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 Wearable and Wireless Sensor System for Real-Time Monitoring of Toxic Environmental Volatile Organic Compounds

An integrated volatile organic toxicants sensor with a Bluetooth device interface has been developed. The device is based on novel tuning fork sensor platform along with a wireless communication/interface technology taken in an integrated system approach. It features high sensitivity and selectivity. The sensitivity and selectivity are accomplished through the use of novel tuning fork sensor modified by design (molecularly imprinted) polymers and selective filtering. Experiments have shown that the device can detect toxic volatile organic compounds (VOCs) under high concentrations of common interferents from flavors and fragrances. Applications of the device for detection of BTEX in real-world situations such as outdoor and gas station VOCs have also been demonstrated. All these features make the device a promising candidate to be deployed in real-world applications, particularly in environmental health and air pollution studies.      

Remaining Capacity Measurement and Analysis of Alkaline Batteries for Wireless Sensor Nodes

In most applications, wireless sensor networks (WSNs) will deploy a large number of distributed sensor nodes in remote or inhospitable places, making batteries their main source of energy; thus, the stored energy is a key resource of a WSN. Sensor nodes should balance their limited resources to increase the lifetime of the network. The knowledge of the available amount of energy becomes an important requirement for the maintenance, implementation of self-management techniques, and viability of the WSN. Therefore, the research of the State-of-Charge (SoC), or the remaining capacity estimation, is of key importance. This paper presents an energy-efficient battery-remaining capacity-estimation technique. The experiments were conducted using the MICA2 wireless sensor node platform, which shows that the voltage-only-based estimation presented an available 18% of the battery maximum capacity, although the battery had been fully discharged, and a current-based estimation technique is presented with minimal hardware intervention.      

钢水连续测温传感器的准确度提高和结构优化

为提高钢水连续测温传感器的准确度和灵敏度,以传感器所形成的在线黑体空腔的实际结构模型、带盖半球-圆筒形腔体为研究对象,建立了结构参数为二次关系的积分发射率的计算公式,并推导出全照区、半照区和不可见区域的自动划分计算公式.详细分析了传感器结构,即黑体空腔的长度、半径、孔径、腔口与探测器之间的距离,以及探测器接收面半径对积分发射率的影响,并在此基础上给出了传感器的优化参数.     

A Wireless, Passive Embedded Sensor for Real-Time Monitoring of Water Content in Civil Engineering Materials

A wireless, passive embedded sensor was applied for real-time monitoring of water content in civil engineering materials such as sands, subgrade soils, and concrete materials. The sensor, which comprised of a planar inductor-capacitor (LC) circuit, was embedded in test samples so that the internal water content of the samples could be remotely measured with a loop antenna by tracking the changes in the sensor's resonant frequency. Since the dielectric constant of water was much higher compared with that of the test samples, the presence of water in the samples increased the capacitance of the LC circuit (capacitance of the capacitor was proportional to the dielectric constant of the medium between its electrodes), thus decreasing the sensor's resonant frequency. Using the described sensor, a study was conducted to investigate the drying rate of sand samples of different grain sizes. A study was also conducted to measure the curing rate of a portland cement concrete slab during casting, and its drying rate after it has been soaked in water. The described sensor technology can be applied for long-term monitoring of localized water content inside soils and sands to understand the environmental health in these media. In addition, this sensor will be useful for monitoring water content within concrete supports and road pavements. The measurement of water content is important for civil engineering infrastructure since excess water may hasten their degradation.      

Illumimote: Multimodal and High-Fidelity Light Sensor Module for Wireless Sensor Networks

We describe the system requirements, design, system integration, and performance evaluation of the Illumimote, a new light-sensing module for wireless sensor networks. The Illumimote supports three different light-sensing modalities: incident light intensity, color intensities, and incident light angle (the angle of ray arrival from the strongest source); and two situational sensing modalities: attitude and temperature. The Illumimote achieves high performance, comparable to commercial light meters, while conforming to the size and energy constraints imposed by its application in wireless sensor networks. We evaluated the performance of our Illumimote for light intensity, color temperature, and incident light angle measurements and verified the function of the attitude sensor. The Illumimote consumes about 90 mW when all features on board are activated. We describe our design and the experiment design for the performance evaluation.     

A Wireless Sensor Network for Cold-Chain Monitoring

This paper deals with a wireless sensor network that was specifically designed to monitor temperature-sensitive products during their distribution with the aim of conforming to the cold-chain assurance requirements. The measurement problems and the constraints that have been encountered in this application are initially highlighted, and then, an architecture that takes such problems into account is proposed. The proposed architecture is based on specifically designed measuring nodes that are inserted into the products to identify their behavior under real operating conditions, e.g., during a typical distribution. Such product nodes communicate through a wireless channel with a base station, which collects and processes the data sent by all the nodes. A peculiarity of the product nodes is the low cost, which allows the information on the cold-chain integrity to be provided to the final customer. The results that refer to the functional tests of the proposed system and to the experimental tests performed on a refrigerated vehicle during a distribution are reported.     

