Adaptive Management Control for Urea-SCR System of Clean Diesel Vehicle

A Urea-SCR system can significantly reduce the tailpipe-out nitrogen oxide (NOx) of a diesel engine vehicle. However, future emission legislations in Europe and U.S.A require the Urea-SCR system both to improve NOx, conversion efficiency and to suppress ammonia(NH3)-slip at the same time. The robustness of the management control of the Urea-SCR system has to be significantly improved in regard to the part-to-part variations of Urea-solution injector and the aging effect of a SCR catalyst. Consequently, the management control was composed of a feedforward controller, a NH3 storage controller and a feedback controller using an NH3 sensor located downstream of the SCR catalyst, and a unique adaptive algorithm was applied to improve the robustness of the management control. As a result, it could improve the robustness of NOx conversion efficiency, and reduce NOx to the lower level than emission legislations' requirement while keeping NH3-slip at slight level.