Bold looseness index calculation device, bolt looseness index calculation method, and bolt looseness index calculation program

Abstract

To provide a bolt looseness index and the like that can remotely determine the looseness of individual bolts without requiring prior operations such as processing on bolts.SOLUTION: A bolt looseness index calculation device performs image processing on moving images obtained by photographing a bolt to be screwed into a screwing object to calculate a bolt looseness index indicating the looseness of the bolt, and the device comprises: a first displacement calculation unit that, on the basis of the moving images, calculates first displacement that is the displacement of the bolt in a measurement direction intersecting the direction in which the bolt is screwed; a second displacement calculation unit that, on the basis of the moving images, calculates second displacement that is the displacement of the rotation angle of the bolt; and an index calculation unit that, on the basis of the set of the first displacement calculated by the first displacement calculation unit and the second displacement calculated by the second displacement calculation unit, calculates the bolt looseness index that is at least one of the correlation coefficient and the regression coefficient between the first displacement and the second displacement.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bolt loosening index calculation device, a bolt loosening index calculation method, and a bolt loosening index calculation program. [Background technology]

[0002] Known methods for detecting loose bolts by remotely photographing them with a camera include a method in which a marker line is drawn with the bolt fastened and then image analysis is used to determine whether the marker line is misaligned (see, for example, Non-Patent Document 1 below).

[0003] Also, a method has been proposed in which the displacement and natural vibration of the entire structure are measured using video images captured by a camera, and loose bolts are detected based on changes in the natural frequency (see, for example, Non-Patent Document 2 below). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Tomotaka Fukuoka, Takahiro Minami, Wataru Urata, and Shin Fujio, "Development of an automated system for checking bolt tightening using image processing," Proceedings of the AI ​​and Data Science Conference, 2020, 1-J1, pp.295-300. [Non-Patent Document 2] Tokuo Tsuji, Tomoyuki Yamazaki, Shuji Nakamura, Yukiya Kurihara, Hidetoshi Seki, "A study on the deterioration diagnosis of aged transmission towers using a high-resolution camera", Journal of Structural Engineering, 2017, Vol.63A, pp.570-580 [Non-Patent Document 3] Masao Shimizu, Takahiro Yano, Masatoshi Okutomi, "High-precision simultaneous estimation method of N parameters representing image deformation and its application to super-resolution", Journal of Information Processing Society of Japan, 2004, 45, SIG13 (CVIM10), pp.83-98 [Non-Patent Document 4] Kobayashi, T., Nakajima, H., Aoki, T., Kawamata, M., and Higuchi, T., "Principles and Applications of Phase-Limiting Correlation Method," Institute of Television Engineers Technical Report, 1996, 20, 41, pp.1-6 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, the method described in Non-Patent Document 1 requires manual advance work to draw marker lines on the bolts. Therefore, it is difficult to apply this method to bolts in locations where access is difficult due to high altitudes, high temperatures, high voltages, etc.

[0006] For example, in the method of Non-Patent Document 2, even if it is possible to estimate the results suggesting a change in the rigidity of the structure, it is difficult to determine which bolts are loose individually. Therefore, a separate confirmation task such as climbing the tower is required.

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide a bolt loosening index calculation device, a bolt loosening index calculation method, and a bolt loosening index calculation program that are capable of remotely determining the loosening of individual bolts without requiring any prior work such as processing the bolts. [Means for solving the problem]

[0008] In order to solve the above problems, a bolt looseness index calculation device according to a first aspect of the present invention is a bolt looseness index calculation device that performs image processing on a moving image obtained by photographing a bolt screwed into a screwing target, and calculates a bolt looseness index indicative of looseness of the bolt, and includes a first displacement calculation unit that calculates a first displacement, which is a displacement of the bolt in a measurement direction intersecting the direction in which the bolt is screwed, based on the moving image, a second displacement calculation unit that calculates a second displacement, which is a displacement of a rotation angle of the bolt, based on the moving image, and an index calculation unit that calculates the bolt looseness index, which is at least one of a correlation coefficient and a regression coefficient between the first displacement and the second displacement, based on a set of the first displacement calculated by the first displacement calculation unit and the second displacement calculated by the second displacement calculation unit.

[0009] In a second aspect of the present invention, in the bolt loosening index calculation device of the first aspect, the measurement direction is parallel to a vibration direction in which the screwed object vibrates.

