Safety protection folding platform for wind tunnel test preparation and design method

Abstract

The application discloses a safety protection folding platform for wind tunnel test preparation and a design method, which comprises a vertical plate fixed on a wind tunnel device, a bearing platform with one side of the bottom hinged to the upper side of the vertical plate, an electric cylinder with the fixed end hinged to the upper side of the vertical plate, the telescopic end of the electric cylinder hinged to the bottom of the bearing platform, an upper connecting rod with one end hinged to the other side of the bottom of the bearing platform, a lower connecting rod with one end hinged to the lower side of the vertical plate and the other end hinged to the other end of the upper connecting rod, and an elastic element with one end connected to the vertical plate and the other end connected to the lower connecting rod. The folding platform has the characteristics of large bearing capacity, low cost, high reliability and the like, can bear large airflow impact, has light weight, large folding range, can bear large load after unfolding and is reliable after folding. The safety protection folding platform is suitable for wind tunnel test preparation and operation platform and can be placed in the internal flow field of the wind tunnel.

Description

Technical Field

[0001] This invention belongs to the field of high-speed aerodynamic testing equipment, specifically relating to a safety protection folding platform and its design method for wind tunnel testing preparation. Background Technology

[0002] High-speed wind tunnels are crucial testing facilities for high-speed aerodynamic experiments, used to accurately simulate and measure the aerodynamic characteristics of aircraft under various conditions. For open-jet wind tunnels, the interior of the test chamber, especially the area supporting the test model, contains numerous deep pits. Most of these pits are blind spots for vehicle operations, and due to their large spans, ground transport vehicles cannot pass through. This presents significant challenges for hoisting, transporting, assembling models, as well as for drilling, welding, and wiring. Currently, temporary scaffolding is used, but because the mechanism may shift at any time, the scaffolding must be frequently erected and dismantled. This method not only affects the efficiency of wind tunnel test preparation but also poses significant safety hazards.

[0003] To prepare for testing in an open-jaw wind tunnel, the deep pit inside the test chamber needs to be filled. However, the mechanism may activate at any time, and the pit needs to be preserved during wind tunnel testing to eliminate flow field interference. Therefore, a folding platform needs to be designed in the pit area. When unfolded, this platform can cover the pit and withstand a certain load, while folding it without affecting the normal operation of the mechanism. Since this device is installed inside the wind tunnel and close to the test model, it needs to be able to withstand a certain wind load, with minimal blockage and minimal weight to reduce equipment load. Summary of the Invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0005] To achieve these objectives and other advantages of the present invention, a safety protection folding platform for wind tunnel test preparation is provided, comprising:

[0006] The upright plate is fixed to the wind tunnel equipment;

[0007] The support platform has its bottom side hinged to the upper side of the upright plate;

[0008] An electric cylinder, the fixed end of which is hinged to the upper side of the upright plate; the telescopic end of the electric cylinder is hinged to the bottom of the supporting platform.

[0009] The upper connecting rod is hinged at one end to the other side of the bottom of the support platform;

[0010] The lower connecting rod has one end hinged to the lower side of the vertical plate, and the other end of the lower connecting rod is hinged to the other end of the upper connecting rod.

[0011] An elastic element, one end of which is connected to the upright plate, and the other end of which is connected to the lower connecting rod;

[0012] Preferably, the bottom side of the supporting platform is hinged to the upper side of the upright plate in the following manner:

[0013] The upper two ends of the upright plate are respectively provided with first hinge seats, and the bottom side of the bearing platform is respectively provided with T-shaped connecting plates that are hinged to the first hinge seats; and the horizontal plate of the T-shaped connecting plate is connected to the bottom of the bearing platform, and the vertical plate of the T-shaped connecting plate is hinged to the first hinge seats.

[0014] Preferably, the fixed end of the electric cylinder is hinged to the upper side of the vertical plate in the following manner:

[0015] A second hinge seat, parallel to the position of the first hinge seat, is provided on the upper center of the upright plate, and the fixed end of the electric cylinder is hinged to the second hinge seat.

[0016] The telescopic end of the electric cylinder is hinged to the bottom of the support platform in the following manner:

[0017] The bottom of the bearing platform is provided with a third hinge seat that is perpendicular to the position of the first hinge seat, and the telescopic end of the electric cylinder is hinged to the third hinge seat.

[0018] When the support platform is in the deployed state, the fixed end of the electric cylinder is in a nearly horizontal state with the second hinge seat; the telescopic end of the electric cylinder is in a nearly vertical state with the third hinge seat.

[0019] When the support platform is in a folded state, the fixed end of the electric cylinder is nearly perpendicular to the second hinge; the telescopic end of the electric cylinder is nearly horizontal to the third hinge.

[0020] Furthermore, the electric cylinder maintains a nearly horizontal position with the support platform when the support platform is in both the unfolded and folded states.

[0021] Preferably, one end of the upper connecting rod is hinged to the other side of the bottom of the supporting platform in the following manner:

[0022] The folding link consisting of the upper link and the lower link is provided in two sets; the two ends of the bottom of the bearing platform are respectively provided with a fourth hinge seat perpendicular to the bearing platform, and one end of the two upper links is respectively hinged to the fourth hinge seat;

[0023] One end of the lower connecting rod is hinged to the lower side of the vertical plate in the following manner:

[0024] The lower sides of the vertical plate are respectively provided with fifth hinge seats perpendicular to the vertical plate, and one end of each of the two upper connecting rods is hinged to the fifth hinge seat.

[0025] The other end of the lower connecting rod is hinged to the other end of the upper connecting rod in the following manner:

[0026] The lower connecting rod is a U-shaped groove connecting rod, and the other end of the upper connecting rod is located in the U-shaped groove of the U-shaped groove connecting rod and is hinged to the U-shaped groove connecting rod;

[0027] When the support platform is in a folded state, the lower connecting rod and the upper connecting rod are also in a folded state, and at this time the upper connecting rod is accommodated in the U-shaped groove of the lower connecting rod.

