WO2024083894A1

WO2024083894A1 - Device and method for the structural monitoring of an object

Info

Publication number: WO2024083894A1
Application number: PCT/EP2023/078948
Authority: WO
Inventors: Jochen Kuhn
Original assignee: Shaw-Almex Industries Limited
Priority date: 2022-10-20
Filing date: 2023-10-18
Publication date: 2024-04-25
Also published as: DE102022127728A1

Abstract

The invention relates to a device (1) for the structural monitoring of an object (6), comprising: - an RFID transponder (2) which is designed to transmit data (N), - a first electric conductor (3) which is coupled to a first antenna connection (2a) of the RFID transponder (2) in an electrically conductive or capacitive manner, - a second electric conductor (4) which is coupled to a second antenna connection (2b) of the RFID transponder (2) in an electrically conductive or capacitive manner, and - a dielectric (5) which is extended over a sensor section (S), wherein the two conductors (3, 4) together with the dielectric (5) arranged between the conductors (3, 4) form a waveguide (S) over the sensor section (S), and at least one of the conductors (3, 4) is formed on the sensor section (S) end facing away from the RFID transponder (2) as an antenna (A). The invention additionally relates to a corresponding object, to a monitoring system, and to a monitoring method.

Description

Device and method for structural monitoring of an object

The invention relates to a device and a method for structural monitoring of an object, in particular for measuring changes in length or distance or deformations or damages of an object or object systems.

Structural monitoring of objects is beneficial or necessary in many areas of daily life. Structural monitoring does not necessarily mean that all doors and windows in a building should be monitored for safety reasons, but also monitoring, for example, expansion joints in bridges, the integrity of conveyor belts or the complete loading of a vehicle.

There are many options for structural monitoring: monitoring by direct vision or, if necessary, by means of a camera, re-measurements, or sensors, e.g. light barriers, magnets and reed contacts or signal wires.

All of these options have the disadvantage that reading or measuring is always cumbersome. You either have to go to the location to carry out the measurement yourself, or to maintain sensors or equip them with new energy sources.

The object of the invention was to overcome the disadvantages of the prior art and to provide a device and a method for structural monitoring of an object, which achieves optimal monitoring with a minimum of effort.

This object is achieved by a device according to claim 1, an object according to claim 7, a monitoring system according to claim 9 and a method according to claim 10.

A device according to the invention is used for structural monitoring of an object, in particular for measuring changes in length or distance or deformations or damages of an object or object systems. The objects can be buildings, e.g. bridges, vehicles, aircraft, roads, These can be storage systems or conveyor belts, e.g. for rock, especially for ore, gold or diamond extraction.

The device according to the invention comprises the following components:

- an RFID transponder designed to send data,

- a first electrical conductor which is electrically conductively or capacitively coupled to a first antenna connection of the RFID transponder,

- a second electrical conductor which is electrically conductively or capacitively coupled to a second antenna connection of the RFID transponder, and

- a dielectric extending over a sensor path, wherein the two conductors together with the dielectric arranged between the conductors form a waveguide over the sensor path and at least one of the conductors is formed as an antenna at the end of the sensor path facing away from the RFID transponder.

RFID transponders are widely known in the state of the art. RFID (radio frequency identification) refers to a technology for transmitter-receiver systems for automatic and contactless data exchange in the near field or far field, especially with UHF RFID.

Typically, an RFID transponder comprises a microchip (often in the millimeter range) and an antenna system. A power source is not necessary for passive transponders, as the power can be supplied externally via the antenna system using an RFID reader.

An RFID system normally comprises a number of RFID transponders, each of which contains at least identification information (“serial numbers”) and a number of RFID readers for reading the data from the RFID transponders (or “transponders” for short). A transponder is coupled to an RFID reader by alternating magnetic fields generated by the RFID reader within a short range or by high-frequency radio waves, which are used not only to transmit data but also to supply the transponder with energy. The RFID reader contains software that controls the actual reading process. Communication between transponders and RFID readers usually takes place in a defined frequency range, which is often subject to regional regulations. For the invention Particularly advantageous frequency ranges are “very high frequencies” (UHF, 300 MHz - 3 GHz), which can have a very long range.

When transmitting data, the RFID transponder usually first sends its serial number (UID) and then, if necessary, further data (UID) using load modulation, i.e. it consumes part of the energy of the alternating field. The RFID reader can detect this.

The basic principle of the invention is based on a special use of the antenna system for data transmission. The antenna system here consists of an antenna part and a waveguide part (sensor section). In this regard, the device comprises two conductors that are connected to the two antenna connections of the RFID transponder. Sometimes one of these antenna connections is also referred to as "ground".

