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Capaci, Francesca. "Contributions to the Use of Statistical Methods for Improving Continuous Production." Licentiate thesis, Luleå tekniska universitet, Industriell Ekonomi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-66256.
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Complexity of production processes, high computing capabilities, and massive datasets characterize today’s manufacturing environments, such as those of continuous andbatch production industries. Continuous production has spread gradually acrossdifferent industries, covering a significant part of today’s production. Commonconsumer goods such as food, drugs, and cosmetics, and industrial goods such as iron,chemicals, oil, and ore come from continuous processes. To stay competitive intoday’s market requires constant process improvements in terms of both effectivenessand efficiency. Statistical process control (SPC) and design of experiments (DoE)techniques can play an important role in this improvement strategy. SPC attempts toreduce process variation by eliminating assignable causes, while DoE is used toimprove products and processes by systematic experimentation and analysis. However,special issues emerge when applying these methods in continuous process settings.Highly automated and computerized processes provide an exorbitant amount ofserially dependent and cross-correlated data, which may be difficult to analyzesimultaneously. Time series data, transition times, and closed-loop operation areexamples of additional challenges that the analyst faces.The overall objective of this thesis is to contribute to using of statisticalmethods, namely SPC and DoE methods, to improve continuous production.Specifically, this research serves two aims: [1] to explore, identify, and outlinepotential challenges when applying SPC and DoE in continuous processes, and [2] topropose simulation tools and new or adapted methods to overcome the identifiedchallenges.The results are summarized in three appended papers. Through a literaturereview, Paper A outlines SPC and DoE implementation challenges for managers,researchers, and practitioners. For example, problems due to process transitions, themultivariate nature of data, serial correlation, and the presence of engineering processcontrol (EPC) are discussed. Paper B further explores one of the DoE challengesidentified in Paper A. Specifically, Paper B describes issues and potential strategieswhen designing and analyzing experiments in processes operating under closed-loopcontrol. Two simulated examples in the Tennessee Eastman (TE) process simulatorshow the benefits of using DoE techniques to improve and optimize such industrialprocesses. Finally, Paper C provides guidelines, using flow charts, on how to use thecontinuous process simulator, “The revised TE process simulator,” run with adecentralized control strategy as a test bed for developing SPC and DoE methods incontinuous processes. Simulated SPC and DoE examples are also discussed.
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Scullin, Michelle E. "Integrating Value Stream Mapping and Simulation." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd898.pdf.
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Appell, Kenneth William. "A mathematical simulation of ETS' limestone emission control process using the method of characteristics fixed-bed configuration/gas-phase mass transport control." Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182276120.
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Propes, Nicholas Chung. "Hybrid Systems Diagnosis and Control Reconfiguration for Manufacturing Systems." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5150.
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A methodology for representing and analyzing manufacturing systems in a hybrid systems framework for control reconfiguration purposes in the presence of defects and failures at the product and system levels is presented. At the top level, a supervisory Petri net directs parts/jobs through the manufacturing system. An object-based hybrid systems model that incorporates both Petri nets at the event-driven level and differential equations at the time-driven level describes the subsystems. Rerouting capabilities utilizing this model at the product and operation levels were explained. Simulations were performed on a testbed model for optimal time and mode transition cost to determine the route for parts. The product level reconfiguration architecture utilizes an adaptive network-based fuzzy inference system (ANFIS) to map histogram comparison metrics to set-point adjustments when product defects were detected. Tests were performed on good and defective plastic parts from a plastic injection molding machine. In addition, a mode identification architecture was described that incorporates both time- and event-driven information to determine the operating mode of a system from measured sensor signals. Simulated data representing the measured process signals from a Navy ship chiller system were used to verify that the appropriate operating modes were detected.
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Sanchez, Urbina Israel. "Optimizing flow of plastic PBT with 45% glass and mineral fiber reinforcement in an injection over mold process using Taguchi, CPk and mold flow simulation software approaches." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Robles, Martínez Ángel. "Modelling, simulation and control of the filtration process in a submerged anaerobic membrane bioreactor treating urban wastewater." Doctoral thesis, Editorial Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/34102.
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El reactor anaerobio de membranas sumergidas (SAnMBR) está considerado como tecnología
candidata para mejorar la sostenibilidad en el sector de la depuración de aguas residuales,
ampliando la aplicabilidad de la biotecnología anaerobia al tratamiento de aguas residuales de
baja carga (v.g. agua residual urbana) o a condiciones medioambientales extremas (v.g. bajas
temperaturas de operación). Esta tecnología alternativa de tratamiento de aguas residuales es
más sostenible que las tecnologías aerobias actuales ya que el agua residual se transforma en
una fuente renovable de energía y nutrientes, proporcionando además un recurso de agua
reutilizable. SAnMBR no sólo presenta las principales ventajas de los reactores de membranas
(i.e. efluente de alta calidad, y pocas necesidades de espacio), sino que también presenta las
principales ventajas de los procesos anaerobios. En este sentido, la tecnología SAnMBR
presenta una baja producción de fangos debido a la baja tasa de crecimiento de los
microorganismos implicados en la degradación de la materia orgánica, presenta una baja
demanda energética debido a la ausencia de aireación, y permite la generación de metano, el
cual representa una fuente de energía renovable que mejora el balance energético neto del
sistema. Cabe destacar el potencial de recuperación de nutrientes del agua residual bien cuando
el efluente es destinado a irrigación directamente, o bien cuando debe ser tratado previamente
mediante tecnologías de recuperación de nutrientes.
El objetivo principal de esta tesis doctoral es evaluar la viabilidad de la tecnología SAnMBR
como núcleo en el tratamiento de aguas residuales urbanas a temperatura ambiente. Por lo tanto,
esta tesis se centra en las siguientes tareas: (1) implementación, calibración y puesta en marcha
del sistema de instrumentación, control y automatización requerido; (2) identificación de los
parámetros de operación clave que afectan al proceso de filtración; (3) modelación y simulación
del proceso de filtración; y (4) desarrollo de estrategias de control para la optimización del
proceso de filtración minimizando los costes de operación.
En este trabajo de investigación se propone un sistema de instrumentación, control y
automatización para SAnMBR, el cual fue esencial para alcanzar un comportamiento adecuado
y estable del sistema frente a posibles perturbaciones. El comportamiento de las membranas fue
comparable a sistemas MBR aerobios a escala industrial. Tras más de dos años de operación
ininterrumpida, no se detectaron problemas significativos asociados al ensuciamiento
irreversible de las membranas, incluso operando a elevadas concentraciones de sólidos en el
licor mezcla (valores de hasta 25 g·L-1
). En este trabajo se presenta un modelo de filtración
(basado en el modelo de resistencias en serie) que permitió simular de forma adecuada el proceso de filtración. Por otra parte, se propone un control supervisor basado en un sistema
experto que consiguió reducir el consumo energético asociado a la limpieza física de las
membranas, un bajo porcentaje de tiempo destinado a la limpieza física respecto al total de
operación, y, en general, un menor coste operacional del proceso de filtración.
Esta tesis doctoral está integrada en un proyecto nacional de investigación, subvencionado por
el Ministerio de Ciencia e Innovación (MICINN), con título ¿Modelación de la aplicación de la
tecnología de membranas para la valorización energética de la materia orgánica del agua
residual y la minimización de los fangos producidos¿ (MICINN, proyecto CTM2008-06809-
C02-01/02). Para obtener resultados representativos que puedan ser extrapolados a plantas
reales, esta tesis doctoral se ha llevado a cabo utilizando un sistema SAnMBR que incorpora
módulos comerciales de membrana de fibra hueca. Además, esta planta es alimentada con el
efluente del pre-tratamiento de la EDAR del Barranco del Carraixet (Valencia, España).Robles Martínez, Á. (2013). Modelling, simulation and control of the filtration process in a submerged anaerobic membrane bioreactor treating urban wastewater [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34102
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Chen, Shuai. "Investigation of FEM numerical simulation for the process of metal additive manufacturing in macro scale." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI048/document.
