粘弹阻尼结构模态灵敏度分析的模态展开方法

建立了粘弹阻尼结构的模态灵敏度分析的模态展开方法,其形式较为简单,与粘性阻尼结构灵敏度分析的模态展开法相类似,计算较为简便。并对有限自由度的离散粘弹阻尼结构的算例进行了振动模态灵敏度分析。     

模糊随机可靠性灵敏度分析方法

 依据模糊随机可靠性灵敏度的基本概念,提出了模糊随机可靠性灵敏度分析的通用数字模拟法,推导了模糊随机可靠性灵敏度数字模拟解的方差和变异系数的计算公式。当模糊变量的隶属函数为正态型时,可以将模糊随机可靠性灵敏度转化为随机可靠性灵敏度,并利用复合函数求导法则求解模糊随机失效概率对正态型隶属函数分布参数的灵敏度。对于工程中常用的对称三角型隶属函数,提出了两种近似等价正态化变换基础上的模糊随机可靠性灵敏度分析方法,这两种将对称三角型隶属函数近似等价为正态型的方法分别是“3σ规则”法和“最大最小”法。算例结果表明：由于“最大最小”法比“3σ规则”法所得的等价正态隶属函数能在形状上更好地近似对称三角型隶属函数,因而“最大最小”变换法更适用于对称三角型隶属函数情况下模糊随机可靠性灵敏度的近似计算。     

发动机连杆的可靠性灵敏度设计

将可靠性设计理论与灵敏度分析方法相结合,讨论了发动机连杆的可靠性灵敏度设计问题,提出了可靠性灵敏度设计的计算方法,给出了可靠性灵敏度的变化规律,研究了设计参数的改变对连杆可靠性的影响,为连杆的可靠性设计提供了理论依据。      

宽容度照相模式射线检测灵敏度分析

使用穿透电压和较大的曝光量可以增大影像的对比度,进而提高射线检测灵敏度。但为了完成对变截面物体的高效率检测,实践中经常会使用较高的透照电压和较小曝光量这种宽容度照相模式,因此带来了检测灵敏度的降低。为了揭示这个过程中灵敏度的变化情况,引入了透照电压和透照电流相互作用的理论分析,设计了以铝材质为研究对象的宽容度照相灵敏度分析模型,结合数据规划分析,描述出宽容度照相模式下检测灵敏度的变化趋势。从理论上说明了宽容度照相模式可具备相当的检测灵敏度,用实践验证了灵敏度的变化规律。可穿透电压提高40%后,检测灵敏度仍满足相关标准要求。宽容度照相具有可靠的检测灵敏度。     

飞行性能评估主导参数选择方法

影响高超声速滑翔飞行器飞行性能的参数有很多,若在飞行性能评估中全部予以考虑会使问题复杂到难以解决,选择主导参数是解决该问题的有效途径。在建立高超声速滑翔飞行器动力学模型的基础上,提出利用灵敏度分析选择主导参数的方法。针对一般灵敏度方法在确定主导参数过程中出现的问题,引入了综合灵敏度的概念。最后,以最大射程评估中的主导参数选择为例,通过数值仿真验证了方法的有效性。     

Sensitivity Considerations in Trajectory Optimization

A technique by which the trajectory optimization problem can be formulated to include the trajectory sensitivity functions in the performance index is presented. It is shown that an explicit steering law, which can be derived for the upper atmospheric flight of a vehicle, is a function of the sensitivity state, adjoint vectors, and the parameters of the chosen trajectory dynamics. The new steering law is compared with the one without sensitivity considerations. A computational method is presented to implement the new steering law.     

