and Machine Learning communities on the last few years, and it is well suited to cope the high variance issue that emerge on the VRFT method with instrumental variable. Also, a more detailed analysis on the use of regularization for identification of multivariable systems, the proof of the optimal regularization matrix and the exposure of the new regularized VRFT properties can be highlighted as novelties of this work.} } - C. S. Poleto, “Estimação dos estados de biorreatores anaeróbicos,” Master Thesis, Porto Alegre, 2018.
[Bibtex]@mastersthesis{Poleto:2018, author = {C. S. Poleto}, title = {Estima\c{c}\~{a}o dos estados de biorreatores anaer\'{o}bicos}, school = {Universidade Federal do Rio Grande do Sul}, year = {2018}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/174538}, abstract = {Anaerobic bioreactors are devices that degrade organic matter, producing methane and fertilizer, whose process is modelled by non-linear systems. This work goals to estimate, through the study of dynamic models and the observation of collected data, the current amount of substrates, bacteria and carbon dioxide in a bioreactor, in the various points of its operation. For this, two filters were used and compared: Extended Kalman and Particles. These filters intent to attenuate the effect of noise on the collected data from the experiment and generate estimates of the system states, which can be used to operate the bioreactor at its maximum production capacity.} } - R. W. P. Silva, “Controle de potência de transmissão proporcional-integral para redes WirelessHART,” Master Thesis, Porto Alegre, 2017.
[Bibtex]@mastersthesis{Silva:2017, author = {R. W. P. Silva}, title = {Controle de pot\^{e}ncia de transmiss\~{a}o proporcional-integral para redes {WirelessHART}}, school = {Universidade Federal do Rio Grande do Sul}, year = {2017}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/163727}, abstract = {Wireless sensor networks (wsns) are being increasingly adopted in monitor and control tasks in the industry. The devices within these networks are battery-powered, and they communicate through radio frequency. Therefore the radios of the devices account for the most of the consumption of the energy stored in the batteries, and the devices’ communication is subject to interference from other networks and industrial machinery. Transmission power control ({TPC}) techniques can be employed to cope with these problems. There are several tpc techniques in the literature, aiming at a wide range of objectives, from energy saving and interference reduction, to network topology control. This work presents the proposal of a ({TPC}) technique in a wireless sensor network that works by employing proportional-integral ({PI}) controllers. Besides the technique itself, a procedure is presented to design the controllers along some algorithms developed to the ideal case, and the case when there is saturation in the available power levels. This work, unlike the other works found in the literature, presents a linear technique that depends only on information that is already available in each device whose power needs to be adjusted. Therefore, the proposed technique can be employed together with more restrictive industrial protocols that limit the information that can be exchanged in the messages. Besides, it further reduces the power consumption and the interference by avoiding unnecessary transmissions. The proposal was validated through simulations and an experiment using real {WirelessHART} devices, presenting good results and proving that it is possible to adjust the transmission power without necessarily using the extra information.} } - C. S. Garcia, “Ajuste baseado em dados de controladores : o método VRFT embarcado em um aplicativo móvel,” Master Thesis, Porto Alegre, 2017.
[Bibtex]@mastersthesis{Garcia:2017, author = {C.S. Garcia}, title = {Ajuste baseado em dados de controladores : o m\'{e}todo {VRFT} embarcado em um aplicativo m\'{o}vel}, school = {Universidade Federal do Rio Grande do Sul}, year = {2017}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/163773}, abstract = {The Virtual Reference Feedback Tuning ({VRFT}) method is a data-driven method employed to tune the parameters of a controller. An advantage of this method lies in the fact that it does not need a detailed knowledge of the process model. This work presents the development of an Android application which employs the {VRFT} method and a newly developed recursive version of it to tune a {PID} controller based upon the data collected from an experiment conducted on the process. The experiment can be set up, started, monitored, and stopped from inside the mobile application. To communicate with the controller a {Bluetooth-Modbus} gateway and an application layer protocol, designed over the Bluetooth serial communication service, are employed, both newly developed. Finally, the entire solution is verified in two steps: first some experiments were conducted on a simulated process, then another experiment was conducted to tune a real commercial controller, both showing good results.} } - W. M. Haselein, “Identificação de modelos dinâmicos para biorreatores Anaeróbicos,” Master Thesis, Porto Alegre, 2017.
[Bibtex]@mastersthesis{Haselein:2017, author = {W. M. Haselein}, title = {Identifica\c{c}\~{a}o de modelos din\^{a}micos para biorreatores Anaer\'{o}bicos}, school = {Universidade Federal do Rio Grande do Sul}, year = {2017}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/163928}, abstract = {Anaerobic bioreactors are systems that use bacteria to degrade organic substrate in oxygen absence and produce Biogas. In this work, mathematical models were proposed to describes the fed-batch anaerobic bioreactors dynamics, taking into account their complexity and many aspects of microorganisms development. The system structure considered the presence or not of mortality rates and adopted a non-linear behavior to the model. Therefore, was necessary the study of computational techniques able to simulate the involved processes. The identification was made through the minimization method of simulation error, which solves an optimization problem that minimizes the sum of quadratic error between the experiment data and system simulation. Tests were applied to verify the model identifiability. Collected data from real experiments in bioreactors were used to validate the developed models.} } - M. A. D. Tocchetto, “Estimador de estados para robô diferencial,” Master Thesis, Porto Alegre, 2017.
[Bibtex]@mastersthesis{Tocchetto:2017, author = {M. A. D. Tocchetto}, title = {Estimador de estados para rob\^{o} diferencial}, school = {Universidade Federal do Rio Grande do Sul}, year = {2017}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/163910}, abstract = {In this dissertation, the performance of three nonlinear-model based estimators - the Extended Kalman Filter, the Unscented Kalman Filter and the Particle Filter - applied to pose estimation of a differential drive robot is compared. A camera was placed above the operating field of the robot to record the experiments in order to extract the map and generate the ground truth so the evaluation of the error can be done at each time step with high accuracy. The performance of each estimator is assessed systematically and numerically for two robot trajectories. The first experimental results showed that all estimators provide large improvements with respect to odometry and that the sensor modeling is critical for their performance. The particle filter showed a better performance than the others on both experiments, however, its high computational cost makes it difficult to implement in a real-time application. The Unscented Kalman Filter showed a similar performance to the Extended Kalman Filter during the first trajectory. However, during the second one (a curvier path) the Unscented Kalman Filter showed a significant improvement over the Extended Kalman Filter. A second experiment was carried out where the robot plans and executes a trajectory. The results showed the robot can reach a predefined location with an accuracy of the same order of magnitude as the obtained during the robot pose estimation.} } - R. Rui, “Estimação de modelos afins por partes em espaço de estados,” PhD Thesis, Porto Alegre, 2016.
[Bibtex]@phdthesis{Rui:2016, author = {R. Rui}, title = {Estima\c{c}\~{a}o de modelos afins por partes em espa\c{c}o de estados}, school = {Universidade Federal do Rio Grande do Sul}, year = {2016}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/156478}, abstract = {This thesis focuses on the state estimation and parameter identification problems of piecewise affine models. Piecewise affine models are obtained when the state domain or the input domain are partitioned into regions and, for each region, a linear or affine submodel is used to describe the system dynamics. We propose a recursive state estimation algorithm and a parameter identification algorithm to a class of piecewise affine models. We propose a Bayesian state estimate which uses the Kalman filter in each submodel. In the this estimator, the cumulative distribution is used to compute the posterior distribution of the state as well as the probability of each submodel. On the other hand, the proposed identification method uses the Expectation Maximization (EM) algorithm to identify the model parameters. We use the cumulative distribution to compute the probability of each submodel based on the system measurements. Subsequently, we use the Kalman smoother to estimate the state and compute a surrogate function for the likelihood function. This function is used to estimate the model parameters. The proposed estimator was used to estimate the state of the nonlinear model for vibrations caused by clearances. Numerical simulations were performed, where we have compared the proposed method to the extended Kalman filter and the particle filter. The identification algorithm was used to identify the model parameters of the JAS 39 Gripen aircraft as well as the nonlinear model for vibrations caused by clearances.} } - T. Salvatori, “Modelagem caixa-preta de biorreatores em modo descontínuo utilizando modelos polinomiais do tipo NAR e NARMA,” Master Thesis, Porto Alegre, 2016.
[Bibtex]@mastersthesis{Salvatori:2016, author = {T. Salvatori}, title = {Modelagem caixa-preta de biorreatores em modo descont\'{i}nuo utilizando modelos polinomiais do tipo {NAR} e {NARMA}}, school = {Universidade Federal do Rio Grande do Sul}, year = {2016}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/148790}, abstract = {Bioreactors, which are explored since antiquity, are systems that are capable of performing the fermentation of organic compounds. Nowadays, they are widely applied due to its diversity of applications. These systems can operate in different fermentation modes: continuous, fed-batch and batch. This last fermentation method along with the process of anaerobic digestion allow organic matter to be degraded and converted into biogas, which is a key factor for clean energy generation. It is thus realized that the study of bioreactors in batch mode and anaerobic digestion process is crucial to the development of research related to renewable energy generation. For a better understanding of the process, some authors have proposed studies based on parameters identification in descriptive nonlinear models, white-box models, which are widely used in bioreactors modeling. The main limitation of this approach is that the system identification procedure using these models can be complex and time-consuming, or even the parameters of the systems may not be identifiable. In order to overcome these difficulties, we propose in this work the use of black-box polynomial models for bioreactor modeling in batch mode, with NAR and NARMA model structures. Black-box models represent real systems using its output, without explicitly considering the inner mechanisms of the system, simplifying the identification procedure. Thus, the aim of this work is to investigate the prediction and monitoring methane production using the black-box models proposed using bioreactor systems in batch and anaerobic digestion process. The investigation uses numerical simulation and experimental data. At first, polynomial models of the types NAR and NARMA are proposed. The parameters from these models using simulation data with and without noise at the output, based on initial conditions proposed in the literature, are estimated. Subsequently we perform validations of these models. The next step is the study of the validity domain of the proposed black-box models, which is performed by testing many different initial conditions of the system that represents bioreactors in batch fermentation mode. Finally, we used real experimental data to perform the estimation of the parameters from the process and validation of models. The results, both simulated and experimental, indicate that the polynomial models NAR and NARMA are appropriate for prediction of methane fermentation in batch bioreactors.} } - D. A. Tesch, “Extensão do iterative feedback tuning para sistemas em cascata com aplicação em controle de quadricópteros,” Master Thesis, Porto Alegre, 2016.
[Bibtex]@mastersthesis{Tesch:2016, author = {D. A. Tesch}, title = {Extens\~{a}o do iterative feedback tuning para sistemas em cascata com aplica\c{c}\~{a}o em controle de quadric\'{o}pteros}, school = {Universidade Federal do Rio Grande do Sul}, year = {2016}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/142681}, abstract = {The methods of data-driven control have the distinction to use the data collected from experiments to perform the tuning of the controller directly and without using any process model. One method already established is the Iterative Feedback Tuning, this method is characterized as an iterative optimization algorithm that aims to minimize the H2 norm performance criterion. The present work proposes an extension based on the classical Iterative Feedback Tuning algorithm for cascade systems with two control loops. The cascade format with two loops is a common structure and widely used in industrial applications. In classical control methods, the tuning of this type of structure usually involves two steps. First, the inner loop is tuned and subsequently the outer loop. The advantage of the proposed data-driven control method is to perform this tuning of both controller simultaneously and concurrently. We choose as an application a unmanned aerial vehicle (UAV) with four rotors, better known as quadcopter. This application has a complex dynamic, since the system is classified as being non-linear and multivariable, demonstrated by the quadcopter dynamic equations. A series of simulations and practical experiments are presented to demonstrate the dynamic model described and also to validate the method CIFT algorithms.} } - G. R. Gonçalves da Silva, “Especificação do modelo de referência em projeto de controladores multivariáveis discretos,” Master Thesis, Porto Alegre, 2016.
[Bibtex]@mastersthesis{Goncalves:2016, author = {G. R. {Gon\c{c}alves da Silva}}, title = {Especifica\c{c}\~{a}o do modelo de refer\^{e}ncia em projeto de controladores multivari\'{a}veis discretos}, school = {Universidade Federal do Rio Grande do Sul}, year = {2016}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/141821}, abstract = {The choice of the reference model is the main task to be performed by the designer in a model reference control design. A poor choice of the reference model may result in a closed-loop performance that bears no resemblance to the specifications and the closedloop may even be unstable. In this work we discuss this issue in the control of multivariable plants. Experimental results in a three tank level control plant show a seemingly correct, yet naive, choice of reference model leading to very poor closed-loop performance. The problem is then analyzed, exposing the naivete of the design example. We start by recognizing the fundamental constraints imposed by the system and then deriving general guidelines respecting these contraints for the effective choice of the reference model in multivariable systems. We also provide a novel formulation to compute the minimal relative degree of each element of the reference model without needing a complete model of the plant. The application of these guidelines to simulations and the three tank plant illustrates their effectiveness.} } - L. A. G. Chía, “Aplicação e melhorias do método de controle VRFT para sistemas multivariáveis,” Master Thesis, Porto Alegre, 2015.
[Bibtex]@mastersthesis{Chia:2015, author = {L. A. G. Ch\'{i}a}, title = {Aplica\c{c}\~{a}o e melhorias do m\'{e}todo de controle {VRFT} para sistemas multivari\'{a}veis}, school = {Universidade Federal do Rio Grande do Sul}, year = {2015}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/127692}, abstract = {Data-driven control methods are a variety of control designs that are developed to use batches of input-output data collected, from the process to be controlled without making explicitly use of parametric models of these processes. Although data driven control methods have been largely used in SISO systems, the extent of this methodology to multivariable processes is yet a necessity, considering that the control design must take into account the multivariable nature of the process, that is, the interaction between different variables involved. The analysis and application of one of these methods is the main objective of this work, which is intended to present and improvement to the existing Virtual Reference Feedback Tuning Method (VRFT) for Multivariable systems, since the methodology disclosed in the literature restricts the application to a limited class of processes. Moreover, in this work it is proposed an extension of the VRFT method to the MIMO case, which does not present restrictions and closed loop performance of each variable can be determined accordingly. The method can be used to tune a centralized or decentralized controller. Furthermore, when the signals are corrupted by noise the use of an instrumental variable and/or an appropriate filter is proposed. All these contributions are demonstrated through simulations as well as tests conducted in a real plant, which showed satisfactory performance demonstrating the applicability of this method in real systems.} } - D. Eckhard, “Ferramentas para melhoria da convergência dos métodos de identificação por erro de predição,” PhD Thesis, Porto Alegre, 2012.
[Bibtex]@phdthesis{Eckhard:2012, author = {D. Eckhard}, title = {Ferramentas para melhoria da converg{\^e}ncia dos m{\'e}todos de identifica{\c{c}}{\~a}o por erro de predi{\c{c}}{\~a}o}, school = {Universidade Federal do Rio Grande do Sul}, year = {2012}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/75872}, abstract = {The Prediction Error Method is related to a non-convex optimization problem. It is usual to apply iterative algorithms to solve this optimization problem. However, iterative algorithms can get stuck at a local minimum of the cost function or converge to the border of the searching space. An analysis of the cost function and sufficient conditions to ensure the convergence of the iterative algorithms to the global minimum are presented in this work. It is observed that this conditions depend on the spectrum of the input signal used in the experiment. This work presents tools to improve the convergence of the algorithms to the global minimum, which are based on the manipulation of the input spectrum.} } - R. Rui, “Modelos com parametrização polinomial: identificabilidade, informatividade e identificação,” Master Thesis, Porto Alegre, 2012.
[Bibtex]@mastersthesis{Rui:2012, author = {R. Rui}, title = {Modelos com parametriza{\c{c}}{\~a}o polinomial: identificabilidade, informatividade e identifica{\c{c}}{\~a}o}, school = {Universidade Federal do Rio Grande do Sul}, year = {2012}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/75874}, abstract = {In white box modeling we obtain a model for a process from the equations of the physical/chimical phenomena involved. These models are parameterized, but the parameters used are often unknown. In these cases it is necessary to perform a parametric identification procedure which represents a highly challenging problem, with many theoretical and practical open questions when the parameters are non- linears in the model. The aim of this work is to present and study a method able to determine whether a predetermined model structure can be identified and that can be used in conjunction with another identification method to identify the system. The method that will be presented is based on differential algebra and is known as Ritt algorithm. The Ritt?s algorithm transforms a predetermined model structure in linear regression in the parameters from which one can use the least squares method or instrumental variables to identify the system. We will present some case studies and realise the analysis of identifiability for each case. For some cases we will identify the system, and then present a study for the consistency and precision of the estimates.} } - T. Neuhaus, “Projeto de controladores não lineares utilizando referência virtual,” Master Thesis, Porto Alegre, 2012.
[Bibtex]@mastersthesis{Neuhaus:2012, author = {T. Neuhaus}, title = {Projeto de controladores n{\~a}o lineares utilizando refer{\^e}ncia virtual}, school = {Universidade Federal do Rio Grande do Sul}, year = {2012}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/71570}, abstract = {This work aims to present some concepts related to linear and nonlinear system identification, as well as the ?concept of virtual reference that, together with data based controller design's theory, provides design framework for nonlinear controllers. The Virtual Reference Feedback Tuning method (VRFT) is used as a basis for the current proposal, where we propose to unite nonlinear system identification algorithms and virtual reference to obtain the ideal controller: the one which makes the system behave as desired in closed loop. It was choosen to model the controller as a rational model due the wide variety of practical systems that can be represented by this model structure. For rational system identification we used an iterative algorithm which, based on the signal from input and output of the pIant, allows to identify the parameters of the pre defined controller structure with the signals obtained by virtual reference. To demonstrate the operation of the proposed identification controller methodology, illustrative examples are presented in situations where the ideal controller can be represented by the class of modeIs, and also when it is not possible.} } - L. Campestrini, “Contribuições para métodos de controle baseados em dados obtidos em apenas um experimento,” PhD Thesis, Porto Alegre, 2010.
[Bibtex]@phdthesis{Campestrini:2010, author = {L. Campestrini}, title = {Contribui{\c{c}}{\~{o}}es para m{\'{e}}todos de controle baseados em dados obtidos em apenas um experimento}, school = {Universidade Federal do Rio Grande do Sul}, year = {2010}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/26865}, abstract ={This work presents some contributions to data-based control methods where data is obtained in only one experiment, in order to make them more attractive to industrial process applications. Using data from experiments on the process, data-based methods estimate the parameters of fixed structure controller, through the minimization of the error between the closed loop response of the system and the desired response, given by a reference model. The Virtual Reference Feedback Tuning - VRFT method is the most expressive method in the literature that estimates the controller parameters using only one batch of data, but this method presents some inconveniences in its formulation which limit its application. In this work, the VRFT method is modified in order to obtain a flexible VRFT method, which minimizes a flexible criterion, and then obtains the controller parameters together with the parameters related to the reference model numerator; thus, if the plant which we want to control is non-minimum phase, then the criterion is able to estimate these zeros and they need to be included in the reference model that will be used in the control design. Besides, when dealing with noisy systems, the VRFT method needs an instrumental variable so the controller parameters estimate is unbiased. In order to eliminate this necessity, a new data-based control is proposed in this work, which is formulated using identification theory. This method can be seen as the identification of a system, where the process transfer function is reparameterized as a function of the ideal controller and the reference model. Besides, we extend the experimental design theory where the problem is solved using LMI constraints to the case of the optimal controller identification method. All these contributions are illustrated through simulations.} } - M. F. Flores da Cunha, “Iterative Feedback Tuning em sistemas sujeitos a não-linearidades não-diferenciáveis,” Master Thesis, Porto Alegre, 2010.
[Bibtex]@mastersthesis{FloresdaCunha:2010, author = {M. F. {Flores da Cunha}}, title = {Iterative Feedback Tuning em sistemas sujeitos a n{\~a}o-linearidades n{\~a}o-diferenci{\'a}veis}, school = {Universidade Federal do Rio Grande do Sul}, year = {2010}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/26866}, abstract = {Data based control methods use data collected from a plant?s ?regular? operation to minimize a performance criterion, typically in quadratic form, without any information about a system?s model. Iterative Feedback Tuning (IFT) is one such method that uses closed-loop operating data to generate an unbiased estimate of the cost criterion gradient, which is then minimized with some form of the Newton method. Results in the literature for IFT applied to non-linear systems require that the non-linearity is differentiable (basically, linearizing the system around an operating point). One practical application of the algorithm to tune a controller for a servomotor system with backlash is the only result found. This work investigates, using simulated and practical examples, the suitability of the use of IFT in systems with non-differentiable non-linearities commonly found in mechanical systems, such as backlash and dead-zone, and saturation, found in every physical system.} } - M. E. Bergel, “Estudo de alternativas para o ajuste de controladores PID utilizando métodos baseados em dados,” Master Thesis, Porto Alegre, 2009.
