JPWO2015141129A1 - SOUND SPEED CALCULATION DEVICE, SOUND SPEED CALCULATION METHOD, AND SOUND SPEED CALCULATION PROGRAM - Google Patents

Abstract

110 A of 1st vibration detection parts detect the 1st vibration W10 which propagates structures (piping 900 grade). The second vibration detection unit 110B detects the second vibration W20 that propagates through the structure. The rise time difference calculation unit 121 calculates a rise time difference Δt that is a time difference between the first rise time ta when the first vibration W10 rises and the second rise time tb when the second vibration W20 rises. The correlation function calculation unit 122 calculates a correlation function between the first vibration W10 and the second vibration W20. The sound speed calculation unit 123 calculates the sound speed c of the structure based on the correlation function, the rise time difference Δt, and the distance D between the first vibration detection unit 110A and the second vibration detection unit 110B. Thereby, the sound speed of the structure (such as the pipe 900) can be calculated more accurately.

Description

  The present invention relates to a sound velocity calculation device and the like, for example, to a device that calculates a sound velocity of vibration propagating through a structure such as a pipe.

  In recent years, various techniques have been proposed and put into practical use as techniques for detecting water leaks in waterworks networks, gas leaks in gas pipes, and leaks in various pipes in chemical plants. As a representative example of this leakage detection technique, an inspection method using a vibration sensor (non-destructive inspection method) is widely known.

  In this non-destructive inspection method, vibration sensors are installed on the ground surface and manholes near pipes and places where they are in contact with the pipes (for example, places where pipes are buried), and vibrations caused by pipe leakage are detected.

  More specifically, for example, a nondestructive inspection method using a correlation method is known. In this inspection method, the location of the leaking part is calculated from the sound speed obtained from the time difference obtained from the cross-correlation coefficient of the vibration sensor that detects two vibrations sandwiching the leaking part and the distance between the two sensors. I can do it. That is, first, a pair of vibration sensors are arranged on a pipe or the like at a predetermined distance so as to sandwich the leaking part on both sides. Vibration sound (leakage vibration) caused by leakage propagates through piping and the like. The time for the vibration sound generated by this leakage to reach each of the pair of vibration sensors is measured. Then, the fluid leakage position is estimated from the product of the difference between the two measured values of the vibration arrival time (vibration arrival time difference) and a preset sound velocity. At this time, in calculating the arrival time difference of vibration, a cross-correlation function of time-series data is calculated, and a time corresponding to the maximum value of the cross-correlation function is used.

  As an invention related to this, Patent Document 1 discloses a technique for detecting a sound wave propagating in a pipe or a pipe wall by reducing the pressure around the leak detection part of the pipe and flowing air from the leak part. It is disclosed. Related inventions are also disclosed in Patent Documents 2 and 3.

JP-A-11-160187 Japanese Patent Laid-Open No. 04-72537 JP 2009-271045 A

  However, in the technique described in Patent Document 1, the speed of sound propagating in a pipe varies greatly depending on the material, shape, and external environment of the pipe when a fluid flows in the pipe. For this reason, there has been a problem that it is difficult to accurately calculate the speed of sound propagating in the pipe.

  As described above, the sound speed is calculated from the time difference of the rising waveform of each vibration sensor signal or the time difference obtained by the cross-correlation function when the vibration sensor is forcedly vibrated around two vibration sensors that are installed in piping and the like. To do. At this time, the vibration is attenuated in the pipes until the vibrations that are vibrated propagate to and reach the vibration sensors, and the arrived signal does not necessarily propagate the vibrations in the same mode. As a result, it is difficult to accurately determine the sound speed in terms of rise time and cross-correlation coefficient, which is the cause of the above problem.

  In addition, higher-order modes and higher harmonics are superimposed on the rising waveform after forced excitation, and it is difficult to accurately determine the sound speed using the cross-correlation function.

  This invention is made | formed in view of such a situation, and the objective of this invention is providing the technique which can calculate the sound speed of a structure more correctly.

  The sound speed calculation device of the present invention includes a first vibration detecting unit that detects a vibration propagating through a structure as a first vibration, and a second vibration that detects a vibration propagating through the structure as a second vibration. Among a plurality of peak values included in the correlation function calculated by the detection means, correlation function calculation means for calculating a correlation function between the first vibration and the second vibration, and the correlation function calculation means Index setting means for setting an index for selecting any one of the peak values; the correlation function calculated by the correlation function calculating means; the index calculated by the index setting means; and the first Sound speed calculating means for calculating the sound speed of the structure based on the distance between the vibration detecting means and the second vibration detecting means.

  The control device of the present invention outputs first and second vibration detection instruction signals that cause the first and second vibration detection means to detect vibration propagating through the structure as first and second vibrations, and Outputting a correlation function calculation instruction signal for calculating a correlation function between the first and second vibrations detected according to the first and second vibration detection instruction signals, and calculating the correlation function calculation instruction signal according to the correlation function calculation instruction signal; Outputting an index setting instruction signal for setting an index for selecting any one of a plurality of peak values included in the correlation function, the correlation function calculated according to the correlation function calculation instruction signal, A sound speed calculation for calculating the sound speed of the structure based on the index calculated according to the index setting instruction signal and the distance between the first vibration detecting means and the second vibration detecting means. And it outputs an instruction signal.

  The signal processing apparatus according to the present invention is calculated by a correlation function calculating unit that calculates a correlation function between the first and second vibrations input from the first and second vibration detecting units, and the correlation function calculating unit. Index setting means for setting an index for selecting any one of the plurality of peak values included in the correlation function; the correlation function calculated by the correlation function calculating means; and the index setting And a sound speed calculating means for calculating the sound speed of the structure based on the index calculated by the section and the distance between the first vibration detecting means and the second vibration detecting means.

  According to the sound velocity calculation method of the present invention, the vibration propagating through the structure is detected as the first vibration by the first vibration detecting means, and the vibration propagating through the structure is detected as the second vibration by the second vibration detecting means. Detecting, calculating a correlation function between the first vibration and the second vibration, and setting an index for selecting one of the plurality of peak values included in the correlation function The sound speed of the structure is calculated based on the correlation function, the index, and the distance between the first vibration detection means and the second vibration detection means.

  The storage medium of the present invention detects the vibration propagating through the structure as the first vibration by the first vibration detecting means, and detects the vibration propagating through the structure as the second vibration by the second vibration detecting means. Calculating a correlation function between the first vibration and the second vibration, and setting an index for selecting any one of the plurality of peak values included in the correlation function; A program for causing a computer to perform a process of calculating a sound speed of the structure based on the correlation function, the index, and a distance between the first vibration detection unit and the second vibration detection unit is stored. .

  According to the sound speed calculation device and the like according to the present invention, the sound speed can be calculated more accurately.

It is a block diagram of the sound speed calculation apparatus in the 1st Embodiment of this invention. It is an operation | movement flowchart of the sound speed calculation apparatus in the 1st Embodiment of this invention. It is a figure which shows the state which installed the 1st vibration detection part and the 2nd vibration detection part in piping. It is a figure which shows the signal output relationship of a control apparatus. It is a block diagram of the sound speed calculation apparatus in the 2nd Embodiment of this invention. It is an operation | movement flowchart of the sound speed calculation apparatus in the 2nd Embodiment of this invention. It is a figure which shows the waveform of a 1st vibration and a 2nd vibration. It is a figure which shows an example of the correlation function between the 1st vibration and the 2nd vibration. It is a figure which shows the signal output relationship of a control apparatus. It is a block diagram of the sound speed calculation apparatus in the 3rd Embodiment of this invention. It is an operation | movement flowchart of the sound speed calculation apparatus in the 3rd Embodiment of this invention. It is a figure which shows an example of a correlation function. It is a figure which shows the signal output relationship of a control apparatus. It is a figure which shows the correlation function obtained in the Example, Comprising: It is a correlation function obtained by the method 1. It is a figure which shows the correlation function obtained in the Example, Comprising: It is a correlation function obtained by the method 2. It is a figure which shows the sound speed computed from the peak of the correlation function computed by the method 1 and the method 2 of an Example, and the sound speed computed from the rise time difference of the 1st and 2nd vibration.

