Fault diagnosis for diesel engines is gaining more and more in importance. Driven by the increasing complexity of the air and exhaust path an improvement of OBD systems requires advanced model based methods of fault diagnosis. The target of this work was the development of a new advanced fault diagnosis system for the air and exhaust path with focus on the charging system and a validation based on real measurement data from an engine test bench. The considered faults are leakages in the intake and exhaust manifolds, restriction in the airfilter, removed blow-by tube, damaged compressor wheel, blocked VTG vanes, restriction behind the intercooler, no air-flow through the intercooler and blocked high-pressure EGR valve. A model based fault diagnosis system for diesel engines applying a new model based approach including a thermodynamic turbocharger model as well as models of the pressures in the storage volumes downstream and upstream of the turbocharger has been developed, parameterized and validated. The developed fault diagnosis system consists of residual calculations with parity equations, transformation from the residuals to symptoms applying filtering, enabling conditions and thresholds and finally operating region dependent evaluation of the developed symptoms in fault-symptom tables. The analysis of symptoms which depend on the operating point has been accomplished considering fault-free and faulty measurement data. A partition of the engine operating area into operation regions has been developed taking closed and open control loops like air mass flow control or boost pressure control of the air and exhaust path into account. The symptom deviations are validated at different operation regions. The detection and diagnosis results of the implemented faults have been verified using measurements from the engine test bench. Therefore, faulty and fault-free test measurements in an engine speed range from 1000 to 3500 rpm and a brake mean effective pressure range from motoring at -5 up to 16 bar have been used for the validation of the diagnosis system. All considered faults can be detected and diagnosed in different considered operating regions using a set of the measured inputs. The developed fault diagnosis system shows good results of fault detection and diagnosis and also shows potential for applications in ECUs of turbocharged diesel engines.
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