Seismic sensor, earthquake detection method, and earthquake detection program

Abstract

To provide a seismic sensor, an earthquake detection method, and an earthquake detection program that can accurately determine if a detected vibration is an earthquake or noise.SOLUTION: A seismic sensor 10 comprises, as shown in Fig.2, an acceleration acquisition unit 21, a direction angle calculation unit 23, a direction angle frequency distribution generation unit 24, and an earthquake determination unit 25. The acceleration acquisition unit 21 detects a vibration and acquires the acceleration of the vibration. The direction angle calculation unit 23 calculates, for the acceleration acquired by the acceleration acquisition unit 21, angles formed by vectors of the accelerations with reference to an original point on a predetermined coordinate plane. The direction angle frequency distribution generation unit 24 generates the frequency distribution of the angles calculated by the direction angle calculation unit 23. The earthquake determination unit 25 determines whether or not the vibration is an earthquake on the basis of the frequency distribution of angles generated by the direction angle frequency distribution generation unit 24.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

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

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

[0004] However, the above-mentioned conventional seismic sensors have the following problems. That is, in the seismic sensor disclosed in the above publication, when analyzing the frequency of the acceleration measured by the acceleration sensor, the frequency of each axis (e.g., X-axis and Y-axis) of the acceleration sensor is calculated. Therefore, it is difficult to analyze vibrations taking into account the vibration characteristics of both axes (e.g., X-axis and Y-axis), making it difficult to accurately determine whether an earthquake has occurred.

[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 whether a detected vibration is an earthquake or noise. [Means for solving the problem]

[0006] The seismic sensor according to the first aspect of the present invention includes an acceleration acquisition unit, an angle calculation unit, an angle frequency distribution generation unit, and an earthquake determination unit. The acceleration acquisition unit detects vibrations and acquires the acceleration of the vibrations. The angle calculation unit calculates the angle formed by the vector of each acceleration, based on an origin on a predetermined coordinate plane, for the accelerations acquired by the acceleration acquisition unit. The angle frequency distribution generation unit generates a frequency distribution of the angles calculated by the angle calculation unit. The earthquake determination unit determines whether the vibrations are an earthquake based on the angle frequency distribution created by the angle frequency distribution generation unit.

[0007] Here, the angle formed by the acceleration vector of the detected vibration with reference to the origin on the coordinate plane of the acceleration is calculated, and it is determined whether the vibration is an earthquake or not based on the frequency distribution of that angle. Here, the predetermined coordinate plane means, for example, the XY plane, XZ plane, or YZ plane among the three axes (X-axis, Y-axis, and Z-axis) of an acceleration sensor that measures acceleration, or, for example, a horizontal plane obtained by extracting acceleration in a non-gravity direction from the acceleration of the three axes of an acceleration sensor that measures acceleration.

[0008] Furthermore, the angle formed by an acceleration vector with respect to the origin in a specified coordinate plane means, for example, the angle formed by the acceleration vector with respect to the X-axis when the starting point of the acceleration vector is aligned with the origin in the coordinate plane (XY plane). Normally, when the detected vibration is an earthquake, it is characterized by vibrations in various directions on a substantially horizontal plane.

[0009] Therefore, this seismic sensor calculates the direction (directional angle) of the acceleration vector on a specified coordinate plane, generates its frequency distribution, and determines whether an earthquake has occurred based on the bias in frequency for each angle. This makes it possible to determine whether or not a vibration is an earthquake by detecting, using the frequency distribution of angles, that the acceleration vector points in all directions, which is a characteristic of vibrations caused by an earthquake. As a result, it is possible to accurately determine whether the detected vibration is an earthquake or noise.

[0010] The 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 that the vibration is an earthquake when the frequency of the angles is generally the same. As a result, if the frequency distribution of the generated angles shows that acceleration vectors pointing at all angles are detected to the same extent overall, it can be determined that this matches the characteristics of vibrations caused by an earthquake, and the vibration can be determined to be an earthquake.

[0011] The seismic sensor according to the third invention is the seismic sensor according to the first or second invention, and the earthquake determination unit determines that the vibration is not an earthquake if there is a bias in the frequency of angles for each angle. As a result, if a bias in the angle of the acceleration vector is detected from the frequency distribution of the generated angles, it can be determined that this matches the characteristics of vibrations caused by noise other than earthquakes, and the vibration can be determined to be not an earthquake.

[0012] The seismic sensor of the fourth invention is a seismic sensor of the first or second invention, wherein the earthquake determination unit calculates the coefficient of variation of the angle frequency from the average value and standard deviation of the angle frequency created in the angle frequency distribution generation unit, and determines that the vibration is an earthquake if the coefficient of variation is smaller than a predetermined threshold value. This makes it possible to easily determine whether the detected vibration is an earthquake by comparing the coefficient of variation calculated based on the average value and standard deviation of the angle frequency with a predetermined threshold value.

[0013] The seismic sensor of the fifth invention is a seismic sensor of the first or second invention, wherein the earthquake determination unit determines whether or not the vibration is an earthquake using any of the mean, median, or mode of the frequency distribution generated by the angle frequency distribution generation unit. This allows highly accurate earthquake detection by analyzing the characteristics of the detected vibrations using any of the mean, median, and mode in the angle frequency distribution.