<First Embodiment>
The configuration of the sound speed calculation device 100 according to the first embodiment of the present invention will be described.

  FIG. 1 is a block diagram of a sound speed calculation apparatus 100 according to the first embodiment of the present invention.

  As shown in FIG. 1, the sound velocity calculation device 100 includes at least a first vibration detection unit 110A, a second vibration detection unit 110B, and a signal processing unit 120.

  As shown in FIG. 1, the first vibration detection unit 110 </ b> A and the second vibration detection unit 110 </ b> B are connected to the signal processing unit 120 by wireless or wired communication. 110A of 1st vibration detection parts and the 2nd vibration detection part 110B are attached to structures (not shown), such as piping, a building, and a bridge.

  The first vibration detection unit 110A and the second vibration detection unit 110B are sensors that can detect vibration in a predetermined direction. The first vibration detection unit 110A and the second vibration detection unit 110B input an electric signal corresponding to the detected amplitude and frequency of the vibration to the signal processing unit 120 as a detection signal. More specifically, the first vibration detection unit 110A detects the vibration propagating through the structure as the first vibration. Then, the first vibration detection unit 110 </ b> A inputs the first vibration to the signal processing unit 120. The second vibration detection unit 110B detects the vibration propagating through the structure as the second vibration. Then, the second vibration detection unit 110B inputs the second vibration to the signal processing unit 120. The first or second vibration includes an elastic wave.

  The first vibration detection unit 110A and the second vibration detection unit 110B include, for example, a piezoelectric vibration sensor, an electromagnetic vibration sensor, a capacitive acceleration sensor, an optical speed sensor, a dynamic strain sensor, an ultrasonic sensor, A microphone or the like can be used.

  As shown in FIG. 1, the signal processing unit 120 is connected to the first vibration detection unit 110A and the second vibration detection unit 110B by wireless or wired connection.

  As shown in FIG. 1, the signal processing unit 120 includes at least a correlation function calculation unit 122, a sound speed calculation unit 123, and an index setting unit 125.

  The correlation function calculation unit 122 calculates a correlation function between the first vibration and the second vibration. Details of the operation of the correlation function calculation unit 122 will be described in the operation description.

  The sound speed calculation unit 123 calculates the sound speed c of the structure based on the correlation function calculated by the correlation function calculation unit 122 and an index set by the index setting unit 125 described later. Details of the operation of the sound speed calculation unit 123 will be described in the operation description.

  The index setting unit 125 sets an index for selecting any one peak value among a plurality of peak values included in the correlation function calculated by the correlation function calculating unit 122. Details of the operation of the index setting unit 125 will be described in the operation description.

  Next, the operation of the sound speed calculation device 100 according to the first embodiment of the present invention will be described.

  FIG. 2 is a diagram illustrating an operation flow of the sound speed calculation apparatus 100.

  As shown in FIG. 2, first, the first vibration detection unit 110A and the second vibration detection unit 110B are installed in a structure such as a pipe (step (STEP: hereinafter referred to as S) S1). Here, it is assumed that the structure is a pipe 900. The pipe 900 is buried in the ground, for example. Further, a fluid (such as water) flows inside the pipe 900. Here, the structure is described as the pipe 900, but the structure is not limited to the pipe 900.

  FIG. 3 is a diagram illustrating a state where the first vibration detection unit 110 </ b> A and the second vibration detection unit 110 </ b> B are installed in the pipe 900. As shown in FIG. 3, the first vibration detection unit 110 </ b> A and the second vibration detection unit 110 </ b> B are provided in the pipe 900 so as to be separated from each other. Here, the distance between the first vibration detection unit 110A and the second vibration detection unit 110B is D. The first vibration detection unit 110A and the second vibration detection unit 110B are attached to the pipe 900 by opening a manhole (not shown) on a road (not shown). Preferably, the first vibration detection unit 110 </ b> A and the second vibration detection unit 110 </ b> B are synchronized with each other via the signal processing unit 120.

  Returning to FIG. 2, the hammering process is performed (S2). That is, as shown in FIG. 3, the pipe 900 is hit with the impulse hammer 130 to forcibly vibrate the pipe 900. The impulse hammer 130 corresponds to the excitation unit of the present invention.

  Returning to FIG. 2, next, each of the first vibration detection unit 110A and the second vibration detection unit 110B uses the vibrations propagating through the structure as the first vibration W10 and the second vibration W20, respectively. Obtain (S3). The process of S3 corresponds to the first vibration detection step and the second vibration detection step of the present invention.

  Note that examples of waveforms of the first vibration W10 and the second vibration W20 will be described later in the description of the embodiment.

  Next, the index setting unit 125 sets an index for selecting one of the plurality of peak values included in the correlation function calculated by the correlation function calculating unit 122. Note that the process of S4 corresponds to the index setting step of the present invention.

  Next, the correlation function calculation unit 122 performs waveform cut-out processing of the first vibration W10 and the second vibration W20 (S5), and performs correlation processing (S6). The process of S6 corresponds to the correlation function calculation step of the present invention. Note that details of the processes of S5 and S6 will be described later in the description of the embodiment.

  Next, the sound speed calculation unit 123 calculates the sound speed of the pipe 900 (structure) (S7).

  Specifically, in the sound speed calculation device 100, the sound speed calculation unit 123 uses the piping 900 (structure) based on the correlation function calculated by the correlation function calculation unit 122 and an index set by an index setting unit 125 described later. The sound speed c of the object) is calculated.

  Heretofore, the operation of the sound speed calculation device 100 according to the first embodiment of the present invention has been described.

  Using the sound speed c calculated by the sound speed calculation device 100, the position of a leak hole (not shown) generated in the pipe 900 can be calculated as follows. Details of this calculation method will be described later in the description of the embodiment.

  Note that a control device 140 that outputs an instruction signal to the first vibration detection unit 110A, the second vibration detection unit 110B, the index setting unit 125, the correlation function calculation unit 122, and the sound speed calculation unit 123 may be newly provided.

  FIG. 4 is a diagram illustrating a signal output relationship of the control device 140. As illustrated in FIG. 4, the control device 140 causes the first vibration detection unit to detect the vibration propagating through the pipe 900 as the first vibration toward the first vibration detection unit 110 </ b> A. A detection instruction signal is output. The control device 140 sets a second vibration detection instruction signal that causes the second vibration detection unit to detect the vibration propagating through the pipe 900 (structure) as the second vibration toward the second vibration detection unit 110B. Output. The control device 140 outputs an index setting instruction signal for setting the index to the index setting unit 125. The control device 140 instructs the correlation function calculation unit 122 to calculate a correlation function between the first and second vibrations W10 and W20 detected according to the first and second vibration detection instruction signals. Output a signal. The control device 140 sets the correlation function calculated according to the correlation function calculation instruction signal, the index calculated according to the index setting instruction signal, and the distance D between the first vibration detection unit 110A and the second vibration detection unit 110B. Based on this, a sound speed calculation instruction signal for calculating the sound speed c of the pipe 900 (structure) is output. Thereby, the instruction processing for operating the main functions of the sound speed calculation device 100 described above can be integrated into the control device 140.

  As described above, the sound velocity calculation apparatus 100 according to the first embodiment of the present invention includes the first vibration detection unit 110A (first vibration detection unit) and the second vibration detection unit 110B (second vibration). Detection means), a correlation function calculation unit 122 (correlation function calculation means), an index setting unit 125 (index setting means), and a sound speed calculation unit 123 (sound speed calculation means). 110 A of 1st vibration detection parts detect the vibration which propagates a structure (for example, piping 900) as the 1st vibration W10. The second vibration detection unit 110B detects the vibration propagating through the structure as the second vibration W20. The correlation function calculation unit 122 calculates a correlation function between the first vibration W10 and the second vibration W20. The index setting unit 125 sets an index for selecting any one peak value among a plurality of peak values included in the correlation function calculated by the correlation function calculating unit 122. The sound speed calculation unit 123 is a distance D between the correlation function calculated by the correlation function calculation unit 122, the index set by the index setting unit 125, and the first vibration detection unit 110A and the second vibration detection unit 110B. Based on the above, the sound velocity c of the structure is calculated.

