A rigid-liquid coupling sloshing experiment device and method based on a six-degree-of-freedom platform

Abstract

The present application relates to the field of complex spacecraft coupling dynamics and control technology, in particular to a rigid-liquid coupling shaking experimental device and method based on a six-degree-of-freedom platform; when the six-degree-of-freedom platform is opened, the clamping-release component clamps the ellipsoidal Cassini tank, so that it is fixed inside the load support structure and moves together with the load support structure; when the six-degree-of-freedom platform is closed, the clamping-release component releases the ellipsoidal Cassini tank, so that the ellipsoidal Cassini tank swings freely, and the gimbal of the rigid-liquid coupling suspension component drives the smooth slider to slide on the scale guide rail, the displacement of the smooth slider is recorded as the rigid-liquid coupling displacement, and the pressure value of the liquid in the ellipsoidal Cassini tank is collected in real time through the pressure collection system. The present application simulates the real situation in the rocket flight process in the ground experiment, thereby simulating the experimental phenomenon of the rigid-liquid coupling shaking of the tank, and solving the problem that it is difficult to simulate this shaking phenomenon in the ground experiment.

Description

Technical Field

[0001] This invention relates to the field of coupled dynamics and control technology for complex spacecraft, and in particular to a rigid-fluid coupled swaying experimental device and method based on a six-degree-of-freedom platform. Background Technology

[0002] In modern aerospace, launch vehicles typically carry a large amount of liquid propellant, which accounts for about 90% of the total launch mass, such as China's Long March series launch vehicles and SpaceX's Falcon 9 series rockets. During flight, rockets are affected by high-altitude aerodynamic disturbances, varying engine thrust, and weightlessness, which can easily induce small-amplitude / nonlinear sloshing of the liquid propellant in the rocket's tanks. This causes low-frequency coupled vibrations between the liquid propellant and the rocket's rigid body, directly affecting the rocket's flight attitude and payload orbital accuracy. Furthermore, under weightlessness, low-frequency coupled vibrations can cause the liquid propellant to exhibit low-speed rotational sloshing, causing it to deviate from the fuel outlet at the bottom of the tank. In this case, some pressurized gas enters the liquid engine piping, leading to gas-liquid mixing and causing malfunctions in the liquid engine, sometimes even resulting in the failure of the entire launch mission. Therefore, liquid propellant management has always been a critical issue in modern aerospace, and in recent years, numerous scholars both domestically and internationally have made progress in addressing the problem of liquid propellant sloshing.

[0003] Currently, ground-based experiments are a cost-effective and widely used research method for studying liquid propellant sloshing. Relevant references are as follows:

[0004] Reference [1] (Abramson H N. The dynamic behavior of liquids in moving containers [R]. NASA SP-106. NASA Special Publication, 1966.) conducted a system experiment on small-amplitude shaking of various regular tank structures such as cylindrical and rectangular tanks under normal ground weight conditions, and obtained the relationship between the excitation frequency f and some experimental phenomena, as well as the parameters of the anti-sway baffle.

[0005] Reference [2] (Li Xu. Mechanical performance analysis of float-type anti-sloshing structure in fuel tank [D]. Harbin: Harbin Institute of Technology, 2016.) explored the effect of covering the free liquid surface of a cylindrical tank with a layer of various floats on the suppression of liquid sloshing from the perspective of passive control of liquid sloshing through a ground scale model experiment.

[0006] Reference [3] (Jin Yulin. Dynamics analysis of liquid sloshing in a storage tank with a novel anti-sloshing structure [D]. Harbin: Harbin Institute of Technology, 2013.) used a ground horizontal vibrator to apply sinusoidal excitation to a flat rectangular storage tank and explored the anti-sloshing effect of a novel "cross-shaped" blade structure that can rotate around a fixed axis.

[0007] Reference [4] (Wu Wenjun, Gao Chaonan, Yue Baozeng, et al. Experiment and dynamic characteristics analysis of nonlinear steady-state sloshing of liquid in cylindrical tank [J]. Journal of Astronautics, 2021, 42(09): 1078-1089.) designed an experimental device for accurate measurement of dynamic sloshing force and sloshing torque of liquid in cylindrical tank. The device uses a horizontal exciter to apply excitation to the cylindrical tank and explores the numerical values ​​of dynamic sloshing force and sloshing torque of liquid under two states: non-rotational sloshing and rotational sloshing.

[0008] Reference [5] (Zhang Haitao, Sun Beibei, Chen Jiandong, et al. Experimental study on large-scale nonlinear sloshing of liquid in moving container [J]. Journal of Southeast University (Natural Science Edition), 2017, 47(01): 33-37.) By applying transverse harmonic excitation to a rectangular liquid-filled tank using a horizontal exciter, the experiment investigated the slapping and resonance phenomena of the liquid in the tank, and measured the liquid pressure time history at a certain point on the side wall of the container using a pressure sensor.

[0009] Reference [6] (Berry RL, Tegart J R. Experimental study of transient liquidmotion in orbiting spacecraft[R]. NASA final Report, NASA-CR-144213, 1976.) proposed using a drop tower experiment to suddenly apply a constant horizontal acceleration excitation to a small Cassini tank falling at a constant acceleration, observe the sloshing law of the liquid in the tank, and conduct a reasonable analysis.

