A Simulation Analysis Method for an Automatic Folding Structure of Double Elastic Rods

Abstract

The present invention discloses a simulation analysis method for an automatic retraction structure of a double elastic rod. The elastic rod is an arc-shaped shell structure with a certain curvature and is often used as the main supporting and load-bearing component of a large spacecraft structure. The elastic rod undergoes a winding and retraction process under the action of an external load. After the locking device is opened, the elastic rod can gradually rebound and unfold by releasing the strain energy generated by bending. The principle is simple, and it is a space deployable mechanism that has been widely used. This method uses the ABAQUS finite element simulation software to assemble according to the actual spatial position of the deployable structure of the elastic rod, considers the interaction between various parts of the structure and the actual contact situation, applies a load to realize the working winding process, and selects the explicit dynamics algorithm for solution in the analysis step. A finite element model of the double elastic rod winding is established using the S4R shell element and mechanical simulation analysis is carried out. The present invention can provide a reference for the cross-section design of the winding elastic rod and the design of the system working prototype.

Description

Technical Field

[0001] The invention relates to a simulation analysis method for a double elastic rod automatic folding structure. The elastic rod is a rod-shaped structure with a circular arc cross section applied in the aerospace field. Background Art

[0002] Space deployable structures are a type of complex aerospace structures developed to solve the size requirements of the structure itself and the volume limitations of the payload compartment of the vehicle. Its characteristics are the transformation of the structural space system and the large changes in shape and size. When the spacecraft is in the deployed state during the working phase, the structure can be folded and retracted first to reduce the space volume when it is to return automatically or be recovered.

[0003] As a type of space deployable structure, the elastic rod extension arm has the characteristics of simple structure, high storage rate and repeatable expansion. As a supporting force-bearing structural element, the extension arm is used in large space deployable antennas, solar arrays, space platforms, etc., and can realize the function of space folding and unfolding. After the elastic rod is unfolded, the stable working state is a circular arc cross-section. During the folding and unfolding process: the elastic rod becomes flat under the action of external load, and is bent, wound and folded under the drive of the reel; when the reel is opened and locked, the elastic rod releases the strain energy generated by the deformation and gradually rebounds and unfolds. At present, the space deployable structure is developing in the direction of multi-function, multi-task and comprehensiveness, and the structural size and mass are also rapidly increasing. Its simulation analysis is particularly important. The numerical simulation analysis method of the elastic rod winding process and the analysis of the mechanical properties of the winding process can provide a reference for the cross-section design of the winding elastic rod and the system prototype design. Summary of the invention

[0004] The purpose of the present invention is to ensure the reliability of the elastic rod space deployable structure in the aerospace field, understand the entire working operation of the system structure while ensuring economic benefits, and design a simulation analysis method for the double elastic rod automatic folding structure. In order to further design the overall structure of the elastic rod space deployable structure, the present invention uses ABAQUS simulation software, based on the actual working conditions of the elastic rod in space, to simulate the dynamic process of the elastic rod winding, and the obtained results not only have a high degree of credibility, but also bring important reference value to practical work.

[0005] The technical solution adopted by the present invention is: a simulation analysis method for a double elastic rod automatic folding structure, comprising the following steps:

[0006] A simulation analysis method for an automatic retracting structure of a double elastic rod. The entire winding process of the double elastic rod under the action of a driving load is as follows: The initial deployed states of the first elastic rods 1 and 2 are arc-shaped. By flattening the center reel pressing piece 9, the elastic rods can be connected to the reel 8. The reel drives the elastic rods to rotate inward and wind. Constrained by the snap ring 5 for axial displacement, the double elastic rods wind alternately through the external guide wheels 6 and the outer guide grooves 3. The simulation process of the entire winding process includes the following steps:

[0007] (1) Geometric model simplification:

[0008] The geometric model of the entire winding of the double elastic rod is simplified into the following components: the first elastic rod 1, the second elastic rod 2, the guide groove 3, the snap ring 5, the external guide wheel 6, and the reel 8.

[0009] (2) Analysis step determination:

[0010] ① Flattening: A cross-section for the connection part is divided at the front end of the elastic rod, and opposite displacement boundary conditions are applied to this area to make it completely flat.

[0011] ② Winding: The reel is applied with a constant rotational speed, and the elastic rod gradually moves through the external guide groove and the circumferentially distributed guide wheels to achieve a uniform winding process.

[0012] (3) Determine the interaction between components:

[0013] The first elastic rods 1 and 2 are connected to the reel through the reel pressing piece. The external guide groove and the circumferentially distributed guide wheels restrict the circumferential direction of the elastic rod, and the snap ring restricts the axial direction of the elastic rod.

