DE10221900A1 - Determination of the radius of curvature of a road uses vehicle speed and yaw measurements in mathematical models to generate output for vehicle control - Google Patents

Abstract

The system has a vehicle speed sensor (2) and a yaw sensor (1), connected to a coupling unit (7), and a steering angle sensor (14). The signals are fed to a processor (8) that computes to a number of mathematical models to determine the radius of curvature of the road. The processor outputs to a multiplier (12) that also receives input from a correction unit (16).

Description

The present invention relates to a method and an apparatus for determining the Curvature of a lane of a vehicle.

Information about the curvature of the lane that a vehicle travels can be used in particular to help the driver when cornering support. For example, the curvature values in so-called adaptive Motor vehicle headlight systems are used to control a cornering light function. The light emission direction of the headlamp is at least partially in the direction of driven curve pivoted. The cornering light function is adaptive Motor vehicle headlight systems are particularly important because the illumination by the low beam of a conventional headlight in the curve is insufficient in many situations. Especially in the case of a left turn (in the following explanations, right-hand traffic assumed; in the case of left-hand traffic, the page information must be turned over accordingly) on the one hand the own lane is poorly lit and on the other hand the blinds Oncoming traffic stronger than in the right-hand bend. It is therefore important for the cornering light function knowing what the course of the road is like in order to get the best possible illumination of the road To reach the course of the road, while at the same time dazzling other road users should be avoided.

In addition, driver assistance systems are known in which various systems for Environment detection of a motor vehicle can be used. With the automatic Distance control is e.g. B. automatically compliance with a sufficient Safety distance to the vehicle in front regulated. With this system it is important to know whether the vehicle is currently cornering or not. With the known automatic distance control, the current curvature value for the vehicle Lane determined with the help of vehicle dynamics sensors. The models, which at the Calculation of the lane curvature are used as a basis, however, have the disadvantage on that they insufficiently curve the road ahead of the vehicle estimated.

This disadvantage can be remedied by calculation methods based on Use navigation data or video sensor data. Such video sensor data will obtained from images that are captured by video cameras and that Visualize vehicle surroundings. Using digital image processing, the obtained are Images evaluated so that the course of the road ahead of the vehicle can be determined can. A disadvantage of the video sensor systems, however, are the very high ones Hardware costs and the still insufficient image processing to determine the road.

For navigation systems, the current location of the vehicle, e.g. B. with a GPS (Global Positionings System) receiver determined. The location determined in this way becomes compared with the data of a digital map and thus the position of the vehicle determined. The exact data can then be obtained from the data on the digital map Determine the course of the road on the lane driven by the vehicle. A disadvantage of the Determination of curvature using navigation data is that it is too imprecise. This is because on the one hand due to the error in determining the current position using the GPS Receiver and on the other hand inaccuracies in digital maps. Furthermore short-term changes in the course of the road cannot be taken into account. In addition, the hardware costs of such a system are relatively high.

It is therefore the object of the present invention, a method and an apparatus to determine the curvature of a lane of a vehicle, with which is the most accurate possible determination of the curvature of the lane, the Process and the system should be feasible at the same time inexpensively.

According to the invention, this object is achieved by a method according to claim 1 and Device according to claim 12 solved, whereby advantageous training and further education result from the subclaims.

According to the invention, the curvature of the lane of the vehicle is determined using vehicle dynamic data calculated. The movement of a vehicle can be caused by different approximation models are described. It was examined which of these models under which conditions are particularly suitable for determining the Curvature of a lane is.

