Patent Application
20200371271
The present invention relates to the field of RFID identification sensors for non-metallic tubes, used to make buried pipes, and in particular an omnidirectional RFID identification sensor suitable for great depths.
Polymers (Polyethylene PE, Polypropylene PP, PVC, PRV etc. . . . ) are materials widely used for the realization of underground pipes, particularly allowing the distribution of water, gas, electricity, telecommunications.
The advantage of detecting and/or identifying underground pipes is clear and first techniques have been developed to enable Radio Field Identification Detection, RFID, of an underground pipeline.
The international patent application WO2011157941 filed on Jun. 14, 2011 by the COMMISSARIAT A L'ENERGIE ATOMATIQUE ET AUX ENERGIES ALTERNATIVES, relates to a wetland antenna which can be used to carry out an RFID sensor/transponder for a pipe buried polymer. That prior art discloses provides a first significant solution to the problem of tolerance vis-à-vis the external environment. That working of such known antenna is illustrated in
However, the implementation of this antenna is very sensitive to the manufacturing process. Indeed, the distributed capacity is a function of three direct parameters: the width of each segment (300t) and (300d), the thickness of the substrate between each segment (300t) and (300d), and the alignment of these segments with each other. Finally, a fourth, indirect parameter, appears to be the value of the permittivity of said substrate, which can vary depending on the humidity and the temperature. Additionally, with regard to the manufacturing cost, the process used requires the mandatory presence of a substrate, which must be printed with double-sided metal tracks.
For its part, RYB has filed a patent application WO 2012/062471 concerning a polymer tube equipped with an identification sensor or RFID tag.
In general, it should be recalled that the wireless communication and contactless identification technology, designated under the name RFID, relates more particularly to the HF field of technology (13.56 MFIz in our example) for which communication is mainly done by magnetic field. In this frequency range the reading distances are generally less than 1 meter. The system then consists of a transmitter (active principle, power generator) and a transponder (passive principle, remote powered)
As illustrated in
The antenna (100) consists of one or more turns enabling part of the electromagnetic emission power of an RFID transmitter located on the ground to be collected. In this regard, the antenna has a minimum area allowing the activation of the RFID chip. In practice, this surface corresponds to the capture of a minimum power in relation to the maximum emission power of the reader, the detection distance and the power requirements of the RFID chip. The number of turns will be related to the minimum activation voltage of the RFID chip.
The antenna has an inductance designated Lant. This inductance value is a function of the geometry of the antenna. As an example, an approximation for a circular antenna composed of N contiguous or superimposed turns, of a radius R and of a diameter of conductor a is the following:
L=μ0*R*N2*(ln(8*R/a)−2) with μ0=4π*10−7 and Ln being the natural Logarithm operator.
The RFID chip can be considered as a capacitor noted Ctag. An example value is around 20 pF (20*10−12F)
The assembly must resonate at a frequency which is close to the frequency of the signal, and as is known to a person skilled in the art, the equation which gives the resonant frequency is: f0=1/2π√{square root over (Lant+Cacc)} with Cacc=C102+Ctag for
If Lant is fixed by the geometry of the antenna, f0 is imposed by the system, there only remains as an adjustment variable Cacc. This value is given to us by the well known relationship:
C
acc=1/4π2*f02*Lant
Other techniques can be used, as in
Furthermore, it should be noted that, to mitigate the effects of frequency drifts (drifts of component values linked to temperature or to dispersion due to tolerance, or to the environments in which the transponders are located), conventional techniques impose a relatively low quality factor (generally around 30 to 40). However, the more the antenna surface and/or the number of turns increases, the more Lant increases, the quality factor being proportional to Lant. The latter therefore increases, until becoming problematic for an industrialist who envisages the mass production of RFID tags for buried polymer pipes. In fact, when Lant increase (be it an increase in surface area or an increase in the number of turns) one notices that Cacc must decrease in order to be able to keep the circuit resonating at value f0. If for a given realization we obtain Lant=11 H (11*10−6H), with for example f0=13.56 MHz (13.56*106 Hz), then Cacc=12.52 pF.
