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Η μερική διαφορική εξίσωση Hamilton-Jacobi-Bellman παράγει τη λύση στο πρόβλημα του υπολογισμού της βέλτιστης ανάδρασης καταστάσεων σε μη γραμμικά δυναμικά συστήματα. Η προσπάθεια ανάπτυξης εύχρηστων και αξιόπιστων μεθόδων αριθμητικής ή προσεγγιστικής επίλυσης της εξίσωσης Hamilton-Jacobi-Bellman έχει τεράστια σημασία στη ρύθμιση διεργασιών γιατί μπορεί να οδηγήσει άμεσα σε εργαλεία σχεδιασμού μη γραμμικών ρυθμιστών. Ειδικότερα, στη ρύθμιση διεργασιών, η απόδοση ενός ρυθμιστικού συστήματος αξιολογείται βάσει ενός τετραγωνικού δείκτη απόδοσης σε άπειρο χρονικό ορίζοντα, και η βέλτιστη ανάδραση καταστάσεων μπορεί να υπολογισθεί μέσω της λύσης της εξίσωσης Hamilton-Jacobi-Bellman, μη εξαρτώμενης από το χρόνο. Στο πρόβλημα της επίλυσης της παραπάνω εξίσωσης παρουσιάζονται σοβαρές δυσκολίες, κυρίως λόγω υπολογιστικής πολυπλοκότητας. Για το λόγο αυτό, οι μέχρι στιγμής πρακτικές εφαρμογές υπήρξαν περιορισμένες. Στην παρούσα εργασία αναπτύσσεται υπολογιστική μέθοδος, βασισμένη στον αλγόριθμο επαναλήψεων Newton-Kantorovich, η οποία επιτυγχάνει πολυωνυμική προσέγγιση της λύσης της μερικής διαφορικής εξίσωσης Hamilton-Jacobi-Bellman υπό μορφή αναπτύγματος σε δυναμοσειρά Taylor. Με τον τρόπο αυτό επιταχύνονται σημαντικά οι υπολογισμοί για τον προσδιορισμό της βέλτιστης ανάδρασης καταστάσεων. Η μέθοδος εφαρμόζεται αρχικά σε ένα παράδειγμα ισοθερμοκρασιακού αντιδραστήρα συνεχούς λειτουργίας με ανάδευση, ο οποίος παρουσιάζει δυναμική συμπεριφορά μη-ελάχιστης φάσης, με μία είσοδο, μία έξοδο και δύο καταστάσεις. Στη συνέχεια, εφαρμόζεται σε παραδείγματα μη ισοθερμοκρασιακού αντιδραστήρα αντίστοιχης δυναμικής συμπεριφοράς, τριών καταστάσεων, πρωτίστως με μία είσοδο και μία έξοδο και κατόπιν με δύο εισόδους και δύο εξόδους. Με ανάπτυξη και εφαρμογή κώδικα MAPLE για κάθε μία περίπτωση χωριστά, υπολογίζονται προσεγγιστικά οι βέλτιστοι νόμοι ανάδρασης και σχεδιάζονται οι βέλτιστες αποκρίσεις των εισόδων και των εξόδων κάθε ενός από τα παραπάνω συστήματα, ενώ ταυτόχρονα γίνεται και καταγραφή των αντίστοιχων χρόνων εκτέλεσης κάθε κώδικα. Τέλος, στην περίπτωση του ισοθερμοκρασιακού αντιδραστήρα, γίνεται σύγκριση της προτεινόμενης μεθόδου με προϋπάρχουσες, κατά κύριο λόγο σε ζητήματα χρόνων εκτέλεσης, αλλά και σε ζητήματα απόδοσης στη ρύθμιση. / The partial differential equation Hamilton-Jacobi-Bellman produces the solution in the problem of calculation of optimal state feedback in non-linear dynamic systems. The effort of designing functional and reliable, numerical or approximate, methods for solving Hamilton-Jacobi-Bellman equation has enormous importance in process control because it can lead directly to tools of planning non-linear regulators. More specifically, in process control, the attribution of a regulating system is evaluated using a quadratic performance index in infinite time horizon, and the optimal state feedback can be calculated by the solution of the non time depended Hamilton-Jacobi-Bellman equation. The problem of solving the equation above encounters serious difficulties, mainly because of the calculation complexity. For this reason, the practical applications existed until now were very few. In the present work a calculating method is developed, based in the iterative algorithm Newton-Kantorovich, which achieves polynomial approach of the solution of partial differential equation Hamilton-Jacobi-Bellman under the form of Taylor series expansion. Thus the calculations for the determination of optimal state feedback are considerably accelerated. The method is initially applied in an example of