[0014] The seismic sensor of the sixth invention is a seismic sensor of the first or second invention, wherein the earthquake determination unit determines whether the vibration is an earthquake using any of the standard deviation, variance, skewness, and kurtosis of the frequency distribution generated by the angle frequency distribution generation unit. This allows highly accurate earthquake detection by analyzing the characteristics of detected vibrations using any of the standard deviation, variance, skewness, and kurtosis in the angle frequency distribution.

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

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

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

[0018] An earthquake detection method according to a tenth aspect of the present invention includes an acceleration acquisition step, an angle calculation step, an angle frequency distribution generation step, and an earthquake determination step. In the acceleration acquisition step, vibrations are detected and the acceleration of the vibrations is acquired. In the angle calculation step, angles formed by vectors of each acceleration with respect to an origin on a predetermined coordinate plane are calculated for the accelerations acquired in the acceleration acquisition step. In the angle frequency distribution generation step, a frequency distribution of the angles calculated in the angle calculation step is generated. In the earthquake determination step, it is determined whether the vibrations are an earthquake based on the frequency distribution of angles created in the angle frequency distribution generation step.

[0019] Here, the angle formed by the acceleration vector of the detected vibration with reference to the origin on the coordinate plane of the acceleration is calculated, and it is determined whether the vibration is an earthquake or not based on the frequency distribution of that angle. Here, the predetermined coordinate plane means, for example, the XY plane, XZ plane, or YZ plane among the three axes (X-axis, Y-axis, and Z-axis) of an acceleration sensor that measures acceleration.

[0020] Furthermore, the angle formed by an acceleration vector with respect to the origin in a specified coordinate plane means, for example, the angle formed by the acceleration vector with respect to the X-axis when the starting point of the acceleration vector is aligned with the origin in the coordinate plane (XY plane). Normally, when the detected vibration is an earthquake, it is characterized by vibrations in various directions on a substantially horizontal plane.

[0021] Therefore, this seismic sensor calculates the direction (directional angle) of the acceleration vector on a specified coordinate plane, generates its frequency distribution, and determines whether an earthquake has occurred based on the bias in frequency for each angle. This makes it possible to determine whether or not a vibration is an earthquake by detecting, using the frequency distribution of angles, that the acceleration vector points in all directions, which is a characteristic of vibrations caused by an earthquake. As a result, it is possible to accurately determine whether the detected vibration is an earthquake or noise.

[0022] An earthquake detection program according to an eleventh aspect of the present invention causes a computer to execute an earthquake detection method including an acceleration acquisition step, an angle calculation step, an angle frequency distribution generation step, and an earthquake determination step. In the acceleration acquisition step, vibrations are detected and the acceleration of the vibrations is acquired. In the angle calculation step, for the accelerations acquired in the acceleration acquisition step, angles formed by vectors of each acceleration with respect to an origin on a predetermined coordinate plane are calculated. In the angle frequency distribution generation step, a frequency distribution of the angles calculated in the angle calculation step is generated. In the earthquake determination step, it is determined whether the vibrations are an earthquake based on the frequency distribution of the angles created in the angle frequency distribution generation step.

[0023] Here, the angle formed by the acceleration vector of the detected vibration with reference to the origin on the coordinate plane of the acceleration is calculated, and it is determined whether the vibration is an earthquake or not based on the frequency distribution of that angle. Here, the predetermined coordinate plane means, for example, the XY plane, XZ plane, or YZ plane among the three axes (X-axis, Y-axis, and Z-axis) of an acceleration sensor that measures acceleration, or, for example, a horizontal plane obtained by extracting acceleration in a non-gravity direction from the acceleration of the three axes of an acceleration sensor that measures acceleration.

[0024] Furthermore, the angle formed by an acceleration vector with respect to the origin in a specified coordinate plane means, for example, the angle formed by the acceleration vector with respect to the X-axis when the starting point of the acceleration vector is aligned with the origin in the coordinate plane (XY plane). Normally, when the detected vibration is an earthquake, it is characterized by vibrations in various directions on a substantially horizontal plane.

[0025] Therefore, this seismic sensor calculates the direction (directional angle) of the acceleration vector on a specified coordinate plane, generates its frequency distribution, and determines whether an earthquake has occurred based on the bias in frequency for each angle. This makes it possible to determine whether or not a vibration is an earthquake by detecting, using the frequency distribution of angles, that the acceleration vector points in all directions, which is a characteristic of vibrations caused by an earthquake. As a result, it is possible to accurately determine whether the detected vibration is an earthquake or noise.

[0026] A seismic sensor according to a twelfth aspect of the present invention includes an acceleration acquisition unit, an angle calculation unit, and an angle frequency distribution generation unit. The acceleration acquisition unit detects vibrations and acquires the acceleration of the vibrations. The angle calculation unit calculates the angle formed by the vector of each acceleration acquired by the acceleration acquisition unit, with the origin on a predetermined coordinate plane as the reference. The angle frequency distribution generation unit generates a frequency distribution of the angles calculated by the angle calculation unit.

