DE102013219662B3 - Method, control unit and system for determining a tread depth of a profile of at least one tire - Google Patents

Abstract

One aspect of the invention relates to a method for determining a tread depth of a profile (1) of at least one tire (2) of a vehicle (3) having at least two tires (2) during operation of the vehicle (3). The method comprises the following steps. There is a determination of a current speed of the vehicle (3). In addition, a determination of a current yaw rate of the vehicle (3). In addition, a determination of a current steering wheel angle of a steering wheel (4) of the vehicle (3). Furthermore, a determination is made of a current skew stiffness of the at least two tires (2) of the vehicle (3) based on the determined current speed, the determined current yaw rate and the determined current steering wheel angle. Furthermore, a determination of at least one parameter of the at least one tire (2) selected from the group consisting of a current tire temperature, a current tire pressure and a current tire load takes place. In addition, a profile depth of the profile (1) of the at least one tire (2) is determined on the basis of the determined instantaneous skew stiffness and the at least one determined parameter.

Description

The invention relates to a method for determining a tread depth of a profile of at least one tire during operation of a vehicle having the tire, a control unit and a system for a vehicle for determining a tread depth of a profile of at least one tire of the vehicle and a computer program product.

From the DE 198 31 732 A1 a method for determining the tread depth in a vehicle tire while driving is known, in which are identified in an initialization phase at the beginning of a trip the vehicle-mounted tires, the tire mold slip at predetermined driving conditions is determined and from a stored in the vehicle map corresponding to the identified Tire and the determined tire mold slip information about the existing tire tread depth is issued.

From the US 2013/0013143 A1 For example, a method of monitoring tire slip stiffness is known using a change in skew stiffness as an indicator of tire wear or pressure loss.

From the US Pat. No. 6,912,896 B2 a method is known in which the profile height can be estimated via the tire slip and the longitudinal stiffness of the tire profile.

From the US 2004/0225423 A1 a method is known wherein tire parameters are determined via the longitudinal stiffness of the tire.

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 allow a further improved determination of the tread 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 tread depth of a profile of at least one tire of a vehicle having at least two tires during operation of the vehicle comprises the following steps according to one aspect of the invention. There is a determination of a current speed of the vehicle. In addition, a determination of a current yaw rate of the vehicle takes place. In addition, a determination of a current steering wheel angle of a steering wheel of the vehicle takes place. Furthermore, a determination is made of a current skew stiffness of the at least two tires of the vehicle based on the determined current speed, the determined instantaneous yaw rate and the determined current steering wheel angle. Furthermore, determining at least one parameter of the at least one tire selected from the group consisting of a current tire temperature, a current tire pressure and a current tire load. In addition, a profile depth of the profile of the at least one tire is determined on the basis of the determined instantaneous skew stiffness and the at least one determined parameter.

In this case, the instantaneous steering angle of the steering wheel is understood here and below as meaning the instantaneous steering angle.

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 determining the instantaneous skew stiffness of the tires of the vehicle based on the above-mentioned variables, determining the at least one parameter of the at least one tire and determining the tread depth based on the determined instantaneous skew stiffness and the at least one determined parameter. As will be explained in more detail below, it is assumed that the skew stiffness depends on the at least one parameter and the tread depth. Thus, by determining the at least one parameter and the skew stiffness or a change in the skew stiffness, the tread depth or a change in the 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, the current skew stiffness is also determined based on a total steering ratio of the vehicle, a wheelbase of the vehicle, a distance of a first wheel axle of the vehicle to a center of gravity of the vehicle and a distance of a second wheel axle of the vehicle to the center of gravity of the vehicle. As a result, the skew stiffness can be determined in a simple manner. The total steering ratio of the vehicle is understood here and below to mean the ratio of the steering wheel angle and the mean steering angle of the wheels of the steered wheel axle of the vehicle. Under the wheelbase is the Distance between the first wheel axle of the vehicle and the second wheel axle of the vehicle understood. The wheelbase is also referred to as the wheelbase of the vehicle.

