WO2002032733A1 - Device and method for detecting a motor vehicle tyre adherence on the ground - Google Patents

Abstract

The invention provides an evaluation (preferably continuous) of the adherence level of a tyre on the ground, designed to detect an unstable adherence capable of resulting quickly into a loss of adherence or extended braking (hence high risk of serious accident) and to warn rapidly the driver and/or systems restoring a non-risky adherence level. The method for evaluating tyre/ground adherence at the contact zone comprises the following steps: (a) evaluating wheel micro-slips of the contact zone A(t); (b) calculating a physical quantity P(t) representing instantaneous adherence; (c) fine-tune monitoring the average adherence evolution; (d) reactive monitoring of the instantaneous adherence evolution; (e) extracting information of unstable adherence or imminent unstable adherence from steps (c) and/or (d); and (f) sending an appropriate signal to the driver and/or means managing situations of unstable adherence, adapted to bring about a restoration of non-risky adherence.

Description

 TQD 171001

Device and method for detecting the grip of a vehicle tire on the ground, and their applications

Technical sector of the invention:

The present invention relates to the technical sector of motor vehicles and more particularly to devices and methods for improving their control, and more particularly to the technical sector of the study of such devices and methods for controlling their tires and the grip conditions thereof. this on the ground, for example on the roadway.

As will be understood by a person skilled in the art, the field of application of the invention is extended to all the devices for detecting or measuring slip or friction.

These can be test means such as roller benches, carts with a central wheel, so-called “fifth wheel” vehicles, friction pendulums, skid carts, etc. or systems on board a vehicle. or a machine.

Goal

The objective of the present invention is to determine the coefficient of grip of tire - ground when driving.

Prior art:

Devices are known which only identify the level of grip during the loss of grip phase, which prevents any anticipation of the incident. These devices are purely reactive or "defensive". TQD 171001 2

There is therefore an important and recognized need for a device and a process which would allow a continuous determination of the level of grip in order to move from a current passive or defensive security logic to an active and anticipatory approach.

Application domain

Any type of vehicle fitted with tires or wheels or in general with treads or any similar system, hereinafter together for "pneumatic" simplicity.

As will be understood by a person skilled in the art, it will be possible, throughout the text, to replace the measurement of "wheel speeds" or "wheel speed" and similar terms (covering, as will be understood by a person skilled in the art, the speed of advancement of the wheel and / or wheel rotation speed (i.e. linear and / or angular speed) by:

• Measurement of hub, suspension or even chassis speeds or accelerations

• Or by force or displacement measurements on elements of the chassis or suspensions

(For simplicity, it will not be mentioned and the assembly will be included in the term "wheel speed" and similar terms, including in the claims).

Indeed, the vehicle advancing over a short time at a substantially constant speed, any modification of the "wheel speed" results in a relative movement of the corresponding hub, but also of the suspension elements and chassis elements. These movements can be measured as a displacement, a speed an acceleration or even an effort via the corresponding sensors. TQD 171001 3

Summary of the invention:

The general object of the present invention is therefore to provide an evaluation of the level of grip of the tire on the ground; to operate - in a completely preferred but non-limiting mode - continuously (and therefore to provide permanent information on the level of grip); to detect a situation of precarious grip which can quickly lead to a loss of grip (and thus to a high risk of serious accident) and to quickly notify the driver and / or systems for managing this level of precarious grip .

The invention therefore generally relates to a method for detecting the grip of a vehicle tire on the ground, characterized in that the level of grip of the tire on the ground is evaluated in a first step, by suitable means. for and capable of providing an assessment of the level of grip of the tire on the ground; it operates - in a completely preferred mode - continuously (and therefore preferably provides permanent information on the level of adhesion); we detect a situation of precarious grip which can lead (possibly quickly) to a loss of grip (and therefore to a high risk of serious accident) and we warn the driver and / or systems of management of precarious grip level .

General remark :

In the present description, we have taken, in the illustrations and in the equations, the default hypothesis of a front-wheel drive or four-wheel drive vehicle of the traction type. Otherwise, it would suffice to replace in the illustrations and equations the front by the rear.

Detailed description of the invention:

It is known that if a torque is applied to a wheel, in particular a driving wheel, the wire (s) incorporated in the carcass ply of the tire at the point TQD 171001 4 or the tire / ground contact area will / will twist, which causes an “apparent slip” called “pseudo-slip”. A person skilled in the art considers that the tire is "deradialized".

We also know that the driver; which generally remains far below the limit adhesion conditions, generally evolves in the field of very low slips or micro-slips. The approach conventionally used in the prior art for ABS ™ (anti-lock braking) and traction control systems, and developed for the measurement and management of slips, is not applicable to the resolution of this technical problem.

In the area of low tire stress, that is to say in particular at low speed, the cause of microgliding essentially resides in the nature of the soil.

At high speed, on the contrary, the ground is hypothesized to have good flatness and good surface homogeneity (otherwise, a high speed would not be conceivable) and is therefore a priori little or very little generator of micro-sliding, the cause being then be mainly attributed to the tire, and not to the ground. The tire will slide in “jerks” and will seek a frequency at which it can recover or “reset”.

Naturally, the distinction between the two situations is not always as clear-cut, which considerably complicates the technical problem posed.

The merit of the invention is to have sought an active and anticipatory technological solution to the technical problem of grip control, while the prior art is massively limited to date to passive and a posteriori detections of loss of adhesion. Another merit of the invention is to have refined and formalized the above concepts, in order to obtain a reliable and general-purpose technology.

According to the general concept of the invention, this consists of a method for evaluating the tire / ground grip at the level of the contact area, which comprises the following steps: TQD 171001 5

(a) evaluation of micro-sliding of the contact area A (t)

(b) calculation of a quantity P (t) representative of the instantaneous adhesion

(c) possibly following the end of the evolution of the average grip.

According to an entirely preferred embodiment, the general method according to the invention further comprises a step:

(d) reactive monitoring of the evolution of instant adhesion.

According to another entirely preferred embodiment, the general method according to the invention comprises a step:

(e) extracting the information on precarious adhesion or imminent precarious adhesion from steps (c) and / or (d) and

(f) sending an appropriate signal to the driver and / or means for active correction of the grip of the tires, adapted to cause a return to non-precarious grip.

Step (a) Evaluation of micro slips:

According to a preferred but non-limiting embodiment, the implementation of step (a) for evaluating micro-slippages comprises the following steps:

ai) measurement of the rotational speeds V (t) of each of the wheels

a2) possibly rearward time adjustment (for two wheels on the same right or left side) corresponding to the time delta t that the vehicle takes to travel a wheelbase (we know that the wheelbase is the distance between the front and rear axles), with the relationship:

delta t = e / Vm TQD 171001 6 where Vm = vehicle forward speed

and e = wheelbase.

