Underwater scanning robot and seabed modeling method

Abstract

The application provides an underwater scanning robot and a ship bottom modeling method, and the application achieves accurate conversion of ship body echo points from sonar relative coordinates to absolute coordinates by laterally installing a multi-beam forward-looking sonar on the underwater scanning robot and combining an inertial navigator, a Doppler speedometer and a depth gauge, and then completes three-dimensional grid modeling of a ship bottom. Compared with a traditional method relying on high-cost professional measuring equipment, the scheme can realize high-precision ship bottom reconstruction by using a lower-cost forward-looking sonar, has the advantages of low cost, flexible deployment, wide adaptability to ship types, can form an intuitive and complete three-dimensional model of the ship bottom, and facilitates non-missing investigation of abnormal attachments and suspicious structures, and significantly improves the efficiency, reliability and traceability of ship bottom detection.

Description

Technical Field

[0001] This invention relates to the field of underwater measurement technology, and more specifically, to underwater scanning robots and methods for modeling the bottom of ships. Background Technology

[0002] In recent years, there have been frequent cases of smuggling drugs and other contraband by attaching them to the hulls of international cargo ships. Currently, a common method for ship hull inspection is to use fixed inspection equipment in conjunction with ship movement. This involves deploying sonar, cameras, or other inspection devices on docks, floating platforms, or specific support structures, and then slowly moving the ship's hull through the inspection area to detect the target. While this method can accomplish a certain degree of hull inspection, it still has many limitations in practical application. Firstly, fixed equipment is highly dependent on the operating environment, typically requiring the ship to move along a predetermined route and speed, which places high demands on port water conditions, berth conditions, and on-site organizational conditions, resulting in poor deployment flexibility. Secondly, different ship types vary significantly in beam, draft, hull curvature, and the distribution of auxiliary structures. Fixed equipment has limited observation angles and coverage, making it difficult to meet the comprehensive inspection needs of various ship types and easily creating blind spots. Furthermore, when the ship's bottom structure is complex or specific areas require focused re-inspection, fixed methods struggle to achieve close-range, detailed scanning of suspected areas, affecting the accuracy and completeness of the inspection results. Especially in applications such as security inspections and anti-smuggling enforcement, the inability to quickly, flexibly, and precisely complete ship bottom inspections can easily lead to the omission of abnormal attachments, failing to meet the demands of high efficiency and high reliability in practical applications. Therefore, there is an urgent need for a ship bottom inspection technology solution that is more flexible in deployment, has a wider range of applications, and provides more precise scanning. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an underwater scanning robot and a method for modeling the bottom of a ship, so as to overcome the shortcomings of the existing technology.

[0004] The above-mentioned technical objective of the present invention is achieved through the following technical solution: In a first aspect, an underwater scanning robot includes: a robot body having intersecting first, second, and third directions; the robot body internally houses: an inertial navigator for providing attitude, acceleration, and angular velocity information of the robot body; a Doppler velocimeter for providing motion velocity information of the robot body; a depth gauge for providing water depth information of the robot body; a multibeam forward-looking sonar for acquiring target information in multiple angular directions; and a thruster module for providing driving force to the robot body; wherein, in the first direction, the multibeam forward-looking sonar is mounted on one side of the robot body in the positive direction; in the third direction, the multibeam forward-looking sonar is mounted on one side of the robot body in the positive direction; the beam emitted by the multibeam forward-looking sonar is perpendicular to the second direction.

[0005] In one embodiment, the inertial navigator is mounted at the center of the robot body in a first direction; in a second direction, the inertial navigator is mounted at the center of the robot body; and in a third direction, the inertial navigator is mounted at the center of the robot body.

[0006] Secondly, the hull modeling method, applied to the underwater scanning robot as described in the first aspect, includes the following steps: S1. Control the underwater scanning robot to move around the hull and use the multibeam forward-looking sonar to scan the hull and obtain sonar echoes. S2. Extract reliable hull echo points from the sonar echoes based on echo intensity and target continuity; S3. Calculate the relative coordinates of the sonar at each of the ship's echo points based on the installation position of the multibeam forward-looking sonar. S4. Use the inertial navigation system and the Doppler velocimeter to convert the relative coordinates of the sonar at each hull echo point into absolute coordinates. S5. Based on the absolute positions of all hull echo points, construct a mesh model of the hull bottom.

[0007] In one embodiment, extracting reliable hull echo points from the sonar echo based on echo intensity and target continuity specifically includes: Extract the point with the strongest echo signal intensity from each beam sampling sequence and use it as the initial target echo point; Determine whether there are other target echo points in a preset neighborhood of the initial target echo point, and whether the number of target echo points in the neighborhood exceeds a predetermined threshold. If yes, mark the initial target echo point as a hull echo point; otherwise, determine that the initial target echo point is an interference point and discard it.

