Method and system for monitoring a status of a tyre

Abstract

Method and system (1) for monitoring a status of a tyre (3) mounted on a wheel (7) of a vehicle (99), where said system (1) comprises an acquisition system (2) structured to acquire a signal (S) representative of a motion of a crown portion (31) of said tyre (3) and a processing unit (8) in communication with said acquisition system (2) and programmed to receive from said acquisition system (2) said signal (S) and to perform the following steps of said method: dividing said signal (S) into a set of signal portions (SP); for each signal portion (SP), calculating a respective value of a parameter (KPI) representative of an average power of said signal of said signal portion (SP); comparing each respective value of said parameter (KPI) with a threshold value (TV); removing from said set each signal portion (SP) corresponding to a respective value of said parameter (KPI) greater than said threshold value (TV) to obtain an elaborated signal (SE); and monitoring a status of said tyre (3) as a function of said elaborated signal (SE).

Description

[0001] DESCRIPTION

[0002] Title: METHOD AND SYSTEM FOR MONITORING A STATUS OF A TYRE

[0003] Technical field of the invention

[0004] The present invention concerns a method and a system for monitoring a status of a tyre, for example a status of integrity or a status of wear of the tyre, for example of the tread.

[0005] State of the art

[0006] Typically a tyre for vehicles has a substantially toroidal structure around a rotation axis of said tyre during the operation, and comprises an equatorial plane orthogonal to said rotation axis, said equatorial plane being typically a plane of (substantial) geometric symmetry (e.g. neglecting possible minor asymmetries, such as a pattern of the tread and / or writings on the sidewalls and / or an internal structure).

[0007] By "crown portion” is meant a portion of tyre positioned at a tread band.

[0008] The terms "radial” and "axial” are used with reference respectively to a substantially perpendicular direction and to a substantially parallel direction to said rotation axis of said tyre.

[0009] The term "tangential” is used with reference to a substantially perpendicular direction both to said radial direction and to said axial direction (e.g. generally directed according to a rolling direction of said tyre).

[0010] The terms "lateral”, "vertical”, and "longitudinal” refer respectively to said axial direction, said vertical direction, and said horizontal direction.

[0011] By "footprint” is meant a portion of an external surface of said tread band that, during a rolling of said tyre mounted and subjected to a load (for example due to the mounting under a vehicle), at each instant is in contact with a rolling surface. Said footprint typically has substantially null curvature (or substantially infinite radius of curvature), or in any case substantially assumes a conformation of said rolling surface. By "footprint area” is meant a respective crown portion corresponding (instantaneously) to said footprint.

[0012] With the expression "lie internally” or "externally to said footprint area” referring to a crown portion, it is meant that said crown portion, due to a rotation of said tyre, is positioned respectively inside or outside said footprint area of said tyre at a given instant / time interval, or at a given (corresponding) angular position / angular position interval. By "passage internally to said footprint area” referring to said crown portion, it is meant an interval, expressed for example in units of time or in degrees of rotation (e.g. with respect to a complete turn), in which said crown portion is positioned, due to a rotation of said tyre, continuously inside said footprint area of said tyre.

[0013] Documents EP2813378, EP3330106, EP3210799, and EP2837510 each describe a method and a respective system for estimating a status of wear of a tyre.

[0014] Documents WO2022144703A1, WO2022144939A1, WO2022144940A1 each describe a method and a respective system for monitoring a status of a tyre.

[0015] Summary of the invention

[0016] In the context of the monitoring of a status of a tyre, the Applicant has found that said known methods involve, in the respective routines of estimation and / or monitoring, the processing of one or more frequencies of at least one vibration mode typical of said tyre and / or of a combination of said typical vibration modes, such as for example one or more among the following modes: lateral translational, vertical translational, horizontal translational, torsional about a rotation axis of said tyre (Y), torsional about a vertical axis (Z), and torsional about a horizontal axis (X - typically perpendicular to said rotation axis of said tyre Y).

[0017] For example, in more detail, the estimation methods of wear described in EP2813378, EP2837510, EP3330106, and EP3210799 use a model of mathematical correlation between at least the frequency of a vertical vibration mode and / or of a torsional vibration mode of said tyre and a thickness of said tread band.

[0018] The monitoring methods described in WO2022144703A1 , WO2022144939A1 , and WO2022144940A1 are based on a comparison between the frequency of a given peak of a frequency spectrum of a signal of motion of said tyre acquired (preferably in lateral direction) in a reference time phase, and the frequency of the same peak in a frequency spectrum of said signal of motion acquired in a subsequent time phase, for example a time phase of wear of said tyre, in order to evaluate a possible deviation of said peak frequency, for example towards higher or lower frequency values. On the basis of an entity and sign of said frequency deviation, a status of said tyre is monitored.

[0019] The Applicant has found that in some cases said monitoring methods result poorly precise.

[0020] In this context, the Applicant has observed that under normal conditions of rolling of said tyre on a road surface, said tyre is typically subjected to multiple external influences that can cause the onset of spurious vibrational components additional to said vibration modes typical of said tyre. Without wishing to be bound to any theory, the Applicant considers that said spurious components in turn negatively interfere with a correct identification of the frequency of a given vibration mode typical, or combination of vibration modes typical, of said tyre, with a consequent worsening of precision and / or reliability characteristics of said methods.

[0021] For example, in fact, in said monitoring methods that provide the evaluation of said peak frequency deviation, said spurious vibrational components can cause the onset of respective spurious peaks in said frequency spectra, which can add to said typical frequency peaks (corresponding to said vibration modes typical of said tyre), compromising the detection thereof. This consequently determines inaccuracies in the comparison between said frequencies, with errors in the evaluation of said status of said tyre, for example quantitative overestimates or underestimates of a monitored state variable of said tyre.

[0022] The Applicant has therefore addressed the problem of further improving the precision and / or reliability of the monitoring of a status of a tyre based on the detection of said typical frequencies of said vibration modes of said tyre.

[0023] According to the Applicant, said problem is solved by a method and a system for monitoring said status of a tyre capable of monitoring said status of said tyre as a function of an elaborated signal representative of a motion of a crown portion of said tyre, wherein said elaborated signal is obtained by filtering a starting signal to remove one or more signal portions having a respective value of a parameter representative of a respective average power of signal greater than a threshold value.

[0024] According to an aspect, the invention relates to a method for monitoring a status of a tyre mounted on a wheel of a vehicle. Said method preferably comprises, during an advancement of said vehicle, acquiring over time a signal representative of a motion of a crown portion of said tyre.

[0025] Said method preferably comprises dividing said signal into a set of signal portions.

[0026] Preferably each signal portion corresponds to at least one respective fraction of a complete turn of said crown portion around a rotation axis of said tyre.

[0027] Said method preferably comprises, for each signal portion of said set, calculating a respective value of a parameter representative of an average power of the signal of said signal portion.

[0028] Said method preferably comprises comparing each respective value of said parameter with a threshold value.

[0029] Said method preferably comprises removing from said set each signal portion corresponding to a respective value of said parameter greater than said threshold value, to obtain an elaborated signal.

[0030] Said method preferably comprises monitoring a status of said tyre as a function of said elaborated signal.

[0031] According to another aspect, the invention concerns a system for monitoring a status of a tyre mounted on a wheel of a vehicle.

[0032] Said system preferably comprises an acquisition system configured to, during an advancement of said vehicle, acquire over time a signal representative of a motion of a crown portion of said tyre.

