Cette thèse a pour but l’étude de la détection basée sur modèle de défauts pour lesmoteurs Diesel produits en grande série. La nécessité d’une surveillance continue del’état de santé des véhicules est maintenant renforcée par la législation Euro VI sur lesémissions polluantes, qui sera probablement rendue encore plus contraignante dans sesprochaines révisions. Dans ce contexte, le développement de stratégies robustes, faciles àcalibrer et valides pour des systèmes dispersés (car produits en grande série) procureraitun avantage considérable aux constructeurs automobile. L’étude développée ici tentede répondre à ces besoins en proposant une méthodologie générique. On utilise desobservateurs adaptatifs locaux pour des systèmes scalaires non linéaires et affines parrapport à l’état, pour résoudre les problèmes de la détection de défauts, de son isolationet de son estimation d’une façon compacte. De plus, les incertitudes liées aux biais demesure et de modèle et aux dérives temporelles nécessitent d’améliorer les méthodes dedétection par l’utilisation de seuils robustes pour éviter les fausses détections. Dans cettethèse, on propose un seuil variable basé sur la condition d’observabilité du paramètreimpacté par le défaut et sur une étude de sensibilité par rapport aux incertitudes surles entrées ou sur le modèle. Cette méthode permet, entre autres, de fournir un outild’analyse pour la sélection des conditions de fonctionnement du système pour lesquelsle diagnostic est plus fiable et plus robuste par rapport aux incertitudes sur les entrées.L’approche présentée a été appliquée avec succès et validée de façon expérimentale surun moteur Diesel pour le problème de détection de fuite dans le système d’admissiond’air, puis dans un environnement de simulation pour le problème de détection dedérive d’efficacité turbine. On montre ainsi ses avantages en termes de fiabilité dedétection, d’effort de calibration, et pour l’analyse des conditions de fonctionnementmoteur adaptées au diagnostic. / The study of model-based fault detection for mass production Diesel engines isthe aim of this thesis. The necessity of continuous vehicles health monitoring is nowenforced by the Euro VI pollutant legislation, which will probably be tightened in itsfuture revisions. In this context developing a robust strategy that could be easilycalibrated and work with different systems (due to production variability) would bea tremendous advantage for car manufacturers. The study developed here tries toanswer to those necessities by proposing a generic methodology based on local adaptiveobservers for scalar nonlinear state-affine systems. The fault detection, isolation andestimation problems are thus solved in a compact way. Moreover, the uncertaintiesdue to measurement or model biases and time drifts lead to the necessity of improvingthe detection methodology by the use of robust thresholds that could avoid undesiredfalse alarms. In this thesis a variable threshold is proposed based on the observabilitycondition and the sensitivity analysis of the parameter impacted by the fault withrespect to input or model uncertainties. This approach allows, among other things, tobe used as an analysis tool for the individuation of the system operating points for whichthe diagnosis is more reliable and more robust to inputs uncertainties. The discussedapproach has been successfully implemented and experimentally tested on a real Dieselengine for the intake leak detection and for the turbine efficiency loss drift detectionin a co-simulation environment showing its advantages in term of detection reliability,calibration effort and engines diagnosis operating condition analysis.