However, this ground input is also used to receive the alternating field of the RFID reader.

The connection of the conductors to the antenna connection can be electrically conductive, which does not just mean that the conductors have to be soldered to the antenna connections, but also that they can simply be placed, glued or clamped. The connection of the conductors to the antenna connection can alternatively be capacitive, which means that there is no electrical line, but rather the conductor and antenna connection are insulated from each other, e.g. by a thin layer of glue or double-sided adhesive tape, and the signal is transmitted via a capacitance between the conductor and the antenna connection.

However, the two conductors do not serve as antennas over their entire length. There is a sensor path in which the conductors are separated from one another by the dielectric, whereby the dielectric is particularly preferably a solid insulator, e.g. a plastic covering of the conductors or an adhesive tape. Over this sensor path, the two conductors together with the dielectric arranged between the conductors form a waveguide.

Since a wave cannot couple into a waveguide (or can only couple very poorly), one of the conductors (as a monopole or dipole) or both conductors (e.g. as a dipole or inverted F-antenna) are formed as an antenna at the end of the sensor path that is facing away from the RFID transponder. If the waveguide is destroyed at one point, e.g. because a weakening line of an object spanned by the waveguide breaks, the RFID transponder is separated from its antenna and can no longer be read or can only be read with great difficulty. This can be used to structurally monitor the object, e.g. as an indication of damage or deformation.

An object according to the invention is in particular a conveyor belt or a building, but can also be a vehicle, a road or an aircraft. Basically, the invention is advantageous for any object whose structure can (and should) be monitored in some way. The object comprises a number of devices according to the invention which are attached to or in the object, in particular in the area of a structural weakening line of the object. They particularly preferably span this weakening line with their sensor path, in particular across or meandering along the course of the weakening line. The object is in particular designed as a conveyor belt and at least one of the devices is arranged in or on the object such that its sensor path runs essentially across the length of the object (e.g. conveyor belt), the device preferably being surrounded by material of the object (e.g. conveyor belt). This allows longitudinal cracks in the conveyor belt to be detected. Embedding it in the material of the conveyor belt protects the device. For example, a transverse strip can be cut out of the surface of the conveyor belt, the device can be placed in the resulting groove and the cut-out element can be glued or vulcanized back in.

A monitoring system according to the invention for structural monitoring of an object comprises an RFID reader and an object according to the invention (with devices according to the invention) or a number of devices according to the invention and an object, wherein the devices are attached or at least attachable to or in the object.

A method according to the invention for structural monitoring of an object, in particular a conveyor belt, a building or a storage system, with a monitoring system according to the invention comprises the following steps:

- Reading data, in particular at least the serial number, of an RFID transponder of one of the devices of the monitoring system with an RFID reader of the monitoring system, wherein the data of the RFID transponder preferably read multiple times before the data of another RFID

T ransponders can be read,

- Deriving a value for a structural change in the object from the number of data read out and/or from an RSSI value measured in addition to the readout.

The value for the structural change in the object can then be output or used to control an alarm device or system.

For example, the value can simply be saved in a data set and used later for evaluation. However, an alarm can also be issued if a structural change (e.g. a crack) has occurred. In addition to or as an alternative to a warning, a process can be stopped, e.g. a conveyor belt can be stopped if one of the devices indicates a crack (due to its failure). The procedure can therefore include the additional step:

- Controlling a process and/or an alarm system by means of the value and/or outputting the value, in particular on a display device and/or in a storage device.

It should be noted that the serial number of a transponder can be read very quickly (often within a second). Although it is certainly possible to read or determine additional information such as the RSSI value (the Received Signal Strength Indicator; a measure of the reception field strength of wireless communication applications) or additional sensor information, the basic principle of the invention already works with a simple reading of the serial number.

If the waveguide is damaged or the antenna is detached from the waveguide, then the transmission is poor, which can be determined using the RSSI value. However, it is quicker to read the serial number. With a very simple monitoring principle, the absence of a "response" from an RFID transponder can be used to conclude that an unfavorable situation has occurred, e.g. damage to the object. However, it may also be the case that, with a poor connection (e.g. poor coupling of antenna to waveguide), the RFID transponder has only sent data for a fraction of the RFID reader's requests. However, this fraction can already be used to derive a measure of the coupling between the antenna and the RFI DT transponder and thus of the distance between the antenna and the waveguide. For example, a conveyor belt has a large number of devices according to the invention that run across the conveyor belt at regular intervals. The RFID transponders are preferably located on one edge of the conveyor belt, where they are best protected from the transported loads. The antennas are then preferably located on the other edge of the conveyor belt and the sensor path (i.e. the waveguide) runs across the width of the conveyor belt. An RFID reader on the edge near the antenna reads the serial numbers of the RFID transponders.

