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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.
1

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.
2

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.
3

Continuous and discrete model-based robust controllers with application to an electric arc furnace cooling system

Shinohara, Asako January 2001 (has links)
No description available.
4

PID Control. Servo/regulation performance and robustness issues

Arrieta Orozco, Orlando 12 November 2010 (has links)
No description available.
5

Analytical design of feedback compensators based on Robustness/Performance and Servo/Regulator trade-offs. Utility in PID control applications

Alcántara Cano, Salvador 05 October 2011 (has links)
Tot i la seva senzillesa, la idea de la realimentació negativa (o "feedback" en anglès) és extremadament poderosa i ha tingut un gran impacte en la societat des de la revolució industrial ençà. En l'actualitat, els sistemes de control estan a tot arreu. A la indústria de processos, per exemple, s'encarreguen de mantenir les variables d'interès aprop dels valors de consigna. Encara més, els sistemes de control han de garantir aquests objectius tot i la presència d'incertesa en el procés i l'existència de pertorbacions. En aquest sentit, la realimentació representa un mecanisme essencial alhora de millorar tant la qualitat com l'eficiència energètica en molts processos de fabricació. El tema cabdal d'aquesta tesi consisteix en el disseny analític de compensadors (també anomenats controladors) fent servir l'esquema convencial en realimentació unitària. El marc adoptat és del control lineal i invariant en el temps (LTI). Encara que la realitat és de naturalesa no lineal, la simplificació al cas lineal no suposa una restricció greu ja que, localment, sempre podem considerar l'aproximació lineal del procés sota control. Posteriorment, el rang d'operació del compensador es pot extendre fent servir algun procediment de control adaptatiu. Des del punt de vista del disseny del controlador, l'escenari considerat planteja, entre d’altres, dos compromisos fonamentals. D'una banda, el controlador haurà de sel·leccionar-se per tal d'assolir un bon balanç entre rendiment i robustesa de modelat. D'altra banda, existeix també un conflicte entre el rendiment tipus "regulatori" (rebuig de pertorbacions) i el rendiment tipus "servo" (seguiment de la consigna), essent de vegades convenient trobar-ne un equilibri entre aquests dos modes de funcionament. L'objectiu d'aquesta tesi és proporcionar procediments de disseny analítics basats en un model de la planta i els compromisos de robustesa/rendiment i servo/regulació. A diferència d'altres mètodes, els procediments presentats eximeixen el dissenyador d'haver de pensar pesos o models de referència adients. A més, els paràmetres de sintonia tenen un significat intuitiu per tal de simplificar l'ajustament dels paràmetres del controlador. Com que els controladors de tipus Proporcional-Integral-Derivatiu (PID) continuen sent els més emprats en la pràctica, s'ha considerat l'aplicació a aquest tipus particular de controlador. Per últim, val a dir que l'apropament analític d'aquesta tesi permet determinar, de manera explícita, com els diferents compromisos considerats afecten l'el·lecció final del controlador. Aquesta característica, creiem, és també valuosa des del punt de vista docent. / La idea de la realimentación negativa (o "feedback" en inglés), si bien sencilla, es extremadamente poderosa y ha tenido un gran impacto en la sociedad desde la revolución industrial. En la actualidad, los sistemas de control están en todas partes. En la industria de procesos, por ejemplo, son los encargados de mantener las variables de interés próximas a los valores de consigna, todo ello pese a la incerteza en el proceso y las perturbaciones externas. En este sentido, la realimentación es la única manera de estabilizar una planta inestable, y se presenta así como un mecanismo esencial en procesos de fabricación con el fin de mejorar la calidad del producto final y la eficiencia energética. El tema central de esta tesis es el diseño analítico de compensadores (también llamados controladores) en realimentación. El marco de control adoptado es del control lineal e invariante en el tiempo (LTI). Aunque la realidad raramente es de naturaleza lineal, la restricción al caso LTI obedece a su simplicidad y al hecho de que, localmente, es siempre posible aproximar un proceso no lineal por otro lineal. Desde este punto de vista, el rango de operación del