[0027] Here, the angle formed by the acceleration vector of the detected vibration with respect to the origin on the coordinate plane is calculated, and a frequency distribution of the angle is generated. Here, the predetermined coordinate plane means, for example, the XY plane, XZ plane, or YZ plane among the three axes (X-axis, Y-axis, and Z-axis) of an acceleration sensor that measures acceleration, or, for example, a horizontal plane obtained by extracting acceleration in a non-gravity direction from the acceleration of the three axes of an acceleration sensor that measures acceleration.

[0028] Furthermore, the angle formed by an acceleration vector with respect to the origin in a specified coordinate plane means, for example, the angle formed by the acceleration vector with respect to the X-axis when the starting point of the acceleration vector is aligned with the origin in the coordinate plane (XY plane). Normally, when the detected vibration is an earthquake, it is characterized by vibrations in various directions on a substantially horizontal plane.

[0029] Therefore, this seismic sensor calculates the direction (direction angle) of the acceleration vector on a predetermined coordinate plane and generates its frequency distribution. This makes it possible to determine whether or not a vibration is an earthquake by detecting, using the frequency distribution of angles, that the acceleration vector points in all directions, which is a characteristic of vibrations caused by an earthquake.

[0030] As a result, it is possible to accurately determine whether the detected vibration is an earthquake or noise. [Effects of the Invention]

[0031] The seismic sensor according to the present invention can accurately determine whether the detected vibration is an earthquake or noise. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a control block diagram showing the configuration of a seismic sensor according to an embodiment of the present invention. [Figure 2] Functional block diagram generated within the seismic sensor in Figure 1. [Figure 3] 3 is a diagram showing the direction angle of an acceleration vector calculated in the direction angle calculation unit of FIG. 2; [Figure 4] 2 is a graph showing the acceleration on the horizontal plane (XY plane) of earthquake vibrations detected by the seismic sensor of FIG. 1. [Figure 5] (a) is a graph showing the angles of the acceleration vectors in the earthquake vibrations in Figure 4, divided into the first, second, third, and fourth quadrants. (b) is a graph showing the frequency distribution of the angles of the acceleration vectors. [Figure 6]2 is a graph showing acceleration on a horizontal plane (XY plane) of daily vibrations (noise) detected by the seismic sensor of FIG. 1. [Figure 7] (a) is a graph showing the angles of acceleration vectors in the daily vibrations (noise) in Figure 4, divided into the first, second, third, and fourth quadrants. (b) is a graph showing the frequency distribution of the angles of acceleration vectors. [Figure 8] 3 is a flowchart showing the process flow of an earthquake detection method performed by the seismic sensor of FIG. 2. [Figure 9] As an example of earthquake determination using the mode, mean, or median of the frequency distribution of direction angles generated by a seismic sensor according to another embodiment of the present invention, (a) is a graph showing the frequency distribution of direction angles when the detected vibration is an earthquake, and (b) is a graph showing the frequency distribution of direction angles when the detected vibration is noise. [Figure 10] As an example of earthquake detection using the variation (standard deviation, variance) from the mode of the frequency distribution of direction angles generated by a seismic sensor according to yet another embodiment of the present invention, (a) is a graph showing the frequency distribution of direction angles when the detected vibration is an earthquake, and (b) is a graph showing the frequency distribution of direction angles when the detected vibration is noise. [Figure 11] As an example of earthquake determination using the kurtosis of the frequency distribution of direction angles generated by a seismic sensor according to yet another embodiment of the present invention, (a) is a graph showing the frequency distribution of direction angles when the detected vibration is an earthquake, and (b) is a graph showing the frequency distribution of direction angles when the detected vibration is noise. DETAILED DESCRIPTION OF THE INVENTION

[0033] A seismic sensor according to one embodiment of the present invention will be described below with reference to FIGS. 1 to 8. FIG. In the present embodiment, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0034] 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.

[0035] (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 electrostatic capacitance between electrodes. The acceleration measured (also called “sampling”) by the acceleration sensor 11 is output to the controller 12. The acceleration sensor 11 has virtual three-dimensional axes (X-axis, Y-axis, and Z-axis), detects acceleration on each axis, and outputs the detected acceleration to the controller 12.

[0036] The controller 12 is, for example, a general-purpose integrated circuit that acquires the acceleration measured by the acceleration sensor 11 at a predetermined period, detects the occurrence of an earthquake based on the acquired acceleration, and calculates an index value indicating the magnitude of the earthquake. Also, the controller 12 operates in different modes, active mode or sleep mode, depending on the situation.

[0037] The sleep mode is a mode in which the controller 12 operates with limited functions, such as stopping the execution of instructions while accepting interrupts, stopping the supply of clocks, etc. In this sleep mode, power consumption can be reduced more than in the active mode. The active mode is a mode in which a process is performed to determine whether the detected vibration is an earthquake or noise, and an index value indicating the magnitude of the earthquake is calculated.

[0038] The function blocks (see FIG. 2) generated when the CPU in the seismic sensor 10 reads the earthquake detection program stored in the memory 13 will be described in detail later. The memory 13 is a temporary storage means such as a RAM (Random Access Memory) or a non-volatile memory such as an EPROM (Erasable Programmable Read Only Memory), and stores, for example, the acceleration measured by the acceleration sensor 11 and threshold values ​​used for earthquake determination.

