由三个向量对构造三对角对称矩阵

文章讨论利用给定的三个向量对构造不可约三对角矩阵、Jacobi矩阵和负Jacobi矩阵的反问题.在求解方法中,将已知的-些关系式等价地转化为线性方程组,利用线性方程组有解的条件,得到了所研究问题有惟一解的充要条件,并给出了数值算法和例子.     

多姿态敏感器测量的信息融合定姿方法研究

基于最优融合估计理论,给出并证明了多敏感器组合姿态确定系统状态最优融合估计形式。设计了基于信息分配的多信息融合联合滤波器结构和算法,分析估计性能,讨论了决定联合滤波器融合的性能信息分配因子选择方法,提出了一种基于协方差阵特征值平方分解的动态自适应信息分配因子确定方法。以某卫星多姿态敏感器组合测量为例,推导了卫星姿态确定的误差状态方程和各子系统的量测方程及观测阵。仿真结果表明：采用联合滤波器对多敏感器卫星姿态确定系统进行信息融合能改善定姿精度,有效抑制滤波发散,并提高整个系统的运算与收敛速度。     

径流与斜流涡轮设计的通流反问题方法

自主发展了径流及斜流涡轮的准三维流线曲率法通流设计程序,应用该程序给出了一项500 N推力级微型涡喷发动机斜流涡轮的气动设计和叶片造型.通过计算流体力学检验和整体叶轮强度检验,该微型斜流涡轮超过了预定的设计指标.为实现径流涡轮和斜流涡轮设计反问题的统一,流线曲率法的S_2,m流面准径向平衡方程是沿流线方向m和流线的准法线方向口写出,该系统也可用于轴流涡轮的设计.采用了在所有计算站上的"全可控涡法"进行气动设计.      

太阳辐射对ER3BP拉格朗日点的影响

为了研究Halo轨道中继通信以及行星际轨道转移等问题,需要首先对拉格朗日点(平动点)的理论进行分析。使用考虑太阳辐射的椭圆型限制性三体建模,代替原有的圆型限制性三体建模,提高了建模的精度。提出了在L1,L2,L3点的更为精确的新解析解,经过Matlab仿真,其相对于精确数值解的误差,分别为Ammar的解析解的13.13%,29.51%,0.46%。     

Modeling of LEO orbital debris populations for ORDEM2008

The NASA Orbital Debris Engineering Model, ORDEM2000, is in the process of being updated to a new version: ORDEM2008. The data-driven ORDEM covers a spectrum of object size from 10 μm to greater than 1 m, and ranging from LEO (low Earth orbit) to GEO (geosynchronous orbit) altitude regimes. ORDEM2008 centimeter-sized populations are statistically derived from Haystack and HAX (the Haystack Auxiliary) radar data, while micron-sized populations are estimated from shuttle impact records. Each of the model populations consists of a large number of orbits with specified orbital elements, the number of objects on each orbit (with corresponding uncertainty), and the size, type, and material assignment for each object. This paper describes the general methodology and procedure commonly used in the statistical inference of the ORDEM2008 LEO debris populations. Major steps in the population derivations include data analysis, reference-population construction, definition of model parameters in terms of reference populations, linking model parameters with data, seeking best estimates for the model parameters, uncertainty analysis, and assessment of the outcomes. To demonstrate the population-derivation process and to validate the Bayesian statistical model applied in the population derivations throughout, this paper uses illustrative examples for the special cases of large-size (>1 m, >32 cm, and >10 cm) populations that are tracked by SSN (the Space Surveillance Network) and also monitored by Haystack and HAX radars operating in a staring mode.     

地面等待模型中的旅客延误时间成本分析与仿真

针对多机场地面等待问题MAGHP(Multi Airport Ground Holding Problem),深入研究了影响旅客延误时间的因素,并将其应用于数学模型中目标函数的计算。将航班延误时间转化为旅客延误时间,提出了一个在航班取消情况下减少旅客延误的新方法,并与多机场地面等待模型进行了比较,仿真结果表明,可以大幅度减少旅客延误时间。     

Low-thrust transfer to Backflip orbits

The aim of the work is to design a low-thrust transfer from a Low Earth Orbit to a “useful” periodic orbit in the Earth–Moon Circular Restricted Three Body Model (CR3BP). A useful periodic orbit is here intended as one that moves both in the Earth–Moon plane and out of this plane without any requirements of propellant mass. This is achieved by exploiting a particular class of periodic orbits named Backflip orbits, enabled by the CR3BP. The unique characteristics of this class of periodic solutions allow the design of an almost planar transfer from a geocentric orbit and the use of the Backflip intrinsic characteristics to explore the geospace out of the Earth–Moon plane. The main advantage of this approach is that periodic plane changes can be obtained by performing an almost planar transfer. In order to save propellant mass, so as to increase the scientific payload of the mission, a low-powered transfer is considered. This foresees a thrusting phase to gain energy from a departing circular geocentric orbit and a second thrusting phase to match the state of the target Backflip orbit, separated by an intermediate ballistic phase. This results in a combined application of a low-thrust manoeuvre and of a periodical solution in the CR3BP to realize a new class of missions to explore the Earth–Moon neighbourhoods in a quite inexpensive way. In addition, a low-thrust transit between two different Backflip orbits is analyzed and considered as a possible extension of the proposed mission. Thus, also a Backflip-to-Backflip transfer is addressed where a low-powered probe is able to experience periodic excursions above and below the Earth–Moon plane only performing almost planar and very short transfers.     

虚拟层次化无线mesh网络信道分配策略

为了获得具备良好的用户分集效果和路由稳定性的无线mesh网络,提出了一种虚拟层次化网络架构.这种无线mesh网络将临近节点聚合为虚拟小区,该小区内部节点不仅能够直接通信,还具有路由转发功能.虚拟小区内部节点之间的连接构成虚拟的底层网络,虚拟小区之间的连接则构成虚拟的顶层网络.为解决虚拟层次化无线mesh网络的信道资源分配问题,提出了一种图着色模型——广义集合T-coloring模型.该模型以虚拟小区为无线信道的分配单位,并采用射频防卫度为无线信道的干扰约束指标,在保证网络连通性的前提下,既降低信道干扰又提高信道利用率.采用虚拟小区分裂方式进一步增加了网络容量也提升了信道分配公平性.仿真结果验证了该策略的有效性.     

多机空战指挥引导不平衡目标分配方法研究

目前,存在多机空战指挥引导不平衡目标分配模型少的问题,提出一种新的多机空战不平衡目标分配方法。结合空战理论与实际,在现有模型的基础上,利用最优控制理论,建立多机空战指挥引导目标分配模型;介绍匈牙利算法和进化匈牙利算法的基本思想和流程,在此基础上将匈牙利算法和进化匈牙利算法相结合来寻求最优方案,并进行仿真分析。结果表明:该方法具有较好的时效性和可靠性,能满足多维条件下的目标分配处理,满足实战需求,为解决多机空战指挥引导不平衡目标分配问题拓展了研究思路。     

能量最优与燃料最优Lambert交会问题

Lambert双脉冲交会问题是航天工程中轨道转移和在轨交会等领域的重要问题,而能量最优和燃料最优Lambert交会问题是针对典型应用背景和工程需求衍生的一类Lambert优化问题。针对能量最优与燃料最优Lambert双脉冲交会问题提出一种基于矢量形式的解析计算方法,给出能量最优和燃料最优Lambert交会问题的矢量形式解析解,同时对2种最优交会问题求解的性质与特点进行了分析对比。仿真结果验证了计算的正确性及燃料最优轨道相比能量最优轨道燃料消耗较少的事实。