JPH0552714A - Dynamic diagnosing method for structure by fluctuation analysis - Google Patents

Abstract

PURPOSE:To diagnose the normal and abnormal dynamic states of a structure by measuring the fluctuation of the structure in the stationary state or in the moving state from the outside. CONSTITUTION:One of two buildings is made to be the target, and a mirror is fixed to one point of this building. Laser beam is projected on this mirror from the other building. The reflected light is detected with a position sensitive detector, and the fluctuation of the reflected light is obtained as the time-series data. The data undergo Fourier transformation, and the value of the low-frequency natural vibration of the object building is measured. Whether the moving state of the object building is normal or not is diagnosed based on the low-frequency natual vibration value. The natural resonance vibration frequency of the structure can be measured in high sensitivity and in high resolution by the very precise spectroscopic method from the outside. Therefore, the diagnosis as to whether the dynamic state of the structure is normal or not can be performed very accurately and readily. This method is very effective for safety control and prediction of danger.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for diagnosing a dynamic state of a structure (a generic name including structures such as bridges and buildings and generators, machines such as engines, and devices) in a stationary state or a motion state, In detail, by shining a light beam on the structure from outside the structure, measuring the reflected light, and analyzing the data obtained by this measurement, the dynamics of the structure are normal or abnormal. The present invention relates to a method of diagnosing the dynamics of a structure for diagnosing whether or not it is.

[0002]

2. Description of the Related Art Structures in a stationary state such as buildings and bridges have recently become huge, and diagnosing their safety has become an extremely important issue in terms of safety management and risk prediction. For this safety diagnosis, it is particularly important to measure how the structure responds to external forces such as wind and earthquake. Although much effort is currently being made on measurement for that purpose, the target of these efforts is mostly measurement of local response, and therefore it is not possible to diagnose whether or not the dynamics of the entire structure are normal.

Further, in a structure such as a generator, a ship, an automobile, or a motor, a turbine in a moving state,
For example, diagnosing the motion state of a cylinder or a rotating shaft is also very important in terms of safety management and risk prediction.

[0004]

Generally speaking, the response of a structure to an external force is a result of each part of the structure responding to an external stress, and the response is generally cross-correlated.
Although the response result of the structure as a whole consists of periodic motions of various frequencies, it is common to find a continuous specific frequency therein, and this specific frequency is the resonance frequency ( Resonance frequency).

Generally, when the response of each part of the structure to the stress from the outside is correlated, the high frequency component is lost and the resonance vibration of the low frequency component remains as a whole. Therefore, if the resonance vibration frequency for this low frequency can be measured, it can be accurately diagnosed whether the dynamic state of the structure is normal. However,
Usually, it is difficult to externally measure the resonance frequency of a structure, and it is particularly difficult to measure low-frequency vibration. Therefore, in reality, the measurement of the low-frequency resonance frequency of the structure is hardly performed. Moreover, it has been pointed out that the low frequency component of the resonance vibration of the structure is an extremely important matter of the structure in the event of an earthquake disaster, for example, in the earthquake in California last year.

On the other hand, in order to accurately diagnose whether or not the dynamic state of the structure in motion is normal, whether or not the cylinder axis or rotation axis of the structure during motion is maintained in the normal position. Measurement, especially when the amount of exercise is changed or the load is changed, the state of dynamic characteristics of the structure, whether the normal state is maintained, etc. Moreover, it is the most important requirement to measure the dynamic state of the structure under the condition that the motion condition is changed, and without this measurement data, accurate diagnosis of normal and abnormal structure dynamics cannot be performed.

Therefore, one object of the present invention is to measure the resonance frequency of a structure in a static state from the outside to diagnose the normal / abnormal of the dynamics of the structure by a fluctuation analysis method of the structure. Is to provide.

Another object of the present invention is to measure a fluctuation of a structure in a motion state from the outside as a function of a stress that causes a motion, and to analyze a structure by fluctuation analysis for diagnosing normality / abnormality of dynamics of the structure. It is to provide a dynamic diagnostic method for.

[0009]

The above object can be achieved by the method for diagnosing the dynamics of a structure by fluctuation analysis according to the present invention. In summary, the present invention analyzes the reflected light received by irradiating a structure in a stationary state or a moving state with a light beam from the outside, receiving reflected light from the structure, and analyzing the received reflected light. And a step of measuring a dynamic characteristic of the structure, which is a dynamic diagnostic method for the structure by fluctuation analysis.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

Example 1 In this example, the low-frequency oscillation natural frequency of a stationary structure was measured by using a laser beam, and the stationary structure to be tested was a building of about 3000 m ² and a three-story building. Use
2 of a two-story building about 15 meters away from this building
A measuring device was installed on the floor. A mirror is fixed to one point of the building to be tested in the horizontal direction from the building where the measuring device is installed, and a laser beam is radiated from the measuring device to the mirror in a substantially horizontal direction, and its reflection The light was detected by the position sensitive device of the measuring device, the fluctuation of the reflected light was acquired as time series data, and this was Fourier transformed. This Fourier transform figure is shown in FIG.

