Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 120-124. / by John Nikolaos Tsitsiklis. / M.S.

Digital control needs discrete time models, but conversion from continuous time, fed by a zero order hold, to discrete time introduces sampling zeros which are outside the unit circle, i.e. non-minimum phase (NMP) zeros, in the majority of the systems. Also, some systems are already NMP in continuous time. In both cases, the inverse problem to find the input required to maintain a desired output tracking, produces an unstable causal control action. The control action will grow exponentially every time step, and the error between time steps also grows exponentially. This prevents many control approaches from making use of inverse models. The problem statement for the existing stable inverse theorem is presented in this work, and it aims at finding a bounded nominal state-input trajectory by solving a two-point boundary value problem obtained by decomposing the internal dynamics of the system. This results in the causal part specified from the minus infinity time; and its non-causal part from the positive infinity time. By solving for the nominal bounded internal dynamics, the exact output tracking is achieved in the original finite time interval. The new stable inverses concepts presented and developed here address this instability problem in a different way based on the modified versions of problem states, and in a way that is more practical for implementation. The statements of how the different inverse problems are posed is presented, as well as the calculation and implementation. In order to produce zero tracking error at the addressed time steps, two modified statements are given as the initial delete and the skip step. The development presented here involves: (1) The detection of the signature of instability in both the nonhomogeneous difference equation and matrix form for finite time problems. (2) Create a new factorization of the system separating maximum part from minimum part in matrix form as analogous to transfer function format, and more generally, modeling the behavior of finite time zeros and poles. (3) Produce bounded stable inverse solutions evolving from the minimum Euclidean norm satisfying different optimization objective functions, to the solution having no projection on transient solutions terms excited by initial conditions. Iterative Learning Control (ILC) iterates with a real world control system repeatedly performing the same task. It adjusts the control action based on error history from the previous iteration, aiming to converge to zero tracking error. ILC has been widely used in various applications due to its high precision in trajectory tracking, e.g. semiconductor manufacturing sensors that repeatedly perform scanning maneuvers. Designing effective feedback controllers for non-minimum phase (NMP) systems can be challenging. Applying Iterative Learning Control (ILC) to NMP systems is particularly problematic. Incorporating the initial delete stable inverse thinkg into ILC, the control action obtained in the limit as the iterations tend to infinity, is a function of the tracking error produced by the command in the initial run. It is shown here that this dependence is very small, so that one can reasonably use any initial run. By picking an initial input that goes to zero approaching the final time step, the influence becomes particularly small. And by simply commanding zero in the first run, the resulting converged control minimizes the Euclidean norm of the underdetermined control history. Three main classes of ILC laws are examined, and it is shown that all ILC laws converge to the identical control history, as the converged result is not a function of the ILC law. All of these conclusions apply to ILC that aims to track a given finite time trajectory, and also apply to ILC that in addition aims to cancel the effect of a disturbance that repeats each run. Having these stable inverses opens up opportunities for many control design approaches. (1) ILC was the original motivation of the new stable inverses. Besides the scenario using the initial delete above, consider ILC to perform local learning in a trajectory, by using a quadratic cost control in general, but phasing into the skip step stable inverse for some portion of the trajectory that needs high precision tracking. (2) One step ahead control uses a model to compute the control action at the current time step to produce the output desired at the next time step. Before it can be useful, it must be phased in to honor actuator saturation limits, and being a true inverse it requires that the system have a stable inverse. One could generalize this to p-step ahead control, updating the control action every p steps instead of every one step. It determines how small p can be to give a stable implementation using skip step, and it can be quite small. So it only requires knowledge of future desired control for a few steps. (3) Note that the statement in (2) can be reformulated as Linear Model Predictive Control that updates every p steps instead of every step. This offers the ability to converge to zero tracking error at every time step of the skip step inverse, instead of the usual aim to converge to a quadratic cost solution. (4) Indirect discrete time adaptive control combines one step ahead control with the projection algorithm to perform real time identification updates. It has limited applications, because it requires a stable inverse.

Bruce Ronald Musicus. / Originally published as thesis (Dept. of Electrical Engineering and Computer Science, Ph.D., 1982). / Includes bibliographies. / Supported in part by the Advanced Research Projects Agency monitored by ONR under Contract N00014-81-K-0742 NR-049-506 Supported in part by the National Science Foundation under Grant ECS80-07102

Thesis (Ph. D.)--York University, 2001. Graduate Programme in Mathematics. / Typescript. Includes bibliographical references (leaves 114-119). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ66358.

Thesis (Ph.D.) - Carleton University, 2005. / Includes bibliographical references (p. 182-193). Also available in electronic format on the Internet.

Thesis (Ph.D.)--University of Delaware, 2005. / Principal faculty adviser: Xiang-Gen Xia, Dept. of Electrical & Computer Engineering. Includes bibliographical references.

