FR3036079A1 - METHOD FOR DETECTING THE SLIDING OF AT LEAST ONE WHEEL OF A MOTOR VEHICLE - Google Patents

Abstract

The invention relates to a method for detecting the sliding of at least one wheel of a motor vehicle (1) on a road, said motor vehicle comprising: a left front wheel (11), a right front wheel (12), a left rear wheel (21) and a right rear wheel (22), and sensors adapted to measure values of the rotational speeds of each of the four wheels. According to the invention, the detection method comprises: a step of processing the measured values to produce at least two processed rotational speed values corresponding to two values of the rotation speed of a virtual wheel (20) that would be distinct; the four wheels of the motor vehicle and which would roll without slipping on the road, each processed value of rotational speed being determined by considering that the four wheels roll without slipping on the road, and - a slip detection step of at least one four wheels according to the comparison of said at least two processed rotational speed values.

Description

TECHNICAL FIELD TO WHICH THE INVENTION RELATES The present invention relates generally to the field of automobile safety and control of the connection between the ground and the wheels of a motor vehicle. It relates more particularly to a method for detecting the sliding of at least one wheel of a motor vehicle on a road, said motor vehicle comprising: - four wheels, including a left front wheel, a right front wheel, a left rear wheel and a right rear wheel, and sensors adapted to measure values of the rotational speeds of each of said four wheels. BACKGROUND TECHNOLOGY When a wheel of a motor vehicle slips on the ground, stability and traction of the motor vehicle are affected. It is then known to determine whether at least one of the wheels of the motor vehicle slips on the ground, in order to correct accordingly the braking torque or the engine torque exerted on the wheels of the motor vehicle.

US 2009/005985 discloses a method for detecting the sliding of a motor vehicle wheel using a location signal provided for example by a GPS system embedded within said vehicle. More specifically, the document US 2009/005985 describes a detection method according to which there is provided a step of comparison between the speed of advance of the vehicle provided by the GPS and the forward speed calculated from the rotational speeds of each wheels. This method has the drawback of requiring the acquisition of a GPS type signal, so that it can not be implemented on all types of vehicles, especially those which are not equipped with a system. geolocation. In addition, the detection method described in document US 2009/005985 proves unreliable when turning the motor vehicle.

OBJECTS OF THE INVENTION In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes a detection method that can be implemented on any type of vehicle and that has a high reliability of detection, especially when turns. More particularly, according to the invention there is provided a detection method comprising: a step of processing said measured values to produce at least two processed rotational speed values corresponding to two values of the rotation speed of a virtual wheel which would be distinct from the four wheels of the motor vehicle and which would roll without sliding on said road, each processed value of rotational speed being determined by considering that said four wheels roll without sliding on the road, and - a step of detection of the slip of at least one of the four wheels depending on comparing said at least two processed rotational speed values. To implement the method of the invention, only the rotational speeds of the wheels of the motor vehicle are necessary. These are acquired in a standard way by sensors fitted to all motor vehicles.

