阅读说明：本技术 一种基于弱磁信号的海缆路由坐标定位方法 (Submarine cable routing coordinate positioning method based on weak magnetic signals ) 是由 李勃 俞炜平 黄文超 林松青 李振海 黄汉权 林宇澄 陈臻旭 吴宗泽 于 2021-08-18 设计创作，主要内容包括：本发明涉及一种基于弱磁信号的海缆路由坐标定位方法,该坐标定位方法使用水下机器人作为平台,水下机器人底部设置有水平的履带,水下机器人上设置有两三轴磁传感器,两三轴磁传感器分别为线圈传感器和磁通门传感器；两三轴传感器的Y轴均指向水下机器人的前进方向,前进方向由履带确定；两三轴传感器的Z轴均垂直于履带；水下机器人上设置有陀螺仪,陀螺仪用于采集水下机器人的姿态信息,并根据姿态信息修正两三轴传感器的数据至标准值；本发明将海缆产生的磁信号根据传感器的接收划分成三个区域,在每个区域中执行相应的策略,使传感器最终靠近海缆,获取海缆坐标。(The invention relates to a submarine cable routing coordinate positioning method based on weak magnetic signals, which uses an underwater robot as a platform, wherein the bottom of the underwater robot is provided with a horizontal crawler belt, and the underwater robot is provided with two three-axis magnetic sensors which are respectively a coil sensor and a fluxgate sensor; y axes of the two triaxial sensors point to the advancing direction of the underwater robot, and the advancing direction is determined by the crawler; the Z axes of the two triaxial sensors are both vertical to the crawler; the underwater robot is provided with a gyroscope, the gyroscope is used for acquiring attitude information of the underwater robot and correcting data of the two triaxial sensors to a standard value according to the attitude information; the invention divides the magnetic signal generated by the submarine cable into three areas according to the receiving of the sensor, and executes corresponding strategies in each area, so that the sensor finally approaches to the submarine cable to acquire the coordinates of the submarine cable.)

1. A submarine cable routing coordinate positioning method based on weak magnetic signals uses an underwater robot as a platform, the bottom of the underwater robot is provided with a horizontal crawler, the underwater robot is provided with two three-axis magnetic sensors, and the submarine cable routing coordinate positioning method is characterized in that,

the two three-axis magnetic sensors are respectively a coil sensor and a fluxgate sensor, the sensitivity of the coil sensor is higher than that of the fluxgate sensor, and the measuring range of the fluxgate sensor is larger than that of the coil sensor; the Y axes of the two three-axis sensors point to the advancing direction of the underwater robot, and the advancing direction is determined by the crawler; the Z axes of the two three-axis sensors are perpendicular to the crawler;

the underwater robot is provided with a gyroscope, and the gyroscope is used for acquiring attitude information of the underwater robot and correcting data of the two three-axis sensors to a standard value according to the attitude information;

obtaining submarine cable routing coordinates according to the following steps:

the coil sensor and the signals acquired by the fluxgate sensor have a fixed conversion relation; setting a threshold value beta, when the intensity of the signal acquired by the coil sensor is lower than the threshold value beta, converting the signal acquired by the coil sensor to obtain an expected signal of the fluxgate sensor at the current position, and correcting the signal acquired by the fluxgate sensor according to the expected signal; when the signal intensity acquired by the coil sensor is higher than beta, converting the signal acquired by the fluxgate sensor to obtain an expected signal of the coil sensor at the current position, and correcting the signal acquired by the coil sensor according to the expected signal;

the underwater robot is put down in a target sea area, and magnetic signals generated by a submarine cable are acquired through the coil sensor and the fluxgate sensor; calculating the position relation between the underwater robot and the submarine cable according to the magnetic signal;

judging the region of the underwater robot according to the magnetic signal, planning a moving path of the underwater robot in the current region according to the change of the magnetic signal, and moving the underwater robot according to the moving path until the underwater robot is close to a submarine cable;

and calculating to obtain the coordinates of the submarine cable according to the coordinates of the underwater robot and the position relationship between the underwater robot and the submarine cable.

2. The submarine cable routing coordinate positioning method based on weak magnetic signals according to claim 1, wherein the coil sensor and the fluxgate sensor are respectively arranged on the front side and the rear side of the underwater robot and connected with the underwater robot through a bracket.

3. The submarine cable routing coordinate positioning method based on weak magnetic signals according to claim 2, wherein the magnetic signals acquired by the two three-axis sensors are subjected to Fourier transform to obtain an amplitude value of a signal with the same frequency as the submarine cable power frequency, and the amplitude value is used as a magnetic signal for calculating the position relationship between the underwater robot and the submarine cable and planning the movement path of the underwater robot.

