Sensor system, transmitting terminal, and transmitting method

Abstract

The objective is to provide a sensor system, a transmitting terminal, and a transmitting method that can suppress the decrease in time estimation accuracy. [Solution] The sensor system of the embodiment comprises one or more sensors, one or more transmitting terminals, and a data collection device. The one or more transmitting terminals comprises a first communication unit and a second communication unit. The first communication unit wirelessly transmits first transmission data, which includes time information used for time estimation, to the data collection device. The second communication unit wirelessly transmits second transmission data, which includes information obtained based on the physical quantities detected by one or more sensors, to the data collection device at a frequency different from the frequency used by the first communication unit. The data collection device comprises a reception time determination unit and a time information processing unit. The reception time determination unit determines the reception time of a plurality of the first transmission data transmitted from the first communication unit. The time information processing unit performs time estimation based on the plurality of the first transmission data and the plurality of reception times.

Description

Technical Field

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

Background Art

[0002] In recent years, due to the power saving and cost reduction of sensors and the development of networks, it has become possible to collect various sensing data. Therefore, there has been an active movement to utilize sensing data. One method of utilizing sensing data is structural health monitoring. Structural health monitoring is a technology that senses physical quantities such as displacement, vibration, and pressure by sensors installed in structures such as bridges, and diagnoses the damage and deterioration state of the structure by various signal processing methods.

[0003] Conventionally, sensing data has been measured by connecting sensors by wire, but wired connection is complicated in installation and management, and has limitations in flexibility and expandability. Therefore, a method of wirelessly transmitting sensing data obtained by sensors by a transmission terminal has been studied. In the case of a system including a plurality of terminal devices using a wireless network, since there are a plurality of clocks, time synchronization is required. Therefore, conventionally, a time estimation method shown in Patent Document 1 has been proposed.

[0004] In the method shown in Patent Document 1, time estimation is performed on the collection device side based on the transmission time included in each of a plurality of transmission data transmitted from the transmission terminal and the reception time of each of the plurality of transmission data. Thereby, the problem of time synchronization can be solved. When transmitting sensing data wirelessly, due to the limitation of the communication bandwidth, data is compressed. For example, data is compressed by transmitting only the feature amount obtained from the sensing data.

[0005] Thus, in conventional structural health monitoring, wireless transmission of AE data typically involves transmitting data with specific features. However, for detailed analysis, waveform data is also necessary in addition to features. Waveform data is much larger in volume than features, making it difficult to transmit large amounts of data when the number of sensors or AE hits is high. Furthermore, conventional time estimation methods require correlating transmission and reception times, making them unsuitable for transmitting waveform data, which takes a long time to transmit, and sometimes resulting in reduced time estimation accuracy. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-13141 [Overview of the project] [Problems that the invention aims to solve]

[0007] The problem that this invention aims to solve is to provide a sensor system, a transmitting terminal, and a transmitting method that can suppress a decrease in time estimation accuracy. [Means for solving the problem]

[0008] The sensor system of the embodiment includes one or more sensors, one or more transmitting terminals, and a data collection device. The one or more sensors detect physical quantities. The one or more transmitting terminals are connected to the one or more sensors. The data collection device collects information transmitted from the one or more transmitting terminals. The one or more transmitting terminals include a first communication unit and a second communication unit. The first communication unit wirelessly transmits first transmission data, which includes time information used for time estimation, to the data collection device. The second communication unit wirelessly transmits second transmission data, which includes information obtained based on the physical quantities detected by the one or more sensors, to the data collection device at a frequency different from the frequency used by the first communication unit. The data collection device includes a reception time determination unit and a time information processing unit. The reception time determination unit determines the reception time of a plurality of the first transmission data transmitted from the first communication unit. The time information processing unit performs time estimation based on the plurality of the first transmission data and the plurality of reception times. [Brief explanation of the drawing]

[0009] [Figure 1] A diagram showing the system configuration of the sensor system in the first embodiment. [Figure 2] A schematic block diagram illustrating the functions of the transmitting terminal in the first embodiment. [Figure 3] A schematic block diagram showing the internal configuration of the signal processing unit in the first embodiment. [Figure 4] A schematic block diagram illustrating the function of the collection device in the first embodiment. [Figure 5] A diagram illustrating the time processing in the first embodiment. [Figure 6] A diagram illustrating the time processing in the first embodiment. [Figure 7] A sequence diagram showing the processing flow performed by the sensor system in the first embodiment. [Figure 8] A diagram showing the system configuration of the sensor system in the second embodiment. [Figure 9] A schematic block diagram illustrating the function of the collection device in the second embodiment. [Figure 10]A sequence diagram showing the processing flow performed by the sensor system in the second embodiment. [Modes for carrying out the invention]

[0010] The sensor system, transmission terminal, and transmission method of the embodiment will be described below with reference to the drawings.

[0011] (First Embodiment) Figure 1 shows the system configuration of the sensor system 100 in the first embodiment. The sensor system 100 comprises a sensor 10, a transmitting terminal 20, and a data collection device 30. The sensor 10 and the transmitting terminal 20 are connected by a wire. The transmitting terminal 20 and the data collection device 30 are connected wirelessly via networks 40-1 and 40-2. Networks 40-1 and 40-2 are networks with different wireless standards. Network 40-1 is an ISM (Industrial, Scientific and Medical band) network that can utilize frequencies such as the 920 MHz band. Network 40-2 is a network that can utilize frequencies such as the 2.4 GHz band and the 5 GHz band. Figure 1 shows a configuration in which the sensor system 100 comprises one sensor 10 and one transmitting terminal 20, but the sensor system 100 may comprise multiple sensors 10 and multiple transmitting terminals 20.

[0012] Sensor 10 is a sensor that detects a physical quantity. Sensor 10 can be, for example, an AE (Acoustic Emission) sensor, an acceleration sensor, a microphone, or a temperature sensor. Sensor 10 may be any other sensor that can detect a physical quantity. Sensor 10 converts the detected physical quantity into an electrical signal. Sensor 10 transmits the electrical signal to the transmitting terminal 20.

[0013] In the following explanation, we will use the example of a sensor 10 that detects elastic waves generated from inside a structure, but the same process will be performed for other types of sensors. Sensor 10 is installed in the structure. Sensor 10 is installed in a position where it can detect elastic waves. For example, sensor 10 is installed on one of the surfaces of the structure: the surface, side, or bottom. Sensor 10 converts the detected elastic waves into an electrical signal, which is a voltage signal. Sensor 10 uses, for example, a piezoelectric element with sensitivity in the range of 10 kHz to 1 MHz. Sensor 10 can be of any type, such as a piezoresistive type that utilizes the piezoresistive effect, a capacitive type that utilizes the change in capacitance, or a piezoelectric type that utilizes the piezoelectric effect.

[0014] In the following explanation, a concrete bridge will be used as an example of a structure, but the structure is not limited to bridges. Any structure that generates elastic waves due to the occurrence or propagation of cracks, or external impacts (e.g., rain, artificial rain, etc.) is acceptable. For example, the structure may be bedrock. Furthermore, the term "bridge" is not limited to structures built over rivers or valleys, but also includes various structures built above ground level (e.g., elevated highways).

