JP2008232965A - Ultrasonic flowmeter, flow rate measurement method, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a computational effort increasing, when speed of flow is high or the bore of a pipe is large, and to reduce misrecognition of reflected echoes. <P>SOLUTION: An ultrasonic flowmeter includes an ultrasonic oscillating means (15) for generating ultrasonic pulses in a constant cycle and outputting it into a fluid to be measured; a continuous pulse oscillating means (15a) for oscillating continuous waves of the same frequency as that of the pulses; an ultrasonic wave receiving means (15) for receiving an ultrasonic echo signal from the fluid; a multiplying means (30a) for multiplying the received ultrasonic echo signal with the continuous waves; a signal analysis means for analyzing the processed signal for calculating position and the speed of an ultrasonic reflector along a measurement line; and an output means (40) for outputting at least one of a flow speed distribution and the flow rate of the fluid from the position and the speed of the ultrasonic reflector calculated by the analysis means. The signal analysis means analog-digitally converts a composited waveform signal, obtained by the multiplying means (30a) and carries out signal analysis by means of a low-pass filter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrasonic flowmeter capable of instantaneously measuring a flow rate of a fluid to be measured from a flow velocity distribution in a measurement region in a time-dependent manner and a technique related thereto.

  As a fluid flow measurement technique, there is an ultrasonic flowmeter that oscillates an ultrasonic pulse with respect to a fluid to be measured and uses an echo signal thereof. Among them, the method called the cross correlation method calculates the velocity of the reflector from the time difference when there is an echo signal from the same reflector for different pulses (reference wave, search wave) for the fluid to be measured, This is a technique for measuring the flow velocity distribution and flow rate using the velocity.

This cross-correlation type ultrasonic flowmeter has a fixed cross-correlation calculation with a constant search window size regardless of the emission period of oscillation τ when calculating the cross-correlation between the reference wave and the search wave. There is a search window method. However, the velocity of the fluid to be measured and the velocity fluctuation vary depending on the position, and it is not always appropriate to set a fixed search window.
Therefore, in order to solve this problem, for example, there is a technique disclosed in Patent Document 1.
JP 2005-208068 A

  The technique disclosed in Patent Document 1 is an error due to misrecognition of cross-correlation by appropriately setting a search range (a size of a search window) necessary for calculating a cross-correlation between a reference wave and a search wave. It is a technology to suppress

Now, as the flow velocity of the fluid to be measured increases, the time difference between the arrival of the reference wave and the search wave increases. Along with this, it is necessary to increase the search range (the size of the search window) required when calculating the cross-correlation between the reference wave and the search wave. For this reason, the calculation amount increases, and an error due to misrecognition of the cross-correlation may occur.
Even when the diameter of the pipe through which the fluid to be measured flows is large, the difference between the arrival times of the reference wave and the search wave is large, and the same problem occurs.

  For example, when an ultrasonic wave oscillated at 1 MHz becomes a reflected wave, the periodic component (for example, 1 μs) therein is very short compared to the time required for calculating the speed. In order to accurately sample this periodic component, a very large number of sampling points are required. Therefore, the calculation amount increases.

The problem to be solved by the present invention is that an ultrasonic flowmeter using a cross-correlation method realizes accurate measurement even when the flow velocity of the fluid to be measured is high or the pipe diameter through which the fluid to be measured flows is large. It is to provide a technology that can be used.
The object of the invention described in claims 1 to 3 is to accurately measure the flow rate of a large-diameter pipe even when the flow velocity of the fluid to be measured is high or the pipe diameter through which the fluid to be measured flows is large. The object is to provide an ultrasonic flowmeter capable of realizing measurement.
The object of the invention described in claims 4 to 6 is to provide a measurement method capable of realizing accurate measurement even when the flow rate of the fluid to be measured is high or the pipe diameter through which the fluid to be measured flows is large. There is.
The object of the invention described in claims 7 to 9 is to provide a measurement program capable of realizing accurate measurement even when the flow rate of the fluid to be measured is high or the pipe diameter through which the fluid to be measured flows is large. There is.

  The present invention proposes a technique capable of suppressing the amount of calculation that increases when the flow rate of the fluid to be measured is high or when the diameter of the pipe through which the fluid to be measured is large, and reducing the misidentification of the reflected echo. And provide the following invention.

(Claim 1)
According to the first aspect of the present invention, there is provided an ultrasonic oscillating means (ultrasonic transducer 15) that generates ultrasonic pulses at a constant period and outputs the ultrasonic pulses to a fluid to be measured, and an ultrasonic wave output from the ultrasonic oscillating means (15). A continuous pulse oscillating means (15a) that oscillates a continuous wave having the same frequency as the pulse; and an ultrasonic echo that is a reflected wave of the ultrasonic pulse that is oscillated by the ultrasonic oscillating means (15) and reflected from the fluid to be measured. An ultrasonic receiving means (15) for receiving the signal, a multiplying means (30a) for multiplying the ultrasonic echo signal received by the ultrasonic receiving means (15) and the continuous wave, and a multiplying means (30a) Analyzing the processed signal and calculating the position and speed of the ultrasonic reflector along the measurement line, and the position and speed of the ultrasonic reflector calculated by the signal analyzing means Output that outputs at least one of flow velocity distribution and flow rate Means (e.g. the display unit 40 such as a monitor output) comprises,
The signal analysis means performs a filtering process by a low-pass filter (30b) on the combined waveform signal obtained by the multiplication means (30a), and performs analog-to-digital conversion on the obtained waveform signal for signal analysis. This is an ultrasonic flowmeter.

(Glossary)
The present invention measures a flow velocity distribution of a fluid flowing through a so-called “large-diameter pipe” or a flow rate by the flow velocity distribution. Here, the “large-diameter pipe” is effective when used for a pipe having a diameter of 1 meter or more, particularly about 3 to 5 meters.
It is preferable that the ultrasonic oscillating means and the ultrasonic receiving means are integrally formed as an ultrasonic transducer in terms of reducing the number of parts.

