Underwater intelligent cable system with shape perception and remote control

Abstract

This underwater intelligent cable system, equipped with morphological perception and remotely operated capabilities, belongs to the fields of underwater robotics, marine inspection, and engineering measurement and control. In this system, one end of the intelligent cable is fixed to a mother ship, while the other end connects to an ROV (Remotely Operated Vehicle) for flexible deployment via towing. A three-core fiber optic grating sensor is integrated within the cable to acquire strain distribution along its length. Multiple sealed measurement boxes are deployed along the cable to collect environmental data and transmit it back to the mother ship. The mother ship is equipped with an FBG demodulator and a data processing and storage system to calculate curvature or deflection based on strain and reconstruct the cable's three-dimensional morphology. To suppress long-distance integral drift, some measurement boxes integrate IMU (Integrated Mutor Unit) outputs attitude data and calculates tangent vectors, which are then fused with FBG continuous curvature constraints for optimized filtering. Environmental measurements are mapped to corresponding spatial coordinates on the morphological curve according to the calibrated positions of each node along the cable length, forming a spatial registration dataset that is visualized, stored, and queried, improving the efficiency and accuracy of large-scale underwater detection.

Description

Technical Field

[0001] This invention relates to an underwater intelligent cable system with shape perception and remote control operation, which belongs to the fields of underwater robots, marine detection and engineering measurement and control technology. Background Technology

[0002] With the continuous advancement of marine information and intelligent sensing technologies, especially the increasing demands for real-time performance, continuity, and accuracy in long-term underwater observation, integrated deployment from offshore platforms to sensor terminals, and underwater survey operations, underwater measurement and control systems not only need to achieve long-distance, interference-resistant data communication and power supply, but also need to possess the ability to acquire and register the spatial location of underwater data in complex sea conditions and operational scenarios, as well as the ability to flexibly deploy and operate according to tasks. Underwater intelligent cable systems with morphological perception and remote control or autonomous operation functions are crucial equipment in the field of underwater surveying. They undertake key tasks such as data acquisition, transmission, and operational safety constraints, and their performance directly affects the effectiveness and reliability of underwater detection work.

[0003] Existing underwater detection systems have the following problems:

[0004] 1) Currently, most underwater detection systems centrally deploy sensors near the underwater robot, forming a "single-point-following" observation mode. In ocean processes and complex environmental fields with significant spatiotemporal gradients, this mode is not representative enough and has low measurement efficiency. When conducting large-scale underwater data analysis, single-point measurements are difficult to form a measurement matrix and a multi-point synchronous observation dataset, resulting in insufficient ability to characterize spatial distribution features and affecting the accuracy and reliability of the analysis.

[0005] 2) Currently, cables, under the combined effects of current, gravity, and ship motion, exhibit complex three-dimensional shapes such as bending, twisting, sagging, and bottom sweeping. Their safety margin and spatial orientation directly affect the safety boundaries of the mission and the reliability of the data. Existing estimations of cable shape are mostly based on simple models combining cable length and cable tension, which are highly dependent on environmental parameters and boundary conditions and are difficult to adapt to dynamic sea conditions. Visual or imaging sonar-based appearance tracking is not robust enough in scenarios with obstruction, low visibility, and bubble interference, and has a limited field of view, making it difficult to cover cable lengths of hundreds of meters.

[0006] 3) Most current underwater surveys involve fixing cables to the area to be surveyed or using survey vessels to tow the survey cables for underwater surveys. This makes it difficult to accurately measure the target area during the measurement process, which limits the measurement range and has a significant impact on the efficiency of underwater surveys.

[0007] 4) Cable morphology reconstruction based on strain distribution of three-core fiber gratings typically requires solving for curvature and deflection by integrating along the cable. Under long-distance conditions, the integration error will accumulate and amplify along the length due to the influence of sensor noise, strain drift, environmental disturbances, and model errors, causing significant deviations in the middle and local sections. Relying solely on endpoint position constraints is often insufficient to effectively suppress middle-section drift, thus affecting the absolute accuracy of the cable morphology and the one-to-one correspondence between physical quantities and spatial positions along the cable, restricting the spatial registration and utilization of physical field data.

[0008] Therefore, there is an urgent need for an underwater intelligent cable system that combines morphological self-sensing, long-distance high-precision reconstruction, spatial registration output, and flexible deployment capabilities via remote control, in order to meet the requirements of large-scale, multi-point synchronous, and highly reliable underwater measurement and control. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an underwater intelligent cable system with morphological perception and remote-controlled actuation. This system achieves real-time three-dimensional morphological and attitude perception of the intelligent cable by distributing measurement nodes along the cable and establishing anti-interference, long-distance underwater communication and power supply links. Simultaneously, it uses ROV movement to tow the underwater intelligent cable, enabling large-area coverage surveys of the survey area. Furthermore, it achieves a one-to-one correspondence between synchronous observation data from multiple points along the cable and their three-dimensional spatial positions, thereby improving underwater operation safety, survey coverage, and data accuracy. To address the problem of large cumulative errors in long-distance morphological reconstruction, this invention introduces IMU attitude and tangent vector observations as discrete directional constraints, which are fused with FBG continuous curvature constraints for correction, improving the robustness and accuracy of long-distance morphological reconstruction.

