Simulation evaluation and optimization method and system for parachute opening impact strength of wheeled air-drop vehicle

Abstract

The invention belongs to the technical field of airdrop and special vehicles, and particularly discloses a wheel type airdrop vehicle parachute opening impact strength simulation evaluation and optimization method and system. Comprising the following steps: performing parachute opening dynamics simulation to obtain an accurate boundary of parachute opening strength impact simulation; performing whole vehicle parachute opening strength dynamic simulation analysis to obtain an analysis result of vehicle body strength and deformation, evaluating the analysis result, outputting design parameters if the analysis result meets requirements, and otherwise, performing failure reason analysis; air-drop system modal analysis is added, and failure reasons are judged; according to failure reasons, partial grids are intercepted or static simulation is adopted to replace dynamic simulation, and a reduction optimization model is obtained; and based on HyperStudy, carrying out multi-objective optimization according to the structural characteristics of the parts of the failure parts and failure reasons. According to the method, high-precision calculation of the re-loading air-drop process of multi-stage parachute opening of multiple parachutes is achieved, and scientific optimization of the parachute opening strength structure of the air-drop vehicle is achieved by optimizing the simulation means.

Description

Technical Field

[0001] The present invention belongs to the technical field of airdrop and special vehicles, and more specifically, relates to a method and system for simulating, evaluating and optimizing the impact strength of a wheeled airdrop vehicle when its parachute is opened. Background Art

[0002] The parachute opening process of heavy-duty airdrop is very complicated. The traction parachute, auxiliary guide parachute, deceleration parachute and main parachute are multiple subsystems working in series. The process has the characteristics of flexible large deformation, strong nonlinearity and strong coupling. The parachute working process is divided into three stages, namely the straightening process, the inflation process and the steady descent process. The parachute inflation stage refers to the entire process from the canopy being stretched to the canopy being full. It is a dynamic process coupled with the structure and the fluid. In the entire airborne process, the dynamic problems involved in the inflation of the parachute are the most complex. During the entire inflation process, the shape, aerodynamic force, mass characteristics and air-added mass of the parachute are undergoing drastic changes. Under the impact of the parachute opening, the hanging object will bear the greatest overload impact, and its posture will experience the greatest amplitude of oscillation. For the wheeled vehicle body without a cargo platform, the entire parachute opening impact strength acts directly on the vehicle body, which puts forward stringent assessment requirements for its body rigidity.

[0003] In the process of developing heavy-duty airdrop equipment, the acquisition of effective parachute data mainly relies on various tests, theoretical analysis methods, and fluid-solid coupling simulation methods. The test method is expensive, has a long cycle, and is not helpful for the design in the early stages of development, and only serves as a subsequent verification. Theoretical calculations will have multiple assumptions: for example, the influence of wind cannot be considered; the elasticity of the parachute rope and sling is not considered; the dynamic characteristics of the parachute are characterized by the added mass and the canopy resistance characteristics (the resistance characteristic parameters need to be determined by experiments), etc. These assumptions cause a large difference between the calculation results and the actual airdrop; the existing simulation of the airdrop process through fluid-solid coupling simulation studies the single-parachute one-stage parachute opening process, and cannot achieve the simulation calculation of the complex parachute opening process of multiple parachutes and multiple stages of parachutes such as heavy-duty airdrop. Since the cargo-free wheeled airdrop vehicle is developed for the first time, there is currently no complete and suitable airdrop parachute opening strength evaluation and optimization method.

[0004] In view of the above shortcomings, this field urgently needs to provide a scientific, comprehensive, systematic, efficient and process-based vehicle body parachute opening impact strength simulation evaluation and optimization method to truly simulate the entire airdrop process of heavy equipment airdrop (excluding the landing phase) and provide a more realistic boundary for subsequent parachute opening strength simulation. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a method and system for simulating, evaluating and optimizing the impact strength of parachute opening of a wheeled airdrop vehicle. The method establishes a dynamic model of the parachute opening process through a computer, inputs the parameters of the special vehicle and the parachute system to quickly calculate the vehicle posture and sling load during the parachute opening and inflation period, and then calls the vehicle body finite element model for dynamic simulation. The parachute opening strength result of the special vehicle is obtained through simulation to evaluate whether the special vehicle meets the design requirements. The optimization object is determined based on the analysis results, and multi-objective simulation optimization is performed to achieve structural optimization. The optimized finite element model is replaced to perform parachute opening dynamics simulation, and finally a vehicle body structure that meets the design requirements is achieved. The present invention solves the problems of high risk, high cost, long cycle, and lag in airdrop parachute opening tests, and can evaluate the strength of the parachute system and special vehicles at the beginning of the design.

