O presente trabalho aborda três tópicos de pesquisa e desenvolvimento em Sistemas de Posicionamento Dinâmico (SPD). Desenvolveu-se uma nova metodologia para o projeto de controlador de posição e aproamento baseada na teoria de controle robusto não-linear por modos deslizantes. O controlador integra uma malha de compensação direta dos esforços ambientais (ondas, vento e correnteza) a uma malha de realimentação que realiza correções de erros residuais. A estrutura não-linear do controlador assegura o desempenho e estabilidade para qualquer aproamento da embarcação. A malha de compensação direta, por sua vez, garante maior faixa de aplicabilidade em termos de condições ambientais, não apresentando degradação de desempenho em condições extremas. A malha de realimentação possui apenas nove parâmetros, existindo equações e regras que tornam suas calibrações simples. Já a malha de compensação direta possui, internamente, modelos para a estimativa das forças ambientais que agem sobre o navio. Graças às características de robustez, o controlador não requer um ajuste refinado dos diversos parâmetros destes modelos e das condições ambientais, podendo-se utilizar estimativas pouco acuradas dos mesmos. O controlador desenvolvido foi testado em simuladores computacionais do VLCC Vidal de Negreiros amarrado pelo sistema turret e de uma barcaça de lançamento de dutos, ambos contendo modelos validados dos esforços ambientais. As simulações emularam erros de modelagem e de estimação das condições ambientais, e confirmaram as boas características de robustez e desempenho do controlador em diversas condições e a facilidade no ajuste de parâmetros. Desenvolveu-se também um modo de controle apropriado para operações com liberdade de aproamento realizadas na Bacia de Campos, onde é comum a incidência de agentes ambientais em direções não alinhadas. Neste modo calcula-se, baseado nas estimativas das condições ambientais, o aproamento que minimiza um funcional relacionando parâmetros operacionais relevantes, como movimento de roll, tração dinâmica em risers, solicitação do sistema de amarração e consumo de combustível. Uma análise numérica de sensibilidade, aplicada ao VLCC Vidal de Negreiros, indicou que o cálculo do aproamento ótimo não apresenta elevada sensibilidade a erros nas estimativas das condições ambientais em condições extremas. Testes numéricos comprovaram também a superioridade do presente modo de controle comparado ao tradicional modo Weather vane nas condições da Bacia de Campos. Como a estimação do espectro de ondas incidentes ainda apresenta problemas técnicos e operacionais, desenvolveu-se também um método de estimação do espectro baseado na medição dos movimentos da embarcação. Utilizou-se uma abordagem paramétrica, cuja sensibilidade a erros no conhecimento da resposta dinâmica da embarcação mostrou-se aceitável. O método foi testado numericamente e validado com resultados de ensaios em tanque de provas. Os erros de estimação foram plenamente compatíveis aos erros admissíveis pelo controlador desenvolvido, alcançando, no caso da altura significativa, o valor máximo de 25%. O método foi comparado à abordagem não paramétrica Bayesiana, muito utilizada em trabalhos correlatos, e apresentou resultados mais acurados. / The present work deals with three research and development topics related to Dynamic Positioning Systems. A new design methodology of ship position and heading controller was developed, based on the robust and nonlinear Sliding Mode Control theory. The controller contains a feedforward action, which compensates environmental forces (wind, waves and current) and a feedback loop, responsible for the elimination of residual errors. The nonlinear formulation of the controller assures performance and stability requirements for all heading angles. The feedforward action guarantees its applicability in a large range of environmental conditions, without performance degradation in severe conditions. The feedback loop contains only nine parameters, which can be calibrated easily by simple equations. The feedforward loop internally contains models for the estimation of the environmental forces acting on the ship. However, due to robustness properties, the controller does not require a fine adjustment of its several parameters and the environmental conditions, allowing the use of non-accurate estimates. The controller was tested in computational simulators of the turret moored VLCC Vidal de Negreiros and of a pipe-laying barge, both comprising validated models of environmental forces. The simulations emulated modeling and environmental conditions estimation errors, confirming the good robustness and performance properties of the controller in several environmental conditions and the simple parameter adjusting process. A control mode adapted for heading-free operations in Campos Basin was also developed, where non-aligned environmental agents frequently happen. In this mode, it is calculated the optimal heading that minimizes a functional relating important operational parameters, such as roll motion, risers dynamic tension, mooring system forces and energy consumption. Estimations of environmental conditions are used in the calculation. However, a numerical sensibility analysis of this control mode applied to the VLCC Vidal de Negreiros indicated that the optimal heading calculation presents low sensibility to errors in these estimations under severe environmental conditions. Numerical trials showed that this control mode is more adequate to Campos Basin conditions compared to the traditional Weather vane mode. Since wave spectrum estimation still presents technical and operational problems, a spectrum estimation method was also developed, based on measurements of ship motions. A parametric method was used, which presented low sensitivity to errors in ship dynamic response functions. The method was numerically tested and validated through towing tank tests. Estimation errors were compatible to the controller admissible errors. For example, the maximum error in significant wave height estimation was 25%, smaller than the errors usually obtained using the non-parametric Bayesian method, widely applied for this class of problems.

