A four-degree-of-freedom combined loading device and method for ocean foundation model test

Abstract

The application discloses a four-freedom-degree combined loading device and method for ocean foundation model test, which comprises a comprehensive loading frame, a loading beam, a loading direction changing mechanism, a guide rail sliding block assembly, a first loading mechanism, a second loading mechanism, a third loading mechanism, a rotating mechanism, a force perception unit, a posture perception unit and a control unit; the loading beam is slidingly installed on the comprehensive loading frame; the loading direction changing mechanism is installed on the top of the comprehensive loading frame; the first loading mechanism and the second loading mechanism are fixedly connected as an integral structure through the guide rail sliding block assembly; the bottoms of the first loading mechanism and the second loading mechanism are respectively hinged to the left side and the right side of the top of the rotating mechanism; and the third loading mechanism is installed on the bottom of the loading beam. The application can realize independent loading and synchronous combined loading of vertical load, horizontal load, moment and torque, and can realize real-time measurement and feedback of the combined load, so that the model test on the bearing performance of the foundation structure under the combined load of the complex ocean environment can be conveniently carried out.

Description

Technical Field

[0001] This invention relates to the technical field of marine geotechnical engineering, and in particular to a four-degree-of-freedom combined loading device and method for marine basic model testing. Background Technology

[0002] With the global energy structure transformation, the new energy industry has developed rapidly. Offshore wind power, due to its advantages of high power generation efficiency, no pollution, low noise, and no land occupation, has become a key new energy industry that countries are focusing on and developing. As a key structure supporting offshore wind power, the wind turbine foundation must not only bear the vertical load generated by the self-weight of the superstructure during long-term service, but also face the horizontal loads, moments, and torques generated by wind, waves, currents, and eccentric loads in the ocean. This results in the foundation being subjected to complex multi-degree-of-freedom combined loads. Under the action of combined loads, studying the load-bearing performance of wind turbine foundations is crucial to ensuring the safety and stability of wind turbine foundations.

[0003] Currently, due to limitations in geotechnical indoor model testing technology, most indoor model testing devices at home and abroad are concentrated on single-degree-of-freedom loading or VHM three-degree-of-freedom loading. It is difficult to simultaneously achieve four-degree-of-freedom combined loading of vertical load, horizontal load, moment, and torque. In the past, the loading mechanisms of the three-degree-of-freedom combined loading devices were independent of each other and had a large volume. Furthermore, the coupled application, synchronous measurement, and feedback control of multi-degree-of-freedom loads were quite difficult, involving complex spatial coupling mechanism principles and control technologies. Therefore, it is of great practical significance to develop a VHMT four-degree-of-freedom combined loading model testing device and realize the coupled application of combined loads to marine foundations to carry out research on the foundation bearing capacity under four-degree-of-freedom combined loading. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a four-degree-of-freedom combined loading device for marine basic model tests. It can realize independent loading and synchronous combined loading of vertical load, horizontal load, moment and torque, and can measure and provide feedback on the combined load in real time, which facilitates the model test of the bearing capacity of the basic structure under the combined load of complex marine environment.

[0005] Another objective of this invention is to provide a four-degree-of-freedom combined loading method for marine basic model testing.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A four-degree-of-freedom combined loading device for marine basic model testing includes an integrated loading frame, a loading beam, a loading reversing mechanism, a guide rail slider assembly, a first loading mechanism, a second loading mechanism, a third loading mechanism, a slewing mechanism, a force sensing unit, an attitude sensing unit, and a control unit. The loading beam is slidably mounted on the integrated loading frame and can move vertically along it. The loading reversing mechanism is mounted on the top of the integrated loading frame and drives the loading beam to move vertically along it. The first and second loading mechanisms are fixedly connected as a single unit via the guide rail slider assembly, which is mounted on the bottom of the loading beam. The guide rail slider assembly drives the first and second loading mechanisms to move horizontally synchronously along the loading beam. The bottoms of the first and second loading mechanisms are hinged to the left and right sides of the top of the slewing mechanism, respectively, to output vertical loads to form vertical loading or moment loading. The third loading mechanism is mounted on the bottom of the loading beam and connected to the guide rail slider assembly, and outputs horizontal loads. The bottom of the slewing mechanism is used to connect to the marine foundation model, and the slewing mechanism can rotate around the vertical axis. Through the cooperation of the first loading mechanism, the second loading mechanism, the third loading mechanism, and the slewing mechanism, a four-degree-of-freedom combined load including vertical load, horizontal load, moment, and torque is output to the marine foundation model. The force sensing unit is set between the slewing mechanism and the marine foundation model to synchronously measure the measured load data of the four-degree-of-freedom combined load. The attitude sensing unit is installed on the slewing mechanism to detect the deflection angle of the slewing mechanism in real time. The control unit is communicatively connected to the first loading mechanism, the second loading mechanism, the third loading mechanism, the slewing mechanism, the loading direction-changing mechanism, the force sensing unit, and the attitude sensing unit, respectively, to control the movement of each mechanism, receive the measured load data and deflection angle, calculate the deviation between the measured load data and the target load data, and coordinate the output of each loading mechanism and perform closed-loop feedback correction based on the deviation and deflection angle to realize the loading control of the four-degree-of-freedom combined load.

[0008] Furthermore, the integrated loading frame includes a base plate, two steel base frames, an upper support plate, longitudinal guide columns, longitudinal lead screws, lead screw support seats, lead screw nuts, and linear bushings. The two steel base frames are symmetrically installed on the left and right sides of the top surface of the base plate. The upper support plates are horizontally spaced above the two steel base frames. Two parallel longitudinal guide columns are provided between each steel base frame and the upper support plate, and a longitudinal lead screw is provided between every two corresponding longitudinal guide columns. The two ends of the longitudinal lead screw are rotatably mounted to the corresponding steel base frame and the upper support plate respectively through lead screw support seats. On the plate; multiple circular holes corresponding to longitudinal lead screws and longitudinal guide posts are respectively opened on the left and right sides of the loading crossbeam. Among them, lead screw nuts are installed in the circular holes corresponding to longitudinal lead screws, and linear bushings are installed in the circular holes corresponding to longitudinal guide posts. The loading crossbeam is slidably guided to the corresponding longitudinal guide posts through each linear bushing, and is driven to the corresponding longitudinal lead screw through each lead screw nut. The longitudinal lead screw is driven to rotate by the loading reversing mechanism, and then the longitudinal lead screw drives the loading crossbeam to move up and down along the longitudinal guide posts.

[0009] Furthermore, the loading reversing mechanism includes a first reducer, a second reducer, a third reducer, a servo motor, and a reversing screw; the first reducer, the second reducer, and the third reducer are respectively installed on the top of the integrated loading frame and arranged sequentially along the left and right directions of the integrated loading frame; the servo motor is installed on the top of the integrated loading frame, and its output end is drivenly connected to the input end of the second reducer; the second reducer has two output ends with opposite rotation directions, and each of its two output ends is connected to a reversing screw; the two reversing screws are respectively drivenly connected to the input ends of the first reducer and the third reducer; the output ends of the first reducer and the third reducer are respectively drivenly connected to the top ends of the two longitudinal screws.