[0010] The technical solution adopted in this invention is: an underwater intelligent cable system with shape perception and remote control operation, which includes a mother ship control platform, an intelligent cable and an ROV actuation unit;

[0011] One end of the smart cable is connected and fixed to the control platform at the mother ship end, and the other end is connected to the ROV actuation unit and is towed by it.

[0012] The smart cable integrates a three-core fiber optic grating sensor for cable shape sensing, a power supply cable, and a communication cable for data transmission. The communication cable uses a CAN bus and / or communication optical fiber.

[0013] The smart cable is equipped with multiple sealed data transmission measurement boxes along its length. Each data transmission measurement box contains an environmental sensor assembly and is connected to the mother ship control platform via the communication cable and receives power via the power supply cable. At least some of the sealed data transmission measurement boxes are equipped with inertial measurement units (IMUs) to output attitude information at the measurement box and calculate the local tangent vector of the cable.

[0014] The mothership-side control platform includes a fiber Bragg grating signal demodulator connected to the three-core fiber Bragg grating sensor, and a data processing and storage system connected to the communication CAN bus and optical communication module. The data processing and storage system is used to receive environmental data from each measurement node and combine it with the strain information output by the fiber Bragg grating signal demodulator to reconstruct the three-dimensional shape of the smart cable body underwater, thereby realizing the visualization of the cable body shape and attitude and the real-time display and storage of the environmental data.

[0015] Furthermore, the data processing and storage system maps the environmental physical quantities of each measurement node to the corresponding spatial coordinate points of the reconstructed three-dimensional morphological curve based on the calibration position of the measurement box in the cable length direction, forming an environmental physical quantity dataset with spatial coordinate markers, thereby realizing the spatial registration and visualization of environmental data.

[0016] Furthermore, the three-core fiber grating sensor is an optical fiber sensing unit containing three fiber cores. The three fiber cores are arranged parallel to each other along the axial direction of the cable body and are distributed at 120° intervals on the cross section, used to measure the strain of the cable body in different directions. The optical fiber signal demodulator uses distributed optical fiber sensing technology to obtain the strain distribution of the fiber grating sensing unit along the length and converts it into the bending curvature and bending deflection at various positions of the cable body.

[0017] Furthermore, the data transmission measurement box includes an environmental sensor assembly, a data communication module, and an electro-optical signal conversion module. The environmental sensor assembly includes a magnetic field sensor, a temperature sensor, and a pressure sensor. The data communication module is used to aggregate data from multiple sensors and then send it to the mother ship's data processing and storage system via a communication cable through the electro-optical signal conversion module. When the measurement box is equipped with an IMU, the data communication module is also used to timestamp the IMU data and encapsulate and upload it synchronously with the environmental data.

[0018] Furthermore, the communication cable is connected in series with the data communication modules of all measurement nodes and the data processing and storage system at the mother ship end to realize bus-type data communication of multiple nodes.

[0019] Furthermore, the data processing and storage system is equipped with a smart cable morphology reconstruction algorithm. Based on the cable body strain information obtained by the fiber optic grating signal demodulator and the pose constraints of the two ends of the smart cable, the algorithm calculates and reconstructs the morphology curve of the smart cable body in three-dimensional space, and obtains the attitude at each point of the smart cable. The position of the smart cable at one end of the mother ship control platform is a known fixed point, and the position of the ROV actuator end is obtained through an ultra-short baseline underwater acoustic positioning system. The position of the ROV actuator end is used as the boundary condition for morphology reconstruction.

[0020] Furthermore, the morphological reconstruction algorithm calculates the attitude output by the IMU into the cable tangent vector at the corresponding position, and inputs the discrete tangent vector constraint together with the continuous curvature and torsion constraints obtained by the three-core fiber grating and the endpoint boundary conditions into the fusion optimization filtering process to correct the cumulative drift caused by the cable integral reconstruction, so as to improve the accuracy and robustness of long-distance morphological reconstruction.

[0021] Furthermore, the overall structure of the smart cable body adopts a hierarchical structure. The three-core fiber optic grating sensor is placed at the core of the smart cable. The three-core fiber optic grating sensor, communication optical fiber, CAN bus and power supply cable constitute the smart cable core. The cable core is filled with filling yarn and has an external protective structure.

[0022] Furthermore, the functions of the mother ship platform include: communication interface configuration, ROV actuation control and operation status monitoring, real-time display of smart cable morphology, morphology reconstruction and fusion correction processing, analysis and display of load sensor measurement information, registration and display of environmental physical quantities and spatial coordinates, and historical data query and analysis.

[0023] The beneficial effects of the present invention are as follows: 1) The cable itself has attitude perception capability: In the present invention, the smart cable is the only sensing object. The attitude and depth information are continuously output along the cable through multiple nodes. The host computer integrates the absolute coordinates of the ROV obtained by underwater acoustic positioning to realize the real-time reconstruction and visualization of the three-dimensional shape of the smart cable, ensuring that each observation data corresponds one-to-one with its spatial position and measurement point attitude, and realizing high-precision measurement of the marine physical field environment.

