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Papageorgiou, Christakis. "Robustness analysis of nonlinear dynamic inversion control laws for flight control applications." Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/272063.
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Pfeiffer, Celaya Carlos Fernando. "Analysis and design of heterogeneous control laws for nonlinear chemical processes /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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CASSARO, MARIO. "Model Reference Adaptive Control Laws: Application to Nonlinear Aeroelastic Systems." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2605774.
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Nonlinear Aeroelastic Control has been a research topic of great interest for
the past few decades. Dierent approaches has been attempted aiming to obtain
better accuracy in the model dynamics description and better control
performance. As far as the aeroelastic mathematical model is concerned,
the scientic world converged in the use of a bi-dimension, two degree of
freedom, plunging and pitching, wing section model, of which the bigger
advantages are to be reproducible experimentally with an appropriate wind
tunnel apparatus and to allow LCO (Limit Cycle Oscillation) exhibition
at low values of wind speed, facilitating parametric studies of the nonlinear
aeroelastic system and its control architecture. A parametric analysis
of the linearized system, typical of aircraft
ight dynamic studies, is employed
to verify and validate the model dynamic properties dependency,
focusing in particular to the eect of stiness reduction as means of failure
simulation. In fact, despite of the recent years
ourishing literature
on aeroelastic adaptive controls, there is a noted lack of robustness and
sensitivity analysis with respect to structural proprieties degradation which
might be associated with a structural failure. Structural mode frequencies
and aeroelastic response, including Limit Cycle Oscillations (LCOs) characteristics,
are signicantly aected by changes in stiness. This leads to
a great interest in evaluating and comparing the adaptation capabilities
of dierent control architectures subjected to large plant uncertainties and
unmodeled dynamics. Motivated by the constantly increasing diusion of
the new L
adaptive control theory, developed for the control of uncertain
non-autonomous nonlinear systems, and by the fact that its application to
aeroelasticity is in its infancy, a deep investigation of this control scheme
properties and performance drew our attention. The new control theory
is conceptually similar to the Model Reference Adaptive Control (MRAC)
theory to which has often been compared indeed for performance evaluation
purpose. In this dissertation, a comprehensive analysis of the new control
theory is obtained by performance evaluation and comparison of four dierent
control schemes, two MRAC and two L
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, focusing the attention on the
states and control input time response, adaptive law parameters' convergence,
transient evolution and fastness, and robustness in terms of tolerance
of uncertainties in o-design conditions. The objective is pursued by re-
writing the aeroelastic model nonlinear equations of motion in an amenable
form to the development of the four dierent control laws. The control laws
are then derived for the appropriate class of plant which the system belongs
to, and design parameter obtained, when necessary, following the mathematical
formulation of the control theories developers. A simulation model
is employed to carry out the numerical analysis and to outline pros and cons
of each architecture, to obtain as nal result the architecture that better ts
the nonlinear aeroelastic problem proposed. This methodology is used to
guarantee a certain robustness in controlling a novel actuation architecture,
developed for
utter suppression of slender/highly
exible wing, based on
a coordinated multiple spoiler stripe, located at fteen percent of the mean
aerodynamic chord. The control actuation system design, manufacturing
and experimental wind tunnel test is part of the dissertation. Two dierent
experimental setup are developed for two dierent purpose. First, a six-axis
force balance test is carried out to validate the numerical aerodynamic results
obtained during the validation process, and to collect the aerodynamic
coecient date base useful for the development of the simulation model of
the novel architecture. The second experimental apparatus, is a two degree
of freedom, plunging/pitching, system on which the prototyped wing section
is mounted to obtain LCO aeroelastic response during wind tunnel experiment.
The nonlinear aeroelastic mathematical formulation is modied to
take into account of the novel actuation architecture and, coupled with the
more robust MRAC control laws derived for the previous model, serves as
benchmark for properties assessment of the overall architecture, for
utter
suppression. The novel control actuation architecture proposed, is successfully
tested in wind tunnel experimentation conrming the validity of the
proposed solution. This dissertation provides a step forward to the denition
of certain MRAC control schemes properties, and together provides a
novel actuation solution for
utter suppression which demonstrates to be a
viable alternative to classical leading and/or trailing-edge
ap architecture or to be used as redundancy to them.
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Keimer, Alexander [Verfasser], and Günter [Akademischer Betreuer] Leugering. "Optimal control of nonlinear nonlocal conservation laws on networks / Alexander Keimer. Gutachter: Günter Leugering." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2014. http://d-nb.info/1075477476/34.
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Frenzel, David [Verfasser]. "Weighted Essentially Non-Oscillatory Schemes in Optimal Control Problems Governed by Nonlinear Hyperbolic Conservation Laws / David Frenzel." München : Verlag Dr. Hut, 2020. http://d-nb.info/1219476986/34.
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Marrekchi, Hamadi. "Dynamic compensators for a nonlinear conservation law." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-05042006-164530/.
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Filippo, Marco. "Stabilizing nonlinear model predictive control in presence of disturbances and off - line approximations of the control law." Doctoral thesis, Università degli studi di Trieste, 2011. http://hdl.handle.net/10077/4519.
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2009/2010<br>One of the more recent and promising approaches to control is the Receding Horizon one. Due to its intrinsic characteristics, this methodology, also know as Model Predictive Control, allows to easily face disturbances and model uncertainties: indeed at each sampling instant the control action is recalculated on the basis of the reached state (closed loop). More in detail, the procedure consists in the minimization of an adequate cost function with respect to a control input sequence; then the first element of the optimal sequence is applied. The whole procedure is then continuously reiterated.
