A displacement inversion method for deepwater riser structures

Abstract

The present invention provides a method for inverting the displacement of a deepwater riser structure, which collects and measures sparse discrete curvature data in real time; obtains continuous curvature data through an interpolation method; draws a continuous curve based on the continuous curvature data and its position information, divides the continuous curve in real time to obtain the length of the continuous curve microelement segment; obtains the relative position information of the middle of the riser and the surface platform, recursively obtains the lower half of the continuous curve equation from the bottom to the middle, and recursively obtains the upper half of the continuous curve equation from the surface to the middle, integrates the upper half and the lower half to obtain the entire continuous curve equation, and calculates the inverted displacement data corresponding to the outer position of the deepwater riser structure at any position. The present invention only relies on real-time monitoring of curvature data to perform deepwater riser structure displacement inversion, and has strong adaptability; and the proposed end error elimination strategy can solve the problem of the end cumulative error amplification effect in the recursive process of the traditional space curve method.

Description

Technical Field

[0001] The invention belongs to the technical field of deepwater riser structure health monitoring based on computer data processing, and in particular relates to a deepwater riser structure displacement inversion method. Background Art

[0002] Deepwater risers are key structures that connect offshore platforms to seabed production systems and are widely used in offshore oil and gas production and other fields. The marine environment is highly complex and uncertain. Risers are subject to multiple loads such as waves, currents, tides, earthquakes, etc. They also face problems such as seawater corrosion and marine biological attachment, which cause complex displacements and deformations in the risers, posing a huge challenge to their structural safety. Once damaged, it will cause huge economic losses and serious environmental pollution. In order to better understand the mechanical behavior of the riser under actual working conditions, an effective displacement inversion method is needed to obtain its true displacement state, which is crucial to ensuring the safety and efficiency of marine resource development operations.

[0003] Traditional structural safety assessment methods based on theoretical calculations and empirical formulas have great limitations and are difficult to accurately consider various complex factors and accidental loads in the actual marine environment. Through displacement inversion, the actual displacement of the riser can be obtained in real time, providing a more accurate and reliable basis for the safety assessment of the structure, so as to timely discover potential safety hazards and take effective maintenance and repair measures. In recent years, with the continuous advancement of sensor technology, data acquisition and transmission technology, a large amount of monitoring data of deepwater risers, such as strain, acceleration, inclination, etc., can be obtained, providing a data basis for the research of displacement inversion methods, making it possible to invert the structural displacement of the riser through the analysis and processing of monitoring data.

[0004] Accurate displacement inversion can grasp the actual deformation of deepwater risers under various loads in real time, timely discover abnormal displacement and potential damage of the structure, provide key information for safety warning and risk assessment of the structure, help prevent catastrophic accidents such as riser fracture and leakage, and ensure the safe operation of marine engineering facilities. At the same time, through in-depth analysis of displacement inversion results, the mechanical properties and response characteristics of deepwater risers in actual use can be grasped, providing a basis for the optimal design and efficient maintenance of risers.