An adaptive array detector with mismatched signal rejection

An adaptive detection algorithm with a sensibility parameter for rejecting unwanted signals is presented. This algorithm is a simple modification of the generalized likelihood ratio (GLR) detector (or test) for detecting a signal in zero mean Gaussian noise with unknown correlation matrix. Specifically, the adaptive detection algorithm is obtained by introducing an arbitrary positive scalar, which is called the sensitivity parameter, into the GLR detector as a multiplier of an already existing quadratic term. The GLR detector then becomes a special case of this detector for the unity sensitivity parameter. It is shown that the sensitivity parameter controls the degree to which unwanted signals are rejected. From numerical examples, it is demonstrated how the sensitivity parameter can be chosen such that unwanted signals, can be rejected while maintaining acceptable detection loss for slightly mismatched signals. Further insight into previous work on adaptive detection is also given     

激光陀螺磁特性研究

本文分析了激光陀螺磁敏感原理,研究了腔内激光束椭偏度的产生机理,设计了高消光比激光束椭偏度测量系统。实验结果表明,激光陀螺磁灵敏度大小与磁场方向有关,输出激光束的椭偏度越大,磁灵敏度越大。研究表明,通过减小输出激光束的椭偏度,可减小激光陀螺磁灵敏度,从而增强激光陀螺环境适应性,提高激光陀螺的成品率。     

A Stochastic Algorithm for Sensitivity Analysis

A direct stochastic sensitivity analysis algorithm is developed for linear dynamical systems having incompletely known input statistics. The new algorithm extends previous results by applying covariance propagation concepts which utilize as a forcing function the sensitivity covariance matrix associated with the uncertainty in the elements of the system input covariance matrix itself. The developed algorithm is evaluated in the context of a generalized sensitivity analysis formulation involving nonlinear transformations on the input signals. Numerical results are provided to demonstrate the usefulness of the new algorithm.     

DESIGNING REDUCED-ORDER CONTROLLERS OF MIXED SENSITIVITY PROBLEM FOR FLIGHT CONTROL SYSTEMS

Based on linear matrix inequalities (LMI), the design method of reduced-order controllers of mixed sensitivity problem is studied for flight control systems. It is shown that there exists a controller with order not greater than the difference between the generalized plant order and the number of independent control variables, if the mixed sensitivity problem is solvable for strict regular flight control plants. The proof is constructive, and an approach to design such a controller can be obtained in terms of a pair of feasible solution to the well-known 3 LMI. Finally, an example of mixed sensitivity problem for a flight control system is given to demonstrate practice of the approach.     

认知不确定性下可靠性灵敏度分析的新指标

传统的可靠性灵敏度指标只考虑了随机不确定性,当结构中还存在认知不确定性时,该指标难以反映出基本变量中认知不确定性对结构可靠性评估结果的影响程度.针对这一问题,引入概率包络来表达结构中的随机不确定性和认知不确定性,在此基础上建立了可靠性灵敏度分析的新指标——认知灵敏度系数,给出了其定义和代表的意义,并基于证据理论提出了认知灵敏度系数的计算方法.算例分析表明,认知灵敏度系数可以反映出基本变量中认知不确定性对结构可靠性评估结果的不确定性的影响程度,从而为有针对性地提高可靠性评估结果的准确性提供依据.另外,基于证据理论的认知灵敏度系数的计算方法适用于极限状态函数为单调、非单调的结构,以及变量服从正态、非正态的结构,具有普适性.     

含旋转铰间隙平面运动机构可靠性灵敏度分析

基于时变运动机构可靠性灵敏度分析方法,考虑机构杆件旋转铰间隙对运动精度的影响,发展出一种计算含旋转铰间隙平面运动机构全局灵敏度指标的分析方法。该方法首先基于该种运动机构的误差函数构建其包络函数,进而解析推导其可靠性计算公式,在此基础上结合时变运动机构全局灵敏度分析方法,求得含旋转铰间隙平面运动机构各全局灵敏度指标的计算公式。最后,将本文所提方法应用到两个具体机构算例,所得结果数据与蒙特卡罗法计算结果相比吻合度高,具有较高的精确度;同时,计算成本也大大降低。     

飞机选型的综合评价与优先权灵敏度分析

 采用多目标决策理论建立了一个多层次的飞机选型的综合评价模型,在此基础上,讨论了优先权灵敏度分析的方法以及在飞机选型问题上的应用。     

巴特沃兹有源滤波器设计中的灵敏度分析

通过对两种巴特沃兹有源滤波器设计方案的灵敏度分析,仿真了电路元件参数灵敏度随 Q 因数的变化规律,从而介绍了一种利用灵敏度分析比较网络设计方案优劣的方法。     

含CL-20的改性双基推进剂的机械感度

1引言为实现固体推进剂高能化,各国均在大力开展HEDM(高能量密度材料)的开发和应用研究[1~3]。在已合成的众多高能量密度材料中,CL-20(六硝基六氮杂异戊兹烷,又称HNIW)以较高的密度比冲、优异的燃烧性能等特征,备受青睐。因此,近些年各国对CL-20单体的合成、表征、热性能、安全     

