空间对接机构对接锁系同步性仿真研究

对接锁系运动同步性指标是空间对接机构实现正常连接和分离的重要技术参数。对接锁系运动同步性仿真的难点在于柔性钢索在ADAMS中的模化问题,通过数学关系以子程序的形式来模拟钢索的作用,以此来研究对接锁系的同步性问题。最后,依据仿真结果指出了影响对锁锁系的同步性问题的主要因素并给出了合理的仿真建议。
     

结构锁解锁同步性影响因素分析

对影响对接机构结构锁解锁同步性的因素进行了研究。建立了结构锁解锁的力学模型,分析了锁钩啮合量、锁钩摩擦力、拉簧力和端面分离力等因素的影响规律,提出了提高结构锁解锁同步性的措施。研究结果经试验验证,解决了分离角速度过大的问题。     

对接机构隔框锁的接触碰撞动力学研究及仿真

为了给空间对接飞行器提供地面试验的参考依据。验证隔框锁结构设计的正确性和对接过程的可行性。本文针对隔框锁实例，在其运动平面内以均匀B样条曲线抉合锁钩外轮廓。并建立起接触碰撞动力学微分方程和仿真模型，分析了刚体碰撞的过程，刚性接触的单边约束条件和考虑变形接触的法向计算方法，文章还提出了基于几何引擎的接触点的实时判别算法，并给出了对接完成锁钩的接触力，动能及动量的仿真曲线图。计算过程稳定，所得结果合理，具有重要的参考价值。     

对接过程中捕获锁质量和锁合面间隙影响分析

采用弹性接触动力学有限元和多刚体动力学方法分别对航天器对接接触碰撞过程和对接机构捕获、缓冲与校正过程进行了数值模拟,对比分析了捕获锁质量对捕获过程的影响及捕获锁锁合面间隙对捕获后对接过程的影响。从仿真结果可以看出,附加质量有利于主、被动对接环之间形成接触滑移,捕获后锁合面间隙引起两飞行器间相对速度震荡,并延迟了碰撞力和缓冲时间。     

空间对接组件中的结构锁及其传动系统

空间对接组件结构锁及其传动系统研究是空间对接技术中的重要组成部分。本文讨论了对接组件几类典型结构锁及其传动系统的结构组成及工作原理,分析比较了它们的特点,为工程应用提供基础。     

空间对接机构结构锁传动原理分析

针对异体同构周边式对接机构，提出了两种结构锁主动锁钩传动方案，分别对其运动原理及特点进行分析比较。数值仿真结果表明，在不同的电机驱动功率、作动时间和执行端行程等条件下，结构锁传动系统应采用不同传动方案。     

对接综合试验台轨迹规划算法研究

为实现模拟空间两飞行器对接动力学过程的对接综合试验台的平稳对接，提出了一种基于加速度控制的轨迹规划算法。给出了不同初始条件下的规划方法，以及时转动自由度的特殊处理。物理试验结果表明，规划模型能精确控制平台从初始零位运动到主被动对接机构初次接触位置，且最后时刻平台姿态与对接试验的初始条件完全吻合。该算法可直接用于对接综合试验台的控制。     

遗传算法在空间对接机构优化设计中的应用

空间对接机构是实现载人航天器空间交会对接的关键系统。捕获锁作为对接机构的组     

对接机构综合试验台运动模拟器建模分析

空间对接机构六自由度综合试验台，是对接机构研制所必须的地面试验设备之一，用于对接机构空间对接过程的仿真试验，全面考核对接机构的捕获与缓冲校正能力。利用虚功原理建立了对接机构综合试验台运动模拟器的多体动力学模型，该模型全面地表征了六自由度运动模拟器的动力学特性，且具有简单、通用的形式，对六自由度运动平台的液压驱动系统进行了建模，从而建立六自由度运动模拟器系统模型。在建立该模型的基础上，使用Simulink对运动模拟器的位置跟踪特性进行了仿真分析，结果表明所设计的控制系统满足工程试验的需求。     

空间飞行器的对接分离与地面模拟试验的仿真分析研究

对两对接飞行器的分离过程和地面模拟试验过程进行了理论分析,论述了两飞行器在分离瞬 间空间分离过程与地面模拟试验过程之间的对应比拟关系;依据地面试验中给出的多种工况 ,利用多体动力学软件ADAMS仿真分析并比对了地面和空间零重力两种环境条件下两飞行器 分离时的运动特性,讨论了地面五自由度对接分离气浮平台模拟两飞行器在空间实际分离时 带来的原理误差影响。     

“爱国者”雷达组网对TBM目标的拦截性能分析

研究了"爱国者"导弹系统对TBM目标的拦截性能,建立了PAC-2的拦截概率模型,依据"爱国者"导弹系统的相关参数进行了仿真分析,并给出了典型弹道下的拦截性能仿真结果.     

