Method for estimating the tread depth of a tyre fitted to a vehicle

Abstract

The invention relates to an estimation method (100) for estimating the tread depth of a given tyre from a set fitted in driving conditions to a given vehicle, the method being implemented by at least one processor of a system that performs the estimation method (100), the at least one processor comprising an analysis application module which applies the items of data representative of the operating characteristics of the given tyre. The invention also relates to a system comprising a communication network that manages the items of data representative of the operating characteristics of a given tyre from a set fitted in driving conditions to a given vehicle that includes the tyre, characterised in that the communication network comprises at least one communication server that allows programmed instructions stored in a memory of one or more processors of the system to be executed in order to implement the disclosed estimation method (100).

Description

[0001] Description

[0002] Title: METHOD FOR ESTIMATING THE TREAD PATTERN HEIGHT OF A TIRE MOUNTED ON A VEHICLE

[0003] Technical Field

[0004] The invention relates to a method for estimating wear on a global scale as well as a method for predicting the end of life of a tire in vehicle use conditions and a system for implementing these methods. More particularly, the invention uses a temperature model to obtain an accurate estimate of tread height allowing a prediction of the remaining life of the tire.

[0005] Context

[0006] In the field of methods for evaluating the wear of a tire in vehicle use conditions, it is frequently considered that a simple and easy way to determine it is to evaluate the overall wear corresponding to the average reduction in the height of the tread (or "tread height"). For this purpose, it is commonly considered to use an intermediate physical quantity sensitive to the wear of the tread of a tire such as, for example, the rolling radius or the pseudo-slip stiffness Kx of the tire. This second quantity represents the slope of the curve representing the longitudinal forces generated by the variation in rotational speed between the wheel center and the tread when the mounted assembly rolls on the road. The sensitivity of the pseudo-slip stiffness is much greater to the overall wear of the tire casing than the sensitivity of the rolling radius.

[0007] Methods are known in the state of the art which use such a second quantity to characterize the overall wear of the tire tread in service. This quantity is in fact sensitive to the reduction in the height of the tread characterizing the overall wear of the tire casing.

[0008] This physical quantity is also sensitive to other parameters such as inflation pressure (or "pressure"), temperature, the load carried by the mounted assembly (or "load") and the nature of the ground on which the mounted assembly rolls (here, "influential parameters"). As disclosed by the Applicant's publication WO2020 / 120923, variations in all of the influential parameters could be taken into consideration to extract the variation in longitudinal stiffness due solely to the reduction in the tread height of the tire. To do this, the recommended solutions consist of taking into account the variations in these influential parameters through additional measurements or additional information.

[0009] Taking into account all the influential parameters (including, but not limited to, load, pressure, temperature and tread height) allows for more precise estimation of overall wear and prediction of tire end-of-life. However, although some approaches also use slip calculation to estimate wear (see, for example, US patent 10,603,962), none seem to use the same type of relationship that allows one to move from pseudo-slip stiffness Kx to tread height. In principle, the increase in pseudo-slip stiffness corresponds to the decrease in tread height. In reality, simulations show that it increases quite significantly with wear regardless of ground roughness. However, it is found that the internal air temperature of a tire does indicate its average thermal state.

[0010] From a physical model, it would be theoretically possible to estimate the remaining tread height of an overall tire fitted to a vehicle and subsequently deduce a remaining service life for this tire. Thus, the disclosed invention focuses on temperature estimation in order to have the most accurate estimate of tread height possible in order to determine the remaining service life of a tire.

[0011] Summary of the invention

[0012] The invention relates to a method for estimating the tread height of an identified tire of an assembly mounted in rolling condition on an identified vehicle, the tire of which has a crown which extends into two sidewalls ending in two beads of revolution around a natural axis of rotation, the crown comprising a tread located radially outside the tire relative to the natural axis of rotation and having an average tread height h, the method implemented by at least one processor of a system which carries out the estimation method, at least one processor comprising an analysis application module which applies the data representative of operating characteristics of the identified tire, characterized in that the estimation method comprises the following steps: a step of identifying a tire of an assembly mounted on a vehicle;

[0013] - a step of choosing a transition function P defined for a portion of road and the rigidity of the tread of the tire; a step of choosing a transfer function F of the mounted assembly between a pseudo-slip rigidity Kx on a reference ground and influential parameters; and, on a predetermined measurement cycle; a step of determining at least one force Fx undergone by the mounted assembly and at least one slip rate G% at the wheel center of the mounted assembly during straight-line rolling of the vehicle comprising variations in acceleration on the portion of dry road; a step of acquiring the usage parameters of the mounted assembly comprising the following steps: a step of determining a load (Z) undergone by the mounted assembly in rolling conditions; a step of determining a temperature (T) of the mounted assembly in rolling conditions;and a step of determining an inflation pressure (P) of the internal cavity of the assembled assembly in rolling condition; characterized in that the temperature is determined according to a mathematical model of the type:;

[0014] T r " u = 0.985 6.25 including T amb i represents the initial temperature in Kelvin, and Pf Tamb f and Pi Tamb t represent the respective pressures at the end and beginning of a predetermined path of the identified tire. In certain embodiments of the method of the invention, a thickness E of the tread of the identified tire is determined according to a mathematical model of the type: whose transfer function F includes at least the inflation pressure P, the temperature T, the load Z and the thickness E of the tread as the influencing factors; and whose first pseudo-slip stiffness Kx reel and a second pseudo-slip stiffness Kxref are linked to the determination of the thickness E.

