Optimal input design concerns the design of an input sequence to maximize the information retrieved from an experiment. The design of the input sequence is performed by optimizing a cost function related to the intended model application. Several approaches to input design have been proposed, with results mainly on linear models. Under the linear assumption of the model structure, the input design problem can be solved in the frequency domain, where the corresponding spectrum is optimized subject to power constraints. However, the optimization of the input spectrum using frequency domain techniques cannot include time-domain amplitude constraints, which could arise due to practical or safety reasons. In this thesis, a new input design method for nonlinear models is introduced. The method considers the optimization of an input sequence as a realization of the stationary Markov process with finite memory. Assuming a finite set of possible values for the input, the feasible set of stationary processes can be described using graph theory, where de Bruijn graphs can be employed to describe the process. By using de Bruijn graphs, we can express any element in the set of stationary processes as a convex combination of the measures associated with the extreme points of the set. Therefore, by a suitable choice of the cost function, the resulting optimization problem is convex even for nonlinear models. In addition, since the input is restricted to a finite set of values, the proposed input design method can naturally handle amplitude constraints. The thesis considers a theoretical discussion of the proposed input design method for identification of nonlinear output error and nonlinear state space models. In addition, this thesis includes practical applications of the method to solve problems arising in wireless communications, where an estimate of the communication channel with quantized data is required, and application oriented closed-loop experiment design, where quality constraints on the identified parameters must be satisfied when performing the identification step. / <p>QC 20141110</p>

No description available.

With recent developments in power conversion technologies and market trends that are driving those technologies toward further miniaturization and greater integration, the need for verifying an empirically based modeling methodology for proprietary power converters such as Power Supply on Chip (PwrSoC) products has risen significantly. This need motivates the investigation of black-box models which require little or no knowledge of the internal workings of a system, for those areas of industry adopting PwrSoC technology as a point-of-load solution. This thesis reports a black-box modeling method tailored to accommodate but not limited to the requirements of a specific commercially available PwrSoC technology.

No description available.

Temperature control has been implemented in friction stir processing and has demonstrated the ability to give improved process control. In order to have optimal control of the process, the parameters of the system to be controlled must be accurately identified. The system parameters change with tool geometry and materials, workpiece materials, and temperature. This thesis presents the use of the relay feedback test to determine the system parameters. The relay feedback test is easy to use and promotes system stability during its use. The results from the relay feedback test can be used to determine controller gains for a PID controller. The use of this method, as well as the quality of the resulting control is demonstrated in this paper.

This thesis presents the formulation and solution of a new problem in systems and control theory, called the Network Realization Problem. Its relationship to other problems, such as State Realization and Structural Identifiability, is shown. The motivation for this work is the desire to completely quantify the conditions for transitioning between different mathematical representations of linear time-invariant systems. The solution to this problem is useful for theorists because it lays a foundation for quantifying the information cost of identifying a system's complete network structure from the transfer function.

[pt] A identificação de sistemas é focalizada sob o ponto de vista da aproximação estocástica. Um sistema sem memória e invariante no tempo, com função completamente desconhecida é identificado por intermédio de uma estimação, que minimiza o critério do erro médio quadrático, tomando como base um conjunto de funções pré- selecionadas e linearmente independentes. A identificação do sistema é obtida através de uma algoritmo recursivo de aproximação estocástica, que converge para o valor real dessa estimativa, com probabilidade 1 e no sentido da média quadrática. Um estudo da aceleração desse algoritmo é efetuado, comprovando a existência de uma seqüência capaz de otimizá-lo. É demonstrada a aplicação desse algoritmo para identificação de um sistema linear e invariante no tempo, entretanto a aceleração da convergência não é mais uma conseqüência do caso anterior. Ainda é apresentada uma tentativa de contornar o problema de acessibilidade dos estados, requerida pelo algoritmo de aproximação estocástica, utilizando simultaneamente à identificação dos parâmetros do sistema, os algoritmos do filtro de Kalman, para estimação dos estados / [en] The stochastic approximation approach is used for systems identification. A memoryless time-invariant system with functional form completely unknow is identified by means of an estimate based on a preselected and linearly independent set of function which minimizes the mean-square-error criterion. The system identification is obtained using a stochastic approximation recursive algorithm, which convergs to a real value of this estimate, with probability 1 and in the mean square sense. The acceleration study of this algorithm is developd by proving the existence of an optimal sequence. The application of this algorithm for a linear timevariant system identification is proved, nevertheless the convergence acceletation is not anymore a consequence of the last case. Next is presented a tentative to by-pass the problem of states accessibility, required for the stochastic approximation, using simultaneously parameters systems identification with the Kalman-filter algorithms for states estimation.