[0008] In one embodiment, calculating the relative coordinates of each of the ship's echo points based on the installation location of the multibeam forward-looking sonar includes: A sonar plane coordinate system is constructed with the center of the multibeam forward-looking sonar as the origin. The axis coincides with the centerline of the beam; the sonar plane coordinate system shaft and The axis is perpendicular; the sonar plane coordinate system is perpendicular to the second direction; Obtain the distance between the ship's echo point and the origin of the sonar plane coordinate system. And the line connecting the hull echo point and the origin of the sonar plane coordinate system with Angle between axes Calculate the x-coordinate of the ship's echo point on the sonar plane coordinate system. and ordinate : .

[0009] In one embodiment, the step of converting the relative coordinates of each ship's echo point into absolute coordinates using the inertial navigation system and the Doppler velocimeter specifically includes: Based on the installation position of the multibeam forward-looking sonar relative to the robot body, the sonar relative coordinates of the ship's echo points are transformed into the body's relative coordinates. Based on the attitude information output by the inertial navigator, a rotation matrix of the robot body is constructed, and the relative coordinates of the body of the hull echo point are converted into local horizontal coordinates using the rotation matrix. The robot body's absolute coordinates are obtained by combining the inertial navigator and the Doppler velocimeter, and the robot body's depth is obtained by using the depth gauge. Using the absolute coordinates of the main body and the depth of the main body, the local horizontal coordinates of the ship's echo point are transformed into absolute coordinates.

[0010] In one embodiment, the process of converting the sonar relative coordinates of the hull echo point into the body relative coordinates based on the installation position of the multibeam forward-looking sonar relative to the robot body includes: ; in, This represents the x-coordinate of the ship's echo point in the sonar plane coordinate system; This represents the ordinate of the ship's echo point in the sonar plane coordinate system; This represents the coordinate components of the target echo point in the underwater robot's carrier coordinate system; Representing the sonar coordinate system The installation angle between the shaft and the first direction; This represents the installation offset of the sonar coordinate system origin relative to the underwater robot carrier coordinate system origin.

[0011] In one embodiment, the step of constructing a rotation matrix for the robot body based on the attitude information output by the inertial navigator, and using the rotation matrix to convert the relative coordinates of the body at the hull echo point into local horizontal coordinates, specifically includes: Based on the roll angle, pitch angle, and heading angle when the robot emits its beam, construct the rotation matrix: ;in, Represents the coordinate system around the carrier The roll rotation matrix of the axis; Represents the coordinate system around the carrier. The tilt and rotation matrix of the axis; Represents the coordinate system around the carrier The heading rotation matrix of the axis; Using a rotation matrix, the relative coordinates of the subject are converted into local horizontal coordinates, including: ;in, This represents the coordinate components of the target echo point in the coordinate system of the underwater robot. This represents the coordinate components of the ship's echo point in the local horizontal coordinate system.

[0012] In one embodiment, transforming the local horizontal coordinates of the hull echo point into absolute coordinates using the absolute coordinates of the main body and the depth of the main body includes: Obtain the absolute coordinates of the robot body in the geographic coordinate system. and main body depth Transforming local horizontal coordinates into absolute coordinates includes: ; in, These represent the absolute coordinates of the ship's echo points in the geographic coordinate system.

[0013] In one embodiment, constructing a mesh model of the ship's bottom based on the absolute positions of all hull echo points specifically includes: Based on the absolute position coordinates of all hull echo points, construct a hull bottom point cloud dataset; Based on the aforementioned ship bottom point cloud dataset, principal component analysis or local geometric analysis is used to determine the normal vector corresponding to each ship hull echo point, so as to construct the normal vector field of the ship bottom surface. A scalar function is defined based on the normal vector field. , so that the scalar function The gradient matches the normal vector field; according to the scalar function Based on the relationship between the normal vector field and the normal vector field, the Poisson equation is established: ;in, Represents the Laplace operator. This represents the divergence of the normal vector field; The Poisson equation is discretized and solved using the multigrid method to obtain the corresponding scalar field. Based on the scalar field, the isosurface is extracted using the moving cube algorithm to generate a three-dimensional polygonal mesh model of the ship's bottom.

[0014] Thirdly, a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the hull modeling method described in the second aspect.

[0015] Fourthly, a computer device includes a memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the steps of the ship bottom modeling method described in the second aspect.

