A Physical Layer Algorithm for Estimation of Number of Tags in UHF RFID Anti-Collision Design

A priori knowledge of the number of tags is crucial for anti-collision protocols in slotted UHF RFID systems.The number of tags is used to decide optimal frame length in dynamic frame slotted ALOHA(DFSA)and to adjust access probability in random access protocols.Conventional researches estimate the number of tags in MAC layer based on statistics of empty slots,collided slots and successful slots.Usually,a collision detection algorithm is employed to determine types of time slots.Only three types are distinguished because of lack of ability to detect the number of tags in single time slot.In this paper,a physical layer algorithm is proposed to detect the number of tags in a collided slot.Mean shift algorithm is utilized,and some properties of backscatter signals are investigated.Simulation results verify the effectiveness of the proposed solution in terms of low estimation error with a high SNR range,outperforming the existing MAC layer approaches.

A Novel Time-aware Frame Adjustment Strategy for RFID Anti-collision

Recently,object identification with radio frequency identification(RFID)technology is becoming increasingly popular.Identification time is a key performance metric to evaluate the RFID system.The present paper analyzes the deficiencies of the state-of-the-arts algorithms and proposes a novel sub-frame-based algorithm with adaptive frame breaking policy to lower the tag identification time for EPC global C1 Gen2 UHF RFID standard.Through the observation of slot statistics in a sub-frame,the reader estimates the tag quantity and efficiently calculates an optimal frame size to fit the unread tags.Only when the expected average identification time in the calculated frame size is less than that in the previous frame size,the reader starts the new frame.Moreover,the estimation of the proposed algorithm is implemented by the look-up tables,which allows dramatically reduction in the computational complexity.Simulation results show noticeable throughput and time efficiency improvements of the proposed solution over the existing approaches.

An Improved Binary Search Anti-Collision Protocol for RFID Tag Identification

Radio frequency identification(RFID)has been widespread used in massive items tagged domains.However,tag collision increases both time and energy consumption of RFID network.Tag collision can seriously affect the success of tag identification.An efficient anti-collision protocol is very crucially in RFID system.In this paper,an improved binary search anti-collision protocol namely BRTP is proposed to cope with the tag collision concern,which introduces a Bi-response mechanism.In Bi-response mechanism,two groups of tags allowed to reply to the reader in the same slot.According to Bi-response mechanism,the BRTP strengthens the tag identification of RFID network by reducing the total number of queries and exchanged messages between the reader and tags.Both theoretical analysis and numerical results verify the effectiveness of the proposed BRTP in various performance metrics including the number of total slots,system efficiency,communication complexity and total identification time.The BRTP is suitable to be applied in passive RFID systems.

Performance Analysis of RFID Framed Slotted Aloha Anti-Collision Protocol

In this paper, we develop a novel mathematical model to estimate the probability distribution function of the number of tags discovered after a certain number of interrogation rounds. In addition, the pdfs of the number of rounds needed to discover all the tags are also calculated. The estimation of such pdfs will be helpful in estimating the number of interrogation rounds and the optimal parameter configuration of the RFID system which in turn will be helpful in estimating the time needed to discover all tags. Our results show that the proposed model accurately predicts the tags detection probability. We then use the proposed model to optimally configure the reader parameters (i.e. the frame size and the number of interrogation rounds).

Distance-Measuring Technology Using LD for Auto Anti-Collision

Auto anti-collision technology is one of the main research subjects of automobiles’ safety technology. Aiming at the key technology of Auto anti-collision, measuring the distance from obstacles, based on the theory of phase laser distance ranging, Laser Diode (LD) distance-measuring system for auto anti-collision has been developed to solve the problem of on-line measuring distance technology in middle to long distance utilizing the good characteristics of LD when modulating its optical intensity and adopting typical kinds of filter techniques in this paper. By theoretical analysis, adopting typical kinds of filter techniques can reduce the interference of strong light, so distance-measuring range can be 0.5–100 m in daytime or 1–200 m at night. And more, from theoretical analysis and experiment result, it can guarantee the high measuring resolution which can be less than 24.5 mm, utilizing the method of two Laser Diode optical intensity modulating wavelength and complimenting precise calibration and revision. The idea of LD distance-measuring technology is novel and feasible and this technology can be applied in Auto anti-collision. Key words laser diode - phase laser distance ranging - filter techniques - auto anti-collision CLC number TH 161 Foundation item: Supported by the National Natural Science Foundation of China (59675080, 59805006) and Wuhan Chenguang Foundation (20025001001)Biography: Zhang Xin-bao (1965-), male, Associate professor, research direction: precise mechanism and instrument.

