Seismic sensor, earthquake detection method, and earthquake detection program

Abstract

A seismic sensor (10) is provided with 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 the relationship between acceleration measured at the acceleration acquisition unit (21) and elapsed time. The frequency detection unit (24) detects the period and amplitude of the generated acceleration waveform. The vibration stop period determination unit (25) determines the stopping of vibration by changing a threshold value of amplitude for determining that vibration has stopped on the basis of the detected period. The earthquake determination unit (26) determines whether the vibration is an earthquake on the basis of the period detected at the frequency detection unit (24) and the result determined at the vibration stop period determination unit (25).

Description

Earthquake sensor, earthquake detection method, and earthquake detection program

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

[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 shutoff signal to shut off the supply of gas, electricity, etc. when they detect earthquake motion of a magnitude equal to or greater than a predetermined value (for example, seismic intensity 5+ or greater). 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 determination period in an earthquake processing period, the seismic sensor including a continuing earthquake determination unit that determines the occurrence of an earthquake based on acceleration measured during the earthquake processing period, and a shutoff determination unit that prevents the output of a shutoff signal regardless of the index value when the continuing earthquake determination unit determines that an earthquake has not occurred.

[0003] Patent No. 6465257

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

[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.

[0006] (Means for solving the problem) A seismic sensor according to a 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 indicating 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 determines whether or not the vibrations have stopped by changing the amplitude threshold for determining whether the vibrations have stopped based on the period detected by the detection unit. The earthquake determination unit determines whether or not 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 according to 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. Note that the period of vibration cessation includes not only a period during which the amplitude of the vibration is completely zero, but also a period during which the amplitude of the vibration is equal to or less than a predetermined threshold.

[0008] One of the characteristics of earthquakes is that there is no period in which vibrations, where the amplitude of the acceleration waveform is below a predetermined value, are almost completely stopped. Therefore, when determining whether an earthquake has occurred, it is important to accurately detect that there are no periods in the acceleration waveform where vibrations are stopped. Furthermore, when the detected vibrations are compared between low-frequency vibrations and high-frequency vibrations, the acceleration of high-frequency vibrations is greater even for the same displacement, which can make it difficult to determine that vibrations have stopped, even when they should.

[0009] This allows the period and amplitude of the acceleration waveform of the detected vibration to be detected, and the amplitude threshold for determining whether the vibration has stopped is changed according to the period. For example, if the period is short (the frequency is high), the threshold amplitude value can be set to a large value, thereby enabling highly accurate determination of whether the vibration has stopped. As a result, it is possible to accurately determine whether high-frequency vibrations such as those occurring in daily life have stopped.

[0010] A seismic sensor according to a second aspect of the present invention is the seismic sensor according to the first aspect of the present invention, wherein 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. This makes it possible to accurately determine whether the vibration is an earthquake by using the total or maximum value of the period during which the amplitude is below the threshold and is determined to have stopped by the vibration stop period determination unit.

[0011] A seismic sensor according to a third 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 ratio of vibration stop time to the total vibration time is smaller than a predetermined ratio threshold. As a result, when the ratio of the time determined by the vibration stop period determination unit to the total vibration is smaller than a predetermined ratio, it is determined that the vibration is likely 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. As a result, when the maximum value of the time determined as vibration stop by the vibration stop period determination unit is smaller than the predetermined threshold, it is determined that the period during which vibration is almost completely stopped is short and therefore is not noise such as daily vibration, and the vibration can be determined to be an earthquake.

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

[0014] A seismic sensor according to a sixth aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, wherein the detection unit uses a zero-crossing method to detect the period and amplitude of the acceleration waveform generated by the acceleration waveform generation unit. The zero-crossing method detects the period (frequency) between the point where a waveform exceeds zero (or a hysteresis value set near zero) and the point where it subsequently falls below zero (a hysteresis value below zero) and then exceeds zero (or a hysteresis value set near zero) again as one period (frequency). While this method makes it more difficult to detect minute vibrations than the peak-based method, which detects the period between two peaks in an acceleration waveform as one period, it is possible to detect the period and amplitude with high accuracy without being affected by minute vibration noise.