[0028] Preferably, a first pin hole is provided on the other end of the lower connecting rod, and a second pin hole is provided on the other end of the upper connecting rod; when the bearing platform is in the unfolded state, the lower connecting rod and the upper connecting rod are in the unfolded state, and at this time the first pin hole and the second pin hole are facing each other, and a safety pin is inserted into the first pin hole and the second pin hole.

[0029] The elastic element is a spring, one end of which is connected to the vertical plate through a first spring seat, and the other end of which is connected to the lower connecting rod through a second spring seat.

[0030] Preferably, the carrier platform includes:

[0031] The frame is welded from rectangular tubular profiles;

[0032] The aluminum perforated plate is welded within the frame.

[0033] The guardrail is made of adapters and aluminum alloy tubing; the guardrail is detachably connected to the perforated plate.

[0034] Preferably, two rigid limiting blocks are provided on the lower end of the upright plate, and buffer rubber pads are provided on the two rigid limiting blocks; and when the folding platform is in the folded state, the two rigid limiting blocks are connected to the rigid limiting of the bearing platform by screws.

[0035] Preferably, the present invention also provides a design method for a safety protection folding platform for wind tunnel test preparation as described above, comprising the following steps:

[0036] Step 1, Preprocessing: Constructing the geometric model, meshing, defining and assigning material properties:

[0037] Step 2: Create and solve the finite element model: Create connection relationships, set boundary conditions, set solution parameters, and perform calculations;

[0038] Step 3, Post-processing: Extract the displacement and stress time history results of each component during the platform's unfolding and folding process; based on the virtual work equation, torque balance, deformation coordination and energy conservation, solve the forces on the electric cylinder and connecting rod under the following conditions: platform unfolding / folding process, unfolding to lock, and brake release under external load. Based on this, optimize the structural dimensions and material parameters so that the electric cylinder load is lower than the rated value and the connecting rod stress meets the allowable requirements.

[0039] Preferably, the force solution for the platform unfolding / folding process is as follows:

[0040] The folding platform is simplified as a planar linkage system, with the coordinate system as follows: the origin O is the center of the revolute joint connecting the T-shaped connecting plate and the first hinge; the x-direction points to the center of the revolute joint connecting the fourth hinge and the upper connecting rod when the platform is fully extended; the y-direction points to the center of the revolute joint connecting the fifth hinge and the lower connecting rod; point B is the center of the revolute joint connecting the upper and lower connecting rods; point D is the center of the revolute joint connecting the fixed end of the electric cylinder and the second hinge; point E is the center of the revolute joint connecting the telescopic end of the electric cylinder and the third hinge; and α is the angle between the line OE and the line DE. i Let OE be the angle between the line containing OE and the X-axis, i.e., the folding angle of the load-bearing platform. Remove the electric cylinder DE and replace it with the active force F. Taking the entire system as the research object, which is an ideal constraint, the folding angle of the load-bearing platform is... i The platform's weight is G, its center of gravity is at the center, and its length is OA. l The length AE from the third hinge to the edge of the bearing platform is l 1 The installation angle between the electric cylinder and the load-bearing platform is α;

[0041] From the equation of virtual work, we can obtain:

[0042]

[0043] in, y G It is the y-coordinate of point G. x E It is the x-coordinate of point E. y E It is the y-coordinate of point E;

[0044] From geometric relations, we can obtain:

[0045]

[0046] Then we have:

[0047]

[0048] Substituting into the virtual work equation, and using δ i The arbitrariness of the result yields:

[0049]

[0050] Therefore, the force F acting on the electric cylinder is:

[0051]

[0052] Therefore, the rotation angle of the folding platform can be determined. i When the folding angle of the load-bearing platform is 0, the electric cylinder has the maximum load, and its value is related to the length of the load-bearing platform. l Position of the electric cylinder hinge l 1. Self-weight G and the installation angle of the electric cylinder and the load-bearing platform α Related to; reasonable design l , l 1. i , G The value of makes F The load should be less than the rated load of the electric cylinder.

[0053] Preferably, the force solution for the deployment, locking, and release of the external load is as follows:

[0054] Once the mechanism is in place, the upper connecting rod AB and the lower connecting rod BC are collinear and connected by a safety pin, so they can be regarded as a whole and the whole can be simplified into a planar rod system; if the electric cylinder brake is locked, the whole structure is obviously statically indeterminate at this time.

[0055] Depend on =0, meaning that with point O as the reference, the net torque is zero, so we can obtain:

[0056]

[0057] in, c When the platform is deployed, the angle between connecting rod AC and the supporting platform is considered; the upper connecting rod AB and the lower connecting rod BC of connecting rod AC are in the deployed state; since the supporting platform AEO has greater rigidity relative to connecting rod AC and electric cylinder DE, for the sake of simplifying the calculation, the supporting platform AEO can be regarded as a rigid body; let the elastic modulus and cross-sectional area of ​​connecting rod AC and electric cylinder DE be E1, E4, A1, and A4 respectively, then the deformation displacement of connecting rod AC and electric cylinder DE in the y direction is:

[0058]

[0059] in, y A F2 is the y-coordinate of point A; F2 is the force on link AC.

[0060] According to the deformation-displacement compatibility equation, we have:

[0061]

[0062] Therefore, we can conclude that:

[0063]

[0064] As can be seen from the above formula, after the platform is deployed, under its own weight load G, the load on the electric cylinder is related to the material properties and cross-sectional area; in this design... The connecting rod bears part of the load, and the electric cylinder experiences relatively less force after the pin is inserted.

[0065] If the upper connecting rod AB and the lower connecting rod BC are collinear and locked together with a pin, and the electric cylinder releases its brake, applying a large external load F1 at the center position, then the load is mainly borne by connecting rod AC, and its force can be easily obtained as follows:

[0066]

[0067] At this point, all you need is... In the formula Allowable stress.

