Au Québec, les producteurs d'aluminium consomment 12% de la puissance totale installée d'Hydro-Québec. Dans un contexte où le prix de l'énergie est en constante progression, les alumineries font donc face à des défis énergétiques de taille ; de plus, la production d'émissions de gaz à effet de serre étant directement reliée à la consommation d'énergie, des défis environnementaux importants s'annoncent pour le futur. Pour répondre à ces défis, une des avenues envisagées concerne la couche de gelée qui est présente dans chacune des cuves d'électrolyse d'aluminium. La couche de gelée a une importance capitale dans le procédé de fabrication d'aluminium, car elle sert de barrière protectrice aux parois réfractaires contre le bain électrolytique très corrosif à haute température. Elle permet également de minimiser les courants horizontaux à l'intérieur de la cuve, ce qui assure sa stabilité magnéto-hydrodynamique et permet d'optimiser l'efficacité de courant du procédé. La méthode traditionnelle pour mesurer le profil de gelée dans une cuve se fait manuellement à l'aide d'une sonde mécanique, mais cette opération nécessite beaucoup de temps ainsi que du personnel qualifié. De plus, ces mesures sont réalisées à une faible fréquence, et nécessitent l'ouverture du capot, ce qui libère beaucoup de chaleur et d'émissions chimiques dans l'atmosphère. Pour pallier aux désavantages de la méthode traditionnelle, ce travail présente le développement d'une méthode inverse (capteur virtuel) qui permet d'estimer en continu, et de manière non-instrusive [i.e. non-intrusive], l'épaisseur de gelée à partir de mesures thermiques (température et/ou flux de chaleur) provenant de capteurs situés dans les parois latérales de la cuve d'électrolyse. Le capteur virtuel est composé d'un filtre de Kalman et d'un estimateur récursif aux moindres-carrés, et il est combiné à une procédure d'identification du procédé en modèles d'état. Cette approche est appliquée pour la première fois dans la résolution d'un problème inverse avec changement de phase et en utilisant des capteurs de flux de chaleur. Parce que pour les alumineries, l'intérêt et le réel défi consistent plutôt à contrôler l'épaisseur de gelée, le capteur virtuel est ensuite combiné à un algorithme de contrôle qui régule le système de refroidissement des parois latérales de la cuve d'électrolyse. Ceci permet alors de contrôler à sa guise l'épaisseur de gelée malgré les perturbations thermiques inhérentes au procédé. La stratégie de contrôle retenue consiste en un contrôleur classique proportionnel-intégral-dérivatif, largement utilisé en industrie. Le capteur virtuel et l'algorithme de contrôle sont ensuite validés pour des conditions d'opérations typiques présentes dans les réacteurs métallurgiques à haute température. Les résultats montrent que la différence entre l'épaisseur réelle de gelée et celle prédite avec le capteur virtuel demeure dans tous les cas inférieure à 5%, tandis que la stratégie de contrôle demeure stable pour chacune des conditions d'opération, assure une erreur nulle en régime permanent ainsi qu'aucun dépassement de consigne, et procure une erreur maximale de 1 x 10[indice supérieur -3] m sur le suivi de la consigne de l'épaisseur de gelée. Pour répondre simultanément à la problématique d'estimation et de contrôle de l'épaisseur de gelée, le présent travail nécessite donc la combinaison de plusieurs domaines traditionnellement séparés (modélisation, transfert de chaleur, identification, méthodes inverses, contrôle) et cette procédure est appliquée pour la première fois dans le procédé d'électrolyse d'aluminium.

