Accurate control method for laying tension of submarine cable in deep and far sea

Abstract

The invention discloses an accurate control method for laying tension of submarine cables in deep and far sea, and belongs to the technical field of ocean engineering. The method comprises the following steps: constructing a mapping model of LAB and T in a submarine cable laying construction environment through finite element software; determining the maximum permissible tension value Tmax and the minimum permissible tension value Tmin of the submarine cable, and determining the safety threshold [Lmin, Lmax] of the LAB according to a mapping model of the LAB and the T; during construction, a real-time numerical value LAB is monitored, then the relation between the LAB and [Lmin, Lmax] is judged, the cable laying speed is controlled according to the relation, and the submarine cable tension is controlled within a safe interval. According to the precise control method for the submarine cable laying tension of the deep and far sea, the submarine cable tension control precision can be greatly improved, it is ensured that the submarine cable laying tension is safe and controllable, and the submarine cable laying construction safety is improved.

Description

Technical Field

[0001] This invention relates to a method for precise control of tension in deep-sea cable laying, belonging to the field of marine engineering technology. Background Technology

[0002] Currently, tension control in deep-sea cable laying mainly relies on two types of methods:

[0003] (1) Direct tension sensing method, which involves installing a tension sensor (clamping device) at the drum machine outlet to directly measure the real-time tension of the submarine cable. This method has the following drawbacks: the ship's swaying causes the sensor signal to oscillate, and the measured data shows that the tension fluctuation is very large, making it impossible to distinguish between the actual tension and environmental noise; for deep-sea large-diameter submarine cables, since the maximum permissible tension for laying is usually large, the existing tension sensor needs to apply a large pressure (gripping force) to the surface of the submarine cable during the clamping process. The submarine cable has weak lateral compressive stiffness and is easily crushed, so it is usually impossible to measure directly, which poses a significant construction safety risk.

[0004] (2) Dynamic model prediction method, which calculates the laying tension curve based on input environmental parameters. This method has the following drawbacks: simulation calculations are difficult to accurately establish a one-to-one correspondence between the theoretical tension of the submarine cable and the actual tension during the laying process, resulting in poor control accuracy and failure to meet construction safety requirements. Summary of the Invention

[0005] To address the aforementioned problems in existing tension control methods for deep-sea submarine cable laying, this invention provides a precise tension control method for deep-sea submarine cable laying. This method uses a three-dimensional laser scanner to precisely measure the spatial curve length L of the submarine cable between the drum machine apex A and the exit point B from the water inlet bridge. AB L is established by combining software simulation. AB - Submarine cable tension mapping model to achieve indirect high-precision determination of submarine cable tension status.

[0006] To solve the above technical problems, the present invention includes the following technical solutions:

[0007] A method for precise tension control during deep-sea cable laying involves a cable-laying vessel equipped with a drum machine. After the cable is wound around the drum machine, it leaves the machine and enters the water via a water inlet bridge. The apex A of the drum machine is considered the point of separation between the cable and the drum machine. There is a suspended section between the drum machine and the water inlet bridge; the point where the cable leaves the water inlet bridge is designated as point B. The length of the spatial curve between points A and B is denoted as L. AB The tension of the suspended section of the submarine cable is denoted as T; the method includes the following steps:

[0008] Step 1: Construct the L-shaped structure under the construction environment of submarine cable laying using finite element software. AB Mapping model with T;

[0009] Step 2: Determine the maximum permissible tension value T of the submarine cable. max and minimum permissible tension value T min According to L AB The characteristic curve in the mapping model with T is used to obtain the submarine cable tension safety threshold [T]. min ,T max The L corresponding to ] AB Safety threshold [L] min ,L max ];

[0010] Step 3: Set up a 3D laser scanner on the deck on one side of the submarine cable to acquire the spatial shape of the cable in real time, generate a point cloud on the cable surface, fit the 3D line shape of the cable, and then calculate the real-time spatial curve length L between points A and B. AB ;

[0011] Step 4: Determine L AB With safety threshold [L] min ,L max The relationship between these parameters is used to control the cable-laying speed; specifically,

[0012] If L min ≤L AB ≤L max Then the tension of the submarine cable is within the safe range;

[0013] If L AB <L min If the tension on the submarine cable is too high, the cable laying speed will be accelerated.

