Novel frameworks for the design of fault-tolerant control using optimal sliding-mode control

Copyright © 2018 John Wiley & Sons, Ltd. This paper describes 2 schemes for a fault-tolerant control using a novel optimal sliding-mode control, which can also be employed as actuator redundancy management for overactuated uncertain linear systems. By using the effectiveness level of the actuators in the performance indexes, 2 schemes for redistributing the control effort among the remaining (redundant or nonfaulty) set of actuators are constructed based on an H2-based optimal sliding-mode control. In contrast to the current sliding-mode fault-tolerant control design methods, in these new schemes, the level of control effort required to maintain sliding is penalised. The proposed optimal sliding-mode fault-tolerant control design schemes are implemented in 2 stages. In the first stage, a state feedback gain is derived using an LMI-based scheme that can assign a number of the closed-loop eigenvalues to a known value whilst satisfying performance specifications. The sliding function matrix related to the particular state feedback derived in the first stage is obtained in the second stage. The difference between the 2 schemes proposed for the sliding-mode fault-tolerant control is that the second one includes a separate control allocation module, which makes it easier to apply actuator constraints to the problem. Moreover, it will be shown that, with the second scheme, we can deal with actuator faults or even failures without controller reconfiguration. We further discuss the advantages and disadvantages of the 2 schemes in more details. The effectiveness of the proposed schemes are illustrated with numerical examples

A framework for optimal actuator/sensor selection in a control system

© 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group. When dealing with large-scale systems, manual selection of a subset of components (sensors/actuators), or equivalently identification of a favourable structure for the controller, that guarantees a certain closed-loop performance, is not very feasible. This paper is dedicated to the problem of concurrent optimal selection of actuators/sensors which can equivalently be considered as the structure identification for the controller. In the context of a multi-channel H 2 dynamic output feedback controller synthesis, we formulate and analyse a framework in which we incorporate two extra terms for penalising the number of actuators and sensors into the variational formulations of controller synthesis problems in order to induce a favourable controller structure. We then develop an explicit scheme as well as an iterative process for the purpose of dealing with the multi-objective problem of controller structure and control law co-design. It is also stressed that the immediate application of the proposed approach lies within the fault accommodation stage of a fault tolerant control scheme. By two numerical examples, we demonstrate the remarkable performance of the proposed approach

