DE102019110805B4 - Method for determining an actual tire size of the tires of a vehicle - Google Patents

Abstract

Method for determining an actual tire size of the tires of a vehicle, the actual tire size of the vehicle being determined while the vehicle is traveling with the aid of a GPS signal by adding a sum of the distance traveled by the vehicle and an accuracy of the GPS signal by the number the number of revolutions of the wheels is divided, characterized in that the actual tire size is determined as a function of a lane evaluation when the vehicle changes lanes, an error between a real and an approximate driving distance when changing lanes is taken into account when determining the actual tire size.

Description

The invention relates to a method for determining an actual tire size of the tires of a vehicle.

The disclosure document DE 10 2016 212 766 A1 discloses methods for determining the tire circumference of a tire of a vehicle. The disclosure document DE 10 2014 216 344 A1 discloses methods for determining the tire radius of a tire of a vehicle.

It is known that different tires are used in the winter season than in the summer season. These tires can differ in vehicle size. Therefore, a vehicle speed displayed on an instrument panel of the vehicle calculated on a standard tire size is not always correct.

The invention is based on the object of specifying a method for determining an actual tire size of the tires of a vehicle.

This object is achieved by a method according to the features of claim 1.

According to the invention, the object is thus achieved in that the actual tire size of the vehicle is determined while the vehicle is in motion with the aid of a GPS signal by adding a sum of the distance traveled by the vehicle and an accuracy of the GPS signal by the number of revolutions of the Wheels is shared. It is provided that the actual tire size is determined as a function of a lane evaluation that determines the lane change of the vehicle, an error between a real and an approximate driving route during a lane change being taken into account when determining the actual tire size.

This has the advantage that the real tire size is determined without a high-quality measuring system, since GPS systems are now included in all vehicles. The proposed solution is therefore based only on the use of software, as a result of which the costs for determining the tire size are reduced.

A tire size stored in the vehicle is advantageously corrected automatically with the actual tire size. As a result of this correction, many driver assistance systems or safety systems in the vehicle have the correct tire size available, which means that the vehicle can be reliably controlled.

In one embodiment, the stored tire size is replaced by the actual tire size if a difference between the stored and the actual tire size exceeds a predetermined limit value. The choice of the limit value ensures that the two tire sizes can be clearly distinguished.

In one variant, a current driving speed of the vehicle is determined using the actual tire size. The determination of the vehicle speed is based on the engine speed, the tire radius and other parameters. By replacing the specified tire size with the actually determined tire size, the vehicle speed is always correctly determined and thus correctly made available to the assistance and safety systems and also correctly displayed to the driver on the dashboard.

In one embodiment, the GPS signal is checked for the presence of a predetermined accuracy before the actual tire size is determined. The more precise the GPS signal, the more precisely the tire size can be determined.

In a further embodiment, the actual tire size is determined as a function of the accuracy of a speed sensor.

The actual tire size is advantageously determined as a function of a load difference on the tires. This is of particular importance since the real tire deformation changes depend on the load change and initial deformations. Deformations of the tires due to different loads on the vehicle can thus also be taken into account when determining the tire size, as a result of which the accuracy of the tire size in the determination is improved.

According to the invention, the actual tire size is determined as a function of a lane evaluation when the vehicle changes lanes. The distance traveled by the vehicle is taken into account by means of the lane evaluation in order to improve the evaluation of the GPS on the tire size.

In one embodiment, an evaluation error is taken into account in the lane evaluation. This evaluation error must be as small as possible so that it is reliably included when determining the tire size.

The invention allows numerous embodiments. One of these will be explained in more detail with reference to the figures shown in the drawing.

• 1 ein Ausführungsbeispiel eines Fahrzeuges zur Durchführung des erfindungsgemäßen Verfahrens,
• 2 ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens,
• 3 eine Prinzipdarstellung für die Bestimmung eines Spurwechsels,
• 4 eine Prinzipdarstellung zur Bestimmung einer Deformation des Fahrzeugreifens,
• 5 ein Ausführungsbeispiel der Abhängigkeit eines Fehlers in Abhängigkeit von der Reifengröße.

Show it:

• 1 an embodiment of a vehicle for carrying out the method according to the invention,
• 2 an embodiment of the method according to the invention,
• 3 a schematic diagram for determining a lane change,
• 4th a schematic diagram for determining a deformation of the vehicle tire,
• 5 an embodiment of the dependency of an error as a function of the tire size.

