Active attitude-adjusting buoyancy cable of underwater layered monitoring system and method for adjusting buoyancy thereof

Abstract

The present application belongs to the technical field of marine environment monitoring, and relates to an active posture-adjusting buoyancy cable of an underwater layered monitoring system and a buoyancy adjusting method thereof. The buoyancy cable comprises, from bottom to top, an anchor system, a releaser, a buoyancy cable storage box and a buoyancy cable. The buoyancy cable comprises, from bottom to top, a bottom anchoring section, a middle main body section and a top node section. The top node section comprises a main cable, a waterproof cable and a buoyancy adjusting unit. The main cable is consistent with the middle main body section. A plurality of buoyancy adjusting units are arranged along the axial direction of the main cable. The active posture-adjusting buoyancy cable of the underwater layered monitoring system and the buoyancy adjusting method thereof can realize active posture correction under the action of sea current. By sensing the posture, tension, depth, flow rate and other sea current working condition information of the cable body in real time, the control system dynamically adjusts the buoyancy of each section, automatically generates a resetting torque opposite to the sea current thrust, and makes the buoyancy cable always maintain a vertical stable posture, thereby ensuring the accuracy of layered monitoring.

Description

Technical Field

[0001] This invention belongs to the field of marine environmental monitoring technology, and relates to an active attitude adjustment buoyancy cable for an underwater stratified monitoring system and its buoyancy adjustment method. Background Technology

[0002] Ocean stratified monitoring refers to an observation technique that synchronously acquires marine physical, biochemical, and ecological parameters at fixed points along different depth layers in a vertical direction, constructing vertical profiles and time series of marine parameters. Fixed-point moored stratified monitoring is a commonly used method for ocean stratified monitoring, widely applied due to its advantage of long-term, fixed-point observation. The basic principle of fixed-point moored stratified monitoring is as follows: First, a base platform is deployed to a specific sea area, sinks to the seabed, and anchors. Second, a buoyancy cable is released from the base and rises vertically using its own buoyancy, with sensors deployed on the cable achieving synchronous stratified observation of marine parameters along the water depth direction. Third, after observation is completed, a release device separates the cable from the mooring, allowing it to rise to the surface for retrieval. The application of fixed-point moored stratified monitoring technology enables long-term monitoring of parameters in the mid-ocean strata, filling the gaps in buoy and moored monitoring areas.

[0003] The buoyancy cables of fixed-point anchored layered monitoring systems are mostly flexible long catenary structures that unfold vertically after deployment using their own buoyancy. However, under the influence of ocean currents, they generate uneven overturning moments, making them prone to attitude instability issues such as tilting and swaying, and even inducing vortex-induced vibration and cable torsion. These problems lead to significant deviations between the actual observed depth and the designed depth, distortion of layered data, and an increased risk of fatigue fracture in the cable structure, severely impacting monitoring accuracy and system reliability. Summary of the Invention

[0004] In view of the above technical problems, the present invention proposes a buoyancy cable and attitude adjustment method for a fixed-point anchorage layered monitoring system that can realize active attitude correction and ensure vertical stability, through segmented variable buoyancy cable body and local buoyancy adaptive compensation.

