FR2815712A1 - Method, for detecting motor vehicle tire adherence to the ground, involves continuous evaluation of micro-slips in contact zone, calculation of magnitude representing instantaneous adherence, and sending warning to driver if needed - Google Patents

Abstract

Method includes the following stages : continuous evaluation of micro-slips in a contact zone (A(t)); calculation of a magnitude (P(t)) representing the instantaneous adherence; deduction of the average adherence; react to the average adherence; extract poor adherence data from stages 3 and/or 4; send an appropriate signal to the driver or active correction system so as to return to a good grip condition. A device permanently measures the rotational speed (Vroue(t)) of each wheel. This measurement may be done by sensors and system used to stop wheel locking and skidding. Elements are used to evaluate, from the engine parameters, the engine torque applied to the driving wheels, either by accelerator position or fuel injection or engine rotational speed or ignition advance signal and relationship to gearbox. Independent claims are also included for (a) the system for continuous evaluation of tire road grip.

Description

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

Objective 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>.

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Il existe donc un besoin important et reconnu pour un dispositif et un procédé qui permettrait une détermination en continu du niveau d'adhérence afin de passer d'une logique actuelle sécuritaire passive ou défensive à une approche active et anticipatrice.

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.

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

'Ou par des mesures d'effort ou de déplacement sur des éléments du châssis ou des suspensions (Par simplicité, on ne le mentionnera pas et l'ensemble sera compris dans le vocable vitesse roue et vocables analogues, y compris dans les revendications). As will be understood by a person skilled in the art, it will be possible, throughout the text, to replace the measurement of the speeds of the wheels or or wheel speed and similar terms (covering as 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: 'Measuring hub or suspension 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.

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Résumé de l'invention :

L'objet général de la présente invention est donc de fournir une évaluation du niveau d'adhérence du pneumatique sur le sol ; d'opérer-selon un mode tout à fait préféré mais non limitatif-en continu (et donc de fournir une information permanente sur le niveau d'adhérence) ; de déceler une situation d'adhérence précaire pouvant conduire rapidement à une perte d'adhérence (et donc à un risque élevé d'accident grave) et d'en avertir rapidement le conducteur et/ou des systèmes de gestion de niveau d'adhérence précaire.

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 nonlimiting 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 vehicle or four-wheel drive type traction. Otherwise, it would suffice to replace in the illustration 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

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ou de la zone de contact pneu/sol va/vont se tordre, ce qui provoque un glissement apparent dénommé pseudo-gtissement . L'homme de métier considère que le pneu se déradialise .

or the tire / ground contact area will / will twist, causing an apparent slip called pseudo-swelling. 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 systems of the ABSTM (anti-locking wheels) and traction control type, 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 ahead then be mainly attributed to the tire, and not to the ground. The tire will slide in spurts 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:

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 (a) evaluation of the micro-slippages of the contact area A (t) (b) calculation of a quantity P (t) representative of the instantaneous adhesion (c) possibly followed at the end of the evolution of the adhesion average.

 According to an entirely preferred embodiment, the general method according to the invention further comprises a step: (d) reactive monitoring of the evolution of the instantaneous adhesion.

According to yet 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 eVou means for active correction of the grip of the tires, adapted to cause a return to non-precarious grip.

Step (a) Evaluation of micro slippages: According to a preferred but nonlimiting embodiment, the implementation of step (a) of evaluation of micro slips comprises the following steps: a1) 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 cover a wheelbase (we know that the wheelbase is the distance between the front and rear axles), with the relation: delta t = e / Vm

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où Vm = vitesse d'avancement du véhicule et e = empattement.

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 the slip and the torque is generally high; A (t) is a simple criterion (mean and standard deviation).

At high speed, the slip is 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: If 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 wheel speed or the 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 anti-lock brakes ABS, 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 is known to those skilled in the art, geometric elements marked either optically or magnetically, and arranged according to a code readable by a sensor). The magnetic encoders of the ContinentaFM 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.