In 1 shows an embodiment of a vehicle for performing the method according to the invention. The vehicle 1 includes a control unit 2 which with a GPS receiver 3 is coupled. In addition, the control unit 2 with a speed sensor 4th coupled to determine the wheel speeds. In the control unit 2 is a tire size determining unit 5 arranged with a vehicle speed determination unit 6th is coupled. In addition, both are units 5 and 6th with a storage unit 7th connected.

In connection with 2 an embodiment of the method according to the invention is to be explained. In block 100 the quality of the from the GPS receiver 2 received GPS signal estimated and estimated the traffic conditions. In block 110 it is checked whether all conditions correspond to the specifications. If this is not the case, a return is made to block 100. If all the conditions are properly present, then in block 120 the tire size determination unit 5 the implemented real-time program started. The actual tire size R _{cal of} the vehicle thus becomes in block 130 1 calculated. Subsequently, the amount of a difference between the actually determined tire size R _cal and a predetermined tire size R _current stored in the memory unit 7th is stored, formed. The amount of this difference is compared in block 140 with a predetermined threshold value β. If this difference in amount is greater than the threshold value β, there is a transition to block 150, where the determined actual tire size R _cal instead of the currently stored tire size R _current in the memory unit 7th is filed. The vehicle speed determination unit 6th now determines the vehicle speed with the new actually determined tire size R _cal . The real-time program is then ended. The program is also terminated in block 160 if the amount of the tire size difference determined in block 140 is less than the threshold value.

The real-time program for determining the actual tire size R _{cal will} be explained in more detail below. In general, there are many sources of influence on the calculation of the tire size. Some of them, such as temperature and humidity, are very small and can therefore be disregarded. Other effects such as the accuracy of a speed sensor, the GPS accuracy, a load difference and an estimation error when changing lanes are taken into account in the calculation. The tire size R _cal is calculated as follows: $${\mathrm{R.}}_{cal}=\frac{\mathrm{S.}+{\epsilon }_{G\mathrm{P.}\mathrm{S.}}+n\cdot {\epsilon }_{\mathrm{C.}\mathrm{L.}}}{2\pi N\left(1+{\epsilon }_N\right)}+\Delta {\mathrm{R.}}_{\mathrm{F.}\mathrm{L.}}$$

This equation 1 is simplified in equation 2. $${\mathrm{R.}}_{cal}=\frac{\mathrm{S.}}{2\pi N}\cdot \frac{1}{1+{\epsilon }_N}\left(1+\frac{{\epsilon }_{G\mathrm{P.}\mathrm{S.}}}{\mathrm{S.}}+\frac{n\cdot {\epsilon }_{\mathrm{C.}\mathrm{L.}}}{\mathrm{S.}}\right)+\Delta {\mathrm{R.}}_{\mathrm{F.}\mathrm{L.}}$$

The number of revolutions N is calculated using the approximate equation 3 linearized. $$\frac{1}{1+{\epsilon }_N}\approx 1-{\epsilon }_N$$

$$R_{cal}=\frac{S}{2\pi N}\cdot \left(1-{\epsilon }_N+\frac{{\epsilon }_{GPS}}{S}-\frac{{\epsilon }_N\cdot {\epsilon }_{GPS}}{S}+\frac{n\cdot {\epsilon }_{CL}}{S}-\frac{n\cdot {\epsilon }_N\cdot {\epsilon }_{CL}}{S}\right)+\Delta R_{FL}$$

It results: $${\mathrm{R.}}_{cal}=\frac{\mathrm{S.}}{2\pi N}\left(1-{\epsilon }_N\right)\left(1+\frac{{\epsilon }_{G\mathrm{P.}\mathrm{S.}}}{\mathrm{S.}}+\frac{n\cdot {\epsilon }_{\mathrm{C.}\mathrm{L.}}}{\mathrm{S.}}\right)+\Delta {\mathrm{R.}}_{\mathrm{F.}\mathrm{L.}}$$

$${\mathrm{R.}}_{cal}=\frac{\mathrm{S.}}{2\pi N}\cdot \left(1-{\epsilon }_N+\frac{{\epsilon }_{G\mathrm{P.}\mathrm{S.}}}{\mathrm{S.}}-\frac{{\epsilon }_N\cdot {\epsilon }_{G\mathrm{P.}\mathrm{S.}}}{\mathrm{S.}}+\frac{n\cdot {\epsilon }_{\mathrm{C.}\mathrm{L.}}}{\mathrm{S.}}-\frac{n\cdot {\epsilon }_N\cdot {\epsilon }_{\mathrm{C.}\mathrm{L.}}}{\mathrm{S.}}\right)+\Delta {\mathrm{R.}}_{\mathrm{F.}\mathrm{L.}}$$

