An unmanned ship sailing type seabed cable passive electromagnetic detection system and positioning method

Abstract

The present invention discloses an unmanned surface vessel (USV) passive electromagnetic detection system and positioning method for submarine cables. The cable detection sensor configuration mainly includes an electromagnetic detection system, a bottom-penetrating altimeter, and a navigation system. The USV detection platform is designed to detect and locate cable route points using a reciprocating navigation method. The navigation route consists of a straight detection path and a transition path between the straight paths. The detection system collects environmental electromagnetic signals along the straight detection line and calculates the location of the cable route points based on the collected signals. Based on the located cable route points, key waypoints on the next detection line are planned, thereby completing the reciprocating navigation of the USV detection platform and the unmanned positioning of cable route points. Compared with methods currently used in engineering practice, the cable detection and positioning method designed in this invention has advantages such as low cost, high efficiency, high accuracy, and no human resource consumption.

Description

Technical Field

[0001] This invention relates to the field of marine engineering and technology, specifically to the detection and maintenance of submarine cable systems, and more specifically, to a passive electromagnetic detection system and positioning method for unmanned surface vessel (USV) submarine cables. Background Technology

[0002] Submarine cables mainly include submarine electrical cables, submarine optical cables, and submarine fiber optic composite cables. Submarine optical cable communication, due to its advantages of high capacity, high quality, and low price, has become the most important international communication method, accounting for over 95% of global international data communication volume. With the rapid development of 5G, cloud services, and other internet-related businesses, the demand for data communication is exploding, leading to a rapid increase in the bandwidth and quantity of submarine optical cables. Submarine electrical cables play a significant role in power transmission fields such as offshore wind power generation and inter-island power transmission. Submarine cables are frequently affected by natural and human factors such as earthquakes and anchoring, often resulting in damage, breakage, or suspension, necessitating real-time updates to cable routing information to provide a basis for cable maintenance operations. Currently, engineering practice often uses surface vessels as detection platforms and handheld electromagnetic detectors, employing a reciprocating patrol method to detect cable routing points. Based on feedback from electromagnetic anomalies observed by personnel, combined with GPS latitude and longitude signals from unmanned vessels, the approximate latitude and longitude information of the cable routing points is roughly determined. This traditional detection method involves personnel conducting detection operations from surface vessels. As a result, this method suffers from problems such as low detection accuracy, high dependence on personnel, and inability to determine the burial or exposure status of submarine cable routes.

[0003] The papers “Research on Submarine Cable Burial Depth Detection Technology” (Electric Wire & Cable, 2005, 3(3):38-42), “Design and Implementation of Submarine Optical Cable Route Tracking System” (Dissertation, Huazhong University of Science and Technology), and “Research on Automatic Submarine Cable Tracking Technology Based on Magnetic Signal Guidance for Underwater Robots” (Dissertation, Huazhong University of Science and Technology) disclose a near-range tracking coverage-type route positioning method for submarine cables. The disclosed detection system mainly includes two isomorphic triaxial electromagnetic detection sensors. The comparative documents, based on different premises, derive a submarine cable route positioning algorithm based on the same sensor configuration scheme, mainly including yaw angle, lateral offset, and vertical offset positioning algorithms. However, this submarine cable detection and positioning algorithm is based on ideal submarine cable electromagnetic signals, while the local electromagnetic noise brought about by the electromagnetic detection platform and the complex underwater electromagnetic environment is difficult to avoid. Therefore, the disclosed submarine cable detection and positioning algorithms often have problems such as unstable submarine cable positioning results and loss of tracking by the detection platform in engineering practice. Therefore, the mobile detection method, which uses a series of multi-point electromagnetic detection sequences to locate a submarine cable route point, has strong fault tolerance and robustness, and is a commonly used submarine cable detection and location method in current engineering practice. Summary of the Invention

[0004] This invention addresses the shortcomings and deficiencies of existing underway submarine cable route detection and positioning methods in engineering practice. It designs an intelligent submarine cable detection and positioning method based on electromagnetic detection sensors using unmanned surface vessels (USVs) to improve detection and positioning accuracy, increase detection efficiency, and reduce manpower and other resource consumption. The invention includes a hardware configuration scheme for submarine cable detection, a detection process design, and an intelligent positioning algorithm. This invention provides a fully automated, unmanned detection system for submarine cable operation and maintenance that conforms to marine engineering practices, aiming to accurately determine the latitude, longitude, and burial depth of submarine cable routes.