[0010] Furthermore, in aspect 3 of the present invention, in the bolt loosening index calculation device of aspect 1 or aspect 2, the first displacement calculation unit calculates the first displacement at the time of interest based on a frame at the time of interest included in the moving image and a frame immediately preceding the frame at the time of interest.

[0011] Furthermore, in a fourth aspect of the present invention, in the bolt loosening index calculation device of any one of the first to third aspects, the second displacement calculation unit calculates the second displacement at the time of interest based on a frame at the time of interest included in the moving image and a frame immediately preceding the frame at the time of interest.

[0012] In order to solve the above problems, a bolt looseness index calculation method according to aspect 5 of the present invention is a bolt looseness index calculation method that performs image processing on a moving image obtained by photographing a bolt screwed into a screwing target to calculate a bolt looseness index indicating looseness of the bolt, wherein a first displacement, which is the displacement of the bolt in a measurement direction intersecting the direction in which the bolt is screwed, is calculated based on the moving image, a second displacement, which is the displacement of the rotation angle of the bolt, is calculated based on the moving image, and the bolt looseness index, which is at least one of a correlation coefficient and a regression coefficient between the first displacement and the second displacement, is calculated based on a set of the calculated first displacement and second displacement.

[0013] In order to solve the above problem, a bolt loosening index calculation program according to a sixth aspect of the present invention causes a computer to calculate a first displacement, which is the displacement of the bolt in a measurement direction intersecting the direction in which the bolt is screwed, based on a moving image obtained by photographing a bolt screwed into a screwing target, calculate a second displacement, which is the displacement of the rotation angle of the bolt, based on the moving image, and calculate a bolt loosening index, which is at least one of a correlation coefficient and a regression coefficient between the first displacement and the second displacement, based on a set of the calculated first displacement and second displacement. Effect of the Invention

[0014] According to the above aspects of the present invention, it is possible to provide a bolt loosening index calculation device, a bolt loosening index calculation method, and a bolt loosening index calculation program that are capable of remotely determining the loosening of individual bolts without requiring any prior work such as processing the bolts. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram showing a system configuration of a bolt loosening index calculation device according to an embodiment of the present invention. FIG. [Diagram 2] FIG. 2 is a diagram showing an example of a frame included in a moving image used in an embodiment of the present invention. [Diagram 3] 10A is a graph showing an example of a vibration direction displacement of a bolt, and FIG. 10B is a graph showing an example of a rotation angle displacement of a bolt. [Figure 4] 13 is a graph showing an example of the relationship between the absolute value of the vibration direction displacement and the absolute value of the rotational angle displacement for each of the cases where (a) the slack added to the bolt is 0°, (b) the slack added to the bolt is 180°, and (c) the slack added to the bolt is 360°. [Diagram 5] 11 is a graph showing an example of changes in correlation coefficient and regression coefficient between the absolute value of vibration direction displacement and the absolute value of rotation angle displacement when the slack applied to a bolt is changed. [Figure 6] 4 is a flowchart showing an example of a bolt loosening index calculation method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A bolt loosening index calculation device, a bolt loosening index calculation method, and a bolt loosening index calculation program according to embodiments of the present invention will be described in detail below with reference to the drawings.

[0017] <Bolt looseness index calculation device> 1 is a block diagram showing a system configuration of a bolt loosening index calculation device 1 according to this embodiment. As shown in Fig. 1, the bolt loosening index calculation device 1 according to this embodiment includes an image input unit 10, a processing unit 20, a storage unit 30, and an index output unit 40.

[0018] The bolt loosening index calculation device 1 performs image processing on a moving image obtained by photographing a bolt screwed (fastened) into a screwing target (fastening target) and calculates (measures) a bolt loosening index that indicates the looseness of the bolt. Examples of screwing targets include structures (e.g., steel towers) that are difficult to approach due to high altitudes, high temperatures, high voltages, etc. However, screwing targets are not limited to these structures and can be changed as appropriate.

[0019] The image input unit 10 inputs a moving image I obtained by photographing the screwing target 200. The image input unit 10 may include a connection interface to which a photographing device such as a camera is connected. The moving image I input to the image input unit 10 is, for example, a moving image having a pixel count of about 1 million pixels (1000×1000 pixels) and a frame rate of about 100 fps (Frames Per Second). Note that the pixel count and frame rate of the moving image I are not limited to the above example and can be changed as appropriate.

