JP7488865B2 - Bolt looseness estimation device, bolt looseness estimation method, and bolt looseness estimation program - Google Patents

Description

The present disclosure relates to a bolt loosening estimation device, a bolt loosening estimation method, and a bolt loosening estimation program.

Conventionally, there is an inspection device that judges the deterioration of an object under inspection. The inspection device includes a hammer device and a vibration detection sensor that are attached to the object under inspection. The hammer device generates a hammering sound when driven. The vibration detection sensor detects the hammering sound that has propagated through the object under inspection, and judges the deterioration state of the object under inspection from the vibration waveform of the hammering sound (see Patent Document 1).

JP 2001-221783 A

The inspection device described in Patent Document 1 is a device for determining deterioration of an object to be inspected, such as a tunnel wall.
However, steel materials fastened with bolts are sometimes used in structures such as steel towers, and the presence or absence of loose bolts may be checked during the inspection of such structures. The inspection device described in Patent Document 1 cannot check the presence or absence of loose bolts, and there has been a demand for an inspection device that can check for loose bolts.

The present disclosure provides a bolt looseness estimation device, a bolt looseness estimation method, and a bolt looseness estimation program that estimate the presence of looseness in a bolt.

One embodiment of a bolt loosening estimation device includes a vibration unit that vibrates a steel material fastened with a bolt while changing the vibration frequency, a microphone unit that can collect the resonance sound that occurs when the bolt resonates in response to the vibration from the vibration unit when the bolt is loose, and an estimation unit that estimates that the bolt is loose based on the resonance sound collected by the microphone unit.

According to one embodiment, it is possible to estimate whether a bolt is loose.

FIG. 1 is a diagram for explaining a bolt loosening estimation device according to an embodiment. FIG. 1 is a block diagram illustrating an estimation device according to an embodiment. 1A is a diagram showing an example of the relationship between time and the intensity of a sound (resonating sound) when the frequency of vibration is gradually changed over time, where (A) is a diagram showing an example of the relationship between time and the intensity of a sound (resonating sound) when there is a loose bolt, and (B) is a diagram showing an example of the relationship between time and the intensity of a sound (resonating sound) when there is no loose bolt. 1A is a diagram showing an example of the relationship between the frequency of vibration and the intensity of vibration when a bolt is loosened, and FIG. 1B is a diagram showing an example of the relationship between the frequency of vibration (excitation) and the intensity of vibration when the bolt vibrates in response to the excitation while changing the frequency of vibration (excitation), and FIG. 1 is a flowchart for explaining a method for estimating bolt loosening according to one embodiment.

One embodiment is described below.

[Outline of the bolt loosening estimation device 100]
First, an overview of a bolt loosening estimation device 100 according to an embodiment will be described.
FIG. 1 is a diagram for explaining a bolt loosening estimation device 100 according to one embodiment.

The bolt loosening estimation device 100 may be configured, for example, as an inspection device capable of inspecting bolt loosening in a bolted structure. The bolt loosening estimation device 100 is not limited to the above-mentioned example device, and may be configured as various devices.
The bolt loosening estimation device 100 may be configured as, for example, an information processing device. The information processing device may be, for example, a computer such as a server, a desktop, a laptop, a tablet, or a smartphone.
In the following, the "bolt loosening estimation device" may be abbreviated to "estimation device."

The estimation device (information processing device) 100 vibrates a steel material (base material) 200 having bolt fastening while changing the vibration frequency. The steel material 200 is used in various structures including steel towers and steel bridges. Therefore, the estimation unit 112 may vibrate a structure using the steel material 200. Here, the estimation device 100 may apply vibration to the steel material 200 (structure) by controlling a vibration execution unit 121 capable of applying vibration to the steel material 200 (structure), including, for example, a vibrator, actuator, and transducer.

It has been found through experiments that if there is looseness in the bolt fastening of the steel material 200, the loose bolt will vibrate (or resonate) in response to vibration applied to the steel material 200. Furthermore, it has been found through experiments that when the bolt vibrates (resonates), a rattling sound (e.g., a resonating sound) is generated. In other words, it has been confirmed through experiments that the natural vibration of the bolt is amplified by the frequency at which a loose bolt (a bolt that is not fastened to the base material by a tightening torque) resonates, generating a resonating sound similar to metal hitting metal.