[0033] Said system preferably comprises a processing unit in communication with said acquisition system.

[0034] Preferably said processing unit is configured to receive from said acquisition system said signal.

[0035] Preferably said processing unit is configured to divide said signal into a set of signal portions. Preferably each signal portion corresponds to at least one respective fraction of a complete turn of said crown portion around a rotation axis of said tyre.

[0036] Preferably said processing unit is configured to, for each signal portion of said set, calculate a respective value of a parameter representative of an average power of the signal of said signal portion.

[0037] Preferably said processing unit is configured to compare each respective value of said parameter with a threshold value.

[0038] Preferably said processing unit is configured to remove from said set each signal portion corresponding to a respective value of said parameter greater than said threshold value, to obtain an elaborated signal.

[0039] Preferably said processing unit is configured to monitor a status of said tyre as a function of said elaborated signal. According to the Applicant, the filtering, from the acquired signal, of the signal portions corresponding temporally to a (localized) increase of the average power of the signal allows obtaining a more precise, reliable, and robust estimation of the monitored state variable of said tyre. In fact, the Applicant has found that the external influences acting on said tyre during the rolling, and generating said spurious vibrational components, correspond, in the majority if not totality of cases, to events in which said tyre interacts with defects of the road surface, and that said events, defined as high-energy events, cause a temporally localized increase of the average power of the signal of the motion of said crown portion of said tyre.

[0040] Therefore, by eliminating from said acquired signal the effects of said high-energy events by removing the corresponding signal portions, it is possible to reduce, even to eliminate, said issues, such as for example the presence of said spurious frequency peaks in said frequency spectra.

[0041] This thus allows increasing the precision, the reliability, and / or the robustness of the estimation or monitoring methods that provide the processing of said signal, in particular of the methods that involve the frequency of at least one vibration mode typical of said tyre and / or provide the analysis of the frequency spectrum of said signal, such as for example said known methods.

[0042] Thanks to said signal portions each corresponding to at least one respective fraction of a complete turn (that is, each signal portion corresponds temporally to at least one portion of complete turn even to a plurality of complete turns) it is possible to obtain the desired discretization of said signal along the time axis (e.g. temporal extension of each signal portion), to obtain the desired sensitivity to said high-energy events in order to remove one or more signal portions adequately circumscribed to said event, reducing the signal information lost and limiting at the same time the computational burden.

[0043] The present invention in one or more of said aspects may comprise one or more of the following preferred features. Preferably said at least one processing unit is configured to perform any embodiment of the method of the present invention.

[0044] In one embodiment, said acquiring said signal is performed in a first operational phase.

[0045] Preferably said method further comprises acquiring over time a further signal representative of said motion of said crown portion in a second operational phase temporally subsequent to said first operational phase. Preferably said acquisition system is configured to, during an advancement of said vehicle, acquire over time, in a second operational phase temporally subsequent to said first operational phase, a further signal representative of the motion of a crown portion of said tyre.

[0046] Preferably said (first or second) operational phase is a time phase of use of said tyre. Preferably said first operational phase is a phase in which said tyre is in a reference status, which advantageously may coincide with a status of said tyre substantially new. Preferably said second operational phase is any phase, subsequent to said first operational phase, of normal use of said tyre.

[0047] Preferably said method comprises obtaining a further elaborated signal representative of said motion of said crown portion starting from said further signal.

[0048] Preferably obtaining said further elaborated signal comprises:

[0049] - dividing said further signal into a set of further signal portions, each further signal portion corresponding to at least one respective fraction of a complete turn of said crown portion around said rotation axis of said tyre;

[0050] - for each further signal portion of said set, calculating a respective further value of a parameter representative of an average power of the signal of said further signal portion;

[0051] - comparing each respective further value of said parameter with a further threshold value;

[0052] - removing from said set each further signal portion corresponding to a respective further value of said parameter resulting greater than said further threshold value, to obtain said further elaborated signal.

[0053] Preferably said method comprises monitoring said status of said tyre also as a function of said further elaborated signal. Preferably monitoring said status of said tyre comprises obtaining a frequency spectrum of said elaborated signal. Preferably monitoring said status of said tyre comprises obtaining a further frequency spectrum of said further elaborated signal.

[0054] Preferably monitoring said status of said tyre is performed as a function of said frequency spectrum of said elaborated signal, and more preferably also as a function of said further frequency spectrum of said further elaborated signal. The Applicant has in fact found that from a comparison between said frequency spectrum and said further frequency spectrum, in particular between frequencies of determined peaks identified in said spectra, it is possible to monitor said status of said tyre in a particularly advantageous manner, as better described below. Preferably monitoring said status of said tyre comprises identifying a determined peak in a plurality of peaks of said frequency spectrum and determining a frequency of said determined peak. Preferably monitoring said status of said tyre comprises identifying a further determined peak in a further plurality of peaks of said further frequency spectrum and determining a further frequency of said further determined peak. The Applicant, without wishing to be bound to any theory, has in fact found that said peaks of said frequency spectrum and said further peaks of said further frequency spectrum are representative of vibration modes of said tyre in said two different operational phases, as described above.

[0055] Preferably monitoring said status of said tyre comprises determining a reference frequency as a function of said frequency of said determined peak.

[0056] Preferably monitoring said status of said tyre comprises determining a current frequency as a function of said further frequency of said further determined peak.

[0057] Preferably said frequency and said further frequency are a modal frequency of a same vibration mode (or of a same combination of vibration modes) of said tyre, more preferably selected in the following group of vibration modes: lateral translational, vertical translational, horizontal translational, torsional about a rotation axis of said tyre, torsional about a vertical axis, and torsional about a horizontal axis. In this way frequencies easily identifiable within said frequency spectrum are used.

[0058] In one embodiment said same vibration mode is the lateral translational mode. The Applicant has in fact found that said mode results sufficiently distinct and recognizable from the other modes in the frequency spectrum, that is, its frequency does not appear disturbed by other vibrational modes.

[0059] Preferably monitoring said status of said tyre is performed as a function of a comparison between said current frequency and said reference frequency, or between two values of a same physical quantity, said two values being correlated respectively to said current frequency and to said reference frequency. With reference to said comparison between frequencies for monitoring said status of said tyre, the Applicant has made the following observations regarding said vibration modes of said tyre, in particular said first six vibration modes of said tyre, that is, said first three translational vibration modes and said first three rotational vibration modes, in which said belt layers are not substantially subjected to deformation. First, the Applicant has found that for a tyre said modal stiffness and said modal mass (or said modal moment of inertia in the case of said rotational modes) may be considered quantities independent from one another. In particular, said modal stiffness is substantially determined by a stiffness of said tyre carcass, whereas said modal mass (or said modal moment of inertia) is substantially determined by the mass of said elastomeric compounds, and in particular predominantly by the mass of said tread band and in part by the sidewall.

[0060] Moreover, said stiffness of said tyre carcass results a parameter that, under conditions of integrity of said tyre, remains substantially constant during the entire operational life of said tyre under equal operating conditions of said tyre (e.g. internal pressure, temperature, vertical load, and travel speed). Moreover, said stiffness of said tyre carcass is predominantly dominated by said pressure of said tyre. From said observations the Applicant has found that it is advantageous to monitor said status of said tyre by comparing said reference frequency and said current frequency, both determined as a function of said modal frequency of a determined vibration mode, or combination of vibration modes, of said tyre, or two values of a same physical quantity correlated to said frequencies, respectively in said first and in said second operational phase. In fact, said determined peak and said further determined peak (identified in the respective spectra, for example on the basis of predetermined same selection criteria) are representative of a same, selected, vibration mode or of a same combination of vibration modes of said tyre in two temporally spaced moments of the life of said tyre.

