Structure evaluation system, signal processing device, structure evaluation method, and computer program

Abstract

To provide a structure evaluation system, a signal processing device, a structure evaluation method, and a computer program with which it is possible to suppress power consumption in an acoustic emission method.SOLUTION: A structure evaluation system according to an embodiment comprises one or more sensors, a signal processing device, and an evaluation unit. The plurality of sensors detect elastic waves generated from a structure. The signal processing device calculates information concerning a frequency distribution by amplitude scale on the basis of the plurality of elastic waves detected by the one or more sensors, respectively, and wirelessly transmits information concerning the calculated frequency distribution by amplitude scale. The evaluation unit evaluates a degradation state of the structure on the basis of information concerning the frequency distribution by amplitude scale transmitted from the signal processing device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a structure evaluation system, a signal processing device, a structure evaluation method, and a computer program. [Background technology]

[0002] In recent years, problems associated with the deterioration of bridges and other structures constructed during the period of rapid economic growth have become apparent. Because the damage caused by an accident to a structure would be immeasurable, various technologies for monitoring the condition of structures have been proposed. For example, one proposed technology for detecting structural damage is the acoustic emission (AE) method, which uses a highly sensitive sensor to detect elastic waves generated by the initiation or propagation of internal cracks. AE is an elastic wave generated by the propagation of cracks in materials. In the AE method, an AE sensor using a piezoelectric element detects the elastic waves as an AE signal (voltage signal). AE signals are detected as a sign of impending material failure. Therefore, the frequency and intensity of AE signals are useful indicators of material integrity. Therefore, research is being conducted on technologies for detecting signs of structural deterioration using the AE method.

[0003] One method for evaluating the integrity of structures based on AE detection is the b-value, derived from an empirical rule known in the field of seismology as the Gutenberg-Richter law. The b-value is an evaluation value obtained from the slope of the frequency distribution by amplitude scale, and is known to correlate with the state of cracks inside the material. The lifespan of structures such as bridges is generally said to be 50 years. Monitoring the integrity of structures over long periods, from several years to several decades, is essential for building a safe and secure society. In particular, it is desirable to detect signs of deterioration inside structures before large-scale damage occurs. Long-term monitoring of structures based on AE detection is considered promising for early detection of signs of deterioration.

[0004] However, conventional AE evaluation methods use relatively high frequency signals, which can result in high power consumption. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 59-175940 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a structure evaluation system, a signal processing device, a structure evaluation method, and a computer program that can reduce power consumption in the acoustic emission method. [Means for solving the problem]

[0007] A structure evaluation system according to an embodiment includes one or more sensors, a signal processing device, and an evaluation unit. The sensors detect elastic waves generated from a structure. The signal processing device calculates information about a frequency distribution by amplitude scale based on the elastic waves detected by each of the one or more sensors, and wirelessly transmits the calculated information about the frequency distribution by amplitude scale. The evaluation unit evaluates the deterioration state of the structure based on the information about the frequency distribution by amplitude scale transmitted from the signal processing device. The signal processing device has a plurality of modes, including an active mode that performs processing based on the frequency distribution by amplitude scale, including processing for calculating information about the frequency distribution by amplitude scale, and a sleep mode that reduces power consumption compared to the active mode by limiting functions. The signal processing device includes a peak hold circuit. The peak hold circuit holds the maximum amplitude value of the elastic wave detected by the one or more sensors at least during the sleep mode. After transitioning to the active mode, the signal processing device calculates information about the frequency distribution by amplitude scale using the maximum amplitude value of the elastic wave held in the peak hold circuit for a predetermined period. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a structure evaluation system according to a first embodiment. [Figure 2] FIG. 1 is a diagram showing an example of the configuration of a signal processing device according to a first embodiment. [Figure 3] FIG. 2 is a sequence diagram showing the flow of processing in the structure evaluation system according to the first embodiment. [Figure 4]FIG. 10 is a diagram showing an example of the configuration of a signal processing device according to a second embodiment. [Figure 5] 6 is a time chart for explaining the operation of the signal processing device according to the second embodiment. [Figure 6] FIG. 10 is a sequence diagram showing the flow of processing in the structure evaluation system according to the second embodiment. [Figure 7] FIG. 10 is a diagram showing an example of the configuration of a signal processing device according to a third embodiment. [Figure 8] 10 is a time chart for explaining the operation of the signal processing device according to the third embodiment. [Figure 9] FIG. 11 is a sequence diagram showing the flow of processing in the structure evaluation system according to the third embodiment. [Figure 10] FIG. 10 is a diagram showing an example of the configuration of a signal processing device according to a fourth embodiment. [Figure 11] FIG. 13 is a diagram showing the relationship between the number of hits for each measurement time in the fourth embodiment. [Figure 12] FIG. 10 is a diagram showing the configuration of a structure evaluation system according to a fifth embodiment. [Figure 13] FIG. 13 is a diagram showing an example of the configuration of a structure evaluation system according to a sixth embodiment. [Figure 14] FIG. 13 is a diagram showing an example of the configuration of a signal processing device according to a sixth embodiment. [Figure 15] FIG. 13 is a sequence diagram showing the flow of processing in the structure evaluation system according to the sixth embodiment. [Figure 16] FIG. 13 is a diagram showing an example of the configuration of a signal processing device according to a seventh embodiment. [Figure 17] FIG. 13 is a sequence diagram showing the flow of processing in the structure evaluation system according to the seventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a structure evaluation system, a signal processing device, a structure evaluation method, and a computer program according to embodiments will be described with reference to the drawings.

[0010] (First embodiment) FIG. 1 is a diagram illustrating an example of the configuration of a structure evaluation system 100 according to a first embodiment. The structure evaluation system 100 is used to evaluate the soundness of a structure 11. In the following description, evaluation refers to determining the degree of soundness of the structure 11, i.e., the state of deterioration of the structure 11, based on a certain standard. In the following description, a bridge made of concrete is used as an example of the structure 11, but the structure 11 is not limited to a bridge. The structure 11 may be any structure that generates elastic wave AE due to the occurrence or progression of a crack or an external impact (e.g., rain, artificial rain, etc.). For example, the structure 11 may range from a small metal structure such as a bearing to a large structure such as a rock mass. Note that bridges are not limited to structures built over rivers, valleys, etc., but also include various structures built above ground level (e.g., highway viaducts).

[0011] Damage that affects the evaluation of the deterioration state of the structure 11 includes, for example, damage inside the structure 11 that interferes with the propagation of elastic wave AE, such as cracks, cavities, and sedimentation. Here, cracks include vertical cracks, horizontal cracks, and diagonal cracks. A vertical crack is a crack that occurs in a direction perpendicular to the surface of the structure 11 on which the sensor is installed. A horizontal crack is a crack that occurs in a direction horizontal to the surface of the structure 11 on which the sensor is installed. A diagonal crack is a crack that occurs in a direction other than horizontal or vertical to the surface of the structure 11 on which the sensor is installed. Sedimentation is deterioration in which concrete turns into sediment, mainly at the boundary between the asphalt and the concrete deck. The specific configuration of the structure evaluation system 100 will be described below.

[0012] The structure evaluation system 100 includes a plurality of sensors 10-1 to 10-P (P is an integer equal to or greater than 2), a signal processing device 20, and a structure evaluation device 30. Each of the plurality of sensors 10-1 to 10-P is connected to the signal processing device 20 by wire. The signal processing device 20 and the structure evaluation device 30 are connected wirelessly. In the following description, when there is no need to distinguish between the sensors 10-1 to 10-P, they will be referred to as sensors 10.

[0013] Although FIG. 1 shows a configuration in which the structure evaluation system 100 includes a plurality of sensors 10, the structure evaluation system 100 may include one or more sensors 10. When the structure evaluation system 100 includes one sensor 10, the sensor 10 is connected to one signal processing device 20 via a wire. When the structure evaluation system 100 includes multiple sensors 10-1 to 10-P, the structure evaluation system 100 may include multiple signal processing devices 20-1 to 20-P. In this case, a configuration in which one sensor 10-p (1≦p≦P) and one signal processing device 20-p are connected via a wire is defined as one set, and the structure evaluation system 100 includes P sets of configurations in which one sensor 10-p and one signal processing device 20-p are connected via a wire. In the following explanation, an example will be described in which the structure evaluation system 100 includes one set of a combination of a sensor 10 and a signal processing device 20.

[0014] As shown in FIG. 1, when a vehicle 12 passes over a structure 11, a load is applied to the road surface due to contact between the tires of the vehicle 12 and the road surface. The load generates a large number of elastic wave AEs within the structure 11. One or more sensors 10 installed on the underside of the structure 11 can detect the elastic wave AEs generated within the structure 11. Note that although an example is shown here in which the elastic wave AEs are generated within the structure 11 by the vehicle 12, other methods for generating elastic wave AEs within the structure 11 may also be used. For example, the elastic wave AEs may be generated by applying an external impact to the structure 11 in a manner other than the running of the vehicle 12, or may be generated by an earthquake or the like.

