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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Estimation of Frequency and Damping of a Rotating System using Mode Enhanced Order Tracking (MEOT) and Virtual Sensor Concept.

Inamdar, Sharang January 2016 (has links)
No description available.
2

Self-organizing maps for virtual sensors, fault detection and fault isolation in diesel engines

Bergkvist, Conny, Wikner, Stefan January 2005 (has links)
This master thesis report discusses the use of self-organizing maps in a diesel engine management system. Self-organizing maps are one type of artificial neural networks that are good at visualizing data and solving classification problems. The system studied is the Vindax(R) development system from Axeon Ltd. By rewriting the problem formulation also function estimation and conditioning problems can be solved apart from classification problems. In this report a feasibility study of the Vindax(R) development system is performed and for implementation the inlet air system is diagnosed and the engine torque is estimated. The results indicate that self-organizing maps can be used in future diagnosis functions as well as virtual sensors when physical models are hard to accomplish.
3

Novel Online Data Cleaning Protocols for Data Streams in Trajectory, Wireless Sensor Networks

Pumpichet, Sitthapon 12 November 2013 (has links)
The promise of Wireless Sensor Networks (WSNs) is the autonomous collaboration of a collection of sensors to accomplish some specific goals which a single sensor cannot offer. Basically, sensor networking serves a range of applications by providing the raw data as fundamentals for further analyses and actions. The imprecision of the collected data could tremendously mislead the decision-making process of sensor-based applications, resulting in an ineffectiveness or failure of the application objectives. Due to inherent WSN characteristics normally spoiling the raw sensor readings, many research efforts attempt to improve the accuracy of the corrupted or “dirty” sensor data. The dirty data need to be cleaned or corrected. However, the developed data cleaning solutions restrict themselves to the scope of static WSNs where deployed sensors would rarely move during the operation. Nowadays, many emerging applications relying on WSNs need the sensor mobility to enhance the application efficiency and usage flexibility. The location of deployed sensors needs to be dynamic. Also, each sensor would independently function and contribute its resources. Sensors equipped with vehicles for monitoring the traffic condition could be depicted as one of the prospective examples. The sensor mobility causes a transient in network topology and correlation among sensor streams. Based on static relationships among sensors, the existing methods for cleaning sensor data in static WSNs are invalid in such mobile scenarios. Therefore, a solution of data cleaning that considers the sensor movements is actively needed. This dissertation aims to improve the quality of sensor data by considering the consequences of various trajectory relationships of autonomous mobile sensors in the system. First of all, we address the dynamic network topology due to sensor mobility. The concept of virtual sensor is presented and used for spatio-temporal selection of neighboring sensors to help in cleaning sensor data streams. This method is one of the first methods to clean data in mobile sensor environments. We also study the mobility pattern of moving sensors relative to boundaries of sub-areas of interest. We developed a belief-based analysis to determine the reliable sets of neighboring sensors to improve the cleaning performance, especially when node density is relatively low. Finally, we design a novel sketch-based technique to clean data from internal sensors where spatio-temporal relationships among sensors cannot lead to the data correlations among sensor streams.
4

Virtual Crank Angle based Cylinder Pressure Sensor / Virtuell Vevvinkel baserad Cylindertryck Sensor

