JP2016024023A - Method of identifying abnormal sound generation position - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of identifying an abnormal sound generation position that can easily determine a generation position of an abnormal sound.SOLUTION: A method of identifying an abnormal sound generation position includes: a delay calculation step of installing a vibration sensor 200 in at least two positions of a pipe network 110 (piping network) to determine a delay of vibration from a cross-correlation function of a waveform obtained by the vibration sensor 200; a first extraction step of extracting the maximum value of a correlation value and a time difference to the maximum value from a cross-correlation function of a predetermined time; a first integration step of repeating the first extraction step for a plurality of times to integrate the maximum value of the correlation value in each time difference; and a determination step of determining a time difference of which an integrated value is the maximum as a transmission time difference Td of an abnormal sound as a result of the first integration step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for specifying an abnormal sound occurrence position.

  Conventionally, as a method for determining the position of leakage in a pipe, there is a method for detecting vibration by a sensor, generating a cross-correlation function from the detected signal, and specifying an abnormal sound generation position using the acoustic propagation velocity. .

  For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 8-226865) discloses that in a noisy environment where no excavation is easy and noisy, a disturbing noise source is eliminated in a non-intrusive manner, and the leakage of the conduit is accurately detected. A method for determining the position of a conduit leak for determining position is disclosed.

  The method of determining the leak position of a conduit described in Patent Document 1 (Japanese Patent Application Laid-Open No. 8-226865) includes: a) first sensors arranged along a conduit so as to obtain a raw plot of a first time difference; Calculating a cross-correlation function from leakage noise data obtained from the pair; and b) from leakage noise data obtained from a second pair of sensors spaced apart along the conduit to obtain a raw plot of the second time difference. Calculating a cross-correlation function; c) smoothing each raw plot of the time difference to obtain a time difference peak for each plot; and d) a known time interval between the first time difference peak and the first sensor pair. Determining the propagation velocity of the conduit against leakage noise, and e) determining the location of the leakage by using the propagation velocity, the second time difference peak, and the spacing between the second sensor pair. It is intended to determine the position of the leakage of the conduit characterized by comprising.

JP-A-8-226865

  Thus, the aging of waterworks or gas pipes has progressed, and fluid leakage from defects has become a problem. Therefore, it is conceivable to apply the method described in Patent Document 1 (Japanese Patent Laid-Open No. 8-226865) to specify the defect position.

  However, in an actual leakage site, external noise such as automobile traffic noise is input in addition to the leakage sound, and may be added to the waveform obtained by each sensor. In this case, when the transmission time difference is obtained from the cross-correlation function, it may indicate the place where the passing sound is generated instead of the leaking sound.

In addition, not only the point where the leaking sound is generated, but the surroundings often vibrate as a whole. In such a case, the peak of the cross-correlation function cannot be clearly identified.
Furthermore, when there are a plurality of leaked portions, it is extremely difficult to identify individual peaks.

An object of the present invention is to provide a method for specifying an abnormal sound occurrence position, which can easily determine the occurrence position of the abnormal sound.
Another object of the present invention is to provide a method for identifying an abnormal sound occurrence position that can easily determine the occurrence positions of a plurality of abnormal sounds.

(1)
A method for identifying an abnormal sound occurrence position according to one aspect includes a delay calculation step in which vibration sensors are installed in at least two locations of a pipe network (piping network), and a vibration delay is obtained from a cross-correlation function of waveforms obtained by the vibration sensor; The first extraction step of extracting the maximum value of the correlation value and the time difference with respect to the maximum value from the cross-correlation function for a predetermined time, and the first extraction step are repeated a plurality of times, and the first of the correlation values at each time difference is integrated. An integration step and a determination step of determining a time difference at which the integrated value is maximum as a result of the first integration step as an abnormal sound transmission time difference.

In this case, the maximum value of the correlation value and the time difference with respect to the maximum value are extracted in the first extraction step, and the maximum value of the correlation value is integrated in the first integration step, thereby easily determining the occurrence position of the abnormal sound. Can do.
That is, the correlation function basically oscillates also in the vicinity of the maximum value. Therefore, only the maximum value of the correlation value is integrated, and other values are deleted to clearly determine the position where the abnormal sound is generated. be able to.

