WO2015055429A1 - Method, control device, and system for identifying a profile depth of a profile of at least one tire - Google Patents

Abstract

The invention relates to a method for identifying a profile depth of a profile (1) of at least one tire (2) by means of an analysis of an oscillation behavior of an oscillation system containing the at least one tire (2) during an operation of a vehicle (3) comprising the at least one tire (2). The method has the following steps. A plurality of values of a momentary tire interior pressure of the at least one tire (2) are identified by means of a pressure sensor. In addition, a frequency spectrum of the oscillation system is identified based on the plurality of identified values of the momentary tire interior pressure. Furthermore, a momentary inherent frequency of the oscillation system is identified based on the identified frequency spectrum. At least one parameter, selected from the group consisting of a momentary tire temperature of the at least one tire (2), a momentary tire interior pressure of the at least one tire (2), a momentary tire load of the at least one tire (2), and a momentary velocity of the vehicle (3), is furthermore identified. A profile depth of the profile (1) of the at least one tire (2) is furthermore identified based on the identified momentary inherent frequency and the at least one identified parameter.

Description

description

Method, control unit and system for determining a tread depth of a profile of at least one tire

The invention relates to a method for determining a tread depth of a profile of at least one tire by means of an analysis of a vibration behavior of a vibration system including the at least one tire during operation of a vehicle having the at least one tire, a control device and a system for a vehicle for determining a tread depth Profiles at least one tire of the vehicle and a computer program product. From DE 197 16 586 Cl a method for determining the tread depth of a vehicle tire on a moving vehicle having the following steps is known: determining an angle of an outer tire point relative to a hub fixed Coordina ^¬ tensystem means of a vehicle-fixed sensor, analyzing the signal supplied by the sensor, Calculating the moment of inertia of the tire belt about the axis of rotation from the rotational stiffness of the tire wall and the determined natural frequency, calculating the current mass and the diameter change of the tire from the determined moment of inertia and the mass function of the tire in Ab ^¬ dependence on the diameter, calculating the profile loss from the change in diameter.

The object of embodiments of the invention is to provide a method, a computer program product, a control device and a system for determining a tread depth of a profile of at least one tire, which has a further improved result. enable profile depth during operation of a vehicle having the tire.

This object is achieved with the subject matter of the independent claims. Advantageous developments emerge from the dependent claims.

A method for determining a profile depth of a profile of at least a tire by means of an analysis of oscillations ^¬ supply behavior of the at least one tire-containing vibration system during an operation of the at least one tire having the vehicle comprises the following steps according to one aspect of the invention. There is a determination of a plurality of values of an instantaneous tire inner pressure of the at least one tire by means of a pressure sensor. In addition, determining a frequency spectrum of the vibra ^¬ tion system based on the plurality of determined values of the current internal tire pressure. In addition, a He ^¬ transmit an instantaneous natural frequency of the vibrating system is carried out based on the determined frequency spectrum. Furthermore, determining at least one parameter selected from the group consisting of a current tire temperature of the at least one tire, an instantaneous tire inner pressure of the at least one tire, a current tire load of ^{¬ at} least one tire and a current speed of the vehicle. Furthermore, a profile depth of the profile of the at least one tire is determined on the basis of the determined instantaneous natural frequency and the at least one determined parameter.

The method according to the said embodiment enables a further improved determination of the tread depth of the profile of the at least one tire during operation of the vehicle having the tire. This is done in particular by the Determining the frequency spectrum and the current natural frequency of the at least one tire containing

A vibration system based on the plurality of detected values of the current internal tire pressure, determining the at least one parameter and determining the tread depth of the profile of the at least one tire based on the determined instantaneous natural frequency and the at least one determined parameter. As will be explained in more detail below, it is assumed that the natural frequency of the vibration system including the at least one tire depends on the at least one parameter and the tread depth. Thus, by determining the at least one parameter as well as the natural frequency or a change in the natural frequency, the tread depth or a change in tread depth can be determined to the greatest extent possible. The sizes mentioned can be determined by means of sensors, which are increasingly available in vehicles. Thus, the number of additionally required for the process components can be reduced advantageously.

In one embodiment of the method, determining the plurality of values of a current tire inflation pressure includes determining a plurality of values of a current inflation tire inflation pressure. In the mentioned embodiment, the vibration system includes the at least one tire, ie a tire material, as well as a filling gas of the tire, for example an air filling of the tire. This is based on the consideration that vibrations of the tire caused by a deformation of the tire in the region of a current tire contact surface, ie in the region of a current contact surface of the tire with, for example, a road, are transmitted to the filling gas of the tire and there lead to local pressure fluctuations of the filling gas. By means of said embodiment, such pressure fluctuations of the filling gases are determined based on data determined by the pressure sensor and used for the determination of the frequency spectrum of the vibration system and its natural frequency.