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La fabrication additive (FA) est devenue une nouvelle alternative pour la fabrication des pièces dans l'industrie. Cependant, il existe encore des limites pour ce procédé, en particulier la forme finale défavorable et les propriétés macroscopiques indésirables des pièces métalliques construites dans les systèmes de FA. La distorsion ou la fissure due à la contrainte résiduelle de ces pièces pose généralement de graves problèmes pour certains types de technologie de la FA métallique. Dans un système de FA, la qualité finale d'une pièce métallique dépend de nombreux paramètres de procédé, qui sont normalement optimisés par une série d'expériences sur des machines de FA. La simulation macroscopique dédiée au procédé de FA est une alternative potentielle pour les pièces métalliques fabriquées par la fabrication additive. Dans cette thèse, nous étudions d'abord le pré-processing de la simulation de FA par la méthode des éléments finis (FEM). Le procédé de fabrication additive est un phénomène multi-physique des champs couplés (champs thermique, mécanique et métallurgique). La simulation macroscopique est réalisée à deux niveaux différents. Au niveau de la couche, la reconstruction du modèle 3D est effectuée à partir du fichier de chemin de balayage de la machine de FA, basée sur la manipulation inverse de l'algorithme d'offsetting-clipping. Au niveau de la pièce, le modèle 3D de CAO est reconstruit dans un maillage des voxels, ce qui est pratique pour une pièce avec une géométrie complexe. Avec les températures de préchauffage différentes et les paramètres du procédé différents, la contrainte résiduelle d'une pièce est analysée. Ces simulations impliquent la technique potentielle pour réduire la contrainte résiduelle par l'optimisation des paramètres du procédé, au lieu de moyens traditionnels par augmenter la température de préchauffage. Basées sur la plateforme de simulation de FEM ci-dessus, deux simulations au niveau de ligne sont également étudiées dans cette thèse, visant à la relation entre le procédé de FA et la qualité finale de la pièce. Ces exemples démontrent la possibilité d'utiliser des simulations macroscopiques pour améliorer le contrôle de la qualité pendant le procédé de FA. Dans la première tâche, l'ensemble de données des paramètres de chauffage et la contrainte résiduelle sont générés par la simulation de FA. La corrélation entre eux est étudiée en utilisant des algorithmes de régression, tel que le réseau neuronal artificiel. Dans la deuxième tâche, un contrôleur de PID pour la boucle de rétroaction puissance-température est intégré dans la simulation de procédé de FA et l'auto-réglage de PID est numériquement étudié au lieu d'utiliser la machine de FA. Les deux tâches montrent le rôle important de la simulation de procédé macroscopique de FA, qui peut remplacer ou combiner les nombreuses expériences essai-erreur dans la fabrication additive métalliqueAdditive manufacturing (AM) has become a new option for the fabrication of metallic parts in industry. However, there are still some limitations for this application, especially the unfavourable final shape and undesired macroscopic properties of metallic parts built in AM systems. The distortion or crack due to the residual stress of these parts leads usually to severe problems for some kinds of metal AM technology. In an AM system, the final quality of a metallic part depends on many process parameters, which are normally optimized by a series of experiments on AM machines. In order to reduce the considerable time consumption and financial expense of AM experiments, the numerical simulation dedicated to AM process is a prospective alternative for metallic part fabricated by additive manufacturing. Because of the multi-scale character in AM process and the complex geometrical structures of parts, most of the academic researches in AM simulation concentrated on the microscopic melting pool. Consequently, the macroscopic simulation for the AM process of a metallic part becomes a current focus in this domain. In this thesis, we first study the pre-processing of AM simulation on Finite Element Method (FEM). The process of additive manufacturing is a multi-physics problem of coupled fields (thermal, mechanical, and metallurgical fields). The macroscopic simulation is conducted in two different levels with some special pre-processing work. For the layer level, the reconstruction of 3D model is conducted from the scan path file of AM machine, based on the inverse manipulation of offsetting-clipping algorithm. For the part level, the 3D model from CAD is reconstructed into a voxel-based mesh, which is convenient for a part with complex geometry. The residual stress of a part is analysed under different preheat temperatures and different process parameters. These simulations imply the potential technique of reducing residual stress by the optimisation of process parameters, instead of the traditional way by increasing preheat temperature. Based on the FEM simulation platform above, two simulations at line level are also studied in this thesis, aiming at the relation between the AM process and part's final quality. These examples demonstrate the feasibility of using macroscopic simulations to improve the quality control during the AM process. In the first task, dataset of heating parameters and residual stress are generated by AM simulation. The correlation between them is studied by using some regression algorithm, such as artificial neural network. In the second task, a PID controller for power-temperature feedback loop is integrated into AM process simulation and the PID auto-tuning is numerically investigated instead of using AM machine. Both of the two tasks show the important role of AM macroscopic process simulation, which may replace or combine with the numerous trial and error of experiments in metal additive manufacturing
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Pitra, Michal. "Adaptivní regulátory s principy umělé inteligence v prostředí MATLAB - B&R." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217708.
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The diploma thesis is focused on an adaptive control, especially in a self-tuning controller area. The thesis is divided into two main parts. The first part deals with identification methods of the adaptive control. The recursive least squares algorithm and the neural network method are the most popular identification methods. These methods are contrasted and the identification quality evaluation is done. The second part compares various types of the adaptive controllers with a non-adjustable PSD controller. The adaptive controllers are investigated from the various identification method point of view. The user graphic interface was realized for the identification and regulatory part. The time behavior of system responses after incoming disturbance and dynamic process changes during simulation systems control is compared with a physical model connected to B&R PLC. The comparison is done with the application of Matlab/Simulink program.
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Margulies, Mathias. "Contrôle optimal du procédé de cristallogenèse Bridgman vertical." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10187.
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Le present travail a ete initie dans le cadre de l'optimisation d'une experience de tirage de cristaux de type bridgman vertical. Notre objectif est de mesurer l'apport potentiel de la mise en oeuvre de methodes numeriques d'optimisation. La qualite finale du cristal obtenu depend d'un grand nombre de parametres et de phenomenes physiques. Une etude bibliographique du travail de simulation existant pour la methode bridgman nous permet d'en isoler les plus influents et de proposer un modele simple pour notre etude. Nous nous fixons comme objectif de determiner un profil thermique de four et un profil de vitesse de tirage au cours du temps (parametres de tirage) tels que la derivee radiale de la temperature dans le materiau au cours de tout le tirage soit minimum (fonction cout) et sous certaines contraintes. Le champ de temperature est solution d'un probleme de stefan avec conditions aux limites de flux non lineaire. Nous donnons un resultat d'existence et d'unicite de la solution et etudions un algorithme semi-discret en temps permettant de resoudre la non-linearite des equations regissant le changement de phase. Le probleme de controle est ensuite etudie sous sa forme discrete en temps et en espace. Nous donnons les expressions des derivees partielles de la fonction cout et des contraintes par rapport aux parametres de controle en fonction de l'etat adjoint, ainsi qu'un resultat d'existence d'une solution au probleme de controle. Enfin, nous proposons une methode de descente pour resoudre le probleme de controle totalement discretise. Nous presentons les resultats obtenus dans une configuration particuliere, et en tirons les conclusions sur le fonctionnement de cette methode et les limites de notre modele.
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Paulson, Joel Anthony. "Modern control methods for chemical process systems." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109672.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 301-322).
Strong trends in chemical engineering have led to increased complexity in plant design and operation, which has driven the demand for improved control techniques and methodologies. Improved control directly leads to smaller usage of resources, increased productivity, improved safety, and reduced pollution. Model predictive control (MPC) is the most advanced control technology widely practiced in industry. This technology, initially developed in the chemical engineering field in the 1970s, was a major advance over earlier multivariable control methods due to its ability to seamlessly handle constraints. However, limitations in industrial MPC technology spurred significant research over the past two to three decades in the search of increased capability. For these advancements to be widely implemented in industry, they must adequately address all of the issues associated with control design while meeting all of the control system requirements including: -- The controller must be insensitive to uncertainties including disturbances and unknown parameter values. -- The controlled system must perform well under input, actuator, and state constraints. -- The controller should be able to handle a large number of interacting variables efficiently as well as nonlinear process dynamics. -- The controlled system must be safe, reliable, and easy to maintain in the presence of system failures/faults. This thesis presents a framework for addressing these problems in a unified manner. Uncertainties and constraints are handled by extending current state-of-the-art MPC methods to handle probabilistic uncertainty descriptions for the unknown parameters and disturbances. Sensor and actuator failures (at the regulatory layer) are handled using a specific internal model control structure that allows for the regulatory control layer to perform optimally whenever one or more controllers is taken offline due to failures. Non-obvious faults, that may lead to catastrophic system failure if not detected early, are handled using a model-based active fault diagnosis method, which is also able to cope with constraints and uncertainties. These approaches are demonstrated on industrially relevant examples including crystallization and bioreactor processes.
by Joel Anthony Paulson.
Ph. D.
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Estrela, Mariely Cordeiro. "Avaliação de uma análise automatizada para determinação de atividade enzimática." Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2875.