Some elements on the calculation of A (t):

^ At low speed, it is the ground which imposes μ-sliding and the torque is generally high;

“^ A (t) is a simple criterion (mean and standard deviation).

At high speed, the μ-slips are linked to the tire, A (t) is based on the harmonics (energy and phase) of the wheel revolution and their coincidence with the tire and ground link modes.

Notes:

In the case where the basic information is obtained by sensors other than the wheel speed sensors, the search for harmonics or phase will be done either by autocorrelation of the basic signal, or by convolution with a signal representative of the speed the wheel or average speed of a set of vehicle wheels. This last signal can come, for example, from the speed information available on all vehicles or from the wheel speed sensors used for ABS.

The wheel speed can, for example, be measured using sensors already installed on the vehicle (sensors used for ABS ™ anti-lock brakes, traction control or trajectory control, and future sensors of this type or the like) or additional such as optical encoders, magnetic encoders, accelerometers (optical or magnetic “encoders” being, as the skilled person knows, geometric elements marked either optically or magnetically, and arranged according to a code readable by a sensor). The magnetic encoders of the Continental ™ process, which consists in inserting magnetic bars in the sidewalls of the tire, could be used according to the invention, but of course absolutely not in the same function, nor to solve the same technical problem. TQD 171001 7

In order to refine the accuracy of the wheel speed measurements, we can conventionally perform a measurement of the time separating two successive counting events (ex: tooth for toothed wheel) or in a variant allowing to increase the accuracy of the measurements and to overcome in particular the lack of regularity of the events (teeth for toothed wheel) and their shape, we will count the time elapsing from an event to itself one turn after. There will thus be an extremely precise measurement of the time taken to complete a wheel revolution and therefore an extremely precise measurement of the wheel speed. This calculation will preferably be carried out for each of the events (teeth for toothed wheel) which punctuate the wheel turn. There will thus be as many extremely precise measurements of the wheel speed for a wheel revolution as there are events (teeth for toothed wheel).

Evaluation of μ-sliding, according to a preferred embodiment of the invention:

An evaluation is carried out for each wheel with calculation, from V (t), of the criterion A (t) representative of the μ-slippages in the contact area, V (t) possibly being the speed of the wheel or any other criterion representative of the speed of the wheel or of its variations, such as signals of acceleration, forces, or displacement and the like, as indicated above. The method can also optionally include a step of implementing means for calculating for each wheel said criterion A (t) which can be, for example, possibly:

m The derivative or variations of Vroue (t) and / or

m The standard deviation of Vroue (t) (standard deviation of the variations in speed of rotation of the front wheel relative to the rear wheel) and / or

α The min max deviation Vroue (t) (min-max deviation of the speed of rotation of the front wheel relative to the rear wheel) and / or

m The instantaneous speed of the wheel Vroue (t) and / or

m The average speed of the wheel over a period T, TQD 171001 8 or, in the energy spectrum of the distribution of the rotational speeds of each wheel:

B The energy over part or all of the harmonics 1 to 64 of Vroue (t) (preferably use frequency bands centered on the harmonics and with a width substantially less than 10 Hz) and / or

B The energy on one or more Vroue frequency bands preferably between 8 and 400 Hz.

or the Vroue (t) phase variations taking for example as criteria:

B The evolution of the Vroue phase (t) and / or

B The standard deviation of the Vroue phase (t) and / or

B The min max deviation of the Vroue phase (t) and or

B The evolution of the average Vroue phase (t) over part or all of the harmonics 1 to 64 (preferably use frequency bands centered on the harmonics and with a width substantially less than 10 Hz) or the phase average over one or more frequency bands between 8 and 400 Hz,

or means to operate by combination of the above methods,

this coefficient can also be optionally weighted by a constant value or a function of Vav (t) or Var (t) to take into account the technological differences of the front and rear train.

The formula used to calculate A (t) may depend on the speed of the vehicle, but also, if this information is available, on the level of excitation. TQD 171001 9 from the ground (information which can be provided for example by the ground link sensors used to measure the attitude of the vehicle or for controlled suspensions and shock absorbers).

Step (b) Instant adhesion:

Assessment of instant adhesion

Calculation of the sliding coefficient G% with front - rear spatial registration.

G% (t) = [Aav (t) - k x Aar (t + Δt) -r] / Aar (t + Δt)

k, r: values to be adjusted according to the vehicle, in a manner accessible to the skilled person;

k can be a variable value, in particular as a function of the steering angle of the steering wheel (The distances traveled in turns by the wheels are different apart from any slip), but also of the axle loads, mounted tires or specific equipment (ex: snow chains) of the pressure of each tire.

Assessment of instant adhesion

Measurement or evaluation from engine computer parameters, of the engine torque C (t) applied to the drive wheels.

Calculation of the quantity P (t) which provides information on the instantaneous adhesion coefficient. TQD 171001 10

P (t) = G% (t) / delta C (t)

With ΔC (t) = Cav (t) -Car (t + Δt)

We then perform the calculation of two values P1 (t) and P2 (t) which will allow:

detailed monitoring of the evolution of average grip P2

• ^ reactive monitoring of the evolution of instantaneous grip P1

Step (c) End monitoring of the evolution of the average grip

P2 () = λ ^A = ^~ t'-T2 V {x) dx

Step (d) Reactive monitoring of the evolution of instant adhesion

TQD 171001 1 1

TQD 171001 1 1

With T1 <T2 in formulas P1 and P2 above.

For purely indicative purposes, an order of magnitude for T1 and T2 is:

T1: A few fractions of seconds to a few seconds (short)

T2: A few seconds to a few tens of minutes (long)

P1 is therefore a reactive function while P2 is a more precise function.

Step (e) Extraction of the final information on precarious adhesion or imminent precarious adhesion:

P1 (t) and P2 (t) are compared with respective thresholds S1 and S2 on the one hand and S3 and S4 on the other.

Thresholds S1 to S4 are parameters to be adjusted as a function of the detection strategy adopted (compromise between speed and detection accuracy) and tests carried out on the vehicle. This adjustment is within the reach of any skilled person.

The thresholds S1, S2, S3 and S4 (as well as the coefficients k and r) can also be weighted by the average forward speed of the vehicle.

A preliminary test is carried out which depends on the type used. A detection is carried out which is either rapid but not very precise or slow and precise. An acceptable and empirical compromise is then achieved between speed of measurement and accuracy of detection.

These tests are followed by counters C1 and C2 which increment and decrement according to the results.

“T> C2 makes it possible to focus more particularly on viscoplanage and on a general state of low adhesion. TQD 171001 12

"| V C1 makes it possible to focus on sudden adhesion losses such as aquaplaning or sheets of ice.

C1 and C2 are counter values which change as a function of the number 5 of exceeding thresholds S1 to S4 per unit of time.

Main advantages of the invention:

As can be seen, the advantages of the general principle of the invention are as follows.

o> Use only pre-existing information.

