Sensing submarine cable riser intelligent monitoring system based on optical fiber sensing

Abstract

The invention provides a sensing submarine cable riser intelligent monitoring system based on optical fiber sensing, and relates to the technical field of riser monitoring, the sensing submarine cable riser intelligent monitoring system comprises a sensing submarine cable module, a riser monitoring module and a riser laying module, the sensing submarine cable module is used for monitoring the deformation state and the stress state of a marine riser in real time, and the riser laying module is used for laying the riser monitoring module. A sensing submarine cable in the sensing submarine cable module is integrated with a plurality of fiber grating array sensors at intervals from head to tail; the riser monitoring module is used for recording and storing the wavelengths of the fiber bragg grating array sensor at different moments in the sensing submarine cable module and inversion marine riser images corresponding to the wavelengths of the fiber bragg grating array sensor according to the floating remote communication demodulation unit so as to adjust the accumulated error of the marine environment and analyze the real-time state of the marine riser; and the riser laying module is used for carrying out coupling laying on the sensing submarine cable and the riser by using a son-mother pipe coupling clamp and putting the sensing submarine cable and the riser into a target sea area. According to the invention, the submarine cable monitoring precision and reliability can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of riser monitoring, and in particular to an intelligent monitoring system for a sensing submarine cable riser based on optical fiber sensing. Background Art

[0002] The high-precision intelligent health detection technology of submarine cables is a frontier hotspot in the current international research and development field of marine intelligent technologies and equipment, and it is also a technical bottleneck restricting the development of offshore resources and energy information transmission in China. With the rapid rise and extremely rapid development momentum of China's new energy industry, it has provided a huge market for submarine pipeline and cable products, and at the same time has put forward relatively high requirements for the real-time monitoring ability of submarine cable products. In recent years, with the development of offshore power generation, submarine cables have become the main means of contemporary intercontinental communication and an important way for information transmission between islands and the mainland, as well as between islands. At the same time, submarine optical cables play a huge role in communication in the military and civilian fields. Especially in international network communication, submarine cables have an irreplaceable position. Therefore, developing submarine cable health monitoring technology is of great significance for supporting and ensuring the continuous use of submarine cables.

[0003] The Chinese patent application with publication number CN115014223B discloses a submarine cable deformation monitoring system based on a sensing grating array, including a monitoring host computer, a grating demodulator, and a monitoring system. The monitoring system includes a flexible carrier and a transmission optical fiber. A number of strain sensing grating arrays are provided on the transmission optical fiber, and the transmission optical fiber is embedded in the flexible carrier. The strain sensing grating arrays are arranged along the axial direction of the submarine cable, and the transmission optical fiber is fixed to the submarine cable. The grating demodulator is used to emit optical signals, obtain and demodulate the optical signals reflected by the strain sensing grating arrays, and obtain the curvature information of the strain sensing grating arrays. The monitoring host computer is used to obtain the morphological monitoring information of the submarine cable according to the curvature information. However, the above solution relies on grating reflection signals to obtain curvature information. During long-term monitoring and large-scale data acquisition, problems such as error accumulation and data redundancy are likely to occur. At the same time, additional image or other auxiliary calibration means may need to be introduced to correct errors, which will lead to a reduction in the monitoring accuracy of submarine cables. Therefore, it is very necessary to provide an intelligent monitoring system for a sensing submarine cable riser based on optical fiber sensing to improve the monitoring accuracy and reliability of submarine cables. Summary of the Invention

[0004] In view of this, the present invention proposes an intelligent monitoring system for a sensing submarine cable riser based on optical fiber sensing. Through the optical fiber grating array sensors evenly distributed on the sensing submarine cable, each monitoring point can collect the local bending, torsion, stretching and other states in real time, thereby realizing the accurate judgment of the state of the marine riser and greatly improving the monitoring accuracy and reliability of submarine cables.

[0005] The present invention provides an intelligent monitoring system for a sensing submarine cable riser based on optical fiber sensing, including a sensing submarine cable module, a riser monitoring module, and a riser laying module. Among them,

[0006] The sensing submarine cable module is used to monitor the deformation state and stress state of the marine riser in real time. Among them, several fiber Bragg grating array sensors are integrated at intervals from head to tail in the sensing submarine cable of the sensing submarine cable module;

[0007] The riser monitoring module is used to record and save the wavelengths of the fiber Bragg grating array sensors in the sensing submarine cable module at different times and the inverted marine riser images corresponding to the wavelengths of the fiber Bragg grating array sensors according to the floating remote communication demodulation unit, so as to adjust the cumulative error of the marine environment and analyze the real-time state of the marine riser;

[0008] The riser laying module is used to couple and lay the sensing submarine cable with the riser by using a mother-daughter pipe coupling fixture and place it in the target sea area.

[0009] On the basis of the above technical solutions, preferably, the sensing submarine cable includes a central strengthening core and a sensing layer and an outer sheath that are sequentially covered on the outer periphery of the central strengthening core from inside to outside. The sensing layer includes a plurality of optical units and a plurality of armored steel wires. The plurality of optical units and the plurality of armored steel wires are distributed in a circular array. The optical unit includes any one of a weak grating array or a multimode optical fiber. A protective layer is coated on the outer periphery of the weak grating array and the multimode optical fiber, and a wrapping tape is wound around the outer periphery of the protective layer.

