Autonomous unmanned submersible

Abstract

An autonomous unmanned underwater vehicle (1) according to one embodiment of the present invention comprises: a position detector (9) which detects a position relative to an underwater structure (10); a propelling device (22); and a control device (7) which controls the propelling device (22) and recognizes the position of the AUV (1). The AUV (1) further comprises: an underwater electric potential sensor for three-dimensionally measuring an underwater electric potential gradient; and a metal electric potential sensor for inspecting an electric field-forming body which is a part of the underwater structure (10) or is a sacrificial anode. The control device (7): identifies the position of the electric field-forming body by mapping an underwater electric field from the electric potential gradient measured by the underwater electric potential sensor in association with the movement of the AUV (1); controls the propelling device (22) such that the AUV (1) moves to and stops at an inspection position where the metal electric potential sensor opposes the electric field-forming body; and causes the metal electric potential sensor to inspect the electric field-forming body in that state.

Description

[Technical Field]

[0001] The present disclosure relates to autonomous underwater vehicles. [Background technology]

[0002] Conventionally, cathodic protection using sacrificial anodes has been used for underwater structures made of steel. Such sacrificial anodes generate an electric field in the water. An electric field is also generated in the water when paint peeling or corrosion occurs on the steel that makes up the underwater structure.

[0003] For example, Patent Document 1 discloses a method for determining the wear state of a sacrificial anode and the state of corrosion and coating deterioration of steel materials by two-dimensionally measuring the underwater potential gradient on a plane perpendicular to the surface of an underwater structure and plotting the results in a three-dimensional graph. Patent Document 1 also describes that the underwater potential gradient may be measured using a remotely operated underwater vehicle (ROV). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-72458 Summary of the Invention [Problem to be solved by the invention]

[0005] When using an ROV, the operator operates the ROV while viewing the video captured by the camera mounted on the ROV. Therefore, even if an ROV is used to inspect an electric field generator, such as a sacrificial anode or exposed or corroded metal part of steel, if the water is too turbid to see the electric field generator in the camera video, it is difficult to get the ROV close to the electric field generator for inspection. Furthermore, using an ROV requires an offshore support vessel and workers, which increases costs.

[0006] In contrast, using an autonomous underwater vehicle (AUV) allows for the inspection of electromagnets regardless of the turbidity of the water, and does not require an offshore support vessel.

[0007] Therefore, an object of the present disclosure is to provide an autonomous unmanned underwater vehicle that can inspect an electric field generating body. [Means for solving the problem]

[0008] The present disclosure provides an autonomous unmanned submersible vessel (AUV) comprising: a position detector that detects its relative position with respect to an underwater structure; a propulsion unit; a control unit that controls the propulsion unit so that the AUV moves along the underwater structure based on the detection results of the position detector and that determines the position of the AUV; an underwater potential sensor that measures the underwater potential gradient in three dimensions; and a metal potential sensor that inspects an electric field generator that is a part of the underwater structure or a sacrificial anode, wherein the control unit identifies the position of the electric field generator by mapping the underwater electric field from the potential gradient measured by the underwater potential sensor as the AUV moves, and controls the propulsion unit so that the AUV moves to and stops at an inspection position where the metal potential sensor faces the electric field generator, and in that state has the metal potential sensor inspect the electric field generator. [Effects of the Invention]

[0009] In accordance with the present disclosure, an autonomous underwater vehicle capable of inspecting electric field forming bodies is provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a side view of an autonomous underwater vehicle according to one embodiment. [Figure 2] FIG. 2 is a perspective view of a carriage and an inspection unit. [Figure 3] FIG. 2 is a side view of the carriage and the inspection unit. [Figure 4] FIG. 10 is a rear view of the carriage and the inspection unit. [Figure 5]5A and 5B are diagrams illustrating an image of an electric field when the sacrificial electrode is cylindrical and surrounds a submarine pipeline, where FIG. 5A is a diagram viewed from the side of the pipeline and FIG. 5B is a cross-sectional view taken along line VB-VB in FIG. 5A. [Figure 6] 1 is an image of the electric field when a sacrificial electrode is installed at a position away from the submarine pipeline. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1 shows an autonomous underwater vehicle (AUV) 1 ​​according to one embodiment. The AUV 1 moves along an underwater structure 10. In this embodiment, the underwater structure 10 is a submarine pipeline. However, the underwater structure 10 does not necessarily have to be a submarine pipeline and may be, for example, a bridge pier.

[0012] Specifically, the AUV 1 includes a main body 21 having a streamlined shape and a propulsion unit 22 provided on the main body 21. In this embodiment, movable vertical and horizontal stabilizers are provided at the rear of the main body 21 as a rudder for changing course and altitude, but the rudder is not limited to this. Note that if the course and altitude can be changed using only the propulsion unit 22, the rudder may be omitted and fixed wings may be provided to stabilize the attitude of the main body 21.

[0013] The propulsion device 22 can apply thrust to the main body 21 in the front-to-rear, left-to-right, and up-down directions of the main body 21, as well as a rotational force in the yaw direction about the up-down axis of the main body 21 and in the pitch direction about the left-to-right axis of the main body 21. For example, the propulsion device 22 may include multiple thrusters oriented in different directions, or may be a single oscillating thruster.