[0015] In certain embodiments of the method of the invention, the method further comprises a step of providing information on the aging state of the identified tire during which the identification of the mounted assembly is used in order to know the history of the use of the identified tire.

[0016] In certain embodiments of the method of the invention, the method further comprises: a step of tracing a point cloud which is carried out from the measured forces Fx and the associated slip rates G% when driving on a portion of dry road, during which an estimation of the first pseudo-slip rigidity K reel is obtained on real ground corresponding to the portion of dry road; and a step of estimating a second pseudo-slip rigidity K refby feeding the transfer function F obtained during the step with the usage parameters measured during the step and the tread height h obtained during the step.

[0017] In certain embodiments of the method of the invention, the passage function P is chosen from a possible plurality of passage functions from a list of potential passage functions P which is representative of the median nature of the road portions that the identified vehicle will encounter.

[0018] In certain embodiments of the method of the invention, the method further comprises a step of evaluating the average tread height by comparing this evaluated average height with the specific heights of the identified tire.

[0019] In certain embodiments of the method of the invention, the method further comprises a step of acquiring the variation AU of a parameter U linked to the use of the tire identified between two acquisitions of the average tread height.

[0020] In certain embodiments of the method of the invention, the method further comprises a step of evaluating the wear rate of the identified tire, this step comprising a step of evaluating the tread at a point of acquisition of the average tread height of the identified tire.

[0021] In certain embodiments of the method of the invention, the method further comprises a step of evaluating the remaining service life of the identified tire, this step comprising a step of evaluating the end-of-life prediction according to the parameter U linked to the use of the identified tire; such that the end-of-life prediction is obtained by combining the results of the identification step, the step of evaluating the average tread height, and the step of evaluating the wear rate of the identified tire.

[0022] The invention also relates to a system comprising a communication network which manages the data representative of operating characteristics of a tire identified from an assembly mounted in driving condition on an identified vehicle in which the tire is incorporated, characterized in that the communication network comprises at least one communication server making it possible to execute programmed instructions stored in a memory of one or more processors of the system to implement the disclosed method.

[0023] Other aspects of the invention will become apparent from the following detailed description.

[0024] Brief description of the drawings

[0025] The nature and various advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which like reference numerals designate like parts throughout, and in which: Figure 1 shows the components of a tire in a meridian plane.

[0026] Figure 2 represents an embodiment of a method for estimating the tread height of a tire of the invention.

[0027] Figures 3 and 4 represent, respectively, an illustration of a temperature simulation curve and an illustration of a simulation curve of average temperature rise of a tire of an assembly mounted on a vehicle.

[0028] Detailed description

[0029] When considering the characteristics of a tire that is the subject of a tread height estimation, its geometry must be taken into account. A tire is an object having a known geometry generally comprising several superimposed layers of rubber (or "layers"), as well as a metal or textile fiber structure constituting a reinforcing carcass of the tire structure. The nature of the rubber and the nature of the reinforcement are chosen according to the desired final characteristics. Figure 1 includes a schematic representation of a tire 10 comprising, in a conventional manner, two circumferential beads intended to allow the tire to be attached to a rim. Each bead includes an annular reinforcing bead. The constitution of a tire is typically described by a representation of its constituents in a meridian plane, that is to say a plane containing the axis of rotation of the tire.The radial, axial and circumferential directions respectively designate the directions perpendicular to the axis of rotation of the tire, parallel to the axis of rotation of the tire, and perpendicular to any meridian plane. The expressions “radially”, “axially” and “circumferentially” respectively mean “in a radial direction”, “in the axial direction” and “in a circumferential direction” of the tire. The expressions “radially inner” and “respectively radially outer” mean “closer, respectively further, from the axis of rotation of the tire, in a radial direction. The tire 10 also comprises a tread 12, added to the outer surface of the tire. The tread 12 intended to come into contact with a ground via a rolling surface 12a.The tire 10 further comprises a crown reinforcement comprising a working reinforcement 14 and a hoop reinforcement 16, the working reinforcement 14 having working layers represented by layers 14a and 14b. The tire 10 also comprises two sidewalls (a sidewall 18 being represented in Figure 1) and two fillers 20 reinforced with a bead wire 22. A radial carcass layer 24 extends from one bead to the other, surrounding the bead wire in a known manner. The tread 12 comprises reinforcements consisting, for example, of superimposed layers comprising known reinforcing threads. In embodiments, the tire may include a rubber 26 which evacuates the static electricity produced during rolling.The tread 12 is delimited, in the radial direction, by two circumferential surfaces, the most radially outer of which is the tread surface 12a and the most radially inner of which is called the tread base surface. The tread base surface (or "bottom surface") is defined as the surface translated from the tread surface radially inward by a radial distance equal to the tread depth. It is common for this depth to decrease on the most axially outer circumferential portions (called "shoulders") of the tread 12. In addition, the tread of a tire is delimited, in the axial direction, by two lateral surfaces. The tread is further constituted by one or more rubber compounds. The expression "rubber compound" designates a rubber composition comprising at least one elastomer and a filler.