O presente trabalho aborda três tópicos de pesquisa e desenvolvimento em Sistemas de Posicionamento Dinâmico (SPD). Desenvolveu-se uma nova metodologia para o projeto de controlador de posição e aproamento baseada na teoria de controle robusto não-linear por modos deslizantes. O controlador integra uma malha de compensação direta dos esforços ambientais (ondas, vento e correnteza) a uma malha de realimentação que realiza correções de erros residuais. A estrutura não-linear do controlador assegura o desempenho e estabilidade para qualquer aproamento da embarcação. A malha de compensação direta, por sua vez, garante maior faixa de aplicabilidade em termos de condições ambientais, não apresentando degradação de desempenho em condições extremas. A malha de realimentação possui apenas nove parâmetros, existindo equações e regras que tornam suas calibrações simples. Já a malha de compensação direta possui, internamente, modelos para a estimativa das forças ambientais que agem sobre o navio. Graças às características de robustez, o controlador não requer um ajuste refinado dos diversos parâmetros destes modelos e das condições ambientais, podendo-se utilizar estimativas pouco acuradas dos mesmos. O controlador desenvolvido foi testado em simuladores computacionais do VLCC Vidal de Negreiros amarrado pelo sistema turret e de uma barcaça de lançamento de dutos, ambos contendo modelos validados dos esforços ambientais. As simulações emularam erros de modelagem e de estimação das condições ambientais, e confirmaram as boas características de robustez e desempenho do controlador em diversas condições e a facilidade no ajuste de parâmetros. Desenvolveu-se também um modo de controle apropriado para operações com liberdade de aproamento realizadas na Bacia de Campos, onde é comum a incidência de agentes ambientais em direções não alinhadas. Neste modo calcula-se, baseado nas estimativas das condições ambientais, o aproamento que minimiza um funcional relacionando parâmetros operacionais relevantes, como movimento de roll, tração dinâmica em risers, solicitação do sistema de amarração e consumo de combustível. Uma análise numérica de sensibilidade, aplicada ao VLCC Vidal de Negreiros, indicou que o cálculo do aproamento ótimo não apresenta elevada sensibilidade a erros nas estimativas das condições ambientais em condições extremas. Testes numéricos comprovaram também a superioridade do presente modo de controle comparado ao tradicional modo Weather vane nas condições da Bacia de Campos. Como a estimação do espectro de ondas incidentes ainda apresenta problemas técnicos e operacionais, desenvolveu-se também um método de estimação do espectro baseado na medição dos movimentos da embarcação. Utilizou-se uma abordagem paramétrica, cuja sensibilidade a erros no conhecimento da resposta dinâmica da embarcação mostrou-se aceitável. O método foi testado numericamente e validado com resultados de ensaios em tanque de provas. Os erros de estimação foram plenamente compatíveis aos erros admissíveis pelo controlador desenvolvido, alcançando, no caso da altura significativa, o valor máximo de 25%. O método foi comparado à abordagem não paramétrica Bayesiana, muito utilizada em trabalhos correlatos, e apresentou resultados mais acurados. / The present work deals with three research and development topics related to Dynamic Positioning Systems. A new design methodology of ship position and heading controller was developed, based on the robust and nonlinear Sliding Mode Control theory. The controller contains a feedforward action, which compensates environmental forces (wind, waves and current) and a feedback loop, responsible for the elimination of residual errors. The nonlinear formulation of the controller assures performance and stability requirements for all heading angles. The feedforward action guarantees its applicability in a large range of environmental conditions, without performance degradation in severe conditions. The feedback loop contains only nine parameters, which can be calibrated easily by simple equations. The feedforward loop internally contains models for the estimation of the environmental forces acting on the ship. However, due to robustness properties, the controller does not require a fine adjustment of its several parameters and the environmental conditions, allowing the use of non-accurate estimates. The controller was tested in computational simulators of the turret moored VLCC Vidal de Negreiros and of a pipe-laying barge, both comprising validated models of environmental forces. The simulations emulated modeling and environmental conditions estimation errors, confirming the good robustness and performance properties of the controller in several environmental conditions and the simple parameter adjusting process. A control mode adapted for heading-free operations in Campos Basin was also developed, where non-aligned environmental agents frequently happen. In