声纳目标运动分析的测度和可观测性

目标运动分析是声纳的一个重要问题,并经过了30多年的认真研究。目标运动分析是建立在从目标信号中提取出的测度的基础上的。不同的测度会引入不同的问题,并有不同的优缺点。因而,目标运动分析可以用从目标信号中提取出的测度来刻画。目标运动分析的特点之一就是在某些态势下目标时不可观测的。为了能够有效地提取出目标参数,选择合适的测度集合和最佳观测者机动至关重要。本文详细讨论了目标运动分析问题的测度、可观测性和最佳观察者机动问题。     

复杂背景下弱小目标检测方法综述

基于图像信息的自动目标检测,在军事及工业领域有着广泛的应用前景.当成像系统和目标的相对位置较远时,目标在图像平面上表现为点状或不稳定斑点状,占有的像素少,信噪比低,在复杂背景下,目标基本上被噪声所淹没,检测比较困难.对这样的弱小目标的检测一直是运动目标探测中一个亟待研究与解决的问题,国内外学者进行了大量的研究.本文对一些典型的检测方法如序贯假设检测法、基于遗传算法的点目标检测与跟踪算法和基于图像对称差分运算的小目标检测方法等进行了分析和研究,阐明了各方法的基本思想、适用范围和优缺点,给出了相应的一些计算公式.最后指出了当前弱小目标检测算法的发展趋势.     

一种有效的机载合成孔径雷达动目标成像方法

为实现机载合成孔径雷达(Synthetic Aperture Radar,简称SAR)实际回波数据中的运动目标聚焦成像,本文在用前置滤波法检测出运动目标的基础上,提出了利用目标子图像匹配方法来估计动目标的方位向速度,得到相应的运动目标聚焦参考函数,然后对运动目标进行聚焦成像,并给出了利用该方法得到的运动目标聚焦图像．成像结果表明,目标子图像匹配方法对动目标成像是有效的,易于工程实现,有实际应用价值．     

声纳目标运动分析的实现方法

目标运动分析是声纳的一个重要问题。为了能够有效地估计目标运动状态,选择适当测度集合是第一步。开发出有力的估计算法是解决目标运动分析的另一个关键步骤。本文简练地回顾了声纳目标运动分析的实现方法。在本文中,目标运动分析被松散地分成两大类。一类是经典的目标跟踪方法的一部分,它把数据融合作为整个估计过程的不可分割的一部分;另一类在估计目标状态时并没有利用数据融合。     

一种被动TMA的可测性问题分析

本文讨论了声纳被动定位中,一般非线性动态系统在基于目标方位测量情形下ＴＭＡ的可测性问题。虽然这是个非线性系统,结果证明它是一个可测的动态系统。     

基于鱼雷导引弹道的目标回声特性研究

将板块元方法应用到鱼雷导引弹道计算中,对运动目标的回声特性进行了研究。用刚性球Rayleigh简正级数解检验了板块元方法对运动目标回声特性的计算,在此基础上把板块元方法应用到鱼雷尾追法、固定提前角法、平行接近法三种导引弹道下复杂Benchmark模型目标回声特性的研究。此方法为研究水下运动目标回声特性提供了重要的理论依据。     

扩展卡尔曼滤波算法初值选取方法

以浮标为发射接收平台,研究了观测量为距离的多基地浮标目标运动分析问题,采用了扩展卡尔曼滤波算法对该问题进行求解。首先采用几何定位方法求取目标的位置,并将其作为扩展卡尔曼滤波算法中目标的初始位置进行迭代计算。从试验数据处理结果可知,此种方法可以加快算法的收敛速度,具有很好的工程应用价值。     

被动定向浮标阵卡尔曼滤波目标跟踪研究

文章研究利用被动定向浮标阵定位跟踪水下机动目标的方法,基于卡尔曼滤波(Kalman Filter, KF)原理提出一种定位跟踪滤波器的具体实现方法。该方法能够整合多枚浮标现在及过去有误差的测量数据,提高定位精度,同时连续输出水下目标运动参数估计从而锁定目标运动轨迹。该方法实现的关键在于建立水下目标与浮标阵的数学迭代运算模型,包括状态空间的动态与观测过程。由于被动定向浮标阵目标跟踪是一个非线性估计问题,而卡尔曼滤波器是线性的,因此文章设计了近似的线性观测方程以利用卡尔曼滤波来解决这个问题。通过计算机仿真研究该滤波器的跟踪效果并与最小二乘法进行比较,估计精度明显高于最小二乘法。同时通过仿真验证该滤波器可以自适应跟踪目标的非稳态运动过程。该方法在工程实践上具有一定应用前景与指导意义。     

基于多信息融合的运动目标跟踪方法

针对复杂环境下多运动目标跟踪的高冲突信息组合问题,在DSmT的理论框架下,提出了一种将局部冲突在局部进行分配的改进证据合并方法来研究多运动目标的跟踪问题.该方法通过深入分析冲突及其相关因素之间的关系,将目标的位置信息与颜色信息进行融合建立起多信息合并的运动目标跟踪模型.仿真实验结果表明:采用该方法可实现互遮挡条件下的多...     