Thus, the implementation of the method is inexpensive and does not require the mounting of additional sensors. By using processed rotational speed values corresponding to two values of the rotational speed of a virtual wheel distinct from the four wheels of the motor vehicle, it is possible to detect a slippage of at least one wheel of the vehicle. when the processed values deviate from each other. Here we mean "virtual wheel" of the motor vehicle, a wheel that: a) in practice does not exist on the motor vehicle; (b) if it were mounted on the motor vehicle so as to come into contact with the ground, it would roll without slipping, and without changing the behavior of the other wheels of the motor vehicle; and c) preferably, is located in the center of the rear axle. As this virtual wheel is attached to the motor vehicle, the detection method 3036079 3 according to the invention is very robust in turns. Other non-limiting and advantageous features of the detection method according to the invention are the following: - between said processing step and said detection step, a step of filtering said at least two processed speed values is provided of rotation for generating at least two filtered values of rotational speed of said virtual wheel by means of a low-pass filter, the cut-off frequency of which is predetermined, the detection of said sliding of the wheel being carried out as a function of said filtered values of rotation speed ; 10 - during said detection step, comparing, on the one hand, the difference, in absolute value, between the largest of the processed values and the smallest of the processed values with a predetermined sliding threshold value, and detecting on the other hand, the sliding of at least one wheel when said deviation is greater than said slip threshold value during a detection time greater than a predetermined timeout value; during said detection step, the difference, in absolute value, between the largest of the filtered values and the smallest of the filtered values is compared with a predetermined slip threshold value, and, on the other hand, the sliding of at least one wheel when said deviation is greater than said sliding threshold value during a detection time greater than a predetermined timeout value; - said left rear wheel and said right rear wheel being carried by a rear axle of said motor vehicle, said virtual wheel is considered placed in the center of said rear axle; During said processing step, a turning radius of the motor vehicle is acquired, and each processed value of rotational speed of the virtual wheel which is determined from the rotational speed of the left front wheel or from the rotational speed of the right front wheel is determined according to a corrected turn radius which is equal to: said turning radius when it is between a minimum turning radius and a predetermined maximum turning radius, to said minimum turn radius when said turning radius is less than the minimum turning radius, or - said maximum turning radius when said turning radius 3036079 4 is greater than the maximum turning radius. said minimum turning radius and said maximum turning radius are chosen as a function of a wheelbase of said motor vehicle; said turning radius, denoted hereinafter R ', is calculated from said measured values of rotation speed of the rear wheels, denoted hereinafter respectively WARg, WARd, according to the relation: R' = RWARg + WARd) / (WARg-WARd)] * (E / 2), where E is the distance between the two rear wheels of the motor vehicle; said calculated turn radius is corrected by a corrective factor making it possible to compensate for the drift of the tires while cornering; Said slip threshold value is determined as a function of the corrected turn radius and / or the average speed of rotation of the two rear wheels. DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT The following description with reference to the accompanying drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be achieved. In the accompanying drawings: FIG. 1 is a block diagram representing the various steps of the detection method according to the invention; Figure 2 is a schematic view of a motor vehicle with its four wheels in a left turn; FIG. 3 represents rotational speed curves of the wheels of the vehicle of FIG. 2 as measured; FIG. 4 represents rotational speed curves of the virtual wheel, after treatment and filtering.

FIG. 2 is a diagrammatic view of a motor vehicle 1 comprising a chassis 2, a rear axle 3 and a front axle 4. The rear axle 3 here carries two rear wheels 21, 22: a rear left wheel 21 and a right rear wheel 22. In the same way, the front axle 4 carries two front wheels 11, 12: 30 a left front wheel 11 and a right front wheel 12. In the vehicle example shown in Figure 2 only the two front wheels 11, 12 are driving and steering, and may turn to the left (as in Figure 2) or to the right, so that the motor vehicle 1 then initiates a turn to the left or right.

The front and rear axles 3, 4 have a length E (see FIG. 2), otherwise called "vehicle lane", and corresponding to the distance between the front wheels 11, 12 between them and the rear wheels 21, 22 between they. The axles 3, 4 of the motor vehicle 1 are here parallel and separated by a distance L, otherwise called "wheelbase" of the vehicle. The four wheels 11, 12, 21, 22 of the motor vehicle 1 roll on a road (not shown) having a more or less uneven profile. Under normal conditions of adherence, the four wheels 11, 12, 21, 22 roll without slipping on the road, the adhesion of the tires being sufficient to ensure a correct connection to the ground of the motor vehicle 1. When the conditions of adhesion deteriorate, for example because of a pavement wet by the rain, it can occur a loss of adhesion, one or more wheels 11, 12, 21, 22 of the motor vehicle 1 can then slip on the road so that the ground connection is no longer ensured and that the road holding is compromised. In order to avoid these dangerous situations for the occupants of the motor vehicle, a method of detecting the sliding of at least one wheel 11, 12, 21, 22 of the motor vehicle 1 is proposed. This detection method can be implemented simply. by using the speeds of rotation of the four wheels 11, 12, 21, 22 of the motor vehicle 1. The motor vehicle 1 comprises for this purpose sensors (not shown) placed near each of the wheels 11, 12, 21, 22 for measuring rotational speed values of each of the four wheels 11, 12, 21, 22.

