A General Method for Sensor Planning in Multi-Sensor Systems: Extension to Random Occlusion

Systems utilizing multiple sensors are required in many domains. In this paper, we specifically concern ourselves with applications where dynamic objects appear randomly and the system is employed to obtain some user-specified characteristics of such objects. For such systems, we deal with the tasks of determining measures for evaluating their performance and of determining good sensor configurations that would maximize such measures for better system performance. We introduce a constraint in sensor planning that has not been addressed earlier: visibility in the presence of random occluding objects. occlusion causes random loss of object capture from certain necessitates the use of other sensors that have visibility of this object. Two techniques are developed to analyze such visibility constraints: a probabilistic approach to determine “average” visibility rates and a deterministic approach to address worst-case scenarios. Apart from this constraint, other important constraints to be considered include image resolution, field of view, capture orientation, and algorithmic constraints such as stereo matching and background appearance. Integration of such constraints is performed via the development of a probabilistic framework that allows one to reason about different occlusion events and integrates different multi-view capture and visibility constraints in a natural way. Integration of the thus obtained capture quality measure across the region of interest yields a measure for the effectiveness of a sensor configuration and maximization of such measure yields sensor configurations that are best suited for a given scenario. The approach can be customized for use in many multi-sensor applications and our contribution is especially significant for those that involve randomly occurring objects capable of occluding each other. These include security systems for surveillance in public places, industrial automation and traffic monitoring. Several examples illustrate such versatility by application of our approach to a diverse set of different and sometimes multiple system objectives. Most of this work was done while A. Mittal was with Real-Time Vision and Modeling Department, Siemens Corporate Research, Princeton, NJ 08540.     

基于数据融合确保目标检测精度的传感器节点布置

在使用无线传感器网络进行目标检测时,如何布置尽可能少的传感器节点而同时实现高的正确检测概率和低的误警率,是关键问题之一.采用数据融合技术,能实现传感器节点之间的协同,从而大幅提高目标检测精度.提出了用于目标检测的精度模型,分析了数据融合半径与传感器节点密度之间的关系,设计聚类方法将目标点组织成布置单元,从高密度单元到低密度单元布置传感器节点覆盖目标区域.仿真结果表明,算法在保证检测精度的同时能有效减少所使用的传感器节点数目.     

Optimal IDS Sensor Placement and Alert Prioritization Using Attack Graphs

We optimally place intrusion detection system (IDS) sensors and prioritize IDS alerts using attack graph analysis. We begin by predicting all possible ways of penetrating a network to reach critical assets. The set of all such paths through the network constitutes an attack graph, which we aggregate according to underlying network regularities, reducing the complexity of analysis. We then place IDS sensors to cover the attack graph, using the fewest number of sensors. This minimizes the cost of sensors, including effort of deploying, configuring, and maintaining them, while maintaining complete coverage of potential attack paths. The sensor-placement problem we pose is an instance of the NP-hard minimum set cover problem. We solve this problem through an efficient greedy algorithm, which works well in practice. Once sensors are deployed and alerts are raised, our predictive attack graph allows us to prioritize alerts based on attack graph distance to critical assets.

锥壳零件自动铺丝变角度轨迹规划算法

基于自动铺丝设备具有可灵活操作的铺放头及铺放所采用的预浸纤维丝宽度窄等特点,提出一种新型的铺层成型算法——变角度丝束铺放,其具有无间隙和无重叠的特点.以锥壳零件为例,首先建立此类零件几何特征的数学模型,推导出锥壳零件上任意轨迹的数学方程;然后提出变角度铺层的成型原理及方法,建立变角度轨迹规划算法的数学模型并推导出锥壳零件上任意变角度铺放路径及路径曲率的数学方程,再结合自动铺丝设备及预浸丝束自身特点对变角度铺层的可铺性进行分析.最后通过仿真实验对文中算法进行了验证.     

可重构系统中的实时任务在线调度与放置算法

有效的任务调度与放置是发挥可重构计算性能优势的重要因素.针对实时任务在二维可重构器件上的在线调度问题,定义了调度算法完全识别的概念,即算法不会拒绝能够成功调度的任务.提出了新的实时在线调度与放置算法,充分利用了任务的时间信息,实现了完全识别的调度.实验表明,与已有的算法相比,新算法显著地改善了调度效果,而运行开销没有明显增加.     