[0039] The memory 13 may be a memory built into the acceleration sensor 11 or the controller 12 . The output unit 14 is, for example, an output terminal included in the controller 12, and when the controller 12 determines that, for example, an earthquake has occurred, information indicating the occurrence and scale of the earthquake is output to another device via the output unit 14. Furthermore, when an earthquake of a predetermined scale or greater is detected, the output unit 14 outputs, for example, a cutoff signal to an external device to stop the supply of energy such as electricity or gas.

[0040] (2) Functional block of seismic sensor 10 As shown in Figure 2, the seismic sensor 10 includes an acceleration acquisition unit 21, a vibration intensity classification / activation determination unit 22, a direction angle calculation unit (angle calculation unit) 23, a direction angle frequency distribution generation unit (angle frequency distribution generation unit) 24, an earthquake determination unit 25, an earthquake magnitude calculation unit 26, an output control unit 27, an offset adjustment unit 28, and a memory unit 29.

[0041] These functional blocks shown in FIG. 2 are configured by the controller 12 receiving acceleration data obtained from the acceleration sensor 11 and reading a program stored in the memory 13. The acceleration acquisition unit 21 acquires measurement data of acceleration in the X-axis, Y-axis, and Z-axis measured at a predetermined cycle by the acceleration sensor 11. Note that 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).

[0042] When performing such low-speed acceleration sampling, the controller 12 basically operates in a sleep mode (standby state or power-saving mode) with low power consumption. In the standby state, the acceleration sensor 11 is in an operating state where it samples at a low speed, so the controller 12 operates in a sleep mode with limited functionality, thereby reducing power consumption.

[0043] Furthermore, when the acceleration acquisition unit 21 acquires vibrations greater than a threshold value preset in the storage unit 29, the acceleration sensor 11 repeats measuring the acceleration at a higher speed (i.e., at a relatively short cycle) than during low-speed sampling. During such high-speed sampling, the controller 12 operates in a sleep mode or an active mode. When the earthquake determination unit 25 (described later) and the like execute processing, the controller 12 operates in active mode (measurement mode). The transition from the power saving mode to the measurement mode is called the activation of the seismic sensor 10.

[0044] The measurement mode is an operating state in which high-speed sampling is performed, so the controller 12 may operate in a sleep mode with limited functionality, or in an active mode with maximum computing power. In the measurement mode, the sampling period is shortened and the controller 12 switches from the sleep mode to the active mode, resulting in higher power consumption than in the power-saving mode.

[0045] The vibration intensity discrimination and activation determination unit 22 is a function on the acceleration sensor 11 side, which compares the acceleration value acquired by the acceleration acquisition unit 21 with the activation threshold value stored in the memory unit 29, and if the acceleration value exceeds the activation threshold value, transitions from power saving mode to measurement mode (activates the seismic sensor 10). In addition, the vibration intensity discrimination / activation determination unit 22 calculates the vibration intensity from the measurement results of the acceleration acquisition unit 21, and if the vibration intensity is equal to or greater than a predetermined magnitude, transitions from the power saving mode to the measurement mode, which consumes more power than the power saving mode (activates the controller 12).

[0046] Here, the vibration intensity classification process performed by the vibration intensity classification / activation determination unit 22 is performed by filtering the acceleration value acquired by the acceleration acquisition unit 21. At this time, the filtered acceleration is stored in the storage unit 29. The direction angle calculation unit (angle calculation unit) 23 calculates the angle (direction angle) of the acceleration vector based on the origin on a predetermined coordinate plane (for example, an XY plane) for the acceleration acquired by the acceleration acquisition unit 21 (see FIG. 3).

[0047] Here, the predetermined coordinate plane means a substantially horizontal XY plane constituted by, for example, the X-axis and the Y-axis among the X-axis, Y-axis, and Z-axis of the acceleration sensor 11. Furthermore, the angle of the acceleration vector with respect to the origin means the angle of the acceleration vector with respect to the X-axis, for example, as shown in Figure 3, when the starting point of the acceleration vector is aligned with the origin on the coordinate plane (XY plane).

[0048] Specifically, when the vibration detected by the acceleration sensor 11 is an earthquake, the vibration caused by the earthquake is characterized by, for example, vibration that generates acceleration in all directions in the XY plane (approximately horizontal plane), as shown in FIG. Here, when the direction angle calculation unit 23 classifies the angles (direction angles) that the acceleration vector based on the origin makes with respect to the X axis among the accelerations in the XY plane in Figure 4 into the first, second, third, and fourth quadrants, the accelerations are arranged almost evenly in each quadrant, as shown in Figure 5(a).

[0049] The direction angle frequency distribution generating unit (angle frequency distribution generating unit) 24 generates a frequency distribution of angles (direction angles) that an acceleration vector with respect to the origin makes with respect to the X axis, as shown in FIG. 5(b). At this time, if the detected vibration is an earthquake as shown in FIG. 4, the frequency distribution will be almost uniform because the acceleration is distributed in various directions in vibrations caused by an earthquake. On the other hand, if the vibration detected by the acceleration sensor 11 is not an earthquake, the vibration is characterized by noise such as everyday vibration, and generates acceleration in a substantially constant direction on the XY plane (substantially horizontal plane), as shown in FIG. 6.

