WO2017005127A1 - 一种基于超高频rfid技术的图书馆典藏方法 - Google Patents

一种基于超高频rfid技术的图书馆典藏方法 Download PDF

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WO2017005127A1
WO2017005127A1 PCT/CN2016/087645 CN2016087645W WO2017005127A1 WO 2017005127 A1 WO2017005127 A1 WO 2017005127A1 CN 2016087645 W CN2016087645 W CN 2016087645W WO 2017005127 A1 WO2017005127 A1 WO 2017005127A1
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Prior art keywords
time
phase difference
books
book
tag
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English (en)
French (fr)
Inventor
陈力军
罗园洁
施庆朴
万凌昊
李颖
陈曦
曾阿凡
王彬
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Nanjing University
Nanjing Tech University
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Nanjing University
Nanjing Tech University
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Priority to US15/739,072 priority Critical patent/US11004017B2/en
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    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
    • G06Q10/00—Administration; Management
    • G06Q10/02—Reservations, e.g. for tickets, services or events
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/0723—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
    • G06K7/10366—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves the interrogation device being adapted for miscellaneous applications

Definitions

  • the invention relates to the field of UHF RFID technology, in particular to a library collection method based on UHF RFID technology.
  • Radio Frequency Identification is a non-contact automatic identification technology that automatically recognizes objects and acquires relevant data stored therein by wireless signals.
  • RFID technology can realize the tracking and positioning of target objects and information sharing after being combined with computer network technology and communication technology.
  • RFID technology has the advantages of non-line-of-sight recognition, fast recognition speed, large data storage capacity, and high security.
  • RFID technology has been widely used in warehousing management, logistics and other service industries, greatly improving its management and operational efficiency, and becoming an important intelligent infrastructure.
  • UHF RFID technology is divided into high frequency and ultra high frequency.
  • UHF RFID technology has revolutionized the library field, such as querying book positioning, fast self-service lending, etc. to start serving borrowers.
  • the book location function is especially important, which greatly shortens the time it takes for borrowers to find books in the library.
  • accurate library collection information is needed. Regular library collection can guarantee library collection. The accuracy of the data.
  • the technical problem to be solved by the present invention is to provide a library collection method based on UHF RFID, which utilizes radio frequency phase in UHF RFID technology to automatically identify each library in the library. The order in which the books are arranged.
  • the present invention discloses a book collection method based on radio frequency phase in UHF RFID technology, which comprises: a method for rejecting non-layer books of bookshelves based on the rate of change of radio frequency phase, based on radio frequency phase with time
  • a method for rejecting non-layer books of bookshelves based on the rate of change of radio frequency phase based on radio frequency phase with time
  • Step 2 preprocessing the information in the triplet tag
  • Step 3 Obtain the change law of the phase of the book, establish a model, analyze the positional relationship between the RFID antenna and the book, and sort the books.
  • step 2 includes:
  • Step 2-1 Divide the triplet tags into different subsets according to different ids, so that the ID information of each subset of the tags is consistent;
  • Step 2-2 obtaining the minimum value of t in all triples, subtracting the minimum value from the time t in each triple, obtaining a time difference, according to the time difference from small to large for each subset
  • the triples are sorted.
  • Step 3 includes:
  • step 3-1 for each triplet in the already ordered subset, the rate of change of the phase difference is sequentially calculated, and the phase difference in which the A rate of change is the largest is selected, and A is a natural number, and the phase difference is changed.
  • the arithmetic mean of the rate is used as the phase difference change rate of the subset, that is, the phase difference change rate of the tag whose tag ID information is id; the present invention preferentially selects five of which have the largest change rate, and when the number of selection is small, there is a certain The contingency, the number is too much, the effect is not very obvious, through experiments found that 5 is the most optimized number, the arithmetic mean of the five phase difference change rate as the phase difference rate of the subset, ie ID information The rate of change of the phase difference for the id tag;
  • Step 3-2 Calculating the phase difference change rate of all subsets.
  • the threshold can be set as the arithmetic mean of all the phase difference change rates.
  • Step 3-3 in the divided book data of the layer, for each subset, according to the phase difference change rate calculated in step 3-2, obtaining a time period in which the phase difference change rate is less than the set threshold, and the time period is The intermediate value is taken as time T 1 ;
  • Step 3-4 For each data in the subset, the phase difference increases with time, and the value changes from increasing to decreasing, that is, the phase difference increases from 0 to the maximum value P (P ⁇ (0, 2 ⁇ ) )), then the period from the maximum value P to 0.
  • the quadratic curve fitting is performed using the least squares method, and the time T 2 at which the highest point is located is calculated according to the fitted curve;
