基于LMS Virtual. Lab的系留气球仿真与优化

系留气球在近地面收放过程中存在俯仰角过大的问题，为了更全面地了解收放过程中不同因素对球体俯仰角的影响，采用LMS Virtua1. Lab建立了带滑轮索具系统的系留气球三维动力学模型进行仿真分析，结果表明，仿真结果与理论计算、测量数据都有较高的符合度。进而运用试验设计( DOE)方法，探索典型风速下球体俯仰角的响应区间。最后基于响应面模型的优化技术，对滑轮索具系统设计进行优化，有效改善了球体在收放过程中俯仰角过大的问题。仿真模型对系留气球系统设计及收放控制有一定的指导作用。     

基于液体静压导轨的大行程快刀伺服系统设计

采用了理论设计和有限元仿真分析相结合的方法,设计了基于液体静压导轨的大行程快刀伺服系统(最大加工行程30mm,行程4mm时频响不低于50Hz).首先,设计得到了基于液体静压导轨的大行程快刀伺服系统的结构模型和相关参数;接着,利用ANSYS/FLUENT软件对液体静压导轨的变形、模态以及油膜压力分布进行仿真分析,并且将油膜刚度的理论计算值和仿真计算值进行比较,验证了导轨设计的可靠性;最后,选用能够满足要求的音圈电机、位置反馈装置以及功能强大的MPAC运动控制器等完成了控制系统的搭建.     

仿真代理在导弹制导半实物仿真试验系统中的应用

针对独立运行的导弹制导半实物仿真试验系统接入联合试验系统的问题，应用了仿真代理的方法。在对原有系统控制关系进行最小化的改造前提下，通过控制接口的转换，实现了半实物仿真试验系统与其它异类异构系统之间的互联，拓展了半实物仿真试验系统的应用。     

WSO-UV project

During last three decades, astronomers have enjoyed continuous access to the 100–300 nm ultraviolet (UV) spectral range where the resonance transitions of the most abundant atoms and ions (at temperatures between 3000 and 300 000 K) reside. This UV range is not accessible from ground-based facilities. The successful International Ultraviolet Explorer (IUE) observatory, the Russian ASTRON mission and successor instruments such as the Galaxy Evolution Explorer (GALEX) mission or the COS and STIS spectrographs on-board the Hubble Space Telescope (HST) prove the major impact of observations in the UV wavelength range in modern astronomy. Future access to space-based observatories is expected to be very limited. For the next decade, the post-HST era, the World Space Observatory – Ultraviolet (WSO–UV) will be the only 2-m class UV telescope with capabilities similar to the HST. WSO–UV will be equipped with instruments for imaging and spectroscopy and it will be a facility dedicated, full-time, to UV astronomy. In this article, we briefly outline the current status of the WSO–UV mission and the science management plan.     

热力学排气系统中节流效应及其冷量利用分析

为更好地理解热力学排气系统(TVS)的运行机理，优化其运行参数，针对节流装置，建立了热力学模型，讨论了节流过程中状态参数的变化规律，对比了单相气体、单相液体节流的性能特性，进一步揭示了焦汤节流效应的原理，分析了不同节流背压下节流前低温工质(液氢和液氧)压力和温度对节流性能的影响，并结合TVS实际应用，阐述了节流最大制冷量的利用效果，提出了优化的TVS工作区间。研究表明：在节流过程不发生相变情况下单相气体节流制冷效应要比单相液体节流制冷效应更加显著；而在节流过程发生相变情况下液体节流至两相后，由于空化吸热导致流体温度降低，对于液氢，0.5MPa的压降可产生接近3 K的温降。对于液体节流，节流前压力对节流过程影响可忽略，〖JP2〗而节流前温度和节流背压对节流过程起主导作用；对于液氢在在轨运行工况下，考虑到节流制冷量的充分利用，同时保证换热过程体积含气率不高于90%，推荐TVS系统中节流背压范围为75～143 kPa。     