[0014] If L AB >L max If the tension of the submarine cable is too low, the cable laying speed will be slowed down.

[0015] In the next step, the L-shaped structure under the construction environment of submarine cable laying is constructed using finite element software. AB When mapping T to a model, the following needs to be considered:

[0016] Environmental parameters, including seabed parameters, wave parameters, ocean current parameters, and sea breeze parameters;

[0017] Ship parameters, including the initial position of the cable-laying vessel, direction of travel, speed of travel, hull structural parameters, and barge motion response amplitude operator;

[0018] The parameters of the drum machine include the geometric features of the winding bearing surface and the side baffles; the contact between the submarine cable and the drum machine is simulated by the normal and tangential stiffness and friction coefficient μ of the drum machine.

[0019] Parameters of the support system for the submarine cable on the entry bridge;

[0020] Submarine cable parameters.

[0021] This invention, by employing the above technical solution, has the following advantages and positive effects compared to existing technologies: The method mainly utilizes finite element software to construct the L-shaped structure under the construction environment of submarine cable laying. AB Mapping model with T; and determine the maximum permissible tension value T of the submarine cable. max and minimum permissible tension value T min According to L AB The mapping model with T determines L. AB Safety threshold [L] min ,L max During construction, real-time monitoring data L... AB Then determine L AB With [L] min ,L max The relationship between [L] and [Y] is used to control the cable laying speed, keeping the cable tension within a safe range. This method utilizes finite element software to construct the L[L] model under the cable laying construction environment. AB The mapping model with T fully considers the mechanical properties of the submarine cable, the contact effects between the cable and the drum motor and the entry bridge (or roller, support frame), and also takes into account the dynamic coupling effects of ocean currents, waves, sea winds, and ship motion. This control method can significantly improve the accuracy of submarine cable tension control. Through comprehensive analysis of various sea state parameters, the optimal L for submarine cable laying can be optimized. AB and safety threshold [L] min ,L max The process control parameters ensure that the tension of the submarine cable laying is safe and controllable, thus improving the safety of submarine cable laying construction. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a method for precisely controlling the tension of deep-sea submarine cable laying according to an embodiment of the present invention;

[0023] Figure 2 L in one embodiment of the present invention AB A schematic diagram of the characteristic curve of T.

[0024] The numbers in the diagram are as follows:

[0025] 1-Seabed; 2-Cable-laying vessel; 3-Drum machine; 4-Inlet bridge; 5-Submarine cable; 6-3D scanner;

[0026] 10 - Maximum permissible tension corresponding to the submarine cable profile; 20 - Minimum permissible tension corresponding to the submarine cable profile; Detailed Implementation

[0027] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for precise tension control in deep-sea cable laying according to the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0028] Example 1

[0029] like Figure 1 As shown, the cable-laying vessel 2 is equipped with a drum machine 3. One end of the submarine cable 5 is coiled on a tray (not shown), and the other end passes through a de-twisting frame (not shown) and then around the drum machine 3. It then enters the water via the inlet bridge 4 and hangs down to the seabed 1. After the cable has been coiled around the drum machine several times, it leaves the drum machine. For ease of analysis, the point where the cable 5 separates from the drum machine 3 is considered to be point A, the highest point of the drum machine. The cable has a suspended section between the drum machine and the inlet bridge before contacting the deck. The point where the cable leaves the inlet bridge is denoted as point B, and the length of the spatial curve between points A and B is denoted as L. AB L AB That is, the actual length of the submarine cable between A and B, with the tension of the suspended section of the cable denoted as T and L. AB The size of L corresponds to T; the larger T is, the larger L is. AB The smaller T is, the smaller L is. AB The larger it is, the smaller it is.

