Model of a Supercharged Diesel Engine with High and Low-Pressure EGR as Part of an NMPC for ECU Implementation

Abstract

The paper focuses on a system and an appropriate controller concept for advanced air management of a turbocharged passenger car diesel engine. The proposed air management system consists of a VTG turbocharger and two separate Exhaust Gas Recirculation (EGR) loops, a cooled or non-cooled high-pressure EGR (HP EGR) and a cooled low-pressure EGR (LP EGR) loop. In the LP EGR loop, the exhaust gas leaving the particulate filter is mixed with fresh air just in front of the compressor inlet. A main model (MM) was created in Simulink to design a Nonlinear Model-based Predictive Controller (NMPC). This model is mainly founded on physical equations, allowing easy adaptation to various systems. MM is a detailed model which was developed first and which is also used for software-in-the-loop (SIL) tests of the controller with the simulated engine. At the beginning of the diesel engine test stage, stationary measurements were conducted to examine the influence of variations of the EGR rate, boost pressure, fresh air mass, etc. These tests were carried out in an open loop without an integrated controller for the air management system. The results were used to optimize the Simulink models. As to the controller concept, a model-based predictive approach is briefly presented which uses a simplified simulation model (a reduced version of a more detailed MM) with real-time capability of the complete air path for providing the system states. For the prediction, an additional, simplified model of the engine's air path system with real-time capability is used.