On the Lagrange and Hill stability of motion in the three-body problem

In the three-body problem, we consider the Lagrange and Hill stability including the Lagrange stability for the manifold of symmetric motions that exists in the case where two of three bodies have equal masses. To analyze the stability, in addition to integrals of energy and angular momentum we use the Lagrange–Jacobi equality. We prove theorems on the Lagrange and Hill stability. The theorem on the Hill stability has effective application in the case where the mass of a body is much less than masses of two other bodies. In this case, as it is known, the model of the restricted three-body problem is usually applied.     

Long term dynamics and optimal control of nano-satellite deorbit using a short electrodynamic tether

This paper studies the long term dynamics and optimal control of a nano-satellite deorbit by a short electrodynamic tether. The long term deorbit process is discretized into intervals and within each interval a two-phase optimal control law is proposed to achieve libration stability and fast deorbit simultaneously. The first-phase formulates an open-loop fast-deorbit control trajectory by a simplified model that assumes the slow-varying orbital elements of electrodynamic tethered system as constant and ignores perturbation forces other than the electrodynamic force. The second phase tracks the optimal trajectory derived in the first phase by a finite receding horizon control method while considering a full dynamic model of electrodynamic tether system. Both optimal control problems are solved by direct collocation method base on the Hermite–Simpson discretization schemes with coincident nodes. The resulting piecewise nonlinear programing problems in the sequential intervals reduces the problem size and improve the computational efficiency, which enable an on-orbit control application. Numerical results for deorbit control of a short electrodynamic tethered nano-satellite system in both equatorial and highly inclined orbits demonstrate the efficiency of the proposed control method. An optimal balance between the libration stability and a fast deorbit of satellite with minimum control efforts is achieved.     

轴承位置对涡轮泵转子系统稳定性的影响研究

针对低温液体火箭发动机涡轮泵转子非线性系统开展了轴承位置对稳定性的影响研究。建立了涡轮泵转子非线性系统的动力学模型,分别研究了理想安装时和非理想安装条件下泵端和涡轮端轴承位置变化对转子系统稳定性的影响,给出了失稳转速随轴向位置的变化规律,为液体火箭发动机涡轮泵转子系统结构设计、故障诊断与安装维护提供理论依据。     

跨音速运输机机身后体对航向静稳定性影响研究

采用课题组开发的CFD数值计算软件分别研究了跨音速上单翼布局运输飞机机身后体对航向静稳定导数的影响。研究过程中选择了两种后体构型型面：圆型面和立椭圆型面．分别对其气动力特性进行了计算分析。结果表明：圆型面后体的机身提供的航向静不稳定导数比立椭圆型面后体的机身提供的航向静不稳定导数大17．5％。     

金属热防护系统动力学建模研究

研究了金属热防护系统的动力学建模及简化计算方法.首先,给出了蜂窝结构面外的等效热导率、比热容、密度和弹性系数的表达式,并给出了算例验证;其次,建立了包括外层蜂窝、中间防热层、内层蜂窝、应变隔离层和承力结构的完整模型,研究了外表面受高温加热情况下结构的热力学响应及弯曲模态;最后,提出了带金属热防护系统的结构弯曲热模态计算...     

飞翼布局无人机的稳定与操纵特性分析研究

从气动和控制综合设计角度,提出了解决飞翼布局无人机稳定能力问题的多轴静不稳定增稳控制规律,通过对多操纵面操纵特性和操纵需求分析给出了操纵面的配置策略.仿真分析表明,所提出的设计方法较好地解决了飞翼布局无人机特殊的稳定与操纵问题.     

化学回热循环中工质热力性质的处理方法

采用VC和Matlab混合编程的方法,编制了CRGT循环中工质（水-水蒸气和空气-湿燃气）的热力性质计算程序。空气和干燃气的热力性质采用理想气体掺混模型,水和蒸汽的热力性质采用IAPWS-IF97标准模型,湿燃气的热力性质采用改进的工程计算方法进行处理。计算结果表明：该方法计算精度高、计算速度快。     

改善铷原子钟物理部分温度系数的研究

铷原子钟的温度系数是决定其长期频率稳定度的关键因素,物理部分的温度系数又是铷原子钟温度系数的重要组成部分.为了改善物理部分的温度系数,在理论分析的基础上开展了试验研究,结果表明:提出的改善物理部分温度系数的措施是有效的.这对于进一步提高星载铷原子钟频率稳定度具有积极作用.     

月球车释放对着陆器稳定性的影响

因基于摇臂式月球车释放机构在月球车释放时对着陆器的倾翻力矩较大,易使着陆器倾翻而导致整个探测任务失败,所以对月球车着陆释放时着陆器稳定性的研究尤为重要.将着陆器腿不等量压缩、月面坡度、低重力环境、释放加速度等因素进行参数化处理;应用D-H坐标法得到基于各参量的支撑多边形坐标以及着陆器和月球车的位姿方程,进而建立了月球车...     

黏性彻体力建模方法及其应用

研究了将Navier-Stokes方程中黏性项简化为黏性彻体力的建模方法,并将该模型加入已有的计算流体力学(CFD)程序中,实现了用三维欧拉方程加黏性彻体力模型快速模拟叶轮机三维非定常流动的方法.使用该方法对进气周向总压畸变条件下的某双级压气机非定常流场进行了模拟,并与雷诺平均的Navier-Stokes(RANS)程...