[0030] The method for precise control of tension in deep-sea submarine cable laying provided by this invention mainly involves constructing the L-shaped tension under the construction environment of the submarine cable laying using finite element software. AB Mapping model with T; and determine the maximum permissible tension value T of the submarine cable. max and minimum permissible tension value T min According to L AB The mapping model with T determines L. AB Safety threshold [L] min ,L max During construction, real-time monitoring data L... AB Then determine L AB With [L] min ,L max The relationship between [the two conditions] is considered, and when the tension exceeds a safety threshold, the cable laying speed is adjusted to control the cable tension within a safe range. Specifically, the precise control method for tension in deep-sea cable laying includes the following steps:

[0031] Step 1: Construct the L-shaped structure under the construction environment of submarine cable laying using finite element software. AB The mapping model with T.

[0032] As an example, OrcaFlex is the most advanced large-scale nonlinear time-domain finite element analysis software in the world for marine engineering. This software can be used for accurate simulation to determine L... AB The correspondence with T. The following are the key steps in the OrcaFlex software simulation:

[0033] (1) Set general parameters, which mainly involve analysis steps and analysis duration.

[0034] (2) Set environmental parameters, including seabed parameters, wave parameters, ocean current parameters, sea breeze parameters, etc.

[0035] (3) Set the hull parameters (vessel), which mainly involve the basic parameters of the powered barge, including initial position, sailing direction, sailing speed, hull structure parameters, barge motion response amplitude operator (RAO) and other hydrodynamic parameters.

[0036] (4) Drum machine parameters: The drum machine is simulated using shape, with the shape type being elastic solid and the specific shape being a cylinder. The winding bearing surface and the structural features of the two side baffles of the drum machine are simulated by setting the position, inner and outer diameters, and length of the cylinder. The contact between the submarine cable and the drum machine is simulated by the drum machine stiffness (normal and tangential) and the coefficient of friction (μ), with the corresponding calculation parameters input.

[0037] (5) After leaving the drum machine and before entering the sea, the submarine cable is supported on the entry bridge (or drum, support rack). The support type of the submarine cable on the hull is selected according to the actual situation, and the corresponding external dimensions, support normal stiffness, and tangential stiffness are entered. Then, parameters such as support path, support path origin, and support spacing are defined.

[0038] (6) The submarine cable is simulated using a line model, and the line types are numerical (general pipe). Based on data provided by the manufacturer, key mechanical properties of the submarine cable are simulated by setting parameters such as the cable's outer diameter, air midline density, axial stiffness, bending stiffness, torsional stiffness, allowable tension, and allowable bending radius. The cable's head end is placed on the power barge's tray and pulled into the drum machine via the untwisting frame. The cable laying process relative to the hull can be simplified using the line feeding function, i.e., by specifying the initial arc length, simulation time, and corresponding payout rate of the cable after leaving the untwisting frame, the entire cable laying process after leaving the untwisting frame is simulated. The other end of the cable is anchored to the seabed. Since the submarine cable must be wound three times along the drum machine after emerging from the untwisting frame to control the laying speed, the initial static shape of the submarine cable can be set using a user-specified method. This involves specifying the initial coordinates of all the node units of the submarine cable to facilitate the cable quickly finding its initial equilibrium state. The initial static shape of the submarine cable should be as short as possible (i.e., taut, corresponding to a maximum tension greater than the permissible tension). Due to the set payout rate during the simulation, which is greater than the ship speed, the cable length continuously increases, causing the cable tension to decrease continuously. Then, the maximum tension reaches the critical internal force—the maximum permissible tension (corresponding to the cable being controlled at maximum tension). As the cable length continues to increase, the cable tension continues to decrease until it reaches zero at the seabed contact point (corresponding to the cable being controlled at minimum tension).

[0039] Through the above simulation, the required L can be obtained. AB The precise numerical relationship with T. For example, such as... Figure 2 As shown, L was simulated using finite element analysis software. AB The characteristic curve of T can also be fitted to a smooth curve, and then the corresponding L can be determined by the tension T. AB Value, through L AB The value can also determine the tension T.

