Device for measuring, by means of an electromagnetic jet, the thickness of the remaining rubber of a tyre identified during retreading

Abstract

The invention relates to a system that implements a process for inspecting a tyre identified during retreading, characterized in that the system comprises a thickness measuring device (100) comprising an electromagnetic jet (106) having a horn antenna (106a), said antenna being extended by a cylinder comprising a cylindrical tip (106b). The invention also relates to a process for inspecting a tyre identified during retreading, the inspection process being implemented by the disclosed system. The invention further relates to a retreading method comprising the inspection process performed by the disclosed system.

Description

[0001] Description

[0002] Device for measuring the thickness of the remaining rubber of an identified tire during retreading using an electromagnetic jet.

[0003] Technical Field

[0004] The invention relates to a device for measuring the thickness by electromagnetic jet of the remaining rubber of an identified tire during retreading.

[0005] Context

[0006] In industrial sectors (such as tire retreading), the measurement and characterization of materials are routinely performed in manufacturing and quality control workshops. In the context of their use, it is often necessary to find new technological approaches to accurately measure spatial distances and to determine the layer thickness of a section of a tire intended for retreading.

[0007] Several technologies have already been tested or developed to determine the thickness of a material (either material to be removed or material intended for inclusion in a product during manufacturing). For example, there are magnetic sensors that use eddy currents, but these do not provide a precise distance measurement because the thickness is averaged over the entire surface of the sensor (the deeper the penetration into the material, the larger the sensor must be). For a system using this type of technology, the spatial resolution is low (due to the sensor size), and therefore the system cannot handle objects with significant curvature.

[0008] Ultrasonic measurements also exist, which require a coupling to perform the measurement. Data interpretation is often difficult, and accuracy can be low.

[0009] In addition, there is thermography which requires direct heating (e.g., by an infrared lamp) or indirect heating (e.g., by induction) of the product being measured, which implies a significant consumption of energy.

[0010] There are also traditional wave sensors whose thickness measurement is performed using terahertz waves (for example, as disclosed in the Applicant's patent FR3117210). Other technologies based on optical technologies have been systematically ruled out since they have little or no penetration into opaque materials.

[0011] Among the measurement methods commonly used to characterize material properties are waveguide and free-space techniques in the microwave range. While these methods are reliable and efficient, they have drawbacks: waveguide measurements are destructive, and free-space measurements require a large, often flat, sample. Furthermore, the long-established "traditional" systems that implement these methods have characteristics directly dependent on the wavelength used, including:

[0012] A spatial resolving power dependent on the diffraction limit defined by the Rayleigh criterion, i.e. approximately A / 2.

[0013] The ability to discriminate and characterize materials (e.g., thickness) depends on the frequency band used. The wider the frequency band, the more precise the characterization.

[0014] Limited penetration into materials, induced by the dispersion of emission power on the wavefront.

[0015] To overcome these limitations, the electromagnetic jet concept was introduced as a method for local free-space characterization (see Ghaddar, Ali et al. “Electromagnetic Jet Towards Characterization Applications,” 17th Microwave and Materials Characterization Days, https: / / hal.science / hal-04059278 (April 2023) (“Ghaddar reference”)). The electromagnetic jet is derived from the photonic jet concept where a dielectric sphere, illuminated by a near-field wave, can focus the wave into a beam whose width is narrower than the diffraction limit (see Ghaddar reference) (citing Chen, Zhigang and Taflove, Allen, “Photonic nanojet enhancement of backscattering of light by nanoparticles: a potential novel visible-light ultramicroscopy technique,” ​​Opt.

[0016] Express, vol. 12, no. 7, p. 1214, doi: 10.1364 / OPEX.12.001214 (2004) ("the Chen reference"). Ghaddar observes that "this beam exhibits high intensity and propagates over several wavelengths in the form of a quasi-plane wave," and thus the photonic jet has been widely studied and applied in industry and laboratory tools.

[0017] Referring to Figure 1 (which corresponds to Figure 1 of the Ghaddar reference), an electromagnetic beam 10 is designed to study the electromagnetic response of a simple material consisting of a substrate with a ground plane on its back face. The electromagnetic response of multilayer systems with different refractive indices can be treated analytically using Maxwell's equations (Maxwell's equations are known to describe the propagation of electromagnetic waves in any type of medium). As an example, the electromagnetic beam 10 includes a horn antenna (or "antenna") 10a made of polytetrafluoroethylene (or "PTFE"). The horn antenna 10a extends along a predetermined height H, which is defined between a predetermined minimum diameter d and a predetermined maximum diameter D. The horn antenna 10a is extended by a cylinder, which is also made of PTFE.This cylinder includes a cylindrical tip 10b with a predetermined height h and a predetermined radius R at the antenna outlet. The cylindrical tip 10b forms a transitional section at the antenna inlet, minimizing reflections due to the change in medium (air / PTFE).

[0018] An electromagnetic wave encounters two different media at the exit of the horn antenna 10a: the cylindrical tip 10b of PTFE in the center, surrounded by air at the ends. The portion of the wave traveling through the air has a faster propagation speed than the portion of the wave propagating through the PTFE. The wavefront at the exit of the horn antenna has a concave shape, and the wave takes on a convex shape at the tip after passing through it (this deformation is explained by the difference in propagation speed between the air and the PTFE). Then, the refraction of the wave towards the air amplifies the convexity of the wave, resulting in a more intense spot at the end of the tip, 5 mm from the tip. Thus, the difference in propagation speed between the air and the PTFE is the cause of the focusing phenomenon of the electromagnetic jet 10.The focused wave exhibits a significant field concentration and appears to be less distorted, to the point that it can be considered approximately planar.