Optimal PMU-based monitoring architecture design for power systems

This paper is dedicated to a new methodology for designing an optimal monitoring architecture by using a limited number of PMUs (Phasor Measurement Units) and PDCs (Phase Data Concentrators). The optimal design problem consists in defining the optimal location of both PMUs and PDCs by maximizing the expected value of the trace of the observability gramian of the power system over a large number of set point scenarios, while minimizing some communication infrastructure costs. Furthermore, a nonlinear dynamical state-observer, based on the Extended Kalman Filter, is proposed. This state-observer allows to take transient phenomena into account for wide-area power systems described by algebraic-differential equations, without needing nonlinear inversion techniques. The overall approach is illustrated with the IEEE 10 generator 39 bus New England power system.     

Camera cooperation for achieving visual attention

In this paper we address the problem of establishing a computational model for visual attention using cooperation between two cameras. More specifically we wish to maintain a visual event within the field of view of a rotating and zooming camera through the understanding and modeling of the geometric and kinematic coupling between a static camera and an active camera. The static camera has a wide field of view thus allowing panoramic surveillance at low resolution. High-resolution details may be captured by a second camera, provided that it looks in the right direction. We derive an algebraic formulation for the coupling between the two cameras and we specify the practical conditions yielding a unique solution. We describe a method for separating a foreground event (such as a moving object) from its background while the camera rotates. A set of outdoor experiments shows the two-camera system in operation.     

Real-Time Camera Tracking for Mobile Devices: The VisiTrack System

This paper presents VisiTrack, a novel approach for video based incremental tracking in real-time. The major objectives in the development of VisiTrack was to design or select algorithms that are well suited for embedded real-time computation. We had a special focus on latency reduction and storage minimization since the algorithms should run on mobile devices like PDAs with the appropriate extension, i.e. mainly a camera, in real-time. The image analysis, camera localization and feature position approximation of VisiTrack are explained in detail. The CV-SDF model, an extension of Synchronous Dataflow graphs (SDF), supporting the principles of linear processing and fine-grained pipelining was defined and applied for the design of all VisiTrack modules in order to fulfill real-time constraints and reduce system latency. Furthermore the camera localization and position approximation include mechanisms for minimization of errors that may arise for instance due to measurement inaccuracies. Current applications of VisiTrack in the augmented reality domain and robotic self localization show its good performance. However VisiTrack is not limited to these application domains.     

传感器网络中协作任务的实时调度

在传感器网络实时监测应用中,大量传感器散布在监测区域中感知监测域的各种环境或监测对象的信息,一组功能有限的传感器往往相互协作地完成一个大的实时感知任务,协作性是传感器网络的重要特性,它要求实时任务之间的资源共享。单纯的实时系统为保证任务的实时性通常采用资源隔离机制而不能很好地解决传感器网络环境中的采集流数据处理的协作性问题。本文基于服务器的调度框架,使用了实时环境中的时间属性,将数据时间与程序时间相结合,从而将应用语义与系统中运行的程序相联系,提出了一种基于时间依赖关系的实时调度模式,并给出了基于此模式的事件驱动并发数据流程图模型及其实现机制。分析表明,该模型能有效地解决传感器网络监测区域中采集流数据处理过程的协作性问题,减少了数据丢失,提高了系统响应的实时性。     

两类非可展曲面零件自动纤维铺放变角度轨迹规划算法

为了避免非可展回转外壳类零件及非可展曲面变截面接头类零件在自动纤维铺放过程中出现除端面以外的剪切和重送现象,简化纤维铺放过程的复杂程度,提出一种针对这2类非可展曲面零件自动纤维铺放变角度轨迹规划算法.首先获取零件外形的数据信息,然后计算不同位置处的纤维铺放角,得到初始轨线上的点,最终获取所有轨迹线;此外,还针对不同零件给出了初始点的获取方法;并针对非可展回转外壳类零件及非可展曲面变截面接头类零件,以CATIA CAA与VC6.0为开发平台,给出了该算法的具体实现步骤.通过计算相邻两丝束之间的间隙或重叠,对文中算法的可行性进行了理论验证.     