[Bibtex]@mastersthesis{Bergel:2009, author = {M. E. Bergel}, title = {Estudo de alternativas para o ajuste de controladores {PID} utilizando m{\'{e}}todos baseados em dados}, school = {Universidade Federal do Rio Grande do Sul}, year = {2009}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/21927}, abstract = {PID controllers are widely used in industrial process control. These controllers must necessarily be properly tuned to ensure the correct operation of the controlled process. In order to meet this need, the so-called tuning methods for PID controllers have emerged, initially proposed by John Ziegler and Nathaniel B. Nichols in 1942. Since then many other controller design methods based on the ideas of Ziegler and Nichols have been proposed, giving rise to a family of related methods. Given the simplicity of implementation and the low computational effort involved, these methods are suitable to be incorporated into the firmware of low cost industrial PID controllers. These methods have generated such a legacy that its use remains intense until the present day. However, with the growing offer of low cost and high performance microcontrollers, the computational effort of a tuning method is becoming less important. This opens up scope for exploring other methods that provide better performance and robustness, possibly at the cost of demanding more computational resources. This study aims to evaluate alternative methods that are compatible with current computational resources. Methods with higher computational effort, such as Virtual Reference Feedback Tuning (VRFT), Iterative Feedback Tuning (IFT) and Iterative Correlation based Tuning (ICbT) are presented as candidates to be incorporated into the firmware of industrial PID controllers. These are direct data-based methods for the adjustment of controllers where the parameters are determined such that the behavior of the closed-loop system is such as to minimize a performance criterion defined a priori. Through this performance criterion one can specify the desired behavior for the closed-loop system. This work analyzes the main characteristics of these methods, results and computational effort. Based on the results of this analysis it is shown that the methods VRFT, IFT and ICbT can be used as an alternative to the adjustment (build into the firmware) of industrial PID controllers.} } - D. Eckhard, “Projeto de controladores baseado em dados : convergência dos métodos iterativos,” Master Thesis, Porto Alegre, 2008.
[Bibtex]@mastersthesis{Eckhard:2008, author = {D. Eckhard}, title = {Projeto de controladores baseado em dados : converg{\^e}ncia dos m{\'e}todos iterativos}, school = {Universidade Federal do Rio Grande do Sul}, year = {2008}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/17625}, abstract = {Data-based control design methods consist of adjusting the parameters of the controller directly from batches of input-output data of the process; no process model is used. The adjustment is done by solving an optimization problem, which searches the argument that minimizes a specific cost function. Iterative algorithms based on the gradient are applied to solve the optimization problem, like the steepest descent algorithm, Newton algorithm and some variations. The only information utilized for the steepest descent algorithm is the gradient of the cost function, while the others need more information like the hessian. Longer and more complex experiments are used to obtain more informations, that turns the application more complicated. For this reason, the steepest descent method was chosen to be studied in this work. The convergence of the steepest descent algorithm to the global minimum is not fully studied in the literature. This convergence depends on the initial conditions of the algorithm and on the step size. The initial conditions must be inside a specific domain of attraction, and how to enlarge this domain is treated by the methodology Cost Function Shaping. The main contribution of this work is a method to compute efficiently the step size, to ensure convergence to the global minimum. Some informations about the process are utilized, and this work presents how to estimate these informations. Simulations and experiments demonstrate how the methods work.} } - L. C. Stevanatto Filho, “Identificação parcial da resposta em frequência de sistemas multivariáveis e sintonia de controladores descentralizados,” Master Thesis, Porto Alegre, 2008.
[Bibtex]@mastersthesis{Stevanatto:2008, author = {L. C. {Stevanatto Filho}}, title = {Identifica{\c{c}}{\~{a}}o parcial da resposta em frequ{\^e}ncia de sistemas multivari{\'a}veis e sintonia de controladores descentralizados}, school = {Universidade Federal do Rio Grande do Sul}, year = {2008}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/15739}, abstract = {It use relay experiments for square multivariable system frequency response and decentralized PID controller tunning.} } - L. Campestrini, “Sintonia de controladores PID descentralizados baseada no método do ponto crítico,” Master Thesis, Porto Alegre, 2006.
[Bibtex]@mastersthesis{Campestrini:2006, author = {L. Campestrini}, title = {Sintonia de controladores {PID} descentralizados baseada no m{\'{e}}todo do ponto cr{\'{i}}tico}, school = {Universidade Federal do Rio Grande do Sul}, year = {2006}, address = {Porto Alegre}, url = {http://hdl.handle.net/10183/17625}, abstract = {PID controllers are widely used in process control, in singlevariable systems as well as in multivariable ones. Yet, many of the controllers found in industry are poorly tuned. One of the simplest tuning method of PID controllers consists in identifying some values which are related to the process characteristics, and simply apply some formulae based on these quantities to determine the parameters of the controllers. Theses quantities are the ultimate gain and the ultimate period of the process, which are directly related to the system stability limit. A very interesting characteristic of this method is that it is easily implemented by an auto-tuning control. Thus, auto-tuning methods of this kind of controllers have been largely used in singlevariable systems, using the relay feedback experiment in order to obtain the ultimate quantities, which are needed to tune the controllers. The relay feedback experiment consists in applying a bang-bang control to the process from which the ultimate quantities are to be identified. This procedure, under some conditions, provides a sustained oscillation in the process? output, from which the ultimate quantities are obtained. Aiming at auto-tuning of PID controllers in multivariable systems, the relay feedback experiment can also be used in order to get the ultimate quantities. Different relay feedback procedures can be applied to multivariable processes, but only one of these can identify the real multivariable ultimate quantities, formally considering the multivariable nature of the process: the decentralized relay feedback (DRF). However, the tuning of the controllers proposed in the literature is based on Ziegler-Nichols like formulae, what seems to be, many times, inappropriate. This work presents a multivariable tuning method of decentralized PID controllers, based on the process? ultimate quantities. This method extends the ultimate point method used in SISO systems to multivariable ones, through multivariable analysis of the problem. The analysis of the ultimate point method used in singlevariable systems shows that a PI or PID controller tuned through formulae based on the process? ultimate quantities will always dislocate the ultimate point to another point in the complex plane, determined by the used formulae. The tuning method proposed in this work dislocates the process? ultimate point of a multivariable process to another point in the complex plane, chosen a priori, modifying the system?s ultimate frequency.} }
Journal Articles
- M. A. Longhi, E. D. Rodríguez, B. Walkley, D. Eckhard, Z. Zhang, J. L. Provis, and A. P. Kirchheim, “Metakaolin-based geopolymers: Efflorescence and its effect on microstructure and mechanical properties,” Ceramics International, vol. 48, iss. 2, pp. 2212-2229, 2022. doi:https://doi.org/10.1016/j.ceramint.2021.09.313
[BibTeX] [Abstract]
Efflorescence in geopolymers results from mobility of excess alkali and consequent crystallization of alkali carbonates. Efflorescence potential of various geopolymers has been reported previously but the knowledge regarding the effect of efflorescence on the microstructure and mechanical properties of geopolymers remains limited. In this work, metakaolin-based geopolymers were exposed to air, partially immersed in water, and fully immersed, to simulate different processes involved in efflorescence formation. The mechanical properties were assessed by compressive, splitting tensile and flexural strengths, and linear deformation. The microstructural features were investigated by SEM, synchrotron XRD, multinuclear MAS NMR, MIP and synchrotron X-ray microtomography. Extensive efflorescence resulted in a reduction of mechanical strength and changes in the nanostructure and microstructure, which is different from observations for Portland cement-based materials, where efflorescence is usually regarded as a surface or aesthetic problem. The understanding of the relationship between efflorescence formation, the synthesis and exposure conditions provides important insight into the manufacturing and application conditions of geopolymer related materials.
@article{Longhi:Rodriguez:Walkley:Eckhard:Zhang:Provis:Kirchheim:2022, title = {Metakaolin-based geopolymers: Efflorescence and its effect on microstructure and mechanical properties}, journal = {Ceramics International}, volume = {48}, number = {2}, pages = {2212-2229}, year = {2022}, issn = {0272-8842}, doi = {https://doi.org/10.1016/j.ceramint.2021.09.313}, url = {https://www.sciencedirect.com/science/article/pii/S0272884221031230}, author = {M. A. Longhi and E. D. Rodríguez and B. Walkley and D. Eckhard and Z. Zhang and J. L. Provis and A. P. Kirchheim}, keywords = {Geopolymer, Metakaolin, Efflorescence, Leaching, Mechanical properties, Durability}, abstract = {Efflorescence in geopolymers results from mobility of excess alkali and consequent crystallization of alkali carbonates. Efflorescence potential of various geopolymers has been reported previously but the knowledge regarding the effect of efflorescence on the microstructure and mechanical properties of geopolymers remains limited. In this work, metakaolin-based geopolymers were exposed to air, partially immersed in water, and fully immersed, to simulate different processes involved in efflorescence formation. The mechanical properties were assessed by compressive, splitting tensile and flexural strengths, and linear deformation. The microstructural features were investigated by SEM, synchrotron XRD, multinuclear MAS NMR, MIP and synchrotron X-ray microtomography. Extensive efflorescence resulted in a reduction of mechanical strength and changes in the nanostructure and microstructure, which is different from observations for Portland cement-based materials, where efflorescence is usually regarded as a surface or aesthetic problem. The understanding of the relationship between efflorescence formation, the synthesis and exposure conditions provides important insight into the manufacturing and application conditions of geopolymer related materials.} } - E. Boeira and D. Eckhard, “pyvrft: A Python package for the Virtual Reference Feedback Tuning, a direct data-driven control method,” SoftwareX, vol. 11, p. 100383, 2020. doi:https://doi.org/10.1016/j.softx.2019.100383
[BibTeX] [Abstract]
In this paper, the pyvrft, a Python package for the data-driven control method known as Virtual Reference Feedback Tuning (VRFT), is presented. Virtual Reference Feedback Tuning is a control design technique that does not use a mathematical model from the process to be controlled. Instead, it uses input and output data from an experiment to compute the controller’s parameters, aiming to minimize an H2 Model Reference criterion. The package implements an unbiased estimate of the controller for MIMO (Multiple-Input Multiple-Output) processes using both least-squares and instrumental variable techniques. The package also provides accessory functions to import data and to perform MIMO systems simulations, together with some examples.
@article{Boeira:Eckhard:2020, title = "pyvrft: A Python package for the Virtual Reference Feedback Tuning, a direct data-driven control method", journal = "SoftwareX", volume = "11", pages = "100383", year = "2020", issn = "2352-7110", doi = "https://doi.org/10.1016/j.softx.2019.100383", url = "http://www.sciencedirect.com/science/article/pii/S2352711019302894", author = "Emerson Boeira and Diego Eckhard", keywords = "Control systems, Data-driven control, VRFT, Python", abstract = "In this paper, the pyvrft, a Python package for the data-driven control method known as Virtual Reference Feedback Tuning (VRFT), is presented. Virtual Reference Feedback Tuning is a control design technique that does not use a mathematical model from the process to be controlled. Instead, it uses input and output data from an experiment to compute the controller’s parameters, aiming to minimize an H2 Model Reference criterion. The package implements an unbiased estimate of the controller for MIMO (Multiple-Input Multiple-Output) processes using both least-squares and instrumental variable techniques. The package also provides accessory functions to import data and to perform MIMO systems simulations, together with some examples." } - R. W. P. da Silva, D. Eckhard, and I. Müller, “PI-based and anti-windup transmission power control for WirelessHART field devices,” IET Wireless Sensor Systems, vol. 10, iss. 4, pp. 137-144, 2020. doi:10.1049/iet-wss.2018.5040
[BibTeX] [Abstract]
In the last couple of decades, the industry saw an increase in the number of wireless sensor networks (WSNs) in replacement of the old cabled technology due to lower deployment and maintenance costs. To keep this momentum, those industrial WSN (IWSN) must assure robustness, scalability, low power, and low maintenance, and the network protocol stack is an important piece of this puzzle. One great dilemma faced by IWSN protocols is how to sustain reliable radio links while avoiding draining too much energy from the battery. In this context, WirelessHART (WH) and ISA SP100.11a, for example require the hardware of the nodes to provide multiple power levels for transmission. Unfortunately, those protocols do not provide a standard procedure to choose between those levels. A simple but inefficient solution often employed simply chooses the highest level available. Seeking a better solution, this proposal presents a transmission power control (TPC) methodology that allows energy saving while sustaining the quality of the communication link employing a simple proportional-integral (PI) controller plus anti-windup. The proposed approach does not rely on special TPC-related packets, which is advantageous in comparison with other approaches from the literature by allowing this work to be fully compliant with existing IWSN protocols.
@ARTICLE{DaSilva:Eckhard:Muller:2020, author={R. W. P. {da Silva} and D. {Eckhard} and I. {Müller}}, journal={IET Wireless Sensor Systems}, title={{PI}-based and anti-windup transmission power control for {WirelessHART} field devices}, year={2020}, volume={10}, number={4}, pages={137-144}, abstract={In the last couple of decades, the industry saw an increase in the number of wireless sensor networks (WSNs) in replacement of the old cabled technology due to lower deployment and maintenance costs. To keep this momentum, those industrial WSN (IWSN) must assure robustness, scalability, low power, and low maintenance, and the network protocol stack is an important piece of this puzzle. One great dilemma faced by IWSN protocols is how to sustain reliable radio links while avoiding draining too much energy from the battery. In this context, WirelessHART (WH) and ISA SP100.11a, for example require the hardware of the nodes to provide multiple power levels for transmission. Unfortunately, those protocols do not provide a standard procedure to choose between those levels. A simple but inefficient solution often employed simply chooses the highest level available. Seeking a better solution, this proposal presents a transmission power control (TPC) methodology that allows energy saving while sustaining the quality of the communication link employing a simple proportional-integral (PI) controller plus anti-windup. The proposed approach does not rely on special TPC-related packets, which is advantageous in comparison with other approaches from the literature by allowing this work to be fully compliant with existing IWSN protocols.}, doi={10.1049/iet-wss.2018.5040}, ISSN={2043-6394}, month={}, } - M. Gevers, A. S. Bazanella, and G. A. Pimentel, “Identifiability of Dynamical Networks With Singular Noise Spectra,” IEEE Transactions on Automatic Control, vol. 64, iss. 6, p. 2473–2479, 2019. doi:10.1109/TAC.2018.2866448
[BibTeX] [Abstract]
This paper addresses the problem of identifiability of dynamical networks in the case where the vector of noises on the nodes does not have full rank. In the full-rank noise case, network identifiability is defined as the capability of uniquely identifying the transfer function matrices describing the network from informative data. This includes the noise model, which can be uniquely defined when the noise vector has full rank. When the noise vector has a singular spectrum, it admits an infinite number of different noise models and the definition of network identifiability must be adapted to demand that the correct noise spectrum be identified from informative data rather than a specific noise model. With this new definition, we show that a network with rank reduced noise is identifiable under the same conditions that apply to a network with full-rank noise.
@ARTICLE{GeversBazanella:Pimentel:2019, author={M. {Gevers} and A. S. {Bazanella} and G. A. {Pimentel}}, journal={IEEE Transactions on Automatic Control}, title={Identifiability of Dynamical Networks With Singular Noise Spectra}, year={2019}, volume={64}, number={6}, pages={2473--2479}, doi={10.1109/TAC.2018.2866448}, abstract={This paper addresses the problem of identifiability of dynamical networks in the case where the vector of noises on the nodes does not have full rank. In the full-rank noise case, network identifiability is defined as the capability of uniquely identifying the transfer function matrices describing the network from informative data. This includes the noise model, which can be uniquely defined when the noise vector has full rank. When the noise vector has a singular spectrum, it admits an infinite number of different noise models and the definition of network identifiability must be adapted to demand that the correct noise spectrum be identified from informative data rather than a specific noise model. With this new definition, we show that a network with rank reduced noise is identifiable under the same conditions that apply to a network with full-rank noise.}, } - C. Lorenzini, A. S. Bazanella, L. F. A. Pereira, and G. R. Gonçalves da Silva, “The generalized forced oscillation method for tuning PID controllers,” ISA Transactions, vol. 87, p. 68–87, 2019. doi:https://doi.org/10.1016/j.isatra.2018.11.014
[BibTeX] [Abstract]
In this paper a generalized tuning methodology for proportional–integral–derivative (PID) controllers is proposed. The methodology is akin to the Ziegler–Nichols forced oscillation method, inheriting fully its practical appeal, but can be applied to much more general classes of plants. This generalization is achieved by employing a relay with adjustable phase (RAP) in a relay feedback experiment, and the tuning consists of formulas based on measurements obtained from this experiment. Experimental results in a liquid processing plant with of-the-shelf industrial equipments illustrate the performance of the methodology and the practical procedures involved in its application, which can be fully automated.
@article{Lorenzini:Bazanella:Pereira:Goncalves:2019, title = "The generalized forced oscillation method for tuning {PID} controllers", journal = "ISA Transactions", volume = "87", pages = "68--87", year = "2019", issn = "0019-0578", doi = "https://doi.org/10.1016/j.isatra.2018.11.014", url = "http://www.sciencedirect.com/science/article/pii/S0019057818304506", author = "C. Lorenzini and A. S. Bazanella and L. F. A. Pereira and G. R. {Gon\c{c}alves da Silva}", keywords = "Fractional-order systems, Frequency domain controller design, Process control, PID controllers, Relay with adjustable phase (RAP) experiment, Ziegler–Nichols (ZN) methods", abstract = "In this paper a generalized tuning methodology for proportional–integral–derivative (PID) controllers is proposed. The methodology is akin to the Ziegler–Nichols forced oscillation method, inheriting fully its practical appeal, but can be applied to much more general classes of plants. This generalization is achieved by employing a relay with adjustable phase (RAP) in a relay feedback experiment, and the tuning consists of formulas based on measurements obtained from this experiment. Experimental results in a liquid processing plant with of-the-shelf industrial equipments illustrate the performance of the methodology and the practical procedures involved in its application, which can be fully automated." } - G. R. Gonçalves da Silva, A. S. Bazanella, C. Lorenzini, and L. Campestrini, “Data-Driven LQR Control Design,” IEEE Control Systems Letters, vol. 3, iss. 1, p. 180–185, 2019. doi:10.1109/LCSYS.2018.2868183
[BibTeX] [Abstract]
This letter presents a data-driven solution to the discrete-time infinite horizon linear quadratic regulator (LQR) problem. The state feedback gain is computed directly from a batch of input and state data collected from the plant. Simulation examples illustrate the convergence of the proposed solution to the optimal LQR gain as the number of Markov parameters tends to infinity. Experiments in an uninterruptible power supply are presented, which demonstrate the practical applicability of the design methodology.
@ARTICLE{Goncalves:Bazanella:Lorenzini:Campestrini:2019, author={G. R. {Gonçalves da Silva} and A. S. {Bazanella} and C. {Lorenzini} and L. {Campestrini}}, journal={IEEE Control Systems Letters}, title={Data-Driven {LQR} Control Design}, year={2019}, volume={3}, number={1}, pages={180--185}, abstract={This letter presents a data-driven solution to the discrete-time infinite horizon linear quadratic regulator (LQR) problem. The state feedback gain is computed directly from a batch of input and state data collected from the plant. Simulation examples illustrate the convergence of the proposed solution to the optimal LQR gain as the number of Markov parameters tends to infinity. Experiments in an uninterruptible power supply are presented, which demonstrate the practical applicability of the design methodology.}, doi={10.1109/LCSYS.2018.2868183}, abstract={This letter presents a data-driven solution to the discrete-time infinite horizon linear quadratic regulator (LQR) problem. The state feedback gain is computed directly from a batch of input and state data collected from the plant. Simulation examples illustrate the convergence of the proposed solution to the optimal LQR gain as the number of Markov parameters tends to infinity. Experiments in an uninterruptible power supply are presented, which demonstrate the practical applicability of the design methodology.} } - J. Hendrickx, M. Gevers, and A. S. Bazanella, “Identifiability of dynamical networks with partial node measurements,” IEEE Transactions on Automatic Control, vol. 64, iss. 6, p. 2240–2253, 2019. doi:10.1109/TAC.2018.2867336
[BibTeX] [Abstract]
Much recent research has dealt with the identifiability of a dynamical network in which the node signals are connected by causal linear transfer functions and are excited by known external excitation signals and/or unknown noise signals. A major research question concerns the identifiability of the whole network-topology and all transfer functions-from the measured node signals and external excitation signals. So far all results on the identifiability of the whole network have assumed that all node signals are measured. This paper presents the first results for the situation where not all node signals are measurable, under the assumptions that, first, the topology of the network is known, and, second, each node is excited by a known external excitation. Using graph theoretical properties, we show that the transfer functions that can be identified depend essentially on the topology of the paths linking the corresponding vertices to the measured nodes. A practical outcome is that, under those assumptions, a network can often be identified using only a small subset of node measurements.
@article{Hendrickx:Gevers:Bazanella:2019, Author = {J. Hendrickx and M. Gevers and A.S. Bazanella}, Journal = {IEEE Transactions on Automatic Control}, Title = {Identifiability of dynamical networks with partial node measurements}, year={2019}, volume={64}, number={6}, pages={2240--2253}, doi={10.1109/TAC.2018.2867336}, abstract={Much recent research has dealt with the identifiability of a dynamical network in which the node signals are connected by causal linear transfer functions and are excited by known external excitation signals and/or unknown noise signals. A major research question concerns the identifiability of the whole network-topology and all transfer functions-from the measured node signals and external excitation signals. So far all results on the identifiability of the whole network have assumed that all node signals are measured. This paper presents the first results for the situation where not all node signals are measurable, under the assumptions that, first, the topology of the network is known, and, second, each node is excited by a known external excitation. Using graph theoretical properties, we show that the transfer functions that can be identified depend essentially on the topology of the paths linking the corresponding vertices to the measured nodes. A practical outcome is that, under those assumptions, a network can often be identified using only a small subset of node measurements.} } - E. Boeira, V. Bordignon, D. Eckhard, and L. Campestrini, “Comparing MIMO Process Control Methods on a Pilot Plant,” Journal of Control, Automation and Electrical Systems, vol. 29, iss. 4, p. 411–425, 2018. doi:10.1007/s40313-018-0387-6
[BibTeX] [Abstract]
This work presents a comparison among three different control strategies for multivariable processes. The techniques were implemented in a pilot plant with coupled control loops, where all steps used to design the controllers were described allowing to establish a trade-off between algorithm complexity, information needed from the process and achieved performance. Two data-driven control techniques are used: multivariable ultimate point method to design a decentralized PID controller and virtual reference feedback tuning to design a centralized PID controller. A mathematical model of the process is obtained and used to design a model-based generalized predictive controller. Experimental results allow us to evaluate the performance achieved for each method, as well as to infer on their advantages and disadvantages.