• 1. Der Schwerpunkt des Fahrzeugs liegt auf Fahrbahnhöhe. Hieraus folgt, dass die im Schwerpunkt angreifende Zentrifugalkraft keine Auswirkungen auf die Radlasten hat. Die zusätzliche Belastung der kurvenäußeren und die Entlastung der kurveninneren Räder werden vernachlässigt. Eine Drehbewegung um die Querachse des Fahrzeugs, das sog. Nicken, und eine Drehbewegung um die Längsachse des Fahrzeugs, das sog. Wanken, werden vernachlässigt.
• 2. Es liegt ein lineares System vor. Dies bedeutet, dass z. B. zwischen aufzubringender Seitenkraft und dem Schräglaufwinkel ein linearer Zusammenhang besteht. Diese Linearisierung ist insbesondere bei Querbeschleunigungen von unter 4 m/s² zulässig. Für Vorder- und Hinterachse gelten unterschiedliche Werte bezüglich der Reifensteifigkeit (Schräglaufbeiwert). Die Verformung der Lenkung wird ebenfalls linear angenommen. Ihre Steifigkeit wird mit der vorderen Reifensteifigkeit zur gesamten Steifigkeit der Vorderachse zusammengefasst.

The so-called single-track model at M. Mitschke is: dynamics of motor vehicles - driving behavior; 2nd edition, volume C, Springer Verlag, Berlin, 1990. To simplify this model, two assumptions are made:

• 1. The center of gravity of the vehicle is at road level. From this it follows that the centrifugal force acting in the center of gravity has no effect on the wheel loads. The additional load on the outside of the curve and the relief on the inside of the curve are neglected. A rotational movement about the transverse axis of the vehicle, the so-called nodding, and a rotational movement about the longitudinal axis of the vehicle, the so-called swaying, are neglected.
• 2. There is a linear system. This means that e.g. B. there is a linear relationship between the lateral force to be applied and the slip angle. This linearization is particularly permissible for lateral accelerations of less than 4 m / s ² . Different values apply to the tire stiffness (slip coefficient) for the front and rear axles. The deformation of the steering is also assumed to be linear. Their rigidity is combined with the front tire rigidity to form the total rigidity of the front axle.

In the single-track model, the curvature of the lane can be known Vehicle speed and known steering wheel angle are calculated, for the vehicle characteristic stiffness values are taken into account. In particular, the Tire stiffness and the deformation of the steering are taken into account.

When driving very slowly, the dynamics of the vehicle can be Model can be described. It is approximately assumed that none Lateral forces and therefore no slip angle occurs on the wheels. The wheels roll in this case without lateral slippage.

Finally, the driving dynamics can also be calculated in the so-called yaw rate model from the time Change of the so-called yaw angle and the center of gravity speed of the vehicle is determined become. The yaw angle describes the rotation of the vehicle around a vertical axis.

Furthermore, the curvature of the lane can be calculated directly from the steering wheel angle are, with this model, not as with the single-track model, corrections due the deformability of vehicle components. Finally, the Curvature from the direct measurement of the lateral acceleration and the Center of gravity speed of the vehicle can be calculated.

It has now been found that the curvature of the lane is particularly good Dependence on the current speed and yaw rate of the vehicle, d. H. the temporal Change the yaw angle, based on either the single track model or the so-called Can calculate yaw rate model. In the single-track model, the curvature is determined using the Vehicle speed and the measured steering wheel angle determined at which Yaw rate model using the measured yaw rate and the vehicle speed.

In the method according to the invention for determining the curvature of a lane of a vehicle you measure the vehicle speed, the yaw rate and the Steering wheel angle. From this one calculates depending on the speed and the measured yaw rate, the curvature of the lane using either a single-track model or using the yaw rate model.

According to an advantageous embodiment of the method according to the invention, if the vehicle speed below a limit speed and the measured Yaw rate is below a limit yaw rate, the curvature of the lane using the Single track model calculated, otherwise using the yaw rate model. The Limit speed is advantageously between 20 km / h and 40 km / h, preferably between 25 km / h and 35 km / h and particularly preferably at 30 km / h. The limit yaw rate is advantageously between 1.5 degrees / s and 2.5 degrees / s, preferably between 1.8 degrees / s and 2.2 Degrees / s and particularly preferred is 2 degrees / s.

It has been found that the single track model at speeds below this limit speeds and at low yaw rates below the specified Limit yaw rates provides particularly precise curvature values. if the Limit speed or the limit yaw rate is exceeded, the yaw rate model provides more accurate Curvature values, so that according to the invention it is used for calculating curvature is used.

