JP7739364B2 - Sensor terminal sheet and structural evaluation system - Google Patents

Description

Embodiments of the present invention relate to a sensor terminal sheet and a structure evaluation system.

In recent years, the aging of infrastructure structures has become a societal issue, making traditional manual maintenance difficult. Structural health monitoring using AE (Acoustic Emission) sensors has attracted attention as a solution to this issue. AE is an ultrasonic wave that occurs when an external force is applied to a material, causing deformation or damage. By installing multiple AE sensors on a structure, the location of the AE source can be determined based on the sensor's position information and the time difference between the AE waves reaching each sensor. This makes it possible to estimate the location of deformation or damage within the structure, enabling health diagnosis and efficient maintenance of the structure.

Conventionally used wired AE sensors require the installation of a large number of sensors, which presents challenges in terms of installation and wiring management. Particularly when monitoring high-altitude and large structures, installing, removing, and wiring AE sensors requires a great deal of effort. This contributes to increased maintenance costs. One effective way to simplify sensor installation and removal is to integrate the sensor array with an adhesive sheet, but because the sensor output is analog, there is a problem in that the amount of wiring increases proportionally as the number of sensors increases.

National Research and Development Agency, National Institute of Advanced Industrial Science and Technology, Dai Nippon Printing Co., Ltd., “Development of a sensor sheet capable of monitoring strain distribution in bridges,” [online], [Retrieved June 28, 2023], Internet <URL: https://www.dnp.co.jp/news/detail/1187697_1587.html> Ken Kobayashi and four others, "Development of a Bridge Sensing System Using Flexible Surface Pattern Sensors," pp. 20-23, [online], [Retrieved June 28, 2023], Internet <URL: https://www.nedo.go.jp/content/100888002.pdf >

The problem that this invention aims to solve is to provide a sensor terminal sheet and structure evaluation system that can suppress the increase in the amount of wiring that accompanies an increase in the number of sensors.

The sensor terminal sheet of this embodiment has multiple sensor terminals and a wiring bus. The multiple sensor terminals each have a sensor, a detection unit, and a communication unit. The sensor detects elastic waves. The detection unit extracts features of the elastic waves based on the elastic waves detected by the sensor. The communication unit transmits the features of the elastic waves extracted by the detection unit via serial communication. The wiring bus connects the multiple sensor terminals. The multiple sensor terminals are arranged at predetermined intervals on a sheet-like substrate and have a layered structure in which the sensor terminals and the wiring bus are laminated with a film.

FIG. 1 is a diagram showing a system configuration of a sensor terminal sheet according to an embodiment. FIG. 2 is a diagram showing an example of the configuration of a wiring bus according to the embodiment. FIG. 2 is a diagram showing an example of the configuration of a wiring bus according to the embodiment. FIG. 2 is a diagram showing an example of the configuration of a sensor terminal according to the embodiment. FIG. 1 is a diagram showing an example of the configuration of a structure evaluation system according to an embodiment. FIG. 1 is a diagram showing an example of the configuration of a structure evaluation device according to an embodiment. FIG. 10 is a diagram showing an example of the arrangement of a sensor terminal sheet in a modified example. FIG. 10 is a diagram showing an example of an arrangement of sensor terminals in a modified example.

The sensor terminal sheet and structure evaluation system of the embodiment will be described below with reference to the drawings.

Figure 1 shows the system configuration of a sensor terminal sheet 10 according to an embodiment. The sensor terminal sheet 10 is a sheet that can be adhered to a structure such as a bridge. In the following explanation, the structure is a bridge, but the structure does not have to be limited to bridges. The structure can be any structure that generates elastic waves due to the occurrence or progression of cracks or external impacts (e.g., rain, artificial rain, etc.). Note that bridges are not limited to structures built over rivers or valleys, but also include various structures built above ground level (e.g., highway viaducts).

The sensor terminal sheet 10 is composed of a substrate 15, multiple sensor terminals 20-1 to 20-n (n is an integer greater than or equal to 2), and a wiring bus 30. The substrate 15 is a flat, tape-like flexible substrate. Because the substrate 15 is flexible, the sensor terminal sheet 10 can be attached to curved structures. The sensor terminal sheet 10 can be wound onto a reel or the like, making it easy to transport and mount on mobile objects such as drones. The multiple sensor terminals 20-1 to 20-n and the wiring bus 30 are arranged on the substrate 15. For example, the multiple sensor terminals 20-1 to 20-n are arranged on the substrate 15 at predetermined intervals. The sensor terminal sheet 10 has a laminated structure in which the multiple sensor terminals 20-1 to 20-n and the wiring bus 30 are laminated with a film.

