Embedded high fidelity variable stiffness fender for multi-ship cooperative operation model test

Abstract

The application discloses an embedded high-fidelity variable stiffness fender device for multi-ship cooperative operation model test, which comprises an embedded box unit, a linear guide unit, a movable pressure-bearing unit and a hybrid elastic unit. By embedding the core mechanical structure into the model ship body, the problem of space interference under the narrow gap working condition is solved. The parallel combination structure of high-fidelity spiral springs and gas springs is adopted to accurately reproduce the nonlinear mechanical properties of the linear growth-constant force energy absorption of the real rubber fender. The linear guide unit realizes multi-degree-of-freedom motion decoupling, and the high-precision force sensor ensures the authenticity of the collision force measurement. The application guarantees the geometric similarity and mechanical fidelity of the model test, provides accurate data support for the safety evaluation of multi-ship cooperative operation, and is suitable for the model test scene related to deep-sea ultra-large module installation.

Description

Technical Field

[0001] This invention belongs to the technical field of marine engineering physical model test equipment, specifically relating to an embedded high-fidelity variable stiffness fender device for multi-ship collaborative operation model testing, a variable stiffness characteristic simulation method, and a three-ship collaborative operation model test method. Background Technology

[0002] As offshore oil and gas resource development expands into deeper waters, the weight and size of offshore superstructure modules continue to increase. Traditional single-vessel lifting and floating installation technologies are no longer sufficient to meet the installation and dismantling needs of ultra-large modules. Multi-vessel collaborative floating operation technology has emerged, with three-vessel collaborative load transfer being a typical application: a central transport barge loads the module, while two side work vessels, through robotic arm mechanisms and ballast water regulation, transfer the module load from the barge to the work vessels. During this process, the lateral spacing between the three vessels is extremely critical. The robotic arm's load-bearing capacity is inversely proportional to its outrigger length; excessive spacing can cause the robotic arm root to experience extremely large bending moments and shear forces, easily leading to structural damage or even catastrophic accidents. Therefore, maintaining an extremely small spacing is essential for operation.

[0003] However, close-range collaborative operations are extremely risky, and ship collisions could cause serious damage. Because on-site maritime operations are limited by ship schedules and weather windows, and daily rates are expensive, opportunities are often limited to a single day. Errors in the plan or equipment failures can lead to huge economic losses and irreversible project delays. Therefore, physical model tests (pool tests) are necessary before on-site operations. Based on the Froude similarity criterion, a scaled-down model is constructed to reproduce the marine environment in a wave pool, exploring the motion response characteristics of multiple ships, identifying risks, and verifying the feasibility of the construction plan.

[0004] However, existing model testing techniques face two major insurmountable problems in simulating multi-ship collaborative operations in "narrow gaps":

[0005] First, there is the problem of installation and boundary condition distortion caused by limited physical space. After scaling down according to the geometric similarity criterion, the physical distance between model ships is usually only a few centimeters or even smaller. Existing general-purpose model sway fenders are mostly external structures, and their thickness often exceeds the design clearance, making installation impossible; even if forced, it will change the initial spacing of the hulls, destroying the geometric similarity boundary conditions of the test. In addition, external fenders will generate additional flow resistance and vortex-induced effects in waves, interfering with the accuracy of the measurement of the hull's hydrodynamic coefficients.

[0006] Secondly, there is the problem of distortion in nonlinear stiffness simulation. Real engineering rubber fenders exhibit significant nonlinear mechanical characteristics: the reaction force initially increases linearly with compression, and after reaching the maximum reaction force, structural buckling occurs, entering a buckling energy absorption plateau period where "displacement increases but reaction force remains relatively constant." This is a critical stage for protecting the robotic arm and the hull structure. However, existing model tests mostly use ordinary linear helical springs to simulate fenders, whose force values ​​continuously increase linearly with compression. This fails to reproduce the "constant force energy absorption" plateau stage, nor can it simulate the overall nonlinear variable stiffness characteristics of real fenders. Consequently, the collision loads measured in the tests deviate significantly from the actual values, making it impossible to provide reliable safety assessment data for actual ship operations.