[0006] To achieve the above object, according to one aspect of the present invention, a method for simulating, evaluating and optimizing the impact strength of a wheeled airdrop vehicle when a parachute is opened is proposed, comprising the following steps:

[0007] Step 1: Perform parachute opening dynamics simulation to obtain the precise boundary of parachute opening strength impact simulation, that is, the parachute opening strength load boundary;

[0008] Step 2: Based on the parachute opening strength load boundary, a whole vehicle parachute opening strength dynamics simulation analysis is performed to obtain the analysis results of the vehicle body strength and deformation, and the analysis results are evaluated. If the evaluation results meet the target requirements, the design parameters are output; otherwise, step 3 is entered to perform failure cause analysis;

[0009] Step 3: Add modal analysis of the airdrop system, analyze the deformation results of the parachute opening strength of the benchmark vehicle body, and determine the cause of failure;

[0010] Step 4: According to the failure cause, a part of the mesh is cut or the static simulation is used to replace the dynamic simulation to reduce the model and obtain a reduced optimization model;

[0011] Step 5: Based on the reduced optimization model and HyperStudy, multi-objective optimization is carried out according to the structural characteristics of the components at the failed parts and the causes of failure, and the optimal structural optimization solution is found.

[0012] As a further preferred embodiment, step one includes the following steps: building an extravehicular dynamics model, and based on the extravehicular dynamics model, building a dynamic finite element simulation model of the auxiliary guide parachute opening stage with the extravehicular simulation results as initial conditions, obtaining the simulation results of the auxiliary guide parachute opening stage through ALE fluid-solid coupling simulation calculation, and based on the simulation results, performing fluid-solid coupling simulation of the deceleration parachute opening stage, and based on the fluid-solid coupling simulation results of the deceleration parachute opening stage, performing fluid-solid coupling simulation of the main parachute opening and steady descent stages, in this way, obtaining the dynamic simulation results of the entire airdrop opening process, such as the time load curve, the time object-parachute angle curve, and the time pitch angle curve.

[0013] As a further preferred embodiment, the input parameters of the extravehicular dynamics model include: environmental parameters, parachute parameters, aircraft parameters and vehicle body parameters;

[0014] The environmental parameters include flight speed and airdrop altitude;

[0015] The parachute parameters include characteristic area, nominal diameter, mass, and drag coefficient;

[0016] The carrier aircraft parameters include roller height, door height, and roller dynamic friction coefficient;

[0017] The vehicle body parameters include mass, center of mass coordinates, and vehicle body shape.

[0018] As a further preferred embodiment, the dynamic finite element simulation model of the auxiliary guided parachute opening stage built with the extravehicular simulation results as initial conditions includes: a parachute model, a simple vehicle model and a flexible sling model. At the same time, the ALE fluid-solid coupling simulation calculation is used to obtain the dynamic influence of the canopy deformation and the changes in the surrounding flow field on the auxiliary guided parachute opening stage, thereby obtaining the vehicle pitch angle, vehicle speed, and object-parachute angle state model.

[0019] As a further preferred embodiment, in step 2, the whole vehicle parachute opening strength dynamics simulation analysis includes:

[0020] Construct the finite element model of the whole vehicle and the landing buffer system. The parachute harness adopts a flexible body model, and non-critical parts are modeled by mass point counterweights to ensure that the overall mass and center of mass of the vehicle body and landing buffer system are consistent with the actual object.

[0021] According to the pitch angle of the parachute opening dynamics simulation, the attitude of the built finite element model relative to the ground is adjusted, and then the angle between the sling and the vehicle body is adjusted according to the object-parachute angle. Then the gravity field is established, and finally the time load curve is loaded at the sling, and the output parameters are set.

[0022] As a further preference, the whole vehicle finite element model includes a vehicle body, a frame model, a powertrain model, a transmission system model, a chassis component, and an airbag frame model.