The sensor terminal sheet 10 has a laminated structure with multiple layers, including a release film, adhesive layer, base layer, conductive layer, insulating layer, and protective layer. The conductive layer may also have multiple layers. The sensor terminal sheet 10 is attached to a structure using an adhesive layer. To efficiently transmit elastic waves generated inside the structure to the sensors, it is desirable to use materials for the adhesive layer and base layer whose acoustic impedance matches the acoustic impedance of the structure. For example, insulating materials such as polyimide, PET, and Kapton may be used for the base film. The overall thickness of the sensor terminal sheet 10 is desirably several tens of microns to several millimeters. The spacing between the sensor terminals 20 on the sensor terminal sheet 10 is desirably several centimeters to 1 meter. Because each sensor terminal 20 is connected to the wiring bus 30 in a daisy chain configuration, the sensor terminal sheet 10 can be cut to any length needed.

Sensor terminals 20-1 to 20-n have a detection function for detecting elastic waves generated inside the structure in which the sensor terminal sheet 10 is installed, and a communication function for transmitting information about the detected elastic waves. In this embodiment, sensor terminals 20-1 to 20-n perform serial communication.

The wiring bus 30 is a bus for serial communication. The configuration of the wiring bus 30 will now be described in detail using Figures 2 and 3. Figures 2 and 3 are diagrams showing an example configuration of the wiring bus 30 in an embodiment. Figure 2 shows a configuration in which the wiring bus 30 has four wires L1 to L4, while Figure 3 shows a configuration in which the wiring bus 30 has five wires L1 to L5. The wiring bus 30 shown in Figure 2 is composed of four wires: a data signal SDA, a clock signal SCL, ground GND, and a power supply Vcc. Adding a Vcc wire makes it possible to incorporate a preamplifier into the sensor. The wiring bus 30 shown in Figure 3 is composed of five wires: SDA, SCL, GND, Vcc, and a reference pulse signal REF.

Figure 4 is a diagram showing an example configuration of a sensor terminal 20 in an embodiment. The sensor terminal 20 includes a sensor 21, a detection unit 22, and a communication unit 23.

The sensor 21 detects elastic waves generated from inside the structure on which the sensor terminal sheet 10 is installed. The sensor 21 is a piezoelectric MEMS (Micro Electro Mechanical Systems) sensor or a piezoelectric film-type sensor. Using a thin sensor such as a piezoelectric MEMS sensor or a piezoelectric film-type sensor as the sensor 21 makes it possible to integrate the sensor, sensor circuit, protective film, and adhesive sheet. Furthermore, by adopting a piezoelectric type sensor 21, a power supply to the sensor 21 is not required during sensing, thereby achieving power savings and simplification of the sensor terminal 20. By peeling off the release film and attaching the sensor terminal sheet 10 to the structure, the amount of work required to install the sensor terminal 20 can be significantly reduced. The sensor 21 converts the detected elastic waves into an electrical signal and outputs it.

The detection unit 22 extracts features of the elastic waves based on the elastic waves detected by the sensor 21. Furthermore, the detection unit 22 calculates the arrival time of the elastic waves at the sensor 21. The detection unit 22 is composed of an amplifier 221, a filter 222, an AD converter 223, and a signal processing unit 224.

The amplifier 221 amplifies the electrical signal output from the sensor 21. The amplifier 221 amplifies the electrical signal to a level that allows it to be processed, for example, by the AD converter 223. The amplifier 221 outputs the amplified electrical signal to the filter 222.

The filter 222 removes noise components outside a specified band. The filter 222 is, for example, a band pass filter (BPF). The electrical signal from which noise has been removed by the filter 222 is input to the AD converter 223.

The AD converter 223 quantizes the noise-removed electrical signal and converts it into a digital signal. The AD converter 223 outputs the digital signal to the signal processing unit 224.

The signal processing unit 224 receives the digital signal output from the AD converter 223 as input. The signal processing unit 224 performs signal processing on the input digital signal. The signal processing performed by the signal processing unit 224 includes, for example, extracting elastic wave features and calculating the arrival time of the elastic wave. The signal processing unit 224 outputs information relating to the elastic wave features and arrival time obtained by the signal processing to the communication unit 23. When outputting the information relating to the elastic wave features and arrival time obtained by the signal processing, the signal processing unit 224 associates a sensor ID with the information. The sensor ID represents identification information for identifying the sensor terminal 20.

