Dissertations / Theses on the topic 'Smith Predictor'

Time delays are unavoidable in many mechanical and electrical systems. The presence of delay typically imposes strict limitations on achievable feedback performance in both continuous and discrete systems. The presence of the delay complicates the design and analysis of a control system as it makes continuous systems infinite dimensional, and it significantly increases the dimensions in discrete systems. This work will propose a method to determine all PID controllers that stabilize the closed-loop system and satisfy weighted sensitivity, robust stability or robust performance constraints for stable time delay systems with a Smith predictor using the frequency response of the system. The Smith predictor works to eliminate the time delay from the characteristic equation and so improves the range of PID controllers that stabilize the system. A comparison between the range of PID controllers with and without Smith predictor is given in this work. This work also proposes a method for finding all PI-PD controllers that stabilize an unstable system with a modified version of the Smith predictor.
Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science

The performance and robustness of the Smith predictor controller has been tested for first and second order processes with time-delay by comparing with PI and PID control. It was assumed that the performance would obviously be better when the time-delay is known. Pareto optimal PI and PID controller tuning curves has been found. The processes studied is divided between five first-order-plus-time-delay and nine second-order-plus-time-delay models. Performance have been defined as a weighted average of the integrated absolute error for a step load change in input and output disturbances. Robustness has been defined in terms of the maximum peak of the sensitivity function (Ms). The Pareto optimal Smith predictor tuning curves have been found. Deterioration in performance and robustness have been evaluated when the process time-delay deviate from the nominal time-delay for which the controllers are optimal. SIMC tuning curves have been compared to the Pareto optimal PI and PID tuning curves, and a method for applying SIMC tuning to Smith predictor controllers have been suggested. The Smith predictor have proven to yield small performance enhancements compared to optimal PI and PID control on second-order processes. For first-order processes the optimal PI and PID controllers have performance superior to the Smith predictor. When the process time-delay varies, even Smith predictor controllers with modest Ms values tend to destabilise. No reason are found for utilising a Smith predictor PI or PID controller over a Pareto optimal PI or PID controller. One will have to tune the Smith predictor to yield very low Ms values to avoid the instability issues when modelling error in the time-delay parameter occurs. The potential increase in performance achieved is easy to compensate with a regular PI or PID controller by tuning it a little tighter.

During the last decades, virtual environments have become very popular and are largely used in many domains as, for example, prototyping, trainings for different devices, assistance in completing difficult tasks, etc. The interaction with the virtual reality, as well as the feedback force, is assured by haptic interfaces. Generally, such systems are affected by communication and processing time-delays, resulting in a deterioration of performances. In this thesis, a complete study of the existing methods, as well as theoretical tools and new solutions, are proposed for the haptic framework. First, a comparative study, based on the experimental results obtained on a 1-dof haptic system, highlights the advantages and drawbacks of the most common control algorithms ported from teleoperation to haptics. Next, the theoretical tools needed in analyzing the stability of the delayed systems in different situations, as well as the physical limitations of the experimental platforms considered, are examined. Besides the standard case of constant time-delays, uncertainties are also considered and modeled by different types of distributions (uniform, normal and gamma distribution with gap). In the sequel, for overcoming the drawback of time-delays, two new approaches are proposed. First, the use of Smith predictor-based control is addressed and a specific solution for haptic systems is developed and discussed. The main idea is to introduce into the Smith predictor the environmental forces by using the additional information from the virtual reality regarding the distances between the controlled virtual object and other objects in the scene. To overcome the loss of performances induced by using a fixed gain in the controllers for all situations (free or restricted motions), the second approach proposes a gain-scheduling Proportional Derivative control strategy depending on the distance until a possible collision. Both approaches are experimentally validated on a 3-dof haptic platform, under different scenarios elaborated gradually from simple situations - free and restricted motion, contacts with moving objects, to more complex situations - virtual box with fixed or moving sides.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2005.
Thesis Advisor(s): Isaac I. Kaminer, Vladimir N. Dobrokhodov. Includes bibliographical references (p. 37-38). Also available online.

Este trabalho apresenta todo um projeto de um sistema de supervisão e controle de um trocador de calor, desde os ensaios experimentais para a elaboração de um modelo matemático até a implementação do sistema de controle e supervisão em microcomputador. O sistema implementado consiste de um software didático e um sistema de aquisição de dados que irão realizar a supervisão e controle de um trocador de calor tipo casco e tubos. Neste software didático é possível implementar o controle PID e suas variações PI-D e I-PD além de permitir a implementação do sistema de controle adaptativo estrutura gain scheduling o qual muda os parâmetros de um controle PID de acordo com a mudança da dinâmica do trocador de calor. Como o trocador de calor apresenta um tempo morto em sua dinâmica, então optou-se por adicionar ao software didático um controle com algoritmo preditivo estrutura Preditor de Smith desta forma é possível realizar ensaios com e sem o algoritmo preditivo para uma comparação de resultados. Este sistema de supervisão e controle do trocador de calor poderá ser usado como ferramenta didática para alunos de diversos cursos, onde é possível realizar ensaios de diferentes estruturas de controle para posterior comparação e estudo de seus resultados. Resultados práticos de todas as estruturas de controle que o software implementa são apresentados e comparados neste trabalho.
This work presents thorough a supervision and control system project of a heat exchanger, from the experimental tests for the mathematical model rising to the control system implementation and supervision in a microcomputer. The implemented system consists of didactic software and a data acquisition system that will perform the supervision and control of a heat exchanger shell and tube type. In this didactic software it is possible to implement the PID control and its variations PI-D and I-PD besides allowing the implementation of the adaptive control system gain scheduling structure, which changes the PID control parameters according to the changes of the heat exchanger dynamics. As the heat exchanger presents dead time on its dynamics, it was opted to add to the didactic software a control with Smith Predictor structure predictive algorithm, thus it is possible to perform tests with and without the predictive algorithm for result comparison. This supervision and control system of the heat exchanger will be able to be used as a didactic tool for students from several courses, where it is possible to perform tests with different control structures to further comparison and study of its results. Pratical results of all the control structures that the software implements are presented and compared in this work.