Like any waveguide, the sensor path here also has a dampening effect on high-frequency signals. It can therefore be advantageous if the waveguide does not exceed a certain maximum length. When monitoring large objects, e.g. very wide conveyor belts, it is advantageous if the sensor path does not run across the entire width of the object, but only over a part of it, and that the entire width is monitored with several sensor paths (of different devices). For example, RFID transponders can be arranged on both sides of a conveyor belt and their sensor paths point towards the middle of the conveyor belt and in particular run (a little) over the middle. The antennas are then preferably arranged in an area of the middle so that the RFID transponders can be read by a centrally arranged RFID reader. Of course, it is also possible in principle for the antennas to be on the sides of the conveyor belt and for the RFID transponders arranged in the area of the middle of the conveyor belt to be read by RFID readers arranged on the sides.

In a preferred conveyor belt, the RFID transponders of the devices are arranged at the edge of the conveyor belt and the antennas in the middle area. The devices are preferably arranged offset from one another, so that an alternating pattern of sensor sections on the left and right is created. With an RFID reader in the middle area, where the antennas are located, the RFID transponders can be read via the relevant antennas. In this way, even wide conveyor belts can be easily monitored despite signal attenuation of the sensor section.

If one of the serial numbers is missing during the readout, which can be checked again by another revolution of the belt and/or by multiple readouts, then it can be assumed that the sensor section (the waveguide) is damaged and a longitudinal crack in the conveyor belt is suspected. Cracks in a road can be easily repaired by driving over the road with a

Vehicles with an RFID reader attached to their floor can be detected. An arrangement in which RFID transponders are arranged on the sides of a roadway, sensor sections extend over at least half of the roadway and antennas are arranged in the middle of the roadway is particularly suitable here.

A bridge can have a device on its expansion joint, with the antenna in particular capacitively coupled to the waveguide and attached to one side of the expansion joint and the rest of the device on the other side. The waveguide allows the RFID transponder to be positioned in a protected location. If the distance of the expansion joint increases, the antenna moves away from the waveguide and the data reading is increasingly disrupted. If the aforementioned vehicle with the RFID reader on the ground now drives over the expansion joint, the RFID transponder can be read multiple times, e.g. 10 times. However, if only 5 serial numbers are received during the reading, a certain distance of the expansion joint can be inferred, which is larger than if 8 serial numbers were received and smaller than if 3 serial numbers were received.

Further particularly advantageous embodiments and developments of the invention emerge from the dependent claims and the following description, wherein the patent claims of a certain category can also be developed according to the dependent claims of another category and features of different embodiments can be combined to form new embodiments.

According to a preferred device, the antenna is formed by one of the two conductors, in particular in the form of a monopole or dipole. Alternatively, the antenna is preferably formed by both conductors, in particular in the form of an inverted F-shaped antenna, particularly preferably in a linearized embodiment. This linearized embodiment has the advantage that it is very easy to manufacture and the device can be manufactured in the form of an elongated strip. It should be noted that the waveguide and antenna complement each other functionally in the invention. The antenna serves to "capture" power and signals for the RFID transponder, the waveguide for conducting them to the RFID transponder. The less power the antenna receives and passes on to the waveguide, the worse the reading of the RFID transponder will be and the greater the risk of errors or the greater the need for the performance of an RFID reader. In addition, the shape of the antenna should harmonize with the elongated structure of the waveguide and take up as little additional space as possible so that the entire device can be arranged in or on an object with minimal effort. A so-called "linearized F-antenna" or an "H-antenna" is particularly advantageous for the device, which are described in more detail below.

A "linearized F-antenna", which could also be called a "d-antenna" or "b-antenna" because of its shape, is, like the inverted F-antenna, an intermediately fed A quarter monopole (or dipole), but which runs in a main direction in the direction of the sensor path. The first conductor runs in a straight line (in the direction of the sensor path) and the second conductor initially describes a loop, which can also be achieved by punching out the loop, with the first conductor running (in a straight line) over this loop and coupling capacitively or electrically conductively with the second conductor after the loop.