[0010] Furthermore, the guide rail slider assembly includes a linear guide rail, a guide rail slider, and a connecting plate; the linear guide rail is installed at the bottom of the loading beam in the left-right direction; the guide rail slider is assembled on the linear guide rail; the top of the connecting plate is connected to the guide rail slider, and its bottom is connected to the first loading mechanism, the second loading mechanism, and the third loading mechanism, respectively.

[0011] Furthermore, the first loading mechanism includes a first mounting frame, a first loading motor, a first ball screw, a first mounting flange, a first guide post, a first loading rod, an upper member of a first connecting rod, and a lower member of a first connecting rod; the first mounting frame is connected to the connecting plate of the guide rail slider assembly; the first screw of the first ball screw is rotatably mounted inside the first mounting frame; the first loading motor is mounted on the top of the first mounting frame, and its output end is connected to the first screw of the first ball screw via transmission; the first screw nut of the first ball screw is fixed to the first mounting flange; the first guide post is arranged vertically within the first mounting frame; the first mounting flange and the first guide post are in sliding guide engagement; the top end of the first loading rod is connected to the first mounting flange, and its bottom end extends downward and is fixedly connected to the top end of the upper member of the first connecting rod; the top end of the lower member of the first connecting rod is hinged to the bottom end of the upper member of the first connecting rod, and its bottom end is hinged to the left side of the top of the rotary mechanism.

[0012] Furthermore, the second loading mechanism includes a second mounting frame, a second loading motor, a second ball screw, a second mounting flange, a second guide post, a second loading rod, and a second connecting rod; the second mounting frame is connected to the connecting plate of the guide rail slider assembly; the second screw of the second ball screw is rotatably mounted inside the second mounting frame; the second loading motor is mounted on the top of the second mounting frame, and its output end is connected to the second screw of the second ball screw via transmission; the second screw nut of the second ball screw is fixed to the second mounting flange; the second guide post is arranged vertically within the second mounting frame; the second mounting flange and the second guide post are in sliding guide engagement; the top end of the second loading rod is connected to the second mounting flange, and its bottom end extends downward and is fixedly connected to the top end of the second connecting rod; the bottom end of the second connecting rod is hinged to the right side of the top of the rotary mechanism.

[0013] Furthermore, the third loading mechanism includes a third loading motor, a transverse lead screw, a horizontal connecting block, and a free-side lead screw support; the third loading motor is fixed to the bottom of the loading beam; one end of the transverse lead screw is connected to the output end of the third loading motor, and the other end passes through the horizontal connecting block and is rotatably connected to the free-side lead screw support; the free-side lead screw support is fixed to the bottom of the loading beam; the horizontal connecting block is connected to the connecting plate of the guide rail slider assembly.

[0014] Furthermore, the rotary mechanism includes a housing, a grooved connecting ring, a rotary servo motor, a planetary reducer, and an electrical slip ring; the top of the housing is provided with a grooved connecting ring for hinged connection of the first loading mechanism and the second loading mechanism; the rotary servo motor is located on the top of the housing and inside the grooved connecting ring; the planetary reducer is fixed inside the housing and is drively connected to the rotary servo motor; the electrical slip ring is located inside the housing and is used to realize electrical signal transmission and prevent wire entanglement during rotation.

[0015] Furthermore, the force sensing unit is a six-dimensional force sensor; the attitude sensing unit is a tilt sensor.

[0016] Another objective of this invention is achieved through the following technical solution:

[0017] A four-degree-of-freedom combined loading method for marine basic model testing is implemented based on the aforementioned four-degree-of-freedom combined loading device for marine basic model testing. The method includes load application, real-time compensation for additional displacement, real-time load measurement and feedback, coordinated control of each loading mechanism, and stable load output. The specific steps are as follows:

[0018] S1, Load application

[0019] Based on the bearing capacity of the foundation and the pre-set test plan in the marine foundation model test, vertical loads, horizontal loads, moment and torque single-degree-of-freedom loads, or multi-degree-of-freedom combined loads are applied to the marine foundation model respectively;

[0020] S1.1 The specific method for applying a single-degree-of-freedom load is as follows:

[0021] Applying vertical load: The first and second loading mechanisms simultaneously output vertical component loads of equal magnitude and downward direction, which are then combined to form the overall vertical load;

[0022] Applying horizontal load: The horizontal load is directly output through the third loading mechanism;

[0023] Applying torque: The first and second loading mechanisms synchronously output vertical loads of equal magnitude and opposite direction, thereby generating torque;

[0024] Applying torque: Torque is directly output through the rotary mechanism;

[0025] S1.2 The specific method for applying two-degree-of-freedom loads is as follows:

[0026] Applying a combination of vertical and horizontal loads: The first and second loading mechanisms simultaneously output vertical component loads of equal magnitude and downward direction to synthesize the overall vertical load; at the same time, the third loading mechanism applies a horizontal load, realizing a two-degree-of-freedom combination loading of vertical and horizontal loads;

[0027] Applying a combination of vertical load and moment: The first loading mechanism and the second loading mechanism output vertical sub-loads V1 and V2 of different magnitudes and downward directions, respectively, with vertical sub-load V2 > vertical sub-load V1, synthesizing the overall vertical load V = V1 + V2, thereby forming a moment M, M = (V2 - V1)L, realizing the two-degree-of-freedom combination loading of vertical load and moment; wherein, the target output loads of the first loading mechanism and the second loading mechanism are respectively: V1 = V / 2 - M / (2L), V2 = V / 2 + M / (2L), where L is the horizontal distance between the center point of the first loading mechanism or the second loading mechanism and the rotary mechanism;

[0028] Applying a combination of horizontal load and torque: The horizontal load is directly output through the third loading mechanism, and the torque is directly output through the rotary mechanism, realizing the two-degree-of-freedom combined loading of horizontal load and torque;

[0029] S1.3 The specific application method of the three-degree-of-freedom load is as follows:

[0030] The application of vertical load, horizontal load, and moment combination: The first and second loading mechanisms output vertical sub-loads V1 and V2 of different magnitudes and downward directions, respectively, to synthesize the overall vertical load V = V1 + V2. The third loading mechanism directly outputs the horizontal load H, and simultaneously generates a moment M, M = (V2 - V1)L, realizing the three-degree-of-freedom combination loading of vertical load, horizontal load, and moment; where the target output loads of the first and second loading mechanisms are respectively: V1 = V / 2 - M / (2L), V2 = V / 2 + M / (2L).

[0031] Applying a combination of horizontal load, moment, and torque: The horizontal load is directly output through the third loading mechanism, while the vertical loads of equal magnitude and opposite direction are output through the first and second loading mechanisms to form a moment M. At the same time, the torque is directly output through the rotary mechanism, realizing the three-degree-of-freedom combination loading of horizontal load, moment, and torque.

[0032] S1.4 The specific application method of the four-degree-of-freedom load is as follows:

[0033] The application of vertical load, horizontal load, moment, and torque combination: The first and second loading mechanisms simultaneously output vertical sub-loads V1 and V2 of different magnitudes and downward directions, synthesizing the overall vertical load V = V1 + V2. The third loading mechanism directly outputs the horizontal load H, at which point a moment M is formed, M = (V2 - V1)L. At the same time, the rotary mechanism directly outputs the torque T, realizing the four-degree-of-freedom combination loading of vertical load, horizontal load, moment, and torque. Among them, the target output loads of the first and second loading mechanisms are V1 = V / 2 - M / (2L) and V2 = V / 2 + M / (2L), respectively.