Emission from cars today is one of the biggest environmental issues, hence stringent government standards have been introduced to decrease emission. Car companies do not only have to satisfy government standards, but also meet consumer demands on increased fuel economy and good drivablility. This report will introduce controllers designed to control the air/fuel ratio in an SI engine. The engine model used is simplified. The engine components modelled include the inlet manifold, fuel dynamics, combustion and exhaust sensor.

Nonlinearities and delays are inherent in the engine dynamics and as such a Smith Predictor is utilised as the basis for controller structure to compensate for the delays. Here the Smith Predictor is combined with feedforwarding of the mass air charge, which is estimated from both the inlet and combustion models. Therefore different ways of merging the estimates are also explored.

A real engine was not accesible, thus simulators were implemented using data sets provided by General Motors. Model errors were introduced to test the controllers performance. The proposed methods should be tested on a real engine to ensure that this isa viable approach, as the simulations show it maybe promising to use in practice.

Phosphorus is often the limiting nutrient of primary productivity in southern Appalachian reservoirs, but its impact on higher trophic levels has not been assessed. Regression analysis was used to examine the relationship between total phosphorus concentrations and estimates of fish standing stock in Smith Mountain Lake (SML) over time and for 22 southern Appalachian reservoirs (SAR) at the same time. ln SML, which had responded to a nutrient reduction program, total phosphorus concentration and fish biomass concurrently declined over an 12-year period; phosphorus concentration accounted for one-third (cove-specific) and two-thirds (whole-Iake) of the annual variation in fish standing stock. Total phosphorus concentration was also the best predictor of fish abundance in SARs, accounting for 84% of the variation in standing stock despite great diversity in reservoir physical, chemical, and biological characteristics. Predictive power was generally higher at lower levels of the food chain (i.e. planktivores, younger fish) than for piscivores. Planktivore response to phosphorus was found to be immediate. Piscivore biomass did not vary significantly with phosphorus, owing in part to poor energy transfer up the food chain and variable management practices. Phosphorus concentration and total fish standing stock appear to have stabilized in SML since 1980. Losses in fish standing stock due to deceased fertility in SML have been partly offset by an increase in coolwater habitat. Aesthetic versus fishery benefits and the complexity of dealing with a longitudinal trophic gradient need to be considered for future management of SML.
Master of Science
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As atividades sócio-econômicas vêm provocando alterações nocivas ao meio ambiente que atualmente assumem proporções mundiais. Graças à maciça utilização de combustíveis fósseis para a geração de energia e às crescentes práticas de desmatamento e queimadas das florestas, a concentração de dióxido de carbono (CO2) na atmosfera vem aumentando drasticamente. Como este gás é o principal responsável pelo efeito estufa, ele tem grande importância nos estudos e na mitigação do aquecimento global. Para justificar o seqüestro de carbono como um dos caminhos para ajudar na solução deste problema, muitos estudos vêm sendo realizados para avaliar os efeitos nas plantas de uma maior concentração desse gás. As câmaras de topo aberto (OTC, do inglês, open top chambers) são estruturas propícias para tais estudos, pois permitem o controle da concentração de CO2 interno sem que outros fatores climáticos como temperatura, umidade e luminosidade sejam demasiadamente alterados. Este trabalho teve como objetivo o desenvolvimento de um sistema para controlar o nível de CO2 no interior de uma OTC. Em termos de instrumentação eletrônica, foram instalados um sensor de CO2 e uma válvula proporcional, integrados a uma placa de aquisição de dados. Um modelo linear relacionando o CO2 na câmara ao sinal elétrico aplicado à válvula proporcional foi obtido aplicando-se técnicas de Identificação de Sistemas aos dados experimentais coletados com o processo operando em malha aberta. Este modelo foi utilizado no projeto de um controlador com compensação de tempo morto, baseado na estrutura de um preditor de Smith. O desempenho do sistema projetado foi analisado através de simulações, antes de implementá-lo na forma de um instrumento virtual. Os testes mostraram que o sistema manteve a concentração de CO2 na câmara próxima do valor de referência (720 ± 35 ppm) mesmo diante de distúrbios externos criados propositadamente durante os ensaios.
The harmful changes to the environment caused by socio-economic activities are now spread worldwide. Due to the massive use of fossil fuels for energy generation, to the increase in deforestation and forest burning, the carbon dioxide (CO2) concentration in the atmosphere has drastically increased. As this gas is the main responsible for the greenhouse effect, it has great importance for the studies and the mitigation of global warming. In order to justify carbon sequestration as an alternative to help solve this problem, many studies have been conducted to evaluate the effect of a greater concentration of this gas on plants. Open-top chambers (OTCs) are well suited for such studies, because they allow the control of the internal CO2 concentration without significantly modifying other environmental factors such as temperature, humidity and luminosity. This work aimed to develop a system to control the CO2 level inside an OTC. In terms of electronic instrumentation, a CO2 sensor and a proportional valve, integrated to a data acquisition board, were used. A linear model relating CO2 in the chamber to the electric signal applied to the proportional valve was obtained applying System Identification techniques to the experimental data collected from the process operating in open-loop mode. This model was used in the project of a controller with dead time compensation, based on the Smith Predictor structure. The performance of the projected system was analyzed through simulations, before implementing it in the form of a virtual instrument. The tests showed that the system kept the CO2 concentration of the chamber near the set-point (720 ± 35 ppm) even in the presence of external disturbances purposely created during the experiments.

