System and Method for Indirect Indication of Tire Pressure Loss

• US 20110210841A1
• Filed: 03/01/2010
• Published: 09/01/2011
• Est. Priority Date: 03/01/2010
• Status: Active Grant

• Current Assignee: International Truck Intellectual Property Co. LLC (Volkswagen AG)
• Original Assignee: International Truck Intellectual Property Co. LLC (Volkswagen AG)
• Inventors: Duan, Huihui, Wang, Zhengming, Jean-Baptiste, Gregory A.
• Granted Patent: US 8,350,688 B2
• Time in Patent Office: Days
• US Class Current: 340/443
• CPC Class Codes: B60C 23/061 by monitoring wheel speed measuring distance traversed on the ground by vehicles G01C22/00

Abstract

A method of indirect tire pressure monitoring for indicating when a pneumatic tire on a wheel at one end of a motor vehicle axle is underpressurized relative to a pneumatic tire on a wheel at an opposite end of the axle while the vehicle is being driven on a road surface. ABS wheel sensors are used as inputs to a devoted processor for indirect tire pressure monitoring.

Claims

1. A method of indirect tire pressure monitoring for indicating when a pneumatic tire on a wheel at one end of a motor vehicle axle is underpressurized relative to a pneumatic tire on a wheel at an opposite end of the axle while the vehicle is being driven on a road surface, the method comprising:

repeatedly calculating difference between a current measurement of effective radius of each tire relative to a reference value for effective radius of the same tire;

processing the calculated differences for each tire and comparing the calculated differences to each other; and

when the comparison of the calculated differences discloses that one of the calculated differences differs from that for the other by more than a defined amount, using that disclosure to determine if an alert for indicating that one tire is too underpressurized relative to the other should be issued.

2. A method as set forth in claim 1 wherein the reference value for effective radius of each tire is determined when the respective tire was initially installed on the axle by processing data representing angular speed of the respective wheel and traveling speed of the vehicle according to an algorithm that repeatedly calculates the effective radius of the respective tire and that calculates the mean of a number of the repeated calculations of the effective radius for the respective tire, that number having been statistically proven to provide each calculated mean with a certain probability of being within a defined margin of error for the calculated mean.

3. A method as set forth in claim 2 wherein the number has been statistically proven to provide each calculated mean with at least a 90% probability of being within a predefined acceptable margin of error for the calculated mean.

4. A method as set forth in claim 2 wherein the effective radius of each tire determined when the respective tire was initially installed on the axle is used as the reference value for a limited time commencing with driving of the vehicle after a period of time during which the vehicle was not driven and which was sufficient to allow the tires to assume substantially ambient temperature.

5. A method as set forth in claim 4 wherein after the limited time has elapsed, the reference value that is used for effective radius of each tire is switched to a measured value for effective radius obtained substantially contemporaneously with elapse of the limited time.

6. A method as set forth in claim 1 comprising obtaining the measurement of effective radius of each tire by processing data from a respective sensor at each wheel that also supplies the same data to an ABS system of the vehicle.

7. A method as set forth in claim 1 wherein the step of processing a current measurement of effective radius of each tire relative to a reference value for effective radius of the same tire comprises calculating each current measurement by calculating the mean of a number of individual measurements of the effective radius and then using the calculated mean for each tire as the current measurement of effective radius of the respective tire in the calculation of difference between a current measurement of effective radius of each tire relative to the reference value for effective radius of the same tire.

8. A method as set forth in claim 1 wherein the step of using disclosure that one of the calculated differences differs from that for the other by more than a defined amount to determine if an alert for indicating that one tire is too underpressurized relative to the other should be issued comprises incrementing or decrementing an alert parameter, and further including issuing an alert when the absolute value of the alert parameter equals a predetermined limit.

9. An indirect tire pressure monitoring system for indicating when a pneumatic tire on a wheel at one end of a motor vehicle axle is underpressurized relative to a pneumatic tire on a wheel at an opposite end of the axle while the vehicle is being driven on a road surface, the system comprising:

a respective sensor at each wheel that supplies the same data to an ABS system of the vehicle and to a devoted processor for indirect tire pressure monitoring; and

wherein the devoted processor is arranged to repeatedly execute an algorithm for calculating difference between a current measurement of effective radius of each tire relative to a reference value for effective radius of the same tire, to process the calculated differences for each tire and compare the calculated differences to each other, and when the comparison of the calculated differences discloses that one of the calculated differences differs from that for the other by more than a defined amount, using that disclosure to determine if an alert for indicating that one tire is too underpressurized relative to the other should be issued.

10. An indirect tire pressure monitoring system as set forth in claim 9 wherein the algorithm operates to determine the reference value for effective radius of each tire when the respective tire was initially installed on the axle by processing data representing rotational velocity of the respective wheel and traveling speed of the vehicle to repeatedly calculate the effective radius of the respective tire and to calculate the mean of a number of the repeated calculations of the effective radius for the respective tire, that number having been statistically proven to provide each calculated mean with a certain probability of being within a defined margin of error for the calculated mean.

11. An indirect tire pressure monitoring system as set forth in claim 10 wherein the number has been statistically proven to provide each calculated mean with at least a 90% probability of being within a predefined margin of error for the calculated mean.

12. An indirect tire pressure monitoring system as set forth in claim 10 wherein algorithm operates to use the effective radius of each tire determined when the respective tire was initially installed on the axle as the reference value for a limited time commencing with driving of the vehicle after a period of time during which the vehicle was not driven and which was sufficient to allow the tires to assume substantially ambient temperature.

13. An indirect tire pressure monitoring system as set forth in claim 12 wherein after the limited time has elapsed, the algorithm operates to switch the reference value from the one that was being used for effective radius of each tire to a measured value for effective radius obtained substantially contemporaneously with elapse of the limited time.

14. An indirect tire pressure monitoring system as set forth in claim 9 wherein the algorithm operates to process a current measurement of effective radius of each tire relative to a reference value for effective radius of the same tire by calculating the means of a number of current measurement of effective radius for the same tire and then using the calculated mean for each tire as the current measurement of effective radius of each tire when calculating difference between a current measurement of effective radius of each tire relative to the reference value for effective radius of the same tire.

15. An indirect tire pressure monitoring system as set forth in claim 9 wherein the algorithm is arranged to use disclosure that one of the calculated differences differs from that for the other by more than a defined amount to determine if an alert for indicating that one tire is too underpressurized relative to the other should be issued by incrementing or decrementing an alert parameter, and then issuing an alert when the absolute value of the alert parameter equals a predetermined limit.

16. A method of calculating a reference value for effective radius of a pneumatic tire on a wheel just installed on an axle of a motor vehicle, and then using the reference value for indirect tire pressure monitoring, the method comprising:

processing data representing rotational velocity of the wheel and traveling speed of the vehicle in a processor according to an algorithm that repeatedly calculates the effective radius of the tire, that calculates the mean of a number of the repeated calculations of the effective radius for the tire that has been statistically proven by prior testing to provide the calculated mean with a certain probability of being within a defined margin of error for the calculated mean, that further processes the calculated mean effective radius with other data, and that causes an alert to be given when a result of the further processing discloses that the alert should be given.