Seismic sensor, earthquake detection method, and earthquake detection program

Abstract

A seismic sensor (10) comprises an acceleration acquiring unit (21), an acceleration waveform generating unit (22), a frequency detecting unit (24), an increase / decrease rate calculating unit (25a), an increase / decrease determining unit (25b), and an earthquake determining unit (26). The frequency detecting unit (24) detects the period and amplitude of an acceleration waveform generated by the acceleration waveform generating unit (22). On the basis of the period and amplitude detected by the frequency detecting unit (24), the increase / decrease rate calculating unit (25a) calculates an increase / decrease rate from the period and amplitude of the acceleration waveform detected last time by the frequency detecting unit (24). The increase / decrease determining unit (25b) compares the increase / decrease rate calculated by the increase / decrease rate calculating unit (25a) with a prescribed threshold value to determine whether vibrations are becoming amplified or attenuated. The earthquake determining unit (26) determines whether the vibrations are an earthquake on the basis of the determination result from the increase / decrease determining unit (25b).

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. Specifically, the seismic sensor disclosed in the above publication determines whether vibration has stopped based solely on acceleration, and therefore determines that noise exists if the peak-to-peak acceleration value over a certain period of time decays monotonically from the previous value. High-frequency vibrations, compared with low-frequency vibrations, tend to produce large acceleration changes with small changes in displacement, and everyday vibrations (noise) are often high-frequency vibrations. Therefore, high-frequency vibrations (noise) often do not decay monotonically, which can lead to the risk of misidentifying everyday vibrations as earthquakes.

[0005] An object of the present invention is to provide a seismic sensor, an earthquake detection method, and an earthquake detection program that can determine with high accuracy whether detected vibrations are earthquakes or noise.

[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, an increase / decrease rate calculation unit, an increase / decrease 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 increase / decrease rate calculation unit calculates the rate of increase / decrease from the period and amplitude of the acceleration waveform previously detected by the detection unit based on the period and amplitude detected by the detection unit. The increase / decrease determination unit compares the rate of increase / decrease calculated by the increase / decrease rate calculation unit with a predetermined amplification rate threshold and / or attenuation rate threshold to determine whether the vibration is amplified or attenuated. The earthquake determination unit determines whether the vibration is an earthquake based on the determination result of the increase / decrease determination unit.

[0007] Here, to detect noise characteristics such as "monotonous decay" and "no change in rate of increase or decrease" and determine whether an earthquake has occurred, the period and amplitude of the acceleration waveform are detected, and the rate of increase or decrease is used to determine whether the waveform is amplified or attenuated. Here, the period and amplitude of the acceleration waveform detected last time by the detection unit refer to the period and amplitude detected in the immediately preceding period.

[0008] This allows the system to determine whether the detected vibration is "monotonically decaying" or "the rate of increase or decrease is almost constant," which are characteristics of noise, using the period and amplitude of the acceleration waveform, thereby making it possible to determine whether the detected vibration is an earthquake or noise with high accuracy.

[0009] The seismic sensor according to the second invention is the seismic sensor according to the first invention, wherein the increase / decrease determination unit determines whether the vibration is amplified or attenuated by varying the increase / decrease rate threshold or the attenuation rate threshold for determining whether the vibration is amplified or attenuated based on the period detected by the detection unit. This solves the problem of high-frequency vibrations, which tend to have large changes in acceleration, being easily determined to be amplified or attenuated by varying the threshold value for determining whether the vibration is amplified or attenuated in accordance with changes in the period (frequency) of the acceleration waveform of the detected vibration, thereby enabling more accurate earthquake detection.

[0010] A seismic sensor according to a third aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, wherein the earthquake determination unit determines that the vibration is an earthquake if the period in which the increase / decrease determination unit determined that the vibration is attenuating does not continue for a predetermined period. As a result, if a period that appears to be monotonically attenuating, which is characteristic of noise such as high-frequency vibration, continues for a predetermined period, the vibration can be determined to be noise, and if it does not continue, the vibration can be determined to be an earthquake.

[0011] A seismic sensor according to a fourth aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, wherein the earthquake determination unit determines that the vibration is an earthquake if the period in which the increase / decrease determination unit determines that the rate of increase / decrease is unchanged does not continue for a predetermined period of time. As a result, if a period in which the rate of increase / decrease, which is characteristic of noise such as high-frequency vibration, does not change continues for a predetermined period of time, the vibration can be determined to be noise, and if the period does not continue, the vibration can be determined to be an earthquake.

