Determining the circumference of a vehicle wheel

Abstract

The invention relates to determining a wheel circumference (R) of a vehicle wheel (11) for a vehicle (10). An intrinsic speed (v) of the vehicle (10) is determined using a radar Doppler measurement method. Furthermore, a characteristic value (K) of the vehicle wheel (11), which is associated with one wheel revolution, is determined. The wheel circumference (R) is determined as a function of the characteristic value (K) and the intrinsic speed (v).

Description

[0001] The invention relates to a method for determining a wheel circumference of a vehicle wheel for a vehicle. Furthermore, the invention relates to a sensor device for determining a wheel circumference of a vehicle wheel for a vehicle. Finally, the invention also relates to a vehicle with a corresponding sensor device.

[0002] Driver assistance systems are used in modern vehicles to automate driving tasks or maneuvers, or at least to support the driver in their tasks. One example is a parking assistant, which can automatically park and / or guide a vehicle in a parking space. In order to control the vehicle, the driver assistance system must be able to estimate the vehicle's position in space or in its surroundings. This estimation is based, for example, on the principle of odometry. This system counts the number of wheel revolutions while the vehicle is moving, thereby determining the distance traveled. In order for the wheel revolutions to be counted correctly, the circumference of the vehicle's wheel must be known.

[0003] US 2016 / 0200155 A1, for example, discloses a method for determining a dynamic wheel radius for a vehicle wheel by determining the vehicle's travel distance based on GPS data and then dividing the travel distance by the number of wheel revolutions. The number of wheel revolutions can be determined, for example, using so-called "wheel ticks."

[0004] A disadvantage of the methods known to date is that estimating the wheel circumference is generally inaccurate. This is due, for example, to the relatively high error tolerance of GPS data when determining a vehicle's route or speed. If the inaccurate wheel circumference is then used for odometric position estimation, it can lead to incorrect calculations of the vehicle's actual position relative to its surroundings. This can lead to the distance to a curb being chosen too large or too small when parking, for example.

[0005] The object of the present invention is to estimate a wheel circumference for a vehicle wheel as precisely as possible.

[0006] The problem is solved by the subject matter of the independent patent claims. Advantageous developments of the invention are disclosed by the dependent patent claims, the description, and the figures.

[0007] The invention is based on the discovery that a vehicle's radar sensor system, used, for example, for environmental monitoring, can be used to calculate wheel size. Radar-based measurement methods have the advantage of allowing the vehicle's own speed or vehicle speed to be determined with particular precision. This highly accurate own speed can then be calculated with the wheel revolutions to determine the wheel circumference.

[0008] To this end, according to one aspect, the invention proposes a method for determining a wheel circumference of a vehicle wheel for a vehicle. In this method, an intrinsic speed of the vehicle is determined or ascertained using a radar Doppler measurement method. Furthermore, a characteristic value of the vehicle, which is associated with a wheel revolution, is determined or ascertained. Depending on the characteristic value and the intrinsic speed, the wheel circumference is then determined or calculated. Preferably, the characteristic value and the intrinsic speed are taken into account with reference to the same time period and / or the same route section.

[0009] Using radar Doppler measurement offers the advantage of being able to determine or estimate the wheel circumference with exceptional accuracy and precision. This effectively prevents miscalculations of the vehicle's position relative to its surroundings. A driver assistance system that uses the wheel circumference to perform driving tasks or maneuvers can thus be designed more reliably.

[0010] In this context, the wheel circumference refers specifically to a measure of the size or dimension of a vehicle's wheel. The wheel circumference indicates, in particular, the wheel circumference as an absolute value. The wheel circumference can also be referred to as the outer circumference or rolling circumference. The wheel circumference thus describes the distance a wheel travels without slipping in one rotation.

[0011] As an alternative to the wheel circumference, it is of course conceivable to determine a characteristic value associated with the wheel circumference, i.e., a characteristic value from which the wheel circumference can be calculated or estimated, in an analogous manner. This characteristic value could, for example, be the radius of the vehicle wheel.