The “signal processing means” includes, for example, an AD converter (32) that performs analog-digital conversion on the ultrasonic echo signal.
Further, for example, a wall filter processing unit (33) may be further provided that performs a filtering process for reducing the clutter noise component by the wall filter on the ultrasonic echo signal digitized by the AD converter (32). In this case, the wall filter processing unit (33) is an n-sequence component that is a reflected wave of ultrasonic pulses periodically oscillated n times (n is 2 or more) by the ultrasonic oscillation means (15). From the ultrasonic echo signal, the signal level of the ultrasonic echo signal is acquired at every predetermined elapsed time from the start time of each series, arranged in order of the number of series, and the corresponding time echo level signal is configured. Fourier transform is performed to obtain a frequency equivalent component of the corresponding time echo level signal. And after rejecting the low frequency equivalent component from the frequency equivalent component of the corresponding time echo level signal, after performing the inverse Fourier transform on the frequency equivalent component of the corresponding time echo level signal in which the low frequency equivalent component is rejected, The digital ultrasonic echo signals are reconstructed by rearranging them in time series.

(Function)
The ultrasonic oscillating means (15) generates an ultrasonic pulse at a constant period (frequency is set to f0) and outputs it in the fluid to be measured. The continuous pulse oscillating means (15a) oscillates a continuous wave having the same frequency (f0) as the ultrasonic pulse. Then, an ultrasonic echo signal (frequency is assumed to be f0 ′), which is a reflected wave of an ultrasonic pulse that is oscillated by the ultrasonic oscillating means (15) and reflected from the fluid to be measured, is used as an ultrasonic receiving means. (15) is received.
When multiplication processing is performed on the ultrasonic echo signal received by the ultrasonic reception means (15) and the continuous wave by the multiplication means (30a), the frequency component of (f0 + f0 ′) and (f0−f0 ′) Frequency components (if f0> f0 ′, (f0′−f0) if f0 <f0 ′).
Of the multiplication result signal, the frequency component (f0 + f0 ′) is cut by the filtering process by the low-pass filter (31b), and only the frequency component (f0−f0 ′) is left. For this reason, the number of sampling points can be reduced, and the amount of data in the calculation for cross-correlation is reduced. Therefore, accurate calculation is possible even in a wide search region (when the pipe diameter is large or when the flow rate of the fluid to be measured is high). The calculation result is output to the output means (40).

(Claim 2)
The invention described in claim 2 includes an ultrasonic oscillation means (15) that generates ultrasonic pulses at a constant cycle and outputs the ultrasonic pulses to the fluid under measurement, and the ultrasonic oscillation means (15) oscillates to generate the fluid under measurement. Ultrasonic wave receiving means (15) for receiving an ultrasonic echo signal which is a reflected wave of an ultrasonic pulse reflected from the signal, and an AD converter for analog-digital conversion of the ultrasonic echo signal received by the ultrasonic wave receiving means (15) (32), digital waveform generation means (15b) for generating a digital wave having the same frequency as the ultrasonic pulse oscillated by the ultrasonic oscillation means (15), and the digital wave and the AD converter (32) A digital mixer (33) that multiplies the ultrasonic digital echo signal digitized by the digital signal, and analyzes the processed signal multiplied by the digital mixer (33), and the position of the ultrasonic reflector along the measurement line Calculate speed Signal analysis means for, and the signal analyzer output unit means for outputting at least one of flow velocity distribution and flow rate of the fluid from the position and speed of the ultrasonic reflector calculated (40), provided with,
The signal analysis means performs signal analysis by executing filtering processing by a low-pass filter on the combined waveform signal obtained by the digital mixer (33).

(Function)
The ultrasonic oscillating means (15) generates an ultrasonic pulse at a constant period (frequency is set to f0) and outputs it into the fluid to be measured, and the ultrasonic oscillating means (15) oscillates to generate the fluid to be measured. The ultrasonic receiving means (15) receives an ultrasonic echo signal that is a reflected wave of the ultrasonic pulse reflected from the ultrasonic wave. The ultrasonic echo signal (with frequency f0 ′) received by the ultrasonic receiving means (15) is analog-digital converted by the AD converter (32).
On the other hand, the digital waveform generating means (15b) generates a digital wave having the same frequency (f0) as the ultrasonic pulse oscillated by the ultrasonic oscillating means (15). Then, the digital mixer (33) multiplies the digital wave and the ultrasonic digital echo signal digitized by the AD converter (32). The processing signal multiplied by the digital mixer (33) is analyzed, and the signal analysis means calculates the position and velocity of the ultrasonic reflector along the measurement line. The signal analysis means performs a filtering process using a low-pass filter on the combined waveform signal obtained by the digital mixer (33), and from the position and velocity of the ultrasonic reflector thus calculated, the flow velocity distribution of the fluid and The output means (40) outputs at least one of the flow rates.
When the multiplication means by the digital mixer 33 is executed, the frequency component (f0 + f0 ′) and the frequency component (f0−f0 ′) (if f0> f0 ′, f0 <f0 ′, (f0′−f0)). Will come to have).
Of this multiplication result signal, the frequency component (f0 + f0 ′) is cut by the filtering process by the digital low-pass filter (34), leaving only the frequency component (f0−f0 ′). For this reason, the number of sampling points can be reduced, and the amount of data in the calculation for cross-correlation is reduced. Therefore, accurate calculation is possible even in a wide search region (when the pipe diameter is large or when the flow rate of the fluid to be measured is high).

(Claim 3)
The invention according to claim 3 limits the ultrasonic flowmeter according to claim 2.
That is, the digital waveform generation means is formed by including a waveform database in which digital waveform data is accumulated, and a digital waveform output means for extracting a desired digital waveform from the waveform database and outputting it to the digital mixer (33). Features.

(Function)
The digital waveform generation means extracts a digital wave having the same frequency as the ultrasonic pulse oscillated by the ultrasonic oscillation means (15) from the waveform database. The digital waveform output means outputs the extracted digital waveform data to the digital mixer (33).
As a digital waveform generating means, a digital waveform is not created every time but is extracted from a database, so that the hardware configuration can be simplified and the operation cost can be reduced.

