Automatic pretreatment format conversion method for parachute inflation finite element simulation

Abstract

The invention provides an automatic pretreatment format conversion method for parachute inflation finite element simulation. The automatic pretreatment format conversion method comprises the following steps: carrying out geometric modeling and finite element mesh division on a canopy and a parachute cord by utilizing Gmsh; a preprocessing format conversion system is developed, grid files and calculation parameters are uploaded, and the conversion system automatically stores, calculates and integrates data and converts preprocessing files into input files needed by finite element calculation; then, finite element simulation analysis of the typical parachute inflation process is carried out through CalculiX, so that the reliability of the automatic conversion function of the pretreatment format is verified; the automatic preprocessing format conversion system suitable for parachute inflation finite element simulation and the graphical user interface of the automatic preprocessing format conversion system are developed, full-automatic processing of files is achieved, the use threshold of a user is lowered, and simulation efficiency and application benefits are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of computational mechanics simulation, and particularly relates to an automated preprocessing format conversion method for finite element simulation of parachute inflation. Background Art

[0002] During the decelerated landing process of manned spaceflight and deep space exploration missions, a parachute is a very important aerodynamic deceleration device. Its main function is to slow down the descent speed of the spacecraft after entering the atmosphere, ensure the safe and stable landing of the spacecraft, especially be able to effectively decelerate at high speeds, reduce the impact force on the spacecraft and astronauts, and ensure a successful landing.

[0003] Spacecraft parachutes are widely used. For example, the "Gemini", "Mercury", "Apollo", "Mars Pathfinder", "InSight", "Perseverance" and other series of spacecraft and detectors in the United States, the "Soyuz", "Vostok" and other series of spacecraft in Russia, and the "Shenzhou", "Tianwen", "Chang'e" and other series of spacecraft and detectors in China all use parachutes for decelerated landing. The parachute made of flexible materials occupies a small space after being packed. After the parachute canopy is filled, it can obtain a drag area dozens or even hundreds of times larger than the original folded state, so as to effectively decelerate the spacecraft.

[0004] The parachute deployment process of a spacecraft is a highly complex and precise multi-stage operation, involving the coordinated work of multiple parachute fabrics and systems to ensure that the spacecraft can decelerate smoothly and land safely after entering the atmosphere.

[0005] The operation process of a spacecraft parachute is as follows: First, when the spacecraft enters the atmosphere, the drogue chute will deploy first. Its function is to help the spacecraft stabilize its attitude and prevent violent rotation or vibration. This stage of deployment usually occurs at a relatively high speed to reduce the mechanical instability generated when entering the atmosphere. Immediately afterwards, the decelerator chute will deploy. It helps the spacecraft significantly slow down its speed through greater drag. It usually deploys when the spacecraft reaches an appropriate speed and altitude to help slow down the violent descent after entering the atmosphere. Finally, when the spacecraft speed is low enough, the main parachute begins to deploy. This is the largest parachute fabric in the parachute system, responsible for the final deceleration and ensuring that the spacecraft can land stably at a low speed.

[0006] Throughout the entire process of the parachute's operation, it is triggered by precise altitude, speed sensors, and an automatic control system, and the parachute canopy is deployed at the appropriate time in different stages to avoid risks caused by premature or delayed deployment. Additionally, the deployment of the parachute needs to consider changes in atmospheric conditions, such as wind speed, air pressure, etc., to ensure smooth operation under any circumstances. The success or failure of the entire parachute deployment process directly affects the safe landing of the spacecraft. Therefore, strict design, simulation, and testing must be carried out to ensure that the parachute canopy can function as planned in each stage, safeguarding the safety of the spacecraft and astronauts.

[0007] During the design process of the parachute system, it is relatively reliant on wind tunnel experiments to obtain effective data. However, wind tunnel experiments usually require a large amount of resources and high costs. Numerical simulation can conduct detailed research and analysis on parachute parameters and performance. It not only significantly reduces the experimental cost, decreases the number of actual tests, and improves time efficiency, but also enables multi-stage numerical simulation, which can accurately simulate the deployment process of the parachute canopy in each stage, the mutual influence between them, and the performance of the entire process. Therefore, numerical simulation work is particularly important for quickly grasping the performance of the parachute system.