Therefore, the estimation device (information processing device) 100 places a microphone unit 122 relatively close to the steel material 200 (structure), and when the microphone unit 122 picks up the resonant sound, it estimates that the bolt is loose based on the resonant sound.
That is, the estimation device (information processing device) 100 installs a vibration execution unit 121 at the base or the like of the structure, and resonates the loose bolts while varying the vibration frequency, and checks whether or not a resonant sound is generated, thereby inspecting whether or not a loose bolt is present in the structure.

[Details of the estimation device 100]
Next, the estimation device 100 according to an embodiment will be described in detail.
FIG. 2 is a block diagram illustrating an estimation device 100 according to an embodiment.

The estimation device 100 includes, for example, a vibration execution unit 121, a microphone unit 122, a communication unit 131, a memory unit 132, a display unit 133, and a control unit 110. The communication unit 131, the memory unit 132, and the display unit 133 may be an embodiment of the output unit. The control unit 110 includes, for example, a vibration unit 111, an estimation unit 112, and an output control unit 113. The control unit 110 may be configured, for example, by a calculation processing unit of the estimation device 100. The control unit 110 (for example, a calculation processing unit) may realize the functions of each unit (for example, the vibration unit 111, the estimation unit 112, and the output control unit 113) by, for example, appropriately reading and executing various programs stored in the memory unit 132.

The vibration execution unit 121 is, for example, a device capable of applying vibration to a steel material (base material) (or a structure, etc.). The vibration execution unit 121 may be, for example, various vibration generating devices including a vibrator, actuator, vibrator, etc. The vibration execution unit may be capable of varying the frequency of the vibration applied to the steel material. As an example, the vibration execution unit may be capable of changing the vibration frequency between 20 Hz and 20,000 Hz and applying vibrations of each frequency to the steel material.

The microphone unit 122 is disposed around a steel material (base material) (or a structure, etc.) to be inspected for loose bolts, for example.
The microphone unit 122 can collect a resonance sound generated when the bolt resonates in response to the vibration applied by the vibration unit 111 if the bolt is loose. For example, there may be one or more microphone units 122. Furthermore, one microphone unit 122 may include one or more microphones.
The microphone unit 122 may be, for example, a microphone group in which a plurality of microphone units 122 are arranged at different positions. In this case, the microphone group (microphone unit 122) may include, for example, a plurality of directional microphones. Each of the plurality of microphone units 122 constituting the microphone group may be arranged at a different position around the steel material (or the structure, etc.). As an example, each of the plurality of microphone units 122 constituting the microphone group may be arranged around the steel material (or the structure, etc.) on three or four sides, etc.
Furthermore, the microphone unit 122 may be, for example, a microphone array including a plurality of microphones. The microphone array may be configured such that a plurality of directional microphones are arranged such that their sound collection directions are in different directions.

The communication unit 131 is, for example, a communication interface capable of transmitting and receiving various information to and from a device (external device) (not shown) external to the information processing device.

The storage unit 132 may store, for example, various information and programs. Examples of the storage unit 132 may be a memory, a solid state drive, a hard disk drive, etc. The storage unit 132 may be, for example, a storage area and a server on the cloud, etc.

The display unit 133 is, for example, a display capable of displaying various characters, symbols, images, etc.

The vibration unit 111 may, for example, vibrate a base material (or a structure, etc.) such as a steel material having bolt fastening by controlling the vibration execution unit 121. In other words, the vibration unit 111 may control the vibration execution unit 121 to apply vibration to a base material (or a structure, etc.) such as a steel material having bolt fastening.

In this case, the vibration unit 111 may vibrate the steel material (base material) having the bolt fastening while changing the vibration frequency. As an example, the vibration unit 111 may change the vibration frequency between 20 Hz and 20,000 Hz to vibrate the steel material (base material). That is, the vibration unit 111 may control the vibration execution unit 121 so that the frequency of the vibration generated by the vibration execution unit 121 gradually changes continuously or stepwise between 20 Hz and 20,000 Hz. In other words, the vibration unit 111 may control the vibration execution unit 121 so that the frequency of the vibration changes over time.
The above-mentioned frequency range is merely an example, and the frequency range may be set according to various parameters including the material having the bolt (e.g., steel, etc.), the material and size of the bolt, and the type and size of the structure.

The estimation unit 112 estimates that the bolt is loose based on the resonant sound collected by the microphone unit 122. In this case, the estimation unit 112 may estimate that the bolt is loose when, for example, the microphone unit 122 collects a resonant sound.