[0020] 2 is a diagram showing an example of frames included in the moving image I. Each frame included in the moving image I includes, for example, the head of the bolt 100 and at least a portion of the screwing target 200 (a portion located around the bolt 100). The left-right direction X in the moving image I coincides with, for example, the horizontal direction, and the up-down direction Y in the moving image I coincides with, for example, the vertical direction. However, the left-right direction X may be inclined relative to the horizontal direction, and the up-down direction Y may be inclined relative to the vertical direction.

[0021] 1, the processing unit 20 according to this embodiment includes a bolt area setting unit 21, a memory control unit 22, a first displacement calculation unit (first displacement measurement unit) 23, a second displacement calculation unit (second displacement measurement unit) 24, and an index calculation unit (index measurement unit) 25. The processing unit 20 performs image processing on the moving image I input to the image input unit 10 to calculate the above-mentioned bolt loosening index, and outputs the calculated bolt loosening index to the index output unit 40.

[0022] The bolt area setting unit 21 sets the bolt area A and stores it in the bolt area storage unit 32 (details of which will be described later) of the storage unit 30. The bolt area A is an area in the moving image I in which the bolt 100 exists (see FIG. 2). The bolt area setting unit 21 may set the bolt area A based on a user's instruction inputted from an input device (not shown), for example. Alternatively, the bolt area setting unit 21 may set the bolt area A automatically or semi-automatically by using a predetermined image recognition process (see, for example, Non-Patent Document 1).

[0023] The storage control unit 22 sequentially stores the moving image I input to the image input unit 10 in the storage unit 30. Specifically, the storage control unit 22 stores the latest frame included in the moving image I input to the image input unit 10 in a latest frame storage unit 34 (described in detail below) of the storage unit 30, and stores the frame immediately before the latest frame in a previous frame storage unit 33 (described in detail below) of the storage unit 30.

[0024] The first displacement calculation unit 23 calculates (measures) a first displacement (first speed) of the bolt 100 based on the moving image I input to the image input unit 10. The first displacement is a displacement (speed) of the bolt 100 in a measurement direction M (see also FIG. 2). Here, the measurement direction M is a direction intersecting the direction in which the bolt 100 is screwed (a direction parallel to the central axis O of the bolt 100). The first displacement is also referred to as a measurement direction displacement (measurement direction speed). The first displacement calculation unit 23 stores the calculated first displacement in a displacement memory unit 35 of the memory unit 30 (details of which will be described later).

[0025] The above-mentioned measurement direction M may be parallel to, for example, the vibration direction V in which the screwing target 200 vibrates. In the following, unless otherwise specified, a case will be described in which the vibration direction V coincides with the left-right direction X and the measurement direction M is parallel to the vibration direction V (left-right direction X). However, the measurement direction M may be inclined with respect to the vibration direction V (left-right direction X), and the vibration direction V may be inclined with respect to the left-right direction X. The vibration of the screwing target 200 may be vibration intentionally caused by vibration (e.g., impact vibration) by an operator, or may be vibration caused by an environmental factor such as wind. Alternatively, the vibration of the screwing target 200 may be vibration intrinsically caused by a vibration mechanism or the like provided in the screwing target 200.

[0026] The first displacement calculation unit 23 calculates the latest first displacement based on, for example, the latest frame stored in the latest frame storage unit 34, the immediately preceding frame stored in the immediately preceding frame storage unit 33, and the vibration direction V (i.e., the measurement direction M) stored in the vibration direction storage unit 31 (details of which will be described later). The first displacement calculation unit 23 may calculate the latest first displacement based on other frames in addition to (or instead of) the latest frame and the immediately preceding frame. However, the configuration in which the first displacement is calculated using the latest frame and the immediately preceding frame is preferable in that it can improve the calculation accuracy of the first displacement, particularly when the vibration frequency of the screwing target 200 is high (for example, about several tens of Hz).

[0027] In addition, the first displacement calculation unit 23 may calculate the displacement of the bolt 100 in the left-right direction X and the displacement of the bolt 100 in the up-down direction Y, and then calculate the first displacement by projecting the calculated displacements in the left-right direction X and the up-down direction Y onto the vibration direction V.