It is in particular from these measured values that the linear speed of the motor vehicle 1 can be determined. Each sensor delivers a signal, generally electrical, for example a voltage, which is representative of the value of the speed of rotation, expressed in radians per second (radish) or in revolutions per minute (rpm), of the wheel to which 30 he is associated. For the rest of the description, the following notations will be used for the different speeds of rotation: WAVg rotational speed of the left front wheel 11; - wAvd: rotation speed of the right front wheel 12; 3036079 6 - WARg: rotational speed of the left rear wheel 21; and - wARd: rotational speed of the right rear wheel 22. In the same way, each representative signal will thus be referenced (see in particular FIG. 1): reference 111 for the signal representative of the value of the speed of rotation of the left front wheel 11; reference 112 for the signal representative of the value of the speed of rotation of the front right wheel 12; reference 121 for the signal representative of the value of the rotational speed of the left rear wheel 21; and reference 122 for the signal representative of the value of the speed of rotation of the right rear wheel. Reference will now be made to FIG. 1, an exemplary implementation of the detection method according to the invention.

According to a particularly advantageous characteristic of the invention, the detection method comprises: a processing step which is represented by the block B1 in FIG. 1; and a detection step which is represented by block B3 in FIG. 1. Advantageously, an intermediate filtering step is provided between the processing step and the detecting step. This filtering step is represented by the block B2 in FIG. 1. During the processing step (block B1), the measured values 111, 112, 121, 122 are used for the rotation speeds WAvg, WAvd, WARg, WARd, to generate at least two, here three, processed values 211, 212, 220 rotational speed. According to the invention, these processed values 211, 212, 220 of rotational speed correspond to three values of the speed of rotation, denoted respectively WAVg_Treated, WAVd_Treated, WAR_moy, that would present a virtual wheel 20 (see Figure 2) of the motor vehicle 1 which is distinct from the four wheels 11, 12, 21, 22 of the motor vehicle 1. Each processed value 211, 212, 220 rotational speed is determined differently: 3036079 7 - or from the speed of rotation WAvg of the left front wheel 11: this is the case of the processed value 211 corresponding to a rotational speed (i) -AVg_treated of the virtual wheel 20; - Or from the speed of rotation WAVd of the right front wheel 12: 5 this is the case of the processed value 212 corresponding to a speed of rotation WAVd treated of the virtual wheel 20; or from the speeds of rotation WARg, WARd of the rear wheels 21, 22: this is the case of the processed value 220 corresponding to a rotational speed wAR_moy of the virtual wheel 20.

Each time, the preceding determination is made assuming that the wheels 11, 12, 21, 22 of the motor vehicle 1 roll without slipping on the road. Preferably, and as shown in FIG. 2, during the processing step, it is considered that the virtual wheel 20 of the automobile vehicle 1 is placed in the center of the rear axle 3. When the motor vehicle 1 starts a turning (left for Figure 2), its trajectory follows a curved direction which can be determined an instantaneous center of rotation 5. It is then defined from the instantaneous center of rotation 5, a radius of 20 turn R 'corresponding to the radius of curvature of the trajectory followed by the virtual wheel 20. This radius of turn R 'can be easily measured if the motor vehicle 1 is equipped with a sensor measuring the yaw rate or the steering wheel angle of the vehicle.

However, advantageously, the actual turning radius R 'is here calculated from the rotation speeds WARg, WARd of the rear wheels 21, 22 measured according to the relationship: R' = [(WARg WARd) / (WARg WARd)] * (E / 2). Advantageously, to compensate for the drift of the tires in turns, the radius of turn R 'calculated previously is corrected by a corrective factor G, so that we have the relationship: R' = [(WARg WARd) / (WARg Ward)] * (E / 2) * G. The value of this corrective factor G is specific to the type of vehicle and in particular to its over- or understeer tendency. A value of corrective factor G equal to 1 corresponds to a "neutral" vehicle and the drift of tires in turns is zero.

The corrective factor G can be adjusted empirically from the measurement of the four rotational speeds of the wheels in a stable turn, in which it is not desired to detect the normal sliding of the wheels. When the motor vehicle 1 advances in a straight line, (front wheels 11, 5 12 parallel to the rear wheels 21, 22), this radius of turn R 'takes very high values (because then WARg WARd), and in the case of a perfectly straight trajectory an infinite value. The processed speed values 211, 212, 220 (11-AVg_treated, WAVd_Treated, WAR_moy of the virtual wheel 20 can then be determined as a function of the rotation speeds WAvg, WAVd, WARg, WARg measured by the sensors, wheelbase L and track E of the motor vehicle 1, thanks to the following relations: R Va = tr = aite Afr'd R (A) CO = AVg _ treats A Vg CO AR mean [Û ° ARg + °) ARd 2 (B) R = min [R. , max (R ', R) 1 In the above relations, the processed speed values 211, 212, 220 ti) - AVg_treated, WAVd_treated of the virtual wheel 20 are determined for a corrected turn radius R (see FIG. relation (B) above) which is equal to: - the radius of turn R 'when it is between a minimum radius of turn Rmin and a maximum radius of turn Rmax predetermined; - the minimum turning radius Rmin when the turning radius R 'is less than the minimum turning radius Rmin; and at the maximum radius of turn Rmax when said turning radius R 'is greater than the maximum radius of turn Rmax.