[0068] Preferably, after the folding platform is unfolded, the upper connecting rod AB and the lower connecting rod BC are fixedly connected by a pin. At this time, a spring is installed between the lower connecting rod BC and the fixed hinge CO. The fixed hinge CO is located between the first hinge seat and the fifth hinge seat. The spring has elastic potential energy due to the tension. When the folding platform needs to be folded, the pin between connecting rods AB and BC is removed, and the electric cylinder is in the released state. At this time, under the action of elastic potential energy, connecting rods AB and BC are no longer collinear, and the rotation angle of connecting rod BC is [missing value]. β Taking the whole as the research object, with degrees of freedom N=1, and using i For a generalized coordinate system, i When the potential energy is 0, the system is in a zero potential energy configuration. The radius of the axis of rotation containing the spring is... r , d Let OC be the spring extension / retraction amount, and AB be the length of the spring. l 3 BC is l 4 Then, according to the law of conservation of energy, we can obtain:

[0069]

[0070] From the geometric positional relationship, we can obtain:

[0071]

[0072] Among them, point H is an auxiliary vertical point introduced for force analysis, and AH is perpendicular to CH;

[0073] The relationship between the spring position r, the spring stiffness k, and the rotation angle β of the connecting rod BC can be obtained from the above formula, providing a reference for spring selection and position setting.

[0074] The present invention has at least the following beneficial effects:

[0075] The folding platform of this invention features high load-bearing capacity, the ability to withstand significant airflow impact, low cost, and high reliability. The platform is lightweight, has a large folding range, can withstand substantial loads when unfolded, and is reliably fixed after folding. The electric cylinder has a short stroke, small size, and low cost, making it highly valuable in engineering applications. This safety-protecting folding platform is suitable for wind tunnel test preparation and operation, and can be placed inside the wind tunnel flow field.

[0076] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0077] Figure 1 This is a schematic diagram of the unfolded state of the folding platform of the present invention;

[0078] Figure 2 This is a structural schematic diagram of the folding platform of the present invention from the bottom view in its unfolded state;

[0079] Figure 3 This is a schematic diagram of the structure of the folding platform of the present invention from a frontal view in its unfolded state;

[0080] Figure 4 This is a schematic diagram of the folding platform of the present invention in its folded state;

[0081] Figure 5 This is a structural schematic diagram of the folding platform of the present invention in a folded state from another perspective.

[0082] Figure 6 This is a coordinate system diagram illustrating the structure and stress analysis of the support platform of the present invention from a folded state to an unfolded state.

[0083] Figure 7 This is a coordinate system diagram for force analysis of the support platform of the present invention when it is in the deployed state;

[0084] Figure 8 This is a coordinate system diagram for force analysis of the selection and placement of springs in the folding platform of this invention. Detailed Implementation

[0085] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0086] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0087] It should be noted that in the description of this invention, the orientations or positional relationships indicated by terms are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this invention. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0088] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0089] Furthermore, in this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Moreover, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0090] See Figure 1-Figure 5 As shown, a safety protection folding platform for wind tunnel test preparation according to the present invention includes:

[0091] Vertical plate 1, which is fixed to the wind tunnel equipment;

[0092] The support platform 2 is hinged to the upper side of the vertical plate 1 on one side of its bottom;

[0093] The electric cylinder 3 has its fixed end 31 hinged to the upper side of the upright plate 1; the telescopic end 32 of the electric cylinder 3 is hinged to the bottom of the bearing platform 2.

[0094] The upper connecting rod 4 is hinged at one end to the other side of the bottom of the bearing platform 2;

[0095] The lower connecting rod 5 has one end hinged to the lower side of the vertical plate 1, and the other end of the lower connecting rod 5 is hinged to the other end of the upper connecting rod 4.

[0096] The elastic element 6 has one end connected to the vertical plate 1 and the other end connected to the lower connecting rod 5.

[0097] Working Principle: Under normal circumstances, the safety protection folding platform of this invention is in a folded state, that is, the angle between the support platform and the upright plate is 0°. When the safety protection folding platform needs to be unfolded, the telescopic end (i.e., piston rod) of the electric cylinder extends, and the support platform drives the upper and lower connecting rods to unfold. When the angle between the folding platform and the upright plate is 90°, the piston rod of the electric cylinder stops extending. At this time, the upper and lower connecting rods of the linkage mechanism are nearly collinear. When the safety protection folding platform needs to be folded up, since the upper and lower connecting rods are nearly collinear at this time, the mechanism is in a dead point region, and the electric cylinder cannot directly drive the linkage mechanism. Therefore, an elastic element is provided between the lower connecting rod and the upright plate. By adjusting the appropriate preload of the elastic element, the electric cylinder can be assisted in the platform folding operation.

[0098] In another technical solution, the bottom side of the supporting platform 2 is hinged to the upper side of the upright plate 1 in the following manner:

[0099] The upper two ends of the upright plate 1 are respectively provided with first hinge seats 7, and the bottom side of the bearing platform 2 is respectively provided with T-shaped connecting plates 8 that are hinged to the first hinge seats 7; and the horizontal plate of the T-shaped connecting plate 8 is connected to the bottom of the bearing platform 2, and the vertical plate of the T-shaped connecting plate 8 is hinged to the first hinge seats 7; in this way, the bearing platform can be folded and unfolded through the first hinge seats and the T-shaped connecting plates, and through the action of the electric cylinder.

[0100] In another technical solution, the fixed end of the electric cylinder is hinged to the upper side of the vertical plate in the following manner:

[0101] A second hinge seat 9, parallel to the position of the first hinge seat 7, is provided on the upper middle part of the upright plate 1. The fixed end 31 of the electric cylinder 3 is hinged to the second hinge seat 9.

[0102] The telescopic end 32 of the electric cylinder 3 is hinged to the bottom of the support platform 2 in the following manner:

[0103] The bottom of the bearing platform 2 is provided with a third hinge seat 10 that is perpendicular to the position of the first hinge seat 7, and the telescopic end 32 of the electric cylinder 3 is hinged to the third hinge seat 10.

[0104] When the support platform 2 is in the unfolded state, the fixed end 31 of the electric cylinder 3 and the second hinge 9 are in a nearly horizontal state; the telescopic end 32 of the electric cylinder 3 and the third hinge 10 are in a nearly vertical state.

