Adaptive Neural Region Tracking Control of Multi-fully Actuated Ocean Surface Vessels

In this paper, adaptive neural network region tracking control is designed to force a group of fully actuated ocean vessels with limited sensing range to track a common moving target region, in the presence of uncertainties and unknown disturbances. In this control concept, the desired objective is specified as a moving region instead of a stationary point, region or a path. The controllers guarantee the connectivity preservation of the dynamic interaction network, and no collisions happen between any ocean vessels in the group. The tracking control design is based on the artificial potential functions, approximation-based backstepping design technique, and Lyapunov's method. It is proved that under the adaptive neural network control law, the tracking error of each ocean vessel converges to an adjustable neighborhood of the origin, although some of them do not access the desired target region directly. Simulation results are presented to illustrate the performance of the proposed approach.      

Visualization of vessel movements

We propose a geographical visualization to support operators of coastal surveillance systems and decision making analysts to get insights in vessel movements. For a possibly unknown area, they want to know where significant maritime areas, like highways and anchoring zones, are located. We show these features as an overlay on a map. As source data we use AIS data: Many vessels are currently equipped with advanced GPS devices that frequently sample the state of the vessels and broadcast them. Our visualization is based on density fields that are derived from convolution of the dynamic vessel positions with a kernel. The density fields are shown as illuminated height maps. Combination of two fields, with a large and small kernel provides overview and detail. A large kernel provides an overview of area usage revealing vessel highways. Details of speed variations of individual vessels are shown with a small kernel, highlighting anchoring zones where multiple vessels stop. Besides for maritime applications we expect that this approach is useful for the visualization of moving object data in general.     

摄像机运动情况下的运动对象检测

在监控应用中,由于场景是已知的,因此可以使用背景减去法检测运动对象.当摄像机进行扫描和倾斜运动时,需要使用多个图像帧才能完整地表示监控场景.如何组织和索引这些背景帧属于摄像机跟踪问题.提出一种无需摄像机标定的背景帧索引和访问方法.这一方法需要使用图像配准技术估计图像初始运动参数.提出一种屏蔽外点的图像配准算法,综合利用线性回归和稳健回归快速估计初始运动参数.为了快速计算连续帧之间的运动参数,提出一种基于四参数模型的优化算法.利用非参数背景维护模型抑制虚假运动象素.室内和户外实验结果表明本文方法是有效的.     

Moving vehicle detection,tracking and traffic parameter estimation from a satellite video: a perspective on a smarter city

ABSTRACT

Satellite remote sensing is undergoing a revolution in terms of sensors and temporal coverage. The possibility of acquiring earth’s surface video from space provides an opportunity to investigate broader applications of remote sensing. High-resolution spaceborne videos can become a vital factor in earth observation. Temporally continuous tracking of moving objects, i.e. vehicles, vessels, or even military equipment on Earth’s surface demands high spatial resolution satellite videos. Detecting moving vehicles in the urban areas from space video can lead governments to a new era of traffic monitoring. Satellite videos will find many applications in the field of traffic monitoring. In this article, first, moving vehicles are detected using background subtraction with 94.7% accuracy. Afterwards, vehicles’ trajectories, average velocities, dynamic velocities, and space-time diagram are estimated and trajectories are classified based on velocities. Finally, the total frame traffic density is computed.     

New trends on moving object detection in video images captured by a moving camera: A survey

This paper presents a survey on the latest methods of moving object detection in video sequences captured by a moving camera. Although many researches and excellent works have reviewed the methods of object detection and background subtraction for a fixed camera, there is no survey which presents a complete review of the existing different methods in the case of moving camera. Most methods in this field can be classified into four categories; modeling based background subtraction, trajectory classification, low rank and sparse matrix decomposition, and object tracking. We discuss in details each category and present the main methods which proposed improvements in the general concept of the techniques. We also present challenges and main concerns in this field as well as performance metrics and some benchmark databases available to evaluate the performance of different moving object detection algorithms.     