When calculating the curvature according to the single-track model are preferred Variables that are characteristic of the rigidity of the vehicle are taken into account.

In the single-track model, the curvature can preferably be calculated using the following formula:


where v _{SP is} the center of gravity speed of the vehicle,
δ _{L is} the steering wheel angle,
i _{L is} the steering ratio,
l is the center distance,
l _V or l _{H is} the distance between the center of gravity and the front or rear axle,
m is the mass of the vehicle,
c _αV or c _{αH is} the stiffness of the front tires or the rear tires, and
c ' _{αV is} the stiffness of the front axle.

In the yaw rate model, the curvature can preferably be calculated using the vehicle speed and the measured yaw rate using the following formula:


where κ is the curvature, dψ / dt is the measured yaw rate and v _{SP is} the center of gravity speed of the vehicle.

The vehicle speed is preferably the center of gravity speed of the Vehicle. It is based on the measured wheel speeds of the vehicle and the Yaw rate determined.

Determined according to an advantageous development of the method according to the invention one uses the single-track model and / or the yaw rate model to curve one Lane of a vehicle traveling on a roadway of known curvature, and calculates one from the determined curvature and the known road curvature speed-dependent correction factor and corrects the calculated curvature in Dependence on the speed by the correction factor. The correction factor results is the quotient of the calculated curvature and known curvature. It has it turned out that the correction factor is in a range between 0.98 and 1.20 lies.

The device according to the invention for determining the curvature of a lane Vehicle includes a vehicle speed sensor, a yaw rate sensor and a steering wheel angle sensor. The device is characterized by a Decision unit that with the vehicle speed sensor and the yaw rate sensor is coupled and the vehicle speed and the measured as input signals Receives yaw rate, and by which depending on the speed and the measured yaw rate as a calculation model either a single track model or a Yaw rate model is selectable. Furthermore, the device is characterized by a Calculation device, by means of which the curvature of the Lane can be calculated, with the single-track model the curvature based on the Vehicle speed and the measured steering angle is determined and at Yaw rate model calculated based on the measured yaw rate and the vehicle speed becomes.

There is preferably a limit speed and a in the decision unit Limit yaw rate stored, the decision unit selecting the single-track model, if the speed is below the limit speed and the yaw rate is below the limit yaw rate, and otherwise selects the yaw rate model as the calculation model.

When selecting the single-track model, the calculation device preferably calculates the curvature using the following formula:


where v _{SP is} the center of gravity speed of the vehicle,
δ _{L is} the steering wheel angle,
i _{L is} the steering ratio,
l is the center distance,
l _V or l _{h is} the distance between the center of gravity and the front or rear axle,
m is the mass of the vehicle,
c _αV or c _{αH is} the stiffness of the front tires or the rear tires, and
c ' _{αV is} the stiffness of the front axle.

According to an advantageous development of the device according to the invention this further includes a storage unit in which correction factors are stored, whereby the correction factors from known and calculated curvatures as a function of Vehicle speeds result. The storage unit is with the Coupled calculation device, so that curvatures calculated by the calculation device can be corrected by the correction factors stored in the storage unit.

The with the inventive method and the inventive device Certain curvatures in the lane of a vehicle are particularly good at Use control of the cornering light function of an adaptive headlight system. In addition, the specific curvature in other driver assistance systems, such as z. B. an automatic distance control can be used.

The invention will now be described using exemplary embodiments with reference to Drawings explained.

Fig. 1 shows an embodiment of the inventive apparatus for determining the curvature schematically shows a traffic lane of a vehicle,

Fig. 2 shows the results of measurements for various curvature models for driving at different speeds,

Fig. 3 shows the calculated according to the single-track values for a test run, as a reference the actual radii of curvature, as well as amount-related error of the single-track model, and

FIG. 4 shows the values calculated for the curve radii for the same measurement run as that on which FIG. 3 is based, according to the yaw rate model, and the amount of error for the yaw rate model.

