Wireless Acoustic Emission Sensor Network for Structural Monitoring

The paper presents a prototype wireless system for the detection of active fatigue cracks in aging railways bridges in real-time. The system is based on a small low-cost sensor node, called an AEPod, that has four acoustic emission (AE) channels and a strain channel for sensing, as well as the capability to communicate in a wireless fashion with other nodes and a base station. AEPods are placed at fracture-critical bridge locations. The strain sensor detects oncoming traffic and triggers the AEPod out of its hibernation mode. As the train stresses the fracture-critical member, acoustic emission and strain data are acquired. The data are compressed and filtered at the AEPod and transmitted off the bridge using cell-phone communication.     

A Mobile Host Approach for Wireless Powering and Interrogation of Structural Health Monitoring Sensor Networks

Wireless sensor networks (WSNs) for structural health monitoring (SHM) applications can provide the data collection necessary for rapid structural assessment after an event such as a natural disaster puts the reliability of civil infrastructure in question. Technical challenges affecting deployment of such a network include ensuring power is maintained at the sensor nodes, reducing installation and maintenance costs, and automating the collection and analysis of data provided by a wireless sensor network. In this work, a new "mobile host" WSN paradigm is presented. This architecture utilizes nodes that are deployed without resident power. The associated sensors operate on a mechanical memory principle. A mobile host, such as a robot or unmanned aerial vehicle, is used on an as-needed basis to charge the node by wireless power delivery and subsequently retrieve the data by wireless interrogation. The mobile host may be guided in turn to any deployed node that requires interrogation. The contribution of this work is the first field demonstration of a mobile host wireless sensor network. The sensor node, referred to as THINNER, capable of collecting data wirelessly in the absence of electrical power was developed. A peak displacement sensor capable of interfacing with the THINNER sensor node was also designed and tested. A wireless energy delivery package capable of being carried by an airborne mobile host was developed. Finally, the system engineering required to implement the overall sensor network was carried out. The field demonstration took place on an out-of-service, full-scale bridge near Truth-or-Consequences, NM.     

Highway Bridge Assessment Using an Adaptive Real-Time Wireless Sensor Network

A real-time wireless sensor network platform capable of maintaining lossless data transmission over several minutes of continuous, high-rate sampling is presented in this paper. The platform was designed specifically to provide the capability to enable expeditious system identification, as well as load rating of highway bridges without compromising the typical data acquisition parameters employed in comparable cable-based tests. Consequently, the hardware signal conditioning interface permits data collection from a variety of sensors typical to structural health monitoring, including accelerometers, strain transducers, and temperature sensors. The embedded software features a proprietary network transmission protocol capable of lossless, real-time delivery of up to 40 measurement channels at an effective sampling rate of 128 samples per second per channel. Documented in this paper is a field study on an end-of-service highway bridge in which ambient vibration monitoring was performed using 60 accelerometers interfaced with 30 wireless sensor nodes operating within one of two simultaneously operating star topology networks. In addition, an experimental load rating of the entire structure was performed through large-scale strain measurement facilitated by the same wireless sensor network platform.     

A Review on Piezoelectric,Magnetostrictive, and Magnetoelectric Materials and Device Technologies for Energy Harvesting Applications

In the coming era of the internet of things (IoT), wireless sensor networks that monitor, detect, and gather data will play a crucial role in advancements in public safety, human healthcare, industrial automation, and energy management. Batteries are currently the power source of choice for operating wireless network devices due to their ease of installation; however, they require periodic replacement due to capacity limitations. Within the scope of the IoT, battery maintenance of the trillion sensor nodes that may be implemented will be practically infeasible from environmental, resource, and labor cost perspectives. In considering individual self‐powered sensor nodes, the idea of harvesting energy from ambient vibrations, heat, and electromagnetic waves has recently triggered noticeable research interest in the academic community. This paper gives an overview of energy harvesting materials and systems. Three main categories are presented: piezoelectric ceramics/polymers, magnetostrictive alloys, and magnetoelectric (ME) multiferroic composites. State‐of‐the‐art harvesting materials and structures are presented with a focus on characterization, fabrication, modeling and simulation, and durability and reliability. Some perspectives and challenges for the future development of energy harvesting materials are also highlighted.

