A method for controlling an SCR catalytic converter (20, 30), comprising detecting (200) concentration values (314, 324; 414, 424) in the exhaust gas downstream of the catalytic converter (20), wherein at least one concentration value for NH.sub.3 and one concentration value for NO.sub.x is detected; calculating (202) modeled concentration values (316, 322; 416, 422) for NH.sub.3 and NO.sub.x downstream of the catalytic converter on the basis of a catalytic converter model, wherein the model comprises an aging parameter (342, 442) which at least partially describes aging of the modeled catalytic converter; comparing (208) the detected concentration values with the modeled concentration values; and, in a manner dependent on the result of the comparison, changing the aging parameter (342, 442) of the model and/or changing a predefined dosing quantity for a reducing agent in the SCR catalytic converter.

Disclosed is a method for control of dosage of a reducing agent into an exhaust stream, which includes: determining at least one sensor signal S.sub.NOx from at least one nitrogen oxides NO.sub.x sensor arranged downstream of at least one of the one or more reduction catalysts as at least one sensor correction value S.sub.NOx_corr, respectively, if: 1) the engine rotates without fuel supply; 2) an exhaust mass flow M′.sub.exh is greater than an exhaust mass flow threshold M′.sub.exh_th; M′.sup.exh>M′.sub.exh_th; and 3) the sensor signal S.sub.NOx has had a value smaller than a sensor signal threshold S.sub.NOx_th; S.sub.NOx<S.sub.NOx_th; during at least a predetermined time period T.sub.con; determining at least one adjusted sensor signal S.sub.NOx_adj based on the at least one sensor signal S.sub.NOx and the at least one sensor correction value S.sub.NOx_corr, respectively; and controlling the dosage of the reducing agent based on the at least one adjusted sensor signal S.sub.NOx_adj.

An exhaust gas after-treatment system for an internal combustion engine 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 treated exhaust gas output. An oxides of nitrogen (NOx) sensor is coupled to 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 operatively associated with the exhaust gas after-treatment system and the internal combustion engine. 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 exhaust gas after-treatment system and internal combustion engine to effect an overall reduction in actual NOx concentration with the exhaust gases.

Technical solutions described herein include an emissions control system for treating exhaust gas in a motor vehicle including an internal combustion engine. The emissions control system includes a model-based controller to control reductant injections into the exhaust gas. Controlling the reductant injections includes determining an amount of NOx and an amount of NH3 at an outlet of the first SCR device, and at an outlet of the second SCR device. The controlling further includes computing an amount of reductants to inject to maintain a first predetermined ratio between the amount of NH3 and the amount of NOx at the outlet of the first SCR device and to maintain a second predetermined ratio between the amount of NH3 and the amount of NOx at the outlet of the second SCR device. Further, the controlling includes sending a command for receipt by the reductant injectors to inject the computed amount of reductants.

A system for regeneration of a particulate filter in a V-pipe exhaust system includes a pair of post-converter universal heated exhaust gas oxygen (UHEGO) sensors disposed at a pair of pipes of the V-pipe exhaust system downstream from a pair of three-way catalytic (TWC) converters and the pair of post-converter UHEGO sensors measure lambda values. The system also includes an engine controller in communication with the pair of post-converter UHEGO sensors. The engine controller is configured to receive and compare measured lambda values from the pair of post-converter UHEGO sensors to a target exhaust gas lambda value for exhaust gas flowing into the particulate filter and provide at least one adjusted target exhaust gas lambda value as a function of a difference between the measured lambda values and the target exhaust gas lambda value.

Technical solutions described herein include an emissions control system for treating exhaust gas in a motor vehicle including an internal combustion engine. The emissions control system includes a model-based controller to control reductant injections into the exhaust gas. Controlling the reductant injections includes determining an amount of NOx and an amount of NH3 at an outlet of the first SCR device, and at an outlet of the second SCR device. The controlling further includes computing an amount of reductants to inject to maintain a first predetermined ratio between the amount of NH3 and the amount of NOx at the outlet of the first SCR device and to maintain a second predetermined ratio between the amount of NH3 and the amount of NOx at the outlet of the second SCR device. Further, the controlling includes sending a command for receipt by the reductant injectors to inject the computed amount of reductants.

A driver circuit drives a heater associated with a sensor in an exhaust system of a vehicle at a duty cycle. A feedback circuit generates a feedback signal indicating a temperature of the sensor. A ramp circuit outputs a first ramping set point indicating a first rate at which the temperature of the sensor is to be changed over a first time period after an engine of the vehicle is turned on, and a second ramping set point indicating a second rate at which the temperature of the sensor is to be changed after the first time period until the temperature of the sensor reaches a predetermined temperature. An error circuit generates first and second error signals based on the feedback signal and the first and second ramping set points. A controller controls the duty cycle of the driver circuit to drive the heater based on one or more gains.

An exhaust gas control apparatus for the internal combustion engine includes a catalyst disposed in an exhaust passage, an upstream air-fuel ratio sensor configured to detect an air-fuel ratio of in-flow exhaust gas that flows into the catalyst, a downstream air-fuel ratio sensor configured to detect an air-fuel ratio of out-flow exhaust gas that flows out of the catalyst, and an electronic control unit configured to control the air-fuel ratio of the in-flow exhaust gas. The electronic control unit is configured to, when a predetermined condition is satisfied, control the air-fuel ratio of the in-flow exhaust gas based on an output from the downstream air-fuel ratio sensor without using an output from the upstream air-fuel ratio sensor. The electronic control unit is configured to, when the predetermined condition is not satisfied, control the air-fuel ratio of the in-flow exhaust gas based on the output from the upstream air-fuel ratio sensor.

A system of controlling ammonia levels in a catalytic exhaust system comprising: means to provide a target value for ammonia slip/ammonia output from said system or a catalytic unit of said system; first comparison means to compare said target value with a feedback value to provide a command value based on said comparison, and means to control the dosing of a reducing agent such as urea into said exhaust system based on said command value; means to input said command value to a transfer function or model to provide an estimated value of ammonia slip/ammonia output from said catalytic unit/system; means to measure actual ammonia slip/ammonia output from said unit/system; second comparison means to compare said actual value with said estimated value; means to provide said feedback value based on the output from said comparison means.

The present invention is provided with: a SOx purge control unit that executes catalyst regeneration processing that maintains the temperature of a NOx occlusion/reduction catalyst at a prescribed recovery temperature; a catalyst temperature estimation unit that estimates catalyst temperature on the basis of the amount of unburnt fuel contained in exhaust and of a catalyst heat generation amount; a second exhaust temperature sensor that is arranged further to an exhaust downstream side than the catalyst and that detects exhaust temperature; and a heat generation amount correction value setting unit that, during the execution of the catalyst regeneration processing, on the basis of an estimated catalyst temperature estimated by the catalyst temperature estimation unit and of an actual exhaust temperature detected by the second exhaust temperature sensor, obtains a heat generation amount correction value that is used to correct the heat generation amount of the catalyst.