[0010] Although numerous scholars have made significant progress in addressing liquid sloshing, current research on low-frequency rigid-liquid coupling sloshing phenomena between liquid propellant and the rocket's rigid body primarily utilizes equivalent mechanical models (simple pendulum model, spring-mass equivalent model, center-of-mass equivalent model, and pulsating sphere model, etc.) for theoretical studies, with few systematic ground-based experimental studies. Furthermore, for ground-based scaled-down model experiments, existing research largely utilizes horizontal exciters to apply sinusoidal excitation to regular propellant tanks (cubic prisms, cylinders, etc.) to observe some experimental phenomena and data. However, in practical engineering, propellant tanks are typically ellipsoidal Cassini tank structures, meaning the middle section is cylindrical and the ends are semi-ellipsoidal; and current technologies using horizontal exciters can only achieve two-dimensional vibration effects of the propellant liquid, such as traveling waves and standing waves, which cannot simulate the actual conditions during rocket flight. Summary of the Invention

[0011] The purpose of this invention is to overcome the problem that existing technologies can only simulate two-dimensional vibration effects in ground experiments when conducting rigid-fluid coupling swaying experiments, and cannot simulate the real situation during rocket flight. Therefore, this invention provides a rigid-fluid coupling swaying experimental device and method based on a six-degree-of-freedom platform.

[0012] To address the various shortcomings of the existing technologies, the present invention aims to provide a rigid-liquid coupling sloshing experimental device based on a six-degree-of-freedom platform. This invention can effectively simulate the rigid-liquid coupling sloshing phenomenon between the rigid body of a rocket and the liquid propellant under real-world conditions. By measuring important parameters such as the rigid-liquid coupling sloshing displacement d and the dynamic pressure P at a fixed point on the inner wall of the propellant tank, it fills the gap in ground-based experimental research on rigid-liquid coupling sloshing problems and addresses the complex parameter problem of obtaining the sloshing law of liquid within the propellant tank, thereby providing a reference for practical engineering applications.

[0013] The rigid-fluid coupled swaying experimental device based on a six-degree-of-freedom platform provided by this invention includes: a six-degree-of-freedom platform, a load support frame 4, a clamping-release component, an ellipsoidal Cassini tank 5, a pressure acquisition system, and a rigid-fluid coupled suspension component 8; wherein...

[0014] The six-degree-of-freedom platform is used to control the load support frame 4 on it to simulate the six-degree-of-freedom motion attitude of the rocket in space. The six-degree-of-freedom motion attitude in space includes: the rocket's lateral, longitudinal, vertical, pitch, yaw and roll motion attitudes.

[0015] When the six-degree-of-freedom platform is opened, the clamping-release component is used to clamp the ellipsoidal Cassini tank 5, fixing it inside the load support structure 4 and moving together with the load support structure 4;

[0016] The rigid-hydraulic coupling suspension component 8 includes: a graduated guide rail 81, a smooth slider 82, and a universal joint 83, wherein...

[0017] The two ends of the scale guide rail 81 are respectively fixed on the top beams on opposite sides of the load support frame 4;

[0018] The smooth slider 82 is slidably connected to the scale guide rail 81;

[0019] The top end of the universal joint 83 is fixedly connected to the lower surface of the smooth slider 82, and its bottom end is connected to the top end of the ellipsoidal Cassini tank 5.

[0020] When the six-degree-of-freedom platform is closed, the clamping-release component is used to release the ellipsoidal Cassini tank 5, allowing the ellipsoidal Cassini tank 5 to swing freely, and drive the smooth slider 82 to slide on the scale guide rail 81 through the universal joint 83, and record the displacement of the smooth slider 82 as the rigid-fluid coupling displacement.

[0021] The pressure acquisition system is used to acquire the pressure value of the liquid in the ellipsoidal Cassini tank 5 in real time.

[0022] As an improvement to the above method, the six-degree-of-freedom platform includes: a worktable 1, a six-degree-of-freedom servo electric cylinder component 3, and a six-degree-of-freedom platform control cabinet 10, wherein,

[0023] The six-degree-of-freedom servo electric cylinder component 3 is fixed on the workbench 1 to simulate the six-degree-of-freedom motion posture in space.

[0024] The six-degree-of-freedom platform control cabinet 10 is used to control the opening or closing of the six-degree-of-freedom servo electric cylinder component 3;

[0025] The load support frame 4 is fixed on the load platform 35 of the six-degree-of-freedom servo electric cylinder component 3, so that its motion posture is the same as that of the load platform 35.

[0026] As an improvement to the above method, the load support frame 4 is further provided with intermediate beams on the underside of the two top beams on which the scale guide rail 81 is installed; each intermediate beam is connected to a section of support profile 42 on its outer side to form a T-shaped beam.

[0027] The clamping-release component includes: two lead screw motor clamping-release assemblies; each lead screw motor clamping-release assembly includes: a support profile 42, a slide rail 43, a slider 44, an arc-shaped fitting part 49, a through-type lead screw motor 11, a lead screw 12, a motor driver 13, and a motor controller 14; wherein,

[0028] The slide rail 43 is fixed above the support profile 42;

[0029] The slider 44 is located above the slide rail 43 and is slidably connected to the slide rail 43;

[0030] The through-type lead screw motor 11 is mounted on the intermediate beam;

[0031] One end of the lead screw 12 is connected to the slider 44, and the other end passes through the through-type lead screw motor 11 and is connected to the arc-shaped fitting part 49;

[0032] The motor controller 14 uses the motor driver 13 to control the through-type lead screw motor 11 to work, so that the lead screw 12 moves back and forth, thereby controlling the arc-shaped fitting part 49 to move forward or backward.