In a further embodiment of the method, a determination of an instantaneous mass of the vehicle also takes place. In the mentioned embodiment, the determination of the instantaneous skew stiffness also takes place based on the determined instantaneous mass of the vehicle. As a result, changes in the mass of the vehicle, for example due to a changed loading state of the vehicle, can be taken into account in the determination of the skew stiffness.

The determination of the tread depth of the profile of the at least one tire may also be based on a type of tire of the at least one tire. The type of tire may also have an influence on the skew stiffness, which in the mentioned embodiment is advantageously taken into account in the determination of the tread depth.

In a further embodiment of the method, a determination of an instantaneous lateral acceleration of the vehicle also takes place. In the mentioned embodiment, the profile depth of the profile of the at least one tire is determined if the determined instantaneous lateral acceleration is within a predetermined range. It is assumed that the yaw rate and the steering wheel angle and a yaw gain derived from these variables can be determined as accurately as possible with moderate lateral dynamics of the vehicle, wherein a lower limit of the predetermined range typically a signal resolution of the determination of the above variables used sensors.

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. As a result, the occupants of the vehicle, in particular the driver of the vehicle, can be informed of a low 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 may be equal to or different from the first predetermined threshold. 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 determined tread depth is thus made available to at least one driver assistance system in the mentioned embodiment. 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 antilock braking system, a driving dynamics control system, in particular an electronic stability program, and an emergency braking system.

Another aspect of the invention relates to a computer program product comprising a computer readable medium and program code stored on the computer readable medium which, when executed on a computing unit, directs the computing unit to execute a method according to any one of the 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 also relates to a control device for a vehicle having at least two tires for determining a tread depth of a profile of at least one tire of the at least two tires of the vehicle. The controller has at least one receiving device for receiving a determined instantaneous speed of the vehicle, a determined current yaw rate of the vehicle, a determined current steering wheel angle of a steering wheel of the vehicle and at least one determined parameter of the at least one tire selected from the group consisting of a current tire temperature, a current tire pressure and a current tire load is formed. In addition, the control unit has a first determination device, which is designed to determine a current skew stiffness of the at least two tires of the vehicle based on the determined instantaneous speed, the determined instantaneous yaw rate and the determined instantaneous steering wheel angle. Furthermore, the control unit has a second determination device, which is designed to determine a tread depth of the profile of the at least one tire based on the determined instantaneous skew stiffness and the at least one determined parameter.

In addition, the control unit may have a transmission device, which is designed to transmit the determined tread depth of the profile of the at least one tire to at least one interface of the vehicle.

The control unit can be designed as an independent control unit for the vehicle or be part of another control unit, for example a control unit of an anti-lock braking system or of a vehicle dynamics control system.

Furthermore, an aspect of the invention relates to a system for a vehicle having at least two tires for determining a tread depth of a profile of at least one tire of the at least two tires 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 at least one tire and has at least one sensor selected from the group consisting of a temperature sensor, a pressure sensor and a tire load sensor. Here and in the following, a tire load sensor is understood to mean a device which is designed to determine at least one parameter by means of which a tire load of the at least one tire can be determined.

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 to avoid repetition, and are particularly suitable for carrying out the method according to the invention, this also the refinements and developments may apply. For this purpose, the control unit and the system can have further suitable devices or components.

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.

1 shows a flowchart of a method for determining a tread depth of a profile of at least one tire according to a first embodiment;

2 shows a flowchart of a method for determining a tread depth of a profile of at least one tire according to a second embodiment;

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

3B shows a schematic representation of the in 3A shown vehicle;

3C shows a schematic cross section of one of the wheels of in 3A shown vehicle;

4 shows a system for determining a tread depth of a profile of at least one tire according to an embodiment.

