联合多站阵元域数据的水下目标检测与跟踪

为了提高复杂海洋环境中目标的检测、跟踪性能,提出一种联合多站阵元域数据的水下目标检测与跟踪方法.该方法采用序列马尔科夫链蒙特卡洛思想对目标进行采样更新,通过对接收概率中的后验概率以及采样函数进行分解展开,并根据多站阵元域数据计算采样粒子的联合似然,在迭代过程中实现目标数目和目标状态的联合估计.研究结果表明,该方法对单目标的平均定位误差在较高信噪比下能够稳定在50 m以内,对多目标随机出入场景中新生及消失目标实现有效检测,同时对强干扰下弱目标及交叉目标实现有效检测跟踪。仿真结果和海试数据均验证该方法具有良好的目标检测与跟踪性能。     

图像的运动目标检测与跟踪算法研究

随着计算机技术、网络工程、电子信息科学技术的发展,信息时代越来越影响着我们的日常生活、学习、工作。目前计算机网络已经深入我们的日常工作过程中,并且占据着无法取代的位置,比如视频图像检测已经运用到多领域。笔者浅要探讨图像的运动目标检测,以及跟踪目标所利用的跟踪算法的探究。     

联合方位-径向速度的粒子滤波目标运动分析

纯方位目标运动分析方法要求观测平台有效机动才能估计目标运动状态,针对这一问题,联合径向速度与方位角作为测量信息对目标进行运动分析,但基于卡尔曼滤波算法进行解算需要已知粗略的目标状态初始值,且收敛时间较长、误差较大,不利于目标实时跟踪.针对以上问题,提出了一种基于粒子滤波的方位径向速度联合目标运动分析方法,建立目标运动状态分析的粒子滤波算法模型,对目标位置和速度等运动要素进行估计.在目标初始状态未知的情况下,一定程度上缩短了收敛时间,减小了估计误差,海试数据处理结果显示:相同条件下,与原有方法相比,本文所提方法收敛时间从35.1 min缩短至30.0 min;跟踪精度从6.1%提高至3.8%,且无需已知目标状态初始值。     

不完全量测下长基线系统的水下目标跟踪算法

针对不完全量测情况下长基线系统对水下目标跟踪精度会下降的问题,提出了最小二乘-容积卡尔曼滤波(Least Squares-Cubature Kalman Filter,LS-CKF)算法。选取容积卡尔曼滤波(Cubature Kalman Filter,CKF)为基本跟踪算法并将其改进为两步滤波模式.增加的第1步滤波使用最小二乘估计优化时间更新阶段的容积点,提高了第2步滤波中量测更新的精度。进一步推导了量测信息为距离时新算法的简化形式,降低了运算复杂度,使其能更好地应用于水下跟踪系统.仿真实验和湖试数据的处理结果表明,在丢失量测数据较多且初始状态误差很大的恶劣情况下,LS-CKF收敛速度比标准CKF算法提升了1倍,且跟踪误差降低10%以上。     

基于核相关滤波的多尺度绝缘子目标跟踪

针对输电线路巡检视频中的绝缘子目标跟踪背景复杂,不能适应绝缘子尺度变化的问题,提出了一种基于核相关滤波的多尺度绝缘子目标跟踪算法。该算法首先提取绝缘子Hog特征,通过最小化决策函数来训练一个分类器,得出绝缘子目标位置,最后引入多尺度估计方法,来确定绝缘子目标的大小,从而提高了绝缘子跟踪的精度。实验结果表明,本文提出的跟踪算法能够适应绝缘子尺度变化且与传统Camshift的算法相比,具有较好的跟踪性能。     

多输入多输出与时反联合的波导声呐有源目标定位

为了提高对浅海静止小目标的探测能力,提出了将多输入多输出和时反处理相结合的波导声呐处理框架。利用收发合置垂直阵,假设目标为点目标,每一个阵元轮流时反发射正交信号照射目标,整个阵接收对应的目标回波。当所有的阵元发射正交信号结束以后,对所有接收的目标回波数据进行分集处理,然后与时反发射驾驶向量做匹配滤波完成对目标的定位。分时发射策略克服了水声信道时延扩展和多普勒扩展导致常规多输入多输出处理接收端不同回波信号分离的困难。采用物理时反发射和数值时反接收聚焦,有助于抑制混响、提高回混比。数值仿真和波导水池实验结果表明多输入多输出时反处理较常规的有源匹配场处理以更高的精度对波导中的目标进行定位。     

目标视频跟踪方法

通过视频跟踪,首先可以得到目标的运动轨迹,继而深入分析,可以获得更有价值的信息内容。本文主要介绍2种流行方法,即基于深度学习的目标跟踪方法以及新近提出的多任务相关粒子滤波方法。     

