JP7105722B2 - Radio current meter - Google Patents

Description

The present invention relates to a radio wave current meter.

Japanese Patent Laid-Open No. 2002-200001 discloses a radio current meter that is installed on a bridge over a river or the like and measures the flow velocity of the river by detecting a reflected wave of a transmitted wave that is radiated to the surface of the river.

JP 2016-114359 A

However, the above-described prior art does not sufficiently consider disturbances during flow velocity measurement. That is, when measuring the flow velocity of a river with a radio current meter, for example, foreign matter such as rain entering the propagation path of the transmitted wave and the reflected wave becomes a disturbance. In order to improve the measurement accuracy of a radio current meter, it is necessary to suppress or eliminate the influence of such disturbances.

The present invention has been made in view of the circumstances described above, and an object of the present invention is to improve measurement accuracy by suppressing or eliminating the influence of disturbance.

In order to achieve the above object, in the present invention, as a first solution related to the radio wave current meter, a transmission wave is irradiated to a measurement point of an observation target, and the transmission wave is reflected at the measurement point and generated A radio wave current meter that acquires a measurement signal based on a reflected wave and measures the flow velocity at the measurement point based on the Doppler signal included in the measurement signal, wherein the spectrum of the measurement signal includes a plurality of peaks. If the Doppler signal is detected, a measure peak portion corresponding to the Doppler signal is identified by evaluating the attribute values of the plurality of peak portions.

As a second solution to the radio wave current meter, in the first solution, when the spectrum has two adjacent peaks on the frequency axis, the attribute of the low frequency peak If the half-value width that is the value is included in the specified half-value width range, and if the half-value width that is the attribute value is larger in the peak portion with a higher frequency than in the peak portion with a lower frequency, the lower frequency A means of recognizing the peak portion as a measurement peak portion corresponding to the Doppler signal is employed.

As a third solution to the radio wave current meter, in the first or second solution, when the spectrum has two adjacent peak portions on the frequency axis, the peak portion with a high frequency If the half-value width that is the attribute value of is included in the prescribed half-value width range, and the half-value width that is the attribute value of the low-frequency peak portion is smaller than the high-frequency peak portion , recognizing the high-frequency peak portion as the measurement peak portion corresponding to the Doppler signal.

As a fourth solution means related to the radio wave current meter, in the first solution means, the attribute values are the frequency fluctuation width Δf _P of the peak power E _P , the power fluctuation width ΔE _P of the peak power E _P , the It includes at least the frequency difference f _T1 between the low-side frequency f ₁ and the low _- side frequency f ₂ that is reduced by the first attenuation amount d ₁ from the peak power EP, and the fluctuation width Δf _{T1 of the frequency difference f T1 .} adopt means.

As a fifth solution to the radio wave current meter, in any one of the first to fourth solutions, if an intensity peak exists in the measurement signal, the measurement signal in a period excluding the intensity peak is A means of measuring the flow velocity at the measurement point based on the measurement point is adopted.

As a sixth solution for the radio-wave current meter, in the fifth solution, a means is adopted in which the intensity peak is excluded when the flow velocity exceeds a predetermined threshold value.

As a seventh solution to the radio-wave current meter, any one of the first to fourth solutions is provided with a vibration sensor, and the period during which the vibration sensor detects vibration equal to or greater than a specified value is excluded. A means of measuring the flow velocity at the measuring point based on the measuring signal of the period is employed.

According to the present invention, it is possible to improve measurement accuracy by suppressing or eliminating the influence of disturbance.

1 is a block diagram showing the configuration of a radio wave current meter A according to first and second embodiments of the present invention; FIG. FIG. 2 is a schematic diagram showing an installation state in a horizontal plane of the radio wave current meter A according to the first and second embodiments of the present invention; 4 is a flow chart showing the operation of the radio wave current meter A according to the first embodiment of the present invention; FIG. 4 is a characteristic diagram showing a time change (a), a first spectrum (b), and a second spectrum (c) of the measurement signal of the radio current meter A according to the first embodiment of the present invention; 8 is a flow chart showing the operation of the radio wave current meter A' according to the second embodiment of the present invention; FIG. 10 is a characteristic diagram showing the spectrum of the measurement signal in the second embodiment of the present invention;

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First embodiment]
First, a first embodiment of the invention will be described.
As shown in FIGS. 1 and 2, the radio current meter A according to the first embodiment is an observation target K based on the Doppler frequency f _d of the reflected wave obtained from the measurement point P of the observation target K such as a river. It is a device for measuring the flow velocity V of A CW Doppler method, a multi-frequency CW method, and an FM-CW method are known as methods for measuring the flow velocity V based on the Doppler frequency _fd .