  • Step 3-5 calculating the weighted average time T 3 of the phase for all the triple data in each subset
  • Step 3-6 using the weight coefficients ⁇ 1 , ⁇ 2 , ⁇ 3 to determine the final time T:
  • T ⁇ 1 * T 1 + ⁇ 2 * T 2 + ⁇ 3 * T 3 ,
  • the books are sorted from front to back, and the book with the smallest time T is ranked first, and then the books are sorted according to the T value from small to large. .
  • the present invention introduces the phase to the library collection for the first time, and accurately implements the library collection. Therefore, the borrower can conveniently and quickly find the book that needs to be borrowed.
  • Another object of the present invention is to sort each book of the inventory, so that the location of each book can be accurately located, which is convenient for the borrower.
  • This method can eliminate the books of the non-this layer of the bookshelf, realize the purpose of reading only the books of this layer, and solve the problem of multi-reading in the library inventory; the method realizes the purpose of sorting the books of the layer, and can Accurately locate the position of each book and improve the accuracy of the library collection.
  • Figure 1 is a diagram showing the positional relationship between an antenna and a bookshelf.
  • Figure 2 is a graph of phase difference as a function of time.
  • Figure 3 is a relative position diagram of the antenna and a book.
  • Figure 4 is a flow chart of an embodiment.
  • the RFID reader emits electromagnetic waves through the antenna, and the electromagnetic waves are reflected back by the tag after reaching the RFID tag, and the RFID reader recognizes the RFID tag by receiving the reflected electromagnetic wave.
  • the emitted electromagnetic wave has an initial transmitting phase
  • the reflected receiving electromagnetic wave has a receiving phase.
  • the library is collected by receiving the phase difference between the phase and the transmitting phase.
  • the Impinj reader R420 can provide recognition support for phase difference, and this embodiment is implemented using Impinj R420. According to the information provided by Impinj, the phase difference varies with distance as follows:
  • phase difference ⁇ represents the phase difference
  • d represents the distance
  • ⁇ represents the wavelength of the electromagnetic wave
  • ⁇ represents other influencing factors.
  • the phase difference ⁇ exhibits a periodic variation with the distance, and the period of change is 2 ⁇ .
  • the antenna moves in the direction parallel to the book, moving far and near, and then moving from near to far. During the movement, the phase difference ⁇ of the book is obtained.
  • the phase difference changes with time as shown in Figure 2.
  • phase difference When from far to near, the phase difference exhibits periodic increment; when from near to far, the phase difference exhibits periodic decrement; the phase difference generally exhibits a symmetrical change.
  • phase difference When the antenna is far away from the tag, the phase difference has a large rate of change with time; when the antenna is closer to the tag, the phase difference has a smaller rate of change with time.
  • H indicates the tagged book
  • the antenna moves from point E to point G
  • point E and point G are symmetric about point F.
  • the lengths of EF and FG are r
  • HF is perpendicular to EG
  • the length of HF is s.
  • the length of the EH is d, which indicates the true distance between the antenna and the tag.
  • the antenna moves the real distance continuously changes. Assume that the center of the tag is at the same height as the center of the reader antenna; the reader antenna moves at a speed of v. Then the true distance d, as time varies t is as follows:
  • the phase difference can be obtained as a function of time:
  • This embodiment provides a method for utilizing phase for UHF RFID library collection, including phase difference data acquisition of receiving phase and transmission phase:
  • the antenna is moved according to the set speed, and the information of the tag is collected during the movement, including the ID information of the tag, the phase difference information, and the time information.
  • the phase is used to solve the problems encountered in the book collection:
  • the tag information will be collected, that is, the triplet sequence is divided according to the id, that is, different book information is first distinguished. If n different ids are collected, this time can be divided into n different data sets, each time A data set represents information from the same book.
  • the collected data has a certain error.
  • the data in each data set is sorted by time, the time in the data set is subtracted from the minimum time, and then the minimum time is set to 0, so that the time changes from 0.
  • the phase difference acquired should satisfy the formula (4). According to the formula (4), the data is processed, and the data having a larger deviation from the formula (4) is excluded.
  • phase difference calculation is performed on each of the n processed data sets: since the data in the data set has been sorted according to time, taking the first data set as an example, assuming that there are m data in the data set, the phase difference is The rate of change is calculated as follows:
  • the five largest rates of change are selected and the average is calculated as the phase change rate var for the data set.
  • the books of each layer are sorted.
  • the existing RFID library collection only counts to each layer, and the granularity of the inventory is each layer of the bookshelf; this is not enough in the library.
  • This embodiment uses the phase to make the inventory granularity reach each book, so that Can make the borrower get accurate Taking the location of each book makes it easier for borrowers to search for books, saving a lot of time for borrowers.
