JP7101462B2 - Methods and sensor devices for determining the permittivity of layers - Google Patents

Description

The present invention relates to a method and a sensor device for determining the dielectric constant and / or wetness of a layer, particularly Sanwa soil.

Accurate knowledge of the wetness of materials and objects is of great importance in many fields. For example, in the field of construction, a limit value is set for the wetness of Sanwa soil, and when covering the floor with parquet or tile, this limit value must be observed in order to avoid the wetness obstacle. Therefore, it is often the case that the wait is longer than necessary to ensure that the predetermined limit is not exceeded.

One option for accurately determining the wetness of Sanwa soil is to place a measuring device on Sanwa soil itself, which is disclosed in, for example, Patent Document 1. However, this kind of wetness sensor is built into Sanwa soil and is not reusable.

International Publication No. 2013/170973A1 Pamphlet

Therefore, there is a demand for a low-cost, easily handleable, and reusable sensor device for determining the wetness of an object such as Sanwa soil.

The present invention is a method for determining the dielectric constant and / or wetness of a layer having the constituent requirements of claim 1, and for determining the dielectric constant and / or wetness of a layer having the constituent requirements of claim 8. Regarding the sensor device.

Therefore, in the first aspect, the present invention relates to a method for determining the dielectric constant and / or wetness of a layer, particularly Sanwa soil. A radar signal is transmitted, the radar signal reflected by the layer is received by at least two receiving devices spaced apart from each other, and each measurement signal is output. The permittivity and / or wetness of the layer is determined depending on the measurement signals output by at least two receivers.

Accordingly, in a second aspect, the invention relates to a sensor device for determining the dielectric constant and / or wetness of a layer having at least one transmitter for transmitting radar signals. Further, the sensor device has at least two receiving devices spaced apart from each other to receive the radar signal reflected by the layer, and an evaluation device for determining the permittivity and / or wetness of the layer. ..

Preferred embodiments are subject to the respective dependent claims.

The present invention makes it possible to accurately determine the dielectric constant or wetness of a layer.

In a preferred development of the method, the wetness of the layer is determined with the help of a known relationship between dielectric constant and wetness. In this way, for example, the wetness of Sanwa soil can be determined, so that it is not necessary to place the wetness sensor directly in Sanwa soil, or it is not necessary to collect a floor sample. The wetness may be, for example, water content, floor moisture, moisture content, or moisture percentage.

In a preferred development of this method, the relationship between permittivity and wetness is stored in a look-up table.

In a preferred development of the method, the layer thickness is determined depending on the measurement signals output by at least two receiving devices. In this way, it is not necessary to determine the additional layer thickness by collecting the sample.

In a preferred development example of this method, the respective comparison amounts are determined by comparing the transmitted radar signal with each radar signal received by the receiving device. The difference between the determined comparative quantity and the model quantity for describing the reflection is determined, and the model quantity depends on the dielectric constant and the layer thickness of the layer as parameter values. The permittivity and / or layer thickness of the layer is determined as a parameter value that minimizes the difference.

In a preferred evolution of the method, the receivers are placed at equal intervals with respect to the surface of the layer. This simplifies the model quantity and allows the permittivity and layer thickness to be determined with even higher accuracy.

In a preferred development of the method, the model quantity takes into account the reflection of the radar signal on the first surface of the layer and the reflection of the radar signal on the second surface.

In a preferred development of the method, the model quantity further considers the multiple reflections of the radar signal between the first surface and the second surface.

In a preferred development of the method, a large number of radar signals are transmitted by transmitting devices spaced apart from each other, and the receiving device is designed to determine the comparative amount for each radar signal of the large number of radar signals.

In a preferred development of this method, the model quantity is determined by applying Fresnel's equations.

In a preferred development of the method, the transmitted radar signal has a frequency between 1.8 and 7 GHz.

In a preferred evolution of the sensor device, the receiver device each includes an antenna with a principal radiation direction that is aligned substantially parallel.

In a preferred development of the sensor device, the receiving device includes antennas whose main radial directions intersect in the central plane between the antennas, respectively. The sensor device preferably has two receiving devices.

The drawing shows:

FIG. 6 is a schematic cross-sectional view showing a sensor device for determining the dielectric constant and / or wetness of a layer based on one embodiment of the present invention. It is a flowchart for demonstrating the method of determining the dielectric constant and / or the wetness of a layer based on one Embodiment of this invention.

Method Step numbering contributes to listability and generally does not imply a particular temporal order. In particular, multiple method steps can be performed simultaneously. The different embodiments can be arbitrarily combined with each other as long as they are meaningful.