It can then be seen that it is practically impossible to carry out a circuit with the components in parallel, as illustrated in
The use of the coupling process illustrated in
Furthermore, it has been found that none of the known solutions, and in particular the aforementioned solution described in the above-mentioned patent application WO 201 1 157941, does not guarantee a good tolerance on the tuning frequency. It can be seen that this frequency f0 will depend on 3 separate direct parameters: the process for producing the turns (100, 200x) (influence on the value of the inductance), the tolerance on the tuning capacities (102, 202x), and finally the tolerances on the parasitic capacities (280x, capacity of (201)). A 4th factor, which is indirect, is the operating temperature, which will introduce a drift of the different values (essentially the capacities) compared to a nominal temperature (typically 25° C.)
For variations due to temperatures, measurements have been taken, and are illustrated in
If the tolerances on the component values are taken into account, for example a variation of 2% on the nominal value of the tuning capacity results in a variation of 130 kHz on the resonance frequency.
Thus, without taking into account other influences (due to the environment in particular) we have a minimum of 270 kHz of possible variation on the resonance frequency.
This particular problem was significantly addressed by the international patent application PCT/EP2017/074142 dated Sep. 22, 2017 filed by the applicant of the present application, claiming priority from the French patent application FR16/10392 dated Sep. 23, 2016, using an ‘RFID tag based on a specific antenna layout comprising:
In this way, an RFID tag is carried out which can allow the identification of a polymer tube buried at great depth.
On the other hand, numerous measurements and experiments have shown that if this RFID tag thus designed makes it possible to detect and identify tubes to a great depth, the effectiveness of this becomes dependent on the position that the latter takes relative to the buried tube.
In a favorable arrangement, the label would be positioned on top of the buried tube, so as to present its antenna in a horizontal plane, and therefore perpendicular to the axis separating it from a surface detector.
In a less favorable arrangement, if the tube is not ideally positioned in its trench—which can happen when the tube is towed inside a trench or a conduit—the label may not appear ideally with an optimal antenna orientation to receive the maximum magnetic flux from the surface detector.
In this situation, the RFID tag may simply not be visible to the surface detector.
The invention aims to solve this crucial problem.
The object of the present invention is to achieve a device for detecting an RFID chip buried at great depth—up to three meters—allowing omnidirectional detection and identification of a non-metallic polymer pipe.
Another object of the present invention is to achieve a device for detecting an RFID chip, or transponder, allowing great tolerance relative to the rotation of the tube relative to its generator axis within the trench or the conduit buried underground.
It is a third object of the present invention to provide a transponder at low manufacturing cost and providing better energy efficiency compared to existing embodiments.
It is another object of the present invention to allow the production of an RFID tag which can be used as a marker integrated into a tube or a pipe laid by towing, that is to say without trench.
The invention achieves these aims by means of a transponder for a wireless communication and contactless identification system, of the RFID type, intended to be affixed to a buried polymer pipe, said transponder comprising:
an RFID chip;
an electronic switching circuit coupled to said RFID chip;
a first antenna coupled to said switching circuit, said first antenna having a surface covering a first part of the external surface of said polymer pipe;
a second antenna coupled to said switching circuit, said second antenna having a surface covering a second part of the external surface of said polymer pipe, said second part being distinct from said first part;
The switching circuit is configured for:
In a preferred embodiment, the transponder comprises a set of three antennas coupled to the switching circuit, the coverage area of each of said first, second and third antennas corresponding to an angle of 120 degrees. The switching circuit is then configured to couple the RFID chip to that among the first, second and third antenna which has the highest voltage, in which said switching circuit decouples the other two antennas having the lowest voltages.
Alternatively, the invention allows the realization of a transponder for a wireless communication and contactless identification system, of the RFID type, intended to be affixed to a buried polymer pipe, which comprises at least:
a first RFID chip associated with a first antenna, said first antenna having a surface covering a first part of the exterior surface of said polymer pipe;
a second RFID chip associated with a second antenna, said second antenna having a surface covering a second part of the external surface of said polymer pipe, said second part being distinct from said first part.
The first and second RFID chips are configured to include a field for storing an identification element, UID, of said second chip and first RFID chip, respectively. The identification elements are used during a communication session between a transponder and an external reader (located on the surface) to determine that the two RFID chips belong to the same buried pipe.
Preferably, the transponder comprises a set of three RFID tags forming a macro-label, covering a surface of the external envelope of the pipe corresponding to an angle of 120 degrees, in such a manner that the set of three RFID tags appears as a sleeve wherein the pipe is being inserted. Each of the three RFID chips associated within the same macro-tag carries in its internal memory the identification elements, UID, of the other two RFID chips, so that a surface reader can associate the three RFID chips with the same pipeline.
