JP2018189397A - Vibration measuring device - Google Patents

Abstract

A vibration measuring apparatus capable of accurately measuring a trend of a vibration occurrence state is provided. A vibration measuring apparatus measures an acceleration due to vibration applied to a measurement object for a predetermined time by an acceleration sensor before a main measurement for measuring a trend of vibration occurrence state, and based on the measured acceleration, an acceleration reference Perform a reference value measurement to calculate the value. In the reference value measurement, the vibration measurement device is configured to vibrate at the maximum frequency assumed to be applied to the measurement object during a predetermined time of one cycle or more of the vibration at the minimum frequency assumed to be applied to the measurement object. The acceleration sensor output is sampled a plurality of times at intervals of 1 cycle or less (step S1100), and the acceleration is averaged by calculating the acceleration reference value (step S1200). In this measurement, the vibration measuring device measures a trend of vibration applied to the measurement object using the calculated acceleration reference value. [Selection] Figure 3

Description

  The present invention relates to a vibration measuring apparatus, and more particularly to a vibration measuring apparatus that measures a trend of a vibration occurrence state.

  Power receiving / distributing equipment such as a switchboard is installed in various environments. In such devices, the occurrence of defects or the lifetime of internal devices are affected by the environment in which they are installed. For example, power distribution equipment used for traffic applications such as roads and railways may be installed in places such as on elevated roads where vibrations are generated constantly or intermittently due to traveling of vehicles and the like. In power receiving and distributing equipment installed in such an environment, troubles due to vibration (for example, loosening of a fastening part due to vibration, disconnection of an electric wire, wear damage of a covering part, etc.) are occasionally seen. Furthermore, the vibration occurrence state of the installation environment may vary due to increase or decrease in traffic volume, structural deterioration of the installation location, or the like.

  Considering these points, it is important to measure the trend of vibration occurrence in the installation environment when determining the specifications of the power receiving and distributing equipment or determining an appropriate implementation policy for maintenance. In addition, it is important to measure the trend of the occurrence of vibration in monitoring the soundness of the installation environment over the long term. Conventionally, a data logger provided with an acceleration sensor has been used to perform vibration measurement. In vibration measurement using a data logger, instantaneous acceleration is recorded at regular intervals.

  Here, it is known that vibrations generated by the passage of a vehicle have a low frequency (for example, 20 Hz or less) and a low acceleration (for example, 0.1 to 0.2 G) at a place such as an overhead. In measurement of the vibration occurrence state, it is necessary to accurately measure acceleration under such conditions. However, an acceleration sensor used for measuring vibration outputs acceleration in a form including gravitational acceleration, and the output varies with respect to the generated acceleration. When measuring a small acceleration, such a variation in output becomes a problem.

  Some acceleration sensors cut gravity acceleration and detect only dynamic acceleration. However, such an acceleration sensor is expensive and has a disadvantage that sensitivity is lowered in a low frequency region. Therefore, it is difficult to accurately measure the acceleration with respect to the above conditions.

  Regarding the variation of the acceleration sensor, Japanese Patent Application Laid-Open No. 2004-228561 discloses a method of correcting the zero point with an output average value during a period in which no external force is applied to the acceleration sensor.

JP-A-6-156184

  In the method disclosed in Patent Document 1, it is necessary to obtain the output average value of the acceleration sensor during a certain period when it is clear that no external force is acting. As described above, the power receiving / distributing device installed on the overhead is subjected to vibration constantly or intermittently due to the passage of the vehicle or the like. Therefore, in such an environment, it is not easy to obtain an output average value during a period in which no external force is acting. Therefore, in the method disclosed in Patent Document 1, it is difficult to accurately measure vibration (acceleration) applied to a measurement object such as a power receiving / distributing device in an environment in which vibration is generated constantly or intermittently.

  Furthermore, the conventional recording method for recording instantaneous acceleration has a disadvantage that the amount of data per hour becomes enormous. When a trend is recorded, the amount of data to be recorded becomes too large, and data processing becomes complicated. Therefore, it becomes difficult to grasp the trend of the vibration occurrence situation. In addition, when recording acceleration data in a memory inside the apparatus, a memory having a large recording capacity is required, and when recording on an external recording medium by communication, a communication apparatus capable of high-speed communication is required. This increases the cost of the device, which also hinders trend measurement.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a vibration measuring apparatus capable of accurately measuring the trend of the vibration occurrence state. is there.

  In order to achieve the above object, a vibration measuring apparatus according to one aspect of the present invention includes an acceleration sensor attached to a measurement object, and one or more cycles of vibration of a minimum frequency assumed to be applied to the measurement object. A reference value for calculating an acceleration reference value consisting of the average of the output of the acceleration sensor measured several times at intervals of one cycle or less of the vibration of the maximum frequency assumed to be applied to the measurement object during a predetermined time And calculating means and trend measuring means for measuring a trend of vibration applied to the measurement object using the acceleration reference value. The trend measuring means includes a difference value calculating means for calculating a difference value between an acceleration due to vibration applied to the measurement object and an acceleration reference value by using an output of the acceleration sensor, and a difference value calculated by the difference value calculating means as a threshold value. The frequency measurement means for measuring the occurrence frequency of the difference value equal to or greater than the threshold value, and the recording means for recording the time series of the occurrence frequency measured by the frequency measurement means on the recording medium.