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qui ponctuent le tour de roue. On aura ainsi autant de mesures extrêmement précise de la vitesse roue pour un tour de roue que d'évènements (dents pour roue dentée). 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 (eg tooth for toothed wheel) or in a variant allowing to increase the accuracy of the measurements and allowing to overcome in particular the lack of regularity of events (teeth for toothed wheel) and their form, we will count the time elapsing from an event to itself a turn after. This will give an extremely precise measurement of the time taken to complete a wheel revolution and therefore an extremely precise measurement of the wheel speed. We will preferably perform this calculation for each of the events (teeth for toothed wheel)

that punctuate the wheel. 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).

critère A (t) représentatif des p-glissements dans l'aire de contact, V (t) pouvant être la vitesse de la roue ou tout autre critère représentatif de la vitesse de la roue ou de ses variations, tels que des signaux d'accélération, d'efforts, ou de déplacement et analogues, comme indiqué plus haut. Le procédé peut comprendre également éventuellement une étape de mise en oeuvre de moyens pour calculer pour chaque roue ledit critère A (t) qui peut être par exemple, éventuellement : * La dérivée ou les variations de Vroue (t) et/ou * L'écart type de Vroue (t) (écart type des variations de vitesse de rotation de la roue avant par rapport à la roue arrière) et/ou . L'écart min max Vroue (t) (écart min-max de la vitesse de rotation de la roue avant par rapport à la roue arrière) et/ou * La vitesse instantanée de la roue Vroue (t) et/ou * La vitesse moyenne de la roue sur une durée T, Assessment of u-alissements. 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 sliding 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, effort, or displacement and the like, as noted 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: * The derivative or the variations of Vroue (t) and / or * L ' standard deviation of Vroue (t) (standard deviation of the variations in speed of rotation of the front wheel with respect to the rear wheel) and / or. The min max deviation Vroue (t) (min-max deviation of the speed of rotation of the front wheel compared to the rear wheel) and / or * The instantaneous speed of the wheel Vroue (t) and / or * The speed wheel average over time T,

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 or, in the energy spectrum of the distribution of the rotational speeds of each wheel: - The energy over some or all of the harmonics 1 to 64 of Vroue (t) (preferably use frequency bands centered on harmonics and of 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 phase variations (t) taking for example as criterion: a The evolution of the Vroue phase (t) and / or a The standard deviation of the Vroue phase (t) and / or a 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 phase average over one or more frequency bands between 8 and 400 Hz, or means for op erect by combination of the above methods, this coefficient can also be optionally weighted by a constant value or function of Vav (t) or Var (t) to take account of the technological differences of the front and rear axle.

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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).

G% (t) = [Aav (t)-k x Aar (t+At)-r]/Aar (t+At) k, r : valeurs à ajuster en fonction du véhicule, de manière accessible à l'homme de métier ; k peut être une valeur variable, notamment en fonction de l'angle de braquage du volant (Les distances parcourues en virage par les roues sont différentes en dehors de tout glissement), mais aussi de la charge des essieux, des pneus montés ou équipements spécifiques (ex : chaînes neige) de la pression de chacun des pneumatiques. Evaluation de l'adhérence instantanée Mesure ou évaluation à partir de paramètres du calculateur moteur, du couple moteur C (t) appliqué aux roues motrices. Step (b) Instant adhesion: Evaluation of instant adhesion Calculation of the slip coefficient G% with front-rear spatial registration.

G% (t) = [Aav (t) -kx Aar (t + At) -r] / Aar (t + At) k, r: values to be adjusted according to the vehicle, in a way 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 instantaneous grip Measurement or assessment from engine computer parameters, of the engine torque C (t) applied to the drive wheels.

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

Avec AC (t) = Cav (t)-Car (t+ At) On effectue ensuite le calcul de deux valeurs P1 (t) et P2 (t) qui vont permettre : .. un suivi fin de l'évolution de l'adhérence moyenne P2 .. un suivi réactif de l'évolution de l'adhérence instantanée P1

Etape (c) Suivi fin de l'évolution de l'adhérence moyenne :

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

With AC (t) = Cav (t) -Car (t + At) We then perform the calculation of two values P1 (t) and P2 (t) which will allow: .. fine monitoring of the evolution of the adhesion average P2 .. reactive monitoring of the evolution of instantaneous grip P1

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

Etape (d) Suivi réactif de l'évolution de l'adhérence instantanée :

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

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Avec T1 < T2 dans les formules P1 et P2 ci-dessus.

With T1 <T2 in formulas P1 and P2 above.

