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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

PID Control of Systems with Hysteresis

Shum, Alex January 2009 (has links)
Hysteresis is exhibited by many physical systems. Smart materials such as piezoelectrics, magnetostrictives and shape memory alloys possess useful properties, especially in the field of micropositioning, but the control of these systems is difficult due to the presence of hysteresis. An accurate model is required to predict the behaviour of these systems so that they can be controlled. Several hysteresis models including the backlash, elastic-plastic and Preisach operators are discussed in detail. Several other models are mentioned. Other control methods for this problem are discussed in the form of a literature review. The focus of this thesis is on the PID control of hysteretic systems. In particular, two systems experiencing hysteresis in their controllers are examined. The hysteresis in each system is described by different sets of assumptions. These assumptions are compared and found to be very similar. In the first system, a PI controller is used to track a reference signal. In the second, a PID controller is used to control a second-order system. The stability and tracking of both systems are discussed. An extension is made to the first system to include the dynamics of a first-order system. The results of the second system are verified to hold for a general first-order system. Simulations were performed with the extension to a first-order system using different hysteresis models.
32

PID Control of Systems with Hysteresis

Shum, Alex January 2009 (has links)
Hysteresis is exhibited by many physical systems. Smart materials such as piezoelectrics, magnetostrictives and shape memory alloys possess useful properties, especially in the field of micropositioning, but the control of these systems is difficult due to the presence of hysteresis. An accurate model is required to predict the behaviour of these systems so that they can be controlled. Several hysteresis models including the backlash, elastic-plastic and Preisach operators are discussed in detail. Several other models are mentioned. Other control methods for this problem are discussed in the form of a literature review. The focus of this thesis is on the PID control of hysteretic systems. In particular, two systems experiencing hysteresis in their controllers are examined. The hysteresis in each system is described by different sets of assumptions. These assumptions are compared and found to be very similar. In the first system, a PI controller is used to track a reference signal. In the second, a PID controller is used to control a second-order system. The stability and tracking of both systems are discussed. An extension is made to the first system to include the dynamics of a first-order system. The results of the second system are verified to hold for a general first-order system. Simulations were performed with the extension to a first-order system using different hysteresis models.
33

The Intelligent Combination of Input Shaping and PID Feedback Control

Huey, John Rogers 10 July 2006 (has links)
Input shaping and Proportional-Integral-Derivative (PID) feedback control are simple, easy-to-implement and generally low cost control strategies. Considering this, it is remarkable that they are also very effective control techniques. In fact, a majority of the world's feedback controllers utilize PID (or the subset PD) control. In addition, input shaping has seen significant use on real-world machines such as cranes, micro-mills, coordinate measuring machines, computer disc drive manufacturing machines, spacecraft, etc. However, despite similarities in effectiveness and ease of implementation, input shaping and PID feedback control are fundamentally different strategies. Input shaping is an anticipatory control scheme capable of enabling quick, low-vibration motions. PID feedback control is reactive in nature, and it is primarily required to deal with problems such as modeling errors, disturbances and nonlinearities. Of course, PID control is also used to reduce vibrations (as in the case of input shaping). But, because it is a reactive controller, it is slower than input shaping at eliminating motion-induced vibration. Given their effectiveness and practicality, as well as the fact that they address important and complimentary control issues, it would be advantageous to combine these two control strategies. The result would still be practical and effective, yet would now address a range of system phenomenon beyond that which is capable by either of the individual control techniques. However, there is a definite gap in the state-of-the-art technology for combining these techniques. For example, little research has addressed the intelligent combination of traditional, outside-the-loop input shaping and PID feedback control. In addition, only a few researchers have attempted to place input shaping filters within feedback loops. This research studies the intelligent combination of input shaping and PID feedback control by developing a concurrent design procedure for outside-the-loop input shaping/PID feedback combinations and by analyzing the effect of placing input shaping filters within feedback loops.
34

An automated virtual tool to compute the entire set of proportional integral derivative controllers for a continuous linear time invariant system