@Article{Boeira:Bordignon:eckhard:Campestrini:2018, abstract={This work presents a comparison among three different control strategies for multivariable processes. The techniques were implemented in a pilot plant with coupled control loops, where all steps used to design the controllers were described allowing to establish a trade-off between algorithm complexity, information needed from the process and achieved performance. Two data-driven control techniques are used: multivariable ultimate point method to design a decentralized PID controller and virtual reference feedback tuning to design a centralized PID controller. A mathematical model of the process is obtained and used to design a model-based generalized predictive controller. Experimental results allow us to evaluate the performance achieved for each method, as well as to infer on their advantages and disadvantages.}, author = {E. Boeira and Bordignon, V. and Eckhard, D. and Campestrini, L.}, title = {Comparing {MIMO} Process Control Methods on a Pilot Plant}, journal = {Journal of Control, Automation and Electrical Systems}, year = {2018}, month = {Aug}, volume = {29}, number = {4}, pages = {411--425}, issn = {2195--3899}, doi = {10.1007/s40313-018-0387-6} } - G. R. Gonçalves da Silva, L. Campestrini, and A. S. Bazanella, “Multivariable Virtual Reference Feedback Tuning for Non-Minimum Phase Plants,” IEEE Control Systems Letters, vol. 2, iss. 1, p. 121–126, 2018. doi:10.1109/LCSYS.2017.2763824
[BibTeX] [Abstract]
When applying model reference control to a non-minimum phase (NMP) plant, it is important to include the NMP (transmission) zero(s) in the reference model, otherwise the controller will tend to cancel out these zeros, often causing loss of internal stability. In data-driven (DD) control it is not possible to conceive a priori a reference model with the NMP zero(s) because no model of the plant is available; accordingly, DD design methods tend to fail in NMP plants. For single-input–single-output plants, this problem has been solved by using a flexible reference model in a DD design. This letter presents an extension of that method for multi-input–multi-output plants.
@article{Goncalves:Campestrini:Bazanella:2018, Abstract = {When applying model reference control to a non-minimum phase (NMP) plant, it is important to include the NMP (transmission) zero(s) in the reference model, otherwise the controller will tend to cancel out these zeros, often causing loss of internal stability. In data-driven (DD) control it is not possible to conceive a priori a reference model with the NMP zero(s) because no model of the plant is available; accordingly, DD design methods tend to fail in NMP plants. For single-input–single-output plants, this problem has been solved by using a flexible reference model in a DD design. This letter presents an extension of that method for multi-input–multi-output plants.}, author={G. R. {Gon{\c c}alves da Silva} and L. Campestrini and A. S. Bazanella}, journal={IEEE Control Systems Letters}, title={Multivariable Virtual Reference Feedback Tuning for Non-Minimum Phase Plants}, year={2018}, volume={2}, number={1}, pages={121--126}, doi={10.1109/LCSYS.2017.2763824}, month={Jan} } - D. Eckhard, L. Campestrini, and E. C. Boeira, “Virtual Disturbance Feedback Tuning,” IFAC Journal of Systems and Control, vol. 3, p. 23–29, 2018. doi:https://doi.org/10.1016/j.ifacsc.2018.01.003
[BibTeX]@article{Eckhard:Campestrini:Boeira:2018, Author = {D. Eckhard and L. Campestrini and E. C. Boeira}, Journal = {IFAC Journal of Systems and Control}, Title = {Virtual Disturbance Feedback Tuning}, volume = {3}, pages = {23--29}, year = {2018}, issn = {2468--6018}, doi = {https://doi.org/10.1016/j.ifacsc.2018.01.003} } - L. Campestrini, D. Eckhard, A. S. Bazanella, and M. Gevers, “Data-driven model reference control design by prediction error identification,” Journal of the Franklin Institute, vol. 354, iss. 6, p. 2828–2647, 2017. doi:10.1016/j.jfranklin.2016.08.006
[BibTeX] [Abstract]
Abstract This paper deals with Data-Driven (DD) control design in a Model Reference (MR) framework. We present a new \{DD\} method for tuning the parameters of a controller with a fixed structure. Because the method originates from embedding the control design problem in the Prediction Error identification of an optimal controller, it is baptized as Optimal Controller Identification (OCI). Incorporating different levels of prior information about the optimal controller leads to different design choices, which allows to shape the bias and variance errors in its estimation. It is shown that the limit case where all available prior information is incorporated is tantamount to model-based design. Thus, this methodology also provides a framework in which model-based design and \{DD\} design can be fairly and objectively compared. This comparison reveals that \{DD\} design essentially outperforms model-based design by providing better bias shaping, except in the full order controller case, in which there is no bias and model-based design provides smaller variance. The practical effectiveness of the design methodology is illustrated with experimental results.
@article{Campestrini:Eckhard:Bazanella:Gevers:2017, Abstract = {Abstract This paper deals with Data-Driven (DD) control design in a Model Reference (MR) framework. We present a new \{DD\} method for tuning the parameters of a controller with a fixed structure. Because the method originates from embedding the control design problem in the Prediction Error identification of an optimal controller, it is baptized as Optimal Controller Identification (OCI). Incorporating different levels of prior information about the optimal controller leads to different design choices, which allows to shape the bias and variance errors in its estimation. It is shown that the limit case where all available prior information is incorporated is tantamount to model-based design. Thus, this methodology also provides a framework in which model-based design and \{DD\} design can be fairly and objectively compared. This comparison reveals that \{DD\} design essentially outperforms model-based design by providing better bias shaping, except in the full order controller case, in which there is no bias and model-based design provides smaller variance. The practical effectiveness of the design methodology is illustrated with experimental results. }, Author = {L. Campestrini and D. Eckhard and A. S. Bazanella and M. Gevers}, Doi = {10.1016/j.jfranklin.2016.08.006}, Issn = {0016--0032}, Journal = {Journal of the Franklin Institute}, Month = {April}, Number = {6}, Pages = {2828--2647}, Title = {Data-driven model reference control design by prediction error identification}, Volume = {354}, Year = {2017} } - D. Eckhard, A. S. Bazanella, C. R. Rojas, and H. Hjalmarsson, “Cost function shaping of the output error criterion,” Automatica, vol. 76, p. 53–60, 2017. doi:http://dx.doi.org/10.1016/j.automatica.2016.10.015
[BibTeX] [Abstract]
Abstract Identification of an output error model using the prediction error method leads to an optimization problem built on input/output data collected from the system to be identified. It is often hard to find the global solution of this optimization problem because in most cases both the corresponding objective function and the search space are nonconvex. The difficulty in solving the optimization problem depends mainly on the experimental conditions, more specifically on the spectra of the input/output data collected from the system. It is therefore possible to improve the convergence of the algorithms by properly choosing the data prefilters; in this paper we show how to perform this choice. We present the application of the proposed approach to case studies where the standard algorithms tend to fail to converge to the global minimum.
@article{Eckhard:Bazanella:Rojas:Hjalmarsson:2017, Abstract = {Abstract Identification of an output error model using the prediction error method leads to an optimization problem built on input/output data collected from the system to be identified. It is often hard to find the global solution of this optimization problem because in most cases both the corresponding objective function and the search space are nonconvex. The difficulty in solving the optimization problem depends mainly on the experimental conditions, more specifically on the spectra of the input/output data collected from the system. It is therefore possible to improve the convergence of the algorithms by properly choosing the data prefilters; in this paper we show how to perform this choice. We present the application of the proposed approach to case studies where the standard algorithms tend to fail to converge to the global minimum. }, Author = {Diego Eckhard and Alexandre S. Bazanella and Cristian R. Rojas and H{\aa}kan Hjalmarsson}, Doi = {http://dx.doi.org/10.1016/j.automatica.2016.10.015}, Issn = {0005--1098}, Journal = {Automatica}, Keywords = {Model fitting}, Pages = {53--60}, Title = {Cost function shaping of the output error criterion}, Url = {//www.sciencedirect.com/science/article/pii/S0005109816304198}, Volume = {76}, Year = {2017}, Bdsk-Url-1 = {//www.sciencedirect.com/science/article/pii/S0005109816304198}, Bdsk-Url-2 = {http://dx.doi.org/10.1016/j.automatica.2016.10.015}} - R. Rui, T. Ardeshiri, H. Nurminen, A. Bazanella, and F. Gustafsson, “State Estimation for a Class of Piecewise Affine State-Space Models,” IEEE Signal Processing Letters, vol. 24, iss. 1, p. 61–65, 2017. doi:10.1109/LSP.2016.2633624
[BibTeX] [Abstract]
We propose a filter for piecewise affine state-space models. In each filtering recursion, the true filtering posterior distribution is a mixture of truncated normal distributions. The proposed filter approximates the mixture with a single normal distribution via moment matching. The proposed algorithm is compared with the extended Kalman filter (EKF) in a numerical simulation, where the proposed method obtains, on average, better root mean square error than the EKF.
@ARTICLE{Rui:Ardeshiri:Nurminen:Bazanella:Gustafsson:2017, abstract={We propose a filter for piecewise affine state-space models. In each filtering recursion, the true filtering posterior distribution is a mixture of truncated normal distributions. The proposed filter approximates the mixture with a single normal distribution via moment matching. The proposed algorithm is compared with the extended Kalman filter (EKF) in a numerical simulation, where the proposed method obtains, on average, better root mean square error than the EKF.}, author={R. {Rui} and T. {Ardeshiri} and H. {Nurminen} and A. {Bazanella} and F. {Gustafsson}}, journal={IEEE Signal Processing Letters}, title={State Estimation for a Class of Piecewise Affine State-Space Models}, year={2017}, volume={24}, number={1}, pages={61--65}, doi={10.1109/LSP.2016.2633624} } - A. S. Bazanella, L. F. A. Pereira, and A. Parraga, “A new method for PID tuning including plants without ultimate frequency,” IEEE Transactions on Control Systems Technology, vol. 25, iss. 2, pp. 637-644, 2017. doi:10.1109/TCST.2016.2557723
[BibTeX] [Abstract]
The classical relay feedback method for tuning proportional-integral-derivative (PID) controllers cannot be applied to plants whose Nyquist diagrams do not cross the negative real axis; these are customarily tuned based on the reaction curve experiment. In this brief, we propose a tuning method based on a modified relay feedback experiment. In this experiment, a transfer function of constant phase in an arbitrarily large range of frequencies is inserted in the loop. The proposed methodology thus unifies the Ziegler-Nichols-like tuning methods, by allowing PID tuning based on relay feedback for a class of plants without ultimate frequency.
@article{Bazanella:Pereira:Parraga:2017, Abstract = {The classical relay feedback method for tuning proportional-integral-derivative (PID) controllers cannot be applied to plants whose Nyquist diagrams do not cross the negative real axis; these are customarily tuned based on the reaction curve experiment. In this brief, we propose a tuning method based on a modified relay feedback experiment. In this experiment, a transfer function of constant phase in an arbitrarily large range of frequencies is inserted in the loop. The proposed methodology thus unifies the Ziegler-Nichols-like tuning methods, by allowing PID tuning based on relay feedback for a class of plants without ultimate frequency.}, Author = {A. S. Bazanella and L. F. A. Pereira and A. Parraga}, Doi = {10.1109/TCST.2016.2557723}, Issn = {637--644}, Journal = {IEEE Transactions on Control Systems Technology}, Number = {2}, Pages = {637-644}, Title = {A new method for PID tuning including plants without ultimate frequency}, Volume = {25}, Year = {2017} } - L. Campestrini, D. Eckhard, L. A. Chía, and E. Boeira, “Unbiased MIMO VRFT with application to process control,” Journal of Process Control, vol. 39, p. 35–49, 2016. doi:10.1016/j.jprocont.2015.12.010
[BibTeX] [Abstract]
Abstract Continuous process industries usually have hundreds to thousands of control loops, most of which are coupled, i.e. one control loop affects the behavior of another control loop. In order to properly design the controllers and reduce the interactions between loops it is necessary to consider the multivariable structure of the process. Usually {MIMO} (multiple-input, multiple-output) controllers are designed using {MIMO} models of the process, but obtaining these models is a task very demanding and time consuming. Virtual Reference Feedback Tuning ({VRFT}) is a data-driven technique to design controllers which do not use a model of the process; all the needed information is collected from input/output data from an experiment. The method is well established for {SISO} (single-input, single-output) systems and there are some extensions to {MIMO} process which assume that all the outputs should have the same closed-loop performance. In this paper we develop a complete framework to {MIMO} {VRFT} which provides unbiased estimates to the optimal {MIMO} controller (when it is possible) even when the closed-loop performances are distinct to each loop. When it is not possible to obtain the optimal controller because the controller class is too restrictive (for example {PID} controllers) then we propose the use of a filter to reduce the bias on the estimates. Also, when the data is corrupted by noise, the use of instrumental variables to eliminate the bias on the estimate should be considered. The article presents simulation examples and a practical experiment on a tree tank system where the goal is to control the level of two tanks.
@article{Campestrini:Eckhard:Chia:Boeira:2016, Abstract = {Abstract Continuous process industries usually have hundreds to thousands of control loops, most of which are coupled, i.e. one control loop affects the behavior of another control loop. In order to properly design the controllers and reduce the interactions between loops it is necessary to consider the multivariable structure of the process. Usually {MIMO} (multiple-input, multiple-output) controllers are designed using {MIMO} models of the process, but obtaining these models is a task very demanding and time consuming. Virtual Reference Feedback Tuning ({VRFT}) is a data-driven technique to design controllers which do not use a model of the process; all the needed information is collected from input/output data from an experiment. The method is well established for {SISO} (single-input, single-output) systems and there are some extensions to {MIMO} process which assume that all the outputs should have the same closed-loop performance. In this paper we develop a complete framework to {MIMO} {VRFT} which provides unbiased estimates to the optimal {MIMO} controller (when it is possible) even when the closed-loop performances are distinct to each loop. When it is not possible to obtain the optimal controller because the controller class is too restrictive (for example {PID} controllers) then we propose the use of a filter to reduce the bias on the estimates. Also, when the data is corrupted by noise, the use of instrumental variables to eliminate the bias on the estimate should be considered. The article presents simulation examples and a practical experiment on a tree tank system where the goal is to control the level of two tanks.}, Author = {L. Campestrini and D. Eckhard and L. A. Ch\'{i}a and E. Boeira}, Date-Modified = {2016-10-02 12:30:37 +0000}, Doi = {10.1016/j.jprocont.2015.12.010}, Issn = {0959--1524}, Journal = {Journal of Process Control}, Pages = {35--49}, Title = {Unbiased {MIMO} {VRFT} with application to process control}, Volume = {39}, Year = {2016}, Bdsk-Url-1 = {http://dx.doi.org/10.1016/j.jprocont.2015.12.010}} - A. S. Bazanella and A. Parraga, “Limit cycles in sampled-data relay feedback systems,” Journal of Control, Automation and Electrical Systems, vol. 27, iss. 3, p. 237–249, 2016. doi:10.1007/s40313-016-0239-1
[BibTeX] [Abstract]
Analysis of limit cycles in relay feedback systems is usually performed in continuous time, even though most such systems are implemented digitally. In this paper, we discuss the limitations of the continuous-time analysis, showing that even for standard plants with reasonable sampling rates its results can be considerably far from the truth. Then, we present a discrete-time analysis of relay feedback systems, providing analytical tools that overcome the limitations of their continuous-time counterparts.
@article{Bazanella:Parraga:2016, Abstract = {Analysis of limit cycles in relay feedback systems is usually performed in continuous time, even though most such systems are implemented digitally. In this paper, we discuss the limitations of the continuous-time analysis, showing that even for standard plants with reasonable sampling rates its results can be considerably far from the truth. Then, we present a discrete-time analysis of relay feedback systems, providing analytical tools that overcome the limitations of their continuous-time counterparts.}, Author = {A. S. Bazanella and A. Parraga}, Doi = {10.1007/s40313-016-0239-1}, Issn = {2195--3899}, Journal = {Journal of Control, Automation and Electrical Systems}, Number = {3}, Pages = {237--249}, Title = {Limit cycles in sampled-data relay feedback systems}, Volume = {27}, Year = {2016}, Bdsk-Url-1 = {http://dx.doi.org/10.1007/s40313-016-0239-1}} - M. Gevers, A. S. Bazanella, D. F. Coutinho, and S. Dasgupta, “Identifiability and excitation of linearly parametrized rational systems,” Automatica, vol. 63, p. 38–46, 2016. doi:10.1016/j.automatica.2015.10.028
[BibTeX] [Abstract]
Abstract This paper establishes identifiability and informativity conditions for a class of deterministic linearly parametrized scalar rational models. The class considered is rational in the state and polynomial in the input. The standard definitions of identifiability and informativity for linear systems are expanded to account for the situation, common for nonlinear deterministic systems, where the identification is achieved either through the application of an informative input or via the response to an informative initial condition. We provide necessary and sufficient conditions for identifiability from the initial state, respectively from the input, as well as necessary and sufficient conditions on the initial state to produce an informative experiment. We also provide sufficient conditions on the input to be informative when the initial condition is unknown and could therefore potentially destroy the transfer of information from the input to the regressor.
@article{Gevers:Bazanella:Coutinho:Dasgupta:2016, Abstract = {Abstract This paper establishes identifiability and informativity conditions for a class of deterministic linearly parametrized scalar rational models. The class considered is rational in the state and polynomial in the input. The standard definitions of identifiability and informativity for linear systems are expanded to account for the situation, common for nonlinear deterministic systems, where the identification is achieved either through the application of an informative input or via the response to an informative initial condition. We provide necessary and sufficient conditions for identifiability from the initial state, respectively from the input, as well as necessary and sufficient conditions on the initial state to produce an informative experiment. We also provide sufficient conditions on the input to be informative when the initial condition is unknown and could therefore potentially destroy the transfer of information from the input to the regressor. }, Author = {M. Gevers and A. S. Bazanella and D. F. Coutinho and S. Dasgupta}, Doi = {10.1016/j.automatica.2015.10.028}, Issn = {0005--1098}, Journal = {Automatica}, Pages = {38--46}, Title = {Identifiability and excitation of linearly parametrized rational systems}, Volume = {63}, Year = {2016}, Bdsk-Url-1 = {http://dx.doi.org/10.1016/j.automatica.2015.10.028}} - L. F. A. Pereira and A. S. Bazanella, “Tuning Rules for Proportional Resonant Controllers,” IEEE Transactions on Control Systems Technology, vol. 23, iss. 5, p. 2010–2017, 2015. doi:10.1109/TCST.2015.2389655
[BibTeX] [Abstract]
In this brief, we propose a particular structure for resonant controllers and a tuning method of the Ziegler-Nichols type for their tuning. Performance criteria for resonant controllers are also defined. The effectiveness of the tuning rules is illustrated by their application and corresponding performance assessment in a test batch consisting of four representative classes of processes. The control performance is analyzed in detail for one particular example, shedding light on the virtues and limitations of the control structure and of the tuning method.
@article{Pereira:Bazanella:2015, Abstract = {In this brief, we propose a particular structure for resonant controllers and a tuning method of the Ziegler-Nichols type for their tuning. Performance criteria for resonant controllers are also defined. The effectiveness of the tuning rules is illustrated by their application and corresponding performance assessment in a test batch consisting of four representative classes of processes. The control performance is analyzed in detail for one particular example, shedding light on the virtues and limitations of the control structure and of the tuning method.}, Author = {L. F. A. Pereira and A. S. Bazanella}, Doi = {10.1109/TCST.2015.2389655}, Issn = {1063--6536}, Journal = {IEEE Transactions on Control Systems Technology}, Keywords = {proportional control;self-adjusting systems;Ziegler-Nichols type;control performance;control structure;performance assessment;performance criteria;proportional resonant controller;tuning method;tuning rules;Frequency response;Oscillators;Process control;Relays;Transfer functions;Tuning;Zinc;Internal model principle;relay feedback;resonant controller;self-tuning control;sinusoid tracking and rejection;sinusoid tracking and rejection.}, Number = {5}, Pages = {2010--2017}, Title = {Tuning Rules for Proportional Resonant Controllers}, Volume = {23}, Year = {2015}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/TCST.2015.2389655}} - L. Campestrini, D. Eckhard, R. Rui, and A. S. Bazanella, “Identifiability Analysis and Prediction Error Identification of Anaerobic Batch Bioreactors,” Journal of Control, Automation and Electrical Systems, vol. 25, iss. 4, p. 438–447, 2014. doi:10.1007/s40313-014-0129-3
[BibTeX] [Abstract]
This paper presents the identifiability analysis of a nonlinear model for a batch bioreactor and the estimation of the identifiable parameters within the prediction error framework. The output data of the experiment are the measurements of the methane gas generated by the process, during 37 days, and knowledge of the initial conditions is limited to the initial quantity of chemical oxygen demand. It is shown by the identifiability analysis that only three out of the eight model parameters can be identified with the available measurements and that identification of the remaining parameters would require further knowledge of the initial conditions. A prediction error algorithm is implemented for the estimation of the identifiable parameters. This algorithm is iterative, relies on the gradient of the prediction error, whose calculation is implemented recursively, and consists of a combination of two classic optimization methods: the conjugated gradient method and the Gauss?Newton method.
