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Gil, Gibin. "Hybrid Numerical Integration Scheme for Highly Oscillatory Dynamical Systems." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/306771.
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Computational efficiency of solving the dynamics of highly oscillatory systems is an important issue due to the requirement of small step size of explicit numerical integration algorithms. A system is considered to be highly oscillatory if it contains a fast solution that varies regularly about a slow solution. As for multibody systems, stiff force elements and contacts between bodies can make a system highly oscillatory. Standard explicit numerical integration methods should take a very small step size to satisfy the absolute stability condition for all eigenvalues of the system and the computational cost is dictated by the fast solution. In this research, a new hybrid integration scheme is proposed, in which the local linearization method is combined with a conventional integration method such as the fourth-order Runge-Kutta. In this approach, the system is partitioned into fast and slow subsystems. Then, the two subsystems are transformed into a reduced and a boundary-layer system using the singular perturbation theory. The reduced system is solved by the fourth-order Runge-Kutta method while the boundary-layer system is solved by the local linearization method. This new hybrid scheme can handle the coupling between the fast and the slow subsystems efficiently. Unlike other multi-rate or multi-method schemes, extrapolation or interpolation process is not required to deal with the coupling between subsystems. Most of the coupling effect can be accounted for by the reduced (or quasi-steady-state) system while the minor transient effect is taken into consideration by averaging. In this research, the absolute stability region for this hybrid scheme is derived and it is shown that the absolute stability region is almost independent of the fast variables. Thus, the selection of the step size is not dictated by the fast solution when a highly oscillatory system is solved, in turn, the computational efficiency can be improved. The advantage of the proposed hybrid scheme is validated through several dynamic simulations of a vehicle system including a flexible tire model. The results reveal that the hybrid scheme can reduce the computation time of the vehicle dynamic simulation significantly while attaining comparable accuracy.
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Nersesov, Sergey G. "Nonlinear Impulsive and Hybrid Dynamical Systems." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7147.
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Modern complex dynamical systems typically possess a
multiechelon hierarchical hybrid structure characterized by
continuous-time dynamics at the lower-level units and logical
decision-making units at the higher-level of hierarchy. Hybrid
dynamical systems involve an interacting countable collection of
dynamical systems defined on subregions of the partitioned state
space. Thus, in addition to traditional control systems, hybrid
control systems involve supervising controllers which serve to
coordinate the (sometimes competing) actions of the lower-level
controllers. A subclass of hybrid dynamical systems are impulsive
dynamical systems which consist of three elements, namely, a
continuous-time differential equation, a difference equation, and
a criterion for determining when the states of the system are to
be reset. One of the main topics of this dissertation is the
development of stability analysis and control design for impulsive
dynamical systems. Specifically, we generalize Poincare's
theorem to dynamical systems possessing left-continuous flows to
address the stability of limit cycles and periodic orbits of
left-continuous, hybrid, and impulsive dynamical systems. For
nonlinear impulsive dynamical systems, we present partial
stability results, that is, stability with respect to part of the
system's state. Furthermore, we develop adaptive control framework
for general class of impulsive systems as well as energy-based
control framework for hybrid port-controlled Hamiltonian systems.
Extensions of stability theory for impulsive dynamical systems
with respect to the nonnegative orthant of the state space are
also addressed in this dissertation. Furthermore, we design
optimal output feedback controllers for set-point regulation of
linear nonnegative dynamical systems. Another main topic that has
been addressed in this research is the stability analysis of
large-scale dynamical systems. Specifically, we extend the theory
of vector Lyapunov functions by constructing a generalized
comparison system whose vector field can be a function of the
comparison system states as well as the nonlinear dynamical system
states. Furthermore, we present a generalized convergence result
which, in the case of a scalar comparison system, specializes to
the classical Krasovskii-LaSalle invariant set theorem. Moreover,
we develop vector dissipativity theory for large-scale dynamical
systems based on vector storage functions and vector supply rates.
Finally, using a large-scale dynamical systems perspective, we
develop a system-theoretic foundation for thermodynamics.
Specifically, using compartmental dynamical system energy flow
models, we place the universal energy conservation, energy
equipartition, temperature equipartition, and entropy
nonconservation laws of thermodynamics on a system-theoretic
basis.
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Kawashima, Hiroaki. "Interval-Based Hybrid Dynamical System for Modeling Dynamic Events and Structures." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/68896.
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Sobotka, Marion. "Hybrid dynamical system methods for legged robot locomotion with variable ground contact." [S.l.] : [s.n.], 2007. http://mediatum2.ub.tum.de/doc/619220/document.pdf.
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Etienne, Lucien. "Eléments d'observation et d'estimation pour les systèmes contrôlés en réseaux." Thesis, Cergy-Pontoise, 2016. http://www.theses.fr/2016CERG0853/document.
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Les systèmes de contrôle en réseau sont un champ actif de recherche, où les différentes composantes du réseau sont spatialement distribué et tentent d'atteindre un objectif global. Ils apparaissent naturellement lors l'interaction d'un système piloté par ordinateur avec le monde physique.Avec les systèmes de contrôle en réseau une classe connexe des systèmes est décrit par les systèmes Cyber-physique, où les capacités de calcul embarqué peuvent interagir avec le monde physique.Dans ce travail, nous allons considérer la tâche classique d'observation et d'estimation et étudier les cas où les contraintes induite par le réseau nécessite une adaptation des mécanismes classique d'observation et d'estimation.Dans les système de contrôle en raison de limitation des capteurs (pour des raisons pratiques telles que la réduction des coûts) certains états ou paramètre du système ne sont pas connus. Dans ce contexte, la notion classique d'observabilitéexprime la capacité de déduire de la mesure les valeurs d'intérêt.Premièrement nous considérons le problème de la réduction de l'échantillonnage par l'utilisation de échantillonnage événementiel et ce pour plusieurs classes de systèmes. Ensuite, une procédure d'estimation et de contrôle sera proposé pour résoudre le problème du consensus dans un système multi-agent.Considérant enfin une dynamique de véhicule plus complexe, nous nous concentrons sur l'estimation du coefficient de frottement de la route pour résoudre un problème de suiviNetwork control systems is an active field of study where interacting component spatially distributed try to achieve a global goal. They naturally emerge from the interaction of computer driven mechanism and the physical world.Along with network control system a related class of systems is described by the so called: Cyber-physical systems, where integrated physical computational capabilities can interact.In this work we will consider the classical task of observation and estimation and investigate cases where network induced constraint calls for adapted observation and estimation scheme.In control system due to limitation in sensors ( for practical reason such as cost reduction) all the value of interest (whether the some unmeasured state or unknown parameter)are unknown. The classical notion of observabilityaccount for the ability to deduce from measurement those value of interest.First sampling reduction by use of event trigger will be studied for several class of systems. Then an estimation and control scheme will be establish to solve the problem of consensus in a multi agents system.Finally considering a more complex vehicle dynamic we focus on the estimation of tire road friction coefficient to solve a tracking problem
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OKUMA, Shigeru, Tatsuya SUZUKI, and Eiji KONAKA. "Safety Verification of Material Handling Systems Driven by Programmable Logic Controller : Consideration of Physical Behavior of Plants." Institute of Electronics, Information and Communication Engineers, 2004. http://hdl.handle.net/2237/14987.
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Hashemi, Nastaran. "Exploring the Nonlinear Dynamics of Tapping Mode Atomic Force Microscopy with Capillary Layer Interactions." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28112.
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Central to tapping mode atomic force microscopy is an oscillating cantilever whose tip interacts with a sample surface. The tip-surface interactions are strongly nonlinear, rapidly changing, and hysteretic. We explore numerically a lumped-mass model that includes attractive, adhesive, and repulsive contributions as well as the interaction of the capillary fluid layers that cover both tip and sample in the ambient conditions common in experiment. To accomplish this, we have developed and used numerical techniques specifically tailored for discontinuous, nonlinear, and hysteretic dynamical systems. In particular, we use forward-time simulation with event handling and the numerical pseudo-arclength continuation of periodic solutions. We first use these numerical approaches to explore the nonlinear dynamics of the cantilever. We find the coexistence of three steady state oscillating solutions: (i) periodic with low-amplitude, (ii) periodic with high-amplitude, and (iii) high-periodic or irregular behavior. Furthermore, the branches of periodic solutions are found to end precisely where the cantilever comes into grazing contact with event surfaces in state space corresponding to the onset of capillary interactions and the onset of repulsive forces associated with surface contact. Also, the branches of periodic solutions are found to be separated by windows of irregular dynamics. These windows coexist with the periodic branches of solutions and exist beyond the termination of the periodic solution. We also explore the power dissipated through the interaction of the capillary fluid layers. The source of this dissipation is the hysteresis in the conservative capillary force interaction. We relate the power dissipation with the fraction of oscillations that break the fluid meniscus. Using forward-time simulation with event handling, this is done exactly and we explore the dissipated power over a range of experimentally relevant conditions. It is found that the dissipated power as a function of the equilibrium cantilever-surface separation has a characteristic shape that we directly relate to the cantilever dynamics. We also find that despite the highly irregular cantilever dynamics, the fraction of oscillations breaking the meniscus behaves in a fairly simple manner. We have also performed a large number of forward-time simulations over a wide range of initial conditions to approximate the basins of attraction of steady oscillating solutions. Overall, the simulations show a complex pattern of high and low amplitude periodic solutions over the range of initial conditions explored. We find that for large equilibrium separations, the basin of attraction is dominated by the low-amplitude periodic solution and for the small equilibrium separations by the high-amplitude periodic solution.Ph. D.