[0005] Due to the multiple limitations of measurement methods, test difficulty and economic cost, it is very difficult to directly measure all the vibration information of deepwater riser structures. In model tests and engineering applications, limited sensors are usually arranged at typical locations to obtain information such as structural strain, acceleration, inclination, etc., and a certain method is used to invert the vibration displacement at any position of the structure to achieve its spatial configuration monitoring and visual expression. Existing displacement inversion methods mainly include visual detection method, mode superposition method, fiber optic shape sensing method and spatial curve reconstruction method. Structural morphology detection and inversion based on visual detection method is a relatively mature technology, which is widely used in skin / wing and civil structure displacement reconstruction. It requires the collection of a large amount of visual data, and the data analysis algorithm is relatively complex. It is not adaptable in the marine field. The modal superposition method inverts the structural displacement in the form of linear superposition of different modal vibration modes. Its main application scenario is to invert the vortex-induced vibration displacement of deepwater riser structures. It is widely used in model test scenarios, but it needs to calculate each order vibration mode, requiring the number of measurement points to exceed the number of vibration modes, and the modal calculation process is cumbersome. Fiber optic shape sensing is the latest research direction in the field of fiber optic sensing in recent years. It uses a combination of several optical fibers with a specific spatial arrangement to measure the position and shape of the optical fiber or the object connected to it. It is mainly used in medical minimally invasive interventional surgery catheter position tracking and other occasions. It is still difficult to achieve high-precision displacement inversion for long-distance structural displacement monitoring of kilometers such as risers / submarine cables. There is currently no directly available series of products. The spatial curve reconstruction method converts the measured strain data into curvature information based on the linear relationship between strain and curvature under the assumption of a flat section, obtains the curvature of each micro-segment through discrete point curvature interpolation, integrates segment by segment and recursively obtains the position coordinates of the endpoints of each micro-segment, and finally fits to form a curve to achieve the inversion of structural displacement or deformation. Based on the point-by-point recursion, there is an error accumulation effect and error amplification effect, which leads to the largest error at the farthest end of the reconstructed curve.

[0006] Invention patent CN202410549330.X discloses a recursive configuration inversion method for non-metallic flexible mixed pipelines. A neural network model is established with the relative positions of different mining ships and mining vehicles and the typical position inclinations of pipe sections as training sets. The model relies on certain deep-sea mining riser structural properties and dimensional parameters. However, there are differences between the deepwater riser structure under actual sea conditions and the data in the design stage. There are certain model and dimensional errors when the pre-trained model is extended to the actual riser structure. At the same time, calculations with marine engineering software will introduce inevitable simplified simulation errors. Therefore, it is not very adaptable when applied under actual sea conditions. Summary of the invention

[0007] In view of the above problems, the present invention provides a deepwater riser structure displacement inversion method, which includes the following process:

[0008] S1, based on n curvature sensors installed at several measuring points with large curvature of deepwater riser structure, real-time collection and measurement of sparse discrete curvature data;

[0009] S2, obtain m continuous curvature data by interpolation method;

[0010] S3, based on the m continuous curvature data and their position information, a continuous curve is drawn, and the continuous curve is divided in real time to obtain m+1 continuous curve micro-element segment lengths. ;

[0011] S4, obtain the relative position information of the middle part of the riser and the surface platform, recursively obtain the lower half continuous curve equation from the bottom to the middle, and recursively obtain the upper half continuous curve equation from the surface to the middle, integrate the upper and lower halves to obtain the entire continuous curve equation, and calculate the coordinates of any position Where ,in That is, the inversion displacement data corresponding to the outer position of the deepwater riser structure.

[0012] Preferably, the S2 obtains m continuous curvature data by interpolation method as follows:

[0013] Based on the measured discrete curvature data The curvature interpolation of n measured discrete curvature data is performed by the piecewise cubic Hermite interpolation method, and m continuous curvature data after interpolation are obtained. ,in For the interpolation curvature data; the number of interpolation curvatures m=the number of measuring point positions n×2+1.

[0014] Preferably, the specific process of S4 is:

[0015] S41, obtaining relative position information of the middle part of the riser and the surface platform;

[0016] According to the deepwater riser bottom position beacon information ( ), the middle position beacon information of the riser ( ) and GPS information of surface and offshore platform location ( ), with the bottom of the deepwater riser as the coordinate origin ( ), calculate the relative position of the middle part of the riser ( ) and the relative position of the surface platform ( ), where the relative positions satisfy the relationship ， ， ， ;

[0017] S42, recursively obtain the continuous curve equation of the lower half from the bottom to the middle;

[0018] The coordinate system is established with the bottom end of the riser as the origin, and the tangent direction of the starting point is Axis, the perpendicular line from the starting point is Axis; the length of the infinitesimal arc between two points of a continuous curve is , For the interpolation points, and Respectively The center and curvature data or curvature radius of the segment micro-circular arc, for Angle with the horizontal line;

[0019] The center of the first infinitesimal segment ( ) coordinate ( ), in the rectangular coordinate system, the arc segment The equation of the continuous curve is:

[0020] ;

[0021] From this, the first interpolation point can be calculated coordinate for:

[0022] ;

[0023] Since the infinitesimal arcs are tangent to each other, the second infinitesimal arc Center coordinate and Center and tangent point On the same straight line, we can obtain:

[0024] ;

[0025] Combining the above two equations, we can get the center of the second infinitesimal arc. coordinate( )for:

[0026] ;

[0027] Thus, the second infinitesimal arc can be obtained The equation of the continuous curve is:

[0028] ;

[0029] Based on the above process, we can obtain The center of the micro-circle coordinate , curvature data , Angle Pass Interpolated curvature data , No. Micro-arc The equation of the continuous curve is:

[0030] ;

[0031] in: ;

[0032] And so on until , get the coordinates of the middle point of the continuous curve ( ), where the coordinates of the middle point are:

[0033] ;

[0034] ;

[0035] S43, taking the position of the surface platform as the starting point and based on the calculation process of S42, obtain the Micro-circular arc The equation of the continuous curve is:

[0036] ;

[0037] And so on until , get the coordinates of the middle point of the continuous curve in the recursive process from top to bottom ( );

[0038] S44, integrating the upper half and the lower half to obtain the equation of the entire continuous curve;

[0039] According to the continuous curve equation of the upper half and the continuous curve equation of the lower half, the continuous curve equation of the whole section is obtained; according to the continuous curve equation, any position can be calculated Where ,in That is, the inversion displacement data corresponding to the outer position of the deepwater riser structure.

[0040] Preferably, the method further includes performing displacement inversion correction according to the middle position of the riser, specifically:

[0041] Compare the relative errors between the middle position obtained from the top-down and bottom-up deduction processes and the actual middle position of the riser. If the relative error is greater than the set threshold, it is necessary to expand the number of interpolation points of the discrete curvature data according to the interpolation method and reduce the spacing between the interpolated curvature data, thereby reducing the relative error of the inverted middle position of the riser.

[0042] Until the relative errors of the middle position obtained in the deduction process from top to bottom and from bottom to top do not exceed the set threshold, the continuous curve equations of the upper and lower halves are integrated into the continuous curve equation of the entire section, and a continuous smooth curve is drawn according to the inverted displacement data to obtain the final displacement at any position of the deepwater riser and complete the displacement inversion of the deepwater riser structure.

[0043] Preferably, the relative error calculation relationship is:

[0044] ;

[0045] in, is the relative error deduced from the bottom to the middle, is the relative error deduced from the surface platform to the middle, ( ) The coordinates of the middle position deduced from the bottom to the middle ，( ) is the coordinate of the middle position deduced from the surface platform to the middle, ( ) Based on the deepwater riser bottom position beacon information ( ) , the middle position beacon information of the riser ( ) and GPS information of surface and offshore platform location ( ), with the bottom of the deepwater riser as the coordinate origin ( ), the calculated relative position coordinates of the middle part of the riser.

[0046] Preferably, if the relative error of the middle position deduced from top to bottom exceeds the set threshold, the discrete curvature data of the lower half is encrypted and interpolated, the number of interpolation points in the S2 process is at least doubled, and the deduction at both ends and the relative error calculation process are continued;

[0047] If the relative error of the middle position deduced from bottom to top exceeds the set threshold, the upper half of the discrete curvature data is encrypted and interpolated, the number of interpolation points in the S2 process is at least doubled, and the two-end deduction and relative error calculation process are continued;

[0048] If the relative errors of the middle positions of both deductions exceed the set threshold, the S2 process needs to expand the number of discrete curvature data interpolation points by at least 1 times, and the deduction and relative error calculation processes at both ends.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] First, the real-time displacement inversion of deepwater riser structure is performed based on sparse and small amount of discrete curvature data. There is no need to infer the relationship between the strain and curvature of the riser structure. It is applicable to more structural forms (steel pipes, flexible pipes and composite pipes, etc.) and can also be extended to long-distance mooring / cable structures.

[0051] Second, the cumulative error elimination strategy can effectively deal with the problem of error amplification at the end of the traditional spatial curve reconstruction method, and improve the accuracy of deepwater riser bottom displacement inversion; the maximum error of the displacement inversion process can be reduced through the middle error correction scheme, which is crucial for the detection / monitoring of the seabed production system;

[0052] Third, the displacement inversion of the deepwater riser structure can be completed using only a small number of curvature monitoring sensors and central position beacons. The number of interpolation times is updated in real time based on the correction error, which has the advantages of low detection cost, high inversion accuracy, and fast calculation rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The figure is a flow chart of the overall process of the inversion method of the present invention.

[0054] Figure 2 This is a schematic diagram of the deepwater oil and gas riser layout scenario of the present invention.

[0055] Figure 3 It is a schematic diagram of the inversion calculation process of the present invention.

[0056] Figure 4 It is a comparison diagram between the displacement inversion and the actual displacement of the deepwater riser structure in an embodiment of the present invention.

[0057] Figure 2 Middle: 1-deepwater riser; 2-curvature sensor; 3-bottom beacon; 4-middle beacon; 5-surface platform GPS; 6-interpolated position. DETAILED DESCRIPTION

[0058] The present invention is further described below in conjunction with the embodiments. 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 ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] The present invention proposes a deepwater riser structure displacement inversion method and its cumulative error elimination strategy. The overall process is as follows: Figure 1As shown, the following steps are included:

[0060] S1, real-time acquisition and measurement of sparse discrete curvature data: n optical fiber curvature sensors are installed at several measuring points with large curvature of the deepwater riser structure. The optical fiber curvature sensors acquire n sparse discrete curvature data in real time. ,in For the Measured curvature data; Deepwater oil and gas riser layout scenarios such as Figure 2 As shown, it includes a deepwater riser 1, a curvature sensor 2, a bottom beacon 3, a middle beacon 4, a surface platform GPS 5, and an interpolation position 6;

[0061] S2, obtain continuous curvature data by interpolation method: according to the measured discrete curvature data The curvature interpolation of n measured discrete curvature data is performed by the piecewise cubic Hermite interpolation method, and m continuous curvature data after interpolation are obtained. ,in For the interpolation curvature data; the number of interpolation curvatures m=the number of measuring point positions n×2+1;

[0062] S3, real-time division of continuous curvature curve micro-element segments: draw a continuous curve based on m continuous curvature data and their position information, and divide the continuous curve in real time to obtain m+1 continuous curve micro-element segment lengths ; The length of the riser micro-element segment Equal to the total length of the continuous curve ÷ the number of continuous curve microelement segments m+1;

[0063] S4, recursively deduce the curve equation from both ends to the middle:

[0064] S41, obtaining relative position information of the middle part of the riser and the surface platform;

[0065] According to the deepwater riser bottom position beacon information , the middle position beacon information of the riser And GPS information of surface and offshore platform location , with the bottom of the deepwater riser as the coordinate origin , calculate the relative position of the middle part of the riser and the relative position of the surface platform ( ), where the relative positions satisfy the relationship ， ， ， ;

[0066] S42, recursively obtain the continuous curve equation of the lower half from the bottom to the middle;

[0067] The coordinate system is established with the bottom end of the riser as the origin, and the tangent direction of the starting point is Axis, the perpendicular line from the starting point is Axis; the length of the infinitesimal arc between two points of a continuous curve is , For the interpolation points, and Respectively The center and curvature data or curvature radius of the segment micro-circular arc, for Angle with the horizontal line;