In a further embodiment of the method, the determination of the frequency spectrum of the oscillation system takes place by means of a Fourier transformation. This allows a simple determination of the frequency spectrum of the vibration system.

The determination of the tread depth of the profile of the at least one tire can be carried out in particular by means of at least one characteristic stored in a memory device and / or by means of at least one table stored in the memory device. The at least one characteristic curve or the at least one table indicates the relationship between the at least one parameter and the natural frequency and / or the tread depth and the natural frequency. The at least one characteristic curve or the at least one table can be based on a model of the at least one tire, that is to say the relationship between the variables mentioned and the natural frequency is already pre-stored in the memory device in this embodiment. Furthermore, the at least one characteristic or the at least one table during a

Driving operation of the vehicle can be determined. In the embodiment, the respective letztge ^¬ called characteristic curve or table thus is first determined in a learning phase, typically after a new exhibiting the tire wheel has been fixed to the vehicle, and used in addition for the determination of the tread depth ^¬ Pro.

In a further embodiment of the method, the profile depth of the profile of the at least one tire is determined also based on a type of tire of the at least one tire. The type of tire can also have an influence on the natural frequency or on the parameters influencing the natural frequency, which in the mentioned embodiment is advantageously taken into account in the determination of the tread depth.

In addition, issuing of a warning message can take place if the determined tread depth of the profile of the at least one tire falls below a first predetermined threshold value. The issuing of the warning message typically takes place inside the vehicle. This allows the occupant of the vehicle, particularly the driver of the vehicle, to indicate a low per ^¬ tread depth.

In a further embodiment of the method, a notification of a service device also takes place if the determined tread depth of the profile of the at least one tire falls below a second predetermined threshold value. The second predetermined threshold value before ^¬ can correspond to the first predetermined threshold value or different from this. As a result, for example, an appointment for an exchange of the tire can be initiated automatically. Furthermore, the determined tread depth of the profile of the at least one tire can additionally or alternatively be transmitted to at least one driver assistance system of the vehicle. The tread depth determined is thus provided at least one driver assistance system provided in said exporting ^¬ approximate shape. As a result, the operation of the driver assistance system can be adapted to the respective determined tread depth. The at least one driver assistance system is, for example, selected from the group consisting of an anti-lock braking system. System, a vehicle dynamics control system, in particular an electronic stability program, and an emergency braking system.

Another aspect of the invention relates to a Computerpro ^¬ program product comprising a computer readable medium and stored on the computer readable medium program code which, when executed on a computing unit, instructs the calculating unit to perform a method according to one of the above embodiments.

The computer program product has the advantages already mentioned in connection with the corresponding embodiments of the method according to the invention, which are not listed again at this point in order to avoid repetitions.

The invention further relates to a control device for a vehicle for determining a tread depth of a profile of at least one tire of the vehicle by means of an analysis of a vibra ^¬ tion behavior of the at least one tire-containing vibration system. The control unit has at least one receiving device which is configured to receive a plurality of determined values of an instantaneous tire inner pressure of the at least one tire and to receive at least one determined parameter selected from the group consisting of a current tire temperature of the at least one tire, an instantaneous tire inner pressure of the tire at least one tire, a current tire load of the at least one tire and a current speed of the vehicle, is formed. In addition, the control unit has a first determination device, which is designed to determine a frequency spectrum of the vibration system based on the plurality of determined values of the instantaneous tire inner pressure. Furthermore, the control unit has a second determination device, which is used to determine a current natural frequency of the vibration system based on the determined frequency spectrum is formed. In addition, the control unit has a third determination device, which is designed to determine a tread depth of the profile of the at least one tire based on the determined instantaneous natural frequency and the at least one determined parameter.

In addition, the control unit may have a transmission device which, for transmitting the determined tread depth of the profile of the at least one tire to at least one

Interface of the vehicle is formed.

The control unit may be formed as a separate control unit for the vehicle or may be part of a further control unit, brake system, for example a control unit of an anti or a driving dynamics control system of the driving ^¬ zeugs or a body control device which is also referred to as a body control module (BCM). Furthermore, an aspect of the invention relates to a system for a vehicle for determining a tread depth of a profile of at least one tire of a wheel of the vehicle. The system has a control unit according to one of the aforementioned embodiments and at least one wheel unit. The at least one wheel unit can be arranged in the wheel, in particular in an interior of the at least one tire, and has at least one sensor selected from the group consisting of a temperature sensor, a pressure sensor, a tire load sensor and a speed sensor.