Power systems damping controllers coordinated design

Orientador: Daniel DottaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A crescente utilização de fontes renováveis aumenta a variabilidade dos pontos de operação e torna mais complexa a modelagem e o controle dos Sistemas de Energia Elétrica (SEE). Diversas estratégias vêm sendo exploradas para assegurar o desempenho adequado desses sistemas. No que diz respeito a EPP (Estabilidade Angular a Pequenas Perturbações), a leitura de sinais remotos, com medição fasorial sincronizada, possibilita estruturas de controle mais sofisticadas e a utilização de dispositivos FACTS (Flexible AC Transmission System) permite atuar sobre diferentes pontos do sistema. Do ponto de vista de projeto, o grande desafio consiste em sintonizar esses diversos dispositivos para que atuem de forma coordenada no desempenho global do sistema. Apesar dos avanços na implementação dessas novas tecnologias, a estratégia mais frequentemente utilizada para garantir o amortecimento das oscilações em sistemas de energia é aplicação de Estabilizadores do Sistema de Potência (ESP). Instalados junto aos reguladores de tensão das máquinas síncronas, esses dispositivos configuram uma estrutura de controle descentralizada. Apesar de estruturalmente mais simples, projetar ESPs decentralizados de forma coordenada representa um desafio ainda maior, dado quantidade limitada de variáveis as quais esses dispositivos têm acesso devido a sua atuação local. No presente trabalho, são apresentadas duas metodologias para o projeto coordenado de controladores para o amortecimento de oscilações em SEE. Em ambas é explorado o projeto de controladores dinâmicos por realimentação de saída, com estrutura descentralizada. O desempenho adequado dos sistemas no âmbito da EPP é alcançado por meio de restrições de mínimo amortecimento impostas aos algoritmos de projeto. A primeira metodologia estudada faz uso da formulação convexa com Desigualdades Matriciais Lineares (LMIs - do inglês Linear Matrix Inequalities) para o projeto de controladores robustos à incertezas politópicas. Um algoritmo já explorado em SEE foi implementado e modificações foram propostas, buscando melhorar seu desempenho. A segunda abordagem utiliza um algoritmo de otimização não convexa para o projeto de controladores de ordem reduzida, por meio da ferramenta computacional HIFOO. Uma metodologia para a inclusão da restrição de mínimo amortecimento nessa ferramenta é proposta. Essa modificação somada a análise de robustez com LMIs resulta em uma metodologia simples e eficiente para o projeto de controladores robustos, de ordem reduzida, para o amortecimento de oscilações. Os algoritmos de projeto são validados com aplicação em dois sistemas pertencentes ao Benchmark Systems for Small-Signal Stability Analysis and Control, o Sistema Equivalente do Sul-Sudeste Brasileiro e o Sistema New England Reduced Model. A análise dos amortecimentos dos modos de oscilação e simulações de distúrbios nos modelos não lineares dos sistemas são realizadas para avaliar o desempenho dos controladores projetadosAbstract: The growing use of renewable sources increases the variability of operating points and makes the modeling and control of Electric Power Systems more complex. Several strategies have been explored to ensure the proper performance of these systems. Regarding small-signal stability, remote signal readings, with synchrophasor measurements, allows more sophisticated control structures and the use of FACTS devices (Flexible AC Transmission System) enables the control action over different points of the system. The challenge, from control project point of view, is to tune these various devices to coordinately act over the systems overall performance. Despite the advances in these new technologies implementations, Power System Stabilizers (PSS) are the most frequently used devices to damp power systems oscillations. Together with the voltage regulators, these controllers are installed directly in the synchronous machines, configuring a decentralized control structure. Although structurally simpler, the coordinated PSS design poses an even greater challenge due to the limited number of variables available in a local control action. In the present work, two methodologies for the coordinated design of power system damping controllers are presented. The output feedback dynamic controllers design, with a decentralized control structure, is explored in both. The small-signal stability performance is achieved by means of minimum damping constraints, imposed on the design algorithms. In the first methodology, the convex formulation with Linear Matrix Inequalities (LMIs) is applied to robust controller design, using polytopic uncertainty representation. A former algorithm, already exploited in power systems small-signal stability problems, was implemented and modifications were proposed, seeking to improve its performance. The second approach uses a nonconvex optimization algorithm to design reduced order controllers, using the HIFOO computational tool. A methodology to include the minimum damping constraint in this tool is proposed. This modification combined with robustness analysis with LMIs results in a simple and efficient method to robust low-order damping controllers design. The design algorithms are validated with the application in two benchmark systems for small-signal stability analysis, the South-Southeast Brazilian Equivalent System and the New England Reduced Model. Linear analysis of oscillation modes and nonlinear time domain simulations are performed to evaluate the designed controllers performanceMestradoEngenharia Eletrica1565394CAPE

Model Order Reduction

An increasing complexity of models used to predict real-world systems leads to the need for algorithms to replace complex models with far simpler ones, while preserving the accuracy of the predictions. This three-volume handbook covers methods as well as applications. This third volume focuses on applications in engineering, biomedical engineering, computational physics and computer science

