Term-by-Term Observer Design Method to Estimate NH3 Storage in SCR Catalyst

This paper presents a nonlinear state-observer applied to the urea-SCR system. Deciding whether to use the actual or the estimated value of the measured states for each term of the state-observer is not trivial. This paper presents a unique method to make these decisions systematically. The method is demonstrated by designing an observer for the urea-SCR system. Performance of the observer designed using this method is then evaluated in the presence of parameter, measurement, and model uncertainty using simulations. Simulation results show that the proposed method is capable of systematically yielding the best structure for a given nonlinear state-observer.