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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Some Aspects of Observer-based Control Design for a Class of Neutral Systems

Kuo, Jim-Ming 18 June 2004 (has links)
In this dissertation, the stabilization problem and observer-based control of neutral systems are investigated. Firstly, the Lyapunov functional theory is used to guarantee the stability of the system under consideration. The delay-dependent and the delay-independent stabilization criteria are proposed to guarantee asymptotic stability for the neutral systems via linear control. Linear matrix inequality (LMI) approach is used to design the observer and the controller. Secondly, by using the same techniques, we will provide an observer-based controller design method. The delay-dependent and the delay-independent stabilization criteria are proposed to guarantee asymptotic stability for the neutral systems with multiple time delays. Finally, a guaranteed-cost observer-based control for the neutral systems is considered. The analysis is also based on Lyapunov functional so as to establish an upper bound on the closed-loop value of a quadratic cost function. Delay-independent stabilization criterion is proposed to guarantee asymptotic stability for the neutral systems via linear control. By using the LMI approach, we will provide a criterion to design the observer gain and the controller gain simultaneously. Some examples and computer simulation results will also be provided to illustrate our main results.
2

Research on Global Stability for Some Uncertain Neural Networks with Multiple Time-varying Delays via LMI Approach

Gau, Ruey-shyan 23 June 2008 (has links)
In this dissertation, we will investigate the global stability for some uncertain neural networks with multiple time-varying delays. These well-known neural networks include delayed cellular neural networks (DCNNs), delayed bidirectional associative memory neural networks (DBAMNNs), and delayed Cohen-Grossberg neural networks (DCGNNs). Delay-dependent and delay-independent criteria will be proposed to guarantee the robust stability of these uncertain delayed neural networks via linear matrix inequality (LMI) approach. Three types of uncertainties on feedback and delayed feedback matrices in these uncertain delayed neural networks will be considered in this study, namely uncertainties with structured perturbation, norm-bounded unstructured perturbation, and interval perturbation. Some numerical examples will be given to illustrate the effectiveness of our results. Some comparisions are made to show that our results are better than some results in recent literature.
3

Robust Control for Inter-area Oscillations

Vance, Katelynn Atkins 03 February 2012 (has links)
In order to reduce the detrimental effects of inter-area oscillations on system stability, it is possible to use Linear Matrix Inequalities (LMIs) to design a multi-objective state feedback. The LMI optimization finds a control law that stabilizes several contingencies simultaneously using a polytopic model of the system. However, the number of cases to be considered is limited by computational complexity which increases the chances of infeasibility. In order to circumvent this problem, this paper presents a method for solving multiple polytopic problems having a common base case. The proposed algorithm determines the necessary polytopic control for a particular contingency and classifies the data as belonging to that polytopic domain. The technique has been tested on an 8-machine, 13 bus, system and has been found to give satisfactory results. / Master of Science
4

Robust multi-H2 output-feedback approach to aerial refuelling automation of large aircraft via linear matrix inequalities

