DE102019202803A1 - Method and system for determining at least one tire characteristic curve for at least one tire of a motor vehicle - Google Patents

Abstract

The invention relates to a method for determining at least one tire characteristic curve for at least one tire (2) of a motor vehicle (1), with state data used by a vehicle sensor system (3) which serve to characterize at least one roadway (4) on which the respective tire (2) is traveling , as well as a maximum adhesion coefficient can be recorded, the vehicle sensor system (3) being coupled to an evaluation and control unit (5) for data transmission, with a corresponding basic tire characteristic stored on the evaluation and control unit (5) being selected, taking into account the recorded status data is modified, the basic tire characteristic curve in the event of a discrepancy between the maximum coefficient of adhesion and a maximum base coefficient of adhesion listed in the basic tire characteristic curve and is stored by the evaluation and control unit (5) as a modified tire characteristic curve in order to control the motor vehicle ( 1) optimize. The invention also relates to a system for determining the at least one tire characteristic curve. In particular, the invention relates to a computer program product.

Description

The present invention relates to a method and a system for determining at least one tire characteristic curve for at least one tire of a motor vehicle. The invention also relates to a computer program product.

In order to be able to make a prediction of the driving operation of a motor vehicle or to enable control of the motor vehicle, driving-dependent status data of the motor vehicle and status data of the roadway on which it is traveling, in particular the surface texture, are to be recorded and corresponding measured variables characterizing the status data are to be determined. For example, a speed of the motor vehicle can be determined by means of a speed sensor on at least one of the wheels. Furthermore, the outside temperature can be determined or the condition of a road surface, for example an icy or damp road, can be detected. It can also be detected whether there is a slip, that is to say a difference between the speed of rotation of the wheel and the speed of movement of the motor vehicle.

From the DE 10 2016 214 065 A1 discloses a method for determining a frictional connection limit between a tire and a surface on which the tire rolls in the longitudinal direction of the tire. A momentary slip of the tire is initially recorded. A current coefficient of adhesion is then determined and a so-called tuple is formed from the detected slip and the current coefficient of adhesion. Furthermore, the maximum frictional connection limit is determined on the basis of the slope of a straight line through the origin through the tuple if the slip is below a first predetermined threshold value. Alternatively, the maximum frictional connection limit is determined on the basis of a tangent slope through the tuple if the slip lies between the first and a second threshold value. The maximum adhesion limit is determined directly on the basis of the adhesion coefficient if the slip is above the second predetermined threshold value.

Based on the prior art, the present invention is based on the object of providing a method and a system for determining at least one tire characteristic curve, with the aid of which driving operation of the motor vehicle can be better monitored and control of the motor vehicle can be optimized. The object is achieved by the subject matter of claims 1 and 5. Further advantageous embodiments can be found in the dependent claims.

According to a method according to the invention for determining at least one tire characteristic curve for at least one tire of a motor vehicle, a vehicle sensor system records state data, which in turn serves to characterize at least one roadway on which the respective tire is traveling, as well as a maximum adhesion coefficient, the vehicle sensor system having an evaluation and control unit is coupled for data transmission, taking into account the recorded status data, a corresponding basic tire characteristic stored on the evaluation and control unit is selected, the basic tire characteristic curve in the event of a discrepancy between the maximum adhesion coefficient and a maximum basic tire curve listed in the basic tire characteristic curve. The adhesion coefficient is modified and stored by the evaluation and control unit as a modified tire characteristic in order to optimize control of the motor vehicle. Typical data on the driving state of the motor vehicle and the surroundings of the motor vehicle, in particular the roadway on which the tires of the motor vehicle are traveling, are recorded by means of the vehicle sensor system.

Taking into account the acquired status data is to be understood as meaning that certain threshold values are stored on the evaluation and control unit in order to divide the status data into status ranges from which the basic tire characteristic curve is selected.

The status data preferably include a road surface condition, surface moisture and / or a roughness of the road surface. In other words, the vehicle sensor system uses suitable measurement systems to record the data on the condition of the roadway which are relevant for determining a tire characteristic. This can be information about a degree of moisture or a degree of icing of the surface of the roadway, for example. Further status data are also conceivable, on the basis of which a meaningful basic tire characteristic can be selected. Driving situations of the motor vehicle are particularly relevant in which a comparatively low friction or a comparatively high slip is to be expected between the tires of the motor vehicle and the road, for example on icy, snow-covered or very wet roads.