[0005] The technical problems solved by this invention mainly include the design of electromagnetic detection sensor configuration schemes for undersea cables (submarine cables), the design of integrated planning and detection processes, and the design of intelligent positioning algorithms for submarine cable routes. The technical solutions adopted by this invention are as follows:

[0006] 1. Passive electromagnetic detection system for submarine cables (undersea cables): The system's sensor configuration is flexible and selectable. The standard configuration of this detection system mainly includes a three-axis orthogonal electromagnetic detector or two single-axis electromagnetic sensors, a bottom-mounted altimeter, and a navigation system (the navigation system is used to determine the absolute position of the unmanned surface vessel (USV) detection platform in the geodetic coordinate system, i.e., latitude / longitude information, and to correlate the absolute position with the electromagnetic detection information and altimeter information according to timestamps; for surface USVs, the navigation system is GPS or BeiDou positioning system; for underwater USVs, the navigation system refers to a combined navigation system, specifically including sensors such as a Doppler log and inertial navigation unit, used to provide the real-time position and attitude of the detection platform underwater).

[0007] 2. The standard configuration of sensors for the underway submarine cable electromagnetic detection system includes interchangeable triaxial orthogonal electromagnetic detectors and single-axis electromagnetic sensors. When a triaxial orthogonal electromagnetic sensor is selected, its three axes are parallel to the three axes of the detection platform body, and its center of action is coplanar with the XOZ plane of the detection platform. When two single-axis electromagnetic sensors are selected, one axis is parallel to the bow X-axis of the detection platform, and the other axis is parallel to the Z-axis of the detection platform. The line connecting the center of action of the two sensors is parallel to the Y-axis of the detection platform.

[0008] 3. Navigation system for the detection platform: The navigation system is mainly used to determine the latitude and longitude information of the submarine cable route point. When the detection platform is an underwater vehicle, the navigation system can be selected as an underwater integrated navigation system; when the detection platform is an unmanned surface vessel, the navigation system can be selected as a GPS navigation and positioning system.

[0009] 4. The planning method and process design for mobile electromagnetic detection, including submarine cable route location methods, mainly include submarine cable route point location optimization algorithms, submarine cable route point prediction algorithms, and mobile waypoint planning algorithms. The initial stage is the submarine cable search stage. Based on the approximate location of the submarine cable route recorded in the submarine cable maintenance log, two initial waypoints are set on both sides of the submarine cable route, ensuring that the straight-line route between the two waypoints is nearly perpendicular to the submarine cable route. The two designated initial waypoints and subsequent designed waypoints are all within the same two-dimensional horizontal plane. For surface unmanned vessels, the designed waypoints and detection routes are located on the water surface. For underwater detection platforms, the designed waypoints and detection routes are located at a specified depth (the specified depth depends on the water depth of the area, and it is necessary to ensure a certain safe navigation distance from the seabed at the specified depth, such as 3-10 meters from the seabed surface). When the detection platform is in a straight-line... During the route exploration phase, when the electromagnetic signal acquisition sequence determines that the conditions for starting the submarine cable positioning algorithm are met, the submarine cable route positioning algorithm is activated, and the location of the submarine cable route point on the straight route is output based on the algorithm (the calculation process is given in the submarine cable route intelligent positioning algorithm as shown in point 5 below); the approximate location of the next submarine cable route point is predicted based on the discovered submarine cable route points (the calculation process is given in the submarine cable route point prediction algorithm as shown in point 6 below), and the critical waypoints are calculated based on the predicted submarine cable route points. The critical waypoints are the two endpoints of the underway straight route (the calculation process is given in the critical waypoint planning algorithm as shown in point 7 below).