Narasimhan, Bharat 15 May 2009 (has links)
This thesis presents the very practical and novel approach of using the Graphical User Interface (GUI) to compute the entire set of Proportional Integral Derivative (PID) controllers given the transfer function or the frequency response of the system under consideration. Though there is a wide spread usage of PID controllers in the industry, until recently no formal algorithm existed on determining a set of PID values that will stabilize the given system. The industry still relies on algorithms like the Ziegler- Nicholas or ad-hoc approaches in determining the value of PID controllers. Also when it comes to model free approaches, the use of Fuzzy logic and Neural network do not guarantee stability of the system. For a continuous Linear Time Invariant system Bhattacharyya and others have developed an algorithm that determines the entire set of PID controllers given the transfer function or just the frequency response of the system. The GUI has been developed based on this theory. The GUI also evaluates the user input performance specifications and generates a subset of stable controllers given the performance criteria for the system. This thesis presents an approach of automating the computation of entire set of stabilizing Proportional Integral Derivative (PID) controllers given the system transfer function or the frequency response data of the system. The Graphical User Interface (GUI) developed bridges the gap between the developed theory and the industry.
35

An automated virtual tool to compute the entire set of proportional integral derivative controllers for a continuous linear time invariant system

Narasimhan, Bharat 10 October 2008 (has links)
This thesis presents the very practical and novel approach of using the Graphical User Interface (GUI) to compute the entire set of Proportional Integral Derivative (PID) controllers given the transfer function or the frequency response of the system under consideration. Though there is a wide spread usage of PID controllers in the industry, until recently no formal algorithm existed on determining a set of PID values that will stabilize the given system. The industry still relies on algorithms like the Ziegler- Nicholas or ad-hoc approaches in determining the value of PID controllers. Also when it comes to model free approaches, the use of Fuzzy logic and Neural network do not guarantee stability of the system. For a continuous Linear Time Invariant system Bhattacharyya and others have developed an algorithm that determines the entire set of PID controllers given the transfer function or just the frequency response of the system. The GUI has been developed based on this theory. The GUI also evaluates the user input performance specifications and generates a subset of stable controllers given the performance criteria for the system. This thesis presents an approach of automating the computation of entire set of stabilizing Proportional Integral Derivative (PID) controllers given the system transfer function or the frequency response data of the system. The Graphical User Interface (GUI) developed bridges the gap between the developed theory and the industry.
36

Improving the algorithm of the LCD Driver IC inspection equipment

Hu, Tsai-Hsien 14 January 2010 (has links)
This thesis would solve the control problem of the contiguous tape which using Reel-to-Reel winder mechanism to load and unload. In the past, some theses solve the speed matching between motors by using specific motor controller or specific mechanism. These designs are too complex and inflexible to suit the variety requirement. In this thesis, I have only used simple vibration mechanism. I hope that the variety requirement could be suited by turning the software. I have compared those results by using different algorithms and different type of sensors. According those results, I wish to find a better control method. During the experimenting, I found that the discontinuous sensor, like Photo-interrupter can not provide enough information about the vibration mechanism. The controller can not turn the motor speed in a short time. In opposition, when using the continuous sensor, like potentiometer can provide more information including the speed and the location of the vibration mechanism. It even provides the moving direction and acceleration. The controller can tune the motor speed by using typical PID control algorithm. I tuned the P¡BI and D parameter by the method provided by Ziegler & Nichols. When working in the factory, there is no problem!
37

Proportional integral derivative control of an oil-heated fractal-like branching microchannel desorber /

Davis, Keith R. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 90-92). Also available on the World Wide Web.
38

Gas turbine control and load sharing of a shipboard power system

Fernandes, Anisha M. C., January 1900 (has links)
Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains x, 84 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 78-80).
39

Estudo e avaliação de metodologias de auto-sintonia de controladores PID visando uma implementação em controlador industrial

Cologni, Mario Andrei January 2008 (has links)
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-graduação em Engenharia de Automação e Sistemas / Made available in DSpace on 2012-10-24T00:18:02Z (GMT). No. of bitstreams: 1 261764.pdf: 1502420 bytes, checksum: 9925ab59a22be5edcb06d92d64c978f6 (MD5) / A sintonia automática de controladores de processos é uma demanda crescente nas aplicações industriais, que busca acelerar as tarefas de comissionamento de malhas de controle e busca melhor desempenho por meio da re-sintonia. O controlador PID, por sua simplicidade e domínio público, continua sendo o mais empregado no controle de processos, apesar das pesquisas e desenvolvimentos recentes de novas técnicas de controle. Apresentam-se, nesta dissertação, o desenvolvimento do conhecimento e a avaliação de estruturas de auto-sintonia de controladores PID. Presta-se foco especial a questões relacionadas com a aplicação em controle de processos na indústria, visando uma implementação em controlador industrial. Quatro estruturas de sintonia automática utilizando o relê realimentado são especialmente abordadas. Os algoritmos de auto-sintonia e de controle são desenvolvidos inicialmente em Matlab e simulações são realizadas em plantas tipo benchmark. A avaliação das topologias é realizada através de indicadores de desempenho e, principalmente, por meio da análise da relação custo-benefício de cada estratégia. Finalmente, um algoritmo PID com auto-sintonia é implementado no controlador lógico programável L40 da WEG/Bosch e experimentado, para estudos de caso, em processos lineares implementados com modelos eletrônicos analógicos.
40