1 FIG. 12 shows a flow chart of a method for determining a tread depth of a profile of at least one tire during operation of a vehicle having the tire according to a first embodiment. The vehicle has at least two tires, wherein the tread depth of a profile of at least one of the at least two tires is determined by means of the method. Typically, the vehicle is a motor vehicle, such as a motorcycle, a passenger car or a truck.

In one step 50 a determination is made of a current speed of the vehicle based on data determined by at least one sensor. The determination of the instantaneous speed typically includes determining a value of a distance traveled by the vehicle in a specific time interval based on the data determined by the at least one sensor. For this purpose, 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. Furthermore, the at least one sensor can be designed as a satellite-supported position detection 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.

It also takes place in one step 60 determining a current yaw rate of the vehicle based on data determined by at least one yaw rate sensor.

In one step 70 A determination is made of a current steering wheel angle of a steering wheel of the vehicle based on data determined by at least one steering wheel angle sensor. The steering wheel angle sensor determines a current Steering angle of the steering wheel and is formed for example as a magnetic sensor.

The steps 50 . 60 and 70 are typically performed substantially simultaneously, that is, the determination of the current speed of the vehicle, the current yaw rate of the vehicle and the current steering wheel angle substantially during a common time interval.

In one step 80 a determination is made of at least one parameter of the at least one tire selected from the group consisting of a current tire temperature, in particular a temperature of a tire material, a current tire pressure and a current tire load. All of the mentioned parameters are preferably determined. These are typically determined by means of a arranged in the at least one tire wheel unit, as will be explained in more detail in connection with the other figures.

In the illustrated embodiment of the method also takes place in one step 90 determining a current mass of the vehicle. Specifically, the instantaneous mass of the vehicle may be determined based on tire load sensors disposed in the tires of the vehicle configured to determine the respective instantaneous tire load, wherein the instantaneous mass of the vehicle is determined from the sum of the instantaneous tire loads. In addition, in the step 90 based on the determined current tire loads of the tires of the vehicle determines a current center of gravity of the vehicle and therefrom a distance of a first wheel axle of the vehicle, such as a front axle, to the determined center of gravity and a distance of a second wheel axle of the vehicle, such as a rear axle, to the center of gravity certainly.

In one step 120 determining an instantaneous skew stiffness of the at least two tires of the vehicle based on that in the step 50 determined instantaneous speed, in the step 60 determined instant yaw rate, the in the step 70 determined instantaneous steering wheel angle and the current mass of the vehicle, the distance of the first wheel axle of the vehicle to the center of gravity of the vehicle and the distance of the second wheel axle of the vehicle to the center of gravity of the vehicle, which in the step 90 were determined. In addition, the instantaneous skew stiffness is determined based on an overall steering ratio of the vehicle and a wheelbase of the vehicle, as will be further explained below. The latter variables can be stored, for example, in a storage device of the vehicle.

It also takes place in one step 130 determining a tread depth or a profile depth change of the profile of the at least one tire based on that in the step 120 determined instantaneous skew stiffness and in the step 80 determined at least one parameter, as will also be explained further below.

The skew stiffness, which is also referred to as cornering stiffness, is defined for example in the context of the so-called linear single-track model. This establishes a relationship between yaw gain GV, ie the ratio between stationary yaw rate and steering wheel angle, and self-steering gradients EG. The response of the vehicle to a steering wheel movement can thereby by means of the relationship GV = V / [i _s (L + V ² * EG)] (1) where V is the instantaneous speed of the vehicle, i _{s is} the overall steering ratio, and L is the wheelbase of the vehicle. The self-steering gradient EG is dependent on the skew stiffnesses of the front wheels c _V and rear wheels c _H and the mass m of the vehicle. It describes how much the vehicle is oversteering, understeering or neutral. The self-steering gradient is defined as part of the aforementioned linear single-track model EG = m · (c · _H L _H - c · _V L _V) / (c · _V c _H · L). (2) In addition to the wheelbase or axis L here L _H and L _{V are defined} as the distance between the rear axle and the center of gravity of the vehicle or front axle and center of gravity of the vehicle. As already explained, the latter values can be measured by the tire modulus via the load distribution of the tires.