[0005] The technical solution provided by this invention is as follows: An active attitude-adjusting buoyancy cable for an underwater stratification monitoring system, comprising, from bottom to top, an anchor system, a release device, a buoyancy cable storage box, and a buoyancy cable connected in sequence; the buoyancy cable is divided into a bottom anchoring section, a middle main body section, and a top node section from bottom to top; the bottom anchoring section is a negative buoyancy section; the middle main body section is a neutral buoyancy section; the top node section is the sensor mounting section, a positive buoyancy compensation section, including a main cable, a waterproof cable, and a buoyancy adjustment unit; the main cable is consistent with the middle main body section; multiple buoyancy adjustment units are arranged along the axial direction of the main cable, which adjust the buoyancy according to the real-time acquired buoyancy cable attitude data and local water depth and current velocity, so that the inclination angle of the main cable is always kept within the set value; wherein, the buoyancy adjustment unit includes a core sensing module, an actuator module, a main control and communication module, and a power supply and structure module; wherein, the core sensing module consists of an inertial measurement unit, a cable axial tension sensor, a current velocity sensor, and a water depth sensor; the inertial measurement unit outputs the... The system includes a node's tilt and azimuth angle sensors, a cable axial tension sensor outputting the real-time tension of the main cable at that node, a current velocity sensor outputting the ocean current velocity at the node's location, and a depth sensor outputting the water depth at that node. The actuator module consists of an airbag, a miniature air pump and solenoid valve assembly, and an airbag pressure sensor. The miniature air pump is connected to the solenoid valve assembly, and the airbag is connected to the solenoid valve assembly via an air tube. The airbag changes the buoyancy distribution by inflating / deflating, generating a reset torque. The airbag pressure sensor monitors the internal pressure of the airbag. The main control and communication module includes an embedded main control unit and an inter-node communication module. The embedded main control unit is used for data acquisition from each sensor at the node, calculating the regulating air volume of the node's airbag, and outputting control commands to the node's airbag actuator module. The inter-node communication module is used for exchanging tilt, azimuth, and data acquisition time data between adjacent nodes, providing basic data for calculating the tilt and azimuth differences between adjacent nodes. The power supply and structure module includes a regulated power management module for power supply to the buoyancy adjustment unit.

[0006] Preferably, the bottom anchoring section of the buoyancy cable adopts a cylindrical solid rod structure, the outer covering layer adopts a thickened stainless steel braided sheath combined with a high-density counterweight composite material, and the inner core adopts a high-strength aramid Kevlar rope.

[0007] Preferably, the central main body section of the buoyancy cable adopts a coaxial multi-layer extruded integrated structure, consisting of a load-bearing core layer, a buoyancy intermediate layer, a buffer damping layer, and an anti-fouling outer sheath from the inside out. The load-bearing core layer is made of high-strength aramid braided tape; the anti-fouling outer sheath is made of silicone anti-fouling elastic rubber. This invention further provides a buoyancy adjustment method for the active attitude adjustment buoyancy cable of the underwater stratification monitoring system, comprising the following steps: (1) Each buoyancy adjustment unit node acquires the tilt angle and azimuth angle of the node position through the inertial measurement unit, obtains the cable tension through the tension sensor, and obtains the ocean current velocity through the current meter; adjacent nodes exchange attitude data through the serial bus to realize the real-time acquisition of the adjacent tilt angle difference and azimuth angle difference. (2) Determine whether buoyancy needs to be adjusted based on the real-time obtained buoyancy cable tilt angle and the set value: when the cable tilt angle is greater than the set angle, start the actuator module to adjust the buoyancy; (3) Calculate the tilt angle correction factor, ocean current density correction factor, upstream area correction factor, adjacent node coupling correction factor and tension coupling correction factor based on the data obtained in step (1); Each node independently completes the calculation of the reset torque: M = ; ; In the formula, M The required reset torque for the buoyancy adjustment unit L 0 represents the buoyancy adjustment lever arm; ρ The density of seawater, g It is the acceleration due to gravity. It is the fluid resistance coefficient. It is the cross-sectional area facing the flow at the node. It is the real-time ocean current velocity at the node; For tilt angle correction factor, For ocean current density correction factor, For the correction factor of the frontal area, For the coupling correction coefficient of adjacent nodes, This is the tension coupling correction factor; (4) Based on the calculated reset torque, calculate the gas volume adjustment amount of the airbag. The calculation formula is as follows: ; In the formula, This represents the volume of gas in the airbag after repositioning. This is the current volume of gas in the airbag; (5) Adjust the amount of gas according to the air volume of the airbag Calculate the inflation / deflation time of the airbag at this node: ; In the formula, Inflation / deflation time of the airbag; The water depth at this node, This refers to the air pump flow rate; (6) Drive the actuator module to inflate / deflate the airbag and realize closed-loop adjustment of the buoyancy cable attitude.

[0008] Preferably, the tilt angle correction factor The calculation formula is as follows: ; ; In the formula, This represents the real-time tilt angle of the node. The maximum design tilt angle for the node, This is the tilt gain coefficient. This represents the depth of the node. This is the cable stiffness coefficient.

[0009] Preferably, the ocean current density correction factor The calculation formula is as follows: ; ; In the formula, This represents the real-time ocean current velocity at that node location. Design ocean current velocities for nodes. This is the velocity gain coefficient. This represents the current density at the current depth.

