Riser real-time joint monitoring system based on distributed optical fiber and ultra-short baseline

Abstract

In the present invention, a location joint monitoring solution based on the state of a distributed optical fiber and based on an ultra-short baseline is used, and the solution consists of a distributed optical fiber monitoring device, an ultra-short baseline positioning device and a health monitoring host computer. The distributed optical fiber monitoring device consists of a distributed optical fiber cable (300), a distributed optical fiber demodulator (421), etc. The ultra-short baseline positioning device consists of an ultra-short baseline array (200), an underwater beacon (100), a signal processing device (411), etc. The health monitoring host computer (431) can perform signal conditioning, digital signal processing and parameter estimation by means of the signal processing device and the distributed optical fiber demodulator and by using acquired data such as key point locations, deformation and postures, and complete space curve reconstruction of an underwater riser by means of a space curve reconstruction algorithm and an existing finite element analysis software platform, thereby realizing visual outputs of an underwater state of a marine riser.

Description

Real-time joint monitoring system for risers based on distributed optical fiber and ultra-short baseline Technical Field

[0001] The present invention belongs to the field of marine engineering technology and is mainly used for health monitoring and positioning of underwater parts of marine facilities. Specifically, it is a real-time joint monitoring system for risers based on distributed optical fiber and ultra-short baseline. Background Art

[0002] Offshore oil risers are a crucial component of the underwater pipeline network in offshore oil and gas development. Exposed to the external influences of the marine environment and typically carrying high-temperature, high-pressure oil and gas, offshore risers are susceptible to damage and destruction. Failure not only causes significant losses to the marine project itself but also leads to severe environmental pollution and secondary disasters. Consequently, research on the health monitoring of offshore platform risers is attracting increasing attention. Due to on-site construction conditions and economic costs, only a limited number of sensors can be deployed on risers to monitor their structural health. Therefore, optimizing the placement of sensors at optimal locations on the risers and obtaining near-realistic information from them is a crucial issue for optimizing offshore platform riser sensor placement. Furthermore, acquiring position and inclination data at key points on the riser is crucial for reflecting the true health of the riser.

[0003] Marine risers are flexible structures with large geometric deformations. Their underwater posture is uncertain under complex conditions, such as pipelaying operations, due to complex factors such as the positional fluctuations of the upper platform, large-scale vortex-induced motion, and seabed contact. Real-time, effective monitoring methods to understand the geometric shape of marine risers and conduct timely condition assessments are crucial for ensuring the safe operation of floating platforms. Currently, underwater posture monitoring of marine risers relies primarily on inclinometers using self-contained data loggers (loggers). This monitoring method is susceptible to interference from local vibrations in the sensor deployment area, raising concerns about the accuracy and real-time nature of the data. Summary of the Invention

[0004] To address the shortcomings and defects of the aforementioned existing technologies, the inventors, through research and development, have designed a combined distributed fiber-optic condition monitoring solution and ultra-short baseline position monitoring solution. This solution utilizes multiple fixed fiber-optic sensors installed on the riser of a semi-submersible platform to monitor the riser's deformation, displacement, and sway, particularly during typhoons. Furthermore, underwater beacons are installed at key points on the riser, and an ultra-short baseline sonar array is installed beneath the platform. This ultra-short baseline sonar monitors the riser's underwater displacement and sway at these key points. This data fusion process provides a true reflection of the riser's underwater condition.

[0005] Specifically, the present invention is achieved as follows:

[0006] In one aspect of the present invention, a real-time joint monitoring system for risers based on distributed optical fiber and ultra-short baseline is provided, comprising:

[0007] Distributed fiber optic cables are installed in pairs at multiple points along the riser surface, covering the entire deployment area. They are used to detect and transmit measured fiber strain information to a distributed fiber optic interrogator. An ultrashort baseline array, installed on the horizontal beam of the riser platform, transmits interrogation signals at regular intervals. Using the ultrashort baseline positioning principle and underwater acoustic response, it calculates the position of the beacon relative to the array center coordinates, enabling real-time monitoring of key point positions and attitude information.