  The reference value calculation means is equal to or less than one cycle of vibration of the maximum frequency assumed to be applied to the measurement object during a predetermined time of one cycle or more of vibration of the minimum frequency assumed to be applied to the measurement object. An acceleration reference value consisting of an average of the outputs of the acceleration sensor measured a plurality of times at intervals of is calculated. That is, the reference value calculation means measures acceleration due to vibration applied to the measurement object with an acceleration sensor, and calculates a center value (center value) in the acceleration fluctuation direction (vibration amplitude direction) as the acceleration reference value. As a result, the reference value can be calculated even if the environment in which the measurement object is installed is an environment in which vibration occurs constantly or intermittently. The trend measuring means calculates the difference value between the acceleration due to the vibration applied to the measurement object and the acceleration reference value by using the output of the acceleration sensor. By calculating the difference value between the acceleration due to the vibration applied to the measurement object and the acceleration reference value, it is possible to cancel an error due to an offset due to characteristic variation of the acceleration sensor, an offset due to gravity acceleration, and the like. Thereby, the measurement accuracy of acceleration improves.

  The trend measuring means further compares the calculated difference value with the threshold value by the frequency measuring means, measures the occurrence frequency of the difference value equal to or greater than the threshold value, and then records the time series of the measured occurrence frequency on the recording medium by the recording means. To do. Since the recording medium records not the acceleration waveform itself but the frequency of occurrence of the difference value equal to or greater than the threshold value, the amount of data recorded on the recording medium can be greatly reduced. That is, the acceleration data can be recorded as a trend of vibration occurrence status or numerical data that is extremely easy to compare for each installation environment. Thereby, even when the trend is recorded, the data processing becomes easy, so that the trend of the vibration occurrence state can be easily grasped. In addition, a recording medium having a large recording capacity is not required, and a communication device capable of high-speed communication even when recording on an external recording medium is not required. As a result, it is possible to provide a vibration measuring apparatus that can accurately measure the trend of the vibration occurrence state at a low cost.

  Preferably, the reference value calculation means is a measurement for measuring the acceleration applied to the measurement object by the acceleration sensor at a time interval of 1/10 or less of the period of vibration of the maximum frequency assumed to be applied to the measurement object. Means and a calculating means for calculating an average of measurement values obtained by the measuring means during a predetermined time as an acceleration reference value.

  More preferably, the predetermined time is a time that is not less than 10 times the period of vibration of the minimum frequency.

  More preferably, the vibration measuring device further includes a maximum value extracting unit for extracting the maximum value of the difference value during the measurement period of the occurrence frequency calculated by the difference value calculating unit as an acceleration maximum value, and the recording unit includes: Along with the occurrence frequency measured by the frequency measuring means, the maximum acceleration value extracted by the maximum value extracting means is recorded on the recording medium.

  More preferably, the frequency measuring means compares the difference value calculated by the difference value calculating means with each of a plurality of threshold values, and measures the occurrence frequency of the difference value equal to or greater than the threshold value for each of the plurality of threshold values. including.

  More preferably, the acceleration sensor includes a three-axis acceleration sensor that detects acceleration in a three-axis direction of a three-dimensional orthogonal coordinate fixed to the acceleration sensor, and the difference value calculation means includes each acceleration in the three-axis direction and an acceleration reference. Means for calculating a difference value with respect to the value, and the frequency measuring means measures the occurrence frequency of the difference value equal to or greater than the threshold value by comparing the largest difference value among the difference values in the three axis directions with the threshold value. The vibration measuring apparatus further includes a maximum value extracting means for extracting, as the acceleration maximum value, the maximum value of the difference values in the three axis directions during the occurrence frequency measurement period calculated by the difference value calculating means. Including.

  As described above, according to the present invention, it is possible to obtain a vibration measuring apparatus capable of accurately measuring the trend of the vibration occurrence state.

It is a block diagram which shows the structure of the vibration measuring device which concerns on this Embodiment. It is a flowchart which shows the control structure of the program performed with the vibration measuring device shown in FIG. It is a detailed flow of step S1000 of FIG. It is a figure for demonstrating the measurement of an acceleration reference value (center value). It is a detailed flow of step S2000 of FIG. It is a figure which shows an example of the time chart at the time of this measurement (The figure which shows the acceleration waveform example of each axial direction in this measurement). It is a figure which shows an example of the measurement result of the vibration generation condition on an underpass and under an overpass.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the drawings. In the following description and drawings, the same reference numerals and names are assigned to the same parts or components. Their functions are also the same. Therefore, detailed description thereof will not be repeated.