[0015] The transmitting terminal 20 is equipped with multiple wireless communication units and communicates wirelessly with the data collection device 30. The multiple wireless communication units include, for example, a first communication unit and a second communication unit. The first communication unit transmits first transmission data to the data collection device 30, which includes at least time information used for time estimation in the data collection device 30. The first communication unit may also transmit feature quantities based on elastic waves detected by the sensor 10 to the data collection device 30. The second communication unit transmits second transmission data to the data collection device 30, which includes predetermined data. Here, the predetermined data is, for example, waveform data of elastic waves detected by the sensor 10.

[0016] The communication speed of the second communication unit is equal to or higher than that of the first communication unit. The first communication unit and the second communication unit may use different frequencies of the same wireless standard, or may use different wireless standards. In the following description, a case where the first communication unit performs wireless communication using the 920 MHz band and the second communication unit performs wireless communication using Wi-Fi (registered trademark) will be described as an example. Note that this is just an example, and any wireless standard may be used as long as the communication speed of the second communication unit is equal to or higher than that of the first communication unit.

[0017] The transmission terminal 20 detects an event based on, for example, an electrical signal output from the sensor 10, and transmits first transmission data including at least either the occurrence time of the detected event (hereinafter referred to as the "event detection time") or the transmission time to the collection device 30 via the first communication unit. Here, an event represents an event that occurs outside or inside the device. In the following embodiments, the event will be described by taking an event that occurs outside the device (for example, detection of an elastic wave) as an example. The transmission time is the time when the transmission terminal 20 transmits the first transmission data to the collection device 30.

[0018] In addition, the transmission terminal 20 attaches the event detection time or the transmission time, or unique identification information to the second transmission data and transmits it to the collection device 30 via the second communication unit. The event detection time or the transmission time, or unique identification information is used to associate the first transmission data and the second transmission data transmitted based on the elastic wave generated by the same event. As described above, in the transmission terminal 20, the first transmission data and the second transmission data are transmitted by different communication units. Therefore, in the collection device 30, it is necessary to associate the first transmission data and the second transmission data based on the elastic wave generated by the same event. For this purpose, the event detection time or the transmission time, or unique identification information is used. Note that when the second transmission data includes unique identification information, the first transmission data also needs to include unique identification information.

[0019] The data collection device 30 collects the first transmission data and the second transmission data transmitted from the transmitting terminal 20. The data collection device 30 collects multiple transmission times and multiple event detection times for each sensor 10 from a single transmitting terminal 20. The data collection device 30 performs processing based on the collected multiple transmission times, multiple event detection times, and the reception time corresponding to each transmission time. The reception time corresponding to the transmission time is the time when the first transmission data, which contains information about the transmission time transmitted from the transmitting terminal 20, is received.

[0020] Furthermore, the data collection device 30 associates the first and second transmission data received at different times. Specifically, the data collection device 30 associates the first and second transmission data based on either the event detection time or transmission time included in the first transmission data, or unique identification information, and either the event detection time or transmission time included in the second transmission data, or unique identification information.

[0021] (Configuration of transmitting terminal 20) Figure 2 is a schematic block diagram showing the functions of the transmitting terminal 20 in the first embodiment. The transmitting terminal 20 includes a receiving unit 21, a BPF 22, an analog-to-digital conversion unit 23, a filter 24, a clock oscillator 25, a time information generation unit 26, a signal processing unit 27, a first communication unit 28, and a second communication unit 29.

[0022] The receiving unit 21 receives the electrical signal output from the sensor 10. This allows the receiving unit 21 to acquire the elastic wave detected by the sensor 10. The receiving unit 21 then outputs the received electrical signal to the BPF 22.

[0023] The BPF22 removes noise from the electrical signal received by the receiver 21. The BPF22 is a bandpass filter for removing noise. The BPF22 outputs the noise-removed signal to the analog-to-digital conversion unit 23.

[0024] The analog-to-digital conversion unit 23 converts the denoised signal output from the BPF 22 into a digital signal by quantizing it. The analog-to-digital conversion unit 23 outputs the digital signal to the filter 24.

[0025] Filter 24 removes noise from the digital signal output from the analog-to-digital conversion unit 23. Filter 24 is a digital filter for removing noise. Filter 24 outputs the digital signal after noise removal to the signal processing unit 27.

[0026] In the following description, the processing performed by the receiving unit 21, BPF 22, analog-to-digital conversion unit 23, and filter 24 will be referred to as preprocessing.

[0027] The clock oscillator 25 generates a clock signal. Specifically, the clock oscillator 25 determines the time interval of 1 second at the transmitting terminal 20. The clock oscillator 25 is configured using, for example, a voltage-variable crystal oscillator such as a VCXO (Voltage-controlled crystal oscillator). The clock oscillator 25 outputs the clock signal to the time information generation unit 26.

[0028] The time information generation unit 26 determines the time at the transmitting terminal 20 according to the clock signal output from the clock oscillator 25. The time information generation unit 26 is, for example, a counter with registers. That is, the time information generation unit 26 counts the edges of the clock signal and stores the cumulative count value from the time the transmitting terminal 20 is powered on as time information in the registers.

[0029] The signal processing unit 27 determines the event detection time and transmission time based on the denoised digital signal output from the filter 24 and the time information generated by the time information generation unit 26. The event detection time may be, for example, a number of clock cycles, or it may be a specific number of hours, minutes, and seconds.

[0030] The signal processing unit 27 is configured using digital circuits. These digital circuits can be implemented, for example, by an FPGA (Field Programmable Gate Array) or a microcomputer. The digital circuits may also be implemented by a dedicated LSI (Large-Scale Integration). The signal processing unit 27 may also incorporate non-volatile memory such as flash memory or removable memory.

[0031] The first communication unit 28 is a communication interface that communicates with the data collection device 30 via the network 40-1. The first communication unit 28 transmits first transmission data, which includes at least one of the event detection time or transmission time determined by the signal processing unit 27, to the data collection device 30 via wireless communication at a first timing. The first transmission data may include characteristics of elastic waves. The first timing may be, for example, the time determined by the signal processing unit 27, or it may be the time after a predetermined period of time has elapsed since the first transmission.

[0032] The radio frequency band used for communication by the first communication unit 28 is, for example, the 920 MHz band. The first communication unit 28 can also transmit at appropriate timings, such as by transmitting the event detection time and transmission time together, or by transmitting the event detection time and transmission time separately.

[0033] The second communication unit 29 is a communication interface that communicates with the acquisition device 30 via the network 40-2. The second communication unit 29 transmits second transmission data, which includes predetermined data output from the signal processing unit 27, to the acquisition device 30 via wireless communication at a second timing. The predetermined data may be, for example, waveform information of elastic waves. The second timing may be, for example, a time determined by the signal processing unit 27, or it may be the timing when the acquisition device 30 requests the transmission of the predetermined data.

[0034] The radio frequency band used for communication by the second communication unit 29 is, for example, the 2.4 GHz or 5 GHz band. As mentioned above, the communication speed of the second communication unit 29 is equal to or greater than the communication speed of the first communication unit 28. Furthermore, if the first communication unit 28 and the second communication unit 29 use different frequencies of the same radio standard, the first communication unit 28 and the second communication unit 29 can communicate wirelessly with the data collection device 30 via the same network 40-1.