As shown in FIG. 1, the radio current meter A is installed at a predetermined distance from the observation target K (water surface), and has a predetermined elevation angle θ with respect to the measurement point P of the observation target K. A transmission wave (radio wave) is emitted as shown in FIG. That is, the radio current meter A is attached to a structure B such as a bridge, and irradiates the observation target K (water surface) with transmission waves from obliquely above.

In addition, as shown in FIG. 2, the radio current meter A emits a transmission wave toward the upstream side with respect to the flow direction F of the water in the observation target K (water surface). That is, the radio wave current meter A is fixedly installed on the structure B provided on the downstream side of the measurement point P, and transmits a transmission wave toward the measurement point P set on the upstream side of the structure B. A reflected wave is acquired by radiating. As for the radiation direction of the transmitted wave, the transmitted wave may be radiated toward the downstream side of the observation target K (water surface).

In addition, although FIG. 2 shows a measurement point P where the direction of water flow F in the horizontal plane is parallel to the radiation direction of the transmitted wave, there are a plurality of measurement points other than the measurement point P on the observation target K (water surface). Measurement points are set in advance.

When some vibration acts on the structure B, the radio current meter A also vibrates. This vibration may be caused by wind, earthquake, water flow, or the like. For example, if the structure B is a bridge, vehicles passing through the bridge may be considered. Vibrations caused by passing vehicles act on the radio current meter A as transient vibrations over a relatively short period of time.

Further, when the structure B is a bridge, the radio current meter A is subjected to continuous vibration at a predetermined frequency due to the structure of the bridge and the like. Such continuous vibrations fluctuate in intensity with changes in the surrounding environment. It should be noted that the vibration acting on the radio current meter A also changes depending on the mounting position with respect to the bridge. That is, the form of vibration acting on the radio current meter A differs between when the radio current meter A is fixed to the main body of the bridge and when the radio current meter A is fixed to the balustrade of the bridge.

As shown in FIG. 1, such a radio wave current meter A includes an antenna 1, a transmission/reception circuit 2, a vibration sensor 3, a signal processing section 4, a display section 5, a communication section 6 and a recording section 7. . The antenna 1 is, for example, a parabolic antenna, and radiates a transmission wave toward an observation target K based on a transmission signal of a predetermined frequency input from the transmission/reception circuit 2, while receiving a reflected wave and transmitting it as a reflected signal to the transmission/reception circuit 2. output to

The transmission wave is irradiated to the observation target K (water surface) through the air as a propagation path D, and part of the transmission wave reflected by the observation target K (water surface) becomes a reflected wave. In addition, this transmission wave is, for example, a microwave. The reflected wave is a radio wave containing a Doppler signal having a frequency component (Doppler frequency f _d ) in which the frequency (wavelength) of the transmitted wave is Doppler-shifted by the flow velocity of water on the observation target K (water surface).

Further, the transmitted wave is affected by a foreign object present in the propagation path D between the antenna 1 and the observation target K (water surface). Moreover, the reflected wave includes not only the Doppler signal but also a noise signal caused by a foreign object. That is, the foreign matter on the propagation path D acts as a disturbance on the Doppler frequency _fd caused by the Doppler shift of the reflected wave, that is, the flow velocity V of the observation target K (water surface) included in the Doppler signal. A typical example of such foreign matter is rain, that is, water droplets that may enter the propagation path D. FIG. The passing direction (falling direction) of this rain is not limited to the vertical direction (gravitational direction), but it changes irregularly due to the influence of wind, etc. Therefore, it constantly fluctuates with the traveling direction of the transmitted and reflected waves. It is possible.

The transmission/reception circuit 2 includes an oscillator for generating a transmission signal, a circulator for demultiplexing the transmission signal, a mixer for mixing the transmission signal and the reflection signal to generate a differential signal, and the like. At the same time, a difference signal between the reflected signal and the transmission signal is extracted, and the difference signal is output to the signal processing unit 4 as a measurement signal.

The vibration sensor 3 detects the vibration described above and outputs a vibration signal indicating the vibration to the signal processing unit 4 . This vibration sensor 3 is, for example, an acceleration sensor having a predetermined sensitive axis.

The signal processing unit 4 calculates the flow velocity V of the observation target K (water surface) by performing predetermined digital signal processing on the measurement signal and the vibration signal based on a pre-stored flow velocity measurement program. That is, the signal processing unit 4 includes an A/D converter that converts analog measurement signals and vibration signals into digital signals (measurement data and vibration data), a nonvolatile memory that stores a flow velocity measurement program, etc., a flow velocity V , a volatile memory that temporarily stores the calculated values of the arithmetic circuit, and an interface circuit that exchanges data with the display unit 5, the communication unit 6, and the recording unit 7, and the like.