[0105] When the support platform 2 is in a folded state, the fixed end 31 of the electric cylinder 3 is in a nearly perpendicular state with the second hinge seat 9; the telescopic end 32 of the electric cylinder 3 is in a nearly horizontal state with the third hinge seat 10.

[0106] Furthermore, the electric cylinder maintains a nearly horizontal position with the support platform when the support platform is in both the unfolded and folded states.

[0107] In the above technical solution, the electric cylinder adopts a near-horizontal installation method. Its fixed end is connected to the vertical plate through a second hinge, and its telescopic end (piston rod) is connected to the bearing platform through a third hinge. This near-horizontal installation method of the electric cylinder allows the electric cylinder to achieve 0°-90° positional changes between the bearing platform and the vertical plate within a small stroke range, which saves both installation space and cost.

[0108] In another technical solution, one end of the upper connecting rod 4 is hinged to the other side of the bottom of the bearing platform 2 in the following manner:

[0109] The folding link consisting of the upper link 4 and the lower link 5 is provided in two sets; the two ends of the bottom of the bearing platform 2 are respectively provided with a fourth hinge seat 11 perpendicular to the bearing platform 2, and one end of the two upper links 4 are respectively hinged to the fourth hinge seat 11.

[0110] The lower connecting rod 5 is hinged to the lower side of the vertical plate 1 in the following manner:

[0111] The lower sides of the vertical plate 1 are respectively provided with fifth hinge seats 12 perpendicular to the vertical plate 1, and one end of the two upper connecting rods 4 are respectively hinged to the fifth hinge seats 12.

[0112] In this way, the two sets of upper connecting rods are hinged to the bottom of the bearing platform 2, and the two sets of lower connecting rods are hinged to the bottom of the upright plate 1. Through the action of the electric cylinder, the bearing platform can be folded and unfolded. In the unfolded state, the two sets of upper connecting rods support the bearing platform.

[0113] In another technical solution, the other end of the lower connecting rod is hinged to the other end of the upper connecting rod in the following manner:

[0114] The lower connecting rod 5 is a U-shaped groove connecting rod, and the other end of the upper connecting rod 4 is located in the U-shaped groove 51 of the U-shaped groove connecting rod and is hinged to the U-shaped groove connecting rod;

[0115] When the supporting platform is in a folded state, the lower connecting rod and the upper connecting rod are also folded, and at this time the upper connecting rod is accommodated in the U-shaped groove of the lower connecting rod;

[0116] In this technical solution, the upright plate is connected to the rear end of the supporting platform through two first hinge seats, and the front end is connected through a linkage mechanism (upper link and lower link); the lower link that is hinged to the upright plate is a U-shaped groove link. This design allows the linkage mechanism to achieve a smaller included angle (the upper link can be accommodated in the U-shaped groove of the lower link), thereby expanding the included angle range between the folding platform and the upright plate.

[0117] In another technical solution, a first pin hole 52 is provided on the other end of the lower connecting rod 5, and a second pin hole 41 is provided on the other end of the upper connecting rod 4; when the bearing platform is in the unfolded state, the lower connecting rod 5 and the upper connecting rod 4 are in the unfolded state, and at this time the first pin hole 52 and the second pin hole 41 are arranged opposite each other, and a safety pin 13 is inserted into the first pin hole 52 and the second pin hole 41.

[0118] In the above technical solution, when the support platform is unfolded, that is, when the angle between the support platform and the upright plate is 90°, the piston rod of the electric cylinder stops extending. At this time, the two connecting rods (upper connecting rod and lower connecting rod) of the linkage mechanism are close to collinear. The equipment needs to bear the load on the support platform in this state. Therefore, after unfolding into place, a safety pin is inserted between the two connecting rods (upper connecting rod and lower connecting rod). The load is mainly borne by the linkage mechanism and the safety pin, and the electric cylinder bears a very small load.

[0119] In another technical solution, the elastic element is a spring, one end of which is connected to the upright plate through a first spring seat, and the other end of which is connected to the lower connecting rod through a second spring seat.

[0120] In the above technical solution, the dead point of the mechanism can be overcome by taking advantage of the characteristics of spring energy recovery and utilization. In this invention, there is a dead point of the mechanism after the safety protection folding platform is unfolded. After the spring is introduced, under the action of the spring force, there is a small angle between the upper and lower connecting rods after the equipment is unfolded. After the safety pin is inserted, the angle disappears, and the bearing platform can bear a large load. When folding is required, the safety pin is removed, and under the action of the spring force, the angle between the upper and lower connecting rods is restored, and the electric cylinder can move smoothly, thereby driving the equipment to the folded state.

[0121] In another technical solution, the carrier platform 2 includes:

[0122] Frame 21 is welded from rectangular tubular profiles;

[0123] Aluminum perforated plate 22, which is welded within the frame;

[0124] The guardrail 23 is made of adapters and aluminum alloy tubing; the guardrail is detachably connected to the perforated plate.

[0125] In the above technical solution, the frame 21, as the main load-bearing component, is welded from rectangular tubular profiles; the aluminum perforated plate 22 is made of aluminum and is welded to the frame; the aluminum perforated plate 22 has a large number of through holes, which not only reduces the weight of the mechanism but also allows for the rapid formation of uniform pressure on both sides when encountering high-pressure airflow in the wind tunnel after folding, thereby reducing the impact of airflow during wind tunnel testing. The guardrail 23 is constructed from adapters and aluminum alloy tubing, making it lightweight. Considering that the guardrail needs to be frequently disassembled and reassembled and can be transported by a transport vehicle after disassembly, the guardrail and the aluminum perforated plate use a mortise and tenon structure instead of screws, allowing for quick insertion and removal. After the guardrail is disassembled, the surface of the aluminum perforated plate is flat, allowing the transport vehicle to pass through the aluminum perforated plate to the upright plate, facilitating the transportation of the test model.

[0126] In another technical solution, two hard limiting blocks 14 are provided on the lower end of the upright plate 1, and buffer rubber pads 15 are provided on the two hard limiting blocks 14; and when the folding platform is in the folded state, the two hard limiting blocks 14 are connected to the bearing platform 2 by screws.

