Passive source magnetic positioning method and device for energized submarine cable

Abstract

The application discloses a kind of passive source magnetic survey positioning method and device of energized submarine cable, it is related to submarine facility detection and positioning technology, the device at least includes three three-component fluxgate sensors arranged in equilateral triangle and an attitude sensor;The realization process of positioning method is: first, the three-component signal of alternating magnetic field excited by target submarine cable and attitude data are collected;Then, based on magnetic field component ratio, an inversion algorithm is constructed, the influence of unknown dynamic load current on the positioning result is eliminated, and the yaw angle, horizontal offset and vertical depth of the submarine cable are solved by using the geometric constraint relationship of three sensor and the optimal baseline selection strategy.The application only uses the power frequency alternating magnetic field of submarine cable itself as passive excitation source, without additional configuration of heavy artificial launching device, and the three sensor array design effectively avoids the calculation failure problem at a specific position, significantly improves the stability, operation efficiency and detection accuracy of line detection.

Description

Technical Field

[0001] This invention relates to submarine facility detection and positioning technology, mainly applied to applications such as route surveying, burial depth detection, and tracking inspection of submarine cables and pipelines. Specifically, it is a passive source magnetic measurement and positioning method and device for energized submarine cables. It utilizes the alternating magnetic field generated by the current of the energized submarine cable itself as a passive excitation source for magnetic anomaly detection and geometric position inversion, belonging to the field of geophysical electromagnetic exploration and marine engineering inspection. Background Technology

[0002] Submarine cables are critical infrastructure for cross-sea power transmission and communication. Affected by ocean currents, geological activity, and anchor damage, energized submarine cables are prone to exposure, suspension, or displacement. Regular inspections to determine their location and burial depth are crucial for ensuring their safe operation. Currently, external inspection methods for submarine cables mainly include optical, acoustic, and magnetic methods. Optical methods (such as underwater cameras) cannot detect buried cables; acoustic methods (such as multibeam sonar and side-scan sonar) can identify exposed targets, but their accuracy in depth detection is limited and they are easily affected by seabed sediment; existing magnetic methods mainly rely on active detection (such as the TSS series pipeline detectors), which require high-power artificial source transmitters mounted on ships. This equipment is bulky, expensive, and difficult to integrate with underwater robots (AUVs) for long-distance, low-cost autonomous cable tracking.

[0003] Utilizing the alternating magnetic field generated by the power frequency AC current transmitted by the submarine cable itself for passive source detection is an effective way to solve the above problems. However, accurate positioning based on the passive source magnetic field faces three major challenges: First, the load current inside the submarine cable changes dynamically and is unknown, and traditional positioning methods that rely on the absolute strength of the magnetic field will introduce large errors; second, there is strong geomagnetic background noise and carrier attitude disturbance in the marine environment, making it difficult to extract effective signals; and third, existing dual-sensor magnetic gradient measurement systems have blind spots where calculations fail at specific relative positions.

[0004] Therefore, developing a passive source magnetic measurement and positioning method and device that can eliminate the influence of unknown current is of great practical significance for improving the efficiency of submarine cable inspection and reducing operating costs. If it can further resist attitude interference and reduce positioning blind spots, its application scope will be even wider. Summary of the Invention

[0005] This invention aims to propose a passive source magnetic field measurement and positioning technology suitable for submarine cables, in order to solve the problem that existing passive source magnetic field positioning technologies cannot meet the application requirements of submarine cables and improve positioning accuracy. To this end, this invention provides a passive source magnetic field measurement and positioning method and apparatus for energized submarine cables. This technology relies solely on the power frequency magnetic field of the energized submarine cable itself, requires no prior knowledge of the current magnitude, and can stably calculate the geometric position of the energized submarine cable.

[0006] Therefore, the present invention provides the following technical solution:

[0007] This invention provides a passive source magnetic field determination and positioning method for energized submarine cables. The method involves deploying a detection device underwater, which includes at least three three-component fluxgate sensors arranged in an equilateral triangle. The method comprises the following steps:

[0008] Step 1: Data acquisition. Using the three-component fluxgate sensor and attitude sensor of the detection device, magnetic field components and attitude data of the detection device are collected around the target energized submarine cable.

