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关键词： 结构健康监测   射频识别   裂纹传感标签   金属裂纹检测  

摘要： 近年我国工业发展迅速,工业厂房的结构安全也愈发引起人们的关注,工业厂房的金属结构长期受工业生产设备产生的振动效应影响,从而厂房金属结构极易产生疲劳损伤。若不能在早期发现工业厂房的承重结构损伤并及时处理,随着其损伤程度加深,结构故障愈发严重,可能会造成难以预估的意外后果,所以对工业厂房金属结构的健康状况监测尤为重要。在结构健康监测领域,无线射频识别技术逐渐成为一个具有应用潜力的结构健康监测研究方向。本文基于无线射频识别技术在结构健康监测领域的应用,针对工业厂房的金属结构裂纹损伤检测展开研究,基于微带天线结构设计了一款金属裂纹传感标签,提出一种基于RFID反向散射信号相位特征的金属结构裂纹检测方法。本文研究工作主要可以概括为:(1)讨论金属环境对射频识别系统的影响与解决方案,基于微带天线结构设计了一款可应用于工业厂房金属结构裂纹损伤检测的金属裂纹传感标签,通过优化辐射面结构,调节标签天线阻抗与谐振频率。制作出的金属裂纹传感标签在金属环境下仿真谐振频率为914.7MHz,谐振频率处回波损耗为-33.94d Bi,抗金属性能与传感性能良好。(2)根据裂纹传感标签相位与其位置相关的特性,提出了一种基于双RFID标签相位的金属裂纹检测方法,设计数据采集方案,对采集得的原始相位流去缠、去噪,通过基于区间的裂纹宽度识别方案与基于KNN分类算法的裂纹宽度识别方案,对该方法检测准确度进行验证,经验证,在两种裂纹宽度识别方案下,该方法检测准确率分别为88.5%与98.25%。(3)为简化基于射频识别技术检测金属结构裂纹的步骤,基于B/S结构设计开发了一款RFID阅读器控制软件,该软件可设置Mercury6阅读器工作参数,控制Mercury6阅读器通过定频读取、扫频读取或单次读取的方式采集标签数据,并将数据实时存储于数据库。

关键词： Substrates   Sensors   Permittivity   Pressure sensors   Permittivity measurement   Three-dimensional displays   Standards   Additive manufacturing (AM)   chipless radio frequency identification (RFID)   nondestructive testing (NDT)   pressure sensor  

摘要： Each sensing application has its own set of unique requirements and constraints that must be satisfied by its sensor. These requirements can include being wireless, passive, noncontact, customizable, multifunctional, and/or minimally invasive, depending on the application. Chipless radio frequency identification (RFID) tags are a type of microwave sensor that has the potential to meet many of these requirements, especially when additive manufacturing (AM) is employed to create customizable substrates that are sensitive to different ranges of environmental measurands. This work examines the potential efficacy of a proposed chipless RFID pressure sensor design approach that utilizes polymer AM substrates. Complex permittivity and stress-strain measurements were conducted to develop a model that relates the resonant frequency of the chipless RFID sensor to pressure, which in turn allows for the design of sensors with customized sensing ranges and sensitivities. This model is based around a standard rectilinear 3-D polymer-printed infill pattern. Custom-infill patterns can be developed to further tune the sensor performance based on a desired application. Electromagnetic (EM) simulations and measurements of fabricated tags, including one design based on the model with a rectilinear infill pattern and two designs that utilize custom-infill patterns, were conducted to illustrate the efficacy of the developed model and sensor design approach. Several possible sources of inconsistency between measurement and simulation are also investigated.

关键词： 3 dimensional   compact   measurement apparatus   polarimetric radar   radar cross section   scatterer  

摘要： In the literature, chipless RF identification (RFID) tags are mostly characterized at normal incidence, where the 3D spherical reading zone of chipless RFID tags has not been characterized. In this paper, compact measurement systems for the characterization of scatterers in 3D spherical read range are presented. Customized support structures are realized for the commercial multi-probe measurement system StarLab from MVG to construct the 3D spherical bistatic and monostatic measurement systems. A graphical user interface (GUI) is programmed to control the measurement systems and to perform postprocessing of the measurements. Owing to these measurement setups, 3D characterizations of three scattering objects are presented: an aluminum sphere, a nondepolarizing rectangular loop based chipless RFID tag, and a depolarization RF Elementary Particle (REP) chipless RFID tag. The measurement setups are capable to characterize any lightweight scatterer.