(Embodiment)
[Constitution]
Referring to FIG. 1, vibration measurement apparatus 50 according to the present embodiment is installed in a power receiving / distributing device installed on an elevated place where vibration is generated constantly or intermittently by traveling of a vehicle, for example. Measure the trend of vibration applied to power distribution equipment (installation environment vibration occurrence status).

  The vibration measuring device 50 includes an acceleration sensor 100, a CPU (Central Processing Unit) 200, a memory 300, and a power source 400. The acceleration sensor 100 is an acceleration sensor IC to which, for example, a MEMS (Micro Electro Mechanical System) technology is applied. The acceleration sensor 100 is a three-axis acceleration sensor that detects accelerations in the three-axis (XYZ-axis) directions of three-dimensional orthogonal coordinates fixed to the acceleration sensor 100. Therefore, in the acceleration sensor 100, at least one axis is offset by about 1 G due to the influence of the gravitational acceleration. Further, depending on the installation angle of the acceleration sensor 100, the influence of the offset on each axis may vary. Furthermore, the gravitational acceleration varies slightly depending on the region.

  The CPU 200 controls the overall operation of the vibration measuring device 50. An output from the acceleration sensor 100 is input to the CPU 200. CPU 200 performs arithmetic processing on the acceleration detected by acceleration sensor 100. The memory 300 includes a RAM (Random access memory), a ROM (Read only memory), and a recording device for recording acceleration data. The recording device includes a nonvolatile recording medium such as a flash memory. The memory 300 stores a program and data for the CPU 200 to execute arithmetic processing and the like. The CPU 200 records data obtained by the arithmetic processing in the memory 300 (recording device). The power source 400 supplies power to each part of the vibration measuring device 50.

  In places such as overpasses, vibrations with low frequency and low acceleration occur due to traffic of vehicles. In the measurement of the trend of the vibration occurrence state, it is necessary to accurately measure the vibration under such conditions (measurement target). On the other hand, in an acceleration sensor used for vibration measurement, an offset error or the like due to characteristic variation occurs. For this purpose, the vibration measuring apparatus 50 performs measurement of an acceleration reference value (hereinafter referred to as “reference value measurement”) for canceling an offset error or the like before the main measurement for measuring the trend of the vibration occurrence state. . The acceleration reference value is a center value (hereinafter referred to as “center value”) in the acceleration fluctuation direction (vibration amplitude direction). This central value is measured by measuring acceleration for a predetermined time of one cycle or more at a predetermined time interval of one cycle or less with respect to vibration of a frequency assumed to be applied to a measurement object (for example, a power distribution device). It is calculated by the average value of the acceleration. The center value thus calculated gives a zero point of the sensor output, as will be described later.

  The vibration measuring device 50 further calculates a difference value between the acceleration detected by the acceleration sensor 100 and the acceleration reference value in the main measurement. That is, the dynamic acceleration is obtained from the difference between the measured acceleration value and the acceleration reference value. The vibration measuring apparatus 50 compares the calculated difference value with a predetermined threshold value that is set in advance, and measures the frequency of occurrence of the difference value (acceleration) that is equal to or greater than the threshold value. The vibration measuring device 50 records the obtained occurrence frequency and the maximum difference value (acceleration maximum value) during the occurrence frequency measurement period in a time series on a predetermined recording medium.

Software configuration
With reference to FIG. 2, a control structure of a computer program executed by the vibration measuring device 50 in order to measure the trend of the vibration occurrence state will be described. This program starts in response to a user's measurement start operation.

  This program is a step S1000 for measuring the acceleration reference value (center value) (reference value measurement), and a step for executing the acceleration measurement (main measurement) for measuring the trend of the vibration occurrence state after step S1000. Including S2000. When the process of step S2000 ends, control returns to step S1000.

  FIG. 3 is a detailed flow of step S1000 of FIG. Referring to FIG. 3, in this routine, the output of acceleration sensor 100 is sampled for T2 seconds (T1 <T2) at a sampling interval of T1 seconds, and the acceleration in each of the three axial directions is measured. Step S1200 is executed after S1100 and the average value of the measured acceleration is calculated for each axial direction. The memory 300 is executed after step S1200 and the calculated average value is used as an acceleration reference value (center value) for each axial direction. And step S1300 which ends this routine.

  Referring to FIG. 4A, the sampling interval T1 is a time interval of 1 cycle or less, more preferably 1/2 cycle or less, more preferably 1 of the maximum frequency vibration assumed to be applied to the measurement object. A time interval of / 10 cycles or less is set. Referring to FIG. 4B, the measurement time T2 is set to a time of 1 cycle or more, preferably 10 cycles or more of the vibration of the minimum frequency assumed to be applied to the measurement object. That is, a plurality of points of data are sampled in one cycle and sampled over a plurality of cycles. By averaging the sampled acceleration data, a center value (center value) in the acceleration fluctuation direction (vibration amplitude direction), that is, an acceleration reference value is obtained.

