${\rm NO}_{\rm x}$ Estimation in Diesel Engines via In-Cylinder Pressure Measurement

Heavy-duty (HD) Diesel engines are designed for on-road and off-road equipment with strongly varying operating conditions. In order to meet emission standards, several combustion control strategies and aftertreatment devices employing actual emission information have been developed. Nitrogen oxides $({\rm NO}_{\rm x})$ emissions are among the most constrained by regulations. In this brief, we present a ${\rm NO}_{\rm x}$ estimation method based on engine speed and indicated pressure measurement. A principal component analysis is performed to describe the information included in the pressure by means of a limited set of variables and $L_{2}$ regularization techniques are used to derive a simple and reliable estimator. The proposed strategy is implemented on a real off-road HD Diesel engine and validated on both static and dynamic standard test cycles.