@article{Campestrini:Eckhard:Rui:Bazanella:2014, Abstract = {This paper presents the identifiability analysis of a nonlinear model for a batch bioreactor and the estimation of the identifiable parameters within the prediction error framework. The output data of the experiment are the measurements of the methane gas generated by the process, during 37 days, and knowledge of the initial conditions is limited to the initial quantity of chemical oxygen demand. It is shown by the identifiability analysis that only three out of the eight model parameters can be identified with the available measurements and that identification of the remaining parameters would require further knowledge of the initial conditions. A prediction error algorithm is implemented for the estimation of the identifiable parameters. This algorithm is iterative, relies on the gradient of the prediction error, whose calculation is implemented recursively, and consists of a combination of two classic optimization methods: the conjugated gradient method and the Gauss?Newton method.}, Author = {L. Campestrini and D. Eckhard and R. Rui and A. S. Bazanella}, Doi = {10.1007/s40313-014-0129-3}, Issn = {2195--3880}, Journal = {Journal of Control, Automation and Electrical Systems}, Number = {4}, Pages = {438--447}, Title = {Identifiability Analysis and Prediction Error Identification of Anaerobic Batch Bioreactors}, Volume = {25}, Year = {2014}, Bdsk-Url-1 = {http://dx.doi.org/10.1007/s40313-014-0129-3}} - D. Eckhard, A. S. Bazanella, C. R. Rojas, and H. Hjalmarsson, “Input design as a tool to improve the convergence of PEM,” Automatica, vol. 49, iss. 11, p. 3282–3291, 2013. doi:10.1016/j.automatica.2013.08.027
[BibTeX] [Abstract]
The Prediction Error Method (PEM) is related to an optimization problem built on input/output data collected from the system to be identified. It is often hard to find the global solution of this optimization problem because the corresponding objective function presents local minima and/or the search space is constrained to a nonconvex set. The shape of the cost function, and hence the difficulty in solving the optimization problem, depends directly on the experimental conditions, more specifically on the spectrum of the input/output data collected from the system. Therefore, it seems plausible to improve the convergence to the global minimum by properly choosing the spectrum of the input; in this paper, we address this problem. We present a condition for convergence to the global minimum of the cost function and propose its inclusion in the input design. We present the application of the proposed approach to case studies where the algorithms tend to get trapped in nonglobal minima.
@article{Eckhard:Bazanella:Rojas:Hjalmarsson:2013, Abstract = {The Prediction Error Method (PEM) is related to an optimization problem built on input/output data collected from the system to be identified. It is often hard to find the global solution of this optimization problem because the corresponding objective function presents local minima and/or the search space is constrained to a nonconvex set. The shape of the cost function, and hence the difficulty in solving the optimization problem, depends directly on the experimental conditions, more specifically on the spectrum of the input/output data collected from the system. Therefore, it seems plausible to improve the convergence to the global minimum by properly choosing the spectrum of the input; in this paper, we address this problem. We present a condition for convergence to the global minimum of the cost function and propose its inclusion in the input design. We present the application of the proposed approach to case studies where the algorithms tend to get trapped in nonglobal minima.}, Author = {D. Eckhard and A. S. Bazanella and C. R. Rojas and H. Hjalmarsson}, Doi = {10.1016/j.automatica.2013.08.027}, Issn = {0005-1098}, Journal = {Automatica}, Number = {11}, Pages = {3282--3291}, Title = {Input design as a tool to improve the convergence of {PEM}}, Volume = {49}, Year = {2013}, Bdsk-Url-1 = {http://dx.doi.org/10.1016/j.automatica.2013.08.027}} - J. M. Gomes da Silva Jr., E. B. Castelan, J. Corso, and D. Eckhard, “Dynamic output feedback stabilization for systems with sector-bounded nonlinearities and saturating actuators,” Journal of the Franklin Institute, vol. 350, iss. 3, p. 464–484, 2013. doi:10.1016/j.jfranklin.2012.12.009
[BibTeX] [Abstract]
In the present work a systematic methodology for computing dynamic output stabilizing feedback control laws for nonlinear systems subject to saturating inputs is presented. In particular, the class of Lur’e type nonlinear systems is considered. Based on absolute stability tools and a modified sector condition to take into account input saturation effects, an \{LMI\} framework is proposed to design the controller. Asymptotic as well as input-to-state and input-to-output (in a L2 sense) stabilization problems are addressed both in regional (local) and global contexts. The controller structure is composed of a linear part, an anti-windup loop and a term associated to the output of the dynamic nonlinearity. Convex optimization problems are proposed to compute the controller considering different optimization criteria. A numerical example illustrates the potentialities of the methodology.
@article{GomesdaSilva:Castelan:Corso:Eckhard:2013, Abstract = {In the present work a systematic methodology for computing dynamic output stabilizing feedback control laws for nonlinear systems subject to saturating inputs is presented. In particular, the class of Lur'e type nonlinear systems is considered. Based on absolute stability tools and a modified sector condition to take into account input saturation effects, an \{LMI\} framework is proposed to design the controller. Asymptotic as well as input-to-state and input-to-output (in a L2 sense) stabilization problems are addressed both in regional (local) and global contexts. The controller structure is composed of a linear part, an anti-windup loop and a term associated to the output of the dynamic nonlinearity. Convex optimization problems are proposed to compute the controller considering different optimization criteria. A numerical example illustrates the potentialities of the methodology.}, Author = {J. M. {Gomes da Silva Jr.} and E. B. Castelan and J. Corso and D. Eckhard}, Doi = {10.1016/j.jfranklin.2012.12.009}, Issn = {0016--0032}, Journal = {Journal of the Franklin Institute}, Number = {3}, Pages = {464--484}, Title = {Dynamic output feedback stabilization for systems with sector-bounded nonlinearities and saturating actuators}, Volume = {350}, Year = {2013}, Bdsk-Url-1 = {http://dx.doi.org/10.1016/j.jfranklin.2012.12.009}} - A. S. Bazanella, X. Bombois, and M. Gevers, “Necessary and sufficient conditions for uniqueness of the minimum in Prediction Error Identification,” Automatica, vol. 48, iss. 8, p. 1621–1630, 2012. doi:10.1016/j.automatica.2012.06.018
[BibTeX] [Abstract]
The contribution of this paper is to establish computable necessary and sufficient conditions on the model structure and on the experiment under which the Prediction Error Identification (PEI) criterion has a unique global minimum. We consider a broad class of rational model structures whose numerator and denominator are affine in the unknown parameter vector; this class encompasses all classical model structures used in system identification. The main results in this paper rely on the standard assumption that the system is in the model set, while some intermediate results are valid even when this assumption does not hold (in particular Theorem 4.2 and Lemma 6.1). This is achieved by first establishing necessary and sufficient conditions on the model structure and on the experiment under which a global minimum is isolated; these conditions must hold locally, at the global minimum. A second contribution is to show that these conditions are equivalent to the nonsingularity of the information matrix at that minimum. For open loop identification and, with some additional constraints also for closed loop identification, the nonsingularity of the information matrix is then also equivalent to the uniqueness of the global minimum.
@article{Bazanella:Bombois:Gevers:2012, Abstract = {The contribution of this paper is to establish computable necessary and sufficient conditions on the model structure and on the experiment under which the Prediction Error Identification (PEI) criterion has a unique global minimum. We consider a broad class of rational model structures whose numerator and denominator are affine in the unknown parameter vector; this class encompasses all classical model structures used in system identification. The main results in this paper rely on the standard assumption that the system is in the model set, while some intermediate results are valid even when this assumption does not hold (in particular Theorem 4.2 and Lemma 6.1). This is achieved by first establishing necessary and sufficient conditions on the model structure and on the experiment under which a global minimum is isolated; these conditions must hold locally, at the global minimum. A second contribution is to show that these conditions are equivalent to the nonsingularity of the information matrix at that minimum. For open loop identification and, with some additional constraints also for closed loop identification, the nonsingularity of the information matrix is then also equivalent to the uniqueness of the global minimum.}, Author = {A. S. Bazanella and X. Bombois and M. Gevers}, Doi = {10.1016/j.automatica.2012.06.018}, Issn = {0005--1098}, Journal = {Automatica}, Number = {8}, Pages = {1621--1630}, Title = {Necessary and sufficient conditions for uniqueness of the minimum in Prediction Error Identification}, Volume = {48}, Year = {2012}, Bdsk-Url-1 = {http://dx.doi.org/10.1016/j.automatica.2012.06.018}} - D. Eckhard and A. S. Bazanella, “Robust convergence of the steepest descent method for data-based control,” International Journal of Systems Science, vol. 43, iss. 10, p. 1969–1975, 2012. doi:10.1080/00207721.2011.563874
[BibTeX] [Abstract]
Iterative data-based controller tuning consists of iterative adjustment of the controller parameters towards the parameter values which minimise an {H2} performance criterion. The convergence to the global minimum of the performance criterion depends on the initial controller parameters and on the step size of each iteration. This article presents convergence properties of iterative algorithms when they are affected by disturbances.
@article{Eckhard:Bazanella:2012, Abstract = {Iterative data-based controller tuning consists of iterative adjustment of the controller parameters towards the parameter values which minimise an {H2} performance criterion. The convergence to the global minimum of the performance criterion depends on the initial controller parameters and on the step size of each iteration. This article presents convergence properties of iterative algorithms when they are affected by disturbances.}, Author = {D. Eckhard and A. S. Bazanella}, Doi = {10.1080/00207721.2011.563874}, Issn = {0020--7721}, Journal = {International Journal of Systems Science}, Number = {10}, Pages = {1969--1975}, Title = {Robust convergence of the steepest descent method for data-based control}, Volume = {43}, Year = {2012}, Bdsk-Url-1 = {http://dx.doi.org/10.1080/00207721.2011.563874}} - D. Eckhard and A. S. Bazanella, “Optimizing the convergence of data-based controller tuning,” Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, vol. 226, iss. 4, p. 563–574, 2012. doi:10.1177/0959651811426062
[BibTeX] [Abstract]
Data-based control design methods most often consist of iterative adjustment of the controller?s parameters towards the parameter values which minimize an Formula performance criterion. Typically, batches of input-output data collected from the system are used to feed directly a gradient descent optimization algorithm ? no process model is used. Two topics are important regarding this algorithm: the convergence rate and the convergence to the global minimum. This paper discusses these issues and provides a method for choosing the step size to ensure convergence with high convergence rate, as well as a test to verify at each step whether or not the algorithm is converging to the global minimum.
@article{Eckhard:Bazanella:2012b, Abstract = {Data-based control design methods most often consist of iterative adjustment of the controller?s parameters towards the parameter values which minimize an Formula performance criterion. Typically, batches of input-output data collected from the system are used to feed directly a gradient descent optimization algorithm ? no process model is used. Two topics are important regarding this algorithm: the convergence rate and the convergence to the global minimum. This paper discusses these issues and provides a method for choosing the step size to ensure convergence with high convergence rate, as well as a test to verify at each step whether or not the algorithm is converging to the global minimum.}, Author = {D. Eckhard and A. S. Bazanella}, Doi = {10.1177/0959651811426062}, Issn = {0959--6518}, Journal = {Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering}, Number = {4}, Pages = {563--574}, Title = {Optimizing the convergence of data-based controller tuning}, Volume = {226}, Year = {2012}, Bdsk-Url-1 = {http://dx.doi.org/10.1177/0959651811426062}} - L. Campestrini, D. Eckhard, M. Gevers, and A. S. Bazanella, “Virtual Reference Feedback Tuning for non-minimum phase plants,” Automatica, vol. 47, iss. 8, p. 1778–1784, 2011. doi:10.1016/j.automatica.2011.04.002
[BibTeX] [Abstract]
Model reference control design methods fail when the plant has one or more non-minimum phase zeros that are not included in the reference model, leading possibly to an unstable closed loop. This is a very serious problem for data-based control design methods, where the plant is typically unknown. In this paper, we extend the Virtual Reference Feedback Tuning method to non-minimum phase plants. This extension is based on the idea proposed in Lecchini and Gevers (2002) for Iterative Feedback Tuning. We present a simple two-step procedure that can cope with the situation where the unknown plant may or may not have non-minimum phase zeros.
@article{Campestrini:Eckhard:Gevers:Bazanella:2011, Abstract = {Model reference control design methods fail when the plant has one or more non-minimum phase zeros that are not included in the reference model, leading possibly to an unstable closed loop. This is a very serious problem for data-based control design methods, where the plant is typically unknown. In this paper, we extend the Virtual Reference Feedback Tuning method to non-minimum phase plants. This extension is based on the idea proposed in Lecchini and Gevers (2002) for Iterative Feedback Tuning. We present a simple two-step procedure that can cope with the situation where the unknown plant may or may not have non-minimum phase zeros.}, Author = {L. Campestrini and D. Eckhard and M. Gevers and A. S. Bazanella}, Doi = {10.1016/j.automatica.2011.04.002}, Issn = {0005--1098}, Journal = {Automatica}, Number = {8}, Pages = {1778--1784}, Title = {Virtual Reference Feedback Tuning for non-minimum phase plants}, Volume = {47}, Year = {2011}, Bdsk-Url-1 = {http://dx.doi.org/10.1016/j.automatica.2011.04.002}} - A. S. Bazanella, M. Gevers, and L. Mišković, “Closed-Loop Identification of MIMO Systems: A New Look at Identifiability and Experiment Design,” European Journal of Control, vol. 16, iss. 3, p. 228–239, 2010. doi:10.3166/ejc.16.228-239
[BibTeX]@article{Bazanella:Gevers:Miskovic:2010, Author = {A. S. Bazanella and M. Gevers and L. Mi{\v{s}}kovi{\'c}}, Doi = {10.3166/ejc.16.228-239}, Issn = {0947-3580}, Journal = {European Journal of Control}, Number = {3}, Pages = {228--239}, Title = {Closed-Loop Identification of {MIMO} Systems: A New Look at Identifiability and Experiment Design}, Volume = {16}, Year = {2010}, Bdsk-Url-1 = {http://dx.doi.org/10.3166/ejc.16.228-239}} - M. Gevers, A. S. Bazanella, X. Bombois, and L. Mišković, “Identification and the Information Matrix: How to Get Just Sufficiently Rich?,” IEEE Transactions on Automatic Control, vol. 54, iss. 12, p. 2828–2840, 2009. doi:10.1109/TAC.2009.2034199
[BibTeX]@article{Gevers:Bazanella:Bombois:Miskovic:2009, Author = {M. Gevers and A. S. Bazanella and X. Bombois and L. Mi{\v{s}}kovi{\'c}}, Doi = {10.1109/TAC.2009.2034199}, Issn = {0018--9286}, Journal = {IEEE Transactions on Automatic Control}, Number = {12}, Pages = {2828--2840}, Title = {Identification and the Information Matrix: How to Get Just Sufficiently Rich?}, Volume = {54}, Year = {2009}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/TAC.2009.2034199}} - L. Campestrini, L. C. Stevanatto Filho, and A. S. Bazanella, “Tuning of Multivariable Decentralized Controllers Through the Ultimate-Point Method,” IEEE Transactions on Control Systems Technology, vol. 17, iss. 6, p. 1270–1281, 2009. doi:10.1109/TCST.2008.2006495
[BibTeX]@article{Campestrini:Stevanatto:Bazanella:2009, Author = {L. Campestrini and L. C. {Stevanatto Filho} and A. S. Bazanella}, Doi = {10.1109/TCST.2008.2006495}, Issn = {1063--6536}, Journal = {IEEE Transactions on Control Systems Technology}, Number = {6}, Pages = {1270--1281}, Title = {Tuning of Multivariable Decentralized Controllers Through the Ultimate-Point Method}, Volume = {17}, Year = {2009}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/TCST.2008.2006495}} - G. Garcia, S. Tarbouriech, J. M. Gomes da Silva Jr., and D. Eckhard, “Finite L2 gain and internal stabilisation of linear systems subject to actuator and sensor saturations,” IET Control Theory Applications, vol. 3, iss. 7, p. 799–812, 2009. doi:10.1049/iet-cta.2008.0221
[BibTeX] [Abstract]
This study addresses the control of linear systems subject to both sensor and actuator saturations and additive L2-bounded disturbances. Supposing that only the output of the linear plant is measurable, the synthesis of stabilising output feedback dynamic controllers, allowing to ensure the internal closed-loop stability and the finite L2-gain stabilisation, is considered. In this case, it is shown that the closed-loop system presents a nested saturation term. Therefore, based on the use of some modified sector conditions and appropriate variable changes, synthesis conditions in a quasi-linear matrix inequality (LMI) form are stated in both regional (local) as well as global stability contexts. Different LMI-based optimisation problems for computing a controller in order to maximise the disturbance tolerance, the disturbance rejection or the region of stability of the closed-loop system are proposed.
@article{Garcia:Tarbouriech:GomesdaSilva:Eckhard:2009, Abstract = {This study addresses the control of linear systems subject to both sensor and actuator saturations and additive L2-bounded disturbances. Supposing that only the output of the linear plant is measurable, the synthesis of stabilising output feedback dynamic controllers, allowing to ensure the internal closed-loop stability and the finite L2-gain stabilisation, is considered. In this case, it is shown that the closed-loop system presents a nested saturation term. Therefore, based on the use of some modified sector conditions and appropriate variable changes, synthesis conditions in a quasi-linear matrix inequality (LMI) form are stated in both regional (local) as well as global stability contexts. Different LMI-based optimisation problems for computing a controller in order to maximise the disturbance tolerance, the disturbance rejection or the region of stability of the closed-loop system are proposed.}, Author = {G. Garcia and S. Tarbouriech and J.M. {Gomes da Silva Jr.} and D. Eckhard}, Doi = {10.1049/iet-cta.2008.0221}, Issn = {1751--8644}, Journal = {IET Control Theory Applications}, Number = {7}, Pages = {799--812}, Title = {Finite {L2} gain and internal stabilisation of linear systems subject to actuator and sensor saturations}, Volume = {3}, Year = {2009}, Bdsk-Url-1 = {http://dx.doi.org/10.1049/iet-cta.2008.0221}} - A. S. Bazanella, M. Gevers, L. Mišković, and B. D. O. Anderson, “Iterative minimization of control performance criteria,” Automatica, vol. 44, iss. 10, p. 2549–2559, 2008. doi:10.1016/j.automatica.2008.03.014
[BibTeX]@article{Bazanella:Gevers:Miskovic:Anderson:2008, Author = {A. S. Bazanella and M. Gevers and L. Mi{\v{s}}kovi{\'c} and B. D. O. Anderson}, Doi = {10.1016/j.automatica.2008.03.014}, Issn = {0005-1098}, Journal = {Automatica}, Number = {10}, Pages = {2549--2559}, Title = {Iterative minimization of control performance criteria}, Volume = {44}, Year = {2008}, Bdsk-Url-1 = {http://dx.doi.org/10.1016/j.automatica.2008.03.014}} - J. M. Gomes da Silva Jr., F. Lescher, and D. Eckhard, “Design of time-varying controllers for discrete-time linear systems with input saturation,” IET Control Theory Applications, vol. 1, iss. 1, p. 155–162, 2007. doi:10.1049/iet-cta:20050415
[BibTeX] [Abstract]
A method for computing time-varying dynamic output feedback controllers for discrete-time linear systems subject to input saturation is proposed. The method is based on a locally valid polytopic representation of the saturation term. From this representation, it is shown that, at each sampling time, the matrices of the stabilising time-varying controller can be computed from the current system output and from constant matrices obtained as a solution of some matrix inequalities. Linear matrix inequality-based optimisation problems are therefore proposed in order to compute the controller aiming at the maximisation of the basin attraction of the closed-loop system, as well as aiming at ensuring a level of {L2} disturbance tolerance and rejection.
@article{GomesdaSilva:Lescher:Eckhard:2007, Abstract = {A method for computing time-varying dynamic output feedback controllers for discrete-time linear systems subject to input saturation is proposed. The method is based on a locally valid polytopic representation of the saturation term. From this representation, it is shown that, at each sampling time, the matrices of the stabilising time-varying controller can be computed from the current system output and from constant matrices obtained as a solution of some matrix inequalities. Linear matrix inequality-based optimisation problems are therefore proposed in order to compute the controller aiming at the maximisation of the basin attraction of the closed-loop system, as well as aiming at ensuring a level of {L2} disturbance tolerance and rejection.}, Author = {J. M. {Gomes da Silva Jr.} and F. Lescher and D. Eckhard}, Doi = {10.1049/iet-cta:20050415}, Issn = {1751--8644}, Journal = {IET Control Theory Applications}, Number = {1}, Pages = {155--162}, Title = {Design of time-varying controllers for discrete-time linear systems with input saturation}, Volume = {1}, Year = {2007}, Bdsk-Url-1 = {http://dx.doi.org/10.1049/iet-cta:20050415}}
Conference Articles
- E. C. Boeira and D. Eckhard, “An optimal regularized instrumental variable method for errors-in-variables identification,” in 2021 60th IEEE Conference on Decision and Control (CDC), 2021, pp. 1592-1597. doi:10.1109/CDC45484.2021.9683683
[BibTeX] [Abstract]
This work addresses the design of theoretical optimal regularization matrices for the instrumental variable method in the errors-in-variables identification framework. The design is based on the asymptotic statistical properties of the regularized instrumental variable estimator and it provides new bounds for the use of regularization in this scenario as well as new ideas to parametrize and estimate the regularization matrix in practical situations. A numerical example shows the effectiveness of the optimal estimator in comparison with the classic least-squares and instrumental variable methods.
