Inter-ship acting force calculation method and ship transverse supply position optimization method

Abstract

The invention discloses an inter-ship acting force calculation method and a ship transverse supply position optimization method, and relates to the technical field of ships. According to the inter-ship acting force calculation method, calculation of the transverse acting force and the torque of the target ship during transverse supply of the two ships is completed based on the theory of fluid mechanics and ship manipulation dynamics, an operator can be helped to predict the dynamic response between the ships in the ship supply process, and motion control of the ships is optimized; and the position of the maximum acting force and moment can be found through simulation, so that high-risk areas are avoided in actual operation, and the safety and stability of the ship in supply operation are ensured. According to the ship transverse replenishment position optimization method, based on the calculated transverse acting force of the target ship, the moment balance of each point in the replenishment process is ensured by dynamically adjusting the replenishment point position, the problem of uneven stress of replenishment equipment is solved, and the safety and reliability of replenishment operation are improved. The method can be applied to ship supply operation under complex sea conditions, and supply safety is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ships, and in particular to a method for calculating inter-ship forces and a method for optimizing the transverse replenishment position of ships. Background Art

[0002] In order to enhance the control of ocean space and the development of marine resources, many maritime powers in the world today have vigorously developed unmanned aerial vehicles, including autonomous surface ships and underwater robots. Autonomous surface ships are widely used due to their strong maneuverability and small targets. However, their disadvantages are also very obvious. Due to their small size, they cannot carry a large amount of fuel, which leads to the need to replenish energy midway during ocean voyages. In addition, due to their small tonnage, compared with traditional manned ships, such ships will be seriously affected by the tail waves of the supply ship during the replenishment process. Therefore, how to realize energy replenishment during navigation has become an important part of realizing the ocean voyage of autonomous surface ships.

[0003] Lateral replenishment between ships is an important maneuvering technology, especially to maintain the combat capability and logistical supply of the fleet during long-term sea voyages. This replenishment method usually involves the supply ship and the receiving ship sailing in parallel at sea, and the fuel and materials are transferred through refueling pipelines, cargo delivery systems, etc. However, during the marine replenishment process, the interaction forces and torques between the two ships bring about complex maneuverability problems. During the replenishment process, due to the superposition of the pressure fields of the two ships in the fluid environment, the attraction and horizontal rotation torque between the ships are caused, which gradually bring the two ships closer, increasing the risk of collision. At present, the replenishment between ships is mainly completed by the high cable between the supply ship and the receiving ship to transport cargo or fuel, and since both ships are large ships, the distance between the two ships is generally 30 to 60 meters, and the force between the two ships during the replenishment process can be ignored. However, for the replenishment of autonomous surface ships, since it is impossible to connect pipelines with devices such as steel cables, most of them will use mechanical arms and other devices for fuel replenishment, which will result in the distance between them and the supply ship being within 10 meters, and the force between ships within 10 meters will endanger the safety of the two ships.

[0004] Therefore, it is very necessary to study the interaction between autonomous surface ships, which not only improves the operational safety of replenishment operations, but also provides important theoretical support for ship manipulation and control technology. The research covers a number of related technical fields such as fluid mechanics, ship manipulation dynamics, ship control technology, and offshore operation safety. This type of technology has important application value in ensuring the safety and stability of the supply ship and the supplied ship during offshore replenishment. Summary of the invention

[0005] The object of the present invention is to provide a method for calculating the inter-ship force and a method for optimizing the position of the transverse replenishment of ships, so as to complete the calculation of the transverse force and moment of the target ship when two ships are transversely replenished.

[0006] In a first aspect of the present invention, a method for calculating inter-vessel forces is provided, the method comprising:

[0007] The lateral force and moment of the target ship when the two ships are supplementing each other laterally are calculated by the following formula:

[0008]

[0009] In the formula, F 1 is the lateral force on the target ship, N 1 C is the moment of horizontal rotation of the target ship around its center of gravity; R and C M are the lateral force coefficient and moment coefficient respectively; ρ is the liquid density, V is the water flow velocity between the two ships, L 1 and T 1 are the length and draft of the target ship respectively; β 1 is the drift angle of the target ship, that is, the yaw angle of the target ship; △β is the angle between the longitudinal sections of the two ships, and a positive value indicates that the lateral distance between the sterns is smaller than the distance between the bows; h 0 represents the initial relative transverse distance between the two ships’ sides; △h is the initial relative transverse distance between the two ships’ sides h 0 The real-time change value, h 0 When increasing, the value is positive;

[0010] Among them, the coefficient A 1 , A 2 , A 3 , A 4 , D 1 , D 2 , D 3 and D 4 as follows:

[0011]

[0012] A 2 =-0.789+0.1(L-1.9) 2 (0.82-0.12L)h 0 -0.12L-0.18

[0013]

[0014] Where, L 2 and T 2 are the length and draft of the other ship respectively; L represents the relative length of the two ships; It represents the relative longitudinal displacement of the two ships' mid-section cross sections; e is a natural constant and π is the circumference of a circle.

