Emissions control system of a combustion engine exhaust system

Abstract

An emissions control system includes a Selective Catalytic Reduction device adapted to reduce emissions, an injector adapted to inject a reductant into the device, a NOx sensor disposed downstream of the device, a controller, an iterative model, and a table. The controller is configured to perform short and long term control by confirming at least one short term criteria is met. Once confirmed, the controller calculates a normalized model error utilizing the model and a signal received from the sensor, and integrates the normalized model error. If the integrated normalized model error exceeds a threshold, the controller proceeds toward the long term control. If a long term criteria is met, a current long term factor and the integrated normalized model error is applied to the table to determine a new long term factor. The new long term factor is multiplied against an energization time of the injector.

What is claimed is: 
     
         1 . An emissions control system for treating exhaust gas of a combustion engine, the emissions control system comprising:
 a Selective Catalytic Reduction (SCR) device adapted to reduce emissions;   a reductant injector adapted to inject a reductant into the SCR device;   a downstream NO x  sensor disposed downstream of the SCR device;   a controller including a processor and an electronic storage medium;   an iterative model stored in the electronic storage medium; and   a lookup table stored in the electronic storage medium, and wherein the processor is configured to perform short term and long term adaptive control by:
 confirming at least one short term enablement criteria is met; 
 calculating a normalized chemical model error utilizing in-part the iterative model and a downstream NO x  signal received from the downstream NO x  sensor; 
 integrating the normalized chemical model error to produce an integrated normalized chemical model error; 
 confirming that the integrated normalized chemical model error exceeds an error threshold; 
 proceeding toward the long term adaptive control; 
 confirming at least one long term adaptation enablement criteria is met; 
 applying a current long term adaptive factor and the integrated normalized chemical model error to the lookup table to determine a new long term adaptive factor; and 
 multiplying the new long term adaptive factor against an energization time of the reductant injector. 
   
     
     
         2 . The emissions control system set forth in  claim 1 , further comprising:
 an upstream NO x  sensor disposed upstream of the reductant injector and the SCR device, wherein the processor is configured to receive an upstream NO x  signal from the upstream NO x  sensor to calculate the normalized chemical model error.   
     
     
         3 . The emissions control system set forth in  claim 1 , wherein the normalized chemical model error is associated with the difference between a model-predicted NO x  level taken from the iterative model, and an actual NO x  level taken form the downstream NO x  signal. 
     
     
         4 . The emissions control system set forth in  claim 3 , wherein the normalized chemical model error is normalized by magnitude. 
     
     
         5 . The emissions control system set forth in  claim 1 , wherein the at least one short term enablement criteria includes at least one of a normalized error being greater than a first threshold, a NO x  gradient being less than a second threshold, a reductant-consumed being greater than a third threshold, a temperature being greater than a fourth threshold and less than a fifth threshold, a temperature gradient being less than a sixth threshold, a reductant storage level deviation being less than a seventh threshold, and a combustion mode. 
     
     
         6 . The emissions control system set forth in  claim 5 , wherein the at least one long term enablement criteria includes at least one of the normalized error being greater than an eighth threshold, the NO x  gradient being less than a ninth threshold, the reductant consumed is greater than a tenth threshold, the temperature is greater than an eleventh threshold and less than a twelfth threshold, the temperature gradient is less than a thirteenth threshold, the reductant storage deviation is less than a fourteenth threshold, and the combustion mode. 
     
     
         7 . The emissions control system set forth in  claim 1 , wherein the at least one short term enablement criteria is independent from the at least one long term enablement criteria. 
     
     
         8 . An emissions control system for treating exhaust gas of a combustion engine, the emissions control system comprising:
 a Selective Catalytic Reduction (SCR) device;   a first NO x  sensor; and   a controller configured to perform short term and long term adaptive control by:
 comparing a first NO x  measurement from the first NO x  sensor with a predicted NO x  value based at least in-part on an initial chemical model, and 
 in response to a short term enablement criteria being met:
 calculating a normalized chemical model error; 
 integrating the normalized chemical model error; and 
 calculating a new long term adaptive factor if the integrated normalized chemical model error exceeds a threshold. 
 
   
     
     
         9 . The emissions control system set forth in  claim 8 , further comprising:
 a lookup table stored in the controller and configured to cross reference a current long term adaptive factor to the integrated normalized chemical model error to calculate the new long term adaptive factor.   
     
     
         10 . The emissions control system set forth in  claim 9 , wherein the normalized chemical model error is equal to a delta between the first NO x  measurement and a predicted NO x  value based on the initial chemical model, and normalized based on magnitude. 
     
     
         11 . The emissions control system set forth in  claim 10 , wherein the first NO x  sensor is located downstream from the SCR device. 
     
     
         12 . The emissions control system set forth in  claim 8 , further comprising:
 a second NO x  sensor, wherein the normalized chemical model error is based on the initial chemical model, the first NO x  measurement, and an upstream NO x  measurement from the second NO x  sensor located upstream from the SCR device, and wherein the first NO x  sensor is located downstream from the SCR device.   
     
     
         13 . The emissions control system set forth in  claim 12 , further comprising:
 a temperature sensor configured to send a temperature measurement to the controller, wherein the initial chemical model is generated by the controller and is at least based on the temperature measurement, the upstream NO x  measurement, and the first NO x  measurement.   
     
     
         14 . The emission control system set forth in  claim 9 , wherein the enablement criteria is a short term enablement criteria. 
     
     
         15 . The emission control system set forth in  claim 14 , wherein the short term enablement criteria includes at least one of a normalized error being greater than a first threshold, a NO x  gradient being less than a second threshold, a reductant-consumed being greater than a third threshold, a temperature being greater than a fourth threshold and less than a fifth threshold, a temperature gradient being less than a sixth threshold, a reductant storage level deviation being less than a seventh threshold, and a combustion mode. 
     
     
         16 . The emission control system set forth in  claim 15 , wherein the long term adaptive factor determination is conducted when a long term adaptation enablement criteria is met. 
     
     
         17 . The emission control system set forth in  claim 16 , wherein the long term adaptation enablement criteria is independent from the short term enablement criteria. 
     
     
         18 . The emission control system set forth in  claim 16 , wherein the long term adaptation enablement criteria includes at least one of the normalized error being greater than an eighth threshold, the NO x  gradient being less than a ninth threshold, the reductant consumed is greater than a tenth threshold, the temperature is greater than an eleventh threshold and less than a twelfth threshold, the temperature gradient is less than a thirteenth threshold, the reductant storage deviation is less than a fourteenth threshold, and the combustion mode. 
     
     
         19 . The emission control system set forth in  claim 18 , wherein the eighth threshold is greater than the first threshold. 
     
     
         20 . The emission control system set forth in  claim 8 , further comprising:
 a reductant injector, wherein the new long term adaptive factor is generally multiplied by an energization time of the reductant injector.