[0012] The radar Doppler measurement method is a well-known technique used, for example, to measure the speed of motor vehicles. To carry out the measurement method, a radar sensor system or radar sensor device with one or more wheel sensors is used. The respective wheel sensor is designed, in particular, as a so-called Doppler radar. This means that it is a radar sensor configured to exploit the Doppler effect, i.e., to incorporate it into the speed measurement. For speed measurement based on the Doppler effect, a radar beam or radar pulse can be emitted into the environment by the respective radar sensor, in particular an associated antenna. If an object is located in the radiation field generated by the antenna, part of the radar beam is reflected and can be received again by the radar sensor or another radar sensor.Due to the Doppler effect, the reflection of the radar beam from the object, particularly in the case of moving objects and / or moving vehicles, causes a change in the frequency of the radiation, the magnitude of which is proportional to the speed of the vehicle and / or object. A frequency difference between the emitted and reflected radiation can therefore be used as a measure of the vehicle's speed.

[0013] The radar Doppler measurement method thus provides the vehicle's own speed as the measurement result. The own speed is preferably specified as a relative speed to the surrounding object. The object could be, for example, another vehicle, a person, traffic infrastructure, or another type of obstacle in the surrounding area, such as a curb.

[0014] The characteristic value assigned to the wheel revolution indicates, in particular, a distance traveled or a path traveled for a complete and / or partial rotation of the wheel relative to the road surface. The characteristic value can thus provide information about the rotational speed of the vehicle wheel. The characteristic value can be determined, for example, by measuring the speed or by determining so-called wheel ticks. Specific examples of the characteristic value will be described in more detail later.

[0015] The invention includes embodiments which provide additional advantages.

[0016] According to one embodiment, to determine the wheel circumference, the characteristic value and the vehicle's own speed are compared. The comparison may, for example, include determining or calculating a ratio of the vehicle's own speed relative to the characteristic value. That is, the vehicle's own speed may be divided by the characteristic value to calculate the wheel circumference.

[0017] According to one embodiment, to determine the wheel circumference, a distance traveled is determined from the vehicle's own speed over a predetermined period of time. The resulting result is compared with the characteristic value determined for the distance.

[0018] The distance traveled can be determined, for example, by integrating the vehicle's own speed over a predetermined period of time. This means that the vehicle's own speed is used to determine how far or how far the vehicle has traveled. A characteristic value for the distance traveled is also determined or measured, such as the speed or the number of ticks. The result of this calculation is the number of wheel revolutions per distance traveled, from which the wheel circumference can be determined.

[0019] According to one embodiment, the characteristic value is determined as a rotational speed of the vehicle wheel. Rotational speed refers, in particular, to one complete revolution per unit of time. The rotational speed is specified, for example, in RPM (revolutions per minute) or RPS (revolutions per second). It is therefore a measure of the rotational speed of the vehicle wheel.

[0020] A wheel sensor, such as a speed sensor or a speed sensor, can be used to determine the rotational speed. The radar sensor is assigned to or mounted on the vehicle wheel. The rotational speed measurement with such a wheel sensor can be based on optical and / or inductive measuring principles, for example.

[0021] According to one embodiment, the characteristic value is determined as a number of circular segments into which the vehicle wheel is divided, which pass a wheel sensor per unit of time as the vehicle wheel rolls. As the wheel passes the wheel sensor, a measurement signal is generated at the wheel sensor that is assigned to a specific path traveled by the vehicle wheel while rolling. The path traveled corresponds to the length of the circular arc of the respective circular segment. The measurement signal is also referred to as a wheel tick. A wheel tick thus corresponds to a measurement signal detected by a sensor when the vehicle wheel rotates or rolls through a predefined angular range specified by the respective circular segment. Depending on the number of wheel ticks detected, the number of complete or partial revolutions of the wheel can be deduced and the wheel circumference can be calculated back.To detect the wheel ticks, for example, for a predetermined period of time, the wheel sensor can detect an incremental encoder.

[0022] According to one embodiment, the characteristic value is determined individually for each vehicle wheel of a vehicle with multiple vehicle wheels. Preferably, the wheel circumference and / or the vehicle's own speed are also determined individually for each vehicle wheel. For this purpose, at least one of the aforementioned radar sensors can be assigned to each vehicle wheel. This has the advantage that all vehicle wheels are considered individually, for example, to estimate the vehicle's position. This allows for particularly precise position determination.

[0023] According to one embodiment, the characteristic value is determined as the average value of all vehicle wheels of a vehicle with multiple vehicle wheels. Preferably, the wheel circumference and / or the vehicle's own speed are also determined analogously as the average value of the vehicle wheels. This results in the advantage that, for example, only one value, rather than multiple values, need be considered for the vehicle wheels when determining the position. Overall, this reduces the computational effort.

