Seismic sensor, earthquake detection method, and earthquake detection program

Abstract

To provide a seismic sensor, an earthquake detection method, and an earthquake detection program that can, for example, accurately determine stop of a high-frequency vibration such as an ordinary vibration.SOLUTION: A seismic sensor 10 comprises an acceleration acquisition unit 21, an acceleration waveform generation unit 22, a frequency detection unit 24, a vibration stop period determination unit 25, and an earthquake determination unit 26. The acceleration waveform generation unit 22 generates an acceleration waveform indicating a relation between acceleration measured by the acceleration acquisition unit 21 and an elapsed time. The frequency detection unit 24 detects a period and amplitude of the generated acceleration waveform. The vibration stop period determination unit 25 changes a threshold of amplitude for determining stop of a vibration on the basis of the detected period to determine the stop of the vibration. The earthquake determination unit 26 determines whether or not the vibration is an earthquake on the basis of the period detected by the frequency detection unit 24 and a result of determination made by the vibration stop period determination unit 25.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a seismic sensor for detecting seismic motion, an earthquake detection method, and an earthquake detection program. [Background technology]

[0002] In recent years, seismic sensors have been used that are built into gas meters, electricity meters, distribution boards, outlets, etc., and that output a cut-off signal to cut off the supply of gas, electricity, etc. when they detect earthquake motion of a magnitude above a predetermined value (for example, seismic intensity 5 or higher). For example, Patent Document 1 discloses a seismic sensor that outputs a shutoff signal when an index value indicating the magnitude of an earthquake is equal to or greater than a threshold value during an earthquake processing period following a judgment period, and that includes a continuing earthquake judgment unit that judges whether an earthquake has occurred based on the acceleration measured during the earthquake processing period, and a shutoff judgment unit that prevents the shutoff signal from being output regardless of the index value when the continuing earthquake judgment unit judges that an earthquake has not occurred. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6465257 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned conventional seismic sensors have the following problems. In other words, the seismic sensor disclosed in the above publication determines whether vibration has stopped based solely on acceleration, so there is a risk that it will mistakenly determine that vibration has stopped if the acceleration of the acceleration waveform falls below a threshold value and a predetermined time has passed. Here, for example, in an installation environment where a seismic sensor mounted on a gas meter or the like is installed, there is a risk that daily vibrations with small amplitude (displacement) and high-frequency components may be judged to be an earthquake, resulting in the gas supply being erroneously stopped.

[0005] An object of the present invention is to provide a seismic sensor, an earthquake detection method, and an earthquake detection program that can accurately determine the cessation of high-frequency vibrations, such as those caused by daily life. [Means for solving the problem]

[0006] The seismic sensor according to the first aspect of the present invention includes an acceleration acquisition unit, an acceleration waveform generation unit, a detection unit, a vibration stop period determination unit, and an earthquake determination unit. The acceleration acquisition unit detects vibrations and acquires the acceleration of the vibrations. The acceleration waveform generation unit generates an acceleration waveform that indicates the relationship between the acceleration measured by the acceleration acquisition unit and elapsed time. The detection unit detects the period and amplitude of the acceleration waveform generated by the acceleration waveform generation unit. The vibration stop period determination unit changes the amplitude threshold for determining that the vibrations have stopped based on the period detected by the detection unit, and determines whether the vibrations have stopped. The earthquake determination unit determines whether the vibrations are an earthquake based on the period detected by the detection unit and the result of determination by the vibration stop period determination unit.

[0007] Here, the amplitude threshold for determining whether the vibration has stopped is changed depending on the period (frequency) of the acceleration waveform of the detected vibration, and based on whether or not there is a period of vibration cessation determined, it is determined whether or not the detected vibration is an earthquake. The vibration stop period includes not only a period in which the vibration amplitude is completely zero, but also a period in which the vibration amplitude is equal to or less than a predetermined threshold value.

[0008] A characteristic of earthquakes is that there is no period in which vibrations are almost stopped, meaning that the amplitude of the acceleration waveform is below a predetermined value. Therefore, when determining whether an earthquake has occurred, it is important to accurately detect that there is no period in which vibrations are stopped in the acceleration waveform. Furthermore, when comparing the detected vibrations between low-frequency vibrations and high-frequency vibrations, even if the displacement is the same, the acceleration of high-frequency vibrations is greater, which may make it difficult to determine that the vibrations have stopped when it should actually be determined that the vibrations have stopped.

[0009] This allows the period and amplitude of the acceleration waveform of the detected vibration to be detected, and the amplitude threshold used to determine whether the vibration has stopped is changed depending on the period.For example, if the period is short (the frequency is high), the threshold amplitude value can be set to a large value, allowing the vibration to be determined to have stopped with high accuracy. As a result, it is possible to determine with high accuracy when high frequency vibrations such as daily life vibrations have stopped.

[0010] The seismic sensor of the second invention is the seismic sensor of the first invention, wherein the earthquake determination unit determines whether the vibration is an earthquake using the total or maximum value of the vibration stop time at which the vibration stop period determination unit determines that the vibration has stopped. This makes it possible to accurately determine whether the vibration is an earthquake by using the total value or maximum value of the period during which the amplitude is equal to or less than the threshold value and is determined to be a vibration stop by the vibration stop period determination unit.