4. The submarine cable routing coordinate positioning method based on weak magnetic signals according to claim 3, wherein when the underwater robot is located in a no-signal area, no-signal area detection is performed, and the underwater robot enters a weak-signal area through the no-signal area detection; the signal-free area is an area which cannot be acquired by the coil sensor or can acquire effective magnetic signals only on part of the axis; the weak signal area is an area where effective magnetic signals can be acquired by each axis of the coil sensor, and the fluxgate sensor cannot acquire the effective magnetic signals or can acquire the effective magnetic signals only on part of the axes; the signal-free area detection comprises the following steps:

the underwater robot is made to descend to a specific height, and a magnetic signal epsilon generated by a submarine cable is acquired through three shafts of the coil sensor_x、ε_yAnd ε_zObtaining the horizontal component of the magnetic signalSetting a threshold value epsilon_p0And ε_z0，

Judging the horizontal component ε_pThe vertical component epsilon_zWith a threshold value epsilon_p0、ε_z0According to the judgment result, the following operations are executed:

P₁if epsilon_z＜ε_z0Then the underwater robot is made to descend until epsilon_z＞ε_z0Then if epsilon_p＞ε_p0Then P is executed₃If epsilon_p＜ε_p0Then P is executed₂If epsilon is not satisfied until the underwater robot descends to the seabed_z＞ε_z0If so, withdrawing the underwater robot, adjusting the lowering position, and lowering again;

P₂if epsilon_p＜ε_p0And is epsilon_z＞ε_z0Setting two horizontal search paths which are vertical to each other, and enabling the underwater robot to move along the two search paths until epsilon_p＞ε_p0Then, P is executed₃；

P₃If epsilon_p＞ε_p0And is epsilon_z＞ε_z0And if so, the underwater robot is considered to enter a weak signal area.

5. The submarine cable routing coordinate positioning method based on weak magnetic signals according to claim 4, wherein when the underwater robot is located in a weak signal area, weak signal area detection is performed, and the underwater robot enters a strong signal area through the weak signal area detection; the strong signal area is an area where effective magnetic signals can be acquired by each shaft of the coil sensor and the fluxgate sensor; the weak signal area detection comprises the following steps:

lowering the underwater robot to the sea floor;

acquiring magnetic signals epsilon generated by submarine cables through X-axis and Y-axis of the coil sensor_1xAnd ε_1yAnd calculating the included angle theta between the Y axis of the coil sensor and the submarine cable route_yThe formula is as follows:

according to the included angle theta_yAdjusting the advancing direction of the underwater robot to be vertical to the submarine cable route;

moving the underwater robot through the crawler;

monitoring the magnetic signals acquired by the coil sensor in the moving process, if the magnetic signals are weakened in the moving process, rotating the advancing direction of the underwater robot by 180 degrees, and enabling the underwater robot to move through the crawler belt, if the magnetic signals are not weakened in the moving process, continuing to move through the crawler belt;

until each shaft of the fluxgate sensor acquires an effective magnetic signal, the underwater robot is considered to enter a strong signal area.

6. The weak magnetic signal-based submarine cable routing coordinate positioning method according to claim 5, wherein the weak signal area detection further comprises distance measurement between the coil sensor and the submarine cable routing, comprising the following steps:

the underwater robot is enabled to move for a distance along the direction perpendicular to the submarine cable route, and magnetic signals epsilon generated by the submarine cable before moving are collected through three axes of the coil sensor_3x、ε_3yAnd ε_3zAnd the magnetic signal epsilon generated by the moved submarine cable_4x、ε_4yAnd ε_4z；

Calculating the magnetic signal epsilon collected by the coil sensor before and after movement₃And ε₄The following are:

calculating a shortened distance dr between the coil sensor and the sea cable route before and after the movement as follows:

wherein dy is the moving distance of the underwater robot; theta_3yThe included angle between the Y axis of the coil sensor and the submarine cable route is set;is the coil sensor and the seaThe angle of depression of the cable routing,

calculating the distance r between the coil sensor and the submarine cable route before moving as follows:

at intervals T, the distance of the coil sensor from the sea cable route is calculated from data generated over the past time T.

7. The weak magnetic signal-based submarine cable routing coordinate positioning method according to claim 5, wherein the weak signal area detection further comprises that the underwater robot moves through the crawler belt at intervals of T₁Acquiring magnetic signals generated by the submarine cable through the coil sensor, and calculating an included angle theta between the Y axis of the coil sensor and the route of the submarine cable_yAccording to the angle theta_yAnd adjusting the advancing direction of the underwater robot to be vertical to the submarine cable route.

8. The submarine cable routing coordinate positioning method based on weak magnetic signals according to claim 5, wherein when the underwater robot is located in a strong signal area, strong signal area detection is performed, and the strong signal area detection comprises the following steps:

collecting magnetic signals epsilon generated by submarine cable through three axes of coil sensor_2x、ε_2y、ε_2zAcquiring a magnetic signal epsilon 'generated by a submarine cable through the three axes of the fluxgate sensor'_2x、ε'_2yAnd epsilon'_2z；

Obtaining a depression angle of the coil sensor, the fluxgate sensor and the submarine cable routeThe tangent of (c) is as follows:

wherein the content of the first and second substances,

if it isExecuting a first relative distance algorithm, otherwise, executing a second relative distance algorithm;

first relative distance algorithm:

p, H is the horizontal distance and the vertical distance between the coil sensor and the submarine cable route respectively;l is the distance between the coil sensor and the fluxgate sensor; theta_2yThe included angle between the Y axis of the coil sensor and the submarine cable route is set;

second relative distance algorithm:

acquiring a height difference dh in a vertical direction and a distance difference dp in a horizontal direction of the magnetic coil sensor and the fluxgate sensor as follows:

dh＝Lsinθ_2ysinλ₂，

dp＝Lsinθ_2ycosλ₂，

wherein λ is₂Acquiring an included angle between the underwater robot and a horizontal plane by the gyroscope;

the following results were obtained:

9. the submarine cable routing coordinate positioning method based on weak magnetic signals according to claim 8, wherein the strong signal area detection further comprises:

acquiring longitude and latitude coordinates (W) of the current underwater robot by a positioning technology₀,J₀)；

Detecting the data obtained according to the strong signal area and the longitude and latitude coordinates (W) of the underwater robot₀,J₀) And calculating the longitude and latitude coordinates (W) of the submarine cable route at the detection point k_k,J_k) The formula is as follows:

W_k＝arcsin(sin(W₀)cos(P_k/R)+cos(W₀)sin(P_k/R)cosθ_2y)，

wherein, P_kAnd converting the horizontal distance between the underwater robot and the submarine cable route at a detection point k into the horizontal distance between the coil sensor and the detection point k, wherein R is the radius of the earth.

10. The submarine cable routing coordinate positioning method based on weak magnetic signals according to claim 9, wherein the strong signal region detection further comprises:

acquiring signals generated by a submarine cable route through the coil sensor, calculating an included angle between the coil sensor and the submarine cable route, keeping the advancing direction of the underwater robot parallel to the submarine cable route according to the included angle, and moving along the direction parallel to the submarine cable route;

the coordinates of the submarine cable route are calculated every certain distance.

Technical Field

The invention relates to a submarine cable routing coordinate positioning method based on weak magnetic signals, and belongs to the technical field of submarine cable positioning.

Background

The submarine cable is positioned by one indispensable step in the operation processes of submarine cable detection, maintenance, fault determination, upgrading and the like, the submarine cable is quickly and accurately positioned, the construction time can be shortened, and the construction efficiency is improved. When the submarine cable is in fault maintenance, the loss caused by the fault can be greatly reduced. Submarine cable laying has many specific difficulties and difficulties in positioning submarine cables compared to over-the-road cables.

At present, the most widely applied submarine cable detection is a technical means based on physical principles such as sound, light, electricity and magnetism. Among them, optical and electrical detection means are greatly limited in use under actual deep water environmental conditions, and are rarely used or used as an auxiliary. The acoustic detection method mainly utilizes a sonar echo technology, and based on a reflected echo principle of acoustic waves, submarine acoustic images with a certain width are obtained to indirectly obtain submarine cable routing information. Although the attenuation of sound waves in seawater is much smaller than that of high-frequency electromagnetic waves, the sound waves cannot penetrate silt covered on the submarine cable, so that the detection effect on the buried cable is not good. The magnetic detection technology is a detection method which is developed earlier and has mature technology in various non-acoustic detections. In the means of detecting the submarine cable, the magnetic detection method has the advantages of strong identification capability, short operation time, good positioning precision, good real-time performance, low cost and the like compared with a sonar technology.

The application document with the application number of 202011366513.6 discloses a double-triaxial electromagnetic detection and route positioning method for submarine cables, which is characterized in that six real-time electromagnetic signals are acquired by two triaxial electromagnetic detection sensors, and coordinates of submarine cable routes are calibrated by the six electromagnetic signals. The method has the advantages that the problem that the distance between the sensor and the submarine cable is long when the detection is started is not solved, if the relative distance between the sensor and the submarine cable is long when the detection is started, effective magnetic signals cannot be acquired, and the subsequent routing positioning cannot be started.

Disclosure of Invention

In order to overcome the problems, the invention provides a submarine cable routing coordinate positioning method based on weak magnetic signals, which divides magnetic signals generated by a submarine cable into three areas according to the receiving of a sensor, executes a corresponding strategy in each area, enables the sensor to be close to the submarine cable, acquires submarine cable coordinates, and enables the sensor to track the submarine cable to acquire favorable submarine cable routing coordinates.

The technical scheme of the invention is as follows:

a submarine cable routing coordinate positioning method based on weak magnetic signals uses an underwater robot as a platform, the bottom of the underwater robot is provided with a horizontal crawler, the underwater robot is provided with two three-axis magnetic sensors, and the submarine cable routing coordinate positioning method is characterized in that,

the two three-axis magnetic sensors are respectively a coil sensor and a fluxgate sensor, the sensitivity of the coil sensor is higher than that of the fluxgate sensor, and the measuring range of the fluxgate sensor is larger than that of the coil sensor; the Y axes of the two three-axis sensors point to the advancing direction of the underwater robot, and the advancing direction is determined by the crawler; the Z axes of the two three-axis sensors are perpendicular to the crawler;

the underwater robot is provided with a gyroscope, and the gyroscope is used for acquiring attitude information of the underwater robot and correcting data of the two three-axis sensors to a standard value according to the attitude information;

obtaining submarine cable routing coordinates according to the following steps:

the coil sensor and the signals acquired by the fluxgate sensor have a fixed conversion relation; setting a threshold value beta, when the intensity of the signal acquired by the coil sensor is lower than the threshold value beta, converting the signal acquired by the coil sensor to obtain an expected signal of the fluxgate sensor at the current position, and correcting the signal acquired by the fluxgate sensor according to the expected signal; when the signal intensity acquired by the coil sensor is higher than beta, converting the signal acquired by the fluxgate sensor to obtain an expected signal of the coil sensor at the current position, and correcting the signal acquired by the coil sensor according to the expected signal;

the underwater robot is put down in a target sea area, and magnetic signals generated by a submarine cable are acquired through the coil sensor and the fluxgate sensor; calculating the position relation between the underwater robot and the submarine cable according to the magnetic signal;

judging the region of the underwater robot according to the magnetic signal, planning a moving path of the underwater robot in the current region according to the change of the magnetic signal, and moving the underwater robot according to the moving path until the underwater robot is close to a submarine cable;

and calculating to obtain the coordinates of the submarine cable according to the coordinates of the underwater robot and the position relationship between the underwater robot and the submarine cable.

Further, the coil sensor and the fluxgate sensor are respectively disposed at a front side and a rear side of the underwater robot and connected to the underwater robot through a bracket.

Further, the magnetic signals acquired by the two triaxial sensors are subjected to Fourier transform to obtain the amplitude of the signal with the same frequency as the power frequency of the submarine cable, and the amplitude is used as the magnetic signal for calculating the position relation between the underwater robot and the submarine cable and planning the moving path of the underwater robot.

Further, when the underwater robot is located in a no-signal area, detecting the no-signal area, and enabling the underwater robot to enter a weak-signal area through the no-signal area detection; the signal-free area is an area which cannot be acquired by the coil sensor or can acquire effective magnetic signals only on part of the axis; the weak signal area is an area where effective magnetic signals can be acquired by each axis of the coil sensor, and the fluxgate sensor cannot acquire the effective magnetic signals or can acquire the effective magnetic signals only on part of the axes; the signal-free area detection comprises the following steps:

the underwater robot is made to descend to a specific height, and a magnetic signal epsilon generated by a submarine cable is acquired through three shafts of the coil sensor_x、ε_yAnd ε_zObtaining the horizontal component of the magnetic signalSetting a threshold value epsilon_p0And ε_z0，

Judging the horizontal component ε_pThe vertical component epsilon_zWith a threshold value epsilon_p0、ε_z0According to the judgment result, the following operations are executed:

P₁if epsilon_z＜ε_z0Then the underwater robot is made to descend until epsilon_z＞ε_z0Then if epsilon_p＞ε_p0Then P is executed₃If epsilon_p＜ε_p0Then P is executed₂If epsilon is not satisfied until the underwater robot descends to the seabed_z＞ε_z0If so, withdrawing the underwater robot, adjusting the lowering position, and lowering again;

P₂if epsilon_p＜ε_p0And is epsilon_z＞ε_z0Setting two horizontal search paths which are vertical to each other, and enabling the underwater robot to move along the two search paths until epsilon_p＞ε_p0Then, holdLine P₃；

P₃If epsilon_p＞ε_p0And is epsilon_z＞ε_z0And if so, the underwater robot is considered to enter a weak signal area.

Further, when the underwater robot is located in a weak signal area, detecting the weak signal area, and enabling the underwater robot to enter a strong signal area through the detection of the weak signal area; the strong signal area is an area where effective magnetic signals can be acquired by each shaft of the coil sensor and the fluxgate sensor; the weak signal area detection comprises the following steps:

lowering the underwater robot to the sea floor;

acquiring magnetic signals epsilon generated by submarine cables through X-axis and Y-axis of the coil sensor_1xAnd ε_1yAnd calculating the included angle theta between the Y axis of the coil sensor and the submarine cable route_yThe formula is as follows:

according to the included angle theta_yAdjusting the advancing direction of the underwater robot to be vertical to the submarine cable route;

moving the underwater robot through the crawler;

monitoring the magnetic signals acquired by the coil sensor in the moving process, if the magnetic signals are weakened in the moving process, rotating the advancing direction of the underwater robot by 180 degrees, and enabling the underwater robot to move through the crawler belt, if the magnetic signals are not weakened in the moving process, continuing to move through the crawler belt;

until each shaft of the fluxgate sensor acquires an effective magnetic signal, the underwater robot is considered to enter a strong signal area.

Further, the weak signal area detection further comprises distance measurement between the coil sensor and a submarine cable route, and the method comprises the following steps:

moving the underwater robot a distance in a direction perpendicular to the submarine cable route and passing the underwater robotThree-axis acquisition of magnetic signals epsilon generated by submarine cable before movement of coil sensor_3x、ε_3yAnd ε_3zAnd the magnetic signal epsilon generated by the moved submarine cable_4x、ε_4yAnd ε_4z；

Calculating the magnetic signal epsilon collected by the coil sensor before and after movement₃And ε₄The following are:

calculating a shortened distance dr between the coil sensor and the sea cable route before and after the movement as follows:

wherein dy is the moving distance of the underwater robot; theta_3yThe included angle between the Y axis of the coil sensor and the submarine cable route is set;the dip angle for the coil sensor and sea cable routing,

calculating the distance r between the coil sensor and the submarine cable route before moving as follows:

at intervals T, the distance of the coil sensor from the sea cable route is calculated from data generated over the past time T.