[0050] Here, when the direction angle calculation unit 23 classifies the angles (direction angles) that the acceleration vector based on the origin makes with respect to the X axis among the accelerations in the XY plane in FIG. 6 into the first, second, third, and fourth quadrants, the accelerations tend to be concentrated in the first and third quadrants, resulting in a bias, as shown in FIG. 7(a). The direction angle frequency distribution generating unit 24 generates a frequency distribution of the angle (direction angle) that the acceleration vector with respect to the origin makes with respect to the X axis, as shown in FIG. 7(b).

[0051] At this time, if the detected vibration is noise as shown in FIG. 6, the direction of acceleration is concentrated in one direction in vibration caused by noise, resulting in a bias in the frequency distribution, such as a peak at a certain angle. That is, when the detected vibration is an earthquake and when it is something other than an earthquake (multiple types of noise), different acceleration distributions and angle frequency distributions of direction angles are generated on a predetermined coordinate plane.

[0052] That is, when the detected vibration is an earthquake, it contains components of various frequency bands in all directions on the XY plane, as shown in FIG. Therefore, the frequency distribution generated by the direction angle frequency distribution generating unit 24 is substantially uniform over the entire angle range of 0° to 180°, as shown in FIG. 5(b), and has little bias. On the other hand, if the detected vibration is not an earthquake but high-frequency vibration noise, as shown in Figure 6, two consecutive acceleration components on the XY plane will be linear and contain high-frequency components.

[0053] Therefore, the frequency distribution generated by the direction angle frequency distribution generating unit 24 is highly biased, with a prominent area around 70 degrees in the angle range of 0 to 180 degrees, as shown in FIG. 7(b). Therefore, in the seismic sensor 10 of this embodiment, since a characteristic of earthquakes is that the direction angle of the acceleration vector is often approximately uniform overall, whether or not the vibration is an earthquake is determined depending on whether or not the frequency distribution of the direction angle is detected to be approximately uniform.

[0054] Specifically, the earthquake determination unit 25 determines whether or not the vibration is an earthquake based on the frequency distribution of direction angles generated by the direction angle frequency distribution generation unit 24. That is, the earthquake determination unit 25 determines that the vibration is an earthquake when the frequency of angles in the frequency distribution of direction angles is generally the same as shown in Fig. 5(b). On the other hand, the earthquake determination unit 25 determines that the vibration is noise, not an earthquake, when the frequency distribution of direction angles shows a bias in the frequency of angles for each angle as shown in Fig. 7(b).

[0055] Here, the earthquake determination unit 25 calculates the coefficient of variation of the angle frequency from the average value and standard deviation of the angle frequency created by the direction angle frequency distribution generation unit 24, and if the coefficient of variation is smaller than a predetermined threshold value, it determines that the vibration is an earthquake. The coefficient of variation is calculated using the following relational expression. Coefficient of variation of angle frequency = standard deviation of angle frequency / mean of angle frequency The earthquake determination unit 25 may use any one of the mean value, median value, and mode value of the frequency distribution generated by the direction angle frequency distribution generation unit 24 to determine whether or not the vibration is an earthquake.

[0056] When the earthquake determination unit 25 determines that an earthquake has occurred, the earthquake scale calculation unit 26 determines whether the earthquake has a seismic intensity of at least a predetermined level. Furthermore, after the earthquake magnitude calculation unit 26 determines that the detected vibration is an earthquake and starts calculating an index indicating the magnitude of the earthquake, if an acceleration waveform that can be considered to be an impact is detected, the earthquake magnitude calculation unit 26 excludes the acceleration waveform and calculates the magnitude of the earthquake.

[0057] The output control unit 27 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 26 is equal to or greater than a predetermined seismic intensity. Here, the predetermined signal output from the output unit 14 includes, for example, a shutoff signal sent to an external device such as an electricity supply device or a gas supply device in order to stop the supply of energy such as electricity or gas.

[0058] When earthquake determination unit 25 determines that the vibration detected by acceleration acquisition unit 21 is noise, offset adjustment unit 28 adjusts the offset amount of the acceleration waveform according to the magnitude of the noise. Then, offset adjustment unit 28 adjusts the offset amount of the acceleration waveform according to the determination result of earthquake determination unit 25. The offset adjustment performed by the offset adjuster 28 detects noise components contained in the measured acceleration as offset components, such as the amount of change in the measurement value that occurs with changes over time in the seismic sensor 10, the amount of change in the measurement value that occurs with temperature changes, and the amount of change in the measurement value that occurs when the orientation of the installed seismic sensor 10 tilts for some reason and the direction of gravitational acceleration relative to the seismic sensor 10 changes. Specifically, the offset adjuster 28 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.

[0059] The memory unit 29 stores, for example, acceleration data acquired by the acceleration acquisition unit 21 or acceleration data after filtering processing, direction angle data calculated by the direction angle calculation unit 23, frequency distribution data generated by the direction angle frequency distribution generation unit 24, the judgment results of the earthquake judgment unit 25, and offset component data used in the offset adjustment unit 28.