The signal processing unit 224 is configured using an analog circuit or a digital circuit. Note that if the signal processing unit 224 is configured using an analog circuit, the AD converter 223 does not need to be provided between the sensor 21 and the signal processing unit 224. In other words, if the signal processing unit 224 is configured using an analog circuit, an electrical signal from which noise has been removed by the filter 222 is input to the signal processing unit 224. The digital circuit is realized, for example, by an FPGA (Field Programmable Gate Array) or a microcomputer. The digital circuit may also be realized by a dedicated LSI (Large-Scale Integration). The signal processing unit 224 may be equipped with non-volatile memory such as flash memory, or removable memory. The following explanation will be given for the case where the signal processing unit 224 is configured using a digital circuit.

Feature quantities of elastic waves include, for example, the waveform amplitude [mV], waveform rise time [usec], gating signal duration [usec], zero-cross count number [times], waveform energy [arb.], frequency [Hz], and RMS (Root Mean Square) value. The waveform amplitude is, for example, the maximum amplitude value of the noise removal signal. The waveform rise time is, for example, the time T1 from when the gating signal starts to rise until the noise removal signal reaches its maximum value. The gating signal duration is, for example, the time from when the gating signal starts to rise until the amplitude becomes smaller than a predetermined value. The zero-cross count number is, for example, the number of times the noise removal signal crosses a reference line that passes through a zero value.

The energy of the waveform is, for example, the value obtained by integrating over time the squared amplitude of the noise-removed signal at each point in time. Note that the definition of energy is not limited to the above example, and may be approximated using, for example, the envelope of the waveform. The frequency is the frequency of the noise-removed signal. The RMS value is, for example, the value obtained by squaring the amplitude of the noise-removed signal at each point in time and taking the square root.

The communication unit 23 performs serial communication with other sensor terminals 20 or external devices. The communication unit 23 transmits, for example, elastic wave feature values extracted by the detection unit 22 and information related to the arrival time to an external device via serial communication. If the sensor terminal 20 is a master terminal, the communication unit 23 transmits information related to the time obtained by the sensor terminal 20 itself to other sensor terminals 20 via the wiring bus 30. If the sensor terminal 20 is not a master terminal, the communication unit 23 receives information related to the time transmitted from the sensor terminal 20 that is the master terminal via the wiring bus 30. The communication unit 23 employs the I2C (Inter-Integrated Circuit) method, a type of clock-synchronized serial communication. I2C is a communication method that transmits data one bit at a time in sequence using a single signal line. Digitally processing the output of the sensor 21 for serial communication solves the problem of increased wiring due to an increase in the number of sensors. This easily reduces wiring and space requirements throughout the device.

In order to accurately determine the location of the source of elastic waves based on the elastic waves detected by the sensors 21 provided in each sensor terminal 20, it is necessary to accurately determine the time difference between the elastic waves arriving at each sensor terminal 20. Digitally processing the output of the sensor 21 for serial communication can avoid increasing the number of lines, but this makes the time synchronization required for positioning more difficult. There are two possible methods for time synchronization. The first method is a method in which an external relay device performs time synchronization by transmitting a reference signal containing information about the time to each sensor terminal 20. The second method is a method in which sensor terminals 20 other than the master terminal perform time synchronization based on the output signal of the sensor terminal 20 that is the master terminal among the multiple sensor terminals 20 provided on the sensor terminal sheet 10.

The first method can be implemented when the wiring bus 30 has four wires as shown in Figure 2. In the first method, an external relay device transmits a reference signal containing time information to each sensor terminal 20, and each sensor terminal 20 can use the reference signal to determine the arrival time difference of the elastic waves at each sensor terminal 20. However, because the source of the elastic waves and the timing of their generation are unknown, the relay device must continue to send the reference signal at regular time intervals. This may result in a high load on the entire system.

The second method can be implemented when the wiring bus 30 has five wires as shown in Figure 3. In the second method, one sensor terminal 20 (e.g., sensor terminal 20-1) is arbitrarily selected from among the multiple sensor terminals 20 and set as the master terminal. The elastic waves detected by sensor terminal 20-1 (e.g., the amplitude of the digitized elastic waves) are transmitted as time information to the sensor terminals 20 other than the master terminal via the reference pulse signal REF on the wiring bus 30.