Ringström, Christopher January 2017 (has links)
Closed-loop combustion control is an on-going field of research for improving reducing engine emissions and increasing efficiency. Cylinder pressure is a key parameter to monitor for combustion feedback. Measuring pressure with a transducer is an option, although being able to estimate the pressure based on the crank angle measurement instead would be beneficial in terms of costs. A virtual crank angle based pressure sensor was therefore developed within this thesis. It was studied how the in-cylinder pressure trace for a full closed cycle could be modelled from a pressure trace from a rigid crankshaft model, the angular velocity measurement and heat release modelling. The pressure trace from the crankshaft model was subjected to a singularity at TDC and torsional oscillations, it was therefore of interest to study whether the singularity could be avoided by modelling the heat release. Further on, the indicated work and total heat released during combustion were estimated from the angular velocity measurements as they are important parameters for determining the heat release trace.   It was found that the indicated work could be approximated by comparing the kinetic power trace, obtained from the measured angular velocity, with the piston power trace, estimated using isentropic pressure curves for the compression and expansion within the cylinder. Accurate results were obtained for operating points at 800 rpm while large deviations were seen for higher speeds as a consequence of larger torsional effect on the angular velocity trace; on the form of perturbed oscillations. The results could be improved from local averaging of the kinetic power trace at the occasions of deceleration, although it could be concluded that only the low speed operating were still accurate enough.   The kinetic power trace was attempted to be corrected for torsional power using angular displacement estimations of the crankshaft nodes from a dynamic crankshaft model. Even though the model seemed to capture the torsional behaviour at parts of the cycle, the oscillations could not be completely removed and it was determined that the final work estimate could not be improved from the torsional power estimate. The torsion was further studied regarding frequency and amplitude of the oscillations within the angular velocity and acceleration trace. No clear relations between the torsional behaviour and operating speed and load could be concluded. Further, since inversion of the dynamic crankshaft model for pressure estimation resulted in an improper solution since before, the model was iterated instead. The pressure trace could thereby be derived accounting for torsion, however the trace still contained oscillations which highlights the challenge of estimating the torsion accurately. The torsion is a complex phenomenon to describe and further development of a model for estimating the torsion with high accuracy for all operating points would improve the virtual pressure sensor significantly.   The heat release was, as a first step, modelled as isochoric and isobaric. These models gave information of the limits of SOC by comparing the indicated work from the resulting pressure trace with the work estimate from the angular velocity measurement. Further, one Wiebe function was parametrised such that the resulting pressure derivative during late combustion was adapted to the trace from the crankshaft model in a least-square sense. This allowed for better adaption as the partial pressure trace was subjected to torsional oscillations. The fitted Wiebe function described the diffusive combustion well but missed out the shape of the premixed combustion. Lastly, a double Wiebe function parametrisation was done where the diffusive combustion function was fitted to the late combustion data and the premixed combustion function was adapted such that the resulting indicated work matched the estimated work. To receive more accurate results, the premixed SOC and duration had to be approximated beforehand from the kinetic power trace. The virtual pressure sensor and most of the sub models were most accurate for low speed operating points. It was concluded that the reason is most probably the torsional effect on the input data to all sub models. It was shown that the crankshaft model can be complemented with heat release estimations which improved the final pressure trace and removed the singularity present around TDC. / Förbränningsåterkoppling är