Such a signal processing unit 4 appropriately outputs the flow velocity V, which is a calculation result, to the display unit 5 , the communication unit 6 and the recording unit 7 . That is, the signal processing unit 4 outputs the flow velocity V to the display unit 5 to display it on the screen, outputs the flow velocity V to the communication unit 6 to transmit it to the outside, and outputs the flow velocity V to the recording unit 7 to record it. .

The display unit 5 is a panel-type display device such as a liquid crystal display device, and displays the flow velocity V input from the signal processing unit 4 on the screen in a predetermined display mode. The communication unit 6 transmits the flow velocity V input from the signal processing unit 4 to the outside via a predetermined communication line. The communication unit 6 conforms to the Internet communication protocol, for example, and transmits the flow velocity V to a predetermined destination address (IP address).

The recording unit 7 is a storage device having a non-volatile storage device with a relatively large storage capacity, such as a hard disk, various memory cards, and/or a USB memory. The recording unit 7 stores the flow velocity V at a plurality of times acquired over a predetermined period as time-series data. When the communication unit 6 receives the time-series data transmission request, the signal processing unit 4 causes the time-series data to be transmitted to the request destination in response to the problem transmission request.

Next, the operation of the radio wave current meter A configured in this manner will be described in detail with reference to FIGS. 3 and 4. FIG.

First, the overall operation of the radio wave current meter A will be described. The signal processing unit 4 performs predetermined signal processing on the measurement signal input from the transmission/reception circuit 2 to reduce the Doppler current caused by the flow velocity V at the measurement point P. The flow velocity V at the measurement point P is calculated by specifying the frequency _fd and substituting the Doppler frequency _fd into the following equation (1).

Here, the constant c in equation (1) is the propagation velocity (light velocity) of the transmitted wave (reflected wave), and the constant f ₀ is the frequency (fundamental frequency) of the transmitted wave (reflected wave). Furthermore, the constant θ is the elevation angle discussed above.

In the calculation (measurement) of such a flow velocity V, the vibration of the structure B that supports the radio current meter A and the foreign matter in the propagation path D of the transmission wave (reflected wave) are detected by the signal processing unit 4 based on the measurement signal. It becomes a disturbance when specifying the Doppler frequency fd. The signal processing of the signal processing unit 4 that excludes such disturbances and specifies the Doppler frequency fd will be described in detail below with reference to FIG.

The signal processing unit 4 converts the measurement signal into a digital signal (measurement data) at a predetermined sampling period and sequentially captures it as time-series data (step S1). As shown in FIG. 4(a), it is determined whether or not there is a portion having a temporarily (locally) large amplitude (step S2).

Then, when the determination result of step S2 is "Yes", that is, when the intensity peak Q exists in the measurement data, the signal processing unit 4 performs processing to exclude the intensity peak Q from the measurement data (step S3 ), the FFT processing of step S4 is performed on the measurement data subjected to this exclusion processing. The signal processing unit 4 directly performs FFT processing (step S4) when the determination result of step S2 is "No", that is, when the intensity peak Q does not exist in the measurement data.

Here, such a strength peak Q occurs when a relatively short-time vibration acts on the structure B, for example, when the structure B is a bridge and a vehicle passes over the bridge. Therefore, the process of excluding the intensity peak Q (step S3) can eliminate the disturbance caused by the vibration acting on the radio current meter A for a relatively short period of time.

Such a short-time vibration is also detected by the vibration sensor 3, and a vibration peak portion Qs corresponding to the intensity peak Q exists in the vibration signal. That is, the signal processing unit 4 performs the process of excluding the intensity peak Q (step S3) even during the period when the vibration sensor 3 detects vibrations equal to or greater than a specified value, that is, even when the vibration peak portion Qs exists in the vibration signal. to eliminate disturbance due to relatively short-time vibration acting on the radio wave current meter A.

The signal processing unit 4 acquires the spectrum (frequency characteristics) of the measurement signal through the FFT processing (step S4). FIGS. 4(b) and 4(c) show an example of the spectrum of the measurement signal. Of these two spectra, the spectrum in FIG. 4(b) shows the case where continuous vibration (continuous vibration) acts on the radio current meter A, while the spectrum in FIG. The case of rainfall, that is, the case where raindrops are present in the propagation path D, is shown.