P1 (t) et P2 (t) sont comparés à des seuils respectifs S1 et S2 d'une part et S3 et S4 d'autre part. Purely as an indication, 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.

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.. C2 makes it possible to focus more particularly on viscopianage and on a general state of low adhesion.

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

Comme on le voit, les avantages du principe général de l'invention sont les suivants. C1 and C2 are counter values which change as a function of the number of thresholds S1 to S4 exceeded 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.

 > Only uses 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 an abrupt change in grip and 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 speeds Vroue (t) of rotation of each of the wheels.

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

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

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:. accelerator pedal position or injection rate,. engine rotation speed, 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 when switching on) In the case of the use of a torque distributor (controlled differential for example), the torque actually applied to each wheel will be taken into account, in particular when cornering, which allows a refined assessment.

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

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 with V = forward speed of the vehicle V is for example calculated from the average speed of the non-driving wheels or the average speed of all the wheels.

roue avant par rapport à la roue arrière) eVou * La vitesse instantanée de la roue Vroue (t) eVou * La vitesse moyenne de la roue sur une durée T. Ou, dans le spectre d'énergie de la distribution des vitesses de rotation de chaque roue : # L'énergie sur une partie ou la totalité des harmoniques 1 à 64 de Vroue (t) (on utilisera de préférence des bandes de fréquence centrées sur les harmoniques et de largeur sensiblement inférieure à 10 Hz) et/ou * L'énergie sur une ou plusieurs bandes de fréquence de Vroue comprises de préférence entre 8 et 400 Hz.

4. It also includes means for calculating for each wheel a criterion A (t) which can be for example: # The derivative or the variations of Vroue (t) eVou # The standard deviation of Vroue (t) (standard deviation of variations in the speed of rotation of the front wheel relative to the rear wheel) eVou 'The min max deviation Vroue (t) (min-max deviation of the rotation speed of the

front wheel relative to the rear wheel) eVou * The instantaneous speed of the wheel Vroue (t) eVou * 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: # The energy on 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 * L 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).

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

 NOTE: These are the frequencies of the Vroue time signal.

 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 corresponds (8 to 400
Hz) which is set on fixed resonances (linked to the structure of the tire and / or vehicle) and no longer harmonics of the wheel speed. We can cite bands wedged for example on: 0.5-3 Hz chassis vertical mode 8-13 Hz wheel vertical mode 15-25 Hz longitudinal wheel mode 40-60 Hz tire winding modes 80-120Hz first tire mode vertical etc ...

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

We can also use the Vroue phase variations (t) by taking for example as criteria: * The evolution of the Vroue phase (t) and / or * The standard deviation of the Vroue phase (t) and / or * 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 of substantially width

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 less than 10 Hz) or the average phase on one or more frequency bands between 8 and 400 Hz, as specified above.

 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 sliding coefficient G% before backward with spatial adjustment before backward.

 G% (t) = [Aav (t) -kx Aar (t + At) -r] / Aar (t + At) k is a coefficient which allows to take into account the distribution of engine or brake 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.

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 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.

In the case of a vehicle comprising 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 carried out for 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.

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 follow-up of the evolution of the average grip and on the other hand a reactive monitoring of the evolution of instant adhesion.

f-' "j,-r2 (grande précision) xr P) (0 = P ((reacM)

f- '"j, -r2 (high precision)

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 With T1 <T2 Order of 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: * C2 makes it possible to focus more particularly on viscoplanage and on a general state of low adhesion.

l'aquaplanage ou les plaques de verglas.

* C1 makes it possible to take an interest in sudden adhesion losses such as

aquaplaning or ice sheets.

Methods and devices to improve the detection accuracy! During braking phases, knowing the braking torque ur eVou of 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.

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La connaissance de la répartition de charge et/ou de la charge totale du véhicule permettent d'améliorer l'extraction des informations finales en pondérant les coefficients S1, S2, S3 et S4 et/ou k et r en fonction de ces derniers éléments.

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 ketr.

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

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La connaissance de la température extérieure permet d'améliorer l'extraction des informations finales en pondérant les coefficients S1, S2, S3 et S4 eVou ketr.

Knowledge of the outside temperature improves the extraction of final information by weighting the coefficients S1, S2, S3 and S4 eVou ketr.

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

Knowing 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, S3 and S4 eVou 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 UniCommSignat tnc. . 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 TYRETM from the company UniCommSignat) nc.