The control device and the system for determining the tread depth have the advantages already mentioned in connection with the corresponding method, which are not listed again at this point in order to avoid repetition, and are particularly suitable for carrying out the method according to the invention, and this may also apply to the embodiments and developments. For this purpose, the control unit and the system can have further suitable devices or components.

In one embodiment of the system the control unit is arranged in ^¬ nerhalb of the wheel unit. Characterized the determination of the tread depth of the at least one tire can be carried out by means of the wheel ^¬ unit and the profile depth of the other components of the vehicle determined to be provided.

In a further embodiment of the system, the control unit is arranged separately from the wheel unit. As a result, the profile depth is determined based on sensor data determined by the wheel unit by means of the control unit arranged separately from the wheel unit.

In addition, the system may have an output device which is designed to output a warning message if the determined tread depth of the profile of the at least one tire falls below a first predetermined threshold value.

In the above-mentioned embodiments, the vehicle is preferably a motor vehicle, in particular a motorcycle, a passenger car or a truck.

Embodiments of the invention will now be described with reference to the accompanying figures.

FIG. 1 shows a flowchart of a method for determining a tread depth of a profile of at least one tire according to an embodiment; 2A shows a schematic representation of a Fre ^¬ spec- trum of a vibration system of wheels and a filling gas at a harmonic periodic excitation of the vibration system at a first tread depth of the tire;

2B shows a schematic representation of a Fre ^¬ spec- trum of the vibration system of wheels and a filling gas at a harmonic periodic excitation of the vibration system at a second tread depth of the tire;

FIG. 3A shows a vehicle with a control device for determining a tread depth of a profile of at least one tire according to an embodiment;

Figure 3B shows a schematic cross-section of one of the wheels of the vehicle shown in Figure 3A; FIG. 4A shows a system for determining a tread depth of a

 Profiles at least one tire according to a first embodiment;

FIG. 4B shows a system for determining a tread depth of a

 Profiles at least one tire according to a second

Embodiment.

FIG. 1 shows a flowchart of a method for determining a tread depth of a profile of at least one tire according to an embodiment.

The determination of the tread depth is carried out by means of an analysis of a vibration behavior of the at least one tire-containing vibration system during operation of a the at least one tire having vehicle. The at least one tire in the embodiment shown is a tire filled with a filling gas, for example air. In the illustrated embodiment, in a step 50, determining a plurality of values of an instantaneous tire inner pressure of the at least one tire by means of a pressure sensor disposed in the tire, ie, determining a plurality of values of a current pressure of the inflation gas in the region of the pressure sensor. Thus, a plurality of pressure values are determined offset in time from one another at different measuring times by means of the pressure sensor.

 In a step 60, a determination of a frequency spectrum of the vibration system based on the plurality of determined values of the current tire inflation pressure takes place. In the shown

Embodiment takes place determining the frequency spectrum of the vibration system in this case by means of a Fourier transform.

In a step 70, as will be explained in more detail in connection with the following figures, a determination of at least one momentary natural frequency of the vibration system based on the determined frequency spectrum.

Furthermore, in step 80, determining at least one parameter selected from the group consisting of a current tire temperature of the at least one tire, an instantaneous tire inner pressure of the at least one tire, a current tire load of the at least one tire and a current speed of the vehicle. In one embodiment of the method, a determination of the instantaneous takes place

Tire internal pressure of the at least one tire by means of the arranged in the tire pressure sensor. In a further embodiment of the method, all of the parameters mentioned are determined. The tire temperature as well as the tire load will be typically determined by means of a arranged in the at least one tire wheel unit. The wheel unit has for this purpose a temperature sensor and a tire load sensor, as will be explained in more detail in connection with the other figures. Furthermore, the pressure sensor arranged in the at least one tire is typically part of the wheel unit.

Determining the instantaneous velocity comprises ty ^¬ pisch legally determining a value of a distance traveled in a given time interval route of the vehicle on ba ^¬ sierend determined by at least one sensor data. The at least one sensor is designed, for example, as a rotational speed sensor for determining a number of revolutions of a wheel of the vehicle having the at least one tire and can be arranged in particular in the wheel unit. In letztge ^¬ called case is determined as to whether the sensor is in the area of the tire footprint, that is the instantaneous contact area between a road surface and the tire is located and it adjusts the number of revolutions in a given time interval loading. Further, the at least one sensor can be formed as Satelli ^¬ tengestützter position-determining sensor. Furthermore, the at least one sensor can be embodied as a radar sensor, lidar sensor, ultrasound sensor or optical camera, and thus a distance of the vehicle to objects identified as stationary can be determined at different points in time, and the traveled distance of the vehicle can be determined therefrom.