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Ibrahim, Faisal. "Vers un outil de simulation de la commande d'un processus dynamique hybride." Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL121N.
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Cette thèse présente une étude de faisabilité de la validation, par simulation de l'ensemble (processus, commande), du cahier des charges du système de commande d'un processus dynamique hybride, après sa formalisation. Elle détaille le problème de la précision de détection des événements, propose une solution et donne les résultats obtenus
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Dreossi, Tommaso. "Calcul d'atteignabilité et synthèse de paramètres pour systèmes dynamiques polynomiaux." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAM096.
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Les systèmes dynamiques sont des importants modèles mathématiques utilisés pour décrire l'évolution temporelle des systèmes.Souvent, les systèmes dynamiques sont équipées avec des paramètres qui permettent les modèles de mieux saisir les caractéristiques des phénomènes abstraits. Une question importante autour des systèmes dynamiques est de déterminer formellement si un modèle (sollicité par ses paramètres) se comporte bien.Dans cette thèse, nous traitons deux questions principales concernant les systèmes dynamiques polynomiaux en temps discret:1) problème de calcul de la d'atteignabilité, i.e., étant donné un ensemble de conditions initiales et un ensemble deparamètres, calculer l'ensemble des états atteignable par le système dans un horizon de temps borné;2) le problème de la synthèse de paramètre, i.e., étant donné un ensemble de conditions initiales,un ensemble de paramètres, et une spécification, trouver l'ensemble de paramètres le plus grandtels que tous les comportements du système fixes de l'ensemble de conditions initiales satisfont la spécification.Le problème de calcul d'atteignabilité pour les systèmes dynamiques non linéaires est bien connu pour être non triviale.Des difficultés surgissent dans le traitement et la représentation des ensembles générés par les transformations non linéaires.Dans cette thèse, nous adoptons une technique courante qui consistede rapprocher les ensembles atteignable avec des ensembles complexes qui sont faciles à manipuler.Le défi est de déterminer précis sur-approximations.Nous proposons des méthodes pour rapprocher finement les images des ensembles utilisant des boîtes,parallelotopes, et une nouvelle structure appelé parallelotope bundle (ce sont des collections de parallelotopes dont les intersections représentent symboliquement polytopes). Ces techniques d'approximation sont les étapes de base de notre algorithme d'accessibilité.La synthèse des paramètres vise à déterminer les valeursdes paramètres tels que le système se comporte comme prévu. Cette fonctionnalité peut êtreutilisé, par exemple, pour régler un modèle qu'il imite la modéliséphénomène avec un niveau suffisant de précision. Les contributions de cettethèse sur le problème de synthèse de paramètres sont de deux ordres. Premièrement,nous définissons une nouvelle sémantique pour le signal logique temporelle (STL) que nous permetde formaliser une spécification et de raisonner sur des ensembles de paramètres et des flux de comportements.Deuxièmement, nous définissons un algorithme pour calculer la sémantique de synthèsed'une formule à l'encontre d'un système dynamique à temps discret. Le résultat de l'algorithmeconstitue une solution conservatrice du problème de la synthèse de paramètre.Les méthodes développées exploitent et améliorent le calcul des coefficients de Bernstein.Les techniques définies dans cette thèse ont été mises en œuvreun tool appelé Sapo. L'efficacité de notre méthode est validéepar l'application de notre tool pour plusieurs systèmes dynamiques polynomiauxDynamical systems are important mathematical models used to describe the temporal evolution of systems.Often dynamical systems are equipped with parameters that allow the models to better capture the characteristicsof the abstracted phenomena. An important question around dynamical systems isto formally determine whether a model (biased by its parameters) behaves well.In this thesis we deal with two main questions concerning discrete-time polynomial dynamical systems:1) the reachability computation problem, i.e, given a set of initial conditions and a set ofparameters, compute the set of states reachable by the system in a bounded time horizon;2) the parameter synthesis problem, i.e., given a set of initial conditions,a set of parameters, and a specification, find the largestset of parameters such that all the behaviors of the system staring from the set ofinitial conditions satisfy the specification.The reachability computation problem for nonlinear dynamical systems is well known for being nontrivial.Difficulties arise in handling and representing sets generated by nonlinear transformations.In this thesis we adopt a common technique that consistsin over-approximating the complex reachable sets with sets that are easy to manipulate.The challenge is to determine accurate over-approximations.We propose methods to finely over-approximate the images of sets using boxes,parallelotopes, and a new data structure called parallelotope bundles (that are collections of parallelotopeswhose intersections symbolically represent polytopes). These approximation techniquesare the basic steps of our reachability algorithm.The synthesis of parameters aims at determining the valuesof the parameters such that the system behaves as expected. This feature can beused, for instance, to tune a model so that it imitates the modeledphenomenon with a sufficient level of precision. The contributions of thisthesis concerning the parameter synthesis problem are twofold. Firstly,we define a new semantics for the Signal Temporal Logic (STL) that allows oneto formalize a specification and reason on sets of parameters and flows of behaviors.Secondly, we define an algorithm to compute the synthesis semanticsof a formula against a discrete-time dynamical system. The result of the algorithmconstitutes a conservative solution of the parameter synthesis problem.The developed methods for both reachability computation and parameter synthesisexploit and improve Bernstein coefficients computation.The techniques defined in this thesis have been implemented ina tool called Sapo. The effectiveness of our methods is validatedby the application of our tool to several polynomial dynamical systems
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Hage-Packhäuser, Sebastian [Verfasser], Michael [Akademischer Betreuer] Dellnitz, and Peter [Akademischer Betreuer] Ashwin. "Structural treatment of time-varying dynamical system networks in the light of hybrid symmetries / Sebastian Hage-Packhäuser. Betreuer: Michael Dellnitz ; Peter Ashwin." Paderborn : Universitätsbibliothek, 2012. http://d-nb.info/1036892042/34.
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Boeuf, Vianney. "Dynamics of a two-level system with priorities and application to an emergency call center." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX120/document.
