Overhead contact wire inspection method and inspection system

Abstract

To provide a method and a system for inspection an overhead line by continuously taking images of the side part of an overhead line from above a railway vehicle running fast and analyzing the images.SOLUTION: In the method and the system for inspecting an overhead line, an imaging device including a lens and an imaging element is arranged in the ceiling part of a railway vehicle so that the imaging device looks up at a predetermined angle of elevation by directing an optical axis from the side lower part of the overhead line to the side part, and the overhead line is imaged. The lens surface of the lens to an imaging surface of the imaging element is inclined from a parallel position so that a focus surface formed near the overhead line for the angle of elevation is obliquely moved in a vertical direction and the overhead line is imaged.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method and an inspection system for capturing images of overhead contact wires from a traveling railway vehicle and performing inspection through image analysis. [Background technology]

[0002] Overhead train lines in railways are long structures that run along the rails (tracks), and there is a demand for automating inspections of these lines from on a traveling train to improve inspection efficiency. Up until now, a method has been proposed in which an imaging device (camera) is mounted on the roof of a railway car, and the car travels while capturing images of the contact wires that supply power to the car and inspects them.

[0003] For example, Patent Document 1 discloses a method (light section method) for measuring the cross-sectional shape of a trolley wire by irradiating the trolley wire with slit-shaped light from above the vehicle and capturing the resulting contour line with a camera. This method describes the use of multiple light sources so that a sufficient amount of light for capturing an image is always available even if the position of the trolley wire changes.

[0004] In addition, a method has been proposed for inspecting overhead electric wires, including not only contact wires but also suspension wires and auxiliary suspension wires, by photographing them from a traveling train.

[0005] Patent Document 2 discloses a system that uses two line cameras mounted on an inspection vehicle to perform non-contact 3D position measurement of overhead train lines including contact wires. First, it states that even if an overhead train line including suspension wires and auxiliary suspension wires other than contact wires is imaged with two line cameras, it is difficult to separate the overhead wire from the background or to identify the type of overhead wire from the obtained image alone. Then, it scans the space including the overhead wire with a laser range sensor that projects a laser beam at a projection angle in a plane approximately perpendicular to the traveling direction of the railway vehicle, measures the position of the overhead wire, and then cuts out the image of the line camera based on this measured position. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2021-179369 A [Patent Document 2] JP 2014-169939 A Summary of the Invention [Problem to be solved by the invention]

[0007] There is a demand for a system that can capture and measure overhead electric wires, including suspension wires and auxiliary suspension wires other than contact wires, from on board a vehicle traveling at high speed, particularly a high-speed vehicle such as a Shinkansen. However, because the "lines" that make up the overhead electric wire, such as contact wires and suspension wires, and the imaging device are located at different positions, it is not easy to obtain images that can be used for inspection, as described in Patent Document 1, for example. In addition, the system disclosed in Patent Document 2 uses a laser range sensor to scan the space including the overhead wires, and this scanning takes a certain amount of time, making it unsuitable for capturing images from on board a vehicle traveling at high speed.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide an inspection method and inspection system that continuously captures images of the side of an overhead contact wire from on board a railway vehicle traveling at high speed, such as a Shinkansen, and performs inspection by image analysis. [Means for solving the problem]

[0009] An inspection method according to the present invention is an overhead contact line inspection method in which images of the side of the overhead contact line are continuously captured from above a traveling railway vehicle and inspection is performed through image analysis, characterized in that an imaging device including a lens and an imaging element is placed on the roof of the railway vehicle so as to point its optical axis from a lower side of the overhead contact line to the side and look up at a predetermined elevation angle, and by tilting the lens surface of the lens from a parallel position with respect to the imaging plane of the imaging element, a focal plane formed in the vicinity of the overhead contact line corresponding to the elevation angle is tilted and moved in the vertical plane direction to image the overhead contact line.

[0010] Furthermore, a system according to the present invention is an overhead contact line inspection system in which an imaging device continuously images the side of the overhead contact line from above a traveling railway vehicle and performs inspection through image analysis, wherein the imaging device includes a lens and an imaging element, and is disposed on the roof of the railway vehicle so as to point its optical axis from a lower side of the overhead contact line to the side and look up at a predetermined elevation angle, and by tilting the lens surface of the lens from a parallel position with respect to the imaging surface of the imaging element, a focal plane formed in the vicinity of the overhead contact line corresponding to the elevation angle is tilted in the vertical direction.