Further, the weak signal area detection also includesThe underwater robot moves through the crawler belt at intervals of T₁Acquiring magnetic signals generated by the submarine cable through the coil sensor, and calculating an included angle theta between the Y axis of the coil sensor and the route of the submarine cable_yAccording to the angle theta_yAnd adjusting the advancing direction of the underwater robot to be vertical to the submarine cable route.

Further, when the underwater robot is located in a strong signal area, detecting the strong signal area, wherein the detecting of the strong signal area comprises the following steps:

collecting magnetic signals epsilon generated by submarine cable through three axes of coil sensor_2x、ε_2y、ε_2zAcquiring a magnetic signal epsilon 'generated by a submarine cable through the three axes of the fluxgate sensor'_2x、ε'_2yAnd epsilon'_2z；

Obtaining a depression angle of the coil sensor, the fluxgate sensor and the submarine cable routeThe tangent of (c) is as follows:

wherein the content of the first and second substances,

if it isExecuting a first relative distance algorithm, otherwise, executing a second relative distance algorithm;

first relative distance algorithm:

p, H is the horizontal distance and the vertical distance between the coil sensor and the submarine cable route respectively;l is the distance between the coil sensor and the fluxgate sensor; theta_2yThe included angle between the Y axis of the coil sensor and the submarine cable route is set;

second relative distance algorithm:

acquiring a height difference dh in a vertical direction and a distance difference dp in a horizontal direction of the magnetic coil sensor and the fluxgate sensor as follows:

dh＝Lsinθ_2ysinλ₂，

dp＝Lsinθ_2ycosλ₂，

wherein λ is₂Acquiring an included angle between the underwater robot and a horizontal plane by the gyroscope;

the following results were obtained:

further, the strong signal region detection further includes:

acquiring longitude and latitude coordinates (W) of the current underwater robot by a positioning technology₀,J₀)；

Detecting the data obtained according to the strong signal area and the longitude and latitude coordinates (W) of the underwater robot₀,J₀) Calculating the longitude and latitude of the submarine cable route at the detection point kCoordinate (W)_k,J_k) The formula is as follows:

W_k＝arcsin(sin(W₀)cos(P_k/R)+cos(W₀)sin(P_k/R)cosθ_2y)，

wherein, P_kAnd converting the horizontal distance between the underwater robot and the submarine cable route at a detection point k into the horizontal distance between the coil sensor and the detection point k, wherein R is the radius of the earth.

Further, the strong signal region detection further includes:

acquiring signals generated by a submarine cable route through the coil sensor, calculating an included angle between the coil sensor and the submarine cable route, keeping the advancing direction of the underwater robot parallel to the submarine cable route according to the included angle, and moving along the direction parallel to the submarine cable route;

the coordinates of the submarine cable route are calculated every certain distance.

The invention has the following beneficial effects:

1. according to the positioning method, magnetic signals generated by the submarine cable are collected through the two three-axis magnetic sensors, the area where the underwater robot is located is divided according to whether the collected magnetic signals are effective or not, and different strategies are executed according to the area where the underwater robot is located. Compared with the prior art, the method greatly improves the application area of the positioning method. When the position that underwater robot transferred is far away from the submarine cable, still can fix a position the submarine cable fast.

2. According to the positioning method, magnetic signals generated by the submarine cable are collected through the coil sensor and the fluxgate sensor, and a fixed conversion relation exists between the signals collected by the coil sensor and the fluxgate sensor. Since the magnetic signal generated by the submarine cable is attenuated quickly in the seawater, the span of the signal range is very large along with the change of the distance between the detection equipment and the submarine cable, and the magnetic sensor with a certain range is difficult to keep linearity under the magnetic field signal with such a large range. Through the cooperation of the high-sensitivity sensor and the wide-range sensor, a proper sensor is selected according to the strength of a signal, and a signal value acquired by the other sensor is corrected through a conversion relation.

3. The positioning method obtains the coordinates of the detection point through the relative distance between the underwater robot and the detection point and the coordinates of the underwater robot. And moving along the submarine cable to obtain the coordinates of each detection point of the submarine cable, and finally obtaining the accurate coordinates of the submarine cable route. In the positioning process, various reasons such as the submarine cable is buried under the sea floor and the sea floor has undulation are considered.

4. The positioning method carries out Fourier transform on the collected magnetic signals to obtain the amplitude of the signals with the same frequency as the power frequency of the submarine cable, and the amplitude is utilized to carry out detection and positioning. Compared with the prior art, the method adopts the instantaneous signals for detection and positioning, and needs to consider the factors of the signal phase, so that the method has lower requirements on equipment, and reduces the data processing difficulty.

Drawings

FIG. 1 is a flow chart of the method of the present invention.

Fig. 2 is a schematic diagram of the no-signal region detection according to the embodiment of the present invention.

