Submersible and method for estimating position of specific point of pipeline

Abstract

A submersible according to one aspect of the present invention is provided with: a hull that is capable of navigating underwater; a propulsion system that generates thrust for allowing the hull to navigate; a camera that is installed in the hull and that captures an image of a water bottom including a pipeline; a sonar that is installed in the hull and that detects the contour of the water bottom; and a control device that controls the propulsion system. The control device acquires the image of the water bottom from the camera, acquires the contour of the water bottom from the sonar, extracts a pair of contour lines corresponding to both end edges of the pipeline in the width direction from the image of the water bottom, extracts a pipeline contour constituting the contour of a portion of the contour of the water bottom between the pair of contour lines, and estimates the position of a specific point of the pipeline on the basis of the shape of the pipeline contour extracted.

Description

Method for estimating specific point positions of submersible vehicles and pipelines

[0001] The present disclosure relates to a method for estimating the position of a specific point on an underwater vehicle and a pipeline.

[0002] Patent Document 1 listed below discloses an autonomous unmanned underwater vehicle that detects the contour of the top surface of a submarine pipeline using a contour detector such as a profiling sonar, extracts an ellipse approximated by a group of points estimated to constitute the contour of the top surface of the submarine pipeline, and calculates the position coordinates of the uppermost point of the extracted ellipse as the position of a specific point, in order to determine the direction in which an underwater pipeline extends.

[0003] Japanese Patent Application Laid-Open No. 2022-158359

[0004] When detecting the contour of the water bottom to estimate the position of a specific point, such as the top point of a pipeline, if there are obstacles such as rocks around the pipeline, the contour of the obstacle may be recognized as part of the pipeline's contour, and the position of the specific point on the pipeline may not be estimated correctly.On the other hand, a method can be considered to estimate the position of a specific point on a pipeline from images taken with a camera.However, because distance cannot be obtained from images taken with a camera, the position of the specific point on the pipeline cannot be estimated correctly.

[0005] Therefore, an object of the present disclosure is to provide an underwater vehicle and a method for estimating the position of a specific point on a pipeline that can accurately estimate the position of the specific point on the pipeline.

[0006] A submersible vehicle according to one aspect of the present disclosure comprises a hull capable of navigating underwater, a propulsion system that generates thrust for propelling the hull, a camera installed on the hull that images the bottom of the water including a pipeline, a sonar installed on the hull that detects the contours of the bottom of the water, and a control device that controls the propulsion system. The control device acquires an image of the bottom of the water from the camera and acquires the contour of the bottom of the water from the sonar, extracts a pair of outlines corresponding to both widthwise edges of the pipeline from the image of the bottom of the water, extracts a pipeline outline which is the outline of the portion of the bottom contour that falls between the pair of outlines, and estimates the position of a specific point of the pipeline based on the shape of the extracted pipeline outline.

[0007] A method for estimating the position of a specific point on a pipeline according to one aspect of the present disclosure extracts a pair of outlines corresponding to both widthwise edges of the pipeline from an image of the bottom of the water including the pipeline captured by a camera, extracts a pipeline outline, which is the outline of the portion of the bottom of the water detected by sonar that is between the pair of outlines, and estimates the position of the specific point on the pipeline based on the shape of the extracted pipeline outline.

[0008] According to the above configuration and method, the position of a specific point in a pipeline can be estimated with high accuracy.

[0009] Fig. 1 is a side view of the submersible vehicle. Fig. 2 is a plan view of the submersible vehicle. Fig. 3 is a block diagram of the control system of the submersible vehicle. Fig. 4 is a flow diagram of a specific point position estimation program. Fig. 5(a) is a diagram showing an example of an image of the bottom of the water, and Fig. 5(b) is a diagram showing an image of a pair of outlines extracted from Fig. 5(a). Fig. 6(a) is a diagram showing an example of the contour of the bottom of the water, and Fig. 6(b) is a diagram showing an image obtained by superimposing Fig. 5(b) and Fig. 6(a).