Hybrid Micropower Source for Wireless Sensor Network

Wireless sensor networks have become a very significant enabling technology in many applications and the use of environmental energy is a feasible source for low-power wireless sensor networks. The challenges of developing a power supply including generation or conversion, storage, and power management are manifold to extend the lifetime of a wireless sensor network. The objective of this research is to develop an intelligent hybrid power system to realize a self-sustaining wireless sensor node. The photovoltaic and thermoelectric generators are adopted as energy converters. The lithium ion battery and ultracapacitor are used as reservoirs. An intelligent power management system has been developed to control the power distribution. The design data and experimental results show that the hybrid micropower source can extend the lifetime of a sensor network.     

Intelligent Real-Time Adaptation for Power Efficiency in Sensor Networks

This paper presents an intelligent, dynamic power conservation scheme for sensor networks in which the sensor network operation is adaptive to both changes in the objects under measurement and the network itself. The conservation scheme switches sensor nodes between a sleep and an active mode in a manner such that the nodes can maximize the time they spend in a power-efficient sleep state, which corresponds to a nonmeasuring and/or nontransmitting mode, while not missing important events. A switching decision is made based on changes (or their absence) in the signals sensed from the environment by an intelligent agent that has been trained to determine whether or not a special event has occurred. This intelligent agent is based on a novel neural network topology that allows for a significant reduction in the resource consumption required for its training and operation without compromising its change detection performance. The scheme was implemented to control a sensor network built from a number of Telos rev. B motes currently available on the market. A few new utilities including an original neural network-based intelligent agent, a “visualizer,” a communication manager, and a scheduler have been designed, implemented, and tested. Power consumption measurements taken in a laboratory environment confirm that use of the designed system results in a significant extension of sensor network lifetime (versus “always on” systems) from a few days to a few years.      

金属镀层膜厚量值溯源方法的研究

对金属镀层膜厚的不同测量方法进行了比较分析,提出通过设计台阶镀层和测量台阶高度的方法,实现镀层量值的直接溯源,并与X荧光分析测量法进行大量的比对测量试验,验证台阶镀层测量方法的正确性.     

Optimum Sensor Placement for Impact Location Using Trilateration

A key problem associated with structural health monitoring (SHM) is the placement of sensors upon a structure to detect the existence, location, and the extent of any damage. Because input data coming from the sensors are groups of measurements, it is arguable that the most widely used approach to SHM nowadays is to consider it as a statistical pattern recognition problem. Artificial neural networks have made a great impact on pattern recognition practice. A problem associated with this monitoring strategy is to find a good compromise between the quality of information achieved by the sensor network, increasing with the sensor density, and the need to keep the minimum weight and instrumentation cost. Thus, the number of sensors must be kept under control, and a search of the optimal location of such sensors needs to be performed. All these aspects have been taken into account in the present work, dealing with the problem of optimum sensor placement for impact location on a multilayered composite structure. Multilayered composite structures may suffer particularly relevant trauma when subject to low‐velocity impacts, as they may produce non‐visible or barely visible damage on the structure surface, while remarkable subsurface delaminations may be present. Such hidden damage, when remaining undetected, may grow to catastrophic failure. To overcome this issue, a neural network approach has been used here to predict the impact locations on a composite panel from time‐dependent data recorded on a set of surface‐mounted piezoelectric sensors during an experimental impact test. A genetic algorithm has been used to find the optimal sensor layout that minimised the error in predicting the impact location. A new approach, based on trilateration, is discussed and compared with the traditional one and is shown to provide the same degree of accuracy at reduced computational cost.     

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 New Wireless Sensor System for Smart Diapers

This letter presents a new wireless sensor system for smart diaper application, which consists of an interrogator circuit, an antenna, and a passive LC resonating sensor tag. The wireless link between the interrogator circuit and the sensor tag is established through the inductive coupling. The wetting of the diaper shifts the resonating frequency of the sensor tag, changing the inductive link, and thus trigger an ldquoonrdquo or ldquooffrdquo condition reflected at the interrogator circuit. With suitable sensor tags, smart diapers can be achieved in a straightforward and low cost approach.     