[0028] In addition, the unit of the first displacement calculated by the first displacement calculation unit 23 can be changed as appropriate. For example, the unit of the first displacement may be pixels. Alternatively, the unit of the first displacement may be a physical unit such as mm / sec. In this case, the first displacement calculation unit 23 may convert pixels into a physical unit based on information for unit conversion, and calculate the first displacement based on the physical unit. Examples of information for unit conversion include, but are not limited to, the focal length of the camera, the distance from the shooting point to the bolt 100, and the size of the pixel. The information for unit conversion may be input to the bolt loosening index calculation device 1 based on, for example, a user's instruction input from an input device (not shown). The configuration using the first displacement converted into a physical unit is preferable in that it can normalize the bolt loosening index described later.

[0029] The second displacement calculation unit 24 calculates (measures) a second displacement (second velocity) of the bolt 100 based on the moving image I input to the image input unit 10. The second displacement is a displacement (angular velocity) of the rotation angle θ of the bolt 100. The second displacement is also called a rotational angle displacement (rotational angular velocity). The second displacement calculation unit 24 stores the calculated second displacement in a displacement memory unit 35 (details of which will be described later) of the memory unit 30.

[0030] The second displacement calculation unit 24 calculates the latest second displacement based on, for example, the latest frame stored in the latest frame storage unit 34, the immediately preceding frame stored in the immediately preceding frame storage unit 33, and the vibration direction V (i.e., the measurement direction M) stored in the vibration direction storage unit 31 (details of which will be described later). The second displacement calculation unit 24 may calculate the latest second displacement based on other frames in addition to (or instead of) the latest frame and the immediately preceding frame. However, the configuration in which the second displacement is calculated using the latest frame and the immediately preceding frame is preferable in that it can improve the calculation accuracy of the second displacement, particularly when the vibration frequency of the screwing target 200 is high (for example, about several tens of Hz).

[0031] By the above-mentioned processing by the displacement calculation units 23, 24, a plurality of pairs of a first displacement and a second displacement (hereinafter referred to as displacement sets) are stored in the displacement storage unit 35. In each displacement set, the first displacement and the second displacement are at the same time. In particular, when the displacement calculation units 23, 24 calculate a displacement set using the latest frame and the immediately preceding frame as described above, each of the displacement sets stored in the displacement storage unit 35 is calculated based on the frame at the time of the displacement set (a time of interest) and the frame immediately preceding the time of interest.

[0032] Specifically, the above-mentioned displacement calculation units 23 and 24 may calculate the first displacement and the second displacement by performing processing using, for example, a digital image correlation method (see, for example, Non-Patent Document 3) or a phase-only correlation method (see, for example, Non-Patent Document 4). These processes can precisely search for areas having the same pattern in multiple images and measure the positional relationship between those areas (horizontal, vertical, depth displacement, rotation angle, etc.). However, as long as the first displacement and the second displacement can be measured by image processing, the specific processing performed by the displacement calculation units 23 and 24 is not particularly limited and can be changed as appropriate.

[0033] The index calculation unit 25 calculates (measures) a bolt looseness index indicating the looseness of the bolt 100, based on a pair of the first displacement calculated by the first displacement calculation unit 23 and the second displacement calculated by the second displacement calculation unit 24. The index calculation unit 25 outputs the calculated bolt looseness index to the index output unit 40.

[0034] Here, the bolt loosening index is at least one of a correlation coefficient and a regression coefficient between the first displacement and the second displacement. Hereinafter, it will be described with reference to Figs. 3 to 5 that the correlation coefficient and the regression coefficient between the first displacement and the second displacement can be suitably used as a bolt loosening index that indicates the looseness of the bolt 100.

[0035] Fig. 3(a) is a graph showing an example of displacement in the vibration direction V of the bolt 100. Fig. 3(b) is a graph showing an example of displacement in the rotation angle θ of the bolt 100. More specifically, the graphs shown in Figs. 3(a) and (b) show the vibration direction displacement and the rotation angle displacement when the worker applies impact vibration to the screw-fastened object 200 four times. The parts shown by the dashed lines in Figs. 3(a) and (b) correspond to the four impact vibrations.

[0036] FIG. 4 is a graph showing an example of the relationship between the absolute value of the vibration direction displacement and the absolute value of the rotational angle displacement when loosening is applied to the bolt 100 screwed into the screwing object 200 (i.e., when the bolt 100 is loosened by a predetermined angle). Each plot shown in FIG. 4 shows a pair of the absolute value of the vibration direction displacement and the absolute value of the rotational angle displacement at the same time. FIG. 4(a) shows a case where the loosening applied to the bolt 100 is 0°, FIG. 4(b) shows a case where the loosening applied to the bolt 100 is 180°, and FIG. 4(c) shows a case where the loosening applied to the bolt 100 is 360°. The straight lines shown in each of FIGS. 4(a) to 4(c) are regression lines between the absolute value of the vibration direction displacement and the absolute value of the rotational angle displacement.