[0060] <Earthquake detection method> The earthquake detection method using the seismic sensor 10 of this embodiment will be described below with reference to the flowchart shown in FIG. That is, in step S11, the acceleration acquisition unit 21 of the seismic sensor 10 acquires the acceleration measured by the acceleration sensor 11.

[0061] Next, in step S12, the direction angle calculation unit 23 calculates an acceleration vector from the acceleration acquired in step S11. Next, in step S13, the direction angle calculation unit 23 calculates the angle (direction angle) of the acceleration vector calculated in step S12 with respect to the origin. Next, in step S14, the direction angle frequency distribution generating unit 24 counts up the frequency (number of times) of the direction angle of the acceleration vector calculated in step S13.

[0062] Next, in step S15, it is determined whether or not the vibration determination process is to be ended. If it is to be ended, the process proceeds to step S16, and if it is not to be ended, the process returns to step S11 and the subsequent processes are repeated. Next, in step S16, the direction angle frequency distribution generating unit 24 calculates the average value of the frequencies of the direction angles counted up in step S14.

[0063] Next, in step S17, the direction angle frequency distribution generating unit 24 calculates the standard deviation of the frequencies of the direction angles counted up in step S14. Next, in step S18, the direction angle frequency distribution generating unit 24 calculates the coefficient of variation of the frequency of the direction angle based on the average value and standard deviation of the frequency of the direction angle calculated in steps S15 and S16.

[0064] Next, in step S19, the earthquake determination unit 25 determines whether or not the following relational expression (1) is satisfied. Coefficient of variation < predetermined threshold (1) If the relational expression (1) is satisfied, the process proceeds to step S20, where the earthquake determination unit 25 determines that the deviation in the frequency of the direction angles is small and a variety of direction angles are recognized because the coefficient of variation is smaller than the threshold, so that there is a high possibility of an earthquake, and the process ends.On the other hand, if the relational expression (1) is not satisfied, the process proceeds to step S21, where the earthquake determination unit 25 determines that the deviation in the frequency of the direction angles is large and that there is a low possibility of an earthquake because the frequency of the direction angles is biased in one direction, and the detected vibration is determined to be not an earthquake (it is noise), and the process ends.

[0065] <Major features> As shown in Fig. 2, the seismic sensor 10 of this embodiment includes an acceleration acquisition unit 21, a direction angle calculation unit 23, a direction angle frequency distribution generation unit 24, and an earthquake determination unit 25. The acceleration acquisition unit 21 detects vibrations and acquires the acceleration of the vibrations. The direction angle calculation unit 23 calculates the angle formed by the vector of each acceleration, based on the origin on a predetermined coordinate plane, for the accelerations acquired by the acceleration acquisition unit 21. The direction angle frequency distribution generation unit 24 generates a frequency distribution of the angles calculated by the direction angle calculation unit 23. The earthquake determination unit 25 determines whether the vibrations are an earthquake or not based on the frequency distribution of angles created by the direction angle frequency distribution generation unit 24.

[0066] This makes it possible to determine whether or not a vibration is an earthquake by detecting, using the frequency distribution of angles, that the acceleration vector points in all directions, which is a characteristic of vibrations caused by an earthquake. As a result, it is possible to accurately determine whether the detected vibration is an earthquake or noise.

[0067] [Other embodiments] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention. (A) In the above embodiment, the present invention has been described as being implemented as a seismic sensor and an earthquake detection method, but the present invention is not limited to this. For example, the present invention may be realized as an earthquake detection program that causes a computer to execute the earthquake detection method using the seismic sensor described above.

[0068] This earthquake detection program is stored in a memory (storage unit) installed in the seismic sensor, and the CPU reads the earthquake detection program stored in the memory and causes the hardware to execute each step. More specifically, the CPU reads the earthquake detection program and executes the acceleration acquisition step, direction angle calculation step, direction angle frequency distribution generation step, and earthquake determination step described above, thereby achieving the same effects as those described above. The present invention may also be realized as a recording medium storing an earthquake detection program.

[0069] (B) In the above embodiment, an example has been described in which the earthquake determination unit 25 performs earthquake determination based on the coefficient of variation of the frequency of the direction angle calculated from the average value and standard deviation in the frequency distribution generated by the direction angle frequency distribution generation unit 24. However, the present invention is not limited to this. For example, the earthquake determination unit may be configured to determine whether the detected vibration is an earthquake using any of the mean, median, and mode of the frequency distribution generated by the angle frequency distribution generation unit.

[0070] Specifically, as shown in Figure 9(a), the average value (or median) of the calculated acceleration vector angle over the entire range of 0° to 180° is compared with the most frequent value of the acceleration vector angle, and if the two values ​​are close, it is determined that the variation in the frequency distribution of the acceleration vector angle is small, and the vibration can be determined to be an earthquake. On the other hand, as shown in Figure 9(b), by comparing the average value (or median) of the calculated acceleration vector angle over the entire range of 0° to 180° with the most frequent value of the acceleration vector angle, it can be determined that the greater the difference between the two values, the greater the variation in the frequency distribution of the acceleration vector angle, and the vibration in question can be determined to be noise rather than an earthquake.

