Wear sensing and wear sensor

Abstract

A method for determining wear of a textured layer attached to a base layer equipped with an ultrasonic transducer is disclosed. The base layer is disposed between the texture layer and the ultrasonic transducer, and the texture layer includes recesses and protrusions. The method includes emitting, by an ultrasonic transducer, ultrasonic waves toward the recess and the protrusion; receiving, by an ultrasonic transducer, ultrasonic echoes of the emitted ultrasonic waves reflected by the recesses and protrusions of the texture layer; and determining a height difference between the recess and the protrusion based on the received ultrasonic echo. The invention also relates to an apparatus for determining wear of a textured layer attached to a base layer and an article comprising said apparatus.

Description

Field of the Invention

[0001] The present invention generally relates to using ultrasonic waves to sense wear of a texture layer attached to a base layer. Background of the Invention

[0003] EP 0413119 relates to a large open center rolling bearing consisting of a single-piece or multi-piece outer ring and an inner ring and rolling elements arranged between them and rolling on tracks, wherein one ring is designed to accommodate an ultrasound probe and the other ring has a coupling surface. One or more rotational coupling surfaces are arranged on one or more outer surfaces of the ring to be tested.

[0004] Overview

[0005] One aspect of the present invention relates to a method for determining the wear of a texture layer attached to a substrate equipped with an ultrasonic transducer. The substrate is placed between the texture layer and the ultrasonic transducer, and the texture layer includes recesses and protrusions. The method comprises:

[0006] emitting ultrasonic waves toward the recess and the protrusion through an ultrasonic transducer;

[0007] receiving, by the ultrasonic transducer, ultrasonic echoes resulting from the reflected emission of the ultrasonic wave from the concavities and convexities of the texture layer; and

[0008] The height difference between the recess and the protrusion is determined based on the received ultrasonic echo.

[0009] It will be appreciated that the present invention allows reducing (or even eliminating) the effects of external temperature on the determination of the wear of the texture layer using an ultrasonic transducer. External temperature variations may result in, for example, thermal expansion of the base layer and / or the transducer. Furthermore, the present invention allows reducing (or even eliminating) the problems typically encountered in the case of complex interfaces, for example between the base layer and the texture layer. It will also be appreciated that the present invention allows remote measurement of the wear of the texture layer in the sense that the ultrasonic transducer does not need to be directly attached to the texture layer. The texture layer may be located in an adverse environment, such that a transducer attached on that side may not operate correctly. Thus, the present invention allows performing on-site wear measurements (thereby avoiding contamination, wear and / or damage to the transducer) even when the texture layer is located in an adverse environment.

[0010] The frequency of the emitted ultrasonic waves may be between 20 kHz and 1000 MHz, preferably between 50 kHz and 500 MHz, even more preferably between 100 kHz and 10 MHz.

[0011] The ultrasonic transducer may include (or consist of) a piezoelectric transducer.

[0012] In an embodiment, determining the height difference comprises determining a time difference (ie a delay) between echoes reflected by the recess and the protrusion, the determination of the height difference being based on the determined time difference.

[0013] Optionally, determining the height difference comprises determining an absorption between echoes reflected by the recess and the protrusion, the determination of the height difference being based on the determined absorption.

[0014] In an embodiment, the method further comprises determining a frequency of a resonance peak of a texture layer attached to the base layer, wherein the frequency of the ultrasonic wave emitted by the ultrasonic transducer is substantially equal to the determined frequency of the resonance peak. The frequency of the emitted ultrasonic wave is preferably included in the full width at half maximum (FWHM) of the resonance peak, more preferably included in the frequency providing a maximum attenuation of -2 dB relative to the maximum value of the peak, and most preferably included in the frequency providing a maximum attenuation of -1 dB relative to the maximum value of the peak. Optionally, the determination of the resonance peak comprises sampling the response of the texture layer attached to the base layer at multiple frequencies (e.g., by emitting multiple ultrasonic waves at different frequencies).

[0015] The method may include determining a phase shift between ultrasonic echoes reflected by valleys and protrusions of the textured layer.Determination of a height difference between the valleys and protrusions may be based on the determined phase shift.