(Claim 4)
The invention described in claim 4 is a method invention corresponding to the invention described in claim 1.
That is, an ultrasonic oscillation procedure that generates an ultrasonic pulse at a constant period and outputs it in the fluid to be measured, and a continuous pulse oscillation that oscillates a continuous wave of the same frequency as the ultrasonic pulse output by the ultrasonic oscillation procedure An ultrasonic reception procedure for receiving an ultrasonic echo signal that is a reflected wave of an ultrasonic pulse that is oscillated by the ultrasonic oscillation procedure and reflected from the fluid to be measured; and received by the ultrasonic reception procedure A multiplication procedure for multiplying the ultrasonic echo signal and the continuous wave, and processing signals multiplied by the multiplication procedure are analyzed to calculate the position and velocity of the ultrasonic reflector along the measurement line A signal analysis procedure, and an output procedure for outputting at least one of the flow velocity distribution and the flow rate of the fluid from the position and velocity of the ultrasonic reflector calculated in the signal analysis procedure. Te, said executes a filtering process by the low-pass filter to the composite waveform signal obtained by multiplying the procedure, the resulting waveform signal from analog to digital converter, characterized in that it has decided to signal analysis.

(Claim 5)
The invention described in claim 5 is a method invention corresponding to the invention described in claim 2.
That is, an ultrasonic oscillation procedure for generating an ultrasonic pulse at a constant period and outputting it in the fluid to be measured, and a reflected wave of the ultrasonic pulse that is oscillated by the ultrasonic oscillation procedure and reflected from the fluid to be measured. An ultrasonic reception procedure for receiving an ultrasonic echo signal, an AD conversion procedure for analog-digital conversion of the ultrasonic echo signal received by the ultrasonic reception procedure by an AD converter, and oscillation by the ultrasonic oscillation procedure A digital waveform generation procedure for generating a digital wave having the same frequency as the ultrasonic pulse generated as a continuous wave, a digital wave generated by the digital waveform generation procedure, and an ultrasonic digital echo signal digitized by the AD converter, The digital signal is multiplied by a digital mixer, and the processed signal multiplied by the multiplication procedure is analyzed. A signal analysis procedure for calculating the position and velocity of the ultrasonic reflector, and an output procedure for outputting at least one of the flow velocity distribution and the flow rate of the fluid from the position and velocity of the ultrasonic reflector calculated in the signal analysis procedure; The signal analysis procedure is characterized in that the combined waveform signal obtained by the digital mixer is subjected to a signal analysis by performing a filtering process using a low-pass filter.

(Claim 6)
The invention described in claim 6 is a method invention corresponding to the invention described in claim 3, and limits the flow rate measuring method described in claim 6.
That is, the digital waveform generation procedure includes a waveform data storage procedure for storing digital waveform data in a waveform database in advance, and a digital waveform output procedure for extracting a desired digital waveform from the waveform database and outputting the digital waveform to the digital mixer. It is characterized by that.

(Claim 7)
The invention described in claim 7 is a computer program invention corresponding to the method invention described in claim 4, and is a computer program for oscillating ultrasonic waves in a fluid to be measured and measuring the flow rate from the reflected waves.
The program generates an ultrasonic pulse at a constant cycle and outputs it in the fluid to be measured, and continuously generates a continuous wave with the same frequency as the ultrasonic pulse output in the ultrasonic oscillation procedure. A pulse oscillation procedure, an ultrasonic reception procedure for receiving an ultrasonic echo signal that is a reflected wave of an ultrasonic pulse that is oscillated in the ultrasonic oscillation procedure and reflected from the fluid to be measured, and an ultrasonic reception procedure A multiplication procedure for multiplying the ultrasonic echo signal received by the continuous wave, and a processing signal multiplied by the multiplication procedure, and analyzing the position and velocity of the ultrasonic reflector along the measurement line. A computer executes a signal analysis procedure to calculate and an output procedure to output at least one of the flow velocity distribution and the flow rate of the fluid from the position and velocity of the ultrasonic reflector calculated by the signal analysis procedure. In the signal analysis procedure, the combined waveform signal obtained by the multiplication procedure is subjected to a filtering process using a low-pass filter, and the obtained waveform signal is converted from analog to digital for signal analysis. Features.

(Claim 8)
The invention described in claim 8 is a computer program invention corresponding to the method invention described in claim 5, and is a computer program for oscillating ultrasonic waves in a fluid to be measured and measuring the flow rate from the reflected waves.
The program includes an ultrasonic oscillation procedure for generating an ultrasonic pulse at a constant period and outputting it in the fluid to be measured, and a reflection of the ultrasonic pulse that is oscillated in the ultrasonic oscillation procedure and reflected from the fluid to be measured. An ultrasonic reception procedure for receiving an ultrasonic echo signal that is a wave, an AD conversion procedure for analog-digital conversion of the ultrasonic echo signal received in the ultrasonic reception procedure by an AD converter, and the ultrasonic oscillation procedure A digital waveform generation procedure for generating a digital wave having the same frequency as the ultrasonic pulse oscillated as a continuous wave, and a digital wave generated by the digital waveform generation procedure and an ultrasonic digital echo digitized by the AD converter The signal is multiplied by a digital mixer using a digital mixer, and the processed signal multiplied by the multiplication procedure is analyzed, and the measurement is performed. A signal analysis procedure for calculating the position and velocity of the ultrasonic reflector along the line, and outputting at least one of the flow velocity distribution and the flow rate of the fluid from the position and velocity of the ultrasonic reflector calculated in the signal analysis procedure The output procedure is executed by a computer, and the signal analysis procedure is characterized in that the combined waveform signal obtained by the digital mixer is subjected to a signal analysis by performing a filtering process using a low-pass filter.

(Claim 9)
The invention described in claim 9 is a computer program corresponding to the invention described in claim 6, and the invention described in claim 8 is limited.
That is, the digital waveform generation procedure includes a waveform data storage procedure for storing digital waveform data in a waveform database in advance, and a digital waveform output procedure for extracting a desired digital waveform from the waveform database and outputting the digital waveform to the digital mixer. It is characterized by that.

  The computer program according to any one of claims 7 to 9 can be provided by being stored in a recording medium. Here, the “recording medium” is a medium that can carry a program that cannot occupy space by itself, such as a flexible disk, a hard disk, a CD-R, an MO (magneto-optical disk), a DVD- R and the like.

According to the first to third aspects of the present invention, even when the flow rate of the fluid to be measured is fast or the pipe diameter through which the fluid to be measured flows is large, An ultrasonic flowmeter capable of realizing the measurement was provided.
According to the invention described in claims 4 to 6, there is provided a measurement method capable of realizing accurate measurement even when the flow rate of the fluid to be measured is high or the pipe diameter through which the fluid to be measured flows is large. I was able to.
According to the seventh to ninth aspects of the present invention, there is provided a measurement program capable of realizing accurate measurement even when the flow rate of the fluid to be measured is high or the pipe diameter through which the fluid to be measured flows is large. I was able to.