[0010] Preferably, the frontal area correction factor The calculation formula is as follows: ; ; In the formula, This represents the real-time tilt angle of the node. The maximum design tilt angle for the node, This is the effective frontal area gain coefficient.

[0011] Preferably, the adjacent node coupling correction coefficient The calculation formula is as follows: ; ; In the formula, For this node With neighboring nodes The difference in tilt angle, For this node With neighboring nodes Azimuth difference, subscript and These represent the adjacent upper and lower nodes, respectively. , Each of these nodes With neighboring nodes Real-time tilt angle, , Each of these nodes With neighboring nodes The heading angle; These are spatial geometric projection coefficients, whose function is to reduce the azimuth difference. Only when the node is tilted Only when the node is vertical will it be converted into the curvature of the cable through geometric projection; when the node is vertical... hour, The azimuth difference only causes rigid body rotation and does not generate additional bending moment; The coupling strength coefficient is... This is the average tilt angle of adjacent nodes.

[0012] Preferably, the tension coupling correction coefficient The calculation formula is as follows: ; ; In the formula, T The real-time axial tension of the cable is measured by a cable tension sensor. T 0 represents the rated tension of the cable. This is the tension gain coefficient.

[0013] The active attitude-adjusting buoyancy cable and buoyancy adjustment method of the underwater stratification monitoring system provided by this invention can achieve active attitude correction under the action of ocean currents. By sensing ocean current conditions such as cable attitude, tension, depth, and current velocity in real time, the control system dynamically adjusts the buoyancy of each segment and automatically generates a reset torque opposite to the thrust of the ocean current, so that the buoyancy cable always maintains a vertical and stable attitude, thereby ensuring the accuracy of stratification monitoring. Attached Figure Description

[0014] Figure 1 This is a diagram showing the overall structure of the underwater stratification monitoring system. Figure 2 This is a structural diagram of the buoyancy adjustment unit; Figure 3 This is a diagram of the internal structure of the buoyancy adjustment unit; Figure 4 A flowchart of the buoyancy adjustment method for the active attitude adjustment buoyancy cable of an underwater stratification monitoring system; In the diagram, 1. Anchorage; 2. Release device; 3. Buoyancy cable storage box; 4. Buoyancy cable; 41. Bottom anchorage section; 42. Middle main body section; 43. Top node section; 4301. Main cable; 4302. Waterproof cable; 4303. Buoyancy adjustment unit; 4304. Inertial measurement unit; 4305. Tension sensor; 4306. Flow velocity sensor; 4307. Water depth sensor; 4308. Airbag; 4309. Miniature air pump; 4310. Solenoid valve assembly; 4311. Airbag pressure sensor; 4312. Air tube; 4313. Main control and communication module; 4314. Pressure chamber; 4315. Regulated power supply management module; 4316. Structural connectors. Detailed Implementation

[0015] To facilitate understanding of the present invention, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and specific examples. The following examples or drawings are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0016] Example 1: This example provides an active attitude-adjusting buoyancy cable for an underwater stratification monitoring system, such as... Figure 1 As shown, the system includes an anchor mooring 1, a release device 2, a buoyancy cable storage box 3, and a buoyancy cable 4. During system deployment, the buoyancy cable is stored in the buoyancy cable storage box 3, and the near-bottom platform is connected to the anchor mooring 1 via the release device 2. During system operation, the hatch on top of the buoyancy cable storage box is opened, and the buoyancy cable 4 rises and unfolds under its own buoyancy. After system operation is complete, the release device 2 is activated to disconnect from the anchor mooring 1, and the buoyancy cable 4 rises to the sea surface for recovery.

[0017] To ensure vertical orientation in seawater, the buoyancy cable 4 employs a segmented variable buoyancy cable body, structurally divided into three parts from bottom to top: a bottom anchoring section 41, a mid-body section 42, and a top node section 43. The bottom anchoring section 41 is a negative buoyancy section, employing a cylindrical solid rod structure. Its outer sheath uses a thickened stainless steel braided sheath combined with a high-density counterweight composite material, while the inner core uses high-strength aramid Kevlar rope. The mid-body section 42 is a neutral buoyancy section, using a coaxial multi-layer extruded integrated structure. From the inside out, it consists of a load-bearing core layer, a buoyancy intermediate layer, a buffer damping layer, and an antifouling outer sheath. The load-bearing core layer uses high-strength aramid braided tape, primarily providing longitudinal tensile strength. When encountering transient strong current impacts, this layer undergoes micro-deformation to absorb energy, preventing a sudden surge in tension that could break the cable. The antifouling outer sheath uses silicone antifouling elastic rubber, with a smooth, low-friction surface that reduces current resistance and prevents biofouling.