[0024] According to one embodiment, a position, i.e., a position and / or orientation of the vehicle in an environment, is estimated based on the determined wheel circumference. The aim is therefore to determine the location and orientation of the vehicle in space. The wheel circumference, as described above, can be used to determine the distance traveled by the vehicle. If additional steering data of the vehicle is known, the direction of travel can also be determined. Such a method is used, for example, in odometry and is relevant for carrying out an automated or semi-automated parking process or maneuver.

[0025] According to one embodiment, for the radar Doppler measurement method, a radar pulse containing a sequential number of chirp signals is emitted to the surroundings of the vehicle. An echo pulse received upon reflection of the radar pulse from an object in the surroundings is subsequently evaluated. The evaluation includes determining a change in the pause times between the chirp signals and / or in the signal frequencies of the chirp signals in the radar pulse and the echo pulse.

[0026] A chirp signal is a signal whose signal frequency changes with the pulse duration. This means that the chirp signal contains several different signal frequencies that are emitted one after the other in a predefined order. For example, there are chirp signals with an increasing signal frequency (chirp up) or chirp signals with a descending signal frequency (chirp down). For environmental detection and analysis, two or more chirp signals are emitted sequentially, i.e. one after the other or at different times, particularly using a radar sensor. The group of emitted chirp signals forms the radar pulse. The emitted and received chirp signals, i.e. the echoes of the chirp signals on the object (echo pulse), are then compared with regard to their signal properties.In particular, it is examined, for example, how the signal frequencies of the individual chirp signals have changed and / or how the pauses between the chirp signals have changed. As described above, the change in the signal properties depends primarily on the Doppler effect. Thus, the change in the signal properties can be used to determine the airspeed.

[0027] The signal frequency of the chirp signals is preferably specified or standardized, in particular by legal requirements for radar use in vehicles. For example, signal frequencies in the range of 44 GHz, 77 GHz, or 79 GHz are permitted for vehicles. The pause times between the chirp signals are usually a few µs. In particular, the pause times are less than 50 µs, preferably less than 20 µs, in particular 10 µs. The number of chirp signals that are transmitted sequentially in a group or in a block with a radar pulse is, in particular, freely selectable. With a radar pulse duration of 6 ms, for example, 100 to 128 chirp signals can be combined or contained in one radar pulse.

[0028] According to one aspect, the invention also relates to a sensor device for determining a wheel circumference of a vehicle. The sensor device comprises a radar sensor device or radar sensor system configured to perform a radar Doppler measurement method for determining the vehicle's own speed.

[0029] For this purpose, the radar sensor device preferably comprises one or more radar sensors, each designed as Doppler radar sensors. Furthermore, the sensor device comprises at least one wheel sensor assigned to the vehicle wheel, wherein the wheel sensor is designed to determine a characteristic value of the vehicle wheel that is assigned to a wheel revolution. "Assigned" here means that the wheel sensor is, for example, attached to the vehicle wheel or fastened there in such a way that the characteristic value can be detected or measured using the wheel sensor. Furthermore, the sensor device comprises a computing unit designed to determine or calculate the wheel circumference as a function of the characteristic value and the vehicle's own speed.

[0030] If a vehicle with multiple wheels is provided, the sensor device preferably comprises one or more wheel sensors for each wheel. The respective radar sensor for measuring the characteristic value is assigned, in particular, to a driver assistance system of the vehicle for vehicle dynamics control (ESP / ESC) and to an anti-lock braking system of the vehicle.

[0031] The computing unit is preferably included in an electronic vehicle guidance system or driver assistance system of the vehicle. For example, the computing unit can be included in an electronic control unit (ECU) of the vehicle.

[0032] A computing unit can be understood, in particular, as a data processing device that contains a processing circuit. The computing unit can therefore, in particular, process data to perform computing operations. This may also include operations for performing indexed access to a data structure, for example, a look-up table (LUT).

[0033] The computing unit can in particular contain one or more computers, one or more microcontrollers and / or one or more integrated circuits, for example one or more application-specific integrated circuits (ASICs), one or more field-programmable gate arrays (FPGAs), and / or one or more single-chip systems (SoCs). The computing unit can also contain one or more processors, for example one or more microprocessors, one or more central processing units (CPUs), one or more graphics processing units (GPUs), and / or one or more signal processors, in particular one or more digital signal processors (DSPs). The computing unit can also contain a physical or virtual network of computers or other of the aforementioned units.