[0012] 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 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 period (frequency) between a point in a waveform where the waveform exceeds zero (or a hysteresis value set near zero) and then falls below zero (a hysteresis value below zero) and then again exceeds zero (or a hysteresis value set near zero).

[0013] 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 the period and amplitude to be detected with high accuracy without being affected by minute vibration noise.

[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, 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 users by outputting a cutoff signal to stop the supply of energy such as electricity or gas, as there may be a risk of fire or gas leak.

[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 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.As a result, by transitioning to the measurement mode that performs earthquake determination 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), it is possible to perform highly accurate earthquake determination while suppressing power consumption.

[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 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 cutoff signal to stop the supply of energy such as electricity or gas, or a warning signal to notify of danger.

[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 a memory unit that stores a table showing the relationship between the period and the amplification factor threshold or the attenuation factor threshold that changes based on the recording period. This allows earthquake detection to be performed by referring to the table showing the relationship between the period and the amplification factor threshold and the attenuation factor threshold stored in the memory unit.

[0018] An earthquake detection method according to a tenth aspect of the present invention includes an acceleration acquisition step, an acceleration waveform generation step, a detection step, an increase / decrease rate calculation step, an increase / decrease determination step, and an earthquake determination step. In the acceleration acquisition step, vibrations are detected and the acceleration of the vibrations is acquired. In the acceleration waveform generation step, an acceleration waveform indicating the relationship between the acceleration measured in the acceleration acquisition step and elapsed time is generated. In the detection step, the period and amplitude of the acceleration waveform generated in the acceleration waveform generation step are detected. In the increase / decrease rate calculation step, an increase / decrease rate from the period and amplitude of the acceleration waveform previously detected in the detection step is calculated based on the period and amplitude detected in the detection step. In the increase / decrease determination step, the increase / decrease rate calculated in the increase / decrease rate calculation step is compared with a predetermined amplification rate threshold and / or attenuation rate threshold to determine whether the vibration is amplified or attenuated. In the earthquake determination step, it is determined whether the vibration is an earthquake based on the determination result in the increase / decrease determination step. Here, in order to detect noise characteristics such as "monotonous decay" and "no change in rate of increase or decrease" and make an earthquake judgment, the period and amplitude of the acceleration waveform are detected, and the rate of increase or decrease is used to determine whether the signal is amplified or attenuated, and the earthquake judgment is made based on the results.

[0019] Here, the period and amplitude of the acceleration waveform detected last time by the detection unit refer to the period and amplitude detected in the immediately preceding period. By using the period and amplitude of the acceleration waveform to determine whether the detected vibration exhibits "monotonically decaying" or "almost constant rate of increase and decrease," which are characteristics of noise, it is possible to determine that other vibrations are earthquakes. As a result, it is possible to determine with high accuracy whether the detected vibration is an earthquake or noise.

[0020] An eleventh 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, an increase / decrease rate calculation step, an increase / decrease determination step, and an earthquake determination step. In the acceleration acquisition step, vibrations are detected and the acceleration of the vibrations is acquired. In the acceleration waveform generation step, an acceleration waveform indicating the relationship between the acceleration measured in the acceleration acquisition step and elapsed time is generated. In the detection step, the period and amplitude of the acceleration waveform generated in the acceleration waveform generation step are detected. In the increase / decrease rate calculation step, a rate of increase / decrease from the period and amplitude of the acceleration waveform previously detected in the detection step is calculated based on the period and amplitude detected in the detection step. In the increase / decrease determination step, the increase / decrease rate calculated in the increase / decrease rate calculation step is compared with a predetermined amplification rate threshold and / or attenuation rate threshold to determine whether the vibration is amplified or attenuated. In the earthquake determination step, it is determined whether the vibration is an earthquake based on the determination result in the increase / decrease determination step.

[0021] Here, to detect noise characteristics such as "monotonous decay" and "no change in rate of increase or decrease" and determine whether an earthquake has occurred, the period and amplitude of the acceleration waveform are detected, and the rate of increase or decrease is used to determine whether the waveform is amplified or attenuated. Here, the period and amplitude of the acceleration waveform detected last time by the detection unit refer to the period and amplitude detected in the immediately preceding period.

