Method for optimizing metal frame structure of ultra-large flat satellite

Abstract

The invention discloses a method for optimizing a metal frame structure of a super-large panel satellite. Relates to the technical field of large metal structure optimization, in particular to the technical field of ultra-large panel satellite metal frame structure optimization. The problem of topological optimization of the whole-satellite metal structure of the large-size flat satellite with wide single-machine mass coverage range and complex working conditions is solved. The method comprises the following steps: S1, establishing a whole satellite finite element model, and setting the side length of a cell; s2, size optimization is carried out to determine the thickness of the structure foundation; s3, topological optimization is carried out to determine the minimum quality constraint; s4, overall index-oriented topological optimization in the overall design area is carried out; s5, topological optimization facing local indexes in the local design area; s6, optimizing the size of the reduced unit; s7, establishing a whole satellite finite element detailed model, and removing rigidity redundancy of the structure; s8, shape optimization is carried out; and S9, verifying the indexes. And a light-weight structural form meeting the structural continuity requirement is obtained by adopting a batch optimization method. The method shortens the satellite structure development period and reduces the structure mass.

Description

Technical Field

[0001] The present invention relates to the technical field of large-size metal structure optimization, and in particular to the technical field of ultra-large flat-panel satellite metal frame structure optimization. Background Art

[0002] Conventional topological analysis methods are mostly used for bracket-type structural design and small-sized satellite structural design. Among them, in terms of bracket products, the current topological optimization in the satellite field is mostly aimed at bracket products. The metal materials are usually titanium alloy, aluminum alloy, etc., the number of loads is small, and the form is relatively simple. Conventional optimization methods can meet the design requirements. In terms of small-sized satellite products, the mass of satellite payloads is generally small and the mass of each unit is not much different. Conventional optimization methods can also be used to obtain a better structural form.

[0003] The above two methods are not sufficient to support the design of the entire metal structure of large-sized flat-panel satellites with a wide single-machine mass coverage and complex working conditions.

[0004] For large-sized satellites, currently, most satellites weighing more than 500 kg use materials such as honeycomb panels, which have certain requirements for structural continuity. Therefore, structural optimization mostly uses size optimization rather than topological optimization. However, for satellites, the mass production performance of metal structures is better than that of honeycomb panel structures, which meets the current demand for rapid networking.

[0005] For flat-panel satellites with more than 50 units, unit masses ranging from tens of grams to hundreds of kilograms, structural dimensions reaching 3000mm×2000mm×170mm, and mechanical conditions including statics and dynamics, the sensitivity of nearby units of different units to the objective function varies greatly, which brings more complexity to structural optimization and increases the difficulty of structural design. Summary of the invention

[0006] In view of the above problems, the present invention discloses a method for optimizing the metal frame structure of an ultra-large flat-panel satellite, which relates to the technical field of large-size metal structure optimization. It effectively solves the problem that the metal structure of a large-size flat-panel satellite with a wide single-machine quality coverage and complex working conditions is difficult to optimize, while meeting the requirements of structural continuity, static and dynamic mechanical indicators, and processability.

[0007] The method comprises the following steps:

[0008] S1. Establish the finite element model of the whole star and set the cell side length;

[0009] S2. Dimension optimization to determine the thickness of the structural foundation;

[0010] S3, topology optimization to determine the minimum mass constraint;

[0011] S4, topology optimization for overall indicators in the overall design area;

[0012] S5. Topology optimization for local indicators in local design areas;

[0013] S6, reduce the unit size and optimize the iteration;

[0014] S7. Establish a detailed finite element model of the entire satellite to remove the stiffness redundancy of the structure;

[0015] S8, shape optimization;

[0016] S9. Establish the final finite element model of the entire satellite and verify the indicators.

[0017] Furthermore, the specific method of establishing the whole satellite finite element model is: in the modeling software, the structure is divided into finite element grids with equal side lengths, the stiffness of all single machines is weakened, all single machines are simplified into mass points, and the mass points are connected to the grid nodes of the single machine structure plate through flexible units. The side length of the finite element grid is the unit cell side length.

