Advanced, robust control strategies for precise emission control of diesel engines during highly dynamic test cycles

摘要

Stringent pollution norms for both light and heavy duty vehicles have led to the development of new strategies and complex technologies. This has resulted in significantly higher functionality with regard to engine controls, thus increasing the amount application work. The emission legislation, which has already been passed for implementation in the near future, demands a further drastic reduction in tailpipe emission of diesel engines. The trend towards higher homogenisation, along with the increasing relevance of emissions, emitted during highly transient operation, require further development of control strategies. Minimizing both system hardware and development costs, will be possible in the future only with the establishment of physical-model based software structures and adaptive control strategies, that can substantially reduce the application effort regarding engine operation. The focus of application development work today is on the compliance to emission regulation and fuel consumption. Particularly, in the passenger car sector, the attribute of high operational comfort with regard to noise and driveability come into play. These attributes are mainly determined by injection parameters and the airflow path of the engine. For further optimization of the transient airflow path regulation in high-dynamic test procedures, the fast, virtual NO{sub}x control is proposed in the first part of the article. This approach offers a lot of promise for the lowering of transient nitrogen oxide emissions in the context of future emission regulations. Furthermore, it displays advantages during the equally necessary stationary emission tuning regarding particulate raw emissions and test cycle fuel consumption (Δ-4%). Also the compensation of production variances and reliability effects can be improved. In the second section of this paper, a cylinder pressure-based closed loop combustion control shall be presented, with which a higher degree of mixture homogenization can be achieved, while taking into consideration and optimising the transient emissions and torque behaviour. Promising concepts, covering the range of small and medium loads, are also shown. Further, a solution concept shall be introduced, that in combination with new performance characteristics of CR injectors, allows real-time control of the injection process at high loads. This helps optimise engine performance with respect to noise, efficiency and emissions.