FIG. 1 shows a schematic cross-sectional view of a sensor device 1 for determining the dielectric constant ε2 and / or the wetness of a layer 22 such as Sanwa soil. The permittivity ε2 here means dielectric conductance. The sensor device 1 is positioned so as to be separated from the layer 22 by the same distance α1 measured perpendicular to the first surface 22a outside the layer 22, the first transmission / reception device 11 and the second transmission / reception device 1. Includes device 12. The spacing α1 may be, for example, between 1 centimeter and 50 centimeters, preferably 5 centimeters. The first transmitter / receiver 11 and the second transmitter / receiver 12 have mutual distances 2B of, for example, between 5 and 50 centimeters, preferably 15 centimeters, and the first transmitter / receiver 11a and the first transmitter / receiver 12a. The receiving device 11b, or the second transmitting device 12a and the second receiving device 12b of the above are included.

The first transmitter 11a and the second transmitter 12a are designed to transmit radar signals toward the first surface 22a of the layer 22. The radar signal is partially reflected by the first surface 22a, but can be partially refracted by the first surface 22a before entering layer 22, where the second inner surface of layer 22 can be penetrated. It is reflected by 22b, travels through layer 22 again, is refracted again on the first surface 22a, and exits layer 22. The first receiving device 11b and the second receiving device 12b are configured to receive the radar signal reflected by the layer 22 and output the measurement signal. The first transmitter / receiver 11 and the second transmitter / receiver 12 are preferably designed as an ultra-wideband radar system having a frequency of 1.8 to 7 GHz. It is preferable that the receiving devices 11b and 12b include antennas whose main radial directions intersect in the central plane between the two antennas, respectively. However, the main radiation direction of the antenna may be aligned in parallel.

The radar signal of the transmitted radar signal is preferably sinusoidal, and the amplitude and / or phase of the radar signal is altered or shifted by reflection at layer 22. Radar signal scattering at layer 22 is generally defined as the quotient of the received and transmitted radar signals described in complex, respectively, and thus by comparison of the transmitted and received radar signals. It can be described by the complex scattering parameter S representing the comparative amount.

The scattering parameter S is determined depending on the reflectance Rk, the transmittance Tk, the frequency f of the radar signal, and the dielectric thickness Del of the complex value of the layer. Here, the dielectric thickness Del is defined as the product of the layer thickness α2 of the layer 22 and the root of the dielectric constant ε2 of the layer 22. The scattering parameter S is calculated based on the following sum over all possible transmissions and reflections.

Here, c0 represents the speed of light in a vacuum. The dielectric constant ε1 of the ambient air between the transceivers 11 and 12 and the layer 22, the dielectric constant ε2 of the layer 22, and the dielectric constant ε3 of the ambient air on the side of the layer 22 facing away from the transmitters 11 and 12. Is generally a complex parameter, i.e. given by the following equation.

In FIG. 1, it corresponds to a radar signal transmitted by the first transmitter 11a, partially reflected by the first surface 22a, partially penetrated into the layer 22 and reflected by the second surface 22b. The first radiation path L1 is shown. The first receiving device 11b receives the reflected radar signal, measures the first scattering parameter S11, and outputs a corresponding measurement signal.

The second radiation path L2 is transmitted from the second transmitting device 12a, is partially reflected by the first surface 22a, partially penetrates into the layer 22, and is reflected by the second surface 22b. Corresponds to the radar signal. The second receiving device 12b receives the reflected radar signal, measures the second scattering parameter S22, and outputs a corresponding measurement signal.

Further, a third optical path L3, which is transmitted by the first transmitting device 11a, hits the first surface 22a at the first incident angles θ1 and 1 with respect to the surface normal line N, and corresponds to the radar signal reflected therethrough is shown in the figure. This reflection is represented by the first reflectance r12. The radar signal is then received by the second receiver 12b.

Finally, a fourth optical path L4, which is transmitted by the first transmitter 11a, first hits the first surface 22a at the second incident angles θ1 and 2 with respect to the surface normal line N, and is refracted there, is shown. This refraction is represented by the first transmittance t12. This radar signal hits the second surface 22b at the third incident angles θ2 and 2 and is reflected there, and this reflection is represented by the second reflectance r23. After passing through layer 22, the radar signal is refracted again at the first surface 22a, which is represented by the second transmittance t21, which is subsequently received by the second receiver 12b.

The overlap of radar signals propagating along the third optical path L3 and the fourth optical path L4 is received by the second receiving device 12b, the third scattering parameter S12 is measured, and the corresponding sensor signal is output. ..