[0018] like Figure 2As shown, the top node segment 43 is the sensor mounting segment, which is a positive buoyancy compensation segment. It adopts a modular structure combining the main cable 4301, the waterproof cable 4302, and the buoyancy adjustment unit 4303. The main cable 4301 is consistent with the middle main body segment. Multiple buoyancy adjustment units are arranged along the axial direction of the main cable 4301. These buoyancy adjustment units can adjust the buoyancy based on real-time acquired buoyancy cable attitude data and local environmental data such as water depth and current velocity, ensuring that the inclination angle of the main cable is always kept within the set value.

[0019] like Figure 3 As shown, the buoyancy adjustment unit 4303 includes a core sensing module, an actuator module, a main control and communication module, and a power supply and structure module. The core sensing module consists of an inertial measurement unit (IMU) 4304, a cable axial tension sensor 4305, a current velocity sensor 4306, and a water depth sensor 4307. The IMU outputs the tilt and azimuth angles of the node, the cable axial tension sensor outputs the real-time tension of the main cable at the node, the current velocity sensor outputs the ocean current velocity at the node's location, and the water depth sensor outputs the water depth at the node. The actuator module consists of an airbag 4308, a miniature air pump 4309, a solenoid valve assembly 4310, and an airbag pressure sensor 4311. The airbag and the solenoid valve are connected via an air tube 4312. The airbag changes the buoyancy distribution of the buoyancy cable by inflating / deflating, generating a reset torque. The miniature air pump 4309 precisely controls the volume of each airbag through the solenoid valve assembly 4310 to achieve buoyancy torque adjustment. The airbag pressure sensor 4311 is used to monitor the internal pressure of the airbag. The main control and communication module 4313 consists of an embedded main control unit, an inter-node communication module, and a clock and synchronization unit. The embedded main control unit is mainly used for data acquisition from the sensors of each node, calculating the regulating air volume of the airbag at that node, and outputting control commands to the airbag actuator module at that node. The inter-node communication module is mainly used for exchanging data such as tilt angle, azimuth angle, and data acquisition time between adjacent nodes, providing basic data for calculating the tilt angle difference and azimuth angle difference between adjacent nodes. The clock and synchronization unit is mainly used to ensure that the data time of adjacent nodes is aligned. The power supply and structure module consists of a pressure-resistant chamber 4314, a regulated power supply management module 4315, and structural connectors 4316. The regulated power supply management module is used for power supply to the buoyancy adjustment unit. This hardware architecture enables localization of sensing, calculation, and control, with minimal data interaction with adjacent nodes, meeting the real-time and robustness requirements of attitude control.

[0020] Example 2: This example also provides a buoyancy adjustment method adapted to the buoyancy cable in Example 1. The basic idea of ​​this buoyancy adjustment method is to dynamically adjust the buoyancy of each segment by sensing the cable's attitude, tension, depth, current velocity, and other ocean current conditions in real time under the action of ocean currents. This automatically generates a reset torque opposite to the thrust of the ocean current, adjusts the attitude of the buoyancy cable, and keeps the buoyancy cable in a vertical and stable attitude, thereby ensuring the accuracy of layered monitoring.

[0021] The process of this buoyancy adjustment method is as follows: Figure 4 As shown, the specific steps include: 1. Sensor data acquisition The IMU of each node (buoyancy adjustment unit) outputs the tilt angle of that node. and azimuth The cable axial tension sensor outputs the real-time tension of the node; the current velocity sensor outputs the real-time ocean current velocity of the node; and the water depth sensor outputs the depth of the node. h .

[0022] Data interaction between adjacent nodes to calculate the angle difference required for 3D coupling and various correction coefficients. .