[0016] In summary, this invention offers the following advantages: By optimizing the lateral mounting method of a multibeam forward-looking sonar on an underwater scanning robot, and combining this with close-to-the-bottom scanning and data processing methods, high-precision 3D modeling of the ship's bottom target is achieved. Compared to solutions using dedicated underwater 3D measurement equipment, this invention can utilize a lower-cost forward-looking sonar to complete the ship's bottom scanning, significantly reducing equipment investment costs. Furthermore, the side-mounted vertical mounting method of the forward-looking sonar improves the coverage of a single scan and overall measurement efficiency. The use of an underwater robot mobile platform instead of fixed equipment, combined with ship movement, offers advantages such as flexible deployment, wide applicability to various ship types, and high scanning precision, better meeting the needs for rapid and comprehensive inspection of the ship's bottom in scenarios such as security checks and anti-smuggling enforcement. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the underwater scanning robot observed along a third direction according to the present invention; Figure 2 This is a schematic diagram of the underwater scanning robot observed along the second direction according to the present invention; Figure 3 This is a schematic diagram of the underwater scanning robot scanning the hull of the ship according to the present invention; Figure 4 This is a flowchart of the ship bottom modeling method of the present invention; Figure 5 This is a schematic diagram of the multi-beam forward-looking sonar transmission beam of the present invention; Figure 6 This is a schematic diagram of the multibeam sonar coordinate system and the robot body coordinate system of the present invention; Figure 7 This is a schematic diagram of the computer structure according to an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0019] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, the simultaneous existence of A and B, or the existence of B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, and c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0020] Those skilled in the art will recognize that the units and algorithm steps described in the embodiments disclosed herein can be implemented using electronic hardware, computer software, or a combination of electronic hardware and software. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0021] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0022] In the several embodiments provided in this application, any function, if implemented as a software functional unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0023] The above description is merely a specific embodiment of this application. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application. The protection scope of this application should be determined by the protection scope of the claims.

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] Example 1 To address the aforementioned problems, this invention provides an underwater scanning robot. For example... Figure 1 , Figure 2 As shown, to describe the robot's structure in detail, it is first necessary to define each direction. A three-dimensional coordinate system is constructed with the robot's center point as the origin. The X-axis is the first direction, and the right side of the X-axis is defined as the positive direction of the X-axis; the Y-axis is the second direction, and the direction towards the robot's head is defined as the positive direction of the Y-axis; the Z-axis is the third direction, and the direction opposite to the direction of gravity is defined as the positive direction of the Z-axis. The X, Y, and Z axes intersect each other. In some preferred embodiments, the X, Y, and Z axes are perpendicular to each other.

[0026] The underwater scanning robot includes a robot body. In some embodiments, the robot body adopts a sealed shell structure to provide mounting bases and underwater protective space for various functional components. The robot body is preferably a pressure-resistant and corrosion-resistant enclosed cabin with internal equipment mounting cavities for mounting components such as inertial navigation systems, Doppler velocimeters, control modules, power modules, and communication modules. Externally, it includes thruster mounting positions, sensor mounting positions, and sealed interfaces. This sealed shell structure effectively prevents water intrusion, protects the stable operation of internal electronic components, and improves the operational reliability of the underwater scanning robot in complex aquatic environments.

[0027] In some embodiments, the underwater scanning robot includes a GPS unit, which is positioned above the robot body or at an adapted location that can protrude above the water surface. The GPS unit receives satellite positioning signals when the underwater scanning robot surfaces, acquiring the robot's position information in a geographic coordinate system or an engineering coordinate system. The GPS unit can be used to correct the robot's position during long-term operation, providing a reference benchmark for underwater positioning results and improving overall positioning accuracy.

[0028] In some embodiments, the underwater scanning robot includes an ultra-short baseline positioning unit (USBL) for acquiring real-time position information during underwater operations. In this embodiment, the USBL is mounted on the top of the robot body and determines the position parameters of the robot body relative to an external reference point through acoustic communication with a surface base station, thereby compensating for the inability of GPS to work directly underwater. The USBL can be used in conjunction with other navigation sensors to improve the continuity and stability of underwater positioning.

[0029] In some embodiments, the underwater scanning robot includes an inertial navigation system (INS) installed inside the robot body. Preferably, the INS is positioned close to the origin of the robot body's coordinate system to reduce the impact of installation deviations on the attitude calculation results. The INS is used to measure the robot body's roll angle, pitch angle, heading angle, acceleration, angular velocity, and other motion parameters in real time, and provides basic data for attitude compensation, coordinate transformation, and motion state estimation of sonar echo points.