[0034] S2, Additional Displacement Real-time Compensation

[0035] During the differential loading process of the first loading mechanism and the second loading mechanism, the rotary mechanism will deflect, causing the preset reference point o of the rotary mechanism to shift, and after the shift, an offset reference point o' is formed.

[0036] By constructing the spatial geometric relationship between the preset reference point o and the offset reference point o´, precise compensation for additional displacement is achieved. The geometric relationship is shown in the following formula:

[0037] (L) AB -L DC ) 2 +L AD 2 =L BC 2 ;

[0038] Among them, L AB L is the distance between the center point of the second loading mechanism and the center point of the rotary mechanism. BC L is the distance between the center point of the second loading mechanism and the center point of the rotary mechanism after deflection. DC L is the horizontal offset distance of the offset reference point o' relative to the preset reference point o; AD This represents the vertical offset distance of the offset reference point o' relative to the preset reference point o;

[0039] The deflection angle θ of the preset reference point o on the rotary mechanism is collected in real time by the attitude sensing unit, and the formula for calculating the horizontal offset distance is: L DC =L AD tanθ;

[0040] Based on the above geometric relationships, the vertical offset distance L of the offset reference point o' relative to the preset reference point o can be calculated. AD and horizontal offset distance L DC That is, the real-time additional vertical displacement Δu z and additional horizontal displacement Δu x The additional vertical displacement Δu is achieved by controlling the loading beam to move vertically along the integrated loading frame via the control unit. z Compensation; by means of the first and second loading mechanisms moving horizontally along with the guide rail slider assembly, an additional horizontal displacement Δu is achieved. x Compensation to eliminate loading position deviation caused by the deflection of the rotary mechanism;

[0041] S3. Real-time load measurement and feedback

[0042] The actual vertical load V borne by the marine foundation model was simultaneously measured using a force sensing unit. m Measured horizontal load H m Measured torque Mm and measured torque T m The measured load data is fed back to the control unit in real time. The control unit compares the measured load data with the target load data, calculates the deviation value of the load for each degree of freedom, and coordinates and corrects the output of each loading mechanism, as follows:

[0043] The output loads of the first and second loading mechanisms are corrected based on the vertical load deviation and moment deviation, as shown in the following formula:

[0044] △V=VV m ; △M=MM m ;

[0045] △V1=△V / 2-△M / (2L), △V2=△V / 2+△M / (2L);

[0046] Where △V represents the vertical load V and the measured vertical load V0. m The deviation value; △M is the difference between the torque M and the measured torque M. m The deviation value; △V1 is the vertical load correction amount of the first loading mechanism; △V2 is the vertical load correction amount of the second loading mechanism;

[0047] The output load of the third loading mechanism is corrected based on the horizontal load deviation, as shown in the following formula:

[0048] △H=HH m ;

[0049] Where △H represents the horizontal load H and the measured horizontal load H m The deviation value;

[0050] The output torque of the rotary mechanism is corrected based on the torque deviation, as shown in the following formula:

[0051] △T=TT m ;

[0052] Where △T represents the difference between the torque T and the measured torque T. m The deviation value;

[0053] S4, Coordinated Control of Each Loading Mechanism

[0054] The control unit coordinates and controls each loading mechanism based on the measured load data from the force sensing unit.

[0055] When the third loading mechanism applies a horizontal load, causing the measured vertical load or measured moment to deviate from the target load data, the control unit compensates for the vertical load deviation and moment deviation by adjusting the output of the first loading mechanism and the second loading mechanism.

[0056] When the torque applied by the slewing mechanism causes the measured vertical load, measured horizontal load, or measured moment to deviate from the target load data, the control unit coordinates and corrects the outputs of the first loading mechanism, the second loading mechanism, and the third loading mechanism according to the deviation of the load of each degree of freedom.

[0057] The output parameters of each loading mechanism are iteratively corrected until the load deviation of each degree of freedom meets the preset requirements, that is, the combined load is determined to have reached the target load data.

[0058] S5, Stable Load Output

[0059] When the measured vertical load, measured horizontal load, measured moment, and measured torque are all within the preset error range, the control unit enters the constant load closed-loop holding state; the force sensing unit continuously collects the measured load data in real time and continuously and dynamically fine-tunes the output parameters of each loading mechanism, so that the four-degree-of-freedom load is always stably maintained within the preset error range, and the test load is stably and continuously output.

[0060] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0061] 1. This invention, through the coordinated operation of the first loading mechanism, the second loading mechanism, the third loading mechanism and the slewing mechanism, can apply vertical loads, horizontal loads, moments and torques separately or simultaneously, breaking through the limitations of multi-degree-of-freedom coordinated loading of marine foundations and realizing four-degree-of-freedom combined loading of marine foundations.

[0062] 2. The present invention achieves flexible application of vertical loads and moments through the co-directional or differential loading of the first loading mechanism and the second loading mechanism, without the need for a separate moment loading mechanism, thus simplifying the structure of the combined loading system.

[0063] 3. This invention outputs torque through a rotary servo motor and a planetary reducer, and sets an electrical slip ring inside the rotary mechanism, which can maintain stable transmission of power and measurement signals during continuous or reciprocating torsional loading, and can avoid the problem of sensor wire entanglement during the rotational installation of marine foundations.

[0064] 4. This invention combines an attitude sensing unit installed on the rotary mechanism to calculate the additional displacement generated during torque loading. By moving the loading beam up and down along the longitudinal guide column and moving each loading mechanism horizontally along the linear guide rail, the additional vertical and horizontal displacements generated by the rotary mechanism during torque loading are compensated in a coordinated manner, thereby improving the authenticity and accuracy of the experiment.

[0065] 5. The present invention places the force sensing unit between the rotating mechanism and the marine foundation model, which can simultaneously acquire vertical load, horizontal load, moment and torque at the same measurement position, reducing the coordinate inconsistency, measurement asynchrony and load conversion error caused by using multiple independent sensors.

[0066] 6. The present invention can synchronize the measured results of the force sensing unit to the control unit. The control unit calculates the corresponding load deviation by comparing the measured values ​​of each load component with the target values, and performs feedback correction on the outputs of the first loading mechanism, the second loading mechanism, the third loading mechanism and the slewing mechanism to form a combined load closed-loop control. Attached Figure Description

[0067] Figure 1 This is a schematic diagram of the overall structure of the loading device of the present invention.

[0068] Figure 2 This is a schematic diagram of the structure in which the various loading mechanisms are connected as one unit in this invention.

[0069] Figure 3 This is a schematic diagram of the structure of the first loading mechanism and the second loading mechanism in this invention.

[0070] Figure 4 This is a schematic diagram of the third loading mechanism in this invention.

[0071] Figure 5 This is a cross-sectional schematic diagram of the rotary mechanism in this invention.

[0072] Figure 6 This is one of the schematic diagrams illustrating the application of a single-degree-of-freedom load in this invention.

[0073] Figure 7 This is the second schematic diagram of the application of a single degree of freedom load in this invention.

[0074] Figure 8 This is the third schematic diagram of the application of a single degree of freedom load in this invention.

[0075] Figure 9 This is the fourth schematic diagram of the application of a single degree of freedom load in this invention.

[0076] Figure 10 This is one of the schematic diagrams illustrating the application of a two-degree-of-freedom load in this invention.

[0077] Figure 11 This is the second schematic diagram of the application of two-degree-of-freedom loads in this invention.