[0007] Therefore, it is necessary to develop an embedded model test device that can adapt to extremely narrow ship spacing and can simulate the variable stiffness characteristics of real fenders with "first linear growth and then constant reaction force" with high fidelity. This is an urgent need to ensure the success of multi-ship collaborative operation model tests and to ensure the safety and economy of actual ship operations. Summary of the Invention

[0008] This invention proposes an embedded high-fidelity variable stiffness fender device, a variable stiffness characteristic simulation method, and a three-ship collaborative operation model test method for multi-ship collaborative operation model testing. The aim is to address the problems existing in current multi-ship collaborative operation model tests regarding fender devices: 1) External structures occupy external space, making installation impossible or disrupting geometrically similar boundary conditions under narrow-gap conditions; 2) A single linear spring cannot reproduce the nonlinear variable stiffness characteristics of a real fender, resulting in insufficient constraint at low compression and excessive stiffness at high compression; 3) It cannot simulate the "constant force energy absorption" platform stage after real fender buckling, leading to distorted collision load measurements and affecting operational safety assessments.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] An embedded high-fidelity variable stiffness fender device for multi-ship collaborative operation model testing includes an embedded box unit, a linear guide unit, a movable pressure-bearing unit, and a hybrid elastic unit;

[0011] The embedded housing unit includes a mounting housing, a fixed base plate, and a mounting flange. The mounting housing has a rectangular box-shaped structure. The fixed base plate is fixed to the bottom of the mounting housing. The mounting flange is located at the front opening of the mounting housing and is bolted to the hull plate. The linear guide unit includes two parallel precision guide shafts and matching linear bearings. The precision guide shafts are fixed to the fixed base plate, and the linear bearings are installed in the movable pressure-bearing unit.

[0012] The movable pressure-bearing unit includes an external anti-collision plate, a high-precision force sensor, and an internal sliding bracket. The high-precision force sensor is connected in series between the external anti-collision plate and the internal sliding bracket. The hybrid elastic unit includes a high-fidelity helical spring and a gas spring, which are arranged in parallel between the internal sliding bracket and the fixed base plate.

[0013] In a preferred embodiment of the present invention, the mounting box is made of transparent acrylic material or high-strength engineering plastic, and its outer wall dimensions are adapted to the mounting slot reserved on the side of the model ship. The front opening of the box is used to accommodate the movement of the movable pressure-bearing unit.

[0014] In a preferred embodiment of the present invention, the fixed base plate is a high-rigidity metal plate with positioning holes and threaded holes for fixing the base of the precision guide shaft, the high-fidelity helical spring and the gas spring.

[0015] In a preferred embodiment of the present invention, a waterproof gasket or silicone is provided between the mounting flange and the hull plate to achieve a waterproof seal and prevent seawater from the wave pool from entering the interior of the hull.

[0016] In a preferred embodiment of the present invention, the precision guide shaft is made of high-strength alloy steel, and its surface is hardened and polished, and it has a clearance fit with the linear bearing.

[0017] In a preferred embodiment of the present invention, the high-precision force sensor is a high-range, high-precision pressure force sensor that directly measures external collision force.

[0018] In a preferred embodiment of the present invention, the high-fidelity helical spring is a high-precision mold spring with a stiffness coefficient that has been rigorously calibrated. It provides linear restoring force in the initial stage of compression, simulating the elastic behavior of the linear growth stage of a real fender.

[0019] In a preferred embodiment of the present invention, the gas spring is filled with high-pressure nitrogen and outputs an approximately constant thrust within a specific stroke range, with a fluctuation range of ≤±3%, simulating the constant force energy absorption stage of a real fender.

