Rocket horizontal modal test free boundary supporting system

Abstract

The utility model provides a free boundary supporting system for a horizontal modal test of a rocket. The free boundary supporting system at least comprises a supporting frame, a free membrane type air spring and a bracket, the supporting frame is of a truss structure, the bottom of the free membrane type air spring is arranged on the upper end face of the supporting frame, and the bracket used for supporting a rocket is arranged on the top of the free membrane type air spring. Freedom degrees of translation, rotation and torsion of the rocket are all provided by the free membrane type air spring, and the bearing capacity and rigidity of the free membrane type air spring can be changed by adjusting internal air pressure of the free membrane type air spring.

Description

TECHNICAL FIELD

[0001] The utility model relates to space launch vehicle technical field especially relates to a rocket horizontal mode test free boundary support system. BACKGROUND

[0002] During the launching and flying of the launch vehicle, it will experience complex vibration environment, in order to ensure the stability and reliability of the rocket structure, it is necessary to carry out modal test on the ground to obtain the modal parameters such as natural frequency, damping ratio and vibration mode of the rocket. However, the rocket is in the free boundary condition in flight, and the ground test is difficult to completely simulate this environment. At present, the industry generally uses elastic rope to suspend the rocket to simulate the boundary condition of the free flight of the rocket. The existing horizontal modal test method has technical difficulties such as great excitation difficulty, inconsistent response caused by uneven mass distribution, and difficulty in dense modal identification. Therefore, in order to realize the acquisition of the dynamic characteristic parameters of the launch vehicle structure, it is urgent to develop a free boundary simulation system suitable for the horizontal modal test of the launch vehicle. UTILITY MODEL CONTENTS

[0003] In order to solve the above technical problems, the utility model provides a rocket horizontal mode test free boundary support system, which simulates the vibration characteristics of the rocket under the free boundary condition, solves the problems in the prior art, and improves the accuracy and reliability of the modal test.

[0004] The utility model provides a rocket horizontal mode test free boundary support system, at least includes: support frame, free membrane type air spring and bracket, the support frame is truss structure, the bottom of free membrane type air spring is located on the upper end surface of support frame, the top of free membrane type air spring is equipped with the bracket for supporting rocket, the degree of freedom of rocket's translation, rotation and torsion is all provided by free membrane type air spring, can change the carrying capacity and rigidity of free membrane type air spring by adjusting the internal air pressure of free membrane type air spring.

[0005] In an embodiment, the support frame includes at least a bottom truss and a top truss, and a pressure vessel is arranged between the bottom truss and the top truss; the pressure vessel stores compressed gas inside, and a sealed flange interface is arranged on the top of the pressure vessel; the free membrane type air spring is arranged on the upper end surface of the top truss, and the bottom of the free membrane type air spring is in communication with the pressure vessel through the sealed flange interface.

[0006] In an embodiment, the bracket includes a middle part and two side parts connected to the middle part from both sides of the middle part; the middle part of the bracket is connected to the free membrane type air spring, and the side parts are arranged in an arc structure suitable for the outer shape of the rocket.

[0007] In one embodiment, the rocket horizontal mode test free boundary support system of the utility model further includes a limiting device arranged on both sides of the bracket along a first direction; the limiting device at least includes a first rigid structure, a first adjusting rod and a first flexible structure; the first rigid structure is installed on the top truss, one end of the first adjusting rod away from the top truss is installed on the first rigid structure; one end of the first flexible structure is connected with the first adjusting rod, and the other end is connected with the middle part of the bracket; the first adjusting rod is controlled to move along the first direction to adjust the elongation and tension degree of the first flexible structure.

[0008] In one embodiment, the rocket horizontal mode test free boundary support system of the utility model further includes a lateral elastic support device arranged on both sides of the bracket along a second direction; the lateral elastic support device at least includes a second rigid structure, a second adjusting rod, a second flexible structure; the second rigid structure is arranged on the top truss, one end of the second adjusting rod away from the top truss is installed on the first rigid structure; one end of the second flexible structure is connected with the second adjusting rod, and the other end is connected with the side part of the bracket; the second adjusting rod is controlled to move along the second direction to adjust the elongation and tension degree of the second flexible structure.