@INPROCEEDINGS{Boeira:Eckhard:2021, author={Boeira, Emerson C. and Eckhard, Diego}, booktitle={2021 60th IEEE Conference on Decision and Control (CDC)}, title={An optimal regularized instrumental variable method for errors-in-variables identification}, year={2021}, volume={}, number={}, pages={1592-1597}, abstract={This work addresses the design of theoretical optimal regularization matrices for the instrumental variable method in the errors-in-variables identification framework. The design is based on the asymptotic statistical properties of the regularized instrumental variable estimator and it provides new bounds for the use of regularization in this scenario as well as new ideas to parametrize and estimate the regularization matrix in practical situations. A numerical example shows the effectiveness of the optimal estimator in comparison with the classic least-squares and instrumental variable methods.}, keywords={}, doi={10.1109/CDC45484.2021.9683683}, ISSN={2576-2370}, month={Dec}} - R. W. P. da Silva and D. Eckhard, “Data-driven Correlation Approach Applied to Load Disturbance Rejection in a Thermal Process,” in 2021 Australian New Zealand Control Conference (ANZCC), 2021, pp. 200-205. doi:10.1109/ANZCC53563.2021.9628299
[BibTeX] [Abstract]
From a practical point of view, adjusting the controller without having to identify the process model has many advantages, for example, when the process is simple but changes a lot during the operation. In this case, there are many direct data-driven methods in the literature which may be employed to adjust a monovariable controller aiming at reference tracking. However, when the control objective is disturbance rejection or regulation, the designer is left with too few choices. The aim of this paper is to provide one new option and show how it can be applied to those control objectives.
@INPROCEEDINGS{DaSilva:Eckhard:2021, author={R. W. P. {da Silva} and D. {Eckhard}}, booktitle={2021 Australian New Zealand Control Conference (ANZCC)}, title={Data-driven Correlation Approach Applied to Load Disturbance Rejection in a Thermal Process}, year={2021}, volume={}, number={}, pages={200-205}, abstract={From a practical point of view, adjusting the controller without having to identify the process model has many advantages, for example, when the process is simple but changes a lot during the operation. In this case, there are many direct data-driven methods in the literature which may be employed to adjust a monovariable controller aiming at reference tracking. However, when the control objective is disturbance rejection or regulation, the designer is left with too few choices. The aim of this paper is to provide one new option and show how it can be applied to those control objectives.}, keywords={}, doi={10.1109/ANZCC53563.2021.9628299}, ISSN={2767-7257}, month={Nov}} - E. Boeira and D. Eckhard, “Regularized impulse response estimation for systems with colored output noise,” in 2021 Australian New Zealand Control Conference (ANZCC), 2021, pp. 18-23. doi:10.1109/ANZCC53563.2021.9628304
[BibTeX] [Abstract]
This paper addresses the use of the regularization feature on impulse response estimation for systems with colored output noise. Firstly, it is shown that the optimal regularization matrix for this scenario is quite different than the optimal for the white noise case and that there is a direct relationship between the Regularized Weighted Least-Squares with a Bayesian perspective of the identification problem for such case. Also, a new Empirical Bayes method, based on the Bayesian perspective, is introduced to estimate the regularization and noise covariance matrices from data. Finally, a numerical example demonstrates that this new methodology outperforms the traditional Regularized Least-Squares, producing better statistical properties and better results for a model fit measure.
@INPROCEEDINGS{Boeira:Eckhard:2021b, author={E. Boeira and D. Eckhard}, booktitle={2021 Australian New Zealand Control Conference (ANZCC)}, title={Regularized impulse response estimation for systems with colored output noise}, year={2021}, volume={}, number={}, pages={18-23}, abstract={This paper addresses the use of the regularization feature on impulse response estimation for systems with colored output noise. Firstly, it is shown that the optimal regularization matrix for this scenario is quite different than the optimal for the white noise case and that there is a direct relationship between the Regularized Weighted Least-Squares with a Bayesian perspective of the identification problem for such case. Also, a new Empirical Bayes method, based on the Bayesian perspective, is introduced to estimate the regularization and noise covariance matrices from data. Finally, a numerical example demonstrates that this new methodology outperforms the traditional Regularized Least-Squares, producing better statistical properties and better results for a model fit measure.}, keywords={}, doi={10.1109/ANZCC53563.2021.9628304}, ISSN={2767-7257}, month={Nov}} - R. Scheid Filho, E. C. Boeira, L. Campestrini, and D. Eckhard, “Data-driven control design for load disturbance rejection by prediction error identification,” in 2021 Australian New Zealand Control Conference (ANZCC), 2021, pp. 92-97. doi:10.1109/ANZCC53563.2021.9628273
[BibTeX] [Abstract]
This paper presents a new direct data-driven control method for the load disturbance problem in a Model Reference Matching framework. It consists in embedding the controller’s design under a prediction error approach, where a flexible reference model is also identified in order to guarantee the causality and stability of the ideal controller. Due to the complexity of the proposed approach, a dedicated iterative optimization algorithm is developed to properly solve the problem. Finally, the statistical properties of the obtained estimates are explored through simulation examples, where the enhancement obtained through the proposed methodology is compared to least-squares and instrumental variable solutions.
@INPROCEEDINGS{ScheidFilho:Boeira:Campestrini:Eckhard:2021, author={R. {Scheid Filho} and E. C. Boeira and L. Campestrini and D. Eckhard}, booktitle={2021 Australian New Zealand Control Conference (ANZCC)}, title={Data-driven control design for load disturbance rejection by prediction error identification}, year={2021}, volume={}, number={}, pages={92-97}, abstract={This paper presents a new direct data-driven control method for the load disturbance problem in a Model Reference Matching framework. It consists in embedding the controller’s design under a prediction error approach, where a flexible reference model is also identified in order to guarantee the causality and stability of the ideal controller. Due to the complexity of the proposed approach, a dedicated iterative optimization algorithm is developed to properly solve the problem. Finally, the statistical properties of the obtained estimates are explored through simulation examples, where the enhancement obtained through the proposed methodology is compared to least-squares and instrumental variable solutions.}, keywords={}, doi={10.1109/ANZCC53563.2021.9628273}, ISSN={2767-7257}, month={Nov}} - R. W. P. da Silva and D. Eckhard, “Data-driven Controller Certification through Vinnicombe Test and Local Rational Models,” in 2020 IEEE Conference on Control Technology and Applications (CCTA), 2020, pp. 231-236. doi:10.1109/CCTA41146.2020.9206310
[BibTeX] [Abstract]
This paper proposes an algorithm to certify a monovariable controller based on the well-known Vinnicombe metric. That metric is known to be too conservative; however, by using a frequency-wise approach and scaling the measured signals the metric may be made less conservative, as already shown in the literature. The calculations depend on the estimation of some frequency response functions (FRF), for which we suggest the use of the Local Rational Models (LRM). Finally, we show that under certain circumstances the controller certification task may be reduced to computing the intersection of a finite number of intervals representing the scaling factors that certify the controller at each frequency.
@INPROCEEDINGS{DaSilva:Eckhard:2020b, author={R. W. P. {da Silva} and D. {Eckhard}}, booktitle={2020 IEEE Conference on Control Technology and Applications (CCTA)}, title={Data-driven Controller Certification through Vinnicombe Test and Local Rational Models}, year={2020}, volume={}, number={}, pages={231-236}, abstract={This paper proposes an algorithm to certify a monovariable controller based on the well-known Vinnicombe metric. That metric is known to be too conservative; however, by using a frequency-wise approach and scaling the measured signals the metric may be made less conservative, as already shown in the literature. The calculations depend on the estimation of some frequency response functions (FRF), for which we suggest the use of the Local Rational Models (LRM). Finally, we show that under certain circumstances the controller certification task may be reduced to computing the intersection of a finite number of intervals representing the scaling factors that certify the controller at each frequency.}, keywords={Frequency control;Closed loop systems;Measurement;Process control;Stability analysis;Computational modeling;Frequency response}, doi={10.1109/CCTA41146.2020.9206310}, ISSN={}, month={Aug}} - R. W. P. da Silva and D. Eckhard, “Extension of the Correlation-based Tuning Method for Load Disturbance Rejection,” in 2019 IEEE 58th Conference on Decision and Control (CDC), 2019, pp. 8386-8391. doi:10.1109/CDC40024.2019.9029360
[BibTeX] [Abstract]
Many industrial processes must follow reference signals that are mostly constant with few or no changes. In this scenario, the disturbance response is usually more relevant than the response to reference changes. However, there is little mention in the current literature of data-driven control methods aiming to solve disturbance rejection problems. This work tries to fill that lacuna by presenting an extension of the well-known data-driven controller design method named Correlation-based Tuning (CbT). That original method seeks to solve the reference tracking problem using the correlation approach from system identification, and the proposed extension applies a similar approach to the load disturbance rejection problem. Simulation examples compare the proposed method with the state-of-the-art disturbance rejection data-driven control method.
@INPROCEEDINGS{DaSilva:Eckhard:2019, author={R. W. P. {da Silva} and D. {Eckhard}}, booktitle={2019 IEEE 58th Conference on Decision and Control (CDC)}, title={Extension of the Correlation-based Tuning Method for Load Disturbance Rejection}, year={2019}, volume={}, number={}, pages={8386-8391}, abstract={Many industrial processes must follow reference signals that are mostly constant with few or no changes. In this scenario, the disturbance response is usually more relevant than the response to reference changes. However, there is little mention in the current literature of data-driven control methods aiming to solve disturbance rejection problems. This work tries to fill that lacuna by presenting an extension of the well-known data-driven controller design method named Correlation-based Tuning (CbT). That original method seeks to solve the reference tracking problem using the correlation approach from system identification, and the proposed extension applies a similar approach to the load disturbance rejection problem. Simulation examples compare the proposed method with the state-of-the-art disturbance rejection data-driven control method.}, keywords={control system synthesis;tuning;data-driven control methods;disturbance rejection problems;data-driven controller design method;reference tracking problem;correlation approach;load disturbance rejection problem;disturbance rejection data-driven control method;correlation-based tuning method;Correlation;Tuning;Process control;Cost function;Sensitivity;Instruments}, doi={10.1109/CDC40024.2019.9029360}, ISSN={2576-2370}, month={Dec}} - D. Eckhard, “Fast Rietveld Method Algorithm for in-situ XRD,” in 29th Annual Users Meeting of the Brazilian Synchrotron Light Laboratory, Campinas, 2019, p. 55–55.
[BibTeX] [Abstract]
X-ray diffraction is an analytical technique used to identify and quantify phases in a crystalline material. In a diffractometer, an X-ray with constant wavelength is directed to the sample which diffracts the wave in many directions with intensities that depend on the structure of the crystal. The result of the experiment is a diffractogram that presents the intensity of the diffracted wave at each measured angle. Each phase of the material results in a different pattern on the diffractogram, in such way that it is possible to quantify the amount of each phase in the sample. The Rietveld refinement method is probably the most used algorithm to refine the structure of crystals and to quantify the amount of each phase. The Rietveld method is based on the solution of a least-squares problem where it is minimized the difference between the diffractogram peaks collected in an experiment and a mathematical model of the crystal. Since the intensity of the peaks is proportional to the quantity of each phase in the sample, the method present good results in phase quantification. In-situ XRD comprises an experiment where many measures are made from the sample in different instances of time, resulting in a sequence of diffractograms that show the changes in the sample with time. It can be used to study and understand chemical reactions that form and consume different crystal in time. For instance, when cement is hydrated, many crystalline materials are consumed and formed until the reaction finishes. In many applications, in-situ XRD produces and huge amount of data, since samples may be collected once per minute for a complete day (or several days) resulting in thousand of diffractograms, where each one usually is close to one megabyte of data, totalizing gigabytes of data. This large amount of data is difficult to save and transport, but much more difficult is to analyze and to extract the information from each diffractogram, and to obtain useful information from these set of diffractograms. This problem is becoming much more relevant with the new sources of light like Sirius in CNPEM, since a brighter light allows shorter samples and therefore many more samples for each day. Rietveld refinement technique is usually performed by specialized people and requires a long time to extract the information of each sample, since many parameters need to be estimated resolving a non-convex optimization problem. Even experienced users may spend from tens of minutes to hours to resolve a single sample. In this work we present a new Matlab Toolbox used to quantify phases of a crystal using the Rietveld Refinement Technique specialized to In-Situ Samples. It is observed that since two consecutive samples present similar diffractograms then the estimated parameters of each sample should be similar, and then the optimal solution of one optimization problem is a good initialization parameter for the next one, resulting in faster time to resolve a sequence of diffractograms. The algorithm is implemented in Matlab and uses parallel programming capabilities to improve performance.
@inproceedings{Eckhard:2019, Address = {Campinas}, Author = {D. Eckhard}, Booktitle = { 29th Annual Users Meeting of the Brazilian Synchrotron Light Laboratory}, publisher = {CNPEM}, Pages = {55--55}, Title = {Fast {Rietveld Method} Algorithm for in-situ {XRD}}, Year = {2019}, Abstract = { X-ray diffraction is an analytical technique used to identify and quantify phases in a crystalline material. In a diffractometer, an X-ray with constant wavelength is directed to the sample which diffracts the wave in many directions with intensities that depend on the structure of the crystal. The result of the experiment is a diffractogram that presents the intensity of the diffracted wave at each measured angle. Each phase of the material results in a different pattern on the diffractogram, in such way that it is possible to quantify the amount of each phase in the sample. The Rietveld refinement method is probably the most used algorithm to refine the structure of crystals and to quantify the amount of each phase. The Rietveld method is based on the solution of a least-squares problem where it is minimized the difference between the diffractogram peaks collected in an experiment and a mathematical model of the crystal. Since the intensity of the peaks is proportional to the quantity of each phase in the sample, the method present good results in phase quantification. In-situ XRD comprises an experiment where many measures are made from the sample in different instances of time, resulting in a sequence of diffractograms that show the changes in the sample with time. It can be used to study and understand chemical reactions that form and consume different crystal in time. For instance, when cement is hydrated, many crystalline materials are consumed and formed until the reaction finishes. In many applications, in-situ XRD produces and huge amount of data, since samples may be collected once per minute for a complete day (or several days) resulting in thousand of diffractograms, where each one usually is close to one megabyte of data, totalizing gigabytes of data. This large amount of data is difficult to save and transport, but much more difficult is to analyze and to extract the information from each diffractogram, and to obtain useful information from these set of diffractograms. This problem is becoming much more relevant with the new sources of light like Sirius in CNPEM, since a brighter light allows shorter samples and therefore many more samples for each day. Rietveld refinement technique is usually performed by specialized people and requires a long time to extract the information of each sample, since many parameters need to be estimated resolving a non-convex optimization problem. Even experienced users may spend from tens of minutes to hours to resolve a single sample. In this work we present a new Matlab Toolbox used to quantify phases of a crystal using the Rietveld Refinement Technique specialized to In-Situ Samples. It is observed that since two consecutive samples present similar diffractograms then the estimated parameters of each sample should be similar, and then the optimal solution of one optimization problem is a good initialization parameter for the next one, resulting in faster time to resolve a sequence of diffractograms. The algorithm is implemented in Matlab and uses parallel programming capabilities to improve performance.} } - E. C. Boeira and D. Eckhard, “Multivariable Virtual Reference Feedback Tuning with Bayesian regularization,” in XXII Congresso Brasileiro de Automática, João Pessoa, 2018, p. 1–8. doi:10.20906/CPS/CBA2018-1060
[BibTeX] [Abstract]
This paper proposes the use of regularization on the multivariable formulation of the Virtual Reference Feedback Tuning (VRFT). When the process to be controlled has a significant amount of noise, the standard VRFT approach, that uses the instrumental variable technique, provides estimates with very poor statistical properties. To cope with that, this paper considers the use of regularization on the estimation procedure, reducing the covariance error at the cost of inserting a small bias. Also, this paper explains different types of regularization matrices and presents the methodology to tune these matrices. In order to demonstrate the benefits of the proposed formulation, a numerical example is presented.
@inproceedings{Boeira:Eckhard:2018, Address = {Jo\~{a}o Pessoa}, Author = {E. C. Boeira and D. Eckhard}, Booktitle = {XXII Congresso Brasileiro de Autom\'{a}tica}, publisher = {{SBA} Sociedade Brasileira de Autom{\'{a}}tica}, Pages = {1--8}, Title = {Multivariable Virtual Reference Feedback Tuning with Bayesian regularization}, Year = {2018}, doi= {10.20906/CPS/CBA2018-1060}, Abstract = {This paper proposes the use of regularization on the multivariable formulation of the Virtual Reference Feedback Tuning (VRFT). When the process to be controlled has a significant amount of noise, the standard VRFT approach, that uses the instrumental variable technique, provides estimates with very poor statistical properties. To cope with that, this paper considers the use of regularization on the estimation procedure, reducing the covariance error at the cost of inserting a small bias. Also, this paper explains different types of regularization matrices and presents the methodology to tune these matrices. In order to demonstrate the benefits of the proposed formulation, a numerical example is presented.} } - J. V. Flores, D. Eckhard, and A. T. Salton, “Modified MIMO Resonant Controller Robust to Period Variation and Parametric Uncertainty,” in 2016 IEEE Conference on Control Applications (CCA), Buenos Aires, 2016, p. 1256–1261. doi:10.1109/CCA.2016.7587979
[BibTeX] [Abstract]
In this work a modified Resonant Controller is proposed to deal with the tracking/rejection problem of periodic signals robust to period variations and parametric uncertainties in the plant. The control strategy is based on a resonant structure in series with a notch filter, which will be responsible to improve the robustness to period variation. A robust state feedback controller is designed by solving a linear matrix inequality (LMI) optimization problem guaranteeing the robust stability of the closed loop system. A numerical example is presented to illustrate the method.
@inproceedings{Flores:Eckhard:Salton:2016, Abstract = {In this work a modified Resonant Controller is proposed to deal with the tracking/rejection problem of periodic signals robust to period variations and parametric uncertainties in the plant. The control strategy is based on a resonant structure in series with a notch filter, which will be responsible to improve the robustness to period variation. A robust state feedback controller is designed by solving a linear matrix inequality (LMI) optimization problem guaranteeing the robust stability of the closed loop system. A numerical example is presented to illustrate the method.}, Address = {Buenos Aires}, Author = {J. V. Flores and D. Eckhard and A. T. Salton}, Booktitle = {2016 {IEEE} Conference on Control Applications ({CCA})}, Date-Modified = {2017-05-30 19:00:28 +0000}, Doi = {10.1109/CCA.2016.7587979}, Keywords = {MIMO systems;closed loop systems;control system synthesis;feedback;linear matrix inequalities;robust control;LMI;MIMO resonant controller robust;closed loop system;control strategy;linear matrix inequality;parametric uncertainty;period variation;periodic signals robust;rejection problem;robust stability;robust state feedback controller designed;tracking problem;Aerospace electronics;Frequency control;Harmonic analysis;MIMO;Resonant frequency;Robustness;Uncertainty}, Month = {Sept}, Pages = {1256--1261}, Publisher = {IEEE}, Title = {Modified {MIMO} Resonant Controller Robust to Period Variation and Parametric Uncertainty}, Year = {2016}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/CCA.2016.7587979}} - A. T. Salton, D. Eckhard, J. V. Flores, G. Fernandes, and G. Azevedo, “Disturbance observer and nonlinear damping control for fast tracking quadrotor vehicles,” in 2016 IEEE Conference on Control Applications (CCA), Buenos Aires, 2016, p. 705–710. doi:10.1109/CCA.2016.7587901
[BibTeX] [Abstract]
This paper considers the design and implementation of a discrete-time fast tracking controller for quadrotor vehicles subject to perturbations. The proposed controller consists of a model-based disturbance observer and a Composite Nonlinear Feedback (CNF) controller. The CNF control law introduces nonlinear damping to the system so that it possesses a fast rise time without overshoot. The least square identification method is applied to develop a model based disturbance observer, thus decoupling the problems of track following and disturbance rejection. Experimental results are provided in order to validate the proposed approach.