A Frame Breaking Based Hybrid Algorithm for UHF RFIDAnti-Collision

Multi-tag collision imposes a vital detrimental effect on reading performanceof an RFID system. In order to ameliorate such collision problem and to improve thereading performance, this paper proposes an efficient tag identification algorithm termedas the Enhanced Adaptive Tree Slotted Aloha (EATSA). The key novelty of EATSA is toidentify the tags using grouping strategy. Specifically, the whole tag set is divided intogroups by a frame of size F. In cases multiple tags fall into a group, the tags of the groupare recognized by the improved binary splitting (IBS) method whereas the rest tags arewaiting in the pipeline. In addition, an early observation mechanism is introduced toupdate the frame size to an optimum value fitting the number of tags. Theoretical analysisand simulation results show that the system throughput of our proposed algorithm canreach as much as 0.46, outperforming the prior Aloha-based protocols.

A Physical Layer Network Coding Based Tag Anti-Collision Algorithm for RFID System

In RFID(Radio Frequency IDentification)system,when multiple tags are in the operating range of one reader and send their information to the reader simultaneously,the signals of these tags are superimposed in the air,which results in a collision and leads to the degrading of tags identifying efficiency.To improve the multiple tags’identifying efficiency due to collision,a physical layer network coding based binary search tree algorithm(PNBA)is proposed in this paper.PNBA pushes the conflicting signal information of multiple tags into a stack,which is discarded by the traditional anti-collision algorithm.In addition,physical layer network coding is exploited by PNBA to obtain unread tag information through the decoding operation of physical layer network coding using the conflicting information in the stack.Therefore,PNBA reduces the number of interactions between reader and tags,and improves the tags identification efficiency.Theoretical analysis and simulation results using MATLAB demonstrate that PNBA reduces the number of readings,and improve RFID identification efficiency.Especially,when the number of tags to be identified is 100,the average needed reading number of PNBA is 83%lower than the basic binary search tree algorithm,43%lower than reverse binary search tree algorithm,and its reading efficiency reaches 0.93.

A Dynamic Multi-ary Query Tree Protocol for Passive RFID Anti-collision

In this paper,a dynamic multi-ary query tree(DMQT)anti-collision protocol for Radio Frequency Identification(RFID)systems is proposed for large scale passive RFID tag identification.The proposed DMQT protocol is based on an iterative process between the reader and tags which identifies the position of collision bits through map commands and dynamically encodes them to optimize slots allocation through query commands.In this way,the DMQT completely eliminates empty slots and greatly reduces collision slots,which in turn reduces the identification time and energy costs.In addition and differently to other known protocols,the DMQT does not need to estimate the number of tags,reducing the protocol implementation complexity and eliminating the uncertainty caused by the estimation algorithm.A numerical analysis shows that DMQT has better performance than other algorithms for a number of tags larger than 300.Meanwhile,when the number of tags is 2000 and the tag identity(ID)length is 128 bits,the total identification time is 2.58 s and the average energy cost for a tag identification is 1.2 mJ,which are 16.9%and 10.4%less than those of state-of-the-art algorithms,respectively.In addition,a DMQT extension based on ACK command has also been presented to deal with capture effect and avoid missing identification.

Synchronous Dynamic Adjusting: An Anti-Collision Algorithm for an RF-UCard System

An RF-UCard system is a contactless smartcard system with multiple chip operating systems and multiple applications. A multi-card collision occurs when more than one card within the reader’s read field and thus lowers the efficiency of the system. This paper presents a novel and enhanced algorithm to solve the multi-card collision problems in an RF-UCard system. The algorithm was originally inspired from framed ALOHA-based anti-collision algorithms applied in RFID systems. To maximize the system efficiency, a synchronous dynamic adjusting (SDA) scheme that adjusts both the frame size in the reader and the response probability in cards is developed and evaluated. Based on some mathematical results derived from the Poisson process and the occupancy problem, the algorithm takes the estimated card quantity and the new arriving cards in the current read cycle into consideration to adjust the frame size for the next read cycle. Also it changes the card response probability according to the request commands sent from the reader. Simulation results show that SDA outperforms other ALOHA-based anti-collision algorithms applied in RFID systems.