[0015] In some embodiments, the relative length L of the two ships is calculated as follows:

[0016]

[0017] Where, L 1 is the captain of the target ship, L 2 is the master of another ship.

[0018] In some of these embodiments, the relative longitudinal displacement of the two midship cross sections The calculation formula is as follows:

[0019]

[0020] Where m represents the longitudinal displacement of the mid-transverse sections of the two ships. If the mid-transverse section of the target ship is behind the mid-transverse section of the other ship, the value is positive.

[0021] In some of these embodiments,

[0022] Where h is the initial distance between the two ships, B 1 Indicates the width of the target ship.

[0023] In some of these embodiments, the vessel is provided with an outward drift angle to resist lateral forces and moments.

[0024] In some of these embodiments, the two vessels are positioned mid-ship during replenishment.

[0025] According to a second aspect of the present invention, a method for optimizing a ship's lateral replenishment position is provided, the method comprising:

[0026] The lateral force F of the target ship is calculated in real time by using the inter-ship force calculation method described in any one of the first aspects. 1 , and then determine the real-time force F of the target ship i ;

[0027] Assume that the target ship has n supply points, and the i-th supply point P i The three-dimensional coordinates of i ,y i ,z i ); According to the center of mass of the target ship (x 0 ,y 0 ,z 0 ), determine the i-th supply point P i The vector r relative to the center of mass i =(xi -x 0 ,y i -y 0 ,z i -z 0 );

[0028] Determine the i-th supply point P i The moment M i =r i ×F i =(x i F y -y i F x ,y i F z -z i F y ,z i F x -x i F z ), where F x 、F y and F z Respectively represent F i The components of the force in the three-dimensional coordinate system;

[0029] Determine the objective function:

[0030]

[0031] In the formula, represents the mean moment of each supply point;

[0032] And set the supply point location range and constraints, where the constraints are as follows:

[0033]

[0034] By minimizing f(x, y, z), the new position of each supply point is solved and the position of the supply point is adjusted.

[0035] In some embodiments, the real-time force F of the target ship is determined. i as follows:

[0036] F i =F 1 -F W -F t -F S

[0037] In the formula, F W F is the lateral force generated by the ship's drift angle to resist the inter-ship effect, t is the pulling or pushing force generated by the manipulator or cable at the supply point, F SIt is the force generated by external disturbances during the replenishment process;

[0038] In some embodiments, the lateral force F W It is expressed as:

[0039]

[0040] Where A is the cross-sectional area of ​​the underwater part of the ship, C is y represents the lateral force coefficient, and U represents the ship speed.

[0041] According to a third aspect of the present invention, there is provided a ship, which is a supply ship or a receiving ship, and which adopts the inter-ship force calculation method described in any one of the first aspects or the ship lateral supply position optimization method described in any one of the second aspects.

[0042] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0043] The inter-ship force calculation method of the present invention completes the calculation of the lateral force and torque of the target ship when the two ships are transversely replenished based on the theory of fluid mechanics and ship maneuvering dynamics. It can help operators predict the dynamic response between ships and optimize the motion control of the ships. The positions of the maximum forces and torques can be found through simulation, thereby avoiding these high-risk areas in actual operations and ensuring the safety and stability of ships in replenishment operations.

[0044] In addition, the ship lateral replenishment position optimization method of the present invention is based on the calculated lateral force of the target ship. By dynamically collecting and adjusting the position of the replenishment point, the torque balance of each point in the replenishment process is ensured, the uneven force problem of the replenishment equipment is reduced, and the safety and reliability of the replenishment operation are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A flow chart of a method for lateral replenishment of an autonomous surface ship taking into account inter-ship effect provided in an embodiment of the present application;

[0046] Figure 2 A schematic diagram of gravitational force and moment between two ships provided in an embodiment of the present application;

[0047] Figure 3 A curve diagram of the lateral interaction force between two ships at different speeds provided in an embodiment of the present application;

[0048] Figure 4 A curve diagram of the interaction torque between two ships at different speeds provided in an embodiment of the present application;