[0015] The seismic sensor according to a seventh aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, further comprising an earthquake scale calculation unit that, when the earthquake determination unit determines that an earthquake has occurred, determines whether the earthquake is equivalent to or greater than a predetermined seismic intensity. As a result, for example, when the earthquake scale is determined to be upper 5 or greater, it is possible to improve the safety of the user by outputting a cutoff signal to stop the supply of energy such as electricity or gas, as there is a risk of a fire or gas leak.

[0016] The seismic sensor according to an eighth aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, further comprising an activation determination unit that calculates the vibration intensity from the measurement results of the acceleration acquisition unit, and, if 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. This allows highly accurate earthquake detection while reducing power consumption by transitioning to the measurement mode, which performs earthquake detection processing using the vibration acceleration waveform, only when the detected vibration intensity is equal to or greater than a predetermined magnitude (e.g., equivalent to a seismic intensity of 4).

[0017] The seismic sensor according to a ninth aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, further comprising an output control unit that outputs a predetermined signal when the earthquake determination unit determines that an earthquake has occurred. As a result, for example, when an earthquake occurs, the output unit can output a cut-off signal to stop the supply of energy such as electricity or gas, or a warning signal to notify 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 a threshold value that changes with each period, thereby making it possible to perform earthquake detection by referring to the table showing the relationship between the threshold value and the period stored in the memory 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 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 determination in the vibration stop period determination step.

[0020] Here, the amplitude threshold for determining whether the vibration has stopped is changed according to 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. Note that the period of vibration cessation includes not only a period during which the amplitude of the vibration is completely zero, but also a period during which the amplitude of the vibration is equal to or less than a predetermined threshold.

[0021] One of the characteristics of earthquakes is that there is no period in which vibrations, where the amplitude of the acceleration waveform is below a predetermined value, are almost completely stopped. Therefore, when determining whether an earthquake has occurred, it is important to accurately detect that there are no periods in the acceleration waveform where vibrations are stopped. Furthermore, when the detected vibrations are compared between low-frequency vibrations and high-frequency vibrations, the acceleration of high-frequency vibrations is greater even for the same displacement, which can make it difficult to determine that vibrations have stopped, even when they should.

[0022] This allows the period and amplitude of the acceleration waveform of the detected vibration to be detected, and the amplitude threshold for determining whether the vibration has stopped is changed according to the period. For example, if the period is short (the frequency is high), the threshold amplitude value can be set to a large value, thereby enabling highly accurate determination of whether the vibration has stopped. As a result, it is possible to accurately determine whether high-frequency vibrations such as those occurring in daily life have stopped.

[0023] A twelfth aspect of the present invention provides an earthquake detection program that 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 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 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 according to 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. Note that the period of vibration cessation includes not only a period during which the amplitude of the vibration is completely zero, but also a period during which the amplitude of the vibration is equal to or less than a predetermined threshold.

[0025] One of the characteristics of earthquakes is that there is no period in which vibrations, where the amplitude of the acceleration waveform is below a predetermined value, are almost completely stopped. Therefore, when determining whether an earthquake has occurred, it is important to accurately detect that there are no periods in the acceleration waveform where vibrations are stopped. Furthermore, when the detected vibrations are compared between low-frequency vibrations and high-frequency vibrations, the acceleration of high-frequency vibrations is greater even for the same displacement, which can make it difficult to determine that vibrations have stopped, even when they should.

[0026] This allows the period and amplitude of the acceleration waveform of the detected vibration to be detected, and the amplitude threshold for determining whether the vibration has stopped is changed according to the period. For example, if the period is short (the frequency is high), the threshold amplitude value can be set to a large value, thereby enabling highly accurate determination of whether the vibration has stopped. As a result, it is possible to accurately determine whether high-frequency vibrations such as those occurring in daily life 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 according to 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. Note that the period of vibration cessation includes not only a period during which the amplitude of the vibration is completely zero, but also a period during which the amplitude of the vibration is equal to or less than a predetermined threshold.

