JP2020085515A - Vibration characteristic detection device and vibration characteristic detection method - Google Patents

Abstract

To improve detection accuracy of a vibration characteristic even with weak vibration.SOLUTION: A vibration characteristic detection device for detecting a vibration characteristic of a measurement object comprises: a plurality of vibration sensors 101; a dominant frequency operation unit (a detection unit 102) for determining a dominant frequency based on a detection waveform of each vibration sensor 101; and representative value operation unit (the detection unit 102) for determining a degree of variation of the dominant frequency for each of a plurality of combinations of the plurality of vibration sensors 101 and determining a representative value of the dominant frequency for a combination of vibration sensors 101 with the smallest degree of vibration.SELECTED DRAWING: Figure 1

Description

The present invention relates to a vibration characteristic detection device and a vibration characteristic detection method for detecting the vibration characteristic of a measurement target such as a structure or a building including a building structure, a bridge, a mechanical device, or the like.

As a technique for judging the safety of a bridge, vibration is applied to the bridge from the outside, this vibration is detected by the vibration detection unit, the vibration waveform is transmitted by wire and temporarily stored in the relay station, and then wirelessly. A technique is known in which the safety of a bridge is judged from the vibration waveform by transmitting it to the measuring section and the judging section of this measuring section.

JP, 7-128182, A

However, in the configuration in which the vibration is forcibly applied as described above, the power consumption increases and it is difficult to perform the detection for a long time. On the other hand, weak vibration that is detected when no forced vibration is applied is greatly affected by noise, and thus it is difficult to reduce variations in detection results.

The present invention has been made in view of the above points, and an object of the present invention is to improve the detection accuracy of vibration characteristics even with weak vibration.

To achieve the above objectives,
The present invention is
A vibration characteristic detection device for detecting a vibration characteristic of a measurement target,
Multiple vibration sensors,
Based on the detection waveform of each vibration sensor, the predominant frequency calculation unit that obtains the predominant frequency,
For each of the plurality of combinations of the plurality of vibration sensors, the degree of variation of the predominant frequency is obtained, and for the combination of the vibration sensors with the smallest degree of variation, a representative value calculation unit that obtains a representative value of the predominant frequency,
It is characterized by having.

As a result, a plurality of vibration sensors are used, and the representative value of the predominant frequency is obtained for the combination of vibration sensors with a small degree of variation, so that measurement data can be largely excluded depending on the magnitude of the detected acceleration. Without this, it is possible to easily obtain high detection accuracy.

According to the present invention, it is possible to improve the detection accuracy of vibration characteristics even with weak vibration.

It is explanatory drawing which shows schematic structure of a vibration characteristic detection apparatus. It is a graph which shows the magnitude|size of the acceleration of detection data, and the distribution of a natural frequency. It is a graph which shows the magnitude|size of the acceleration of other detection data, and the distribution of a natural frequency. It is a flowchart which shows a detection process. It is a flow chart which shows natural frequency extraction processing of a combination of a sensor.

Hereinafter, as an embodiment of the present invention, an example of a vibration characteristic detecting device for detecting a vibration characteristic of a building structure will be described with reference to the drawings.

For example, as shown in FIG. 1, the vibration characteristic detecting device is based on a plurality of, for example, about 20 vibration sensors 101 installed in a building structure 100 such as a building or a bridge, and a detection waveform of each vibration sensor 101. A detection unit 102 that detects the natural frequency and the like of the building structure 100, and a transmission unit 103 that transmits the detection result to a server device (not shown) and the like. Here, the installation location of the vibration sensor 101 is not particularly limited in order to obtain the natural frequency, and the same natural frequency can be obtained regardless of where the building structure 100 is measured.