均衡化特征匹配的非刚体细胞形态跟踪

提出利用均衡化特征匹配来进行非刚性细胞形体跟踪的方法。采用重启动的随机游走方法建立并求解特征匹配概率模型,利用双向均衡方法对匹配邻接矩阵进行均衡化处理,得到指定目标与待跟踪目标之间的精确匹配,以获得目标的定位跟踪结果。同时利用特征匹配结果进行目标的自动标定,并应用图像分割方法进行目标的精确轮廓跟踪。实验结果表明,将该方法应用于视频中动态背景下的运动细胞形态跟踪时,在背景相似度较高及目标迅速移动的条件下,表现出了良好的性能,与同类方法相比可获得较高的定位精度以及更为准确的目标轮廓。     

Semi-supervised vision-based maritime surveillance system using fused visual attention maps

This paper presents a vision-based system for maritime surveillance, using moving PTZ cameras. The proposed methodology fuses a visual attention method that exploits low-level image features appropriately selected for maritime environment, with appropriate tracker, without making any assumptions about environmental or visual conditions. The offline initialization is based on large graph semi-supervised technique. System’s performance was evaluated with videos from cameras placed at Limassol port and Venetian port of Chania. Results suggest high detection ability, despite dynamically changing visual conditions and different kinds of vessels, all in real time.     

短程线主动轮廓跟踪算法的研究--在复杂背景和非刚性运动目标跟踪中的应用

在复杂背景下对多个非刚性目标进行跟踪是计算机视觉中的一个难点。在短程线主动轮廓模型的基础上，利用力场正则化方法，并加入运动边缘信息，提出了一种在复杂背景下多个非刚性目标进行跟踪的方法。该方法由运动检测和跟踪两部分组成：运动检测利用运动边缘信息对运动目标的运动做出检测，让轮廓曲线运动到目标轮廓附近；跟踪利用当前帧中的静态边缘信息对运动检测的结果加以修正，而跟踪这一步引入的偏差将在下一帧的运动检测中得到修正。实验表明该方法能够有效地在复杂背景中对多个非刚性运动目标进行跟踪。     

基于水平集的多运动目标时空分割与跟踪

针对背景运动时的运动目标分割问题,提出了一种对视频序列中的多个运动目标进行分割和跟踪的新方法。该方法着眼于运动的且较为复杂的背景,首先利用光流约束方程和背景运动模型建立一个基于时空域的能量函数,然后用该函数进行背景运动速度的估算和运动目标的分割和跟踪。而时空域中的运动目标的最佳分割,乃是通过使该能量函数最小化来驱动时空曲面演化实现。时空曲面的演化采用了水平集PDEs(Partial Differential Equations)方法。实验中,用实际的图像序列验证了该算法及其数值实现。实验表明,该方法能够同时进行背景运动速度的估算、运动目标的分割和跟踪。     

基于OpenCV的视频运动目标检测与跟踪

针对视频文件中运动目标检测与跟踪这一问题,提出一种先检测后跟踪的方法.首先利用平均背景法完成对背景模型的更新,从而检测出运动目标,在此基础上利用投影法来投影出运动目标的大小,最后再利用MeanShift算法对运动目标进行跟踪.在跟踪过程中,通过OpenCV编写程序实现对运动目标的检测与跟踪.实验验证,该方法在实现运动目标的精确检测与跟踪的基础上,减少了运算量,提高了跟踪的速度.     