     

Hybrid Energy Harvesters: Toward Sustainable Energy Harvesting

Recently, sustainable green energy harvesting systems have been receiving great attention for their potential use in self‐powered smart wireless sensor network (WSN) systems. In particular, though the developed WSN systems are able to advance public good, very high and long‐term budgets will be required in order to use them to supply electrical energy through temporary batteries or connecting power cables. This report summarizes recent significant progress in the development of hybrid nanogenerators for a sustainable energy harvesting system that use natural and artificial energies such as solar, wind, wave, heat, machine vibration, and automobile noise. It starts with a brief introduction of energy harvesting systems, and then summarizes the different hybrid energy harvesting systems: integration of mechanical and photovoltaic energy harvesters, integration of mechanical and thermal energy harvesters, integration of thermal and photovoltaic energy harvesters, and others. In terms of the reported hybrid nanogenerators, a systematic summary of their structures, working mechanisms, and output performances is provided. Specifically, electromagnetic induction, triboelectric, piezoelectric, photovoltaic, thermoelectric, and pyroelectric effects are reviewed on the basis of the individual and hybrid power performances of hybrid nanogenerators and their practical applications with various device designs. Finally, the perspectives on and challenges in developing high performance and sustainable hybrid nanogenerator systems are presented.     

微型电磁式振动能量采集器的研究进展

随着低功耗无线传感网络和微机电系统的迅速发展,供电问题正成为它们进入实用化、产业化的一大障碍。现有的一个解决方案是微型电磁式振动能量采集器。首先给出电磁式振动能量采集器的工作原理、物理模型和设计原则,然后详细介绍目前国内外各研究小组研制的电磁式振动能量采集器的几何模型、结构参数、输出结果和技术特点,最后简单分析电磁式振动能量采集器面临的困难、挑战和发展趋势。     

Double bridge circuit for self‐validated structural health monitoring strain measurements

In structural health monitoring (SHM) applications, sensor faults and structural damage need to be assuredly discriminated. A self‐diagnosis strain sensor operating in a continuous online SHM scenario is considered. The strain sensor is based on full electric resistance strain gauge Wheatstone bridges. The state of the art shows that such a sensor has not yet been developed. The loop current step response (LCSR) is a well‐known method to detect strain gauge debonding. However, applying the LCSR method to a full strain gauge Wheatstone bridge has some limitations analysed in this paper. To enable the use of the LCSR method in an online SHM scenario, the double bridge circuit is proposed in this work. Two new strain gauge debonding fault detection methods and a new debonding fault isolation method—based on the double bridge circuit measurements—are proposed and evaluated. Two new sensor fusion weighting approaches are also proposed and evaluated—to achieve strain gauge debonding fault tolerance on the double bridge circuit. The experimental results show that the proposed methods can detect, isolate, and tolerate a strain gauge grid debonding fault and can be applied in an online SHM self‐diagnosis sensor scenario.     

Service life prediction of structural systems using lifetime functions with emphasis on bridges

In order to adequately handle the huge increase in traffic over the past three decades, most North American and European countries invested enormous funds in building highway networks. Nowadays, most of these networks are complete or close to completion. The biggest challenge highway agencies and departments of transportation face is the maintenance of these networks, keeping them safe and serviceable, with limited funds. The use of consistent measures of safety is fundamental for the development of optimum strategies for bridge maintenance. The analysis of safety on a component basis is a gross approximation of the real system performance of a bridge. In this paper, a model using lifetime functions to evaluate the overall system probability of survival of existing bridges, under maintenance or no maintenance, is proposed. In this model, bridges are modeled as systems of independent and/or correlated components. The proposed model is applied to an existing bridge located in Denver, Colorado, and the optimal maintenance strategy of this bridge is obtained in terms of service life extension and cumulative maintenance cost.     