When acquiring such a spectrum of the measurement signal, the signal processing unit 4 evaluates the amplitude change of the spectrum to determine whether or not there are a plurality of peaks in the spectrum, that is, whether there are peaks in the spectrum of the measurement signal. It is determined whether or not a plurality of items are included (step S5).

When continuous vibration acts on the radio current meter A, the spectrum of the measurement signal, as shown in FIG. In addition to the measurement peak portion, a peak portion Rs (first disturbance signal) caused by continuous vibration is included in a frequency band lower than the peak portion Rv. That is, when continuous vibration acts on the radio current meter A, the spectrum of the measurement signal includes at least two adjacent peaks Rv and Rs on the frequency axis.

Here, for the peak portion Rv (regular Doppler signal) caused by the flow velocity V at the measurement point P, the possible range of the half width (flow velocity half width range), which is the attribute value of the peak portion Rv, is confirmed by prior verification or the like. This flow velocity half width range is stored in the signal processing unit 4 in advance. In addition, regarding the peak portion Rs (first disturbance signal) caused by continuous vibration, the possible range of the half-value width (continuous vibration half-value width range), which is the attribute value of the peak portion Rs, is determined by prior verification or the like. confirmed to be significantly smaller than

In addition, regarding the peak part Rs (first disturbance signal) caused by continuous vibration, when the peak frequency is converted into the flow velocity based on the following formula (1), it is verified in advance that it will be several m / s or less. has been confirmed by Further, the continuous vibration half-value width range is stored in advance in the signal processing section 4, similarly to the flow velocity half-value width range.

The signal processing unit 4 uses the characteristics of the spectrum of the measurement signal when such continuous vibration occurs to perform the first peak portion evaluation process on the spectrum (step S6). That is, the signal processing unit 4 determines that the half-value width of the lower frequency peak Rs is included in the specified continuous vibration half-value width range, and that the higher frequency peak Rv is the lower frequency peak. Two adjacent peak portions Rv and Rs on the frequency axis are evaluated under the first evaluation condition that the half width is larger than that of the portion Rs.

Then, when the first evaluation condition is satisfied, the signal processing unit 4 selects the peak portion Rs having the lower frequency among the two adjacent peak portions Rv and Rs on the frequency axis as the first disturbance signal. Eliminate as That is, the signal processing unit 4 recognizes the peak portion Rv with the higher frequency as the peak portion caused by the flow velocity V at the measurement point P, that is, the normal Doppler signal.

Subsequently, in the spectrum of the measurement signal, as shown in FIG. 4C, in addition to the peak portion Rv (normal Doppler signal) caused by the flow velocity V at the measurement point P, a frequency band higher than the peak portion Rv includes a peak portion Ra (second disturbance signal) caused by rainfall. That is, even when rainfall occurs on the propagation path D, the spectrum of the measurement signal includes at least two adjacent peaks Rv and Ra on the frequency axis.

Here, for the peak portion Rv (regular Doppler signal) caused by the flow velocity V at the measurement point P, the flow velocity half width range is stored in advance in the signal processing unit 4 as described above. In addition, for the peak portion Ra (second disturbance signal) caused by rainfall, the possible range of the half-value width (rainfall half-value width range), which is the attribute value of the peak portion Ra, is significantly larger than the above-described flow velocity half-value width range. This has been confirmed by preliminary verification or the like, and is stored in advance in the signal processing unit 4 in the same manner as the above-described flow velocity half-value width range and continuous vibration half-value width range.

The signal processing unit 4 uses the characteristics of the spectrum of the measurement signal during rain to perform the second peak evaluation process on the spectrum (step S7). That is, the signal processing unit 4 determines that the half-value width of the higher frequency peak Ra is included in the specified rainfall half-value width range, and that the lower frequency peak Rv Using the second evaluation condition that the half-value width is smaller than Ra, two adjacent peak portions Rv and Ra on the frequency axis are evaluated.

Then, when the second evaluation condition is satisfied, the signal processing unit 4 converts the peak portion Ra having the higher frequency from the two adjacent peak portions Rv and Ra on the frequency axis to the second disturbance signal. Eliminate as That is, the signal processing unit 4 recognizes the peak portion Rv with the lower frequency as the peak portion caused by the flow velocity V at the measurement point P, that is, the normal Doppler signal.

Here, in FIG. 4B, only the peak portion Rv caused by the flow velocity V and the peak portion Rs caused by the continuous vibration are included, and in FIG. Although the spectrum including only Rv and the peak Ra due to rainfall is shown, continuous vibration and rainfall may occur at the same time. A spectrum in such a case includes three adjacent peaks Rv, Rs, and Ra on the frequency axis.