  As described above, the index setting unit 125 sets an index for selecting any one peak value among the plurality of peak values included in the correlation function calculated by the correlation function calculating unit 122. Thereby, an index can be prepared as an object to be compared with the phase difference between the first vibration W10 and the second vibration W20 indicated by the correlation function. Further, the correlation function calculation unit 122 calculates a correlation function between the first vibration W10 and the second vibration W20. Then, the sound speed calculation unit 123 compares the index with the phase difference between the first vibration W10 and the second vibration W20 indicated by the correlation function. The correlation function may have a plurality of peaks corresponding to the phase difference between the first vibration W10 and the second vibration W20. At this time, the sound speed calculation unit 123 selects the phase difference closest to the index among the phase differences corresponding to the plurality of peaks. Thereby, the phase difference between the first vibration W10 and the second vibration W20 can be calculated more accurately. Then, the sound speed calculation unit 123 calculates the sound speed c of the pipe 900 (structure) based on the selected phase difference and the distance D between the first vibration detection unit 110A and the second vibration detection unit 110B. . As a result, the sound speed calculation device 100 can calculate the sound speed c of the structure (pipe 900) more accurately.

  The control device 140 according to the first embodiment of the present invention uses the first and second vibrations W10 and W20 as vibrations propagating through the structure (pipe 900) to the first and second vibration detection units 110A and 110B. First and second vibration detection instruction signals to be detected are output. Control device 140 also outputs a correlation function calculation instruction signal for calculating a correlation function between first and second vibrations W10 and W20 detected according to the first and second vibration detection instruction signals. The control device 140 outputs an index setting instruction signal for setting an index for selecting any one of the plurality of peak values included in the correlation function calculated according to the correlation function calculation instruction signal. The control device 140 determines the distance D between the correlation function calculated according to the correlation function calculation instruction signal, the index calculated according to the index setting instruction signal, and the first vibration detection unit 110A and the second vibration detection unit 110B. Based on the above, a sound speed calculation instruction signal for calculating the sound speed c of the structure (pipe 900) is output. Thereby, the instruction processing for operating the main functions of the sound speed calculation device 100 described above can be integrated into the control device 140.

  The signal processing apparatus according to the first embodiment of the present invention includes a correlation function calculation unit 122, an index setting unit 125, and a sound speed calculation unit 123. The correlation function calculation unit 122 calculates a correlation function between the first vibration W10 and the second vibration W20 input from the first and second vibration detection units 110A and 110B. The index setting unit 125 sets an index for selecting any one peak value among a plurality of peak values included in the correlation function calculated by the correlation function calculating unit 122. The sound speed calculation unit 123 is a distance D between the correlation function calculated by the correlation function calculation unit 122, the index set by the index setting unit 125, and the first vibration detection unit 110A and the second vibration detection unit 110B. Based on the above, the sound velocity c of the structure is calculated. The signal processing apparatus of the present invention corresponds to the signal processing unit 120. This signal processing device also has the same effect as the sound speed calculation device 100 described above.

  The sound speed calculation method according to the first embodiment of the present invention includes a first vibration detection step, a second vibration detection step, a correlation function calculation step, an index setting step, and a sound speed calculation step. . In the first vibration detection step, the vibration propagating through the structure is detected as the first vibration W10 by the first vibration detection unit 110A. In the second vibration detection step, the vibration propagating through the structure is detected as the second vibration W20 by the second vibration detection unit 110B. In the correlation function calculating step, a correlation function is calculated between the first vibration W10 and the second vibration W20. In the index setting step, an index for selecting one of the plurality of peak values included in the correlation function calculated in the correlation function calculating step is set. In the sound speed calculation step, the correlation function calculated in the correlation function calculation step, the index calculated in the index setting step, and the distance D between the first vibration detection unit 110A and the second vibration detection unit 110B. Based on this, the sound speed of the structure is calculated. This method also has the same effect as the sound speed calculation device 100 described above.

  The sound speed calculation program according to the first embodiment of the present invention causes a computer to perform the steps shown in the sound speed calculation method described above. This program also provides the same effects as the sound speed calculation device 100 described above. The storage medium according to the first embodiment of the present invention stores a program that causes a computer to perform the steps shown in the sound velocity calculation method. This storage medium also has the same effect as the sound speed calculation device 100 described above.

<Second Embodiment>
The configuration of the sound speed calculation device 100a according to the second embodiment of the present invention will be described.

  FIG. 5 is a block diagram of a sound speed calculation apparatus 100a according to the second embodiment of the present invention. In FIG. 5, constituent elements equivalent to those shown in FIG. 1 are denoted by the same reference numerals as those shown in FIG. 1.

  As shown in FIG. 5, the sound speed calculation device 100a includes at least a first vibration detection unit 110A, a second vibration detection unit 110B, and a signal processing unit 120a.

  Here, FIG. 1 and FIG. 5 are compared. In FIG. 1, the signal processing unit 120 includes a correlation function calculation unit 122, a sound speed calculation unit 123, and an index setting unit 125. In contrast, in FIG. 5, the signal processing unit 120 a includes a correlation function calculation unit 122, a sound speed calculation unit 123, and a rise time difference calculation unit 121. In this respect, FIG. 1 and FIG. 5 are different from each other. That is, the signal processing unit 120a shown in FIG. 5 includes a rise time difference calculation unit 121 instead of the index setting unit 125 of FIG.

  As shown in FIG. 5, the signal processing unit 120a is connected to the first vibration detection unit 110A and the second vibration detection unit 110B by wireless or wired connection.

  As shown in FIG. 5, the signal processing unit 120 a includes at least a rise time difference calculation unit 121, a correlation function calculation unit 122, and a sound speed calculation unit 123.

  The rise time difference calculation unit 121 receives the first vibration and the second vibration from the signal processing unit 120a. Then, the rise time difference calculation unit 121 calculates the time difference between the first rise time ta, which is the time (time) when the first vibration rises, and the second rise time tb, which is the time (time) when the second vibration rises. The rise time difference Δt is calculated. Details of the operation of the rise time difference calculation unit 121 will be described in the operation description. Note that the first rise time ta is when the magnitude of the first vibration is equal to or greater than a predetermined threshold. Similarly, the second rise time tb is when the magnitude of the second vibration is equal to or greater than a predetermined threshold.

  The sound speed calculation unit 123 calculates the sound speed c of the structure based on the correlation function calculated by the correlation function calculation unit 122 and the rise time difference Δt calculated by the rise time difference calculation unit 121. Details of the operation of the sound speed calculation unit 123 will be described in the operation description.

  Next, the operation of the sound speed calculation device 100a according to the second embodiment of the present invention will be described.

  FIG. 6 is a diagram showing an operation flow of the sound speed calculation apparatus 100a. In the following description, detailed description of the same processing as in the description of FIG.

  As shown in FIG. 6, first, the first vibration detection unit 110A and the second vibration detection unit 110B are installed in a structure such as a pipe (S1).

  Next, a hammering process is performed (S2).

  Next, each of the first vibration detection unit 110A and the second vibration detection unit 110B uses the first vibration W10 and the second vibration W20 as vibrations propagating through the structure as the first vibration W10 and the second vibration W20. 2 vibrations W20 are acquired (S3).

  FIG. 7 is a diagram illustrating waveforms of the first vibration W10 and the second vibration W20. In FIG. 7, the horizontal axis is time t, and the vertical axis is the vibration level (for example, vibration acceleration).