[0008] Underwater beacons are installed at key points on the riser to transmit underwater positioning acoustic signals. Signal processing equipment is installed on the dry end of the riser platform and connected to the ultra-short baseline array. It can receive, transmit and process detection signal data, perform signal conditioning, digital signal processing and parameter estimation, and then send it to the health monitoring main computer;

[0009] Distributed fiber demodulator, installed on the dry end of the riser platform, connected to the distributed fiber optic cable, is used to demodulate the received real-time fiber optic signal and transmit it to the health monitoring main computer.

[0010] The health monitoring main computer is installed on the dry end of the riser platform and is connected to the signal processing equipment and distributed fiber optic demodulator. It is used to complete the positioning and attitude telemetry of key points based on the ultra-short baseline positioning principle, obtain the curvature data through polynomial interpolation processing and calculation, and obtain the geometric coordinates of the riser through the spatial curve reconstruction algorithm.

[0011] Furthermore, the distributed optical fiber cable arranges another pair of optical fibers at 90° intervals along the axial direction of the riser, and the two pairs of optical fibers obtain two spatial orthogonal curvatures, and the required curvature is obtained by vector superposition calculation.

[0012] Furthermore, the health monitoring main computer can realize the sensing of temperature and strain on the optical fiber based on the fiber optic sensing technology of the Brillouin effect, taking advantage of the fact that the offset of the Brillouin frequency is related to the axial strain and temperature change of the optical fiber, and can analyze the strain value of the corresponding position of the optical fiber based on the Brillouin frequency shift of the optical fiber.

[0013] Another aspect of the present invention provides a method for real-time joint monitoring of risers based on distributed optical fiber and ultra-short baseline, which comprises the following steps:

[0014] Step S1, obtain the real-time riser monitoring data fed back by the distributed optical fiber, and demodulate to obtain the strain data of the monitoring point on the riser; the demodulation includes: based on the relationship formula Δf between Brillouin scattering frequency shift, strain and temperature B =C T ΔT+Cε Δε is used to analyze the strain value of the optical fiber, where Δf B , ΔT, Δε are the changes of fiber Brillouin frequency shift and temperature and strain respectively, C T and C ε is the temperature and strain sensitivity coefficient of the distributed optical fiber. The bare optical fiber is calibrated before laying to obtain C T and C ε ;

[0015] Step S2: The ultrashort baseline array periodically transmits an inquiry signal and receives a response signal transmitted by the underwater beacon, performing signal conditioning, digital signal processing, and parameter estimation;

[0016] Step S3: Obtain optical fiber strain information on the riser surface and key point position and posture information measured by an ultra-short baseline positioning device;

[0017] Step S4: reconstruct the spatial curve. Two pairs of optical fibers arranged 90° apart along the axial direction of the riser are used to obtain two spatial orthogonal curvatures. The required curvature data is obtained by vector superposition calculation. The geometric coordinates of the riser are obtained by the spatial curve reconstruction algorithm.

[0018] Furthermore, step S2 further includes: using the ultra-short baseline array to calculate the position of the beacon relative to the center coordinates of the array, and monitoring the horizontal offset data of key points in real time; and simultaneously performing real-time telemetry on the attitude of the beacon rigidly connected to the riser, thereby obtaining the inclination angle of the marine riser in real time.

[0019] Among them, the ultra-short baseline sonar positioning equation is: H=[R 2 -x 2 -y 2 ] 1 / 2

[0020] Where:

[0021] x, y - the coordinate position of the underwater target relative to the ultra-short baseline array;

[0022] H - the depth of the located target underwater;

[0023] R - the distance between the ultra-short baseline array and the beacon;

[0024] D - the length of the array baseline;

[0025] c - average underwater sound speed;

[0026] τx, τy are the time differences between the two receiving units in the X and Y directions, respectively. The attitude sensor provides real-time attitude data of the array, which is used to correct the positioning data.