this mode, it is calculated the optimal heading that minimizes a functional relating important operational parameters, such as roll motion, risers dynamic tension, mooring system forces and energy consumption. Estimations of environmental conditions are used in the calculation. However, a numerical sensibility analysis of this control mode applied to the VLCC Vidal de Negreiros indicated that the optimal heading calculation presents low sensibility to errors in these estimations under severe environmental conditions. Numerical trials showed that this control mode is more adequate to Campos Basin conditions compared to the traditional Weather vane mode. Since wave spectrum estimation still presents technical and operational problems, a spectrum estimation method was also developed, based on measurements of ship motions. A parametric method was used, which presented low sensitivity to errors in ship dynamic response functions. The method was numerically tested and validated through towing tank tests. Estimation errors were compatible to the controller admissible errors. For example, the maximum error in significant wave height estimation was 25%, smaller than the errors usually obtained using the non-parametric Bayesian method, widely applied for this class of problems.

In this thesis a class of robust non-linear controllers for a gantry crane system are discussed. The gantry crane has three degrees of freedom, all of which are interrelated. These are the horizontal traverse of the cart, the vertical motion of the goods (i.e. rope length) and the swing angle made by the goods during the movement of the cart. The objective is to control all three degrees of freedom. This means achieving setpoint control for the cart and the rope length and cancellation of the swing oscillations. A mathematical model of the gantry crane system is developed using Lagrangian dynamics. In this thesis it is shown that a model of the gantry crane system can be represented as two sub models which are coupled by a term which includes the rope length as a parameter. The first system will consist of the cart and swing dynamics and the other system is the hoist dynamics. The mathematical model of these two systems will be derived independent of the other system. The model that is comprised of the two sub models is verified as an accurate model of a gantry crane system and it will be used to simulate the performance of the controllers using Matlab. For completeness a fully coupled mathematical model of the gantry crane system is also developed. A detailed design of a gain scheduled sliding mode controller is presented. This will guarantee the controller's robustness in the presence of uncertainties and bounded matched disturbances. This controller is developed to achieve cart setpoint and swing control while achieving rope length setpoint control. A non gain scheduled sliding mode controller is also developed to determine if the more complex gain scheduled sliding mode controller gives any significant improvement in performance. In the implementation of both sliding mode controllers, all system states must be available. In the real-time gantry crane system used in this thesis, the cart velocity and the swing angle velocity are not directly available from the system. They will be estimated using an alpha-beta state estimator. To overcome this limitation and provide a more practical solution an optimal output feedback model following controller is designed. It is demonstrated that by expressing the system and the model for which the system is to follow in a non-minimal state space representation, LQR techniques can be used to design the controller. This produces a dynamic controller that has a proper transfer function, and negates the need for the availability of all system states. This thesis presents an alternative method of solving the LQR problem by using a generic eigenvalue solution to solve the Riccati equation and thus determine the optimal feedback gains. In this thesis it is shown that by using a combination of sliding mode and H??? control techniques, a non-linear controller is achieved which is robust in the presence of a wide variety of uncertainties and disturbances. A supervisory controller is also described in this thesis. The supervisory control is made up of a feedforward and a feedback component. It is shown that the feedforward component is the crane operator's action, and the feedback component is a sliding mode controller which compensates as the system's output deviates from the desired trajectory because of the operator's inappropriate actions or external disturbances such as wind gusts and noise. All controllers are simulated using Matlab and implemented in real-time on a scale model of the gantry crane system using the program RTShell. The real-time results are compared against simulated results to determine the controller's performance in a real-time environment.