[0035] (Configuration of signal processing unit 27) Figure 3 is a schematic block diagram showing the internal configuration of the signal processing unit 27 in the first embodiment. The signal processing unit 27 consists of an event signal generation unit 271, a feature extraction unit 272, an event time determination unit 273, a detection signal generation unit 274, a communication time determination unit 275, a first memory 276, a waveform information generation unit 277, and a second memory 278.

[0036] The event signal generation unit 271 generates a gate signal indicating whether the waveform of the input denoised digital signal is sustained. The event signal generation unit 271 is implemented, for example, by an envelope detector and a comparator. The envelope detector detects the envelope of the denoised digital signal. The envelope is extracted, for example, by squaring the denoised digital signal and performing a predetermined process (for example, processing using a low-pass filter or a Hilbert transform) on the squared output value. The comparator determines whether the envelope of the denoised digital signal is above a predetermined threshold.

[0037] The event signal generation unit 271 outputs a first gate signal to the feature extraction unit 272, the event time determination unit 273, and the waveform information generation unit 277 when the envelope of the denoised digital signal exceeds a first threshold, indicating that the waveform of the denoised digital signal is continuing. The output of the first gate signal indicates that an event has occurred. On the other hand, the event signal generation unit 271 outputs a second gate signal to the feature extraction unit 272, the event time determination unit 273, and the waveform information generation unit 277 when the envelope of the denoised digital signal falls below the first threshold, indicating that the waveform of the denoised digital signal is no longer continuing. The output of the second gate signal indicates that the event has ended. In other words, elastic waves are generated during the period from when the first gate signal is output from the event signal generation unit 271 until when the second gate signal is output.

[0038] As a method for detecting the occurrence of an event, ChangeFinder or AIC (Akaike's Information Criterion) may be used. In the event signal generation unit 271, a configuration was shown in which it is determined whether or not the waveform of the noise-reduced signal is persistent based on the envelope, but the event signal generation unit 271 may also perform processing on the noise-reduced signal itself or on the signal to which the absolute value has been applied.

[0039] The feature extraction unit 272 receives the denoised digital signal output from the filter 24 and the gate signal output from the event signal generation unit 271 as inputs. The feature extraction unit 272 uses the denoised digital signal input while the first gate signal is being input to extract the features of the denoised digital signal. The feature extraction unit 272 does not perform any processing while the second gate signal is being input. The features are information that indicates the characteristics of the denoised digital signal. In other words, the features of the denoised digital signal are the features of the elastic wave detected by the sensor 10.

[0040] Features include, for example, waveform amplitude [mV], waveform rise time [usec], gate signal duration [usec], zero-cross count [times], waveform energy [arb.], frequency [Hz], and RMS (Root Mean Square) value. The feature extraction unit 272 outputs the extracted features to the detection signal generation unit 274. When the feature extraction unit 272 outputs parameters related to the features, it associates the sensor ID with the parameters related to the features. The sensor ID represents identification information for identifying the sensor 10.

[0041] The amplitude of the waveform is, for example, the maximum amplitude value in the denoised digital signal. The rise time of the waveform is, for example, the time T1 from the start of the rising edge of the gate signal until the denoised signal reaches its maximum value. The duration of the gate signal is, for example, the time from the start of the rising edge of the gate signal until the amplitude becomes smaller than a preset value. The zero-crossing count is, for example, the number of times the denoised digital signal crosses a reference line passing through zero.

[0042] The energy of the waveform is, for example, the time integral of the squared amplitude of the denoised digital signal at each point in time. Note that the definition of energy is not limited to the above example; it may also be approximated using, for example, the waveform envelope. The frequency is the frequency of the denoised digital signal. The RMS value is, for example, the value obtained by squaring the amplitude of the denoised digital signal at each point in time and taking the square root.

[0043] The event time determination unit 273 receives either the first gate signal or the second gate signal output from the event signal generation unit 271, and the time information output from the time information generation unit 26. The event time determination unit 273 determines the event detection time based on the input gate signal. Specifically, the event time determination unit 273 determines the time when the envelope becomes greater than or equal to the first threshold, i.e., the time when the first gate signal is input, as the event detection time. The event time determination unit 273 outputs time information indicating the determined event detection time to the detection signal generation unit 274. If the event detection time is used to associate with the second transmission data transmitted by the second communication unit 29, the event time determination unit 273 may output time information indicating the determined event detection time to the waveform information generation unit 277. The event time determination unit 273 does not perform any processing while the second gate signal is input.

[0044] The detection signal generation unit 274 generates detection information by associating the feature quantities output from the feature quantity extraction unit 272 with time information indicating the event detection time output from the event time determination unit 273. The detection signal generation unit 274 outputs the generated detection information to the first memory 276.

[0045] The communication time determination unit 275 receives time information output from the time information generation unit 26. The communication time determination unit 275 monitors the first communication unit 28 and determines the transmission time. The communication time determination unit 275 may determine the transmission time before transmitting the first transmission data and notify the first communication unit 28, thereby causing the first communication unit 28 to perform wireless communication at the notified time. The transmission time generally refers to the start time, but is not limited to this as long as it is a single time. For example, the first communication unit 28 may output a signal to the outside when it starts transmitting, and the communication time determination unit 275 may determine the transmission time based on that signal. The communication time determination unit 275 may determine the transmission time during wireless transmission and incorporate the transmission time into the transmission data transmitted by the first communication unit 28, or it may transmit the transmission time after the wireless transmission is completed.

[0046] Furthermore, the communication time determination unit 275 may associate the information indicating the determined transmission time with the detection information stored in the first memory 276. In addition, if the transmission time is used to associate with the second transmission data transmitted by the second communication unit 29, the communication time determination unit 275 may output the time information indicating the determined transmission time to the waveform information generation unit 277.

[0047] The first memory 276, for example, has a dual-port RAM and stores at least the detection information output from the detection signal generation unit 274. If information indicating the transmission time is obtained from the communication time determination unit 275, the first memory 276 stores the transmission time in association with the detection information.

[0048] The waveform information generation unit 277 receives the denoised digital signal output from the filter 24 and the gate signal output from the event signal generation unit 271 as input. The waveform information generation unit 277 generates waveform information from the denoised digital signal input between the time the first gate signal is input and the time the second gate signal is input. In this way, the waveform information generation unit 277 determines the data (e.g., waveform information) to be transmitted by the second communication unit 29 based on the signal strength of the denoised digital signal (e.g., the signal strength of the elastic wave). The waveform information generation unit 277 stores the generated waveform information in the second memory 278. When storing the waveform information in the second memory 278, the waveform information generation unit 277 adds the event detection time, transmission time, or unique identification information as a header or footer.

[0049] The waveform information generation unit 277 may use memory such as a shift register to generate waveform information from the denoised digital signal that has been input since before the first gate signal was input. The waveform information generation unit 277 may also store the data from the time the second gate signal is input up to a certain time (greater than or equal to 0), or, in order to reduce memory usage, it may generate waveform information from the time the first gate signal is input up to a certain time.

[0050] The second memory 278 stores the waveform information generated by the waveform information generation unit 277. The second memory 278 has a multilayer structure and stores one waveform (one piece of waveform information) at a time. For example, the second memory 278 has a 4000 x 5 multilayer structure, and when one waveform arrives, it stores signals 1 to 4000, and when the next waveform arrives, it stores it in the next layer.