In step 90, a profile depth of the profile of the at least one tire is determined on the basis of the determined instantaneous natural frequency and the at least one determined parameter.

This is based on the consideration that a change in the profile depth of the profile leads to a change in the instantaneous genfrequenz or the current natural frequencies of the vibration system leads. Vibrations arise from the fact that during the rolling of the tire on a roadway, a deformation of the tire in the area of a current tire is on stand area. By rolling the tire, a certain part of the tire is periodically in physical contact with the road surface. This leads to a periodic excitation force on the tire. The periodicity of the force depends on the speed of the vehicle, ie with increasing speed decreases the period and the excitation frequency. This periodic excitation causes vibrations in the tire material that are transferred to the inflation gas within the tire. This leads to local pressure changes of the filling gas, for example in a tire mode to a local pressure increase in the area of the current tire contact patch. These pressure changes can be detected by the pressure sensor disposed in the tire with high resolution accuracy and high sampling rate. As a model for the vibrations associated with the excitations, the vibration of a mass attached to a spring can be considered. The vibration behavior of such

Vibration system is given by where f the

Oscillation frequency, k is the spring constant of the spring and m is the mass of the oscillating body. Transferred to the vibra ^¬ tion system of tires and filling gas, this means that the natural frequencies of this, external suggestions exposed

Vibration system depend on the mass of the tire, wherein the mass of the tire also changes with changing tread depth. This leads to a change in the tread depth to a change in the natural frequencies, as will be explained in connection with the following figures. In addition, the current tire internal pressure P, the current tire temperature T, the current load or the current tire load L and the instantaneous speed v of the vehicle, the natural frequencies of the vibration system. The natural frequencies f _x , _raw , which are generated by the local pressure changes thus depend on several factors, as represented by the following relationship: f _x , _raw = fx, raw (P, T, v, L, tread depth).

For example, with filter mechanisms such as a linear regression, the influences of the different factors on the natural frequencies can be considered and thus corrected. Be pressure, temperature, speed and load dependencies ^¬ eliminated by measuring and compensation measures, the remaining influencing variable is the profile depth which can be estimated on the natural frequencies thus. For example, a filtered natural frequency f _{x can be} obtained by the following relationship: f _x = f _x ,

raw ^_ Ci · P-C2 * -C3 · vc ₄ · L, where Ci, C2, C3 and c _{4 are} constants.

The determination of the profile depth of the profile of at least one tire can also be effected by means of at least one, stored in a SpeI ^¬ chervorrichtung characteristic curve and / or by means of at least one, stored in the storage device table. The at least one characteristic curve or the at least one table indicates the relationship between the at least one parameter and the natural frequency and / or the tread depth and the natural frequency.

Typically, steps 50 to 90 are carried out continuously during operation of the vehicle, ie the tread depth is determined continuously during the driving operation. In this case, both an absolute value of the tread depth can be determined as well as a change in tread depth relative to a previously determined or predetermined tread depth value. To determine the absolute value of the tread depth, one based on a Subtraction of change in the instantaneous natural frequency change in the tread depth subtracted from the previously determined or predetermined tread depth value. Furthermore, in the embodiment shown, the determined tread depth of the profile of the at least one tire is transmitted in a step 100 to at least one driver assistance system of the vehicle, for example to an ABS or ESP system. As a result, the operation of the driver assistance system can be adapted to the respective determined tread depth.

In a step 110 it is determined whether the determined Pro ^¬ tread depth of the profile of at least one tire is below a certain threshold before ^¬, for example 2 mm. If the determined tread depth does not fall below the predetermined threshold, steps 50 to 110 are repeatedly executed.

If, on the other hand, the determined tread depth falls below the predetermined threshold value, in a step 120, a warning message is output by means of an output device of the vehicle. Furthermore, in this case, a notification of a service device, for example for an appointment to replace the corresponding tire, automatically take place.

Figure 2A shows a schematic representation of a frequency spectrum of a vibration system of tire and inflation gas at a harmonic periodic excitation of the vibration system at a first tread depth of the tire. For example, the first tread depth corresponds to a full tire tread. In FIG. 2A, the frequency is plotted on the abscissa and the spectral power density is plotted on the ordinate. , _n

 15

As shown in Figure 2A, the vibration system has multiple natural frequencies due to multiple modes that the tire possesses. These are located at the respective local maximum values of the spectral power density. An ideal distribution of the natural frequencies is shown in FIG. 2A by means of broken lines. However, due to the damping properties of the tire material, the distribution typically has a continuous curve shown in FIG. 2A, which results when the periodic excitation frequency or its harmonic lies in the range of at least one of the natural frequencies. Due to the harmonic excitation of the vibration system, the spectral Leis ^¬ tung dense thereby decreases with increasing frequency.

