Model-Based Control Development for Future Diesel Engines

摘要

Heavy duty diesel vehicles compliant with current Euro VI/ EPA13 emission limits employ aftertreatment systems based on DOC/DPF technology for soot and particulate matter reduction and SCR catalysts with urea dosing for NO x reduction. Traditionally, the majority of the control systems used for urea dosing are map based. However, increasing system complexity combined with real-world performance requirements are a strong motivation to switch to a model-based control approach. Firstly, this article describes a model-based design approach for aftertreatment control development. Focus is on urea dosing control for Euro VI level SCR systems. To achieve the legal emissions limits, including in-service conformity over the vehicle lifetime, advanced model-based control strategies enable maximal NOx conversion in combination with minimum ammonia slip, while ensuring robustness against real-life disturbances. Simulation and experimental results of the control system are presented, which demonstrate the performance and robustness properties. Following this model-based approach, a concept study is performed to explore aftertreatment and control technologies to achieve ultra-low NO x emissions as will be imposed by regulatory bodies in the near future. It is shown that aftertreatment concepts with Passive NOx Adsorber and SCR on DPF are most promising. To optimize overall engine-aftertreatment performance, the model-based control approach is extended towards Integrated Emission Management (IEM). Based on the actual system state, this supervisory controller minimizes operating costs at each instant in time under all operating conditions. This is key for cost-optimal and robust performance.