[0009] In one embodiment, the first rigid structure includes a side bending truss, a limiting plate and an extension truss; the first end of the side bending truss is installed on the top truss, the second end is arranged towards the middle part of the bracket, and the limiting plate is arranged on the second end of the side bending truss; one end of the extension truss is connected with the back of the bending plate, and the other end is installed with the first adjusting rod; one end of the first flexible structure is connected with the first adjusting rod, and the other end is connected with the middle part of the bracket after penetrating through the limiting plate.

[0010] In any one of the above embodiments, the pressure container is provided with an inflation hole, and an inflation valve is connected to the inflation hole to inflate the pressure container, and the pressure of the pressure container is measured by a pressure gauge; the top of the pressure container is provided with a safety valve, and the bottom is provided with a drain valve.

[0011] In one embodiment, the top surface of the two side parts of the bracket is used to support the rocket, and the bottom surface is provided with a protective baffle, and one end of the protective baffle away from the bracket is provided with a buffer pad; one end of the second flexible structure is connected with the second adjusting rod, and the other end is connected with the protective baffle.

[0012] In one embodiment, the free membrane air spring comprises an upper end plate, a rubber capsule body and a lower end plate connected in sequence; the upper end plate is connected with the bracket, one part of the lower end plate is connected with the top truss, and the other part is provided with a hole for connecting the rubber capsule body with the pressure container; the hole of the lower end plate is in sealing connection with the sealing flange interface.

[0013] In one embodiment, the support frame further comprises a walking device, a brake device and a locking device arranged on the bottom truss; after being transferred to a test site by the walking device, the frame is stopped by the brake device and locked and fixed by the locking device.

[0014] The rocket horizontal modal test free boundary support system provided by the utility model has at least one of the following beneficial effects:

[0015] Firstly, the utility model utilizes the nonlinear characteristics and variable stiffness characteristics of the air spring to simulate the modal test free boundary, ensures that the natural vibration frequency remains almost unchanged under the conditions of axial and radial bearing, so that the free boundary support system has almost unchanged characteristics, and the free boundary under the rocket flight state is approximately simulated.

[0016] Secondly, the utility model effectively improves the precision and reliability of the modal test, the support system can accurately simulate the dynamic response of the rocket under the free boundary condition, eliminates the error caused by the traditional boundary condition, and thus greatly improves the precision of the modal test and the reliability of the result.

[0017] Thirdly, the utility model can adjust the stiffness of the air spring according to the pressure change, reduces a large amount of physical simulation and complex adjustment in the traditional test, increases the test flexibility, shortens the test period, and reduces the test cost.

[0018] Fourthly, the utility model can be quickly adjusted according to different rocket models and test requirements, greatly enhances the flexibility and adaptability of the test, can simulate various complex flight environments and boundary conditions, and provides the possibility for the all-round performance evaluation of the rocket.

[0019] After reading the specific embodiments and after viewing the drawings, those skilled in the art will realize additional features and advantages. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0021] Figure 1 is a schematic diagram of a free boundary support system supporting a rocket according to an embodiment of the present application.

[0022] Figure 2 is a schematic diagram of the overall structure of a free boundary support system according to an embodiment of the present application

[0023] Figure 3 is a schematic diagram of the control flow of a control assembly of a free boundary support system according to an embodiment of the present application.

[0024] Figure 4 is a schematic diagram of the structure of a free membrane air spring according to an embodiment of the present application.

[0025] Figure 5 is a schematic diagram of the structure of a limiting device according to an embodiment of the present application.

[0026] Figure 6 is a schematic diagram of the structure of a lateral elastic support device according to an embodiment of the present application.

[0027] Figure 7 is a schematic diagram of the structure of a bracket according to an embodiment of the present application.

