Engine mass airflow sensor fault detection via an adaptive oxygen fraction observer

In this paper, an adaptive observer, which can simultaneously estimate the oxygen fraction states and unknown intake mass air flow rate, is designed for a Diesel engine equipped with a dual-loop exhaust gas recirculation (EGR) system. A previously developed dynamic model and oxygen fraction observer for the air-path loop of the Diesel engine are introduced as the foundation of this work. As the measurement accuracy of the mass airflow (MAF) sensor may degrade due to aging phenomenon, the impact of MAF signal error on the performance of the previously developed Luenberger-like oxygen fraction observer is investigated through experimental results. To detect the measurement error and to correct the estimation error, the detailed procedure of developing the adaptive observer is presented. The observer´s performance is validated against the experimental data.