@inproceedings{Salton:Eckhard:Flores:Fernandes:Azevedo:2016, Abstract = {This paper considers the design and implementation of a discrete-time fast tracking controller for quadrotor vehicles subject to perturbations. The proposed controller consists of a model-based disturbance observer and a Composite Nonlinear Feedback (CNF) controller. The CNF control law introduces nonlinear damping to the system so that it possesses a fast rise time without overshoot. The least square identification method is applied to develop a model based disturbance observer, thus decoupling the problems of track following and disturbance rejection. Experimental results are provided in order to validate the proposed approach.}, Address = {Buenos Aires}, Author = {A. T. Salton and D. Eckhard and J. V. Flores and G. Fernandes and G. Azevedo}, Booktitle = {2016 IEEE Conference on Control Applications (CCA)}, Doi = {10.1109/CCA.2016.7587901}, Keywords = {control system synthesis;damping;discrete time systems;feedback;helicopters;least squares approximations;nonlinear control systems;observers;perturbation techniques;CNF controller;composite nonlinear feedback controller;discrete-time fast tracking controller design;disturbance rejection;fast tracking quadrotor vehicles;least square identification method;model-based disturbance observer;nonlinear damping control;perturbations;track following problems;Control systems;Damping;Mathematical model;Observers;Sensors;Vehicle dynamics;Vehicles}, Month = {Sept}, Pages = {705--710}, Publisher = {IEEE}, Title = {Disturbance observer and nonlinear damping control for fast tracking quadrotor vehicles}, Year = {2016}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/CCA.2016.7587901}} - R. Scheid Filho, D. Eckhard, G. R. Gonçalves da Silva, and L. Campestrini, “Application of Virtual Reference Feedback Tuning to a non-minimum phase pilot plant,” in 2016 IEEE Conference on Control Applications (CCA), Buenos Aires, 2016, p. 1318–1323. doi:10.1109/CCA.2016.7587989
[BibTeX] [Abstract]
Virtual Reference Feedback Tuning (VRFT) is a data-driven technique used to design controllers without the need of a process model, only input-output data is utilized. When the process has non-minimum phase (NMP) zeros, the original method usually presents poor performance, because scarcely the reference model has the same NMP zeros as the process. To overcome this problem, a flexible criterion has been proposed to the VRFT method, in a way that both the controller parameters and the NMP zeros of the process are estimated together. In this paper we present the application of the VRFT method with flexible criterion to the level control of a MIMO pilot plant. We show that a sequential controller design may incorporate NMP behavior to the process. We then use the VRFT method with flexible criterion to design the controller using only closed-loop data from the process.
@inproceedings{Scheid:Eckhard:Goncalves:Campestrini:2016, Abstract = {Virtual Reference Feedback Tuning (VRFT) is a data-driven technique used to design controllers without the need of a process model, only input-output data is utilized. When the process has non-minimum phase (NMP) zeros, the original method usually presents poor performance, because scarcely the reference model has the same NMP zeros as the process. To overcome this problem, a flexible criterion has been proposed to the VRFT method, in a way that both the controller parameters and the NMP zeros of the process are estimated together. In this paper we present the application of the VRFT method with flexible criterion to the level control of a MIMO pilot plant. We show that a sequential controller design may incorporate NMP behavior to the process. We then use the VRFT method with flexible criterion to design the controller using only closed-loop data from the process.}, Address = {Buenos Aires}, Author = {R. {Scheid Filho} and D. Eckhard and G. R. {Gon\c{c}alves da Silva} and L. Campestrini}, Booktitle = {2016 IEEE Conference on Control Applications (CCA)}, Doi = {10.1109/CCA.2016.7587989}, Keywords = {MIMO systems;closed loop systems;control system synthesis;feedback;MIMO pilot plant;VRFT;closed-loop data;data-driven technique;level control;nonminimum phase pilot plant;nonminimum phase zeros;sequential controller design;virtual reference feedback tuning;Adaptation models;Data models;Process control;Standards;Transfer functions;Tuning;Valves}, Month = {Sept}, Pages = {1318--1323}, Publisher = {IEEE}, Title = {Application of Virtual Reference Feedback Tuning to a non-minimum phase pilot plant}, Year = {2016}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/CCA.2016.7587989}} - D. Tesch, D. Eckhard, and A. S. Bazanella, “Iterative feedback tuning for cascade systems,” in 2016 European Control Conference (ECC), Aalborg, 2016, p. 495–500. doi:10.1109/ECC.2016.7810333
[BibTeX] [Abstract]
Iterative Feedback Tuning (IFT) is a data-driven method used to tune parameters of feedback controllers minimising an H2 criterion. The method uses data from experiments to estimate the gradient of the criterion, and uses iterative quasinewton algorithms to adjust the controllers. When the method is used in cascade systems, usually the inner loop is firstly adjusted, and after the outer loop. In this article we describe an extension to the IFT method that adjusts both inner and outer loop at the same time using only data from closed-loop experiments at each iteration.
@inproceedings{Tesch:Eckhard:Bazanella:2016, Abstract = {Iterative Feedback Tuning (IFT) is a data-driven method used to tune parameters of feedback controllers minimising an H2 criterion. The method uses data from experiments to estimate the gradient of the criterion, and uses iterative quasinewton algorithms to adjust the controllers. When the method is used in cascade systems, usually the inner loop is firstly adjusted, and after the outer loop. In this article we describe an extension to the IFT method that adjusts both inner and outer loop at the same time using only data from closed-loop experiments at each iteration.}, Address = {Aalborg}, Author = {D. Tesch and D. Eckhard and A. S. Bazanella}, Booktitle = {2016 European Control Conference (ECC)}, Doi = {10.1109/ECC.2016.7810333}, Keywords = {Cost function;Electronic mail;Iterative methods;Mathematical model;Transfer functions;Tuning}, Month = {June}, Pages = {495--500}, Title = {Iterative feedback tuning for cascade systems}, Year = {2016}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/ECC.2016.7810333}} - L. D. Sartori and D. Eckhard, “Tratamento do fator de decaimento exponencial para o Modelo Diebold-Li no ajuste da ETTJ brasileira,” in Congresso Nacional de Matemática Aplicada e Computacional, Gramado, 2016. doi:10.5540/03.2017.005.01.0122
[BibTeX]@inproceedings{sartori:eckhard:2016, Address = {Gramado}, Author = {L. D. Sartori and D. Eckhard}, Booktitle = {Congresso Nacional de Matem\'{a}tica Aplicada e Computacional}, Date-Added = {2016-10-02 13:10:20 +0000}, Date-Modified = {2016-10-02 13:12:57 +0000}, Doi = {10.5540/03.2017.005.01.0122}, Title = {Tratamento do fator de decaimento exponencial para o Modelo {Diebold-Li} no ajuste da {ETTJ} brasileira}, Year = {2016}, Bdsk-Url-1 = {http://dx.doi.org/10.5540/03.2017.005.01.0122}} - D. A. Tesch, D. Eckhard, and W. C. Guarienti, “Pitch and Roll control of a Quadcopter using Cascade Iterative Feedback Tuning,” in 4th IFAC Symposium on Telematics Applications, Porto Alegre, 2016, p. 30–35. doi:10.1016/j.ifacol.2016.11.118
[BibTeX] [Abstract]
Quadcopter is a type of Unmanned Aerial Vehicle which is lifted and propelled by four rotors. The vehicle has a complex non-linear dynamic which makes the tuning of the roll and pitch controllers difficult. Usually the control design is based on a mathematical model which is strongly related to physical components of vehicle: mass, moment of inertia and aerodynamic. When a tool is attached to the vehicle, a new model must be computed to redesign the controllers. In this article we will adjust the controllers of a real experimental quadcopter using the Cascade Iterative Feedback Tuning method. The method is data-driven, so it does not uses a model for the vehicle; all it uses is input-output data collect from the closed-loop system. The method minimizes the \{H2\} error between the desired response and the actual response of the vehicle angle using the Newton-Raphson algorithm. The method achieves the desired performance without the need of the vehicle model, with low cost and low complexity.
@inproceedings{Tesch:Eckhard:Guarienti:2016, Abstract = {Quadcopter is a type of Unmanned Aerial Vehicle which is lifted and propelled by four rotors. The vehicle has a complex non-linear dynamic which makes the tuning of the roll and pitch controllers difficult. Usually the control design is based on a mathematical model which is strongly related to physical components of vehicle: mass, moment of inertia and aerodynamic. When a tool is attached to the vehicle, a new model must be computed to redesign the controllers. In this article we will adjust the controllers of a real experimental quadcopter using the Cascade Iterative Feedback Tuning method. The method is data-driven, so it does not uses a model for the vehicle; all it uses is input-output data collect from the closed-loop system. The method minimizes the \{H2\} error between the desired response and the actual response of the vehicle angle using the Newton-Raphson algorithm. The method achieves the desired performance without the need of the vehicle model, with low cost and low complexity.}, Address = {Porto Alegre}, Author = {D. A. Tesch and D. Eckhard and W. C. Guarienti}, Booktitle = {4th {IFAC} Symposium on Telematics Applications}, Date-Modified = {2017-05-30 18:58:51 +0000}, Doi = {10.1016/j.ifacol.2016.11.118}, Issn = {2405--8963}, Pages = {30--35}, Publisher = {IFAC}, Title = {Pitch and Roll control of a Quadcopter using Cascade Iterative Feedback Tuning}, Year = {2016}, Bdsk-Url-1 = {http://dx.doi.org/10.1016/j.ifacol.2016.11.118}} - R. P. da Silva, D. Eckhard, I. Müller, J. M. Winter, C. E. Pereira, and J. C. Netto, “PI-based Transmission Power Control for WirelessHART Field Devices,” in 4th IFAC Symposium on Telematics Applications, Porto Alegre, 2016, p. 343–348. doi:10.1016/j.ifacol.2016.11.159
[BibTeX] [Abstract]
Wireless networks are gaining space in industrial environments due to the low installation costs and low maintenance. Robustness is also one of the main requirements for these systems to be adopted, and, in this context, WirelessHART (WH), ISA SP100.11a, and WIA-PA protocols met these characteristics. In order to provide low maintenance, these protocols must provide reliable radio links while keeping low power consumption to allow battery powered devices. Unfortunately, the standards of these protocols do not impose any RF power modulation technique, which is a form to increase even more the battery endurance of a wireless field device. Instead, RF power levels are fixed and selected by commissioning, and must allow the longest link per device. In this case, devices in closer ranges waste energy during transmissions, as they could save energy by modulating the RF power. This paper presents a RF power modulation technique that employs a proportional-integral controller and allows reduction of energy consumption while keeping the robustness of RF links. A proof of concept of the power modulation technique is implemented and verified showing good results and proving that the proposed controller is feasible. The proposal has the advantage to be fully compatible with the standard.
@inproceedings{Silva:Eckhard:Muller:Winter:Pereira:Netto:2016, Abstract = {Wireless networks are gaining space in industrial environments due to the low installation costs and low maintenance. Robustness is also one of the main requirements for these systems to be adopted, and, in this context, WirelessHART (WH), ISA SP100.11a, and WIA-PA protocols met these characteristics. In order to provide low maintenance, these protocols must provide reliable radio links while keeping low power consumption to allow battery powered devices. Unfortunately, the standards of these protocols do not impose any RF power modulation technique, which is a form to increase even more the battery endurance of a wireless field device. Instead, RF power levels are fixed and selected by commissioning, and must allow the longest link per device. In this case, devices in closer ranges waste energy during transmissions, as they could save energy by modulating the RF power. This paper presents a RF power modulation technique that employs a proportional-integral controller and allows reduction of energy consumption while keeping the robustness of RF links. A proof of concept of the power modulation technique is implemented and verified showing good results and proving that the proposed controller is feasible. The proposal has the advantage to be fully compatible with the standard. }, Address = {Porto Alegre}, Author = {R. P. da Silva and D. Eckhard and I. M{\"u}ller and J. M. Winter and C. E. Pereira and J. C. Netto}, Booktitle = {4th {IFAC} Symposium on Telematics Applications}, Date-Modified = {2017-05-30 18:59:11 +0000}, Doi = {10.1016/j.ifacol.2016.11.159}, Issn = {2405--8963}, Pages = {343--348}, Publisher = {IFAC}, Title = {{PI}-based Transmission Power Control for {WirelessHART} Field Devices}, Year = {2016}, Bdsk-Url-1 = {http://dx.doi.org/10.1016/j.ifacol.2016.11.159}} - R. W. P. da Silva, V. Brusamarello, D. Eckhard, C. E. Pereira, J. C. Netto, and I. Müller, “Contactless Battery Charger Controller for Wireless Sensor Node,” in Symposium on Instrumentation Systems, Circuits and Transducers (INSCIT), Belo Horizonte, 2016.
[BibTeX]@inproceedings{Silva:Brusamarello:Eckhard:Pereira:Netto:Muller:2016, Address = {Belo Horizonte}, Author = {R. W. P. da Silva and V. Brusamarello and D. Eckhard and C. E. Pereira and J. C. Netto and I. M\"{u}ller}, Booktitle = {Symposium on Instrumentation Systems, Circuits and Transducers (INSCIT)}, Date-Added = {2016-10-02 12:41:15 +0000}, Date-Modified = {2016-10-02 12:47:56 +0000}, Title = {Contactless Battery Charger Controller for Wireless Sensor Node}, Year = {2016}} - R. Rui, T. Ardeshiri, and A. S. Bazanella, “Identification of Piecewise Affine State-Space Models via Expectation Maximization,” in 2016 IEEE Conference on Control Applications, Buenos Aires, 2016, p. 1066–1071.
[BibTeX]@inproceedings{Rui:Ardeshiri:Bazanella:2016, Address = {Buenos Aires}, Author = {R. Rui and T. Ardeshiri and A. S. Bazanella}, Booktitle = {2016 IEEE Conference on Control Applications}, Pages = {1066--1071}, Publisher = {IEEE}, Title = {Identification of Piecewise Affine State-Space Models via Expectation Maximization}, Year = {2016}} - T. Salvatori, G. A. Pimentel, and A. S. Bazanella, “Evaluation of Polynomial Models to Predict Methane Production in Batch Mode Bioreactors,” in European Control Conference, Aalborg, 2016.
[BibTeX]@inproceedings{Salvatori:Pimentel:Bazanella:2016, Address = {Aalborg}, Author = {T. Salvatori and G. A. Pimentel and A. S. Bazanella}, Booktitle = {European Control Conference}, Publisher = {IFAC}, Title = {Evaluation of Polynomial Models to Predict Methane Production in Batch Mode Bioreactors}, Year = {2016}} - W. Haselein, C. Poleto, O. Konrad, and D. Eckhard, “Identificação de parâmetros de um modelo dinâmico para biorretores anaeróbicos,” in 7a Conferência Internacional de Materiais e Processos para Energias Renováveis, Porto Alegre, 2016, p. 1–7.
[BibTeX]@inproceedings{Haselein:Poleto:Konrad:Eckhard:2016, Address = {Porto Alegre}, Author = {W. Haselein and C. Poleto and O. Konrad and D. Eckhard}, Booktitle = {7a Confer{\^e}ncia Internacional de Materiais e Processos para Energias Renov{\'a}veis}, Pages = {1--7}, Title = {Identifica{\c{c}}{\~a}o de par{\^a}metros de um modelo din{\^a}mico para biorretores anaer{\'o}bicos}, Year = {2016}} - A. Corleta, C. Lorenzini, J. V. Flores, and L. Campestrini, “Data-driven control design applied to uninterruptible power supplies,” in 2016 IEEE Conference on Control Applications, Buenos Aires, 2016, p. 1312–1317.
[BibTeX]@inproceedings{Corleta:Lorenzini:Flores:Campestrini:2016, Address = {Buenos Aires}, Author = {A. Corleta and C. Lorenzini and J. V. Flores and L. Campestrini}, Booktitle = {2016 IEEE Conference on Control Applications}, Pages = {1312--1317}, Publisher = {IEEE}, Title = {Data-driven control design applied to uninterruptible power supplies}, Year = {2016}} - G. R. Gonçalves da Silva, L. Campestrini, and A. S. Bazanella, “Multivariable VRFT: an approach for systems with non-minimum phase transmission zeros,” in 2016 IEEE Conference on Control Applications, Buenos Aires, 2016, p. 1324–1328.
[BibTeX]@inproceedings{Goncalves:Campestrini:Bazanella:2016, Address = {Buenos Aires}, Author = {G. R. {Gon\c{c}alves da Silva} and L. Campestrini and A. S. Bazanella}, Booktitle = {2016 IEEE Conference on Control Applications}, Pages = {1324--1328}, Publisher = {IEEE}, Title = {Multivariable {VRFT}: an approach for systems with non-minimum phase transmission zeros}, Year = {2016}} - D. Eckhard and L. Campestrini, “Análise do uso de modelos discretizados para identifica\caão de modelos de biorreatores anaeróbicos,” in Proceeding Series of the Brazilian Society of Applied and Computational Mathematics, Natal, 2015, p. 10059-1 – 10059-7. doi:10.5540/03.2016.004.01.0059
[BibTeX]@inproceedings{Eckhard:Campestrini:2015, Address = {Natal}, Author = {D. Eckhard and L. Campestrini}, Booktitle = {Proceeding Series of the Brazilian Society of Applied and Computational Mathematics}, Doi = {10.5540/03.2016.004.01.0059}, Pages = {10059-1 -- 10059-7}, Title = {An\'{a}lise do uso de modelos discretizados para identifica\c{a}\~{a}o de modelos de biorreatores anaer\'{o}bicos}, Year = {2015}, Bdsk-Url-1 = {http://dx.doi.org/10.5540/03.2016.004.01.0059}} - D. Eckhard, A. A. D. de Mattos, and D. Tesch, “Aplicação do método VRFT no projeto de controle de quadricópteros,” in Proceeding Series of the Brazilian Society of Applied and Computational Mathematics, Natal, 2015, p. 10092-1 – 10092-7. doi:10.5540/03.2016.004.01.0092
[BibTeX]@inproceedings{Eckhard:Mattos:Tesch:2015, Address = {Natal}, Author = {D. Eckhard and A. A. D. de Mattos and D. Tesch}, Booktitle = {Proceeding Series of the Brazilian Society of Applied and Computational Mathematics}, Doi = {10.5540/03.2016.004.01.0092}, Pages = {10092-1 -- 10092-7}, Title = {Aplica{\c{c}}{\~a}o do m{\'e}todo {VRFT} no projeto de controle de quadric{\'o}pteros}, Year = {2015}, Bdsk-Url-1 = {http://dx.doi.org/10.5540/03.2016.004.01.0092}} - C. S. Garcia, D. Eckard, J. C. Netto, C. E. Pereira, and I. Müller, “Bluetooth Enabled Data Collector for Wireless Sensor Networks,” in 2015 Brazilian Symposium on Computing Systems Engineering (SBESC), Foz do Iguaçu, 2015, p. 54–57. doi:10.1109/SBESC.2015.17
[BibTeX] [Abstract]
The wireless sensor networks (WSN) are gradually gaining attention because it is a key technology for the Internet of Things. For most of these networks, the data is usually collected in a manual way, by removing a memory unit or connecting the collector node to a personal computer. This is a constraint, because it demands the manipulation of the collector radio by the operator, which consists in a problem in practical applications. The main goal of this work is to present a non-invasive alternative way to collect the data by means of Bluetooth technology. The approach allows the development of hermetic devices, which is a desirable feature for practical deployment of the sensor nodes.
@inproceedings{Garcia:Eckhard:Netto:Pereira:Muller:2015, Abstract = {The wireless sensor networks (WSN) are gradually gaining attention because it is a key technology for the Internet of Things. For most of these networks, the data is usually collected in a manual way, by removing a memory unit or connecting the collector node to a personal computer. This is a constraint, because it demands the manipulation of the collector radio by the operator, which consists in a problem in practical applications. The main goal of this work is to present a non-invasive alternative way to collect the data by means of Bluetooth technology. The approach allows the development of hermetic devices, which is a desirable feature for practical deployment of the sensor nodes.}, Address = {Foz do Igua\c{c}u}, Author = {C. S. Garcia and D. Eckard and J. C. Netto and C. E. Pereira and I. M\"{u}ller}, Booktitle = {2015 Brazilian Symposium on Computing Systems Engineering (SBESC)}, Doi = {10.1109/SBESC.2015.17}, Pages = {54--57}, Publisher = {IEEE}, Title = {Bluetooth Enabled Data Collector for Wireless Sensor Networks}, Year = {2015}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/SBESC.2015.17}} - M. Gevers and A. S. Bazanella, “Identification in dynamic networks: Identifiability and experiment design issues,” in 2015 54th IEEE Conference on Decision and Control (CDC), Osaka, 2015, p. 4005–4010. doi:10.1109/SBESC.2015.17
[BibTeX] [Abstract]
Recently attention has been paid to the identification of networks of linear time-invariant dynamical systems. One of the problems of interest is the identification of a particular transfer function within the network on the basis of available measurements. This raises the question of which signals need to be measured and which external excitation signals need to be present in the network in order to yield a consistent estimate of this desired transfer function. This paper examines the properties of the estimated transfer function in terms of bias error and variance error, for different models of the network. The main contribution is the derivation of sufficient richness conditions on the external signals for the consistent identification of the desired transfer function.