基于高斯核相关滤波的多特征融合的目标跟踪

为了解决跟踪过程中光照、快速变形等干扰因素,提出一种基于高斯核函数的多特征融合的跟踪算法。首先将HOG和颜色特征融合,采用PCA降维技术进行多特征降维,利用循环矩阵获得训练样本并用最小二乘分类器训练样本获得核滤波模板,对跟踪效果有明显的改善。针对遮挡问题,通过设置阈值检测遮挡并保存成功跟踪时的模板作为训练样本训练新模型来解决。通过对视频序列对比实验表明,该算法具有更高的精确度与鲁棒性。     

改进的贝叶斯压缩感知目标方位估计

针对基于高斯先验模型的贝叶斯压缩感知在目标方位(Direction Of Arrival,DOA)估计中可能出现明显随机伪峰的问题,改进了高斯先验模型,并在此基础上提出了一种贝叶斯压缩感知目标方位估计方法。通过波束输出噪声背景预估与二值指示变量标记,并引入基于信号先验方差的噪声方差估计方法,与变分贝叶斯推断相结合改进目标方位估计性能和优化迭代收敛过程。利用32元线阵对改进算法进行数值仿真处理和分析结果表明,该改进方法不仅可以准确估计目标信号的方位,而且可以显著地减少空间谱中伪峰的数量。实际海上实验数据处理结果表明,使用改进后的贝叶斯压缩感知方法进行DOA估计,可以显著地抑制空间谱中随机的伪峰,提高波束输出峰值背景比,具有更强的目标检测能力。     

EKF与UKF的目标跟踪算法应用与对比

目标跟踪是计算机视觉领域的重要研究方向之一,在精确制导、人机交互、机器人导航等诸多领域广泛应用。在高斯噪声环境下,扩展卡尔曼滤波器(EKF)是将非线性函数展开成Taylor级数,一阶EKF算法简单,计算量小,适用于弱非线性系统;二阶EKF精度高于一阶EKF,需要计算二阶雅克比矩阵,计算量大。文章研究了EKF与UKF的目标跟踪算法应用与对比。无迹卡尔曼滤波(UKF)用一系列确定的样本来逼近状态的后验概率密度,没有忽略高阶项,适用于所有非线性系统。文章对目标跟踪模型进行了仿真,结果表明,UKF滤波精度明显高于EKF滤波,二阶EKF滤波精度较一阶EK F有所提高。     

钢筋混凝土构件承载力统一计算模式研究

基于复杂受力下钢筋混凝土构件的受力相关性,以弯扭相关性作为连接剪扭相关性和压弯相关性的桥梁,推导了钢筋混凝土构件承载力计算的统一计算式,考虑了压弯剪扭四种受力状态的受力相关性。由该计算式推得的单一受力和复合受力状态下的承载力计算式与国内外试验数据符合较好,计算式不仅适用于所有单一受力状态下的承载力计算,还适用于压弯、剪扭、弯扭、弯剪和压剪5个两相关计算,弯剪扭、压弯剪三相关计算以及压弯剪扭四相关计算。按统一计算式得到的配筋量比GB 50010-2002《混凝土结构设计规范》的配筋量更为合理,且计算结果与试验结果吻合较好。     

Spatiotemporal matching method for tracking pavement distress using high-frequency detection data

Various algorithms based on deep learning have achieved promising results in pavement distress detection. However, the detected distresses are not tracked throughout the life cycle. In long-term application scenarios, pavement distresses may take on different forms due to image acquisition mode, distress development, and environmental change, which make tracking distresses a tough question. We present in this study a spatiotemporal matching method based on high-frequency real pavement distress datasets. Pavement distresses of fixed routes were collected 30 times over 5 months, and distresses with spatiotemporal information were obtained at time series. We apply image rectification, stitching and distress class, and bounding box generation algorithms for pre-processing to align the collected images to the same-detail level and angle. A four-step spatiotemporal matching module is designed, including global positioning system (GPS) filtering, class filtering, relative position filtering, and distress feature filtering. The results reveal that the comprehensive rank-3 hit rate of the matching method reaches 88.73%, and the method is robust to environmental factors, which helps show performance decay of distresses and the effect of maintenance operations. It is concluded that the spatiotemporal matching method is convenient to operate, and it lays the foundation for an agency to track distress evolution and make timely treatment of distresses in the life cycle.     