[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.

[0030] Effect of the Invention 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.

[0031] 2 is a control block diagram showing the configuration of a seismic sensor according to one embodiment of the present invention. FIG. 1 is a functional block diagram generated within the seismic sensor of FIG. 1. FIG. 2 is a graph illustrating a zero-crossing method for detecting the frequency of an acceleration waveform of detected vibration. (a) is a graph showing an example of an acceleration waveform of low-frequency vibration. (b) is a graph showing an example of an acceleration waveform of high-frequency vibration. (a) is a graph showing that the displacement for determining that vibration has stopped is 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, according to frequency. FIG. 2 is a flowchart showing the processing flow of an earthquake detection method executed by the seismic sensor of FIG. 2.

[0032] A seismic sensor according to one embodiment of the present invention will be described below with reference to FIGS. 1 to 6. In this embodiment, more detailed explanation than necessary may be omitted. For example, detailed explanations of well-known matters or redundant explanations of substantially identical configurations 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 explanation to enable those skilled in the art to fully understand the present invention, and does not intend for them to limit the subject matter recited 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 the 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, which 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] The controller 12 also operates in two different modes, active mode and sleep mode, depending on the situation. In sleep mode, the controller 12 operates with limited functionality, such as halting execution of instructions while accepting interrupts and halting clock supply. In sleep mode, power consumption can be reduced more than in active mode.

[0036] The active mode is a mode in which the detected vibrations are determined to be earthquakes or noise, and an index value indicating the magnitude of the earthquake is calculated. The functional blocks (see FIG. 2) generated by the CPU in the seismic sensor 10 when it 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 an earthquake has occurred, information indicating the occurrence and magnitude of the earthquake is output to another device via the output unit 14. When an earthquake of a predetermined magnitude 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 blocks of the 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] 2, each of the functional blocks is configured by the controller 12 receiving acceleration data acquired from the acceleration sensor 11 and reading a program stored in the memory 13. The acceleration acquisition unit 21 acquires measurement data of acceleration measured at a predetermined cycle by the acceleration sensor 11. The acceleration acquisition unit 21 normally acquires measurement data of acceleration measured repeatedly at a relatively low speed (i.e., at a relatively large measurement cycle).

[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 the 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 memory unit 30, the acceleration sensor 11 repeatedly measures 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 sleep mode or active mode. Note that when the earthquake determination unit 26 (described later) and other units execute processing, the controller 12 operates in active mode (measurement mode). The transition from power-saving mode to measurement mode is called activating the seismic sensor 10.

[0042] The measurement mode is an operating state in which high-speed sampling is performed, and 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 greater power consumption than in the power-saving mode.

[0043] The acceleration waveform generator 22 generates an acceleration waveform that indicates the relationship between the acceleration measured by the acceleration acquirer 21 and elapsed time (see FIG. 4(a) and the like). The vibration intensity discriminator / activation determiner 23 is a function of the acceleration sensor 11 that compares the acceleration value acquired by the acceleration acquirer 21 with an activation threshold value stored in the memory 30, and if the acceleration value exceeds the activation threshold value, transitions from the power saving mode to the measurement mode (activates the seismic sensor 10).

[0044] Furthermore, 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 a measurement mode that consumes more power than the power saving mode (activates the controller 12). Here, the vibration intensity discrimination process performed by the vibration intensity discrimination / activation determination unit 23 is implemented by filtering the acceleration values ​​acquired by the acceleration acquisition unit 21. At this time, the filtered acceleration is stored in the memory unit 30.

