铝合金平板超高速撞击声发射信号S2模态特征分析

对铝合金平板上形成的超高速撞击(HVI)声发射(AE)信号S2模态的特征进行研究,分析其与损伤模式之间的关系。以3 mm厚5A06铝合金平板为研究对象,通过数值仿真获得不同撞击工况下的超高速撞击声发射信号,提取信号中的S2模态,并分析其幅值、能量、频谱等特征。结果表明,S2模态能量随传播距离呈指数衰减;分别随撞击弹丸直径和撞击速度的增加先下降后上升,且在弹丸直径与靶板厚度相近、临界撞击速度时最低。S2模态的中心频率随弹丸直径的增加而降低;随撞击速度的增加而增加;随传播距离的增加向1500 kHz移动。S2模态小波包系数呈凹性的频域范围分别随撞击速度和弹丸直径的增大变窄。在此基础上,当靶板形成穿孔损伤时,可根据S2模态的中心频率推测弹丸的直径;在传播距离和弹丸直径已知的前提下,可根据S2模态小波包系数呈凹性的频域范围推测撞击速度。     

一种适用于空间监视跟踪的递推滤波算法

针对空间监视跟踪环境中对于包含角变量的状态向量估计存在精度较低的缺点,利用Gauss von Mises（GVM）多变量概率密度分布,提出一种基于矩匹配的GVM参数估计方法,并在此基础上改进GVM分布的确定性采样方法,建立针对GVM分布的递推滤波算法,该算法充分考虑了流形的内蕴结构,克服了传统滤波方法假设状态向量定义于欧氏空间及采用欧氏空间中高斯分布模型的局限性。仿真结果表明,该滤波算法能有效估计状态变量的后验概率分布,对角变量的估计精度明显优于扩展卡尔曼滤波方法(EKF)。     

空间机械臂关节零部件对关节总刚度的影响分析

大型空间机械臂关节用大传动比多级行星齿轮传动的复杂性给刚度分析和减小质量都带来了困难,用传统的有限元法进行关节刚度分析还需解决复杂的建模问题。文章针对上述问题,采用集中参数法和刚度串联原理建立了复杂传动系统关节等效刚度的计算模型,分析了各级齿轮扭转刚度对关节总扭转刚度的影响,为空间机械臂大传动比关节的轻量化高刚度优化设计提供了技术途径。     

空间机器人一体化仿真系统的研究与实现

为对空间机器人关键算法进行验证和评估,开发了一套一体化仿真系统。该系统基于模块化设计思想,由遥测遥控接口、轨迹规划与控制、系统动力学模型、系统3D几何模型、相机成像模型、图像处理与位姿测量、碰撞检测与安全预警等模块组成。其中,3D实体模型及仿真场景由OSG(Open Scene Graph)建立,各关键模块的算法采用C语言编程实现,可对空间机器人执行在轨任务的关键算法进行闭环验证。最后对两种典型工况进行了仿真实验,结果表明了该系统的有效性。     

Recent Development and Preliminary Results of Chinese Meridian Project

The Meridian Project is a ground-based network program to monitor solar-terrestrial space environment, which consists of a chain of 15 ground-based observatories located roughly along 120°E longitude and 30°N latitude. The Meridian project started in 2008, and its construction was completed by 2011. The integration and test phase of the Meridian Project conducted in 2011 demonstrated its observation capabilities as expected. The project will be in full operation in 2012. This report gives an overview of the recent development and preliminary results of the Meridian Project since 2010.      

GNSS接收机中一种新的射频干扰抑制级联方法

为了减少系统复杂度和提高系统实时性,提出了一种新的级联算法。首先,通过三系数滤波器模型对连续波干扰进行建模,从而形成一种非线性卡尔曼自适应滤波器,并利用该滤波器作为预处理器对每路中的窄带干扰进行抑制。随后,将各路滤波器的输出送入空时自适应处理器中进行宽带干扰的抑制。仿真结果表明,在匹配谱干扰环境下,特别是在窄带干扰从卫星信号方向入射时,新算法相对于普通的空时和空频自适应处理表现出了更加优越的性能。     