[0011] According to this feature, there is no mechanism that mechanically operates in association with continuous imaging, and as a result, it becomes possible to continuously image the side of the overhead contact wire from on a railway vehicle traveling at high speed, such as a Shinkansen, and perform inspection through image analysis. [Brief description of the drawings]

[0012] [Figure 1] 1 is a front view (partially a block diagram) of a main part of an overhead contact wire inspection system in one embodiment according to the present invention. [Diagram 2] FIG. 1 is a diagram illustrating the principle of a focal plane when a lens surface is tilted. [Diagram 3] FIG. 13 is a diagram showing the focal range when the lens surface is tilted. [Figure 4] FIG. 13 is a diagram illustrating the principle of an imaging range when a lens is translated along a lens surface. [Diagram 5] FIG. 1 shows cross-sectional views of (a) an overhead contact wire and (b) a contact wire. [Figure 6] FIG. 2A is a front view and FIG. 2B is a top view of an imaging device and an illumination device with a polarizing filter attached. [Figure 7] (a) is an example of an image captured without a polarizing filter, and (b) is an example of an image captured with a polarizing filter. [Figure 8] 1 is a schematic diagram of a light beam when a gradation filter is used in an illumination device. [Figure 9]The images are obtained without (a) using a gradation filter and with (b), along with enlarged images of the key parts ((c) and (d)). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of an overhead contact wire inspection method and inspection system according to the present invention will be described with reference to Figs.

[0014] As shown in Fig. 1, an overhead contact line inspection system 10 includes an imaging device 3, a lighting device 4, and a control device 5. The imaging device 3 and the lighting device 4 are connected to the control device 5, and images acquired by the imaging device 3 can be transmitted to the control device 5 for recording and analysis. The control device 5 is also equipped with a driver capable of electrically operating the imaging device 3, and can perform operations such as switching ON / OFF of image capture by the imaging device 3. Meanwhile, the lighting device 4 has a built-in driver that performs the electrical operation, and receives an operation signal from the control device 5 to enable ON / OFF switching, adjustment of light intensity, and the like. As the control device 5, for example, a personal computer can be used.

[0015] The imaging device 3 and the lighting device 4 are installed inside a windshield 2 provided on the roof portion 1a of the railway vehicle 1, and are arranged so as to face upward through a window 2a opening at the top of the windshield 2.

[0016] The imaging device 3 is disposed so that its optical axis is directed through the window 2a toward the side of the overhead train line 20 and viewed at a predetermined elevation angle. That is, the imaging device 3 is located at the lower side of the overhead train line 20. In particular, it is preferable that the imaging device 3 is disposed at the left and right ends of the roof portion 1a with respect to the traveling direction of the railcar 1, thereby making the elevation angle as small as possible and bringing the imaging device 3 closer to the side directly facing the side of the overhead train line 20.

[0017] Moreover, the lighting device 4 is disposed near the imaging device 3 so that the optical axis is directed toward the overhead train line 20. It is also preferable that a plurality of lighting devices 4 are disposed and used separately so that the light amount and the like can be adjusted to an appropriate level for imaging the overhead train line 20.

[0018] The imaging device 3 can also continuously image the overhead contact wire 20 while the railway vehicle 1 is traveling. That is, images are obtained intermittently at a predetermined frame rate, and the obtained series of images are recorded as continuous images by the control device 5. Images can then be extracted from the continuous images according to a predetermined rule, and image analysis can be performed to inspect the overhead contact wire 20 and its surrounding metal fittings. The mounting positions and angles of the imaging device 3 and the lighting device 4 are all adjusted and fixed before the railway vehicle 1 starts traveling, so that no mechanical operation is required while the railway vehicle 1 is traveling.

[0019] Incidentally, overhead electric lines generally have multiple suspension wires, contact wires, etc. arranged vertically, and in the inspection system 10, the imaging device 3 is positioned so as to face the side of the overhead electric wire in order to image these overhead electric lines at once.

[0020] 2, the imaging device 3 includes an imaging element 31 and a lens 32', and has an optical axis A directed diagonally upward toward the overhead train line 20 at an elevation angle α. In this case, the imaging element 31 of the imaging device 3 is disposed on a plane perpendicular to the optical axis A, and faces the overhead train line 20 directly.