[0033] When the six-degree-of-freedom servo electric cylinder component 3 is activated, the through-type lead screw motor 11, based on the control of the motor controller 14, causes the lead screw 12 to move toward the ellipsoidal Cassini tank 5, so as to control the arc-shaped fitting component 49 to fit tightly against the outer surface of the ellipsoidal Cassini tank 5.

[0034] When the six-degree-of-freedom servo electric cylinder component 3 is closed, the through-type lead screw motor 11, based on the control of the motor controller 14, causes the lead screw 12 to move toward the support profile 42, so as to control the arc-shaped fitting 49 away from the ellipsoidal Cassini tank 5.

[0035] As an improvement to the above method, a telescopic screw 48 is also provided between the lead screw 12 and the arc-shaped fitting part 49.

[0036] As an improvement to the above method, the six-degree-of-freedom servo electric cylinder component 3 includes: a lower base 31, six servo electric cylinders 32, an upper universal joint 33, a lower universal joint 34, and a load platform 35; wherein...

[0037] The lower base 31 is fixedly connected to the workbench 1 via a parallel pressure plate 2;

[0038] The six servo electric cylinders 32 are configured as three groups of servo electric cylinders 32 spaced 120 degrees apart. Each group consists of two closely adjacent servo electric cylinders 32, which are arranged above the lower base 31. Their lower ends are connected to the lower base 31 through the lower universal joint 34, and their upper ends are connected to the load platform 35 through the upper universal joint 33.

[0039] As an improvement to the above method, the ellipsoidal Cassini tank 5 includes: an upper cover and a lower tank; wherein, the upper cover and the lower tank are connected by a flange ring 51, and the flange ring 51 has several evenly distributed through holes 52, and the upper cover and the lower tank structure of the ellipsoidal Cassini tank 5 are assembled together by bolt assemblies passing through the through holes 52.

[0040] The ellipsoidal Cassini tank 5 has two pressure holes 53 on its side wall, and the probe part of the pressure sensor 6 of the pressure acquisition system is installed in the two pressure holes 53.

[0041] As an improvement to the above method, the pressure acquisition system includes: a pressure sensor 6 and an intelligent data acquisition instrument 7; wherein,

[0042] The pressure sensor 6 is a piezoresistive pressure sensor, and its probe is installed in the pressure hole 53 on the side wall of the ellipsoidal Cassini tank 5.

[0043] The pressure sensor 6 transmits the liquid pressure value to the computer 9 via the intelligent data acquisition instrument 7.

[0044] To achieve another objective of the present invention, the present invention provides a rigid-fluid coupling swaying experimental method based on a six-degree-of-freedom platform, implemented using the aforementioned rigid-fluid coupling swaying experimental device based on a six-degree-of-freedom platform, comprising the following steps:

[0045] Step 1) Move the slider 82 to the midpoint of the scale guide rail 81 and keep the ellipsoidal Cassini tank 5 stably and statically suspended;

[0046] Step 2) The clamping-release component is used to tightly fit the ellipsoidal Cassini tank 5, so that the ellipsoidal Cassini tank 5 is in a clamped state;

[0047] Step 3) Based on the motion posture requirements of the experimental platform, set the simulation parameters of the six-degree-of-freedom servo electric cylinder component 3; and control the six-degree-of-freedom servo electric cylinder component 3 to work based on the simulation parameters through the six-degree-of-freedom platform control cabinet 10;

[0048] Step 4) After the liquid movement pattern within the ellipsoidal Cassini tank 5 becomes clear, the six-degree-of-freedom servo electric cylinder component 3 is stopped by the six-degree-of-freedom platform control cabinet 10, bringing it to a stationary state; simultaneously, the clamping-release component is moved away from the ellipsoidal Cassini tank 5, allowing the ellipsoidal Cassini tank 5 to swing freely, and the smooth slider 82 is driven to slide on the scale guide rail 81 via the universal joint 83; the ellipsoidal Cassini tank 5 undergoes rigid-fluid coupled motion under the action of the liquid sloshing force within it;

[0049] Step 5) Record the displacement of the smooth slider 82 as the rigid-liquid coupling displacement, and collect the pressure value of the liquid in the ellipsoidal Cassini tank 5 in real time through the pressure acquisition system.

[0050] As an improvement to the above method, the simulation parameters include: vibration peak value D, vibration frequency f, and phase angle θ of each servo electric cylinder 32.

[0051] The rigid-fluid coupled swaying experimental device and method based on a six-degree-of-freedom platform described in this invention have the following advantages compared with the prior art:

[0052] 1) The rigid-liquid coupling swaying experimental device based on a six-degree-of-freedom platform described in this invention uses a six-degree-of-freedom servo electric cylinder component 3 as the experimental excitation device. Compared with using a horizontal vibrator to realize the two-dimensional small-amplitude swaying of the liquid in the tank, this invention can better simulate the multi-dimensional (lateral, longitudinal, vertical, pitch, yaw, roll) vibration effects of a rocket under the influence of high-altitude aerodynamic interference forces and the changing thrust of the liquid engine.

[0053] 2) The rigid-liquid coupling swaying experimental device based on a six-degree-of-freedom platform described in this invention uses a scaled-down ellipsoidal Cassini tank 5. Compared with flat rectangular and cylindrical tanks, this invention is closer to the liquid propellant tanks used in actual engineering. Not only are the experimental phenomena closer to the real situation, but it can also serve as a ground-based preliminary research project to provide reference for actual engineering.