[0127] In this technical solution, two hard limit blocks are provided on the upright plate to restrict the position of the folding platform after folding. In order to reduce the impact generated when the folding platform is folded to the hard limit, a buffer rubber pad is set on the hard limit block. Since the entire device is in the wind tunnel flow field, after folding to the position, the aluminum perforated plate and the hard limit block can be connected by screws to ensure the reliability of the equipment in the folded state.

[0128] In this invention, the driving and load-bearing components are designed separately: an electric cylinder drives the entire device; when the safety protection folding platform moves, the main load is its own weight, and the electric cylinder has a small load, thus reducing the size of the driving mechanism, saving space, and allowing for a larger operating range. However, when the safety protection folding platform is unfolded, it needs to withstand a very large load. At this time, a safety pin is inserted between the upper and lower connecting rods, and the load is mainly supported by the upper and lower connecting rods and the safety pin, greatly enhancing the device's load-bearing capacity. This partitioned design effectively resolves the contradiction between small size and large load-bearing capacity.

[0129] In this invention, the dead point of the mechanism is overcome by utilizing the energy recovery and utilization characteristics of springs. In this invention, a dead point exists in the mechanism after the safety protection folding platform is unfolded. By introducing springs, a small angle exists between the upper and lower connecting rods after the equipment is unfolded, under the action of spring force. This angle disappears after the safety pin is inserted, allowing the platform to withstand a larger load. When folding is required, the safety pin is removed, and the angle between the upper and lower connecting rods is restored under the action of spring force, allowing the electric cylinder to operate smoothly and thus driving the equipment to the folded state.

[0130] Example 1:

[0131] A design method for a safety protection folding platform for wind tunnel test preparation, as described above, is characterized by comprising the following steps:

[0132] Step 1: Pre-processing

[0133] Constructing the geometric model: Using 3D software, model the folding platform according to its structure and actual dimensions, and simplify the pins (pins are provided between the two relatively rotating parts), screws, buffer rubber pads 15, electric cylinder motors and cables (electric cylinder power supply and control cables) and other parts that have little impact on the force solution of the electric cylinder; set the cylinder body and the bearing platform of the electric cylinder as rigid bodies, and the rest as flexible bodies;

[0134] Mesh generation: The upper connecting rod, lower connecting rod, and telescopic end of the electric cylinder are key load-bearing components and are divided into hexahedral structured meshes, while the rest are tetrahedral unstructured meshes. Mesh refinement is also performed on areas with high load (the safety pin area between the upper and lower connecting rods) to improve computational accuracy while saving computational resources.

[0135] Define and assign material properties: Create a material constitutive model according to the materials involved in the model, and assign materials to each component according to the actual situation (the material of frame 21 and aluminum perforated plate 22 is 7075Al, the material of electric cylinder 3 is 40Cr, and the material of the other components is 30CrMnSi).

[0136] Step 2: Create and solve the finite element model:

[0137] Establish connection relationships: The upright plate 1 is set with a ground-fixed joint; the connection between the upright plate 1 and the rigid limiting block 14, the first hinge seat 7, the second hinge seat 9, and the fifth hinge seat 12 is set as a fixed joint; the connection between the frame 21 and the third hinge seat 10, the fourth hinge seat 11, the T-shaped connecting plate 8, and the aluminum perforated plate 22 is set as a fixed joint; the connection between the lower connecting rod 5 and the fifth hinge seat 12 is set as a revolute joint; the connection between the upper connecting rod 4 and the fourth hinge seat 11 is set as a revolute joint; the connection between the first hinge seat 7 and the T-shaped connecting plate 8 is set as follows: The connection between the third hinge 10 and the telescopic end 32 of the electric cylinder is set as a revolute joint, the connection between the fixed end 31 of the electric cylinder and the second hinge 9 is set as a revolute joint, and the connection between the fixed end 31 of the electric cylinder and the telescopic end 32 is set as a prismatic joint. The damping between each kinematic joint is ignored. The upper connecting rod 4 and the lower connecting rod 5 are set as frictional contact with a friction coefficient of 0.15. The contact algorithm adopts the augmented Lagrange multiplier method, the contact stiffness is set to 0.5, and the automatic bisection method is enabled.

[0138] Boundary conditions are set: The overall gravity environment is set according to the actual direction (gravity is the side perpendicular to the bearing platform and pointing to the lower connecting rod after the platform is fully extended) to calculate the force of the electric cylinder under its own weight load; the initial condition is that the bearing platform is in the extended state (at this time it is not fully extended, and it is 0.5° away from the fully extended state, otherwise the mechanism is in a dead point state and the finite element calculation cannot converge). A spring connection is set between the vertical plate and the lower connecting rod, with a spring preload of 1000N and a stiffness of 32.4N / mm;

[0139] Set the solution parameters and perform the calculation: Set 7 load steps, each load step is set to automatic load step size, the initial load step is 25, the minimum and maximum load steps are 20 and 250 respectively, and the large deformation option is enabled for all load steps; 0-0.4s, the speed change between the fixed end 31 and the telescopic end 32 of the electric cylinder is 0-16mm / s; 0.4-6.8s, the speed between the fixed end 31 and the telescopic end 32 of the electric cylinder is constant at 16mm / s; 6.8-7s, the speed change between the fixed end 31 and the telescopic end 32 of the electric cylinder is 16-0mm / s; 7-7. For 4s, the velocity change between the fixed end 31 and the telescopic end 32 of the electric cylinder is 0-(-16) mm / s; for 7.4-13.8s, the velocity change between the fixed end 31 and the telescopic end 32 of the electric cylinder is constant at -16 mm / s; for 13.8-14s, the velocity change between the fixed end 31 and the telescopic end 32 of the electric cylinder is -16-(-8) mm / s; for 14-14.2s, the velocity change between the fixed end 31 and the telescopic end 32 of the electric cylinder is -8-0 mm / s; solve for the displacement and stress of each component during the process of the bearing platform unfolding to complete folding;

[0140] Step 3, Post-processing: Extract the displacement and stress time history results of each component during the platform's unfolding and folding process; based on the virtual work equation, torque balance, deformation coordination and energy conservation, solve the forces on the electric cylinder and connecting rod under the following conditions: platform unfolding / folding process, unfolding to lock, and brake release under external load. Based on this, optimize the structural dimensions and material parameters so that the electric cylinder load is lower than the rated value and the connecting rod stress meets the allowable requirements.