Application of Ship Maneuvering Simulator's Technology on Research of Vessels Automatic Anti-Collision

In this paper, the authors make a summary of current situation of research on the Auto Anti-Collision, briefly introduce the components and functions of the NSACA Simulation Platform and bring forward the project to realize the simulation of an Automatic Anti-Collision control, based on the NSACA Simulation Platform. Finally give typical examples from a great deal of simulating tests and analyze them.

Novel Tag Anti-Collision Algorithm with Adaptive Grouping

For RFID tags, a Novel Tag Anti-collision Algorithm with Grouping (TAAG) is proposed. It divides tags into groups and adopts a deterministic method to identify tags within group. TAAG estimates the total number of tags in systems from group identifying result and then adjusts the grouping method accordingly. The performance of the proposed TAAG algorithm is compared with the conventional tag anti-collision algorithms by simulation experiments. According to both the analysis and simulation result, the proposed algorithm shows better performance in terms of throughput, total slots used to identify and total cycles.

Research on Anti-collision Capability and Safety Supervision Measures of the Nanjing Yangtze River Bridge

With the vigorous development of inland river shipping economy,the trend of large ships passing Nanjing Yangtze River Bridge is obvious.The standard formula of ship collision force is selected by comparing the empirical calculation formulas.Four representative ship types are selected for calculation and analyzing of collision force.It is concluded that the anti-collision ability of the Nanjing Yangtze River Bridge does not meet the requirement of large ship collision force when the speed is more than 8-knots.From the perspective of active collision avoidance,this paper puts forward the navigation safety supervision countermeasures.A conceptual model of guided pulley anti-collision device is designed from the perspective of passive anti-collision.The research results provide references for safety supervision and anti-collision measures for the bridge.

Identifying multiple influential spreaders in complex networks based on spectral graph theory

One of the hot research topics in propagation dynamics is identifying a set of critical nodes that can influence maximization in a complex network.The importance and dispersion of critical nodes among them are both vital factors that can influence maximization.We therefore propose a multiple influential spreaders identification algorithm based on spectral graph theory.This algorithm first quantifies the role played by the local structure of nodes in the propagation process,then classifies the nodes based on the eigenvectors of the Laplace matrix,and finally selects a set of critical nodes by the constraint that nodes in the same class are not adjacent to each other while different classes of nodes can be adjacent to each other.Experimental results on real and synthetic networks show that our algorithm outperforms the state-of-the-art and classical algorithms in the SIR model.

Simulation Analysis on Navigation Indexes of Wanzhou Yangtze River Highway Bridge after the Anti-Collision Device Construction by Ship Model Test

After the anti-collision facility construction of Wanzhou Yangtze River Highway Bridge, the conditions of navigation in bridge area are complex. In order to study the navigation conditions of the reach and layout optimization measures, ensuring the safety of the ship navigation test has been carried out on the ship model navigation in the bridge area. According to the requirements of the maximum safety limit of the ship model test, the paper puts forward the best route, the control method and the difficulty of navigation through the analysis of the test results, and finally gives the recommendations and suggestions.

排岩机履带行走装置接地比压分布规律研究

针对目前接地比压分布不均匀问题,本文以排岩机为例,建立了履带行走装置接地比压计算数学模型。基于Solidworks、MATLAB软件,对排岩机重心空间坐标值与其受料臂旋转角度、排料臂上仰角度及车体回转支承旋转角度进行了拟合。进一步通过ANSYS Workbench仿真软件,证明了所建接地比压计算模型的正确性。研究分析了接地比压随受料臂旋转角度、排料臂上仰角度、排岩机车体回转支承旋转角度的变化趋势。这里研究成果可为各种履带行走设备整机的设计及其工作地基的处理提供一定的参考。

排岩机输送系统驱动机构模糊故障分析

排岩机皮带输送系统具有高运速、变倾角、运量大、且物料波动大的特点,因此在使用过程中故障时有发生,对故障的合理预估有助于实施主动维护,缩短维修时间,避免发生恶性大事故。在故障数据少而产生较大不确定性的情况下,本文对排岩机带式输送机驱动机构进行了故障树分析,求取了机构迄今为止的故障率和重要度指标贡献率,找出了高频失效零部件受料臂子系统左侧尼龙柱销等,继而对机构了进行可靠性评估与分析,评估结果可靠度为0.37,远低于工程应用要求,分析了可靠度低的原因并提出了对机构中一些对零部件设计与维修的注意事项,为后续维修性分析并实施主动维修提供技术指导。