As an alternative or in addition, the status data include information from an anti-lock braking system (ABS) and / or a traction control system (ASR). An anti-lock braking system counteracts the possible locking of the wheels when the vehicle brakes by reducing the brake pressure, whereas ASR, also known as traction control, ensures that the wheels do not spin when the vehicle starts and the vehicle does not spin when cornering can break out sideways. From the systems mentioned, data can be extracted from which, in particular, maximum adhesion coefficients can be determined, which are used by the evaluation and control unit to compare and modify the basic tire characteristic. Corresponding maximum adhesion coefficients can advantageously be determined for each road condition. Other driver assistance systems are also conceivable that provide meaningful data, in particular on the current maximum coefficient of adhesion.

A driven or braked tire always has a slip with respect to the road surface on which it rolls, which is higher or lower depending on the tangential forces to be transmitted. The coefficient between the tangential force and the normal force is called the coefficient of adhesion or coefficient of friction. Its maximum, i.e. the maximum adhesion coefficient, indicates the maximum force a tire can transmit with a given normal force.

The acquired status data are made available to the evaluation and control unit which is connected to the vehicle sensor system and which receives the information, processes it further and compares it with databases or basic tire characteristics stored on the evaluation and control unit. In other words, one or more basic tire characteristics are stored in advance on the evaluation and control unit for each previously defined road condition. These can be supplied by the respective tire manufacturer or based on empirical data previously determined through tests.

First of all, the evaluation and control unit decides on the basis of the status data, in particular the condition of the roadway, which basic tire characteristic curve is used for comparison with the real status data. This basic tire characteristic curve has a maximum basic adhesion coefficient which is compared with the maximum adhesion coefficient which is obtained, for example, from the data of the anti-lock braking system and / or the traction control system. If the maximum basic adhesion coefficient and the recorded, i.e. current maximum adhesion coefficient, are identical, the basic tire characteristic is not modified. However, if the adhesion coefficients differ, the maximum adhesion coefficient and, based on this, the tire characteristic curve is modified by means of functions or calculation models stored on the evaluation and control unit. A modified tire characteristic curve and a modified maximum adhesion coefficient are then available on the evaluation and control unit. The course of the tire characteristic curve is generated based on the recorded or modified maximum adhesion coefficient in combination with the functions or arithmetic models already stored on the evaluation and control unit.

If a modified tire characteristic curve with a modified maximum adhesion coefficient is generated and stored on the evaluation and control unit, it can replace the basic tire characteristic curve or it can also be saved as a further data record. In the further operation of the motor vehicle, this (first) modified tire characteristic curve with the (first) modified maximum adhesion coefficient is used in the event of a recurring roadway condition and compared with a new recorded maximum adhesion coefficient, with no modification analogous to the manner described for an identical maximum adhesion coefficient the first modified tire characteristic takes place. In the event of a deviation in the adhesion coefficient, on the other hand, the first modified maximum adhesion coefficient and the first modified tire characteristic curve are modified, which is stored by the evaluation and control unit as the second modified tire characteristic curve. This makes it possible, for example, for the road conditions dry, wet, icy, etc. to implement a constant adaptation of the tire characteristic curve, whereby in particular any wear and tear on the tires that has already occurred can be taken into account. The driving behavior of the motor vehicle can therefore be better monitored.

The modified tire characteristic curve is preferably determined continuously or at defined time intervals. In particular, a determination can take place when a road condition changes, for example when it rains or the road suddenly becomes icy.

A system according to the invention for determining at least one tire characteristic curve for at least one tire of a motor vehicle comprises a vehicle sensor system which is designed to acquire status data, which in turn serve to characterize at least one roadway on which the respective tire is traveling, as well as a maximum coefficient of adhesion, the vehicle sensor system having a Evaluation and control unit is coupled for data transmission, with a corresponding base tire characteristic stored on the evaluation and control unit being selectable, taking into account the recorded status data, the base tire characteristic curve in the event of a discrepancy between the maximum adhesion coefficient and one in the basic tire characteristic curve listed maximum basic adhesion coefficient is modifiable and can be stored by the evaluation and control unit as a modified tire characteristic in order to optimize control of the motor vehicle. It is therefore a constantly learning system, which tire characteristics of the at least one tire in the case of recurring roadway conditions or other Checked status data or status data changes and, if necessary, modified so that monitoring, prediction and control of the motor vehicle is optimized.

The vehicle sensor system can be arranged, for example, in the front area of the motor vehicle, in particular in the area of the front wheels, but also on the rear wheels of the motor vehicle, in order to be able to determine the status data required to select the corresponding basic tire characteristic. Furthermore, the system can be designed in such a way that a respective tire characteristic curve is determined for several or all tires of the motor vehicle in order to make monitoring and control of the motor vehicle even more precise.

