FR3107471A1 - VEHICLE WHEEL WITH ESTIMATED GRIP POTENTIAL BY MEASUREMENT OF RESISTANCE - Google Patents

Abstract

A wheel (R1) equips a vehicle (V) traveling on a surface and comprises: - a rim (JR) on which is mounted a tire (PN) comprising a rolling surface (SR) contacting this surface and two conductive elements (EC ) emerging at this rolling surface (SR) respectively in two neighboring zones, - a measuring device (DM) connected to the two conductive elements (EC) and measuring an electrical resistance between the latter (EC), and - a processor (PR) and a memory (MD) performing operations consisting in estimating the grip potential of the tire (PN) on the surface as a function of this measured electrical resistance. Figure to be published with abstract: Fig. 1

Description

VEHICLE WHEEL WITH ESTIMATED GRIP POTENTIAL BY RESISTANCE MEASUREMENT

Technical field of the invention

The invention relates to wheeled vehicles, and more precisely to the estimation of the adhesion potential of at least one of the wheels of such vehicles.

State of the art

Certain vehicles, generally terrestrial (and possibly automotive), comprise wheels each comprising a rim on which a tire is mounted. As those skilled in the art know, the grip (or grip potential) of at least one of the wheels of a vehicle is a parameter which is important to know when it is desired to control at least partially automated the driving of this vehicle (and in particular its trajectory).

For example, this grip can be estimated and then used by a trajectory control device dedicated to anti-skid (generally called ESP (“Electronic Stability Program”) or ESC (“Electronic Stability Control”)) or anti-skid. - slippage (generally called ASR (“Acceleration Slip Regulation”) or TCS (“Traction Control System”).

Usually, the trajectory control device estimates the adhesions of the wheels of at least one train in order to detect a loss of adhesion resulting from skidding or skidding. The more precise the estimate of the grip of a wheel, the more effective the solution determined by the trajectory control device to counteract a loss of grip, and the more the estimate of the maximum torque that can be transmitted by this wheel can be precise.

In addition, the inter-vehicle safety distance can also be adapted according to the estimated stopping distance based on knowledge of grip.

Currently, the adherence of a drive wheel of a vehicle can, for example, be done by comparing the current speed of this vehicle to the estimated speed of movement of this drive wheel, itself deduced from the speed of rotation of the latter. This technique used to estimate the grip of a wheel, like other known techniques, is not very precise.

It has also been proposed in the patent document DE-A1 102018008287 to equip the tire of a wheel of a vehicle with a capacitive sensor determining the humidity of the road, then to estimate the grip potential of this tire based on this moisture measurement. The capacitive sensor is a small element and therefore it can only deliver a measurement once per revolution of the wheel, when it is in contact with the road, which does not offer great reactivity.

The object of the invention is therefore in particular to propose a new technique for estimating the adhesion potential of a wheel of a vehicle.

Presentation of the invention

It proposes in particular for this purpose a wheel, intended to equip a vehicle capable of traveling on a surface, and comprising a rim on which is mounted a tire comprising a rolling surface intended to contact this surface.

This wheel is characterized by the fact:

- that his tire comprises two conductive elements emerging at the level of the rolling surface respectively in two neighboring zones, and

- that it comprises a measuring device connected to the two conductive elements and measuring an electrical resistance between the latter, and at least one processor and at least one memory arranged to carry out the operations consisting in estimating a grip potential of the tire on the surface as a function of this measured electrical resistance.

Thanks to the invention, we have an estimate of the adhesion potential of a wheel which is more precise than that obtained with the techniques of the prior art, and possibly provided more quickly and more frequently.

The wheel according to the invention may comprise other characteristics which may be taken separately or in combination, and in particular:

- each conductive element may have an annular shape and may extend over the circumference of the tire;

- each conductive element can be a strip made of an electrically conductive rubber;

- each conductive element can be housed in a housing defined in the tire in one of the two neighboring zones, and can be fixedly attached to the tire by gluing;

- its processor and its memory can be arranged to carry out the operations consisting in estimating the grip potential of the tire as a function of a temperature outside the vehicle;

- its processor and its memory can be arranged to carry out the operations consisting in generating an alarm message when the estimated grip potential is below a chosen threshold;

- its processor and its memory can be arranged to carry out the operations consisting in generating an alarm message intended to be displayed on at least one screen present in the vehicle and/or broadcast by at least one loudspeaker present in the vehicle.