@inproceedings{Gevers:Bazanella:2015, Abstract = {Recently attention has been paid to the identification of networks of linear time-invariant dynamical systems. One of the problems of interest is the identification of a particular transfer function within the network on the basis of available measurements. This raises the question of which signals need to be measured and which external excitation signals need to be present in the network in order to yield a consistent estimate of this desired transfer function. This paper examines the properties of the estimated transfer function in terms of bias error and variance error, for different models of the network. The main contribution is the derivation of sufficient richness conditions on the external signals for the consistent identification of the desired transfer function.}, Address = {Osaka}, Author = {M. Gevers and A. S. Bazanella}, Booktitle = {2015 54th IEEE Conference on Decision and Control (CDC)}, Doi = {10.1109/SBESC.2015.17}, Keywords = {design of experiments;identification;linear systems;transfer functions;bias error;dynamic network;experiment design issues;external excitation signals;identifiability;identification;linear time-invariant dynamical systems;transfer function identification;variance error;Closed loop systems;Delays;Estimation;Interconnected systems;Network topology;Transfer functions}, Pages = {4005--4010}, Publisher = {IEEE}, Title = {Identification in dynamic networks: Identifiability and experiment design issues}, Year = {2015}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/SBESC.2015.17}} - I. Müller, J. M. Winter, C. E. Pereira, J. C. Netto, and D. Eckhard, “Automatic RF power adjustment for WirelessHART field devices,” in 2014 IEEE International Conference on Industrial Technology, Busan, 2014, p. 749–753. doi:10.1109/ICIT.2014.6895025
[BibTeX] [Abstract]
Industrial wireless networks are gradually being adopted in industry, especially due to the low installation costs and low maintenance provided by these systems. For the use in harsh environments, the communication system should provide reliable radio links and low power to allow battery powered devices. In this context, WirelessHART, ISA SP100.11a and WIA-PA protocols were developed to meet these requirements. The standards of these protocols define a minimum number of RF fixed power and selectable only by commissioning. Within this scenario, it is important to adapt RF power modulation, a procedure already used in several communication protocols to minimize the energy consumption of transceivers while maintaining link quality. In this paper, three ways to modulate RF power are analyzed within WirelessHART field devices. A specific approach that works in a decentralized way is developed and the results show it can save 50\% of energy in certain cases. The proposal has the extra advantage to be compatible with the standard.
@inproceedings{Muller:Winter:Pereira:Netto:Eckhard:2014, Abstract = {Industrial wireless networks are gradually being adopted in industry, especially due to the low installation costs and low maintenance provided by these systems. For the use in harsh environments, the communication system should provide reliable radio links and low power to allow battery powered devices. In this context, WirelessHART, ISA SP100.11a and WIA-PA protocols were developed to meet these requirements. The standards of these protocols define a minimum number of RF fixed power and selectable only by commissioning. Within this scenario, it is important to adapt RF power modulation, a procedure already used in several communication protocols to minimize the energy consumption of transceivers while maintaining link quality. In this paper, three ways to modulate RF power are analyzed within WirelessHART field devices. A specific approach that works in a decentralized way is developed and the results show it can save 50\% of energy in certain cases. The proposal has the extra advantage to be compatible with the standard.}, Address = {Busan}, Author = {I. M\"{u}ller and J. M. Winter and C. E. Pereira and J. C. Netto and D. Eckhard}, Booktitle = {2014 IEEE International Conference on Industrial Technology}, Doi = {10.1109/ICIT.2014.6895025}, Pages = {749--753}, Publisher = {IEEE}, Title = {Automatic {RF} power adjustment for {WirelessHART} field devices}, Year = {2014}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/ICIT.2014.6895025}} - M. Tocchetto, A. S. Bazanella, L. Guimarães, J. L. Fragoso, and A. Parraga, “An Embedded Classifier of Lung Sounds Based on the Wavelet Packet Transform and ANN,” in 19th IFAC World Congress, Cape Town, 2014, p. 2975–2980. doi:10.3182/20140824-6-ZA-1003.01638
[BibTeX]@inproceedings{Tocchetto:Bazanella:Guimaraes:Fragoso:Parraga:2014, Address = {Cape Town}, Author = {M. Tocchetto and A. S. Bazanella and L. Guimar{\~a}es and J.L. Fragoso and A. Parraga}, Booktitle = {19th IFAC World Congress}, Doi = {10.3182/20140824-6-ZA-1003.01638}, Pages = {2975--2980}, Publisher = {IFAC}, Title = {An Embedded Classifier of Lung Sounds Based on the Wavelet Packet Transform and ANN}, Year = {2014}, Bdsk-Url-1 = {http://dx.doi.org/10.3182/20140824-6-ZA-1003.01638}} - A. Schildt, L. F. A. Pereira, and A. S. Bazanella, “Sintonia de controladores ressonantes baseado em dados aplicado a fontes ininterruptas de energia,” in XX Congresso Brasileiro de Automática, Belo Horizonte, 2014, p. 2260–2267.
[BibTeX]@inproceedings{Schildt:Pereira:Bazanella:2014, Address = {Belo Horizonte}, Author = {A. Schildt and L. F. A. Pereira and A. S. Bazanella}, Booktitle = {XX Congresso Brasileiro de Autom\'atica}, Pages = {2260--2267}, Publisher = {SBA}, Title = {Sintonia de controladores ressonantes baseado em dados aplicado a fontes ininterruptas de energia}, Year = {2014}} - G. R. Gonçalves da Silva, L. Campestrini, and A. S. Bazanella, “Automating the choice of the Reference Model for data-based control methods applied to PID controllers,” in XX Congresso Brasileiro de Automática, Belo Horizonte, 2014, p. 1088–1095.
[BibTeX]@inproceedings{Goncalves:Campestrini:Bazanella:2014, Address = {Belo Horizonte}, Author = {G. R. {Gon{\c{c}}alves da Silva} and L. Campestrini and A. S. Bazanella}, Booktitle = {XX Congresso Brasileiro de Autom\'atica}, Pages = {1088--1095}, Publisher = {SBA}, Title = {Automating the choice of the Reference Model for data-based control methods applied to {PID} controllers}, Year = {2014}} - A. S. Bazanella, M. Gevers, D. Coutinho, and R. Rui, “Identifiability and excitation of a class of rational systems,” in 53rd IEEE Conference on Decision and Control, Los Angeles, 2014, pp. 6522-6527. doi:10.1109/CDC.2014.7040412
[BibTeX]@inproceedings{Bazanella:Gevers:Coutinho:Rui:2014, Address = {Los Angeles}, Author = {A. S. Bazanella and M. Gevers and D. Coutinho and R. Rui}, Booktitle = {53rd IEEE Conference on Decision and Control}, Doi = {10.1109/CDC.2014.7040412}, Pages = {6522-6527}, Publisher = {IEEE}, Title = {Identifiability and excitation of a class of rational systems}, Year = {2014}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/CDC.2014.7040412}} - D. Eckhard, L. Campestrini, E. Boeira, and J. M. Gomes da Silva Jr., “Aplicação de métodos de controle baseado em dados em um sistema de controle de nível industrial,” in XVI Congreso Latinoamericano de Control Automático, Cancún, 2014, p. 1410–1415.
[BibTeX] [Abstract]
Os métodos de projeto de controladores baseado em dados são um conjunto de técnicas utilizadas para ajustar os ganhos de controladores, que não utilizam um modelo matemático do processo na sintonia dos parâmetros. Alguns destes métodos são o Iterative Feedback Tuning (IFT), Correlation based Tuning (CbT), Virtual Reference Feedback Tuning (VRFT) e Optimal Controller Identification (OCI). Apesar de algumas destas t{ é}cnicas existirem por mais de uma década, são encontrados poucos trabalhos na literatura que demonstram a aplicabilidade dos métodos em sistemas industriais. Neste trabalho duas técnicas de projeto de controladores baseado em dados não-iterativas (VRFT e OCI) são aplicadas em em um sistema de controle de n{\’\i}vel industrial, que utiliza uma rede Foundation Fieldbus H1. O trabalho demostra que as técnicas apresentadas podem ser aplicadas com facilidade em sistemas industriais gerando repostas dinâmicas satisfatórias.
@inproceedings{Eckhard:Campestrini:Boeira:GomesdaSilva:2014, Abstract = {Os m{\'e}todos de projeto de controladores baseado em dados s{\~a}o um conjunto de t{\'e}cnicas utilizadas para ajustar os ganhos de controladores, que n{\~a}o utilizam um modelo matem{\'a}tico do processo na sintonia dos par{\^a}metros. Alguns destes m{\'e}todos s{\~a}o o Iterative Feedback Tuning (IFT), Correlation based Tuning (CbT), Virtual Reference Feedback Tuning (VRFT) e Optimal Controller Identification (OCI). Apesar de algumas destas t{ \'e}cnicas existirem por mais de uma d{\'e}cada, s{\~a}o encontrados poucos trabalhos na literatura que demonstram a aplicabilidade dos m{\'e}todos em sistemas industriais. Neste trabalho duas t{\'e}cnicas de projeto de controladores baseado em dados n{\~a}o-iterativas (VRFT e OCI) s{\~a}o aplicadas em em um sistema de controle de n{\'\i}vel industrial, que utiliza uma rede Foundation Fieldbus H1. O trabalho demostra que as t{\'e}cnicas apresentadas podem ser aplicadas com facilidade em sistemas industriais gerando repostas din{\^a}micas satisfat{\'o}rias.}, Address = {Canc{\'u}n}, Author = {D. Eckhard and L. Campestrini and E. Boeira and J. M. {Gomes da Silva Jr.}}, Booktitle = {XVI Congreso Latinoamericano de Control Autom\'{a}tico}, Pages = {1410--1415}, Publisher = {AMCA}, Title = {Aplica\c{c}\~{a}o de m\'etodos de controle baseado em dados em um sistema de controle de n\'ivel industrial}, Year = {2014}} - A. S. Bazanella and T. Neuhaus, “Tuning Nonlinear Controllers with the Virtual Reference Approach,” in 19th IFAC World Congress, Cape Town, 2014, pp. 10269-10274. doi:10.3182/20140824-6-ZA-1003.00562
[BibTeX]@inproceedings{Bazanella:Neuhaus:2014, Address = {Cape Town}, Author = {A. S. Bazanella and T. Neuhaus}, Booktitle = {19th IFAC World Congress}, Doi = {10.3182/20140824-6-ZA-1003.00562}, Pages = {10269-10274}, Publisher = {IFAC}, Title = {Tuning Nonlinear Controllers with the Virtual Reference Approach}, Year = {2014}, Bdsk-Url-1 = {http://dx.doi.org/10.3182/20140824-6-ZA-1003.00562}} - M. Gevers, A. S. Bazanella, D. Coutinho, and S. Dasgupta, “Identifiability and excitation of polynomial systems,” in 52nd IEEE Conference on Decision and Control, Firenze, 2013, pp. 4278-4283. doi:10.1109/CDC.2013.6760547
[BibTeX]@inproceedings{Gevers:Bazanella:Coutinho:Dasgupta:2013, Address = {Firenze}, Author = {M. Gevers and A. S. Bazanella and D. Coutinho and S. Dasgupta}, Booktitle = {52nd IEEE Conference on Decision and Control}, Doi = {10.1109/CDC.2013.6760547}, Pages = {4278-4283}, Publisher = {IEEE}, Title = {Identifiability and excitation of polynomial systems}, Year = {2013}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/CDC.2013.6760547}} - A. S. Bazanella and R. Rui, “Identification of arbitrary model parameterizations: the uses of Ritt’s algorithm,” in XIX Congresso Brasileiro de Automática, Campina Grande, 2012, p. –.
[BibTeX]@inproceedings{Bazanella:Rui:2012, Address = {Campina Grande}, Author = {A. S. Bazanella and R. Rui}, Booktitle = {XIX Congresso Brasileiro de Autom{\'{a}}tica}, Pages = {--}, Publisher = {SBA}, Title = {Identification of arbitrary model parameterizations: the uses of Ritt's algorithm}, Year = {2012}} - L. Campestrini, D. Eckhard, A. S. Bazanella, and M. Gevers, “Model Reference Control Design by Prediction Error Identification,” in 16th IFAC Symposium on System Identification, Brussels, 2012, p. 1478–1483. doi:10.3182/20120711-3-BE-2027.00190
[BibTeX] [Abstract]
This paper studies a one-shot (non-iterative) data-based method for Model Reference (MR) control design. It shows that the optimal controller can be obtained as the solution of a Prediction Error (PE) identification problem that directly estimates the controller parameters through a reparametrization of the input-output model. The standard tools of PE Identification can thus be used to analyze the statistical properties (bias and variance) of the estimated controller. It also shows that, for MR control design, direct and indirect data-based methods are essentially equivalent.
@inproceedings{Campestrini:Eckhard:Bazanella:Gevers:2012, Abstract = {This paper studies a one-shot (non-iterative) data-based method for Model Reference (MR) control design. It shows that the optimal controller can be obtained as the solution of a Prediction Error (PE) identification problem that directly estimates the controller parameters through a reparametrization of the input-output model. The standard tools of PE Identification can thus be used to analyze the statistical properties (bias and variance) of the estimated controller. It also shows that, for MR control design, direct and indirect data-based methods are essentially equivalent.}, Address = {Brussels}, Author = {L. Campestrini and D. Eckhard and A. S. Bazanella and M. Gevers}, Booktitle = {16th {IFAC} Symposium on System Identification}, Doi = {10.3182/20120711-3-BE-2027.00190}, Pages = {1478--1483}, Publisher = {IFAC}, Title = {Model Reference Control Design by Prediction Error Identification}, Year = {2012}, Bdsk-Url-1 = {http://dx.doi.org/10.3182/20120711-3-BE-2027.00190}} - L. Campestrini, D. Eckhard, O. Konrad, and A. S. Bazanella, “Identificação não-linear de um biorreator através da minimização do erro de predição,” in XIX Congresso Brasileiro de Automática, Campina Grande, 2012, p. 3066–3072.
[BibTeX] [Abstract]
This work presents a non-linear identification of a bioreactor through the minimization of the prediction error, where the output data are the measurements of the methane gas generated by the process, during 37 days. Since the chosen model is non-linear, an iterative method is used to obtain the model parameters. This method depends on the cost function?s gradient, whose calculus is implemented recursively, since it does not have a closed form. The algorithm used in the minimization of the cost function is a combination of two methods: the gradient method and the Newton-Raphson method. The model obtained is validated with output data from the process and it reproduces the behavior of the bioreactor with good precision.
@inproceedings{Campestrini:Eckhard:Konrad:Bazanella:2012, Abstract = {This work presents a non-linear identification of a bioreactor through the minimization of the prediction error, where the output data are the measurements of the methane gas generated by the process, during 37 days. Since the chosen model is non-linear, an iterative method is used to obtain the model parameters. This method depends on the cost function?s gradient, whose calculus is implemented recursively, since it does not have a closed form. The algorithm used in the minimization of the cost function is a combination of two methods: the gradient method and the Newton-Raphson method. The model obtained is validated with output data from the process and it reproduces the behavior of the bioreactor with good precision.}, Address = {Campina Grande}, Author = {L. Campestrini and D. Eckhard and O. Konrad and A. S. Bazanella}, Booktitle = {XIX Congresso Brasileiro de Autom{\'{a}}tica}, Pages = {3066--3072}, Publisher = {SBA}, Title = {Identifica\c{c}\~{a}o n\~{a}o-linear de um biorreator atrav\'{e}s da minimiza\c{c}\~{a}o do erro de predi\c{c}\~{a}o}, Year = {2012}} - D. Eckhard, H. Hjalmarsson, C. Rojas, and M. Gevers, “Mean-Squared Error Experiment Design for Linear Regression Models,” in 16th IFAC Symposium on System Identification, Brussels, 2012, p. 1629–1634. doi:10.3182/20120711-3-BE-2027.00339
[BibTeX] [Abstract]
This work solves an experiment design problem for a linear regression problem using a reduced order model. The quality of the model is assessed using a mean square error measure that depends linearly on the parameters. The designed input signal ensures a predefined quality of the model while minimizing the input energy.
@inproceedings{Eckhard:Hjalmarsson:Rojas:Gevers:2012, Abstract = {This work solves an experiment design problem for a linear regression problem using a reduced order model. The quality of the model is assessed using a mean square error measure that depends linearly on the parameters. The designed input signal ensures a predefined quality of the model while minimizing the input energy.}, Address = {Brussels}, Author = {D. Eckhard and H. Hjalmarsson and C. Rojas and M. Gevers}, Booktitle = {16th {IFAC} Symposium on System Identification}, Doi = {10.3182/20120711-3-BE-2027.00339}, Pages = {1629--1634}, Publisher = {IFAC}, Title = {Mean-Squared Error Experiment Design for Linear Regression Models}, Year = {2012}, Bdsk-Url-1 = {http://dx.doi.org/10.3182/20120711-3-BE-2027.00339}} - M. F. Flores da Cunha and A. S. Bazanella, “Virtual Reference Feedback Tuning with dead zone compensation,” in XIX Congresso Brasileiro de Automática, Campina Grande, 2012, p. –.
[BibTeX]@inproceedings{FloresdaCunha:Bazanella:2012, Address = {Campina Grande}, Author = {M. F. {Flores da Cunha} and A. S. Bazanella}, Booktitle = {XIX Congresso Brasileiro de Autom{\'{a}}tica}, Pages = {--}, Publisher = {SBA}, Title = {Virtual Reference Feedback Tuning with dead zone compensation}, Year = {2012}} - D. Eckhard, A. S. Bazanella, C. Rojas, and H. Hjalmarsson, “On the Convergence of the Prediction Error Method to Its Global Minimum,” in 16th IFAC Symposium on System Identification, Brussels, 2012, p. 698–703. doi:10.3182/20120711-3-BE-2027.00371
[BibTeX] [Abstract]
The Prediction Error Method (PEM) is related to an optimization problem built on input/output data collected from the system to be identified. It is often hard to find the global solution of this optimization problem because the corresponding objective function presents local minima and/or the search space is constrained to a nonconvex set. The existence of local minima, and hence the difficulty in solving the optimization, depends mainly on the experimental conditions, more specifically on the spectrum of the input/output data collected from the system. It is therefore possible to avoid the existence of local minima by properly choosing the spectrum of the input; in this paper we show how to perform this choice. We present sufficient conditions for the convergence of PEM to the global minimum and from these conditions we derive two approaches to avoid the existence of nonglobal minima. We present the application of one of these two approaches to a case study where standard identification toolboxes tend to get trapped in nonglobal minima.
@inproceedings{Eckhard:Bazanella:Rojas:Hjalmarsson:2012, Abstract = {The Prediction Error Method (PEM) is related to an optimization problem built on input/output data collected from the system to be identified. It is often hard to find the global solution of this optimization problem because the corresponding objective function presents local minima and/or the search space is constrained to a nonconvex set. The existence of local minima, and hence the difficulty in solving the optimization, depends mainly on the experimental conditions, more specifically on the spectrum of the input/output data collected from the system. It is therefore possible to avoid the existence of local minima by properly choosing the spectrum of the input; in this paper we show how to perform this choice. We present sufficient conditions for the convergence of PEM to the global minimum and from these conditions we derive two approaches to avoid the existence of nonglobal minima. We present the application of one of these two approaches to a case study where standard identification toolboxes tend to get trapped in nonglobal minima.}, Address = {Brussels}, Author = {D. Eckhard and A.S. Bazanella and C. Rojas and H. Hjalmarsson}, Booktitle = {16th {IFAC} Symposium on System Identification}, Doi = {10.3182/20120711-3-BE-2027.00371}, Pages = {698--703}, Publisher = {IFAC}, Title = {On the Convergence of the Prediction Error Method to Its Global Minimum}, Year = {2012}, Bdsk-Url-1 = {http://dx.doi.org/10.3182/20120711-3-BE-2027.00371}} - D. Eckhard and A. S. Bazanella, “On the global convergence of identification of output error models,” in 18th IFAC World congress, Milan, 2011, p. 9058–9063. doi:10.3182/20110828-6-IT-1002.03566
[BibTeX] [Abstract]
The Output Error Method is related to an optimization problem based on a multi-modal criterion. Iterative algorithms like the steepest descent are usually used to look for the global minimum of the criterion. This algorithms can get stuck at a local minimum. This paper presents sufficient conditions about the convergence of the steepest descent algorithm to the global minimum of the cost function. Moreover, it presents constraints to the input spectrum which ensure that the convergence conditions are satisfied. This constraints are convex and can easily be included in an experiment design approach to ensure the convergence of the iterative algorithms to the global minimum of the criterion.
@inproceedings{Eckhard:Bazanella:2011, Abstract = {The Output Error Method is related to an optimization problem based on a multi-modal criterion. Iterative algorithms like the steepest descent are usually used to look for the global minimum of the criterion. This algorithms can get stuck at a local minimum. This paper presents sufficient conditions about the convergence of the steepest descent algorithm to the global minimum of the cost function. Moreover, it presents constraints to the input spectrum which ensure that the convergence conditions are satisfied. This constraints are convex and can easily be included in an experiment design approach to ensure the convergence of the iterative algorithms to the global minimum of the criterion.}, Address = {Milan}, Author = {D. Eckhard and A. S. Bazanella}, Booktitle = {18th {IFAC} World congress}, Doi = {10.3182/20110828-6-IT-1002.03566}, Pages = {9058--9063}, Publisher = {IFAC}, Title = {On the global convergence of identification of output error models}, Year = {2011}, Bdsk-Url-1 = {http://dx.doi.org/10.3182/20110828-6-IT-1002.03566}} - D. Eckhard and A. S. Bazanella, “Data-based controller tuning: Improving the convergence rate,” in 49th IEEE Conference on Decision and Control, Atlanta, 2010, p. 4801–4806. doi:10.1109/CDC.2010.5717584
[BibTeX] [Abstract]
Data-based control design methods most often consist of iterative adjustment of the controller’s parameters towards the parameter values which minimize an H2 performance criterion. Typically, batches of input-output data collected from the system are used to feed directly a gradient descent optimization – no process model is used. The convergence to the global minimum of the performance criterion depends on the initial controller parameters, as well as on the size and direction of the steps taken at each iteration. This paper discusses these issues and provides a method for choosing the search direction and the step size at each optimization step so that convergence to the global minimum is obtained with high convergence rate.
