KR100799148B1 - Method for detecting decrease in inner pressure of tire using gps speed information - Google Patents

Abstract

By using GPS position measurement information on the driving condition of the vehicle and collecting data only when stable dynamic load radius measurement is possible, accurate dynamic load radius can be calculated by comparing GPS speed information and tire rotation speed information to reduce tire pressure drop. Provided are a method, a device and a calculation program for detecting with excellent precision.

The present invention compares an effective dynamic load radius with an initial value previously stored as a dynamic load radius at normal internal pressure, and determines a decrease in the internal pressure of a tire from the magnitude of change in the dynamic load radius. The speed of the vehicle is calculated from the information acquired by the GPS device, and the calculated speed of the vehicle by the GPS device is continuously compared with the rotation speed of the tire obtained by the tire rotation speed detection device provided in the tire rotation part of the vehicle. And calculating the apparent dynamic load radius of the tire while driving, and determining the apparent dynamic load radius as valid only when it is determined from the GPS position measurement information that the driving state is traveling straight on at a constant speed.

Description

Determination method of internal pressure drop of tire using WPS speed information {METHOD FOR DETECTING DECREASE IN INNER PRESSURE OF TIRE USING GPS SPEED INFORMATION}

1 is a flowchart for calculating a dynamic load radius of a tire and executing a calculation program for detecting a decrease in the internal pressure of the tire.

Fig. 2 is a flowchart of a calculation program in the case of using the average value of the measured values in order to improve the measurement (calculation) accuracy of the dynamic load radius, and in the case of using the statistical method to select data to be used for calculating the average value.

The present invention relates to a method for implementing a device for detecting a reduction in the internal pressure of a tire at low cost with excellent precision.

JP-A-2005-186739, JP-A-2003-146037 and JP-A-2003-94920 disclose a method for detecting a drop in tire pressure from vehicle speed, distance and number of revolutions of a tire calculated from GPS information. have.

However, in order to detect the decrease in the internal pressure of the tire from the speed of the vehicle and the tire rotation speed calculated from the GPS information, the change in the tire rotation speed should only be detected by the decrease in the internal pressure. In other words, it is necessary to exclude the change in the rotational speed caused by the running state of the vehicle.

JP-A-2003-94920 discloses a method of detecting a decrease in tire air pressure by comparing the driving trajectory of the vehicle calculated from the tire rotation information with the driving trajectory of the vehicle obtained from the vehicle position information using GPS. There is no mention of excluding a change in rotational speed caused by the running state of the vehicle.

JP-A-2005-186739 and JP-A-2003-146037 specify the driving state from the comparison of the rotational state of the tires, but when the internal pressure drop of the tire occurs, the relationship between the mutual rotational speeds of the four wheels is The balance is already broken and the exact driving condition cannot be specified.

Also, a method of detecting a decrease in the internal pressure of a tire by calculating the dynamic load radius of the tire from the travel distance and the tire rotation speed calculated from the GPS information is also known, but the change in the rotation speed caused by the running state of the vehicle is sufficiently excluded. In this case, the precision is insufficient.

An object of the present invention, by using the GPS position measurement information on the driving state of the vehicle, at the same time collecting the data only when the dynamic load radius can be measured stably, by comparing the GPS speed information and tire rotation speed information, the exact dynamic load radius It is to provide a method, an apparatus and a program for calculating the pressure difference and detecting the reduction in the internal pressure of a tire with excellent accuracy.

A first embodiment of the present invention provides a method for determining a drop in tire pressure from the magnitude of change in dynamic load radius by comparing an effective dynamic load radius with an initial value previously stored as the dynamic load radius at normal internal pressure. The dynamic load radius calculates the speed of the vehicle while driving from information acquired by the GPS device, and calculates the speed of the vehicle by the GPS device and the tire obtained by the tire rotation speed detection device provided in the four-wheel tire rotation part of the vehicle. By comparing the rotational speeds of the tires in turn and calculating the apparent dynamic load radius of the tire while driving, and determining the apparent dynamic load radius as valid only when it is determined from the GPS position measurement information that the driving state is traveling straight on the flat road at a constant speed. It is obtained.

Even when the dynamic load radius value is determined to be valid continuously, when the magnitude of the change in the dynamic load radius measurement exceeds the set change amount, it is preferable to invalidate any measurement value and determine the decrease in the internal pressure only by the measurement values other than the invalid measurement value.