continuous stirred tank reactor, with non-minimum phase dynamic behavior, with one input, one output and two state variables. Afterwards, it is applied in examples of not isothermal reactor of the same dynamic behavior, three state variables, firstly with one input and one output variables and then with two input and two output variables. Using the symbolic program MAPLE, a code was developed for each case separately, which calculates approximately the optimal feedback laws and designs the optimal responses of the inputs and outputs of each of the systems above, while the corresponding times of implementation of each code are simultaneously recording. Finally, in the case of isothermal reactor, a comparison is made between the proposed and preexisting methods, mainly in the base of the time of implementations and the regulation performance.

The choice of technology for automotive actuators is driven by the need of high power to size ratio. In general, electro-pneumatic actuators are preferred for application around the engine as they are compact, powerful and require simple controlling devices. Specially, Variable Geometry Turbochargers (VGTs) are almost always controlled with electro-pneumatic actuators. This is a challenging application because the VGT is an important part of the engine air path and the latter is responsible for intake and exhaust air quality and exhaust emissions control. With government regulations on vehicle pollutant emissions getting stringent by the year, VGT control requirements have also increased. These regulations and requirements can only be fulfilled with precise dynamic control of the VGT through its actuator. The demands on actuator control include robustness against uncertainty in operating conditions, fast and smooth positioning without vibration, limited number of measurements. Added constraints such as nonlinear dynamic behavior of the actuator, friction and varying aerodynamic forces in the VGT render classical control methods ineffective. These are the main problems that form the core of this thesis.In this work, we have addressed the above mentioned problems, using model based control complemented with robust control methods to overcome operational uncertainties and parametric variations. In the first step, a detailed physical model of an electro-pneumatic actuator has been developed; taking into account the nonlinear characteristics originating from air compressibility and friction. Means to compensate for aerodynamic force have been studied and implemented in the next step. These include model parametric adaptation and one dimensional CFD (Computational Fluid Dynamics) modeling. The complete model has been experimentally validated and a sensitivity analysis has been conducted to identify the parameters which have the greatest impact upon the actuator's behavior. The detailed simulation model has then been simplified to make it suitable for control purposes while keeping its essential behavioral characteristics (i.e. transients and dynamics). Next, robust controllers have been developed around the model for the control objective of accurate actuator positioning in presence of operational uncertainty. An important constraint in commercial actuators is that they provide output feedback only, as they are only equipped with low-cost position sensors. This hurdle has been overcome by introducing observers in the control loop, which estimate other system states from the output feedback. The estimation and control algorithms have been validated in simulation and experimentally on diesel engine test benches.