En esta tesis se desarrolla el diseño de un sistema de control basado en un predictor de Smith modificado mediante un compensador anticipatorio, para el control efectivo de plantas con retardos de tiempo dominante y sometidas al efecto de perturbaciones externas. En el capítulo 1 se expone el estado del arte de los sistemas de control de plantas con retardos de tiempo dominante, mostrando las principales contribuciones científicas realizadas en los últimos 30 años abordando la problemática actual. En el capítulo 2 se muestran algunos ejemplos de plantas típicas con retardos de tiempo inherentes, la caracterización de las mismas y los problemas asociados. Como objeto de estudio se seleccionó un horno siderúrgico de una industria de fabricación de planchones de acero. Mediante la aplicación de las herramientas de identificación de sistemas se obtiene un modelo matemático de dicha planta. En el capítulo 3, se diseña un controlador basado en un PS modificado mediante un compensador anticipatorio para el control de plantas con retardos de tiempo y sometidas al efecto de perturbaciones medibles, localizadas en la entrada de la planta, sobre la planta y a la salida de la planta. Se muestran resultados comparativos de simulación del sistema de control desarrollado. En el capítulo 4 se realiza un análisis de robustez del controlador diseñado considerando diferentes escenarios de perturbaciones externas. Para tal fin, se utilizaron los índices de desempeño IAE (integral del error absoluto) e ISE (integral del error cuadrático). Se realiza una propuesta de implementación práctica del controlador diseñado. Finalmente, se ofrecen las conclusiones generales y las recomendaciones.
Tesis

Este trabalho apresenta uma proposta de solução para compensar o atraso variável, característico de redes IP. O preditor de Smith é tradicionalmente usado para compensar atrasos, mas no caso deste tipo de rede um fator importante que pode degradar o controle do sistema são as grandes variações nos atrasos sofridos pelas mensagens. Para tratar este problema, este trabalho baseia-se na criação de uma estrutura de dados de armazenamento para a saída do preditor de Smith, possibilitando a comparação do valor de saída da planta com o valor adequado guardado na estrutura. Para determinação do valor correspondente, este está associado a um índice calculado com o tempo de roundtrip obtido de informações dos pacotes de dados proveniente da planta. Para se chegar a tal solução, foi analisada nas primeiras seções a influência do atraso em malhas de controle e posteriormente um estudo do estado da arte para tipos de controle sobre redes IP. Ao final é apresentada uma análise experimental, demonstrando resultados promissores da aplicação desta proposta.
This work presents a solution to compensate the varying delay, characteristic of IP networks. The Smith predictor is traditionally used to compensate delays but in this type of networks an other important factor that can destabilize the system is the large jitter of the delay. In order to solve this problem, the solution presented here is based on a data structure to save the output from the model of the plant used by the Smith predictor, that make possible to compare the output from the plant with the corresponding value in the structure. In order to take the correspondent value, it is associated to an index which is calculated with the roundtrip obtained from the informations in the packet arrived from the plant. In order to formulate this solution, it was analised in the first sections the influence of the delay in control systems and then a study of the state of art of the control systems over IP networks. At the end, an experimental analise to demonstrate the good result of the application of this solution is presented.

