EGO sensor based robust output control of EGR in diesel engines

In diesel engines, exhaust gas recirculation (EGR) is an efficient method for reducing NO_x. EGR rates are commonly set according to the expected engine behavior, without considering the actual composition of the exhaust gases. In this paper, a new control system for EGR in passenger cars is presented, based on an exhaust gas oxygen (EGO) sensor as indicator of the combustion state as well as on a robust design approach to cope with the parameter variations. The proposed control has been designed for and tested on an Audi TDI engine and has been found to yield a similar performance as the conventional controllers for the standard engine, in spite of the transport delays between combustion process and measurement. Due to the presence of feedback, reduced sensitivity and/or detectability of wear, production irregularities, changes of operating conditions and calibration faults are expected from long-time measurements