Method for detecting a deflated tire on a vehicle
First Claim
1. A method for detecting loss of pressure in a tire of a motor vehicle having four wheels and a tire on each wheel, said method comprisingmeasuring the speeds Vij of each of the four wheels a plurality of times (n) in a first time interval,adding the plurality of speeds for each wheel to produce four wheel speed column sums SUMVj where ##EQU10## and j=1, 2, 3, 4, adding the four wheel speed column sums SUMVj to form a speed total X,forming a between column variation SSC based on the four column sums SUMVj and the speed total X,forming a between row variation SSR based on the four column sums SUMVj and the wheel speeds Vij,forming a value F based on the ratio SSC/SSR,comparing F to a first predetermined threshold corresponding to a first predetermined pressure loss, andactuating a driver warning device when said F value exceeds said first predetermined threshold.
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Abstract
Wheel speed values for each of four wheels are collected and analyzed for a statistical variation which would indicate low tire pressure. Prior to analysis, and following reset of the system, calibration factors are determined for each of the wheels to compensate rolling radius variations, and subsequently used to correct all wheel speed values. The corrected speed values are then filtered to exclude values which represent wheel slippage, rough road fluctuations, vehicle cornering, and uphill or downhill travel. When a sufficient number of values have been collected, an F-value is calculated substantially according to the statistical method "analysis of the variance", and the F-value is compared to an empirically determined value corresponding to a predetermined pressure loss. This comparison can provide the basis for a driver warning. Since a larger F-value indicates a larger statistical difference in wheel speeds, the value can be rechecked after a further interval for additional pressure loss.
59 Citations
17 Claims
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1. A method for detecting loss of pressure in a tire of a motor vehicle having four wheels and a tire on each wheel, said method comprising
measuring the speeds Vij of each of the four wheels a plurality of times (n) in a first time interval, adding the plurality of speeds for each wheel to produce four wheel speed column sums SUMVj where ##EQU10## and j=1, 2, 3, 4, adding the four wheel speed column sums SUMVj to form a speed total X, forming a between column variation SSC based on the four column sums SUMVj and the speed total X, forming a between row variation SSR based on the four column sums SUMVj and the wheel speeds Vij, forming a value F based on the ratio SSC/SSR, comparing F to a first predetermined threshold corresponding to a first predetermined pressure loss, and actuating a driver warning device when said F value exceeds said first predetermined threshold.
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17. Method for detecting the loss of pressure in a tire of a motor vehicle having four wheels and a tire on each wheel, said method comprising
measuring the speeds Vij of each of the four wheels a plurality of times (m) in a calibration time interval, determining wheel calibration factors four each of the four wheels based on said plurality (m) of measured speeds for each of said four wheels, said wheel calibration factors discounting variations in rolling radii of the four wheels, measuring the speeds Vij of each of the four wheels a plurality of times (n) in a first time interval subsequent to said calibration time interval, modifying said wheel speeds by said calibration factors during said first time interval and any subsequent time intervals, adding the plurality of speeds for each wheel to produce four wheel speed column sums SUMVj where ##EQU17## and j=1, 2, 3, 4, adding the four wheel speed column sums SUMVj to form a speed total X, forming a between column variation SSC based on the four column sums SUMVj and the speed total X, forming a between row variation SSR based on the four column sums SUMVj and the wheel speeds Vij, forming a value F based on the ratio SSC/SSR, comparing F to a first predetermined threshold corresponding to a first predetermined pressure loss, and actuating a driver warning device when said F value exceeds said first predetermined threshold.
Specification