[0016] In an embodiment, the method may further comprise comparing the determined frequency of the formant of the texture layer attached to the base layer with the expected frequency of the formant, for example stored in a database.

[0017] The determination of the height difference may include mapping the received ultrasound echoes to the height difference using a lookup table, a database, and / or an artificial intelligence model that maps the received ultrasound echoes to the height difference between the recess and the protrusion.

[0018] The method may further include transmitting the determined height difference to a remote receiver, for example, via at least one of Bluetooth, Bluetooth Low Energy, Zigbee, Z-Wave, NFC, RFID, and 6LoWPAN protocols.

[0019] The substrate can include metal materials, such as aluminum, copper, iron, tin, gold, lead, silver, titanium, uranium and zinc or any combination thereof. The substrate can include composite materials, such as reinforced concrete, fiber reinforced polymers (such as carbon fiber reinforced polymers, glass reinforced plastics). The polymer can be thermoplastic or thermosetting. Exemplary thermosetting composite materials can add aramid fibers and carbon fibers in an epoxy resin matrix. Typically, one of the components of the composite material can be structured, such as structured into a grid or equivalent. Typical examples of the substrate can include stone, steel, PMMA, nylon, alu-dibond (a LDPE layer sandwiched between two aluminum layers).

[0020] The texture layer may include (or consist of) the following: silicone foam, natural rubber (possibly containing polyester components), polychloroprene (chloroprene), polyurethane, acrylic, alkyd enamel, acrylonitrile butadiene styrene (ABS), polyoxymethylene (POM / acetal), fluoropolymers (PTFE, PFA, PVDF, FEP, ETFE), polysulfones (PAS, PPS / PPSU, PES, PSU, PSF), polyetherimide (PEI), polyaryletherketone (PAEK), polyamide-imide (PAI), polyimide (PI), inorganic enamels and ceramics, as well as mixtures or combinations of the individual phases of the above layer materials.

[0021] The incident angle of the emitted ultrasonic wave can be substantially perpendicular to the surface of at least one of the recess and the protrusion. Preferably, the incident angle can deviate from the normal incidence by no more than 10°, more preferably by no more than 5°, and even more preferably by no more than 2° relative to the normal incidence.

[0022] The transmitted ultrasonic wave may be a pulsed ultrasonic wave. Alternatively, the transmitted ultrasonic wave may be a continuous ultrasonic wave. Of course, the ultrasonic transducer may transmit a pulsed ultrasonic wave and a continuous ultrasonic wave in sequence.

[0023] The method may comprise storing the frequencies of the resonant peaks of the texture layer attached to the base layer, for example in a database, preferably instead of determining the height difference. In one embodiment, a plurality of resonant peaks may be stored.

[0024] Another aspect of the invention relates to an apparatus for determining the wear of a texture layer attached to a base layer. The texture layer comprises recesses and protrusions. The apparatus comprises:

[0025] an ultrasonic transducer configured to transmit ultrasonic waves toward the recesses and protrusions and to receive ultrasonic echoes where the transmitted ultrasonic waves are reflected by the recesses and protrusions of the texture layer;

[0026] A controller is configured to determine a height difference between the recess and the protrusion based on the received ultrasonic echo.

[0027] Determining the height difference may include determining a time difference between echoes reflected by the recess and the protrusion, the determination of the height difference being based on the determined time difference.

[0028] Determining the height difference may include determining an absorption between echoes reflected by the recess and the protrusion, the determination of the height difference being based on the determined absorption.

[0029] In an embodiment, a controller is operably connected to the ultrasonic transducer, the controller being configured to determine the frequency of a resonance peak of a texture layer attached to a base layer. The controller may be configured to operate the ultrasonic transducer to emit ultrasonic waves at a frequency substantially equal to the determined frequency of the resonance peak. The frequency of the emitted ultrasonic waves is preferably included in the full width at half maximum (FWHM) of the resonance peak, more preferably included in the frequency providing a maximum attenuation of -2 dB relative to the maximum value of the peak, and most preferably included in the frequency providing a maximum attenuation of -2 dB relative to the maximum value of the peak.

[0030] The controller may also be configured to determine a phase shift between ultrasonic echoes reflected by valleys and protrusions of the texture layer.Determination of a height difference between valleys and protrusions may be based on the determined phase shift.