基于计算机视觉人行桥挠度影响线非接触式识别

该文将便携式相机与无线传感器结合,开发了一种人致挠度影响线非接触式识别系统,避免了传统识别方法需要长时间阻断交通、耗费大量人力物力等不足,可用于运营状态下的桥梁影响线识别。通过便携式相机获取桥上行人行为,引入遮挡模型改进YOLO算法识别桥上行人,跟踪目标行人坐标变化得到行人位置信息,结合无线传感器得到的行人荷载作为结构输入数据。通过视觉识别技术跟踪结构行为获得人行荷载作用下的位移响应作为结构输出数据。根据结构输入输出数据反算人行荷载作用下桥梁挠度影响线。对初始影响线进行高阶滤波处理,消除环境和其他因素干扰,然后利用多项式分段拟合实测桥梁影响线进而得到具有准静态特性的挠度影响线,可为结构工程师准确高效地提供桥梁损伤检测依据。     

Estimation of Electric Charge Output for Piezoelectric Energy Harvesting

Abstract: Piezoelectric materials (PZT) can be used as mechanisms to transfer mechanical energy, usually ambient vibration, into electrical energy that can be stored and used to power other devices. With the recent advances in wireless and micro‐electro‐mechanical‐systems (MEMS) technology, sensors can be placed in exotic and remote locations. As these devices are wireless it becomes necessary that they have their own power supply. The power supply in most cases is the conventional battery; however, problems can occur when using batteries because of their finite life span. Because most sensors are being developed so that they can be placed in remote locations such as structural sensors on a bridge or global positioning service (GPS) tracking devices on animals in the wild, obtaining the sensor simply to replace the battery can become a very expensive task. Furthermore, in the case of sensors located on civil structures, it is often advantageous to embed them, making access impossible. Therefore, if a method of obtaining the untapped energy surrounding these sensors was implemented, significant life could be added to the power supply. One method is to use PZT materials to obtain ambient energy surrounding the test specimen. This captured energy could then be used to prolong the power supply or in the ideal case provide endless energy for the sensors lifespan. The goal of this study is to develop a model of the PZT power harvesting device. This model would simplify the design procedure necessary for determining the appropriate size and vibration levels necessary for sufficient energy to be produced and supplied to the electronic devices. An experimental verification of the model is also performed to ensure its accuracy.     

应用于无线传感器节点的微小型复合能源收集系统(英文)

设计并实现了一种可应用于无线传感器节点的复合能源系统样机,基于一种无线地磁交通流传感器,提出了本文的设计目标.选择太阳能、风能、应变能作为系统的能量源.根据这3种不同能量源的特性,对能量管理模块与能量储存模块进行了针对性设计,最后实现并测试了样机.实验结果表明,该样机可连续35 h在3.55 V电压下输出50mW的电能.     

Energy Scavenging From Low-Frequency Vibrations by Using Frequency Up-Conversion for Wireless Sensor Applications

This paper presents an electromagnetic (EM) vibration-to-electrical power generator for wireless sensors, which can scavenge energy from low-frequency external vibrations. For most wireless applications, the ambient vibration is generally at very low frequencies (1-100 Hz), and traditional scavenging techniques cannot generate enough energy for proper operation. The reported generator up-converts low-frequency environmental vibrations to a higher frequency through a mechanical frequency up-converter using a magnet, and hence provides more efficient energy conversion at low frequencies. Power is generated by means of EM induction using a magnet and coils on top of resonating cantilever beams. The proposed approach has been demonstrated using a macroscale version, which provides 170 nW maximum power and 6 mV maximum voltage. For the microelectromechanical systems (MEMS) version, the expected maximum power and maximum voltage from a single cantilever is 3.97 muW and 76 mV, respectively, in vacuum. Power level can be increased further by using series-connected cantilevers without increasing the overall generator area, which is 4 mm². This system provides more than an order of magnitude better energy conversion for 10-100 Hz ambient vibration range, compared to a conventional large mass/coil system.     

