FR3058519A1 - METHOD FOR DETERMINING THE PRESSURE OF A TIRE - Google Patents

Abstract

The invention relates to a method for determining the pressure of a tire (1) mounted on a vehicle (7), comprising the following steps: acquisition by a microphone (10) of an acoustic response of said tire (1) obtained under the effect of a mechanical impulse biasing of said tire at standstill, - processing of said acoustic response in the frequency domain by an automated data processing unit (9), said processing comprising: - identification on the acoustic response in the frequency domain of the frequency of a peak of spectrum corresponding to a maximum of spectral amplitude, - determination of a tire pressure from data connecting frequencies to pressures.

Description

Holder (s): COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN Limited partnership with shares, MICHELIN RECHERCHE ET TECHNIQUE S.A. Limited company.

Extension request (s)

Agent (s): REGIMBEAU.

(54) METHOD FOR DETERMINING THE PRESSURE OF A TIRE.

FR 3 058 519 - A1 _ The invention relates to a method for determining the pressure of a tire (1) mounted on a vehicle (7), comprising the following steps:

- Acquisition by a microphone (10) of an acoustic response of said tire (1) obtained under the effect of an impulse mechanical stress on said stopped tire,

processing of said acoustic response in the frequency domain by an automated data processing unit (9), said processing comprising:

- identification of the acoustic response in the frequency domain of the frequency of a spectrum peak corresponding to a maximum of spectral amplitude,

- determination of a tire pressure from data linking frequencies to pressures.

METHOD FOR DETERMINING THE PRESSURE OF A TIRE

GENERAL TECHNICAL AREA AND CONTEXT OF THE INVENTION

The present invention relates to determining the pressure of a tire.

More specifically, the invention proposes a method which exploits the acoustic response of a tire under the effect of an impulse mechanical stress to deduce the pressure thereof.

It advantageously finds application for the control and / or monitoring of any type of tire: tires for agricultural equipment, heavy goods vehicles, passenger vehicles, motorcycles or quads, etc.

We conventionally know that when a tire is mounted on a vehicle, it is important to monitor not only its wear, but also the conditions under which it is used: inflation pressure, vehicle load, etc.

The wear of a tire can be easily checked by a simple visual inspection of the tread carved into the tread or, if necessary, by using a tool of the depth gauge type.

The parameters of use such as the tire pressure or the vehicle load are more difficult to grasp, or in any event require expensive equipment, in particular because of the large number of wheels of a Heavy Vehicle, whose total permissible laden weight is greater than 3.5 tonnes, but may rise above 26 tonnes, or even 32 tonnes, which requires additional axles. Their control or monitoring requires the use of complex tools (pressure gauge, balance for weighing the vehicle, etc.).

There is therefore a need for a technique for controlling and / or monitoring the conditions of use of a vehicle tire which makes it possible to obtain information relating to at least one parameter for using the tire in a particularly simple manner. , without the need for large and expensive tools.

PRESENTATION OF THE INVENTION

An object of the invention is to allow the determination of the pressure of a vehicle tire which is simple to implement and inexpensive.

To this end, a method for determining the pressure of a tire mounted on a vehicle is proposed, comprising the following steps:

- Acquisition by a microphone of an acoustic response of said tire obtained under the effect of an impulse mechanical stress on said stopped tire,

processing of said acoustic response in the frequency domain by an automated data processing unit, said processing comprising the following steps:

- identification of the acoustic response in the frequency domain of the frequency of a spectrum peak corresponding to a maximum of spectral amplitude,

- determination of a tire pressure from data linking frequencies to pressures.

This process is advantageously supplemented by the following characteristics, taken alone or in any of their technically possible combinations:

the data linking frequencies to pressures establish a linear relationship between a pressure and a frequency for at least part of a frequency range;

the data connecting frequencies to pressures are functions of the type of tire, and the method comprises a step of informing the type of tire, which conditions a selection of the data linking frequencies to pressures in a database;

the tire type information is carried out using an information input device;

the tire type is indicated by reading, by an electronic reader, an identifier contained in or on the tire;

- the impulse mechanical stress results from a blow struck on a crown area of the tire constituting a tread;

- the frequency of a spectrum peak corresponding to a maximum spectral amplitude is identified over a frequency range between 50 Hz and 500 Hz.

The invention also relates to a computer program product comprising program code instructions for executing the method according to the invention, when said program is executed on a computer.