[0141] Extraction of solution results: Extract the displacement and stress changes of each component over time during the process of unfolding to full folding of the bearing platform, and observe the changes in the magnitude of the force between the fixed end 31 and the telescopic end 32 of the electric cylinder;

[0142] Theoretical calculation results analysis: The force solution for the platform's unfolding / folding process is (i.e., the process of the platform changing from a folded state to an unfolded state):

[0143] Because the mechanism operates at a relatively slow speed, it can be considered a quasi-static process. The masses of the connecting rods (the upper and lower connecting rods have relatively small masses compared to the bearing platform, and their impact on the electric cylinder's force is small, so they can be ignored), the T-shaped connecting plate 8, the hinge seats (third hinge seat 10, fourth hinge seat 11), and the damping between components are neglected. The entire system is simplified to a planar rod system; that is, the coordinate system is (e.g., ...). Figure 6 (As shown): O is the center of the revolute joint connecting the T-shaped connecting plate and the first hinge; the x-direction points to the center of the revolute joint connecting the fourth hinge and the upper connecting rod when the platform is fully extended; the y-direction points to the center of the revolute joint connecting the fifth hinge and the lower connecting rod; point B is the center of the revolute joint connecting the upper and lower connecting rods; point D is the center of the revolute joint connecting the fixed end of the electric cylinder and the second hinge; point E is the center of the revolute joint connecting the telescopic end of the electric cylinder and the third hinge; α is the angle between the line OE and the line DE. i Let OE be the angle between the line containing OE and the X-axis, i.e., the folding angle of the load-bearing platform. Remove the electric cylinder DE and replace it with the active force F. Taking the entire system as the research object, which is an ideal constraint, the folding angle of the load-bearing platform is... i The platform's weight is G, its center of gravity is at the center, and its length is OA. l The length AE from the third hinge to the edge of the bearing platform is l 1 The installation angle between the electric cylinder and the load-bearing platform is α;

[0144] From the equation of virtual work, we can obtain:

[0145]

[0146] in, y G It is the y-coordinate of point G. x E It is the x-coordinate of point E. y E It is the y-coordinate of point E;

[0147] From geometric relations, we can obtain:

[0148]

[0149] Then we have:

[0150]

[0151] Substituting into the virtual work equation, and using δ i The arbitrariness of the result yields:

[0152]

[0153] Therefore, the force F acting on the electric cylinder is:

[0154]

[0155] Therefore, the rotation angle of the folding platform can be determined. i When the folding angle of the load-bearing platform is 0, the electric cylinder has the maximum load, and its value is related to the length of the load-bearing platform. l Position of the electric cylinder hinge l 1. Self-weight G and the installation angle of the electric cylinder and the load-bearing platform α Related to; reasonable design l , l 1. i , G The value of makes F The load should be less than the rated load of the electric cylinder.

[0156] The force solution for the deployment, locking, and release of the external load is as follows: that is, the bearing platform is in the deployed state:

[0157] Once the mechanism is in place, the upper link AB and the lower link BC are collinear and connected by a safety pin. They can be considered as a single unit, simplified as a planar rod system, with the coordinate system as follows: Figure 7 As shown; if the electric cylinder brake is locked, the entire structure is obviously statically indeterminate at this time;

[0158] Depend on =0, meaning that with point O as the reference, the net torque is zero, so we can obtain:

[0159] ;

[0160] in, c When the platform is deployed, the angle between connecting rod AC and the supporting platform is considered; the upper connecting rod AB and the lower connecting rod BC of connecting rod AC are in the deployed state; since the supporting platform AEO has greater rigidity relative to connecting rod AC and electric cylinder DE, for the sake of simplifying the calculation, the supporting platform AEO can be regarded as a rigid body; let the elastic modulus and cross-sectional area of ​​connecting rod AC and electric cylinder DE be E1, E4, A1, and A4 respectively, then the deformation displacement of connecting rod AC and electric cylinder DE in the y direction is:

[0161] ;

[0162] in, y A F2 is the y-coordinate of point A; F2 is the force on link AC.

[0163] According to the deformation-displacement compatibility equation, we have:

[0164]

[0165] Therefore, we can conclude that:

[0166]

[0167] As can be seen from the above formula, after the platform is deployed, under its own weight load G, the load on the electric cylinder is related to the material properties and cross-sectional area; in this design... The connecting rod bears part of the load, and the electric cylinder experiences relatively less force after the pin is inserted.

[0168] If the upper connecting rod AB and the lower connecting rod BC are collinear and locked together with a pin, and the electric cylinder releases its brake, applying a large external load F1 at the center position, then the load is mainly borne by connecting rod AC, and its force can be easily obtained as follows:

[0169]

[0170] At this point, all you need is... In the formula Allowable stress;

[0171] After the folding platform is unfolded, the upper connecting rod AB and the lower connecting rod BC are fixedly connected by a pin. At this time, a spring is installed between the lower connecting rod BC and the fixed hinge CO. The fixed hinge CO is located between the first hinge seat and the fifth hinge seat. The spring has elastic potential energy due to the tension. When the folding platform needs to be folded, the pin between connecting rods AB and BC is removed, and the electric cylinder is in the released state. At this time, under the action of elastic potential energy, connecting rods AB and BC are no longer collinear, and the rotation angle of connecting rod BC is [missing value]. β ;like Figure 8 As shown, taking the whole as the research object, with degrees of freedom N=1, and using... i For a generalized coordinate system, i When the potential energy is 0, the system is in a zero potential energy configuration. The radius of the axis of rotation containing the spring is... r , d Let OC be the spring extension / retraction amount, and AB be the length of the spring. l 3 BC is l 4 Then, according to the law of conservation of energy, we can obtain:

[0172]

[0173] From the geometric positional relationship, we can obtain:

[0174]

[0175] Among them, point H is an auxiliary vertical point introduced for force analysis, and AH is perpendicular to CH;

[0176] The relationship between the spring position r, the spring stiffness k, and the rotation angle β of the connecting rod BC can be obtained from the above formula, providing a reference for spring selection and position setting.

