卫星表面材料物性与电荷积累

卫星表面在地磁亚暴环境下积累电荷的现象是必然的。由于表面间物性的差别,这种积累将是不均衡的,然而一旦建立了电势差,那末表面与表面,表面与构架间就会存在电荷交换,使电势差逐渐趋于减小。文章试图通过物理模型的建立,由此推导出面间电势差变化与表面电势值及表面的电导、电容的关系,从而建立一种明确的数学模型,以利卫星表面充电状态的分析。     

Design and application of an Electric Tail Rotor Drive Control (ETRDC) for helicopters with performance tests

With the development of electric helicopters’ motor technology and the widespread use of electric drive rotors, more aircraft use electric rotors to provide thrust and directional control. For a helicopter tail rotor, the wake of the main rotor influences the tail rotor’s inflow and wake. In the procedure of controlling, crosswind will also cause changes to the tail disk load. This paper describes requirements and design principles of an electric motor drive and variable pitch tail rotor system. A particular spoke-type architecture of the motor is designed, and the performance of blades is analyzed by the CFD method. The demand for simplicity of moving parts and strict constraints on the weight of a helicopter makes the design of electrical and mechanical components challenging. Different solutions have been investigated to propose an effective alternative to the mechanical actuation system. A test platform is constructed which can collect the dynamic response of the thrust control. The enhancement of the response speed due to an individual motor speed control and variable-pitch system is validated.     

基于粒子群算法的电帆轨迹优化设计

电帆是一种利用太阳风动量的新颖的无工质空间推进系统,文章研究了以电帆为对象的行星际转移轨迹优化问题。以地球轨道转移到火星、金星轨道为任务对象,采用连续推力模型,研究极坐标系下最小时间转移轨迹优化设计问题。提出了两种基于粒子群算法(PSO)的直接优化方法,避免对协态变量初值敏感的两点边值问题（TPBVP）求解。方法一是通过打靶法直接离散化控制量输入,将最优控制问题转化为非线性规划参数优化问题,采用PSO算法寻优,获得近似最优的转移轨迹。方法二是针对任何连续控制律曲线都能以一定精度的多项式函数进行曲线拟合的特性,设计逼近最优转移轨迹控制律的多项式函数,通过PSO算法优化多项式函数参数获得逼近最优解的转移轨迹。仿真结果表明采用上述两种方法进行转移轨迹优化设计,具有随机猜测初值、全局收敛、鲁棒性强的特点。     

Optimal nodal flyby with near-Earth asteroids using electric sail

The aim of this paper is to quantify the performance of an Electric Solar Wind Sail for accomplishing flyby missions toward one of the two orbital nodes of a near-Earth asteroid. Assuming a simplified, two-dimensional mission scenario, a preliminary mission analysis has been conducted involving the whole known population of those asteroids at the beginning of the 2013 year. The analysis of each mission scenario has been performed within an optimal framework, by calculating the minimum-time trajectory required to reach each orbital node of the target asteroid. A considerable amount of simulation data have been collected, using the spacecraft characteristic acceleration as a parameter to quantify the Electric Solar Wind Sail propulsive performance. The minimum time trajectory exhibits a different structure, which may or may not include a solar wind assist maneuver, depending both on the Sun-node distance and the value of the spacecraft characteristic acceleration. Simulations show that over 60% of near-Earth asteroids can be reached with a total mission time less than 100 days, whereas the entire population can be reached in less than 10 months with a spacecraft characteristic acceleration of 1 mm/s².     

Spectroscopic data and Stark broadening of Cu I and Ag I spectral lines: Selection and analysis

Optical emission and linear laser absorption spectroscopy techniques were used in investigation of plasma with copper and silver admixture. The method of selection of spectral lines and spectroscopic data with the aim of diagnostics of multicomponent air plasma with two metal vapors admixture was developed. Energy level populations behavior on the Boltzmann plot were used for Cu I and Ag I spectroscopic data selection. In this way the selection of spectroscopic data for some of Cu I and Ag I lines was realized. Stark broadening parameters of Cu I and Ag I were examined. Experimentally obtained temperature and electron density radial distributions were used in the calculation of plasma composition in the assumption of local thermodynamic equilibrium. Linear laser absorption spectroscopy was used to examine the state of plasma.     