S

Distanz, welche durch das Fahrzeug gefahren wurde

εGPS

Genauigkeitszustand des GPS-Signals

εCL

Fehlerabschätzung des Spurwechsels

εN

Genauigkeit des Drehzahlsensors

n

Anzahl der Fahrspurwechsel

N

Umdrehungszahl

ΔRFL

Lastabhängige Fehlerabschätzung

In these equations:

S.

Distance driven by the vehicle

εGPS

Accuracy status of the GPS signal

εCL

Error estimation of the lane change

εN

Speed sensor accuracy

n

Number of lane changes

N

Number of revolutions

ΔRFL

Load-dependent error estimation

$$R_{real}=\frac{S}{2\pi N}$$

In equation 5, the parameters ε _N , ε _CL and ε _{GPS are} less than 1, which is why the product of two of these parameters is very small and can be neglected in further consideration.

$${\mathrm{R.}}_{real}=\frac{\mathrm{S.}}{2\pi N}$$

If equation 7 is inserted into equation 6, the following results for the tire size R _cal : $${\mathrm{R.}}_{cal}={\mathrm{R.}}_{real}\cdot \left(1-{\epsilon }_N+\frac{{\epsilon }_{G\mathrm{P.}\mathrm{S.}}}{\mathrm{S.}}+\frac{n\cdot {\epsilon }_{\mathrm{C.}\mathrm{L.}}}{\mathrm{S.}}+\frac{\Delta {\mathrm{R.}}_{\mathrm{F.}\mathrm{L.}}}{{\mathrm{R.}}_{real}}\right)$$

In order to obtain a high level of accuracy, an accurate speed sensor should be selected. The accuracy should not exceed 0.5%. The effect of the GPS signal depends on the distance traveled and the quality of the GPS signal. In general, the standard GPS system (SPS) has an accuracy of 22.5 m. A better GPS signal Precise Positioning Service (PPS) provides an accuracy of 9 m. In addition, with an additional differential measuring system, the accuracy can be reduced to 0.02 m to be improved. In normal use, when the signal quality is 11.7 m, the impact of GPS inaccuracy can be reduced to 0.5% after driving a distance of 2340 m.

die Fehlerart beschrieben werden als $$\frac{n\cdot {\epsilon }_{CL}}{S}=k\left(S\right)\cdot {\epsilon }_{CL}$$

wobei gilt:

Sw

Distanz in Fahrtrichtung während des Spurwechsels,

SL

Distanz senkrecht zu der Fahrtrichtung,

SRW

Tatsächlicher Weg für den Spurwechsel

SRWR

Vereinfachter Weg für den Spurwechsel

Vsclar

Schätzfaktor für den real geschätzten Weg zum tatsächlichen Weg

εCLM

Genauigkeit des Drehratensensor.

In 3 is a basic diagram for a lane change of the vehicle. Assuming that the frequency of the lane change K (S) is below a limit value, for example t / km, then you can use $$\text{n}=\text{K}\left(\text{S.}\right)*\text{s}$$

the type of error can be described as $$\frac{n\cdot {\epsilon }_{\mathrm{C.}\mathrm{L.}}}{\mathrm{S.}}=k\left(\mathrm{S.}\right)\cdot {\epsilon }_{\mathrm{C.}\mathrm{L.}}$$

where:

Sw

Distance in the direction of travel while changing lanes,

SL

Distance perpendicular to the direction of travel,

SRW

Actual way to change lanes

SRWR

Simplified way to change lanes

Vsclar

Estimation factor for the real estimated route to the actual route

εCLM

Yaw rate sensor accuracy.

