Proportional controllers: Direct method for stability analysis and MATLAB implementation

In most cases, the cost of a control system increases based on its complexity. Proportional (P) controller is the simplest and most intuitive structure for the implementation of linear control systems. The difficulty to find the stability range of feedback systems with P controllers, using the Routh-Hurwitz criterion, increases with the order of the plant. For high order plants, the stability range cannot be easily obtained from the investigation of the coefficient signs in the first column of the Routh's array. A direct method for the determination of the stability range is presented. The method is easy to understand, to compute, and to offer the students a better comprehension on this subject. A program in MATLAB language, based on the proposed method, design examples, and class assessments, is provided in order to help the pedagogical issues. The method and the program enable the user to specify a decay rate and also extend to proportional-integral (PI), proportional-derivative (PD), and proportional-integral-derivative (PID) controllers.

A method for plotting the complementary root locus using the root-locus (positive gain) rules

The root-locus method is a well-known and commonly used tool in control system analysis and design. It is an important topic in introductory undergraduate engineering control disciplines. Although complementary root locus (plant with negative gain) is not as common as root locus (plant with positive gain) and in many introductory textbooks for control systems is not presented, it has been shown a valuable tool in control system design. This paper shows that complementary root locus can be plotted using only the well-known construction rules to plot root locus. It can offer for the students a better comprehension on this subject. These results present a procedure to avoid problems that appear in root-locus plots for plants with the same number of poles and zeros.

Design of fuzzy regulators with optimal initial conditions compensation

In almost all cases, the goal of the design of automatic control systems is to obtain the parameters of the controllers, which are described by differential equations. In general, the controller is artificially built and it is possible to update its initial conditions. In the design of optimal quadratic regulators, the initial conditions of the controller can be changed in an optimal way and they can improve the performance of the controlled system. Following this idea, a LNU-based design procedure to update the initial conditions of PI controllers, considering the nonlinear plant described by Takagi-Sugeno fuzzy models, is presented. The importance of the proposed method is that it also allows other specifications, such as, the decay rate and constraints on control input and output. The application in the control of an inverted pendulum illustrates the effectively of proposed method.

Sistema de tração elétrica flexível baseado em veículos trólebus para alimentação com redes CC e ou CA

Este artigo apresenta os principais resultados e o detalhamento da metodologia e equações de controle de um retificador monofásico pré-regulador de 150kW para sistema trólebus. A estrutura proposta possibilita a Correção ativa do Fator de Potência (CFP) com baixos níveis de Distorção Harmônica Total (DHT) na corrente, em conformidade com a norma internacional IEC 61000-3-4. Fruto de um projeto de Pesquisa, Desenvolvimento e Inovação (P) junto à empresa AES Eletropaulo Metropolitana de São Paulo, em parceria com a empresa de transporte Himalaia S.A., o projeto possui como principais objetivos estimular o interesse para a expansão das linhas de trólebus a partir de uma plataforma de alimentação de menor custo de instalação e manutenção, sem a necessidade de subestações retificadoras, e, com vistas a promover a melhoria da qualidade de vida nos grandes centros urbanos. Nessa nova modalidade proposta para o sistema de alimentação, o trólebus pode ser alimentado tanto pelas redes convencionais em corrente contínua (CC) quanto pelas redes de distribuição em corrente alternada (CA), mantendo-se a disposição a dois fios dos sistemas CC, sendo as mudanças de rede de alimentação (CC ou CA) monitoradas e controladas digitalmente. Todo o sistema de gerenciamento e controle do conversor é realizado digitalmente por FPGA XC3S200. Na evolução do sistema proposto, os autores pretendem inclusive eliminar as linhas aéreas de alimentação, através da utilização de postos de alimentação em CA, especialmente desenvolvidos para os pontos de embarque/desembarque de passageiros para este veículo de transporte coletivo, eliminando-se os aspectos visuais negativos das redes de alimentação deste modal, e, reduzindo-se as falhas de operação do sistema.