[0011] The seismic sensor of the third invention is the seismic sensor of the second invention, wherein the earthquake determination unit determines that the vibration is an earthquake when the ratio of the vibration stop time to the total vibration time is smaller than a predetermined ratio threshold. As a result, if the proportion of the time determined by the vibration stop period determination unit to be a vibration stop to the total vibration is smaller than a predetermined proportion, it can be determined that there is a high possibility that it is not noise such as daily vibration, and the vibration can be determined to be an earthquake.

[0012] A seismic sensor according to a fourth aspect of the present invention is the seismic sensor according to the second aspect of the present invention, wherein the earthquake determination unit determines that vibration is an earthquake when the maximum value of the vibration stop time is smaller than a predetermined maximum threshold value. As a result, if the maximum time determined by the vibration stop period determination unit to be a vibration stop is smaller than a predetermined threshold value, it can be determined that the period during which the vibration has almost stopped is short and therefore is not noise such as daily vibration, and the vibration can be determined to be an earthquake.

[0013] The seismic sensor of the fifth invention is a seismic sensor of the first or second invention, wherein the vibration stop period determination unit sets the result obtained by differentiating the predetermined amplitude for determining that vibration has stopped and the displacement for determining that vibration has stopped according to the period as the threshold value for determination. This allows the threshold to be set to a larger value when the period of the acceleration waveform of the detected vibration is short (high frequency), thereby accurately detecting the vibration stop period for high-frequency vibrations and improving the accuracy of earthquake determination.

[0014] The seismic sensor of the sixth invention is the seismic sensor of the first or second invention, wherein the detection unit detects the period and amplitude of the acceleration waveform generated by the acceleration waveform generation unit using a zero-crossing method. Here, the zero-crossing method is a method of detecting one cycle (frequency) between the point where a waveform exceeds zero (or a hysteresis set near zero), then falls below zero (a hysteresis value below zero), and then exceeds zero (or a hysteresis set near zero). This makes it more difficult to detect minute vibrations compared to the peak method, which detects the time between peaks in the acceleration waveform as one cycle, but it allows for highly accurate detection of the cycle and amplitude without being affected by minute vibration noise.

[0015] The seismic sensor of the seventh invention is a seismic sensor of the first or second invention, and further comprises an earthquake magnitude calculation unit that, when the earthquake determination unit determines that an earthquake has occurred, determines whether the earthquake is of a predetermined seismic intensity or greater. This allows for, for example, if the magnitude of the earthquake is judged to be upper 5 or higher on the seismic intensity scale, there is a risk of fire or gas leaks, and a shut-off signal can be output to stop the supply of energy such as electricity or gas, thereby improving the safety of users.

[0016] The seismic sensor of the eighth invention is a seismic sensor of the first or second invention, and further includes an activation determination unit that calculates the vibration intensity from the measurement results of the acceleration acquisition unit, and when the vibration intensity is equal to or greater than a predetermined magnitude, transitions from a power saving mode to a measurement mode that consumes more power than the power saving mode. This allows the device to switch to a measurement mode that performs earthquake detection processing using the vibration acceleration waveform only when the strength of the detected vibration is equal to or greater than a predetermined magnitude (e.g., equivalent to a seismic intensity of 4), thereby enabling highly accurate earthquake detection while reducing power consumption.

[0017] The seismic sensor of the ninth invention is the seismic sensor of the first or second invention, and further comprises an output control unit that outputs a predetermined signal when the earthquake determination unit determines that an earthquake has occurred. This allows, for example, when an earthquake occurs, the output unit to output a cutoff signal to stop the supply of energy such as electricity or gas, or a warning signal to warn of danger.

[0018] The seismic sensor according to a tenth aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, further comprising a memory unit that stores a table showing the relationship between the period and the threshold value that changes for each period. This allows earthquake determination to be performed by referring to a table showing the relationship between thresholds and periods stored in the storage unit.

[0019] An earthquake detection method according to an eleventh aspect of the present invention includes an acceleration acquisition step, an acceleration waveform generation step, a detection step, a vibration stop period determination step, and an earthquake determination step. The acceleration acquisition step detects vibration and acquires the acceleration of the vibration. The acceleration waveform generation step generates an acceleration waveform that indicates the relationship between the acceleration measured in the acceleration acquisition step and elapsed time. The detection step detects the period and amplitude of the acceleration waveform generated in the acceleration waveform generation step. The vibration stop period determination step determines whether or not the vibration has stopped by changing an amplitude threshold value for determining whether or not the vibration has stopped based on the period detected in the detection step. The earthquake determination step determines whether or not the vibration is an earthquake based on the period detected in the detection step and the result of determination in the vibration stop period determination step.

[0020] Here, the amplitude threshold for determining whether the vibration has stopped is changed depending on the period (frequency) of the acceleration waveform of the detected vibration, and based on whether or not there is a period of vibration cessation determined, it is determined whether or not the detected vibration is an earthquake. The vibration stop period includes not only a period in which the vibration amplitude is completely zero, but also a period in which the vibration amplitude is equal to or less than a predetermined threshold value.

[0021] A characteristic of earthquakes is that there is no period in which vibrations are almost stopped, meaning that the amplitude of the acceleration waveform is below a predetermined value. Therefore, when determining whether an earthquake has occurred, it is important to accurately detect that there is no period in which vibrations are stopped in the acceleration waveform. Furthermore, when comparing the detected vibrations between low-frequency vibrations and high-frequency vibrations, even if the displacement is the same, the acceleration of high-frequency vibrations is greater, which may make it difficult to determine that the vibrations have stopped when it should actually be determined that the vibrations have stopped.