[0024] 2) Remote towing and flexible deployment capabilities: This invention combines flexible smart cables with the mobility of ROVs, overcoming the location limitations of traditional fixed-layout sensor cables. Through remote control or autonomous ROV movement, the smart cable can be rearranged in three-dimensional space, allowing for more flexible and diverse tasks compared to fixed submarine observation cables. For example, the ROV can tow the smart cable to perform a circumferential inspection of the ship's hull and submarine pipelines, enabling a wide-area environmental parameter scan—something that traditional single ROVs or static sensor networks cannot achieve alone.

[0025] 3) Multi-point synchronous environmental monitoring capability: Up to several to dozens of measurement nodes on the smart cable can work simultaneously, equivalent to a distributed sensor network, acquiring environmental data from different spatial locations at the same time. This three-dimensional monitoring capability can depict spatial gradients and distributions, such as the spatial range of magnetic field anomalies, far surpassing the sporadic data from single-point measurements by ROVs. The types of node sensors can be flexibly configured according to the task, possessing strong scalability and application potential.

[0026] 4) Data Fusion and Intuitive Visualization Capabilities: The mothership-side system fuses cable morphology with multi-sensor data and displays it graphically, making the information clearer. Three-dimensional attitude visualization helps operators understand the underwater scene, while real-time overlay of sensor measurement results provides immediate environmental feedback. For example, when the cable passes over a magnetic target, the magnetic field reading at that node on the interface increases significantly, allowing the operator to determine the target's location and achieve intelligent decision support through human-machine interaction.

[0027] 5) Up-dimensional vectorization and matrix-style three-dimensional physical quantity output capability: This invention integrates the continuous curvature and torsion information of the three-core FBG with the tangent vector constraints of the attitude calculation of some node IMUs. By optimizing and correcting at the mother ship end to suppress long-distance integral drift, the attitude and tangent vector sequence along the cable are obtained in real time. The environmental measurements of each node are calibrated according to the cable length and mapped to the three-dimensional coordinate points of the reconstructed curve and bound to the attitude direction, so that the measurements are expanded into high-dimensional feature vector data containing "coordinates + direction", forming a large-scale matrix-style three-dimensional physical quantity dataset that is updated with the movement of the ROV.

[0028] The features and advantages of the present invention will be described in detail through embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of the underwater intelligent cable system of the present invention.

[0030] Figure 2 This is a schematic diagram of the overall structure of the underwater intelligent cable fixed-point detection system of the present invention.

[0031] Figure 3 This is a cross-sectional structural diagram of the smart cable body of the present invention.

[0032] Figure 4 It refers to the external structure of the measuring box.

[0033] Figure 5 This is an overall module diagram of the underwater intelligent cable system with shape perception and remote control operation.

[0034] Figure 6 It refers to signal transmission and conversion when using optical fiber for communication.

[0035] Figure 7 This is a schematic diagram of the mother ship's platform receiving signals.

[0036] In the diagram: 1. Mothership control platform; 2. Smart cable; 3. ROV actuation unit; 4. Twisted pair communication conductor; 5. Power supply conductor; 6. Single twisted insulation layer; 7. Power supply protection layer; 8. Twisted pair insulation layer; 9. Twisted pair shielding layer; 10. Single twisted shielding layer; 11. Three-core fiber optic grating sensor; 12. Communication fiber optic cable; 13. Cable core; 14. Smart cable protection layer; 15. Armor layer; 16. Data transmission measurement box; 17. Umbilical cable; 18. USBL positioning system; 19. Surface float. Detailed Implementation

[0037] The underwater intelligent cable system of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0038] One end of the intelligent cable is connected to a fixing device on the mother ship, and the other end is connected to the rear rack of the ROV. When the ROV moves underwater in a controlled manner, it pulls the intelligent cable to move synchronously, enabling spatial deployment and actuation of the cable. This system does not involve the design of the ROV umbilical cable; the ROV only serves as an actuation module for executing the deployment of the intelligent cable. The entire system achieves integrated sensing and actuation functions of the intelligent cable, mother ship, and ROV. The intelligent cable itself is equivalent to a flexibly deployable sensor array. The ROV provides power to tow this array to the target location. The data processing and storage system on the mother ship is responsible for morphological reconstruction, data fusion, spatial registration, and visualization output, enabling the cable to possess morphological and attitude self-sensing capabilities and environmental awareness.

[0039] 1. Intelligent cable body structure;

[0040] a. Internally integrated core components;

[0041] Shape sensing unit: The smart cable body integrates a three-core fiber Bragg grating sensor for sensing the shape of the cable. This three-core fiber Bragg grating sensor is a multi-core fiber Bragg grating with three parallel and equal-length fiber cores arranged in an equilateral triangle at 120° and embedded in the optical fiber. It is used to measure the strain at various locations of the cable and is embedded along the entire length of the smart cable.

[0042] Communication transmission unit: The intelligent cable body integrates communication cables for data transmission, including a CAN bus and / or communication optical fiber; if communication optical fiber is used, the system also includes an optical communication module: the electro-optical conversion module at the data acquisition end in the measurement box, the communication optical fiber for data transmission, and the photoelectric conversion module at the mother ship end, to transmit data.