[0078] Figure 12 This is the third schematic diagram of the application of two-degree-of-freedom loads in this invention.

[0079] Figure 13 This is a schematic diagram of the application of a three-degree-of-freedom load in this invention.

[0080] Figure 14 This is a schematic diagram of the application of a four-degree-of-freedom load in this invention.

[0081] Figure 15 This is a spatial geometric diagram of the preset reference point o and the offset reference point o´ in this invention. Detailed Implementation

[0082] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0083] Example 1:

[0084] like Figure 1As shown, this embodiment provides a four-degree-of-freedom combined loading device for marine basic model testing, including an integrated loading frame, a loading beam 2, a loading reversing mechanism, a guide rail slider assembly, a first loading mechanism 5, a second loading mechanism 6, a third loading mechanism 7, a slewing mechanism 8, a force sensing unit 9, an attitude sensing unit 10, and a control unit. The loading beam 2 is slidably mounted on the integrated loading frame and can move vertically along the integrated loading frame. The loading reversing mechanism is mounted on the top of the integrated loading frame and is used to drive the loading beam 2 to move vertically along the integrated loading frame. The first loading mechanism 5 and the second loading mechanism 6 are fixedly connected as an integral structure by the guide rail slider assembly, which is mounted on the bottom of the loading beam 2. The guide rail slider assembly drives the first loading mechanism 5 and the second loading mechanism 6 to move horizontally synchronously along the loading beam 2. The bottoms of the first loading mechanism 5 and the second loading mechanism 6 are respectively hinged to the left and right sides of the top of the slewing mechanism 8 to output vertical loads to form vertical loading or moment loading. The third loading mechanism 7 is mounted on the bottom of the loading beam 2 and connected to the guide rail slider assembly. The system is used to output horizontal loads; the bottom of the slewing mechanism 8 is used to connect to the marine foundation model, and the slewing mechanism 8 can rotate around the vertical axis; through the cooperation of the first loading mechanism 5, the second loading mechanism 6, the third loading mechanism 7 and the slewing mechanism 8, a four-degree-of-freedom combined load including vertical load, horizontal load, moment and torque is output to the marine foundation model; the force sensing unit 9 is set between the slewing mechanism 8 and the marine foundation model, and is used to synchronously measure the measured load data of the four-degree-of-freedom combined load; the attitude sensing unit 10 is installed on the slewing mechanism 8, and is used to detect the deflection angle of the slewing mechanism 8 in real time; the control unit is communicatively connected to the first loading mechanism 5, the second loading mechanism 6, the third loading mechanism 7, the slewing mechanism 8, the loading direction changing mechanism, the force sensing unit 9 and the attitude sensing unit 10, respectively, and is used to control the movement of each mechanism, receive the measured load data and deflection angle, calculate the deviation between the measured load data and the target load data, and coordinate the output of each loading mechanism and perform closed-loop feedback correction according to the deviation and deflection angle to realize the loading control of the four-degree-of-freedom combined load.

[0085] In a specific example, the overall dimensions of the integrated loading frame are 7.0m × 3.0m × 3.8m, which can accommodate large-sized model boxes for various foundation installations and loading tests. The integrated loading frame specifically includes a base plate 101, two steel base frames 102, an upper support plate 103, longitudinal guide columns 104, longitudinal lead screws 105, lead screw support seats 106, lead screw nuts 107, and linear bushings 108. The base plate 101 is composed of multiple welded steel plates, which are connected and fixed to the ground with high-strength bolts to provide stable loading. Loading conditions; two steel base frames 102 are symmetrically welded to the left and right sides of the top surface of the base plate 101; upper support plates 103 are horizontally spaced above the two steel base frames 102; two parallel longitudinal guide columns 104 are provided between each steel base frame 102 and the upper support plate 103, and the two ends of the longitudinal guide columns 104 can be connected to the steel base frame 102 and the upper support plate 103 respectively through longitudinal guide column sleeves 109 and longitudinal guide column locking nuts 110; a longitudinal screw 1 is provided between every two corresponding longitudinal guide columns 104. 05, wherein the longitudinal guide post 104 has a diameter of 120mm, and the longitudinal lead screw 105 has a diameter of 80mm; both ends of the longitudinal lead screw 105 are rotatably mounted on the corresponding steel base frame 102 and upper support plate 103 respectively through lead screw support seats 106; multiple circular holes corresponding to the longitudinal lead screw 105 and the longitudinal guide post 104 are respectively opened on the left and right sides of the loading beam 2, wherein a lead screw nut 107 is installed in the circular hole corresponding to the longitudinal lead screw 105, and a linear guide screw nut 107 is installed in the circular hole corresponding to the longitudinal guide post 104. Bushing 108; The loading beam 2 is slidably guided by each linear bushing 108 and the corresponding longitudinal guide post 104, and is driven by each screw nut 107 and the corresponding longitudinal screw 105; The longitudinal screw 105 is driven by the loading reversing mechanism, which drives the longitudinal screw 105 to rotate, and then the longitudinal screw 105 drives the loading beam 2 to move up and down along the longitudinal guide post 104 to compensate for the additional vertical displacement of the rotary mechanism 8 caused by the applied torque. The vertical stroke is 0~1500mm.

[0086] In a specific example, the loading reversing mechanism includes a first reducer 301, a second reducer 302, a third reducer 303, a servo motor 304, and a reversing screw 305. The first reducer 301, the second reducer 302, and the third reducer 303 are respectively installed on the top of the integrated loading frame and arranged sequentially along the left and right directions of the integrated loading frame. The three reducers are of the same model. The servo motor 304 is installed on the top of the integrated loading frame, and its output end is connected to the input end of the second reducer 302 through a locking ring to realize the transmission connection between the two. The second reducer 302 has two output ends with opposite rotation directions, and each of its two output ends is connected to a reversing screw 305. The two reversing screws 305 are respectively connected to the input ends of the first reducer 301 and the third reducer 303 in a one-to-one transmission connection. The output ends of the first reducer 301 and the third reducer 303 are respectively connected to the top ends of the two longitudinal screws 105 in a one-to-one transmission connection.

[0087] In a specific example, such as Figure 2 As shown, the guide rail slider assembly includes a linear guide rail 401, a guide rail slider 402, and a connecting plate 403. The linear guide rail 401 is installed at the bottom of the loading beam 2 in the left-right direction. The guide rail slider 402 is assembled on the linear guide rail 401. The top of the connecting plate 403 is connected to the guide rail slider 402 by bolts, and its bottom is connected to the first loading mechanism 5, the second loading mechanism 6, and the third loading mechanism 7 respectively. The connecting plate 403 can move laterally to compensate for the additional horizontal displacement of the rotary mechanism 8 caused by the applied torque. The lateral stroke is 0~800mm, and the specific stroke can be adjusted according to the actual model box size.