[0018] Furthermore, the specific method of determining the thickness of the structural foundation by the size optimization is: taking the fundamental frequency of the entire satellite and the dynamic response of a single fixed point as constraints, minimizing the mass as the goal, and obtaining the thickness of the structural foundation by size optimization.

[0019] Furthermore, the specific method of determining the minimum mass constraint by topology optimization is: taking the fundamental frequency of the whole satellite and the dynamic response of the fixed point of a single machine as constraints, taking the minimum mass as the goal, and obtaining the minimum mass constraint through topology optimization.

[0020] Furthermore, the overall design area is a complete satellite structure; the specific method of the topology optimization oriented to the overall indicators is: taking the fundamental frequency of the whole satellite, the dynamic response of the single-machine fixed point and the minimum mass constraint as constraints, and minimizing the flexibility as the goal, and obtaining the topology optimization structure oriented to the overall indicators through topology optimization.

[0021] Furthermore, the local design area is: taking the topology optimization structure oriented to the overall index as the non-design area, and taking the structure outside the non-design area as the local design area; the specific method of the topology optimization oriented to the local overall index is: taking the upper limit of the displacement of the mass point as the constraint and the minimum flexibility as the goal, and obtaining the topology optimization structure oriented to the local index through topology optimization.

[0022] Furthermore, the reducing unit size is to proportionally reduce the unit cell side length, and a further lightweight structure is calculated. The optimization iteration represents repeating steps S4, S5 and S6 for the further lightweight structure. When the lightweight structure cannot simultaneously meet the constraints and objectives of step S4 or S5 during the optimization iteration, the optimization iteration is terminated to obtain a structural plate model with a continuous single-machine fixed point structure.

[0023] Furthermore, the establishment of the whole satellite finite element detailed model is, in the modeling software, connecting the structural plate model with the continuous single-machine fixed point structure and the single-machine model of the restoring stiffness through a rigid unit; the method for obtaining the single-machine model of the restoring stiffness is to carry out detailed modeling of the single machine to obtain the single-machine model of the restoring stiffness with accurate mass and stiffness, and the removal of the stiffness redundancy of the structure is to optimize the size of the structural plate model with the continuous single-machine fixed point structure in the whole satellite finite element detailed model to obtain a lightweight structural plate.

[0024] Furthermore, the shape optimization is to adaptively adjust the lightweight structural panel according to the process to obtain the final structure.

[0025] Furthermore, the specific method of establishing the final finite element model of the whole satellite is to re-divide the finite element mesh of the detailed finite element model of the whole satellite to obtain the final finite element model of the whole satellite. The verification index is to simulate and calculate the fundamental frequency of the whole satellite through the final finite element model of the whole satellite in the modeling software, and use the mechanical conditions provided by the rocket as input to simulate and calculate the dynamic response of the single fixed point of the structural plate of the whole satellite, and obtain the results of the dynamic response of the fundamental frequency of the whole satellite and the single fixed point of the structural plate of the whole satellite, and verify the index conformity of the fundamental frequency and dynamic response of the whole satellite.

[0026] The beneficial effects of the method of the present invention are:

[0027] The present invention proposes an optimization design method for flat-panel satellite metal structures with large structural dimensions, wide unit mass coverage, and complex working conditions. By weakening the unit stiffness to increase the sensitivity of the unit fixed point to the objective function, topological calculation obtains a relatively accurate lower limit constraint on the structural mass, rather than relying on empirically given mass fractions. The method of batch optimization for the whole and the local is used to obtain a lightweight structure that meets the requirements of structural continuity, static and dynamic mechanical indicators, and processability. This design method greatly shortens the structural development cycle of satellites, reduces the proportion of structural mass, can be adapted to high-capacity processes such as casting, and improves satellite mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the method described in an embodiment of the present invention;

[0029] Figure 2 Schematic diagram of the entire satellite structure before topology optimization, where 1 is the optimized front cover and 2 is the optimized front bottom frame;

[0030] Figure 3 Figure 3 is a schematic diagram of the entire satellite structure after topology optimization, where 3 is the optimized rear cover and 4 is the optimized rear bottom frame. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] This embodiment provides a method for optimizing the metal frame structure of a super-large flat-panel satellite. The flowchart of the method is as follows: Figure 1 , the method comprises the following steps:

[0033] S1. Establish a finite element model of the entire star and set the unit cell side length.