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O Instituto de Biologia Molecular do Paraná (IBMP) atua na produção de insumos para detecção de doenças. Em parceria com Bio-Manguinhos (Fiocruz) é atualmente responsável pelo fornecimento do módulo de amplificação do KIT NAT Brasileiro para o diagnóstico molecular de HIV (AIDS), HCV (Hepatite C) e HBV (Hepatite B), entre outros produtos para diagnóstico in vitro. O teste molecular consiste basicamente, na amplificação do material genético do vírus (DNA ou RNA) através da técnica de PCR (reação em cadeia pela polimerase) em tempo real, que possibilita a detecção do agente patógeno a partir de pequenas quantidades de ácido nucleico presente na amostra. A reação de PCR ocorre pela atividade da Taq DNA Polimerase, uma enzima termostável amplamente utilizada para replicação seletiva de fragmentos de DNA. Esta enzima foi isolada a partir de uma bactéria termofílica, denominada Thermus aquaticus e é produzida pelo IBMP, sendo considerada um insumo de alta criticidade. Uma das etapas de controle do processo produtivo dessa enzima é a avaliação do extrato bruto enzimático e a determinação da atividade da enzima purificada. O método de quantificação consiste em avaliar a atividade enzimática através da metodologia de PCR convencional, seguida por uma análise do perfil eletroforético das amostras em gel de agarose. No entanto, a metodologia empregada atualmente apresenta uma grande subjetividade, visto que a interpretação dos resultados pode sofrer variações quando analisados por diferentes operadores. O objetivo do presente trabalho é avaliar a implementação de uma análise automatizada dos resultados através do processamento digital de imagens, que além de facilitar sobremaneira as rotinas laboratoriais, pode ser a chave para resultados com maior grau de precisão e repetibilidade, eliminando assim o viés subjetivo do analista. A nova metodologia de análise implica em menor interferência do analista na interpretação dos resultados. O método proposto foi testado em um conjunto de imagens e os resultados obtidos foram comparados com os valores da análise manual atualmente utilizada. Os resultados foram considerados promissores, pois a análise automatizada, além de reduzir significativamente o tempo de análise, possibilita uma padronização dos resultados.The Molecular Biology Institute of Paraná (IBMP) acts in the production of inputs for detection of diseases. In partnership with Bio-Manguinhos (Fiocruz), it is currently responsible for manufacturing the amplification module of the Brazilian NAT KIT for HIV (AIDS), HCV (Hepatitis C) and HBV (Hepatitis B), besides other products for molecular diagnostics. The molecular test basically consists of amplifying the genetic material of the virus (DNA or RNA) through the real-time PCR (polymerase chain reaction) technique, which enables detection of the pathogen from small amounts of nucleic acid present in the sample. The PCR reaction occurs by the activity of Taq DNA Polymerase, a thermostable enzyme widely used for selective replication of DNA fragments. This enzyme was isolated from a thermophilic bacterium, called Thermus aquaticus and is produced by the IBMP, being considered an input of high criticality. One of the steps in controlling the production process of this enzyme is the evaluation of the enzymatic extract and the determination of the activity of the purified enzyme. The quantification method consists in evaluating the enzymatic activity through the conventional PCR methodology, followed by an analysis of the electrophoretic profile of the agarose gel samples. However, the methodology currently used presents a great subjectivity, since the interpretation of results can suffer variations when analyzed by different operators. The objective of the present work is to evaluate the implementation of an automated analysis of the results through digital image processing, which in addition to facilitating the laboratory routines, can be the key to results with a greater degree of precision and repeatability, thus eliminating the subjective bias of the analyst. The new methodology of analysis implies less interference of the analyst in the interpretation of the results. The proposed method was tested in a set of images and the obtained results were compared with the values of the manual analysis currently used. The results were considered promising because the automated analysis, besides significantly reducing the analysis time, allows a standardization of the results.
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Sneesby, Martin G. "Simulation and control of reactive distillation." Thesis, Curtin University, 1998. http://hdl.handle.net/20.500.11937/2555.
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Reactive distillation has enormous potential for the economical synthesis of tertiary ethers. Methyl tert-butyl ether (MTBE) has been commercially produced with this technology since the early 1980s and it appears that the process also has application for Ethyl tert-butyl ether (ETBE) and other ethers. However, the combination of reaction and distillation in a single unit operation produces a process complexity that inhibits expeditious design and tight control, and presents a technology risk for potential developers. This particularly applies to hybrid reactive distillation where both reactive and non-reactive column sections are employed.The steady state simulation of a series of reactive distillation columns and processes for the production of ETBE and MTBE illuminated a number of important issues related to the optimal design techniques. Many of these issues are peculiar to reactive distillation and would not reasonably be anticipated without a priori knowledge of the phenomena involved. For example, the addition of theoretical equilibrium stages and an increase in the reflux ratio do not always have a directionally equivalent effect. The trade-off between energy consumption and capital cost which is the basis for most distillation designs cannot always be applied to reactive distillation. Importantly, the use of standard modelling techniques for equilibrium processes was also validated for reactive distillation design.The use of residue curve diagrams and reactive residue curve diagrams for the design of reactive distillation processes was investigated and shown to provide useful information regarding the feasibility of reaction-separations. Combined with simulation tools (e.g. Pro/II and SpeedUp), these techniques form the basis of a proposed design strategy for hybrid reactive distillation. It is important to apply these design tools appropriately and to select the correct process for a given application. The optimal design must also consider economics and the relative values of products, reactants and energy. These issues were studied with respect to ETBE production for gasoline oxygenation.The complexity of hybrid reactive distillation not only presents design challenges but potentially makes the process more difficult to control. Dynamic simulations of ETBE and MTBE reactive distillation processes were used to explore some unusual dynamic phenomena and to elucidate the process non-linearity and bidirectionality of reactive distillation. The presence of multiple steady states for some reactive distillation columns has been documented previously but the analysis of this behaviour has been incomplete and somewhat flawed. It was shown that the distinction between molar inputs and physically realisable mass or volumetric inputs is crucial and that multiplicity could be present in one case and not in the other. Multiplicity that is only observed with molar inputs (relatively common) was termed pseudo-multiplicity. Pseudo-multiplicity has few implications for the operation and control of practical reactive distillation processes although most literature examples of multiple steady states fall into this category. Four distinct causes of output multiplicity were identified including one new cause, reaction hysteresis, which is only applicable to hybrid reactive distillation. It was shown, using dynamic simulations, that transitions between parallel steady states are possible for a range of physically realisable and practical disturbances. This contrasts with other work in the area, which examines only unrealisable events and control schemes.An extensive analysis of reactive distillation control was also undertaken with respect to ETBE and MTBE hybrid columns. Manual (open-loop) control was shown to be impractical due to the need to sustain the operating conditions at close to the optimal values in order to produce acceptable process performance. One-point composition control was found to be relatively easy to implement and effective with either an energy-balance or a material-balance control scheme provided only one steady state was present. Where multiple steady states exist, there are restrictions on the feasible control structures due to unavoidable instability in the inventory controllers. For example, if multiple steady states exist for the one value of the reboiler duty, only the bottoms product draw rate can be used to control the reboiler sump level. Thus, a material-balance control structure that uses the reboiler duty to control the sump level cannot be implemented in practice. Two-point control was also investigated and found to effectively prevent transitions between parallel steady states. Although more complex and difficult to implement than one-point control, a two-point scheme could be used successfully to control both the product composition and the reactant conversion and this could be desirable in some cases.A reactive distillation pilot plant was designed and operated for ETBE synthesis from ethanol and a locally available refinery hydrocarbon stream. The design of the pilot plant was based on simulation studies and the objective of operating in the industrially significant ranges of product purity and isobutene conversion. A fully automatic control system was designed and installed on the pilot plant to permit precise control of the manipulated variables and the framework to implement a range of control structures and schemes.Keywords: reactive distillation; process simulation; process design; process control; dynamic simulation; multiplicity; bidirectionality; distillation control; inferential control; pilot plant design and operation.
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Spirito, Mario. "Simulation, control and optimization of asphalt drying process." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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Il documento presentato punta alla descrizione del lavoro svolto dal DEI in collaborazione con l'azienda Marini-Fayat la quale ha sviluppato un prototipo innovativo per l'essiccazione di asfalti.
L'obiettivo di tale collaborazione ha riguardato principalmente attività di studio della letteratura circa il processo di essiccazione degli asfalti, la sua modellazione e il controllo dell'intero impianto rispettandone i vincoli imposti.
Il lavoro si svolto nel seguente modo, dopo lo studio della letteratura sull'argomento, due tipologie di modello sono state sviluppate: un "Evaluation model" che divideva l'impianto in sezioni concatenate di lunghezza fissata e voleva descrivere in maniera fine i comportamenti fisici del sistema, a questo si è aggiunto lo sviluppo di un "control model" con l'obiettivo di riportare solo i fenomeni principali di questo processo di essiccazione, portando così a una maggiore leggerezza computazionale.
Al fine di testare le azioni di controllo si sono pensati degli esperimento per la stima dei parametri di sistema. Una volta noti tali parametri è stato possibile convalidare l'effettiva funzionalità dei controllori sviluppati sul più leggero e performante "control model" con ottimi risultati.
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Zhao, Jian 1963. "Simulation of boiler drum process dynamics and control." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61104.
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This thesis presents a mathematical process model for the dynamic analysis of a vertical reheat boiler and the application of this model to the optimal design of a drum water level controller. A numerical finite difference technique is used to formulate this model.The control system contains two loops, a feedfoward loop using the steam flow and drum pressure signals as the input and a feedback loop using the deviation of the measured drum water level from its set point as an input. The feedback loop is an incremental PID controller with an adjustable proportional gain. The feedfoward loop is designed to directly actuate the control devices before the "swell" and "shrinkage" in the boiler water level occur. The feedforward controller output signal is summed along with the output of the PID controller to establish the set point for the control actuator. This scheme is effective because steam flow changes are immediately fed forward to change the final feedwater set point for the control actuator. In this way, feedwater flow tracks steam flow and any disturbances in the feedwater system will be arrested quickly.