  The present invention will be described with reference to embodiments and drawings. The drawings used individually are shown in FIGS.

(Figure 1)
FIG. 1 schematically shows the system configuration of an ultrasonic flow velocity distribution meter and a flow meter according to the present invention.
The personal computer ("PC" 11 in the figure) and the ultrasonic flow velocity distribution and flow measurement program that can be read and executed by the personal computer 11 cooperate with each other, and the ultrasonic flow velocity distribution for the pipe 18 through which the fluid to be measured flows. It functions as a meter and a flow meter. That is, the ultrasonic velocity distribution and flow measurement program is installed in the hard disk built in the personal computer 11.

An ultrasonic transducer 15 is fixed to the pipe 18.
The ultrasonic transducer 15 is installed on the pipe 18 from the outside at a predetermined installation angle θ. The ultrasonic pulse transmitted from the ultrasonic transducer 15 is incident and suspended (mixed) in the measured fluid 17 flowing in the pipe 18 along the measurement line ML shown in FIG. Is reflected by. The reflected wave reflected by the ultrasonic reflector (bubble 48) returns to the ultrasonic transducer 15. This signal is multiplied by the signal by the ultrasonic pulse transmitter 15a (or the digital waveform generator 15b).

Although illustration is omitted, the above-described transducer 15 is generally installed in the pipe 18 via an acoustic coupler in order to match the acoustic impedance.
At the time of ultrasonic flow velocity distribution and flow rate measurement, for example, processing operations associated with measurements such as control of the frequency of ultrasonic pulses transmitted by the transducer 15 and gain adjustment when receiving reflected waves (hereinafter referred to as “basic processing operations”). "), Various functions are realized by the preset basic process PG20. The basic process PG20 is recorded and stored in a recording means readable by the personal computer 11 such as a hard disk built in the personal computer 11, for example.

(FIGS. 2 and 4)
FIG. 2 is a functional block diagram of the ultrasonic flow velocity distribution meter and the flow meter according to the first embodiment, and FIG. 4 conceptually shows an ultrasonic processing procedure.
The ultrasonic transducer 15 functions as burst wave transmitting means and ultrasonic receiving means.
The burst wave transmitting means in the ultrasonic transducer 15 transmits a burst wave having a frequency f0 at a predetermined repetition frequency. The ultrasonic pulse oscillator 15a oscillates a continuous wave having the same frequency f0 as the burst wave.

  The multiplying unit 30a multiplies the reflected wave of the burst wave received by the ultrasonic wave receiving unit and the continuous wave. When the frequency of the ultrasonic echo signal received by the ultrasonic transducer 15 is f0 ′ and this multiplication process is executed, the frequency component of (f0 + f0 ′) and the frequency component of (f0−f0 ′) (f0> f0 ′) , F0 <f0 ′, (f0′−f0)).

(Fig. 5)
FIG. 5 conceptually shows the filtering function by the low-pass filter.
By cutting the frequency component of (f0 + f0 ′) by the filtering process by the low-pass filter (31b), only the frequency component of (f0−f0 ′) remains. As a result, the number of sampling points can be reduced in the calculation in the subsequent flow velocity distribution calculation, and the amount of data in the calculation for cross-correlation is reduced.
For this reason, it is possible to narrow the calculation range when calculating the flow velocity distribution to be executed later, and to reduce the burden on the hardware.

The signal applied to the low pass filter 30b is sent to the ultrasonic control unit 25. The ultrasonic control unit 25 includes an AD converter 32 and a WF processing unit 33 using a wall filter.
The digital signal after AD conversion is temporarily stored as digital data in a memory (not shown) built in the personal computer 11, for example. The digital data stored in the memory can be recorded in a recording means readable by the personal computer 11 such as a hard disk built in the personal computer 11, a flexible disk, a CD-ROM, a DVD-ROM, or an MO. Further, the resolution of the AD converter 32 is, for example, 8 bits and the sampling frequency can be up to 500 MHz.

  The wall filter is a filter that reduces clutter noise components. In this case, the wall filter processing unit 33 performs ultrasonic echoes for n series, which are reflected waves of ultrasonic pulses periodically oscillated n times (n is 2 or more) by the ultrasonic oscillating means 15. The signal level of the ultrasonic echo signal is obtained from the signal at every predetermined elapsed time from the start time of each series, arranged in order of the number of series, and the corresponding time echo level signal is Fourier transformed. The frequency equivalent component of the corresponding time echo level signal is obtained. And after rejecting the low frequency equivalent component from the frequency equivalent component of the corresponding time echo level signal, after performing the inverse Fourier transform on the frequency equivalent component of the corresponding time echo level signal in which the low frequency equivalent component is rejected, The digital ultrasonic echo signals are reconstructed by rearranging them in time series.

However, this may not be necessary when the clutter noise component is reduced by the multiplication means 30a or the low-pass filter 30b described above. The procedure in that case is indicated by a two-dot broken line.
The electrical signal processed by the ultrasonic control unit 25 is used by the flow velocity distribution calculation unit 37 to calculate the flow velocity distribution. When it is desired to output the flow velocity distribution, the display means 40 (the display of the personal computer 11 or the like) outputs it. The procedure in that case is indicated by a two-dot broken line.

  In order to calculate the flow rate using the result of calculating the flow velocity distribution in the flow velocity distribution calculation unit 37, the flow rate calculation unit 38 executes an integral operation or the like to calculate the flow rate per unit time. In other words, the flow rate calculation unit 38 receives the flow rate distribution data calculated by the flow rate distribution calculation unit 37, and uses the received flow rate distribution data to convert the flow rate distribution in the pipe 18 along the internal area of the pipe 18. To calculate the flow rate. That is, the integral calculation process for calculating the flow rate is performed by the calculation processing means such as the CPU of the personal computer 11 executing the ultrasonic flow velocity distribution and flow rate measurement program. The result is output by the display means 40.

(Figure 3)
FIG. 3 shows a functional block diagram of the ultrasonic flow velocity distribution meter and the flow meter according to the second embodiment.
In this embodiment, the ultrasonic pulse oscillator 15a used in the first embodiment is not used, and a digital waveform generator 15b is used instead.
The ultrasonic transducer 15 functions as a burst wave transmitting unit and an ultrasonic receiving unit that receives a reflected wave (ultrasonic echo signal) of the burst wave.