[0051] Next, the hardware of the transmitting terminal 20 will be described. Power for the transmitting terminal 20 is supplied from an external power source, primary battery, secondary battery, solar cell, energy harvester, etc. The transmitting terminal 20 is implemented using analog and digital circuits. The digital circuits are implemented, for example, by an FPGA or microcomputer. They may also be implemented by a dedicated LSI. The transmitting terminal 20 may also be equipped with non-volatile memory such as flash memory or removable memory.

[0052] (Configuration of collection device 30) Figure 4 is a schematic block diagram showing the functions of the data collection device 30 in the first embodiment. The data collection device 30 includes a clock oscillator 31, a time information generation unit 32, a first communication unit 33, a reception time determination unit 34, a time information processing unit 35, a second communication unit 36, and an information correspondence unit 37.

[0053] The clock oscillator 31 generates a clock signal. Specifically, the clock oscillator 31 determines the time width of one second in the data acquisition device 30. The clock oscillator 31 is configured using, for example, a variable voltage crystal oscillator such as a VCXO. The clock oscillator 31 outputs the clock signal to the time information generation unit 32.

[0054] The time information generation unit 32 determines the time in the data acquisition device 30 according to the clock signal output from the clock oscillator 25. The time information generation unit 32 is, for example, a counter with a register. That is, the time information generation unit 32 counts the edges of the clock signal and stores the cumulative count value from the time the data acquisition device 30 is powered on as time information in the register.

[0055] The first communication unit 33 is a communication interface that communicates with the transmitting terminal 20 via the network 40-1. The first communication unit 33 receives the first transmission data transmitted from the transmitting terminal 20.

[0056] The reception time determination unit 34 determines the reception time based on the received signal. Specifically, the reception time determination unit 34 determines the time when the first transmission data transmitted from the transmitting terminal 20 by the first communication unit 33 is received as the reception time. The reception time generally refers to, but is not limited to, the reception start time, the time the preamble is discovered, or the time the synchronization word is discovered.

[0057] The time information processing unit 35 estimates the event detection time at the time of the event by statistically processing the transmission time contained in each of the multiple received first transmission data and the reception time of each first transmission data.

[0058] The second communication unit 36 ​​is a communication interface that communicates with the transmitting terminal 20 via the network 40-2. The second communication unit 36 ​​receives the second transmission data transmitted from the transmitting terminal 20. The second communication unit 36 ​​may also request the transmitting terminal 20 to transmit the second transmission data in response to an external request. In this case, the second communication unit 36 ​​sends either the event detection time, the transmission time, or unique identification information to the transmitting terminal 20 so that the transmitting terminal 20 can identify the requested second transmission data. As a result, the transmitting terminal 20 can transmit the second transmission data, which includes waveform information identified by the event detection time, the transmission time, or the unique identification information.

[0059] The information correspondence unit 37 stores one or more first transmission data received by the first communication unit 33 and one or more second transmission data received by the second communication unit 36. The information correspondence unit 37 then associates the first transmission data received by the first communication unit 33 with the second transmission data received by the second communication unit 36. Specifically, the information correspondence unit 37 associates the first transmission data with the second transmission data based on either the event detection time, transmission time, or unique identification information contained in the first transmission data, or the event detection time, transmission time, or unique identification information contained in the second transmission data.

[0060] For example, when performing mapping using unique identification information, the information mapping unit 37 uses the unique identification information contained in the first transmission data to be mapped to identify a second transmission data containing unique identification information that matches that unique identification information. The information mapping unit 37 then maps the identified second transmission data to the first transmission data.

[0061] Figures 5 and 6 are diagrams illustrating the time processing in the first embodiment. As shown in Figure 5, when an event occurs, the transmitting terminal 20 obtains the event detection time using the event time determination unit 273 and transmits first transmission data including the event detection time information to the collection device 30 using the first communication unit 28. Specifically, first, when an event occurs, the transmitting terminal 20 determines the time T0 when the event occurred as the event detection time. Next, the transmitting terminal 20 generates first transmission data including the event detection time T0 and the transmission time T1, and transmits the generated first transmission data to the collection device 30 at time T1. The collection device 30 receives the first transmission data transmitted from the transmitting terminal 20. The collection device 30 determines the time T1' when it received the first transmission data as the reception time. Each time the collection device 30 receives first transmission data including at least the transmission time from the transmitting terminal 20, the reception time determination unit 34 determines the reception time. As shown in Figure 5, if an event occurs before the transmission operation, the transmission by the transmitting terminal 20 will be put on hold and will start when it becomes possible to transmit.

[0062] Figure 6 shows the relationship between the transmission time of the transmitting terminal 20 and the reception time of the data collection device 30. The data collection device 30 obtains the graph shown in Figure 6 based on the reception time information and the transmission time information transmitted from the transmitting terminal 20. For example, the data collection device 30 can obtain relationships related to time, such as transmission time T1 and reception time T1', and transmission time T4 and reception time T4'. In this embodiment, the data collection device 30 obtains the relationship between counter values ​​by statistically processing the timestamps and counter values ​​of multiple transmitted data, and estimates the event detection time. The relationship between counter values ​​can be obtained by regression analysis, for example, by the least squares method or PCA (Principal Component Analysis). In this case, the event detection time can be estimated from the relationship y=ax+b. When obtaining the relationship between counter values, either parametric or nonparametric methods may be used. Furthermore, it is not necessary to wait for all events to occur; it is possible to estimate the event detection time if two or more transmission times and two or more reception times are obtained between one transmitting terminal 20 and the data collection device 30. For specific estimation methods, the method described in Patent Document 1 (Japanese Patent Publication No. 2021-13141) is used.

[0063] The collection device 30 uses multiple transmission times to determine the time difference (for example, the difference between T3 and T2 ΔT) 32 ) may be calculated. In this case, the collection device 30 can convert the event detection time into the necessary information without directly estimating it.

[0064] Compared to using only the reception timestamp (reception time) or estimation methods such as ETA in conventional technology, errors related to the clock and errors caused by priority processing in the microprocessor are averaged out. Therefore, errors in event detection time can be reduced. In addition, since the event detection time is converted to a counter value in the receiving-side data collection device 30, comparisons between multiple terminals become easier. For this reason, it is extremely useful for applications with high sampling rates, such as position determination using sensors.

[0065] (operation) Figure 7 is a sequence diagram showing the processing flow of the sensor system 100 in the first embodiment. Sensor 10 detects a physical quantity (step S101). For example, sensor 10 detects an elastic wave. Sensor 10 converts the detected elastic wave into an electrical signal. Sensor 10 transmits the electrical signal to the transmitting terminal 20 (step S102). The receiving unit 21 of the transmitting terminal 20 receives the electrical signal transmitted from sensor 10. The transmitting terminal 20 performs preprocessing on the received electrical signal (step S103). As a result, the signal processing unit 27 of the transmitting terminal 20 receives a digital signal after noise reduction.

[0066] The event signal generation unit 271 of the signal processing unit 27 detects the occurrence of an event based on the denoised digital signal (step S104). The event signal generation unit 271 outputs a first gate signal to the feature extraction unit 272, the event time determination unit 273, and the waveform information generation unit 277. The feature extraction unit 272 extracts features from the denoised digital signal that is input at the timing when the first gate signal output from the event signal generation unit 271 is input (step S105). The feature extraction unit 272 outputs the extracted features to the detection signal generation unit 274.