[0009] Step 2: Detection and positioning. Calculate the yaw angle, horizontal offset, and vertical depth of the energized submarine cable relative to the detection device using the magnetic field components and attitude data to achieve passive source magnetic positioning.

[0010] For the yaw angle, based on the magnetic field components collected by each three-component fluxgate sensor, the covariance of the magnetic field x-component and y-component is introduced to locate and obtain the estimated yaw angle corresponding to each three-component fluxgate sensor, and then fused to obtain the yaw angle.

[0011] For vertical depth, an inversion algorithm based on the ratio of magnetic field components is introduced to achieve detection. That is, it is calculated based on the ratio of the magnetic field components of two three-component fluxgate sensors. The ratio of magnetic field components is defined as: the ratio K of the z component of the magnetic field to the y component of the magnetic field.

[0012] The horizontal offset is calculated based on the vertical depth.

[0013] Optionally, three three-component fluxgate sensors are defined as sensor 1, sensor 2, and sensor 3, respectively, and the coordinate system of the detection device... Central point Located at the position of the attitude sensor, that is, at the midpoint of the line connecting sensors 2 and 3; The axis points towards the heading of the detection device; The axis points to the right side of the detection device; The axis points vertically downwards;

[0014] The model for the vertical depth is as follows:

[0015] or or ;

[0016] In the formula, Z is the vertical depth of the energized submarine cable relative to the detection device, and L is the distance between every two adjacent three-component fluxgate sensors, i.e. the side length of an equilateral triangle. The yaw angle of the energized submarine cable relative to the detection device; The ratios K of sensors 1, 2, and 3 are respectively; the perpendicular distance from sensor 1 to the line connecting sensors 2 and 3. .

[0017] Optionally, when calculating the vertical depth, first obtain the effective projection length of the connection baseline of each pair of three-component fluxgate sensors on the normal plane perpendicular to the direction of the energized submarine cable, and then select the ratio K of the two three-component fluxgate sensors with the largest effective projection length to calculate the vertical depth.

[0018] The ratio of any three-component fluxgate sensor The calculation formula is:

[0019] ;

[0020] In the formula, For covariance; The roll angle of the i-th three-component fluxgate sensor is removed by attitude correction. With pitch angle The x-component and y-component of the magnetic field afterward; sgn is the z-component of the magnetic field acquired by the i-th three-component fluxgate sensor after attitude correction; sgn is the sign function.

[0021] Optionally, three three-component fluxgate sensors are defined as sensor 1, sensor 2, and sensor 3, respectively, and the coordinate system of the detection device... Central point Located at the position of the attitude sensor, that is, at the midpoint of the line connecting sensors 2 and 3; The axis points towards the heading of the detection device; The axis points to the right; The axis points vertically downwards;

[0022] The relationship model between the horizontal offset and the vertical depth is as follows:

[0023] ;

[0024] In the formula, Z represents the vertical depth of the energized submarine cable relative to the detection device, and Y represents the horizontal offset of the energized submarine cable relative to the detection device. The ratio K of sensors 2 and 3 are respectively.

[0025] Optionally, the yaw angle of the energized submarine cable relative to the detection device is taken as the average of the estimated yaw angle values ​​corresponding to the three-component fluxgate sensors, i.e.:

[0026] ;

[0027] In the formula, The yaw angle of the energized submarine cable relative to the detection device; These are the estimated yaw angle values ​​corresponding to the three-component fluxgate sensor.

[0028] Optionally, the covariance of the x and y components of the magnetic field is introduced for localization, and the estimated yaw angle corresponding to any three-component fluxgate sensor is obtained. The model is:

[0029] ;

[0030] In the formula, Let be the covariance between the x and y components of the magnetic field; The roll angle of the i-th three-component fluxgate sensor is removed by attitude correction. With pitch angle The x-component and y-component of the magnetic field afterward; They are respectively The magnetic measurement data is smoothed by the root mean square after passing through a sliding window of size N; sgn is the sign function, and arctan is the arctangent function.