[0054] 3) The rigid-liquid coupling sloshing experimental device based on a six-degree-of-freedom platform described in this invention combines a six-degree-of-freedom platform with a ground-based rigid-liquid coupling sloshing experiment, allowing the tank and liquid to move under the multidimensional harmonic excitation of the six-degree-of-freedom platform, resulting in a more realistic simulation. This invention employs a combination of a six-degree-of-freedom servo electric cylinder component 3 and an ellipsoidal Cassini tank 5. By appropriately controlling the vibration peak value D, vibration frequency f, and six independent phase angles θ of the six-degree-of-freedom servo electric cylinder component 3, the liquid inside the tank exhibits a large-scale sloshing phenomenon. The load is suspended using a graduated guide rail 81 and a universal joint 83, and the tank is clamped and released as needed by the clamping-release mechanism. This effectively simulates the experimental phenomenon of rigid body and liquid coupling sloshing, solving the problem of simulating this sloshing phenomenon in ground-based experiments.

[0055] 4) The rigid-liquid coupling swaying experimental device based on a six-degree-of-freedom platform described in this invention uses a graduated guide rail 81 to suspend the left-right swaying ellipsoidal Cassini tank 5 and the liquid, measuring the rigid-liquid coupling swaying displacement d; two pressure sensors 6 measure the fixed-point dynamic pressure P of the liquid in the tank during the swaying process, fully acquiring experimental data of the liquid in the tank during the rigid-liquid coupling swaying process. Based on this, a reasonable quantitative correspondence is analyzed between the rigid-liquid coupling swaying displacement d, the fixed-point dynamic pressure P, and the input vibration peak value D, vibration frequency f, and independent phase angle θ of the six electric cylinders. Attached Figure Description

[0056] Figure 1This is a schematic diagram of the storage tank clamping state of a rigid-liquid coupling swaying experimental device based on a six-degree-of-freedom platform according to an embodiment of the present invention.

[0057] Figure 2 This is a schematic diagram of the tank release state of a rigid-liquid coupling swaying experimental device based on a six-degree-of-freedom platform according to an embodiment of the present invention.

[0058] Figure 3 This is a schematic diagram showing the overall system operation of the experimental apparatus in this embodiment of the invention;

[0059] Figure 4 This is a schematic diagram of the structure of the six-degree-of-freedom servo electric cylinder in an embodiment of the present invention;

[0060] Figure 5 This is a schematic diagram of the clamping-release component structure in an embodiment of the present invention;

[0061] Figure 6 This is a schematic diagram of the rigid-fluid coupling suspension component structure in an embodiment of the present invention;

[0062] Figure 7(a) is a front view of the ellipsoidal Cassini tank structure in an embodiment of the present invention;

[0063] Figure 7(b) is a cross-sectional view of the ellipsoidal Cassini tank structure along AA in Figure 7(a).

[0064] Attached Figure Labels

[0065] 1. Worktable; 2. Parallel pressure plate; 3. Six-DOF servo electric cylinder component; 31. Lower base; 32. Servo electric cylinder; 33. Upper universal joint; 34. Lower universal joint; 35. Load platform; 4. Load support frame; 41. Support plate; 42. Support profile; 43. Slide rail; 44. Slider; 45. T-shaped fixing block; 46. Motor fixing block; 47. Rectangular fixing block; 48. Telescopic screw; 49. Arc-shaped fitting part; 5. Ellipsoidal Cassini. 51. Storage tank; 52. Flange ring; 53. Through hole; 54. Pressure hole; 6. Pressure sensor; 7. Intelligent data acquisition instrument; 8. Rigid-hydraulic coupling suspension component; 81. Scale guide rail; 82. Smooth slider; 83. Universal joint; 84. Slider-universal joint connector; 85. Universal joint-storage tank connector; 9. Computer; 10. Six-degree-of-freedom platform control cabinet; 11. Through-type lead screw motor; 12. Lead screw; 13. Motor driver; 14. Motor controller. Detailed Implementation

[0066] The technical solutions provided by the present invention will be further illustrated below with reference to the embodiments.

[0067] The present invention provides a rigid-liquid coupling swaying experimental device based on a six-degree-of-freedom platform. The experimental device includes: a six-degree-of-freedom platform control cabinet 10, a six-degree-of-freedom servo electric cylinder component 3, a load support frame 4 (clamping-release component), a rigid-liquid coupling suspension component 8, and a liquid dynamic pressure measurement system.

[0068] Hereinafter, specific embodiments will be described with reference to the accompanying drawings. Furthermore, the specific embodiments shown below do not limit the scope of the invention as described in the claims. Additionally, the entirety of the configurations represented in the following specific embodiments is not limited to those necessary for the solution of the invention described in the claims.