关键词： 射频识别   相位   手势识别   智能感知识别  

摘要： 随着物联网和人工智能等技术的飞速发展,基于物联网的“人-机-物”智能感知识别技术成为当前研究的热点方向。在众多的感知识别技术中,基于无线通信的射频识别(Radio Frequency Identification,RFID)技术因其有效的数据处理和非视距通信等独特优势,被广泛应用于身份认证、物流追踪和室内定位等各个领域。本文针对物联网感知识别层的RFID技术,从RFID信号特征的角度出发,探讨了移动终端与RFID标签的互联以及基于RFID标签的手势识别这两种方法的研究和实现。本文的主要贡献和研究内容总结如下:(1)提出了移动终端与RFID标签的互联的方法。本文设计了基于同步机制的配对算法,通过用户预定义的手势动作对RFID设备的相位数据与智能手机捕获的加速度传感器数据的影响,实现了智能手机与RFID标签的配对。为了解决RFID数据传输中的噪声污染问题,本文采用了离散小波去噪处理。本文所提出的算法经实验验证具有可行性和实用性,并在移动终端和RFID标签互联方面具有潜在的应用价值。(2)提出了基于RFID标签进行手势识别的方法。本文设计并实现了两个算法:手势初始、结束分割点检测算法和基于DTW-KNN的手势识别算法。这两个算法分别实现了从RFID阅读器设备采集的相位数据中提取手势动作数据和进行不同手势动作的识别。在算法实现过程中,通过SG平滑滤波对采集到的原始数据进行去噪处理,以降低由于实验设备等自然原因造成的误差。提出的RFID手势识别相对于传统手势识别具有更好的隐私保护、准确性和稳定性,同时也更加便携和灵活,因此具有更好的应用前景。(3)构建了原型系统以验证提出方法的合理性和可行性。本文从应用的角度出发,结合硬件设备、整体架构设计、模块功能设计以及相关表的结构设计,实现了手势识别和RFID标签的权限认证功能,并对整个系统进行了功能性测试。该原型系统的构建,验证了本文提出的互联方法和手势识别方法具有可行性。

关键词： Chipless RFID reader   chipless tags   frequency-domain   software-defined radio (SDR)   vector background subtraction  

摘要： This article presents a high-performance frequency-domain chipless RFID reader with vector background subtraction capabilities, implemented in a software-defined radio (SDR) for the first time. The proposed reader is low-cost, compact size, and versatile. It is implemented in a USRP N210 paired to a modified CBX-40 daughterboard, enabling magnitude and phase data acquisition in a monostatic (one antenna) set up. The reader can perform a vector background subtraction operation between two complex measurements (with and without a chipless tag) to suppress the self-interference (SI) that hinders the response of the tag and provide 40 dB of dynamic range. To demonstrate the performance of the reader, the spectral signatures of three frequency-coded (FC) tags with four resonant frequencies are captured over the 1.5-4-GHz band scanned with 10-MHz resolution in 251 ms, obtaining comparable measurements to those of an expensive laboratory vector network analyzer (VNA) from 20 to 40 cm. The detected resonant frequency offset between both devices is Delta f(r) <= 4.18% . It is also demonstrated that the proposed reader can track a resonant frequency shift and therefore be used in real-time sensing applications.

