In-Cylinder Pressure-Based Low-Pressure-Cooled Exhaust Gas Recirculation Estimation Methods for Turbocharged Gasoline Direct Injection Engines

This paper proposes three different methods to estimate the low-pressure cooled exhaust gas recirculation (LP-EGR) mass flow rate based on in-cylinder pressure measurements. The proposed LP-EGR models are designed with various combustion parameters (CP), which are derived from (1) heat release analysis, (2) central moment calculation, and (3) principal component analysis (PCA). The heat release provides valuable insights into the combustion process, such as flame speed and energy release. The central moment calculation enables quantitative representations of the shape characteristics in the cylinder pressure. The PCA also allows the extraction of the influential features through simple mathematical calculations. In this paper, these approaches focus on extracting the CP that are highly correlated to the diluent effects of the LP-EGR, and the parameters are used as the input states of the polynomial regression models. Moreover, in order to resolve the effects of cycle-to-cycle variations on the estimation results, a static model-based Kalman filter is applied to the CP for the practically usable estimation. The fast and precise performance of the proposed models was validated in real-time engine experiments under steady and transient conditions. The proposed LP-EGR mass flow model was demonstrated under a wide range of steady-states with an R² value over 0.98. The instantaneous response of the cycle-basis LP-EGR estimation was validated under transient operations.