Closed-loop control of a SCR system using a NOx sensor cross-sensitive to NH3

This paper proposes a control strategy for an automotive selective catalytic reduction (SCR) system using a NO_x sensor in a feedback loop. As is representative of real world applications, the employed NO_x sensor is cross-sensitive to NH₃, which induces several complexities. In particular the ambiguity of the measurements could be detrimental to the closed loop response, as it generates multiple equilibrium points (artefacts), besides the point of practical interest. A study of the closed-loop dynamics is performed in the vicinity of each point, which shows that the closed loop system naturally converges to the point of interest not to the artefacts. Experimental results obtained after a detailed calibration method illustrate the relevance and performance of the proposed approach.