EGO Sensors Based Robust Output Control of EGR in Diesel Engines

In diesel engines, exhaust gas recirculation (EGR) is an efficient method for reducing NOx. 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 poerating conditioins and calibrations faults are expected from long-time measurements.