[0037] Fig. 5 is a graph showing an example of changes in correlation coefficient and regression coefficient between the absolute value of vibration direction displacement and the absolute value of rotation angle displacement when changing the slack added to bolt 100. The dashed line L shown in Fig. 5 indicates the amount of slack when bolt 100 is manually tightened.

[0038] As shown in Fig. 3, the vibration direction displacement and the rotational angular displacement of the bolt 100 occur in time synchronization with impact vibration of the screwed object 200. As shown in Figs. 4 and 5, the greater the looseness of the bolt 100, the greater the correlation coefficient between the absolute value of the vibration direction displacement and the absolute value of the rotational angular displacement at the same time. Similarly, the greater the looseness of the bolt 100, the greater the regression coefficient (slope of the regression line) between the absolute value of the vibration direction displacement and the absolute value of the rotational angular displacement at the same time. Therefore, both of these correlation coefficients and regression coefficients can be suitably used as bolt looseness indexes that indicate the looseness of the bolt 100.

[0039] The index calculation unit 25 may, for example, extract a plurality of displacement sets stored in the displacement storage unit 35 over a time period before and after vibration of the screwing target 200 (hereinafter, extraction target period), and calculate the above-mentioned bolt loosening index based on the displacement sets included in the extracted displacement sets. Here, the extraction target period may be set based on a user's instruction inputted from an input device (not shown), for example. Alternatively, the index calculation unit 25 or the like may be configured to detect a steep change in the first displacement or the second displacement, and the period before and after the change may be automatically set as the extraction target period. However, the method of setting the extraction target period is not limited to the above example, and may be changed as appropriate. The index calculation unit 25 may also calculate the bolt loosening index based on all of the obtained displacement sets.

[0040] The storage unit 30 includes a vibration direction storage unit 31, a bolt area storage unit 32, a previous frame storage unit 33, a latest frame storage unit 34, and a displacement storage unit 35. The storage unit 30 stores the moving image I input to the image input unit 10 and various information (data) processed by the processing unit 20. The storage unit 30 is realized by, for example, a volatile or non-volatile memory, a HDD (Hard Disk Drive), an SSD (Solid State Drive), or the like.

[0041] The vibration direction storage unit 31 stores the vibration direction V of the screwing target 200. The vibration direction V may be set based on a user's instruction inputted from an input device (not shown), for example. Alternatively, the vibration direction V may be calculated by performing a principal component analysis or the like on the displacement of the bolt 100 in a plane intersecting the central axis O of the bolt 100.

[0042] The bolt region storage unit 32 stores the bolt region A set by the bolt region setting unit 21. The previous frame storage unit 33 stores the latest frame included in the moving image I input to the image input unit 10. The latest frame storage unit 34 stores the frame immediately before the latest frame. The displacement storage unit 35 stores the first displacement and the second displacement calculated by the displacement calculation units 23 and 24.

[0043] The index output unit 40 outputs the bolt loosening index calculated by the index calculation unit 25 of the processing unit 20. The index output unit 40 may output the bolt loosening index to the outside, or may output the bolt loosening index to the outside by displaying it. In other words, the index output unit 40 may include, for example, an output interface such as a USB (Universal Serial Bus) port, or a display device such as a liquid crystal display device.

[0044] The bolt loosening index calculation device 1 can be realized by a computer such as a personal computer or a workstation. When the bolt loosening index calculation device 1 is realized by a computer, the functions of each unit of the bolt loosening index calculation device 1 are realized by a program for realizing those functions being executed by a CPU (Central Processing Unit) provided in the computer. In other words, the functions of each unit of the bolt loosening index calculation device 1 are realized by the cooperation of software and hardware resources. The bolt loosening index calculation device 1 may be realized by using hardware such as a Field-Programmable Gate Array (FPGA), a Large Scale Integration (LSI), or an Application Specific Integrated Circuit (ASIC).

[0045] <Bolt looseness index calculation method> Fig. 6 is a flowchart showing an example of a bolt loosening index calculation method according to this embodiment. The process of the flowchart shown in Fig. 6 is started, for example, when a user instructs the bolt loosening index calculation device 1 to start index calculation. It is assumed that a moving image I captured by an imaging device such as a camera has been input to the image input unit 10 of the bolt loosening index calculation device 1. In addition, for the sake of simplicity of explanation, it is assumed that the vibration direction V of the screwed object 200 has been stored in advance in the vibration direction storage unit 31.

