NOx-sensorn är grundläggande i det moderna efterbehandlingssystemet och dess pålitlighet är avgörande för att kunna leva upp till rådande emissionslagkrav. Livslängden samt sensorns beteende i slutet av denna varierar betydligt. Om en NOx sensor med oberäkneligt beteende inte upptäcks av fordonets styrsystemet kan det orsaka omfattande verkstadsbesök eller i värsta fall brott mot emissionslagkrav. Examensarbetet involverar identifiering av olika sensorfellägen, tidiga tecken till dessa fellägen, förstå och identifiera förhållanden mellan olika sensorparametrar och analysera sensorbeteendet vid sensorlivslängdens slutskede. NOx sensorn är en relativt ny sensor och fordonsindustrin har ännu inte en fullständig förståelse för dess beteende. Litteraturstudien täcker olika fellägena så som fastnat värde, förskjutet värde, förstärkning av värdet, felaktiga svängningar samt långsam respons. Även effekterna av åldrande i NOx sensorn beskrivs. Litteraturstudien diskuterar också diagnoser av sensorer i allmänhet samt diagnoser specifikt för NOx sensorer. Uppsatsarbetet involverar också en experimentell studie där NOx sensorer utsätts för statiska och fluktuerande gasflöden i en motortestbädd. Fellägen i NOx sensorer kan observeras i parametrarna för NOx-värde och oxidationsnivå. I den version av NOx sensorn som användes observerades det också att parametrarna felaktig NOx och felaktig O2 visar samma felkod samtidigt. Dock är inte parametrarna för felaktig NOx och felaktig O2 relaterade till parametrarna för värmningsstatus, felaktig värmare och värmeelementets temperatur. Sensorns status gällande ogiltiga NOx-mätningar är större än eller lika med antalet ogiltiga O2-mätningar. Resultatet gäller framför allt sensormodell Continental 2.8 NOx sensorer. Även logik för en monitor gällande felaktiga svängningar utvecklas baserat på standardavvikelse och NOx statusparametern för ogiltig mätning. / The NOx sensor is essential in the modern after-treatment system and the reliability of the sensor is crucial for any emission-based legislation. The life span of a sensor varies a lot as well as the behaviour previous to its end of life. If a NOx sensor with erratic behaviour is not discovered by the control system it may cause extensive workshop effort or in worst case exceed legal requirements. The thesis work involves identifying different sensor failure modes, precursors to these failure modes, understanding and identifying relationships between different sensor parameters, and analysing the sensor behaviour especially towards the end of life. The NOx sensor is a relatively new sensor and the vehicle industry does not yet have a complete understanding of its behaviour. The literature study covers the different failure modes namely stuck, offset, gain, oscillations, and slow response and their causes along with the effects of ageing in NOx sensors. It also discusses the diagnosis of faulty sensors in general and faulty NOx sensors. The thesis work also involves an experimental study where the NOx sensors are subjected to static and transient gas flow tests in an engine testbed. Failure modes in NOx sensors are observable in NOx concentration and actual oxidation measurement parameters. It was also observed in the version of the NOx sensor used that Error NOx and Error O2 parameters show the same fault code at the same time. Although, the Error NOx and Error O2 parameters are not related to the heater parameters, Heater status, Error heater, and Temperature of heating element. The number of invalid flags set in NOx status is greater than or equal to the number of invalid flags in O2 status. The mentioned parameters are concerning Continental 2.8 NOx sensors. The logic for the oscillatory fault monitor is developed based on standard deviation and an invalid flag check on the NOx status parameter.

In automotive industry there is a growing need for predicting the failure of a component, to achieve the cost saving and customer satisfaction. As failure in a component leads to the work breakdown for the customer. This paper describes an effort in making a prediction failure monitoring model for NOx sensor in trucks. It is a component that used to measure the level of nitrogen oxide emission from the truck. The NOx sensor has chosen because its failure leads to the slowdown of engine efficiency and it is fragile and costly to replace. The data from a good and contaminated NOx sensor which is collated from the test rigs is used the input to the model. This work in this paper shows approach of complementing the Deep Learning models with Machine Learning algorithm to achieve the results. In this work LSTMs are used to detect the gain in NOx sensor and Encoder-Decoder LSTM is used to predict the variables. On top of it Multiple Linear Regression model is used to achieve the end results. The performance of the monitoring model is promising. The approach described in this paper is a general model and not specific to this component, but also can be used for other sensors too as it has a universal kind of approach.