[0010] On the basis of the above technical solutions, preferably, the sensing layer includes a first optical unit and a second optical unit. The first optical unit includes the weak grating array and the protective layer and the wrapping tape that are sequentially covered on the outer periphery of the weak grating array from inside to outside. The second optical unit includes the multimode optical fiber and the protective layer and the wrapping tape that are sequentially covered on the outer periphery of the multimode optical fiber from inside to outside.

[0011] More preferably, the second optical unit or the armored steel wire is arranged between any two adjacent first optical units.

[0012] More preferably, the included angle formed by the connection line between the optical unit and the axis of the central strengthening core and the connection line between the axis of the central strengthening core and any remaining optical unit is 120°.

[0013] More preferably, the reflectivity of the weak grating array is 1% to 0.0001%, and the distance between any two adjacent weak grating arrays is 0.5 m.

[0014] More preferably, the central strengthening core is a steel wire, and the armored steel wire and the optical unit are stranded around the central strengthening core at an angle of 12°.

[0015] More preferably, the weak grating array is distributed on the entire sensing submarine cable. The weak grating array is used for distributed measurement of the overall strain of the marine riser and for inverse shape reconstruction of the riser. The multimode optical fiber is also distributed on the entire sensing submarine cable. The multimode optical fiber is used to monitor the temperature and vibration signals during the operation of the marine riser, and to monitor the overall state and leakage state of the marine riser.

[0016] More preferably, the riser monitoring module includes a floating platform and a riser monitoring cloud platform. Among them, the floating platform includes an equipment cabin, a buoyancy cabin, deck fittings, a bottom bilge plate, a lamp bracket, a comprehensive weather station, an azimuth sensor, and a single-point current meter. The floating platform is used to achieve unmanned autonomous monitoring and remote communication transmission at sea. The riser monitoring cloud platform includes a demodulation control module and a remote communication module. The riser monitoring cloud platform is arranged in the equipment cabin. The demodulation control module is used to demodulate, identify, and manage the measurement data of the sensing submarine cable to monitor multiple physical parameters. The remote communication module is configured for signal transceiver.

[0017] More preferably, the mother-daughter pipe coupling fixture includes a single-sided semi-circular lower base of the riser, a double-sided semi-circular groove-shaped upper part on the riser cable side, a single-sided semi-circular upper base of the cable, a rubber protection gasket, and a cable protection washer. The double-sided semi-circular groove-shaped upper part on the riser cable side is provided with two semi-circular grooves with opposite opening directions and diameters corresponding to the diameters of the sensing submarine cable and the riser respectively. The single-sided semi-circular lower base of the riser, the double-sided semi-circular groove-shaped upper part on the riser cable side, and the single-sided semi-circular upper base of the cable are all provided with threaded holes for connection and fixation. The single-sided semi-circular lower base of the riser, the double-sided semi-circular groove-shaped upper part on the riser cable side, and the single-sided semi-circular upper base of the cable are sequentially fixedly connected by bolts to form two cylindrical holes for placing the sensing submarine cable and the riser respectively. The cable protection washer is arranged in the cylindrical hole corresponding to the sensing submarine cable formed by the single-sided semi-circular lower base of the riser and the double-sided semi-circular groove-shaped upper part on the riser cable side. The rubber protection gasket is arranged in the cylindrical hole corresponding to the marine riser formed by the double-sided semi-circular groove-shaped upper part on the riser cable side and the single-sided semi-circular upper base of the cable.

[0018] The intelligent monitoring system for a sensing submarine cable riser based on optical fiber sensing provided by the present invention has the following beneficial effects compared with the prior art:

[0019] (1) Through the fiber Bragg grating array sensors evenly distributed on the sensing submarine cable, each monitoring point can collect the local bending, torsion, tension and other states in real time. This distributed monitoring can not only capture local anomalies, but also comprehensively reflect the overall force and deformation of the entire riser. With the floating remote communication demodulation unit, the system can record the wavelength changes of each sensor in real time, and the wavelength changes directly correspond to the stress or deformation received by the sensor. By comparing and analyzing with the built-in calibration data, the accuracy and stability of data collection are greatly improved, thus achieving an accurate judgment of the state of the marine riser, greatly enhancing the monitoring accuracy and reliability of the submarine cable. At the same time, the riser laying module uses a mother-daughter pipe coupling fixture to tightly couple the sensing submarine cable with the riser, which not only ensures that the sensor can closely adhere to the surface of the riser during monitoring, reducing data distortion, but also greatly simplifies the operation processes of installation, maintenance and replacement, reducing the construction difficulty and labor cost.