[0034] The relevant operations of step S1 are introduced with a specific example:

[0035] Create a package containing Figure 2 The finite element model of the whole satellite including the optimized front cover plate 1 and the optimized front bottom frame 2 is shown. In the modeling software, the structure is divided into finite element grids with equal side lengths, the stiffness of all single machines is weakened, the sensitivity of the unit density near all fixed points of the single machine to the target is improved, all single machines are simplified into mass points, and the mass points are connected to the grid nodes of the single machine structure plate through flexible units. The side length of the finite element grid is the unit cell side length, and the unit cell side length is set to 10 mm.

[0036] S2. Dimension optimization to determine the thickness of the structural foundation.

[0037] The relevant operations of step S2 are introduced with a specific example:

[0038] Taking the fundamental frequency of the whole satellite greater than 20 Hz and the dynamic response of a single fixed point less than 10 g as constraints and the minimum mass as the goal, the structural foundation thickness of the optimized front cover plate (1) and the optimized front bottom frame (2) are obtained. The structural thickness used for optimization should be more than twice the structural foundation thickness to avoid the structure being in a critical state, resulting in too small a removable amount of the structure and affecting the optimization effect.

[0039] S3. Topology optimization determines the minimum mass constraint.

[0040] The relevant operations of step S3 are introduced with a specific example:

[0041] For topological optimization of large-sized metal structures, in addition to constraining the fundamental frequency of the entire satellite and the dynamic response of a single fixed point, it is also necessary to constrain the mass of the structure. Otherwise, the goal and the constraint both point to a large mass of the structure and the result will not converge. Among them, if the mass constraint is too large, the structure will be affected by the minimum flexibility and take the upper limit of the mass, that is, it is impossible to obtain an extremely lightweight structure. If the mass constraint is too small, other constraint indicators will be out of tolerance. In order to obtain a relatively accurate minimum mass of the structure, the mass should not be defined according to a mass fraction less than a certain percentage. A round of mass value selection should be carried out before the optimization work officially begins. The minimum mass is first taken as the goal, and the fundamental frequency of the entire satellite is greater than 20Hz and the dynamic response of a single fixed point is less than 10g as constraints. The minimum mass constraint is 70kg obtained through topological optimization.

[0042] S4. Topology optimization for overall indicators within the overall design area.

[0043] The relevant operations of step S4 are introduced with a specific example:

[0044] The complete satellite structure is used as the overall design area, the fundamental frequency of the satellite is greater than 20Hz, the dynamic response of the single fixed point is less than 10g, and the minimum mass constraint is 70kg. The minimum flexibility is the goal, and the topology optimization structure facing the overall index is obtained through topology optimization. At the same time, the result cloud map is used to determine whether there are non-conforming items outside the constraints. If there are non-conforming items, the constraints should be adjusted to continue iteration.

[0045] S5. Topology optimization for local indicators in local design areas.

[0046] The relevant operations of step S5 are introduced with a specific example:

[0047] Since the cell densities near units of different masses have different sensitivities to the target, affected by the unified threshold, the optimization result may show the lack of cells near small-mass units, and cannot cover all the fixed points of the units. Therefore, local optimization is still needed.

[0048] The above-mentioned topology optimization structure oriented to the overall indicators is taken as the non-design area, and the structure outside the non-design area is taken as the local design area. In the local design area, the indicators oriented to local characteristics such as the upper limit of mass point displacement are taken as constraints, and the minimum flexibility is taken as the goal. The topology optimization structure oriented to the local indicators is obtained through topology optimization. The upper limit of mass point displacement is a step-by-step given value, which is classified at intervals of 0.5. In this embodiment, the constraints on the upper limit of mass point displacement of a single machine are specifically 0.5mm, 1mm, 1.5mm, and 2mm.