RF Energy Transmission for a Low-Power Wireless Impedance Sensor Node

The proper management of energy resources is essential for any wireless sensing system. With applications that span industrial, civil, and aerospace infrastructure, it is necessary for sensors and sensor nodes to be physically robust and power efficient. In many applications, a sensor network must operate in locations that are difficult to access, and often these systems have a desired operational lifespan which exceeds that of conventional battery technologies. In the present study, the use of microwave energy is examined as an alternate method for powering compact, deployable wireless sensor nodes. A prototype microstrip patch antenna has been designed to operate in the 2.4 GHz ISM band and is used to collect directed radio frequency (RF) energy to power a wireless impedance device that provides active sensing capabilities for structural health monitoring applications. The system has been demonstrated in the laboratory, and was deployed in field experiments on the Alamosa Canyon Bridge in New Mexico in August 2007. The transmitted power was limited to 1 W in field tests, and was able to charge the sensor node to 3.6 V in 27 s. This power level was sufficient to measure two piezoelectric sensors and transmit data back to a base station on the bridge.      

Evaluation of power extraction circuits on piezo‐transducers operating under low‐frequency vibration‐induced strains in bridges

The concept of piezoelectric energy harvesting (PEH) provides a promising solution for perpetually running low‐power electronic devices such as wireless sensor networks by harvesting ambient vibrations generated from civil structures such as long span bridges, city flyovers, elevated metro corridors, which are constantly under dynamic loads. However, its successful industrial‐scale deployment on civil structures is still not realised because of the low‐frequency of vibrations (typically <5 Hz) encountered there, coupled with the low levels of voltage generation. The vast majority of PEH‐related studies have only focused on PEH configurations and geometries, Often entailing secondary structures. d₃₁ mode, which is the most natural mode of excitation, has not been investigated in depth for piezo‐patches directly bonded on the main structure. Studies, which have focused on electronic conditioning circuitry, have been restricted to typically high‐voltage and high‐frequency scenarios only. This paper focuses on systematically studying the issues inflicting energy harvesting from the ambient vibrations induced flexural strains civil structures, such as city flyovers, using piezo elements in d₃₁ mode. Vibration measurements are first undertaken from a typical city flyover consisting of steel girders supporting a reinforced concrete (RC) deck. The basic site measurements are employed to perform a laboratory‐based parametric study to investigate the influence of parameters such as vibration frequency, voltage, and circuit components like diodes on PEH. On the basis of the experimental results, it can be concluded that power in microwatts range can be typically harvested from these civil structures through directly bonded piezo patches in d₃₁ mode. However, there are still issues associated with electronic circuitry accompanying harvesters, such as diodes and storage elements. The same are summarised and future directions envisioned.     

Energy Harvesting Research: The Road from Single Source to Multisource

Energy harvesting technology may be considered an ultimate solution to replace batteries and provide a long‐term power supply for wireless sensor networks. Looking back into its research history, individual energy harvesters for the conversion of single energy sources into electricity are developed first, followed by hybrid counterparts designed for use with multiple energy sources. Very recently, the concept of a truly multisource energy harvester built from only a single piece of material as the energy conversion component is proposed. This review, from the aspect of materials and device configurations, explains in detail a wide scope to give an overview of energy harvesting research. It covers single‐source devices including solar, thermal, kinetic and other types of energy harvesters, hybrid energy harvesting configurations for both single and multiple energy sources and single material, and multisource energy harvesters. It also includes the energy conversion principles of photovoltaic, electromagnetic, piezoelectric, triboelectric, electrostatic, electrostrictive, thermoelectric, pyroelectric, magnetostrictive, and dielectric devices. This is one of the most comprehensive reviews conducted to date, focusing on the entire energy harvesting research scene and providing a guide to seeking deeper and more specific research references and resources from every corner of the scientific community.     

无线传感器网络的流量自适应分簇算法协议

在分析LEACH路由协议算法的缺点的基础上,提出了一种用于无线传感器网络的基于流量自适应的TDMA分簇算法协议.该协议根据当前节点数据流量的变化,自适应地调整该节点在其簇内通信的时隙长度,减少节点空闲时消耗的能量和节点从睡眠到活跃状态来回切换的能量.仿真实验结果表明,与LEACH协议簇内时隙分配算法相比,运用这种新的时隙分配算法,可以节省节点的能量,提高网络的生存时间,改善网络性能.     