The vehicle sensor system preferably comprises a camera system, a radar system and / or a lidar system. Camera systems record the road surface optically, with radar systems comprising detection and location methods and devices based on electromagnetic waves. In contrast, lidar systems enable optical distance or speed measurement by means of laser beams. With systems of this type it is possible to precisely and reliably record roadway conditions or further condition data that are required for the determination or selection of the basic tire characteristic curve or an already modified tire characteristic curve.

The vehicle sensor system preferably comprises at least one wheel speed sensor. The wheel speed sensor can be arranged, for example, in the aforementioned anti-lock braking system or in the traction control system. Using the at least one wheel speed sensor, it is possible to detect a slip of the respective tire and to draw conclusions about the current maximum coefficient of adhesion.

The method according to the invention can in particular be carried out by a computer or by the evaluation and control unit. The method can thus be implemented in software. In this respect, the corresponding software is an independently salable product. The invention therefore also relates to a computer program product with machine-readable instructions which, when executed on a computer or on an evaluation and control unit, convert the computer and / or the evaluation and control unit to a control logic of the system for determining at least one tire characteristic curve upgrade or cause to carry out a method according to the invention.

• 1 eine stark vereinfachte schematische Ansicht eines Kraftfahrzeugs mit einem System zur Ermittlung von Reifenkennlinien für einen Reifen des Kraftfahrzeugs,
• 2 ein Kurvendiagramm mit mehreren Reifenkennlinien zwischen einem Schlupf eines Reifens des Kraftfahrzeugs gemäß 1 und seinem Kraftschlussbeiwert, und
• 3 ein Kurvendiagramm mit den Reifenkennlinien gemäß 2 sowie einer modifizierten Reifenkennlinie.

A preferred exemplary embodiment of the invention is explained in more detail below with reference to the figures, the same or similar elements being provided with the same reference symbols. Here shows

• 1 a greatly simplified schematic view of a motor vehicle with a system for determining tire characteristics for a tire of the motor vehicle,
• 2 a curve diagram with several tire characteristics between a slip of a tire of the motor vehicle according to 1 and its coefficient of adhesion, and
• 3 a curve diagram with the tire characteristics according to 2 as well as a modified tire characteristic.

According to 1 has a motor vehicle 1 two vehicle axles, namely a front and a rear axle 9 , 10 on, being on the front and rear axles 9 , 10 two wheels each 6th with a respective one on a wheel rim 11 arranged tires 2 are attached. For perspective reasons, there is only one wheel here 6th the front axle 9 and a wheel 6th the rear axle 10 shown. The respective non-visible wheels are designed analogously to this.

The car 1 has a system according to the invention for determining at least one tire characteristic curve for each tire 2 on that a vehicle sensor system 3 comprises, which are used to acquire condition data for characterizing at least one of the respective tires 2 traffic lane 4th serve, as well as a maximum adhesion coefficient is formed.

The vehicle sensors 3 includes one in the front area of the motor vehicle 1 arranged camera 7th that shows a road condition in the direction of travel of the motor vehicle 1 in front of the respective tire 2 traffic lane 4th determined. The camera 7th is perpendicular to the direction of travel or to the roadway 4th aligned. In the following, the state of the road is exemplarily divided into four different states, namely dry, wet, snowy and icy. In other words, it is from the camera 7th detects whether the road is dry or wet, or whether it is covered with snow or ice. Further subdivisions of the road conditions are also conceivable.

The vehicle sensor system also includes 3 multiple wheel speed sensors 8th each on the wheels 6th of the motor vehicle 1 are arranged. The wheel speed sensors 8th are present in an - not shown - anti-lock braking system of the motor vehicle 1 integrated, but can also be provided separately. Using the wheel speed sensors 8th can draw conclusions about the slip of the wheels 6th of the motor vehicle 1 and thus obtained from a current maximum adhesion coefficient.

In the motor vehicle 1 is an evaluation and control unit 5 arranged for data transmission with the vehicle sensors 3 is coupled. The evaluation and control unit 5 receives from the camera 7th precise information about the current state of the road 4th and from the wheel speed sensors 8th further data for determining the current maximum coefficient of adhesion. The evaluation and control unit therefore calculates 5 from the data from the wheel speed sensors 8th the current maximum coefficient of adhesion 18th who is in 3 is shown in more detail. This information is referred to here as status data and includes, in particular, a road surface, surface moisture and / or a roughness of the road 4th .

2 and 3 show a diagram with several basic tire characteristics 12 , 13 , 14th , 15th between one on the abscissa 16 applied slip and one on the ordinate 17th applied coefficient of adhesion.

