Fast Predictive Oxygen Charge Control of a Diesel Engine

Every control system of a diesel engine tries to supply the combustion chamber with the mixture of fresh gas and recirculated exhaust gas adequate to the requested injection quantity. Usually, this mixture is expressed in particular by a combination of intake manifold pressure, measured locally, and fresh air flow measured at a substantial distance from the combustion chamber. As the amount of exhaust recirculation is subject to many disturbances and uncertainties, standard control approaches are not satysfying, especially during transients, and the emission targets are met essentially by reducing the dynamics of fuel injection by so called smoke maps. In this paper, we discuss the possibility to design an oxygen charge control which estimates the available oxygen amount in the intake manifold - after the mixture of fresh and recirculated exhaust gas - using an oxygen sensor. To reduce the effect of modeling errors or of bandwidth limitations, the comparison with the standard choice of variables is performed using data based multilinear models and an explicit MPC to compute the control signals. Comparisons performed on a production engine on a dynamic test bench confirm that the approach is able to provide a better oxygen control during transients.