[0022] This allows the system to determine whether the detected vibration is "monotonically decaying" or "the rate of increase or decrease is almost constant," which are characteristics of noise, using the period and amplitude of the acceleration waveform, thereby making it possible to determine whether the detected vibration is an earthquake or noise with high accuracy.

[0023] A seismic sensor according to a twelfth aspect of the present invention includes an acceleration acquisition unit, an acceleration waveform generation unit, a detection unit, an increase / decrease rate calculation unit, and an increase / decrease 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 increase / decrease rate calculation unit calculates the rate of increase / decrease from the period and amplitude of the acceleration waveform previously detected by the detection unit, based on the period and amplitude detected by the detection unit. The increase / decrease determination unit compares the rate of increase / decrease calculated by the increase / decrease rate calculation unit with a predetermined amplification rate threshold and / or attenuation rate threshold to determine whether the vibration is amplified or attenuated.

[0024] Here, the period and amplitude of the acceleration waveform are detected as a vibration analysis to detect noise characteristics such as "monotonous decay" and "no change in rate of increase or decrease" and to determine whether an earthquake has occurred. The rate of increase or decrease is used to determine whether the waveform is amplified or attenuated. Here, the period and amplitude of the acceleration waveform detected by the detection unit last time refer to the period and amplitude detected in the immediately preceding period.

[0025] This allows the system to determine whether the detected vibration is "monotonically decaying" or "the rate of increase or decrease is almost constant," which are characteristics of noise, using the period and amplitude of the acceleration waveform, thereby making it possible to determine whether the detected vibration is an earthquake or noise with high accuracy.

[0026] 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.

[0027] 4 is a control block diagram showing the configuration of a seismic sensor according to one embodiment of the present invention. A functional block diagram generated within the seismic sensor of FIG. 1. Graphs explaining a zero-crossing method for detecting the frequency of the acceleration waveform of detected vibration. (a) is a graph showing the change in displacement amplitude with respect to the displacement period for determining whether vibration is amplifying or attenuating based on the current displacement amplitude. (b) is a graph showing the change in acceleration amplitude with respect to the acceleration period obtained by differentiating (a) twice. (c) is a graph showing the relationship (table) between the acceleration period obtained by differentiating (a) twice and the increase / decrease rate threshold for determining increase / decrease. (d) is a flowchart showing the processing flow of an earthquake detection method executed by the seismic sensor of FIG. 2.

[0028] A seismic sensor according to one embodiment of the present invention will be described below with reference to Figures 1 to 6. Note that in this embodiment, more detailed explanation than necessary may be omitted. For example, detailed explanations of already 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.

[0029] 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.

[0030] (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. 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 "sampled") 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, and detects the occurrence of an earthquake and calculates an index value indicating the magnitude of the earthquake based on the acquired acceleration.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] (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, an increase / decrease rate calculation unit 25a, an increase / decrease determination unit 25b, 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.

[0035] 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).

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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. The vibration intensity discriminator / activation determiner 23 is a function on the acceleration sensor 11 side that compares the acceleration value acquired by the acceleration acquirer 21 with an activation threshold value stored in the memory 30, and transitions from the power saving mode to the measurement mode (activates the seismic sensor 10) if the acceleration value exceeds the activation threshold value.

[0040] 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.

[0041] 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.

[0042] The width of the hysteresis value, which is set in advance 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 increase / decrease rate calculation unit 25a calculates the rate of increase / decrease from the period and amplitude of the acceleration waveform previously detected by the frequency detection unit 24, based on the period and amplitude of the acceleration waveform detected by the frequency detection unit 24. That is, in order to monitor changes in the period and amplitude of the acceleration waveform, the increase / decrease rate calculation unit 25a compares the previous period and amplitude with the current period and amplitude to calculate the increase / decrease rate (amplification rate, attenuation rate) of the acceleration waveform.

[0043] The increase / decrease determination unit 25b compares the increase / decrease rate calculated by the increase / decrease rate calculation unit 25a with a predetermined amplification rate threshold and / or attenuation rate threshold to determine whether the vibration is amplified, attenuated, or unchanged. That is, as shown in Fig. 4(a), the increase / decrease determination unit 25b sets a region where it is determined to be unchanged, a region where it is determined to be amplified, and a region where it is determined to be attenuated, based on the current amplitude of the displacement. At this time, the amplitude of the acceleration changes depending on its period (frequency), as shown in the graph shown in Fig. 4(b), which is obtained by differentiating the graph shown in Fig. 4(a) twice.

