Fault Diagnosis of Exhaust Gas Recirculation and Variable Geometry Turbocharger Systems in a Passenger Car Diesel Engine Based on a Sliding Mode Observer for Air System States Estimation

In this paper, we propose a sliding mode observer based fault diagnosis algorithm for diesel engines with exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems. The nonlinear sliding mode observer is proposed for precise states estimation of air system in diesel engines. Based on the estimation results of the observer and the limited sensor information in mass-produced engines, a residual generation model is derived. A modified cumulative summation algorithm is applied to the residual generation model for robust fault detection and isolation of the EGR and VGT systems. The proposed observer based fault diagnosis algorithm is implemented on a real-time embedded system, and the bypass function of an engine management system (EMS) is applied to generate multiple types of fault conditions in the systems. As a result of this study, estimation performance of the proposed observer is validated and successful fault diagnosis of the EGR and VGT systems is demonstrated through engine experiments.