It is shown that an incremental PID controller plus adapt feedfoward compensator can be successfully employed for the control of water level in such a plant.
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Cameron, Ewan A. "Enhancement of process control using real-time simulation." Thesis, University of Edinburgh, 1989. http://hdl.handle.net/1842/10860.
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Yang, Hualong, and 阳华龙. "Statistical process control charts with known and estimatedparameters." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B50900018.
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Monitoring and detection of abrupt changes for multivariate processes are becoming increasingly important in modern manufacturing environments. Typical equipment may have multiple key variables to be measured continuously. Hotelling's 〖T 〗^2and CUSUM charts were widely applied to solve the problem of monitoring the mean vector of multivariate quality measurements. Besides, a new multivariate cumulative sum chart (MCUSUM) is introduced where the target shift mean is assumed to be a weighted sum of principal directions of the population covariance matrix. In practical problems, estimated parameters are needed and the properties of control charts differ from the case where the parameters are known in advance. In particular, it has been observed that the average run length (ARL), a performance indicator of the control charts, is larger when the estimated parameters are used. As a first contribution we provide a general and formal proof of the phenomenon. Also, to design an efficient 〖T 〗^2 or CUSUM chart with estimated parameters, a method to calculate or approximate the ARL function is necessarily needed. A commonly used approach consists in tabulating reference values using extensive Monte-Carlo simulation. By a different approach in thesis, an analytical approximation for the ARL function in univariate case is provided, especially in-control ARL function, which can help to directly set up control limits for different sample sizes of Phase I procedure instead of conducting complex simulation.published_or_final_version
Statistics and Actuarial Science
Master
Master of Philosophy
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Jamnarnwej, Panisuan. "Methods for detection of small process shifts." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/24518.
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Olsson, Markus. "Simulation Comparison of Auto-Tuning Methods for PID Control." Thesis, Linköping University, Department of Electrical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11106.
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Auto-tuning has become an important function in distributed control systems (DCS) and is especially appreciated in large industries that can have hundreds of controllers. In the DCS 800xA manufactured by ABB, there is an auto-tuning method implemented based on a relay experiment to determine the ultimate gain and the ultimate period, with which the PID parameters are obtained using the modified Ziegler-Nichols tuning rules. The tuning procedure can then proceed with a step identification experiment to get additional parameters for kappa-tau tuning. In the previous DCS, called Advant, there was another auto-tuning approach implemented. This method was based on dominant pole design, which included an identification of the process. The purpose of this thesis is to compare these auto-tuning methods, to investigate if the dominant pole placement method should be migrated to the 800xA system.
Automatisk trimning har blivit en viktig funktion i distribuerade styrsystem (DCS och är speciellt av intresse för stora industrier som kan ha flera hundra regulatorer. Den automatiska trimningen som idag är implementerad i ABB:s DCS 800xA är baserad på ett reläexperiment för att bestämma den ultimata förstärkningen och den ultimata periodtiden. Modifierade Ziegler-Nichols trimningsregler används sedan för att bestämma PID parametrarna. Vidare kan trimningen fortsätta med ett stegsvars-experiment för att erhålla ytterliggare parametrar och trimma med kappa-tau metoden. Den automatiska trimningsmetoden som var implementerad i tidigare DCS, Advant, var baserad på dominant polplacering med identifiering av processen. Syftet med detta examensarbete är att jämföra dessa automatiska trimningsmetoder för att undersöka om den tidigare trimningsmetoden baserad på dominant polplacering ska implementeras i 800xA systemet.
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Sneesby, Martin G. "Simulation and control of reactive distillation." Curtin University of Technology, School of Chemical Engineering, 1998. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=10629.
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Reactive distillation has enormous potential for the economical synthesis of tertiary ethers. Methyl tert-butyl ether (MTBE) has been commercially produced with this technology since the early 1980s and it appears that the process also has application for Ethyl tert-butyl ether (ETBE) and other ethers. However, the combination of reaction and distillation in a single unit operation produces a process complexity that inhibits expeditious design and tight control, and presents a technology risk for potential developers. This particularly applies to hybrid reactive distillation where both reactive and non-reactive column sections are employed.The steady state simulation of a series of reactive distillation columns and processes for the production of ETBE and MTBE illuminated a number of important issues related to the optimal design techniques. Many of these issues are peculiar to reactive distillation and would not reasonably be anticipated without a priori knowledge of the phenomena involved. For example, the addition of theoretical equilibrium stages and an increase in the reflux ratio do not always have a directionally equivalent effect. The trade-off between energy consumption and capital cost which is the basis for most distillation designs cannot always be applied to reactive distillation. Importantly, the use of standard modelling techniques for equilibrium processes was also validated for reactive distillation design.The use of residue curve diagrams and reactive residue curve diagrams for the design of reactive distillation processes was investigated and shown to provide useful information regarding the feasibility of reaction-separations. Combined with simulation tools (e.g. Pro/II and SpeedUp), these techniques form the basis of a proposed design strategy for hybrid reactive distillation. It is important to apply these design tools appropriately and to ++select the correct process for a given application. The optimal design must also consider economics and the relative values of products, reactants and energy. These issues were studied with respect to ETBE production for gasoline oxygenation.The complexity of hybrid reactive distillation not only presents design challenges but potentially makes the process more difficult to control. Dynamic simulations of ETBE and MTBE reactive distillation processes were used to explore some unusual dynamic phenomena and to elucidate the process non-linearity and bidirectionality of reactive distillation. The presence of multiple steady states for some reactive distillation columns has been documented previously but the analysis of this behaviour has been incomplete and somewhat flawed. It was shown that the distinction between molar inputs and physically realisable mass or volumetric inputs is crucial and that multiplicity could be present in one case and not in the other. Multiplicity that is only observed with molar inputs (relatively common) was termed pseudo-multiplicity. Pseudo-multiplicity has few implications for the operation and control of practical reactive distillation processes although most literature examples of multiple steady states fall into this category. Four distinct causes of output multiplicity were identified including one new cause, reaction hysteresis, which is only applicable to hybrid reactive distillation. It was shown, using dynamic simulations, that transitions between parallel steady states are possible for a range of physically realisable and practical disturbances. This contrasts with other work in the area, which examines only unrealisable events and control schemes.An extensive analysis of reactive distillation control was also undertaken with respect to ETBE and MTBE hybrid columns. Manual (open-loop) control was shown to be impractical due to ++
the need to sustain the operating conditions at close to the optimal values in order to produce acceptable process performance. One-point composition control was found to be relatively easy to implement and effective with either an energy-balance or a material-balance control scheme provided only one steady state was present. Where multiple steady states exist, there are restrictions on the feasible control structures due to unavoidable instability in the inventory controllers. For example, if multiple steady states exist for the one value of the reboiler duty, only the bottoms product draw rate can be used to control the reboiler sump level. Thus, a material-balance control structure that uses the reboiler duty to control the sump level cannot be implemented in practice. Two-point control was also investigated and found to effectively prevent transitions between parallel steady states. Although more complex and difficult to implement than one-point control, a two-point scheme could be used successfully to control both the product composition and the reactant conversion and this could be desirable in some cases.A reactive distillation pilot plant was designed and operated for ETBE synthesis from ethanol and a locally available refinery hydrocarbon stream. The design of the pilot plant was based on simulation studies and the objective of operating in the industrially significant ranges of product purity and isobutene conversion. A fully automatic control system was designed and installed on the pilot plant to permit precise control of the manipulated variables and the framework to implement a range of control structures and schemes.Keywords: reactive distillation; process simulation; process design; process control; dynamic simulation; multiplicity; bidirectionality; distillation control; inferential control; pilot plant design and operation.
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Al-Taweel, Younus. "Diagnostics and simulation-based methods for validating Gaussian process emulators." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/19873/.
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Emulation is a statistical technique that can be utilised for estimating model simulations when the computer models are too computationally expensive to run. Emulators need to be subjected to a validation process since various assumptions have to be made. One assumption is that the computer model output is thought of as a realization of a Gaussian process with a mean and a covariance function. The computer model, however, is not a random sample from the Gaussian process distribution. In this thesis, we develop a graphical diagnostic that can be used to investigate whether the Gaussian process assumption is suitable for building emulators. Diagnostic methods can be used to assess the validity of the statistical model in order to investigate the best probability model for describing the computer model. However, it is not always possible to derive the required reference distribution for some diagnostics analytically. In this thesis, a simulation-based method is developed based on simulating samples from the posterior distribution of the output function. This simulation-based method can be used to obtain the reference distribution of diagnostics that cannot be obtained analytically. The observed diagnostic values will be `consistent' with the simulated diagnostic values if the Gaussian process emulator is valid.
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Shi, Ruijie. "Subspace identification methods for process dynamic modeling /." *McMaster only, 2001.
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Strong, Mark J. (Mark Joseph). "Statistical methods for process control in automobile body assembly." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10922.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996, and Thesis (M.S.)--Massachusetts Institute of Technology, Sloan School of Management, 1996.Includes bibliographical references (p. 117-120).
by Mark J. Strong.