Preferably, each of the antennas associated with the same RFID chip comprises:
a set of antenna segments made up of electrical conductors constituting at least a first and a second antenna element,
a printed circuit comprising an RFID chip and at least one tuning capacity as well as a connector allowing the electrical coupling of said antenna segments. The antenna segments are arranged close to each other, at a distance of less than 3 mm and preferably less than 1 mm, so as to allow the appearance of coupling capacitances capable of widening the tolerance band on the frequency RFID resonance.
Preferably, the RFID chips include means of communication of the identity, the characteristics of manufacture of the tube, and the location of the tube.
More specifically, the transponder is intended for the identification of a fluid distribution pipe (e.g. drinking water) or gas, protection of electric cable or fiber optic cable.
Other characteristics, object and advantages of the invention will appear on reading the description and the drawings below, given only by way of non limiting examples. In the accompanying drawings:
We will now consider a particular embodiment of an RFID transponder intended for producing an omnidirectional RFID tag for a pipe or pipe intended to be buried underground, which becomes significantly insensitive to the orientation of the pipe in the trench. We typically consider the example of a HDPE (High Density Polyethylene) tube, suitable for the construction of a pipeline for the supply of drinking water, gas distribution, sanitation, protection of electric cable and optical fiber. Consider in particular the example of a polyethylene multilayer tube for buried pressure pipes, consisting of a high density polyethylene tube PE 80 or PE 100 meeting the standard EN1555. More specifically, the RFID tag will be used to transmit information relating to the identity, manufacturing characteristics of the tube, and the location of the tube.
The presentation successively describes:
The presentation will take up a significant part of the teaching of application PCT/EP2017/074142.
Referring to
In the embodiment illustrated in
In general, each antenna element consists of one or more individual physical conductive elements—or antenna segments designated by the generic reference 200x (not shown in
Thus, the antenna elements 203-1, . . . 203-x can take various and varied configurations, based on multiple combinations of antenna segments 200x.
In general, each antenna segment 200x consists of an electrical conductor, isolated or not, arranged within a multi-strand or single-strand cable, without restriction of section. Each antenna segment 200x can differ from another in the same embodiment, both in geometry and in the number of turns, thus allowing great possibilities of variation in the design of the RFID tag.
With regard to the capacitors 202-1, 202-2, . . . 202-x shown in
The antenna segments 200x composing the antenna elements 203-1, . . . , 203-x, can be arranged on a support according to different embodiments, as illustrated in
More specifically,
A second topology is illustrated in
Finally,
The topologies illustrated in
Clearly, there are no limits in the possibilities of combining the different topologies illustrated.
We will now describe, with reference to
In general, the connector 281 is made to allow the electrical coupling of the different antenna segments, to each other but also to the capacitors (s) 202-1, 202-2, . . . 202x, and to the RFID chip 201, in order to realize the oscillating element, as shown in the electrical diagram of
In its simplest form, the connector can be based on a integrated circuit on which is disposed, the RFID chip 201, and the different capacitor(s) 202-1, 202-2, . . . 202x.
For the sake of simplicity, there has been shown, in the embodiments of
The different antenna segments are electrically connected via electrodes 284 and 285, which may be any number.
For example, the connector 281 of
The printed circuit/connector includes:
The printed circuit also includes:
In a preferred embodiment which is illustrated in the diagram of
Referring to
More specifically, the printed circuit includes a first input electrode 284-1, a second input electrode 284-2, a third input electrode 284-3, a fourth input electrode 284-4, a fifth electrode input 284-5 and a sixth input electrode 284-6 allowing the connection of a first end of a first antenna segment 801, of a first end of a second antenna segment 802, of a first end of a third segment d antenna 803, of a first end of a fourth antenna segment 804, of a first end a fifth antenna segment 805 and of a first end of a sixth antenna segment 806, respectively.
The printed circuit further comprises a seventh output electrode 285-1), an eighth output electrode 285-2, a ninth output electrode 285-3, a tenth output electrode 285-4, an eleventh output electrode 285-5 and a twelfth output electrode 285-6 allowing the connection of a second end of the first antenna segment 801, of a second end of the second antenna segment 802, of the second end of the third antenna segment 803, of the second end of the fourth antenna segment 804, of the second end of the fifth antenna segment 805 and the sixth antenna segment 806, respectively.
