混凝土结构中钢筋腐蚀监测无线传感器

钢筋腐蚀对混凝土结构的耐久性和安全性有很大影响.基于LC电路原理,通过钢丝腐蚀断裂的信号监测混凝土中钢筋腐蚀,研究钢筋腐蚀监测无线传感器机理.应用EWB软件对传感器电路进行模拟与分析,从理论上研究谐振频率变化与钢丝腐蚀断裂的关系.设计钢筋腐蚀无线传感器并进行了实验研究,结果表明:通过谐振频率监测钢丝是否腐蚀断裂是完全可行的,设计的开关型传感器可解决钢丝腐蚀过程中信号丢失问题.通过实验研究了传感器的封装材料和封装方法.     

Monitoring corrosion of reinforcement in concrete structures via fiber Bragg grating sensors

Corrosion of steel and rebar in concrete structures is one of the most frequent reasons for civil infrastructure failures. Thus, improving the effective corrosion sensor technology can greatly reduce cost and provide safe structures with long service lives. However, assessing the corrosion condition of rebars is not simple because they are buried in concrete. In this paper, using fiber Bragg grating (FBG), a corrosion sensor for monitoring steel rebars embedded in a concrete structure is developed and validated by experiments. Based on the fact that the volume and diameter of a rebar embedded in concrete will enlarge due to corrosion, an FBG packaged with fiber-reinforced plastics (FRP) is wrapped on the steel bar. During corrosion, the increase in the bar diameter leads to the increase in fiber strain, which can be measured by the shift of the wavelength of FBG. Performances of the corrosion sensor are validated by accelerating corrosion in lab experiments. The corrosion sensor is embedded in a concrete specimen put in a 5% sodium chloride solution with a constant current. Experimental results show that the corrosion sensor can monitor the concurrence of corrosion of rebars in concrete. The corrosion extent can be quantitatively evaluated through the change in the wavelength of FBG. Therefore, the corrosion sensor developed in this paper is feasible for monitoring the early corrosion of rebars in concrete.     

Development of an integrated wireless sensor network micro-environmental monitoring system

Wireless Sensor Network (WSN) is increasingly popular in the field of micro-environmental monitoring due to its promising capability. However, most systems using WSN for environmental monitoring reported in the literature are developed for specific applications without functions for exploiting user's data processing methods. In this paper, a new system is designed in detail to perform micro-environmental monitoring taking the advantages of the WSN. The application-oriented hardware working style is designed, and the system platform for data acquisition, validation, processing and visualization is systematically presented. Several strategies are proposed to guarantee the system capability in terms of extracting useful information, visualizing events to their authentic time are also described. Moreover, a web-based surveillance subsystem is presented for remote control and monitoring. In addition, the system is extensible for engineers to carry their own data analysis algorithms. Experimental results are to show the path reliability and real-time characteristics, and to display the feasibility and applicability of the developed system into practical deployment.     

Design of a wireless measurement system based on WSNs for large bridges

The structural vibration detection for large bridges is critical. A wireless measurement system based on Wireless Sensor Networks (WSNs) for large bridges was developed in this paper. The overall architecture of the wireless system is introduced; the design of wireless nodes and the principle of the central station are given in detail. Experiments are conducted in the laboratory and the Nanjing IV Yangtze River Bridge to verify the performance of the designed system. Experimental results show that the performances of the designed system are improved in the transmission distance. The system anti-jamming ability and data transmission packet loss rate are also improved compared to traditional wireless sensor systems. Meanwhile, with the external sensing interfaces, the system has a superior performance in characteristics of high sensitivity and ultra low frequency. It can easily and quickly carry out structural vibration detection for a large bridge in its construction, future operation, and maintenance periods with strong practicality and high application value.     

Study of consensus-based time synchronization in wireless sensor networks

Recently, various consensus-based protocols have been developed for time synchronization in wireless sensor networks. However, due to the uncertainties lying in both the hardware fabrication and network communication processes, it is not clear how most of the protocols will perform in real implementations. In order to reduce such gap, this paper investigates whether and how the typical consensus-based time synchronization protocols can tolerate the uncertainties in practical sensor networks through extensive testbed experiments. For two typical protocols, i.e., Average Time Synchronization (ATS) and Maximum Time Synchronization (MTS), we first analyze how the time synchronization accuracy will be affected by various uncertainties in the system. Then, we implement both protocols on our sensor network testbed consisted of Micaz nodes, and investigate the time synchronization performance and robustness under various network settings. Noticing that the synchronized clocks under MTS may be slightly faster than the desirable clock, by adopting both maximum consensus and minimum consensus, we propose a modified protocol, MMTS, which is able to drive the synchronized clocks closer to the desirable clock while maintaining the convergence rate and synchronization accuracy of MTS.     