[0010] 5. The core of the intelligent positioning algorithm for submarine cable routes, namely the iterative optimization algorithm, is as follows:

[0011]

[0012] 6. The submarine cable route prediction algorithm, for the second submarine cable route point and the subsequent submarine cable route point prediction algorithms, are given as follows:

[0013]

[0014]

[0015] 7. The critical waypoint planning algorithm is given as follows:

[0016]

[0017] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0018] 1. Compared with traditional submarine cable detection methods, the passive electromagnetic detection method for submarine cables designed in this invention achieves unmanned submarine cable detection, reduces the consumption of human and material resources, and can significantly improve detection accuracy and efficiency.

[0019] 2. The passive electromagnetic detection configuration scheme and positioning method for submarine cables designed in this invention can be applied to various types of marine vehicles or detection platforms, such as autonomous underwater robots, hybrid underwater robots, autonomous unmanned vessels, surface unmanned vessels, and remotely operated underwater robots.

[0020] 3. The passive electromagnetic detection sensor configuration scheme for submarine cables designed in this invention is simple and feasible. It only requires a three-axis electromagnetic detection sensor to be fixedly installed on the marine vehicle platform. Compared with the tracking detection method in the prior art, it reduces the number of sensors and simplifies the installation of the electromagnetic detection sensor. The altimeter and integrated navigation system are standard sensing configurations for conventional vehicles.

[0021] 4. Compared with the tracking and detection methods in the prior art, the submarine cable routing and positioning algorithm designed in this invention is bridged with the vehicle motion planning algorithm only through a determined route point and is separated from the tracking and control process of navigation. This ensures stable navigation performance during the vehicle's detection process. Therefore, the designed submarine cable routing and positioning method has stronger fault tolerance and robustness.

[0022] 5. Compared with the submarine cable tracking and detection in the prior art, the submarine cable route positioning algorithm designed in this invention has stronger signal fault tolerance because the positioning and optimization of a single submarine cable route point is based on a series of electromagnetic signal groups collected on a straight route. This reduces the impact of local abnormal electromagnetic noise on the positioning results.

[0023] 6. In the submarine cable detection and route positioning method designed in this invention, the detection platform only needs to navigate at a certain depth on the horizontal plane for navigation and detection, that is, constant depth navigation, thereby reducing the risk of bottoming out caused by insufficient maneuverability of the vehicle when navigating near the seabed. Therefore, the designed submarine cable detection and positioning method can improve the navigation safety of the unmanned surface vessel detection platform. Attached Figure Description

[0024] Figure 1 Passive detection and positioning process of unmanned surface vessel (USV) for submarine cable navigation;

[0025] Figure 2 This invention provides the configuration and positioning system framework for the passive detection system of a submarine cable.

[0026] Figure 3 The following are the mounting configuration schemes for electromagnetic detection sensors on unmanned surface vessel (USV) detection platforms (taking USV as an example): (a) a three-axis orthogonal electromagnetic detector mounting scheme and (b) a dual single-axis electromagnetic detector mounting scheme.

[0027] Figure 4 This is a flowchart of the submarine cable positioning and planning algorithm of the present invention;

[0028] Figure 5 This invention provides a framework for submarine cable route point localization algorithms (taking particle swarm optimization as an example). Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further explained in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] Figure 1 This invention relates to the passive detection and positioning process of unmanned surface vessel (USV) submarine cable. Figure 2 This is a schematic diagram illustrating the software and hardware configuration of a mobile submarine cable passive detection system constructed according to a preferred embodiment of the present invention, as well as the information interaction between its modules. Figure 2 As shown, the detection sensor configuration of this invention, namely the combined measurement system, is mainly used to collect environmental electromagnetic signals and bottom altitude information, including an electromagnetic detection sensor, a bottom altimeter, and a detection platform navigation system. The submarine cable positioning and planning algorithm of this invention is mainly used to locate the submarine cable route point and plan the submarine cable detection route, including a swarm intelligent positioning algorithm and an online route planning algorithm. The relationship between the units is as follows: the combined measurement system feeds back electromagnetic detection signal sequences with added address stamps and bottom altitude signals at fixed intervals; the submarine cable route intelligent positioning algorithm locates the submarine cable route point based on the above information; the online route planning algorithm plans the detection route based on the submarine cable route positioning result and generates critical path points; the vehicle navigation and control performs vehicle tracking control based on the guidance of the critical path points, thereby performing repeated detection and positioning of the submarine cable route, thus forming a closed loop of "detection-positioning-planning-tracking-detection".