[0027] Furthermore, in step S4, the space curve reconstruction algorithm includes the following steps:

[0028] Step S5, reading the distributed strain data and key point position information and posture, segmenting and differentiating along the length of the riser, and calculating the spatial curvature of each micro-segment through polynomial interpolation processing;

[0029] Step S6: construct the micro-segment space coordinate system and the osculating plane, and calculate the end point coordinates based on the curvature and the starting point coordinates;

[0030] Step S7: transform the coordinate system to the next micro-segment motion coordinate system, repeat step S6, and output the coordinates of the end point of each micro-segment;

[0031] Step S8: Based on the data interface of the finite element analysis software platform and the fitting curve, a visual model is output.

[0032] The working principle of this invention is as follows: On one hand, distributed fiber optic sensors are installed at multiple points on the platform riser to monitor its deformation, displacement, and sway in real time, particularly during typhoons. First, distributed fiber optic condition monitoring is implemented: fiber optic sensors are installed at multiple points on the riser, utilizing the principle of Brillouin scattering to monitor its deformation, displacement, and sway in real time. Brillouin scattering is the process of generating scattered light waves when light propagates through an optical fiber and encounters temperature or strain changes. By measuring the frequency offset of these scattered light waves, the temperature and strain changes at the corresponding optical fiber location can be determined, thereby monitoring the riser's condition.

[0033] Another aspect of the present invention involves installing underwater beacons at key points and an ultra-short baseline sonar array beneath the platform. This ultra-short baseline sonar provides real-time monitoring of the underwater displacement and attitude sway of key points on the riser. Ultra-short baseline-based position monitoring involves installing underwater beacons at key points on the riser and an ultra-short baseline sonar array beneath the riser platform. The ultra-short baseline array periodically transmits interrogation signals, to which the beacons respond. By calculating the time difference between the response signals received by the ultra-short baseline array, the position of the beacon (the key point on the riser) relative to the baseline can be calculated, thereby enabling real-time monitoring of the underwater displacement and attitude sway of the riser.

[0034] Finally, the data obtained from these two monitoring methods are fused to more accurately determine the real-time status of the riser. The specific process involves demodulating and interpolating the strain values ​​obtained by the fiber optic sensor to obtain the spatial curvature of the riser. Ultra-short baseline positioning is then used to obtain the position information of key points on the riser, and a spatial curve reconstruction algorithm is used to obtain the geometric coordinates of the riser. Finally, data fitting is performed using a finite element analysis software platform to output a morphological visualization model of the riser, enabling real-time monitoring and assessment of the riser's status.

[0035] Processing equipment is installed at the dry-end monitoring center. It monitors key locations, such as the underwater riser and umbilical cable connection points, 24 hours a day (primarily monitoring attitude, displacement, sway, and deformation). Using this acquired position, deformation, and attitude data, and leveraging a finite element software platform, the curves of the underwater riser are reconstructed, allowing for visualization of the riser's shape.

[0036] The above technical solution provides real-time and effective monitoring of the geometric shape of marine risers and timely status assessment. This invention can achieve real-time health monitoring of the underwater portion of marine facilities and the positioning of key points. It also enables visual output of the actual status of the underwater risers, allowing for timely status assessment, fault diagnosis, and damage identification, which is of great significance for ensuring the safe operation of floating platforms. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a schematic diagram of the structure of a real-time joint monitoring system for risers based on distributed optical fiber and ultra-short baseline according to the present invention;

[0038] FIG2 is a schematic diagram of the composition of a real-time joint monitoring system for risers based on distributed optical fiber and ultra-short baseline according to the present invention;

[0039] FIG3 is a flow chart of curve reconstruction and visualization output;

[0040] The invention comprises: an underwater beacon (100), an ultrashort baseline array (200), a distributed optical fiber (300), an ultrashort baseline signal processing device (411), a distributed optical fiber demodulator (421), and measurement data sent to a health monitoring main computer (431). DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0042] Example 1: A real-time joint monitoring system for risers based on distributed optical fiber and ultra-short baseline, comprising distributed optical fiber monitoring equipment, ultra-short baseline positioning equipment, and a health monitoring host computer.

[0043] The schematic diagram of the platform riser monitoring is shown in Figure 1. The components installed underwater are:

[0044] 1) Underwater beacons 100 installed at key points on the riser;

[0045] 2 Ultra-short baseline array 200 installed on the horizontal beam of the platform;

[0046] 3. Distributed optical fiber installed on the riser of the monitoring platform. The above-water equipment is the riser monitoring dry end equipment placed in the platform workshop.

[0047] The system consists of the underwater beacon 100, the ultrashort baseline array (200), and the ultrashort baseline signal processing device 411 in the dry-end equipment, which constitutes the ultrashort baseline positioning equipment to measure the position and attitude of the key nodes of the riser. The distributed optical fiber 300 laid on the riser to be tested and the distributed optical fiber demodulator 421 in the dry-end equipment constitute the distributed optical fiber monitoring equipment to measure the riser deformation. The measurement data of the above two sets of equipment are sent to the health monitoring main computer 431 for data fusion, spatial curve reconstruction and other processing, so as to realize the visualization output of the riser status.

[0048] The distributed optical fiber 300 is laid on the surface of the platform riser that needs to be monitored. After the equipment is powered on, it monitors the strain of the riser in real time and transmits the monitored optical fiber signal to the health monitoring workshop in real time. The distributed optical fiber demodulator 421 demodulates the signal to obtain the strain data of the monitoring point on the riser.

[0049] At the same time, the ultra-short baseline positioning equipment in the health monitoring workshop transmits an inquiry signal at a certain period. After receiving the inquiry signal, the beacon 100 installed at the key point of the riser transmits a corresponding response signal. The response signal is received by the ultra-short baseline array 200 and sent to the signal processing equipment 411 in the health monitoring workshop via a cable for signal conditioning, digital signal processing and parameter estimation, and then sent to the health monitoring main computer 431. According to the ultra-short baseline positioning principle, the positioning of the key point and attitude telemetry are completed.

[0050] The health monitoring main computer 431 first obtains the optical fiber strain information on the riser surface and the key point position and posture information measured by the ultra-short baseline positioning device, then calculates and processes the curvature data through polynomial interpolation, obtains the geometric coordinates of the riser through the spatial curve reconstruction algorithm, and finally realizes the visualization output of the actual status of the underwater riser through the finite element software platform.

[0051] Distributed fiber optic sensing utilizes Brillouin effect-based fiber optic sensing technology, which offers the unique advantages of long-distance, high-precision, continuous distribution, and multi-parameter sensing. The Brillouin frequency offset is related to the axial strain and temperature changes experienced by the fiber, and this relationship is exploited to enable temperature and strain sensing on the fiber.

[0052] The relationship between Brillouin scattering frequency shift and strain and temperature is as follows: Δf B =C T ΔT+C ε Δε (1)

[0053] Where Δf B , ΔT, Δε are the changes of fiber Brillouin frequency shift and temperature and strain respectively, C T and C ε is the temperature and strain sensitivity coefficient of the distributed optical fiber. The bare optical fiber is calibrated before laying to obtain C T and C ε When any portion of a fiber experiences strain or temperature changes, the Brillouin frequency shift at that location will also change. Through professional calibration and analysis of measurement results, the optical fiber can directly become a sensor for measurement. Using an optical time domain analyzer, the Brillouin frequency shift of any portion of the fiber can be measured and the strain value at any location on the fiber can be analyzed with high measurement accuracy.

[0054] The ultra-short baseline positioning device is composed of an underwater beacon 100, an ultra-short baseline array 200, a signal processing device 411, etc.