For such a case, in the first embodiment, the flow velocity half width range and continuous Since the three peak portions Rv, Rs, and Ra are evaluated using the vibration half-value width range and the rainfall half-value width range, the peak portion Rv (normal Doppler signal) caused by the flow velocity V at the measurement point P can be accurately specified. It is possible.

When the signal processing unit 4 identifies the peak portion Rv (normal Doppler signal) caused by the flow velocity V at the measurement point P in this way, the frequency (peak frequency) having the largest amplitude in the peak portion Rv is set as the Doppler frequency _fd . Extract (step S8). In this extraction process of the Doppler frequency _fd , the Doppler frequency _fd is specified by smoothing the peak portion Rv whose level fluctuates in small increments, for example, by performing a moving average process.

After specifying the Doppler frequency _fd in this manner, the signal processing unit 4 calculates the flow velocity V at the measurement point P by substituting the Doppler frequency _fd into the above equation (1) (step S9). Then, the signal processing unit 4 outputs the flow velocity V to the display unit 5, the communication unit 6 and/or the recording unit 7, thereby causing screen display, transmission and/or recording.

According to the first embodiment as described above, it is possible to suppress or eliminate the influence of the vibration acting on the radio current meter A and the disturbance caused by foreign matter present in the propagation path D of the transmission wave (reflected wave). Therefore, it is possible to improve the measurement accuracy of the flow velocity V as compared with the conventional technique.

[Second embodiment]
Next, a second embodiment of the invention will be described with reference to FIGS. 5 and 6. FIG.
The above-described first embodiment is based on the premise that the three peaks Rv, Rs, and Ra have a clear frequency magnitude relationship, but the second embodiment does not require this premise. be.

As shown in FIG. 1, the radio wave current meter A' according to the second embodiment has the same functional configuration as the radio wave current meter A according to the first embodiment, but has signal processing different from that of the signal processing unit 4. is provided with a signal processing unit 4' for performing That is, the functional difference between the radio wave current meter A' according to the second embodiment and the radio wave current meter A according to the first embodiment lies in the content of signal processing for measurement signals and vibration signals.

This signal processing unit 4', like the signal processing unit 4 of the first embodiment, calculates the flow velocity V of the observation target K (water surface) based on the processing procedure shown in FIG. Steps Sa1 to Sa11 shown in FIG. 6 are performed instead of S7. That is, the signal processing unit 4 ′ recognizes the peak portion Rv (measurement peak portion) caused by the flow velocity V at the measurement point P from the spectrum of the measurement signal and the vibration signal (spectrum including a plurality of peak portions). It differs from the signal processing unit 4 of the embodiment. Details of the evaluation processing of the peak portion in the signal processing unit 4' will be described below with reference to FIGS. 5 and 6. FIG.

First, the parameters used in the evaluation process of the peak portion will be described with reference to FIG. This parameter is an attribute value of a peak portion related to the spectrum obtained by FFT processing of the measurement signal and the vibration signal, and is a unique value for each peak portion included in the spectrum. Specifically, as shown in FIG. 5, the parameters are the peak power E _P , the frequency fluctuation width Δf _P of the frequency (peak frequency f _P ) at the peak power E _P , the power fluctuation width ΔE _P of the peak power E _P is.

Also, this parameter is the frequency difference (first frequency width f _T1 ) between the low-side frequency f ₁ and the low-side frequency f ₂ , which are lowered by the first attenuation amount d ₁ from the peak power E _P , and the first frequency width f T1 . The fluctuation width of the frequency width f _{T1 ( first} fluctuation width _{Δf T1} ) _, and the frequency difference ( second frequency width f _T2 ) and fluctuation width (second fluctuation width Δf _T2 ).

The signal processing unit 4′ performs the evaluation process shown in FIG. 6 using each parameter related to each peak portion, thereby obtaining the peak portion Rv caused by the flow velocity V at the measurement point P, that is, the measurement corresponding to the normal Doppler signal. Certified as a peak. That is, the signal processing unit 4′ acquires a plurality of spectra by sequentially performing FFT processing (step S3) by sequentially capturing the measurement signal and the vibration signal at predetermined time intervals, and all peaks included in each spectrum Each parameter is obtained for (step Sa1).

Here, since the signal processing unit 4' acquires the above-described parameters for all peak portions of a plurality of spectra, the same parameters for the individual peak portions are acquired for the number of spectra.

Then, the signal processing unit 4′ compares the peak power E _P of all peak parts with the first threshold TH ₁ to determine whether there is a peak part whose peak power E _P is equal to or greater than the first threshold TH ₁ . (step Sa2). In other words, the signal processing unit 4' selects peak portions having a peak power E _P equal to or greater than the _first threshold value TH1 among all the peak portions as candidates for the peak portions Rv (measurement peak portions).