The signal processing unit 224 of each sensor terminal 20 other than the master terminal calculates the arrival time of the elastic wave at each sensor terminal 20 based on the time difference between the rising edge of the elastic wave hit gate, which indicates the arrival timing of the detected elastic wave, and information related to the time information (reference pulse signal). The time difference can be measured by counting the interval between the rising edges of two gate signals using clocks. Another time difference measurement method may be a TDC (Time-To-Digital Converter), which measures the time difference between two gate signals with high precision based on the propagation delay of the logic gates. The TDC calculates the time difference by taking the logical OR of the start pulse and stop pulse that have passed through multiple stages of logic gates, and calculating the time difference by multiplying the number of delay gates whose output has changed by the delay time per gate. The delay time per gate is, for example, on the order of 10 ps, allowing for highly accurate time difference measurement.

The sensor terminal sheet 10 configured as described above can suppress an increase in the number of wiring required as the number of sensors increases. Specifically, the sensor terminal sheet 10 includes multiple sensor terminals 20 and a wiring bus 30. Each of the multiple sensor terminals 20 includes a sensor 21, a detection unit 22, and a communication unit 23. The sensor 21 detects elastic waves. The detection unit 22 extracts elastic wave features based on the elastic waves detected by the sensor 21. The communication unit 23 transmits the elastic wave features extracted by the detection unit 22 via serial communication. The wiring bus 31 connects the multiple sensor terminals 20 together. The multiple sensor terminals 20 are arranged at predetermined intervals on a sheet-like substrate 15 and have a laminated structure in which the sensor terminals 20 and the wiring bus 30 are laminated with film. In this way, the sensor terminal sheet 10 digitally processes the output of the sensor terminals 20 and transmits it via serial communication. This suppresses an increase in the number of wiring required as the number of sensors increases. Furthermore, the number of wires in the entire device can be reduced, allowing for a smaller sensor terminal sheet 10.

Furthermore, the sensor terminal sheet 10 makes it easy to install sensors by integrating multiple sensor terminals 20 with an adhesive sheet.

(System using the sensor terminal sheet 10)
Next, a structure evaluation system 100 using the above-described sensor terminal sheet 10 will be described. Fig. 5 is a diagram showing an example of the configuration of the structure evaluation system 100 in an embodiment. The structure evaluation system 100 is used to evaluate the soundness of a structure. In the following description, evaluation means determining the degree of soundness of a structure, i.e., the state of deterioration of a structure, based on a certain criterion.

Damage that affects the assessment of a structure's deterioration state includes damage inside the structure that interferes with the propagation of elastic waves 11, such as cracks, cavities, and sedimentation. Here, cracks include vertical cracks, horizontal cracks, and diagonal cracks. Vertical cracks are cracks that occur in a direction perpendicular to the road surface. Horizontal cracks are cracks that occur horizontally to the road surface. Diagonal cracks are cracks that occur in a direction other than horizontal or vertical to the road surface. Sedimentation is deterioration in which concrete turns into sediment, mainly at the boundary between the asphalt and concrete deck.

The structure evaluation system 100 comprises multiple sensor terminal sheets 10-1 to 10-m (m is an integer greater than or equal to 2), multiple relay devices 60-1 to 60-m, and a structure evaluation device 70. The multiple sensor terminal sheets 10-1 to 10-m and the multiple relay devices 60-1 to 60-m are connected via connectors 50-1 to 50-m. The multiple relay devices 60-1 to 60-m and the structure evaluation device 70 are connected wirelessly.

Each sensor terminal 20-1-1 to 20-1-n is linked to relay device 60-1 via wiring bus 30-1. Each sensor terminal 20-m-1 to 20-m-n is linked to relay device 60-m via wiring bus 30-m. Each sensor terminal 20-1-1 to 20-1-n, 20-m-1 to 20-m-n transmits data containing the extracted elastic wave features (at least the elastic wave amplitude) and information regarding the elastic wave arrival time to relay devices 60-1 to 60-m via I2C communication.