[0055] The ultra-short baseline positioning equipment uses the ultra-short baseline positioning principle to calculate the position of the beacon relative to the center coordinates of the array in the form of underwater acoustic response, and monitors the horizontal offset data of key points in real time; at the same time, it performs real-time telemetry on the posture of the beacon rigidly connected to the riser, thereby obtaining the inclination angle of the marine riser in real time.

[0056] The ultra-short baseline sonar positioning equation is: H=[R 2 -x 2 -y 2 ] 1 / 2 (4)

[0057] Where:

[0058] x, y - the coordinate position of the underwater target relative to the ultra-short baseline array;

[0059] H - the depth of the located target underwater;

[0060] R - the distance between the ultra-short baseline array and the beacon;

[0061] D - the length of the array baseline;

[0062] c - average underwater sound speed;

[0063] τx, τy are the time differences between the two receiving units receiving signals in the X and Y directions respectively.

[0064] The attitude sensor provides real-time attitude data of the array to correct the positioning data.

[0065] The target depth can be measured by using the above formula (4) or by using the double-pulse interval telemetry method.

[0066] The spatial curve reconstruction algorithm is based on the principles of differential geometry, which states that the geometric shape of a curve can be uniquely determined by its curvature. This curvature is calculated based on the strain information acquired by the sensors. To account for three-dimensional spatial curvature, another pair of optical fibers can be placed 90° apart along the riser axis. These two pairs of optical fibers generate two orthogonal spatial curvatures, which are then calculated by vector superposition to obtain the desired curvature. Distributed optical fiber strain sensors can cover the entire deployment area, providing the curve reconstruction algorithm with comprehensive measured data to reduce cumulative errors.

[0067] The riser attitude online monitoring system first obtains the optical fiber strain information, key point positions and attitude information of the riser surface, calculates and processes the curvature data through polynomial interpolation, obtains the geometric coordinates of the riser through a spatial curve reconstruction algorithm, and finally realizes the visualization output of the actual status of the underwater riser through a finite element software platform.

[0068] The distributed optical fiber 300 is laid on the surface of the platform riser that needs to be monitored. After the equipment is powered on, it monitors the strain of the riser in real time and transmits the monitored optical fiber signal to the health monitoring workshop in real time. The distributed optical fiber demodulator 421 demodulates the signal to obtain the strain data of the monitoring point on the riser.

[0069] At the same time, the ultra-short baseline positioning equipment in the health monitoring workshop transmits an inquiry signal at a certain period. After receiving the inquiry signal, the beacon 100 installed at the key point of the riser transmits a corresponding response signal. The response signal is received by the ultra-short baseline array 200 and sent to the signal processing equipment 411 in the health monitoring workshop via a cable for signal conditioning, digital signal processing and parameter estimation, and then sent to the health monitoring main computer 431. According to the ultra-short baseline positioning principle, the positioning of the key point and attitude telemetry are completed.

[0070] The health monitoring main computer 431 first obtains the optical fiber strain information on the riser surface and the key point position and posture information measured by the ultra-short baseline positioning device. It then performs quadratic function fitting on the monitoring point data to obtain the curvature data of any point in the optical fiber deployment area (such as Formula 7 and Formula 8). The geometric coordinates of the riser are obtained through a spatial curve reconstruction algorithm. Finally, the actual status of the underwater riser is visualized through a finite element software platform.

[0071] The geometric shape of the curve can be uniquely determined by the curvature, which is calculated based on the strain information obtained by the sensor. If the outer radius of the bending tube is R, the axial normal strain of the arc on the outer wall of a micro segment is ε1, and the arc angle is θ, then the curvature radius ρ of the micro segment (the curvature is expressed as ρ -1 ), and the relationship with the axial normal strain can be based on the plane section assumption: that is, no axial tension and compression occurs in the neutral plane before and after bending, and its length is θρ. If axial tension occurs on the outside of the tube wall, its length is θ(ρ+R). When the influence of optical fiber tensile strain is not considered, according to the definition of engineering strain:

[0072] When considering the influence of optical fiber tensile strain, the measured data ε1 and ε2 of two axially symmetric optical fibers are used, and the subtraction of the two is also obtained:

[0073] From equations (5) and (6), we can see that the strain information on the riser surface can be measured to obtain the curvature radius ρ of the micro segment. The curvature of multiple points on the riser surface can be obtained by The curvature change curve ρ is fitted by the quadratic function -1 =ms 2 +ns+l (7)

[0074] ρ -1 Indicates curvature, s is the arc length from the corresponding detection point to the starting point, m, n, l are fitting coefficients, and the curvature of three consecutive detection points is known. The arc lengths from the corresponding detection point to the starting point are s1, s2, and s3 (the coordinates of the starting point are measured by the ultra-short baseline positioning system), then

[0075] After calculating the fitting coefficient, the curvature at any point in space can be obtained. Similarly, based on the curvature data of multiple positions measured by distributed optical fiber, the position and curvature changes of the entire riser monitoring area can be obtained by sliding fitting. Finally, the actual status of the underwater riser can be visualized through the finite element software platform.

[0076] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A real-time joint monitoring system for risers based on distributed optical fiber and ultra-short baseline, characterized by include: Distributed optical fiber cables are installed in pairs at multiple points along the surface of the riser, covering the entire deployment area, and are used to detect and transmit the measured optical fiber strain information to the distributed optical fiber demodulator; the ultra-short baseline array is installed on the horizontal beam of the riser platform, and can emit interrogation signals at a certain period. Using the ultra-short baseline positioning principle, the position of the beacon relative to the center coordinates of the array is calculated in the form of underwater acoustic response, and the position and attitude information of key points are monitored in real time; The underwater beacon is installed at the key point of the riser and is used to transmit underwater positioning sound signals. The signal processing equipment is installed on the dry end of the riser platform and connected to the ultra-short baseline array. It can receive, transmit and process the detection signal data, perform signal conditioning, digital signal processing and parameter estimation, and then send it to the health monitoring main computer; A distributed optical fiber demodulator is installed on the dry end of the riser platform and connected to the distributed optical fiber cable to demodulate the received real-time optical fiber signal and transmit it to the health monitoring main computer; The health monitoring main computer is installed on the dry end of the riser platform and connected to the signal processing equipment and distributed fiber optic demodulator. It is used to complete the positioning and attitude telemetry of key points based on the ultra-short baseline positioning principle, obtain the curvature data through quadratic function fitting and calculation, and obtain the geometric coordinates of the riser through the space curve reconstruction algorithm.

2. The real-time joint monitoring system for risers based on distributed optical fiber and ultra-short baseline according to claim 1 is characterized in that: The distributed optical fiber cable arranges another pair of optical fibers at intervals of 90 degrees along the axial direction of the riser, and the two pairs of optical fibers obtain two spatial orthogonal curvatures, and the required curvature is obtained by vector superposition calculation.

3. The real-time joint monitoring system for risers based on distributed optical fiber and ultra-short baseline according to claim 1 is characterized in that: The health monitoring main computer can use the fiber optic sensing technology based on the Brillouin effect. It uses the fact that the offset of the Brillouin frequency is related to the axial strain and temperature change of the optical fiber to realize the sensing of temperature and strain on the optical fiber. It can also analyze the strain value of the corresponding position of the optical fiber based on the Brillouin frequency shift of the optical fiber.