In this way, even in a straight line where the turning radius R 'is theoretically infinite, rotated speed values 211, 212, 220 can be determined from the corrected corner radius R. Advantageously, the minimum radius of turn Rmin and the maximum radius of turn Rmax are chosen and fixed before the treatment step, according to the wheelbase L of the motor vehicle 1.

For example, Rmin = 0.5 * L and Rmax = 1000 * L are chosen. The processed value 220 of the rotation speed wAR_moy of the virtual wheel 20 determined from the rotation speeds WARg, WARd measured for the rear wheels 21, 22 here corresponds simply to the arithmetic mean of the WARg WARd rotation speeds measured for the wheels. rear 21, 22 of the vehicle 1, considering that the two rear wheels 21, 22 roll without sliding. The three relations (A) above provide, both in a straight line and during a right or left turn, the speed of rotation that would have the virtual wheel 20 positioned in the center of the rear axle 3 of the vehicle automobile 1.

These relationships make it possible to understand that, if the four wheels 11, 12, 21, 22 roll without abnormally sliding on the ground, then the three values processed 211, 212, 220 all correspond to the same speed of the virtual wheel 20. After the processing step, one can advantageously provide a filtering step 20 (see block B2 of Figure 1) processed values 211, 212, 220 speeds of rotation (i) -AVg_Treated, WAVd_Treated, WAR_moy of the virtual wheel 20 on the one hand, to suppress the measurement noise generated by the sensors and, on the other hand, to eliminate frequencies which are not relevant for the detection of slip. It will be noted that, as a variant, a filtering could have been applied to the measured values of rotational speeds of the four wheels of the motor vehicle, before their treatment described above. Preferably, this filtering step comprises a low-pass type filtering of the processed speed values 211, 212, 220 to generate corresponding filtered speed values 311, 312, 320 (see FIG. 1). respectively noted bi WAVd_tr_filt, WAR_moy_tilt. This low-pass filtering is characterized by its cut-off frequency fc, expressed in Hz, or by its cutoff pulse wc, expressed in rad / s. This filtering step, which is not essential in the detection method, nevertheless makes it possible to suppress the high frequencies, beyond the cut-off frequency fc, of the measurement spectrum, which are associated either with noise of measuring, or to rapid changes in rotational speeds due to the profile of the road. When the filtering step is not implemented, the detection step 5 which will be described below is then implemented directly by using as input values of the block B3 (see FIG. processed 211, 212, 220 rotational speeds --AVg_Treated, WAVd_treated, WAR_moy. The filtering step makes it possible to improve the detection reliability of the slippage of a wheel during the detection step.

In a simple manner, and in sufficient practice, the low-pass filtering performed by the block B2 during the filtering step of the method is a first-order filtering. In one variant, provision could be made for higher order filtering, for example second-order low-pass filtering. This then makes it possible to improve the filtering dynamics. During the detection step (see block B3 of FIG. 1), a comparison is made of the filtered values 311, 312, 320 of rotation speed --AVg_tr_filt, WAVd_tr_filt, WAR_moy_tilt produced at the end of the step of Previous filtering and according to this comparison, it delivers a signal 400 which is a Boolean signal 20 which is "1" if the slip of a wheel is detected and "0" otherwise. In a preferred embodiment, during this detection step, the difference £, in absolute value, is compared between the largest of the filtered values 311, 312, 320, and the smallest of the filtered values 311, 312, 320 with a predetermined sliding threshold value Sgliss. We therefore have the following relation for the deviation ε = 1111aX (WAVg_tr_tilt, WAVd_tr_filt, WAR_moy_tilt) rn in (WAVg_tr_tilt, WAVd_tr_filt, WAR_moy_tilt) I. If this difference c is greater than the threshold value Be, predetermined to slip during a duration As a result of the detection rate D greater than a predetermined time delay value, then the slip of at least one wheel is detected and the signal 400 at the output of the block B3 is set to "1". In other words, the logic of block B3 is as follows: if E> Sgliss during D> Temp then slip detected; - otherwise, no slip detected. Thanks to this logic, it is then possible to detect the drift of one of the filtered (or processed) values relative to the others. The predetermined sliding threshold value Sgliss is a setting parameter of the detection method. Advantageously, the threshold value Sgliss varies according to the corrected turn radius R (see above) and / or the average speed of rotation WAR_moy I (or the average speed of rotation wAR_moy when there no filtering) of the two rear wheels 21, 22. In particular, when the corrected turn radius R decreases, the slip threshold value Sgliss is increased so as to compensate for the natural drift of the tires of the motor vehicle 1. when the processed value of rotation speed wAR_moy or the filtered value of rotation speed WAR_moy _fin increases, the threshold value Sgliss is increased because the natural slip of the tires is greater when the speed of the motor vehicle 1 is high.