Realimentação da derivada dos estados em sistemas multivariáveis lineares usando LMIs

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Metodologia para rastreamento com modificação dos zeros e rejeição de distúrbio aplicada a sistemas incertos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Stabilizability and Disturbance Rejection with State-Derivative Feedback

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Vibration Attenuation in Rotating Machines Using Smart Spring Mechanism

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Sliding mode for detection and accommodation of computation time delay fault

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Um framework baseado em modelos para desenvolvimento de sistemas multimídia distribuídos autoadaptativos

Distributed multimedia systems have highly variable characteristics, resulting in new requirements while new technologies become available or in the need for adequacy in accordance with the amount of available resources. So, these systems should provide support for dynamic adaptations in order to adjust their structures and behaviors at runtime. This paper presents an approach to adaptation model-based and proposes a reflective and component-based framework for construction and support of self-adaptive distributed multimedia systems, providing many facilities for the development and evolution of such systems, such as dynamic adaptation. The propose is to keep one or more models to represent the system at runtime, so some external entity can perform an analysis of these models by identifying problems and trying to solve them. These models integrate the reflective meta-level, acting as a system self-representation. The framework defines a meta-model for description of self-adaptive distributed multimedia applications, which can represent components and their relationships, policies for QoS specification and adaptation actions. Additionally, this paper proposes an ADL and architecture for model-based adaptation. As a case study, this paper presents some scenarios to demonstrate the application of the framework in practice, with and without the use of ADL, as well as check some characteristics related to dynamic adaptation

MoSAC: um módulo para seleção de configurações arquiteturais baseado em critérios de QoS no contexto de sistema distribuídos autoadaptativos

The process for choosing the best components to build systems has become increasingly complex. It becomes more critical if it was need to consider many combinations of components in the context of an architectural configuration. These circumstances occur, mainly, when we have to deal with systems involving critical requirements, such as the timing constraints in distributed multimedia systems, the network bandwidth in mobile applications or even the reliability in real-time systems. This work proposes a process of dynamic selection of architectural configurations based on non-functional requirements criteria of the system, which can be used during a dynamic adaptation. This proposal uses the MAUT theory (Multi-Attribute Utility Theory) for decision making from a finite set of possibilities, which involve multiple criteria to be analyzed. Additionally, it was proposed a metamodel which can be used to describe the application s requirements in terms of the non-functional requirements criteria and their expected values, to express them in order to make the selection of the desired configuration. As a proof of concept, it was implemented a module that performs the dynamic choice of configurations, the MoSAC. This module was implemented using a component-based development approach (CBD), performing a selection of architectural configurations based on the proposed selection process involving multiple criteria. This work also presents a case study where an application was developed in the context of Digital TV to evaluate the time spent on the module to return a valid configuration to be used in a middleware with autoadaptative features, the middleware AdaptTV

Estendendo CRefine para o suporte de táticas de refinamento

The use of increasingly complex software applications is demanding greater investment in the development of such systems to ensure applications with better quality. Therefore, new techniques are being used in Software Engineering, thus making the development process more effective. Among these new approaches, we highlight Formal Methods, which use formal languages that are strongly based on mathematics and have a well-defined semantics and syntax. One of these languages is Circus, which can be used to model concurrent systems. It was developed from the union of concepts from two other specification languages: Z, which specifies systems with complex data, and CSP, which is normally used to model concurrent systems. Circus has an associated refinement calculus, which can be used to develop software in a precise and stepwise fashion. Each step is justified by the application of a refinement law (possibly with the discharge of proof obligations). Sometimes, the same laws can be applied in the same manner in different developments or even in different parts of a single development. A strategy to optimize this calculus is to formalise these application as a refinement tactic, which can then be used as a single transformation rule. CRefine was developed to support the Circus refinement calculus. However, before the work presented here, it did not provide support for refinement tactics. The aim of this work is to provide tool support for refinement tactics. For that, we develop a new module in CRefine, which automates the process of defining and applying refinement tactics that are formalised in the tactic language ArcAngelC. Finally, we validate the extension by applying the new module in a case study, which used the refinement tactics in a refinement strategy for verification of SPARK Ada implementations of control systems. In this work, we apply our module in the first two phases of this strategy

O efeito da autocorrelação no desempenho do gráfico T2 de hotelling: caso bivariado

The chart of control of Hotelling T2 has been the main statistical device used in monitoring multivariate processes. Currently the technological development of control systems and automation enabled a high rate of collection of information of the production systems in very short time intervals, causing a dependency between the results of observations. This phenomenon known as auto correlation causes in the statistical control of the multivariate processes a high rate of false alarms, prejudicing in the chart performance. This entails the violation of the assumption of independence and normality of the distribution. In this thesis we considered not only the correlation between two variables, but also the dependence between observations of the same variable, that is, auto correlation. It was studied by simulation, the bi variate case and the effect of auto correlation on the performance of the T2 chart of Hotelling.

Haptic Stabilization of Posture in Adults With Intellectual Disabilities Using a Nonrigid Tool

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The CMS experiment at the CERN LHC

The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 10(34)cm(-2)s(-1) (10(27)cm(-2)s(-1)). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4 pi solid angle. Forward sampling calorimeters extend the pseudo-rapidity coverage to high values (vertical bar eta vertical bar <= 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.