[0010] (Overall Configuration) An embodiment will now be described. First, the overall configuration of the submersible vehicle 100 will be described. Fig. 1 is a side view of the submersible vehicle 100, and Fig. 2 is a plan view of the submersible vehicle 100. The submersible vehicle 100 according to this embodiment is an autonomous underwater vehicle (AUV). However, the submersible vehicle 100 is not limited to an autonomous underwater vehicle.

[0011] The submersible vehicle 100 according to this embodiment travels along a pipeline 101 laid on the seabed while collecting position data of the pipeline 101 and performing non-contact inspections. Note that the "seabed" includes the bottom of the ocean and the bottom of a lake. The submersible vehicle 100 according to this embodiment estimates the position of a specific point, such as the highest point of the pipeline 101. Once the highest point of the pipeline 101 is known, the submersible vehicle 100 can travel along the pipeline 101.

[0012] 1, the submersible vehicle 100 includes a hull 11, a propulsion system 12, a camera 13, and a sonar 14. These components will be described below in order.

[0013] <Hull> The hull 11 is configured to be able to navigate underwater. In Fig. 1, the left and right sides of the paper are the front and rear of the hull 11, respectively, and the top and bottom of the paper are the top and bottom of the hull 11, respectively. Furthermore, in Fig. 2, the left and right sides of the paper are the front and rear of the hull 11, respectively, and the top and bottom of the paper are the right and left sides of the hull 11, respectively. Under normal circumstances, the hull 11 navigates forward. When the hull 11 navigates along the pipeline 101, the fore-and-aft direction of the hull 11 and the extension direction of the pipeline 101 are parallel.

[0014] <Propulsion System> The propulsion system 12 generates thrust for propelling the hull 11. As shown in FIG. 1 , the propulsion system 12 includes a main propulsion thruster 31 that generates forward thrust and two horizontal thrusters 32 (front and rear) that apply lateral forces to the hull 11. As shown in FIG. 2 , the propulsion system 12 also includes two vertical thrusters 33 (front and rear) that apply vertical forces to the hull 11. The propulsion system 12 also includes a steering device (not shown) that can change the course of the hull 11. This allows the propulsion system 12 to propel the hull 11 in any direction and at any attitude. However, the propulsion system 12 is not limited to the above configuration and may include, for example, an oscillating thruster that can change the direction of thrust generation in addition to generating thrust.

[0015] <Camera> The camera 13 is a device capable of capturing images of the bottom of the water. In this embodiment, the camera 13 is installed in the front part of the underside of the hull 11, as shown in Fig. 1. Furthermore, as shown in Fig. 2, the camera 13 is located in the center of the hull 11 in the left-right direction. The imaging range of the camera 13 in this embodiment includes the bottom of the water diagonally below and forward of the hull 11. Therefore, when the hull 11 navigates along the pipeline 101, the imaging range of the camera 13 includes the pipeline 101.

[0016] <Sonar> The sonar 14 is a device that acquires information about the bottom of the water using sound waves. The sonar 14 is, for example, a profiling sonar. The sonar 14 of this embodiment can detect the contour of the bottom of the water, including the pipeline 101. As shown in FIG. 1, the sonar 14 is installed in the front part of the underside of the hull 11. Furthermore, as shown in FIG. 2, the sonar 14 is located in the center of the hull 11 in the left-right direction.

[0017] As shown in Fig. 2, the sonar 14 emits acoustic beams 41 radially (in a fan shape) when viewed from above and below. Also, as shown in Fig. 1, the sonar 14 emits each acoustic beam 41 diagonally downward and forward. That is, the sonar 14 emits the acoustic beams 41 toward a portion of the pipeline 101 forward of the hull 11. Therefore, when the hull 11 navigates along the pipeline 101, the detection range of the sonar 14 includes the pipeline 101. In this embodiment, all or part of the imaging range of the camera 13 overlaps with the detection range of the sonar 14.