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Model predictive control (MPC) has gained great acceptance in the industry since it was developed and first applied about 25 years ago [1]. It has established its place mainly in the advanced control community. Traditionally, MPC configurations are developed and commissioned by control experts. MPC implementations have usually been only worthwhile to apply on processes that promise large profit increase in return for the large cost of implementation. Thus the scale of MPC applications in terms of number of inputs and outputs has usually been large. This is the main reason why MPC has not made its way into low-level loop control. In recent years, academia and control system vendors have made efforts to broaden the range of MPC applications. Single loop MPC and multiple PID strategy replacements for processes that are difficult to control with PID controllers have become available and easier to implement. Such processes include deadtime-dominant processes, override strategies, decoupling networks, and more. MPC controllers generally have more "knobs" that can be adjusted to gain optimum performance than PID. To solve this problem, general PID replacement MPC controllers have been suggested. Such controllers include forward modeling controller (FMC)[2], constraint LQ control[3] and adaptive controllers like ADCO[4]. These controllers are meant to combine the benefits of predictive control performance and the convenience of only few (more or less intuitive) tuning parameters. However, up until today, MPC controllers generally have only succeeded in industrial environments where PID control was performing poorly or was too difficult to implement or maintain. Many papers and field reports [5] from control experts show that PID control still performs better for a significant number of processes. This is on top of the fact that PID controllers are cheaper and faster to deploy than MPC controllers. Consequently, MPC controllers have actually replaced only a small fraction of PID controllers. This research shows that deficiencies in the feedback control capabilities of MPC controllers are one reason for the performance gap between PID and MPC. By adopting knowledge from PID and other proven feedback control algorithms, such as statistical process control (SPC) and Fuzzy logic, this research aims to find algorithms that demonstrate better feedback control performance than methods commonly used today in model predictive controllers. Initially, the research focused on single input single output (SISO) processes. It is important to ensure that the new feedback control strategy is implemented in a way that does not degrade the control functionality that makes MPC superior to PID in multiple input multiple output (MIMO) processes. / text

An artificial neural network is a mathematical black-box modelling tool. This tool can be used to model complex non-linear multivariable processes. In attempting to create an inverse process model of an industrial linear low density polyethylene reactor, several interesting results were encountered. Both time-invariant algebraic and time-invariant dynamic models could adequately represent the process, provided an identified 50-minute time lag was taken into account. A novel variation of the traditional IMC controller was implemented which used two inverse neural network process models. This was named Inverse Internal Model Control (IIMC). This controller was initially tested on a real multivariable pump-tank system and showed promising results. The IIMC controller was adapted to an on-line version for the polymer plant control system. The controller was run in open loop mode to compare the predictions of the controller with the actual PID ratio controllers. It was hoped that by incorporating neural network models into the controller, they would take the non-linearity and coupling of the variables into account, which the present PID controllers are unable to do. The existing PID controllers operate on separate loops involving the two main feeds (co-monomer and hydrogen) to the reactor, which constitute aspects of the control system in which the scope for advanced control exists. Although the control loop was not closed, the groundwork has been laid to implement a novel controller that could the operation of the plant. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2001.

The benefits of good loop tuning in the process industries have long been recognized. Ensuring that controllers are kept well-configured despite changes in process dynamics can bring energy and material savings, improved product quality as well as reduced downtime. A number of loop tuning packages therefore exist that can, on demand, check the state of a loop and adjust the controller as necessary. These methods generally apply some form of upset to the process to identify the current plant dynamics, against which the controller can then be evaluated. A simple approach to the automatic tuning of PI controllers injects variable frequency sinewaves into the loop under normal plant operation. The method employs a phase-locked loop-based device called a phase-frequency/estimation and uses 'design-point' rules, where the aim is for the Nyquist locus of the loop to pass through a particular point on the complex plane. A number of advantages are offered by the scheme: it can carry out both 'one shot' tuning and continuous adaptation, the latter even with the test signal set to a lower amplitude than that of noise. A published article is included here that extends the approach to PID controllers, with simulations studies and real-life test showing the method to work consistently well for a for a wide range of typical process dynamics, the closed-loop having a response that compares well with that produced by standard tuning rules. The associated signal processing tools are tested by applying them to the transmitter of a Coriolis mass-flow meter. Schemes are devised for the tracking and control of the second mode of measurementtube oscillation alongside the so-called 'driven mode', at which the tubes are usually vibrated, leading to useful information being made available for measurement correction purposes. Once a loop has been tuned, it is important to assess it periodically and to detect any performance losses resulting from events such as changes in process or disturbance dynamics and equipment malfunction such as faulty sensors and actuators. Motivated by the effective behaviour of the controller tuners, a loop monitor developed here, also using probing sinewaves coupled with 'design-point' ideas. In this application, the effect on the process must be minimal, so the device must work with lower still SNRs. Thus it is practical to use a fixed-frequency probing signal, together with a different tool set for tracking it. An extensive mathematical framework is developed describing the statistical properties of the signal parameter estimates, and those of the indices derived from these estimates indicating the state of the loop. The result is specific practical guidelines for the application of the monitor (e.g. for the choices of test signal amplitude and test duration). Loop monitoring itself has traditionally been carried out by passive methods that calculate various performance indicators from routine operating data. Playing a central role amongst these metrics is the Harris Index (HI) and its variants, which compare the output variance to a 'minimum achievable' figure. A key advantage of the active monitor proposed here is that it is able not only to detect suboptimal control but also to suggest how the controller should be adjusted. Moreover, the monitor’s index provides a strong indication of changes in damping factor. Through simple adjustments to the algorithm (by raising the amplitude of the test signal or adding high frequency dither to the control signal), the method can be applied even in the presence of actuator non-linearity, allowing it to identify the cause of performance losses. This is confirmed by real-life trials on a non-linear flow rig.

