Method for processing information in a tire pressure monitoring system

1. A method of measuring an undesired pressure drop in a tire of a vehicle and generating a warning signal responsive thereto, comprising the steps of:

establishing a reference temperature;

determining at least one pressure warning threshold at the reference temperature;

measuring gauge pressure and gauge temperature within a tire cavity;

correcting the gauge pressure to a corrected pressure value at the reference temperature;

calculating from a series of corrected gauge pressure measurements a leak rate;

comparing the corrected pressure value at the calculated leak rate against the pressure warning threshold;

generating a warning signal based upon the comparison of the corrected pressure value at the calculated leak rate against the pressure warning threshold.

2. A method according to claim 1 , further comprising:

taking at least a second measurement of gauge pressure and gauge temperature within the tire cavity;

correcting the second measured gauge pressure to a second corrected pressure value at the reference temperature;

determining an estimated corrected pressure value by averaging the first and second filtered pressure values.

3. A method according to claim 2 , wherein the estimated corrected pressure value represents an exponential average of the first and second corrected pressure values.

4. A method according to claim 1 , further comprising:

measuring successive sample data points of pressure and temperature within a tire cavity;

determining a characteristic curve of pressure to differential temperature based upon the successive data points;

calculating a slope of a boundary of the characteristic curve;

determining a zero intercept value of the characteristic curve representing a reference pressure value at the reference temperature.

5. A method according to claim 4 , further comprising:

adjusting the boundary of the characteristic curve to compensate for measurement error.

6. A method according to claim 1 , further comprising:

making at least a second measurement of gauge pressure and gauge temperature within the tire cavity;

correcting the second measured gauge pressure to a second corrected pressure value at the reference temperature;

determining the leak rate based upon the change between the first and second corrected pressure values;

predicting based upon the leak rate the anticipated time that the corrected pressure value of the tire will cross the pressure warning threshold;

generating a warning signal indicative of the anticipated time.

7. A method according to claim 6 , further comprising:

establishing a time left threshold on the value of anticipated time at which the corrected pressure value will cross the low pressure warning threshold;

determining whether the anticipated time is less than the threshold; and

generating a warning signal when the anticipated time is less than the threshold.

8. A method of measuring an undesired pressure drop in a tire of a vehicle and generating a warning signal responsive thereto, comprising the steps of:

establishing a reference temperature;

determining at least one pressure warning threshold at the reference temperature;

measuring gauge pressure and gauge temperature within a tire cavity;

correcting the gauge pressure to a filtered pressure value at the reference temperature;

comparing the filtered pressure value against the pressure warning threshold;

generating a warning signal upon an undesired pressure drop in the tire;

establishing a time left threshold on the value of anticipated time at which the filtered pressure value will cross the low pressure warning threshold;

determining whether the anticipated time is less than the threshold;

generating a warning signal when the anticipated time is less than the threshold;

developing data points from a series of successive measurements of pressure and temperature;

establishing a probability threshold value;

computing a time left probability based upon a plurality of recent said data points;

comparing the time left probability against the probability threshold value; and

generating a warning signal when the time left probability exceeds the probability threshold value.

9. A method of measuring an undesired pressure drop in a tire of a vehicle and generating a warning signal responsive thereto, comprising the steps of:

establishing a reference temperature;

determining at least one pressure warning threshold at the reference temperature;

measuring gauge pressure and gauge temperature within a tire cavity;

correcting the gauge pressure to a filtered pressure value at the reference temperature;

comparing the filtered pressure value against the pressure warning threshold;

generating a warning signal upon an undesired pressure drop in the tire;

developing data points from a series of successive measurements of gauge pressure and gauge temperature;

determining a pressure-temperature map based upon the data points and separated by boundaries defined by the Ideal Gas Law;

classifying each data point into a one of a plurality of states;

calculating state probabilities for each data point;

forming a vector of probabilities for each data point;

determining a current state vector representing an average of the vector of probabilities of each data point in the series of successive measurements;

identifying a state with a maximum probability; and

reporting the state of maximum probability.

10. A method according to claim 9 , wherein the plurality of states are classified as acceptable, cautionary, and unacceptable.

11. A method of identifying a leak rate in a tire of a vehicle, comprising the steps of:

establishing a reference temperature;

taking a finite number of sample data points of gauge pressure and gauge temperature within a tire cavity;

compensating the measured pressure data into filtered pressure values at the reference temperature;

applying a recursive linear least squares regression filter to the pressure data to estimate a pressure leak rate.

12. A method of identifying a leak rate in a tire of a vehicle, comprising the steps of:

establishing a reference temperature;

taking a finite number of sample data points of gauge pressure and gauge temperature within a tire cavity;

compensating the measured pressure data into filtered pressure values at the reference temperature;

applying a recursive linear least squares regression filter to the pressure data to estimate a pressure leak rate and

wherein the measured pressure data is compensated into filtered pressure values at the reference temperature utilizing the Ideal Gas Law.

13. A method according to claim 12 , wherein the reference temperature is the first temperature measured in the cavity of a system start up.

14. A method according to claim 13 , wherein the reference temperature is the ambient temperature.

15. A method of monitoring tire air pressure in a rolling vehicle, comprising:

recording measured data pairs comprising values for pressure and temperature;

determining a characteristic curve for the measured data pairs;

determining filtered pressure values of the data pairs at a reference temperature utilizing the Ideal Gas Law;

comparing the filtered pressure values of the data pairs against at least one pressure threshold value; and

determining a zero intercept offset value corresponding to a measurement error factor.

16. A method of monitoring tire air pressure in a rolling vehicle, comprising:

recording measured data pairs comprising values for pressure and temperature;

determining a characteristic curve for the measured data pairs;

determining filtered pressure values of the data pairs at a reference temperature utilizing the Ideal Gas Law;

comparing the filtered pressure values of the data pairs against at least one pressure threshold value; and

determining a pressure leak rate based upon the measured data pairs.

17. A method according to claim 16 , further comprising:

applying a change detector to reset the leak rate filter in the event that the leak rate undergoes a substantial change.

18. A method of monitoring tire air pressure in a rolling vehicle, comprising:

recording measured data pairs comprising values for pressure and temperature;

determining a characteristic curve for the measured data pairs;

determining filtered pressure values of the data pairs at a reference temperature utilizing the Ideal Gas Law;

comparing the filtered pressure values of the data pairs against at least one pressure threshold value;

classifying each measured data pair into one of a plurality of states; and

calculating state probabilities for each measured data pair by means of a fuzzy logic.

19. A method according to claim 18 , further comprising:

forming a vector of probabilities for each measured data pair;

determining a current state vector representing an average of the vector of probabilities of each measured data pair in a finite series of successive measurements;

identifying a state with a maximum probability; and

reporting the state of maximum probability.