基于反馈线性化的可重复使用运载器上升段闭环制导

可重复使用运载器上升段轨迹跟踪是通过姿态跟踪间接实现的,采用开环制导方式,气动或者推力的不确定性可能会导致轨迹末端高度偏差较大,因此研究一种合适的闭环制导方式是非常必要的.本文采用基于输入输出反馈线性化的技术设计上升段标准轨道的跟踪方法,结合上升段飞行特点,动力爬升段和无动力爬升段分别通过反馈线性化技术将高度转化成与俯仰角和迎角的线性关系,然后通过线性系统技术设计闭环制导律,易于工程实现.非线性仿真结果表明,设计的制导策略能很好地实现轨迹跟踪.     

基于功势的燃气轮机燃气马力效率研究

基于燃气马力的物理内涵,推导出了燃气轮机各部件的燃气马力效率的表达式。根据各种效率具有“同时归一”的特性,从理论分析和数值计算上进行了验证。分析了各种参数对燃气马力效率的影响。结果表明：燃气马力效率不仅和部件效率有紧密的自然关系,还和其他热力参数(例如压比)有内在的逻辑关联。并从燃料燃烧的燃气马力效率的角度优化了压气机压比。     

Monocular Vision-based Two-stage Iterative Algorithm for Relative Position and Attitude Estimation of Docking Spacecraft

Visual sensors are used to measure the relative state of the chaser spacecraft to the target spacecraft during close range rendezvous phases. This article proposes a two-stage iterative algorithm based on an inverse projection ray approach to address the relative position and attitude estimation by using feature points and monocular vision. It consists of two stages: absolute orientation and depth recovery. In the first stage, Umeyama's algorithm is used to fit the three-dimensional (3D) model set and estimate the 3D point set while in the second stage, the depths of the observed feature points are estimated. This procedure is repeated until the result converges. Moreover, the effectiveness and convergence of the proposed algorithm are verified through theoretical analysis and mathematical simulation.     

CO_2激光烧蚀水所形成气蚀空穴机理研究

分析了激光烧蚀液体时形成表面空穴的机理。利用高速相机获得CO2激光烧蚀蒸馏水的流场照片,对空穴的发展过程进行了分析,发现空穴的快速发展期在最初的100μs内,之后在几百μs内保持平衡。用简单模型计算了不同能流密度下,空穴平衡时的形状,并分析了模型的局限性。研究结果对于揭示激光烧蚀水产生推力的机理有重要意义,有利于促进水工质激光推进的发展。     

载人飞船有效载荷搭载技术及试验验证

载人飞船飞行任务中搭载的有效载荷设备质量、体积大并且安装要求苛刻,而返回舱内空间狭小且舱内环境复杂。针对这个问题,文章提出了通过改装返回舱座椅作为有效载荷搭载安放的方案。经过试验验证表明,该方案对飞船的影响很小,并且满足有效载荷设备搭载要求。     

Fourier methods for turbomachinery applications

Rapid increase in computing power has made a huge difference in scales and complexities of the problems in turbomachinery that we can tackle by use of computational fluid dynamics (CFD). It is recognised, however, that there is always a need for developing efficient methods for applications to blade designs. In a design cycle, a large number of flow solutions are sought to interact iteratively or concurrently with various options, opportunities and constraints from other disciplines. This basic requirement for fast prediction methods in a multi-disciplinary design environment remains unchanged, regardless of computer speed. And it must be recognised that the multi-disciplinary nature of blading design increasingly influences outcomes of advanced gas turbine and aeroengine developments. Recently there has been considerable progress in the Fourier harmonic modelling method development for turbomachinery applications. The main driver is to develop efficient and accurate computational methodologies and working methods for prediction and analysis of unsteady effects on aerothermal performance (loading and efficiency) and aeroelasticity (blade vibration due to flutter and forced response) in turbomachinery. In this article, the developments and applications of this type of methods in the past 20 years or so are reviewed. The basic modelling assumptions and various forms of implementations for the temporal Fourier modelling approach are presented and discussed. Computational examples for realistic turbomachinery configurations/flow conditions are given to illustrate the validity and effectiveness of the approach. Although the major development has been in the temporal Fourier harmonic modelling, some recent progress in use of the spatial Fourier modelling is also described with demonstration examples.     

考虑燃料均衡的卫星编队队形重构技术

在卫星编队队形重构过程中,如何在实现编队整体燃料消耗较少的同时使得各子卫星燃料消耗均衡,能够有效地提高卫星编队整体的寿命。提出了一种基于虚拟中心位置可变的卫星编队队形重构新方法。该方法以虚拟中心位置为寻优变量,以首末脉冲时刻可优化的双脉冲规划作为单星轨道机动策略,将编队队形重构问题转化为混合0-1数学规划问题。仿真结果表明,该优化算法在实现整体燃料次优的同时,兼顾了各星当前的燃料剩余水平,实现了各子卫星的燃料均衡。     

直接再入大气的月球返回轨道设计研究

直接再入大气的月球返回轨道是月球采样返回任务普遍采用的飞行方案。文章将月-地转移轨道设计与再入大气仿真相结合,通过两级修正策略和落点匹配使月球返回轨道既满足再入界面约束又满足再入点地理位置约束。两条分别采用弹道式和弹道-升力式再入的月球返回轨道的计算结果表明,此方法是有效的。     

引入材料参数的弯管中性层偏移解析模型

中性层偏移是表征管材弯曲内外侧不均匀变形程度的关键参数。基于弯管截面力矩平衡条件,建立了引入材料参数的管材弯曲变形中性层偏移解析模型,针对管材数控绕弯和压弯过程对所建模型从多个方面进行了评估,研究了不同几何和材料等管材本征参数下的管材弯曲中性层偏移规律。结果表明:应用于TA18钛管数控绕弯,发现所建解析模型与已有解析方法预测精度相当,但能考虑材料参数影响,且相较于有限元模拟,本文解析模型更接近实验结果;应用于A6063铝合金管和AZ31镁合金管压弯过程,并与Hasegawa解析方法相较,发现本文解析模型能够准确预测拉压不对称对压弯中性层偏移的影响;弯曲半径减小,弯管直径增大,中性层向弯曲内侧移动;拉压屈服强度比减小,厚向异性指数增大,中性层向弯曲内侧移动。     

Flight Record of the Long March Series of Launch Vehicles

(Continued)THE 67TH LAUNCHOn May 15, 2002, a LM-4B launch vehicle lifted off with FY-1D meteorological satellite and HY-1A oceanic satellite from Tai-yuan Satellite Launch Center and laun