[0015] The sensor 10 detects elastic wave AE generated from inside the structure 11. For example, the sensor 10 detects elastic wave AE generated when a vehicle 12 passes over the structure 11. The sensor 10 is installed at a position where it can detect elastic wave AE. For example, the sensor 10 is installed on a surface different from the surface on which a load is applied to the structure 11. If the surface on which the load is applied is the road surface of the structure 11, the sensor 10 is installed on either the side or bottom surface of the structure 11. The sensor 10 converts the detected elastic wave AE into an AE signal, which is an electrical signal. In the following explanation, an example will be given in which the sensor 10 is installed on the bottom surface of the structure 11. Here, if the structure evaluation system 100 includes multiple sensors 10-1 to 10-P, the sensors 10-1 to 10-P are arranged on the bottom surface of the structure 11 at different intervals in the vehicle traveling axis direction and in a direction perpendicular to the vehicle traveling axis. An area surrounded by one or more sensors 10-1 to 10-P is the area of ​​the structure 11 to be evaluated.

[0016] The sensor 10 uses a piezoelectric element having sensitivity in the range of, for example, 10 kHz to 1 MHz. A more suitable sensor 10 is a piezoelectric element having sensitivity in the range of 100 kHz to 200 kHz. The sensor 10 may be of a resonance type having a resonance peak within a frequency range or a broadband type with suppressed resonance, but any type of sensor 10 is acceptable. The sensor 10 may detect elastic wave AE using a voltage output type, a resistance change type, or a capacitance type, but any detection method is acceptable. The sensor 10 may have a built-in amplifier.

[0017] An acceleration sensor may be used instead of the sensor 10. In this case, the acceleration sensor detects elastic wave AE generated in the structure 11. The acceleration sensor converts the detected elastic wave AE into an AE signal by performing the same processing as the sensor 10.

[0018] The signal processing device 20 receives the AE signal output from the sensor 10 as input. The signal processing device 20 calculates information about the frequency distribution by amplitude scale based on the AE signal output from the sensor 10 for a predetermined period of time. The information about the frequency distribution by amplitude scale is, for example, the frequency distribution by amplitude scale, an a-value, or a b-value. The frequency distribution by amplitude scale is a distribution showing the frequency of the maximum amplitude obtained from each AE signal for a predetermined period of time. In the frequency distribution by amplitude scale, the horizontal axis represents the maximum amplitude and the vertical axis represents the frequency. The a-value represents the intercept obtained by linearly approximating the frequency distribution by amplitude scale. The b-value represents the slope obtained by linearly approximating the frequency distribution by amplitude scale.

[0019] The signal processing device 20 wirelessly transmits transmission data including information about the calculated frequency distribution by amplitude scale to the structure evaluation device 30. The signal processing device 20 may include one or more of the frequency distribution by amplitude scale, the a value, or the b value as information about the frequency distribution by amplitude scale. When the signal processing device 20 transmits the frequency distribution by amplitude scale as information about the frequency distribution by amplitude scale, it may transmit only the difference from the frequency distribution by amplitude scale transmitted previously. In the following explanation, an example will be described in which the b value is used as information about the frequency distribution by amplitude scale.

[0020] The signal processing device 20 is configured using an analog circuit or a digital circuit. The digital circuit is realized by, for example, an FPGA (Field Programmable Gate Array) or a microcomputer. By using a non-volatile FPGA, power consumption during standby can be reduced. The digital circuit may also be realized by a dedicated LSI (Large-Scale Integration). The signal processing device 20 may be equipped with a non-volatile memory such as a flash memory or a removable memory.

[0021] The structure evaluation device 30 evaluates the deterioration state of the structure 11 using information on the frequency distribution by amplitude scale transmitted from the signal processing device 20. The structure evaluation device 30 includes a communication unit 31, a control unit 32, a memory unit 33, and a display unit 34.

[0022] The communication unit 31 receives transmission data transmitted from the signal processing device 20. For example, the communication unit 31 may receive the transmission data by requesting the transmission data from the signal processing device 20 in response to an external instruction. The communication unit 31 outputs the received transmission data to the control unit 32.

[0023] The control unit 32 controls the entire structure evaluation device 30. The control unit 32 is configured using a processor such as a CPU (Central Processing Unit) and a memory. The control unit 32 functions as an acquisition unit 321 and an evaluation unit 322 by executing a program.

[0024] Some or all of the functional units of the acquisition unit 321 and the evaluation unit 322 may be realized by hardware (including circuitry) such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA, or may be realized by a combination of software and hardware. The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, and non-transitory storage media such as storage devices built into a computer system, such as a hard disk. The program may be transmitted via a telecommunications line.

[0025] Some of the functions of the acquisition unit 321 and the evaluation unit 322 do not need to be pre-installed in the structure evaluation device 30, and may be realized by installing an additional application program in the structure evaluation device 30.

[0026] The acquisition unit 321 acquires various types of information. For example, the acquisition unit 321 acquires information related to the amplitude scale frequency distribution included in the transmission data received by the communication unit 31. The acquisition unit 321 stores the acquired information related to the amplitude scale frequency distribution in the storage unit 33 and outputs it to the evaluation unit 322.

[0027] The evaluation unit 322 evaluates the deterioration state of the structure 11 based on information on the frequency distribution by amplitude scale. Specifically, when the information on the frequency distribution by amplitude scale is a b value, the evaluation unit 322 performs evaluation based on the b value. Evaluation based on the b value may be performed by the method described in the following reference 1. The following reference 1 describes that the larger the b value, the more sound the structure is evaluated to be. (Reference 1: IS Colombo, I. Main, and M. Forde, “Assessing damage of reinforced concrete beam using 'b-value' analysis of acoustic emission signals,” Journal of materials in civil engineering, vol. 15, no. 3, pp. 280-286, 2003.)

[0028] Therefore, the evaluation unit 322 evaluates that the state of the structure 11 is healthy when the b value is greater than a first threshold (e.g., 1.7). Healthy represents a state in which there is almost no damage within the structure 11 and it can be assumed that no deterioration has occurred. The evaluation unit 322 evaluates that the state of the structure 11 is normal when the b value is greater than a second threshold (e.g., 1.2) and less than the first threshold. Normal represents a state in which damage has occurred within the structure 11 but it can be assumed that no immediate action is required at this time. The evaluation unit 322 evaluates that the state of the structure 11 is deteriorated when the b value is less than the second threshold.

[0029] When the information on the amplitude scale frequency distribution is an amplitude scale frequency distribution, the evaluation unit 322 calculates a b value based on the amplitude scale frequency distribution, and then performs evaluation based on the calculated b value.

[0030] The storage unit 33 stores information relating to one or more amplitude frequency distributions acquired by the acquisition unit 321. The storage unit 33 is configured using a storage device such as a magnetic hard disk drive or a semiconductor storage device.

[0031] The display unit 34 displays information under the control of the control unit 32. For example, the display unit 34 displays the evaluation results of the evaluation unit 322. The display unit 34 is an image display device such as a liquid crystal display or an organic EL (Electro Luminescence) display. The display unit 34 may be an interface for connecting an image display device to the structure evaluation device 30. In this case, the display unit 34 generates a video signal for displaying the identification results and outputs the video signal to the image display device connected to the display unit 34.

[0032] 2 is a diagram showing an example of the configuration of the signal processing device 20 according to the first embodiment. The signal processing device 20 includes an AFE 210, an ADC 220, a maximum amplitude detection unit 230, an amplitude scale frequency distribution calculation unit 240, a slope calculation unit 250, and a wireless transmission unit 260.

[0033] The AFE 210 performs filtering on the AE signal output from the sensor 10. The AFE 210 outputs the filtered signal to the ADC 220. The AFE 210 is configured with a receiving unit 211 and a BPF 212.

[0034] The receiving unit 211 receives the AE signal output from the sensor 10. The receiving unit 211 outputs the received AE signal to the BPF 212.

[0035] The BPF 212 removes noise from the AE signal received by the receiving unit 211. For example, the BPF 212 is a band-pass filter that removes, as noise, frequency bands other than a specific frequency band from the AE signal. The BPF 212 outputs the analog signal after noise removal (hereinafter referred to as the "noise-removed analog signal") to the ADC 220.

[0036] The ADC 220 is an analog-to-digital converter that quantizes the noise-removed analog signal output from the BPF 212 and converts it into a digital signal.

[0037] The maximum amplitude detector 230 detects the maximum amplitude based on the digital signal converted by the ADC 220 .

[0038] The amplitude magnitude-specific frequency distribution calculation unit 240 collects information on maximum amplitudes detected by the maximum amplitude detection unit 230 for a predetermined period. The amplitude magnitude-specific frequency distribution calculation unit 240 calculates the amplitude magnitude-specific frequency distribution using the collected information on maximum amplitudes for the predetermined period. The predetermined period may be, for example, a predetermined number of hours, days, weeks, or months. Alternatively, it may be a period until a predetermined number of AE signals are detected (number of AE hits). The predetermined period or the predetermined number of AE hits may be recorded in advance in the signal processing device 20 as a fixed value, but more flexible evaluation can be achieved by configuring it to be variable by sending a command wirelessly from the structure evaluation device 30.

[0039] The gradient calculation unit 250 calculates the b value using the amplitude scale frequency distribution calculated by the amplitude scale frequency distribution calculation unit 240. The gradient calculation unit 250 may calculate the a value using the amplitude scale frequency distribution calculated by the amplitude scale frequency distribution calculation unit 240.

[0040] The wireless transmitting unit 260 generates transmission data including b values ​​of 1 or more calculated by the gradient calculating unit 250, and transmits the generated transmission data wirelessly to the structure evaluation device 30. The wireless transmitting unit 260 may generate transmission data each time a b value is obtained and transmit it wirelessly to the structure evaluation device 30, or may hold the b values ​​for a certain period of time and, after the certain period of time has passed, generate transmission data including the held b values ​​of 1 or more and transmit it wirelessly to the structure evaluation device 30, or may generate transmission data including the b values ​​when a predetermined number of b values ​​have been obtained and transmit it wirelessly to the structure evaluation device 30. The wireless transmitting unit 260 performs wireless communication using, for example, LPWN (Low Power Wide Area) technology.