compensador puede extenderse posteriormente mediante planificación de ganancia o control adaptable. Respecto a la configuración de control, esta tesis considera el esquema convencional en realimentación unitaria. En el escenario considerado, tenemos por un lado que el controlador debe diseñarse para proporcionar un buen compromiso entre el rendimiento y la robustez ante incerteza en el proceso. Por otro lado, también existe un conflicto entre el rendimiento tipo "servo" (seguimiento de la referencia o consigna) y el rendimiento tipo "regulatorio" (rechazo de las perturbaciones), siendo a veces deseable encontrar un equilibrio entre ambos modos de funcionamiento. El objetivo de esta tesis es proporcionar procedimientos de diseño analíticos basados en un modelo del proceso y los compromisos de robustez/rendimiento y servo/regulación. En los métodos propuestos no es necesario que el diseñador seleccione pesos o modelos de referencia como pasa con otros enfoques. Además, los parámetros de sintonía tienen un significado intuitivo con el fin de simplificar el ajuste de los parámetros del controlador. Debido a que los controladores de tipo Proporcional-Integral-Derivativo (PID) son ampliamente utilizados en la industria, se ha considerado la aplicación a este tipo de controladores. Por último, mencionar que el enfoque analítico de la tesis permite plasmar, de forma explícita, cómo los diferentes compromisos considerados influyen en la elección final del compensador. Esta característica es también valiosa desde el punto de vista de la docencia del control automático. / The concept of (negative) feedback, albeit simple, is extremely powerful, and has since the Industrial Revolution changed our world dramatically. Nowadays, control systems are everywhere. In process industry, for example, they keep the manipulated variables close to the set-points in spite of disturbances and changes in the plant. Moreover, feedback provides the only means to stabilize unstable processes. This way, the feedback mechanism reveals essential for improving product quality and energy efficiency, which yields better (sustainable) economy. The theme of this thesis is on analytical design of feedback compensators through linear control theory. The restriction to the Linear Time Invariant (LTI) case is not severe in the sense that most processes are well modeled locally by LTI systems. The operating range of the controller can then be extended using gain scheduling or adaptation. Within this work, the standard single-loop feedback configuration is assumed. Among the control objectives, stability and robustness are important considerations because of the presence of uncertainty in practice. Apart from that, the controller faces servo (set-point tracking) and regulation (disturbance rejection) objectives. In the considered scenario, it is well-known that there is an inherent compromise between robustness and performance. In general, the servo and regulation objectives are also conflicting and sometimes a balance is desirable. An example is in cascade configurations: the inner loop should be tuned based on tracking as it receives the set-points from the master loop. However, the inner loop may also need acceptable load disturbance suppression capabilities. Another good example is found in Model Predictive Control (MPC) applications due to frequent changes of set-points by the server. Finally, there may be a trade-off between the response to disturbances entering at the input and at the output of the plant, which can be understood as a servo/regulator trade-off too. The goal of this thesis is to provide model-based design procedures in terms of the Robustness/Performance and Servo/Regulator trade-offs, and give insight into how the tuning depends on the process parameters. In the presented methods, the designer is not required to choose weighting functions nor reference models as in other approaches, and the involved parameters have a clear meaning to facilitate the tuning process. Because PID controllers are prevalent in industry, application to PID tuning is considered most of the times. Although numerical methods for controller derivation may yield superior performance than analytical ones, the latter category has been preferred for several reasons. First, analytical procedures help understand the problem at hand. Second, when applied to low-order models, well-motivated tuning rules which are simple and easy to memorize can be obtained. These features are very desirable from the operator's point of view as well as for teaching purposes.
6

Comparação do desempenho de um sistema de refrigeração para resfriamento de liquido, controlado a diferentes modos de controle / Comparison of the system performancefor liquid refrigeration, controlled cooling the different ways of control

Silva, Flávio Vasconcelos da, 1971- 03 August 2018 (has links)
Orientador: Vivaldo Silveira Junior / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-03T18:07:49Z (GMT). No. of bitstreams: 1 Silva_FlavioVasconcelosda_D.pdf: 8477864 bytes, checksum: b9d2c7a02954b442eb703a56737e2367 (MD5) Previous issue date: 2003 / Resumo: O trabalho consiste na montagem e instrumentação de um protótipo de refrigeração para resfriamento de líquido (Chiller) que permita a implementação de sistemas de controle convencionais (PID e PI) e controle fuzzy. O uso do controle fuzzy nos processos industriais vem crescendo rapidamente nas últimas décadas, principalmente em processos de difícil modelagem matemática, devido à sua capacidade de atuar no sistema baseando-se apenas no conhecimento especialista e na capacidade de inter-relacionar todas as variáveis do processo. Em um ciclo de refrigeração a eficiência do sistema esta diretamente ligada à capacidade de manter as temperaturas e pressões correspondentes às exigidas pelo processo. As temperaturas de evaporação e condensação possuem uma grande influência quanto ao consumo de energia e desempenho geral do sistema frigorífico, sendo altamente influenciada por perturbações externas; o controle da temperatura do fluido secundário do chiller (propileno glicol) está diretamente ligada à qualidade do produto a ser resfriado, por essas razões essas temperaturas foram definidas como variáveis a serem controladas, sendo utilizadas como variáveis manipuladas as freqüências de rotação, do compressor e da bomba alternativa, e o fechamento da válvula de controle. Foram realizados, inicialmente, ensaios de conhecimento do comportamento dinâmico do sistema, frente a perturbações, utilizando a metodologia de planejamento experimental onde foram conhecidas as magnitudes dos efeitos individuais e de interação das variáveis do sistema. A realização de ensaios de controle, utilizando estratégias SISO (Single Input - Single Output) e SIMO (Single Input - Multi Output), permitiu a definição das melhores malhas de controle através da análise dos parâmetros de erro e da demanda de energia elétrica do sistema / Abstract: A prototype of refrigeration system in a chiller plant was assembled and instrumented for development of a conventional and fuzzy controllers. Fuzzy controls are increasingly being applied to industrial process especially in process with complex mathematical modeling. The capacity of action in a system controlled by a fuzzy logic is based only on a expert knowledge and its capacity to interact with all variables of process. The efficiency in a cycle of refrigeration is directly related to system capacity to maintain the temperatures and pressures values corresponding to process demand. Evaporating and condensing temperatures have a great influence on electrical demand and general performance of the cooling system. Being highly influenced by external disturbs. In a secondary fluid of the chiller (propylene glycol), the temperature control is associated with the product quality to be cooled. Then, evaporating and condensing temperatures were assumed as controlled variables The manipulated variables were: compressor and reciprocating pump rotation frequencies and position of pneumatic control valve. Experiments of dynamic behavior knowledge of the system were done applying the experimental design methodology to evaluate the individuals and interactions effects of the systems variables under disturbances. Control experiments were developed using SISO (Single Input ¿ Single Output) and SIMO (Single Input ¿ Multi Output) strategies. The time-integral performance criteria and electrical energy consume allowed to define the best control loops / Doutorado / Doutor em Engenharia de Alimentos
7

Thermoelectric Cooler Based Temperature Controlled Environment Chamber Design for Application in Optical Systems

Zhang, Scott N. 14 May 2013 (has links)
Temperature control is widely sought after in regards to optical systems as their optical parameters often show dependence on temperature. Examples include diode lasers, multiplexing systems, optical amplifiers, and filters all of whom have a high sensitivity to temperature. This thesis presents a temperature controlled environment chamber actuated by a thermoelectric cooler. The design of which provides a simple, multi-applicable solution for temperature control in optical devices. The final device is comprised of three sub-areas of design. Each subsystem was custom built and applied in the final assembly -- including a digitally implemented signal generator, an error correction controller, and the environment chamber heat sink structure. The signal generator is used as input for a switched-mode based Peltier driver found commercially. A feedback error controller compensates the driver for temperature control. Both systems are implemented with microcontroller units. The environment chamber heat sink assembly is designed specifically to handle the thermal energy generated by the thermoelectric cooler. All of the systems were tested collectively for functionality. The input signal generator achieved its design goals and is capable of creating specific profiles in the temperature response. Error controller performance was reasonable in set-point tracking for continuous input signals. Step input responses are tuned for minimal settling time and overshoot. Temperature resolution in the thermistor response is around 0.1•C after digital filtering. The thermal design achieved its goal of operating in an ambient environment up to 54°C. Low temperature ambient environment operation has been confirmed to 8°C. / Master of Science
8

Load Simulation and Investigation of PID Control for Resonant Elastic Systems

Lundin, Sara January 2007 (has links)
<p>The purpose of this Master Thesis is to improve the driving performance of mine hoists. The work is divided into two parts. The first and main part deals with simulation of the rope elongation that occurs at load changes in the mine hoist. A mathematical load model of the elongation in the ropes at a mine hoist is made for four types of mine hoists. Mass less springs and dampers are used to get the elastic behaviour of the ropes.</p><p>The mathematical model is implemented in Matlab and Simulink for all four hoist types to make load simulations possible. The implementation in the laboratory HoistLab is made by modifying an existing program with the line elongation functionality. It is only done for the tower mounted friction hoist. There are several functions that are modified to make the simulations realistic.</p><p>The task for the second part of this Master Thesis is to do a pilot study to decide if it is worth making further investigations about how the derivative part will improve the drive performances. A PI controller is designed and gives an acceptable rollback as result when the brakes are released. Then the controller model is extended with the derivative part, D-part, which improves the results essentially. It is still too uncertain how sensitive the system will be for noise when using the derivative part, but the performance potential is clear so the recommendation is to make further investigations.</p> / <p>Syftet med detta examensarbete är att förbättra driftegenskaperna för gruvspel. Arbetet är uppdelat i två olika delar. Den första och största delen handlar om simulering av den lintöjning som uppkommer vid lastförändringar i gruvspel. Matematiska modeller för detta är framtagna för fyra olika sorters typer av gruvspel. Elasticiteten i linorna är modellerad genom masslösa fjädrar och dämpare.</p><p>De matematiska sambanden är implementerade i Matlab och som modeller i Simulink för att utföra simuleringar. I HoistLab är modellen realiserad genom att utöka ett befintligt lastsimuleringsprogram med de nya funktionerna för lintöjning. Detta är utfört enbart för den toppmonterade typen av friktionsspel. Ett flertal funktioner fick ändras för att få realistiska simuleringar.</p><p>Den andra delen av examensarbetet går ut på att göra en förstudie kring den deriverande delen i PID-regulatorer och hur den påverkar gruvspelets prestanda. För denna del är en PI-regulator som ger ett acceptabelt resultat av backgången när bromsarna släpps designad. Därefter är modellen utökad med den deriverande delen, D-delen, vilket ger väsentligt bättre resultat. Det är dock osäkert hur bruskänsligt systemet blir när den deriverande delen används men eftersom förbättringspotentialen är tydlig är rekommendationen att göra vidare undersökningar kring D-delen.</p>
9

Synthesis of PID controller from empirical data and guaranteeing performance specifications.

Lim, Dongwon 15 May 2009 (has links)
For a long time determining the stability issue of characteristic polynomials has played avery important role in Control System Engineering. This thesis addresses the traditionalcontrol issues such as stabilizing a system with any certain controller analyzingcharacteristic polynomial, yet a new perspective to solve them. Particularly, in this thesis,Proportional-Integral-Derivative (PID) controller is considered for a fixed structuredcontroller. This research aims to attain controller gain set satisfying given performancespecifications, not from the exact mathematical model, but from the empirical data of thesystem. Therefore, instead of a characteristic polynomial equation, a speciallyformulated characteristic rational function is investigated for the stability of the systemin order to use only the frequency data of the plant. Because the performance satisfactionis highly focused on, the characteristic rational function for the investigation of thestability is mainly dealt with the complex coefficient polynomial case rather than realone through whole chapters, and the mathematical basis for the complex case is prepared.For the performance specifications, phase margin is considered first since it is avery significant factor to examine the system’s nominal stability extent (nominal performance). Second, satisfying H norm constraints is handled to make a more robustclosed loop feedback control system. Third, we assume undefined, but bounded outsidenoise, exists when estimating the system’s frequency data. While considering theseuncertainties, a robust control system which meets a given phase margin performance, isattained finally (robust performance).In this thesis, the way is explained how the entire PID controller gain setssatisfying the given performances mentioned in the above are obtained. The approachfully makes use of the calculating software e.g. MATLAB® in this research and isdeveloped in a systematically and automatically computational aspect. The result ofsynthesizing PID controller is visualized through the graphic user interface of acomputer.
10

Synthesis of PID controller from empirical data and guaranteeing performance specifications.

Lim, Dongwon 15 May 2009 (has links)
For a long time determining the stability issue of characteristic polynomials has played avery important role in Control System Engineering. This thesis addresses the traditionalcontrol issues such as stabilizing a system with any certain controller analyzingcharacteristic polynomial, yet a new perspective to solve them. Particularly, in this thesis,Proportional-Integral-Derivative (PID) controller is considered for a fixed structuredcontroller. This research aims to attain controller gain set satisfying given performancespecifications, not from the exact mathematical model, but from the empirical data of thesystem. Therefore, instead of a characteristic polynomial equation, a speciallyformulated characteristic rational function is investigated for the stability of the systemin order to use only the frequency data of the plant. Because the performance satisfactionis highly focused on, the characteristic rational function for the investigation of thestability is mainly dealt with the complex coefficient polynomial case rather than realone through whole chapters, and the mathematical basis for the complex case is prepared.For the performance specifications, phase margin is considered first since it is avery significant factor to examine the system’s nominal stability extent (nominal performance). Second, satisfying H norm constraints is handled to make a more robustclosed loop feedback control system. Third, we assume undefined, but bounded outsidenoise, exists when estimating the system’s frequency data. While considering theseuncertainties, a robust control system which meets a given phase margin performance, isattained finally (robust performance).In this thesis, the way is explained how the entire PID controller gain setssatisfying the given performances mentioned in the above are obtained. The approachfully makes use of the calculating software e.g. MATLAB® in this research and isdeveloped in a systematically and automatically computational aspect. The result ofsynthesizing PID controller is visualized through the graphic user interface of acomputer.

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