直升机旋翼试验台动力学分析及建模

直升机旋翼动平衡试验台是一种主要的直升机旋翼测试设备之一,对试验台进行动力学分析和建模可以提高试验台的控制精度和试验的效果.在分析试验台结构和功能的基础上,简化了桨叶变距拉杆的载荷,通过对自动倾斜器的受力分析,得出了旋翼系统的动态模型.通过对液压系统和旋翼系统的联合仿真,分析了系统在旋翼姿态变化时的动态响应和交互耦合影响,初步了解了系统在各种不同负载特性下的响应,为试验台的姿态调节、激振的精度提高和进行理论研究提供基础,并为地面旋翼试验台系统的设计和控制提供依据.     

控制力矩陀螺框架高精度周期随动控制

为实现控制力矩陀螺框架伺服系统的高精度周期随动控制,采用比例积分微分(PID,Proportion Integration Differentiation)控制器结合重复控制器的控制方式,PID控制器实现框架伺服系统静态和匀速运动的高精度控制,插入式重复控制器实现对周期性输入信号的精确跟踪.对控制力矩陀螺框架系统进行了建模,设计了PID控制器与插入式重复控制器,并分析了重复控制器的稳定性条件、稳态跟踪性能和对扰动的抑制能力.仿真结果和实验结果表明:采用插入式重复控制器使控制力矩陀螺跟踪1Hz给定速度信号时的稳态跟踪误差大幅减少.PID控制器结合插入式重复控制器结构简单,两者可分开独立设计,参数设计容易.     

ZnO纳米颗粒薄膜的制备与光致发光特性研究

利用高分子包覆法(Polymer Capping Method)在Si衬底上生长了颗粒分布均匀、致密的纳米ZnO薄膜.样品的形貌和光学性能分别使用SEM,AFM和PL谱进行表征.实验发现,前驱体溶液的pH值对纳米颗粒的分散性和尺寸有很大影响,进而影响紫外发光峰位.在本实验条件下,随纳米颗粒尺寸增大,PL谱的紫外发光峰红移,符合量子尺寸效应.     

Study of the Enhancement Events of Relativistic Electron at the Geosynchronous Orbit

The high flux of energetic electron on geostationary orbit can induce many kinds of malfunction of the satellite there, within which the bulk-charging is the most significant that several broadcast satellite failures were confirmed to be due to this effect. The electron flux on geostationary orbit varies in a large range even up to three orders accompanied the passage of interplanetary magnetic cloud and the following geomagnetic disturbances. Upon the investigation of electron flux enhancement events, two types of events were partitioned as recurrent events and random ones. Both of the two kinds of events relate to the interplanetary conditions such as solar wind parameters, IMF etc and their evolution characters as well. As for the recurrent events, we found that, (1) all of the events exhibits periodic recurrence about 27 days, (2) significant increase of electron flux relates to interplanetary index and characters of their distribution, (3) the electron flux also has relation to solar activity index. An artificial neural network was constructed to estimate the flux I day ahead. The random electron flux enhancement events are rare and present different distribution figures to the recurrent ones. The figure of the random events and the conditions of their occurrence is also discussed in this paper.      

后缘喷流对三角翼前缘涡的影响

本实验应用染色液流动显示技术和激光测速技术 (LDV)研究了 6 0°后掠三角翼在后缘差动喷流、对称喷流情况下前缘涡破裂位置、涡核的空间分布、涡核的速度分布以及三角翼背风面流动结构随迎角的演化等。实验结果表明 ,喷流增大了三角翼前缘涡涡核保持高速度的区域 ,推迟了涡核减速的位置 ,在大迎角情况下 ,对称喷流有助于消除由前缘涡振荡引起的“摇滚”现象。     

一种改进的声反卷积相关声源定位方法

基于传声器阵列的声源定位算法的性能优劣决定了气动噪声试验检测中气动噪声源定位成像的准确性。为了提高相关声源定位方法的稳健性和准确性，提出一种改进的声反卷积相关声源定位方法——D-MACS（Developed-Mapping of Acoustic Correlated Sources）方法。该方法的特点是：在传统MACS方法的基础上，将声反卷积模型进行改进，使模型体现出声场空间扫描点声压互谱矩阵与互谱波束形成输出矩阵之间的数学关系，其最终获得的声源定位结果，能够提高MACS方法声源定位辨识的稳健性和准确性。通过仿真信号研究和声学风洞环境中的声源定位试验研究，比较了DAS（Delay And Sum beamformming）、DAMAS-C（Deconvolution Approach for the Mapping of Acoustic Correlated Sources）、MACS和D-MACS这4种方法的声源定位性能，验证了D-MACS方法在声源定位性能上的优势。     

Guidepost-based autonomous orbit determination method for GEO satellite

Guidepost-based navigation system is a novel autonomous orbit determination method for the GEO satellite. The system is achieved by using the camera imaging function to obtain the guidepost images and the GNSS signal receiver to obtain the pseudoranges between the GEO and the navigation satellites. Due to the high altitude of GEO satellite and the time-varying sunlight condition in the space environment, it may be difficult to obtain object image points and the distance measurements of GNSS because of the weak visibility of the guideposts. To deal with the problem, a novel integrated orbit determination system is presented. The Earth landmarks, the in-orbit spacecraft and GNSS navigation satellites whose line-of-sights and the distance can be easily obtained are used at the same time as information for the GEO satellite navigation based on the observability conditions analysis. The observability of the GEO satellite navigation system is analyzed through the physical observability, the mathematical observability and the engineering observability through the observing geometry, the rank of observability matrix and the Cramer-Rao lower bound (CRLB) respectively. Besides, the maximum correntropy unscented Kalman filter (MCUKF) algorithm is applied to improve the estimation stability of the system in the presence of non-Gaussian noises. The simulation indicates the feasibility of the proposed scheme.     

典型散射体低频特性估计

本文探讨了几种典型金属物体的低频散射问题。介绍了低频散射截面的计算方法；对计算结果进行了分析；并就雷达目标低频散射特性提出了作者的观点。     

利用透视投影基本方程选定透视形象的参数分析

在工程设计中，有些内容往往是工程设计人员根据一些不完整的历史资料萌发创作意念并概略地草构出透视表现图，虽然，在绘制标准的透视图时，这些资料所提供的参数是不够的，本文通过对物体三个主方向及其透视图中几何关系和矢量关系的分析，利用透视投影本方程由一已知物体的部分透视，确定其进行透视投影的全部参数，为透视变换和利用计算机绘制透视图提供了有效的基础条件。