Transmitting terminal, measurement system, and control method

Abstract

To provide a transmitting terminal, a measurement system, and a control method that can improve the efficiency of transmitting data required for evaluating a structure.SOLUTION: A transmitting terminal of an embodiment has a receiving unit, a communication unit, and a signal processing unit. The receiving unit receives elastic waves output from a sensor that detects the elastic waves generated inside a structure. The communication unit wirelessly transmits transmission data stored in a transmission buffer memory that stores transmission data based on the received elastic waves. The signal processing unit controls elastic wave measurement processing based on the number of pieces of data stored in the transmission buffer memory and an elapsed time since the time when the elastic waves have been detected.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Embodiments of the present invention relate to a transmission terminal, a measurement system, and a control method.

Background Art

[0002] When a traffic load is applied to a structure such as a bridge, AE (Acoustic Emission) occurs due to the progress of cracks and friction inside the structure. By installing sensors on a surface different from the surface to which the load is applied (for example, the lower surface of the structure), elastic waves generated inside the structure can be detected. Conventionally, elastic waves generated when a vehicle passes are detected by sensors installed on the lower surface of the structure, and the soundness of the structure is evaluated based on the density of the sources of the detected multiple elastic waves. However, until now, the acquisition of measurement data by wired connection has been the mainstream, and in recent years, the acquisition of measurement data by wireless has been studied.

[0003] The number of elastic waves generated when a vehicle passes can be several hundred or more depending on the soundness of the structure. Depending on the frequency band of the wireless communication standard used and the number of sensors to be measured, there is a limit to the wireless transmission speed. Therefore, there is a possibility that not all the data detected by the sensors can be transmitted. Although it is not necessary to transmit all the data, it is desired that the data necessary for evaluating the structure can be transmitted efficiently.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a transmission terminal, a measurement system, and a control method capable of improving the transmission efficiency of data required for evaluating a structure.

Means for Solving the Problem

[0006] The transmission terminal according to the embodiment includes a receiving unit, a communication unit, and a signal processing unit. The receiving unit receives the elastic wave output from a sensor that detects an elastic wave generated inside the structure. The communication unit wirelessly transmits the transmission data stored in a transmission buffer memory that stores the transmission data based on the received elastic wave. The signal processing unit controls the elastic wave measurement process based on the number of data stored in the transmission buffer memory and the elapsed time from the time when the elastic wave is detected.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Embodiments for Carrying Out the Invention

[0008] Hereinafter, a transmission terminal, a measurement system, and a control method according to an embodiment will be described with reference to the drawings.

[0009] (First Embodiment) FIG. 1 is a diagram showing the system configuration of a measurement system 100 according to the first embodiment. The measurement system 100 includes a sensor 10, a transmission terminal 20, and a collection device 30. The sensor 10 and the transmission terminal 20 are connected by wire. The transmission terminal 20 and the collection device 30 are wirelessly connected via a network NW. The network NW is, for example, in the 920 MHz band or Bluetooth (registered trademark). The wireless connection between the transmission terminal 20 and the collection device 30 does not need to be limited, and any communication method may be used as long as wireless communication is possible. FIG. 1 shows a configuration in which the measurement system 100 includes one sensor 10 and one transmission terminal 20, but the measurement system 100 may include a plurality of sensors 10 and transmission terminals 20, respectively.

[0010] The sensor 10 is a sensor that detects a physical quantity. The sensor 10 is, for example, an AE sensor, an acceleration sensor, a microphone, a temperature sensor, or the like. The sensor 10 may be other sensors as long as it can detect a physical quantity. The sensor 10 converts the detected physical quantity into an electrical signal. The sensor 10 transmits the electrical signal to the transmission terminal 20.

[0011] As an example, a case where the sensor 10 is installed on a structure such as a bridge through which a vehicle or the like passes will be described. The structure may be any structure as long as elastic waves are generated due to the occurrence or progress of cracks or external impacts (for example, rain, artificial rain, etc.). Note that the bridge is not limited to a structure erected over a river, valley, etc., and also includes various structures provided above the ground (for example, an elevated bridge on a highway). The structure may be a plate-like member. The sensor 10 is installed, for example, on a surface of the structure (for example, the lower surface) different from the surface on which the vehicle travels.

[0012] The transmitting terminal 20 transmits transmission data including time information to the collecting device 30. For example, the transmitting terminal 20 detects an event based on the electrical signal output from the sensor 10, and transmits transmission data including the occurrence time of the detected event (hereinafter referred to as "event detection time") to the collecting device 30. Here, an event represents an event that occurs outside or inside the device. In the following embodiments, the event will be described by taking an event that occurs outside the device (for example, an event based on the detection result of a sensor) as an example. Hereinafter, the sensor 10 and the transmitting terminal 20 may be configured as one device, and that one device is called a sensor terminal.

[0013] The collecting device 30 collects the transmission data transmitted from the transmitting terminal 20.

[0014] FIG. 2 is a diagram showing a functional configuration example of the transmitting terminal 20 in the first embodiment. The transmitting terminal 20 includes a receiving unit 21, a BPF 22, an analog-to-digital conversion unit 23, a filter 24, a clock oscillator 25, a time information generation unit 26, a signal processing unit 27, and a communication unit 28.

[0015] The receiving unit 21 receives the electrical signal transmitted from the sensor 10. The receiving unit 21 outputs the received electrical signal to the BPF 22.

[0016] The BPF 22 is a band-pass filter that removes noise from the electrical signal received by the receiving unit 21 or extracts only the necessary band. The BPF 22 outputs the signal after noise removal to the analog-to-digital conversion unit 23. The BPF 22 is an analog filter.

[0017] The analog-to-digital conversion unit 23 converts the analog signal into a digital signal by quantizing the signal after noise removal output from the BPF 22. The analog-to-digital conversion unit 23 outputs the digital signal to the filter 24.

[0018] Filter 24 removes noise from the digital signal output from the analog-to-digital conversion unit 23 and extracts only the necessary band. Filter 24 outputs the signal after noise removal to the signal processing unit 27. Filter 24 is a digital filter. In the following description, the processes performed by the BPF 22, the analog-to-digital conversion unit 23, and the filter 24 will be described as preprocessing.

[0019] The clock oscillator 25 generates a clock signal. Specifically, the clock oscillator 25 determines the time width of 1 second in the transmission terminal 20. The clock oscillator 25 is configured using, for example, a voltage-controlled crystal oscillator such as a VCXO (Voltage controlled xtal oscillators). The clock oscillator 25 outputs the clock signal to the time information generation unit 26.

[0020] The time information generation unit 26 determines the time in the transmission terminal 20 according to the clock signal output from the clock oscillator 25. The time information generation unit 26 is, for example, a counter having a register. That is, the time information generation unit 26 counts the edges of the clock signal and stores the cumulative count value from the power-on of the transmission terminal 20 in the register as time information.

[0021] The signal processing unit 27 determines the event detection time and the transmission time based on the noise-removed digital signal output from the filter 24 and the time information generated by the time information generation unit 26. For example, the signal processing unit 27 may determine the time indicated by the time information generated by the time information generation unit 26 as the event detection time at the timing when the noise-removed digital signal output from the filter 24 is input. For example, the signal processing unit 27 may determine the time indicated by the time information generated by the time information generation unit 26 as the transmission time at the timing when it causes the communication unit 28 to transmit transmission data. The event detection time may be, for example, the number of clock counts, or it may be the hour, minute, and second. Further, the signal processing unit 27 extracts a feature amount of the noise-removed digital signal. The feature amount is information indicating the feature of the signal. For example, the feature amount is the amplitude [mV] of the waveform, the rise time [usec] of the waveform, the duration time [usec] of the gate signal, the zero-cross count number [times], the energy [arb.] of the waveform, and the frequency [Hz], etc.

[0022] The amplitude of the waveform is, for example, the value of the maximum amplitude in the noise-removed signal. The rise time of the waveform is, for example, the time T1 from the start of the rise of the gate signal until the noise-removed signal reaches the maximum value. The duration time of the gate signal is, for example, the time from the start of the rise of the gate signal until the amplitude becomes smaller than a preset value. The zero-cross count number is, for example, the number of times the noise-removed signal crosses a reference line passing through the zero value.

[0023] The energy of the waveform is, for example, a value obtained by time-integrating the square of the amplitude of the noise-removed signal at each time point. Note that the definition of the energy is not limited to the above example, and it may be approximated using, for example, the envelope of the waveform. The frequency is the frequency of the noise-removed signal.