The error s _CL describes the actual distance between the drive and the measured distance $${\epsilon }_{\mathrm{C.}\mathrm{L.}}={\mathrm{S.}}_{\mathrm{W.}}-{\mathrm{S.}}_{\mathrm{R.}\mathrm{W.}}\cdot \frac{{\mathrm{S.}}_{sOll}-{\mathrm{S.}}_{ist}}{{\mathrm{S.}}_{sOll}}={\mathrm{S.}}_{\mathrm{W.}}-{\mathrm{S.}}_{\mathrm{R.}\mathrm{W.}}\cdot \left(1+{\epsilon }_{\mathrm{C.}\mathrm{L.}\mathrm{M.}}\right)$$

On the other hand, the real driving distance S _RW can be approximated as S _RWR: $${\epsilon }_{\mathrm{C.}\mathrm{L.}}={\mathrm{S.}}_{\mathrm{W.}}-V_{sklar}\cdot {\mathrm{S.}}_{\mathrm{R.}\mathrm{W.}\mathrm{R.}}\cdot \left(1+{\epsilon }_{\mathrm{C.}\mathrm{L.}\mathrm{M.}}\right)={\mathrm{S.}}_{\mathrm{W.}}-V_{sklar}\cdot \sqrt{{\mathrm{<figure-callout\; id="2"\; label="S.\; \omega "\; filenames="DE102019110805B4\_0026.png"\; state="\{\{state\}\}">S.</figure-callout>}}_{\omega }^{}+{\mathrm{S.}}_{\mathrm{L.}}^2}\cdot \left(1+{\epsilon }_{\mathrm{C.}\mathrm{L.}\mathrm{M.}}\right)$$

If equation 12 is used in equation 11, the result is: $$\frac{n\cdot {\epsilon }_{\mathrm{C.}\mathrm{L.}}}{\mathrm{S.}}=k\left(\mathrm{S.}\right)\cdot {\epsilon }_{\mathrm{C.}\mathrm{L.}}=k\left(\mathrm{S.}\right)\cdot \left({\mathrm{S.}}_{\mathrm{W.}}-V_{sklar}\cdot \sqrt{{\mathrm{<figure-callout\; id="2"\; label="S.\; \omega "\; filenames="DE102019110805B4\_0026.png"\; state="\{\{state\}\}">S.</figure-callout>}}_{\omega }^{}+{\mathrm{S.}}_{\mathrm{L.}}^2}\cdot \left(1+{\epsilon }_{\mathrm{C.}\mathrm{L.}\mathrm{M.}}\right)\right)$$

In one embodiment, at a distance S _L perpendicular to the lane of 3.5 m and a distance Sw in the direction of travel during the lane change of 50 m, and a frequency of the lane change K (S) of 1 / km, a scaling _factor V sclar = 1 , 1 and the accuracy of the yaw rate sensor ε _CLM of 1%, the effect of the estimation error is reduced to 0.75%.

In addition, a load difference has a great influence on the determination of the tire size, since the actual tire deformation changes are changed by a load change. In 4th shows a basic illustration of the sizes for a deformation of the tire. The relationship between tire deformation and load is approximated by Equation 14. $${\mathrm{F.}}_{\mathrm{L.}}=2p_{0}b\sqrt{2rx-{\mathrm{<figure-callout\; id="2"\; label="x"\; filenames="DE102019110805B4\_0026.png"\; state="\{\{state\}\}">x</figure-callout>}}^2}$$

$$\begin{array}{l}x=r-\sqrt{r^2-\frac{F_L^2}{4P_0^2{b}^2}}=0\\ r-x=\sqrt{r^2-\frac{F_L^2}{4P_0^2{b}^2}}.\end{array}$$

wobei

FL

die Last auf dem Fahrzeugreifen,

FLo

die Anfangslast auf dem Fahrzeug,

po

den Anfangsdruck,

b

die Breite des Reifens,

x

die Deformation des Reifens,

x0

die Anfangsdeformation,

r

Radius des undeformierten Reifens

ΔFL

Lastdifferenz und

α

Koeffizient der Lastdifferenz

darstellt.In Equation 15, this Equation 14 is written as an equivalent $$\begin{array}{l}{\mathrm{F.}}_{\mathrm{L.}}^2=\mathrm{4th}{p}_0^2{b}^2\left(rx-x^2\right)\\ x^2-2rx+\frac{{\mathrm{F.}}_{2}2}{\mathrm{4th}{\mathrm{P.}}_0^{2}b2}=0\\ x=\frac{1}{2}\cdot 2r\pm \sqrt{\mathrm{4th}{r}^2-\frac{\mathrm{4th}{\mathrm{F.}}_{\mathrm{L.}}^2}{\mathrm{4th}{\mathrm{P.}}_0^2{b}^2}}=0\end{array}$$

