A rigid-flexible coupling dynamics simulation method for landing cushion mechanism
By adding flexible modules to the arrow body structure and defining buffer mechanical properties, establishing a rigid-flexible coupled dynamic model, the problem of high difficulty and high calculation in multi-body dynamic simulation analysis in the existing technology is solved, and the problem of high difficulty in modeling of flexible bodies is realized. More accurate description of dynamic responses and efficiency improvements provide reference for the structural design of the landing buffer mechanism and soft landing experiments.
Patent Information
- Application Number
- CN202110841098.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-07-24
- Publication Date
- 2024-12-13
- Estimated Expiration
- 2041-07-24
AI Technical Summary
The prior art is difficult to accurately describe the movement of flexible body members in multibody dynamic simulation analysis, resulting in a large difference in simulation results from the actual situation, and the calculation amount is large, making it difficult to effectively use HYPERMESH and LS-DYNA simulation software for rigid-flex coupling modeling. .
Add flexible modules to the arrow body structure to define buffer mechanical properties. By meshing, setting contact relationships, material properties and flexible connections in HYPERMESH and LS-DYNA, a rigid-flexible coupling dynamic model is established to reduce the difficulty of modeling and Reduce the calculation amount.
It improves the accuracy of simulation analysis results, simplifies the finite element model, improves the kinetic solution efficiency, and can more accurately describe the dynamic response of the landing buffer mechanism, shortens the R&D cycle and reduces costs and risks.
Smart Images
Figure CN113609725B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of multi-body dynamics simulation analysis, and in particular relates to a rigid-flexible coupling dynamics simulation method for a landing buffer mechanism. Background Art
[0002] The dynamic simulation of the landing buffer mechanism has important research significance for the structural optimization of the landing buffer mechanism and the soft landing process test. The current research on the dynamic simulation method of the landing buffer mechanism mainly focuses on the multi-rigid body dynamic simulation analysis, which can only describe the rigid body motion. When there are large flexible body components, the simulation results are quite different from the actual results. The full flexible body simulation modeling is difficult and the calculation is very large. How to use HYPERMESH and LS-DYNA simulation software, adopt the rigid-flexible coupling method to model, perform dynamic simulation of the landing buffer mechanism, and improve the accuracy of the simulation analysis results is very challenging and has become a technical problem that needs to be solved urgently. Summary of the invention
[0003] The purpose of the present invention is to provide a rigid-flexible coupling dynamic simulation method for a landing buffer mechanism in view of the shortcomings of multi-rigid body dynamic simulation analysis and full flexible body simulation, and to add a flexible module, i.e., a discrete beam unit involved in buffering energy absorption, to a rocket body structure dominated by a rigid structure, and to establish a flexible revolute connection. For the buffering energy absorption unit, its buffering mechanical characteristics are defined, i.e., the pre-input load-displacement curve, and finally a rigid-flexible coupling assembly model is obtained to reduce the difficulty of modeling, relatively reduce the amount of calculation, and more accurately describe the real dynamic response of the landing buffer mechanism.
[0004] To achieve the above object, the technical solution adopted by the present invention is:
[0005] A rigid-flexible coupling dynamics simulation method for a landing buffer mechanism comprises the following steps:
[0006] Step 1: Geometry processing and meshing:
[0007] In Solidworks, retain the main dimensional features, create a simplified rocket assembly model, save it in x_t format, and import it into HYPERMESH for meshing;
[0008] Step 2, set the contact relationship:
[0009] Establish rigid body constraints between connected rigid bodies, and set automatic single-surface contact relationships between other two components;
[0010] Step 3, set materials and properties:
[0011] Set the material of each component, assign unit properties to the rocket body and the connecting joint shell, the main landing leg is a flexible discrete beam unit, the auxiliary landing leg is a common beam unit, the center of mass is a mass unit, and other components are solid units;
[0012] Step 4: Establish flexible connection:
[0013] Establish flexible connections (RBE3) between the landing legs and the landing leg joints, and between the landing legs and the foot pads, that is, define rotational joint constraints;
[0014] Step 5, apply loads and define constraints:
[0015] Apply a gravity field to all components (LOAD_BODY_X), input the initial velocity to the rocket assembly model, and constrain the ground;
[0016] Step 6, simulation calculation:
[0017] After setting the calculation time, step size, and output parameters in the control card, export the K file to LS-DYNA for solution to complete the rigid-flexible coupling dynamics simulation of the landing buffer mechanism.