  Returning to FIG. 6, next, the rise time difference calculation unit 121 calculates the rise time difference Δt (S8). That is, the rise time difference calculation unit 121 calculates a rise time difference Δt that is a time difference between the first rise time ta that is the time when the first vibration rises and the second rise time tb that the second vibration rises. The process of S8 corresponds to the rise time difference calculating step of the present invention.

  Here, between the rise time ta of the first vibration W10 detected by the first vibration detection unit 110A and the rise time tb of the second vibration W20 detected by the second vibration detection unit 110B, Damping of vibrations in the pipe 900 and the outside environment may occur. Similarly, the vibration does not always propagate to the first vibration detection unit 110A and the second vibration detection unit 110B. For this reason, the rise time difference calculation unit 121 does not always see the rise of the same propagation vibration when calculating the rise time difference Δt.

  Therefore, here, the rising times ta and tb of the first and second vibrations W10 and W20 are set as follows. That is, first, an average value of the vibration amplitude levels of the dark vibration of the signal output included in the first and second vibrations W10 and W20 detected by the first and second vibration detection units 110A and 110B is acquired. A value that is twice the average value of the vibration level of the dark vibration is set as the threshold value. And when the peak of the vibration level of the first and second vibrations W10 and W20 is continuous five times and exceeds the set threshold value, the time when the threshold value is first exceeded (first time) is set as the first and second vibrations. The rising times ta and tb of the vibrations W10 and W20 are set. Note that the threshold at this time may not be twice the average value of the vibration amplitude level of the dark vibration. Further, the number of times exceeding the threshold is not limited to five, but is preferably three or more. The threshold value here may be either a positive value or a negative value when the vibration is defined with 0 (zero) as the center reference of vibration.

  Next, the correlation function calculation unit 122 performs waveform cut-out processing of the first vibration W10 and the second vibration W20 (S5), and performs correlation processing (S6). The process of S6 corresponds to the correlation function calculation step of the present invention.

  Here, as shown in FIG. 7, in the first vibration W <b> 10 and the second vibration W <b> 20, the vibration waveform immediately after rising may include many high-order vibration modes and many harmonics. . For this reason, due to the observation of different propagation vibrations, an error occurs in the cross-correlation function, and it may be difficult to calculate an accurate time difference.

  Therefore, in the sound speed calculation device 100a, the correlation function calculation unit 122 performs a cross-correlation process only on the low-order mode attenuation signal after the time tm has elapsed from the rise time tb of the second vibration detection unit 110B synchronized in time. . Note that the low-order mode refers to, for example, a mode that is not higher than the highest order mode that is not attenuated. As a result, errors due to the superposition of harmonics and higher-order modes can be reduced, and the accuracy of sound speed calculation can be increased.

  First, the waveform cut-out process (S5) of the first vibration W10 and the second vibration W20 will be described.

  Here, the end of the waveform used in the correlation process (S6) is determined. In the vibration after the forced excitation, the times tv and tw until the vibrations of the first vibration W10 and the second vibration W20 are completely attenuated are calculated as follows. First, the correlation function calculation unit 122 acquires the average value of the vibration amplitude level of the dark vibration of the signal output detected by the first vibration detection unit 110A and the second vibration detection unit 110B. The correlation function calculation unit 122 sets a threshold value that is twice this average value. Then, when the peak of the vibration amplitude level of the first vibration W10 and the second vibration W20 falls below the threshold value five times in succession, the correlation function calculation unit 122 performs the fifth attenuation time tv, tw of each vibration. And The threshold value at this time may not be twice the average value of the vibration amplitude level of the dark vibration. Further, the number of times that falls below the threshold is not limited to five, but is preferably three or more.

  In addition, as described above, preferably, the correlation function calculation unit 122 attenuates the low-order mode after the time tm (see FIG. 7) has elapsed from the rise time tb of the second vibration detection unit 110B synchronized in time. Cross-correlate only the signal.

  The time tm at this time is calculated by the correlation function calculator 122 as follows. That is, in order to extract the attenuation waveform after the higher-order mode and the harmonics are attenuated, the correlation function calculation unit 122 uses the first vibration detection unit 110A and the second vibration detection unit 110B acquired by the first vibration detection unit 110B. Peaks of the vibration W10 and the second vibration W20 are taken. A waveform in which only the low-order mode remains and the time interval of each peak is constant is set as a damped vibration by the correlation function calculation unit 122. For example, when the time interval of the vibration waveforms of the first and second vibrations W10 and W20 after a certain time t has become a constant value five times continuously, the correlation function calculation unit 122 rises the first peak. Time tm from The number of thresholds for setting the time tm is not limited to five, but is preferably three or more.

  In the description of FIG. 7, the method of determining the time tm is set based on the rise time tb. On the other hand, it is also possible to determine retroactively from the end of the attenuation waveform. For example, the time tm can be set as follows. The threshold value is twice the average value of the vibration amplitude level of the dark vibration of the signal output of the first and second vibrations W10 and W20 described above. When the peak of the amplitude level of the first and second vibrations W10 and W20 falls continuously five times, the fifth time is set as the vibration attenuation time. A peak in which only the low-order mode remains after going back from the end of the attenuation waveform and the peak time interval is not constant for five consecutive times can be set as the time tm from the rising edge.

  Next, the correlation process (S6) of the correlation function calculation unit 122 will be described.

  FIG. 8 is a diagram illustrating an example of a correlation function between the first vibration W10 and the second vibration W20. In FIG. 8, the horizontal axis is time t, and the vertical axis is the cross-correlation coefficient.

  FIG. 8 shows the correlation function calculated by the correlation function calculation unit 122 for the waveforms cut out by the waveform cut-out process (S5 in FIG. 6) of the first vibration W10 and the second vibration W20. That is, as shown in FIG. 7, the correlation function calculation unit 122 calculates a correlation function for the waveform from the rise time tb to the time tm of the second vibration W20.

  Next, returning to FIG. 6, the sound speed calculation unit 123 calculates the sound speed of the pipe 900 (structure) (S7). As shown in FIG. 8, the correlation function has a plurality of peaks 501 at the same level. At this time, it is difficult to determine how much the phases of the first vibration W10 and the second vibration W20 are shifted. For this reason, in calculating the sound speed of the pipe 900, it is necessary to determine which peak should be adopted. The process of S7 corresponds to the sound speed calculation step of the present invention.

  Here, the plurality of peaks 501 shown in FIG. 8 appear due to the cross-correlation processing in the low-order mode. For this reason, the plurality of peaks 501 have a longer wavelength than a waveform in which higher-order modes are superimposed. Therefore, the phase shift for one wavelength is large, and a large shift from the true value is caused by the shift of one wavelength. Thus, although it does not change if it is a short wavelength such as a high-order mode, in the low-order mode, it shifts greatly from the original peak.

  Therefore, in the sound speed calculation device 100a, the sound speed calculation unit 123 uses the piping 900 (structure) based on the correlation function calculated by the correlation function calculation unit 122 and the rise time difference Δt calculated by the rise time difference calculation unit 121. Is calculated. That is, first, the sound velocity calculation unit 123 corresponds to the rise time difference Δt (time difference between the first rise time ta and the second rise time tb) calculated by the rise time difference calculation unit 121 and the plurality of peaks 501. Contrast with phase difference. Next, the sound speed calculation unit 123 selects the phase difference closest to the rise time difference Δt among the phase differences corresponding to the plurality of peaks 501. Then, the sound speed calculation unit 123 calculates the sound speed c of the pipe 900 (structure) based on the selected phase difference and the distance D between the first vibration detection unit 110A and the second vibration detection unit 110B. .

  The operation of the sound speed calculation device 100a according to the first embodiment of the present invention has been described above.

  Using the sound speed c calculated by the sound speed calculation device 100a, the position of a leak hole (not shown) generated in the pipe 900 can be calculated as follows.

  When a leak hole is generated in the pipe 900, the fluid flowing in the pipe 900 leaks from the leak hole. At this time, vibration having a frequency corresponding to the state (shape, size, etc.) of the leak hole is generated from the leak hole and propagates through the pipe 900 or the fluid flowing in the pipe 900.