[0023] As a further preferred embodiment, in step three, a modal analysis of the airdrop system is added, and the deformation result animation of the parachute opening strength analysis of the benchmark vehicle body is compared to determine whether the cause of the failure is caused by insufficient stiffness. If it is not a stiffness problem, it is determined to be a local strength problem.

[0024] As further preferred, step 4 includes the following steps:

[0025] Coarsen the mesh of the entire dynamic simulation model to reduce the number of meshes;

[0026] Conduct sensitivity analysis on the dynamics simulation model to identify the key areas of the dynamics simulation model;

[0027] Define sub-models in critical areas, ensure detailed meshes in these areas, and ensure that interface displacements and stresses match between the sub-models and the coarsened dynamic simulation model;

[0028] Analyze the distribution of loads and boundary conditions, and for varying loads, calculate equivalent static loads to simplify loads and boundary conditions;

[0029] According to the results of modal analysis and load simplification, set the constraints and objective function in the optimization process;

[0030] Adopting adaptive response surface method to execute optimization algorithm, iteratively searching for the optimal solution, that is, obtaining the optimal reduced optimization model;

[0031] Verify the reliability of the reduced optimization model.

[0032] As further preferred, step five comprises the following steps:

[0033] Through HyperStudy, multi-objective optimization is carried out, a HyperStudy model is established, the reduced model is added, variables, constraints and objectives are established and modified, and a new model is generated, and the solver is used to solve the optimal solution of the new model.

[0034] According to another aspect of the present invention, a wheeled airdrop vehicle parachute opening impact strength simulation evaluation and optimization system is provided, which is used to implement the method of any embodiment or a combination of multiple embodiments described above, including:

[0035] The first main control module is used to perform parachute opening dynamics simulation to obtain the precise boundary of parachute opening strength impact simulation, that is, the parachute opening strength load boundary;

[0036] The second main control module is used to perform a dynamic simulation analysis of the vehicle's parachute opening strength based on the parachute opening strength load boundary to obtain the analysis results of the vehicle body strength and deformation, and evaluate the analysis results. If the evaluation results meet the target requirements, the design parameters are output; otherwise, the process proceeds to step three to analyze the failure causes;

[0037] The third main control module is used to add modal analysis of the airdrop system, analyze the deformation results of the parachute opening strength of the vehicle body, and determine the cause of failure;

[0038] The fourth main control module is used to cut off part of the grid or replace the dynamic simulation with the static simulation according to the failure cause, so as to reduce the model and obtain the reduced optimization model;

[0039] The fifth main control module is used to carry out multi-objective optimization based on the reduced optimization model and HyperStudy according to the structural characteristics of the components at the failure site and the failure causes, and to find the optimal structural optimization solution.

[0040] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0041] 1. The present invention can quickly and accurately evaluate the strength and structure of the vehicle body when the parachute is opened, and carry out targeted multi-objective optimization to achieve the optimal vehicle body structure, improve work efficiency, and reduce research and development costs.

[0042] 2. The present invention realizes high-precision calculation of the heavy-load airdrop process of multiple parachutes and multi-stage parachute opening through the combination of cross-sectional equivalence, restart, flexible slings, ALE fluid-solid coupling and other technologies, which is more scientific and objective; and realizes scientific optimization of the parachute opening strength structure of the airdrop vehicle through advanced optimization simulation means.

[0043] 3. The process of the present invention first determines whether it is a stiffness or strength problem, then sets optimization variables for different problems, performs multi-objective optimization of thickness, shape, and size to find the optimal solution of the optimization result, and comprehensively and systematically solves the existing problems. It truly achieves a comprehensive and systematic analysis of the vehicle problem.

[0044] 4. The present invention uses this method to quickly verify whether the vehicle body structure meets the requirements in the early stage of design, and quickly optimizes the unsatisfactory structural positions, which is very efficient compared to traditional test verification methods; in the optimization stage, model reduction is first performed before optimization, which can greatly reduce the optimization time and improve the efficiency afterwards.

[0045] 5. The present invention uses HyperStudy to perform multi-objective optimization, automating the design process and reducing the need for manual iteration. The combined use of sensitivity analysis and modal analysis can quickly identify key design areas, making the selection of design variables more accurate.

