OBD of De-NOx-Systems - Requirements for Software Development and Calibration for 2010 and Beyond 2008-01-1322

Worldwide OBD legislation has and will be tightened drastically. In the US, OBD II for PC and the introduction of HD OBD for HD vehicles in 2010 will be the next steps. Further challenges have come up with the introduction of active exhaust gas aftertreatment components to meet the lower future emission standards, especially with the implementation of combined DPF-De-NOx-systems for PC and HD engines.

Following such an increase in complexity, more comprehensive algorithms and software have to be developed to cope with the legislative requirements for exhaust gas aftertreatment devices. The calibration has to assure the proper functionality of OBD under all driving situations and ambient conditions. The increased complexity can only be mastered when new and efficient tools and methodologies are applied for both algorithm design and calibration. Consequently, OBD requirements have to be taken into account right from the start of engine development.

A new simulation-based development methodology for both algorithm design and calibration was developed by AVL and successfully applied to the integration of SCR systems in series production programs. OBD monitoring algorithms for SCR systems could be developed and validated using simulation models, long before components, final specifications or even the system layout was available. In turn, component tolerance specifications and system layout proposals compliant with the OBD requirements could be generated by the simulation-based methodology.

Whereas the calibration strategies are different for HD and PC applications, the final aim, avoiding unnecessary MIL illuminations, is the same for both. Using such a simulation-based methodology, including a model for engine and the exhaust gas aftertreatment components and an automated data analyzing tool, the calibration time on engine test bench and in vehicle can be reduced considerably. A big advantage of such a procedure is the strong reduction of the verification effort in fleet testing and the easy, automated data analysis. Hence a time efficient and cost saving project approach could be established. This paper describes the single steps of this methodology up to SOP (Start of Production), underlined by experiences gained in projects for PC OBD II and HD OBD.