The relay devices 60-1 to 60-m transfer the transmission data obtained from each of the sensor terminals 20-1-1 to 20-1-n, 20-m-1 to 20-m-n to the structure evaluation device 70 via wireless communication. It is desirable that the relay devices 60-1 to 60-m include at least a first communication unit, a second communication unit, and a memory. The first communication unit performs I2C communication with each of the sensor terminals 20. The second communication unit performs wireless communication with the structure evaluation device 70. The memory temporarily stores the transmission data.

The structure evaluation device 70 analyzes the transmission data collected from the relay devices 60-1 to 60-m and estimates the state and location of deterioration of the structure. This enables the diagnosis of the structure's health and efficient maintenance and management. An address is assigned to each sensor terminal 20, and data is sent and received between the sensor terminal 20 designated by the master. This allows the usage interval of the sensor terminal to be adjusted to an integer multiple of the sensor placement interval. Sensor terminals 20 that do not have an address assigned can also be used as spare sensor terminals.

Figure 6 is a diagram showing an example configuration of a structure evaluation device 70 in an embodiment. The structure evaluation device 70 includes a communication unit 71, a control unit 72, a memory unit 73, and a display unit 74. The communication unit 71 receives one or more pieces of transmission data transferred from each relay device 60.

The control unit 72 controls the entire structure evaluation device 70. The control unit 72 is configured using a processor such as a CPU (Central Processing Unit) and memory. By executing a program, the control unit 72 functions as an acquisition unit 721, an event extraction unit 722, a position determination unit 723, a distribution generation unit 724, and an evaluation unit 725.

Some or all of the functional units of the acquisition unit 721, event extraction unit 722, position determination unit 723, distribution generation unit 724, and evaluation unit 725 may be implemented by hardware such as an ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), 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 (Read Only Memory), and CD-ROMs, as well as non-transitory storage media such as hard disks built into computer systems. The program may also be transmitted via telecommunications lines.

Some of the functions of the acquisition unit 721, event extraction unit 722, position determination unit 723, distribution generation unit 724, and evaluation unit 725 do not need to be pre-installed in the structure evaluation device 70, and may be realized by installing additional application programs in the structure evaluation device 70.

The acquisition unit 721 acquires various information. For example, the acquisition unit 721 acquires transmission data received by the communication unit 71. The acquisition unit 721 acquires transmission data for the evaluation period. The acquisition unit 721 stores the acquired transmission data in the storage unit 73.

The event extraction unit 722 extracts transmission data for one event from the transmission data for the evaluation period stored in the memory unit 73. An event refers to an elastic wave generating event that occurs in a structure. In this embodiment, the elastic wave generating event is a vehicle passing over the road surface. When one event occurs, elastic waves are detected at approximately the same time by multiple sensors 21. In other words, the memory unit 73 stores transmission data related to elastic waves detected at approximately the same time. Therefore, the event extraction unit 722 sets a predetermined time window and extracts all transmission data whose arrival time falls within the range of the time window as transmission data for one event. The event extraction unit 722 outputs the extracted transmission data for one event to the positioning unit 723.

The time window range Tw may be determined using the elastic wave propagation velocity v in the target structure and the maximum sensor spacing dmax so that it is in the range Tw ≥ dmax/v. To avoid erroneous detection, it is desirable to set Tw to as small a value as possible, so in practice Tw = dmax/v can be used. The elastic wave propagation velocity v may be determined in advance.

The positioning unit 723 locates the position of the elastic wave source based on the sensor position information and the sensor ID and time information contained in each of the multiple transmission data extracted by the event extraction unit 722.

The sensor position information includes information about the installation position of the sensor terminal 20, associated with the sensor ID. The sensor position information includes information about the installation position of the sensor terminal 20, such as latitude and longitude, or horizontal and vertical distances from a reference position of the structure. The positioning unit 723 stores the sensor position information in advance. The sensor position information may be stored in the positioning unit 723 at any time before the positioning unit 723 performs positioning of the elastic wave source.

The sensor position information may be stored in the memory unit 73. In this case, the positioning unit 723 acquires the sensor position information from the memory unit 73 when positioning is performed. A Kalman filter, least squares method, or the like may be used to locate the position of the elastic wave source. The positioning unit 723 outputs the position information of the elastic wave source obtained during the evaluation period to the distribution generation unit 724.

The distribution generation unit 724 receives as input the position information of the multiple elastic wave sources output from the position determination unit 723. The distribution generation unit 724 uses the input position information of the multiple elastic wave sources to generate an elastic wave source distribution. The elastic wave source distribution represents a distribution showing the positions of the elastic wave sources. More specifically, the elastic wave source distribution is a distribution in which points indicating the positions of the elastic wave sources are shown on virtual data representing the structure to be evaluated, with the horizontal axis representing the distance in the traffic direction and the vertical axis representing the distance in the width direction.