[0014] A position detector 9 is provided at the front of the main body 21, and a control device 7 and an inertial navigation system (INS) 8 are provided inside the main body 21.

[0015] The position detector 9 detects the relative position with respect to the underwater structure 10. In this embodiment, the position detector 9 is a sonar that emits an acoustic beam to obtain position information of the underwater structure 10. However, the position detector 9 may also be a laser range finder that emits a light beam.

[0016] The control device 7 controls the propulsion device 22 based on the detection result of the position detector 9 so that the main body 21 moves along the underwater structure 10. In other words, the main body 21 moves so as to follow the underwater structure 10, which is the submarine pipeline, while maintaining a constant distance to the underwater structure 10.

[0017] With respect to the control device 7, the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, application-specific integrated circuits (ASICs), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0018] The inertial navigation system 8 includes an accelerometer that detects acceleration in the direction in which each of three mutually perpendicular axes extends, and a gyro sensor that detects angular velocity around each of the three axes, and calculates the direction and distance of movement of the main body 21 from a reference position, as well as the current attitude of the main body 21.

[0019] Based on the moving direction and moving distance of the main body 21 from the reference position calculated by the inertial navigation system 8, the control device 7 calculates and grasps the position (longitude, latitude, depth) of the main body 21 in the geographic coordinate system.

[0020] An arm 23 is attached to the underside of the main body 21 via a drive mechanism 24. The drive mechanism 24 includes a first drive unit 25 that rotates the arm 23 about the vertical axis of the main body 21, and a second drive unit 26 that swings the arm 23 about the horizontal axis of the main body 21. The first drive unit 25 and the second drive unit 26 are controlled by the control device 7 in accordance with the relative position of the main body 21 with respect to the underwater structure 10 and the current attitude of the main body 21.

[0021] The cart 3 is connected to the tip of the arm 23 via a coupler 27. The coupler 27 connects the cart 3 to the tip of the arm 23 so that the arm 23 can swing around the left-right axis and the up-down axis of the cart 3. An inspection unit 4 is attached to the cart 3.

[0022] 2 to 4, the carriage 3 includes a plate-shaped base 31 parallel to the underwater structure 10, and a cover 32 covering the front of the base 31. Two pairs of wheels 35 that roll on the underwater structure 10 are attached to the base 31 via brackets 34 and mounting seats 33. In this embodiment, since the underwater structure 10 is a submarine pipeline with a circular cross section, each wheel 35 is inclined at about 45 degrees relative to the up-down direction of the carriage 3.

[0023] The inspection unit 4 includes an underwater potential sensor 5 that measures the potential gradient in water in three dimensions, a metal potential sensor 6 (not shown in Figure 4) that inspects an electric field generator which is part of an underwater structure 10 (exposed metal part or corroded part) or a sacrificial electrode 11 (see Figures 5A, 5B or Figure 6), and a support that supports the underwater potential sensor 5 and the metal potential sensor 6.

[0024] The sacrificial electrode 11 may be cylindrical and surround the submarine pipeline, which is the underwater structure 10, as shown in Figures 5A and 5B, or may be installed at a location away from the submarine pipeline, as shown in Figure 6. The sacrificial electrode 11 generates an electric field as shown in Figures 5A and 5B or 6. Even if the paint peels off or corrosion occurs on the submarine pipeline, the exposed metal or corroded part will generate an electric field as shown in Figures 5A and 5B.

[0025] The underwater electric potential sensor 5 includes a first reference electrode 51, a second reference electrode 52, and a third reference electrode 53 located on the surface facing the underwater structure 10, and a fourth reference electrode 54 located above the facing surface. The second reference electrode 52 is located on the facing surface away from the first reference electrode 51 in a first direction X, and the third reference electrode 53 is located on the facing surface away from the first reference electrode 51 in a second direction Y perpendicular to the first direction X. The fourth reference electrode 54 is located on the facing surface away from the first reference electrode 51 in a third direction perpendicular to the first direction X and the second direction Y. The first to fourth reference electrodes 51 to 54 are electrochemical electrodes, and examples of electrochemical electrodes include a silver / silver chloride electrode and a saturated calomel electrode.

[0026] In this embodiment, since the underwater structure 10 is a submarine pipeline, the first direction X is the axial direction of the submarine pipeline, and the second direction Y is a horizontal direction perpendicular to the axial direction of the submarine pipeline. In addition, in the portion of the submarine pipeline that is parallel to the horizontal plane, the third direction Z is a vertical direction.

[0027] The metal potential sensor 6 tests an electric field generator by measuring the potential of the metal that generates the electric field. The metal potential sensor 6 is composed of a metal tip and a reference electrode for establishing metal conductivity with the test object. The shorter the distance between the liquid junction between the metal tip and the reference electrode, the higher the accuracy of the test.