[0028] Figure 8 is an enlarged view of a free membrane air spring part according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] The features and exemplary embodiments of each aspect of the present application will be described in detail below, in order to make the purpose, technical solutions and advantages of the present application more clear and apparent, the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present application, for exemplary description of the principles of the present application, and are not configured to limit the present application. In addition, the components in the drawings are not necessarily drawn to scale. For example, the size of some components in the drawings can be enlarged for other components or regions, to help understand the embodiments of the present application.

[0030] The orientation words appearing in the following description are the directions shown in the drawings, and are not to limit the specific structure of the embodiments of the utility model. In the description of the utility model, it is to be explained that, unless otherwise specified, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected, it can be directly connected, or indirectly connected through intermediate medium. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to specific circumstances.

[0031] In addition, the terms "including", "containing", "having" or any other variants thereof are intended to cover non-exclusive inclusion, so that the inclusion of a series of element structures or components not only includes those elements, but also includes other elements not explicitly listed or inherent in the structure, component. Without more limitation, the element defined by the statement "including" does not exclude the presence of additional same elements in the article or device including the element.

[0032] Spatial relationship terms such as "below", "under", "under", "low", "above", "on", "high" are used to facilitate the description to explain the position of one element relative to the second element, which is intended to cover different orientations of the device in addition to the orientations shown in the drawings. In addition, for example, "one element is on / under another element" can mean that the two elements are in direct contact, or that there are other elements between the two elements. In addition, terms such as "first", "second", etc. are also used to describe various elements, regions, parts, etc., and should not be considered as limiting. Similar terms represent similar elements throughout the description.

[0033] For those skilled in the art, the utility model can be implemented without some of these specific details. The following description of the embodiments is only to provide a better understanding of the utility model by showing examples of the utility model.

[0034] The rocket is in a free boundary condition in flight, and it is difficult to completely simulate this environment on the ground, and only approximate simulation can be achieved. For horizontal mode test, theoretically, the actual state of the vehicle flying in the air should be simulated on the ground, which is an unrestrained state, namely the so-called "free-free" state, which is fundamentally impossible in practice. The usual practice is to use springs, flexible suspension, etc. to obtain an approximate free-free system. In order to minimize the influence of elastic support elements on the measurement of modal parameters of the vehicle, as soft as possible, the natural frequency of the rigid body vibrating on the elastic support element is as low as possible, that is, the stiffness of the elastic support element is as low as possible.

[0035] In the simulation of the existing free boundary, the cylindrical spring, the disc spring, the rubber rope, the air cushion and the like are usually adopted, the supporting single group has low bearing, the self-vibration frequency is fixed and cannot be adjusted, and the lowest self-vibration frequency is only reduced to about 0.6 Hz. With the increase of the volume and weight of the product, the elastic frequency is reduced, and then the required free boundary rigid body frequency is reduced, therefore, the simulation of the free boundary of the large liquid rocket horizontal mode test has great difficulty. In view of the deficiency of the prior art, the technical problem to be solved by the utility model is to provide a free boundary simulation device for liquid rocket horizontal mode test, which can simulate the free boundary in the horizontal state, ensure that the additional mass and the additional stiffness of the boundary simulation are within the engineering allowable range, effectively increase the effectiveness, safety and stability of the free boundary simulation, and more accurately obtain the vibration characteristics of the rocket structure and reduce the test cost.

[0036] Referring to Figure 1 、 Figure 2 、 Figure 3 and Figure 4 , the utility model provides a rocket horizontal mode test free boundary supporting system, at least includes: support frame 1, free membrane type air spring 3 and bracket 5. Wherein the support frame 1 is truss structure, as the installation foundation of whole supporting system, free membrane type air spring 3 bottom is set on support frame 1 upper end face, and free membrane type air spring 3 top is equipped with the bracket 5 for supporting rocket 10. The degrees of freedom of rocket 10 located on bracket 5 when carrying out mode test are all provided by free membrane type air spring 3, and six degrees of freedom of free membrane type air spring 3 are all released, realize the free boundary simulation in horizontal state. The free boundary supporting system of the utility model can carry out the inflation adjustment of free membrane type air spring 3 by manual or automatic mode, and then change the carrying capacity and stiffness of free membrane type air spring 3.