[0021] Generally, the lens 32' is arranged so that its lens surface 32'a is parallel to the imaging surface 31a of the imaging element 31 so as to face the imaging element 31. Then, a focal plane 33' that is in focus is formed near the overhead train line 20 corresponding to the elevation angle α. In this case, the focal plane 33' faces the imaging element 31 and the lens 32'. In other words, the focal plane 33' is parallel to the imaging surface 31a and is a plane whose normal is the optical axis A inclined at the elevation angle α.

[0022] On the other hand, as described above, the overhead contact wires 20 are arranged vertically. In other words, the focal plane 33' is inclined relative to the plane in which the overhead contact wires 20 are arranged vertically. For this reason, if an image of a plurality of the overhead contact wires 20 is taken at once with an imaging device having the focal plane 33', there is a high possibility that a part of the overhead contact wire 20 will be located beyond the focal range, resulting in an out-of-focus image. In particular, the overhead contact wires 20 are often arranged at different heights depending on the presence or absence of structures such as tunnels and elevated structures, which makes it more difficult to obtain a focused image. Furthermore, the overhead contact wires 20 have a contact wire 21 that slides against the current collector of the pantograph, but are arranged with a displacement from side to side to avoid uneven wear on a specific part of the current collector. Taking this displacement into account, it becomes even more difficult to obtain a focused image. In such a case, it may be possible to consider using multiple imaging devices with different focal points to expand the focal range. However, increasing the size of the device attached to the roof portion 1a of the railway vehicle 1 is not preferable because it reduces aerodynamic characteristics and increases noise.

[0023] Therefore, in this embodiment, the lens surface 32a of the lens 32 is tilted from a parallel position to the imaging surface 31a, and the focal plane 33 is tilted in this direction so as to approach a vertical plane extending in the vertical direction. At this time, the focal plane 33 is formed in the vicinity of the overhead electric wire 20 corresponding to the elevation angle α. In this case, by bringing the focal plane 33 closer to the vertical plane, it becomes easier to include the entire overhead electric wire 20 within the focal range. It is preferable to make the focal plane 33 a vertical plane, which makes this even easier. The angle of the focal plane 33 is determined by the Scheimpflug principle. That is, the imaging surface 31a, the lens surface 32a, and the focal plane 33 intersect on the same straight line L. When the imaging surface 31a is determined in advance, it is preferable to set the straight line L in consideration of the focal length, and adjust the mounting angle of the lens 32 so that the lens surface 32a is tilted from a parallel position to the imaging surface 31a.

[0024] 3, when lens surface 32'a is parallel to imaging surface 31a, focal range R1 (depth of field) is likely to include a portion of overhead train line 20 that is distant above and below, because the focal range R1 is divided into front and back by a plane perpendicular to optical axis A. On the other hand, when lens surface 32a is tilted with respect to imaging surface 31a and focusing surface 33 is made vertical, focal range R2 is divided into front and back by a vertical plane, making it easy to include overhead train line 20 that is distant above and below, within it. By keeping the overhead train line 20 within the focal range, it is also easy to obtain an image that can be used for inspection.

[0025] By tilting and moving the focal plane 33 closer to the vertical direction in this manner, it becomes possible to fit the overhead train wires 20, which are arranged vertically and displace vertically as the railway vehicle 1 travels, within the focal range while keeping the imaging device 3 fixed to the roof 1a of the railway vehicle 1. Therefore, even without a mechanism that mechanically operates with continuous imaging, it is possible to obtain images of the side of the overhead train wires 20 that can be used for inspection. For example, even with a railway vehicle that travels at high speeds such as a Shinkansen, it is possible to obtain images necessary for image analysis and perform inspection because it does not have a mechanically operating mechanism.

[0026] The imaging device 3 may be provided on each of the left and right sides. Using two imaging devices 3 results in a wider focusing range, which is preferable.

[0027] Furthermore, as shown in FIG. 4, the lens 32 may be translated along the lens surface 32a. For example, the lens 32 is translated upwards on the paper so that the central axis C of the lens 32 is shifted to become a new central axis C-1. The central axis C intersects with the optical axis A, which coincides with the center of the image sensor 31, at the center of the lens 32, but the new central axis C-1 does not intersect with the optical axis A at the center of the lens 32. In other words, it is in a position shifted from the center of the image sensor 31. At this time, the focal plane 33 obtained by the lens 32-1 at the moved position does not change, but the imaging range 34 indicated by the dotted arrow on the focal plane 33 moves to the imaging range 34-1 indicated by the solid arrow. In other words, the imaging range 34 can be moved and adjusted by moving the central axis C of the lens 32 and translating the lens 32 along the lens surface 32a. Here, the imaging range 34 is moved upward, but it can also be moved downward. By adjusting the imaging range in this manner, the overhead train line 20 and its peripheral fittings can be more reliably included within a fixed viewing angle, making it possible to more reliably obtain the images necessary for image analysis.

[0028] As shown in Fig. 5(a), an overhead train line 20 has a contact wire 21 at the bottom. In this example, an auxiliary suspension wire 22 is provided above that, and a suspension wire 23 is provided at the top. Also, as shown in Fig. 5(b), the bottom side of the contact wire 21 is worn down by sliding against the current collector of the pantograph, forming a flat sliding surface 21a.

[0029] Therefore, as shown in Fig. 6(a), when a set of an imaging device 3 and an illumination device 4 is provided on each of the left and right sides, when the illumination device 4 on the opposite side (the right side in Fig. 6) across the overhead electric train line 20 including the trolley wire 21 illuminates the trolley wire 21 from below, the light is specularly reflected by the sliding surface 21a. This may cause a phenomenon called whiteout, in which the sliding surface 21a is extremely bright in the image obtained by the imaging device 3 (on the left side in Fig. 6), and the surrounding image also becomes white and loses gradation. In other words, such whiteout is likely to occur when the illumination devices 4 are provided on the opposite left and right sides of the imaging device 3 across the overhead electric train line 20.

[0030] 6(b), it is also preferable to attach a pair of polarizing filters oriented perpendicular to each other to each of the imaging device 3 and the lighting device 4. In this case, the polarizing filters are installed on each of the imaging device 3 and the lighting device 4 so that the polarization planes of the light that has passed through and is polarized are perpendicular to each other. For example, in the example of the same figure, the polarization plane of the camera polarizing filter 35 attached to the imaging device 3 may be set to the horizontal direction (left-right on the page) relative to the traveling direction of the railway car 1, and the polarization plane of the lighting polarizing filter 41 attached to the lighting device 4 may be set to the front-rear direction (up-down on the page).

[0031] In this way, the light emitted from the lighting device 4 is polarized by the lighting polarizing filter 41, specularly reflected by the sliding surface 21a of the trolley wire 21, and cut by the camera polarizing filter 35 of the imaging device 3 while maintaining its polarization. On the other hand, some of the light that strikes other parts or the sliding surface 21a is diffusely reflected, loses its polarization, and passes through the camera polarizing filter 35. Therefore, only the specularly reflected light is removed, and whiteout in the obtained image can be suppressed.

[0032] For example, Figure 7 shows an example of capturing an image of a stainless steel ruler. As shown in Figure 7(a), in the image obtained without using a polarizing filter, whiteout occurred around the surface of the stainless steel ruler. On the other hand, as shown in Figure 7(b), in the image obtained when a polarizing filter was attached to both the lighting device and the imaging device so that the polarization planes were perpendicular to each other, whiteout was suppressed. In other words, by using polarizing filters in the above combination, it was possible to obtain an image that is more suitable for image analysis.

[0033] In addition, when a pair of the imaging device 3 and the lighting device 4 is installed on the left and right, the installation positions of the pair on the left and right may be shifted forward and backward. In this case, the light specularly reflected by the sliding surface 21a from the lighting device 4 can be prevented from reaching the imaging device 3, and the above-mentioned blown out highlights can be suppressed.

[0034] Also, as shown in FIG. 8, it is preferable that the lighting device 4 changes the amount of light along the imaging position of the focal plane 33. In particular, the suspension wire 23 at the highest position of the overhead train line 20 and the trolley wire 21 at the lowest position are significantly different in distance from the lighting device 4 below. Therefore, if the lighting device 4 is illuminated with a uniform light beam, the suspension wire 23 will be darker than the trolley wire 21. Therefore, it is preferable to irradiate the light beam 45 with the amount of light adjusted so that the upper side is brighter and the lower side is darker within the imaging range along the focal plane 33. For example, it is preferable to include a gradation filter 42 in the light path of the lighting device 4, which gradually changes the amount of light transmission depending on the position, thereby obtaining the above-mentioned light beam 45.

[0035] As shown in Fig. 9, the presence or absence of the gradation filter 42 was compared. That is, Fig. 9(a) shows an image without the gradation filter, and Fig. 9(b) shows an image with the gradation filter attached to the lighting device and included in the light path. In particular, by comparing Fig. 9(c) and Fig. 9(d), which are enlarged views of the trolley wire 21, it was found that the blown-out highlights that occurred without the gradation filter (Fig. 9(c)) were suppressed with the gradation filter (Fig. 9(d)). In other words, it is believed that the gradation filter suppressed the amount of light irradiated to the trolley wire 21, which is located low, thereby suppressing the blown-out highlights.

[0036] This method of changing the amount of light may be used in combination with the use of a polarizing filter, as described above, to obtain an image with appropriate brightness while suppressing overexposure.

[0037] Although the representative embodiment of the present invention and the associated modifications have been described above, the present invention is not necessarily limited thereto and may be modified as appropriate by those skilled in the art. In other words, those skilled in the art will be able to find various alternative embodiments and modifications without departing from the scope of the appended claims. [Explanation of symbols]

[0038] 1. Railway vehicles 3. Imaging device 4. Lighting equipment 10 Inspection System 20 Overhead line 31 Image sensor 31a Imaging surface 32 Lens 32a Lens surface 33 Focus plane A optical axis α elevation angle

Claims

1. An overhead contact line inspection method for inspecting an overhead contact line by continuously capturing images of a side portion of the overhead contact line while illuminating the side portion with a lighting device from above a traveling rail vehicle and analyzing the images, comprising: an imaging device including a lens and an imaging element is disposed on a roof of the railway vehicle so as to orient an optical axis from a lower lateral side of the overhead contact line to the lateral side and look up at a predetermined elevation angle; and an imaging surface of the lens is tilted from a parallel position with respect to an imaging surface of the imaging element to tilt and move a focal plane formed in the vicinity of the overhead contact line corresponding to the elevation angle in a vertical plane direction to image the overhead contact line; a focusing device that focuses the focusing light on the focusing position of the focusing surface and the focusing light that is focused on the focusing position of the focusing surface;

2. 2. The overhead contact wire inspection method according to claim 1, wherein the lens is translated along the lens surface so that a central axis of the lens is shifted from a center of the imaging element to capture an image of the overhead contact wire.

3. 3. The overhead train line inspection method according to claim 1, wherein the lighting devices are arranged at opposing left and right positions of the imaging device across the overhead train line, with their optical axes directed toward the overhead train line, and the lighting devices and the imaging device are each provided with a pair of polarizing filters oriented perpendicular to each other.

4. An overhead contact line inspection system that performs inspection by image analysis by continuously capturing images of the side of the overhead contact line with an imaging device while illuminating the side of the overhead contact line with a lighting device from above a traveling railway vehicle, the imaging device includes a lens and an imaging element, and is disposed on the roof of the railway vehicle so as to orient an optical axis from a lower lateral side of the overhead electric rail to the lateral side and look up at a predetermined elevation angle, and a lens surface of the lens is tilted from a parallel position with respect to an imaging surface of the imaging element to tilt and move a focal plane formed in the vicinity of the overhead electric rail corresponding to the elevation angle in a vertical plane direction; The overhead contact line inspection system is characterized in that the lighting device provides lighting that changes the amount of light along an imaging position of the focal plane that is tilted and moved in a vertical plane direction.

5. 5. The overhead contact line inspection system according to claim 4, wherein the imaging device translates the lens along the lens surface so that a central axis of the lens is shifted from a center of the imaging element.

6. 6. The overhead contact line inspection system according to claim 4, wherein the lighting device includes a gradation filter in an optical path.

7. 7. The overhead train line inspection system according to claim 6, wherein the lighting devices are arranged at opposing left and right positions of the imaging device across the overhead train line, with their optical axes directed toward the overhead train line, and the lighting devices and the imaging devices are each provided with a pair of polarizing filters oriented perpendicular to each other.

Images