The received ultrasonic echo signal is sent to the ultrasonic control unit 25. The ultrasonic control unit 25 includes a BPF processing unit 31 that performs filtering for extracting the same frequency band as the used ultrasonic wave in the received ultrasonic echo signal (hereinafter referred to as a bandpass filtering process = BPF process), and an ultrasonic wave. An AD converter 32 that converts an echo signal from an analog signal to a digital signal and a digital mixer 33 are provided.
The band-pass filter processing unit 31 is not essential, and the ultrasonic echo signal received by the ultrasonic receiving unit may be sent to the AD converter 32 suddenly.

  The digital mixer 33 includes a digital wave having the same frequency as the ultrasonic pulse oscillated by the ultrasonic wave oscillating means (15) by the digital waveform generating means 15b, an ultrasonic echo signal digitized by the AD converter 32, and the like. Is multiplied. Assuming that the frequency of the digitized ultrasonic echo signal is f0 ′, this multiplication process results in a frequency component of (f0 + f0 ′) and a frequency component of (f0−f0 ′) (f0 <f0 ′ when f0> f0 ′). In this case, it becomes (f0′−f0)).

By cutting the frequency component of (f0 + f0 ′) by the filtering process by the low-pass filter (31b), only the frequency component of (f0−f0 ′) remains. As a result, the number of sampling points can be reduced in the calculation in the subsequent flow velocity distribution calculation, and the amount of data in the calculation for cross-correlation is reduced.
For this reason, it is possible to narrow the calculation range when calculating the flow velocity distribution to be executed later, and to reduce the burden on the hardware.

  The signal filtered by the digital low-pass filter 34 is subjected to wall filter processing by the WF processing unit 33 if necessary, and the position and velocity of the reflector 48 are calculated by the reflector position / velocity calculation unit 36. . The processed electrical signal is used by the flow velocity distribution calculation unit 37 to calculate the flow velocity distribution. The flow velocity distribution calculator 37 obtains a velocity distribution by plotting the position and velocity of the ultrasonic reflector group calculated by the reflector position / velocity calculator 36. The plot processing of the position and velocity of the ultrasonic reflector group is performed by the calculation processing means such as the CPU of the personal computer 11 executing the ultrasonic flow velocity distribution and flow measurement program.

When it is desired to output the flow velocity distribution calculated here, the display means 40 outputs it. The procedure in that case is indicated by a two-dot broken line.
In order to calculate the flow rate by using the result of calculating the flow velocity distribution in the flow velocity distribution calculation unit 37, the flow rate calculation unit executes an integral operation or the like to calculate the flow rate per unit time. The result is output by the display means 40.

(Fig. 6)
FIG. 6 is an explanatory diagram for explaining the relationship between the trigger signal and ultrasonic echo signal reception waveform and the sampling timing of the AD converter 32.
The horizontal axis represents the time axis, the vertical axis represents the signal level, the upper stage shows the time change of the trigger signal, the middle stage shows the time change of the received waveform of the ultrasonic echo signal, and the lower stage shows the sampling timing of the AD converter 32. As shown in the upper part of FIG. 6, for example, pulse signals are output one after another as the trigger signal at predetermined time (τ) intervals. The timing of reception of the ultrasonic echo signal and the sampling of the AD converter 32 are controlled in accordance with the timing of the trigger signal.

  As shown in the lower part of FIG. 6, the AD converter 32 performs digital sampling processing on the ultrasonic echo signal for an extremely short time width, for example, every 1 μs to obtain the digital ultrasonic echo signal, that is, the time series of the required number of series. Data (for example, 512 series) is acquired. When the AD converter 32 completes the acquisition of time series data for the required number of series, the WF processing unit 33 executes WF processing on the digital ultrasonic echo signal as a WF processing step. The WF processing unit 33 reduces clutter noise. The ultrasonic echo signal for which the WF process has been completed is subjected to signal analysis by a signal analysis procedure.

  In the present invention, it is possible to extract an echo signal when there is a frequency change by multiplying the same signal as the oscillated ultrasonic pulse and executing processing by a low-pass filter, which is equivalent to WF processing. effective. Therefore, WF processing is not always necessary.

  Signal analysis refers to obtaining a velocity distribution along the measurement line (diameter direction line of the stainless steel pipe 18a) ML of the fluid 17 flowing in the pipe 18 by analyzing the ultrasonic echo signal using the cross-correlation method, or ML. Is obtained, and the flow rate is obtained by integrating the obtained flow velocity distribution along the internal area of the stainless steel pipe 18a.

  The signal analysis procedure includes a reflector position / velocity calculating step for calculating the position and velocity of the ultrasonic reflector group in the fluid, and a position of the ultrasonic reflector group in the fluid calculated in the reflector position / velocity calculating step. And a flow rate distribution calculating step for calculating a flow velocity distribution of the fluid from the velocity, and a flow rate calculating step for calculating a flow rate by performing an integral operation along the internal area of the pipe 18 for the flow velocity distribution calculated in the flow velocity distribution calculating step.

  In the signal analysis of the ultrasonic echo signal as the signal analysis procedure, first, the reflector position / velocity calculation unit 36 calculates the position and velocity of the ultrasonic reflector group as a reflector position / velocity calculation step. The position and velocity of the ultrasonic reflector group are calculated in a very short time width, for example, a continuous series of digital ultrasonic echo signals sampled 512 series every 1 μs, that is, a reflected wave included in the nth series (see Wave) 45 and the cross-correlation between the reflected wave (search wave) 46 included in the (n + 1) th series (n is an integer satisfying 1 <n <511).

  The calculation of the cross-correlation between the reference wave 45 and the search wave 46 as the cross-correlation calculation processing step is performed by setting the size of the search window using the variable search window method, and in the necessary search range in the search wave 46 Cross correlation with 45 is performed from n = 1 to n = 511. Then, the cross-correlation between the reference wave 45 and the search wave 46 is calculated, and when the correlation value is equal to or greater than a certain value (threshold value), a phase specifying step that regards the reflected wave from the same ultrasonic reflector is executed, Then, the phase difference between the reference wave 45 and the search wave 46 specified in the phase difference calculating step is obtained, and the position / velocity calculating step for calculating the position and velocity of the ultrasonic reflector from the phase difference is executed.

