基于希尔伯特-黄算法瞬时测频的DSP实现

文章阐述了希尔伯特-黄瞬时测频技术的基本原理,介绍了希尔伯特．黄瞬时测频算法的DSP软件实现,包括系统软件设计框架介绍、子系统任务划分、DSP／BIOS的应用、BOOT模块、数据处理模块和HPI模块等内容,并给出了实际系统的性能分析。     

风洞分布式支撑天平测力试验技术研究

采用双尾支撑测量形式的加工、装配误差会使系统内应力过大,影响测量精度。针对某“双机身”飞机CTS 风洞试验气动力测量需求,发展基于多维力天平内置的风洞分布式支撑天平测力试验技术;研制具有消除系统内应力功能的双支撑系统,提出两种6 分量双支撑天平校准及测力方法,并对数据处理和双支撑系统可靠性进行检验加载、对比分析和验证。结果表明：风洞分布式支撑天平测力试验技术能够有效消除双支撑天平系统由于过约束而导致的固有装配内应力,双支撑天平系统各部分连接、测量可靠;两种校准测力方法测量精度相当,均能达到单台应变天平测量误差水平,可满足风洞试验测量精度需求;综合考虑现有校准设备校准能力,最终采用“合成式校准测力”方法进行的风洞试验,获得了满意的试验测力精度。     

Form-finding methods for deployable mesh reflector antennas

Deployable high-frequency mesh reflector antennas for future communications and obser- vations are required to obtain high gain and high directivity. In order to support these new missions, reflectors with high surface accuracy are widely required. The form-finding analysis of deployable mesh reflector antennas becomes more vital which aims to determine the initial surface profile formed by the equilibrium prestress distribution in cables to satisfy the surface accuracy requirement. In this paper, two form-finding methods for mesh reflector antennas, both of which include two steps, are pro- posed. The first step is to investigate the prestress design only for the cable net structure as the circum- ferential nodes connected to the supporting truss are assumed fixed. The second step is to optimize the prestress distribution of the boundary cables connected directly to the supporting truss considering the elastic deformation of the antenna structure. Some numerical examples are carried out and the simulation results demonstrate the proposed form-finding methods can warrant the deformed antenna reflector surface matches the one by design and the cable tension forces fall in a specified range.     

Passive inter-modulation scattering analysis of reflector considering contact nonlinearity

 Passive inter-modulation (PIM) is a form of nonlinear distortion caused by the inherent nonlinearities of the passive devices and components in RF/microwave system. It will degenerate the performance of communication system with broad-band channel and high-sensitivity receiver. Therefore, it is necessary to construct a model to simulate this process in order to predict the level of PIM. This paper is aimed at constructing some plate models with one-dimensional and two-dimensional contact nonlinearity sections illuminated by two-tone waves, and calculating the scattered field at a fixed-point in space using time-domain physical optics method. By taking fast Fourier transform (FFT), we get the spectrum of the scattered field and then analyze the generated PIM products. At the end of this paper, some numerical examples are presented to show the influence rules of the relative factors on PIM. The results indicate the variation of the level of PIM with the number of the nonlinear regions, the nonlinear spacing, and the incident power levels.     

“动中通”三轴天线跟踪机理研究

基于捷联跟踪式三轴天线“动中通”系统推导了天线姿态角求解算法,并且定义了天线俯仰角和方位角范围。针对工程中出现的三轴天线“动中通”系统在低纬度地区跟踪卫星时天线方位角跳变的情况,在理论分析的基础上结合仿真得出了天线姿态角突变的机理。由于卫星矢量在车体系内水平两个坐标分量的符号会出现改变,从而引起天线方位角的突变,引起伺服系统驱动能力不足,致使跟踪中断。最后针对该问题设计了两种解决方案。     

Experimental investigation on deformation behavior of TJ-1 lunar soil simulant subjected to principal stress rotation

The knowledge of mechanical properties of lunar soil is of fundamental importance for the coming exploration of the Moon. This paper aims to investigate the fundamental deformation behavior of lunar soil and the effects of the intermediate principal stress coefficient, deviatoric stress ratio, and mean stress during the principal stress rotation. First, an improved technique was proposed to generate homogeneous samples based on the Multi-layer Undercompaction Method. Second, three series of tests on TJ-1 lunar soil simulant under the principal stress rotation were performed with a hollow cylinder apparatus at Tongji University, China. In each series of tests, only one value of the three variables mentioned above was changed while the others were kept constant. The test results demonstrate that the rotation of principal stress can result in significant plastic deformation, volumetric strain, and non-coaxiality (non-coincidence of the increment direction of principal plastic strain with the principal stress direction) of TJ-1 lunar soil simulant. In addition, it is found that the intermediate principal stress coefficient, deviatoric stress ratio, and mean stress have different influences on the four strain components, i.e. _εz,_εr,_εθ${\epsilon }_z\text{,}{\epsilon }_{\text{r}}\text{,}{\epsilon }_{\theta }$ and _γzθ${\gamma }_{z\theta }$, volumetric strain, and non-coaxiality during the principal stress rotation. The influence of deviatoric stress ratio is relatively stronger than the others. Therefore, the influence of principal stress rotation on the deformation behavior of lunar soil should be taken into account carefully in the design and construction of facilities on the lunar surface in the future.     

薄壁铸件基准面加工工装改进

针对薄壁铸件精基准面机械加工精度低、变形大的问题,分析了工装改进的原因,对工装的主要结构进行了改进,并以实例辅助说明,改进后的工装应用效果良好。     

基于优度评价的反辐射导弹攻击方式效能评估

分析影响反辐射导弹（ARM）攻击方式的主要衡量指标,建立指标模型,利用改进的层次分析法确定指标权重,并建立各种攻击方式对应指标的关联函数,通过优度评价法,对几种典型ARM攻击方式作战效能进行评价,为ARM攻击方式的选择提供了一种有效的方法。     

基于JPDA的单站多目标无源定位

复杂电磁环境下,对多目标的定位成为单站无源定位的重要问题。研究了单站只测角定位体制下,多点源测角后如何利用多个方向圆锥角进行多目标定位的问题,对雷达多目标跟踪的JPDA算法进行了改进,并做了典型场景下的仿真实验,对单站多目标无源定位技术的研究提供了理论和实验支持。     

弦支组合网架结构可靠度分析

根据张弦梁结构的思想提出由组合网架和索通过支杆相连而形成的预应力结构即弦支组合网架结构。建立一弦支组合网架结构的计算模型,利用ANSYS有限元软件分析结构基于位移性能下的正常使用极限可靠度。经软件分析得出在所给几何尺寸、材料特性、预应力、恒荷载以及活荷载等随机变量作用下,结构基于位移正常使用极限状态下的可靠度是良好的;对结构位移影响最大的变量是预应力,影响最小的变量是混凝土板肋的截面尺寸;可靠度为95%的结构最大位移值是60mm。