基于局部模型匹配的目标轮廓跟踪

在复杂背景下,传统轮廓跟踪方法会发生漂移,甚至丢失目标。针对上述问题,提出一种基于局部模型匹配（LMM）的目标轮廓跟踪算法。利用超像素技术结合EMD相似性度量构建局部特征模型,从而进行局部模型匹配。结合粒子滤波的Snake模型作提取目标轮廓,实现目标轮廓精确跟踪。实验结果表明,该算法在目标形变、部分遮挡、复杂背景等条件下均具有较高的跟踪成功率。与多种目标轮廓跟踪算法进行对比,该算法具有较高的准确性和鲁棒性。     

Adaptive control and constrained control allocation for overactuated ocean surface vessels

In this article, the constrained control allocation is proposed for overactuated ocean surface vessels with parametric uncertainties and unknown external disturbances. The constrained control allocation is transformed into a convex quadratic programming problem and a recurrent neural network is employed to solve it. To complete the control allocation, the control command is derived via the backstepping method. Adaptive tracking control is proposed for the full-state feedback case using the backstepping technique and the Lyapunov synthesis. It is proved that the proposed adaptive tracking control is able to guarantee semi-global uniform ultimate boundedness of all signals in the closed-loop system. Then, the obtained control command is distributed to each actuator of overactuated ocean vessels. Finally, simulation studies are presented to illustrate the effectiveness of the proposed adaptive tracking control and the constrained control allocation scheme.     

基于改进高斯混合模型的实时运动目标检测与跟踪*

为提高运动目标检测与跟踪的可靠性,提出了一种基于改进高斯混合模型的实时运动目标检测与跟踪算法。该算法建立可自动调节分布数目的高斯混合背景模型,通过背景减除获取前景图像;利用目标相邻帧的连续性分割运动目标;在此基础上将传统的颜色直方图模型进行改进,提高目标颜色分布的可信度,进而根据目标的位置、大小和颜色构造运动目标全局匹配相似度函数,实时完成运动目标检测与跟踪。利用大量的监控视频数据进行验证,结果表明,与传统的检测跟踪算法相比,该算法减少了计算量,提高了复杂背景情况下运动目标检测与跟踪的可靠性。     

Real time multiple objects tracking and identification based on discrete wavelet transform

A new method for detecting and tracking multiple moving objects based on discrete wavelet transform and identifying the moving objects by their color and spatial information is proposed in this paper. Many tracking algorithms have better performance under static background but get worse results under background with fake motions. Therefore, most of the tracking algorithms are used indoors instead of outdoor environment. Since discrete wavelet transform has a nice property that it can divide a frame into four different frequency bands without loss of the spatial information, it is adopted to solve this problem due to the fact that most of the fake motions in the background can be decomposed into the high frequency wavelet sub-band. In tracking multiple moving objects, many applications have problems when objects pass across each other. Color and spatial information are used in this paper to solve this problem. The experimental results prove the feasibility and usefulness of the proposed method.     

Layered Representation of a Video Shot with Mosaicing

: This paper presents a motion segmentation method useful for representing efficiently a video shot as a static mosaic of the background plus sequences of the objects moving in the foreground. This generates an MPEG-4 compliant, layered representation useful for video coding, editing and indexing. First, a mosaic of the static background is computed by estimating the dominant motion of the scene. This is achieved by tracking features over the video sequence and using a robust technique that discards features attached to the moving objects. The moving objects get removed in the final mosaic by computing the median of the grey levels. Then, segmentation is obtained by taking the pixelwise difference between each frame of the original sequence and the mosaic of the background. To discriminate between the moving object and noise, temporal coherence is exploited by tracking the object in the binarised difference image sequence. The automatic computation of the mosaic and the segmentation procedure are illustrated with real sequences experiments. Examples of coding and content-based manipulation are also shown. Received: 31 August 2000, Received in revised form: 18 April 2001, Accepted: 20 July 2001     

复杂背景下感兴趣运动目标的跟踪算法

针对由于复杂背景的干扰而导致不能准确跟踪感兴趣运动目标的问题,提出一种基于多特征自适应融合的粒子滤波跟踪算法。首先在HSV颜色空间中得到感兴趣运动目标的加权颜色分布模型,然后利用不变矩特征来消除背景中相似颜色物体和光照变化的干扰,两种特征通过自适应调整权重来更新粒子权值而融合于粒子滤波算法中,从而能够准确和稳定地跟踪运动目标。实验证明,该算法在运动目标平移、姿态变化、遮挡、光照变化及相似颜色干扰等复杂背景下都能够准确地进行跟踪,对背景干扰具有很强的鲁棒性。     

