多传感器数据融合时权的最优分配原则

对多个同类传感器的输出数据进行融合时多采用和权平均法,权的分配对融合效果的影响十分明显。作利用多元统计理论分析了权的分配对融合精度的影响,推导出了权的最优分配原则,并采用多个陀螺仪对某一旋转角速度的实际测量进行了仿真,实验证实这种权的分配原则是最优的。     

测量融合组合导航方法研究

讨论了测量融合组合导航的两种方法,提出并研究了应用极大似然的估计的测量融合方法,并将该方法与基于线性一均方估计的测量融合方法作了比较。仿真研究表明测量融合方法在组合导航系统中具有良好的应用价值,特别是基于极大似然估计的测量融合方法,充分利用了测量值的冗余信息,其融合效果更好,组合系统的精度也有较大幅度的提高。     

基于UKF的INS/GNSS/CNS组合导航最优数据融合方法

为了提高INS/GNSS/CNS组合系统的导航精度,提出了一种基于UKF的多传感器最优数据融合方法。该方法具有两层融合结构,第一层中,GNSS和CNS分别通过两个局部UKF滤波器与INS组合,以并行的方式获得INS/GNSS和INS/CNS子系统的局部最优状态估值;第二层中,根据线性最小方差准则推导出一种矩阵加权数据融合算法,对局部状态估值进行融合,获取系统状态的全局最优估计。提出的方法无需采用方差上界技术对局部状态进行去相关处理,克服了联邦卡尔曼滤波(FKF)及其优化形式存在的缺陷。仿真结果表明,相比于FKF,提出方法的导航精度可至少提高36.4%;相比于UKF-FKF,其导航精度也可至少提高21.0%。     

基于H∞滤波的变权多通道数据融合方法研究

在对多通道定位数据进行数据融合中，采用H∞滤波可有效地解决各传感器数据误差模型不确定的滤波和状态估计问题。但由于数据采样时刻及精度的不一致性，对于多通道数据的融合应采用变权融合方式，以提高融合后数据的可靠性。该由此给出了一种基于H∞滤波的变权数据融合计算方法，通过对实测实时数据的仿真计算表明，其方法具有很好的实用性。     

基于低成本IMU的捷联航姿系统软件设计与实现

在已设计好的捷联航姿系统硬件平台基础上,集传感器信息处理模块、航姿解算模块和信息融合模块于一体,综合设计了基于低成本IMU的捷联航姿系统软件算法.特别是在信息融合模块中采用了基于模糊推理的变加权系数多传感器信息融合算法,从而实现对惯性数据的融合,减小了系统随时间积累的航姿误差,保证航姿系统的精度指标满足要求(静态航姿精度±1.0°,动态航姿精度±2.5°).软件算法的验证采用低成本MT9-B惯性测量组件的实测数据分别进行了静、动态实验.实验结果表明,所设计的软件算法可时实进行低成本陀螺的零偏估计与补偿,并能准确地进行多传感器信息融合,从而能够有效地提高系统的航姿精度.     

融合伪距和载波相位的DGPS/惯性组合导航

本文利用卡尔曼滤波方法对码伪距测量和载波相位测量进行了最优融合，并得到了融合后的伪距测量误差标准差曲线，用融合后的伪距作为观测量和惯导系统进行组合，可以有效地提高导航精度，避免整周模糊度的确定。本文研究了这种组合导航系统，进行了仿真试验，仿真结果表明该组合系统的精度得到了很大的提高，定位精度在1m以内，是一种高精度的导航系统。     

组合导航非等间隔联合滤波

组合导航系统中各种导航设备数据更新频率的不同会导致联合滤波算法无法在每个计算周期都融合局部滤波器的信息，从而导致信息丢失和引入人为误差。为此提出了一种可以最优融合不同测量周期信息的非等间隔联合滤波算法，并且给出了算法的最优性证明。这种算法通过设定不同的计算周期和融合周期，实现了非等间隔测量信息的最优融合。     

多尺度递归融合估计在组合导航系统中的应用

多尺度递归融合估计是对多传感器系统进行的基于尺度的融合估计算法.利用小波变换中多尺度分析的思想,构造出多尺度动态模型,利用该模型对粗尺度上的状态估计值进行修正,递归获得最细尺度上基于全局测量值的最优估计值,该估计值是方差最小意义下的最优估计.将此算法应用于SINS/GPS组合导航系统中,仿真结果表明,应用该算法能取得较好的效果,获得了比仅在单一尺度上进行kaIman融合估计更好的结果,有效地提高了组合导航系统的精度.     

一种有效的不同类型传感器多目标跟踪融合算法

提出了不同类型传感器多目标跟踪的一种改进的分层融合算法，该算法不仅适合于不同类型同步数据融合，而且适合于不同类型传感器异步数据融合。仿真结果显示了该融合算法的有效性。     

基于RBF网络的信息融合在SAMS故障诊断中的应用

针对卫星姿态测量系统(SAMS)，将径向基函数RBF(Radial Basis Function)网络和多传感器信息融合技术相结合，并将其应用在系统的故障检测与诊断中。研究结果表明，此方法是可行有效的，可以提高系统的测量精度和性能。     

一种基于直接计算高阶奇异积分的断裂力学双边界积分方程分析法

相对于有限元法,边界单元法在求解断裂问题上有着独特的优势,现有的边界单元法中主要有子区域法和双边界积分方程法.采用一种改进的双边界积分方程法求解二维、三维断裂问题的应力强度因子,对非裂纹边界采用传统的位移边界积分方程,只需对裂纹面中的一面采用面力边界积分方程,并以裂纹间断位移为未知量直接用于计算应力强度因子.采用一种高阶奇异积分的直接法计算面力边界积分方程中的超强奇异积分;对于裂纹尖端单元,提供了三种不同形式的间断位移插值函数,采用两点公式计算应力强度因子.给出了多个具体的算例,与现存的精确解或参考解对比,可得到高精度的计算结果.     