[0046] 6. The model reduction technique of the present invention allows the use of computing resources to be reduced while maintaining sufficient accuracy. Through mesh simplification and sub-modeling techniques, more design variables can be evaluated in a shorter time, thereby exploring a wider design space with limited resources.

[0047] 7. This invention can systematically improve product performance through precise sensitivity analysis and modal analysis, combined with HyperStudy's multi-objective optimization capabilities. The optimized design not only meets the goals of minimizing mass and volume ratio, but also ensures product compliance in key performance indicators, such as the maximum deformation and first-order bending torsion mode limits. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a control flow chart of a wheeled airdrop vehicle parachute opening impact strength simulation evaluation and optimization method involved in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0050] like Figure 1 As shown, an embodiment of the present invention provides a method for simulating, evaluating and optimizing the impact strength of a wheeled airdrop vehicle when its parachute is opened.

[0051] More specifically, in one embodiment of the present invention, a method for simulating, evaluating and optimizing the impact strength of a wheeled airdrop vehicle when a parachute is opened includes:

[0052] Step 1: Parachute opening dynamics simulation and load extraction.

[0053] Accurate parachute opening strength load boundary is a necessary condition for conducting parachute opening impact strength analysis of vehicle body. The accurate boundary of parachute opening strength impact simulation is obtained through the following process.

[0054] ①. Escape phase: First, build an escape dynamics model, input environmental parameters including speed and airdrop altitude; parachute parameters including characteristic area, nominal diameter, mass, drag coefficient; aircraft parameters including roller height, door height, roller dynamic friction coefficient; vehicle parameters including mass, center of mass coordinates, and vehicle shape. Through simulation calculation, obtain the speed, vehicle pitch angle, pitch angular velocity and other parameters of the airdrop system when it leaves the aircraft.

[0055] ②. Auxiliary guide parachute opening stage: The dynamic finite element simulation model of the auxiliary guide parachute opening stage is built with the extravehicular simulation results as the initial conditions, including the parachute model, the simple vehicle model, and the flexible sling model. Considering the influence of wind speed, the simulation results of this stage are obtained through ALE fluid-solid coupling simulation calculation (taking into account the deformation of the canopy and the changes in the surrounding flow field). The results include the vehicle pitch angle, vehicle speed, and the object-parachute angle state model and data;

[0056] ③. Deceleration parachute opening stage: Through the complete restart function, the end of the auxiliary guide parachute opening stage model calculation is taken as the initial moment of this stage, and the deceleration parachute finite element model is added to realize the fluid-solid coupling simulation of this stage.

[0057] ④. Main parachute opening and steady descent stage: The complete restart function is used to take the end of the model calculation of the deceleration parachute opening stage as the initial moment of this stage, and the main parachute finite element model is added to realize the fluid-solid coupling simulation of this stage.

[0058] Through the above simulation, we finally obtain the dynamic simulation results of the whole process of parachute opening, such as time load curve, time object-parachute angle curve, time pitch angle curve, etc.

[0059] In this step, the load and posture required for the parachute opening strength are extracted through parachute opening dynamics simulation, which solves the current problem of being unable to accurately realize the dynamic calculation of heavy-duty airdrops with multiple parachutes and multiple stages of opening. In addition, the parachute opening impact strength calculation is performed on the vehicle body to obtain the stress, strain and deformation results of the vehicle body under the parachute opening impact strength working condition. The load and posture in the 100ms period before and after the main parachute is opened are used for dynamic simulation, which takes into account the dynamic characteristics of the structure and shortens the calculation time.

[0060] Step 2: Dynamic simulation analysis of parachute opening strength.

[0061] This step includes finite element modeling and simulation calculation of the entire vehicle.

[0062] ①. Finite element modeling of the whole vehicle and landing cushion system: The finite element model of the whole vehicle includes the body, frame model, powertrain model, transmission system model, and other chassis parts, airbag racks, etc. At the same time, the parachute harness adopts a flexible body model, and non-critical parts are modeled by mass point counterweights to ensure that the overall mass and center of mass of the vehicle body and landing cushion system are consistent with the actual object.

[0063] ②. Analysis of the vehicle's parachute opening strength: First, adjust the posture of the built finite element model relative to the ground according to the pitch angle of the parachute opening dynamics simulation; then adjust the angle between the sling and the vehicle body according to the object-parachute angle; then establish the gravity field; finally, load the time load curve at the sling, set the output parameters and submit the calculation.