[0037] Further, the control assembly 4 can be used to monitor and control the free membrane type air spring 3. The control assembly 4 at least includes sequentially communicatively connected acquisition module 41, controller 42 and execution module 43. The acquisition module 41 at least acquires the pressure data of the free membrane type air spring 3 and sends it to the controller 42, the controller 42 receives the data and judges and then sends the action instruction to the execution module 43, and the execution module 43 inflates or deflates the free membrane type air spring 3.

[0038] Specifically, before the modal test, the two free boundary support systems of the utility model are placed in a row with a distance, and the test rocket 10 is placed above the two free support boundary systems 9A and 9B, and each set of free support boundary system can work independently without interference. After the test starts, first, the preset pressure is sent to the execution module 43 through the controller 42, the execution module 43 is used to inflate the free membrane type spring 3 to adjust its pressure to the preset pressure, and at the same time, the actual pressure of the free membrane type air spring 3 is collected by the collection module 41 and sent to the controller 42, the controller 42 compares the actual pressure and the preset pressure, if the actual pressure exceeds the preset pressure by a certain range, the execution module 43 is controlled to deflate the free membrane type air spring 3, if the actual pressure does not reach the preset pressure, the execution module 43 is controlled to inflate the free membrane type air spring 3. The above process will be carried out synchronously with the modal test until the test is completed, so that the load capacity and stiffness of the free membrane type air spring 3 can be adaptively adjusted according to different pressures, not only the free boundary condition is effectively and accurately simulated, but also the test can be quickly adjusted according to different rocket models and test requirements, greatly enhancing the flexibility and adaptability of the test.

[0039] In one embodiment, the support frame 1 at least comprises a bottom truss 11 and a top truss 12, and a pressure container 2 is arranged between the bottom truss 11 and the top truss 12. The pressure container 2 stores compressed gas inside, and a sealing flange interface for connecting with the free membrane type air spring 3 is arranged at the top of the pressure container 2. The free membrane type air spring 3 is arranged on the upper end surface of the top truss 12, and the bottom of the free membrane type air spring 3 is connected with the pressure container 2 through the sealing flange interface, so that the pressure of the free membrane type air spring 3 is consistent with the pressure in the pressure container 2. The bottom of the free membrane type air spring 3 is also connected with the top truss 12 through bolts.

[0040] The free membrane type air spring 3 in the embodiment of the utility model is a flexible and sealed damping element, which is a composite of rubber and metal vulcanization, and at least comprises an upper end plate 31, a lower end plate 32 and a rubber capsule 33. The upper end plate 31 is fixedly connected with the bracket 5, and the lower end plate 32 is fixedly connected with the top truss 12 on one part and connected with the sealing flange interface of the pressure container 2 on the other part to realize the communication between the pressure container 2 and the rubber capsule 33. The free boundary support system of the embodiment can inflate the rubber capsule 33 through the pressure container 2, so as to provide the free membrane type air spring 3 with stiffness. The stiffness of the commonly used ordinary steel spring is a constant value, so its natural frequency changes with the change of load, while the air spring has nonlinear characteristics, and the stiffness changes with the change of load, so the natural frequency is almost unchanged under any load.

[0041] At the same time, referring to Figure 2 , Figure 3 , Figure 5 , Figure 6 and Figure 7In one embodiment, the bracket 5 is a thin-walled aluminum welded structure, and the top thereof is an arc-shaped smooth connecting surface for supporting the rocket body. The bracket 5 at least comprises a middle portion 51 and two side portions (a first side portion 52 and a second side portion 53) connected to the middle portion 51 from both sides of the middle portion 51. The middle portion 51 of the bracket 5 is connected to the upper end 31 of the free membrane air spring 3, and the two side portions of the bracket 5 are arranged to adapt to the arc-shaped structure of the rocket outer surface.