[0043] CAN Bus: A Controller Area Network (CAN) bus running through the intelligent cable body, consisting of a pair of twisted-pair communication wires that connect the data communication modules of all measurement nodes and the data processing and storage system on the mother ship in series, enabling multi-node bus-type data communication. In one implementation, a CAN bus running the entire length of the cable, composed of two-core twisted-pair wires, passes through all node measurement boxes and connects to the data transceiver module on the mother ship. The data acquisition modules of all nodes communicate with the host computer on the mother ship via the bus protocol, enabling multi-node data uploading and command issuance. Another implementation involves embedding a communication optical fiber within the cable. Each node transmits data to the mother ship via an optical interface using time-division multiplexing or wavelength-division multiplexing. Each node contains an electro-optical converter that converts electrical signals into optical signals, which are then transmitted through the communication optical fiber within the intelligent cable body.

[0044] Power Supply Unit: The intelligent cable body integrates a power supply cable for power supply. The power supply cable includes at least two conductive wires (composed of two copper wires). The mother ship control platform includes a DC power supply module, which continuously supplies power to the intelligent cable body through the conductive wires. The mother ship provides stable DC power, which is transmitted along the cable to the measurement boxes of each node to power the sensors and electronic modules within the node. Each measurement node obtains power from the conductive wires in parallel and is regulated by the power management circuit (internal step-down voltage regulator circuit) of this node before being used by its internal electronic components to obtain the required operating voltage.

[0045] The overall structure of the smart cable adopts a hierarchical structure. The three-core fiber optic sensor is placed at the core of the smart cable. The three-core fiber optic sensor, communication optical fiber, communication CAN bus and power supply line constitute the smart cable core. The cable core is filled with filler yarn and has an outer protective structure. The overall design of the cable fully considers the safety and durability of underwater use. The power and signal lines are covered with waterproof insulation materials and shielding layers. The optical fiber and conductors are protected by tensile materials and seawater corrosion resistant outer sheaths to ensure long-term reliable operation of the smart cable under underwater tensile and bending conditions.

[0046] b. External measurement node (sealed measurement box);

[0047] Arrangement and Fixing: Multiple sealed measurement boxes (node-type measurement boxes) are arranged along the length of the intelligent cable body. These measurement nodes are set at intervals as needed along the cable axis and are firmly and sealed on the outside of the cable body. The outer shell of each measurement box is fixed to the outside of the intelligent cable body by adhesive locking, and has a streamlined structure to reduce underwater resistance.

[0048] Internal components: Each measurement box contains an environmental sensor assembly, which communicates with the mother ship's control platform via a communication cable and obtains power via a power supply cable.

[0049] Environmental sensor components may include magnetic field sensors, temperature sensors, pressure sensors, etc.; specifically, a triaxial magnetometer is used to measure the underwater magnetic field strength, a temperature sensor is used to measure the water temperature, a pressure sensor is used to measure the water pressure at that depth, and other optional sensors.

[0050] Each measurement node has a built-in data acquisition and communication electronic module (such as a microprocessor, CAN transceiver / photoelectric conversion module, power supply module, etc.) to read and aggregate data from various sensors, perform digital processing, and send the data to the mother ship's data processing and storage system via communication cables.

[0051] Preferably, at least some of the measurement boxes further integrate an IMU module to output the attitude information at the measurement box; the node side can timestamp the IMU data and environmental data and upload them synchronously so that the mother ship can perform fusion reconstruction and spatial registration.

[0052] 2. Mother ship control platform;

[0053] a. Hardware components;

[0054] The mothership-side control platform includes a fiber Bragg grating signal demodulator connected to a three-core fiber Bragg grating sensor, a data processing and storage system connected to a communication CAN bus and / or optical communication module, and a DC power supply module to provide stable DC power to the power supply cables.

[0055] Fiber Bragg grating signal demodulator: Connected to the three-core fiber Bragg grating sensor inside the smart cable, it demodulates the optical signal of the three-core fiber Bragg grating sensor to obtain distributed strain data. Through fiber Bragg grating demodulation technology, it acquires fiber strain or grating wavelength offset data at various positions along the cable in real time and converts it into digital signals for input into the data processing and storage system.

[0056] Data processing and storage system: Composed of an industrial computer or dedicated processor, including a CAN bus interface module (for communication with the CAN bus) and an optical fiber data interface module (for receiving signals transmitted by the optical communication module), used to receive environmental data and IMU data from each measurement node, and combine the strain information output by the demodulator to perform morphological reconstruction, fusion correction, spatial registration, visualization and data storage analysis; the software module includes morphological reconstruction, data fusion and visualization.

[0057] DC power supply module: It is part of the mother ship's control platform and provides stable DC power to the power supply cables.

[0058] b. Core functions;

[0059] Morphology Reconstruction: Data Processing and Storage System Configuration of Smart Cable Morphology Reconstruction Algorithm: Based on the strain information along the cable obtained by the fiber optic demodulator, the curvature and deflection are calculated, and the initial three-dimensional morphology curve of the smart cable is obtained by integration under the Frenet–Serret framework; where the mother ship end is a known fixed point, and the ROV end position is given in real time by the USBL positioning system and used as the end boundary condition.