[0044] In the example shown in FIG. 4( a ), in the region with a short period (high frequency), the amplitude of the displacement is amplified when comparing the previous period (the previous cycle) with the current period. However, in the example shown in FIG. 4( b ), the amplitude of the acceleration is attenuated when comparing the previous period with the current period. This poses a problem in conventional seismic sensors, where this is mistakenly determined as attenuation. In the seismic sensor 10 of this embodiment, as shown in FIG. 5 , the magnitude of the increase / decrease rate threshold (%) is varied with respect to the period of the acceleration waveform to determine whether the amplitude of the acceleration waveform of the detected vibration increases or decreases. In the seismic sensor 10, the increase / decrease determination unit 25 b sets a larger threshold for the increase / decrease determination as the period of the acceleration waveform becomes shorter (the frequency becomes higher), as shown in FIG. 5 . On the other hand, the increase / decrease determination unit 25 b sets a smaller threshold for the increase / decrease determination as the period of the acceleration waveform becomes longer (the frequency becomes lower), as shown in FIG. 5 .

[0045] As a result, by changing the value of the threshold for determining whether the vibration is increased or decreased in accordance with a change in the period (frequency) of the acceleration waveform of the detected vibration, the threshold value can be set to a large value for high-frequency vibrations that tend to have large changes in acceleration, thereby solving the problem of high-frequency vibrations being easily determined to have been amplified or attenuated. As a result, for example, by storing the graph (table) shown in Figure 5 in the storage unit 30, the increase / decrease determination unit 25b can make a determination by changing the magnitude of the threshold for determining whether the vibration is increased or decreased in accordance with the period (frequency) of the detected vibration.

[0046] Here, when the detected vibration is not an earthquake but noise, characteristic features that appear include, for example, a "monotonically decaying" rate of increase or decrease in the amplitude of the acceleration waveform, or "the rate of increase or decrease hardly changes." Specifically, earthquake vibrations are characterized by constantly vibrating in various directions, not being monotonically decaying, and the rate of increase or decrease being prone to change. On the other hand, vibrations caused by noise such as everyday vibrations tend to be monotonically decaying, and generally have almost no change in the rate of increase or decrease.

[0047] Therefore, the seismic sensor 10 of this embodiment detects that vibrations other than earthquakes (noises such as everyday vibrations) tend to decay monotonically and that the rate of increase or decrease hardly changes, and thereby determines that other vibrations are earthquakes. The earthquake determination unit 26 determines whether the vibration is an earthquake or not based on the period and amplitude detected by the frequency detection unit 24 and the result of the determination by the increase / decrease determination unit 25b.

[0048] Specifically, the earthquake determination unit 26 determines that the vibration is an earthquake if the period in which the increase / decrease determination unit 25b determines that the vibration is attenuating does not continue for a predetermined period. That is, if the period in which the increase / decrease determination unit 25b determines that the vibration is attenuating continues for a predetermined period, the earthquake determination unit 26 determines that the vibration is monotonically decaying and determines that the vibration is noise. Furthermore, the earthquake determination unit 26 determines that the vibration is an earthquake if the period in which the increase / decrease determination unit 25b determines that the rate of increase / decrease is unchanged does not continue for a predetermined period. That is, if the period in which the increase / decrease determination unit 25b determines that the rate of increase / decrease is unchanged continues for a predetermined period, the earthquake determination unit 26 determines that the vibration exhibits the characteristics of noise and determines that the vibration is an earthquake.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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 thresholds used to determine increase or decrease in the increase / decrease determination unit 25b (see Figure 5), the determination results in the earthquake determination unit 26, data on offset components used in the offset adjustment unit 29, etc.

[0053] <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 for the current period generated in step S12 using the zero-crossing method.

[0054] Next, in step S14, the frequency detection unit 24 detects the period and amplitude of the acceleration waveform of the immediately previous period (previous period) generated in step S12 using the zero-crossing method. Next, in step S15, the increase / decrease rate calculation unit 25a obtains thresholds (amplification rate threshold, attenuation rate threshold (see FIG. 5)) for determining an increase or decrease in the amplitude of the acceleration waveform that changes depending on the period (frequency) of the acceleration waveform of the immediately previous period detected in step S14 from a graph (table) (see FIG. 5) stored in the storage unit 30.