[0088] In a specific example, such as Figure 3As shown, the first loading mechanism 5 includes a first mounting frame 501, a first loading motor 502, a first ball screw 503, a first mounting flange 504, a first guide post 505, a first loading rod 506, an upper member 507 of a first connecting rod, and a lower member 508 of a first connecting rod. The first mounting frame 501 is connected to the connecting plate 403 of the guide rail slider assembly. The first screw of the first ball screw 503 is rotatably mounted inside the first mounting frame 501. The first loading motor 502 is mounted on the top of the first mounting frame 501, and its output end is connected to the first screw of the first ball screw 503. The first lead screw nut of lever 503 is fixed to the first mounting flange 504; the first guide post 505 is arranged vertically in the first mounting bracket 501; the first mounting flange 504 and the first guide post 505 are in sliding guide engagement; the top end of the first loading rod 506 is connected to the first mounting flange 504, its bottom end extends downward and is fixedly connected to the top end of the upper member 507 of the first connecting rod; the top end of the lower member 508 of the first connecting rod is hinged to the bottom end of the upper member 507 of the first connecting rod through a tapered roller bearing 509, and its bottom end is hinged to the left side of the top of the rotary mechanism 8 through a tapered roller bearing 510.

[0089] In a specific example, such as Figure 3 As shown, the second loading mechanism 6 includes a second mounting bracket 601, a second loading motor 602, a second ball screw 603, a second mounting flange 604, a second guide post 605, a second loading rod 606, and a second connecting rod 607. The second mounting bracket 601 is connected to the connecting plate 403 of the guide rail slider assembly. The second screw of the second ball screw 603 is rotatably mounted inside the second mounting bracket 601. The second loading motor 602 is mounted on the top of the second mounting bracket 601, and its output end is connected to the first screw of the second ball screw 603. The two ball screws are connected by a drive; the second ball screw nut of the second ball screw 603 is fixed on the second mounting flange 604; the second guide post 605 is arranged vertically in the second mounting bracket 601; the second mounting flange 604 and the second guide post 605 are in sliding guide engagement; the top end of the second loading rod 606 is connected to the second mounting flange 604, and its bottom end extends downward and is fixedly connected to the top end of the second connecting rod 607; the bottom end of the second connecting rod 607 is hinged to the right side of the top of the rotary mechanism 8 through a tapered roller bearing 608.

[0090] In a specific example, such as Figure 4As shown, the third loading mechanism 7 includes a third loading motor 701, a transverse lead screw 702, a horizontal connecting block 703, and a free-side lead screw support 704; the third loading motor 701 is fixed to the bottom of the loading beam 2; one end of the transverse lead screw 702 is connected to the output end of the third loading motor 701, and the other end passes through the horizontal connecting block 703 and is rotatably connected to the free-side lead screw support 704; the free-side lead screw support 704 is fixed to the bottom of the loading beam 2; the horizontal connecting block 703 is connected to the connecting plate 403 of the guide rail slider assembly, connecting the third loading mechanism 7, the first loading mechanism 5, and the second loading mechanism 6 into a whole.

[0091] In a specific example, such as Figure 5 As shown, the rotary mechanism 8 includes a housing 801, a grooved connecting ring 802, a rotary servo motor 803, a planetary reducer 804, and an electrical slip ring 805. The top of the housing 801 is provided with a grooved connecting ring 802 for hinged connection of the first loading mechanism 5 and the second loading mechanism 6. The rotary servo motor 803 is located on the top of the housing 801 and inside the grooved connecting ring 802. The planetary reducer 804 is fixed inside the housing 801 and is connected to the rotary servo motor 803 for transmission. The electrical slip ring 805 is located inside the housing 801 and is used to realize electrical signal transmission and prevent wire entanglement during rotation.

[0092] The three tapered roller bearings allow for flexible rotation of the corresponding rods and facilitate the rotation of the grooved connecting ring 802.

[0093] In a specific example, force sensing unit 9 is a six-dimensional force sensor; attitude sensing unit 10 is a tilt sensor.

[0094] In a specific example, the maximum vertical loading force of the first loading mechanism 5 and the second loading mechanism 6 is 12kN, the maximum horizontal loading force of the third loading mechanism 7 is 12kN, the maximum output torque of the slewing mechanism 8 is 300N·m, the loading rate range is 0.01~5mm / s, the force control accuracy is 0.1%, and the displacement control accuracy is 0.5mm. The first loading mechanism 5 and the second loading mechanism 6 output different magnitudes of force or displacement through force control or displacement control modes, so that the slewing mechanism 8 produces a rotation angle of ±30°.

[0095] Example 2:

[0096] This embodiment also provides a four-degree-of-freedom combined loading method for marine basic model testing, based on a four-degree-of-freedom combined loading device for marine basic model testing in Embodiment 1. The method includes load application, real-time compensation of additional displacement, real-time load measurement and feedback, coordinated control of each loading mechanism, and stable load output. The specific steps are as follows:

[0097] S1, Load application

[0098] Based on the bearing capacity of the foundation and the pre-set test plan in the marine foundation model test, vertical loads, horizontal loads, moment and torque single-degree-of-freedom loads, or multi-degree-of-freedom combined loads are applied to the marine foundation model respectively;

[0099] S1.1 The specific method for applying a single-degree-of-freedom load is as follows:

[0100] like Figure 6 As shown, when a vertical load V is applied: the first loading mechanism 5 and the second loading mechanism 6 simultaneously output vertical sub-loads V1 of equal magnitude and downward direction, and synthesize the overall vertical load V = 2V1.

[0101] like Figure 7 As shown, the horizontal load H is applied: the horizontal load H is directly output through the third loading mechanism 7;

[0102] like Figure 8 As shown, the applied torque M is generated by the synchronous output of vertical load V1 and vertical load V2 of equal magnitude and opposite direction by the first loading mechanism 5 and the second loading mechanism 6, thereby forming a torque M, M=2V1×L, where L is the horizontal distance between the center point of the first loading mechanism 5 or the second loading mechanism 6 and the rotation mechanism 8.

[0103] like Figure 9 As shown, the applied torque T is directly output through the rotary mechanism 8;

[0104] S1.2 The specific method for applying two-degree-of-freedom loads is as follows:

[0105] like Figure 10 As shown, a combination of vertical and horizontal loads is applied: the first loading mechanism 5 and the second loading mechanism 6 simultaneously output vertical sub-loads V1 of equal magnitude and downward direction, synthesizing the overall vertical load V=2V1; at the same time, the third loading mechanism 7 applies a horizontal load H, realizing the two-degree-of-freedom combination loading of vertical and horizontal loads.

[0106] like Figure 11 As shown, a combination of vertical load and moment is applied: the first loading mechanism 5 and the second loading mechanism 6 output vertical sub-loads V1 and V2 of different magnitudes and downward directions, respectively, with vertical sub-load V2 > vertical sub-load V1, synthesizing the overall vertical load V = V1 + V2, thereby forming a moment M, M = (V2 - V1)L, realizing the two-degree-of-freedom combination loading of vertical load and moment; wherein, the target output loads of the first loading mechanism 5 and the second loading mechanism 6 are respectively: V1 = V / 2 - M / (2L), V2 = V / 2 + M / (2L);

[0107] like Figure 12As shown, a combination of horizontal load and torque is applied: the horizontal load H is directly output through the third loading mechanism 7, and the torque T is directly output through the slewing mechanism 8, thus realizing the two-degree-of-freedom combination loading of horizontal load and torque;

[0108] S1.3 The specific application method of the three-degree-of-freedom load is as follows:

[0109] like Figure 13 As shown, a combination of vertical load, horizontal load, and moment is applied: the first loading mechanism 5 and the second loading mechanism 6 output vertical sub-loads V1 and V2 of different magnitudes and downward directions, respectively, to synthesize the overall vertical load V = V1 + V2. The third loading mechanism 7 directly outputs the horizontal load H, while simultaneously generating a moment M, M = (V2 - V1)L, thus achieving a three-degree-of-freedom combination loading of vertical load, horizontal load, and moment; wherein, the target output loads of the first loading mechanism 5 and the second loading mechanism 6 are respectively: V1 = V / 2 - M / (2L), V2 = V / 2 + M / (2L).