[0031] The installation method for the electromagnetic detection sensor and its height is set as follows. When using a single triaxial electromagnetic detection sensor, the two orthogonal axes should be perpendicular to each other in the heading and lateral directions of the detection platform, respectively, and the sensor's center of action should be located within the plane of symmetry of the detection platform. When using two single-axis electromagnetic detection sensors, the central axes of the two sensors should be orthogonal and parallel to the heading and lateral directions of the detection platform, respectively, and the distance between the centers of action of the two sensors should be minimized.

[0032] Figure 4This is a flowchart of the submarine cable positioning and planning algorithm. In the initial detection phase, two waypoints are designated on both sides of the submarine cable route based on the cable maintenance log, ensuring the line connecting these two waypoints is approximately perpendicular to the cable route. During the unmanned surface vessel's (USV) navigation, environmental electromagnetic signals and bottom elevation signals are simultaneously acquired. The electromagnetic signal data is periodically used to determine if the cable positioning algorithm's activation conditions are met. If not, vehicle tracking and electromagnetic signal detection continue. When the activation conditions are met, the cable route positioning algorithm is executed, outputting the cable route point's location and burial depth. Then, based on the existing cable route location, the location of the next cable route point and key waypoints are predicted and planned. Guided by the planned waypoints, vehicle tracking and electromagnetic signal acquisition continue. In each control cycle, the remaining onboard energy is checked; if insufficient, cable tracking and detection cease.

[0033] The activation condition for the submarine cable route location algorithm refers to the activation of the swarm intelligence-based algorithm when the electromagnetic signal radiated by the submarine cable, sensed by the electromagnetic detection sensor, attenuates to a certain limit. The degree of electromagnetic signal attenuation is measured by the difference in signal components along the horizontal and vertical axes of the electromagnetic detection sensor. Specifically, the activation condition includes the upper and lower bounds of the effective electromagnetic noise sequence that can be used for the electromagnetic location algorithm.

[0034] Because the electromagnetic sequences acquired by electromagnetic detection sensors contain electromagnetic noise interference, and the actual useful signal quantity available for submarine cable positioning algorithms is limited, the following algorithm is used to determine the lower bound of the electromagnetic sequence that can be practically used for submarine cable positioning:

[0035]

[0036] Similarly, the upper bound of the electromagnetic sequence signal that can actually be used for submarine cable positioning is determined by the following algorithm:

[0037]

[0038] Among them, inc l and inc u These are the electromagnetic signal sequence values ​​used in the submarine cable positioning algorithm. and and The sliding filter values, used for determining the lower and upper bounds of the effective electromagnetic signal sequence, are given as follows:

[0039]

[0040]

[0041] Among them, D h-v,i =V h,i -Vv,i V is the difference between the electromagnetic signals along the horizontal and vertical axes at time i. h,i and V h,i These represent the signal values ​​along the horizontal and vertical axes at time i, respectively; V h-v,max The maximum value of the difference between the electromagnetic sequence signals in the horizontal and vertical axes is expressed by the following expression: V h-v,max =max(V h -V v V h V is the sequence of electromagnetic signals acquired along the horizontal axis. v is the electromagnetic signal sequence acquired in the vertical axis direction; a and n are positive constants, and (n+1) is the length of the electromagnetic signal sequence used for smoothing filtering.

[0042] The submarine cable route point prediction algorithm is as follows. Submarine cable route point The prediction algorithm is as follows:

[0043]

[0044] in, and The coordinates of the two previously determined submarine cable route points; ρ is a constant representing the distance between the survey lines; The heading angle of the vector from the first submarine cable route point to the second predicted submarine cable route point is used to plan the critical path points on the second straight-line detection route, i.e., the two endpoints of the straight-line route.