Discrete-Time CSVIU Systems : analysis and control by norms study

Orientador: João Bosco Ribeiro do ValDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Esta dissertação trata do problema de análise e controle por normas para sistemas incertos. Em especial será abordada uma classe de sistemas predominantemente afetados por incertezas denominados de ''sistemas pouco conhecidos''. A fim de particularizar o cenário a ser investigado, suponha que se deseja construir o modelo linearizado de uma planta. Admita porém que o desconhecimento com respeito ao sistema real seja tal que apenas se disponha de informação o suficiente para confeccionar um modelo matemático grosseiro não fiel ao seu comportamento real. Sobre esta perspectiva, a modelagem CSVIU (Control and State Variation Increase Uncertainty) propõe um sistema Estocástico Linear Invariante no Tempo (LIT) cuja as incertezas que emergem do processo modelado sejam proporcionais à distância ao equilíbrio. Ao se fazer a síntese de controle, esta traz consigo o conceito de um controlador cauteloso. Destacam-se duas condições de custo para o computo das normas H2 e Hoo de um sistema estocástico, estas são: custo $\alpha$-descontado e custo médio a longo prazo. A noção de alpha-observabilidade e observabilidade (alpha = 1) aqui desenvolvidas para sistemas CSVIU, objetivam garantir que tem-se acesso total à energia interna do sistema através da variável de observação e, deste modo, a finitude das medidas de energia consideradas indicarão também a estabilidade do sistema no sentido pretendido. O problema de computar o desempenho por normas para sistemas CSVIU é solucionado por intermédio da Teoria da Programação Dinâmica (PD) utilizando-se da propriedade de convexidade da Função Valor. Adicionalmente, a solução em norma Hoo utiliza-se também de conceitos advindos da Teoria dos Jogos Diferencias, uma vez que esta abordagem permite conceitualmente que uma segunda variável exerça influência sobre o sistema (variável de perturbação). Tal variável é introduzida ao problema de controle, de maneira que uma lei de controle CSVIU robusta seja obtidaAbstract: This dissertation deals with the problem of analysis and control by norms for uncertain systems. It will be approached the class of system predominantly affected by uncertainties, such systems are denominated ''poorly known systems''. To pave the way toward the intended investigation, suppose one wishes to build the linearized model of the plant of an uncertain system. However, let us assume that the uncertainty regarding the real system is such that one barely has information on its dynamics, just enough to obtain a rough mathematical model of the system. With that motivation, the CSVIU (Control and State Variation Increase Uncertainty) model proposes a stochastic Linear Time-Invariant (LTI) System model, for which the uncertainties arising from the poor modeling are proportionally related to the distance of the state system to the equilibrium. The synthesis of control gives rise to a controller of precautionary behavior. In computing the H2 and Hoo norms of a stochastic system, it is considered two cost conditions: alpha-discounted cost and the averaged long run cost. The alpha-observability and observability (alpha=1) notions are developed for CSVIU systems, both to ensure full access to the internal energy of the system through the observation variable. In this way, the finiteness of the measured energy leads to the system stability in the corresponding sense. The problem of evaluating the performance of CSVIU systems by norms is settled through Dynamic Programming Theory (DP) by using the convexity property of the Value Function. Besides, the Hoo norm solution adopts Differential Games Theory, since such an approach admits a second variable influencing the system trajectory states (disturbing variable). Such a variable is included in the control problem in such a way that a robust CSVIU control law is achievedMestradoAutomaçãoMestre em Engenharia Elétrica303352/2018-3CNP

System- and Data-Driven Methods and Algorithms

An increasing complexity of models used to predict real-world systems leads to the need for algorithms to replace complex models with far simpler ones, while preserving the accuracy of the predictions. This two-volume handbook covers methods as well as applications. This first volume focuses on real-time control theory, data assimilation, real-time visualization, high-dimensional state spaces and interaction of different reduction techniques

Automation of the anesthetic process: New computer-based solutions to deal with the current frontiers in the assessment, modeling and control of anesthesia

The current trend in automating the anesthetic process focuses on developing a system for fully controlling the different variables involved in anesthesia. To this end, several challenges need to be addressed first. The main objective of this thesis is to propose new solutions that provide answers to the current problems in the field of assessing, modeling and controlling the anesthetic process. Undoubtedly, the main handicap to the development of a comprehensive proposal lies in the absence of a reliable measure of analgesia. This thesis proposes a novel fuzzy-logic-based scheme to evaluate the impact of including a new variable in a decision-making process. This scheme is validated by way of a preliminary analysis of the Analgesia Nociception Index (ANI) monitor on analgesic drug titration. Furthermore, the capacity of the ANI monitor to provide information to replicate the decisions of the experts in different clinical situations is studied. To this end, different artificial intelligence-based algorithms are used: specifically, the suitability of this index is evaluated against other variables commonly used in clinical practice. Regarding the modeling of anesthesia, this thesis presents an adaptive model that allows characterizing the pharmacological interaction effects between the hypnotic and analgesic drug on the depth of hypnosis. In addition, the proposed model takes into account both inter- and intra-patient variabilities observed in the response of the subjects. Finally, this work presents the synthesis of a robust optimal PID controller for regulating the depth of hypnosis by considering the effect of the uncertainties derived from the patient's pharmacological response. Moreover, a study is conducted on the limitations introduced when using a PID controller versus the development of higher order solutions under the same clinical and technical considerations

Commande par mode glissant de paliers magnétiques actifs économes en énergie : une approche sans modèle