[0020] This invention provides a method for simulating the variable stiffness characteristics based on the above-mentioned device, comprising the following steps:

[0021] Step S1: Parameter configuration. Based on the model scaling ratio, calculate the initial stiffness and maximum force parameters of the target model fender, select suitable high-fidelity helical springs and gas springs, construct a parallel elastic system, and calculate the goodness-of-fit R. 2 Ensure that the goodness of fit is not less than 94%;

[0022] Step S2, the linear simulation stage: when the external hull contacts and pushes the external anti-collision plate to produce a small displacement, the high-fidelity helical spring in the hybrid elastic element plays a dominant role, and the total reaction force of the system is F=K. spring •x, Kspring Let x be the stiffness of the helical spring and x be the compression displacement, simulating the linear growth stage of a real fender;

[0023] Step S3, constant force simulation stage: when the compression displacement reaches the set threshold and the force of the high-fidelity helical spring accumulates to the maximum, the gas spring enters the main working section. Its output of approximately constant thrust is superimposed with the helical spring force, so that the total reaction force of the system remains relatively constant. Even if the displacement continues to increase, the reaction force does not change significantly, simulating the buckling energy absorption platform stage of a real fender.

[0024] This invention provides a test method for a three-ship cooperative operation model based on the above-mentioned device, comprising the following steps:

[0025] Step T1: Groove the hull. At the fender installation position of the middle transport barge model, cut a rectangular through hole according to the cross-sectional dimensions of the installation box.

[0026] Step T2, embedding and fixing: push the fender device into the hull as a whole, adjust the position of the device to ensure that the outer surface of the external anti-collision plate is flush with the outer surface of the side of the hull, and fix it to the hull plate with bolts through the bolt holes of the mounting flange;

[0027] Step T3, sealing treatment: lay a waterproof gasket or apply silicone between the installation flange and the hull plate, compact it and tighten the bolts to ensure the watertightness of the connection and prevent seawater from the wave pool from entering the hull.

[0028] Step T4, spatial verification: Measure the net distance between the middle transport barge model and the two side workboat models to confirm that the distance conforms to the design scale value and has no deviation;

[0029] Step T5: Test run. Start the wave generator to simulate the marine environment and monitor the relative motion of the three ships. When the distance between the ships decreases to the contact threshold, record the collision force data and ship motion response data from the high-precision force sensor to complete the test.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. Solving the problem of interference in narrow gap space: The embedded design hides the core mechanical structure inside the hull, with only the external anti-collision plate flush with the outer plate of the hull, without occupying external space. This ensures that the spacing between the model ships strictly conforms to the scale of the actual ship design, guaranteeing geometric similarity. At the same time, it avoids the flow resistance and vortex-induced effect generated by the external structure, ensuring accurate measurement of hydrodynamic coefficients.

[0032] 2. High-fidelity simulation of nonlinear stiffness characteristics: The parallel structure of helical springs and gas springs accurately reproduces the full-stage mechanical behavior of the real fender from linear growth to constant force energy absorption through the principle of stiffness superposition, with a goodness of fit of over 94%, solving the problem of distortion in simulation of a single linear spring.

[0033] 3. Accurate measurement of collision force: The front-mounted, series-connected high-precision force sensor directly captures the collision signal, and the measured value is completely consistent with the actual interaction force between the hulls, avoiding the error caused by bottom measurement and providing reliable data for safety assessment.

[0034] 4. Motion decoupling protection for elastic elements: The linear guide unit constrains the direction of motion, counteracts lateral forces and bending moments, and ensures that the elastic elements only bear axial pressure, avoiding damage and extending the service life of the device.

[0035] 5. Easy installation and maintenance: The integrated design facilitates overall embedding and disassembly, and the transparent acrylic mounting box makes it easy to observe the status of internal components, reducing maintenance costs. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments or prior art, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This invention provides a schematic diagram of the installation position of an embedded high-fidelity variable stiffness fender device for multi-ship collaborative operation model testing.

[0038] Figure 2 This is a schematic diagram of an embedded high-fidelity variable stiffness fender device for multi-ship collaborative operation model testing, provided by an embodiment of the present invention.

[0039] Figure 3 This is an exploded view of an embedded high-fidelity variable stiffness fender device for multi-ship collaborative operation model testing, provided by an embodiment of the present invention.