[0049] Figure 5A schematic diagram of a motion state of a non-operating supply ship provided in an embodiment of the present application; wherein: Figure 5 (a) is a schematic diagram of the ship's attraction performance when not in operation. Figure 5 (b) is a simulated ship route map. Figure 5 (c) is a real-life simulation of a navigation simulator;

[0050] Figure 6 A schematic diagram of the motion state of a supply ship with a given torque provided in an embodiment of the present application; wherein: Figure 6 (a) is the ship attraction performance when the moment is given. Figure 6 (b) is a simulated ship route map. Figure 6 (c) is a real-life simulation of a navigation simulator;

[0051] Figure 7 An input interface diagram of a ship-to-ship force calculation system provided in an embodiment of the present application;

[0052] Figure 8 This is a diagram of an output interface of a system for calculating inter-vessel forces provided in an embodiment of the present application. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments provided in this application, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0054] Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in this field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0055] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those of ordinary skill in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0056] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "a", "the" and the like involved in this application do not indicate a quantitative limitation, and may represent the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there may be three relationships, for example, "A and / or B" can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the objects before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0057] The present application provides a method for calculating the inter-ship force and a method for optimizing the lateral replenishment position of a ship, which relates to the field of ship engineering technology, fluid mechanics and interaction force analysis, and in particular to the field of ship simulation and digital modeling technology. Figure 1 As shown, the present application includes: proposing the influence of the inter-ship effect on the ship replenishment during the lateral replenishment of an autonomous surface ship; using Python software to simulate the maneuvering motion during the ship replenishment to complete the calculation of the gravity and torque between the two ships and the system design; using a navigation simulator for virtual simulation; and finding a reasonable safe replenishment location plan for the lateral replenishment of an autonomous surface ship considering the inter-ship effect.

[0058] This application uses rudder angle or dual-jet engine differential adjustment to balance the forces between ships so that they can stably and efficiently perform tracking tasks and prevent autonomous surface ships from colliding with supply ships during the replenishment process. In addition, based on the theory of fluid mechanics and ship maneuvering dynamics, digital simulation and analog simulation are used to analyze the motion state of ships under different working conditions, and the optimal replenishment position between ships is obtained to ensure the safety and efficiency of the replenishment process.

[0059] First, this application proposes the influence of the inter-ship effect on the ship replenishment during the lateral replenishment of autonomous surface ships, and applies the theory of fluid mechanics and ship maneuvering dynamics in traditional ship motion to the practical problem of autonomous surface ship replenishment: In most current studies, researchers regard the autonomous surface ship under study as the motion equation of an object far away from other ships, and the measurement of its related parameters when conducting dynamic or kinematic analysis of autonomous surface ships is mostly based on an autonomous surface ship far away from other ships. However, in actual scene applications, autonomous surface ships will inevitably approach the mother ship. This situation not only occurs during the ship replenishment process, but also in the autonomous ship formation and the mother ship's recovery of the autonomous surface ship, where there will be fluid dynamics and torques interacting between ships.

[0060] The mechanism of generating such forces is analyzed in detail in works such as fluid mechanics and ship operation dynamics. Since this process involves complex mechanical relationships, the forces are simplified here and it is assumed that the center of gravity of the autonomous surface ship is located at the center of the ship. Figure 2 As shown in the figure, when the ships are supplying each other laterally, the two ships will be affected by the same fluid effect as the shore effect, so that both of them will be affected by the force and torque that converges between the two ships. Due to the influence of the superposition of the pressure field around the supply ship, an attraction F is generated between the two ships that makes them approach each other. 1 , and each of them has a moment N of horizontal rotation around the center of gravity 1 To avoid collision between the two ships, both ships should have an outward drift angle. At this time, the ship will generate a moment N to resist the inward turning of the bow. w and an outward force F w .

[0061] In summary, it is inevitable that the autonomous surface ship will be affected by the interaction force between ships during the fuel replenishment process. Therefore, in the research of autonomous surface ship replenishment, autonomous surface ship formation navigation, and autonomous surface ship entering and leaving the mother ship, the attraction F that makes the two close to each other is 1 And the moment N that makes both sides rotate horizontally around their center of gravity 1 It is very necessary to study the calculation and operation scheme.

[0062] like Figure 1As shown, the present application completes the calculation of the gravity and torque between two ships based on the theories of fluid mechanics and ship maneuvering dynamics.