  By installing the first and second vibration detection units 110A and 110B in the pipe 900, it can be detected that a leak hole has been formed, and the position of the leak hole can be detected. At this time, the first and second vibration detection units 110A and 110B are installed in the pipe 900 so that the leakage hole is disposed between the first vibration detection unit 110A and the second vibration detection unit 110B.

  Then, for example, it is confirmed whether or not a component (peak at a specific frequency) in which a leak hole is not formed appears in the vibration (signal) detected by the first and second vibration detection units 110A and 110B. Thereby, it can be known whether or not a leak hole is formed in the pipe 900.

  Further, by detecting the leakage vibration with the first and second vibration detection units 110A and 110B, the position of the leakage hole can be specified using, for example, a correlation method.

  Here, for specifying the leakage position (position of the leakage hole) by the correlation method, the time difference until the vibration propagates to the first and second vibration detection units 110A and 110B in synchronization with the time, and the first It is necessary to know in advance the sound speed of the pipe 900 in which the second vibration detection units 110A and 110B are installed. The time difference until the vibration propagates to the first and second vibration detection units 110A and 110B may be measured after forcibly exciting the surroundings of the first and second vibration detection units 110A and 110B. .

  The speed of sound of the pipe 900 is generally calculated as follows. That is, first, the pipe 900 is forcibly vibrated. Next, from the propagation time difference of the excitation vibration to the first and second vibration detection units 110A and 110B and the distance D (known distance) between the first vibration detection unit 110A and the second vibration detection unit 110B. Calculate the speed of sound.

  However, in this case, the sound speed of the pipe 900 may vary greatly due to changes in the surrounding environment associated with the material, shape, burial, and the like of the pipe 900 itself.

  Therefore, in the sound speed calculation device 100a, the sound speed calculation unit 123 uses the piping 900 (structure) based on the correlation function calculated by the correlation function calculation unit 122 and the rise time difference Δt calculated by the rise time difference calculation unit 121. Is calculated. As a result, the sound speed c can be calculated more accurately without being affected by changes in the surrounding environment caused by the material, shape, burial, and the like of the pipe 900 itself. Therefore, the leak position can be specified more accurately by using the sound speed c calculated by the sound speed calculation apparatus 100.

  Note that a control device 140a that outputs an instruction signal to the first vibration detection unit 110A, the second vibration detection unit 110B, the rise time difference calculation unit 121, the correlation function calculation unit 122, and the sound speed calculation unit 123 may be newly provided. .

  FIG. 9 is a diagram illustrating a signal output relationship of the control device 140a. As illustrated in FIG. 9, the control device 140 a causes the first vibration detection unit to detect the vibration propagating through the pipe 900 as the first vibration toward the first vibration detection unit 110 </ b> A. A detection instruction signal is output. The control device 140a outputs a second vibration detection instruction signal that causes the second vibration detection unit to detect the vibration propagating through the pipe 900 (structure) as the second vibration toward the second vibration detection unit 110B. Output. The control device 140a outputs a rise time difference calculation instruction signal for calculating a rise time difference Δt, which is a time difference between the first rise time ta and the second rise time tb, to the rise time difference calculation unit 121. The control device 140a instructs the correlation function calculation unit 122 to calculate a correlation function between the first and second vibrations W10 and W20 detected according to the first and second vibration detection instruction signals. Output a signal. The control device 140a includes the correlation function calculated according to the correlation function calculation instruction signal, the rise time difference Δt calculated according to the rise time difference calculation instruction signal, and the first vibration detection unit 110A and the second vibration detection unit 110B. Based on the distance D, a sound speed calculation instruction signal for calculating the sound speed c of the pipe 900 (structure) is output. Thereby, the instruction processing for operating the main functions of the above-described sound speed calculation device 100a can be concentrated in the control device 140.

  As described above, the sound speed calculation device 100a according to the second embodiment of the present invention includes the first vibration detection unit 110A (first vibration detection means) and the second vibration detection unit 110B (second vibration). Detection means), a rise time difference calculation unit 121 (rise time difference calculation means), a correlation function calculation unit 122 (correlation function calculation means), and a sound speed calculation unit 123 (sound speed calculation means). 110 A of 1st vibration detection parts detect the vibration which propagates a structure (for example, piping 900) as the 1st vibration W10. The second vibration detection unit 110B detects the vibration propagating through the structure as the second vibration W20. The rise time difference calculation unit 121 calculates a rise time difference Δt that is a time difference between the first rise time ta that is the time when the first vibration W10 rises and the second rise time tb that is the time when the second vibration W20 rises. calculate. The correlation function calculation unit 122 calculates a correlation function between the first vibration W10 and the second vibration W20. The sound speed calculation unit 123 includes a correlation function calculated by the correlation function calculation unit 122, a rise time difference Δt calculated by the rise time difference calculation unit 121, and the first vibration detection unit 110A and the second vibration detection unit 110B. The sound speed c of the structure is calculated based on the distance D.

  As described above, the rise time difference calculation unit 121 calculates the rise time difference Δt that is the time difference between the first rise time ta and the second rise time tb. Thereby, the rise time difference Δt can be prepared as a comparison target with the phase difference between the first vibration W10 and the second vibration W20 indicated by the correlation function. Further, the correlation function calculation unit 122 calculates a correlation function between the first vibration W10 and the second vibration W20. Then, the sound speed calculation unit 123 compares the phase difference between the first vibration W10 and the second vibration W20 indicated by the correlation function with the rise time difference Δt. The correlation function may have a plurality of peaks 501 corresponding to the phase difference between the first vibration W10 and the second vibration W20. At this time, the sound speed calculation unit 123 selects a phase difference with the closest rise time difference Δt among the phase differences corresponding to the plurality of peaks 501. Thereby, the phase difference between the first vibration W10 and the second vibration W20 can be calculated more accurately. Then, the sound speed calculation unit 123 calculates the sound speed c of the pipe 900 (structure) based on the selected phase difference and the distance D between the first vibration detection unit 110A and the second vibration detection unit 110B. . As a result, the sound speed calculation device 100a can calculate the sound speed c of the structure (pipe 900) more accurately.

  In addition, in the sound velocity calculation apparatus 100a according to the second embodiment of the present invention, the correlation function calculation unit 122 performs the first operation after a predetermined time tm has elapsed from a later time among the first and second rise times ta and tb. A correlation function is calculated between the second vibration W20 and the second vibration W20. As a result, errors due to the superposition of harmonics and higher-order modes can be reduced, and the accuracy of sound speed calculation can be increased.

  That is, as shown in FIG. 7, in the first vibration W10 and the second vibration, the vibration shape immediately after rising may include many high-order vibration modes and many harmonics. For this reason, due to the observation of different propagation vibrations, an error occurs in the cross-correlation function, and it may be difficult to calculate an accurate time difference. Therefore, in the sound speed calculation device 100a, the correlation function calculation unit 122 performs a cross-correlation process only on the low-order mode attenuation signal after the time tm has elapsed from the rise time tb of the second vibration detection unit 110B synchronized in time. . As a result, errors due to the superposition of harmonics and higher-order modes can be reduced, and the accuracy of sound speed calculation can be increased.

  In the sound speed calculation device 100a according to the second embodiment of the present invention, the correlation function calculation unit 122 starts with the first rise time ta, the second rise time ta, and the second rise time ta, The correlation function is calculated with a predetermined time tm as a time until a predetermined number of amplitude peaks of the correlation function appear from a later time in tb. As a result, errors due to superposition of harmonics and higher-order modes can be reduced more efficiently, and the accuracy of sound speed calculation can be further increased.

  The sound speed calculation device 100a according to the second embodiment of the present invention includes an excitation unit (excitation means) that applies vibration to a structure. As a result, the vibration levels of the first vibration W10 and the second vibration W20 can be amplified. As a result, the first vibration detection unit 110A and the second vibration detection unit 110B can more easily detect the first vibration W10 and the second vibration W20.