[0110] Applying a combination of horizontal load, moment, and torque: The horizontal load H is directly output through the third loading mechanism 7, while the vertical loads V1 and V2 of equal magnitude and opposite direction are output through the first loading mechanism 5 and the second loading mechanism 6 to form a moment M, M=2V1×L. At the same time, the torque T is directly output through the rotary mechanism 8, realizing the three-degree-of-freedom combination loading of horizontal load, moment, and torque.

[0111] S1.4 The specific application method of the four-degree-of-freedom load is as follows:

[0112] like Figure 14 As shown, a combination of vertical load, horizontal load, moment, and torque is applied: Vertical sub-loads V1 and V2 of different magnitudes and downward directions are simultaneously output through the first loading mechanism 5 and the second loading mechanism 6, synthesizing the overall vertical load V = V1 + V2. A horizontal load H is directly output through the third loading mechanism 7, forming a moment M, M = (V2 - V1)L. Simultaneously, a torque T is directly output through the rotary mechanism 8, achieving a four-degree-of-freedom combination of vertical load, horizontal load, moment, and torque. The target output loads of the first loading mechanism 5 and the second loading mechanism 6 are respectively: V1 = V / 2 - M / (2L), V2 = V / 2 + M / (2L).

[0113] S2, Additional Displacement Real-time Compensation

[0114] During the differential loading process of the first loading mechanism 5 and the second loading mechanism 6, the rotary mechanism 8 will deflect, causing the preset reference point o of the rotary mechanism 8 to shift, and after the shift, an offset reference point o' is formed.

[0115] like Figure 15As shown, by constructing the spatial geometric relationship between the preset reference point o and the offset reference point o´, precise compensation for additional displacement is achieved; by constructing a right trapezoid ABCD, since the side lengths AB and BC of the trapezoid are equal, then L AB =L BC Then the geometric equation for right triangle EBC is:

[0116] (L) AB -L DC ) 2 +L AD 2 =L BC 2 ;

[0117] Among them, L AB L is the distance between the center point of the second loading mechanism and the center point of the rotary mechanism. BC L is the distance between the center point of the second loading mechanism and the center point of the rotary mechanism after deflection. DC L is the horizontal offset distance of the offset reference point o' relative to the preset reference point o; AD This represents the vertical offset distance of the offset reference point o' relative to the preset reference point o;

[0118] The attitude sensing unit 10 collects the deflection angle θ of the preset reference point o on the rotary mechanism 8 in real time, and the formula for calculating the horizontal offset distance is: L DC =L AD tanθ;

[0119] Based on the above geometric relationships, the vertical offset distance L of the offset reference point o' relative to the preset reference point o can be calculated. AD and horizontal offset distance L DC That is, the real-time additional vertical displacement Δu z and additional horizontal displacement Δu x The loading beam 2 is moved vertically along the longitudinal guide post 104 by the control unit to complete the additional vertical displacement Δu. z Compensation; by means of the first loading mechanism 5 and the second loading mechanism 6 moving horizontally with the connecting plate 403, an additional horizontal displacement Δu is achieved. x Compensation to eliminate the loading position deviation caused by the deflection of the rotary mechanism 8;

[0120] S3. Real-time load measurement and feedback

[0121] The actual vertical load V borne by the marine foundation model was simultaneously measured using the force sensing unit 9. m Measured horizontal load H m Measured torque M m and measured torque T mThe measured load data is fed back to the control unit in real time. The control unit compares the measured load data with the target load data, calculates the deviation value of the load for each degree of freedom, and coordinates and corrects the output of each loading mechanism, as follows:

[0122] The output loads of the first loading mechanism 5 and the second loading mechanism 6 are corrected based on the vertical load deviation and moment deviation, as shown in the following formula:

[0123] △V=VV m ; △M=MM m ;

[0124] △V1=△V / 2-△M / (2L), △V2=△V / 2+△M / (2L);

[0125] Where △V represents the vertical load V and the measured vertical load V0. m The deviation value; △M is the difference between the torque M and the measured torque M. m The deviation value; △V1 is the vertical load correction amount of the first loading mechanism 5; △V2 is the vertical load correction amount of the second loading mechanism 6;

[0126] The output load of the third loading mechanism 7 is corrected based on the horizontal load deviation, as shown in the following formula:

[0127] △H=HH m ;

[0128] Where △H represents the horizontal load H and the measured horizontal load H m The deviation value, i.e. the correction amount of the third loading mechanism 7;

[0129] The output torque of the rotary mechanism 8 is corrected based on the torque deviation, as shown in the following formula:

[0130] △T=TT m ;

[0131] Where △T represents the difference between the torque T and the measured torque T. m The deviation value, i.e. the correction amount of the rotary mechanism 8;

[0132] S4, Coordinated Control of Each Loading Mechanism

[0133] The control unit coordinates and controls each loading mechanism based on the measured load data from the force sensing unit 9.

[0134] When the third loading mechanism 7 applies a horizontal load, causing the measured vertical load or measured moment to deviate from the target load data, the control unit compensates for the vertical load deviation and moment deviation by adjusting the output of the first loading mechanism 5 and the second loading mechanism 6.

[0135] When the torque applied by the slewing mechanism 8 causes the measured vertical load, measured horizontal load, or measured moment to deviate from the target load data, the control unit coordinates and corrects the outputs of the first loading mechanism 5, the second loading mechanism 6, and the third loading mechanism 7 according to the deviation of the loads of each degree of freedom.

[0136] The output parameters of each loading mechanism are iteratively corrected until the load deviation of each degree of freedom meets the preset requirements, that is, the combined load is determined to have reached the target load data.

[0137] S5, Stable Load Output

[0138] When the measured vertical load, measured horizontal load, measured moment, and measured torque are all within the preset error range, the control unit enters the constant load closed-loop holding state; the force sensing unit 9 continuously collects the measured load data in real time and continuously and dynamically fine-tunes the output parameters of each loading mechanism, so that the four-degree-of-freedom load is always stably maintained within the preset error range, and the test load is stably and continuously output.

[0139] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A four-degree-of-freedom combined loading device for marine basic model testing, characterized in that: The system includes a comprehensive loading frame, a loading beam, a loading reversing mechanism, a guide rail slider assembly, a first loading mechanism, a second loading mechanism, a third loading mechanism, a slewing mechanism, a force sensing unit, an attitude sensing unit, and a control unit. The loading beam is slidably mounted on the comprehensive loading frame and can move vertically along it. The loading reversing mechanism is mounted on the top of the comprehensive loading frame and drives the loading beam to move vertically along it. The first and second loading mechanisms are fixedly connected as a single unit via the guide rail slider assembly, which is mounted on the bottom of the loading beam. The guide rail slider assembly drives the first and second loading mechanisms to move horizontally synchronously along the loading beam. The bottoms of the first and second loading mechanisms are hinged to the left and right sides of the top of the slewing mechanism, respectively, to output vertical loads to form vertical loading or moment loading. The third loading mechanism is mounted on the bottom of the loading beam and connected to the guide rail slider assembly, and outputs horizontal loads. The bottom of the slewing mechanism... The rotary mechanism, designed for connection to a marine foundation model, is capable of rotating around a vertical axis. Through the coordinated operation of the first, second, and third loading mechanisms and the rotary mechanism, a four-degree-of-freedom combined load, including vertical load, horizontal load, moment, and torque, is output to the marine foundation model. A force sensing unit is positioned between the rotary mechanism and the marine foundation model to synchronously measure the measured load data of the four-degree-of-freedom combined load. An attitude sensing unit is mounted on the rotary mechanism to detect its deflection angle in real time. The control unit is communicatively connected to the first, second, and third loading mechanisms, the rotary mechanism, the loading direction-changing mechanism, the force sensing unit, and the attitude sensing unit. It controls the movement of each mechanism, receives measured load data and deflection angles, calculates the deviation between the measured load data and the target load data, and coordinates and corrects the outputs of each loading mechanism based on the deviation and deflection angle, thereby achieving loading control of the four-degree-of-freedom combined load.