[0063] With reference to books on maneuverability and ship driving and with the help of a model designed by Soviet scientist Dumashek, we studied the experimental data and compiled the following formula:

[0064]

[0065] In the formula, F 1 , N 1 That is, the lateral interaction force (or attractive force) and the moment of this force on the cross section of the supply ship, C R and C M is the interaction force and torque coefficient, ρ is the liquid density, L 1 and T 1 are the length and draft of the ship, V corresponds to the water velocity between the two ships, β 1 is the drift angle of the ship under study (i.e. the yaw angle of the ship under study), Δβ is the angle between the longitudinal sections of the two ships, a positive value indicates that the lateral distance between the sterns is smaller than the distance between the bows, and Δh is the change in the lateral distance (from h 0 Start of lateral distance change).

[0066] Among them, the coefficient A 1 , A 2 , A 3 , A 4 , D 1 , D 2 , D 3 and D 4 as follows:

[0067]

[0068] In the formula, A 1 A coefficient that represents the lateral force between the supply ship and the autonomous surface ship, which depends on the ship length (L), draft (T 2 ), and the distance between the two ships (h 0 ). This formula describes the lateral force between the two ships, which changes with the draft, length and lateral distance of the ships.

[0069] A 2 =-0.789+0.1(L-1.9) 2 (0.82-0.12L)h 0 -0.12L-0.18

[0070] In the formula, A 2 Indicates the correction factor affecting the lateral force, correction A 1The influence of ship length (L) and relative distance (h 0 ). 2 The calculation of response forces has been further adjusted, especially to accommodate ships of different lengths.

[0071]

[0072] In the formula, A 3 It represents the coefficient related to the lateral relative motion between the two ships, and further adjusts the effect of the response force. A3 considers the relative longitudinal displacement (m) between the two ships to affect the distribution of the action.

[0073]

[0074] In the formula, A 4 It is a correction factor for A3, which is mainly used to reduce the calculation task and ensure that the influence of the relative node on a certain moment is correctly reflected. This is a minor modification term used to deal with complex fluid dynamics effects.

[0075]

[0076] Where D 1 A coefficient that represents the transverse moment between ships, which depends on the length (L), draft (T2) and transverse distance (h 0 ). The effects of the relative timing of the two ships and the distance between them on the transverse moment are described, taking into account the geometric characteristics and hydrodynamic parameters of the ships.

[0077]

[0078] Where D 2 Indicates the correction factor affecting the lateral moment, correction D 1 This is a modification parameter, mainly to modify the calculation of D1, especially for ships of different lengths.

[0079]

[0080] Where D 3 The coefficients related to the lateral relative motion between the two ships are expressed, taking into account the effect of the relative timing on the lateral moment, making the moment action more accurate.

[0081]

[0082] Where D 4 It means D 3The correction coefficient further modifies the calculation result of the lateral moment to ensure the accuracy of the calculation. It is mainly used to deal with smaller hydrodynamic effects to ensure the accuracy of the calculation process.

[0083] Furthermore, the remaining parameters are as follows:

[0084]

[0085] In the formula, h 0 represents the initial relative transverse distance between the two ships’ sides; B 1 represents the width of the target ship; h represents the initial distance between the two ships’ sides, and Δh represents the distance h 0 The change in value (when the value increases, it is positive), that is, the distance h between the current moment and the initial moment 0 The change in the distance between the previous and next moments, in other words, 0 The initial distance h is the distance between the sides of the two ships at the initial moment.

[0086]

[0087] In the formula, represents the relative longitudinal displacement of the mid-sections of the two ships; m represents the longitudinal displacement of the mid-sections of the two ships. If the mid-section of the studied ship is behind the mid-section of the partner ship, the value is positive.

[0088]

[0089] Where L represents the relative length of the two ships; β 1 represents the drift angle of the studied ship. If the water current comes from the side without a partner ship, the drift angle is positive. Δγ represents the angle between the longitudinal sections of the two ships. If the transverse distance between the two sterns is less than the transverse distance between the two bows, the angle is positive.

[0090] In the above formula, the angle code 1 of the scales L, B and T corresponds to the ship being studied, and the angle code 2 corresponds to the partner ship. Therefore, both the supply ship and the receiving ship can become the ship being studied, that is, the target ship, and the other ship is the partner ship. In addition, since the forces are mutual, when the forces and moments of the target ship are calculated, the forces and moments of the other ship can also be obtained.

[0091] In this way, the interaction force and moment between the two ships when they are replenished laterally can be calculated.