[0060] To suppress the cumulative drift caused by long-distance integral reconstruction, the system further utilizes the IMU output attitude of some measurement boxes and solves the local tangent vector as a discrete direction constraint to introduce into the fusion correction process. Together with the FBG continuous curvature constraint and the endpoint boundary conditions, it is optimized or filtered to obtain a higher-precision three-dimensional cable path in the geographic coordinate system.

[0061] Data processing, spatial registration and display: The platform receives environmental sensing data and IMU data from each node on the cable through the communication interface, and obtains cable morphology perception data from the fiber optic demodulator; it timestamps each data point, and maps the node measurements to the corresponding spatial coordinate points of the reconstructed 3D morphology curve according to the node's calibrated position along the cable length, thereby realizing spatial registration and display of environmental data and attachment of attitude information (up-dimensional output); the processed morphology and environmental information are displayed in real time through a visualization interface.

[0062] Data storage and analysis: The data processing and storage system supports data storage and retrieval, and can replay and analyze historical cable morphology changes and environmental parameters to facilitate fault diagnosis and scientific research.

[0063] The mother ship control software functions include communication interface configuration, ROV actuation control and operation status monitoring, real-time display of smart cable morphology, parsing and display of load sensor measurement information, and historical data query and analysis.

[0064] When using the above technical solution, the following steps are included:

[0065] S1 and ROV move in a controlled manner underwater, pulling the smart cable body to move synchronously, realizing the spatial deployment and operation of the smart cable.

[0066] S2. Each sealed measurement box on the smart cable body collects environmental data such as magnetic field, temperature, and pressure through environmental sensor components; when the measurement box integrates an IMU, it synchronously collects attitude data and timestamps it.

[0067] S3. The data acquisition and communication module built into the measurement node aggregates, digitizes, and encapsulates sensor data; when optical communication is used, the node converts electrical signals into optical signals through an electro-optical conversion module.

[0068] S4. Data is transmitted to the mother ship's data processing and storage system via a communication CAN bus (twisted pair communication wire) or an optical communication module (communication optical fiber).

[0069] S5. The fiber Bragg grating signal demodulator at the mother ship end demodulates the optical signal of the three-core fiber Bragg grating sensor to obtain distributed strain data and transmit it to the data processing and storage system.

[0070] S6. The data processing and storage system is based on distributed strain calculation of curvature and deflection. It obtains continuous curvature and deflection functions through interpolation and integrates them to obtain the initial three-dimensional morphological curve. At the same time, it introduces the fixed point at the mother ship end and the USBL positioning at the ROV end as endpoint boundary conditions for iterative correction to achieve geographic coordinate system registration.

[0071] S7. When the IMU is set, the system calculates the IMU attitude as the tangent vector at the corresponding position, and uses it as the discrete direction constraint, along with the FBG continuous curvature constraint and endpoint boundary conditions, to input the fusion optimization filtering process, correct the cumulative drift, and output the corrected three-dimensional morphological curve and attitude sequence.

[0072] S8. Based on the calibrated position of the measurement node in the cable length direction, the system maps the environmental measurement values ​​to the corresponding spatial coordinate points of the corrected three-dimensional morphological curve, forming environmental data with spatial coordinate markers (upgraded-dimensional dataset); the mother ship end control software realizes the visualization of the cable attitude, real-time display and storage of environmental data, and supports historical data query and analysis and ROV actuation control.

[0073] To achieve real-time 3D morphological perception, remote control actuation, multi-node environmental parameter monitoring, real-time data transmission and visualization, and attitude information appended to environmental data for underwater cables, this invention provides an underwater intelligent cable system consisting of a mother ship end, an intelligent cable body, and an ROV, possessing morphological perception and remote control / autonomous actuation functions. This system integrates a three-core fiber optic grating sensor within the intelligent cable body to acquire strain and attitude information of each cable segment in real time, accurately reconstructing the underwater 3D spatial morphology. Simultaneously, using the curvature and deflection obtained from the three-core fiber optic grating sensor, interpolation and the Frenet-Serret equation are applied to obtain the tangent vector, normal vector, and subnormal vector at each point on the intelligent cable. The system measures the attitude and adds it to environmental data to achieve data dimensionality enhancement. Using an ROV as a traction actuation unit, it can remotely control the deployment and retrieval of smart cables in specific underwater areas, flexibly adjusting the cable shape and position to achieve active spatial deployment. By deploying several sensor nodes on the cable, it can simultaneously collect environmental parameters such as magnetic field, temperature, and pressure at multiple locations along the line, constructing a spatially distributed underwater environmental survey network. It can also rely on a transmission network combining optical communication modules and CAN bus to transmit morphological and sensor data back to the mother ship in real time. After being integrated and processed by the host computer system, it provides an intuitive three-dimensional attitude visualization interface and real-time display, storage, and historical query functions for environmental data.