[0034] According to one aspect, the invention also relates to a vehicle with a corresponding sensor device, as described above by way of example. The vehicle is preferably designed as a motor vehicle, in particular as a passenger car or passenger bus, or as a truck or motorcycle.

[0035] Preferably, the vehicle comprises at least one driver assistance system or electronic vehicle guidance system to which the sensor device is assigned, or which uses the measurement results of the sensor device for the assigned driver assistance function. Preferably, the electronic vehicle guidance system is configured to perform or carry out a position estimation of the vehicle using the wheel circumference, in particular by means of odometry.

[0036] An electronic vehicle guidance system can be understood as an electronic system that is designed to guide a vehicle fully automatically or autonomously, in particular without requiring driver intervention. The vehicle automatically performs all required functions, such as steering, braking, and / or acceleration maneuvers, monitoring and detecting road traffic, and responding accordingly. In particular, the electronic vehicle guidance system can implement a fully automatic or fully autonomous driving mode of the motor vehicle according to level 5 of the SAE J3016 classification. An electronic vehicle guidance system can also be understood as an advanced driver assistance system (ADAS), which supports the driver in partially automated or semi-autonomous driving.In particular, the electronic vehicle guidance system can implement a partially automated or semi-autonomous driving mode according to levels 1 to 4 according to the SAE J3016 classification.

[0037] Further embodiments of the sensor device according to the invention and the vehicle according to the invention follow directly from the various embodiments of the method according to the invention, and vice versa. In particular, individual features and corresponding explanations as well as advantages relating to the various embodiments of the method according to the invention can be transferred analogously to corresponding embodiments of the sensor device according to the invention and the vehicle according to the invention. In particular, the sensor device according to the invention and the vehicle according to the invention are designed or programmed to carry out a method according to the invention.

[0038] The invention is explained in more detail below with reference to specific embodiments and associated schematic drawings. In the figures, identical or functionally equivalent elements may be provided with the same reference numerals. The description of identical or functionally equivalent elements may not necessarily be repeated for different figures.

[0039] Showing: Fig. 1 is a schematic representation of a vehicle with a sensor device for determining a wheel circumference of a vehicle wheel of the vehicle, and Fig. 2 a schematic process flow diagram for a method for determining the wheel circumference.

[0040] Fig. 1 shows a schematic representation of a vehicle 10 from a top view or bird's eye view. The vehicle 10 is, for example, a passenger car. Fig. 1 shows the vehicle 10 in an environment U. In the environment U, there are several parking spaces 17 or parking areas. Two of the parking spaces 17 are occupied. This means that other vehicles, for example, third-party vehicles 16, are parked or left there. Between the two occupied parking spaces 17 there is a free parking space 18. The vehicle 10 is to be parked in the free parking space 18. Parking is to take place automatically or automated. For this purpose, the vehicle 10 includes a driver assistance system 19 (not shown in detail) to assist the driver with parking. The driver assistance system 19 can be designed as a so-called parking assistant or as a so-called parking aid.

[0041] The driver assistance system 19 is intended to automatically perform or implement all functions required for parking assistance to perform a driving maneuver to park in the free parking space 18. This includes, for example, planning a trajectory T and following the trajectory T, which specifies a path or route for the vehicle to park, taking into account the environment U. In particular, it is a matter of recognizing or perceiving objects in the environment U, such as the other vehicles 16, as a limitation or obstacle to parking. The planning and implementation of functions for performing the driving maneuver shown as an example using a driver assistance system 19 for parking assistance are known per se.

[0042] To track the trajectory T, i.e., to implement the associated driving maneuvers, such as steering and / or acceleration and / or braking maneuvers, the driver assistance system 19 can, for example, use odometry. Odometry is a known method for estimating or determining a current situation, i.e., a position and / or orientation, for a vehicle in an environment. It is a method for distance measurement. In wheel-driven systems, such as the vehicle 10, which, for example, comprises four vehicle wheels 11, the number of wheel revolutions is counted or determined, in particular between two measurement times. In addition, for example, a steering angle of the individual vehicle wheels 11 can be taken into account, and thus the direction of the vehicle movement can be estimated or determined.

[0043] In order for the position estimation by means of the driver assistance system 19 to function correctly, it is important to know the wheel circumference R of the vehicle wheels 11 or at least one of the vehicle wheels 11. For this purpose, the vehicle 10 in the exemplary embodiment according to Fig. 1 shows a sensor device 12 for determining the wheel circumference R. Sensor device 12 may be included in the driver assistance system 19. Alternatively, the sensor device 12 or parts of the sensor device 12 may be included in another driver assistance system or other components of the vehicle 10.

