【作者】 田大可；

【导师】 刘荣强；

【作者基本信息】 哈尔滨工业大学 ， 机械设计及理论， 2011， 博士

【摘要】 空间可展开机构是人类进行空间探测活动不可缺少的航天装备,空间可展开机构中研究最活跃、发展潜力最大的一个分支是空间可展开天线,空间可展开天线是近二三十年来随着航天科技的快速发展而产生的一种新型空间结构,自产生以来便受到许多发达国家和科研机构的高度重视。本文以口径大小变化灵活的模块化空间可展开天线支撑桁架为研究对象,开展了可展开天线基本单元的构型综合与优选方法、模块化可展开天线支撑桁架的空间几何模型、动力学特性分析、结构优化及展开实验等方面的研究工作。可展开天线构型的创新设计是可展开天线相关理论研究中最基础的问题。可展开天线支撑桁架也称为背架,通常由若干个模块或基本单元组成,为了设计形式新颖、收纳率大、占用空间小的可展开天线,以6种典型可展开天线基本单元为基础,基于图论理论,建立了4种基本单元的拓扑图模型,分析了构件及运动副的拓扑对称性,提出了可展开天线基本单元的构型综合方法。针对可展开天线模块化结构基本单元的设计要求,建立了构型方案的模糊综合评价数学模型,对构型方案进行了优选。为了保证天线的形面精度,提高天线的工作效率,对模块化可展开天线支撑桁架进行了空间几何建模。首先,针对球形支撑桁架与抛物面形工作表面形状差异的问题,提出了一种抛物面形天线工作表面的球面拟合方法。其次,按照等尺寸与不等尺寸两种类型的模块,基于齐次坐标变换方法,建立了两种支撑桁架的空间几何模型,分析了等尺寸模块建模时存在的连接偏差并给出了调整的方法,对不等尺寸模块的几何模型进行了验证。模块化可展开天线支撑桁架展开口径大、刚度低,在姿态调整和在轨运行等阶段要经历较为复杂的动力学环境,可能会随之产生许多动力学问题。采用ANSYS软件,建立了支撑桁架的有限元模型,基于子空间法对其进行了模态分析,得到了结构的固有频率和振型,分析了结构在周期载荷作用下的频率响应,研究了中心杆、弦杆、斜腹杆、竖杆和拉索等参数对支撑桁架固有频率的影响,从而给出了提高1阶固有频率的有效措施。质量与刚度是衡量可展开天线结构性能的两个重要参数,将这两个参数作为目标函数对结构的杆件参数进行了优化。首先,根据BP神经网络的基本原理,建立了用于优化的预测模型,并进行了泛化能力检验。其次,将目标函数进行构造处理,采用遗传算法对预测模型进行了优化,确定了支撑桁架各杆件的设计参数。在优化的基础上,对驱动机构及模块结构的方案进行了设计。最后,研制了一个模块化可展开天线支撑桁架的原理样机及一套零重力模拟实验装置,对样机进行了展开精度实验和动力学实验。采用摄影测量的方法获取了支撑桁架关键点的空间坐标,分析了支撑桁架的形面精度、重复展开精度和关键点的误差情况,将实验数据与理论分析进行了对比验证。采用单点激振多点拾振的方式对支撑桁架进行了自由状态下的模态实验,并将实验结果与有限元仿真结果进行了对比,验证了支撑桁架有限元模型的正确性。更多还原

【Abstract】 Space deployable structures are the essential aerospace equipment to space exploration activities. Space deployable antenna is one of the most active research fields of space deployable structure, which has the huge development potential. Space deployable antenna is a new type of space structure, which is produced with the rapid development of aerospace science and technology in recent years. From then on, many countries and institutions have paid more attention to this research field. Taking truss structure of modular space deployable antenna as the research object, configuration synthesis and optimization of basic frame for space deployable antenna, spatial geometry modeling of truss structure, dynamic characteristics analysis, structural optimization and deployment precision test have been studied in this paper.Configuration creative design of deployable antenna is the most basic problem of related theoretical research. Truss structure is usually composed of several modules or basic frames. To design novel deployable antenna, taking six typical basic frames as the research foundation, four kinds of topological graph models of basic frame are obtained based on graph theory. The topological symmetry of members and kinematic pairs are analyzed. The synthesis method of basic frame for deployable antenna is proposed. According to the design requirements of basic frame for modular structure, comprehensive evaluation models are built, then an optimal configuration is obtained.To ensure the surface precision and improve working efficiency, spatial geometry model of truss structure is presented. To solve the problem of the difference between the shape of the paraboloid working surface and the spherical truss structure, a fitting method of working surface is proposed. Then the truss structure is classified into two types: the same size module and different size module, spatial geometry models of truss structure are presented based on the homogeneous coordinate transformation method. The influencing factors on connection deviation of the same size module are analyzed, and the adjusting method of that is proposed. Geometry model of different size module is verified.Modular deployable antenna has two characteristics: large aperture, weak stiffness, so in the course of attitude adjustment and on-orbit operation of antenna, many dynamic problems may be produced such as coupling interference between antenna and satellite, and impact vibration under space debris. The finite element model is built by using ANSYS software. The modal analysis of truss structure was carried out, and the natural frequencies and corresponding vibration modes of structure are obtained. The harmonic response analysis is carried out by full method. At last, the influence of structure parameters such as center beam, chord, diagonal beam, vertical beam and crossing cable on natural frequency of structure is studied, and the method to improve the first natural frequency is proposed.Mass and deployment stiffness are two important parameters for deployable antenna. Taking the mass and the first order natural frequency as the objective functions, the structural parameters of truss structure are optimized. At first, according to the basic idea of BP neural network, prediction model is constructed, and generalization capacity of neural network is tested by means of testing samples. Then, sub-goals multiplication and division is adopted to unify the multi-objective optimization to a single-objective function. The optimization analysis is performed by genetic algorithm, and the design parameters of truss structure are obtained. On this basis, the driving mechanism and module structure are designed.A set of truss structure prototype of modular deployable antenna and zero gravity simulation mechanism are manufactured successfully. Deployment precision test and dynamic test of truss structure are carried out. Spatial coordinates of key point are obtained by photogrammetry. Surface precision, repeated deployment precision and errors of key point are analyzed, then experimental results and theoretical analysis are compared with each other. Using the way of single input multiple output, modal experment of truss structure is carried out in free state. Comparing with the experimental results, the results show that the finite element model is right.更多还原