A microgravity simulation device based on a parallel mechanism

Abstract

A microgravity simulation device based on a parallel mechanism, which relates to a microgravity simulation device. The base includes a fixed bottom plate and a moving platform at one end of its surface. The moving platform is equipped with an active-side moving stage, and the opposite end of the fixed bottom plate is equipped with a passive-side moving stage. The moving stage is designed based on the Stewart parallel structure and includes an upper platform, a lower platform, and six electric telescopic rods hinged between the two. The six-axis force sensor is fixed on the upper surface of the moving stage, and a fixed tooling is installed on the six-axis force sensor for docking module clamping and positioning. The active-side moving stage provides the target position for docking and releases the docking signal, and the passive-side moving stage conducts microgravity simulation. It can quickly and accurately make a follow-up reaction to simulate weightless actions, and has the characteristics of adjustable structural parameters, maintainability, reusability, three-dimensional space simulation, no simulation test time limit, and high simulation accuracy.

Description

Technical Field

[0001] The present invention relates to a microgravity simulation device, especially a microgravity simulation device based on a parallel mechanism, and belongs to the technical field of aerospace machinery application research. Background Art

[0002] During spaceflight, weightlessness inevitably occurs. Therefore, during the ground test phase, the impact of weightlessness must be taken into account. Currently, the main methods for simulating the space microgravity environment on the ground are the drop tower method, the parabolic flight method, the water floating method, the suspension method, and the air suspension method.

[0003] The drop tower method relies on the free fall of an object from an initial height to achieve a microgravity state during the free fall motion phase [1,2,3] . By using the drop tower method to simulate weightlessness, its advantages are: high simulation accuracy, high safety of the test equipment, good repeatability, and the ability to conduct weightlessness simulation tests in three-dimensional space; its disadvantages are: the overall structure cost of the microgravity drop tower is high, the size of the test chamber limits the volume and mass of the test object, making it difficult to achieve high versatility, and due to the height limitation of the microgravity drop tower, there is only about 10s of weightlessness simulation test time, which is limited in the simulation test of large space equipment models.

[0004] The parabolic flight method uses a weightless aircraft as the test carrier. When the weightless aircraft flies along a parabolic trajectory, a certain degree of weightless environment can be achieved inside the aircraft cabin [4] . Its advantages are: relatively high accuracy of microgravity simulation, good repeatability of the test equipment, i.e., the weightless aircraft, and the ability to conduct microgravity simulation tests in three-dimensional space; its disadvantages are: the cost of the test equipment, i.e., the weightless aircraft, is relatively expensive, the microgravity simulation time is affected by the flight height of the aircraft, the available simulation time is short, and the external dimensions and weight of the test object are limited by the size of the aircraft cabin.

[0005] The water floating method refers to a method of placing the test object in water and using the buoyancy generated by floating equipment or water to offset gravity, thereby achieving microgravity simulation [5] . Its advantages are: the microgravity simulation time is not restricted by conditions, it can simulate large-sized and heavy space equipment, and it can conduct microgravity simulation tests in three-dimensional space at the same time; its disadvantages are: due to the existence of resistance and turbulence phenomena in water, it is difficult to ensure good test accuracy. In addition, space equipment cannot be directly placed in the water tank for testing, and additional waterproof encapsulation treatment is required to ensure its sealing performance, which will increase additional maintenance costs.

[0006] The suspension method is a method of compensating for the gravity of space equipment through a rope suspension mechanism, an additional pulley group, and a counterweight unit to achieve ground microgravity simulation [6,7], which has been widely used in the ground tests of deployable antennas. Its advantages are as follows: the structure of the suspension system is relatively simple and easy to implement; the time of microgravity simulation tests is not restricted by conditions, and weightlessness tests in three-dimensional space can be achieved. Its disadvantages are as follows: for the truss used to fix the top of the rope, its structure will become complicated along with the complexity of the spacecraft flight trajectory, and the movement friction and wear of the guide rail mechanism following the truss will affect the test accuracy of the suspension method.