The number of samples per cycle is preferably 10 or more. Moreover, it is preferable to measure the acceleration for a period of 10 cycles or more. Specifically, when the maximum frequency of vibration assumed to be applied to the measurement object is F1 (Hz), the sampling interval T1 is preferably set to a time that satisfies the following expression (1). As a result, the number of samplings per cycle with respect to the maximum frequency is 10 or more. Furthermore, when the minimum frequency of vibration assumed to be applied to the measurement object is F2 (Hz), the measurement time T2 is preferably set to a time that satisfies the following expression (2). Thereby, the acceleration data is sampled at the sampling interval T1 for a time of 10 cycles or more with respect to the minimum frequency.

  When the frequency (target frequency) of vibration applied to the power receiving / distributing device (measurement object) is, for example, 1 Hz to 20 Hz, T1 = 1/200 (5 ms) and T2 = 10/1 (10 s) can be set. In this case, the number of samplings (number of measurements = T2 / T1) is 2000. By setting the sampling interval T1 and the measurement time T2 in this way, sufficient acceleration data for averaging can be obtained. Therefore, by calculating the average value of these data, the average value (center value) can be substantially regarded as the zero point of the sensor output.

FIG. 5 is a detailed flow of step S2000 of FIG. Referring to FIG. 5, this routine includes a counter variable n for counting the occurrence frequency of acceleration equal to or higher than a preset threshold H, a counter variable m for counting the number of repetitions of processing, and a variable ΔG _max . Initialize these variables by substituting 0 for each, and are executed after step S2100 and after step S2100, and measure acceleration for each of the three axial directions in T3 seconds (T1 <T3) at a sampling interval of T1 seconds. And step S2110 of reading the acceleration reference value stored in the memory 300 and calculating the difference value ΔG between each measured acceleration and the acceleration reference value as an absolute value. In step S2110, acceleration is measured T3 / T1 times in each axial direction, and a difference value ΔG from the acceleration reference value (center value) is calculated as an absolute value for each acceleration.

This routine is further executed after step S2110, and the maximum value of all axial difference values ΔG measured during the measurement time T3 is represented as a representative value representing the maximum acceleration value in each axial direction. a step S2120 of calculating a .DELTA.G _m, is performed after step S2120, it determines whether or representative value .DELTA.G _m is preset threshold H (e.g. 0.05 G), the control flow depending on the result of determination a step S2130 of branches, in step S2130, is executed when the representative value .DELTA.G _m is determined to be the threshold value H or more, and step S2140 to increment the counter variable n, is performed after step S2120, the representative value .DELTA.G _m step S215 but to determine whether or not more than the value of the variable .DELTA.G _max, and branching the control flow depending on the result of determination If, in step S2150, it is executed when the representative value .DELTA.G _m is determined to be greater than or equal to the value of the variable .DELTA.G _max, and a step S2160 substituting the representative value .DELTA.G _m variable .DELTA.G _max.

The routine further after step S2140, or in step S2130, if the representative value .DELTA.G _m is determined not to be the threshold value H above, and, after step S2160, or in step S2150, the representative value .DELTA.G _m variables .DELTA.G It is executed when it is determined that the value is not greater than or equal to the value of _max , and is executed after step S2170 for incrementing the counter variable m and step S2170, and whether or not the value of the counter variable m is equal to a predetermined number of repetitions N, And step S2180 that determines whether or not the processing of step S2110 to step S2170 has been repeated a predetermined number of times (N times), and branches the flow of control according to the determination result. If it is determined in step S2180 that the value of counter variable m is not equal to N, control returns to step S2110.

This routine Further, in step S2180, is executed when the value of the counter variable m is determined to be equal to N, the representative value .DELTA.G _m threshold H or more acceleration frequency of the detected period, i.e. more than the threshold value H Step S2190 for calculating the occurrence frequency of acceleration (n / N × 100 (%)), and executed after step S2190, the calculated occurrence frequency and the value of the variable ΔG _max are recorded in the memory 300 (recording device). And step S2200 for ending this routine.

[Operation]
The vibration measuring apparatus 50 according to the present embodiment operates as follows.

  When the power of the vibration measuring device 50 is turned on and a measurement start instruction is given by the user, the vibration measuring device 50 starts trend measurement of the vibration occurrence state. Referring to FIG. 2, vibration measurement device 50 (CPU 200) periodically performs reference value measurement (measurement of acceleration reference value (center value)) before the main measurement for measuring the trend of vibration occurrence status. Is executed (step S1000).

  Referring to FIG. 3, in the reference value measurement, vibration measurement apparatus 50 first samples the output of acceleration sensor 100 for T2 seconds at a sampling interval of T1 seconds, and measures the acceleration for each of the three axial directions ( Step S1100). The sampling interval T1 is set to, for example, a time that satisfies the above equation (3). The measurement time T2 is set to, for example, a time that satisfies the above formula (4).

