Model-based control system design in a urea-SCR aftertreatment system based on NH3 sensor feedback

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Department of Mechanical Engineering-Engineering Mechanics


This paper presents preliminary control system simulation results in a urea-selective catalytic reduction (SCR) aftertreatment system based on NH 3 sensor feedback. A four-state control-oriented lumped parameter model is used to analyze the controllability and observability properties of the urea-SCR plant. A model-based estimator is designed via simulation and a control system is developed with design based on a sliding mode control framework. The control system based on NH3 sensor feedback is analyzed via simulation by comparing it to a control system developed based on NOX sensor feedback. Simulation results show that the NH3 sensor-based strategy performs very similarly in comparison to a NOX sensor-based strategy. The control system performance metrics for NOX index, urea index, urea usage, and NH3 slip suggest that the NO X sensor can be a potential alternative to a NOX sensor for urea-SCR control applications.

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Copyright © 2009 KSAE. Publisher’s version of record:

Publication Title

International Journal of Automotive Technology