(2)
A method for identifying an abnormal sound occurrence position according to another aspect is a delay calculation step in which vibration sensors are installed at least at two locations of a pipe network (piping network) and a vibration delay is obtained from a cross-correlation function of waveforms obtained by the vibration sensor. And a second extraction step for extracting a time difference that maximizes the correlation value from a cross-correlation function for a predetermined time, and a second extraction step that repeats the second extraction step a plurality of times, and integrating the number of times that the correlation value at each time difference becomes maximum. And a determination step of determining a time difference at which the integrated value is the maximum as a result of the second integration step as an abnormal sound transmission time difference.

In this case, the occurrence position of the abnormal sound can be easily determined by extracting the time difference that maximizes the correlation value by the second extraction step and integrating the number of times that the correlation value becomes maximum by the second integration step. .
In other words, the correlation function basically oscillates around the maximum value as a whole, so only the number of times that the correlation value is maximized is added, and other values are deleted, so that the location of the abnormal sound is clearly determined. Can be determined.

(3)
According to a third aspect of the invention, there is provided an abnormal sound generation position specifying method according to one aspect or another aspect, wherein the vibration sensor has at least one resonance point in a frequency band of abnormal sound vibration. A resonance type vibration sensor may be used.

  In this case, it is easy to increase the sensitivity of the vibration sensor, and it is easy to capture abnormal sounds.

(4)
According to a fourth aspect of the invention, there is provided an abnormal sound generation position specifying method according to one aspect or another aspect, the abnormal sound generation position specifying method according to any one of the third invention, wherein the resonance frequency of the vibration sensor is: It may be 0.1 Hz or more and 500 Hz or less.

In this case, since the resonance frequency of the vibration sensor is in the range of 0.1 Hz to 500 Hz, it is possible to increase the sensitivity to vibration sound due to fluid leakage of a synthetic resin pipe or the like.
Moreover, since the vibration transmitted through the pipe attenuates as the distance increases, the magnitude of vibration energy transmitted to the vibration sensor is not the same. The waveform that reaches the vibration sensor is biased to a specific frequency component ratio under the influence of the pipe type, the diameter, the embedment status, or the like. In general, since the low frequency component reaches a far distance, the installation interval (installation span) of the vibration sensor can be lengthened.

It is a schematic diagram for demonstrating the condition of the identification method of an abnormal sound generation position. It is a schematic diagram which shows an example of a vibration sensor. It is a flowchart which shows an example of the identification method of the abnormal sound generation position concerning this Embodiment. It is a flowchart which shows the other example of FIG. It is a schematic diagram for demonstrating the cross correlation function concerning this invention. It is a schematic diagram for explaining integration processing according to the present invention. It is a schematic diagram for demonstrating frequency processing of the maximum value concerning this invention. It is a schematic diagram for demonstrating the conventional cross correlation function.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<Situation explanation of the method for identifying the location of abnormal sound>
FIG. 1 is a schematic diagram for explaining a situation of a method for specifying an abnormal sound occurrence position.

  As shown in FIG. 1, a pipe network 110 is provided in the ground. The pipe network 110 is provided with vertical holes (manholes) 120 at regular intervals. In the present embodiment, vertical holes 120 are provided at intervals between point A and point B. In this case, vibration sensors 200 are provided in the vertical holes 120 at point A and point B in FIG.

<Description of vibration sensor>
FIG. 2 is a schematic diagram illustrating an example of a vibration sensor.

As shown in FIG. 2, the vibration sensor 200 according to the present embodiment uses a resonance type vibration sensor 200.
The vibration sensor 200 of FIG. 2 includes a pedestal 210, support columns 220, thin film electrodes 230 and 240, lead wires 231 and 241, a piezoelectric element 250 and a weight 260.

  As shown in FIG. 2, in the vibration sensor 200, a support 220 is fixed on an iron base 210. A piezoelectric element 250 is provided at the upper end of the support 220. One end of the piezoelectric element 250 is cantilevered by the upper end of the column 220.

A pair of upper and lower thin film electrodes 230 and 240 formed by applying silver paste on both surfaces of the piezoelectric element 250 are provided. The column 220 and the pair of thin film electrodes 230 and 240 are insulated.
A weight 260 is placed on the other end of the piezoelectric element 250 and on the thin film electrode 230.

A lead wire 231 is connected to the thin film electrode 230, and a lead wire 241 is connected to the thin film electrode 240.
The potential difference output from the lead wires 231 and 241 is output as a vibration waveform by a processing device such as a computer.