In addition, the microphone unit 122 may collect not only the resonance sound but also the surrounding environmental sound (environmental sound). On the other hand, it has been estimated through experiments that the resonance sound of a bolt when the bolt is loose occurs in approximately a specific frequency band. As an example, the frequency of the bolt resonance sound is often higher than the frequency of environmental sound (e.g., wind noise, etc.).
Therefore, the estimation unit 112 may identify a resonant sound based on the frequency of the sound collected by the microphone unit 122, and may estimate that the bolt is loose when the resonant sound is present.
As described above, the vibration unit 111 controls the vibration execution unit 121 to vibrate the steel material (or the structure, etc.), for example, while changing the frequency of the vibration applied to the steel material. The estimation unit 112 may acquire sounds collected by the microphone unit 122 during the series of vibrations, and may estimate that the bolt is loose when a sound (resonant sound) is acquired by the microphone unit 122 when the steel material is vibrated at a frequency at which a resonant sound of the bolt is generated.
In this case, the estimation unit 112 may, for example, set a threshold value for sound intensity in advance, and if the sound (sound picked up by the microphone unit 122) generated when the steel material is vibrated at a frequency at which the bolt resonates is greater than the threshold value, it may be estimated that the bolt is loose.

Figure 3 is a diagram showing an example of the relationship between time and the intensity of sound (resonant sound) when the vibration frequency is gradually changed over time. Figure 3(A) is a diagram showing an example of the relationship between time and the intensity of sound (resonant sound) when there is a loose bolt. Figure 3(B) is a diagram showing an example of the relationship between time and the intensity of sound (resonant sound) when there is no loose bolt. In Figures 3(A) and 3(B), the horizontal axis indicates time, and the vertical axis indicates sound intensity.

As described above, the resonance sound due to the looseness of the bolt appears in a specific frequency band. Note that the specific frequency band may differ depending on the material and the degree of looseness. On the other hand, when the bolt is not loose, no resonance sound is generated.
That is, when the bolt is loose, if the frequency for vibrating the base material is gradually changed over time, an example of the intensity of the sound collected by the microphone unit 122 is as shown in FIG. 3A. On the other hand, when the bolt is not loose, if the frequency for vibrating the base material is gradually changed over time, an example of the intensity of the sound collected by the microphone unit 122 is as shown in FIG. 3B. The horizontal axes (time) of FIG. 3A and FIG. 3B correspond to each other and indicate the same vibration frequency at the same time. When FIG. 3A and FIG. 3B are compared, there is a difference in the intensity of the sound between A1 and B1, and between A2 and B2. From the relationship between FIG. 3A and FIG. 3B, it can be seen that a difference in the intensity of the sound occurs at a specific frequency when vibrating a loose bolt.

Figure 4 is a diagram showing an example of the relationship between vibration frequency and vibration intensity. Figure 4(A) is a diagram showing an example of the relationship between the vibration (excitation) frequency when there is looseness in the bolt and the vibration intensity when the bolt resonates in response to the excitation while changing the vibration (excitation) frequency. Figure 4(B) is a diagram showing an example of the relationship between the vibration (excitation) frequency and vibration intensity in an exciter that vibrates a base material having bolt fastening. In Figures 4(A) and 4(B), the horizontal axis indicates frequency and the vertical axis indicates vibration intensity. Note that in Figure 4(A), a vibration meter is placed on the bolt to obtain the vibration intensity according to the frequency.

The horizontal axis (frequency) of Figure 4 (A) and Figure 4 (B) shows the corresponding frequencies. Comparing Figure 4 (A) and Figure 4 (B), there is a difference in vibration intensity between C and D. From the relationship between Figure 4 (A) and Figure 4 (B), it can be seen that for a loose bolt, there is a difference in the vibration intensity of the vibrator at a specific frequency in response to the vibration applied by the vibrator (the bolt resonates).

Therefore, it is estimated that at the frequency (or frequency band) of the resonant sound generated when a bolt is loose, the intensity of the resonant sound when the bolt is loose will be greater than the intensity of the sound when the bolt is not loose.
Therefore, the estimation unit 112 may estimate that the bolt is loose based on the sound intensity corresponding to the frequency of the sound collected by the microphone unit 122 and a reference sound intensity corresponding to the frequency of the sound generated when a steel material with no loose bolt is vibrated. Specifically, the estimation unit 112 may compare the sound intensity corresponding to the frequency of the sound collected by the microphone unit 122 with a reference intensity corresponding to the same frequency, and estimate that the bolt is loose when the intensity of the sound collected by the microphone unit 122 is greater than the reference intensity.