The distribution generation unit 724 generates an elastic wave source density distribution using the elastic wave source distribution. The elastic wave source density distribution represents a distribution in which density values calculated according to the number of elastic wave sources included in each predetermined region in the elastic wave source distribution are indicated. Specifically, the distribution generation unit 724 first divides the elastic wave source distribution into multiple regions by dividing it into predetermined sections. Next, the distribution generation unit 724 calculates the density of each region by dividing the number of elastic wave sources located within the region by the area of the region. The distribution generation unit 724 then generates an elastic wave source density distribution by assigning the calculated density value for each region to each region. In this way, the distribution generation unit 724 generates an elastic wave source density distribution by calculating the density for the region to be evaluated.

The evaluation unit 725 evaluates the deterioration state of the structure in which the sensor terminal sheet 10 is installed, using the elastic wave source density distribution generated by the distribution generation unit 724. For example, the evaluation unit 725 evaluates areas in the elastic wave source density distribution where the density of elastic wave sources is equal to or greater than a threshold as healthy areas, and evaluates areas where the density of elastic wave sources is less than the threshold as damaged areas.

The storage unit 73 stores transmission data for the evaluation period acquired by the acquisition unit 721. The storage unit 43 is configured using a storage device such as a magnetic hard disk drive or semiconductor storage device.

The display unit 74 displays the evaluation results under the control of the evaluation unit 725. For example, the display unit 74 may display the corrected elastic wave source density distribution as the evaluation result, or may display areas that appear to be damaged in a different display format from other areas. The display unit 74 is an image display device such as a liquid crystal display or an organic EL (Electro Luminescence) display. The display unit 74 may also be an interface for connecting the image display device to the structure evaluation device 70. In this case, the display unit 74 generates a video signal for displaying the evaluation results and outputs the video signal to the image display device connected to it.

(Variation 1)
In the above-described embodiment, the multiple sensor terminals 20 included in the sensor terminal sheet 10 are arranged in a row, but there are no particular limitations on the arrangement of the multiple sensor terminals 20 included in the sensor terminal sheet 10. For example, the multiple sensor terminals 20 included in the sensor terminal sheet 10 may be arranged in a radial, annular, or polygonal shape.

(Variation 2)
In the above-described embodiment, the sensor terminal sheets 10 are arranged one-dimensionally, but the sensor terminal sheets 10 may also be arranged two-dimensionally. FIG. 7 is a diagram showing an example of an arrangement of the sensor terminal sheets 10 in a modified example. In the example shown in FIG. 7, multiple sensor terminal sheets 10-1 to 10-m are connected to one relay device 60 via a wiring cable 75. This configuration makes it possible to reduce the number of relay devices 60. Although not shown in FIG. 7, the arrangement of the sensor terminal sheets 10-1 to 10-m is not limited to the arrangement shown in FIG. 7, and they may also be arranged in a radial, circular, or polygonal shape.

(Variation 3)
In the above-described embodiment, the sensor terminals 20 are arranged one-dimensionally, but the sensor terminals 20 may be arranged two-dimensionally. FIG. 8 is a diagram showing an example of an arrangement of the sensor terminals 20 in a modified example. In the example shown in FIG. 8, a set of multiple sensor terminals 20 is arranged in parallel on the substrate 15 provided on one sensor terminal sheet 10. This configuration makes it easier to arrange the sensor terminals 20 and also makes it possible to reduce the number of relay devices 60. Note that, although not shown in FIG. 8, the arrangement of the sensor terminals 20 provided on the sensor terminal sheet 10 is not limited to the arrangement shown in FIG. 8, and the sensor terminals 20 may be arranged in a radial, circular, or polygonal shape.

(Variation 4)
In the above-described embodiment, the resonant frequencies of the sensors 21 included in each of the plurality of sensor terminals 20 may be the same, or at least some of the sensors 21 may have different resonant frequencies.