[0024] Furthermore, the signal processing unit 27 has a transmission buffer memory (FIFO: First In First Out). The transmission buffer memory is a temporary recording medium for storing transmission data transmitted by the communication unit 28. The transmission buffer memory is, for example, a dual-port RAM (Random Access Memory). The signal processing unit 27 temporarily stores, as transmission data, the parameters related to the extracted feature amounts in association with the event detection time and the sensor ID in the transmission buffer memory. The sensor ID represents identification information for identifying the sensor 10 installed in the area to be evaluated for the soundness of the structure (hereinafter referred to as the "evaluation area").

[0025] Furthermore, the signal processing unit 27 controls the timing at which the communication unit 28 transmits the transmission data. Therefore, the signal processing unit 27 has at least two flags internally. The at least two flags are FlagX and FlagY. FlagX and FlagY are each represented by a value of "0" or "1". Note that the signal processing unit 27 also has flags other than FlagX and FlagY, but here, FlagX and FlagY will be described as an example. Other flags will be described when the corresponding flags appear.

[0026] FlagX is a flag indicating whether or not to permit the execution of the measurement operation related to AE measurement, storage in the transmission buffer memory, or transmission of transmission data. The value "0" of FlagX means that the execution of the measurement operation is permitted. The value "1" of FlagX means that the execution of the measurement operation is not permitted, that is, the measurement operation is stopped. Hereinafter, as an example, the transmission of transmission data will be described as an example of the measurement operation. FlagY is a flag indicating whether or not the transmission buffer memory is empty (the storage amount of the memory is 0). The value "0" of FlagY means that the transmission buffer memory is empty. The value "1" of FlagY means that the transmission buffer memory is not empty.

[0027] Furthermore, based on the above-mentioned FlagX and FlagY, the signal processing unit 27 determines whether the processing conditions are satisfied. The processing conditions are the conditions for processing the elastic waves detected by the sensor 10 in the signal processing unit 27. For example, it is the case where the value of FlagX is "0" and the value of FlagY is "0". That is, the signal processing unit 27 determines that the processing conditions are satisfied when transmission is permitted and the transmission buffer memory is empty. On the other hand, the signal processing unit 27 determines that the processing conditions are not satisfied when transmission is not permitted or the transmission buffer memory is not empty.

[0028] The communication unit 28 is a communication interface that communicates with the collection device 30 via the network NW. When transmission data is stored in the transmission buffer memory of the signal processing unit 27, the communication unit 28 transmits the transmission data stored in the transmission buffer memory to the collection device 30 in order by wireless communication in a FIFO manner.

[0029] The radio frequency band used for the communication of the communication unit 28 is, for example, a band such as 2.4 GHz or 920 MHz. The communication unit 28 can transmit at an appropriate timing, such as collectively transmitting separately from the output timing from the signal processing unit 27 or transmitting individually, using the storage unit.

[0030] Next, the hardware of the transmission terminal 20 will be described. The power of the transmission terminal 20 is supplied from an external power source, a primary battery, a secondary battery, a solar cell, an energy harvester, or the like. The transmission terminal 20 is realized by an analog circuit and a digital circuit. The digital circuit is realized by, for example, an FPGA (Field Programmable Gate Array) or a microcomputer. It may also be realized by a dedicated LSI (Large-Scale Integration). Further, the transmission terminal 20 may be equipped with a non-volatile memory such as a flash memory or a removable memory.

[0031] FIG. 3 is a diagram for explaining a method of measuring elastic waves in the first embodiment. In FIG. 3, as an example of the method of measuring elastic waves, it is considered to evaluate internal damage of a structure based on elastic waves generated by a running part (for example, a tire) of a vehicle V running on a road surface. When the vehicle V passes over the road surface, a large number of elastic waves are generated in the structure due to the interaction between the tire and the road surface and deflection due to a load or the like. The generated elastic waves propagate inside the structure and are detected by each sensor 10 installed on a surface (for example, the bottom surface) different from the road surface. In this way, the elastic waves can be measured by installing each sensor 10 on a surface (for example, the bottom surface) different from the road surface. By using the data obtained from each sensor 10, it is possible to estimate the detection amount of the elastic waves and the position of the elastic wave generation source, and diagnose the soundness of the structure based on the concentration degree, the distribution density, and the like.

[0032] Every time the vehicle V passes by, a series of AE hits (elastic wave groups) are generated. The transmission terminal 20 needs to wirelessly transmit data of a plurality of elastic waves that are a series of AE hits generated when the vehicle V passes by. However, when the vehicles V pass by one after another, there is a high possibility that the next vehicle V will pass by before the wireless transmission by the transmission terminal 20 is completed. Also, when the number of passing vehicles V is large, there may be a problem of memory overflow in the transmission terminal 20. Since the soundness of the structure shows different results depending on the measurement time and the like, it is necessary to normalize by the traffic volume of the vehicles. Therefore, this problem can be solved by determining whether measurement is possible for each vehicle. Hereinafter, a specific configuration for solving this problem will be described.

[0033] FIG. 4 is a diagram for explaining the outline of a control method for AE measurement in the first embodiment. In FIG. 4, a configuration in which four vehicles V1, V2, V3, and V4 pass is shown. When the vehicles V1, V2, V3, and V4 pass, an elastic wave (point P1 in FIG. 4) is generated as shown in FIG. 4. The transmission terminal 20 acquires an electrical signal based on the generated elastic wave from the sensor 10, performs necessary signal processing on the elastic wave, and then wirelessly transmits it to the collection device 30. The transmission terminal 20 detects an elastic wave group in real time. The elastic wave group is a general term for a plurality of elastic waves generated in a short period. The method for detecting the elastic wave group is, here, when the time difference between the current time and the last AE hit time (the detection time of the elastic wave) is equal to or more than a certain period.

[0034] When the elastic wave group arrives, the transmission terminal 20 performs AE measurement, starts wireless transmission while temporarily storing data related to the elastic wave in the transmission buffer memory. After the detection of one elastic wave group is completed, the transmission terminal 20 generates a stop signal as needed and stops the AE measurement. The detection of the elastic wave group means that the elastic wave is simply detected by the sensor 10 without performing processes such as feature amount extraction. The stop signal is a signal for performing any one of the stop of the AE measurement, the stop of storage in the transmission buffer memory, or the stop of transmission of transmission data. The timing for generating the stop signal is determined based on the time difference between the current time and the last AE hit and the memory count. For example, the timing for generating the stop signal is when the time difference between the current time and the last AE hit is equal to or more than the threshold value X and the memory count is equal to or more than the threshold value Y. Hereinafter, a state in which any one of the stop of the AE measurement, the stop of storage in the transmission buffer memory, or the stop of transmission of transmission data is performed is referred to as a stop state. Therefore, the transmission terminal 20 enters the stop state based on the stop signal.

[0035] The threshold value X may be determined based on the inter-vehicle distance and the vehicle speed. The threshold value Y is 1 or more. This is a value corresponding to false detection due to single noise. For example, even when a small number of AE hits that can transmit radio waves in a short period of time occur, such as those generated by animals, motorcycles, or floating objects, the system will stop. Therefore, by setting a certain memory count threshold value, it is possible to prevent it from stopping in the case of a small number. The threshold value X is an aspect of the first threshold value, and the threshold value Y is an aspect of the second threshold value.

[0036] Even when the next elastic wave group occurs after the detection of the elastic wave group has ended, if there is still transmission data remaining in the transmission buffer memory, the transmitting terminal 20 does not perform measurement of that elastic wave group. Then, the transmitting terminal 20 continues to transmit the transmission data stored in the transmission buffer memory. After that, the transmitting terminal 20 generates a release signal as necessary and starts AE measurement again based on the generated release signal. For example, the release signal is generated by a signal generation unit provided inside the signal processing unit 27 and received by a functional unit that performs signal processing provided inside the signal processing unit 27. Here, the functional unit that performs signal processing is, for example, a functional unit for performing feature quantity extraction.

[0037] The release signal is a signal for starting any one of AE measurement, starting storage in the transmission buffer memory, or starting transmission of transmission data. The timing for generating the release signal is determined based on the time difference between the current time and the last AE hit and the memory count. For example, the timing for generating the release signal is when the time difference between the current time and the last AE hit is equal to or greater than the threshold value Z and the memory count is less than the threshold value W. The threshold value Z is determined based on the vehicle interval, speed, etc. when passing through the structure in order to completely exclude the elastic wave group generated while the measurement is stopped. The threshold value W may be 0 when, for example, all radio transmissions are completed. It is not limited to this number depending on the number of hits of the elastic wave group. Hereinafter, a state in which any one of starting AE measurement, starting storage in the transmission buffer memory, or starting transmission of transmission data is being performed is referred to as a release state. Therefore, the transmitting terminal 20 enters the release state based on the release signal. The threshold value Z is an aspect of the third threshold value, and the threshold value W is an aspect of the fourth threshold value.