The device for determining the curvature of a lane of a vehicle comprises a yaw rate sensor 1 , a vehicle speed sensor 2 and a steering wheel angle sensor 14 . These sensors 1 , 2 and 14 determine the vehicle speed, the yaw rate and the steering wheel angle while driving.

As yaw rate sensor 1 , speed sensor 2 and steering wheel angle sensor 14 , sensors can be used, for example, which deliver the data for an electronic stability program (ESP) for driving dynamics control. Traditionally, the electronic stability program as driving dynamics sensors comprises a total of four wheel speed sensors, a steering wheel angle sensor, a yaw rate sensor and a lateral acceleration sensor. The data of this regulation are made available via a bus connection and can also be used in this way to calculate the lane curvature.

Vehicle speed is understood here to mean the speed v _{SP of} the vehicle's center of gravity. It is not measured directly, but determined from the signals of the individual wheel speeds. Since the trajectory of the vehicle's center of gravity is a superposition of a purely translational movement with the speed | v _SP | and the rotational movement with the angular velocity dψ / dt, which is the same for each point of the vehicle, the center of gravity velocity can be calculated as follows:

≙ _SP = ≙ _i - ≙ _i × d ≙ / dt

The yaw rate vector dψ / dt has only one component in the vertical direction. The distances r _i are the distances from the respective wheel contact point to the center of gravity of the vehicle.

The wheel speeds of the front axle must still be around the steering angle Getting corrected. Because the wheel speed sensors only share the speed in the Can measure the wheel plane, there is an error for the axis direction of the wheel but is advantageously corrected with a known float angle.

• 1. Die Bremse ist betätigt. Es wird in diesem Fall der Maximalwert der berechneten Schwerpunktgeschwindigkeiten für die einzelnen Räder ausgewählt:
  
  v_SP = max(v_SP1, v_SP2, v_SP3, v_SP4)
  
• 2. Die Bremse ist nicht betätigt. Es wird in diesem Fall der Mittelwert der berechneten Schwerpunktgeschwindigkeiten der nicht angetriebenen Achse verwendet:
  Die vorstehend erläuterte Berechnung der Fahrzeuggeschwindigkeit wird in der Einheit 5 durchgeführt. Als Eingangsgrößen dienen die Geschwindigkeiten der einzelnen Räder, die Gierrate sowie die Information, ob das Bremspedal betätigt ist. Als Ausgangsgröße überträgt die Einheit 5 die Fahrzeuggeschwindigkeit an die Einheiten 6, 11 und 14.

In addition to the measured values of the wheel speeds and the yaw rate, the speed sensor 2 also detects whether the brake pedal is actuated. A distinction is then made between two cases when calculating the center of gravity:

• 1. The brake is applied. In this case, the maximum value of the calculated center of gravity speeds for the individual wheels is selected:
  
  v _SP = max (v _SP1 , v _SP2 , v _SP3 , v _SP4 )
  
• 2. The brake is not applied. In this case the average of the calculated center of gravity speeds of the non-driven axis is used:
  The above-described calculation of the vehicle speed is carried out in the unit 5 . The speeds of the individual wheels, the yaw rate and the information as to whether the brake pedal is actuated serve as input variables. Unit 5 transmits the vehicle speed to units 6 , 11 and 14 as an output variable.

The yaw rate determined by the yaw rate sensor 1 is also transmitted to the unit 3 , in which the absolute amount of the yaw rate is formed. This absolute amount is finally transferred to unit 4 . In unit 4 , the measured yaw rate is compared with a limit yaw rate stored in unit 4 . If the measured yaw rate exceeds the stored limit yaw rate, the unit 4 transmits a corresponding signal to the unit 7 . Furthermore, the measured yaw rate is transmitted to the units 9 and 11 , as will be explained later. In the exemplary embodiments of the present invention, the limit yaw rate is in a range between 1.5 degrees / s and 2.5 degrees / s, preferably in a range between 1.8 degrees / s and 2.2 degrees / s and in a particularly preferred range The exemplary embodiment is the limit yaw rate 2 degrees / s.