In addition, the yaw gain GV is defined by the yaw rate Ω _Z and the steering wheel angle LW. GV = Ω _Z / LW. (3) As already explained, both variables are measured directly by ESP systems via sensors, for example. Thus, their signals are available on a bus system of the vehicle, such as a CAN bus.

Substituting the equations (1) and (3) and assuming that the skew stiffnesses of the front wheels c _V and the rear wheels c _{H are} equal, that is, the relationship c _V = c _H , is the Yaw reinforcement GV Thus, a measure of an average instantaneous slip stiffness of the tires of the vehicle. This in turn depends on the current tire pressure P, the current tire temperature T, the instantaneous load L 'and the tread depth of the tread of the tire, as represented by the following relationship: c _V = c _V (P, T, L ', tread depth) C _H = C _H (P, T, L ', tread depth).

Typically, the skew stiffness of a pneumatic tire increases with increasing tire pressure. On the other hand, an increasing tire temperature and an increasing tire load typically lead to a reduction of the skew stiffness. The influence of a tire pressure change on a change in the skew stiffness is approximately equal to the influence of a profile depth change on a change in the skew stiffness. Furthermore, the influence of a tire temperature change on a change in the skew stiffness is approximately equal to the influence of a tire load change on a change in the skew stiffness, but less than the influence of a tire pressure change on a change in the skew stiffness. The influences mentioned here are typically dependent on the type of tire, wherein the type of tire or the type of tire can be stored in a storage device of the vehicle, in particular in a storage device of the wheel unit arranged in the at least one tire.

The mentioned dependencies can be taken into account by determining the mentioned parameters in the determination of the instantaneous skew stiffness and thus compensated. If the pressure, temperature and load dependencies are eliminated by measuring and compensating measures, the remaining influencing variable is the average tread depth of all tires of the vehicle, which can thus be estimated via the yaw gain.

The parameters on which the compensation method is based can be determined here by an application method. The determination of the instantaneous skew stiffness takes place, for example, by means of at least one characteristic stored in a memory device. The at least one characteristic curve indicates the relationship between the tire slip resistance and the tire pressure, the tire temperature or the tire load. The at least one characteristic may be based on a model of the tire, that is, the relationship between the skew stiffness and the aforementioned tire parameters is already pre-laid in the storage device in this embodiment. Furthermore, the at least one characteristic can be determined during a driving operation of the vehicle. For example, these parameters can be learned by the system in a known new set of tires with full profile. In the latter embodiment, therefore, the respective characteristic is first determined in a learning phase, typically after a new wheel has been attached to the vehicle, and further used for determining the instantaneous skew stiffness.

Typically, the steps become 50 to 130 during operation of the vehicle continuously running, that is, the tread depth is determined continuously during driving. 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, a change in the tread depth determined on the basis of a change in the instantaneous skew stiffness of the tires is subtracted from the previously determined or predetermined tread depth value.

2 FIG. 12 shows a flow chart of a method for determining a tread depth of a profile of at least one tire during operation of a vehicle having the tire according to a second embodiment. The vehicle has at least two tires and is for example once again a motorcycle, a passenger car or a truck.

In one step 50 A determination is made of a current speed of the vehicle based on data determined by at least one sensor, in accordance with the step 50 the in 1 shown first embodiment.

It also takes place in one step 60 determining a current yaw rate of the vehicle based on data determined by at least one yaw rate sensor according to the step 60 the in 1 shown first embodiment.

In one step 70 a determination is made of a current steering wheel angle of a steering wheel of the vehicle based on data determined by at least one steering wheel angle sensor, according to the step 70 the in 1 shown first embodiment.