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La Tesis Doctoral estudia la observaci'on en tiempo real de la concentraci'on en el colector de escape de 'oxidos de nitr'ogeno (NOx) y del dosado en motores diesel sobrealimentados (¿ '1 ). Para ello se combinan dos fuentes de informaci'on diferentes: ¿ Sensores capaces de proporcionar una media de dichas variables, ¿ y modelos orientados a control que estiman estas variables a partir de otras medidas del motor. El trabajo parte de la evaluaci'on de la precisi'on de los sensores, realizada mediante la comparaci'on de su medida con la proporcionada por equipos anal'¿ticos de alta precisi'on, que son usados como est'andares de calibraci'on est'atica. Tambi'en se desarrollan en la Tesis m'etodos para la calibraci'on de la din'amica del sensor; dichos m'etodos permiten identi¿car un modelo de comportamiento del sensor y revelar su velocidad de respuesta. En general, estos sensores demuestran ser precisos pero relativamente lentos. Por otra parte, se proponen modelos r'apidos para la estimaci'on de NOx y ¿ '1 . Estos m'etodos, basados en relaciones f'¿sicas, tablas de par'ametros y una serie de correcciones, emplean las medidas proporcionadas por otros sensores con el ¿n de proporcionar una estimaci'on de las variables de inter'es. Los modelos permiten una estimaci'on muy r'apida, pero resultan afectados por efectos de deriva que comprometen su precisi'on. Con el ¿n de aprovechar las caracter'¿sticas din'amicas del modelo y mantener la precisi'on en estado estacionario del sensor, se proponen t'ecnicas de fusi'on de la informaci'on basadas en la aplicaci'on de ¿ltros de Kalman (KF). En primer lugar, se dise¿na un KF capaz de combinar ambas fuentes de informaci'on y corregir en tiempo real el sesgo entre las dos se¿nales. Posteriormente, se estudia la adaptaci'on en tiempo real de los par'ametros del modelo con el ¿n de corregir de forma autom'atica los problemas de deriva asociados al uso de modelos. Todos los m'etodos y procedimientos desarrollados a lo largo de la presente Tesis Doctoral se han aplicado de forma experimental a la estimaci'on de NOx y ¿ '1 . De forma adicional, la Tesis Doctoral desarrolla aspectos relativos a la transferencia de estos m'etodos a los motores de serie. / The dissertation covers the problem of the online estimation of diesel engine exhaust concentrations of NOx and '1. Two information sources are utilised: ¿ on-board sensors for measuring NOx and '1, and ¿ control oriented models (COM) in order to predict NOx and '1. The evaluation of the static accuracy of these sensors is made by comparing the outputs with a gas analyser, while the dynamics are identified on-board by perform- ing step-like transitions on NOx and '1 after modifying ECU actuation variables. Different methods for identifying the dynamic output of the sensors are developed in this work; these methods allow to identify the time response and delay of the sensors if a sufficient data set is available. In general, these sensors are accurate but present slow responses. Afterwards, control oriented models for estimating NOx and '1 are proposed. Regarding '1 prediction, the computation is based on the relative fuel-to-air ratio, where fuel comes from an ECU model and air mass flow is measured by a sensor. For the case of NOx, a set-point relative model based on look-up tables is fitted for representing nominal engine emissions with an exponential correction based on the intake oxygen variation. Different corrections factor for modeling other effects such as the thermal loading of the engine are also proposed. The model is able to predict NOx fast with a low error and a simple structure. Despite of using models or sensors, model drift and sensor dynamic deficiencies affect the final estimation. In order to solve these problems, data fusion strategies are proposed by combining the steady-state accuracy of the sensor and the fast estimation of the models by means of applying Kalman filters (KF). In a first approach, a drift correction model tracks the bias between the model and the sensor but keeping the fast response of the model. In a second approach, the updating of look-up tables by using observers is coped with different versions based on the extended Kalman filter (EKF). Particularly, a simplified KF allows to observe the parameters with a low computational effort. Finally, the methods and algorithms developed in this work are combined and applied to the estimation of NOx and '1. Additionally, the dissertation covers aspects relative to the implementation of the methods in series engines. / Blanco Rodríguez, D. (2013). Modelling and observation of exhaust gas concentrations for diesel engine control [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/32666 / TESIS / Premios Extraordinarios de tesis doctorales

Le problème étudié dans cette thèse est la commande en boucle fermée d'un système SCR (Réduction Sélective Catalytique) par l'urée tel qu'utilisé dans les systèmes de dépollution des gaz d'échappement des moteurs diesel automobiles. Une première contribution du manuscrit est en un modèle détaillé de la SCR, soulignant de la nature distribuée (1D) du système considéré, et plusieurs réductions successives de ce modèle de simulation conduisant à un modèle plus simple, utilisable à des fins de synthèse de contrôleur. Une seconde contribution consiste à prendre en compte la sensibilité au NH3 du capteur de NOx utilisé pour la rétroaction lors du développement d'algorithmes de commande (observateur d'état, boucle de rétroaction, séquencement de gain, interprétation du signal capteur). L'observateur-contrôleur présenté possède plusieurs points d'équilibre dues à la sensibilité du capteur de sortie. On montre que seul le point d'intérêt pratique est asymptotiquement stable, les autres étant instables naturellement, rendus instables par une implémentation spécifique ou aisémentdétectés comme indésirables. Ces deux contributions ont été testées expérimentalement et validées. En résumé, la méthode de contrôle proposée dans cette thèse permet, à partir d'un moteur conforme aux exigences Euro 5 et avec une procédure de pré-conditionnement du catalyseur, de satisfaire la norme Euro 6. / The problem studied in this thesis is the closed-loop control of a urea-SCR (urea Selective Catalytic Reduction) as used in aftertreatment systems of diesel vehicles. A first contribution of the thesis is a detailed model for the SCR, highlighting the distributed (1D) nature of the considered system, and several successive reductions of this simulation model leading to a simpler one, better-suited for control design purposes. A second contribution consists in considering the sensitivity to NH3 of the NOx sensor used in a feedback loop, in the development of the control algorithms (state observer, feedback, gain scheduling, measurement interpretation). The ambiguity of the output measurement could be detrimental to the closed loop response, as it generates multiple equilibrium points (artefacts), besides the point of practical interest. A study of the closed-loop dynamics is performed in the vicinity of each point, which shows that the closed loop system naturally converges to the point of interest not to the artefacts. Both contributions have been tested and validated experimentally. In summary, the method proposed in this thesis might allow an engine equipped with Euro 5 hardware to satisfy Euro 6 standard using a preconditioning procedure of the catalyst.