[0064] Step 3: Analyze and evaluate the results.

[0065] Through step 2, the analysis results of vehicle body strength and deformation are obtained and compared with the target values ​​to evaluate whether the target is met.

[0066] Step 4: Failure cause analysis.

[0067] Through step three, add the airdrop system modal analysis, compare the deformation result animation of the parachute opening strength analysis of the benchmark vehicle body, and judge whether the failure is caused by insufficient stiffness. If not, determine it as a local strength problem. In this step, the failure evaluation target is that the maximum stress of each component is lower than the yield strength of the material. For structures that do not meet the target, use modal analysis to determine whether it is a stiffness problem or a strength problem to find the real cause of the failure.

[0068] Step 5: Reduce the model.

[0069] For the problems analyzed in step 4, the optimization model is reduced by intercepting part of the grid, replacing the dynamic simulation with the static simulation, etc., so as to achieve rapid iteration of the optimization process and improve the optimization efficiency. In this step, the model is reduced by various methods according to the true cause of failure to improve the optimization iteration efficiency.

[0070] Step 6: Structural optimization simulation.

[0071] After completing the optimization model building in step 5, multi-objective optimization is carried out through HyperStudy for practical problems. In this step, multi-objective optimization is carried out according to the structural characteristics of the parts and components at the failure site and the causes of failure, and the optimal structural optimization solution is found. The details are as follows:

[0072] ①. Establish a hyperstudy model. First, add the reduced model in step 5, then establish modification variables (such as sheet metal thickness,), constraints (such as the maximum and minimum deformation variables at certain positions, and the first-order bending torsion mode must not exceed a certain value) and goals (such as minimum mass and minimum volume ratio) and generate a new model;

[0073] ②. Hyperstudy calls the solver to solve the problem (various commonly used solvers can be called, and you can choose the required solver according to your own model).

[0074] ③. Extract the results from the result file.

[0075] Step 7: Optimize structural strength simulation verification.

[0076] After completing the optimization in step 6, import the optimized model into step 2 to re-verify whether the optimized model meets the target requirements. If so, the whole process ends.

[0077] More specifically, in one embodiment of the present invention, the reduction model includes the following process steps:

[0078] Step 1: Mesh preprocessing

[0079] 1. Mesh coarsening: Coarsening the mesh of the entire model to reduce the number of meshes. The new number of meshes can be determined by the following formula: Where r is the preset simplification ratio.

[0080] 2. Identification of key areas: Use sensitivity analysis tools to identify key areas, retain the detailed mesh in these areas, and simplify other areas. In an optional embodiment, the key areas in the model are identified through sensitivity analysis:

[0081]

[0082] Among them, Si is the sensitivity coefficient of the i-th design variable, f is the objective function, and xi is the design variable.

[0083] Step 2: Modal Analysis

[0084] 1. Perform modal analysis: Perform modal analysis on the simplified model to determine the key modes and natural frequencies. The calculation formula for modal analysis is:

[0085]

[0086] Where, ω is the natural frequency, K is the stiffness matrix, and M is the mass matrix.

[0087] 2. Extract key modes: Based on the modal analysis results, extract the modes that have the greatest impact on the structural response.

[0088] Step 3: Define sub-models based on failure causes

[0089] 1. Define submodel areas: Define submodels in key areas and ensure detailed meshes in these areas.

[0090] 2. Set sub-model boundary conditions: Ensure that the interface displacement and stress between the sub-model and the global model match.

[0091] Step 4: Material property simplification

[0092] 1. Material model replacement: Replace complex material models with simpler ones in non-critical areas.

[0093] 2. Adjust material parameters: Adjust material parameters such as elastic modulus according to simplification requirements.

[0094] Step 5: Simplify loads and boundary conditions

[0095] 1. Analyze load distribution: Analyze the distribution of loads and boundary conditions to determine whether they can be simplified.

[0096] 2. Equivalent static load calculation: For the variable load, calculate the equivalent static load: Peq = ∫P(x)dx. Where Peq is the equivalent static load and P(x) is the variable load distribution.

[0097] Step 6: Optimize model preparation

[0098] 1. Define design variables: Define design variables in HyperStudy, such as sheet metal thickness, material properties, etc.