[0007] The air suspension method is a method to generate an air film on an air floating platform through the air flow generated by high pressure, lift the object to be tested, and then offset gravity to achieve microgravity simulation. [8,9] . Its advantages are as follows: the R & D and manufacturing cost of the air suspension device is relatively low compared with other methods; the friction between the equipment and the platform is small, so a relatively high simulation accuracy can be achieved; the time of microgravity simulation is not restricted by conditions, and microgravity simulation of large volume and high load can be realized. Its disadvantages are as follows: microgravity simulation is limited to two-dimensional planes, and the air suspension simulation technology in three-dimensional space is not yet mature.

[0008] Although the above five existing methods can all conduct microgravity simulation, they all belong to full physical simulation, that is, the accuracy that the simulation system can achieve completely depends on the parameters of the system itself. If modification is required, the structure or materials of the system need to be changed, and the implementation is relatively complex. Therefore, how to establish a flexible simulation system with variable structural parameters, how to design a microgravity simulation system on the basis of accurately and comprehensively reflecting the mapping relationship between force and displacement, and how to design a microgravity simulation device on the premise of taking into account characteristics such as maintainability, reusability, three-dimensional space simulation, no restriction on simulation test time, and high simulation accuracy are the problems that need to be solved urgently at present.

[0009] [1] Tian Dake, Fan Xiaodong, Zheng Xijian, et al. Research Status and Prospect of Microgravity Environment Simulation for Space Deployable Antennas [J]. Chinese Journal of Mechanical Engineering, 2021, 57(03): 11-25.

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[0011] [3] Zhang Xiaoqian, Yuan Longgen, Wu Wendong, et al. Several Key Technologies of the 100-meter Drop Tower Experimental Facility of the National Microgravity Laboratory [J]. Science in China Series E: Technological Sciences, 2005, (05): 523-34.

[0012] [4]BLOCK J,BAGER A,BEHRENS J,et al.A self-deploying and self-stabilizing helical antenna for small satellites[J].Acta Astronaut,2013,86:88-94.

[0013] [5]Sun,C.,Chen,S.,Yuan,J.,Zhu,Z.:A Six-DOF Buoyancy Tank MicrogravityTest Bed with Active Drag Compensations[J].Microgravity ScienceandTechnology.2017,29(5):391-402.

[0014] [6]Zhang Jiabo,Wang Hui,Li Yun,et al.Gravity unloading technology of solar wing based on vacuum negative pressure adsorption[J].Journal of Mechanical Engineering,2020,56(05):202-10.

[0015] [7]Peng Hao,He Baiyan.New method for gravity compensation of spaceborne loop antenna[J].China Mechanical Engineering,2019,30(04):379-84.

[0016] [8]RYBUS T,SEWERYN K,OLES J,et al.Application ofaplanar air-bearingmicrogravity simulator for demonstration of operations required for anorbital capture with amanipulator[J].ActaAstronaut,2019,155:211-29.

[0017] [9]Yang Guoyong,Wang Hongguang,Jiang Yong,et al.Analysis of gravity unloading accuracy of air-bearing test bed[J].Journal of Mechanical Engineering,2019,55(05):1-10. Summary of the Invention

[0018] In view of the problems existing in the existing microgravity simulation methods, which are difficult to meet the simulation requirements during the docking process of space modules, the present invention provides a microgravity simulation device based on a parallel mechanism. It constructs a ground microgravity simulation device based on the Stewart parallel structure for the docking process of space modules, which can quickly and accurately make a follow-up reaction to simulate weightless actions, and has the characteristics of adjustable structural parameters, maintainability, reusability, three-dimensional space simulation, no limitation on simulation test time, and high simulation accuracy.