The detection unit 102 is specifically configured by using, for example, a microcomputer having a calculation unit, a storage unit, and the like, and based on the detection waveform of each vibration sensor 101, the process is described in detail below. For each combination of the predominant frequency calculation unit that obtains the frequency (spectral peak) and the above plurality of vibration sensors 101, the degree of variation in the predominant frequency is obtained, and the combination of the vibration sensors with the smallest degree of variation is predominant. It functions as a representative value calculation unit that obtains a representative value of the frequency. In addition, the natural frequency determination unit that obtains the dominant frequency closest to the representative value of the dominant frequency as the natural frequency, the representative value of the dominant frequency, or the above-mentioned natural frequency, and the representative value of the past dominant frequency, Or, the difference with the natural frequency is a predetermined lower threshold value or more, and, when the predetermined upper limit threshold value or less, a representative value of the predominant frequency, or an effectiveness determination unit that determines the natural frequency as valid, Vibration characteristic change detection that detects changes in the vibration characteristics of the building structure based on the difference between the typical value of the dominant frequency or the natural frequency and the typical value of the dominant frequency in the past or the natural frequency It can also function as a department. The detection unit 102 sends the detection data obtained by the vibration sensor 101 to the server or the like as it is, so that the server or the like performs the above-described processing, or the combination of the detection unit 102 and the server or the like allows It is also possible to perform processing such as.

In the vibration characteristic detecting device as described above, a minute vibration, that is, a minute movement is usually detected due to various factors even in a state where no forced vibration is applied. Such small vibrations are, for example, vertical vibrations and examples of the relationship between the magnitude of acceleration (RMS: root mean square) and the natural frequency for the vibrations in the perpendicular direction to FIGS. 2 and 3. As shown in (1), the frequency of detection of vibrations with a relatively small acceleration is very high, and such vibrations are usually affected by noise and the variation in natural frequency also increases. Therefore, generally, conventionally, a measured value with a large acceleration (removing one with a small RMS of acceleration) or a measured value with a large SN ratio is extracted or a forced vibration is added so that the variation in natural frequency becomes small. Then, the vibration characteristic is detected. On the other hand, the vibration characteristic detecting device of the present embodiment obtains a representative value such as an average value based on the detected waveforms of the plurality of vibration sensors 101, even if the natural frequency has a large variation, to thereby reduce the influence of noise. It is possible to reduce the noise and improve the detection accuracy of the vibration characteristic. Hereinafter, an example of specific processing contents performed by the detection unit 102 will be described with reference to FIGS. 4 and 5.

(S101) First, the vibration waveform data from each vibration sensor 101 is input.

(S102) Next, the vibration waveform data of the vibration sensor 101 whose noise is equal to or lower than a certain value, or whose signal is equal to or higher than a certain value, or whose detected acceleration level is equal to or higher than a predetermined threshold value is selected. Since the influence of noise can be reduced by obtaining the representative value as described below, this processing does not necessarily have to be performed. Further, even when it is performed, the threshold value can be set small. As a result, for example, as shown in the following (Table 1), it is possible to easily maintain a large amount of selected data, as compared with the case where the influence of noise is reduced mainly by excluding data with a low detection level. ..

(S103) Based on the vibration waveform data of each selected vibration sensor 101, frequency analysis such as discrete Fourier transform is performed.

(S104) The predominant frequency is detected based on the result of the frequency analysis.

(S105) Next, the natural frequency is extracted based on the combination of the plurality of vibration sensors 101. Specifically, for example, the processes of (S201) to (S206) shown in FIG. 5 are performed.

(S201) First, a combination of the plurality of vibration sensors 101 is set. Specifically, for example, about 20 vibration sensors 101 may be divided into several pieces, or a larger number of sets may be set that can be selected in an overlapping manner. Further, there may be a sensor that is not selected for each vibration mode.

(S202) For each of the above combinations of the vibration sensor 101, the degree of variation in the dominant frequency is obtained. Specifically, for example, the variation (dispersion) with respect to the average value, the variation with respect to the median value, the sum of absolute values of the differences from the average value, and the like are obtained.

(S203) The combination of the vibration sensors 101 having the smallest variation is selected.

(S204) It is determined whether or not the degree of variation in the combination of the selected vibration sensors 101 is equal to or less than a predetermined threshold value. Then, the detection process based on the vibration waveform data at this point is completed.

(S205) If the degree of variation is less than or equal to a predetermined threshold value, a representative value such as an average value or a median value is obtained.

(S206) The predominant frequency of any of the vibration sensors 101 that is closest to the representative value is selected as the natural frequency of the building structure 100. The representative value may be directly used as the natural frequency.