  In this way, when the correlation value between the reference wave 45 and the search wave 46 is a certain value (threshold value) or more, it is regarded as a reflected wave from the same ultrasonic reflector and the ultrasonic wave is reflected in the fluid 17. The position and speed of each ultrasonic reflector are calculated. Then, the flow velocity distribution calculating unit 37 calculates the flow velocity distribution of the fluid 17 to be measured from the position and velocity of the ultrasonic reflector group calculated as the flow velocity distribution calculating step.

  The flow velocity distribution calculation unit 37 calculates the flow velocity distribution of the fluid 17 to be measured from the position and velocity data of the obtained ultrasonic reflector group. The calculated flow velocity distribution of the fluid 17 to be measured is regarded as the velocity of the ultrasonic reflector group suspended in the fluid 17, and the pipe 18 (stainless steel is obtained from the position and velocity data of the obtained ultrasonic reflector group. The relationship between the position of the pipe 18a) and the velocity of the ultrasonic reflector group at that position, that is, the flow velocity distribution of the fluid 17 in the pipe 18 is calculated.

  The signal analysis procedure includes a reflector position / velocity calculation step, a flow velocity distribution calculation step, and a flow rate calculation step. However, the signal analysis procedure includes a reflector position / velocity calculation step and a flow velocity distribution calculation step. The form provided with. In this case, the ultrasonic flow velocity distribution meter and the flow meter 10 calculate only the flow velocity distribution of the fluid to be measured 17 in the pipe 18 and do not calculate the flow rate, and the flow velocity is displayed on a display means such as a display of the personal computer 11. The distribution is displayed.

(Fig. 7)
FIG. 7 is a process for explaining the ultrasonic flow velocity distribution and flow measurement processing method performed by the personal computer 11 executing the ultrasonic flow velocity distribution and flow measurement program in the ultrasonic flow velocity distribution meter and flow meter shown in FIG. FIG.
That is, the ultrasonic flow velocity distribution and flow rate measurement processing method obtains the flow velocity distribution and flow rate of the fluid 17 by performing signal processing on the received ultrasonic echo signal and signal analysis of the ultrasonic echo signal after the signal processing. A signal analysis procedure.

  The signal processing procedure includes a BPF processing step for performing BPF processing for extracting the same frequency band as the used ultrasonic wave from the received ultrasonic echo signal, an AD conversion step for AD converting the ultrasonic echo signal, and an ultrasonic echo signal. And a WF processing step for reducing clutter noise components superimposed on the.

  The signal analysis procedure includes a reflector position / velocity calculating step for calculating the position and velocity of the ultrasonic reflector group in the fluid 17 to be measured, and the ultrasonic reflector group calculated in the reflector position / velocity calculating step. A flow velocity distribution calculating step for calculating a flow velocity distribution of the fluid from the position and velocity; and a flow rate calculating step for calculating a flow rate of the fluid 17 from the flow velocity distribution calculated in the flow velocity distribution calculating step.

  In the present invention, it is possible to extract an echo signal when there is a frequency change by multiplying the same signal as the oscillated ultrasonic pulse and executing processing by a low-pass filter, which corresponds to WF processing. There is an effect. Therefore, WF processing is not always necessary.

First, arithmetic processing means such as a CPU built in the personal computer 11 reads out and executes the ultrasonic flow velocity distribution and the flow measurement PG 12, and performs a signal processing procedure (steps S1 to S3) and a signal analysis procedure (steps S4 to S6). Execute.
In the signal processing procedure in the ultrasonic flow velocity distribution and flow rate measurement processing method, the BPF processing step is performed in step S1, the AD conversion step is performed in step S2, and the WF processing step is performed in step S3.

(Fig. 8)
FIG. 8 is a process flow diagram showing more detailed processing steps of the reflector group position / velocity calculating step (step S4) in the signal analysis procedure.
The reflector group position / velocity calculating step in step S4 includes a cross-correlation calculating step (step S21), a phase specifying step (step S22), a phase difference calculating step (step S23), and a position / velocity calculating step (step). S24) and a search completion determination step (step S25).

  In the reflector group position / velocity calculation step, first, a cross-correlation calculation processing step is performed in step S21, and the cross-correlation between the reference wave 45 and the search wave 46 by the cross-correlation method is calculated to calculate a correlation value. The correlation value is calculated by setting the size of the search window of the search wave 46 by the variable search window method and calculating the cross-correlation with the reference range of the reference wave 45 in the search range of the search wave 46. . When the calculation of the correlation value is completed, the cross-correlation calculation processing step (step S21) is completed, and then the phase specifying step is performed in step S22.

  In the phase identification step of step S22, the phase of the search wave 46 having a relationship in which the correlation value obtained in the cross correlation calculation processing step (step S21) is equal to or greater than the threshold value s is identified. The threshold s is set before or during execution of the PG. The phase identification step (step S22) is completed, and then a phase difference calculation step is performed in step S23.

In the phase difference calculation step of step S23, the phase difference between the phase of the identified search wave 46 and the phase referred to by the reference wave 45 is calculated. When the calculation of the phase difference is completed, the phase difference calculation step (step S23) is completed, and then the position / velocity calculation step is performed in step S24.
In the position / velocity calculating step of step S24, the position and velocity of the ultrasonic reflector within the search range of the search wave 46 are calculated from the calculated phase difference. When the calculation of the position and velocity of the ultrasonic reflector within the search range of the search wave 46 is completed, the position / velocity calculation step (step S24) is completed, and then the search completion determination step of step S25 is performed.

  In the search completion determination step of step S25, it is determined whether or not the search has been completed for all search ranges searched in the search wave 46. If the search has not been completed for all search ranges (NO in step S25), the process proceeds to step S21, and the processing steps after step S21 are repeated. By repeating the processing steps after step S21, the position and speed of the ultrasonic reflector group flowing in the fluid 17 are calculated. On the other hand, when the search has been completed for all the search ranges (YES in step S25), the reflector group position / velocity calculating step is terminated.