Målet med det här arbetet var att implementera och bygga ett komplett testsystem för reglering som efterfrågades av företaget Prevas AB i Karlstad. De önskade ett testsystem som reglerar en vattentemperatur som de kan använda på kontoret för att genomföra egna tester, analyser samt lära nyanställda medarbetare mer om automation. Testsystemet har även ett tillhörande HMI (Machine Human Interface) som användaren styr regleringen ifrån. Regleringen i testsystemet använder PID(Proportional–integral–derivative)-reglering och är inställd med lambdametoden. PID-reglering är den vanligaste använda metoden inom tillverkningsindustrin för reglering, men trots det är det många av dagens PID-regleringar som underpresterar. En anledning är slitage i mekaniska ställdonen som finns i processerna. För att utvärdera att testsystemet fungerar samt för att visa vad det kan användas till, har en mindre analys av ett mekaniskt ställdon genomförts, där antalet tillslag för ett ställdon i det byggda systemet undersökts. Testsystemet som byggdes uppfyller de krav som ställts från Prevas och de är nöjda med resultatet. Analysen som genomfördes visade att testsystemet fungerade och kan användas till den typen av test. Analysen i sig visade att simulationen som implementerats i testsystemet inte fungerade som den skulle och därmed är några testresultat ogiltiga. Rapporten presenterar hur ett testsystem för reglering kan implementeras och sedan vad det kan användas till.

Across the country members of the workforce are being laid off due to downsizing. Most of those people work for large corporations and have access to important company documents. There have been several studies suggesting that employees are taking critical information after learning they will be laid off. This becomes an issue and a threat to a corporation's security. Corporations are then placed in a position to make sure sensitive documents never leave the company. In this study we build a system that is used to assist corporations and systems administrators. This system will prevent users from taking sensitive documents. The system used in this study helps to maintain a level of security that is not only beneficial but is a crucial part of managing a corporation, and enhancing its ability to compete in an aggressive market.

The GE Healthcare Life sciences organization develop and manufacture bioreactors, mixers, filtration skids and chromatography systems used together in a biomanufacturing platform. The platform is monitored and controlled by a distributed control system through a Programmable Logic Controller (PLC). The automation software controlling the platform is today tested and verified together with the physical units. The software use PROFIBUS, an industry standard for industrial automation, for communication and control of the units. Limited access to the physical units is usually a bottleneck and it's difficult to test abnormal situations to make sure the correct alarms are triggered. To reduce the hardware dependency and to provide support during test and verification, a virtual environment is developed to simulate the behavior of a bioreactor during execution. A .NET application has been developed together with a mathematical framework to simulate a cell culture and to return relevant process parameters such as pH, dissolved oxygen, temperature and weight. The results show that it's possible to simulate a bioreactor and to communicate with the control system. The software can be a valuable tool when developing and testing automation software but should not be used for process optimization or tuning of control parameters.

