A sensor-based SLAM algorithm for camera tracking in virtual studio

This paper addresses a sensor-based simultaneous localization and mapping （SLAM） algorithm for camera tracking in a virtual studio environment. The traditional camera tracking methods in virtual studios are vision-based or sensor-based. However, the chroma keying process in virtual studios requires color cues, such as blue background, to segment foreground objects to be inserted into images and videos. Chroma keying limits the application of vision-based tracking methods in virtual studios since the background cannot provide enough feature information. Furthermore, the conventional sensor-based tracking approaches suffer from the jitter, drift or expensive computation due to the characteristics of individual sensor system. Therefore, the SLAM techniques from the mobile robot area are first investigated and adapted to the camera tracking area. Then, a sensor-based SLAM extension algorithm for two dimensional （2D） camera tracking in virtual studio is described. Also, a technique called map adjustment is proposed to increase the accuracy＇ and efficiency of the algorithm. The feasibility and robustness of the algorithm is shown by experiments. The simulation results demonstrate that the sensor-based SLAM algorithm can satisfy the fundamental 2D camera tracking requirement in virtual studio environment.     

Distributed environment representation and object localization system in intelligent space

A kind of new environment representation and object localization scheme is proposed in the paper aiming to accomplish the task of object operation more efficiently in intelligent space.First,a distributed environment representation method is put forward to reduce storage burden and improve the system’s stability.The layered topological maps are separately stored in different landmarks attached to the key positions of intelligent space,so that the robot can search the landmarks on which the map information can be read from the QR code,and then the environment map can be built autonomously.Map building is an important prerequisite for object search.An object search scheme based on RFID and vision technology is proposed.The RFID tags are attached to the target objects and reference objects in the indoor environment. A fixed RFID system is built to monitor the rough position(room and local area)of target and a mobile RFID system is constructed to detect the targets which are not in the covering range of the fixed system.The existing area of target is determined by the time sequence of reference tags and target tags,and the accurate position is obtained by onboard vision system at a short distance.The experiments demonstrate that the distributed environment representation proposed in the paper can fully meet the requirements of object localization,and the positioning scheme has high search efficiency,high localization accuracy and precision,and a strong anti-interference ability in the complex indoor environment.     

Target tracking in wireless sensor networks using adaptive measurement quantization

Quantization/compression is usually adopted in wireless sensor networks (WSNs) since each sensor node typically has very limited power supply and communication bandwidth.We consider the problem of target tracking in a WSN with quantized measurements in this paper.Attention is focused on the design of measurement quantizer with adaptive thresholds.Based on the probability density function (PDF) of the signal amplitude measured at a random location and by maximizing the entropy,an adaptive design method for quantization thresholds is proposed.Due to the nonlinear measuring and quantization models,particle filtering (PF) is adopted in the fusion center (FC) to estimate the target state.Posterior Cram’er-Rao lower bounds (CRLBs) for tracking accuracy using quantized measurements are also derived.Finally,a simulation example on tracking single target with noisy circular trajectories is provided to illustrate the effectiveness of the proposed approach.     

Design and implementation of vision-based transport for a mobile robot via Kalman filter

A vision-based scheme for object recognition and transport with a mobile robot is proposed in this paper. First, camera calibration is experimentally performed with Zhenyou Zhang’s method, and a distance measurement method with the monocular camera is presented and tested. Second, Kalman filtering algorithm is used to predict the movement of a target with HSI model as the input and the seed filling algorithm as the image segmentation approach. Finally, the motion control of the pan-tilt camera and mobile robot is designed to fulfill the tracking and transport task. The experiment results demonstrate the robust object recognition and fast tracking capabilities of the proposed scheme.     

距离交会算法在无线传感网络节点定位中的应用

Knowing the locations of nodes in wireless sensor networks (WSN) is essential for many applications. Nodes in a WSN can have multiple capabilities and exploiting one or more of the capabilities can help to solve the localization problem. In this paper, we assume that each node in a WSN has the capability of distance measurement and present a location computation technique called linear intersection for node localization. We also propose an applied localization model using linear intersection and do some concerned experiments to estimate the location computation algorithm.     

