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Sampleddata models for linear and nonlinear systemsYuz Eissmann, Juan Ignacio January 2006 (has links)
Continuoustime systems are usually modelled by differential equations arising from physical laws. However, the use of these models in practice requires discretisation. In this thesis we consider sampleddata models for linear and nonlinear systems. We study some of the issues involved in the sampling process, such as the accuracy of the sampleddata models, the artifacts produced by the particular sampling scheme, and the relations to the underlying continuoustime system. We review, extend and present new results, making extensive use of the delta operator which allows a clearer connection between a sampleddata model and the underlying continuoustime system. In the first part of the thesis we consider sampleddata models for linear systems. In this case exact discretetime representations can be obtained. These models depend, not only on the continuoustime system, but also on the artifacts involved in the sampling process, namely, the sample and hold devices. In particular, these devices play a key role in determining the sampling zeros of the discretetime model. We consider robustness issues associated with the use of discretetime models for continuoustime system identification from sampled data. We show that, by using restricted bandwidth frequency domain maximum likelihood estimation, the identification results are robust to (possible) undermodelling due to the sampling process. Sampleddata models provide a powerful tool also for continuoustime optimal control problems, where the presence of constraints can make the explicit solution impossible to find. We show how this solution can be arbitrarily approximated by an associated sampleddata problem using fast sampling rates. We also show that there is a natural convergence of the singular structure of the optimal control problem from discrete to continuoustime, as the sampling period goes to zero. In Part II we consider sampleddata models for nonlinear systems. In this case we can only obtain approximate sampleddata models. These discretetime models are simple and accurate in a well defined sense. For deterministic systems, an insightful observation is that the proposed model contains sampling zero dynamics. Moreover, these correspond to the same dynamics associated with the asymptotic sampling zeros in the linear case. The topics and results presented in the thesis are believed to give important insights into the use of sampleddata models to represent linear and nonlinear continuoustime systems. / PhD Doctorate

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Stochastic Optimal Control: The DiscreteTIme CaseBertsekas, Dimitir P., Shreve, Steven 03 March 2004 (has links)
No description available.

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Optimal Control Applied to a Mathematical Model for VancomycinResistant EnterococciLowden, Jonathan 11 April 2015 (has links)
Enterococci bacteria that cannot be treated eectively with the antibiotic vancomycin are termed VancomycinResistant Enterococci (VRE). In this thesis, we develop a mathematical framework for determining optimal strategies for prevention and treatment of VRE in an Intensive Care Unit (ICU). A system of ve ordinary dierential equations describes the movement of ICU patients in and out of dierent states related to VRE infection. Two control variables representing the prevention and treatment of VRE are incorporated into the system. An optimal control problem is formulated to minimize the VRErelated deaths and costs associated with controls over a nite time period. Pontryagin's Minimum Principle is used to characterize optimal controls by deriving a Hamiltonian expression and dierential equations for ve adjoint variables. Numerical solutions to the optimal control problem illustrate how hospital policy makers can use our mathematical framework to investigate optimal costeective prevention and treatment schedules during a VRE outbreak. / McAnulty College and Graduate School of Liberal Arts; / Computational Mathematics / MS; / Thesis;

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A Weighted Residual Framework for Formulation and Analysis of Direct Transcription Methods for Optimal ControlSingh, Baljeet 2010 December 1900 (has links)
In the past three decades, numerous methods have been proposed to transcribe optimal control problems (OCP) into nonlinear programming problems (NLP). In this dissertation work, a unifying weighted residual framework is developed under which most of the existing transcription methods can be derived by judiciously choosing test and trial functions. This greatly simplifies the derivation of optimality conditions and costate estimation results for direct transcription methods. Under the same framework, three new transcription methods are devised which are particularly suitable for implementation in an adaptive refinement setting. The method of Hilbert space projection, the least square method for optimal control and generalized moment method for optimal control are developed and their optimality conditions are derived. It is shown that under a set of equivalence conditions, costates can be estimated from the Lagrange multipliers of the associated NLP for all three methods. Numerical implementation of these methods is described using BSplines and global interpolating polynomials as approximating functions. It is shown that the existing pseudospectral methods for optimal control can be formulated and analyzed under the proposed weighted residual framework. Performance of Legendre, Gauss and Radau pseudospectral methods is compared with the methods proposed in this research. Based on the variational analysis of firstorder optimality conditions for the optimal control problem, an posteriori error estimation procedure is developed. Using these error estimates, an hadaptive scheme is outlined for the implementation of least square method in an adaptive manner. A timescaling technique is described to handle problems with discontinuous control or multiple phases. Several reallife examples were solved to show the efficacy of the hadaptive and timescaling algorithm.