[0020] (2) Through the weak grating array arranged along the entire length of the sensing submarine cable, the distributed measurement of the overall strain of the marine riser is realized. The multimode optical fibers evenly distributed on the same sensing submarine cable can monitor the temperature and vibration signals in real time, comprehensively detect the working state and leakage situation, and ensure the all-round monitoring of the structural health. The alternating setting of the first optical unit and the second optical unit, and the connection line between any two adjacent first optical units and the central strengthening core forms an angle of 120°, forming a reasonable spatial layout to ensure the acquisition of monitoring data in multiple directions and at multiple angles, improving the overall monitoring accuracy and reliability. The first and second optical units are both designed with multiple layers of protection such as a protective layer and a wrapping tape, which can effectively resist common interference factors such as mechanical, chemical and temperature in the marine environment, thus ensuring the long-term stable and reliable working state of the sensor. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 It is a framework schematic diagram of the sensing submarine cable riser intelligent monitoring system provided by the present invention;

[0023] Figure 2 It is an overall schematic diagram of the sensing submarine cable riser intelligent monitoring system provided by the present invention;

[0024] Figure 3 It is a cross-sectional schematic diagram of the sensing submarine cable provided by the present invention;

[0025] Figure 4Explosion view of the mother-daughter pipe coupling fixture provided by the present invention;

[0026] Figure 5 Structural schematic of the floating platform and the riser provided by the present invention;

[0027] Figure 6 Laying schematic diagram of the sensing submarine cable provided by the present invention.

[0028] Explanation of reference numerals: 1, sensing submarine cable module; 11, central strengthening core; 12, sensing layer; 121, optical unit; 1211, weak grating array; 1212, protective layer; 1213, wrapping tape; 1213, multimode optical fiber; 122, armor wire; 13, outer sheath; 2, riser monitoring module; 3, riser laying module; 31, lower semi-circular base on one side of the riser; 32, upper double semi-circular groove type on the submarine cable side of the riser; 33, upper semi-circular base on one side of the submarine cable; 34, rubber protection gasket; 35, submarine cable protection washer. Detailed implementation manners

[0029] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0030] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, terms such as "a" or "one" do not indicate a quantity limitation, but indicate the existence of at least one. The terms "connected" or "coupled" and the like are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0031] As Figure 1 and Figure 2 shown, the present invention provides a laser device for 3D printing of high-reflection materials, including a sensing submarine cable module 1, a riser monitoring module 2 and a riser laying module 3, wherein,

[0032] The sensing submarine cable module 1 is used to monitor the deformation state and stress state of the marine riser in real time. Among them, several fiber Bragg grating array sensors are integrated at intervals from head to tail in the sensing submarine cable of the sensing submarine cable module 1.

[0033] In this embodiment, as Figure 3 shown, the sensing submarine cable includes a central strengthening core 11, a sensing layer 12 and an outer sheath 13 that are sequentially covered on the outer periphery of the central strengthening core 11 from the inside to the outside. The sensing layer 12 includes a plurality of optical units 121 and a plurality of armored steel wires 122. The plurality of optical units 121 and the plurality of armored steel wires 122 are distributed in a circular array. The optical unit 121 includes any one of a weak grating array 1211 or a multimode optical fiber 1213. A protective layer 1212 is coated on the outer peripheries of the weak grating array 1211 and the multimode optical fiber 1213, and a wrapping tape 1213 is wound around the outer periphery of the protective layer 1212.

[0034] Further, the sensing layer 12 includes a first optical unit 121 and a second optical unit 121. The first optical unit 121 includes a weak grating array 1211, a protective layer 1212 and a wrapping tape 1213 that are sequentially covered on the outer periphery of the weak grating array 1211 from the inside to the outside. The second optical unit 121 includes a multimode optical fiber 1213, a protective layer 1212 and a wrapping tape 1213 that are sequentially covered on the outer periphery of the multimode optical fiber 1213 from the inside to the outside. A second optical unit 121 or an armored steel wire 122 is arranged between any two adjacent first optical units 121. The included angle formed by the connection line between the optical unit 121 and the axis of the central strengthening core 11 and the connection line between the remaining any other optical unit 121 and the axis of the central strengthening core 11 is 120°. The reflectivity of the weak grating array 1211 is 1% - 0.0001%, and the distance between any two adjacent weak grating arrays 1211 is 0.5 m. The reflectivity of the weak grating array 1211 is 1% - 0.0001%, and the distance between any two adjacent weak grating arrays 1211 is 0.5 m. The weak grating array 1211 is distributed on the whole sensing submarine cable. The weak grating array 1211 is used for distributed measurement of the overall strain of the marine riser and for inverse shape of the riser. The multimode optical fiber 1213 is also distributed on the whole sensing submarine cable. The multimode optical fiber 1213 is used to monitor the temperature and vibration signals during the operation of the marine riser, and to monitor the overall state and leakage state of the marine riser.

[0035] In this embodiment, the distributed measurement of the overall strain of the marine riser is realized through the weak grating array 1211 arranged along the entire length of the sensing submarine cable. The multimode optical fibers 1213 evenly distributed on the same sensing submarine cable can monitor temperature and vibration signals in real time, comprehensively detect the working state and leakage situation, and ensure the all-round monitoring of the structural health. The alternating arrangement of the first optical unit 121 and the second optical unit 121, and the connection line between any two adjacent first optical units 121 and the central strengthening core 11 forms an angle of 120°, forming a reasonable spatial layout to ensure the acquisition of monitoring data in multiple directions and at multiple angles, improving the overall monitoring accuracy and reliability. The first and second optical units 121 are both designed with multiple layers of protection including the protective layer 1212 and the wrapping tape 1213, which can effectively resist common mechanical, chemical, and temperature interference factors in the marine environment, thus ensuring the long-term stable and reliable working state of the sensor. The weak grating array 1211 and the multimode optical fibers 1213 are arranged together to realize the simultaneous detection of multiple parameters such as strain, temperature, vibration, and leakage on the same sensing submarine cable, forming a collaborative monitoring system. This information fusion provides richer and more comprehensive data support for the health assessment of the marine riser, facilitating accurate diagnosis and early warning.