[0071] (C) In the above embodiment, an example has been described in which the earthquake determination unit 25 performs earthquake determination based on the coefficient of variation of the frequency of the direction angle calculated from the average value and standard deviation in the frequency distribution generated by the direction angle frequency distribution generation unit 24. However, the present invention is not limited to this.

[0072] For example, the earthquake determination unit may be configured to determine whether an earthquake has occurred based on the degree of variation in angles when the standard deviation and variance of the frequency in the frequency distribution are within a predetermined threshold value. Specifically, standard deviation and variance represent the degree of dispersion in a distribution, and the smaller the value, the less dispersion there is. Furthermore, vibrations caused by earthquakes are characterized by the fact that the dispersion is neither extremely large nor extremely small around the angle of the most frequent value.

[0073] Specifically, as shown in Figure 10(a), if the calculated angle (direction angle) of the acceleration vector is close to the most frequent value of the angle of the acceleration vector in the entire range of 0° to 180° and the frequency of other angles is close, it can be determined that there is a large variation in the frequency distribution of the angle of the acceleration vector, and the vibration can be determined to be an earthquake. On the other hand, as shown in Figure 10(b), the greater the deviation of the frequencies of other angles from the most frequent value of the acceleration vector angle in the entire range of the calculated acceleration vector angle (direction angle) from 0° to 180°, the smaller the variation in the frequency distribution of the acceleration vector angle can be determined, and the vibration can be determined to be noise rather than an earthquake.

[0074] (D) In the above embodiment, an example has been described in which the earthquake determination unit 25 performs earthquake determination based on the coefficient of variation of the frequency of the direction angle calculated from the average value and standard deviation in the frequency distribution generated by the direction angle frequency distribution generation unit 24. However, the present invention is not limited to this. For example, the earthquake determination unit may be configured to determine whether or not the detected vibration is an earthquake using the kurtosis of the frequency distribution generated by the angle frequency distribution generation unit. Here, the kurtosis in the frequency distribution of angles generated by the direction angle frequency distribution generating unit 24 means the degree of peaking (degree of variation) of the normal distribution in the frequency distribution graph. In other words, high kurtosis in a normal distribution means that the frequency of a particular angle is exceptionally high, which corresponds to the linear vibrations seen in noise such as daily vibrations.

[0075] As a result, as shown in Figure 11(a), if the kurtosis of the calculated acceleration vector angle is small over the entire range of 0° to 180°, it can be determined that the variation in the frequency distribution of the acceleration vector angle is small, and the vibration can be determined to be an earthquake. On the other hand, as shown in Figure 11(b), if the kurtosis of the calculated acceleration vector angle is large over the entire range of 0° to 180°, it can be determined that the variation in the frequency distribution of the acceleration vector angle is small, and the vibration can be determined to be noise rather than an earthquake.

[0076] (E) In the above embodiment, an example has been described in which the XY plane of the acceleration sensor 11 is set as a predetermined coordinate plane and the angle of the acceleration vector with respect to the origin is calculated. However, the present invention is not limited to this. For example, the predetermined coordinate plane set for calculating the angle of the acceleration vector may be the XZ plane or the YZ plane among the three axes (X-axis, Y-axis, and Z-axis) of the acceleration sensor, or may be, for example, a horizontal plane obtained by extracting acceleration in a non-gravity direction from the acceleration of the three axes of the acceleration sensor that measures acceleration.

[0077] (F) In the above embodiment, an example has been described in which the seismic sensor 10 is provided with the earthquake determination unit 25 that performs earthquake determination based on the frequency distribution generated by the direction angle frequency distribution generation unit 24. However, the present invention is not limited to this.

[0078] For example, the seismic sensor may be configured to analyze the detected vibrations but not to determine whether an earthquake has occurred. In this case, the frequency distribution generated by the angle frequency distribution generation unit can be transmitted to an external device (e.g., an external server device) and earthquake determination can be performed on the external device side, thereby achieving the same effect as described above.

[0079] <Additional Notes> The seismic sensor according to the first invention is an acceleration acquisition unit that detects vibration and acquires the acceleration of the vibration; an angle calculation unit that calculates an angle between a vector of each acceleration acquired by the acceleration acquisition unit and an origin on a predetermined coordinate plane; an angle frequency distribution generation unit that generates a frequency distribution of the angles calculated by the angle calculation unit; an earthquake determination unit that determines whether the vibration is an earthquake based on the frequency distribution of the angles created by the angle frequency distribution generation unit; It is equipped with:

[0080] The seismic sensor according to the second invention is the seismic sensor according to the first invention, When the frequencies of the angles are generally the same, the earthquake determination unit determines that the vibration is an earthquake. The seismic sensor according to the third invention is the seismic sensor according to the first or second invention, When there is a bias in the frequency of the angles for each angle, the earthquake determination unit determines that the vibration is not an earthquake.

[0081] A seismic sensor according to a fourth aspect of the present invention is a seismic sensor according to any one of the first to third aspects of the present invention, The earthquake determination unit calculates the coefficient of variation of the angle frequency from the average value and standard deviation of the angle frequency created by the angle frequency distribution generation unit, and determines that the vibration is an earthquake if the coefficient of variation is smaller than a predetermined threshold value.