Este trabalho descreve o desenvolvimento de um sistema de controle com compensação de tempo morto aplicado a um ventilador para simular os efeitos do vento em modelos de embarcações. O sistema é instalado no tanque de provas do Departamento de Engenharia Naval da Escola Politécnica da USP. Um sistema de controle baseado em computador é elaborado para a realização dos testes e validação, procedendo-se inicialmente a identificação do sistema a ser controlado. Na malha de controle, o sinal de referência é a velocidade do vento desejada em uma distância pré-definida do ventilador e pode ser tanto um valor constante (representando um vento constante) ou um valor variante no tempo (representando uma rajada de vento). O sistema atuador consiste de um inversor de frequência que aciona o ventilador e a velocidade do vento é medida por um anemômetro, cujo sinal é usado como realimentação para o controlador. A sintonia da malha é realizada pelo método do modelo interno (IMC) e o efeito do tempo morto é observado nos testes, aplicando-se o compensador baseado no Preditor de Smith para minimizá-lo. Pelos resultados dos ensaios, conclui-se que o Preditor de Smith melhora o desempenho do sistema de geração de vento.
This paper describes the development of a control system with dead time compensation applied to a fan to simulate wind effects in models of vessels. The system is installed on the academic towing tank of the Naval Architecture and Oceanic Engineering Department of the University of São Paulo. A control system based on computer is designed for testing and validation, proceeding initially to identify the system to be controlled. In the control loop, the set-point is the desired speed of the wind on a pre-defined distance from the fan and it can be either a constant value (representing a constant wind) or a time-varying value (representing a wind gust). The actuator system consists of a frequency-inverter that drives the fan and the wind speed is measured by an anemometer, whose signal is used as feedback to the controller. The tuning of the controller is made by the internal model control (IMC) and the effect of dead time is observed in the tests, applying the compensator based on Smith Predictor to minimize it. Through the results from the tests, it was concluded that the Smith Predictor improves the performance of the wind generation system.

Master thesis is focused on the philosophy of design adaptive controller. In the theoretic part are described parts of the adaptive controller, which belongs parts as online identification by recursive least-squares method and PSD controller, which can set its parameters according to identified system (use Z-N method). The part of control system with transport delay is situated at the conclusion of the theoretic part, there are focused on Smith predictor. Practical part is focused on verification of all algorithms, which was performed on models and real systems.

Master thesis is focused on the philosophy of design adaptive controller. In the theoretic part are described parts of the adaptive controller, which belongs parts as online identification by recursive least-squares method and PSD controller, which can set its parameters according to identified system (use Z-N method). The part of control system with transport delay is situated at the conclusion of the theoretic part, there are focused on Smith predictor. Practical part is focused on verification of all algorithms, which was performed on models and real systems.

Enhancing mineral processing techniques is a permanent challenge in the mineral and metal industry. Indeed to satisfy the requirements on the final product (metal) set by the consuming market, control is often applied on the mineral processing whose product, the ore concentrate, constitutes the input material of the extractive metallurgy. Therefore much attention is paid on mineral processing units and especially on concentration plants. As the ore size reduction procedure is the critical step of a concentrator, it turns out that controlling a grinding circuit is crucial since this stage accounts for almost 50 % of the total expenditure of the concentrator plant. Moreover, the product particle size from grinding stage influences the recovery rate of the valuable minerals as well as the volume of tailing discharge in the subsequent process.

The present thesis focuses on an industrial application, namely the Kolwezi concentrator (KZC) double closed-loop wet grinding circuit. As any industrial wet grinding process, this process offers complex and challenging control problems due to its configuration and to the requirements on the product characteristics. In particular, we are interested in the modelling of the process and in proposing a control strategy to maximize the product flow rate while meeting requirements on the product fineness and density.

A mathematical model of each component of the circuit is derived. Globally, the KZC grinding process is described by a dynamic nonlinear distributed parameter model. Within this model, we propose a mathematical description to exhibit the increase of the breakage efficiency in wet operating condition. In addition, a relationship is proposed to link the convection velocity to the feed ore rate for material transport within the mills.

All the individual models are identified from measurements taken under normal process operation or from data obtained through new specific experiments, notably using the G41 foaming as a tracer to determine material transport dynamics within the mills. This technique provides satisfactory results compared to previous studies.

Based on the modelling and the circuit configuration, both steady-state and dynamic simulators are developed. The simulation results are found to be in agreement with the experimental data. These simulation tools should allow operator training and they are used to analyse the system and to design the suitable control strategy.

As the KZC wet grinding process is a Multi-Input Multi-Output (MIMO) system, we propose a decentralized control scheme for its simplicity of implementation. To overcome all the control issues, a Double Internal Model Control (DIMC) scheme is proposed. This strategy is a feedforward-feedback structure based on the use of both a modified Disturbance Observer (DOB) and a Proportional-Integral Smith-Predictor (PI-SP). A duality between the DOB and PI-SP is demonstrated in design method. The latter is exploited to significantly simplify the design procedure. The designed decentralized controllers are validated in simulation on the process linearized model. A progressive implementation of the control strategy is proposed in the context of the KZC grinding circuit where instrumentation might not be obvious to acquire./

Améliorer les techniques de traitement de minerais est un défi permanent dans l'industrie des minéraux et des métaux. En effet, pour satisfaire aux exigences du produit fini (métal ) fixées par le marché de consommation, la commande automatique est souvent appliquée à l'usine du traitement de minerais dont le produit, le concentré, constitue la matière première de la métallurgie extractive. Une attention particulière est donc dévolue aux unités de traitement de minerais et en particulier aux concentrateurs. Comme le processus de réduction des dimensions granulométriques du minerai est l'étape critique d'un concentrateur, il s'avère que la commande d'un circuit de broyage est cruciale, car ce stade représente près de 50 % des dépenses totales de l' usine de concentration. De plus, la dimension granulométrique du produit de l'étape de broyage influe sur le taux de récupération des minéraux utiles ainsi que sur le volume des rejets du processus ultérieur.