  In the sound velocity calculation apparatus 100a according to the second embodiment of the present invention, the correlation function calculation unit 122 has a structure in which the magnitude of vibration after the vibration is applied to the structure by the vibration unit is determined by the vibration unit. The correlation function is calculated by setting the time when the amplitude is smaller than the average value of the correlation function before the vibration is applied to the object as the end time of the predetermined time tm. As a result, errors due to superposition of harmonics and higher-order modes can be reduced more efficiently, and the accuracy of sound speed calculation can be further increased.

  The control device 140a according to the second embodiment of the present invention uses the first and second vibration detection units 110A and 110B as vibrations propagating through the structure (pipe 900) as first and second vibrations W10 and W20. First and second vibration detection instruction signals to be detected are output. In addition, the control device 140a sets a rise time difference Δt that is a time difference between the first rise time ta that is the time when the first vibration W10 rises and the second rise time tb that is the time when the second vibration W20 rises. A rise time difference calculation instruction signal to be calculated is output. The control device 140a outputs a correlation function calculation instruction signal for calculating a correlation function between the first and second vibrations W10 and W20 detected according to the first and second vibration detection instruction signals. The control device 140a includes the correlation function calculated according to the correlation function calculation instruction signal, the rise time difference Δt calculated according to the rise time difference calculation instruction signal, and the first vibration detection unit 110A and the second vibration detection unit 110B. Based on the distance D, a sound speed calculation instruction signal for calculating the sound speed c of the structure (pipe 900) is output. Thereby, the instruction process for operating the main functions of the above-described sound speed calculation device 100a can be integrated into the control device 140a.

  The sound speed calculation method according to the second embodiment of the present invention includes a first vibration detection step, a second vibration detection step, a rise time difference calculation step, a correlation function calculation step, and a sound speed calculation step. Yes. In the first vibration detection step, the vibration propagating through the structure is detected as the first vibration W10 by the first vibration detection unit 110A. In the second vibration detection step, the vibration propagating through the structure is detected as the second vibration W20 by the second vibration detection unit 110B. In the rise time difference calculation step, a rise time difference Δt that is a time difference between the first rise time ta that is the time when the first vibration W10 rises and the second rise time tb that is the time when the second vibration W20 rises is calculated. To do. In the correlation function calculating step, a correlation function is calculated between the first vibration W10 and the second vibration W20. In the sound speed calculation step, the correlation function calculated in the correlation function calculation step, the rise time difference Δt calculated in the rise time difference calculation step, and the distance D between the first vibration detection unit 110A and the second vibration detection unit 110B. Based on the above, the sound speed of the structure is calculated. This method also has the same effect as the sound speed calculation device 100a described above.

  The sound speed calculation program according to the second embodiment of the present invention causes a computer to perform the steps shown in the sound speed calculation method described above. This program also has the same effect as the sound speed calculation device 100a described above. The storage medium according to the second embodiment of the present invention stores a program that causes a computer to perform the steps shown in the sound velocity calculation method. This storage medium also has the same effect as the sound speed calculation device 100a described above.

<Third Embodiment>
The configuration of the sound speed calculation device 100b according to the third embodiment of the present invention will be described.

  FIG. 10 is a block diagram of a sound speed calculation device 100b according to the third embodiment of the present invention. In FIG. 10, components equivalent to those shown in FIG. 1 and FIG. 5 are given the same symbols as those shown in FIG. 1 and FIG.

  As illustrated in FIG. 10, the sound speed calculation device 100b includes a first vibration detection unit 110A, a second vibration detection unit 110B, and a signal processing unit 120b.

  As shown in FIG. 10, the signal processing unit 120b is connected to the first vibration detection unit 110A and the second vibration detection unit 110B by radio or wire.

  Here, FIG. 1 and FIG. 10 are compared. As shown in FIG. 1, the signal processing unit 120 includes a correlation function calculation unit 122, a sound speed calculation unit 123, and an index setting unit 125. On the other hand, as shown in FIG. 10, the signal processing unit 120 b includes a correlation function calculation unit 122, a sound speed calculation unit 123, and a sound speed data table 124. That is, the signal processing unit 120b shown in FIG. 10 includes a sound speed data table 124 instead of the index setting unit 125 of FIG.

  The sound speed data table 124 stores the sound speed reference value cs of the pipe 900 (structure) for each frequency.

  In addition, here, the sound speed calculation unit 123 includes the correlation function calculated by the correlation function calculation unit 122, the sound speed reference value cs of the pipe 900 (structure) stored in the sound speed data table 124, and the first vibration detection. The sound velocity c of the pipe 900 (structure) is calculated based on the distance D between the part 110A and the second vibration detection part 110B.

  Next, the operation of the sound speed calculation device 100b according to the third embodiment of the present invention will be described.

  FIG. 11 is a diagram illustrating an operation flow of the sound speed calculation apparatus 100b. In the following description, detailed description of the same processing as in the description of FIG.

  As shown in FIG. 11, first, the first vibration detection unit 110A and the second vibration detection unit 110B are installed in a pipe 900 (structure) such as a pipe (S1).

  Next, a hammering process is performed (S2).

  Next, each of the first vibration detection unit 110A and the second vibration detection unit 110B acquires the vibration propagating through the structure as the first vibration W10 and the second vibration W20, respectively (S3).

  Next, the correlation function calculation unit 122 performs waveform cut-out processing of the first vibration W10 and the second vibration W20 (S5), and performs correlation processing (S6). The process of S6 corresponds to the correlation function calculation step of the present invention. The processes of S5 and S6 are as described above.

  Next, a plurality of sound speeds are compared with the sound speed reference value cs of the pipe 900 (structure) stored in the sound speed data table 124 from the correlation function calculated in the correlation process (S6) (S9).

  FIG. 12 is a diagram illustrating an example of a correlation function. Here, as shown in FIG. 12, first, a plurality of peaks P1, P2, and P3 are extracted from the correlation function calculated in the correlation processing (S6). Next, phase differences ΔT1, ΔT2, and ΔT3 corresponding to the plurality of peaks P1, P2, and P3 are calculated. Next, based on the distance D between the first vibration detection unit 110A and the second vibration detection unit 110B and the phase differences ΔT1, ΔT2, ΔT3, the sound speeds c1, c2 corresponding to the peaks P1, P2, P3 , C3 is calculated. Then, the sound speeds c1, c2, and c3 corresponding to the peaks P1, P2, and P3 are compared with the sound speed reference value cs of the pipe 900 (structure) stored in the sound speed data table 124.

  Next, the sound speed calculation unit 123 calculates the sound speed of the pipe 900 (structure) (S10). Based on the comparison process in S8, the sound speed calculation unit 123 calculates the sound speed closest to the sound speed reference value cs of the pipe 900 (structure) among the sound speeds c1, c2, and c3 corresponding to the peaks P1, P2, and P3. Calculated as the speed of sound c of the pipe 900 (structure).

  The operation of the sound speed calculation device 100b according to the third embodiment of the present invention has been described above.

  Note that a control device 140b that outputs an instruction signal to the first vibration detection unit 110A, the second vibration detection unit 110B, the correlation function calculation unit 122, and the sound speed calculation unit 123 may be newly provided.

  FIG. 13 is a diagram illustrating a signal output relationship of the control device 140b. As illustrated in FIG. 13, the control device 140b causes the first vibration detection unit to detect the vibration propagating through the pipe 900 as the first vibration toward the first vibration detection unit 110A. A detection instruction signal is output. The control device 140b sends a second vibration detection instruction signal that causes the second vibration detection unit to detect the vibration propagating through the pipe 900 (structure) as the second vibration toward the second vibration detection unit 110B. Output. The control device 140b instructs the correlation function calculation unit 122 to calculate a correlation function between the first and second vibrations W10 and W20 detected according to the first and second vibration detection instruction signals. Output a signal. The control device 140b includes the correlation function calculated according to the correlation function calculation instruction signal, the sound speed reference value cs of the pipe 900 (structure) stored in the sound speed data table 124, the first vibration detection unit 110A and the second vibration detection unit 110A. Based on the distance D between the vibration detectors 110B, a sound speed calculation instruction signal for calculating the sound speed c of the pipe 900 (structure) is output. Thereby, the instruction processing for operating the main functions of the above-described sound speed calculation device 100b can be integrated into the control device 140b.

