CONTROL APPARATUS AND METHOD HAVING CONTROL CLOSED LOOP OBSERVER CONFIGURATION FOR SCR/SCRF COMPONENT

An exhaust gas after-treatment system for an internal combustion engine that includes a selective catalyst reduction on filter (SCRF) exhaust gas after-treatment device in communication with exhaust gases from the internal combustion engine and having a treated exhaust gas output. An oxides of nitrogen (NOx) sensor is coupled to the treated exhaust gases and has a NOx sensor output signal that isNOx and ammonia (NH3) cross-sensitive. A closed loop observer (CLO) is operatively coupled to receive the NOx sensor output signal and provides a NOx concentration signal to an electronic control unitthat is operatively associated with the exhaust gas after-treatment system and the internal combustion engine. The CLO output at least includes an exhaust gas NOx concentration estimate and the ECU is arranged to be operable upon the NOx concentration estimate to control the exhaust gas after-treatment system and the internal combustion engine to effect an overall reduction in actual NOx concentration with the exhaust gas