[0019] To achieve the above object, the present invention adopts the following technical solutions: A microgravity simulation device based on a parallel mechanism, comprising a base, an active-side moving platform, an active-side six-axis force sensor, an active-side fixing tooling, an active-side docking module, a passive-side docking module, a passive-side fixing tooling, a passive-side six-axis force sensor, and a passive-side moving platform; The base includes a fixed bottom plate and a moving platform installed on one end of its surface and capable of moving back and forth under the control of a lead screw motor. The active-side moving platform is fixedly installed on the surface of the moving platform. The passive-side moving platform is fixedly installed at the opposite end of the surface of the fixed bottom plate. The passive-side moving platform is designed based on the Stewart parallel structure and includes an upper platform, a lower platform, and six electric telescopic rods hinged to the edges between the two. The electric telescopic rods use a servo motor as the power source and are transmission-connected through a reducer in the middle. The active-side moving platform has the same structure as the passive-side moving platform. The active-side six-axis force sensor is fixed on the upper surface of the active-side moving platform, and the passive-side six-axis force sensor is fixed on the upper surface of the passive-side moving platform. The active-side fixing tooling is installed on the upper surface of the active-side six-axis force sensor for clamping and positioning the active-side docking module. The passive-side fixing tooling is installed on the upper surface of the passive-side six-axis force sensor for clamping and positioning the passive-side docking module. The active interface provided on the docking side of the active-side docking module can pull closer and lock the passive interface provided on the docking side of the passive-side docking module through a locking hook. During the microgravity simulation process, the active-side moving platform is used to provide the target position for docking and release the docking signal. When the passive-side moving platform detects the docking signal, the passive-side six-axis force sensor collects the force on the passive-side docking module, and the six-axis external force is obtained through the calculation and processing of the control system. Through coordinate transformation and dynamic calculation, the mapping in the six-axis direction of the passive-side moving platform is realized. The telescopic amount and telescopic speed of each electric telescopic rod are obtained through the inverse solution of the control system to achieve microgravity simulation.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention constructs a ground microgravity simulation device based on the Stewart parallel structure for the docking process of space modules, which is used to detect the force conditions of space modules during the docking process and can quickly and accurately make a follow-up reaction to simulate weightless actions. Since in the space weightless state, the modules will collide during the locking process, but it is difficult for ordinary docking tests to imitate the real state of space docking, which may lead to damage to the interfaces and impairment of performance during the actual docking process. The microgravity simulation device of the present invention effectively compensates for the disadvantages of traditional microgravity simulation technologies, such as long test preparation time and short weightless time. It has the characteristics of adjustable structural parameters (fully gravity compensation for zero gravity can be achieved), maintainability, reusability, three-dimensional space simulation, no simulation test time limit, and high simulation accuracy, and is of great significance for the design of future reconfigurable modular space structures and new weightlessness simulation tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is an isometric view of the overall structure of the microgravity simulation device of the present invention;

[0022] Figure 2 is Figure 1 the front view of

[0023] Figure 3 is an isometric view of the driven-side moving platform of the present invention;

[0024] Figure 4 is an isometric view of the assembled structure of the driven-side fixing tooling of the present invention;

[0025] Figure 5 is an isometric view of the assembled structure of the active-side fixing tooling of the present invention;

[0026] Figure 6 is an isometric view of the base of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] As Figures 1 to 6 shown, a microgravity simulation device based on a parallel mechanism includes a base 1, an active-side moving platform 2, an active-side six-axis force sensor 3, an active-side fixing tooling 4, an active-side docking module 5, a driven-side docking module 6, a driven-side fixing tooling 7, a driven-side six-axis force sensor 8, and a driven-side moving platform 9.

[0029] Combined Figure 6 As shown, the base 1 includes a fixed bottom plate 1-1 and a moving platform 1-2 installed on one end of its surface and capable of moving back and forth under the control of a displacement driving mechanism. The displacement driving mechanism can use a lead screw motor to achieve displacement control, and a sealing cover 1-3 is provided outside to prevent the lead screw motor from being exposed to the outside world, playing a role of protection and isolation. In addition, a plurality of height-adjusting feet 1-4 are provided at the bottom edge of the base 1. The plurality of height-adjusting feet 1-4 can be adjusted in height by rotation in the form of threaded connection, so as to facilitate the leveling of the entire base 1.

[0030] Combined Figure 2 and Figure 6 As shown, an active side moving platform 2 is fixedly installed on the surface of the moving platform 1-2. The active side moving platform 2 is used to provide a target position for docking and release a docking signal. A driven side moving platform 9 is fixedly installed at the opposite end of the surface of the fixed bottom plate 1-1. The driven side moving platform 9 is used to realize microgravity simulation. The moving platform 1-2 provides an additional degree of freedom for module docking, facilitating the disassembly, installation and adjustment of the test piece before and after the test, and can also participate in the microgravity simulation test when needed to expand the distance of microgravity simulation.