HierTrack: an energy-efficient cluster-based target tracking system forwireless sensor networks

Target tracking is a typical and important application of wireless sensor networks(WSNs).Existing target tracking protocols focus mainly on energy efficiency,and little effort has been put into network management and real-time data routing,which are also very important issues for target tracking.In this paper,we propose a scalable cluster-based target tracking framework,namely the hierarchical prediction strategy(HPS),for energyefficient and real-time target tracking in large-scale WSNs.HPS organizes sensor nodes into clusters by using suitable clustering protocols which are beneficial for network management and data routing.As a target moves in the network,cluster heads predict the target trajectory using Kalman filter and selectively activate the next round of sensors in advance to keep on tracking the target.The estimated locations of the target are routed to the base station via the backbone composed of the cluster heads.A soft handoff algorithm is proposed in HPS to guarantee smooth tracking of the target when the target moves from one cluster to another.Under the framework of HPS,we design and implement an energy-efficient target tracking system,HierTrack,which consists of 36 sensor motes,a sink node,and a base station.Both simulation and experimental results show the efficiency of our system.     

Level Set method for license plate localization technology

Localization of license plate is an important factor in license plate recognition system. Currently although there are some methods for the localization, some limits such as low accuracy exist. So a better method should be found to solve this problem. Level Set, which has been proved efficient currently, gives new prospect to license plate localization. In this paper, based on the original thought of Level Set method, the Mumford-Shah model with Level Set method is obtained, further the finite difference and a third order TVD （Total Variation Diminishing） Runge-Kutta time discretization scheme is analyzed, and applied in license plate image localization. Computation results show that better edge detection results from level set method are obtained compared to other edge detection methods such as Roberts, Sobel and Canny. Level Set method drops much edge of non-target area which has a lot of value to target edge detection and target position tracking.     

Cooperative Target Tracking of Multiple Autonomous Surface Vehicles Under Switching Interaction Topologies

This paper is concerned with the cooperative target tracking of multiple autonomous surface vehicles(ASVs) under switching interaction topologies.For the target to be tracked,only its position can be measured/received by some of the ASVs,and its velocity is unavailable to all the ASVs.A distributed extended state observer taking into consideration switching topologies is designed to integrally estimate unknown target dynamics and neighboring ASVs’ dynamics.Accordingly,a novel kinematic controlle...     

An adaptive fuzzy design for fault-tolerant control of MIMO nonlinear uncertain systems

This paper presents a novel control method for accommodating actuator faults in a class of multiple-input multiple-output (MIMO) nonlinear uncertain systems.The designed control scheme can tolerate both the time-varying lock-in-place and loss of effectiveness actuator faults.In each subsystem of the considered MIMO system,the controller is obtained from a backstepping procedure;an adaptive fuzzy approximator with minimal learning parameterization is employed to approximate the package of unknown nonlinear functions in each design step.Additional control effort is taken to deal with the approximation error and external disturbance together.It is proven that the closed-loop stability and desired tracking performance can be guaranteed by the proposed control scheme.An example is used to show the effectiveness of the designed controller.     

Target tracking based on the extended H-infinity filter in wireless sensor networks

In this paper, we propose a new target tracking approach for wireless sensor networks (WSNs) by using the extended H-infinity filter. First, the extended H-infinity filter for nonlinear discrete-time systems is deduced through the Krein space analysis scheme. Then, the proposed extended H-infinity filtering algorithm is applied to target tracking in wireless sensor networks. Finally, experiments are conducted through a small wireless sensor network test-bed. Both experimental and simulation results illustrate that the extended H-infinity filtering algorithm is more accurate to track a moving target in wireless sensor networks than using the extended Kalman filter in the case of having no knowledge of the statistics of the environment and the target to be tracked.     

基于改进的洪泛广播和粒子滤波的无线传感器网络节点定位

针对目前移动无线传感器网络定位问题存在的不足,提出了一种基于改进的洪泛广播机制和粒子滤波的节点定位算法。对于一个给定的未知节点,首先采用改进的洪泛广播机制,从离它最近的锚节点得到的有效平均跳距来计算出它到它的所有邻居节点的距离。然后采用一种差分误差校正算法,以减小平均跳距中由于多跳累积造成的测量误差;其次,采用粒子滤波和虚拟锚节点来减小预测区域,得到更有效的粒子预测区域,从而进一步减小对未知节点位置的估计误差。仿真结果表明,所提算法与定位算法DV-Hop、蒙特卡罗Baggio（MCB）和基于测试的蒙特卡罗定位（MCL）相比,能够有效地抑制冗余广播和减小与节点定位相关的消息开销,以较低的通信成本实现较高精度的定位性能。     

使用移动锚节点的增量式自定位算法研究

无线传感网节点自定位技术是许多相关应用的前提和基础,目前已提出多种定位算法,但大多用于静态无线传感网。针对使用移动锚节点定位场景提出一种基于测距的算法PMAIL（PSO-based Mobile Anchor Incremental Localization）,将节点精度分级,选择高等级参考节点进行增量式定位,同时使用粒子群算法（PSO）求解加权误差方程,得到最优位置估计。算法不局限于特定测距方式,锚节点可同时支持常见的移动sink数据收集和网络管理等功能。仿真表明算法有较高的网络覆盖率,精度提高接近9%。     

无线传感器网络中一种基于高斯马尔可夫移动模型的自适应定位方法

针对无线传感器网络, 本文提出了一种基于高斯马尔科夫移动模型的自适应定位方法. 该方法由速度调整策略、中垂线策略和虚拟斥力策略组成. 速度调整策略可以使移动锚节点根据环境的改变自动的调整它的速度. 中垂线策略对移动锚节点的轨迹进行局部调整, 保证所有未知节点获得足够的非线性锚坐标. 而虚拟斥力策略不仅可以促使移动锚节点快速的离开已定位节点, 还能使它从边界外面快速的返回监测区域. 理论分析和仿真结果表明, 提出的方法可以达到较好的性能.     

A lightweight soft-state tracking framework for dense mobile ad hoc networks

In a mobile ad hoc network, tracking protocols need to deal with–in addition to the mobility of the target–the mobility of the intermediate nodes that maintain a track toward the target. To address this problem, we propose the MDQT (Mobility-enhanced Distributed QuadTree) tracking framework. MDQT employs a static cell abstraction to mask the mobility of the nodes and provide the illusion of a logical static network overlaid on the mobile network. MDQT implements this virtual static network layer in a lightweight/communication-free manner by exploiting the soft-state principle and the snooping feature of wireless communication.Through simulation, we study the impacts of the mobile node percentage and target mobility speed on the system performance. Simulation results show that the success rate of tracking is mostly unaffected by the speed of mobile nodes, but degrades slightly with the increases in mobile node percentage. On the other hand, the cost measurements (latency, average hops, and retry rate) are more sensitive to the mobility speed, and remain unaffected by the increase of mobile node percentage—owing to our soft-state design approach. We find that even at very high mobility speeds (50 m/s), low update rates (1 update per second), and 100% node mobility, the success rate of MDQT tracking is above 85% and the latency is comparable with that of static networks.     

Grid-Scan定位算法的虚拟锚节点策略改进

针对无线传感器网络中Grid-Scan算法定位精度较低的问题,提出了一种基于虚拟锚节点策略的Grid-Scan定位算法。具体做了三个方面的工作：对未知节点设置可定位阈值,邻居锚节点数大于可定位阈值的未知节点使用Grid-Scan算法进行定位,定位后的节点升级为虚拟锚节点;邻居锚节点数小于可定位阈值的未知节点利用极大似然法完成定位,定位后的节点升级为虚拟锚节点;锚节点及虚拟锚节点共同参与对剩余未知节点的定位。仿真结果表明,改进算法在不同锚节点密度、不同通信半径和不同栅格大小的网络中以及通过不规则传播模型后都具有较好的定位精度。     

