Adaptive soot mass estimation in a vehicle exhaust after-treatment device

1. A method of estimating a total amount of soot in a diesel particulate filter comprising:

monitoring a pressure differential across the diesel particulate filter;

monitoring an engine speed and an engine load from an engine in fluid communication with the diesel particulate filter;

determining a first soot mass estimate from the monitored pressure differential, the first soot mass estimate having an associated confidence indicator based on the monitored engine speed and engine load;

determining a second soot mass estimate from the monitored engine speed and engine load; and

outputting the first soot mass estimate if the confidence indicator is above a predetermined threshold, and outputting the second soot mass estimate if the confidence indicator is below the predetermined threshold.

2. The method of claim 1 , further comprising generating a particulate filter regeneration request if the outputted soot mass estimate exceeds a threshold.

3. The method of claim 1 , wherein determining a first soot mass estimate from the monitored pressure differential includes selecting a value from a delta-pressure lookup table according to the monitored pressure differential.

4. The method of claim 1 , wherein determining a second soot mass estimate from the monitored engine speed and engine load includes:

selecting an instantaneous engine soot mass output value from an engine-out lookup table according to the monitored engine speed and engine load; and

integrating the instantaneous engine soot mass output value.

5. The method of claim 4 , further comprising modifying the engine-out lookup table using a difference between the first soot mass estimate and second soot mass estimate.

6. The method of claim 5 , wherein the engine-out lookup table includes a plurality of points representing engine soot production at different engine speed/engine load combinations;

wherein modifying the engine-out lookup table includes:

monitoring a time that the engine operates at each respective engine speed/engine load combination; and

apportioning a total correction factor to each respective point of the plurality of points according to the amount of time the engine operates at that point.

7. A system for monitoring a particulate filter of an exhaust after-treatment device in fluid communication with an engine of a vehicle, the system comprising:

a first fluid tube disposed in fluid communication with the exhaust after-treatment device and between the particulate filter and the engine;

a second fluid tube disposed in fluid communication with the exhaust after-treatment device and on an opposite side of the particulate filter from the first fluid tube;

a differential pressure module in communication with the first fluid tube and the second fluid tube and configured to generate a delta-pressure signal corresponding to a pressure drop between the first fluid tube and the second fluid tube; and

a controller in communication with the differential pressure module and configured to:

receive the delta-pressure signal;

monitor an engine speed and an engine load from the engine;

determine a first soot mass estimate from the received delta-pressure signal, the first soot mass estimate having an associated confidence indicator based on the monitored engine speed and engine load;

determine a second soot mass estimate from the monitored engine speed and engine load;

output the first soot mass estimate if the confidence indicator is above a predetermined threshold, and output the second soot mass estimate if the confidence indicator is below the predetermined threshold; and

generate a particulate filter regeneration request if the soot mass estimate exceeds a threshold.

8. The system of claim 7 , wherein the controller is configured to determine a first soot mass estimate from the received delta-pressure signal by selecting a value from a delta-pressure lookup table according to the received delta-pressure signal.

9. The system of claim 7 , wherein the controller is configured to determine a second soot mass estimate from the monitored engine speed and engine load by:

selecting an instantaneous engine soot mass output value from an engine-out lookup table according to the monitored engine speed and engine load; and

integrating the instantaneous engine soot mass output value.

10. The system of claim 9 , wherein the controller is further configured to modify the engine-out lookup table using a difference between the first soot mass estimate and second soot mass estimate.

11. The system of claim 10 , wherein the engine-out lookup table includes a plurality of points representing engine soot production at different engine speed/engine load combinations;

wherein the controller is configured to modify the engine-out lookup table by:

monitoring a time that the engine operates at each respective engine speed/engine load combination; and

apportioning a total correction factor to each respective point of the plurality of points according to the amount of time the engine operates at that point.

12. A method of providing a soot mass estimate in a vehicle exhaust after-treatment device comprising:

obtaining a first pressure signal from a first fluid tube disposed in fluid communication with the exhaust after-treatment device and between a particulate filter and an engine;

obtaining a second pressure signal from a second fluid tube disposed in fluid communication with the exhaust after-treatment device and on an opposite side of the particulate filter from the first fluid tube;

determining an exhaust gas pressure drop across the particulate filter from the first pressure signal and the second pressure signal;

determining a first soot mass estimate from the monitored exhaust gas pressure drop;

monitoring an engine speed and an engine load from an engine in fluid communication with the vehicle exhaust after-treatment device;

determining a confidence value for the first soot mass estimate using the monitored engine speed and engine load;

determining a second soot mass estimate from the monitored engine speed and engine load; and

providing the first soot mass estimate if the confidence indicator is above a predetermined threshold, and providing the second soot mass estimate if the confidence indicator is below the predetermined threshold.

13. The method of claim 12 , further comprising generating a particulate filter regeneration request if the provided soot mass estimate exceeds a threshold.

14. The method of claim 12 , wherein determining a first soot mass estimate from the monitored exhaust gas pressure drop includes selecting a value from a delta-pressure lookup table according to the monitored exhaust gas pressure drop.

15. The method of claim 12 , wherein determining a second soot mass estimate from the monitored engine speed and engine load includes:

selecting an instantaneous engine soot mass output value from an engine-out lookup table according to the monitored engine speed and engine load; and

integrating the instantaneous engine soot mass output value.

16. The method of claim 15 , further comprising modifying the engine-out lookup table using a difference between the first soot mass estimate and second soot mass estimate.

17. The method of claim 16 , wherein the engine-out lookup table includes a plurality of points representing engine soot production at different engine speed/engine load combinations;

wherein modifying the engine-out lookup table includes:

monitoring a time that the engine operates at each respective engine speed/engine load combination; and

apportioning a total correction factor to each respective point of the plurality of points according to the amount of time the engine operates at that point.