M.S.
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Huan, Z., and G. D. Jordaan. "Thermal process and novel control methods for spin-casting." Journal for New Generation Sciences, Vol 4, Issue 1: Central University of Technology, Free State, Bloemfontein, 2006. http://hdl.handle.net/11462/490.
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Published ArticleThe quality of spin casting products and mould life are critically dependent on thermal conditions they undergo. In order to improve the performance of production and to optimise the spin-casting process, characteristics of the thermal process was firstly identified by means of the measurement and simulation. Furthermore the investigation of the developed control methods, including the thermal property substitute method and mixture method of the metal powder, was kept on the effect of air-cooling induced automatically from the spinning of the mould on the thermal process.
The air cooling system was developed to optimise the thermal process during casting, utilising a theoretical analysis of the air-flow characteristics in a cooling tube submerged in a silicon mould and the characteristics of convection heat transfer associated with the mould and cast part. A numerical simulation of the casting process was also adopted in the analysis. The effect of the developed system on the thermal process was determined experimentally and it was found that a system of aircooling, automatically induced from the spinning of the mould, is feasible in optimisation of the thermal process.
The developed control methods can be applied to the practice of spin casting individually or collectively according to the specific situations and requirements.
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Mäkynen, R. (Riku). "Some data-driven methods in process analysis and control." Bachelor's thesis, University of Oulu, 2018. http://urn.fi/URN:NBN:fi:oulu-201808222647.
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Data-driven methods such as artificial neural networks have already been used in the past to solve many different problems such as medical diagnoses or self-driving cars and thus the material shown here can be of use in many different fields of science. a Few studies that are related to data-driven methods in the field of process engineering will be explored in this thesis.
The most important finding related to neural network predictive controller was its better performance in the control of a heat exchanger when compared to several other controller types. The benefits of this approach were both energy savings and faster control. Another finding related to Evolutionary Neural Networks (EvoNNs) was the fact that it can be used to filter out the noise that is contained in the measurement data.
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Chai, Qinqin. "Computational methods for solving optimal industrial process control problems." Thesis, Curtin University, 2013. http://hdl.handle.net/20.500.11937/1227.
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In this thesis, we develop new computational methods for three classes of dynamic optimization problems: (i) A parameter identification problem for a general nonlinear time-delay system; (ii) an optimal control problem involving systems with both input and output delays, and subject to continuous inequality state constraints; and (iii) a max-min optimal control problem arising in gradient elution chromatography.In the first problem, we consider a parameter identification problem involving a general nonlinear time-delay system, where the unknown time delays and system parameters are to be identified. This problem is posed as a dynamic optimization problem, where its cost function is to measure the discrepancy between predicted output and observed system output. The aim is to find unknown time-delays and system parameters such that the cost function is minimized. We develop a gradient-based computational method for solving this dynamic optimization problem. We show that the gradients of the cost function with respect to these unknown parameters can be obtained via solving a set of auxiliary time-delay differential systems from t = 0 to t = T. On this basis, the parameter identification problem can be solved as a nonlinear optimization problem and existing optimization techniques can be used. Two numerical examples are solved using the proposed computational method. Simulation results show that the proposed computational method is highly effective. In particular, the convergence is very fast even when the initial guess of the parameter values is far away from the optimal values.Unlike the first problem, in the second problem, we consider a time delay identification problem, where the input function for the nonlinear time-delay system is piecewise-constant. We assume that the time-delays—one involving the state variables and the other involving the input variables—are unknown and need to be estimated using experimental data. We also formulate the problem of estimating the unknown delays as a nonlinear optimization problem in which the cost function measures the least-squares error between predicted output and measured system output. This estimation problem can be viewed as a switched system optimal control problem with time-delays. We show that the gradient of the cost function with respect to the unknown state delay can be obtained via solving a auxiliary time-delay differential system. Furthermore, the gradient of the cost function with respect to the unknown input delay can be obtained via solving an auxiliary time-delay differential system with jump conditions at the delayed control switching time points. On this basis, we develop a heuristic computational algorithm for solving this problem using gradient based optimization algorithms. Time-delays in two industrial processes are estimated using the proposed computational method. Simulation results show that the proposed computational method is highly effective.For the third problem, we consider a general optimal control problem governed by a system with input and output delays, and subject to continuous inequality constraints on the state and control. We focus on developing an effective computational method for solving this constrained time delay optimal control problem. For this, the control parameterization technique is used to approximate the time planning horizon [0, T] into N subintervals. Then, the control is approximated by a piecewise constant function with possible discontinuities at the pre-assigned partition points, which are also called the switching time points. The heights of the piecewise constant function are decision variables which are to be chosen such that a given cost function is minimized. For the continuous inequality constraints on the state, we construct approximating smooth functions in integral form. Then, the summation of these approximating smooth functions in integral form, which is called the constraint violation, is appended to the cost function to form a new augmented cost function. In this way, we obtain a sequence of approximate optimization problems subject to only boundedness constraints on the decision variables. Then, the gradient of the augmented cost function is derived. On this basis, we develop an effective computational method for solving the time-delay optimal control problem with continuous inequality constraints on the state and control via solving a sequence of approximate optimization problems, each of which can be solved as a nonlinear optimization problem by using existing gradient-based optimization techniques. This proposed method is then used to solve a practical optimal control problem arising in the study of a real evaporation process. The results obtained are highly satisfactory, showing that the proposed method is highly effective.The fourth problem that we consider is a max-min optimal control problem arising in the study of gradient elution chromatography, where the manipulative variables in the chromatographic process are to be chosen such that the separation efficiency is maximized. This problem has three non-standard characteristics: (i) The objective function is nonsmooth; (ii) each state variable is defined over a different time horizon; and (iii) the order of the final times for the state variable, the so-called retention times, are not fixed. To solve this problem, we first introduce a set of auxiliary decision variables to govern the ordering of the retention times. The integer constraints on these auxiliary decision variables are approximated by continuous boundedness constraints. Then, we approximate the control by a piecewise constant function, and apply a novel time-scaling transformation to map the retention times and control switching times to fixed points in a new time horizon. The retention times and control switching times become decision variables in the new time horizon. In addition, the max-min objective function is approximated by a minimization problem subject to an additional constraint. On this basis, the optimal control problem is reduced to an approximate nonlinear optimization problem subject to smooth constraints, which is then solved using a recently developed exact penalty function method. Numerical results obtained show that this approach is highly effective.Finally, some concluding remarks and suggestions for further study are made in the conclusion chapter.
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Pirgul, Khalid, and Jonathan Svensson. "Verification of Powertrain Simulation Models Using Machine Learning Methods." Thesis, Linköpings universitet, Fordonssystem, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166290.
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This thesis is providing an insight into the verification of a quasi-static simulation model based on the estimation of fuel consumption using machine learning methods. Traditional verification using real test data is not always available. Therefore, a methodology consisting of verification analysis based on estimation methods was developed together with an improving process of a quasi-static simulation model. The modelling of the simulation model mainly consists of designing and implementing a gear selection strategy together with the gearbox itself for a dual clutch transmission dedicated to hybrid application. The purpose of the simulation model is to replicate the fuel consumption behaviour of vehicle data provided from performed tests. To verify the simulation results, a so-called ranking model is developed. The ranking model estimates a fuel consumption reference for each time step of the WLTC homologation drive cycle using multiple linear regression. The results of the simulation model are verified, and a scoring system is used to indicate the performance of the simulation model, based on the correlation between estimated- and simulated data of the fuel consumption. The results show that multiple linear regression can be an appropriate approach to use as verification of simulation models. The normalised cross-correlation power is also examined and turns out to be a useful measure for correlation be-tween signals including a lag. The developed ranking model is a fast first step of evaluating a new vehicle configuration concept.
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Alici, Semra. "Dynamic data reconciliation using process simulation software and model identification tools." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3025133.
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Botha, Paul Jacobus. "Detecting change in complex process systems with phase space methods." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019/508.
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Bahbah, Chahrazade. "Advanced numerical methods for the simulation of the industrial quenching process." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM012.