Structural health monitoring of bridges with piezoelectric AE sensors

Monitoring the health of structures using acoustic emission technique offers many advantages such as early and quick detection of damage in real-time inexpensively. This paper is concerned with health monitoring of infrastructure hardware like highway bridges using this technique for timely intervention preventing catastrophic failure. Both experimental and numerical investigations were undertaken to determine the effectiveness and applicability of the method in the case of bridge superstructures. Three types of representative bridge girders of steel, reinforced concrete and prestressed concrete were designed, fabricated and monitored in the laboratory for structural integrity under cyclic loads with the help of an acoustic emission sensor system. After laboratory work, wavelet and Fourier transform techniques were applied to the recorded signals for de-noising and to diagnose the damaged state of the structure. Finally the locations of the cracks were determined by using the artificial neural network (ANN) approach.     

Decentralized random decrement technique for efficient data aggregation and system identification in wireless smart sensor networks

Smart sensors have been recognized as a promising technology with the potential to overcome many of the inherent difficulties and limitations associated with traditional wired structural health monitoring (SHM) systems. The unique features offered by smart sensors, including wireless communication, on-board computation, and cost effectiveness, enable deployment of the dense array of sensors that are needed for monitoring of large-scale civil infrastructure. Despite the many advances in smart sensor technologies, power consumption is still considered as one of the most important challenges that should be addressed for the smart sensors to be more widely adopted in SHM applications. Data communication, the most significant source of the power consumption, can be reduced by appropriately selecting data processing schemes and the related network topology. This paper presents a new decentralized data aggregation approach for system identification based on the Random Decrement Technique (RDT). Following a brief overview of the RDT, which is an output-only system identification approach, a decentralized hierarchical approach is described and shown to be suitable for implementation in the intrinsically distributed computing environment found in wireless smart sensor networks (WSSNs). RDT-based decentralized data aggregation is then implemented on the Imote2 smart sensor platform based on the Illinois Structural Health Monitoring Project (ISHMP) Services Toolsuite. Finally, the efficacy of the RDT method is demonstrated experimentally in terms of the required data communication and the accuracy of identified dynamic properties.     

曲线梁桥地震响应的简化分析方法

曲线梁桥的平面不规则性引起的弯扭耦合效应,导致了地震响应的复杂性。对弹性支座上的刚性桥面系统建立了具有刚度偏心的简单曲线梁桥模型,给出了自振特性和地震响应的简化计算方法。通过数值模拟比较,系统地分析了各种影响因素及其对曲线梁桥动力响应的影响规律和计算图表,可以在抗震初步设计中参考使用。     

Intelligent Sensing System Based on Hybrid Nanogenerator by Harvesting Multiple Clean Energy

The inexhaustible mechanical kinetic energy can be extracted from wind and flowing water. Besides, flowing water also possesses electrostatic energy owing to the triboelectric charges caused by contacting with surrounding media, such as air. Here, a rotating hybridized triboelectric nanogenerator (TENG) has been established, by comprising of a water‐TENG (W‐TENG), a disk‐TENG (D‐TENG), and an electromagnetic generator (EMG), which has been explored for simultaneously harvesting energies from flowing water and wind. The W‐TENG is fabricated by wheel blades, polyvinylidene fluoride (PVDF), superhydrophobic polytetrafluoroethylene (PTFE), and aluminum to harvest the electrostatic energy. Moreover, the flowing water and wind impact on the wheel blades also causes the rotation motion of D‐TENG and EMG, resulting in being converted into electricity. At the rotation speed of 200 rpm, the short circuit current of D‐TENG and EMG can reach 0.4 μA and 7 mA, respectively. The open circuit voltage of W‐TENG can be up to 10 V at a flowing water rate of 60 ml s^?1. Besides, the hybridized NG is demonstrated to harvest water and wind energy and to act as a power source to charge a lithium battery or capacitor, which can drive LEDs, PH monitoring system, and wireless temperature and humidity sensing system. All these results show the potentials of the hybridized NG for harvesting multiple types of energies from the environment and constructing different self‐powered systems.