卫星数据搜集系统(DCS)的技术现状与改进概念探索

对当前国际上流行的 DCS系统进行简介及评述 ,指出各自的优缺点 ,并提出多普勒频率补偿、自主计算开机时间和捷径点发报两种构想进行革新     

箔条质心干扰中的发射和机动决策仿真研究

针对反舰导弹的来袭方位、作战海域的海况,如何确定干扰弹的发射方案和舰艇的规避机动方案是箔条质心干扰战术运用需要解决的关键问题。采用动态仿真的方法,分析了箔条质心干扰的效果与反舰导弹威胁方向、干扰弹发射舷角、舰艇规避机动方向、作战海域的风速风向等要素的关系,得出了质心干扰时干扰弹发射和舰艇机动的一些原则。     

直扩通信系统中码跟踪环的抗干扰性能

同步是通信的基础。文章分析了直扩通信系统码跟踪中常用的一种非相关延迟锁定环在连续波(CW)干扰、高斯白噪声和部分频带干扰下的跟踪误差方差,并通过仿真验证了理论推导结果,所得的结论对于延迟锁定环路的分析和设计有重要意义。     

细节信息容量与MTF相关分析

文章从信息容量的角度出发,对图像宏观质量做出评价,再通过研究图像的细节信息容量参数,对在宏观上质量相当的图像做出更进一步的评价,挑选出边缘清晰、纹理等细节信息丰富的图像。然后将该评价参数与Ealing仪测得的调制传递函数(MTF)值的变化趋势作曲线回归分析,实验结果表明,细节信息容量与数字成像系统的MTF值的变化有着很好的正相关关系,这对评价数字成像系统MTF变化情况具有较好的实际应用价值。     

突发通信系统中的OFDM同步技术研究

在突发通信中,要求系统的同步能够达到快速准确,以便通信的顺利进行。文章针对应用于突发系统中的OFDM的同步问题做了深入研究,分析了系统中主要存在的三种同步:符号同步、样值同步以及载波同步的原理,并给出了具体实现算法。仿真结果表明,所给出的方案是可行的。     

一个ATS平行测试程序的实现

自动测试系统(ATS)测试软件通常设计为一系列的数据采集、计算、显示(打印)的组合串,此法虽能完成给定的任务,但效率较低。本文介绍了一个ATS测试软件的平行程序设计方法,文中讨论了该软件的程序结构、通讯和同步,也介绍了ATS的系统配置、被测仪表特点及特殊要求。     

Measuring performance: Moving NASA Earth science products into the mainstream user community

Demonstrating performance of the applications of Earth observation satellite-based science data products and services is increasingly a requirement of government research agencies. We present efforts from the NASA-funded Earth Observing System Data and Information System's Synergy Project to measure performance in the development of applications from NASA research and development projects. We summarize challenges in monitoring performance and share our experience in evolving metrics over a 5-year project life. We demonstrate how to adapt project management processes and metrics from the information technology (IT) industry to Earth observation applications research and development. A roadmap for adapting IT processes and developing metrics and examples of quantitative and qualitative metrics are provided. Our findings suggest that designing and implementing these IT metrics will enhance project success, as defined by the degree of penetration of NASA products into the user community and level of non-NASA funding secured.     

Exchange of meteorites (and life?) between stellar systems

It is now generally accepted that meteorite-size fragments of rock can be ejected from planetary bodies. Numerical studies of the orbital evolution of such planetary ejecta are consistent with the observed cosmic ray exposure times and infall rates of these meteorites. All of these numerical studies agree that a substantial fraction (up to one-third) of the ejecta from any planet in our Solar System is eventually thrown out of the Solar System during encounters with the giant planets Jupiter and Saturn. In this paper I examine the probability that such interstellar meteorites might be captured into a distant solar system and fall onto a terrestrial planet in that system within a given interval of time. The overall conclusion is that it is very unlikely that even a single meteorite originating on a terrestrial planet in our solar system has fallen onto a terrestrial planet in another stellar system, over the entire period of our Solar System's existence. Although viable microorganisms may be readily exchanged between planets in our solar system through the interplanetary transfer of meteoritic material, it seems that the origin of life on Earth must be sought within the confines of the Solar System, not abroad in the galaxy.     

Chaotic exchange of solid material between planetary systems: implications for lithopanspermia

Abstract We examined a low-energy mechanism for the transfer of meteoroids between two planetary systems embedded in a star cluster using quasi-parabolic orbits of minimal energy. Using Monte Carlo simulations, we found that the exchange of meteoroids could have been significantly more efficient than previously estimated. Our study is relevant to astrobiology, as it addresses whether life on Earth could have been transferred to other planetary systems in the Solar System's birth cluster and whether life on Earth could have been transferred from beyond the Solar System. In the Solar System, the timescale over which solid material was delivered to the region from where it could be transferred via this mechanism likely extended to several hundred million years (as indicated by the 3.8-4.0?Ga epoch of the Late Heavy Bombardment). This timescale could have overlapped with the lifetime of the Solar birth cluster (～100-500?Myr). Therefore, we conclude that lithopanspermia is an open possibility if life had an early start. Adopting parameters from the minimum mass solar nebula, considering a range of planetesimal size distributions derived from observations of asteroids and Kuiper Belt objects and theoretical coagulation models, and taking into account Oort Cloud formation models, we discerned that the expected number of bodies with mass>10?kg that could have been transferred between the Sun and its nearest cluster neighbor could be of the order of 10(14) to 3·10(16), with transfer timescales of tens of millions of years. We estimate that of the order of 3·10(8)·l (km) could potentially be life-bearing, where l is the depth of Earth's crust in kilometers that was ejected as the result of the early bombardment. Key Words: Extrasolar planets-Interplanetary dust-Interstellar meteorites-Lithopanspermia. Astrobiology 12, 754-774.