[0023] (1) The tilt angle of the node itself θ The tilt angle directly affects the reset torque; the larger the tilt angle, the greater the torque required for reset. To characterize the amplification effect of the node's tilt on the required reset torque, a tilt angle correction factor is used. K 1 is defined as: ; ; In the formula, The real-time tilt angle of the node (rad). The maximum design tilt angle (rad) for the node. This is the tilt gain coefficient. The depth (m) of the node. This is the cable stiffness coefficient.

[0024] (2) Ocean current speed v Fluctuations in the current can cause significant changes in the hydrodynamic load, thus affecting the magnitude of the foundation moment. As shown in the fluid drag resistance formula, drag resistance is proportional to the square of the current velocity, and consequently, the foundation moment is also proportional to the square of the current velocity. To characterize the amplification effect of the hydrodynamic load on the recovery moment, a correction factor for the current density is used. K 2 is defined as: ; ; In the formula, This represents the real-time ocean current velocity (m / s) at that node location. Design ocean current velocities for nodes. This is the velocity gain coefficient. Current density at current depth (kg / m) 3 ).

[0025] (3) When the node is tilted, the frontal area S The projection of the node along the ocean current direction changes, leading to a reduction in the effective frontal area, which in turn affects drag and foundation moment. The frontal area correction factor characterizes the effect of the reduction in effective frontal area caused by node tilt on the reset moment; the larger the tilt angle, the smaller the effective frontal area and the smaller the drag. Frontal area correction factor K 3 is defined as: ; ; In the formula, The real-time tilt angle of the node (rad). The maximum design tilt angle (rad) for the node. This is the effective frontal area gain coefficient.

[0026] (4) In the deep-sea flexible cable system, adjacent nodes are connected by the cable to form a strongly coupled dynamic system. The attitude differences between adjacent nodes exist in three-dimensional space, including both tilt angle difference (pitch direction) and azimuth angle difference (torsion direction). Both are transmitted through cable bending and torsion to generate additional coupled bending moments, affecting the node's restoring moment. Based on the theory of spatial beam bending and torsion, the coupling effect between adjacent nodes consists of two parts: one is the planar bending moment generated by the tilt angle difference in the pitch direction, and the other is the spatial bending and torsional moment generated by the azimuth angle difference in the torsion direction. In order to characterize the amplification effect of the coupled bending moment generated by the three-dimensional attitude differences between adjacent nodes through cable bending and torsion on the node's restoring moment, the coupling correction coefficient between adjacent nodes is used. K 4 is defined as: ; ; In the formula, For this node With neighboring nodes The difference in tilt angle, For this node With neighboring nodes Azimuth difference, subscript and These represent the adjacent upper and lower nodes, respectively. , Each of these nodes With neighboring nodes Real-time tilt angle, , Each of these nodes With neighboring nodes The heading angle; These are spatial geometric projection coefficients, whose function is to reduce the azimuth difference. Only when the node is tilted Only when the node is vertical will it be converted into the curvature of the cable through geometric projection; when the node is vertical... hour, The azimuth difference only causes rigid body rotation and does not generate additional bending moment; The coupling strength coefficient is... This is the average tilt angle of adjacent nodes.

[0027] (5) The magnitude of the axial tension of the cable body will change the equivalent bending stiffness of the system. The greater the tension, the higher the reset efficiency. In order to characterize the influence of the axial tension of the cable body on the equivalent stiffness of the system, and further correct the amplification effect of the reset torque, the tension coupling correction coefficient is used. K 5 is defined as: ; ; In the formula, T The real-time axial tension (N) of the cable body is measured by the cable tension sensor. T 0 represents the rated tension of the cable (N). This is the tension gain coefficient.

[0028] 3. Calculate the total restoring torque: Horizontal thrust of ocean current on a node of the buoyancy cable F x The flow rate, nodal cross-sectional area, and fluid resistance coefficient are the determining factors, and the calculation formula is as follows: ; In the formula, Seawater density (kg / m³) 3 ), It is the fluid resistance coefficient. It is the cross-sectional area of ​​the node facing the airflow (m²) 2 ), It is the real-time ocean current velocity (m / s) at that node.