关键词： 图书整理   室内定位技术   定位   RFID定位   RSS  

摘要： 图书馆日常管理包括图书整理、借还、上架等工作,在馆藏日益增加的图书馆内,单纯人工操作的方法已无法高效、准确地完成图书管理工作。基于RFID技术的无人智慧图书馆管理系统应运而生,但是快速、准确自动甄别放错图书,将错架图书精准下架一直是图书馆急需解决的难题。针对上述难题,本文研究了一种基于RFID定位技术的智能错架图书拣选系统,通过单个RFID阅读器定位书籍,对书架书籍分层扫描、错架书甄别和拣选,代替图书管理员的查错和分拣工作。该系统主要实现两项功能:有序清点书架图书,找出错架书籍,记录图书信息;对甄别的错架图书进行精准定位,获取错书相对位置信息,方便错书下架。本文主要工作如下:⑴研究基于信号强度的RFID定位原理,介绍RFID定位系统组成,对RFID工作原理、特点和优势进行详细说明,叙述常见基于信号强度的RFID定位算法,分析基于测距模型和基于指纹的非测距算法的优点与不足。⑵设计了基于RFID定位的错架图书定位拣选系统整体方案,并研究了面向书籍分拣的RFID定位算法。搭建试验平台与试验环境,进行硬件选型和软件设计,设计了书架多层同步扫描与单层顺序扫描两种系统定位拣选方案。根据接收到不同层级不同位置书籍标签的信号强度的比较试验,确定了书架单层顺序扫描的最后方案。构建HFSS电磁仿真模型,获得阅读器天线电磁辐射范围与方向强度数据,结合Friis传输公式理论计算和阅读器接收信号的速度,获得RFID阅读器扫描最佳位置与发射功率等指导数据。⑶构建了基于RSS的高密度图书定位模型,实现图书定位。通过设置拣选系统多组关键参数进行多次试验,得到阅读器扫描区域内所有图书标签RSS序列与扫描次数。通过filter函数建立滤波模型,提取每个图书标签RSS的特征值m RSS。利用图书标签的特征值m RSS与图书标签实际坐标位置数据,构建基于LM-rational拟合方法的图书定位模型,结合图书标签扫描次数对图书排序,获得错架书籍的位置信息。⑷实现错架书籍自动拣选系统开发与实验。试验证明:基于RFID定位的图书馆错架书籍自动拣选系统可以准确、稳定的获取错架书籍位置信息,系统错书层级扫描概率为100%,层内错书定位平均绝对误差为1.59cm,具有较高的鲁棒性。

关键词： Temperature sensors   Oils   Sensors   Reservoirs   Monitoring   Temperature measurement   Temperature distribution   Chipless radio frequency identification (RFID) sensors   microwave wireless sensors   processing of wave EM sensor data   thermal cold chain sensors  

摘要： A food-safe cost-effective time-temperature indicator (TTI) sensor for cold chain disruption detection at the item level is proposed. The sensor is based on the radar cross section (RCS) readout from a chipless square split ring resonator (SSRR) exposed to organic oils with customizable melting temperatures and defined flow paths. The inclusion of several oil mixtures into the same sensor allows for the determination of a range of configurable temperatures/times. The same sensor has two modes of operation: one for threshold detection and another for gradual change detection. These modes depend on the orientation of the sensor on the packaging and the influence of gravity. The provided design, along with a convenient signal conditioning strategy, accurately detects four time exposure thresholds in the 7-30 min range when placed in upright position at ambient temperature, while it exhibits linear response between 10 and 30 min just by turning it by 90 degrees. Prospective future directions are also discussed.

关键词： Dipole antennas  

摘要： novel wideband circularly polarized (CP) dipole antenna for RFID/WiMAX/WLAN applications is presented. A pair of crossed fan-shaped dipoles printed on both sides of the substrate are used as the primary radiating elements. The antenna achieves circular polarization by using a 90 phase shifted microstrip line between the dipoles. By changing the edge of fan dipoles into Minkowski fractal curve, miniaturization and wide bandwidth of the antenna can be realized. Besides, incorporating the U-slot into the fractal crossed dipoles can obtain a wider bandwidth. The test results show that the proposed antenna achieves a wide impedance bandwidth of 63.2% (1.9-3.7 GHz) for VSWR < 2 and a 3-dB axial ratio (AR) bandwidth of 42.9% (2.2-3.4 GHz). The maximum gain in the operating frequency band can reach 7 dBi. The proposed antenna has good radiation characteristics in both low and high frequencies, which makes it a candidate for applications of RFID, WLAN, WiMAX, and other communication systems.