In the present example, the evaluation and control unit 5 based on the recorded status data, in particular based on the road surface, initially one of four on the evaluation and control unit 5 stored basic tire characteristics 12 , 13 , 14th , 15th selected. The first tire characteristic 12 corresponds to a dry road condition and the second tire characteristic curve 13 corresponds to a wet road condition. The third tire characteristic 14th corresponds to a snow-covered road condition and the fourth tire characteristic 15th corresponds to an icy road condition. The evaluation and control unit 5 detected that the motor vehicle 1 a snow-covered road 4th drives on, which is why the third basic tire characteristic curve 14th is selected.

To 3 becomes one for the current road condition, namely the snow-covered road 4th , determined maximum adhesion coefficient 18th with one in the third basic tire curve 14th listed maximum basic adhesion coefficient 19th , where the current maximum coefficient of adhesion 18th is smaller than that in the third basic tire characteristic 14th stored maximum basic adhesion coefficient 19th . This corresponds to the real maximum coefficient of adhesion 18th not the one on the evaluation and control unit 5 deposited coefficient 19th . The control of the motor vehicle 1 is therefore not optimal. This is done by the evaluation and control unit 5 recognized, with the following the third basic tire characteristic 14th is adjusted or modified and as a modified tire characteristic 20th from the evaluation and control unit 5 is saved. With the help of the modified tire characteristic 20th is a control, monitoring and prediction of the driving operation of the motor vehicle 1 optimized.

In the event that in a later driving operation by means of the vehicle sensors 3 again a snow-covered road 4th is detected, the evaluation and control unit would 5 no longer on the basic tire characteristic 14th , but rather on the modified tire characteristic 20th fall back to a comparison between the modified maximum adhesion coefficient 18th and a newly determined - not shown here - maximum adhesion coefficient. In other words, there is constant adaptation and modification of all in the evaluation and control unit 5 stored tire characteristics taking into account the respective condition data as well as tire wear 2 so that a control of the motor vehicle 1 is optimized. A modified tire characteristic curve is preferably determined continuously.

List of reference symbols

1

Motor vehicle

2

tires

3

Vehicle sensors

4th

roadway

5

Evaluation and control unit

6th

wheel

7th

camera

8th

Wheel speed sensor

9

Front axle

10

Rear axle

11

Wheel rim

12

First tire curve

13

Second tire characteristic

14th

Third tire characteristic

15th

Fourth tire characteristic

16

abscissa

17th

ordinate

18th

Determined maximum adhesion coefficient

19th

Maximum basic adhesion coefficient

20th

Modified tire characteristic

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102016214065 A1 [0003]

Claims (8)

A method for determining at least one tire characteristic curve for at least one tire (2) of a motor vehicle (1), with a vehicle sensor system (3) providing status data which in turn serve to characterize at least one roadway (4) on which the respective tire (2) is traveling, as well as a maximum adhesion coefficient can be recorded, the vehicle sensor system (3) being coupled to an evaluation and control unit (5) for data transmission, with a corresponding basic tire characteristic stored on the evaluation and control unit (5) being selected, taking into account the status data recorded, with the basic tire characteristic is modified in the event of a discrepancy between the maximum traction coefficient and a maximum base traction coefficient listed in the basic tire characteristic and stored as a modified tire characteristic by the evaluation and control unit (5) in order to control the motor vehicle (1) optimize. Procedure according to Claim 1 , characterized in that the modified tire characteristic is determined continuously or at defined time intervals. Method according to one of the preceding claims, characterized in that the status data include a road surface condition, surface moisture and / or a roughness of the roadway (4). Method according to one of the preceding claims, characterized in that the status data comprise information from an anti-lock braking system and / or a system for traction control. System for determining at least one tire characteristic curve for at least one tire (2) of a motor vehicle (1), comprising a vehicle sensor system (3) which is used to record status data which in turn is used to characterize at least one roadway (4) on which the respective tire (2) serve, as well as a maximum adhesion coefficient, the vehicle sensor system (3) being coupled to an evaluation and control unit (5) for data transmission, with a corresponding basic tire characteristic stored on the evaluation and control unit (5) taking into account the recorded status data can be selected, the basic tire characteristic curve being modifiable in the event of a discrepancy between the maximum traction coefficient and a maximum base traction coefficient listed in the basic tire characteristic curve and being storable as a modified tire characteristic curve by the evaluation and control unit (5) in order to control the motor vehicle (1) optimize. System according to Claim 5 , characterized in that the vehicle sensor system (3) comprises a camera system, a radar system and / or a lidar system. System according to one of the Claims 5 or 6th , characterized in that the vehicle sensor system (3) comprises at least one wheel speed sensor (8). Computer program product containing machine-readable instructions which, when executed on a computer and / or on an evaluation and control unit (5), convert the computer and / or the evaluation and control unit (5) into a control logic of the system Determination of at least one tire characteristic curve according to the Claims 5 to 7th upgrade, and / or induce a process according to one of the Claims 1 to 4th execute.

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