  As described above, vibrations with a low frequency (for example, 20 Hz or less) and a low acceleration (for example, 0.1 to 0.2 G) are generated at a place such as an elevated place where an object to be measured such as a power distribution device is installed. With reference to FIG. 4, by setting the sampling interval T1 to a time satisfying the above expression (3), the acceleration of 10 or more per cycle with respect to the maximum frequency among the frequencies to be measured (for example, 20 Hz or less). Data can be sampled. Furthermore, by setting the measurement time T2 to a time that satisfies the above equation (4), acceleration data can be sampled for a period of 10 cycles or more with respect to the minimum frequency among the frequencies to be measured.

  Referring to FIG. 3 again, vibration measurement device 50 calculates an acceleration reference value (center value) by averaging the measured accelerations (step S1200). The vibration measuring device 50 stores the calculated acceleration reference value in the memory 300 (step S1300). As described above, the vibration measurement device 50 performs the reference value measurement for T2 seconds, thereby acquiring the acceleration data necessary and sufficient to calculate the effective acceleration reference value (center value). The vibration measuring device 50 calculates an average value of the acquired acceleration data, thereby obtaining an acceleration reference value (center value) that can be substantially regarded as a zero point of the sensor output.

When the reference value measurement is completed, the vibration measuring device 50 performs the main measurement for measuring the trend of the vibration occurrence state. Referring to FIG. 5, first, vibration measurement apparatus 50 initially sets counter variable n for counting the frequency of occurrence of acceleration equal to or higher than the threshold, counter variable m for counting the number of repetitions of processing, and variable ΔG _max . (Step S2100). When the initialization is completed, the vibration measuring device 50 samples the output of the acceleration sensor 100 for T3 seconds at a sampling interval of T1 seconds, and measures the acceleration for each of the three axial directions. The vibration measuring device 50 reads the acceleration reference value and calculates the difference value ΔG between each measured acceleration and the acceleration reference value as an absolute value (step S2110).

Subsequently, the vibration measuring apparatus 50 extracts the maximum value of all the axial difference values ΔG measured during the measurement time T3 as a representative value ΔG _m representing the maximum value in each axial direction ( Step S2120). Vibration measurement device 50 is configured to compare a representative value .DELTA.G _m a preset threshold H, compares the representative value .DELTA.G _m the value of the variable .DELTA.G _max. If representative value ΔG _m is equal to or greater than threshold value H (YES in step S2130), vibration measurement device 50 increases the value of counter variable n by 1 (step S2140). If representative value ΔG _m is equal to or greater than the value of variable ΔG _max (YES in step S2150), vibration measurement apparatus 50 substitutes the value of representative value ΔG _m for variable ΔG _max and updates the value of variable ΔG _max (step S2150). S2160). Since the initial value of the variable ΔG _max is “0”, the value of the representative value ΔG _m is substituted into the variable ΔG _max during the first measurement. If representative value ΔG _m is smaller than threshold value H (NO in step S2130), the value of counter variable n is not updated (not counted). Similarly, when representative value ΔG _m is smaller than the value of variable ΔG _max (NO in step S2150), the value of variable ΔG _max is not updated.

When these processes are completed, the vibration measuring device 50 increases the value of the counter variable m for counting the number of repetitions by 1 (step S2170). The vibration measuring device 50 determines whether or not these series of processes have been repeated N times. If it has not been repeated N times (NO in step S2180), the processing in steps S2110 to S2170 is repeated. When this series of processes is repeated N times (YES in step S2180), vibration measurement apparatus 50 determines the occurrence frequency (n / N × 100 (%)) of acceleration (difference value ΔG) equal to or higher than threshold value H by the number of measurements ( N) is calculated as the generation ratio (step S2190). The vibration measuring device 50 records the calculated occurrence frequency in the memory 300 (recording device) in association with the value of the variable ΔG _max (step S2200).

When the main measurement is completed, the vibration measurement device 50 performs the reference value measurement (step S1000 in FIG. 2) again. When the acceleration reference value is measured, the vibration measuring device 50 performs the main measurement again (step S2000 in FIG. 2). The vibration measuring device 50 measures the trend of vibration applied to the power receiving / distributing device by recording the occurrence frequency and the variable ΔG _max in time series in the memory 300 (recording device).

For example, the sampling interval T1, the measurement time T2, the measurement time T3, and the number of repetitions N are set as follows.
Sampling interval T1: 0.005 sec (5 ms)
Measurement time T2: 10 sec
Measurement time T3: 36 sec
Number of repetitions N: 100 times

With this setting, the vibration measuring device 50 performs the reference value measurement in 10 seconds, and then performs the main measurement for 3600 seconds. The vibration measuring device 50 records the occurrence frequency of acceleration equal to or higher than the threshold value and the acceleration maximum value (value of the variable ΔG _max ) in the memory 300 every 3610 seconds. The vibration measuring device 50 logs acceleration data at a frequency of about once per hour and records a vibration trend of the installation environment of the power receiving / distributing device.