[0092] In this embodiment, the supply ship is selected as a 903-type supply ship with a length of 171.4 meters, a width of 24.6 meters, a draft of 9 meters, and a full load displacement of 20,530 tons. The power system is 2 diesel engines, dual-shaft dual-propeller propulsion, a cruising speed of 18 knots, a supply speed of 10 to 14 knots, a maximum speed of 20 knots, a maximum wind resistance of 12 levels, and a cruising range of about 10,000 nautical miles. The entire ship can carry 6,600 tons of fuel (including aviation fuel), 750 tons of fresh water (drinking water, boiler water), 630 tons of dry goods (food, ammunition, etc.) and a receiving ship, i.e., an autonomous surface ship, with a length of 30 meters, a width of 5 meters, and a draft of 1 meter. The main dimensions are shown in Table 1.

[0093] Table 1 Main dimensions of supply ships and autonomous surface ships

[0094]

[0095] This embodiment uses Python software to simulate the force between two ships during ship replenishment, including: using the numpy data package in Python to calculate the above formula, and using matplotlib.pylot to simulate the calculated results. Define the function calculate_interaction_forces in the program to calculate the interaction force and torque. Define the function plot_interaction_forces_speed_variation in the program to draw the image of the force and torque changing with the distance under the speed, such as Figure 3 and Figure 4 As shown, the program is designed to calculate the forces acting on the two ships when the distance between them ranges from 0 to 15 meters, and a comparative experiment is conducted at different speeds.

[0096] The program is encapsulated into a force and torque calculation system between the two ships, including: This program is a Python-based GUI simulation tool that uses libraries such as Tkinter, NumPy and Matplotlib to simulate the interaction force and torque between two ships at different speeds and distances. The program creates a graphical user interface through Tkinter. Users can input parameters such as the length, width, draft depth, and ship speed of the supply ship and the supply ship. After clicking the button, the program will calculate the force and torque between the two ships based on the input. The core calculation part uses NumPy for numerical calculations, while Matplotlib is used to draw a curve chart of force and torque changing with the distance between ships. The program visualizes the calculation results and dynamically displays the maximum force and torque and their corresponding distance positions. By integrating complex physical calculations in an intuitive interface, the program facilitates users to quickly obtain mechanical data of interaction between ships through simple interactive operations, and has high operability and extensibility.

[0097] Calculation data of the gravitational forces and moments between two ships Virtual simulation using the nautical simulator includes: The nautical simulator equipment contains a variety of modeling software, including MODEL WIZARD 3D DATABASE EDITING TOOL, which is used to develop and modify high-quality marine simulation area databases and ship models. SHIP MODEL TOOLKIT, for real-time hydrodynamic ship motion simulation for external software applications. SHIP MODEL LIBRARY, which contains more than 600 highly realistic and model-accurate models to date, and the number is still increasing. MATHEMATICAL MODELLING, which is highly accurate, so the simulator can be used as an effective tool for research and feasibility studies, for designing ports, channels and docks, etc. VIRTUAL SHIP YARDSOFTWARE, for developing and editing ship motion, engine and propulsion models, as well as controlling and recording results. SEAGULL3DVISUALIZATION TOOLKIT, for developing real-time 3D applications that realistically simulate the sea surface, waves, wind force and direction. SAILING AREA LIBRARY covers almost all important shipping areas, straits and ports of call, as well as a wide area of ​​inland waterways. CARDINAL SOFTWARE for 3D is used to support 3D flow field analysis and prediction for specific consulting or R&D projects.

[0098] Through the above system analysis, a reasonable operation plan for lateral replenishment of autonomous surface ships is designed and formulated.

[0099] When supplying at different speeds in the middle of the ship, the movement state of the supplied ship is not greatly affected, because although the interaction force between the two ships increases with the increase in speed, the flow force generated by the water flow that balances it also increases. When the supply ship supplies at different positions, the movement state of the receiving ship is relatively large. When the supply ship is far ahead of the receiving ship or far behind the receiving ship, the supply process is more dangerous, while when the middle of the two ships is close to the transverse position, it is conducive to lateral supply.

[0100] When supplying at different ship distances, the main consideration is that when the ship distance is small, the mutual suction and torque are large, which is not conducive to maneuvering and is prone to accidents; when the ship distance is large, the load on the supply device is large. Through simulation calculation, when the ship distance is 10 meters and the speed is 15 meters per second, the forces and torques on the supplied ship are basically balanced when the steering angle of the supplied ship is about -4° to -5°. Figure 5 As shown, Figure 5 (a) shows the motion trajectory of the ship model when the ship takes countermeasures in the python digital simulation experiment. Since this force is used to resist the attraction between the two ships, the route will produce certain error fluctuations during the replenishment process. Figure 5(b) and (c) in the figure respectively show the ship's trajectory diagram and the ship model simulation real-life image on the ship navigation simulator.