[0044] The sensor device 12 comprises a radar sensor device 13, at least one wheel sensor 14, and a computing unit 15. In the present exemplary embodiment, four wheel sensors 14 are provided, each of the wheel sensors 14 being assigned to one of the vehicle wheels 11. The radar sensor device 13 comprises, in particular, at least one radar sensor, which is preferably designed as a so-called Doppler radar. Such a Doppler radar is known from automotive technology and is used, for example, for speed measurement using the Doppler effect. The computing unit 15 can, for example, be comprised of an electronic control unit (ECU). The ECU can, for example, take over the planning and implementation of the desired driving maneuvers for parking. The computing unit 15 can, for example, comprise one or more microcontrollers or microprocessors.

[0045] Based on Fig. 2, an exemplary method for operating the sensor device 12 for determining the wheel circumference R can be described in more detail. Fig. 2 shows a schematic process flow diagram with individual process steps for a method for determining the wheel circumference R.

[0046] In a step S1 of the method, an airspeed v of the vehicle 10 is determined using the radar Doppler measurement method. The radar Doppler measurement can be carried out, for example, using the wheel sensor device 13 of the vehicle. In this case, a radar pulse is transmitted or output to the surroundings U of the vehicle 10, for example, using the radar sensor. The radar pulse is preferably composed of several sequential chirp signals. In the chirp signals or chirps, the signal frequency changes over the pulse duration, for example in a chirp-up or a chirp-down. The signal frequency of the chirp signals is, for example, standardized for the use of radar in the vehicle sector and can, for example, be in a range of 49 GHz, 77 GHz or 79 GHz. Sequential here means that a predetermined pause time is present or maintained between two consecutive chirp signals.The pause time between two consecutive chirps can be, for example, 10 µs. A radar pulse can, for example, contain 128 such chirps and be emitted over a duration of 6 ms.

[0047] If an object, such as the other vehicles 16, is present in the environment U, the transmitted radar pulse can be reflected by the object. The respective radar sensor can receive the reflection of the radar pulse as an echo pulse. Due to the Doppler effect, the signal frequencies of the chirp signals and / or the pause times between the chirp signals are changed compared to the originally transmitted radar pulse, in particular compressed or stretched out. This change depends, in a known manner, on how the vehicle 10 moves relative to the object.

[0048] The wheel sensor device 13 can now evaluate this echo pulse based on the change in a known manner and compare the transmitted and received chirps with each other with regard to their signal properties. As a result of the comparison, the evaluation provides information about the vehicle's own speed v. The own speed v is, in particular, available as a relative speed.

[0049] In a step S2 of the method, a characteristic value K of the respective vehicle wheel 11, which is assigned to one wheel revolution, is determined. The respective characteristic value K is measured or recorded, for example, using the wheel sensor 14 assigned to the respective vehicle wheel 11. Depending on the design of the characteristic value K, the wheel sensor 14 can be designed, for example, as a rotational speed sensor or speed sensor or as a tick sensor, in particular as an incremental encoder. The characteristic value K can accordingly be measured, for example, as a rotational speed or in the form of so-called wheel ticks. The rotational speed is specified, for example, in RPM or RPS and describes one complete revolution of the respective vehicle wheel 11. The wheel ticks are a measured variable in which a number of predefined, preferably identical circular segments, into which the vehicle wheel 11 is divided, are measured, which pass the corresponding wheel sensor 14 per unit of time as the vehicle wheel 11 rolls.For example, the vehicle wheel 11 can be divided into 96 circular segments. Thus, at a center angle of approximately 3.7 degrees, one tick would be measurable for each. With conventional vehicle wheel dimensions, this corresponds to approximately 2 cm of traveled distance when rolling the respective vehicle wheel 11.

[0050] In the present exemplary embodiment, the characteristic value K is determined individually for each vehicle wheel 11. Alternatively, however, it is also possible to determine the characteristic value K as the average value of some or all vehicle wheels 11 of the vehicle 10.

[0051] The vehicle's own speed v and the respective characteristic value K are measured or determined, in particular, between two predetermined measurement times, i.e., within a predetermined period of time and / or along a predetermined route section while performing the driving maneuver. This allows the two variables to be compared with each other.