The invention also relates to a system for determining the pressure of a tire mounted on a vehicle, said system comprising:

a microphone adapted to acquire an acoustic response of said tire with mechanical impulse stress on said stopped tire,

- an automated data processing unit configured to identify on the acoustic response in the frequency domain a frequency of a spectrum peak corresponding to a maximum of spectral amplitude, and to determine a tire pressure from data linking frequencies at pressures.

It is specified here that it is possible to use existing microphones, as long as they meet the acquisition criteria allowing the implementation of the invention.

PRESENTATION OF THE FIGURES

Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting, and which should be read with reference to the appended drawings among which:

FIG. 1 schematically illustrates a tire mounted on a rim of a vehicle,

- Figure 2 schematically illustrates the implementation of an embodiment of the invention applied to an agricultural vehicle;

- Figure 3 is a diagram schematically illustrating several steps of a method according to a possible embodiment of the invention;

FIG. 4 illustrates a recording of three impulse acoustic responses of tires with the same load and at different pressures;

- Figure 5 illustrates the amplitudes in the frequency domain of the responses of Figure 4;

FIG. 6 illustrates an example of frequency-pressure relationship for the tire of the example of FIGS. 4 and 5.

DETAILED DESCRIPTION

General reminders on the structure of a tire

FIG. 1 illustrates a tire 1 mounted on a rim 2. Such a tire 1 comprises on the one hand an apex zone 3 constituting a tread having treads, and on the other hand sidewalls 4 ending in low zones 5 These generally include a bead and a bead to allow mounting of the tire 1 on the rim 2. The rim 2 is itself connected to the vehicle by an axle (not shown). The tire thus allows the connection between the vehicle and the ground.

A tire 1 is comprised of a flexible envelope containing a gaseous interior under pressure, typically air. The rim 2 being undeformable, this force applied to the tire 1 deforms the latter, as illustrated in FIG. 2. The part of the crown 3 under the rim 2 becomes flat, which increases the contact surface of the tire with the ground, while the sidewalls 4 swell: the tire 1 deforms. This deformation is all the more pronounced when the pressure is low.

Example system

Referring to FIG. 2 which schematically illustrates a system according to an embodiment of the invention applied to an agricultural vehicle, such a system comprises a microphone 10 and an automated data processing unit 9. They can be separate and distinct, or else be arranged as here within the same device, such as for example a pocket terminal such as a smart mobile phone, in which case the microphone 10 is that of the pocket terminal, and the automated data processing unit 9 is the processor of said pocket terminal. The following description is made in this case.

As illustrated, the automated data processing unit 9 can be a pocket terminal such as a smart mobile phone, comprising a processor and a memory. It can also be a computer comprising a processor and a memory. The microphone 10 is suitable for acquiring an acoustic response of said tire 1 with mechanical impulse stress thereof, when the tire is stopped. The automated data processing unit 9 is configured to identify on the acoustic response in the frequency domain a frequency of a spectrum peak corresponding to a maximum spectral amplitude, and to determine a tire pressure from data linking frequencies to pressures.

Example of implementation

With reference to FIG. 3, the first step S1 of the method consists in applying to the tire 1 an impulse mechanical stress when the vehicle is stopped. Preferably, the impulse mechanical stress results from a blow on a crown area 3 of the tire constituting a tread. This typically involves applying a short blow to the tire, for example by means of a kick given to the tire 1 by an operator 8 as shown, or by striking the tire 1 with a tool such as a hammer. . The simplicity of this maneuver means that it can be implemented by the driver of the vehicle 7 as operator 8.

It is also possible, in order to better control the characteristics of the acoustic pulse, to provide a controllable mechanical device for striking the tire 1 or the rim 2 with a predetermined force. Such a device can for example be placed on the surface of the tire 1 or of the rim 2, and following the action of a command, a movable member of this device strikes the tire 1 or the rim 2.

Following this impulse mechanical stress on the tire 1, certain natural modes of vibration of the tire are excited, which leads to the formation of sound waves which propagate in and around the tire 1, producing a sound. It is the acoustic response of tire 1 to this mechanical impulse stress. The second step S2 consists in acquiring the acoustic response of the tire by means of the microphone 10. It is specified here that the natural modes of vibration of the tire depend on the geometry of the tire, but also on its rigidities, which themselves depend on the pressure. inside the tire.

