Application of Model-Based Controller on a Heavy-Duty Dual Selective Catalytic Reduction Aftertreatment

Commercial vehicles require advanced engine and aftertreatment (AT) systems to meet upcoming nitrogen oxides (NO_x) and carbon dioxide (CO₂) regulations. This article focuses on the development and calibration of a model-based controller (MBC) for an advanced diesel AT system. The MBC was first applied to a standard AT system including a diesel particulate filter (DPF) and selective catalytic reduction (SCR) catalyst. Next, a light-off SCR (LO-SCR) was added upstream of the standard AT system. The MBC was optimized for both catalysts for a production engine where the diesel exhaust fluid (DEF) was unheated for both SCRs. This research shows that the tailpipe (TP) NO_x could be reduced by using MBC on both catalysts. The net result was increased NO_x conversion efficiency by one percentage point on both the LO-SCR and the primary SCR. The CO₂ emissions were slightly reduced, but this effect was not significant. Finally, the MBC was used with a final setup representative of future AT systems which included standard insulation on the catalysts and optimal DEF dosing controls. This final configuration resulted in an improved NO_x and CO₂ such that the composite Federal Test Procedure (FTP) NO_x was 0.060 g/hp-hr and the composite FTP CO₂ was 508.5 g/hp-hr. The article details this cycle along with the low-load cycle (LLC) and beverage cycle. More technologies are required to meet the future California Air Resources Board (CARB) 2027 standard, which will be shown in future work.