In this thesis, we will focus in particular on robust control of constrained systems. This is motivated by the fact that, in practice, every real system is subjected to uncertainties, disturbances and constraints, in particular on state and input (for instance, plants can work without being damaged only in a limited set of configurations and, on the other side, control actions must be compatible with actuators' physical limits).
With regard to the first aspect, maintaining the closed loop stability even in presence of disturbances or model mismatches can result in an essential strategy: moreover it can be exploited in order to design an approximate stabilizing controller, as it will be shown. The control input values are obtained recurring to a Nearest Neighbour technique or, in more favourable cases, to a Neural Network based approach to the exact RH law, which can be then calculated off line: this implies a strong improvement related to the applicability of MPC policy in particular in terms of on line computational burden. The proposed scheme is capable to guarantee stability even for systems that are not stabilizable by means of a continuous feedback control law.
Another interesting framework in which the study of the influence of uncertainties on stability can lead to significant contributions is the networked MPC one. In this case, due to the absence of physical interconnections between the controller and the systems to be controlled, stability can be obtained only taking into account of the presence of disturbances, delays and data losses: indeed this kind of uncertainties are anything but infrequent in a communication network. The analysis carried out in this thesis regards interconnected systems and leads to two distinct procedures, respectively stabilizing the linear systems with TCP protocol and nonlinear systems with non-acknowledged protocol. The core of both the schemes resides in the online solution of an adequate reduced horizon optimal control problem.<br>Una delle strategie di controllo emerse più recentemente, più promettenti e di conseguenza più studiate negli ultimi anni è quella basata sull'approccio Receding Horizon. Grazie alle caratteristiche che contraddistinguono questa tecnica, cui si fa spesso riferimento anche col nome di Model Predictive Control, risulta piuttosto agevole trattare eventuali disturbi e incertezze di modellazione; tale metodo prevede infatti il calcolo di un nuovo ingresso di controllo per ciascun istante di campionamento, in seguito alla minimizzazione ad ogni passo di un'opportuna funzione di costo rispetto ad una sequenza di possibili futuri ingressi, inizializzata sulla base del valore dello stato del sistema all'istante considerato. Il controllo è dato dal primo elemento di tale sequenza ottima; tutto questo viene continuamente ripetuto, il che comporta un aggiornamento costante del segnale di controllo. Gli inconvenienti di questa tecnica risiedono nelle elevate risorse computazionali e nei tempi di calcolo richiesti, così da ridurne drasticamente l'applicabilità specie nel caso di sistemi con elevata dinamica.
In questa tesi ci si concentrerà sulle caratteristiche di robustezza del controllore: l'importanza di quest'analisi risiede nel fatto che ogni sistema reale è soggetto a incertezze e disturbi di varia origine cui bisogna far fronte durante le normali condizioni di funzionamento. Inoltre, la capacità di gestire errori di modellazione, come si vedrà, può essere sfruttata per ottenere un notevole incremento delle prestazioni nella stima del valore da fornire in ingresso all'impianto: si tratta di ripartire l'errore complessivo in modo da garantirsi dei margini che consentano di lavorare con un'approssimazione della legge di controllo, come specificato più avanti.
In tutto il lavoro si considereranno sistemi vincolati: l'interesse per questa caratteristica dipende dal fatto che nella pratica vanno sempre tenuti in considerazione eventuali vincoli su stato e ingressi: basti pensare al fatto che ogni impianto è progettato per lavorare solo all'interno un determinato insieme di configurazioni, determinato ad esempio da vincoli fisici su attuatori, sensori e così via: non riporre sufficiente attenzione in tali restrizioni può risultare nel danneggiamento del sistema di controllo o dell'impianto stesso.
Le caratteristiche di stabilità di un sistema controllato mediante MPC dipendono in modo determinante dalla scelta dei parametri e degli attributi della funzione di costo da minimizzare; nel seguito, con riferimento al caso dei sistemi non lineari, saranno forniti suggerimenti e strumenti utili in tal senso, al fine di ottenere la stabilità anche in presenza di disturbi (che si assumeranno opportunamente limitati). Successivamente tale robustezza verrà sfruttata per la progettazione di controllori stabilizzanti approssimati: si dimostrerà infatti che, una volta progettato adeguatamente il sistema di controllo “esatto” basato su approccio RH e conseguentemente calcolati off-line i valori ottimi degli ingressi su una griglia opportunamente costruita sul dominio dello stato, il ricorso a una conveniente approssimazione di tali valori non compromette le proprietà di stabilità del sistema complessivo, che continua per di più a mantenere una certa robustezza. Da notare che ciò vale anche per sistemi non stabilizzabili mediante legge di controllo feedback continua: la funzione approssimante può essere ottenuta in questo caso con tecniche di tipo Nearest Neighbour; qualora invece la legge di controllo sia sufficientemente regolare si potrà far ricorso ad approssimatori smooth, quali ad esempio le reti neurali. Tutto ciò comporta un notevole miglioramento delle prestazioni del controllore RH sia dal punto di vista del tempo di calcolo richiesto che (nel secondo caso) della memoria necessaria ad immagazzinare i parametri del controllore, risultando nell'applicabilità dell'approccio basato su MPC anche al caso di sistemi con elevata dinamica.