[0031] Combined Figure 3As shown, the driven side motion platform 9 is designed based on the Stewart parallel structure, including an upper platform 9-1 and a lower platform 9-7, six upper Hooke's hinges 9-2 are arranged on the edge of the lower surface of the upper platform 9-1, and the six upper Hooke's hinges 9-2 are arranged adjacent to each other in pairs, and the three groups of upper Hooke's hinges 9-2 are arranged at equal angles, and six lower Hooke's hinges 9-6 are arranged on the edge of the upper surface of the lower platform 9-7, and the six lower Hooke's hinges 9-6 are arranged adjacent to each other in pairs, and the three groups of lower Hooke's hinges 9-6 are arranged at equal angles, and the three groups of upper Hooke's hinges 9-2 and the three groups of lower Hooke's hinges 9-6 are arranged in a staggered manner, and each corresponding upper Hooke's hinge 9-2 and lower Hooke's hinge 9-6 are arranged in a staggered manner. -6 are hingedly connected by an electric telescopic rod 9-3, the electric telescopic rod 9-3 uses a servo motor 9-4 as a power source, the electric telescopic rod 9-3 is divided into two sections, the main cylinder and the telescopic cylinder, and a ball screw is arranged inside for transmission. The telescopic cylinder and the main cylinder can only be telescopically moved relative to each other in the axial direction, the screw of the ball screw is coaxially connected to the bottom end of the main cylinder, and the nut of the ball screw is fixed to the bottom end of the telescopic cylinder. The output end of the servo motor 9-4 is provided with a reducer 9-5 and is connected to the screw of the ball screw. The position between the telescopic cylinder and the main cylinder is changed by controlling the forward and reverse rotation of the screw of the ball screw to realize the telescopic action of the electric telescopic rod 9-3. Among them, the lower platform 9-7 is fixed, the upper Hooke's hinge 9-2 has three degrees of freedom, the lower Hooke's hinge 9-6 has two degrees of freedom, and the electric telescopic rod 9-3 has one degree of freedom, so that the upper platform 9-1 has six degrees of freedom, realizing microgravity simulation in six-dimensional directions. The active side motion platform 2 and the driven side motion platform 9 have the same structure.

[0032] Combination Figure 1 As shown, the active side six-dimensional force sensor 3 and the driven side six-dimensional force sensor 8 have the same structure and are sealed by packaging covers respectively. The active side six-dimensional force sensor 3 is fixed on the upper surface of the active side motion platform 2 to monitor the force process and issue an overload warning when the force exceeds the set threshold. The driven side six-dimensional force sensor 8 is fixed on the upper surface of the driven side motion platform 9 to detect the force condition during the module docking process in a microgravity environment and transmit the data to the acquisition system for subsequent processing.

[0033] Combination Figure 2 As shown, the active side fixing tooling 4 and the driven side fixing tooling 7 have the same structure. The active side fixing tooling 4 is installed on the upper surface of the active side six-dimensional force sensor 3 for clamping and positioning the active side docking module 5, and the driven side fixing tooling 7 is installed on the upper surface of the driven side six-dimensional force sensor 8 for clamping and positioning the driven side docking module 6.

[0034] Combination Figure 5As shown, the active-side fixing tooling 4 includes an active-side mounting plate 4-5. A number of screw holes are machined on the surface of the active-side mounting plate 4-5, and a plurality of active-side front-back direction L-shaped clamping strips 4-3 and active-side left-right direction L-shaped clamping strips 4-4 are fixed by bolts to clamp and fix the active-side docking module 5. The first auxiliary mounting frame 4-1 and the second auxiliary mounting frame 4-2 of the active side can be respectively arranged on the left and right sides of the active-side mounting plate 4-5 for carrying cameras and marking blocks, and real-time monitoring and auxiliary guidance are carried out during the module docking process to better complete the docking.

[0035] Combined with Figure 4 As shown, the driven-side fixing tooling 7 includes a driven-side mounting plate 7-5. A number of screw holes are machined on the surface of the driven-side mounting plate 7-5, and a plurality of driven-side front-back direction L-shaped clamping strips 7-3 and driven-side left-right direction L-shaped clamping strips 7-4 are fixed by bolts to clamp and fix the driven-side docking module 6. The first auxiliary mounting frame 7-1 and the second auxiliary mounting frame 7-2 of the driven side can be respectively arranged on the left and right sides of the driven-side mounting plate 7-5 for carrying cameras and marking blocks, and real-time monitoring and auxiliary guidance are carried out during the module docking process to better complete the docking.