Fig. 3 is a schematic diagram of weak signal region detection according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a state of relative distance calculation according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating another state of relative distance calculation according to an embodiment of the present invention.

Detailed Description

The invention is described in detail below with reference to the figures and the specific embodiments.

Example one

A submarine cable routing coordinate positioning method based on weak magnetic signals uses an underwater robot as a platform, the bottom of the underwater robot is provided with a horizontal crawler belt, the underwater robot is provided with two three-axis magnetic sensors, and the submarine cable routing coordinate positioning method is characterized in that,

the two three-axis magnetic sensors are respectively a coil sensor and a fluxgate sensor, the sensitivity of the coil sensor is higher than that of the fluxgate sensor, the measuring range of the fluxgate sensor is larger than that of the coil sensor, and the signal range span is very large along with the change of the distance between the detection equipment and the submarine cable due to the fact that the attenuation of a magnetic signal generated by the submarine cable in seawater is fast. The coil sensor is easier to manufacture into a sensor with high sensitivity, and the fluxgate sensor is easier to manufacture into a sensor with large measuring range. In this embodiment, the coil sensor with high sensitivity is selected to detect a weak signal, and the fluxgate sensor with large measurement range is selected to detect a strong signal.

In the embodiment, special arrangement needs to be carried out on the moving directions, so that one of the directions pointed by the crawler belts is taken as the advancing direction of the underwater robot, and the other direction is taken as the retreating direction; the Z axes of the two three-axis sensors are perpendicular to the crawler; each axis of the two three-axis magnetic sensors is standardized, the difficulty of data processing is reduced, and the data of the two three-axis sensors and the underwater robot can be converted.

The underwater robot is provided with a gyroscope, and the gyroscope is used for acquiring attitude information of the underwater robot and correcting data of the two three-axis sensors to a standard value according to the attitude information; when the underwater robot is positioned on the seabed, due to the fact that the sea bottom surface is uneven, each shaft of the two three-shaft sensors is inclined, and data collected by each shaft needs to be corrected to be in a standard state. The signals collected by each part of the invention are all corrected.

Obtaining submarine cable routing coordinates according to the following steps:

the coil sensor and the fluxgate sensor acquire signals which have a fixed conversion relation, and the conversion relation is determined by each parameter and the installation position of the two triaxial sensors; setting a threshold value beta, when the intensity of the signal acquired by the coil sensor is lower than the threshold value beta, converting the signal acquired by the coil sensor to obtain an expected signal of the fluxgate sensor at the current position, and correcting the signal acquired by the fluxgate sensor according to the expected signal; when the signal intensity acquired by the coil sensor is high and beta, converting the signal acquired by the fluxgate sensor to obtain an expected signal of the coil sensor at the current position, and correcting the signal acquired by the coil sensor according to the expected signal; in this embodiment, the ability of the coil sensor to detect weak signals is improved by adjusting the coil of the coil sensor. The coil sensor cannot detect a direct current field, and interference of geomagnetic signals can be avoided. When the target signal is weak, the fluxgate sensor is greatly interfered by the geomagnetic signal. Therefore, when the target signal is weak, the magnetic signal acquired by the fluxgate sensor is corrected by the magnetic signal acquired by the coil sensor. The coil sensor is difficult to ensure the measurement linearity when the signal intensity is high, and the fluxgate sensor has better linearity for large signal measurement, so that the magnetic signal acquired by the coil sensor is corrected through the magnetic signal acquired by the fluxgate sensor when the signal intensity is high.

The underwater robot is put down in a target sea area, and magnetic signals generated by a submarine cable are acquired through the coil sensor and the fluxgate sensor;

judging the region of the underwater robot according to the magnetic signal, planning a moving path of the underwater robot in the current region according to the change of the magnetic signal, and moving the underwater robot according to the moving path until the underwater robot is close to a submarine cable;

and calculating to obtain the coordinates of the submarine cable according to the coordinates of the underwater robot and the position relationship between the underwater robot and the submarine cable.

In this embodiment, the coil sensor and the fluxgate sensor are respectively disposed at a front side and a rear side of the underwater robot and connected to the underwater robot through a bracket. The farther the distance between the two triaxial sensors is, the errors caused by the measurement precision and the noise of the device can be reduced, and the positioning of the submarine cable is facilitated. And the coil sensor is arranged on the front side of the moving direction, so that the coil sensor can reach signal saturation firstly, and the subsequent detection in a signal-free area and a signal-weak area is facilitated.

In this embodiment, the magnetic signals acquired by the two three-axis sensors are subjected to fourier transform to obtain an amplitude of a signal having the same frequency as a power frequency of a submarine cable, and the amplitude is used as a magnetic signal for calculating a position relationship between the underwater robot and the submarine cable and planning a moving path of the underwater robot. In the existing technical scheme, the instantaneous value of the magnetic signal directly acquired by the sensor is correspondingly calculated. The method has the disadvantages that because the signals generated by the submarine cable are alternating, the phases of the signals need to be considered during calculation, and the magnetic signals acquired by the two sensors need to be synchronously processed, so that the magnetic signals used for calculation are generated at the same moment. According to the invention, the amplitude of the signal which is the same as the power frequency (working frequency) of the submarine cable is obtained by carrying out Fourier transform on the collected magnetic signal, and the phase interference is avoided by calculating according to the amplitude. The magnetic signals in the formulas of the invention are all signal amplitudes which are subjected to Fourier transform and screening.

