航天产品可靠性增长试验指南应用探讨

<航天产品可靠性增长试验指南>是航天产品开展可靠性试验的重要依据,应用广泛,文中讨论了该指南在产品状态控制、试验方案设计、故障处理等方面的实际应用问题,建议应用实施时加强剪裁,明确技术要求,以保证试验的质量和有效性.     

航天静力学试验计价模型设计研究

在典型航天静力学试验结构化分解基础上,采用成本估算关系式法、Delphi法和统计分析等方法,研究分析了试验不同阶段影响价格的软硬件因素,筛选出主要因素,利用价格—因素关系式法设计计价模型.基于历史试验费用数据,获得静力试验专家经验计价公式,建立统计计价模型.对统计计价模型进行回归分析,对比价格预测值与实际试验价格,进行...     

民机复合材料目视检查中的眼动与疲劳检测

疲劳是导致民机复合材料结构目视检查差错的重要诱因，疲劳检测对于减少人的差错，保障飞行安全具有重要意义。对基于眼动行为的疲劳度量与检测方法进行了研究，建立了民机复合材料结构目视检查实验场景，利用Tobii眼动仪提取了正常状态和疲劳状态下的目视检查眼动数据，分析了瞳孔直径、平均注视时间、平均注视频率、平均眼跳时间、平均眼跳频率、注视热点与轨迹和扫视速度等眼动行为与疲劳的关系，进而提取了能表征疲劳的瞳孔直径、平均注视时间和扫视速度3种眼动指标，以该指标构建特征向量，利用支持向量机（SVM）方法构建了目视检查疲劳检测模型。研究发现疲劳状态下的目视检查平均注视时间更长，扫视速度更慢、瞳孔直径减小，右瞳孔减小程度更大，核函数为径向基函数和高斯函数的SVM方法对疲劳的检测效果好。研究结果表明，利用SVM方法训练由瞳孔直径、平均注视时间和扫视速度构成的眼动特征向量能有效检测目视检查中的疲劳状态。     

Application of Active Flow Control Technique for Gust Load Alleviation

A new gust load alleviation technique is presented in this paper based on active flow control. Numerical studies are conducted to investigate the beneficial effects on the aerodynamic characteristics of the quasi "Global Hawk" airfoil using arrays of jets during the gust process. Based on unsteady Navier-Stokes equations, the grid-velocity method is introduced to simulate the gust influence, and dynamic response in vertical gust flow perturbation is investigated for the airfoil as well. An unsteady surface transpiration boundary condition is enforced over a user specified portion of the airfoil’s surface to emulate the time dependent velocity boundary conditions. Firstly, after applying this method to simulate typical NACA0006 airfoil gust response to a step change in the angle of attack, it shows that the indicial responses of the airfoil make good agreement with the exact theoretical values and the calculated values in references. Furthermore, gust response characteristic for the quasi "Global Hawk" airfoil is analyzed. Five kinds of flow control techniques are introduced as steady blowing, steady suction, unsteady blowing, unsteady suction and synthetic jets. The physical analysis of the influence on the effects of gust load alleviation is proposed to provide some guidelines for practice. Numerical results have indicated that active flow control technique,as a new technology of gust load alleviation, can affect and suppress the fluid disturbances caused by gust so as to achieve the purpose of gust load alleviation.     

运输机空投控制器设计(英文)

重物空投过程中,飞行器各飞行参数随着货物舱内移动发生连续的变化,当货物投放瞬间则发生突变。随着空投货物重量的增加,这一过程将严重恶化飞行器飞行品质和操控特性。本文在简化的空投飞行方程基础上,研究反演和切换控制方法以解决这一过程中的飞行状态保持和扰动抑制(包括大范围飞行状态,飞行员操纵误差和系统量测延迟等)问题,所得控制策略也可用于驾驶员空投操纵的指令参考。利用反演理论,推导了自适应控制器以稳定运输机飞行状态,并提出了协调的切换控制方法解决飞机在货物离机过程中出现的状态跳变问题。仿真结果表明所提控制方法在不仅能有效保持系统状态,并能在较大飞行范围内具有较好的鲁棒性。     

Space Debris Reentry Analysis Methods and Tools

The reentry of uncontrolled spacecraft may be broken into many pieces of debris at an altitude in the range of 75-85 km. The surviving fragments could pose great hazard and risk to ground and people. In recent years, methods and tools for predicting and analyzing debris reentry and ground risk assessment have been studied and developed in National Aeronautics and Space Ad-ministration (NASA), European Space Agency (ESA) and other organizations, including the group of the present authors. This paper reviews the current progress on this topic of debris reentry briefly. We outline the Monte Carlo method for uncertainty analysis, breakup prediction, and parameters affecting survivability of debris. The existing analysis tools can be classified into two categories, i.e. the object-oriented and the spacecraft-oriented methods, the latter being more accurate than the first one. The past object-oriented tools include objects of only simple shapes. For more realistic simulation, here we present an object-oriented tool debris reentry and ablation prediction system (DRAPS) developed by the present authors, which introduces new object shapes to 15 types, as well as 51 predefined motions and relevant aerodynamic and aerothermal models. The aerodynamic and aerothermal models in DRAPS are validated using direct simulation Monte Carlo (DSMC) method.     

A novel approximation of basic probability assignment based on rank-level fusion

Belief functions theory is an important tool in the field of information fusion. However, when the cardinality of the frame of discernment becomes large, the high computational cost of evidence combination will become the bottleneck of belief functions theory in real applications. The basic probability assignment (BPA) approximations, which can reduce the complexity of the BPAs, are always used to reduce the computational cost of evidence combination. In this paper, both the cardinalities and the mass assignment values of focal elements are used as the criteria of reduction. The two criteria are jointly used by using rank-level fusion. Some experiments and related analyses are provided to illustrate and justify the proposed new BPA approximation approach.     

一种基于LZW算法的PDW数据压缩方法

PDW数据是ESM设备获得的重要情报之一,是分析目标辐射源信号特征的关键数据。在某些分布式ESM系统中,为了实时获取PDW数据,需要将PDW数据通过无线数据链下传。分析了PDW数据压缩在分布式ESM系统中应用的必要性,介绍了LZW压缩算法的基本原理和实现方法,最后详细介绍了关联比较器与LZW算法相接结合的PDW数据压缩的实现方法。