OPTICS聚类与目标区域概率模型的多运动目标跟踪

目的 针对多运动目标在移动背景情况下跟踪性能下降和准确度不高的问题,本文提出了一种基于OPTICS聚类与目标区域概率模型的方法。方法 首先引入了Harris-Sift特征点检测,完成相邻帧特征点匹配,提高了特征点跟踪精度和鲁棒性;再根据各运动目标与背景运动向量不同这一点,引入了改进后的OPTICS加注算法,在构建的光流图上聚类,从而准确的分离出背景,得到各运动目标的估计区域;对每个运动目标建立一个独立的目标区域概率模型(OPM),随着检测帧数的迭代更新,以得到运动目标的准确区域。结果 多运动目标在移动背景情况下跟踪性能下降和准确度不高的问题通过本文方法得到了很好地解决,Harris-Sift特征点提取、匹配时间仅为Sift特征的17%。在室外复杂环境下,本文方法的平均准确率比传统背景补偿方法高出14%,本文方法能从移动背景中准确分离出运动目标。结论 实验结果表明,该算法能满足实时要求,能够准确分离出运动目标区域和背景区域,且对相机运动、旋转,场景亮度变化等影响因素具有较强的鲁棒性。     

干扰环境下运动目标跟踪的背景滤波

基于Mean Shift的目标跟踪算法,在目标发生明显尺度变化或存在背景干扰的情况下,跟踪就会失败。为此,针对跟踪过程中的背景干扰问题,提出根据目标运动状态进行背景滤波的目标跟踪算法。根据目标跟踪过程中产生的运动轨迹估计目标位移和速度,沿着目标可能的运动方向的反方向对候选区域进行背景滤波,滤波区域宽度根据目标位移大小确定。实验结果表明,改进后的算法对背景信息具有较好的鲁棒性,提高目标跟踪的可靠性。     

Assessing the effectiveness of direct gesture interaction for a safety critical maritime application

Multi-touch interaction, in particular multi-touch gesture interaction, is widely believed to give a more natural interaction style. We investigated the utility of multi-touch interaction in the safety critical domain of maritime dynamic positioning (DP) vessels. We conducted initial paper prototyping with domain experts to gain an insight into natural gestures; we then conducted observational studies aboard a DP vessel during operational duties and two rounds of formal evaluation of prototypes—the second on a motion platform ship simulator. Despite following a careful user-centred design process, the final results show that traditional touch-screen button and menu interaction was quicker and less erroneous than gestures. Furthermore, the moving environment accentuated this difference and we observed initial use problems and handedness asymmetries on some multi-touch gestures. On the positive side, our results showed that users were able to suspend gestural interaction more naturally, thus improving situational awareness.     

PTZ自主跟踪中的全景视频生成

提出了一种在单PTZ摄像机自主跟踪过程中生成全景视频的方法。该方法在自主跟踪目标的同时,生成目标在大场景上运动的全景视频,可应用于PTZ摄像机监控场所。该方 法将全景视频看作全景背景图像和当前目标图像的叠加：首先利用Mean Shift跟踪方法逐帧获取目标区域图像并保存;然后利用相邻两帧视频图像的竖直方向投影匹配和Harris角 点匹配结果合成全景背景,与传统的配准方法相比,大大降低了匹配运算的复杂度,使全景背景的生成能够实时进行,并记录每帧图像到背景图像的变换参数;最后逐帧将目标区 域图像变换到背景图像上得到全景视频。本文方法与传统的全景视频生成方法相比,无需人工控制摄像机的转动,也无需手工对齐视频帧,整个过程全部自动完成。