[0018] Preferably, in step 1, the grid is divided into the rocket body, the main landing leg connection joint and the auxiliary landing leg connection joint into 2D grids, and the foot pad and the ground are divided into 3D solid grids, wherein the foot pad includes upper and lower layers of grids; the main landing leg and the auxiliary landing leg are represented by creating a beam unit (Beam), a center of mass is created and placed in the rocket body and connected to the rocket body through a 2D grid, and the height of the lowest point of the overall rocket model from the ground is set.
[0019] Preferably, in step 3, when setting materials and properties, the rocket body and landing leg connection joints are assigned rigid body materials and shell unit properties; the main landing legs are assigned general nonlinear discrete beam materials and the load curve is input, and the discrete beam unit properties; the auxiliary landing legs are assigned ordinary steel materials and ordinary beam unit properties; the upper layer of the foot pad is rigid body material and solid unit properties, and the lower layer of the foot pad is aluminum alloy material and solid unit properties; the landing ground is concrete material, solid unit properties, and center of mass mass unit properties.
[0020] Preferably, in step 4, when establishing the flexible connection mode, flexible connections (RBE3) are adopted between the main landing legs and the main landing legs, between the main landing legs and the foot pads, and between the auxiliary landing legs and the auxiliary landing legs, and the translational degrees of freedom in the X, Y, and Z directions are constrained; a rigid connection is adopted between the lower end point node of the auxiliary landing leg and the foot pad.
[0021] Preferably, in step 5, when applying loads and defining constraints, a gravity field (LOAD_BODY_X) is applied to all components, that is, a body acceleration of 9.8 m / s is given in the vertical direction. 2 , input the initial velocity to the assembly model consisting of the rocket body, landing leg connection joints and foot pads, and impose constraints on the bottom nodes of the landing ground.
[0022] Compared with the prior art, the present invention has the following obvious outstanding substantial features and significant advantages:
[0023] 1. The present invention assigns shell unit properties to the rocket body and landing leg connection joints, and defines the weight by adding the center of mass, which greatly simplifies the finite element model and improves the efficiency of dynamic solution;
[0024] 2. The present invention combines the features of HYPERMESH and LS-DYNA software, makes key energy-absorbing and buffering components such as the main landing legs flexible, quickly establishes a rigid-flexible coupling dynamic model of the entire rocket buffer system, and can accurately describe the dynamic response of the landing buffer mechanism;
[0025] 3. The present invention provides a reference for further structural design and optimization of landing cushion mechanisms and rocket soft landing experiments, which can effectively shorten the R&D cycle, improve the quality of mechanism design, and reduce R&D costs and risks. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 It is a flow chart of the method of the preferred embodiment of the present invention.
[0027] Figure 2 It is the geometric model of the rocket of the preferred embodiment method of the present invention.
[0028] Figure 3 It is a rocket rigid-flexible coupling dynamics model of the preferred embodiment method of the present invention.
[0029] Figure 4 It is the buffering mechanical characteristic curve of the main landing leg of the preferred embodiment method of the present invention.
[0030] Figure 5 It is the load response curve of the main landing leg during the soft landing simulation process of the preferred embodiment method of the present invention. DETAILED DESCRIPTION
[0031] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments:
[0032] Embodiment 1:
[0033] See also Figure 1 A rigid-flexible coupling dynamics simulation method for a landing buffer mechanism comprises the following steps:
[0034] Step 1: Geometry processing and meshing:
[0035] In Solidworks, retain the main dimensional features, create a simplified rocket assembly model, save it in x_t format, and import it into HYPERMESH for meshing;
[0036] Step 2, set the contact relationship:
[0037] Establish rigid body constraints (CONSTRAINED_RIGID_BODIES) between connected rigid bodies, and set automatic single-surface contact relationships (CONTACT_AUTOMATIC_SINGLE_SURFACE) between other components;
[0038] Step 3, set materials and properties:
[0039] Set the material of each component, assign unit properties to the rocket body and the connecting joint shell, the main landing leg is a flexible discrete beam unit, the auxiliary landing leg is a common beam unit, the center of mass is a mass unit, and other components are solid units;
[0040] Step 4: Establish flexible connection:
[0041] Flexible connections (RBE3) are established between the landing legs and the landing leg connection joints, and between the landing legs and the foot pads, that is, rotational joint constraints are defined.