[0029] When the buoyancy cable tilt angle is At this time, a node of the buoyancy cable needs to be reset by the local buoyancy adjustment, that is, the reverse torque generated by the buoyancy adjustment. for: ; In the formula, The theoretical torque of the node foundation is calculated using the following formula: ; in, Equal to the buoyancy adjustment required for reset , This represents the volume of gas inside the airbag after repositioning. The buoyancy adjustment lever arm (m).

[0030] The comprehensive coupling correction coefficient is calculated using the following formula: .

[0031] 3. Based on the real-time obtained buoyancy cable tilt angle Determine whether buoyancy adjustment is needed based on the set value: when the cable tilt angle... greater than the set angle When this happens, the actuator module is activated to adjust the buoyancy.

[0032] Based on the calculated reset torque The formula for calculating the gas volume adjustment amount of the airbag is as follows: ; In the formula, This is the current volume of gas in the airbag.

[0033] Adjust the amount of gas in the airbag according to its volume. Calculate the inflation / deflation time of the airbag at this node: ; In the formula, Inflation / deflation time of the airbag; The water depth at this node is (m). air pump flow rate (m³) 3 / min).

[0034] 4. The drive actuator module inflates / deflates the airbag, monitors the airbag pressure in real time, and prevents over-inflation or over-distension. It also re-acquires attitude information to achieve closed-loop adjustment of the buoyancy cable's attitude.

Claims

1. An active attitude-adjusting buoyancy cable for an underwater stratification monitoring system, characterized in that: The structure, from bottom to top, includes an anchor system, a release device, a buoyancy cable storage box, and a buoyancy cable connected in sequence. The buoyancy cable is further divided into a bottom anchoring section, a middle main body section, and a top node section from bottom to top. The bottom anchoring section is a negative buoyancy section; the middle main body section is a neutral buoyancy section; and the top node section is the sensor mounting section, a positive buoyancy compensation section, including the main cable, a waterproof cable, and a buoyancy adjustment unit. The main cable is aligned with the middle main body section. Multiple buoyancy adjustment units are arranged along the axial direction of the main cable. Each buoyancy adjustment unit includes a core sensing module, an actuator module, a main control and communication module, and a power supply and structure module. The core sensing module consists of an inertial measurement unit, a cable axial tension sensor, a current velocity sensor, and a water depth sensor. The inertial measurement unit outputs the tilt angle and azimuth angle of the node, the cable axial tension sensor outputs the real-time tension of the main cable at the node, and the current velocity sensor outputs the location of the node. The current velocity is measured, and the depth sensor outputs the water depth of the node. The actuator module consists of an airbag, a miniature air pump and solenoid valve assembly, and an airbag pressure sensor. The miniature air pump is connected to the solenoid valve assembly, and the airbag is connected to the solenoid valve assembly via an air tube. The airbag changes the buoyancy distribution by inflating / deflating, generating a reset torque. The airbag pressure sensor is used to monitor the internal pressure of the airbag. The main control and communication module includes an embedded main control unit and an inter-node communication module. The embedded main control unit is used for data acquisition from each sensor of the node, calculating the regulating air volume of the airbag of the node, and outputting control commands to the actuator module of the airbag of the node. The inter-node communication module is used for exchanging tilt angle, azimuth angle, and data acquisition time data between adjacent nodes, providing basic data for calculating the tilt angle difference and azimuth angle difference between adjacent nodes. The power supply and structure module includes a regulated power supply management module for power supply to the buoyancy adjustment unit.

2. The active attitude-adjusting buoyancy cable of the underwater stratification monitoring system according to claim 1, characterized in that: The bottom anchoring section of the buoyancy cable adopts a cylindrical solid rod structure, the outer covering layer adopts a thickened stainless steel braided sheath combined with a high-density counterweight composite material, and the inner core adopts a high-strength aramid Kevlar rope.

3. The active attitude-adjusting buoyancy cable of the underwater stratification monitoring system according to claim 1, characterized in that: The main body section of the buoyancy cable adopts a coaxial multi-layer extrusion integrated structure, which consists of a load-bearing core layer, a buoyancy intermediate layer, a buffer damping layer, and an anti-fouling outer sheath from the inside out. The load-bearing core layer is made of high-strength aramid braided tape, and the anti-fouling outer sheath is made of silicone anti-fouling elastic rubber.

