Ammonia (NH
A control system includes an upstream nitrogen oxide (NO x ) control module that increases an upstream NO x level based on an initial upstream NO x level in an exhaust system, and an ammonia (NH 3 ) storage condition detection module that detects a NH 3 storage condition based on a difference in a downstream NO x level before and after the upstream NO x level is increased. A method includes increasing an upstream NO x level based on an initial upstream NO x level in an exhaust system, and detecting an NH 3 storage condition based on a difference in a downstream NO x level before and after the upstream NO x level is increased.
1. A control system, comprising:
a first electronic circuit configured to increase an upstream nitrogen oxide (NO x ) level for a predetermined period, wherein said upstream NO x level is a NO x level upstream from a selective catalytic reduction (SCR) catalyst in an exhaust system;
a second electronic circuit configured to detect a NH 3 storage condition based on a magnitude of a difference between a first downstream NO x level measured downstream from said SCR catalyst before said upstream NO x level is increased and a second downstream NO x level measured downstream from said SCR catalyst after said upstream NO x level is increased;
a third electronic circuit configured to determine a total NO x mass entering said SCR catalyst as a result of said increase in said upstream NOx level, wherein said first electronic circuit is configured to adjust said predetermined period based on said total NOx mass;
a fourth electronic circuit configured to adjust at least one of a dosing agent injection amount and said upstream NOx level based on said NH 3 storage condition and at least one of:
adjust said dosing agent injection amount using a dosing valve of a dosing system; and
adjust said upstream NOx level using at least one of an exhaust gas recirculation (EGR) valve, actuating a throttle valve, and actuating a fuel injector; and
at least one of said dosing valve, said EGR valve, and said throttle valve.
2. The control system of claim 1 wherein said second electronic circuit is configured to detect a NH 3 slip condition when said difference is less than a minimum downstream NO x level change.
3. The control system of claim 1 wherein said second electronic circuit is configured to detect a low NH 3 storage level condition when said difference is greater than a maximum downstream NO x level change.
4. The control system of claim 1 wherein said first electronic circuit is configured to increase said upstream NOx level by increasing mass airflow (MAF).
5. The control system of claim 1 wherein said first electronic circuit is configured to increase said upstream NO x level by advancing injection timing.
6. The control system of claim 1 wherein said third electronic circuit is configured to determine said total NO x mass based on at least one of an exhaust temperature and said upstream NO x level.
7. A control system, comprising:
a first electronic circuit configured to increase an upstream nitrogen oxide (NO x ) level for a predetermined period, wherein said upstream NO x level is a NO x level upstream from a selective catalytic reduction (SCR) catalyst in an exhaust system;
a second electronic circuit configured to detect a NH 3 storage condition based on a magnitude of a difference between a first downstream NO x level measured downstream from said SCR catalyst before said upstream NO x level is increased and a second downstream NO x level measured downstream from said SCR catalyst after said upstream NO x level is increased;
a third electronic circuit configured to determine a filtered NO x level by filtering said upstream NO x level at a frequency that limits an increase in said filtered NO x level caused by increasing said upstream NO x level for said predetermined period;
a fourth electronic circuit configured to (i) control a dosing agent injection amount based on said filtered NO x level, (ii) adjust at least one of said dosing agent injection amount and said upstream NOx level based on said NH 3 storage condition, and (iii) at least one of:
adjust said dosing agent injection amount using a dosing valve of a dosing system; and
adjust said upstream NOx level using at least one of an exhaust gas recirculation (EGR) valve, actuating a throttle valve, and actuating a fuel injector; and
at least one of said dosing valve, said EGR valve, and said throttle valve.
8. A method, comprising:
increasing an upstream nitrogen oxide (NO x ) level for a predetermined period, wherein said upstream NO x level is a NO x level upstream from a selective catalytic reduction (SCR) catalyst in an exhaust system;
detecting an ammonia (NH 3 ) storage condition based on a magnitude of a difference between a first downstream NO x level measured downstream from said SCR catalyst before said upstream NO x level is increased and a second downstream NO x level measured downstream from said SCR catalyst after said upstream NO x level is increased;
determining a total NO x mass entering said SCR catalyst as a result of said increase in said upstream NOx level;
adjusting said predetermined period based on said total NO x mass;
adjusting at least one of a dosing agent injection amount and said upstream NOx level based on said NH 3 storage condition; and
at least one of:
adjusting said dosing agent injection amount using a dosing valve of a dosing system; and
adjusting said upstream NOx level using at least one of an exhaust gas recirculation (EGR) valve, actuating a throttle valve, and actuating a fuel injector.
9. The method of claim 8 further comprising detecting a NH 3 slip condition when said difference is less than a minimum downstream NO x level change.
10. The method of claim 8 further comprising detecting a low NH 3 storage level condition when said difference is greater than a maximum downstream NO x level change.
11. The method of claim 8 further comprising increasing said upstream NO x level by increasing mass airflow (MAF).
12. The method of claim 8 further comprising increasing said upstream NO x level by advancing injection timing.
13. The method of claim 8 further comprising determining said total NO x mass based on at least one of an exhaust temperature and said upstream NO x level.
14. A method, comprising:
increasing an upstream nitrogen oxide (NO x ) level for a predetermined period, wherein said upstream NO x level is a NO x level upstream from a selective catalytic reduction (SCR) catalyst in an exhaust system;
detecting an ammonia (NH 3 ) storage condition based on a magnitude of a difference between a first downstream NO x level measured downstream from said SCR catalyst before said upstream NO x level is increased and a second downstream NO x level measured downstream from said SCR catalyst after said upstream NO x level is increased; determining a filtered NO x level by filtering said upstream NO x level at a frequency that limits an increase in said filtered NO x level caused by increasing said upstream NO x level for said predetermined period;
controlling a dosing agent injection amount based on said filtered NO x level;
adjusting at least one of said dosing agent injection amount and said upstream NOx level based on said NH 3 storage condition; and
at least one of:
adjusting said dosing agent injection amount using a dosing valve of a dosing system; and
adjusting said upstream NOx level using at least one of an exhaust gas recirculation (EGR) valve, actuating a throttle valve, and actuating a fuel injector.
15. The control system of claim 1 wherein said first electronic circuit is configured to increase said upstream NOx level by a first amount that is based on said upstream NOx level before said upstream NOx level is increased.
16. The method of claim 8 further comprising increasing said upstream NOx level by a first amount that is based on said upstream NOx level before said upstream NOx level is increased.
17. The control system of claim 1 wherein said first, second, and third electronic circuits include at least one of an Application Specific Integrated Circuit (ASIC), a processor and memory including one or more programs, and a combinational logic circuit.
18. The control system of claim 7 wherein said first, second, third, and fourth electronic circuits include at least one of an Application Specific Integrated Circuit (ASIC), a processor and memory including one or more programs, and a combinational logic circuit.