[0022] This allows the period and amplitude of the acceleration waveform of the detected vibration to be detected, and the amplitude threshold used to determine whether the vibration has stopped is changed depending on the period.For example, if the period is short (the frequency is high), the threshold amplitude value can be set to a large value, allowing the vibration to be determined to have stopped with high accuracy. As a result, it is possible to determine with high accuracy when high frequency vibrations such as daily life vibrations have stopped.

[0023] An earthquake detection program according to a twelfth aspect of the present invention causes a computer to execute an earthquake detection method including an acceleration acquisition step, an acceleration waveform generation step, a detection step, a vibration stop period determination step, and an earthquake determination step. The acceleration acquisition step detects vibrations and acquires the acceleration of the vibrations. The acceleration waveform generation step generates an acceleration waveform indicating the relationship between the acceleration measured in the acceleration acquisition step and elapsed time. The detection step detects the period and amplitude of the acceleration waveform generated in the acceleration waveform generation step. The vibration stop period determination step determines whether or not the vibrations have stopped by changing an amplitude threshold value for determining whether or not the vibrations have stopped based on the period detected in the detection step. The earthquake determination step determines whether or not the vibrations are an earthquake based on the period detected in the detection step and the result of the determination made in the vibration stop period determination step.

[0024] Here, the amplitude threshold for determining whether the vibration has stopped is changed depending on the period (frequency) of the acceleration waveform of the detected vibration, and based on whether or not there is a period of vibration cessation determined, it is determined whether or not the detected vibration is an earthquake. The vibration stop period includes not only a period in which the vibration amplitude is completely zero, but also a period in which the vibration amplitude is equal to or less than a predetermined threshold value.

[0025] A characteristic of earthquakes is that there is no period in which vibrations are almost stopped, meaning that the amplitude of the acceleration waveform is below a predetermined value. Therefore, when determining whether an earthquake has occurred, it is important to accurately detect that there is no period in which vibrations are stopped in the acceleration waveform. Furthermore, when comparing the detected vibrations between low-frequency vibrations and high-frequency vibrations, even if the displacement is the same, the acceleration of high-frequency vibrations is greater, which may make it difficult to determine that the vibrations have stopped when it should actually be determined that the vibrations have stopped.

[0026] This allows the period and amplitude of the acceleration waveform of the detected vibration to be detected, and the amplitude threshold used to determine whether the vibration has stopped is changed depending on the period.For example, if the period is short (the frequency is high), the threshold amplitude value can be set to a large value, allowing the vibration to be determined to have stopped with high accuracy. As a result, it is possible to determine with high accuracy when high frequency vibrations such as daily life vibrations have stopped.

[0027] A seismic sensor according to a thirteenth aspect of the present invention includes an acceleration acquisition unit, an acceleration waveform generation unit, a detection unit, and a vibration stop period determination unit. The acceleration acquisition unit detects vibrations and acquires the acceleration of the vibrations. The acceleration waveform generation unit generates an acceleration waveform that indicates the relationship between the acceleration measured by the acceleration acquisition unit and elapsed time. The detection unit detects the period and amplitude of the acceleration waveform generated by the acceleration waveform generation unit. The vibration stop period determination unit changes the amplitude threshold for determining that the vibrations have stopped based on the period detected by the detection unit, and determines whether the vibrations have stopped.

[0028] Here, the amplitude threshold for determining whether the vibration has stopped is changed depending on the period (frequency) of the acceleration waveform of the detected vibration, and based on whether or not there is a period of vibration cessation determined, it is determined whether or not the detected vibration is an earthquake. The vibration stop period includes not only a period in which the vibration amplitude is completely zero, but also a period in which the vibration amplitude is equal to or less than a predetermined threshold value.

[0029] This allows the period and amplitude of the acceleration waveform of the detected vibration to be detected, and the amplitude threshold used to determine whether the vibration has stopped is changed depending on the period.For example, if the period is short (the frequency is high), the threshold amplitude value can be set to a large value, making it possible to determine with high accuracy whether the vibration has stopped. [Effects of the Invention]

[0030] The seismic sensor according to the present invention can determine with high accuracy when high frequency vibrations such as those caused by daily life have stopped. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a control block diagram showing the configuration of a seismic sensor according to an embodiment of the present invention. [Figure 2] Functional block diagram generated within the seismic sensor in Figure 1. [Figure 3] 6 is a graph illustrating a zero-crossing method for detecting the frequency of an acceleration waveform of detected vibration. [Figure 4] 1A is a graph showing an example of an acceleration waveform of low-frequency vibration, and FIG. 1B is a graph showing an example of an acceleration waveform of high-frequency vibration. [Figure 5] (a) is a graph showing that the displacement for determining the cessation of vibration was set to 0.5 cm. (b) is a graph showing the change in the threshold value of the acceleration amplitude obtained by differentiating the amplitude of (a) twice, depending on the frequency. [Figure 6] 3 is a flowchart showing the flow of processing in an earthquake detection method executed by the seismic sensor of FIG. 2; DETAILED DESCRIPTION OF THE INVENTION

[0032] A seismic sensor according to one embodiment of the present invention will be described below with reference to FIGS. 1 to 6. FIG. In the present embodiment, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art. Furthermore, the applicant provides the accompanying drawings and the following description to enable those skilled in the art to fully understand the present invention, and they are not intended to limit the subject matter described in the claims.