Energy harvester for a wireless sensor in a boiler environment

Wireless sensors have become a focus of study in the field of measurement technologies. The power supply of many wireless sensors is based on batteries or external power sources. However, there is increasing interest in finding solutions where the batteries can be leaved away and the power for the wireless sensors is produced from the environment in which the sensors operate. The technologies required are called energy harvesting or scavenging technologies.This paper introduces the principles, modeling and a practical implementation of a self-powering solution for a wireless sensor for energy boilers or other hot reactor vessels. With the aid of energy solution introduced, the wireless sensor can operate autonomously without any batteries. One of the design targets in this work was that the top part of harvester’s mechanics must fit to the opening or assembly tube of diameter less than 15 mm in the boiler wall reserved for standard instrument assemblies. So the top of harvester collects and conducts thermal energy to element generating electricity from it. The harvester and further the measuring and communication electronics are mounted outside the hot area.The harvester solution introduced in the paper can produce about 114 mW power, when top of harvester mechanics was inserted to the test oven heated to temperature of +500 °C. The sensor function or type is not defined nor limited in this study. The electric energy generated by harvester can be used to power, for example, temperature, heat flux, flow, vibration or other little energy needing sensors.     

金属腐蚀在线监测系统的研制

基于电化学线性极化和弱极化测定方法，本文设计了一种金属腐蚀速率在线监测系统．成功地实现了金属腐蚀速率和极化电阻的自动在线监测和实时数据显示。对比实验表明．监测系统性能稳定．测量速度快、测量结果可信。     

热电耦合无线传感能量管理系统及其在精密主轴热监测中的应用

针对无线传感器热电耦合自供能存在的输出电量低和电压波动等问题,提出一种新型能量管理系统电路拓扑结构及基于最优时间的充放电控制策略,以保证自供能无线传感器在各种主轴转速条件下稳定工作。建立了机床主轴的热网络模型,分析了热发电能量管理系统输入特性。然后,设计了能量管理系统的多电容电路拓扑结构,并通过电容充放电时间参数的优化计算,获取最优的热发电平均输出功率。实验研究证实了在主轴不同转速下热发电构件及能量管理系统可以使无线传感器稳定的工作。对不同的电容充电和放电时间设置方案进行了比对,验证了最优时间控制策略的优越性。最后,利用热电耦合自供能无线传感器和传统有线传感器所监测的温度数据分别进行了主轴轴向热变形建模实验,结果表明：采用无线传感器可以监测有线传感器难以配置的主轴核心部件,从而获取和主轴热变形具有更高相关性的温度数据,使所建热变形预测模型的误差减少约40%以上。     

无线传感网络的节能策略分析

无线传感网络应用广泛,其能量损耗是限制大规模应用的因素之一。本文分析总结近年来多篇文献在传感、处理和通信3个功能模块上的节能策略研究,并对各种MAC协议和路由协议进行优缺点的综合比较,希望对节能选择具有一定的指导意义,并对无线传感网络节能发展趋势进行简要展望。     

基于WSN的博物馆环境监测系统

由于温、湿度等环境因素对文物的保存有着至关重要的作用,为了能够完好地保存博物馆中的文物,必须对其环境因素进行监测,而传统的手工监测方法存在着许多不足之处。为解决以上问题,提出了一种基于无线传感器网络（WSN）的博物馆环境监测系统,通过部署在博物馆藏馆内的传感器节点来实时地采集温、湿度等环境信息,并将数据传输至汇聚节点继而传送给后台处理程序,利用程序对各个藏馆的环境数据进行监测和处理。研究结果表明,该系统可以有效、稳定地对博物馆环境因素进行监测及处理,以保证文物良好的储存环境。     

超精密磨床振动和温度无线监测系统研究

开发了一套基于无线传输理论的精密磨床振动和温度无线监测系统,传感器和红外测温仪采集到的振动和温度信号接入相关的调理电路,经无线传输设备以一定的格式发送至远端的控制PC上.在状态监测控制端,基于Visual Basic 6.0开发的在线监测软件,显示振动信号幅域、频域处理结果以及温度信号的最高温度值和温度值曲线,以此判断机床是否处于正常工作状态.     

Experimental assessment of a wireless communications platform for the built and natural heritage

Wireless sensor networks have become extremely popular in a number of fields in recent years, the cultural heritage among them. To date, however, communications quality has not been technically validated in any of the various built (churches, museums, archaeological sites) or natural (caves, lava tubes) heritage scenarios. The present study establishes methodology for assessing the quality of wireless communications and validating the network used, both of which are essential to guaranteeing accurate long-term monitoring in heritage scenarios. Parameters such as signal strength, link quality, range and success rate were analysed with a view to preventing transmission failure and ensuring reliable monitoring for the preventive conservation of the cultural heritage.     