[0031] Optionally, after acquiring the magnetic field components in step 1, a preprocessing operation is also performed, specifically:

[0032] First, the original magnetic field components are subjected to Fast Fourier Transform. Then, the alternating magnetic field signal generated by the energized submarine cable is extracted by bandpass filtering at the target frequency. Finally, the inverse Fast Fourier Transform is performed to restore the time domain signal.

[0033] Roll angle measured using attitude sensor With pitch angle Through rotation matrix and The roll angle in the original magnetic field component With pitch angle Removal, rotation matrix and They are represented as follows:

[0034] ;

[0035] ;

[0036] Set a sliding window The root mean square value of the corrected magnetic field components is calculated to smooth the signal.

[0037] The present invention also provides a detection device, which is applied to the above-mentioned passive source magnetic field measurement and positioning method to realize passive source magnetic field measurement and positioning.

[0038] Optionally, the detection device is equipped with a non-magnetic rigid frame, three three-component fluxgate sensors, an attitude sensor, and an altimeter;

[0039] The non-magnetic rigid frame is a non-magnetic support structure;

[0040] The three three-component fluxgate sensors are fixed on a non-magnetic rigid frame, and their geometric centers form an equilateral triangle with a side length of L.

[0041] The attitude sensor is located at the midpoint of the line connecting the two three-component fluxgate sensors;

[0042] The altimeter is installed at the geometric center of the equilateral triangle.

[0043] The present invention also provides a detection system, including an underwater body and the detection device as described in claim 8, wherein the detection device is disposed on the underwater body.

[0044] Compared with the prior art, the present invention achieves the following progress and effects:

[0045] 1. To address the technical obstacles caused by the dynamic and unknown changes in the load current inside submarine cables, this invention designs an array structure composed of three three-component fluxgate sensors. Based on this, an inversion algorithm based on the ratio of magnetic field components is derived. The design of the magnetic field component ratio can effectively eliminate the interference of the unknown and dynamically changing load current inside the submarine cable on the positioning results, and realize the inversion of the submarine cable position under the condition of unknown dynamic current changes.

[0046] 2. To address the technical challenges of extracting effective signals from strong geomagnetic background noise and carrier attitude disturbances in the marine environment, this invention further optimizes the technical solution by introducing a rotation matrix of carrier attitude data for correction, thereby achieving stable inversion of submarine cable yaw angle, horizontal offset, and vertical depth under environmental noise and attitude disturbance conditions.

[0047] 3. To address the technical obstacle of existing dual-sensor magnetic gradient measurement systems having a blind zone of solution failure at specific relative positions, this invention further optimizes the technical solution. Based on a three-sensor array structure, supplemented by a discrimination algorithm based on the maximum effective projection length and covariance combination discrimination, the solution blind zone of traditional dual-sensor magnetic measurement systems is eliminated to a certain extent, significantly improving the robustness and environmental adaptability of the inversion algorithm of this invention. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the passive source magnetic position detection device provided in an embodiment of the present invention;

[0049] Figure 2This is a schematic diagram of the coordinate system and the distribution of the three-component fluxgate sensors of the passive source magnetic position detection device;

[0050] Figure 3 These are schematic diagrams illustrating four different yaw angles, where diagram a represents the yaw angle. Figure b shows the yaw angle. Figure c shows the yaw angle. ; d represents the yaw angle ;

[0051] Figure 4 This is a schematic diagram showing the orientation of the three types of fluxgates. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other. It should be noted that the terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0054] The overall structure of the passive source magnetic potential detection device (hereinafter referred to as the detection device) provided in an embodiment of the present invention is as follows: Figure 1 As shown, the device includes at least: a non-magnetic rigid frame, three three-component fluxgate sensors, an attitude sensor, and an altimeter.

[0055] Non-magnetic rigid frame: As the supporting structure of the entire passive source magnetic position detection device, it is made of non-magnetic materials (such as high-strength engineering plastics, aluminum alloys, etc.) to ensure that no additional magnetic interference is introduced and to ensure that the relative geometric position between each sensor remains constant during operation; the technical solution of this invention has no specific requirements for the construction of the non-magnetic rigid frame.