ett aktuellt forskningsområde inom utvecklingsarbetet för att minska utsläpp och öka verkningsgraden hos förbränningsmotorer. Cylindertryck är en viktig parameter att mäta . Ett alternativ är att använda en tryckgivare men det skulle vara mer kostnadseffektivt att kunna uppskatta trycket baserat på vevvinkeln som redan idag mäts i motorer. Därav utvecklades en virtuell sensor för uppskattning av cylindertrycket genom detta examensarbete. Studien har berört hur tryck spår, bitvis noggranna för kompressionen och expansionen, från en stel vevaxelmodell kan kompletteras med modeller för värmeavgivningen från förbränningen för att erhålla ett fullt tryck spår. För att kunna bygga och utveckla modellerna utvecklades en metod för att bestämma det indikerade arbetet baserat på den uppmätta varvtalssignalen som beror mycket på hur förbränningen skett och är därmed en viktig parameter vid modellerande av värmeavgivningen.   Det indikerade arbetet kunde uppskattas genom att jämföra den kinetiska effekten med den effekt som kolvarna totalt bidrog med. Det upptäcktes att offseten mellan kurvorna motsvarade effekten av förlusterna och lasten som därmed kunde bestämmas vid de punkter där momentet från cylindrarna var i jämvikt. Den kinetiska effekten beräknades från varvtalssignalen medan effekten från kolvarna uppskattades genom att använda isentropiska tryckkurvor för kompressionen och expansionen, innan och efter förbränningen respektive. Relativt noggranna resultat erhölls för arbetspunkterna med ett varvtal på 800 rpm medan större avvikelser inträdde vid högre varvtal. Anledningen till detta var att torsionssvängningar influerade varvtalssignalen mer vid högre varvtal. Resultaten kunde förbättras genom lokal medelvärdesbildning av den kinetiska effekten vid de decelerationer som sker efter förbränningen i respektive cylinder. II   Torsionens inverkan på vevaxelns dynamik uppskattades genom att använda estimeringar av förvridningen av vevaxeln från en dynamisk vevaxelmodell. Uppskattningen tycktes vara tillräckligt noggrann inom vissa intervall men det var inte möjligt att avlägsna torsionssvängningarna i kinetiska effektspåret för hela cykeln. Uppskattningen av indikerat arbete kunde därför inte förbättras genom denna torsionsuppskattning. Torsionen var vidare studerad i form av frekvens och amplitud av svängningarna inom varvtalssignalen. Inga tydliga samband kunde säkerställas mellan svängningarna och arbetspunkternas varvtal och last. Detta tyder på att torsionen är för komplex att förutse. Vidare, då invertering av den dynamiska vevaxelmodellen tidigare visat sig ge en oriktig lösning kunde modellen istället itereras för att bestämma tryck spåret likt tidigare gjort för den stela vevaxelmodellen. Torsionssvängningarna influerade dock fortfarande det resulterande tryck spåret. Det finns stor potential att förbättra den virtuella sensorn om torsionen kan uppskattas noggrant för alla arbetspunkter.   Värmeavgivningen från förbränning var först modellerad som isochorisk och isobarisk i två respektive modeller. Dessa modeller gav information om gränsvärdena för tändningen genom att finna den tändning för modellerna som resulterade i samma arbete som det tidigare estimerade indikerade arbetet. Därefter anpassades en Wiebe funktion så att den resulterande tryckderivatan minsta-kvadrat anpassades till tryckderivatan från vevaxelmodellen under den sena förbränningen där vevaxelmodellen var mest noggrann. Wiebe funktion gav en bra anpassning till den senare diffusiva förbränningen men var inte tillräcklig för att beskriva den förblandade förbränningen. Slutligen anpassades två Wiebe funktioner där den diffusiva förbränningen anpassades likt för singel Wiebe-funktions anpassningen medan den förblandade förbränningen anpassades så att det resulterande arbetet stämde med det uppskattade indikerade arbetet. För att få bättre resultat bestämdes den förblandade förbränningens start och duration från uppskattningen av den kinetiska effekten innan anpassningen.   Den virtuella trycksensorn och de flesta av dess delmodeller var mest noggranna för arbetspunkterna vid låga varvtal. Slutsatsen var att det var främst på grund av torsionssvängningarnas påverkan på insignalerna till delmodellerna som noggrannheten föll för de högra varvtalen. Genom denna studie visades det att deltrycksspåret från vevaxelmodellen kunde kompletteras med en modell för värmeavgivningen för att slutligen få en bättre uppskattning av hela tryck spåret där singulariteten vid TDC kunde undvikas.
5