[0074] The underwater intelligent cable system of the present invention achieves integrated sensing and actuation functions of intelligent cable, mother ship, and underwater robot through the above-mentioned structural design. The intelligent cable body is equivalent to a flexibly deployable sensor array. The ROV provides power to tow this array to the target location, while the data processing and storage system at the mother ship end is responsible for sensing and decision-making, transforming the cable into an intelligent device with self-sensing of shape and attitude and environmental perception. Example 1

[0075] See Figure 1As shown, the underwater intelligent cable system of this invention comprises three main parts: a mother ship-end control platform 1, an intelligent cable 2, and an ROV actuation unit 3. One end of the intelligent cable 2 is connected to the mother ship-end control platform 1 via a deck pulley and a fixed bracket, while the other end is connected to the stern attachment point of the ROV actuation unit 3. The mother ship-end control platform 1 includes a cable winch, a fiber optic demodulator, and a data processing and storage system, used for releasing and retrieving the intelligent cable and processing the cable's sensor data. During operation, the mother ship-end control platform 1 transmits commands to the ROV actuation unit 3 via an umbilical cable 17, thereby controlling the operation of the ROV actuation unit 3. The ROV actuation unit 3 is launched into the water and operated via its own independent umbilical cable, then attaches the end of the intelligent cable 2 to its rear connector. When the ROV actuation unit 3 is navigating underwater, it pulls the intelligent cable 2 to move synchronously, causing the cable to unfold and penetrate the area to be monitored. For example, during a seabed patrol mission, the mother ship's control platform 1 moves slowly forward, the ROV actuator 3 travels along a predetermined path, and the smart cable 2 is laid on the seabed or suspended above the seabed as the ROV actuator 3 moves, forming a U-shaped towing arc from the mother ship's control platform 1 to the ROV actuator 3. (See also...) Figure 2 As shown, the underwater intelligent cable fixed-point detection system consists of three main parts: a surface float 19, an intelligent cable 2, and an ROV actuation unit 3. The surface float is fixedly floating on the sea surface to be measured. One end of the intelligent cable 2 is fixed to the surface float 19, and the other end is connected to the tail attachment point of the ROV actuation unit 3. During operation, the ROV actuation unit 3 drags the intelligent cable 2. The underwater data is stored in the surface float 19 and collected periodically.

[0076] It should be noted that the intelligent cable 2 is designed with near-neutral buoyancy, allowing it to float in the water and preventing excessive sag and sinking. The tensile core of the cable body ensures that it can withstand the traction force of the ROV actuation unit 3 and the tension of ocean currents. At the same time, the outer sheath of the cable is smooth and wear-resistant, reducing resistance when towed in the water. Because the intelligent cable of this invention has more internal sensors and node devices than traditional cables, its diameter is slightly larger, but it can still be retrieved and deployed by the mother ship's winch. Each measuring node is designed as a streamlined, small compartment that fits tightly with the cable body, avoiding a surge in water resistance or cable entanglement.

[0077] During system deployment, the intelligent cable 2 is first connected sequentially to all measurement nodes and ROV end interfaces on the mother ship's deck. Then, the fiber Bragg grating signal demodulator and data processing and storage system on the mother ship are activated. After the ROV actuation unit 3 enters the water, the end of the intelligent cable is quickly secured to the ROV's stern attachment point. Next, the cable is slowly released, maintaining appropriate slack between the cable end and the ROV to avoid excessive tension during movement. As the ROV submerges to the target water depth and begins operation, the mother ship's system continuously collects fiber optic strain data and node sensor data from the intelligent cable. The operator can see a three-dimensional curve representing the intelligent cable extending from the mother ship to the ROV through the host computer interface, with its shape updated in real time. When the ROV actuation unit 3 turns or moves, the curve shape of the intelligent cable 2 changes accordingly. The entire system automatically runs a shape reconstruction algorithm in the background. After the task is completed, the ROV actuation unit 3 tows the intelligent cable 2 back to the vicinity of the mother ship, the ship's winch retrieves the cable, and finally, the ROV actuation unit 3 releases the cable end to complete the recovery. Example 2

[0078] See Figure 3 The smart cable of this embodiment includes: a pair of twisted-pair communication conductors 4 and two power supply conductors 5. Each twisted-pair communication conductor 4 is covered with a single-twisted insulation layer 6 and a single-twisted shielding layer 10. The twisted-pair communication conductors 4 and the communication optical fiber 12 are integrated, and their outer sides are covered with twisted-pair insulation layers 8 and twisted-pair shielding layers 9. Each power supply conductor 5 is covered with a power supply protection layer 7. At the core of the smart cable 2, there is a three-core fiber optic sensor 11 and a communication optical fiber 12, which together with the filling layer and axial reinforcing member constitute the cable core 13. The outer side of the cable core 13 is provided with a smart cable protection layer 14 and an armor layer 15. This cable core design realizes the power supply function of the data transmission measurement box 16. The pair of twisted-pair communication conductors 4 can transmit high and low signal levels, forming a differential circuit, which can transmit various data signals, such as location information and sensor information. Moreover, each measurement box can communicate asynchronously with each other, thereby greatly improving communication efficiency. In addition, the electrical parameters of each line are precisely matched and optimized to ensure that each line does not interfere with each other, ensuring the reliability of data transmission and the stability of power supply.