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Dans cette thèse, nous analysons la dynamique de systèmes à événements discrets avec synchronisation et priorités, au moyen de réseaux de Petri et de réseaux de files d'attente.Nous appliquons cela à l'évaluation de performance d'un centre d'appels d'urgence.Notre motivation de départ est pratique. Pendant la durée de ce travail, un nouveau centre d'appels d'urgence a été mis en place pour l'agglomération parisienne, traitant les appels pour la police et les pompiers.La nouvelle organisation traite les appels en deux niveaux.Un premier niveau d'opérateurs répond aux appels, identifie les appels urgents et traite les appels non urgents.Les opérateurs de second niveau sont spécialistes (policiers ou pompiers) et traitent les demandes d'intervention.Quand un appel est identifié au niveau 1 comme très urgent, l'opérateur reste en ligne avec l'appelant jusqu'à ce qu'un opérateur de niveau 2 réponde. De plus, l'appel est prioritaire.Une conséquence de cette procédure est que, lorsqu'aucun opérateur de niveau 2 n'est disponible, les opérateurs de niveau 1 attendent avec ces appels très urgents, et la capacité du niveau 1 diminue.Nous nous intéressons à l'évaluation de performance de divers systèmes correspondant à cette description générale, dans des situations de saturation.Nous proposons trois modèles différents pour traiter ce type de systèmes.Les deux premiers sont des modèles de réseaux de Petri temporisés.Nous enrichissons les classiques réseaux de Petri à choix libres en autorisant des situations de conflit où le routage est résolu par des priorités.La principale difficulté est alors que l'opérateur de la dynamique n'est plus monotone.Dans un premier modèle, nous proposons une dynamique discrète pour cette classe de réseaux de Petri, avec des temps de séjour constants sur les places.Nous prouvons que les variables compteurs d'une exécution du réseau sont les solutions d'un système affine par morceaux, avec retards.Nous étudions les régimes stationnaires de cette dynamique, et caractérisons les régimes affines comme solutoins d'un système affine par morceaux, qui peut être vu comme un système sur le semi-corps de germes tropical (min plus).Les applications numériques montrent cependant que la convergence ne se fait pas toujours vers ces régimes stationnaires affines.Le second modèle est une transformation continue du précédent. Pour la même classe de réseaux de Petri, nous proposons une dynamique sous forme d'équations différentielles discontinues.Nous établissons l'existence et l'unicité de la solution.L'objectif de cette modélisation est d'obtenir un système plus simple dans lequel les pathologies du temps discret disparaissent. Nous montrons que les régimes stationaires sont les mêmes que ceux de la dynamique discrète. Les simulations numériques semblent montrer que la convergence s'obtient effectivement dans ce cas.Nous modélisons aussi le centre d'appels d'urgence comme un réseau de files d'attente, prenant ainsi en compte le caractère aléatoire des différentes variables du centre d'appel.Pour ce système, nous prouvons que la dynamique, après une transformation d'échelle, converge vers une limite fluide, qui correspond au système d'équations différentielles précédent.Cela conforte notre seconde modélisation.Les principaux outils de la preuve de convergence sont le calcul stochastique pour les processus de Poisson, les formulations de Skorokhod généralisées, ou encore des arguments de couplage.Ainsi, nos trois modèles d'un même centre d'appels d'urgence définissent un même comportement asymptotique schématique, décrivant différentes phases de congestion du centre.Dans une seconde partie de cette thèse, nous analysons des simulations poussées, prenant en compte les nombreux détails de notre étude de cas. Les simulations confirment le comportement schématique prédit par nos modèles mathématiques. Nous discutons aussi des interactions complexes provenant de la nature hétérogène du niveau 2In this thesis, we analyze the dynamics of discrete event systems with synchronization and priorities, by the means of Petri nets and queueing networks.We apply this to the performance evaluation of an emergency call center.Our original motivation is practical. During the period of this work, a new emergency call center became operative in Paris area, handling emergency calls to police and firemen.The new organization includes a two-level call treatment. A first level of operators answers calls, identifies urgent calls and handles (numerous) non-urgent calls.Second level operators are specialists (policemen or firemen) and handle emergency demands.When a call is identified at level 1 as extremely urgent, the operator stays in line with the call until a level 2 operator answers. The call has priority for level 2 operators.A consequence of this procedure is that, when level 2 operators are busy, level 1 operators wait with extremely urgent calls, and the capacity of level 1 diminishes.We are interested in the performance evaluation of various systems corresponding to this general description, in stressed situations.We propose three different models addressing this kind of systems.The first two are timed Petri net models.We enrich the classical free choice Petri nets by allowing conflict situations in which the routing is solved by priorities.The main difficulty in this situation is that the operator of the dynamics becomes non monotone.In a first model, we consider discrete dynamics for this class of Petri nets, with constant holding times on places.We prove that the counter variables of an execution of the Petri net are solutions of a piecewise linear system with delays.As far as we know, this proof is new, even for the class of free choice nets, which is a subclass of ours.We investigate the stationary regimes of the dynamics, and characterize the affine ones as solutions of a piecewise linear system, which can be seen as a system over a tropical (min-plus) semifield of germs.Numerical experiments show that, however, convergence does not always holds towards these affine stationary regimes.The second model is a ``continuization'' of the previous one. For the same class of Petri nets, we propose dynamics expressed by differential equations, so that the tokens and time events become continue.For this differential system with discontinuous righthandside, we establish the existence and uniqueness of the solution.By using differential equations, we aim at obtaining a simpler model in which discrete time pathologies disappear. We show that the stationary regimes are the same as the stationary regimes of the discrete time dynamics.Numerical experiments tend to show that, in this setting, convergence effectively holds.We also model the emergency call center described above as a queueing system, taking into account the randomness of the different call center variables.For this system, we prove that, under an appropriate scaling, the dynamics converges to a fluid limit which corresponds to the differential equations of our Petri net model.This provides support for the second model.Stochastic calculus for Poisson processes, generalized Skorokhod formulations and coupling arguments are the main tools used to establish this convergence.Hence, our three models of an identical emergency call center yield the same schematic asymptotic behavior, expressed as a piecewise linear system of the parameters, and describing the different congestion phases of the system.In a second part of this thesis, simulations are carried out and analyzed, taking into account the many subtleties of our case study (for example, we construct probability distributions based on real data analysis).The simulations confirm the schematic behavior described by our mathematical models.We also address the complex interactions coming from the heterogeneous nature of level 2
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Hanselmann, Thomas. "Approximate dynamic programming with adaptive critics and the algebraic perceptron as a fast neural network related to support vector machines." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0005.
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[Truncated abstract. Please see the pdf version for the complete text. Also, formulae and special characters can only be approximated here. Please see the pdf version of this abstract for an accurate reproduction.] This thesis treats two aspects of intelligent control: The first part is about long-term optimization by approximating dynamic programming and in the second part a specific class of a fast neural network, related to support vector machines (SVMs), is considered. The first part relates to approximate dynamic programming, especially in the framework of adaptive critic designs (ACDs). Dynamic programming can be used to find an optimal decision or control policy over a long-term period. However, in practice it is difficult, and often impossible, to calculate a dynamic programming solution, due to the 'curse of dimensionality'. The adaptive critic design framework addresses this issue and tries to find a good solution by approximating the dynamic programming process for a stationary environment. In an adaptive critic design there are three modules, the plant or environment to be controlled, a critic to estimate the long-term cost and an action or controller module to produce the decision or control strategy. Even though there have been many publications on the subject over the past two decades, there are some points that have had less attention. While most of the publications address the training of the critic, one of the points that has not received systematic attention is training of the action module.¹ Normally, training starts with an arbitrary, hopefully stable, decision policy and its long-term cost is then estimated by the critic. Often the critic is a neural network that has to be trained, using a temporal difference and Bellman's principle of optimality. Once the critic network has converged, a policy improvement step is carried out by gradient descent to adjust the parameters of the controller network. Then the critic is retrained again to give the new long-term cost estimate. However, it would be preferable to focus more on extremal policies earlier in the training. Therefore, the Calculus of Variations is investigated to discard the idea of using the Euler equations to train the actor. However, an adaptive critic formulation for a continuous plant with a short-term cost as an integral cost density is made and the chain rule is applied to calculate the total derivative of the short-term cost with respect to the actor weights. This is different from the discrete systems, usually used in adaptive critics, which are used in conjunction with total ordered derivatives. This idea is then extended to second order derivatives such that Newton's method can be applied to speed up convergence. Based on this, an almost concurrent actor and critic training was proposed. The equations are developed for any non-linear system and short-term cost density function and these were tested on a linear quadratic regulator (LQR) setup. With this approach the solution to the actor and critic weights can be achieved in only a few actor-critic training cycles. Some other, more minor issues, in the adaptive critic framework are investigated, such as the influence of the discounting factor in the Bellman equation on total ordered derivatives, the target interpretation in backpropagation through time as moving and fixed targets, the relation between simultaneous recurrent networks and dynamic programming is stated and a reinterpretation of the recurrent generalized multilayer perceptron (GMLP) as a recurrent generalized finite impulse MLP (GFIR-MLP) is made. Another subject in this area that is investigated, is that of a hybrid dynamical system, characterized as a continuous plant and a set of basic feedback controllers, which are used to control the plant by finding a switching sequence to select one basic controller at a time. The special but important case is considered when the plant is linear but with some uncertainty in the state space and in the observation vector, and a quadratic cost function. This is a form of robust control, where a dynamic programming solution has to be calculated. ¹Werbos comments that most treatment of action nets or policies either assume enumerative maximization, which is good only for small problems, except for the games of Backgammon or Go [1], or, gradient-based training. The latter is prone to difficulties with local minima due to the non-convex nature of the cost-to-go function. With incremental methods, such as backpropagation through time, calculus of variations and model-predictive control, the dangers of non-convexity of the cost-to-go function with respect to the control is much less than the with respect to the critic parameters, when the sampling times are small. Therefore, getting the critic right has priority. But with larger sampling times, when the control represents a more complex plan, non-convexity becomes more serious.