Virtual Crank Angle based Cylinder Pressure Sensor / Virtuell Vevvinkel baserad Cylindertryck Sensor

Ringström, Christopher January 2017 (has links)
Closed-loop combustion control is an on-going field of research for improving reducing engine emissions and increasing efficiency. Cylinder pressure is a key parameter to monitor for combustion feedback. Measuring pressure with a transducer is an option, although being able to estimate the pressure based on the crank angle measurement instead would be beneficial in terms of costs. A virtual crank angle based pressure sensor was therefore developed within this thesis. It was studied how the in-cylinder pressure trace for a full closed cycle could be modelled from a pressure trace from a rigid crankshaft model, the angular velocity measurement and heat release modelling. The pressure trace from the crankshaft model was subjected to a singularity at TDC and torsional oscillations, it was therefore of interest to study whether the singularity could be avoided by modelling the heat release. Further on, the indicated work and total heat released during combustion were estimated from the angular velocity measurements as they are important parameters for determining the heat release trace. It was found that the indicated work could be approximated by comparing the kinetic power trace, obtained from the measured angular velocity, with the piston power trace, estimated using isentropic pressure curves for the compression and expansion within the cylinder. Accurate results were obtained for operating points at 800 rpm while large deviations were seen for higher speeds as a consequence of larger torsional effect on the angular velocity trace; on the form of perturbed oscillations. The results could be improved from local averaging of the kinetic power trace at the occasions of deceleration, although it could be concluded that only the low speed operating were still accurate enough. The kinetic power trace was attempted to be corrected for torsional power using angular displacement estimations of the crankshaft nodes from a dynamic crankshaft model. Even though the model seemed to capture the torsional behaviour at parts of the cycle, the oscillations could not be completely removed and it was determined that the final work estimate could not be improved from the torsional power estimate. The torsion was further studied regarding frequency and amplitude of the oscillations within the angular velocity and acceleration trace. No clear relations between the torsional behaviour and operating speed and load could be concluded. Further, since inversion of the dynamic crankshaft model for pressure estimation resulted in an improper solution since before, the model was iterated instead. The pressure trace could thereby be derived accounting for torsion, however the trace still contained oscillations which highlights the challenge of estimating the torsion accurately. The torsion is a complex phenomenon to describe and further development of a model for estimating the torsion with high accuracy for all operating points would improve the virtual pressure sensor significantly. The heat release was, as a first step, modelled as isochoric and isobaric. These models gave information of the limits of SOC by comparing the indicated work from the resulting pressure trace with the work estimate from the angular velocity measurement. Further, one Wiebe function was parametrised such that the resulting pressure derivative during late combustion was adapted to the trace from the crankshaft model in a least-square sense. This allowed for better adaption as the partial pressure trace was subjected to torsional oscillations. The fitted Wiebe function described the diffusive combustion well but missed out the shape of the premixed combustion. Lastly, a double Wiebe function parametrisation was done where the diffusive combustion function was fitted to the late combustion data and the premixed combustion function was adapted such that the resulting indicated work matched the estimated work. To receive more accurate results, the premixed SOC and duration had to be approximated beforehand from the kinetic power trace. The virtual pressure sensor and most of the sub models were most accurate for low speed operating points. It was concluded that the reason is most probably the torsional effect on the input data to all sub models. It was shown that the crankshaft model can be complemented with heat release estimations which improved the final pressure trace and removed the singularity