La présente thèse porte sur une application industrielle, à savoir le concentrateur de Kolwezi (KZC qui est un circuit de broyage humide à double boucle fermée. Comme tout processus industriel de broyage humide, ce procédé présente une problématique de commande complexe et difficile en raison de sa configuration et des exigences relatives aux caractéristiques du produit. En particulier, nous nous intéressons à la modélisation de ce procédé et à proposer une stratégie adéquate de commande dans le but de maximiser le débit de production tout en respectant les exigences quant à la finesse et à la densité de la pulpe produite.

Un modèle mathématique de chaque composant du circuit a été déterminé. Globalement, le processus de broyage de KZC est décrit par un modèle dynamique non linéaire à paramètres distribués. Dans ce modèle, une description mathématique de l'augmentation de l'efficacité du broyage en milieu humide est proposée. En outre, nous avons proposé une relation liant la vitesse de convection au débit d'alimentation de minerais dans le modèle du transport de la matière à l'intérieur des broyeurs.

Tous les modèles mathématiques ont été identifiés à partir de mesures prises sur le procédé en fonctionnement d'équilibre stable ou à partir des données obtenues grâce à des nouvelles expériences spécifiques, notamment en utilisant le moussant G41 comme traceur pour déterminer la dynamique de transport de la matière dans les broyeurs. Cette technique a produit des résultats cohérents par rapport aux études antérieurs réalisées au moyen du traceur colorant ou radioactif.

Les simulateurs statique et dynamique ont été développés sur la base de la modélisation mathématique et de la configuration du circuit. Les résultats des simulations sont en accord avec les données expérimentales. Ces outils de simulation devraient permettre la formation des opérateurs et ont été utilisés pour analyser le système et concevoir la stratégie de commande la plus appropriée.

Comme le processus de broyage humide de KZC est un système à plusieurs grandeurs d'entrée et plusieurs grandeurs de sortie, nous avons proposé une structure de commande décentralisée en raison de sa simplicité de mise en œuvre .Afin de surmonter tous les problèmes de commande, un schéma de commande à double modèle interne (CDMI) est proposée. Cette stratégie est une structure à anticipation - rétroaction basée sur l'utilisation d'un observateur de perturbations (OBP) et d'un Prédicteur de Smith doté d'un régulateur Proportionnel-Intégral (PS-PI). Une dualité entre l'OBP et le PS-PI est démontrée dans la méthode de conception. Cette propriété est exploitée pour simplifier considérablement la procédure de conception. Les régulateurs décentralisés ainsi conçus sont validés en simulation sur le modèle linéarisé du procédé. Une mise en œuvre progressive de la stratégie de commande est proposée dans le contexte du circuit de broyage de KZC où l'instrumentation peut ne pas être évidente à acquérir.

Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

Since 2006 Further Education and Training (FET) Colleges have been recapitalised through massive government investment in order to improve infrastructure, implement a more relevant curriculum and assist college learners financially to gain access to the different learning programmes. A new curriculum with 11 programmes was introduced and implemented under the National Certificate Vocational (NCV). The results of the 2007 examinations, were disappointing and in general, the national performance of the learners was dismal. Policy requirements for certification and promotion to the next level stipulated that learners need to pass all 7 subjects in a programme. The main aim of the study was to identify variables that are the best predictors of academic success of first year FET students. Thus, if these predictors are considered during the admission process of first year FET students, it could lead to overall improved first year pass rate at FET Colleges and contribute towards the enhancement of human resources and economical development of our country. In order to achieve the research aim and objectives, a literature study and an empirical investigation were conducted. The literature study focussed on cognitive and non-cognitive factors that contribute to academic success of students at colleges. The empirical investigation departed from a positivist paradigm to determine which variables contributed the best towards the prediction of academic success of first year NCV Level 2 students at FET Colleges and a quantitative non-experimental, ex post facto approach was followed .The results of the General Scholastic Aptitude Test (GSAT), the Learning and Study Strategies Inventory – High School version (LASSI-HS), grade mark average and biographical details of the registered first year NCV Level 2 students of the Vuselela FET College (Potchefstroom and Klerksdorp campuses) in 2008 (n=309), were used to determine whether any of these variables significantly predicted the academic success of these students. The investigation revealed that: • None of the LASSI-HS scales were predictors of academic success of the first year NCV Level 2 students; • The GSAT (Total) was a predictor of academic success of these students; • None of the biographical variables, i.e. age or gender, were predictors of academic success; and • Grade mark average on students’ last school reports, was a predictor of academic success. These findings revealed that Grade mark average, and GSAT-(Total) (which is also an indication of intelligence quotient (IQ)) were the best predictors of academic success of first year NCV Level 2 students at the Potchefstroom and Klerksdorp campuses of the Vuselela FET College.
Thesis (MEd (Educational Psychology))--North-West University, Potchefstroom Campus, 2013.