[0036] The optical unit 121 is composed of a stainless steel tube, an inner protective layer 1212, and an optical fiber. The optical fiber is in a tightly wrapped form, and then the outer surface of the optical fiber is the protective layer 1212 and the wrapping tape 1213 to ensure that the tightly wrapped optical fiber does not move in the optical unit 121. The outermost layer is the stainless steel tube for support and protection. The extrusion process is used to extrude an insulating sheath on the outer layer of the submarine cable core. The sheath can transfer stress well, transfer the load received by the cable to the grating, and has a high coupling efficiency.

[0037] In an example, the sensing submarine cable contains 300 * 2 * 3 = 1800 sensors, and the data volume of each sensor per second is 8 bytes. The sampling frequency of the demodulator is 100 Hz, and the average value is taken for every 100 groups of sampled data. It is expected to transmit sampled data at 1 Hz per second, and the data volume transmitted per second is approximately 0.0137 MB. The bandwidth required for the camera is 2 M / s. The data volume in a week is about 1200 GB. The data is stored in a combination of local storage and cloud storage, and the device is built-in with a 512G storage module. Since the area number segment where the offshore equipment is located will change and network interruption may occur, the demodulator is set to actively request communication with the cloud server (fixed IP) every 5 seconds to achieve the function of continuous data transmission in case of network interruption.

[0038] The riser monitoring module 2 is used to record and save the wavelengths of the fiber grating array sensors and the inverted marine riser images corresponding to the wavelengths of the fiber grating array sensors of the sensing submarine cable module 1 at different times according to the floating remote communication demodulation unit, so as to adjust the cumulative error of the marine environment and analyze the real-time state of the marine riser.

[0039] In this embodiment, the riser monitoring module 2 includes a floating platform and a riser monitoring cloud platform. Among them, the floating platform includes an equipment cabin, a buoyancy cabin, deck fittings, a bottom bilge plate, a lamp bracket, a comprehensive meteorological station, an azimuth sensor, and a single-point current meter. The floating platform is used to achieve unmanned autonomous monitoring and remote communication transmission at sea. The riser monitoring cloud platform includes a demodulation control module and a remote communication module. The riser monitoring cloud platform is arranged in the equipment cabin. The demodulation control module is used to demodulate, identify, and manage the measurement data of the sensing cable to monitor multiple physical parameters. The remote communication module is configured for signal transceiver. The remote communication module is equipped with protocol conversion (UDP-TCP), WIFI+ communication, and a gateway to meet the dynamic and real-time requirements of riser monitoring and ensure that the equipment can receive stable signals even in remote sea areas.

[0040] The connector of the demodulation control module in the riser monitoring cloud platform adopts a customized 16-core watertight connector to realize the connection of the sensing optical cable inside and outside the instrument cabin of the sea trial platform. A transfer cabin is designed on the floating platform to realize the connection between the sensing optical cable at the construction site and the connector. Through the connector, after the instrument cabin is integrated and tested in the laboratory, it can be quickly docked with the sensing optical cable on site. At the same time, the connector has longitudinal water-blocking ability, which can ensure the safety of the instrument cabin under long-term test conditions.

[0041] Furthermore, the power supply module of the intelligent monitoring system for the sensing cable riser mainly consists of a high-efficiency solar panel, a maintenance-free battery, and a charging control module. The three jointly output 12V voltage to supply power to the buoy equipment, which can ensure the long-term continuous power supply of the buoy power system to the buoy equipment and has overvoltage and overcurrent protection. The power consumption of its main equipment is about 2W for the meteorological equipment, 20W for the demodulator, 12W for the camera, and 12W for the CPE, totaling about 60W.

[0042] The riser laying module 3 is used to couple and lay the sensing cable with the riser using a mother-daughter pipe coupling fixture and place it in the target sea area.

[0043] Please refer to Figure 4, the mother - son pipe coupling fixture includes a semi - circular lower base 31 on one side of the riser, a double - semi - circular groove - type upper part 32 on the cable side of the riser, a semi - circular upper base 33 on one side of the cable, a rubber protection gasket 34 and a cable protection washer 35. The double - semi - circular groove - type upper part 32 on the cable side of the riser has two semi - circular grooves with opposite opening directions, and the diameters of the two semi - circular grooves respectively correspond to the diameters of the sensing cable and the riser. The semi - circular lower base 31 on one side of the riser, the double - semi - circular groove - type upper part 32 on the cable side of the riser, and the semi - circular upper base 33 on one side of the cable are all provided with threaded holes for connection and fixation. The semi - circular lower base 31 on one side of the riser, the double - semi - circular groove - type upper part 32 on the cable side of the riser, and the semi - circular upper base 33 on one side of the cable are sequentially and fixedly connected by bolts to form two cylindrical holes for placing the sensing cable and the riser respectively. The cable protection washer 35 is arranged in the cylindrical hole corresponding to the sensing cable formed by the semi - circular lower base 31 on one side of the riser and the double - semi - circular groove - type upper part 32 on the cable side of the riser, and the rubber protection gasket 34 is arranged in the cylindrical hole corresponding to the ocean riser formed by the double - semi - circular groove - type upper part 32 on the cable side of the riser and the semi - circular upper base 33 on one side of the cable.