[0030] Referring to the figures, in which the same numbers identify identical elements, Figure 2 represents a flow diagram of an embodiment of a method for estimating the tread height of a tire mounted on a vehicle (or "estimation method" or "method) 100 of the invention. The estimation method of the invention is based on the state of wear of an identified tire on an identified vehicle, being defined by a remaining tread height. It is understood that a state of wear is represented by one or more values ​​representative of the difference existing between the new state (represented by a tire that has never been mounted on a vehicle) and the worn state (represented by a tire withdrawn from use due to reaching the withdrawal threshold by wear).The wear condition can take the form of a unit value such as the minimum tread height, a set of values ​​defining the tread height in a meridian plane of the tire (e.g., a 2D profile) or a set of values ​​defining the tread height on all or part of the external surface of the tire (e.g., a 3D profile).

[0031] As used herein, the “remaining life” of an identified tire refers to its residual wear potential based on the values ​​of the parameters influencing its longevity. The influencing parameters include the load, pressure, temperature and tread height of the identified tire. The remaining life can be determined continuously or at regular, predefined or sporadic intervals by collecting data corresponding to the parameters influencing the life of the identified tire. Based on the collected data, the method of the invention can define a current wear condition of the tire to determine the remaining life of the identified tire.

[0032] More particularly, the estimation method of the invention is based on the estimation of the temperature as an influential parameter in determining the pseudo-slip stiffness Kx. The pseudo-slip stiffness Kx is calculated from the data transmitted by the vehicle and the slip to then give a tread height for each tire.

[0033] This calculation, which allows the transition from the pseudo-slip stiffness Kx to the tread height, is also called the "transfer function F". Obtaining the transfer function F is carried out through a characterization campaign included in the group comprising numerical simulation and experimental measurements.

[0034] This transfer function F requires pseudo-slip stiffness evaluations Kx of an assembly mounted on the same reference ground (by "mounted assembly", it is understood that the tire-brake-wheel assembly is concerned). These evaluations can be carried out experimentally on the same ground by varying the various influential parameters either using a means of moving the mounted assembly such as a vehicle or a trailer or on a measuring bench. Similarly, these evaluations can be simulated numerically by modeling, for each evaluation, the same reference ground. This second option is inexpensive when the transfer functions F have to be carried out for the entire dimensional range of a tire model or for various components of the mounted assembly. It is understood that the two types of characterizations could be combined in order to validate a numerical model on a tire dimension or a particular mounted assembly.The characterization could then be extended numerically over the dimensional range of the tire or variants of the structural components of the assembled assembly.

[0035] The manner of obtaining this transfer function F is well described in the Applicant's publication WO2020 / 120923. As disclosed, obtaining the transfer function F is carried out by using a mathematical model of the type:

[0036] - Or

[0037] M>o and h ref, are constants: oj, and a are real numbers; are influential factors; and h is the tread height. This form of transfer function is suitable for calibrating experimental results; it allows covering a wide range of values ​​for all influential parameters instead of focusing around a nominal position through a limited development for example. In addition, the influential parameters are here independent of each other, thus facilitating the identification of the parameters of the transfer function F. Finally, this transfer function is focused on the interaction of a single soil, the reference soil, with the assembled assembly.

[0038] It is necessary to take into account the influence of the nature of the ground through an indicator, the passage function p. It is considered that the sensitivity of the pseudo-slip stiffness Kx to this coupling between the mounted assembly and the various grounds is integrated only in the passage function p. The chosen indicator is linked to the mounted assembly and in particular its interaction with the ground which is expressed through the stiffness of the tire tread which is the structural element of the tire in contact with the ground. The passage function P is linked to the portion of road characterized by its geographical location (represented, for example, by one or more GPS data). It is understood that a fixed function could be taken for this quantity P knowing the sensitivity of the pseudo-slip stiffness Kx of the mounted assembly according to the nature of the ground, according to the state of the tire and to an estimate of the nature of the real ground of the portion of road.Considering the interaction between the ground and the mounted assembly is a key factor for a quality identification of the tread height h.

[0039] Obtaining the passage function P, which is also disclosed in the Applicant's publication WO2020 / 120923, comprises the following steps: a step of carrying out a set of measurement cycles associated with various portions of dry road in the same state cycle of the mounted assembly; a step of obtaining, for each measurement cycle, a first pseudo-slip stiffness on real ground and a second longitudinal pseudo-slip stiffness on reference ground; a step of obtaining, for each measurement cycle, a difference X between the first and second pseudo-slip stiffness; a step of defining a target measurement cycle from among the set of measurement cycles by identifying the one that has the smallest difference X; and a step of assigning the identity function to the passage function P defined for the portion of road associated with the target measurement cycle.

[0040] The term "measurement cycle" here means that the mounted assembly is in iso condition of use for parameters such as inflation pressure P, temperature T and load Z experienced. It is understood that the term "iso condition" refers to variations in these parameters during the measurement cycle which are insignificant compared to the average value of these parameters over the entire measurement cycle. In addition, the tread height h and any other influential parameter associated with the state of the mounted assembly are considered to be invariant during the same measurement cycle. Indeed, the measurement cycle has a duration much shorter than the duration necessary to observe a variation in the state of the mounted assembly.

[0041] The term "assembly state cycle" here means that the influential parameters of a second group H are constant over the duration of the cycle. On the other hand, the parameters of a first group G linked to use can vary over the duration of this cycle.