[0177] In this invention, kinematic simulation and finite element method (FEM) calculations shorten the model design time and reduce trial-and-error costs. While the electric cylinder and springs use standard components, the rest are designed non-standard. This equipment has a compact structure, high load-bearing requirements, and a large range of motion. The spring specifications and their placement, in particular, significantly impact the overall operation of the equipment, posing a significant challenge to design capabilities. Combining kinematic simulation and FEM calculations assists in the selection of standard components and the design of non-standard component dimensions, verifying the feasibility of the design and selection.

[0178] In this invention, the internal environment of the wind tunnel is taken into full consideration, taking into account factors suitable for operation inside the wind tunnel. Pressure equalization holes are designed for weak components to reduce the impact of high-speed airflow on the equipment. Simultaneously, the projected area in the flow direction after folding, i.e., the model blockage degree, is minimized to reduce the equipment's interference with the wind tunnel flow field. Specifically, the safety protection platform is placed inside the wind tunnel, and during testing, it is in either a fully extended or folded state. According to the wind tunnel flow field blockage degree calculation formula, the ratio of the projected area in the direction shown in the structural diagram (with the protective railing removed) to the cross-sectional area of ​​the wind tunnel test section is the blockage degree. Clearly, the blockage degree is greatest after full extension. Therefore, the projected area is calculated based on the platform after full extension, requiring the minimum projected area while simultaneously meeting strength and stiffness requirements. For the safety protection platform, the blockage degree mainly depends on the projected dimensions of the supporting platform, upper connecting rod, and lower connecting rod, i.e.:

[0179] S = A 1+ A 2+ A 3, A 1- A 3 represents the projected area of ​​the supporting platform, upper link, and lower link, where... A 1= l 1× h 1, l 1 represents the length of the platform. h 1 represents the height of the support platform; A 2= l 2× h 2, l 2 represents the length of the upper connecting rod. h 2 represents the height of the upper connecting rod; A 3= l 3× h 2, l 3 represents the length of the lower connecting rod. h 3 represents the height of the lower connecting rod.

[0180] For the load-bearing platform, the main stress is bending stress, and its maximum stress is: , F To bear the load on the platform, b 1 represents the width of the support platform; the maximum displacement is: , E 1.I 1 respectively bears the elastic modulus and moment of inertia of the platform material.

[0181] The upper connecting rod mainly bears compressive stress, and its maximum stress is: , F 2 represents the load on the upper connecting rod. b 2 represents the width of the upper connecting rod. h 2 represents the height of the upper connecting rod; the maximum displacement is: , E 2 represents the elastic modulus of the upper connecting rod material.

[0182] The lower connecting rod mainly bears compressive stress, and its maximum stress is: , F 2 represents the load on the lower link (same as the upper link). b 3 represents the width of the lower connecting rod. h 3 represents the height of the lower connecting rod, and t represents the thickness of the U-shaped groove interface; the maximum displacement is: , E 2 represents the elastic modulus of the lower connecting rod material (same as the upper connecting rod).

[0183] The sum of the projected areas of the above components S The minimum prerequisite is that all strength and stiffness requirements are met, that is: These are the allowable stresses of the materials for the load-bearing platform and the upper and lower connecting rods, respectively, and n is the safety factor. The allowable deformations are specified for the load-bearing platform and the upper and lower connecting rods, respectively.

[0184] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A safety protection folding platform for wind tunnel test preparation, characterized in that, include: The upright plate is fixed to the wind tunnel equipment; The support platform has its bottom side hinged to the upper side of the upright plate; An electric cylinder, the fixed end of which is hinged to the upper side of the upright plate; the telescopic end of the electric cylinder is hinged to the bottom of the supporting platform. The upper connecting rod is hinged at one end to the other side of the bottom of the support platform; The lower connecting rod has one end hinged to the lower side of the vertical plate, and the other end of the lower connecting rod is hinged to the other end of the upper connecting rod. An elastic element, one end of which is connected to the upright plate, and the other end of which is connected to the lower connecting rod; The lower connecting rod is provided with a first pin hole at the other end, and the upper connecting rod is provided with a second pin hole at the other end. When the bearing platform is in the unfolded state, the lower connecting rod and the upper connecting rod are in the unfolded state, and at this time the first pin hole and the second pin hole are facing each other, and a safety pin is inserted into the first pin hole and the second pin hole. The elastic element is a spring, one end of which is connected to the upright plate through a first spring seat, and the other end of which is connected to the lower connecting rod through a second spring seat.

2. The safety protection folding platform for wind tunnel test preparation as described in claim 1, characterized in that, The bottom side of the support platform is hinged to the upper side of the upright plate in the following manner: The upper two ends of the upright plate are respectively provided with first hinge seats, and the bottom side of the bearing platform is respectively provided with T-shaped connecting plates that are hinged to the first hinge seats; and the horizontal plate of the T-shaped connecting plate is connected to the bottom of the bearing platform, and the vertical plate of the T-shaped connecting plate is hinged to the first hinge seats.

3. The safety protection folding platform for wind tunnel test preparation as described in claim 2, characterized in that, The fixed end of the electric cylinder is hinged to the upper side of the vertical plate in the following manner: A second hinge seat, parallel to the position of the first hinge seat, is provided on the upper center of the upright plate, and the fixed end of the electric cylinder is hinged to the second hinge seat. The telescopic end of the electric cylinder is hinged to the bottom of the support platform in the following manner: The bottom of the bearing platform is provided with a third hinge seat that is perpendicular to the position of the first hinge seat, and the telescopic end of the electric cylinder is hinged to the third hinge seat. When the support platform is in the deployed state, the fixed end of the electric cylinder is in a nearly horizontal state with the second hinge seat; the telescopic end of the electric cylinder is in a nearly vertical state with the third hinge seat. When the support platform is in a folded state, the fixed end of the electric cylinder is nearly perpendicular to the second hinge; the telescopic end of the electric cylinder is nearly horizontal to the third hinge. Furthermore, the electric cylinder maintains a nearly horizontal position with the support platform when the support platform is in both the unfolded and folded states.