2. The four-degree-of-freedom combined loading device for marine basic model testing according to claim 1, characterized in that: The integrated loading frame includes a base plate, two steel base frames, an upper support plate, longitudinal guide columns, longitudinal lead screws, lead screw support seats, lead screw nuts, and linear bushings. The two steel base frames are symmetrically installed on the left and right sides of the top surface of the base plate. The upper support plates are horizontally spaced above the two steel base frames. Two parallel longitudinal guide columns are provided between each steel base frame and the upper support plate, and a longitudinal lead screw is provided between every two corresponding longitudinal guide columns. The two ends of the longitudinal lead screw are rotatably mounted on the corresponding steel base frame and the upper support plate respectively through lead screw support seats. The loading beam has multiple circular holes on its left and right sides, each corresponding to a longitudinal lead screw and a longitudinal guide post. A lead screw nut is installed in the hole corresponding to the longitudinal lead screw, and a linear bushing is installed in the hole corresponding to the longitudinal guide post. The loading beam is slidably guided to the corresponding longitudinal guide post via the linear bushings and is connected to the corresponding longitudinal lead screw via the lead screw nut. The longitudinal lead screw is connected to the loading reversing mechanism, which drives the longitudinal lead screw to rotate, thereby causing the loading beam to move up and down along the longitudinal guide post.

3. The four-degree-of-freedom combined loading device for marine basic model testing according to claim 2, characterized in that: The loading and reversing mechanism includes a first reducer, a second reducer, a third reducer, a servo motor, and a reversing screw. The first, second, and third reducers are respectively installed on the top of the integrated loading frame and arranged sequentially along the left-right direction of the integrated loading frame. The servo motor is installed on the top of the integrated loading frame, and its output end is drivenly connected to the input end of the second reducer. The second reducer has two output ends with opposite rotation directions, and each of its two output ends is connected to a reversing screw. The two reversing screws are drivenly connected to the input ends of the first and third reducers respectively. The output ends of the first and third reducers are drivenly connected to the top ends of the two longitudinal screws respectively.

4. The four-degree-of-freedom combined loading device for marine basic model testing according to claim 1, characterized in that: The guide rail slider assembly includes a linear guide rail, a guide rail slider, and a connecting plate; the linear guide rail is installed at the bottom of the loading beam in the left-right direction; the guide rail slider is assembled on the linear guide rail; the top of the connecting plate is connected to the guide rail slider, and its bottom is connected to the first loading mechanism, the second loading mechanism, and the third loading mechanism respectively.

5. The four-degree-of-freedom combined loading device for marine basic model testing according to claim 4, characterized in that: The first loading mechanism includes a first mounting frame, a first loading motor, a first ball screw, a first mounting flange, a first guide post, a first loading rod, an upper member of a first connecting rod, and a lower member of a first connecting rod. The first mounting frame is connected to the connecting plate of the guide rail slider assembly. The first screw of the first ball screw is rotatably mounted inside the first mounting frame. The first loading motor is mounted on the top of the first mounting frame, and its output end is connected to the first screw of the first ball screw via transmission. The first screw nut of the first ball screw is fixed to the first mounting flange. The first guide post is arranged vertically inside the first mounting frame. The first mounting flange and the first guide post are in sliding guide engagement. The top end of the first loading rod is connected to the first mounting flange, and its bottom end extends downward and is fixedly connected to the top end of the upper member of the first connecting rod. The top end of the lower member of the first connecting rod is hinged to the bottom end of the upper member of the first connecting rod, and its bottom end is hinged to the left side of the top of the rotary mechanism.

6. The four-degree-of-freedom combined loading device for marine basic model testing according to claim 4, characterized in that: The second loading mechanism includes a second mounting bracket, a second loading motor, a second ball screw, a second mounting flange, a second guide post, a second loading rod, and a second connecting rod. The second mounting bracket is connected to the connecting plate of the guide rail slider assembly. The second lead screw of the second ball screw is rotatably mounted inside the second mounting bracket. The second loading motor is mounted on the top of the second mounting bracket, and its output end is connected to the second lead screw of the second ball screw via transmission. The second lead screw nut of the second ball screw is fixed to the second mounting flange. The second guide post is arranged vertically within the second mounting bracket. The second mounting flange and the second guide post are in sliding guide engagement. The top end of the second loading rod is connected to the second mounting flange, and its bottom end extends downward and is fixedly connected to the top end of the second connecting rod. The bottom end of the second connecting rod is hinged to the right side of the top of the rotary mechanism.

7. The four-degree-of-freedom combined loading device for marine basic model testing according to claim 4, characterized in that: The third loading mechanism includes a third loading motor, a transverse lead screw, a horizontal connecting block, and a free-side lead screw support; the third loading motor is fixed to the bottom of the loading beam; one end of the transverse lead screw is connected to the output end of the third loading motor, and the other end passes through the horizontal connecting block and is rotatably connected to the free-side lead screw support; the free-side lead screw support is fixed to the bottom of the loading beam; the horizontal connecting block is connected to the connecting plate of the guide rail slider assembly.

8. The four-degree-of-freedom combined loading device for marine basic model testing according to claim 1, characterized in that: The rotary mechanism includes a housing, a grooved connecting ring, a rotary servo motor, a planetary reducer, and an electrical slip ring. The top of the housing has a grooved connecting ring for hinged connection between the first and second loading mechanisms. The rotary servo motor is located on the top of the housing and inside the grooved connecting ring. The planetary reducer is fixed inside the housing and is connected to the rotary servo motor for transmission. The electrical slip ring is located inside the housing and is used to transmit electrical signals during rotation and prevent wire entanglement.

9. A four-degree-of-freedom combined loading device for marine basic model testing according to claim 1, characterized in that: The force sensing unit is a six-dimensional force sensor; the attitude sensing unit is a tilt sensor.