In the case where the dynamic load radius value is continuously determined to be valid, it is preferable to calculate the average value of each of the four wheels and determine the internal pressure drop based on the average value.

It is preferable to determine the internal pressure drop of the tire by comparing the dynamic load radius value determined to be valid with an initial value previously stored as the dynamic load radius value of every speed at normal internal pressure based on the calculated speed of the vehicle by the GPS device at that time. Do.

The dynamic load radius value determined to be valid and the result of measuring the dynamic load radius based on the calculation speed of the vehicle by the GPS device at that time are classified, and the initial value previously stored as the dynamic load radius value of the speed at normal internal pressure is compared. It is preferable to determine the fall of the internal pressure of a tire by doing this.

It is preferable to determine the decrease in the internal pressure by the average value of each of the four wheels only when a predetermined number for each speed range is stored in a specific time range and the magnitude of the parent dispersion of each of the four wheels is smaller than a predetermined value. .

When it is determined that the internal pressure of the coaxial two-wheels is lowered, the average value of the change amount from the initial value of the dynamic load radius of the front shaft two wheels is compared with the average value of the change amount from the initial value of the dynamic load radius of the rear shaft two wheels. When is larger than a predetermined value, it is preferable to generate a road surface slippage or a load alarm separately from the determination of the internal pressure drop.

The second embodiment of the present invention relates to an apparatus for determining a reduction in tire pressure from a magnitude of change in dynamic load radius by comparing an effective dynamic load radius with an initial value previously stored as a dynamic load radius at normal internal pressure. The dynamic load radius calculates the speed of the vehicle while driving from information acquired by the GPS device, and calculates the speed of the vehicle by the GPS device and the tire obtained by the tire rotation speed detection device provided in the four-wheel tire rotation part of the vehicle. By comparing the rotational speeds of the tires in turn and calculating the apparent dynamic load radius of the tire while driving, and determining the apparent dynamic load radius as valid only when it is determined from the GPS position measurement information that the driving state is traveling straight on the flat road at a constant speed. Obtained.

The third embodiment of the present invention is a computer readable program that records a calculation program that compares an effective dynamic load radius with an initial value previously stored as a dynamic load radius at normal internal pressure, and determines a reduction in tire pressure from the magnitude of change in dynamic load radius. A recording medium is provided, wherein the effective dynamic load radius calculates a speed of a vehicle while driving from information obtained by a GPS device, and calculates a speed of the vehicle by the GPS device and a tire provided at a tire rotation part of the vehicle. Comparing the rotational speeds of the tires acquired by the rotational speed detection device in order to calculate the apparent dynamic load radius of the tires while driving, and only when it is determined from the GPS position measurement information that the driving condition is to go straight on the flat road at a constant speed. Obtained by determining the apparent dynamic load radius to be valid.

When the GPS speed calculation time and the tire rotation speed calculation time are different, it is preferable to correct one of the results of the calculation speed to a speed in consideration of the time change with respect to the time difference, and to calculate the dynamic load radius by comparing the speeds sequentially.

Due to the widespread use of car navigation systems, GPS devices are attached to many vehicles. Therefore, the position measuring technique by GPS device is also improved, and the device (GPS type | formula speedometer VBOX by Race Logic Inc of England) specialized in calculating a speed is also currently sold.

The inventor of the present application devised a system for detecting a decrease in air pressure of a tire by using a calculation speed (hereinafter, referred to as GPS speed) by a speedometer using GPS information.

Assuming that the tire has no slip, it is possible to calculate the dynamic load radius R of the tire by using the GPS speed as the speed of the vehicle and comparing the speed of the vehicle with the rotational speed of the tire (the number of revolutions per unit time) at that time. Can be.

V (m / s) = 2πR (m) ・ Freq (Hz) / N (number)

Here, N is the number of teeth per axle rotation of the tire rotation speed detection device, and Freg (Hz) is the number of teeth of the rotation speed detection device counted per second.

Where V is replaced by the output of the GPS speedometer Vgps (km / h),

Vgps (km / h) = 2πR (m) Freq (Hz) 3.6 / N (count)

Therefore, R (m) = (N / 2 pi · 3.6) Vgps (km / h) / freq (Hz). (One)

In the case of N = 48, the dynamic load radius is

R (m) = 2.122066 Vgps (km / h) / Freq (Hz). (One)'

As described above, when the influence of the slip ratio can be eliminated in the straight running, the dynamic load radius of the tire during the running can be measured (calculated).

