Research of flexible beam impact dynamics based on space probe-cone docking mechanism

The issue considered in this paper is the dynamic behavior of flexible probe based on space probe-cone docking mechanism in the docking process. The theoretical model of docking impact dynamics based on flexible beam is built according to the Lagrange Analytical Mechanics theory. The contact problem is solved by using Hertz point-surface contact model. Assumed Modes Method is introduced to describe the deformation of flexible beam. Runge–Kutta numerical method is used to solve this theoretical model. Results of the theoretical model show a good agreement with the experimental and MSC.Patran/Dytran simulation results. Moreover, the influence of flexible beam parameter on docking impact process is analyzed based on the theoretical model.     

引入位置参数的三参数Weibull过程及 其点估计方法

为解决Weibull过程在零时刻时强度函数值为零或无穷、工程上拟合不好的问题,引入位置参数对Weibull过程进行了修正.综合运用迭代拟合法、相关系数法以及极大似然法,给出了三参数Weibull过程强度参数、形状参数以及位置参数的点估计方法.并给出了有关可靠性特征量的估计.实例验证表明了该方法能够满足工程上可修系统用Weibull过程进行拟合的需求.      

一种网络环境中的故障诊断模型

结合故障诊断的需求和存在的问题,提出了一种以故障症状、故障假设、诊断操作和观测操作节点为基本元素,并具有网络结构的诊断模型.在该模型基础之上,遵循诊断过程独立的假设,解决实际诊断过程中操作依赖关系的问题,提出了一种基于诊断贝叶斯网络DBN(Diagnosis Bayesian Network)的故障诊断算法.同时通过引入观测操作,加快诊断的速度并且降低诊断代价.试验表明,与P/C更新算法比较,该算法能更有效地降低诊断代价,实现快速故障诊断,较好解决了操作依赖的复杂故障诊断问题.      

高精度ENO格式在喷管流动模拟中的应用

本文分析了ＥＮＯ格式的特点,并应用于Ｅｕｌｅｒ方程和全ＮＳ方程的迁移项和压力项,模拟了各种喷管流动。首先计算了ＪＰＬ喷管流动,取得了和实验一致的结果,分析了喷管内产生弱激波的原因;其次计算了非定常二维喷管流动,给出了相应的计算结果,并分析了壁面附近流场的拓扑结构;最后计算了摆动喷管的流动及推力矢量计算,取得了推力随摆角变化的规律,和实验结果表明基本一致。     

Influence of aircraft surface distribution on electromagnetic scattering characteristics

In this paper, two typical stealth aircraft concepts (wing fuselage blended and flying-wing) were designed. Then three gradually changed surface distribution models with the same plan-form for each concept were created. Based on the multilevel fast multipole algorithm (MLFMA), the vertical polarization transmitting/vertical polarization receiving (VV) and horizontal polariza-tion transmitting/horizontal polarization receiving (HH) radar cross section (RCS) characteristics were simulated with five frequencies between 0.1 and 1.0 GHz. The influences and mechanisms of aircraft surface distribution on electromagnetic scattering characteristics were investigated. The results show that for the wing fuselage blended concept, the VV RCS of this frequency range is higher than the HH RCS in most cases, while it is just the opposite for the flying-wing concept. As for the two aircraft concepts, the RCS levels of HH and VV both decrease with the frequency increasing, but the HH RCS has a faster downward trend. The surface distribution has little influ-ence on HH RCS characteristics. On the contrary, it has a significant impact on VV RCS charac-teristics, and the amplitude of the VV RCS increases with the surface thickness.     

Transient aeroelastic responses and flutter analysis of a variable-span wing during the morphing process

To investigate the transient aeroelastic responses and flutter characteristics of a variablespan wing during the morphing process,a novel frst-order state-space aeroelastic model is proposed.The time-varying structural model of the morphing wing is established based on the Euler-Bernoulli beam theory with time-dependent boundary conditions.A nondimensionalization method is used to translate the time-dependent boundary conditions to be time-independent.The time-domain aerodynamic forces are calculated by the reduced-order unsteady vortex lattice method.The morphing parameters,i.e.,wing span length and morphing speed,are of particular interest for understanding the fundamental aeroelastic behavior of variable-span wings.A test case is proposed and numerical results indicate that the flutter characteristics are sensitive to both of the two morphing parameters.It could be noticed that the aeroelastic characteristics during the wing extracting process are more serious than those during the extending process at the same morphing speed by transient aeroelastic response analysis.In addition,a faster morphing process can get better aeroelastic performance while the mechanism comlexity will arise.     

刷式密封中泄漏流动的多孔介质数值模型

通过对刷式密封的刷子中泄漏流动特点的分析,可以把刷子当作多孔介质来处理,从而建立刷子多孔介质的泄漏流动模型,这样可以简化刷子中复杂的泄漏流动,便于计算工程实际密封中环形刷子的泄漏量。      

航空发动机自适应神经网络PID控制

本文提出了一种航空发动机多变量自适应神经网络 PID控制方法, 采用基于共轭梯度的神经网络学习算法在线整定控制器参数。该控制器的设计无需知道发动机精确模型, 具有响应速度快、抗干扰能力强和鲁棒性好等优点。控制器不仅算法简单, 实现容易, 而且适用范围广。      

激光全息照相实验计算机辅助软件的编制

本文介绍了针对激光全息照相实验的计算机辅助软件的编制。其中主要是用于离面位移显示和计算的干涉等值线条纹图的实时处理，包括条纹的采取、存储、二值化和细化等部分，应用图形显示技术，使计算机的显示器在显示操作界面的同时也显示所采集的图像。系统具有良好的用户界面，易于掌握使用。     

非定常气动力计算中的偶极子格网法

从亚音速、跨音速和超音速三个方面叙述了非定常气动力计算中的偶极子格网法，且给出了其基本解法和计算实例。