Review of uncertainty-based multidisciplinary design optimization methods for aerospace vehicles

This paper presents a comprehensive review of Uncertainty-Based Multidisciplinary Design Optimization (UMDO) theory and the state of the art in UMDO methods for aerospace vehicles. UMDO has been widely acknowledged as an advanced methodology to address competing objectives of aerospace vehicle design, such as performance, cost, reliability and robustness. However the major challenges of UMDO, namely the computational complexity and organizational complexity caused by both time-consuming disciplinary analysis models and UMDO algorithms, still greatly hamper its application in aerospace engineering. In recent years there is a surge of research in this field aiming at solving these problems. The purpose of this paper is to review these existing approaches systematically, highlight research challenges and opportunities, and help guide future efforts. Firstly, the UMDO theory preliminaries are introduced to clarify the basic UMDO concepts and mathematical formulations, as well as provide a panoramic view of the general UMDO solving process. Then following the UMDO solving process, research progress of each key step is separately surveyed and discussed, specifically including uncertainty modeling, uncertainty propagation and analysis, optimization under uncertainty, and UMDO procedure. Finally some conclusions are given, and future research trends and prospects are discussed.     

通道间延迟时间差评价结果的不确定度

介绍了四参数正弦波最小二乘法评价通道间延迟时间差指标及不确定度分析和评价过程，同时给出了一个分析评价实例。该过程及结论可应用在对于测量标准进行相应指标的不确定度分析上，也可用于估计指标本身的不确定度。     

洛氏硬度标准装置不确定度的评定

详细给出了洛氏硬度标准装置不确定度的评定方法及步骤。     

微波场强自动计量测试研究

介绍了微波场强计量测试的原理方法 ,主要介绍了在中文 WINDOWS95环境下利用 VB6 .0语言编程进行自动计量测试的研究情况以及测量不确定度分析。     

基于鲁棒H∞滤波的追踪卫星相对导航算法研究

针对追踪卫星存在轨道机动的情况,在模型存在不确定参数和非高斯噪声输入时,研究了基于鲁棒H∞滤波理论的相对导航算法.该算法采用线性不等式技术,根据Lyapunov稳定性原理推导出具有范数有界不确定参数离散系统的鲁棒H∞滤波器存在的充要条件,并将滤波器的设计转化为一个凸优化的求解问题.将该算法应用到追踪卫星导航中,仿真结果表明该算法在大轨道机动下有效且能消除模型不确定性和非高斯噪声对系统造成的不利影响.     

霍尔推力器羽流发散角的定向探针测量方法

针对霍尔推力器的聚焦型束流,提出了一种利用定向探针在近场区快速测算羽流发散角的方法,并且还能获到喷口附近离子通流密度的分布及扩散特性。不确定度分析显示,利用该方法计算羽流发散角的偏差来源主要是离子电流的径向截断,但对于聚焦型等离子体束流在合理选择测量位置的情况下,其测算不确定度最小可达到±1%。     

虚拟仪器校准探讨

简要介绍了虚拟仪器的组成原理及技术特性,探讨了虚拟仪器校准方法,提出了虚拟仪器校准的注意事项,分析了虚拟仪器校准中影响测量不确定度因素。     

一种基于单定向耦合器比较法的8 mm小功率校准系统

介绍了一种基于单定向耦合器比较法组建的8mm小功率校准系统,讨论了校准原理、系统组成、校准不确定度,通过分析和实验证明系统作为8mm小功率座的校准是可行的.     

A novel method for importance measure analysis in the presence of epistemic and aleatory uncertainties

For structural systems with both epistemic and aleatory uncertainties, research on quantifying the contribution of the epistemic and aleatory uncertainties to the failure probability of the systems is conducted. Based on the method of separating epistemic and aleatory uncertainties in a variable, the core idea of the research is firstly to establish a novel deterministic transition model for auxiliary variables, distribution parameters, random variables, failure probability, then to propose the improved importance sampling(IS) to solve the transition model. Furthermore,the distribution parameters and auxiliary variables are sampled simultaneously and independently;therefore, the inefficient sampling procedure with an ‘‘inner-loop' for epistemic uncertainty and an‘‘outer-loop' for aleatory uncertainty in traditional methods is avoided. Since the proposed method combines the fast convergence of the proper estimates and searches failure samples in the interesting regions with high efficiency, the proposed method is more efficient than traditional methods for the variance-based failure probability sensitivity measures in the presence of epistemic and aleatory uncertainties. Two numerical examples and one engineering example are introduced for demonstrating the efficiency and precision of the proposed method for structural systems with both epistemic and aleatory uncertainties.     

Uncertainty propagation for statistical impact prediction of space debris

Predictions of the impact time and location of space debris in a decaying trajectory are highly influenced by uncertainties. The traditional Monte Carlo (MC) method can be used to perform accurate statistical impact predictions, but requires a large computational effort. A method is investigated that directly propagates a Probability Density Function (PDF) in time, which has the potential to obtain more accurate results with less computational effort. The decaying trajectory of Delta-K rocket stages was used to test the methods using a six degrees-of-freedom state model. The PDF of the state of the body was propagated in time to obtain impact-time distributions. This Direct PDF Propagation (DPP) method results in a multi-dimensional scattered dataset of the PDF of the state, which is highly challenging to process. No accurate results could be obtained, because of the structure of the DPP data and the high dimensionality. Therefore, the DPP method is less suitable for practical uncontrolled entry problems and the traditional MC method remains superior. Additionally, the MC method was used with two improved uncertainty models to obtain impact-time distributions, which were validated using observations of true impacts. For one of the two uncertainty models, statistically more valid impact-time distributions were obtained than in previous research.