[0061] In case, therefore, a deviation of said current frequency from said reference frequency occurs, or a deviation of the respective values of said physical quantity, it is possible to conclude that there has been a change in said status of said tyre since the frequency of said selected vibration mode(s) or the value of said physical quantity correlated to said frequency has varied. Said change in said status of said tyre could for example consist of a variation of said modal mass (or modal moment of inertia) (e.g. due to wear of said tread band) or of a variation of said modal stiffness (e.g. due to a loss of integrity of said tyre, for example due to damage or break, which may have caused for example a lowering of said internal pressure of said tyre and / or a damage of said carcass).

[0062] In this regard, the filtering of said signal and of said further signal performed by removing respectively said signal portions and said further signal portions as described above contributes in a particularly advantageous manner to said monitoring of said tyre by means of a comparison between said frequencies. In fact, by filtering said signals from said high-energy events, said effects due to said events are reduced, or even eliminated, first among all the presence of said spurious frequency peaks, with a consequent improvement of the precision in determining said respective peak frequencies.

[0063] Preferably said physical quantity is a mass or a moment of inertia or a stiffness of said tyre. Preferably said mass or moment of inertia or stiffness are respectively a modal mass or a modal moment of inertia or a modal stiffness of said tyre.

[0064] Preferably said mass or moment of inertia or stiffness are correlated to said respective frequency by means of the following mathematical formula: k = f2■ m where k is said stiffness, f is said respective frequency, and m is said mass or said moment of inertia. The Applicant has found that for example for said first six vibration modes of said tyre said relation correlates said modal stiffness k (which typically depends on one or more operating parameters of said tyre), said modal frequency f (which typically depends on said one or more operating parameters), and said modal mass m for said translational modes, or said moment of inertia m for said rotational modes (which typically do not depend on the value of said operating parameters).

[0065] Preferably said status of said tyre comprises a status of structural integrity of said tyre.

[0066] Preferably said method comprises determining a status of loss of structural integrity of said tyre on condition that said current frequency is lower than said reference frequency.

[0067] Preferably said status of said tyre comprises a status of wear of said tyre.

[0068] Preferably said method comprises determining a status of wear of said tyre on condition that said current frequency is greater than said reference frequency.

[0069] The Applicant has in fact found that, at least for said first six vibration modes of said tyre in which said belt layers are not subjected to deformation, the square of said modal frequency (f) is directly proportional to said modal stiffness (k) and inversely proportional to said modal mass (m), with said three quantities linked by the mathematical relation f = Since said modal stiffness is substantially determined by said stiffness of said tyre carcass whereas said modal mass is substantially determined by the mass of said elastomeric compounds, said quantities remain substantially constant or at most decrease during the operational life of said tyre (under equal operating parameters of said tyre): for example, it is typically not possible for a significant increase of said stiffness of said carcass or an increase of said mass of said elastomeric compounds during the use of said tyre. Therefore, in case of wear of said tyre in which, for example, a reduction of the mass of said tread is observed, a decrease of said modal mass of said tyre with respect to said reference modal mass (that of said tyre new and not worn) will be observed, with a consequent increase of said modal frequency. Conversely, in case of loss of structural integrity in which said stiffness of said carcass decreases, a reduction of said modal stiffness with respect to said reference modal stiffness (that of said tyre in said reference status) will be observed, with a consequent decrease of said modal frequency.

[0070] In one embodiment, monitoring said status of said tyre is performed in discrete mode or substantially continuously over time, more preferably during said second operational phase. For example, said monitoring of said status of said tyre may be performed every determined mileage with arbitrarily variable spacing (e.g. greater than or equal to 300 km and / or less than or equal to 800 km) or very close spacing (e.g. less than or equal to 100 km). In this way it is possible to balance reliable monitoring and computational burden.

[0071] Preferably said method comprises filtering said signal to eliminate or reduce from said signal each part of said signal temporally corresponding (at least) to a respective passage of said crown portion inside a footprint area of said tyre. In this way the accuracy and / or the reliability of said elaborated signal is improved, for example reducing the risk of false positives in the comparison between said value of said parameter and said threshold value. Without wishing to be bound to any theory, the Applicant has in fact found that when said crown portion transits in said footprint area of said tyre due to the rolling of said tyre, said passage generally introduces sudden variations in said signal representative of said motion which may result in alterations of said signal and therefore of said parameter representative of said average power of signal. In this way moreover, especially in case of monitoring said status as a function of said comparison between frequencies, it is possible to filter the part of said signal of motion in which said crown portion is substantially constrained to said rolling surface, and thus little or not at all correlated to corresponding changes in said status of said tyre, allowing improving the quality of said signal.

[0072] In one embodiment filtering said signal is performed in the time domain. In this way it is performable in a simple manner.

[0073] Preferably said dividing said signal into said set of signal portions is performed in the time domain.

[0074] Preferably said signal temporally corresponds to at least 100 complete turns of said crown portion, more preferably at least 200 complete turns, and / or not more than 1000 complete turns, more preferably not more than 700 complete turns. The Applicant has experimentally found that said value intervals represent a good compromise between high reliability and precision of said spectral analysis (depending on the temporal length of said acquired signal) and relative requirement of memory capacity, processing capability, acquisition time, and / or energy consumption.

[0075] Preferably each signal portion is obtained by dividing said signal into time intervals of predefined maximum duration. In this way said division is simple.

[0076] Preferably each signal portion has a temporal duration equal to, or comprised within, said predefined maximum duration.

[0077] Preferably said predefined maximum duration and / or each signal portion corresponds to at least one complete turn of said crown portion, more preferably at least two, and / or not more than five complete turns, more preferably not more than four.

[0078] In one embodiment, each signal portion and / or said predefined maximum duration corresponds to an acquisition time interval greater than or equal to 50 seconds, more preferably greater than or equal to 100 seconds, and / or less than or equal to 250 seconds, more preferably less than or equal to 200 seconds (e.g. without constraints on the number of complete turns of said crown portion corresponding thereto).

[0079] Said temporal intervals of duration of each signal portion have proven particularly suitable for balancing effectiveness of discretization of said signal and computational effort and / or acquisition time and / or energy consumption.

[0080] In one embodiment each signal portion corresponds to (only) said fraction of complete turn of said crown portion. For example, each signal portion corresponds to half a complete turn. In this way the precision is improved.

[0081] Preferably said dividing said signal is performed also as a function of one or more values or ranges of values of one or more operating parameters of said tyre. In this way the precision and / or reliability of said method is further improved. In fact, the Applicant has found that said signal representative of said motion of said crown portion may vary significantly as said operating parameters of said tyre vary, such as for example pressure, temperature, etc., for example undergoing overall shifts towards higher or lower average values. In such circumstance, for example, a single threshold value for comparing each signal portion would lead to errors in the identification of said signal portions corresponding to said high-energy events (for example because said portion would result having high average power not due to a high-energy event but because it corresponds to operating parameters of said tyre different and such as to cause an overall higher signal). Therefore, the Applicant has found particularly advantageous to compare separately signal data corresponding to substantially same values or ranges of said operating parameters, grouping ("clustering”) said data into respective sets ("clusters”) also as a function of said operating parameters and for example calculating a respective threshold value for each set of signal data for said comparison.

