An underwater cluster anchor cable inspection method

Abstract

This invention provides a method for inspecting underwater clustered anchor cables. The inspection vessel unit is equipped with a multi-beam pan-tilt unit, a positioning module, and a communication module. The method includes the following steps: Pre-inspection preparation: acquiring the laying foundation information of the underwater clustered anchor cables in the inspection area, as well as marine environmental data; dividing the inspection area into several inspection zones; conducting inspection work for each inspection zone: adaptive inspection path planning; Inspection scanning: using several inspection vessel units to conduct inspection work according to the initial inspection path, acquiring underwater point cloud data, recording timestamps, and simultaneously recording the position of the inspection vessel unit corresponding to each underwater point cloud data; Point cloud data processing: unifying the underwater point cloud data obtained by the multi-beam pan-tilt unit into a geodetic coordinate system; detecting and identifying the cloud points corresponding to the anchor cables from the scanned point cloud model to obtain a complete anchor cable point cloud model; and analyzing the working status of the anchor cables based on the anchor cable point cloud model.

Description

Technical Field

[0001] This invention relates to the field of underwater engineering inspection technology, and in particular to an inspection method for underwater clustered anchor cables. Background Technology

[0002] In marine engineering fields such as marine ranching, offshore wind power, and deep-sea cage aquariums, clustered anchor cables are the core load-bearing structure ensuring the overall stability of the equipment, and their working condition directly affects the safe operation of marine engineering facilities. Clustered anchor cables operate for extended periods in complex marine environments and are susceptible to damage from factors such as ocean currents, marine organism erosion, entanglement in fishing nets, and abrasion from reefs, resulting in broken wires, corrosion, deformation, and burial. If these damages are not detected and addressed promptly, they may lead to anchor cable failure, potentially causing major safety accidents such as capsizing or drifting of engineering facilities.

[0003] Currently, the main methods for inspecting underwater clustered anchor cables include manual diving inspection, single-beam sonar inspection, and inspection by underwater robots (ROVs) equipped with cameras. Among these, manual diving inspection is greatly limited by environmental factors such as water depth, current, and visibility, resulting in high operational risks, low efficiency, and difficulty in covering large-scale clustered anchor cables. Single-beam sonar inspection can only achieve single-point scanning, with a narrow inspection range and low imaging resolution, making it impossible to comprehensively capture the overall condition and minor damage of the anchor cables. While ROV-equipped camera inspection can obtain intuitive images, it is significantly affected by seawater turbidity, resulting in poor imaging quality in high-turbidity waters. Furthermore, a single ROV can only inspect one or a few anchor cables at a time, making it inefficient for inspecting large-scale clustered anchor cables and unable to meet the inspection needs of clustered marine engineering projects.

[0004] Multibeam sonar technology, with its advantages of wide coverage and high imaging resolution, has been applied in fields such as underwater topographic mapping and target detection. However, when applied to the inspection of underwater clustered anchor cables in marine ranches, several technical bottlenecks remain: First, existing multibeam equipment is mostly fixedly installed on underwater vehicles or large ships. Underwater vehicles have limited endurance and operating range, while large ships have high operating costs and poor flexibility, making them difficult to adapt to the complex nearshore and shallow sea operating environments of marine ranches. Second, there is a lack of adaptive inspection path planning strategies for clustered anchor cables, which easily leads to repeated scanning or missed scanning during the inspection process. Third, in the massive point cloud data collected by multibeam sonar, it is difficult to distinguish anchor cable targets from seabed backgrounds, marine organisms, and other interfering targets, resulting in low damage identification accuracy. Fourth, the inspection range of a single platform carrying multibeam equipment is limited, making it difficult to achieve efficient synchronous inspection of large-scale clustered anchor cables. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an inspection method for underwater cluster anchor cables, which can achieve full coverage, high efficiency, and high precision inspection of underwater cluster anchor cables and accurately identify anchor cable damage.

[0006] To achieve the above objectives, the present invention provides an inspection method for underwater clustered anchor cables, which employs an inspection vessel unit. The inspection vessel unit is equipped with a multi-beam pan-tilt unit, a positioning module, and a communication module. The inspection method includes the following steps:

[0007] S1. Preparations before the inspection:

[0008] S11. Obtain the laying foundation information of underwater cluster anchor cables in the inspection area; obtain marine environmental data of the inspection area;

[0009] S12. Based on the laying foundation information of underwater cluster anchor cables and marine environmental data, the inspection area is divided into several inspection zones.