[0079] See Figure 4The data transmission measurement box 16 internally includes multiple sensors and electronic units. A typical node configuration includes: a triaxial magnetic sensor, a temperature sensor, a pressure sensor, a microprocessor, a CAN transceiver, a power module, a photoelectric conversion module, and preferably, an IMU module. The magnetic sensor detects changes in the surrounding magnetic field, while the temperature and pressure sensors detect local underwater parameters. The microprocessor periodically reads the values ​​from each sensor, packages them into data frames, and sends them via the CAN transceiver or via optical fiber through photoelectric conversion. The power module converts the bus voltage to the low voltage required by each device. The node program periodically broadcasts data to the bus using polling or interrupt triggering. To reduce bus load, different transmission cycles can be set for each node. Example 3

[0080] This embodiment presents a method for morphological reconstruction and data fusion. The fiber Bragg grating signal demodulator at the mothership end demodulates the strain data from the three-core fiber Bragg grating sensor along its length (using distributed demodulation techniques such as optical frequency domain reflection), and outputs distributed strain data along the cable. The data processing and storage system calculates the cable's bending curvature at corresponding locations based on the distributed strain data. and torsional deflection The continuous functions of curvature and deflection are obtained through interpolation (e.g., cubic spline interpolation); the three-dimensional coordinates of the fixed point at the mother ship end and the USBL positioning at the ROV end are used as the endpoint boundary conditions; the initial cable shape is obtained by numerical integration based on the Frenet-Serret framework; and the three-dimensional path in the geographic coordinate system is obtained by iterative correction of the endpoint deviation.

[0081] To suppress the cumulative drift caused by long-distance integration, at least some measurement nodes are equipped with IMUs and output attitude information. The data processing and storage system, in conjunction with the node installation and calibration relationship, calculates the IMU attitude as the cable tangent vector at the node, which is then introduced into the fusion correction process as a discrete direction constraint. The fusion process uses the FBG continuous curvature constraint, endpoint boundary conditions, and IMU discrete tangent vector constraint together for optimization or filtering correction to obtain the corrected three-dimensional morphological curve and attitude sequence.

[0082] Regarding the fusion of morphological and sensor data: The host computer saves the calibrated discrete three-dimensional coordinate sequence of the cable and maps each measurement node to the corresponding arc length position on the curve according to the fixed installation position of each node along the cable length (for example, if node A is 100 m from the mother ship end, then the coordinates of the corresponding arc length point are found on the curve). Environmental data from each node are associated with the latest morphological curve according to the timestamp and combined into sensor data with spatial coordinate markers. The fused data is used for graphical display and stored in the database: The host computer refreshes the display of the current three-dimensional curve of the cable at a set frequency and marks the position of each node on the curve with icons; selecting a node icon can display the environmental measurement value and attitude information of that node; all data is recorded in chronological order for query playback and event analysis.

[0083] In a preferred embodiment, to suppress the cumulative drift caused by curvature and deflection integrals under long-distance conditions and improve the absolute accuracy of cable 3D morphology reconstruction, the data processing and storage system further introduces IMU attitude observation based on the endpoint boundary conditions, constructs an FBG-IMU fusion correction model, and corrects and solves the cable morphology curve. The fusion correction model takes the cable 3D morphology curve to be solved as the object and includes at least the following constraints: The first constraint is a continuous curvature and deflection consistency constraint, which calculates the curvature and deflection distribution along the cable based on the distributed strain information obtained from the three-core FBG demodulation, constraining the curvature and deflection of the curve to be solved along the arc length direction to be consistent with or have the smallest deviation from the FBG calculation results; the second constraint is an endpoint boundary condition constraint, with the mother ship end fixed point as the starting boundary and the ROV end 3D coordinates obtained from USBL positioning as the ending boundary, constraining the two endpoints of the curve to be solved to match the boundary conditions or have the minimum endpoint error, so as to achieve the morphology curve in... The first constraint is registration in the geographic coordinate system; the second constraint is the IMU discrete tangent vector constraint. For measurement nodes equipped with IMUs, based on the attitude information output by the IMUs and combined with the calibration relationship between the node coordinate system and the cable coordinate system, the cable tangent vector at the node is calculated. The constraint is to ensure that the tangent vector of the curve to be solved at the corresponding arc length position is consistent with the observed tangent vector or has the smallest direction error, thereby forming direction anchor points at several discrete positions along the cable to suppress mid-section drift; the third constraint is the smoothness and physical rationality constraint, which is used to suppress high-frequency bending of the curve shape and ensure that the curve shape changes continuously, smoothly and in accordance with the physical rationality of the cable's flexible deformation.

[0084] In one embodiment, the data processing and storage system combines the above constraints according to preset weights to form a fusion correction target, and uses iterative optimization or filtering methods to solve for the corrected three-dimensional morphological curve: when using iterative optimization, the initial curve obtained by curvature integral is used as the initial value, and the curve parameters are updated iteratively to gradually converge the endpoint error, direction error, and curvature consistency error to the threshold; when using filtering, the state of the cable morphological curve is used as the estimation object, and the state is updated and corrected using FBG curvature and torsion as continuous observations, IMU tangent vectors as discrete observations, and USBL endpoints as boundary observations, thereby obtaining the corrected morphological curve and attitude sequence. Preferably, when the USBL update frequency is lower than the FBG / IMU sampling frequency, the most recent valid USBL value can be retained or interpolated to participate in the endpoint constraint; when the number of IMU nodes is limited, they are preferably arranged near the middle and end of the cable to enhance the constraint capability for long-distance cumulative error. Through the above-mentioned fusion correction process, the output three-dimensional morphology curve of the cable has a smaller cumulative drift error compared to the result based solely on the curvature integral of FBG. In particular, it has higher directional stability and absolute position accuracy in the middle section of the cable, thereby improving the reliability and usability of the environmental data spatial registration and the upgraded output dataset.