[0068] The center of the first infinitesimal segment ) coordinate , in the rectangular coordinate system, the arc segment The equation of the continuous curve is:

[0069] ;

[0070] From this, the first interpolation point can be calculated coordinate( )for:

[0071] ;

[0072] Since the infinitesimal arcs are tangent to each other, the second infinitesimal arc Center coordinate and Center and tangent point On the same straight line, we can obtain:

[0073] ;

[0074] Combining the above two equations, we can get the center of the second infinitesimal arc. coordinate( )for:

[0075] ;

[0076] Thus, the second infinitesimal arc can be obtained The equation of the continuous curve is:

[0077] ;

[0078] Similar to the above process, get The center of the micro-circle coordinate , curvature data , Angle Pass Interpolated curvature data , No. Micro-circular arc The equation of the continuous curve is:

[0079] ;

[0080] in: ;

[0081] And so on until , get the coordinates of the middle point of the continuous curve ( ), where the coordinates of the middle point are:

[0082] ;

[0083] ;

[0084] S43, taking the position of the surface platform as the starting point and based on the calculation process of S42, obtain the Micro-circular arc The equation of the continuous curve is:

[0085] ;

[0086] And so on until , get the coordinates of the middle point of the continuous curve in the recursive process from top to bottom ( );

[0087] The deduction process is as follows Figure 3 As shown;

[0088] S44, integrating the upper half and the lower half to obtain the equation of the entire continuous curve;

[0089] According to the continuous curve equation of the upper half and the continuous curve equation of the lower half, the continuous curve equation of the whole section is obtained; according to the continuous curve equation, any position can be calculated Where ,in That is, the inversion displacement data corresponding to the outer position of the deepwater riser structure;

[0090] S5, displacement inversion correction is performed based on the middle position of the riser:

[0091] Compare the relative errors between the middle position obtained from the top-down and bottom-up deduction processes and the actual middle position of the riser. If the relative error is greater than the set threshold, it is necessary to expand the number of interpolation points of the discrete curvature data according to the interpolation method and reduce the spacing between the interpolated curvature data, thereby reducing the relative error of the inverted middle position of the riser. The relative error calculation relationship is:

[0092] ;

[0093] in, is the relative error deduced from the bottom to the middle, is the relative error deduced from the surface platform to the middle, ( ) The coordinates of the middle position deduced from the bottom to the middle ，( ) is the coordinate of the middle position deduced from the surface platform to the middle, ( ) Based on the deepwater riser bottom position beacon information ( ) , the middle position beacon information of the riser ( ) and GPS information of surface and offshore platform location ( ), with the bottom of the deepwater riser as the coordinate origin ( ), the calculated relative position coordinates of the middle part of the riser;

[0094] If the relative error of the middle position deduced from top to bottom exceeds the set threshold, the discrete curvature data of the lower half is encrypted and interpolated, the number of interpolation points in the S2 process is at least doubled, and the S42, S44 and S5 processes are continued;

[0095] If the relative error of the middle position deduced from bottom to top exceeds the set threshold, the upper half of the discrete curvature data is encrypted and interpolated, the number of interpolation points in the S2 process is at least doubled, and the S43, S44 and S5 processes are continued;

[0096] If the relative errors of the middle positions of the two deductions exceed the set threshold, the S2 process needs to expand the number of discrete curvature data interpolation points by at least 1 times, and continue to execute the S3, S4 and S5 processes;

[0097] S6. Repeat the update until the accuracy requirement is met: Repeat S5 until the relative errors of the middle position obtained from the top-to-bottom and bottom-to-top deduction processes do not exceed the set threshold. At this time, the continuous curve equations of the upper and lower halves are integrated into the continuous curve equation of the entire section. A continuous smooth curve is drawn according to the inverted displacement data to obtain the final displacement at any position of the deepwater riser, thereby completing the displacement inversion of the deepwater riser structure.