More specifically, the estimation unit 112 acquires a sound (target sound) collected by the microphone unit 122 during a series of vibrations when, for example, the vibration execution unit 121 is controlled to vibrate a steel material (or a structure, etc.) that is to be estimated for loosening of a bolt while changing the vibration frequency by the vibration unit 111. Similarly, the estimation unit 112 acquires in advance a sound (reference sound) collected by the microphone unit 122 during a series of vibrations when, for example, the vibration execution unit 121 is controlled to vibrate a reference steel material (or a structure, etc.) that is not loose in the bolt while changing the vibration frequency by the vibration unit 111. The estimation unit 112 may compare the target sound with the reference sound based on, for example, the frequency (or frequency band) of a resonant sound that occurs when the bolt is loose, and estimate that the bolt is loose when the intensity of the target sound is greater than the intensity of the reference sound.

Also, different from the above, the estimation unit 112 may estimate that the bolt is loosened based on the trained model and the resonant sound collected by the microphone unit 122. The trained model may be a model that has learned the relationship between a sound (e.g., a resonant sound, etc.) generated when a steel material (base material) (or a structure, etc.) is vibrated when the bolt is loosened, and a sound generated when a steel material (base material) (or a structure, etc.) is vibrated when the bolt is not loosened. In this case, the trained model may be a model that has learned teacher data (correct answer labels) such as a sound generated when a steel material (or a structure, etc.) is vibrated while changing the vibration frequency (e.g., between 20 Hz and 20,000 Hz, etc.) and a resonant sound (a sound generated when a bolt is loosened).
The trained model may be generated, for example, by a learning process performed by a learning unit (not shown) arranged in the control unit 110. Alternatively, the trained model may be generated, for example, by a learning process performed by a learning device (not shown) external to the estimation device 100. The estimation unit 112 may acquire the trained model from, for example, the learning unit or the learning device.
The estimation unit 112 may, for example, input the sound collected by the microphone unit 122 to the above-described trained model and output an estimation result as to whether the sound contains a resonant sound. When estimating that a resonant sound is present, the estimation unit 112 may, for example, estimate that a bolt is loose.

For example, when multiple microphone units 122 are arranged, the estimation unit 112 may estimate that a loose bolt is located (or that there is an area where a loose bolt is located, etc.) near the microphone unit 122 that collected the strongest sound among the multiple microphone units 122. In this case, multiple microphone units 122 may be arranged at different positions around the steel material (or structural part, etc.) that has bolt fastening. As an example, when the structure is a long structure, etc., the microphone units 122 may be arranged at predetermined lengths. In addition, the estimation unit 112 may identify the microphone unit 122 with the strongest sound intensity based on correspondence information that associates the sound (sound information) collected by the microphone unit 122, identification information that can identify the microphone unit 122, and position information related to the position where the microphone unit 122 is arranged, and specify the position of the microphone unit 122.

Alternatively, for example, when the microphone unit 122 is a microphone group composed of the above-mentioned multiple microphone units 122, the estimation unit 112 may estimate the position (or area, etc.) where the resonance sound occurs based on the intensity of the resonance sound acquired by the multiple microphone units 122. That is, the estimation unit 112 may estimate, for example, a position (or direction, etc.) where the intensity (volume) of the resonance sound collected by each of the multiple microphone units 122 is relatively high, and estimate that the loose bolt is located near an intersection obtained by combining the positions (or directions, etc.) estimated by the multiple microphone units 122, that is, an area where positions where the intensity of the resonance sound is relatively high are gathered, or a position (or area, etc.) including an intersection where directions where the resonance sound is relatively high overlap.

Alternatively, for example, when the microphone unit 122 is the above-mentioned microphone array, the estimation unit 112 may identify the microphone that picks up the resonant sound with the highest intensity (volume) among the multiple directional microphones that make up the microphone array, and estimate that the loose bolt is located in the direction of the identified microphone (directional direction).

In addition, when vibrating steel material (or a structure, etc.) while changing the vibration frequency (e.g., 20 Hz to 20,000 Hz), the resonant sound of the bolt (the sound produced when the bolt is loose) does not occur at only one specific frequency, but often exists at multiple frequencies in the audible range (the range of frequencies to be changed). The estimation unit 112 can estimate that the bolt is loose by collecting at least one resonant sound from among the multiple resonant sounds produced when the frequency is changed using the microphone unit 122. In this case, the estimation unit 112 estimates that the bolt is loose if it can collect at least one resonant sound within the range of frequencies to be changed, thereby improving the accuracy of estimating the looseness of the bolt.