> Uses knowledge of the tire and the ground connection.

> Continuously assesses the level of grip without requiring heavy tire loads.

> Allows rapid detection of a sudden change in grip and 5 fine detection of the average grip level.

The invention relates to the method which has just been described, as well as the devices for implementing this method, the essential elements of which will be given below, and the vehicles equipped with these devices and / or implementing this method. .

As can be seen, the general principle of the invention, in its "device" aspect, resides in the following sequential operations:

1. The device comprises means for permanently measuring the speed Vroue (t) of rotation of each of the wheels.

This measurement can, for example, be carried out using the sensors and the conditioning used for anti-lock or anti-skid devices. TQD 171001 13

We can for example use wheel speed sensors for ABS ™ devices such as those developed by the company Siemens Automotive ™ and equipping for example the Rover ™ 75 vehicle.

5 2. It also includes means for measuring or evaluating from engine computer parameters, the engine torque C applied to the drive wheels.

The evaluation can be carried out using the following measurements or data:

B accelerator pedal position or injection rate,

o B motor rotation speed,

B gearbox ratio (or calculation of this ratio from the average speed of the drive wheels and engine speed and / or "lambda" sensor at the exhaust pipe, and / or advance signal to the ignition)

5 If a torque distributor (controlled differential for example) is used, account will be taken, in particular when cornering, of the torque actually applied to each wheel, which allows a refined assessment.

3. It also includes means for performing a front-rear time registration corresponding to the time Δt that the vehicle takes to travel a wheelbase e (or the difference between the two wheels or sets of wheels considered).

Δt = e / V

with V = vehicle speed

V is for example calculated from the average speed of the non-driving wheels or the average speed of all the wheels. TQD 171001 14

4. It also includes means for calculating for each wheel a criterion A (t) which can be for example:

B The derivative or variations of Vroue (t) and / or

B The standard deviation of Vroue (t) (standard deviation of the variations in speed of rotation of the front wheel relative to the rear wheel) and / or

B The min max deviation Vroue (t) (min-max deviation of the speed of rotation of the front wheel with respect to the rear wheel) and / or

B The instantaneous speed of the wheel Vroue (t) and / or

B The average speed of the wheel over a period of time T.

Or, in the energy spectrum of the distribution of the rotational speeds of each wheel:

B The energy over part or all of the harmonics 1 to 64 of Vroue (t) (preferably use frequency bands centered on the harmonics and with a width substantially less than 10 Hz) and / or

B The energy on one or more Vroue frequency bands preferably between 8 and 400 Hz.

(NOTE: This is another way (energy vision) of evaluating A (t) which can replace the previous one (time vision) or be combined with it.

A third method which can also replace the previous ones (temporal vision) or be combined with it is the "phase" (see below).

These three methods are classic and complementary: the time signal, its module, its phase).

NOTE: These are the frequencies of the Vroue time signal. TQD 171001 15

The harmonics will then be found on the multiple frequencies of the rotation frequency corresponding to the average speed of the wheel.

Generally the tire harmonics work in multiples with each other, and are significant up to harmonic 64. Beyond this, we arrive in the vibro-acoustic domain to which the second proposed band (8 to 400 Hz) corresponds which is set on fixed resonances (related to the structure of the tire and / or the vehicle) and no longer harmonics of the wheel speed. We can cite bands wedged for example on:

0.5-3 Hz vertical chassis mode

8-13 Hz vertical wheel mode

15-25 Hz longitudinal wheel mode

40-60 Hz tire winding modes

80-120Hz first tire mode in vertical

etc ...

Those skilled in the art are fully aware of these data and these distinctions.

One can also use the Vroue phase variations (t) by taking for example as criteria:

B The evolution of the Vroue phase (t) and / or

B The standard deviation of the Vroue phase (t) and / or

B The min max deviation of the Vroue phase (t) and / or

B The evolution of the average Vroue phase (t) over part or all of the harmonics 1 to 64 (preferably use frequency bands centered on the harmonics and with a width substantially less than 10 Hz) or the phase average over one or more frequency bands between 8 and 400 Hz, as specified above. TQD 171001 16

We can also operate by combining the methods which have just been described.

This coefficient can also be weighted by a constant value or a function of Vav (t) or Var (t) to take into account the technological differences of the front and rear train.

The formula used for the calculation of A (t) can depend on the speed of the vehicle, but also, if this information is available, on the level of excitation of the ground (information which can be provided for example by the ground link sensors used to measure the attitude of the vehicle or for controlled suspensions and shock absorbers).

The invention covers methods and devices which use or include means suitable for accessing this information.

5. It includes means for calculating a slip coefficient

G% front rear with spatial rear front registration.

G% (t) = [Aav (t) - k x Aar (t + Δt) -r] / Aar (t + Δt)

k is a coefficient which makes it possible to take into account the distribution of engine or braking torque between the compared wheels.

r is a coefficient which makes it possible to take account of the rolling resistance linked to the tires, to the elements of the ground connection and to the train settings. TQD 171001 1 7

Preferably take a front wheel and a rear wheel located on the same side of the vehicle.

Alternatively, we can take the average of the front wheels and the average of the rear wheels.

5 In the case of a vehicle with more than two axles, only one or part of the front wheels and one or part of the rear wheels will be retained.

The calculation can also be performed for any drive wheel with respect to any non-drive wheel, or between two wheels or sets of wheels on which the applied torque is known and o different.

6. It includes means for calculating an instantaneous coefficient P (t) which provides information on the instantaneous adhesion coefficient.

P (t) = G% (t) / delta C (t)

7. It calculates two values P2 (t) and P1 (t) which will allow on the one hand a fine monitoring of the evolution of the average grip and on the other hand a reactive monitoring of the evolution of the grip instant.

(réactif)P1 ( ^~

(reagent)

P2 (/)? (X) dx x = t-T2 (high precision)

With T1 <T2 TQD 171001 18

Magnitude :

T1: A few fractions of seconds to a few seconds

T2: A few seconds to a few tens of minutes

8. Extraction of final information

The device according to the invention comprises means for operating the extraction of final information, in particular means such as:

P1 and P2 are then compared with respective thresholds: S1 and S2 on the one hand and S3 and S4 on the other.

These tests or trials are followed by counters which increment and decrement according to the results of the tests or trials.

The C1 and C2 counters provide the following information:

B C2 makes it possible to focus more particularly on viscoplanage and a general state of poor adhesion.

B C1 makes it possible to focus on sudden loss of adhesion such as aquaplaning or ice sheets.

Methods and devices for improving the accuracy of detection /

During braking phases, knowing the braking torque and / or its front-to-rear distribution makes it possible to use the method presented above. This knowledge also makes it possible to improve the extraction of final information by weighting the coefficients S1, S2, S3 and S4 and / or k and r as a function of these latter elements.

