Complex Air Path Management Systems and Necessary Controller Structures for Future High Dynamic Requirements 2009-01-1616

The future worldwide emission regulations will request a drastic decrease of Diesel engine tailpipe emissions. Depending on the planned application and the real official regulations, a further strong decrease of engine out emissions is necessary, even though the utilized exhaust after-treatment systems are very powerful. To reduce NOx emissions internally, the external exhaust gas recirculation (EGR) is known as the most effective way. Due to the continuously increasing requirements regarding specific power, dynamic behavior and low emissions, future air path systems have to fulfill higher requirements and, consequently, become more and more complex, e.g. arrangements with a 2-stage turbo charging or 2-stage EGR system with different stages of cooling performance. The integration of all these high efficient sub-systems will lead to a very complex ECU structure, even considering additional operating modes for different needs like DPF regeneration or SCR heating strategies, and, thus, result in significantly amplified calibration effort, if one has to cover a clear improvement regarding emissions on the one side and one has to ensure a robust, convenient and dynamic engine behavior under real conditions on the other side. Convenience especially means that the driver will not notice all the necessary sub-systems and their control functions, e.g. the change of the various operating modes when regenerating the particulate trap. Until now, closed or open loop control algorithms with a calibration via especially applied sensors represent the current state-of-the-art. The actual development status of sensors as well as future requirements lead to the conclusion, that this way will not cover all future requirements regarding accuracy, dynamic behavior and durability. Furthermore, the calibration efforts have to be strongly reduced, especially with respect to the upcoming numbers of vehicle variants. The only way to combine all these requirements is to introduce smart, intelligent and adaptive control strategies. Beside this, modern control algorithms should be able to cover part-to-part deviations of the used sensors by minimized calibration effort even for these diagnoses. This paper introduces the most important features and results of a modern control algorithm for future Diesel engine applications. In a first step, the so-called “fast and virtual NOx controller” will be described. This virtual NOx controller provides a great capability to decrease transient engine-out emissions and to consider fuel consumption in any test scenario. Also scattering and long term durability effects can be covered with such an algorithm. In a second step, first results with this controller strategy are depicted.