[0052] Finally, in a step S3, the wheel circumference R is determined or calculated. The calculation is preferably carried out by means of the computing unit 15. For this purpose, the respective characteristic value K and the vehicle's own speed v are transferred to the computing unit 15 as input variables. The computing unit 15 can determine the wheel circumference R or rolling circumference of the respective vehicle wheel 11, in particular as an absolute value, from the input variables according to a predetermined calculation rule. For this purpose, for example, the determined characteristic value K and the determined vehicle's own speed v can be compared with one another. The comparison can, for example, comprise relating the vehicle's own speed v to the characteristic value K, i.e. the wheel ticks or the rotational speed.For example, if an own speed v of 2 m / s is determined by means of the radar sensor system and the wheel sensors 14 output a wheel speed of one wheel rotation per second, the wheel circumference R can be calculated to be 2 m by forming the ratio.

[0053] In an alternative calculation method, it is possible, for example, to determine a distance traveled from the determined airspeed v for a specific period of time. To do this, the airspeed v can be integrated over the predetermined period of time. The resulting distance can be compared, for example, with the wheel ticks measured along this distance or the speed determined for this distance.

[0054] The computing unit 15 can now use the determined wheel circumference R, for example, to estimate the location, i.e., the position and / or orientation of the vehicle in the environment U. This means that the determined wheel circumference R can be passed on to or used by the driver assistance system for the parking assistance described above, particularly using odometry. The wheel circumference R determined from the described method is particularly accurate due to the use of Doppler radar. This effectively prevents misjudgments, for example, when determining the distance to objects in the environment U.

[0055] Overall, the embodiments show the estimation of a wheel circumference by using the radar Doppler measurement method. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2016 / 0200155 A1

[0003]

Claims

[1] Method for determining a wheel circumference (R) of a vehicle wheel (11) for a vehicle (10), characterized by , that an own speed (v) of the vehicle (10) is determined by means of a radar Doppler measuring method, a characteristic value (K) of the vehicle wheel (11) associated with one wheel revolution is determined, and the wheel circumference (R) is determined as a function of the characteristic value (K) and the vehicle's own speed (v). [2] Method according to claim 1, wherein the characteristic value (K) and the vehicle speed (v) are compared to determine the wheel circumference (R). [3] Method according to claim 1, wherein, in order to determine the wheel circumference (R) from the vehicle's own speed (v), a travelled distance is determined for a predetermined period of time, and the result is compared with the characteristic value (K) determined for the distance. [4] Method according to one of the preceding claims, wherein a rotational speed of the vehicle wheel (11) is determined as the characteristic value (K). [5] Method according to one of the preceding claims 1 to 3, wherein a number of circle segments into which the vehicle wheel (11) is divided is determined as the characteristic value (K), which pass a wheel sensor (14) per unit of time when the vehicle wheel (11) rolls. [6] Method according to one of the preceding claims, wherein the characteristic value (K) is determined individually for each vehicle wheel (11) of a vehicle (10) having a plurality of vehicle wheels (11). [7] Method according to one of the preceding claims, wherein the characteristic value (K) is determined as the mean value of all vehicle wheels (11) of a vehicle (10) with a plurality of vehicle wheels (11). [8] Method according to one of the preceding claims, wherein a position and / or orientation of the vehicle (10) in an environment (U) is estimated as a function of the determined wheel circumference (R). [9] Method according to one of the preceding claims, wherein for the radar Doppler measuring method, a radar pulse which sequentially contains a plurality of chirp signals is output to an environment (U) of the vehicle (10), and an echo pulse which is received upon reflection of the radar pulse at an object in the environment (U) is evaluated, wherein the evaluation comprises determining a change in pause times between the chirp signals and / or in signal frequencies of the chirp signals in the radar pulse and in the echo pulse. [10] Sensor device (12) for determining a wheel circumference (R) of a vehicle wheel (11) for a vehicle (10), characterized by a radar sensor device (13) which is designed to carry out a radar Doppler measuring method for determining an airspeed (v) of the vehicle (10), at least one wheel sensor (14) associated with the vehicle wheel (11), wherein the wheel sensor (14) is designed to determine a characteristic value (K) of the vehicle wheel (11) associated with a wheel revolution, and a computing unit (15) which is designed to determine the wheel circumference (R) as a function of the characteristic value (K) and the vehicle's own speed (v). [11] Vehicle (10) with a sensor device (12) according to claim 10.

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