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Schinkel, Michael. "Nondeterministic hybrid dynamical systems." Thesis, University of Glasgow, 2002. http://theses.gla.ac.uk/1853/.
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This thesis is concerned with the analysis, control and identification of hybrid dynamical systems. The main focus is on a particular class of hybrid systems consisting of linear subsystems. The discrete dynamic, i.e., the change between subsystems, is unknown or nondeterministic and cannot be influenced, i.e. controlled, directly. However changes in the discrete dynamic can be detected immediately, such that the current dynamic (subsystem) is known. In order to motivate the study of hybrid systems and show the merits of hybrid control theory, an example is given. It is shown that real world systems like Anti Locking Brakes (ABS) are naturally modelled by such a class of linear hybrids systems. It is shown that purely continuous feedback is not suitable since it cannot achieve maximum braking performance. A hybrid control strategy, which overcomes this problem, is presented. For this class of linear hybrid system with unknown discrete dynamic, a framework for robust control is established. The analysis methodology developed gives a robustness radius such that the stability under parameter variations can be analysed. The controller synthesis procedure is illustrated in a practical example where the control for an active suspension of a car is designed. Optimal control for this class of hybrid system is introduced. It is shows how a control law is obtained which minimises a quadratic performance index. The synthesis procedure is stated in terms of a convex optimisation problem using linear matrix inequalities (LMI). The solution of the LMI not only returns the controller but also the performance bound. Since the proposed controller structures require knowledge of the continuous state, an observer design is proposed. It is shown that the estimation error converges quadratically while minimising the covariance of the estimation error. This is similar to the Kalman filter for discrete or continuous time systems. Further, we show that the synthesis of the observer can be cast into an LMI, which conveniently solves the synthesis problem.
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Gurcan, Fatih. "A Hybrid Movie Recommender Using Dynamic Fuzzy Clustering." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12611667/index.pdf.
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Recommender systems are information retrieval tools helping users in their information
seeking tasks and guiding them in a large space of possible options. Many hybrid
recommender systems are proposed so far to overcome shortcomings born of pure
content-based (PCB) and pure collaborative filtering (PCF) systems. Most studies on
recommender systems aim to improve the accuracy and efficiency of predictions. In
this thesis, we propose an online hybrid recommender strategy (CBCFdfc) based on
content boosted collaborative filtering algorithm which aims to improve the prediction
accuracy and efficiency. CBCFdfc combines content-based and collaborative characteristics
to solve problems like sparsity, new item and over-specialization. CBCFdfc uses
fuzzy clustering to keep a certain level of prediction accuracy while decreasing online
prediction time. We compare CBCFdfc with PCB and PCF according to prediction
accuracy metrics, and with CBCFonl (online CBCF without clustering) according to
online recommendation time. Test results showed that CBCFdfc performs better than
other approaches in most cases. We, also, evaluate the effect of user-specified parameters
to the prediction accuracy and efficiency. According to test results, we determine
optimal values for these parameters. In addition to experiments made on simulated
data, we also perform a user study and evaluate opinions of users about recommended movies. The results that are obtained in user evaluation are satisfactory. As a result,
the proposed system can be regarded as an accurate and efficient hybrid online movie
recommender.
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Becker, Basil, and Holger Giese. "Cyber-physical systems with dynamic structure : towards modeling and verification of inductive invariants." Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2012/6243/.
Full textAbstract:
Cyber-physical systems achieve sophisticated system behavior exploring the tight interconnection of physical coupling present in classical engineering systems and information technology based coupling. A particular challenging case are systems where these cyber-physical systems are formed ad hoc according to the specific local topology, the available networking capabilities, and the goals and constraints of the subsystems captured by the information processing part.
In this paper we present a formalism that permits to model the sketched class of cyber-physical systems. The ad hoc formation of tightly coupled subsystems of arbitrary size are specified using a UML-based graph transformation system approach. Differential equations are employed to define the resulting tightly coupled behavior. Together, both form hybrid graph transformation systems where the graph transformation rules define the discrete steps where the topology or modes may change, while the differential equations capture the continuous behavior in between such discrete changes. In addition, we demonstrate that automated analysis techniques known for timed graph transformation systems for inductive invariants can be extended to also cover the hybrid case for an expressive case of hybrid models where the formed tightly coupled subsystems are restricted to smaller local networks.Cyber-physical Systeme erzielen ihr ausgefeiltes Systemverhalten durch die enge Verschränkung von physikalischer Kopplung, wie sie in Systemen der klassichen Igenieurs-Disziplinen vorkommt, und der Kopplung durch Informationstechnologie. Eine besondere Herausforderung stellen in diesem Zusammenhang Systeme dar, die durch die spontane Vernetzung einzelner Cyber-Physical-Systeme entsprechend der lokalen, topologischen Gegebenheiten, verfügbarer Netzwerkfähigkeiten und der Anforderungen und Beschränkungen der Teilsysteme, die durch den informationsverabeitenden Teil vorgegeben sind, entstehen. In diesem Bericht stellen wir einen Formalismus vor, der die Modellierung der eingangs skizzierten Systeme erlaubt. Ein auf UML aufbauender Graph-Transformations-Ansatz wird genutzt, um die spontane Bildung eng kooperierender Teilsysteme beliebiger Größe zu spezifizieren. Differentialgleichungen beschreiben das kombinierte Verhalten auf physikalischer Ebene. In Kombination ergeben diese beiden Formalismen hybride Graph-Transformations-Systeme, in denen die Graph-Transformationen diskrete Schritte und die Differentialgleichungen das kontinuierliche, physikalische Verhalten des Systems beschreiben. Zusätzlich, präsentieren wir die Erweiterung einer automatischen Analysetechnik zur Verifikation induktiver Invarianten, die bereits für zeitbehaftete Systeme bekannt ist, auf den ausdrucksstärkeren Fall der hybriden Modelle.
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Carter, Rebekah. "Verification of liveness properties on hybrid dynamical systems." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/verification-of-liveness-properties-on-hybrid-dynamical-systems(8817319c-a63f-4cf3-927d-a2ddf69139b4).html.
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A hybrid dynamical system is a mathematical model for a part of the real world where discrete and continuous parts interact with each other. Typically such systems are complex, and it is difficult to know how they will behave for general parameters and initial conditions. However, the method of formal verification gives us the ability to prove automatically that certain behaviour does or does not happen for a range of parameters in a system. The challenge is then to define suitable methods for proving properties on hybrid systems.This thesis looks at using formal verification for proving liveness properties on hybrid systems: a liveness property says that something good eventually happens in the system. This work presents the theoretical background and practical application of various methods for proving and disproving inevitability properties (a type of liveness) in different classes of hybrid systems. The methods combine knowledge of dynamical behaviour of a system with the brute-force approach of model checking, in order to make the most of the benefits of both sides. The work on proving liveness properties is based on abstraction of dynamical systems to timed automata. This thesis explores the limits of a pre-defined abstraction method, adds some dynamical knowledge to the method, and shows that this improvement makes liveness properties provable in certain continuous dynamical systems. The limits are then pushed further to see how this method can be used for piecewise-continuous dynamical systems. The resulting algorithms are implemented for both classes of systems.In order to disprove liveness properties in hybrid systems a novel framework is proposed, using a new property called deadness. Deadness is a dynamically-aware property of the hybrid system which, if true, disproves the liveness property by means of a finite execution: we usually require an infinite execution to disprove a liveness property. An algorithm is proposed which uses dynamical properties of hybrid systems to derive deadness properties automatically, and the implementation of this algorithm is discussed and applied to a simplified model of an oilwell drillstring.
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Denman, William. "Automated verification of continuous and hybrid dynamical systems." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708809.
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Parish, Julie Marie Jones. "Direct linearization of continuous and hybrid dynamical systems." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2407.
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Schöllig, Angela. "Optimal Control of Hybrid Systems with Regional Dynamics." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19874.
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In this work, hybrid systems with regional dynamics are considered. These are systems where transitions between different dynamical regimes occur as the continuous state of the system reaches given switching surfaces. In particular, the attention is focused on the optimal control problem associated with such systems. More precisely, given a specific cost function, the goal is to determine the optimal path of going from a given starting point to a fixed final state during an a priori specified time horizon.