[0042] In order to increase the support reliability, the free boundary support system of the embodiment of the utility model further comprises a limiting device 6 arranged on both sides of the bracket 5 along the first direction S1. The limiting device 6 at least comprises a first rigid structure 61, a first adjusting rod 62 and a first flexible structure 63. The first rigid structure 61 is installed on the top truss 12, the first adjusting rod 62 is installed on the end of the first rigid structure 61 away from the top truss 1, and the first flexible structure 63 is connected to the first adjusting rod 62 at one end and connected to the middle portion 51 of the bracket 5 at the other end. In order to facilitate the connection of the first flexible structure 63, the middle portion 51 of the bracket is provided with an interface for connecting the first flexible structure 63 on both sides in the first direction S1.

[0043] The free boundary support system of the embodiment can adjust the limiting devices on both sides of the bracket, control the first adjusting rod 62 to move along the first direction S1, and then adjust the elongation and tension of the corresponding first flexible structure 63 until the bracket 5 is in the neutral position in the first direction S1. The limiting device in the embodiment can also limit the bracket and the rocket from excessively deviating from the test position in the first direction S1 through flexible support during the modal test.

[0044] Further, the free boundary support system of the embodiment of the utility model further includes lateral elastic support device 7 which is arranged on both sides of bracket 5 along second direction S2. Lateral elastic support device 7 at least includes second rigid structure 71, second adjusting rod 72 and second flexible structure (not marked in the drawing). Second rigid structure 71 is arranged on top truss 12, and second adjusting rod 72 is installed on the end of first rigid structure 71 away from top truss 12. One end of second flexible structure 73 is connected with second adjusting rod 72, and the other end is connected with the side of bracket 5. The top of both sides (side 51 and side 52) of bracket 5 is used to support the rocket, and protective baffle 54 is arranged at the position close to middle part 51 at the bottom of side 51 and side 52 respectively. Second flexible structure 73 is connected with bracket 5 through protective baffle 54 to support bracket 5, so that bracket 5 keeps neutral position in second direction S2. In addition, a buffer pad is arranged on the end face of the bottom (the end away from the bracket) of protective baffle 54 to provide protection when bracket 5 and top truss 12 contact. When the rocket rotates excessively in second direction S2 during modal test, the end face of protective baffle 54 provided with the buffer pad contacts top truss 12, so that the maximum rotation angle of the bracket and the rocket in this direction can be limited, and the bracket is protected from damage.

[0045] The free boundary support system of the embodiment can adjust two lateral elastic support devices respectively, control corresponding second adjusting rod 72 to move along second direction S2, and then adjust the elongation and tension degree of corresponding second flexible structure 73 until bracket 5 keeps neutral position in second direction S2. The lateral elastic support device in the embodiment can also limit the excessive deviation of the bracket and the rocket from the test position in second direction S2 through flexible support during modal test.

[0046] Further, first rigid structure 61 includes side bending truss 611, limiting plate 612 and extension truss 613. The first end of side bending truss 611 is installed on top truss 12, and the second end is arranged towards middle part 51 of bracket 5. Limiting plate 612 is arranged on the second end of side bending truss 611. One end of extension truss 613 is connected with the back of side bending truss 611, and the other end is installed with first adjusting rod 62. Limiting hole is opened in limiting plate 612 along the direction towards middle part 51 of the bracket, one end of first flexible structure 63 is connected with first adjusting rod 62, and the other end penetrates through the limiting hole of limiting plate 612 and is connected with middle part 51 of the bracket. The inner wall of the limiting hole of limiting plate 612 will limit the movement of first flexible structure 63, so that the movement range of middle part 51 of the bracket can be restricted, and the limiting ability of the limiting device of the embodiment in more degrees of freedom is improved.

[0047] In any one of the above embodiments, the way to adjust the elongation of the first adjusting rod and the second adjusting rod can be hand wheel adjustment or servo motor adjustment.