[0056] Three three-component fluxgate sensors are fixed to a non-magnetic rigid frame. In this embodiment, they are numbered sensor 1, sensor 2, and sensor 3, respectively. The geometric centers of the three three-component fluxgate sensors form a side with a length of... An equilateral triangle, such as Figure 2As shown. In this embodiment, sensor 1 is located at the vertex of the equilateral triangle; sensors 2 and 3 are located at the two endpoints of the base of the equilateral triangle, respectively; the length of the line connecting sensors 2 and 3 is... According to geometric relationships, the perpendicular distance from sensor 1 to the line connecting sensors 2 and 3 is... .

[0057] In one specific embodiment, the side length Set as The corresponding high Approximately In other feasible embodiments, the dimensions can be adaptively adjusted and designed according to the actual application scenario and accuracy requirements, and the present invention does not impose specific limitations on this.

[0058] Attitude sensor: Installed at the midpoint of the line connecting sensors 2 and 3. This attitude sensor is used to measure the pitch angle of the passive source magnetic positioning and detection device carrier in real time during its movement. and roll angle This provides data for subsequent coordinate system rotation correction. It should be understood that in other feasible embodiments, the attitude sensor is not limited to the midpoint of the line connecting sensor 2 and sensor 3. Theoretically, it can be installed at any position as long as its coordinate system corresponds to that of the fluxgate sensor. Furthermore, some fluxgate sensor models have a built-in attitude sensor, in which case the attitude sensor does not need to be installed. In this embodiment, it is assumed that the two are separate; therefore, an attitude sensor is installed at the midpoint of the line connecting sensor 2 and sensor 3.

[0059] Altimeter: Mounted at the geometric center of an equilateral triangle. This altimeter is used to measure the vertical distance between the device itself and the seabed surface in real time. This provides a benchmark for subsequent calculations of the burial depth of energized submarine cables. In practical applications, the distance between the device and the seabed is monitored at all times to avoid collisions, and the height of the device above the seabed is recorded for subsequent data processing and reference.

[0060] It should be understood that Figure 1 The passive source magnetic field measurement and positioning device shown is only an example. The technical solution of the present invention is limited to having a non-magnetic rigid frame and three three-component fluxgate sensors mounted on the non-magnetic rigid frame, and the three three-component fluxgate sensors are arranged in an equilateral triangle. In other feasible embodiments, the architecture of the passive source magnetic field measurement and positioning device can be adaptively adjusted without departing from the above limitations.

[0061] like Figure 2 As shown, the coordinate system of the passive source magnetic position detection device The origin of this embodiment Located at the position of the attitude sensor (i.e., the midpoint of the line connecting sensors 2 and 3); The axis points to the heading of the passive source magnetic position detection device; The axis points to the right; The axis points vertically downwards. In the coordinate system... Below: In this embodiment, the coordinates of the attitude sensor are (0,0,0); the coordinates of sensor 1 are: The coordinates of sensor #2 are: The coordinates of sensor #3 are: The coordinates of the altimeter are: .

[0062] This invention also proposes a passive source magnetic field determination and positioning method for energized submarine cables. The core of this method lies in: based on the three-component magnetic field data collected by three three-component fluxgate sensor arrays, combined with attitude correction and magnetic field ratio processing, to achieve the determination of the yaw angle of energized submarine cables under unknown current. Horizontal offset and vertical distance A stable solution is obtained, thus accurately locating the energized submarine cable. The reasoning is as follows:

[0063] In a spatial rectangular coordinate system, according to the quasi-static approximation condition, a energized submarine cable can be equivalent to an infinitely long straight conductor, which at the observation point... The frequency domain expressions for each component of the magnetic flux density generated at that location are:

[0064] (1);

[0065] (2);

[0066] (3);