[0069] Please see Figures 1-7(b) The rigid-fluid coupling swaying experimental device based on a six-degree-of-freedom platform provided in this embodiment includes a worktable 1 for supporting a six-degree-of-freedom servo electric cylinder component 3, a load support frame 4, and an ellipsoidal Cassini tank 5. The worktable 1 plays a role in increasing the weight and fixing the entire experimental device, preventing the experimental device from shifting due to the excessively fast vibration frequency of the six-degree-of-freedom servo electric cylinder component 3 during the experiment. The worktable 1 is a T-slot worktable 1. The six-degree-of-freedom servo electric cylinder component 3 is fixedly connected to the T-slot worktable 1 through a parallel pressure plate 2. The lower base 31 of the six-degree-of-freedom servo electric cylinder component 3 is in contact with the surface of the T-slot worktable 1. The parallel pressure plate 2 has a through groove in the middle, and there is a bolt assembly in the through groove. The top of the bolt is set in the T-slot of the T-slot worktable 1. One end of the parallel pressure plate 2 presses against the surface of the lower base 31. The bolt is fitted in the middle through groove of the parallel pressure plate 2 and is tightened with a nut. There is a support bolt at the rear end of the through groove to keep the rear end and front end of the parallel pressure plate 2 horizontal, ensuring that the structure between the lower base 31 and the T-slot worktable 1 is firm. The servo electric cylinder 32 is located above the lower base 31 and consists of 6 independent servo electric cylinders. The lower base 31 is connected to each servo electric cylinder 32 through 6 lower universal joints 34. The other end of each servo electric cylinder 32 is connected to the load platform 35 through an upper universal joint 33.

[0070] Above the load platform 35 are mainly the load support frame 4, the ellipsoidal Cassini tank 5, the pressure sensor 6, and the rigid-hydraulic coupling suspension component 8. The support plate 41 is above the load platform 35 and is firmly fixed to the load platform 35 by the support plate-load platform fixing assembly. The support plate-load platform fixing assembly consists of 8 bolt assemblies. There are 8 through holes arranged in a cross shape on the support plate 41 and the load platform 35. The above 8 bolts are used in conjunction with these 8 through holes to firmly fix the two together. On both sides of the support plate 41, there are 5 profile-support plate fixing assemblies. Each profile-support plate fixing assembly includes a through hole and a T-bolt. The through hole corresponds exactly to the groove of the profile 42. The T-bolt assembly is used to fix the profile 42 to the support plate 41. The spatial layout of the support profile 42 is a large cuboid structure. The support profiles 42 at the intersection of the spaces are fixed by several fixing angle brackets, so that the support profile 42 can be stably built into a cuboid shape to meet the sliding range requirements of the ellipsoidal Cassini tank 5 during the test.

[0071] The clamping-release component is composed of multiple structures, including a support profile 42, a slide rail 43, a slider 44, a T-shaped fixing block 45, a motor fixing block 46, a rectangular fixing block 47, a telescopic screw 48, an arc-shaped fitting part 49, a through-type lead screw motor 11, a lead screw 12, a motor driver 13, and a motor controller 14. In this embodiment of the invention, except for the motor controller 14, each of the above structures consists of two sets, each set symmetrically distributed on the left and right sides of the above cuboid structure, and firmly fixed by the support profile 42 and fixing angle brackets. A "T"-shaped horizontal plane structure is formed by arranging part of the support profile 42. The through-type lead screw motor 11 is placed on the crossbeam of the "T". The lead screw 12 passes through the through-type lead screw motor 11, with one end pointing towards the ellipsoidal Cassini tank 5, and the other end perpendicular to the crossbeam of the "T" and pointing outward. A pad of a certain thickness can be placed between the through-type lead screw motor 11 and the crossbeam of the "T" to ensure that the lead screw 12 is at a suitable horizontal height. The motor fixing block 46 is a planar multi-hole plate structure, which is placed vertically against the surface of the through-type lead screw motor 11. The motor fixing block 46 is fixed to the through-type lead screw motor 11 by bolt assembly on one hand, and to the aforementioned pad plate by bolt assembly on the other hand. The pad plate is also fixed to the support profile 42 by bolt assembly. In this way, the through-type lead screw motor 11, the motor fixing block 46, and the pad plate can be firmly fixed to the overall structure of the present invention. Both ends of the lead screw 12 have a flat surface cut out on the basis of cylindrical threads. On the side near the ellipsoidal Cassini tank 5, the head of the lead screw 12 is screwed onto a rectangular fixing block 47. The rectangular fixing block 47 is rectangular in shape, with a threaded through hole on the axis. There are several threaded holes on one side of the rectangular fixing block 47, and bolt assemblies are used to fit into these holes to fix the lead screw 12. The telescopic screw 48 has a threaded structure and is screwed onto the other side of the threaded through hole of the rectangular fixing block 47. The telescopic screw 48 connects the rectangular fixing block 47 to the arc-shaped fitting part 49. The arc-shaped fitting part 49 has a curved surface structure with a certain curvature, which is 60° in this embodiment. By using two arc-shaped fitting parts 49 on the left and right, the ellipsoidal Cassini tank 5 can be seamlessly clamped during the experiment, preventing it from swinging left and right in the clamped state. The other end of the lead screw 12 is connected to the T-shaped fixing block 45, which also passes through the axis of the T-shaped fixing block 45, and one end of the lead screw 12 is fixed to the T-shaped fixing block 45 by a bolt assembly. The lower end of the T-shaped fixing block 45 is fixed to the slider 44, and the slide rail 43 is also fixed to the support profile 42 by bolt assembly. The slider 44 can move left and right on the slide rail 43 under the drive of the lead screw 12. The motor controller 14 controls the through-type lead screw motor 11 through the motor driver 13. The through-type lead screw motor 11 can control the forward and backward movement of the lead screw 12. In this way, the clamping-release component can move forward and backward on the arc-shaped fitting part 49 at one end of the lead screw 12 under the drive of the through-type lead screw motor 11 and by using the lead screw 12.In this embodiment, two sets of the above-mentioned devices are used, respectively placed on the left and right sides of the ellipsoidal Cassini tank 5, so that the ellipsoidal Cassini tank 5 can be clamped and released simultaneously. This is to ensure that the liquid-filled ellipsoidal Cassini tank 5 is clamped during the vibration of the six-degree-of-freedom servo electric cylinder component 3, so that it is consistent with the motion state of the load platform. When the movement of the six-degree-of-freedom servo electric cylinder component 3 is paused, the motor controller 14 and the motor driver 13 are used to control and drive the two through-type lead screw motors 11 to execute the release command. The arc-shaped fitting part 49 quickly moves backward to both sides. At this time, only the rigid-hydraulic coupling suspension component 8 suspends the ellipsoidal Cassini tank 5. The liquid-filled ellipsoidal Cassini tank 5 will start to swing freely left and right. The function of the rigid-hydraulic coupling suspension component 8 and the motion of the liquid-filled ellipsoidal Cassini tank 5 after release will be described in detail below. It should be noted that the clamping-release mechanism is not limited to the form of this embodiment. Any device that can firmly fix and release the ellipsoidal Cassini tank 5, ensuring that the ellipsoidal Cassini tank 5 moves in the same posture as the entire platform in the clamped state, and that can quickly release the ellipsoidal Cassini tank 5 and allow it to move freely after a release command is issued, is acceptable. Furthermore, the size of the ellipsoidal Cassini tank 5 can be changed according to actual needs. Within a reasonable range based on the principle of scaled-down models, this clamping-release device can meet the requirements of ground experiments.