[0044] In one example, first place the rubber protection washer in the groove on the semi - circular lower base 31 on one side of the riser. The thickness of the rubber protection washer is adapted to the width in the groove. Pass the cross - section of the riser through the rubber protection washer and place it in the semi - circular groove of the semi - circular lower base 31 on one side of the riser. The installation steps of the double - semi - circular groove - type upper part 32 on the cable side of the riser are similar to the above - mentioned installation method, and there is also a groove for placing the rubber protection washer. There is a groove with a radius the same as the outer diameter of the cable in the double - semi - circular groove - type upper part 32 on the cable side of the riser. A cable protection washer 35 is placed in this groove. The length of this washer is the same as the axial length of the semi - circular upper base 33 on one side of the cable. The cable protection washer 35 wraps around the sensing cable, and the edge of the washer is aligned with the edge of the semi - circular upper base 33 on one side of the cable. Among them, the semi - circular lower base 31 on one side of the riser, the double - semi - circular groove - type upper part 32 on the cable side of the riser, and the semi - circular upper base 33 on one side of the cable are all designed with threaded holes, and the three are connected by suitable bolts to ensure the stability of the connection.

[0045] Please refer to Figure 5 , the sensing cable is fixed on the riser through the fixture to form a mother - son pipe. The riser is connected to the buoy through a catenary. The schematic diagram of the layout in the sea area is shown in Figure 5. For the ocean riser, 2 steel catenaries are used to connect to the hinge at the bottom of the buoy. In the suspension area where the riser is connected to the platform, a bend limiter is used to limit the sway of the head of the riser to prevent the combined load on the cable from being too large and causing its failure. Design a test device according to the deformation monitoring requirements of the ocean riser. One end of the cable accesses the inlet on the buoy deck through the wire - laying groove designed on the buoy and is connected to the connectors and demodulation and communication equipment on the buoy to ensure the benchmark of the initial data of the cable.

[0046] In this embodiment, through the fiber Bragg grating array sensors evenly distributed on the sensing submarine cable, each monitoring point can collect the local bending, torsion, stretching and other states in real time. This distributed monitoring can not only capture local anomalies, but also comprehensively reflect the overall stress and deformation of the entire riser. With the floating remote communication demodulation unit, the system can record the wavelength changes of each sensor in real time, and the wavelength changes directly correspond to the stress or deformation received by the sensor. By comparing and analyzing with the built-in calibration data, the accuracy and stability of data collection are greatly improved, thus realizing the accurate judgment of the state of the marine riser, greatly enhancing the monitoring accuracy and reliability of the submarine cable. At the same time, the riser laying module 3 uses a mother-daughter pipe coupling fixture to tightly couple the sensing submarine cable with the riser, which not only ensures that the sensor can closely fit the surface of the riser during monitoring, reduces data distortion, but also greatly simplifies the operation processes of installation, maintenance and replacement, reduces the construction difficulty and labor cost.

[0047] In this embodiment, as a test monitoring system for simulating the loads on oil and gas pipelines in the ocean, a small buoy is used as the floating platform. Compared with the real oil and gas floating platform, it has lower cost and is more convenient to operate. The buoy is equipped with a demodulation control module and a remote communication module, which can realize data collection, demodulation processing and sending to the cloud. The demodulation module consists of a weak grating demodulator and a DTS. To meet the requirements of the equipment for long-term operation in the marine environment, the original 220V power supply module is adjusted to use 12V DC power supply, and the power consumption is reduced from 25W to 20W; a 4G module is added to provide remote communication capabilities on the basis of the network cable. The weak grating demodulator can demodulate the wavelength change data of the weak grating in the submarine cable, and calculate the strain value at this grating point through theory. The weak grating data is used to combine with the algorithm to invert the shape, and at the same time, the obtained strain data is used to check the strength of the riser; the optical frequency domain reflectometry demodulator is used to demodulate the multimode optical fiber 1213, and distributed temperature sensing (DTS) is used for temperature detection to realize the detection of pipeline breakage and leakage, and provide temperature compensation for strain inversion of the shape. The mother-daughter pipe composed of the riser and the submarine cable fixture can well simulate the real strain situation of the riser under the combined action of ocean currents and other loads in the ocean. Among them, the submarine cable has a small stiffness and can completely deform with the deformation of the riser, which better reflects the shape of the pipeline. The submarine cable is made by stranding and extrusion. The optical unit 121 and the armor wire 122 are stranded at a certain angle and are insulated and protected by the outer sheath 13, ensuring the overall strength and sensing performance of the submarine cable.