[0099] 2. Set constraints and objectives: According to the results of modal analysis and load simplification, set the constraints and objective functions in the optimization process.

[0100] Step 7: Perform optimization

[0101] 1. Select the optimization algorithm: Select a suitable optimization algorithm, such as adaptive response surface method (ARSM).

[0102] 2. Iterative optimization: Execute the optimization algorithm and iteratively search for the optimal solution: x k+1 =x k +Δx, where xk+1 is the design variable for the next iteration, xk is the design variable for the current iteration, and Δx is the change in the design variable.

[0103] Step 8: Verify and adjust

[0104] 1. Model verification: Import the optimized model into a detailed finite element model for verification.

[0105] 2. Result evaluation: Evaluate whether the optimized model meets the design objectives and constraints.

[0106] 3. Adjust and Iterate: Based on the validation results, make necessary adjustments to the model and possibly re-execute the optimization process.

[0107] In summary, the evaluation method of the present invention is to establish a dynamic model of the parachute opening process through a computer, input the parameters of the special vehicle and the parachute system to quickly calculate the vehicle posture and sling load during the parachute opening and inflation period, and then call the vehicle body finite element model for dynamic simulation. The special vehicle parachute opening strength result is obtained through simulation to evaluate whether the special vehicle meets the design requirements. The optimization object is determined based on the analysis results, and multi-objective simulation optimization is performed to achieve structural optimization. The optimized finite element model is replaced to perform parachute opening dynamics simulation, and finally a vehicle body structure that meets the design requirements is achieved. The present invention solves the problems of high risk, high cost, long cycle, and lag in airdrop parachute opening tests, and the strength of the parachute system and special vehicles can be evaluated at the beginning of the design.

[0108] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A wheeled airdrop vehicle parachute opening impact strength simulation evaluation and optimization method, characterized in that: The following steps are involved: Step 1: Perform parachute opening dynamics simulation to obtain the precise boundary of parachute opening strength impact simulation, that is, the parachute opening strength load boundary; Step 2: Based on the parachute opening strength load boundary, a whole vehicle parachute opening strength dynamics simulation analysis is performed to obtain the analysis results of the vehicle body strength and deformation, and the analysis results are evaluated. If the evaluation results meet the target requirements, the design parameters are output; otherwise, step 3 is entered to perform failure cause analysis; Step 3: Add modal analysis of the airdrop system, analyze the deformation results of the parachute opening strength of the benchmark vehicle body, and determine the cause of failure; Step 4: According to the failure cause, a part of the mesh is cut or the static simulation is used to replace the dynamic simulation to reduce the model and obtain a reduced optimization model; Step 5: Based on the reduced optimization model and HyperStudy, multi-objective optimization is carried out according to the structural characteristics of the components at the failed parts and the causes of failure, and the optimal structural optimization solution is found.

2. A wheeled airdrop vehicle parachute opening impact strength simulation evaluation and optimization method according to claim 1, characterized in that: Step one includes the following steps: building an extravehicular dynamics model, building a dynamic finite element simulation model of the auxiliary guide parachute opening stage based on the extravehicular dynamics model and taking the extravehicular simulation results as initial conditions, obtaining the simulation results of the auxiliary guide parachute opening stage through ALE fluid-solid coupling simulation calculation, performing fluid-solid coupling simulation of the deceleration parachute opening stage based on the simulation results and the restart technology, performing fluid-solid coupling simulation of the main parachute opening and steady descent stages based on the fluid-solid coupling simulation results of the deceleration parachute opening stage and the restart technology, and in this way, obtaining the dynamics simulation results of the entire airdrop opening process, such as the time load curve, the time object-parachute angle curve, and the time pitch angle curve.

3. A wheeled airdrop vehicle parachute opening impact strength simulation evaluation and optimization method according to claim 2, characterized in that: The input parameters of the extravehicular dynamics model include: environmental parameters, parachute parameters, aircraft parameters and vehicle body parameters; The environmental parameters include flight speed and airdrop altitude; The parachute parameters include characteristic area, nominal diameter, mass, and drag coefficient; The carrier aircraft parameters include roller height, door height, and roller dynamic friction coefficient; The vehicle body parameters include mass, center of mass coordinates, and vehicle body shape.