It also takes place in one step 80 determining at least one parameter of the at least one tire selected from the group consisting of a current tire temperature, a current tire pressure, and a current tire load. Further, in one step 90 determining a current mass of the vehicle and therefrom a current center of gravity of the vehicle and a distance of a first wheel axle or a second wheel axle of the vehicle to the determined Main emphasis. The steps 80 and 90 correspond to the steps 80 and 90 the in 1 shown first embodiment.

In one step 100 In the embodiment shown, a determination is made of a momentary lateral acceleration of the vehicle, that is to say a momentary acceleration of the vehicle in a vehicle transverse direction. For example, to a change in the lateral velocity of the vehicle is determined in a given time interval.

In one step 110 it is determined if the in the step 100 certain instantaneous lateral acceleration is within a predetermined range. For example, it is determined whether the instantaneous lateral acceleration is between 0.2 · g and 0.7 · g, where g is the gravitational acceleration of the earth.

If in the step 110 determining that the instantaneous lateral acceleration is not within the predetermined range, the steps become 50 to 110 repeatedly executed.

If, in contrast, in the step 110 is determined that the instantaneous lateral acceleration is within the predetermined range, takes place in one step 120 determining a current skew stiffness of the at least two tires of the vehicle. The step 120 corresponds to the step 120 the in 1 shown first embodiment.

It also takes place in one step 130 determining a tread depth of the profile of the at least one tire based on that in the step 120 determined instantaneous skew stiffness and in the step 80 determined at least one parameter, according to the step 130 the in 1 shown first embodiment.

Furthermore, the determined tread depth of the profile of the at least one tire in the illustrated embodiment is in one step 140 transmitted 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 one step 150 it is determined whether the determined tread depth of the profile of the at least one tire falls below a predetermined threshold, for example 2 mm.

If the determined tread depth does not fall below the predetermined threshold, the steps become 50 to 110 and optionally 120 to 150 repeatedly executed.

If, on the other hand, the determined tread depth falls below the predetermined threshold value, this takes place in one step 160 issuing a warning message 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.

3A shows a schematic representation of a vehicle 3 with a control unit 11 for determining a tread depth of a profile of a tire 2 at least one wheel 24 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, wherein of the four wheels in 3A a front wheel and a rear wheel are shown. Further details will be explained in connection with the following figures.

In addition shows 3B a schematic representation of the in 3A shown vehicle 3 , Components with the same functions as in 3A are denoted by the same reference numerals and will not be explained again below.

In 3B are a distance L _{V of} a first wheel axle 5 of the vehicle 3 , which forms a front axle, to a momentary center of gravity 6 of the vehicle 3 and a distance L _{H of} a second wheel axle 7 of the vehicle 3 , which forms a rear axle, to the center of gravity 6 shown. Furthermore, in 3B a wheelbase L of the vehicle 3 that is the distance of the first wheel axle 5 of the vehicle 3 to the second wheel axle 7 of the vehicle 3 shown. In addition, one direction of rotation of the vehicle 3 around a yaw axis of the vehicle 3 in 3B schematically represented by an arrow A. The yaw axis is the vehicle vertical axis of a vehicle-fixed coordinate system with the focus 6 as origin and extends perpendicular to the in 3B represented drawing level.

3C shows a schematic, enlarged cross section of one of the wheels 24 of in 3A shown vehicle. Components with the same functions as in the 3A and 3B are denoted by the same reference numerals and will not be explained again below.

As in 3C is shown, the tire points 2 of the wheel 24 a schematically illustrated profile 1 with a tread depth t _P on. The tread depth t _P is the distance of a tread schematically represented by a broken line 23 of the tire 2 to a schematic by means of a solid line illustrated tire side approach 22 of the profile 1 ,

Furthermore, in 3C a wheel unit 18 shown in the tire 2 is arranged. Is such a tire unit or wheel unit 18 directly in the laces, that is in the contact surface between a roadway 25 and the tire 2 , or installed on the inside of the tread, the wheel unit 18 In addition, the interaction between the road 25 and the tire 2 detect 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 known Laces and known tire pressure from the tire load can be determined. Thus, parameters can be determined by said sensors by means of which the instantaneous tire load of the tire 2 can be determined.