[0040] Step 2: Determine the maximum permissible tension value T of the submarine cable. max and minimum permissible tension value T min According to L AB The characteristic curve in the mapping model with T is used to obtain the submarine cable tension safety threshold [T]. min ,T max The L corresponding to ]AB Safety threshold [L] min ,L max ].

[0041] It should be noted that the maximum tension of the submarine cable can be determined according to the technical documents provided by the manufacturer. The minimum tension of the submarine cable occurs at the seabed contact point, requiring that there be no coiling or tangling at this point. Generally, the tension at the seabed contact point should not be under pressure. However, the tension of the submarine cable in the suspended section between the drum machine and the entry bridge is not zero. It is necessary to simulate the tension in the suspended section when the tension at the seabed contact point is zero. This is the minimum tension of the submarine cable that needs to be controlled during construction. The maximum permissible tension value T of the submarine cable is... max and minimum permissible tension value T min It can be set as needed, but it will definitely be between the maximum and minimum tension of the submarine cable. Figure 1 The diagram shows the cable profile 10 corresponding to the maximum permissible tension and the cable profile 20 corresponding to the minimum permissible tension.

[0042] Step 3: Set up a 3D laser scanner on the deck on one side of the submarine cable to acquire the spatial shape of the cable in real time, generate a point cloud on the cable surface, fit the 3D line shape of the cable, and then calculate the real-time spatial curve length L between points A and B. AB .

[0043] Step 4: Determine L AB Does it exceed the safety threshold? [L] min ,L max ],

[0044] If L min ≤L AB ≤L max Then the tension of the submarine cable is within the safe range;

[0045] If L AB <L min If the tension on the submarine cable is too high, the cable laying speed will be accelerated.

[0046] If L AB >L max If the tension of the submarine cable is too low, the cable laying speed will be slowed down.

[0047] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0048] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for precise control of tension in deep-sea submarine cable laying, characterized in that, The cable-laying vessel is equipped with a drum machine. After the submarine cable is wound around the drum machine, it leaves the drum machine and enters the water via the inlet bridge. The apex A of the drum machine is considered the point of separation between the submarine cable and the drum machine. There is a suspended section between the submarine cable and the inlet bridge. The point where the submarine cable leaves the inlet bridge is denoted as point B. The length of the submarine cable's spatial curve between points A and B is denoted as L. AB The tension of the suspended section of the submarine cable is denoted as T; the method includes the following steps: Step 1: Construct the L-shaped structure under the construction environment of submarine cable laying using finite element software. AB Mapping model with T; Step 2: Determine the maximum permissible tension value T of the submarine cable. max and minimum permissible tension value T min According to L AB The characteristic curve in the mapping model with T is used to obtain the submarine cable tension safety threshold [T]. min ,T max The L corresponding to ] AB Safety threshold [L] min ,L max ]; Step 3: Set up a 3D laser scanner on the deck on one side of the submarine cable to acquire the spatial shape of the cable in real time, generate a point cloud on the cable surface, fit the 3D line shape of the cable, and then calculate the real-time spatial curve length L of the submarine cable between points A and B. AB ; Step 4: Determine L AB With safety threshold [L] min ,L max The relationship between these parameters is used to control the cable-laying speed; specifically, If L min ≤L AB ≤L max Then the tension of the submarine cable is within the safe range; If L AB <L min If the tension on the submarine cable is too high, the cable laying speed will be accelerated. If L AB >L max If the tension of the submarine cable is too low, the cable laying speed will be slowed down.

2. As described in claim 1, characterized in that, In step one, the L-shaped structure under the construction environment of submarine cable laying is constructed using finite element software. AB When mapping T to a model, the following needs to be considered: Environmental parameters, including seabed parameters, wave parameters, ocean current parameters, and sea breeze parameters; Ship parameters, including the initial position of the cable-laying vessel, direction of travel, speed of travel, hull structural parameters, and barge motion response amplitude operator; The parameters of the drum machine include the geometric features of the winding bearing surface and the side baffles; the contact between the submarine cable and the drum machine is simulated by the normal and tangential stiffness and friction coefficient μ of the drum machine. Parameters of the support system for the submarine cable on the entry bridge; Submarine cable parameters.

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