Moving device

Abstract

This moving device travels on the surface of a magnetic body, the moving device comprising: a device body part (housing 100); drive units 101 that are provided at least on both sides of the device body part, are connected to the device body part via a link mechanism, and are attracted to the surface of the magnetic body by magnetic force; and auxiliary magnets 204 that are provided to the drive units 101 so as to be set away from the surface of the magnetic body and that assist the attraction of the drive units 101 to the surface of the magnetic body.

Description

Mobile device

[0001] The present disclosure relates to a mobile device. In particular, the present disclosure relates to a mobile device used for inspecting defects such as thinning and cracks generated by corrosion or damage of a magnetic material such as a steel structure.

[0002] In hollow steel structures such as pipes, tanks, gas holders, or chimneys, corrosion or damage may occur. Various inspection methods for inspecting defects such as thinning and cracks generated at this time are known. As a method for inspecting a wide range of inspection target members, for example, Patent Document 1 discloses a method using an inspection device that travels while adsorbing to the surface of a steel structure. However, in the inspection device shown in Patent Document 1, the position of the magnet crawler is fixed with respect to the inspection device main body. Therefore, depending on the curvature of the steel structure, the contact area of the magnet crawler becomes small. As a result, stable travel of the inspection device is difficult.

[0003] To solve this problem, for example, Patent Documents 2 and 3 disclose an inspection device in which magnetic wheels are connected to a main body portion via a link mechanism (articulated joint, hinge). The magnetic wheels of this inspection device can tilt with respect to the main body portion.

[0004] International Publication No. 2022 / 024478, Japanese Patent Application Laid-Open No. 2023-551298, Japanese Patent Application Laid-Open No. 2017-512975

[0005] In the inspection devices of Patent Documents 2 and 3, the magnetic wheels can tilt with respect to the main body portion. Therefore, the angle of the magnetic wheels can be changed according to the curvature of the inspection target member, and it is possible to correspond to various inspection target members. However, in the inspection devices of Patent Documents 2 and 3, since they are adsorbed to the inspection target member only by the magnetic force of the magnetic wheels, the contact pressure (surface pressure) between the magnetic wheels and the surface of the inspection target member becomes strong, and there is a risk of damaging the surface of the inspection target member by the magnetic wheels during travel. In addition, there is a limit only with the magnetic force of the magnetic wheels, and it is also difficult to increase the magnetic force.

[0006] In view of the above facts, an object of the present disclosure is to provide a mobile device that can be stably adsorbed to the surface of a magnetic material and can suppress damaging the surface of the magnetic material during travel.

[0007] (1) A mobile device according to one embodiment of the present disclosure is a mobile device that travels on the surface of a magnetic material, comprising: a main body of the device; a drive unit provided at least on both sides of the main body of the device and connected to the main body of the device via a link mechanism, and attracted to the surface by magnetic force; and an auxiliary magnet provided at a distance from the surface of the drive unit to assist the attraction of the drive unit to the surface.

[0008] (2) In one embodiment of the present disclosure, in (1), the drive unit comprises a magnet-embedded crawler having a permanent magnet embedded on its surface.

[0009] (3) In one embodiment of the present disclosure, in (2), the auxiliary magnet is provided on the rotating shaft of the magnet-embedded crawler and is rotatable together with the magnet-embedded crawler.

[0010] (4) In one embodiment of the present disclosure, in (1) to (3), the link mechanism is composed of a hinge and a length-adjustable damper.

[0011] (5) In one embodiment of the present disclosure, in (1) to (4), auxiliary wheels are provided at the lower part of the main body of the device, which are height-adjustable relative to the main body of the device and which make contact with the surface.

[0012] (6) In one embodiment of the present disclosure, in (5), an inspection device for inspecting the magnetic material is provided on the main body of the apparatus at a distance from the surface, and the height of the inspection device relative to the surface is adjustable in accordance with the auxiliary wheels.

[0013] The mobile device of this disclosure can be stably adsorbed to the surface of a magnetic material, and can also suppress scratching of the surface of the magnetic material during travel.

[0014] Figure 1 is an external view of a mobile device in one embodiment of the present disclosure. Figure 2A is a front view of the mobile device in one embodiment of the present disclosure attached to a flat surface. Figure 2B is a front view of the mobile device in one embodiment of the present disclosure attached to a curved surface in the direction of the pipe axis. Figure 3A is a side view of the mobile device in one embodiment of the present disclosure attached to a flat surface. Figure 3B is a side view of the mobile device in one embodiment of the present disclosure attached to a curved surface in the direction of the circumferential orientation. Figure 4 is a diagram of the storage section for the inspection device provided in the mobile device in one embodiment of the present disclosure. Figure 5 is a front view and a side view of a magnet-embedded crawler in one embodiment of the present disclosure. Figure 6 is a graph of the flaw detection results using the mobile device in one embodiment of the present disclosure.

[0015] A mobile device according to one embodiment of the present disclosure will be described below with reference to the drawings.

[0016] (Overall Structure) As shown in Figure 1, the mobile device of this embodiment is a device that travels on the surface of a magnetic material, and comprises a device body (housing 100) and a drive unit 101. The device body (housing 100) and the drive unit 101 are connected to each other via a link mechanism. In this embodiment, the magnetic material is, for example, a steel structure such as a pipe, tank, gas holder or chimney, and in particular a hollow steel structure with a curved surface. In this specification, the surface refers to the outer or inner surface of a hollow structure.

[0017] (Main body of the device (housing 100)) As shown in Figure 1, in this embodiment, the housing 100 of the mobile device is composed of two front and rear housing sections 102 and a central housing section 103. Also, as shown in Figure 2A, the central housing section 103 has an inspection device 206 and auxiliary wheels 205 fixed to the inspection device 206.

[0018] The two front and rear housing sections 102 and the central housing section 103 are aligned in the direction of travel of the mobile device. The front and rear housing sections 102 and the central housing section 103 are connected to each other by a link mechanism. As a result, as shown in Figure 3A, when traveling on a flat magnetic surface, the front and rear housing sections 102 and the central housing section 103 are parallel to the magnetic surface, allowing the device to travel along the plane. Furthermore, as shown in Figure 3B, even when traveling on a magnetic surface that is curved in the direction of travel, the front and rear housing sections 102 are tilted relative to the central housing section 103 to follow the curve, allowing the device to travel along the curved surface.

[0019] The two front and rear housing sections 102 and the central housing section 103 house, for example, a battery for supplying power to various parts of the mobile device and a control device that enables wireless communication with various parts of the mobile device. The housed battery can supply power to the drive motor of the drive unit 101, the inspection device 206, and the control device. The control device controls the drive motor and outputs inspection data from the inspection device 206. By communicating wirelessly from the control device to a remote control PC (notebook PC, etc.), the mobile device can be communicated and controlled wirelessly from a remote location. Here, communication from the control device to the control PC (notebook PC, etc.) may be wireless or wired. As shown in Figure 4, the inspection device 206 is housed inside the central housing section 103. The sensor portion of the inspection device 206 is exposed at the bottom of the central housing section 103 and is mounted so as to be separated from the magnetic surface.

[0020] (Drive Unit 101) As shown in Figure 1, in this embodiment, two drive units 101 are provided, one on each side of the housing 100. Also, as shown in Figures 2A and 3A, the drive unit 101 has two magnet-embedded crawlers 202, a handle 203, an auxiliary magnet 204, a sliding frame 300, and a length-adjustable intermediate turnbuckle 301. The two magnet-embedded crawlers 202 are arranged side by side in the direction of travel of the moving device. The drive unit 101 and the front and rear housing units 103 are connected by a link mechanism consisting of a length-adjustable damper 200 and a hinge 201.

[0021] As shown in Figure 1, the moving device of this embodiment is equipped with two drive units 101. The two drive units 101 each have the same structure and are independent of each other. Therefore, each drive unit 101 can perform different operations simultaneously.

[0022] Figures 2A and 2B show front views of the mobile device when it is attached to a flat surface and a curved surface perpendicular to the direction of travel, respectively. As shown in Figure 2A, when the mobile device travels on a flat magnetic surface, the housing 100 and the drive units 101 provided on both sides of the housing 100 are parallel to the magnetic surface. As a result, the mobile device can travel along the magnetic surface. Also, as shown in Figure 2B, when the mobile device travels on a curved magnetic surface perpendicular to the direction of travel, the drive units 101 on both sides of the housing 100 are inclined relative to the housing 100 along the curved surface. As a result, the mobile device can travel along the curved surface.

[0023] Figures 3A and 3B show side views of the mobile device when attached to a flat surface and a curved surface curved in the direction of travel, respectively. As shown in Figure 3A, when the mobile device travels on a flat magnetic surface, the housing 100 and the drive units 101 provided on both sides of the housing 100 are parallel to the magnetic surface. As a result, the mobile device can travel along the magnetic surface. Also, as shown in Figure 3B, when the mobile device travels on a curved magnetic surface that is curved in the direction of travel, the two magnet-embedded crawlers 202 located in front of and behind the drive unit 101 are inclined relative to the housing 100 along the curved surface. As a result, the mobile device can travel along the curved surface.

[0024] (Magnet-embedded crawler 202) Figure 5 shows an enlarged front view and side view of the magnet-embedded crawler 202 provided on the drive unit 101. As shown in Figures 3A and 5, the magnet-embedded crawler 202 has a permanent magnet 502 embedded in the rubber crawler 500 on the surface, and a timing belt 501 and a length-adjustable relay turnbuckle 301 on the back side. Also, as shown in the side view of Figure 5, in this embodiment the magnet-embedded crawler 202 has a roughly triangular shape and contacts the pulley on the drive unit 101 at three points.

[0025] The magnet-embedded crawler 202 ensures an attractive force to the magnetic material surface using the permanent magnet 502. Because the magnet-embedded crawler 202 contacts the magnetic material surface with its rubber portion, it can suppress the occurrence of scratches on the magnetic material surface. Furthermore, the magnet-embedded crawler 202 can run stably when contacting curved surfaces, tapered sections, and stepped sections. A timing belt 501 is bonded to the back surface of the magnet-embedded crawler 202. Power from the drive motor is transmitted to this timing belt 501 by a pulley in the drive unit 101. This rotates the magnet-embedded crawler 202, allowing the mobile device to move.

[0026] Thus, the drive unit 101 is composed of a magnet-embedded crawler 202. This allows for a larger contact area between the drive unit 101 and the magnetic surface compared to when the drive unit 101 is composed of wheels, and reduces the contact pressure (surface pressure) on the magnetic surface, thereby suppressing scratches on the magnetic surface during operation.

[0027] As shown in Figure 3A, the magnet-embedded crawler 202 is equipped with a length-adjustable intermediate turnbuckle 301. This allows the contact area of ​​the magnet-embedded crawler 202 with the magnetic surface to be adjusted. The length-adjustable intermediate turnbuckle 301 can be adjusted manually. Each of the two drive units 101 is fitted with a handle 203. Workers can grasp the handles 203 to transport the mobile device, attach it to the magnetic surface, and detach it from the magnetic surface.

[0028] (Auxiliary magnet 204) The drive unit 101 is also equipped with an auxiliary magnet 204 that assists in the attraction of the drive unit 101 to the magnetic surface.

[0029] The auxiliary magnets 204 are ring-shaped magnets attached to both the front and rear ends of the lower part of the magnet-embedded crawler 202, that is, to both ends of the two rotating shafts of the magnet-embedded crawler 202. In this embodiment, 16 auxiliary magnets 204 are attached to the mobile device. The lower surface of the magnet-embedded crawler 202 is in contact with the magnetic material surface. On the other hand, the auxiliary magnets 204 are attached at a distance from the magnetic material surface overall. In this embodiment, because the auxiliary magnets 204 are attached to the rotating shafts of the magnet-embedded crawler 202, they can rotate together with the rotation of the magnet-embedded crawler 202. The mobile device may also be equipped with a horizontal bar (scraper) or the like near the surface of the auxiliary magnets 204. This allows the auxiliary magnets 204 to be removed by rotating them to bring them into contact with the horizontal bar if foreign matter adheres to them while the mobile device is running. Note that the auxiliary magnets 204 do not necessarily need to rotate together with the magnet-embedded crawler 202. Also, the auxiliary magnets 204 do not need to be attached to the rotating shafts of the magnet-embedded crawler 202. The auxiliary magnet 204 may be a permanent magnet. Furthermore, the auxiliary magnet 204 does not have to be ring-shaped; the magnetic force may be adjusted by changing the position, number, or size of the auxiliary magnet 204.

[0030] (Link Mechanism) As shown in Figures 2A and 3A, in this embodiment, the link mechanism is composed of a hinge 201 and a length-adjustable damper 200. The length-adjustable damper 200 can be manually adjusted in length by an extendable ball screw. The length-adjustable damper 200 can be adjusted in length by the curvature of the magnetic surface. This makes it possible for the moving device to tilt the drive unit 101 along the curved surface of the magnetic surface. Furthermore, when the moving device is in motion, the length-adjustable damper 200 extends and retracts, making it possible to rotate the moving device on curved surfaces and tapered sections. Here, the length-adjustable damper 200 may be a spring damper.

[0031] In this embodiment, the moving device is composed of two front and rear housing sections 102, one central housing section 103, and two drive units 101. The front and rear housing sections 102 and the central housing section 103, as well as the front and rear housing sections 102 and the drive units 101 at both ends thereof, are connected by a hinge 201, which is a link mechanism, and a length-adjustable damper 200. As a result, as shown in Figures 2B and 3B, the front and rear housing sections 102 and the two drive units 101 can be tilted around the central housing section 103 to match the curved surface of the magnetic material.

[0032] (Inspection device 206) As shown in Figure 4, an inspection device 206 for inspecting a magnetic material is provided at the lower part of the central housing portion 103 of the mobile device. Note that the mobile device does not necessarily need to have an inspection device 206. Alternatively, an inspection device 206 equipped with one or more sensors may be provided at least one location on the two front and rear housing portions 102 or the central housing portion 103 that constitute the mobile device. The inspection device 206 is positioned at a distance from the surface of the magnetic material. In this embodiment, the inspection device 206 is, for example, a flaw detection device for inspecting the surface of the magnetic material, and is specifically composed of an eddy current sensor, a leakage flux sensor, an ultrasonic thickness sensor, or an electromagnetic ultrasonic thickness sensor. Note that the inspection device 206 is not limited to a flaw detection device, but may also be an imaging device for photographing the surface of the magnetic material. There may be one inspection device 206 or multiple inspection devices 206 may be provided. If multiple inspection devices 206 are provided, each inspection device 206 may be equipped with multiple similar sensors, or each may be equipped with different sensors and imaging devices.

[0033] In this embodiment, the lower part of the central housing 103 of the mobile device is provided with a plurality of auxiliary wheels 205 (a total of four in this embodiment, located in the front, back, left, and right directions) that can adjust the height of the inspection device 206 relative to the magnetic surface. The height of the auxiliary wheels 205 can be manually adjusted according to the height between the lower surface of the central housing 103 of the mobile device and the magnetic surface, allowing the auxiliary wheels 205 to make contact with the magnetic surface. This stabilizes the posture of the central housing 103, in which the inspection device 206 is incorporated, when the mobile device is in motion. The height of the auxiliary wheels 205 may be adjustable by replacing them with auxiliary wheels 205 of different sizes. The auxiliary wheels 205 may also be made of a resin such as urethane.

[0034] Furthermore, one or both ends of the inspection device 206 are fixed to the auxiliary wheels 205. This allows the height or angle of the inspection device 206 to change in accordance with the height of the auxiliary wheels 205 when the height of the auxiliary wheels 205 is adjusted. In this way, by changing the height or angle of the inspection device 206 according to the height between the lower surface of the central housing 103 and the magnetic material surface (height of the auxiliary wheels 205), the distance (lift-off) between the magnetic material surface and the inspection device 206 can always be kept constant. This also enables the inspection device 206 to perform inspections of magnetic materials stably.

[0035] Furthermore, an encoder can be attached to the drive motor that drives the magnet-embedded crawler 202. This makes it possible to acquire travel distance data of the mobile device. In addition, the inspection data and travel distance data of the inspection device 206 can be associated with each other.

[0036] (Inspection Method) While the above-described mobile device is running on the surface of the magnetic material, the inspection of the magnetic material can be performed using the inspection device 206 incorporated into the housing 100 of the mobile device.

[0037] (When traveling on a flat surface) As shown in Figures 2A and 3A, when the mobile device travels on a flat surface of a magnetic material, the magnet-embedded crawler 202 of the drive unit 101 makes contact with the magnetic material surface. Therefore, sufficient frictional force for travel can be obtained by sliding with the magnetic material surface. At this time, the auxiliary magnets 204 at both ends of the magnet-embedded crawler 202 are not in contact with the magnetic material surface. The auxiliary magnets 204 assist the attractive force of the magnet-embedded crawler 202. In addition, since the auxiliary magnets 204 do not come into contact with the magnetic material surface when traveling, they do not scratch the magnetic material surface.

[0038] Furthermore, the front and rear housing sections 102 and the drive unit 101 of the mobile device are connected by a link mechanism. Since the space between the front and rear housing sections 102 and the drive unit 101 is not rigid, the mobile device can pivot. In addition, the central housing section 103 is in contact with the magnetic surface by auxiliary wheels 205. Therefore, the posture of the central housing section 103 as it travels on the magnetic surface can be stabilized. Also, since the height of the inspection device 206 changes in conjunction with the auxiliary wheels 205, the distance between the inspection device 206 and the magnetic surface can be kept constant when performing an inspection.

[0039] (When traveling on a curved surface) As shown in Figure 2B, when the mobile device travels on a curved surface of a magnetic material that is curved in a direction perpendicular to the direction of travel, the length of the length-adjustable damper 200 connecting the front and rear housing sections 102 and the drive section 101 can be manually adjusted to match the curvature of the magnetic material surface. As a result, the drive sections 101 on both sides of the housing 100 are inclined relative to the housing 100 along the curved surface of the magnetic material. As shown in Figure 3B, when the mobile device travels on a curved surface of a magnetic material that is curved in the direction of travel, the length of the length-adjustable damper 200 connecting the front and rear housing sections 102 and the central housing section 103 can be manually adjusted to match the curvature of the magnetic material surface. As a result, the front and rear housing sections 102 can be inclined relative to the central housing section 103 in accordance with the curvature. Furthermore, by adjusting the height of the auxiliary wheels 205 of the central housing 103 to match the curvature of the magnetic surface, or by replacing the auxiliary wheels 205, the auxiliary wheels 205 can be brought into contact with the magnetic surface, thereby stabilizing the posture of the central housing 103 while it is in motion. The inspection device 206, attached to the lower part of the central housing 103, changes in height and angle in conjunction with the auxiliary wheels 205. Therefore, the inspection device 206 can maintain a constant distance from the magnetic surface when performing inspections. The front and rear housings 102 and drive unit 101 of the mobile device are connected by a link mechanism. Since the space between the front and rear housings 102 and drive unit 101 is not rigid, the mobile device can pivot.

[0040] Furthermore, by manually adjusting the length of the length-adjustable relay turnbuckle 301 located inside the magnet-embedded crawler 202 of the drive unit 101, the tension of the magnet-embedded crawler 202 can be adjusted to match the curvature of the magnetic surface. The magnet-embedded crawler 202 obtains high frictional force by sliding on the magnetic surface. As a result, the moving device can travel stably.

[0041] Furthermore, the sliding frame 300 of the drive unit 101 can be removed by sliding it toward the direction of travel or toward the opposite direction of travel. The length-adjustable intermediate turnbuckle 301 is connected by a nut in the center and can therefore be divided into two parts. With the length-adjustable intermediate turnbuckle 301 divided into two parts, the magnet-embedded crawler 202 can be compressed, and the magnet-embedded crawler 202 can be attached and detached while compressed. This makes maintenance of the magnet-embedded crawler 202 easier.

[0042] (Effects) According to this embodiment, the magnet-embedded crawler 202 is attracted to the magnetic surface by magnetic force. As a result, the contact surface of the magnet-embedded crawler 202 is reliably attracted to and in contact with the magnetic surface. High frictional force can be obtained from the magnetic surface as the magnet-embedded crawler 202 slides. In addition, the moving device can travel stably even directly under the magnetic surface and over steps. Furthermore, to assist the attractive force of the magnet-embedded crawler 202, an auxiliary magnet 204 is arranged in the drive unit 101, separated from the magnetic surface. As a result, the attractive force of the magnet-embedded crawler 202 can be weakened compared to when only the magnet-embedded crawler 202 is attracted to the magnetic surface, and the occurrence of scratches on the magnetic surface during the movement of the moving device can be suppressed. In addition, a stable attractive force can be obtained even when the magnetic surface is curved, tapered, or stepped.

[0043] In particular, the tension of the magnet-embedded crawler 202 can be adjusted using the length-adjustable intermediate turnbuckle 301. The tension of the magnet-embedded crawler 202 can be adjusted to match the curved surface of the magnetic material. This allows for higher frictional force against the magnetic material surface and stable running. The length-adjustable intermediate turnbuckle 301 can be disassembled into two parts in the middle. This facilitates the replacement of the magnet-embedded crawler 202.

[0044] Further, the drive unit 101 of the mobile device and the front and rear housing parts 102 are connected by a link mechanism constituted by a hinge 201 and a length-adjustable damper 200. The hinge 201 can limit the front and rear housing parts 102 to tilt only in the width direction or the traveling direction of the mobile device. Also, the length of the length-adjustable damper 200 can be adjusted according to the curvature and taper of the magnetic body, and the tiltable angle of the front and rear housing parts 102 can be adjusted. Thereby, stable traveling, turning in place, and turning-back traveling are possible even on the curved surface and the tapered part of the magnetic body surface.

[0045] Further, by adjusting the height of the auxiliary wheel 205 attached to the central housing part 103 or replacing the auxiliary wheel 205, the central housing part 103 is grounded to the magnetic body surface by the auxiliary wheel 205. Thereby, traveling in a stable posture becomes possible as compared with the case where only the drive unit 101 is grounded. Also, by changing the height or angle of the inspection device 206 in conjunction with the auxiliary wheel 205, the inspection device 206 can be tilted along the curved surface and the tapered surface of the magnetic body surface. Thereby, the distance (lift-off) between the magnetic body surface and the inspection device 206 can always be made constant, and stable inspection is possible.

[0046] Further, the two front and rear housing parts 102 and the central housing part 103 store a battery for power supply and a control device enabling wireless communication. Therefore, the mobile device can also be wirelessly controlled. In addition, by connecting a power cable or a communication cable to the mobile device, the mobile device can also be controlled by wire.

[0047] (Example) Figure 6 is an example of the present disclosure and is a graph of the flaw detection results when flaw detection inspection was performed as an example of inspection. A wireless mobile device was attached axially along the pipe surface of a magnetic pipe with a pipe size of 1200 A in accordance with the A designation of the Japanese Industrial Standards (JIS), and the wireless mobile device traveled straight while performing flaw detection. An encoder was attached to the drive motor for driving the crawler 202 with a built-in magnet, and the inspection data was associated with the travel distance data. At that time, the mobile device used three eddy current flaw detection sensors as the inspection device 206. From the flaw detection results in Figure 6, the detection signal for each travel distance (pipe length) can be obtained. When traveling on the bead, which is the welded part of the pipe, a large detection signal value (change in eddy current distribution) was detected. Also, when traveling on the periphery of the wall thickness reduction part, a large detection signal value (change in eddy current distribution) was detected. By previously determining a threshold value (dotted line) and comparing it with the detection signal value, abnormalities such as wall thickness reduction of the magnetic material can be detected.

[0048] Although the embodiments of the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications or corrections based on the present disclosure. Therefore, it should be noted that these modifications or corrections are included in the scope of the present disclosure. For example, each component can be divided into a plurality of components or combined into one.

[0049] 100 Housing 101 Drive unit 102 Front and rear housing parts 103 Central housing part 200 Length adjustable damper 201 Hinge 202 Crawler with built-in magnet 203 Handle 204 Auxiliary magnet 205 Auxiliary wheel 206 Inspection device 300 Slide-type frame 301 Length adjustable intermediate turnbuckle 500 Rubber crawler 501 Timing belt 502 Permanent magnet

Claims

1. A mobile device for traveling on the surface of a magnetic material, comprising: a main body; drive units provided at least on both sides of the main body and connected to the main body via a link mechanism, and attracted to the surface by magnetic force; and auxiliary magnets provided at a distance from the surface to the drive unit and assisting the attraction of the drive unit to the surface.

2. The mobile device according to claim 1, wherein the drive unit comprises a magnet-embedded crawler having a permanent magnet embedded on its surface.

3. The mobile device according to claim 2, wherein the auxiliary magnet is provided on the rotating shaft of the magnet-embedded crawler and is rotatable together with the magnet-embedded crawler.

4. The moving device according to any one of claims 1 to 3, wherein the link mechanism comprises a hinge and a length-adjustable damper.

5. The mobile device according to any one of claims 1 to 4, wherein the lower part of the main body of the device is provided with auxiliary wheels that are height-adjustable relative to the main body of the device and that make contact with the surface.

6. The mobile device according to claim 5, wherein the main body of the device is provided with an inspection device for inspecting the magnetic material at a distance from the surface, and the height of the inspection device relative to the surface can be adjusted in accordance with the auxiliary wheels.

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