Decentralized Delayed-State Information Filter (DDSIF): A new approach for cooperative decentralized tracking

This paper presents a decentralized data fusion approach to perform cooperative perception with data gathered from heterogeneous sensors, which can be static or carried by robots. In particular, a decentralized delayed-state information filter (DDSIF) is described, in which full-state trajectories (that is, delayed states) are considered to fuse the information. This approach allows obtaining an estimation equal to that provided by a centralized system and reduces the impact of communication delays and latency in the estimation. The sparseness of the information matrix maintains the communication overhead at a reasonable level. The method is applied to cooperative tracking, and some results in disaster management scenarios are shown. In this kind of scenario, the target might move in both open-field and indoor areas, so the fusion of data provided by heterogeneous sensors is beneficial. The paper also shows experimental results with real data and integrating several sources of information.     

网格化曲面的固定角度铺丝轨迹规划算法

研究适用于网格化曲面的自动铺丝固定角度算法,对现有固定角度算法及其优缺点进行归纳,阐述了铺放曲面网格化的优势和应用STL文件进行网格划分的原因.提出了2类网格化曲面固定角度自动铺丝轨迹规划算法.针对算法在网格化曲面轨迹规划过程中可能出现的顶点情况和无解情况,分析了它们产生的原因,并提出了相应的解决方案.通过采用基于VC++编程实现了文中算法,并由计算结果绘制轨迹线,验证了其正确性和合理性.将固定算法引入网格化曲面,增大了算法适用范围,降低了规划难度,提高了规划效率.     

Optimal pressure sensor placement and assessment for leak location using a relaxed isolation index: Application to the Barcelona water network

Water distribution networks are large complex systems affected by leaks, which often entail high costs and may severely jeopardise the overall water distribution performance. Successful leak location is paramount in order to minimize the impact of these leaks when occurring. Sensor placement is a key issue in the leak location process, since the overall performance and success of this process highly depends on the choice of the sensors gathering data from the network. Common problems when isolating leaks in large scale highly gridded real water distribution networks include leak mislabelling and the obtention of large number of possible leak locations. This is due to similarity of leak effect in the measurements, which may be caused by topological issues and led to incomplete coverage of the whole network. The sensor placement strategy may minimize these undesired effects by setting the sensor placement optimisation problem with the appropriate assumptions (e.g. geographically cluster alike leak behaviors) and by taking into account real aspects of the practical application, such as the acceptable leak location distance. In this paper, a sensor placement methodology considering these aspects and a general sensor distribution assessment method for leak diagnosis in water distribution systems is presented and exemplified with a small illustrative case study. Finally, the proposed method is applied to two real District Metered Areas (DMAs) located within the Barcelona water distribution network.     

基于移动Sink的自组织视频传感网络目标跟踪算法

基于自组织视频传感网络的目标跟踪方法利用节点的分布式观测能力,实现目标的精确跟踪。在研究视频节点观测投射模型和通信模型的基础上,提出一种基于移动Sink的自组织视频传感网络目标跟踪算法MSTTA。该算法包括感知信息聚合和目标位置评估两个部分,利用节点分类机制周期性地更新网络拓扑以适应Sink位置的变化,根据目标运动状态预测目标位置的评估节点小组。仿真实验表明,MSTTA算法能够适应Sink移动带来的网络拓扑变化,具有较高的目标跟踪精度。     

基于Orbital Shrinking的数据中心虚拟机最优放置算法

摘要：虚拟机放置技术能够控制智能电网数据中心物理服务器的资源使用,将有效提升资源使用效率。虚拟机放置策略的思路主要基于时间、空间、计算资源和能耗的综合均衡,其主要面临的瓶颈包括鲁棒性和灵活性的平衡矛盾,以及有限资源的非均衡分配问题。根据当前电力数据中心结构复杂和资源利用率低的问题,本文提出一种基于Orbital Shrinking的数据中心虚拟机最优放置算法,首先研究虚拟机放置的数据中心适用性问题,有效地从多维目标优化和边界动态约束这2方面分析数据中心的资源状态。基于Orbital Shrinking模型,建立计算资源、时空状态和能耗条件的多维背包模型,实现虚拟机放置策略的整体平衡。通过实验仿真表明,新算法能够有效提升数据中心服务器的计算资源利用效率9.8%,降低数据处理时延10.3 s。     