The printed circuit of
Preferably, the first, second and third antenna segments 801, 802 and 803 are integrated within a first three-wires electric cable and the fourth, fifth and sixth antenna segments 804, 805 and 806 are integrated into the within a second three-wire cable, as illustrated in the embodiment of
The arrangement of the antenna segments (200x) implemented in one of the embodiments (
The structure of the antennas is determined so that the conductors are spaced 1 to 3 mm apart. In one of our embodiments, the conductors are molded 3 by 3 strands with a component having an εr≅5. This gives us a linear capacity (280) between each of the 3 strands taken 2 to 2 with a value between 50 and 75 pF/m.
The plurality of antenna segments (200x) forms the sensing surface, this surface must be sufficient to meet the need for the power supply of the RFID chip (201). The total number of turns from the plurality of antenna segments is such that the voltage across the RFID chips (201) is sufficient to activate it.
The frequency tuning is the first result of the serialization of a part of the inductance of the global antenna (plurality of (200x)) and others by the plurality of capacities (202x) connected in series.
However, the distributed capacities (280), although having a small impact on the resonance frequency, nevertheless plays a role in the calculation of the tuning capacity.
But the real role of these distributed capacities (280) is, on the one hand, to attenuate the influence of the parasitic capacities introduced by the external environment, and on the other hand, to allow a widening of the tolerance on the frequency agree as shown in
On some examples of embodiments, we will look at what variation in the tuning frequency guarantees us a decrease of less than 10 cm in the maximum reading distance. Two tests relate to embodiments carried out according to the teaching of the aforementioned patent application WO2011157941 (M1), while two other embodiments (M2, M3) relate to the invention.
On a test realization (M1), the turns were spaced 10 mm from each other, so that the distributed capacity is reduced to the maximum, and we get:
fera4,min=13.525 MHz and fM1,max=13.745 MHz, thus ΔM1=220 kHz
On the embodiment of
feis2,min=13.495 MHz and fM2,max=13.825 MHz, thus ΔM2=330 kHz
This represents a 50% improvement in the tolerance band.
On existing realizations, corresponding to the teaching of the aforementioned patent application WO2011157941 (M1), an estimate has been made of the width of the tolerance band (
fhum,min=13.535 MHz and fhum,max=13.810 MHz, thus Δhum=275 kHz
In the embodiment (M3) of
feis2,min=13.540 MHz and fM3,max=13.930 MHz, thus ΔM3=390 kHz
This represents an increase of more than 40% in the tolerance band.
In addition, in this embodiment (M3), the antenna surface is 63 cm2, compared to the 132 cm2 of the solution permitted by the patent application WO2011157941 cited above, for a detection distance greater than 30 cm (180 cm instead of 150 cm). In an embodiment described above, a reading distance of 144 cm was obtained for an area of 19.6 cm2. From an interpolation curve (calculated from various embodiments), it could be estimated that an area of 23.25 cm2 was necessary to reach 150 cm, or 6 times less area than the recommended solution by the aforementioned patent application WO2011157941.
As we can see, the invention therefore makes it possible to significantly increase the tolerance range of the tuning frequency, and in addition, to gain energy efficiency, since we need less capture area compared to tags. existing for the same detection distance.
2) First Embodiment: Omnidirectional RFID Tab with Disconnectable Antennas
This first embodiment will be described in relation to
More specifically,
Each of the two antennas 11 and 12 is coupled to an electronic circuit 20 comprising within it, or itself coupled to a single RFID chip 21.
In practice, several configurations are possible for placing two RFID antennas one next to the other, juxtaposed or not, according to various criteria and required performance. Once attached to the pipe, we can cover these polypropylene antennas to ensure protection.
The outputs of switches 16 and 17 are coupled to the RFID chip 21 so that, as a function of the voltage sensed by each of the antennas 11 and 12, the comparator 15 controls the two switches 16 and 17 to:
More specifically, the first tripler comprises:
Similarly, the second tripler includes:
The circuit of
The electronic switching circuit 20 makes it possible, as we have seen, to couple two antennas to a single RFID chip.