结构非概率可靠性灵敏度分析方法

 结构非概率可靠性的灵敏度分析对工程中非概率问题的分析预测和优化具有重要的指导作用。基于结构非概率可靠性指标理论,提出了结构非概率可靠性的灵敏度分析方法。针对极限状态函数为线性的情况,推导出了非概率可靠性灵敏度的解析解。在此基础上,结合函数线性化理论,提出了求解极限状态函数为非线性情况的非概率可靠性灵敏度的近似解析方法。基于求解非概率可靠性指标的优化方法,并结合差分理论,提出了求解非概率可靠性灵敏度的优化方法。给出了算例分析,结果表明了所提方法的可行性。     

Tear Resistance of Orthogonal Kevlar-PWF-reinforced TPU Film

This work seeks to investigate the notch sensitivity and fracture behaviour of orthogonal Kevlar-plain woven fabric (PWF)-reinforced thermoplastic polyurethanes (TPU) film applied to high altitude balloon. Four types of specimens are implemented to measure notched strength and fracture toughness by conducting static tension and tear tests on an MTS system respectively. The damage and failure mechanisms are discussed and the results for notched strength and tear resistance are evaluated and compared with each other. From the experiments, it is found that the notch sensitivity of the film increases with the increase in the size of the hole, but the notch sensitivity and the stress concentration of the notch are insignificant and there is a decrease of only about 4%-10% in tensile strength for the notched specimens with different hole sizes in diameter compared with the unnotched specimen. In contrast, the tear resistance containing a central slit with only 1 mm length is about half of tensile strength of the unnotched film, which implies that the tear resistance exists an significant notch sensitivity. The results of this study provide an insight into notch sensitivity and fracture behaviour of the Kevlar-PWF-reinforced TPU film and constitute a fundamental basis for the design of high altitude balloon.     

Sensitivity Analysis for Safety Design Verification of General Aviation Reciprocating Aircraft Engine

This paper presents an application of global sensitivity analysis for system safety analysis of reciprocating aircraft engine. Compared with local sensitivity analysis results, global sensitivity analysis could provide more information on parameter interactions, which are significant in complex system safety analysis. First, a deterministic aviation reciprocating engine thermodynamics model is developed and parameters of interest are defined as random variables. Then, samples are generated by Monte Carlo method for the parameters used in engine model on the basis of definition of factor distribution. Eventually, results from engine model are generated and importance indices are calculated. Based on the analysis results, design is improved to satisfy the airworthiness requirements. The results reveal that by using global sensitivity analysis, the parameters could be ranked with respect to their importance, including first order indices and total sensitivity indices. By reducing the uncertainty of parameters and adjusting the range of inputs, safety criteria would be satisfied.     

On the Sensitivity of a Fixed-Point Smoothing Algorithm

This paper presents a simple approach to the derivation of sensitivity measures of smoothing algorithms. It is proposed that the known sensitivity results of the Kalman filtering algorithm be utilized along with the state augmentation approach for this purpose. The sensitivity measures so obtained are easier to compute than the ones available in the literature. It is then shown that the fixed-point smoothing algorithm, derived recently by Biswas and Mahalanabis [1], [2], is less sensitive to model parameter variations than the algorithm studied by Griffin and Sage [7], [8]. The case of a satellite tracking problem is presented by way of illustrating the results.     

大L＊脉冲发动机内弹道性能的实验研究

本文介绍了远程火箭中间段制导地面动态联试用的大Ｌ＊脉冲发动机内弹道性能实验研究的情况，包括静态点火试验、动态旋转试验和高低温环境试验的情况。试验数据与设计数据符合良好。试验结果表明，脉冲发动机的主要性能满足与弹上控制系统动态联试的要求，但也带有大Ｌ＊发动机的某些明显特点。