present around TDC. / Förbränningsåterkoppling är ett aktuellt forskningsområde inom utvecklingsarbetet för att minska utsläpp och öka verkningsgraden hos förbränningsmotorer. Cylindertryck är en viktig parameter att mäta . Ett alternativ är att använda en tryckgivare men det skulle vara mer kostnadseffektivt att kunna uppskatta trycket baserat på vevvinkeln som redan idag mäts i motorer. Därav utvecklades en virtuell sensor för uppskattning av cylindertrycket genom detta examensarbete. Studien har berört hur tryck spår, bitvis noggranna för kompressionen och expansionen, från en stel vevaxelmodell kan kompletteras med modeller för värmeavgivningen från förbränningen för att erhålla ett fullt tryck spår. För att kunna bygga och utveckla modellerna utvecklades en metod för att bestämma det indikerade arbetet baserat på den uppmätta varvtalssignalen som beror mycket på hur förbränningen skett och är därmed en viktig parameter vid modellerande av värmeavgivningen. Det indikerade arbetet kunde uppskattas genom att jämföra den kinetiska effekten med den effekt som kolvarna totalt bidrog med. Det upptäcktes att offseten mellan kurvorna motsvarade effekten av förlusterna och lasten som därmed kunde bestämmas vid de punkter där momentet från cylindrarna var i jämvikt. Den kinetiska effekten beräknades från varvtalssignalen medan effekten från kolvarna uppskattades genom att använda isentropiska tryckkurvor för kompressionen och expansionen, innan och efter förbränningen respektive. Relativt noggranna resultat erhölls för arbetspunkterna med ett varvtal på 800 rpm medan större avvikelser inträdde vid högre varvtal. Anledningen till detta var att torsionssvängningar influerade varvtalssignalen mer vid högre varvtal. Resultaten kunde förbättras genom lokal medelvärdesbildning av den kinetiska effekten vid de decelerationer som sker efter förbränningen i respektive cylinder. Torsionens inverkan på vevaxelns dynamik uppskattades genom att använda estimeringar av förvridningen av vevaxeln från en dynamisk vevaxelmodell. Uppskattningen tycktes vara tillräckligt noggrann inom vissa intervall men det var inte möjligt att avlägsna torsionssvängningarna i kinetiska effektspåret för hela cykeln. Uppskattningen av indikerat arbete kunde därför inte förbättras genom denna torsionsuppskattning. Torsionen var vidare studerad i form av frekvens och amplitud av svängningarna inom varvtalssignalen. Inga tydliga samband kunde säkerställas mellan svängningarna och arbetspunkternas varvtal och last. Detta tyder på att torsionen är för komplex att förutse. Vidare, då invertering av den dynamiska vevaxelmodellen tidigare visat sig ge en oriktig lösning kunde modellen istället itereras för att bestämma tryck spåret likt tidigare gjort för den stela vevaxelmodellen. Torsionssvängningarna influerade dock fortfarande det resulterande tryck spåret. Det finns stor potential att förbättra den virtuella sensorn om torsionen kan uppskattas noggrant för alla arbetspunkter. Värmeavgivningen från förbränning var först modellerad som isochorisk och isobarisk i två respektive modeller. Dessa modeller gav information om gränsvärdena för tändningen genom att finna den tändning för modellerna som resulterade i samma arbete som det tidigare estimerade indikerade arbetet. Därefter anpassades en Wiebe funktion så att den resulterande tryckderivatan minsta-kvadrat anpassades till tryckderivatan från vevaxelmodellen under den sena förbränningen där vevaxelmodellen var mest noggrann. Wiebe funktion gav en bra anpassning till den senare diffusiva förbränningen men var inte tillräcklig för att beskriva den förblandade förbränningen. Slutligen anpassades två Wiebe funktioner där den diffusiva förbränningen anpassades likt för singel Wiebe-funktions anpassningen medan den förblandade förbränningen anpassades så att det resulterande arbetet stämde med det uppskattade indikerade arbetet. För att få bättre resultat bestämdes den förblandade förbränningens start och duration från uppskattningen av den kinetiska effekten innan anpassningen. Den virtuella trycksensorn och de flesta av dess delmodeller var mest noggranna för arbetspunkterna vid låga varvtal. Slutsatsen var att det var främst på grund av torsionssvängningarnas påverkan på insignalerna till delmodellerna som noggrannheten föll för de högra varvtalen. Genom denna studie visades det att deltrycksspåret från vevaxelmodellen kunde kompletteras med en modell för värmeavgivningen för att slutligen få en bättre uppskattning av hela tryck spåret där singulariteten vid TDC kunde undvikas.
6