[0019] It is understood that the cylindrical tip 10b of the electromagnetic beam 10 is not limited to the geometry shown in Figure 1. For example, the cylindrical tip 10b could be replaced by two or more concentric cylinders, by an elongated rectangular tip, or by another geometry that functions as an equivalent to the cylindrical tip 10a. Thus, it is appreciated that there is good agreement between the response of a material detected by an electromagnetic beam like the one shown in Figure 1 and a theoretical response of that material when illuminated by a plane wave. By using this type of beam focused near or below the diffraction limit, the electromagnetic beam makes it possible to offer new measurement systems in industry, including in the microwave and terahertz ranges.This method, which performs localized measurements in free space without damage, has favorable characteristics, including, but not limited to:

[0020] Stronger penetration into carbonaceous materials compared to conventional methods;

[0021] Increased spatial accuracy (A / 10 minimum instead of X / 2 by conventional systems);

[0022] A very localized and homogeneous focus;

[0023] Excellent detection and discrimination of materials; and the ability to characterize metallic oxidation.

[0024] In the field of tire manufacturing and maintenance, retreading is a process used to restore a worn tire to working order by renewing the tread compound and the ply(ies). During the retreading process, the old tread material is removed and replaced with new material. Referring to Figure 2, when retreading a tire identified as P, the worn casing is "carded" (see the "Carded Area" in Figure 2). This means that the maximum thickness of the remaining tread (see the "Uncarded Worn Area" in Figure 2) is removed, leaving the minimum amount of rubber above the first ply N (which is a metallic and / or textile and / or other material known in the tire industry).

[0025] The electromagnetic jet concept has recently seen increasing progress due to its applications in detection and imaging, ranging from the optical domain to microwave frequencies. Thus, the disclosed invention employs an innovative electromagnetic jet sensor that enables near-field detection and / or measurement, allowing for the measurement of remaining tread thickness while maintaining good spatial accuracy during the retreading of an identified tire.

[0026] Summary of the invention

[0027] The invention relates to a system that implements an inspection process for an identified tire during retreading, characterized in that the system comprises: a thickness measurement device including an electromagnetic jet device incorporating a horn antenna that extends along a predetermined height defined between a predetermined minimum diameter and a predetermined maximum diameter, the horn antenna being extended by a cylinder including a cylindrical tip having a predetermined height and a predetermined radius at the exit of the antenna; a means of generating signals in a predetermined frequency band, the emitted frequency band of which is chosen according to the properties of the identified tire;and a communication network that manages the data entering the system from the measuring device, the communication network incorporating one or more communication servers, each comprising one or more processors operationally connected to a memory configured to store an application for analyzing data representative of the tires identified to be inspected, the processor(s) comprising an analysis application execution module configured to perform data processing, the processor(s) of which are configured to execute programmed instructions stored in the memory which, when executed by the processor(s), lead them to implement the following steps of the inspection process:;

[0028] - a first step in which the system measurement device uses at least one method among: a spectroscopy method in the frequency domain - cavity resonance or a spectroscopy method in the time domain - resonance of the followed by a step of calculating a fast Fourier transform;

[0029] - a second stage in which the reference spectrum is divided by a reference spectrum;

[0030] - a third step performing an Inverse Fourier Transform before specific signal processing to denoise data from the Inverse Fourier Transform, so that the specific signal processing is carried out in the time domain;

[0031] - a fourth signal processing step including a thickness calculation according to the following expression: cAt 6 i ~ 2n tWhere: e; represents the thickness of a layer i; c represents the speed of light; - At represents the propagation delay between two diopters representing an input interface and an output interface of layer i; and ni represents the real part of the refractive index of the material of layer i; and a final step involving a calculation of a fast Fourier transform made on the signal obtained after the specific signal processing of the third step, so that, at the end of the inspection process, the processed frequency transfer function is obtained.

[0032] In one embodiment of the system of the invention, the electromagnetic jet of the measuring device is made of polytetrafluoroethylene.

[0033] In one embodiment of the system of the invention, the measuring device comprises a robot having a measuring peripheral supported by a pivoting elongated arm, the measuring peripheral extending from the elongated arm to a free end which allows the installation of the electromagnetic jet device; so that the attachment of the electromagnetic jet device is made in such a way as to allow its rotation relative to the free end and also to allow its spinning around a predefined axis of rotation during the inspection process.

[0034] In one embodiment of the system of the invention, the means for generating signals from the measuring device includes a synthesizer disposed at the free end of the measuring device.

[0035] In one embodiment of the system of the invention, the frequency band emitted by the means for generating signals is between 20 and 40 GHz inclusive.

[0036] In one embodiment of the system of the invention, the electromagnetic jet has a variable resolution depending on the contrast of the materials from X / 10 to A / 100.

[0037] In one embodiment of the system of the invention, the system further comprises a vector network analyzer (VNA).

[0038] The invention also relates to a process for inspecting an identified tire during retreading, the inspection process being implemented by a system as previously disclosed, characterized in that the inspection process comprises the following steps; a first step of implementing a spectroscopy method in the frequency domain - cavity resonance or a spectroscopy method in the time domain - cavity resonance followed by a step of calculating a fast Fourier transform; a second step in which the spectrum determined in the first step is divided by a reference spectrum; a third step of implementing an Inverse Fourier Transform before specific signal processing to denoise data from the Inverse Fourier Transform, so that the specific signal processing is carried out in the time domain;a fourth signal processing step comprising a thickness calculation according to the following expression:;

[0039] Where: e; represents the thickness of a layer i; c represents the speed of light;

[0040] At represents the propagation delay between two diopters representing an input interface and an output interface of layer i; and n'i represents the real part of the refractive index of the material of layer i; and a final step comprising a calculation step of a Fast Fourier Transform (FFT) made on the signal obtained after the processing of the specific signal of the third; so that, at the end of the inspection process, the processed frequency transfer function is obtained.