人因工程学在飞机驾驶舱空间布局设计中的应用

回顾了当前驾驶舱设计中人因工程学的研究进展,重点探讨了人因工程学研究方法在飞机驾驶舱空间布局设计中的具体应用,总结了设计中需要遵循的原则,并对驾驶舱设计进一步的研究提出了若干建议。     

静电拉伸空间薄膜反射镜面形控制机理研究

薄膜反射镜将解决反射镜孔径与重量相互制约的问题. 采用静电拉伸法控制薄膜反射镜面形, 具有结构简单、反射镜面形易于控制等优点, 其原理为利用静电场上库仑力作用使薄膜产生面形变化, 生成所需的光学曲面. 由于薄膜变形力学, 以及静电场理论的复杂性, 目前薄膜成形及其面形控制在理论分析上仍未有定量的结果. 本文主要以单电极静电场中的薄膜反射镜面形为考察因素, 通过数值计算的方法得到薄膜反射镜上的静电力分布, 运用有限元分析获得该分布下的反射镜面形, 并将其与理想面形进行比较. 提出采用多电极闭环控制可获得更高的控制精度, 对静电拉伸薄膜的研究具有一定的指导意义.      

Capacity building in space law and space policy

A high level of expertise in space policy and law is required to initiate and keep pace with the expansion of space activities, including those undertaken by the private space industry. Space activities generally refer to those undertakings that are carried out with the use of several technologies for the exploration and utilization of outer space often for scientific, military, economic and social proposes within international and national policy and regulatory frameworks. Space policies and legal regimes determine the scope, nature, pace, possibility and development of space undertakings. Therefore, appropriate space policies and regulatory regimes, both at the international and national levels, are indispensable for the initiation, operation and enhancement of space activities. There are various regulatory models and approaches for regulating space activities, and for building capacity in space law and space policy. It is imperative to have the appropriate human resources and capabilities in the development and implementation of space policies and space legal regimes. This crucial requirement has been well recognized in the more advanced space-faring nations, but not to the same level in other space-faring or space-aspiring nations.     

Canadian advanced life support capacities and future directions

Canada began research on space-relevant biological life support systems in the early 1990s. Since that time Canadian capabilities have grown tremendously, placing Canada among the emerging leaders in biological life support systems. The rapid growth of Canadian expertise has been the result of several factors including a large and technically sophisticated greenhouse sector which successfully operates under challenging climatic conditions, well planned technology transfer strategies between the academic and industrial sectors, and a strong emphasis on international research collaborations. Recent activities such as Canada’s contribution of the Higher Plant Compartment of the European Space Agency’s MELiSSA Pilot Plant and the remote operation of the Arthur Clarke Mars Greenhouse in the Canadian High Arctic continue to demonstrate Canadian capabilities with direct applicability to advanced life support systems. There is also a significant latent potential within Canadian institutions and organizations with respect to directly applicable advanced life support technologies. These directly applicable research interests include such areas as horticultural management strategies (for candidate crops), growth media, food processing, water management, atmosphere management, energy management, waste management, imaging, environment sensors, thermal control, lighting systems, robotics, command and data handling, communications systems, structures, in-situ resource utilization, space analogues and mission operations. With this background and in collaboration with the Canadian aerospace industry sector, a roadmap for future life support contributions is presented here. This roadmap targets an objective of at least 50% food closure by 2050 (providing greater closure in oxygen, water recycling and carbon dioxide uptake). The Canadian advanced life support community has chosen to focus on lunar surface infrastructure and not low Earth orbit or transit systems (i.e. microgravity applications). To advance the technical readiness for the proposed lunar missions, including a lunar plant growth lander, lunar “salad machine” (i.e. small scale plant production unit) and a full scale lunar plant production system, a suite of terrestrial developments and analogue systems are proposed. As has been successfully demonstrated by past Canadian advanced life support activities, terrestrial technology transfer and the development of highly qualified personnel will serve as key outputs for Canadian advanced life support system research programs. This approach is designed to serve the Canadian greenhouse industry by developing compliance measures for mitigating environmental impact, reducing labour and energy costs as well as improving Canadian food security, safety and benefit northern/remote communities.