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Extended Kalman Filter Estimator for NH 3 Storage, NO, NO 2 and NH 3 Estimation in a SCR
Technical Paper
2013-01-1581
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
This paper focuses on the development of an Extended Kalman
Filter for estimating internal species concentration and storage
states of an SCR using NOX and NH₃ sensors. The motivation for
this work was twofold. First, knowledge of internal states may be
useful for onboard diagnostic strategy development. In particular,
significant errors between the outlet NOX or NH₃ sensors,
reconstructed from estimated states, and the measured NOX or NH₃
concentrations may aid OBD strategies that attempt to identify
particular system failure modes. Second, the EKF described
estimates not only stored ammonia but also NO, NO₂ and NH₃ gas
concentrations within and exiting the SCR. Exploiting knowledge of
the individual species concentrations, instead of lumping them
together as NOX, can yield improved closed loop urea controller
performance in terms of reduced urea consumption and better NOX
conversion.
The model used for EKF development was calibrated to transient
engine data using a 2010 Cummins ISB engine with a production
aftertreatment system consisting of a DOC, CPF and SCR. The EKF was
then exercised for three different SCR outlets, sensor
configurations: NOX only, NH₃ only and both NOX and NH₃. The
EKF-estimated outlet NO, NO₂, and NH₃ concentrations were compared
to measured experimental data using a mass spectrometer. Not
surprisingly, the case where both NOX and NH₃ were measured at
the SCR outlet and used as input to the EKF yielded the best
results. The next best performance was achieved using only the NH₃
sensor. This was likely due to a better estimate of the NH₃ storage
within the SCR and thus better estimates of the effect of the
reactions. The results of the NOX sensor only case might be
improved by using a better model of the NOX sensor.
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Citation
Surenahalli, H., Parker, G., and Johnson, J., "Extended Kalman Filter Estimator for NH3 Storage, NO, NO2 and NH3 Estimation in a SCR," SAE Technical Paper 2013-01-1581, 2013, https://doi.org/10.4271/2013-01-1581.Also In
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