Here, for each peak portion, since a plurality of peak powers E _P are acquired as one of the parameters in step Sa1, the signal processing unit 4' _obtains a representative value (for example, The determination in step Sa2 is made by comparing the average value) with the _first threshold value TH1.

Then, the signal processing section 4' initially selects the peak portion _R1 having the largest peak power E _P among all the peak portions (step Sa3). Then, the signal processing unit 4' determines whether or not the power variation width _ΔEP of the peak portion _R1 is equal to or less than the _second threshold TH2 by referring to the parameters related to the peak portion _R1 (step Sa4). The _second threshold TH2 is a single value set based on the power variation width (teaching data) of various peaks Rv, Rs, and Ra previously obtained from a plurality of observation targets K.

That is, as a result of confirming the properties of various peak portions Rv, Rs, and Ra for a plurality of observation targets K, the power fluctuation width of the peak portion Rv (measurement peak portion) is relatively small, but the peak portion Rs and It was confirmed that the power fluctuation width of the peak portion Ra due to rainfall is relatively large. The second threshold TH ₂ is set based on the characteristics of the power fluctuation range in the peak portion Rv (measurement peak portion) and the peak portions Rs and Ra, and is a value capable of distinguishing between the two. .

Subsequently, the signal processing unit 4' determines whether or not the frequency fluctuation width _ΔfP of the peak portion _R1 is within the _third threshold TH3 (step Sa5). The third threshold TH ₃ is a value set based on the frequency variation width (teaching data) of various peak portions Rv, Rs, and Ra obtained in advance from a plurality of observation targets K, and the above-described second threshold Unlike TH ₂ (single value), it consists of a lower limit and an upper limit.

That is, as a result of confirming the properties of various peak portions Rv, Rs, and Ra for a plurality of observation targets K, the frequency fluctuation width of the peak portion Rv (measurement peak portion) is medium, but the peak portion Rs due to continuous vibration It was confirmed that the frequency variation width of the peak portion Ra due to rainfall was relatively large. The _third threshold TH3 is set based on the characteristics of the frequency fluctuation width in the peak portion Rv (measurement peak portion) and the peak portions Rs and Ra, and the peak portion Rv (measurement peak portion) is It can be discriminated against the peak portions Rs and Ra.

Then, the signal processing unit 4' determines whether or not the first frequency width _fT1 of the peak portion _R1 is within the _fourth threshold TH4 (step Sa6). The fourth threshold TH ₄ is a value set based on the frequency variation width (teaching data) of various peaks Rv, Rs, and Ra obtained in advance from a plurality of observation targets K, and the above-described third threshold Like TH ₃ , it consists of a lower limit value and an upper limit value.

That is, as a result of confirming the properties of various peak portions Rv, Rs, and Ra for a plurality of observation targets K, the first frequency width of the peak portion Rv (measurement peak portion) is medium, but the peak portion caused by continuous vibration It was confirmed that the first frequency width of Rs is relatively small, and that the first frequency width of the peak Ra caused by rainfall is relatively large. The fourth threshold TH ₄ is set based on the characteristics of the first frequency width in the peak portion Rv (measurement peak portion) and the peak portions Rs and Ra, and the peak portion Rv (measurement peak portion) can be identified for the peaks Rs, Ra.

Then, the signal processing unit 4' determines whether or not the _first variation width _ΔfT1 of the peak portion R1 is within the _fifth threshold TH5 (step Sa7). The fifth threshold TH ₅ is a value set based on the frequency variation width (teaching data) of various peak portions Rv, Rs, and Ra obtained in advance from a plurality of observation targets K, and the above-described fourth threshold Like TH ₄ , it consists of a lower limit value and an upper limit value.

That is, as a result of confirming the properties of various peak portions Rv, Rs, and Ra for a plurality of observation targets K, the first fluctuation width of the peak portion Rv (measurement peak portion) is medium, but the peak portion caused by continuous vibration It was confirmed that the first variation width of Rs is relatively small, and the first variation width of the peak portion Ra caused by rainfall is relatively large. The fifth threshold TH ₅ is set based on the characteristics of the first fluctuation width in the peak portion Rv (measurement peak portion) and the peak portions Rs and Ra, and the peak portion Rv (measurement peak portion) can be identified for the peaks Rs, Ra.

Then, the signal processing unit 4' determines whether or not the second frequency width _fT2 of the peak portion _R1 is within the _sixth threshold TH6 (step Sa8). The sixth threshold TH ₆ is a value set based on the frequency variation width (teaching data) of various peak portions Rv, Rs, and Ra obtained in advance from a plurality of observation targets K, and is a value set based on the above-described fifth threshold Like TH ₅ , it consists of a lower limit and an upper limit.