Self-organizing maps for virtual sensors, fault detection and fault isolation in diesel engines

Bergkvist, Conny, Wikner, Stefan January 2005 (has links)
<p>This master thesis report discusses the use of self-organizing maps in a diesel engine management system. Self-organizing maps are one type of artificial neural networks that are good at visualizing data and solving classification problems. The system studied is the Vindax(R) development system from Axeon Ltd. By rewriting the problem formulation also function estimation and conditioning problems can be solved apart from classification problems. </p><p>In this report a feasibility study of the Vindax(R) development system is performed and for implementation the inlet air system is diagnosed and the engine torque is estimated. The results indicate that self-organizing maps can be used in future diagnosis functions as well as virtual sensors when physical models are hard to accomplish.</p>
7

Tolérance aux Défaillances par Capteurs Virtuels : application aux Systèmes de Régulation d'un Turboréacteur / Virtual Sensors for Fault-Tolerant System : application to a Jet Engine Control Systems

Souami, Yani 16 July 2015 (has links)
L'industrie aéronautique évolue dans un contexte concurrentiel qui encourage les motoristes et avionneurs à réduire les coûts de production et à améliorer leurs services aux compagnies aériennes tels que la réduction des coûts d'exploitation et de maintenances des avions. Afin de relever ce défi économique, nous proposons dans cette thèse de remplacer l'architecture de régulation actuelle de certains équipements du turboréacteur, par une architecture simplifiée plus économe en capteurs et harnais en remplaçant la redondance matérielle des capteurs par une redondance analytique. Ainsi, en cas de fonctionnement anormal, les capteurs virtuels proposés pourront être utilisés pour consolider la prise de décision sur l'état du capteur par des tests de cohérence et de validation croisée et le cas échéant se substituer aux mesures.Dans ce travail de thèse, on s'est intéressé à la surveillance des systèmes de régulation de géométries variables (régulation du flux d'air en entrée et la quantité de carburant) avec comme contrainte forte la non-modification des paramètres des lois de commande existantes et le maintien de l'opérabilité du turboréacteur avec une dégradation des performances acceptables selon les spécifications du cahier des charges.Pour répondre à ces contraintes opérationnelles, une approche FTC (Fault Tolerant Control) passive est proposée. Cette approche nommée, AVG-FTC (Aircraft Variables Geometries-Fault-Tolerant Control) s'articule autour de plusieurs sous-systèmes mis en cascades. Elle tient compte du caractère instationnaire des systèmes étudiés, des différents couplages entre géométries variables et des incertitudes de modélisation. Ainsi, l'approche utilise un modèle neuronal du capteur couplé à un observateur de type Takagi-Sugeno-LPV (Linéaire à Paramètres Variant) et à un estimateur non linéaire robuste de type NEKF (Filtre de Kalman Étendu Neuronal) qui permet de produire une estimation temps réel des grandeurs surveillées. En utilisant la plateforme de prototypage et de tests du motoriste, nous avons pu évaluer l'approche AVG-FTC en simulant plusieurs scénarios de vol en présence de défaillances. Ceci a permis de montrer les performances de l'approche en termes de robustesse, de garantie de stabilité des boucles de régulations et d'opérabilité du turboréacteur. To improve the availability, a solution that aircraft manufacturers and suppliers adopt was the fault tolerance. / Over the years, market pressure has ensured that engine manufacturers invest in technology to provide clean, quiet, affordable, reliable, and efficient power. One of the last improvements is the introduction of virtual sensors that make use of non-like signals (analytical redundancy). This, is expected to improve weight, flight safety and availability. However, this new approach has not been widely investigated yet and needs further attention to remove its limitations for certificated applications.The concept of virtual sensors goes along with fault tolerance control strategies that help in limiting disruptions and maintenance costs. Indeed, a fault-tolerant control (FTC) scheme, allows for a leaner hardware structure without decreasing the safety of the system.We propose in this thesis work, to monitor through a passive FTC architecture, the Variables Geometries subsystems' of the engine: the VSV (Variable Stator Vane) and FMV (Fuel Metering Valve). A strong constrains, is not to change the parameters of the existing controllers. The approach named AVG-FTC (Variable Geometries Aircraft-Fault-Tolerant Control) is based on several cascaded sub-systems that allow to deal with the Linear Parameter Varying (LPV) model of the systems and modelling errors. The proposed FTC scheme uses a neural model of the sensor associated with a Takagi-Sugeno observer and a Neuronal Extended Kalman Filter Neural (NEKF) to account for those dynamics that cannot be explained with the LPV model to produce a real-time estimate of the monitored outputs. In case of sensor abnormality, the proposed virtual sensors can then be used as an arbitrator for sensor monitoring or as a healthy sensor used by the controller. To evaluate the approach, serval closed-loop simulations, on SNECMA jet-engine simulator have been performed. The results for distinct flight scenarios with different sensors faults have shown the capabilities of the approach in terms of stability and robustness.
8

Thermique des mini-canaux : comportement instationnaire et approche convolutive / Heat transfer in mini-channels : unsteady behaviour and convolutive approach