As will be explained in more detail below, based on in 3B not shown sensors of the wheel unit 18 determined parameters of the tire 2 as well as based on other parameters of the vehicle also has an instantaneous tread depth of the profile 1 of the tire 2 be determined during operation of the vehicle.

In addition shows 4 a system 17 for determining a tread depth of a profile of at least one tire of the in 3A and 3B shown vehicle. Components with the same functions as in the 3A to 3C are denoted by the same reference numerals and will not be explained again below. For clarity, the vehicle is in 4 not shown in detail.

The system 17 has a controller 11 and a wheel unit for each wheel or tire of the vehicle 18 on, in 4 for reasons of clarity, only such a wheel unit 18 is shown.

The wheel unit 18 is locatable in the respective tire and has in each case a temperature sensor in the embodiment shown 19 for determining a current tire temperature, a pressure sensor 20 for determining a current tire pressure and a tire load sensor 21 for determining a current tire load, for example as associated with 3C explained on. Furthermore, the wheel unit 18 a storage device 31 on, wherein in the storage device 31 For example, data relating to a type of tire and / or age of the tire may be stored. In particular, characteristic tire properties, such as tire stiffness, in particular a reference tire stiffness for new tires, tire type, age, dimension, DOT number and treadwear rating, can be deposited and made available. In addition, the wheel unit points 18 a transmitting device 32 on, by means of which said data via a radio link to the control unit 11 can be transmitted. Furthermore, the wheel unit 18 one in 4 Not shown energy storage device for supplying power to said components of the wheel unit 18 on.

The control unit 11 has a receiving device 12 on, for receiving a means of the temperature sensor 19 determined instantaneous tire temperature, one by means of the pressure sensor 20 determined instantaneous tire pressure and one by means of the tire load sensor 21 determined instantaneous tire load from the transmitter 32 the wheel unit 18 is trained.

Furthermore, the receiving device 12 for receiving by means of a speed sensor 28 determined instantaneous speed of the vehicle, one by means of a yaw rate sensor 27 determined instantaneous yaw rate of the vehicle and one by means of a steering wheel angle sensor 26 determined instantaneous steering wheel angle of a steering wheel 4 formed of the vehicle. This is the receiving device 12 via a signal line 38 with a control unit 29 connected, which is formed in the embodiment shown as ABS or ESP control unit. The control unit 29 is also via a signal line 35 with the speed sensor 28 , via a signal line 36 with the yaw rate sensor 27 and via a signal line 37 with the steering wheel angle sensor 26 connected.

The control unit 11 also has a first detection device 13 which is designed to determine a momentary skew stiffness of the tires of the vehicle. The determination of the skew stiffness is carried out in the embodiment shown based on the determined instantaneous speed, the determined instantaneous yaw rate, the determined instantaneous steering wheel angle, for example, stored in a non-illustrated storage device total steering ratio of the vehicle, a wheelbase of the vehicle, which also in the storage device is stored, and as explained above, the distance of a first wheel axle or a second wheel axle of the vehicle to a current center of gravity of the vehicle. This is the first investigative device 13 via a signal line 39 with the receiving device 12 connected.

Furthermore, the control unit 11 a second detection device 14 on, which is designed to determine a tread depth of the profile of the at least one tire based on the determined instantaneous skew stiffness and the determined current tire temperature, the determined instantaneous tire pressure and the determined instantaneous tire load. The second investigative device 14 is via a signal line 40 with the receiving device 12 as well as via a signal line 41 with the first detection device 13 connected.