[0033] (1) Configuration of the seismic sensor 10 As shown in FIG. 1, the seismic sensor 10 according to this embodiment includes an acceleration sensor 11, a controller 12, and a memory 13.

[0034] The acceleration sensor 11 is, for example, an acceleration sensor using a piezoelectric element or an acceleration sensor that detects electrostatic capacitance between electrodes. The acceleration measured (also called “sampling”) by the acceleration sensor 11 is output to the controller 12. The controller 12 is, for example, a general-purpose integrated circuit that acquires the acceleration measured by the acceleration sensor 11 at a predetermined period, detects the occurrence of an earthquake based on the acquired acceleration, and calculates an index value indicating the magnitude of the earthquake.

[0035] Also, the controller 12 operates in different modes, active mode or sleep mode, depending on the situation. The sleep mode is a mode in which the controller 12 operates with limited functions, such as stopping the execution of instructions while accepting interrupts, stopping the supply of clocks, etc. In this sleep mode, power consumption can be reduced more than in the active mode.

[0036] The active mode is a mode in which a process is performed to determine whether the detected vibration is an earthquake or noise, and an index value indicating the magnitude of the earthquake is calculated. The function blocks (see FIG. 2) generated when the CPU in the seismic sensor 10 reads the earthquake detection program stored in the memory 13 will be described in detail later. The memory 13 is a temporary storage means such as a RAM (Random Access Memory) or a non-volatile memory such as an EPROM (Erasable Programmable Read Only Memory), and stores, for example, the acceleration measured by the acceleration sensor 11 and threshold values ​​used for earthquake determination.

[0037] The memory 13 may be a memory built into the acceleration sensor 11 or the controller 12 . The output unit 14 is, for example, an output terminal included in the controller 12, and when the controller 12 determines that, for example, an earthquake has occurred, information indicating the occurrence and scale of the earthquake is output to another device via the output unit 14. Furthermore, when an earthquake of a predetermined scale or greater is detected, the output unit 14 outputs, for example, a cutoff signal to an external device to stop the supply of energy such as electricity or gas.

[0038] (2) Functional block of seismic sensor 10 As shown in Figure 2, the seismic sensor 10 includes an acceleration acquisition unit 21, an acceleration waveform generation unit 22, a vibration intensity classification / activation determination unit 23, a frequency detection unit 24, a vibration stop period determination unit 25, an earthquake determination unit 26, an earthquake magnitude calculation unit 27, an output control unit 28, an offset adjustment unit 29, and a memory unit 30.

[0039] These functional blocks shown in FIG. 2 are configured by the controller 12 receiving acceleration data obtained from the acceleration sensor 11 and reading a program stored in the memory 13. The acceleration acquiring unit 21 acquires measurement data of acceleration measured at a predetermined period by the acceleration sensor 11. Note that the acceleration acquiring unit 21 normally acquires measurement data of acceleration measured repeatedly at a relatively low speed (i.e., at a relatively large measurement period).

[0040] When performing such low-speed acceleration sampling, the controller 12 basically operates in a sleep mode (standby state or power-saving mode) with low power consumption. In the standby state, the acceleration sensor 11 is in an operating state where it samples at a low speed, so the controller 12 operates in a sleep mode with limited functionality, thereby reducing power consumption.

[0041] Furthermore, when the acceleration acquisition unit 21 acquires vibrations greater than a threshold value preset in the storage unit 30, the acceleration sensor 11 repeats measuring the acceleration at a higher speed (i.e., at a relatively short cycle) than during low-speed sampling. During such high-speed sampling, the controller 12 operates in a sleep mode or an active mode. When the earthquake determination unit 26 (described later) and the like execute processing, the controller 12 operates in active mode (measurement mode). The transition from the power saving mode to the measurement mode is called the activation of the seismic sensor 10.

[0042] The measurement mode is an operating state in which high-speed sampling is performed, so the controller 12 may operate in a sleep mode with limited functionality, or in an active mode with maximum computing power. In the measurement mode, the sampling period is shortened and the controller 12 switches from the sleep mode to the active mode, resulting in higher power consumption than in the power-saving mode.

[0043] The acceleration waveform generating unit 22 generates an acceleration waveform that indicates the relationship between the acceleration measured by the acceleration acquiring unit 21 and the elapsed time (see FIG. 4(a) and the like). The vibration intensity discrimination and activation determination unit 23 is a function on the acceleration sensor 11 side, which compares the acceleration value acquired by the acceleration acquisition unit 21 with the activation threshold value stored in the memory unit 30, and if the acceleration value exceeds the activation threshold value, transitions from power saving mode to measurement mode (activates the seismic sensor 10).

[0044] In addition, the vibration intensity discrimination / activation determination unit 23 calculates the vibration intensity from the measurement results of the acceleration acquisition unit 21, and if the vibration intensity is equal to or greater than a predetermined magnitude, transitions from the power saving mode to the measurement mode, which consumes more power than the power saving mode (activates the controller 12). Here, the vibration intensity classification process performed by the vibration intensity classification / activation determination unit 23 is performed by filtering the acceleration value acquired by the acceleration acquisition unit 21. At this time, the filtered acceleration is stored in the storage unit 30.