[0082] A seismic sensor according to a fifth aspect of the present invention is a seismic sensor according to any one of the first to fourth aspects of the present invention, The earthquake determination unit determines whether the vibration is an earthquake using any one of the mean, median, and mode of the frequency distribution generated by the angle frequency distribution generation unit. A seismic sensor according to a sixth aspect of the present invention is a seismic sensor according to any one of the first to fifth aspects of the present invention, The earthquake determination unit determines whether the vibration is an earthquake using any one of the standard deviation, variance, skewness, and kurtosis of the frequency distribution generated by the angle frequency distribution generation unit.

[0083] The seismic sensor according to the seventh invention is the seismic sensor according to any one of the first to sixth inventions, The earthquake detection unit further includes an earthquake magnitude calculation unit that determines whether the earthquake is equivalent to or greater than a predetermined seismic intensity when the earthquake determination unit determines that an earthquake has occurred. The seismic sensor according to an eighth aspect of the present invention is the seismic sensor according to any one of the first to seventh aspects of the present invention, The device further includes an activation determination unit that calculates the vibration intensity from the results acquired by 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.

[0084] A seismic sensor according to a ninth aspect of the present invention is a seismic sensor according to any one of the first to eighth aspects of the present invention, The earthquake detection unit further includes an output control unit that outputs the predetermined signal when it is determined that an earthquake has occurred. [Industrial Applicability]

[0085] The seismic sensor of the present invention has the effect of being able to accurately determine whether detected vibrations are earthquakes or noise, and is therefore widely applicable to various devices that analyze vibrations such as earthquakes. [Explanation of symbols]

[0086] 10 Seismic Sensor 11 Acceleration sensor 12 Controllers 13. Memory 14 Output section 21 Acceleration acquisition section 22 Vibration intensity classification / startup determination section (startup determination section) 23 Direction angle calculation unit (angle calculation unit) 24 Direction angle frequency distribution generator (angle frequency distribution generator) 25 Earthquake Determination Department 26 Earthquake scale calculation department 27 Output control section 28 Offset adjustment section 29 Memory section

Claims

1. an acceleration acquisition unit that detects vibration and acquires the acceleration of the vibration; an angle calculation unit that calculates an angle between a vector of each acceleration acquired by the acceleration acquisition unit and an origin on a predetermined coordinate plane; an angle frequency distribution generation unit that generates a frequency distribution of the angles calculated by the angle calculation unit; an earthquake determination unit that determines whether the vibration is an earthquake based on the frequency distribution of the angles created by the angle frequency distribution generation unit; A seismic sensor equipped with:

2. The earthquake determination unit determines that the vibration is an earthquake when the frequency of the angles is generally the same. The seismic sensor according to claim 1 .

3. The earthquake determination unit determines that the vibration is not an earthquake when there is a bias in the frequency of the angles for each angle. The seismic sensor according to claim 1 or 2.

4. the earthquake determination unit calculates a coefficient of variation of the frequency of the angle from the average value and standard deviation of the frequency of the angle created by the angle frequency distribution generation unit, and determines that the vibration is an earthquake when the coefficient of variation is smaller than a predetermined threshold value. The seismic sensor according to claim 1 or 2.

5. the earthquake determination unit determines whether the vibration is an earthquake using any one of a mean value, a median value, and a mode value of the frequency distribution generated by the angle frequency distribution generation unit. The seismic sensor according to claim 1 or 2.

6. the earthquake determination unit determines whether the vibration is an earthquake using any one of standard deviation, variance, skewness, and kurtosis of the frequency distribution generated by the angle frequency distribution generation unit. The seismic sensor according to claim 1 or 2.

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

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

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

10. an acceleration acquisition step of detecting vibration and acquiring the acceleration of the vibration; an angle calculation step of calculating an angle formed by a vector of each acceleration with respect to an origin on a predetermined coordinate plane for the accelerations acquired in the acceleration acquisition step; an angle frequency distribution generating step of generating a frequency distribution of the angles calculated in the angle calculating step; an earthquake determination step of determining whether the vibration is an earthquake based on the frequency distribution of the angles created in the angle frequency distribution generation step; An earthquake detection method comprising:

11. an acceleration acquisition step of detecting vibration and acquiring the acceleration of the vibration; an angle calculation step of calculating an angle formed by a vector of each acceleration with respect to an origin on a predetermined coordinate plane for the accelerations acquired in the acceleration acquisition step; an angle frequency distribution generating step of generating a frequency distribution of the angles calculated in the angle calculating step; an earthquake determination step of determining whether the vibration is an earthquake based on the frequency distribution of the angles created in the angle frequency distribution generation step; An earthquake detection program that causes a computer to execute an earthquake detection method comprising:

12. an acceleration acquisition unit that detects vibration and acquires the acceleration of the vibration; an angle calculation unit that calculates an angle between a vector of each acceleration acquired by the acceleration acquisition unit and an origin on a predetermined coordinate plane; a frequency distribution generation unit that generates a frequency distribution of the angles calculated by the angle calculation unit; A seismic sensor equipped with:

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