[0055] At this time, the thresholds for determining whether the acceleration waveform is increasing or decreasing (amplification factor threshold, attenuation factor threshold) are set to be larger as the period of the acceleration waveform becomes shorter (high frequency), and are set to be smaller as the period of the acceleration waveform becomes longer (low frequency), as described above. Next, in step S16, the increase / decrease rate calculation unit 25a calculates the increase / decrease rate based on the amplitude of the acceleration waveform from the previous period (the period immediately preceding) and the amplitude of the acceleration waveform from this time.

[0056] Next, in step S17, the increase / decrease determination unit 25b determines whether the increase / decrease rate calculated in step S16 is greater than the amplification factor threshold value for increase / decrease determination obtained from the graph (table) shown in Fig. 5. If it is determined that the increase / decrease rate is greater than the amplification factor threshold value, the process proceeds to step S18, and if it is determined that the increase / decrease rate is equal to or less than the amplification factor threshold value, the process proceeds to step S19.

[0057] Next, in step S18, since it was determined in step S17 that the rate of increase or decrease is greater than the amplification rate threshold, the increase or decrease determination unit 25b determines that the vibration has been amplified. Next, in step S19, the earthquake determination unit 26 determines whether amplification has continued for a certain period of time. Here, if amplification has continued for a certain period of time, it is determined that the vibration has the characteristics of an earthquake, and step S20 is skipped and the process proceeds to step S21. On the other hand, if amplification has not continued for a certain period of time, the process proceeds to step S20.

[0058] Next, in step S20, since it was determined in step S19 that amplification has not continued for a certain period of time, the earthquake determination unit 26 determines whether the vibration determination has ended. If it is determined that the vibration determination has ended, the process proceeds to step S21, and if it is determined that the vibration determination has not ended, the process returns to step S11 and repeats the following processing. Next, in step S21, since it was determined in step S19 that amplification has not continued for a certain period of time and it was determined in step S20 that the vibration determination has ended, or since it was determined in step S19 that amplification has continued for a certain period of time, the earthquake determination unit 26 determines that the vibration is an earthquake and ends the processing.

[0059] On the other hand, in step S22, since it was determined in step S17 that the rate of increase or decrease calculated in step S16 is equal to or less than the amplification rate threshold, the increase or decrease determination unit 25b determines whether the rate of increase or decrease calculated in step S16 is less than the attenuation rate threshold. If the increase or decrease determination unit 25b determines that the amplification rate is less than the attenuation rate threshold, the process proceeds to step S23, and if it determines that the amplification rate is equal to or greater than the attenuation rate threshold, the process proceeds to step S24.

[0060] Next, in step S23, since it was determined in step S22 that the rate of increase or decrease is less than the attenuation rate threshold, the increase or decrease determination unit 25b determines that the vibration is attenuating, and the process proceeds to step S25. On the other hand, in step S24, since it was determined in step S17 that the rate of increase or decrease calculated in step S16 is less than or equal to the amplification rate threshold and since it was determined in step S22 that the rate of increase or decrease is greater than or equal to the attenuation rate threshold, the increase or decrease determination unit 25b determines that the vibration is in the "no change" region between the amplification rate threshold and the attenuation rate threshold shown in FIG.

[0061] Next, in step S25, since the earthquake determination unit 26 determined in step S23 that the vibration is attenuating, or determined in step S24 that the rate of increase or decrease of the amplitude of the vibration acceleration waveform is not changing, the increase or decrease determination unit 25b determines whether (a) the period of attenuation has continued for a certain period, or (b) the period of no change has continued for a certain period. Here, if the condition (a) or (b) is satisfied, the process proceeds to step S28. On the other hand, if the condition (a) or (b) is not satisfied, the process proceeds to step S26.

[0062] Next, in step S26, since it was determined in step S25 that the detected vibration is not a vibration that is "monotonically attenuated" or "does not change for a certain period of time" characteristic of noise, the earthquake determination unit 26 determines whether or not the vibration determination has been completed. If it is determined that the vibration determination has been completed, the process proceeds to step S27, but if it is determined that the vibration determination has not been completed, the process returns to step S11 and the following processing is repeated.

[0063] Next, in step S27, it is determined that the vibration detected in step S25 is not a vibration that is "monotonically decaying" or "does not change for a certain period of time" that is characteristic of noise, and since it is determined in step S26 that the vibration determination has ended, it is determined that the vibration is an earthquake and the process ends. On the other hand, in step S28, it is determined that the vibration detected in step S25 is a vibration that is characteristic of noise, so the earthquake determination unit 26 determines that the vibration is noise and the process ends.