[0008] There are many common commercial finite element software on the market currently (such as ANSYS, COMSOL, etc.). Although they provide powerful functions and efficient solvers in solid mechanics simulation, they usually require high licensing fees. In addition, since they are usually closed-source codes, users cannot freely access and modify the underlying codes, which means that users are restricted in the development and optimization for specific requirements (such as complex material models, custom boundary conditions, or contact problems), and are also restricted in large deformation, nonlinear analysis, and parallel computing, etc.

[0009] Another commonly used method is to integrate open-source solvers such as Gmsh and Calculix. Use the open-source finite element mesh generation tool Gmsh to complete the geometric modeling, finite element mesh generation, and boundary condition setting of a typical parachute canopy and suspension lines, and use the finite element software Calculix to achieve the finite element simulation analysis of the inflation process of a typical parachute. This method can handle the numerical simulation of solid mechanics with large deformation and nonlinear materials. However, in the process of using this method, the correct definition and transfer of physical groups, the quality of mesh generation, and the compatibility of element types, as well as the material properties and boundary conditions in the input INP format file, still need to be improved. In addition, complex geometries or large-scale models may lead to difficulties in mesh generation or low solution efficiency. Summary of the Invention

[0010] Objective of the Invention: The technical problem to be solved by the present invention is to provide an automated preprocessing format conversion method for parachute inflation finite element simulation, based on the open-source software platforms of Gmsh and Calculix. According to the framework of existing solid simulation solvers and the characteristics of finite element simulation data structures, cross-platform data interaction is achieved, and finally an automated preprocessing format conversion method for parachute inflation finite element simulation is obtained.

[0011] The method of the present invention includes the following steps:

[0012] Step 1: Use the open-source finite element mesh generation tool Gmsh to complete the geometric modeling and finite element mesh division of a typical parachute canopy and suspension lines;

[0013] Step 2: Establish a preprocessing format conversion system, and collect the finite element mesh files and calculation parameters of the canopy and suspension lines uploaded by the user through the conversion system;

[0014] Step 3: The conversion system reads the node and element information of the finite element mesh file, stores it in an array, calculates the input data required for Calculix simulation, and finally integrates and processes the file;

[0015] Step 4: Input the parameter file obtained by running the conversion system into the Calculix solver to achieve the finite element simulation analysis of the typical parachute inflation process and verify the reliability of the automatic conversion function of the conversion system.

[0016] In Step 1, use the open-source finite element mesh generation tool Gmsh to perform parametric modeling on the canopy and suspension lines, establish a GEO file suitable for the cross-parachute geometry, and export it as an INP file in Gmsh. The INP file only needs to modify the size parameters of the parachute to generate the finite element mesh files of the canopy and suspension lines desired by the user.

[0017] In Step 1, add an increment ΔL (generally 0.001 times the length of the parachute side) to the node coordinates at the end of each suspension line. This operation is to prepare for defining the contact equation between the canopy nodes and the suspension line nodes in Step 3.

[0018] In Step 2, establish a preprocessing format conversion system with a graphical user interface based on the Tkinter library and Python. When the conversion system operates, it needs to select the INP files corresponding to the canopy and suspension lines, as well as select the location of the output folder. The calculation parameters that need to be input include the elastic modulus and density of the canopy and suspension lines, as well as the calculation time interval and total calculation time.

[0019] Step 3 includes the following steps:

[0020] Step 3-1: The conversion system collects the finite element mesh files and calculation parameters of the parachute canopy and suspension lines uploaded by the user in Step 2 through a graphical user interface, and automatically obtains the user's working directory;

[0021] Step 3-2: Read the finite element mesh files of the parachute canopy and suspension lines uploaded by the user respectively. By defining the node class, store the node numbers and coordinates in the node class array. By defining the element class and using regular expressions to obtain the element type name of Gmsh (Gmsh refers to a finite element mesh generation tool), find the corresponding Calculix element type name, and store the element numbers and the node numbers that make up the element in the element class array;

[0022] Step 3-3: Record the nodes of the parachute canopy in the temporary file B1. To place the parachute canopy and suspension lines of the parachute in the same coordinate, arrange the node numbers of the suspension lines after those of the parachute canopy and record them in the temporary file B2; Record the elements of the parachute canopy in the temporary file B3, and discretize the suspension lines into elements of type B32 and record them in the temporary file B4;