关键词： Ammonia   Carbon nanotubes   Wireless communication   Wireless sensor networks   Resonant frequency   Costs   Adsorption   Ammonia (NH ₃) detection   frequency offset   impedance change   passive detection   radio frequency identification (RFID)-inspired  

摘要： High concentrations of ammonia (NH3) pose a potential threat to human and animal/plant health. Active detection methods such as semiconductor, electrochemical, and optical methods have been used for NH3 detection. These methods increase energy consumption and heat accumulation, which may affect the performance of detection systems. Therefore, the research on passive NH(3 )detection methods is of great significance. In our study, a passive wireless sensor for NH3 detection based on carbon nanotube (CNT)-loaded chipless radio frequency identification (CRFID) was considered, which have the advantages of low cost, passive wireless ability, miniaturization, universality, and long life. However, path loss, tag position, and actual environmental interference can affect detection efficiency. In order to better improve the robustness of NH3 detection, the principle of CNT-loaded RFID-inspired NH3 detection was introduced in our study. High-frequency simulator structure (HFSS) simulation and fabrication for RFID-inspired sensors based on metal ink material printing is proposed, which operated at the central frequency of 2.4 GHz. The resistance value changes when the NH3 concentration is 0-200 mg/L, which shows a negative growth coefficient after absorbing NH3. Furthermore, detection and analysis in real and simulated environments were derived, such as power reflection coefficient, tag angle, path loss, identification distances, and phase. The measurement comparison outside the laboratory environment and cross-sensitivity of CO2 was also carried out. The result provides a reliable theoretical and practical basis for passive wireless NH3 detection and is of great significance for environmental quality assessment and food safety traceability information disclosure.

关键词： 射频识别(RFID)   RFID网络优化   麻雀搜索算法   多目标优化  

摘要： 射频识别(Radio Frequency Identification,RFID)作为物联网的一项重要技术,一直受到技术发展的推动,它被广泛应用不同的场合,使人们日常生活更加便捷。在带来便捷的同时产生一些问题,如阅读器的数量的选择、位置的摆放、标签的分布等,这些问题会影响到RFID网络的效率和质量。为了得到一个优秀性能的RFID网络系统,本文通过多种方式改进麻雀搜索算法(Sparrow search algorithm,SSA),将其应用求解RFID网络优化(RFID Network Planning,RNP)问题,并采用多种不同的优化方法,进行RFID网络系统的部署优化,从而提升系统的整体效率。本文开展研究的具体工作如下:1.提出一种针对缺点改进的麻雀搜索算法应用于RFID网络优化。针对算法后期种群多样性差和陷入局部最优的缺点,使用精英反向策略初始化种群,并且防止陷入局部最优解的情况,在加入者位置更新公式中引入Lévy飞行策略。改进算法使用基准函数的测试验证算法性能,再使用线性加权的优化方法用于求解RNP问题,与三种不同算法进行比较,实验结果表明改进算法能够得到比其他算法更好的RNP问题优化效果。2.提出一种蜉蝣和麻雀搜索混合算法应用于RFID网络优化。算法利用蜉蝣算法(Mayfly optimization algorithm,MA)的结构和交叉合并策略,先把种群分为雌雄两个部分。引入Circle混沌映射初始化种群,随后在发现者公式中增加非线性惯性权重,加入者公式中使用Lévy飞行策略。算法采用CEC2017测试套件验证性能,再使用线性加权优化方法用于RNP问题仿真实验,通过与五种不同的算法进行对比分析,实验结果证明该算法能够寻找到综合性能更好的解决方案。3.提出一种多策略的麻雀搜索算法应用于RFID网络优化。算法把种群分为雌雄两个种群,并在每次迭代后使用MA算法中变异和交叉合并策略。使用精英反向策略初始化种群,随后采用海鸥优化算法(Seagull optimization algorithm,SOA)的搜索策略改变原有麻雀发现者的搜索方式。算法使用CEC2017测试套件进行算法性能评估,再使用分层的优化方法用于求解RNP问题,与五种不同算法进行对比分析,结果表明该算法能够找到使用阅读器数量最少,覆盖最高和干扰最少的优化方案。4.提出一种改进多目标麻雀搜索算法应用于RFID网络优化。算法使用Logistic-tent混沌映射初始化种群,改进其拥挤度计算方式,并在发现者和加入者公式中融入白鲸优化算法(Beluga whale optimization,BWO)的探索和开发阶段,最后使用一种灵活的变异策略。在三种不同系列的基准测试函数中,验证改进算法的多样性和收敛性。并使用多目标pareto优化方法求解RNP问题,实验使用模糊决策方法折中选择最优方案。通过与三种不同的算法进行对比分析,实验结果表明,该算法能够得到多样性和收敛性更好的RFID网络优化方案的解集。