[0048] When the riser is subjected to various ocean loads, the riser deforms, and the submarine cable also deforms accordingly through the fixture. The change in the shape of the cable causes the stranded optical unit 121 to deform accordingly. The deformation causes the wavelength of the light reflected by the grating to change. Through the fiber optic grating demodulator in the buoy in cooperation with the wavelength division multiplexing technology and the time division multiplexing technology, the wavelength data of this monitoring process is obtained. The recorded data will be stored locally in the buoy, and the processor combines the above three-dimensional reconstruction algorithm with the wavelength data monitored by the weak grating to obtain the shape of the entire riser. At the same time, the data monitored by the grating array can calculate the strain magnitude and bending moment distribution at the key parts. All the original data and the inverted and stress distribution diagrams after processing will be uploaded to the cloud through communication. During the whole process, the touchdown point will be subjected to a large bending moment and stress, which is a position prone to damage in the riser structure. Using the weak grating array 1211 optical unit 121 to monitor the stress and bending moment distribution values of the key parts can accurately monitor the strain changes generated by the riser under external forces, serving as the structural monitoring of the riser; for the suspended part of the pipe section, under the combined action of loads such as ocean currents and the movement of the upper platform, this pipe section often maintains a large deformation state, and real-time shape monitoring of this part of the pipe section is required. The weak grating optical unit 121 monitors the distribution of bending moment and stress in the length direction of the pipe fitting. Its low reflectivity characteristic can, to a certain extent, avoid excessive reflection interference of optical signals in the complex underwater environment.

[0049] In one example, a sensing submarine cable is used to monitor the stress state and deformation state of a marine riser in real time. At the same time, an ROV (Remotely Operated Vehicle) is used to regularly calibrate the attitude of the riser to ensure the accuracy and reliability of the monitoring. The existing deformation inversion algorithm calculates the existing position information of each point based on the displacement change of the initial state of each point. Due to the complex load conditions in the marine environment and the problem of error accumulation in the existing deformation inversion algorithm based on the Frenet frame, the error of the long-term deformation monitoring results of the submarine cable and the riser is too large and difficult to achieve. Combining image recognition technology, the shape of the corresponding pipeline is regularly calibrated and calibrated by an underwater robot to solve the problem of data distortion caused by cumulative errors in the marine environment, making the monitoring of the deformation state of the submarine cable highly credible. The floating platform includes an equipment cabin, a buoyancy cabin, deck outfittings, a bottom bilge plate and a lamp bracket, and is equipped with devices such as an integrated weather station, an azimuth sensor, a single-point current meter and a ship automatic identification system. At the same time, in combination with the requirements of the fiber optic sensing system, a transfer bin and connectors are installed on the deck to realize the data transmission of the sensing submarine cable - demodulator. At the same time, in combination with the communication conditions in the test sea area and the requirement of large data volume transmission of fiber optic sensing, combined with the marine communication gateway CPE, remote communication of 5G signals in the laying area 35 kilometers offshore is realized, and the change of the wavelength of the fiber Bragg grating array sensor in the sensing submarine cable and the real-time transmission of calibration data are realized. Build a complete circuit, optical path and signal link for the sensing submarine cable - riser intelligent monitoring system. Solve the problems of power supply, demodulation and data transmission of fiber optic sensing. The sensing submarine cable - riser intelligent monitoring cloud platform is configured with a display interface for the buoy and the sensing submarine cable, realizing the real-time display and fault warning functions of the buoy and riser states.

[0050] For the discrete curvature and torsion information measured by the optical unit 121 of the submarine cable, based on the three-dimensional reconstruction algorithm of the Frenet frame, from the measured wavelength data of the optical unit 121 of the submarine cable to the strain data, and combined with temperature compensation to eliminate the influence of temperature on the wavelength, the decoupling calculation of curvature and torsion is realized. Finite element analysis is carried out on the layout spacing and interpolation quantity of the weak gratings inside the optical cable, and the discrete curvature and torsion information is analyzed by using the spline interpolation function. A mathematical model from the strain signal to the pipeline shape is established, calibrated in combination with the coordinates collected by the image, and the three-dimensional shape reconstruction of the submarine cable is carried out to invert the deformation shape of each pipe section of the SCR, so as to realize the accurate monitoring of its shape.

[0051] (1) Three-dimensional inversion algorithm (displacement and relative coordinates) P1

[0052] When the riser deforms, the submarine cable will also deform accordingly through the fixture, resulting in a change in the central wavelength of the grating. An optical fiber grating demodulator can demodulate the real-time wavelength change of the corresponding grating. The wavelength data recorded by the demodulator is uploaded to the cloud server. By using the wavelength data in combination with the strain-temperature sensing principle, multiplexing technology, and temperature compensation technology, the discrete strain value corresponding to the grating position is calculated and stored in the cloud. Based on the basic sensing principle of curvature and torsion and the measured strain value, considering the comprehensive factors of bending and torsion through curvature-torsion decoupling, the discrete curvature and torsion corresponding to each grating measurement point are calculated and solved. Subsequently, through the spline interpolation function, the finite and discrete curvature and torsion information is converted into more continuous curvature and torsion data. This method can divide the curve into multiple segments without the need for piecewise fitting.

[0053] When the curvature and torsion are known, to overcome the inflection point error problem, the curvature and torsion are decomposed orthogonally in space. By numerically solving the mathematical matrix based on the Frenet frame, the principal normal vector, binormal vector, and tangent vector of each point can be obtained. Combining the spatial vector decomposition formula with the spatial coordinates of the initial monitoring point, the arc length parameter expression of the entire space curve can be obtained, and the spatial curve of the sensing optical cable can be acquired. After obtaining the spatial shape of the sensing optical cable, the shape reconstruction of the pipeline can be completed through the spatial position mapping relationship between the sensing optical cable and the pipeline.

[0054] (2)ROV (image) - Output relative position P2

[0055] After calibrating the corresponding pipeline shape based on the ROV underwater robot image recognition and adopting the edge detection algorithm to solve the cumulative error. The ROV underwater robot collects images and performs preprocessing, imports the OpenCV library, and performs grayscale conversion and filtering to improve the image quality.