The control unit 11 also has a transmission device in the embodiment shown 15 on, the transmission device 15 for transmitting the determined tread depth of the profile of the at least one tire to at least one interface 16 of the vehicle is formed. The transmission device 15 is via a signal line 42 with the second detection device 14 as well as via a signal line 43 with the interface 16 connected. the interface 16 is via a signal line 44 with a communication unit 34 of the vehicle, via a signal line 45 with an output device 33 of the vehicle and via a signal line 46 with at least one driver assistance system 8th connected to the vehicle. The communication unit 34 is designed for example as a mobile communication unit. The output device 33 is typically designed as an optical and / or acoustic output device. The driver assistance system 8th is designed for example as a brake assist or emergency brake system.

The second investigative device 14 In the embodiment shown, it is further configured to determine whether an instantaneous lateral acceleration of the vehicle is within a predetermined range. The instantaneous lateral acceleration of the vehicle can be from a in 4 Sensor not shown in detail of the vehicle determines and to the receiving device 12 be transmitted. If the second detection device 14 determined that the instantaneous lateral acceleration of the vehicle is not within the predetermined range, the determination of the tread depth can be omitted or in such situations already determined values of the tread depth can be discarded.

In addition, the second detection device 14 formed in the embodiment shown to determine 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 sent by the output device 33 of the vehicle. Furthermore, by means of the communication unit 34 automatically a notification of a service facility done, for example, for an appointment to replace the corresponding tire.

In addition, the controller indicates 11 In the embodiment shown, a computing unit 10 on. The arithmetic unit 10 has a computer readable medium 9 and a processing unit 30 on. The processing unit 30 For example, it can be designed as an electronic processor, in particular as a microprocessor or microcontroller. The computer-readable medium 9 can for example be designed as EEPROM, flash memory or flash EEPROM or NVRAM. On the computer readable medium 9 is stored program code, which when on the arithmetic unit 10 is executed, the arithmetic unit 10 derives the above-mentioned embodiments of the method for determining the tread depth, in particular those in the 1 and 2 shown embodiments, to carry out by means of the elements mentioned here.

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 adhesion between the tire and the road surface, ie the grip, is heavily 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 a tire profile optimized for the respective weather conditions. 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 a minimum profile 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. As a result, specific hazardous situations, especially aquaplaning and loss of grip on snow-covered roads, and associated accidents can be avoided.

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. It can thus be estimated whether the tire in question still has sufficient profile for the coming season or should be replaced.

LIST OF REFERENCE NUMBERS

1

profile

2

tires

3

vehicle

4

steering wheel

5

wheel axle

6

main emphasis

7

wheel axle

8th

Driver assistance system

9

medium

10

computer unit

11

control unit

12

receiving device

13

detecting device

14

detecting device

15

transmission device

16

interface

17

system

18

wheel unit

19

temperature sensor

20

pressure sensor

21

Tire load sensor

22

approach

23

tread

24

wheel

25

roadway

26

Steering wheel angle sensor

27

Yaw rate sensor

28

speed sensor

29

control unit

30

processing unit

31

storage device

32

transmitting device

33

output device

34

communication unit

35

signal line

36

signal line

37

signal line

38

signal line

39

signal line

40

signal line

41

signal line

42

signal line

43

signal line

44

signal line

45

signal line

46

signal line

50

step

60

step

70

step

80

step

90

step

100

step

110

step

120

step

130

step

140

step

150

step

160

step

A

arrow

L _V

distance

L _H

distance

L

wheelbase

Claims (12)

