A urea injection control method in an exhaust after-treatment system includes: performing an ammonia slip prevention logic that adjusts a urea injection amount based on the highest temperature during a predetermined period of time from an end point of filter regeneration to a thermal equilibrium point when a temperature of a selective catalytic reduction (SCR) catalyst is higher than or equal to a predetermined threshold temperature at the end point of the filter regeneration; and adjusting a urea injection amount based on an ammonia storage amount map when the temperature of the SCR catalyst is lower than or equal to the predetermined threshold temperature at the end point of the filter regeneration. In particular, the thermal equilibrium point is a point at which a temperature of a filter is close or equal to an exhaust gas temperature.

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 is NOx and ammonia (NH.sub.3) 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 unit that 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 gases.

Selective catalytic reduction device (SCR) assessment methods include, while communicating exhaust to the SCR, determining a first temperature differential (dT) between a modeled exotherm phase temperature and a measured SCR exotherm outlet exhaust temperature, comparing the first dT to a first threshold, and determining that the SCR performance is suitable if the first dT is below the first threshold, or, if the first dT is above the first threshold, communicating exhaust gas to the SCR during a water endotherm phase, determining a second dT between a modeled endotherm phase temperature and a measured SCR endotherm phase outlet exhaust temperature, comparing the second dT to a second threshold, and determining that the SCR performance is suitable if the second dT is above the second threshold, or determining that the SCR performance is unsuitable if the second dT is below the second threshold. Performance can be SCR reductant storage capacity.

An on-board diagnostic for a particle filter of a vehicle exhaust system records repeating data about flow and pressure around the particle filter. Data is recorded in virtual data bins having successive thresholds or filters within a numerical scale. Each data point is typically recorded in several bins to permit a rapid calculation of averaged data for use in the diagnostic. Sensitivity of less frequently recorded data is preserved, while giving quickly delivery of a result from the diagnostic.

Selective catalytic reduction device (SCR) assessment methods include, while communicating exhaust to the SCR, determining a first temperature differential (dT) between a modeled exotherm phase temperature and a measured SCR exotherm outlet exhaust temperature, comparing the first dT to a first threshold, and determining that the SCR performance is suitable if the first dT is below the first threshold, or, if the first dT is above the first threshold, communicating exhaust gas to the SCR during a water endotherm phase, determining a second dT between a modeled endotherm phase temperature and a measured SCR endotherm phase outlet exhaust temperature, comparing the second dT to a second threshold, and determining that the SCR performance is suitable if the second dT is above the second threshold, or determining that the SCR performance is unsuitable if the second dT is below the second threshold. Performance can be SCR reductant storage capacity.

A method determines a sensor error of a sensor in an exhaust gas system of a motor vehicle. One step of the method involves determining at least one actual sensor signal of the sensor. Another step of the method involves determining at least one target sensor signal of the sensor by means of a model. A further step of the method involves determining the sensor error of the sensor according to a deviation between the actual sensor signal of the sensor and the target sensor signal of the sensor.

One exemplary embodiment is a method of operating a system comprising an internal combustion engine system, and an exhaust aftertreatment system comprising an SCR catalyst, and an electronic control system. The method comprises operating the electronic control system to perform the acts of determining a predicted temperature value indicative of a predicted future temperature of the SCR catalyst, determining a temperature profile value using the predicted temperature value and a current temperature value indicative of a current temperature of the SCR catalyst, operating a controller to provide an output indicating a difference between the temperature profile value and a temperature target, determining a heat request using the output of the controller, filtering the heat request using a prediction horizon, and controlling operation of the engine system using the filtered heat request to increase a temperature of the SCR catalyst.

An exhaust gas purifying apparatus for an internal combustion engine, in which a NOx absorbing catalyst and a NOx concentration sensor for detecting a NOx concentration in exhaust gases of the engine, are provided in an exhaust passage of the engine. A rich spike for temporarily enriching the air-fuel ratio is performed, and an execution timing of the rich spike is determined based on a detected output from the NOx concentration sensor. Performing the rich spike is determined to be unnecessary during a reducing state period from the time the rich spike ends to the time a preset time period has elapsed, and is also determined to be unnecessary when a change tendency of the detected output is determined to be an output decreasing state where the detected output is decreasing. The execution timing of the rich spike is determined using the detected output when the change tendency is determined to be an output staying/increasing state where the detected output is staying at a constant value or increasing after the end timing of the reducing state period.

Disclosed are model predictive control (MPC) systems, methods for using such MPC systems, and motor vehicles with selective catalytic reduction (SCR) employing MPC control. An SCR-regulating MPC control system is disclosed that includes an NOx sensor for detecting nitrogen oxide (NOx) input received by the SCR system, catalyst NOx sensors for detecting NOx output for two SCR catalysts, and catalyst NH3 sensors for detecting ammonia (NH3) slip for each SCR catalyst. The MPC system also includes a control unit programmed to: receive desired can conversion efficiencies for the SCR catalysts; determine desired can NOx outputs for the SCR catalysts; determine maximum NH3 storage capacities for the SCR catalyst; calculate the current can conversion efficiency for each SCR catalyst; calculate an optimized reductant pulse-width and/or volume from the current can conversion efficiencies; and, command an SCR dosing injector to inject a reductant into an SCR conduit based on the calculated pulse-width/volume.

An automotive vehicle includes an internal combustion engine and an exhaust system. The exhaust treatment system includes a dosing system that injects NH.sub.3 into an exhaust gas stream generated by the engine. An SCR device stores an amount of the NH.sub.3 and converts NOx into diatomic nitrogen (N.sub.2) and water (H.sub.2O) based on the stored amount of the NH.sub.3. The vehicle further includes an SCR status estimator device and a controller. The SCR status estimator device determines an NH.sub.3 coverage ratio (R), which indicates a stored amount of NH.sub.3 with respect to a maximum NH.sub.3 storage capacity of the SCR device. The controller determines a target NOx reduction efficiency (.sub.NOx) of the SCR device, and an NH.sub.3 coverage ratio set point (R.sub.sp) based on the .sub.NOx. The controller also generates an NH.sub.3 control signal (u) that controls the dosing system based on a comparison between the R and the R.sub.sp.