In addition, when the internal pressure decreases, the dynamic load radius of the tire decreases. Therefore, if the dynamic load radius of a tire in running can be measured, the fall of internal pressure of a tire can be detected.

Regarding the output frequency and the output accuracy of the GPS speedometer, when using the above-described VBOX, the accuracy of 0.1 km / h is published at an output of 20 Hz.

According to this precision, at least 0.1% accuracy can be obtained when the speed is at least 10 km / h. Therefore, since the change of the dynamic load radius of the general tire which says when the internal pressure of a tire was reduced by 25% is several% of 10 minutes, detection accuracy is enough.

However, in order to accurately measure (calculate) the dynamic load radius of a tire, it is necessary to prevent the influence of a change in tire rotation speed caused by a cause other than the change in tire internal pressure, which is the purpose of the measurement. That is, the measurement data of the tire rotation speed affected by the cause other than the tire internal pressure should be excluded as invalid data so as not to be used for the calculation of the dynamic load radius.

The change in slip rate is noticeable when the vehicle accelerates or decelerates. In addition, when traveling on a slope, even if driving at a constant speed, the slip ratio of the driving wheel is changed by the influence of gravity acceleration.

In addition, since the rotation speed is different between the driving trajectory of the inner ring side and the traveling trajectory of the outer ring side when the steering wheel is turned, the measurement result of the dynamic load radius is affected.

(1) As a countermeasure, it has been devised to use GPS positioning information. In order to determine whether it is traveling straight or not, the direction of travel can be obtained from the GPS position measurement information, and whether or not it is traveling straight can be determined from the amount of change per unit time in the direction of travel. In addition, in order to determine whether or not the vehicle is traveling on the flat road, it is possible to obtain the altitude of the vehicle from the GPS position measurement information in the same manner, and to determine whether the vehicle is traveling on the flat road from the change amount per unit time of altitude. It can be determined. In addition, with respect to acceleration and deceleration, it is possible to determine the constant speed travel as the magnitude of the acceleration by time derivative of the calculated GPS speed information.

Therefore, by using the GPS information with high accuracy, it is possible to determine the driving condition of the vehicle and to provide a specific criterion so that the data of the tire rotation speed can limit the range of the driving condition suitable for the calculation of the dynamic load radius.

(2) Even when the running conditions are limited, the detection accuracy of the rotational speed of the tire is important for the measurement of the dynamic load radius. The rotation speed of a tire may include instantaneous fluctuations, such as the influence of the unevenness of the road surface, and the case of passing through the cover of the manhole. As a method of excluding these fluctuation components, even when the fluctuation occurs continuously even in the dynamic load radius determined in (1) above, a method of determining whether or not it is appropriate from the change amount is devised.

(3) In addition, even when the variation of the measured value was small, a method of further improving the precision was devised by using the average value as a representative value.

(4) The dynamic load radius of a tire is known to be affected by speed. That is, the tread portion is stretched by the centrifugal force caused by the rotation of the tire, and the circumferential length of the tire becomes long, and as a result, the rotational speed becomes slow. In addition, when the load is large, the ground area of the tire increases, the dynamic load radius decreases, and as a result, the rotational speed becomes high. In addition, the load is influenced not only by the number and load of the crew, but also by the aerodynamic force generated as the vehicle travels. As a countermeasure, a method of presetting a reference value based on speed and comparing the speed value using GPS has been devised.

(5) As another method, it was devised to classify the measurement result of dynamic load radius by GPS speed. Thereby, the internal pressure fall determination which excludes the influence of a speed can be made by previously storing the reference value of the dynamic load radius in each speed range at the time of a normal breakdown voltage as an initial value.

(6) In the above method, since the precision can be improved by using a statistical means, a method using the statistical means is devised.

(7) In addition, the slip ratio of the tire of the drive wheel is affected by the ease of sliding on the road surface. As a countermeasure, it has been devised to consider the difference between the measured values of the dynamic load radius of the front wheel and the rear wheel from the reference value as indices. On the road surface on which slip easily occurs, only the rotational speed on the driving wheel side increases, and the measurement result of the dynamic load radius tends to determine that the internal pressure is lowered. In order to inform the driver of such a phenomenon, an alarm for a road slip is generated together with the internal pressure alarm. Also, in relation to the influence of the load, the axle load of the front and rear axles changes when the load is extremely large, so that the detection can be performed by setting the difference between the change of the front wheel and the rear wheel as an index in the same manner. In addition, the driver can also be notified of the influence of the dynamic load radius due to the load.