Hydraulic systems are widely applied in industry for position or force control. However, due to hydraulic system nonlinearities, it is difficult to achieve a precise model valid over a large range of frequencies and movements. The work in this dissertation focuses on a high performance hydraulic test bench which involves three main hydraulic components, i.e. two high performance servovalves, a double rod actuator, and a specific intermediate block connecting the servovalves and actuator. This rig has been designed for testing aerospace or automotive components in real conditions (e.g. wear and ageing effects). The main objectives of this dissertation are first the development of a virtual prototype based on a precise model which is derived from the physical principles and experimental works, and then second the synthesis of several nonlinear control laws of this actuation system in a large operating range with a good robustness to the perturbations. The proposed model based on Bond Graph shows a very good agreement with experimental results not only at low frequencies, but also at high frequencies. Moreover, its performances are improved at high frequencies by introducing the dynamic effects due to the intermediate block. Besides, multivariable and monovariable control strategies, based on respectively the backstepping and the model-free method, are developed and implemented on the test bench. All the control strategies proposed have been validated by simulations and experiments. Results show they lead to better tracking precision and robustness performance compared to the conventional control techniques.

Current submerged science projects such as VENUS and NEPTUNE have revealed the need for small, low-cost and easily deployed underwater remotely operated vehiclemanipulator (ROVM) systems. Unfortunately, existing small remotely operated underwater vehicles (ROV) are not equipped to complete the complex and interactive submerged tasks required for these projects. Therefore, this thesis is aimed at adapting a popular small ROV into a ROVM that is capable of low-cost and time-efficient underwater manipulation. To realize this objective, the coordinated control of ROVM systems is required, which, in the context of this research, is defined as the collection of hardware and software that provides advanced functionalities to small ROVM systems. In light of this, the primary focus of this dissertation is to propose various technical building blocks that ultimately lead to the realization of such a coordinated control system for small ROVMs. To develop such a coordinated control of ROVM systems, it is proposed that ROV and manipulator motion be coordinated optimally and intelligently. With coordination, the system becomes redundant: there are more degrees of freedom (DOF) than required. Hence, the extra DOFs can be used to achieve secondary objectives in addition to the primary end-effector following task with a redundancy resolution scheme. This eliminates the standard practice of holding the ROV stationary during a task and uncovers significant potential in the small ROVM platform. In the proposed scheme, the ROV and manipulator motion is first coordinated such that singular configurations of the manipulator are avoided, and hence dexterous manipulation is ensured. This is done by using the ROV's mobility in an optimal, coordinated manner. Later, to accommodate a more comprehensive set of secondary objectives, a fuzzy based approach is proposed. The method considers the human pilot as the main operator and the fuzzy machine as an artificial assistant pilot that dynamically prioritizes the secondary objectives and then determines the optimal motion. Several model-based control methodologies are proposed for small ROV/ROVM systems to realize the desired motion produced by the redundancy resolution, including an adaptive sliding-mode control, an upper bound adaptive sliding-mode control with adaptive PID layer, and an H∞ sliding-mode control. For the unified system (redundancy resolution and controller), a new human-machine interface (HMI) is designed that can facilitate the coordinated control of ROVM systems. This HMI involves a 6-DOF parallel joystick, and a 3-D visual display and a graphical user interface (GUI) that enables a human pilot to smoothly interact with the ROVM systems. Hardware-in-theloop simulations are carried out to evaluate the performance of the coordination schemes. On the thrust allocation side, a novel fault-tolerant thrust allocation scheme is proposed to distribute forces and moments commanded by the controller over the thrusters. The method utilizes the redundancy in the thruster layout of ROVM systems. The proposed scheme minimizes the largest component of the thrust vector instead of the two-norm, and hence provides better manoeuvrability. In the first phase of implementation, a small inspection-class ROV, a Saab-Seaeye Falcon™ ROV, is adopted. To improve the navigation, a navigation skid is designed that contains a Doppler Velocity Log, a compass, an inertial measurement unit, and acoustic position data. The sensor data is blended using an Extended Kalman Filter. The developed ROV system uses the upper bound adaptive sliding-mode control with adaptive PID layer. The theoretical and practical results illustrate that the proposed tools can transform, a small, low-cost ROVM system into a highly capable, time-efficient system that can complete complex subsea tasks. / Graduate

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 135-144).