[0042] In the estimation method 100 of the invention, the estimation of tire wear is carried out on the basis of a determination of a thickness E of the tread of an identified tire. This thickness E is determined according to a mathematical model of the type: whose transfer function F includes at least the inflation pressure P, the temperature T, the load Z and the thickness E of the tread as the influencing factors. A first pseudo-slip stiffness Kx reel and a second pseudo-slip stiffness Kx refare linked to the determination of the thickness E. In this embodiment of the method of the invention, the force Fx, at least one slip rate g%, the load Z, the inflation pressure P and the temperature T are determined as described above.

[0043] The skilled person understands that the operation of the tire is therefore influenced by its condition. This is mainly determined by the temperature of the rubber, the inflation pressure, the remaining tread height and the load level supported by the tire. Knowledge of these parameters, via direct or indirect measurement, is therefore fundamental in order to analyze the operation of the tire to determine wear and other operating parameters (including, without limitation, grip, rolling resistance, and / or endurance).

[0044] The estimation method 100 of the invention comprises the following steps: a step of identifying a tire of an assembly mounted on a vehicle; a step of acquiring a passage function P defined for a portion of road and the rigidity of the tread of the tire; a step of acquiring a transfer function F of the mounted assembly between a pseudo-slip rigidity Kx on a reference ground and influential factors, including the inflation pressure P, the temperature T and the load Z undergone, and the tread height h of the identified tire;

[0045] On a predetermined measurement cycle; a step of determining at least one force Fx undergone by the mounted assembly and at least one slip rate g% at the wheel center of the mounted assembly during straight-line driving of the vehicle comprising acceleration variations on the dry road portion; a step of determining a load undergone by the mounted assembly in driving conditions; a step of determining a temperature of the mounted assembly in driving conditions; and a step of determining an inflation pressure of the internal cavity of the mounted assembly in driving conditions; characterized in that the temperature is determined according to a mathematical model of the type:

[0046] T pneu = 0.985 * P p fTamb f ^ * (T amb f + 6.25

[0047] ^Tamb i whose T amb i represents the initial temperature in Kelvin, and Pf Tamb f and Pi Tamb trepresent the respective pressures at the end and beginning of a predetermined journey of an identified tire from an assembly fitted to an identified vehicle. The model has been validated on realistic usage cycles of the “Motorway”, “Road” and “Urban” type. Referring again to the figures, Figure 3 represents an illustration of a tire temperature simulation curve over five (5) realistic cycle cycles. Figure 4 represents an illustration of a tire temperature average rise simulation curve over the three types of realistic usage cycles.Figures 3 and 4 show an illustration of the simulation curves of a mounted assembly consisting of one of the following tires: a 205 / 55R16 Michelin tire from the Primacy4 RT range; a 205 / 55R16 Michelin tire from the CrossClimate+ range; a 225 / 45R18 Michelin tire from the Pilot Sport 4 range; and a 225 / 45R18 Michelin tire from the Pilot Sport 4 range (worn).

[0048] The assumptions underlying this model are as follows:

[0049] The ideal gas law is valid.

[0050] There is no loss of air or addition of air in the tire cavity between the times when the pressure at the start and the pressure at the end of the simulated journey are measured.

[0051] The pressure at the start is considered to be measured with an internal air temperature equal to the ambient temperature (therefore, the assembled assembly comprising the tire, wheel and cavity is in thermal equilibrium with the ambient temperature). In Figures 3 and 4, the simulation on realistic cycles shows that due to the variations in stress and ambient temperature throughout the cycle, the tire temperature varies constantly during rolling. It is therefore concluded that in real use, the tire is permanently in thermal transient. There is indeed an average tire thermal transient, the amplitude of which depends on the type of cycle (motorway cycle, road cycle, urban cycle).

[0052] The following parameters were retained in the simulations carried out:

[0053] Tire load: 40% to 100% of ETRTO load, in 5% steps;

[0054] Starting pressure (“initial pressure”): from 1.8 to 2.8 bar, in steps of 0.1 bar;

[0055] Speed: from 30 to 150 km / h, in steps of 10 km / h; and Ambient temperature: from -10°C to +40°C, in steps of 10°C.

[0056] Each simulation was carried out under constant conditions (load, speed, temperature, etc.). The tire is subject to recommended inflation and load conditions as defined in particular by the European standards of the "European Tyre and Rim Technical Organization" or "ETRTO" in its "Standards Manual 2020 - Commercial Vehicle Tyres". The compression and shear deformations of the raised elements delimiting the tread pattern condition the pressures in contact with the ground and therefore the wear.

[0057] It is submitted that there is a link between the internal air temperature of the tire and the stabilized temperature of the tire. It is found that the temperature of the tire is generally higher than the temperature of the rim at which it is mounted. In addition, the exchange surface between the tire and the internal air is much larger than between the internal air and the rim.

[0058] By building the model to determine a tire temperature of a set mounted on an identified vehicle, the simulations draw the following lessons:

[0059] Ambient temperature is essential in the model.

[0060] An average model on the four (4) tires gives a result that is substantially identical to the models specific to each tire.

[0061] The variables Fz, V, and two variables from the triplet (Pi, Pf, Tair) seem necessary.

[0062] The assumption made in the simulations is that the initial pressure corresponds to an internal air temperature equal to the ambient temperature. By using the ideal gas law (PV=nRT), it appears obvious that the ambient temperature and the stabilized internal air temperature are highly correlated with the initial pressure and the final stabilized pressure.