That is, as a result of confirming the properties of various peak portions Rv, Rs, and Ra for a plurality of observation targets K, the second frequency width of the peak portion Rv (measurement peak portion) is medium, but the peak portion caused by continuous vibration It was confirmed that the second frequency width of Rs is relatively small, and that the second frequency width of the peak Ra caused by rainfall is relatively large. The sixth threshold TH ₆ is set based on the characteristics of the second frequency width in the peak portion Rv (measurement peak portion) and the peak portions Rs and Ra, and the peak portion Rv (measurement peak portion) can be identified for the peaks Rs, Ra.

Further, the signal processing unit 4' determines whether or not the second variation width _ΔfT2 of the peak portion _R1 is within the _seventh threshold TH7 (step Sa9). The seventh threshold TH ₇ is a value set based on the frequency variation width (teaching data) of various peak portions Rv, Rs, and Ra obtained in advance from a plurality of observation targets K, and the above-described sixth threshold Like _TH6 , it consists of a lower limit and an upper limit.

That is, as a result of confirming the properties of various peak portions Rv, Rs, and Ra for a plurality of observation targets K, the second fluctuation width of the peak portion Rv (measurement peak portion) is medium, but the peak portion caused by continuous vibration It was confirmed that the second variation range of Rs is relatively small, and the second variation range of peak portion Ra caused by rainfall is relatively large. The seventh threshold TH ₇ is set based on the characteristics of the second fluctuation width in the peak portion Rv (measurement peak portion) and the peak portions Rs and Ra, and the peak portion Rv (measurement peak portion) can be identified for the peaks Rs, Ra.

Then, the signal processing unit 4' recognizes that the peak portion _R1 is a measurement peak portion when the conditions of steps Sa4 to Sa9 are satisfied (step Sa10). On the other hand, if the signal processing section 4' does not satisfy any of the conditions of steps Sa4 to Sa9, it selects the peak section _R2 having the next largest peak power EP (step _Sa11 ), and then selects the peak section R2 (step Sa11). It is evaluated whether or not the peak portion _R2 is the peak portion Rv (measurement peak portion) by judging whether or not the conditions of ˜Sa9 are satisfied.

The signal processing unit 4′ determines whether or not the candidates for the peak portion Rv (measurement peak portion) detected in step Sa2 satisfy the conditions of steps Sa4 to Sa9, so that each candidate becomes the peak portion Rv (measurement peak portion). peak). If no peak portion is detected in step Sa2, the signal processing section 4' determines that the peak portion Rv (measured peak portion) is not included in the spectrum (step Sa12).

According to the second embodiment as described above, even if the magnitude relationship of the frequencies of the three peaks Rv, Rs, and Ra is not clear, the vibration and transmission acting on the radio wave current meter A' It is possible to suppress or eliminate the influence of disturbance caused by foreign matter present in the propagation path D of the wave (reflected wave), thereby improving the measurement accuracy of the flow velocity V compared to the conventional art.

It should be noted that the present invention is not limited to the above-described embodiments, and for example, the following modifications are conceivable.
(1) In each of the above embodiments, only the measurement of the flow velocity V was described, but the present invention is not limited to this. For example, in addition to the operation mode (flow velocity measurement mode) in which the radio current velocity meter A measures the flow velocity V (flow velocity of water) at the measurement point P in the observation target K such as a river (flow velocity measurement mode), the flow velocity V of the debris flow at the observation target K is measured. When the operation mode (debris flow measurement mode) is provided, transient vibration may occur in the measurement data due to the debris flow in the debris flow measurement mode.

In such a case, the difference in properties is used to distinguish between transient vibrations caused by a debris flow and transient vibrations such as when a vehicle passes over a bridge. That is, when the intensity peak Q is included in the measurement signal, or during the period when the vibration sensor 3 detects vibrations equal to or greater than a specified value, the calculation processing of the flow velocity V is performed without performing the exclusion processing in step S3, and continuous vibration is performed. If the flow velocity (velocity) calculated based on the peak frequency of the resulting peak portion Rs exceeds a predetermined threshold value, the exclusion process of step S3 is performed.

(2) In each of the above embodiments, the peak portion Rs caused by continuous vibration and the peak portion Ra caused by rainfall are detected based on only the spectrum of the measurement signal or the combination of the spectrum of the measurement signal and the vibration signal of the vibration sensor 3. Although excluded as a disturbance, the present invention is not limited to this. For example, when detecting the presence or absence of rainfall at the measurement site by providing a rainfall sensor, the peak portion that causes disturbance may be excluded depending on whether it is raining or not.