[0031] The controller may be configured to compare the determined frequency of the formant of the texture layer attached to the base layer with the expected frequency of the formant, for example stored in a database.

[0032] Determining the height difference may include mapping the received ultrasound echoes to the height difference using a lookup table, a database, and / or an artificial intelligence model that maps the received ultrasound echoes to the height difference between the recess and the protrusion. The mapping may be performed by a controller.

[0033] The weight of the device may be in the interval 1 g to 10 g, preferably in the interval 2 g to 9 g, most preferably in the interval 3 g to 7 g.

[0034] The device may also include a transmitter selected from the group consisting of: a Bluetooth transmitter, a low-energy Bluetooth transmitter, a Zigbee transmitter, a Z-Wave transmitter, an NFC transmitter, an RFID transmitter, and a 6LoWPAN transmitter, the transmitter being configured to transmit the determined height difference to a remote receiver. The transmitter may be controlled by a controller so that the controller may operate the transmitter to transmit the determined height difference to the remote receiver. In an embodiment, the controller may determine whether the determined height difference is below a threshold or greater than a threshold. If the determined height difference is below a threshold, the controller may operate the transmitter to transmit an alarm signal in addition to or in lieu of transmitting the determined height difference.

[0035] The controller may be configured to store, for example in a database, the frequencies of the resonance peaks of the texture layer attached to the base layer, preferably instead of determining the height differences.

[0036] Another aspect of the present invention relates to an article comprising a device as disclosed herein, the article comprising a texture layer and a base layer, the texture layer being attached to the base layer, the base layer being interposed between the texture layer and an ultrasonic transducer of the device, the texture layer comprising recesses and protrusions.

[0037] The ultrasound transducer may be embedded in the substrate.

[0038] In this document, the verb "to comprise" and the expression "to be comprised of" are used as open transition phrases, meaning "to include" or "to consist at least of". Unless the context implies otherwise, the use of singular word forms is intended to include the plural, unless the cardinal number "one" is used: here "one" means "exactly one". Ordinal numbers ("first", "second", etc.) are used in this document to distinguish different instances of a common object; the use of these expressions does not imply a particular order, importance, or ranking. In addition, when multiple instances of an object are referenced by an ordinal number, this does not necessarily mean that there are no other instances of the object (unless it is clear from the context). When referring to "an embodiment", "one embodiment", "multiple embodiments", etc., it means that these embodiments can be combined with each other. An embodiment can relate to various aspects of the present invention, unless it is clear from the context that it is incompatible with a specific aspect. In addition, the features of the embodiments can be used in the combinations explicitly presented, and these features can also be combined across embodiments without departing from the present invention, unless it is clear from the context that the features cannot be combined. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Preferred non-limiting embodiments of the present invention will now be described in detail by way of example with reference to the accompanying drawings, in which:

[0041] Figure 1 : shows a simplified view of an article according to one aspect of the present invention;

[0042] Figure 2 : shows the typical response of a base layer attached to a texture layer to ultrasonic excitation;

[0043] Figure 3 : A graph showing a typical response of a base layer attached to a texture layer to ultrasonic excitation;

[0044] Figure 4 : shows the typical response of a base layer attached to a texture layer to ultrasonic excitation;

[0045] Figure 5: shows a typical response of a base layer attached to a texture layer to ultrasonic excitation; and

[0046] Figure 6 : shows the typical response of a base layer attached to a texture layer to ultrasonic excitation.

[0047] The reader's attention is drawn to the fact that the drawings are not drawn to scale. In addition, for the sake of clarity, the ratios between height, length and / or width may not be correctly represented.

[0048] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0049] Figure 1 An article 10 is shown comprising a device 12, a base layer 14 and a texture layer 16. The texture layer 16 is attached to the base layer 14, for example by an adhesive, by gluing, by lamination, etc. The texture layer 16 may also be obtained by etching the base layer 14 or in other words by machining the base layer 14.