[0042] Step 5, apply loads and define constraints:
[0043] Apply a gravity field to all components (LOAD_BODY_X), input the initial velocity to the rocket assembly model, and constrain the ground;
[0044] Step 6, simulation calculation:
[0045] After setting the calculation time, step size, and output parameters in the control card, export the K file to LS-DYNA for solution to complete the rigid-flexible coupling dynamics simulation of the landing buffer mechanism.
[0046] This embodiment is based on the rigid-flexible coupling dynamic simulation method of the landing buffer mechanism. A flexible module, that is, a discrete beam unit that participates in buffering and energy absorption, is added to the rocket body structure, which is mainly a rigid structure, and a flexible revolute connection is established. For the buffering and energy absorption unit, its buffering mechanical characteristics are defined, and finally a rigid-flexible coupling assembly model is obtained to reduce the modeling difficulty, relatively reduce the amount of calculation, and more accurately describe the real dynamic response of the landing buffer mechanism.
[0047] Embodiment 2:
[0048] This embodiment is basically the same as the first embodiment, with the following special features:
[0049] The meshing in step 1 is to divide the rocket body, the main landing leg connection joint and the auxiliary landing leg connection joint into 2D meshes, and the foot pad and the ground into 3D solid meshes (Solidmesh), wherein the foot pad includes two layers of meshes. The main landing leg and the auxiliary landing leg are represented by creating beam elements (Beam), the center of mass is created and placed in the rocket body and connected to the rocket body through a 2D mesh, and the height of the lowest point of the rocket overall model from the ground is set.
[0050] In the step 3, the materials and properties are set to assign rigid body (RIGID) materials and shell unit (SHELL) properties to the rocket body and landing leg connection joints; general nonlinear discrete beam material (GENERAL_NONLINEAR_1DOF_DISCRETE_BEAM) to the main landing leg, and input the load curve and discrete beam unit properties; ordinary steel material and ordinary beam unit properties to the auxiliary landing leg; rigid body (RIGID) material and entity unit properties to the upper layer of the foot pad, and aluminum alloy material and entity unit properties to the lower layer of the foot pad; concrete material, entity unit properties and center of mass mass unit properties to the landing ground.
[0051] In the flexible connection method in step 4, flexible connection RBE3 is used between the main landing leg and the main landing leg connection joints, between the main landing leg and the foot pad, and between the auxiliary landing leg and the auxiliary landing leg connection joints, and the translational degrees of freedom in the X, Y, and Z directions are constrained; a rigid connection (CONSTRAINED_EXTRA_NODES_SET) is used between the lower endpoint node of the auxiliary landing leg and the foot pad.
[0052] The load and constraint application method in step 5 applies a gravity field (LOAD_BODY_X) to all components, that is, a body acceleration of 9.8 m / s is given in the vertical direction. 2 , input the initial velocity to the assembly model consisting of the rocket body, landing leg connection joints and foot pads, and impose constraints on the bottom nodes of the landing ground.
[0053] This embodiment assigns shell unit properties to the rocket body and landing leg connection joints, and defines weight by adding the center of mass, which greatly simplifies the finite element model and improves the efficiency of dynamic solution; this embodiment integrates the characteristics of HYPERMESH and LS-DYNA software, makes key buffer and energy-absorbing components such as the main landing legs flexible, and quickly establishes a rigid-flexible coupling dynamic model of the entire rocket buffer system, which can accurately describe the dynamic response of the landing buffer mechanism; this embodiment provides a reference for further structural design, optimization and rocket soft landing experiments of the landing buffer mechanism, which can effectively shorten the R&D cycle, improve the quality of mechanism design, and reduce R&D costs and risks.
[0054] Embodiment three:
[0055] See also Figure 1 to Figure 5 A rigid-flexible coupling dynamics simulation method for a landing buffer mechanism includes the following steps:
[0056] Step 1: Geometry processing and meshing:
[0057] In Solidworks, see Figure 2 The original model components include the rocket body 1, the connection joint 2, the main landing leg 3, the auxiliary landing leg 4 and the foot pad 5. The small parts in the assembly, such as bolts, pins, transmission devices and the fillets and chamfers on each component, are deleted, and the key dimensions of the key components are retained. Since the main landing leg and the auxiliary landing leg have a relatively complex structure, they are directly deleted. The connection joints and foot pads are simplified into rectangular modules. Finally, only the rocket body, connection joints and foot pads are retained; save it as an x_t file and import it into HYPERMESH to mesh the model. See Figure 3 ; The rocket body, main landing leg connection joints and auxiliary landing leg connection joints are divided into 2D grids, and the foot pad is divided into 3D solid grids (Solidmesh). The foot pad includes upper and lower grids. The ground is described by directly creating 3D solid grids. The main landing leg and the auxiliary landing leg are represented by beam elements (Beam) to simplify the landing legs. The center of mass is created and placed in the rocket body and connected to the rocket body through a 2D grid. The rocket axis is set to be perpendicular to the ground, and the lower end of the foot pad is moved to a height of 0.8m from the ground.