FIG. 4 shows three illustrative examples of temporal changes in amplitude of acoustic responses to impulse mechanical stress which have thus been acquired for the same tire with unchanged load and at different pressures:

a first response 30, above, corresponding to a tire inflated to 8.9 bars,

a second response 31, in the middle, corresponding to the same tire inflated to 7.5 bars,

- a third response 32, below, corresponding to the same tire inflated to 6.0 bars.

The impulse mechanical stress here results from a brief blow struck with a hammer in the middle of the crown area of the tire, on the side opposite the ground contact area. In this example, the vehicle is a DAF XF440 heavy-duty tractor with more than 40 tonnes of total permissible laden weight. The tire in this example is fitted to the right front wheel, under the cabin. The tire is of the type 315/70 R22.5, i.e. a width of 315 mm, a ratio between the sidewall height and the section width of the tire of 70, of radial structure and with an internal diameter of 22.5 inches ( or 57.15 cm).

After recording the acoustic response of the tire, the microphone 10 transmits the response to the automated data processing unit 9 which receives said impulse acoustic response from the microphone 10 and processes this response in the frequency domain (step S3).

The response is first converted into the frequency domain (step S31) to obtain the frequency spectrum of the impulse acoustic response. Any conventional method can be used, adapted to the format of the data representative of the impulse acoustic response, such as for example the Fourier transformation. We can also use a method more suited to impulse signals, such as a Yule-Walker parametric analysis.

The frequency spectrum of the impulse acoustic response is thus obtained. From this spectrum, we identify on the response in the frequency domain the frequency of a spectrum peak corresponding to a maximum spectral amplitude. From this frequency, the tire pressure can be determined using data relating frequencies to pressures.

The inventors have in fact discovered that the frequency acoustic response of a tire, the characteristics of which depend on the pressure in the tire, exhibits, in the frequency domain, an easily identifiable peak whose frequency can be directly related to the pressure.

FIG. 5 illustrates the amplitudes of the spectra with respect to the frequency for the three acoustic responses of FIG. 4. More precisely, the amplitudes have been normalized with respect to the respective maximum of each of the spectra.

In Figure 6 are shown:

a first curve 41 in thick lines corresponds to the acoustic response of the tire at 8.9 bars,

a second curve 42 in thin lines corresponds to the acoustic response of the tire at 7.5 bars,

a third dashed curve 43 corresponds to the acoustic response of the tire at 6 bars.

For each of the curves, it is easy to see the presence of a spectrum peak corresponding to a maximum of spectral amplitude:

the first curve 41, in thick lines and corresponding to a pressure of 8.9 bars, has a spectrum peak 44 located around a frequency of 96.2 Hz,

the second curve 42, in thin line and corresponding to a pressure of 7.5 bars, has a spectrum peak 45 located around a frequency of 89.2 Hz,

- The third curve 43, in dashed lines and corresponding to a pressure of 6.0 bars, has a spectrum peak 46 located around a frequency of 82.6 Hz.

It appears that the frequency of the spectrum peak varies with pressure. More specifically, the frequency of the spectrum peak decreases with pressure. FIG. 6 shows the correspondence between the pressure (in bars) and the frequency of the spectrum peak corresponding to a maximum spectral amplitude for the three tests presented above. It can be seen that a linear relationship is established between the frequency of the spectrum peak and the pressure. Under the test conditions, an affine relation of directing coefficient of approximately 4.5 Hz per bar of pressure is obtained.

From such a relation, it is easy to construct data relating frequencies to pressures for a given tire. As in the example above, the data linking frequencies to pressures can establish a mathematical function between a frequency and a pressure, such as for example a linear relationship between a pressure and a frequency for at least part of a range. frequency, typically located around a nominal inflation frequency. Other mathematical relationships can of course exist (polynomial, exponential, logarithmic, ...). It is also possible that different mathematical relationships are used for different pressure ranges for the same tire. In the case where one or more mathematical functions link the frequencies and the pressures, it suffices to apply the appropriate function to the recorded frequency to obtain the tire pressure.

It is also possible that the data linking frequencies to pressures are not linked to any mathematical function, but are presented as a set of frequency and pressure couples. The tire pressure can then be determined as being the pressure associated with the frequency closest to the frequency of the spectrum peak among the frequencies of the data connecting frequencies to pressures. It is also possible to make a linear interpolation between the two closest frequencies, or any other approach.