[0041] When the signal processing device 20 transmits only the amplitude-scale frequency distribution as information regarding the amplitude-scale frequency distribution, the signal processing device 20 does not need to include the slope calculation unit 250. The signal processing device 20 may be configured to be able to select whether to transmit the amplitude-scale frequency distribution, the a value, or the b value as information regarding the amplitude-scale frequency distribution. When configured in this manner, the amplitude-scale frequency distribution calculation unit 240 is connected to both the slope calculation unit 250 and the wireless transmission unit 260. When the signal processing device 20 transmits the a value or the b value as information regarding the amplitude-scale frequency distribution, the amplitude-scale frequency distribution is output from the amplitude-scale frequency distribution calculation unit 240 to the slope calculation unit 250, and when the signal processing device 20 transmits the amplitude-scale frequency distribution as information regarding the amplitude-scale frequency distribution, the amplitude-scale frequency distribution is output from the amplitude-scale frequency distribution calculation unit 240 to the wireless transmission unit 260.

[0042] FIG. 3 is a sequence diagram showing the flow of processing in the structure evaluation system 100 according to the first embodiment. The sensor 10 detects an elastic wave AE (step S101). The sensor 10 converts the detected elastic wave AE into an AE signal. The sensor 10 transmits the AE signal to the signal processing device 20 (step S102). Note that every time the sensor 10 detects an elastic wave AE, it converts the elastic wave AE into an AE signal and transmits the AE signal to the signal processing device 20.

[0043] The AFE 210 performs preprocessing on the AE signal transmitted from the sensor 10 (step S103). Specifically, the AFE 210 performs filtering on the AE signal. As a result, a noise-removed analog signal based on the AE signal is generated. The AFE 210 outputs the noise-removed analog signal to the ADC 220. The ADC 220 receives the noise-removed analog signal output from the AFE 210 as input and converts the input noise-removed analog signal into a digital signal (step S104). The ADC 220 outputs the digital signal to the maximum amplitude detection unit 230.

[0044] The maximum amplitude detection unit 230 detects the maximum amplitude of the digital signal output from the ADC 220 (step S105). The maximum amplitude detection unit 230 outputs information about the detected maximum amplitude to the amplitude scale frequency distribution calculation unit 240. The processes from step S101 to step S105 are repeated for a predetermined period. The predetermined period may be, for example, a predetermined number of hours, days, weeks, or months. Alternatively, it may be a period until a predetermined number of AE signal detections (AW hits) is reached. This allows the amplitude scale frequency distribution calculation unit 240 to acquire multiple pieces of information about maximum amplitudes. The amplitude scale frequency distribution calculation unit 240 calculates the amplitude scale frequency distribution using the information about the maximum amplitudes for the predetermined period (step S106). The amplitude scale frequency distribution calculation unit 240 outputs the calculated amplitude scale frequency distribution to the slope calculation unit 250.

[0045] The gradient calculation unit 250 calculates the b-value using the frequency distribution by amplitude scale output from the amplitude scale frequency distribution calculation unit 240 (step S107). Specifically, the gradient calculation unit 250 calculates the b-value by determining the gradient of the frequency distribution by amplitude scale. The gradient calculation unit 250 outputs the calculated b-value to the wireless transmission unit 260. The wireless transmission unit 260 generates transmission data including one or more b-values ​​output from the gradient calculation unit 250, and transmits the generated transmission data wirelessly to the structure evaluation device 30 (step S108).

[0046] The communication unit 31 of the structure evaluation device 30 receives the transmission data transmitted from the signal processing device 20. The communication unit 31 outputs the received transmission data to the acquisition unit 321. The acquisition unit 321 acquires a b value of 1 or more included in the transmission data. The acquisition unit 321 stores the acquired b value of 1 or more in the storage unit 33 and outputs it to the evaluation unit 322. The evaluation unit 322 performs evaluation based on the b value of 1 or more (step S109).

[0047] The example shown in Fig. 3 explains the processing when the structure evaluation system 100 includes one set of one sensor 10 and one signal processing device 20. If the structure evaluation system 100 includes multiple sets, the processing from step S101 to step S108 may be performed for each set. The evaluation unit 322 may perform evaluation based on each b value included in the transmission data sent from each signal processing device 20. If there are multiple b values, the evaluation unit 322 may take a statistical value of the multiple b values ​​and perform evaluation. This also applies to the following embodiments.

[0048] The structure evaluation system 100 configured as described above includes one or more sensors 10 that detect elastic wave AE generated from a structure, a signal processing device 20 that calculates information about a frequency distribution by amplitude scale based on each elastic wave detected by the one or more sensors 10 and wirelessly transmits the calculated information about the frequency distribution by amplitude scale, and a structure evaluation device 30 that evaluates the deterioration state of the structure based on the information about the frequency distribution by amplitude scale transmitted from the signal processing device 20. In this way, by having the signal processing device 20 transmit only information about the frequency distribution by amplitude scale (e.g., b-value) to the structure evaluation device 30, the bit rate can be significantly reduced, and as a result, power consumption can be reduced.

[0049] Furthermore, the structure evaluation system 100 allows for the use of long-distance wireless transmission methods such as LPWA due to the reduced bit rate, which makes it possible to measure elastic wave AE over a wide area and expand the evaluation range.

[0050] Furthermore, the structure evaluation system 100 can reduce power consumption, enabling long-term monitoring. Furthermore, unlike conventional systems, it is not necessary to acquire all of the features of elastic wave AE; it is sufficient to acquire only the amplitude of elastic wave AE. This simplifies the device configuration.

[0051] (Second embodiment) In the first embodiment, a configuration in which the signal processing device is always running is described, whereas in the second embodiment, a configuration in which the signal processing device is not always running but is started when an elastic wave is detected is described.

[0052] Conventionally, an event-driven configuration has been proposed in which a signal processing device is activated when an elastic wave is generated, rather than being constantly activated. However, even event-driven measurement requires sufficient power to measure features at startup. Therefore, a long sleep time is required for long-term measurement, and elastic waves cannot be acquired during the sleep time. Furthermore, event-driven measurement requires a long startup time, which may result in an inability to accurately measure the elastic wave that triggered startup. In contrast, the structure evaluation system of the second embodiment solves the above problem by using a peak hold circuit. A specific configuration will be described below. Note that the system configuration of the structure evaluation system 100 of the second embodiment is the same as that of the first embodiment, with only the configuration of the signal processing device being different. Therefore, the following description will focus on the differences from the first embodiment.

[0053] The signal processing device 20a has multiple modes, including an active mode and an idle mode, and transitions from the idle mode to the active mode upon detection of elastic wave AE. The idle mode is a mode in which power consumption is reduced compared to the active mode by limiting functions. When the signal processing device 20a operates in the idle mode, some of the components of the signal processing device 20a stop functioning. The signal processing device 20a is in the idle mode until it transitions to the active mode. When the signal processing device 20a transitions to the active mode, it performs processing based on the frequency distribution by amplitude scale. As shown in the first embodiment, the processing based on the frequency distribution by amplitude scale includes processing such as detecting the maximum amplitude, calculating the frequency distribution by amplitude scale, and calculating the a-value or b-value.

[0054] 4 is a diagram showing an example of the configuration of a signal processing device 20a according to the second embodiment. The signal processing device 20a includes an AFE 210a, an ADC 220a, a maximum amplitude detection unit 230a, an amplitude scale frequency distribution calculation unit 240, a slope calculation unit 250, a wireless transmission unit 260, an interrupt control unit 270, a power supply unit 280, and a discharge control unit 290. The amplitude scale frequency distribution calculation unit 240, the slope calculation unit 250, and the wireless transmission unit 260 are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0055] When the signal processing device 20a operates in the sleep mode, the functions of the ADC 220a, the maximum amplitude detection unit 230a, the amplitude-scale frequency distribution calculation unit 240, the slope calculation unit 250, the wireless transmission unit 260, and the discharge control unit 290 are stopped. That is, the ADC 220a, the maximum amplitude detection unit 230a, the amplitude-scale frequency distribution calculation unit 240, the slope calculation unit 250, the wireless transmission unit 260, and the discharge control unit 290 do not perform any processing.

[0056] The AFE 210a performs filtering, peak holding, and trigger generation on the AE signal output from the sensor 10. The AFE 210a includes a receiving unit 211, a BPF 212, a peak hold circuit 213, and a trigger generation circuit 214.

[0057] The peak hold circuit 213 receives the noise-removed analog signal output from the BPF 212 as an input. The peak hold circuit 213 holds the peak value of the amplitude of the noise-removed analog signal. The peak hold circuit 213 is an existing peak hold circuit configured, for example, with a diode, a capacitor, a discharge resistor, a discharge switch, etc. The time constant of the peak hold circuit 213 is determined based on the resonant frequency of the sensor 10. Note that the time constant of the peak hold circuit 213 is desirably determined to be a value longer than the time required for the signal processing device 20 to transition to the operating mode and start processing after the trigger generation circuit 214 generates a trigger. The peak hold circuit 213 discharges the held peak value under the control of the discharge control unit 290.

[0058] The trigger generation circuit 214 generates an operation signal (H) for transitioning to the operation mode when the signal level of the analog signal output from the peak hold circuit 213 exceeds a first threshold value related to the signal level (hereinafter referred to as the "first signal threshold value"). The trigger generation circuit 214 outputs the generated operation signal to the interrupt control unit 270.