  The piezoelectric element 250 is formed of a stretched film (PVDF film) of polyvinylidene fluoride which is a polymer piezoelectric material.

  When the specific parameters are the elasticity E of the piezoelectric material, the cross-sectional secondary moment J, the length L1, the width b, and the height h, the spring constant k is expressed as follows.

^{k = 3EJ / L1 3 (J} = bh 3/12) ··· (1)

  The resonance frequency fo of the system composed of the piezoelectric element 250 and the weight 260 is expressed as follows.

  fo = √ (k / M) / 2π (2)

  The resonance type vibration sensor 200 according to the present embodiment is set such that the resonance value is in a range of 0.1 Hz to 500 Hz. This resonance frequency fo is suitable for investigating leakage of fluid in a synthetic resin tube.

<Flowchart of Method for Specifying Abnormal Sound Generation Position>
Next, a method for identifying the abnormal sound occurrence position will be described with a specific example.

In the method for identifying the abnormal sound generation position according to the present embodiment, the vibration sensor 200 is installed in at least two places (point A and point B) of the pipe network 110, and abnormal sound or vibration generated due to a defect in the pipe network 110 or the like. Is detected by the vibration sensor 200.
This is a method for specifying an abnormal sound generation position in which the vibration transmission time difference Td is obtained from the cross-correlation function of the waveform input to each vibration sensor 200 and the abnormal sound generation position is specified from the transmission time difference Td and the vibration propagation velocity V.

  In FIG. 1, it is assumed that fluid leakage has occurred at a distance L from the vibration sensor 200 at point A. In this case, the leaking sound propagates a distance (L + N) that is longer than the distance L of the vibration sensor 200 at the point A by a distance N before reaching the vibration sensor 200 at the point B.

  Accordingly, assuming that the distance between the vibration sensor 200 at the point A and the vibration sensor 200 at the point B is D, the transmission time difference Td at which the leakage sound arrives at the vibration sensor 200 at the point A and the vibration sensor 200 at the point B is The propagation speed V of the leaked sound and the distance between the two vibration sensors can be determined by the following equation, where D is the distance.

Td = N / V (3)
Or
N = D-2L (4)

By substituting equation (4) into equation (3),
L = (D−V · Td) / 2 (5)
It can be expressed as.
As described above, the distance L can be obtained.

  Subsequently, a specific example of the method for specifying the abnormal sound occurrence position according to the present embodiment will be described. FIG. 3 is a flowchart showing an example of a method for specifying an abnormal sound occurrence position according to the present embodiment.

  First, as shown in FIG. 3, the waveform of the leaking sound is acquired from the vibration sensor 200 at the point A of the pipe network 110 (step S11). Next, the waveform of the leaked sound is subjected to Fourier transform processing (step S12), and a Fourier spectrum A is acquired (step S13).

  Similarly, a leaked sound waveform is acquired from the vibration sensor 200 at point B of the pipe network 110 (step S21). Next, the waveform of the leaked sound is subjected to Fourier transform processing (step S22), and a Fourier spectrum B is acquired (step S23).

<Fourier Transform Processing (Step S12 and Step S22)>
In the Fourier transform process, a waveform of a predetermined time starting from the same time is extracted from the waveforms obtained by the vibration sensor 200 at the point A and the vibration sensor 200 at the point B, and the waveform is subjected to the Fourier transform process. Assuming that the Fourier spectrum is X (f), X (f) is expressed as a complex function as shown in the following equation (6).

X (f) = ∫ _−∞ ^∞ x (t) e ^−j2πft dt (6)
Expression (6) can be expressed separately as a real part and an imaginary part, as in the following Expression (7).

X (f) = XR (f) + jX _I (f) = | X (f) | e ^{jθ (f)} (7)

If the Fourier spectrum X _A (f) obtained from the waveform at point A and the Fourier spectrum obtained from the waveform at point B are X _B (f), then the complex conjugate of X _A (f) and X _B (f) The absolute value of the product is the cross spectrum (step S31). That the cross spectrum shows a large value means that the correlation value between the frequency components of the two spectra is large in the frequency band, and the magnitude of both frequency components is large.

  Subsequently, as shown in FIG. 3, the cross spectrum is inversely Fourier transformed (step S32) to obtain a cross-correlation function (step S33). From this peak value, the transmission time difference Td can be obtained by taking the cross-correlation.

