【作者】 陈钦；

【导师】 杨乐平；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2010， 博士

【摘要】 随着空间技术和应用的快速发展,在轨补给、维修、营救和空间碎片处理已成为航天领域的重要前沿问题,引领着空间系统体系结构转型和空间基础设施建设的发展方向。安全、自主的空间非合作目标捕获是解决上述问题的重要基础和关键技术瓶颈,也是体现当今航天技术发展水平的重要标志之一。本文探讨了空间非合作目标捕获的空间绳网系统概念,对相关理论问题进行了深入研究,开展了动力学仿真和初步的地面原理试验。首先,针对空间目标捕获需求,对多种空间捕获方法和手段进行了对比分析,提出了能够有效避免碰撞危险、具有容错捕获能力、应用灵活的空间绳网捕获系统概念,形成了面向空间非合作目标在轨捕获的系统方案;围绕空间绳网系统总体设计,提出了基于无向图的绳网结构设计、平面绳网与三维绳网、机械储能自适应收口机构等概念;考虑载体航天器相对运动特点和空间捕获任务的灵活性要求,提出了空间绳网捕获V-bar、R-bar、H-bar等三种基本任务模式。其次,针对空间绳网捕获系统多回路非树结构特征和刚柔耦合动力学特性,引入无向图描述绳索各段之间及绳索与牵引质量块之间的连接关系,运用集中质量法建立绳索质点系动力学模型,与牵引质量块刚体动力学模型结合形成刚柔耦合动力学模型,进而提出并建立了具有拓扑结构描述、绳段自动划分、动力学模型自动处理等先进功能的空间绳网系统设计分析方法,研制开发了相应的仿真算法和软件。对空间绳网捕获工作过程中的碰撞与接触动力学进行了初步研究。第三,通过对平面绳网和三维绳网的动力学仿真,对其发射展开工作过程与特性进行了系统分析。平面绳网发射展开仿真结果表明:平面绳网发射展开经历匀速展开、稳定飞行和碰撞变形三个阶段,绳网在稳定飞行段能够自然维持适于捕获的形状;发射角度和绳索阻尼系数是直接影响平面绳网发射展开特性的两个主要设计参数,可以进行优化设计;无论系统采用V-bar、R-bar或H-bar哪种任务模式,基本不影响平面绳网发射展开的性能指标。三维绳网发射展开仿真结果表明:三维绳网自然发射展开不能形成稳定飞行阶段;采用连接绳索被动开环阻力控制方法可以解决三维绳网发射展开的网形控制问题,形成稳定飞行过程并保持适合捕获的网形。第四,针对空间绳网发射过程中绳网的结构变形与振荡等物理现象,对理想绳索的冲击加载过程进行了理论研究,通过仿真得到了绳索物理非线性和几何非线性对绳索中应力波传播影响的重要结论:绳索始终张紧的情况下,应力波线性叠加原理有效,绳索中应力波的传播过程与刚性杆相同;当绳索经历“张紧—松弛”的变迁过程——绳索质点从被拉伸转换到被压缩并在这个过程中获得了视速度,则绳索中应力波能量逐步衰减,绳索中应力波的传播无法用线性叠加原理解释。最后,在系统设计、仿真分析的基础上,提出了空间绳网系统地面原理试验和空中投放试验的总体技术方案,研制了采用牵引质量块火药弹射方式的绳网发射机构地面原理样机和绳网机械储能自适应收口机构原理样机,在国内首次成功进行了空间绳网系统飞艇空中投放试验。地面发射原理试验演证了空间绳网发射的可行性,测量结果与仿真结果吻合,表明仿真模型正确可用;飞艇空中投放试验验证了偏置发射与机械储能自适应收口机构的设计原理与工作可靠性,结果表明机械储能自适应收口机构原理正确、结构合理、功能有效。总之,论文对空间绳网系统原理和任务特性进行了系统分析,深入研究了空间绳网系统柔性动力学和刚柔耦合动力学现象,建立了空间绳网任务设计的理论框架,并通过地面原理试验考核验证了空间绳网系统主要机构设计与仿真结果,为空间绳网系统工程研制提供了重要的方法、模型和分析结果。更多还原

【Abstract】 As the rapid development of space technology and application, on-orbit refueling, maintenance, rescue and space debris handling has become the top issues in space domain, leading the transformation of space systems architecture and space infrastructures development direction. The autonomous and safe capture of a non-cooperative target is an important foundation to solve the above problems and bottlenecks of the key technologies; and is the indication of the development of space technologies. An orbit net capture concept for non-cooperative space target was proposed and related issues were investigated, and dynamic simulations were performed along with a series of ground tests of prototype systems.Firstly, based on the analysis of the concept of space capture, different space capture methods were compared to show the features and advantages of the net-capture system. Through the analysis of the process of the net capture mission, a net capture system design was derived. The net-shotting scheme with four weights, an undirected graph method to design net structures of flexible cables, the division of planar net structures and 3D net structures, and mechanical automating net-closing devices, were proposed. Three net capture scenarios were given as a V-bar, an R-bar and an H-bar net capture, with which were some performances indexes of net-capture systems.Secondly, the dynamics of net capture systems was divided into the dynamics of rigid bodies and the dynamics of flexible cable structures. A dumped-mass method was utilized to derive a particle system model of the flexible cable structure, which was coupled with the connected rigid bodies to compose the coupling dynamics of the net capture system. A set of algorithms, which form the base of a computer-aid dynamic analysis software of net structures, were given to compute the coupling equations of motion of the systems automatically, with any given structure of net capture systems. Based on the algorithms, object-oriented simulation software was implemented. A primary investigation of the dynamics of impact and contact during the net capture were performed.Thirdly, dynamic aspects of planar nets and 3D nets were investigated by simulations. The process of casting of a planar net was concluded as spreading, flying and collapsing. Different mission scenarios, as V-bar, R-bar and H-bar capture, were considered as feasible as the simulations showed. Two design parameters, casting angle and damping ratio, were considered to be crucial to the net capture mission, further simulations and analysis showed opportunities of optimization. The simulation of casting of a 3D net showed that extra control was needed to keep the net structure in an advantageous shape for capturing; a simple control scheme was proved to be effective with simulations. Fourthly, the dynamics of ideal cable under impact was investigated to attempt to reveal the cable dynamics behind the collapsing of net structure when casting. The equations of motion for a flexible cable with snatch load acting at its ends are derived from the one-dimension continuum model, which are integrated with the finite difference method to investigate the processes of stress-waves propagating in cables and reflecting at a fixed end or a free end. The stress-waves propagation can reveal the underlying process when the cable changes between slack and tense. The results of stress-waves and energy analysis show the non-linear aspects of stress wave’s propagation due to the physical and geometrical non-linearity of the cable.Finally, schemes of net casting ground test and net castings on an aero ship were proposed. The results obtained in ground test and casting on an aero ship show the feasibility of the concept and design of the net capture system, especially the casting device and the net closing device. Dynamic models and simulations are verified with the data collected in ground test.To sum up, a systematic investigation of a net capture system was performed, in which the coupling dynamics of flexible cable structure and rigid bodies were modeled and simulated, and which provides a theory framework of the design of net capture systems. Ground tests of the net capture system prototype are important complement of the analysis and the investigation, which build a base to implement the orbit net capture system.更多还原