Example two

On the basis of the first embodiment, when the underwater robot is positioned in a no-signal area, detecting the no-signal area, and enabling the underwater robot to enter the weak-signal area through the no-signal area; the signal-free area is an area which cannot be acquired by the coil sensor or can acquire effective magnetic signals only on part of the axis; the weak signal area is an area where effective magnetic signals can be acquired by each axis of the coil sensor, and the fluxgate sensor cannot acquire the effective magnetic signals or can acquire the effective magnetic signals only on part of the axes; the effective magnetic signal is information contained in the acquired signal and can be used for analyzing the position of the submarine cable; the signal-free area detection comprises the following steps:

the underwater robot is made to descend to a specific height, and a magnetic signal epsilon generated by a submarine cable is acquired through three shafts of the coil sensor_x、ε_yAnd ε_zObtaining the horizontal component of the magnetic signalSetting a threshold value epsilon_p0And ε_z0；

Judging the horizontal component ε_pThe vertical component epsilon_zWith a threshold value epsilon_p0、ε_z0According to the judgment result, the following operations are executed:

P₁if epsilon_z＜ε_z0And detecting the route of the submarine cable along the vertical direction at the moment, and enabling the underwater robot to descend until epsilon_z＞ε_z0And then, the coil sensor is close to the submarine cable route in the vertical direction, at the moment, the Z axis of the coil sensor can acquire effective magnetic signals, and if epsilon is epsilon_p＞ε_p0Then P is executed₃If epsilon_p＜ε_p0Then P is executed₂If the epsilon is not satisfied until the underwater robot descends to the seabed_z＞ε_z0If the underwater robot is far away from the submarine cable, the underwater robot is retracted, the lowering position is adjusted, and the underwater robot is lowered again;

P₂if epsilon_p＜ε_p0And is epsilon_z＞ε_z0And if the coil sensor is close to the submarine cable route in the vertical direction, setting two horizontal search paths which are vertical to each other, referring to fig. 1, considering that the submarine cable is shallow in buried depth, if at least one of the two horizontal search paths which are vertical to each other is intersected with the submarine cable route, and enabling the underwater robot to move along the two search paths until epsilon_p＞ε_p0Then, P is executed₃；

P₃If epsilon_p＞ε_p0And is epsilon_z＞ε_z0And if so, the underwater robot is considered to enter a weak signal area.

Weak signal area detection is the initial step of submarine cable route location in this embodiment, and the purpose of weak signal area detection is from the region that can't gather submarine cable route production signal with underwater robot, the region that introduces to gather. The existing technical scheme does not design the moving mode of the underwater robot in a signal-free area. In the embodiment, the underwater robot is close to the submarine cable by using the incomplete signals under the condition of being far away from the submarine cable through the acquisition capacity of the coil sensor to the weak signals, so that the detection capacity of the underwater robot to the submarine cable in a signal-free area is improved. And enabling the underwater robot to be close to the submarine cable quickly.

EXAMPLE III

On the basis of the second embodiment, when the underwater robot is positioned in a weak signal area, detecting the weak signal area, and enabling the underwater robot to enter a strong signal area through the detection of the weak signal area; the strong signal area is an area where effective magnetic signals can be acquired by each shaft of the coil sensor and the fluxgate sensor; the weak signal area detection comprises the following steps:

lowering the underwater robot to the sea floor;

acquiring magnetic signals epsilon generated by submarine cables through X-axis and Y-axis of the coil sensor_1xAnd ε_1yAnd calculating the included angle theta between the Y axis of the coil sensor and the submarine cable route_yReferring to fig. 3, the formula is as follows:

according to the included angle theta_yAdjusting the advancing direction of the underwater robot to be vertical to the submarine cable route;

moving the underwater robot through the crawler;

after adjustment, only the moving direction of the crawler belt is perpendicular to the submarine cable route, and whether the advancing direction is close to the submarine cable route or the submarine cable route can not be judged, so that the magnetic signals acquired by the coil sensor are monitored in the moving process, if the magnetic signals are weakened in the moving process, the advancing direction of the underwater robot is rotated by 180 degrees, the underwater robot is made to move through the crawler belt, and if the magnetic signals are not weakened in the moving process, the underwater robot continues to move through the crawler belt;

until each shaft of the fluxgate sensor acquires an effective magnetic signal, the underwater robot is considered to enter a strong signal area.