The following notes are provided regarding the sensor terminal sheet 10 shown in this embodiment.
(Additional Note)
The following notes are disclosed:
a sensor (e.g., sensor 21) that detects elastic waves; and a detection unit (e.g., detection unit 22) that extracts a feature of the elastic waves based on the elastic waves detected by the sensor.
a communication unit (e.g., a communication unit 23) that transmits the feature amount of the elastic wave extracted by the detection unit via serial communication;
A sensor terminal (for example, the sensor terminal 20) comprising:

According to at least one embodiment described above, the sensor terminal sheet 10 has multiple sensor terminals 20 and a wiring bus 30. The multiple sensor terminals 20 each have a sensor 21, a detection unit 22, and a communication unit 23. The sensor 21 detects elastic waves. The detection unit 22 extracts elastic wave features based on the elastic waves detected by the sensor 21. The communication unit 23 transmits the elastic wave features extracted by the detection unit 22 via serial communication. The wiring bus 31 connects the multiple sensor terminals 20 together. The multiple sensor terminals 20 are arranged at predetermined intervals on a sheet-like substrate 15, and by having a laminated structure in which the sensor terminals 20 and the wiring bus 30 are laminated with film, an increase in the number of wires associated with an increase in the number of sensors can be suppressed.

While 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 may be embodied in a variety of other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are within the scope of the invention and its equivalents as defined in the claims, as well as the scope and spirit of the invention.

10, 10-1 to 10-m...sensor terminal sheet, 15...board, 20, 20-1 to 20-n, 20-1-1 to 20-1-n, 20-m-1 to 20-m-n...sensor terminal, 21...sensor, 22...detection unit, 23...communication unit, 30, 30-1 to 30-m...wiring bus, 50, 50-1 to 50-m...connector, 60, 60-1 to 60-m...relay device, 70...structure evaluation device, 221...amplifier, 222...filter, 223...AD converter, 224...signal processing unit

Claims (10)

a sensor for detecting elastic waves;
a detection unit that extracts a feature amount of the elastic wave based on the elastic wave detected by the sensor;
a communication unit that transmits the feature amount of the elastic wave extracted by the detection unit via serial communication;
a plurality of sensor terminals each including
a wiring bus connecting the plurality of sensor terminals;
Equipped with
The sensor terminal sheet has a laminated structure in which the plurality of sensor terminals are arranged at predetermined intervals on a sheet-like substrate and are laminated together with the wiring bus with a film. any one of the plurality of sensor terminals is designated as a master terminal, and a detection unit of the sensor terminal designated as the master terminal determines an arrival time of the elastic wave, and outputs a reference pulse signal including information on the determined arrival time of the elastic wave to the sensor terminals other than the master terminal via the wiring bus.
The sensor terminal sheet according to claim 1 . The detection unit included in the sensor terminal other than the master terminal further
calculating the arrival time of the elastic wave based on the time difference between a rise time indicating the arrival timing of the elastic wave detected by the device itself and a time indicated by information on the arrival time of the elastic wave included in the reference pulse signal;
The sensor terminal sheet according to claim 2 . the communication unit included in each of the plurality of sensor terminals transmits the feature amount of the elastic wave extracted by the detection unit and information related to the arrival time of the elastic wave to an external device via a relay device.
The sensor terminal sheet according to claim 3 . The laminated structure is composed of a release film, an adhesive layer, a base layer, a conductive layer, an insulating layer, and a protective layer, and the conductive layer is composed of one or more layers.
The sensor terminal sheet according to claim 1 or 2. The acoustic impedance of the adhesive layer and the base layer is matched to the acoustic impedance of a structure in which the plurality of sensor terminals are installed.
The sensor terminal sheet according to claim 5 . the plurality of sensor terminals are arranged one-dimensionally or two-dimensionally on the sheet-like substrate;
The sensor terminal sheet according to claim 1 or 2. the sensor included in each of the plurality of sensor terminals is a piezoelectric MEMS (Micro Electro Mechanical Systems) sensor or a piezoelectric film type sensor;
The sensor terminal sheet according to claim 1 or 2. Some of the sensors included in each of the plurality of sensor terminals have different resonant frequencies,
The sensor terminal sheet according to claim 1 or 2. The sensor terminal sheet according to claim 1 or 2;
one or more relay devices that receive transmission data including at least the feature quantity of the elastic wave obtained by the sensor terminal sheet from the sensor terminal sheet via the serial communication and transfer the received transmission data;
a structure evaluation device that evaluates a deterioration state of the structure in which the sensor terminal sheet is installed based on the transmission data transferred from the one or more relay devices; and
A structural evaluation system comprising: