JP7697352B2 - Submarine structure detection system - Google Patents

Description

The present invention relates to an undersea structure detection system, and more particularly to an undersea structure detection system that detects undersea structures installed on the seabed by moving a magnetic sensor along the seabed.

Conventionally, a submarine structure detection system is known that detects submarine structures by moving a magnetic sensor along the seabed (see, for example, Patent Document 1).

The above-mentioned Patent Document 1 discloses a magnetic exploration device (submarine structure detection system) that uses magnetism to detect submarine structures installed on the seabed while moving along the seabed. The magnetic exploration device disclosed in the above-mentioned Patent Document 1 is equipped with a combination sensor in which magnetic sensors are combined in two or more rows, one above the other. The magnetic exploration device disclosed in the above-mentioned Patent Document 1 is arranged with at least one pair of combination sensors facing each other in parallel on the same plane. In addition, the magnetic exploration device disclosed in the above-mentioned Patent Document 1 is configured to detect submarine pipelines by detecting magnetism emitted from the submarine pipeline buried in the seabed while moving along the seabed by being towed by a survey vessel, thereby detecting the submarine pipeline.

Japanese Patent Application Laid-Open No. 62-148877

Here, although it is not disclosed in the above Patent Document 1, it is considered that the submarine pipeline (submarine structure) is made of steel pipes (iron), and that a corrosion protection layer formed of a metal other than iron to prevent rust is provided so as to cover the outer surface of the steel pipe. When the corrosion protection layer is damaged, the surface of the submarine structure is exposed at the damaged part of the corrosion protection layer. In this case, there is a disadvantage that corrosion of the submarine structure occurs from the exposed part of the submarine structure. When the corrosion protection layer is damaged, a current flows between the exposed damaged part of the submarine structure and the corrosion protection layer due to the difference in ionization tendency between the metal constituting the submarine structure and the corrosion protection layer. As in the above Patent Document 1, in a configuration equipped with a magnetic sensor, it is possible to detect the damaged part by detecting the magnetic field caused by the current flowing between the damaged part and the corrosion protection layer. However, the detection accuracy of the magnetic field caused by the current flowing between the damaged part and the corrosion protection layer may decrease due to noise such as geomagnetism. Therefore, in the configuration disclosed in the above Patent Document 1, there is a problem that it is difficult to detect the presence or absence of the submarine structure and the presence or absence of damage to the corrosion protection layer with high accuracy.

This invention has been made to solve the above problems, and aims to provide an undersea structure detection system that is capable of detecting the presence or absence of an undersea structure and accurately detecting the presence or absence of damage to the corrosion protection layer provided on the undersea structure.

In order to achieve the above object, in one aspect of the present invention, a submarine structure detection system detects metallic submarine structures installed on the seabed and detects the presence or absence of damage to a corrosion protection layer installed on the submarine structure and formed of a metal having a different ionization tendency from the metal that constitutes the submarine structure, and includes a potential difference sensor that detects the potential difference caused by the current flowing between the submarine structure and the corrosion protection layer, a magnetic sensor that detects the magnetism in the sea, a submarine structure detection unit that detects the presence or absence of a submarine structure based on the magnetic signal output by the magnetic sensor, and a damage detection unit that detects the presence or absence of damage to the corrosion protection layer based on the magnetic signal and the electric field signal output by the potential difference sensor.

The submarine structure detection system in the first aspect includes a submarine structure detection unit that detects the presence or absence of a submarine structure by a magnetic signal output by a magnetic sensor. As a result, the presence or absence of a submarine structure can be detected by acquiring a magnetic signal. The submarine structure detection system in the first aspect includes a damage detection unit that detects the presence or absence of damage to the corrosion protection layer by the magnetic signal output by the magnetic sensor and the electric field signal output by a potential difference sensor that detects the potential difference caused by the current flowing between the submarine structure and the corrosion protection layer. As a result, unlike a configuration that detects the presence or absence of damage to the corrosion protection layer only by a magnetic signal, the presence or absence of damage to the corrosion protection layer can be detected by both the magnetic signal generated by the current flowing between the submarine structure and the corrosion protection layer and the electric field signal based on the potential difference caused by the current flowing between the submarine structure and the corrosion protection layer. Therefore, the presence or absence of damage to the corrosion protection layer can be detected more accurately than a configuration that detects the presence or absence of damage to the corrosion protection layer only by a magnetic signal. As a result, it is possible to provide an undersea structure detection system that can detect the presence or absence of undersea structures and can accurately detect the presence or absence of damage to the corrosion protection layer provided on the undersea structure.

1 is a diagram showing an overall configuration of an undersea structure detection system according to an embodiment; 1 is a block diagram showing a configuration of an undersea structure detection system according to an embodiment. FIG. 2 is a schematic diagram for explaining an arrangement of a potential difference sensor and a magnetic sensor according to one embodiment. 1 is a schematic diagram for explaining a configuration in which an undersea structure detection system according to an embodiment acquires a reference magnetic signal; 1 is a functional block diagram for explaining a configuration in which a discrimination unit detects the presence or absence of a submarine structure and the presence or absence of damage to a corrosion protection layer according to an embodiment. FIG. 1 is a schematic diagram for explaining a configuration in which an undersea structure detection unit according to one embodiment acquires a depth position of an undersea structure; FIG. Graph (A) illustrates a reference magnetic signal, graph (B) illustrates a magnetic signal when the anticorrosion layer is damaged, and graph (C) illustrates a differential magnetic signal. 1A is a graph for explaining an electric field signal when there is no damage to the anticorrosion layer, and FIG. 1B is a graph for explaining an electric field signal when there is damage to the anticorrosion layer. 11 is a flowchart illustrating a process in which a submarine structure detection unit detects the presence or absence of a submarine structure according to an embodiment. 10 is a flowchart illustrating a process in which a damage detection unit detects the presence or absence of damage to a corrosion protection layer according to an embodiment.

The following describes an embodiment of the present invention with reference to the drawings.

The configuration of an undersea structure detection system 100 according to one embodiment will be described with reference to Figures 1 to 8.

(Configuration of the undersea structure detection device)
First, with reference to FIG. 1, a configuration of an undersea structure detection system 100 according to an embodiment will be described.

The submarine structure detection system 100 is a submarine structure detection system that detects a metallic submarine structure 90 provided on the seabed 80. The submarine structure 90 is a pipeline provided on the seabed 80. That is, the submarine structure detection system 100 is configured to detect the presence or absence of a pipeline provided on the seabed 80. The submarine structure detection system 100 is also a submarine structure detection system that detects the presence or absence of damage 6a in a corrosion protection layer 6 provided on the submarine structure 90 and formed of a metal having a different ionization tendency from the metal constituting the submarine structure 90. That is, the submarine structure detection system 100 is configured to detect the presence or absence of damage to a pipeline provided on the seabed 80. The submarine structure 90 is formed, for example, of a steel material (iron material).

The pipeline includes, for example, a steel pipe with an anticorrosive layer 6 covering the outer surface to prevent rust. The anticorrosive layer 6 is formed, for example, from a zinc alloy. When damage 6a occurs in the anticorrosive layer 6, as shown by arrow 7, a current flows from the part where the damage 6a occurs to the anticorrosive layer 6 through seawater due to the difference in ionization tendency between the metal constituting the submarine structure 90 and the anticorrosive layer 6. The pipeline is an example of a "submarine structure" in the claims. In the example shown in FIG. 1, the anticorrosive layer 6 provided on the submarine structure 90 is hatched for convenience.

As shown in FIG. 1, the submarine structure detection system 100 includes a potential difference sensor 1, a magnetic sensor 2, and a computer 3. In this embodiment, the submarine structure detection system 100 also includes a mobile body 4. The potential difference sensor 1 and the magnetic sensor 2 are provided on the mobile body 4. The computer 3 is provided on the ship 5.

The potential difference sensor 1 is configured to detect a potential difference caused by a current flowing between the submarine structure 90 and the anticorrosion layer 6. The potential difference sensor 1 is configured to output an electric field signal 30 (see FIG. 2) based on a potential difference caused by a current flowing in the sea between the submarine structure 90 and the anticorrosion layer 6. In this embodiment, the potential difference sensor 1 is configured to output an electric field signal 30 measured while being moved by the mobile body 4. The potential difference sensor 1 includes, for example, a silver/silver chloride electrode. The position at which the potential difference sensor 1 is provided on the mobile body 4 will be described later.

The magnetic sensor 2 is configured to detect the magnetism in the sea. The magnetic sensor 2 is also configured to output a magnetic signal 31 (see FIG. 2) based on the magnetism in the sea. The magnetic sensor 2 is provided on the moving body 4. In this embodiment, the magnetic sensor 2 is configured to output a magnetic signal 31 measured while being moved by the moving body 4. The magnetic sensor 2 is configured to output a magnetic signal 31 in the up-down direction of the moving body 4 and in two directions perpendicular to each other in a plane perpendicular to the up-down direction. The magnetic sensor 2 includes, for example, a three-axis magnetometer.

The computer 3 is configured to detect the undersea structure 90 based on the magnetic signal 31 output from the magnetic sensor 2. The computer 3 is also configured to detect the presence or absence of damage 6a of the anticorrosion layer 6 based on the magnetic signal 31 and the electric field signal 30 output from the potential difference sensor 1. In this embodiment, the damage 6a of the anticorrosion layer 6 is, for example, corrosion of the anticorrosion layer 6. That is, in this embodiment, the computer 3 is configured to detect the presence or absence of corrosion of the anticorrosion layer 6. The computer 3 detects the presence or absence of damage 6a of the anticorrosion layer 6 by detecting whether or not the surface of the undersea structure 90 is exposed due to the corrosion of the anticorrosion layer 6 and whether or not a current (corrosion current) flows between the undersea structure 90 and the anticorrosion layer 6. The computer 3 is also configured to control the movement of the mobile body 4. Details of the configuration of the computer 3 to detect the presence or absence of the undersea structure 90 and the configuration to detect the presence or absence of damage 6a of the anticorrosion layer 6 will be described later.

The mobile body 4 is provided with a magnetic sensor 2 and a potential difference sensor 1, and is configured to be movable underwater. In this embodiment, the mobile body 4 is configured to move both the potential difference sensor 1 and the magnetic sensor 2 as a unit. The mobile body 4 is also provided with a depth gauge (not shown) that acquires depth information of the mobile body 4 in the sea, and a distance sensor (not shown) that acquires the distance from the mobile body 4 to a measurement target. The mobile body 4 is configured to be able to travel underwater. The mobile body 4 is also configured to be able to move underwater unmanned. The mobile body 4 is a so-called AUV (Autonomous Underwater Vehicle). The detailed configuration of the mobile body 4 will be described later.

As shown in FIG. 2, the computer 3 includes a processor 10, a memory unit 11, a mobile object information acquisition unit 12, a signal acquisition unit 13, and an alarm unit 14.

The processor 10 is configured to detect the presence or absence of a submarine structure 90 (see FIG. 1). The processor 10 is also configured to detect the presence or absence of damage 6a (see FIG. 1) in the corrosion protection layer 6 (see FIG. 1) provided on the submarine structure 90. The processor 10 includes, for example, a CPU (Central Processing Unit), a microprocessor, and an FPGA (Field-Programmable Gate Array) configured for determining the position of the submarine structure 90. Details of the configuration of the processor 10 for detecting the presence or absence of a submarine structure 90 and the configuration for detecting the presence or absence of damage 6a in the corrosion protection layer 6 will be described later.

The memory unit 11 stores a reference magnetic signal 20 acquired in advance. The memory unit 11 is also configured to store a reference distance 21, which is the distance between the magnetic sensor 2 and the submarine structure 90 when the reference magnetic signal 20 is acquired. The memory unit 11 also stores various programs executed by the processor 10. The memory unit 11 includes a non-volatile storage device. The non-volatile storage device is, for example, a hard disk drive, a solid state drive, etc.

The reference magnetic signal 20 is a magnetic signal output by the magnetic sensor 2 at a position where the distance between the moving body 4 and the submarine structure 90 is the reference distance 21. The reference distance 21 is the distance between the moving body 4 and the submarine structure 90 when the reference magnetic signal 20 is acquired. The reference magnetic signal 20 and the reference distance 21 are acquired in advance and stored in the memory unit 11. The reference magnetic signal 20 is used to detect the presence or absence of the submarine structure 90 and the presence or absence of damage 6a in the corrosion protection layer 6. The reference magnetic signal 20 and the reference distance 21 are also used to acquire the depth position 25 (see FIG. 6) of the submarine structure 90 when the submarine structure 90 is present. The reference distance 21 is not used to detect the presence or absence of damage 6a in the corrosion protection layer 6.

The mobile object information acquisition unit 12 is configured to acquire mobile object information 22 including information on the acceleration and attitude of the mobile object 4. The mobile object information acquisition unit 12 is also configured to output the acquired mobile object information 22 to the processor 10. The mobile object information acquisition unit 12 includes, for example, a wireless communication device and an input/output interface.

The signal acquisition unit 13 is configured to acquire an electric field signal 30 from a potential difference sensor 1 provided on the moving body 4. The signal acquisition unit 13 is also configured to acquire a magnetic signal 31 from the magnetic sensor 2. The signal acquisition unit 13 is also configured to output the acquired electric field signal 30 and magnetic signal 31 to the processor 10. The signal acquisition unit 13 includes, for example, a wireless communication device and an input/output interface.

The notification unit 14 is configured to notify a first detection result 40a (see FIG. 5), which is the detection result of the presence or absence of the submarine structure detection unit 10a. The notification unit 14 is also configured to notify a second detection result 40b (see FIG. 5), which is the detection result of the presence or absence of damage 6a in the corrosion protection layer 6. The notification unit 14 is, for example, a liquid crystal display device. The notification unit 14 may also be an electroluminescence display device or a projector.

The moving body 4 includes a control unit 4a, a communication unit 4b, a moving body information measuring unit 4c, and a propulsion mechanism 4d.

The control unit 4a is configured to control the moving body 4. The control unit 4a includes, for example, a CPU.

The communication unit 4b is configured to communicate with the computer 3 under the control of the control unit 4a. Specifically, the communication unit 4b is configured to receive information on the direction in which to move the moving object 4 from the computer 3, and to transmit to the computer 3 the electric field signal 30 output by the potential difference sensor 1, the magnetic signal 31 output by the magnetic sensor 2, and the moving object information 22. The communication unit 4b includes, for example, a wirelessly connectable transmitting/receiving device.

The mobile object information measuring unit 4c is configured to acquire information on the acceleration and attitude of the mobile object 4. The attitude information is a vector that represents the attitude of the mobile object 4 in the sea. The mobile object information measuring unit 4c includes, for example, an acceleration sensor in three axial directions, ie, the up-down direction of the mobile object 4 and two mutually orthogonal directions in a plane perpendicular to the up-down direction.

The propulsion mechanism 4d is configured to provide a propulsive force to the moving body 4 under the control of the control unit 4a. The propulsion mechanism 4d includes a propeller (not shown) and a drive source (not shown) that drives the propeller. The propulsion mechanism 4d may be a so-called screw configuration that obtains propulsive force by rotating the propeller to paddle the water, or may be a so-called water jet propulsion mechanism that obtains propulsive force by ejecting a high-pressure water flow backward.

<Arrangement of Potential Difference Sensor and Magnetic Sensor>
Next, the arrangement of the potential difference sensor 1 and the magnetic sensor 2 in the mobile object 4 will be described with reference to FIG.

As shown in FIG. 3, the potential difference sensor 1 includes a pair of electrodes. Specifically, the potential difference sensor 1 includes a first electrode 1a and a second electrode 1b as the pair of electrodes. The potential difference sensor 1 is configured to detect the potential difference between the first electrode 1a and the second electrode 1b.

The pair of potential difference sensors 1 (first electrode 1a and second electrode 1b) are arranged on the moving body 4 so as to be aligned vertically at a predetermined interval. The magnetic sensor 2 is provided at a position between the pair of electrodes. That is, the first electrode 1a and second electrode 1b and the magnetic sensor 2 are arranged so as to be aligned vertically at a predetermined interval. In other words, the first electrode 1a and second electrode 1b and the magnetic sensor 2 are arranged on the moving body 4 so that their positions in the traveling direction of the moving body 4 are approximately equal.

Acquiring a reference magnetic signal
Next, a configuration in which the undersea structure detection system 100 (see FIG. 1) acquires the reference magnetic signal 20 (see FIG. 2) will be described with reference to FIG. 4.

The submarine structure detection system 100 is configured to acquire the reference magnetic signal 20, for example, when the submarine structure 90 is laid. Specifically, the submarine structure detection system 100 acquires the reference magnetic signal 20 by detecting the magnetism emitted from the submarine structure 90 while moving the mobile body 4. At this time, the distance acquired by the distance sensor provided on the mobile body 4 is stored as the reference distance 21 together with the reference magnetic signal 20 in the memory unit 11 (see FIG. 2).

The submarine structure detection system 100 also acquires the reference magnetic signal 20 after the submarine structure 90 has been laid and before damage 6a (see FIG. 1) occurs to the corrosion protection layer 6 of the submarine structure 90.

Detection of undersea structures and damage to anticorrosive layers
Next, referring to Figure 5, a configuration in which the processor 10 detects the presence or absence of an undersea structure 90 (see Figure 1), and a configuration in which the processor 10 detects the presence or absence of damage 6a (see Figure 1) in the corrosion protection layer 6 (see Figure 1) will be described.

As shown in FIG. 5, the processor 10 has a submarine structure detection unit 10a, a damage detection unit 10b, and a signal correction unit 10c as functional blocks. In other words, the processor 10 functions as the submarine structure detection unit 10a, the damage detection unit 10b, and the signal correction unit 10c by executing a program stored in the memory unit 11.

In this embodiment, the submarine structure detection system 100 acquires the electric field signal 30 and the magnetic signal 31 while moving the mobile body 4 (see FIG. 1). Therefore, the electric field signal 30 and the magnetic signal 31 may change depending on the attitude of the mobile body 4. Therefore, in this embodiment, the signal correction unit 10c is configured to correct the attitude of the mobile body 4 for the magnetic signal 31 and the electric field signal 30 based on the mobile body information 22. Specifically, the signal correction unit 10c acquires information on the acceleration and attitude of the mobile body 4 by acquiring the mobile body information 22 from the mobile body information acquisition unit 12. Then, the signal correction unit 10c acquires the corrected electric field signal 30a by performing a filter process and an orthogonality correction process on the electric field signal 30 using the acquired information on the acceleration and attitude of the mobile body 4. That is, the signal correction unit 10c performs a correction process on the electric field signal 30 to convert the coordinate system of the potential difference sensor 1 into an absolute coordinate system in the horizontal and vertical directions. This allows the signal correction unit 10c to obtain corrected electric field signals 30a in two directions that are perpendicular to each other in the vertical direction and in the horizontal plane.

The signal correction unit 10c also uses the acquired acceleration and attitude information of the moving body 4 to perform filter processing and orthogonality correction processing on the magnetic signal 31 to acquire a corrected magnetic signal 31a. That is, the signal correction unit 10c performs a correction process on the magnetic signal 31 to convert the coordinate system of the magnetic sensor 2 into an absolute coordinate system in the horizontal and vertical directions. This allows the signal correction unit 10c to acquire corrected magnetic signals 31a in two directions that are orthogonal to each other in the vertical direction and in the horizontal plane. The signal correction unit 10c outputs the corrected electric field signal 30a to the damage detection unit 10b. The signal correction unit 10c also outputs the corrected magnetic signal 31a to the submarine structure detection unit 10a and the damage detection unit 10b.

The submarine structure detection unit 10a is configured to detect the presence or absence of a submarine structure 90 based on the magnetic signal 31 output by the magnetic sensor 2. In this embodiment, the submarine structure detection unit 10a is configured to detect the presence or absence of a submarine structure 90 based on the corrected magnetic signal 31a, which is the magnetic signal 31 after attitude correction has been performed by the signal correction unit 10c.

The submarine structure detection unit 10a acquires the corrected magnetic signal 31a acquired by the signal correction unit 10c. The submarine structure detection unit 10a determines whether or not a submarine structure 90 (see FIG. 1) is present based on the amplitude 51 (see FIG. 7(B)) of the corrected magnetic signal 31a. Specifically, the submarine structure detection unit 10a determines that a submarine structure 90 is present when the amplitude 51 of the corrected magnetic signal 31a is equal to or greater than a predetermined magnitude. The submarine structure detection unit 10a also determines that a submarine structure 90 is not present when the amplitude 51 of the corrected magnetic signal 31a is smaller than the predetermined magnitude.

When the submarine structure detection unit 10a determines that a submarine structure 90 is present, it acquires the depth position 25 (see FIG. 6) of the submarine structure 90 based on the reference magnetic signal 20 and the magnetic signal 31. In this embodiment, the submarine structure detection unit 10a acquires the reference magnetic signal 20 and the reference distance 21 from the memory unit 11. The submarine structure detection unit 10a acquires the depth position 25 of the submarine structure 90 using the reference magnetic signal 20, the reference distance 21, and the corrected magnetic signal 31a.

(Detecting the depth position of undersea structures)
Next, referring to Fig. 6, a configuration in which the submarine structure detection unit 10a (see Fig. 2) acquires the depth position 25 of the submarine structure 90 will be described. In this embodiment, the submarine structure detection unit 10a is configured to detect the depth position 25 of the submarine structure 90 based on the magnitude of the magnetic signal 31 (see Fig. 2). Specifically, the submarine structure detection unit 10a is configured to detect the depth position 25 of the submarine structure 90 based on the amplitude 50 (see Fig. 7(A)) of the waveform of the reference magnetic signal 20 (see Fig. 2), the reference distance 21 (see Fig. 2), and the amplitude 51 (see Fig. 7(B)) of the magnetic signal 31.

Here, it is known that the magnitude of the magnetic signal 31 is inversely proportional to the cube of the distance between the submarine structure 90 and the mobile body 4. Therefore, by comparing the amplitude 50 of the reference distance 21 with the amplitude 51 of the magnetic signal 31, it is possible to obtain the ratio of the reference distance 21 to the distance 23 between the submarine structure 90 and the mobile body 4, and therefore the distance 23 between the submarine structure 90 and the mobile body 4 can be obtained.

The submarine structure detection unit 10a (see FIG. 2) also obtains the distance 24 from the sea surface 81 to the mobile body 4 based on a depth gauge provided on the mobile body 4. The submarine structure detection unit 10a then obtains the depth position 25 of the submarine structure 90 by adding the distance 23 between the submarine structure 90 and the mobile body 4 and the distance 24 from the sea surface 81 to the mobile body 4. In other words, the depth position 25 of the submarine structure 90 is the distance from the sea surface 81 to the submarine structure 90.

Referring again to FIG. 5, the submarine structure detection unit 10a outputs a first detection result 40a, which is a detection result of the presence or absence of a submarine structure 90, to the notification unit 14. In this embodiment, when the submarine structure detection unit 10a determines that a submarine structure 90 is present, it outputs a message to the notification unit 14 that the submarine structure 90 has been detected as the first detection result 40a. When the submarine structure detection unit 10a determines that a submarine structure 90 is not present, it outputs a message to the notification unit 14 that the submarine structure 90 has not been detected as the first detection result 40a. When a submarine structure 90 is present, the submarine structure detection unit 10a also outputs the depth position 25 of the submarine structure 90 as the first detection result 40a.

The damage detection unit 10b is configured to detect the presence or absence of damage 6a (see FIG. 1) in the corrosion protection layer 6 (see FIG. 1) based on the magnetic signal 31 and the electric field signal 30 output by the potential difference sensor 1.

The damage detection unit 10b is configured to detect the presence or absence of damage 6a in the corrosion protection layer 6 based on the magnetic component caused by the current flowing between the location where the damage 6a occurred in the corrosion protection layer 6 of the submarine structure 90 and the corrosion protection layer 6, and the component of the current included in the electric field signal 30. Specifically, the damage detection unit 10b is configured to acquire the magnetic component caused by the current based on the reference magnetic signal 20 and the magnetic signal 31. In this embodiment, the damage detection unit 10b acquires the corrected electric field signal 30a and the corrected magnetic signal 31a acquired by the signal correction unit 10c. The damage detection unit 10b is configured to detect the presence or absence of damage 6a in the corrosion protection layer 6 based on the corrected magnetic signal 31a and the corrected electric field signal 30a, which is the electric field signal 30 after the attitude correction is performed by the signal correction unit 10c.

When the submarine structure detection unit 10a determines that a submarine structure 90 is present, the damage detection unit 10b determines whether or not there is damage 6a in the corrosion protection layer 6 provided on the submarine structure 90. Specifically, the damage detection unit 10b detects the presence or absence of damage 6a based on the corrected electric field signal 30a output by the signal correction unit 10c, the corrected magnetic signal 31a output by the signal correction unit 10c, and the reference magnetic signal 20 stored in the memory unit 11.

In this embodiment, the corrosion protection layer 6 is formed of a metal with a different ionization tendency from the metal that constitutes the undersea structure 90. Therefore, if there is damage 6a in the corrosion protection layer 6, a current flows from the damage 6a to the corrosion protection layer 6 as shown by arrow 7 (see FIG. 1) based on the difference in ionization tendency. In this case, a magnetism is generated due to the current flowing from the damage 6a to the corrosion protection layer 6. The magnetic sensor 2 (see FIG. 1) outputs a magnetic signal 31 including the magnetism generated due to the current flowing from the damage 6a to the corrosion protection layer 6.

Here, the magnetic signal 31 contains noise caused by geomagnetic components, etc., in addition to magnetic components caused by the current flowing from the damage 6a to the corrosion protection layer 6. In a state in which noise is included, it is difficult to distinguish the magnetic field caused by the current flowing from the damage 6a to the corrosion protection layer 6. Therefore, in this embodiment, the damage detection unit 10b is configured to detect the presence or absence of damage 6a in the corrosion protection layer 6 based on a differential magnetic signal 32 (see FIG. 7(C)), which is a signal obtained by subtracting the reference magnetic signal 20 from the magnetic signal 31. The damage detection unit 10b acquires the differential magnetic signal 32, which is the difference between the corrected magnetic signal 31a and the reference magnetic signal 20.

In this embodiment, the damage detection unit 10b is configured to detect the presence or absence of damage 6a in the corrosion protection layer 6 based on the first peak 60 (see FIG. 7(C)) of the differential magnetic signal 32 and the second peak 62 (see FIG. 8(B)) of the electric field signal 30. Specifically, the damage detection unit 10b determines whether or not there is damage 6a based on whether or not the differential magnetic signal 32 includes a first peak 60 based on magnetism caused by a current flowing from the damage 6a to the corrosion protection layer 6.

In addition, in this embodiment, the damage detection unit 10b is configured to detect the position of the damage 6a in the corrosion protection layer 6 based on a first acquisition position 61 (see FIG. 7(C)), which is the acquisition position of the first peak 60, and a second acquisition position 63 (see FIG. 8(B)), which is the acquisition position of the second peak 62. Specifically, the damage detection unit 10b acquires the first acquisition position 61 based on the time when detection of the damage 6a started and the travel distance of the mobile body 4 when the first peak 60 was acquired. Furthermore, the damage detection unit 10b acquires the second acquisition position 63 based on the time when detection of the damage 6a started and the travel distance of the mobile body 4 when the second peak 62 was acquired.

When the damage detection unit 10b detects damage 6a in the anticorrosion layer 6, the damage detection unit 10b acquires a message indicating that the damage 6a exists in the anticorrosion layer 6 as the second detection result 40b. When the damage 6a exists in the anticorrosion layer 6, the damage detection unit 10b acquires the position of the damage 6a as the second detection result 40b. When the damage 6a does not exist in the anticorrosion layer 6, the damage detection unit 10b acquires a message indicating that the damage 6a does not exist in the anticorrosion layer 6 as the second detection result 40b. The damage detection unit 10b outputs the acquired second detection result 40b to the notification unit 14. When there is no submarine structure 90, the damage detection unit 10b does not determine whether or not the damage 6a exists in the anticorrosion layer 6, and therefore does not acquire the second detection result 40b. In other words, when there is no submarine structure 90, the damage detection unit 10b does not output the second detection result 40b to the notification unit 14.

The notification unit 14 displays the first detection result 40a input from the submarine structure detection unit 10a. When the second detection result 40b is input from the damage detection unit 10b, the notification unit 14 displays the second detection result 40b together with the first detection result 40a.

<Signal waveforms>
Next, the magnetic signal 31 detected by the magnetic sensor 2 and the electric field signal 30 detected by the potential difference sensor 1 will be described with reference to Fig. 7 and Fig. 8. Note that the example shown in Fig. 7 is a conceptual diagram, and in reality, the magnetic signal 31 includes noise such as geomagnetism. The example shown in Fig. 8 is also a conceptual diagram, and in reality, the electric field signal 30 includes noise such as potential difference in the surrounding environment.

Figure 7 (A) is a graph 70 showing a reference magnetic signal 20 that was acquired in advance and stored in the memory unit 11 (see Figure 2). In the graph 70, the vertical axis represents the magnetic force, and the horizontal axis represents the distance traveled by the moving object 4 (see Figure 1).

The reference magnetic signal 20 shown in graph 70 is a magnetic signal detected by the magnetic sensor 2 (see FIG. 1) at the reference distance 21 (see FIG. 2). In other words, the reference magnetic signal 20 is a signal acquired when there is no damage 6a (see FIG. 1) in the corrosion protection layer 6 (see FIG. 1), and therefore does not include a peak due to the damage 6a.

Figure 7 (B) is a graph 71 showing the corrected magnetic signal 31a output by the magnetic sensor 2 (see Figure 1) and corrected by the signal correction unit 10c (see Figure 5). In the graph 71, the vertical axis is the magnetic force, and the horizontal axis is the moving distance of the moving body 4 (see Figure 1). The example shown in Figure 7 (B) is the corrected magnetic signal 31a when the corrosion protection layer 6 (see Figure 1) has a damage 6a (see Figure 1). Therefore, the corrected magnetic signal 31a shown in Figure 7 (B) includes a first peak 60, which is a magnetic component caused by the current flowing from the damage 6a to the corrosion protection layer 6. The first peak 60 includes a positive first peak 60a and a negative first peak 60b. The positive first peak 60a is a peak that appears at the position of the start point of the current flowing from the damage 6a to the corrosion protection layer 6. The negative first peak 60b is a peak that appears at the position of the end point of the current flowing from the damage 6a to the corrosion protection layer 6.

Figure 7 (C) is a graph 72 showing the differential magnetic signal 32 acquired by the undersea structure detection unit 10a (see Figure 5). In the graph 72, the vertical axis is magnetic force, and the horizontal axis is the moving distance of the moving body 4 (see Figure 1). The differential magnetic signal 32 includes a first peak 60, which is a magnetic component caused by the current flowing from the damage 6a (see Figure 1) to the corrosion protection layer 6 (see Figure 1). In addition, since the differential magnetic signal 32 is a signal obtained by subtracting the reference magnetic signal 20 from the corrected magnetic signal 31a (see Figure 5), noise caused by the geomagnetism around the undersea structure 90 (see Figure 1) is removed. In other words, the differential magnetic signal 32 is a signal with a high SNR (signal noise ratio) of the magnetic component (first peak 60) caused by the current flowing from the damage 6a to the corrosion protection layer 6.

Figure 8 (A) is a graph 73 showing the electric field signal 30b when there is no damage 6a (see Figure 1) in the corrosion protection layer 6 (see Figure 1). In the graph 73, the vertical axis represents the magnetic force, and the horizontal axis represents the distance traveled by the moving body 4 (see Figure 1). When there is no damage 6a, no current flows from the submarine structure 90. Therefore, the electric field signal 30b shown in the graph 73 is a signal that does not include a peak.

Figure 8 (B) shows the corrected electric field signal 30a when there is damage 6a (see Figure 1) in the corrosion protection layer 6 (see Figure 1). In the graph 74, the vertical axis is magnetic force, and the horizontal axis is the moving distance of the moving body 4 (see Figure 1). When there is damage 6a, a current flows from the damage 6a to the corrosion protection layer 6. Therefore, the electric field signal 30b includes a second peak 62 caused by the current flowing from the damage 6a to the corrosion protection layer 6. The second peak 62 includes a positive second peak 62a and a negative second peak 62b. The positive second peak 62a is a peak that appears at the position of the start point of the current flowing from the damage 6a to the corrosion protection layer 6. The negative second peak 62b is a peak that appears at the position of the end point of the current flowing from the damage 6a to the corrosion protection layer 6.

When damage 6a exists in the corrosion protection layer 6, a first peak 60 (see FIG. 7(C)) caused by a current flowing from the damage 6a to the corrosion protection layer 6 is detected, and a second peak 62 is also detected. Because the potential difference sensor 1 and the magnetic sensor 2 are moved together by the moving body 4 (see FIG. 1), the position of the damage 6a in the corrosion protection layer 6 can be obtained based on the position of the first peak 60 (first acquisition position 61 (see FIG. 7(C))) and the position of the second peak 62 (second acquisition position 63).

The first acquisition position 61 includes a first acquisition position 61a corresponding to the positive first peak 60a and a first acquisition position 61b corresponding to the negative first peak 60b. Therefore, the damage detection unit 10b can obtain the start and end points of the current flowing between the corrosion protection layer 6 and the damage 6a (the surface of the submarine structure 90) by obtaining the first acquisition position 61a corresponding to the positive first peak 60a and the first acquisition position 61b corresponding to the negative first peak 60b.

The second acquisition position 63 also includes a second acquisition position 63a corresponding to the positive second peak 62a and a second acquisition position 63b corresponding to the negative second peak 62b. Therefore, the damage detection unit 10b can acquire the start and end points of the current flowing between the corrosion protection layer 6 and the damage 6a (the surface of the submarine structure 90) by acquiring the second acquisition position 63a corresponding to the positive second peak 62a and the second acquisition position 63b corresponding to the negative second peak 62b.

<Detection processing of undersea structures>
Next, a process in which the submarine structure detection system 100 detects the presence or absence of the submarine structure 90 will be described with reference to FIG.

In step 101, the submarine structure detection unit 10a (see FIG. 5) acquires the magnetic signal 31 (see FIG. 2) output by the magnetic sensor 2 (see FIG. 1). Specifically, the submarine structure detection unit 10a acquires the corrected magnetic signal 31a (see FIG. 5) corrected by the signal correction unit 10c (see FIG. 5).

In step 102, the submarine structure detection unit 10a (see FIG. 2) determines whether or not the submarine structure 90 (see FIG. 1) has been detected. Specifically, the submarine structure detection unit 10a determines whether or not the submarine structure 90 has been detected based on whether or not the magnitude of the amplitude 51 (see FIG. 7(B)) of the corrected magnetic signal 31a is equal to or greater than a predetermined magnitude. If the submarine structure 90 has been detected, the process proceeds to step 103. If the submarine structure 90 has not been detected, the process proceeds to step 107.

In step 103, the submarine structure detection unit 10a obtains a message indicating that the submarine structure 90 has been detected as the first detection result 40a (see FIG. 5).

In step 104, the undersea structure detection unit 10a acquires the reference magnetic signal 20 (see FIG. 2) stored in the memory unit 11 (see FIG. 2).

In step 105, the submarine structure detection unit 10a acquires the depth position 25 of the submarine structure 90, as shown in FIG. 6.

In step 106, the notification unit 14 (see FIG. 2) notifies the first detection result 40a. Specifically, the notification unit 14 notifies the depth position 25 of the submarine structure 90 and a message that the submarine structure 90 has been detected. The process then ends.

Also, if the process proceeds from step 102 to step 107, in step 107, the submarine structure detection unit 10a obtains a message indicating that the submarine structure 90 was not detected as the first detection result 40a.

In step 108, the notification unit 14 notifies the first detection result 40a. Specifically, the notification unit 14 notifies a message that the submarine structure 90 was not detected. The process then ends. The submarine structure detection unit 10a repeats the processes of steps 101 to 108 at a predetermined interval.

Next, referring to FIG. 10, the process in which the submarine structure detection system 100 detects the presence or absence of damage 6a (see FIG. 1) in the corrosion protection layer 6 (see FIG. 1) provided on the submarine structure 90 (see FIG. 1) will be described. The process shown in FIG. 10 is executed when it is determined in the process shown in FIG. 9 that a submarine structure 90 is present. That is, when the process shown in FIG. 10 starts, the processor 10 (see FIG. 2) has acquired the magnetic signal 31 (see FIG. 2) and the reference magnetic signal 20 (see FIG. 2).

In step 200, the damage detection unit 10b (see FIG. 5) acquires the differential magnetic signal 32 (see FIG. 7(C)). Specifically, the damage detection unit 10b acquires the differential magnetic signal 32 based on the difference between the corrected magnetic signal 31a (see FIG. 2) and the reference magnetic signal 20.

In step 201, the damage detection unit 10b acquires the position of the first peak 60 (first acquired position 61 (see FIG. 7(C))). Specifically, the damage detection unit 10b acquires the first acquired position 61 based on the travel distance of the moving body 4 when the first peak 60 is detected.

In step 202, the damage detection unit 10b acquires the electric field signal 30 (see FIG. 2). Specifically, the damage detection unit 10b acquires the corrected electric field signal 30a (see FIG. 5) that has been corrected by the signal correction unit 10c (see FIG. 5).

In step 203, the damage detection unit 10b acquires the position of the second peak 62 (second acquisition position 63 (see FIG. 8(B))). Specifically, the damage detection unit 10b acquires the second acquisition position 63 based on the distance traveled by the moving body 4 when the second peak 62 is detected. Note that the processing of steps 200 and 201 and the processing of steps 202 and 203 may be performed in any order.

In step 204, the damage detection unit 10b determines whether or not a first peak 60 or a second peak 62 is present. Specifically, the damage detection unit 10b determines whether or not a first peak 60 is detected in the differential magnetic signal 32, or whether or not a second peak 62 is detected in the corrected electric field signal 30a. If either the first peak 60 or the second peak 62 is detected, the process proceeds to step 205. If neither the first peak 60 nor the second peak 62 is detected, the process proceeds to step 208.

In step 205, the damage detection unit 10b acquires the position of the damage 6a in the corrosion protection layer 6 based on the peaks. If both the first peak 60 and the second peak 62 are detected, the damage detection unit 10b acquires the position of the damage 6a in the corrosion protection layer 6 based on the first acquisition position 61 and the second acquisition position 63. If only one of the first peak 60 and the second peak 62 is detected, the damage detection unit 10b acquires the position of the damage 6a in the corrosion protection layer 6 based on the acquisition position of either peak.

In step 206, the damage detection unit 10b obtains a message indicating that damage 6a in the corrosion protection layer 6 has been detected as the second detection result 40b (see FIG. 5).

In step 207, the notification unit 14 (see FIG. 5) notifies the second detection result 40b.

If the process proceeds from step 204 to step 208, in step 208, the damage detection unit 10b obtains a message indicating that no damage 6a was detected in the corrosion protection layer 6 as the second detection result 40b. Then, the process proceeds to step 207.

That is, when processing proceeds from step 206 to step 207, a message indicating that damage 6a to the corrosion protection layer 6 has been detected is reported as the second detection result 40b in step 207. Also, when processing proceeds from step 208 to step 207, a message indicating that damage 6a to the corrosion protection layer 6 has not been detected is reported as the second detection result 40b in step 207.

(Effects of this embodiment)
In this embodiment, the following effects can be obtained.

In this embodiment, as described above, the submarine structure detection system 100 is a submarine structure detection system that detects a metallic submarine structure 90 provided on the seabed 80 and detects the presence or absence of damage 6a in a corrosion protection layer 6 that is provided on the submarine structure 90 and is formed of a metal having a different ionization tendency from that of the submarine structure 90. The system includes a potential difference sensor 1 that detects the potential difference caused by the current flowing between the submarine structure 90 and the corrosion protection layer 6, a magnetic sensor 2 that detects the magnetism in the sea, a submarine structure detection unit 10a that detects the presence or absence of the submarine structure 90 based on a magnetic signal 31 output by the magnetic sensor 2, and a damage detection unit 10b that detects the presence or absence of damage 6a in the corrosion protection layer 6 based on the magnetic signal 31 and the electric field signal 30 output by the potential difference sensor 1.

As a result, the submarine structure detection system 100 includes a submarine structure detection unit 10a that detects the presence or absence of a submarine structure 90 using the magnetic signal 31 output by the magnetic sensor 2, and thus can detect the presence or absence of a submarine structure 90 by acquiring the magnetic signal 31. The submarine structure detection system 100 also includes a damage detection unit 10b that detects the presence or absence of damage 6a in the corrosion protection layer 6 using the magnetic signal 31 output by the magnetic sensor 2 and the electric field signal 30 output by the potential difference sensor 1 that detects the potential difference caused by the current flowing between the submarine structure 90 and the corrosion protection layer 6. As a result, unlike a configuration that detects the presence or absence of damage 6a in the corrosion protection layer 6 using only the magnetic signal 31, the presence or absence of damage 6a in the corrosion protection layer 6 can be detected using both the magnetic signal 31 generated due to the current flowing between the submarine structure 90 and the corrosion protection layer 6 and the electric field signal 30 based on the potential difference caused by the current flowing between the submarine structure 90 and the corrosion protection layer 6. Therefore, compared to a configuration that detects the presence or absence of damage 6a in the corrosion protection layer 6 using only the magnetic signal 31, the presence or absence of damage 6a in the corrosion protection layer 6 can be detected with high accuracy. As a result, it is possible to provide a submarine structure detection system 100 that can detect the presence or absence of a submarine structure 90 and can accurately detect the presence or absence of damage 6a in the corrosion protection layer 6 provided on the submarine structure 90.

In addition, the above embodiment has the following additional advantages:

That is, in this embodiment, as described above, the damage detection unit 10b is configured to detect the presence or absence of damage 6a in the corrosion protection layer 6 based on the magnetic component caused by the current flowing between the location of the damage 6a in the corrosion protection layer 6 of the submarine structure 90 and the corrosion protection layer 6, and the current component included in the electric field signal 30. As a result, the damage detection unit 10b detects the presence or absence of damage 6a in the corrosion protection layer 6 based on the magnetic component caused by the current flowing between the location of the damage 6a in the corrosion protection layer 6 and the corrosion protection layer 6, and the current component included in the electric field signal 30. Therefore, the detection accuracy of the damage 6a in the corrosion protection layer 6 can be improved compared to a configuration in which the damage 6a in the corrosion protection layer 6 is detected using only one of the magnetic signal 31 and the electric field signal 30.

In addition, as described above, this embodiment further includes a memory unit 11 that stores the previously acquired reference magnetic signal 20, and the damage detection unit 10b is configured to acquire the magnetic component caused by the current based on the reference magnetic signal 20 and the magnetic signal 31. As a result, even if the magnetic signal 31 contains noise such as geomagnetic field, the magnetic component caused by the current flowing between the location where the damage 6a of the corrosion protection layer 6 has occurred and the corrosion protection layer 6 can be easily acquired. As a result, it is possible to suppress a decrease in the detection accuracy of the damage 6a of the corrosion protection layer 6 caused by noise such as geomagnetic field.

In addition, in this embodiment, as described above, the damage detection unit 10b is configured to detect the presence or absence of damage 6a in the corrosion protection layer 6 based on the first peak 60 of the differential magnetic signal 32, which is a signal obtained by subtracting the reference magnetic signal 20 from the magnetic signal 31, and the second peak 62 of the electric field signal 30. This makes it possible to detect the presence or absence of damage 6a in the corrosion protection layer 6 based on whether or not the first peak 60 is included in the differential magnetic signal 32 and whether or not the second peak 62 is included in the electric field signal 30. As a result, the presence or absence of damage 6a in the corrosion protection layer 6 can be easily detected.

In addition, in this embodiment, as described above, the damage detection unit 10b is configured to detect the position of the damage 6a in the corrosion protection layer 6 based on the first acquisition position 61, which is the acquisition position of the first peak 60, and the second acquisition position 63, which is the acquisition position of the second peak 62. As a result, by acquiring the first acquisition position 61 and the second acquisition position 63, the position of the damage 6a in the corrosion protection layer 6 can be easily acquired.

In addition, in this embodiment, as described above, the memory unit 11 is configured to store the reference distance 21, which is the distance between the magnetic sensor 2 and the submarine structure 90 when the reference magnetic signal 20 is acquired, and the submarine structure detection unit 10a is configured to detect the depth position 25 of the submarine structure 90 based on the amplitude 50 of the waveform of the reference magnetic signal 20, the reference distance 21, and the amplitude 51 of the magnetic signal 31. As a result, even if the submarine structure 90 is buried in sand on the seabed 80 and cannot be seen, for example, it is possible to acquire the depth position 25 of the submarine structure 90, so that the position of the submarine structure 90 can be acquired with high accuracy.

In addition, in this embodiment, as described above, the magnetic sensor 2 and the potential difference sensor 1 are provided, and the mobile body 4 capable of moving underwater is further provided. This allows the magnetic sensor 2 and the potential difference sensor 1 to be moved together. Therefore, when there is damage 6a in the corrosion protection layer 6, the detection timing of the first peak 60 in the magnetic signal 31 and the detection timing of the second peak 62 in the electric field signal 30 become approximately equal. As a result, for example, compared to a configuration in which the magnetic sensor 2 and the potential difference sensor 1 are moved separately, the position of the damage 6a in the corrosion protection layer 6 can be easily obtained based on the positions of the first peak 60 and the second peak 62.

In addition, in this embodiment, as described above, the potential difference sensor 1 includes a pair of electrodes (first electrode 1a and second electrode 1b), and the pair of potential difference sensors 1 are arranged vertically at a predetermined interval on the moving body 4, and the magnetic sensor 2 is provided at a position between the pair of electrodes. This allows the pair of electrodes and the magnetic sensor 2 to be arranged in a direction perpendicular to the traveling direction of the moving body 4. Therefore, for example, when detection is performed while moving the moving body 4 along the direction in which the submarine structure 90 extends, the pair of electrodes and the magnetic sensor 2 can be easily arranged in a position perpendicular to the submarine structure 90. As a result, the position of the first peak 60 and the position of the second peak 62 can be made approximately equal, so that the position of the damage 6a in the corrosion protection layer 6 can be obtained even more easily.

In addition, in this embodiment, as described above, the mobile body information acquisition unit 12 that acquires mobile body information 22 including information on the acceleration and attitude of the mobile body 4, and the signal correction unit 10c that corrects the attitude of the mobile body 4 for the magnetic signal 31 and the electric field signal 30 based on the mobile body information 22 are further provided. The submarine structure detection unit 10a is configured to detect the presence or absence of a submarine structure 90 based on the corrected magnetic signal 31a, which is the magnetic signal 31 after the attitude correction by the signal correction unit 10c, and the damage detection unit 10b is configured to detect the presence or absence of damage 6a in the anticorrosion layer 6 based on the corrected magnetic signal 31a and the corrected electric field signal 30a, which is the electric field signal 30 after the attitude correction by the signal correction unit 10c. As a result, it is possible to detect the presence or absence of a submarine structure 90 and the presence or absence of damage 6a in the anticorrosion layer 6 without correcting the attitude of the mobile body 4. Therefore, unlike a configuration in which the presence or absence of an undersea structure 90 and the presence or absence of damage 6a in the anticorrosion layer 6 are detected while correcting the attitude of the mobile body 4, the presence or absence of an undersea structure 90 and the presence or absence of damage 6a in the anticorrosion layer 6 can be detected without controlling the attitude of the mobile body 4. As a result, it is possible to improve the degree of freedom of movement of the mobile body 4, and therefore the degree of freedom of detection of the presence or absence of the undersea structure 90 and the presence or absence of damage 6a in the anticorrosion layer 6 can be improved.

In addition, in this embodiment, as described above, the moving body 4 is provided with the magnetic sensor 2, the potential difference sensor 1, and a propulsion mechanism 4d that provides a propulsive force to the moving body 4, and is configured to be able to travel underwater. This allows for an improved degree of freedom of movement of the moving body 4 compared to a configuration in which the moving body 4 is moved by being towed by a ship 5, for example.

In addition, in this embodiment, as described above, the submarine structure 90 is a pipeline installed on the seabed 80, the submarine structure detection unit 10a is configured to determine the presence or absence of a pipeline, the damage 6a in the corrosion protection layer 6 is corrosion of the corrosion protection layer 6, and the damage detection unit 10b is configured to detect the presence or absence of corrosion of the pipeline. This makes it possible to provide a submarine structure detection system 100 that is suitable for detecting the presence or absence of a pipeline and the presence or absence of corrosion of the pipeline.

(Modification)
It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the description of the embodiments above, and further includes all modifications (variations) within the meaning and scope of the claims.

For example, in the above embodiment, an example of a configuration in which the damage detection unit 10b acquires a magnetic component caused by a current based on the reference magnetic signal 20 and the magnetic signal 31 and detects the presence or absence of damage 6a in the corrosion protection layer 6 is shown, but the present invention is not limited to this. For example, the damage detection unit 10b may be configured to detect the presence or absence of damage 6a in the corrosion protection layer 6 without using the reference magnetic signal 20.

In addition, in the above embodiment, an example of a configuration in which the damage detection unit 10b acquires the differential magnetic signal 32 has been shown, but the present invention is not limited to this. For example, the damage detection unit 10b does not need to acquire the differential magnetic signal 32. However, if the damage detection unit 10b does not acquire the differential magnetic signal 32, the accuracy of detecting the presence or absence of damage 6a in the corrosion protection layer 6 decreases due to noise such as geomagnetism. Therefore, it is preferable to configure the damage detection unit 10b to acquire the differential magnetic signal 32.

In addition, in the above embodiment, an example of a configuration in which the submarine structure detection unit 10a acquires the depth position 25 of the submarine structure 90 has been shown, but the present invention is not limited to this. For example, the submarine structure detection unit 10a does not need to acquire the depth position 25 of the submarine structure 90.

In the above embodiment, an example was shown in which the mobile body 4 is configured to be capable of autonomous travel, but the present invention is not limited to this. For example, the mobile body 4 may be configured to move through the sea by being towed by a ship 5.

In the above embodiment, an example of a configuration in which the submarine structure detection system 100 includes a signal correction unit 10c has been shown, but the present invention is not limited to this. For example, the submarine structure detection system 100 does not need to include a signal correction unit 10c. However, if the submarine structure detection system 100 does not include a signal correction unit 10c, the detection accuracy of the presence or absence of a submarine structure 90 and the detection accuracy of the presence or absence of damage 6a in the corrosion protection layer 6 will decrease. Therefore, it is preferable that the submarine structure detection system 100 includes a signal correction unit 10c.

In addition, in the above embodiment, an example of a configuration in which the computer 3 and the mobile object 4 communicate via wireless communication is shown, but the present invention is not limited to this. For example, the computer 3 and the mobile object 4 may be connected by wire and configured to perform wired communication.

In addition, in the above embodiment, an example of a configuration in which the damage detection unit 10b determines that there is damage 6a in the corrosion protection layer 6 when either the first peak 60 or the second peak 62 is detected is shown, but the present invention is not limited to this. For example, the damage detection unit 10b may be configured to determine that there is damage 6a in the corrosion protection layer 6 when both the first peak 60 and the second peak 62 are detected.

In the above embodiment, for convenience of explanation, an example was shown in which the control processing of the submarine structure detection unit 10a and the control processing of the damage detection unit 10b were explained using a flow-driven flowchart in which the processing is performed in sequence according to a processing flow, but the present invention is not limited to this. In the present invention, the control processing of the submarine structure detection unit 10a and the control processing of the damage detection unit 10b may be performed by event-driven processing in which processing is performed on an event-by-event basis. In this case, the processing may be completely event-driven, or event-driven and flow-driven may be combined.

[Aspects]
It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

(Item 1)
A submarine structure detection system for detecting a metallic submarine structure provided on the seabed and detecting the presence or absence of damage to a corrosion protection layer provided on the submarine structure and formed of a metal having a different ionization tendency from that of the metal constituting the submarine structure, comprising:
a potential difference sensor that detects a potential difference caused by a current flowing between the submarine structure and the corrosion protection layer; and
A magnetic sensor that detects underwater magnetism;
a submarine structure detection unit that detects the presence or absence of the submarine structure based on the magnetic signal output by the magnetic sensor;
a damage detection unit that detects the presence or absence of damage to the corrosion protection layer based on the magnetic signal and the electric field signal output by the potential difference sensor.

(Item 2)
2. The submarine structure detection system according to claim 1, wherein the damage detection unit is configured to detect the presence or absence of damage to the corrosion protection layer based on a magnetic component caused by the current flowing between a location of the submarine structure where damage has occurred in the corrosion protection layer and the corrosion protection layer, and a component of the current included in the electric field signal.