  FIG. 6 is a time chart showing an example of an acceleration waveform in each axial direction (X-axis direction, Y-axis direction, and Z-axis direction) in this measurement. The number of times of measurement (repetition number N) is 100 times. However, in FIG. 6, an acceleration waveform example is shown by a difference value ΔG that does not take an absolute value. With reference to FIG. 6, the calculation of the occurrence frequency in the main measurement will be described in more detail.

In the first measurement, the acceleration in the Y-axis direction is maximum. Therefore, the maximum acceleration (ΔG _m ) in the Y-axis direction is compared with a threshold value. Since the maximum acceleration in the Y-axis direction exceeds the threshold value, the vibration measurement device 50 increases the counter for counting the occurrence frequency by 1 (count 1). In FIG. 6, a period during which acceleration equal to or greater than the threshold is detected (acceleration greater than or equal to the threshold) is indicated by an arrow L. In the second measurement, the acceleration in the Y-axis direction is the maximum. However, in the second measurement, since the maximum acceleration (ΔG _m ) in the Y-axis direction does not exceed the threshold value, the frequency is not counted. In the third measurement, since the acceleration in the Z-axis direction is the maximum, this maximum acceleration (ΔG _m ) is compared with a threshold value. Since the maximum acceleration in the Z-axis direction exceeds the threshold value, the vibration measuring device 50 increases the counter by 1 (count 2). During this period, the maximum acceleration in the Y-axis direction also exceeds the threshold value, but is not used for counting because it is smaller than the maximum acceleration in the Z-axis direction. In FIG. 6, a period in which acceleration equal to or greater than the threshold value is detected in this way but is not used for counting is indicated by a dashed arrow M. Similarly, in the fourth measurement, since the acceleration in the X-axis direction is the maximum and this maximum acceleration (ΔG _m ) exceeds the threshold value, the vibration measuring device 50 increases the counter by 1 (count 3). Such a process is repeated 100 times. For example, at the 99th measurement, the acceleration in the Y-axis direction is the maximum acceleration (ΔG _m ), and the acceleration exceeds the threshold value. Assume that the count number at this time is 36 (count 36), for example, and acceleration (difference value) equal to or greater than the threshold value was not measured at the 100th measurement. In this case, there are 36 periods during which acceleration equal to or greater than the threshold is detected, and the frequency of occurrence of acceleration equal to or greater than the threshold is calculated as 36% (= 36/100 × 100).

[Effects of the present embodiment]
As is clear from the above description, the following effects can be obtained by using the vibration measuring apparatus 50 according to the present embodiment.

  The vibration measuring device 50 has a sampling interval T1 of one cycle or less of vibration of the maximum frequency of vibration assumed to be applied to the measurement object, and a measurement time T2 of one cycle or more of vibration of the minimum frequency assumed. The acceleration is measured, and the average value of the measured acceleration is calculated as the acceleration reference value. As a result, the reference value can be calculated even if the environment in which the measurement object is installed is an environment in which vibration occurs constantly or intermittently. The vibration measurement device 50 calculates the difference value between the acceleration due to vibration applied to the measurement object and the acceleration reference value, so that an error due to a deviation in the installation angle of the acceleration sensor 100 and an offset due to a characteristic variation of the acceleration sensor 100 are obtained. And errors due to offsets due to gravitational acceleration can be canceled. In addition, the sensitivity drift of the acceleration sensor 100 can be corrected by periodically calculating the acceleration reference value. Thereby, the measurement accuracy of acceleration improves.

  The vibration measuring device 50 further compares the calculated difference value ΔG with a predetermined threshold value H set in advance, and measures the frequency of occurrence of the difference value (acceleration) equal to or greater than the threshold value H. The vibration measuring device 50 records the occurrence frequency in the memory 300 in time series together with the maximum acceleration value. The vibration measuring device 50 does not record the acceleration waveform itself, but the frequency of occurrence of a difference value greater than or equal to the threshold value H, that is, the frequency of occurrence of acceleration greater than or equal to the threshold value H, and the occurrence frequency measurement period Is recorded in the memory 300. Thereby, the amount of data recorded in the memory 300 can be greatly reduced. That is, the acceleration data can be recorded as a trend of vibration occurrence status or numerical data that is extremely easy to compare for each installation environment. Even when the trend is recorded, the data processing becomes easy, so the trend of the vibration occurrence state can be easily grasped. In addition, a recording medium having a large recording capacity becomes unnecessary. When data is recorded on an external recording medium instead of the memory 300, a communication device capable of high-speed communication is not necessary.