[0045] Specifically, once the first submarine cable route point is determined, the prediction algorithm for the second submarine cable route point is as follows:

[0046]

[0047] The critical path planning algorithm is as follows. For the next critical path point, Given the heading angle of the vector from the known submarine cable route point to the next predicted submarine cable route point, the planning algorithm for the two endpoints of the critical path, i.e., the straight-line detection route, is as follows:

[0048]

[0049] The slope of the straight line connecting the known submarine cable route point to the next predicted submarine cable route point in the geodetic coordinate system.

[0050] The algorithm flow for locating submarine cable routing points is as follows: Figure 5 As shown, the algorithm flow is described below:

[0051] (1) Select the Region of Interest (ROI) to define the approximate control location of the submarine cable route point. The ROI is defined by the point on the survey line with the maximum value of the electromagnetic signal sequence (x). ext ,y ext ,z ext A cuboid centered at z ext The height of this point detected by the altimeter is W, its width is L, its length is H, and the eight vertices of the region of interest are as follows:

[0052]

[0053] in, The current heading of the survey line; (X) 1,u ,Y 1,u Z 1,u ), (X 1,l ,Y 1,l Z 1,l ), (X 2,u ,Y 2,u Z 2,u ), (X 2,l ,Y 2,l Z 2,l ), (X 3,u ,Y 3,u Z 3,u ), (X 3,l ,Y 3,l Z 3,l ), (X 4,u ,Y 4,u Z 4,u ) and (X 4,l ,Y 4,l Z 4,l ) are the coordinates of the eight vertices of the cuboid.

[0054] (2) Taking the particle swarm optimization algorithm as an example, determine the size of the particle swarm (e.g., m particles), and initialize the spatial position vector (x) of each particle i (i = 1…m). i ,y i ,z i ) and flight velocity vector (v xi ,v yi ,v zi This allows all particles to be evenly distributed within the region of interest.

[0055] (3) For each particle i, evaluate its fitness F(x) based on the electromagnetic detection sensor signal sequence. i,t ), F(x) i,t () represents the fitness of particle i in the t-th optimization cycle. The fitness is calculated as follows:

[0056]

[0057] Among them, V hj and V vj These are the electromagnetic detection signals along the horizontal and vertical axes at position j, respectively. hiij and V vij These are the virtual electromagnetic signals calculated for particle i at position j along the horizontal and vertical axes, respectively, where m is the total number of particles in the population, and V... hiij and V vij The calculation method is as follows:

[0058]

[0059] Among them, (x j ,y j (x) represents the position coordinates of the spacecraft at detection point j, and (x) represents the position coordinates of the spacecraft at detection point j. i ,y i ,z i Let be the coordinate position of individual i in the group, and c be a constant.

[0060] (4) In the first iteration, particle number 1 is taken as the global optimal particle, and its fitness is the global optimal fitness F(g). The spatial coordinates of the global optimal particle are denoted as p. g The fitness calculated for the first cycle of all particles is taken as the individual historical best fitness F(p) of each particle. i The position corresponding to the best fitness in each particle's personal history is denoted as p. i .

[0061] (5) Compare the fitness functions of all particles with the global optimal fitness F(g) and the personal historical optimal fitness F(p) of each particle respectively. i Compare the fitness of particle i with its historical best fitness F(g). When the fitness of particle i is greater than F(g), update it to the global best fitness F(g). When the fitness of particle i is greater than its historical best fitness F(p), update it to the global best fitness F(g). i When ), update it to the individual's historical best fitness F(p). i ).

[0062] (6) After the loop comparison is completed, update the spatial velocity vector and spatial position vector of the particle respectively. The update algorithm is as follows:

[0063]

[0064] Among them, v i (t) and x i (t) represents the velocity vector and position vector of particle i in the current period, respectively; x i (t+1) and v i(t+1) represent the position and velocity vectors of particle i in the next cycle; v max The maximum flight speed of the particles is set; c1 and c2 are the individual and group learning factors, respectively; r1 and r2 are the random parameters for updating the particles.