[0038] In the example shown in FIG. 4, after completing transmission of the group of elastic waves generated in conjunction with the passage of vehicle V1 (hereinafter referred to as the "first elastic wave group"), the transmitting terminal 20 continues to measure the group of elastic waves generated in conjunction with the passage of vehicle V2 (hereinafter referred to as the "second elastic wave group") because the conditions for generating a stop signal are not met. As shown in FIG. 4, there is a large amount of data for the second elastic wave group, and transmission has not been completed by the time the third elastic wave group is detected. In this case, the transmitting terminal 20 does not measure the third elastic wave group and continues to transmit the data for the second elastic wave group. In this way, the conditions for generating a stop signal are met by the time the transmitting terminal 20 detects the group of elastic waves generated in conjunction with the passage of vehicle V3 (hereinafter referred to as the "third elastic wave group"). Therefore, the transmitting terminal 20 does not measure the third elastic wave group.

[0039] Thereafter, the transmitting terminal 20 completes the transmission of the data of the second elastic wave group, and when the transmitting terminal 20 detects the elastic wave group (hereinafter referred to as the "fourth elastic wave group") generated in association with the passage of vehicle V4, the conditions for generating a release signal are met. Therefore, the transmitting terminal 20 starts measuring the fourth elastic wave group again. By performing such control, it becomes possible to measure one elastic wave group associated with the passage of one vehicle V, and when evaluating the soundness of the structure, it becomes possible to normalize it to one vehicle passing.

[0040] 5 is a flowchart showing the flow (part 1) of the elastic wave detection process performed by the transmitting terminal 20 in the first embodiment. The process in FIG. 5 is executed when an elastic wave is detected by the sensor 10 and output to the transmitting terminal 20. The transmitting terminal 20 executes the process in FIG. 5 every time an elastic wave is detected by the sensor 10.

[0041] The receiving unit 21 receives the electrical signal transmitted from the sensor 10 (step S101). The receiving unit 21 outputs the received electrical signal to the BPF 22. The BPF 22, the analog-digital conversion unit 23, and the filter 24 perform preprocessing on the electrical signal output from the receiving unit 21 (step S102). The filter 24 outputs the preprocessed electrical signal to the signal processing unit 27. When the preprocessed electrical signal is input to the signal processing unit 27, the signal processing unit 27 determines whether the processing conditions are satisfied (step S103). The signal processing unit 27 determines, for example, whether the value of FlagX is "0". As will be described later, the condition for the value of FlagX to be "0" is that the value of FlagY is "0". That is, when the value of FlagX is "0", the value of FlagY is also "0". Therefore, the signal processing unit 27 can determine whether the processing conditions are satisfied by checking whether the value of FlagX is "0".

[0042] When the signal processing unit 27 determines that the processing conditions are not satisfied (step S103-NO), the signal processing unit 27 does not store the preprocessed electrical signal output from the filter 24 in the transmission buffer memory (step S104). This is the state in which the transmission terminal 20 has stopped AE measurement due to the stop signal described above. On the other hand, when the signal processing unit 27 determines that the processing conditions are satisfied (step S103-YES), the signal processing unit 27 detects the occurrence of an event based on the preprocessed electrical signal output from the filter 24 (step S105). An event represents an elastic wave generation event that has occurred in the structure. The elastic wave generation event in the present embodiment is the passage of a vehicle on the road surface. The case where the processing conditions are satisfied is the state in which the transmission terminal 20 has started AE measurement by the release signal described above.

[0043] The signal processing unit 27 extracts feature quantities using the preprocessed electrical signal output from the filter 24 (step S106). The method for extracting feature quantities is the same as existing methods. Further, the signal processing unit 27 determines the event detection time t based on the preprocessed electrical signal output from the filter 24 and the time information output from the time information generation unit 26 eventto determine (step S107). The signal processing unit 27 determines the parameter related to the extracted feature amount, the determined event detection time t event and the sensor ID are associated with each other and temporarily stored in the transmission buffer memory as transmission data (step S108).

[0044] FIG. 6 is a flowchart showing the flow of data transmission processing performed by the transmission terminal 20 in the first embodiment. The processing in FIG. 6 is executed when transmission data is stored in the transmission buffer memory included in the signal processing unit 27. The communication unit 28 checks the transmission buffer memory included in the signal processing unit 27 and reads out the oldest transmission data in order by the FIFO method (step S201). The communication unit 28 transmits the read transmission data to the collection device 30 by wireless communication (step S202).

[0045] FIG. 7 is a flowchart showing the flow of processing related to FlagX included in the signal processing unit 27 in the first embodiment. The processing in FIG. 7 is executed every time a clock is input by an FPGA or the like constituting the transmission terminal 20.

[0046] When a clock is input, the signal processing unit 27 updates the current time (step S301). Thereafter, the signal processing unit 27 determines whether the value of FlagY is "1" (step S302). When the signal processing unit 27 determines that the value of FlagY is not "1" (step S302-NO), the signal processing unit 27 sets the value of FlagX to "0" (step S303). Thereafter, the processing of step S301 is executed.

[0047] On the other hand, when the signal processing unit 27 determines that the value of FlagY is "1" (step S302-YES), the signal processing unit 27 determines the current time t nоw to obtain the information of (step S304). For example, the signal processing unit 27 obtains the time indicated by the time information generated by the time information generation unit 26 as the current time t nоw at the timing when the clock is input. The signal processing unit 27 determines the last event detection time tevent and the current time t nоw Calculate the time difference dt from it (step S305). The signal processing unit 27 determines whether the calculated time difference dt exceeds a threshold value X (step S306).

[0048] When the signal processing unit 27 determines that the calculated time difference dt does not exceed the threshold value X (step S306 - NO), the signal processing unit 27 repeatedly executes the processing after step S301. When the time difference dt does not exceed the threshold value X, it is highly likely that elastic waves generated by the passage of the same vehicle have been detected. Thereby, elastic waves generated by the passage of the same vehicle can be acquired as a group of data.

[0049] When the signal processing unit 27 determines that the calculated time difference dt exceeds the threshold value X (step S306 - YES), the signal processing unit 27 sets the value of FlagX to "1" (step S307). Thereby, the signal processing unit 27 generates a stop signal and shifts to a stop state based on the generated stop signal. Thereafter, the processing of step S301 is executed.

[0050] FIG. 8 is a flowchart showing the flow of processing related to FlagY included in the signal processing unit 27 in the first embodiment. The processing in FIG. 8 is executed every time a clock is input to an FPGA or the like constituting the transmission terminal 20.

[0051] When a clock is input, the signal processing unit 27 updates the current time (step S401). Thereafter, the signal processing unit 27 determines whether the value of FIFO_RESETn is "1" (step S402). FIFO_RESETn is a flag indicating whether a release signal has been received. The value "1" of FIFO_RESETn means that a release signal has not been received. The value "0" of FIFO_RESETn means that a release signal has been received. When the signal processing unit 27 receives a release signal in a functional unit that generates the release signal and performs signal processing, it sets the value of FIFO_RESETn to "0", and when the generation of the release signal stops, it sets the value of FIFO_RESETn to "1".

[0052] When the signal processing unit 27 determines that the value of FIFO_RESETn is not "1" (FIFO_RESETn = 0) (step S402 - NO), the signal processing unit 27 sets the value of FlagY to "0" (step S403). Further, since the value of FlagY has become "0", the signal processing unit 27 will execute the process of step S303 in FIG. 7. That is, the signal processing unit 27 sets the value of FlagX to "0". Thereby, the measurement operation is restarted (for example, the processes shown in FIGS. 5 and 6). Then, the process of step S401 is executed. On the other hand, when the signal processing unit 27 determines that the value of FIFO_RESETn is "1" (step S402 - YES), the signal processing unit 27 nоw acquires the information of the current number cntFIFO of the transmission buffer memory (step S404). For example, the signal processing unit 27 refers to the transmission buffer memory and acquires the number of transmission data remaining in the transmission buffer memory as the current number cntFIFO nоw of the transmission buffer memory. The signal processing unit 27 determines whether the current number cntFIFO nоw of the transmission buffer memory is equal to or greater than the threshold value Y (step S405).