Figure 2B shows a schematic representation of a frequency spectrum of the vibration system of tire and inflation gas at a harmonic periodic excitation of the vibration system at a second tread depth of the tire. The second tread depth of the tire is less than the first tread depth of the tire. For example, the second tread depth corresponds to a low tread profile. The course of the frequency spectrum at the second profile depth is shown in FIG. 2B by means of a dot-dash line. In addition, the course of the frequency ^¬ spectrum is shown in the first tread depth by means of a Runaway ^¬ solid line. In addition, in FIG. 2B the respective ideal distributions of the natural frequencies are shown by means of broken lines.

As shown in Figure 2B, due to the reduced tread depth and the associated lower mass of the tire, the natural frequencies shift towards higher frequencies. The displacement of the natural frequencies is shown in FIG. 2B by means of an arrow. As a result, the tread depth can be determined, for example, by determining a value fo of a natural frequency with a full tire tread and a value fo 'of a shifted natural frequency with a reduced tire tread.

FIG. 3A shows a schematic representation of a vehicle 3 with a control unit 9 for determining a tread depth of a profile of a tire 2 of at least one wheel 17 of the vehicle 3.

The vehicle 3 is in the illustration shown a motor vehicle in the form of a passenger car and has a total of four wheels, each with a tire 2 in the form of a pneumatic tire, of the four wheels in Figure 3A, a front wheel and a rear wheel are shown. Further details will be explained in connection with the following figures.

3B shows a schematic, enlarged cross section of one of the wheels 17 of the vehicle shown in FIG. 3A. Components with the same functions as in FIG. 3A are identified by the same reference numerals and will not be explained again below.

As shown in FIG. 3B, the tire 2 of the wheel 17 has a schematically represented profile 1 with a tread depth t _P. The tread depth t _P is the distance of a tread 23 of the tire 2 schematically represented by a broken line to a tire-side lug 22 of the profile 1 shown schematically by a solid line.

Further, in Figure 3B a wheel unit 18 is shown, which is arranged in the tire ^¬ 2 and on a tire inner surface of tire 2 at. Is such a tire unit or wheel unit 18 in the region of the Laces or in the area of a Tire contact surface 30, ie in the region of the contact surface between a road 24 and the tire 2 or on the inside of the tread of the tire 2, the wheel unit 18 can also detect the interaction between the road 24 and the tire 2 directly, for example via an acceleration sensor, a shock sensor or a piezo element. Such sensors detect the deformation of the tire unit. The deformation is essentially due to the tire curvature, which changes significantly in particular when entering and leaving the laces. Thus, the latitudinal length can be measured very accurately and used to determine the latitude area. With a known Latsch area and known tire pressure from the Rei ^¬ fenlast can be determined. Thus, parameters can be determined by means of which the instantaneous tire load of the tire 2 can be determined by said sensors.

As will be explained in more detail below, based on parameters of the tire 2 not shown in detail in FIG. 3B and based on further parameters of the vehicle, an instantaneous tread depth of the tread 1 of the tire 2 can be determined during operation of the vehicle ,

For this purpose, Figure 4A shows a system 16 for determining a profile depth of a profile of at least one tire of the Darge in Figure 3A ^¬ set vehicle 3 by means of an analysis of oscillations ^¬ supply behavior of the at least one tire-containing vibration system according to a first embodiment. Components with the same functions as in FIGS. 3A and 3B are identified by the same reference symbols and will not be explained again below. For reasons of ^clarity , the vehicle 3 and the other components are shown schematically in FIG. 4A. The system 16 has a control unit 9 and, for each wheel or tire of the vehicle 3, a wheel unit 18, wherein in FIG. 4A only one such wheel unit 18 is shown for reasons of clarity. The control unit 9 is arranged separately from the wheel unit 18 in the embodiment shown. The control unit 9 can be designed as an independent control unit for the vehicle 3 or be part of another control unit, for example a control unit of an anti-lock braking system or a vehicle dynamics control system or a body control unit, which is also referred to as body control modules (BCM).