基于SOC的卫星姿轨控系统通用电模拟器设计

在某型卫星地面电联试过程中,对该卫星的姿态轨道控制系统进行接口分析及信号统计,针对其接口复杂性、信号多样性的特点,提出采用片上系统(Systemona Chip,SOC)芯片对所有部件模拟器进行通用化设计。文中给出了该型卫星通用型电模拟器硬件平台设计方案以及陀螺、反作用轮和通用接口模块的硬件配置说明,针对该型卫星姿态轨道控制系统电联试要求,对所有部件按真实接口配置成电模拟器,形成通用接口箱、敏感器电模拟器箱和执行机构电模拟器箱,并通过CAN(Controller Area Network)总线接入闭环仿真,对太阳捕获、地球捕获及正常模式进行了仿真测试,仿真结果表明通用电模拟器满足设计要求,对其他卫星的地面电联试有很好的参考价值。     

基于LabVIEW的电动舵机智能检测系统设计与实现

以LabVIEW为应用程序开发平台设计了电动舵机智能检测系统,该系统改变原有手动测试为智能测试,自动化程度高,多种信号综合,以上限264M的PXI总线型高性能计算机为控制核心,采用信号集成和转换技术,实现不同性质信号的综合变换与处理,测试项目和准确度满足电动舵机的测试要求.     

Equatorial F-region vertical ion drifts during quiet solar maximum

Median values of ionosonde h′F data acquired at Ibadan (Geographic:7.4°N, 3.9°E, Magnetic: dip 6°S, and magnetic declination, 3°W), Nigeria, West Africa, have been used to determine vertical ion drift (electric field) characteristics in the postsunset ionosphere in the African region during a time of high solar activity (average F_10.7 −208). The database spans from January and December 1958 during the era of International Geophysical Year (IGY) for geomagnetic quiet conditions. Bimonthly averaged diurnal variations patterns are very similar, but differ significantly in magnitude and in the evening reversal times. Also, monthly variations of F-region vertical ion drift reversal times inferred from the time of h′F maximum indicates early reversal during equinoxes and December solstice months except for the month of April. Late reversal is observed during the June solstice months. The equatorial evening prereversal enhancement in vertical ion drift (V_zp) occurs largely near 1900 LT with typical values 20–45 m/s. Comparison of Ibadan ionosonde V_zp with the values of prereversal peak velocity reported for Jicamarca (South America), Kodaikanal (India), and Scherliess and Fejer global model show considerable disparity. The changes of postsunset peak in virtual height of F-layer (h′F_P) with prereversal velocity peak V_zp are anti-correlated. Investigation of solar effects on monthly values of V_zp and h′F_P revealed that these parameters are independent of monthly averaged solar flux intensity during quiet-time sunspot maximum conditions.     

电动无人机动力系统建模与实验

基于叶素修正理论和三维机翼气动系数计算公式,提出了一种分析双叶定距螺旋桨的新方法.并根据外转子无刷电动机工作原理及其特性,建立起电动无人机动力系统性能特性计算的数学模型.使用该模型分析了17组不同螺旋桨和电动机的零空速实验数据,结果表明:该模型原理正确,精度较高,且具有良好的工程操作性,能够有效提高电动无人机动力参数设计的可信度和精度.      

应用3D SPECK的视频编码方法

在基于提升格式的真三维小波包分解的基础上通过定义空间块结构, 实现了SPECK算法的真三维扩展。该方法不涉及运动估计和运动补偿, 具有计算量较小、编码快、低复杂的特点, 产生的视频流是完全嵌入的。实验结果表明该方法能够快速的高效的压缩视频图像, 是一种很有潜力的视频压缩编码方法。