Another preferred antenna structure is referred to here as an "H-antenna". In this antenna, the first and second conductors are connected to one another at their ends so that they form an inductance. A connection in this section is preferably an electrically conductive connection, but it can also be a capacitive or inductive connection, since high-frequency alternating currents flow. The waveguide is therefore basically preferably short-circuited at its end. In an end region at a predetermined distance from the connected end of the waveguide, at least one antenna is connected to one of the conductors via an electrically conductive connecting piece; preferably, each of the two conductors has an antenna that is connected to this conductor via a connecting piece. An antenna is preferably a dipole antenna or a monopole antenna and in particular has the shape of a straight conductor, which is arranged in particular parallel to the relevant conductor of the waveguide, but can also be arranged obliquely or orthogonally to the relevant conductor of the waveguide. In a parallel alignment, the antenna, conductor and connector form an H-shaped structure, which gives the antenna structure its name. The distance between the position at which the connector is connected to the conductor and the connected end of the waveguide is preferably a multiple of half a readout wavelength (under the influence of the dielectric). An antenna is preferably arranged next to or above the respective conductor and is electrically insulated from it (except for an electrically conductive connection via the connector). If each of the conductors is connected to an antenna, these antennas are preferably arranged mirror-symmetrically or rotationally symmetrically with a rotation of 180° to each other. A particularly advantageous reading of the RFID transponder is achieved if at least one antenna is a dipole antenna that is aligned asymmetrically to the connecting piece, i.e. is not connected to the connecting piece exactly at its center, with a division of the antenna arms in the range of the ratios 2:1 to 4:5 being particularly preferred.

This H-antenna, like the d-antenna, can also be an independent invention in itself. It solves the problem of creating an inexpensive and powerful antenna that is robust against mechanical influences. It can be constructed very flat, making it ideal for installation in a conveyor belt. Of course, it can have other features that are described here in connection with other antenna shapes, e.g. it can be formed from cables or metal strips.

An antenna according to the invention for a device with an RFID transponder for structural monitoring of an object comprises the following components:

- a first electrical conductor, which can be electrically or capacitively coupled with a coupling end to a first antenna connection of the RFID transponder,

- a second electrical conductor, which can be electrically or capacitively coupled with a coupling end to a second antenna connection of the RFID transponder, and

- a dielectric extended over a sensor path, wherein the two conductors together with the dielectric arranged between the conductors form a waveguide over the sensor path and at least one of the conductors is formed as an antenna at the end of the sensor path facing away from the coupling ends and wherein the antenna is a d-antenna or an H-antenna.

Preferably, an antenna is formed in a metal strip in the form of a punch at the end of a waveguide, in particular a monopole, dipole, an F antenna, an H antenna or a d antenna. The antenna structure is preferably designed such that it couples into the waveguide capacitively or electrically conductively. According to a preferred device, the two conductors with the dielectric over the sensor path are designed as a symmetrical two-wire line, coaxial cable or strip line. The course can be straight or meandering, whereby a course meandering in one direction is also considered to be "extended straight" because it also has a strip shape. A conductor is preferably designed as a flat strip, tape, net or grid. However, a conductor can also preferably be designed as a cable or as an electrically conductive structure printed on a surface. The two conductors can be of the same type (e.g. two cables or two strips) or different (e.g. one is a flat strip or a net and the other is a cable).

One or both conductors can preferably be divided into a waveguide part and an antenna part in the area where they are formed as an antenna, with the antenna part and waveguide part preferably being capacitively coupled to one another. This has the advantage that the antenna part and waveguide part can be reversibly separated from one another and reunited. This means that deformations can be measured reversibly. For example, one of the conductors is designed as a monopole or dipole. At the end of the waveguide, the two parts of the conductor (waveguide part and antenna part) are capacitively coupled to one another. If the antenna is formed by both conductors, both conductors at the end of the waveguide (waveguide part and antenna part) are preferably capacitively coupled to one another (each conductor separately).

According to a preferred device, one of the conductors is designed as a metal strip and the other conductor as a cable guided over the metal strip, this device being equipped in particular with a monopole antenna at one end. This embodiment has the advantage that a meandering course can be easily achieved by means of the cable. According to another preferred device, both conductors are designed in the form of a symmetrical twin line, in particular with a monopole, dipole antenna or inverted F antenna at one end. This embodiment has the advantage that it can be manufactured very inexpensively. According to a further preferred device, both conductors are designed as metal strips in the form of a strip line, in particular with a monopole antenna, dipole antenna, d-antenna, H-antenna or inverted F antenna at one end. This embodiment has the advantage that it can be made very flat.