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.

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For example: 'using an external temperature sensor already present on the vehicle or additional, we will determine if there is no risk of ice,' using a hygrometric measurement (for example at 'using the automatic wiper trigger sensor) or the lack of use of the wipers when driving, we will estimate if we are in the presence of dry ground' and using an estimate of the type of ground, we will estimate if we are in the presence of good ground (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)).

que les valeurs P1 (t) et P2 (t) restent dans la majorité des cas inférieures au premier jeu de seuils (respectivement S1 et S3) et très inférieurs au deuxième jeu de seuils (respectivement S2 et S4). L'auto apprentissage peut également être mis à profit pour ajuster la valeur des coefficients k et r pour abaisser la valeur de A (t) afin que P1 (t) et P2 (t) restent dans la majorité des cas inférieurs au premier jeu de seuil (respectivement S1 et S3) et très inférieurs au deuxième jeu de seuils (respectivement S2 et S4). If we are in these conditions (absence of risk of ice, dry soil, good soil), atoms we will adapt the thresholds for, over the self-learning period,

that 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). 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.

<Desc / Clms Page number 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.

puisque leur zone de fonctionnement se situe au delà de la zone des micro glissements.

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 field of very low slips (hatched area), shows that the approaches type ABS or conventional traction control are not suitable

since their operating zone is located beyond the micro-sliding zone.

Fx : Effort longitudinal Fy : Effort transversal On observe sur ce graphique que les conducteurs évoluent généralement dans la zone des faibles glissements, zone qui n'est pas couverte par les dispositifs classiques tels que l'ABSTM. F: Force generated by the tire with "Fx + Fy)

Fx: Longitudinal force Fy: Transversal force We observe on this graph that the conductors generally move in the zone of weak slips, zone which is not covered by the traditional devices such as ABSTM.

On the other hand, it is noted that the present device, if it operates in the field of validity of the ABSTM and of the traction control, functions in addition in the

<Desc / Clms Page number 23>

low slip area which corresponds to more than 95% of the probability of the presence of drivers. FIG. 2 represents the basic diagram of the invention - FIG. 3 represents a diagram making it possible to schematically illustrate an installation on a generic vehicle, with:
RD gear wheel
ABS pneumatic ABSTM P sensor
M hub
CALC ABSTM computers, trajectory stability control, traction control VA driver warning light (and / or audible alarm) CELECT electrical wiring BC Box for conditioning and processing of adhesion level RV Speed controller AV, AR front, rear EXAMPLE: FIG. 3 shows a layout diagram.

Development vehicle: Rover 75 TM

<Desc / Clms Page number 24>

On utilise pour la mesure des vitesses roues les capteurs préexistants de marque Siemens Automotive sur le véhicule et utilisés pour l'ABS Bosch TM

Les signaux issus de ces capteurs sont ensuite acheminés vers un boîtier central positionné à proximité du calculateur ABSTM.

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

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

partir des paramètres fournis par le calculateur moteur (notamment : position de la pédale d'accélérateur, richesse du mélange air-essence et régime moteur et/ou sonde lambda au niveau du pot d'échappement, et/ou signal d'avance à l'allumage) et de l'évaluation du rapport de boîte de vitesse utilisé. This central unit is made up of two electronic stages: e 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 the state of adhesion) e The digital stage, articulated around a 4-bit microcontroller, preferably 8 bits, or 16 bits, or a microprocessor or any other computer, and which performs all of the treatments. 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 at

from the parameters supplied by the engine control unit (in particular: position of the accelerator pedal, richness of the air-fuel mixture and engine speed and / or lambda probe at the exhaust pipe, and / or advance signal to l 'ignition) and evaluation of the gearbox ratio used.

<Desc / Clms Page number 25>

Ce dernier est déterminé à partir de l'information vitesse fournie par les capteurs de vitesses roues et du régime moteur et/ou sonde lambda au niveau du pot d'échappement, et/ou signal d'avance à l'allumage reprise sur le calculateur moteur. A partir de l'ensemble de ces données, l'étage de traitement numérique

évalue les micro-glissements à l'aide d'un algorithme utilisant notamment la transformation d'Hadamard (élimine les stockages des données et les opérations multiplication ou addition trop complexes pour un microcontrôleur notamment 8 bits) appliquée au signal en quadrature de phase (élimination de la phase).