[0101] Based on the above-mentioned lateral force calculation, this application proposes a dynamic replenishment position optimization system based on real-time collected force data. The system obtains the force parameters of each key position in the replenishment process through sensors, and uses real-time optimization algorithms to comprehensively analyze these data, so as to automatically and dynamically adjust the replenishment position when the ship or sea conditions change, thereby reducing the uneven force between ships. By optimizing the distribution of replenishment positions, the system can enhance the stability of replenishment under unstable sea conditions, thereby significantly improving the efficiency and safety of replenishment. This system is suitable for a variety of replenishment locations and different types of ships, and can achieve safer and more reliable replenishment operations in complex environments.

[0102] Assume that there are n key supply locations for the supply equipment (such as robotic arms, cables, etc.), respectively represented by P i (x i ,y i ,z i ) represents the three-dimensional coordinates of the i-th position. The real-time force information is the force F i , force F i By F i =F 1 -F W -F t -F S Calculated, where F 1 is the attraction caused by the inter-ship effect, F W F is the lateral force generated by the ship's drift angle to resist the inter-ship effect, t is the pulling or pushing force generated by the robot arm or cable, F S It is the force generated by external interference during the replenishment process of the ship, which can be measured by sensors.

[0103] Based on the theory of ship maneuvering mechanics, the lateral force F W It can be expressed as:

[0104]

[0105] Where A is the cross-sectional area of ​​the underwater part of the ship, C y Indicates the lateral force coefficient, which is related to the drift angle and the rudder angle. The lateral force coefficient C y It is usually determined by experimental data or empirical formula, and U represents the ship speed (m / s).

[0106] Set up constraints:

[0107]

[0108] Among them, the moment Mi Calculated by the following formula:

[0109] M i =r i ×F i =(x i F y -y i F x ,y i F z -z i F y ,z i F x -x i F z )

[0110] Among them, F x 、F y and F z They represent the force components of the supply point in the three-dimensional coordinate system, r i It is the supply point P i (x i ,y i ,z i ) is the vector relative to the center of mass of the ship, r i =(x i -x 0 ,y i -y 0 ,z i -z 0 ), (x 0 ,y 0 ,z 0 ) are the coordinates of the centroid reference point.

[0111] In addition, the location range of the supply point needs to be set and cannot exceed the hull range.

[0112] When the ship or sea conditions change, the forces collected in real time will change. The replenishment position is dynamically adjusted through the optimization algorithm to achieve force balance under the new mechanical conditions. The algorithm process is as follows:

[0113] (1) Initialization parameters: Read the force F at each position i and P i (x i ,y i ,z i )coordinate.

[0114] (2) Constructing the objective function: With uniform force as the goal, construct the objective function f(x, y, z) to minimize the force difference at all key positions. The objective function can be defined as:

[0115]

[0116] in, is the mean value of the torque at each position. Assuming there are n supply points, the torque M of each supply point is i =(M ix ,M iy ,M iz ),but:

[0117]

[0118] (3) Solving the optimal position: Use the method of minimizing f(x, y, z) (such as gradient descent, particle swarm algorithm, genetic algorithm, etc.) to find the new supply position coordinates.

[0119] (4) Update the supply point: Adjust the position of the supply point according to the new coordinates to ensure that the next operation meets the balance condition.

[0120] (5) Iteration: Execute the above steps repeatedly, monitor and adjust the location of the supply point in real time to adapt to dynamic environmental changes.

[0121] The system dynamically collects and adjusts the replenishment position to ensure the balance of forces and moments at each point during the replenishment process, reduce the problem of uneven force on the replenishment equipment, and improve the safety and reliability of the replenishment operation. The system has significantly improved safety and adaptability in practical applications and can be used for ship replenishment operations in complex sea conditions.

[0122] In summary, this application first proposes to calculate the gravity and moment between two ships based on the theory of fluid mechanics and ship maneuvering dynamics:

[0123] In the visualization results of using Python program to calculate the gravity and torque between two ships based on the theory of fluid mechanics and ship maneuvering dynamics, the most intuitive are two curve graphs, see Figure 3 and Figure 4 , which respectively show the interaction forces and moments between the two ships at different speeds as the lateral distance changes. These graphs reflect the important dynamic characteristics of autonomous surface ships during lateral replenishment operations.