[0067] In the formula, This is the effective value of the current, i.e., the unknown current. The permeability of the medium, Let t be the angular frequency and t be the time. and These represent the horizontal offset and vertical distance of the observation point relative to the axis of the energized submarine cable, respectively. Observation points The magnetic field generated at the location has three components; it should be understood that when using this device to detect energized submarine cables, there are actually two coordinate systems, namely, a coordinate system with reference to the submarine cable itself. (hereinafter referred to as the submarine cable coordinate system), and the coordinate system with reference to the device itself. (Hereinafter referred to as the device coordinate system) (See details) Figure 2 (Origin of submarine cable coordinate system) On the axis of the submarine cable The axis runs along the coastal cable route. The axis is horizontal to the right. The axis points vertically downwards; the origin of the device's coordinate system. Located at the midpoint of the line connecting sensors 2 and 3, it should be understood that in this embodiment, although the attitude sensor is also located at the midpoint of the line connecting sensors 2 and 3, and at the origin of the device coordinate system... While they overlap, in other feasible embodiments the attitude sensor can be placed anywhere because all components of the entire device are rigidly connected, and the attitude angle measured by the device remains unchanged when the attitude angle of the device changes, so it can be placed anywhere. The axis points to the direction of the device. Pointing to the right, The axis points vertically downwards. Using the aforementioned coordinate system as a reference, the position of the attitude sensor in the device's coordinate system is the origin. The positions of sensors 1, 2, and 3 in the device's reference system are respectively... , , The position of the altimeter in the device's reference frame is . Let the initial phase of the current (rad) be denoted as , which is usually set to in the analysis. To simplify calculations.

[0068] As can be seen from equations (1)-(3), each magnetic field component Amplitude and unknown current Proportional. To eliminate unknown current. Influence, defining the perpendicular component of the magnetic field With the horizontal component of the magnetic field The ratio is , based on observation point For example, under ideal conditions, the ratio K satisfies:

[0069] (4);

[0070] From formula (4), we can see that the ratio The K-value depends only on the geometric position of the observation point relative to the energized submarine cable, and is independent of the current intensity; that is, it is the ideal form of the K-value expression. The above mathematical model is also applicable to any point. This constitutes the theoretical basis for the technical solution of this invention to locate the point without knowing the current.

[0071] To achieve accurate geometric inversion, the yaw angle of the passive source magnetic position detection device must first be determined. This invention utilizes the covariance and sign relationship between magnetic field components to define the yaw angle estimate of the i-th three-component fluxgate sensor. for:

[0072] (5);

[0073] In the formula, Let be the covariance between the x and y components of the magnetic field; The roll angle of the i-th three-component fluxgate sensor is removed by attitude correction. With pitch angle The x-component and y-component of the magnetic field afterward; They are respectively The data is smoothed by the root mean square after passing through a sliding window of size N; sgn is the sign function.

[0074] By analyzing the sign of the covariance and , The amplitude can uniquely determine the yaw direction of the energized submarine cable relative to the sensor.

[0075] To improve noise immunity, this embodiment uses the average value of the calculation results from the three-component fluxgate sensor as the yaw angle of the device. :

[0076] (6);

[0077] Obtain the yaw angle of the device Afterwards, the origin of the coordinate system of the passive source magnetic position detection device. Located at the midpoint of the line connecting the 2nd and 3rd sensors, If the axis points towards the heading, then the origin... The horizontal offset relative to the energized submarine cable is The vertical distance is Then the first A three-component fluxgate sensor ( Compared to the horizontal offset of the submarine cable axis satisfy:

[0078] (7);

[0079] Combining equation (4) and equation (7), we obtain the system of equations:

[0080] (8);

[0081] (9);

[0082] It should be understood that formula (4) is the ratio of K value under the absolutely ideal state based on formula (1)-(3). Under the ideal state, only the y component has a signal and the x component is 0. However, in actual engineering, due to the influence of attitude, the y component signal will deflect, causing some x components to have a signal. Therefore, the x and y signals should be combined for calculation. In actual applications, formula (9) is used to calculate the ratio, which is more in line with the actual working conditions of the application scenario.

[0083] Equation (9) contains three unknowns ( , , The overdetermined system of equations ( ). Traditional dual-sensor systems can only construct two equations, which can lead to the denominator term approaching zero and causing solution failure at certain angles (such as when the axis of a powered submarine cable is perpendicular to the baseline of a sensor). This invention employs a three-component fluxgate sensor array to provide redundant observation information. The baseline between any two three-component fluxgate sensors is defined. Effective projected length on the normal plane perpendicular to the direction of the energized submarine cable ,exist:

[0084] (10);

[0085] In the formula, , , These represent the effective projected lengths corresponding to sensors 2-3, 1-2, and 1-3, respectively. By comparison , , The size is determined by selecting the set of three-component fluxgate sensor data with the largest effective projected length for vertical distance measurement. The solution is as follows: the larger the effective projection length, the greater the spatial span of the three-component fluxgate sensor in the direction perpendicular to the energized submarine cable, the more significant the magnetic field gradient it covers, and the more stable and reliable the solution results.