Η παρούσα διδακτορική διατριβή εντάσσεται στο πλαίσιο που αφορά στο πεδίο ελέγχου συστημάτων ισχύος και ειδικότερα στην εφαρμογή προηγμένων μεθόδων στην ανάλυση και τον έλεγχο στρεφόμενων ηλεκτρικών μηχανών οδηγούμενων από ηλεκτρονικές διατάξεις ισχύος. Ειδικότερα, λαμβάνοντας υπόψη τα ακριβή μη γραμμικά μοντέλα των μετατροπέων ισχύος και των ηλεκτρικών μηχανών, αναλύεται η μορφή και η συμπεριφορά των ολοκληρωμένων συστημάτων που χρησιμοποιούνται για την οδήγηση των μηχανών και αποδεικνύεται ότι τα μοντέλα αυτά μπορούν να περιγραφούν με τη γενική παθητική Hamiltonian μορφή. Οι ηλεκτρονικές διατάξεις ισχύος που μελετώνται είναι ο μετατροπέας ΣΡ/ΣΡ ανύψωσης τάσης και ο τριφασικός μετατροπέας σε λειτουργία ανορθωτή και μετατροπέα, ενώ επίσης μελετώνται οι μηχανές ΣΡ ξένης διέγερσης και με διέγερση σε σειρά καθώς επίσης και η τριφασική επαγωγική μηχανή. Έχοντας αναπτύξει τα πλήρη μοντέλα, προτείνεται ένας νέος μη γραμμικός νόμος ελέγχου κατάλληλος για τη γενική παθητική Hamiltonian μορφή των συστημάτων τα οποία περιλαμβάνουν διακοπτικούς μετατροπείς ισχύος. Μια εκτενής μη γραμμική μαθηματική ανάλυση αποδεικνύει ότι ο προτεινόμενος νόμος ελέγχου εγγυάται ευστάθεια και σύγκλιση στο επιθυμητό σημείο ισορροπίας για το σύστημα κλειστού βρόχου. Ο έλεγχος αυτός εφαρμόζεται για τον έλεγχο κινητήρων ΣΡ οδηγούμενων από μετατροπέα ΣΡ/ΣΡ ανύψωσης τάσης καθώς και στην τριφασική επαγωγική μηχανή. Η ανάλυση και η εφαρμογή του ελέγχου οδηγεί στην ανάγκη για επεκτάσεις στη μορφή του ώστε να αυξηθεί η σθεναρότητά του ως προς τις αρχικές συνθήκες, να βελτιωθεί η μεταβατική του συμπεριφορά και να εφαρμοστεί κατάλληλα σε τριφασικούς μετατροπείς ισχύος ώστε να εγγυάται συγκεκριμένες λειτουργίες όπως γραμμική διαμόρφωση. Με την εφαρμογή του ελέγχου στην επαγωγική μηχανή, προτείνεται μια πλήρης σχεδίαση που λειτουργεί είτε βασιζόμενη στη λογική του προσανατολισμένου πεδίου, είτε πλήρως ανεξάρτητα από αυτή, ενώ μελετάται και η συμπεριφορά του σε καταστάσεις εξασθένησης πεδίου. Τέλος, η λογική του ελέγχου επιβεβαιώνεται σε ένα σύστημα ανεμογεννήτριας συνδεδεμένης στο δίκτυο μέσω πλήρους συστήματος μετατροπέων ισχύος με διασύνδεση συνεχούς ρεύματος. Σε όλες τις περιπτώσεις παρουσιάζονται προσομοιώσεις και κατά το δυνατό πειραματικά αποτελέσματα μέσω κατάλληλων εργαστηριακών διατάξεων. / The present PhD dissertation is addressed in the research field of control of power systems and more precisely in providing advanced methods for the analysis and control of electrical machines driven by power devices. Particularly, taking into account the accurate nonlinear models of the power converters and the electrical machines, the structure and the behavior of the complete models used for machine driving are analyzed based on the generalized Hamiltonian-passive form. The power converters discussed are the DC/DC boost converter and the three-phase power converter used as a rectifier or an inverter, while the separately-excited and the series-connected DC motors along with the three-phase induction machine are studied as well. After providing the complete dynamic models, a new nonlinear control scheme suitable for the generalized Hamiltonian-passive systems with switching devices is proposed. Using an extended mathematical analysis, it is proven that the proposed controller guarantees stability and convergence to the desired equilibrium for the closed-loop system. The proposed control application is tested for DC drive systems fed by DC/DC boost converters as well as for induction motor systems fed by AC/DC/AC converters. The control analysis and application leads to the extension of the control structure in order to increase the robustness with respect to the initial conditions, to improve the transient performance and to be suitably applied in three-phase power converter systems, guaranteeing simultaneously certain operating constraints such as linear modulation. For the case of the induction motor control, a complete form of the controller is proposed that acts either in the frame of field-orientation or independently from it, while the controller is also studied in field-weakening conditions. Finally, the controller performance is studied in a wind generating system connected to the grid through a full-scale power converter. In all cases, simulation results are presented while experimental results are provided where possible by using suitable laboratory testbeds.