[0053] When the signal processing unit 27 determines that the current number cntFIFO nоw of the transmission buffer memory is equal to or greater than the threshold value Y (step S405 - YES), the signal processing unit 27 sets the value of FlagY to "1" (step S406). Since the value of FlagY has become "1", the signal processing unit 27 will execute the processes after step S304 in FIG. 7. Further, the signal processing unit 27 executes the process of step S401. On the other hand, when the signal processing unit 27 determines that the current number cntFIFO nоw of the transmission buffer memory is less than the threshold value Y (step S405 - NO), the signal processing unit 27 repeatedly executes the processes after step S401.

[0054] Fig. 9 is a flowchart showing the flow of processing performed by the signal processing unit 27 in the first embodiment. The processing in Fig. 9 is processing for generating a state in which transmission is stopped and the transmission buffer memory is empty. The processing in Fig. 9 is executed every time a clock is input to an FPGA or the like constituting the transmitting terminal 20.

[0055] When the clock is input, the signal processing unit 27 updates the current time (step S501). After that, the signal processing unit 27 updates the current number of transmission buffer memories cntFIFO nоw The signal processing unit 27 acquires the information if the value of FlagX is "1" and the current number of transmission buffer memories is cntFIFO (step S502). nоw is equal to or less than the threshold value W (step S503). nоw is not equal to or less than the threshold value W (step S503-NO), the signal processing unit 27 sets the value of Empty_and_Suspend to "0" (step S504). Then, the process of step S501 is executed. Empty_and_Suspend is a flag indicating whether the measurement operation has been stopped (for example, FlagX=1) and whether the current number of transmission buffer memories is equal to or less than a certain number.

[0056] On the other hand, if the signal processing unit 27 determines that the value of FlagX is "1" and the current number of transmission buffer memories is cntFIFO nоw is equal to or less than the threshold value W (step S503-YES), the signal processing unit 27 sets the value of Empty_and_Suspend to "1" (step S505). After that, the process of step S501 is executed.

[0057] Fig. 10 is a flowchart showing the flow of processing performed by the signal processing unit 27 in the first embodiment. The processing in Fig. 10 is a specific example of the processing shown in Fig. 8. The processing in Fig. 10 is executed every time a clock is input to an FPGA or the like that constitutes the transmitting terminal 20.

[0058] When a clock is input, the signal processing unit 27 updates the current time (step S601). After that, the signal processing unit 27 determines whether the value of FIFO_RESETn is "1" (step S602). When the signal processing unit 27 determines that the value of FIFO_RESETn is not "1" (step S602 - NO), the signal processing unit 27 sets the value of Empty_Once to "0" (step S603). Empty_Once is a flag that allows the release signal to operate only once. After that, the process of step S601 is executed. Empty_Once is a flag to prevent FIFO_RESETn from always becoming 0 when a signal satisfying the release signal is received. For example, Empty_Once is used so that no reset or the like is applied when the transmission buffer memory is used by a signal different from the event.

[0059] On the other hand, when the signal processing unit 27 determines that the value of FIFO_RESETn is "1" (step S602 - YES), the signal processing unit 27 determines whether the value of Empty_Once is "0", the value of FlagX is "1", the value of Empty_and_Suspend is "1", and the value of Prev_Empty_and_Suspend is "0" (step S604). When the signal processing unit 27 determines that the value of Empty_Once is "0", the value of FlagX is "1", the value of Empty_and_Suspend is "1", and the value of Prev_Empty_and_Suspend is "0" (step S604 - YES), the signal processing unit 27 sets the value of Empty_Once to "1" (step S605). Prev_Empty_and_Suspend is for delaying the update so that Empty_Once reacts only once as a pulse during the time update.

[0060] Thereafter, the signal processing unit 27 updates the value of Prev_Empty_and_Suspend with the value of Empty_and_Suspend (step S606). Then, the processing of step S601 is executed. In the processing of step S604, if the signal processing unit 27 determines that the value of Empty_Once is "0", the value of FlagX is "1", the value of Empty_and_Suspend is "1", and the value of Prev_Empty_and_Suspend is not "0" (step S604-NO), the signal processing unit 27 updates the value of Prev_Empty_and_Suspend with the value of Empty_and_Suspend (step S606). For example, the signal processing unit 27 overwrites the value of Prev_Empty_and_Suspend with the value of Empty_and_Suspend. Then, the processing of step S601 is executed. Using the signal created in this way, FIFO_RESETn is generated as shown in Equation 1.

[0061] FIFO_RESETn ← (NOT Empty_and_Suspend) OR (NOT Empty_Once)…Formula 1

[0062] In equation 1, when the value of Empty_and_Suspend is "1" and the value of Empty_Once is "1", the state becomes FIFO_RESETn0 and a release signal is generated.

[0063] In the case of the flowchart shown in Fig. 5, it is assumed that an event group is detected and the next process, event extraction, starts at any time after transmission is completed. Therefore, a process for solving the problem shown in Fig. 5 will be described with reference to Fig. 11. Fig. 11 is a flowchart showing the flow (part 2) of the elastic wave detection process performed by the transmitting terminal 20 in the first embodiment. The process of Fig. 11 is executed when an elastic wave is detected by the sensor 10 and output to the transmitting terminal 20. The transmitting terminal 20 may execute the process of Fig. 11 instead of Fig. 5 every time an elastic wave is detected by the sensor 10.

[0064] The receiving unit 21 receives the electrical signal transmitted from the sensor 10 (step S701). The receiving unit 21 outputs the received electrical signal to the BPF 22. The BPF 22, the analog-to-digital conversion unit 23, and the filter 24 perform preprocessing on the electrical signal output from the receiving unit 21 (step S702). The filter 24 outputs the preprocessed electrical signal to the signal processing unit 27. The signal processing unit 27 detects the occurrence of an event based on the preprocessed electrical signal output from the filter 24 (step S703). The signal processing unit 27 extracts feature quantities using the preprocessed electrical signal output from the filter 24 (step S704). Further, the signal processing unit 27 determines the event detection time t event based on the preprocessed electrical signal output from the filter 24 and the time information output from the time information generation unit 26 (step S705).

[0065] Thereafter, the signal processing unit 27 determines whether the storage condition is satisfied (step S706). The storage condition is a condition for storing the extracted feature quantities and the like as transmission data in the transmission buffer memory, and is that FlagX = 0 is satisfied. When the signal processing unit 27 determines that the storage condition is not satisfied (step S706-NO), the signal processing unit 27 does not store the preprocessed electrical signal output from the filter 24 in the transmission buffer memory (step S707). That is, the signal processing unit 27 discards the preprocessed electrical signal output from the filter 24 as not being a transmission target. On the other hand, when the signal processing unit 27 determines that the storage condition is satisfied (step S706-YES), the signal processing unit 27 associates the parameters related to the extracted feature quantities, the determined event detection time t event and the sensor ID, and temporarily stores them in the transmission buffer memory as transmission data (step S708).

[0066] Fig. 12 is a flowchart showing the flow of processing for recognizing a group of events that occurred while the transmitting terminal 20 was stopped in the first embodiment. The processing in Fig. 12 is executed when an elastic wave is detected by the sensor 10 and output to the transmitting terminal 20. The transmitting terminal 20 executes the processing in Fig. 12 every time an elastic wave is detected by the sensor 10.

[0067] When the clock is input, the signal processing unit 27 updates the current time (step S801). nоw For example, the signal processing unit 27 acquires the information of the current time t at the timing when the clock is input. nоw The signal processing unit 27 acquires the last event detection time t event and the current time t nоw The signal processing unit 27 calculates the time difference dt between the time t and the time t (step S803). The signal processing unit 27 determines whether the calculated time difference dt exceeds a threshold value U (step S804). The threshold value U is one aspect of the eighth threshold value.

[0068] If the signal processing unit 27 determines that the calculated time difference dt does not exceed the threshold value U (step S804-NO), the signal processing unit 27 sets the value of FlagU to "0" (step S805). FlagU is a flag used to generate a release signal. Thereafter, the signal processing unit 27 repeatedly executes the processes from step S801 onwards. If the signal processing unit 27 determines that the calculated time difference dt exceeds the threshold value U (step S804-YES), the signal processing unit 27 sets the value of FlagU to "1" (step S806). Thereafter, the process of step S801 is executed. The FlagU created in this way is added to generate FIFO_RESETn as shown in equation 2. As a result, when FlagU=1, FIFO_RESETn becomes 0 depending on other conditions, and a release signal is generated.