[0050] On the side opposite to the texture layer 16, a device 12 is provided. The device 12 comprises an ultrasonic transducer 18 (e.g. a piezoelectric transducer) in direct contact with the base layer 14. In other words, the base layer 14 is interposed between the texture layer 16 and the ultrasonic transducer 18 of the device 12. In one embodiment, the ultrasonic transducer 18 or even the entire device 12 may be (at least partially or completely) embedded in the base layer 14. The ultrasonic transducer 18 may be attached to the base layer 14, for example, by an adhesive, by gluing, etc.

[0051] The texture layer 16 includes recesses 20 and protrusions 22 on its surface on the side opposite to the base layer 14 .

[0052] The base layer 14 may include a metallic material, such as aluminum, copper, iron, tin, gold, lead, silver, titanium, uranium and zinc, or any combination thereof. The base layer 14 may include a composite material, such as reinforced concrete, a fiber-reinforced polymer (e.g., a carbon fiber reinforced polymer, a glass reinforced plastic). The polymer may be thermoplastic or thermosetting. Exemplary thermosetting composite materials may include aramid fibers and carbon fibers in an epoxy resin matrix or a rubber matrix. Typically, one of the components of the composite material may be structured, such as being structured as a grid or equivalent, which may or may not be metallic. Typical examples of base layers may include stone, steel, PMMA, nylon, alu-dibond (a LDPE layer sandwiched between two aluminum layers). The base layer 14 may include a plurality of sublayers.

[0053] The texture layer may include (or consist of) the following: silicone foam, natural rubber (possibly containing polyester components), polychloroprene (chloroprene), polyurethane, acrylic, alkyd enamel, acrylonitrile butadiene styrene (ABS), polyoxymethylene (POM / acetal), fluoropolymers (PTFE, PFA, PVDF, FEP, ETFE), polysulfones (PAS, PPS / PPSU, PES, PSU, PSF), polyetherimide (PEI), polyaryletherketone (PAEK), polyamide-imide (PAI), polyimide (PI), inorganic enamels and ceramics, as well as mixtures or combinations of the individual phases of the above layer materials.

[0054] In an embodiment, the composition of the base layer 14 is different from the composition of the texture layer 16 .

[0055] The ultrasonic transducer 18 is controlled by the controller 24. When operated by the controller 24, the ultrasonic transducer 18 can emit one or more ultrasonic waves directed to the texture layer 16 and the base layer 14. The one or more ultrasonic waves can be pulsed or continuous or a combination thereof. In particular, the ultrasonic transducer 18 can emit one or more ultrasonic waves toward the recesses 20 and the protrusions 22.

[0056] One or more ultrasonic waves propagate in the base layer 14 and the texture layer 16. Then, the one or more ultrasonic waves may be reflected by an interface, for example, by an interface between the base layer 14 and the texture layer 16, thereby generating a first reflected wave r1. One or more ultrasonic waves may also be reflected by an interface between the texture layer 16 and a medium in which the texture layer is located, thereby generating additional reflected waves r2 and r3. Then, the reflected waves r1, r2, and r3 may be received by the ultrasonic transducer 18.

[0057] The reflected wave received by the transducer is an echo wave in which the transmitted one or more ultrasonic waves are reflected by the interface as described above.

[0058] The received waves may then be processed by the controller 24 for determining, for example, a height difference between the recess 20 and the protrusion 22 based on, for example, a time difference (delay) Δt of the reception of the ultrasonic echo and / or the absorption of the echo of the transmitted ultrasonic wave. Typical height differences may be in the interval of 0.01 mm to 30 mm, preferably in the interval of 0.1 mm to 5 mm, and most preferably in the interval of 0.2 mm to 3 mm.

[0059] The device may further include a transmitter 26 selected from the group consisting of a Bluetooth transmitter, a low energy Bluetooth transmitter, a Zigbee transmitter, a Z-Wave transmitter, an NFC transmitter, an RFID transmitter, and a 6LoWPAN transmitter. The transmitter may be configured to transmit, for example, the determined height difference and / or any information provided by the controller, such as the location of one or more resonance peaks, etc., to a remote receiver. The controller may be configured to operate the transmitter 26.

[0060] The device may also be equipped with a power supply (AC) 28 for powering the components of the device. The controller 24 may be configured to act as a power management system for the device 12, thereby powering, for example, the ultrasound transducer 18, the transmitter 26, or any other component via the power supply (AC) 28.