4. The buoyancy adjustment method of the active attitude adjustment buoyancy cable of the underwater stratification monitoring system according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Each buoyancy adjustment unit node acquires the tilt angle and azimuth angle of the node position through the inertial measurement unit, obtains the cable tension through the tension sensor, and obtains the ocean current velocity through the current meter; adjacent nodes exchange attitude data through the serial bus to realize the real-time acquisition of the adjacent tilt angle difference and azimuth angle difference. (2) Determine whether buoyancy needs to be adjusted based on the real-time obtained buoyancy cable tilt angle and the set value: when the cable tilt angle is greater than the set angle, start the actuator module to adjust the buoyancy; (3) Calculate the tilt angle correction factor, current density correction factor, upstream area correction factor, adjacent node coupling correction factor, and tension coupling correction factor based on the data obtained in step (1); each node independently completes the reset torque calculation: M = ； ； In the formula, M The required reset torque for the buoyancy adjustment unit L 0 represents the buoyancy adjustment lever arm; ρ The density of seawater, g It is the acceleration due to gravity. It is the fluid resistance coefficient. It is the cross-sectional area facing the flow at the node. It is the real-time ocean current velocity at the node; For tilt angle correction factor, For ocean current density correction factor, For the correction factor of the frontal area, For the coupling correction coefficient of adjacent nodes, This is the tension coupling correction factor; (4) Based on the calculated reset torque, calculate the gas volume adjustment amount of the airbag. The calculation formula is as follows: ； In the formula, This represents the volume of gas in the airbag after repositioning. This is the current volume of gas in the airbag; (5) Adjust the amount of gas according to the air volume of the airbag Calculate the inflation / deflation time of the airbag at this node: ； In the formula, Inflation / deflation time of the airbag; The water depth at this node, This refers to the air pump flow rate; (6) Drive the actuator module to inflate / deflate the airbag and realize closed-loop adjustment of the buoyancy cable attitude.

5. The buoyancy adjustment method for the active attitude adjustment buoyancy cable of the underwater stratification monitoring system according to claim 4, characterized in that: Tilt angle correction factor The calculation formula is as follows: ； ； In the formula, This represents the real-time tilt angle of the node. The maximum design tilt angle for the node, This is the tilt gain coefficient. This represents the depth of the node. This is the cable stiffness coefficient.

6. The buoyancy adjustment method for the active attitude adjustment buoyancy cable of the underwater stratification monitoring system according to claim 4, characterized in that: Ocean current density correction factor The calculation formula is as follows: ； ； In the formula, This represents the real-time ocean current velocity at that node location. Design ocean current velocities for nodes. This is the velocity gain coefficient. This represents the current density at the current depth.

7. The buoyancy adjustment method for the active attitude adjustment buoyancy cable of the underwater stratification monitoring system according to claim 4, characterized in that: Frontal area correction factor The calculation formula is as follows: ； ； In the formula, This represents the real-time tilt angle of the node. The maximum design tilt angle for the node, k 3 represents the effective frontal area gain coefficient.

8. The buoyancy adjustment method for the active attitude adjustment buoyancy cable of the underwater stratification monitoring system according to claim 4, characterized in that: Adjacent node coupling correction coefficient The calculation formula is as follows: ； ； In the formula, For this node With neighboring nodes The difference in tilt angle, For this node With neighboring nodes Azimuth difference, subscript and These represent the adjacent upper and lower nodes, respectively. , Each of these nodes With neighboring nodes Real-time tilt angle, , Each of these nodes With neighboring nodes The heading angle; These are spatial geometric projection coefficients, whose function is to reduce the azimuth difference. Only when the node is tilted Only when the node is vertical will it be converted into the curvature of the cable through geometric projection; when the node is vertical... hour, The azimuth difference only causes rigid body rotation and does not generate additional bending moment; The coupling strength coefficient is... This is the average tilt angle of adjacent nodes.

9. The buoyancy adjustment method for the active attitude adjustment buoyancy cable of the underwater stratification monitoring system according to claim 4, characterized in that: Tension Coupling Correction Coefficient The calculation formula is as follows: ； ； In the formula, T The real-time axial tension of the cable is measured by a cable tension sensor. T 0 represents the rated tension of the cable. k 5 represents the tension gain coefficient.

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