The inventors have however discovered that the most promising results can be obtained by associating, in this embodiment, not two but three antennas with a single RFID chip according to a very specific arrangement, and illustrated in
Referring to
Each of the three antennas 51-53 is coupled to an electronic switching circuit 50, which may or may not be similar to that already described above, and the switching circuit 50 is configured to couple the RFID chip to that among the first, second and third antenna which has the highest voltage.
The switching circuit thus ensures the coupling of this specific antenna to the RFID chip while decoupling the other two antennas having the lowest voltages.
In this way, it is possible to produce, according to this first embodiment, an omnidirectional RFID transponder capable of operating to a great depth.
We will now describe another particularly effective embodiment.
We now describe a second embodiment, which turns out to be the embodiment particularly preferred by the inventors, and which makes it possible to avoid the use of the electronic switching circuit.
In general, the inventors have discovered the possibility of obtaining omnidirectional detection, insensitive to the orientation of the pipe in the trench, provided that a specific RFID chip associated with each of the antennas is provided and that a logical processing of the communication likely to occur between the RFID chips and the transmitter . . . .
Such a transponder will be composed of:
To allow the transponder to operate, provision is also made to insert in each of the RFID chips logical information making it possible to communicate the grouping of the two RFID chips produced within the pipeline. In a particular embodiment, the first RFID chip is configured to include a field allowing the storage of an identification element or serial number, Unique Identifier (UID), of the second RFID chip. Conversely, the second RFID chip is configured to include a field allowing the storage of an identification element, UID, of the first RFID chip.
The RFID chips are then configured to transmit this information to a surface detector or reader as soon as they are activated. Thus the surface detector becomes informed of the logical grouping produced between the two RFID chips, and incidentally can determine that the two RFID chips belong to the same buried polymer pipe.
In a particularly effective embodiment, inspired by the arrangement of
Preferably, as illustrated in
We can see that the transponder includes:
As in the configuration of
So when a chip is activated by the detector, it will be able to send it the UID number of the two other RFID chips associated with it within the same RFID tag. From this moment, the detector knows that these three UID identification numbers are associated within the same group. The software executed within the surface detector can then, whatever one of the three chips activated during detection/localization, treat it correctly as if it saw only one RFID transponder located on the pipeline.
We now describe, in relation to
In a step 91, the surface detector starts an RFID transmission or an attempt of transmission by generating an electromagnetic signal intended for the recognition of an RFID tag buried in the ground.
In a step 92, the method detects a potential activation of one of the three RFID chips belonging to the same logical grouping, for example the chip 61. In general, only the RFID chip 61-71-81 will be activated, which will be associated with a most favorably positioned antenna and which will receive sufficient energy from the surface detector. Once activated, the communication operates according to the standard provided for in the RFID standard and which, for the sake of brevity, it is not necessary to reproduce here.
It will simply be noted that, in a step 93, the surface detector receives communication of the information stored in the newly activated chip, in particular by reading the content of the specific field of the RFID chip intended for the storage of the UIDs of potentially associated chips within the same transponder. Thus, the surface detector receives communication by the RFID chip 61 from the two other identifiers of the chips 71 and 81 which form the same logical unit within the transponder fixed on the pipe 10.
In a step 94, the surface detector then proceeds to store the UID identifiers of the two other sister chips of the newly activated RFID chip 61. This storage takes place in a local database stored in the memory of the surface detector.
Then, in a step 95, the detector compares the UID number of the newly activated chip with the numbers already stored in memory in the aforementioned database.
If the UID number does not appear to be already stored, then the process goes to a step 96 where the activation of the RFID chip 61 is confirmed as allowing an update of the database of discovered pipes.
On the contrary, if the test in step 95 proves to be positive, that is to say that the UID number of the activated chip corresponds to a number already previously stored in memory, then the detector does not take into consideration the UID of the newly activated chip to update the database of discovered pipelines, because it belongs to a logical grouping already detected beforehand and therefore to an already identified transponder.
The process described thus makes it possible, as can be seen, to avoid the detector concluding that there are two separate pipes, respectively associated with two separate RFID chips. Such logical processing thus considerably simplifies the solution and the development of an omnidirectional RFID transponder, since it is no longer necessary to consider the design and manufacture of an electronic switching circuit.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1771307 | Dec 2017 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/083546 | 12/4/2018 | WO | 00 |