4. The safety protection folding platform for wind tunnel test preparation as described in claim 1, characterized in that, The upper connecting rod is hinged to the other side of the bottom of the bearing platform in the following manner: The folding link consisting of the upper link and the lower link is provided in two sets; the two ends of the bottom of the bearing platform are respectively provided with a fourth hinge seat perpendicular to the bearing platform, and one end of the two upper links is respectively hinged to the fourth hinge seat; One end of the lower connecting rod is hinged to the lower side of the vertical plate in the following manner: The lower sides of the vertical plate are respectively provided with fifth hinge seats perpendicular to the vertical plate, and one end of each of the two upper connecting rods is hinged to the fifth hinge seat. The other end of the lower connecting rod is hinged to the other end of the upper connecting rod in the following manner: The lower connecting rod is a U-groove connecting rod, and the other end of the upper connecting rod is located in the U-groove of the U-groove connecting rod and is hinged to the U-groove connecting rod; When the support platform is in a folded state, the lower connecting rod and the upper connecting rod are also in a folded state, and at this time the upper connecting rod is accommodated in the U-shaped groove of the lower connecting rod.

5. The safety protection folding platform for wind tunnel test preparation as described in claim 1, characterized in that, The carrier platform includes: The frame is welded from rectangular tubular profiles; The aluminum perforated plate is welded within the frame. The guardrail is made of adapters and aluminum alloy tubing; the guardrail is detachably connected to the perforated plate.

6. The safety protection folding platform for wind tunnel test preparation as described in claim 1, characterized in that, Two rigid limit blocks are provided on the lower end of the upright plate, and buffer rubber pads are provided on the two rigid limit blocks; and when the folding platform is in the folded state, the two rigid limit blocks are connected to the rigid limit of the bearing platform by screws.

7. A design method for a safety protection folding platform for wind tunnel test preparation as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1, Preprocessing: Constructing the geometric model, meshing, defining and assigning material properties: Step 2: Create and solve the finite element model: Create connection relationships, set boundary conditions, set solution parameters, and perform calculations; Step 3: Post-processing: Extract the displacement and stress time history results of each component during the platform's unfolding and folding process; Based on the virtual work equation, torque balance, deformation coordination and energy conservation, the forces on the electric cylinder and connecting rod under the following conditions are solved: platform unfolding / folding process, unfolding to lock, and brake release under external load. Based on this, the structural dimensions and material parameters are optimized so that the electric cylinder load is lower than the rated value and the connecting rod stress meets the allowable requirements.

8. The design method of the safety protection folding platform for wind tunnel test preparation as described in claim 7, characterized in that, The force solution for the platform's unfolding / folding process is as follows: The folding platform is simplified as a planar rod system, with the coordinate system as follows: O is the center of the rotational joint connecting the T-shaped connecting plate and the first hinge; the x-direction points to the center of the rotational joint connecting the fourth hinge and the upper connecting rod when the platform is fully unfolded (center A); the y-direction points to the center of the rotational joint connecting the fifth hinge and the lower connecting rod (center C); point B is the center of the rotational joint connecting the upper and lower connecting rods; point D is the center of the rotational joint connecting the fixed end of the electric cylinder and the second hinge; point E is the center of the rotational joint connecting the telescopic end of the electric cylinder and the third hinge; α is the angle between the line OE and the line DE; θ is the angle between the line OE and the X-axis, i.e., the folding angle of the bearing platform; the electric cylinder DE is removed and replaced by the active force F; the entire system is considered as the research object, with ideal constraints; the folding angle of the bearing platform is θ; the self-weight of the bearing platform is G; the center of gravity is at the center position; and the length of the bearing platform OA is... l The length AE from the third hinge to the edge of the bearing platform is l 1 The installation angle between the electric cylinder and the load-bearing platform is α; From the equation of virtual work, we can obtain: in, y G It is the y-coordinate of point G. x E It is the x-coordinate of point E. y E It is the y-coordinate of point E; From geometric relations, we can obtain: Then we have: Substituting into the virtual work equation and taking advantage of the arbitrariness of δɵ, we obtain: Therefore, the force F acting on the electric cylinder is: 。 9. The design method of the safety protection folding platform for wind tunnel test preparation as described in claim 8, characterized in that, The force solution for the deployment, locking, and release of the external load is as follows: Once the mechanism is in place, the upper connecting rod AB and the lower connecting rod BC are collinear and connected by a safety pin, so they can be regarded as a whole and the whole can be simplified into a planar rod system; if the electric cylinder brake is locked, the whole structure is obviously statically indeterminate at this time. Depend on =0, meaning that with point O as the reference, the net torque is zero, so we can obtain: in, γ When the platform is deployed, the angle between connecting rod AC and the supporting platform is considered; the upper connecting rod AB and the lower connecting rod BC of connecting rod AC are in the deployed state; since the supporting platform AEO has greater rigidity relative to connecting rod AC and electric cylinder DE, for the sake of simplifying the calculation, the supporting platform AEO can be regarded as a rigid body; let the elastic modulus and cross-sectional area of ​​connecting rod AC and electric cylinder DE be E1, E4, A1, and A4 respectively, then the deformation displacement of connecting rod AC and electric cylinder DE in the y direction is: in, y A F2 is the y-coordinate of point A; F2 is the force on link AC. According to the deformation-displacement compatibility equation, we have: Therefore, we can conclude that: In this design The connecting rod bears part of the load, and the electric cylinder experiences relatively less force after the pin is inserted. If the upper connecting rod AB and the lower connecting rod BC are collinear and locked together with a pin, and the electric cylinder releases its brake, applying a large external load F1 at the center position, then the load is mainly borne by connecting rod AC, and its force can be easily obtained as follows: At this point, all you need is... In the formula Allowable stress.

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