[0059] The ADC 220a is enabled to operate by power supplied from the power supply unit 280, and operates based on timing information generated by the interrupt control unit 270. The ADC 220a is an analog-to-digital converter that quantizes the peak value signal of the amplitude of the noise-removed analog signal held by the peak hold circuit 213 and converts it into a digital signal.

[0060] The maximum amplitude detector 230a detects the maximum amplitude based on the digital signal converted by the ADC 220a, and outputs information on the detected maximum amplitude to the amplitude scale frequency distribution calculator 240 and the discharge controller 290.

[0061] The interrupt control unit 270 switches the operation mode of the signal processing device 20a based on the signal output from the trigger generation circuit 214. When the signal output from the trigger generation circuit 214 is an operation signal, the interrupt control unit 270 switches the operation mode of the signal processing device 20a from the sleep mode to the operation mode. In this case, the interrupt control unit 270 instructs the power supply unit 280 to supply power to the stopped functional units. As a result, power is supplied from the power supply unit 280 to the stopped functional units, and the stopped functional units become operable. Furthermore, the interrupt control unit 270 generates timing information for the ADC 220a to operate and outputs it to the ADC 220a.

[0062] The interrupt control unit 270 switches the operation mode of the signal processing device 20a from the operation mode to the sleep mode when the operation signal has been measured for a certain period of time, when the operation mode has been set for a certain period of time, or after discharge by the discharge control unit 290. In this case, the interrupt control unit 270 instructs the power supply unit 280 to stop supplying power. As a result, the power supply from the power supply unit 280 to the functional units stops, and the operations of the ADC 220a, maximum amplitude detection unit 230a, amplitude scale frequency distribution calculation unit 240, slope calculation unit 250, wireless transmission unit 260, and discharge control unit 290 stop.

[0063] The power supply unit 280 supplies power to the entire signal processing device 20a or to some functional units of the signal processing device 20a. The power supply unit 280 is any one of a primary battery, a secondary battery, a solar cell, an energy harvester, or the like.

[0064] The discharge control unit 290 discharges the peak hold circuit 213 in accordance with the input voltage. For example, the discharge control unit 290 discharges the peak hold circuit 213 upon acquiring information on the maximum amplitude output from the maximum amplitude detection unit 230. After discharging the peak hold circuit 213, the discharge control unit 290 may generate a pause signal for transitioning the signal processing device 20a to a pause mode. In this case, the discharge control unit 290 outputs the generated pause signal to the interrupt control unit 270. In accordance with the pause signal output from the discharge control unit 290, the interrupt control unit 270 switches the operation mode of the signal processing device 20a from the active mode to the pause mode.

[0065] FIG. 5 is a time chart illustrating the operation of the signal processing device 20a according to the second embodiment. As shown in FIG. 5, at time t1, if the trigger generation circuit 214 determines that the signal level of the analog signal output from the peak hold circuit 213 exceeds the first signal threshold, the trigger generation circuit 214 generates an operation signal. The trigger generation circuit 214 outputs the generated operation signal to the interrupt control unit 270. The interrupt control unit 270 transitions the signal processing device 20a to an operation state based on the operation signal output from the trigger generation circuit 214. The signal processing device 20a prepares for startup between time t1 and time t2 using power supplied from the power supply unit 280, and starts up at time t2. Note that an elastic wave AE is still input to the signal processing device 20a between time t1 and time t2, and the peak hold circuit 213 holds the peak value of the input elastic wave AE.

[0066] At time t2, when the signal processing device 20a enters the operating mode, the interrupt control unit 270 generates timing information and outputs it to the ADC 220a. The ADC 220a performs processing at time t3 based on the timing information generated by the interrupt control unit 270. At this time, the ADC 220a performs analog-to-digital conversion on the peak value signal held in the peak hold circuit 213. Thereafter, at time t4, the discharge control unit 290 discharges the peak value held by the peak hold circuit 213.

[0067] Fig. 6 is a sequence diagram showing the processing flow of the structure evaluation system 100 in the second embodiment. At the start of the processing in Fig. 6, some functional units of the signal processing device 20a are assumed to be in a suspended state. In Fig. 6, the same processes as in Fig. 3 are assigned the same reference numerals as in Fig. 3, and their explanations will be omitted.

[0068] When the processes from step S101 to step S103 are completed, the peak hold circuit 213 holds the peak value (signal with maximum amplitude) of the noise-removed analog signal output from the BPF 212 (step S201). The trigger generation circuit 214 generates an operation signal when the signal level of the analog signal output from the peak hold circuit 213 exceeds a first signal threshold. Here, it is assumed that the signal level of the analog signal exceeds the first signal threshold. The trigger generation circuit 214 generates an operation signal and outputs the generated operation signal to the interrupt control unit 270.

[0069] The interrupt control unit 270 switches the operation mode of the signal processing device 20a from the sleep mode to the active mode based on the operation signal output from the trigger generation circuit 214. This activates the function units of the signal processing device 20a that were inactive (step S202). Furthermore, the trigger generation circuit 214 generates timing information to control the operation timing of the ADC 220a (step S203).

[0070] The ADC 220a quantizes the signal of the peak value of the amplitude of the noise-removed analog signal held by the peak hold circuit 213 and converts it into a digital signal at an operation timing based on the timing information generated by the trigger generation circuit 214 (step S204). The ADC 220a outputs the digital signal to the maximum amplitude detection unit 230a. The maximum amplitude detection unit 230a detects the maximum amplitude based on the digital signal output from the ADC 220a (step S205). The maximum amplitude detection unit 230a outputs information about the detected maximum amplitude to the amplitude scale frequency distribution calculation unit 240 and the discharge control unit 290.

[0071] The discharge control unit 290 discharges the peak hold circuit 213 in accordance with the information on the maximum amplitude output from the maximum amplitude detection unit 230a (step S206). As a result, the signal of the peak value of the amplitude of the noise-removed analog signal held by the peak hold circuit 213 is discharged. The processes from step S101 to step S206 are repeated for a predetermined period. As the peak hold circuit 213 discharges, the signal level of the analog signal output from the peak hold circuit 213 decreases. The interrupt control unit 270 switches the operation mode of the signal processing device 20a from the operation mode to the sleep mode in accordance with the following: the operation signal has been measured for a certain period of time; the operation mode has been in operation for a certain period of time; or after discharge by the discharge control unit 290.

[0072] As a result, the operation of some of the functional units of the signal processing device 20a is stopped. Meanwhile, the processes from step S106 to step S109 are executed between the discharge control by the discharge control unit 290 and the stop of the operation of some of the functional units of the signal processing device 20a.

[0073] The structure evaluation system 100 of the second embodiment configured as described above can achieve the same effects as those of the first embodiment. Furthermore, in the structure evaluation system 100 of the second embodiment, the signal processing device 20a is not constantly running, so it is possible to reduce power consumption more than in the first embodiment.

[0074] The structure evaluation system 100 in the second embodiment has an event-driven configuration, just like the conventional one, but is equipped with a peak hold circuit 213, so it can hold the peak value of the noise-removed analog signal input before all of the functional units of the signal processing device 20a are activated. Then, after all of the functional units of the signal processing device 20a are activated, processing is performed based on the amplitude-scale frequency distribution, using the peak value of the noise-removed analog signal that has already been held. This solves the problem of the conventional event-driven configuration, of not being able to accurately measure the elastic wave AE that triggered activation. As a result, evaluation accuracy can be improved.

[0075] (Third embodiment) In the second embodiment, since the timing of the end of a single elastic wave is unknown, when a long-duration elastic wave occurs, the elastic wave may be split and detected even if it is a single elastic wave. Conversely, when multiple short-duration elastic waves occur, the multiple elastic waves may be detected as a single elastic wave. Therefore, in the third embodiment, a configuration for appropriately detecting a single elastic wave will be described. Note that the system configuration of the structure evaluation system 100 in the third embodiment is the same as that in the second embodiment, with only the configuration of the signal processing device being different. Therefore, the following description will focus on the differences from the second embodiment.

[0076] The signal processing device 20b has a plurality of modes, including an active mode and an inactive mode, and transitions to the active mode upon detection of elastic wave AE. When the signal processing device 20b operates in the inactive mode, some of the components of the signal processing device 20b stop functioning. The signal processing device 20b is in the inactive mode until transitioning to the active mode. When the signal processing device 20b transitions to the active mode, it performs processing based on the frequency distribution by amplitude scale.

[0077] 7 is a diagram showing an example of the configuration of a signal processing device 20b according to the third embodiment. The signal processing device 20b includes an AFE 210b, an ADC 220a, a maximum amplitude detection unit 230a, an amplitude scale frequency distribution calculation unit 240, a slope calculation unit 250, a wireless transmission unit 260, an interrupt control unit 270, a power supply unit 280, and a discharge control unit 290. The configuration other than the AFE 210b is the same as that of the second embodiment, and therefore description thereof will be omitted.

[0078] The AFE 210b performs filtering, peak holding, and trigger generation on the AE signal output from the sensor 10. The AFE 210b is composed of a receiving unit 211, a BPF 212, a peak hold circuit 213, and a trigger generation circuit 214b.