4. A method for real-time joint monitoring of risers based on distributed optical fiber and ultra-short baseline, characterized in that: The real-time joint monitoring system for risers according to any one of claims 1 to 3 is implemented, comprising the following steps: Step S1, obtaining real-time riser monitoring data fed back by distributed optical fiber, and obtaining strain data of monitoring points on the riser after demodulation; the demodulation includes: based on the relationship formula Δf between Brillouin scatter frequency shift and strain and temperature B =C T ΔT+C ε Δε is the strain value of the optical fiber, where Δf B , ΔT, Δε are the changes of fiber Brillouin frequency shift and temperature and strain respectively, C T and C ε is the temperature and strain sensitivity coefficient of the distributed optical fiber. The bare optical fiber is calibrated before laying to obtain C T and C ε ; Step S2, the ultra-short baseline array periodically transmits an inquiry signal, receives a response signal transmitted by the underwater beacon, and performs signal conditioning, digital signal processing and parameter estimation; Step S3, obtaining optical fiber strain information on the riser surface and key point position and posture information measured by an ultra-short baseline positioning device; Step S4, reconstructing the space curve, obtaining two spatial orthogonal curvatures based on two pairs of optical fibers arranged 90° apart along the axial direction of the riser, obtaining the required curvature data through superposition calculation, and obtaining the geometric coordinates of the riser through the space curve reconstruction algorithm.

5. The method for real-time joint monitoring of risers based on distributed optical fiber and ultra-short baseline according to claim 4 is characterized in that: The step S2 also includes: using the ultra-short baseline array to calculate the position of the beacon relative to the center coordinates of the base array, and monitoring the horizontal offset data of the key points in real time; and simultaneously performing real-time telemetry on the attitude of the beacon rigidly connected to the riser, so as to obtain the inclination angle of the marine riser in real time. Among them, the ultra-short baseline sonar positioning equation is: H=[R 2 -x 2 -y 2 ] 1 / 2 Where: x, y - the coordinate position of the underwater target relative to the ultra-short baseline array; H - the depth of the located target underwater; R – the distance between the ultra-short baseline array and the beacon; D - the length of the array baseline; c – average underwater sound speed; τx, τy - the time difference between the two receiving units receiving signals in the X and Y directions respectively. The attitude sensor provides the real-time attitude data of the array to correct the positioning data.

6. The method for real-time joint monitoring of risers based on distributed optical fiber and ultra-short baseline according to claim 5 is characterized in that: In step S4, the space curve reconstruction algorithm includes the following steps: Step S5, reading the distributed strain data and the position information and posture of the key points, segmenting and interpolating based on the length direction of the riser, and calculating the spatial curvature of each micro-segment through polynomial interpolation processing; Step S6, constructing a micro-segment space coordinate system and an osculating plane, and calculating the end point coordinates from the curvature and the starting point coordinates; Step S7, transform the coordinate system to the next micro-segment motion coordinate system, repeat step S6, and output the coordinates of the end point of each micro-segment; Step S8: output a visualization model based on the finite element analysis software platform data interface and curve fitting.

7. The method for real-time joint monitoring of risers based on distributed optical fiber and ultra-short baseline according to claim 5, characterized in that: The steps of fitting a quadratic function through monitoring point data to obtain curvature data of any point in the optical fiber deployment area include: According to the definition of engineering strain: When considering the influence of optical fiber tensile strain, the measured data ε1 and ε2 of two axially symmetrical optical fibers are used, and the subtraction of the two is also obtained: It can be seen from equation (5) or (6) that the strain information on the riser surface can be measured to obtain the curvature radius ρ of the micro segment. The curvature of multiple points on the riser surface can be obtained by Fitting the curvature change curve through quadratic function ρ -1 =ms 2 +ns+l ρ -1 represents the curvature, s is the arc length from the corresponding detection point to the starting point, m, n, l are fitting coefficients, and the curvature of three consecutive detection points is known. The arc lengths from the corresponding detection point to the starting point are s1, s2, and s3 (the coordinates of the starting point are measured by the ultra-short baseline positioning system), then After calculating the fitting coefficient, the curvature at any point in space can be obtained. Recursively, the position and curvature changes of the entire riser monitoring area can be obtained by sliding fitting based on the curvature data of multiple positions measured by distributed optical fibers. Finally, the actual status of the underwater riser can be visualized through the finite element software platform.

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