  When the reflector group position / velocity calculating step (step S4) is completed in the signal analysis procedure, the flow velocity distribution calculating step (step S5) is subsequently performed. In the flow velocity distribution calculating step in step S5, the relationship between the position and velocity of the ultrasonic reflector group, that is, the flow velocity distribution is calculated from the reflector group position and velocity calculated in the reflector group position / velocity calculating step. When calculating the flow velocity distribution, the velocity of all the ultrasonic reflectors acquired at the same position at the same corresponding time (for example, corresponding time τ1) in each series is calculated by averaging or squaring.

  When the flow velocity distribution is calculated, the flow velocity distribution calculation step (step S5) is completed, and then the flow rate calculation step (step S6) is performed. In the flow rate calculation step of step S6, the flow rate is calculated by integrating the flow velocity distribution in the calculated pipe 18 along the internal area of the pipe 18. At this time, information necessary for the integral calculation other than the flow velocity distribution such as the inner diameter D of the pipe 18 is input and set before the ultrasonic flow velocity distribution and flow rate measurement processing is performed.

  When the calculation of the flow rate is completed, the flow rate calculation step (step S6) is completed, and the signal analysis procedure completes all the processing steps. When the signal analysis procedure is completed, the entire processing procedure in the ultrasonic flow velocity distribution and flow rate measurement processing method is completed. The display of the ultrasonic flow velocity distribution and the flow measurement processing result is performed by reading out and executing the basic processing program after the arithmetic processing means such as a CPU built in the personal computer 11 completes the entire processing procedure of the ultrasonic flow velocity distribution and flow measurement program. That is done.

(Wall filter)
In the ultrasonic flow velocity distribution meter and the flow meter 10, when the metal pipe 18 is used as the fluid pipe for guiding the fluid 17 to be measured, when the flow velocity distribution and the flow rate of the measurement target fluid 17 are measured, the received ultrasonic echo signal is In addition, a noise component called clutter noise is significantly superimposed. Due to this noise component, it is possible to obtain incorrect tracer particle position and velocity information. In order to avoid this, the clutter noise reduction processing by the WF processing unit 33 described above is executed. Hereinafter, a clutter noise reduction processing method using WF will be described.

(Fig. 9)
FIG. 9 illustrates a time series change of the trigger signal, the ultrasonic echo signal, and the clutter noise.
Each series of clutter noise is substantially the same in any series, and is a noise that attenuates and oscillates as time passes. The clutter noise is noise in which the noise corresponding to the number of series slides and is superimposed by the time difference τ, and thus has various frequency components and n peaks for each start time of the 1st to nth series.

The conventional filtering process using LPF and HPF and the filtering process using BPF cannot effectively filter the clutter noise having various frequency components, and the portion where the clutter noise is generated is caused by the ultrasonic pulse from the tracer particle group. The signal was analyzed as a reflected signal, and the clutter noise was mistakenly regarded as an effective signal.
Therefore, a filtering process (WF process) using WF is executed to prevent the clutter noise from being recognized as an effective signal and to sufficiently reduce the clutter noise with respect to the effective signal. In the WF process, first, a corresponding time echo level signal is acquired from a digital ultrasonic echo signal.

  The present invention can be used in the flow meter and current meter manufacturing industry, the flow meter and current meter sales and maintenance business, the plant maintenance and maintenance business, and the computer program production and maintenance business related to plant control. There is.

1 is a measurement system schematically showing an embodiment of an ultrasonic flow velocity distribution meter and a flow meter according to the present invention, and is a schematic configuration diagram of the measurement system applied to experimental equipment. The functional block diagram of the ultrasonic flow velocity distribution meter which is 1st embodiment, and a flowmeter. The functional block diagram of the ultrasonic flow velocity distribution meter and flowmeter which are 2nd embodiment. The figure which shows notionally the multiplication of the ultrasonic wave in this invention. The figure which shows notionally the function of the low-pass filter in this invention. Explanatory drawing explaining the relationship between a trigger signal and an ultrasonic echo signal reception waveform, and the timing of sampling of AD converter. The processing flow figure which shows the signal processing procedure and signal analysis procedure of the ultrasonic flow velocity distribution and flow measurement processing method according to the present invention. The processing flow figure which shows the reflector position and speed calculation process by the flow velocity distribution and flow measurement processing method concerning this invention. Explanatory drawing explaining the time series change (lower stage) of a trigger signal (upper stage), an ultrasonic echo signal (middle stage), and clutter noise.

Explanation of symbols

11 PC
14 Signal Line 15 Transducer 15a Ultrasonic Pulse Oscillator 15b Digital Waveform Generator 17 Measured Fluid 18 Metal Pipe 18a Stainless Steel Pipe 30a Multiplier 30b Low Pass Filter 31 BPF Processing Unit 32 AD Converter 33 WF Processing Unit 34 Digital Low Pass Filter 36 Reflection Body position / velocity calculation unit 37 Flow velocity distribution calculation unit 38 Flow rate calculation unit 40 Display means (output means)
43 Fluid piping installation container 45 Reference wave 46 Search wave 48 Bubble (reflector)

Claims (9)