[0065] (7) After each loop, check if the maximum allowed number of loops has been reached. When the maximum allowed number of loops has been reached, end the particle swarm algorithm and output the coordinates p of the globally optimal particle. g The algorithm checks whether the fitness function of the globally optimal particle has reached a pre-set threshold. If it exceeds the threshold, the particle swarm optimization algorithm terminates and outputs the coordinates p of the globally optimal particle. g .

[0066] (8) End the submarine cable route positioning algorithm, output and save the global optimal particle coordinates p g This will be used as the final result for determining the location of the submarine cable route. (z) g -d g This represents the positioning result of the submarine cable burial depth, where z g Let d be the z-coordinate of the globally optimal particle. g The height gauge feedback value is the sampling point closest to the globally optimal particle.

[0067] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various similar changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for locating submarine cable routes based on a passive electromagnetic detection system for unmanned surface vessels (USVs), the detection system comprising a set of three-axis orthogonal electromagnetic sensors or two sets of single-axis electromagnetic sensors, a bottom-penetrating altimeter, and a navigation system, characterized in that: a) Electromagnetic detection system: used to sense the electromagnetic field radiated by the submarine cable in the underwater space in the horizontal and vertical directions, that is, the horizontal axis and the vertical axis, which are perpendicular to each other, and to collect spatial electromagnetic signals; the composition of the magnetic detection system is relatively flexible: a set of three-axis orthogonal electromagnetic detection sensors or two sets of single-axis electromagnetic detection sensors can meet the detection requirements in the horizontal and vertical directions. b) Installation method of electromagnetic detection system: When using a set of three-axis orthogonal electromagnetic detection sensors, the X, Y, and Z axes of the sensor are parallel to the X, Y, and Z axes of the detection platform, respectively, and the center of action of the sensor is located in the left and right symmetrical plane of the unmanned surface vessel detection platform; when using two sets of single-axis electromagnetic detection sensors, the axis of one set of sensors is parallel to the heading direction of the detection platform, i.e., the X-axis, and the axis of the other set of sensors is parallel to the Z-axis of the detection platform, and the line connecting the center of action of the two sets of sensors is parallel to the Y-axis of the detection platform, and the two sets of sensors are tightly connected together; c) Altimeter: Used to detect the height distance between the unmanned surface vessel and the seabed surface in real time. Combined with the submarine cable route point location results, the burial depth of the submarine cable route point is determined. The altimeter detection data will correspond one-to-one with the data collected by the magnetic detection system according to the timestamp, and will be used to assist in defining the region of interest during the execution of the submarine cable route point location algorithm. d) Navigation system: The navigation system is used to determine the absolute position of the unmanned surface vessel (USV) detection platform in the geodetic coordinate system, i.e., latitude / longitude information, and to correspond the absolute position with electromagnetic detection information and altimeter information according to timestamps; for surface unmanned vehicles, the navigation system is GPS or Beidou positioning system; for underwater unmanned hulls, the navigation system refers to a combined navigation system, specifically including a Doppler log and an inertial navigation unit. The unmanned surface vessel (USV) passive electromagnetic detection system for submarine cables is suitable for various detection platforms, including surface unmanned vessels, autonomous underwater vehicles (AUVs), remotely operated underwater vehicles (ROVs), and hybrid underwater vehicles (HIUVs). The cable positioning algorithms employed include cable route point localization algorithms, cable route point prediction algorithms, and onboard waypoint planning algorithms, as follows: a) Submarine cable routing point location algorithm: Based on a swarm intelligence optimization algorithm, each individual in the swarm is considered as a potential submarine cable routing point. The update and iteration algorithm for each individual in the swarm is as follows: in, and The position update rates of individual i at time t and time t+1 are respectively. and These represent the spatial locations of individual i at time t and time t+1, respectively, which are the potential spatial locations of submarine cable routing points. , and All are non-negative constants, representing the inertia factor, individual acceleration constant, and population acceleration constant, respectively, which affect the speed of population optimization and the acceleration capabilities of individual and population optimization; ROI is the region of interest, used to limit the position update of the individual iteration process; b) Submarine cable route point prediction algorithm: This algorithm is used to predict the position coordinates of submarine cable route points on the next survey line, and then used for waypoint planning in underway surveys; the position prediction algorithm for the second submarine cable route point and subsequent submarine cable route points is given as follows: in, and These are the predicted coordinates of the second submarine cable route point and subsequent submarine cable route points, respectively. and These are the locations of the first and i-th submarine cable route points that have been detected, respectively. and These are the coordinates of the first and second specified waypoints, respectively. and These are the heading angles of the vector from the first submarine cable route point to the second predicted submarine cable route point, and the heading angles of the vector from the known submarine cable route point to the next predicted submarine cable route point, respectively. The distance between two specified submarine cable route points, i.e., the distance between two adjacent straight-line routes; c) Transit-based waypoint planning algorithm: This algorithm is used to plan the next survey line so that the survey platform can conduct transit-based reciprocating surveys of the submarine cable, including key waypoints on the survey line and the course of the survey line; the algorithm is given as follows: in, This is a key waypoint on the next survey line. For the heading of the next survey line, The slope of the straight line connecting the known submarine cable route point to the next predicted submarine cable route point in the geodetic coordinate system.