[0049] S6. Reduce the cell size and optimize the iterations.

[0050] The relevant operations of step S6 are introduced with a specific example:

[0051] The cell side length determines the maximum and minimum size of the topology optimization, so the topology structure will be affected by the cell side length. The small cell size calculation method is very computationally intensive and resource-intensive, so the large cell size calculation method is used in the early stage. When the continuity of the single-machine fixed point structure meets the index and the approximate structural form is obtained, the small cell size calculation method is used to reduce the cell size from 10mm to 5mm in proportion, and the further lightweight structure is calculated. Steps S4, S5 and S6 are repeated for the further lightweight structure. When the lightweight structure cannot simultaneously meet the constraints and objectives of step S4 or S5 during the optimization iteration process, the optimization iteration is terminated to obtain a structural plate model with a continuous single-machine fixed point structure.

[0052] S7. Establish a detailed finite element model of the entire satellite and remove the stiffness redundancy of the structure.

[0053] The relevant operations of step S7 are introduced with a specific example:

[0054] In order to carry out topology optimization, the stiffness of the single machine is weakened and simplified to a mass point, which is connected to the structural plate of the single machine through a flexible unit. In fact, the stiffness of the single machine contributes to the structural stiffness to a certain extent. Therefore, the structural plate model with a continuous single machine fixed point structure obtained after topology optimization has a certain stiffness redundancy.

[0055] In order to remove the redundancy of structural stiffness, in the modeling software, the stiffness of the single machine itself is restored, and the single machine is modeled in detail to obtain a single machine model with restored stiffness that has accurate mass and stiffness. The structural plate model with continuous single machine fixed point structure and the single machine model with restored stiffness are connected through rigid units to establish a detailed finite element model of the entire satellite; the size of the structural plate model with continuous single machine fixed point structure in the detailed finite element model of the entire satellite is optimized to remove the redundancy of structural stiffness and obtain a lightweight structural plate. Among them, a super unit model can be established for a complex single machine to save calculation time.

[0056] S8. Shape optimization.

[0057] The relevant operations of step S8 are introduced with a specific example:

[0058] Taking into account the convenience of assembly, the structure of the lightweight structural panel is adaptively adjusted according to the process to be selected, and its shape is optimized to obtain the final structure: Figure 3 Shown are an optimized rear cover plate (3) and an optimized rear bottom frame (4).

[0059] S9. Establish the final finite element model of the entire satellite and verify the indicators.

[0060] The relevant operations of step S9 are introduced with a specific example:

[0061] In the modeling software, the finite element detailed model of the whole satellite is re-divided into finite element meshes to obtain the final finite element model of the whole satellite. In the final finite element model of the whole satellite, the fundamental frequency of the whole satellite is simulated and calculated, and the mechanical conditions provided by the rocket are used as input to simulate and calculate the dynamic response of a single fixed point of the structural plate of the whole satellite. The fundamental frequency of the whole satellite is 21.6 Hz, and the maximum dynamic response of a single fixed point of the structural plate of the whole satellite is 8.2 g. The above calculation structure verifies the conformity of the indicators that the fundamental frequency of the whole satellite is not less than 20 Hz and the dynamic response of a single fixed point is less than 10 g.

Claims

1. A method for optimizing the metal frame structure of a super-large flat-panel satellite, characterized in that: The method comprises the following steps: S1. Establish the finite element model of the whole star and set the cell side length; S2. Dimension optimization to determine the thickness of the structural foundation; S3, topology optimization to determine the minimum mass constraint; S4, topology optimization for overall indicators in the overall design area; S5. Topology optimization for local indicators in local design areas; S6, reduce the unit size and optimize the iteration; S7. Establish a detailed finite element model of the entire satellite to remove the stiffness redundancy of the structure; S8, shape optimization; S9. Establish the final finite element model of the entire satellite and verify the indicators.