  As described above, according to the vibration measuring apparatus 50, it is possible to accurately measure the trend of the vibration occurrence state in the installation environment of the measurement object while greatly reducing the data capacity. Moreover, such a vibration measuring device 50 can be provided at low cost.

  Note that the sensor should be firmly fixed to the measurement object in view of the original meaning of vibration sensing that detects vibration applied to the measurement object. However, as shown in the present embodiment, when the vibration of the measurement target is a low frequency fine vibration, for example, when the target frequency is a low frequency of 20 Hz or less, the purpose of the vibration measurement is not fixed firmly. Can be achieved. Therefore, the vibration measuring device 50 (acceleration sensor 100) may be fixed with a plug-in socket, for example. If comprised in this way, replacement | exchange of the vibration measuring apparatus 50 (acceleration sensor 100) will become easy.

  Next, an experiment performed to confirm the effect of the vibration measuring device 50 will be described.

In this experiment, a sensor having the following specifications was used as the acceleration sensor.
(1) Measurement axis: XYZ axis (up / down / front / back / left / right)
(2) Measurement range: ± 2G
(3) Resolution: 0.004G
(4) Offset error: ± 0.04G

  In FIG. 7, the measurement result of the vibration generation condition of a switchboard (distribution apparatus) is shown. FIG. 7 (A) shows the vibration generation status of the switchboard installed on the overpass, and FIG. 7 (B) shows the vibration generation status of the switchboard installed under the overpass. Referring to FIG. 7, it can be seen that vibrations are always generated in the installation environment on the overhead as compared with the installation environment on the overhead. In addition, in the installation environment on an elevated route, the frequency of vibration of 0.1 G or less is very high. When the trend of the vibration occurrence situation in such an environment is recorded with the above-described occurrence frequency, the minimum value of the threshold needs to be about 0.05G. When the offset error of the acceleration sensor is ± 0.04G, this offset error is a value that cannot be ignored.

  Therefore, the acceleration reference value was measured in the same manner as in the above embodiment using the acceleration sensor, and the effect of reducing the offset error by taking the difference from the acceleration reference value was investigated. The sampling interval T1 is 0.005 sec (5 ms), and the measurement time T2 is 10 sec. Table 1 below shows the vibration generation conditions when measuring the acceleration reference value and the comparison result of the offset error depending on whether or not the acceleration reference value is corrected.

  Referring to Table 1, vibration generation conditions are no vibration, vibration of frequency 10 Hz (amplitude 0.3 G), vibration of frequency 20 Hz (amplitude 1.2 G), and sweep of frequency 10 Hz to 20 Hz (amplitude 0.3 to 4 conditions of vibration of 1.2G). The acceleration reference value was measured under each vibration condition, and the offset error was corrected by taking the difference between the offset error and the acceleration reference value. In the case of no correction, the offset error is a maximum of 0.04 G, which is the offset error of the acceleration sensor. On the other hand, in the case of correction, the offset error was less than 0.01G. Thus, it was confirmed that the offset error can be effectively canceled by correcting with the acceleration reference value.

(Modification)
In the above-described embodiment, an example in which one threshold value for measuring the frequency of occurrence of acceleration is shown, but the present invention is not limited to such an embodiment. A plurality of threshold values may be set. In this case, for each set threshold value, the frequency of occurrence of a difference value equal to or greater than the threshold value may be measured.

  In the above-described embodiment, an example in which the acceleration in each of the three axial directions is measured using the three-axis acceleration sensor has been described, but the present invention is not limited to such an embodiment. For example, the acceleration of one axis (for example, the gravitational direction) in the three axis directions may be measured, and the trend of the vibration occurrence state may be measured using the measured acceleration.

In the embodiment described above, by measuring the difference value .DELTA.G of the acceleration in each axial direction in the three axial directions, but the maximum value of the difference value .DELTA.G of all axial shows an example in which the representative value .DELTA.G _m, the The invention is not limited to such an embodiment. For example, the vector length of the vector sum of each difference value .DELTA.G of each axial or as a representative value .DELTA.G _m. In this case, although an operation for calculating the vector length of the vector sum is required, the acceleration can be detected more accurately. Further, for example, the maximum value for each axial difference value .DELTA.G, respectively, may be as a representative value .DELTA.G _m along each axis. In this case, each representative value ΔG _m is compared with the threshold value H for each axial direction. In FIG. 6, the period indicated by the broken-line arrow M for each axis corresponds to this. Incidentally, as shown in the above embodiment, if the maximum value of the difference value .DELTA.G of all axial and representative value .DELTA.G _m, it is possible to reflect the third axis direction information calculated is facilitated.

  In the above-described embodiment, an example of a vibration measuring device that measures only vibration (acceleration) has been described, but the present invention is not limited to such an embodiment. It is good also as a measuring device which served as sensing other than vibration sensing. For example, in addition to the acceleration sensor, a sensor such as a temperature sensor, a humidity sensor, or an odor sensor may be mounted on the vibration measuring device so as to be able to measure temperature, humidity, odor, and the like. Further, by installing a communication function in the vibration measuring apparatus, the trend data of the vibration occurrence state may be recorded on an external recording medium. Thereby, vibration etc. can be monitored remotely.