某型飞机阻力伞抛放系统故障模式分析

针对某型飞机阻力伞系统放伞、抛伞故障,通过分析系统的组成、工作原理、常见故障模式以及故障原因,提出了改进建议,为该型飞机阻力伞抛放系统故障的排除提供思路。     

RTK model and positioning performance analysis using Galileo four-frequency observations

This paper proposes a real-time kinematic (RTK) model that uses one common reference satellite for the Galileo system with four frequency observations. In the proposed model, the double-differenced (DD) pseudorange and carrier phase biases among the different frequencies are estimated as unknown parameters to recover the integer features of the DD ambiguities among the different frequencies for ambiguity resolution and precise positioning. Analysis results show that the E5a, E5b, and E5 frequencies have virtually the same performance in terms of the positioning accuracy, observation residuals, and ratio values of ambiguity resolution. However, the E1 frequency performs worse than the E5a, E5b, and E5 frequencies. The RTK results for the combination of multiple frequencies are much better than those for a single-frequency observation, the coordinates’ standard deviation is improved about 20–30%, and the ambiguity fix time is improved about 10%.     

Geometric error analysis of an over-constrained parallel tracking mechanism using the screw theory

This paper deals with geometric error modeling and sensitivity analysis of an overconstrained parallel tracking mechanism. The main contribution is the consideration of overconstrained features that are usually ignored in previous research. The reciprocal property between a motion and a force is applied to tackle this problem in the framework of the screw theory. First of all, a nominal kinematic model of the parallel tracking mechanism is formulated. On this basis, the actual twist of the moving platform is computed through the superposition of the joint twist and geometric errors. The actuation and constrained wrenches of each limb are applied to exclude the joint displacement. After eliminating repeated errors brought by the multiplication of wrenches, a geometric error model of the parallel tracking mechanism is built. Furthermore,two sensitivity indices are defined to select essential geometric errors for future kinematic calibration. Finally, the geometric error model with minimum geometric errors is verified by simulation with SolidWorks software. Two typical poses of the parallel tracking mechanism are selected, and the differences between simulation and calculation results are very small. The results confirm the correctness and accuracy of the geometric error modeling method for over-constrained parallel mechanisms.     

基于特征的数控编程技术在航空企业的推广应用

针对国内航空企业飞机结构件数控编程中存在的重复工作量大、效率低、质量不稳定、规范性差等问题,通过面向多主机厂推广基于特征的数控编程技术,切实提高飞机结构件数控编程的效率与质量.首先概述了基于特征的快速程编(FBM NUAA)系统的整体架构,并且介绍了基于特征的数控编程技术在多家主机厂中的推广与应用情况,以及前期推广中遇到的问题,并提出了解决方案.根据多主机厂多机型过百项飞机结构件的实际应用结果表明采用基于特征的快速程编系统进行数控编程,刀轨平均自动生成率超过90％,编程时间较传统编程方式平均缩短70％以上.     

A data-driven approach to modeling high-density terminal areas: A scenario analysis of the new Beijing,China airspace

Airports are being developed and expanded rapidly in China to accommodate and pro-mote a growing aviation market. The future Beijing Daxing International Airport (DAX) will serve as the central airport of the JingJinJi megaregion, knitting the Beijing, Tianjin, and Hebei regions together. DAX will be a busy airport from its inception, relieving congestion and accommodating growth from Beijing Capital International Airport (PEK), currently the second busiest airport in the world in passengers moved. We aim to model terminal airspace designs and possible conflicts in the future Beijing Multi-Airport System (MAS). We investigate standard arrival procedures and mathematically model current and future arrival trajectories into PEK and DAX by collecting large quantities of publicly available track data from historical arrivals operating within the Beijing terminal airspace. We find that (1) trajectory models constructed from real data capture aberrations and deviations from standard arrival procedures, validating the need to incorporate data on histor-ical trajectories with standard procedures when evaluating the airspace and (2) given all existing constraints, DAX may be restricted to using north and east arrival flows, constraining the capacity required to handle the increases in air traffic demand to Beijing. The results indicate that the termi-nal airspace above Beijing, and the future JingJinJi region, requires careful consideration if the full capacity benefits of the two major airports are to be realized.