[0045] The frequency detection section 24 detects the period (frequency) and amplitude of the acceleration waveform generated by the acceleration waveform generation section 22, for example, by a zero-crossing method. The zero-crossing method is a method that detects the time between the point where a waveform crosses zero (or a hysteresis value set near zero) and the next point where it crosses zero (or a hysteresis value set near zero) as one cycle (frequency) (see Figure 3). Compared to the peak method, which detects the time between one waveform peak and the next peak as one cycle, the zero-crossing method makes it more difficult to detect minute vibrations, but it eliminates the effects of noise near zero acceleration (within the hysteresis range) and can detect frequencies with high accuracy without being affected by minute vibration noise around the peak value.

[0046] The width of the hysteresis value that is set in advance when performing detection using the zero-cross method shown in FIG. 3 is adjusted as appropriate depending on the type and magnitude of the vibration to be detected. The vibration stop period determining unit 25 changes the amplitude threshold for determining whether the vibration has stopped, based on the period detected by the frequency detecting unit 24, and determines whether the vibration has stopped. Here, a characteristic feature that appears as a characteristic of an earthquake is, for example, that the vibration stop period included in the acceleration waveform is shorter than a predetermined period.

[0047] Specifically, earthquake vibrations are characterized by constant vibrations in various directions and almost no periods during which the vibrations stop, whereas vibrations caused by noise, such as those from everyday life, generally include periods during which the vibrations stop. Therefore, the seismic sensor 10 of this embodiment detects whether or not there is a period in which vibrations have almost stopped, as a characteristic of an earthquake, and determines whether or not an earthquake has occurred.

[0048] As shown in FIGS. 4(a) and 4(b), the vibration stop period determination unit 25 determines whether or not there is a vibration stop period by using a threshold value that changes depending on the cycle (frequency). Specifically, when the detected vibration is a low-frequency vibration (long period of acceleration waveform) as shown in FIG. 4(a), the vibration stop period determination unit 25 sets a small acceleration threshold value and determines a period in which the amplitude of acceleration is smaller than this threshold value to be a vibration stop period.

[0049] On the other hand, when the detected vibration is a high-frequency vibration (short period of the acceleration waveform) shown in Figure 4(b), the vibration stop period determination unit 25 sets the acceleration threshold higher than that for low-frequency vibration, and determines that the period in which the acceleration amplitude is smaller than this threshold is a vibration stop period. As a result, even when high-frequency vibrations with larger acceleration are detected even with the same displacement, the threshold value for determining the vibration stop period is set higher than that for low-frequency vibrations, making it possible to determine with high accuracy whether or not there is a vibration stop period.

[0050] Here, as shown in Fig. 5(a), if it is determined that vibration has stopped when the amplitude of the displacement is 0.5 cm or less, the threshold for determining the vibration stop period is set to be larger as the period of the acceleration waveform becomes shorter, i.e., the higher the frequency, as shown in the graph of Fig. 5(b) obtained by differentiating this amplitude twice.On the other hand, the threshold is set to be smaller for the period of the acceleration waveform becoming longer, i.e., the lower the frequency.

[0051] As a result, for example, by storing the graph (table) shown in Figure 5(b) in the memory unit 30, the vibration stop period determination unit 25 can make a determination by changing the threshold for determining the vibration stop period depending on the period (frequency) of the detected vibration. The earthquake determination unit 26 determines whether or not the vibration is an earthquake based on the period detected by the frequency detection unit 24 and the result of determination by the vibration stop period determination unit 25 .

[0052] Specifically, the earthquake determination unit 26 determines whether the detected vibration is an earthquake or not by using the total or maximum value of the vibration stop time at which the vibration stop period determination unit 25 determines that the vibration has stopped. More specifically, the earthquake determination unit 26 determines that the detected vibration is an earthquake if the ratio of the vibration stop time to the total vibration time is smaller than a predetermined ratio threshold. Alternatively, the earthquake determination unit 26 determines that the detected vibration is an earthquake if the maximum value of the vibration stop time is smaller than a predetermined maximum threshold.

[0053] When the earthquake determination unit 26 determines that an earthquake has occurred, the earthquake magnitude calculation unit 27 determines whether the earthquake has a seismic intensity of at least a predetermined level. Furthermore, after the earthquake magnitude calculation unit 27 determines that the detected vibration is an earthquake and starts calculating an index indicating the magnitude of the earthquake, if an acceleration waveform that can be considered to be an impact is detected, the earthquake magnitude calculation unit 27 excludes the acceleration waveform and calculates the magnitude of the earthquake.

[0054] The output control unit 28 controls the output of a signal from the output unit 14, which outputs a predetermined signal, depending on whether the magnitude of the earthquake calculated by the earthquake magnitude calculation unit 27 is equal to or greater than a predetermined seismic intensity. Here, the predetermined signal output from the output unit 14 includes, for example, a shutoff signal sent to an external device such as an electricity supply device or a gas supply device in order to stop the supply of energy such as electricity or gas.

[0055] When earthquake determination unit 26 determines that the vibration detected by acceleration acquisition unit 21 is noise, offset adjustment unit 29 adjusts the offset amount of the acceleration waveform according to the magnitude of the noise. Then, offset adjustment unit 29 adjusts the offset amount of the acceleration waveform according to the determination result of earthquake determination unit 26 made based on the acceleration waveform. The offset adjustment performed by the offset adjuster 29 detects noise components contained in the measured acceleration as offset components, such as the amount of change in the measurement value that occurs with changes over time in the seismic sensor 10, the amount of change in the measurement value that occurs with temperature changes, and the amount of change in the measurement value that occurs when the orientation of the installed seismic sensor 10 tilts for some reason and the direction of gravitational acceleration relative to the seismic sensor 10 changes. Specifically, the offset adjuster 29 calculates, for example, the median of the maximum and minimum values ​​of the acceleration determined to be noise, or the average value of the acceleration, as the offset component.

