传感器网络的可定位性条件

针对两个节点集合,提出了一组可定位性条件.可定位性条件包含两部分:两个集合之间需要的连接边的数目,以及如何布置这些连接边.本文将每组节点和它们的内部连接边刻画成一个距离图.两个节点集合之间的可定位性判定等同于两个融合图的全局刚性测试.针对两个融合图的可定位性,给出了一系列的充要条件.     

路径规划的可定位性研究

针对传统路径规划中没有将路径上各点的可定位性考虑进来,导致机器人在跟踪路径时由于定位误差过大导致跟踪失败,提出了一种新的路径评价函数将路径上各点可定位性进行考虑。分析常用定位算法中定位误差传递特性,采用将定位方差分别以[X]-[Y]平面定位结果的分布范围与朝向角的估计方差代表的方法,综合考虑路径安全性与长度性能,形成新的路径评价函数。实验结果表明,新的评价函数可以使得路径规划获得一条在可定位性、安全性、长度三方面总体最优的路径。     

基于概率栅格地图的移动机器人可定位性估计

基于广泛使用的概率栅格地图,提出了一种移动机器人可定位性估计方法.通过对定位Fisher信息矩阵进行栅格离散化,提出了静态可定位性矩阵,该矩阵适用于已知地图条件下的离线估计.在此基础上,针对在线估计中环境存在的非预期动态变化问题,采用局部感知的未知障碍物影响因子来修正静态可定位性矩阵,进而得到动态可定位性矩阵,该矩阵定量描述了机器人可定位性能力及其方向性.各种典型环境下的机器人实验结果表明了所提方法的有效性.     

How the Location of the Range Sensor Affects EKF-based Localization

The article proposes a solution to map-based self-localization for an autonomous robot operating in cluttered and crowded environments. To detect features for localization, 2D laser range-finders traditionally scan a plane parallel to the floor. This work hypothesizes the existence of a ??low frequency cross-section?? of the 3D Workspace where cluttered and dynamic environments become ??more regular?? and ??less dynamic??. The contribution of the article is twofold. First, an ??unevenness index?? U is introduced to quantitatively measure the complexity of the environment as it would be perceived if the laser range-finder were located at different heights from the floor. The article shows that, by choosing the laser scanning plane to statistically minimize U (in most cases, above the heads of people), it is possible to deal more efficiently with non-linearities in the measurement model, moving objects and occluded features. Second, it is demonstrated that, when adopting an extended Kalman filter for position tracking (a very common and widely used technique in real-world scenarios), the a posteriori covariance of the estimated robot pose converges faster, on average, when U is lower, which leads to better localization performance. Experimental results show hours of continuous robot operation in real-world, cluttered and crowded environments.     

一种改进的煤矿井下指纹定位匹配算法

煤矿井下环境复杂多变,对人员精确定位技术挑战很大。目前矿井巷道中采用基于接收信号强度指示RSSI(Received Signal Strength Indication)的位置指纹定位算法存在定位目标漂移、抖动和定位精度不高等问题。提出一种改进的指纹定位匹配算法,该算法将K邻近算法和最短历史路径匹配法联合并利用速度限定位置估计补偿算法对定位精度进行修正。利用在煤矿巷道中的实测数据,对改进的匹配算法进行了验证与误差分析。仿真结果表明,改进后的算法能够提高定位精度,满足矿井人员定位、目标跟踪和目标轨迹查询等要求。     

面向定位应用的无人机的悬停位置和飞行路径优化

无人机的一种典型应用是对地面目标进行定位.本文考虑,在无人机的飞行过程中,无人机在特定位置悬停,并广播信标信号.若地面节点与无人机悬停位置的距离满足通信范围,即可监测到无人机的信标信号,当地面节点监测到3个及以上不同悬停位置的信标信号时,即可使用多边定位法对自身进行定位.文中主要解决了如何选择悬停位置以及如何在悬停位置给定的情况下优化无人机飞行路径的问题,提出了两种无人机的悬停方案,并规划了两种方案下无人机的飞行路径,证明了两种悬停方案下提出的路径均为最短回路.通过模拟实验,验证了所提方案可以实现对待覆盖区域的完全覆盖,使任意地面节点均可实现定位;并且该方案可以通过调整无人机飞行高度和悬停方案中的网格大小,来提高定位精度.     

GPS拒止环境下基于定位置信度的多无人机协同定位方法

GPS拒止环境下的无人机定位问题是目前亟需研究和解决的一个难点问题.针对无人机集群系统在GPS拒止环境下的协同定位问题展开研究,首先,提出了定位置信度的概念,用于量化GPS拒止环境下无人机的定位准确程度;其次,提出了一种基于定位置信度的多无人机协同定位方法,该方法在基于持久性激励的相对定位法的基础上,利用定位置信度,自...     

基于骨架提取的水下传感器网络刚性定位判别研究

水下传感器网络可用于海洋资源勘测、污染监测和战术监视等领域,已成为无线传感器网络方向的研究热点.在水下三维空间中如何对位置未知的节点进行可定位性判别,并实施有效定位,从而为水下监测应用提供位置信息是一个基础的关键问题.该文引入刚性图理论,提出了一种基于骨架提取的水下传感器网络刚性定位判别方法.该方法首先将水下传感器网络构建为无向图,然后通过“伪节点剔除”和“割边剔除”等策略提取具有全局刚性的子图,即网络的骨架,从而完成网络及节点可定位性的判别,最后利用层次分析法对可定位节点进行“定位可信度”综合排序,为定位计算提供指导和依据.大量仿真实验结果表明该方法在不同网络规模、节点密度和网络连通性情况下均具有较高的判别成功率和有效性.     

一种基于边松弛的大规模WSN分簇定位算法

针对大规模WSN定位问题中,基于半定规划的分簇定位算法在分簇不均匀及节点密度较大时,部分簇会出现定位计算复杂度过高的问题,提出了一种新的基于边松弛的分簇定位算法-EES-Cluster.该算法通过对每一个网络簇子图进行边的松弛预处理,减少了边的数目;在网络分簇数目较少时,能有效降低定位过程的计算复杂度,同时较好地保持较高的定位精度,减小簇头节点信息融合的功耗.仿真实验及分析表明,EES-Cluster算法能有效降低分簇定位算法的计算复杂度,提高大规模WSN的定位效率.     

Simultaneous Parameter Calibration,Localization, and Mapping

Abstract

The calibration parameters of a mobile robot play a substantial role in navigation tasks. Often these parameters are subject to variations that depend either on changes in the environment or on the load of the robot. In this paper, we propose an approach to simultaneously estimate a map of the environment, the position of the on-board sensors of the robot, and its kinematic parameters. Our method requires no prior knowledge about the environment and relies only on a rough initial guess of the parameters of the platform. The proposed approach estimates the parameters online and it is able to adapt to non-stationary changes of the configuration. We tested our approach in simulated environments and on a wide range of real-world data using different types of robotic platforms.     

移动定位技术和移动定位系统

移动终端的位置是移动互联网中的关键信息.本文从移动定位技术、典型的移动定位系统及当前研究热点等方面对其进行了阐述.     

一种自适应的分布式副本定位方法

提出了一种在数据网格环境下的自适应的分布式副本定位方法SADRL．该方法利用索引结点和本地副本定位结点实现对同一个数据文件的多个副本的快速定位；将副本定位索引信息平均分布在多个索引结点上，并且能够自适应索引结点的动态加入或退出：同时利用本地副本定位节点完成本地副本的查询定位。理论分析和实验表明，SADRL能够快速由逻辑文件名定位其索引结点。具有负载均衡、可扩展和高效的特点。     

How Client Capabilities,Vendor Configuration,and Location Impact BPO Outcomes

Despite the increasing use of onshore and offshore business process outsourcing (BPO), a comprehensive literature review [38] finds that there has been limited empirical research on BPO outcomes. This article responds to the call for research by developing and testing a conceptual model for BPO outcomes using data from 50 firms publicly traded in the U.S., including 38 firms in the Forbes Global 2000. We find that client firm capabilities, vendor configuration, and country location lead to interesting tradeoffs in the BPO quality, cost, and time outcomes. For example, while multi-sourcing offers advantages such as risk mitigation, client firms encounter reduced BPO time benefits when they use multiple vendors. While onshore BPO can lead to an improved quality, higher onshore labor costs result in lower BPO cost savings. And while offshore destinations such as India offer lower labor costs, time zone differences lead to reduced BPO time benefits.     

Integrating Exploration, Localization, Navigation and Planning with a Common Representation

Two major themes of our research include the creation of mobile robot systems that are robust and adaptive in rapidly changing environments, and the view of integration as a basic research issue. Where reasonable, we try to use the same representations to allow different components to work more readily together and to allow better and more natural integration of and communication between these components. In this paper, we describe our most recent work in integrating mobile robot exploration, localization, navigation, and planning through the use of a common representation, evidence grids.     

Location privacy: going beyond K-anonymity,cloaking and anonymizers

With many location-based services, it is implicitly assumed that the location server receives actual users locations to respond to their spatial queries. Consequently, information customized to their locations, such as nearest points of interest can be provided. However, there is a major privacy concern over sharing such sensitive information with potentially malicious servers, jeopardizing users’ private information. The anonymity- and cloaking-based approaches proposed to address this problem cannot provide stringent privacy guarantees without incurring costly computation and communication overhead. Furthermore, they require a trusted intermediate anonymizer to protect user locations during query processing. This paper proposes a fundamental approach based on private information retrieval to process range and K-nearest neighbor queries, the prevalent queries used in many location-based services, with stronger privacy guarantees compared to those of the cloaking and anonymity approaches. We performed extensive experiments on both real-world and synthetic datasets to confirm the effectiveness of our approaches.     

Efficient Regular Data Structures and Algorithms for Dilation, Location, and Proximity Problems

In this paper we investigate data structures obtained by a recursive partitioning of the multi- dimensional input domain into regions of equal size. One of the best known examples of such a structure is the quadtree . It is used here as a basis for more complex data structures. We also provide multidimensional versions of the stratified tree by van Emde Boas [vEB]. We show that under the assumption that the input points have limited precision (i.e., are drawn from the integer grid of size u ) these data structures yield efficient solutions to many important problems. In particular, they allow us to achieve O(log log u) time per operation for dynamic approximate nearest neighbor (under insertions and deletions) and exact on-line closest pair (under insertions only) in any constant number of dimensions. They allow O(log log u) point location in a given planar shape or in its expansion (dilation by a ball of a given radius). Finally, we provide a linear time (optimal) algorithm for computing the expansion of a shape represented by a region quadtree. This result shows that the spatial order imposed by this regular data structure is sufficient to optimize the operation of dilation by a ball. Received January 19, 1999; revised November 4, 1999.     

TBFL和SAFL方法熵分析

为TBFL(testing-based fault localization)方法和SAFL(similarity-aware fault localization)方法构造了熵模型,并用该模型对Dicing方法、TARANTULA方法、SAFL方法在一个实例上进行分析比较。结果表明,熵模型可以为构造以及分析TBFL方法和SAFL方法提供一个原则性框架。     

Vagueness and Rough Location

This paper deals with the representation and the processing of information about spatial objects with indeterminate location like valleys or dunes (objects subject to vagueness). The indeterminacy of the location of spatial objects is caused by the vagueness of the unity condition provided by the underlying human concepts valley and dune. We propose the notion of rough, i.e., approximate, location for representing and processing information about indeterminate location of objects subject to vagueness. We provide an analysis of the relationships between vagueness of concepts, indeterminacy of location of objects, and rough approximations using methods of formal ontology. In the second part of the paper we propose an algebraic formalization of rough location, and hence, a formal method for the representation of objects subject to vagueness on a computer. We further define operations on those representations, which can be interpreted as union and intersection operations between those objects. The discussion of vagueness of concepts, indeterminacy of location, rough location and the relationships between these notions contributes to the theory about the ontology of geographic space. The formalization presented can provide the foundation for the implementation of vague objects and their location indeterminacy in GIS.     

基于用户偏好和位置分布的假位置生成方法

传统的基于k-匿名机制的假位置生成算法生成的假位置的合理性较低,易被攻击者利用边信息进行攻击.针对此问题,提出了SPDGM算法.首先,定义语义加权有向图,描述语义的时间分布和语义转移关系;其次,为解决仅考虑位置历史概率产生的抵抗能力弱的问题,提出了位置可信度,统一考虑了位置历史概率和大众的评价信息;再次,为避免假位置分...