智能视频监控运动目标检测技术浅谈

在视频监控智能分析序列中,运动目标检测正处于行业应用的前沿和发展方向,其在智能视频监控过程中发挥了举足轻重的作用。笔者根据工作研究实践,对智能视频监控运动目标检测技术进行了简要的阐述。     

方位时延的TMA算法及其可观测性研究

设计了一种新型的水下被动目标运动分析系统,以测得的方位序列和到达不同传感器的时间延迟为基础,建立了状态方程和观测方程。利用非线性系统的可观测性定理分析了该系统,得出了基于方位时延量测水下被动TMA系统的可观测性结论并分析了可观测度。运用扩展卡尔曼滤波算法,对被动定位性能进行了分析。通过计算机仿真实验,验证了得到的可观测性结论。仿真结果同时也表明,该水下被动TMA系统具有收敛速度快、精度高、稳定性好等优点,有着良好的应用前景。     

一种基于运动模型的水下目标方位预处理方法

为了改善纯方位目标运动分析方法的性能,提出了一种水下目标方位预处理方法。该方法利用目标运动模型对观测方位序列进行预处理,经仿真验证,与常规的多项式拟合方法相比,能够有效降低水下目标方位观测量的估计误差,提高了目标运动分析的性能,可获得更高的运动参数估计精度。     

Three dimensional passive underwater target motion analysis using correlated data fusion

In this paper a new method of passive underwater TMA (target motion analysis) using data fusion is presented. The findings of this research are based on an understanding that there is a powerful sonar system that consists of many types of sonar but with one own-ship, and that different target parameter measurements can be obtained simultaneously. For the analysis 3 data measurements, passive bearing, elevation and multipath time-delay, are used, which are divided into two groups: a group with estimates of two preliminary target parameter obtained by dealing with each group measurement independently, and a group where correlated estimates are sent to a fusion center where the correlation between two data groups are considered so that the passive underwater TMA is realized. Simulation results show that curves of parameter estimation errors obtained by using the data fusion have fast convergence and the estimation accuracy is noticeably improved. The TMA algorithm presented is verified and is of practical significance because it is easy to be realized in one ship.     

Thermomechanical ageing (TMA) of 2014 aluminium alloy for aerospace applications

Various thermomechanical ageing (TMA) treatments for 2014 Al-alloy have been developed which include partial peak ageing, warm rolling and further ageing to peak hardness at 160°C. Electron microscopic studies reveal that the TMA treatments affect substantially the ageing characteristics. The TMA-Ib treatment yields finest?′ needles having longitudinal dimensions of ～400 Å. TMA treatment leads to precipitate-dislocation network of different magnitudes. Among the TMA treatments, the TMA IIb treatment results in thickest precipitate-dislocation tangles. In addition to?′, two types of dispersoids Al₄CuMg₅Si₄ and Al₁₂ (Fe, Mn)₃Si have been observed. The density or concentration of these dispersoids is drastically reduced due to TMA treatments. Thus an optimum TMA treatment i.e. TMA-IIb has been developed which results in a significant improvement in the mechanical properties of 2014 Al-alloy.     

Characterization of the kinetic behavior of resin modified Glass-ionomer cements by DSC, TMA and ultrasonic wave propagation

In this study the isothermal kinetic behavior of two resin modified glass ionomer cements (RMGIC) and a dental composite have been compared by differential scanning calorimetry (DSC) and thermo-mechanical analysis (TMA). The simultaneous evolution of the multiple reactions occurring in RMGIC has been analyzed not only by DSC and TMA but also by ultrasonic wave propagation using the pulse-echo technique. The propagation of ultrasonic waves, acting as a dynamic mechanical deformation at high frequencies, is proportional to the longitudinal bulk moduli of the material and may be used to measure the changes of mechanical properties induced by a chemical reaction as occurs in RMGIC. TMA and ultrasonic analysis have been used to monitor the acid-base reaction of RMGIC in dark conditions. Moreover an RMGIC presenting a double reactive mechanism in dark conditions, a thermally activated radical polymerization and an acid-base reaction are studied using these experimental techniques. Finally DSC and TMA results obtained during photopolymerization of an RMGIC and of a dental composite have been compared.     

高分子量聚苯硫醚的热分析

用ＤＳＣ和ＴＭＡ测定了高分子量聚苯硫醚树脂的玻璃化转变温度,结果温主、熔点等热转变参数,研究了热退火处理对这些转变参数的影响,结果表明,两种方法测定的ＰＰＳ的热转变温度是一致的。     

Simulation study of passive target motion analysis

In this paper, the problem of underwater passive target motion analysis (TMA) in three dimensions is discussed using the measurements of passive bearings and elevation and frequency on the condition that acoustic source and observer are in different horizontal planes. Simulation results with both of the PLE (pseudo-linear estimation) and MLE (Maximum likelihood estimation) show that the TMA method is effective in oceanic environment. Its error covariance curves tend to its Cramer-Rao lower bounds.