According to a preferred device, the RFID transponder is arranged between the two electrical conductors. For example, one conductor is located above and the other Conductor under the RFID transponder. The antenna connections do not necessarily have to be on the same side of the RFID transponder, since with appropriate shaping of the conductor one can capacitively couple to an antenna connection on the other side of the RFID transponder. It is preferred that one of the electrical conductors at least partially covers one surface of the RFID transponder and the other electrical conductor at least partially covers the opposite surface of the RFID transponder. There could also be full coverage, which could shield the RFID transponder from external fields. However, complete coverage must not be provided for all transponders, since depending on the design of the transponder structure, an internal loop structure could be short-circuited and the system would no longer function. Therefore, partial coverage can represent a good compromise between coupling and shielding.

The waveguide part is preferably ribbon-shaped and is formed in particular from metal ribbons, e.g. from stainless steel. Alternatively, it can be formed from strands that run parallel to each other. However, it can also be formed from a ribbon and a strand.

According to a preferred device, at least one of the conductors is elastically formed in the longitudinal direction of the sensor path, in particular from spring steel or by means of a wave shape, zigzag shape or a fold. This results in a greater tolerance of the device to tensile forces or flexing forces. Particularly when used in conveyor belts on which heavy, angular loads are transported, the waveguide should not be damaged during normal operation, but only if a tear occurs in the belt. An elasticity of the device has an advantageous effect in this regard. The waveguide preferably has a wave shape, which is advantageous for flexibility. If the waveguide is belt-shaped, the waves are preferably aligned along the surface normal of the belt.

The waveguide is preferably encapsulated, in particular for use in a conveyor belt. For this purpose, it can be cast in a plastic material (e.g. identical to the plastic material of a conveyor belt) or bonded between adhesive tapes, in particular Kapton tapes.

According to a preferred embodiment, the ends of the two conductors forming the waveguide which are facing away from the antenna (i.e. those ends which are intended to be coupled with the RFID transponder) with two flat contacts that are formed on a circuit board. These contacts can be, for example, copper contacts on this circuit board. Each of the two conductors is connected to its own contact, e.g. soldered or welded. The contacts are arranged on the circuit board so that they correspond to the arrangement of the antenna connections of the RFID transponder. The RFID transponder is preferably shaped as an adhesive label and glued to the circuit board so that the antenna connections are above the two contacts. Since the conductors are connected to the contacts, it is preferred that the RFID transponder is glued to the side of the circuit board that faces away from the contacts. The coupling between contacts and antenna connections is capacitive in this case.

A preferred device additionally comprises at least one sensor from the group of temperature sensors, pressure sensors, humidity sensors, acceleration sensors, brightness sensors and magnetic field sensors. The device is preferably designed to send sensor data from the at least one sensor via the RFID transponder. However, it should be noted here that reading the sensor and sending its data could take a relatively long time. In this regard, it can be advantageous to send this data only a few times (e.g. only once or twice) and the serial number of the RFID transponder more frequently.

The sensor path does not necessarily have to be particularly long. For some applications, it may be sufficient if the sensor path (i.e. the waveguide) is a few centimeters long (especially shorter than 10 cm) or even just a few millimeters long (especially shorter than 1 cm). The main thing is that the waveguide can be destroyed or the antenna can be separated from the waveguide.

Since objects can be subject to wear and tear in addition to destruction, it is advantageous to embed several devices or at least their sensor sections in the object at different distances from the surface of the object. This is particularly advantageous for conveyor belts (with regard to their transport surface). For example, recesses of different depths can be created in a conveyor belt or recesses can be provided with spacers of different thicknesses under the devices so that different sensor sections run at different distances from the surface of the object, e.g. the conveyor belt. It is also possible to embed the sensor sections of different devices one above the other in a recess. If the surface is now worn, the sensor sections closest to this surface are destroyed first by mechanical stress and/or flexing, which indicates wear.

The arrangement of devices at different heights can certainly be done in combination with a staggered arrangement of devices. In this way, even spatially extensive objects, e.g. very wide conveyor belts, can be effectively monitored with regard to their wear.

It is quite possible that objects do not have a homogeneous interior, but rather structures that serve to provide strength. For example, conveyor belts can have mats made of a fabric, e.g. glass fiber mats, in their interior (often in the middle) or wire ropes that are often arranged below the middle (seen from the conveyor surface). The devices can be arranged both above and below such a structure. Reading does not necessarily have to take place from the side facing away from the structure. The structure can also be located between the antenna and the RFID reader. As far as wire ropes are concerned, they can have a positive effect on signal transmission due to their reflective properties.

As far as fabric mats, especially glass fiber mats, are concerned, these can also have a positive effect on signal transmission and also have a reducing effect on the attenuation of the sensor path. It is therefore preferred that the device has a fabric mat on at least one side, which completely covers at least the antenna and/or the waveguide (and preferably also the RFID transponder). Such a fabric mat can also have a beneficial effect on the stability of the device due to its mechanical properties.