[0061] The controller may operate the device through specific programming or through specially designed hardware such as an application specific integrated circuit (ASIC), a digital signal processor (DSP), or a programmable logic circuit such as an FPGA. The controller may include memory or have access to memory to provide a persistence layer.

[0062] The weight of the device may be in the interval of 1 g to 10 g, preferably in the interval of 2 g to 9 g, most preferably in the interval of 3 g to 7 g. The size of the device may be in the range of 5 mm to 20 mm, preferably in the range of 6 mm to 15 mm, even more preferably in the range of 8 mm to 10 mm. The thickness of the device may be in the range of 1 mm to 10 mm, preferably in the range of 2 mm to 7 mm, even more preferably in the range of 3 mm to 5 mm. In operation, the device may have a low power consumption, for example a low power consumption from 1 mW to 100 mW, preferably a low power consumption from 10 mW to 50 mW, even more preferably a low power consumption from 20 mW to 40 mW.

[0063] Figure 2 A typical signal obtained by an ultrasonic transducer when transmitting an ultrasonic pulse as disclosed above is shown. Four peaks are detected by the ultrasonic transducer 18. The first peak is associated with the transmitted wave, and with delays in sequence or reception, the echoes are r1, r2 and r3. The time Δt between r2 and r3 provides an indication of the height difference between the recess and the protrusion. The difference in absorption between the two peaks can also provide such an indication of the height difference.

[0064] By providing a differential measurement of the texture layer, the present invention allows reducing (or even eliminating) the effect of external temperature on the wear of the texture layer determined with an ultrasonic transducer. Furthermore, the differential measurement allows eliminating any complexity created by the base layer (such as, for example, a complex interface between the base layer and the texture layer). It will also be appreciated that the apparatus according to the present invention allows in situ probing of the article indirectly in terms of not being in direct contact with the texture layer.

[0065] In the context of this article, wear of the texture layer can take many forms, such as material loss (thereby reducing its thickness), ridges, impurities, contamination (such as additional layers, such as biofilms), defects (such as cracks, corrosion), etc. In other words, wear involves changes in the texture layer during use relative to the texture layer expected to be produced in the factory.

[0066] exist Figure 3 ] is an example of measurements that may be obtained by probing a texture layer 16 attached to a base layer 14 with the device 12. The graph plotted is:

[0067] Upper left curve: s 11 The imaginary part of s 11 Nyquist plot that varies with the real part of ;

[0068] Upper middle curve: s 11 Bode plot of the modulus of as a function of the transmitted ultrasonic frequency;

[0069] Upper right graph: Bode plot of the modulus of Z as a function of the transmitted ultrasonic frequency;

[0070] Lower left graph: Nyquist plot of the imaginary part of Z as a function of the real part of Z;

[0071] Middle and lower curve graph: s 11 Bode plot of the phase variation of the transmitted ultrasonic frequency; and

[0072] Bottom right graph: Bode plot of the phase of Z as a function of the transmitted ultrasonic frequency.

[0073] s 11 The modulus of (called the reflection coefficient) represents the reflected power from the texture layer 16 attached to the base layer 14, while s 11 The phase of shows the phase shift of the reflected wave relative to the transmitted wave. Z corresponds to the impedance of the ultrasonic transducer and can vary depending on the received ultrasonic wave.

[0074] For each graph, three samples were probed. The first was the original brick alone as a base layer (triangles). The second was the brick with layer A attached (squares), and the third was the brick with layer B attached (lines).

[0075] The stone brick is 7 mm thick, layer A is a 3.2 mm thick silicone foam (RS stock number: 733-6810) and layer B is a 1.5 mm thick natural rubber sheet with a polyester fiber insert in its center (RS stock number: 506-3078). The density of the natural rubber is 1.5 g / cm 3 .

[0076] The graph shows a resonance peak at about 1 MHz. This peak provides better resolution for determining height differences or absorption.

[0077] Figure 4 yes Figure 3 A zoomed in view of the vicinity of the resonance peak of the lower right graph of . The graph shows the phase difference (or its absence) caused by the thickness difference of the layer. The phase difference can then be mapped to the height difference, for example using a lookup table, a database and / or an artificial intelligence model that maps the phase difference to the height difference. It should be noted that the phase difference is directly related to the time difference through the speed of sound in a particular medium.