[0069] FIFO_RESETn ← (NOT Empty_and_Suspend) OR (NOT Empty_Once) OR (NOT FlagU) … Equation 2

[0070] In Equation 2, when the value of Empty_and_Suspend is “1”, the value of Empty_Once is “1”, and the value of FlagU is “1”, FIFO_RESETn becomes 0 and a release signal is generated.

[0071] According to the measurement system 100 configured as described above, the transmission terminal 20 includes a receiving unit 21 that receives the elastic wave output from the sensor 10 that detects the elastic wave generated inside the structure, a communication unit 28 that wirelessly transmits the transmission data stored in the transmission buffer memory that stores the transmission data based on the received elastic wave, and a signal processing unit 27 that controls the elastic wave measurement process based on the number of data stored in the transmission buffer memory and the elapsed time from the time when the elastic wave was last detected. Thereby, it is possible to control the AE measurement in consideration of the number of data stored in the transmission buffer memory and the elapsed time from the time when the elastic wave was last detected. The elapsed time from the time when the elastic wave was last detected is the elapsed time from the time when the elastic wave generated by the passage of one vehicle was last detected. Therefore, the AE measurement is controlled based on how much of the transmission data based on the elastic wave generated by the passage of one vehicle remains in the transmission buffer memory. Therefore, it is possible to prevent a situation where the transmission buffer memory overflows and transmission data cannot be sent. Therefore, it is possible to improve the transmission efficiency of the data required for the evaluation of the structure.

[0072] The transmitting terminal 20 controls either the elastic wave measurement, the transmission by the communication unit 28, or the storage of the transmission data in the transmission buffer memory. As a result, control such as stopping the transmission of the transmission data or the storage of the transmission data in the transmission buffer memory while performing the elastic wave measurement becomes possible. Therefore, control such as wanting to perform the elastic wave measurement but stopping the transmission of the transmission data also becomes possible. Thus, convenience can be improved.

[0073] The transmitting terminal 20 is the elapsed time, which is the time difference dt between the event detection time t event of the last occurrence and the current time t nоw When the elapsed time exceeds the threshold value X and the number of data stored in the transmission buffer memory is equal to or greater than the threshold value Y, the elastic wave measurement or the storage of the transmission data in the transmission buffer memory is stopped, and the communication unit 28 is made to perform the transmission. As a result, while suppressing an increase in the storage capacity of the transmission buffer memory in response to the elastic wave generated by the passage of a new vehicle, the transmission of the transmission data can be performed. Therefore, it becomes possible to improve the transmission efficiency of the data required for the evaluation of the structure.

[0074] The transmitting terminal 20 is the elapsed time, which is the time difference dt between the event detection time t event of the last occurrence and the current time t nоw When the elapsed time exceeds the threshold value Z and the number of data stored in the transmission buffer memory is less than the threshold value W, the stop of the elastic wave measurement or the storage of the transmission data in the transmission buffer memory is released. As a result, the measurement of the elastic wave generated by the passage of a new vehicle can be started.

[0075] (Modification Example 1) Depending on the number of memories in the transmission buffer memory, it may be more efficient to manage multiple vehicles without separating them one by one. Therefore, the transmission terminal 20 may be configured to set the number of measured vehicles N (threshold value N) and stop the measurement when the vehicle count number n becomes equal to or greater than the threshold value (N ≦ n). The processing in this case will be described with reference to FIGS. 13 and 14. FIGS. 13 and 14 are diagrams for explaining the outline of the control method for AE measurement in the first modification of the first embodiment. The signal processing unit 27 acquires information on the current time t nоw and calculates the time difference dt between the event detection time t event at which the last event occurred and the current time t nоw . As shown in FIG. 13, when the time difference dt exceeds the threshold value M, the signal processing unit 27 sets the vehicle count number n = n + 1. Note that when the time difference dt continues to exceed the threshold value M, the signal processing unit 27 regards it as the same vehicle and sets the vehicle count number n = n. Further, as shown in FIG. 14, when the number of elastic waves (AE number) in one vehicle is less than the threshold value L, the signal processing unit 27 does not count the number of vehicles. That is, when the number of elastic waves generated during the period in which the time difference dt exceeds the threshold value M is less than the threshold value L, the signal processing unit 27 does not count it as one vehicle. This is for eliminating noise and the like. The transmission terminal 20 sets the vehicle count number n to 0 every time a release signal is received. The threshold value M is one aspect of the fifth threshold value. The threshold value L is one aspect of the sixth threshold value.

[0076] (Modification 2) Instead of the threshold value N shown in Modification Example 1, it may be divided by a group of vehicles (successive vehicles). Depending on the number of memories in the transmission buffer memory, there may be cases where it is more efficient to manage multiple vehicles without separating them one by one. Therefore, as described above, the threshold value X is a threshold value compared with the time difference for recognizing one vehicle, but it is also possible to specify a threshold value X' > the threshold value X so that when the vehicles are close to each other or when they are recognized as a group of vehicles to improve efficiency. In that case, the threshold value X' is determined by the vehicle speed and the maximum allowable inter-vehicle distance (to be divided). The signal processing unit 27 measures until the time difference dt exceeds the threshold value X'. That is, the signal processing unit 27 measures the elastic waves generated by the passage of a plurality of vehicles until the time difference dt exceeds the threshold value X'. The threshold value X' is one aspect of the seventh threshold value.

[0077] (Second Embodiment) In the first embodiment, the case where the number of transmission terminals is one was described as an example. By the control shown in the first embodiment, it is possible to efficiently measure the elastic wave group by the vehicle V, but in the evaluation of soundness, it is necessary to measure the same vehicle V with a plurality of transmission terminals. Therefore, in the second embodiment, a method for controlling AE measurement when a plurality of transmission terminals are provided will be described.

[0078] FIG. 15 is a diagram showing the system configuration of the measurement system 100a in the second embodiment. The measurement system 100a includes K (K is an integer of 2 or more) sensors 10, K transmission terminals 20, and a collection device 30. The K sensors 10 and the K transmission terminals 20 are connected by wire. For example, between the sensor 10-1 and the transmission terminal 20-1, and between the sensor 10-K and the transmission terminal 20-K are connected by wire. The K transmission terminals 20 and the collection device 30 are wirelessly connected via the network NW. The wireless connection between the K transmission terminals 20 and the collection device 30 does not need to be limited, and any communication method may be used as long as wireless communication is possible.

[0079] The configuration of each transmitting terminal 20 is the same as the configuration described in the first embodiment. In the transmitting terminal 20 in the second embodiment, part of the processing performed by the signal processing unit 27 is different from that in the first embodiment. Also, part of the processing performed by the collection device 30 in the second embodiment is different from the collection device 30 in the first embodiment. Hereinafter, the description will focus on the differences from the first embodiment.

[0080] With reference to FIGS. 16 and 17, an overview of the control method for AE measurement in the second embodiment will be described. FIGS. 16 and 17 are diagrams for explaining the overview of the control method for AE measurement in the second embodiment. In FIG. 16, a plurality of sensors 10 are installed in a structure, and transmitting terminals 20-1 and 20-2 connected to each sensor 10 are shown in a state of performing AE measurement. The transmitting terminals 20-1 and 20-2 detect elastic waves generated by the passage of vehicles V1, V2, V3, and V4 respectively. However, since the elastic waves generated vary depending on the arrangement position of the sensors 10 on the structure, they are different for each transmitting terminal 20. Therefore, differences may occur in the event detection time, the number of hits, etc. for each transmitting terminal 20.

[0081] As shown in FIG. 16, assume that after the measurement of the first elastic wave group is performed in the transmitting terminals 20-1 and 20-2, the measurement of the second elastic wave group is performed. Here, assume that in the transmitting terminal 20-1, it takes a long time to transmit the large amount of the second elastic wave group measured, and in the transmitting terminal 20-2, the small amount of the second elastic wave group measured is transmitted quickly and the transmission is completed. In this case, the transmitting terminal 20-1 will not perform the measurement of the third elastic wave group, and the transmitting terminal 20-2 will perform the measurement of the third elastic wave group. In such a case, the measurements of the transmitting terminal 20-1 and the transmitting terminal 20-2 may deviate.