The latter is determined from the speed information provided by the wheel speed and engine speed sensors and / or lambda probe at the exhaust pipe, and / or ignition advance signal taken up on the computer. engine. From all of this data, the digital processing stage

assesses micro-slippages using an algorithm using notably Hadamard's transformation (eliminates data storage and multiplication or addition operations too complex for a microcontroller, in particular 8 bits) applied to the signal in phase quadrature (elimination phase).

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.

la valeur d'allumage et la valeur d'extinction permet d'éviter un clignotement désagréable de la diode lors du changement d'état. 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 go out again until the two counters have returned below 173. The difference between

the ignition value and the extinction value make 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

<Desc / Clms Page number 26>

 type using them, which will be directly accessible to those skilled in the art on reading this application, their own knowledge.

Claims (34)

 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 body; 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 eVou of the management systems of precarious grip level. 2 Method according to claim 1 characterized in that it comprises the following steps: (a) evaluation of micro-slippages of the contact area A (t) (b) calculation of a quantity P (t) representative of the instant adhesion (c) possibly followed at the end of the evolution of the average adhesion. 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: <Desc / Clms Page number 28>

 (e) extracting the information on precarious adhesion or imminent precarious adhesion from steps (c) and / or (d) and (f) of 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 slippages: your implementation of step (a) of evaluation of micro slips comprises the following steps: al) measurement wheel speeds or wheel speed

 (covering the speed of advancement of the wheel and / or the speed of rotation of the wheel, 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, in particular measurement of the rotational speeds V (t) of each of the wheels a2) possibly time adjustment front rear (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 <Desc / Clms Page number 29>  where Vm = vehicle forward speed and e = wheelbase. or else characterized by: Stage (a) Evaluation of micro-slippages: a1) means for measuring the rotational speeds V (t) of each of the wheels a2) optionally means for time registration before rear (for two wheels on the same right side or left) 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 relation: delta t = e / Vm

 where Vm = vehicle forward speed and e = wheelbase. 6 Method according to any one of claims 1 to 5 characterized in that, if! Basic information would be 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, either 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 latter signal being able to come for example from the speed information available on the set of vehicles or wheel speed sensors used for ABS. <Desc / Clms Page number 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 anti-lock brakes ABS, 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 accuracy of the wheel speed measurements, it will be possible to carry out a time measurement 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 u-gtissements is carried out, for each wheel with calculation, from V (t), of the criterion A (t) representative of the p- 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 possibly include a step of implementing means for calculating for each wheel said criterion A (t) which can be, for example, possibly: * The derivative or the variations of Vroue ( t) eVou * The standard deviation of Vroue (t) (standard deviation of the variations in speed of rotation of the front wheel compared to the rear wheel) eVou <Desc / Clms Page number 31>

 '' 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 a The instantaneous speed of the wheel Vroue (t) and / or La average speed of the wheel over a duration T, or, in the energy spectrum of the distribution of the rotational speeds of each wheel: - The energy over some or all of the harmonics 1 to 64 of Vroue (t) ( it is preferable to use frequency bands centered on the harmonics and with a width substantially less than 10 Hz) and / or at energy on one or more Vroue frequency bands preferably between 8 and 400 Hz. Vroue phase (t) taking for example as criteria: a The evolution of the Vroue phase (t) and / or a The standard deviation of the Vroue phase (t) and / or - The min max deviation of the Vroue (t) phase and / or The evolution of the average Vroue (t) phase over some or all of the harmonics 1 to 64 (we will use pref No. of frequency bands centered on the harmonic and of a width substantially less than 10 Hz) or the average phase over one or more frequency bands between 400 Hz and 8, or means to operate a combination of the methods above, <Desc / Clms Page number 32>

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

 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: Evaluation of instant adhesion Calculation of the slip coefficient G% with front-rear spatial registration.  G% (t) = [Aav (t) -kx Aar (t + At) -r] / Aar (t + At) k, r (values to be adjusted depending on the vehicle) k can be a variable value, in particular in depending on the steering angle of the steering wheel (the distances traveled in bends by the wheels being different apart from any slip), but also the axle load, tires mounted or specific equipment (eg chains

 snow) of the pressure of each tire. <Desc / Clms Page number 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 AC (t) = Cav (t) -Car (t + At) We then perform the calculation of two values P1 (t) and P2 (t) which will allow:

 .. a close monitoring of the evolution of the average adhesion P2 .. a reactive monitoring of the evolution of the instantaneous adhesion P1 (cf. step c) 11 Method according to any one of claims 1 to 10 characterized in what it includes Step (c) End monitoring of the evolution of average grip: <Desc / Clms Page number 34>

 Jx = t P 2 (t) 4x = t'-T2 P (x) dx

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

 Pl (t) = j rlP (xwx

 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 (lang)

 12 Method according to any one of claims 1 to 11 characterized in that it comprises: Step (e) Extraction of ('final information of 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. A preliminary test is carried out which depends on the type used. <Desc / Clms Page number 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.  Cl makes it possible to focus on sudden loss of adhesion such as aquaplaning or patches of ice. 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 a completely 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) <Desc / Clms Page number 36>  (b) means for calculating a quantity P (t) representative of the instantaneous adhesion (c) possibly means for monitoring the development of the average adhesion.  15 Device according to any one of claims 13 or 14 characterized in that it further comprises: (d) means capable of carrying out reactive monitoring of 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: a1) means for measuring the rotational speeds V (t) of each of the wheels a2) possibly time registration means front rear (for two wheels on the same right or left side) corresponding <Desc / Clms Page number 37>

 at the time delta t that the vehicle takes to cover a wheelbase (we know that the wheelbase is the distance which separates the front and rear axles), with the rotation: delta t = e / Vm where Vm = forward speed of the vehicle 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 will be done 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 from the speed information available on all the vehicles or from the wheel speed sensors used for the ABSTM . 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 anti-lock brakes ABS, 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, H 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 <Desc / Clms Page number 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 preferably perform this calculation for each of the events (teeth for cogwheel) that punctuate the turn of the wheel, thus obtaining as many extremely precise measurements of the wheel speed for a turn of the wheel as there are events (teeth for cogwheel). 21 Device according to any one of claims 13 to 20

 characterized in that it comprises means for carrying out an evaluation of the u-gtissements, for each calculation wheel, from V (t), of the criterion A (t) representative of the p-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: Evaluation of instant adhesion Means of calculation of the slip coefficient G% with front-rear spatial registration.  G% (t) = [Aav (t) -kx Aar (t + At) -r] / Aar (t + At) k, r (values to be adjusted depending on the vehicle) k can be a variable value, in particular in depending on the steering angle of the steering wheel (the distances traveled in bends by the wheels being different apart from any slip), but also the axle load, tires mounted or specific equipment (eg chains

 snow) of the pressure of each tire.

 Assessment of instant adhesion <Desc / Clms Page number 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 AC (t) = Cav (t) -Car (t + At) 23 Device according to any one of claims 13 to 22 characterized in that it includes means for permanently measuring the speed Vroue (t) of rotation of each of the wheels, this measurement being able to be carried out using the sensors and the packaging used for the anti-lock braking or traction control devices, such as for example sensors of wheel speeds for ABSTM devices such as those developed by the company Siemens Automotive and equipping for example the Rover "75 vehicle.  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, <Desc / Clms Page number 40>  - the evaluation can be carried out from the following measurements or data obtained by the following means: * accelerator pedal position or injection flow rate, 'engine rotation speeds,. gearbox report (or calculation of this ratio from the average speed of the drive wheels and engine speed and / or lambda probe at the exhaust pipe, and / or ignition advance signal) 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 performing a front-rear time registration corresponding to the time At that the vehicle takes to travel a wheelbase e (or the difference between the two wheels or sets of wheels considered).  At = eN with V = forward speed of the vehicle 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: a The derivative or the variations of Vroue (t) and or <Desc / Clms Page number 41>  a Standard deviation of Vroue (t) (standard deviation of the variations in speed of rotation of the front wheel with respect to the rear wheel) and / or - 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 - The instantaneous speed of the wheel Vroue (t) and / or "The average speed of the wheel over a period T, or, in the spectrum of energy of the distribution of the rotational speeds of each wheel: a The energy over some or all of the harmonics 1 to 64 of Vroue (t) (preferably use frequency bands centered on the harmonics and of substantially smaller width at 10 Hz) and / or the energy on one or more Vroue frequency bands preferably between 8 and 400 Hz. or the Vroue phase variations (t) taking for example as a criterion:. of the Vroue phase (t) and / or. The standard deviation of the Vroue phase (t) and / or * The min max deviation of the Vroue phase (t) and / or. The evolution of the Vroue phase (t) averaged over part or all of the harmonics 1 to 64 (preferably use frequency bands centered on the harmonics and of width substantially less than 10 Hz) or the average phase on one or more frequency bands between 8 and 400 Hz, <Desc / Clms Page number 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 account of the technological differences of the front and rear axle ar and the formula used for the calculation of A (t) may 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 for measure the attitude of the vehicle or for piloted suspensions and shock absorbers). 27 Device according to any one of claims 1 to 26 characterized in that it comprises means for calculating a sliding coefficient G% before rear with spatial registration before rear.  G% (t) = [Aav (t) -kx Aar (t + At) -r] / Aar (t + At) k is a coefficient which allows to take into account the distribution of engine or brake 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, using