[0078] The lookup tables, databases and / or artificial intelligence models may be accessed locally, such as where a persistence layer is located in a persistence layer of a controller, or remotely, such as via communications from a transmitter to a remote server that includes the lookup tables, databases and / or artificial intelligence models.

[0079] It is noteworthy that the frequency shift Δf of the resonance peak occurs depending on the material (layer A or layer B) attached to the base layer, allowing a determination whether the attached layer is indeed the expected layer. This may be particularly advantageous for determining whether a small foreign object made of a different material than the base layer 14 and the texture layer 16 is stuck in a recess. The detection of a small foreign object in a recess may also be an indication that the determined height difference may not be accurate. In addition, during wear, one or more additional layers, such as biofilms, may form on top of the texture layer. Since the resonance peaks may be shifted, the presence of a biofilm may be detected by the present invention.

[0080] exist Figure 5 In Figure 1, three samples were probed. The first was the original brick alone as a base layer (circles). The second was the brick with layer B attached (crosses), and the third was the brick with 2 layers of B attached (lines).

[0081] Figure 5 The phase difference resulting from the thickness difference of one layer B compared to two layers B is shown. Here too, the height difference can be determined by the mapping as disclosed above. Also, as expected, no frequency shift occurs.

[0082] Other materials can also be detected, such as Figure 6 As shown. Figure 6In the present invention, an alu-dibond composite material (LDPE layer sandwiched between two aluminum layers) is used as the base layer, to which the (2) layers A or B are attached. Here, the frequency shift can also be determined in the case of the detection of an additional material. In addition, the phase shift can also be determined as described above.

[0083] It should be noted that the same analysis can be performed with other graphs representing the absorption of the emitted wave, such as |s11| versus frequency, |Z| versus frequency.

[0084] In an embodiment, multiple transducers may be used. For example, a first transducer may be configured to transmit ultrasound toward a recess, and a second transducer may be configured to transmit ultrasound toward a protrusion.

[0085] The article may be a parquet floor strip (e.g. wear, loss of protective varnish), a boat hull (e.g. loss of protective paint or addition of biofilm), a fluid transport pipe (e.g. corrosion, loss of internal protective coating), the stone tiles of a wall (e.g. loss of paint or protective coating), a glass window (e.g. loss of protective infrared or UV coating), a swimming pool liner or synthetic wall (e.g. loss of protective rubber coating), with the advantage that the device 12 is protected and never exposed to the harsh environment.

[0086] Although specific embodiments have been described in detail herein, it will be appreciated by those skilled in the art that various modifications and substitutions to these details may be developed in light of the overall teachings of the present disclosure. Therefore, the particular arrangements disclosed are intended to be illustrative only and not limiting of the scope of the present invention, which is given by the full breadth of the appended claims and any and all equivalents thereof.

Claims

1. A method for determining the wear of a texture layer attached to a substrate, the substrate being provided with an ultrasonic transducer, the substrate being interposed between the texture layer and the ultrasonic transducer, the texture layer comprising recesses and protrusions, the method comprising: emitting ultrasonic waves toward the recess and the protrusion by the ultrasonic transducer; receiving, by the ultrasonic transducer, ultrasonic echoes resulting from the emitted ultrasonic wave being reflected by the concave portions and the protrusions of the texture layer; and A height difference between the recess and the protrusion is determined based on the received ultrasonic echo.

2. The method according to claim 1, wherein: Determining the height difference includes determining a time difference between echoes reflected by the recess and the protrusion, and the determination of the height difference is based on the determined time difference.

3. The method according to any one of claims 1 to 2, wherein: Determining the height difference includes determining absorption between echoes reflected by the recess and the protrusion, the determination of the height difference being based on the determined absorption.

4. A method according to any one of claims 1 to 3, comprising determining the frequency of a resonant peak of the texture layer attached to the base layer, wherein: The frequency of the ultrasonic wave emitted by the ultrasonic transducer is substantially equal to the determined frequency of the resonance peak.