[0058] Step 2, set the contact relationship:
[0059] Establish rigid body constraints (CONSTRAINED_RIGID_BODIES) between the rocket body and the main landing leg connection joint and the auxiliary landing retraction connection joint. The rocket body is the main rigid body, the connection joint is the slave rigid body, and automatic single-surface contact relationships (CONTACT_AUTOMATIC_SINGLE_SURFACE) are set between other two components. The dynamic and static friction coefficients are set to 0.2.
[0060] Step 3, set materials and properties:
[0061] The rocket body and landing leg connection joints use rigid body (RIGID) material and are given shell element (SHELL) properties; the main landing leg uses general nonlinear discrete beam material (GENERAL_NONLINEAR_1DOF_DISCRETE_BEAM) and defines buffer mechanical properties, see Figure 4 Load-displacement curve; assign discrete beam unit properties; the auxiliary landing legs are made of ordinary steel with a density of 7850kg / m3 , elastic modulus 210Gpa, Poisson's ratio 0.3, given the properties of ordinary beam elements; the upper layer of the foot pad is made of rigid body (RIGID) material, given the properties of solid elements, and the lower layer of the foot pad is made of aluminum alloy material with a density of 2700kg / m 3 , elastic modulus 70GPa, yield strength 260MPa, Poisson's ratio 0.33, given entity unit attributes; the landing surface is made of concrete material, with an elastic modulus of 25.5GPa, given entity unit attributes, and the center of mass is given mass unit attributes, with a mass of 2t;
[0062] Step 4: Establish flexible connection:
[0063] Flexible connections (RBE3) are used between the main landing legs and the main landing legs, between the main landing legs and the foot pads, and between the auxiliary landing legs and the auxiliary landing legs, and the translational degrees of freedom in the X, Y, and Z directions are constrained; rigid connections (CONSTRAINED_EXTRA_NODES_SET) are used between the nodes at the lower end points of the auxiliary landing legs and the foot pads. Since the auxiliary landing legs cannot be extended or deformed, the landing leg joints only rotate in one direction to simulate the real landing mechanism rotational pair;
[0064] Step 5, apply loads and define constraints:
[0065] Apply a gravity field (LOAD_BODY_X) to all components, that is, give a body acceleration of 9.8m / s in the vertical direction 2 , input the initial vertical velocity of 2.5m / s to the assembly model consisting of the rocket body, landing leg connection joints and foot pads, in the negative direction of the X-axis, and apply constraints to the bottom nodes of the landing ground;
[0066] Step 6, simulation calculation:
[0067] In the control card, set the calculation time to 4s and the step length to 0.004s. Output the kinetic energy, support reaction force, displacement and other parameters for each step length. Export the K file to LS-DYNA for solution. After the calculation is completed, the main landing leg buffer load response is obtained. Figure 5 , and the main landing leg buffer stroke is obtained to be 0.018m.
[0068] This embodiment establishes a rigid-flexible coupling dynamic model for the inverted tripod rocket landing buffer mechanism. In view of the shortcomings of multi-rigid body dynamics and full flexible body simulation analysis, the main landing legs involved in buffering and energy absorption are converted into flexible discrete beam units, and the rocket body and connecting joints are shell units, which reduces the number of grids. The flexible main landing legs and other rigid body components constitute a rigid-flexible coupling model. Based on this model, simulation calculations of the simultaneous landing of the four legs of the rocket are carried out, which greatly improves the calculation efficiency and more accurately describes the dynamic response of the rocket soft landing.