[0063] The term "identified tire" (in the singular or plural) is used herein to refer to a tire that is mounted on an identified vehicle (being a tire still in service on the identified vehicle). The identified tire may include one or more sensors known to generate or capture data, such as data corresponding to an operational environment of the identified vehicle or a part thereof. The sensors may include a set of sensors to provide data regarding the operating characteristics of the identified tire. The sensors may include, for example, speed sensor(s), acceleration sensor(s), traction-related sensor(s), braking-related sensor(s), and / or a combination of sensors to collect data regarding one or more aspects of the dynamic situation of the identified tire.The sensors may also provide stored data regarding the identification of the identified tire (including, without limitation, its production, distribution and / or storage origin, its production date, its retreading history if applicable and its mounting position and history).

[0064] In embodiments, the sensors are of the type that provide measurements of the temperature and pressure of the mounted assembly. These sensors can be chosen from TMS (or "Tire Mounted Sensor") type sensors placed on the inner rubber of the tire identified at the crown in such a way that the sensor is substantially in the median plane of the tire. The load undergone by the mounted assembly is applied using the cylinder of the measuring bench where a dynamometric hub measures the vertical force Fz applied as well as the longitudinal Fx and axial Fy components. The measurement is carried out at imposed force by controlling the vertical force Fz applied. A variation in torque around the axis of rotation of the mounted assembly is applied to the wheel center of the mounted assembly via the measuring bench. The applied torque is measured using the dynamometric hub.In addition, the position of the rotation axis of the mounted assembly relative to the rolling ground is measured as well as the rotation speed of the wheel center of the mounted assembly through an encoder mounted between the stator and the rotor of the rotation axis of the measuring bench. Finally, the scrolling of the ground is also controlled by the machine.

[0065] The determination of the various parameters of the mounted assembly must be carried out in a short time corresponding to the measurement cycle. All state-of-the-art means respecting this constraint can be used. Thus, pressure and temperature measurements will be conventionally obtained by direct or indirect sensors. For example, a pressure sensor in fluid communication with the internal cavity of the mounted assembly is a direct measurement of the inflation pressure. For example, a temperature sensor of the fluid contained in the internal cavity is an indirect measurement of the temperature of the mounted assembly (and in particular of the tread pattern of the tire). The use of a thermal model taking into account the heat exchanges between the various components (internal fluid, components of the mounted assembly and external fluid) and according to the various transmission modes (radiation, convection, conduction) is necessary.Of course, a measurement using a thermocouple implanted in the tire is a more direct measurement of the temperature, but this is difficult to implement since it requires a structural modification of the tire casing.

[0066] In embodiments, these sensors are selected from sensors packaged in electronic systems attached to the mounted assembly (such as, for example, TPMS (or “Tire Pressure Monitoring System”) mounted to the valve) or TMS attached to the internal wall of the tire delimiting the internal cavity.

[0067] More direct measurements at the mounted assembly level can also be considered. For example, calibrating a periodic signal at the wheel revolution allows extracting a longitudinal dimension, characteristic of the contact between the tire casing and the ground for a given mounted assembly. In this case, a sensor sensitive to the radial and / or longitudinal deformation of the tire is considered (for example, an accelerometer or piezoelectric element type sensor). The use of charts between this characteristic dimension and the inflation pressure allows an evaluation of the load undergone by the mounted assembly to be obtained. It is understood that other equivalent devices can also be used.

[0068] Another characteristic evaluated in the determination of the pseudo-slip stiffness Kx is the slip rate G% of the wheel center mounted assembly. This quantity can be estimated directly by the data provided by the electronic systems on board the vehicle (for example, the ABS system). It can also be evaluated through three elementary parameters which are the rotation speed of the wheel center mounted assembly, the rolling radius of the mounted assembly and the forward speed of the vehicle.

[0069] The rotational speed can be simply obtained by a wheel revolution encoder coupled to a clock. The rolling radius of the mounted assembly, which is not very sensitive to wear, is obtained using the distance traveled by the vehicle and the number of revolutions made by the mounted assembly to cover this distance. Finally, the forward speed of the vehicle is obtained by means of a high-frequency measuring device to have sufficient precision (for example, a device of the RT 3000 type).

[0070] Finally, the overall wear of the tire is assessed in real time by the almost simultaneous determination of the parameters of the mounted assembly, which are the conditions of use, influencing the pseudo-slip rigidity Kx of the mounted assembly and the state parameters of the mounted assembly and in particular of the tire which have been determined over a possibly longer period. In particular, it is necessary to take into account the influence of the nature of the ground through an indicator (i.e., the passage function P).

[0071] To implement the method of the invention by computer means, a system is provided which comprises at least one communication network (or "network") which manages the data incoming to the system from various sources (for example, from at least one device of the TMS type or of the TPMS type). The communication network incorporates one or more communication servers (or "servers") each comprising one or more processors operatively connected to a memory. The memory is configured to store an application for analyzing data representative of the operating characteristics of the identified tire. The one or more processors comprise an analysis application execution module whose one or more processors are capable of executing programmed instructions stored in the memory to carry out the steps of the estimation method 100.The input data to the system performing the estimation process may include general information regarding the identified tire. The general information includes stored data regarding the identification of the identified tire (including, without limitation, its production origin, distribution and / or storage, production date, retreading history if applicable and its mounting position and history). The corresponding data of an identified tire could be managed by an entity that manages the use of one or more vehicles to which a tire of the same type is mounted (for example, such an entity may include one or more persons and / or one or more companies) and / or the manufacturer of such tires.