In this embodiment, the ability of the coil sensor to collect weak signals is utilized, a single sensor is utilized to detect the submarine cable route, and the submarine cable route is close to the submarine cable route

Example four

On the basis of the third embodiment, the weak signal area detection further comprises distance measurement between the coil sensor and the submarine cable route, and can help an operator to judge the distance between the underwater robot and the submarine cable route, and the method comprises the following steps:

the underwater robot is enabled to move for a distance along the direction perpendicular to the submarine cable route, and magnetic signals epsilon generated by the submarine cable before moving are collected through three axes of the coil sensor_3x、ε_3yAnd ε_3zAnd the magnetic signal epsilon generated by the moved submarine cable_4x、ε_4yAnd ε_4z；

Calculating the magnetic signal epsilon collected by the coil sensor before and after movement₃And ε₄The following are:

calculating a shortened distance dr between the coil sensor and the sea cable route before and after the movement as follows:

wherein dy is the moving distance of the underwater robot; theta_3yThe included angle between the Y axis of the coil sensor and the submarine cable route is set;the dip angle for the coil sensor and sea cable routing,due to the undulations and obstacles present in the sea floor level, some deflection is inevitable although the underwater robot is moving in a direction perpendicular to the submarine cable route. Therefore, the dip angle of the underwater robot and the included angle between the underwater robot and the submarine cable are considered when calculating the shortened distance.

Calculating the distance r between the coil sensor and the submarine cable route before moving as follows:

and in the weak signal area detection process, calculating the distance between the coil sensor and the submarine cable route by using data generated in the past time T at intervals of time T. Namely, the distance between the underwater robot and the submarine cable route is updated by taking the time T as an interval, so that an operator can conveniently monitor whether the moving direction is correct. Since the distance of the probe device relative to the submarine cable route is much greater than the distance of the structures between the probe device parts, the distance of the structures from the submarine cable route can be seen as an approximation.

In another specific embodiment, the weak signal area detection further comprises that the underwater robot moves through the crawler belt at intervals of T₁Acquiring magnetic signals generated by the submarine cable through the coil sensor, and calculating an included angle theta between the Y axis of the coil sensor and the route of the submarine cable_yAccording to the angle theta_yAnd adjusting the advancing direction of the underwater robot to be vertical to the submarine cable route. In the process that the underwater robot is close to the submarine cable route, the advancing direction of the underwater robot is periodically adjusted to be perpendicular to the submarine cable route, and the phenomenon that the underwater robot deviates from the submarine cable route after moving for a long time due to unevenness of a seabed plane is avoided.

EXAMPLE five

On the basis of the third embodiment, when the underwater robot is located in a strong signal area, the strong signal area is detected, and the strong signal area detection comprises the following steps:

collecting magnetic signals epsilon generated by submarine cable through three axes of coil sensor_2x、ε_2y、ε_2zThrough the triaxial epsilon 'of the fluxgate sensor'_2x、ε'_2yAnd epsilon'_2z；

Obtaining a depression angle of the coil sensor, the fluxgate sensor and the submarine cable routeThe tangent of (c) is as follows:

p, H is the horizontal distance and the vertical distance between the coil sensor and the submarine cable route respectively; p 'and H' are respectively the horizontal distance and the vertical distance between the fluxgate sensor and the submarine cable route;

if it isExecuting a first relative distance algorithm, otherwise, executing a second relative distance algorithm; when in useWhen the two triaxial magnetic sensors and the submarine cable are routed on the same straight line, the calculation of the relative distance needs to be carried out through different algorithms;

referring to fig. 4, the first relative distance algorithm:

wherein the content of the first and second substances,l is the distance between the coil sensor and the fluxgate sensor; theta_2yThe included angle between the Y axis of the coil sensor and the submarine cable route is set;

second relative distance algorithm:

referring to fig. 5, a height difference dh in a vertical direction and a distance difference dp in a horizontal direction of the magnetic coil sensor and the fluxgate sensor are obtained as follows:

dh＝Lsinθ_2ysinλ₂，

dp＝Lsinθ_2ycosλ₂，

wherein λ is₂Acquiring an included angle between the underwater robot and a horizontal plane by the gyroscope;

the following results were obtained:

and accurate coordinates of the submarine cable route can be obtained through the relative distance between the coil sensor and the submarine cable route.

The strong signal region detection further includes:

acquiring longitude and latitude coordinates (W) of the current underwater robot by a positioning technology₀,J₀)；

Detecting the data obtained according to the strong signal area and the longitude and latitude coordinates (W) of the underwater robot₀,J₀) And calculating the longitude and latitude coordinates (W) of the submarine cable route at the detection point k_k,J_k) The formula is as follows:

W_k＝arcsin(sin(W₀)cos(P_k/R)+cos(W₀)sin(P_k/R)cosθ_2y)，

wherein, P_kThe horizontal distance between the underwater robot and the submarine cable route at the detection point k is obtained through conversion of the horizontal distance between the coil sensor and the detection point k, the conversion relation is determined according to the specific structure of the detection equipment and parameters of the sensor, the horizontal distance between the coil sensor and the detection point k is obtained through a relative distance algorithm, and R is the radius of the earth.

The strong signal region detection further includes:

acquiring signals generated by a submarine cable route through the coil sensor, calculating an included angle between the coil sensor and the submarine cable route, keeping the advancing direction of the underwater robot parallel to the submarine cable route according to the included angle, and moving along the direction parallel to the submarine cable route;

the coordinates of the submarine cable route are calculated every certain distance. And finally obtaining the complete submarine cable routing coordinate.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures made by using the contents of the specification and the drawings of the present invention or directly or indirectly applied to other related technical fields are included in the scope of the present invention.