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La trempe est une méthode de traitement thermique où un métal chaud est refroidi rapidement à l’aide d’un medium. Le but est de donner au métal une certaine microstructure afin d’atteindre les performances mécaniques requises. Ce procédé a des impacts directs sur l’évolution propriétés mécaniques, contrôle de la microstructure et libération des contraintes résiduelles. Afin de réaliser un procédé optimal, il est essentiel de contrôler correctement les transformations de phase qui ont lieu dans l’alliage, et ainsi obtenir la microstructure présentant les propriétés thermomécaniques souhaitées. Cette thèse est réalisée en collaboration avec la société Linamar Montupet spécialisée dans la fabrication de composants en aluminium pour l’industrie automobile. Ils s’intéressent à la trempe des pièces métalliques dans les liquides pouvant vaporiser. La vaporisation est le principal phénomène qui anime le système. L’objectif de cette thèse est donc de définir un cadre numérique capable de simuler le procédé de trempe à l’échelle industrielle. Différents aspects seront étudiés: (i) analyser et simuler les interactions liquide-vapeur-solide avec changement de phase, (ii) simuler des interactions fluide-solide pour pouvoir prédire le comportement thermomécanique du solide. Les résultats des développements numériques seront validés par des confrontations avec les expériences proposées par le partenaire industrielQuenching is a heat treatment method where a hot metal part is cooled down rapidly with the help of a quenchant. The purpose of such process is to give a certain microstructure to the metal in order to achieve the required mechanical performance. This process has direct impacts on changing mechanical properties, controlling microstructure and releasing residual stresses. Good control of quenching is essential for correctly controlling the phase changes that take place within the alloy, and obtain the microstructure exhibiting the desired thermomechanical properties. This Phd is done in collaboration with the company Linamar Montupet specialized in the manufacture of complex cast alumnium components for the automotive industry. They are interested in the quenching of metallic parts in liquid quenchants that can vaporize. The vaporizationis generally the leading phenomenon that drives the system. Indeed, the cooling of the part is strongly conditioned by the behavior of the surrounding fluid that extracts the heat therein.Thus, the objective of this thesis is to set a numerical framework able to simulate the quenching process at an industrial scale. In this thesis, different aspects will be studied: (i) analyze and simulate the liquid-vapor-solid interactions with phase change, (ii) simulate fluid-solid interactions to be able to predict the thermomechanical behavior of the solid. The results coming from these numerical development will be validated by confrontations with the experiments proposed in agreement with the industrial partner
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Lanhede, Daniel. "Non-parametric Statistical Process Control : Evaluation and Implementation of Methods for Statistical Process Control at GE Healthcare, Umeå." Thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-104512.
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Statistical process control (SPC) is a toolbox to detect changes in the output of a process distribution. It can serve as a valuable resource to maintain high quality in a manufacturing process. This report is based on the work on evaluating and implementing methods for SPC in the process of chromatography instrument manufacturing at GE Healthcare, Umeå. To handle low volume and non-normally distributed process output data, non-parametric methods are considered. Eight control charts, three for for Phase I analysis, and five for Phase II analysis, are evaluated in this study. The usability of the charts are assessed based on ease of interpretation and the performance to detect distributional changes. The later is evaluated with simulations. The result of the project is the implementation of the RS/P-chart, suggested by Capizzi et al (2013), for Phase I analysis. Of the considered Phase I methods (and simulation scenarios), the RS/P-chart has the highest overall probability, of detecting a variety of distributional changes. Further, the RS/P-chart is easily interpreted, facilitating the analysis. For Phase II analysis, the use of two control charts, one based on the Mann-Whitney U statistic, suggested by Chakraborti et al (2008), and one on the Mood test statistic for dispersion, suggested by Ghute et al (2014), have been implemented. These are chosen mainly based on the ease of interpretation. To reduce the detection time for changes in the process distribution, the change-point chart based on the Cramer Von Mises statistic, suggested by Ross et al (2012), could be used instead. Using single observations, instead of larger samples, this chart is updated more frequently. However, this efficiently increases the false alarm rate and the chart is also considered much more difficult to interpret for the SPC practitioner.Statistisk processkontroll (SPC) är en samling verktyg för att upptäcka förändringar, i fördelningen, hos utfallen i en process. Det kan fungera som en värdefull resurs för att upprätthålla en hög kvalitet i en tillverkningsprocess. Denna rapport är baserad på arbetet med att utvärdera och implementera metoder för SPC i en monteringsprocess av kromatografiinstrument på GE Healthcare, Umeå. Åtta styrdiagram, tre för för fas I analys, och fem för fas II analys, studeras i denna rapport. Användbarheten hos styrdiagrammen bedöms efter hur enkla de är att tolka och förmågan att upptäcka fördelningsförändringar. Den senare utvärderas med simuleringar. Resultatet av projektet är införandet av RS/P-metod, utvecklad av Capizzi et al (2013), för analysen i fas I. Av de utvärderade metoderna, (och simuleringsscenarier), har RS/P-diagrammet den högsta övergripande sannolikheten, för att upptäcka en mängd olika fördelningsförändringar. Vidare är metodens grafiska diagram lätt att tolka, vilket underlättar analysen. För fas II analys, har två styrdiagram, ett baserat på Mann-Whitney's U teststatistika, som föreslagits av Chakraborti et al (2008), och ett på Mood's teststatistika för spridning, som föreslagits av Ghute et al (2014), implementerats. Styrkan i dessa styrdiagram ligger främst i dess enkla tolkning. För snabbare identifiering av processförändringar kan styrdiagrammet baserat på Cramer von Mises teststatistika, som föreslagits av Ross et al (2012), användas. Baserat på enskilda observationer, istället för stickprov, har styrdiagrammet en högre uppdateringsfrekvens. Detta leder dock till ett ökat antal falska larm och styrdiagrammet anses dessutom vara avsevärt mycket svårare att tolka för SPC-utövaren.
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Liu, Pi-Shien 1960. "Real-time process control and simulation for chemical mix facility." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276673.
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The purpose of this study is to design a real-time control and simulation system for a chemical mix facility. A simulation circuit board and software simulation in an IBM personal computer emulated the real-time chemical mix facility. A second personal computer controlled the plant. The parallel port in the IBM PC computer serves as a communication path between the controlled and controlling system. Results show that the simulation can assist the design of the actual system.
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Godfrey, Simon. "Honeywell Experion System: Configuration, simulation and process control software interoperability." Thesis, Godfrey, Simon (2016) Honeywell Experion System: Configuration, simulation and process control software interoperability. Honours thesis, Murdoch University, 2016. https://researchrepository.murdoch.edu.au/id/eprint/35817/.
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The use of automated distributed control systems has become a widely discussed topic as industry attempts to maximise efficiency. An increase in automation technology has resulted in demand for “industry ready” graduate engineers with knowledge and experience with such technologies. Murdoch University (Murdoch) provides students with exposure to industry standard automation systems such as Honeywell’s Experion Process Knowledge System (PKS), a Distributed Control System (DCS) designed for the control and optimisation of industrial plants.
Presently, Murdoch uses Experion to monitor and control its pilot plant, exposing instrumentation and control students to the configuration and control of an industrial plant. Additionally, Murdoch holds a second Experion simulation license providing the ability to program and simulate process and control strategies. This project scope was to explore several key areas of the Experion simulation system followed by the development of a series of learning materials to facilitate the teaching of the Experion system to students for a new unit to be introduced at Murdoch University in 2017.
The methodology adopted to achieve the project outcome involved developing a comprehensive understanding of Experion and its associated applications, before building a series of example simulation programs for the purpose of implementing and testing a variety of Experion’s control strategies. Additionally, real-time control of the Experion simulation programs, using third party process control software, was achieved. The successful interoperability of MATLAB, Simulink, and LabVIEW with Experion provides an avenue for implementing advanced control strategies both in simulation and on Murdoch’s pilot plant.
At the conclusion of the project, an extensive list of learning materials was produced, providing comprehensive procedures to enact tasks within the Experion system. This includes initial setup and configuration, development of simulated programs and associated Human Machine Interface (HMI) displays, the implementation of control strategies, and third party process control software interoperability. These learning materials provide students with an enhanced learning experience, giving them the skills and exposure required to thrive in the automation engineering industry as a Murdoch University graduate.
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Jaeckle, Christiane M. "Product and process improvement using latent variable methods." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0006/NQ42853.pdf.
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de, Roulhac Selma Lee. "COMPARISON OF CHEMICAL PROCESS SIMULATION PROGRAMS FOR EDUCATION." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275282.
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Moradi, Mohammed Hasan. "New modelling and control methods with application to combined cycle power plants." Thesis, University of Strathclyde, 2002. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21157.
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This thesis reports the analysis and modelling required to build a software simulation of combine cycle power plants. A new MIMO PID controller tuning method and a novel predictive PID controller design method for MIMO systems are also described in the thesis. The emphasis of this work is on simulation; identification and controller design methods. The thesis begins with an account of the combined cycle power plant modelling and simulation development. This culminates in a library of different blocks and subsystems of combined cycle power plants. The simulation development shows how the steady state and dynamic behaviour of combined cycle power plants can be simulated and implemented in the SMULINK and MATLAB environment using per unit models, which are suitable for control design. In the identification stage, the relay identification method is used to identify the critical points of the system for a newly defined criterion at bandwidth frequency. Then, the identified critical points are used to tune PID controllers. The thesis then outlines multivariable PID tuning methods and makes a comparison between these methods and the new relay identification method concerning their robustness for MIMO systems. The last two chapter of thesis are concerned with a new predictive PID controller design method for both SISO and MIMO systems. This methodology is concerned with the design of PID controllers, which have similar features to the model-based predictive controller. Generalized Predictive Control (GPC) design principles are used to develop the PID control with predictive capabilities for both SISO and MIMO systems. The combined cycle power plant simulation, especially the boiler subsystem, is used as an example throughout the thesis.