Switched electronic systems are used in a huge number of everyday domestic and industrial utilities: liquid crystal displays, home appliances, lighting, personal computers, power plants, transportation vehicles and so on. Efficient operations of all such applications depend on the essential "hidden work" done by switched electronic systems, whose behavior is determined by a suitable interconnection and control of analog and digital devices. As a motivation of this work, we consider the DC-DC power converters. This thesis contributes to provide hybrid and nonlinear control problem solutions to several types of power converters. In the first part we are interested in the problem of voltage regulation of power converters operating in discontinuous conducting mode. Two power converters are considered: the boost converter and the buck-boost converter. The system does not admit a (continuous--time) average model approximation, hence is a hybrid system where the control objective is the generation of a periodic orbit and the actuator commands are switching times. Our main contribution is a simple robust algorithm that gives explicit formulas for the switching times without approximations. Simulation and experimental results that illustrate the robustness of the scheme to parameter uncertainty, as well as performance comparisons with current practice, are presented. In the second part a class of power converters that can be globally stabilized with an output-feedback PI controller has been identified. Moreover, we will prove that the I&I observer can be combined with the PI controller preserving the GAS properties of the closed-loop. The class is characterized by a simple linear matrix inequality. The new controller is illustrated with the widely-popular, and difficult to control, single-ended primary inductor converter, for which simulation and experimental results are presented.

In this paper we examine the stabilization of LTI discrete-time systems with control input constraints in the form of saturation nonlinearities. This kind of constraint is usually introduced to simulate the effect of actuator limitations. Since global controllability can not be assumed in the presence of constrained control, the controllable regions and their characterizations are analyzed first. We present an efficient algorithm for finding controllable regions in terms of their boundary hyperplanes (inequality constraints). A previously open question about the exact number of irredundant boundary hyperplanes is also resolved here. The main result of this research is a time-optimal nonlinear controller which stabilizes the system on its controllable region. We give analgorithm for on-line computation of control which is also implementable for high-order systems. Simulation results show superior response even in the presence of disturbances.

In this paper we examine the stabilization of LTI discrete-time systems with control input constraints in the form of saturation nonlinearities. This kind of constraint is usually introduced to simulate the effect of actuator limitations. Since global controllability can not be assumed in the presence of constrained control, the controllable regions and their characterizations are analyzed first. We present an efficient algorithm for finding controllable regions in terms of their boundary hyperplanes (inequality constraints). A previously open question about the exact number of irredundant boundary hyperplanes is also resolved here. The main result of this research is a time-optimal nonlinear controller which stabilizes the system on its controllable region. We give analgorithm for on-line computation of control which is also implementable for high-order systems. Simulation results show superior response even in the presence of disturbances.