It should be noted that the frequency of the spectrum peak corresponding to a maximum of spectral amplitude is generally located:

- between 20 Hz and 200 Hz for a truck tire, the total permissible laden weight of which is greater than 3.5 tonnes,

- between 50 Hz and 500 Hz for a passenger vehicle tire, the total permissible laden weight of which is less than 3.5 tonnes.

Thus, the identification of the frequency of a spectrum peak corresponding to a maximum spectral amplitude can be done over a frequency range between 20 Hz and 500 Hz, and more precisely between 20 Hz and 200 Hz for a tire of heavy vehicle and between 50 Hz and 500 Hz for a passenger vehicle tire.

The link between the frequency of the acoustic response and the pressure can only be established over a determined pressure range, so that the data linking frequencies to pressures can be restricted to this range. Typically, the range of exploitable pressures can correspond to the nominal inflation pressure of the tire, and extend to more or less 30% thereof.

Furthermore, the data linking frequencies to pressures generally depend on the type of tire. It may therefore be necessary to supply the automated data processing unit with the type of tire whose pressure is to be determined.

Several approaches can be taken in this regard. The tire type information can be carried out using an information input device connected to the automated data processing unit 9, for example a keyboard or a touch screen, typically in the case where the processing unit Data Automation 9 is a smart mobile phone.

In order to prevent the operator 8 from entering information on the type of tire, which can prove to be tedious and a source of error, it is also possible that the information of the type of tire is carried out by reading a identifier contained in or on the tire by an electronic reader. The identifier can for example be encoded in an electronic chip, for example a radio identification chip (RFID), or even in a visual element such as a barcode. The electronic reader is of course adapted to read the identifier, and is a function of the form of the identifier. The electronic reader can for example be a radiofrequency communication device or an optical reader.

The type of tire thus informed then conditions a selection of the data relating frequencies to pressures in a database. To this end, the automated data processing unit 9 can have access to a database grouping, for each of a plurality of tire types, data relating frequencies to pressures. This database can be contained in a memory of the automated data processing unit, or else be accessible via a remote server with which the automated data processing unit 9 can communicate. For example, the automated data processing unit 9 can connect to a communication network such as the Internet to transmit the type of tire entered or the identifier of the tire, and receive in return the data relating frequencies to pressures. specific to this type of tire.

The invention is not limited to the embodiment described and shown in the appended figures. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without thereby departing from the scope of protection of the invention.

Claims (11)

Claims 1. Method for determining the pressure of a tire (1) mounted on a vehicle (7), comprising the following steps: - Acquisition by a microphone of an acoustic response of said tire (1) obtained under the effect of an impulse mechanical stress on said stopped tire, - processing of said acoustic response in the frequency domain by an automated data processing unit (9), characterized in that said processing comprises: - identification of the acoustic response in the frequency domain of the frequency of a spectrum peak corresponding to a maximum of spectral amplitude, - determination of a tire pressure from data linking frequencies to pressures. 2. Method according to any one of the preceding claims, in which the data linking frequencies to pressures establish a linear relationship between a pressure and a frequency for at least part of a frequency range. 3. Method according to any one of the preceding claims, in which the data connecting frequencies to pressures are a function of the type of tire, and the method comprises a step of informing the type of tire, which conditions a selection of the data connecting frequencies at pressures in a database. 4. Method according to the preceding claim, wherein the information of the type of the tire is carried out using an information input member. 5. Method according to claim 3, in which the information of the type of the tire is carried out by the reading, by an electronic reader, of an identifier contained in or on the tire. 6. Method according to any one of the preceding claims, in which the impulse mechanical stress results from a blow struck on a crown area (3) of the tire constituting a tread. 7. Method according to any one of the preceding claims, in which the frequency of a spectrum peak corresponding to a maximum spectral amplitude is identified over a frequency range between 20 Hz and 500 Hz. 5 8. A computer program product comprising program code instructions for executing the method according to any one of the preceding claims, when said program is executed on a computer. 9. System for determining the pressure of a tire (1) mounted on a vehicle 10 (7), said system comprising: - a microphone (10) adapted to acquire an acoustic response of said tire with impulse mechanical stress on said stopped tire, - an automated data processing unit (9) configured to identify on the acoustic response in the frequency domain a frequency of a spectrum peak 15 corresponding to a maximum spectral amplitude, and for determining a tire pressure from data relating frequencies to pressures. 2/5 FIG 3 3/5