[0010] S2. Conduct inspection work for each inspection zone, including:

[0011] S21. Adaptive inspection path planning: Based on the laying foundation information of underwater cluster anchor cables and marine environmental data within the inspection zone, and combined with the scanning working range of the multi-beam pan-tilt unit, the initial inspection path is planned. The initial inspection path includes the initial navigation path and the initial scanning path.

[0012] S22, Inspection Scan: Several inspection vessel units are used to carry out inspection work according to the initial inspection path. The multi-beam pan-tilt unit performs underwater scanning to acquire underwater point cloud data and record the timestamp. At the same time, the positioning module records the position of the inspection vessel unit corresponding to each underwater point cloud data.

[0013] S3, Point Cloud Data Processing:

[0014] S31. Combining the timestamp and the location information of the inspection vessel unit, the underwater point cloud data obtained by the multi-beam pan-tilt unit is unified into the geodetic coordinate system to obtain the corresponding scanned point cloud model.

[0015] S32. Detect and identify the cloud points corresponding to the anchor cable from the scanned point cloud model to obtain a complete anchor cable point cloud model.

[0016] S4. Analyze the working status of the anchor cable based on the anchor cable point cloud model.

[0017] Furthermore, in step S21, both the initial navigation path and the initial scanning path include a main scanning path segment that is parallel to the anchor cable's direction on the horizontal plane.

[0018] Furthermore, in step S21, the initial scanning path completely covers the bottom surface of the inspection zone, and the adjacent segments of the initial scanning path overlap in the width direction, with the width of the overlapping area accounting for 15% to 20% of the width of the initial scanning path.

[0019] Furthermore, in step S22, during navigation, the inspection vessel unit adjusts its operation based on the real-time location information and real-time marine environment data obtained by the positioning module, dynamically corrects the actual inspection path, and ensures that the deviation between the actual inspection path and the initial inspection path does not exceed the required value.

[0020] Furthermore, in step S21, a complex scanning area is determined based on the laying foundation information of the underwater cluster anchor cables and marine environmental data within the inspection zone, and a corresponding complex path segment is set in the initial inspection path based on the complex scanning area; in step S22, the inspection vessel unit adopts a fan-shaped scanning strategy in the complex path segment and reduces the navigation speed of the inspection vessel unit to 1~2m / s.

[0021] Furthermore, the inspection vessel unit is equipped with an underwater detection component, which includes an underwater camera and a turbidity sensor. In step S22, based on the actual scanning situation and the turbidity data collected by the underwater detection component, the pitch angle of the multibeam sonar is controlled to place the anchor cable target in the scanning center area, and the power of the multibeam sonar is adjusted. At the same time, the underwater camera simultaneously captures image data of the anchor cable.

[0022] Further, in step S22, during the patrol inspection, the inspection vessel unit determines whether there are seabed obstacles on the navigation path based on marine environmental data and real-time scanning conditions, and determines whether the multi-beam gimbal device in its working state will encounter seabed obstacles, and determines whether to perform an avoidance operation. If avoidance is required, one of the following methods is selected: Method A: Determine whether retracting the multi-beam gimbal device can avoid the seabed obstacle. If so, the inspection vessel unit does not change its navigation path and retracts the multi-beam gimbal device; Method B: Control the navigation path of the inspection vessel unit to avoid the seabed obstacle, while the multi-beam gimbal device continues scanning.

[0023] Furthermore, in step S31, the original point cloud data is first preprocessed, including noise reduction, and a statistical filtering algorithm is used to remove discrete points caused by ocean current interference and measurement noise; then the preprocessed underwater point cloud data is unified into the geodetic coordinate system.

[0024] Furthermore, in step S32, a line detection method based on the RANSAC algorithm is used to accurately find target points that conform to the line model from the scanned point cloud model, extract the line features of the anchor cable, and optimize the extracted anchor cable point cloud through a morphological filtering algorithm to obtain a complete anchor cable point cloud model.

[0025] Preferably, step S4 includes: analyzing the changes in the working state of the anchor cable at different times, including changes in diameter, surface flatness and morphological characteristics, and identifying damage types including wire breakage, corrosion thinning, deformation and burial, based on the anchor cable point cloud model obtained from scanning at different times.