[0036] Combined with Figure 1 、 Figures 4 to 5 As shown, the active-side docking module 5 and the driven-side docking module 6 are the objects to be detected. The active interface 5-2 of the active-side docking module 5 is fixed by the active module mounting frame 5-1, and the driven interface 6-2 of the driven-side docking module 6 is fixed by the driven module mounting frame 6-1. During the docking process of the active-side docking module 5 and the driven-side docking module 6, the active interface 5-2 is matched with the pin hole of the driven interface 6-2 through a taper pin for positioning, and the locking hook on the active interface 5-2 extends to pull the driven interface 6-2 closer and lock it.

[0037] The performance indicators of the microgravity simulation device of the present invention are as follows:

[0038] Microgravity simulation yaw motion range coverage: 0 - 580 mm, speed coverage: 0 - 0.5 m / s; yaw simulation accuracy: better than or equal to 0.018 mm.

[0039] Microgravity simulation axial motion range coverage: 0 - 580 mm, speed coverage: 0 - 0.5 m / s; axial simulation accuracy: better than or equal to 0.012 mm.

[0040] Microgravity simulation vertical motion range coverage: 0 - 210 mm, speed coverage: 0 - 0.5 m / s; vertical simulation accuracy: better than or equal to 0.014 mm.

[0041] Microgravity simulation roll angle range coverage: ±24°, speed coverage: 0 - 15° / s; roll simulation accuracy: better than or equal to 0.003°.

[0042] Microgravity simulation pitch angle range coverage: ±24°, speed coverage: 0 - 15° / s; pitch simulation accuracy: better than or equal to -0.002°.

[0043] Microgravity simulation yaw angle range coverage: ±30°, speed coverage: 0 - 15° / s; yaw simulation accuracy: better than or equal to 0.012°.

[0044] Payload: 500 kg in the vertical direction; 300 kg in the horizontal direction.

[0045] Response time: 0.15 s.

[0046] The microgravity simulation device of the present invention needs to establish a mapping relationship between the external forces received by the platform and the movement of the platform. Therefore, after the platform senses the external forces and calculates the movement distance in real time, the platform should make a fast and accurate movement response. In view of the high requirements for the real-time performance and accuracy of the forward solution, therefore, a numerical method based on Gauss-Newton iteration is used to perform the operation of the kinematic forward solution.

[0047] When the driven side detects the docking signal released by the active side, the force on the docking module 6 of the driven side is collected by the six-dimensional force sensor 8 on the driven side. The sensing signal outputs a voltage signal through the amplifier and is transmitted to the control system through the data acquisition card. The control system performs calculation and processing on the collected signal to obtain the six-dimensional external force of the docking module 6 of the driven side, and through coordinate transformation and dynamic calculation, realizes the mapping in the six-dimensional directions of the moving platform 9 on the driven side (rotation around the X, Y, and Z axes and translation in the X, Y, and Z directions). The control system obtains the elongation amount and elongation speed of each electric telescopic rod 9-3 of the moving platform 9 on the driven side through the inverse solution, and outputs a control signal to the driver through the motion control card to complete the motion control of the moving platform 9 on the driven side.

[0048] The active side and the driven side are controlled by separate control systems, both of which use an industrial control computer as the core controller to handle system-level tasks of high-level management and control, and can ensure good reliability, real-time performance, human-computer interaction, and environmental adaptability. In addition, the industrial control computer is equipped with a variety of industrial control protocol interfaces in large numbers, with strong scalability. The active side and the driven side are respectively equipped with data acquisition cards to collect the voltage signals of the six-axis force sensor 3 on the active side and the six-axis force sensor 8 on the driven side. Both adopt the differential input mode and have high anti-interference ability. The driven side is equipped with a motion control card to control the six servo motors 9-4 of the driven side motion platform 9. The active side is equipped with a motion control card to control, in addition to the six servo motors of the active side motion platform 2, the lead screw motor of the mobile platform 1-2. The absolute position of the servo motor encoder is read through an industrial serial port server. The industrial control computers on the active side and the driven side achieve data transmission through a specific communication module.

[0049] Data acquisition adopts the method of combining an industrial control computer IPC and a data acquisition card. The data acquisition card is a special computer function expansion board card used to realize the function of data acquisition. It can collect the analog / digital signals output by the measured sensor at a certain preset frequency and transmit them to the upper computer for subsequent processing.