[0046] (Step S11) When the processing of the flowchart shown in Fig. 6 starts, the processing of step S11 is performed first. In the processing of step S11, the storage control unit 22 stores the latest frame included in the moving image I input to the image input unit 10 in the latest frame storage unit 34, and stores the frame immediately before the latest frame in the previous frame storage unit 33. After the processing of step S11 is performed, the processing of step S12 is performed.

[0047] (Step S12) In the process of step S12, the first displacement calculation unit 23 calculates a first displacement based on the latest frame stored in the latest frame storage unit 34, the immediately preceding frame stored in the immediately preceding frame storage unit 33, and the vibration direction V (i.e., the measurement direction M) stored in the vibration direction storage unit 31. In addition, the second displacement calculation unit 24 calculates a second displacement based on the latest frame stored in the latest frame storage unit 34 and the immediately preceding frame stored in the immediately preceding frame storage unit 33. After the process of step S12 is performed, the process of step S13 is performed.

[0048] (Step S13) In the process of step S13, the first displacement calculation unit 23 stores the first displacement calculated in the process of step S12 in the displacement storage unit 35. In addition, the second displacement calculation unit 24 stores the second displacement calculated in the process of step S12 in the displacement storage unit 35. Through this process, the displacement storage unit 35 stores a pair of the first displacement and the second displacement at the same time (i.e., a displacement pair).

[0049] (Step S14) In the process of step S14, the processing unit 20 judges whether or not the repetition of the processes of steps S11 to S13 described above is to be ended. For example, it is judged whether or not the user has instructed the bolt loosening index calculation device 1 to end the repetition. Alternatively, it may be judged whether or not the number of times the processes of steps S11 to S13 have been repeated exceeds a predetermined number. If the processing unit 20 judges that the repetition has not ended (if the judgment result of step S14 is "NO"), the process returns to the process of step S11, and the processes of steps S11 to S13 are performed again. On the other hand, if the processing unit 20 judges that the repetition has ended (if the judgment result of step S14 is "YES"), the process of step S15 is performed.

[0050] (Step S15) In the process of step S15, index calculation unit 25 calculates a bolt loosening index indicating looseness of bolt 100 based on the displacement set stored in displacement memory unit 35. As described above, the bolt loosening index is at least one of the correlation coefficient and the regression coefficient between the first displacement and the second displacement. Thereafter, index calculation unit 25 outputs the calculated bolt loosening index to index output unit 40, and the series of processes shown in FIG. 6 ends.

[0051] <Summary> As described above, the bolt loosening index calculation device 1 according to this embodiment is a bolt loosening index calculation device that performs image processing on a moving image I obtained by photographing the bolt 100 screwed into the screwing target 200 to calculate a bolt loosening index indicating the loosening of the bolt 100, and includes a first displacement calculation unit 23 that calculates a first displacement that is a displacement of the bolt 100 in a measurement direction M intersecting the direction in which the bolt 100 is screwed based on the moving image I, a second displacement calculation unit 24 that calculates a second displacement that is a displacement of the rotation angle of the bolt 100 based on the moving image I, and an index calculation unit 25 that calculates a bolt loosening index that is at least one of a correlation coefficient and a regression coefficient between the first displacement and the second displacement based on a pair of the first displacement calculated by the first displacement calculation unit 23 and the second displacement calculated by the second displacement calculation unit 24. Also, the bolt loosening index calculation method according to this embodiment calculates the first displacement based on the moving image I, calculates the second displacement based on the moving image I, and calculates the above-mentioned bolt loosening index based on the pair of the calculated first displacement and second displacement.

[0052] According to this configuration, the looseness of the bolt 100 can be determined by image processing without performing a preliminary operation such as drawing a marker line on the bolt 100. Furthermore, since the bolt looseness index is calculated based on the displacement of the bolt 100, for example, a plurality of bolt areas A are set corresponding to each of the plurality of bolts 100, and the bolt looseness index is calculated independently for each bolt 100 by the above-mentioned processing, thereby making it possible to remotely determine the looseness of each bolt 100. Therefore, the bolt looseness index calculation device 1 according to this embodiment can efficiently inspect the looseness of bolts 100 located at high places or in dangerous places.