The invention is explained in more detail below with reference to the attached figures using exemplary embodiments. In the various figures, identical components are provided with identical reference numbers. The figures are generally not to scale. They show:

Figure 1 shows an example of a device according to the invention in side view,

Figure 2 shows an example of a device according to the invention from above, Figure 3 shows an example of a strip-shaped device from above,

Figure 4 an example of a folding of ladders in side view,

Figure 5 shows an example of a device according to the invention with a parallel line from above,

Figure 6 shows an example of a device according to the invention,

Figure 7 shows an example of an object according to the invention and a monitoring system according to the invention in a perspective view,

Figure 8 is a block diagram of an embodiment of a method according to the invention,

Figure 9 shows an example of an object according to the invention with devices according to the invention in plan view,

Figure 10 shows an example of an object according to the invention with devices according to the invention in side view.

Figure 1 shows an example of a device 1 according to the invention for structural monitoring of an object 6 (see e.g. Figure 7). The device 1 comprises an RFID transponder 2, a first electrical conductor s, a second electrical conductor 4 and a dielectric 5 extended over a sensor path S.

The RFID transponder 2, which is designed to send data N, is electrically or capacitively coupled to the two conductors 3, 4 at its antenna connections 2a, 2b (see following figures). For coupling, the conductors 3, 4 do not necessarily have to be soldered to the antenna connections 2a, 2b, but they can also be placed on them, clamped to them or glued to them, whereby it is not dramatic if there is a thin layer of adhesive between the conductors 3, 4 and the antenna connection 2a, 2b, since in this case a capacitive connection is present. As can be seen in this side view, the conductors 3, 4 run parallel to each other across the sensor path, but are electrically insulated from each other by the dielectric 5 and thus form a waveguide S into which waves from the outside cannot couple or can only couple very poorly. This waveguide S serves as a conductor for waves that couple to the antenna A at its end and for signals from the RFID transponder 2 at its other end, which are emitted via the antenna A (or taken from the field as a load).

If the waveguide S is severed somewhere on the sensor path S or the antenna A is separated from the waveguide S, the RFID transponder can neither receive nor transmit and an RFID reader 7 (see Figure 7) can no longer read it.

Figure 2 shows an example of a device 1 according to the invention, in which the antenna A is formed by the first conductor 3 and has the shape of a monopole. The first conductor 3 (e.g. a cable) runs in a wave-like manner over a band-shaped second conductor 4.

As can be clearly seen in the view from behind (framed in dashed lines), the first conductor 3 lies directly on the first antenna connection 2a and couples with it, e.g. electrically conductively. The second conductor 4 lies under the RFID transponder and couples with the second antenna connection 2b capacitively.

Figure 3 shows an example of a strip-shaped device 1 from above. The two conductors 3, 4 are designed as a strip line with the intermediate (and therefore not visible) dielectric 5 over the sensor section S. The antenna A is formed from the two conductors 3, 4 as an inverted F antenna.

Figure 4 shows an example of a folding of conductors 3, 4 in side view. Unlike a cable (see Figure 2), which can simply be laid in the form of a wave to increase elasticity, this is not so easy to do with strips. Shown here are two strip-shaped conductors 3, 4, such as those shown in Figure 3, for example, which are folded to create elasticity.

Figure 5 shows an example of a device 1 according to the invention, in which the two conductors 3, 4 with the dielectric 5 are connected via the sensor path S as a symmetrical two-wire line. As can be clearly seen in the view from behind (framed in dashed lines), both conductors 3, 4 lie directly on the antenna connections 2a and couple with them. Figure 6 shows an example of a device according to the invention in which waveguides S and antennas A extend to both sides of the RFID transponder 2. This can be read from both sides (with a limited range) and can provide location information in this regard. If the reading from the right does not work, there is damage to the right of the RFID transponder 2; if the reading from the left does not work, there is damage to the left of the RFID transponder 2.

This example also shows a special antenna structure that enables a very inexpensive design with strip-shaped conductors 3, 4. This is a "linearized F antenna", which could also be called a "d antenna" or "b antenna" because of its shape. Like the inverted F antenna, it is an intermediately fed A/4 monopole, but it runs in a main direction in the direction of the sensor section S. One of the conductors 3, 4 (the second conductor 4 on the left and the first conductor 3 on the right) runs in a straight line and the other conductor 4, 3 (the first conductor 3 on the left and the second conductor 4 on the right) initially describes a loop, which was achieved here by punching out, with one conductor 3, 4 in turn running (in a straight line) over this loop and coupling capacitively or electrically conductively to the other conductor after the loop. This makes it possible to create a space-saving, strip-shaped device.