[0050] Motion control adopts the method of combining an industrial control computer IPC and a motion control card. The motion control card processes tasks with high real-time requirements that are not system-level, and performs real-time control of the motor position and speed, interpolation, etc. The IPC, on the other hand, processes system-level overall coordination tasks such as system parameter configuration, system diagnosis, and system communication.

[0051] During the microgravity simulation process, it is assumed that the active docking module 5 and the driven docking module 6 have a rigid collision at a certain point, and the acting forces generated are F1 and F2 acting on the two docking modules respectively. Then the dynamic equations are as follows:

[0052]

[0053]

[0054] In the formula, m1 and m2 are the masses of the two docking modules respectively, c1 and c2 are the damping forces suffered by the two docking modules in the space environment respectively, k1 and k2 are the stiffnesses suffered by the two docking modules in the space environment respectively, x1 = [x1, y1, z1] T and x2 = [x2, y2, z2] T are the position vectors of the centers of mass of the two docking modules relative to the origin of the coordinate system respectively. Since in space docking, the damping force suffered by the docking module comes from air resistance, and the stiffness comes from external constraints, and the two values are extremely small, they are thus ignored, and the simplified result is:

[0055]

[0056] At this time, the acceleration of the driven-side docking module 6 relative to the driving-side docking module 5 is:

[0057]

[0058] Assume that the initial time is t0, and by integration, the velocity of the driven-side docking module 6 relative to the driving-side docking module 5 is:

[0059]

[0060] Integrating again, the position of the driven-side docking module 6 relative to the driving-side docking module 5 is:

[0061]

[0062] The torques generated by the collision acting on the two docking modules are M1 and M2 respectively. According to Euler's equation, we can obtain:

[0063]

[0064]

[0065] In the formula, are the moment of inertia matrices of the two docking modules respectively, and ω1 and ω2 are the angular velocity vectors of the two docking modules respectively.

[0066] Based on the above differential equations, the angular velocity vectors ω1 and ω2 of the two docking modules can be solved, and the angular velocity ω of the driven-side docking module 6 relative to the driving-side docking module 5 21 = ω2 - ω1.

[0067] Integrating, the angle of the driven-side docking module 6 relative to the driving-side docking module 5 is:

[0068]

[0069] Thus, the position and angle of the driven-side docking module 6 relative to the driving-side docking module 5 are [x 21 T R 21 T T = [x 21 , y 21 , z 21 , Rx 21 , Ry 21 , Rz 21 T ​​Since the position of the active docking module 5 in the coordinate system is known and the position of the passive docking module 6 relative to the active docking module 5 has been solved, the absolute position of the passive docking module 6 in the coordinate system can be obtained. Furthermore, according to the inverse kinematics of the parallel mechanism, the elongation and elongation speed of the six electric telescopic rods 9-3 on the passive side can be obtained, realizing the mapping of force and displacement of the passive docking module 6 and performing microgravity simulation.

[0070] The actual operation process is carried out according to the following steps:

[0071] Step 1: Installation of the docking module

[0072] Move the mobile platform 1-2 to the farthest end of the fixed base plate 1-1. Install the active docking module 5 on the active side mounting plate 4-5, and install a camera and a marker block on the first auxiliary mounting frame 4-1 and the second auxiliary mounting frame 4-2 on the active side as docking auxiliary devices. Clamp and fix the active docking module 5 in the front-back and left-right directions through the front-back L-shaped clamping strip 4-3 and the left-right L-shaped clamping strip 4-4 on the active side. Install the passive docking module 6 on the passive side mounting plate 7-5, and install a camera and a marker block on the first auxiliary mounting frame 7-1 and the second auxiliary mounting frame 7-2 on the passive side as docking auxiliary devices. Clamp and fix the passive docking module 6 in the front-back and left-right directions through the front-back L-shaped clamping strip 7-3 and the left-right L-shaped clamping strip 7-4 on the passive side;

