Adaptive control of SCR urea injection to compensate errors

1. Method for controlling a selective catalytic reduction injection system having a storage tank, a pump, a delivery line, and an injection nozzle, comprising:

monitoring the selective catalytic reduction injection system;

determining a selective catalytic reduction injector system effective area ratio;

comparing the selective catalytic reduction injector system effective area ratio to a threshold;

calculating a compensation factor upon surpassing the threshold; and

modifying the commanded injected mass according to the calculated compensation factor.

2. The method of claim 1 , wherein determining the selective catalytic reduction injection system effective area ratio comprises monitoring an actual injected mass and a commanded injected mass.

3. The method of claim 2 , wherein the actual injected mass is calculated from monitored parameters in a dynamic model method.

4. The method of claim 3 , wherein calculation of the actual injected mass comprises integrating monitored parameters to determine actual flow characteristics.

5. The method of claim 2 , wherein the actual injected mass is calculated from monitored parameters in a filter method.

6. The method of claim 5 , wherein the filter method comprises a state-space equation to determine actual flow characteristics.

7. The method of claim 2 wherein the actual injected mass is calculated from monitored parameters in a dynamic model method and in a filter method.

8. The method of claim 1 , wherein the threshold comprises one of an upper threshold and a lower threshold.

9. The method of claim 1 , wherein calculating the compensation factor upon surpassing the threshold comprises determination of a temperature effect.

10. The method of claim 9 , wherein determination of the temperature effect is based upon pump pressure.

11. The method of claim 9 , wherein determination of the temperature effect is based upon look-up tables.

12. Method for controlling fluid injection from a selective catalytic reduction injection system to achieve a requested fluid flow into an exhaust flow from an internal combustion engine during engine operation, the method comprising:

monitoring operational parameters of the selective catalytic reduction injection system including a commanded injected mass and an exhaust flow pressure;

determining an actual injected mass;

calculating an effective area ratio;

comparing the effective area ratio to a desired effective area ratio; and

modifying an injector control signal to adjust the effective area ratio to match the desired effective area ratio.

13. The method of claim 12 , wherein the actual injected mass is determined by an integration method.

14. The method of claim 12 , wherein the actual injected mass is determined by a filter method.

15. The method of claim 12 , wherein the actual injected mass is determined by an integration and a filter method.

16. The method of claim 12 , wherein monitoring operational parameters of the selective catalytic reduction injection system further includes monitoring a temperature of the fluid.

17. The method of claim 16 , wherein the temperature of the fluid is used to determine actual injected mass.

18. The method of claim 12 , wherein calculating the effective area ratio determines an amount of over dosing or under dosing.

19. The method of claim 12 , wherein modifying the injector control signal to adjust the effective area ratio to match the desired effective area ratio includes calculating a gain to modify the injector control signal.