On the other side, an H-antenna is shown. Basically, it is preferred that the antennas on both sides are constructed the same. However, different antennas can also be possible. In the "H-antenna" antenna, the first conductor 3 and the second conductor 4 are electrically connected to one another at their ends. In the end regions of the conductors 3, 4, an antenna A is connected to the respective conductor on each side via a connecting piece V. These antennas A are designed as dipole antennas and are arranged parallel to the respective conductor 3, 4, so that an H-shape is created on each side. For advantageous reception, the antennas A are arranged rotationally symmetrically with a rotation of 180° to one another.

Figure 7 shows an example of an object 6 according to the invention and a monitoring system 8 according to the invention in a perspective view.

The object 6 here is a conveyor belt 6 and comprises a number of devices 1 as shown in the previous figures. These devices 1 are inserted into grooves R of the conveyor belt 6 and by closing the grooves R. In the case of conveyor belts 6 such as those used to transport coal or stone, this can be done, for example, by first cutting out a strip of the material of the conveyor belt 6 to form the groove R, then inserting the device 1 and finally gluing or vulcanizing the cut-out strip back in. The dielectric 5 of the device 1 can certainly be formed from melted and solidified material of the conveyor belt 6 or the strip.

A device 1 with a meandering course of the conductors 3, 4, as can be seen in Figures 2 and 5, for example, can run lengthways over a weld seam or splicing seam of the conveyor belt (i.e., transversely to the belt and lengthways to the transverse line of weakness). If this line of weakness breaks, the meandering waveguide S also breaks.

To form a monitoring system 8 for structural monitoring of an object 6, the devices 1 should all be located in the object 6. They can then be read by an RFID reader 7, which is positioned here at the edge of the conveyor belt 6, where the antennas on the devices 1 are located.

Figure 8 shows a block diagram of an embodiment of a method according to the invention for structural monitoring of an object 6 with a monitoring system 8 as shown, for example, in Figure 7 (where the conveyor belt 6 is fully equipped with the devices 1).

In step I, data N, here possibly only a serial number N, of an RFID transponder 2 of one of the devices 1 of the monitoring system 8 is read out using an RFID reader 7 of the monitoring system 8. The data N can be read out several times from the RFID transponder 2 before the data N of another RFID transponder 2 is read out.

In step II, a value W for a structural change in the object 6 is derived from the number of data N read out. Other data can also be read out for this purpose, e.g. an RSSI value. However, it is sufficient to simply determine how often a serial number N has been reported back (e.g. not once: "There is a defect", less than readout attempts: "There could be an impairment"). In step III, this value is saved for later investigations or statistics and is used to issue a warning if it is detected that a critical condition exists, e.g. if a serial number N of an RFID transponder could not be received. With regard to Figure 7, it should be noted that in a conveyor belt 6, the RFID transponders 2 are regularly and repeatedly moved past the RFID reader 7, so that a certain statistical evaluation is possible. In a monitored road or bridge, an RFID reader 7 can simply be mounted on the floor of a vehicle and driven over several times for statistics.

Figure 9 shows an example of an object 6 according to the invention in the form of a conveyor belt 6, with devices 1 according to the invention in a top view. The RFID transponders 2 of the devices 1 are located at the edge of the conveyor belt 6 and the antennas A in the middle area. The devices 1 are arranged offset so that an alternating pattern of sensor sections S on the left and right results. With an RFID reader 7 in the middle area, where the antennas A are located, the RFID transponders 2 can be read via the relevant antennas A. In this way, even wide conveyor belts 6 can be easily monitored despite signal attenuation of the sensor section S.

Figure 10 shows an example of an object 6 according to the invention in the form of a conveyor belt 6 with devices 1 according to the invention in a side view. The devices 1 are located here at different depths of the conveyor belt 6. The devices 1 located at the top are the first to be destroyed when the conveyor surface wears out (here in the picture above). This allows a degree of wear to be indicated. As can be seen in the picture, devices 1 can also be arranged directly on top of one another. The arrangement shown here can certainly also be present in this form in Figure 9, i.e. an offset arrangement can be present in combination with an arrangement at different depths.

Finally, it should be pointed out once again that the devices described in detail above are merely exemplary embodiments which can be modified in a variety of ways by a person skilled in the art without departing from the scope of the invention. Furthermore, the use of the indefinite articles "a" or "an" does not exclude the possibility that the features in question may also be present multiple times. Likewise, terms such as "element" or "device" do not exclude the possibility that these may also consist of several, possibly spatially separate subunits. The expression “a number” is to be understood as meaning that the number is greater than zero (i.e. “at least one”).

