Simultaneous control of NOx, soot and fuel economy of a diesel engine with dual-loop EGR and VNT using economic MPC

Abstract This paper proposes a nonlinear Economic Model Predictive Control (eMPC) strategy for the airpath management of diesel engines with dual-loop Exhaust Gas Recirculation (EGR) and Variable Nozzle Turbocharger (VNT). The controller directly controls the VNT and dual-loop EGR valves to simultaneously minimise NOx, soot and pumping loss. The novelty of this management strategy is to use a merged controller to replace a conventional combination of supervisory and tracking controllers, as well as eliminating the offline determination of the intake manifold pressure and cylinder oxygen concentration set points. The eMPC computes the set points online based on the engine operating condition, state feedback and the weightings of each economic objective, namely NOx, soot and fuel economy. The eMPC is simulated with an experimentally validated EURO 6 2L four-cylinder engine model. The performance of the eMPC is compared to a production controller over the Worldwide harmonised Light vehicles Test Cycles (WLTC). Compared to the production controller, the eMPC demonstrates NOx and soot emission reductions as well as improved torque tracking and fuel economy.