Un altro ambito in cui lo studio dell'influenza delle incertezze e dei disturbi sulla stabilità richiede una notevole attenzione è quello dei sistemi networked; anche in questo caso il ricorso all'MPC può portare a ottimi risultati di stabilità robusta, a patto di individuare un' opportuna struttura per il sistema complessivo ed effettuare scelte adeguate per il problema di ottimizzazione. In particolare, si considererà il caso di trasmissione di dati tra un controllore
centralizzato e le varie parti dell'impianto in assenza di collegamento fisico diretto. Lo studio della stabilità dovrà allora tenere in considerazione la presenza di perdite di pacchetti o ritardi di trasmissione, condizioni tutt'altro che infrequenti per le reti.
Saranno quindi proposte due distinte procedure, che si dimostreranno essere in grado di garantire robustezza a sistemi rispettivamente lineari comunicanti con protocolli di tipo TCP e non lineari in presenza di protocolli UDP. Questo secondo caso è senz'altro il più complesso ma allo stesso tempo il più concreto tra i due. Il nucleo del controllo è ancora basato su una tecnica MPC, ma stavolta il controllore è chiamato a risolvere il problema di ottimizzazione su un orizzonte “ridotto”, che consente la gestione dei ritardi e di eventuali perdite di pacchetto su determinati canali. La lunghezza dell'orizzonte dipenderà dalla presenza o meno dei segnali di ricezione del pacchetto (acknowledgement).<br>XXIII Ciclo<br>1977
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Hakala, Tim. "Settling-Time Improvements in Positioning Machines Subject to Nonlinear Friction Using Adaptive Impulse Control." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/1061.
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A new method of adaptive impulse control is developed to precisely and quickly control the position of machine components subject to friction. Friction dominates the forces affecting fine positioning dynamics. Friction can depend on payload, velocity, step size, path, initial position, temperature, and other variables. Control problems such as steady-state error and limit cycles often arise when applying conventional control techniques to the position control problem. Studies in the last few decades have shown that impulsive control can produce repeatable displacements as small as ten nanometers without limit cycles or steady-state error in machines subject to dry sliding friction. These displacements are achieved through the application of short duration, high intensity pulses. The relationship between pulse duration and displacement is seldom a simple function. The most dependable practical methods for control are self-tuning; they learn from online experience by adapting an internal control parameter until precise position control is achieved. To date, the best known adaptive pulse control methods adapt a single control parameter. While effective, the single parameter methods suffer from sub-optimal settling times and poor parameter convergence. To improve performance while maintaining the capacity for ultimate precision, a new control method referred to as Adaptive Impulse Control (AIC) has been developed. To better fit the nonlinear relationship between pulses and displacements, AIC adaptively tunes a set of parameters. Each parameter affects a different range of displacements. Online updates depend on the residual control error following each pulse, an estimate of pulse sensitivity, and a learning gain. After an update is calculated, it is distributed among the parameters that were used to calculate the most recent pulse. As the stored relationship converges to the actual relationship of the machine, pulses become more accurate and fewer pulses are needed to reach each desired destination. When fewer pulses are needed, settling time improves and efficiency increases. AIC is experimentally compared to conventional PID control and other adaptive pulse control methods on a rotary system with a position measurement resolution of 16000 encoder counts per revolution of the load wheel. The friction in the test system is nonlinear and irregular with a position dependent break-away torque that varies by a factor of more than 1.8 to 1. AIC is shown to improve settling times by as much as a factor of two when compared to other adaptive pulse control methods while maintaining precise control tolerances.
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Bouadi, Hakim. "Contribution to flight control law design and aircraft trajectory tracking." Thesis, Toulouse, INSA, 2013. http://www.theses.fr/2013ISAT0001/document.
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Compte tenu de la forte croissance du trafic aérien aussi bien dans les pays émergents que dans les pays développés soutenue durant ces dernières décennies, la satisfaction des exigences relatives à la sécurité et à l’environnement nécessite le développement de nouveaux systèmes de guidage. L’objectif principal de cette thèse est de contribuer à la synthèse d’une nouvelle génération de lois de guidage pour les avions de transport présentant de meilleures performances en terme de suivi de trajectoire. Il s’agit en particulier d’évaluer la faisabilité et les performances d’un système de guidage utilisant un référentiel spatial. Avant de présenter les principales approches utilisées pour le développement de lois de commande pour les systèmes de pilotage et de guidage automatiques et la génération de directives de guidage par le système de gestion du vol, la dynamique du vol d’un avion de transport est modélisée en prenant en compte d’une manière explicite les composantes du vent. Ensuite, l’intérêt de l’application de la commande adaptative dans le domaine de la conduite automatique du vol est discuté et une loi de commande adaptative pour le suivi de pente est proposée. Les principales techniques de commande non linéaires reconnues d’intérêt pour le suivi de trajectoire sont alors analysées. Finalement, une loi de commande référencée dans l’espace pour le guidage vertical d’un avion de transport est développée et est comparée avec l’approche temporelle classique. L’objectif est de réduire les erreurs de poursuite et mieux répondre aux contraintes de temps de passage en certains points de l’espace ainsi qu’à une possible contrainte de temps d’arrivée<br>Safety and environmental considerations in air transportation urge today for the development of new guidance systems with improved accuracy for spatial and temporal trajectory tracking.The main objectives of this thesis dissertation is to contribute to the synthesis of a new generation of nonlinear guidance control laws for transportation aircraft presenting enhanced trajectory tracking performances and to explore the feasibility and performances of a flight guidance system developed within a space-indexed reference with the aim of reducing tracking errors and ensuring the satisfaction of overfly time constraints as well as final arrival time constraint. Before presenting the main approaches for the design of control laws for autopilots and auto-guidance systems devoted to transport aircraft and the way current Flight Management Systems generates guidance directives, flight dynamics of transportation aircraft, including explicitly the wind components, are presented. Then, the interest for adaptive flight control is discussed and a self contained adaptive flight path tracking control for various flight conditions taking into account automatically the possible aerodynamic and thrust parametric changes is proposed. Then, the main recognized nonlinear control approaches suitable for trajectory tracking are analyzed. Finally an original vertical space-indexed guidance control law devoted to aircraft trajectory tracking is developed and compared with the classical time-indexed approach
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Junca, Stéphane. "Oscillating waves for nonlinear conservation laws." Habilitation à diriger des recherches, Université Nice Sophia Antipolis, 2013. http://tel.archives-ouvertes.fr/tel-00845827.