[0018] The acoustic beam 41 emitted from the sonar 14 is reflected by the bottom of the water (the surface of the bottom of the water and the surface of any objects located on the bottom of the water). The time from when the acoustic beam 41 is emitted until the reflected wave returns to the sonar 14 varies depending on the height of the bottom of the water. Therefore, the contour of the bottom of the water can be detected based on this time. In this embodiment, each point at which the acoustic beam 41 is reflected from the bottom of the water is a detection point, and the contour of the bottom of the water can be detected by connecting the detection results of these detection points. Note that although the sonar 14 in this embodiment detects the contour of the bottom of the water as multiple points (see FIG. 6( a)), the sonar 14 may also detect the contour of the bottom of the water as a line.

[0019] (Configuration of Control System) Next, the configuration of the control system of the submersible vehicle 100 will be described. Fig. 3 is a block diagram of the control system of the submersible vehicle 100 according to this embodiment. As shown in Fig. 3, the submersible vehicle 100 is equipped with a control device 15. The control device 15 of this embodiment is mounted on the submersible vehicle 100. However, part or all of the control device 15 may be mounted on equipment other than the submersible vehicle 100, and the submersible vehicle 100 may be communicably connected to the control device 15 via a network, for example.

[0020] The control device 15 is a device that performs various arithmetic processes and controls various devices. The control device 15 has a processor, a volatile memory, a non-volatile memory, an I / O interface, etc. Various programs including a specific point position estimation program described below are stored in the non-volatile memory of the control device 15, and the processor performs arithmetic processes using the volatile memory based on each program.

[0021] 3, the control device 15 of this embodiment is communicatively connected to the propulsion system 12 and can adjust the attitude, navigation direction, and navigation speed of the hull 11 by sending control signals to the propulsion system 12. The control device 15 is also communicatively connected to the camera 13 and can acquire images captured by the camera 13. The control device 15 is also communicatively connected to the sonar 14 and can acquire the contour of the water bottom from the sonar 14.

[0022] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), 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.

[0023] (Specific Point Position Estimation Program) Next, the specific point position estimation program executed by the control device 15 will be described. FIG. 4 is a flow diagram of the specific point position estimation program. The specific point position estimation program is a program that estimates the position of a specific point of the pipeline 101. In this embodiment, the cross section of the pipeline 101 is circular, and the specific point is the uppermost point (top) of the pipeline 101. However, the specific point is not limited to the uppermost point of the pipeline 101, and may be, for example, the center point of the cross section of the pipeline 101.

[0024] As shown in FIG. 4, when the specific point position estimation program is started, the control device 15 first acquires an image of the water bottom from the camera 13 and acquires the contour of the water bottom from the sonar 14 (step S1).

[0025] Fig. 5(a) is a diagram showing an example of an image of the water bottom acquired by the control device 15 from the camera 13. The image of the water bottom in Fig. 5(a) includes a pipeline 101 as well as an obstacle 102 located near the pipeline 101.

[0026] FIG. 6( a) is a diagram showing an example of the contour of the water bottom acquired by the control device 15 from the sonar 14. FIG. 6( a) also shows a contour image 42, which is an image of the contour of the water bottom. The control device 15 may acquire the contour image 42 as the contour of the water bottom from the sonar 14, or may generate the contour image 42 by imaging the data of the contour of the water bottom acquired from the sonar 14. The black circles in FIG. 6( a) correspond to each detection point of the sonar 14. The left-right position of the black circles in FIG. 6( a) corresponds to the left-right position of the corresponding detection point. The up-down position of the black circles in FIG. 6( a) corresponds to the proximity of the corresponding detection point to the sonar 14, i.e., the up-down position.