[0082] In one embodiment, for example, said method comprises first dividing said signal as a function of said one or more values or ranges of values of said one or more operating parameters to obtain a set of macro-portions of signal corresponding to (at least) a same value or range of values of said one or more operating parameters. Preferably said method subsequently comprises performing said dividing said signal, more preferably said set of macroportions of signal, into said set of signal portions.

[0083] In an (alternative) embodiment, said method comprises first dividing said signal into said set of signal portions. Preferably said method subsequently comprises performing said dividing said signal as a function of said one or more values or ranges of values of said one or more operating parameters, grouping (e.g. classifying / allocating) said signal portions into one or more subsets of signal portions, each subset corresponding to (at least) one value or range of values of said one or more parameters.

[0084] Preferably said one or more operating parameters are selected from the group: pressure, travel speed, temperature, and vertical load. Said parameters have proven to be the most relevant.

[0085] Preferably said method comprises, during said acquiring said signal, detecting said one or more values or ranges of values of said one or more operating parameters.

[0086] Preferably said method comprises correlating said signal, more preferably each value of said signal, to said values or ranges of values of said one or more operating parameters. In this way each acquired signal datum is characterized according to said operating conditions of said tyre at the moment of acquisition.

[0087] In one embodiment said method comprises calculating a respective threshold value for each of said macro-portions of signal.

[0088] In one embodiment said method comprises calculating a respective threshold value for each segment of signal obtained from the union of said signal portions belonging to a same subset of signal portions.

[0089] Preferably said comparing each respective value of said parameter with said threshold value comprises comparing each respective value of said parameter with said respective threshold value of said macro-portion of signal (or of said signal segment) to which said signal portion corresponds. In this way the precision and / or reliability is improved. Preferably said acquiring said signal is performed by means of (at least) one detection device fixed to an inner surface of said tyre in correspondence with said crown portion. Preferably said acquisition system comprises (at least) one detection device fixed to an inner surface of said tyre in correspondence with said crown portion. In this way the precision is increased since said detection device may for example effectively simulate said crown portion. Preferably said signal is an accelerometric signal representative of at least one component of an acceleration, more preferably linear, experienced by said crown portion of said tyre. According to the Applicant, said acceleration signal, in particular linear acceleration, has proven to be the most suitable for the present purposes, for example in terms of reliability and / or precision, since for example it typically results the one most affected by said high-energy events.

[0090] In one embodiment said signal is a velocity signal (or a displacement / deformation signal) representative of at least one component (axial, radial and / or tangential) of a linear velocity (or of a displacement / deformation) of said crown portion of said tyre.

[0091] Preferably said detection device comprises at least one sensor suitable for detecting an accelerometric signal (or a velocity signal or a displacement / deformation signal) representative of at least one component (up to three components) of an acceleration (or of a velocity or of a displacement / deformation), more preferably linear, experienced by said crown portion of said tyre.

[0092] Preferably said at least one component of said acceleration is selected from the group: axial component, radial component, and tangential component.

[0093] Preferably said at least one component of said acceleration is said axial component. In this way said acquired signal is highly advantageous for monitoring said status of said tyre, in particular in combination with said monitoring performed by means of comparison between said frequencies. In fact, the Applicant considers that said frequency spectrum of said axial component contains a substantial contribution of relatively few vibration modes of said tyre, thereby resulting cleaner than said spectra of said other components (i.e. radial and tangential) and allowing a more accurate and reliable determination of said status of said tyre.

[0094] Preferably said acquiring said signal is performed on condition that a travel speed of said vehicle is greater than or equal to 20 km / h, more preferably greater than or equal to 30 km / h, and / or less than or equal to 80 km / h, more preferably less than or equal to 70 km / h. The Applicant has verified that in said interval of travel speed of said vehicle it is possible to obtain good quality of said signal of motion for the purposes of said processing. Preferably said respective value of said parameter is calculated as a function of a normalization of said signal of said signal portion. In this way said respective value of said parameter results robust.

[0095] Preferably said threshold value, more preferably each respective threshold value, is calculated as a function of a parameter representative of a dispersion index, for example a statistical index of dispersion, of said signal, more preferably of said corresponding macro-portion of signal or signal segment. For example, each threshold value may be calculated as a function of a standard deviation or of a median absolute deviation of said signal. In this way said comparison with said parameter representative of said average power is facilitated and / or improved.

[0096] In one embodiment, each respective threshold value is calculated as a function of the respective values of said parameter of each signal portion belonging to said corresponding macro-portion or signal segment.

[0097] Preferably one or more of the, more preferably all the, features described so far with reference to one or more among said signal, said signal portions, said threshold value (and / or said respective threshold values), and said respective value of said parameter, may be referred also respectively to one or more among said further signal, said further signal portions, said further threshold value, and each respective further value of said parameter.

[0098] Brief description of the figures

[0099] Figure 1 schematically shows a vehicle equipped with a monitoring system according to the present invention; Figure 2 schematically shows a detail of Figure 1 ;

[0100] Figure 3 shows a partial section of Figure 2;

[0101] Figure 3b schematically shows a monitoring system according to the present invention;

[0102] Figure 4 shows a logic block diagram of a method according to the present invention;

[0103] Figure 4b shows an example of a signal acquired in the method according to the present invention;

[0104] Figure 5 shows a detail of a logic block of the diagram of Figure 4;

[0105] Figure 6 shows a comparison between frequency spectra of a raw signal and of an elaborated signal in accordance with the method according to the present invention;

[0106] Figure 7 shows a result of a simulation of the method according to the present invention.

[0107] Detailed description of some embodiments of the invention

[0108] The features and the advantages of the present invention will be further clarified by the following detailed description of some embodiments of the present invention, presented by way of example and not limitation, with reference to the attached figures.

[0109] Figure 1 schematically shows a monitoring system 1 of a status of a tyre 3 according to the present invention, installed on board a vehicle 99. Said vehicle 99 may be any vehicle with an internal combustion engine and / or an electric engine, with two or more driving wheels.

[0110] Exemplarily said vehicle 99 comprises four wheels 7 (distributed on two axles), each provided with a respective tyre 3 (also partially shown in Figure 2). In one embodiment (not shown) said vehicle 99 may have three or more axles.

[0111] Said system 1 exemplarily comprises an acquisition system 2 configured to, during an advancement of said vehicle 99 on a road surface (not shown), acquire over time a signal S representative of a motion of a crown portion 31 of said tyre 3.

[0112] More in detail, said acquisition system 2 exemplarily comprises a detection device 4 for each tyre 3 (Figures 1 and 2) by means of which said signal S is acquired, as better described below. For example, said detection device 4 may be of the type described in one of the following documents in the name of the same Applicant: WO 2018 / 065846 A1 , WO 2019 / 123118 A1 , WO 2020 / 026281 A1 , WO 2020 / 026282 A1.

[0113] Exemplarily each detection device 4 is fixed to an inner surface 5 of the respective tyre 3, in correspondence with said crown portion 31 of said respective tyre 3 (Figure 2). In particular, said detection device 4 may be fixed to a liner of said tyre 3, typically by means of gluing (for example by means of a structural adhesive or by means of a pressure-sensitive adhesive - PSA). Preferably said detection device 4 may be fixed substantially in correspondence with an equatorial plane 200 of said tyre 3. Additional detection devices (not shown) may be positioned more laterally on said inner surface of said tyre 3 and / or in different angular positions along the internal circumference of said tyre 3.