Further, a radar signal reflected by the first surface 22a to the second surface 22b and received by the first receiving device 12b is transmitted by the second transmitting device 12a, and each optical path is a third optical path L3. Or, it is exactly opposite to the fourth optical path L4. The receiving device 12b measures the corresponding fourth scattering parameter S21 and outputs a sensor signal.

The sensor device 1 uses the scattering parameters S11, S12, S21, and S22 measured by the first receiving device 11b and the second receiving device 12b to determine the layer thickness α2 and the dielectric constant ε2 of the layer 22. It includes the configured evaluation device 13.

The incident angles θy and j inside the layer 22, particularly the third incident angles θ2 and 2, can be calculated by Snell's law of refraction, that is, by the following equation, depending on the second incident angles θ1 and 2. ..

The half distance B between the first transmitting / receiving device 11 and the second transmitting / receiving device 12 depends on the incident angles θ1, 1, θ1, 2, the distance α1 from the layer 22, and the layer thickness α2 of the layer 22. It can be determined by the following equation.

According to the Fresnel refraction equation, the first reflectance r12, the second reflectance r23, the first transmittance t12, and the second transmittance t21 have incident angles θ1, 1, θ1, 2, and a transmitter / receiver 11. The real part ε1'of the complex dielectric constant ε1 of the ambient air between 12 and the object 22, the real part ε2' of the complex dielectric constant of the layer 22, and the ambient air on the opposite side of the transceivers 11 and 12. It can be calculated depending on the real part ε3'of the complex dielectric reflectance ε3 of, and the following equation is applied in that case.

The dielectric thickness Del1 of the ambient air and the dielectric thickness Del2 of the layer 22 also have an incident angle θ1, 1, θ1, 2, a dielectric constant ε1, ε2, a distance α1 between the transmission / reception devices 11 and 12 and the layer 22, and the layer 22. It depends on the layer thickness α2 of, and is given by the following equation.

The scattering parameter S for describing the transmission of the radar signal from the first transmission / reception device 11 to the second transmission / reception device 12 is calculated by the following equation in this example based on the above general equation.

Correspondingly, this equation represents the model quantity for describing the reflection. The evaluation device 13 uses the first scattering parameter S11 measured by the first receiving device 11b and / or the second scattering parameter S22 measured by the second receiving device 12b as the above-mentioned equation for the scattering parameter S. The dielectric thickness, that is, the product of the layer thickness α2 and the root of the dielectric constant ε2, is changed as a fitting parameter. The product of the layer thickness α2 and the root of the dielectric constant ε2 is determined by the best fitting. Further, the evaluation device 13 uses the third scattering parameter S12 measured by the second receiving device 12b and / or the fourth scattering parameter S21 measured by the first receiving device 11b as the above-mentioned equation for the scattering parameter. The best fitting is configured to fit using, substituting the determined product of the layer thickness α2 and the root of the permittivity ε2, and changing either the layer thickness α2 or the permittivity ε2 as the fitting parameter. Determined by. The evaluator 13 uses the determined product of the roots of the layer thickness α2 and the dielectric constant ε2 to calculate the corresponding remaining amount.

Thus, the evaluator 13 determines the layer thickness α2 and the permittivity ε2 of the layer 22 as free parameters of the equation for the scattering parameter S that sets the model quantity by adaptation or fitting of these quantities. , It is configured to minimize the difference between the equation for the scattering parameter S and each measured scattering parameter S. This can be done, for example, by minimizing the root mean square. In this way, the evaluation device 13 simultaneously determines the layer thickness α2 and the dielectric constant ε2 of the layer 22.

Further, the evaluation device 13 is configured to determine the wetness of the layer 22 by using the determined dielectric constant ε2 of the layer 22. The evaluator 13 preferably has a look-up table for which the empirical relationship between the permittivity ε2 and the wetness is conserved depending on the known material properties of the layer 22.

The second transmitter 12a is optional. For example, in another embodiment, only the second receiving device 12b may be provided instead of the second transmitting / receiving device 12. Only the first scattering parameter S11 is measured by the first receiving device 11b, the third scattering parameter S12 is measured by the second receiving device 12b, and the evaluation device 13 measures the layer thickness α2 and the dielectric constant ε2 of the layer 22. Is configured to be determined by the fitting of the measured scattering parameters S11, S12 according to the equation for the scattering parameter S.

In another embodiment, the equation for the scattering parameter S described above is extended by considering multiple reflections inside layer 22, and fitting by the evaluator 13 is performed accordingly.

In another embodiment, the layer 22 can have a plurality of lower layers, and the appropriate permittivity or layer thickness of each layer can be determined by the evaluation device 13 by fitting according to the appropriate scattering parameter S. can.