[0056] Subsequently, the Canny edge detection algorithm is used to identify the pipeline shape. The cv2.GaussianBlur() function is used to perform Gaussian filtering on the image to remove noise, and the cv2.Sobel() function is used to calculate the gradients of the image in the horizontal and vertical directions. Then, non-maximum suppression is performed to exclude the local maximum points in non-edge directions, thereby refining the edges. Finally, each pixel point in the weak edge image is traversed through a double loop, the boundary pixels are excluded, and only the weak edge points connected to the strong edge points are retained, and the processed edge image is displayed.

[0057] Based on the edge image obtained by edge detection, the contour extraction algorithm will connect continuous edge points into a closed curve, and the cv2.findContours function is used for contour extraction. For a circular pipeline, the Hough circle transform is used to select and extract features of target points, mapping the edge points of the circle in the image to a curve in the Hough space to obtain the center coordinates (x, y) of each circle. Based on the pixel coordinate system conversion to physical coordinates, through projective transformation, combined with the internal and external parameters of camera calibration, the pixel coordinates are converted into physical coordinates.

[0058] (3) P1 is calibrated based on P2, and the initial coordinates of P1 are reset.

[0059] By identifying these calibration objects or reference points in the image, comparing their image coordinates with known physical coordinates, and using mathematical methods such as the least squares method to solve the parameters in the coordinate conversion process, the coordinates of the target points are corrected to obtain more accurate physical coordinates. The physical coordinates of the riser collected and output by the ROV are brought into the initial coordinates in the three-dimensional inversion algorithm, and the curve with re-calibrated coordinates is solved, and error analysis is performed with the curve output by the inversion algorithm.

[0060] A high-precision coordinate system calibration method based on feature point mapping for the spatial curve coordinates P1 generated by the three-dimensional inversion algorithm and the relative position coordinates P2 of the pipeline obtained by ROV image recognition. At the initial part of the pipeline, 3 spatial feature points are set to establish an accurate corresponding relationship between P1 and P2; a rigid body transformation model between P1 and P2 is constructed, which includes elements such as translation, rotation, and scale unification. The least squares method is used to fit the feature point pairs, and through the method of singular value decomposition (SVD), the optimal rotation matrix and translation vector can be solved to eliminate the errors in the initial coordinates of P1; finally, the solved rotation matrix is applied to all coordinate points of P2 to make the coordinate axis direction of P consistent with the theoretical coordinate system of P1, and the initial origin of P1 is adjusted with the translation vector to make the inversion coordinates of the feature points in P1 coincide with the image recognition coordinates. By iteratively optimizing the accuracy of feature point matching, it is ensured that the deviation between the two coordinates after calibration is within the range allowed by the project.

[0061] As Figure 6 shown, for the above-mentioned intelligent monitoring system for the sensing submarine cable riser based on optical fiber sensing, the present application also provides a laying method for a floating monitoring system, and the steps are as follows:

[0062] The riser laying module 3 is used to couple and lay the sensing submarine cable with the riser into the target sea area by using a riser coupling fixture. Among them, the riser is a catenary riser (SCR), and several fiber Bragg grating array sensors are integrated at intervals from the head to the tail in the sensing submarine cable.

[0063] Preparation stage: The catenary riser is manufactured in sections and connected by flanges and bolts. After assembly at the dock, one end is connected to the buoy through a steel catenary. The submarine cable and the riser are prepared for installation by clamps according to the above steps, and the cable is connected to the buoy. Use the hoist (A-frame) at the stern of the ship and several winches arranged on the same side as the hoist to lift the buoy and the riser to one side of the ship, and wait to be transported to the target sea area.

[0064] Laying stage: After arriving at the target sea area, the first winch at the bow end slowly pays out the cable. After paying out for a period of time, the adjacent second winch pays out the cable, and the cables are paid out in sequence according to the arrangement order of the winches. During this process, the riser is monitored in real time using the submarine cable. Especially when the riser touches the bottom for the first time, the stress condition of the riser is monitored at all times to prevent the riser from being damaged under the combined action of external loads. When the riser is completely immersed in the sea, the hoist places the buoy on the sea surface, and at the same time, the mooring buoy is also arranged on the sea surface to complete the laying.

[0065] The above is only the preferred embodiment of the present invention, and it is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An intelligent monitoring system for a sensing submarine cable riser based on optical fiber sensing, characterized in that, It includes a sensing submarine cable module (1), a riser monitoring module (2), and a riser laying module (3). Among them, the sensing submarine cable module (1) is used to monitor the deformation state and stress state of the marine riser in real time. Among them, a number of fiber Bragg grating array sensors are integrated at intervals from head to tail in the sensing submarine cable of the sensing submarine cable module (1); the riser monitoring module (2) is used to record and save the wavelengths of the fiber Bragg grating array sensors in the sensing submarine cable module (1) at different times and the inverted marine riser images corresponding to the wavelengths of the fiber Bragg grating array sensors according to the floating remote communication demodulation unit, so as to adjust the cumulative error of the marine environment and analyze the real-time state of the marine riser; the riser laying module (3) is used to couple and lay the sensing submarine cable with the riser by using a mother-daughter pipe coupling clamp and place it in the target sea area.