[0069] In summary, the rigid-flexible coupling dynamic simulation method of the landing buffer mechanism of the above embodiment of the present invention has the following operating steps: simplify the rocket assembly model in Solidworks, save it in x_t format, and import it into HYPERMESH to divide the mesh; establish rigid body constraints between mutually connected rigid bodies, and set automatic single-sided contact relationships between other two components; set the material of each component, the rocket body and the connection joint attributes as shell units, the main and auxiliary landing legs as beam units, the center of mass as mass units, and the others as solid units; establish flexible connections (RBE3) between the landing legs and the landing leg connection joints, and between the landing legs and the foot pads; apply a gravity field to all components, give an initial velocity, and impose constraints on the ground; set the calculation time, step size, and output parameters in the control card, and export the K file to LS-DYNA for solution. The above-mentioned embodiment of the present invention realizes the construction of a rigid-flexible coupling dynamic model of the landing buffer mechanism, simplifies the complex landing legs into beam units, and makes the main landing legs flexible, which greatly improves the calculation efficiency, can accurately describe the dynamic response of the landing buffer mechanism, and provide a reference basis for the structural design, optimization and soft landing experiment of the landing buffer mechanism.
[0070] The above describes the embodiments of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention should be equivalent replacement methods. As long as they meet the purpose of the invention and do not deviate from the technical principles and inventive concepts of the present invention, they belong to the protection scope of the present invention.
Claims
1. A rigid-flexible coupling dynamics simulation method for a landing buffer mechanism, characterized in that: The steps include: Step 1: Geometry processing and meshing: In Solidworks, the main dimensional features are retained, a simplified rocket assembly model is established, saved in x_t format, and imported into HYPERMESH for meshing; the meshing is to divide the rocket body, the main landing leg connection joints and the auxiliary landing leg connection joints into 2D meshes, and the foot pads and the ground into 3D solid meshes, where the foot pads include upper and lower layers of meshes; the main landing legs and auxiliary landing legs are represented by beam elements Beam, the center of mass is created and placed in the rocket body and connected to the rocket body through 2D meshes, and the height of the lowest point of the overall rocket model from the ground is set; Step 2, set the contact relationship: Establish rigid body constraints between connected rigid bodies, and set automatic single-surface contact relationships between other two components; Step 3, set materials and properties: Set the material of each component, assign unit properties to the rocket body and the connecting joint shell, the main landing leg is a flexible discrete beam unit, the auxiliary landing leg is a common beam unit, the center of mass is a mass unit, and other components are solid units; Step 4: Establish flexible connection: Establish flexible connection RBE3 between the landing leg and the landing leg joint, and between the landing leg and the foot pad, that is, define the rotational joint constraint; Step 5, apply loads and define constraints: Apply gravity field LOAD_BODY_X to all components, input initial velocity to the rocket assembly model, and constrain the ground; Step 6, simulation calculation: After setting the calculation time, step size, and output parameters in the control card, export the K file to LS-DYNA for solution to complete the rigid-flexible coupling dynamics simulation of the landing buffer mechanism.
2. The rigid-flexible coupling dynamics simulation method of the landing buffer mechanism according to claim 1, characterized in that: In step 3, when setting materials and properties, the rocket body and landing leg connection joints are assigned rigid body materials and shell unit properties; the main landing leg is assigned a general nonlinear discrete beam material and the load curve is input, and the discrete beam unit properties; the auxiliary landing leg is assigned an ordinary steel material and an ordinary beam unit property; the upper layer of the foot pad is a rigid body material and a solid unit property, and the lower layer of the foot pad is an aluminum alloy material and a solid unit property; the landing ground is assigned a concrete material, a solid unit property, and a center of mass mass unit property.
3. The rigid-flexible coupling dynamics simulation method of the landing buffer mechanism according to claim 1, characterized in that: In step 4, when establishing the flexible connection mode, flexible connection RBE3 is used between the main landing leg and the main landing leg connection joint, between the main landing leg and the foot pad, and between the auxiliary landing leg and the auxiliary landing leg connection joint, and the translational degrees of freedom in the X, Y, and Z directions are constrained; a rigid connection is used between the lower end point node of the auxiliary landing leg and the foot pad.
4. The rigid-flexible coupling dynamics simulation method of the landing buffer mechanism according to claim 1, characterized in that: In step 5, when applying loads and defining constraints, a gravity field LOAD_BODY_X is applied to all components, that is, an acceleration of 9.8 m / s² is given in the vertical direction, an initial velocity is input to the assembly model consisting of the rocket body, landing leg connection joints and foot pads, and constraints are applied to the bottom nodes of the landing ground.