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The manuscript presents my research on hyperbolic Partial Differential Equations (PDE), especially on conservation laws. My works began with this thought in my mind: ''Existence and uniqueness of solutions is not the end but merely the beginning of a theory of differential equations. The really interesting questions concern the behavior of solutions.'' (P.D. Lax, The formation and decay of shock waves 1974). To study or highlight some behaviors, I started by working on geometric optics expansions (WKB) for hyperbolic PDEs. For conservation laws, existence of solutions is still a problem (for large data, $L^\infty$ data), so I early learned method of characteristics, Riemann problem, $BV$ spaces, Glimm and Godunov schemes, \ldots In this report I emphasize my last works since 2006 when I became assistant professor. I use geometric optics method to investigate a conjecture of Lions-Perthame-Tadmor on the maximal smoothing effect for scalar multidimensional conservation laws. With Christian Bourdarias and Marguerite Gisclon from the LAMA (Laboratoire de \\ Mathématiques de l'Université de Savoie), we have obtained the first mathematical results on a $2\times2$ system of conservation laws arising in gas chromatography. Of course, I tried to put high oscillations in this system. We have obtained a propagation result exhibiting a stratified structure of the velocity, and we have shown that a blow up occurs when there are too high oscillations on the hyperbolic boundary. I finish this subject with some works on kinetic équations. In particular, a kinetic formulation of the gas chromatography system, some averaging lemmas for Vlasov equation, and a recent model of a continuous rating system with large interactions are discussed. Bernard Rousselet (Laboratoire JAD Université de Nice Sophia-Antipolis) introduced me to some periodic solutions related to crak problems and the so called nonlinear normal modes (NNM). Then I became a member of the European GDR: ''Wave Propagation in Complex Media for Quantitative and non Destructive Evaluation.'' In 2008, I started a collaboration with Bruno Lombard, LMA (Laboratoire de Mécanique et d'Acoustique, Marseille). We details mathematical results and challenges we have identified for a linear elasticity model with nonlinear interfaces. It leads to consider original neutral delay differential systems.
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Aceves, Alejandro Borbolla. "Snell's laws at the interface between nonlinear dielectrics." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184467.
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A theory is presented which describes the global reflection and transmission characteristics of a self-focused channel propagating at an oblique angle of incidence to an interface separating two or more self-focusing nonlinear dielectric media. A complete characterization of the different behavior of the channel is given in the proper parameter space. In the dominant region, the nonlinear wavepacket representing the self-focused channel is represented as an equivalent particle moving in an equivalent potential. The dynamics of the particle is described by Newton's equations of motion, with the asymptotic propagation paths of the channel being read off from the associated phase planes of the equivalent potential. This theory provides therefore, the nonlinear Snell's Laws of refleciton or transmission since the particle dynamics gives the critical angle of total reflection and in the case of transmission, the corresponding angle of transmission. This theory also gives the stability characteristics of nonlinear surface waves, which had only been partially established in the past through numerical simulations. Finally, some applications of the theory are presented such as the design of an all-optical power adjustable spatial scanning element and an all optical switch. Extensions of the theory to waveguides with multiple interfaces are also given and possible new directions are also suggested.
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Manchanda, Sunil. "Nonlinear process control." Thesis, University of Newcastle Upon Tyne, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336269.
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Sriniwas, Ganti Ravi. "Nonlinear model predictive control." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/10267.
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Rysdyk, Rolf T. "Adaptive nonlinear flight control." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/12108.
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Fahmy, Sherif Farid Fahmy. "Nonlinear robust H∞ control." Thesis, University of Sheffield, 2006. http://etheses.whiterose.ac.uk/14887/.
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A new theory is proposed for the full-information finite and infinite horizontime robust H∞ control that is equivalently effective for the regulation and/or tracking problems of the general class of time-varying nonlinear systems under the presence of exogenous disturbance inputs. The theory employs the sequence of linear-quadratic and time-varying approximations, that were recently introduced in the optimal control framework, to transform the nonlinear H∞ control problem into a sequence of linearquadratic robust H∞ control problems by using well-known results from the existing Riccati-based theory of the maturing classical linear robust control. The proposed method, as in the optimal control case, requires solving an approximating sequence of Riccati equations (ASRE), to find linear time-varying feedback controllers for such disturbed nonlinear systems while employing classical methods. Under very mild conditions of local Lipschitz continuity, these iterative sequences of solutions are known to converge to the unique viscosity solution of the Hamilton-lacobi-Bellman partial differential equation of the original nonlinear optimal control problem in the weak form (Cimen, 2003); and should hold for the robust control problems herein. The theory is analytically illustrated by directly applying it to some sophisticated nonlinear dynamical models of practical real-world applications. Under a r -iteration sense, such a theory gives the control engineer and designer more transparent control requirements to be incorporated a priori to fine-tune between robustness and optimality needs. It is believed, however, that the automatic state-regulation robust ASRE feedback control systems and techniques provided in this thesis yield very effective control actions in theory, in view of its computational simplicity and its validation by means of classical numerical techniques, and can straightforwardly be implemented in practice as the feedback controller is constrained to be linear with respect to its inputs.