$$\begin{array}{l}x=r-\sqrt{r^2-\frac{{\mathrm{F.}}_{\mathrm{L.}}^2}{\mathrm{4th}{\mathrm{P.}}_0^2{b}^2}}=0\\ r-x=\sqrt{r^2-\frac{{\mathrm{F.}}_{\mathrm{L.}}^2}{\mathrm{4th}{\mathrm{P.}}_0^2{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="DE102019110805B4\_0026.png"\; state="\{\{state\}\}">b</figure-callout>}}^2}}.\end{array}$$

in which

FL

the load on the vehicle tire,

FLo

the initial load on the vehicle,

po

the initial pressure,

b

the width of the tire,

x

the deformation of the tire,

x0

the initial deformation,

r

Radius of the undeformed tire

ΔFL

Load difference and

α

Coefficient of the load difference

represents.

beschrieben ist. Die Änderung der Last wird in Gleichung 18 beschrieben. $$\mathrm{\Delta }{F}_L=F_L-F_{L0}=\alpha F_{L0}-F_{L0}=\left(\alpha -1\right)F_{L0}$$

α stellt dabei den Faktor dar, um wieviel die Anfangslast verglichen wird. Werden die Gleichungen 16 und 18 in die Gleichung 17 eingesetzt, ergibt sich $$\mathrm{\Delta }{R}_{FL}=\frac{F_{L0}}{2p_{0}b\sqrt{4P_0^2{b}^2{r}^2-F_{L0}^2}}\left(1-\alpha \right)F_{L0}$$

Since the deformation x of the tire must be smaller than the radius r of the tire, the solution is given in equation 16, where the change in the radius r from the current load S _L to the initial load F _Lo in $$\mathrm{\Delta }{\mathrm{R.}}_{\mathrm{F.}\mathrm{L.}}={\frac{d\left(r-x\right)}{d{\mathrm{F.}}_{\mathrm{L.}}}|}_{{\mathrm{F.}}_{\mathrm{L.}}={\mathrm{F.}}_{\mathrm{L.}}0}\mathrm{\Delta }{\mathrm{F.}}_{\mathrm{L.}}$$

is described. The change in load is described in Equation 18. $$\mathrm{\Delta }{\mathrm{F.}}_{\mathrm{L.}}={\mathrm{F.}}_{\mathrm{L.}}-{\mathrm{F.}}_{\mathrm{L.}0}=\alpha {\mathrm{F.}}_{\mathrm{L.}0}-{\mathrm{F.}}_{\mathrm{L.}0}=\left(\alpha -1\right){\mathrm{F.}}_{\mathrm{L.}0}$$

α represents the factor by how much the initial load is compared. If equations 16 and 18 are inserted into equation 17, the result is $$\mathrm{\Delta }{\mathrm{R.}}_{\mathrm{F.}\mathrm{L.}}=\frac{{\mathrm{F.}}_{\mathrm{L.}0}}{2p_{0}b\sqrt{\mathrm{4th}{\mathrm{P.}}_0^2{b}^2{r}^2-{\mathrm{F.}}_{\mathrm{L.}0}^2}}\left(1-\alpha \right){\mathrm{F.}}_{\mathrm{L.}0}$$

Equation 19 is shown in simplified form in. $$\mathrm{\Delta }{\mathrm{R.}}_{\mathrm{F.}\mathrm{L.}}=\frac{\left(1-\alpha \right){\mathrm{F.}}_{\mathrm{L.}0}^2}{2p_{0}b\sqrt{\mathrm{4th}{\mathrm{P.}}_0^2{b}^2{r}^2-\mathrm{4th}{\mathrm{P.}}_0^2{b}^2\left(2r{x}_0-x_0^2\right)}}=\frac{\left(1-\alpha \right){\mathrm{F.}}_{\mathrm{L.}0}^2}{\mathrm{4th}{p}_0^2\left|r-x_0\right|}=\frac{\left(1-\alpha \right)\cdot \left(2r{x}_0-x_0^2\right)}{r-x_0}$$

The actual radius of the tire is described by $${\mathrm{R.}}_{real}-r-x_0$$

If equation 21 is entered in equation 20, a normalized equation 22 is obtained. $$\frac{\mathrm{\Delta }{\mathrm{R.}}_{\mathrm{F.}\mathrm{L.}}}{{\mathrm{R.}}_{real}}=\frac{\left(1-\alpha \right)\cdot \left(2r{x}_0-x_0^2\right)}{{\left(r-x_0\right)}^2}=\left(1-\alpha \right)\frac{2\frac{x_0}{r}-{\left(\frac{x_0}{r}\right)}^2}{{\left(1-\frac{x_0}{r}\right)}^2}$$