碩士
國立中正大學
化學工程研究所
89
Time delay, resulting from material and energy transportation lag, measurement delay, etc.,is a common phenomenon in many chemical processes. Another problems in chemical processes were parametric uncertainties. Many design techniques and conventional control algorithms such as PID cannot be directly applied to processes with dominant time delay and uncertainties. However, the Smith predictor is suitable for regulating systems with dominant time delay. The quantitative feedback theory (QFT) is an excellent design technique of uncertain feedback systems having robust stability and robust performance specifications. The crux of the QFT is a transformation of robust stability and robust performance specifications into domains in the complex plane, referred as bounds, which a nominal loop transmission Lo(s) should lie within. In this thesis, applying a branch-and-bound zero inclusion algorithm to obtain templates and solving the corresponding quadratic inequalities, the QFT bounds of Smith predictor was computed by Pivoting procedure to reduce the amount of calculation.An optimization algorithm is proposed for design optimal Smith predictor, which minimizes the asymptotic loop gain of a system subject QFT constraints. The algorithm is simple and can be used to automate the loop-shaping step of the QFT design procedure.

碩士
國立臺灣大學
化學工程學研究所
89
Time delay can be found in many chemical engineering processes . But it is a problem which can't be tuned good by PID controller.Smith Predictor can reject time delay in control system,and it really has better performance than original PID controller.But the original one degree of freedom Smith Predictor is not so good for any process if there exists disturbance especially for an integrated process. Many researches have been done to solve the problem.They have proposed structures that can improve the disadvantages of the oringinal Smith Predictor, but it still have much disadvantage,too.We hope our proposed structure can improve not only the disadvantages of original Smith Predictor but also the disadvantages of its correction proposed by their researches. In this thesis,we disscuss the model based predictive control, and then introduce the IMC theory.We use IMC theory to design the Smith Predictor, and propose a 2 DOF structure.Finally we simulate much processes to find the optimal parameter.

碩士
國立臺灣大學
化學工程研究所
77
Smith Predictor ，MAC ，DMC ，IMC ，等控制理論，其設計的理念，均是針對設定 點的變化，而未對負荷干擾做任何的處理。而後雖有AP被提出，針對擾動做處理，但 其對負荷動態的依賴相當大，實用性不高。本文針對負荷擾動提出一個近似時延補償 器，這個近似時延補償器在使用上相當簡便，只須知道Robust stability，Perform- ance，和Bandwidth 三個限制即可設計，不須事先知道負荷動態而能應付各種負荷擾 動，甚至當系統有高頻模式誤差或noise 存在時，其均能有效應付。

碩士
國立臺北科技大學
電機工程研究所
103
In a complex control system, time delay usually causes the system unstable and could decrease the efficiency of the system. Contrary to the Remote Control System of visual servoing for a Micro Aerial Vehicles (MAV), vision delay could be the most serious problem. If the scheme of delay compensation is not well designed, MAV would be unstable during the flight. Therefore, time delay compensation would be the most important issues in a remote visual servo control system. This paper proposes a multi-model Smith predictor, in which the feedback loop design is based on the multi-model time delay estimator, to compensate the delay time during the visual servoing of a MAV, so that it could be controlled to avoid the obstacles and fly along the lines. We build multiple models of MAV using System Identification toolbox of Matlab. Combining the formula of image projection, the camera sensor model and the simulation environment of visual servoing could be established. In the simulation, we designed the flying controller to avoid the obstacles or fly alone the lines. Considering the effect of time delay during the flight, the multi-model Smith predictor is designed to compensate it. By finding the reference feature points and lines on the image, the deviation between the image error of observation and the image error of delay estimation model could be evaluated to infer the delay time and compensate the control error. In the experiment, the captured image is transferred into the similar feature map for extracting the reference line. The task of flying along the lines is achieved by using the multi-model Smith predictor to compensate the effect of delay time.

碩士
國立交通大學
機械工程系所
103
In semiconductor manufacturing, after finishing every process, wafer should be sent to the metrology equipment to measure the accuracy of production. It will consume different time to send the wafer to metrology equipment. If measurement delay is too long, it will cause Run-to-Run Controller to be unable to update the recipe immediately. This will then lower the accuracy of the process outcome and affects the yield rate. In this thesis, we use optimal prediction to design PDOB as inner loop, which can predict future stochastic disturbance by using past and current data values to improve the effect of time delay to the system. And we use Smith predictor as outer loop, which can reduce the oscillation caused by model mismatch.

碩士
國立交通大學
機械工程學系
100
This thesis presents a new structure which can be applied to stable, unstable, integrating minimum-phase or non-minimum-phase time delay system. This structure is combined modified Smith Predictor and doubly coprime factorization transformer structure: Vidyasagar’s structure. One can use this method to track performance and attenuate disturbance. Furthermore, if there is some uncertainty in the plant, one can deal with Small gain theorem and find a robustness controller to control the plant.