The key characteristic of the approach presented in this thesis is a hierarchical decomposition of the hybrid optimal control problem, yielding to a framework which allows a solution on different levels of control. On the highest level of abstraction, the regional structure of the state space is taken into account and a discrete representation of the connections between the different regions provides global accessibility relations between regions. These are used on a lower level of control to formulate the main theorem of this work, namely, the Hybrid Bellman Equation for multimodal systems, which, in fact, provides a characterization of global optimality, given an upper bound on the number of transitions along a hybrid trajectory. Not surprisingly, the optimal solution is hybrid in nature, in that it depends on not only the continuous control signals, but also on discrete decisions as to what domains the system's continuous state should go through in the first place.
The main benefit with the proposed approach lies in the fact that a hierarchical Dynamic Programming algorithm can be used to representing both a theoretical characterization of the hybrid solution's structural composition and, from a more application-driven point of view, a numerically implementable calculation rule yielding to globally optimal solutions in a regional dynamics framework. The operation of the recursive algorithm is highlighted by the consideration of numerous examples, among them, a heterogeneous multi-agent problem.
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Plotnik, Aaron M. "Applied estimation for hybrid dynamical systems using perceptional information /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Goletz, Christoph-Marian. "Semiclassical hybrid dynamics for open quantum systems." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-70342.
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In this work the semiclassical hybrid dynamics is extended in order to be capable of treating open quantum systems considering finite baths. The corresponding phenomena, i.e. decoherence and dissipation, are investigated for various scenarios.
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Peters, Karsten. "Hybrid systems modeling manufacturing and front dynamics." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971895147.
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Morgenstern, Frederik Stephan Franz. "Charge transfer dynamics in hybrid nanocrystal systems." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708746.
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Hui, Qing. "Nonlinear dynamical systems and control for large-scale, hybrid, and network systems." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24635.
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Thesis (Ph.D.)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Haddad, Wassim; Committee Member: Feron, Eric; Committee Member: JVR, Prasad; Committee Member: Taylor, David; Committee Member: Tsiotras, Panagiotis
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Ben, Salah Jaâfar. "Analyse et commande des systèmes non linéaires complexes : application aux systèmes dynamiques à commutation." Phd thesis, Université Claude Bernard - Lyon I, 2009. http://tel.archives-ouvertes.fr/tel-00599364.
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Ce mémoire de thèse présente deux nouvelles approches pour l'analyse et la commande des systèmes non-linéaires complexes, comme les systèmes dynamiques à commutation de la classe des convertisseurs d'énergie électrique. Ces systèmes ont plusieurs modes de fonctionnement et ont un point de fonctionnement désiré qui, en général, n'est le point d'équilibre d'aucun des modes. Dans cette classe de systèmes, la commutation d'un mode de fonctionnement à un autre est commandée selon une loi qui doit être synthétisée. Par conséquent, la synthèse de commande implique l'étude des conditions qui permettent à un cycle limite stable de s'établir au voisinage du point de fonctionnement désiré, puis de la trajectoire de commande qui permet de l'atteindre en respectant les contraintes physiques de comportement (courant maximum supporté par les composants,. . .) ou les contraintes de temps (durée minimum entre deux commutations,. . .). Le cycle limite sera qualifié d'hybride car il est composé de plusieurs dynamiques(deux dans ces travaux).La première méthode développée s'appuie sur les propriétés géométriques des champs de vecteurs et est une extension d'une partie des travaux de thèse de Manon au LAGEP. Une condition nécessaire et suffisante d'existence et de stabilité d'un cycle limite hybride composé d'une séquence de deux modes de fonctionnement dans IR2 est présentée. Ce cycle définit la région finale à atteindre par le système depuis son état initial, par une trajectoire déterminée de manière optimale selon un critère donné (durée totale, énergie dépensée, . . .). La méthode proposée est appliquée aux convertisseurs d'énergie Buck et Buck-Boost alimentant une charge résistive. Une extension à IRn a été proposée et démontrée. Elle est illustrée sur un système non-linéaire dans IR3.La deuxième méthode est développée dans IR2 et basée sur la théorie de Lyapunov, bien connue en automatique pour étudier la stabilité des systèmes non-linéaires et concevoir des commandes stabilisantes.Il s'agit de déterminer par une approche géométrique, une fonction de Lyapunov quadratique commune aux deux modes de fonctionnement du système, qui permette d'obtenir un cycle limite hybride stable le plus proche possible du point de fonctionnement désiré et une commande stabilisante directe des interrupteurs
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Stockton, Nicklas O. "Hybrid Genetic Fuzzy Systems for Control of Dynamic Systems." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1523635312922039.
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Houshmand, Arian. "Multidisciplinary Dynamic System Design Optimization of Hybrid Electric Vehicle Powertrains." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479822276400281.
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Najafi, Masoud Nikoukhah Ramine. "Solveur numérique pour les systèmes algébro-différentiels hybrides The numerical solver for the simulation of the hybrid dynamical systems /." Créteil : Université de Paris-Val-de-Marne, 2005. http://doxa.scd.univ-paris12.fr:80/theses/th0232529.pdf.
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Sogokon, Andrew. "Direct methods for deductive verification of temporal properties in continuous dynamical systems." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20952.
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This thesis is concerned with the problem of formal verification of correctness specifications for continuous and hybrid dynamical systems. Our main focus will be on developing and automating general proof principles for temporal properties of systems described by non-linear ordinary differential equations (ODEs) under evolution constraints. The proof methods we consider will work directly with the differential equations and will not rely on the explicit knowledge of solutions, which are in practice rarely available. Our ultimate goal is to increase the scope of formal deductive verification tools for hybrid system designs. We give a comprehensive survey and comparison of available methods for checking set invariance in continuous systems, which provides a foundation for safety verification using inductive invariants. Building on this, we present a technique for constructing discrete abstractions of continuous systems in which spurious transitions between discrete states are entirely eliminated, thereby extending previous work. We develop a method for automatically generating inductive invariants for continuous systems by efficiently extracting reachable sets from their discrete abstractions. To reason about liveness properties in ODEs, we introduce a new proof principle that extends and generalizes methods that have been reported previously and is highly amenable to use as a rule of inference in a deductive verification calculus for hybrid systems. We will conclude with a summary of our contributions and directions for future work.
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McDonough, Joshua. "System Dynamics Modeling and Development of a Design Procedure for Short-term Alternative Energy Storage Systems." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1308287500.
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Stellato, Bartolomeo. "Mixed-integer optimal control of fast dynamical systems." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:b8a7323c-e36e-45ec-ae8d-6c9eb4350629.
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Many applications in engineering, computer science and economics involve mixed-integer optimal control problems. Solving these problems in real-time is a challenging task because of the explosion of integer combinations to evaluate. This thesis focuses on the development of new algorithms for mixed-integer programming with an emphasis on optimal control problems of fast dynamical systems with discrete controls. The first part proposes two reformulations to reduce the computational complexity. The first reformulation avoids integer variables altogether. By considering a sequence of switched dynamics, we analyze the switching time optimization problem. Even though it is a continuous smooth problem, it is non-convex and the cost function and derivatives are hard to compute. We develop a new efficient method to compute the cost function and its derivatives. Our technique brings up to two orders of magnitude speedups with respect to state-of-the-art tools. The second approach reduces the number of integer decisions. In hybrid model predictive control (MPC) the computational complexity grows exponentially with the horizon length. Using approximate dynamic programming (ADP) we reduce the horizon length while maintaining good control performance by approximating the tail cost offline. This approach allows, for the first time, the application of such control techniques to fast dynamical systems with sampling times of only a few microseconds. The second part investigates embedded branch-and-bound algorithms for mixed-integer quadratic programs (MIQPs). A core component of these methods is the solution of continuous quadratic programs (QPs). We develop OSQP, a new robust and efficient general-purpose QP solver based on the alternating direction method of multipliers (ADMM) and able, for the first time, to detect infeasible problems. We include OSQP into a custom branch-and-bound algorithm suitable for embedded systems. Our extension requires only a single matrix factorization and exploits warm-starting, thereby greatly reducing the number of ADMM iterations required. Numerical examples show that our algorithm solves small to medium scale MIQPs more quickly than commercial solvers.
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Helal, Magdy. "A HYBRID SYSTEM DYNAMICS-DISCRETE EVENT SIMULATIONAPPROACH TO SIMULATING THE MANUFACTURING ENTERPRISE." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2349.