An improvement in the program of the present invention is to secure time synchronization. If the speed calculation time by a GPS speedometer and the time to calculate the rotation speed of a tire do not correspond, the exact dynamic load radius is not calculated. In consideration of these visual errors, it was devised to estimate and calculate the velocity at the same time by correcting any velocity measurement value by the visual difference according to the magnitude of the change.

Based on the technical matters described above, a calculation program for calculating the dynamic load radius of the tire and detecting the internal pressure drop of the tire will be described with reference to the flowcharts of FIGS. 1 and 2.

In FIG. 1, in step S1, S2, the rotation speed of each wheel is acquired (calculated) based on the output signal of the wheel (tire) rotation speed detection apparatus.

In steps S3 and S4, the traveling speed of the vehicle is acquired based on the GPS information.

In step S5, either the calculation time of the rotational speed of the wheel or the calculation time of the GPS speed is calculated by interpolation of the numerical values at the simultaneous angle with the other, and the simultaneous numerical values are calculated to synchronize.

In step S6, the dynamic load radius of each wheel is calculated from the rotational speed of each wheel and the GPS speed of the vehicle.

In step S7, step S8 and step S9, the rate of change of the GPS position measurement information is calculated, and on the basis of this rate of change of time, the ascending and descending speeds on the slope, the right turn angular speed and the left turn angular speed due to handling, etc. The numerical value regarding the running condition of is computed. The acceleration and deceleration may be calculated in any of steps S4 and S9.

In step S10, under various driving conditions, a combination of dynamic load radius, GPS speed, and positional information change rate is acquired to form a database, and the database is initialized. This database also includes each decision criterion.

In step S11, it is judged by comparing with the respective criterion reference values whether or not the running condition satisfies conditions such as constant speed running, traveling on the flat road, and straight running, so that the data obtained during the actual running is for detecting the internal pressure of the tire. It is determined whether or not the data is suitable. In the case of inadequate data, such data is excluded without use as data for detecting the internal pressure of the tire, and the excluded data is returned to the routine of remeasurement. The change rate of the dynamic load radius is also excluded from the internal pressure detection data of the tire when it is estimated to be an unstable running condition or a road surface state compared with the reference value. However, this excluded data may be used separately for the alarm signal for abnormality of the road surface or loading situation in steps S15 and S16.

 In step S12, the difference d between the initial value of the dynamic load radius databased for each speed and the measured value of the dynamic load radius is calculated according to the GPS speed.

In step S13, the difference d calculated in step S12 is compared with a reference value. If the difference d is larger than the reference value, an internal pressure (lowering) alarm is issued in step S14, and if the difference d is smaller than the reference value, the flow returns to the remeasurement routine.

2 is a flowchart of a calculation program in the case of using a method of using an average value of the measured values in order to improve the accuracy of the measurement (calculation) of the dynamic load radius, and of using a statistical means to select data to be used for calculating the average value.

Steps S1 to S11 show a calculation process equivalent to that of the flowchart of Fig. 1, and in step S101, the measurement of dynamic load radius is classified (divided) according to the grade of GPS speed.

In step S102, N (e.g., 30) measurements of the dynamic load radius classified in step S101 are accumulated for each speed class.

In step S103, the variation of the dynamic load radius data for each GPS speed class accumulated by N in step S102 is determined by the variance, and is determined to be valid data when the dispersion value σ ² is smaller than the reference value.

 In step S104, the average value of the dynamic load radius is calculated based on the data determined to be valid in step S103.

In step S105, the average value of the dynamic load radius calculated in step S104 is compared with the initial value, and when the difference is large, an internal pressure (lowering) alarm is generated in step S106.

In step S107, the average value of the front wheels and the rear wheels of the average value of the dynamic load radius calculated in step S104 are compared, and when the value difference between the front wheels and the rear wheels is large, the low friction coefficient (μ) or the loading abnormality on the road surface is estimated. In step S108, an alarm for abnormal road surface or abnormal loading is generated.

Although each flowchart of FIG. 1 and FIG. 2 shows a part of the calculation program used for the tire internal pressure fall detection method which concerns on this invention as another flowchart, it is possible to embed these partial calculation programs in one calculation program.