[0064] <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, an increase / decrease rate calculation unit 25a, an increase / decrease determination unit 25b, 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 indicating 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 increase / decrease rate calculation unit 25a calculates the rate of increase / decrease from the period and amplitude of the acceleration waveform previously detected by the frequency detection unit 24, based on the period and amplitude detected by the frequency detection unit 24. The increase / decrease determination unit 25b compares the increase / decrease rate calculated by the increase / decrease rate calculation unit 25a with a predetermined amplification rate threshold and / or attenuation rate threshold to determine whether the vibration is amplified or attenuated. The earthquake determination unit 26 determines whether the vibration is an earthquake or not based on the determination result of the increase / decrease determination unit 25b.

[0065] This allows the system to determine whether the detected vibration is "monotonically decaying" or "the rate of increase or decrease is almost constant," which are characteristics of noise, using the period and amplitude of the acceleration waveform, thereby making it possible to determine whether the detected vibration is an earthquake or noise with high accuracy.

[0066] [Other Embodiments] While 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. 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 above-described seismic sensor.

[0067] 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, increase / decrease rate calculation step, increase / decrease 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 the earthquake detection program.

[0068] (B) In the above embodiment, an example was described in which the period and amplitude of the acceleration waveform are detected to detect noise characteristics such as "monotonous decay" and "no change in the rate of increase or decrease," and any other vibrations are determined to be earthquakes. However, the present invention is not limited to this. For example, a configuration may be used in which the period and amplitude of the acceleration waveform are detected to detect either "monotonous decay" or "no change in the rate of increase or decrease," which are noise characteristics, and an earthquake is determined.

[0069] (C) In the above embodiment, an example was described in which a threshold value for determining an amplification factor and a threshold value for determining an attenuation factor were used to determine whether the amplitude of the acceleration waveform of the detected vibration is amplified, attenuated, or unchanged. However, the present invention is not limited to this. For example, if it is not determined that the amplitude of the acceleration waveform of the detected vibration is unchanged, a configuration may be used in which only one threshold value for determination is set and whether the amplitude is amplified or attenuated.

[0070] (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).

[0071] (E) In the above embodiment, an example was described in which the seismic sensor 10 includes an earthquake determination unit 26 that performs earthquake determination based on the determination result of the increase / decrease determination unit 25b. However, the present invention is not limited to this. For example, the seismic sensor may be configured to perform processes up to calculation of the increase / decrease rate and increase / decrease determination, but not to perform earthquake determination. In this case, the determination result of the increase / decrease determination unit may be transmitted to an external device (e.g., an external server device), and the external device may perform earthquake determination, thereby achieving the same effect as described above.

[0072] (F) In the above embodiment, an example was given in which a vibration is determined to be an earthquake when the vibration continues to be amplified for a certain period of time, or when the vibration does not continue to be amplified for a certain period of time, or when the vibration does not continue to be attenuated or unchanged for a certain period of time, and the vibration determination is completed. However, the present invention is not limited to this.

[0073] For example, the ratio of amplification, attenuation, and no change and the maximum number of consecutive times may be recorded until the vibration determination is completed, and then, at the time when the vibration determination is completed, an earthquake or noise may be determined based on the ratio and the maximum number of consecutive times.

[0074] <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; an increase / decrease rate calculation unit that calculates a rate of increase / decrease from the period and amplitude of the acceleration waveform previously detected by the detection unit based on the period and amplitude detected by the detection unit; an increase / decrease determination unit that compares the increase / decrease rate calculated by the increase / decrease rate calculation unit with a predetermined amplification rate threshold and / or attenuation rate threshold to determine whether the vibration is amplified or attenuated; and an earthquake determination unit that determines whether the vibration is an earthquake based on the determination result of the increase / decrease determination unit.

[0075] 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 increase / decrease determination unit determines whether the vibration is increasing / decreasing or attenuating by changing the amplification factor threshold or the attenuation factor threshold for determining whether the vibration is increasing / decreasing or attenuating based on the period detected by the detection unit.A seismic sensor according to a third aspect of the present invention is the seismic sensor according to the first or second aspect of the present invention, wherein the earthquake determination unit determines that the vibration is an earthquake if the period during which the increase / decrease determination unit determined that the vibration is attenuating does not continue for a predetermined period.