[0030] In some embodiments, the underwater scanning robot further includes a Doppler velocimeter (DVL), which is mounted on the bottom of the robot body or at a suitable location for velocity measurement, and is used to measure the robot body's velocity relative to the water or seabed. The Doppler velocimeter can output the robot's velocity components in multiple directions and can be combined with an inertial navigation unit for navigation calculations to obtain continuous displacement information of the robot body during underwater operations, improving the accuracy of echo point absolute position calculations.

[0031] In some embodiments, the underwater scanning robot further includes a depth gauge mounted on the robot body, preferably near the multibeam forward-looking sonar, for measuring real-time depth information at the location of the robot body or the acoustic center of the sonar. Because the depth gauge is installed close to the sonar, depth errors caused by spatial differences can be reduced. This depth information is used to establish the vertical coordinates of the hull echo points and to provide a depth reference for three-dimensional spatial positioning and model reconstruction.

[0032] In some embodiments, the robot body is further provided with a thruster module, which enables the robot to swim along a predetermined trajectory. Preferably, in the second direction, the thruster module is located on the side closer to the negative direction of the second direction, so that the robot can swim along the positive direction of the second direction.

[0033] In some embodiments, the multibeam forward-looking sonar is mounted on the side of the robot body as the main measuring device for scanning the bottom of the ship. The multibeam forward-looking sonar is used to emit sound waves in multiple angular directions and receive target echoes to obtain distance information and echo intensity information at different locations on the bottom surface of the ship.

[0034] Furthermore, in the first direction, the multibeam forward-looking sonar is preferably installed on the side closest to the positive direction of the first direction; in the third direction, the multibeam forward-looking sonar is preferably installed on the side closest to the positive direction of the third direction, and the beam emitted by the multibeam forward-looking sonar is perpendicular to the second direction, i.e., as shown in the image. Figure 2 As shown, the multibeam forward-looking sonar is oriented towards the upper right and emits multibeam sound waves there. By controlling the underwater scanning robot to move around the hull and controlling the multibeam forward-looking sonar to emit sound waves towards the bottom of the hull, the multibeam forward-looking sonar can acquire a portion of the cross-sectional echo information of the corresponding area on the bottom of the hull at each measurement moment. As the underwater scanning robot continues to travel along the keel of the ship, the multibeam forward-looking sonar continuously scans different positions on the bottom of the ship, thereby gradually acquiring multiple sets of cross-sectional data of the bottom of the ship along the direction of the travel path. Furthermore, by adjusting the underwater scanning robot's travel trajectory, travel altitude, and relative distance to the hull, continuous coverage scanning of different areas of the bottom of the ship can be achieved, ensuring that all parts of the bottom of the ship can be effectively detected by the multibeam forward-looking sonar, reducing blind spots and missed areas.

[0035] After scanning, the echo data acquired by the multibeam forward-looking sonar, combined with the pose and depth information output by the inertial navigation system, Doppler velocimeter and depth gauge, can be used to extract, transform and fuse the ship's echo points at each measurement time, thereby constructing a high-precision three-dimensional model of the ship's bottom. This facilitates intuitive and complete identification and analysis of ship bottom attachments, abnormal structures or suspicious targets.

[0036] Furthermore, in the first direction, the inertial navigator is installed at the center of the robot body; in the second direction, the inertial navigator is installed at the center of the robot body; and in the third direction, the inertial navigator is installed at the center of the robot body. Specifically, the inertial navigator is preferably installed in the central region inside the robot body, that is, in the first, second, and third directions, the inertial navigator is positioned close to the geometric center of the robot body or the origin of the carrier coordinate system. By arranging the inertial navigator at the center of the robot body, the attitude, angular velocity, and acceleration information measured by the inertial navigator can more accurately represent the overall motion state of the robot body, reducing the lever error and attitude calculation error introduced by the installation position offset. Especially when the underwater scanning robot is turning, lifting, lateral movement, or navigating close to the surface of the hull, if the inertial navigator is deviated too much from the center position, the measurement accuracy can be easily affected by local vibration, additional rotation radius, or structural sway. By adopting the above-mentioned central installation method, it is convenient to use the data output by the inertial navigation system as the attitude reference in the robot's main coordinate system. It is also beneficial to perform unified calibration, fusion calculation and coordinate transformation with the data from the Doppler velocimeter, depth gauge and multibeam forward sonar, thereby improving the accuracy of hull echo point positioning and hull bottom 3D modeling.