[0098] This embodiment takes a deepwater oil and gas riser as an example to illustrate the specific implementation of the present invention. The riser is 20m long, with fixed constraints at both ends, a density of 7850kg / m3, an elastic modulus of 206GPa, and a Poisson's ratio of 0.3. Considering the uniform flow condition, a uniformly distributed load is uniformly applied to the structure with an amplitude of 500N / m.

[0099] The one-way recursion is changed to a two-way recursion, that is, recursion from both ends of the structure to the midpoint, thereby eliminating the accumulated error in the latter half. Eight measuring points are evenly set, 8 discrete curvature data are obtained, 200 interpolations are performed to obtain 200 continuous curvature data, and the riser displacement inversion is performed using the two-way recursion method proposed in the present invention. Figure 4 It can be seen that the bidirectional recursive displacement inversion curve is closer to the true displacement curve. The average Euclidean distance of 10-20m of the bidirectional recursive displacement inversion method is 0.1372, and the average Euclidean distance of the one-way recursive displacement inversion method is 0.4987. It can be seen that the bidirectional recursive method is more effective in eliminating the end error of the riser structure displacement inversion, and the error is reduced by 72.49%.

[0100] As shown in Table 1, the influence of the displacement inversion accuracy of the two-way recursion method and the one-way recursion method under different measuring point spacings is explored. As the measuring point spacing increases, the average Euclidean distance of the two-way recursion method and the one-way recursion method gradually increases, but the average Euclidean distance of the two-way recursion method is smaller than that of the one-way recursion method. The error of the two-way recursion method under the condition of 2.5m measuring point spacing is 0.1372, which is smaller than the error of the one-way recursion method under the condition of 0.5m measuring point spacing, which is 0.1400. Therefore, it can be seen that the two-way recursion method can use a smaller number of sensors to achieve accurate inversion of structural displacement, which is only 1 / 5 of the number of sensors of the one-way recursion method, with lower detection cost, higher monitoring accuracy, and wider practical value.

[0101] Table 1 Recursive error at different measuring point spacings

[0102]

[0103] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0104] Although the above describes the specific implementation methods of the present invention, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A deepwater riser structure displacement inversion method, characterized in that: The process includes: S1, based on n curvature sensors installed at several measuring points of the deepwater riser structure, real-time collection and measurement of sparse discrete curvature data; S2, obtain m continuous curvature data by interpolation method; S3, based on the m continuous curvature data and their position information, a continuous curve is drawn, and the continuous curve is divided in real time to obtain m+1 continuous curve micro-element segment lengths. ; S4, obtain the relative position information of the middle part of the riser and the surface platform, recursively obtain the lower half continuous curve equation from the bottom to the middle, and recursively obtain the upper half continuous curve equation from the surface to the middle, integrate the upper and lower halves to obtain the entire continuous curve equation, and calculate any position Where ,in That is, the inversion displacement data corresponding to the outer position of the deepwater riser structure; the specific process is: S41, obtaining relative position information of the middle part of the riser and the surface platform; According to the deepwater riser bottom position beacon information ( ), the middle position beacon information of the riser ( ) and GPS information of surface and offshore platform location ( ), with the bottom of the deepwater riser as the coordinate origin ( ), calculate the relative position of the middle part of the riser ( ) and the relative position of the surface platform ( ), where the relative positions satisfy the relationship ， ， ， ; S42, recursively obtain the continuous curve equation of the lower half from the bottom to the middle; The coordinate system is established with the bottom end of the riser as the origin, and the tangent direction of the starting point is Axis, the perpendicular line from the starting point is Axis; the length of the infinitesimal arc between two points of a continuous curve is , For the interpolation points, and Respectively The center and curvature data or curvature radius of the segment micro-circular arc, for Angle with the horizontal line; The center of the first infinitesimal segment ( ) coordinate ( ), in the rectangular coordinate system, the arc segment The equation of the continuous curve is: From this, the first interpolation point can be calculated coordinate( )for: Since the infinitesimal arcs are tangent to each other, the second infinitesimal arc Center coordinate( )and Center and tangent point On the same straight line, we can obtain: Combining the above two equations, we can get the center of the second infinitesimal arc. coordinate( )for: Thus, the second infinitesimal arc can be obtained The equation of the continuous curve is: Based on the above process, we can obtain -1 The center of the micro-circle coordinate( ), curvature data , Angle Pass Interpolated curvature data , No. Micro-arc The equation of the continuous curve is: in: ; And so on until , get the coordinates of the middle point of the continuous curve ( ); S43, taking the position of the surface platform as the starting point and based on the calculation process of S42, obtain the Micro-arc The equation of the continuous curve is: And so on until , get the coordinates of the middle point of the continuous curve in the recursive process from top to bottom ( ); S44, integrating the upper half and the lower half to obtain the equation of the entire continuous curve; According to the continuous curve equation of the upper half and the continuous curve equation of the lower half, the continuous curve equation of the whole section is obtained; according to the continuous curve equation, any position can be calculated Where ,in That is, the inversion displacement data corresponding to the outer position of the deepwater riser structure.