[0040] Figure 4 This invention provides a top view of an embedded high-fidelity variable stiffness fender device for multi-ship collaborative operation model testing.

[0041] Figure 5 This invention provides a deformation-force relationship diagram of an embedded high-fidelity variable stiffness fender for multi-ship collaborative operation model testing, comparing the target value with the simulated value. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The terms "upper," "lower," "front," "rear," "left," and "right," etc., used when describing the installation position or direction of the structure or components in this embodiment are based on the orientation shown in the accompanying drawings. They are merely for convenience of description, used to distinguish the relative positions of various components or directions, and do not represent the orientation of the system or functional components in this embodiment during use.

[0043] This invention provides an embedded high-fidelity variable stiffness fender device for multi-ship collaborative operation model testing, which is particularly suitable for model testing of "narrow gap" operation scenarios such as three-ship collaborative load transfer, and can accurately simulate the nonlinear mechanical behavior of real ship fenders. Figure 1 The embedded high-fidelity variable stiffness fender is located on both sides of the hull of the middle transport barge 11 in the three-ship collaborative operation model. This corresponds to the docking area between the middle transport barge 11 and the port and starboard installation vessels 12 and 13 during the actual three-ship collaborative load transfer operation. This location is a pre-designed installation interface on the side of the model hull, precisely within the surplus empty space area of ​​the hull's waterline. It neither exceeds the hull's external contour nor occupies the design clearance between the vessels. It accurately corresponds to the lateral position where the two working vessels may come into contact or collide, ensuring collision protection requirements when the three vessels maintain a very small distance during operation.

[0044] like Figure 2 , Figure 3 and Figure 4 As shown, an embedded high-fidelity variable stiffness fender device for multi-ship collaborative operation model testing includes an embedded box unit, a linear guide unit, a movable pressure-bearing unit, and a hybrid elastic unit. After the units are integrated and assembled, they are embedded into the interior of the model ship hull, with only the external anti-collision plate 6 flush with the outer plate of the ship hull.

[0045] The embedded enclosure unit serves as the mounting base and load-bearing frame for the device. The embedded enclosure unit includes a mounting enclosure 1, a fixing base plate 2, and a mounting flange 3. The mounting enclosure 1 has a rectangular box-shaped structure. The fixing base plate 2 is fixed to the bottom of the interior of the mounting enclosure 1. The mounting flange 3 is located at the front opening of the mounting enclosure 1 and is bolted to the hull plate.

[0046] The linear guide unit is used to constrain the motion direction of the movable pressure-bearing unit and decouple multi-degree-of-freedom motion. The linear guide unit includes two parallel precision guide shafts 4 and matching linear bearings 5. The precision guide shafts 4 are fixed to the fixed base plate 2, and the linear bearings 5 ​​are installed on the movable pressure-bearing unit.

[0047] The movable pressure-bearing unit serves as a force receiving and transmitting component. It includes an external anti-collision plate 6, a high-precision force sensor 7, and an internal sliding bracket 8. The high-precision force sensor 7 is connected in series between the external anti-collision plate 6 and the internal sliding bracket 8.

[0048] The hybrid elastic unit adopts a parallel combination structure, consisting of two elastic elements with different characteristics, to simulate the nonlinear variable stiffness characteristics of a real fender. The hybrid elastic unit includes a high-fidelity helical spring 9 and a gas spring 10, which are arranged in parallel between the internal sliding bracket 8 and the fixed base plate 2.

[0049] Mounting housing 1 is made of transparent acrylic or high-strength engineering plastic. Its outer wall dimensions are adapted to the mounting slots pre-drilled on the side of the model boat. The front opening of the housing is used to accommodate the movement of the movable pressure-bearing unit. The fixing base plate 2 is a high-rigidity metal plate with positioning holes and threaded holes for fixing the base of the precision guide shaft 4, the high-fidelity helical spring 9, and the gas spring 10. The mounting flange 3 is located at the front opening of the mounting housing 1, extending outward to form a flange. The flange has bolt holes for bolting to the outer plate of the model boat. A waterproof gasket or silicone sealant is placed between the flange and the hull plate to achieve a waterproof seal.