 possibly the average of the front wheels and the average of the rear wheels. <Desc / Clms Page number 43>  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 follow-up of the evolution of the grip average and

 on the other hand, reactive monitoring of the evolution of instant adhesion.

 xPI J. r = <-yi "" (react) f)

 / = f P) = j, (high precision)

 With T1 <T2 Order of magnitude: T1: A few fractions of seconds to a few seconds T2: A few seconds to a few tens of minutes <Desc / Clms Page number 44>  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 to 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 counters C1 and C2 are capable of providing the following information "C2 makes it possible to focus more particularly on viscoplanage and on a general state of low adhesion.  . C1 makes it possible to focus on sudden adhesion losses such as aquaplaning or ice sheets. 30 Device according to any one of claims 13 to 29 caracténsé in that one uses means of access to the braking pressures and their distribution by wheel. and / or t means for accessing the knowledge of the load distribution and / or of the total load of the vehicle, such as for example the body height sensors used in particular for adjusting the attitude of the headlights, 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 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 <Desc / Clms Page number 45>  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 accessing the knowledge of the inside temperature of the tire (tire temperature or temperature of the tire). 'enclosed air') which can for example be obtained using temperature sensors installed in the wheels, such as a device such as SMART TYRETM from the company UniCommSignal Inc. TM, and / or means of access to knowledge the internal pressure of the tire which can be obtained, for example, using pressure sensors installed in the wheels, such as a device such as the

 T TM SMART TIRE from 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. like 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 trigger sensor automatic wipers) or the lack of use of the wipers when driving, presence of dry ground. and using means of estimation of the type of soil, in order to estimate if one is in the presence of good soil (low energy in the low frequencies of the <Desc / Clms Page number 46>  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. like 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 we will adapt the thresholds so that, over the self-learning period, the values P1 (t) and P2 (t) remain in most cases lower than the first set of thresholds ( S1 and S3 respectively) and much lower than the second set of thresholds (S2 and S4 respectively). 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). <Desc / Clms Page number 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 data set is obtained as follows: for the measurement of the wheel speeds the pre-existing sensors of the Siemens Automotive TM brand on the vehicle and used for Bosch TM ABS - 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 adhesion) <Desc / Clms Page number 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 speeds are initially 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-fuel mixture and engine speed and / or lambda sensor at 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 from 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 composed of a light-emitting diode and a pictogram, such as the one provided below, inserted in the table edge is on. It never turns off <Desc / Clms Page number 49>  only when the two counters are ironed 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 as a function of the indication of the level of grip and of the distance from the previous vehicle detected with the aid of 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 TM - for the measurement of wheel speeds the pre-existing sensors of the Siemens Automotive TM brand on the vehicle and used for the 'ABS Bosch 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 the state of adhesion) <Desc / Clms Page number 50>

 . The digital stage, articulated 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-fuel mixture and

 engine speed and / or lambda probe at the muffler, and / or engine ignition advance signal) and the evaluation of the gearbox ratio used, the latter being determined from the speed information provided by the wheel speed and engine speed sensors (and / or lambda probe at the exhaust pipe, and / or ignition advance signal) from 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 have returned to below 173, l 'difference <Desc / Clms Page number 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 provided in parallel to a cruise control which has been modified to modulate its speed in function the indication of the grip level 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.