Magnetic Array Assisted Triboelectric Nanogenerator Sensor for Real‑Time Gesture Interaction

In human-machine interaction,robotic hands are useful in many scenarios.To operate robotic hands via gestures instead of handles will greatly improve the convenience and intuition of human-machine interaction.Here,we present a magnetic array assisted sliding triboelectric sensor for achieving a real-time gesture interaction between a human hand and robotic hand.With a finger’s traction movement of flexion or extension,the sensor can induce positive/negative pulse signals.Through counting the pulses in unit time,the degree,speed,and direction of finger motion can be judged in realtime.The magnetic array plays an important role in generating the quantifiable pulses.The designed two parts of magnetic array can transform sliding motion into contact-separation and constrain the sliding pathway,respectively,thus improve the durability,low speed signal amplitude,and stability of the system.This direct quantization approach and optimization of wearable gesture sensor provide a new strategy for achieving a natural,intuitive,and real-time human-robotic interaction.     

Fiber-Optic Sensor for Web Velocity Measurement

The design and development of a new fiber-optic sensor for measuring the velocity of a continuous material (also called a web) in material processing systems is described. The development of the proposed sensor is based on the dual beam laser Doppler velocimetry technique and the unique properties of different types of optical fibers. The developed sensor is capable of measuring the true web transport velocity as opposed to the existing methods which infer web transport velocity based on the roller angular speed. Since the sensor design utilizes fibers, signal processing can be performed away from the measurement area, and as a result the sensor can be used in harsh environments within the web processing line. The proposed sensor has been constructed and experiments have been conducted on an experimental web platform. The performance of the sensor is evaluated for a range of web velocities and different web materials. Sensor design, its construction, and a representative sample of the results are presented and discussed.     

电容传感微小孔径的测量方法

分析了电容传感器的基本原理,推导了电容传感器测量小孔内径的数学模型,组建了电容传感微孔测量系统。研究了Ф3mm微孔电容传感器的制作方法及测量系统的标定方法．所制作的测孔传感器经标定后,测量分辨率达到0．01μm．该测量系统操作简单,可通过USB接口、结合测量软件在计算机上直接读出微小孔的内径值。     

A New Instrument for Real-Time Ethernet Performance Measurement

Ethernet is now becoming a popular physical layer for industrial communications due to its reliability, performance, and widespread use. Its actual cutting edge is a minimum cycle time on the order of 100 mus and a jitter of 1 mus. Usually, high-cost laboratory devices are used to log network traffic, but they are still not suitable for an industrial environment. In this paper, a field-programmable-gate-array-based instrument is proposed to log 100-Mb/s Ethernet frames, assigning them a high-resolution time stamp. Full-duplex full-rate network traffic is duplicated and sent through two auxiliary Ethernet ports to a personal-computer-based monitor station for frame analysis. A prototype has been realized to verify feasibility and performance. Results show that the proposed instrument introduces a maximum delay of about 500 ns. The measurement capabilities are comparable with commercial instruments: The time-stamp assignment has a jitter of 150 ns measured on a test frame set.     

航空遥感器定位误差分析

首先简要介绍了航空遥感器的重要用途。然后依次介绍了成像坐标变换过程、定位原理,从而得到目标位置的计算公式,接着归纳了定位误差的影响因素,并完成了定位误差的推导,最后根据公式分析了各因素的影响程度。     

Thickness Measurement for Thin Films and Coatings Using Millimeter Waves

An accurate technique for measuring the thickness of dielectric thin films and coatings is presented in this paper. Millimeter-wave sensors operated at 80 GHz are placed near the sample surface. A better than m sensitivity of the phase of the received signal with respect to sample thickness can be achieved. A theoretical model consisting of a vertical electric dipole over a two-layer structure is used to generate calibration information and to guide the optimization of sensor placement. To facilitate the theoretical study, we devise an efficient and reliable numerical algorithm for evaluating Sommerfeld integrals. This algorithm surpasses the performance of conventional numerical methods and renders fast convergence even in the worst-case scenario, when the transmitter and the receiver have the same elevation and the materials are lossless.     

Experimental Characterization of Wireless Sensor Networks for Industrial Applications

The effects of interference in the setup of wireless sensor networks (WSNs) represent a critical issue, and as such, it needs to be carefully addressed. To this aim, helpful information can be achieved through measurements to be carried out in advance on suitable prototypes and testbeds. In this paper, the measurement of industrial WSN performance is dealt with. In particular, a suitable testbed enlisting IEEE 802.15.4 wireless sensor nodes is presented along with the results of some experiments carried out even in the presence of interference. The purpose is to show how to evaluate some specific parameters of a WSN employed for industrial applications to obtain useful information for its setup optimization in the presence of interference. The analysis will show that from the measurement of these parameters (number of failed pollings, polling round-trip time, experimental cycle time, and alarm latency), interference effects can effectively be recognized, and the network setup can be optimized.