[0023] Step 3-4: Read the temporary file B2, calculate and output the normal vector in the direction of the suspension lines to a temporary file. The calculation method is as follows: Calculate the direction vector of the suspension line in the Cartesian coordinate system based on the coordinates of the two end nodes of the suspension line;

[0024] First, calculate the direction vector of the suspension line:

[0025]

[0026] where dx, dy, and dz respectively represent the lengths of the suspension line in the x, y, and z directions in the Cartesian coordinate system;

[0027] Then, calculate the normal vector: Under the condition that the parachute canopy is perpendicular to the x-axis, the normal vector of the suspension line includes two cases in space: The first case is that the component in the y direction is 0, and the second case is that the component in the z direction is 0. Therefore, the calculation formula is:

[0028] If dy = 0

[0029] norm y = 0.0

[0030]

[0031] Otherwise, norm z = 0.0

[0032]

[0033] where, norm x, norm y , norm z They are the components of the normal vector in the x, y, and z directions respectively;

[0034] Step 3-5: Read the nodes of the parachute canopy and suspension lines, find the connected nodes on the parachute canopy and suspension lines (the spatial distance is less than 0.001 times the side length of the parachute canopy), and define the contact equation into the temporary file B5;

[0035] Step 3-6: Integrate the temporary files B1 to B5, and automatically add the calculation parameters uploaded by the user in Step 2. Through the conversion system, obtain the six calculation files C1, C2, C3, C4, C5, and C6 required by Calculix.

[0036] In Step 3-5, the definition of the contact equation includes: finding the canopy node with the minimum Euclidean distance from the end node of each suspension line to the end node of the suspension line, and dividing the end node of the suspension line and the canopy node into pairs. Define that the relative change rate of the x coordinate, the relative change rate of the y coordinate, and the relative change rate of the z coordinate of each pair of two nodes are zero;

[0037] Define the contact equation of the canopy node and the suspension line node as:

[0038] d1 = d2

[0039] where d1 is the displacement of the canopy at the contact point between the canopy and the suspension line, and d2 is the displacement of the suspension line at the contact point between the canopy and the suspension line;

[0040] In Step 3-6, C1 is a materials.inp file used to record the physical properties of materials;

[0041] C2 is a contact.equ file used to record the positional relationship between the end node of the suspension line and the nearest canopy node, and set the positional relationship so that the derivative of the relative displacement between the end node of the suspension line and the nearest canopy node is always 0;

[0042] C3 is an all.msh file used to record the numbers and coordinates of the canopy and suspension line nodes, the way the canopy and suspension line nodes are combined into elements, the numbers of the elements, and the canopy and suspension line nodes that make up the elements;

[0043] C4 is a cables.nam file, and C5 is a canopy.nam file. C4 and C5 are respectively used to record the node numbers belonging to the suspension lines and the node numbers belonging to the canopy;

[0044] C6 is a file for execution in the open-source finite element software Calculix, and the file name is recorded as FSI_case.inp.

[0045] In step 4, according to the characteristics of the parachute in the actual use scenario, the nodes at the intersection of the suspension lines are fixed by using the method of single-point constraint. Loads with a set distribution are applied to the parachute canopy nodes according to the simulation requirements, the parameter file is configured, and then the CCX solver is used to execute the file FSI_case.inp, and the CGX module of the open-source finite element software Calculix is used to visualize the simulation results, obtaining the numerical simulation results of the force and deformation of the parachute, so as to verify the reliability of the conversion system.

[0046] The present invention also provides an electronic device, including a processor and a memory, the memory stores program codes, and when the program codes are executed by the processor, the processor is caused to execute the steps of the method.

[0047] The present invention also provides a storage medium, storing a computer program or instruction, and when the computer program or instruction runs on a computer, the steps of the method are executed.

[0048] Compared with the prior art, the present invention has the following beneficial effects: The present invention develops an automated preprocessing format conversion system and its graphical user interface applicable to the finite element simulation of parachute inflation, realizes the full automation of file processing, reduces the user's usage threshold, and improves the simulation efficiency and application benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The following further specifically describes the present invention in conjunction with the drawings and specific embodiments, and the above and / or other advantages of the present invention will become clearer.

[0050] Figure 1 It is a processing flow chart of the present invention.

[0051] Figure 2 It is the text of the GEO file of the parachute canopy.

[0052] Figure 3 It is the text of the GEO file of the suspension lines.

