计及桁架柔性的环形天线找形方法研究

发布时间：2018-12-10 07:53

【摘要】：环形天线由周边桁架、前/后索网及纵向索阵组成的索网结构、以及附着在前索网上的金属反射网组成,具有大口径、质量轻、收纳率高的特点,是目前比较理想的天线结构形式。反射面的形面精度是星载环形天线电性能的重要指标,影响着信号的通讯质量。索网结构作为金属反射网的支撑结构,其成形状态直接决定了反射面的形态。然而索网结构的成形状态与索段预张力分布是不可分割的一个整体。对索网结构进行优化设计,即是在满足形面精度的要求下对索段预张力进行配置,该过程通常又叫做“找形”。而索网结构的“找形”又受到桁架变形、铰链刚度等多因素影响。文章主要工作与研究成果如下:首先,分析索网结构找形结果评价指标,将形面精度和索段张力均匀性作为主要设计目标。固定索网结构边界节点,以索段力密度为设计变量,以网面均方根误差为目标函数,并以索段张力比和张力上下限作为约束条件,建立基于力密度法的天线索网结构找形优化模型。找形算例显示,采用该方法可使索网达到较高的网面精度和较均匀的索网预张力。其次,结合力密度法与有限元法,提出一种计及桁架柔性变形的找形方法,主要分三步进行。采用有限元法获得边界索段残余预张力及桁架节点位移,更新桁架节点坐标,把边界索段预张力当成已知量,建立新的基于力密度法的优化数学模型,优化得到其余索段上的预张力。最后,为替代第三章中有限元建模与分析环节,提高找形效率,采用矩阵位移法建立环形桁架刚度方程。针对边界索梁组合结构,以平衡态下桁架所受载荷为优化变量,以该载荷与索段上残余预张力差值为目标函数建立优化数学模型,对索梁耦合变形进行分析。该方法使得柔性桁架索网结构一体化找形分析成为可能,并为揭示柔性桁架、弹性铰链、柔性索网的耦合变形机理奠定了基础。
[Abstract]:The ring antenna is composed of peripheral truss, front / rear cable net and longitudinal cable array, as well as metal reflecting net attached to front cable net. It has the characteristics of large aperture, light weight and high acceptance rate. It is an ideal antenna structure at present. The shape accuracy of the reflector is an important index of the electrical performance of the spaceborne ring antenna, which affects the communication quality of the signal. As the supporting structure of metal reflecting net, the forming state of cable mesh structure directly determines the shape of reflection surface. However, the forming state of cable-net structure and the pretension distribution of cable segment are an inseparable whole. The optimal design of cable-net structure is to configure the pretension of cable section under the requirement of precision of shape plane. This process is usually called "shape finding". The shape-finding of cable-net structure is affected by many factors such as truss deformation, hinge stiffness and so on. The main work and research results are as follows: firstly, the evaluation index of the shape finding result of cable mesh structure is analyzed, and the precision of shape plane and the tension uniformity of cable segment are taken as the main design objectives. The fixed cable net structure boundary node takes the cable segment force density as the design variable, takes the root mean square error of the mesh surface as the objective function, and takes the tension ratio of the cable segment and the upper and lower limits of the tension as the constraint conditions. Based on the force density method, the shape finding optimization model of sky cue-net structure is established. An example of shape finding shows that this method can achieve higher mesh accuracy and uniform cable mesh pretension. Secondly, combining force density method and finite element method, a shape finding method considering the flexible deformation of truss is put forward, which is mainly divided into three steps. The residual pretension of the boundary cable segment and the displacement of the truss joint are obtained by using the finite element method, and the coordinates of the truss joint are updated, and the pretension of the boundary cable segment is taken as the known quantity, and a new optimization mathematical model based on the force density method is established. The pretension on the rest of the cables is optimized. Finally, in order to replace the finite element modeling and analysis in chapter 3 and improve the efficiency of shape finding, the stiffness equation of annular truss is established by matrix displacement method. According to the boundary cable-beam composite structure, the load of truss under equilibrium state is taken as the optimization variable, and the difference between the load and residual pretension on the cable segment is taken as the objective function to establish the optimization mathematical model, and the coupled deformation of cable-beam is analyzed. This method makes it possible to integrate the form-finding analysis of flexible truss cable-net structure, and lays a foundation for revealing the coupling deformation mechanism of flexible truss, elastic hinge and flexible cable-net.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU399

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