[0041] In one embodiment of the inspection process of the invention, the fourth step of the inspection process comprises: a step to obtain the refractive index of a portion of the identified tire, where the refractive index is represented by the following expression: n = n' + in" where: n' represents the real part of the complex refractive index related to the propagation velocity of Fonde; and n" represents the imaginary part of the complex refractive index related to the absorption of Fonde; and a step to determine the behavior of Fonde through the materials it passes through, in which the angle of refracted Fonde is governed by the following expression: n x sin 61 = n2sin 03; where: ni represents the refractive index of a first substrate; and n2 represents the refractive index of a second substrate.

[0042] - 0i is an angle of incidence of the incident wave, 62 is an angle of reflection of the reflected wave and 03 is an angle of refraction of the refracted wave.

[0043] In one embodiment of the inspection process of the invention, the fourth step of the inspection process further includes a step to determine the refractive index of the identified tire parts for a given frequency band according to the following expression:

[0044] Where: ei represents the thickness of layer i; c represents the speed of light;

[0045] Af represents the frequency difference between two successive resonances; and m represents the real part of the refractive index of the material in layer i.

[0046] In one embodiment of the inspection process of the invention, each resonance of the two successive resonances is an exact resonance.

[0047] When the wavelength of the wave penetrating layer i is a submultiple of the thickness ei of layer i, the wave enters into exact resonance with layer i or substrate.

[0048] In one embodiment of the inspection process of the invention, during the fourth stage of the inspection process, each interface in the time domain generates Gaussians which are discriminated in the form of the center of the Gaussians.

[0049] The invention further relates to a retreading process comprising the disclosed inspection process.

[0050] In one embodiment of the retreading process of the invention, the retreading process further comprises at least one of the following steps: a step of positioning an identified tire in a processing space where the inspection device processes it; and a step of carrying out a repair process of the identified tire using at least one suitable processing tool.

[0051] Other aspects of the invention will become evident from the following detailed description.

[0052] Brief description of the drawings

[0053] The nature and various advantages of the invention will become more evident upon reading the following detailed description, together with the accompanying drawings, on which the same reference numbers designate identical parts throughout, and in which:

[0054] [Fig 1] Figure 1 represents an embodiment of an electromagnetic jet used by the invention.

[0055] [Fig 2] Figure 2 represents a schematic view of a tire during retreading having carded and non-carded areas.

[0056] [Fig 3] Figure 3 represents a schematic view demonstrating a link between A / and A / .

[0057] [Fig 4] Figure 4 represents a schematic view of an electromagnetic wave and the relationship between its frequency and the round-trip propagation time.

[0058] [Fig 5] Figure 5 represents an embodiment of a measuring device of the invention which implements an inspection process of the tire(s) identified during retreading.

[0059] [Fig 6A], [Fig 6B], [Fig 6C] Figures 6A, 6B, 6C represent a comparison of the spatial resolution obtained during detection according to different examples of a horn antenna.

[0060] [Fig 7] Figure 7 represents a schematic view of a simulation in which the plane background is very localized and focused at the output of a perturbator.

[0061] [Fig 8] Figure 8 represents a flow diagram of an inspection process implemented by the measuring device of the invention during a retreading process

[0062] [Fig 9] [Fig 10] Figure 9 and Figure 10 represent diopters representing interfaces between two layers of a substrate.

[0063] [Fig H] Figure 11 represents resonance points that correspond to different frequencies or wavelengths in a substrate.

[0064] [Fig 12] Figure 12 represents a ratio between the refractive indices of the substrates.

[0065] [Fig 13] Figure 13 shows a schematic cross-sectional view of one embodiment of a known tire. [Fig 14] Figure 14 shows a uniform focal width of an electromagnetic beam used by the measuring device of Figure 5 with respect to an identified tire.

[0066] Detailed description

[0067] To understand the measurement system of the invention and the use of the electromagnetic beam, it is helpful to begin with the underlying theoretical study. It is understood that electromagnetic phenomena are represented using the electric field (E) and the magnetic field (H), which are two vector physical quantities. The intrinsic properties of a medium are represented by electrical permittivity (e), electrical conductivity (cr), magnetic permeability (p), and magnetic losses (p”). Electrical conductivity and magnetic loss characterize the capacity of a medium to absorb the electrical and magnetic energy of a wave propagating through it (see Gazave, Julien, “Contribution to the implementation of numerical simulation methods for studying the vulnerability of electrical systems subjected to the radiative and electromagnetic environment of the Laser Mégajoule,” Thesis No. 70-2007, University of Limoges (2007)).

[0068] In the frequency domain, the inventors observed that the reflection coefficient exhibits an alternation of constructive and destructive resonances. Considering that the frequency difference A / between two successive resonances corresponds to the time Ai for the wave to propagate back and forth in a substrate (i.e., a "medium"), Figure 3 represents a diagram to demonstrate this relationship between A / - etAi. Figure 3 illustrates the penetration of an electromagnetic wave (or "EM wave") onto the upper surface of a substrate at time i, the arrival of the EM wave at the lower surface at time i + Ai / 2, and the return of the EM wave to the upper surface at time i + Ai. The interference observed in the reflection spectrum corresponds to the result of the superposition of the incident wave and the wave that returned to the upper surface after being reflected from the lower surface. Based on this, the thickness of a sample can be determined from the reflection coefficient in the frequency domain. Figure 4 represents the schematic of an EM wave and the relationship between its frequency and the round-trip propagation time. The Fourier transform allows the signal to be converted from the time domain to the frequency domain (or vice versa): where the signal F(m) is the reflection coefficient of the EM wave measured in frequency sweep (c represents the frequency angular frequency of the EM wave).

