一种小行星探测陆标导航方法

针对小行星探测下降着陆段精确相对导航问题,提出了一种基于Stereophotoclinometry(SPC)陆标的相对导航方法.该方法先采用SPC光照模型渲染陆标的预测图像,再利用双线性插值从观测图像中生成陆标的提取图像.通过组合相关匹配实现预测图像与提取图像的高精度匹配,得到陆标中心点对应观测图像位置,即可利用N点透...     

Impact of gravitation on gaseous pollutant source identification

 It is necessary to identify a gaseous pollutant source rapidly so that prompt actions can be taken, but this is one of the difficulties in the inverse problem areas. In this paper, an approach to identifying a sudden continuous emission pollutant source based on single sensor information is developed to locate a source in an enclosed space with a steady velocity field. Because the gravity has a very important influence on the gaseous pollutant transport and the source identification, its influence is analyzed theoretically and a conclusion is drawn that the velocity of fluid is a key factor to effectively help weaken the gravitational influence. Further studies for a given 2-D case by using the computational fluid dynamics (CFD) method show that when the velocity of inlet is less than one certain value, the influence of gravity on the pollutant transport is very significant, which will change the velocity field obviously. In order to quantitatively judge the practical applicability of identification approach, a synergy degree of the velocity fields before and after a source appearing is proposed as a condition for considering the influence of gravity. An experimental device simulating pollutant transmission was set up and some experiments were conducted to verify the practical application of the above studies in the actual gravitational environment. The results show that the proposed approach can successfully locate the sudden constant source when the experimental situations meet the identified conditions.     

三星时差定位系统的有源校正算法

针对三星时差（TDOA）定位系统中,由星历误差和时间同步误差导致无法精确定位的问题,提出一种基于正交投影的两步迭代有源校正算法。该算法首先利用正交投影将时间同步误差从观测方程剔除,然后引入一个与辐射源位置和星历误差有关的中间变量,通过对中间变量的最优估计消除星历误差对定位精度的影响,最后利用中间变量求解出目标辐射源位置。仿真结果表明,所提算法定位性能的仿真值和理论值均可以达到克拉美-罗界（CRLB）,当TDOA观测噪声较小且有3个以上参考源时,可以完全校正星历误差和时间同步误差对定位精度的影响。     

高轨飞行器主动段双向测控陆基导航方案

高轨飞行器主动段飞行过程中,倒置GPS导航等传统陆基导航方案存在资源需求高、导航精度差等问题.研究了地天地双向测控(TT&C)陆基导航方案和天地天双向测控陆基导航方案,建立了时序分析模型,阐述了天地天双向测控陆基导航方案的定位数据使用延迟约为地天地双向测控陆基导航方案的1/2.通过理论分析推导和仿真验证,对比了不同陆基...     

Enhancement and Validation of the IDES Orbital Debris Environment Model

Orbital debris environment models are essential in predicting the characteristics of the entire debris environment, especially for altitude and size regimes where measurement data is sparse. Most models are also used to assess mission collision risk. The IDES (Integrated Debris Evolution Suite) simulation model has recently been upgraded by including a new sodium–potassium liquid coolant droplet source model and a new historical launch database. These and other features of IDES are described in detail. The accuracy of the IDES model is evaluated over a wide range of debris sizes by comparing model predictions to three major types of debris measurement data in low Earth orbit. For the large-size debris population, the model is compared with the spatial density distribution of the United States (US) Space Command Catalog. A radar simulation model is employed to predict the detection rates of mid-size debris in the field of view of the US Haystack radar. Finally, the small-size impact flux relative to a surface of the retrieved Long Duration Exposure Facility (LDEF) spacecraft is predicted. At sub-millimetre sizes, the model currently under-predicts the debris environment encountered at low altitudes by approximately an order of magnitude. This is because other small-size debris sources, such as paint flakes have not yet been characterised. Due to the model enhancements, IDES exhibits good accuracy when predicting the debris environment at decimetre and centimetre sizes. Therefore, the validated initial conditions and the high fidelity future traffic model enables IDES to make long-term debris environment projections with more confidence.     

销钉接触对电位法测试精度影响的边界元分析

 用边界元法分析了销钉接触对3种电流输入方式下紧凑拉伸试样的电位函数影响。结果表明,销钉接触对电位测试精度有显著影响。试验中应首先考虑对俏钉孔进行绝缘。当不可能对销钉孔进行绝缘时,应对电位函数进行修正或变换电流输入位置。     

工艺装备结构与孔系加工精度的工艺分析

根据公差项目的特征要求，对某产品零件孔系加工的生产实际进行了工艺分析，对造成零件孔系加工误差的各项因素进行了定性和定量分析，找出了造成误差的根本原因是工艺装备结构设计带来的系统误差过大和加工工艺方法的缺陷的影响。在此分析的基础上对工艺装备的设计进行了改进，并对加工工艺进行了相应的调整，达到了预期的加工目的。这种技术工作方法，对生产现场的工程技术人员来说是基本要求，也是解决机械制造工艺问题的有效途径。     

概念设计阶段飞机起飞总重的估算

介绍了概念设计阶段飞机起飞总重估算的思路，特别是按照这种处理问题的思路提供了飞机起飞总重估算所用到的一个公式及其推演过程。公式是着眼于第三代／第四代飞机起飞总重估算建立的，当然适用于该类飞机起飞总重的估算。     

直线电机在划片机中的应用

介绍了直线电机在划片机中的应用,结果表明,直线电机在高精度定位和进给方面,性能优异。     

归零压差式攻角传感器位置误差低速风洞校测试验

本文介绍归零压差式攻角传感器位置误差风洞校测试验方法、项目、数据处理和校测结果。附录中给出了传感器精度指标计算例题。