The time delay value Temp is a constant setting parameter of the system. It improves the reliability of detection of the sliding of a wheel 11, 12, 21, 22 of the motor vehicle 1. It represents the confirmation time for the detection of the sliding of a wheel. When the difference c determined above indicates, in comparison with the sliding threshold value Sgliss, that a sliding of one of the wheels takes place, it is then possible to know which wheel 11, 12, 21, 22 is in dragging by comparing the filtered values 311, 312, 320 (or simply treated 211, 212, 220 in the absence of filtering) rotation speeds -AVg_tr_tilt, WAVd_tr_filt, WAR_moy_filt (or WAVg_Treated, WAVd treated, WAR_moy) wheels 11, 12, 21, 22 with each other. For example, if the filtered value 311 of the rotation speed -AVg_tr_tilt of the left front wheel 11 is very different from the two other filtered values 312, 320, then a sliding of the left front wheel 11 of the motor vehicle 1 is detected thanks to the detection method.

FIG. 3 shows the representative signals 111, 112, 121, 122 of the rotation speeds WAvg, WAVd, WARg, WARd measured by the sensors over time, denoted here t and expressed in seconds (s). Note that the values of these rotational speeds WAvg, WAVd, WARg, WARd vary and have differences between them more or less important over time t.

3036079 12 As shown in Figure 1, is carried out according to the detection method of the invention at a processing step (block B1 of Figure 1), and here also to a filtering step (block B2) of these signals Representatives 111, 112, 121, 122 to obtain here three filtered speed values 311, 312, 320 (1) COAVd_tr_filt WAR_rmy_fift. The curves obtained for these filtered values 311, 312, 320 are shown in FIG. 4. It is observed on this curve that the filtered values 311, 312, 320 are very close to, or almost identical, so that during the step of processing 10 (block B3 of FIG. 1) the signal 400 delivered is equal to "0" indicating that no slip is detected for the motor vehicle 1. The present invention is in no way limited to the embodiment described and shown but the person skilled in the art will be able to make any variant that fits his mind.

Moreover, once the sliding of one of the wheels is detected by the detection method, suitable strategies can be implemented to control the engine torque or the braking in order to compensate for the loss of adhesion of the wheel. of the motor vehicle whose slip has been detected. For example, the engine torque applied to the detected slippage wheel 20 may be reduced to provide differential integrity and improve motor vehicle traction. Finally, the detection method can also be used to detect deflation or abnormal wear of a tire. For this, compared to the case of the detection of a slip, it is necessary to set the threshold value So 'slip to a much lower value and the delay time Temp to a much greater value than the values used for the detection of slip . Indeed, with respect to the sliding of a wheel, deflation or abnormal wear of a tire cause a much smaller gap c between the three filtered values bi COAVd_tr_filt, WAR_moy_Mt. It is therefore necessary to confirm for a longer delay time Temp to avoid false detections. In addition, a long confirmation time is justified by the fact that the deflation or the wear of a tire does not instantly compromise the stability, the motor skills and / or the braking distance of the motor vehicle and therefore quick detection is not necessary.