2. The intelligent monitoring system for sensing submarine cable risers based on optical fiber sensing according to claim 1, wherein The sensing submarine cable includes a central strengthening core (11), a sensing layer (12) and an outer sheath (13) that are sequentially covered on the outer periphery of the central strengthening core (11) from inside to outside. The sensing layer (12) includes a plurality of optical units (121) and a plurality of armored steel wires (122). The plurality of optical units (121) and the plurality of armored steel wires (122) are distributed in a circular array. The optical unit (121) includes any one of a weak grating array (1211) or a multimode optical fiber (1213). Both the weak grating array (1211) and the multimode optical fiber (1213) are coated with a protective layer (1212) on the outer periphery, and a wrapping tape (1213) is wound around the outer periphery of the protective layer (1212).

3. The intelligent monitoring system for the sensing submarine cable riser based on optical fiber sensing according to claim 2, wherein, The sensing layer (12) includes a first optical unit (121) and a second optical unit (121). The first optical unit (121) includes the weak grating array (1211), the protective layer (1212) and the wrapping tape (1213) that are sequentially covered on the outer periphery of the weak grating array (1211) from inside to outside. The second optical unit (121) includes the multimode optical fiber (1213), the protective layer (1212) and the wrapping tape (1213) that are sequentially covered on the outer periphery of the multimode optical fiber (1213) from inside to outside.

4. The intelligent monitoring system for sensing submarine cable risers based on optical fiber sensing according to claim 3, characterized in that, The second optical unit (121) or the armored steel wire (122) is arranged between any two adjacent first optical units (121).

5. The intelligent monitoring system for sensing submarine cable risers based on optical fiber sensing according to claim 4, characterized in that, The included angle formed by the connection line between the optical unit (121) and the axis of the central strengthening core (11) and the connection line between any other optical unit (121) and the axis of the central strengthening core (11) is 120°.

6. The intelligent monitoring system for a sensing submarine cable riser based on optical fiber sensing according to claim 2, wherein The reflectivity of the weak grating array (1211) is 1% - 0.0001%, and the distance between any two adjacent weak grating arrays (1211) is 0.5 m.

7. The intelligent monitoring system for a sensing submarine cable riser based on optical fiber sensing according to claim 2, characterized in that, The central strengthening core (11) is a steel wire, and the armored steel wire (122) and the optical unit (121) are twisted around the outer periphery of the central strengthening core (11) at an angle of 12°.

8. The intelligent monitoring system for a sensing submarine cable riser based on optical fiber sensing according to claim 2, wherein, The weak grating array (1211) is distributed along the entire sensing submarine cable. The weak grating array (1211) is used for distributed measurement of the overall strain of the marine riser and for inverse shape reconstruction of the riser. The multimode optical fiber (1213) is also distributed along the entire sensing submarine cable. The multimode optical fiber (1213) is used to monitor the temperature and vibration signals during the operation of the marine riser, and to monitor the overall state and leakage state of the marine riser.

9. The intelligent monitoring system for sensing submarine cable risers based on optical fiber sensing according to claim 1, characterized in that, The riser monitoring module (2) includes a floating platform and a riser monitoring cloud platform. Among them, the floating platform includes an equipment cabin, a buoyancy cabin, deck fittings, a bottom bilge plate, a lamp bracket, a comprehensive weather station, an azimuth sensor, and a single-point current meter. The floating platform is used to achieve unmanned autonomous monitoring and remote communication transmission at sea. The riser monitoring cloud platform includes a demodulation control module and a remote communication module. The riser monitoring cloud platform is arranged in the equipment cabin. The demodulation control module is used to demodulate, identify, and manage the measurement data of the sensing submarine cable to monitor multiple physical parameters. The remote communication module is configured for signal transceiver.

10. The intelligent monitoring system for sensing submarine cable risers based on optical fiber sensing according to claim 1, characterized in that, The mother-daughter pipe coupling fixture includes a single-side semi-circular lower base (31) of the riser, a double-side semi-circular groove-type upper part (32) on the riser-cable side, a single-side semi-circular upper base (33) of the cable, a rubber protection gasket (34), and a cable protection washer (35). The double-side semi-circular groove-type upper part (32) on the riser-cable side is provided with two semi-circular grooves with opposite opening directions and diameters corresponding to the diameters of the sensing submarine cable and the riser respectively. The single-side semi-circular lower base (31) of the riser, the double-side semi-circular groove-type upper part (32) on the riser-cable side, and the single-side semi-circular upper base (33) of the cable are all provided with threaded holes for connection and fixation. The single-side semi-circular lower base (31) of the riser, the double-side semi-circular groove-type upper part (32) on the riser-cable side, and the single-side semi-circular upper base (33) of the cable are sequentially fixedly connected by bolts to form two cylindrical holes for placing the sensing submarine cable and the riser respectively. The cable protection washer (35) is arranged in the cylindrical hole corresponding to the sensing submarine cable formed by the single-side semi-circular lower base (31) of the riser and the double-side semi-circular groove-type upper part (32) on the riser-cable side. The rubber protection gasket (34) is arranged in the cylindrical hole corresponding to the marine riser formed by the double-side semi-circular groove-type upper part (32) on the riser-cable side and the single-side semi-circular upper base (33) of the cable.

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