[0072] The term "processor" (or, alternatively, the term "programmable logic circuit") means one or more devices capable of processing and analyzing data and including one or more software programs for processing them (e.g., one or more integrated circuits known to those skilled in the art as being included in a computer, one or more controllers, one or more microcontrollers, one or more microcomputers, one or more programmable logic controllers (or "PLCs"), one or more application-specific integrated circuits, one or more neural networks, and / or one or more other known equivalent programmable circuits). The processor includes one or more software programs for processing the data captured by the system that performs the estimation process as well as one or more software programs for identifying and locating variances and identifying their sources to correct them.In the system that performs the method of the invention, the memory may include both volatile and non-volatile memory devices. The non-volatile memory may include solid-state memories, such as NAND flash memory, "keep-alive memory" (or "KAM") for saving various operating variables while the processor is powered off, magnetic and optical storage media, or any other suitable data storage device that retains data when the system (and / or a facility incorporating the system) is turned off or loses power. The volatile memory may include static and dynamic RAM that stores program instructions and data, including a learning application.

[0073] The processor may also refer to a reference (e.g., a size chart of various tires) to make a final determination of a parameter or parameters of the identified tire. The reference may include known tire parameters corresponding to a plurality of known commercially available tires. The tire reference may include measurements corresponding to a plurality of commercially available tires. For example, for a tire of size 225 / 50R17, the number "225" identifies the tire cross-sectional area in millimeters, the number "50" indicates the sidewall aspect ratio, and the measurement "R17" represents the rim diameter in inches (being approximately 43.18 centimeters). With further reference to the figures, and particularly to Figure 2, a detailed description is provided by way of example of embodiments of the estimation method 100 of the invention.The estimation method is implemented by at least one processor of a system that performs the estimation method 100.

[0074] As used herein, the term “method” or “process” may include one or more steps performed by at least one computer system having one or more processors to execute instructions that perform the steps. Unless otherwise indicated, any sequence of steps is exemplary and does not limit the described methods to any particular sequence.

[0075] By launching the method of the invention, the estimation method 100 comprises a step 102 of identifying the mounted assembly comprising the identified tire. This step can be done by assigning the identifier of the components of the mounted assembly associated with the vehicle in a database. During this step, the identification of the mounted assembly makes it possible to define a characteristic tread height (such as, for example, the tread height in new condition and the tread height at the end of the tire's life).

[0076] The estimation method 100 further comprises a step 104 of choosing a passage function P from a list of potential passage functions P which is representative of the median nature of the road portions that the vehicle will encounter. The identification of the mounted assembly carried out during step 102 makes it possible to know the rigidity of the tread of the tire, which makes it possible to estimate one or a few passage functions P each associated with a road portion characterized by macroroughness from among a possible plurality of passage functions.

[0077] The estimation method 100 further comprises a step 106 of choosing the transfer function F which links the pseudo-sliding stiffness Kx to the tread height h. The identification of the mounted assembly carried out during step 102 also makes it possible to choose the transfer function F of the corresponding mounted assembly whose influential parameters are represented by the load Z, the pressure, the temperature T and the tread height h.

[0078] The estimation method 100 further comprises a step 108 of providing information on the aging state of the identified tire. This uses the identification of the mounted assembly (performed during the identification step 102) in order to know the history of the use of the identified tire. This history can be provided through the interrogation of one or more databases (either external or present on the vehicle or present on the server(s) of the system which performs the estimation method 100). If the aging state of the identified tire only concerns the age of the product or the total number of cycles performed or kilometers traveled, the information can be present on the mounted assembly through an electronic device (for example, a device of the TMS or TPMS type). This step 108 takes place during a state cycle comprising the measurement cycle allowing the evaluation of the average thickness of the tire.

[0079] The estimation method 100 further comprises a step 110 of acquiring the forces Fx measured at the wheel center of the mounted assembly and the associated slip rates G%. This step is carried out during straight-line driving on a dry road comprising acceleration and deceleration phases. In the absence of direct forces Fx at the wheel center, access to characteristics of the identified vehicle allows an estimation of the forces Fx at the wheel center (such as, for example, the torque applied to the wheel center around the natural axis of rotation of the mounted assembly during acceleration or deceleration phases).

[0080] The estimation method 100 further comprises a step 112 of acquiring the usage parameters of the mounted assembly. These acquired parameters may include, without limitation, the inflation pressure P, the temperature T of the tire of the mounted assembly and the load Z applied (or the characteristics of the identified vehicle allowing the load Z to be obtained, including, without limitation, its static mass, the filling state of the fuel tank and the indication of the number of seat belts fastened). This step 112 must be carried out just before, during or after the straight line driving carried out during the previous step 110.

[0081] In one embodiment of the estimation method 100, the step 112 of acquiring the usage parameters of the mounted assembly comprises the following steps: a step of determining a load undergone by the mounted assembly in rolling conditions; a step of determining a temperature of the mounted assembly in rolling conditions; and a step of determining an inflation pressure of the internal cavity of the mounted assembly in rolling conditions.