The wheel unit 18, which is also referred to as a wheel unit (WU) and, for example, part of a tire pressure monitoring system (TPMS) of the vehicle, which is also referred to as TPMS (TPMS, Tire Pressure Monitoring System), can be arranged in the respective wheel, for example an inner surface of the tire opposite a tread of the tire, or on a valve or on a valve seat on a rim of the respective wheel. In the embodiment shown, the wheel unit 18 has in each case a pressure sensor 4 for determining an instantaneous tire inner pressure, a temperature sensor 19 for determining a current tire temperature and a tire load sensor 20 for determining a current tire load, for example as explained in connection with FIG. 3B. In the illustrated embodiment, the pressure sensor 4 is designed to determine a gas pressure of a gas present in an interior of the respective tire which forms a tire filling gas, for example air or nitrogen. Furthermore, the wheel unit 18 has a storage device 25, wherein, for example, data relating to a type of tire and / or age of the tire can be stored in the storage device 25. In particular, characteristic tire properties, such as, for example, tire rigidity, in particular a reference marginal slip stiffness for new tires, tire type, age, dimension, DOT number and treadwear rating, deposited and made available. In addition, the wheel unit 18 has a transmitting device 26, by means of which the said data can be transmitted to the control unit 9 via a radio link. Furthermore, the wheel unit 18 has an energy storage device (not shown in greater detail in FIG. 4A) for supplying energy to said components of the wheel unit 18.

The control unit 9 includes a receiving apparatus 10 which determined for receiving a plurality of means of the pressure sensor 20, values of a current tire pressure, a detected by the temperature sensor 19 current tire fentemperatur and a means of the tire load sensor 20 he ^¬ mediated current tire load of the transmission device 26 the wheel unit 18 is formed.

Further, the receiving apparatus 10 is adapted to receive a detected by a speed sensor 21 current Ge ^¬ speed of the vehicle. 3 For this purpose, the Emp ^¬ catching device 10 is connected via a signal line 32 with the speed sensor 21st The control unit 9 also has a first determination device 11, which is used to determine a frequency spectrum of the

Vibration system is formed based on the plurality of detected values of the current internal tire pressure. For this purpose, the first determination device 11 is connected to the receiving device 10 via a signal line 33.

Furthermore, the control unit 9, a second discovery ^¬ device 12 which for determining at least one instantaneous eigenfrequency of a plurality of natural frequencies of vibration is formed system based on the determined frequency spectrum. The second determination device 12 is connected to the first determination device 11 via a signal line 34 for this purpose.

Moreover, the control unit 9 on a third Determined ^¬ averaging device 13 on the at least one ascertained momentary natural frequency and a determined parameter is formed for determining a profile depth of the profile of at least one tire based the at least. The third determination device 13 is connected to the second determination device 12 via a signal line 35 and to the reception device 10 via a signal line 36. In the embodiment shown, the third determination device 13 is designed to determine the tread depth of the profile of the at least one tire by means of at least one characteristic stored in a memory device 5 and / or by means of at least one table stored in the memory device 5. The at least one characteristic curve or the at least one table indicates the relationship between the at least one parameter and the natural frequency and / or the tread depth and the natural frequency.

The control unit 9 has in the embodiment shown also a transmission device 14, whereby the transfer Mitt ^¬ averaging device 14 is configured to transmit the determined profile depth of the profile of at least one tire of at least one interface 15 of the vehicle. 3 The About ^¬ averaging means 14 is connected thereto via a signal line 37 with the third detecting device 13 as well via a signal line 38 to the interface of 15 °.

The interface 15 is connected via a signal line 41 to a communication unit 29 of the vehicle 3, via a signal line 40 with an output device 28 of the vehicle 3 and connected via a signal line 39 with at least one Fahrerassis ^¬ tenzsystem 6 of the vehicle 3. The communication ^¬ unit 29 is formed, for example, as a mobile communication unit. The output device 28 is typi cally ^¬ designed as optical and / or acoustic output device. The driver assistance system 6 is designed, for example, as a brake assist or emergency braking system, wherein the determined tread depth of the profile of the at least one tire is transmitted to the driver assistance system 6 and the operation of the driver assistance system 6 can thereby be adapted to the respective determined tread depth.

The third determination device 13 is further formed in the embodiment shown for determining whether the determined tread depth of the profile of the tire falls below a predetermined threshold. If this is the case, a warning message can be issued by means of the output device 28 of the vehicle 3. Furthermore, by means of the communication unit 29, a notification of a service device can take place automatically, for example for an appointment to replace the corresponding tire.