[0014] During the flattening and winding of the elastic rod, there are contact and friction situations between the components of the model. The tangential attribute of the contact property is set to a penalty constraint, and its penalty coefficient is defined according to the actual contact situation. The normal attribute is set to a hard contact. Different face-to-face contacts are defined between different components, and the finite slip method is used for each analysis step.

[0015] The interaction between the flat end of the elastic rod and the reference point is established by using a kinematic coupling constraint (*Kinematic coupling) to couple the rotational degrees of freedom of all nodes in the flat section with the reference point; a hinge connection section is established between the reference point of the elastic rod and the reference point of the reel to realize the connection control of the reel to the elastic rod.

[0016] Rigid body constraints (*Rigid Body) are applied to the external guide wheels, guide grooves, and snap rings, and the deformation of the corresponding parts is not considered. The motion of the rigid body completely depends on the motion of its control point, and each guiding mechanism and the reel are used as the contact master surface during the contact process.

[0017] The horizontal section at the end of the elastic rod is connected to the reel using a binding (*tie) connection to simulate the actual connection relationship between the two components.

[0018] (4) Application of boundary conditions:

[0019] According to the actual folding mechanism of the deployable structure of the elastic rod, corresponding boundary conditions are applied to each component during its contraction and winding process.

[0020] In the analysis step of the flattening process, opposite displacements are applied on both sides of the cross-section at the end of the elastic rod, causing the elastic deformation of the arc surface until it completely becomes flat. As the load is applied, the contact surface between the elastic rod and the reel gradually increases. In the analysis step of the winding process, only a uniform angular velocity in the axial direction is applied to the reel, and the other degrees of freedom are completely constrained.

[0021] In the analysis steps of the entire flattening and winding processes, the circumferential guide wheels, guide grooves, and retaining rings are fixed, and their six degrees of freedom are completely constrained.

[0022] (5) Mesh generation:

[0023] Since the general 4-node linear reduced integration shell element S4R has stable performance and is suitable for large deformation problems of structures, the S4R shell element is used to establish the finite element model of the elastic rod.

[0024] (6) Finite element analysis and solution:

[0025] This calculation model involves the large deformation problem of the elastic rod during the multi-body connection and winding process, and the explicit dynamic method is used for solution calculation to simulate complex geometric non-linear situations.

[0026] (7) Evaluation and correction of calculation results:

[0027] Combined with the mechanical knowledge of the winding process, the stress and energy of the finite element simulation calculation results are evaluated and error analyzed. If the simulation results do not converge, the simulation-related settings such as the analysis step, the interaction between components, and the application of boundary conditions are re-determined.

[0028] Among them, there is an interaction between the rods with two circular arc cross-sections during the winding process of the elastic rod. The rotation of the reel can realize the winding process of the two elastic rods, and the folding efficiency is higher.

[0029] Among them, the flattening analysis step is used in the simulation process to achieve the function of the reel pressing piece.

[0030] Among them, the explicit dynamic method is used for the solution calculation of the model to solve the large deformation problem of the elastic rod during the multi-body connection and winding process.

[0031] The advantages of the present invention compared with the prior art are:

[0032] (1) The present invention elaborates on the precise analysis and numerical simulation method for the contraction process of the elastic rod space deployable structure using ABAQUS software, making the solution results closer to the actual situation;

[0033] (2) Through continuous optimization and summarization of the final results of the present invention, breakthroughs can be made in structural analysis methods and configuration innovations, with the expectation of being helpful for future research. Description of the Drawings

[0034] Figure 1 is the flowchart of the method of the present invention

[0035] Figure 2 is the geometric model diagram of the elastic rod

[0036] Figure 3 is the overall assembly diagram of the double elastic rod deployable structure

[0037] Figure 4 is the elastic rod connection assembly diagram of the double elastic rod deployable structure

[0038] Figure 5 is the finite element model diagram of the double elastic rod winding simulation Detailed Embodiment

[0039] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0040] As Figure 1 shown, the simulation analysis method of the double elastic rod retraction structure mainly includes the simplification of the geometric model, determination of the analysis steps, determination of the interaction between components, application of boundary conditions, mesh generation, and finite element analysis and solution.

[0041] As Figure 2 shown, the initial deployed state of the first elastic rod 1 and the second elastic rod 2 is a thin-walled circular arc shell structure with a simple structural form, which can realize its own deployment by using the elastic strain energy accumulated during folding deformation.

[0042] Figure 3 and Figure 4 The assembly diagrams of the elastic rod retraction structure in show that the main components include: the first elastic rod 1, the second elastic rod 2, the guide groove 3, the outer shell 4, the retaining ring 5, the external guide wheel 6, the fixing screw 7, the winding drum 8, and the winding drum pressing piece 9. The entire winding working process of the double elastic rod under the action of the driving load is as follows: The first elastic rod 1 and 2 can be connected to the winding drum 8 by flattening the central winding drum pressing piece 9, and the rotation of the winding drum drives the elastic movement. During the overall winding process of the elastic rod, the retaining ring 5 restricts the axial displacement, and the external guide wheel 6 and the outer guide groove 7 restrict the circumferential displacement.