@inproceedings{Eckhard:Bazanella:2010, Abstract = {Data-based control design methods most often consist of iterative adjustment of the controller's parameters towards the parameter values which minimize an H2 performance criterion. Typically, batches of input-output data collected from the system are used to feed directly a gradient descent optimization - no process model is used. The convergence to the global minimum of the performance criterion depends on the initial controller parameters, as well as on the size and direction of the steps taken at each iteration. This paper discusses these issues and provides a method for choosing the search direction and the step size at each optimization step so that convergence to the global minimum is obtained with high convergence rate.}, Address = {Atlanta}, Author = {D. Eckhard and A. S. Bazanella}, Booktitle = {49th IEEE Conference on Decision and Control}, Doi = {10.1109/CDC.2010.5717584}, Pages = {4801--4806}, Publisher = {IEEE}, Title = {Data-based controller tuning: Improving the convergence rate}, Year = {2010}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/CDC.2010.5717584}} - D. Eckhard, M. E. Bergel, and A. S. Bazanella, “Análise comparativa dos métodos de ajuste de controladores baseados em dados,” in XVIII Congresso Brasileiro de Automática, Bonito, 2010, p. 1620–1626.
[BibTeX] [Abstract]
This work addresses data-based control design. The properties inherent to data-based design are discussed under a common theoretical framework. The computational cost is estimated with relation to memory space and number of elementar operations. Simulations present a comparision between the studied methods.
@inproceedings{Eckhard:Bergel:Bazanella:2010, Abstract = {This work addresses data-based control design. The properties inherent to data-based design are discussed under a common theoretical framework. The computational cost is estimated with relation to memory space and number of elementar operations. Simulations present a comparision between the studied methods.}, Address = {Bonito}, Author = {D. Eckhard and M. E. Bergel and A. S. Bazanella}, Booktitle = {XVIII Congresso Brasileiro de Autom\'atica}, Pages = {1620--1626}, Publisher = {SBA}, Title = {An\'{a}lise comparativa dos m\'etodos de ajuste de controladores baseados em dados}, Year = {2010}} - M. F. Flores da Cunha and A. S. Bazanella, “On Iterative Feedback Tuning for systems with nonsmooth nonlinearities,” in XVIII Congresso Brasileiro de Automática, Bonito, 2010, p. –.
[BibTeX]@inproceedings{FloresdaCunha:Bazanella:2010, Address = {Bonito}, Author = {M. F. {Flores da Cunha} and A. S. Bazanella}, Booktitle = {XVIII Congresso Brasileiro de Autom\'atica}, Pages = {--}, Publisher = {SBA}, Title = {On Iterative Feedback Tuning for systems with nonsmooth nonlinearities}, Year = {2010}} - D. Eckhard and A. S. Bazanella, “Optimizing the Convergence of Data-Based Controller Tuning,” in European Control Conference 2009, Budapest, 2009, p. 910–915.
[BibTeX] [Abstract]
Data-based control design methods most often consist of iterative adjustment of the controller’s parameters towards the parameter values which minimize an H2 performance criterion. Typically, batches of input-output data collected from the system are used to feed directly a gradient descent optimization – no process model is used. The convergence to the global minimum of the performance criterion depends on the initial controller parameters and on the step size of each iteration. This paper discusses these issues and provides a method for choosing the step size to ensure convergence to the global minimum utilizing the lowest possible number of iterations.
@inproceedings{Eckhard:Bazanella:2009, Abstract = {Data-based control design methods most often consist of iterative adjustment of the controller's parameters towards the parameter values which minimize an H2 performance criterion. Typically, batches of input-output data collected from the system are used to feed directly a gradient descent optimization - no process model is used. The convergence to the global minimum of the performance criterion depends on the initial controller parameters and on the step size of each iteration. This paper discusses these issues and provides a method for choosing the step size to ensure convergence to the global minimum utilizing the lowest possible number of iterations.}, Address = {Budapest}, Author = {D. Eckhard and A. S. Bazanella}, Booktitle = {European Control Conference 2009}, Pages = {910--915}, Publisher = {IEEE}, Title = {Optimizing the Convergence of Data-Based Controller Tuning}, Url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7074520&isnumber=7069761}, Year = {2009}, Bdsk-Url-1 = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7074520&isnumber=7069761}} - D. Eckhard, L. Campestrini, M. E. Bergel, and A. S. Bazanella, “Data-Based Control Design for a Process Class with Guaranteed Convergence to the Globally Optimum Controller,” in European Control Conference 2009, Budapest, 2009, p. 993–998.
[BibTeX] [Abstract]
This work addresses data-based (DB) control design; the properties and limitations inherent to DB design are discussed under a common theoretical framework and illustrated through experimental results. Theoretical results concerning the convergence and precision are discussed and specified for a particular class of processes. Two DB methods, representative of this design approach, are used to illustrate the general properties of DB design: the Virtual Reference Feedback Tuning (VRFT) and the Iterative Feedback Tuning (IFT).
@inproceedings{Eckhard:Campestrini:Bergel:Bazanella:2009, Abstract = {This work addresses data-based (DB) control design; the properties and limitations inherent to DB design are discussed under a common theoretical framework and illustrated through experimental results. Theoretical results concerning the convergence and precision are discussed and specified for a particular class of processes. Two DB methods, representative of this design approach, are used to illustrate the general properties of DB design: the Virtual Reference Feedback Tuning (VRFT) and the Iterative Feedback Tuning (IFT).}, Address = {Budapest}, Author = {D. Eckhard and L. Campestrini and M. E. Bergel and A. S. Bazanella}, Booktitle = {European Control Conference 2009}, Pages = {993--998}, Publisher = {IEEE}, Title = {Data-Based Control Design for a Process Class with Guaranteed Convergence to the Globally Optimum Controller}, Url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7074534&isnumber=7069761}, Year = {2009}, Bdsk-Url-1 = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7074534&isnumber=7069761}} - L. Campestrini, M. Gevers, and A. S. Bazanella, “Virtual Reference Feedback Tuning for Non Minimum Phase Plants,” in European Control Conference 2009, Budapest, 2009, p. 1955–1960.
[BibTeX]@inproceedings{Campestrini:Gevers:Bazanella:2009, Address = {Budapest}, Author = {L. Campestrini and M. Gevers and A. S. Bazanella}, Booktitle = {European Control Conference 2009}, Date-Modified = {2016-07-13 19:56:21 +0000}, Pages = {1955--1960}, Publisher = {EUCA}, Title = {Virtual Reference Feedback Tuning for Non Minimum Phase Plants}, Year = {2009}} - A. G. S. Conceição, C. Carvalho, E. R. Rohr, D. Porath, D. Eckhard, and L. F. A. Pereira, “A Neural Network Strategy Applied in Autonomous Mobile Localization,” in European Control Conference 2009, Budapest, 2009, p. 4439–4444.
[BibTeX] [Abstract]
In this article, a new approach to the problem of indoor navigation based on ultrasonic sensors is presented, where artificial neural networks (ANN) are used to estimate the position and orientation of a mobile robot. This approach proposes the use of three Radial Basis Function (RBF) Networks, where environment maps from an ultrasonic sensor and maps synthetically generated are used to estimate the robot localization. The mobile robot is mainly characterized by its real time operation based on the Matlab/Simulink environment, where the whole necessary tasks for an autonomous navigation are done in a hierarchical and easy reprogramming way. Finally, practical results of real time navigation related to robot localization in a known indoor environment are shown.
@inproceedings{Conceicao:Carvalho:Rohr:Porath:Eckhard:Pereira:2009, Abstract = {In this article, a new approach to the problem of indoor navigation based on ultrasonic sensors is presented, where artificial neural networks (ANN) are used to estimate the position and orientation of a mobile robot. This approach proposes the use of three Radial Basis Function (RBF) Networks, where environment maps from an ultrasonic sensor and maps synthetically generated are used to estimate the robot localization. The mobile robot is mainly characterized by its real time operation based on the Matlab/Simulink environment, where the whole necessary tasks for an autonomous navigation are done in a hierarchical and easy reprogramming way. Finally, practical results of real time navigation related to robot localization in a known indoor environment are shown.}, Address = {Budapest}, Author = {A. G. S. Concei{\c c}{\~a}o and C. Carvalho and E. R. Rohr and D. Porath and D. Eckhard and L. F. A. Pereira}, Booktitle = {European Control Conference 2009}, Pages = {4439--4444}, Publisher = {IEEE}, Title = {A Neural Network Strategy Applied in Autonomous Mobile Localization}, Url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7075099&isnumber=7069761}, Year = {2009}, Bdsk-Url-1 = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7075099&isnumber=7069761}} - A. S. Bazanella, X. Bombois, and M. Gevers, “Connecting Informative Experiments, the Information Matrix and the Minima of a Prediction Error Identification Criterion,” in 15th IFAC Symposium on System Identification, Saint-Malo, 2009, p. 675–680. doi:10.3182/20090706-3-FR-2004.00112
[BibTeX]@inproceedings{Bazanella:Bombois:Gevers:2009, Address = {Saint-Malo}, Author = {A. S. Bazanella and X. Bombois and M. Gevers}, Booktitle = {15th {IFAC} Symposium on System Identification}, Doi = {10.3182/20090706-3-FR-2004.00112}, Pages = {675--680}, Publisher = {IFAC}, Title = {Connecting Informative Experiments, the Information Matrix and the Minima of a Prediction Error Identification Criterion}, Year = {2009}, Bdsk-Url-1 = {http://dx.doi.org/10.3182/20090706-3-FR-2004.00112}} - D. Eckhard, J. M. Gomes da Silva Jr., S. Tarbouriech, and C. Prier, “Output dynamic feedback controller design for disturbance attenuation taking into account both sensor and actuator saturation,” in XVII Congresso Brasileiro de Automática, Juiz de Fora, 2008, p. –.
[BibTeX] [Abstract]
In this work, a systematic methodology to design dynamic output feedback controllers, for linear control systems presenting both actuator and sensor saturations, is proposed. A theoretical condition that ensures that the trajectories of the closed-loop system are bounded for L2 disturbances, while ensuring internal global asymptotic stability is stated. From this theoretical condition an LMI-based optimization problem to compute the controller aiming at minimizing the induced L2 gain between the disturbance and the regulated output is proposed.
@inproceedings{Eckhard:GomesdaSilva:Tarbouriech:Prieur:2008, Abstract = {In this work, a systematic methodology to design dynamic output feedback controllers, for linear control systems presenting both actuator and sensor saturations, is proposed. A theoretical condition that ensures that the trajectories of the closed-loop system are bounded for L2 disturbances, while ensuring internal global asymptotic stability is stated. From this theoretical condition an LMI-based optimization problem to compute the controller aiming at minimizing the induced L2 gain between the disturbance and the regulated output is proposed.}, Address = {Juiz de Fora}, Author = {D. Eckhard and J. M. {Gomes da Silva Jr.} and S. Tarbouriech and C. Prier}, Booktitle = {XVII Congresso Brasileiro de Autom\'atica}, Pages = {--}, Publisher = {SBA}, Title = {Output dynamic feedback controller design for disturbance attenuation taking into account both sensor and actuator saturation}, Year = {2008}} - J. V. Flores, D. Eckhard, and J. M. Gomes da Silva Jr., “On the Tracking Problem for Linear Systems subject to Control Saturation,” in 17th IFAC World congress, Seul, 2008, p. 14168–14173. doi:10.3182/20080706-5-KR-1001.02402
[BibTeX] [Abstract]
This paper addresses the problem of tracking constant references for linear systems subject to control saturation. Considering an unitary output feedback loop, containing an integral action, conditions in LMI form are proposed to compute a state feedback and an integrator anti-windup gain. These conditions ensure that the trajectories of the closed-loop system are bounded in an invariant ellipsoidal set, provided that the initial conditions are taken in this set and the references and the disturbances belong to a certain admissible set. Based on these conditions, optimization problems aiming at the maximization of the invariant set of admissible states and/or the maximization of the set of admissible references/disturbances are proposed.
@inproceedings{Flores:Eckhard:GomesdaSilva:2008, Abstract = {This paper addresses the problem of tracking constant references for linear systems subject to control saturation. Considering an unitary output feedback loop, containing an integral action, conditions in LMI form are proposed to compute a state feedback and an integrator anti-windup gain. These conditions ensure that the trajectories of the closed-loop system are bounded in an invariant ellipsoidal set, provided that the initial conditions are taken in this set and the references and the disturbances belong to a certain admissible set. Based on these conditions, optimization problems aiming at the maximization of the invariant set of admissible states and/or the maximization of the set of admissible references/disturbances are proposed.}, Address = {Seul}, Author = {J. V. Flores and D. Eckhard and J. M. {Gomes da Silva Jr.}}, Booktitle = {17th {IFAC} World congress}, Doi = {10.3182/20080706-5-KR-1001.02402}, Pages = {14168--14173}, Publisher = {IFAC}, Title = {On the Tracking Problem for Linear Systems subject to Control Saturation}, Year = {2008}, Bdsk-Url-1 = {http://dx.doi.org/10.3182/20080706-5-KR-1001.02402}} - M. Gevers, L. Mišković, and A. S. Bazanella, “Informative data: how to get just sufficiently rich?,” in 47th IEEE Conference on Decision and Control, Cancún, 2008, p. 1962–1967. doi:10.1109/CDC.2008.4738735
[BibTeX]@inproceedings{Gevers:Miskovic:Bazanella:2008, Address = {Canc{\'u}n}, Author = {M. Gevers and L. Mi{\v{s}}kovi{\'c} and A. S. Bazanella}, Booktitle = {47th IEEE Conference on Decision and Control}, Doi = {10.1109/CDC.2008.4738735}, Pages = {1962--1967}, Publisher = {IFAC}, Title = {Informative data: how to get just sufficiently rich?}, Year = {2008}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/CDC.2008.4738735}} - A. S. Bazanella, M. Gevers, L. Mišković, and B. D. O. Anderson, “Closed-loop identification of MIMO systems: a new look at identifiability and experiment design,” in European Control Conference, Kos, 2007, p. 5694–5699.
[BibTeX]@inproceedings{Bazanella:Gevers:Miskovic:2007, Address = {Kos}, Author = {A. S. Bazanella and M. Gevers and L. Mi{\v{s}}kovi{\'c} and B. D. O. Anderson}, Booktitle = {European Control Conference}, Pages = {5694--5699}, Publisher = {EUCA}, Title = {Closed-loop identification of {MIMO} systems: a new look at identifiability and experiment design}, Year = {2007}} - A. S. Bazanella, M. Gevers, L. Mišković, and B. D. O. Anderson, “On the shape of H2 performance criteria,” in 3rd IFAC Symposium on System Structure and Control, Foz do Iguaçu, 2007, p. 190–195. doi:10.3182/20071017-3-BR-2923.00032
[BibTeX]@inproceedings{Bazanella:Gevers:Miskovic:Anderson:2007, Address = {Foz do Igua{\c{c}}u}, Author = {A. S. Bazanella and M. Gevers and L. Mi{\v{s}}kovi{\'c} and B. D. O. Anderson}, Booktitle = {3rd IFAC Symposium on System Structure and Control}, Doi = {10.3182/20071017-3-BR-2923.00032}, Pages = {190--195}, Publisher = {IFAC}, Title = {On the shape of H2 performance criteria}, Year = {2007}, Bdsk-Url-1 = {http://dx.doi.org/10.3182/20071017-3-BR-2923.00032}} - L. Campestrini, P. R. Barros, and A. S. Bazanella, “Auto-tuning of PID controllers for MIMO processes by relay feedback,” in IFAC Symposium on Advance Control of Chemical Processes, Gramado – RS – Brazil, 2006, p. 451–456.
[BibTeX]@inproceedings{Campestrini:Barros:Bazanella:2006, Address = {Gramado - RS - Brazil}, Author = {L. Campestrini and P.R. Barros and A.S. Bazanella}, Booktitle = {IFAC Symposium on Advance Control of Chemical Processes}, Date-Added = {2016-07-13 19:56:34 +0000}, Date-Modified = {2016-07-13 19:57:06 +0000}, Owner = {adchem06}, Pages = {451--456}, Timestamp = {2011.05.05}, Title = {Auto-tuning of PID controllers for MIMO processes by relay feedback}, Year = {2006}} - L. Campestrini and A. S. Bazanella, “Tuning of multivariable PID controllers through the Ultimate Point Method,” in IEEE Conference on Decision and Control, San Diego, 2006, p. 1834–1839. doi:10.1109/CDC.2006.377478
[BibTeX]@inproceedings{Campestrini:Bazanella:2006, Address = {San Diego}, Author = {L. Campestrini and A. S. Bazanella}, Booktitle = {IEEE Conference on Decision and Control}, Doi = {10.1109/CDC.2006.377478}, Pages = {1834--1839}, Publisher = {IEEE}, Title = {Tuning of multivariable {PID} controllers through the Ultimate Point Method}, Year = {2006}, Bdsk-Url-1 = {http://dx.doi.org/10.1109/CDC.2006.377478}} - L. Campestrini and A. S. Bazanella, “Projeto de controladores PID com conhecimento parcial da resposta em frequência,” in XVI Congresso Brasileiro de Automática, Salvador, 2006, p. 1088–1095.
[BibTeX]@inproceedings{Campestrini:Bazanella:2006b, Address = {Salvador}, Author = {L. Campestrini and A. S. Bazanella}, Booktitle = {XVI Congresso Brasileiro de Autom\'atica}, Pages = {1088--1095}, Publisher = {SBA}, Title = {Projeto de controladores {PID} com conhecimento parcial da resposta em frequ\^{e}ncia}, Year = {2006}} - L. Campestrini, F. R. Maioli, and A. S. Bazanella, “Projeto de controladores com conhecimento parcial da resposta em frequência,” in XVI Congresso da Sociedade Brasileira de Automatica, Salvador – BA, 2006, pp. 2963-2968.
[BibTeX]@inproceedings{Campestrini:Maioli:Bazanella:2006, Address = {Salvador - BA}, Author = {L. Campestrini and F.R. Maioli and A.S. Bazanella}, Booktitle = {XVI Congresso da Sociedade Brasileira de Automatica}, Date-Added = {2016-07-13 19:57:24 +0000}, Date-Modified = {2016-07-13 19:57:43 +0000}, Owner = {cba06}, Pages = {2963-2968}, Timestamp = {2011.05.05}, Title = {Projeto de controladores com conhecimento parcial da resposta em frequ\^{e}ncia}, Year = {2006}} - D. Eckhard, F. M. Schaf, J. M. Gomes da Silva Jr., and C. E. Pereira, “Uma Plataforma de Experimentação Remota para Ensino de Controle,” in XVI Congresso Brasileiro de Automática, Salvador, 2006, p. 2305–2310.
[BibTeX] [Abstract]
This paper presents a remote experimentation plataform with didactic purposes. Fisically, the plataform is basically composed by a system of coupled tanks, where the sensors and actuators are intelligent equipements which use a Foundation Fieldbus communication protocol. A supervisory system and a web server interface the experiments with internet. A distance education plataform is therefore developed to provide access to the experiments, on-line courses, and to assist the student-instructor communication.
@inproceedings{Eckhard:Schaf:GomesdaSilva:Pereira:2006, Abstract = {This paper presents a remote experimentation plataform with didactic purposes. Fisically, the plataform is basically composed by a system of coupled tanks, where the sensors and actuators are intelligent equipements which use a Foundation Fieldbus communication protocol. A supervisory system and a web server interface the experiments with internet. A distance education plataform is therefore developed to provide access to the experiments, on-line courses, and to assist the student-instructor communication.}, Address = {Salvador}, Author = {D. Eckhard and F. M. Schaf and J. M. {Gomes da Silva Jr.} and C. E. Pereira}, Booktitle = {XVI Congresso Brasileiro de Autom\'atica}, Pages = {2305--2310}, Publisher = {SBA}, Title = {Uma Plataforma de Experimenta{\c c}{\~a}o Remota para Ensino de Controle}, Year = {2006}} - A. S. Bazanella, G. H. M. Arruda, and P. R. Barros, “Relay oscillations in discrete-time systems,” in XIII Congresso Brasileiro de Automática, 2002.
[BibTeX]@inproceedings{Bazanelle:Arruda:Barros:2002, Adress = {Natal - RN}, Author = {A.S. Bazanella and G.H.M. Arruda and P.R. Barros}, Booktitle = {XIII Congresso Brasileiro de Autom\'atica}, Date-Added = {2016-07-13 19:54:42 +0000}, Date-Modified = {2016-07-13 19:55:18 +0000}, Owner = {funcao_descritiva_discreta}, Timestamp = {2011.05.05}, Title = {Relay oscillations in discrete-time systems}, Year = {2002}} - A. Fischman, A. S. Bazanella, J. M. Dion, L. Dugard, and A. S. e Silva, “Application of linear matrix inequalities to the design of robust coordinated controllers in power systems,” in 2nd IFAC Symposium on Robust Control Design, Bucarest, 1997.
[BibTeX]@inproceedings{Fischman:Bazanella:Dion:Dugard:Silva:1997, Address = {Bucarest}, Author = {A. Fischman and A.S. Bazanella and J.M. Dion and L. Dugard and A.S. e Silva}, Booktitle = {2nd IFAC Symposium on Robust Control Design}, Date-Added = {2016-07-13 19:59:57 +0000}, Date-Modified = {2016-07-13 20:00:17 +0000}, Owner = {araoROCOND}, Timestamp = {2011.05.05}, Title = {Application of linear matrix inequalities to the design of robust coordinated controllers in power systems}, Year = {1997}}