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With the advances in the information and computing technologies, the ways the manufacturing enterprise systems are being managed are changing. More integration and adoption of the system perspective push further towards a more flattened enterprise. This, in addition to the varying levels of aggregation and details and the presence of the continuous and discrete types of behavior, created serious challenges for the use of the existing simulation tools for simulating the modern manufacturing enterprise system. The commonly used discrete event simulation (DES) techniques face difficulties in modeling such integrated systems due to increased model complexity, the lack of data at the aggregate management levels, and the unsuitability of DES to model the financial sectors of the enterprise. System dynamics (SD) has been effective in providing the needs of top management levels but unsuccessful in offering the needed granularity at the detailed operational levels of the manufacturing system. On the other hand the existing hybrid continuous-discrete tools are based on certain assumptions that do not fit the requirements of the common decision making situations in the business systems. This research has identified a need for new simulation modeling approaches that responds to the changing business environments towards more integration and flattened enterprise systems. These tools should be able to develop comprehensive models that are inexpensive, scalable, and able to accommodate the continuous and discrete modes of behavior, the stochastic and deterministic natures of the various business units, and the detail complexity and dynamic complexity perspectives in decision making. The research proposes and develops a framework to combine and synchronize the SD and DES simulation paradigms to simulate the manufacturing enterprise system. The new approach can respond to the identified requirements in simulating the modern manufacturing enterprise systems. It is directed toward building comprehensive simulation models that can accommodate all management levels while explicitly recognizing the differences between them in terms of scope and frequency of decision making as well as the levels of details preferred and used at each level. This SDDES framework maintains the integrity of the two simulation paradigms and can use existing/legacy simulation models without requiring learning new simulation or computer programming skills. The new framework uses a modular structure by which the SD and DES models are treated as members of a comprehensive simulation. A new synchronization mechanism that that maintains the integrity of the two simulation paradigms and is not event-driven is utilized to coordinate the interactions between the simulation modules. It avoids having one simulation paradigm dominating the other. For communication and model management purposes the SDDES formalism provides a generic format to describe, specify, and document the simulation modules and the information sharing processes. The SDDES controller which is the communication manager, implements the synchronization mechanism and manages the simulation run ensuring correct exchange of data in terms of timeliness and format, between the modules. It also offers the user interface through which users interact with the simulation modules.Ph.D.
Department of Industrial Engineering and Management Systems
Engineering and Computer Science
Industrial Engineering PhD
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Siu, Daniel. "Stochastic Hybrid Dynamic Systems: Modeling, Estimation and Simulation." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4405.
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Stochastic hybrid dynamic systems that incorporate both continuous and discrete dynamics have been an area of great interest over the recent years. In view of applications, stochastic hybrid dynamic systems have been employed to diverse fields of studies, such as communication networks, air traffic management, and insurance risk models. The aim of the present study is to investigate properties of some classes of stochastic hybrid dynamic systems.
The class of stochastic hybrid dynamic systems investigated has random jumps driven by a non-homogeneous Poisson process and deterministic jumps triggered by hitting the boundary. Its real-valued continuous dynamic between jumps is described by stochastic differential equations of the It\^o-Doob type. Existing results of piecewise deterministic models are extended to obtain the infinitesimal generator of the stochastic hybrid dynamic systems through a martingale approach. Based on results of the infinitesimal generator, some stochastic stability results are derived. The infinitesimal generator and stochastic stability results can be used to compute the higher moments of the solution process and find a bound of the solution.
Next, the study focuses on a class of multidimensional stochastic hybrid dynamic systems. The continuous dynamic of the systems under investigation is described by a linear non-homogeneous systems of It\^o-Doob type of stochastic differential equations with switching coefficients. The switching takes place at random jump times which are governed by a non-homogeneous Poisson process. Closed form solutions of the stochastic hybrid dynamic systems are obtained. Two important special cases for the above systems are the geometric Brownian motion process with jumps and the Ornstein-Uhlenbeck process with jumps. Based on the closed form solutions, the probability distributions of the solution processes for these two special cases are derived. The derivation employs the use of the modal matrix and transformations.
In addition, the parameter estimation problem for the one-dimensional cases of the geometric Brownian motion and Ornstein-Uhlenbeck processes with jumps are investigated. Through some existing and modified methods, the estimation procedure is presented by first estimating the parameters of the discrete dynamic and subsequently examining the continuous dynamic piecewisely.
Finally, some simulated stochastic hybrid dynamic processes are presented to illustrate the aforementioned parameter-estimation methods. One simulated insurance example is given to demonstrate the use of the estimation and simulation techniques to obtain some desired quantities.
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Nwankwo, Ebuka. "Dynamic behaviour of blast loaded hybrid structural systems." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24426.
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A hybrid system consists of two or more different constituent materials combined to form a single system to achieve increased mechanical properties and structural performances. The combinations of constituent materials are on a macroscopic level. The improved performances achieved in hybrid systems are in fatigue, impact, corrosion resistance, weight savings, and improved strength to weight performances. The increasing demand for high-performance and lightweight structures forms the motivation for this thesis. In the light of these, three different hybrid systems under different blast scenarios have been studied and the reason for their high-performance over monolithic systems discussed. The possibility of debonding of the strengthening composite patch from the stainless steel panel in a hybrid system of strengthened blast wall leads to the study of fibre metal laminates (FMLs) and lap joints. Since composites, form a significant part of these hybrid systems, simplified damage models for composites are developed and applied to the various hybrid systems studied in order to investigate their overall response. First, this thesis presents a hybrid system of a stainless steel blast wall with retrofitting composite patches. An analytical model, which allows for multiple deformation modes, is developed to study the hybrid system of strengthened blast wall. Maximum displacements predicted by the analytical models correlated well with maximum displacements predicted by the numerical models of the proposed hybrid system in Abaqus. It is observed that fibre fracture, which is a more detrimental failure mode, did not occur in the composite patch in the numerical model. The hybrid system of composite strengthened blast walls allows for increased energy absorption by the development four plastic hinges compared to the development of three plastic hinges of the monolithic system. This behaviour renders it superior to a monolithic system in a gas explosion scenario. In order to simplify the system presented in Chapter 3, an analytical solution for evaluating the maximum displacement of a continuous system with semi-rigid supports subjected to pulse loads is presented. The maximum elastic displacement presented by the numerical models in Chapter 3 is compared with the maximum displacement presented by the simplified model. The limitation of the simplified model is subsequently discussed. Using the simplified model, an elastic pressure-impulse diagram for the blast wall studied in Chapter 3 is presented under typical hydrocarbon explosions. In addition, unique pulse-shape independent pressure-impulse diagrams for elastic and elastic-plastic responses are developed using dimensionless parameters for typical high explosive events. However, the major limitations of this model are its inability to account for membrane effect, travelling plastic hinge, support shear hinge and connection pull-in. Secondly, the response of an FML is studied in order to obtain an insight into debonding between composite and metal, which was assumed to be prevented in Chapter 3. An FML was chosen because of the availability of experimental data on the blast response for this kind of hybrid system in the open literature. In addition, other researchers have proven that FMLs performed better the monolithic aluminium with similar areal density. A modified Hashin model is used to model damage in the composite layers of fibre metal laminates (FMLs) under blast loads. The FML studied comprises 2024-O aluminium alloys (O represents the temper of the aluminium alloy-i.e.no heat treatment) and woven glass-fibre/polypropylene composites. Thus, this work presents an improved and simplified model to analyse the damage initiation, damage progression, and failure of the aluminium layers and the three-dimensional woven composite layers. In order to gain an insight on how bonded substrates influence the stress in adhesive layers and because interfacial stresses cannot be obtained directly from cohesive elements in Abaqus (i.e. adhesive layers in the studied FML), an analytical model to predict the maximum peel and shear stresses in an elastic adhesive in a single lap joint (metal-metal adherends) subjected to transverse pulse loads is presented. The analytical model for a metal-adhesive-metal system, which was validated with numerical models in Abaqus, gave an insight into the relationship of interfacial stresses in adhesive layers with bonded layers. Inference drawn from this model supports the assumption that bonded materials with similar in-plane stiffness would result in minimal interfacial stresses under blast scenarios as originally assumed in Chapter 3. Finally, a lap joint with similar adherends under in-plane blast load is compared with a hybrid system of metal and composite lap joint. The interfacial stresses produced by the hybrid system showed some reduction and fibre failure was not observed in the composite. This reinforces the improved performance of hybrid systems.
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Bolien, Mario. "Hybrid testing of an aerial refuelling drogue." Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.761036.