汶川地震诱发文家沟巨型滑坡 碎屑流基本特征及成因机制初步分析

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2008年5月12日,汶川M80地震在四川省绵竹市清平乡文家沟内诱发一巨型滑坡。通过现场调查得知,滑坡前后缘高差455m,厚度20～30m,滑面为基岩层面,初始方量2750×107m3。滑体在运动中转化为碎屑流。滑坡-碎屑流总的水平运动距离为4022m,垂直运动距离为1443m,遗留的堆积物体积达5×107m3。滑坡距映秀—北川断裂仅36km,位于其下盘,地震烈度达XI度。滑坡导致文家沟中48人遇害,并形成一条完整的地震次生地质灾害链。初步分析表明滑坡启动速度快,滑坡向碎屑流转化过程明显、地点明确。碎屑流运动过程复杂,伴有强烈的“气垫效应”和“前缘气浪冲击效应”。作者认为,文家沟滑坡的高启动速度是长持时强烈地震动作用的结果,与山体的猛烈碰撞是导致滑体解体并转化为碎屑流的原因。     

Preface: Orbits around asteroid

One of the core issues in modern celestial mechanics is the orbital dynamics in the near-regime gravitational field of as- teroids, which provides deep insights into the mathematical nature of a class of nonlinear systems, and plays as a critical basis for in situ explorations of different science goals. Lots of efforts have been made to reveal the characteristics of orbital motion in the vicinity of asteroids, and to improve the skills of asteroid research in methodology.     

Effet de l'anisotropie élastique cristalline sur la distribution des facteurs de Schmid à la surface des polycristauxInfluence of crystalline elasticity anisotropy on Schmid factor distribution at the free surface of polycrystals

Experimental studies of the plasticity mechanisms of polycrystals are usually based on the Schmid factor distribution supposing crystalline elasticity isotropy. A numerical evaluation of the effect of crystalline elasticity anisotropy on the apparent Schmid factor distribution at the free surface of polycrystals is presented. Cubic elasticity is considered. Order II stresses (averaged on all grains with the same crystallographic orientation) as well as variations between averages computed on grains with the same crystallographic orientation but with different neighbour grains are computed. The Finite Element Method is used. Commonly studied metals presenting an increasing anisotropy degree are considered (aluminium, nickel, austenite, copper). Concerning order II stresses in strongly anisotropic metals, the apparent Schmid factor distribution is drifted towards small Schmid factor values (the maximum Schmid factor is equal to 0.43 instead of 0.5) and the slip activation order between characteristic orientations of the crystallographic standard triangle is modified. The computed square deviations of the stresses averaged on grains with the same crystallographic orientation but with different neighbour grains are a bit higher than the second order ones (inter-orientation scatter). Our numerical evaluations agree quantitatively with several observations and measures of the literature concerning stress and strain distribution in copper and austenite polycrystals submitted to low amplitude loadings. Hopefully, the given apparent Schmid factor distributions could help to better understand the observations of the plasticity mechanisms taking place at the free surface of polycrystals. To cite this article: M. Sauzay, C. R. Mecanique 334 (2006).     

Nonlinear behavior of matrix-inclusion composites under high confining pressure: application to concrete and mortar

This paper is devoted to a micromechanics-based simulation of the response of concrete to hydrostatic and oedometric compressions. Concrete is described as a composite made up of a cement matrix in which rigid inclusions are embedded. The focus is put on the role of the interface between matrix and inclusion which represent the interfacial transition zone (ITZ). A plastic behavior is considered for both the matrix and the interfaces. The effective response of the composite is derived from the modified secant method adapted to the situation of imperfect interfaces. To cite this article: T.H. Le et al., C. R. Mecanique 336 (2008).     

Dynamics and Breakup of Viscoelastic Liquids (A Review)

The phenomena of hydrodynamic breakup of liquid jets, drops, films, bridges, and filaments are reviewed for liquids with viscoelastic properties. The reasons for breakup are capillary instabilities, collisions with rigid obstacles, and other forms of dynamic action. The relationship between the properties of the liquids and the features of the breakup process is discussed.     

Flow stability analysis and excitation using pulsating jets

Classical flow stability applied to transition from laminar to turbulent flow may also describe the behavior of vorticity fluctuations created by a pulsating jet placed along a solid boundary. A numerical laminar flow experiment involving a pulsating jet placed along the surface of a duct with flow separation downstream, resulted in eliminating most part of the separated flow region. Applying the same approach to a turbulent flow, it was possible to develop a turbulent stability flow formulation and apply successfully turbulent pulsating jet flow separation control. To cite this article: D. Skamnakis, K. Papailiou, C. R. Mecanique 333 (2005).