[0045] The frequency detection unit 24 detects the period (frequency) and amplitude of the acceleration waveform generated by the acceleration waveform generation unit 22, for example, using a zero-crossing method. The zero-crossing method detects the period between a point in a waveform where the waveform exceeds zero (or a hysteresis value set near zero) and the next point where the waveform exceeds zero (or a hysteresis value set near zero) as one period (frequency) (see FIG. 3 ). Compared to the peak method, which detects the period between one peak in the waveform and the next peak as one period, the zero-crossing method makes it more difficult to detect minute vibrations. However, it can eliminate the influence of noise near zero acceleration (within the hysteresis range) and detect frequencies with high accuracy without being affected by minute vibration noise around the peak value.

[0046] The width of the hysteresis value, which is preset when performing detection using the zero-crossing 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 determination unit 25 determines whether or not the vibration has stopped by changing the amplitude threshold for determining that the vibration has stopped, based on the period detected by the frequency detection unit 24. Here, a characteristic feature that appears as a characteristic of an earthquake is, for example, a vibration stop period included in the acceleration waveform that 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. On the other hand, vibrations caused by noise, such as everyday vibrations, generally include periods during which the vibrations stop. Therefore, the seismic sensor 10 of this embodiment detects whether or not there is a period during which the vibrations have almost stopped as a characteristic of an earthquake, and determines whether or not an earthquake has occurred.

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

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

[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 value 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 value is set to be smaller for the period of the acceleration waveform becoming longer, i.e., the lower the frequency.

[0051] 5(b) is stored in the storage unit 30, the vibration stop period determination unit 25 can make a determination by changing the threshold value for determining the vibration stop period according to the period (frequency) of the detected vibration. The earthquake determination unit 26 determines whether the vibration is an earthquake or not based on the period detected by the frequency detection unit 24 and the result of the determination by the vibration stop period determination unit 25.

[0052] Specifically, the earthquake determination unit 26 determines whether the detected vibration is an earthquake 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 scale calculation unit 27 determines whether the earthquake has a seismic intensity of at least a predetermined level. After the earthquake determination unit 26 determines that the detected vibrations are an earthquake and starts calculating an index indicating the magnitude of the earthquake, if the earthquake scale calculation unit 27 detects an acceleration waveform that can be considered to be an impact, it calculates the magnitude of the earthquake by excluding the acceleration waveform.

[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 cutoff 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 the earthquake determination unit 26 determines that the vibration detected by the acceleration acquisition unit 21 is noise, the offset adjustment unit 29 adjusts the offset amount of the acceleration waveform according to the magnitude of the noise. The offset adjustment unit 29 then adjusts the offset amount of the acceleration waveform according to the determination result of the earthquake determination unit 26 based on the acceleration waveform. The offset adjustment performed by the offset adjustment unit 29 detects noise components contained in the measured acceleration as offset components, such as changes in measurement values ​​that occur due to changes in the seismic sensor 10 over time, changes in measurement values ​​that occur due to temperature changes, and changes in measurement values ​​that occur when the orientation of the installed seismic sensor 10 is tilted for some reason and the direction of gravitational acceleration relative to the seismic sensor 10 changes. Specifically, the offset adjustment unit 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 on 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 Figure 6. 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 generation 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) (see FIG. 4(b)) stored in the storage unit 30. 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 acquired in step S14 to determine whether the relationship of amplitude < vibration stop threshold is satisfied. If this relationship is satisfied, the process proceeds to step S16, and if this relationship is not satisfied, 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 is 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 for which vibration has been stopped continuously). Next, in step S18, it is determined whether or not the vibration determination is to be completed. Here, if it is determined that the vibration determination has been completed, the process proceeds to step S19, and if it is determined that the vibration determination has not yet been 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 total time during which vibration was detected. Next, in step S20, the earthquake determination unit 26 determines whether either of the following relational expressions (1) or (2) is satisfied: Vibration stop period (proportion) < Vibration stop period threshold (1); Vibration stop period (maximum) < Vibration stop period 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 vibration stop period is short and therefore highly likely to be an earthquake, and determines the detected vibration to be an earthquake, and terminates processing. 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 vibration stop period is long and therefore unlikely to be an earthquake, and determines the detected vibration to be not an earthquake (noise), and terminates processing.