Claase, Etienne H. 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In recent years the aviation industry has shown an interest in the airborne refuelling of large transport aircraft to enable increased payload mass at take-off and to extend aircraft range. Due to the large volume of fuel to be transferred, a boom and receptacle refuelling system with a larger fuel transfer rate is employed. The refuelling operation is particularly difficult and strenuous for the pilot of the receiver aircraft, because the position of the receptacle relative to the tanker aircraft must be maintained within a narrow window for a relatively long period of time. The airborne refuelling of a large aircraft is typically much more difficult than that of a fighter aircraft, since the large aircraft is more sluggish, takes much longer to refuel, and has a relatively large distance between its refuelling receptacle and its centre of mass. These difficulties provide the motivation for developing flight control laws for Autonomous In-Flight Refuelling (AIFR) to alleviate the workload on the pilot. The objective of the research is to design a flight control system that can regulate the receptacle of a receiver aircraft to remain within the boom envelope of a tanker aircraft in light and medium turbulence. The flight control system must be robust to uncertainties in the aircraft dynamic model, and must obey actuator deflection and slew rate limits. Literature on AIFR shows a wide range of approaches, including Linear Quadratic Regulator (LQR), μ-synthesis and neural-network based adaptive control, none of which explicitly includes constraints on actuator amplitudes, actuator rates and regulation errors in the design/synthesis. A new approach to designing AIFR flight control laws is proposed, based on Linear Matrix Inequality (LMI) optimisation. The relatively new LMI technique enables optimised regulation of stochastic systems subject to time-varying uncertainties and coloured noise disturbance, while simultaneously constraining transient behaviour and multiple outputs and actuators to operate within their amplitude, saturation and slew rate limits. These constraints are achieved by directly formulating them as inequalities. / AFRIKAANSE OPSOMMING: Die lugvaart industrie toon huidiglik ’n belangstelling in die brandstof oordrag tussen twee groot vervoervliegtuie gedurende vlug, met die doel om die maksimum opstyggewig kapasiteit sowel as die maksimum ononderbroke vlugafstand vermoë van die hervulde vliegtuig te vermeerder. ’n Boom hervulling-stelsel word geïmplementeer om die hoë spoed van brandstof oordrag te voorsien. Die verrigting van vluggebonde hervulling van ’n groot, trae vliegtuig is moeiliker en meer veeleisend as bv. van ’n vegvliegtuig, veral vir die vlieënier van die hervulde vliegtuig, wat sy boom-skakel moet reguleer binne ’n relatiewe klein boom bewegingsruimte vir ’n relatiewe lang tydperk. Die kinematika betrokke speel ook ’n groter rol in ’n groot hervulde vliegtuig a.g.v. die langer afstand tussen die boom-skakel en die massa middelpunt/ draaipunt. Hierdie bied die motivering om ’n beheerstelsel te ontwikkel wat die taak outomaties uitvoer. Die doel van die navorsing is om ’n beheerstelsel te ontwerp wat die boom-skakel van die hervulde vliegtuig outomaties reguleer binne die bewegingsruimte van die boom, gedurende ligte en matige turbulensie. Daar word van die beheerder vereis om robuust te wees teen onsekerhede in die vliegtuig se meganika, sowel as om die beheer oppervlaktes en turbines van die vliegtuig binne hul defleksie-, wringkrag- en sleurtempo-perke te hou. Daar bestaan reeds ’n groot verskeidenheid van benaderings tot die outomatisering van luggebonde hervulling, onder andere LQR, μ-sintese en neurale-netwerk gebaseerde aanpasbare beheer, waarvan geeneen perke op aktueerders en regulasie foute direk in die ontwerp insluit nie. ’n Nuwe benadering word voorgestel wat gebaseer is op Linear Matrix Inequality (LMI) optimering. Die LMI tegniek is relatief nuut in die gebruik van beheerstelsel ontwerp. Dit stel die ontwerper in staat om ’n stogastiese stelsel, onderworpe aan tydvariante-stelsel-variasie en gekleurde ruis versteurings, optimaal te reguleer, terwyl aktueerders en stelsel gedrag direk beperk word.
5

Coordinated Control of Inter-area Oscillations using SMA and LMI

Pal, Anamitra 13 March 2012 (has links)
The traditional approach to damp inter-area oscillations is through the installation of Power System Stabilizers (PSSs) which provide damping control action through excitation control systems of the generating units. However, study of recent blackouts has shown that the control action provided by a PSS alone is not sufficient for damping oscillations in modern power systems which operate under stressed conditions. An integrated form of control using remote measurements to coordinate the different control elements present in the system is the need of the hour. One way of implementing such a coordinated control is through the development of a Linear Matrix Inequality (LMI)-based polytopic model of the system that guarantees pole placement for a variety of operating conditions. The size of the polytopic formulation is an issue for application of LMIs to large systems. The use of Selective Modal Analysis (SMA) alleviates this problem by reducing the size of the system. The previous attempts have used a model containing all the and modes, with SMA being used to eliminate all the other states. In practical applications the resulting system was still found to be too large to use in a polytopic model. This thesis presents an algorithm to reduce the size of the system to the relevant modes of oscillations. A 16 machine, 68 bus equivalent model of the New England-New York interconnected power system is used as the test case with DC lines and SVCs acting as the control. The algorithm is then applied to a 127-bus equivalent model of the WECC System. The use of ESDs as a form of control is also demonstrated. The results indicate that the proposed control successfully damps the relevant modes of oscillations without negatively damping the other modes. The control is then transferred to a more detailed 4000+ bus model of the WECC system to realize its performance on real-world systems. / Master of Science
6

Estabilidade de sistemas amostrados com atuadores saturantes em magnitude e taxa de variação