[0026] As described above, the inspection method of the present invention has the following beneficial effects:

[0027] 1. The inspection vessel unit adopts an unmanned surface vessel (USV) equipped with a multi-beam sonar device. USVs have the advantages of flexibility, long endurance, and low operating costs, and can adapt to complex operating environments such as nearshore and shallow seas of marine ranches. Compared with traditional large ships or underwater vehicles, it greatly improves the flexibility and coverage of operations. At the same time, the electric gimbal enables flexible angle adjustment of the multi-beam sonar from 0 to 360° horizontally and from -45° to 90° pitch, which can adapt to the characteristics of scattered and complex anchor cable distribution, effectively eliminating blind spots and achieving full coverage scanning of anchor cables. Furthermore, the collaborative inspection mode of multiple inspection vessel units can further improve the inspection efficiency of large-scale anchor cable clusters, solving the problem of low inspection efficiency of traditional single-platform inspections.

[0028] 2. Based on the laying foundation information of underwater clustered anchor cables (three-dimensional distribution model of clustered anchor cables) and marine environmental data of the inspection area, the improved AI algorithm can adaptively plan the path according to the set requirements. It can achieve accurate planning and dynamic correction of the inspection path, and can also plan assembly points, supply points and emergency shelter areas to ensure the integrity of the inspection coverage. By avoiding ocean currents, strong winds and obstacles, it optimizes inspection efficiency, improves operational safety, and avoids the problems of repeated scanning and missed scanning.

[0029] 3. Through a series of data processing algorithms such as statistical filtering, RANSAC line detection, and morphological filtering, the anchor cable target and interference target can be accurately distinguished, and a complete anchor cable point cloud model can be constructed. It can also be combined with image data collected by underwater cameras for verification. Based on the feature analysis of diameter change, surface flatness and other features displayed by the anchor cable point cloud model, various damage types such as broken wires, corrosion and deformation can be accurately identified, and the damage level can be scientifically assessed, thus improving the accuracy and reliability of damage identification. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the inspection method of the present invention. Detailed Implementation

[0031] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0032] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and objectives of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0033] It should also be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or may be connected to an intermediary component. When a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to the other component through an intermediary component.

[0034] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0035] See Figure 1 This invention provides a method for inspecting underwater clustered anchor cables, wherein the underwater clustered anchor cables can be anchor cables for marine ranches, anchor cables for other marine facilities, or anchor cables for water facilities in lakes or other bodies of water. The inspection method employs an inspection vessel unit, which is equipped with a multi-beam pan-tilt unit, a positioning module, and a communication module, etc. Specifically, the inspection vessel unit includes the following components:

[0036] Unmanned surface vessel (USV): It has a propulsion system that provides power for navigation. It can navigate autonomously according to control commands, allowing it to travel along a calculated path. It can also be remotely controlled via a communication module.

[0037] Multibeam gimbal device: fixed in the middle of the deck of the unmanned vessel, including an electric gimbal and a multibeam sonar. The electric gimbal drives the multibeam sonar to rotate, preferably with the ability to achieve angle adjustment in the horizontal range of 0~360° and the pitch range of -45°~90°.

[0038] Positioning module: may include one or more of the following: shipborne GNSS positioning system, ultra-short baseline (USBL) positioning system and inertial navigation system (INS), which can achieve accurate positioning of the unmanned vessel itself and underwater targets.

[0039] Communication module: Used to communicate with the water control center, and can achieve two-way data interaction through wireless communication (5G / BeiDou) and underwater acoustic communication.

[0040] Underwater detection components include an underwater camera and a turbidity sensor. The underwater camera is used to take underwater pictures while the inspection vessel is navigating, and the turbidity sensor is used to detect water turbidity, which can be used to assist in verifying anchor cable damage and collecting marine environmental parameters.

[0041] The inspection method of the present invention includes the following steps:

[0042] S1. Preparations before the inspection:

[0043] S11. Obtain the foundation information for the underwater cluster of anchor cables in the inspection area; obtain marine environmental data for the inspection area. The foundation information specifically includes the number, distribution location, direction, length, diameter, anchor coordinates, and laying depth of the anchor cables. This information can be determined based on the design and laying scheme of the cluster of anchor cables. Preferably, a three-dimensional distribution model of the cluster of anchor cables is established based on this information to provide a clear and intuitive understanding of the underwater cluster of anchor cables. The marine environmental data for the inspection area includes water depth, current velocity, current direction, seawater turbidity, wind speed and direction, and seabed topography data.