This knowledge can be obtained from the braking pressures and their distribution by wheel. TQD 171001 19

Knowing the load distribution and / or the total load of the vehicle makes it possible to improve the extraction of the final information by weighting the coefficients S1, S2, S3 and S4 and / or k and r as a function of these latter elements.

This knowledge can be provided for example by the ride height sensors used in particular for adjusting the attitude of the headlights.

Knowledge of the dynamic wheel load improves the extraction of final information by weighting the coefficients S1, S2, S3 and S4 and / or k and r.

Knowledge of the dynamic load on the wheel can be evaluated, for example, from an inertial unit, and / or sensors inserted in the ground connection and used in particular for controlling the shock absorbers and suspensions.

Knowledge of the steering wheel angle can be used in the evaluation of the coefficient k for comparing wheel speeds, or even an additional factor to weight G% (t). The steering wheel angle can also be used to invalidate measurements beyond a limit steering angle. The measurement results are then considered to be non-existent for the entire duration of the overshoot of the limit angle, the counters C1 and C2 then remain unchanged.

Knowledge of the steering wheel angle can be obtained from information already available for certain devices such as electronic stability control.

Knowledge of outdoor humidity makes it possible to improve the extraction of final information by weighting the coefficients S1, S2, S3 and S4 and / or ket r.

This knowledge can for example be obtained using rain sensors used for example for piloting the windscreen wipers. TQD 171001 20

Knowledge of the outside temperature makes it possible to improve the extraction of final information by weighting the coefficients S1, S2, S3 and S4 and / or k and r.

This knowledge can, for example, be obtained using temperature sensors frequently installed on vehicles.

Knowledge of the internal temperature of the tire (tire temperature or temperature of the enclosed air) improves the extraction of final information by weighting the coefficients S1, S2, S 3 and S4 and / or k and r.

This knowledge can for example be obtained using temperature sensors installed in the wheels. We could for example use a device such as SMART TIRE from the company UniCommSignal Inc. ™.

Knowledge of the internal pressure of the pneumatic envelope makes it possible to improve the extraction of final information by weighting the coefficients S1, S2, S3 and S4 and / or k and r.

This knowledge can for example be obtained using pressure sensors installed in the wheels.

We could for example use a device such as SMART TIRE ™ from the company UniCommSignal Inc. ™

Thresholds S1, S2, S3 and S4 can also be adjusted by self-learning. A learning period will then be used during which it will be estimated that the coefficient of adhesion does not vary and is of a predetermined level.

We will identify the external context for this. TQD 171001 21

For example :

• using an external temperature sensor already present on the vehicle or additional, it will be determined whether there is no risk of ice,

- using a hygrometric measurement (for example using the automatic wiper trigger sensor) or the lack of use of the wipers when driving, it will be estimated whether there is a dry soil

- and using an estimation of the type of soil, we will estimate if we are in the presence of good soil (low energy in the low frequencies of the wheel speed signal or in a frequency band centered around the vertical wheel mode typically located at 12 Hz)).

If we are in these conditions (no risk of ice, dry soil, good soil), then we will adapt the thresholds so that, over the self-learning period, the values P1 (t) and P2 (t) remain within the majority of cases below the first set of thresholds (respectively S1 and S3) and very much below the second set of thresholds (respectively S2 and S4).

Self-learning can also be used to adjust the value of the coefficients k and r to lower the value of A (t) so that P1 (t) and P2 (t) remain in most cases lower than the first set of threshold (respectively S1 and S3) and much lower than the second set of thresholds (respectively S2 and S4).

Self-learning can be launched on an external command (on-board computer, tire monitoring system, pressure monitoring system, on-board or remote diagnosis and maintenance, etc.) or by human intervention (operator or driver). In a variant, the self-learning can be carried out continuously and in parallel with the operation of the adhesion detector. TQD 171001 22

Self-learning eliminates the effects of different types of tires, whether they are of different brands or types (for example snow tires fitted on a single axle) or their condition (for example different wear on the front axles and back).

The invention covers the methods and devices implementing, or comprising, at least part of the information (and means of access to this information) which have been described in the present application, in various combinations which will depend on the requirements of the manufacturers and standards.

Other characteristics and advantages of the invention will be better understood on reading the description which follows, and with reference to the appended drawing in which:

FIG. 1 represents the force F generated by the tire as a function of the slip; this curve, knowing that the driver generally evolves in the area of very low slips (hatched area), shows that approaches such as ABS or conventional traction control are not suitable since their operating area is located beyond the area of micro slips.

F: Force generated by the tire with ^{F =} ^ ^{Fx + Fv} )

Fx: Longitudinal force

Fy: transverse force

It can be seen in this graph that the conductors generally travel in the area of low slip, an area which is not covered by conventional devices such as ABS ™.

On the other hand, it is noted that the present device, if it operates in the field of validity of ABS ™ and traction control, also functions in the TQD 171001 23 low slip area which corresponds to more than 95% of the probability of the presence of conductors.

Figure 2 shows the block diagram of the invention

FIG. 3 represents a diagram making it possible to illustrate diagrammatically an implantation on a generic vehicle, with:

RD gear wheel

ABS ABS ™ sensor

P pneumatic

M hub

CALC ABS ™ computers, trajectory stability control, traction control

VA driver warning light (and / or audible alarm)

CELECT electrical wiring

B C Adhesive level conditioning and processing unit

RV Cruise control

FR, AR front, rear

EXAMPLE:

FIG. 3 shows a layout diagram.

Development vehicle: Rover 75 ™ TQD 171001 24

Pre-existing Siemens Automotive ™ sensors on the vehicle are used for the measurement of wheel speeds and used for Bosch ABS

TM

The signals from these sensors are then routed to a central box positioned near the ABS ™ computer.

This central unit is made up of two electronic stages:

• The analog stage which conditions the incoming analog and digital signals, contains the power supply board as well as the outgoing signal conditioning board (analog: dashboard indicator, digital: information on grip status)

• The digital stage, built around a 4-bit microcontroller, preferably 8-bit, or 16-bit, or a microprocessor or any other computer, and which performs all of the processing.

The signals from the wheel speed sensors are first conditioned by the analog input stage in order to be digitized and used by the digital processing stage.

The engine torque applied to the drive wheels (front wheels) is evaluated from the parameters provided by the engine control unit (in particular: position of the accelerator pedal, richness of the air - petrol mixture and engine speed and / or "lambda" sensor at level of the exhaust pipe, and / or ignition advance signal) and of the evaluation of the gearbox ratio used. TQD 171001 25

The latter is determined from the speed information provided by the wheel speed and engine speed sensors and / or "lambda" sensor at the exhaust, and / or ignition advance signal resumed on the engine control unit.

From all of these data, the digital processing stage evaluates micro-slippages using an algorithm using notably Hadamard's transformation (eliminates data storage and excessively complex multiplication or addition operations for a microcontroller, in particular 8 bits) applied to the signal in phase quadrature (phase elimination).