[0056] The memory unit 30 stores, for example, acceleration data acquired by the acceleration acquisition unit 21 or acceleration data after filtering processing, a graph (table) of threshold values ​​used for judgment in the vibration stop period judgment unit 25 (see Figure 5(b)), the judgment results in the earthquake judgment unit 26, data of offset components used in the offset adjustment unit 29, etc.

[0057] <Earthquake detection method> The earthquake detection method using the seismic sensor 10 of this embodiment will be described below with reference to the flowchart shown in FIG. That is, in step S11, the acceleration acquisition unit 21 of the seismic sensor 10 acquires the acceleration measured by the acceleration sensor 11. Next, in step S12, the acceleration waveform generating unit 22 generates an acceleration waveform using the acceleration acquired in step S11. Next, in step S13, the frequency detection unit 24 detects the period and amplitude of the acceleration waveform generated in step S12 using the zero-crossing method.

[0058] Next, in step S14, the vibration stop period determination unit 25 acquires a threshold value for determining whether or not there is a vibration stop period, which changes depending on the period (frequency) detected in step S13, from the graph (table) stored in the memory unit 30 (see Figure 4(b)). At this time, as described above, the acquired threshold value is set to be larger as the period of the acceleration waveform becomes shorter (high frequency), and is set to be smaller as the period of the acceleration waveform becomes longer (low frequency).

[0059] Next, in step S15, the amplitude of the acceleration waveform of the detected vibration is compared with the vibration stop threshold value acquired in step S14 to determine whether or not the relationship of amplitude<vibration stop threshold value is satisfied. If this relationship is satisfied, the process proceeds to step S16, and if not, the process proceeds to step S18. Next, in step S16, since it was determined in step S15 that the amplitude of the acceleration waveform of the detected vibration was smaller than the vibration stop threshold, it is determined that the vibration has almost stopped, and the vibration stop period determination unit 25 updates the vibration stop time (total) as data for finally calculating the vibration stop time (percentage).

[0060] Next, in step S17, the vibration stop period determination unit 25 updates the vibration stop time (the maximum time during which vibration has been stopped continuously). Next, in step S18, it is determined whether or not the vibration determination is to be completed. If it is determined that the vibration determination is completed, the process proceeds to step S19, and if it is determined that the vibration determination is not yet completed, the process proceeds to step S11.

[0061] Next, in step S19, the vibration stop period determination unit 25 updates the vibration stop period (proportion) calculated by dividing the total vibration stop period by the entire period during which vibration was detected. Next, in step S20, the earthquake determination unit 26 determines whether or not either of the following relational expressions (1) and (2) is satisfied. Vibration stop time (percentage) < threshold of vibration stop percentage (1) Vibration stop time (max) < vibration stop maximum threshold (2) If relational expression (1) or (2) is satisfied, the process proceeds to step S21, where the earthquake determination unit 26 determines that the period of vibration cessation is short and therefore the possibility of an earthquake is high, and the process ends. On the other hand, if neither relational expression (1) nor (2) is satisfied, the process proceeds to step S22, where the earthquake determination unit 26 determines that the period of vibration cessation is long and therefore the possibility of an earthquake is low, and the detected vibration is determined to be not an earthquake (it is noise), and the process ends.

[0062] <Major features> As shown in FIG. 2, the seismic sensor 10 of this embodiment includes an acceleration acquisition unit 21, an acceleration waveform generation unit 22, a frequency detection unit 24, a vibration stop period determination unit 25, and an earthquake determination unit 26. The acceleration acquisition unit 21 detects vibrations and acquires the acceleration of the vibrations. The acceleration waveform generation unit 22 generates an acceleration waveform that indicates the relationship between the acceleration measured by the acceleration acquisition unit 21 and elapsed time. The frequency detection unit 24 detects the period and amplitude of the acceleration waveform generated by the acceleration waveform generation unit 22. The vibration stop period determination unit 25 determines whether or not the vibrations have stopped by changing the amplitude threshold value for determining whether or not the vibrations have stopped, based on the period detected by the frequency detection unit 24. The earthquake determination unit 26 determines whether or not the vibrations are an earthquake, based on the period detected by the frequency detection unit 24 and the result of determination by the vibration stop period determination unit 25.

[0063] This allows the period and amplitude of the acceleration waveform of the detected vibration to be detected, and the amplitude threshold used to determine whether the vibration has stopped is changed depending on the period.For example, if the period is short (the frequency is high), the threshold amplitude value can be set to a large value, allowing the vibration to be determined to have stopped with high accuracy. As a result, it is possible to determine with high accuracy when high frequency vibrations such as daily life vibrations have stopped.

[0064] [Other embodiments] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention. (A) In the above embodiment, the present invention has been described as being implemented as a seismic sensor and an earthquake detection method, but the present invention is not limited to this.

[0065] For example, the present invention may be realized as an earthquake detection program that causes a computer to execute the earthquake detection method using the seismic sensor described above. This earthquake detection program is stored in a memory (storage unit) installed in the seismic sensor, and the CPU reads the earthquake detection program stored in the memory and causes the hardware to execute each step. More specifically, the CPU reads the earthquake detection program and executes the acceleration acquisition step, acceleration waveform generation step, detection step, vibration stop period determination step, and earthquake determination step, thereby achieving the same effects as those described above. The present invention may also be realized as a recording medium storing an earthquake detection program for a seismic sensor.