[0082] In this embodiment, the temperature is determined according to a mathematical model of the type:

[0083] T pneu = 0.985 * P p fTamb f ^ * (T amb f ) + 6.25

[0084] ^Tamb i whose T amb i represents the initial temperature in Kelvin, and Pf Tamb f and Pi Tamb trepresent the respective pressures at the end and beginning of a predetermined path of the identified tire. The estimation method 100 further comprises a step 114 of plotting a point cloud associated with the doublet of values ​​(Fx, g%). This step is carried out using the forces Fx measured or evaluated and the associated slip rates g% when driving on the dry road portion. During this step, only the set of points for which the tire does not slip on the road portion is retained from this point cloud. Finally, the linear regression line of all the points retained is identified. The slope of this regression line corresponds to the estimation of a first pseudo-slip stiffness Kx on real ground corresponding to the dry road portion. It is understood that this step can be carried out between two measurement cycles.

[0085] The estimation method 100 further comprises a step 116 of estimating a second pseudo-slip rigidity Kx by feeding the transfer function F obtained during step 104 with the usage parameters measured during step 112 (for example, the reference conditions Z, P and T) and the tread height h obtained during step 102. Depending on the sensitivity of the characteristics of the mounted assembly to aging, this step can also be coupled with step 108 in which an evaluation of the aging of the mounted assembly is carried out.

[0086] The estimation method 100 further comprises a step 118 of evaluating the average tread height and consequently the overall wear of the identified tire by comparing this evaluated average height with the specific heights of the tire (for example, the tread height in the new state and at the end of life of the tire). For this, a relationship linking the results of steps 104, 110 and 112 is applied, the result of which is the average height h associated with the state cycle of the identified tire. In the case where the second pseudo-slip stiffness Kx (obtained during step 116) is defined using the transfer function F (obtained during step 106). As presented above, this transfer function is the product of power functions of independent influential parameters. Thus, the tread height h can be isolated from this transfer function F.We assume here that the passage function P is constant with the average sculpture height.

[0087] The estimation method 100 further comprises a step 120 of acquiring the variation AU of a parameter U linked to the use of the identified tire between two acquisitions of the average tread height. The parameter U may be, for example, the number of rotation cycles around the natural axis of rotation or the number of kilometers traveled by the tread or the time of use of the identified tire. The two acquisitions (hl, h2) of the average tread height may be, for example, two evaluations carried out by the method corresponding to two states of wear of the identified tire or an evaluation of the average tread height combined with the new state of the identified tire or a measurement of the average height of the identified tire by an external measuring means.

[0088] The estimation method 100 further comprises a step 122 of evaluating the wear rate of the identified tire. This step comprises evaluating the tread at a point of acquisition of the average tread height of the identified tire. For this, it is necessary to have both the variation AU of the parameter U linked to the use of the identified tire (obtained during the previous step 120) and the variation of the corresponding average height Ah. The variation Ah represents the difference between the two obtained values ​​(hl, h2) having served as reference points for the variation AU during the previous step 120. The ratio of the variation of the average height Ah to the variation of the parameter linked to the use of the tire AU defines the wear rate of the average tread height according to the parameter U.

[0089] The estimation method 100 comprises a final step 124 of evaluating the remaining service life of the identified tire. This step consists of evaluating the end-of-life prediction according to the parameter U linked to the use of the identified tire. This is obtained by combining the results of the identification step 102, the step 118 of evaluating the average tread height, and the step 122 of evaluating the wear rate of the identified tire.

[0090] The estimation method 100 of the invention may be carried out by the control of the PLC and may include pre-programming of the management information. For example, a setting of the method may be associated with the parameters of the identified tire, the parameters of the mounted assembly incorporating the identified tire and / or the properties of the vehicles to which the identified tire is intended to be mounted. The system carrying out the estimation method 100 of the invention (and / or an installation incorporating this system) may easily repeat one or more steps of the estimation method 100 in a predetermined order.

[0091] The system performing the estimation method 100 of the invention (and / or a facility incorporating this system) may include pre-programming of management information. For example, a process setting may be associated with the parameters of typical vehicles in which the system operates. In embodiments of the invention, the system performing the estimation method 100 of the invention (and / or a facility incorporating this system) may receive voice commands or other audio data representing, for example, a step or a stop of the process. A generated response may be represented audibly, visually, tactilely (for example, using a haptic interface) and / or virtually and / or augmentedly. This response, associated with the corresponding data, may be recorded in a neural network.

[0092] For all embodiments of the system, a monitoring system could be implemented. At least part of the monitoring system may be provided in a portable device such as a mobile network device (e.g., a mobile phone, a laptop computer, one or more network-connected wearable devices (including “augmented reality” and / or “virtual reality” devices), network-connected wearables, and / or any combinations and / or equivalents).

[0093] In one embodiment, the estimation method 100 of the invention may comprise a step of training a system to recognize values ​​representative of the tread heights (for example, values ​​of the internal diameter and the external diameter of the identified tire in the new condition) and to make a comparison with targeted values ​​(for example, the tread height values ​​associated with the known corresponding service lives). Each step of the training may include a classification generated by self-learning means. This classification may include, without limitation, the parameters of the mounted tires, the vehicle configurations, the expected service lives for a particular tire, and the expected values ​​at the end of an ongoing estimation process.

