US Patent 8061126 Nitrogen oxide estimation downstream of a selective catalytic reduction catalyst

A dosing control system comprises a selective catalytic reduction (SCR) analysis module, a dosing management module, an adjustment module, and an error module. The SCR analysis module estimates ammonia (NH3) stored by an SCR catalyst, a maximum NH3 storage capacity of the SCR catalyst, and a nitrogen oxides (NOx) measurement for a NOx sensor downstream of the SCR catalyst. The dosing management module controls dosing agent injection upstream of the SCR catalyst based on the maximum NH3 storage capacity and the NH3 stored. The adjustment module outputs an adjusted estimate of the NOx measurement based on the estimate of the NOx measurement, cross-sensitivity of the NOx sensor, and a delay period for exhaust flow. The error module selectively adjusts at least one of the NH3 stored and the maximum NH3 storage capacity based on a difference between the adjusted estimate and NOx measured by the NOx sensor.