[0048] In addition, the volume of the pressure container in the embodiment is not less than 300L, the pressure container is communicated with the free membrane type air spring to expand the air chamber space of the free membrane type air spring, and the air spring stiffness can be adjusted by changing the gas medium in the pressure container. The pressure container is provided with an inflation hole, the inflation hole is connected with an inflation valve, the inflation of the pressure container is realized by controlling the opening of the inflation valve, and the pressure of the pressure container is measured by a screwed pressure gauge. The top of the pressure container is also provided with a safety valve, and the bottom is provided with a drain valve. The safety valve is screwed with the pressure container and located at the top of the pressure container, and the drain valve is screwed with the pressure container and located at the bottom of the pressure container.

[0049] Referring to Figure 2 、 Figure 3 and Figure 8 In one embodiment, the collection module 41 of the embodiment comprises at least a pressure sensor (not marked in the figure) arranged on the side surface of the free membrane type air spring 3, a height adjusting valve 411, and a laser displacement sensor 412 arranged on the top end surface of the truss 12. The pressure sensor is a static pressure sensor, when subjected to external pressure, the strain gauge deforms to change its resistance value, and the force can be calculated by measuring the change of the resistance value, so as to realize the monitoring of the pressure of the free membrane type air spring. The height adjusting valve 411 is used to dynamically perceive the direct height change of the free membrane type air spring 3, and can complete the intake or exhaust action in time to adjust the height of the free membrane type air spring 3. The laser displacement sensor 412 is a high-precision sensor for measuring the position and deformation of an object by laser, and the distance between the object and the sensor is obtained by calculating the light point position on the CCD array through the emission of laser and the collection of reflected light. When the free boundary support system of the embodiment is used to support the rocket to carry out the horizontal modal test, the pressure sensor, the height adjusting valve and the laser displacement sensor respectively transmit the collected data to the controller, the controller calculates the actual pressure of the free membrane type air spring according to the received data, compares the calculated actual pressure with the preset pressure, and sends corresponding action instructions to the execution module according to the comparison result.

[0050] The collection module 41 of the embodiment also comprises an inertial measurement unit 413 arranged on the side surface of the middle part 51 of the bracket 5. The inertial measurement unit 413 is used to measure the acceleration in the linear motion and the angular velocity in the rotary motion of the bracket, so as to quickly identify the position deviation of the bracket and the rocket during the test.

[0051] In any one of the above embodiments, the trolley is a truss structure with the functions of bearing, walking, braking and locking. The moving device arranged on the bottom truss comprises at least a walking device, a braking device and a locking device. The walking device is bolted at one end to the bottom truss and cooperates with the ground at the other end, and the walking device enables the trolley to freely walk axially relative to the ground. The braking device is arranged at the four corners of the bottom truss, and the braking device is provided with a plurality of hydraulic brake diaphragms. The locking device comprises at least an L-shaped machining part connected to the bottom truss at one end, and the other end of the L-shaped machining part is provided with a plurality of long holes, and a plurality of hand wheels are arranged at the long holes and can move in the up-down direction to lock the trolley to the ground.

[0052] Before the test starts, the entire support system can be transferred to the test site by using the walking device, and after being transferred to the position, the braking device is used to stop, and the locking device is used to lock the trolley in the test area, so as to facilitate the horizontal modal test of the rocket. After the test is completed, the rocket is removed, the locking device is unlocked, and the walking device is used to push the free boundary support system away from the test area.

[0053] In the above embodiments, the free boundary support system of the utility model is used in cooperation with the lateral elastic supporting device and the limiting device, can limit and protect the bracket and the rocket in the direction of each degree of freedom, can guarantee that the height of the bracket and the test rocket does not exceed the limited value, and can guarantee the safety of the bracket and the test rocket in the test suspension state.

[0054] The above embodiments can be combined with each other, and have corresponding technical effects.

[0055] The above only describes the preferred embodiments of the utility model, and does not limit the utility model, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A free boundary support system for horizontal mode testing of a rocket, characterized in that, At least comprising: a support frame, a free diaphragm air spring and a bracket; the support frame is a truss structure, the free diaphragm air spring is arranged on the upper end surface of the support frame, and the bracket for supporting the rocket is arranged on the top of the free diaphragm air spring; The translational, rotational and torsional degrees of freedom of the rocket are provided by the free diaphragm air spring, and the load capacity and stiffness of the free diaphragm air spring can be changed by adjusting the internal gas pressure of the free diaphragm air spring.