[0082] Therefore, as shown in FIG. 17, when the transmission buffers of the transmission terminals 20-1 and 20-2 become empty, the transmission terminals 20-1 and 20-2 generate a memory empty signal indicating that the transmission buffer is empty, and transmit the generated memory empty signal to the collection device 30. When the collection device 30 can receive the memory empty signals from all the necessary transmission terminals 20, the collection device 30 transmits a synchronization signal to each transmission terminal 20. Here, the necessary transmission terminals 20 represent the transmission terminals 20 for which it is desired to synchronize the measurement start timing, and it is not necessary for all the transmission terminals 20 included in the measurement system 100a. The collection device 30 may determine the necessary transmission terminals 20 based on the identification information of a plurality of transmission terminals 20 preset by a user or the like. Each transmission terminal 20 resumes AE measurement based on the synchronization signal transmitted from the collection device 30. For example, each transmission terminal 20 resumes AE measurement at the timing when it receives the synchronization signal transmitted from the collection device 30, or based on the time indicated by the time information included in the synchronization signal. By such control, it is possible to synchronize the vehicles to be measured among the transmission terminals 20, and efficient measurement can be performed. The timing for the transmission terminals 20-1 and 20-2 to transmit the memory empty signal may be not only when the transmission buffer becomes empty, but also when the number of memories falls below a predetermined number.

[0083] The transmission terminals 20-1 and 20-2 not only notify the collection device 30 at the timing when the memory empty signal is generated, but also attach a memory count to the memory empty signal and detect the necessary transmission terminals 20 at the time of transmitting the synchronization signal by the determination of the collection device 30. Also, depending on the number and arrangement of the sensor terminals, it is also conceivable to collect and manage the position information of each sensor terminal and optimize the transmission timing of the synchronization signal.

[0084] As described above, the collection device 30 in the second embodiment includes a signal generation unit that generates a synchronization signal based on the memory empty signals received from each transmission terminal 20, and a communication unit that performs wireless communication with each transmission terminal 20.

[0085] FIG. 18 is a flowchart showing the flow of processing related to FlagX included in the signal processing unit 27 in the second embodiment. The processing in FIG. 18 is executed every time a clock is input by an FPGA or the like constituting the transmission terminal 20. In FIG. 18, the same processing as in FIG. 10 is denoted by the same reference numerals as in FIG. 10, and the description thereof is omitted.

[0086] In the process of step S604, when the signal processing unit 27 determines that the value of Empty_Once is "0", the value of FlagX is "1", the value of Empty_and_Suspend is "1", and the value of Prev_Empty_and_Suspend is "0" (step S604 - YES), the signal processing unit 27 sets the value of Empty_Once to "1" and sets the value of Empty_Trig to "1" (step S901). The transmission terminal 20 transmits a memory empty signal to the collection device 30 at the timing when the value of Empty_Trig becomes "1". Thereafter, the signal processing unit 27 updates the value of Prev_Empty_and_Suspend with the value of Empty_and_Suspend (step S606). Thereafter, the process of step S601 is executed.

[0087] In the process of step S604, when the signal processing unit 27 determines that the value of Empty_Once is "0", the value of FlagX is "1", the value of Empty_and_Suspend is "1", and the value of Prev_Empty_and_Suspend is not "0" (step S604 - NO), the signal processing unit 27 sets the value of Empty_Trig to "0" (step S902). Thereafter, the signal processing unit 27 updates the value of Prev_Empty_and_Suspend with the value of Empty_and_Suspend (step S606). Thereafter, the process of step S601 is executed.

[0088] The collection device 30 receives the memory empty signal from each transmitting terminal 20, and generates a synchronization signal when it can receive the memory empty signals from all the necessary transmitting terminals 20. The collection device 30 transmits the generated synchronization signal to each transmitting terminal 20. When the transmitting terminal 20 receives the synchronization signal from the collection device 30, it generates a signal of Wireless_Flagn = 0 only once, and generates a release signal in a state where all the flags become 0. That is, by adding the Wireless_Flagn signal, FIFO_RESETn is generated as in Equation 3. As a result, FIFO_RESETn becomes 0 and a release signal is generated.

[0089] FIFO_RESETn ← (NOT Empty_and_Suspend) OR (NOT Empty_Once) OR (NOT FlagU) OR Wireless_Flagn … Equation 3

[0090] In Equation 3, when the value of Empty_and_Suspend is "1", the value of Empty_Once is "1", the value of FlagU is "1", and the value of Wireless_Flagn is "0", FIFO_RESETn becomes 0 and a release signal is generated.

[0091] In the second embodiment, depending on the installation position of the sensor 10 and the settings for event extraction, the number of event detections and timings differ for each transmitting terminal 20. Therefore, in a certain transmitting terminal 20, when only a small number of events occur, it is conceivable that the memory empty signal is not generated. Therefore, any one of the following processes (Countermeasure 1) to (Countermeasure 3) may be performed.

[0092] (Countermeasure 1) When the collection device 30 has not received radio signals for a certain period of time (threshold value A) after the previous release, even if there is no memory empty signal, it virtually generates a memory empty signal. That is, when there is a transmitting terminal 20 that should have received a memory empty signal but has not received it for a certain period of time (threshold value A) based on the timing when the synchronization signal was transmitted, the collection device 30 processes it as if it has received a memory empty signal from the transmitting terminal 20 that should have received a memory empty signal but has not received it for a certain period of time (threshold value A). The transmitting terminal 20 that should have received a memory empty signal but has not received it refers to a transmitting terminal 20 that has not transmitted a memory empty signal from the transmitting terminal 20, or a transmitting terminal 20 that has transmitted a memory empty signal but has not been received by the collection device 30. The collection device 30 transmits a synchronization signal to one or more transmitting terminals 20 that are the transmission sources of the memory empty signal and to the transmitting terminals 20 from which the memory empty signal has not been obtained. This makes it possible to prevent the overall measurement from stopping due to a transmitting terminal 20 with low sensitivity.

[0093] In the case of this configuration, it is necessary to forcibly stop the AE measurement of the transmitting terminal 20 that should have received a memory empty signal but has not received it. Therefore, the collection device 30 generates a forced stop signal to stop the operation of the corresponding transmitting terminal 20, and transmits the generated forced stop signal to the corresponding transmitting terminal 20. The forced stop signal is a signal for stopping operations such as AE measurement being performed by the transmitting terminal 20. When the transmitting terminal 20 receives the forced stop signal, it generates a stop signal.

[0094] FIG. 19 is a flowchart showing the flow of processing related to FlagX included in the signal processing unit 27 in the second embodiment. The processing in FIG. 19 is executed every time a clock is input to an FPGA or the like constituting the transmitting terminal 20. In FIG. 19, the same processing as in FIG. 7 is denoted by the same reference numerals as in FIG. 7, and the description thereof is omitted.

[0095] After the process of step S304, the signal processing unit 27 determines whether it has received a forced stop signal (step S1001). If the signal processing unit 27 determines that it has received a forced stop signal (step S1001 - YES), the signal processing unit 27 executes the process of step S307. That is, when the signal processing unit 27 receives a forced stop signal via the communication unit 28, it sets the value of FlagX to "1" (step S307). Thereby, the signal processing unit 27 generates a stop signal and transitions to a stopped state based on the generated stop signal. Thereafter, the process of step S301 is executed.

[0096] On the other hand, if the signal processing unit 27 determines that it has not received a forced stop signal (step S1001 - NO), the signal processing unit 27 executes the processes after step S305.

[0097] FIG. 20 is a flowchart showing the flow of processing related to FlagY included in the signal processing unit 27 in the second embodiment. The processing in FIG. 20 is executed each time a clock is input to an FPGA or the like constituting the transmission terminal 20. In FIG. 20, the same processes as those in FIG. 8 are denoted by the same reference numerals as in FIG. 8, and the description thereof is omitted.

[0098] In the process of step S402, if the signal processing unit 27 determines that the value of FIFO_RESETn is "1" (step S402 - YES), the signal processing unit 27 determines whether it has received a forced stop signal (step S1101). If the signal processing unit 27 determines that it has received a forced stop signal (step S1101 - YES), the signal processing unit 27 executes the process of step S406. That is, when the signal processing unit 27 receives a forced stop signal via the communication unit 28, it sets the value of FlagY to "1" (step S406).

[0099] On the other hand, if the signal processing unit 27 determines that it has not received a forced stop signal (step S1101 - NO), the signal processing unit 27 executes the processes after step S404.

[0100] (Countermeasure 2) The transmitting terminal 20 notifies the collecting device 30 of the state information indicating the state of its own device (for example, the situation of the transmitting terminal 20, the measurement situation, the buffer amount, etc.) at the timing of starting or ending the measurement, after a certain period has elapsed since the start of the measurement, or after a certain period has elapsed since the end of the measurement. Further, the transmitting terminal 20 sets a certain threshold value and notifies the situation when the memory amount of the transmission buffer reaches (falls below) the set threshold value. The collecting device 30 generates a synchronization signal or the like based on the state information received from each transmitting terminal 20.