[0079] Unlike the second embodiment, the trigger generation circuit 214b receives the noise-removed analog signal output from the BPF 212 as input. The trigger generation circuit 214b detects the envelope of the input noise-removed analog signal and generates an operation signal when the signal level of the envelope exceeds a first signal threshold and then falls below a second signal threshold. The second signal threshold is, for example, a value smaller than the first signal threshold. As described above, when the signal level of the envelope exceeds the first signal threshold and then falls below the second signal threshold, this means that elastic wave AE is no longer detected after it was detected. In this way, the trigger generation circuit 214b generates an operation signal when a condition indicating that elastic waves are no longer detected after they were detected is met.

[0080] The trigger generation circuit 214b is composed of a second peak hold circuit with a time constant different from that of the peak hold circuit 213, and a comparator. The second peak hold circuit holds the peak value of the amplitude of the noise-removed analog signal and generates an envelope. The second peak hold circuit is an existing peak hold circuit composed of, for example, a diode, a capacitor, a discharge resistor, a discharge switch, etc. The time constant of the second peak hold circuit is, for example, greater than t / 2 of the operating period of the sensor 10 and less than twice the operating period t.

[0081] The comparator generates the activation signal when the signal level of the envelope output from the second peak hold circuit exceeds the first signal threshold and then falls below the second signal threshold.

[0082] The trigger generation circuit 214b may also be configured by combining multiple comparators (e.g., a first comparator and a second comparator) and a low-pass filter (LPF). In this configuration, when the noise-removed analog signal is input to the first comparator and exceeds a first signal threshold, the first comparator outputs a detection signal (H). The LPF is applied to the detection signal (H) output from the first comparator, and a filtered signal is output. The filtered signal output from the LPF is input to the second comparator. When the signal level of the input filtered signal exceeds a second signal threshold, the second comparator generates an activation signal. In this way, the trigger generation circuit 214b may generate a signal corresponding to an envelope capable of detecting the start and end of a single elastic wave.

[0083] FIG. 8 is a time chart illustrating the operation of the signal processing device 20b according to the third embodiment. As shown in FIG. 8, at time t1, the trigger generation circuit 214b generates an activation signal when the signal level of the envelope of the noise-removed analog signal output from the BPF 212 exceeds the first signal threshold and then falls below the second signal threshold (when the trigger changes from an ON state to an OFF state). The trigger generation circuit 214b outputs the generated activation signal to the interrupt control unit 270. The interrupt control unit 270 transitions the signal processing device 20b to an active state based on the activation signal output from the trigger generation circuit 214b. The signal processing device 20b prepares for startup between time t2 and time t3 using power supplied by the power supply unit 280, and starts up at time t3. Note that an elastic wave AE is also input to the signal processing device 20b between time t1 and time t3, and the peak hold circuit 213 holds the peak value of the input elastic wave AE.

[0084] At time t3, when the signal processing device 20b enters the operating mode, the interrupt control unit 270 generates timing information and outputs it to the ADC 220a. The ADC 220a performs processing at time t4 based on the timing information generated by the interrupt control unit 270. At this time, the ADC 220a performs analog-to-digital conversion on the peak value signal held in the peak hold circuit 213. Thereafter, at time t5, the discharge control unit 290 discharges the peak values ​​held in the peak hold circuit 213 and the trigger generation circuit 214b.

[0085] Fig. 9 is a sequence diagram showing the processing flow of the structure evaluation system 100 in the third embodiment. At the start of the processing in Fig. 9, some functional units of the signal processing device 20b are assumed to be in a suspended state. In Fig. 9, the same processes as in Fig. 6 are assigned the same reference numerals as in Fig. 6, and their explanations will be omitted.

[0086] When the processes from step S101 to step S103 are completed, the BPF 212 outputs the pre-processed noise-removed analog signal to the peak hold circuit 213 and the trigger generation circuit 214b. The peak hold circuit 213 holds the peak value of the noise-removed analog signal output from the BPF 212 (step S201). The second peak hold circuit of the trigger generation circuit 214b holds the peak value of the noise-removed analog signal output from the BPF 212. When the signal level of the noise-removed analog signal input to the second peak hold circuit exceeds the first signal threshold and then falls below the second signal threshold, the comparator determines that the activation condition is satisfied and generates an operation signal (step S301). The trigger generation circuit 214b outputs the generated operation signal to the interrupt control unit 270. This causes the processes from step S202 onwards to be executed.

[0087] According to the structure evaluation system 100 of the third embodiment configured as described above, the envelope is detected to detect the timing of the end of one elastic wave AE, thereby making it possible to appropriately detect one elastic wave AE.

[0088] (Modification of the third embodiment) In the above-described embodiment, the trigger generation circuit 214b is configured to generate an activation signal when the signal level of the envelope of the noise-removed analog signal exceeds a first signal threshold and then falls below a second signal threshold. Alternatively, the trigger generation circuit 214b may be configured to incorporate a NOT circuit into the output of the trigger generation circuit 214b. In this configuration, the interrupt control unit 270 sets the activation signal to (H).

[0089] (Fourth embodiment) In the first to third embodiments, the information related to time is reduced. In the fourth embodiment, a configuration will be described in which time information is acquired when the maximum amplitude is detected, and information related to the time hit density such as the number of hits / time and the frequency distribution of amplitude scales over time is calculated, thereby making it possible to determine changes over time.

[0090] 10 is a diagram illustrating an example configuration of a signal processing device 20c according to the fourth embodiment. The signal processing device 20c includes an AFE 210b, an ADC 220a, a maximum amplitude detection unit 230a, an amplitude scale frequency distribution calculation unit 240c, a slope calculation unit 250c, a wireless transmission unit 260, an interrupt control unit 270, a power supply unit 280, a discharge control unit 290, and a clock unit 295. The signal processing device 20c differs from the third embodiment in the configurations of the amplitude scale frequency distribution calculation unit 240c, the slope calculation unit 250c, and the clock unit 295. Note that while FIG. 10 illustrates the configuration of the signal processing device 20c based on the third embodiment, the signal processing device 20c may have a configuration based on the first or second embodiment.

[0091] When the signal processing device 20c has a configuration based on the first embodiment, the signal processing device 20c is configured to include an AFE 210, an ADC 220, and a maximum amplitude detection unit 230 instead of the AFE 210b, the ADC 220a, and the maximum amplitude detection unit 230a, and is configured not to include the interrupt control unit 270, the power supply unit 280, and the discharge control unit 290. When the signal processing device 20c has a configuration based on the second embodiment, the signal processing device 20c is configured to include an AFE 210a instead of the AFE 210b.

[0092] The clock unit 295 is an RTC (Real Time Clock) that generates time information, and outputs the time information at which the maximum amplitude is detected by the maximum amplitude detection unit 230a to the amplitude scale frequency distribution calculation unit 240c.

[0093] The amplitude scale frequency distribution calculation unit 240c calculates the amplitude scale frequency distribution including time information based on the time information generated by the clock unit 295. The amplitude scale frequency distribution including time information is a distribution in which time information is associated with each maximum amplitude used to calculate the amplitude scale frequency distribution. This makes it possible to know at what time each maximum amplitude was detected.

[0094] The slope calculation unit 250c calculates the b-value using the amplitude-scale frequency distribution including the time information calculated by the amplitude-scale frequency distribution calculation unit 240c. The slope calculation unit 250c may calculate the b-value using the amplitude-scale frequency distribution calculated by the amplitude-scale frequency distribution calculation unit 240c. Furthermore, the slope calculation unit 250c calculates the number of hits for each time period using the amplitude-scale frequency distribution including the time information. Specifically, the slope calculation unit 250c calculates one maximum amplitude value as one hit, and calculates the number of hits for each time period based on the time information associated with the maximum amplitude value. Hereinafter, the distribution indicating the number of hits for each time period will be referred to as the amplitude frequency distribution. Note that the time width is set in advance.

[0095] Fig. 11 is a diagram showing the relationship between the number of hits for each measurement time in the fourth embodiment. In Fig. 11, the horizontal axis represents time, and the vertical axis represents the number of hits. As shown in Fig. 11, by calculating the number of hits at each time, it is possible to obtain the change over time.

[0096] (Fifth embodiment) In the fifth embodiment, a configuration will be described in which a signal processing device is started up in two stages. Specifically, in the fifth embodiment, the signal processing device is started up in a first stage in which the entire signal processing device is started up in response to the generation of an elastic wave, and in a second stage in which some functional units of the signal processing device are started up by the method described in the second to fourth embodiments.

[0097] Fig. 12 is a diagram showing the configuration of a structure evaluation system 100d in the fifth embodiment. The structure evaluation system 100d includes a plurality of sensors 10-1 to 10-P, an activation control unit 15, a signal processing device 20d, and a structure evaluation device 30. Each of the plurality of sensors 10-1 to 10-P and the signal processing device 20d are connected by wire. The activation control unit 15 and the signal processing device 20d are connected by wire. The signal processing device 20d and the structure evaluation device 30 are connected wirelessly. In the fifth embodiment, unlike the second to fourth embodiments, the entire signal processing device 20d is in a sleep state.

[0098] 12 shows a configuration in which the structure evaluation system 100d includes a plurality of sensors 10, but the structure evaluation system 100d may include one or more sensors 10. When the structure evaluation system 100d includes one sensor 10, the sensor 10 and one signal processing device 20d are connected by wire. When the structure evaluation system 100d includes a plurality of sensors 10, the structure evaluation system 100d may include a plurality of signal processing devices 20d. In this case, a configuration in which one sensor 10-p and one signal processing device 20d-p are connected by wire is considered as one set, and the structure evaluation system 100d includes P sets of configurations in which one sensor 10-p and one signal processing device 20d-p are connected by wire.