Resonant enhancement of a passive coil-capacitance loop in eddy current sensing path

A passive resonant coupling loop was composed by connecting an inductive coil with a capacitance element in series. Without any electric connection with measurement circuits, the loop is coaxially inserted into the sensing path between the sensing coil and metallic target of an eddy current proximity sensor. When the sensor is working around the natural frequency of the resonant loop, the mutual coupling between the sensing coil and metallic target is efficiently improved. Home-made eddy current proximity sensing coils are experimentally tested in frequencies around 800 kHz. The results indicate that the equivalent inductance of the sensing coil performs more sensitively to metallic target distance. Thus the higher sensitivity and resolution of proximity sensor will be expected.     

基于WSN的电力线受力监测系统

由于电力线在严重覆冰的情况下常常导致断线、倒塔等事故,而电力公司却不能预测电力线何时将要断裂,且事发后不能快速确定具体位置,以致无法及时抢修。为解决这些问题,设计了一种基于无线传感器网络(WSN)的电力线受力监测系统,通过部署在电力线上的传感器节点来实时采集电力线的受力参数,并将状态数据传输至汇聚节点,由汇聚节点通过GPRS网络传送至监控终端,监控终端对可能出现的电力线断裂情况进行预警。研究结果表明,该系统可以减少传统人工监测的高额成本,并提高监测的可靠性。     

塔式起重机监控中无线复合传感器的设计

利用ZigBee无线技术和数据级融合算法设计了一种复合传感器,以监控塔式起重机的吊钩/吊臂运动的方向和速度.通过分析和试验表明,该复合传感器可靠性高,易实现编程,安装使用更方便,功耗低,满足了塔式起重机监控系统的要求.同时,解决了吊钩/吊臂的运行状态实时采集和布线难的问题,对塔式起重机的安全运行和准确吊装有重要的工程实际意义.     

链式无线传感器网络移动目标二元协同感知策略

对链式无线传感器网络中移动目标的感知是对运动目标跟踪定位的基础,如何在节点能量有限情况下准确感知移动目标是其主要技术之一.为此,提出了一种基于节点相邻步距间协作的二元协同感知策略.首先提出目标感知节点集求解算法和目标运动感知模型;其次,融合当前感知概率和历史感知经验,建立移动目标感知概率求解模式,并相应地提出了二元协同感知算法;以矿井巷道内的人员定位监测为工程仿真实例,进一步进行了二元协同感知策略、全节点感知策略与单节点感知策略的性能比较,结果表明,二元协同感知策略能有效解决单个感知策略易存在检测漏洞与全节点感知策略通信量大的缺点,提高移动目标的感知概率,延长了网络的生存寿命.最后,以建筑物楼道长廊中的人员定位监测作为实际环境测试平台,测试了二元协同感知策略的性能变化,其结果显示出实际环境测试结果与理论仿真值变化趋势基本相同,从而验证了二元协同感知策略的实际有效性.     

基于无线传感技术的大型起重机械监测系统开发与应用

简要介绍了ASHM实验室近两年在基于无线传感技术的大型起重机械健康监测技术研究方面所取得的阶段性研究成果,研究成果已在现场进行应用试验,效果良好.该系统主要由无线传感器系统、数据采集网关、数据处理服务器与结构健康评估系统组成.大型起重机械结构健康监测技术不仅能够实现对起重机械结构健康状况进行实时监测,且能及时捕获起重机械结构失效的前兆,预防突发性灾难事故,从而避免重大人员伤亡与财产损失.     

面向实时监测的无线传感网低功耗通信策略

现场监测是无线传感网的主要应用领域之一,具有部署周期长、节点电池供电、感知数据实时上传等特点。针对此类数据采集应用的特点,提出了一种基于前导序列唤醒机制的媒体访问控制(MAC)层调度策略。通过对数据上传路径的节点唤醒时间的协调调度,减小了发送节点前导序列的长度,降低了节点的能耗和信道竞争的开销,提高了异常数据上传的实时性。对于多跳树形网络,本策略与现有的低功耗MAC协议进行了能耗分析对比。通过仿真和实验,验证了本策略的有效性,在保证数据实时性和投递率的同时,大大提高了网络寿命。     

基于无线传感器网络的实验室环境监控系统设计

针对目前实验室环境监控系统结构臃肿、造价昂贵等不足,应用无线传感器网络设计了实验室环境监控系统,阐述了实验室环境监控系统的实现。与传统的有线集中监控模式相比,该系统克服了传统监控系统需要布线的不足,并且测量准确,易于部署,便于扩充,有利于降低系统构建成本。     

Prototype design and experimental evaluation of wireless measurement nodes for road safety

The paper presents the design and the experimental evaluation of prototypes of measurement nodes that are part of the Wireless Active Guardrail System (WAGS). The WAGS is an innovative infrastructure, allowing increasing traffic safety on roads, by monitoring vehicle speed, proximity between vehicle and guardrail, impact of a vehicle with the guardrail, and several environmental parameters. In particular, in this paper, the designs and prototypes of the nodes dealing with speed and proximity measurements are presented. Then, all the phases of their experimental evaluation are reported and discussed.