The concepts of engine downsizing and down-speeding offer reductions in CO2 emissions from passenger cars. These reductions are achieved by reducing pumping and friction losses at part-load operation. Conventionally, rated torque and power for downsized units are recovered by means of turbocharging. The transient response of such engines is, however, affected by the static and dynamic characteristics of the turbo-machinery. Recent advances in engine simulation and control tools have been employed for the purpose of the research reported in this thesis to identify and verify possible air-path enhancements. A systematic method for evaluating various turbocharger assistance concepts is proposed and discussed in this thesis. To ensure a fair comparison of selected candidate systems, an easily reconfigurable controller providing a close-to-optimal operation, while satisfying physical limits, is formulated. This controller is based on the Model Predictive Control framework and uses a linearised mean value model to optimise the predicted behaviour of the engine. Initially, the controller was applied to a 1D simulation model of a conventional light-duty Diesel engine, for which the desired closed-loop features were verified. This procedure was subsequently applied to various air-path enhancement systems. In this thesis, a turbocharger electric assistance and various concepts based on compressed gas injection were considered. The capability of these systems to improve engine response during third gear tip-in manoeuvre was quantified. This investigation was also complemented with a parametric study of how effectively each of the considered methods used its available resources. As a result, injecting compressed gas into the exhaust manifold was identified as an effective method, which to date has attracted limited attention from engine research community. The effectiveness of the exhaust manifold assistance was experimentally verified on a light-duty Diesel engine. The sensitivity of the improvements to compressed gas supply parameters was also investigated. This led to the development of the BREES system: a low component count, compressed gas based system for reducing turbo-lag. It was shown that during braking manoeuvres a tank can be charged to the level sufficient for a subsequent boost assistance event. Such a functionality was implemented with a very limited set of additional components and only minor changes to the standard engine control.

Today's globally competitive market and its associated environmental and social issues of sustainable development are major challenges for the automobile industry. To meet them, the industry needs to invest in high performance development tools. For improving engine performance in terms of consumption and emission, the interactions between the subsystems of the engine air-path need to be understood. This thesis followed two major axes of research in this context. First, the problems related to the modeling of the global air-path system were studied, which include the airflow characteristics between the different subsystems of the air-path, high frequency combustion modeling and pulsating airflow, and estimation of the exhaust aerodynamic force on the vanes of variable geometry turbochargers (VGT). The detailed modeling study was used for developing an engine air-path simulator, which takes into account these interactions and predicts the influence of subsystems on the global air-path. The second axis of research was focused on modeling of mechatronic actuators of the air-path, taking into account their nonlinear behavior due to friction and changes in operating conditions. A generic nonlinear dynamic model was developed and included in the simulator. This model can be adapted to most commercial actuators. The complete simulator has been implemented using AMESim for engine and air-path modeling, and Simulink for control. It has been parameterized according to the specifications of a commercial diesel engine and validated against experimental data. Finally, robust local controllers were studied for actuator position control, aimed at guaranteeing the performance of the actuators under parametric uncertainty and external disturbances. An advanced controller was developed, which adapts to changes in friction characteristics of the actuator and external load changes. The performance of all controllers has been demonstrated experimentally.

Characterisation of modern complex powertrains is a time consuming and expensive process. Little effort has been made to improve the efficiency of testing methodologies used to obtain data for this purpose. Steady-state engine testing is still regarded as the golden standard, where approximately 90% of testing time is wasted waiting for the engine to stabilize. Rapid dynamic engine testing, as a replacement for the conventional steady-state method, has the potential to significantly reduce the time required for characterisation. However, even by using state of the art measurement equipment, dynamic engine testing introduces the problem that certain variables are not directly measurable due to the excitation of the system dynamics. Consequently, it is necessary to develop methods that allow the observation of not directly measurable quantities during transient engine testing. Engine testing for the characterisation of the engine air-path is specifically affected by this problem since the air mass flow entering the cylinder is not directly measurable by any sensor during transient operation. This dissertation presents a comprehensive methodology for engine air charge characterisation using dynamic test data. An observer is developed, which allows observation of the actual air mass flow into the engine during transient operation. The observer is integrated into a dual-ramp testing procedure, which allows the elimination of unaccounted dynamic effects by averaging over the resulting hysteresis. A simulation study on a 1-D gas dynamic engine model investigates the accuracy of the developed methodology. The simulation results show a trade-off between time saving and accuracy. Experimental test result confirm a time saving of 95% compared to conventional steady-state testing and at least 65% compared to quasi steady-state testing while maintaining the accuracy and repeatability of conventional steady-state testing.

No description available.