[0114] Exemplarily said crown portion 31 coincides with a portion of said tyre 3, typically but not necessarily three- dimensional, positioned in correspondence with said tread band and, substantially, underlying a base surface of said detection device 4 (that is, the surface by means of which said device is fixed to said inner surface 5). Optionally said crown portion 31 may be identified with a portion of said tyre having an extension greater than said base surface of said detection device 4.

[0115] In general, the surface extension of said crown portion 31 may be identified arbitrarily.

[0116] In detail, each detection device 4 exemplarily comprises a sensor 41 (shown only schematically in Figure 3b) suitable for detecting said signal S.

[0117] Exemplarily each detection device 4 further comprises an electronic unit 40 and an electric power supplier 47, for example a button battery, for the electric supply of the electric and electronic components of said electronic unit and / or of said device 4. Said electronic unit comprises for example a printed circuit board ("Printed Circuit Board” or "PCB”) on which said electric and electronic components of said electronic unit are mounted, including said sensor 41 and any further sensors, and on which electrically conductive traces for electric interconnection between said various electric and electronic components of said electronic unit are formed (for example by means of known abrasion or etching techniques).

[0118] Exemplarily said electronic unit 40 may comprise, in addition to said sensor 41 , also one or more further sensors, for detecting one or more operating parameters of said tyre and / or further physical quantities. By way of non-limiting example, said operating parameters and / or said further physical quantities that may be detected may comprise: temperature, tyre deformations, pressure, speed. Examples of sensors suitable for said purposes may be temperature sensors, pressure sensors, strain gauges, accelerometers, optical sensors, magneto-resistive sensors, inertial sensors, gyroscopes, etc.

[0119] With reference to Figure 3b, by way of example only, said electronic unit 40 may further comprise a processing and transmission system 43 operatively associated with at least said sensor 41 , and typically also with each further sensor, for processing and transmitting one or more data detected by said sensor; for example, said processing and transmission system 43 is configured for the transmission to instrumentation available on board said vehicle 99 on which said tyre is mounted. Said processing and transmission system may for example comprise a microprocessor or integrated circuit (for example of the ASIC - "Application Specific Integrated Circuit” type) for performing a processing and / or analysis of said data coming from said sensor 41 , to make them suitable for the transmission from said detection device 4 to a receiver external to said tyre, and an antenna for transmitting said data and / or receiving further data, for example to and from said onboard instrumentation of said vehicle.

[0120] Exemplarily, moreover, said detection device 4 comprises a container configured to contain said electronic unit and said electric power supplier. More in detail, said container comprises a base 45 and a housing body 42 having a plan-view extension comprised within said plan-view extension of said base. Typically, moreover, said container comprises at least one opening or through hole in communication with an internal volume of said device in which said electronic unit 40 is housed, to allow the detection of pressure by at least one sensor of said electronic unit 40.

[0121] Exemplarily said system 1 further comprises a processing unit 8 (shown only schematically in Figures 1 and 3b by means of a dashed box) in communication with said acquisition system 2, and in greater detail with each said detection device 4, for example by means of radio and / or wired signal. More in detail, in the example shown, said processing unit 8 exemplarily comprises a remote unit 81 installed on board said vehicle, and (at least) part (e.g. the microprocessor or integrated circuit) of said processing and transmission system 43 of each of said detection devices 4 (Figure 3b).

[0122] In general, the present invention contemplates any arrangement and / or logical and / or physical distribution of said processing unit, which may for example be a single physical and / or logical unit or be composed of several distinct and cooperating physical and / or logical units (as in the case described and shown here), said units being placeable, in whole or in part, in one or more of the following: said detection device, in particular in one or more of said sensors and / or in said processing and transmission system 43, said tyre (external to said detection device), said rim, on board said vehicle, a remote station in communication with said vehicle.

[0123] Exemplarily (not shown) said processing unit 8 is further connected, exemplarily by means of a communication line (with or without wires), to a display device, for example a screen of the onboard computer of said vehicle, to transmit the result of said monitoring of said status of said tyre.

[0124] In use, said system 1 allows performing a method for monitoring a status TC of a tyre 3 mounted on a wheel 7 of said vehicle 99 according to the present invention.

[0125] An embodiment of the method according to the present invention will be described below with reference to Figures 4 to 7. What follows will be described with reference to a given tyre 3 provided with the respective detection device 4, but may be conceptually extended to each of said tyres 3 of said vehicle 99.

[0126] First, said method exemplarily comprises, during the advancement of said vehicle 99 (which typically causes the rolling of at least one tyre 3), acquiring over time said signal S representative of said motion of said crown portion 31 of said tyre 3 by means of said detection device 4 associated with said tyre.

[0127] Exemplarily said signal S is an accelerometric signal representative of at least one component of a linear acceleration, selected from the group axial component, radial component, and tangential component, experienced by said crown portion 31 of said tyre 3.

[0128] In detail, said at least one component of said acceleration is exemplarily said (only) axial component.

[0129] Exemplarily said signal S comprises a plurality of acquired values of axial acceleration of said crown portion of said tyre. For example, said signal S is a digital signal (e.g. a vector). For example, said signal S may be plotted as shown in Figure 4b in a purely arbitrary manner, where on the ordinate axis said component of linear acceleration, specifically said axial component, is conceptually represented, for example expressed in m / s2, and on the abscissa axis said progressive number of sampling values. Alternatively (not shown) said signal S may be plotted as a function of time or of degrees of rotation with respect to said complete rotation (e.g. an angular interval between 0°-360°, or said entire complete rotation).

[0130] In one embodiment (not shown) said signal S is a velocity signal (or a displacement / deformation signal) representative of at least one component (axial, radial and / or tangential) of a linear velocity (or of a displacement / deformation) of said crown portion 31 .

[0131] Exemplarily, not shown, said signal S may be obtained after analog-to-digital conversion of a corresponding analog signal produced by said sensor, optionally suitably processed (e.g. by means of a calibration curve) to obtain a vector of acquired values of acceleration expressed exemplarily in m / s2. Alternatively, said signal S may be expressed in a scale of pure integer numbers.

[0132] Exemplarily acquiring said signal S is performed in an acquisition window corresponding to a plurality of complete turns WT, also non-consecutive, of said crown portion 31 around said rotation axis 100 of said tyre (that is, in a complete rotation of said detection device 4 around said rotation axis 100 of said tyre 3), for example equal to at least two hundred complete turns.

[0133] Exemplarily said processing unit 8 is programmed to receive from said acquisition system 2, and in greater detail from said detection device 4, said signal S.

[0134] Exemplarily said processing unit 8 is further programmed to perform the following operations provided by said method, symbolically shown in Figure 4 and, in greater detail, in Figure 5.

[0135] Exemplarily said method comprises dividing, in the time domain, said signal S into a set of signal portions SP having predefined maximum temporal duration dT, exemplarily equal to 180 seconds.

[0136] Exemplarily each signal portion SP corresponds to at least one fraction of a respective complete turn WT, more in detail to at least three complete turns, of said crown portion 31 around said rotation axis 100 of said tyre 3.

[0137] Exemplarily it is further provided acquiring said signal S in a predetermined interval of linear speeds of said vehicle, for example between 20 and 50 km / h.

[0138] In an alternative embodiment each signal portion SP corresponds only to said fraction of complete turn of said crown portion 31 , for example half a complete turn.

[0139] For example, the number of complete turns performed by said crown portion 31 may be determined starting from said signal S and / or from other signals detectable by said detection device 4 mounted in said tyre 3, such as for example starting from a radial acceleration signal (also acquirable by said sensor 41), as for example known.

[0140] Exemplarily said method comprises filtering said signal S, for example by means of a Hanning, rectangular, Hamming, or Gauss window, to eliminate or reduce from said signal S each part of said signal temporally corresponding to a respective passage of said crown portion 31 inside a footprint area (not shown) of said tyre 3. Figure 4b exemplarily shows said signal S in which said part SM of signal temporally corresponding to said passage in said footprint area is shown, which, in this embodiment, is filtered (e.g. removed) from said signal S.

[0141] Exemplarily filtering said signal S is performed in the time domain. In an alternative embodiment filtering said signal S is performed in the frequency domain.

[0142] Exemplarily filtering said signal may be performed before or after dividing said signal S into said set of signal portions SP.

[0143] Exemplarily dividing said signal S is performed also as a function of one or more values or ranges of values of one or more operating parameters OP of said tyre 3, for example selected from the group: pressure, travel speed, temperature, and vertical load.

[0144] For example, with regard to at least pressure, temperature, and travel speed, said values or said ranges of values of said parameters may be detected by said detection device 4 mounted on said tyre 3. For example, it is provided, during acquiring said signal S, detecting said one or more values or said ranges of values of said one or more operating parameters and correlating said signal, more preferably each value of said signal, to said values or ranges of values of said one or more operating parameters.

[0145] In the embodiment shown, said method exemplarily comprises first dividing said signal S as a function of a value or of a range of values of said one or more operating parameters OP of said tyre to obtain a set of macro-portions of signal MPS each corresponding to a respective value or range of values of at least one operating parameter OP. Exemplarily, Figure 5 shows two arbitrary macro-portions MPS1 and MPS2 of said set of macro-portions of signal MPS. For example, said macro-portion MPS1 corresponds to a first value or range of values of a given operating parameter (e.g. a pressure value equal to about 260 kPa), whereas said macro-portion MPS2 corresponds to a second value or range of values of said given operating parameter (e.g. a pressure value equal to about 250 kPa). In general, said signal may be divided into an arbitrary number of macro-portions, as a function of desired operating parameters and / or respective values or ranges of values characterizing said given tyre at the moment of acquiring said signal S.

[0146] Exemplarily said method subsequently comprises dividing said set of macro-portions of signal MPS into said set of signal portions SP. More in detail, for this purpose, each macro-portion of signal MPS is divided in the time domain into signal portions SP according to the criteria described above.

[0147] Alternatively (not shown) it may be provided first to divide the entire signal S into said set of signal portions SP and subsequently to perform said division of said signal S as a function of said one or more values or said ranges of values of said one or more operating parameters, grouping (e.g. cl assifying / al locating) said signal portions SP into one or more subsets of signal portions, each subset corresponding to (at least) one value or range of values of said one or more operating parameters. For both embodiments, regardless of the approach adopted, the final result exemplarily comprises groupings of signal portions SP as a function of said values or said ranges of values of said one or more operating parameters OP.

[0148] Exemplarily said method comprises, for each signal portion SP of said set, calculating a respective value of a parameter KPI representative of an average power of the signal of said signal portion SP. For example, each respective value of said parameter KPI may be calculated as a function of a normalization of said signal of the corresponding signal portion SP, for example by means of a norm function or a root mean square function ("root mean square” or RMS).

[0149] For example, in the time domain, each respective value of said parameter KPI may be calculated by means of the following formula: norm! a)2

[0150] KPI = - = RMS (a)2where a is the vector corresponding to said signal portion SP in the time domain, N is the size of said vector, and "norm” is said norm function.

[0151] In the frequency domain each respective value of said parameter KPI may for example be calculated by means of the following formula:

[0152] KPI = X[f]X*[f] where "X[f]” is the vector corresponding to said signal portion SP in the frequency domain (obtained through the FFT of said vector "a”) and “X*[f]” is the complex conjugate of the vector corresponding to said signal portion SP in said frequency domain.

[0153] Exemplarily said method comprises comparing each respective value of said parameter KPI with a threshold value TV.

[0154] In detail, said method exemplarily comprises calculating a respective threshold value TV for each macro-portion of signal MPS, and then comparing each respective value of said parameter KPI with said respective threshold value TV of said macro-portion of signal MPS (or of said signal segment, see below) to which said corresponding signal portion SP belongs (Figure 5).

[0155] For this purpose, each respective threshold value TV is exemplarily calculated as a function of a parameter representative of a dispersion index, for example a statistical index of dispersion, of said signal of said corresponding macro-portion, for example as a function of a standard deviation or of a median absolute deviation of said signal. More in detail, each respective threshold value is calculated as a function of said values of said parameter KPI of all said signal portions SP belonging to said respective macro-portion of signal MPS. For example, each respective threshold value TV may be calculated by means of the following formula:

[0156] TV = m(KPI(SP ) + y * s(WP / (SP)) where m(KPI (SP)) is the arithmetic mean of said KPI of all said signal portions SP of a given macro-portion of signal MPS (or signal segment), s(KPI(SP)) is said standard deviation of said KPI of all said signal portions SP of said given macro-portion of signal MPS, and j is a constant multiplicative factor chosen arbitrarily, for example equal to 3.

[0157] Alternatively (not shown) said method may comprise calculating a respective threshold value for each signal segment obtained from the union of said signal portions belonging to a same subset of signal portions, for example in a manner analogous to said macro-portions of signal.

[0158] Exemplarily said method therefore comprises removing from said set each signal portion SP corresponding to a respective value of said parameter KPI resulting greater than said respective threshold value TV of said corresponding macro-portion (or said segment) of signal, to obtain an elaborated signal SE representative of said motion of said crown portion 31 of said tyre 3.

[0159] In detail, for each macro-portion of signal MPS a respective elaborated sub-signal may be obtained by removing, from each said macro-portion of signal MPS, said signal portions SP whose respective value of said parameter KPI has resulted greater than said respective threshold value TV.

[0160] Exemplarily, therefore, all said elaborated sub-signals may be combined with one another to obtain said elaborated signal SE.

[0161] With reference to Figure 5, it shows in detail a routine 500 for obtaining said elaborated signal SE as described above.

[0162] In particular, Figure 5 conceptually shows the obtaining of said values of said parameters KPI and said respective threshold value TV2 calculated for said macro-portion of signal MPS2 and the comparison between said values of said parameters KPI and said threshold value TV2. In the example, two signal portions SP are in particular shown having respective values of said parameter KPI1 , KPI2 lower than said respective threshold value TV2 and therefore selected to obtain said elaborated signal SE (in detail said respective elaborated sub-signal given by the union of all said signal portions SP of said macro-portion MPS2 that are selected), and a third signal portion SP which is instead removed since said respective value of said parameter KPI3 has resulted greater than said respective threshold value TV2.

[0163] Exemplarily said method therefore comprises monitoring said status TC of said tyre 3 as a function of said elaborated signal SE.

[0164] More in detail, said method exemplarily comprises monitoring said status of said tyre as a function of a comparison between a reference frequency, obtained starting from said elaborated signal SE, and a current frequency, obtained starting from a further elaborated signal SFE, obtained in an analogous manner to said elaborated signal SE but starting from a further raw signal SF acquired temporally subsequent to said signal S.

[0165] The Applicant has in fact found that said status of said tyre may be advantageously monitored starting from said comparison between frequencies, as will be described below in greater detail.

[0166] In order to monitor said tyre, acquiring said signal S is exemplarily performed in a first operational phase t1 , for example corresponding to a reference status of said tyre, for example a status of said tyre substantially new.

[0167] Exemplarily it is also provided acquiring said further signal SF likewise representative of said motion of said crown portion 31 , however in a second operational phase t2 temporally subsequent to said first operational phase t1 , and therefore representative of an occurred use of said tyre. For example, said second operational phase may start after a travel distance of about 1000 km after the end of said first operational phase t1 .

[0168] Exemplarily said further signal SF comprises all the features of said signal S and is exemplarily acquired in a manner analogous to said signal S.

[0169] Exemplarily said method therefore comprises obtaining said further elaborated signal SFE starting from said further signal SF in a manner analogous to what has been described above for said elaborated signal SE, that is, filtering said further signal SF by removing respective further signal portions for which said respective further value of said parameter representative of said average power of said signal has resulted greater than a further threshold value, more preferably greater than a respective further threshold value (in a manner analogous to what has been described above for said respective threshold values).

[0170] For example, it is provided to calculate each respective further parameter and each respective further threshold value in a manner analogous to what has been described above, with reference to said further signal.

[0171] In order to determine said reference frequency and said current frequency, said method exemplarily comprises performing the following steps.

[0172] In detail, it is first exemplarily provided to obtain (not shown), by means of frequency analysis, a frequency spectrum of said elaborated signal SE and a further frequency spectrum of said further elaborated signal SFE. For example, said frequency spectrum and said further frequency spectrum are obtained by calculating a respective fast Fourier transform (FFT) or by performing a power spectral density (PSD) operation on said elaborated signal SE and said further elaborated signal SFE, respectively.

[0173] It is therefore provided identifying a determined peak in a plurality of peaks of said frequency spectrum of said elaborated signal SE and a further determined peak in a further plurality of peaks of said further frequency spectrum of said further elaborated signal SFE.

[0174] For example, said identified peak is, for both said spectra, said first-order peak, typically comprised in the 30-80 Hz band. Advantageously said peak corresponds to, or comprises, said first lateral vibration mode of said tyre. Exemplarily said method therefore comprises determining a frequency of said determined peak (that is, the frequency at which said determined peak occurs) and a further frequency of said further determined peak.

[0175] Exemplarily it is then provided determining said reference frequency as a function of said frequency of said determined peak and said current frequency as a function of said further frequency of said further determined peak. Preferably said reference frequency coincides with said frequency of said determined peak and said current frequency coincides with said further frequency of said further determined peak.

[0176] Exemplarily said status of said tyre may be monitored as a function of said comparison between said frequencies or between two values of a same physical quantity, said two values being correlated respectively to said current frequency and to said reference frequency.

[0177] For example, said same physical quantity is a modal mass or a modal moment of inertia or a modal stiffness of said tyre. In one example, said modal mass or said modal moment of inertia or said modal stiffness are correlated to said respective frequency (reference or current) by means of the following mathematical formula: k = f2■ m where k is said stiffness, f is said respective frequency, and m is said mass or said moment of inertia.

[0178] Exemplarily said status of said tyre comprises a structural integrity status of said tyre and / or a wear status of said tyre, and said method comprises determining said structural integrity loss status of said tyre on condition that said current frequency is lower than said reference frequency and / or determining said wear status of said tyre on condition that said current frequency is greater than said reference frequency.

[0179] The Applicant has in fact found that, at least for the first six vibration modes of said tyre in which said belt layers are not subject to deformation, the square of said modal frequency (f) is directly proportional to said modal stiffness (k) and inversely proportional to said modal mass (m). Since said modal stiffness is substantially determined by said stiffness of said carcass whereas said modal mass is substantially determined by said mass of said elastomeric compounds, said quantities remain substantially constant or at most decrease during the operational life of said tyre. Therefore, in case of said wear of said tyre in which, for example, a reduction of said tread mass occurs, a decrease of said modal mass of said tyre with respect to said reference modal mass (that of said new non-worn tyre) will be observed, with a consequent increase of said modal frequency. Conversely, in case of said structural integrity loss in which said stiffness of said carcass decreases, a reduction of said modal stiffness with respect to said reference modal stiffness (that of said tyre in said reference status) will be observed, with a consequent decrease of said modal frequency.

[0180] It follows that it is of fundamental importance to be able to determine with high precision and reliability said reference frequency and said current frequency. However, as also described above, in case of real rolling conditions of said tyre, spurious vibrational components are introduced into said typical vibration modes of said tyre. Without wishing to be bound by any theory, the Applicant has observed that this results in the presence, in said frequency spectra of said signals SE and SFE, of spurious frequency peaks which, in general, may add to said typical frequency peaks of said vibration modes of said tyre, with a consequent deterioration in the precision of detection of said respective peak frequencies.

[0181] The contribution of said spurious frequency peaks may be qualitatively appreciated with reference to Figure 6. It indeed shows, in a purely arbitrary manner, a comparison between a frequency spectrum FS1 (dashed line) of a signal representative of a motion of a crown portion of tyre processed by removal of said signal portions temporally corresponding to said high-energy events as described above, such as, for example, said elaborated signal SE or said further elaborated signal SFE, and a frequency spectrum FS2 (continuous line) of a signal representative of said same motion of said crown portion, however not filtered from said high-energy events.

[0182] In particular, with reference to said peak PK shown (which may conceptually represent said determined peak and / or said further determined peak), it is possible to appreciate how said filtering of said signal by removal of said high- energy signal portions removes said effects of said high-energy events and therefore said contribution of said spurious frequency peaks. It follows a modification in said shape of said peak, exemplarily in terms of lower height, but above all of lower peak frequency.

[0183] Said filtering of said signal by removal of said high-energy events therefore makes it possible to obtain a more precise and / or reliable and / or robust identification of said frequency of said determined peak and of said further determined peak, and consequently of said reference frequency and of said current frequency.

[0184] In one embodiment, monitoring said status of said tyre may be performed with one of said monitoring methods described in said above-mentioned prior documents in the name of the same Applicant: WO2022144703A1, WO2022144939A1, WO2022144940A1, in which said signals from which said frequency spectra are obtained correspond respectively to said elaborated signal and to said further elaborated signal. In other words, said filtering of said acquired signal to obtain said elaborated signal SE as described in the present solution may also be configured as a pre-processing phase of said acquired signals in order to perform one of said monitoring methods described in said above-mentioned documents.

[0185] The advantage, for example in terms of greater precision and / or reliability, of monitoring said status of said tyre as a function of a signal filtered to remove said signal portions corresponding to said high-energy events as taught by the present solution, with respect to a monitoring based on a signal not subjected to said filtering, may be qualitatively appreciated with reference to the example shown in Figure 7.

[0186] Figure 7 indeed graphically compares a direct measurement (curve R4) of said variable of said status of said tyre "average tread depth” ATD, expressed for example in mm, as a function of said tyre mileage TM ("tire mileage”), that is, said total distance travelled by said tyre, expressed for example in km, with respectively a first estimate R5 of said variable of said status, obtained with a monitoring method based on a signal not filtered from said high- energy events, and a second estimate R6 of said same aforesaid variable of said status, obtained instead with said monitoring method according to the present invention, and therefore based on said filtered signal.

[0187] In the example shown, said monitoring methods used to obtain respectively said first and said second estimate of said average tread depth are analogous to one another, for example both based on said comparison between said current frequency and said reference frequency as described in the present invention and / or as described in one or more of said above-mentioned prior documents WO2022144703A1, WO2022144939A1 , WO2022144940A1 , except for said respective signals that are used to obtain said frequency spectra (for the purpose described above) which, for said estimate R6, coincide with signals processed by filtering said signal portions, whereas for said estimate R5 they are signals from which said contributions of said high-energy events have not been removed. For example, said determined peak and each said further determined peak correspond for each of said estimates R5 and R6 to said first-order peak of said frequency spectrum of said accelerometric signal of said axial component of said acceleration, and therefore corresponding to (or comprising) said peak of said lateral translational vibration mode of said tyre.

[0188] Each sampling point of said estimates R5 and R6 (with the exception of said first sampling point which corresponds to said direct measurement and therefore may represent said reference) corresponds to a respective further signal SF acquired each time in a respective second operational phase temporally subsequent to the previous one (for example after a fixed interval of kilometres travelled), from which a respective current frequency is for example obtained which is compared with said reference frequency.

[0189] Specifically, with regard to said estimate R6, said signal and each said respective further signal is acquired in a vehicle-speed window comprised between 22.5 km / h and 47.5 km / h.

[0190] Furthermore, still for said monitoring method of said estimate R6, said division of said signal and of each said respective further signal is performed into respective signal portions having maximum temporal duration equal to 180 seconds, and furthermore said signal and each said further signal is also divided as a function of pressurevalue intervals of amplitude 10 kPa centred on a respective reference value.

[0191] Whereas, with reference to said curve R4, it may be observed, as expected, that said average tread depth ATD decreases as said tyre mileage TM increases due to wear, it is likewise evident that said estimate R6 globally approximates said measurement results better than said estimate R5. Conversely, it may be observed that said estimate R5 provides on average lower results of said average tread depth than said estimate R6, that is, it tends on average to overestimate said tread wear. Without wishing to be bound by any theory, the Applicant believes that said overestimation is due to the presence of said effects of said high-energy events which with high probability have led to a modification of said frequency spectrum (of said signal and / or of one or more of said respective further signals), and to a less precise identification of said frequency of said peak of said selected typical vibration mode of said tyre.

[0192] It is therefore observed that said removal of said high-energy events according to the present invention ultimately allows a more precise and / or reliable monitoring of said status of said tyre with respect to said same estimation phases carried out on signals not filtered from said high-energy events.

Claims

1. CLAIMS1 . Method for monitoring a status of a tyre (3) mounted on a wheel (7) of a vehicle (99), the method comprising:- during an advancement of said vehicle (99), acquiring over time a signal (S) representative of a motion of a crown portion (31) of said tyre (3);- dividing said signal (S) into a set of signal portions (SP), each signal portion (SP) corresponding to at least one respective fraction of a complete turn (WT) of said crown portion (31) around a rotation axis (100) of said tyre (3);- for each signal portion (SP) of said set, calculating a respective value of a parameter (KPI) representative of an average power of the signal of said signal portion (SP);- comparing each respective value of said parameter (KPI) with a threshold value (TV);- removing from said set each signal portion (SP) corresponding to a respective value of said parameter (KPI) greater than said threshold value (TV), to obtain an elaborated signal (SE) representative of said motion of said crown portion (31) of said tyre (3);- monitoring a status of said tyre (3) as a function of said elaborated signal (SE).

2. Method according to claim 1, comprising filtering said signal (S) to eliminate or reduce from said signal (S) each part (SM) of the signal (S) temporally corresponding to a respective passage of said crown portion (31) inside a footprint area of said tyre (3).

3. Method according to any one of the precious claims, wherein each signal portion (SP) is generated by a number of said respective complete turns (WT) greater than or equal to two and less than or equal to four and / or corresponds to an acquisition time interval greater than or equal to 100 seconds and less than or equal to 200 seconds.

4. Method according to any one of the previous claims, wherein said dividing of said signal (S) is also performed as a function of one or more values or ranges of values of one or more operating parameters (OP) of said tyre (3), wherein said one or more operating parameters (OP) are selected from the group: pressure, travel speed, temperature, and vertical load.

5. Method according to any one of the previous claims, wherein said monitoring of said status of said tyre (3) comprises obtaining a frequency spectrum of said elaborated signal (SE) and monitoring said status of said tyre (3) as a function of said frequency spectrum of said elaborated signal (SE).

6. Method according to claim 5, wherein said acquiring said signal (S) is performed in a first operational phase (t1), wherein said method comprises acquiring (10) a further signal (SF) representative of the motion of said crown portion (31) in a second operational phase (t2) temporally subsequent to said first operational phase (t1) and performing the steps of the method according to any one of the previous claims to obtain a further elaborated signal (SFE) from said further signal (SF), wherein said monitoring said status of said tyre (3) comprises obtaining a further frequency spectrum of said further elaborated signal (SFE), and wherein said monitoring said status of said tyre (3) is performed as a function of said frequency spectrum and said further frequency spectrum.

7. Method according to any one of the previous claims, wherein said acquiring said signal (S) is performed by means of a detection device (70) fixed to an inner surface (5) of said tyre (3) in correspondence with said crownportion (31), wherein said signal (S) is an accelerometric signal representative of at least one component of a linear acceleration experienced by said crown portion (31) of said tyre (3), and wherein said at least one component of the acceleration is selected from the group: axial component, radial component, and tangential component.

8. Method according to any one of the previous claims, wherein said threshold value (TV) is calculated as a function of a parameter representative of a dispersion index of said signal (S).

9. System for monitoring a status of a tyre (3) mounted on a wheel (7) of a vehicle (99), the system comprising:- an acquisition system (2) configured to, during an advancement of said vehicle (99), acquiring over time a signal (S) representative of a motion of a crown portion (31) of said tyre (3);- a processing unit (8) in communication with said acquisition system (2), wherein said processing unit is configured to:- receive from said acquisition system (2) said signal (S);- divide said signal (S) into a set of signal portions (SP), each signal portion (SP) corresponding to at least one respective fraction of a complete turn (WT) of said crown portion (31) around a rotation axis (100) of said tyre (3);- for each signal portion (SP) of said set, calculate a respective value of a parameter (KPI) representative of an average power of the signal of said signal portion (SP);- compare each respective value of said parameter (KPI) with a threshold value (TV);- remove from said set each signal portion (SP) corresponding to a respective value of said parameter (KPI) greater than said threshold value (TV), to obtain an elaborated signal (SE) representative of said motion of said crown portion (31) of said tyre (3);- monitor a status of said tyre (3) as a function of said elaborated signal (SE).

10. System (1) according to claim 9, wherein said acquisition system (2) comprises at least one detection device (4) fixed to an inner surface (5) of said tyre (3) at said crown portion (31), wherein said detection device (4) comprises at least one sensor configured to detect an accelerometric signal representative of at least one component of a linear acceleration experienced by said crown portion (31) of said tyre (3), wherein said at least one component of the acceleration is selected from the group: axial component, radial component, and tangential component, and wherein said processing unit (8) is further programmed to perform said method according to any one of claims 2 to 8.

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