It then calculates the instantaneous grip and extracts using two parameters from counters the final information (C1, C2).

The counters have been configured to change between 0 and 255.

If one of the two counters becomes greater than 192, an indicator light composed of a light-emitting diode and a pictogram, such as the one provided below, inserted in the dashboard is lit. It does not re-extinguish until the two counters have returned below 173. The difference between the ignition value and the extinction value makes it possible to avoid an unpleasant flashing of the diode during the change of state.

This information is provided in parallel to a cruise control which has been modified to modulate its speed according to the indication of the level of grip and the distance from the previous vehicle detected using a distance sensor.

The invention also covers all the embodiments and all the applications of the methods and devices described, and vehicles of all TQD 171001 26 type using them, which will be directly accessible to those skilled in the art on reading this application, from their own knowledge.

Claims

TQD 171001 27 1 Method for detecting the grip of a vehicle tire on the ground, characterized in that the level of grip of the tire on the ground is evaluated in a first step, by means suitable for and capable of providing an assessment of the level of grip of the tire on the ground; it operates - in a completely preferred mode - continuously (and therefore preferably provides permanent information on the level of adhesion); we detect a situation of precarious grip which can lead (possibly quickly) to a loss of grip (and therefore to a high risk of serious accident) and we warn the driver and / or systems of management of precarious grip level . 2 Method according to claim 1 characterized in that it comprises the following steps: (a) evaluation of micro-sliding of the contact area A (t) (b) calculation of a quantity P (t) representative of the instantaneous adhesion (c) possibly following the end of the evolution of the average grip. 3 Method according to claim 1 or 2 characterized in that said method further comprises a step: (d) reactive monitoring of the evolution of instant adhesion. 4 Method according to any one of claims 1 to 3 characterized in that it comprises a step: TQD 171001 28 (e) extracting the information on precarious adhesion or imminent precarious adhesion from steps (c) and / or (d) and (f) sending an appropriate signal to the driver and / or means for active correction of the grip of the tires, adapted to cause a return to non-precarious grip. 5 Method according to any one of claims 1 to 4 characterized by: Step (a) Evaluation of micro slips: the implementation of step (a) for assessing micro-slippages includes the following steps: ai) the measurement of "wheel speeds" or "wheel speed" (covering the speed of advancement of the wheel and / or the speed of rotation of the wheel, ie linear and / or angular speed) through : • Measurement of hub, suspension or even chassis speeds or accelerations or by force or displacement measurements on elements of the chassis or suspensions - in particular the measurement of the rotational speeds V (t) of each of the wheels a2) possibly rearward time adjustment (for two wheels on the same right or left side) corresponding to the time delta t that the vehicle takes to travel a wheelbase (we know that the wheelbase is the distance between the front and rear axles), with the relationship: delta t = e / Vm TQD 171001 29 where Vm = vehicle forward speed and wheelbase. or characterized by: Step (a) Evaluation of micro slips: ai) means for measuring the rotational speeds V (t) of each of the wheels a2) optionally, rear rear time registration means (for two wheels on the same right or left side) corresponding to the time delta t that the vehicle takes to travel a wheelbase (we know that the wheelbase is the distance between the front axles and back), with the relation: delta t = e / Vm where Vm = vehicle speed and e = wheelbase. 6 Method according to any one of claims 1 to 5 characterized in that, in the case where the basic information is obtained by sensors other than the "wheel speed" sensors, the search for harmonics or phase is will either be by autocorrelation of the basic signal, or by convolution with a signal representative of the speed of the wheel or of the average speed of a set of wheels of the vehicle, this last signal being able to come for example from the information speed available on all vehicles or wheel speed sensors used for ABS. TQD 171001 30 7 Method according to any one of claims 1 to 6 characterized in that the wheel speed is measured using sensors already installed on the vehicle (sensors used for ABS ™ anti-lock brakes, traction control or trajectory control) or additional such as optical encoders, magnetic encoders, accelerometers (optical or magnetic "encoders" being geometric elements marked either optically or magnetically, and arranged according to a code readable by a sensor). 8 Method according to any one of claims 1 to 7 characterized in that, in order to refine the precision of the wheel speed measurements, it will be possible to carry out a measurement of the time separating two successive counting events (eg tooth for toothed wheel) or, in a variant making it possible to increase the accuracy of the measurements and making it possible in particular to overcome the irregularity of events (teeth for toothed wheel) and of their shape, the time elapsing from an event to itself one turn after, and we will preferably perform this calculation for each of the events (teeth for cogwheel) that punctuate the wheel turn, thus obtaining as many extremely precise measurements of the wheel speed for a wheel turn as events (teeth for toothed wheel). 9 Method according to any one of claims 1 to 8 characterized in that an evaluation of the μ-slips is carried out, for each wheel with calculation, from V (t), of the criterion A (t) representative of the μ- slip in the contact area, V (t) possibly being the speed of the wheel or any other criterion representative of the speed of the wheel or of its variations, such as signals of acceleration, forces, or displacement and the like, and characterized in that it can also optionally include a step of implementing means for calculating for each wheel said criterion A (t) which can be, for example, possibly: B The derivative or variations of Vroue (t) and / or B The standard deviation of Vroue (t) (standard deviation of the variations in speed of rotation of the front wheel relative to the rear wheel) and / or TQD 171001 31 B The min max deviation Vroue (t) (min-max deviation of the speed of rotation of the front wheel with respect to the rear wheel) and / or B The instantaneous speed of the wheel Vroue (t) and / or B The average speed of the wheel over a period T, or, in the energy spectrum of the distribution of the rotational speeds of each wheel: B The energy over part or all of the harmonics 1 to 64 of Vroue (t) (preferably use frequency bands centered on the harmonics and with a width substantially less than 10 Hz) and / or The energy on one or more Vroue frequency bands preferably between 8 and 400 Hz. or the Vroue (t) phase variations taking for example as criteria: The evolution of the Vroue (t) phase and / or B The standard deviation of the Vroue phase (t) and / or B The min max deviation of the Vroue phase (t) and / or The evolution of the average Vroue phase (t) over part or all of the harmonics 1 to 64 (preferably use frequency bands centered on the harmonics and with a width substantially less than 10 Hz) or the average phase on one or more frequency bands between 8 and 400 Hz, or means to operate by combination of the above methods, TQD 171001 32 this coefficient can also be optionally weighted by a constant value or function of Vav (t) or Var (t) to take into account the technological differences of the front axle front and rear axle, and the formula used for the calculation of A (t) can depend on the speed of the vehicle, but also, if this information is available, on the level of excitation of the ground (information which can be provided for example by the ground link sensors used to measure the attitude of the vehicle or for controlled suspensions and shock absorbers). 10 Method according to any one of claims 1 to 9 characterized in that it comprises: Step (b) Instant adhesion: Assessment of instant adhesion Calculation of the sliding coefficient G% with front - rear spatial registration. G% (t) ≈ [Aav (t) - k x Aar (t + Δt) -r] / Aar (t + Δt) k, r (values to be adjusted depending on the vehicle) k may be a variable value, in particular as a function of the steering angle of the steering wheel (the distances traveled in turns by the wheels being different apart from any slip), but also of the axle loads, of the tires fitted or of specific equipment (ex: snow chains) of the pressure of each tire. TQD 171001 33 Assessment of instant adhesion Measurement or evaluation from engine computer parameters, of the engine torque C (t) applied to the drive wheels. Calculation of the quantity P (t) which provides information on the instantaneous adhesion coefficient. P (t) = G% (t) / delta C (t) With ΔC (t) = Cav (t) -Car (t + Δt) We then perform the calculation of two values P1 (t) and P2 (t) which will allow: detailed monitoring of the evolution of average grip P2 • reactive monitoring of the evolution of instant adhesion P1 (cf. step c) 11 Method according to any one of claims 1 to 10 characterized in that it comprises Step (c) End monitoring of the evolution of the average grip: TQD 171001 34