In unit 6 , the vehicle speed calculated in unit 5 is compared with a limit speed and it is determined whether this limit speed is exceeded. If the limit speed is exceeded, the unit 6 transmits a corresponding signal to the unit 7 . In the exemplary embodiments of the present invention, the limit speed is in a range between 20 km / h and 40 km / h, preferably in a range between 25 km / h and 35 km / h and is 30 km / h in a particularly preferred exemplary embodiment.

In decision unit 7 , depending on the measured vehicle speed and the measured yaw rate, either the single-track model or the yaw rate model is selected as the calculation model for the curvature. If the measured or determined vehicle speed is below the limit speed and the measured yaw rate is below the limit yaw rate, the single-track model is selected, otherwise the yaw rate model. This selection is transmitted to the calculation device 8 .

The curvature of the lane is calculated in the calculation device 8 on the basis of the selected calculation model, ie either using the single-track model or the yaw rate model. If the calculation is based on the single-track model, the curvature in the computing unit 9 is calculated using the following formula:


where v _{SP is} the center of gravity speed of the vehicle,
δ _{L is} the steering wheel angle,
i _{L is} the steering ratio,
l is the center distance,
l _V or l _{H is} the distance between the center of gravity and the front or rear axle,
m is the mass of the vehicle,
c _αV or c _{αH is} the stiffness of the front tires or the rear tires, and
c ' _{αV is} the stiffness of the front axle.

For this purpose, the computing unit 9 receives the vehicle speed from the unit 5 and the steering wheel angle from the sensor 14 . The stiffness data for the respective vehicle are stored in a storage unit.

If the yaw rate model was selected as the calculation model, the curvature in connection with the unit 11 is calculated as follows:


where dψ / dt is the measured yaw rate, ie the temporal change in the yaw angle, and v _{SP is} the center of gravity speed of the vehicle. With this formula, the change in the slip angle β was neglected. It has been found that, for normal situations on country roads, the swimming angle β is in the range of | β | <0.5 to 0.8 degrees. The change in the slip angle dβ / dt is small in comparison to the yaw rate dψ / dt and can therefore be neglected.

Finally, the calculated curvatures can be corrected using correction factors. The correction factors depend on the speed. They are stored in the storage unit 14 for the single-track model and the yaw rate model. They were determined as follows:
For curvatures of roads with geometry known from road maps, the value ranges of the measured driving dynamics signals, ie in particular the yaw rate and the wheel speeds, and the most frequently occurring values are determined depending on the vehicle speed. These values are used to calculate the curvature and are related to the actual curvature. The quotient of the calculated curvature and the curvature taken from the road maps forms the correction factor. It has been found that the correction factor is in a range between 0.98 and 1.20. The correction factor of one is selected for areas of curvature and speed in which no measurement data is available.

The correction factors and the selection of the model are transmitted from the storage unit 14 and the unit 7 to the correction factor calculation unit 16 via the unit 15 . The calculated curvature is transmitted from the calculation device 8 to the multiplication unit 12 , from the correction factor calculation unit 16 the corresponding correction factor. These two values are multiplied together in the multiplication unit 12 and output to the unit 13 .

In order to be able to compare the calculation models for the curvature used in the exemplary embodiments of this invention, ie the single-track model and the yaw rate model, with other models for calculating the curvature, comparative measurements were carried out. A test vehicle was used for the measurements, in which the sensor signals wheel speeds, steering angle, yaw rate and lateral acceleration of the electronic stability program ESP, the driver brakes information "and the time signal of a watch were recorded. The measurements were carried out on a dry road and with a constant load. Before the start of the test New tires of the type "Continental ContiSportContact" and the dimension 205/55 R16 were put on and run in approx. 1000 km. Before each measurement, the tire pressure was checked and the tires warmed up. The vehicle-specific parameters required for the single-track model were measured Circle with a radius of R = 205 m. For a better understanding, the analyzed curvatures κ are represented as radius values R = 1 / κ. The circular path was traversed at speeds ranging between 10 km / h and 110 km / h. The results of the curvature or radius calculation The different curvature models are shown in FIG. 2. The mean values for the radius and the ranges of the standard deviation are shown. The area delimited by the standard deviation is indicated by the narrow bars.