[0073] Step 2: Setting the target position on the active side

[0074] Adjust the mobile platform 1-2 to make the active moving platform 2 move closer to the passive moving platform 9. Stop moving when roughly reaching the target position, and perform precise adjustment of the position through the active moving platform 2. The active control system drives the servo motor through the motion control card to realize the control of the six electric telescopic rods. The elongation of each rod is obtained by the control system according to the inverse solution. The upper platform position of the active moving platform 2 is calculated in real time by the forward solution based on the feedback data of the encoders of each rod. During the precise position adjustment process, the six-dimensional force sensor 3 on the active side real-time collects the force on the active docking module 5 in the six-dimensional direction, transmits it to the control system through the data acquisition card and performs real-time feedback. If the force in one or several directions exceeds the set threshold, an overload warning is issued;

[0075] Step 3: Setting the initial position on the passive side

[0076] The initial position is adjusted through the driven-side moving platform 9. The driven-side control system drives the servo motor 9-4 through the motion control card to control the six electric telescopic rods 9-3. The telescopic amount of each rod is obtained by the control system according to the inverse solution. The position of the upper platform 9-1 of the driven-side moving platform 9 is calculated in real time through the forward solution based on the feedback data of the encoders of each rod.

[0077] Step 4: Start microgravity simulation

[0078] The active-side control system starts the locking action control program, releases the docking signal, and the locking hook extends in the active interface 5-2 for locking. The six-axis force sensor 3 on the active side collects the forces on the active-side docking module 5 in six directions in real time, transmits them to the active-side control system through the data acquisition card for real-time feedback. When excessive load is detected, the locking action is immediately terminated. The driven-side control system detects the docking signal released by the active side and starts the microgravity simulation program. The driven interface 6-2 is hooked by the locking hook. The six-axis force sensor 8 on the driven side collects the forces on the driven-side docking module 6 in six directions in real time, and through coordinate transformation and dynamic calculation, realizes the mapping in six directions on the driven-side moving platform 9 (rotation around the X, Y, and Z axes and translation in the X, Y, and Z directions). The driven-side control system obtains the telescopic amount and telescopic speed of each electric telescopic rod 9-3 of the driven-side moving platform 9 through the inverse solution, outputs control signals to the driver through the motion control card, completes the motion control of the driven-side moving platform 9, and thus realizes microgravity simulation. All sensor data is recorded and stored in real time through an independently running data program.

[0079] Step 5: End microgravity simulation

[0080] When the locking hook of the active interface 5-2 is locked with the driven interface 6-2, the active-side control system and the driven-side control system stop working simultaneously, end the microgravity simulation, and export the stored sensor data.