(S106) (FIG. 4) As the difference between the natural frequency obtained as described above and the natural frequency obtained in the past becomes smaller than a predetermined lower limit threshold value, those natural frequencies become more accurate. Whether or not they match, more specifically, for example, whether or not three or more significant digits match, is confirmed. If they match, the detection process ends. That is, when such a highly accurate detection result is generated, it is assumed that a strong forced vibration is acting from the outside, and such a detection result may be excluded.

(S107) If the difference between the natural frequency obtained in (S105) and the natural frequency obtained in the past exceeds a predetermined lower limit threshold, the obtained natural frequency becomes the building structure. It is output as the natural frequency as the vibration characteristic of 100.

As described above, while using the plurality of vibration sensors 101, the measurement data is not largely excluded depending on the magnitude of the detected acceleration and the like, and the predominant frequency of the predominant frequency obtained for each combination of the plurality of vibration sensors 101 is By making it possible to obtain the natural frequency according to the degree of variation, it is possible to easily exclude the influence of unreliable measurement data while leaving a slight change in the natural frequency. It is possible to easily obtain high detection accuracy even in a short time measurement).

Therefore, by continuously performing the above-described measurement, the vibration of the building structure 100 is based on the difference between the natural frequency obtained as described above and the natural frequency obtained in the past. Even if the change in the characteristic is small and the change in the natural frequency due to the deterioration of the building structure 100 is small, the reliability of the detection can be increased.

In addition, when there is an extraneous vibration (such as steady vibration due to a vehicle), it usually affects only the vibration of a specific sensor, and the predominant frequency that appears in only one such sensor is the structure. However, it is highly possible that other sensors will not have dominant frequencies other than the natural frequencies of the structure, so that the effects of extraneous vibrations can be reduced.

100 Building Structure 101 Vibration Sensor 102 Detector 103 Transmitter

Claims (7)

A vibration characteristic detection device for detecting a vibration characteristic of a measurement target,
Multiple vibration sensors,
Based on the detection waveform of each vibration sensor, the predominant frequency calculation unit that obtains the predominant frequency,
For each of the plurality of combinations of the plurality of vibration sensors, the degree of variation of the predominant frequency is obtained, and for the combination of the vibration sensors with the smallest degree of variation, a representative value calculation unit that obtains a representative value of the predominant frequency,
A vibration characteristic detecting device comprising: The vibration characteristic detecting device according to claim 1, wherein
The above-mentioned predominant frequency calculation unit obtains the predominant frequency for the detected waveforms of all the vibration sensors. The vibration characteristic detecting device according to any one of claims 1 to 2,
The vibration characteristic detecting device, wherein the representative value calculation unit obtains a representative value of the predominant frequency when the smallest degree of variation is less than or equal to a predetermined threshold value. The vibration characteristic detecting device according to any one of claims 1 to 3,
Further, the vibration characteristic detecting device is characterized by further comprising a natural frequency determining unit that obtains a dominant frequency closest to the representative value of the dominant frequencies as a natural frequency. The vibration characteristic detecting device according to any one of claims 1 to 4,
Furthermore, the representative value of the predominant frequency, or the natural frequency, and the difference between the representative value of the predominant frequency of the past, or the natural frequency, when the difference exceeds a predetermined lower threshold, the representative of the predominant frequency A vibration characteristic detecting device, comprising: a validity determining unit that determines that the value or the natural frequency is valid. The vibration characteristic detecting device according to any one of claims 1 to 5,
Further, based on the difference between the representative value of the dominant frequency or the natural frequency and the representative value of the past dominant frequency or the natural frequency, a vibration characteristic for detecting a change in the vibration characteristic of the measurement target. A vibration characteristic detecting device having a change detecting section. A vibration characteristic detection method for detecting a vibration characteristic of a measurement target,
Based on the detected waveforms of multiple vibration sensors, the predominant frequency calculation step for obtaining the predominant frequency,
For each of a plurality of combinations of the plurality of vibration sensors, the degree of variation of the dominant frequency is obtained, and for the combination of the vibration sensors with the smallest degree of variation, a representative value calculation step of obtaining a representative value of the dominant frequency,
A method for detecting vibration characteristics, which comprises: