Apparatus, system, and method for catalyst presence detection
A system to detect the presence of a catalyst includes an exhaust gas tube, a first temperature sensing device, a second temperature sensing device, a flow rate measurement device, and a processing device. The first temperature sensing device measures a first temperature of exhaust gas upstream of the exhaust gas tube. The second temperature sensing device measures a second temperature of the exhaust gas downstream of the exhaust gas tube. The processing device estimates an expected time delay between the measured inlet and outlet exhaust gas temperatures corresponding to a system with a catalyst present. The processing device may also determine the presence of a catalyst by comparing the measured second temperature to the measured first temperature and comparing the measured second temperature to an estimated delayed first temperature associated with the expected time delay.
1. A method for detecting the presence of a catalyst, the method comprising:
measuring a flow rate of exhaust gas within an exhaust gas tube;
measuring an inlet temperature of the exhaust gas at an inlet of the exhaust gas tube;
calculating an expected temperature time delay as a function of the measured flow rate;
measuring an outlet temperature of the exhaust gas at an outlet of the exhaust gas tube;
calculating a delayed inlet temperature based on the calculated expected temperature time delay and the inlet temperature;
calculating a first difference between the measured outlet temperature and the inlet temperature and a second difference between the measured outlet temperature and the delayed inlet temperature;
determining a catalyst is not present if the first difference is the same or smaller than the second difference, and a catalyst is present if the second difference is smaller than the first difference.
2. The method of claim 1 , further comprising:
outputting an error message if the first difference is the same or smaller than the second difference, the error message indicating that the catalyst is not present.
3. The method of claim 1 , further comprising comparing a gain of a first temperature detection device that measures the inlet temperature of the exhaust gas at the inlet of the exhaust gas tube and a gain of a second temperature detection device that measures the outlet temperature of the exhaust gas at the out of the exhaust gas tube to calibrate the first temperature detection device and the second temperature detection device.
4. The method of claim 1 , wherein calculating the expected temperature time delay as a function of the measured flow rate is performed via a Padé approximation of a pure time delay transfer function.
5. The method of claim 1 , further comprising:
determining if a flow rate of the exhaust gas falls within a first predetermined range; and
if the flow rate of the exhaust gas falls within the first predetermined range, calculating the expected temperature time delay.
6. The method of claim 1 , further comprising;
determining if the inlet temperature of the exhaust gas falls within a second predetermined range;
determining if the outlet temperature of the exhaust gas falls within a third predetermined range; and
calculating the delayed inlet temperature if the inlet temperature falls within the second predetermined range and the outlet temperature falls within the third predetermined range.
7. The method of claim 1 , further comprising;
determining a change rate of the inlet temperature of the exhaust gas;
determining if the change rate of the inlet temperature falls within a fourth predetermined range; and
calculating the delayed inlet temperature if the change rate falls within the fourth predetermined range.
8. A method for detecting the presence of a catalyst in an exhaust gas tube, the method comprising:
measuring a flow rate of exhaust gas within an exhaust gas tube;
measuring an inlet temperature of the exhaust gas at an inlet of the exhaust gas tube;
calculating an expected temperature time delay as a function of the measured flow rate;
measuring an outlet temperature of the exhaust gas at an outlet of the exhaust gas tube;
calculating a delayed inlet temperature based on the calculated expected temperature time delay and the inlet temperature;
calculating a similarity value by comparing the outlet temperature of the exhaust gas to: (1) the inlet temperature of the exhaust gas; and (2) the delayed inlet temperature;
comparing the similarity value to a predetermined threshold; and
determining if a catalyst is present or not present based on the comparison between the similarity value and the predetermined threshold.
9. The method of claim 8 , further comprising, if it is determined that the catalyst is not present, reporting that the catalyst is not present.
10. The method of claim 8 , wherein calculating the similarity value comprises solving an optimization problem.
11. The method of claim 8 , wherein calculating the similarity value comprises using a recursive least squares algorithm.
12. The method of claim 8 , wherein calculating the expected temperature time delay as a function of the measured flow rate is performed via a Padé approximation of a pure time delay transfer function.
13. The method of claim 10 , wherein the optimization problem includes
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and wherein â is the estimated similarity value, T o is the outlet temperature, T i is the inlet temperature, D is the expected delay, k is a discrete sample time, and the summation is over a predefined number of samples preceding the current time.
14. The method of claim 10 , wherein the optimization problem includes
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and wherein â is an optimal or estimated similarity value, g is an inlet temperature sensor gain error correction, h is an inlet temperature sensor offset error correction, T o is the outlet temperature, T i is the inlet temperature, D is the expected delay, k is a discrete sample time, and the summation is over a predefined number of samples preceding the current time.
15. The method of claim 8 , wherein comparing the similarity value to the predetermined threshold includes determining if the similarity value is above or below the predetermined threshold, and wherein the similarity value is above the predetermined threshold if the outlet temperature of the exhaust gas is similar to the inlet temperature of the exhaust gas, and wherein the similarity value is below the predetermined threshold if the outlet temperature of the exhaust gas is similar to the delayed inlet temperature.
16. The method of claim 15 , wherein the catalyst is not present if the outlet temperature of the exhaust gas is similar to the inlet temperature, and the catalyst is present if the outlet temperature of the exhaust gas is similar to the delayed inlet temperature.
17. The method of claim 8 , further comprising:
measuring a plurality of time delays between measuring the inlet temperature of the exhaust gas and measuring the outlet temperature of the exhaust gas,
wherein the expected temperature time delay is calculated based on the plurality of measured time delays.
18. The method of claim 8 , further comprising:
determining if a flow rate of the exhaust gas falls within a first predetermined range; and
if the flow rate of the exhaust gas falls within the first predetermined range, calculating the expected temperature time delay.
19. The method of claim 8 , further comprising;
determining if the inlet temperature of the exhaust gas falls within a second predetermined range;
determining if the outlet temperature of the exhaust gas falls within a third predetermined range; and
calculating the delayed inlet temperature if the inlet temperature falls within the second predetermined range and the outlet temperature falls within the third predetermined range.
20. The method of claim 8 , further comprising;
determining a change rate of the inlet temperature of the exhaust gas;
determining if the change rate of the inlet temperature falls within a fourth predetermined range; and
calculating the delayed inlet temperature if the change rate falls within the fourth predetermined range.