[0050] Two precision guide shafts 4 are provided, parallel and symmetrically distributed on both sides inside the mounting housing 1. Their northern ends are fixed to the fixed base plate 2, while their southern ends are suspended pointing towards the opening of the housing. The precision guide shafts 4 are made of high-strength alloy steel, and their surfaces are hardened and polished. The precision guide shafts 4 and linear bearings 5 ​​are clearance-fitted. The linear bearings 5 ​​are installed on both sides of the internal sliding bracket 8 of the movable pressure-bearing unit, with a clearance fit to the precision guide shafts 4, ensuring that the movable pressure-bearing unit can only move linearly along the hull's transverse direction (Sway direction) along the guide shaft axis, thus counteracting the effects of shear force and bending moment on the elastic element.

[0051] The external anti-collision plate 6 is a rectangular flat plate made of high-strength aluminum alloy. After installation, its outer surface is flush with or only protrudes 1-2mm from the side hull of the model boat, directly contacting the other vessel and transmitting the collision force. The high-precision force sensor 7 is a high-range, high-precision pressure-type force sensor, installed in series between the external anti-collision plate 6 and the internal sliding bracket 8. The front end of the sensor is rigidly connected to the back of the external anti-collision plate 6 by bolts, and the rear end is fixedly connected to the internal sliding bracket 8, ensuring that all external collision force flows through the sensor and realizing direct measurement of the collision force. The internal sliding bracket 8 is made of alloy steel in one piece. The front end is fixedly connected to the high-precision force sensor 7, and the two sides have openings to install linear bearings 5, which are sleeved on the precision guide shaft 4. The rear end abuts against the hybrid elastic unit, which is used to evenly distribute the pressure transmitted from the external anti-collision plate to the hybrid elastic unit.

[0052] Two sets of high-fidelity helical springs 9 are symmetrically arranged between the internal sliding bracket 8 and the fixed base plate 2. High-precision molded springs are selected, and their stiffness coefficients are rigorously calibrated. They provide linear restoring force in the initial stage of compression, simulating the elastic behavior of a real fender during the linear growth phase. In this embodiment, the helical springs play a dominant role in the initial stage of compression, providing linear restoring force and simulating the elastic behavior of a real rubber fender under small deformations.

[0053] Two sets of gas springs 10 are arranged in parallel with high-fidelity helical springs 9. The cylinder end of each gas spring 10 is bolted to the fixed base plate 2, and the piston rod end abuts against the back of the internal sliding bracket 8. The gas spring 10 is filled with high-pressure nitrogen (an inert gas). Through a specially designed air chamber structure, it outputs an approximately constant thrust within a specific stroke range, with a fluctuation range of ≤±3%, simulating the constant force energy absorption stage after buckling of a real fender. In this embodiment, when the compression exceeds a certain threshold (the helical spring force accumulates to a certain level), the gas spring enters its main working section. At this point, even if the displacement continues to increase, the increment of the reaction force provided by the gas spring is minimal, thus simulating the characteristics of a real fender's "post-buckling reaction platform."

[0054] This invention provides a method for simulating the variable stiffness characteristics based on the above-mentioned device, comprising the following steps:

[0055] Step S1: Parameter configuration. Based on the model scaling ratio, calculate the initial stiffness and maximum force parameters of the target model fender. Select suitable high-fidelity helical spring 9 and gas spring 10 to construct a parallel elastic system and calculate the goodness-of-fit R. 2 To ensure a goodness of fit of no less than 94%.

[0056] like Figure 5 As shown in Figure 5, the initial stiffness required for the target model fender is calculated based on the model's scaling ratio and compared with the target value. The maximum force is 10.4553 N. To determine the system's fit, a goodness-of-fit metric is introduced. For reference, the calculation formula is as follows: ,in For the sum of squared residuals, The sum of squared deviations is used to calculate the goodness of fit, which is 94.48%, indicating a good fit.