The invention also proposes a vehicle capable of circulating on a surface and comprising at least one wheel of the type of that presented above.

For example, this vehicle can be of land type, and optionally of automobile type.

Brief description of figures

Other characteristics and advantages of the invention will appear on examination of the detailed description below, and of the appended drawings, in which:

schematically and functionally illustrates a motor vehicle comprising a trajectory control device and two embodiments of wheels according to the invention,

schematically illustrates, in a cross-sectional view, an embodiment of a wheel according to the invention, and

schematically and functionally illustrates an embodiment of a wheel computer according to the invention.

Detailed description of the invention

The aim of the invention is in particular to propose a wheel R1 intended to equip a vehicle V and capable of estimating the grip potential of its tire PN.

In what follows, it is considered, by way of non-limiting example, that the vehicle V is terrestrial and of the automobile type. This is for example a car, as illustrated without limitation in Figure 1. But the invention is not limited to this type of vehicle. It relates in fact to any type of vehicle that can circulate at least temporarily on a surface, such as for example a road or a track, and comprising at least one wheel allowing it to move. Consequently, the invention relates not only to land vehicles (commercial vehicles, camper vans, motorcycles, minibuses, coaches, trucks, road construction machinery, construction machinery, agricultural vehicles and karts), but also to certain aircraft.

There is schematically shown in Figure 1 an embodiment of a vehicle V comprising, in particular, a front axle comprising two wheels R1 right and left, according to the invention, a rear axle comprising two wheels R2 right and left, conventional, and a DC trajectory control device.

It will be noted that the vehicle V could comprise only one wheel R1 according to the invention or else only wheels R1 according to the invention.

Each wheel R1 (here of the front axle) comprises a rim JR on which is mounted a tire PN, a measuring device DM and at least one processor PR and at least one memory MD.

Each JR rim is here coupled to a pivot which is also coupled to at least one suspension arm and to which the caliper of the vehicle's braking system V is fixedly attached.

Each tire PN comprises a rolling surface SR, which is intended to contact the surface on which the vehicle V is traveling, and two conductive elements EC, which emerge at the level of the rolling surface SR respectively in two neighboring zones. It will be understood that each tire PN must be made of an electrically insulating rubber.

Each measuring device DM is connected to the two conductive elements EC of the tire PN of its wheel R1 and is arranged so as to measure an electrical resistance between these two conductive elements EC. For this purpose, the measuring device DM is connected to the two conductive elements EC via two electrical paths which cross the tire PN. These electrical paths can be made with conductive rubber, which eliminates the problem of sealing.

Furthermore, the measuring device DM can be fixedly secured to the rim JR, preferably by electrically isolating its two faces, as illustrated without limitation in FIGS. 1 and 2. However, in a variant embodiment, it could be fixedly secured to the inside tire PN.

For example, each measuring device DM can include an ohmmeter responsible for measuring the electrical resistance between the two conductive elements EC.

The processor PR and the memory MD are arranged to perform the operations consisting in estimating the grip potential of the tire PN of a wheel R1 on the surface on which the vehicle V is traveling, as a function of the electrical resistance which is measured by the associated DM measuring device.

It is in fact considered here that the greater the quantity of water present between the surface on which the vehicle V travels and the rolling surface SR of the tire PN, the lower the electrical resistance between the two conductive elements EC will be. , even if water (or ice or snow) conducts little electricity, and therefore the more the grip will be degraded. Conversely, the lower the quantity of water present between the surface on which the vehicle V travels and the rolling surface SR of the tire PN, the greater the electrical resistance between the two conductive elements EC, and therefore the greater the potential grip will be high .