[0081] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent conditions of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0082] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment contains only an independent technical solution. This narrative style of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A microgravity simulation device based on a parallel mechanism, characterized in that: It includes a base (1), an active-side moving platform (2), an active-side six-axis force sensor (3), an active-side fixing tooling (4), an active-side docking module (5), a passive-side docking module (6), a passive-side fixing tooling (7), a passive-side six-axis force sensor (8), and a passive-side moving platform (9); the base (1) includes a fixed bottom plate (1-1) and a moving platform (1-2) installed on one end of its surface and capable of moving back and forth under the control of a lead screw motor. The active-side moving platform (2) is fixedly installed on the surface of the moving platform (1-2). The passive-side moving platform (9) is fixedly installed at the opposite end of the surface of the fixed bottom plate (1-1). The passive-side moving platform (9) is designed based on the Stewart parallel structure and includes an upper platform (9-1), a lower platform (9-7), and six electric telescopic rods (9-3) hinged to the edges between the two. The electric telescopic rods (9-3) use a servo motor (9-4) as the power source and are transmission-connected with a reducer (9-5) in the middle. The active-side moving platform (2) has the same structure as the passive-side moving platform (9). The active-side six-axis force sensor (3) is fixed on the upper surface of the active-side moving platform (2). The passive-side six-axis force sensor (8) is fixed on the upper surface of the passive-side moving platform (9). The active-side fixing tooling (4) is installed on the upper surface of the active-side six-axis force sensor (3) for clamping and positioning the active-side docking module (5). The passive-side fixing tooling (7) is installed on the upper surface of the passive-side six-axis force sensor (8) for clamping and positioning the passive-side docking module (6). The active interface (5-2) provided on the docking side of the active-side docking module (5) can pull closer and lock the passive interface (6-2) provided on the docking side of the passive-side docking module (6) through a locking hook. During the microgravity simulation process, the active-side moving platform (2) is used to provide the target position for docking and release the docking signal. When the passive-side moving platform (9) detects the docking signal, the force on the passive-side docking module (6) is collected by the passive-side six-axis force sensor (8). The six-axis external force is obtained through the solution and processing of the control system, and the mapping in the six-axis direction of the passive-side moving platform (9) is realized through coordinate transformation and dynamic solution. The telescopic amount and telescopic speed of each electric telescopic rod (9-3) are obtained through the inverse solution of the control system to achieve microgravity simulation. During the microgravity simulation process of the device, it is assumed that the active-side docking module (5) and the passive-side docking module (6) have a rigid collision, and the acting forces generated act on the two docking modules respectively as F 1 and F 2. Then the dynamic equation is as follows: In the formula, m 1 and m 2 are the masses of the two docking modules respectively, c 1 and c 2 are the damping forces suffered by the two docking modules in the space environment respectively, k 1 and k 2 are the stiffnesses suffered by the two docking modules in the space environment respectively, x 1 = x 1, y 1, z 1] T and x 2 = x 2, y 2, z 2] T are the position vectors of the centers of mass of the two docking modules relative to the origin of the coordinate system, and after simplification, we get: ， At this time, the acceleration of the driven-side docking module (6) relative to the active-side docking module (5) is: Set the initial time to t 0, and integrate to obtain the speed of the driven-side docking module (6) relative to the driving-side docking module (5) as: Integrating again gives the position of the driven-side docking module (6) relative to the active-side docking module (5) as: The torques generated by the collision act on the two docking modules, respectively, as M 1 and M 2. According to Euler's equation, we get: In the formula, and are the inertia matrices of rotation of two docking modules respectively, ω 1 and ω 2 are the angular velocity vectors of two docking modules respectively; The angular velocity vectors of the two docking modules can be solved according to the above differential equation ω 1 and ω 2, the angular velocity of the driven-side docking module (6) relative to the driving-side docking module (5) ω 21 = ω 2 - ω 1; Integrating gives the angle of the driven-side docking module (6) relative to the active-side docking module (5) as: The position and angle of the driven-side docking module (6) relative to the active-side docking module (5) are thus obtained as x 21 T R 21 T T = x 21 , y 21 , z 21 , Rx 21 , Ry 21 , Rz 21 T , and then the absolute position of the driven-side docking module (6) in the coordinate system is obtained. Furthermore, according to the inverse kinematics of the parallel mechanism, the elongation amounts and elongation speeds of the six electric telescopic rods (9-3) of the driven-side moving platform (9) are obtained, realizing the mapping of force and displacement of the driven-side docking module (6) and performing microgravity simulation.​​​ 2. The microgravity simulation device based on a parallel mechanism according to claim 1, characterized in that: A sealing cover (1-3) is provided outside the lead screw motor on the base (1).

3. The microgravity simulation device based on a parallel mechanism according to claim 1, characterized in that: A plurality of height-adjusting feet (1-4) are provided at the bottom edge of the base (1), and the overall leveling of the base (1) is achieved by adjusting the heights of the plurality of height-adjusting feet (1-4).

4. A microgravity simulation device based on a parallel mechanism according to claim 1, characterized in that: The active-side fixing tooling (4) includes an active-side mounting plate (4-5). A number of screw holes are machined on the surface of the active-side mounting plate (4-5), and a plurality of active-side front-back direction L-shaped clamping bars (4-3) and active-side left-right direction L-shaped clamping bars (4-4) are fixed by bolts to clamp and fix the active-side docking module (5); the driven-side fixing tooling (7) includes a driven-side mounting plate (7-5). A number of screw holes are machined on the surface of the driven-side mounting plate (7-5), and a plurality of driven-side front-back direction L-shaped clamping bars (7-3) and driven-side left-right direction L-shaped clamping bars (7-4) are fixed by bolts to clamp and fix the driven-side docking module (6).

5. The microgravity simulation device based on a parallel mechanism according to claim 4, characterized in that: An active-side first auxiliary mounting frame (4-1) and an active-side second auxiliary mounting frame (4-2) are respectively provided on the left and right sides of the active-side mounting plate (4-5) for mounting cameras and marker blocks; a driven-side first auxiliary mounting frame (7-1) and a driven-side second auxiliary mounting frame (7-2) are respectively provided on the left and right sides of the driven-side mounting plate (7-5) for mounting cameras and marker blocks, and the docking process is assisted and guided by real-time monitoring.

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