[0053] Figure 4 It is a schematic diagram of the geometric modeling of the parachute canopy in Gmsh.

[0054] Figure 5 It is a schematic diagram of the geometric modeling of the suspension lines in Gmsh.

[0055] Figure 6 It is a schematic diagram of the graphical interface of the conversion system.

[0056] Figure 7 It is the data of the experimental example in the specific implementation method.

[0057] Figure 8It is a schematic diagram of the structural dynamics simulation of a parachute. Specific implementation mode

[0058] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0059] An embodiment of the present invention adopts an automated preprocessing format conversion method for finite element simulation of parachute inflation. The flowchart of the method is shown in Figure 1 , including:

[0060] Step 1: Use the open-source finite element mesh generation tool Gmsh to complete the geometric modeling, finite element mesh division, and boundary condition setting of a typical parachute canopy and suspension lines.

[0061] Step 2: Establish a preprocessing format conversion system, and collect the finite element mesh files and calculation parameters of the canopy and suspension lines uploaded by the user through the conversion system.

[0062] Step 3: The conversion system reads the node and element information of the finite element mesh file, stores it in an array, calculates the input data required for Calculix simulation, and finally integrates and processes the file.

[0063] Step 4: Input the parameter file obtained by running the conversion system into the Calculix solver to realize the finite element simulation analysis of the inflation process of a typical parachute and verify the reliability of the automatic conversion function of the conversion system.

[0064] In step 1, the open-source finite element mesh generation tool Gmsh is used to complete the geometric modeling, finite element mesh division, and boundary condition setting of a typical parachute canopy and suspension lines. In order to facilitate the division of different types of meshes, the canopy and suspension lines correspond to two files.

[0065] As Figure 2 and Figure 3 shown, in this embodiment, GEO files suitable for the canopy and suspension lines of the cruciform parachute geometry are respectively written and exported as INP files in Gmsh. In the GEO file, only the size parameters of the parachute need to be modified to generate the finite element mesh files of the canopy and suspension lines desired by the user. As Figure 4 and Figure 5 shown, they are respectively schematic diagrams of the canopy and suspension lines drawn using Gmsh.

[0066] It should be noted that the canopy and the suspension lines are two files, which will result in the coincidence of the node numbers of the canopy and the suspension lines. In order to ensure that the canopy and the suspension lines are connected together, a small increment ΔL (generally 0.001 times the side length of the canopy) needs to be added to the node coordinates at the end of each suspension line. This operation is also prepared for defining the contact equation between the canopy nodes and the suspension line nodes in step 3.

[0067] In step 2, the finite element mesh files and calculation parameters of the canopy and the suspension lines uploaded by the user are collected through the conversion system.

[0068] A pre-processing format conversion system with a graphical user interface is established based on the Tkinter library and Python. Figure 6 As shown in the schematic diagram of the graphical interface, when the conversion system operates, it is necessary to select the INP files corresponding to the canopy and the suspension lines, as well as the location of the output folder. The calculation parameters that need to be input include the elastic modulus and density of the canopy and the suspension lines, as well as the calculation time interval and the total calculation time.

[0069] For the example of the present invention (as Figure 7 shown), the file names of the canopy and the suspension lines to be processed are selected in the folder. The elastic moduli of the canopy and the suspension lines are set to 9.576e7 and 2.394e8 respectively, and the densities of the canopy and the suspension lines are 1.933e3 and 4.38e2. The calculation time interval is 2.e-3, and the total calculation time is 8.0. Finally, it is desired to output the file to a folder called calculix.

[0070] In step 3, the node and element information of the above-mentioned collected files is read, stored in an array, and the input data required for Calculix simulation is calculated. Finally, the files are integrated and processed.