(Item 3)
A storage unit that stores a reference magnetic signal obtained in advance is further provided,
3. The undersea structure detection system according to claim 2, wherein the damage detection unit is configured to acquire the magnetic component caused by the current based on the reference magnetic signal and the magnetic signal.

(Item 4)
4. The submarine structure detection system according to item 3, wherein the damage detection unit is configured to detect the presence or absence of damage to the corrosion protection layer based on a first peak of a differential magnetic signal, which is a signal obtained by subtracting the reference magnetic signal from the magnetic signal, and a second peak of the electric field signal.

(Item 5)
5. The submarine structure detection system according to item 4, wherein the damage detection unit is configured to detect a position of damage to the corrosion protection layer based on a first acquisition position that is an acquisition position of the first peak and a second acquisition position that is an acquisition position of the second peak.

(Item 6)
the storage unit is configured to store a reference distance that is a distance between the magnetic sensor and the submarine structure when the reference magnetic signal is acquired,
6. The submarine structure detection system according to any one of items 3 to 5, wherein the submarine structure detection unit is configured to detect a depth position of the submarine structure based on the amplitude of a waveform of the reference magnetic signal, the reference distance, and the amplitude of the magnetic signal.

(Item 7)
7. The undersea structure detection system according to any one of items 1 to 6, further comprising a mobile body that is provided with the magnetic sensor and the potential difference sensor and is movable underwater.

(Item 8)
The potential difference sensor includes a pair of electrodes;
the pair of potential difference sensors are provided on the moving body so as to be aligned vertically at a predetermined interval;
8. The undersea structure detection system according to claim 7, wherein the magnetic sensor is provided at a position between a pair of the electrodes.

(Item 9)
a mobile object information acquisition unit that acquires mobile object information including information on the acceleration and attitude of the mobile object;
a signal correction unit that corrects the attitude of the moving body for the magnetic signal and the electric field signal based on the moving body information,
the submarine structure detection unit is configured to detect the presence or absence of the submarine structure based on a corrected magnetic signal, which is the magnetic signal after the attitude correction has been performed by the signal correction unit,
9. The submarine structure detection system according to item 7 or 8, wherein the damage detection unit is configured to detect the presence or absence of damage to the corrosion protection layer, based on the corrected magnetic signal and a corrected electric field signal, which is the electric field signal after attitude correction has been performed by the signal correction unit.

(Item 10)
The submarine structure detection system according to any one of items 7 to 9, wherein the moving body is provided with the magnetic sensor, the potential difference sensor, and a propulsion mechanism that provides a propulsive force to the moving body, and is configured to be capable of traveling underwater.

(Item 11)
the submarine structure is a pipeline installed on the seabed,
The submarine structure detection unit is configured to determine the presence or absence of the pipeline,
the damage to the anticorrosion layer is corrosion of the anticorrosion layer,
11. The submarine structure detection system according to any one of claims 1 to 10, wherein the damage detection unit is configured to detect the presence or absence of corrosion of the pipeline.

1 Potential difference sensor 1a First electrode (pair of electrodes)
1b Second electrode (a pair of electrodes)
2 Magnetic sensor 4 Mobile body 4d Propulsion mechanism 6 Corrosion protection layer 6a Damage 10a Submarine structure detection unit 10b Damage detection unit 10c Signal correction unit 12 Mobile body information acquisition unit 20 Reference magnetic signal 21 Reference distance 25 Depth position 30 Electric field signal 30a Corrected electric field signal 31 Magnetic signal 31a Corrected magnetic signal 32 Differential magnetic signal 50 Amplitude of reference magnetic signal 51 Amplitude of magnetic signal 60, 60a, 60b First peak 61, 61a, 61b First acquisition position 62, 62a, 62b Second peak 63, 63a, 63b Second acquisition position 80 Seabed 90 Submarine structure (pipeline)
100 Submarine structure detection system

Claims (11)

A submarine structure detection system for detecting a metallic submarine structure provided on the seabed and detecting the presence or absence of damage to a corrosion protection layer provided on the submarine structure and formed of a metal having a different ionization tendency from that of the metal constituting the submarine structure, comprising:
a potential difference sensor that detects a potential difference caused by a current flowing between the submarine structure and the corrosion protection layer; and
A magnetic sensor that detects underwater magnetism;
a submarine structure detection unit that detects the presence or absence of the submarine structure based on the magnetic signal output by the magnetic sensor;
a damage detection unit that detects the presence or absence of damage to the corrosion protection layer based on the magnetic signal and the electric field signal output by the potential difference sensor. The submarine structure detection system according to claim 1, wherein the damage detection unit is configured to detect the presence or absence of damage to the anticorrosion layer based on a magnetic component caused by the current flowing between the location of the anticorrosion layer of the submarine structure where damage has occurred and the anticorrosion layer, and a component of the current included in the electric field signal. A storage unit that stores a reference magnetic signal obtained in advance is further provided,
The submarine structure detection system according to claim 2 , wherein the damage detection unit is configured to acquire the magnetic component caused by the electric current based on the reference magnetic signal and the magnetic signal. The submarine structure detection system according to claim 3, wherein the damage detection unit is configured to detect the presence or absence of damage to the corrosion protection layer based on a first peak of a differential magnetic signal, which is a signal obtained by subtracting the reference magnetic signal from the magnetic signal, and a second peak of the electric field signal. The submarine structure detection system according to claim 4, wherein the damage detection unit is configured to detect the position of damage to the anticorrosion layer based on a first acquisition position that is the acquisition position of the first peak and a second acquisition position that is the acquisition position of the second peak. the storage unit is configured to store a reference distance that is a distance between the magnetic sensor and the submarine structure when the reference magnetic signal is acquired,
The undersea structure detection system according to any one of claims 3 to 5, wherein the undersea structure detection unit is configured to detect the depth position of the undersea structure based on the amplitude of the waveform of the reference magnetic signal, the reference distance, and the amplitude of the magnetic signal. The undersea structure detection system according to any one of claims 1 to 6, further comprising a mobile body that is provided with the magnetic sensor and the potential difference sensor and is capable of moving underwater. The potential difference sensor includes a pair of electrodes;
the pair of potential difference sensors are provided on the moving body so as to be aligned vertically at a predetermined interval;
The undersea structure detection system according to claim 7 , wherein the magnetic sensor is provided at a position between a pair of the electrodes. a mobile object information acquisition unit that acquires mobile object information including information on the acceleration and attitude of the mobile object;
a signal correction unit that corrects the attitude of the moving body for the magnetic signal and the electric field signal based on the moving body information,
the submarine structure detection unit is configured to detect the presence or absence of the submarine structure based on a corrected magnetic signal, which is the magnetic signal after the attitude correction has been performed by the signal correction unit,
9. The submarine structure detection system according to claim 7 or 8, wherein the damage detection unit is configured to detect the presence or absence of damage to the corrosion protection layer based on the corrected magnetic signal and a corrected electric field signal, which is the electric field signal after attitude correction has been performed by the signal correction unit. The undersea structure detection system according to any one of claims 7 to 9, wherein the moving body is provided with the magnetic sensor, the potential difference sensor, and a propulsion mechanism that provides a propulsive force to the moving body, and is configured to be capable of traveling underwater. the submarine structure is a pipeline installed on the seabed,
The submarine structure detection unit is configured to determine the presence or absence of the pipeline,
the damage to the anticorrosion layer is corrosion of the anticorrosion layer,
The submarine structure detection system according to any one of claims 1 to 10, wherein the damage detection unit is configured to detect the presence or absence of corrosion of the pipeline.

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