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Nyberg, J. (Jens). "Characterisation and control of the zinc roasting process." Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514276108.
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Abstract
Increasing efficiency is a necessary target for an industrial roaster nowadays. This thesis presents some studies on efficiency improvement in the zinc roasting process - process characterisation, control design, implementation and testing.
The thesis focuses on the roaster, i.e. on research regarding the phenomena in the roaster furnace. By learning more about the roasting mechanism, particle size growth and dynamics of the furnace, new control implementations have been developed. More measurements, analyses and calculated variables have been added to give more information on the state of the furnace. New control variables have been introduced to give the operators more opportunities to set the conditions so that they are more suitable for the actual concentrate feed mixture. Equipment modifications have also been done. In this research, both laboratory and plant experiments have been performed together with thermodynamic evaluations and calculations. It has been necessary to make plant trials in order to obtain information about the impacts of different variables on the process. Only full-scale experiments give reliable results of the behaviour of an industrial furnace. The experiments with the roaster furnace have emphasised the study of both the metallurgy and the dynamics of the roasting process. The on-line calculated oxygen coefficient and its active control have proved important. The particle size distribution analysis of the furnace calcine has been shown to be a significant source of information for evaluating the state of the roasting furnace.
The main target is to improve the economic performance. The key is to be able to be flexible in using different kinds of raw materials, because the main income is the treatment charge. The trend is that concentrates are becoming finer, which increases the challenges for roaster furnace control. The capability to use low-grade concentrates is also a major challenge and improves the economic result.
Research and development on the boiler and mercury removal has also been part of this work for many reasons. Improved boiler performance and mercury removal gives more freedom in choosing concentrates and operating the roaster furnace. The approach has been the same as in the roaster furnace research and development work.
Control improvements based on existing knowledge, such as fuzzy control systems for controlling the furnace temperature and mercury removal, did stabilize the process, but they did not solve all the problems regarding process stability. The research and development concept of this thesis has provided the extra knowledge needed for further improvement of process control. The results of the process characterisation have led to the implementation of a new and effective control strategy.
The research and development carried out has improved performance in a number of ways: increased running time of the furnace and boiler, in-depth knowledge of roasting phenomena which led to new control methods and instructions for the operators, improved quality of sulphuric acid and a method to control its quality, measurements and analyses that give valuable information of the state of the process – all of which are now in use.
In the future, the emphasis will be placed on the research and development of roaster furnace performance, which will be a great challenge. Control of the roaster furnace is the key to the economic success of the roasting process and more information about these phenomena is needed for improving and optimising control.
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Deo, Shalaka C. "Smooth flexible models of nonhomogeneous Poisson processes fit to one or more process realizations /." Online version of thesis, 2009. http://hdl.handle.net/1850/11173.
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Chuo, John 1969. "Dynamic risk adjustment of prediction models using statistical process control methods." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28583.
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Thesis (S.M.)--Harvard-MIT Division of Health Sciences and Technology, 2004.Includes bibliographical references (p. 67-70).
Introduction. Models that represent mathematical relationships between clinical outcomes and their predictors are useful to the decision making process in patient care. Many models, such as the score of neonatal physiology (SNAP II) that predicts in-hospital mortality, have been well validated on several large populations. However, the performance profile of such models in the midst of changing predictor-outcome relationships or newly appearing outcome predictors have not been well studied. We address this problem using statistical process control (SPC) techniques in a novel way. Although widely used in the manufacturing industry to maintain high quality in critical processes, SPC's value to healthcare has begun only recently to gain attention from decision makers. It has been used to construct risk-adjusted charts to track outcomes in the intensive care unit and the surgical arena, and to monitor hospital acquired infections. However, there are no reports of using SPC techniques to scrutinize the performance quality of a clinical model over time. The series of experiments in this manuscript show that the deterioration of a model's performance can be a useful indicator of unexpected changes in the environment that it represents; therefore, defining when a model is statistically not performing according to expectations is the first step towards determining the causes of clinical variations that might impact patient healthcare. Methods. We obtained a database of 3437 newborns admitted to 7 Neonatal Intensive Care Units in the New England area from October 1994 to January 1996. We chronologically arranged the patients by birthday and grouped them into 14 sequential periods; thereby establishing a time-sequenced database to be used in our SPC experiments.
(cont.) Each of the first thirteen periods contained 250 cases, while the last period had the remaining 187 cases. Several versions of the database were constructed by altering patient data in order to simulate various clinical scenarios--we either introduced graded changes in predictor values and mortality outcomes, or added new predictors. We analyzed the prediction performance pattern of the SNAP II model as applied to periods 1 to 14 in the original and modified versions of our database. The quality parameter tracked by our SPC charts is the C-index, which has been shown to be equivalent to the area under the Receiver Operating Characteristic curve and a well accepted indicator of a model's predictive performance. We introduced the 'deterioration index' as a quantitative measure of performance degradation that permitted us to compare results among experiments. Results. Applying the SNAP II model to the unaltered database, we showed that the c-indices remained well within statistically acceptable boundaries over time. This supported the generalizability of the SNAPII model as well as allowed us to use the mean and standard deviation of the c-indices as control values for our later experiments. In chapter 5, we showed that the model's performance can be degraded beyond acceptable limits by variations in the database (high deterioration index). The index depends on how much the changes in the database affect the existing predictor-outcome relationships. We also showed how the deterioration index can be used to assess and rank contributions of predictors to the model over time. In chapter 6, we showed that model performance ...
by John Chuo.
S.M.
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Tse, Shuetfung. "Models of micro positioning and methods for surface grinding process control /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?MECH%202008%20TSE.
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Cox, Steven. "Simulation and control of univariate and multivariate set-up dominant process." Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11383/.
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This thesis explores the use of statistically valid process improvement tools in low-volume applications. Setting out the following research questions: How can the Six Sigma Measure and Analyse phases of a chronic quality problem be statistically validated in a low-volume process? How can a statistically valid approach for process control be implemented in a low-volume process? And how can this tool be extended to fit multivariate processes and can the calculation of control parameter adjustments be automated? In answer, the thesis presents an enhanced PROcess VAriation Diagnosis Tool (PROVADT) method, driving a Six Sigma improvement project through the Measure and Analyse phases. PROVADT provides a structured sampling plan to perform a Multi-Vari study, Isoplot, Gage R&R and Provisional Process Capability in as few as twenty samples and eighty measurements, making the technique suited to low-volume applications. The enhanced PROVADT method provides a Gage R&R without confounded variation sources, as was the case in the original method, and its practical application was demonstrated through two case studies. Process control tools for low-volume, high-variety manufacturing applications were developed. An adjustable traffic-light chart, with control limits linked to tolerance and simple decision rules, was used for monitoring univariate processes. This tool, the Set-Up Process Algorithm (SUPA), uses probability theory to provide 98% confidence that the process is operating at a pre-specified minimum level of Cp in as few as five samples. SUPA was extended to deal with high-complexity applications, resulting in multivariate SUPA (mSUPA). mSUPA maintains SUPA’s principles, but presents the information about multiple process features on one chart, rather than multiple univariate charts. To supplement the mSUPA tool, a theoretical method for calculating optimal process adjustment when a multivariate process is off-target was introduced, combining discrete-event simulation and numerical optimisation to calculate adjustments.
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Barkhuizen, Marlize. "Analysis of process data with singular spectrum methods." Thesis, Stellenbosch : University of Stellenbosch, 2003. http://hdl.handle.net/10019.1/16252.
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Thesis (MScIng)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: The analysis of process data obtained from chemical and metallurgical engineering systems is a crucial aspect of the operating of any process, as information extracted from the data is used for control purposes, decision making and forecasting. Singular spectrum analysis (SSA) is a relatively new technique that can be used to decompose time series into their constituent components, after which a variety of further analyses can be applied to the data. The objectives of this study were to investigate the abilities of SSA regarding the filtering of data and the subsequent modelling of the filtered data, to explore the methods available to perform nonlinear SSA and finally to explore the possibilities of Monte Carlo SSA to characterize and identify process systems from observed time series data. Although the literature indicated the widespread application of SSA in other research fields, no previous application of singular spectrum analysis to time series obtained from chemical engineering processes could be found. SSA appeared to have a multitude of applications that could be of great benefit in the analysis of data from process systems. The first indication of this was in the filtering or noise-removal abilities of SSA. A number of case studies were filtered by various techniques related to SSA, after which a number of neural network modelling strategies were applied to the data. It was consistently found that the models built on data that have been prefiltered with SSA outperformed the other models. The effectiveness of localized SSA and auto-associative neural networks in performing nonlinear SSA were compared. Both techniques succeeded in extracting a number of nonlinear components from the data that could not be identified from linear SSA. However, it was found that localized SSA was a more reliable approach, as the auto-associative neural networks would not train for some of the data or extracted nonsensical components for other series. Lastly a number of time series were analysed using Monte Carlo SSA. It was found that, as is the case with all other characterization techniques, Monte Carlo SSA could not succeed in correctly classifying all the series investigated. For this reason several tests were used for the classification of the real process data. In the light of these findings, it was concluded that singular spectrum analysis could be a valuable tool in the analysis of chemical and metallurgical process data.