[0071] The conversion system is used to automatically execute the following steps, only need to click the execute operation:

[0072] Step 3-1, the conversion system collects the finite element mesh files and calculation data of the canopy and the suspension lines uploaded by the user in step 2 through the graphical user interface, and automatically obtains the user's working directory. If the program does not obtain the correct data, it will remind the user to check the files;

[0073] Step 3-2: Read the finite element mesh files of the parachute canopy and suspension lines uploaded by the user respectively. By defining the node class, each variable of the node class should contain its number and the three coordinate information of x, y, and z. Store all the node class variables in the node class array. By defining the element class, each variable of the element class should contain its number, element type information, and the sequence numbers of all the nodes that make up this element. The element type determines how many nodes this element is composed of. In the example of the present invention, the mesh generated in Step 1 is a planar triangle (CPS6) composed of 6 nodes, and the element type name of Gmsh is obtained by using regular expressions to find the corresponding Calculix element type name. The name of CPS6 in Calculix in the example of the present invention is S6. Finally, store the element number and the node numbers that make up the element in the element class array. For example, in the example of the present invention, the parachute canopy has 5313 nodes, and the coordinates of the 1643rd node are (10.287, 1.500, -0.125). There are 2560 elements, and the 519th element is a triangle composed of 6 nodes numbered 118, 1472, 117, 1703, 1704, and 133;

[0074] Step 3-3: Record the nodes of the parachute canopy in the temporary file B1. In order to make the parachute canopy and suspension lines of the parachute in the same coordinate, arrange the node sequence numbers of the suspension lines after those of the parachute canopy and record them in the temporary file B2. In the example of the present invention, since the parachute canopy has 5313 nodes, start recording the node sequence numbers of the suspension lines from 5314. The purpose of modifying the node numbers of the suspension lines is to finally merge the nodes of the parachute canopy and suspension lines into the same file; record the elements of the parachute canopy in the temporary file B3, discretize the suspension lines into B32 type elements, which are a straight line composed of three nodes, arrange the element sequence numbers of the suspension lines after those of the parachute canopy, and record them in the temporary file B4;

[0075] Step 3-4: Read the temporary file B2, calculate and output the normal vector in the direction of the suspension line to a temporary file;

[0076] Normal vector calculation method: Calculate the direction vector of the suspension line in the Cartesian coordinate system according to the coordinates of the two end nodes of the suspension line. In the example of the present invention, since there are twenty suspension lines, there are twenty normal vectors ( Figure 5 are screenshots of the 17th to 20th ones among them. The information in the figure is for Step 4 to process the one-dimensional straight line of the suspension line into a three-dimensional cube in Calculix);

[0077] First, calculate the direction vector of the suspension line:

[0078]

[0079]

[0080] Where dx, dy, and dz are the lengths of the suspension lines in the x, y, and z directions in the Cartesian coordinate system.

[0081] Then calculate the normal vector: There are only two cases for the normal vector of the suspension lines in space (under the condition that the parachute canopy is perpendicular to the x-axis), either the y-component is 0 or the z-component is 0. Therefore, the calculation formula is:

[0082] If dy = 0

[0083] norm y = 0.0

[0084]

[0085] Otherwise norm z = 0.0

[0086]

[0087] Where norm x and norm y and norm z are the components of the normal vector in the x, y, and z directions respectively.

[0088] Step 3 - 5: Read the nodes of the parachute canopy and the suspension lines, find the connected nodes on the parachute canopy and the suspension lines (the spatial distance is less than 0.001 times the side length of the parachute canopy), and define the contact equations into the temporary file B6. In the example of the present invention, since there are twenty suspension lines, there are twenty groups of contact equations. For example Figure 6 records that the relationship between the 5327th and the 1st nodes in the 1(x) direction and the 2(y) direction is -x1 + x 5327 = 0, -y1 + y 5327 = 0. Of course, there are more than just these two equations. The ultimate goal is to ensure that the relative positions of these paired nodes remain unchanged during the calculation, just like the parachute canopy and the suspension lines are tied together in reality;

[0089] Define the contact equations: Find the parachute canopy node with the minimum Euclidean distance from the end node of each suspension line to the end node of the suspension line, divide them into pairs, and define the relative change rate of the x coordinate, the relative change rate of the y coordinate, and the relative change rate of the z coordinate of the two nodes in each group to be zero;

[0090] And define the contact equation between the parachute canopy node and the suspension line node:

[0091] d1 = d2

[0092] Where d1 is the displacement of the parachute canopy at the contact point between the parachute canopy and the suspension line, and d2 is the displacement of the suspension line at the contact point between the parachute canopy and the suspension line.

[0093] Step 3-6: Integrate the temporary files B1 to B5, and automatically add the calculation parameters input by the user in Step 2. Through the conversion system, obtain six calculation files C1, C2, C3, C4, C5, and C6 required by Calculix.