[0099] Like the sensor 10, the activation control unit 15 is installed on a surface different from the surface on which the load is applied to the structure 11. The activation control unit 15 is a sensor that detects the approach of the vehicle 12, and an acceleration sensor can be used. The approach of the vehicle can be detected from the acceleration generated by the passage of the vehicle 12. Note that a MEMS (Micro Electro Mechanical System) acceleration sensor is preferable from the viewpoint of low power consumption. When the activation control unit 15 detects the approach of the vehicle 12, it outputs an activation signal to the signal processing device 20d to cause the signal processing device 20d to enter a signal reception mode. Putting the signal processing device 20d into the signal reception mode means causing the signal processing device 20d to receive the AE signal output from the sensor 10. In other words, the signal processing device 20d does not receive the AE signal output from the sensor 10 until it acquires the activation signal from the activation control unit 15. This reduces the power consumption of the signal processing device 20d.

[0100] The signal processing device 20d has a plurality of modes, including an active mode, a sleep mode, and a signal reception mode, and transitions to the signal reception mode based on a startup signal output from the startup control unit 15. The internal configuration of the signal processing device 20d is the same as that of any of the second to fourth embodiments. Here, the internal configuration of the signal processing device 20d will be described as being the same as that of the second embodiment. When transitioning to the signal reception mode, the signal processing device 20d activates functional units other than those activated in the active mode. The functional unit other than those activated in the active mode is, for example, the AFE 210a. When activated in response to the startup signal output from the startup control unit 15, the AFE 210a of the signal processing device 20d performs processing similar to that shown in the second embodiment.

[0101] According to the structure evaluation system 100d of the fifth embodiment configured as above, it is possible to further reduce power consumption.

[0102] (Sixth embodiment) In the first to fifth embodiments, a configuration in which a signal processing device transmits information about the frequency distribution by amplitude scale to a structure evaluation device has been described as a configuration for reducing power consumption. In contrast, in the sixth embodiment, a configuration will be described in which power consumption can be reduced without necessarily transmitting information about the frequency distribution by amplitude scale, by performing startup based on a peak hold circuit as shown in the second to fourth embodiments.

[0103] 13 is a diagram showing an example of the configuration of a structure evaluation system 100e in the sixth embodiment. The structure evaluation system 100e is used to evaluate the soundness of a structure 11. The structure evaluation system 100e includes a plurality of sensors 10-1 to 10-P, a signal processing device 20e, and a structure evaluation device 30e. Each of the plurality of sensors 10-1 to 10-P and the signal processing device 20e are connected by wire. The signal processing device 20e and the structure evaluation device 30e are connected wirelessly.

[0104] 13 shows a configuration in which the structure evaluation system 100e includes a plurality of sensors 10, but the structure evaluation system 100e may include one or more sensors 10. When the structure evaluation system 100e includes one sensor 10, the sensor 10 is connected to one signal processing device 20e by wire. When the structure evaluation system 100e includes a plurality of sensors 10-1 to 10-P, the structure evaluation system 100e may include a plurality of signal processing devices 20e-1 to 20e-P. In this case, a configuration in which one sensor 10-p and one signal processing device 20e-p are connected by wire is considered as one set, and the structure evaluation system 100e includes P sets of configurations in which one sensor 10-p and one signal processing device 20e-p are connected by wire.

[0105] The signal processing device 20e has multiple modes, including an operating mode and a standby mode, and transitions to the operating mode upon detection of elastic wave AE. The signal processing device 20e is in the standby mode until transitioning to the operating mode. When transitioning to the operating mode, the signal processing device 20e performs processing based on elastic wave AE. Processing based on elastic wave AE includes detection of maximum amplitude and calculation of amplitude frequency distribution. Note that the processing based on elastic wave AE is not limited to this, and energy calculation may also be performed. The signal processing device 20e wirelessly transmits transmission data including information about the elastic wave AE obtained by processing based on elastic wave AE to the structure evaluation device 30e. In the following explanation, an example will be described in which amplitude frequency distribution is used as information about elastic wave AE.

[0106] The signal processing device 20e is configured using an analog circuit or a digital circuit. The digital circuit is realized by, for example, an FPGA or a microcomputer. By using a non-volatile FPGA, power consumption during standby can be reduced. The digital circuit may be realized by a dedicated LSI. The signal processing device 20e may be equipped with a non-volatile memory such as a flash memory or a removable memory.

[0107] The structure evaluation device 30e evaluates the deterioration state of the structure 11 based on the information related to the elastic wave AE transmitted from the signal processing device 20e.

[0108] The structure evaluation device 30e includes a communication unit 31, a control unit 32e, a storage unit 33e, and a display unit 34. The communication unit 31 and the display unit 34 included in the structure evaluation device 30e are similar to those in the first to fifth embodiments.

[0109] The control unit 32e controls the entire structure evaluation device 30e. The control unit 32e is configured using a processor such as a CPU and a memory. The control unit 32e executes a program to function as the acquisition unit 321 and the evaluation unit 322e.

[0110] Some or all of the functional units of the acquisition unit 321 and the evaluation unit 322e may be realized by hardware (including circuitry) such as ASIC, PLD, or FPGA, or by a combination of software and hardware. The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, and non-transitory storage media such as storage devices built into computer systems, such as hard disks. The program may be transmitted via a telecommunications line.

[0111] Some of the functions of the acquisition unit 321 and the evaluation unit 322e do not need to be pre-installed in the structure evaluation device 30e, and may be realized by installing an additional application program in the structure evaluation device 30e.

[0112] The evaluation unit 322e evaluates the deterioration state of the structure 11 based on the information on elastic wave AE acquired by the acquisition unit 321. Specifically, when the information on elastic wave AE is an amplitude frequency distribution, the evaluation unit 322e performs an evaluation based on the Kaiser effect. The Kaiser effect is a phenomenon in which, if the structure 11 is healthy when a preload is removed and then reloaded, almost no elastic wave AE is detected until the preload is applied. As such, if the structure 11 is healthy, almost no elastic wave AE is detected until the preload is applied. Therefore, if many elastic wave AEs are detected, it is highly likely that the structure 11 is deteriorating. Therefore, the evaluation unit 322e evaluates the structure as healthy by referring to the amplitude frequency distribution if there is no time period in which the number of hits is greater than or equal to a threshold. On the other hand, the evaluation unit 322e evaluates the structure as deteriorating by referring to the amplitude frequency distribution if there is a time period in which the number of hits is greater than or equal to a threshold. Furthermore, for example, by using multiple sensors 10 and multiple signal processing devices 20e, it is possible to display areas of advanced deterioration by interpolating and plotting representative values ​​of elastic wave AE at sensor positions over a certain period of time as a two-dimensional map. The representative values ​​of elastic wave AE are characteristic quantities related to elastic wave AE, such as the number of AE hits over a certain period of time, maximum amplitude, and duration.

[0113] The storage unit 33e stores information on the frequency distribution of one or more amplitudes included in the transmission data acquired by the acquisition unit 321. The storage unit 33e is configured using a storage device such as a magnetic hard disk device or a semiconductor storage device.

[0114] 14 is a diagram showing an example of the configuration of a signal processing device 20e according to the sixth embodiment. The signal processing device 20e includes an AFE 210a, an ADC 220a, a maximum amplitude detection unit 230a, a wireless transmission unit 260, an interrupt control unit 270, a power supply unit 280, a discharge control unit 290, a clock unit 295, and a calculation unit 300. The signal processing device 20e differs in configuration from the signal processing device 20a in that it does not include the amplitude scale frequency distribution calculation unit 240 and the slope calculation unit 250, but instead includes the clock unit 295 and the calculation unit 300. The other components of the signal processing device 20e are the same as those of the signal processing device 20a. The following description will focus on the differences.

[0115] When the signal processing device 20e operates in the sleep mode, the functions of the ADC 220a, the maximum amplitude detection unit 230a, the wireless transmission unit 260, the discharge control unit 290, and the calculation unit 300 are stopped. That is, the ADC 220a, the maximum amplitude detection unit 230a, the wireless transmission unit 260, the discharge control unit 290, and the calculation unit 300 do not perform any processing.

[0116] The clock unit 295 is an RTC that generates time information and outputs to the calculation unit 300 time information at which the maximum amplitude is detected by the maximum amplitude detection unit 230a.

[0117] The calculation unit 300 collects time information generated by the clock unit 295 and information on maximum amplitude detected by the maximum amplitude detection unit 230a for a predetermined period of time. The calculation unit 300 calculates a frequency distribution of amplitude using the collected information on maximum amplitude for the predetermined period of time and the time information.

[0118] Fig. 15 is a sequence diagram showing the processing flow of the structure evaluation system 100e in the sixth embodiment. At the start of the processing in Fig. 15, some functional units of the signal processing device 20e are assumed to be in a suspended state. In Fig. 15, the same processes as in Fig. 6 are assigned the same reference numerals as in Fig. 6, and their explanations will be omitted.

[0119] When the processes from step S101 to step S103 are completed, the peak hold circuit 213 holds the peak value of the noise-removed analog signal output from the BPF 212 (step S401). The trigger generation circuit 214 generates an operation signal when the signal level of the analog signal output from the peak hold circuit 213 exceeds a first signal threshold. Here, it is assumed that the signal level of the analog signal exceeds the first signal threshold. The trigger generation circuit 214 generates the operation signal and outputs the generated operation signal to the interrupt control unit 270.