Instead of the complex measurement value of the dielectric constant ε2, the real part, the imaginary part, the amplitude, or the phase of the radar signal may be evaluated and fitted, and the wetness may be appropriately determined by the evaluation device 13.

In another embodiment, the interval from the first transmitter / receiver 11 to the layer 22 and the interval from the second transmitter / receiver 12 to the layer 22 may be different.

In another embodiment, radar signal filtering, especially polarization, can be performed.

FIG. 2 shows a flowchart for explaining a method of determining the dielectric constant ε2 and / or the wetness of the layer 22.

In the first method step S1, the radar signal is transmitted by the first transmission device 11a or the second transmission device 12a in particular.

In the next method step S2, the radar signal reflected by the layer 22 is received and measured by at least two receiving devices 11b, 12b spaced apart from each other. It should be noted that the receivers 11b, 12b are not symmetrically arranged about the transmitters 11a, 12a used to emit the radar signal, thereby the radar signal measured by the receivers 11b, 12b. The progress times of the above are to be different from each other.

Each comparison amount is determined by comparing the transmitted radar signal with the respective radar signals received by the receiving devices 11b and 12b. This comparative amount may be, in particular, the respective scattering parameters S11, S12, S21, S22.

In the next step S3, the permittivity ε2 and / or the wetness of the layer 22 is measured depending on the measurement signals output by the receiving devices 11b and 12b.

Therefore, it is preferable to determine the difference between the determined comparative quantity and the model quantity for describing the reflection, where the model quantity is the dielectric constant ε2 of the layer 22 and the layer thickness as parameter values. It depends on α2. As the model quantity, the mathematical formula of the scattering parameter S defined above can be applied.

The dielectric constant ε2 and the layer thickness α2 of the layer 22 are preferably determined as parameter values that minimize the difference.

The degree of wetness can be determined by a look-up table using the determined dielectric constant ε2.

1 Sensor device 11a, 12a Transmitter device 11b, 12b Receiver device 13 Evaluation device 22 Layer 22a First surface 22b Second surface ε2 Permittivity S1 Transmission S2 Reception S3 Judgment

Claims (10)

Dielectric constant of layer (22) (ε2))ofIn the judgment method
It has each of the following steps, i.e.
A radar signal is transmitted (S1),
The radar signal reflected by the layer (22) is received (S2) by at least two receiving devices (11b, 12b) spaced apart from each other, and each measurement signal is output.
Dielectric constant of layer (22) (ε2))But, Determined (S3) depending on the measurement signals output by at least two receiving devices (11b, 12b).,
Each comparison amount is determined by comparing the transmitted radar signal with each radar signal received by the receiving device (11b, 12b), and the determined comparison amount and the model amount for describing the reflection are used. The difference between them is determined, the model quantity is determined depending on the dielectric constant (ε2) and the layer thickness (α2) of the layer (22) as parameter values, and the dielectric constant (ε2) of the layer (22) is determined by the above. Determined as a parameter value that minimizes the difference Ru
Method. The method according to claim 1, wherein the wetness of the layer (22) is determined by using a known relationship between the dielectric constant (ε2) and the wetness. The method according to claim 1 or 2, wherein the layer thickness (α2) of the layer (22) is determined depending on the measurement signals output by at least two receiving devices (11b, 12b). The method according to claim 3 , wherein the layer thickness (α2) of the layer (22) is determined as a parameter value that minimizes the difference. The model quantity is any one of claims 1 to 4, considering the reflection of the radar signal on the first surface (22a) of the layer (22) and the reflection of the radar signal on the second surface (22b). The method described in the section . The method of claim 5, wherein the model quantity further considers multiple reflections of radar signals between the first surface (22a) and the second surface (22b). 23. Of claims 1 to 6, a large number of radar signals are transmitted by transmitting devices spaced apart from each other, and the receiving devices (11b, 12b) are designed to determine a comparison amount for each radar signal of the large number of radar signals. The method according to any one. In the sensor device (1) for determining the dielectric constant (ε2 ) of the layer (22) based on the method according to any one of claims 1 to 7.
At least one transmitter (11a, 12a) for transmitting radar signals, and
At least two receivers (11b, 12b) spaced apart from each other to receive the radar signal reflected by layer (22).
A sensor device having an evaluation device (13) for determining the dielectric constant (ε2 ) of the layer (22). The sensor device according to claim 8, wherein the receiving device (11b, 12b) includes an antenna having a main radiation direction aligned substantially in parallel. The sensor device according to claim 8, wherein the receiving devices (11b, 12b) include antennas whose main radial directions intersect in a central plane between the antennas.

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