Nonlinear Model Predictive Engine Airpath Control with Dual-Loop Exhaust Gas Recirculation and Variable Nozzle Turbocharger

Abstract

—The control of engine airpath is a constrained multi-objective tracking problem. Multiple control variables including Exhaust Gas Recirculation (EGR) and Variable Nozzle Tur-bocharger (VNT) valve positions are simultaneously adjusted to accommodate fast, slow and coupled nonlinear airpath dynamics. This work proposes a Nonlinear Model Predictive Controller (NMPC) that exploits a convex and multi-rate prediction model for the real-time airpath control of a compression ignition engine equipped with dual-loop EGR and VNT. The benefits of the approach is verified using simulation study against a EURO 6 production-line controller and Hardware-in-the-Loop (HiL) implementation using a 480MHz processor that is comparable to nominal engine control units. The NMPC demonstrates improved control performances including reduced tracking error for intake manifold pressure, oxygen concentration and torque by 12.23%, 21.45% and 26.99%, respectively, as well as a 0.98% fuel economy improvement than the production-line controller. These benefits hold even with simulated 5% and 10% sensor noises, under one set of objective weightings over the World-wide harmonized Light vehicles Test Cycles (WLTC). The HiL implementation of the NMPC shows the average and maximum computational time of 1.80 ms and 2.94 ms, respectively, across the WLTC, which are below the required 10 ms control interval.