[0072] The ellipsoidal Cassini tank 5 is a modular structure, consisting of an upper cover and a lower tank. A flange ring 51 connects the upper cover and the lower tank, each with eight evenly distributed through holes 52. Bolts are used to assemble the upper cover and lower tank of the ellipsoidal Cassini tank 5 through these through holes 52. On one side of the tank body, there are two pressure holes 53, one upper and one lower. A probe portion of a pressure sensor 6 is installed in each of the two pressure holes 53. The other side of the pressure sensor 6 is connected to an intelligent data acquisition instrument 7 via a transmission line. The system is then connected to computer 9 via a transmission line, and the liquid dynamic pressure image is displayed using professional analysis software. A universal joint-tank connector 85 and four bolt through holes are provided on the top of the ellipsoidal Cassini tank 5's upper cover. The universal joint-tank connector 85 is fixed to the top of the ellipsoidal Cassini tank 5 using bolt assemblies and the aforementioned four bolt through holes. The lower end of the universal joint-tank connector 85 connects to the ellipsoidal Cassini tank 5, and the upper end connects to a universal joint 83. The universal joint 83 connects the slider-universal joint connector 84 and the universal joint-tank connector 85 together. A scale guide rail 81 spans the crossbeam of the supporting profile 42 and is fixed by bolt assemblies. A movable, smooth slider 82 with sufficiently low friction is located on the scale guide rail 81. The scale guide rail 81 and the smooth slider 82 are placed horizontally upside down. The smooth slider 82 is connected to the slider-universal joint connector 84 by bolt assemblies. In this way, the scale guide rail 81, the smooth slider 82, the slider-universal joint connector 84, the universal joint 83, the universal joint-tank connector 85, and the ellipsoidal Cassini tank 5 can be connected into a whole.

[0073] The rigid-hydraulic coupling suspension component 8 and the clamping-release component are used together during the experiment. At the beginning of the experiment, the smooth slider 82 is first moved to the midpoint of the scale guide rail to keep the ellipsoidal Cassini tank 5 stably suspended and stationary. Then, the through-type lead screw motor 11 controls the lead screw 12 to push the two arc-shaped fitting parts 49 to tightly fit the ellipsoidal Cassini tank 5, and it is in a clamped state. The computer 9 is turned on, and the computer 9 sets the input peak value D, frequency f and independent phase angle θ of the six electric cylinders through the six-degree-of-freedom platform control software. It also uses the six-degree-of-freedom platform control cabinet 10 to control the six-degree-of-freedom servo electric cylinder component 3 to move according to the predetermined posture. At this time, the ellipsoidal Cassini tank 5 follows the six-degree-of-freedom servo electric cylinder component under the fixation of the clamping-release component. As component 3 moves, the liquid inside the ellipsoidal Cassini tank 5 will also exhibit small-amplitude / non-linear sloshing. After the liquid inside the tank exhibits a certain sloshing pattern, press the pause button, and the six-degree-of-freedom servo electric cylinder component 3 will stop moving. At the same time, the motor controller 14 controls the two lead screws 12 to move to both sides, and the arc-shaped fitting component 49 begins to move away from the ellipsoidal Cassini tank 5. The liquid-filled ellipsoidal Cassini tank 5 also begins rigid-fluid coupling motion under the action of the sloshing of the liquid inside. Because the coefficient of friction between the smooth slider 82 and the scale guide rail 81 is small enough, the ellipsoidal Cassini tank 5 will move back and forth on the scale guide rail 81. The sliding distance is the rigid-fluid coupling displacement d. Finally, the ellipsoidal Cassini tank 5 will stop swinging left and right and stay at a certain point.