Palmeira, Alessandra Helena Kimura January 2015 (has links)
Neste trabalho, aborda-se o problema de estabilidade de sistemas com dados amostrados periodicamente, na presença de atuadores saturantes em posição e em taxa de variação. Os atuadores são modelados como sistemas de primeira ordem com saturação de entrada (saturação de magnitude) e do estado (saturação de taxa de variação). No modelo, considera-se que o sinal de controle é mantido constante entre dois instantes de amostragem consecutivos, enquanto as dinâmicas da planta linear e do atuador saturante são em tempo contínuo, i.e., não é feita discretização do sistema. O efeito da amostragem aperiódica é considerado através de um looped -funcional, derivado do funcional de Lyapunov-Krasovskii. O método desenvolvido relaciona uma função quadrática de Lyapunov e o funcional, considerando a amostragem assíncrona e o atuador saturante. Assim, se a derivada temporal do funcional ao longo das trajetórias do sistema for definida negativa, verifica-se que a função de Lyapunov é estritamente decrescente nos instantes de amostragem. Os efeitos das saturações são considerados por meio do uso da condição de setor generalizada. A partir do looped-funcional, da função de Lyapunov e das relações de setor generalizadas, são formuladas condições que permitem caracterizar a estabilidade e projetar ganhos estabilizantes da origem do sistema amostrado, em contexto local e global, através de algoritmos baseados na solução de LMIs. São propostas condições para maximização da estimativa da região de atração da origem ou, dado um conjunto de condições iniciais, para maximização do limite superior do intervalo de amostragem. As condições estabelecidas são válidas para o sistema com acesso a todos os estados, como também, no caso dos estados do atuador não estarem disponíveis `a medição. / This work addresses the problems of stability and stabilization of sampled-data systems taking into account aperiodic sampling and magnitude and rate saturating actuactors. The actuators are represented by a first-order system subject to input (magnitude saturation) and state (rate) saturation. In the considered model, the control signal is assumed to be constant between two successive sampling instants, while the dynamics of the linear plant and the saturating actuator are in continuous-time, i.e., no discretization is performed. The aperiodic sampling is taken into account from the method based on the input delay approach via looped-functional, derived from a time-dependent Lyapunov-Krasovskii functional. The developed method is based on a particular functional, that is related to a Lyapunov function. It is shown that if the time derivative of the looped- functional along the trajectories of the continuous-time system is strictly negative, then the Lyapunov function is strictly decreasing at sampling instants. The actuator saturations are taken into account from the use of a generalized sector condition. From the looped-functional, the Lyapunov function and the generalized sector conditions, the developed results lead to conditions that can be solved as LMI prob- lems for asymptotic stability assessment and stabilization local or global of the origin of the sampled-data system. Convex optimization problems are developed to com- pute an estimate of the region of attraction or, given a set of admissible initial conditions, compute the maximal admissible inter-sampling time for which the con- vergence of the trajectories to the origin is ensured. Theorical results are valid for systems with access to all the states, and also for the case that actuator states are not available to the measurement.
7

Estabilidade de sistemas amostrados com atuadores saturantes em magnitude e taxa de variação