Examples of various initial data values used in the calculation programs shown in Figs. 1 and 2 and reference values used for various determinations are described below, listing the applied vehicle model and the applied tire model.

In addition, an embodiment showing the results of an actual driving test for confirming the performance of the tire internal pressure detection method of the present invention as shown in the flowcharts of FIGS. 1 and 2 will be described below, and an actual driving test including a test course will be described below. The condition of is also described.

Type of test vehicle: Audi A4

GPS speedometer: V-B0XII (made by Race Logic Co)

Test location: Okayama test course and surrounding roads at Sumitomo Rubber Industries, Ltd

test requirements

Type of tire: 205 / 55R16 SP9000

Standard internal pressure: 220 kPa (front wheel), 210 kPa (rear wheel).

40% decompression: 132 kPa (front wheel), 126 kPa (rear wheel)

Initial value of dynamic load radius

@ 40 ± 20 km / h Front wheels: 304.9 mm Rear wheels: 304.5 mm

@ 80 ± 20 km / h Front wheels: 305.2 mm Rear wheels: 304.8 mm

@ 120 ± 20 km / h Front wheels: 306.0 mm Rear wheels: 305.6 mm

@ 160 ± 20 km / h Front wheels: 307.4 mm Rear wheels: 307.0 mm

Judgment standard of running condition

Drive straight: Change in driving direction information (0 to 360 degrees) for 1 second is within 1 degree

Determination of slope: The change of altitude information for 5 seconds is within 1 m

Acceleration and deceleration: time derivative of GPS speed is within 0.1 G

Classification speed: 20 to 60 km / h, 60 to 100 km / h, 100 to 140 km / h, 140 to 180 km / h

Determination of variance: 3O accumulation σ ² <0.1

Comparison threshold between front and rear wheels: at least 1%

Calculation method = [(average average of front wheel measurement / initial average value of front wheel)-(average average of rear wheel measurement / initial average value of rear wheel)] × 100

Visual correction when calculating speed

Difference between GPS acquisition time and tire rotation speed acquisition time = 0.2 seconds

GPS calibration speed (T) = GPS (T-1) + [GPS (T)-GPS (T-1)] × 0.8

Example 1

Driving condition 1: Two people ride, the vehicle travels on the ring road at a speed of 110 to 130 km / h, and various handling roads at a speed of 60 km / h.

In either case, it was possible to detect a reduction in the dynamic load radius of the decompression tire by at least 0.5%.

Example 2

Driving condition 2: Ride 2 persons, vehicle travels below 60 km / h on public roads (up and down on mountain roads and gravel roads)

In either case, it was possible to detect a reduction in the dynamic load radius of the decompression tire by at least 0.5%.

Example 3

Driving condition 3: 2 people riding, the vehicle is driving on the artificial road having a low friction coefficient (μ). 2 passengers ride at speeds below 40 km / h

Front wheels: 2.1%, Rear wheels: 0.72% (Difference between front and rear wheels = 1.38%)

In either case, it was possible to detect a reduction in the dynamic load radius of the decompression tire by at least 0.5%, and also the difference between the front and rear wheels exceeding 1%, so that a road surface (load) alarm can occur.

Example 4

Driving condition 4: Ride 2 persons, drive below 60 km / h with 100 kg of cargo

Front wheel: 0.68%, Rear wheel: 2.03% (Difference between front and rear wheels = 1.35%)

In either case, it was possible to detect a reduction in the dynamic load radius of the decompression tire by at least 0.5%, and also the difference between the front and rear wheels exceeding 1%, so that a road surface (load) alarm can occur.

As described above, in any of the embodiments, the drop in the internal pressure can be detected by calculating the exact dynamic load radius and determining the case where the change of at least 0.5% occurs as the breakdown voltage.

In addition, in the case of the running time and the load load on the road having a low friction coefficient μ, slip and load alarms can be generated, respectively.

According to the present invention, by using the GPS position measurement information for the driving state of the vehicle, and collecting data only when stable dynamic load radius measurement is possible, by calculating the exact dynamic load radius by comparing the GPS speed information and tire rotation speed information, the tire It is possible to provide a method, an apparatus, and a program for detecting a drop in the breakdown voltage with excellent accuracy.