The output control unit 113 may, for example, control the output unit to output the result estimated by the estimation unit 112. An example of the result estimated by the estimation unit 112 may be at least one of a group of an estimation result that a bolt is loose and an estimation result of the position of the loose bolt. The output unit may be, for example, the communication unit 131, the storage unit 132, the display unit 133, etc.
As an example, the output control unit 113 may control the communication unit 131 to transmit information related to the estimation result of the estimation unit 112 to an outside (an external device (not shown)). The external device may be, for example, a server or a terminal outside the estimation device (information processing device) 100.
As another example, the output control unit 113 may control the storage unit 132 to store information related to the estimation result of the estimation unit 112 .
As another example, the output control unit 113 may control the display unit 133 to display the estimation result of the estimation unit 112 .

[Bolt looseness estimation method (information processing method)]
Next, a bolt loosening estimation method (information processing method) according to one embodiment will be described.
FIG. 5 is a flowchart for explaining a method for estimating bolt loosening according to one embodiment.

In step ST101, the vibration unit 111 vibrates the base material (or structure, etc.) while changing the vibration frequency. The base material may be, for example, a steel material with bolts. As an example, the vibration unit 111 may change the vibration frequency between 20 Hz and 20,000 Hz to vibrate the base material (or structure, etc.). In this case, the vibration unit 111 may control the vibration execution unit 121 to apply vibration to the base material (or structure, etc.).

In step ST102, the microphone unit 122 collects sound. In this case, if the bolt is loose, the microphone unit 122 collects the resonance sound that occurs when the bolt resonates in response to the vibration applied in step ST101.

In step ST103, the estimation unit 112 estimates that the bolt is loose, based on the sound (e.g., resonance sound) collected in step ST102.
In this case, the estimation unit 112 may identify the resonant sound based on the frequency of the sound collected in step ST102, and may estimate that the bolt is loose when the resonant sound is present.
Furthermore, the estimation unit 112 may estimate that the bolt is loose based on the sound intensity according to the frequency of the sound collected in step ST102 and a reference sound intensity according to the frequency of the sound generated when a steel material with no loose bolt is vibrated. Specifically, the estimation unit 112 may compare the sound intensity according to the frequency of the sound collected in step ST102 with a reference intensity according to a frequency that is the same as the frequency, and estimate that the bolt is loose when the intensity of the sound collected by the microphone unit 122 is greater than the reference intensity.
Alternatively, the estimation unit 112 may estimate that the bolt is loose, based on the trained model and the sound collected in step ST102. The trained model may be a model that has learned a sound (e.g., a resonance sound, etc.) that is generated when the base material (or the structure, etc.) is vibrated when the bolt is loose, and a sound that is generated when the base material (or the structure, etc.) is vibrated when the bolt is not loose.

As an example, the output control unit 113 may control the output unit to output the result estimated in step ST103. The output unit may be, for example, the communication unit 131, the memory unit 132, and the display unit 133.

Each unit of the above-described estimation device (information processing device) 100 may be realized as a function of a computer's arithmetic processing device, etc. That is, the vibration unit 111, the estimation unit 112, and the output control unit 113 (control unit 110) of the estimation device (information processing device) 100 may be realized as a vibration function, an estimation function, and an output control function (control function) by a computer's arithmetic processing device, etc.
The estimation program (information processing program) can cause a computer to realize each of the above-mentioned functions. The estimation program (information processing program) may be recorded in a non-transitory computer-readable recording medium, such as a memory, a solid-state drive, a hard disk drive, or an optical disk. The recording medium may be referred to as a non-transitory computer-readable medium, for example.
As described above, each unit of the estimation device (information processing device) 100 may be realized by a processing device of a computer or the like. The processing device or the like is configured by, for example, an integrated circuit or the like. Therefore, each unit of the estimation device (information processing device) 100 may be realized as a circuit constituting the processing device or the like. That is, the vibration unit 111, the estimation unit 112, and the output control unit 113 (control unit 110) of the estimation device (information processing device) 100 may be realized as a vibration circuit, an estimation circuit, and an output control circuit (control circuit) constituting the processing device of a computer or the like.
The vibration execution unit 121 and the microphone unit 122, as well as the communication unit 131, the storage unit 132, and the display unit 133 (output unit) of the estimation device (information processing device) 100 may be realized as, for example, a vibration execution function and a microphone function including the functions of an arithmetic processing device, as well as a communication function, a storage function, and a display function (output function). The vibration execution unit 121 and the microphone unit 122, as well as the communication unit 131, the storage unit 132, and the display unit 133 (output unit) of the estimation device (information processing device) 100 may be realized as a vibration execution circuit and a microphone circuit, as well as a communication circuit, a storage circuit, and a display circuit (output circuit) by being configured by, for example, an integrated circuit, etc. In addition, the vibration execution unit 121 and the microphone unit 122, as well as the communication unit 131, the memory unit 132 and the display unit 133 (output unit) of the estimation device (information processing device) 100 may be configured, for example, as a vibration execution unit 121 device and a microphone device, as well as a communication device, a memory device and a display device (output device) by being configured by a plurality of devices.