[0120] The interrupt control unit 270 switches the operation mode of the signal processing device 20e from the sleep mode to the active mode based on the operation signal output from the trigger generation circuit 214. This activates the function units of the signal processing device 20e that were inactive (step S402). Furthermore, the trigger generation circuit 214 generates timing information to control the operation timing of the ADC 220a (step S403).

[0121] The ADC 220a quantizes the signal of the peak value of the amplitude of the noise-removed analog signal held by the peak hold circuit 213 and converts it into a digital signal at an operation timing based on the timing information generated by the trigger generation circuit 214 (step S404). The ADC 220a outputs the digital signal to the maximum amplitude detection unit 230a. The maximum amplitude detection unit 230a detects the maximum amplitude based on the digital signal output from the ADC 220a (step S405). The maximum amplitude detection unit 230a outputs information about the detected maximum amplitude to the calculation unit 300 and the discharge control unit 290. The clock unit 295 outputs information about the time when the maximum amplitude detection unit 230a detected the maximum amplitude to the calculation unit 300.

[0122] The discharge control unit 290 discharges the peak hold circuit 213 in accordance with the maximum amplitude information output from the maximum amplitude detection unit 230a (step S406). As a result, the signal of the peak value of the amplitude of the noise-removed analog signal held by the peak hold circuit 213 is discharged. In the signal processing device 20e, the processes from step S101 to step S406 are repeated for a predetermined period. As a result, the calculation unit 300 can acquire multiple combinations of maximum amplitude information and time information.

[0123] Discharging the peak hold circuit 213 reduces the signal level of the noise-removed analog signal input to the peak hold circuit 213. The interrupt control unit 270 switches the operation mode of the signal processing device 20e from the operation mode to the sleep mode when the operation signal is measured for a certain period of time, when the operation mode has been in operation for a certain period of time, or after discharge by the discharge control unit 290.

[0124] As a result, the operation of some of the functional units of the signal processing device 20e is stopped. Meanwhile, during the period from when the discharge control unit 290 starts discharge control to when the operation of some of the functional units of the signal processing device 20e is stopped, the calculation unit 300 calculates the amplitude frequency distribution using the information on the maximum amplitude for a predetermined period and the time information (step S407). The calculation unit 300 outputs the calculated amplitude frequency distribution to the wireless transmission unit 260. The wireless transmission unit 260 generates transmission data including the amplitude frequency distribution output from the calculation unit 300, and transmits the generated transmission data wirelessly to the structure evaluation device 30e (step S408).

[0125] The communication unit 31 of the structure evaluation device 30e receives the transmission data transmitted from the signal processing device 20e. The communication unit 31 outputs the received transmission data to the acquisition unit 321. The acquisition unit 321 acquires a frequency distribution of amplitudes included in the transmission data. The acquisition unit 321 stores the acquired frequency distribution of amplitudes in the storage unit 33e and outputs it to the evaluation unit 322e. The evaluation unit 322e performs evaluation based on the frequency distribution of amplitudes (step S409).

[0126] According to the structure evaluation system 100e configured as described above, the signal processing device 20e is not constantly running, thereby reducing power consumption. Furthermore, although the structure evaluation system 100e has an event-driven configuration similar to conventional systems, it is equipped with a peak hold circuit 213, which allows it to hold the peak value of the noise-reduced analog signal input before all functional units of the signal processing device 20e are started. Then, after all functional units of the signal processing device 20e are started, processing based on the elastic wave AE is performed based on the peak value of the noise-reduced analog signal that has already been held. This solves the problem of inability to accurately measure the elastic wave AE that triggered startup, which was a problem with conventional event-driven configurations. As a result, evaluation accuracy can be improved.

[0127] (Seventh embodiment) In the seventh embodiment, as in the third embodiment, a configuration will be described in which a second peak hold circuit with a different time constant is used in the trigger generation circuit. Note that the system configuration of the structure evaluation system 100e in the seventh embodiment is the same as that of the sixth embodiment, and only the configuration of the signal processing device is different. Therefore, the following description will focus on the differences from the sixth embodiment.

[0128] The signal processing device 20f has multiple modes, including an active mode and an inactive mode, and transitions to the active mode upon detection of elastic wave AE. When the signal processing device 20f operates in the inactive mode, some of the components of the signal processing device 20f stop functioning. The signal processing device 20f is in the inactive mode until it transitions to the active mode. When the signal processing device 20f transitions to the active mode, it performs processing based on elastic wave AE.

[0129] 16 is a diagram showing an example of the configuration of a signal processing device 20f according to the seventh embodiment. The signal processing device 20f includes an AFE 210b, an ADC 220a, a maximum amplitude detection unit 230a, a wireless transmission unit 260, an interrupt control unit 270, a power supply unit 280, a discharge control unit 290, a clock unit 295, and a calculation unit 300. The configuration other than the AFE 210b is the same as that of the sixth embodiment, and the configuration of the AFE 210b is the same as that of the AFE 210b shown in the third embodiment, so a description thereof will be omitted.

[0130] Fig. 17 is a sequence diagram showing the processing flow of the structure evaluation system 100e in the seventh embodiment. At the start of the processing in Fig. 17, some functional units of the signal processing device 20f are assumed to be in a suspended state. In Fig. 17, the same processes as in Fig. 15 are assigned the same reference numerals as in Fig. 15, and their explanations will be omitted.

[0131] When the processes from step S101 to step S103 are completed, the BPF 212 outputs the pre-processed noise-removed analog signal to the peak hold circuit 213 and the trigger generation circuit 214b. The peak hold circuit 213 holds the peak value of the noise-removed analog signal output from the BPF 212 (step S401). The second peak hold circuit of the trigger generation circuit 214b holds the peak value of the noise-removed analog signal output from the BPF 212. When the signal level of the noise-removed analog signal input to the second peak hold circuit exceeds the first signal threshold and then falls below the second signal threshold, the comparator determines that the activation condition is satisfied and generates an operation signal (step S501). The trigger generation circuit 214b outputs the generated operation signal to the interrupt control unit 270. This causes the processes from step S402 onwards to be executed.

[0132] According to the structure evaluation system 100e of the seventh embodiment configured as described above, the envelope is detected to detect the timing of the end of one elastic wave AE, thereby making it possible to appropriately detect one elastic wave AE.

[0133] (Modification of the seventh embodiment) In the above-described embodiment, the trigger generation circuit 214b is configured to generate an activation signal when the signal level of the noise-removed analog signal exceeds the first signal threshold and then falls below the second signal threshold. Alternatively, the trigger generation circuit 214b may be configured to incorporate a NOT circuit between the second peak hold and the comparator. In this configuration, the interrupt control unit 270 sets the activation signal to (H).

[0134] (Modification common to the sixth and seventh embodiments) The structure evaluation system 100e may be configured to start up the signal processing devices 20e and 20f in two stages, as shown in the fifth embodiment. When configured in this way, the structure evaluation system 100e further includes a start-up control unit 15.

[0135] (Modifications common to the first to seventh embodiments) In each of the above embodiments, a configuration using the ADCs 220 and 220a has been described, but multiple comparators may be used instead of the ADCs 220 and 220a. In such a configuration, the maximum amplitude detection units 230 and 230a detect the maximum amplitude based on the noise-removed analog signals input to the multiple comparators.

[0136] According to at least one of the embodiments described above, by having a plurality of sensors 10 that detect elastic wave AE generated from a structure, a signal processing device 20 that calculates information regarding the frequency distribution by amplitude scale based on each elastic wave detected by the plurality of sensors 10 and transmits the calculated information regarding the frequency distribution by amplitude scale by wireless, and an evaluation unit 322 that evaluates the deterioration state of the structure based on the information regarding the frequency distribution by amplitude scale transmitted from the signal processing device 20, it is possible to reduce power consumption in the acoustic emission method.

[0137] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0138] 10, 10-1 to 10-P...sensor, 15...activation control unit, 20, 20a, 20b, 20c, 20d, 20e, 20f...signal processing device, 30, 30e...structure evaluation device, 31...communication unit, 32, 32e...control unit, 33, 33e...storage unit, 34...display unit, 321...acquisition unit, 322...evaluation unit, 210, 210a...AFE, 211...receiving unit, 212...BP F, 213... peak hold circuit, 214, 214b... trigger generation circuit, 220, 220a... ADC, 230, 230a... maximum amplitude detection unit, 240, 240c... amplitude scale frequency distribution calculation unit, 250, 250c... gradient calculation unit, 260... wireless transmission unit, 270... interrupt control unit, 280... power supply unit, 290... discharge control unit, 295... clock unit, 300... calculation unit

Claims

1. one or more sensors for detecting elastic waves generated by the structure; a signal processing device that calculates information about a frequency distribution by amplitude scale based on the plurality of elastic waves detected by each of the one or more sensors, and wirelessly transmits the calculated information about the frequency distribution by amplitude scale; an evaluation unit that evaluates a deterioration state of the structure based on information about the frequency distribution by amplitude scale transmitted from the signal processing device; Equipped with The signal processing device includes: a plurality of modes including an active mode that performs processing based on the amplitude scale frequency distribution, including processing for calculating information about the amplitude scale frequency distribution, and a sleep mode that is a mode that reduces power consumption compared to the active mode by limiting functions; a peak hold circuit that holds a value of a maximum amplitude of the elastic wave detected by the one or more sensors at least during the sleep mode; After transitioning to the operating mode, the structural evaluation system calculates information about the frequency distribution by amplitude scale using the maximum amplitude value of the elastic wave held in the peak hold circuit for a predetermined period of time.