[0027] The contour of the water bottom in Figure 6(a) includes two convex portions. Of these, the convex portion in the center in the left-right direction corresponds to the contour of the pipeline 101, and the convex portion to the right of the center in the left-right direction corresponds to the contour of the obstacle 102 (see Figure 5(a)). However, based on only the contour image 42 in Figure 6(a), the control device 15 cannot determine which part of the contour of the water bottom in Figure 6(a) corresponds to the contour of the pipeline 101.

[0028] Next, the control device 15 extracts a pair of outline lines 51 corresponding to both widthwise edges of the pipeline 101 from the image of the water bottom acquired in step S1 (step S2). Figure 5(b) is a diagram showing an image 52 (hereinafter referred to as an "outline line image") of the pair of outline lines 51 extracted from the image shown in Figure 5(a). For example, the boundary between the object and the background may be detected from the difference in brightness between adjacent parts in the image of the water bottom shown in Figure 5(a), and the detected boundary may be approximated by a least squares method to obtain a straight line as the outline line 51.

[0029] Next, the control device 15 extracts a pipeline contour 43 corresponding to the contour of the pipeline 101 from the contour of the water bottom acquired in step S1 (step S3). In this embodiment, the control device 15 extracts the contour of the portion of the water bottom contour acquired in step S1 that falls between the pair of outline lines 51 as the pipeline contour 43. Specifically, as shown in Figure 6(b), the contour image 52 in Figure 5(b) is superimposed on the contour image 42 in Figure 6(a). Then, from the contour of the water bottom in the contour image 42, the contour that falls between the pair of outline lines 51 (the portion formed by the white circle in Figure 6(b)) is extracted as the pipeline contour 43.

[0030] When the contour image 42 and the outline image 52 are superimposed, the relative positions of the two images 42, 52 are adjusted and the sizes of the two images 42, 52 are also adjusted so that the detection range of the sonar 14 in the outline image 52 matches the range of the contour of the water bottom in the contour image 42. In this embodiment, the contour image 42 is moved downward by a predetermined displacement amount and reduced by a predetermined magnification. However, the adjustment of the relative positions and the adjustment of the size described above may be omitted by setting the installation location and angle of view of the camera 13 in advance.

[0031] Next, the control device 15 estimates the position of the specific point of the pipeline 101 (step S4). In this embodiment, the uppermost point position, which is the position of the specific point of the pipeline 101, is estimated based on the shape of the pipeline outline 43 extracted in step S3. Specifically, as shown by the dashed line in FIG. 6(b), an ellipse 44 approximated by the pipeline outline 43 is extracted using the least squares method, and the position of the uppermost point of the extracted ellipse 44 is estimated to be the position of the uppermost point of the pipeline 101. Note that the ellipse 44 may be a circle. After step S4, the process returns to step S1 and repeats each step.

[0032] This concludes the description of the specific point position estimation program. The control device 15 of the submersible vehicle 100 according to this embodiment controls the propulsion system 12 so that the hull 11 passes over the uppermost point of the pipeline 101 estimated by the specific point position estimation program. This allows the submersible vehicle 100 to move along the pipeline 101.

[0033] As described above, in this embodiment, the pipeline contour 43 is extracted from the contour of the bottom of the water using an image of the bottom of the water, and the position of a specific point of the pipeline 101 is estimated based on the extracted pipeline contour 43.Therefore, even if an obstacle 102 is located near the pipeline 101, the position of a specific point of the pipeline 101 can be estimated with high accuracy.

[0034] (Summary) The first item disclosed in this specification is a submersible vehicle comprising a hull capable of navigating underwater, a propulsion system that generates thrust for propelling the hull, a camera installed on the hull that images the bottom of the water including a pipeline, a sonar installed on the hull that detects the contours of the bottom of the water, and a control device that controls the propulsion system, wherein the control device acquires an image of the bottom of the water from the camera and acquires the contour of the bottom of the water from the sonar, extracts a pair of outlines corresponding to both widthwise edges of the pipeline from the image of the bottom of the water, extracts a pipeline outline which is the outline of the portion of the bottom outline that is between the pair of outlines, and estimates the position of a specific point of the pipeline based on the shape of the extracted pipeline outline.

[0035] According to this configuration, the pipeline contour is extracted from the contour of the water bottom, and the position of the specific point is estimated based on the shape of the extracted pipeline contour, so that the position of the specific point on the pipeline can be estimated with high accuracy.

[0036] The second item disclosed in this specification is a submersible vehicle described in the first item, in which the control device superimposes a contour image that visualizes the contour of the bottom of the water with an outline image that is an image of the pair of outline lines, and extracts the contour of the portion of the contour of the bottom of the water that is located between the pair of outline lines as the pipeline contour.

[0037] This configuration allows the pipeline outline to be easily extracted from the contour of the water bottom.

[0038] The third item disclosed in this specification is the submarine vehicle described in the second item, in which the control device, when superimposing the contour image and the outline image, superimposes the contour image and the outline image so that the sonar detection range in the outline image and the range of the contour of the bottom of the water in the contour image coincide.

[0039] According to this configuration, the pipeline contour can be extracted with high precision.

[0040] A fourth item disclosed in this specification is a submersible vehicle described in any one of the first to third items, in which the control device controls the propulsion system so that the hull passes over the estimated specific point position of the pipeline.

[0041] This configuration allows the submersible vehicle to navigate along the pipeline accurately.

[0042] The fifth item disclosed in this specification is a method for estimating the position of a specific point on a pipeline, which involves extracting a pair of outlines corresponding to both widthwise edges of a pipeline from an image of the bottom of the water including the pipeline taken by a camera, extracting a pipeline outline, which is the outline of the portion of the bottom of the water detected by sonar that is between the pair of outlines, and estimating the position of a specific point on the pipeline based on the shape of the extracted pipeline outline.

[0043] According to this method, the pipeline outline is extracted from the contour of the water bottom, and the position of the specific point is estimated based on the shape of the extracted pipeline outline, so that the position of the specific point on the pipeline can be estimated with high accuracy.

[0044] REFERENCE SIGNS LIST 11 hull 12 propulsion system 13 sonar 14 camera 15 control device 42 contour image 43 pipeline contour 51 outer contour 52 outer contour image 100 submersible vehicle 101 pipeline

Claims

1. A submersible vehicle comprising: a hull capable of navigating underwater; a propulsion system that generates thrust for propelling the hull; a camera installed on the hull that images the bottom of the water including a pipeline; a sonar installed on the hull that detects the contours of the bottom of the water; and a control device that controls the propulsion system, wherein the control device acquires images of the bottom of the water from the camera and acquires the contour of the bottom of the water from the sonar, extracts a pair of outlines corresponding to both widthwise edges of the pipeline from the image of the bottom of the water, extracts a pipeline outline which is the outline of the portion of the bottom outline that is between the pair of outlines, and estimates the position of a specific point on the pipeline based on the shape of the extracted pipeline outline.

2. The submersible vehicle described in claim 1, wherein the control device superimposes a contour image that visualizes the contour of the bottom of the water with an outline image that is an image of the pair of outline lines, and extracts the contour of the portion of the contour of the bottom of the water that is located between the pair of outline lines as the pipeline contour.

3. The submersible vehicle described in claim 2, wherein the control device superimposes the contour image and the outline image so that the sonar detection range in the outline image and the range of the contour of the bottom of the water in the contour image coincide.

4. The submersible vehicle according to claim 1, wherein the control device controls the propulsion system so that the hull passes over the estimated specific point position of the pipeline.

5. A method for estimating the position of a specific point on a pipeline, which comprises extracting a pair of outlines corresponding to both widthwise edges of the pipeline from an image of the bottom of the water including the pipeline taken by a camera, extracting a pipeline outline which is the outline of the portion of the bottom of the water detected by sonar that is between the pair of outlines, and estimating the position of a specific point on the pipeline based on the shape of the extracted pipeline outline.

Images