(3) In each of the above embodiments, two peak portions Rv and Rs adjacent on the frequency axis, two peak portions Rv and Ra adjacent on the frequency axis, or three peak portions Rv and Rs adjacent on the frequency axis , Ra to calculate the flow velocity V at the measurement point P by extracting the peak portion Rv (normal Doppler signal) caused by the flow velocity V, but the present invention is not limited to this. That is, the disturbance signal is not limited to the peak portion Rs (first disturbance signal) caused by continuous vibration and the peak portion Ra (second disturbance signal) caused by rainfall.

(4) In the first embodiment, the processing procedure of the signal processing unit 4 shown in FIG. 3 is merely an example, and the present invention is not limited to this. Other orders may be used if desired.

(5) In each of the above-described embodiments, a case has been described in which transmission waves are emitted toward the upstream side of the observation target K (water surface) as shown in FIG. 2, but the present invention is not limited to this. That is, the transmission wave may be radiated toward the downstream side.

(6) In the above-described second embodiment, the parameters that are the attribute values of each peak included in the spectrum are the frequency fluctuation width Δf _P , the power fluctuation width ΔE _P , the first frequency width f _T1 , the first fluctuation width Δf _T1 , Although the second frequency width f _T2 and the second variation width Δf _T2 are employed, the present invention is not limited thereto. For example, the second frequency width f _T2 and the second variation width Δf _T2 may be omitted, and the first frequency width f _T1 , the first variation width Δf _T1 , the second frequency width f _T2 and the second variation width Δf _T2 , a third frequency width f _T3 and a third variation width Δf _T3 may be added.

A, A' Radio current meter B Structure D Propagation path K Observation target P Measuring point 1 Antenna 2 Transmission/reception circuit 3 Vibration sensor 4, 4' Signal processing unit 5 Display unit 6 Communication unit 7 Recording unit

Claims (6)

A measurement point of an observation target is irradiated with a transmission wave, a measurement signal is obtained based on a reflected wave generated by reflection of the transmission wave at the measurement point, and the measurement point is obtained based on a Doppler signal included in the measurement signal. A radio wave current meter that measures the flow velocity of
If the spectrum of the measurement signal includes a plurality of peaks, the measurement peak corresponding to the Doppler signal is identified by evaluating the attribute values of the plurality of peaks ,
When the spectrum has two adjacent peak portions on the frequency axis, the half-value width, which is the attribute value of the low-frequency peak portion, is included in a specified half-value width range, and When the half width, which is the attribute value, of the high peak portion is larger than that of the low frequency peak portion, the low frequency peak portion is recognized as the measurement peak portion corresponding to the Doppler signal . Radio wave current meter. When the spectrum has two adjacent peak portions on the frequency axis, the half-value width, which is the attribute value of the high-frequency peak portion, is included in a prescribed half-value width range, and When the half-value width, which is the attribute value, of the low peak portion is smaller than that of the high frequency peak portion, the high frequency peak portion is recognized as the measurement peak portion corresponding to the Doppler signal. The radio wave current meter according to claim 1. A measurement point of an observation target is irradiated with a transmission wave, a measurement signal is obtained based on a reflected wave generated by reflection of the transmission wave at the measurement point, and the measurement point is obtained based on a Doppler signal included in the measurement signal. A radio wave current meter that measures the flow velocity of
If the spectrum of the measurement signal includes a plurality of peaks, the measurement peak corresponding to the Doppler signal is identified by evaluating the attribute values of the plurality of peaks,
The attribute values are a frequency variation width Δf _P of the peak power EP, a power variation width ΔE P of _the peak power EP, a low _- side frequency f ₁ that is lower than the peak power _EP by a first attenuation amount d ₁ , and A radio current meter characterized by including at least a frequency difference f _T1 from a low frequency side frequency f ₂ and a variation width Δf T1 of the _frequency difference f _T1 . 4. The method according to any one of claims 1 to 3, wherein when an intensity peak is present in the measurement signal, the flow velocity at the measurement point is measured based on the measurement signal during a period excluding the intensity peak. radio current meter. 5. The radio wave current meter according to claim 4, wherein said intensity peak is excluded when said flow velocity exceeds a predetermined threshold value . Equipped with a vibration sensor,
4. The method according to any one of claims 1 to 3, characterized in that the flow velocity at the measurement point is measured based on the measurement signal during a period excluding a period during which the vibration sensor detects vibrations equal to or greater than a specified value. The radio-controlled current meter described.

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