  As described above, the sound speed calculation device 100b according to the third embodiment of the present invention includes the sound speed data table 124 instead of the index setting unit 125 according to the first embodiment. This sound speed data table 124 stores the sound speed reference value cs of the pipe 900 (structure). In addition, the sound speed calculation unit 123 includes the correlation function calculated by the correlation function calculation unit 122, the sound speed reference value cs of the pipe 900 (structure) stored in the sound speed data table 124, the first vibration detection unit 110A, Based on the distance D between the second vibration detection units 110B, the sound velocity c of the pipe 900 (structure) is calculated.

  As described above, the sound speed reference value cs of the pipe 900 (structure) is stored in the sound speed data table 124. In addition, the sound speed calculation unit 123 includes the correlation function calculated by the correlation function calculation unit 122, the sound speed reference value cs of the pipe 900 (structure) stored in the sound speed data table 124, the first vibration detection unit 110A, Based on the distance D between the second vibration detection units 110B, the sound velocity c of the pipe 900 (structure) is calculated. That is, the sound speed calculation unit 123 extracts a plurality of peaks (for example, P1, P2, and P3 in FIG. 12) of the correlation function calculated by the correlation function calculation unit 122, and corresponds to the plurality of peaks P1, P2, and P3. A phase difference (a phase difference between the first vibration W10 and the second vibration W20) is calculated. The sound speed calculation unit 123 calculates a plurality of sound speed candidate values (for example, c1, c2, c3) from the phase differences corresponding to the plurality of peaks P1, P2, and P3 and the distance D. The sound speed calculation unit 123 compares the calculated sound speed candidate values c1, c2, and c3 with the sound speed reference value cs of the pipe 900 (structure) stored in the sound speed data table 124. Then, based on the comparison process in S9, the sound speed calculation unit 123 has the sound speed closest to the sound speed reference value cs of the pipe 900 (structure) among the sound speeds c1, c2, and c3 corresponding to the peaks P1, P2, and P3. Is calculated as the sound velocity c of the pipe 900 (structure). Thereby, the sound speed calculation device 100b can calculate the sound speed c of the pipe 900 (structure) while always referring to the sound speed reference value cs of the pipe 900 (structure). As a result, the sound speed calculation device 100b can calculate the sound speed c of the structure (pipe 900) more accurately.

  In the sound speed calculation method according to the third embodiment of the present invention, the index setting step according to the first embodiment is omitted. In the sound speed calculation step, the correlation function calculated in the correlation function calculation step, the sound speed reference value cs of the pipe 900 (structure) stored in the sound speed data table 124, the first vibration detection unit 110A and the second vibration detection unit 110A. The sound speed c of the pipe 900 (structure) is calculated based on the distance D between the vibration detection units 110B. This method also has the same effect as the sound speed calculation device 100b described above.

  The sound speed calculation program according to the third embodiment of the present invention causes a computer to perform the steps shown in the sound speed calculation method described above. This program also provides the same effects as the sound speed calculation devices 100 and 100a described above. The storage medium according to the third embodiment of the present invention stores a program that causes a computer to perform the steps shown in the sound velocity calculation method. Even with this storage medium, the same effects as those of the sound velocity calculation devices 100 and 100a described above can be obtained.

[Example]
The sound speed c of the pipe 900 through which the fluid flows was calculated using the sound speed calculation apparatus 100a according to the second embodiment of the present invention.

  In the following evaluation, the sound velocity c (A) calculated using the entire output waveforms of the first vibration detection unit 110A and the second vibration detection unit 110B, the first vibration detection unit 110A, and the second vibration detection unit It is compared with the sound speed c (B) calculated using only the attenuation waveform of 110B.

  Here, a polyvinyl chloride pipe (PVC (polyvinyl chloride) pipe) is used for the pipe 900. Further, water was allowed to flow into the pipe 900. In addition, the first vibration detection unit 110A and the second vibration detection unit 110B were attached to the pipe 900 at a position 5 m away.

  Then, the impulse hammer 130 was used for impulse excitation at a position 2 m away from the first vibration detection unit 110A.

  Here, the material of the pipe 900 is PVC, and the first and second vibration detectors 110A and 110B are piezoelectric vibration sensors that detect only one axial direction, but this is not restrictive.

  As described above, the sound velocity c (A) calculated using the entire output waveforms of the first vibration detection unit 110A and the second vibration detection unit 110B, the first vibration detection unit 110A, and the second vibration detection unit 110B. The sound velocity c (B) calculated using only the attenuation waveform of was calculated by the following method.

  (Method 1) The sound velocity c (A) is calculated using the entire waveform from when the impulse vibration is applied until the vibration is attenuated to the dark vibration level.

  (Method 2) The sound velocity c (B) is calculated by correlating the waveform from the waveform after the impulse excitation to the attenuation signal until the vibration is attenuated to the dark vibration level after a fixed time of 0.4 msec.

  14A and 14B are diagrams showing the correlation function obtained in the example. FIG. 14A is a correlation function obtained by Method 1. FIG. 14B is a correlation function obtained by Method 2. 14A and 14B, the horizontal axis is time t, and the vertical axis is the cross-correlation coefficient.

  As shown in FIG. 14A, in the correlation function obtained by the method 1, three peaks P111, P112, and P113 appear. As shown in FIG. 14B, in the correlation function obtained by the method 2, three peaks P114, P115, and P116 appear.

  FIG. 15 is a diagram illustrating the sound speed calculated from the peak of the correlation function calculated by the method 1 and the method 2 of the embodiment and the sound speed calculated from the rise time difference Δt of the first and second vibrations W10 and W20.

  In FIG. 1 (whole waveform) corresponds to P111 in FIG. The sound velocity c (A1) of 1 (whole waveform) was about 2000 (m / s). In FIG. 2 (whole waveform) corresponds to P112 in FIG. The sound speed c (A2) of 2 (whole waveform) was about 1040 (m / s). In FIG. 3 (whole waveform) corresponds to P113 in FIG. The sound velocity c (A3) of 3 (whole waveform) was about 5000 (m / s).

  Further, the peak No. in FIG. 1 (attenuation waveform only) corresponds to P114 in FIG. The sound velocity c (B1) of 1 (only the decay waveform) was about 173 (m / s). In FIG. 2 (attenuation waveform only) corresponds to P115 in FIG. The sound velocity c (B2) of 2 (only the decay waveform) was about 372 (m / s). In FIG. 3 (only the attenuation waveform) corresponds to P116 in FIG. The sound velocity c (B3) of 3 (only the attenuation waveform) was −6000 (m / s).

  Further, as shown in FIG. 15, the sound velocity c (C) calculated from the rise time difference Δt between the first vibration detection unit 110A and the second vibration detection unit 110B synchronized in time is about 500 (m / s). there were.

  As shown in FIG. 15, regarding the sound speed c (A) calculated by the technique 1, the peak No. 1 (whole waveform), peak no. 2 (whole waveform) and peak no. Among the sound speeds c (A1), c (A2), and c (A3) of 3 (whole waveform), the one closest to the sound speed c (C) calculated from the rise time difference Δt is the peak No. The sound velocity was 2 (whole waveform) c (A2) (= 1040 (m / s)).

  On the other hand, as shown in FIG. 15, with respect to the sound speed c (B) calculated by the method 2, the peak No. 1 (attenuation waveform only), peak no. 2 (attenuation waveform only) and peak no. Among the sound speeds c (B1), c (B2), and c (B3) of sound speeds 3 (attenuation waveform only), the one closest to the sound speed c (C) calculated from the rise time difference Δt is the peak No. The sound velocity was c (B2) (= 372 (m / s)) of 2 (attenuated waveform only).