O desperdício de alimentos desde sua produção até o consumo, encontra-se, atualmente, no patamar de um terço de tudo o que é produzido no mundo. Durante a etapa de transporte, principalmente de alimentos com alta perecibilidade, tais como frutas e hortaliças, ocorrem perdas consideráveis devido à não utilização de tecnologia adequada de conservação e sua utilização é restrita devido ao seu alto custo. Durante o transporte refrigerado rodoviário de produtos agrícolas perecíveis, a carga transportada é suscetível à diversas aberturas de porta do caminhão refrigerado para a realização das entregas ao longo do percurso. Quando isso ocorre uma carga térmica de massa de ar entra no ambiente refrigerado elevando a temperatura neste momento, causando prejuízos em relação à qualidade do alimento transportado. Desta forma, é proposto neste trabalho uma etapa de pré-resfriamento em momento anterior à abertura das portas do caminhão refrigerado, a fim de se manter a temperatura dentro da faixa ideal de conservação. Para isso utilizou-se a estratégia do Controle PID na redução da temperatura antes da abertura de portas e após estas serem fechadas. Foi obtido um modelo em que foram simuladas aberturas de portas de um caminhão refrigerado utilizando técnicas de controle com o objetivo de manter a temperatura do ar do ambiente refrigerado dentro da faixa ideal. Os resultados obtidos indicam o potencial da utilização do controle de sistemas aliado à estratégia do pré-resfriamento na manutenção da temperatura auxiliando na preservação dos atributos de qualidade de alimentos transportados. Além disso, avalia-se que este modelo possa ser aplicado ao transporte refrigerado de outros alimentos. / Food waste, from its production up to its consumption, currently accounts for one-third of all the food produced in the world. During the transport stage, especially of highly perishable foods, such as fruit and vegetables, considerable losses occur due to not using adequate preservation technology; its use is limited owing to its high cost. Over the refrigerated road transport of perishable agricultural products, the load transported is susceptible to different door openings of the refrigerated truck for the deliveries along the route. When this occurs, an air mass thermal load enters the refrigerated environment elevating the temperature, causing damages to the quality of the food transported. Hence, this work proposes a pre-cooling stage at the moment prior to opening the doors of the refrigerated truck, so as to keep the temperature within the ideal preservation range. For this, PID Controller was employed for reducing the temperature before doors are opened and after they are closed. A model was obtained, whereby the door openings of a refrigerated truck were simulated using control techniques aiming to maintain the temperature of the refrigerated environment air within the ideal range. The results indicate the potential of using the system control combined with the pre-cooling strategy for keeping the temperature, aiding to preserve the quality attributes of the food transported. Besides, this model is believed to be able to be applied to the refrigerated transport of other foods.

Submitted by Caroline Xavier (caroline.xavier@pucrs.br) on 2017-06-30T18:25:54Z No. of bitstreams: 1 DIS_LIVIA_NORA_BRANDALISE_PARCIAL.pdf: 6570989 bytes, checksum: b62ad256dd548bf41239e556f8d77cc1 (MD5) / Approved for entry into archive by Caroline Xavier (caroline.xavier@pucrs.br) on 2017-06-30T18:26:01Z (GMT) No. of bitstreams: 1 DIS_LIVIA_NORA_BRANDALISE_PARCIAL.pdf: 6570989 bytes, checksum: b62ad256dd548bf41239e556f8d77cc1 (MD5) / Made available in DSpace on 2017-06-30T18:26:08Z (GMT). No. of bitstreams: 1 DIS_LIVIA_NORA_BRANDALISE_PARCIAL.pdf: 6570989 bytes, checksum: b62ad256dd548bf41239e556f8d77cc1 (MD5) Previous issue date: 2017-03-20 / Background: Personality traits are an important construct in the study of obesity, both to understand its influence on this condition?s origins and to evaluate its role in responses to treatments, such as bariatric surgery. The main models used so far, are based on dimensions of normal personality traits, bringing conflicting results. Hence, there is a demand for instruments that can give more accuracy and improve the study of the personality in this population capturing more dysfunctional traits. In a special section for emerging measures, the new edition of the Diagnostic Statistical Manual of Psychiatric Disorders (DSM-5) proposed an instrument to measure personality mal-adaptive traits: the Personality Inventory for DSM-5 (PID-5), whose psychometric properties have been tested in several samples and localities. Despite promising results, PID-5 has not yet been evaluated psychometrically in other clinical populations where the "personality" construct can have an important impact (in etiologic and prognostic ways), such as obese candidates for bariatric surgery. Objective: The aim of this study is to investigate the psychometric properties of the PID-5 in the evaluation of pathological personality traits in obese candidates for bariatric surgery. This constitutes a fundamental step to assess whether the instrument keeps its original technical features allowing its use and correct interpretation in this population. Setting: Centro da Obesidade e S?ndrome Metab?lica, Pontif?cia Universidade Cat?lica do Rio