[0086] If D 23 If the maximum value is reached, the inversion of the vertical distance Z is based on the data from the three-component fluxgate sensors 2 and 3, specifically:

[0087] 11);

[0088] If D 12 If the vertical distance Z is at its maximum, then the inversion is based on the data from the three-component fluxgate sensors 1 and 2, specifically:

[0089] (12);

[0090] If D 13 If the vertical distance Z is maximized, then the inversion is based on the data from the three-component fluxgate sensors 1 and 3, specifically:

[0091] (13);

[0092] After obtaining the vertical distance Z, the horizontal offset Y can be calculated using the following formula:

[0093] (14);

[0094] This strategy ensures in principle that at any yaw angle, there is always a pair of sensors in a relatively strong magnetic field gradient region, thereby eliminating to some extent the solution blind zone present in traditional dual-sensor magnetic measurement systems and significantly improving the robustness and environmental adaptability of the positioning algorithm.

[0095] In the above inversion algorithm Positive and negative determine It means shifting to the left or right; The positive or negative sign of the signal determines the relative offset position between the submarine cable and the detection device.

[0096] in, B represents the value of the i-th sensor after angle correction. x With B y The covariance of the component before RMS (Root Mean Square) processing; the sign of this parameter remains consistent across all fluxgate sensors, and it is only related to the yaw angle of the cable axis and the device axis. There are a total of [number missing]. Figure 3 The four types of situations are shown below:

[0097] Because the target submarine cable carries alternating current, there are two current directions. Under ideal conditions, when the current direction is the same as the arrow on the submarine cable, the positive and negative values ​​of the parameters corresponding to various cases are shown in Table 1:

[0098] Table 1. Positive and negative values ​​of parameters for different yaw angles.

[0099]

[0100] When the current direction is opposite to the arrow on the submarine cable, B x With B y Positive and negative are also opposite, therefore they do not affect The sign of α. It is easy to see from Table 1 that in the two cases of α = 0° / 180° and α = 90° / -90°, its... Since all values ​​are 0, when they approach 0, it is still necessary to determine their B. x With B y signal, B x If the value is small and tends to 0, then α = 0° / 180°, B y If the value is small and tends to 0, then α = 90° / -90°.

[0101] B represents the value of the i-th sensor after angle correction. y With B zThe covariance of the components before RMS processing; this parameter varies across different fluxgate sensors depending on their geometric position relative to the submarine cable, and can be categorized into three types, such as... Figure 4 As shown, the fluxgate is located on the left side of the submarine cable, the fluxgate is located on the Z-axis of the submarine cable, and the fluxgate is located on the right side of the submarine cable:

[0102] Table 2 shows the sign of the parameters for different situations when the current direction is the same as the arrow on the submarine cable:

[0103] Table 2. Positive and negative values ​​of parameters for different fluxgate orientations.

[0104]

[0105] When the current direction is opposite to the arrow on the submarine cable, B y With B z Positive and negative are also opposite, therefore they do not affect The positive and negative aspects.

[0106] comprehensive and The positioning results were summarized in 4 groups, totaling 38 different arrangements, of common relative position conditions between the detection device and the submarine cable. The versatility and effectiveness of the positioning algorithm of this invention were determined by qualitative analysis. The statistical information is shown in Tables 3-6.

[0107] Table 3. Statistical Analysis of Positive and Negative Parameters under the -90°<α<0° Condition

[0108]

[0109] Table 3 shows the changes in the positive and negative values ​​of the covariance of each sensor when the yaw angle is between -90° and 0° for 13 operating conditions. Among them, - / 0 / + indicates that in the initial state when the device is not moving, the parameter is initially negative, becomes 0 at a certain time point after the device starts moving, and then becomes positive and no longer changes; 0 / + indicates that in the initial state when the device is not moving, the parameter is initially negative 0, and then becomes positive at a certain time point and no longer changes.