Next, as shown in FIG. 3, the cross correlation function is integrated (step S34). Here, the integration processing is to integrate only the maximum value indicating the maximum correlation value. Details of the cross correlation function integration processing will be described later.
Finally, a value having a large peak value is selected using the integrated maximum value, and a position calculation process is performed (step S35). Although this selection can be performed arbitrarily, for example, a selection having 50% or more of the peak value may be selected.

<Other examples>
FIG. 4 is a flowchart showing another example of FIG.

  First, the flowchart shown in FIG. 4 differs from the flowchart shown in FIG. 3 in the following points. Since other processes are the same, description thereof is omitted.

  The flowchart shown in FIG. 4 includes the frequency processing of the maximum value in step S34a instead of the integration processing in step S34 of FIG.

  The maximum frequency processing is a process of adding the frequency of the portion where the peak value of the correlation value appears.

<Examples and Comparative Examples>
Hereinafter, Examples and Comparative Examples were carried out using actual water pipes (φ250 cast iron pipe).

<Example 1>
The vibration sensors 200 were respectively installed on the valve heads of gate valves provided in water pipes (φ250 cast iron pipes) having two water leakage points. The installation location of the vibration sensor 200 was two.

  After synchronization, the vibration waveform was measured at each location and stored in the logger. The distance between the two vibration sensors 200 was 68 m. The sampling rate of the logger was 50 kHz, and a waveform for 60 seconds (60 waveform data for 1 second) was acquired. The waveform was analyzed using a computer.

  FIG. 5 is a schematic diagram illustrating an example of a cross-correlation function, and FIG. 6 is a schematic diagram illustrating an example of integration processing.

  FIG. 7 is a schematic diagram for explaining the maximum frequency processing according to the present invention.

  In the cross-correlation function shown in FIG. 5, the vertical axis represents the correlation value, and the horizontal axis represents the transmission time difference Td. In the integration processing shown in FIG. 6, the vertical axis indicates the integrated value of the correlation value, and the horizontal axis indicates the transmission time difference Td. In the maximum value frequency processing shown in FIG. 7, the vertical axis represents the maximum frequency value, and the horizontal axis represents the transmission time difference Td.

FIG. 5 shows a correlation waveform in the first one second, and shows only a positive correlation value.
The transmission time difference Td at which the correlation value shown in FIG. 5 reaches a peak was −0.00262 seconds, and the maximum correlation value at the peak value was 3495.

  Next, FIG. 6 is obtained by integrating the transmission time difference Td at which the correlation value reaches a peak 60 times and the maximum correlation value according to the transmission time difference Td. That is, in step S34 shown in FIG. 3, a plurality of cross-correlation functions are acquired, and only the peak value of the correlation value of each cross-correlation function is acquired according to the transmission time difference Td and integrated. As a result, as shown in FIG. 6, peak values P1 and P2 appear at different transmission time differences Td.

  Next, FIG. 7 shows the result of integrating the transmission time difference Td at which the correlation value reaches a peak 60 times and the number of times the correlation value has reached the maximum value according to the transmission time difference Td. That is, in step S34a shown in FIG. 4, a plurality of cross-correlation functions are obtained, and the frequency of only the peak value of the correlation value of each cross-correlation function is obtained and calculated according to the transmission time difference Td. . As a result, as shown in FIG. 7, peak values P1 and P2 appear at different time differences Td.

As shown in FIG. 6 and FIG. 7, by using the method for specifying the abnormal sound generation position according to the present invention, it is possible to clearly discriminate two locations of the water leakage locations having the peak values P1 and P2. Of the two peak values obtained here, the transmission time difference Td of the peak value P1 was -0.00262 seconds, and the transmission time difference Td of the peak value P2 was 0.0182 seconds.
Here, since the speed of sound in the φ250 cast iron pipe is about 1200 m / sec, the water leakage point was calculated to be a distance of 35.6 m and 23.1 m from one vibration sensor 200.

<Comparative example>
FIG. 8 is a schematic diagram for explaining a conventional cross-correlation function. FIG. 8 integrates cross-correlation functions for each second from waveform data (60 waveform data for one second) similar to the embodiment shown in FIG.
Thus, the graph shown in FIG. 8 did not show a big difference from the graph shown in FIG. 5, and it was difficult to discriminate between the two peaks of the water leakage location.