This means that the actual tire deformation changes depend on the load change and the initial deformation. Assuming that the empty vehicle weighs 1 t with one passenger and the current vehicle has a weight of 1.2 t, since 4 people have been seated in the vehicle, the coefficient of the load difference is α = 1.2. The initial deformation of the tire is 2%, so a relative change in deformation change of 0.8 is expected. This error can be prevented with a precise weight sensor.

When equation 8 is transformed, the total relative measurement error of the system described can be represented in $${\epsilon }_{\mathrm{R.}}=\frac{{\mathrm{R.}}_{cal}-{\mathrm{R.}}_{real}}{{\mathrm{R.}}_{real}}={\epsilon }_N+\frac{{\epsilon }_{G\mathrm{P.}\mathrm{S.}}}{\mathrm{S.}}+\frac{n\cdot {\epsilon }_{\mathrm{C.}\mathrm{L.}}}{\mathrm{S.}}+\frac{\mathrm{\Delta }{\mathrm{R.}}_{\mathrm{F.}\mathrm{L.}}}{{\mathrm{R.}}_{real}}$$

z. B. $${\epsilon }_N+\frac{{\epsilon }_{GPS}}{S}+\frac{n\cdot {\epsilon }_{Cl}}{S}+\frac{\mathrm{\Delta }{R}_{FL}}{R_{real}}<2.4\%$$

After changing tires, the tire size can be increased or decreased by approximately 1 inch. Therefore, as shown in Equation 24, the measurement system requires ½ inch accuracy. $${\epsilon }_{\mathrm{R.}}<\frac{1}{2}incH=\frac{in\mathrm{<figure-callout\; id="2"\; label="c\; H"\; filenames="DE102019110805B4\_0026.png"\; state="\{\{state\}\}">c</figure-callout>}H}{2\ast {\mathrm{R.}}_{real}}=\mathrm{A.}ccuracy$$

z. B. $${\epsilon }_N+\frac{{\epsilon }_{G\mathrm{P.}\mathrm{S.}}}{\mathrm{S.}}+\frac{n\cdot {\epsilon }_{\mathrm{C.}l}}{\mathrm{S.}}+\frac{\mathrm{\Delta }{\mathrm{R.}}_{\mathrm{F.}\mathrm{L.}}}{{\mathrm{R.}}_{real}}<2.4\%$$

5 shows the relationship between the tire size and the required distal accuracy. If the tire size is 17 inches, an accuracy of 2.4% is assumed, assuming that in the last part of this description the total relative system error was expected to be 2.37.

List of reference symbols

1

vehicle

2

Control unit

3

GPS receiver

4th

Speed sensor

5

Tire size determination unit

6th

Vehicle speed determination unit

7th

Storage unit

Claims (8)

Method for determining an actual tire size of the tires of a vehicle, the actual tire size of the vehicle being determined while the vehicle is traveling with the aid of a GPS signal by adding a sum of the distance traveled by the vehicle and an accuracy of the GPS signal by the number the number of revolutions of the wheels is divided, characterized in that the actual tire size is determined as a function of a lane evaluation when the vehicle changes lanes, an error between a real and an approximate driving distance when changing lanes is taken into account when determining the actual tire size. Procedure according to Claim 1 , characterized in that a tire size stored in the vehicle is corrected with the actual tire size. Procedure according to Claim 2 , characterized in that the stored tire size is replaced by the actual tire size if an amount of a difference between the stored and the actual tire size exceeds a predetermined threshold value. Procedure according to Claim 3 , characterized in that a current driving speed of the vehicle is determined with the actual tire size. Method according to at least one of the preceding claims, characterized in that before the actual tire size is determined, the GPS signal is checked for the presence of a predetermined accuracy. Method according to at least one of the preceding claims, characterized in that the actual tire size is determined as a function of the accuracy of a speed sensor. Method according to at least one of the preceding Claims 1 to 5 , characterized in that the actual tire size is determined as a function of a load difference on the tire. Procedure according to Claim 1 , characterized in that an evaluation error is taken into account in the lane evaluation.

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