2. The method for optimizing the metal frame structure of a super-large flat-panel satellite according to claim 1, characterized in that: The specific method of establishing the whole satellite finite element model is: in the modeling software, the structure is divided into finite element grids with equal side lengths, the stiffness of all single machines is weakened, all single machines are simplified into mass points, and the mass points are connected to the grid nodes of the single machine structure plate through flexible units. The side length of the finite element grid is the unit cell side length.

3. The method for optimizing the metal frame structure of a super-large flat-panel satellite according to claim 1, characterized in that: The specific method of determining the thickness of the structural foundation by size optimization is: taking the fundamental frequency of the entire satellite and the dynamic response of a single fixed point as constraints, minimizing the mass as the goal, and obtaining the thickness of the structural foundation by size optimization.

4. The method for optimizing the metal frame structure of a super-large flat-panel satellite according to claim 2, characterized in that: The specific method of determining the minimum mass constraint by topology optimization is: taking the fundamental frequency of the whole satellite and the dynamic response of the fixed point of a single machine as constraints, minimizing the mass as the goal, and obtaining the minimum mass constraint through topology optimization.

5. The method for optimizing the metal frame structure of a super-large flat-panel satellite according to claim 4, characterized in that: The overall design area is the complete satellite structure; the specific method of the topology optimization oriented to the overall indicators is: taking the fundamental frequency of the whole satellite, the dynamic response of the fixed point of a single machine and the minimum mass constraint as constraints, and minimizing the flexibility as the goal, and obtaining the topology optimization structure oriented to the overall indicators through topology optimization.

6. The method for optimizing the metal frame structure of a super-large flat-panel satellite according to claim 5, characterized in that: The local design area is: taking the topology optimization structure oriented to the overall index as the non-design area, and taking the structure outside the non-design area as the local design area; the specific method of the topology optimization oriented to the local overall index is: taking the upper limit of the mass point displacement as the constraint and the minimum flexibility as the goal, and obtaining the topology optimization structure oriented to the local index through topology optimization.

7. The method for optimizing the metal frame structure of a super-large flat-panel satellite according to claim 2, characterized in that: The reducing unit size is to proportionally reduce the unit cell side length, and a further lightweight structure is calculated. The optimization iteration means repeatedly executing steps S4, S5 and S6 for the further lightweight structure. When the lightweight structure cannot simultaneously meet the constraints and objectives of step S4 or S5 during the optimization iteration process, the optimization iteration is terminated to obtain a structural plate model with a continuous single-machine fixed point structure.

8. The method for optimizing the metal frame structure of a super-large flat-panel satellite according to claim 7, characterized in that: The method of establishing the detailed finite element model of the whole satellite is to connect the structural plate model with the continuous single-machine fixed point structure and the single-machine model of the restoring stiffness through a rigid unit in the modeling software; the method of obtaining the single-machine model of the restoring stiffness is to carry out detailed modeling of the single machine to obtain the single-machine model of the restoring stiffness with accurate mass and stiffness; the method of removing the stiffness redundancy of the structure is to optimize the size of the structural plate model with the continuous single-machine fixed point structure in the detailed finite element model of the whole satellite to obtain a light-weight structural plate.

9. The method for optimizing the metal frame structure of a super-large flat-panel satellite according to claim 8, characterized in that: The shape optimization is to adaptively adjust the lightweight structural panel according to the process to obtain the final structure.

10. The method for optimizing the metal frame structure of a super-large flat-panel satellite according to claim 8, characterized in that: The specific method of establishing the final finite element model of the whole satellite is to re-divide the finite element grid of the detailed finite element model of the whole satellite to obtain the final finite element model of the whole satellite. The verification index is to simulate and calculate the fundamental frequency of the whole satellite through the final finite element model of the whole satellite in the modeling software, and use the mechanical conditions provided by the rocket as input to simulate and calculate the dynamic response of the single fixed point of the structural plate of the whole satellite, obtain the results of the dynamic response of the fundamental frequency of the whole satellite and the single fixed point of the structural plate of the whole satellite, and verify the index conformity of the fundamental frequency and dynamic response of the whole satellite.

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