[0067] The event time determination unit 273 determines the time when the first gate signal is input as the event detection time (step S106). The event time determination unit 273 outputs time information indicating the determined event detection time to the detection signal generation unit 274. The waveform information generation unit 277 generates waveform information based on the denoised digital signal input at the timing when the first gate signal is input (step S107). The waveform information generation unit 277 stores the generated waveform information in the second memory 278. At this time, the waveform information generation unit 277 adds either the event detection time, transmission time, or unique identification information as a header or footer to the waveform information.

[0068] The detection signal generation unit 274 receives the feature quantities output from the feature quantity extraction unit 272 and the time information indicating the event detection time output from the event time determination unit 273. The detection signal generation unit 274 generates detection information by associating the feature quantities with the time information indicating the event detection time, and outputs the generated detection information to the first memory 276.

[0069] The communication time determination unit 275 receives time information generated by the time information generation unit 26. The communication time determination unit 275 determines the transmission time based on the input time information (step S108). The communication time determination unit 275 outputs the determined transmission time information to the first communication unit 28. The first communication unit 28 generates first transmission data including detection information stored in the first memory 276 and the transmission time output from the communication time determination unit 275. The first communication unit 28 transmits the generated first transmission data to the collection device 30 (step S109).

[0070] The second communication unit 29 generates second transmission data, which includes waveform information stored in the second memory 278. The second communication unit 29 transmits the generated second transmission data to the acquisition device 30 (step S110). In Figure 7, for illustrative purposes, a configuration is shown in which the first transmission data and the second transmission data are transmitted in sequence, but the second transmission data does not necessarily have to be transmitted. For example, the second transmission data may be transmitted at a timing requested by the acquisition device 30, or at a timing when the amount stored in the second memory 278 exceeds a certain threshold. Thus, the first transmission data and the second transmission data do not necessarily have to be transmitted at close intervals.

[0071] The first communication unit 33 of the data collection device 30 receives the first transmission data transmitted from the transmitting terminal 20. The first communication unit 33 outputs the received first transmission data to the reception time determination unit 34, the time information processing unit 35, and the information correspondence unit 37. The second communication unit 36 ​​of the data collection device 30 receives the second transmission data transmitted from the transmitting terminal 20 (step S111). The second communication unit 36 ​​outputs the received second transmission data to the information correspondence unit 37. The information correspondence unit 37 stores the first transmission data and the second transmission data (step S112).

[0072] The reception time determination unit 34 determines the reception time based on the time information generated by the time information generation unit 32 and the first transmission data output from the first communication unit 33 (step S113). Specifically, the reception time determination unit 34 determines the reception time as the time indicated by the time information at the time the first transmission data was obtained. The reception time determination unit 34 outputs the determined reception time information to the time information processing unit 35. The time information processing unit 35 associates the first transmission data output from the first communication unit 33 with the reception time information output from the reception time determination unit 34 and stores them in a storage unit (not shown).

[0073] The processes described above from steps S101 to S113 are repeated a predetermined number of times. As a result, the time information processing unit 35 stores multiple first transmission data and multiple reception times. When a predetermined number of first transmission data and reception time information has been stored, the time information processing unit 35 determines the relationship between the transmission time and reception time based on the transmission time information contained in the multiple first transmission data stored in the storage unit and the multiple reception time information (step S114). Specifically, the time information processing unit 35 uses the information of multiple transmission times and the information of multiple reception times to obtain the graph shown in Figure 6. After that, the time information processing unit 35 estimates the event detection time based on the relationship between the transmission time and reception time obtained from the obtained graph (step S115). The time information processing unit 35 may output the event detection time to the information correspondence unit 37.

[0074] The information matching unit 37 associates one or more stored first transmission data with one or more second transmission data (step S116). The information matching unit 37 may also associate the event detection time information output from the time information processing unit 35. The matching process by the information matching unit 37 may be performed at a predetermined timing or at a timing instructed.

[0075] According to the sensor system 100 configured as described above, the transmitting terminal 20 includes a first communication unit 28 that wirelessly transmits first transmission data, which includes time information used for time estimation, to the collection device 30, and a second communication unit 29 that wirelessly transmits second transmission data, which includes information (e.g., waveform information) obtained based on physical quantities (elastic waves) detected by one or more sensors 10, to the collection device 30 at a frequency different from the frequency used by the first communication unit 28. The collection device 30 also includes a reception time determination unit 34 that determines the reception times of a plurality of first transmission data transmitted from the first communication unit 28, and a time information processing unit 35 that performs time estimation based on the plurality of first transmission data and the plurality of reception times.

[0076] As a result, the time information used for time estimation is transmitted from a different communication unit than the other information. Furthermore, since the first communication unit 28 and the second communication unit 29 are communication units that use different frequencies, they do not interfere with each other's communication. This allows the data collection device 30 to receive the time information used for time estimation. As a result, time estimation can be performed with high accuracy. Therefore, it becomes possible to suppress a decrease in the accuracy of time estimation.

[0077] Furthermore, the data collection device 30 includes an information matching unit 37 that associates the second transmission data transmitted from the second communication unit 29 with the first transmission data transmitted from the first communication unit 28. This allows data transmitted from different communication units to be associated and stored. Therefore, convenience can be improved.

[0078] In particular, the second transmitted data includes identification information for associating it with the first transmitted data (for example, the event detection time, the transmission time of the first transmitted data, or unique identification information for the first transmitted data). The information matching unit 37 then associates the second transmitted data with the first transmitted data based on the identification information contained in the second transmitted data. This makes it easy for the collection device 30 to associate the information.

[0079] The first communication unit 28 transmits first transmission data, which further includes feature quantities obtained based on physical quantities, to the collection device 30 wirelessly. The second communication unit 29 also transmits second transmission data, which includes waveform information of physical quantities, to the collection device 30 wirelessly. In this way, waveform information, which has a large data transmission volume, is transmitted to the collection device 30 from a different communication unit than the communication unit that transmits the time information used for time estimation. Therefore, the situation in which the transmission of waveform information prevents the transmission of time information used for time estimation can be reduced. As a result, it is possible to suppress the decrease in estimation accuracy of time estimation due to the transmission of waveform information.

[0080] (Second embodiment) In the second embodiment, a configuration will be described in which the sensor system 100 shown in the first embodiment is applied to the localization of an elastic wave source.

[0081] Figure 8 shows the system configuration of the sensor system 100a in the second embodiment. The sensor system 100a comprises a sensor 10, a transmitting terminal 20, and a data collection device 30a. The sensor 10 and the transmitting terminal 20 are connected by a wire. The transmitting terminal 20 and the data collection device 30a are connected wirelessly via networks 40-1 and 40-2. The sensor system 100a comprises n units (n is an integer of 3 or more) of the sensor 10 and the transmitting terminal 20.