[0110] Table 40°<α<90° Working Condition Parameter Positive and Negative Analysis Statistics

[0111]

[0112] Table 4 shows the changes in the positive and negative values ​​of the covariance of each sensor when the yaw angle is between 0° and 90° for 13 operating conditions. Among them, + / 0 / - indicates that in the initial state when the device is not moving, the parameter is initially positive and negative, becomes 0 at a certain time point after the device starts moving, and then becomes negative and no longer changes; 0 / - indicates that in the initial state when the device is not moving, the parameter is initially positive and negative and no longer changes.

[0113] Table 5. Statistical Analysis of Positive and Negative Parameters under α=0° / 180° Operating Condition

[0114]

[0115] Table 5 shows the covariance of each sensor under seven operating conditions when the yaw angle is 0° or 180°. Ideally, the covariance does not change under these conditions.

[0116] Specifically, when α = 90° / -90°, B y At this point, it is 0, when B... y When the value is 0 or approaches 0, call Used for location determination, as shown in Table 6.

[0117] Table 6. Statistical Analysis of Positive and Negative Parameters under α=90° / -90° Operating Conditions

[0118]

[0119] Table 6 shows the covariance of each sensor under five operating conditions when the yaw angle is 90° or -90°. As can be seen from equation (1), the y component is zero under ideal conditions. Meaningless, therefore call The distinction is made as follows: + / 0 / - indicates that in the initial state when the device is not moving, the parameter is initially positive or negative (+), becomes 0 at a certain point in time after the device starts moving, and then becomes negative and no longer changes; 0 / - indicates that in the initial state when the device is not moving, the parameter is initially positive or negative (0), and then becomes negative at a certain point in time and no longer changes.

[0120] The statistical data above clearly shows that the covariance-based positioning algorithm has a consistent and simple judgment logic under different working conditions. With the support of the three fluxgate sensors, the number of working conditions that can be located and distinguished and the convenience are significantly improved compared with the dual-sensor detection system. In particular, the data in Table 6 shows that the relative position of the submarine cable and the detection device can be roughly determined without precise horizontal offset calculation, which is impossible for the dual-sensor detection system.

[0121] In some embodiments, the present invention also provides a detection system, including an underwater body and the above-described detection device, wherein the detection device is disposed on the underwater body, similar to... Figure 1 As shown.

[0122] Finally, it should be noted that the above description is merely a preferred embodiment of the technical solution of the present invention, and its purpose is to explain the technical logic of the present invention in detail, rather than to impose an absolute limitation on the scope of protection. Any equivalent substitutions or engineering evolutions made within the core control concept and technical architecture of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A passive source magnetic field determination and positioning method for an energized submarine cable, characterized in that: A detection device is deployed underwater, the device being equipped with at least three three-component fluxgate sensors arranged in an equilateral triangle; the method includes the following steps: Step 1: Data acquisition. Using the three-component fluxgate sensor of the detection device, magnetic field components and attitude data of the detection device are collected around the target energized submarine cable. Step 2: Detection and positioning. Calculate the yaw angle, horizontal offset, and vertical depth of the energized submarine cable relative to the detection device using the magnetic field components to achieve passive source magnetic positioning. For the yaw angle, based on the magnetic field components collected by each three-component fluxgate sensor, the covariance of the magnetic field x-component and y-component is introduced to locate and obtain the estimated yaw angle corresponding to each three-component fluxgate sensor, and then fused to obtain the yaw angle. For vertical depth, an inversion algorithm based on the ratio of magnetic field components is introduced to achieve detection, that is, it is calculated based on the ratio of the magnetic field components of two three-component fluxgate sensors. The ratio of magnetic field components is defined as the ratio K of the z component of the magnetic field to the y component of the magnetic field under ideal conditions. The horizontal offset is calculated based on the vertical depth.