[0066] (B) In the above embodiment, an example has been described in which the earthquake determination unit 26 determines whether the detected vibration is an earthquake or not by using the total or maximum value of the vibration stop period. However, the present invention is not limited to this. For example, earthquake determination may be performed using other parameters (algorithms) such as the presence or absence of a vibration stop period or a median value, in addition to the total value or maximum value of the vibration stop period.

[0067] (C) In the above embodiment, the seismic sensor 10 is described as having a storage unit 30 that stores a table showing the relationship between the period and the threshold value for determining the stop period, which changes for each period. However, the present invention is not limited to this. For example, a table showing the relationship between the threshold value for determining the stop period and the period may be stored outside the seismic sensor (e.g., a server device, cloud space, etc.), and the vibration stop period determination unit may access external storage means as necessary to make a determination.

[0068] (D) In the above embodiment, an example has been described in which the frequency detection unit 24 detects the period and amplitude of the acceleration waveform using the zero-crossing method, but the present invention is not limited to this. For example, instead of the zero-crossing method, the period and amplitude of the acceleration waveform may be detected by FFT (Fast Fourier Transform).

[0069] (E) In the above embodiment, an example has been described in which earthquake determination is performed using the total or maximum value of vibration stop periods, but the present invention is not limited to this. For example, the seismic sensor may determine whether or not there is a vibration cessation period included in the acceleration waveform of the detected vibration, and does not perform earthquake determination.

[0070] (F) In the above embodiment, an example was described in which the amplitude of the acceleration waveform corresponding to a displacement amplitude of 0.5 cm or less was used as the threshold value for determining the vibration stop period. However, the present invention is not limited to this. For example, the amplitude of the displacement that is used as the basis for calculating the threshold value of the amplitude of the acceleration waveform is not limited to 0.5 cm, and may be another value.

[0071] (G) In the above embodiment, an example has been described in which the seismic sensor 10 is provided with the earthquake determination unit 26 that performs earthquake determination based on the determination result of the vibration stop period determination unit 25. However, the present invention is not limited to this. For example, the seismic sensor may perform processing up to determining whether or not there is a period of vibration suspension (vibration analysis processing), but may not perform earthquake determination.

[0072] In this case, the determination result of the vibration stop period determination unit is transmitted to an external device (for example, an external server device, etc.), and the earthquake determination is performed on the external device side, thereby achieving the same effect as above.

[0073] <Additional Notes> The seismic sensor according to the first invention is an acceleration acquisition unit that detects vibration and acquires the acceleration of the vibration; an acceleration waveform generating unit that generates an acceleration waveform indicating a relationship between the acceleration measured by the acceleration acquiring unit and elapsed time; a detection unit that detects the period and amplitude of the acceleration waveform generated by the acceleration waveform generation unit; a vibration stop period determination unit that determines whether or not the vibration has stopped by changing an amplitude threshold value for determining that the vibration has stopped based on the period detected by the detection unit; and an earthquake determination unit that determines whether the vibration is an earthquake based on the period detected by the detection unit and the result of determination by the vibration stop period determination unit; It is equipped with:

[0074] The seismic sensor according to the second invention is the seismic sensor according to the first invention, The earthquake determination unit determines whether the vibration is an earthquake by using the total or maximum value of the vibration stop time during which the vibration stop period determination unit determines that the vibration has stopped. The seismic sensor according to the third invention is the seismic sensor according to the second invention, The earthquake determination unit determines that the vibration is an earthquake when the ratio of the vibration stop time to the total vibration time is smaller than a predetermined ratio threshold.

[0075] A seismic sensor according to a fourth aspect of the present invention is the seismic sensor according to the second aspect of the present invention, The earthquake determination unit determines that the vibration is an earthquake when the maximum value of the vibration stop time is smaller than a predetermined maximum threshold value. A seismic sensor according to a fifth aspect of the present invention is a seismic sensor according to any one of the first to fourth aspects of the present invention, The vibration stop period determining unit sets, as a threshold value for determination, a result obtained by differentiating a preset amplitude for determining that vibration has stopped and a displacement for determining that vibration has stopped according to a period.

[0076] A seismic sensor according to a sixth aspect of the present invention is a seismic sensor according to any one of the first to fifth aspects of the present invention, The detection unit detects the period and amplitude of the acceleration waveform generated by the acceleration waveform generation unit using a zero-crossing method. The seismic sensor according to the seventh invention is the seismic sensor according to any one of the first to sixth inventions, The earthquake detection unit further includes an earthquake magnitude calculation unit that determines whether the earthquake is equivalent to or greater than a predetermined seismic intensity when the earthquake determination unit determines that an earthquake has occurred.

[0077] The seismic sensor according to an eighth aspect of the present invention is the seismic sensor according to any one of the first to seventh aspects of the present invention, The device further includes an activation determination unit that calculates the vibration intensity from the measurement results of the acceleration acquisition unit, and when the vibration intensity is equal to or greater than a predetermined magnitude, transitions from a power saving mode to a measurement mode that consumes more power than the power saving mode.