[0082] In the following description, sensors 10-1 to 10-n will be referred to as "sensor 10" if they are not distinguished. In the following description, transmitting terminals 20-1 to 20-n will be referred to as "transmitting terminal 20" if they are not distinguished. Figure 8 shows a case where one sensor 10 is connected to one transmitting terminal 20, but multiple sensors 10 may be connected to one transmitting terminal 20. Furthermore, when describing functional parts within the device separately, each functional part shall be distinguished by adding a sub-number. For example, when describing the functional part of transmitting terminal 20-1, the sub-number -1 shall be added to distinguish it from the functional parts of other devices.

[0083] Sensor system 100a differs from sensor system 100 in that it includes multiple sensors 10 and a transmitting terminal 20, and replaces the collection device 30 with a collection device 30a. Sensor system 100a is otherwise identical to sensor system 100. The following explanation will focus on the differences from sensor system 100.

[0084] The data collection device 30a performs the same processing as the data collection device 30 in the first embodiment. Furthermore, the data collection device 30a determines the location of the elastic wave source based on the feature quantities contained in the transmitted data transmitted from each transmitting terminal 20.

[0085] (Configuration of collection device 30a) Figure 9 is a schematic block diagram showing the functions of the data collection device 30a in the second embodiment. The data collection device 30a includes a clock oscillator 31, a time information generation unit 32, a first communication unit 33, a reception time determination unit 34, a time information processing unit 35, a second communication unit 36, an information correspondence unit 37, and a position determination unit 38.

[0086] The position determination unit 38 receives the estimated event detection time and detection information output from the time information processing unit 35. Based on the input estimated event detection time and detection information, the position determination unit 38 determines the position of the elastic wave source.

[0087] Figure 10 is a sequence diagram showing the processing flow of the sensor system 100a in the second embodiment. In Figure 10, multiple sensors 10 are collectively referred to as a sensor group, and multiple transmitting terminals 20 are collectively referred to as a transmitting terminal group. In Figure 10, sensor 10-1 is connected to transmitting terminal 20-1, sensor 10-2 is connected to transmitting terminal 20-2, and sensor 10-3 is connected to transmitting terminal 20-3.

[0088] The sensor group detects a physical quantity (step S101). For example, sensors 10-1 to 10-3 detect elastic waves. Sensors 10-1 to 10-3 convert the detected elastic waves into electrical signals. Sensors 10-1 to 10-3 transmit the electrical signals to the connected transmitting terminals 20-1 to 20-3 (step S102). The receiving units 21-1 to 21-3 of the transmitting terminals 20-1 to 20-3 receive the electrical signals transmitted from sensors 10-1 to 10-3. The transmitting terminals 20-1 to 20-3 perform preprocessing on the received electrical signals (step S103). As a result, the signal processing units 27-1 to 27-3 of the transmitting terminals 20-1 to 20-3 receive digital signals after noise reduction.

[0089] The event signal generation units 271-1 to 271-3 of the signal processing units 27-1 to 27-3 detect the occurrence of an event based on the digital signal after noise reduction (step S104). The event signal generation units 271-1 to 271-3 output a first gate signal to the feature extraction units 272-1 to 272-3, the event time determination units 273-1 to 273-3, and the waveform information generation units 277-1 to 277-3. The feature extraction units 272-1 to 272-3 extract features from the digital signal after noise reduction that is input at the timing when the first gate signal output from the event signal generation units 271-1 to 271-3 is input (step S105). The feature extraction units 272-1 to 272-3 output the extracted features to the detection signal generation units 274-1 to 274-3.

[0090] The event time determination units 273-1 to 273-3 determine the time when the first gate signal is input as the event detection time (step S106). The event time determination units 273-1 to 273-3 output time information indicating the determined event detection time to the detection signal generation units 274-1 to 274-3. The waveform information generation units 277-1 to 277-3 generate waveform information based on the denoised digital signal input at the timing when the first gate signal is input (step S107). The waveform information generation units 277-1 to 277-3 store the generated waveform information in the second memory 278-1 to 278-3. At this time, the waveform information generation units 277-1 to 277-3 add either the event detection time, transmission time, or unique identification information as a header or footer to the waveform information.

[0091] The detection signal generation units 274-1 to 274-3 receive feature quantities output from the feature quantity extraction units 272-1 to 272-3 and time information indicating the event detection time output from the event time determination units 273-1 to 273-3. The detection signal generation units 274-1 to 274-3 generate detection information by associating the feature quantities with the time information indicating the event detection time, and output the generated detection information to the first memory units 276-1 to 276-3.

[0092] The communication time determination units 275-1 to 275-3 receive time information generated by the time information generation units 26-1 to 26-3. The communication time determination units 275-1 to 275-3 determine the transmission time based on the input time information (step S108). The communication time determination units 275-1 to 275-3 output the determined transmission time information to the first communication units 28-1 to 28-3. The first communication units 28-1 to 28-3 generate first transmission data including detection information stored in the first memory 276-1 to 276-3 and the transmission time output from the communication time determination units 275-1 to 275-3. The first communication units 28-1 to 28-3 transmit the generated first transmission data to the collection device 30a (step S109).

[0093] The second communication units 29-1 to 29-3 generate second transmission data, which includes waveform information stored in the second memory units 278-1 to 278-3. The second communication units 29-1 to 29-3 transmit the generated second transmission data to the acquisition device 30a (step S110). In Figure 10, for illustrative purposes, a configuration is shown in which the first and second transmission data are transmitted sequentially, but the second transmission data does not necessarily have to be transmitted. For example, the second transmission data may be transmitted at a timing requested by the acquisition device 30a, or at a timing when the amount stored in the second memory units 278-1 to 278-3 exceeds a certain threshold. Thus, the first and second transmission data do not necessarily have to be transmitted at close intervals.

[0094] The first communication unit 33 of the data collection device 30 receives the first transmission data transmitted from the transmitting terminals 20-1 to 20-3. The first communication unit 33 outputs the received first transmission data to the reception time determination unit 34, the time information processing unit 35, and the information correspondence unit 37. The second communication unit 36 ​​of the data collection device 30a receives the second transmission data transmitted from the transmitting terminals 20-1 to 20-3 (step S111). The second communication unit 36 ​​outputs the received second transmission data to the information correspondence unit 37. The information correspondence unit 37 stores the first transmission data and the second transmission data (step S112).

[0095] The reception time determination unit 34 determines the reception time based on the time information generated by the time information generation unit 32 and the first transmission data output from the first communication unit 33 (step S113). Specifically, the reception time determination unit 34 determines the reception time as the time indicated by the time information at the time the first transmission data was obtained. The reception time determination unit 34 outputs the determined reception time information to the time information processing unit 35. The time information processing unit 35 associates the first transmission data output from the first communication unit 33 with the reception time information output from the reception time determination unit 34 and stores them in a storage unit (not shown).

[0096] The processes described above from steps S101 to S113 are repeated a predetermined number of times. As a result, the time information processing unit 35 stores multiple first transmission data and multiple reception times. When a predetermined number of first transmission data and reception time information has been stored, the time information processing unit 35 determines the relationship between the transmission time and reception time based on the transmission time information contained in the multiple first transmission data stored in the storage unit and the multiple reception time information (step S114). Specifically, the time information processing unit 35 uses the information of multiple transmission times and the information of multiple reception times to obtain the graph shown in Figure 6. After that, the time information processing unit 35 estimates the event detection time based on the relationship between the transmission time and reception time obtained from the obtained graph (step S115). The time information processing unit 35 outputs the event detection time and detection information to the location determination unit 38. The time information processing unit 35 may also output the event detection time to the information correspondence unit 37.