[0094] 6. The method according to claim 5, wherein in Step 3-6, C1 is a materials.inp file for recording the physical properties of materials;

[0095] C2 is a contact.equ file for recording the positional relationship between the end nodes of the suspension lines and the nearest canopy nodes, and setting the positional relationship such that the derivative of the relative displacement between the end nodes of the suspension lines and the nearest canopy nodes is constantly 0;

[0096] C3 is an all.msh file for recording the numbers and coordinates of the canopy and suspension line nodes, the way the canopy and suspension line nodes are combined into elements, the numbers of the elements, and the canopy and suspension line nodes that make up the elements;

[0097] C4 is a cables.nam file, C5 is a canopy.nam file, and C4 and C5 are respectively used to record the node numbers belonging to the suspension lines and the node numbers belonging to the canopy;

[0098] C6 is a file for execution in the open-source finite element software Calculix, and the file name is recorded as FSI_case.inp.

[0099] In Step 4, use the open-source finite element software Calculix to perform a finite element simulation analysis of the typical parachute inflation process to verify the reliability of the preprocessing format conversion function of the developed conversion system.

[0100] According to the characteristics of the parachute in the actual usage scenario, use the method of single-point constraint to fix the nodes at the intersection of the suspension lines, apply loads distributed according to the settings to the canopy nodes according to the simulation requirements, and configure the parameter file.

[0101] After completing the configuration of the parameter file, run the input file FSI_case.inp using the CCX solver by executing the command ccx FSI_case. After the calculation is completed, use the CGX module of CalculiX for visualization processing, and the command is cgx -b FSI_case.frd. Through CGX, the force-bearing conditions, deformation modes, stress concentration areas, etc. of the parachute can be observed. For example, Figure 8As shown, it is the solid mechanics simulation results within 8 seconds after applying a uniform load on the parachute canopy. This schematic diagram is presented as an animated graph in CalculiX, enabling clear observation of the force change process of the parachute and verifying the correctness of the method.

[0102] In summary, the present invention is an automated preprocessing format conversion system for parachute inflation finite element simulation. It mainly studies the preprocessing system that fully automates format conversion during the finite element simulation process, involves geometric modeling of part of the parachute canopy and suspension lines, as well as solid mechanics simulation of the parachute and visualization of the results.

[0103] The present invention has developed an automated preprocessing format conversion system for parachute inflation finite element simulation and its graphical user interface, achieving full automation of file processing, reducing the user's usage threshold, and improving the simulation efficiency and application benefits.

[0104] The present invention provides an automated preprocessing format conversion method for parachute inflation finite element simulation. There are many methods and ways to specifically implement this technical solution. The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention. Each component not clearly defined in this embodiment can be implemented using existing technologies.

Claims

1. An automated pre-processing format conversion method for parachute inflation finite element simulation, characterized in that: The following steps are involved: Step 1: Use the open source finite element mesh generation tool Gmsh to complete the geometric modeling and finite element mesh generation of a typical parachute canopy and parachute rope; Step 2, establishing a pre-processing format conversion system, through which the finite element mesh files and calculation parameters of the canopy and parachute ropes uploaded by the user are collected; Step 3, the conversion system reads the node and unit information of the finite element mesh file, stores it in an array, calculates the input data required for Calculix simulation, and finally integrates the file; Step 4: Input the parameter file obtained by running the conversion system into the Calculix solver to implement finite element simulation analysis of a typical parachute inflation process and verify the reliability of the automatic conversion function of the conversion system.

2. The method according to claim 1, characterized in that In step 1, the open source finite element mesh generation tool Gmsh is used to parametrically model the canopy and parachute ropes, a GEO file suitable for the geometry of the cross parachute is created, and it is exported as an INP file in Gmsh. The INP file only needs to modify the size parameters of the parachute to generate the finite element mesh file of the canopy and parachute ropes that the user wants.

3. The method according to claim 2, characterized in that In step 1, add an increment ΔL to the node coordinates at the end of each parachute line.

4. The method according to claim 3, characterized in that: In step 2, a pre-processing format conversion system with a graphical user interface is established based on the Tkinter library and Python. When operating the conversion system, it is necessary to select the INP files corresponding to the canopy and parachute ropes, and select the location of the output folder. The calculation parameters that need to be input include the elastic modulus and density of the canopy and parachute ropes, as well as the calculation time interval and the total calculation time.