[0124] Figure 3The force intensity is shown as the distance between the two ships changes. When the lateral distance between the two ships is close, the force is usually large because the hydrodynamic interference between the ships is significant and there is a strong fluid interaction. This force can be expressed as thrust or suction, affecting the attitude and balance of the ship and may cause unstable lateral motion. As the distance between the ships increases, the force gradually decreases, indicating that the interference effect of the ship decays with the increase of distance. It is also particularly obvious in the image. When the distance between the two ships is greater than 10m and the speed is less than 20m / s, the force between the two ships is basically close to zero, but as the distance between the two ships gradually decreases, the force between the two ships shows a sharp upward trend within 6 meters. When the distance between the two ships is within 1m, the force between the two ships can reach 300~400N when the speed of the two ships reaches 10m / s, and when the speed between the two ships reaches 20m / s, the force between the two ships can reach more than 600N.

[0125] Figure 4 The figure shows the torque curve as the distance changes. The torque reflects the rotation trend caused by the lateral action between the two ships, which is particularly important for the direction control of the ship during the replenishment operation. The change of torque directly affects whether the ship can maintain its course and stability during the lateral replenishment process. When the torque is too large, it may cause the ship to deflect and increase the difficulty of maneuvering. Therefore, understanding the distribution of torque is of great significance for the heading control of autonomous ships. When the distance between the two ships is greater than 10m, the torque curve is very stable in performance, and there is no significant change in the slope. The two ships can basically maintain a good parallel state, but when the distance between the two ships is less than 6m, the torque of the ship changes sharply. When the two ships are parallel at 10m / s, the torque between the two ships can reach 500N*m. When the speed of the two ships reaches 20m / s, the torque can reach 2000N*m and even the bow shake may occur.

[0126] In summary, combined with the background of lateral replenishment of autonomous surface ships, accurate calculation and visualization of interaction forces and moments can help operators predict the dynamic response between ships and optimize the motion control of ships. Through simulation results, users can find the location of maximum forces and moments, thereby avoiding these high-risk areas in actual operations and ensuring the safety and stability of ships in replenishment operations.

[0127] Then, Python software is used to simulate the force between the two ships during ship replenishment:

[0128] When an autonomous surface ship performs a lateral replenishment mission at sea, it can be assumed that two ships (the replenishment ship and the autonomous surface ship) are used. The first ship is maneuvered according to the heading, while the second ship is maneuvered according to the longitudinal and lateral displacement relative to the receiving cargo ship to maintain a given distance between the two ships' sides and make the mid-longitudinal sections of the two ships approximately parallel in a straight line. However, this ideal situation is difficult to produce in the actual replenishment process. When the two ships approach each other, the influence of the force between the two ships will cause the need to control the forces and moments of both ships during the replenishment process.

[0129] like Figure 5 As shown in the figure, the supplied ship does not consider the inter-ship effect and uses a simple trajectory tracking algorithm to supply during the parallel process of the two ships. It can be seen that when the two ships are far apart, the motion trajectories of the two ships meet the needs of ship supply tracking, and the supplied ship is in an overtaking state. However, when it reaches the middle of the supply ship, due to the high speed of the ship and the distance between the two ships gradually less than 10m, and no measures are taken to resist the inter-ship force, the two ships will inevitably collide. Figure 5 (a) shows the trajectory of the ship model in the Python digital simulation experiment when the ship does not take any countermeasures. Figure 5 (b) and (c) in the figure respectively show the ship's trajectory diagram and the ship model simulation real-life image on the ship navigation simulator.

[0130] like Figure 6 As shown in the figure, when the supply ship is in the overtaking state, when it travels to the middle of the supply ship, due to the high speed of the ship and the distance between the two ships gradually becoming less than 10m, measures are taken to resist the force between the ships, and the trajectory of the supply ship shows small fluctuations. This fluctuation is to resist the force between the ships, so the two ships will not collide. Figure 6 (a) shows the trajectory of the ship model in the Python digital simulation experiment when the ship does not take any countermeasures. Figure 6 (b) and (c) in the figure respectively show the ship's trajectory diagram and the ship model simulation real-life image on the ship navigation simulator.

[0131] Finally, the program is packaged into a force test system between two ships:

[0132] The program is called ShipInteraction, and it can calculate the interaction forces and moments when two ships are replenished laterally, such as Figure 7 and Figure 8As shown. Users input ship parameters (such as size and draft) as well as relative distance and speed, and the program can calculate the attractive force and torque and perform dynamic simulation. It contains two functions: calculate_interaction_forces for mechanical calculations and plot_interaction_forces for visualizing results. Users input data through the GUI, and the program calculates and displays the curves of force and torque changing with distance, as well as the position and value of the maximum value to help assess risks. The program helps users understand the dynamic response of ships, optimize navigation control, and reduce replenishment risks.

[0133] Based on the above-mentioned method embodiment, the present application also provides a ship, which can be a supply ship or a receiving ship. The ship adopts the above-mentioned inter-ship force calculation method to calculate the inter-ship force or adopts the above-mentioned ship lateral supply position optimization method to optimize the supply point position.