We thus have an estimate of the adhesion potential of a wheel R1 which is more precise than that obtained with the techniques of the prior art.

For example, the adhesion potential can be estimated as a function of the electrical resistance measured by using a correspondence table stored (for example in the memory MD) and establishing a correspondence between electrical resistances and adhesion potentials. As a variant, it is possible to use a mathematical function making it possible to determine the adhesion potential as a function of at least the electrical resistance measured.

It will be noted that the processor PR can, for example, be a digital signal processor (or DSP (“Digital Signal Processor”)). This processor PR can comprise integrated (or printed) circuits, or else several integrated (or printed) circuits connected by wired or wireless connections. By integrated (or printed) circuit is meant any type of device capable of performing at least one electrical or electronic operation.

It will also be noted that the memory MD is live in order to store instructions for the implementation by the processor PR of its functionalities.

In the example illustrated without limitation in FIG. 1, the processor PR and the memory MD are part of a computer CA, produced in the form of a combination of electrical or electronic circuits or components (or “hardware”) and of software modules (or “software”), and coupled (directly or indirectly) to the DC trajectory control device. But this is not mandatory. Furthermore, in the example illustrated without limitation in FIG. 2, the computer CA is fixedly attached to the rim JR. But in a variant embodiment, it could be fixedly secured inside the tire PN or offset in/on the vehicle V. This last alternative can in particular be implemented when the communications between the measuring device DM and the processor PR ( or computer CA) are done wirelessly, for example using the RFID technique ("Radio Frequency IDentification"), the electrical supply of the measuring device DM then being done via a receiving antenna that comprises the latter (DM) and the computer CA to be associated with an RFID box responsible for receiving the information (according to a principle similar to that used for pressure measurement).

It will also be noted that it is advantageous for the processor PR and the memory MD to be arranged in such a way as to perform the operations consisting in estimating

the adhesion potential of the associated tire PN as a function, moreover, of the temperature outside the vehicle V, as well as possibly of the type of tire PN (supplier and model). Indeed, the electrical conductivity of water varies slightly depending on its physical state, which depends on the outside temperature. Consequently, this option improves the precision of the estimation of the grip potential of the tire PN. The temperature outside the vehicle V can be provided by a temperature sensor fitted to the vehicle V or by meteorological information received in the vehicle V (by a communication module by way of waves which it comprises permanently or by a communicating device temporarily present in the vehicle V because it accompanies a passenger). This communicating device can, for example, be an intelligent mobile telephone (or “smartphone”) or a communicating electronic tablet.

In the presence of the last option, when using a correspondence table, the latter integrates the outside temperature, as well as possibly the type of tire. Similarly, in the variant with a mathematical function, the latter also has the outside temperature as a variable, as well as possibly the type of tire.

It will also be noted, as illustrated without limitation in FIG. 1, that each conductive element EC can have an annular shape and extend over the circumference of the tire PN. This makes it possible to perform measurements of the electrical resistance regardless of the position of the wheel R1 with respect to a reference position. But it would be possible to use conductive elements EC having a partially annular shape and therefore extending over part of the circumference of the tire PN.

It will also be noted that each conductive element EC can be a strip made of an electrically conductive rubber. For example, it may be a special type of synthetic rubber that includes graphite. This allows the EC conductive elements to wear out at roughly the same rate as their PN tire, and therefore prevents them from degrading the road surfaces.

The two strips EC are integrated substantially parallel to each other in their respective neighboring zones and emerge in the open air on the rolling surface SR in order to be able to be in direct contact with the surface on which the vehicle V is traveling.

It will also be noted that each conductive element EC can be housed in a housing which is defined in the tire PN in one of the two neighboring zones, and can be fixedly secured to the tire PN by gluing. But they can also be integrated during the manufacture of the PN tire, and more specifically during the installation of its various components.