As is apparent from the figure of FIG. 1, the Fourier transform figure of the fluctuation (rocking) of the relative position of the two buildings is
In addition to the pattern that decays exponentially with increasing frequency, it shows a sharp peak at 18.75 Hz (hertz), and this specific frequency is considered to be the natural low-frequency frequency of the experimental building. ..

Two experiments were conducted to confirm this. First, the same measurement was performed while giving an impact to the table on which the measuring device is placed. The resulting Fourier transform diagram is shown in FIG. As is clear from the figure in FIG.
The position and basic pattern of the 8.75 Hz peak (the peak indicated by the arrow in the figure) did not differ from the figure in FIG.
New peaks were found at 32.25 Hz and 43.25 Hz. These latter peaks are considered to be the natural frequencies of the measuring device. Next, the same measurement was performed by continuously giving a shock (impact) to the portion of the experimental building where the mirror was fixed. The resulting Fourier transform figure is shown in FIG. As is clear from the figure of FIG. 3, a sharp rise appears near the frequency zero on the background of the pattern that exponentially attenuates as the frequency increases, and the peak at 18.75 Hz becomes 1
It was found that there was a slight shift to the high frequency side at 9.3125 Hz.

From the above experimental results, it can be concluded that the frequency near 18 Hz is the natural resonance vibration frequency of the experimental building. As described above, according to the present invention, since the natural resonance vibration frequency of the structure in a stationary state can be measured from the outside with high sensitivity and high resolution by extremely precise spectroscopy,
By measuring the natural resonance vibration frequency of the structure when necessary, it is possible to extremely accurately and easily diagnose whether or not the dynamic state of the structure is normal, which is very effective in safety management and risk prediction.

Embodiment 2 In this embodiment, laser light is used to measure fluctuations and tilts of the axis of the rotating shaft of a structure in motion (collectively referred to as eccentricity). The eccentricity of the rotation axis is measured by selecting the motor as the structure in motion, irradiating the rotation axis with laser light, and measuring the arrival point of the reflected light from the motor on the detector. did. The arrival point of the reflected light varies depending on the degree of eccentricity. This difference was detected as a time series function by a position sensitive device, and the detected signal was subjected to Fourier transform for frequency decomposition.

4 to 6 show three types of "weak", "medium", and "strong".
5 is a Fourier transform diagram of the result of measuring the eccentricity of the rotation axis of a small motor whose rotation speed can be switched in stages, and FIG. 4 is a Fourier transform diagram when the rotation speed of the motor is weak, and FIG.
Is the Fourier transform diagram when the motor speed is medium,
FIG. 6 shows Fourier transform figures when the rotation speed of the motor is high. As you can see from the figure in Figure 4,
When the rotation speed of the motor is weak, the frequency distribution of the deviation due to the Fourier transform has three corresponding parts, that is, the first region showing a logarithmic attenuation pattern in the range of 0 to 500 Hz which is the region of the lowest frequency. , 500-1 which is the intermediate frequency range
The second region showing a mountain-shaped pattern in the range of 000 Hz and the higher frequency region of 1200 to 1400 Hz
And a third region showing a gentle mountain-shaped pattern. Further, when the number of rotations of the motor is medium, as can be understood from the figure in FIG. 5, the entire pattern of the deviation due to the Fourier transform is the same as that in FIG. is doing. That is, compared to the figure in FIG.
The first region shifts to 900 to 1000 Hz, and the center of the second region is 1500 Hz. And the third
Area is outside the measurement area. Further, as can be understood from the figure of FIG. 6, when the rotation speed of the motor is high, the first region in the figure of FIG. 4 reaches 1800 Hz.

The above results indicate the dynamic state of the rotary shaft of the motor,
In particular, this is nothing but the fact that it was possible to actually measure that fluctuation fluctuates depending on the rotation conditions. Measuring the dynamic state of a structure, especially its fluctuations, as a function of the stresses that cause it, is of great importance in diagnosing whether the structure's dynamics are normal. It was extremely difficult. According to the present invention, since this measurement can be performed, the normality / abnormality of the dynamics of the structure can be accurately diagnosed, which is very effective in safety management and risk prediction.