[0037] In summary, this embodiment provides an underwater scanning robot. By laterally mounting a multibeam forward-looking sonar to the underwater scanning robot and combining it with an inertial navigation system, a Doppler velocimeter, and a depth gauge, it achieves precise conversion of the ship's echo points from relative sonar coordinates to absolute coordinates, thereby completing the 3D mesh modeling of the ship's bottom. Compared to traditional methods that rely on high-cost professional measurement equipment, this solution can achieve high-precision ship bottom reconstruction using lower-cost forward-looking sonar, offering advantages such as low cost, flexible deployment, and wide applicability to a wide range of ship types. Simultaneously, it can generate an intuitive and complete 3D model of the ship's bottom, facilitating the thorough investigation of abnormal attachments and suspicious structures, significantly improving the efficiency, reliability, and traceability of ship bottom inspection.

[0038] Example 2 Please see Figure 4 The hull modeling method, applied to the underwater scanning robot as described in Example 1, specifically includes the following steps: S1. Control the underwater scanning robot to move around the hull to be inspected, and use the multibeam forward-looking sonar mounted on the robot body to continuously scan the hull and obtain the corresponding sonar echo data. Preferably, the underwater scanning robot travels along the keel of the ship and maintains a preset distance from the bottom of the hull during the journey, so that the multibeam forward-looking sonar can continuously acquire cross-sectional information of local areas of the hull bottom. By adjusting the underwater scanning robot's travel path, travel altitude, and relative position to the hull, continuous coverage scanning of different areas of the hull bottom can be achieved, thereby obtaining multiple sets of measurement data of the hull bottom surface, providing a data foundation for subsequent 3D modeling.

[0039] S2. After acquiring the sonar echo, reliable hull echo points are extracted from the sonar echo based on echo intensity and target continuity. Specifically, the point with the strongest echo signal intensity can be extracted from each beam sampling sequence as the initial target echo point. Since the initially extracted points may contain noise points, interference points, or pseudo-target points generated by stray echoes, further discrimination based on target continuity is necessary. Figure 5 As shown, specifically: it is determined whether there are other target echo points within a preset neighborhood of the initial target echo point, and whether the number of target echo points within the neighborhood exceeds a predetermined threshold; if it exceeds the predetermined threshold, it indicates that the point has a certain degree of spatial continuity and stability, and can be marked as a hull echo point; if it does not exceed the predetermined threshold, or if there are no other target echo points within the neighborhood of the target echo point, then the initial target echo point is determined to be an interference point and discarded. Through the above method, isolated noise points can be effectively removed, improving the reliability of hull echo point extraction.

[0040] S3. After extracting reliable hull echo points, calculate the relative coordinates of each hull echo point based on the installation position of the multibeam forward-looking sonar. Specifically, construct a sonar plane coordinate system with the center of the multibeam forward-looking sonar as the origin, wherein the sonar plane coordinate system... The axis coincides with the beam centerline, the shaft and The axis is perpendicular, and the sonar plane coordinate system is perpendicular to the second direction of the robot body. For any hull echo point, the distance between the hull echo point and the origin of the sonar plane coordinate system is obtained. And the line connecting the hull echo point and the origin relative to Angle between axes Then, the abscissa of the hull echo point in the sonar plane coordinate system is calculated. and ordinate ,in: This allows us to obtain the relative positions of each ship's echo points in the sonar coordinate system.

[0041] S4. Use an inertial navigation system and a Doppler velocimeter to convert the relative coordinates of the sonar at each hull echo point into absolute coordinates. This process may include the following sub-steps.

[0042] S41, such as Figure 6 As shown, based on the installation position of the multibeam forward-looking sonar relative to the robot body, the sonar relative coordinates of the hull echo points are transformed into the body relative coordinates. Specifically, according to the attitude relationship and installation offset parameters of the multibeam forward-looking sonar mounted on the robot body, the hull echo points are transformed from the sonar plane coordinate system to the underwater robot carrier coordinate system. Preferably, the following relationship can be used: ; in, This represents the x-coordinate of the ship's echo point in the sonar plane coordinate system; This represents the ordinate of the ship's echo point in the sonar plane coordinate system; This represents the coordinate components of the target echo point in the underwater robot's carrier coordinate system; Representing the sonar coordinate system The installation angle between the shaft and the first direction; This represents the installation offset of the sonar coordinate system origin relative to the origin of the underwater robot's carrier coordinate system. Through the above transformation, the position of the hull echo point relative to the robot's main body can be obtained.

[0043] Subsequently, the rotation matrix of the robot's main body is calculated using an inertial navigator and a Doppler velocimeter, and the relative coordinates of the main body at the hull echo point are converted into local horizontal coordinates. Specifically, at the moment the sonar emits its beam, the inertial navigator outputs the robot's roll angle, pitch angle, and heading angle, denoted as follows: , and Construct a rotation matrix based on the roll angle, pitch angle, and heading angle: ; in, Represents the coordinate system around the carrier The roll rotation matrix of the axis, ; Represents the coordinate system around the carrier. The tilt and rotation matrix of the axis. ; Represents the coordinate system around the carrier The yaw rotation matrix of the axis. .

[0044] Therefore, the attitude rotation matrix This can be further expanded to: Let the coordinates of the ship's echo point in the underwater robot's coordinate system be... The coordinates of the ship's echo point in the local horizontal coordinate system are: ;in, This represents the coordinate components of the target echo point in the coordinate system of the underwater robot. This represents the coordinate components of the ship's echo point in the local horizontal coordinate system.

[0045] Furthermore, the absolute coordinates of the robot's main body are calculated using an inertial navigator and a Doppler velocimeter, and the depth of the robot's main body is obtained using a depth gauge. Specifically, the inertial navigator and the Doppler velocimeter can output the absolute coordinates of the robot's main body in an external reference coordinate system through a combined navigation method, such as the planar coordinates in a local engineering coordinate system, a local geographic coordinate system, or other preset coordinate systems. The depth gauge is used to output the depth value corresponding to the robot body or the acoustic center of the sonar. .

[0046] After obtaining the absolute coordinates and depth of the robot body, the local horizontal coordinates of the hull echo points can be transformed into absolute coordinates. Preferably, the following relationship can be used: ; in, These represent the absolute coordinates of the hull echo points in the external reference coordinate system. By superimposing these coordinates, the hull echo points measured at each moment can be unified under the same spatial reference frame, thereby forming three-dimensional point cloud data of the hull bottom.

[0047] S5. After obtaining the absolute positions of all hull echo points, construct a mesh model of the hull bottom based on the absolute positions of all hull echo points.

[0048] Specifically, let the first The absolute coordinates of each hull echo point in the external reference coordinate system are: ;in, ; ; In the formula, , , Indicates the first The coordinate components of each ship's echo point in the local horizontal coordinate system , Indicates the first sonar launch The absolute planar coordinates of the robot body in the external reference coordinate system during the secondary beam phase. This represents the depth value of the robot's main body or the acoustic center of the sonar at the corresponding moment. The absolute coordinates of all hull echo points constitute the hull bottom point cloud dataset. ,in, This represents the total number of hull echo points extracted.

[0049] Furthermore, in order to reconstruct the continuous ship bottom surface from the discrete point cloud, the reconstruction can first be based on the aforementioned ship bottom point cloud dataset. Calculate the normal vector for each hull echo point. In some embodiments, for any point... Select its range within the preset neighborhood. A set of 10 neighboring points constitutes a local neighborhood point set. And calculate the center point of the local neighborhood: Then construct the local covariance matrix: For the covariance matrix Perform eigenvalue decomposition and take the eigenvector corresponding to the smallest eigenvalue as the point. normal vector Therefore, the set of normal vectors corresponding to each echo point of the hull can be obtained: This allows us to construct a discrete normal vector field for the ship's bottom surface. This normal vector reflects the orientation information of the local surface of the ship's bottom, which is beneficial for subsequent reconstruction of the continuous surface.

[0050] Furthermore, to avoid inconsistent normal vector directions at different points affecting the surface reconstruction accuracy, the normal vectors can be uniformly oriented based on the sonar observation direction. Specifically, the normal vectors can be made... The corresponding measurement time corresponds to the sonar acoustic center pointing towards the ship's echo point. The direction satisfies the preset orientation relationship, thereby ensuring that the normal vector field has overall consistency.

[0051] After obtaining the point cloud coordinates and corresponding normal vectors, an implicit scalar function is constructed. This is to make the gradient of the scalar function approximate the aforementioned normal vector field as closely as possible. In other words, for any point in space near the bottom surface of the ship... Each is defined as a scalar value , so that its gradient It can characterize the local variation trend of the ship's bottom surface. In some embodiments, the implicit surface can be fitted by minimizing the following energy function: ;in, This represents a vector field obtained by interpolating discrete point normal vectors. This represents the reconstructed spatial region where the point cloud at the bottom of the ship is located. After finding the extremum of the above energy function, the corresponding Poisson equation can be obtained: In the context of discrete point clouds, it can also be denoted as: ;in, Represents the Laplace operator. This represents the divergence of the normal vector field. The physical meaning of this equation is that by constraining the gradient distribution of the implicit function through the normal vector field, a continuous surface consistent with the geometry of the point cloud can be recovered.

[0052] Furthermore, a regular mesh, octree mesh, or other hierarchical discrete mesh can be established within a three-dimensional space encompassing all the point cloud of the ship's hull, and the aforementioned Poisson equation can be discretized into a system of linear equations. Preferably, the reconstructed spatial range can be automatically determined based on the coordinates of all point cloud points, for example, taking: , , .

[0053] in, These represent the minimum and maximum values ​​of the absolute coordinates of all hull echo points along each coordinate axis. In this way, the aforementioned... , , The discrete point cloud representation is uniformly mapped to the reconstructed voxel space.

[0054] After discretization, the Poisson equation is solved numerically using the multigrid method to obtain the implicit scalar field in the entire reconstructed space. The multigrid method can iteratively approximate the solution of the equation at different resolution levels, thereby improving the solution efficiency and taking into account the computational stability when reconstructing large-scale ship bottom point clouds.

[0055] In obtaining the implicit scalar field Subsequently, a moving cubes algorithm is used to extract preset isosurfaces to generate a three-dimensional polygonal mesh model of the ship's bottom. Preferably, it can be taken as follows: As a reconstructed isosurface, among which, For the preset threshold, the zero isosurface or the isosurface threshold adaptively determined according to the point cloud distribution is preferred. The moving cube algorithm traverses each voxel unit, determines the value state of the scalar field at the voxel vertex, and interpolates between adjacent voxels to generate triangular patches, ultimately forming a continuous closed or locally continuous ship bottom surface mesh.

[0056] Therefore, all the absolute coordinates of the hull echo points calculated by the aforementioned steps No longer existing merely as discrete spatial points, they are further reconstructed into a geometrically continuous three-dimensional mesh model of the ship's bottom. This three-dimensional mesh model can more intuitively reflect the surface morphology of the ship's bottom, local protrusions, depressions, and the location and size information of attached anomalies, thus facilitating subsequent identification, measurement, and verification of suspicious targets.

[0057] Using the above method, local cross-sectional data acquired by multibeam forward-looking sonar at different measurement times can be uniformly converted into three-dimensional point clouds in the same reference coordinate system, and further reconstructed into a continuous and complete three-dimensional mesh model of the ship's bottom. This model not only intuitively reflects the overall morphology of the ship's bottom, but also facilitates the rapid identification, quantitative analysis, and subsequent verification of attachments, abnormal protrusions, or suspicious targets on the ship's bottom, thereby significantly improving the completeness, accuracy, and practicality of ship bottom inspection work.

[0058] Example 3 A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the ship bottom modeling method as described in Embodiment 2.

[0059] Example 4 In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 7 As shown, the computer device includes a processor, memory, network interface, and database connected via a system bus. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and database. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. When the computer program is executed by the processor, it implements a ship hull modeling method.

[0060] Those skilled in the art will understand that Figure 7 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0061] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0062] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An underwater scanning robot, characterized in that, Includes: a robot body, the robot body having intersecting first, second and third directions; The robot body has the following internal features: An inertial navigation system is used to provide information on the robot's attitude, acceleration, and angular velocity. Doppler velocimeters are used to provide information on the motion speed of the robot's main body; Depth gauges are used to provide water depth information for the robot's main body; Multibeam forward-looking sonar is used to acquire target information from multiple angular directions; The thruster module is used to provide driving force to the robot body; In the first direction, the multibeam forward-looking sonar is mounted on one side of the robot body in the positive direction; in the third direction, the multibeam forward-looking sonar is mounted on one side of the robot body in the positive direction; the beam emitted by the multibeam forward-looking sonar is perpendicular to the second direction.

2. The underwater scanning robot according to claim 1, characterized in that, In a first direction, the inertial navigator is installed at the center of the robot body; in a second direction, the inertial navigator is installed at the center of the robot body; in a third direction, the inertial navigator is installed at the center of the robot body.

3. A method for modeling the bottom of a ship, applied to the underwater scanning robot as described in claim 1, characterized in that, Includes the following steps: S1. Control the underwater scanning robot to move around the hull and use the multibeam forward-looking sonar to scan the hull and obtain sonar echoes. S2. Extract reliable hull echo points from the sonar echoes based on echo intensity and target continuity; S3. Calculate the relative coordinates of the sonar at each of the ship's echo points based on the installation position of the multibeam forward-looking sonar. S4. Use the inertial navigation system and the Doppler velocimeter to convert the relative coordinates of the sonar at each hull echo point into absolute coordinates. S5. Based on the absolute positions of all hull echo points, construct a mesh model of the hull bottom.

4. The ship bottom modeling method according to claim 3, characterized in that, The extraction of reliable hull echo points from the sonar echo based on echo intensity and target continuity specifically includes: Extract the point with the strongest echo signal intensity from each beam sampling sequence and use it as the initial target echo point; Determine whether there are other target echo points in a preset neighborhood of the initial target echo point, and whether the number of target echo points in the neighborhood exceeds a predetermined threshold. If yes, mark the initial target echo point as a hull echo point; otherwise, determine that the initial target echo point is an interference point and discard it.

5. The ship bottom modeling method according to claim 3, characterized in that, The calculation of the relative coordinates of each of the ship's echo points based on the installation position of the multibeam forward-looking sonar includes: A sonar plane coordinate system is constructed with the center of the multibeam forward-looking sonar as the origin. The axis coincides with the centerline of the beam; the sonar plane coordinate system shaft and The axis is perpendicular; the sonar plane coordinate system is perpendicular to the second direction; Obtain the distance between the ship's echo point and the origin of the sonar plane coordinate system. And the line connecting the hull echo point and the origin of the sonar plane coordinate system with Angle between axes Calculate the x-coordinate of the ship's echo point on the sonar plane coordinate system. and ordinate : .

6. The ship bottom modeling method according to claim 3, characterized in that, The process of converting the relative coordinates of each ship's echo point into absolute coordinates using the inertial navigation system and the Doppler velocimeter specifically includes: Based on the installation position of the multibeam forward-looking sonar relative to the robot body, the sonar relative coordinates of the ship's echo points are transformed into the body's relative coordinates. Based on the attitude information output by the inertial navigator, a rotation matrix of the robot body is constructed, and the relative coordinates of the body of the hull echo point are converted into local horizontal coordinates using the rotation matrix. The robot body's absolute coordinates are obtained by combining the inertial navigator and the Doppler velocimeter, and the robot body's depth is obtained by using the depth gauge. Using the absolute coordinates of the main body and the depth of the main body, the local horizontal coordinates of the ship's echo point are transformed into absolute coordinates.

7. The method for modeling the hull of a ship according to claim 6, characterized in that, The process of converting the sonar relative coordinates of the ship's echo points into the body's relative coordinates based on the installation position of the multibeam forward-looking sonar relative to the robot's main body includes: ； in, This represents the x-coordinate of the ship's echo point in the sonar plane coordinate system; This represents the ordinate of the ship's echo point in the sonar plane coordinate system; This represents the coordinate components of the target echo point in the underwater robot's carrier coordinate system; Representing the sonar coordinate system The installation angle between the shaft and the first direction; This represents the installation offset of the sonar coordinate system origin relative to the underwater robot carrier coordinate system origin.

8. The method for modeling the hull of a ship according to claim 7, characterized in that, The process of constructing a rotation matrix for the robot body based on the attitude information output by the inertial navigator, and using the rotation matrix to convert the relative coordinates of the body at the hull echo point into local horizontal coordinates, specifically includes: Based on the roll angle, pitch angle, and heading angle when the robot emits its beam, construct the rotation matrix: ;in, Represents the coordinate system around the carrier The roll rotation matrix of the axis; Represents the coordinate system around the carrier. The tilt and rotation matrix of the axis; Represents the coordinate system around the carrier The heading rotation matrix of the axis; Using a rotation matrix, the relative coordinates of the subject are converted into local horizontal coordinates, including: ;in, This represents the coordinate components of the target echo point in the coordinate system of the underwater robot. This represents the coordinate components of the ship's echo point in the local horizontal coordinate system.

9. The method for modeling the hull of a ship according to claim 8, characterized in that, The process of transforming the local horizontal coordinates of the ship's echo points into absolute coordinates using the absolute coordinates of the main body and the depth of the main body includes: Obtain the absolute coordinates of the robot body in the geographic coordinate system. and main body depth Transforming local horizontal coordinates into absolute coordinates includes: ； in, These represent the absolute coordinates of the ship's echo points in the geographic coordinate system.

10. The method for modeling the hull of a ship according to claim 9, characterized in that, The process of constructing a mesh model of the ship's bottom based on the absolute positions of all hull echo points specifically includes: Based on the absolute position coordinates of all hull echo points, construct a hull bottom point cloud dataset; Based on the aforementioned ship bottom point cloud dataset, principal component analysis or local geometric analysis is used to determine the normal vector corresponding to each ship hull echo point, so as to construct the normal vector field of the ship bottom surface. A scalar function is defined based on the normal vector field. , so that the scalar function The gradient matches the normal vector field; according to the scalar function Based on the relationship between the normal vector field and the normal vector field, the Poisson equation is established: ;in, Represents the Laplace operator. This represents the divergence of the normal vector field; The Poisson equation is discretized and solved using the multigrid method to obtain the corresponding scalar field. Based on the scalar field, the isosurface is extracted using the moving cube algorithm to generate a three-dimensional polygonal mesh model of the ship's bottom.

Images