[0097] The information matching unit 37 associates one or more stored first transmission data with one or more second transmission data (step S116). The information matching unit 37 may also associate the event detection time information output from the time information processing unit 35. The matching process by the information matching unit 37 may be performed at a predetermined timing or at a timing instructed.

[0098] The location determination unit 38 determines the location of the source of the elastic wave based on the event detection time and detection information (step S201). Specifically, the location determination unit 38 first calculates the similarity of the feature information contained in each piece of detection information, and divides the multiple pieces of detection information into groups based on whether the similarity of the feature information is above a predetermined threshold. The location determination unit 38 then recognizes the detection information contained in the same group as detection information from the same source.

[0099] Similarity is determined by the distance between feature information. That is, the closer the distance between different feature information, the greater the similarity. The positioning unit 38 calculates the distance between feature information using a predetermined distance function. The distance function is a function that calculates, for example, the standard Euclidean distance, the Minkowski distance, or the Mahalanobis distance. In particular, the Mahalanobis distance makes it possible to calculate the distance considering the correlation between feature information, which can improve the accuracy of group classification. Next, the positioning unit 38 calculates time difference information of the reception times of elastic waves between multiple sensors 10 by comparing the estimated event detection times associated with feature information (feature information of detection information included in the same group) whose similarity is above a predetermined threshold. Based on the position information between sensors 10, the time difference information, and the propagation speed of the elastic waves, the positioning unit 38 identifies the position information of the source of the elastic wave.

[0100] With the sensor system 100a configured as described above, the same effects as in the first embodiment can be obtained.

[0101] Furthermore, the sensor system 100a estimates the event detection time for each sensor 10 based on the information obtained from each sensor 10. Specifically, the data collection device 30a estimates the event detection time by applying a correction that reduces the time error. Therefore, the data collection device 30a can accurately determine the location of the event source by locating it based on the corrected event detection time.

[0102] (modified version) In positioning, the accuracy of the arrival time is crucial. Therefore, to ensure sufficient communication capacity, a maximum acquisition time may be defined for the waveform information generated by the signal processing unit 27.

[0103] (Modification 1 common to the first and second embodiments) In the embodiment described above, the waveform information generation unit 277 is configured to generate waveform information based on the timing at which the first gate signal is input. The first gate signal is a signal output at the rising edge timing of the elastic wave. In this way, the threshold for outputting the first gate signal to detect the rising edge timing of the elastic wave is basically set low. If the waveform information generation unit 277 generates waveform information based on the timing at which the first gate signal is input, it may also transmit unnecessary denoised digital signals (for example, denoised digital signals with small amplitudes) that are not used for processing as waveform data. Therefore, the waveform information generation unit 277 may be configured to generate waveform information for denoised digital signals that are used for processing as waveform data. In this configuration, the waveform information generation unit 277 may generate waveform information based on the timing at which a denoised digital signal with an amplitude of 2 or more is detected. The second threshold is a value greater than the first threshold.

[0104] (Modification 2 common to the first and second embodiments) The waveform information generation unit 277 may determine whether or not to generate waveform information based on feature quantities. For example, the waveform information generation unit 277 may determine whether or not to generate waveform information based on the rise time of the waveform or the hit interval as feature quantities. In some cases, the same waveform may be observed consecutively due to reflection, etc. In this case, it is meaningless to generate waveform information for all waveforms. Therefore, the waveform information generation unit 277 generates waveform information based on the first observed waveform when the same waveform is observed consecutively based on the hit interval. Also, if the rise time of the waveform is large, it is assumed that the amplitude is also large. Therefore, the waveform information generation unit 277 may generate waveform information based on the timing when a denoised digital signal is detected in which the rise time of the waveform is above a certain threshold.

[0105] (Modification 3 common to the first and second embodiments) In the embodiment described above, the second communication unit 29 is shown to be in a state where it is always operating. For time estimation in the acquisition devices 30 and 30a, the first transmission data transmitted by the first communication unit 28 is necessary, but the second transmission data transmitted by the second communication unit 29 is not. Therefore, the second communication unit 29 may be in a dormant state. A dormant state is a state for saving power, and may be, for example, a sleep state or a state in which operation is stopped. In this configuration, the second communication unit 29 may be started when predetermined conditions are met. For example, the second communication unit 29 may transition to an activated state when predetermined conditions are met, such as when an arbitrary time has arrived or when it has received a signal transmitted from the acquisition devices 30 and 30a. The second communication unit 29 then transmits the second transmission data, which includes waveform information stored in the second memory 278, to the acquisition devices 30 and 30a. This makes it possible to save power.

[0106] (Modification 4 common to the first and second embodiments) In the embodiment described above, the first communication unit 28 transmits first transmission data including detection information (including feature quantities) and transmission time, and the second communication unit 29 transmits second transmission data including waveform information. In contrast, the first communication unit 28 may transmit first transmission data including some feature quantities, event detection time, and transmission time, and the second communication unit 29 may transmit second transmission data including all feature quantities. In this configuration, the signal processing unit 27 does not need to include a waveform information generation unit 277. The feature quantity extraction unit 272 uses the denoised digital signal input while the first gate signal is input to extract feature quantities from the denoised digital signal. The feature quantity extraction unit 272 stores the extracted feature quantities in the second memory 278. The feature quantity extraction unit 272 also uses the denoised digital signal whose amplitude exceeds a second threshold to extract feature quantities from the denoised digital signal. The feature quantity extraction unit 272 outputs the extracted feature quantities to the detection signal generation unit 274. As a result, some of the feature quantities extracted from the denoised digital signal input to the signal processing unit 27 are transmitted by the first communication unit 28. Then, all of the feature quantities extracted from the denoised digital signal input to the signal processing unit 27 are transmitted by the second communication unit 29.

[0107] (Modification 5 common to the first and second embodiments) In the embodiment described above, the first communication unit 28 transmits first transmission data including detection information (including feature quantities) and transmission time, and the second communication unit 29 transmits second transmission data including waveform information. When the first communication unit 28 transmits feature quantities in this way, the number of transmissions depends on the number of elastic wave data. Therefore, if there are many elastic waves or depending on the intensity of the elastic waves, problems may arise in which it is difficult to adjust the second threshold, etc. For example, when using TDMA (Time Division Multiple Access) to avoid radio collisions, radio transmissions are made for Y seconds every X seconds.

[0108] Therefore, the first communication unit 28 may be configured to transmit first transmission data including time information based on a dummy event, and the second communication unit 29 may be configured to transmit second transmission data including all feature quantities. In this configuration, the signal processing unit 27 does not need to include a waveform information generation unit 277. Here, a dummy event is an event whose occurrence has not been detected by the event signal generation unit 271 and is an event that has not actually occurred. In other words, a dummy event is a virtual event. More specifically, the transmitting terminal 20 generates a dummy event and then transmits first transmission data including the transmission time to the collection devices 30, 30a. The dummy event may be generated by the communication time determination unit 275, by the first communication unit 28, or by the transmitting terminal 20 newly equipped with a dummy event generation unit. The feature quantity extraction unit 272 uses the denoised digital signal input while the first gate signal is input to extract feature quantities from the denoised digital signal. The feature extraction unit 272 stores the extracted features in the second memory 278. As a result, the second transmission data containing the features is sent from the second communication unit 29 to the collection devices 30 and 30a.