In addition, in the embodiment shown, the control unit 9 has an arithmetic unit 8. The arithmetic unit 8 has a computer-readable medium 7 and a processing unit 27. The processing unit 27 may be designed, for example, as an electronic processor, in particular as a microprocessor or microcontroller. The computer-readable medium 7, for example, as EEPROM, flash memory or

Flash EEPROM or NVRAM be formed. Program code which, when executed on the arithmetic unit 8, guides the arithmetic unit 8, stores the abovementioned embodiments of the method on the computer-readable medium 7 for determining the tread depth, in particular the embodiment shown in FIG. 1, by means of the elements mentioned in this case. FIG. 4B shows a system 16 for determining a tread depth of a profile of at least one tire of the vehicle 3 illustrated in FIG. 3A by means of an analysis of a vibration behavior of a vibration system including the at least one tire according to a second embodiment. Components having the same functions as in FIG. 4A are identified by the same reference symbols and will not be explained again below. For reasons of clarity, the vehicle 3 and the other components are again shown schematically in FIG. 4B.

The second embodiment shown in FIG. 4B differs from the first embodiment shown in FIG. 4A in that the control unit 9 and the speed sensor 21 are arranged within the wheel unit 18. As a result, the profile depth of the at least one tire can be determined by means of the wheel unit 18.

The speed sensor 21 is designed to determine a number of revolutions of the tire having the wheel of the vehicle 3. For this purpose, as explained above, it is determined whether the speed sensor 21 is in the range of

Tire loading surface, ie the current contact surface between a roadway and the tire, and determines therefrom the number of revolutions of the wheel in a certain time interval. From the determined number of revolutions and the value of the circumference of the tire, which is stored, for example, in the storage device 25, the instantaneous speed of the vehicle 3 can then be determined. Furthermore, the pressure sensor 4 is connected via a signal line 42, the temperature sensor 19 via a signal line 43, the tire load sensor 20 via a signal line 44 and the speed sensor 21 via a signal line 45 to the receiving device 10.

The third determination device 13 is connected to the transmission device 14 via a signal line 37, the transmission device 14 in turn being designed to transmit the determined tread depth of the profile of the at least one tire to the at least one interface 15 of the vehicle 3. In the embodiment shown, the transmission device 14 includes the transmission device 26, by means of which the value of the determined tread depth can be transmitted via a radio link to a receiving device 31 of the vehicle 3 and from there to the at least one interface 15. The receiving device 31 is connected to the at least one interface 15 via a signal line 47. The interface 15 is in turn connected at least via the signal line 41 to the communication unit 29 of the vehicle 3, on the Sig ^¬ nalleitung 40 to the output device 28 of the vehicle 3 and via the signal line 39 with the one Fahreras ^¬ sistenzsystem 6 of the vehicle. 3

The tread depth of a tire has a significant influence on the behavior of the vehicle. This is especially true in critical driving situations. On the one hand, the maximum frictional connection between the tire and the road surface, that is, the grip, is strongly dependent on the respective road surface conditions, for example the

Road surface or the presence of snow or ice on the road surface. On the other hand, the adhesion for the respective conditions can be optimized by certain tire properties. This includes, in particular, one due to weather conditions optimized tire tread. The effectiveness of the tire profile is largely determined by the tread depth. For example, in aquaplaning the water between the road and the tire can no longer be displaced due to an insufficient profile.

Thus, can be ensured by a sufficient tread depth of the best possible adhesion between the tire and the road, especially in critical driving situations. Therefore, there are typically legal requirements for one

Minimum tread depth, which may also vary seasonally.

By means of the present invention, a method, a computer program product as well as a control device and a system are made available with which the profile depth can be estimated or determined while driving. This information can be made available to the driver, in particular, so that he replaces tires with insufficient tread depth in good time. This will help to avoid specific hazards, especially aquaplaning and loss of grip on snow-covered roads, and concomitant accidents.

Furthermore, the determined tread depth can be made available to other vehicle systems, in particular active safety systems, for example an ABS or ESP. As a result, the control strategies of the relevant vehicle systems can be adapted to the reduced grip situation and thus optimized.

In addition, the medium-term temporal profile of the tread depth allows conclusions for the seasonal tire change. This can be used to estimate whether the tire in question still has enough profile for the upcoming season or should be replaced.