WWW中缓存模型的优化设计

ＷＷＷ提供了方便的手段来访问远程信息资源，对于Ｗｅｂ用户而言，衡量Ｗｅｂ服务质量的一个重要指标就是检索信息所花费的时间。缩短检索时间的途径很多，此文主要介绍通过设置缓存机制，降低用户对资源访问请求次数，达到缩短用户直观感觉上的检索时间的方法。并讨论一种基于Ｃ／Ｓ结构的缓存模型，提出了新的缓存替换算法，综合考虑了文档长度，网络负载等参数，实现了缓存模型的优化。经过实验验证，该算法优于目前的缓存替换算法。     

传感网络在水电边坡变形优化检测中应用仿真

在水电边坡变形的检测过程中,需要根据坡变幅度,布置传感节点,传递相关数据,由于坡变幅度一般都伴随不规则起伏,造成传感器节点传递的信号无法形成线性特征,传统的检测方法为了克服非线性变化,需要在大起伏区域布置多个节点,以保证检测的准确性,一旦水电边坡规模大,地质条件较为复杂,将会导致检测节点过多,降低了检测效率。为解决上述问题,提出采用坡变估计模型的水电边坡变形优化传感器检测方法。构建传感网络水电边坡变形检测模型,分别对大坡变区域进行模型的坡变参数预估、参数精估、检验模型适应性、模型修正和模型预报,根据上述模型进行模型最优化评测,实现传感网络在水电边坡变形优化检测。实验结果表明,利用改进算法进行水电边坡变形优化检测,可以减小检测误差、提高检测的准确性,提高检测效率。     

Sensor Placement for Sensing Coverage and Data Precision in Wireless Sensor Networks

We present a novel paradigm of sensor placement concerning data precision and estimation. Multiple abstract sensors are used to measure a quantity of a moving target in the scenario of a wireless sensor network. These sensors can cooperate with each other to obtain a precise estimate of the quantity in a real-time manner. We consider a problem on planning a minimum-cost scheme of sensor placement with desired data precision and resource consumption. Measured data is modeled as a Gaussian random variable with a changeable variance. A gird model is used to approximate the problem. We solve the problem with a heuristic algorithm using branch-and-bound method and tabu search. Our experiments demonstrate that the algorithm is correct in a certain tolerance, and it is also efficient and scalable.     

射频能量捕获异构无线传感网的能量源最少化布置方法

电池供电的无线传感器网络的应用由于电池更换的不便利甚至不可能而受到极大的限制。考虑具有射频能量捕获能力的异构无线传感器网络,网络节点的能量捕获输出功率需求不一样。在已知传感节点数目和位置的情况下,研究如何布置射频能量源(Energy Transmitters,ETs)从而满足所有节点的能量捕获输出功率需求并且最小化ETs数目。首先建模出该最少化ETs的布置问题,为深入了解该问题提供了理论基础;然后提出了一种复杂度较低的贪婪式ETs布置方法和一种复杂度略高些的基于粒子群优化的ETs布置方法。仿真结果表明,与贪婪式方法相比,基于粒子群优化的方法能找到ETs略微更少的布置方案,但其由于复杂度略高,因此可用于节点数目不是很多的场景,而贪婪式方法则可用于节点数目较多的场景。     

无线网状网中面向负载均衡的网关部署算法

综合考虑网关数量和网关负载均衡两方面因素,提出一种基于力的贪婪启发式分簇算法,在此基础上对杂交粒子群优化进行改进,给出一种适用于无线网状网的网关部署算法。仿真实验结果表明,该算法能以较少的网关数量实现网络负载均衡,从而提高吞吐量,改善网络性能。