Non-contact floating fan mooring tension monitoring method

Abstract

The invention discloses a non-contact floating fan mooring tension monitoring method, which comprises the following steps of: establishing a coordinate transformation matrix between a local coordinate system and a global coordinate system of a platform by virtue of a Kaldan angle on the basis of six-degree-of-freedom motion monitoring data of the platform; coordinates of the mooring fairlead in the local coordinate system of the platform are converted into coordinates in a global coordinate system through a conversion matrix; for tensioning type mooring, the distance between two space points can be calculated by knowing the position of a fairlead and the position of a mooring anchor point, so that the mooring tension is calculated; for catenary mooring, a dynamic analysis model of the catenary mooring can be established on the basis of a vector finite element method, the model can perform dynamic calculation as long as the position of a fairlead is used as input, and then the function of dynamic mooring tension monitoring is achieved. According to the non-contact floating fan mooring tension monitoring method, tension monitoring can be conducted on catenary type mooring and tensioning type mooring at the same time.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering structure condition monitoring, and particularly relates to a non-contact method for monitoring the mooring tension of floating wind turbines. Background Technology

[0002] In recent years, the number of floating wind turbine demonstration projects in China has been increasing. Considering the numerous cases of failure of offshore floating structures, monitoring the mooring tension of floating wind turbines has become an essential part of the construction process. Currently, load cells are typically used to measure the mooring tension.

[0003] However, load cells are typically located in critical stress areas of the structure, making them difficult to replace. Engineering practice shows that the lifespan of these sensors is relatively short compared to the platform's lifespan. Therefore, multiple sensor replacements are required during the service life of the floating wind turbine, increasing operating costs. Furthermore, for tension leg floating wind turbines, on-site sensor replacement is difficult or prohibitively expensive, potentially leading to a lack of mooring tension monitoring capabilities in the latter part of the turbine's service life.

[0004] Therefore, there is an urgent need to design a non-contact method for monitoring the mooring tension of floating wind turbines to solve the problems mentioned above. Summary of the Invention

[0005] To address the technical problem mentioned in the background art that weighing sensors are generally located in critical stress-bearing parts of the structure, making them difficult to replace and having a relatively short service life, a non-contact floating wind turbine mooring tension monitoring method is provided to solve the problem of indirect monitoring of mooring tension.

[0006] To achieve the above objectives, the specific technical solution of the non-contact floating wind turbine mooring tension monitoring method of the present invention is as follows: A non-contact method for monitoring mooring tension of floating wind turbines indirectly monitors the mooring tension status in real time through motion monitoring data from a platform. The method mainly includes the following steps: S1. Establish a global coordinate system and a local coordinate system for the floating wind turbine; S2. Establish the coordinate transformation matrix between the local coordinate system and the global coordinate system using Cardan angles; S3. Using the monitored platform pitch, roll, and tilt angle data as the values ​​of the Cardan angles, calculate the value of each element in the coordinate transformation matrix; S4. Using the platform translation motion monitoring data and the position of the cable guide hole in the local coordinate system, calculate the position of the cable guide hole in the global coordinate system with the help of the coordinate transformation matrix; S5. Based on the spatial coordinates of the guide hole and the anchor point, the axial tension value of each mooring anchor cable can be calculated; for tensioned mooring, the operation steps are as follows: S5.1 Calculate the distance between the cable guide hole and the anchor point. ; S5.2 Initial length of tensioned mooring anchor cable Calculate the elongation of the mooring anchor cable; S5.3 Calculate the mooring tension according to the axial tension formula in mechanics of materials; S6. For catenary mooring, first use the vector finite element method to establish a dynamic analysis model of the mooring anchor cable, and then input the position coordinates of the guide hole in the global coordinate system into the dynamic mooring model to calculate the mooring tension.

[0007] Furthermore, based on the monitoring data of the floating platform, the initial position of the floating platform is determined, mainly including the following steps: S1. Set the initial position coordinates of a floating platform. Calculate the initial mooring tension at this location. ; S2, The platform position coordinates monitored at time t are: The mooring load monitored at time t is ; S3, will relative to the initial position The difference is used to obtain the displacement increment. ; S4, Using displacement increment Calculate load increment Then calculate the mooring load at time t; S5. Compare the mooring load at time t obtained from the calculation. The mooring load at time t obtained from monitoring If the absolute value of the difference between the two is less than an infinitesimally small value, it indicates that the assumed initial position of the platform is correct; if the difference between the two is large, it indicates that the assumed initial position is incorrect, and the initial position should be modified. S6. Repeat S1-S5 until the absolute value of the difference between the calculated load and the monitored load is within the set error limit, then the initial position can be determined.

[0008] Furthermore, in S2, the 6-DOF motion monitoring data of the floating wind turbine platform is obtained through GPS sensors, and the values ​​of 3 rotation angles are used as the values ​​of the Cardan angles to calculate the value of the transformation matrix.

[0009] Furthermore, in S4, the coordinates of each cable guide hole position in the local coordinate system are measured, and then the position coordinates of the cable guide hole in the global coordinate system are calculated through the transformation matrix.

[0010] Furthermore, in S5, for tensioned mooring, the mooring tension can be calculated by calculating the spatial distance between the guide hole and the anchor point, and then based on the formula for elongation and axial force.

[0011] Furthermore, in S6, for catenary mooring, a dynamic analysis model of the catenary mooring is first established using the vector finite element method. Then, the spatial coordinates of the guide hole are input into the dynamic mooring model, and the model can then calculate the dynamic mooring tension of the catenary mooring.

[0012] Furthermore, it also includes determining the balance position of the floating wind turbine platform, which mainly includes the following steps: S1. First, assume a floating wind turbine platform equilibrium position vector and calculate the mooring tension value at that position; S2. The displacement change vector of the floating wind turbine platform at time t is obtained by subtracting the position vector of the floating wind turbine platform monitored by GPS from the assumed equilibrium position vector. S3. Calculate the change in mooring tension using the displacement change of the floating platform, and then sum this change in mooring tension with the mooring tension value at the equilibrium position to obtain the mooring tension value calculated at time t.

[0013] Furthermore, the calculated mooring tension value at time t is subtracted from the monitored mooring tension value at time t. If the difference is less than an infinitesimally small value, it indicates that the assumed platform equilibrium position is correct; if the difference is large, it indicates that the assumed equilibrium position is incorrect. The equilibrium position is then modified until the difference between the calculated and monitored mooring tensions is within the set error limit, at which point the iterative calculation ends.

[0014] The non-contact floating wind turbine mooring tension monitoring method of the present invention has the following advantages: (1) No additional tension monitoring sensors are used, reducing the number of sensors required and saving construction costs; (2) The motion monitoring sensors of the floating platform are not installed at the critical structure of the mooring system, so as not to damage the integrity of the original structure; (3) It avoids directly placing sensors on the mooring system, and sensor replacement does not require detaching the mooring, thus improving the convenience of maintenance and replacement; (4) The platform motion monitoring sensor is placed on the platform, so the sensor will not be corroded by seawater, which improves the service life of the sensor and increases the reliability of monitoring. (5) For in-service floating platforms, there is no need to install mooring tension monitoring sensors underwater. Mooring tension can be easily monitored simply by installing motion monitoring GPS on the platform. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the global and local coordinates of a floating wind turbine with a tension leg, representing the non-contact floating wind turbine mooring tension monitoring method of the present invention. Figure 2 This is a schematic diagram of the global and local coordinate systems of a semi-shallow floating wind turbine in the non-contact floating wind turbine mooring tension monitoring method of the present invention; Figure 3 This is a flowchart of the non-contact floating wind turbine mooring tension monitoring method of the present invention; Figure 4 This is a flowchart of the platform initial position determination method in the non-contact floating wind turbine mooring tension monitoring method of the present invention; Figure 5 This is a flowchart of the platform balance position determination method in the non-contact floating wind turbine mooring tension monitoring method of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0018] The following is a reference to the appendix. Figure 1 To be continued Figure 5 The non-contact floating wind turbine mooring tension monitoring method of the present invention is described, as a preferred embodiment: S1. Establish a global coordinate system and a local coordinate system to describe the spatial motion of the steel body. The global coordinate system is fixed to the ground. This indicates that its coordinate axes are... The local coordinate system is fixed on the floating wind turbine platform, using This indicates that its coordinate axes are... ; S2. Establish a global coordinate system using Cardan angles. and local coordinate system The coordinate transformation matrix T between them, Cardan angles are used , and The expression for the coordinate transformation matrix is: S3. Select a point on the platform as the origin of the local coordinate system, install a GPS sensor at this point, and use GPS to collect real-time 6-DOF motion data of the floating wind turbine platform. This data is a function of time, and the position at time t is represented by a vector. This means that the three rotation angle data of the platform collected at each moment are used as the values ​​of the Cardan angle, which are then substituted into the expression of the transformation matrix T to calculate the value of each element of the transformation matrix. S4. Measure the position coordinates of each cable guide hole in the platform's local coordinate system on site. Use it as a vector This is represented by the transformation matrix T, which is then used to calculate the position coordinates of the cable guide hole in the global coordinate system at each moment. S5. For tensioned mooring, after calculating the coordinates of the guide hole position in the global coordinate system, calculate the distance between the guide hole and the anchor point. Spatial distance: S6. The length of a tensioned mooring under pretension is: The elongation of the tensioned mooring at time t is Calculate the mooring tension at time t using relevant formulas from mechanics of materials: S7. Monitoring the mooring tension of a catenary moor requires establishing a dynamic mooring analysis model using the vector finite element method, and then determining the position coordinates of the guide hole in the global coordinate system. The steps for establishing a dynamic mooring analysis model using the vector finite element method are as follows: The input is then fed into the dynamic mooring analysis model, and the mooring tension is finally calculated. S7.1 Establishing a dynamic finite element model of mooring: S7.2 Determine the position coordinates of the upper node of the catenary mooring at time step n+1 (i.e., the position coordinates of the guide hole in the global coordinate system at a certain moment). S7.3. Based on the positions of the remaining nodes in the model except for the upper endpoint at time steps n and n-1, and the node loads of these nodes at time step n, the central difference method is used to calculate the node positions of these nodes at time step n+1. S7.4 Calculate the node velocity and acceleration based on the node positions at time steps n-1, n, and n+1; S7.5 Calculate the transformation matrix and parameters such as the additional mass of the mooring cable from the node coordinates at the (n+1)th time step; S7.6. The Morison equation is used to calculate the hydrodynamic load on the mooring cable at time step n+1, and the axial tension calculation formula is used to calculate the nodal internal forces at time step n+1. S7.7 Update node coordinates. Let the node position at step n+1 be the node position at time step n, and let the node position at time step n-1 be the node position at time step n-1. Use the position coordinates of the cable hole at the next moment obtained from S7.3 as the new coordinates of the upper end point of the model mooring. Repeat the above calculation steps until the specified calculation time. S7.8. The position coordinates of the cable guide hole can be established through the operations in (1)-(6) above. With mooring tension Relationship Thus, the mooring tension of the catenary mooring is obtained; S8. Method for determining the platform's equilibrium position: Due to installation errors in actual engineering projects, and the continuous movement of the floating wind turbine from installation to completion, it is difficult to know its equilibrium position information. Therefore, the method proposed above will have a large monitoring error. Here, a step-by-step iterative correction method is proposed for equilibrium position identification. The operation process is as follows: S8.1 First, assume the equilibrium position vector of a floating platform. Calculate the initial mooring tension at this location. ; S8.2, The platform position vector monitored at time t is: The mooring load monitored at time t is ; S8.3, will relative to the initial position The difference is used to obtain the displacement increment. ; S8.4 The mooring load increment calculated using this displacement increment is: Therefore, the mooring load calculated at time t is ; S8.5, calculate the load at time t. The mooring load at time t obtained from monitoring Comparison: S8.6 If the absolute value of the difference between the two is less than an infinitesimally small value. If the result is positive, it indicates that the assumed equilibrium position of the platform is correct, and the calculation ends. S8.7 If the absolute value of the difference between the two is greater than This indicates that the assumed equilibrium position is incorrect. The equilibrium position is then modified, and the above steps are repeated until the absolute value of the difference between the calculated mooring load and the monitored mooring load is less than [a certain value]. The iteration process ends, and the equilibrium position is obtained.

[0019] Based on a non-contact floating wind turbine mooring tension monitoring method, this invention can monitor dynamic mooring tension. The angle monitoring method assumes that the mooring anchor cable is in a state of static equilibrium, and a small change in the angle during mooring movement may lead to a large change in mooring tension, resulting in a larger error in the angle monitoring method. It is applicable to both tensioned mooring and catenary mooring. This method can also monitor the mooring tilt angle and motion pattern, making it very suitable for digital twin modeling of floating wind turbines.

[0020] Furthermore, based on the proposed method for determining the balance position of a floating wind turbine, the low-frequency slow drift motion of the floating wind turbine can also be monitored.

[0021] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A non-contact method for monitoring mooring tension of a floating wind turbine, which indirectly monitors the mooring tension state in real time through motion monitoring data of a platform, characterized in that... The main steps include: S1. Establish a global coordinate system and a local coordinate system for the floating wind turbine; S2. Establish the coordinate transformation matrix between the local coordinate system and the global coordinate system using Cardan angles; S3. Using the monitored platform pitch, roll, and tilt angle data as the values ​​of the Cardan angles, calculate the value of each element in the coordinate transformation matrix; S4. Using the platform translation motion monitoring data and the position of the cable guide hole in the local coordinate system, calculate the position of the cable guide hole in the global coordinate system with the help of the coordinate transformation matrix; S5. Based on the spatial coordinates of the guide hole and the anchor point, the axial tension value of each mooring anchor cable can be calculated; for tensioned mooring, the operation steps are as follows: S5.1 Calculate the distance between the cable guide hole and the anchor point. ; S5.2 Initial length of tensioned mooring anchor cable Calculate the elongation of the mooring anchor cable; S5.3 Calculate the mooring tension according to the axial tension formula in mechanics of materials; S6. For catenary mooring, first use the vector finite element method to establish a dynamic analysis model of the mooring anchor cable, and then input the position coordinates of the guide hole in the global coordinate system into the dynamic mooring model to calculate the mooring tension.

2. The non-contact floating wind turbine mooring tension monitoring method according to claim 1, characterized in that, Determining the initial position of the floating platform based on monitoring data mainly includes the following steps: S1. Set the initial position coordinates of a floating platform. Calculate the initial mooring tension at this location. ; S2, The platform position coordinates monitored at time t are: The mooring load monitored at time t is ; S3, will relative to the initial position The difference is used to obtain the displacement increment. ; S4, Using displacement increment Calculate load increment Then calculate the mooring load at time t; S5. Compare the mooring load at time t obtained from the calculation. The mooring load at time t obtained from monitoring If the absolute value of the difference between the two is less than an infinitesimally small value, it indicates that the assumed initial position of the platform is correct; if the difference between the two is large, it indicates that the assumed initial position is incorrect, and the initial position should be modified. S6. Repeat S1-S5 until the absolute value of the difference between the calculated load and the monitored load is within the set error limit, then the initial position can be determined.

3. The non-contact floating wind turbine mooring tension monitoring method according to claim 1, characterized in that, In S2, the 6-DOF motion monitoring data of the floating wind turbine platform is obtained through GPS sensors, and the values ​​of three rotation angles are used as the values ​​of the Cardan angles to calculate the value of the transformation matrix.

4. The non-contact floating wind turbine mooring tension monitoring method according to claim 1, characterized in that, In S4, the coordinates of each cable guide hole in the local coordinate system are measured, and then the position coordinates of the cable guide hole in the global coordinate system are calculated through the transformation matrix.

5. The non-contact floating wind turbine mooring tension monitoring method according to claim 1, characterized in that, In S5, for tensioned mooring, the mooring tension can be calculated by calculating the spatial distance between the guide hole and the anchor point, and then based on the formula for elongation and axial force.

6. The non-contact floating wind turbine mooring tension monitoring method according to claim 1, characterized in that, In S6, for catenary mooring, the dynamic analysis model of the catenary mooring is first established using the vector finite element method. Then, the spatial coordinates of the guide hole are input into the dynamic mooring model, and the model can calculate the dynamic mooring tension of the catenary mooring.

7. The non-contact floating wind turbine mooring tension monitoring method according to claim 1, characterized in that, It also includes determining the balance position of the floating wind turbine platform, which mainly includes the following steps: S1. First, assume a floating wind turbine platform equilibrium position vector and calculate the mooring tension value at that position; S2. The displacement change vector of the floating wind turbine platform at time t is obtained by subtracting the position vector of the floating wind turbine platform monitored by GPS from the assumed equilibrium position vector. S3. Calculate the change in mooring tension using the displacement change of the floating platform, and then sum this change in mooring tension with the mooring tension value at the equilibrium position to obtain the mooring tension value calculated at time t.

8. The non-contact floating wind turbine mooring tension monitoring method according to claim 7, characterized in that, The difference between the calculated mooring tension value at time t and the monitored mooring tension value at time t is calculated. If the difference is less than an infinitesimally small value, it indicates that the assumed platform equilibrium position is correct. If the difference is large, it indicates that the assumed equilibrium position is incorrect. The equilibrium position is then modified until the difference between the calculated mooring tension and the monitored mooring tension is within the set error limit, at which point the iterative calculation ends.

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