Palmeira, Alessandra Helena Kimura January 2015 (has links)
Neste trabalho, aborda-se o problema de estabilidade de sistemas com dados amostrados periodicamente, na presença de atuadores saturantes em posição e em taxa de variação. Os atuadores são modelados como sistemas de primeira ordem com saturação de entrada (saturação de magnitude) e do estado (saturação de taxa de variação). No modelo, considera-se que o sinal de controle é mantido constante entre dois instantes de amostragem consecutivos, enquanto as dinâmicas da planta linear e do atuador saturante são em tempo contínuo, i.e., não é feita discretização do sistema. O efeito da amostragem aperiódica é considerado através de um looped -funcional, derivado do funcional de Lyapunov-Krasovskii. O método desenvolvido relaciona uma função quadrática de Lyapunov e o funcional, considerando a amostragem assíncrona e o atuador saturante. Assim, se a derivada temporal do funcional ao longo das trajetórias do sistema for definida negativa, verifica-se que a função de Lyapunov é estritamente decrescente nos instantes de amostragem. Os efeitos das saturações são considerados por meio do uso da condição de setor generalizada. A partir do looped-funcional, da função de Lyapunov e das relações de setor generalizadas, são formuladas condições que permitem caracterizar a estabilidade e projetar ganhos estabilizantes da origem do sistema amostrado, em contexto local e global, através de algoritmos baseados na solução de LMIs. São propostas condições para maximização da estimativa da região de atração da origem ou, dado um conjunto de condições iniciais, para maximização do limite superior do intervalo de amostragem. As condições estabelecidas são válidas para o sistema com acesso a todos os estados, como também, no caso dos estados do atuador não estarem disponíveis `a medição. / This work addresses the problems of stability and stabilization of sampled-data systems taking into account aperiodic sampling and magnitude and rate saturating actuactors. The actuators are represented by a first-order system subject to input (magnitude saturation) and state (rate) saturation. In the considered model, the control signal is assumed to be constant between two successive sampling instants, while the dynamics of the linear plant and the saturating actuator are in continuous-time, i.e., no discretization is performed. The aperiodic sampling is taken into account from the method based on the input delay approach via looped-functional, derived from a time-dependent Lyapunov-Krasovskii functional. The developed method is based on a particular functional, that is related to a Lyapunov function. It is shown that if the time derivative of the looped- functional along the trajectories of the continuous-time system is strictly negative, then the Lyapunov function is strictly decreasing at sampling instants. The actuator saturations are taken into account from the use of a generalized sector condition. From the looped-functional, the Lyapunov function and the generalized sector conditions, the developed results lead to conditions that can be solved as LMI prob- lems for asymptotic stability assessment and stabilization local or global of the origin of the sampled-data system. Convex optimization problems are developed to com- pute an estimate of the region of attraction or, given a set of admissible initial conditions, compute the maximal admissible inter-sampling time for which the con- vergence of the trajectories to the origin is ensured. Theorical results are valid for systems with access to all the states, and also for the case that actuator states are not available to the measurement.
8

Estabilidade de sistemas amostrados com atuadores saturantes em magnitude e taxa de variação

Palmeira, Alessandra Helena Kimura January 2015 (has links)
Neste trabalho, aborda-se o problema de estabilidade de sistemas com dados amostrados periodicamente, na presença de atuadores saturantes em posição e em taxa de variação. Os atuadores são modelados como sistemas de primeira ordem com saturação de entrada (saturação de magnitude) e do estado (saturação de taxa de variação). No modelo, considera-se que o sinal de controle é mantido constante entre dois instantes de amostragem consecutivos, enquanto as dinâmicas da planta linear e do atuador saturante são em tempo contínuo, i.e., não é feita discretização do sistema. O efeito da amostragem aperiódica é considerado através de um looped -funcional, derivado do funcional de Lyapunov-Krasovskii. O método desenvolvido relaciona uma função quadrática de Lyapunov e o funcional, considerando a amostragem assíncrona e o atuador saturante. Assim, se a derivada temporal do funcional ao longo das trajetórias do sistema for definida negativa, verifica-se que a função de Lyapunov é estritamente decrescente nos instantes de amostragem. Os efeitos das saturações são considerados por meio do uso da condição de setor generalizada. A partir do looped-funcional, da função de Lyapunov e das relações de setor generalizadas, são formuladas condições que permitem caracterizar a estabilidade e projetar ganhos estabilizantes da origem do sistema amostrado, em contexto local e global, através de algoritmos baseados na solução de LMIs. São propostas condições para maximização da estimativa da região de atração da origem ou, dado um conjunto de condições iniciais, para maximização do limite superior do intervalo de amostragem. As condições estabelecidas são válidas para o sistema com acesso a todos os estados, como também, no caso dos estados do atuador não estarem disponíveis `a medição. / This work addresses the problems of stability and stabilization of sampled-data systems taking into account aperiodic sampling and magnitude and rate saturating actuactors. The actuators are represented by a first-order system subject to input (magnitude saturation) and state (rate) saturation. In the considered model, the control signal is assumed to be constant between two successive sampling instants, while the dynamics of the linear plant and the saturating actuator are in continuous-time, i.e., no discretization is performed. The aperiodic sampling is taken into account from the method based on the input delay approach via looped-functional, derived from a time-dependent Lyapunov-Krasovskii functional. The developed method is based on a particular functional, that is related to a Lyapunov function. It is shown that if the time derivative of the looped- functional along the trajectories of the continuous-time system is strictly negative, then the Lyapunov function is strictly decreasing at sampling instants. The actuator saturations are taken into account from the use of a generalized sector condition. From the looped-functional, the Lyapunov function and the generalized sector conditions, the developed results lead to conditions that can be solved as LMI prob- lems for asymptotic stability assessment and stabilization local or global of the origin of the sampled-data system. Convex optimization problems are developed to com- pute an estimate of the region of attraction or, given a set of admissible initial conditions, compute the maximal admissible inter-sampling time for which the con- vergence of the trajectories to the origin is ensured. Theorical results are valid for systems with access to all the states, and also for the case that actuator states are not available to the measurement.
9