As described above, according to the method for specifying an abnormal sound generation position according to the present embodiment, the transmission time difference Td can be obtained clearly and accurately even when there are a plurality of sound sources.
Furthermore, in the present invention, instead of simply integrating the cross-correlation function, after calculating the transmission time difference Td that maximizes the correlation value from each measurement, only the results at the transmission time difference Td are integrated.

The integration may be performed by integration of the maximum correlation value as shown in FIG. 6, or may be performed by the frequency of the maximum value of the correlation value as shown in FIG. As a result, it is possible to clearly identify the peak value even in a leaky sound in which vibration occurs as a whole, and to specify the abnormal sound generation position (leakage location).
In the above description, integration is performed, but the present invention is not limited to this, and addition may be performed.

  The waveform used for calculating the cross-correlation function is preferably 5 sec or less because it takes a long calculation time if it is too long. For example, when trying to identify the leak location by measuring for 2 minutes, the calculation of the transmission time difference Td from the cross-correlation function of 5 seconds rather than the calculation of the transmission time difference Td from the cross-correlation function of the waveform for 1 minute twice. It is better to go 24 times. Furthermore, it is more preferable to calculate the transfer time difference Td 120 times from the 1-second cross-correlation function.

  On the other hand, if the waveform to be sampled is too short, the reliability of the calculation result of the transmission time difference Td is lowered. For example, the speed of sound transmitted through a water pipe varies depending on the pipe type or caliber. In particular, the speed of sound transmitted through the vinyl chloride tube is slow, and in the case of φ75, it is about 400 m / sec.

  Therefore, if the distance between the two vibration sensors 200 is 100 m, the transmission time in this section is about 0.25 seconds. It is preferable to obtain a cross-correlation function using a waveform having a time exceeding 0.25 seconds. More preferably, it is 2 times (0.5 seconds) or more of 0.25 seconds.

  The method for specifying the abnormal sound generation position can be applied to various pipe networks 110. For example, in addition to detecting leaks from water supply pipes, it is also used for detecting leaks in various pipes other than water supply, or for detecting leakage of fluids such as chemicals in pipes for chemicals in factories. be able to.

  In the present invention, step S34 corresponds to “first extraction step and first integration step”, and steps S11,..., S13, S21,..., S23, S31,. , Step S34a corresponds to "second extraction step and second integration step", and the determination of whether or not 50% or more after steps S34, 34a corresponds to "determination step", and steps S11,. S35 corresponds to “a method for identifying an abnormal sound occurrence position”, and the vibration sensor 200 corresponds to “a vibration sensor, a resonance type vibration sensor”.

  A preferred embodiment of the present invention is as described above, but the present invention is not limited thereto. It will be understood that various other embodiments may be made without departing from the spirit and scope of the invention. Furthermore, in this embodiment, although the effect | action and effect by the structure of this invention are described, these effect | actions and effects are examples and do not limit this invention.

110 Pipe network 200 Vibration sensor

Claims (4)

A delay calculating step of installing a vibration sensor in at least two locations of a pipe network (piping network), and obtaining a vibration delay from a cross-correlation function of a waveform obtained by the vibration sensor;
A first extraction step of extracting a maximum value of correlation values and a time difference with respect to the maximum value from a cross-correlation function at a predetermined time;
A first integration step of repeating the first extraction step a plurality of times, and integrating the maximum correlation value at each time difference;
A determination step of determining a time difference at which the integrated value is the maximum as a result of the first integration step as a transmission time difference of the abnormal sound. A delay calculating step of installing a vibration sensor in at least two locations of a pipe network (piping network), and obtaining a vibration delay from a cross-correlation function of a waveform obtained by the vibration sensor;
A second extraction step of extracting a time difference that maximizes the correlation value from a cross-correlation function for a predetermined time;
A second integration step of repeating the second extraction step a plurality of times and integrating the number of times that the correlation value at each time difference becomes maximum;
A determination step of determining a time difference at which the integrated value is the maximum as a result of the second integration step as a transmission time difference of the abnormal sound.   The method for specifying an abnormal sound generation position according to claim 1 or 2, wherein the vibration sensor is a resonance type vibration sensor having at least one resonance point in a frequency band of vibration of abnormal sound. The method for specifying an abnormal sound generation position according to any one of claims 1 to 3, wherein a resonance frequency of the vibration sensor is 0.1 Hz to 500 Hz.

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