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Design of Model Reference Adaptive Tracking Controllers for Mismatched Uncertain Dynamic SystemsChang, ChaoChin 17 July 2002 (has links)
Based on the Lyapunov stability theorem, an optimal model reference adaptive control (OMRAC) scheme with perturbation estimation is presented in this thesis to solve robust tracking problems. The plant considered belongs to a class of MIMO perturbed dynamic systems with input nonlinearity and time varying delay in the state. The proposed control scheme contains three types of controllers. The first one is a linear feedback controller, which is an optimal controller if there is no perturbation. The second one is an adaptive controller, it is used for adapting the unknown upper bound of perturbation estimation error. The last one is the perturbation estimation mechanism. The property of uniformly ultimately boundness is proved under the proposed control scheme, and the effects of each design parameter on the dynamic performance is analyzed. Two numerical examples are given for demonstrating the feasibility of the proposed methodology.

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Lossless convexification of optimal control problemsHarris, Matthew Wade 30 June 2014 (has links)
This dissertation begins with an introduction to finitedimensional optimization and optimal control theory. It then proves lossless convexification for three problems: 1) a minimum time rendezvous using differential drag, 2) a maximum divert and landing, and 3) a general optimal control problem with linear state constraints and mixed convex and nonconvex control constraints. Each is a unique contribution to the theory of lossless convexification. The first proves lossless convexification in the presence of singular controls and specifies a procedure for converting singular controls to the bangbang type. The second is the first example of lossless convexification with state constraints. The third is the most general result to date. It says that lossless convexification holds when the state space is a strongly controllable subspace. This extends the controllability concepts used previously, and it recovers earlier results as a special case. Lastly, a few of the remaining research challenges are discussed. / text

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Riccati Equations in Optimal Control TheoryBellon, James 21 April 2008 (has links)
It is often desired to have control over a process or a physical system, to cause it to behave optimally. Optimal control theory deals with analyzing and finding solutions for optimal control for a system that can be represented by a set of differential equations. This thesis examines such a system in the form of a set of matrix differential equations known as a continuous linear timeinvariant system. Conditions on the system, such as linearity, allow one to find an explicit closed form finite solution that can be more efficiently computed compared to other known types of solutions. This is done by optimizing a quadratic cost function. The optimization leads to solving a Riccati equation. Conditions are discussed for which solutions are possible. In particular, we will obtain a solution for a stable and controllable system. Numerical examples are given for a simple system with 2x2 matrix coefficients.

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FuelEfficient HeavyDuty Vehicle PlatooningAlam, Assad January 2014 (has links)
The freight transport industry faces big challenges as the demand for transport and fuel prices are steadily increasing, whereas the environmental impact needs to be significantly reduced. Heavyduty vehicle (HDV) platooning is a promising technology for a sustainable transportation system. By semiautonomously governing each platooning vehicle at small intervehicle spacing, we can effectively reduce fuel consumption, emissions, and congestion, and relieve driver tension. Yet, it is not evident how to synthesise such a platoon control system and how constraints imposed by the road topography affect the safety or fuelsaving potential in practice. This thesis presents contributions to a framework for the design, implementation, and evaluation of HDV platooning. The focus lies mainly on establishing fuelefficient platooning control and evaluating the fuelsaving potential in practice. A vehicle platoon model is developed together with a system architecture that divides the control problem into manageable subsystems. Presented results show that a significant fuel reduction potential exists for HDV platooning and it is favorable to operate the vehicles at a small intervehicle spacing. We address the problem of finding the minimum distance between HDVs in a platoon without compromising safety, by setting up the problem in a game theoretical framework. Thereby, we determine criteria for which collisions can be avoided in a worstcase scenario and establish the minimum safe distance to a vehicle ahead. A systematic design methodology for decentralized intervehicle distance control based on linear quadratic regulators is presented. It takes dynamic coupling and engine response delays into consideration, and the structure of the controller feedback matrix can be tailored to the locally available state information. The results show that a decentralized controller gives good tracking performance and attenuates disturbances downstream in the platoon for dynamic scenarios that commonly occur on highways. We also consider the problem of finding a fuelefficient controller for HDV platooning based on road grade preview information under road and vehicle parameter uncertainties. We present two model predictive control policies and derive their fuelsaving potential. The thesis finally evaluates the fuel savings in practice. Experimental results show that a fuel reduction of 3.9–6.5 % can be obtained on average for a heterogenous platoon of HDVs on a Swedish highway. It is demonstrated how the savings depend on the vehicle position in the platoon, the behavior of the preceding vehicles, and the road topography. With the results obtained in this thesis, it is argued that a significant fuel reduction potential exists for HDV platooning. / <p>QC 20140527</p>

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Maximizacao da potencia de um reator esferico refletido com distribuicao de combustivel otimizadaREADE, JOAMAR R.V. 09 October 2014 (has links)
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01289.pdf: 1054597 bytes, checksum: 34d39eecaf38000806cab1b17e2437f0 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Energia Atomica  IEA

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Maximizacao da potencia de um reator esferico refletido com distribuicao de combustivel otimizadaREADE, JOAMAR R.V. 09 October 2014 (has links)
Made available in DSpace on 20141009T12:30:37Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 20141009T14:00:48Z (GMT). No. of bitstreams: 1
01289.pdf: 1054597 bytes, checksum: 34d39eecaf38000806cab1b17e2437f0 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Energia Atomica  IEA

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