碩士
國立交通大學
機械工程系所
98
Significantly the dead-time has a great influence on the stability of systems, which make the process more difficult to control. Therefore, this thesis presents a discrete dead-time compensator to improve the performance and capability of disturbance rejection for dead-time systems. It applied predictive DOB and Smith predictor structure to compensate output delay and input disturbance for stable and integrating plants. The proposed structure consists of two parts: the inner loop and the outer loop. Firstly the PDOB can be designed to reject any kind of deterministic disturbances, including step disturbance, ramp disturbance and sine disturbance. Also, the property of DOB structure can approach the real plant to the nominal plant. The PDOB based on DOB structure has an additional predictive filter, which eliminate the time delay of estimated disturbance. Because of the property enhances disturbance rejection performance of traditional DOB for dead-time systems especially for periodic disturbance. Secondly, the Smith predictor structure is capable to suppress the effects of time delay. Seeing that the stability is influenced by the model mismatch and model mismatch will always exist in the process. In this thesis, we propose a robust controller which compensates the effect of time delay and reject deterministic disturbance to satisfy the robust stability.

碩士
國立臺北科技大學
電機工程研究所
103
Due to the rapid development of the Internet, a remote control system is widely brought to the attention. In real situation applications, traditional control is unable to live up to the requirement, so the related research is of great importance. In the transmission process of network control systems, the variation of delay time depends on the number of users and others transmission factors. However, delay time will influence the performance of the network control systems and affect the stability of control system. Smith predictor is designed to be simple, but requires an accurate system model and time model so as to strengthen the architecture of network delay compensation. Among conventional methods of estimation, variable delay can be estimated, but continuous long delay time could result in inaccurate estimations. Therefore, this paper focuses on estimating delay time under the environment of a variable time delay. This paper proposes the support vector regression to estimate the delay time. Round-trip time is measured between the user and control systems, and then the measured values for training and prediction are produced by support vector regression. The predicted time will be able to provide the estimation time of system architecture. The simulation results show that the proposed method can predict delay accurately, which enables the compensation architecture to compensate effectively for the delay. This method can also be applied successfully to AC 200W servo motor network control system. Thus, this study can achieve accurate estimations in the environment of the variable delay and enable the compensation architecture to effectively compensate effect of the delay time.

碩士
國立中正大學
機械系
88
Abstract One of the limitations for the piezoactuator to achieve high tracking control accuracy is due to its inherent hysteresis effect. Two precise hysteresis models were developed in the past to describe the hysteresis behavior, however the developed models are highly nonlinear and the controller design based on the models is complicated and time consuming. In this paper, we propose an approximate model using a variable gain and time-delay together with a structural response function to represent the model of the piezoelectric actuator with hysteresis. Open loop experiments are performed to estimate the parameters of the approximate model. Based on the proposed model, a Smith predictor based robust H¥ controller is developed. The uncertainties due to the variable gain and time-delay are included in the design process. Simulation and experiments on tracking control of several sinusoidal waveforms of input frequency at 10, 30 and 50Hz, and a 50Hz band-limited random signal show that the tracking error can be reduced to be less than 2% of the maximum traveling path with the robust controller design. The agreement of the simulation results with the experimental results validates the idea of using the approximate model as the design basis.