2. The rocket horizontal mode test free boundary support system of claim 1, wherein, The support frame at least comprises a bottom truss and a top truss, and a pressure container is arranged between the bottom truss and the top truss; the pressure container stores compressed gas inside, and a sealing flange interface is arranged on the top of the pressure container; The free diaphragm air spring is arranged on the upper end surface of the top truss, and the bottom of the free diaphragm air spring is communicated with the pressure container through the sealing flange interface.

3. The rocket horizontal mode test free boundary support system of claim 2, wherein, The bracket comprises a middle part and two side parts connected to the middle part on both sides of the middle part; the middle part of the bracket is connected to the free diaphragm air spring, and the side parts are arranged in an arc structure suitable for the outer shape of the rocket.

4. The rocket horizontal mode test free boundary support system of claim 3, wherein, Further comprising a limiting device arranged on both sides of the bracket in a first direction; The limiting device at least comprises a first rigid structure, a first adjusting rod and a first flexible structure; the first rigid structure is mounted on the top truss, the first adjusting rod is mounted on one end of the first rigid structure away from the top truss; one end of the first flexible structure is connected with the first adjusting rod, and the other end is connected with the middle part of the bracket; The first adjusting rod is controlled to move in the first direction to adjust the elongation and tension of the first flexible structure.

5. The horizontal mode test free boundary support system for rockets of claim 4, wherein, Further comprising a lateral elastic support device arranged on both sides of the bracket in a second direction; The lateral elastic support device at least comprises a second rigid structure, a second adjusting rod and a second flexible structure; the second rigid structure is arranged on the top truss, the second adjusting rod is mounted on one end of the first rigid structure away from the top truss; one end of the second flexible structure is connected with the second adjusting rod, and the other end is connected with the side part of the bracket; The second adjusting rod is controlled to move in the second direction to adjust the elongation and tension of the second flexible structure.

6. The horizontal mode test free boundary support system for rockets of claim 5, wherein, The first rigid structure comprises a side bending truss, a limiting plate and an extension truss; the first end of the side bending truss is mounted on the top truss, the second end of the side bending truss is arranged towards the middle part of the bracket, and the limiting plate is arranged on the second end of the side bending truss; one end of the extension truss is connected with the back of the side bending truss, and the other end of the extension truss is mounted with the first adjusting rod; One end of the first flexible structure is connected with the first adjusting rod, and the other end of the first flexible structure is connected with the middle part of the bracket after penetrating through the limiting plate.

7. The horizontal mode test free boundary support system of any one of claims 2 to 5, wherein, The pressure container is provided with a charging hole, and an inflating valve is arranged outside the charging hole to charge the pressure container, and a pressure gauge is used to measure the pressure of the pressure container; The top of the pressure container is provided with a safety valve, and the bottom of the pressure container is provided with a drain valve.

8. The horizontal mode test free boundary support system of a rocket of claim 5, wherein, The top surface of the two side parts of the bracket is used to support the rocket, and the bottom surface is provided with a protective baffle, and the end of the protective baffle away from the bracket is provided with a buffer pad; The second flexible structure is connected with the second adjusting rod at one end and with the protective baffle at the other end.

9. The horizontal mode test free boundary support system of a rocket of claim 2, wherein, The free membrane type air spring comprises an upper end plate, a rubber capsule body and a lower end plate connected in sequence; the upper end plate is connected with the bracket, and a part of the lower end plate is connected with the top truss, and the other part is provided with a hole for connecting the rubber capsule body and the pressure container; The hole of the lower end plate is in sealing connection with the sealing flange interface.

10. The horizontal mode test free boundary support system of a rocket of claim 1, wherein, The support frame further comprises a walking device, a brake device and a locking device arranged on the bottom truss; after the support frame is transferred to the test site by the walking device, the support frame is stopped by the brake device, and the support frame is locked and fixed by the locking device.

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