2. the signal processing device detects maximum amplitudes of the plurality of elastic waves, and calculates information about the amplitude scale frequency distribution based on the detected maximum amplitudes of the plurality of elastic waves. The structure evaluation system according to claim 1 .

3. The signal processing device includes: a calculation unit that calculates information about the amplitude frequency distribution; an interrupt control unit that transitions the signal processing device from the sleep mode to the active mode when the signal level of the elastic wave output from the peak hold circuit exceeds a first threshold; Furthermore, after transitioning to the operating mode, the calculation unit calculates information regarding the frequency distribution by amplitude scale using the maximum amplitude value of the elastic wave held by the peak hold circuit for a predetermined period. The structure evaluation system according to claim 1 or 2.

4. The signal processing device includes: a calculation unit that calculates information about the amplitude frequency distribution; an interrupt control unit that detects a signal corresponding to an envelope of an elastic wave, and when a condition indicating that an elastic wave is no longer detected after the detection of the elastic wave is satisfied, transitions the signal processing device from the sleep mode to the operation mode; Furthermore, after transitioning to the operating mode, the calculation unit calculates information regarding the frequency distribution by amplitude scale using the maximum amplitude value of the elastic wave held by the peak hold circuit for a predetermined period. The structure evaluation system according to claim 1 or 2.

5. The signal processing device includes: Further comprising a clock unit for acquiring time information, the calculation unit calculates information about the amplitude scale frequency distribution including time information when the maximum amplitude value of each elastic wave is detected. The structure evaluation system according to claim 3 .

6. the signal processing device calculates, as information regarding the frequency distribution by amplitude scale, any one of the frequency distribution by amplitude scale, an intercept obtained by linearly approximating the frequency distribution by amplitude scale, or a slope obtained by linearly approximating the frequency distribution by amplitude scale; The structure evaluation system according to claim 1 or 2.

7. The signal processing device changes at least the period for calculating the information about the frequency distribution by amplitude scale or the number of elastic wave hits in response to a command wirelessly transmitted from the structure evaluation device. The structure evaluation system according to claim 1 or 2.

8. one or more sensors for detecting elastic waves generated by the structure; a signal processing device that stores a value of a maximum amplitude of the elastic wave detected by each of the one or more sensors, calculates information about the elastic wave using the stored value of the maximum amplitude of the elastic wave for a predetermined period, and wirelessly transmits the calculated information about the elastic wave; an evaluation unit that evaluates a deterioration state of the structure based on information about the transmitted elastic waves; Equipped with The signal processing device includes: The device has a plurality of modes, including an operating mode in which processing based on the elastic waves is performed, including processing for calculating information about the elastic waves, and a sleep mode in which power consumption is reduced compared to the operating mode by limiting functions, a peak hold circuit that holds a value of a maximum amplitude of the elastic wave detected by the one or more sensors at least during the sleep mode; After transitioning to the operating mode, the structural evaluation system calculates information about the elastic wave using the maximum amplitude value of the elastic wave held in the peak hold circuit.

9. The signal processing device includes: a calculation unit that calculates information about the elastic wave; an interrupt control unit that transitions the signal processing device from the sleep mode to the active mode when the signal level of the elastic wave output from the peak hold circuit exceeds a first threshold; Furthermore, After the transition to the operating mode, the calculation unit calculates information about the elastic waves using the maximum amplitude values ​​of the elastic waves held in the peak hold circuit. The structure evaluation system according to claim 8 .

10. The signal processing device includes: a calculation unit that calculates information about the elastic wave; an interrupt control unit that detects a signal corresponding to an envelope of an elastic wave, and when a condition indicating that an elastic wave is no longer detected after the detection of the elastic wave is satisfied, transitions the signal processing device from the sleep mode to the operation mode; Furthermore, the calculation unit calculates information about the elastic wave by using the maximum amplitude value of the elastic wave held by the peak hold circuit for a predetermined period after the transition to the operating mode. The structure evaluation system according to claim 8 .

11. The plurality of modes further includes a signal reception mode for detecting the elastic wave, The signal processing device includes: a startup control unit that transitions the signal processing device from the sleep mode to the signal reception mode; an interrupt control unit that transitions the signal processing device to the operating mode; Furthermore, the activation control unit activates some of the functional units by transitioning the signal processing device to the signal reception mode when detecting the approach of a vehicle traveling through the structure; the interrupt control unit causes the signal processing device to transition to the operating mode when a predetermined condition is satisfied, thereby activating the remaining functional units; The structure evaluation system according to claim 1 or 8.

12. a calculation unit that calculates information about a frequency distribution by amplitude scale based on a plurality of elastic waves detected by one or more sensors that detect elastic waves generated from a structure; a wireless transmission unit that wirelessly transmits information about the frequency distribution by amplitude scale calculated by the calculation unit to a structure evaluation device that evaluates a deterioration state of the structure; Equipped with a plurality of modes including an active mode that performs processing based on the amplitude scale frequency distribution, including processing for calculating information about the amplitude scale frequency distribution, and a sleep mode that is a mode that reduces power consumption compared to the active mode by limiting functions; a peak hold circuit that holds a value of a maximum amplitude of the elastic wave detected by the one or more sensors at least during the sleep mode; The calculation unit is a signal processing device that, after transitioning to the operating mode, calculates information about the frequency distribution by amplitude scale using the maximum amplitude value of the elastic wave held in the peak hold circuit for a predetermined period.

13. a peak hold circuit that holds the maximum amplitude value of the elastic waves detected by each of one or more sensors that detects elastic waves generated from the structure; a wireless transmission unit that calculates information about the elastic wave using the maximum amplitude value of the elastic wave held by the peak hold circuit for a predetermined period, and wirelessly transmits the calculated information about the elastic wave to a structure evaluation device that evaluates the deterioration state of the structure; Equipped with The device has a plurality of modes, including an operating mode in which processing based on the elastic waves is performed, including processing for calculating information about the elastic waves, and a sleep mode in which power consumption is reduced compared to the operating mode by limiting functions, the peak hold circuit holds a value of a maximum amplitude of the elastic wave detected by the one or more sensors at least during the sleep mode; After transitioning to the operating mode, the signal processing device calculates information about the elastic wave using the maximum amplitude value of the elastic wave held by the peak hold circuit.

14. Calculating information about a frequency distribution by amplitude scale based on a plurality of elastic waves detected by one or more sensors that detect elastic waves generated from the structure; wirelessly transmitting information about the calculated amplitude frequency distribution; assessing a deterioration state of the structure based on the information on the frequency distribution by amplitude scale transmitted wirelessly; a signal processing device having a plurality of modes, an operating mode in which processing based on the frequency distribution by amplitude scale, including processing for calculating information about the frequency distribution by amplitude scale, and a sleep mode in which power consumption is reduced compared to the operating mode by limiting functions, the signal processing device having a peak hold circuit that holds a value of a maximum amplitude of the elastic wave detected by the one or more sensors at least during the sleep mode; After the signal processing device has transitioned to the operating mode, information about the frequency distribution by amplitude scale is calculated using the maximum amplitude value of the elastic wave held by the peak hold circuit for a predetermined period. Structural evaluation methods.

15. storing a value of the maximum amplitude of the elastic waves detected by each of one or more sensors that detects the elastic waves generated from the structure; Calculating information about the elastic wave using the stored maximum amplitude value of the elastic wave for a predetermined period; wirelessly transmitting the calculated information about the elastic wave; evaluating a deterioration state of the structure based on information about the elastic waves transmitted wirelessly; a signal processing device having a plurality of modes, an operating mode in which processing based on the elastic waves is performed, including processing for calculating information about the elastic waves, and a sleep mode in which power consumption is reduced compared to the operating mode by limiting functions, and a peak hold circuit provided in the signal processing device holds a value of a maximum amplitude of the elastic waves detected by the one or more sensors at least during the sleep mode; After the signal processing device has transitioned to the operating mode, the maximum amplitude value of the elastic wave held by the peak hold circuit is used for a predetermined period to obtain information about the elastic wave. Structural evaluation methods.

16. On the computer, a calculation step of calculating information about a frequency distribution by amplitude scale based on a plurality of elastic waves detected by one or more sensors that detect elastic waves generated from the structure; a wireless transmission step of wirelessly transmitting information about the frequency distribution by amplitude scale calculated in the calculation step to a structure evaluation device that evaluates the deterioration state of the structure; Let it run, A computer program for calculating information about the frequency distribution by amplitude scale using the maximum amplitude value of the elastic wave held in a peak hold circuit that holds at least the maximum amplitude value of the elastic wave detected by the one or more sensors for a predetermined period of time during a sleep mode, which is a mode in which power consumption is reduced compared to the operation mode by limiting functions, after the computer has transitioned to an operation mode in which processing based on the frequency distribution by amplitude scale, including processing to calculate information about the frequency distribution by amplitude scale, is performed.

17. On the computer, a calculation step of calculating information about the elastic waves using elastic waves detected by one or more sensors for detecting elastic waves generated from the structure for a predetermined period of time; a wireless transmission step of wirelessly transmitting information about the elastic waves calculated in the calculation step to a structure evaluation device that evaluates the deterioration state of the structure; Let it run, A computer program for calculating information about the elastic wave using the maximum amplitude value of the elastic wave held in a peak hold circuit that holds at least the maximum amplitude value of the elastic wave detected by the one or more sensors during a sleep mode, which is a mode that reduces power consumption compared to the operation mode by limiting functions, after the computer transitions to an operation mode in which processing based on the elastic wave is performed, including processing that calculates information about the elastic wave.

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