[0057] Step S2, the linear simulation stage: when the external hull contacts and pushes the external anti-collision plate 6 to produce a small displacement, the high-fidelity helical spring 9 in the hybrid elastic element plays a dominant role, and the total reaction force of the system is F=K. spring •x, K spring Let x be the stiffness of the helical spring and x be the compression displacement, simulating the linear growth stage of a real fender.

[0058] Step S3, constant force simulation stage: when the compression displacement reaches the set threshold and the force of the high-fidelity helical spring 9 accumulates to the maximum, the gas spring 10 enters the main working section. Its output of approximately constant thrust is superimposed with the helical spring force, so that the total reaction force of the system remains relatively constant. Even if the displacement continues to increase, the reaction force does not change significantly, simulating the buckling energy absorption platform stage of a real fender.

[0059] This embodiment details how to use the above-mentioned device to achieve a high-fidelity simulation of the nonlinear mechanical curve of a real fender. The typical stress curve of a real marine engineering rubber fender is divided into three stages: Stage I (linear segment): In the initial contact stage, the reaction force increases rapidly and linearly with the compression. Stage II (gas spring energy absorption segment): After reaching the maximum force, the rubber structure buckles, and the reaction force remains relatively constant within a large displacement range (the main stage of gas spring energy absorption).

[0060] This invention provides a test method for a three-ship cooperative operation model based on the above-mentioned device, comprising the following steps:

[0061] Step T1: Groove the hull. At the fender installation position of the middle transport barge model, cut a rectangular through hole according to the cross-sectional dimensions of the installation box 1.

[0062] Step T2, embedding and fixing: push the fender device into the hull as a whole, adjust the position of the device to ensure that the outer surface of the external anti-collision plate 6 is flush with the outer surface of the side of the hull, and fix it to the hull plate with bolts through the bolt holes of the mounting flange 3.

[0063] Step T3, sealing treatment: lay a waterproof gasket or apply silicone between the installation flange 3 and the hull plate, compact it and tighten the bolts to ensure the watertightness of the connection and prevent seawater from the wave pool from entering the hull.

[0064] Step T4, spatial verification: Measure the net distance between the middle transport barge model and the two side workboat models to confirm that the distance conforms to the design scale value and has no deviation;

[0065] Step T5: Test run. Start the wave generator to simulate the marine environment and monitor the relative motion of the three ships. When the distance between the ships is reduced to the contact threshold, record the collision force data of the high-precision force sensor 7 and the ship motion response data to complete the test.

[0066] In this embodiment, the two ships move relative to each other under the wave-generating action of the wave generator. When the gap narrows to 0mm, the working ship contacts the external anti-collision plate of the device. The internal guiding unit of the device ensures that even when the waves cause the ship to pitch, the device will not jam, but will smoothly compress along the normal direction. The application of the device in actual narrow-gap model tests highlights the advantages of the embedded design.

[0067] In summary, regarding the spatial interference problem caused by the scaling effect, in model tests of multi-ship collaborative operations (especially three-ship load transfer), after scaling down according to the geometric similarity criterion, the physical gap between the model hulls is usually only a few centimeters due to the "narrow gap" design of the actual ship operation. The thickness of the traditional external model fender itself is often greater than this gap, making installation impossible, or forcibly installing it changes the initial design distance between the hulls, severely damaging the geometric similarity boundary conditions of the test. This invention adopts an embedded box structure design based on the hull side slots: abandoning the traditional external mounting mode, it designs an integrated device including a mounting box, internal guides, and elastic elements. This device is embedded entirely inside the model hull, with only the contact panel flush with the outer plate of the hull, significantly reducing the volume of the fender on the outside of the hull. Using the principle of space displacement: utilizing the extra cabin space inside the model hull due to the draft design, the main mechanical structure of the fender (springs, guide pillars, base) is "hidden" inside the hull's waterline. By prefabricating installation interfaces on the side, the load-bearing surface of the fender becomes part of the hull, rather than an add-on. The resulting technical benefits are: 1. Guaranteed geometric similarity: It perfectly solves the fender arrangement problem under narrow clearance conditions, ensuring that the ship spacing in model tests strictly conforms to the actual ship design requirements. 2. Elimination of hydrodynamic interference: The embedded design avoids additional flow resistance and vortex-induced effects generated by externally mounted fenders in waves, ensuring the accuracy of hull hydrodynamic coefficient measurements.