[0101] (Countermeasure 3) The collecting device 30 transmits an Ack request to the transmitting terminal 20 after a certain period has elapsed or as appropriate. The Ack request is a signal for requesting the transmitting terminal 20 to transmit state information. When the transmitting terminal 20 receives the Ack request, it transmits the state information to the collecting device 30. The collecting device 30 generates a synchronization signal or the like based on the state information that is a response to the Ack request received from each transmitting terminal 20.

[0102] According to the second embodiment configured as described above, when the number of data stored in the transmission buffer memory of the plurality of transmitting terminals 20 is less than the threshold value W, the transmitting terminals 20 transmit a memory empty signal to the collecting device 30, start measuring the elastic wave after receiving the synchronization signal transmitted from the collecting device 30, and the collecting device 30 generates a synchronization signal when a memory empty signal is obtained from a predetermined number of the plurality of transmitting terminals 20, and transmits the generated synchronization signal to the predetermined number of transmitting terminals 20. Thereby, it is possible to synchronize the measurement start timing among the plurality of transmitting terminals 20 that need to measure the elastic wave generated in the same vehicle.

[0103] (Modification 1) In the above-described embodiment, if the timing at which the transmission terminal 20 changes from the stopped state to the released state due to the release signal is the timing at which the vehicle is passing by, there is a possibility that AE measurement may be started halfway. Therefore, the timing at which the process is started in the transmission terminal 20 may be delayed. In this case, the timing at which wireless communication can be performed may be different from the timing at which measurement is desired to be started. Therefore, the collection device 30 may attach time information to the synchronization signal, and after receiving the synchronization signal, the transmission terminal 20 may perform processing assuming that the processing conditions are satisfied after the passage of time.

[0104] (Modification Example 2) In the above-described embodiment, if the timing at which the transmission terminal 20 changes from the stopped state to the released state due to the release signal is the timing at which the vehicle is passing by, the measurement (storage) timing may be shifted depending on the transmission terminal 20. Therefore, if an elastic wave group is being generated at the timing when the transmission terminal 20 receives the release signal, the transmission terminal 20 may start measurement from the next vehicle group. The transmission terminal 20 acquires information on the current time t nоw and continuously calculates the time difference dt between the acquired current time t nоw and the event detection time t event at which the last event occurred. The transmission terminal 20 starts measurement when the time difference dt exceeds the threshold U at the timing of receiving the synchronization signal, or when the time difference dt exceeds the threshold U after receiving the synchronization signal.

[0105] (Modification Example 3) The collection device 30 designates the process of Modification Example 1 in the first embodiment. The collection device 30 transmits the release signal including the number N of vehicles to be measured. The transmission terminal 20 generates a stop signal after the number M of vehicles to be measured.

[0106] (Modification Example 4) Depending on the traffic conditions, the number of AE occurrences, or the noise situation, it may be more efficient to adapt the threshold to the environment or the like. For example, the threshold X may be determined by the transmitting terminal 20 based on the inter-vehicle distance and the vehicle speed, or the collecting device 30 may transmit the threshold to the transmitting terminal 20, and the transmitting terminal 20 may correct the threshold X based on the received threshold. Note that the threshold is not limited to the threshold X, and all the thresholds described in the above-described embodiments are applicable. That is, it is possible to correct all the thresholds described in the above-described embodiments.

[0107] (Modification Example 5) (Countermeasure 1) and (Countermeasure 2) may be executed in combination. When a certain sensor 10 has recognized a vehicle and finished measurement, other sensors 10 should also finish at approximately the same time. Therefore, when the time TT has passed since the timing when the collecting device 30 has received the memory empty signal from a certain transmitting terminal 20, the collecting device 30 transmits a forced stop signal to other transmitting terminals 20. The time TT is, for example, a number defined by the maximum sensor distance and the vehicle speed passing through.

[0108] (Modification Example 6) Among the plurality of transmission terminals 20, at least one transmission terminal 20 executes the processing in the first embodiment, and the other transmission terminals 20 may be synchronized with that timing. There is a possibility that the cancellation signal and the timing of vehicle passage may overlap, or that the stop signal may not work properly depending on the sensor positions and sensitivities of the sensors of the plurality of terminals. Therefore, the timing of measurement (storage) is determined by one or more transmission terminals 20, and measurement (storage) is performed at the same timing by sharing the measurement timing with the other transmission terminals 20. The collection device 30 transmits a synchronization signal to the plurality of transmission terminals 20, and the plurality of transmission terminals 20 generate a cancellation signal and start measurement (storage). When a stop signal is generated by a certain transmission terminal 20-1, the collection device 30 is notified that the stop signal has been generated. The collection device 30 transmits a forced stop signal to the other transmission terminals 20 so as to match the measurement (storage) stop of the transmission terminal 20-1. Thereby, when the elastic wave is extremely small or large, or when it is desired to synchronize between the plurality of transmission terminals 20 in the measurement of different structures, the measurement timing at the transmission terminal 20-1 can be matched. Instead of generating a forced signal only at the transmission terminal 20-1, a combination of a plurality of transmission terminals 20 may be used. Also, for example, when determining the timing at the upstream transmission terminal 20, the stop start time considering the sensor distance may be used from the cancellation signal until the actual stop.

[0109] (Modification 7) When a cancellation signal is generated during vehicle passage in the transmission terminal 20, there is a possibility that the measurement timing may deviate from that of the other transmission terminals 20. Therefore, after transmitting the transmission data stored in the transmission buffer memory of the transmission terminal 20, it is canceled at a timing when the vehicle has not passed. One or more transmission terminals 20 shift to the stopped state by the stop signal, and then obtain the information of the current time t nоw and continuously calculate the time difference dt between the obtained current time t nоw and the last event detection time t event at which an event occurred. When the time difference dt exceeds the threshold U, the transmission terminal 20 notifies the collection device 30 that the vehicle has passed after the measurement stop. After receiving the notifications from the plurality of transmission terminals 20, the collection device 30 immediately transmits a synchronization signal.

[0110] (Third Embodiment) In the third embodiment, in order to cope with single-shot noise or the like, for example, a vehicle detection sensor is installed in a structure, and a configuration will be described in which measurement starts at a transmission terminal upon a vehicle detection signal from the vehicle detection sensor.

[0111] FIG. 21 is a diagram showing the system configuration of the measurement system 100b in the third embodiment. The measurement system 100b includes K sensors 10, one or more vehicle detection sensors 15, K transmission terminals 20, and a collection device 30. The K sensors 10 and the K transmission terminals 20 are connected by wire. For example, between the sensor 10-1 and the transmission terminal 20-1, between the sensor 10-K and the transmission terminal 20-K, between the vehicle detection sensor 15 and the transmission terminal 20-1, and between the vehicle detection sensor 15 and the transmission terminal 20-K are connected by wire. The K transmission terminals 20 and the collection device 30 are wirelessly connected via a network NW.

[0112] The vehicle detection sensor 15 is a device capable of detecting a vehicle such as a camera, a magnetic sensor, an acceleration sensor, or a strain sensor. When the vehicle detection sensor 15 detects a vehicle, it transmits a notification indicating that the vehicle has been detected to the collection device 30. The vehicle detection sensor 15 detects, for example, that the vehicle V has passed upstream of the sensor 10 as shown in FIG. 21.

[0113] The collection device 30 transmits a synchronization signal in consideration of the state of the transmission buffer memory of each transmission terminal 20 in response to a notification from the vehicle detection sensor 15.

[0114] In the configuration of the measurement system 100b shown in FIG. 21, the vehicle detection sensor 15 is configured to directly transmit a notification indicating that the vehicle has been detected to the collection device 30. However, the measurement system 100b may have the configuration shown in FIG. 22. FIG. 22 is a diagram showing another system configuration of the measurement system 100b in the third embodiment. The measurement system 100b shown in FIG. 22 further includes a detection information transmission terminal 40. The detection information transmission terminal 40 receives a notification indicating that the vehicle has been detected transmitted from the vehicle detection sensor 15. The detection information transmission terminal 40 is a terminal that transmits the received notification to the collection device 30. Note that the detection information transmission terminal 40 may transmit the received notification as it is (for example, without processing the raw data output from the vehicle detection sensor 15) to the collection device 30 via the network NW, or may process the received notification as vehicle detection information obtained from the vehicle detection sensor 15 and then transmit it to the collection device 30 via the network NW. When processing as vehicle detection information, the detection information transmission terminal 40 will transmit filter processing and analysis results to the collection device 30 for the raw data output from the vehicle detection sensor 15. When raw data is transmitted from the detection information transmission terminal 40, the collection device 30 will analyze the raw data to detect the vehicle.