It will also be noted that the processor PR and the memory MD can be arranged in such a way as to perform the operations consisting in generating an alarm message when the estimated adhesion potential is below a chosen threshold. This alarm message can be intended for the driver of the vehicle V (if the latter (V) is not fully automated (or autonomous) driving) and/or for a device on board the vehicle V and using (or taking into account) grip potential information. In the case of autonomous driving, knowledge of the grip potential makes it possible to adapt the safety distances between vehicles

When the alarm message is at least intended for the driver of the vehicle V, the processor PR and the memory MD can be arranged so as to generate an alarm message intended to be displayed on at least one screen present in the vehicle V and /or broadcast by at least one loudspeaker present in the vehicle V. For example, the screen can be part of the central handset CC, installed in (or on) the dashboard or the possible central console, or else of the vehicle dashboard V. But alternatively the screen can be part of the aforementioned communicating device. Also for example, the loudspeaker can be part of the vehicle V permanently. But as a variant, the loudspeaker can be part of the aforementioned communicating device.

It will also be noted, as illustrated without limitation in FIG. 1, that the adhesion potential information can be advantageously (but in particular) used by the trajectory control device DC fitted to the vehicle V. For example, this control device of trajectory DC can be dedicated to anti-skid (it can then be of the ESP or ESC type, in particular) or to anti-skid (it can then be of the ASR or TCS type, in particular).

But the adhesion potential information could also be used, for example, by an adaptive cruise control (with a safety distance adapted according to the adhesion potential).

It will also be noted, as illustrated without limitation in FIG. 3, that the computer CA can also comprise, in addition to its random access memory MD and its processor PR, a mass memory MM, in particular for storing the measured electrical resistance and any temperature outside the vehicle V, and intermediate data involved in all its calculations and processing. Furthermore, this calculator CA can also comprise an input interface IE for receiving at least the measured electrical resistance and any temperature outside the vehicle V to use them in calculations or processing, possibly after the have been shaped and/or demodulated and/or amplified, in a manner known per se, by means of a digital signal processor PR′. In addition, this CA computer can also include an IS output interface, in particular to deliver the estimated adhesion potential and any alarm messages.

Claims (10)

Wheel (R1) for a vehicle (V) suitable for running on a surface, said wheel (R1) comprising a rim (JR) on which is mounted a tire (PN) comprising a rolling surface (SR) intended to contact said surface , characterized in that said tire (PN) comprises two conductive elements (EC) emerging at the level of said running surface (SR) respectively in two neighboring zones, and in that it further comprises i) a measuring device ( DM) connected to said two conductive elements (EC) and measuring an electrical resistance between the latter (EC), and ii) at least one processor (PR) and at least one memory (MD) arranged to perform the operations consisting in estimating a potential grip of said tire (PN) on the surface as a function of said measured electrical resistance. Wheel according to Claim 1, characterized in that each conductive element (EC) has an annular shape and extends over the circumference of the said tire (PN). Wheel according to Claim 1 or 2, characterized in that each conductive element (EC) is a strip made of an electrically conductive rubber. Wheel according to one of Claims 1 to 3, characterized in that each conductive element (EC) is housed in a housing defined in the said tire (PN) in one of the said two neighboring zones, and fixedly secured to the said tire (PN) by gluing. Wheel according to one of Claims 1 to 4, characterized in that the said processor (PR) and the said memory (MD) are arranged to carry out the operations consisting in estimating the said grip potential of the tire (PN) as a further function of a temperature outside said vehicle (V). Wheel according to one of Claims 1 to 5, characterized in that the said processor (PR) and the said memory (MD) are arranged to carry out the operations consisting in generating an alarm message when the said estimated adhesion potential is lower than a chosen threshold. Wheel according to one of Claims 1 to 6, characterized in that the said processor (PR) and the said memory (MD) are arranged to carry out the operations consisting in generating an alarm message intended to be displayed on at least one screen present in said vehicle (V) and/or broadcast by at least one loudspeaker present in said vehicle (V). Vehicle (V) suitable for running on a surface, characterized in that it comprises at least one wheel (R1) according to one of the preceding claims. Vehicle according to Claim 8, characterized in that it is of the terrestrial type. Vehicle according to Claim 9, characterized in that it is of the automobile type.