Step (d) Reactive monitoring of the evolution of instant adhesion: Pl <7) = V (x) dx x = t-T \ With T1 <T2 in formulas P1 and P2 above. an order of magnitude for T1 and T2 being: T1: A few fractions of seconds to a few seconds (short) T2: A few seconds to a few tens of minutes (long) 12 Method according to any one of claims 1 to 11 characterized in that it comprises: Step (e) Extraction of the final information on precarious adhesion or imminent precarious adhesion: P1 (t) and P2 (t) are compared with respective thresholds S1 and S2 on the one hand and S3 and S4 on the other hand, the thresholds S1 to S4 being parameters to be adjusted as a function of the detection strategy adopted ( compromise between speed and detection accuracy) and tests performed on the vehicle, the thresholds S1, S2, S3 and S4 (as well as the coefficients k and r) can also be weighted by the average forward speed of the vehicle. We carry out a preliminary test which depends on the typing used - TQD 171001 35 A detection is carried out which is either rapid but not very precise or slow and precise. An acceptable and empirical compromise is then achieved between speed of measurement and accuracy of detection. These tests are followed by counters C1 and C2 which increment and decrement according to the results. "^ C2 makes it possible to focus more particularly on viscoplanage and a general state of poor adhesion. • f C1 makes it possible to focus on sudden adhesion losses such as aquaplaning or ice sheets. C1 and C2 being counter values which change as a function of the number of thresholds S1 to S4 being exceeded per unit of time. 13 Device for detecting the grip of a vehicle tire on the ground, characterized in that it comprises means for assessing, in a first step, the level of grip of the tire on the ground, that is to say means suitable for and capable of providing an assessment of the level of grip of the tire on the ground; able to operate - in an entirely preferred mode - continuously (and therefore preferably to provide permanent information on the level of adhesion); means for detecting and: or calculating a situation of precarious grip which can lead (possibly quickly) to a loss of grip (and therefore a high risk of serious accident) and means for warning the driver and / or warning, or interact with precarious grip level management systems, already existing or not on the vehicle. 14 Device according to claim 13 characterized in that it comprises (a) means for evaluating micro-sliding of the contact area A (t) TQD 171001 36 (b) means for calculating a quantity P (t) representative of the instantaneous adhesion (c) possibly means for monitoring the evolution of the average grip. 15 Device according to any one of claims 13 or 14 characterized in that it further comprises: (d) means capable of reactively monitoring the evolution of instantaneous adhesion. 16 Device according to any one of claims 13 to 15 characterized in that it comprises: (e) means for extracting information from precarious adhesion or imminent precarious adhesion from steps (c) and / or (d) and (f) means for sending an appropriate signal to the driver and / or to means for active correction of the grip of the tires, adapted to cause a return to non-precarious grip. 17 Device according to any one of claims 13 to 16 characterized by: Step (a) Evaluation of micro slips: ai) means for measuring the rotational speeds V (t) of each of the wheels a2) optionally, rear rear time registration means (for two wheels on the same right or left side) corresponding TQD 171001 37 at time delta t that the vehicle takes to travel a wheelbase (we know that the wheelbase is the distance between the front and rear axles), with the relation: delta t = e / Vm where Vm = vehicle speed and e = wheelbase. 18 Device according to any one of claims 13 to 17 characterized in that, in the case where the basic information is obtained by sensors other than the "wheel speed" sensors, the search for harmonics or phase takes place. will make either by means of autocorrelation of the basic signal, or by means of convolution with a signal representative of the speed of the wheel or of the average speed of a set of wheels of the vehicle, this latter signal being able to come for example speed information available on all vehicles or wheel speed sensors used for ABS ™. 19 Device according to any one of claims 13 to 18 characterized in that the wheel speed is measured using sensors already installed on the vehicle (sensors used for ABS ™ anti-lock brakes, traction control or trajectory control) or additional such as optical encoders, magnetic encoders, accelerometers (optical or magnetic "encoders" being geometric elements marked either optically or magnetically, and arranged according to a code readable by a sensor). 20 Device according to any one of claims 13 to 19 characterized in that, in order to refine the accuracy of the wheel speed measurements, it comprises means for measuring the time separating two successive counting events (eg tooth for toothed wheel) or, in a variant making it possible to increase the accuracy of the measurements and TQD 171001 38 allowing to overcome in particular the irregularities of events (teeth for toothed wheel) and their shape, we will count the time elapsing from an event to itself a turn after, and means to perform preferably this calculation for each of the events (teeth for toothed wheel) which punctuate the wheel turn, thus obtaining as many extremely precise measurements of the wheel speed for one wheel turn as there are events (teeth for toothed wheel). 21 Device according to any one of claims 13 to 20 characterized in that it comprises means for carrying out an evaluation of the μ-slips, for each calculation wheel, from V (t), of the representative criterion A (t) μ-sliding in the contact area. 22 Device according to any one of claims 13 to 21 characterized in that it comprises: Step (b) Instant adhesion: Assessment of instant adhesion Means for calculating the sliding coefficient G% with front - rear spatial registration. G% (t) = [Aav (t) - k x Aar (t + Δt) -r] / Aar (t + Δt) k, r (values to be adjusted depending on the vehicle) k may be a variable value, in particular as a function of the steering angle of the steering wheel (the distances traveled in turns by the wheels being different apart from any slip), but also of the axle load, of the tires fitted or of specific equipment (ex: snow chains) of the pressure of each tire. Assessment of instant adhesion TQD 171001 39 Means of measurement or evaluation from parameters of the engine computer, of the engine torque C (t) applied to the drive wheels. Means for calculating the quantity P (t) which provides information on the instantaneous adhesion coefficient. P (t) = G% (t) / delta C (t) With ΔC (t) = Cav (t) -Car (t + Δt) 23 Device according to any one of claims 13 to 22 characterized in that it comprises means for permanently measuring the Vroue speeds (t) of rotation of each of the wheels, this measurement being able to be carried out using sensors and packaging used for anti-lock or anti-skid devices, such as for example wheel speed sensors for ABS ™ devices such as those developed by the company Siemens Automotive ™ and equipping for example the vehicle Rover ™ 75. 24 Device according to any one of claims 13 to 23 characterized in that it also comprises means for measuring or evaluating from parameters of the engine computer, the engine torque C applied to the drive wheels, TQD 171001 40 the evaluation can be carried out using the following measurements or data obtained by the following means: B accelerator pedal position or injection rate, B motor rotation speed, B gearbox ratio (or calculation of this ratio from the average speed of the drive wheels and engine speed and / or "lambda" sensor at the exhaust pipe, and / or advance signal to the ignition) and, in the case of using a torque distributor (controlled differential for example) means for taking into account, in particular when cornering, the torque actually applied to each wheel. 