2. A deepwater riser structure displacement inversion method according to claim 1, characterized in that: The S2 obtains m continuous curvature data by interpolation method as follows: Based on the measured discrete curvature data The curvature interpolation of n measured discrete curvature data is performed by the piecewise cubic Hermite interpolation method, and m continuous curvature data after interpolation are obtained. ,in For the interpolation curvature data; the number of interpolation curvatures m=the number of measuring point positions n×2+1.

3. A deepwater riser structure displacement inversion method according to claim 1, characterized in that: It also includes the process of displacement inversion correction based on the middle position of the riser, specifically: Compare the relative errors between the middle position obtained from the top-down and bottom-up deduction processes and the actual middle position of the riser. If the relative error is greater than the set threshold, it is necessary to expand the number of interpolation points of the discrete curvature data according to the interpolation method and reduce the spacing between the interpolated curvature data, thereby reducing the relative error of the inverted middle position of the riser. Until the relative errors of the middle position obtained in the deduction process from top to bottom and from bottom to top do not exceed the set threshold, the continuous curve equations of the upper and lower halves are integrated into the continuous curve equation of the entire section, and a continuous smooth curve is drawn according to the inverted displacement data to obtain the final displacement at any position of the deepwater riser and complete the displacement inversion of the deepwater riser structure.

4. A deepwater riser structure displacement inversion method as claimed in claim 3, characterized in that: The relative error calculation relationship is: in, is the relative error deduced from the bottom to the middle, is the relative error deduced from the surface platform to the middle, ( ) The coordinates of the middle position deduced from the bottom to the middle ， ( ) is the coordinate of the middle position deduced from the surface platform to the middle, ( ) Based on the deepwater riser bottom position beacon information ( ) , the middle position beacon information of the riser ( ) and GPS information of surface and offshore platform location ( ), with the bottom of the deepwater riser as the coordinate origin ( ), the calculated relative position coordinates of the middle part of the riser.

5. A deepwater riser structure displacement inversion method as claimed in claim 3, characterized in that: If the relative error of the middle position in the deduction from top to bottom exceeds the set threshold, the discrete curvature data in the lower half is encrypted and interpolated, the number of interpolation points in the S2 process is at least doubled, and the deduction at both ends and the relative error calculation process are continued; If the relative error of the middle position deduced from bottom to top exceeds the set threshold, the upper half of the discrete curvature data is encrypted and interpolated, the number of interpolation points in the S2 process is at least doubled, and the two-end deduction and relative error calculation process are continued; If the relative errors of the middle positions of both deductions exceed the set threshold, the S2 process needs to expand the number of discrete curvature data interpolation points by at least 1 times, and the two-end deduction and relative error calculation processes.

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