[0043] Figure 5The simplified finite element model of the double elastic rod folding structure shown includes the following components: the first elastic rod 1, the second elastic rod 2, the guide groove 3, the retaining ring 5, the external guide wheel 6, and the reel 8. Relevant settings for simulation analysis are carried out according to the actual working mode of the double elastic rod folding structure.

[0044] The parts not elaborated in detail in the present invention belong to the well-known technology in the field.

[0045] As mentioned above, only some specific implementation manners in the present invention are described, but the protection scope of the present invention is not limited thereto. Any equivalent changes, modifications, equal-proportion amplifications or reductions made according to the design spirit in the present invention should be covered within the protection scope of the present invention.

Claims

1. A simulation analysis method for an automatic folding structure of a double elastic rod. The entire winding process of the double elastic rod under the action of a driving load is as follows: The initial unfolded state of the double elastic rod is arc-shaped. By flattening the pressing piece of the central reel, the elastic rod is connected to the reel; the reel drives the elastic rod to rotate inward and wind. Constrained by the retaining ring for axial displacement, the double elastic rod realizes alternating winding through the external guide wheel and the external guide groove in sequence. It is characterized in that The simulation process of the entire winding process includes the following steps: (1) Simplification of the geometric model: The geometric model of the entire double-elastic rod winding is simplified into the following components: the first elastic rod, the second elastic rod, the guide groove, the retaining ring, the external guide wheel, and the reel; (2) Determination of the analysis step: Flattening: Cross-sections for the connection part are divided at the front ends of the first elastic rod and the second elastic rod. Opposite displacement boundary conditions are applied to the cross-sections of the connection parts of the first elastic rod and the second elastic rod, so that the cross-sections of the connection parts of the first elastic rod and the second elastic rod are completely flattened; Winding: The reel is applied with a constant rotational speed, and the first elastic rod and the second elastic rod gradually move through the external guide groove and the circumferentially distributed guide wheels to achieve a uniform winding process; (3) Determination of the interaction between components: The first elastic rod and the second elastic rod are connected to the reel through the reel pressing plate. The external guide groove and the circumferentially distributed guide wheels realize the circumferential restriction of the first elastic rod and the second elastic rod, and the retaining ring realizes the axial constraint of the first elastic rod and the second elastic rod; During the flattening and winding processes of the first elastic rod and the second elastic rod, there are contact and friction situations between the components of the model; The tangential property of the contact property is set to penalty constraint, and its penalty coefficient is defined according to the actual contact situation. The normal property is set to hard contact; different face-to-face contacts are defined between different components, and the finite slip method is used for each analysis step; The motion coupling constraint is used to establish the interaction between the flattened ends of the first elastic rod and the second elastic rod and the reference point, so that the rotational degrees of freedom of all nodes in the flattened section are coupled with the reference point; A hinge connection section is established between the reference points of the first elastic rod and the second elastic rod and the reference point of the reel to realize the connection control of the reel to the elastic rod; Rigid body constraints are applied to the external guide wheels, guide grooves, and retaining rings; The motion of the rigid body completely depends on the motion of its control point, and the external guide wheel, guide groove, retaining ring, and reel are used as the contact master surfaces during the contact process; The binding connection interaction is used between the horizontal sections at the ends of the first elastic rod and the second elastic rod and the reel to simulate the actual connection relationship between the two components; (4) Application of boundary conditions: In the analysis step of the flattening process, displacements in opposite directions are applied to both sides of the end cross-sections of the first elastic rod and the second elastic rod, so that the arc surface elastically deforms until it is completely flattened; As the load is applied, the contact surface between the first elastic rod and the second elastic rod and the reel gradually increases; In the analysis step of the winding process, only a uniform angular velocity in the axial direction is applied to the reel, and the other degrees of freedom are completely constrained; In the analysis steps of the entire flattening and winding processes, the circumferential guide wheels, guide grooves, and retaining rings are fixed and their six degrees of freedom are completely constrained; (5) Mesh generation: The finite element model of the elastic rod is established using the S4R shell element; (6) Finite element analysis and solution: Regarding the large deformation problem of the elastic rod occurring during the multi-body connection winding process, the explicit dynamic method is used for solution calculation to simulate complex geometric nonlinear situations; (7) Evaluation and correction of the calculation results: Combined with the mechanical knowledge of the winding process, evaluate the stress and energy of the finite element simulation calculation results and conduct error analysis. If the simulation results do not converge, re-determine the analysis steps, the interaction between components, and the application of boundary conditions.

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