[0078] A seismic sensor according to a ninth aspect of the present invention is a seismic sensor according to any one of the first to eighth aspects of the present invention, The earthquake detection unit further includes an output control unit that outputs a predetermined signal when it is determined that an earthquake has occurred. A seismic sensor according to a tenth aspect of the present invention is a seismic sensor according to any one of the first to ninth aspects of the present invention, The device further includes a storage unit that stores a table indicating the relationship between the threshold value that changes for each period and the period. [Industrial Applicability]

[0079] The seismic sensor of the present invention has the effect of being able to accurately determine the cessation of high-frequency vibrations, such as those caused by daily life, and is therefore widely applicable to various devices that detect and analyze vibrations. [Explanation of symbols]

[0080] 10 Seismic Sensor 11 Acceleration sensor 12 Controllers 13. Memory 14 Output section 21 Acceleration acquisition section 22 Acceleration waveform generator 23 Vibration intensity classification / startup determination section (startup determination section) 24 Frequency detection unit (detection unit) 25 Vibration stop period determination unit 26 Earthquake Determination Department 27 Earthquake scale calculation department 28 Output control section 29 Offset adjustment section 30 Storage section

Claims

1. an acceleration acquisition unit that detects vibration and acquires the acceleration of the vibration; an acceleration waveform generating unit that generates an acceleration waveform indicating a relationship between the acceleration measured by the acceleration acquiring unit and elapsed time; a detection unit that detects the period and amplitude of the acceleration waveform generated by the acceleration waveform generation unit; a vibration stop period determination unit that determines whether or not the vibration has stopped by changing an amplitude threshold value for determining that the vibration has stopped based on the period detected by the detection unit; and an earthquake determination unit that determines whether the vibration is an earthquake based on the period detected by the detection unit and the result of determination by the vibration stop period determination unit; A seismic sensor equipped with:

2. the earthquake determination unit determines whether the vibration is an earthquake by using a total value or a maximum value of vibration stop times at which the vibration stop period determination unit determines that the vibration has stopped. The seismic sensor according to claim 1 .

3. The earthquake determination unit determines that the vibration is an earthquake when a ratio of the vibration stop time to the total vibration time is smaller than a predetermined ratio threshold. The seismic sensor according to claim 2.

4. The earthquake determination unit determines that the vibration is an earthquake when the maximum value of the vibration stop time is smaller than a predetermined maximum threshold. The seismic sensor according to claim 2.

5. the vibration stop period determination unit sets a result obtained by differentiating a predetermined amplitude for determining that vibration has stopped and a displacement for determining that vibration has stopped according to a period as a threshold for determination; The seismic sensor according to claim 1 or 2.

6. the detection unit detects the period and amplitude of the acceleration waveform generated by the acceleration waveform generation unit using a zero-crossing method. The seismic sensor according to claim 1 or 2.

7. The apparatus further includes an earthquake magnitude calculation unit that, when the earthquake determination unit determines that an earthquake has occurred, determines whether the earthquake has a seismic intensity of at least a predetermined level. The seismic sensor according to claim 1 or 2.

8. The device further includes an activation determination unit that calculates the vibration intensity from the measurement result of the acceleration acquisition unit, and when the vibration intensity is equal to or greater than a predetermined magnitude, transitions from the power saving mode to a measurement mode that consumes more power than the power saving mode. The seismic sensor according to claim 1 or 2.

9. The earthquake determination unit further includes an output control unit that outputs a predetermined signal when the earthquake determination unit determines that an earthquake has occurred. The seismic sensor according to claim 1 or 2.

10. The method further includes a storage unit that stores a table indicating a relationship between the threshold value that changes for each period and the period. The seismic sensor according to claim 1 or 2.

11. an acceleration acquisition step of detecting vibration and acquiring the acceleration of the vibration; an acceleration waveform generating step of generating an acceleration waveform indicating a relationship between the acceleration measured in the acceleration acquiring step and elapsed time; a detection step of detecting a period and an amplitude of the acceleration waveform generated in the acceleration waveform generation step; a vibration stop period determination step of determining whether or not the vibration has stopped by changing an amplitude threshold value for determining that the vibration has stopped based on the period detected in the detection step; an earthquake determination step of determining whether the vibration is an earthquake based on the period detected in the detection step and the result of the determination in the vibration stop period determination step; An earthquake detection method comprising:

12. an acceleration acquisition step of detecting vibration and acquiring the acceleration of the vibration; an acceleration waveform generating step of generating an acceleration waveform indicating a relationship between the acceleration measured in the acceleration acquiring step and elapsed time; a detection step of detecting a period and an amplitude of the acceleration waveform generated in the acceleration waveform generation step; a vibration stop period determination step of determining whether or not the vibration has stopped by changing an amplitude threshold value for determining that the vibration has stopped based on the period detected in the detection step; an earthquake determination step of determining whether the vibration is an earthquake based on the period detected in the detection step and the result of the determination in the vibration stop period determination step; An earthquake detection program that causes a computer to execute an earthquake detection method comprising the steps of:

13. an acceleration acquisition unit that detects vibration and acquires the acceleration of the vibration; an acceleration waveform generating unit that generates an acceleration waveform indicating a relationship between the acceleration measured by the acceleration acquiring unit and elapsed time; a detection unit that detects the period and amplitude of the acceleration waveform generated by the acceleration waveform generation unit; a vibration stop period determination unit that determines whether or not the vibration has stopped by changing an amplitude threshold value for determining that the vibration has stopped based on the period detected by the detection unit; and A seismic sensor equipped with:

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