25 Device according to any one of claims 13 to 24 characterized in that it also comprises means for carrying out a time adjustment front - rear corresponding to the time Δt that the vehicle takes to travel a wheelbase e (or the difference between the two wheels or sets of wheels considered). Δt = e / V with V = vehicle speed V being for example calculated from the average speed of the non-driving wheels or the average speed of all the wheels. 26 Device according to any one of claims 13 to 25 characterized in that it also comprises means for calculating for each wheel a criterion A (t) which can be for example: The derivative or variations of Vroue (t) and / or TQD 171001 41 m The standard deviation of Vroue (t) (standard deviation of the variations in speed of rotation of the front wheel compared to the rear wheel) and / or a The min max deviation Vroue (t) (min-max deviation of the speed of rotation of the front wheel with respect to the rear wheel) and / or B The instantaneous speed of the wheel Vroue (t) and / or B The average speed of the wheel over a period T, or, in the energy spectrum of the distribution of the rotational speeds of each wheel: B The energy over some or all of the harmonics 1 to 64 of Vroue (t) (preferably use frequency bands centered on the harmonics and with a width substantially less than 10 Hz) el / or m The energy on one or more Vroue frequency bands preferably between 8 and 400 Hz. or the Vroue (t) phase variations taking for example as criteria: a The evolution of the Vroue phase (t) and / or B The standard deviation of the Vroue phase (t) and / or B The min max deviation of the Vroue phase (t) and / or B The evolution of the average Vroue phase (t) over part or all of the harmonics 1 to 64 (preferably use frequency bands centered on the harmonics and with a width substantially less than 10 Hz) or the phase average over one or more frequency bands between 8 and 400 Hz, TQD 171001 42 or means for operating by combination of the above methods, this coefficient can also be weighted by a constant value or function of Vav (t) or Var (t) to take into account the technological differences of the front and rear axle and the formula used for the calculation of A (t) can depend on the speed of the vehicle, but also, if this information is available, on the level of excitation of the ground (information which can be provided for example by the ground link sensors used to measure the attitude of the vehicle or for controlled suspensions and shock absorbers). 27 Device according to any one of claims 1 to 26 characterized in that it comprises means for calculating a slip coefficient G% front rear with spatial rear front registration. G% (t) = [Aav (t) - k x Aar (t + Δt) -r] / Aar (t + Δt) k is a coefficient which makes it possible to take into account the distribution of engine or braking torque between the compared wheels. r is a coefficient which makes it possible to take account of the rolling resistance linked to the tires, to the elements of the ground connection and to the train settings. preferably using means positioned on a front wheel and a rear wheel located on the same side of the vehicle, optionally using the average of the front wheels and the average of the rear wheels. TQD 171001 43 and, in the case of a vehicle comprising more than two axles, only means positioned at the level of one or a part of the front wheels, and of one or a part of the rear wheels will be retained. or means positioned at any drive wheel relative to any non-drive wheel, or between two wheels or sets of wheels on which the applied torque is known and different. 28 Device according to any one of claims 13 to 27 characterized in that it comprises means for calculating an instantaneous coefficient P (t) which provides information on the instantaneous coefficient of adhesion. P (t) = G% (t) / delta C (t) And means to calculate two values P2 (t) and P1 (t) which will allow on the one hand a fine monitoring of the evolution of the average grip and on the other hand a reactive monitoring of the evolution of the instant adhesion. Pl (/) = P (fe.,. _A ^J x = ι-n ^ (reactive) x = t P2 (/) P (x) dx x = t-T2 (high precision) With T1 <T2 Magnitude : T1: A few fractions of seconds to a few seconds TQD 171001 44 T2: A few seconds to a few tens of minutes 29 Device according to any one of claims 13 to 28 characterized in that it comprises means for operating the extraction of final information, in particular means such as: P1 and P2 are then compared with respective thresholds: S1 and S 2 on the one hand and S3 and S4 on the other. these tests or trials are followed by counters which increment and decrement according to the results of the tests or trials. - C1 and C2 meters are able to provide the following information B C2 makes it possible to focus more particularly on viscoplanage and a general state of poor adhesion. B C1 makes it possible to focus on sudden loss of adhesion such as aquaplaning or ice sheets. 30 Device according to any one of claims 13 to 29 characterized in that means are used to access the braking pressures and their distribution by wheel. and / or t means of access to knowledge of the load distribution and / or of the total load of the vehicle, such as for example the ride height sensors used in particular for adjusting the headlight trim, and / or means for accessing the knowledge of the dynamic load on the wheel, for example from an inertial unit, and / or sensors inserted in the ground connection and used in particular for controlling the shock absorbers and suspensions, and / or TQD 171001 45 means of access to the knowledge of the steering angle, which can be obtained from information already available for certain devices such as electronic stability control, and / or means of access to the knowledge of the external hygrometry which can for example be obtained using rain sensors serving for example for piloting the windscreen wipers, and / or means of access to the knowledge of the outside temperature which can for example be obtained using temperature sensors frequently installed on vehicles, and / or means of access to the knowledge of the internal temperature of the pneumatic envelope (temperature of the tire or temperature of the enclosed air) which can for example be obtained using temperature sensors installed in the wheels, such as a device such as SMART TIRE ™ from the company UniCommSignal Inc. ™, and / or means of access to the knowledge of the internal pressure of the pneumatic envelope which can for example be obtained using pressure sensors installed in the wheels, such as a device such as the SMART TIRE ™ from the company UniCommSignal Inc. ™. 31 Device according to any one of claims 13 to 30 characterized in that the thresholds S1, S2, S3 and S4 can also be adjusted by self-learning and a learning period will then be used during which it is estimated that the coefficient of adhesion does not vary and is of a predetermined level, identifying for this the external context. For example • using an external temperature sensor already present on the vehicle or additional, no risk of ice, ^B using a hygrometric measurement (for example using the automatic wiper trigger sensor) or the lack of use of the wipers when driving, presence of dry ground TQD 171001 46 - and using means of estimating the type of soil, in order to estimate if there is good soil (low energy in the low frequencies of the wheel speed signal or in a frequency band centered around the vertical wheel mode typically located at 12 Hz)). 