[0068] Addressing the inability to simulate the "constant force energy absorption (buckling)" plateau stage: After reaching the design reaction force peak, a real fender undergoes structural buckling, entering a plateau period where "displacement increases but the reaction force remains relatively constant." This is a crucial energy absorption stage for protecting the robotic arm and hull structure. Ordinary springs experience a continuous linear increase in force during compression, making it impossible to simulate this "force saturation" phenomenon. This invention utilizes a "constant force stage" simulation mechanism based on the characteristics of gas springs: introducing a gas spring with specific mechanical properties as the core load-bearing element, specifically designed to simulate the constant force stage after fender buckling. It employs an approximate isobaric expansion / compression principle: the gas spring is filled with high-pressure inert gas, and within a specific piston stroke segment, its output force mainly depends on the internal gas pressure and the piston rod area. Due to the cavity volume design, the internal gas pressure changes gradually during compression, allowing for an approximately constant thrust output, perfectly matching the mechanical characteristics after fender buckling. The resulting technical effects include: 1. Accurate reproduction of extreme conditions: successfully reproducing the special mechanical behavior of "continued deformation, zero stiffness (constant force)" in physical model tests. 2. Verify operational safety: It can realistically simulate how the fender absorbs energy through constant force deformation when the distance between ships is further reduced due to an accident, thereby accurately assessing the impact protection effect on the operating robotic arm.

[0069] To address the inability of traditional linear springs to simulate the nonlinear "variable stiffness" characteristics of real ship fenders: Real ship engineering rubber fenders exhibit significant hyperelasticity and nonlinearity, with their force-displacement curves showing nonlinear growth. Existing model tests often use single-stiffness helical springs, which follow Hooke's law and exhibit a purely linear relationship. This single-linear simulation leads to insufficient reaction force at low compression (insufficient constraint) and excessive reaction force at high compression (overly stiff), resulting in distorted hull motion response data. This invention employs a high-fidelity piecewise fitting system combining mechanical and gas springs: innovatively constructing a parallel combined elastic module of "mechanical helical spring + gas spring." Through the physical parallel connection of the two, piecewise superposition and nonlinear fitting of stiffness are achieved. Using the principle of stiffness superposition: in the initial stage of compression, the helical spring provides the main initial linear stiffness (simulating the elastic segment of rubber in the initial stage of compression); as the compression increases, the gas spring intervenes or works in conjunction, utilizing the differences in characteristics of different elastic elements to reconstruct a nonlinear envelope that closely approximates the real rubber fender. The resulting technical benefits include: 1. Improved simulation fidelity: The system can flexibly adjust the helical spring stiffness and gas spring parameters based on the performance curve of the target fender, achieving high-precision reproduction of the "soft-to-hard" change process of the real fender. 2. Optimized load prediction: The system makes the inter-ship collision force measured in the model test closer to the real value, avoiding overestimation of the load due to excessive stiffness of the model fender.

[0070] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An embedded high-fidelity variable stiffness fender device for multi-ship collaborative operation model testing, characterized in that, Includes embedded housing units, linear guide units, movable pressure-bearing units, and hybrid elastic units; The embedded box unit includes a mounting box (1), a fixed base plate (2), and a mounting flange (3). The mounting box (1) is a rectangular box structure. The fixed base plate (2) is fixed to the bottom of the inside of the mounting box (1). The mounting flange (3) is located at the front opening of the mounting box (1) and is bolted to the hull plate. The linear guide unit includes two parallel precision guide shafts (4) and matching linear bearings (5). The precision guide shafts (4) are fixed to the fixed base plate (2), and the linear bearings (5) are installed in the movable pressure-bearing unit. The active pressure-bearing unit includes an external anti-collision plate (6), a high-precision force sensor (7), and an internal sliding bracket (8). The high-precision force sensor (7) is connected in series between the external anti-collision plate (6) and the internal sliding bracket (8). The hybrid elastic unit includes a high-fidelity helical spring (9) and a gas spring (10), which are arranged in parallel between the internal sliding bracket (8) and the fixed base plate (2).