Orientador: Hugo Enrique Hernández-Figueroa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-16T06:54:22Z (GMT). No. of bitstreams: 1 Claudio_Kleucio_D.pdf: 3139134 bytes, checksum: 900508bd03693258d7011b6af9debd55 (MD5) Previous issue date: 2010 / Resumo: O método de elementos finitos é largamente empregado na modelagem de problemas de eletromagnetismo. A modelagem implícita deste método recai em resolver sistemas de equações lineares esparsas, esta etapa é de alto custo computacional. Este trabalho propõe alternativas com o objetivo de melhorar o desempenho computacional das aplicações provenientes de formulações via elementos finitos, através do aproveitamento de soluções de sistemas de equações lineares por métodos direto e iterativo, para simular dispositivos ópticos com as características físicas alteradas constantemente. Na solução dos sistemas de equações, utilizou-se o método direto com Small Rank Adjustment e o método iterativo gradiente bi-conjugado estabilizado precondicionado com análises de reaproveitamento do precondicionador ILUT. Nos estudos desenvolvidos obteve-se um melhor desempenho computacional quando se utilizou o método iterativo. Estes resultados são de grande importância na área de otimização de dispositivos fotônicos tais como acopladores, filtros, demultiplexadores, etc, pois a otimização destes dispositivos consiste em avaliar várias configurações do espaço de busca, implicando em resolver vários sistemas de equações lineares similares provenientes do método de elementos finitos. / Abstract: The Finite Element Method is one of the most popular numerical tools in electromagnetics. Implicit schemes require the solution of sparse linear equation systems, this step demands a lot of computational time. This work proposes alternatives enhancements to obtain better computational performance of such implicit schemes. This was made through the improvement of direct and iterative methods, for problems which may be interpreted as perturbations of a given original one. This is very important specially in the optimization process of devices, due to the fact that one needs to solve many linear systems with little changes at each step, to explore the search space, so many perturbed linear systems are solved to obtain the optimum device. For direct methods the Small Rank Adjustment technique was used, while for iterative methods, the Preconditioned Gradient Stabilized Biconjugate Method reusing the preconditioner, were adopted. The applications were focused on the design of photonic devices, like couplers, filters, demultiplexers, etc. / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica

Orientador: Vera Lucia da Rocha Lopes / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica / Made available in DSpace on 2018-08-10T21:50:16Z (GMT). No. of bitstreams: 1 LopezErazo_TulioEmiro_M.pdf: 12666478 bytes, checksum: df86afcc58096ac12697d7d0fefe8ee5 (MD5) Previous issue date: 2007 / Resumo: No presente trabalho estudamos métodos numéricos que resolvem um problema de programação não linear com restrições lineares de desigualdade e de igualdade, os quais não fazem uso explícito do gradiente da função objetivo nem tampouco de aproximações ao mesmo. Um método de decréscimo su_ciente e um método de decréscimo simples são estudados. O primeiro, procura melhores valores para a função objetivo ao longo de um conjunto de direções, as quais geram positivamente o cone poliedral convexo no ponto atual. O segundo método procura melhorar o valor da função objetivo ao longo de um conjunto de direções, as quais, dependendo do ponto atual, ou geram positivamente todo o espaço Rn, ou geram positivamente o cone poliedral convexo em tal ponto. Algoritmos dos métodos, comentários das implementa ções feitas e testes numéricos de tais implementações com problemas da coleção Hock-Schittkowski são feitos ao final do trabalho / Abstract: In the present work we study numerical methods that solve a problem of nonlinear programming with linear inequality and equality constraints, which do not make explicit use either neither of the gradient of the objective function nor approaches to the same one. A method of su_cient decrease and a method of simple decrease are studied. The _rst one, looks for better values for the objective function throughout a set of directions, which positively generate the convex polyhedral cone in the current point. The second method looks for to improve the value of the objective function throughout a set of directions, which, depending on the current point, either generates positively the whole spaces, or positively generates the convex polyhedral cone in this point. Algorithms of the methods, commentaries of the implementations done and numerical tests of such implementations with problems of the Hock-Schittkowski collection are made at the end of the work / Mestrado / Mestre em Matemática Aplicada

Orientador: Roberto Andreani / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-08-04T05:03:19Z (GMT). No. of bitstreams: 1 Gaujoux_RenaudGilles_M.pdf: 1743739 bytes, checksum: a3548a59bc983f4398cb0136c62c1d6a (MD5) Previous issue date: 2005 / Resumo: Esta dissertação trata da aplicação de um método de tipo Newton generalizado aos sistemas KKT. Graças às funções chamadas de NCP, o sistema KKT pode ser reformulado como uma equação do tipo H(z) = O, onde H é uma função semi-suave. Nos preliminares teóricos apresentamos os conceitos importantes para a análise desse tipo de sistema quando a função involvida não é diferenciável. Trata-se de subdiferencial, semi-suavidade, semi-derivada. Então, usando um ponto de vista global, descrevemos de uma vez só as diferentes generalizações do método de Newton, apresentando as condições suficientes de convergência local. Uma versão globalizada do método é também detalhada. Com o fim de aplicar o algoritmo à reformulação semi-suave do sistema KKT, estudamos as propriedades da função H, primeiro independentemente da função NCP usada. Então analisamos o caso de três funções NCP particulares: a função do Mínimo, a função de Fischer-Burmeister, a função de Fischer-Burmeister Penalizada. Apresentamos os resultados de testes numéricos que comparam o desempenho do algoritmo quando usa as diferentes funções NCP acima / Abstract: This work deals with the use of generalized Newton type method to solve KKT systems. By the mean of so called NCP functions, any KKT system can be writen as an equation of type H(z) = O, where H is a semismooth function. In a teorical preliminaries part, we present some key notions for the analysis of such a type of system, whose the involved function is not differentiable. It deals with subdifferential, semismoothness, semiderivative. Then, tackling the problem with a very general point of view, we make a unified description of different generalizations of N ewton method, giving sufficient local convergence conditions. More over, we detail a possible globalization of such methods. In order to use this global algorithm to solve semismooth form of KKT systems, we study some of the H function's properties, first without specifying any underlying NCP function, and then in the case of three known NCP functions: the minimum function, the Fischer-Burmeister function and the penalized Fischer-Burmeister function. Finally, we give the results of numerical tests, which compare the algorithm's performance for each of these three NCP functions / Mestrado / Matematica Aplicada / Mestre em Matemática Aplicada

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 124-127. / by Enrique J. Laya. / M.S.