[0109] In the data collection devices 30 and 30a, time estimation is possible by correcting the arrival time received in the second transmission data using the time estimation result based on the first transmission data. The second communication unit 29 may transmit each time a feature quantity is stored in the second memory 278, or it may transmit when a predetermined number of feature quantities are stored in the second memory 278 or when a predetermined time has elapsed.

[0110] (Modification 6 common to the first and second embodiments) To improve time accuracy, the first communication unit 28 may transmit first transmission data, including the transmission time, at regular intervals.

[0111] (Modification 7 common to the first and second embodiments) When the first communication unit 28 and the second communication unit 29 use different frequencies of the same radio standard, the data to be transmitted may be switched depending on the communication strength. For example, the transmitting terminal 20 transmits the data including feature quantities and time information indicating the transmission time using the communication unit with the best communication strength. In this configuration, the transmitting terminal 20 measures the communication strength of both the first communication unit 28 and the second communication unit 29 and controls them to transmit the data including feature quantities and time information indicating the transmission time to the collection devices 30, 30a using the communication unit with the best communication strength. This makes it possible to more reliably transmit information on high-priority feature quantities and transmission time information used for time estimation to the collection devices 30, 30a.

[0112] According to at least one embodiment described above, one or more transmitting terminals 20 include a first communication unit 28 that wirelessly transmits first transmission data containing time information used for time estimation to the collection devices 30, 30a, and a second communication unit 29 that wirelessly transmits second transmission data containing information obtained based on physical quantities to the collection devices 30, 30a at a frequency different from the frequency used by the first communication unit 28. Furthermore, the collection devices 30, 30a include a reception time determination unit 34 that determines the reception time of a plurality of first transmission data transmitted from the first communication unit 28, and a time information processing unit 35 that performs time estimation based on the plurality of first transmission data and the plurality of reception times, thereby suppressing a decrease in time estimation accuracy.

[0113] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0114] 10, 10-1 to 10-n... sensors, 20, 20-1 to 20-n... transmitting terminals, 21... receiving section, 22... BPF, 23... analog-to-digital conversion section, 24... filter, 25... clock oscillator, 26... time information generation section, 27... signal processing section, 28... first communication section, 29... second communication section, 271... event signal generation section, 272... feature quantity extraction section, 273... event time determination section, 274... detection signal generation section, 275... communication time determination section, 276... first memory, 277... waveform information generation section, 278... second memory, 30, 30a... collection device, 31... clock oscillator, 32... time information generation section, 33... first communication section, 34... reception time determination section, 35... time information processing section, 36... second communication section, 37... information association section, 38... position calibration section, 40-1, 40-2... network

Claims

1. A sensor system comprising one or more sensors for detecting physical quantities, one or more transmitting terminals connected to the one or more sensors, and a collection device for collecting information transmitted from the one or more transmitting terminals, The one or more transmitting terminals mentioned above are: A first communication unit that wirelessly transmits first transmission data, which includes time information used for time estimation, to the collection device, A second communication unit transmits second transmission data, which includes information obtained based on the physical quantity detected by the one or more sensors, to the collection device wirelessly at a frequency different from the frequency used by the first communication unit, Equipped with, The aforementioned collection device is A reception time determination unit that determines the reception time of a plurality of first transmission data transmitted from the first communication unit, A time information processing unit that performs time estimation based on a plurality of first transmission data and a plurality of reception times, A sensor system equipped with the following features.

2. The aforementioned collection device is The system further includes an information matching unit that associates the second transmission data transmitted from the second communication unit with the first transmission data transmitted from the first communication unit. The sensor system according to claim 1.

3. The second transmission data includes identification information for associating it with the first transmission data. The aforementioned information correspondence attachment unit is, Based on the identification information, the second transmission data and the first transmission data are associated. The sensor system according to claim 2.

4. The identification information is one of the following: the time the event was detected, the time the first transmission data was transmitted, or unique identification information for the first transmission data. The sensor system according to claim 3.

5. The system further comprises an information generation unit that determines data to be transmitted by the second communication unit based on the signal strength of the physical quantity or the characteristic quantity of the physical quantity. The sensor system according to any one of claims 1 to 4.

6. The aforementioned first communications unit is, The first transmission data, which further includes feature quantities obtained based on the aforementioned physical quantities, is transmitted wirelessly to the collection device. The aforementioned second communications unit is, The second transmission data, which includes waveform information of the physical quantity as information obtained based on the physical quantity, is transmitted wirelessly to the collection device. The sensor system according to any one of claims 1 to 4.

7. The aforementioned second communications unit is, The second transmission data, which includes the characteristic quantities of the physical quantity as information obtained based on the physical quantity, is transmitted wirelessly to the collection device. The aforementioned first communications unit is, The first transmission data, which further includes a feature quantity obtained based on the physical quantity that exceeds a certain threshold, is transmitted to the collection device. The sensor system according to any one of claims 1 to 4.

8. The aforementioned first communications unit is, Based on a virtually generated event, the first transmission data is transmitted wirelessly to the collection device. The aforementioned second communications unit is, The second transmission data, which includes the characteristic quantities of the physical quantity as information obtained based on the physical quantity, is transmitted wirelessly to the collection device. The sensor system according to any one of claims 1 to 4.

9. The communication speed of the second communication unit is equal to or greater than that of the first communication unit. The sensor system according to any one of claims 1 to 4.

10. The second communication unit is in a dormant state and is activated when predetermined conditions are met. The sensor system according to any one of claims 1 to 4.

11. The aforementioned collection device is The system further includes a location determination unit for determining the source of the event that generates the aforementioned physical quantity. The one or more sensors and the one or more transmitting terminals are a plurality of sensors and a plurality of transmitting terminals. The aforementioned time information processing unit estimates the detection time of the occurrence event for each transmitting terminal, The positioning unit calculates time difference information for events using the estimated detection time of the event for each transmitting terminal, and locates the source of the event based on the calculated time difference information, the position information of each transmitting terminal, and the propagation speed of the physical quantity detected by each of the multiple sensors. The sensor system according to any one of claims 1 to 4.

12. A transmitting terminal in a sensor system comprising one or more sensors for detecting physical quantities, one or more transmitting terminals connected to the one or more sensors, and a collection device for collecting information transmitted from the one or more transmitting terminals, A first communication unit that wirelessly transmits first transmission data, which includes time information used for time estimation, to the collection device, A second communication unit transmits second transmission data, which includes information obtained based on the physical quantity detected by the one or more sensors, to the collection device wirelessly at a frequency different from the frequency used by the first communication unit, A transmitting terminal equipped with the following features.

13. A transmission method performed by a transmitting terminal in a sensor system comprising one or more sensors for detecting physical quantities, one or more transmitting terminals connected to the one or more sensors, and a collection device for collecting information transmitted from the one or more transmitting terminals, The first communication unit transmits first transmission data, which includes time information used for time estimation, wirelessly to the collection device. The second communication unit transmits second transmission data, which includes information obtained based on the physical quantities detected by the one or more sensors, to the collection device wirelessly at a frequency different from the frequency used by the first communication unit. Sending method.

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