2. The method according to claim 1, characterized in that: Define three three-component fluxgate sensors as sensor 1, sensor 2, and sensor 3, respectively, and define the coordinate system of the detection device. Central point Located at the midpoint of the line connecting sensors 2 and 3; The axis points towards the heading of the detection device; The axis points to the right side of the detection device; The axis points vertically downwards; The model for the vertical depth is as follows: or or ; In the formula, Z is the vertical depth of the energized submarine cable relative to the detection device, and L is the distance between every two adjacent three-component fluxgate sensors, i.e. the side length of an equilateral triangle. The yaw angle of the energized submarine cable relative to the detection device; The ratios K of sensors 1, 2, and 3 are respectively; the perpendicular distance from sensor 1 to the line connecting sensors 2 and 3. .

3. The method according to claim 1, characterized in that: When calculating the vertical depth, first obtain the effective projection length of the connection baseline of each pair of three-component fluxgate sensors on the normal plane perpendicular to the direction of the energized submarine cable, and then select the ratio K of the two three-component fluxgate sensors with the largest effective projection length to calculate the vertical depth. The ratio of any three-component fluxgate sensor The calculation formula is: ； In the formula, For covariance; The roll angle of the i-th three-component fluxgate sensor is removed by attitude correction. With pitch angle The x-component and y-component of the magnetic field afterward; sgn is the z-component of the magnetic field acquired by the i-th three-component fluxgate sensor after attitude correction; sgn is the sign function.

4. The method according to claim 1, characterized in that: Define three three-component fluxgate sensors as sensor 1, sensor 2, and sensor 3, respectively, and define the coordinate system of the detection device. Central point Located at the midpoint of the line connecting sensors 2 and 3; The axis points towards the heading of the detection device; The axis points to the right; The axis points vertically downwards; The relationship model between the horizontal offset and the vertical depth is as follows: ； In the formula, Z represents the vertical depth of the energized submarine cable relative to the detection device, and Y represents the horizontal offset of the energized submarine cable relative to the detection device. The ratio K represents the ratio of sensor number 2 to sensor number 3.

5. The method according to claim 1, characterized in that: The yaw angle of the energized submarine cable relative to the detection device is taken as the average of the estimated yaw angle values ​​corresponding to the three-component fluxgate sensors, i.e.: ； In the formula, The yaw angle of the energized submarine cable relative to the detection device; These are the estimated yaw angle values ​​corresponding to the three-component fluxgate sensor.

6. The method according to claim 1, characterized in that: Introducing the covariance positioning of the x and y components of the magnetic field, the estimated yaw angle for any three-component fluxgate sensor is... The model is: ； In the formula, Let be the covariance between the x and y components of the magnetic field; The roll angle of the i-th three-component fluxgate sensor is removed by attitude correction. With pitch angle The x-component and y-component of the magnetic field afterward; They are respectively The magnetic measurement data is smoothed by the root mean square after passing through a sliding window of size N; sgn is the sign function, and arctan is the arctangent function.

7. The method according to claim 6, characterized in that: After acquiring the magnetic field components in step 1, a preprocessing operation is also performed, specifically: First, the original magnetic field components are subjected to Fast Fourier Transform. Then, the alternating magnetic field signal generated by the energized submarine cable is extracted by bandpass filtering at the target frequency. Finally, the inverse Fast Fourier Transform is performed to restore the time domain signal. Roll angle measured using attitude sensor With pitch angle Through rotation matrix and The roll angle in the original magnetic field component With pitch angle Remove, rotate matrix and They are represented as follows: ； ； Set a sliding window The root mean square value of the corrected magnetic field components is calculated to smooth the signal.

8. A detection device, characterized in that: The detection device uses the method described in any one of claims 1-7 to achieve passive source magnetic positioning.

9. The detection device according to claim 8, characterized in that: The detection device is equipped with a non-magnetic rigid frame, three three-component fluxgate sensors, an attitude sensor, and an altimeter. The non-magnetic rigid frame is a non-magnetic support structure; The three three-component fluxgate sensors are fixed on a non-magnetic rigid frame, and their geometric centers form an equilateral triangle with a side length of L. The attitude sensor is located at the midpoint of the line connecting the two three-component fluxgate sensors; The altimeter is installed at the geometric center of the equilateral triangle.

10. A detection system, characterized in that: It includes an underwater vehicle and the detection device as described in claim 8, wherein the detection device is disposed on the underwater vehicle.

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