[0044] S12. Based on the laying foundation information of underwater cluster anchor cables and marine environmental data, the inspection area is divided into several inspection zones.

[0045] Specifically, a three-dimensional distribution model of the underwater anchor cables can be established based on the laying foundation information, combined with marine environmental data. The area can be divided according to the principle of facilitating unified work in inspection zones. Each inspection zone should be non-overlapping and complete, filling the entire inspection area. The size of each inspection zone can be determined based on its inspection workload. Simultaneously, marine environmental data can be referenced, grouping locations with similar or identical marine environmental data into the same inspection zone. Each inspection zone includes several anchor cables, and all anchor cables are located within their corresponding inspection zone, without spanning multiple inspection zones. This way, the inspection vessel unit does not need to cross zones when completely scanning an anchor chain.

[0046] S13. Pre-inspection debugging: Debug various functions of the inspection vessel unit, including parameter calibration of the multibeam sonar, angle accuracy test of the electric gimbal, positioning accuracy verification of the positioning module, autonomous navigation performance test of the unmanned vessel, and stability test of the communication link.

[0047] S2. Conduct inspection work for each inspection zone. The inspection work for each inspection zone is the same, including:

[0048] S21. Adaptive Inspection Path Planning: Based on the basic information of underwater cluster anchor cable laying and marine environmental data within the inspection zone, and combined with the scanning working range of the multi-beam sonar, the initial inspection path is planned. The initial inspection path includes the initial navigation path and the initial scanning path. The initial navigation path is the navigation route of the inspection vessel unit, and the initial scanning path is the path formed by the inspection vessel unit controlling the multi-beam sonar to scan the seabed area. The width of the initial scanning path at a certain point is determined by the conical beam width of the multi-beam sonar and the water depth at that point (which determines the distance from the sonar to the seabed). The initial scanning path is generally parallel to the initial navigation path on the horizontal plane, but there may be a slight deviation.

[0049] In this invention, the planning of the initial navigation path and the initial scanning path can be carried out in the following ways depending on whether the scan needs to completely cover the inspection area: 1) Full coverage method: The initial scanning path formed by the operation of the inspection vessel unit covers the entire bottom surface of the inspection area. At this time, the initial navigation path and the initial scanning path can be S-shaped (i.e., back-and-forth navigation) or spiral-shaped (similar to a mosquito coil). The spacing between adjacent segments in the initial navigation path is determined according to the water depth (i.e., the distance from the seabed to the sonar) and the width of the conical beam of the multibeam sonar, so that there is a certain overlap area between adjacent segments in the width direction in the initial scanning path, and the width of the overlap area accounts for 15% to 20% of the width of the initial scanning path, that is, the overlap rate is 15% to 20%. 2) Partial Coverage Method: If the number, location, and length of anchor cables within the inspection zone are determined, and there is no need to consider whether there will be any omissions, the initial navigation path and initial scanning path can be planned based on the number, location, and length of anchor cables within the inspection zone. This ensures that the initial scanning path mainly covers the location of the anchor cables and a certain area around them, that is, all anchor chains are within the scope of the initial scanning path, while other underwater locations without anchor chains can be left unscanned.

[0050] In this embodiment, preferably, the initial inspection path when above the anchor chain position is parallel to the direction of the anchor cable, that is, both the initial navigation path and the initial scanning path include a main scanning path segment that is parallel to the direction of the anchor cable on the horizontal plane, so that the anchor cable can be scanned clearly.

[0051] As a preferred design, when planning the initial navigation path and initial scanning path, the complex scanning area is determined based on the laying foundation information of the underwater cluster anchor cables and marine environmental data within the inspection zone. The complex scanning area refers to the area with complex conditions that requires key scanning, including areas where anchor cables turn, intersect, or approach the anchor. Correspondingly, based on the complex scanning area, a corresponding complex path segment is set in the initial inspection path, and the subsequent inspection vessel unit needs to pay attention to key scanning when navigating in the complex path segment.

[0052] In this embodiment, as a preferred design, an AI algorithm is used to plan the initial navigation path and initial scanning path for the initial inspection route. The input includes the underwater cluster anchor cable laying foundation information and marine environmental data within the inspection zone. Combined with operational boundary requirements, the anchor cable orientation is used as the core constraint. Other constraints include navigation distance and time requirements, the inspection vessel unit avoiding risk areas as much as possible (risk areas are defined based on marine environmental data), and an overlap rate of 15%~20%. The AI ​​algorithm automatically iteratively calculates and plans the initial navigation path and initial scanning path to meet these requirements, ensuring a main scanning path segment along the anchor cable orientation. Simultaneously, based on conditions such as the maximum working range of the inspection vessel unit, the assembly point, resupply point, and emergency refuge area for the inspection vessel unit can be planned and recorded in the unmanned surface vessel's control system. This system can automatically control the unmanned surface vessel to navigate to the assembly point, resupply point, and emergency refuge area.

[0053] When planning the initial inspection path and initial scanning path of the inspection vessel unit, the path of multiple inspection vessel units operating simultaneously can be considered. In this case, the initial inspection path and initial scanning path can be composed of multiple separate paths, or they can be a complete and continuous path. In subsequent actual inspections, different inspection vessel units are responsible for different sections of the path.

[0054] S22. Inspection Scan: Several inspection vessel units are used to conduct inspection work according to the initial inspection path. The multi-beam gimbal device performs underwater scanning to acquire underwater point cloud data. Simultaneously, the positioning module records the position of the inspection vessel unit corresponding to each underwater point cloud data, along with the corresponding time and heading, using the time as the timestamp for the underwater point cloud data. At this point, the underwater point cloud data includes not only anchor cable point cloud data but also point cloud data of underwater topography and various other objects on the underwater surface. Preferably, the multi-beam sonar acquisition frequency of the multi-beam gimbal device is 10~20Hz, and the sampling accuracy is 1cm.

[0055] As a preferred design, during navigation, the inspection vessel unit adjusts its course based on real-time position information and marine environmental data acquired by the positioning module, dynamically correcting the actual inspection path to ensure that the deviation between the actual and initial inspection paths does not exceed the required value. Specifically, the real-time marine environmental data can be obtained from other existing marine monitoring systems or from a corresponding marine monitoring system installed on the inspection vessel unit, including information such as wind direction and speed, and water current direction and speed. The position information of the inspection vessel unit acquired in real-time by the positioning module is compared with the initial navigation path to determine if any deviation has occurred. When the deviation exceeds the preset initial navigation path by more than the required value, for example, more than 3 meters, the power and heading of the inspection vessel unit are adjusted accordingly based on wind direction and speed, and water current direction and speed, so that the deviation between the actual and initial navigation paths does not exceed 3 meters, and the deviation between the actual and initial scanning paths meets the requirements. In addition, preferably, when severe environmental conditions such as strong winds and rapid currents are determined by marine environmental data, the actual navigation path of the inspection vessel unit is automatically adjusted so that it sails to a pre-set emergency evacuation area for shelter.

[0056] As a preferred design, based on the basic information of the underwater cluster anchor cable laying within the inspection zone, complex scanning areas are identified at locations such as anchor cable turns, intersections, and proximity to anchors. For complex scanning areas, the inspection vessel unit adopts a fan-shaped scanning strategy when navigating complex path sections, controlling the electric pan-tilt unit to drive the multi-beam sonar to adjust the scanning angle and scan the complex scanning area. The inspection vessel unit's sailing speed is reduced to 1~2 m / s, thereby achieving full coverage and high-precision scanning of the complex scanning area.

[0057] When multiple inspection vessel units carry out inspection operations simultaneously, the location and navigation status of each inspection vessel unit can be monitored in real time by the positioning module at the maritime control center, and collaborative control commands can be issued by the wireless communication module to avoid operational conflicts and collisions.

[0058] As a preferred design, during the inspection process, the patrol vessel unit dynamically adjusts the scanning angle and parameters of the multibeam sonar via a motorized pan-tilt unit based on real-time scanning of the anchor cable. When the anchor cable target is detected, the multibeam sonar's pitch angle is adjusted to -15° to 30° to ensure the anchor cable target is in the center of the scan area. When the water turbidity data collected by the underwater detection components exceeds a preset threshold, the transmission power of the multibeam sonar is increased to improve detection stability. Simultaneously, the underwater camera captures image data of the anchor cable to assist in subsequent damage verification.

[0059] As a preferred design, during navigation and inspection, the patrol vessel unit also determines whether there are seabed obstacles (including seabed protrusions, reefs, etc.) along the navigation route based on marine environmental data and real-time scanning conditions. It also determines whether the multi-beam gimbal device in its working state will encounter seabed obstacles and whether to avoid them. If avoidance is required, at least one of the following methods should be selected: 1) Method A: Determine whether retracting the multi-beam gimbal device can avoid the seabed obstacle. If so, the patrol vessel unit will not change its navigation path and will retract the multi-beam gimbal device. Specifically, the electric gimbal will be controlled to raise the multi-beam sonar elevation angle to 60°~90°, that is, to rise a certain distance, so that the patrol vessel unit will not encounter the seabed obstacle when raising the multi-beam sonar elevation angle without changing the navigation route. This method can be used when there is no anchor chain at the obstacle and retracting the multi-beam gimbal device will not affect the scanning of the anchor chain. 2) Method B: The inspection vessel unit changes its course to avoid seabed obstacles. The multi-beam sonar continues scanning. Since the sonar's working width is greater than the inspection vessel's width, if there is an anchor cable at the seabed obstacle, the sonar can cover the cable near the edge of its working range, thus maintaining scanning of the cable. After passing the seabed obstacle, the inspection vessel returns to its original course. In some cases, the inspection vessel unit can also raise the multi-beam sonar while changing its course, providing double protection to prevent the multi-beam sonar from hitting seabed obstacles and being damaged.

[0060] S3, Point Cloud Data Processing:

[0061] S31. Combining the timestamp and the location information of the inspection vessel unit, the underwater point cloud data scanned by the multi-beam pan-tilt unit is unified into the geodetic coordinate system to obtain the corresponding scanned point cloud model. Specifically, the underwater point cloud data scanned by the multi-beam pan-tilt unit is the position relative to the inspection vessel unit. Combining the inspection vessel unit's location information (i.e., its position information in the geodetic coordinate system) and parameters such as the timestamp, the underwater point cloud data can be transformed into the geodetic coordinate system.

[0062] In this embodiment, preferably, before unifying the underwater point cloud data to the geodetic coordinate system, the collected raw point cloud data is preprocessed, including noise reduction, using statistical filtering algorithms to remove discrete points caused by ocean current interference and measurement noise. Simultaneously, the underwater image data obtained from the underwater camera is also sharpened to remove water scattering interference.

[0063] In this embodiment, preferably, the ICP (Iterative Closest Point) algorithm can be used to register the point cloud data collected by each inspection vessel unit. Utilizing the timestamps corresponding to the underwater point cloud data and the location information of the inspection vessel units, combined with information such as scanning angles, the underwater point cloud data is fused into a unified geodetic coordinate system. The ICP algorithm is a mature and commonly used standard algorithm in the field of 3D point cloud registration, and its details will not be elaborated further. Alternatively, other existing methods can also be used to unify the underwater point cloud data scanned by the multi-beam pan-tilt unit into a geodetic coordinate system.

[0064] S32. Detect and identify the cloud points corresponding to the anchor cable from the scanned point cloud model to obtain a complete anchor cable point cloud model. Since the obtained scanned point cloud model includes cloud points corresponding to the anchor cable, as well as cloud points of the underwater terrain and other objects, it is necessary to identify the cloud points corresponding to the anchor cable to establish a simple anchor cable point cloud model that does not include other debris, so as to facilitate the observation of changes in the anchor cable.

[0065] In this embodiment, preferably, a line detection method based on the RANSAC algorithm is adopted to accurately find target points that conform to the line model from the scanned point cloud model, which are used as cloud points corresponding to the anchor cable. The line features of the anchor cable are extracted, and the extracted anchor cable point cloud is optimized by a morphological filtering algorithm to obtain a complete anchor cable point cloud model. Specifically, the RANSAC algorithm (Random Sample Consensus) is a robust fitting algorithm. Its core purpose is to accurately identify and filter target points (i.e., cloud points of the anchor cable) that conform to the line model from the fused point cloud data containing a large number of outliers (noise / anomalies) such as ocean current interference, measurement noise, underwater background and obstacles, so as to achieve effective separation of anchor cable targets from various interference targets. For the extracted anchor cable point cloud data, a morphological filtering algorithm is used for optimization. The specific process is as follows: First, the anchor cable point cloud is projected onto a two-dimensional plane to generate a corresponding binary mask; then, a small interference region in the binary mask is removed through an erosion operation, and then a dilation operation is used to fill the holes and defects in the mask; finally, the optimized binary mask is restored to three-dimensional point cloud data to obtain a complete and clean anchor cable point cloud model. In addition, in other embodiments, other suitable existing recognition algorithms can also be used to detect and identify the cloud points corresponding to the anchor cable from the scanned point cloud model.

[0066] S4. Based on the anchor cable point cloud model, analyze the working status of the anchor cable:

[0067] The point cloud models of anchor cables obtained from scanning at different times were analyzed to examine changes in the working state of the anchor cables, including changes in diameter, surface flatness, and morphological characteristics, thereby identifying damage types including wire breakage, corrosion thinning, deformation, and burial. Furthermore, damage level assessment indicators were established, including damage area, depth, and length, classifying anchor cable damage into three levels: minor damage (e.g., damage area ≤ 5%), moderate damage (e.g., 5% < damage area ≤ 15%), and severe damage (e.g., damage area > 15%).

[0068] S5. Inspection Result Output and Feedback:

[0069] The inspection results from the inspection vessel units are transmitted to the surface control center via a communication module. The surface control center collects the anchor cable point cloud model and analyzes its operational status to generate a cluster anchor cable inspection report. This report includes the inspection trajectory of each anchor cable, point cloud image, damage type, damage location, damage level, and corresponding repair recommendations. For identified moderate and severe damage areas, the corresponding inspection vessel units are controlled to return to the corresponding waters for a secondary, detailed scan to verify the accuracy of the damage identification results. The inspection report and the secondary verification results are then pushed to the operation and maintenance management terminal, providing a basis for anchor cable maintenance decisions.

[0070] As can be seen from the above, the inspection method of the present invention has the following beneficial effects:

[0071] 1. The inspection vessel unit adopts an unmanned surface vessel (USV) equipped with a multi-beam sonar device. USVs have the advantages of flexibility, long endurance, and low operating costs, and can adapt to complex operating environments such as nearshore and shallow seas of marine ranches. Compared with traditional large ships or underwater vehicles, it greatly improves the flexibility and coverage of operations. At the same time, the electric gimbal enables flexible angle adjustment of the multi-beam sonar from 0 to 360° horizontally and from -45° to 90° pitch, which can adapt to the characteristics of scattered and complex anchor cable distribution, effectively eliminating blind spots and achieving full coverage scanning of anchor cables. Furthermore, the collaborative inspection mode of multiple inspection vessel units can further improve the inspection efficiency of large-scale anchor cable clusters, solving the problem of low inspection efficiency of traditional single-platform inspections.

[0072] 2. Based on the laying foundation information of underwater clustered anchor cables (three-dimensional distribution model of clustered anchor cables) and marine environmental data of the inspection area, the improved AI algorithm can adaptively plan the path according to the set requirements. It can achieve accurate planning and dynamic correction of the inspection path, and can also plan assembly points, supply points and emergency shelter areas to ensure the integrity of the inspection coverage. By avoiding ocean currents, strong winds and obstacles, it optimizes inspection efficiency, improves operational safety, and avoids the problems of repeated scanning and missed scanning.

[0073] 3. Through a series of data processing algorithms such as statistical filtering, RANSAC line detection, and morphological filtering, the anchor cable target and interference target can be accurately distinguished, and a complete anchor cable point cloud model can be constructed. It can also be combined with image data collected by underwater cameras for verification. Based on the feature analysis of diameter change, surface flatness and other features displayed by the anchor cable point cloud model, various damage types such as broken wires, corrosion and deformation can be accurately identified, and the damage level can be scientifically assessed, thus improving the accuracy and reliability of damage identification.

[0074] 4. Real-time data interaction and collaborative control between the inspection vessel unit and the surface control center ensure stable data transmission. Combined with a secondary fine-scan verification mechanism and underwater image-assisted verification, the accuracy of damage identification results is further guaranteed. The generated inspection report contains complete damage information and repair recommendations, providing comprehensive and reliable decision-making basis for the operation and maintenance of marine ranch anchor cables, significantly improving the safe operation and maintenance level of marine ranch facilities. In summary, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial application value.

[0075] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for inspecting underwater clustered anchor cables, characterized in that: The inspection is carried out using an inspection vessel unit, which is equipped with a multi-beam pan-tilt unit, a positioning module, and a communication module. The inspection method includes the following steps: S1. Preparations before the inspection: S11. Obtain the laying foundation information of underwater cluster anchor cables in the inspection area; obtain marine environmental data of the inspection area; S12. Based on the laying foundation information of underwater cluster anchor cables and marine environmental data, the inspection area is divided into several inspection zones. S2. Conduct inspection work for each inspection zone, including: S21. Adaptive inspection path planning: Based on the laying foundation information of underwater cluster anchor cables and marine environmental data within the inspection zone, and combined with the scanning working range of the multi-beam pan-tilt unit, the initial inspection path is planned. The initial inspection path includes the initial navigation path and the initial scanning path. S22, Inspection Scan: Several inspection vessel units are used to carry out inspection work according to the initial inspection path. The multi-beam pan-tilt unit performs underwater scanning to acquire underwater point cloud data and record the timestamp. At the same time, the positioning module records the position of the inspection vessel unit corresponding to each underwater point cloud data. S3, Point Cloud Data Processing: S31. Combining the timestamp and the location information of the inspection vessel unit, the underwater point cloud data obtained by the multi-beam pan-tilt unit is unified into the geodetic coordinate system to obtain the corresponding scanned point cloud model. S32. Detect and identify the cloud points corresponding to the anchor cable from the scanned point cloud model to obtain a complete anchor cable point cloud model. S4. Analyze the working status of the anchor cable based on the anchor cable point cloud model.

2. The inspection method according to claim 1, characterized in that: In step S21, both the initial navigation path and the initial scanning path include a main scanning path segment that is parallel to the direction of the anchor cable on the horizontal plane.

3. The inspection method according to claim 1, characterized in that: In step S21, the initial scanning path completely covers the bottom surface of the inspection zone, and the adjacent segments of the initial scanning path overlap in the width direction, with the width of the overlapping area accounting for 15% to 20% of the width of the initial scanning path.

4. The inspection method according to claim 1, characterized in that: In step S22, during navigation, the inspection vessel unit adjusts its operation based on the real-time location information and real-time marine environment data obtained by the positioning module, dynamically corrects the actual inspection path, and ensures that the deviation between the actual inspection path and the initial inspection path does not exceed the required value.

5. The inspection method according to claim 1, characterized in that: In step S21, a complex scanning area is determined based on the laying foundation information of the underwater cluster anchor cables and marine environmental data within the inspection zone, and a corresponding complex path segment is set in the initial inspection path based on the complex scanning area; in step S22, the inspection vessel unit adopts a fan-shaped scanning strategy in the complex path segment and reduces the navigation speed of the inspection vessel unit to 1~2m / s.

6. The inspection method according to claim 1, characterized in that: The inspection vessel unit is equipped with an underwater detection component, which includes an underwater camera and a turbidity sensor. In step S22, based on the actual scanning situation and the turbidity data collected by the underwater detection component, the pitch angle of the multibeam sonar is controlled to place the anchor cable target in the scanning center area, and the power of the multibeam sonar is adjusted. At the same time, the underwater camera simultaneously captures image data of the anchor cable.

7. The inspection method according to claim 1, characterized in that: In step S22, during navigation and inspection, the inspection vessel unit determines whether there are seabed obstacles on the navigation path based on marine environmental data and real-time scanning conditions, and determines whether the multi-beam gimbal device in its working state will encounter seabed obstacles, and determines whether to perform an avoidance operation. If avoidance is required, one of the following methods is selected: Method A: Determine whether retracting the multi-beam gimbal device can avoid the seabed obstacle. If so, the inspection vessel unit does not change its navigation path and retracts the multi-beam gimbal device; Method B: Control the navigation path of the inspection vessel unit to avoid the seabed obstacle, while the multi-beam gimbal device continues scanning.

8. The inspection method according to claim 1, characterized in that: In step S31, the original point cloud data is first preprocessed, including noise reduction, and a statistical filtering algorithm is used to remove discrete points caused by ocean current interference and measurement noise; then the preprocessed underwater point cloud data is unified into the geodetic coordinate system.

9. The inspection method according to claim 1, characterized in that: In step S32, a line detection method based on the RANSAC algorithm is used to accurately find target points that conform to the line model from the scanned point cloud model, extract the line features of the anchor cable, and optimize the extracted anchor cable point cloud through a morphological filtering algorithm to obtain a complete anchor cable point cloud model.

10. The inspection method according to claim 1, characterized in that: Step S4 includes: analyzing the changes in the working state of the anchor cable at different times, including changes in diameter, surface flatness and morphological characteristics, and identifying damage types including wire breakage, corrosion thinning, deformation and burial, based on the anchor cable point cloud model obtained from scanning at different times.

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