Temperature modified control set point for UEGO control during engine warm up

Abstract

An emissions control system for a vehicle configured to travel on a road is provided. The system typically includes a catalyst coupled to the exhaust gas path; a linear universal exhaust gas oxygen (UEGO) sensor coupled to the exhaust gas path upstream of the catalyst and configured to measure oxygen content in exhaust gas from the engine upstream of the catalyst; a heated exhaust gas oxygen (HEGO) sensor positioned adjacent the catalyst and configured to measure oxygen content in exhaust gas from the engine; a temperature sensor coupled to the engine; and a controller coupled to the engine and configured to receive an input signal from the HEGO sensor that is indicative of oxygen content in the exhaust gas, to receive an input signal from the temperature sensor that is indicative of engine temperature, to adjust the HEGO sensor input signal based on the input signal from the temperature sensor, and to control the air-fuel ratio based on the adjusted HEGO sensor input during engine warm up.

1 . An emissions control system for an on-road vehicle having an engine and associated exhaust gas path, the system comprising: 
 a catalyst coupled to the exhaust gas path;    a linear universal exhaust gas oxygen (UEGO) sensor coupled to the exhaust gas path upstream of the catalyst and configured to measure oxygen content in exhaust gas from the engine upstream of the catalyst;    a heated exhaust gas oxygen (HEGO) sensor positioned adjacent the catalyst and configured to measure oxygen content in exhaust gas from the engine;    a temperature sensor coupled to the engine; and    a controller coupled to the engine and configured to receive an input signal from the HEGO sensor that is indicative of oxygen content in the exhaust gas, to receive an input signal from the temperature sensor, to adjust the HEGO sensor input signal based on the input signal from the temperature sensor, and to control the air-fuel ratio based on the adjusted HEGO sensor input during engine warm up.    
   
   
       2 . The system of  claim 1 , wherein the temperature sensor is an engine coolant temperature sensor configured to measure an engine coolant temperature.  
   
   
       3 . The system of  claim 2 , wherein the wherein the controller is further configured to adjust the HEGO signal based on air mass.  
   
   
       4 . The system of  claim 3 , wherein the controller is configured to lookup a downstream set point from a look up table that relates engine coolant temperature and air mass to downstream voltage set point.  
   
   
       5 . The system of  claim 4 , wherein the controller is configured to subtract the HEGO voltage from the downstream set point, to determine a downstream voltage error.  
   
   
       6 . The system of  claim 5 , wherein the controller includes a relay configured to output a low value if the downstream voltage error is positive, and to output a high voltage if the downstream voltage error is not positive.  
   
   
       7 . The system of  claim 6 , wherein the controller is configured to multiply the downstream voltage error by a high gain amplifier, and to send the result to a first integrator, to thereby generate a bias signal.  
   
   
       8 . The system of  claim 7 , wherein the controller is configured to multiply the voltage error by a low gain amplifier and send the result to a second integrator, the second integrator being configured to update a long-term correction term stored in keep alive memory.  
   
   
       9 . The system of  claim 2 , wherein the controller includes an inner loop controller and an outer loop controller, the outer loop controller being configured to receive as input the input signal from the HEGO sensor and being configured to output a set point to the inner loop controller, and the inner loop controller being configured to receive as input a signal from the UEGO sensor and to command an air fuel ratio based on the set point and the UEGO sensor signal.  
   
   
       10 . The system of  claim 9 , wherein the controller is configured to adjust the HEGO sensor input signal by trimming the HEGO sensor input signal at the outer loop controller, based on a measured engine coolant temperature, during warm up of the engine.  
   
   
       11 . The system of  claim 10 , wherein the controller is also configured to trim the HEGO sensor input signal at the outer loop controller, based on a determined air mass.  
   
   
       12 . The system of  claim 11 , wherein the controller is configured to trim the HEGO sensor input signal by a voltage determined from a look-up table that relates engine coolant temperature and air mass to downstream voltage set point values.  
   