5. The method according to claim 4, characterized in that Step 3 includes the following steps: Step 3-1, the conversion system collects the finite element mesh files and calculation parameters of the canopy and parachute ropes uploaded by the user in step 2 through a graphical user interface, and automatically obtains the user's working directory; Step 3-2, respectively read the finite element mesh files of the canopy and the parachute rope uploaded by the user, store the node number and coordinates in the node class array by defining the node class, and obtain the Gmsh unit type name by defining the unit class and using regular expressions to find the corresponding Calculix unit type name, and store the unit number and the node number of the unit in the unit class array; Step 3-3, record the nodes of the canopy into temporary file B1. In order to make the canopy and the parachute rope of the parachute be in the same coordinate, the node number of the parachute rope is arranged after the canopy and recorded in temporary file B2; record the unit of the canopy in temporary file B3, discretize the parachute rope into B32 type units and record them in temporary file B4; Step 3-4, read the temporary file B2, calculate and output the normal vector of the parachute line direction to a temporary file, the calculation method is: calculate the direction vector of the parachute line in the Cartesian coordinate system according to the coordinates of the nodes at both ends of the parachute line; First calculate the parachute line direction vector: Where dx, dy, and dz represent the lengths of the parachute rope in the x, y, and z directions in the Cartesian coordinate system respectively; Then calculate the normal vector: Under the condition that the canopy is perpendicular to the x-axis, the normal vector of the parachute rope includes two cases in space: in the first case, the component in the y direction is 0, and in the second case, the component in the z direction is 0. The calculation formula is: If dy=0 norm y =0.0 Otherwise norm z =0.0 Among them, norm x , norm y , norm z are the components of the normal vector in the x, y, and z directions respectively; Step 3-5, read the canopy and parachute rope nodes, find the nodes connected on the canopy and parachute rope, and define the contact equation in the temporary file B5; Step 3-6, integrate temporary files B1~B5, and automatically add the calculation parameters uploaded by the user in step 2. Through the conversion system, the 6 calculation files C1, C2, C3, C4, C5 and C6 required by Calculix are obtained.

6. The method according to claim 5, characterized in that In step 3-5, the contact equation is defined as follows: finding the canopy node with the smallest Euclidean distance between each parachute line end node and the parachute line end node, and dividing the parachute line end nodes and the canopy nodes into a group of two, and defining the relative change rate of the x coordinates of the two nodes in each group to be zero, the relative change rate of the y coordinates to be zero, and the relative change rate of the z coordinates to be zero; The contact equations defining the canopy nodes and the parachute line nodes are: d1=d2 Where d1 is the displacement of the canopy at the contact point between the canopy and the parachute rope, and d2 is the displacement of the parachute rope at the contact point between the canopy and the parachute rope.

7. The method according to claim 6, characterized in that In steps 3-6, C1 is a materials.inp file, which is used to record the physical properties of the material; C2 is a contact.equ file, which is used to record the positional relationship between the end node of the parachute line and the nearest canopy node, and sets the positional relationship so that the derivative of the relative displacement between the end node of the parachute line and the nearest canopy node is always 0; C3 is an all.msh file, which is used to record the numbers and coordinates of the canopy and parachute line nodes, the way the canopy and parachute line nodes are combined into units, the unit numbers, and the canopy and parachute line nodes that make up the unit; C4 is a cables.nam file, and C5 is a canopy.nam file. C4 and C5 are used to record the node numbers of the parachute ropes and the node numbers of the canopy respectively. C6 is a file used to execute in the open source finite element software Calculix, and the file name is FSI_case.inp.

8. The method according to claim 7, characterized in that In step 4, according to the characteristics of the parachute in the actual use scenario, the node at the intersection of the parachute ropes is fixed by the single-point constraint method, and the load with the set distribution is applied to the canopy node according to the simulation requirements. The parameter file is configured, and then the CCX solver is used to execute the file FSI_case.inp. The simulation results are visualized using the CGX module of the open source finite element software Calculix to obtain the numerical simulation results of the force and deformation of the parachute, thereby verifying the reliability of the conversion system.

9. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores program codes, and when the program codes are executed by the processor, the processor executes the steps of the method according to any one of claims 1 to 8.

10. A storage medium, characterized in that: A computer program or instruction is stored, and when the computer program or instruction is run on a computer, the steps of the method according to any one of claims 1 to 8 are executed.

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