Method for determining a profile depth of a profile ( 1 ) at least one tire ( 2 ) of at least two tires ( 2 ) ( 3 ) during operation of the vehicle ( 3 ), the method comprising the steps of: - determining a current speed of the vehicle ( 3 ), - determining a current yaw rate of the vehicle ( 3 ), - determining a current steering wheel angle of a steering wheel ( 4 ) of the vehicle ( 3 ), - determining a momentary skew stiffness of the at least two tires ( 2 ) of the vehicle ( 3 ) based on the determined current speed, the determined current yaw rate and the determined current steering wheel angle, - determining at least one parameter of the at least one tire ( 2 ) selected from the group consisting of a current tire temperature, a current tire pressure and a current tire load, - determining a profile depth of the profile ( 1 ) of the at least one tire ( 2 ) based on the determined instantaneous skew stiffness and the at least one determined parameter. The method of claim 1, wherein determining the current skew stiffness is further based on an overall steering ratio of the vehicle. 3 ), a wheelbase of the vehicle ( 3 ), a distance of a first wheel axle ( 5 ) of the vehicle ( 3 ) to a focus ( 6 ) of the vehicle ( 3 ) and a distance of a second wheel axle ( 7 ) of the vehicle ( 3 ) on the focus ( 6 ) of the vehicle ( 3 ) he follows. Method according to claim 1 or claim 2, wherein additionally determining a current mass of the vehicle ( 3 ) and wherein determining the instantaneous skew stiffness is also based on the determined instantaneous mass of the vehicle ( 3 ) he follows. Method according to one of the preceding claims, wherein determining the tread depth of the profile ( 1 ) of the at least one tire ( 2 ) also based on a type of tire of the at least one tire ( 2 ) he follows. Method according to one of the preceding claims, wherein additionally determining a current lateral acceleration of the vehicle ( 3 ) and wherein determining the tread depth of the profile ( 1 ) of the at least one tire ( 2 ) occurs if the determined instantaneous lateral acceleration is within a predetermined range. Method according to one of the preceding claims, wherein in addition a warning message is issued if the determined profile depth of the profile ( 1 ) of the at least one tire ( 2 ) falls below a first predetermined threshold. Method according to one of the preceding claims, wherein in addition a notification of a service facility takes place if the determined tread depth of the profile ( 1 ) of the at least one tire ( 2 ) falls below a second predetermined threshold. Method according to 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 ( 8th ) of the vehicle ( 3 ) is transmitted. Computer program product comprising a computer readable medium ( 9 ) and on the computer-readable medium ( 9 stored program code which, when stored on a computer unit ( 10 ) is executed, the arithmetic unit ( 10 ) to carry out a method according to any one of the preceding claims. Control unit for at least two tires ( 2 ) vehicle ( 3 ) for determining a tread depth of a profile ( 1 ) at least one tire ( 2 ) of the at least two tires ( 2 ) of the vehicle ( 3 ), comprising - at least one receiving device ( 12 ) configured to receive a detected instantaneous speed of the vehicle ( 3 ), a determined instantaneous yaw rate of the vehicle ( 3 ), a determined current steering wheel angle of a steering wheel ( 4 ) of the vehicle ( 3 ) and at least one determined parameter of the at least one tire ( 2 ), selected from the group consisting of a current tire temperature, a current tire pressure and a current tire load, - a first determination device ( 13 ) adapted to determine a momentary skew stiffness of the at least two tires ( 2 ) of the vehicle ( 3 ) based on the determined instantaneous speed, the determined instantaneous yaw rate and the determined current steering wheel angle, - a second determination device ( 14 ) adapted to determine a tread depth of the profile ( 1 ) of the at least one tire ( 2 ) based on the determined instantaneous skew stiffness and the at least one determined parameter. Control unit according to claim 10, further comprising a transmission device ( 15 ) adapted to convey the determined tread depth of the profile ( 1 ) of the at least one tire ( 2 ) to at least one interface ( 16 ) of the vehicle ( 3 ). System for at least two tires ( 2 ) vehicle ( 3 ) for determining a tread depth of a profile ( 1 ) at least one tire ( 2 ) of the at least two tires ( 2 ) of the vehicle ( 3 ), comprising a control unit ( 11 ) according to claim 10 or claim 11 and at least one wheel unit ( 18 ), wherein the at least one wheel unit ( 18 ) in the at least one tire ( 2 ) can be arranged and has at least one sensor selected from the group consisting of a temperature sensor ( 19 ), a pressure sensor ( 20 ) and a tire load sensor ( 21 ).

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