32 Method according to any one of claims 1 to 12 characterized in that the thresholds S1, S2, S3 and S4 are adjusted by self-learning and a learning period is used during which it is estimated that the coefficient of adhesion does not vary not and is of a predetermined level, identifying for this the external context. For example • using an external temperature sensor already present on the vehicle or additional, no risk of ice, • using a hygrometric measurement (for example using the automatic wiper trigger sensor) or the lack of use of the wipers when driving, presence of dry ground • and using means of estimating the type of soil, in order to estimate whether there is good soil (low energy in the low frequencies of the wheel speed signal or in a frequency band centered around the vertical wheel mode typically located at 12 Hz)). 33 Method according to any one of claims 1 to 12 and 32, characterized in that if one is in these conditions (absence of risk of ice, dry soil, good soil), then the thresholds will be adapted so that, over the period self-learning, the values P1 (t) and P2 (t) remain in the majority of cases lower than the first set of thresholds (respectively S1 and S3) and much lower than the second set of thresholds (respectively S2 and S4). 34 Method according to any one of claims 1 to 12 and 32 and 33, characterized in that self-learning is used to adjust the value of the coefficients k and r to lower the value of A (t) so that P1 (t) and P2 (t) remain in the majority of cases lower than the first set of thresholds (respectively S1 and S3) and much lower than the second set of thresholds (respectively S2 and S4). TQD 171001 47 35 Method according to any one of claims 1 to 12 and 32 to 34, characterized in that the self-learning is launched on an external command (on-board computer, tire monitoring system, pressure monitoring system, diagnosis and on-board or remote maintenance ...) or by human intervention (operator or driver) or in that self-learning is carried out continuously and in parallel with the operation of the adhesion detector device. 36 Method according to any one of claims 1 to 12 and 31 to 35, characterized in that from the set of data, a digital processing stage evaluates the micro-slips using an algorithm using in particular Hadamard's transformation (eliminates data storage and multiplication or addition operations that are too complex for a microcontroller, in particular 8 bits) applied to the signal in phase quadrature (phase elimination). 37 Method according to any one of claims 1 to 12 and 31 to 36, characterized in that said set of data is obtained as follows: for the measurement of wheel speeds the pre-existing Siemens Automotive ™ sensors on the vehicle and used for Bosch ABS TM the signals from these sensors are then routed to a central box positioned near the ABS ™ computer. said central unit is composed of two electronic stages: • The analog stage which conditions the incoming analog and digital signals, contains the power supply board as well as the outgoing signal conditioning board (analog: and / or digital, dashboard indicator and / or information on the status of the adhesion) TQD 171001 48 • The digital stage, structured around a 4-bit microcontroller, preferably 8-bit, or 16-bit, or a microprocessor or any other computer, and which performs all of the processing, the signals from the wheel speed sensors are first conditioned by the analog input stage in order to be digitized and used by the digital processing stage. the engine torque applied to the drive wheels (front wheels) is evaluated from the parameters provided by the engine control unit (in particular: position of the accelerator pedal, richness of the air - petrol mixture and engine speed and / or "lambda" sensor at level of the muffler, and / or ignition advance signal) and of the evaluation of the gearbox ratio used, the latter being determined from the speed information provided by the wheel speed sensors and of the engine speed and / or "lambda" probe at the exhaust pipe, and / or ignition advance signal resumed on the engine control unit. and in that, from all of this data, the digital processing stage evaluates the micro-slips using an algorithm using notably the Hadamard transformation (eliminates data storage and operations multiplication or addition too complex for an 8-bit microcontroller) applied to the phase quadrature signal (phase elimination). and then calculates the instantaneous adhesion and extracts, using two parameters from counters, the final information (C1, C2). the counters have been configured to change between 0 and 255. If one of the two counters becomes greater than 192, an indicator light composed of a light-emitting diode and a pictogram, such as the one provided below, inserted in the dashboard is lit. It never turns off TQD 171001 49 only when the two counters have returned below 173. The difference between the ignition value and the extinction value makes it possible to avoid an unpleasant flashing of the diode during the change of state, this information is supplied in parallel to a cruise control which has been modified to modulate its speed as a function of the indication of the level of grip and the distance from the previous vehicle detected using a distance sensor. 38 Device according to any one of claims 13 to 31 characterized in that one uses, on a development vehicle: Rover 75 ™ for the measurement of wheel speeds the pre-existing Siemens Automotive ™ sensors on the vehicle and used for Bosch ABS TM the signals from these sensors are then routed to a central box positioned near the ABS ™ computer. said central unit is composed of two electronic stages: • The analog stage which conditions the incoming analog and digital signals, contains the power supply board as well as the outgoing signal conditioning board (analog: dashboard indicator, digital: information on grip status) TQD 171001 50 • The digital stage, built around a 4-bit microcontroller, preferably 8-bit, or 16-bit, or a microprocessor or any other computer, and which performs all of the processing. the signals from the wheel speed sensors are first conditioned by the analog input stage in order to be digitized and used by the digital processing stage. the engine torque applied to the drive wheels (front wheels) is evaluated from the parameters provided by the engine control unit (in particular: position of the accelerator pedal, richness of the air - petrol mixture and engine speed and / or "lambda" sensor at level of the muffler, and / or engine ignition advance signal) and of the evaluation of the gearbox ratio used, the latter being determined from the speed information provided by the speed sensors wheels and engine speed (and / or "lambda" sensor at the exhaust pipe, and / or ignition advance signal) taken up on the engine control unit. and in that, from all of this data, the digital processing stage evaluates the micro-slips using an algorithm using notably the Hadamard transformation (eliminates data storage and operations multiplication or addition too complex for an 8-bit microcontroller) applied to the phase quadrature signal (phase elimination), and then calculates the instantaneous adhesion and extracts, using two parameters from counters, the final information (C1, C2), the counters have been configured to change between 0 and 255. if one of the two counters becomes greater than 192, an indicator light composed of a light-emitting diode and a pictogram, such as the one provided below, inserted in the dashboard is on and does not go out again until the two counters are ironed below 173, the gap TQD 171001 51 between the ignition value and the extinction value to avoid an unpleasant flashing of the diode during the change of state, this information is supplied in parallel to a cruise control which has been modified to modulate its speed as a function of the indication of the level of grip and the distance from the previous vehicle detected using a distance sensor. 39 Vehicles characterized in that they are equipped with at least part of the devices, and / or implement at least part of the methods described in any one of claims 1 to 38.