[0053] Furthermore, the measurement direction M may be parallel to the vibration direction V in which the screwing target 200 vibrates. This configuration can improve the calculation accuracy of the first displacement, and can improve the calculation accuracy of the bolt loosening index.

[0054] Furthermore, the first displacement calculation unit 23 may calculate the first displacement at the time of interest based on the frame at the time of interest included in the moving image I and the frame immediately before the frame at the time of interest. With this configuration, it is possible to improve the calculation accuracy of the first displacement, particularly when the vibration frequency of the screwing target 200 is high (for example, about several tens of Hz). This makes it possible to improve the calculation accuracy of the bolt loosening index.

[0055] The second displacement calculation unit 24 may also calculate the second displacement at the time of interest based on the frame at the time of interest included in the moving image I and the frame immediately preceding the frame at the time of interest. This configuration can improve the calculation accuracy of the second displacement, particularly when the vibration frequency of the screwing target 200 is high (for example, about several tens of Hz). This can improve the calculation accuracy of the bolt loosening index.

[0056] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0057] For example, in the above embodiment, the latest first and second displacements are calculated every time the latest frame of the video I is updated, but the method of calculating the first and second displacements is not limited to this. For example, after the video I is stored in the storage unit 30, the first and second displacements at an arbitrary time may be calculated based on a frame at an arbitrary time (a time of interest) included in the video I and a frame immediately before the frame at the arbitrary time, etc.

[0058] Moreover, the bolt loosening index calculation device 1 may further include a warning unit that issues a warning when the bolt loosening index exceeds a predetermined value.

[0059] In addition, within the scope of the spirit of the present invention, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, and the above-described embodiments and variations may be combined as appropriate. [Explanation of symbols]

[0060] 1...Bolt loosening index calculation device 23...First displacement calculation unit 24...Second displacement calculation unit 25...Index calculation unit 100...Bolt 200...Threaded object

Claims

1. A bolt loosening index calculation device that performs image processing on a moving image obtained by photographing a bolt screwed into a screwing target, and calculates a bolt loosening index indicating looseness of the bolt, a first displacement calculation unit that calculates a first displacement, which is a displacement of the bolt in a measurement direction that intersects with a direction in which the bolt is screwed, based on the moving image; a second displacement calculation unit that calculates a second displacement, which is a displacement of a rotation angle of the bolt, based on the moving image; an index calculation unit that calculates the bolt loosening index, which is at least one of a correlation coefficient and a regression coefficient between the first displacement and the second displacement, based on a pair of the first displacement calculated by the first displacement calculation unit and the second displacement calculated by the second displacement calculation unit; A bolt loosening index calculation device comprising:

2. The measurement direction is parallel to a vibration direction in which the screw-fitting object vibrates. The bolt loosening index calculation device according to claim 1 .

3. 3. The bolt loosening index calculation device according to claim 1, wherein the first displacement calculation unit calculates the first displacement at the time of interest based on a frame at the time of interest included in the moving image and a frame immediately before the frame at the time of interest.

4. 3. The bolt loosening index calculation device according to claim 1, wherein the second displacement calculation unit calculates the second displacement at the time of interest based on a frame at the time of interest included in the moving image and a frame immediately before the frame at the time of interest.

5. A bolt loosening index calculation method for calculating a bolt loosening index indicating a looseness of the bolt by performing image processing on a moving image obtained by photographing a bolt screwed into a screwing target, Calculating a first displacement, which is a displacement of the bolt in a measurement direction intersecting a direction in which the bolt is screwed, based on the moving image; Calculating a second displacement, which is a displacement of a rotation angle of the bolt, based on the moving image; calculating the bolt loosening index, which is at least one of a correlation coefficient and a regression coefficient between the first displacement and the second displacement, based on a pair of the calculated first displacement and the second displacement; How to calculate the bolt loosening index.

6. On the computer, Calculating a first displacement, which is a displacement of the bolt in a measurement direction intersecting a direction in which the bolt is screwed, based on a moving image obtained by photographing the bolt screwed into the object to be screwed; Calculating a second displacement, which is a displacement of a rotation angle of the bolt, based on the moving image; calculating a bolt loosening index, which is at least one of a correlation coefficient and a regression coefficient between the first displacement and the second displacement, based on a pair of the calculated first displacement and the second displacement; A bolt loosening index calculation program for carrying out this task.

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