Controle H∞ chaveado para sistemas não lineares incertos descritos por modelos fuzzy T-S considerando região de operação e saturação do sinal de controle /

Oliveira, Diogo Ramalho de. January 2017 (has links)
Orientador: Marcelo Carvalho Minhoto Teixeira / Resumo: Esta tese propõe projetos de controle H∞ chaveado para uma classe de sistemas não lineares incertos descritos por modelos fuzzy Takagi-Sugeno (T-S) com funções de pertinência desconhecidas. Os projetos de controle necessitam somente dos limites inferiores e superiores das não linearidades do sistema, que podem depender de parâmetros incertos da planta. Em diversas aplicações práticas, em virtude das restrições operacionais dos equipamentos, no projeto de controle é necessário considerar que a lei de controle está sujeita à saturação do atuador. Primeiramente, utilizando uma metodologia encontrada na literatura para resolver o problema da saturação do atuador, propõe-se uma lei de controle chaveada que escolhe um ganho do controlador de realimentação do vetor de estado, que pertence a um conjunto de ganhos conhecidos, que minimiza a derivada da função de Lyapunov do tipo quadrática. Este procedimento elimina a necessidade de encontrar as expressões das funções de pertinência para implementar a lei de controle, garante um desempenho H∞ ao sistema realimentado e assegura que as trajetórias do vetor de estado permanecem dentro de uma região de operação na qual o modelo fuzzy T-S é válido. Adicionalmente, adota-se uma outra metodologia para resolver o problema da saturação do atuador, que utiliza o sinal de controle para compor um vetor de estado expandido. Desta forma, os limites do sinal de controle fazem parte da região de operação na qual o sistema não linear incerto é exatame... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This thesis proposes local H∞ switched control designs for a class of uncertain nonlinear plants described by Takagi-Sugeno (T-S) fuzzy models with unknown membership functions. The control designs require only the lower and upper bounds of the system nonlinearities and of the system linear parameters, which can depend on uncertain parameters. In practical applications, due to the operational restrictions of the equipments, in the control design, it is necessary to consider that the control law is subject to actuator saturation. First, using a methodology found in the literature to solve the actuator saturation problem, one proposes a switched control law that chooses a state-feedback controller gain, which belongs to a given set of gains, that minimizes the time derivative of a quadratic Lyapunov function. This procedure eliminates the necessity of finding the membership function expressions to implement the control law, guarantees an H∞ performance and ensures that the state trajectory remains within a region in which the T-S fuzzy model is valid. In addition, the actuator saturation problem is approached with another methodology, using the control signal to compose an extended state vector. Then, the region in which the uncertain nonlinear system is exactly represented via T-S fuzzy models is composed by the bounds of the control signal. A switched control law, which chooses an extended state-feedback controller gain, is proposed. The design conditions avoid the presence o... (Complete abstract click electronic access below) / Doutor
10

Controle H∞ chaveado para sistemas não lineares incertos descritos por modelos fuzzy T-S considerando região de operação e saturação do sinal de controle / On local H∞ switched controller design for uncertain T-S fuzzy systems subject to actuator saturation