  • the time period with the smallest change rate is obtained.
  • the intermediate value of the time period is obtained as the time T 1 .
  • the quadratic curve is fitted to the section in which the phase difference change trend in the phase difference curve changes from increasing to decreasing. Based on the fitted curve, the time T 2 at which the highest point is located is calculated.
  • the time T 3 is obtained by using the formula (7).
  • the first data set is taken as an example.
  • the data set has m data, and the time is the weighted average time of the phase.
  • weight coefficients ⁇ 1 , ⁇ 2 , ⁇ 3 it can be set according to the actual situation.
  • phase-based library collection process of this embodiment is shown in FIG.
  • the front shelf is divided into three layers, from top to bottom, the first layer, the second layer, and the third layer; the back shelf is also divided into three layers, from top to bottom, the first layer, the second layer, and the third layer.
  • a 1 , A 2 , and A 3 respectively denote the first layer, the second layer, and the third layer of the front bookcase; and B 1 , B 2 , and B 3 denote the first layer and the second layer of the back shelf. ,the third floor. It is assumed that each of A 1 , A 2 , A 3 , B 1 , B 2 , and B 3 has 30 books.
  • each book an RFID tag is attached, and the books are placed neatly on each floor of the bookshelf in the normal way.
  • the RFID tag information is bound to the book information, and the binding result is saved in the database; this can ensure that the RFID tag and the book are in one-to-one correspondence, and when the RFID tag information is read, the corresponding book information can be determined.
  • an RFID tag also called a layer mark, is used to mark each layer of the bookshelf; When the shelf is set, the layer label is bound to the book of the layer, and the binding result is saved to the database; when the RFID layer label is read, the number of books in the layer should be obtained from the database.
  • the antenna T of the reader is facing the A 2 layer, the vertical distance between the antenna T and A 2 is 35 cm, and the antenna moves at a speed of 0.1 m/s.
  • the vertical distance between the antenna and A 2 is always the same during the movement.
  • the antenna T always moves parallel to the bookshelf.
  • the process of library collection is: reading the layer mark, obtaining how many books should be in the layer from the database, that is, the query result; moving the reader antenna to scan the label to obtain the scan result; comparing the scan result with the query result to obtain the collection
  • the result the correct book, the wrong book, the lost book; the wrong book means: the book that should not be at this level is mistakenly placed on the layer, the lost book refers to: the book that should have been on this layer, the collection Did not find it.
  • the reader antenna first reads the layer 2 label of the A 2 layer and obtains the query result from the database; when the reader antenna moves, the book is scanned to obtain the scan result.
  • Obtain the information of the tag the ID information of the tag, the phase difference information, and the time information. Due to the wide range of UHF RFID recognition and indoor multipath effects, it is easy to read other bookshelves and other books on the shelf during library collection.
  • the scan results at this time include other layers: books in A 1 , A 3 , B 1 , B 2 , and B 3 . Therefore, when the scan results are directly compared with the query results, the obtained collection results are apparent. It is not correct.
  • the label change rate is analyzed and processed; since the antenna is moving at a constant speed, the farther from the antenna, the smaller the average rate of change of the phase difference with time. Since the antenna T is facing the A 2 layer, the distance between the antenna T and the A 2 layer book is the closest, and the average rate of change of the phase difference with time is the largest.
  • the A 2 layer can be distinguished from the books of A 1 , A 3 , B 1 , B 2 , and B 3 layers, and the books other than the A 2 layer in the scan result can be removed. New scan results, and use the new scan results to compare with the query results to obtain the collection results and achieve the purpose of the book collection.
  • the existing RFID library collection only counts to each layer, and the granularity of the inventory is each layer of the bookshelf; this is not enough in the library, using the phase, so that the inventory granularity reaches each book, so that the borrowing can be made. Accurately obtaining the location of each book makes it easier for borrowers to search for books, saving a lot of time for borrowers.
  • the time period in which the rate of change is the smallest is obtained.
  • the intermediate value of the time period is taken as the time T 1 .
  • the quadratic curve is fitted to the section in which the phase difference change trend in the phase difference change curve changes from increasing to decreasing. Based on the fitted curve, the time T 2 at which the highest point is located is calculated.
  • the present invention provides a library collection method based on UHF RFID technology.
  • UHF RFID technology There are many methods and ways to implement the technical solution.
  • the above description is only a preferred embodiment of the present invention, and it should be noted that it is common to the technical field.
  • the skilled person will be able to make several modifications and refinements without departing from the principles of the invention, and such modifications and refinements are also considered to be within the scope of the invention.
  • the components that are not clear in this embodiment can be implemented by the prior art.