Orientador: Cláudio Kitano / Resumo: Este trabalho apresenta um estudo teórico e experimental de um sistema de controle não linear baseado em estrutura variável e modos deslizantes desenvolvido para interferômetro de dois feixes. O sistema proposto apresenta alta precisão, robustez e, além disso, é simples e de baixo custo, aumentando a capacidade de medição para diferentes aplicações de sensores interferométricos. Comparado a outras técnicas de controle aplicadas a interferometria óptica, esta técnica apresenta importantes vantagens e leva em consideração a característica não linear do interferometro, aumentando seu poder de medição. Consequentemente, um circuito de reset não é necessário, o interferometro pode trabalhar em ambientes com grandes perturbações, a montagem e ajuste dos parâmetros é mais simples (fácil implementação), com simples configuração e custo efetivo, atingindo alta robustez e acurácia. Comparado as técnicas de demodulação baseado no espectro do sinal (J1..J4), o sistema proposto tem faixa dinâmica e resolução maiores, podendo medir atraso no tempo e operar com formas de onda arbitrárias. Além disso, aperfeiçoa os métodos de demodulação temporais aumentando a precisão para sinais de baixa amplitude, mantendo a condição de quadratura (ponto máximo de sensibilidade) e, portanto, elimina o efeito do desvanecimento do sinal, mesmo diante de grandes perturbações ao redor do sistema como, vibrações, variações de temperatura e correntes de ar. A estabilidade do sistema linearizado foi estudada atr... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work presents the theoretical and experimental study of a nonlinear control system designed for two beam optical interferometry based on variable structure and sliding modes. The proposed system presents high accuracy, robustness and, furthermore, is simple and low cost, increasing the measurement capability for different applications of interferometric sensors. Compared with other control techniques applied in optical interferometry, this control technique presents important features and takes in account the nonlinear characteristic of the interferometer, increasing its measurement capability. Consequently, a reset circuit is not necessary, the interferometer can work in harsh environments, the assembly and adjustment of the parameters is simpler (easy implementation), with simple setup and the effective cost, achieving high robustness and accuracy. Regarding demodulation techniques based on signal spectrum (J1..J4), the proposed system has a higher dynamic range, resolution, can measure time delay and operate with arbitrary signal waveforms. Also, it improves the temporal demodulation methods increasing the accuracy for small amplitude signals, maintaining the quadrature condition (maximum point of sensitivity) and, therefore, eliminates the effect of signal fading, even under strong external disturbances around the interferometer setup such as vibration, temperature variation and air current flow. The stability of the linearized system was studied through the Lyapunov... (Complete abstract click electronic access below) / Doutor

Avec la forte augmentation actuelle et future du trafic aérien, les questions relatives à la capacité, la sécurité et les effets environnementaux du transport aérien vont se poser de façon chaque fois plus critique. L'objectif général de cette thèse est de contribuer à l'amélioration de l'opération et de l'organisation du trafic aérien dans cette perspective de croissance. Le premier objectif spécifique de cette thèse est de faire la synthèse d'une loi de commande permettant aux avions de transport de suivre avec précision une trajectoire 3D+T. Le deuxième objectif spécifique de cette thèse est d'introduire une organisation particulière des corridors aériens, les airstreams, compatible avec la loi de guidage développée et permettant d'utiliser au mieux la capacité du corridor. Ainsi