[0069] To study this basic conversion from frequency domain to time domain, the inventors consider a signal representing the reflection coefficient of a substrate, calculated analytically from Maxwell's equations.

[0070] Referring again to the figures, in which the same numbers identify identical elements, Figure 5 illustrates an embodiment of a measuring device (or "device") 100 of the invention. The measuring device 100 can be part of a retreading system 300 (or "system") in which an inspection process is performed during the retreading of one or more tires. The measuring device 100 of the invention implements such an inspection process, enabling the measurement, by electromagnetic jet, of the thickness of a tire (and / or a portion of a tire) during retreading. In one embodiment of the measuring device 100 of the invention, the measuring device 100 comprises a robot having a measuring peripheral 102 supported by an elongated pivoting arm 104. The measuring device 102 extends from the extended arm 104 to a free end 102a which allows the installation of an electromagnetic jet device 106.The electromagnetic jet 106, being of the type shown in Figure 1, comprises a horn antenna 106a and a cylindrical tip 106b, both made of PTFE. The electromagnetic jet device 106 is mounted in such a way as to allow its rotation about its longitudinal axis and also to allow its rotation around a predefined axis of rotation during an inspection process. For example, the electromagnetic jet device 106 can be attached to the measuring device 102 by screwing an adapter onto the free end 102a of the measuring device. It is understood that the electromagnetic jet device 106 can be attached to the measuring device 102 by one or more known means of attachment (including, without limitation, welding, bonding, and equivalent methods).Thus, the robot facilitates the inspection of a variety of tires without interrupting the rotation and / or spinning of the electromagnetic jet device 106. The measuring device 100 is set in motion so that the measuring device 102 can perform the inspection of an identified tire during retreading. The term "identified tire" (in the singular or plural) is used here to refer to an individual tire being retreaded and present in the physical environment of the system incorporating the measuring device 100 (the physical environment being, for example, a retreading plant incorporating the measuring device 100).

[0071] It is understood that the configuration of measuring device 100 is given by way of example. For example, measuring device 100 may include a fixed robot installed in a manufacturing facility, attached, for example, to a support from which the robot extends (e.g., a base not shown). In this case, it is understood that the robot may be attached to a ceiling, a wall, a floor, or any support that allows the inspection process to be carried out. It is understood that measuring device 100 may include at least one mobile robot. By "mobile," it is understood that the measuring device may be set in motion either by integrated means of motion (e.g., one or more integrated motors) or by non-integrated means of motion (e.g., one or more mobile means, including autonomous mobile means).It is understood that the measuring device 100 can be a conventional industrial robot or a collaborative robot or even a delta or cable robot.

[0072] Referring again to Figure 5, the measuring device 100 further includes a means for generating signals in a predetermined frequency band. For example, the measuring device 100 includes a synthesizer 108 located at the free end 102a of the measuring device 102. It is understood that the frequency band emitted by the synthesizer 108 is chosen according to the characteristics of the tires intended for an inspection process. In one embodiment, the chosen frequency band is between 20 and 40 GHz inclusive.

[0073] The use of the electromagnetic jet device 106 allows for precise control of the width and length of a plane wave pocket thanks to the design of a dielectric disruptor. Thus, the narrow width of the electromagnetic jet emitted by the electromagnetic jet device 106 (given the major diameter of the cylindrical nozzle 106b) allows the measurement to be focused on a very small area. This property enables the achievement of exceptional spatial resolution (as described below). Furthermore, the width of the electromagnetic jet is "straight" and "stable" along the length of a useful inspection area, resulting in homogeneous spatial resolution over a distance of a few wavelengths. The combination of these characteristics, along with the refractive properties of the electromagnetic jet, promotes the concentration of the plane wave intensity within the useful area.Once past the useful zone, Fonde diverges again in the form of spherical waves. The electromagnetic jet maintains a uniform focal width, thus ensuring consistent accuracy. Concentrating the wave intensity within the useful zone allows for better penetration of absorbing materials.

[0074] Incorporating the electromagnetic jet allows the detection limit to be lowered below the conventional diffraction limit (which is on the order of V²). Conventionally, the diffraction limit is based on calculations for standard optical systems. Most often, the Rayleigh criterion is used as a reference. This technique cannot be applied to the electromagnetic jet, so another method of comparison between different systems must be found. In this case, known methods associated with the full width at half maximum (FWHM) of the main lobe of the Airy disk generated by the analyzed system are used.

[0075] To perform an inter-system comparison independent of wavelength (or operating frequency), a dimensionless ratio called d / X is used, where d is the FWHM width and A is the wavelength. By comparing different conventional systems, particularly the empty horn antenna shown in Figure 6A and the horn antenna equipped with a Fresnel lens shown in Figure 6B, with the example of the electromagnetic jet device 106 represented by the horn antenna with the cylindrical tip in Figure 6C, it is observed that the electromagnetic jet allows us to fall well below the equivalent characteristics compared to the conventional diffraction limit (as shown below in Table 1).

[0076] [Table 1]

[0077] The electromagnetic jet has a variable resolution depending on the contrast of the materials from IO to V100.