[0085] The above embodiments are only used to illustrate the present invention. Any equivalent transformations and improvements made on the basis of the technical solutions of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. An underwater intelligent cable system with shape perception and remote control actuation, characterized in that: The system comprises a mother ship end control platform, an intelligent cable and an ROV actuating unit; One end of the intelligent cable is fixedly connected to the mother ship end control platform, and the other end is connected to the ROV actuating unit and is dragged by the ROV actuating unit; The intelligent cable is internally integrated with a three-core fiber Bragg grating sensor for cable body shape sensing, a power cable and a communication cable for data transmission, and the communication cable adopts a CAN bus and / or a communication optical fiber; A plurality of sealed data transmission and measurement boxes are arranged along the length direction of the intelligent cable, each data transmission and measurement box is provided with an environmental sensor assembly, and is in communication connection with the mother ship end control platform through the communication cable and obtains power through the power cable; at least one data transmission and measurement box is provided with an inertial measurement unit (IMU) for outputting attitude information at the measurement box and solving a local tangent vector of the cable body. The mother ship end control platform comprises a fiber Bragg grating signal demodulator connected to the three-core fiber Bragg grating sensor, and a data processing and storage system connected to the communication CAN bus and the optical communication module, the data processing and storage system is used for receiving environmental data of each measurement node and mapping the environmental data to corresponding spatial coordinate points of a reconstructed three-dimensional shape curve according to the calibrated positions of the measurement boxes in the cable length direction, forming environmental physical quantity data with spatial coordinate markers and performing real-time display and storage query; The data processing and storage system is also used for reconstructing a three-dimensional shape of the intelligent cable body under water in combination with strain information output by the fiber Bragg grating signal demodulator, realizing visualization of the cable body shape and attitude, and fusing and correcting the strain reconstruction result and the tangent vector and attitude observation provided by the IMU to suppress cumulative errors of long-distance shape reconstruction; The data processing and storage system is configured with an intelligent cable shape reconstruction algorithm, the bending curvature and bending flexibility along the cable are calculated based on the cable body strain information obtained by the fiber Bragg grating signal demodulator, and the shape curve of the intelligent cable body in the three-dimensional space is integrated to reconstruct the shape curve, and the attitude of each point of the intelligent cable is obtained; the position of the intelligent cable at one end of the mother ship end control platform is a known fixed point, the position of the ROV actuating unit end is obtained by an ultra-short baseline underwater acoustic positioning system, and the position of the ROV actuating unit end is used as a boundary condition for shape reconstruction; the intelligent cable shape reconstruction algorithm outputs the attitude calculated by the IMU as the tangent vector of the cable body at the corresponding position, and inputs the tangent vector, the continuous curvature and flexibility constraints of the FBG and the end point boundary condition into a fusion optimization filtering process together, to correct the cumulative drift of the integrated reconstruction curve.

2. The intelligent underwater cable system with shape perception and remote actuation according to claim 1, wherein: The three-core fiber Bragg grating sensor is a fiber sensing unit containing three cores, the three cores are arranged in parallel along the cable body axis and are distributed at an interval of 120° in the cross section, for measuring strain in different directions of the cable body; the fiber Bragg grating signal demodulator adopts a distributed fiber sensing technology to obtain the strain distribution of the fiber sensing unit along the length, and converts it into the bending curvature and bending flexibility of each position of the cable body.

3. The intelligent underwater cable system with shape perception and remote actuation according to claim 1, wherein: The data transmission measurement box comprises an environmental sensor assembly, a data communication module and an electro-optical signal conversion module, the environmental sensor assembly comprises a magnetic field sensor, a temperature sensor and a pressure sensor; the data communication module is used for gathering data of various sensors into environmental data, time stamping IMU attitude data and synchronously packaging and uploading the environmental data and the IMU attitude data at a corresponding moment, and sending to a mother ship end data processing and storage system through the electro-optical signal conversion module through a communication cable.

4. The intelligent underwater cable system with shape perception and remote actuation according to claim 1, wherein: The communication cable is connected in series with the data communication modules of all the measurement nodes and the mother ship end data processing and storage system to realize bus type data communication of multiple nodes.

5. The intelligent underwater cable system with shape perception and remote actuation according to claim 1, wherein: The overall structure of the intelligent cable body adopts a hierarchical structure, the three-core fiber grating sensor is placed at the center of the intelligent cable, the three-core fiber grating sensor, the communication optical fiber, the CAN bus and the power cable constitute an intelligent cable core, the core is filled with filling yarn, and an outer protective structure is attached.

6. The underwater intelligent cable system with shape perception and remote actuation according to claim 1, wherein: The functions of the mother ship end control platform include: communication interface configuration, ROV actuation control and running state monitoring, real-time display of the intelligent cable shape, shape correction based on endpoint boundary conditions and IMU-FBG fusion constraints, analysis and display of bearing sensor measurement value information, registration display of measurement node environmental physical quantities and three-dimensional shape curve space coordinates, historical data query and analysis.

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