4. A wheeled airdrop vehicle parachute opening impact strength simulation evaluation and optimization method according to claim 2, characterized in that: The dynamic finite element simulation model of the auxiliary guide parachute opening stage built with the extravehicular simulation results as initial conditions includes: a parachute model, a simple vehicle model and a flexible sling model. At the same time, the ALE fluid-solid coupling simulation calculation is used to obtain the dynamic influence of the canopy deformation and the change of the surrounding flow field on the auxiliary guide parachute opening stage, so as to obtain the vehicle pitch angle, vehicle speed, and object-parachute angle state model.

5. A wheeled airdrop vehicle parachute opening impact strength simulation evaluation and optimization method according to claim 1, characterized in that: In step 2, the whole vehicle parachute opening strength dynamics simulation analysis includes: Construct the finite element model of the whole vehicle and the landing buffer system. The parachute harness adopts a flexible body model, and non-critical parts are modeled by mass point counterweights to ensure that the overall mass and center of mass of the vehicle body and landing buffer system are consistent with the actual object. According to the pitch angle of the parachute opening dynamics simulation, the attitude of the built finite element model relative to the ground is adjusted, and then the angle between the sling and the vehicle body is adjusted according to the object-parachute angle. Then the gravity field is established, and finally the time load curve is loaded at the sling, and the output parameters are set.

6. A wheeled airdrop vehicle parachute opening impact strength simulation evaluation and optimization method according to claim 5, characterized in that: The whole vehicle finite element model includes a vehicle body, a frame model, a powertrain model, a transmission system model, a chassis component, and an airbag frame model.

7. The method for simulating, evaluating and optimizing the impact strength of a wheeled airdrop vehicle when opening a parachute according to claim 1, characterized in that: In step three, add modal analysis of the airdrop system, compare the deformation result animation of the parachute opening strength analysis of the benchmark vehicle body, and determine whether the cause of failure is caused by insufficient stiffness. If not, determine that it is a local strength problem.

8. A wheeled airdrop vehicle parachute opening impact strength simulation evaluation and optimization method according to claim 7, characterized in that: Step 4 includes the following steps: Coarsen the mesh of the entire dynamic simulation model to reduce the number of meshes; Conduct sensitivity analysis on the dynamics simulation model to identify the key areas of the dynamics simulation model; Define sub-models in critical areas, ensure detailed meshes in these areas, and ensure that interface displacements and stresses match between the sub-models and the coarsened dynamic simulation model; Analyze the distribution of loads and boundary conditions, and for varying loads, calculate equivalent static loads to simplify loads and boundary conditions; According to the results of modal analysis and load simplification, set the constraints and objective function in the optimization process; Adopting adaptive response surface method to execute optimization algorithm, iteratively searching for the optimal solution, that is, obtaining the optimal reduced optimization model; Verify the reliability of the reduced optimization model.

9. The method for simulating, evaluating and optimizing the impact strength of a wheeled airdrop vehicle when opening a parachute according to claim 7, characterized in that: Step five includes the following steps: Through HyperStudy, multi-objective optimization is carried out, a HyperStudy model is established, the reduced model is added, variables, constraints and objectives are established and modified, and a new model is generated, and the solver is used to solve the optimal solution of the new model.

10. A wheeled airdrop vehicle parachute opening impact strength simulation evaluation and optimization system, characterized in that: include: The first main control module is used to perform parachute opening dynamics simulation to obtain the precise boundary of parachute opening strength impact simulation, that is, the parachute opening strength load boundary; The second main control module is used to perform a dynamic simulation analysis of the vehicle's parachute opening strength based on the parachute opening strength load boundary to obtain the analysis results of the vehicle body strength and deformation, and evaluate the analysis results. If the evaluation results meet the target requirements, the design parameters are output; otherwise, the process proceeds to step three to analyze the failure causes; The third main control module is used to add modal analysis of the airdrop system, analyze the deformation results of the parachute opening strength of the vehicle body, and determine the cause of failure; The fourth main control module is used to cut off part of the grid or replace the dynamic simulation with the static simulation according to the failure cause, so as to reduce the model and obtain the reduced optimization model; The fifth main control module is used to carry out multi-objective optimization based on the reduced optimization model and the structural characteristics of the components at the failure site and the failure causes, and to find the optimal structural optimization solution.

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