Tese de Doutoramento em Engenharia Industrial e Sistemas
Na grande maioria dos procedimentos cirúrgicos torna-se necessário realizar o controlo da Pressão Arterial (PA) para, com isto, assegurar da melhor forma a saúde do paciente. Para reduzir os riscos de uma complicação, é imprescindível diminuir a PA o mais rápido possível. A infusão contínua de medicamentos vasodilatadores, como é o caso do nitroprussiato de sódio (NPS), reduz de forma rápida a pressão arterial na maior parte dos pacientes. Entretanto, cada paciente possui uma diferente sensibilidade à infusão do NPS. Nestes sistemas, os parâmetros e os atrasos são inicialmente desconhecidos e variantes no tempo. Desta forma, este trabalho tem como objetivo principal o desenvolvimento de uma metodologia capaz de controlar de forma automática a PA na presença de parâmetros incertos e de elevados atrasos. Para tal, foi desenvolvida uma metodologia multi-modelo onde, para cada modelo, existe um controlador especificamente sintonizado com um mecanismo adaptativo que decide qual o controlador que deve ser o dominante para uma determinada planta (paciente), denominado por Controlador Preditivo Multi-Modelo Adaptativo (MMAPC). Através da realização de uma análise de sensibilidade à variação dos parâmetros da planta e testes de robustez, é possível mostrar a robustez do sistema, respeitando todas as restrições clínicas impostas pelo problema. Os resultados obtidos mostraram que o MMAPC apresentou melhor desempenho (menor tempo de acomodação, 𝑇#, e menor undershoot) na maioria dos casos simulados, quando comparado com outro método que recorre ao uso de controladores clássicos, como é o caso do controlador PI multi-modelo. Além disso, o Preditor de Smith no algoritmo Generalized Predictive Control, baseado no Preditor Smith Modelo Múltiplo (MMSPGPC), fornece um controlo mais rápido, com um tempo de acomodação médio aproximado de 290 s (máximo de 375 s e mínimo de 150 s) e undershoot médio de 1,1 mmHg (máximo de 9,5 mmHg e mínimo 0,0 mmHg), em todos os casos simulados, comparado ao Controlador Preditivo Generalizado Multi-Modelo (MMGPC). Assim, este controlador ao combinar estas duas estratégias, MMAC com o controlo preditivo, é um sistema de controlo automático da PA robusto, mesmo para uma ampla gama de valores de parâmetros e em condições incertas.
In most surgical procedures, it is necessary to perform the control of the blood pressure (BP) in order to ensure the patient's health. To reduce the risk of complications, it is imperative to reduce high blood pressure as soon as possible. Continuous infusion of vasodilator drugs, such as sodium nitroprusside (Nipride), rapidly reduces blood pressure in most patients. However, each patient has a different sensitivity to infusion of Nipride. The parameters and the time delays of the system are initially unknown. Moreover, the parameters of the transfer function associated with a particular patient are time varying. So, the main objective of this study is to develop a methodology capable of automatically controlling blood pressure in the presence of uncertainty of parameters and high time delays. For this, a multi-model methodology was developed where, for each model, a controller specifically tuned with an adaptive mechanism that decides which controller should be the dominant for a certain plant (patient) is designed, called Multi-Model Predictive Controller Adaptive (MMAPC). At the end of the study, a sensitivity analysis and a robustness test, were performed. By performing a sensitivity analysis to the variation of plant parameters and a robustness test it is possible to show the strength of the system respecting all the clinical restrictions imposed by the problem. The results showed that the MMAPC presented better performance (lower settling time and undershoot) in most of the simulated cases, when compared to other method that uses classic controllers, such as the multimodal PI controller. Moreover, the Smith Predictor in the Multiple Model Smith Predictor based Generalized Predictive Control algorithm (MMSPGPC) provides a superior performance with mean settling time of 290 s (maximum of 375 e minimum of 150s) and mean undershoot of 1.1 mmHg (maximum 9.5 mmHg e minimum 0.0 mmHg), in all simulated cases compared to Multiple Model Generalized Predictive Controller (MMGPC). Thus, this controller, combining these two strategies, MMAC with the predictive control, is a robust blood pressure control system even for a wide range of parameter values and under uncertain conditions.

Dissertação de Mestrado em Engenharia Informática apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Diabetes is a huge health problem that is a ecting more and more people over the time. When it comes to diagnosing such disease in people, doctors make their diagnoses based on some proper tests and may not take into consideration other factors that are related to the disease. The creation of tools that can analyse information about the current health status of patients can support doctors by providing more information for the diagnosis. Since there is still no cure for this disease, a person who has been diagnosed with diabetes has to control his blood sugar level between some thresholds. This is extremely important as non-controlled level of glucose can lead the subject to severe health complications and compromise his lifestyle. Tools that forecast the subject's glucose level within a prediction horizon may let the individual take preemptive actions to avoid crossing the normal thresholds. This thesis aims to investigate machine learning methods for such problems. These types of methods are already being used in the medicine and will allow us to come up with computational models that o er more relevant data to support the medical team when it comes to diagnosing diabetes in people and avoid thresholds overpassing when patients are controlling their glucose level. Both these problems represent highly challenging tasks. For the diabetes diagnosis problem, we built several models, tuned and tested them using the PIMA dataset. A key contribution of this work is the diverse methods introduced, analysed and tested to handle missing values present in the dataset. The method of substituting the missing values by the mean of the features considering the class they belong to along with Random Forest yielded the best results with an accuracy of 87.66%. Regarding the glucose level ii predictions we also created various models based on real patient datasets provided by Associa c~ao Protectora dos Diab eticos de Portugal(APDP), which are an important asset. Besides, two prediction methods namely direct and iterative prediction methods were investigated and tested. From the computational experiments, the Linear Regression with direct prediction method is the most advantageous combination resulting on an RMSE average of 14.25 mg/dL and 23.46 mg/dL for 30 and 60 minutes ahead prediction. Both these domains represent highly challenging tasks and our methods demonstrate that we can attain excellent performance on these tasks. From an application standpoint, there remains many challenging problems in both Diabetes Diagnosis and Prediction of Glucose. Indeed, in the advent of the Internet of Things by combining many sensors available with our methods, we will come to reach a Smart Monitor Health System able to prevent, diagnosis, treatment and after care for the society in general.

碩士
國立清華大學
電機工程學系
90
Power control is an important issue in a direct sequence code division multiple access (DS-CDMA) cellular mobile radio system. Higher communication link quality and better system capacity can not be achieved under fading and interference unless an appropriate power control mechanism is employed. In previous research, there is not a good way to treat the round-trip delay and the uncertainties of interferences and noises in the closed-loop power control problem. In this thesis, a robust Smith prediction filter is proposed to efficiently overcome the round-trip delay problem and override the effect of uncertainties of interferences and noises to achieve a robust signal-to-interference-plus-noise ratio (SINR) tracking from the minimax perspective. A fixed-order smith prediction filter is constructed to achieve this minimax power control performance via genetic algorithm. Finally several simulation results are given to confirm the performance of the proposed method.