The estimation device 100 can combine one or any two or more of the above-mentioned multiple units.
In this disclosure, the term "information" is used, but the term "information" can be replaced with "data" and the term "data" can be replaced with "information."

[Modification]
Next, a modification of the above-described embodiment will be described.

(First Modification)
In the above embodiment, an example has been described in which a steel material having bolt fastening is vibrated to estimate the presence of loosening of the bolt. However, the present embodiment is not limited to this example, and the loosening of the bolt may be estimated when the bolt is fastened to various materials (for example, plastic materials, resin materials such as fluororesin, etc.). The material having bolt fastening may be referred to as the base material.
The bolt is not particularly limited as long as it is made of a material that can produce resonant sound, and may be made of various materials including steel, plastic, and resin materials.

(Second Modification)
In the above-described embodiment, the control unit 110 (estimation unit 112) of the estimation device 100 is configured to acquire the sound (resonant sound) collected by the microphone unit 122, but the present invention is not limited to this example.
That is, the control unit 110 of the estimation device 100 may include, for example, an acquisition unit that acquires sound (sound information). The acquisition unit may be configured as an acquisition function as one function of the arithmetic processing device, or may be configured as an acquisition circuit that constitutes the arithmetic processing device.

The acquisition unit may, for example, acquire sound information regarding sounds collected by the microphone unit 122.

The acquisition unit may also acquire sound information from an external device (e.g., a server, an airborne object, etc.) (not shown) outside the estimation device 100 via the communication unit, for example.
The server, for example, acquires and stores sound information related to sound collected by the microphone unit 122. In this case, the server may store identification information capable of identifying the position where the microphone unit 122 is disposed or the structure or the like when the microphone unit 122 collected the sound in association with the sound information when the sound was collected by the microphone unit 122.
The flying object may be, for example, a drone equipped with a microphone unit, and may fly around a structure equipped with a base material (e.g., steel material, etc.) to be inspected for loose bolts. For example, by mounting a microphone unit on a flying object and flying it around the base material (e.g., structure, etc.), it becomes possible to estimate whether a bolt is loose even if the bolt is located relatively far from the position of the vibration execution unit (vibration point). Note that, similar to the case where multiple microphone units 122 are arranged in the above-mentioned embodiment, multiple flying objects may be flown at different positions around the same base material (or structure, etc.).
The acquisition unit of the estimation device 100 may, for example, identify a structure to be inspected for loose bolts based on the identification information and acquire sound information corresponding to the structure from a server. The acquisition unit of the estimation device 100 may also acquire, for example, sound (sound information) transmitted from an air vehicle and collected by a microphone unit.

In addition, for example, when an external memory (not shown) in which sounds (sound information) collected by the microphone unit 122 are recorded is inserted into an interface (not shown) arranged in the estimation device 100, the acquisition unit may acquire the sound information from the external memory.

The estimation unit 112 of the estimation device 100 may identify a resonant sound based on the sound (sound information) acquired by the acquisition unit, and may estimate that the bolt is loose when the resonant sound is present.

(Third Modification)
In addition, the estimation unit 112 may compare multiple pieces of sound information obtained at different times (e.g., times t1, t2, ...) for the same base material (or structure, etc.) that can be identified by, for example, referring to identification information, and estimate that a bolt is loose based on the sound intensity corresponding to the frequency of the sound information (sound) at a relatively new time (e.g., t2, etc.) and the sound intensity corresponding to the frequency of the sound information (sound) at a relatively old time (e.g., t1, etc.).
That is, an inspection for loosening of bolts in a structure or the like may be performed, for example, at a predetermined timing. Also, loosening of a bolt may occur over time. Therefore, when inspecting for loosening of bolts in a structure or the like, the estimation unit 112 may compare, for example, the most recent sound in time (sound collected by the microphone unit 122) with a past sound in time (sound collected by the microphone unit 122), and estimate that the bolt is loose when the intensity of the most recent sound is greater than the intensity of the past sound at a corresponding frequency (frequency band) (for example, a frequency at which a resonant sound occurs).