[0115] FIG. 23 is a diagram for explaining the outline of the control method regarding AE measurement in the third embodiment. As shown in FIG. 23, each time the vehicles V1, V2, and V3 pass by, the vehicle detection sensor 15 detects the vehicle and notifies the collection device 30 of the vehicle detection information. However, at the timing when the vehicles V1, V2, and V3 are detected, the collection device 30 has not received the memory empty signal from each transmission terminal 20. Therefore, the collection device 30 does not generate a synchronization signal.

[0116] On the other hand, at the timing when the vehicle V4 is detected, the collection device 30 has received the memory empty signal from each transmission terminal 20. Therefore, the collection device 30 generates a synchronization signal and transmits it to each transmission terminal 20. Thereafter, each transmission terminal 20 resumes measurement based on the synchronization signal.

[0117] According to the third embodiment configured as described above, by measuring only the signals through which the vehicle is surely passing, it is possible to reduce noise in the soundness evaluation. Further, after the wireless transmission, the terminal can shift to the standby state (including analog and edge processing), and it is also possible to reduce the power consumption.

[0118] (Modification example) In the above-described embodiment, the measurement system 100b is shown to include one vehicle detection sensor 15, but the measurement system 100b may include a plurality of vehicle detection sensors 15. For example, when the measurement system 100b includes two vehicle detection sensors 15, one vehicle detection sensor 15 may be installed upstream of the sensor 10, and the other vehicle detection sensor 15 may be installed downstream of the sensor 10. Here, the vehicle detection sensor 15 installed upstream is referred to as the upstream vehicle detection sensor, and the vehicle detection sensor 15 installed downstream is referred to as the downstream vehicle detection sensor.

[0119] Thereby, when the vehicle is detected by the upstream vehicle detection sensor, the collection device 30 notifies the plurality of transmission terminals 20 of the start of measurement, and in response to the detection of the vehicle by the downstream vehicle detection sensor, the plurality of transmission terminals 20 start wireless transmission, so that the efficiency of the wireless band can be improved. In this case, after the vehicle is detected by the upstream vehicle detection sensor, even if the time determined by the vehicle speed and the distance between the vehicle detection sensors (the distance between the upstream vehicle detection sensor and the downstream vehicle detection sensor) has elapsed and the vehicle is not detected by the downstream vehicle detection sensor, the collection device 30 may request the plurality of transmission terminals 20 to clear the transmission buffer memory in preparation for the next measurement.

[0120] (Modification example 1 common to the first to third embodiments) In each of the above-described embodiments, the signal processing unit 27 is shown to include a transmission buffer memory, but the transmission buffer memory may be provided in the communication unit 28. When configured in this way, the signal processing unit 27 may perform processing by referring to the transmission buffer memory provided in the communication unit 28.

[0121] According to at least one embodiment described above, the transmission terminal 20 includes a receiving unit 21 that receives an elastic wave output from a sensor 10 that detects an elastic wave generated inside a structure, and a communication unit 28 that wirelessly transmits transmission data stored in a transmission buffer memory that stores the transmission data based on the received elastic wave. By including a signal processing unit 27 that controls elastic wave measurement processing based on the number of data stored in the transmission buffer memory and the elapsed time from the time when the elastic wave was last detected, the transmission efficiency of the data required for evaluating the structure can be improved.

[0122] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0123] 10, 10-1 to 10-K... sensors, 15... vehicle detection sensor, 20, 20-1 to 20-K... transmission terminals, 30... collection device, 21... receiving unit, 22... BPF, 23... analog-to-digital conversion unit, 24... filter, 25... clock oscillator, 26... time information generation unit, 27... signal processing unit, 28... communication unit, 100, 100a, 100b... measurement systems

Claims

1. A receiving unit that receives the elastic wave output from a sensor that detects an elastic wave generated inside a structure, A communication unit that wirelessly transmits the transmission data stored in a transmission buffer memory that stores the transmission data based on the received elastic wave, A signal processing unit that controls elastic wave measurement processing based on the number of data stored in the transmission buffer memory and the elapsed time from the time when the elastic wave was detected, A transmitting terminal comprising the same.

2. The signal processing unit As the elastic wave measurement processing, controls any one of elastic wave measurement, transmission by the communication unit, or storage of transmission data in the transmission buffer memory, The transmitting terminal according to Claim 1.

3. The signal processing unit When the elapsed time exceeds a first threshold value and the number of data stored in the transmission buffer memory is equal to or greater than a second threshold value, stops elastic wave measurement or storage of transmission data in the transmission buffer memory, and causes the communication unit to perform transmission, The transmitting terminal according to Claim 2.

4. The signal processing unit When the elapsed time exceeds a third threshold value and the number of data stored in the transmission buffer memory is less than a fourth threshold value, cancels the stop of elastic wave measurement or storage of transmission data in the transmission buffer memory, The transmitting terminal according to Claim 3.

5. The signal processing unit Counts the number of vehicles based on the received elastic wave, and controls the elastic wave measurement processing when the counted number of vehicles reaches a predetermined number of vehicles, The transmitting terminal according to any one of Claims 1 to 4.

6. The signal processing unit Resets the count of the number of vehicles after controlling the elastic wave measurement processing, counts the number of vehicles at the timing when the elapsed time exceeds a fifth threshold value, and does not count the number of vehicles while the elapsed time exceeds the fifth threshold value, The transmitting terminal according to Claim 5.

7. The signal processing unit Does not count the number of vehicles when the elastic wave generated during the period in which the elapsed time exceeds the fifth threshold value is less than a sixth threshold value, The transmitting terminal according to Claim 6.

8. The signal processing unit Measures a plurality of vehicles using a seventh threshold value determined by a vehicle speed greater than the first threshold value and a specified maximum inter-vehicle distance, The transmitting terminal according to any one of Claims 1 to 4.

9. A measurement system comprising a plurality of transmitting terminals according to claim 1 and a collecting device that collects transmission data transmitted from the plurality of transmitting terminals, wherein the plurality of transmitting terminals, when the number of data stored in the transmission buffer memory is less than a fourth threshold value, transmit a memory signal indicating that the capacity of the transmission buffer memory is vacant to the collecting device, start measuring elastic waves after receiving a synchronization signal transmitted from the collecting device, wherein the collecting device, when the memory signal is obtained from a predetermined number of transmitting terminals among the plurality of transmitting terminals, generates the synchronization signal and transmits the generated synchronization signal to the predetermined number of transmitting terminals. A measurement system.

10. further comprising one or more vehicle detection sensors for detecting the passage of a vehicle, wherein the collecting device, when the memory signal is obtained from the predetermined number of transmitting terminals at the timing when a vehicle is detected by the one or more vehicle detection sensors, generates the synchronization signal. The measurement system according to claim 9.

11. wherein the collecting device, if the memory signal is not obtained from some of the transmitting terminals during a predetermined period among the periods during which measurement is being performed in the plurality of transmitting terminals, one or more transmitting terminals that are the source of the memory signal and the synchronization signal is transmitted to the transmitting terminals that have not obtained the memory signal. The measurement system according to claim 9.

12. wherein the collecting device, transmits a forced stop signal for forcibly stopping the elastic wave measurement process to the transmitting terminals that have not obtained the memory signal, any one of the plurality of transmitting terminals, stops measuring elastic waves when the forced stop signal is received. The measurement system according to claim 10.

13. wherein the plurality of transmitting terminals, at a predetermined timing, transmit state information indicating the state of their own device to the collecting device, or transmit the state information to the collecting device in response to a request for transmission of the state information from the collecting device. wherein the collecting device, transmits the synchronization signal based on the state information transmitted from the plurality of transmitting terminals. The measurement system according to claim 9.

14. wherein the plurality of transmitting terminals, at the timing of receiving the synchronization signal, start measurement when the time difference between the current time and the time when the elastic wave was last detected exceeds an eighth threshold value, or when the time difference exceeds the eighth threshold value after receiving the synchronization signal. The measurement system according to claim 9.

15. Receiving the elastic wave output from a sensor that detects the elastic wave generated inside the structure, Wirelessly transmitting the transmission data stored in a transmission buffer memory that stores the transmission data based on the received elastic wave, Controlling elastic wave measurement processing based on the number of data stored in the transmission buffer memory and the elapsed time from the time when the elastic wave was detected. Control method.

Images