AFRIKAANSE OPSOMMING: Die analise van chemise en metallurgiese prosesdata wat verkry is vanaf chemiese of metallurgiese ingenieursstelsels is ‘n baie belangrike aspek in die bedryf van enige proses, aangesien die inligting wat van die data onttrek word vir prosesbeheer, besluitneming of die bou van prosesmodelle gebruik kan word. Singuliere spektrale analise is ‘n relatief nuwe tegniek wat gebruik kan word om tydreekse in hul onderliggende komponente te ontbind. Die doelwitte van hierdie studie was om ‘n omvattende literatuuroorsig oor die ontwikkeling van die tegniek en die toepassing daarvan te doen, beide in die ingenieursindustrie en in ander navorsingsvelde, die navors van die moontlikhede van SSA aangaande die verwydering van geraas uit die data en die gevolglike modellering van die skoon data te ondersoek, ‘n ondersoek te doen na sommige van die beskikbare tegnieke vir nie-lineêre SSA en laastens ‘n studie te maak van die potensiaal van Monte Carlo SSA vir die karakterisering en identifikasie van data verkry vanaf prosesstelsels. Ten spyte van aanduidings in die literatuur dat SSA wydverspreid toegepas word in ander navorsingsvelde, kon geen vorige toepassings gevind word van SSA op chemiese prosesse nie. Dit wil voorkom asof die chemiese nywerhede groot baat kan vind by SSA van prosesdata. Die eerste aanduiding van hierdie voordele was in die vermoë van SSA om geraas te verwyder uit tydreekse. ‘n Aantal tipiese gevalle is ondersoek deur van verskeie benaderings tot SSA gebruik te maak. Nadat die geraas uit die tydreekse van die toetsgevalle verwyder is, is neurale netwerke gebruik om die prosesse te modelleer. Daar is herhaaldelik gevind dat die modelle wat gebou is op data wat eers deur SSA skoongemaak is, beter presteer as die wat slegs op die onverwerkte data gepas is. Die effektiwiteit van lokale SSA en auto-assosiatiewe neurale netwerke om nie- lineêre SSA toe te pas is ook vergelyk. Albei tegnieke het daarin geslaag om nie- lineêre hoofkomponente van die data te onttrek wat nie geïdentifiseer kon word deur die lineêre benadering nie. Daar is egter gevind dat lokale SSA ‘n meer betroubare tegniek is, aangesien die autoassosiatiewe neurale netwerke nie op sommige van die datastelle wou leer nie en vir ander tydreekse sinnelose hoofkomponente onttrek het. Laastens is ‘n aantal tydreekse geanaliseer met behulp van Monte Carlo SSA. Soos met alle ander karakteriseringstegnieke, kon Monte Carlo SSA nie daarin slaag om al die tydreekse wat ondersoek is korrek te identifiseer nie. Om hierdie rede is ‘n kombinasie van toetse gebruik om die onbekende tydreekse te klassifiseer. In die lig van al hierdie bevindinge, is die gevolgtrekking gemaak dat singuliere spektrale analise ‘n waardevolle hulpmiddel kan wees in die analise van chemiese en metallurgiese prosesdata.
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Roger, Thierry. "Modélisation du comportement de réacteurs chimiques semi-fermés à double enveloppe et à fluide unique." Rouen, 1993. http://www.theses.fr/1993ROUES036.
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La première partie de cette étude concerne l'écriture d'un modèle simplifié mais suffisamment pertinent pour être représentatif du comportement d'un réacteur chimique semi-fermé et de son contenu. La seconde partie présente la mise en oeuvre d'un logiciel destiné à la simulation, l'estimation paramétrique, l'optimisation et la commande de procédés de la chimie fine à partir de ce modèle qui, dans un but de généralisation, est mis sous la forme d'équation d'état et formellement linéarisé. Le programme écrit en langage orienté objet C++, de conception modulaire et évolutive, autorise l'extension du système constitué du réacteur et du mélange réactionnel à d'autres éléments tels qu'une colonne de rectification. Il permet également d'envisager, sans trop de difficulté, le passage au réacteur continu. Il utilise pour le calcul une représentation matricielle des données qui se traduit par une exploitation des résultats de l'automatique plus aisée. La validation du modèle, menée dans des réacteurs en acier émaillé et en verre d'une capacité de cinq litres, a été opérée pour des séquences de chauffage et de refroidissement d'espèces inertes, la synthèse du diacétate de résorcinol et une réaction acide fort-base forte. Des études effectuées en parallèle ont utilisé ce programme sur des systèmes réactionnels plus complexes, de polycondensation, mis en oeuvre sur d'autres réacteurs (en acier inoxydable de 10 litres), les résultats obtenus ont été satisfaisants. Une installation pilote, dont le système de chauffage-refroidissement est basé sur le principe du mono-fluide, a été réalisée. Des régulateurs simples, implantés sur un automate programmable, permettent le contrôle de la température du fluide caloporteur. L'architecture matérielle retenue pour le contrôle et la commande de l'installation pilote propose l'insertion d'un calculateur dans le schéma classique constitué d'un superviseur et d'un automate programmable. Le dialogue entre ces trois éléments est opérationnel et permet la conduite de l'installation pilote en mode manuel ou automatique
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Ouyang, Jintao. "Cumulative quantity control chart and maintenance strategies for industrial processes." Thesis, Click to view the E-thesis via HKUTO, 2004. http://sunzi.lib.hku.hk/hkuto/record/B31121184.
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Preece, Adam. "An investigation into methods to aid the simulation of turbulent separation control." Thesis, University of Warwick, 2008. http://wrap.warwick.ac.uk/94093/.
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The reduction of drag on commercial aircraft is an active field of study especially with environmental pressures to reduce the carbon emissions associated with climate change. To this end, the AEROMEMS-II project was commissioned by the EU with a view to investigate methods for reducing drag by using MEMS devices for controlling separation. One method for investigating flow control devices is to use the field of Computational Fluid Dynamics (CFD) to simulate the flow interactions produced in flow control applications and assess their effect. Simulating such flows can be computationally expensive so a number of methods have been investigated here to assess their use in flow control simulation applications. The first of these is the Immersed Boundary Method (IBM) which allows complex geometries to be simulated using simple cartesian grid CFD codes. IBMs are found to reduce requirements whilst maintaining flow resolution and accuracy. Next is the use of turbulence modelling with wall functions to reduce the need for fine grids near any solid surfaces. This method is found to work well and can allow the grid spacing near the wall to be 100 times coarser than with no wall functions applied. Finally, Detached Eddy Simulation (DES) has been considered as a method for allowing unsteady flow control structures to be simulated without being damped by conventional turbulence modelling. Each of these methods is presented, implemented and validated against known flow cases to assess their abilities fully. All three methods have then been applied together to a known experimental turbulent flow-control set-up at the University of Lille (fellow partners in the AEROMEMS-II project) in order to assess the feasibility of using all of these methods together to simulate flow control. All three of these methods are seen to work well together although not always with the same effect.
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龐維宗 and Wai-chung Pong. "Interstage stock control for series production lines with variable operation times." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1985. http://hub.hku.hk/bib/B31207054.
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Dong, Shijie, of Western Sydney Hawkesbury University, and Faculty of Science and Technology. "Robust nonlinear process control by L2 finite gain theory." THESIS_FST_XXX_Dong_S.xml, 1998. http://handle.uws.edu.au:8081/1959.7/386.
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This thesis focuses on nonlinear robust process control synthesis and analysis. The theoretical fundamental is the L2 finite gain theory. The aim of this research is to gain better understanding of this theory and develop new process control synthesis and analysis methods for nonlinear processes with model uncertainties and unmeasured disturbances.The current nonlinear process control methods are examined in this thesis. The research scopes of this study are described as follows: 1/. To characterize the most common process control problems such as zero-offset requirement, presentation of model uncertainties and unknown disturbance in the L2 finite gain theory framework and solve the basic theoretical issues concerned in controller design. 2/. To solve numerical computation problems arising in the nonlinear controller. 3/. To investigate the relationship between robustness requirement and performance requirement for nonlinear systems in the L2 finite gain theory framework. 4/. To consider the common phenomenon such as time-delay in the new developed methods. 5/. To investigate the advantages of the controller based on the L2 finite gain theory over the current nonlinear control methods. A series of new systematic robust process control synthesis approaches are the main contributions of this study. Simulations show the potential of these newly developed methods.Doctor of Philosophy (PhD)
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Flores-Cerrillo, Jesus MacGregor John F. "Quality control for batch processes using multivariate latent variable methods /." *McMaster only, 2003.
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Von, Raubenheimer Albert Ludwich. "Strategic supply chain management using simulation." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-12012005-092956/.
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Barr, Tina Jordan. "Performance of quality control procedures when monitoring correlated processes." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/25497.
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Bakshi, Bhavik Ramesh. "Multi-resolution methods for modeling, analysis and control of chemical process operations." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13203.
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