  From this, it can be seen that since the method 2 has a more likely value, it is possible to accurately calculate the sound speed.

  In addition, the speed of sound for comparison required for calculating the speed of sound c is known for a known PVC material instead of the rising times ta and tb of the first vibration detection unit 110A and the second vibration detection unit 110B. Sound speed table (example: literature value 400 m / s) may be used.

  The apparatus of each embodiment of the present invention includes a CPU (Central Processing Unit), a memory, and a program loaded in the memory (a program stored in the memory from the stage of shipping the apparatus in advance, (Including programs downloaded from storage media such as CDs (Compact Discs) and servers on the Internet, etc.), storage units such as hard disks that store the programs, and network connection interfaces. Realized by combination. It will be understood by those skilled in the art that there are various modifications to the implementation method and apparatus.

  In addition, the block diagram used in the description of each embodiment of the present invention shows functional unit blocks rather than hardware unit configurations. In these drawings, each device is described as being realized by one device, but the means for realizing it is not limited to this. That is, it may be a physically separated configuration or a logically separated configuration.

  The present invention has been described above using the above-described embodiment as an exemplary example. However, the present invention is not limited to the above-described embodiment. That is, the present invention can apply various modes that can be understood by those skilled in the art within the scope of the present invention.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2014-053292 for which it applied on March 17, 2014, and takes in those the indications of all here.

100, 100a, 100b Sound velocity calculation device 110A First vibration detection unit 110B Second vibration detection unit 120, 120a, 120b Signal processing unit 121 Rise time difference calculation unit 122 Correlation function calculation unit 123 Sound velocity calculation unit 124 Sound velocity data table 125 Indicator Setting unit 130 Impulse hammer 140, 140a, 140b Controller 900 Piping

Claims (17)

First vibration detecting means for detecting vibration propagating through the structure as the first vibration;
Second vibration detection means for detecting vibration propagating through the structure as second vibration;
Correlation function calculating means for calculating a correlation function between the first vibration and the second vibration;
Index setting means for setting an index for selecting any one of a plurality of peak values included in the correlation function calculated by the correlation function calculating means;
Based on the correlation function calculated by the correlation function calculating means, the index calculated by the index setting means, and the distance between the first vibration detecting means and the second vibration detecting means, A sound speed calculation device comprising sound speed calculation means for calculating the sound speed of a structure. The index setting means includes
Rise time difference calculation that calculates a rise time difference that is a time difference between a first rise time that is a rise time of the first vibration and a second rise time that is a time of rise of the second vibration as the index. Means,
The sound speed calculating means is
Based on the correlation function calculated by the correlation function calculation means, the rise time difference calculated by the rise time difference calculation means, and a distance between the first vibration detection means and the second vibration detection means. The sound speed calculation device according to claim 1, wherein the sound speed of the structure is calculated. Instead of the index setting means,
A sound speed data table for storing a sound speed reference value of the structure;
The sound speed calculating means is
The correlation function calculated by the correlation function calculation means, the sound speed reference value of the structure stored in the sound speed data table, and the distance between the first vibration detection means and the second vibration detection means The sound speed calculation device according to claim 1, wherein the sound speed of the structure is calculated based on   The correlation function calculating means calculates the correlation function between the first vibration and the second vibration after a predetermined time has elapsed from a later time of the first and second rising times. Sound velocity calculation apparatus given in any 1 paragraph of ~ 3.   The correlation function calculating means displays a predetermined number of peak portions of the amplitude of the correlation function that occur from a later time of the first and second rise times to a later time of the first and second rise times. The sound speed calculation device according to claim 4, wherein the correlation function is calculated with a time until a predetermined time.   The sound speed calculation device according to any one of claims 1 to 5, further comprising an excitation unit that applies vibration to the structure.   The correlation function calculating means is configured so that the amplitude of the correlation function after the vibration is applied to the structure by the vibration unit is the correlation before the vibration is applied to the structure by the vibration unit. The sound speed calculation device according to claim 6, wherein the correlation function is calculated using a time when the time is less than a predetermined number of times as an average value of the amplitude of the function as an end time of the predetermined time. Outputting first and second vibration detection instruction signals for causing the first and second vibration detecting means to detect the vibration propagating through the structure as the first and second vibrations;
Outputting a correlation function calculation instruction signal for calculating a correlation function between the first and second vibrations detected according to the first and second vibration detection instruction signals;
Outputting an index setting instruction signal for setting an index for selecting any one of a plurality of peak values included in the correlation function calculated according to the correlation function calculation instruction signal;
Based on the correlation function calculated according to the correlation function calculation instruction signal, the index calculated according to the index setting instruction signal, and the distance between the first vibration detection means and the second vibration detection means. A control device for outputting a sound speed calculation instruction signal for calculating the sound speed of the structure. Correlation function calculating means for calculating a correlation function between the first and second vibrations input from the first and second vibration detection units;
Index setting means for setting an index for selecting any one of a plurality of peak values included in the correlation function calculated by the correlation function calculating means;
Based on the correlation function calculated by the correlation function calculating unit, the index calculated by the index setting unit, and the distance between the first vibration detecting unit and the second vibration detecting unit, the structure A signal processing device comprising: a sound speed calculating means for calculating the sound speed of an object. The index setting means includes
Rise time difference calculation that calculates a rise time difference that is a time difference between a first rise time that is a rise time of the first vibration and a second rise time that is a time of rise of the second vibration as the index. Means,
The sound speed calculating means is
Based on the correlation function calculated by the correlation function calculation means, the rise time difference calculated by the rise time difference calculation means, and a distance between the first vibration detection means and the second vibration detection means. The signal processing device according to claim 9, wherein a sound speed of the structure is calculated. Instead of the index setting means,
A sound speed data table for storing a sound speed reference value of the structure;
The sound speed calculating means is
The correlation function calculated by the correlation function calculation means, the sound speed reference value of the structure stored in the sound speed data table, and the distance between the first vibration detection means and the second vibration detection means The signal processing device according to claim 9, wherein the speed of sound of the structure is calculated based on: The vibration propagating through the structure is detected as the first vibration by the first vibration detecting means,
The vibration propagating through the structure is detected as the second vibration by the second vibration detecting means,
Calculating a correlation function between the first vibration and the second vibration;
Setting an index for selecting any one of the plurality of peak values included in the correlation function;
A sound speed calculation method for calculating a sound speed of the structure based on the correlation function, the index, and a distance between the first vibration detection unit and the second vibration detection unit. The index is set based on a rise time difference that is a time difference between a first rise time that is a time when the first vibration rises and a second rise time that is a time when the second vibration rises,
The sound speed of the structure is calculated based on the correlation function, the rise time difference, and the distance between the first vibration detection unit and the second vibration detection unit. The sound speed calculation method. Omit the process of setting the indicator,
The sound speed of the structure is calculated by calculating the correlation function, the sound speed reference value of the structure stored in the sound speed data table, and the distance between the first vibration detecting means and the second vibration detecting means. The sound speed calculation method according to claim 12, which is performed based on the following. The vibration propagating through the structure is detected as the first vibration by the first vibration detecting means,
The vibration propagating through the structure is detected as the second vibration by the second vibration detecting means,
Calculating a correlation function between the first vibration and the second vibration;
Setting an index for selecting any one of the plurality of peak values included in the correlation function;
A program for causing a computer to perform a process of calculating a sound speed of the structure based on the correlation function, the index, and a distance between the first vibration detection unit and the second vibration detection unit is stored. Storage medium. The index is set based on a rise time difference that is a time difference between a first rise time that is a time when the first vibration rises and a second rise time that is a time when the second vibration rises,
The sound speed of the structure is calculated based on the correlation function, the rise time difference, and the distance between the first vibration detection unit and the second vibration detection unit. Storage media. Omit the process of setting the indicator,
The sound speed of the structure is calculated by calculating the correlation function, the sound speed reference value of the structure stored in the sound speed data table, and the distance between the first vibration detecting means and the second vibration detecting means. The storage medium according to claim 15, which is performed based on

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