基于激光与视觉融合的船舶扫描和吊具防撞系统及方法

为解决岸边集装箱起重机在船舶上方作业时,由于司机操作以及潮汐、大风等环境因素对作业安全产生影响的问题,文中提出了一种基于激光和视觉融合的船舶扫描和吊具防撞系统及方法,通过激光扫描和视觉采集,对岸边集装箱起重机下的船舶轮廓进行完整扫描与识别,满足船舶的纵向位移、船舶上船槽及集装箱锁孔的精确定位,精确测量岸边集装箱起重机吊具的高度值和小车的位置信息,实现集装箱海陆侧软着陆,有助于提高岸边集装箱起重机的自动化效率。

深中通道锚碇上方大节段钢箱梁吊装卸船方案比选及吊具设计

深中通道伶仃洋大桥东、西泄洪区非通航孔桥为跨径110 m的连续钢箱梁桥,有2孔钢箱梁上跨伶仃洋大桥海中锚碇。因中山大桥提前合龙,受通航限制,该区域共20片大节段钢箱梁(4片长86.1 m,重1097 t;16片长110 m,重1408 t)需由武船中山基地码头船运至中铁南方基地码头吊装卸船,转运后再由“天一号”运架一体船取梁。根据中铁南方基地码头2台2000 t龙门吊情况,进行大节段钢箱梁吊装卸船方案比选及配套吊具设计。对单钩单梁、双钩单梁、双钩双梁3种吊装卸船方案进行分析,考虑经济性和操作便利性,选择双钩双梁方案。根据吊装需要,设计4套相同的吊具(主要由扁担梁、销轴、绳轮、绳圈和卸扣等组成),110 m和86.1 m大节段钢箱梁分别设置16套和12套吊点,每根扁担梁下设4个吊耳。采用MIDAS软件建立钢箱梁及扁担梁整体模型,分析钢箱梁、吊具及连接构件的力学性能。结果表明:钢箱梁、钢箱梁吊耳及连接螺栓、扁担梁、扁担梁吊耳及销轴的受力均满足规范要求。设计的吊具已成功应用于20片大节段钢箱梁的吊装卸船施工。

基于IGWO-BP-PID的管廊吊具液压缸同步控制研究

综合管廊吊装吨位重且存在偏载起吊的不利工况,易发生危险事故。为保证管廊节段偏载吊装工况下的安全稳定性,提高吊具液压缸组的同步控制精度,提出IGWO-BP-PID与状态差值反馈同步控制策略。通过分析专用吊具结构及液压原理,将液压缸按纵向分为2组。通过在GWO中对灰狼位置进行更新,实现IGWO对BP-PID参数的优化。采用3种控制器进行系统控制分析,验证IGWO-BP-PID的控制效果。最后,采用IGWO-BP-PID与状态差值反馈相结合的同步控制策略,对吊具液压缸组进行AMESim/Simulink联合仿真,并与试验数据进行对比分析。研究结果表明:IGWO-BP-PID控制器无超调量、具有更好的控制效果;相比于常规PID控制,该方法缩短了液压缸组震荡调节时间,同步控制精度更高;试验验证了管廊吊具同步控制策略的有效性,满足工程施工要求。

某型翻转吊具索节裂纹原因分析及工艺改进

针对某型翻转吊具索节新品使用前磁粉探伤检查中出现多处裂纹的问题,文中建立了以索具裂纹为顶事件的故障树,从设计、加工、装配、使用等4个方面,逐级梳理造成该顶事件的9个底事件。通过对索具裂纹故障树分析和取样机理分析得出,锻造产生的应力、终锻温度偏低、锻造毛坯尺寸小、加工余量小、探伤时机不恰当,加之抛丸工序和镀锌层的干扰,影响了磁粉探伤的检测结果,导致出厂合格的吊具在使用方复检时出现裂纹问题。根据索具裂纹产生的原因,通过加强原材料复验、优化锻造工艺、改善加工工艺等措施解决了索具裂纹问题,对此类吊索具产生裂纹的原因分析方法与实际问题的解决具有指导意义。