[0028] Next, the control performed by the control device 7 will be explained in more detail. First, the control device 7 identifies the position of the electric field generator by mapping the underwater electric field from the potential gradient measured by the underwater electric potential sensor 5 as the AUV 1 moves. Next, the control device 7 controls the propulsion device 22 so that the AUV 1 moves to and stops at the inspection position where the metal potential sensor 6 faces the electric field generator, and then has the metal potential sensor 6 inspect the electric field generator in that state.

[0029] As described above, in the AUV 1 of this embodiment, the underwater electric potential sensor 5 measures the electric potential gradient in water in three dimensions, making it possible to identify the position of the electric field generator. Furthermore, once the position of the electric field generator is identified, the control device 7 controls the AUV 1 to autonomously move to the inspection position and autonomously inspect it. Therefore, the AUV 1 can be used to inspect the electric field generator.

[0030] (Variation) The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present disclosure.

[0031] For example, the control device 7 may control the propulsion device 22 to slow down the speed of the AUV 1 when the distance from the AUV 1 to the electrostatic field generator falls below a predetermined value. With this configuration, the slowing down of the AUV 1 allows the underwater potential gradient to be measured at finer distance intervals, making it possible to accurately identify the position of the electrostatic field generator.

[0032] (summary) In a first aspect, the present disclosure provides an autonomous unmanned submersible vessel (AUV), comprising: a position detector that detects its relative position with respect to an underwater structure; a propulsion device; a control device that controls the propulsion device so that the AUV moves along the underwater structure based on the detection results of the position detector and that determines the position of the AUV; an underwater potential sensor that measures the underwater potential gradient in three dimensions; and a metal potential sensor that inspects an electric field generator that is a part of the underwater structure or a sacrificial anode, wherein the control device maps the underwater electric field from the potential gradient measured by the underwater potential sensor as the AUV moves, identifies the position of the electric field generator, and controls the propulsion device so that the AUV moves to and stops at an inspection position where the metal potential sensor faces the electric field generator, and then has the metal potential sensor inspect the electric field generator in that state.

[0033] With the above configuration, the underwater electric potential sensor measures the underwater electric potential gradient three-dimensionally, making it possible to identify the position of the electric field generator. Furthermore, once the position of the electric field generator is identified, the control device controls the electric field generator to autonomously move to the inspection position and perform the inspection. Therefore, the electric field generator can be inspected using an autonomous underwater vehicle.

[0034] As a second aspect, in the first aspect, for example, the underwater potential sensor may include a first reference electrode, a second reference electrode positioned on the surface facing the underwater structure away from the first reference electrode in a first direction, a third reference electrode positioned on the facing surface away from the first reference electrode in a second direction perpendicular to the first direction, and a fourth reference electrode positioned away from the first reference electrode in a third direction perpendicular to the first and second directions.

[0035] As a third aspect, in the second aspect, for example, the underwater structure may be a submarine pipeline, and the first direction may be an axial direction of the submarine pipeline.

[0036] As a fourth aspect, in any of the first to third aspects, the control device may control the propulsion device to reduce the speed of the autonomous unmanned underwater vehicle when the distance from the autonomous unmanned underwater vehicle to the electric field generating device falls below a predetermined value. With this configuration, the reduction in the speed of the autonomous unmanned underwater vehicle allows the underwater electric potential gradient to be measured at fine distance intervals, thereby enabling the position of the electric field generating device to be accurately identified.

Claims

1. An autonomous underwater vehicle, a position detector for detecting a relative position with respect to the underwater structure; a propulsion device; a control device that controls the propulsion device so that the autonomous unmanned underwater vehicle moves along the underwater structure based on the detection results of the position detector, and that determines the position of the autonomous unmanned underwater vehicle; an underwater potential sensor that measures the potential gradient in water three-dimensionally; a metal potential sensor for inspecting an electric field forming body that is a part of the underwater structure or a sacrificial anode; The control device identifies the position of the electric field generator by mapping the underwater electric field from the potential gradient measured by the underwater electric potential sensor as the autonomous unmanned underwater vehicle moves, controls the propulsion device so that the autonomous unmanned underwater vehicle moves to and stops at an inspection position where the metal potential sensor faces the electric field generator, and has the metal potential sensor inspect the electric field generator in that state.

2. 2. The autonomous unmanned underwater vehicle according to claim 1, wherein the underwater electric potential sensor comprises: a first reference electrode; a second reference electrode located on a surface facing the underwater structure and spaced apart from the first reference electrode in a first direction; a third reference electrode located on the facing surface and spaced apart from the first reference electrode in a second direction orthogonal to the first direction; and a fourth reference electrode located on the facing surface and spaced apart from the first reference electrode in a third direction orthogonal to the first and second directions.

3. The autonomous underwater vehicle according to claim 2 , wherein the underwater structure is a submarine pipeline, and the first direction is an axial direction of the submarine pipeline.

4. 4. The autonomous unmanned underwater vehicle according to claim 1, wherein the control device controls the propulsion device so that the speed of the autonomous unmanned underwater vehicle decreases when the distance from the autonomous unmanned underwater vehicle to the electric field generating device becomes equal to or less than a predetermined value.

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