  In the above-described embodiment, an example in which the occurrence frequency of acceleration equal to or higher than the threshold and the maximum acceleration value during the occurrence frequency measurement period are recorded in the memory in time series has been described. However, the present invention includes such an embodiment. It is not limited. One of the occurrence frequency and the maximum acceleration value may be recorded in the memory in time series.

  In the above embodiment, the example using the triaxial acceleration sensor capable of measuring the acceleration in the triaxial direction has been described, but the present invention is not limited to such an embodiment. For example, a uniaxial acceleration sensor that measures only acceleration in one axis direction or a biaxial acceleration sensor that measures only acceleration in two axes may be used.

  In the above embodiment, during a measurement time T2 of one cycle or more of the assumed minimum frequency vibration at a sampling interval T1 of one cycle or less of the vibration of the maximum frequency assumed to be applied to the measurement object, Although an example in which the acceleration is measured and the average value of the measured acceleration is calculated as the acceleration reference value has been shown, the present invention is not limited to such an embodiment. The sampling interval T1 may be a time shorter than one period of vibration of the maximum frequency of vibration assumed to be applied to the measurement object. Further, the measurement time T2 may be a time longer than one cycle of the assumed minimum frequency vibration.

  In the above embodiment, an example is shown in which the difference value ΔG between the acceleration detected by the acceleration sensor and the acceleration reference value is calculated as an absolute value. However, the present invention is not limited to such an embodiment. The difference value ΔG may not be an absolute value.

  The embodiment disclosed herein is merely an example, and the present invention is not limited to the embodiment described above. The scope of the present invention is indicated by each claim of the claims after taking into account the description of the detailed description of the invention, and all modifications within the meaning and scope equivalent to the wording described therein are included. Including.

50 Vibration measuring device 100 Acceleration sensor 200 CPU
300 Memory 400 Power supply T1 Sampling interval T2, T3 Measurement time

Claims (5)

An acceleration sensor attached to the measurement object;
A plurality of vibrations at intervals of not more than one period of vibration of the maximum frequency assumed to be applied to the measurement object during a predetermined time of not less than one period of vibration of the minimum frequency assumed to be applied to the measurement object. Reference value calculating means for calculating an acceleration reference value consisting of an average of the outputs of the acceleration sensor measured once,
A trend measuring means for measuring a trend of vibration applied to the measurement object using the acceleration reference value;
The trend measuring means includes
A difference value calculating means for calculating a difference value between the acceleration due to vibration applied to the measurement object and the acceleration reference value using an output of the acceleration sensor;
A frequency measurement means for comparing the difference value calculated by the difference value calculation means with a threshold and measuring the occurrence frequency of the difference value equal to or greater than the threshold;
A vibration measuring apparatus including recording means for recording a time series of the occurrence frequency measured by the frequency measuring means on a recording medium. The reference value calculation means includes
Measurement means for measuring acceleration applied to the measurement object by the acceleration sensor at a time interval of 1/10 or less of a period of vibration of the maximum frequency assumed to be applied to the measurement object;
Calculating means for calculating an average of measured values by the measuring means during the predetermined time as the acceleration reference value;
The vibration measuring apparatus according to claim 1, wherein the predetermined time is a time that is ten times or more of a period of vibration of the minimum frequency. The vibration measuring apparatus further includes a maximum value extracting unit for extracting the maximum value of the difference value during the measurement period of the occurrence frequency calculated by the difference value calculating unit as an acceleration maximum value,
The vibration measuring apparatus according to claim 1, wherein the recording unit records the acceleration maximum value extracted by the maximum value extracting unit together with the occurrence frequency measured by the frequency measuring unit on the recording medium. .   The frequency measuring unit compares the difference value calculated by the difference value calculating unit with each of a plurality of threshold values, and measures a frequency of occurrence of a difference value equal to or greater than the threshold value for each of the plurality of threshold values. The vibration measuring device according to any one of claims 1 to 3, further comprising: The acceleration sensor includes a three-axis acceleration sensor that detects acceleration in three-axis directions of three-dimensional orthogonal coordinates fixed to the acceleration sensor,
The difference value calculating means includes means for calculating a difference value between each acceleration in the three axis directions and the acceleration reference value,
The frequency measuring means includes means for comparing the largest difference value among the difference values in the three axis directions with the threshold value and measuring the occurrence frequency of the difference value equal to or greater than the threshold value,
The vibration measuring apparatus further includes a maximum value extracting means for extracting the maximum value of the difference values in the three axis directions during the measurement period of the occurrence frequency calculated by the difference value calculating means as the acceleration maximum value. The vibration measuring device according to claim 1 or 2.

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