Further measurements not shown here were made for radii in a range between 15 m and 305 m performed. For the single-track model, it follows that regardless of the curvature or the radius with little scatter is calculated for the speed becomes. The validity limit of the. Was only at high lateral accelerations> 0.65 g linear single-track model exceeded.

The Ackermann model only delivered accurate curvature values for the slowest speed at 13 km / h. For higher speeds, the curvatures calculated were very great inaccurate.

In the yaw rate model, deviations of the calculated curvature occur actual curvature especially at low speeds. At speeds, that correspond to a yaw rate of> 4 degrees / s are those with the yaw rate model The calculated curvature values are subject to only slight scatter and provide very good results Curvature values.

The curvature calculations with the lateral acceleration model are in most Cases significantly falsified. The radius is particularly useful for higher speeds calculated too small.

The wheel speed difference model of the rear axle calculates the radius at less Speed relatively accurate, but the standard deviation is very large. at At higher speeds, the radius is calculated too small, especially at large curve radii. The wheel speed difference model of the Front axle.

As a result of these measurements it turned out that the single track model and the Yaw rate model is particularly well suited for the curvature calculation, the Single track model at lower speeds and lower yaw rates is preferred and yaw rate at higher speeds and higher yaw rates.

In order to determine the preferred range of the single-track model and the yaw rate model more precisely, further measurements were carried out on a test track in which radii in the range from 400 to 500 m occurred. The results of these measurements and calculations are shown in FIG. 3 for the single-track model and in FIG. 4 for the yaw rate model . Curves 1 show the reference values for the radii on the test route, curve 2 of FIG. 3 shows the calculated radii on the basis of the Single track model, curve 2 of FIG. 4 shows the calculated radii on the basis of the yaw rate model, and curves 3 each show the amount of error of the single track model or the yaw rate model, represented as the difference between the actual curvature and the calculated curvature.

These measurements show greater differences between the two models than with the round trips.

The results of the measurements can be summarized as follows:
The single track model and the yaw rate model provide the most accurate curvature values. Taking into account the cross-slope of the road, the yaw rate model is the only one of the models examined that is insensitive to cross-slope. The yaw rate model has greater accuracy at higher yaw rates. For low speeds below a certain limit speed, the single-track model is therefore selected for the curvature calculation if the yaw rate is below a limit yaw rate. For yaw rates above the limit yaw rate and for speeds above the limit speed, the yaw rate model is used to calculate the curvature. The limit speed is advantageously in a range between 20 km / h and 40 km / h, preferably in a range between 25 km / h and 35 km / h and particularly preferably 30 km / h. The limit yaw rate is advantageously in a range between 1.5 degrees / s and 2.5 degrees / s, preferably in a range between 1.8 degrees / s and 2.2 degrees / s, and is particularly preferably 2 degrees / s.

Claims (16)

1. A method for determining the curvature of a lane of a vehicle, in which one measures the vehicle speed, the yaw rate and the steering wheel angle, characterized in that, depending on the measured vehicle speed and the measured yaw rate, the curvature of the lane using a single-track model using the vehicle speed and of the measured steering wheel angle or using a yaw rate model using the measured yaw rate and the vehicle speed. 2. The method according to claim 1, characterized, that if the vehicle speed is below a limit speed and the measured yaw rate are below a limit yaw rate, the curvature of the lane is calculated using the single-track model, otherwise using the yaw rate model. 3. The method according to claim 2, characterized, that the limit speed between 20 km / h and 40 km / h and the limit yaw rate is between 1.5 degrees / s and 2.5 degrees / s. 4. The method according to claim 1, characterized, that the limit speed between 25 km / h and 35 km / h and the limit yaw rate is between 1.8 degrees / s and 2.2 degrees / s. 5. The method according to claim 2, characterized, that the limit speed is 30 km / h and the limit yaw rate is 2 degrees / s. 6. The method according to any one of the preceding claims, characterized, that in the single-track model, in the calculation of the curvature, data which for the Rigidity of the vehicle are characteristic. 7. The method according to any one of the preceding claims, characterized in that the curvature is calculated in the single-track model using the following formula:


where v _{SP is} the center of gravity speed of the vehicle,
δ _{L is} the steering wheel angle,
i _{L is} the steering ratio,
l is the center distance,
l _V or l _{H is} the distance between the center of gravity and the front or rear axle,
m is the mass of the vehicle,
c _αV or c _{αH is} the stiffness of the front tires or the rear tires, and
c ' _{αV is} the stiffness of the front axle. 8. The method according to any one of the preceding claims, characterized in that the curvature is calculated using the yaw rate model using the following formula:


where κ is the curvature, dψ / dt is the measured yaw rate and v _{SP is} the center of gravity speed of the vehicle. 9. The method according to any one of the preceding claims, characterized, that the vehicle speed is the center of gravity of the vehicle and that the rotational speeds of the wheels of the vehicle are measured and the center of gravity of the vehicle from the speeds of the wheels and the yaw rate is calculated. 10. The method according to any one of the preceding claims, characterized, that the one in advance by means of the single track model and / or the yaw rate model Curvature of a lane of a vehicle that determines a lane is known Curvature travels, and from the specific curvature and the known Lane curvature calculated a speed-dependent correction factor, and that the calculated curvature depending on the speed by the correction factor is corrected. 11. The method according to claim 10, characterized, that the correction factor is the quotient of the calculated curvature and known curvature and that the correction factor is in a range between 0.98 and 1.20. 12. Device for determining the curvature of a lane of a vehicle, comprising a vehicle speed sensor ( 2 ), a yaw rate sensor ( 1 ) and a steering angle sensor ( 14 ), characterized by - A decision unit ( 7 ), which is coupled to the vehicle speed sensor ( 2 ) and the yaw rate sensor ( 1 ) and receives the vehicle speed (v _SP ) and measured yaw rate (dψ / dt) as input signals and by which depending the speed (v _SP ) and the measured yaw rate (dψ / dt), a single track model or a yaw rate model can be selected as the calculation model, and - A calculation device ( 8 , 9 , 11 ) by means of which the curvature of the lane can be calculated on the basis of the selected model, the curvature being determined on the basis of the vehicle speed and the measured steering angle in the single-track model and on the basis of the measured yaw rate and the vehicle speed in the case of the yaw rate model is calculated. 13. The apparatus according to claim 12, characterized in that a limit speed and a limit yaw rate is stored in the decision unit ( 7 ), and that the decision unit ( 7 ) selects the single-track model if the speed is below the limit speed and the yaw rate is below the limit yaw rate and otherwise select the yaw rate model as the calculation model. 14. The device according to claim 12 or 13, characterized in that the calculation device ( 8 , 9 ) calculates the curvature by the following formula when selecting the single-track model:


where v _{SP is} the center of gravity speed of the vehicle,
δ _{L is} the steering wheel angle,
i _{L is} the steering ratio,
l is the center distance,
l _V or l _{H is} the distance between the center of gravity and the front or rear axle,
m is the mass of the vehicle,
c _αV or c _{αH is} the stiffness of the front tires or the rear tires, and
c ' _{αV is} the stiffness of the front axle. 15. Device according to one of claims 12 to 14, characterized in that the calculation unit calculates the curvature using the following formula when selecting the vehicle speed and yaw rate as the calculation model:


where κ is the curvature, dψ / dt is the measured yaw rate and v _{SP is} the center of gravity speed of the vehicle. 16. The device according to one of claims 12 to 15, characterized in that a storage unit ( 14 ) is also contained, in which correction factors are stored, the correction factors resulting from known and calculated curvatures as a function of vehicle speeds, and that the storage unit ( 14 ) is coupled to the calculation unit ( 8 , 9 , 11 , 16 ), so that curvatures calculated by the calculation unit ( 8 , 9 , 11 , 16 ) can be corrected by the correction factors stored in the storage unit ( 14 ).