[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 for determining whether the vibration has stopped is changed according to the period. For example, if the period is short (the frequency is high), the threshold amplitude value can be set to a large value, thereby enabling highly accurate determination of whether the vibration has stopped. As a result, it is possible to accurately determine whether high-frequency vibrations such as those occurring in daily life 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 spirit and scope of the invention. (A) In the above embodiment, an example in which the present invention is realized as a seismic sensor and an earthquake detection method has been described. However, 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 a seismic sensor described above. This earthquake detection program is stored in a memory (storage unit) installed in the seismic sensor, and a CPU loads the earthquake detection program stored in the memory and causes the hardware to execute each step. More specifically, the CPU loads the earthquake detection program and executes the acceleration acquisition step, acceleration waveform generation step, detection step, vibration cessation period determination step, and earthquake determination step described above, thereby achieving the same effects as 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 was described in which the earthquake determination unit 26 determines whether or not a detected vibration is an earthquake 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 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 with each period. However, the present invention is not limited to this. For example, the table showing the relationship between the period and the threshold value for determining the stop period may be stored outside the seismic sensor (e.g., in a server device, cloud space, etc.), and the vibration stop period determination unit may access the external storage means as needed to make a determination.

[0068] (D) In ​​the above embodiment, an example was described in which the frequency detection unit 24 detects the period and amplitude of the acceleration waveform using a zero-crossing method. However, 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 using an FFT (Fast Fourier Transform).

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

[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 for determining the vibration stop period. However, the present invention is not limited to this. For example, the displacement amplitude used as the basis for calculating the threshold for the acceleration waveform amplitude is not limited to 0.5 cm and may be another value.

[0071] (G) In the above embodiment, an example was described in which the seismic sensor 10 is equipped with the earthquake determination unit 26 that determines whether an earthquake has occurred based on the determination result from the vibration stop period determination unit 25. However, the present invention is not limited to this. For example, the seismic sensor may be configured to perform processing up to determining whether or not a vibration stop period has occurred (vibration analysis processing), but not to 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] <Notes> The seismic sensor of the first invention comprises: an acceleration acquisition unit that detects vibrations and acquires the acceleration of the vibrations; an acceleration waveform generation unit that generates an acceleration waveform that indicates the relationship between the acceleration measured by the acceleration acquisition 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 the vibrations have stopped by changing an amplitude threshold for determining that the vibrations have stopped based on the period detected by the detection unit; and an earthquake determination unit that determines whether the vibrations are an earthquake based on the period detected by the detection unit and the result determined by the vibration stop period determination unit.

[0074] A seismic sensor according to a second invention is the seismic sensor according to 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. A seismic sensor according to a third invention is the seismic sensor according to 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.

[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, wherein 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. A seismic sensor according to a fifth aspect of the present invention is the seismic sensor according to any one of the first to fourth aspects of the present invention, wherein the vibration stop period determination unit sets, as a determination threshold, a result obtained by differentiating a preset amplitude for determining that vibration has stopped with 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 the seismic sensor according to any one of the first to fifth aspects of the present 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.A seismic sensor according to a seventh aspect of the present invention is the seismic sensor according to any one of the first to sixth aspects of the present invention, further comprising an earthquake scale calculation unit that, when the earthquake determination unit determines that an earthquake has occurred, determines whether the earthquake is equivalent to or greater than a predetermined seismic intensity.

[0077] The seismic sensor of the eighth invention is a seismic sensor of any one of the first to seventh inventions, 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.

[0078] A seismic sensor according to a ninth aspect of the present invention is the seismic sensor according to any one of the first to eighth aspects of the present invention, further comprising an output control unit that outputs a predetermined signal when the earthquake determination unit determines that an earthquake has occurred.A seismic sensor according to a tenth aspect of the present invention is the seismic sensor according to any one of the first to ninth aspects of the present invention, further comprising a memory unit that stores a table showing the relationship between the threshold value that changes for each period and the period.