Grande do Sul (COM-PUCRS), Porto Alegre, Brazil Methods: Cross-sectional study involving 312 medical records of patients who applied for bariatric surgery. We collected demographic data and scores from instruments applied in the psychiatric evaluation routine. The reliability of facets and domains was evaluated through internal consistency indices and the unidimensionality of facets was verified through factorial methods. Exploratory Structural Equations Modeling was performed to test the higher order structure of the model. To investigate convergent validity, linear correlations were calculated between PID-5 scales and instrument scores of correlated constructs (depression, anxiety, defensive styles, and quality of life). Given the characteristic of the sample, we also correlated PID-5 with body mass index (BMI) and binge eating symptoms. Data was analyzed by Factor and Mplus softwares. Results: Facets were unidimensional, with the exception of Risk Taking, better explained by two factors. We replicate the higher order structure of 5 factors of the original model, with good congruence coefficients. The internal consistency of the domains was satisfactory, however, some facets showed fragility of internal consistency, mainly when calculated with more robust methods. In general, the domains and facets correlated as expected with correlated constructs. Conclusion: This study found evidences of adequate psychometric properties of PID-5 for a sample of obese candidates for bariatric surgery. Our results indicate that the instrument is appropriate to be applied in this population, consistently evaluating personality domains and facets of the DSM-5 model. More studies in other centers are needed to replicate and reinforce our findings. / Introdu??o: Tra?os de personalidade s?o um construto importante no estudo da obesidade, tanto para entender sua influ?ncia na g?nese desta condi??o, quanto para avaliar o papel que desempenham nas respostas aos tratamentos, como a cirurgia bari?trica. At? o momento, os principais instrumentos utilizados para o estudo desta rela??o baseiam-se em modelos que avaliam dimens?es de tra?os normais da personalidade, trazendo resultados conflitantes. Existe portanto, uma demanda por instrumentos que possam fornecer maior acur?cia e aperfei?oar o estudo da personalidade nesta popula??o, captando tra?os mais disfuncionais. Em uma se??o especial para medidas emergentes, a nova edi??o do Manual Estat?stico Diagn?stico dos Transtornos Psiqui?tricos (DSM-5) prop?s um instrumento para mensurar tra?os mal-adaptativos de personalidade: o Personality Inventory for DSM-5 (PID-5), cujas propriedades psicom?tricas vem sendo testadas em diversas amostras e localidades. A despeito de promissores resultados, o PID-5 ainda n?o foi avaliado psicometricamente em outras popula??es cl?nicas onde o construto ?personalidade? pode ter um impacto importante (em termos etiol?gicos e progn?sticos), como a constitu?da por obesos candidatos a cirurgia bari?trica. Objetivo: Investigar as propriedades psicom?tricas do PID-5 na avalia??o dos tra?os patol?gicos de personalidade em pacientes obesos candidatos a cirurgia bari?trica. Esta ? uma etapa metodol?gica fundamental para verificar se o instrumento mant?m suas caracter?sticas t?cnicas originais viabilizando seu uso e correta interpreta??o nesta popula??o. Local: Centro da Obesidade e S?ndrome Metab?lica, Pontif?cia Universidade Cat?lica do Rio Grande do Sul (COM-PUCRS), Porto Alegre, Brasil M?todos: Estudo transversal envolvendo 312 prontu?rios de pacientes candidatos a cirurgia bari?trica. Foram coletados dados demogr?ficos e escores de instrumentos aplicados na rotina de avalia??o psiqui?trica pr?-operat?ria. A fidedignidade das facetas e dom?nios do PID-5 foi avaliada atrav?s de ?ndices de consist?ncia interna e a unidimensionalidade das facetas atrav?s de m?todos fatoriais. O teste da estrutura de ordem superior foi realizado por meio do Modelagem de Equa??es Estruturais Explorat?rias. Para investigar a validade convergente, foram calculadas correla??es lineares entre as escalas do PID-5 e os escores de instrumentos de construtos correlatos (depress?o, ansiedade, estilos defensivos e qualidade de vida). Dada a caracter?stica da amostra, tamb?m correlacionamos o instrumento com o ?ndice de massa corporal (IMC) e sintomas compulsivos alimentares. Os dados foram analisados pelos softwares Factor e Mplus. Resultados: As facetas de personalidade apresentaram-se de forma unidimensional, ? ?nica exce??o de Exposi??o a Riscos, melhor explicada por dois fatores. Replicamos a estrutura de ordem superior de 5 fatores do modelo original, com bons coeficientes de congru?ncia. A consist?ncia interna dos dom?nios foi satisfat?ria, entretanto algumas facetas demonstraram fragilidades de consist?ncia interna, sobretudo calculados com m?todos mais robustos. De forma geral, os dom?nios e facetas correlacionaram-se de forma esperada com os construtos correlatos. Conclus?o: Este estudo encontrou evid?ncias de propriedades psicom?tricas adequadas do PID-5 para uma amostra de obesos graves candidatos a cirurgia bari?trica. Nossos resultados indicam que o instrumento ? apropriado para ser aplicado nesta popula??o, avaliando coerentemente os dom?nios e facetas da personalidade do modelo DSM-5. Mais estudos em outros centros s?o necess?rios para replicar e refor?ar nossos achado.