Claims (10)

REVENDICATIONS1. Method for detecting the sliding of at least one wheel of a motor vehicle (1) on a road, said motor vehicle (1) comprising: - four wheels (11, 12, 21, 22), including a left front wheel ( 11), a right front wheel (12), a left rear wheel (21) and a right rear wheel (22), and - sensors adapted to measure values (111, 112, 121, 122) of the rotational speeds ( WAvg, WAVd, WARg, WARd) of each of said four wheels (11, 12, 21, 22), characterized in that it comprises: a processing step (B1) of said values (111, 112, 121, 122) measured to produce at least two rotated speed processing values (211, 212, 220) corresponding to two values of the rotation speed (I.) -AVg_Treated, WAVd processed, WAR_moY) of a virtual wheel (20) which would be distinct from the four wheels (11, 12, 21, 22) of the motor vehicle (1) and which would roll without sliding on said road, each processed speed value (211, 212, 220) determined by considering that said four wheels (11, 12, 21, 22) roll without slipping on the road, and - a step of detecting (B3) the sliding of at least one of the four wheels (11, 12, 21, 22) according to the comparison of said at least two processed speed values (211, 212, 220). 2. Detection method according to claim 1, comprising, between said processing step (B1) and said detecting step (B3), a step of filtering (B2) said at least two processed values (211, 212, 220) of rotational speed for generating at least two filtered speed values (311, 312, 320) (w WAVd_tr_filt, WAR_moy_tilt) of said virtual wheel (20) by means of a low-pass filter, whose cutoff frequency (fa) is predetermined, the detection of said sliding of the wheel being performed according to said filtered values (311, 312, 320) of rotation speed. 3. Detection method according to claim 1, wherein, during said detection step (B3): the difference (c), in absolute value, between the largest of the values treated is compared on the one hand; (211, 212, 220) and the smallest of the processed values (211, 212, 220) with, on the other hand, a predetermined sliding threshold value (Sgliss), and - the slip of at least a wheel when said deviation (c) is greater than said slip threshold value (Sgli ') during a detection time (D) greater than a predetermined timing value (Temp). 4. Detection method according to claim 2, in which, during said detection step: the difference (c), in absolute value, between the largest of the filtered values (311, 312, 320) and the smaller of the filtered values (311, 312, 320) with, on the other hand, a predetermined sliding threshold value (Sgli '), and - the slip of at least one wheel is detected when said gap (E) is greater than said slip threshold value (Sgli ') during a detection time (D) greater than a predetermined timing value (Temp). 15 5. Detection method according to one of claims 1 to 4, wherein, said left rear wheel (21) and said right rear wheel (22) being carried by a rear axle (3) of said motor vehicle (1), said virtual wheel (20) is considered placed in the center of said rear axle (3). 6. The detection method as claimed in claim 5, wherein, during said processing step (B1), a turning radius (R ') of the motor vehicle (1) is acquired, and according to which each processed value (211, 212) of the rotational speed (ffi -AVg_Treated, WAVtreated) of the virtual wheel (20) which is determined from the rotation speed (WAvg) of the left front wheel (11) or from the rotational speed ( wAvd) of the right front wheel (12) is determined according to a corrected turn radius (R) which is equal to: - said turning radius (R ') when it is between a minimum turning radius (Rmin) and a predetermined maximum turn radius (Ri-Fm); - minimum turning radius radius (Rmin) when said turning radius (R ') is less than the minimum turning radius (Rmin); and 30 - said maximum radius of turn (Rmax) when said turning radius (R ') is greater than the maximum turning radius (Rmax). 7. Detection method according to claim 6, wherein said minimum radius of turn (Rmin) and said maximum radius of turn (Rmax) are chosen according to a wheelbase (L) of said motor vehicle (1). 3036079 16 8. Detection method according to one of claims 5 and 6, wherein said turning radius (R ') is calculated from said values (121, 122) measured speed of rotation (WARg, WARd) of the rear wheels ( 21, 22) according to the relation: R '= RwARg-FwARd) / (wARg-wARd)] * (E / 2), where E represents the distance between the two rear wheels (21, 22) of the motor vehicle ( 1). 9. The detection method according to claim 8, wherein said calculated radius of turn (R ') is corrected by a correction factor (G) to compensate for the drift of tires in turns. 10. A detection method according to claim 6 in dependence on claim 3 or 4, wherein said slip threshold value (So ') is determined as a function of the corrected turn radius (R) and / or the average speed rotation (wAR_moy) of the two rear wheels (21, 22).