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Hybrid testing is an emerging technique for system emulation that uses a transfer system composed of actuators and sensors to couple physical tests of a critical component or substructure to a numerical simulation of the remainder of a system and its complete operating environment. The realisation of modern real-time hybrid tests for multi-body contact-impact problems often proves infeasible due to (i) hardware with bandwidth limitations and (ii) the unavailability of control schemes that provide satisfactory force and position tracking in the presence of sharp non-linearities or discontinuities. Where this is the case, the possibility of employing a pseudo-dynamic technique remains, enabling tests to be conducted on an enlarged time scale thus relaxing bothbandwidth and response time constraints and providing inherent loop stability. Exploiting the pseudo-dynamic technique, this thesis presents the development of Robotic Pseudo-Dynamic Testing (RPsDT), a dedicated method that specifically targets the realisation of hybrid tests for multi-body contact-impact problems using commercial off- the shelve (COTS) industrial robotic manipulators. The RPsDT method is evaluated in on-ground studies of air-to-air refuelling (AAR) maneuvers with probe-hose-drogue systems where the critical contact and coupling phase is tested pseudo-dynamicallywith full-scale refuelling hardware while the flight regime is emulated in simulation. It is shown that the RPsDT method can faithfully reproduce the dominant contact impact phenomena between probe and drogue while minor discrepancies result from the absence of rate-dependant damping in the force feedback measurements. In combination with full-speed robot controlled contact tests, reliable estimates for impact forces, strain distributions and drogue responses to off-centre hits are obtained providing extensive improvements over current predictive capabilities for the in-flight behaviour of refuelling hardware and it is concluded that the technique shows great promise for industrial applications.
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Zhao, Xiaobing. "A Penalty Function-Based Dynamic Hybrid Shop Floor Control System." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195300.
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To cope with dynamics and uncertainties, a novel penalty function-based hybrid, multi-agent shop floor control system is proposed in this dissertation. The key characteristic of the proposed system is the capability of adaptively distributing decision-making power across different levels of control agents in response to different levels of disturbance. The subordinate agent executes tasks based on the schedule from the supervisory level agent in the absence of disturbance. Otherwise, it optimizes the original schedule before execution by revising it with regard to supervisory level performance (via penalty function) and disturbance. Penalty function, mathematical programming formulations, and quantitative metrics are presented to indicate the disturbance levels and levels of autonomy. These formulations are applied to diverse performance measurements such as completion time related metrics, makespan, and number of late jobs. The proposed control system is illustrated, tested with various job shop problems, and benchmarked against other shop floor control systems. In today's manufacturing system, man still plays an important role together with the control system Therefore, better coordination of humans and control systems is an inevitable topic. A novel BDI agent-based software model is proposed in this work to replace the partial decision-making function of a human. This proposed model is capable of 1) generating plans in real-time to adapt the system to a changing environment, 2) supporting not only reactive, but also proactive decision-making, 3) maintaining situational awareness in human language-like logic to facilitate real human decision-making, and 4) changing the commitment strategy adaptive to historical performance. The general purposes human operator model is then customized and integrated with an automated shop floor control system to serve as the error detection and recovery system. This model has been implemented in JACK software; however, JACK does not support real-time generation of a plan. Therefore, the planner sub-module has been developed in Java and then integrated with the JACK. To facilitate integration of an agent, real-human, and the environment, a distributed computing platform based on DOD High Level Architecture has been used. The effectiveness of the proposed model is then tested in several scenarios in a simulated automated manufacturing environment.
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Promkam, Ratthaprom [Verfasser], and Sergey [Gutachter] Dashkovskiy. "Hybrid Dynamical Systems: Modeling, Stability and Interconnection / Ratthaprom Promkam ; Gutachter: Sergey Dashkovskiy." Würzburg : Universität Würzburg, 2019. http://d-nb.info/1199267163/34.
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Weightman, Andrew Patrick Hayes. "A hybrid modelling technique applied to smart dynamic systems." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426855.
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Patra, Ramakanta. "A model for Hybrid Dynamic Beam Movement with Specific Application to Wind Energy Units." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76847.
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The aim of this thesis is to present a structural model for a wind turbine and its supporting pylon, to analyze and simulate attendant vibration phenomena and to suggest and simulate an appropriate control procedure. A wind turbine can be described as an elastic system consisting of distributed parameter, beam and rod type, elements coupled to a rotating lumped mass generator/turbine component at one end. We allow for both lateral and torsional movements of the beam. Solution methods for related vibration and control problems are suggested and analyzed. Results of computations for sample problems are presented. Applications of control of structural vibrations in wind energy units using proof mass type actuators as part of the tip mass are also analyzed.Master of Science
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Kahraman, Mustafa. "Modelling Functional Dynamical Systems By Piecewise Linear Systems With Delay." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608962/index.pdf.
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Many dynamical systems in nature and technology involve delays in the interaction of variables forming the system. Furthermore, many of such systems involve external inputs or perturbations which might force the system to have arbitrary initial function. The conventional way to model these systems is using delay differential equations (DDE). However, DDEs with arbitrary initial functions has serious problems for finding analytical and computational solutions. This fact is a strong motivation for considering abstractions and approximations
for dynamical systems involving delay. In this thesis, the piecewise linear systems with delay on piecewise constant part which is a useful subclass of hybrid dynamical systems is studied. We introduced various representations of these systems and studied the state transition conditions. We showed that there exists fixed point and periodic stable solutions. We modelled the genomic regulation of fission
yeast cell cycle. We discussed various potential uses including approximating the DDEs and finally we concluded.
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Flaßkamp, Kathrin [Verfasser]. "On the optimal control of mechanical systems - hybrid control strategies and hybrid dynamics / Kathrin Flaßkamp." Paderborn : Universitätsbibliothek, 2014. http://d-nb.info/1047636069/34.
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Thota, Phanikrishna. "Analytical and Computational Tools for the Study of Grazing Bifurcations of Periodic Orbits and Invariant Tori." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/26196.
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The objective of this dissertation is to develop theoretical and
computational tools for the study of qualitative changes in the dynamics of
systems with discontinuities, also known as nonsmooth or hybrid dynamical
systems, under parameter variations. Accordingly, this dissertation is
divided into two parts.
The analytical section of this dissertation discusses mathematical tools for
the analysis of hybrid dynamical systems and their application to a series
of model examples. Specifically, qualitative changes in the system dynamics
from a nonimpacting to an impacting motion, referred to as grazing
bifurcations, are studied in oscillators where the discontinuities are
caused by impacts. Here, the study emphasizes the formulation of conditions
for the persistence of a steady state motion in the immediate vicinity of
periodic and quasiperiodic grazing trajectories in an impacting mechanical
system. A local analysis based on the discontinuity-mapping approach is
employed to derive a normal-form description of the dynamics near a grazing
trajectory. Also, the results obtained using the discontinuity-mapping
approach and direct numerical integration are found to be in good agreement.
It is found that the instabilities caused by the presence of the square-root
singularity in the normal-form description affect the grazing bifurcation
scenario differently depending on the relative dimensionality of the state
space and the steady state motion at the grazing contact.
The computational section presents the structure and applications of a
software program, TC-HAT, developed to study the bifurcation analysis of
hybrid dynamical systems. Here, we present a general boundary value problem
(BVP) approach to locate periodic trajectories corresponding to a hybrid
dynamical system under parameter variations. A methodology to compute the
eigenvalues of periodic trajectories when using the BVP formulation is
illustrated using a model example. Finally, bifurcation analysis of four
model hybrid dynamical systems is performed using TC-HAT.Ph. D.
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Rodriguez, Ramon, and Pamplona David Sanchéz. "DYNAMIC MODELING OF HYBRID PV/THERMAL SOLAR SYSTEM FOR HYDROGEN PRODUCTION." Thesis, University of Gävle, University of Gävle, Department of Technology and Built Environment, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-3580.
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Cross, Patrick Wilson. "System Modeling and Energy Management Strategy Development for Series Hybrid Vehicles." Thesis, Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24785.
Full textAbstract:
A series hybrid electric vehicle is a vehicle that is powered by both an engine and a battery pack. An electric motor provides all of the mechanical motive power to the transmission. Engine power is decoupled from the transmission by converting engine power into electricity which powers the electric motor. The mechanical decoupling of the engine from the transmission allows the engine to be run at any operating point (including off) during vehicle operation while the battery back supplies or consumes the remaining power. Therefore, the engine can be operated at its most efficient operating point or in a high-efficiency operating region.
The first objective of this research is to develop a dynamic model of a series hybrid diesel-electric powertrain for implementation in Simulink. The vehicle of interest is a John Deere M-Gator utility vehicle. This model serves primarily to test energy management strategies, but it can also be used for component sizing given known load profiles for a vehicle.
The second objective of this research is to develop and implement multiple energy management strategies of varying complexity from simple thermostat control to an optimal control law derived using dynamic programming. These energy management strategies are then tested and compared over the criteria of overall fuel efficiency, power availability, battery life, and complexity of implementation. Complexity of implementation is a critical metric for control designers and project managers.