Fuzzy logic systems (FLSs) are well known in the literature for their ability to model linguistics and system uncertainties. Due to this ability, FLSs have been successfully used in modeling and control applications such as medicine, finance, communications, and operations research. Moreover, the ability of higher order fuzzy systems to handle system uncertainty has become an interesting topic of research in the field. In particular, type-2 FLSs (T2 FLSs), systems consisting of fuzzy sets with fuzzy grades of membership, a feature that type-1 (T1) does not offer, are most well-known for this capability. The structure of T2 FLSs allows for the incorporation of uncertainty in the input membership grades, a common situation in reasoning with physical systems. General T2 FLSs have a complex structure, thus making them difficult to adopt on a large scale. As a result, interval T2 FLSs (IT2 FLSs), a special class of T2 FLSs, have recently shown great potential in various applications with input-output (I/O) system uncertainties. Due to the sophisticated mathematical structure of IT2 FLSs, little to no systematic analysis has been reported in the literature to use such systems in control design. Moreover, to date, designers have distanced themselves from adopting such systems on a wide scale because of their design complexity. Furthermore, the very few existing control methods utilizing IT2 fuzzy logic control systems (IT2 FLCSs) do not guarantee the stability of their system. Therefore, this thesis presents a systematic method for designing stable IT2 Takagi-Sugeno-Kang (IT2 TSK) fuzzy systems when antecedents are T2 fuzzy sets and consequents are crisp numbers (A2-C0). Five new inference mechanisms are proposed that have closed-form I/O mappings, making them more feasible for FLCS stability analysis. The thesis focuses on control applications for when (a) both plant and controller use A2-C0 TSK models, and (b) the plant uses T1 Takagi-Sugeno (T1 TS) and the controller uses IT2 TS models. In both cases, sufficient stability conditions for the stability of the closed-loop system are derived. Furthermore, novel linear matrix inequality-based algorithms are developed for satisfying the stability conditions. Numerical analyses are included to validate the effectiveness of the new inference methods. Case studies reveal that a well-tuned IT2 TS FLCS using the proposed inference engine can potentially outperform its T1 TSK counterpart, a result of IT2 having greater structural flexibility than T1. Moreover, due to the simple nature of the proposed inference engine, it is easy to implement in real-time control systems. In addition, a novel design methodology is proposed for IT2 TSK FLC for modular and reconfigurable robot (MRR) manipulators with uncertain dynamic parameters. A mathematical framework for the design of IT2 TSK FLCs is developed for tracking purposes that can be effectively used in real-time applications. To verify the effectiveness of the proposed controller, experiments are performed on an MRR with two degrees of freedom which exhibits dynamic coupling behavior. Results show that the developed controller can outperform some well-known linear and nonlinear controllers for different configurations. Therefore, the proposed structure can be adopted for the position control of MRRs with unknown dynamic parameters in trajectory-tracking applications. Finally, a rigorous mathematical analysis of the robustness of FLSs (both T1 and IT2) is presented in the thesis and entails a formulation of the robustness of FLSs as a constraint multi-objective optimization problem. Consequently, a procedure is proposed for the design of robust IT2 FLSs. Several examples are presented to demonstrate the effectiveness of the proposed methodologies. It was concluded that both T1 and IT2 FLSs can be designed to achieve robust behavior in various applications. IT2 FLSs, having a more flexible structure than T1 FLSs, exhibited relatively small approximation errors in the several examples investigated. The rigorous methodologies presented in this thesis lay the mathematical foundations for analyzing the stability and facilitating the design of stabilizing IT2 FLCSs. In addition, the proposed control technique for tracking purposes of MRRs will provide control engineers with tools to control dynamic systems with uncertainty and changing parameters. Finally, the systematic approach developed for the analysis and design of robust T1 and IT2 FLSs is of great practical value in various modeling and control applications.