Efficient and accurate sensor network localization

Wireless sensor networks (WSN) have great potential in ubiquitous computing. However, the severe resource constraints of WSN rule out the use of many existing networking protocols and require careful design of systems that prioritizes energy conservation over performance optimization. A key infrastructural problem in WSN is localization—the problem of determining the geographical locations of nodes. WSN typically have some nodes called seeds that know their locations using global positioning systems or other means. Non-seed nodes compute their locations by exchanging messages with nodes within their radio range. Several algorithms have been proposed for localization in different scenarios. Algorithms have been designed for networks in which each node has ranging capabilities, i.e., can estimate distances to its neighbours. Other algorithms have been proposed for networks in which no node has such capabilities. Some algorithms only work when nodes are static. Some other algorithms are designed specifically for networks in which all nodes are mobile. We propose a very general, fully distributed localization algorithm called range-based Monte Carlo boxed (RMCB) for WSN. RMCB allows nodes to be static or mobile and that can work with nodes that can perform ranging as well as with nodes that lack ranging capabilities. RMCB uses a small fraction of seeds. It makes use of the received signal strength measurements that are available from the sensor hardware. We use RMCB to investigate the question: “When does range-based localization work better than range-free localization?” We demonstrate using empirical signal strength data from sensor hardware (Texas Instruments EZ430-RF2500) and simulations that RMCB outperforms a very good range-free algorithm called weighted Monte Carlo localization (WMCL) in terms of localization error in a number of scenarios and has a similar computational complexity to WMCL. We also implement WMCL and RMCB on sensor hardware and demonstrate that it outperforms WMCL. The performance of RMCB depends critically on the quality of range estimation. We describe the limitations of our range estimation approach and provide guidelines on when range-based localization is preferable.     

基于动态分簇的移动目标追踪方法

针对无线传感器网络（WSN）中目标追踪的准确性低、网络能耗过高和网络生命周期短等问题,提出基于动态分簇的移动目标追踪技术。首先,构建了双层环状动态分簇的拓扑模型（TRDC）,并提出了动态分簇的更新算法;其次,在质心定位算法基础上,考虑到节点的能量,提出了基于功率级别的质心定位（CLPL）算法;最后,为了进一步减小网络的能耗,改进CLPL算法,提出了随机性定位算法。在仿真实验中,与静态簇相比,网络周期延长了22.73%;与非环状簇相比,丢失率降低了40.79%;而追踪准确性与基于接受信号强度值（RSSI）算法相差不大。所提的追踪技术能够有效保证追踪准确度,同时降低网络能耗,减小目标丢失率。     

一种用于移动传感器网络的定位算法

无线传感器网络作为一种全新的信息获取和处理技术,可以在广泛的应用领域内实现复杂的大规模监测和追踪任务。在传感器网络中,定位问题已经是很多无线传感器网络应用的关键,以前的大多数定位算法只适用于静态网络。设计了一种适用于锚节点和普通节点都自由移动的移动传感器网络的定位算法,该算法结合Monte Carlo和RSSI方法,通过约束选取样点的样本空间,仿真结果显示同比提高了算法精度。     

移动节点路径规划和几何限制的无线传感器网络定位算法

提出一种利用移动节点的无需测距的无线传感器网络定位算法.该算法中,移动节点以垂直路径两次穿过未知节点通信半径范围,从而获得通信区域边界附近多个航标位置;航标点连线的中垂线形成几何限制区域,该区域中心即为未知节点的估计位置.与其它基于几何限制区域的算法相比,本算法计算复杂度低、定位精度高.仿真实验结果显示本算法相比于其它算法,定位精度提高10％～40％不等.     

基于虚拟力的无线传感器与执行器网络测距定位算法

针对无线传感器与执行器网络(WSAN)的传感器节点定位问题,提出了一种基于虚拟力的无线传感器与执行器网络测距定位算法,使用移动的执行器节点替代传统无线传感器网络(WSN)定位算法中的锚节点,并将虚拟力模型引入基于信号到达时间(TOA)的定位算法。该算法在利用虚拟力驱动执行器节点逼近提出定位请求的传感器节点的同时,根据信号传输时间计算节点间的距离完成节点定位。仿真结果表明,提出的定位算法使得节点定位成功率提高20%左右,平均定位时间以及定位开销均小于传统TOA算法,适用于实时性要求高、执行器节点数量较少的场合。