An ultrasonic oscillating means for generating an ultrasonic pulse at a constant period and outputting it in a fluid to be measured;
Continuous pulse oscillation means for oscillating a continuous wave of the same frequency as the ultrasonic pulse output by the ultrasonic oscillation means;
Ultrasonic receiving means for receiving an ultrasonic echo signal that is a reflected wave of an ultrasonic pulse that is oscillated by the ultrasonic oscillation means and reflected from the fluid to be measured;
Multiplication means for multiplying the ultrasonic echo signal received by the ultrasonic reception means and the continuous wave;
Analyzing the processing signal multiplied by the multiplication means, and calculating the position and velocity of the ultrasonic reflector along the measurement line;
Output means for outputting at least one of the flow velocity distribution and the flow rate of the fluid from the position and velocity of the ultrasonic reflector calculated by the signal analysis means,
The signal analysis means performs signal analysis by performing analog-to-digital conversion on a waveform signal obtained by executing filtering processing by a low-pass filter on the combined waveform signal obtained by the multiplication means. Sonic flow meter. An ultrasonic oscillating means for generating an ultrasonic pulse at a constant period and outputting it in a fluid to be measured;
An ultrasonic receiving means for receiving an ultrasonic echo signal that is a reflected wave of an ultrasonic pulse that is oscillated by the ultrasonic oscillating means and reflected from the fluid to be measured;
An AD converter for analog-to-digital conversion of an ultrasonic echo signal received by the ultrasonic receiving means;
Digital waveform generating means for generating a digital wave having the same frequency as the ultrasonic pulse generated by the ultrasonic oscillating means as a continuous wave;
A digital mixer for multiplying the digital wave and the ultrasonic digital echo signal digitized by the AD converter;
Analyzing the processed signal multiplied by the digital mixer, and calculating the position and velocity of the ultrasonic reflector along the measurement line;
Output means for outputting at least one of the flow velocity distribution and the flow rate of the fluid from the position and velocity of the ultrasonic reflector calculated by the signal analysis means,
The ultrasonic flowmeter according to claim 1, wherein the signal analysis means performs signal analysis by performing filtering processing by a low-pass filter on the combined waveform signal obtained by the digital mixer.   The digital waveform generation means includes a waveform database in which digital waveform data is stored, and a digital waveform output means for extracting a desired digital waveform from the waveform database and outputting the digital waveform to the digital mixer. The ultrasonic flowmeter according to claim 2. An ultrasonic oscillation procedure for generating ultrasonic pulses at a constant period and outputting them in the fluid to be measured;
A continuous pulse oscillation procedure for oscillating a continuous wave of the same frequency as the ultrasonic pulse output in the ultrasonic oscillation procedure;
An ultrasonic reception procedure for receiving an ultrasonic echo signal that is a reflected wave of an ultrasonic pulse that is oscillated in the ultrasonic oscillation procedure and reflected from the fluid under measurement;
A multiplication procedure for multiplying the ultrasonic echo signal received by the ultrasonic reception procedure and the continuous wave;
Analyzing the processed signal multiplied by the multiplication procedure, calculating the position and velocity of the ultrasonic reflector along the measurement line,
An output procedure for outputting at least one of the flow velocity distribution and the flow rate of the fluid from the position and velocity of the ultrasonic reflector calculated in the signal analysis procedure,
The signal analysis procedure is characterized in that a signal analysis is performed by analog-digital conversion of a waveform signal obtained by performing filtering processing by a low-pass filter on the combined waveform signal obtained by the multiplication procedure. Flow measurement method. An ultrasonic oscillation procedure for generating ultrasonic pulses at a constant period and outputting them in the fluid to be measured;
An ultrasonic reception procedure for receiving an ultrasonic echo signal that is a reflected wave of an ultrasonic pulse that is oscillated by the ultrasonic oscillation procedure and reflected from the fluid under measurement;
AD conversion procedure for analog-digital conversion of the ultrasonic echo signal received by the ultrasonic reception procedure by an AD converter;
A digital waveform generation procedure for generating a digital wave having the same frequency as the ultrasonic pulse oscillated in the ultrasonic oscillation procedure as a continuous wave;
A multiplication procedure for multiplying the digital wave generated by the digital waveform generation procedure and the ultrasonic digital echo signal digitized by the AD converter by a digital mixer;
Analyzing the processed signal multiplied by the multiplication procedure, calculating the position and velocity of the ultrasonic reflector along the measurement line,
An output procedure for outputting at least one of the flow velocity distribution and the flow rate of the fluid from the position and velocity of the ultrasonic reflector calculated in the signal analysis procedure,
The flow rate measuring method according to claim 1, wherein the signal analysis procedure includes performing a signal analysis by performing a filtering process using a low-pass filter on the combined waveform signal obtained by the digital mixer.   The digital waveform generation procedure includes a waveform data storage procedure for storing digital waveform data in a waveform database in advance, and a digital waveform output procedure for extracting a desired digital waveform from the waveform database and outputting the digital waveform to the digital mixer. The flow rate measuring method according to claim 5, wherein the flow rate is measured. A computer program for oscillating ultrasonic waves in a fluid to be measured and measuring the flow rate from the reflected waves,
The program generates an ultrasonic pulse at a constant period and outputs it into the fluid to be measured.
A continuous pulse oscillation procedure for oscillating a continuous wave of the same frequency as the ultrasonic pulse output in the ultrasonic oscillation procedure;
An ultrasonic reception procedure for receiving an ultrasonic echo signal that is a reflected wave of an ultrasonic pulse that is oscillated in the ultrasonic oscillation procedure and reflected from the fluid under measurement;
A multiplication procedure for multiplying the ultrasonic echo signal received by the ultrasonic reception procedure and the continuous wave;
Analyzing the processed signal multiplied by the multiplication procedure, calculating the position and velocity of the ultrasonic reflector along the measurement line,
An output procedure for outputting at least one of the flow velocity distribution and the flow rate of the fluid from the position and velocity of the ultrasonic reflector calculated in the signal analysis procedure; and
The signal analysis procedure is characterized in that a signal analysis is performed by analog-digital conversion of a waveform signal obtained by performing filtering processing by a low-pass filter on the combined waveform signal obtained by the multiplication procedure. Computer program. A computer program for oscillating ultrasonic waves in a fluid to be measured and measuring the flow rate from the reflected waves,
The program generates an ultrasonic pulse at a constant period and outputs it into the fluid to be measured.
An ultrasonic reception procedure for receiving an ultrasonic echo signal that is a reflected wave of an ultrasonic pulse that is oscillated by the ultrasonic oscillation procedure and reflected from the fluid under measurement;
AD conversion procedure for analog-digital conversion of the ultrasonic echo signal received by the ultrasonic reception procedure by an AD converter;
A digital waveform generation procedure for generating a digital wave having the same frequency as the ultrasonic pulse oscillated in the ultrasonic oscillation procedure as a continuous wave;
A multiplication procedure for multiplying the digital wave generated by the digital waveform generation procedure and the ultrasonic digital echo signal digitized by the AD converter by a digital mixer;
Analyzing the processed signal multiplied by the multiplication procedure, calculating the position and velocity of the ultrasonic reflector along the measurement line,
An output procedure for outputting at least one of the flow velocity distribution and the flow rate of the fluid from the position and velocity of the ultrasonic reflector calculated in the signal analysis procedure; and
The computer program according to claim 1, wherein the signal analysis procedure includes performing a filtering process using a low-pass filter on the synthesized waveform signal obtained by the digital mixer and performing signal analysis.   The digital waveform generation procedure includes a waveform data storage procedure for storing digital waveform data in a waveform database in advance, and a digital waveform output procedure for extracting a desired digital waveform from the waveform database and outputting the digital waveform to the digital mixer. The computer program according to claim 8, wherein the computer program is characterized.

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