[0074] Using this invention, by appropriately controlling the input peak value D, frequency f, and independent phase angle θ of the six electric cylinders, the liquid inside the clamped ellipsoidal Cassini tank 5 will exhibit different experimental phenomena (small-amplitude / nonlinear swaying) under different parameter conditions. After the ellipsoidal Cassini tank 5 is released, it will move back and forth on the scale guide rail 81 through the universal joint 83 and various connecting components, thereby measuring the rigid-fluid coupling displacement d. During this experiment, the dynamic pressure value P of the liquid inside the ellipsoidal Cassini tank 5 can be measured using the pressure sensor 6, so as to measure the parameter information inside the ellipsoidal Cassini tank 5 in the ground experiment as much as possible, in order to provide reference for practical engineering applications.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. It should be noted that any modifications, equivalent substitutions, or improvements made by those skilled in the art without departing from the scope of the technology disclosed in this invention should be included within the protection scope of this invention.

[0076] The key points of this invention are:

[0077] 1) The scaled-down model of the ellipsoidal Cassini tank 5 structure presents significant challenges in actual manufacturing. As a result, many scholars have only conducted ground-based experimental studies on cuboid and cylindrical tanks with simpler structures and manufacturing processes. However, the ellipsoidal Cassini tank 5 is the most commonly used tank structure in actual engineering. Therefore, in the study of rigid-fluid coupling problems, this invention selects the ellipsoidal Cassini tank 5.

[0078] 2) Clamping-release component: This clamping-release structure is one of the products independently conceived and designed in this invention. This device ingeniously enables the ellipsoidal Cassini tank 5 to maintain consistency with the motion state of the six-degree-of-freedom servo electric cylinder component 3 when it moves, and can quickly detach from the arc-shaped fitting component 49 when the six-degree-of-freedom servo electric cylinder component 3 stops working, so as not to hinder the free motion state of the ellipsoidal Cassini tank 5. In this way, the simulation of the six-degree-of-freedom rigid-fluid coupling phenomenon can be realized in ground experiments.

[0079] 3) Rigid-fluid coupling suspension component 8. This suspension structure and the method for measuring the rigid-fluid coupling displacement d are products of independent thinking and design in this invention. Using this device, not only can the ellipsoidal Cassini tank 5 be suspended, preventing the tank from contacting other equipment and affecting the simulation of experimental phenomena, but also, under the action of rigid-fluid coupling swaying force, the device can support the ellipsoidal Cassini tank 5 to slide back and forth on the scale guide rail 81, so that the rigid-fluid coupling displacement d can be measured in ground experiments.

[0080] 4) Six-degree-of-freedom servo electric cylinder component 3: This system controls the extension and retraction of the six servo electric cylinders 32 by inputting the input peak value D, frequency f and independent phase angle θ of the six electric cylinders, thereby driving the sinusoidal vibration of the entire load platform 35. This system is cleverly combined with the liquid sloshing problem, so that the liquid exhibits multi-degree-of-freedom sloshing. In addition, by using the rigid-liquid coupling suspension component 8, the rigid-liquid coupling phenomenon can be simulated in ground experiments.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A rigid-fluid coupled swaying experimental device based on a six-degree-of-freedom platform, characterized in that, include: The system comprises a six-degree-of-freedom platform, a load support frame (4), a clamping-release component, an ellipsoidal Cassini tank (5), a pressure acquisition system, and a rigid-hydraulic coupling suspension component (8); among which, The six-degree-of-freedom platform is used to control the load support frame (4) on it to simulate the six-degree-of-freedom motion attitude of the rocket in space, wherein the six-degree-of-freedom motion attitude of the space includes: the rocket's lateral, longitudinal, vertical, pitch, yaw and roll motion attitudes. When the six-degree-of-freedom platform is opened, the clamping-release component is used to clamp the ellipsoidal Cassini tank (5) and fix it inside the load support structure (4), so that it moves together with the load support structure (4); The rigid-hydraulic coupling suspension component (8) includes: a graduated guide rail (81), a smooth slider (82), and a universal joint (83), wherein, The two ends of the scale guide rail (81) are respectively fixed on the top beams on opposite sides of the load support frame (4); The smooth slider (82) is slidably connected to the scale guide rail (81); The top end of the universal joint (83) is fixedly connected to the lower surface of the smooth slider (82), and its bottom end is connected to the top end of the ellipsoidal Cassini tank (5). When the six-degree-of-freedom platform is closed, the clamping-release component is used to release the ellipsoidal Cassini tank (5), allowing the ellipsoidal Cassini tank (5) to swing freely, and drive the smooth slider (82) to slide on the scale guide rail (81) through the universal joint (83), and record the displacement of the smooth slider (82) as the rigid-fluid coupling displacement; The pressure acquisition system is used to acquire the pressure value of the liquid in the ellipsoidal Cassini tank (5) in real time; The load support frame (4) is provided with intermediate beams on the underside of the two top beams on which the scale guide rail (81) is installed; each intermediate beam is connected to a section of support profile (42) on its outer side to form a T-shaped beam. The clamping-release component includes: two lead screw motor clamping-release assemblies; each lead screw motor clamping-release assembly includes: a support profile (42), a slide rail (43), a slider (44), an arc-shaped fitting piece (49), a through-type lead screw motor (11), a lead screw (12), a motor driver (13), and a motor controller (14); wherein, The slide rail (43) is fixed above the support profile (42); The slider (44) is located above the slide rail (43) and is slidably connected to the slide rail (43); The through-type lead screw motor (11) is mounted on the intermediate beam; One end of the lead screw (12) is connected to the slider (44), and the other end passes through the through-type lead screw motor (11) and is connected to the arc-shaped fitting part (49); The motor controller (14) uses the motor driver (13) to control the through-type lead screw motor (11) to work, so that the lead screw (12) moves back and forth, thereby controlling the arc-shaped fitting part (49) to move forward or backward; When the six-degree-of-freedom servo electric cylinder component (3) is turned on, the through-type lead screw motor (11) is controlled by the motor controller (14) to move the lead screw (12) toward the ellipsoidal Cassini tank (5) so as to control the arc-shaped fitting part (49) to fit tightly against the outer surface of the ellipsoidal Cassini tank (5); When the six-degree-of-freedom servo electric cylinder component (3) is closed, the through-type lead screw motor (11) moves the lead screw (12) toward the support profile (42) based on the control of the motor controller (14) to control the arc-shaped fitting (49) away from the ellipsoidal Cassini tank (5).

