This paper presents an experimentally validated control-oriented model and an observer for diesel oxidation catalyst (DOC)-diesel particulate filter (DPF) system in the context of exhaust gas NO and concentration estimations. NO and have different reaction characteristics within DPF and selective catalytic reduction (SCR) systems, two most promising diesel engine aftertreatment systems. Although the majority of diesel engine-out emissions is NO, the commonly used DOC located upstream of a DPF and a SCR can convert a considerable amount of NO to . Knowledge of the ratio in exhaust gas is thus meaningful for the control and diagnosis of DPF and SCR systems. Existing onboard sensors cannot differentiate NO and , and such a sensory deficiency makes separate considerations of NO and in SCR control design challenging. To tackle this problem, a control-oriented dynamic model, which can capture the main NO and dynamics from engine-out, through DOC, and to DPF, was developed. Due to the computational limitation concerns, DOC and DPF are assumed to be standard continuously stirred tank reactors in order to obtain a 0D ordinary differential equation model. Based on the model, an observer, with the measurement from a commercially available sensor, was designed to estimate the NO and concentrations in the exhaust gas along the aftertreatment systems. The stability of the observer was shown through a Lyapunov analysis assisted by insight into the system characteristics. The control-oriented model and the observer were validated with engine experimental data and the measured concentrations by a Horiba gas analyzer. Experimental results show that the model can accurately predict the main engine-out/DOC/DPF dynamics very well in semisteady-state tests. For the proposed observer, the predictions converge to the model values and estimate the NO and concentrations in the aftertreatment system well.
NO and Concentration Modeling and Observer-Based Estimation Across a Diesel Engine Aftertreatment System
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Hsieh, M., and Wang, J. (April 7, 2011). "NO and Concentration Modeling and Observer-Based Estimation Across a Diesel Engine Aftertreatment System." ASME. J. Dyn. Sys., Meas., Control. July 2011; 133(4): 041005. https://doi.org/10.1115/1.4003380
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