[pt] No presente trabalho faz-se inicialmente um apanhado das principais técnicas usadas na Identificação de Processos Físicos, cuja finalidade é servir de subsidio bibliográfico para outros trabalhos futuros (Cap. I, II e III). É dado ênfase aos problemas existentes na identificação de sistemas não estacionários tendo em vista a sua importância um projeto de Sistemas de Controle Auto – Adaptativos. Foi desenvolvido um método de identificação, usando a Técnica do Modelo Adaptativo (Cap. IV). Fez-se a simulação analógica do modelo adaptativo, no computador ANALAC 110 (comp. Analógico a corrente alternada) tendo em vista as facilidades permitidas pelos comandos gel, e CI dos seus integradores. Verificou-se a validade da simulação no ANALAC, testando-se a convergência do método em vários exemplos, cujos resultados são conhecidos. Os resultados são apresentados no Anexo 1. Posteriormente, estudou-se a possibilidade de tratar este mesmo problema em computador digital (IBM-1130) (Cap. IV e 3). No anexo II são apresentados os fluxogramas e programas FORTRAN, relativos a técnica digital. / [en] The subject of this paper is to give a summary of the more important techniques used in Identification of Physical Process, the purpose being that of serving as a bibliografical reference to future works (chap´s I, II and III). Special attention is given to problems of Identification in time varying systems, with the object the designing Auto-Adaptive Control Systems. Methods of Identification were developed using Adaptative Model Technique (Chap IV). Analog simulation of the adaptative model was performed on the ANALAC (Alternating Current Analog Computer) utilising the GEL and CI Integrator Modules. The simulation results were verified by testing the convergence of various examples, whose solutions are well know. The results are given in the Anex 1. In addition the feasibility of solving this same problem on a digital computer (IBM 1130) was considered (chap IV. 3). In the Anex 2, FORTRAN programs of the digital technics are presented.

A study of the nonlinear vibrations of metallic cantilever beams and plates subjected to transverse harmonic excitations is presented. Both experimental and theoretical results are presented. The primary focus is however on the transfer of energy between widely spaced modes via modulation. This phenomenon is studied both in the presence and absence of a one-to-one internal resonance. Reduced-order models using Galerkin discretization are also developed to predict experimentally observed motions. A good qualitative agreement is obtained between the experimental and numerical results. Experimentally the energy transfer between widely spaced modes is found to be a function of the closeness of the modulation frequency to the natural frequency of the first mode. The modulation frequency, which depends on various parameters like the amplitude and frequency of excitation, damping factors, etc., has to be near the natural frequency of the low-frequency mode for significant transfer of energy from the directly excited high-frequency mode to the low-frequency mode. An experimental parametric identification technique is developed for estimating the linear and nonlinear damping coefficients and effective nonlinearity of a metallic cantilever beam. This method is applicable to any single-degree-of-freedom nonlinear system with weak cubic geometric and inertia nonlinearities. In addition, two methods, based on the elimination theory of polynomials, are proposed for determining both the critical forcing amplitude as well as the jump frequencies in the case of single-degree-of-freedom nonlinear systems. An experimental study of the response of a rectangular, aluminum cantilever plate to transverse harmonic excitations is also conducted. Various nonlinear dynamic phenomena, like two-to-one and three-to-one internal resonances, external combination resonance, energy transfer between widely spaced modes via modulation, period-doubled motions, and chaos, are demonstrated using a single plate. It is again shown that the closeness of the modulation frequency to the natural frequency of the first mode dictates the energy transfer between widely spaced modes. / Ph. D.

A method for developing transient, predictive models of gas turbine engine performance using system identification techniques in conjunction with test cell data has been successfully demonstrated. Test cell data were obtained for both transient and steady-state operation from two F402-RR-406A USMC AV-8B engines at the Naval Aviation Depot (NADEP), Cherry Point, North Carolina. One engine was run to gather a single set of steady-state data consisting of 24 subsets of five seconds of data. The other engine was run to obtain two sets of transient data, recorded at three different rates of engine acceleration for each set. The acceleration rates of 3, 25, and 100 degrees of throttle per second were preset in the test cell controls. These rates correspond to the angular velocity of the fuel throttle during an acceleration. Each of these six transient test runs consisted of 25 seconds of data. Data were captured at a rate of five Hertz over the engine operating range from idle (26% Low Pressure spool speed) to full military power (105% LP spool speed) for all cases. A BASIC code developed at the NADEP required significant modification before it could be used to reduce the data. The modified code generated engine operating points consisting of mass flow rate, total pressure ratio, spool speed, and rate of acceleration for the inner fan, outer fan, and high pressure compressor. Finally, a multivariate regression technique using the SAS language was developed in cooperation with the Virginia Tech Statistical Consulting Center. This technique was used to generate a closed-form model of each component capable of predicting operating points at spool speeds and acceleration rates intermediate to those measured. / Master of Science