Abstract : Over the past three decades, various fields have witnessed a successful application of active magnetic bearing (AMB) systems. Their favorable features include supporting high-speed rotation, low power consumption, and rotor dynamics control. Although their losses are much lower than roller bearings, these losses could limit the operation in some applications such as flywheel energy storage systems and vacuum applications. Many researchers focused their efforts on boosting magnetic bearings energy efficiency via minimizing currents supplied to electromagnetic coils either by a software solution or a hardware solution. According to a previous study, we adopt the hardware solution in this thesis. More specifically, we investigate developing an efficient and yet simple control scheme for regulating a permanent magnet-biased active magnetic bearing system. The control objective here is to suppress the rotor vibrations and reduce the corresponding control currents as possible throughout a wide operating range. Although adopting the hardware approach could achieve an energy-efficient AMB, employing an advanced control scheme could achieve a further reduction in power consumption. Many advanced control techniques have been proposed in the literature to achieve a satisfactory performance. However, the complexity of the majority of control schemes and the potential requirement of powerful platform could discourage their application in practice. The motivation behind this work is to improve the closed-loop performance without the need to do model identification and following the conventional procedure for developing a model-based controller. Here, we propose applying the hybridization concept to exploit the classical PID control and some nonlinear control tools such as first- and second-order sliding mode control, high gain observer, backstepping, and adaptive techniques to develop efficient and practical control schemes. All developed control schemes in this thesis are digitally implemented and validated on the eZdsp F2812 control board. Therefore, the applicability of the proposed model-free techniques for practical application is demonstrated. Furthermore, some of the proposed control schemes successfully achieve a good compromise between the objectives of rotor vibration attenuation and control currents minimization over a wide operating range.Résumé: Au cours des trois dernières décennies, divers domaines ont connu une application réussie des systèmes de paliers magnétiques actifs (PMA). Leurs caractéristiques favorables comprennent une capacité de rotation à grande vitesse, une faible consommation d'énergie, et le contrôle de la dynamique du rotor. Bien que leurs pertes soient beaucoup plus basses que les roulements à rouleaux, ces pertes pourraient limiter l'opération dans certaines applications telles que les systèmes de stockage d'énergie à volant d'inertie et les applications sous vide. De nombreux chercheurs ont concentré leurs efforts sur le renforcement de l'efficacité énergétique des paliers magnétiques par la minimisation des courants fournis aux bobines électromagnétiques soit par une solution logicielle, soit par une solution matérielle. Selon une étude précédente, nous adoptons la solution matérielle dans cette thèse. Plus précisément, nous étudions le développement d'un système de contrôle efficace et simple pour réguler un système de palier magnétique actif à aimant permanent polarisé. L'objectif de contrôle ici est de supprimer les vibrations du rotor et de réduire les courants de commande correspondants autant que possible tout au long d'une large plage de fonctionnement. Bien que l'adoption de l'approche matérielle pourrait atteindre un PMA économe en énergie, un système de contrôle avancé pourrait parvenir à une réduction supplémentaire de la consommation d'énergie. De nombreuses techniques de contrôle avancées ont été proposées dans la littérature pour obtenir une performance satisfaisante. Cependant, la complexité de la majorité des systèmes de contrôle et l'exigence potentielle d’une plate-forme puissante pourrait décourager leur application dans la pratique. La motivation derrière ce travail est d'améliorer les performances en boucle fermée, sans la nécessité de procéder à l'identification du modèle et en suivant la procédure classique pour développer un contrôleur basé sur un modèle. Ici, nous proposons l'application du concept d'hybridation pour exploiter le contrôle PID classique et certains outils de contrôle non linéaires tels que contrôle par mode glissement du premier et du second ordre, observateur à grand gain, backstepping et techniques adaptatives pour développer des systèmes de contrôle efficaces et pratiques. Tous les systèmes de contrôle développés dans cette thèse sont numériquement mis en oeuvre et évaluées sur la carte de contrôle eZdsp F2812. Par conséquent, l'applicabilité des techniques de modèle libre proposé pour l'application pratique est démontrée. En outre, certains des régimes de contrôle proposés ont réalisé avec succès un bon compromis entre les objectifs au rotor d’atténuation des vibrations et la minimisation des courants de commande sur une grande plage de fonctionnement