dans une première étape est introduite la dynamique de guidage des avions de transport, ainsi que les systèmes de guidage et de gestion du vol des avions modernes. Ensuite les principaux éléments de l'organisation de la gestion et du contrôle du trafic aérien sont introduits. La loi de guidage 3D+T est développée, simulée et ses performances sont analysées. L'étude d'une manœuvré de changement de voie dans un airstream est alors menée et mise en œuvre dans le cadre de la gestion du trafic à l'intérieur de celui-ci. Finalement les conclusions et perspectives de cette étude sont présentées / With the increase in air traffic, surely a question of flight efficiency (delays), environment impact and safety arise. This calls for improvements in accuracy of spatial and temporal trajectory tracking. The first main objective of this thesis is to contribute to the synthesis of a space-indexed nonlinear guidance control law for transportation aircraft presenting enhanced tracking performances and to explore the performances and feasibility of a flight guidance control law which is developed based on a space-indexed reference to track a 3D+T reference trajectory using nonlinear dynamic inversion control. The proposed guidance control law present reduced tracking errors and able to meet more easily overfly time constraints. Before presenting the main approaches for the design of the 3D+T guidance control laws; the modern flight guidance and flight dynamics of transportation aircraft, including explicitly wind components are first introduced. Then, a description of the current and modern air traffic organization including the organization of air traffic in high density flow will be shown and this will lead to a description of the Airstreams concept. This proposed concept is to organize main traffic flows in congested airspace along airstreams which are characterized by a three dimensional (3D) common reference track (ASRT). Finally, a scenario to perform basic maneuvers inside the airstream following a 3D+T trajectory using a common space-indexed will be developed and will be used to illustrate the traffic management along an airstream.

Made available in DSpace on 2014-06-11T19:28:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-05Bitstream added on 2014-06-13T20:08:53Z : No. of bitstreams: 1 arbex_hc_me_bauru.pdf: 6292419 bytes, checksum: 8c3b08ad3eb377db975bacb303c4ceda (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O propósito deste trabalho foi estudar as não linearidades na dinâmica de sistemas mecânicos e eletromecânicos. Entre eles inclui-se um corpo em levitação. As não linearidades levam o movimento da estrutura para o Efeito Sommerfeld. Por este fato, o trabalho do motor fica próximo ou na frequência de ressonância. Quando a estrutura atinge a condição de ressonância, a melhor parte da energia é consumida para gerar vibrações de grande amplitude sem nenhuma mudança sensível na frequência do motor. Neste trabalho, foi verificado o fenômeno para alguns sistemas não ideais inclusive o sistema com levitação magnética, discutindo uma forma de conduzir o sistema à condição de ressonância e evitar o absorvedor de energia que ocorre com o efeito Sommerfeld / This paper studies the nonlinearities in dynamics of mechanics and electro mechanics non ideal systems. One of them is a magnetically levitated body. These nonlinearities lead the motion of the structure to the Sommerfeld Effect. For this reason the motor's near or in resonance frequency. When the structure achieves resonance condition, the best part of the energy is consumed to generate large amplitude vibration, with no sensitive change in the motor frequency. In this paper, is checked whether the phenomenon in some non ideal systems and also, if occurs with magnetic levitation. Will be discussed how to drive the system to ressonance condition and to avoid the energy sink that occurs with the Sommerfeld effect