Fuzzy logic systems (FLSs) are well known in the literature for their ability to model linguistics and system uncertainties. Due to this ability, FLSs have been successfully used in modeling and control applications such as medicine, finance, communications, and operations research. Moreover, the ability of higher order fuzzy systems to handle system uncertainty has become an interesting topic of research in the field. In particular, type-2 FLSs (T2 FLSs), systems consisting of fuzzy sets with fuzzy grades of membership, a feature that type-1 (T1) does not offer, are most well-known for this capability. The structure of T2 FLSs allows for the incorporation of uncertainty in the input membership grades, a common situation in reasoning with physical systems. General T2 FLSs have a complex structure, thus making them difficult to adopt on a large scale. As a result, interval T2 FLSs (IT2 FLSs), a special class of T2 FLSs, have recently shown great potential in various applications with input-output (I/O) system uncertainties. Due to the sophisticated mathematical structure of IT2 FLSs, little to no systematic analysis has been reported in the literature to use such systems in control design. Moreover, to date, designers have distanced themselves from adopting such systems on a wide scale because of their design complexity. Furthermore, the very few existing control methods utilizing IT2 fuzzy logic control systems (IT2 FLCSs) do not guarantee the stability of their system. Therefore, this thesis presents a systematic method for designing stable IT2 Takagi-Sugeno-Kang (IT2 TSK) fuzzy systems when antecedents are T2 fuzzy sets and consequents are crisp numbers (A2-C0). Five new inference mechanisms are proposed that have closed-form I/O mappings, making them more feasible for FLCS stability analysis. The thesis focuses on control applications for when (a) both plant and controller use A2-C0 TSK models, and (b) the plant uses T1 Takagi-Sugeno (T1 TS) and the controller uses IT2 TS models. In both cases, sufficient stability conditions for the stability of the closed-loop system are derived. Furthermore, novel linear matrix inequality-based algorithms are developed for satisfying the stability conditions. Numerical analyses are included to validate the effectiveness of the new inference methods. Case studies reveal that a well-tuned IT2 TS FLCS using the proposed inference engine can potentially outperform its T1 TSK counterpart, a result of IT2 having greater structural flexibility than T1. Moreover, due to the simple nature of the proposed inference engine, it is easy to implement in real-time control systems. In addition, a novel design methodology is proposed for IT2 TSK FLC for modular and reconfigurable robot (MRR) manipulators with uncertain dynamic parameters. A mathematical framework for the design of IT2 TSK FLCs is developed for tracking purposes that can be effectively used in real-time applications. To verify the effectiveness of the proposed controller, experiments are performed on an MRR with two degrees of freedom which exhibits dynamic coupling behavior. Results show that the developed controller can outperform some well-known linear and nonlinear controllers for different configurations. Therefore, the proposed structure can be adopted for the position control of MRRs with unknown dynamic parameters in trajectory-tracking applications. Finally, a rigorous mathematical analysis of the robustness of FLSs (both T1 and IT2) is presented in the thesis and entails a formulation of the robustness of FLSs as a constraint multi-objective optimization problem. Consequently, a procedure is proposed for the design of robust IT2 FLSs. Several examples are presented to demonstrate the effectiveness of the proposed methodologies. It was concluded that both T1 and IT2 FLSs can be designed to achieve robust behavior in various applications. IT2 FLSs, having a more flexible structure than T1 FLSs, exhibited relatively small approximation errors in the several examples investigated. The rigorous methodologies presented in this thesis lay the mathematical foundations for analyzing the stability and facilitating the design of stabilizing IT2 FLCSs. In addition, the proposed control technique for tracking purposes of MRRs will provide control engineers with tools to control dynamic systems with uncertainty and changing parameters. Finally, the systematic approach developed for the analysis and design of robust T1 and IT2 FLSs is of great practical value in various modeling and control applications.

No description available.

The stringent regulations of emission levels from heavy duty vehicles create a demand for new methods for reducing harmful emissions from diesel engines. This thesis deals with the modelling of the nitrogen oxide (NOx) emissions from heavy duty vehicles using a selective catalyst as an aftertreatment system, utilising ammonia (NH3) for its reduction. The process of the selective catalytic reduction (SCR) is nonlinear, since the result of the chemical reactions involved depends on the load operating point and the temperature. The purpose of this thesis is to investigate different methods for nonlinear system identification of SCR systems with control applications in mind. The main focus of the thesis is on finding suitable techniques for effective NOx reduction without the need of over dosage of ammonia. By using data collected from a simulator together with real measured data, new black-box identification techniques are developed. Scaling and convergence properties of the proposed algorithms are analysed theoretically. Some of the resulting models are used for controller development using e.g. feedback linearisation techniques, followed by validation in a simulator environment. The benefits of nonlinear modelling and control of the SCR system are highlighted in a comparison with control based on linear models of the system. Further, a multiple model approach is investigated for simultaneous control of NOx and tailpipe ammonia. The results indicate an improvement in terms of ammonia slip reduction in comparison with models that do not take the ammonia slip into account. Another approach to NOx reduction is achieved by controlling the SCR temperature using techniques developed for LPV systems. The results indicate a reduction of the accumulated NOx.