[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.

[0080] REFERENCE SIGNS LIST 10 Seismic sensor 11 Acceleration sensor 12 Controller 13 Memory 14 Output unit 21 Acceleration acquisition unit 22 Acceleration waveform generation unit 23 Vibration intensity classification and activation determination unit (activation determination unit) 24 Frequency detection unit (detection unit) 25 Vibration stop period determination unit 26 Earthquake determination unit 27 Earthquake magnitude calculation unit 28 Output control unit 29 Offset adjustment unit 30 Storage unit

Claims

1. A seismic sensor comprising: an acceleration acquisition unit that detects vibrations and acquires the acceleration of the vibrations; an acceleration waveform generation unit that generates an acceleration waveform that shows the relationship between the acceleration measured by the acceleration acquisition 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 the vibrations have stopped by changing an amplitude threshold for determining that the vibrations have stopped based on the period detected by the detection unit; and an earthquake determination unit that determines whether the vibrations are an earthquake based on the period detected by the detection unit and the result determined by the vibration stop period determination unit.

2. The seismic sensor of claim 1, wherein the earthquake determination unit determines whether the vibration is an earthquake or not 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.

3. The seismic sensor according to claim 2, 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.

4. The seismic sensor according to claim 2, wherein 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.

5. A seismic sensor as described in claim 1 or 2, wherein the vibration stop period determination unit sets the result obtained by differentiating the amplitude for determining that vibration has stopped, which is a preset value, with the displacement for determining that vibration has stopped according to the period, as the threshold value for determination.

6. A seismic sensor as described in claim 1 or 2, 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.

7. The seismic sensor according to claim 1 or 2, further comprising 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.

8. A seismic sensor as described in claim 1 or 2, further comprising 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.

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

10. The seismic sensor according to claim 1 or 2, further comprising a memory unit for storing a table showing the relationship between the threshold value that changes for each period and the period.

11. An earthquake detection method comprising: an acceleration acquisition step of detecting vibrations and acquiring the acceleration of the vibrations; an acceleration waveform generation step of generating an acceleration waveform showing the relationship between the acceleration measured in the acceleration acquisition step and elapsed time; a detection step of detecting the period and amplitude of the acceleration waveform generated in the acceleration waveform generation step; a vibration stop period determination step of determining whether the vibrations have stopped by changing an amplitude threshold for determining whether the vibrations have stopped based on the period detected in the detection step; and an earthquake determination step of determining whether the vibrations are an earthquake based on the period detected in the detection step and the result determined in the vibration stop period determination step.

12. An earthquake detection program that causes a computer to execute an earthquake detection method, comprising: an acceleration acquisition step of detecting vibrations and acquiring the acceleration of the vibrations; an acceleration waveform generation step of generating an acceleration waveform showing the relationship between the acceleration measured in the acceleration acquisition step and elapsed time; a detection step of detecting the period and amplitude of the acceleration waveform generated in the acceleration waveform generation step; a vibration stop period determination step of determining whether the vibrations have stopped by changing an amplitude threshold for determining whether the vibrations have stopped based on the period detected in the detection step; and an earthquake determination step of determining whether the vibrations are an earthquake based on the period detected in the detection step and the result determined in the vibration stop period determination step.

13. A seismic sensor comprising: an acceleration acquisition unit that detects vibrations and acquires the acceleration of the vibrations; an acceleration waveform generation unit that generates an acceleration waveform showing the relationship between the acceleration measured by the acceleration acquisition unit and elapsed time; a detection unit that detects the period and amplitude of the acceleration waveform generated by the acceleration waveform generation unit; and a vibration stop period determination unit that determines whether the vibrations have stopped by changing an amplitude threshold for determining that the vibrations have stopped based on the period detected by the detection unit.

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