2. The rigid-fluid coupled swaying experimental device based on a six-degree-of-freedom platform according to claim 1, characterized in that, The six-degree-of-freedom platform includes: a worktable (1), a six-degree-of-freedom servo electric cylinder component (3), and a six-degree-of-freedom platform control cabinet (10), wherein, The six-degree-of-freedom servo electric cylinder component (3) is fixed on the worktable (1) to simulate the motion posture of six degrees of freedom in space; The six-degree-of-freedom platform control cabinet (10) is used to control the opening or closing of the six-degree-of-freedom servo electric cylinder component (3); The load support frame (4) is fixed on the load platform (35) of the six-degree-of-freedom servo electric cylinder component (3) so that it has the same motion posture as the load platform (35).

3. The rigid-fluid coupled swaying experimental device based on a six-degree-of-freedom platform according to claim 1, characterized in that, A telescopic screw (48) is also provided between the lead screw (12) and the arc-shaped fitting (49).

4. The rigid-fluid coupled swaying experimental device based on a six-degree-of-freedom platform according to claim 1, characterized in that, The six-degree-of-freedom servo electric cylinder component (3) includes: a lower base (31), six servo electric cylinders (32), an upper universal joint (33), a lower universal joint (34), and a load platform (35); wherein, The lower base (31) is fixedly connected to the workbench (1) via a parallel pressure plate (2); The six servo electric cylinders (32) are configured as three groups of servo electric cylinders (32) evenly arranged in the circumference. Each group includes two closely adjacent servo electric cylinders (32) and are arranged together above the lower base (31). Their lower ends are connected to the lower base (31) through the lower universal joint (34) and their upper ends are connected to the load platform (35) through the upper universal joint (33).

5. The rigid-fluid coupled swaying experimental device based on a six-degree-of-freedom platform according to claim 1, characterized in that, The ellipsoidal Cassini tank (5) includes: an upper cover and a lower tank; wherein, the upper cover and the lower tank are connected by a flange ring (51), and the flange ring (51) has several evenly distributed through holes (52), and the upper cover and the lower tank of the ellipsoidal Cassini tank (5) are assembled together by bolt assemblies passing through the through holes (52); The ellipsoidal Cassini tank (5) has two pressure holes (53) on its side wall, and the probe of the pressure sensor (6) of the pressure acquisition system is installed in the two pressure holes (53).

6. The rigid-fluid coupled swaying experimental device based on a six-degree-of-freedom platform according to claim 1, characterized in that, The pressure acquisition system includes: a pressure sensor (6) and an intelligent data acquisition instrument (7); wherein, The pressure sensor (6) is a piezoresistive pressure sensor, and its probe is installed in the pressure hole (53) on the side wall of the ellipsoidal Cassini tank (5); The pressure sensor (6) transmits the liquid pressure value to the computer (9) via the intelligent data acquisition instrument (7).

7. A rigid-fluid coupling swaying experiment method based on a six-degree-of-freedom platform, implemented using the rigid-fluid coupling swaying experiment device based on a six-degree-of-freedom platform as described in any one of claims 1-6, comprising the following steps: Step 1) Move the slider (82) to the midpoint of the scale guide rail (81) and keep the ellipsoidal Cassini tank (5) stable and stationary. Step 2) The clamping-release component is used to tightly fit the ellipsoidal Cassini tank (5), so that the ellipsoidal Cassini tank (5) is in a clamped state; Step 3) Based on the motion posture requirements of the experimental platform, set the simulation parameters of the six-degree-of-freedom servo electric cylinder component (3); and control the six-degree-of-freedom servo electric cylinder component (3) to work based on the simulation parameters through the six-degree-of-freedom platform control cabinet (10); Step 4) After the liquid movement pattern in the ellipsoidal Cassini tank (5) becomes obvious, the six-degree-of-freedom servo electric cylinder component (3) is stopped by the six-degree-of-freedom platform control cabinet (10) and placed in a stationary state; at the same time, the clamping-release component is moved away from the ellipsoidal Cassini tank (5), so that the ellipsoidal Cassini tank (5) swings freely and drives the smooth slider (82) to slide on the scale guide rail (81) through the universal joint (83); the ellipsoidal Cassini tank (5) performs rigid-liquid coupling motion under the action of the liquid sloshing force inside it; Step 5) Record the displacement of the smooth slider (82) as the rigid-liquid coupling displacement, and collect the pressure value of the liquid in the ellipsoidal Cassini tank (5) in real time through the pressure acquisition system.

8. The rigid-fluid coupled swaying experimental method based on a six-degree-of-freedom platform according to claim 7, characterized in that, The simulation parameters include: vibration peak value D, vibration frequency. f and the phase angle of each servo electric cylinder (32) θ .

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