Oliveira, Diogo Ramalho de [UNESP] 31 May 2017 (has links)
Submitted by DIOGO RAMALHO DE OLIVEIRA null (diogo.oliveira.ee@gmail.com) on 2017-06-22T14:35:42Z No. of bitstreams: 1 Tese_Diogo.pdf: 2317981 bytes, checksum: fa048901c893f57ba87ceec19383ae14 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-06-22T17:28:20Z (GMT) No. of bitstreams: 1 oliveira_dr_dr_ilha.pdf: 2317981 bytes, checksum: fa048901c893f57ba87ceec19383ae14 (MD5) / Made available in DSpace on 2017-06-22T17:28:20Z (GMT). No. of bitstreams: 1 oliveira_dr_dr_ilha.pdf: 2317981 bytes, checksum: fa048901c893f57ba87ceec19383ae14 (MD5) Previous issue date: 2017-05-31 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Esta tese propõe projetos de controle H∞ chaveado para uma classe de sistemas não lineares incertos descritos por modelos fuzzy Takagi-Sugeno (T-S) com funções de pertinência desconhecidas. Os projetos de controle necessitam somente dos limites inferiores e superiores das não linearidades do sistema, que podem depender de parâmetros incertos da planta. Em diversas aplicações práticas, em virtude das restrições operacionais dos equipamentos, no projeto de controle é necessário considerar que a lei de controle está sujeita à saturação do atuador. Primeiramente, utilizando uma metodologia encontrada na literatura para resolver o problema da saturação do atuador, propõe-se uma lei de controle chaveada que escolhe um ganho do controlador de realimentação do vetor de estado, que pertence a um conjunto de ganhos conhecidos, que minimiza a derivada da função de Lyapunov do tipo quadrática. Este procedimento elimina a necessidade de encontrar as expressões das funções de pertinência para implementar a lei de controle, garante um desempenho H∞ ao sistema realimentado e assegura que as trajetórias do vetor de estado permanecem dentro de uma região de operação na qual o modelo fuzzy T-S é válido. Adicionalmente, adota-se uma outra metodologia para resolver o problema da saturação do atuador, que utiliza o sinal de controle para compor um vetor de estado expandido. Desta forma, os limites do sinal de controle fazem parte da região de operação na qual o sistema não linear incerto é exatamente representado via modelos fuzzy T-S. Uma lei de controle chaveada, que utiliza a realimentação do vetor de estado expandido, é proposta. As condições de projeto evitam a presença de uma possível descontinuidade do sinal de controle, eliminam a necessidade de obter as expressões das funções de pertinência para implementar a lei de controle, garantem um desempenho H∞ e asseguram que as trajetórias do vetor de estado e do sinal de controle permanecem dentro de uma região de operação na qual o modelo fuzzy T-S é válido. Por fim, três exemplos são apresentados. O primeiro exemplo estuda o controle de um sistema caótico denominado Lorenz. Mostra que, para distúrbios de grande magnitude, os procedimentos propostos apresentaram melhores resultados do que os obtidos com outro método recentemente encontrado na literatura, que considera o pleno acesso às funções de pertinência. No segundo exemplo, uma implementação prática em um sistema de controle de uma suspensão ativa de bancada, considerando uma mola não linear e falha no atuador, confirma a eficácia da abordagem proposta. O último exemplo utiliza um pêndulo invertido para abordar o problema de controle considerando a estabilidade local do sistema. As simulações ilustram que o esquema proposto, que utiliza o vetor de estado expandido, é capaz de evitar uma possível descontinuidade do sinal de controle. / This thesis proposes local H∞ switched control designs for a class of uncertain nonlinear plants described by Takagi-Sugeno (T-S) fuzzy models with unknown membership functions. The control designs require only the lower and upper bounds of the system nonlinearities and of the system linear parameters, which can depend on uncertain parameters. In practical applications, due to the operational restrictions of the equipments, in the control design, it is necessary to consider that the control law is subject to actuator saturation. First, using a methodology found in the literature to solve the actuator saturation problem, one proposes a switched control law that chooses a state-feedback controller gain, which belongs to a given set of gains, that minimizes the time derivative of a quadratic Lyapunov function. This procedure eliminates the necessity of finding the membership function expressions to implement the control law, guarantees an H∞ performance and ensures that the state trajectory remains within a region in which the T-S fuzzy model is valid. In addition, the actuator saturation problem is approached with another methodology, using the control signal to compose an extended state vector. Then, the region in which the uncertain nonlinear system is exactly represented via T-S fuzzy models is composed by the bounds of the control signal. A switched control law, which chooses an extended state-feedback controller gain, is proposed. The design conditions avoid the presence of a possible discontinuity of the control signal, eliminate the necessity of finding the membership function expressions to implement the control law, guarantee an H∞ performance and ensure that the state trajectory and the control signal remain within a region in which the T-S fuzzy model is valid. Finally, three examples are presented. The first example studies the control of a chaotic Lorenz system. It shows that, for disturbances with large magnitude, the proposed procedures provided better results than the obtained with another recent method found in the literature, that considers full access to the membership functions. In the second example, a practical implementation of an active suspension control system, considering a nonlinear spring and an actuator fault, confirms the effectiveness of the proposed approach. The last example uses an inverted pendulum system to address the local stability control problem. The simulations illustrate that the control scheme, which uses the extended state vector, is able to avoid a possible discontinuity of the control signal. / CNPq: 142035/2013-0

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