[0134] It should be pointed out that the technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not 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. In addition, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, and two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0135] It is easy for a person skilled in the art to understand that the above-mentioned embodiments only express several implementation methods of the present application, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for calculating inter-ship forces, characterized in that: The method includes: The lateral force and moment of the target ship when the two ships are supplementing each other laterally are calculated by the following formula: Where F1 is the lateral force of the target ship, N1 is the moment of horizontal rotation of the target ship around the center of gravity; C R and C M are the lateral force coefficient and moment coefficient respectively; ρ is the liquid density, V is the water flow velocity between the two ships, L1 and T1 are the length and draft of the target ship respectively; β1 is the drift angle of the target ship, that is, the yaw angle of the target ship; △β is the angle between the longitudinal sections of the two ships, and a positive value indicates that the lateral distance between the sterns is smaller than the distance between the bows; h0 indicates the initial relative lateral distance between the sides of the two ships; △h is the real-time change value of the initial relative lateral distance h0 between the sides of the two ships, and this value is positive when h0 increases; Among them, the coefficients A1, A2, A3, A4, D1, D2, D3 and D4 are as follows: <h2 style=";text-align:left;direction:ltr">A2 = -0.789 + 0.1 (L - 1.9)<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> (0.82-0.12L)h0<h2 style=";text-align:left;direction:ltr"> -0.12L-0.18 Where L2 and T2 are the length and draft of the other ship respectively; L represents the relative length of the two ships; It represents the relative longitudinal displacement of the two ships' mid-section cross sections; e is a natural constant and π is the circumference of a circle.

2. The method for calculating inter-vessel forces according to claim 1, characterized in that: The calculation formula of the relative length L of the two ships is as follows: Where L1 is the length of the target ship and L2 is the length of the other ship.

3. The method for calculating inter-vessel forces according to claim 1, characterized in that: Relative longitudinal displacement of the mid-ship cross sections The calculation formula is as follows: Where m represents the longitudinal displacement of the mid-transverse sections of the two ships. If the mid-transverse section of the target ship is behind the mid-transverse section of the other ship, the value is positive.

4. The method for calculating inter-vessel forces according to claim 1, characterized in that: Where h is the initial distance between the two ships’ sides, and B1 is the width of the target ship.

5. The method for lateral replenishment of autonomous surface ships considering inter-ship effects according to claim 1 is characterized in that: The ship is given an outward drift angle to resist lateral forces and moments.

6. The method for lateral replenishment of autonomous surface ships considering inter-ship effects according to claim 1 is characterized in that: When supplying, keep the middle parts of the two ships in the transverse position.

7. A method for optimizing the position of ship lateral replenishment, characterized in that: The method includes: By using the method for calculating the inter-ship force according to any one of claims 1 to 6, the lateral force F1 of the target ship is calculated in real time, and then the real-time force F of the target ship is determined. i ; Assume that the target ship has n supply points, and the i-th supply point P i The three-dimensional coordinates of i ,y i ,z i ); According to the center of mass of the target ship (x0, y0, z0), determine the i-th supply point P i Vector r relative to the center of mass i =(x i -x0,y i -y0,z i -z0); Determine the i-th supply point P i The moment M i =r i ×F i =(x i F y -y i F x ,y i F z -z i F y ,z i F x -x i F z ), where F x 、F y and F z Respectively represent F i The components of the force in the three-dimensional coordinate system; Determine the objective function: In the formula, represents the mean moment of each supply point; And set the supply point location range and constraints, where the constraints are as follows: By minimizing f(x, y, z), the new position of each supply point is solved and the position of the supply point is adjusted.

8. The method for optimizing the ship's lateral replenishment position according to claim 7, characterized in that: Determine the real-time force F of the target ship i as follows: F i =F1-F W -F t -F S In the formula, F W F is the lateral force generated by the ship's drift angle to resist the inter-ship effect, t is the pulling or pushing force generated by the manipulator or cable at the supply point, F S It is the force generated by external interference during the replenishment process.

9. The method for optimizing the ship's lateral replenishment position according to claim 8, characterized in that: Lateral force F W It is expressed as: Where A is the cross-sectional area of ​​the underwater part of the ship, C is y represents the lateral force coefficient, and U represents the ship speed.

10. A ship, characterized in that: The ship is a supply ship or a receiving ship, and the ship adopts the inter-ship force calculation method described in any one of claims 1 to 6 or the ship lateral supply position optimization method described in any one of claims 7 to 9.

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