Hadad, Waseem Al 22 September 2016 (has links)
Un modèle semi-analytique permettant de simuler le transfert thermique conjugué dans un mini/macro canal plan soumis à des sources de chaleur surfaciques localisées sur les faces externes et variantes en fonction du temps, a été présenté et vérifié. Plus le diamètre hydraulique du canal est petit, plus la caractérisation expérimentale interne (mesure des températures et des flux) en régime thermique permanent ou transitoire à l'aide des capteurs internes est délicate. Une méthode non-intrusive permettant d'estimer les conditions internes à partir des mesures de température par thermographie infrarouge sur les faces externes et d'un modèle semi-analytique, a été effectuée. Comme le coefficient de transfert convectif forcé classique perd son sens en régime instationnaire, une approche alternative basée sur une fonction de transfert, valable pour un système linaire et invariant dans le temps a été mise en œuvre. Cette fonction peut être calculée analytiquement (uniquement pour une géométrie simple) ou estimée expérimentalement (géométrie complexe). Grâce au caractère intrinsèque de cette fonction de transfert, deux capteurs virtuels ont été conçus : capteur virtuel de température et détecteur d'encrassement permettent respectivement d'estimer les températures internes et de détecter l'encrassement qui peut avoir lieu dans l'échangeur à partir des mesures de températures sur les faces externes / A semi-analytical model allowing to simulate the transient conjugate heat transfer in mini/macro plane channel subject to a heat source(s) localized on the external face(s), was presented and verified. The developed model takes into account advection-diffusion in the fluid and conduction in the solid. As the hydraulic diameter of the channel becomes small, the internal experimental characterization (measurement of temperature and heat flux) using internal sensors become tricky because internal sensors located may compromise the structural integrity of the whole system. A non-intrusive method for estimating the internal conditions from infrared temperature measurements on the external faces using the semi-analytical model was performed. Since the classic convective heat transfer coefficient loses its meaning in transient state, an alternative approach based on a transfer function, valid for Linear Time-Invariant (LTI) systems, was highlighted. This function can be calculated analytically only for a simple geometry. For complex geometries it can be estimated experimentally. Thanks to intrinsic character of this function, two characterization methods were designed. The first to estimate the temperature at a point from a measurement at another point in the system (virtual temperature sensor). The second method concerns the detection of fouling layers that may appear in the heat exchanger from temperature measurements on the external faces
9

[pt] DESENVOLVIMENTO E VALIDAÇÃO DE SENSOR LIDAR VIRTUAL / [en] DEVELOPMENT AND VALIDATION OF A LIDAR VIRTUAL SENSOR

GUILHERME FERREIRA GUSMAO 25 June 2020 (has links)
[pt] As tecnologias de imageamento em três dimensões (3D) vêm tendo seu uso cada vez mais disseminado no meio acadêmico e no setor industrial, especialmente na forma de nuvens de pontos, uma representação matemática da geometria e superfície de um objeto ou área. No entanto, a obtenção desses dados pode ainda ser cara e demorada, reduzindo a eficiência de muitos procedimentos que são dependentes de um grande conjunto de nuvens de pontos, como a geração de datasets para treinamento de aprendizagem de máquina, cálculo de dossel florestal e inspeção submarina. Uma solução atualmente em voga é a criação de simuladores computacionais de sistemas de imageamento, realizando o escaneamento virtual de um cenário feito a partir de arquivos de objetos 3D. Este trabalho apresenta o desenvolvimento de um simulador de sistema LiDAR (light detection and ranging) baseado em algoritmos de rastreamento de raio com paralelismo (GPU raytracing), com o sensor virtual modelado por parâmetros metrológicos e calibrado por meio de comparação com um sensor real, juntamente com um gerador flexível de cenários virtuais. A combinação destas ferramentas no simulador resultou em uma geração robusta de nuvens de pontos sintéticas em cenários diversos, possibilitando a criação de datasets para uso em testes de conceitos, combinação de dados reais e virtuais, entre outras aplicações. / [en] Three dimensional (3D) imaging technologies have been increasingly used in academia and in the industrial sector, especially in the form of point clouds, a mathematical representation of the geometry and surface of an object or area. However, obtaining this data can still be expensive and time consuming, reducing the efficiency of many procedures dependent on a large set of point clouds, such as the generation of datasets for machine learning training, forest canopy calculation and subsea survey. A trending solution is the development of computer simulators for imaging systems, performing the virtual scanning of a scenario made from 3D object files. At the end of this process, synthetic point clouds are obtained. This work presents the development of a LiDAR system simulator (light detection and ranging) based on parallel ray tracing algorithms (GPU raytracing), with its virtual sensor modeled by metrological parameters. A way of calibrating the sensor is displayed, by comparing it with the measurements of a real LiDAR sensor, in addition to surveying error models to increase the realism of the virtual scan. A flexible scenario creator was also implemented to facilitate interaction with the user. The combination of these tools in the simulator resulted in a robust generation of synthetic point clouds in different scenarios, enabling the creation of datasets for use in concept tests, combining real and virtual data, among other applications.

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