对称三角线性调频水声通信信号的同步检测方法

同步捕获是水声通信中的重要环节。基于分数阶傅里叶变换(FRFT)可提高对称三角线性调频波(STLFM)的信号同步捕获精度。理论分析表明,对称三角线性调频波在同步窗口正确时,其分数阶傅里叶变换(FRFT)域上具有双尖峰对称性。利用FRFT域上两个尖峰的位置偏移可估计并矫正同步信号的多普勒频移与时间延迟,进而利用FRFT域上两个尖峰的峰值差可实现对同步跟踪环路的精细调整。水声传播仿真和五缘湾浅海信道测试结果表明,在相同时间带宽乘积情况下,所提同步方法的同步误差均值比线性调频(LFM)同步方法低1/3,同步误差均方误差上降低至1/5~1/10,具有更好的准确性和稳定性。     

An anomalous event detection and tracking method for a tunnel look-ahead ground prediction system

The complicated geological conditions and unexpected geological hazards beyond the face of a tunnel are challenging problems for tunnel construction, which can cause great loss of life and property. While the geological surveys conducted before tunnel construction can provide rough information of construction site, they are not sufficiently accurate for predicting the sudden geological condition changes in local areas. Within the EU NETTUN project, an on-board ground prediction system consisting of multiple ground penetrating radars (GPR) and seismic sensors were developed to “see through” the ground and provide the local ground information behind the excavation front surface of a TBM (Tunnel Boring Machine). In order to facilitate the interpretation of the imaging data captured by this system, an automatic event detection and tracking method is presented in this paper. Anomalous 2D features are detected on each radar profile and reconstructed into a 3D accumulator; then, probable 3D events are detected from the accumulator and tracked at subsequent locations based on the information from multiple sets of radar data. The detection results can be used to generate alarms or be sent to human operators for interactive interpretation. The proposed method was evaluated using two sets of GPR data captured in a designed test field. Experimental results show that the buried targets can be correctly detected by the proposed event detection and tracking method. The proposed method is sufficiently flexible to cope with variations on the spatial configuration of on-board sensors.     

水下连续波有源探测的回波检测算法

研究线性调频连续波在水下探测中的信号模型、回波信号的检测和目标参数估计方法,通过分析回波信号与发射信号间的差拍信号,提出差拍-分数阶傅里叶变换结构的处理算法。为了减少分数阶傅里叶变换二维搜索时的计算量,首先使用Radon-Ambiguity变换估计差拍信号的调频斜率,再做相应阶次的分数阶傅里叶变换。数值仿真说明提出的算法能够有效消除线性调频连续波的距离-速度耦合现象,准确估计目标参数。通过湖上试验比较线性调频脉冲信号和线性调频连续波的处理增益,提出的算法处理的连续波比匹配滤波方法处理的脉冲信号处理增益大13 dB。研究结果表明该算法在连续波水下探测中可行有效,不仅能够准确估计目标参数,还具有良好的检测性能。     

一种快速水声目标波达方向估计方法

以基追踪为重构算法的水声目标波达方向估计方法在实际的应用中往往运算速度较慢,针对这一问题,在分析水声目标空间稀疏特性的基础上,结合压缩感知理论框架下波达方向估计的特点,提出一种快速水声目标波达方向估计方法。该方法通过逐步减小逼近参数的方式来得到l_0范数最优解,实现水声目标信号的波达方向估计。通过计算机仿真从成功率、运算时间、分辨角度等多个方面与基追踪算法进行比较分析,实验表明:在成功率和分辨角度上所提出算法与基追踪算法性能相当,但运算时间却仅仅是基追踪算法的1/11。     

A design method for flaming fire detection

The scientific basis of a design method for the detection of flaming fires is reviewed. The equations required to calculate detector spacings are included and the selection of appropriate design input parameters is discussed. Limitations of the method and areas for further research are identified. The design method has been implemented and proposed for inclusion in NFPA Standard 72E-1984 as Appendix C by the 72E-M Committee. Center for Fire Safety Studies Worcester Polytechnic Institute     

A qualitative energy-based unified representation for buildings

This paper presents the development of energy-based unified representations for buildings called Archi Bond Graphs and then specialises them as qualitative Archi Bond Graphs that combine graphical representations and qualitative equations. They can be applied to simulations of people behaviour and people-energy behaviour in space-people systems, building energy flows and building energy variations in different building energy systems, and energy interactions between these building subsystems. The applicability of qualitative Archi Bond Graphs is demonstrated through a building simulation for the dynamic energy interactions between the space-people system and building energy systems, including lighting system, and hydraulic system in a town-house design.     

A rule-based fault detection method for air handling units

Air handling unit performance assessment rules (APAR) is a fault detection tool that uses a set of expert rules derived from mass and energy balances to detect faults in air handling units (AHUs). Control signals are used to determine the mode of operation of the AHU. A subset of the expert rules which correspond to that mode of operation are then evaluated to determine whether a fault exists. APAR is computationally simple enough that it can be embedded in commercial building automation and control systems and relies only upon the sensor data and control signals that are commonly available in these systems. APAR was tested using data sets collected from a “hardware-in-the-loop” emulator and from several field sites. APAR was also embedded in commercial AHU controllers and tested in the emulator.