[0076] A seismic sensor according to a fourth invention is the seismic sensor according to any one of the first to third inventions, wherein the earthquake determination unit determines that the vibration is an earthquake when the period during which the increase / decrease determination unit determines that the rate of increase / decrease is unchanged does not continue for a predetermined period.A seismic sensor according to a fifth invention is the seismic sensor according to any one of the first to fourth inventions, 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.

[0077] The seismic sensor according to a sixth invention is the seismic sensor according to any one of the first to fifth inventions, further comprising an earthquake magnitude 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. The seismic sensor according to a seventh invention is the seismic sensor according to any one of the first to sixth inventions, further comprising an activation determination unit that calculates the intensity of the vibration from the measurement results of the acceleration acquisition unit, and, when the intensity of the vibration 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] 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, further comprising an output control unit that outputs the predetermined signal when the earthquake determination unit determines that an earthquake has occurred. The 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 a memory unit that stores a table showing the relationship between the period and the amplification factor threshold or the attenuation factor threshold that changes based on 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) 25a Increase / decrease rate calculation unit 25b Increase / decrease 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 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; an increase / decrease rate calculation unit that calculates the rate of increase / decrease from the period and amplitude of the acceleration waveform previously detected by the detection unit based on the period and amplitude detected by the detection unit; an increase / decrease determination unit that compares the increase / decrease rate calculated by the increase / decrease rate calculation unit with a predetermined amplification rate threshold and / or attenuation rate threshold to determine whether the vibration is amplified or attenuated; and an earthquake determination unit that determines whether the vibration is an earthquake based on the determination result of the increase / decrease determination unit.

2. The seismic sensor of claim 1, wherein the increase / decrease determination unit determines whether the signal is increasing / decreasing or attenuating by changing the amplification factor threshold or the attenuation factor threshold for determining whether the signal is increasing / decreasing or attenuating based on the period detected by the detection unit.

3. The seismic sensor according to claim 1 or 2, wherein the earthquake determination unit determines that the vibration is an earthquake if the period during which the increase / decrease determination unit determines that the vibration is attenuating does not continue for a predetermined period.

4. The seismic sensor according to claim 1 or 2, wherein the earthquake determination unit determines that the vibration is an earthquake if the period during which the increase / decrease determination unit determines that the rate of increase / decrease is unchanged does not continue for a predetermined period.

5. 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.

6. 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.

7. A seismic sensor as described in claim 1 or 2, further comprising an activation determination unit that calculates the intensity of the vibration from the measurement results of the acceleration acquisition unit, and when the intensity of the vibration 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.

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

9. The seismic sensor according to claim 1 or 2, further comprising a memory unit for storing a table showing the relationship between the period and the amplification factor threshold or the attenuation factor threshold, which changes based on the period.

10. 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 indicating 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; an increase / decrease rate calculation step of calculating a rate of increase / decrease from the period and amplitude of the acceleration waveform previously detected in the detection step based on the period and amplitude detected in the detection step; an increase / decrease determination step of comparing the increase / decrease rate calculated in the increase / decrease rate calculation step with a predetermined amplification rate threshold and / or attenuation rate threshold to determine whether the vibration is an earthquake or not; and an earthquake determination step of determining whether the vibration is an earthquake or not based on the determination result in the increase / decrease determination step.

11. 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 indicating 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; an increase / decrease rate calculation step of calculating a rate of increase / decrease from the period and amplitude of the acceleration waveform previously detected in the detection step, based on the period and amplitude detected in the detection step; an increase / decrease determination step of comparing the increase / decrease rate calculated in the increase / decrease rate calculation step with a predetermined amplification rate threshold and / or attenuation rate threshold to determine whether the vibrations are amplified or attenuated; and an earthquake determination step of determining whether the vibrations are an earthquake, based on the determination result in the increase / decrease determination step.

12. 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; an increase / decrease rate calculation unit that calculates the rate of increase / decrease from the period and amplitude of the acceleration waveform previously detected by the detection unit based on the period and amplitude detected by the detection unit; and an increase / decrease determination unit that compares the rate of increase / decrease calculated by the increase / decrease rate calculation unit with a predetermined amplification rate threshold and / or attenuation rate threshold to determine whether the vibration is amplified or attenuated.

Images