【作者】 徐彦；

【导师】 关富玲；

【作者基本信息】 浙江大学 ， 结构工程， 2009， 博士

【摘要】 为了实现星载天线的大口径、低能耗、轻质量、小运载体积,和机械可展开天线相比,充气可展开薄膜天线结构技术具有很多的优点,是未来大口径甚至超大口径天线的理想选择。天线工作状态的形面精度是天线最重要的结构指标,直接影响天线的电性能和使用。充气可展开天线能否最终可靠有序地展开并保持其工作状态,是航天任务能否成功的关键。本文对充气可展开天线的高精度反射面实现技术、褶皱分析方法、展开过程分析等几个关键问题进行了深入系统的研究。论文首先在大量查阅国内外文献的基础上,总结了国内外空间充气可展开结构的应用情况及研究现状,对课题的研究意义和研究思路进行阐述。给出了张量表示的薄膜结构的几何非线性有限元法。薄膜采用9节点Lagrangian曲面单元和三角形单元,索采用两节点直线单元。提出了假想衰减项法,用以分析无预应力薄膜结构,避免了刚度矩阵奇异而不能求解的问题。据此编写了充气薄膜结构的有限元分析程序。为实现天线的高精度反射面,分别研究比较了两种成形理论。针对平面—抛物面型充气可展开天线反射面,利用弹性力学分析形面,研究了天线在轨时温度变化对反射面形面的影响,并用自编程序进行验证。针对拼接抛物反射面,为了实现充气变形后的反射面逼近抛物面,经过保形分析,裁剪设计,裁剪片拼接,分析得到充气变形前的曲面,在充气气压作用下变形成最终的高精度充气反射面。利用自编程序对拼接抛物天线反射面进行反射面精度的参数分析,包括材料属性、厚度、内压、反射面焦距等。针对地面验证试验的三种实验姿态,分析重力对反射面形面的影响;对2米口径充气可展开天线结构的工作状态,利用有限元软件ABAQUS建立有限元模型,分析结构的固有频率和对应振型,分析中考虑了充气气体和反射面薄膜之间的流固耦合作用,采用声音介质模拟充气气体对结构振动的作用。研究了天线结构设计参数的选择对结构动力性能的影响。褶皱现象大量出现在充气可展开薄膜结构中,在自编的有限元程序中增加褶皱分析模块。用综合准则判别薄膜处于三种不同的受力状态:张拉、褶皱、松弛。利用张力场理论分析褶皱发生的区域和方向,分析充气展开天线的褶皱出现情况。基于弹簧-质点系统提出了新的褶皱处理方法,此方法不但能分析褶皱的区域和方向,能够预测褶皱的三维形状和大小。从树叶的仿生学出发,总结出平面薄膜结构的几种折叠方式。建立弹簧—质点系统描述薄膜材料,模拟薄膜结构的展开过程。薄膜展开过程中薄膜不可避免地发生自身的接触碰撞,提出了自接触对的判别准则,采用罚函数法有效地解决薄膜自接触问题。对三种折叠方式的薄膜的展开过程进行比较,叶外折叠方式和Miura折叠法比较适合平面薄膜的折叠。开发了充气可展开薄膜结构展开过程仿真程序,详细介绍了程序的流程图。设计了充气圆环管、充气反射面和充气直管的折叠方式,分析展开驱动力的作用机理和简化模型,利用流体场理论分析气囊内的气压变化,利用展开过程仿真软件对模型进行展开过程分析,得到展开过程的各个状态和各个点的展开速度。分析结果也验证了折叠方式的合理性。研制2m口径的充气反射面模型,介绍了花边设计和加工工艺。基于PhotoModeler软件建立的非接触摄像测量系统对其进行测量实验。通过反复的测量和形面调整,验证了高精度充气薄膜反射面的可实现性。对形面的误差来源进行了分析,给出了形面调整的方法。更多还原

【Abstract】 To realize large caliber, low-power, light weight, limit volume of the satellite antenna, compare to mechinics deployment antenna, the inflatable antenna structure technology have many advantages and is one of the best choice for large antenna. The shape precision of reflector on orbit is the most important target of the antenna, which affect the electric and work performance of the antenna directly. Whether the inflatable antenna can deploy to final configuration reliably is the key point that spaceflight mission can be successful. The theories to obtain high precision of inflatable reflector, wrinkle analysis technology and the deploy dynamics simulation of inflatable antenna are investigated in this thesis.Firstly, after referring a lot of pertinent literature world widely, the application of inflatable antenna structure and the research actuality of its key technology were summarized. Also the research significance is presented.Geometry nonlinear FEM of membrane was described by tensor form 9 node Lagrangian element and 3 node element was selected for membrane and 2 node linear element was selected for cable. Hypothesis damp term method was advanced to analyze non-prestress membrane structure. This method solved the problem from the singularity of stiffness matrix. The nonlinear FEA program for inflatable structure was compiled by FORTRAN and MATLAB.To obtain high precision of inflatable reflector, two kinds of figuration theories were investigated and compared. The first one is titled as plan- parabolic reflector. The elastic theory analysis was finished. Based on these works, the influence that temperature variety affects on the reflector precision on orbit was researched and the result was validated by FORTRAN program. The second one is titled as seaming parabolic reflector. For the deformed surface is required to be paraboloid, the theoretical studies, conformal analysis, cutting-pattern, membrane film seaming and then inflatable were described. The seaming parabolic reflector was chose in the following research.Precision analyses of inflatable reflector by nonlinear FEA program were conducted, and all important design parameters such as inflation pressure, membrane thickness, material characteristics and pre-tension stress of cable were investigated. The gravity influence in the reflector was compared under three postures and chooses one of them as final experiment posture. Analysis model of 2m antenna in ABAQUS was built to analyze natural frequencies and corresponding modes of the inflatable reflector structure. The analyses work has considered fluid-structure interaction between inflatable gas and the membrane material in reflector structure. This dissertation employed the 3D solid acoustic elements of standard FE software to simulate the inflation gas influence. The effects of all important design parameters on the modes were investigated.Wrinkling phenomenon exists broadly and affects the performances of the antenna structure. The distortion stress and strain of the structure were analyzed based on the source code written in MATLAB. Mixed criterion was used to evaluate the three states of membrane material: taut、wrinkled and slack. The TF method was used to forecast the direction and region of membrane wrinkle expediently. Then the wrinkle phenomenon appeared in inflatable reflector was investigated. A new method based on spring-mass system is advanced. This method can forecast not only the direction and region of wrinkle but also the shape and size of wrinkle.Some new fold patterns were developed for membrane structures from genuinely biomimetic. The spring-mass system is used to describe structural behavior of membrane material during deployment process. During development, self-contact or collision of the membrane occurs. The rule used to identify the self-contact elements is advanced and a penalty function method is developed to treat this difficult problem. The deployment processes of a two-dimensional membrane folded by three fold patterns were analyzed. The simulation code for inflatable membrane structure was described and the function of each part of module was introduced. The fold configuration and non-stress of tube, torus and parabolic reflector were built. The deployable mechanism and analytic model were researched to obtain deployable force and moment. The liquid theory was used to analyze the inflatable pressure in the ballonet. The deployment process was simulated by the code. Each state during deploy process and the velocity of each node were obtain. The simulation result validates the feasibility of fold method.A 2-meter ground demonstration space antenna reflector was design and manufactured. Non-contact Photogrammetric measure system was built on the base of PhotoModeler software packages. The steps of reflector precision measure of ultra-lightweight space structures were introduced on three experiment postures. High precision inflatable reflector was achieved after repeat precision measure and shape adjust. The error source of reflector was analyzed and shape adjust methods were introduced.更多还原