[0094] It is understood that several distinct learning methods are possible, including supervised learning (in which the algorithm trains on a set of labeled data and modifies itself until it is able to obtain the desired result), unsupervised or semi-supervised learning (in which the data is not labeled so that the network can adapt to increase the accuracy of the algorithm), reinforcement learning (in which the algorithm is reinforced for positive results and punished for negative results) and active learning (the algorithm gradually requests examples and labels to refine its prediction) (see https: / / www.lebigdata.fr / reseau-de-neurons-artificiels-definition).

[0095] The terms "at least one" and "one or more" are used interchangeably. Ranges that are presented as "between a and b" encompass the values ​​"a" and "b".

[0096] Although particular embodiments of the disclosed apparatus have been illustrated and described, it will be understood that various changes, additions, and modifications may be practiced without departing from the spirit and scope of the present disclosure. Accordingly, no limitations should be imposed on the scope of the disclosed invention except those set forth in the appended claims.

Claims

Claims 1. A method for estimating (100) the tread height of an identified tire of an assembly mounted in rolling condition on an identified vehicle, the tire of which has a crown which extends into two sidewalls ending in two beads of revolution around a natural axis of rotation, the crown comprising a tread located radially outside the tire relative to the natural axis of rotation and having an average tread height h, the method implemented by at least one processor of a system which carries out the estimation method (100), the at least one processor comprising an analysis application module which applies the data representative of operating characteristics of the identified tire, characterized in that the estimation method (100) comprises the following steps: a step of identifying (102) a tire of an assembly mounted on a vehicle; -a step of choosing (104) a passage function P from a list of potential passage functions P which is representative of the median nature of the road portions that the vehicle will encounter, making it possible to estimate one or more passage functions P each associated with a road portion and the rigidity of the tire tread; a step of choosing (106) a transfer function F of the mounted assembly between a pseudo-slip rigidity Kx on a reference ground and influential parameters represented by the load Z, the pressure, the temperature T and the tread height A; and, over a predetermined measurement cycle; a step of determining (110) at least one force Fx undergone by the mounted assembly and at least one slip rate G% at the wheel center of the mounted assembly during straight-line travel of the vehicle comprising acceleration variations on the dry road portion;a step of acquiring (112) the usage parameters of the mounted assembly comprising the following steps: a step of determining a load (Z) undergone by the mounted assembly in rolling conditions; a step of determining a temperature (T) of the mounted assembly in rolling conditions; and; a step of determining an inflation pressure (P) of the internal cavity of the assembled assembly in rolling condition; characterized in that the temperature is determined according to a mathematical model of the type: T pneu = 0.985 6.25 including T amb i represents the initial temperature in Kelvin, and Pf Tamb f and Pi Tamb t represent the respective pressures at the end and start of a predetermined path of the identified tire.

2. The estimation method (100) of claim 1, in which a thickness E of the tread of the identified tire is determined according to a mathematical model of the type: whose transfer function F includes at least the inflation pressure P, the temperature T, the load Z and the thickness E of the tread as the influencing factors; and whose first pseudo-slip stiffness Kx reel and a second pseudo-slip stiffness Kx ref are linked to the determination of the thickness E.

3. The estimation method (100) of claim 1 or claim 2, further comprising a step of providing information (108) on the aging state of the identified tire during which the identification of the mounted assembly is used in order to know the history of the use of the identified tire.

4. The estimation method (100) of claim 2, further comprising: a step of tracing (114) a point cloud which is carried out from the measured forces Fx and the associated slip rates G% when driving on a portion of dry road, during which an estimation of the first pseudo-slip rigidity K reel is obtained on real ground corresponding to the portion of dry road; and a step of estimation (116) of a second pseudo-slip rigidity K ref in feeding the transfer function F obtained during the choosing step (106) with the usage parameters measured during the acquisition step (112) and the sculpture height h obtained during the choosing step (106).

5. The estimation method (100) of any one of claims 1 to 4, wherein the passage function P is chosen from a possible plurality of passage functions from a list of potential passage functions P which is representative of the median nature of the road portions that the identified vehicle will encounter.

6. The estimation method (100) of any one of claims 1 to 5, further comprising a step of evaluating (118) the average tread height by comparing this evaluated average height with the specific heights of the identified tire.

7. The estimation method (100) of claim 6, further comprising a step of acquiring (120) the variation AU of a parameter U linked to the use of the tire identified between two acquisitions of the average tread height.

8. The estimation method (100) of claim 7, further comprising a step of evaluating (122) the wear rate of the identified tire, this step comprising a step of evaluating the tread at a point of acquisition of the average tread height of the identified tire.

9. The estimation method (100) of claim 8, comprising a step of evaluating (124) the remaining life of the identified tire, this step comprising a step of evaluating the end-of-life prediction according to the parameter U linked to the use of the identified tire; such that the end-of-life prediction is obtained by combining the results of the identification step (102), the step of evaluating (118) the average tread height, and the step of evaluating (122) the wear rate of the identified tire.

10. A system comprising a communications network that manages data representative of operating characteristics of a tire identified from an assembly mounted in rolling condition on an identified vehicle in which the tire is incorporated, characterized in that the communication network comprises at least one communication server making it possible to execute programmed instructions stored in a memory of one or more processors of the system to implement the method of any one of claims 1 to 9.

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