List of reference symbols

1 device

2 RFID transponders 2a antenna connection

2b Antenna connection

3 conductors

4 conductors

5 Dielectric 6 Object / Conveyor belt

7 RFID reader

8 Monitoring system

A antenna

N Serial number / data R Groove

S Sensor path / waveguide

V connector

W value

Claims

Patent claims

1. Device (1) for structural monitoring of an object (6), comprising:

- an RFID transponder (2) designed to send data (N),

- a first electrical conductor (3) which is electrically conductively or capacitively coupled to a first antenna connection (2a) of the RFID transponder (2),

- a second electrical conductor (4) which is electrically conductively or capacitively coupled to a second antenna connection (2b) of the RFID transponder (2), and

- a dielectric (5) extending over a sensor path (S), wherein the two conductors (3, 4) together with the dielectric (5) arranged between the conductors (3, 4) form a waveguide (S) over the sensor path (S), and wherein at least one of the conductors (3, 4) is formed as an antenna (A) at the end of the sensor path (S) facing away from the RFID transponder (2).

2. Device according to claim 1, wherein the antenna (A) is formed by one of the two conductors (3, 4), in particular in the form of a monopole or dipole, or wherein the antenna (A) is formed by both conductors (3, 4), in particular in the form of an inverted F-shaped antenna (A), particularly preferably in the form of a linearized F-antenna or an H-antenna, preferably wherein the antenna is formed in a metal strip in the form of a punch at the end of a waveguide.

3. Device according to one of the preceding claims, wherein the two conductors (3, 4) with the dielectric (5) over the sensor path (S) are designed as a symmetrical two-wire line, coaxial cable or strip line or wherein a conductor (3, 4) is designed as a strip, band, net or grid and/or a conductor (3, 4) is designed as a cable and/or a conductor (3, 4) is designed as an electrically conductive structure printed on a surface, preferably wherein

- one of the conductors (3, 4) is designed as a metal strip and the other conductor (4, 3) is designed as a cable guided over the metal strip, in particular with a monopole antenna at one end or

- both conductors (3, 4) are designed in the form of a symmetrical twin line, in particular with a monopole antenna, dipole antenna or inverted F antenna at one end, or both conductors (3, 4) are designed as metal strips in the form of a stripline, in particular with a monopole antenna, dipole antenna or inverted F-antenna at one end.

4. Device according to one of the preceding claims, wherein the RFID transponder (2) is arranged between the two electrical conductors (3, 4), preferably wherein one of the electrical conductors (3, 4) at least partially covers a surface of the RFID transponder (2) and the other electrical conductor (4, 3) at least partially covers the opposite surface of the RFID transponder (2).

5. Device according to one of the preceding claims, wherein at least one of the conductors (3, 4) is elastically formed in the longitudinal direction of the sensor section (S), in particular from spring steel or by means of a wave shape, zigzag shape or a fold.

6. Device according to one of the preceding claims, additionally comprising at least one sensor from the group consisting of temperature sensors, pressure sensors, humidity sensors, acceleration sensors, brightness sensors and magnetic field sensors, wherein the device is designed to send sensor data of the at least one sensor via the RFID transponder (2).

7. Object (6), in particular a conveyor belt (6) or a building, comprising a number of devices (1) according to one of the preceding claims, wherein the number of devices (1) are attached to or in the object (6), in particular in the region of a structural weakening line of the object (6).

8. Object according to claim 7, wherein the object (6) is designed as a conveyor belt (6) and at least one of the devices (1) is arranged in or on the object (6) such that its sensor path (S) runs substantially transversely to the length of the object (6), wherein the device (1) is preferably surrounded by material of the object (6).

9. Monitoring system (8) for structural monitoring of an object (6), the monitoring system (8) comprising

- an RFID reader (7) and - an object (6) according to claim 7 or 8 or a number of devices (1) according to one of claims 1 to 6 and an object (6), wherein the devices (1) are attached or at least attachable to or in the object (6).

10. Method for structural monitoring of an object (6), in particular a

Conveyor belt (6), a building or a storage system, with a monitoring system (8) according to claim 9, the method comprising the steps:

- Reading of data (N), in particular at least one serial number (N), of a

RFID transponder (2) of one of the devices (1) of the monitoring system (8) with an RFID reader (7) of the monitoring system (8), wherein the data (N) of the RFID transponder (2) are preferably read out several times before the data (N) of another RFID transponder (2) are read out,

- Deriving a value (W) for a structural change in the object (6) from the number of data read out (N) and/or from an RSSI value measured in addition to the readout.