10. A four-degree-of-freedom combined loading method for marine basic model testing, characterized in that: Based on the four-degree-of-freedom combined loading device for marine basic model testing as described in any one of claims 1 to 9, the method includes load application, real-time compensation for additional displacement, real-time load measurement and feedback, coordinated control of each loading mechanism, and stable load output. The specific steps are as follows: S1, Load application Based on the bearing capacity of the foundation and the pre-set test plan in the marine foundation model test, vertical loads, horizontal loads, moment and torque single-degree-of-freedom loads, or multi-degree-of-freedom combined loads are applied to the marine foundation model respectively; S1.1 The specific method for applying a single-degree-of-freedom load is as follows: Applying vertical load: The first and second loading mechanisms synchronously output vertical component loads of equal magnitude and downward direction, which are then combined to form the overall vertical load; Applying horizontal load: The horizontal load is directly output through the third loading mechanism; Applying torque: The first and second loading mechanisms synchronously output vertical loads of equal magnitude and opposite direction, thereby generating torque; Applying torque: Torque is directly output through the rotary mechanism; S1.2 The specific method for applying two-degree-of-freedom loads is as follows: Applying a combination of vertical and horizontal loads: The first and second loading mechanisms simultaneously output vertical component loads of equal magnitude and downward direction to synthesize the overall vertical load; at the same time, the third loading mechanism applies a horizontal load, realizing a two-degree-of-freedom combination loading of vertical and horizontal loads; Applying a combination of vertical load and moment: The first loading mechanism and the second loading mechanism output vertical sub-loads V1 and V2 of different magnitudes and downward directions, respectively, with vertical sub-load V2 > vertical sub-load V1, synthesizing the overall vertical load V = V1 + V2, thereby forming a moment M, M = (V2 - V1)L, realizing the two-degree-of-freedom combination loading of vertical load and moment; wherein, the target output loads of the first loading mechanism and the second loading mechanism are respectively: V1 = V / 2 - M / (2L), V2 = V / 2 + M / (2L), where L is the horizontal distance between the center point of the first loading mechanism or the second loading mechanism and the rotary mechanism; Applying a combination of horizontal load and torque: The horizontal load is directly output through the third loading mechanism, and the torque is directly output through the slewing mechanism, realizing a two-degree-of-freedom combination loading of horizontal load and torque; S1.3 The specific application method of the three-degree-of-freedom load is as follows: The application of vertical load, horizontal load, and moment combination: The first and second loading mechanisms output vertical sub-loads V1 and V2 of different magnitudes and downward directions, respectively, to synthesize the overall vertical load V = V1 + V2. The third loading mechanism directly outputs the horizontal load H, and simultaneously generates a moment M, M = (V2 - V1)L, realizing the three-degree-of-freedom combination loading of vertical load, horizontal load, and moment; where the target output loads of the first and second loading mechanisms are respectively: V1 = V / 2 - M / (2L), V2 = V / 2 + M / (2L). Applying a combination of horizontal load, moment, and torque: The horizontal load is directly output through the third loading mechanism, while the vertical loads of equal magnitude and opposite direction are output through the first and second loading mechanisms to form a moment M. At the same time, the torque is directly output through the rotary mechanism, realizing the three-degree-of-freedom combination loading of horizontal load, moment, and torque. S1.4 The specific application method of the four-degree-of-freedom load is as follows: The application of vertical load, horizontal load, moment, and torque combination: The first and second loading mechanisms simultaneously output vertical sub-loads V1 and V2 of different magnitudes and downward directions, synthesizing the overall vertical load V = V1 + V2. The third loading mechanism directly outputs the horizontal load H, at which point a moment M is formed, M = (V2 - V1)L. At the same time, the rotary mechanism directly outputs the torque T, realizing the four-degree-of-freedom combination loading of vertical load, horizontal load, moment, and torque. Among them, the target output loads of the first and second loading mechanisms are V1 = V / 2 - M / (2L) and V2 = V / 2 + M / (2L), respectively. S2, Additional Displacement Real-time Compensation During the differential loading process of the first loading mechanism and the second loading mechanism, the rotary mechanism will deflect, causing the preset reference point o of the rotary mechanism to shift, and after the shift, an offset reference point o' is formed. By constructing the spatial geometric relationship between the preset reference point o and the offset reference point o´, precise compensation for additional displacement is achieved. The geometric relationship is shown in the following formula: (L AB -L DC ) 2 +L AD 2 =L BC 2 ; Among them, L AB L is the distance between the center point of the second loading mechanism and the center point of the rotary mechanism. BC L is the distance between the center point of the second loading mechanism and the center point of the rotary mechanism after deflection. DC L is the horizontal offset distance of the offset reference point o' relative to the preset reference point o; AD This represents the vertical offset distance of the offset reference point o' relative to the preset reference point o; The deflection angle θ of the preset reference point o on the rotary mechanism is collected in real time by the attitude sensing unit, and the formula for calculating the horizontal offset distance is: L DC =L AD tanθ; Based on the above geometric relationships, the vertical offset distance L of the offset reference point o' relative to the preset reference point o can be calculated. AD and horizontal offset distance L DC That is, the real-time additional vertical displacement Δu z and additional horizontal displacement Δu x The additional vertical displacement Δu is achieved by controlling the loading beam to move vertically along the integrated loading frame via the control unit. z Compensation; by means of the first and second loading mechanisms moving horizontally along with the guide rail slider assembly, an additional horizontal displacement Δu is achieved. x Compensation to eliminate loading position deviation caused by the deflection of the rotary mechanism; S3. Real-time load measurement and feedback The actual vertical load V borne by the marine foundation model was simultaneously measured using a force sensing unit. m Measured horizontal load H m Measured torque M m and measured torque T m The measured load data is fed back to the control unit in real time. The control unit compares the measured load data with the target load data, calculates the deviation value of the load for each degree of freedom, and coordinates and corrects the output of each loading mechanism, as follows: The output loads of the first and second loading mechanisms are corrected based on the vertical load deviation and moment deviation, as shown in the following formula: △V=VV m ;△M=MM m ; △V1=△V / 2-△M / (2L), △V2=△V / 2+△M / (2L); Where △V represents the vertical load V and the measured vertical load V0. m The deviation value; △M is the difference between the torque M and the measured torque M. m The deviation value; △V1 is the vertical load correction amount of the first loading mechanism; △V2 is the vertical load correction amount of the second loading mechanism; The output load of the third loading mechanism is corrected based on the horizontal load deviation, as shown in the following formula: △H=H-H m ; Where △H represents the horizontal load H and the measured horizontal load H m The deviation value; The output torque of the rotary mechanism is corrected based on the torque deviation, as shown in the following formula: △T=T-T m ; Where △T represents the difference between the torque T and the measured torque T. m The deviation value; S4, Coordinated Control of Each Loading Mechanism The control unit coordinates and controls each loading mechanism based on the measured load data from the force sensing unit. When the third loading mechanism applies a horizontal load, causing the measured vertical load or measured moment to deviate from the target load data, the control unit compensates for the vertical load deviation and moment deviation by adjusting the output of the first loading mechanism and the second loading mechanism. When the torque applied by the slewing mechanism causes the measured vertical load, measured horizontal load, or measured moment to deviate from the target load data, the control unit coordinates and corrects the outputs of the first loading mechanism, the second loading mechanism, and the third loading mechanism according to the deviation of the load of each degree of freedom. The output parameters of each loading mechanism are iteratively corrected until the load deviation of each degree of freedom meets the preset requirements, that is, the combined load is determined to have reached the target load data. S5, Stable Load Output When the measured vertical load, measured horizontal load, measured moment, and measured torque are all within the preset error range, the control unit enters the constant load closed-loop holding state; the force sensing unit continuously collects the measured load data in real time and continuously and dynamically fine-tunes the output parameters of each loading mechanism, so that the four-degree-of-freedom load is always stably maintained within the preset error range, and the test load is stably and continuously output.

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