[Aspects and Effects of the Present Embodiment]
Next, one aspect of this embodiment and the effects of each aspect will be described. Note that each aspect described below is an example at the time of filing, and this embodiment is not limited to the aspects described below. In other words, this embodiment is not limited to the aspects described below, and may be realized by appropriately combining each of the above-mentioned parts. In addition, a lower aspect may be able to cite any of the higher aspects.
In addition, the effects described below are merely examples, and the effects of each aspect are not limited to those described below. In addition, each aspect may, for example, exhibit at least one of the effects described below.

(Aspect 1)
One embodiment of a bolt looseness estimation device comprises a vibration unit that vibrates a steel material fastened with a bolt while changing the vibration frequency, a microphone unit that can collect resonance sounds produced when the bolt resonates in response to vibration by the vibration unit if the bolt is loose, and an estimation unit that estimates that the bolt is loose based on the resonance sounds collected by the microphone unit.
That is, the estimation device determines whether a bolt is loose by vibrating a base material such as steel and checking the resonance sound generated by a loose bolt located away from the vibration point.
This enables the estimation device to estimate that a bolt is loose.
Furthermore, even when estimating loosening of bolts in a structure that includes steel materials, it is possible to estimate the loosening of bolts from the surroundings of the structure (e.g., from the ground, etc.). That is, even if the structure is a steel tower, it is possible to estimate the loosening of bolts without a worker climbing the tower. Therefore, the estimation device can prevent accidents such as falls of workers performing estimation work, and ensure the safety of the workers.

(Aspect 2)
In one embodiment of the bolt loosening estimation device, the estimation unit may identify a resonant sound based on the frequency of the sound collected by the microphone unit, and estimate that the bolt is loose if the resonant sound is present.
The resonant sound that occurs when a bolt is loose is thought to occur at a specific frequency (or frequency band). The estimation device changes the frequency at which the steel material is vibrated, and if a sound occurs at the above-mentioned specific frequency (or frequency band), estimates that the sound is a resonant sound. Therefore, if the estimation device estimates that there is a resonant sound, it can estimate that there is a loose bolt.

(Aspect 3)
In one embodiment of a bolt looseness estimation device, the estimation unit may estimate that a bolt is loose based on the sound intensity corresponding to the frequency of the sound picked up by the microphone unit and a reference sound intensity corresponding to the frequency of the sound generated when vibrating steel material with no loose bolts.
In other words, when a resonant sound occurs due to a loose bolt, the estimation device determines whether the bolt is loose by comparing a bolt that is normally fastened in the base material with a bolt that has come loose and focusing on the difference in the intensity and frequency of the bolt sound.
As described above, it is believed that the resonant sound generated when the bolt is loosened has a specific frequency (or frequency band). Therefore, the estimation device compares the intensity of the sound collected by the microphone unit at that specific frequency with the intensity of a reference sound (reference intensity) based on a base material with no loose bolts, and determines whether the intensity of the sound collected by the microphone unit is greater than the reference intensity. If the intensity of the sound collected by the microphone unit is greater than the reference intensity, the estimation device can estimate that the bolt is loose.

(Aspect 4)
In one embodiment of a bolt loosening estimation device, the estimation unit compares the sound intensity corresponding to the frequency of the sound picked up by the microphone unit with a reference intensity corresponding to the same frequency, and estimates that the bolt is loose if the sound intensity picked up by the microphone unit is greater than the reference intensity.
The estimation device can estimate that the bolt is loose if the intensity of the sound picked up by the microphone unit is greater than a reference intensity based on the frequency (or frequency band) of the resonant sound that occurs when the bolt is loose.

(Aspect 5)
In one embodiment of a bolt looseness estimation device, the estimation unit may estimate that a bolt is loose based on a trained model that has learned the sound produced when steel is vibrated when the bolt is loose and the sound produced when steel is vibrated when the bolt is not loose, and the resonant sound collected by the microphone unit.
The estimation device inputs the sound collected by the microphone unit into the trained model and estimates the presence of a resonance sound. If it estimates that a resonance sound is present, the estimation device can estimate that a bolt is loose.