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Wu, Jian. "Numerical Smoothness of ENO and WENO Schemes for Nonlinear Conservation Laws." Bowling Green State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1307575652.
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Zhang, Zhengru. "Moving mesh methods for convection-dominated equations and nonlinear conservation laws." HKBU Institutional Repository, 2003. http://repository.hkbu.edu.hk/etd_ra/512.
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Sampathnarayanan, Balaji. "Analysis and Design of Stable and Optimal Energy Management Strategies for Hybrid Electric Vehicles." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1357079732.
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Coclite, Giuseppe Maria. "Control Problems for Systems of Conservation Laws." Doctoral thesis, SISSA, 2003. http://hdl.handle.net/20.500.11767/4262.
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Marson, Andrea. "Approximation, Stability and Control for Conservation Laws." Doctoral thesis, SISSA, 1999. http://hdl.handle.net/20.500.11767/4379.
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Zhong, Weigang. "Entropy stable approximations of nonlinear conservations [sic] laws and related fluid equations." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/7296.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.<br>Thesis research directed by: Applied Mathematics and Scientific Computation Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Nevistić, Vesna. "Constrained control of nonlinear systems." Online version, 1997. http://bibpurl.oclc.org/web/26200.
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Rutherford, Simon John. "Modelling driver nonlinear steering control." Thesis, University of Cambridge, 2007. https://www.repository.cam.ac.uk/handle/1810/252062.
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Tatlicioglu, Enver. "Control of nonlinear mechatronic systems." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1193079994/.
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Grönberg, Fredrik. "Crowd Control of Nonlinear Systems." Thesis, KTH, Reglerteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-138438.
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We study a multi-agent system in R2 where agents have unicycle dynamics with time varying speed and control inputs corresponding to acceleration and angular velocity. The system has a dynamic communication topology based on proximity. We propose a novel decentralized control algorithm derived from a double integrator model using a pairwise potential function. By using an energy function we show that a leaderless system converges to a set where connected agents have equal direction and velocity and potential contributions to the control action cancel each other out. The concept of formation density is defined and studied by numerical simulation. We find a relation between parameters of the controller and the system that makes the system converge to a formation with low density, corresponding to agents being at appropriate distances from each other, also when agents are not restricted to communicating only with their closest neighbors. The algorithm is tested for a system with leaders and properties of this system are investigated numerically. The results confirm that the proportion of leaders needed to guide a certain proportion of the agent in average is nonlinear and decreasing with respect to the number of agents.
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Rong, Q. "Multiple-model based nonlinear control." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412562.
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Samavat, Mohmoud. "Robust control of nonlinear systems." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327647.
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Wlassich, John J. (John James). "Nonlinear force feedback impedance control." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/15032.
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Bedrossian, Nazareth Sarkis. "Nonlinear control using linearizing transformations." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/27998.
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Ashour, Osama Naim. "Nonlinear Control of Plate Vibrations." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/26266.
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A nonlinear active vibration absorber to control the vibrations of plates is investigated. The absorber is based on the saturation phenomenon associated with dynamical systems with quadratic nonlinearities and a two-to-one internal resonance. The technique is implemented by coupling a second-order controller with the plate's response through a sensor and an actuator. Energy is exchanged between the primary structure and the controller and, near resonance, the plate's response saturates to a small value.
Numerical as well as experimental results are presented for a cantilever rectangular plate. For numerical studies, finite-element methods as well as modal analysis are implemented. The commercially available software ABAQUS is used in the finite-element analysis together with a user-provided subroutine to model the controller. For the experimental studies, the plate is excited using a dynamic shaker. Strain gages are used as sensors, while piezoelectric ceramic patches are used as actuators. The control technique is implemented using a dSPACE digital signal processing board and a modeling software (SIMULINK). Both numerical and experimental results show that the control strategy is very efficient.
A numerical study is conducted to optimize the location of the actuators on the structure to maximize its controllability. In this regard, the control gain is maximized for the PZT actuators. Furthermore, a more general method is introduced that is based on a global measure of controllability for linear systems.
Finally, the control strategy is made adaptive by incorporating an efficient frequency-measurement technique. This is validated by successfully testing the control strategy for a non-conventional problem, where nonlinear effects hinder the application of the non-adaptive controller.<br>Ph. D.
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Niemoczynski, Bogdan. "Nonlinear Control of Magnetic Signatures." Master's thesis, Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/360321.
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Electrical Engineering<br>M.S.E.E.<br>Magnetic properties of ferrite structures are known to cause fluctuations in Earth's magnetic field around the object. These fluctuations are known as the object's magnetic signature and are unique based on the object's geometry and material. It is a common practice to neutralize magnetic signatures periodically after certain time intervals, however there is a growing interest to develop real time degaussing systems for various applications. Development of real time degaussing system is a challenging problem because of magnetic hysteresis and difficulties in measurement or estimation of near-field flux data. The goal of this research is to develop a real time feedback control system that can be used to minimize magnetic signatures for ferrite structures. Experimental work on controlling the magnetic signature of a cylindrical steel shell structure with a magnetic disturbance provided evidence that the control process substantially increased the interior magnetic flux. This means near field estimation using interior sensor data is likely to be inaccurate. Follow up numerical work for rectangular and cylindrical cross sections investigated variations in shell wall flux density under a variety of ambient excitation and applied disturbances. Results showed magnetic disturbances could corrupt interior sensor data and magnetic shielding due to the shell walls makes the interior very sensitive to noise. The magnetic flux inside the shell wall showed little variation due to inner disturbances and its high base value makes it less susceptible to noise. This research proceeds to describe a nonlinear controller to use the shell wall data as an input. A nonlinear plant model of magnetics is developed using a constant to represent domain rotation lag and a gain function to describe the magnetic hysteresis curve for the shell wall. The model is justified by producing hysteresis curves for multiple materials, matching experimental data using a particle swarm algorithm, and observing frequency effects. The plant model is used in a feedback controller and simulated for different materials as a proof of concept.<br>Temple University--Theses
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Ali, Imran. "Spacecraft nonlinear attitude control with bounded control input." Thesis, University of Glasgow, 2010. http://theses.gla.ac.uk/1717/.
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The research in this thesis deals with nonlinear control of spacecraft attitude stabilization and tracking manoeuvres and addresses the issue of control toque saturation on a priori basis. The cascaded structure of spacecraft attitude kinematics and dynamics makes the method of integrator backstepping preferred scheme for the spacecraft nonlinear attitude control. However, the conventional backstepping control design method may result in excessive control torque beyond the saturation bound of the actuators. While remaining within the framework of conventional backstepping control design, the present work proposes the formulation of analytical bounds for the control torque components as functions of the initial attitude and angular velocity errors and the gains involved in the control design procedure. The said analytical bounds have been shown to be useful for tuning the gains in a way that the guaranteed maximum torque upper bound lies within the capability of the actuator and, hence, addressing the issue of control input saturation. Conditions have also been developed as well as the generalization of the said analytical bounds which allow for the tuning of the control gains to guarantee prescribed stability with the additional aim that the control action avoids reaching saturation while anticipating the presence of bounded external disturbance torque and uncertainties in the spacecraft moments of inertia. Moreover, the work has also been extended blending it with the artificial potential function method for achieving autonomous capability of avoiding pointing constraints for the case of spacecraft large angle slew manoeuvres. The idea of undergoing such manoeuvres using control moment gyros to track commanded angular momentum rather than a torque command has also been studied. In this context, a gimbal position command generation algorithm has been proposed for a pyramid-type cluster of four single gimbal control moment gyros. The proposed algorithm not only avoids the saturation of the angular momentum input from the control moment gyro cluster but also exploits its maximum value deliverable by the cluster along the direction of the commanded angular momentum for the major part of the manoeuvre. In this way, it results in rapid spacecraft slew manoeuvres. The ideas proposed in the thesis have also been validated using numerical simulations and compared with results already existing in the literature.
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Kachroo, Pushkin. "Optimal and Feedback Control for Hyperbolic Conservation Laws." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28009.
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This dissertation studies hyperbolic partial differential equations for Conservation Laws motivated by traffic control problems. New traffic models for multi-directional flow in two dimensions are derived and their properties studied. Control models are proposed where the control variable is a multiplicative term in the flux function. Control models are also proposed for relaxation type systems of hyperbolic PDEs. Existence of optimal control for the case of constant controls is presented. Unbounded and bounded feedback control designs are proposed. These include advective, diffusive, and advective-diffusive controls. Existence result for the bounded advective control is derived. Performance of the relaxation model using bounded advective control is analyzed. Finally simulations using Godunov scheme are performed on unbounded and bounded feedback advective controls.<br>Ph. D.
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Horne, Laura Christine 1961. "Norms, laws and the provision of social control." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/288750.
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A society can use two kinds of controls to ensure that individuals comply with its rules. They are legal control and normative control. Legal control refers to punishment of deviant behavior by a legal institution that is supported by taxes. Normative control refers to punishment by individuals themselves who personally take action against a deviant. This research investigates the relationship between these two types of control--specifically, how change in the strength of one control institution affects the strength of the other. A theoretical argument is developed, suggesting two conclusions: (1) cohesive communities with strong normative controls facilitate the growth of strong legal systems; and (2) investment in the legal system, for example, in police and prisons, will weaken normative controls and thus the ability of communities to address social problems like crime in more informal ways. In other words, strong communities contribute to the growth of the legal system which in turn weakens the communities on which it depends. An experiment is conducted to test these and subsidiary hypotheses. In the experiment, subjects interact with each other using computers. They make decisions about sanctioning and about responding to the sanctioning decisions of others. Resulting changes in the strengths of the two types of control are measured.
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Savvidis, Petros. "Nonlinear control : an LPV nonlinear predictive generalised minimum variance perspective." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27947.
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This thesis describes new developments in nonlinear controllers for industrial applications. It first introduces the Nonlinear Generalised Minimum Variance (NGMV) control algorithm, for Linear Parameter Varying systems (LPV). This combines the benefits of the basic NGMV algorithm in dealing with nonlinearities, where a black box input model can be used, and adds an option to also approximate a nonlinear system with an LPV output subsystem. The models can therefore represent LPV systems and characteristics including saturation, discontinuities and time-varying dynamics. The next major contribution is in the nonlinear predictive control algorithms proposed that are also using the LPV model structure. The simplest is the Nonlinear Generalized Predictive Control (NGPC) algorithm that relates to the best known model predictive control law for linear systems. The final predictive control solution is one that may be specialized to either the NGMV or NGPC cases and is therefore the most general. This is referred to as a Nonlinear Predictive Generalized Minimum Variance Controller (NPGMV). When the algorithms use only the LPV structure to approximate the nonlinear system the solutions are particularly simple in unconstrained and constrained versions, and are relatively light computationally for implementation. Three representative industrial design examples have been chosen to validate the algorithms for different Bandwidth (BW) and nonlinear characteristics. All three examples were based on real application problems with company interest. In the first example (small BW) the basic state-space and LPV versions of the algorithm are used for the auto-manoeuvring and dynamic positioning of marine vessel. In this application the parameter variations were representative of wave disturbance changes with sea state, rather than due to approximating nonlinear behaviour. Actuator constraints were considered in the design. In the second industrial example (medium BW) the LPV-NPGMV was implemented for controlling the blade pitch and generator torque of a 5MW offshore wind turbine. The main objective here was to maintain the power produced at the rated value which requires compensation against wind disturbances, so that wind speed is the varying parameter. The LPV-NPGMV controller produced here used a parameterised system model involving the wind speed so that the controller performance changed with wind conditions. Actuator constraints were included and statistical performance assessed. The third example (fast BW) explores the stabilisation of a 2-axis gyroscopic electro-optical turret used in surveillance applications. This application was designed and employed on a real system. Because of the limitations imposed by BW requirements and the memory of the digital controller, only the basic state-space version of the algorithm was possible to implement. The main objective in this problem was to improve the tracking performance around the NADIR singularity point (a discontinuity) in the trajectory. In all three examples the NGMV controllers showed notable improvement in comparison to the baseline controllers without the need for scheduled gains or re-configuration when moving across different operating points.
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Yavuzoglu, Emre. "Steering Laws For Control Moment Gyroscope Systems Used In Spacecraft Attitude Control." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1098441/index.pdf.
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In this thesis, the kinematic properties of Single Gimballed Control Moment Gyroscopes (SGCMGs) are investigated. Singularity phenomenon inherent to them is explained. Furthermore, existing steering laws with their derivations are given.
A novel steering law is developed that may provide singularity avoidance or may be used for quick transition through a singularity with small torque errors. To avoid singularity angular momentum trajectory of the maneuver is to be simulated in advance for the calculation of singularity free gimbal histories. The steering law, besides accurately generating required torques, also pushes the system to follow trajectories closely if there is a small difference between the planned and the realized momentum histories. Thus, it may be used in a feedback system. Also presented are number of approaches for singularity avoidance or quick transition through a singularity. The application of these ideas to the feedback controlled spacecraft is also presented. Existing steering laws and the proposed method are compared through computer simulations. It is shown that the proposed steering law is very effective in singularity avoidance and quick transition through singularities. Furthermore, the approach is demonstrated to be repeatable even singularity is encountered.
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Tjønnås, Johannes. "Nonlinear and Adaptive Dynamic Control Allocation." Doctoral thesis, Norwegian University of Science and Technology, Department of Engineering Cybernetics, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2320.
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<p>This work addresses the control allocation problem for a nonlinear over-actuated time-varying system where parameters a¢ ne in the actuator dynamics and actuator force model may be assumed unknown. Instead of optimizing the control allocation at each time instant, a dynamic approach is considered by constructing update-laws that represent asymptotically optimal allocation search and adaptation. A previous result on uniform global asymptotic stability (UGAS) of the equilibrium of cascaded time-varying systems, is in the thesis shown to also hold for closed (not necessarily compact) sets composed by set-stable subsystems of a cascade. In view of this result, the optimal control allocation approach is studied by using Lyapunov analysis for cascaded set-stable systems, and uniform global/local asymptotic stability is guaranteed for the sets described by; the system dynamics, the optimizing allocation update-law and the adaptive update-law.</p><p>The performance of the proposed control allocation scheme is demon- strated throughout the thesis by simulations of a scaled-model ship manoeuvred at low-speed. Furthermore, the application of a yaw stabilization scheme for an automotive vehicle is presented. The stabilization strategy consists of; a high level module that deals with the vehicle motion control objective (yaw rate reference generation and tracking), a low level module that handles the braking control for each wheel (longitudinal slip control and maximal tyre road friction parameter estimation) and an intermediate level dynamic control allocation module. The control allocation module generates longitudinal slip reference for the low level brake controller and commands front wheel steering angle corrections, such that the actual torque about the yaw axis tends to the desired torque calculated by the high level module. The conditions for uniform asymptotic stability are given and the scheme has been implemented in a realistic nonlinear multi-body vehicle simulation environment. The simulation cases show that the control strategy stabilizes the vehicle in extreme manoeuvres where the nonlinear vehicle yaw dynamics otherwise become unstable in the sense of over- or understeering.</p>
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Karagiannis, Dimitrios. "Nonlinear adaptive control design with applications." Thesis, Imperial College London, 2005. http://hdl.handle.net/10044/1/8320.
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Ali, Shaaban Aerospace Civil & Mechanical Engineering Australian Defence Force Academy UNSW. "Intelligent adaptive control for nonlinear applications." Awarded by:University of New South Wales - Australian Defence Force Academy, 2008. http://handle.unsw.edu.au/1959.4/39185.
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The thesis deals with the design and implementation of an Adaptive Flight Control technique for Unmanned Aerial Vehicles (UAVs). The application of UAVs has been increasing exponentially in the last decade both in Military and Civilian fronts. These UAVs fly at very low speeds and Reynolds numbers, have nonlinear coupling, and tend to exhibit time varying characteristics. In addition, due to the variety of missions, they fly in uncertain environments exposing themselves to unpredictable external disturbances. The successful completion of the UAV missions is largely dependent on the accuracy of the control provided by the flight controllers. Thus there is a necessity for accurate and robust flight controllers. These controllers should be able to adapt to the changes in the dynamics due to internal and external changes. From the available literature, it is known that, one of the better suited adaptive controllers is the model based controller. The design and implementation of model based adaptive controller is discussed in the thesis. A critical issue in the design and application of model based control is the online identification of the UAV dynamics from the available sensors using the onboard processing capability. For this, proper instrumentation in terms of sensors and avionics for two platforms developed at UNSW@ADFA is discussed. Using the flight data from the remotely flown platforms, state space identification and fuzzy identification are developed to mimic the UAV dynamics. Real time validations using Hardware in Loop (HIL) simulations show that both the methods are feasible for control. A finer comparison showed that the accuracy of identification using fuzzy systems is better than the state space technique. The flight tests with real time online identification confirmed the feasibility of fuzzy identification for intelligent control. Hence two adaptive controllers based on the fuzzy identification are developed. The first adaptive controller is a hybrid indirect adaptive controller that utilises the model sensitivity in addition to output error for adaptation. The feedback of the model sensitivity function to adapt the parameters of the controller is shown to have beneficial effects, both in terms of convergence and accuracy. HIL simulations applied to the control of roll stabilised pitch autopilot for a typical UAV demonstrate the improvements compared to the direct adaptive controller. Next a novel fuzzy model based inversion controller is presented. The analytical approximate inversion proposed in this thesis does not increase the computational effort. The comparisons of this controller with other controller for a benchmark problem are presented using numerical simulations. The results bring out the superiority of this technique over other techniques. The extension of the analytical inversion based controller for multiple input multiple output problem is presented for the design of roll stabilised pitch autopilot for a UAV. The results of the HIL simulations are discussed for a typical UAV. Finally, flight test results for angle of attack control of one of the UAV platforms at UNSW@ADFA are presented. The flight test results show that the adaptive controller is capable of controlling the UAV suitably in a real environment, demonstrating its robustness characteristics.
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Lemch, Ekaterina S. "Nonlinear and hierarchical hybrid control systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0032/NQ64600.pdf.
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Maalouf, Elie. "Nonlinear control of wheeled mobile robots." Mémoire, Montréal : École de technologie supérieure, 2005. http://wwwlib.umi.com/cr/etsmtl/fullcit?pMR06031.
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Thèse (M. Ing.)--École de technologie supérieure, Montréal, 2005.<br>"Thesis presented to École de technologie supérieure as a partial requirement to obtain a masters in electrical engineering". Bibliogr.: f. [140]-142. Également disponible en version électronique.
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Nath, Nitendra. "Nonlinear control techniques for robot manipulators." Connect to this title online, 2006. http://etd.lib.clemson.edu/documents/1173994815/.
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Kim, Byoung Soo. "Nonlinear flight control using neural networks." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/12242.
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Chryssochoos, Ioannis. "Optimization based control of nonlinear systems." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399165.
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Zhu, Quan Min. "Identification & control of nonlinear systems." Thesis, University of Warwick, 1989. http://wrap.warwick.ac.uk/62723/.
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This thesis investigates some problems on nonlinear system identification, parameter estimation, and signal processing. Random signal spectral analysis and system frequency response estimation are studied from incomplete time series. Both recursive and direct estimators are presented based on either an unbiased or minimum mean square error criterion. Nonlinear system identification and parameter estimation are studied. A quantisation technique is developed to give a clear geometrical interpretation for structure detection and parameter estimation. A new concept, state amplitude distance between current and previous operating states, is introduced, and results in a Variable Weighted Least Squares (VWLS) algorithm. A modified version makes on-line application possible. Jump resonance is predicted by the VWLS algorithm as one of the applications. Self-tuning controllers, including a nonlinear general predictive controller and a nonlinear deadbeat controller, are designed. A vector backward shift operator is defined to simplify the expression of the Hammerstein model, and is introduced to analyse the general feedback controller design problem for nonlinear plant described by the Hammerstein model. A fast root-solver developed facilitates nonlinear model treatment in on-line applications. Theoretical results are confirmed by simulation studies.
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Zhang, Guoming. "Model reference control for nonlinear plants." Thesis, University of Manchester, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314208.
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Youssef, Ahmed Medhat Mohamed. "Nonlinear predictive flight control system design." Thesis, University of Strathclyde, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401502.
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Bekit, Biniam Weldai. "Robust nonlinear control of robot manipulators." Thesis, King's College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321945.
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Alrashidi, Azizah. "Nonlinear control for non-Newtonian flows." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5777/.
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PDE-constrained optimization is an important area in the field of numerical analysis, with problems arising in a wide variety of applications including optimal design, optimal control and parameter estimation. The aim of such problems is to minimize a functional J(u,d) whilst adhering to constraints posed by a system of partial differential equations (PDE), with u and d used respectively to denote the state and control of the system. In this thesis, we describe the steady-state generalized Stokes equations for incompressible fluids. We proceed to derive the weak formulation of the problem, and show that the resulting system may be written in terms of a mixed formulation of the Stokes problem. Based on this formulation, the problem is discretized through use of the Galerkin finite element method, before investigating control problems based on the generalized Stokes equations, along with numerical experimentation. This work will be used to achieve the main aim of this thesis, namely the exploration and investigation of solution methods for optimal control problems constrained by non- Newtonian flow. Ultimately, an iterative solution method designed for such problems coupled with an appropriate preconditioning strategy will be described and analyzed, and used to produce effective numerical results.
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Sanders, Seth Robert. "Nonlinear control of switching power converters." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14426.
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