_,

 26

Reference sign list

1 profile

 2 tires

 3 vehicle

 4 pressure sensor

 5 storage device

6 driver assistance system

7 medium

 8 arithmetic unit

 9 control unit

 10 receiving device

11 detection device

12 detection device

13 detection device

14 transmission device

15 interface

 16 system

 17 wheel

 18 wheel unit

 19 temperature sensor

 20 tire load sensor

 21 speed sensor

22 approach

 23 tread

 24 lane

 25 storage device

26 transmitting device

 27 processing unit

28 output device

 29 communication unit

30 tire footprint

31 receiving device

32 signal line signal line

signal line

signal line

signal line

signal line

signal line

signal line

signal line

signal line

signal line

signal line

signal line

signal line

signal line

signal line

step

 step

 step

 step

 step

 step

 step

 step

Natural frequency natural frequency profile depth

Claims

Method for determining a tread depth of a profile (1) of at least one tire (2) by means of an analysis of a vibration behavior of a vibration system including the at least one tire (2) during operation of a vehicle (3) having the at least one tire (2) Method comprises the following steps:  Determining a plurality of values of an instantaneous tire inner pressure of the at least one tire (2) by means of a pressure sensor (4), Determining a frequency spectrum of the vibration ^¬ system based on the plurality of determined values of the current internal tire pressure, Determining a current natural frequency of the vibration system based on the determined frequency ^¬ spectrum, Determining at least one parameter selected from the group consisting of a current tire temperature of the at least one tire (2), an instantaneous tire inner pressure of the at least one tire (2), a current tire load of the at least one tire (2), and a current vehicle speed (3), determining a tread depth of the profile (1) of the ^{¬ at} least one tire (2) based on the determined instantaneous natural frequency and the at least one determined parameter. The method of claim 1, wherein determining the plurality of current tire inflation pressure values includes determining a plurality of current tire inflation gas pressure values. 3. The method of claim 1 or claim 2, wherein the determination of the frequency spectrum of the vibration system is carried out by means of a Fourier transform. 4. The method according to any one of the preceding claims, wherein the determination of the tread depth of the profile (1) of the at least one tire (2) by means of at least one stored in a memory device (5) characteristic and / or table. 5. The method according to any one of the preceding claims, wherein the determination of the tread depth of the profile (1) of the at least one tire (2) also takes place based on a type of tire of the at least one tire (2). 6. The method according to any one of the preceding claims, wherein in addition a warning message is issued if the determined tread depth of the profile (1) of the at least one tire (2) falls below a first predetermined threshold. 7. The method according to any one of the preceding claims, wherein in addition a notification of a service device takes place if the determined tread depth of the profile (1) of the at least one tire (2) falls below a second predetermined threshold. 8. The method according to any one of the preceding claims, wherein the determined tread depth of the profile (1) of the at least one tire (2) to at least one driver assistance system (6) of the vehicle (3) is transmitted. A computer program product comprising a computer readable medium (7) and on the computer readable medium (7). stored program code, which, when executed on a computing unit (8), the computing unit (8) instructs to carry out a method according to any one of the preceding claims. Control device for a vehicle (3) for determining a profile depth of a profile (1) at least one tire (2) of the vehicle (3) by means of an analysis of oscillations ^¬ supply behavior of the at least one tire (2)-containing vibration system, comprising at least one receiving device (10) adapted to receive a plurality of detected values of a current tire pressure of at least one tire (2) and for receiving at least one ermit ^¬ telten parameter selected from the group consisting of a current tire temperature of the at least one tire (2 ), an instantaneous tire inner pressure of the at least one tire (2), a current tire load of the at least one tire (2) and a current speed of the vehicle (3), a first detecting device (11) configured to determine a frequency spectrum of the vibration ^¬ systems based on the plurality of determined values of the current tire pressure, a second determination device (12) configured to determine a current natural frequency of the vibration system based on the determined frequency ^¬ spectrum, a third determination device (13) designed to determine a tread depth of the profile (1) of the ^{¬ at} least one tire (2) based on the determined instantaneous natural frequency and the at least one determined parameter. 11. Control device according to claim 10, further comprising a transmission device (14) designed to transmit the determined tread depth of the profile (1) of the at least one tire (2) to at least one interface (15) of the vehicle (3). 12. System for a vehicle (3) for determining a tread depth of a profile (1) of at least one tire (2) of a wheel (17) of the vehicle (3), comprising a control unit (9) according to claim 10 or claim 11 and at least one wheel unit (18), wherein the at least one wheel unit (18) in the wheel (17) can be arranged, and having at least one sensor selected from the group consisting of a temperature ^¬ tursensor (19), a pressure sensor (4), a tire load sensor (20) and a speed sensor (21). 13. System according to claim 12, wherein the control device (9) within the wheel unit (18) is arranged. 14. System according to claim 12, wherein the control unit (9) is arranged separately from the wheel unit (18). The system of any one of claims 12 to 14, further comprising an output device (28) adapted to output a warning message if the determined tread depth of the tread (1) the at least one tire (2) a first vorbe ^¬ agreed threshold below.