2. The submarine cable route positioning method according to claim 1, characterized in that: The submarine cable positioning algorithm is activated when the acquired electromagnetic signal attenuates to a certain extent. The electromagnetic signal used for the submarine cable positioning algorithm must have distinct characteristics. The algorithms for determining the lower and upper bounds of the electromagnetic sequence actually used for submarine cable positioning are as follows: in, and These are the electromagnetic signal sequence values ​​used in the submarine cable positioning algorithm. and , and The sliding filter values, used for determining the lower and upper bounds of the effective electromagnetic signal sequence, are given as follows: in, Let be the difference between the electromagnetic signals along the horizontal and vertical axes at time i. and These are the signal values ​​along the horizontal and vertical axes at time i, respectively; The maximum value of the difference between the electromagnetic sequence signals in the horizontal and vertical axes is expressed by the following expression: , This is a sequence of electromagnetic signals acquired along the horizontal axis. This is a sequence of electromagnetic signals acquired along the vertical axis. , n is a positive constant, and n+1 is the length of the electromagnetic signal sequence used for smoothing filtering.

3. The submarine cable route positioning method according to claim 1, characterized in that: The fitness of individuals in the population is evaluated using the following fitness evaluation function: For each particle i, its fitness is evaluated based on the electromagnetic detection sensor signal sequence. , This represents the fitness of particle i in the t-th optimization cycle. The fitness is calculated as follows: in, and These are the electromagnetic detection signals at position j along the horizontal and vertical axes, respectively. and These are the virtual electromagnetic signals calculated for particle i at position j along the horizontal and vertical axes, respectively, where m is the total number of particles in the swarm. and The calculation method is as follows: in, Here are the coordinates of the spacecraft's position at detection point j. Let be the coordinates of individual i in the group. It is a constant.

4. The submarine cable route positioning method according to claim 1, characterized in that: The region of interest (ROI) is used to define the location of submarine cable route points, and the ROI is defined by the point with the maximum value of the electromagnetic signal sequence on the survey line. A cuboid centered on the central point. The height of this point is measured by the altimeter. The region of interest has a width of W, a length of L, and a height of H. The eight vertices of the region of interest are as follows: in, The current heading of the survey line; , , , , , , and These are the coordinates of the eight vertices of the cuboid.

5. A positioning method for an unmanned surface vessel (USV)-based passive electromagnetic detection system for submarine cables, implemented based on the submarine cable route positioning method of any one of claims 1-4, characterized in that: The unmanned surface vessel (USV) detection platform uses a reciprocating navigation method to detect and locate submarine cable route points. The reciprocating navigation route consists of a straight detection route and a transition route between the straight routes. The detection system collects environmental electromagnetic signals on the straight measurement line segment and calculates the location of the submarine cable route points based on the collected electromagnetic signals. Based on the location of the detected submarine cable route points, it plans the key route points on the next measurement line, thereby completing the reciprocating navigation of the detection platform and the unmanned location of submarine cable route points.

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