Abordagem inovadora no projeto de controladores PID

Faccin, Flavio January 2004 (has links)
O controlador PID é o algoritmo de controle mais difundido nas unidades industriais em todo o mundo. Além de estar disponível em praticamente todas as plataformas de controle comerciais, ele é um algoritmo robusto, de fácil entendimento, e capaz de prover performance satisfatória para uma grande variedade de processos industriais. No entanto, seu desempenho para a grande maioria dos casos está muito aquém do esperado. Estimativas mostram que apenas 20% das malhas de controle industriais estejam funcionando de forma adequada, diminuindo a variabilidade do processo. Assim, devido a necessidade de melhorar o desempenho das malhas de controle industriais, foi desenvolvida uma metodologia complexa, porém intuitiva, através da qual é possível sintetizar controladores do tipo PID de qualquer parametrização, baseada em um problema de otimização no domínio da freqüência, que minimiza a diferença entre a resposta do sistema em malha fechada frente à uma variação do tipo degrau unitário, e uma resposta específica desejada, representada pela função desempenho alcançável (FDA). Diversas alternativas foram propostas para automatizar todo o procedimento e facilitar a sua utilização, porém foi deixado um grau de liberdade para o usuário alterar o nível de desempenho desejado, através da variação de um único parâmetro que indica a velocidade da resposta da FDA. Adicionalmente, foi feita uma série de recomendações sobre como variar o nível de desempenho desejado, respeitando as restrições inerentes do processo e os limites de estabilidade para diferentes tipos de casos. Para processos mais complexos, onde o comportamento dinâmico não é representado de forma satisfatória por um único modelo nominal, foi desenvolvida uma metodologia alternativa, adequada para um sistema multi-modelos, caracterizado por um conjunto de modelos lineares representativos de diferentes pontos de operação. Esta metodologia é uma extensão da original, porém, com a resolução de um problema de otimização multiobjetivo com formulação do tipo minmax, onde minimiza-se o máximo desvio entre a resposta em malha fechada de cada modelo considerado e uma única FDA. Neste tipo de abordagem, é estabelecido um compromisso entre o desempenho atingido em todos os pontos de operação, quando controlado por um único controlador PID. / The PID controller is the most widespread used control algorithm in the industrial plants of the whole world. Besides it is available in practically all commercial control system, it is a robust algorithm, easily understood, able to provide satisfactory performance for a number of industrial processes. Nevertheless, its performance for most of the cases is below than the desired. Estimates show that just 20% of the industrial control loops are found to work well, decreasing the processes variability. Thus, due to the need of improving the performance of the industrial control loops, a complex, but intuitive methodology was developed, by which it is possible to synthesize PID controllers of any parameterization, based on a frequency domain optimization problem, that minimizes the difference between the unit step response of the closed loop system and a desired specific response, represented by the attainable performance function (APF). A lot of alternatives were purposed to turn the whole procedure automatic and simple, however, there is a degree of freedom, by which the practitioner can vary the desired performance level, changing only one parameter, which indicates the APF response speed. In addition, a number of recommendations about how to vary the desired performance level were done, respecting the inherent process constraints and the stability boundaries for different kind of cases. For more complex processes, where the dynamic behavior is not well represented by only one nominal model, an alternative methodology was developed, suitable for a multi-model system, that is specified by a set of linear models, each one representing a different operating point. This methodology is the sequence of the original one, but formulated as a min-max multiobjective optimization problem, where it is minimized the maximum deviation between the closed loop response of each considered model and only one APF. In this kind of approach, it is possible to have a trade-off among the performance reached in all operating points, when controlled by only one PID controller.

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