   
       13 . The system of  claim 2 , wherein the controller is configured to calculate an inferred catalyst temperature based at least in part on the measured engine coolant temperature.  
   
   
       14 . The system of  claim 13 , wherein the inferred catalyst temperature is further calculated based on measured air mass, engine speed, spark advance, intake air temperature, air fuel ratio, and a time value.  
   
   
       15 . The system of  claim 13 , wherein the controller is configured to adjust the HEGO sensor input signal based on the inferred catalyst temperature, by looking up a downstream voltage set point from a look up table that relates inferred catalyst temperatures to downstream voltage set points, and by subtracting the HEGO sensor input signal from the downstream voltage set point.  
   
   
       16 . The system of  claim 1  wherein the temperature sensor is an exhaust temperature sensor positioned in an exhaust path of the engine and configured to measure a temperature of exhaust gases of the engine.  
   
   
       17 . An emissions control system for an on-road vehicle having an engine and associated exhaust gas path, the system comprising: 
 an air-fuel controller coupled to the engine and including an inner loop controller configured receive a signal from a UEGO sensor positioned in the exhaust gas path, and an outer loop controller configured to receive a signal from a HEGO sensor positioned adjacent the catalyst, the air-fuel controller being configured to trim the HEGO sensor signal that is input into the outer loop controller, based on a measured engine coolant temperature during warm up of the engine.    
   
   
       18 . A method for controlling an air-fuel ratio in an on-road vehicle having an engine and associated exhaust gas path, the exhaust gas path including a linked linear universal exhaust gas oxygen (UEGO) sensor positioned upstream of a catalyst in the exhaust gas path, and a heated exhaust gas oxygen (HEGO) sensor positioned adjacent the catalyst, the method comprising: 
 at an air-fuel controller coupled to the engine, and during engine warm up: 
 receiving an input signal from the HEGO sensor that is indicative of oxygen content in the exhaust gas;  
 receiving an input signal from the engine coolant sensor that is indicative of engine coolant temperature;  
 adjusting the HEGO sensor input signal based on the engine coolant temperature input signal; and  
 controlling the air-fuel ratio based on the adjusted HEGO sensor input.  
   
   
   
       19 . The method of  claim 18 , further comprising, adjusting the HEGO signal based on air mass.  
   
   
       20 . The method of  claim 19 , further comprising determining a downstream set point from a look up table that relates engine coolant temperature and air mass to downstream voltage set point.  
   
   
       21 . The method of  claim 20 , further comprising subtracting the HEGO voltage from the downstream set point, to determine a downstream voltage error.  
   
   
       22 . The method of  claim 21 , further comprising passing the downstream voltage error through a relay configured to output a low value if the downstream voltage error is positive, and to output a high voltage if the downstream voltage error is not positive.  
   
   
       23 . The system of  claim 22 , further comprising multiplying the downstream voltage error by a high gain amplifier, and sending the result to a first integrator, to thereby generate a bias signal.  
   
   
       24 . The method of  claim 23 , further comprising multiplying the downstream voltage error by a low gain amplifier and sending the result to a second integrator, the second integrator being configured to update a long-term correction term stored in keep alive memory.  
   
   
       25 . A method for controlling an air-fuel ratio in an on-road vehicle having an engine and associated exhaust gas path, the exhaust gas path including a linked linear universal exhaust gas oxygen (UEGO) sensor positioned upstream of a catalyst in the exhaust gas path, and a heated exhaust gas oxygen (HEGO) sensor positioned adjacent the catalyst, the method comprising: 
 receiving an input signal from the HEGO sensor that is indicative of oxygen content in the exhaust gas;    receiving an input signal from the engine coolant sensor that is indicative of engine coolant temperature;    trimming the HEGO sensor input signal based on the engine coolant temperature input signal; and    determining a set point for downstream control module based on the trimmed HEGO sensor input, the downstream control module being configured to receive feedback from the UEGO sensor, and command an air fuel ratio of the engine based on the feed back from the UEGO sensor and the set point.