Claims (10)

As a method of judging the reduction in the internal pressure of a tire from the magnitude of change in the dynamic load radius by comparing the effective dynamic load radius with an initial value previously stored as the dynamic load radius at normal internal pressure, The effective dynamic load radius is The speed of the vehicle while driving is calculated from the information acquired by the GPS device, and the output speed of the vehicle by the GPS device and the angle obtained by each tire rotation speed detection device provided in each tire rotation part of the four wheels of the vehicle. Calculate the apparent dynamic load radius of each tire on the basis of the rotation speed of the tire, The apparent dynamic load radius is determined to be valid only when it is determined from the positioning information of the GPS that the driving condition is straight along the flat road at a constant speed. The internal pressure drop determination method of a tire obtained by making it. The method of claim 1, even when the dynamic load radius value is determined to be valid continuously, when the magnitude of the change in the dynamic load radius measurement exceeds the set change amount, any measurement value is invalidated and the drop in internal pressure is reduced only by measurement values other than the invalid measurement value. The internal pressure drop determination method of a tire which is to determine. The method of claim 1, wherein the average value of each of the four wheels is calculated when the dynamic load radius value is continuously determined to be effective, and the internal pressure drop is determined based on the average value. The dynamic load radius value according to any one of claims 1 to 3, which is stored in advance as a dynamic load radius value of every speed at normal internal pressure, based on the dynamic load radius value determined to be valid and the calculated speed of the vehicle by the GPS apparatus at that time. A method for determining the reduced internal pressure of a tire which determines a decrease in the internal pressure of a tire by comparing the initial values thus obtained. The dynamic load radius value determined as valid according to any one of claims 1 to 3, and the result of measuring the dynamic load radius on the basis of the calculated speed of the vehicle by the GPS device at that time are classified, and at normal breakdown voltage. The method of claim 1, wherein the pressure drop of the tire is determined by comparing an initial value previously stored as the dynamic load radius value of each speed of the tire. 4. The method according to claim 3, wherein for each speed range, a predetermined number of dynamic load radius values for calculating the population variance are stored in a specific time range, and only if the magnitude of the population variance of each of the four wheels is smaller than the predetermined value. The method of determining the internal pressure drop of a tire that determines the decrease in the internal pressure based on the average of each of the four wheels. The average value of the amount of change from the initial value of the dynamic load radius of the two front axles, and the dynamic load of the rear axle two wheels according to any one of claims 1 to 3, when it is determined that the internal pressure of the coaxial two wheels is lowered. A method for determining the decrease in the pressure resistance of a tire, wherein the average value of the amount of change from the initial value of the radius is compared, and when the difference is larger than the predetermined value, a road surface slippage or a load warning is generated separately from the determination of the decrease in pressure resistance. An apparatus for determining a drop in tire pressure from a magnitude of change in dynamic load radius by comparing an effective dynamic load radius with an initial value previously stored as a dynamic load radius at normal internal pressure, The effective dynamic load radius is The speed of the vehicle while driving is calculated from the information acquired by the GPS device, and the calculated speed of the vehicle by the GPS device and the tires obtained by each tire rotation speed detection device provided in each tire rotation part of the four wheels of the vehicle. Calculate the apparent dynamic load radius of the tire while driving, based on the rotational speed, The apparent dynamic load radius is determined to be valid only when it is determined from the positioning information of the GPS that the driving condition is straight along the flat road at a constant speed. The internal pressure drop determination apparatus of a tire obtained by making it. A computer-readable recording medium which records a calculation program for comparing the effective dynamic load radius with an initial value previously stored as the dynamic load radius at normal internal pressure, and determining a decrease in the pressure resistance of a tire from the magnitude of change in the dynamic load radius. The effective dynamic load radius is The speed of the vehicle while driving is calculated from the information acquired by the GPS device, and the calculated speed of the vehicle by the GPS device and the tires obtained by each tire rotation speed detection device provided in each tire rotation part of the four wheels of the vehicle. Calculate the apparent dynamic load radius of the tire while driving, based on the rotational speed, The apparent dynamic load radius is determined to be valid only when it is determined from the positioning information of the GPS that the driving condition is straight along the flat road at a constant speed. A computer-readable recording medium which records a calculation program obtained by. 10. The tire according to claim 9, wherein when the GPS speed calculation time and the tire rotation speed calculation time are different, one of the results of the calculation speed is corrected to a speed in consideration of a time change with respect to the time difference, and each tire is based on the modified speed. A computer-readable recording medium having recorded thereon a calculation program which calculates an effective dynamic load radius by calculating an apparent dynamic load of.

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