(Aspect 6)
In one aspect of the bolt loosening estimation device, the vibration unit may vary the vibration frequency between 20 Hz and 20,000 Hz to vibrate the steel material.
If a bolt is loose, it is believed that the bolt will resonate at a vibration frequency between 20 Hz and 20,000 Hz. Therefore, the estimation device can estimate that a bolt is loose.

(Aspect 7)
One embodiment of a bolt looseness estimation method includes a vibration step in which a vibration unit vibrates a steel material fastened with a bolt while changing the vibration frequency, a sound collection step in which a microphone unit collects a resonance sound produced when the bolt resonates in response to vibration by the vibration unit if the bolt is loose, and an estimation step in which an estimation unit estimates that the bolt is loose based on the resonance sound collected by the microphone unit.
As a result, the bolt loosening estimation method can achieve the same effects as the bolt loosening estimation device of the above-mentioned aspect.

(Aspect 8)
One embodiment of a bolt looseness estimation program provides a computer that receives sound collected by a microphone unit with a vibration function that vibrates steel material fastened with a bolt while changing the vibration frequency, and an estimation function that estimates that the bolt is loose based on the resonant sound produced when the bolt resonates in response to vibration caused by the vibration function when the resonant sound is collected by the microphone unit if the bolt is loose.
As a result, the bolt loosening estimation program can achieve the same effects as the bolt loosening estimation device of the above-mentioned aspect.

100 Bolt looseness estimation device (information processing device)
110 Control unit 111 Vibration unit 112 Estimation unit 113 Output control unit 121 Vibration execution unit 122 Microphone unit 131 Communication unit 132 Storage unit 133 Display unit 200 Steel material (base material)

Claims (8)

A vibration unit that vibrates the steel material having the bolt fastening while changing the vibration frequency;
a microphone unit including a plurality of directional microphones capable of collecting a resonance sound generated when the bolt resonates in response to the excitation by the excitation unit when the bolt is loose;
an estimation unit that identifies a microphone that has picked up a resonance sound with the highest sound intensity among the resonance sounds picked up by the microphone unit, and estimates that the bolt is loose in a direction having directivity of the identified microphone ;
A bolt loosening estimation device comprising: 2. The bolt loosening estimation device according to claim 1, wherein the estimation unit identifies a resonant sound based on a frequency of the sound collected by the microphone unit, and estimates that the bolt is loose when the resonant sound is present. 2. A bolt loosening estimation device as described in claim 1, wherein the estimation unit estimates that a bolt is loose based on a sound intensity corresponding to a frequency of the sound collected by the microphone unit and a reference sound intensity corresponding to a frequency of a sound generated when a steel material with no loose bolt is vibrated. The bolt loosening estimation device according to claim 3, wherein the estimation unit compares the sound intensity according to the frequency of the sound picked up by the microphone unit with a reference intensity according to the same frequency, and estimates that the bolt is loose if the sound intensity picked up by the microphone unit is greater than the reference intensity. The bolt loosening estimation device of claim 1, wherein the estimation unit estimates that a bolt is loose based on a trained model that has learned the sound generated when steel is vibrated when the bolt is loose and the sound generated when steel is vibrated when the bolt is not loose, and the resonant sound collected by the microphone unit. The bolt loosening estimation device according to any one of claims 1 to 5, wherein the vibration unit varies a vibration frequency between 20 Hz and 20,000 Hz to vibrate the steel material. A vibration step of vibrating the steel material having the bolt fastening while changing the vibration frequency by the vibration unit;
a sound collection step of collecting, by a microphone unit including a plurality of directional microphones , a resonance sound generated when the bolt resonates in response to the excitation by the excitation unit when the bolt is loose;
an estimation step of identifying a microphone that has collected a resonance sound having the highest sound intensity among the resonance sounds collected by the microphone unit, and estimating that a bolt is loose in a direction having directivity of the identified microphone ;
A method for estimating bolt looseness. A computer receives sound collected by a microphone unit including a plurality of directional microphones .
A vibration function for vibrating the bolted steel material while changing the vibration frequency;
an estimation function for identifying a microphone that has collected the strongest resonance sound among the resonance sounds collected by the microphone unit when the bolt resonates in response to the excitation by the excitation function in the case where the bolt is loose, and for estimating that the bolt is loose in the direction of the directivity of the identified microphone ;
A bolt loosening estimation program that makes this possible.

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