[0078] As one might expect, the electromagnetic jet offers the possibility of utilizing the generated plane waves, and consequently, all the common characterization methods associated with plane waves, as well as other methods more specific to the electromagnetic jet. Electromagnetic jet characterization is performed within the jet's useful region; currently, it is restricted to the plane wave region. Referring to Figure 7, a simulation is shown in which the plane wave is highly localized in a focused area at the perturbator's output (represented in the figure by the "plane wave pocket"). Within a material with a higher refractive index than air (for example, an eraser with n=3.15), the plane wave vector is very pronounced, and the waves are significantly plane. This region forms the basis of all electromagnetic jet-based measurements.Thus, characterization is understood as the determination of one or more properties of a material or complex structure of different kinds (for example, a multilayer product that is part of an identified tire).

[0079] It is understood that frequency domain spectroscopy (FDS) and time domain spectroscopy (TDS) are used in all areas of electromagnetic spectroscopy. Therefore, these methods are also applicable to electromagnetic beam spectroscopy. The FDS method, with its extended measurement time, is suitable for thick layers. The TDS method, with its rapid measurement time, is suitable for thin layers.

[0080] With reference to Figures 8 to 13, a detailed description is given by way of example of embodiments of an inspection process performed by the measuring device 100 of the invention. It is understood that a system incorporating the measuring device 100 can implement the process in any physical environment without prior knowledge of the tires to be inspected.

[0081] As used here, the term “process” or “procedure” may include one or more steps performed by at least one computer system comprising one or more processors to execute instructions that perform the steps. Unless otherwise specified, any sequence of steps is given as an example and does not restrict the processes described to any particular sequence.

[0082] By initiating an implementation of the inspection process that is part of a retreading process, the process includes a first step (see "Step 1" in Figure 8) in which the measuring device 100 employs either a frequency domain spectroscopy-cavity resonance (FDS-CR) or a time domain spectroscopy-cavity resonance (TDS-CR) method. Each method is an additive treatment to the conventional FDS or TDS method, which uses standing waves to measure thickness. This approach is therefore based on the frequency domain, unlike conventional FDS and TDS methods, which use the time domain.Using the frequency domain increases the accuracy, dispersion, and stability of the measurement compared to the time domain approach, while having a restricted frequency band with a fine frequency step.

[0083] The first step in the inspection process involves calculating a Fast Fourier Transform (FFT). This calculation preserves the essential characteristics of the spectra while reducing the amount of computation required. When implementing the FDS-CR method, the FFT calculation step is not required. When implementing the TDS-CR method, the FFT calculation step is required.

[0084] It is observed that when working with conventional TDS or FDS, the process for determining the thickness of a section of an identified tire remains the same, regardless of whether the section of the tire to be inspected is single-layer or multi-layer. The resulting time transfer function of the FDS or TDS (from a signal processing step of an inspection process implemented by measuring device 100) (see Step 4 of Figure 8) provides most of the data necessary for calculating the thickness in metric units.

[0085] Referring again to Figure 8 and further to Figures 9 and 10, in the time domain, a diopter represents an interface between two layers 11 and 12. During the signal processing stage of an inspection process implemented by the measurement device, each interface (or diopter) (1, 2, 3) generates Gaussians that are discriminated as the center of the Gaussians (or "peaks") (see peaks 1, 2, 3 in Figure 10). Various techniques can be used to improve the detection of the Gaussians representing the diopters. This step also allows for improvement of the signal-to-noise ratio through various techniques (including, but not limited to, filtering, windowing, deconvolution, likelihood algorithms, and artificial intelligence on time series).

[0086] This approach is relevant for a thickness measurement system using a conventional THz measuring machine with a very wide frequency band (e.g., 110–170 GHz or 220–330 GHz) and a large measurement step (e.g., 151 measurements in this band). In contrast, electromagnetic jet technology allows the use of a vector network analyzer (or "VNA") with an extremely fine frequency step (around 1000 measurements in the band) to compensate for the narrow frequency band used (around 20–40 GHz).

[0087] During the use of the frequency domain in the first stage of the inspection process, the phenomenon of standing waves (and, more specifically, the constructive and destructive resonances that occur in a substrate during a frequency scan) allows for maximum utilization of VNA capabilities (in fine frequency scanning) while minimizing the impact of the narrow usable frequency band with the electromagnetic beam (22-40 GHz). This data is supported by the SI1 reflection coefficient obtained from the quadrupole (samples / substrate) analysis using the VNA. This method uses the same basic principles as Fabry-Perrot interferometers. When the thickness of a substrate is precisely a fraction of a wavelength, the wave resonates with the substrate, and the resonance becomes destructive. During the frequency scan at the measurement point, the wave penetrates the material and is reflected at each interface (or "diopter").The inspection process includes a second step (see "Step 2" in Figure 8) in which the spectrum resulting from step 1 is divided by a reference spectrum.

[0088] More specifically, the reference spectrum is representative of a calibration spectrum of device 100 in order to take into account measurement errors inherent in device 100 generated for example by the attenuation of connector signals, interference generated by the environment of device 100.

[0089] Referring to Figure 11, if the wavelength is a submultiple of the thickness, the wave resonates exactly with the substrate, and the Fonde return signal is at its minimum (low point). If the Fonde wavelength is not a submultiple of the thickness but a fraction thereof, Fonde resonates constructively or destructively. Thus, the low points of the curve are the resonance points that correspond to the different frequencies where the wavelength in the substrate is "synchronized" with the substrate thickness; Fonde is stationary.

[0090] It is difficult to directly use the frequency-domain data from the second stage of the inspection process: it is noisy and therefore requires appropriate signal processing. Thus, the inspection process includes a third stage (see "FEstage 3" in Figure 8) of performing an Inverse Fourier Transform (or "iFFT") before specific signal processing to denoise the iFFT data (e.g., by filtering, windowing, etc.). More precisely, the specific signal processing includes denoising (e.g., by filtering, windowing, etc.) the iFFT data. In this way, the desired signal processing is carried out for practical reasons in the time domain. More precisely, the desired signal processing includes the iFFT and the specific signal processing.Once the signal has been "cleaned" or denoised, it is necessary to return to the frequency domain to take full advantage of this method.

[0091] The inspection process includes a fourth step (see "Step 4" in Figure 8) of signal processing for an inspection process implemented by the measuring device 100. This step includes a thickness calculation that is very similar to that of the time domain. However, this calculation involves a frequency difference A / instead of a time difference At. The thickness of a layer is calculated as follows: cAt

[0092] 6i = 2rq

[0093] Where: e; represents the thickness of layer i; c represents the speed of light;

[0094] At represents the time delay between two diopters (being the input interface and the output interface of the layer); and m represents the real part of the refractive index of the material of layer i.

[0095] During this fourth step, to calculate the thickness of a tire product identified for inspection, its refractive index, a dimensionless value, must be obtained. In an absorbing medium, the refractive index is represented as a complex number: n = n' + in” where: n' represents the real part of the complex refractive index related to the Fonde propagation speed; and n” represents the imaginary part of the complex refractive index related to Fonde absorption.

[0096] The refractive index also allows us to determine the behavior of the wave through the materials it passes through, thanks to Snell's law. Referring to Figure 12, a substrate Medium 1 is defined by the refractive index ni, and a substrate Medium 2 is defined by the refractive index n2. The reflected wave has the same angle as the incident wave, i.e., θi = θ2.

[0097] Thus, the angle of the refracted wave is governed by the following expression:

[0098] More specifically, 0i is an angle of incidence of the incident wave, 02 is an angle of reflection of the reflected wave and 03 is an angle of refraction of the refracted wave.

[0099] It should be noted that if the incident wave is perpendicular (vertical) to Medium 2, it will be reflected along this same normal (and therefore return to the same point). This is the most favorable case for thickness measurement. System 300, incorporating measuring device 100, therefore uses a position perpendicular to the product being measured.

[0100] If the identified tire components composing the layers are previously characterized (i.e., the complex refractive index of the layers is known), the calculation remains simple and only requires a reflection measurement. It is therefore possible to determine the refractive index of the identified tire components for a given frequency band by creating charts on calibrated materials and using the thickness measurement equation adapted for determining the refractive index.

[0101] Where: ei represents the thickness of layer i; c represents the speed of light;

[0102] Af represents the frequency difference between two successive resonances; and m represents the refractive index of the material in layer i, more precisely the real part of the refractive index of the material in layer i.

[0103] The inspection process includes a final step (see "Step 5" in Figure 8) in which a Fast Fourier Transform (FFT) calculation is repeated on the cleaned or denoised signal obtained after the specific processing of the third step. At the end of the inspection process (see "Output" in Figure 8), the processed frequency transfer function is obtained. With the electromagnetic beam, the frequency band is limited. However, it is possible to perform a large number of measurement points, and the signal can be cleaned. In this way, Tonde is modified to create an extremely high resolution area that distinguishes the details of the material from a substrate, allowing for more precise material separation and / or characterization. By performing more measurement points, it becomes possible to detect and clean up "peaks" to return to the time domain.

[0104] Referring to Figures 13 and 14, the inspection process is applied within the framework of a retreading process that includes the inspection process. When considering the characteristics of a tire to be retreaded, its geometry must be taken into account. A tire is an object with a known geometry, generally comprising several superimposed layers of rubber (or "layers"), as well as a metallic or textile fiber structure forming a carcass that reinforces the tire's structure. The type of rubber and the type of reinforcement are chosen according to the desired final characteristics. Figure 13 includes a schematic representation of a 200 tire, which typically includes two circumferential beads designed to allow the tire to be mounted on a rim. Each bead includes an annular reinforcing bead.The construction of a tire is typically described by a representation of its components in a meridian plane, that is, a plane containing the tire's axis of rotation. The radial, axial, and circumferential directions respectively refer to the directions perpendicular to the tire's axis of rotation, parallel to the tire's axis of rotation, and perpendicular to any meridian plane. The terms "radially," "axially," and "circumferentially" mean, respectively, "along a radial direction," "along the axial direction," and "along a circumferential direction" of the tire. The terms "radially inside" and "radially outside" mean "closer to, or farther from, the tire's axis of rotation, respectively, along a radial direction."

[0105] The tire 200 also includes a tread 202 intended to make contact with the ground via a tread surface 202a. It is reinforced by a casing, or "carcass," which generally comprises a plurality of reinforcing layers, each having a plurality of reinforcing cords embedded in a layer of rubber-based material. More specifically, a crown casing includes a working casing 204 and a reinforcement casing 206. The working casing 204 has working layers represented by layers 204a and 204b.

[0106] The tire 200 also includes two sidewalls (one sidewall 208 being shown in Figure 13) and two reinforced ribs 210 with a bead 212. A radial carcass layer 214 extends from one rib to the other, surrounding the bead in a known manner. The tread 202 has reinforcements consisting, for example, of superimposed layers incorporating known reinforcing wires. In some embodiments, the tire may include a rubber compound 216 that dissipates static electricity generated during rolling. The tread 202 is delimited, along the radial direction, by two circumferential surfaces, the outermost radial surface being the tread surface 202a and the innermost radial surface being called the tread base.The tread depth (or "bottom surface") is defined as the area of ​​the tread surface translated radially inward by a radial distance equal to the tread depth. It is common for this depth to decrease over the outermost axially circumferential portions (called "shoulders") of the tread.

[0107] Furthermore, the tread of a tire is delimited, along the axial direction, by two lateral surfaces. The tread is also made up of one or more rubber compounds. The term "rubber compound" refers to a rubber composition comprising at least one elastomer and a filler.

[0108] To achieve optimal wet grip, cutouts are incorporated into the tread 12. A cutout is defined as a well, groove, incision, or circumferential groove, creating a space that opens onto the tread surface 12a. The performance of a tread pattern must remain sufficiently consistent despite wear to ensure the tire's longevity. Consequently, a certain thickness of rubber material must be maintained between the bottom face of the cutouts (grooves or grooves) and the reinforcing elements to guarantee the tire's durability. For example, grooves must be wide enough to allow the evacuation of liquid present on the road surface, regardless of the tread wear stage 202.Referring to Figure 14, an electromagnetic jet generated by the electromagnetic jet device 106 maintains a uniform focal width (and therefore uniform accuracy) with respect to a tire P' identified for retreading. The concentration of the emitted wave intensity in the useful zone allows for better penetration of the absorbing materials of the tire P'. In this application, these characteristics make it possible to follow transverse and longitudinal curvatures (for example, at the tire shoulders) as closely as possible to their evolution, and they also allow for the same measurement certainty regarding the product depth compared to a convergent wave or an eddy current sensor.

[0109] Tires that can be processed by the Inspection Device 100 during the retreading process include grooved and slotted tires (but it is understood that the repair device is also capable of processing slick tires). A system that includes the Inspection Device 100 does not require knowledge of a tire's architecture to control the thickness. Therefore, this approach allows retreading plants to adapt to unknown architectures and, consequently, enables the precise retreading of various tire types.

[0110] A retreading process incorporating the inspection process includes other known steps, including: a step of positioning an identified tire in a processing space where the inspection device 100 processes it; and a step of carrying out a repair process of the identified tire using at least one suitable processing tool.

[0111] To properly manage the handling of the measuring device 100 (for example, the handling of the robot and the positioning of the electromagnetic jet device 106 as shown in Figure 5), the tires being inspected must be identified. Thus, the detection data could refer to a plurality of representative recordings of the tire positions (and the products incorporated within them) tracked over time.For example, detection data may include one or more positions from recordings of the positions of a reference point on a portion of an identified tire over time or at defined time intervals; sensor data taken over time; a video stream that has been processed using a computer vision technique; and / or data indicating the operating status of measuring device 100 over time. In some cases, detection data may include data representative of one or more continuous movements of measuring device 100 before it stops to inspect one or more products of an identified tire during an inspection process. The detection system could therefore be configured to generate motion data for measuring device 100.

[0112] To implement the computer-based inspection process, an industrial system 300 incorporating a measuring device 100 may include a communication network 301 (or "network") that manages incoming data to the system from various sources (for example, from at least one measuring device 100). The communication network incorporates one or more communication servers 302 (or "servers"), each comprising one or more processors 303 operationally connected to a memory 304. The memory 304 is configured to store an application for analyzing representative data of the tires and products being analyzed. The processor(s) 303 include an analysis application execution module 305 that performs data processing, and the processor(s) are capable of executing programmed instructions 306 stored in the memory to implement the steps of the inspection process.

[0113] The input data of a system incorporating the measuring device 100 may include general information about the identified tire. General information includes stored data concerning the identification of the inspected tire (including, without limitation, its place of production, production date, materials incorporated in its production, and geometric parameters).

[0114] The inspection process may incorporate a machine learning method based on data obtained from the inspected tire. The algorithm used analyzes the tire (and the products incorporated within it) to position and operate the measuring device 100. It is understood that such a process may be part of an existing manufacturing process. One or more neural networks (e.g., one or more CNNs) may be trained with ground truth data generated using sensor data representative of the movement of the measuring device 100, including the positioning of the measuring device 102 and the electromagnetic jet device 106.

[0115] The industrial system incorporating the measuring device 100 of the invention (and / or an installation incorporating this system) may include pre-programmed management information. For example, an inspection process setting may be associated with the parameters of typical physical environments in which the system operates. In embodiments of the invention, the measuring device 100 (and / or an industrial system incorporating this device) may receive voice commands or other audio data representing, for example, an inspection start or stop. A request may be made that includes a request for the current status of an ongoing inspection cycle. A generated response may be represented audibly, visually, tactilely (for example, using a haptic interface), and / or virtually and / or augmented. This response, along with the corresponding data, may be stored in a neural network.For all implementations of the automated repair system, a monitoring system could be implemented. At least part of the monitoring system could be provided in a portable device such as a mobile network device (e.g., a mobile phone, a laptop, one or more portable network-connected devices (including augmented reality and / or virtual reality devices), wearable network-connected clothing / jewelry, and / or any combination thereof). It is conceivable that detection and comparison steps could be performed iteratively.

[0116] The terms "at least one" and "one or more" are used interchangeably. Ranges presented as being "between a and b" encompass the values ​​"a" and "b".

[0117] Although specific embodiments of the disclosed apparatus have been illustrated and described, it will be understood that various changes, additions, and modifications can be made without departing from the spirit or scope of this disclosure. Therefore, no limitations should be imposed on the scope of the invention described except those set forth in the appended claims.

Claims

Demands 1. A system (300) that implements an inspection process for an identified tire during retreading, characterized in that the system comprises: a thickness measuring device (100) including an electromagnetic jet device (106) incorporating a horn antenna (106a) that extends along a predetermined height (H) defined between a predetermined minimum diameter (c / ) and a predetermined maximum diameter (£>), the horn antenna (106a) being extended by a cylinder including a cylindrical tip (106b) having a predetermined height (7?) and a predetermined radius (R) at the antenna outlet; a means of generating signals (108) in a predetermined frequency band, the emitted frequency band of which is chosen according to the properties of the identified tire;and a communication network (301) which manages the incoming data of the system from the measuring device (100), the communication network incorporating one or more communication servers (302) each comprising one or more processors (303) operationally connected to a memory (304) configured to store an application for analyzing data representative of the tires identified to be inspected, the processor(s) comprising an execution module (305) of the analysis application configured to perform the data processing, the processor(s) of which are configured to execute programmed instructions (306) stored in the memory which, when executed by the processor(s) lead them to implement the following steps of the inspection process:; - a first step in which the measuring device (100) of the system employs at least one method among: a frequency domain spectroscopy - cavity resonance (FDS-CR) method or a time domain spectroscopy - cavity resonance (TDS-CR) method followed by a step of calculating a fast Fourier transform (FFT); - a second stage in which the reference spectrum is divided by a reference spectrum; - a third step performing an Inverse Fourier Transform (iFFT) before specific signal processing to denoise data from the Inverse Fourier Transform (iFFT), so that the specific signal processing is carried out in the time domain; - a fourth signal processing step including a thickness calculation according to the following expression: Where: e; represents the thickness of a layer i; c represents the speed of light; At represents the propagation delay between two interfaces representing an input interface and an output interface of layer i; and 10- m represents the real part of the refractive index of the material of layer i; and a final step involving a calculation of a Fast Fourier Transform (FFT) made on the signal obtained after the specific signal processing of the third step, so that, at the end of the inspection process, the processed frequency transfer function is obtained. 15 2. The system according to claim 1, wherein the electromagnetic jet (106) of the measuring device (100) is made of polytetrafluoroethylene (PTFE).

3. The system according to claim 1 or claim 2, wherein the measuring device (100) comprises a robot having a measuring peripheral (102) supported by an arm 20 elongated (104) pivoting, the measuring device (102) extending from the elongated arm (104) to a free end (102a) which allows the installation of the electromagnetic jet device (106); so that the attachment of the electromagnetic jet device (106) is made in such a way as to allow its rotation relative to the free end (102a) and also allowing its threading 25 around a predefined axis of rotation during the inspection process.

4. The system according to any one of claims 1 to 3, wherein the means for generating signals (108) from the measuring device (100) comprises a synthesizer (108) disposed at the free end (102a) of the measuring device (102). 30 5. The system according to any one of claims 1 to 4, wherein the strip of The frequency emitted by the means of generating signals is between 20 and 40 GHz inclusive.

6. The system according to any one of claims 1 to 5, wherein the electromagnetic jet has a variable resolution depending on the contrast of the materials from X / 10 to 100.

7. The system according to any one of claims 1 to 6, further comprising a vector network analyzer (VNA).

8. A process for inspecting an identified tire during retreading, the inspection process being implemented by a system (300) according to any one of claims 1 to 7, characterized in that the inspection process comprises the following steps; a first step of implementing a frequency-domain spectroscopy-cavity resonance (FDS-CR) method or a time-domain spectroscopy-cavity resonance (TDS-CR) method followed by a step of calculating a fast Fourier transform (FFT); a second step in which the spectrum determined in the first step is divided by a reference spectrum; a third step of implementing an inverse Fourier transform (iFFT) before specific signal processing to denoise data from the inverse Fourier transform (iFFT), such that the specific signal processing is carried out in the time domain;a fourth signal processing step comprising a thickness calculation according to the following expression:; Where: e; represents the thickness of a layer i; c represents the speed of light; At represents the propagation delay between two diopters representing an interface input and output interface of layer i; and n'i represents the real part of the refractive index of the material of layer i; and a final step comprising a calculation step of a Fast Fourier Transform (FFT) made on the signal obtained after the specific signal processing of the third; so that, at the end of the inspection process, the processed frequency transfer function is obtained.

9. The inspection process according to claim 8, wherein the fourth stage of the inspection process comprises: a step to obtain the refractive index of a portion of the identified tire, wherein the refractive index is represented by the following expression: n = n' + in” where: n' represents the real part of the complex refractive index related to the propagation velocity of Fonde; and n” represents the imaginary part of the complex refractive index related to the absorption of Fonde; and a step to determine the behavior of Fonde through the materials it passes through, wherein the angle of refracted Fonde is governed by the following expression: where: ni represents the refractive index of a first substrate (11); and n2 represents the refractive index of a second substrate (12), - 9i is an angle of incidence of incident ground, 02 is an angle of reflection of reflected ground and 03 is an angle of refraction of refracted ground.

10. The inspection process according to claim 9, wherein the fourth step of the inspection process further comprises a step for determining the refractive index of the identified tire parts for a given frequency band according to the following expression: Where: e; represents the thickness of layer i; c represents the speed of light; Af represents the frequency difference between two successive resonances; and m represents the real part of the refractive index of the material in layer i.

11. The inspection process according to claim 10, wherein each resonance of the two successive resonances is an exact resonance.

12. The inspection process according to any one of claims 8 to 11, wherein, during the fourth stage of the inspection process, each interface (1, 2, 3) in the time domain generates Gaussians which are discriminated in the form of the center of the Gaussians.

13. A retreading process comprising the inspection process according to any one of claims 8 to 12.

14. The retreading process of claim 13, further comprising at least one of the following steps: a step of positioning an identified tire in a processing space where the inspection device (100) processes it; and a step of carrying out a repair process of the identified tire using at least one suitable processing tool.

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