The results show that simple point-based control logic can improve upon thermostat control if engine efficiency maps are known. All control method results depend on the load profile being used for a specific application.
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Chen, Shang. "Reachability problems for systems with linear dynamics." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/22331.
Full textAbstract:
This thesis deals with reachability and freeness problems for systems with linear dynamics, including hybrid systems and matrix semigroups. Hybrid systems are a type of dynamical system that exhibit both continuous and discrete dynamic behaviour. Thus they are particularly useful in modelling practical real world systems which can both flow (continuous behaviour) and jump (discrete behaviour). Decision questions for matrix semigroups have attracted a great deal of attention in both the Mathematics and Theoretical Computer Science communities. They can also be used to model applications with only discrete components. For a computational model, the reachability problem asks whether we can reach a target point starting from an initial point, which is a natural question both in theoretical study and for real-world applications. By studying this problem and its variations, we shall prove in a formal mathematical sense that many problems are intractable or even unsolvable. Thus we know when such a problem appears in other areas like Biology, Physics or Chemistry, either the problem itself needs to be simplified, or it should by studied by approximation. In this thesis we concentrate on a specific hybrid system model, called an HPCD, and its variations. The objective of studying this model is twofold: to obtain the most expressive system for which reachability is algorithmically solvable and to explore the simplest system for which it is impossible to solve. For the solvable sub-cases, we shall also study whether reachability is in some sense easy or hard by determining which complexity classes the problem belongs to, such as P, NP(-hard) and PSPACE(-hard). Some undecidable results for matrix semigroups are also shown, which both strengthen our knowledge of the structure of matrix semigroups, and lead to some undecidability results for other models.
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Hassan, Mohamed. "INELASTIC DYNAMIC BEHAVIOR AND DESIGN OF HYBRID COUPLED WALL SYSTEMS." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4437.
Full textAbstract:
A key consideration in seismic design of buildings is to ensure that the lateral load resisting system has an appropriate combination of strength, stiffness and energy dissipation capacity. Hybrid coupled wall systems, in which steel beams are used to couple two or more reinforced concrete shear walls in series, can be designed to have these attributes and therefore have the potential to deliver good performance under severe seismic loading. This research presents an investigation of the seismic behavior of this type of structural system. System response of 12- and 18-story high prototypes is studied using transient finite element analyses that accounts for the most important aspects of material nonlinear behavior including concrete cracking, tension stiffening, and compressive behavior for both confined and unconfined concrete as well as steel yielding. The developed finite element models are calibrated using more detailed models developed in previous research and are validated through numerous comparisons with test results of reinforced concrete walls and wall-beam subassemblages. Suites of transient inelastic analyses are conducted to investigate pertinent parameters including hazard level, earthquake record scaling, dynamic base shear magnification, interstory drift, shear distortion, coupling beam plastic rotation, and wall rotation. Different performance measures are proposed to judge and compare the behavior of the various systems. The analyses show that, in general, hybrid coupled walls are particularly well suited for use in regions of high seismic risk. The results of the dynamic analyses are used to judge the validity of and to refine a previously proposed design method based on the capacity design concept and the assumption of behavior dominated by the first vibration mode. The adequacy of design based on the pushover analysis procedure as promoted in FEMA-356 (2000) is also investigated using the dynamic analysis results. Substantial discrepancies between both methods are observed, especially in the case of the 18-story system. A critical assessment of dynamic base shear magnification is also conducted, and a new method for estimating its effects is suggested. The method is based on a modal combination procedure that accounts for presence of a plastic hinge at the wall base. Finally, the validity of limitations in FEMA-368 (2000) on building height, particularly for hybrid coupled wall systems, is discussed.Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil and Environmental Engineering
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Zhu, Jiasong. "A self-learning short-term traffic forecasting system through dynamic hybrid approach." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B39634516.
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Zhu, Jiasong, and 朱家松. "A self-learning short-term traffic forecasting system through dynamic hybrid approach." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39634516.
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Alanezi, Ahmad Qatnan. "Dynamic coupling of air culvert air conditioning hybrid cooling system in buildings." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=17832.
Full textAbstract:
Active and passive cooling methods have been the subject of much investigation. Nevertheless, there remains a significant opportunity to utilise the so-called "responsive building elements" and to arrange for cooperative deployment with downsized, conventional HVAC systems. The integration of an air culvert with an active cooling system along with associated control is the subject of this thesis. The issues studied within this thesis are as follows. The quantification of air culvert thermal efficacy. The elaboration of an integrated system design method that accounts for the transient interaction between the air culvert and the air conditioning systems. The requirement for hybrid system control when deployed within different climates. The ESP-r system was adopted within the present work. A ground temperature model was established for the hot/dry climate location selected and validated against measured soil temperature profiles. A culvert model was derived and verified empiricall y and by inter-model comparison. Results showed that the ESP-r model can robustly quantify the thermal performance of an air culvert. The culvert was then coupled to a residential villa situated in the hot/arid climate domain and its contribution explored. A constant air volume air-conditioning system was then linked to the culvert-building model and used to research approaches to the control of such a hybrid cooling system. A general control strategy was then devised corresponding to specific objectives and constraints. Results confirmed that the final control set-up can be implemented for a culvert/HVAC hybrid cooling system regardless of climate type, with cooling load matching in excess of 85% keeping indoor resultant temperatures within comfort threshold limits. The project conclusion is that a culvert may be deployed in a manner that allows significant down-sizing of conventional cooling plant, thereby achieving both capital and running costs savings without appreciable loss.
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Saleheen, Firdous. "BIMODAL DYNAMIC IMAGING SYSTEM FOR TUMOR CHARACTERIZATION USING HYBRID HIERARCHICAL STATISTICAL CONTROL." Diss., Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/465968.
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Electrical and Computer EngineeringPh.D.
Conventional medical imaging technologies for cancer diagnosis utilize fixed geometric configuration of the source and the detector to image the target. In this dissertation, we hypothesize that dynamic utilization of source and detector geometry will lead to better performance of medical imaging devices. Interrogating a target in a three dimensional space requires cooperation and coordination between the source and detector positions. The goal of this dissertation is to develop a dynamic imaging method, which will improve the tumor characterization performance, and provide a control scheme appropriate for the dynamic interrogation. This dissertation proposes a bimodal dynamic imaging (BDI) method for improving tumor characterization and a hybrid hierarchical statistical control scheme for the autonomous control of the sources and detectors. The tactile imaging sensor has high specificity but low sensitivity in tumor characterization. The spectral sensor has high sensitivity but low specificity. The BDI system integrates the tactile sensing and the spectral sensing modalities with the capability of dynamic positioning of the source and detector to determine the mechanical and spectral properties of a tumor. The tactile sensing can estimate the mechanical properties of the tumor, such as size, depth, and elastic modulus, while the spectral sensing can determine the absorption coefficient of the tumor through diffuse optical imaging. These properties help us characterize the tumor, and differentiate cancerous tissues from healthy tissues. We designed and experimentally evaluated the BDI system for estimating the size, depth, elastic modulus, and absorption coefficient of embedded inclusions. The system performance in characterizing mechanical properties was then compared to that of the tactile imaging sensor. The proposed BDI method was experimentally validated using fabricated bimodal phantom. The experimental results showed that the tactile imaging system (TIS) estimated the tumor phantom size with 7.23% error; BDI measured the size with 0.8% error. The TIS depth estimation error was 41.83%; BDI reduced the depth measurement error to 20.00%. The TIS elastic modulus estimation error was 96.80%; the BDI method showed 74.79% error. Additionally, BDI estimated the absorption coefficient with 14%-25% estimation error. For further improvement the system performance, this bimodal imaging system is implemented on a dual-arm robot, Baxter, where the laser source and the tactile imaging sensors were mounted on the end-effectors. Each arm of Baxter robot has seven Degree-of- Freedom. This provides more flexibility in terms of interrogating the target compared to the fixed geometric configuration. We devised a hybrid statistical controller for maneuvering the source and the detector of the system. In this control architecture, a high-level supervisory controller was used for the functions at a higher level for coordinating two arms. At lower level, a full-state feedback statistical controller was used to facilitate the minimum position variation. A linear model for the dual-arm Baxter robot was derived for testing the proposed architecture. We performed the simulations of hybrid hierarchical statistical controller on the Baxter model for trajectory tracking. The simulation studies demonstrated accurate sequential task execution for the bimodal dynamic imaging system using a hybrid hierarchical statistical control.
Temple University--Theses