Example 3 The fluctuation when a load was further applied to the rotary shaft of the motor used in Example 2 and a stress was applied to the shaft core was measured by the same method as in Example 2 above. FIG. 7 is a Fourier transform diagram when an iron rod having a length of 2 cm is connected to the rotating shaft of the motor. As can be seen from the diagram of FIG. 7, it was found that when a load is applied, the logarithmic attenuation pattern in the first region of 500 Hz or less is significantly amplified as compared with the no-load pattern shown in FIG. ..

Further, FIG. 8 shows a Fourier transform diagram of a result obtained by performing the same measurement while changing the load iron bar to 10 cm.
As is clear from the figure of FIG. 8, it is recognized that the logarithmic attenuation pattern in the first region of 500 Hz or less is more significantly amplified when the load is increased, and further, in the region of 700 Hz to 1.5 KHz. A new large fluctuation amplitude was observed at.

The experimental results of the second and third embodiments are as follows.
For structures that are in motion, when the strength of the motion or the load applied to the structure is changed, the effect of the condition change can be measured externally while maintaining the motion of the structure. Nothing else. It has been impossible to externally measure the fluctuation of the structure in the motion state while changing the control condition of the motion. Therefore, the diagnostic method of the present invention that realizes this is the structure in the static state. It can be said that this is a truly epoch-making diagnostic method that has been long-awaited in this technical field, since it can very accurately diagnose the normality / abnormality of the dynamic state of the structure in motion.

The diagnostic method of the present invention is not limited to the structures shown in the above embodiments, but is equally applicable to buildings such as bridges and buildings, and machines and devices such as generators and engines. It goes without saying that the same effect can be obtained.

[0022]

As is apparent from the above description, according to the present invention, the resonance frequency peculiar to the structure in a stationary state, particularly the resonance frequency (fluctuation) in the low frequency region, can be extremely accurately controlled from the outside. High sensitivity and high resolution can be measured by spectroscopy, and fluctuations of a structure in motion can be measured externally with high sensitivity and high resolution by extremely precise spectroscopy. Whether or not the body dynamics are normal can be accurately and easily diagnosed. Thus, it is possible to extremely accurately confirm the safety of stationary structures such as buildings and bridges, and structures in motion such as generators, ships, automobiles, motors, and turbines.
It has a remarkable effect of being very effective in safety management and risk prediction. Furthermore, there is also an effect that it becomes possible to design and construct safety management / danger prevention measures in a feedback manner based on the analysis of the fluctuation of the structure.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a Fourier transform figure of time series data obtained from a stationary structure by the diagnostic method of the present invention.

FIG. 2 is a characteristic diagram showing a Fourier transform diagram of time-series data obtained from a stationary structure by the diagnostic method of the present invention when a table on which the measurement system is mounted is impacted.

FIG. 3 is a characteristic diagram showing a Fourier transform diagram of time-series data obtained from the stationary structure by the diagnostic method of the present invention by impacting the stationary structure with the diagnostic method of the present invention.

FIG. 4 is a characteristic diagram showing a Fourier transform diagram of time-series data obtained by the diagnostic method of the present invention when the rotation speed of the motor is weak from the rotation axis of the motor.

FIG. 5 is a characteristic diagram showing a Fourier transform diagram of time series data obtained by the diagnostic method of the present invention when the rotation speed of the motor is medium from the rotation axis of the motor.

FIG. 6 is a characteristic diagram showing a Fourier transform diagram of time-series data obtained by the diagnostic method of the present invention when the rotation speed of the motor is strong from the rotation axis of the motor.

FIG. 7 is a characteristic diagram showing a Fourier transform diagram of time-series data obtained by a diagnostic method of the present invention from a rotation shaft of a motor when a steel rod having a length of 2 cm is loaded on the rotation shaft of the motor.

FIG. 8 is a characteristic diagram showing a Fourier transform diagram of time-series data obtained by a diagnostic method of the present invention from a rotating shaft of a motor when a 10 cm-long iron rod is loaded on the rotating shaft of the motor.

Claims (3)

[Claims] 1. A structure in which a stationary or moving structure is externally irradiated with a light beam, reflected light from the structure is received, and the received reflected light is analyzed to analyze the structure. Dynamics of a structure by fluctuation analysis, which comprises the step of measuring the dynamic characteristics of the structure. 2. A step of externally irradiating a specific portion of the structure in a stationary state with a light beam, and a step of receiving reflected light from the specific portion of the structure to obtain time-series data, A step of measuring the resonance frequency of the structure by Fourier transforming the data, and a method for diagnosing the dynamic state of the structure by fluctuation analysis. 3. A step of irradiating a structure in a motion state with a light beam from the outside, a step of receiving reflected light from the structure to obtain time-series data, and Fourier transforming the data to obtain the data. A method for diagnosing the dynamics of a structure by fluctuation analysis, which comprises a step of measuring the fluctuation of the structure.