5. A method according to any one of claims 1 to 4, comprising determining a phase shift between ultrasonic echoes reflected by the valleys and protrusions of the textured layer.

6. A method according to claim 4, comprising comparing the determined frequency of the formant of the texture layer attached to the base layer with an expected frequency of the formant, for example stored in a database.

7. The method according to any one of claims 1 to 6, wherein: The determining of the height difference includes mapping the received ultrasonic echoes to the height difference using a lookup table, a database and / or an artificial intelligence model that maps the received ultrasonic echoes to the height difference between the recess and the protrusion.

8. The method according to any one of claims 1 to 7, further comprising transmitting the determined height difference to a remote receiver, for example via at least one of Bluetooth, Bluetooth Low Energy, Zigbee, Z-Wave, NFC, RFID and 6LoWPAN protocols.

9. The method according to any one of claims 1 to 8, wherein: The base layer includes a metal material.

10. The method according to any one of claims 1 to 9, wherein: The incident angle of the transmitted ultrasonic wave is perpendicular to a surface of at least one of the recess and the protrusion.

11. The method according to any one of claims 1 to 10, wherein: The emitted ultrasonic wave is a pulsed ultrasonic wave.

12. A method according to any one of claims 1 to 11, comprising storing the frequencies of the resonance peaks of the texture layer attached to the base layer, for example in a database, preferably instead of determining the height differences.

13. An apparatus for determining the wear of a textured layer attached to a base layer, the textured layer comprising recesses and protrusions, the apparatus comprising: an ultrasonic transducer configured to transmit ultrasonic waves toward the concave portions and the protrusions and to receive ultrasonic echoes in which the transmitted ultrasonic waves are reflected by the concave portions and the protrusions of the texture layer; and A controller is configured to determine a height difference between the recess and the protrusion based on the received ultrasonic echo.

14. The device according to claim 13, wherein: Determining the height difference includes determining a time difference between echoes reflected by the recess and the protrusion, and the determination of the height difference is based on the determined time difference.

15. The apparatus according to any one of claims 13 to 14, wherein: Determining the height difference includes determining absorption between echoes reflected by the recess and the protrusion, the determination of the height difference being based on the determined absorption.

16. The apparatus according to any one of claims 13 to 15, wherein: The controller is operably connected to the ultrasonic transducer, the controller being configured to determine a frequency of a resonance peak of the texture layer attached to the base layer, wherein the controller is configured to operate the ultrasonic transducer to transmit ultrasonic waves having a frequency substantially equal to the determined frequency of the resonance peak.

17. The apparatus according to any one of claims 13 to 15, wherein: The controller is also configured to determine a phase shift between ultrasonic echoes reflected by the valleys and protrusions of the textured layer.

18. The apparatus of claim 16, the controller being configured to compare the determined frequency of the formant of the texture layer attached to the base layer with an expected frequency of the formant, for example stored in a database.

19. The apparatus according to any one of claims 13 to 18, wherein: The determining of the height difference includes mapping the received ultrasonic echoes to the height difference using a lookup table, a database and / or an artificial intelligence model that maps the received ultrasonic echoes to the height difference between the recess and the protrusion.

20. Apparatus according to any one of claims 13 to 19, wherein: The weight of the device lies in the interval of 1 g to 10 g.

21. The device of any one of claims 13 to 20, further comprising a transmitter selected from the group consisting of a Bluetooth transmitter, a Bluetooth Low Energy transmitter, a Zigbee transmitter, a Z-Wave transmitter, an NFC transmitter, an RDFID transmitter, and a 6LoWPAN transmitter, the transmitter being configured to transmit the determined height difference to a remote receiver.

22. Apparatus according to any one of claims 13 to 21, wherein: The controller is configured to store the frequency of the resonance peak of the texture layer attached to the base layer, for example in a database, preferably instead of determining the height difference.

23. An article comprising a device according to any one of claims 12 to 20, the article comprising a texture layer and a base layer, the texture layer being attached to the base layer, the base layer being interposed between the texture layer and an ultrasonic transducer of the device, the texture layer comprising recesses and protrusions.

24. The article of claim 23, wherein: The ultrasonic transducer is embedded in the substrate.

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