2. The embedded high-fidelity variable stiffness fender device according to claim 1, characterized in that, The mounting box (1) is made of transparent acrylic material, and its outer wall size is adapted to the mounting slot reserved on the side of the model ship. The front opening of the box is used to accommodate the movement of the movable pressure unit.

3. The embedded high-fidelity variable stiffness fender device according to claim 2, characterized in that, The fixed base plate (2) is a metal plate with positioning holes and threaded holes for fixing the base of the precision guide shaft (4), the high-fidelity helical spring (9) and the gas spring (10).

4. The embedded high-fidelity variable stiffness fender device according to claim 3, characterized in that, A waterproof gasket or silicone sealant is provided between the mounting flange (3) and the hull plate.

5. The embedded high-fidelity variable stiffness fender device according to claim 4, characterized in that, The precision guide shaft (4) is made of high-strength alloy steel, and its surface is hardened and polished. It has a clearance fit with the linear bearing (5).

6. The embedded high-fidelity variable stiffness fender device according to claim 5, characterized in that, The high-precision force sensor (7) is a high-range, high-precision pressure force sensor that directly measures external collision force.

7. The embedded high-fidelity variable stiffness fender device according to claim 6, characterized in that, The high-fidelity helical spring (9) is a high-precision mold spring with a stiffness coefficient that has been strictly calibrated. It provides linear restoring force in the initial stage of compression, simulating the elastic behavior of the linear growth stage of a real fender.

8. The embedded high-fidelity variable stiffness fender device according to claim 7, characterized in that, The gas spring (10) is filled with high-pressure nitrogen.

9. A method for simulating the variable stiffness characteristics based on the device described in claim 8, characterized in that, Includes the following steps: Step S1, parameter configuration: Based on the model scaling ratio, calculate the initial stiffness and maximum force parameters of the target model fender, select suitable high-fidelity helical springs (9) and gas springs (10), construct a parallel elastic system, and calculate the goodness of fit R. 2 ; Step S2, the linear simulation stage, when the external hull contacts and pushes the external anti-collision plate (6) to produce a small displacement, the high-fidelity helical spring (9) in the hybrid elastic unit plays a dominant role, and the total reaction force of the system is F=K. spring •x, K spring Let x be the stiffness of the helical spring and x be the compression displacement, simulating the linear growth stage of a real fender; Step S3, constant force simulation stage: when the compression displacement reaches the set threshold and the force value of the high-fidelity helical spring (9) accumulates to the maximum, the gas spring (10) enters the main working section to simulate the buckling energy absorption platform stage of the real fender.

10. A test method for a three-ship cooperative operation model based on the device described in claim 8, characterized in that, Includes the following steps: Step T1: Groove the hull. At the fender installation position of the middle transport barge model, cut a rectangular through hole according to the cross-sectional dimensions of the installation box (1). Step T2, embedding and fixing: push the entire fender device into the hull, adjust the position of the device, and ensure that the outer surface of the external anti-collision plate (6) is flush with the outer surface of the side of the hull. Fix it to the hull plate with bolts through the bolt holes of the mounting flange (3). Step T3, sealing treatment: lay a waterproof gasket or apply silicone between the installation flange (3) and the hull plate, compact it and tighten the bolts to ensure the water tightness of the connection and prevent seawater from the wave pool from entering the hull. Step T4, spatial verification: Measure the net distance between the middle transport barge model and the two side workboat models to confirm that the distance conforms to the design scale value and has no deviation; Step T5, test run, start the wave generator to simulate the marine environment, monitor the relative motion of the three ships, when the distance between the ships is reduced to the contact threshold, record the collision force data of the high-precision force sensor (7) and the ship motion response data to complete the test.

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