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Abstract

本发明公开了一种基于超高频RFID技术的图书馆典藏方法，包括如下步骤：步骤1，使用RFID读取设备读取附着在每本图书上的RFID标签，RFID读取设备对应每组图书读取的信息包括：标签的ID信息id，采集到当前标签的相位差θ、以及采集到当前标签的时间t，用三元组Tag＝<id、t、θ>表示RFID读取设备对应每组图书读取的信息；步骤2，对三元组Tag中的信息进行预处理；步骤3，获取图书相位的变化规律，建立模型、分析RFID天线和图书的位置关系进行图书排序。本发明首先利用射频相位将盘点过程中多读到的其他层图书剔除，然后再将本层图书进行排序，从而可以准确地定位出每一本图书所在的位置，方便借阅者。

Description

一种基于超高频RFID技术的图书馆典藏方法 技术领域
本发明涉及一种超高频RFID技术领域，特别是一种基于超高频RFID技术的图书馆典藏方法。
背景技术
无线射频识别(Radio Frequency Identification,RFID)是一种非接触式的自动识别技术，通过无线信号自动识别物体并获取其中存储的相关数据。RFID技术作为物联网感知层重要的感知技术，在与计算机网络技术、通信技术结合之后可以实现目标物体的跟踪定位以及信息共享。RFID技术具有非视线识别、识别速度快、数据存储容量大、安全性高等优点。RFID技术已经广泛应用于仓储管理、物流等服务行业，极大的提高了其管理和运作效率，成为重要的智能化基础设施。
目前RFID技术分为高频和超高频两种，随着超高频RFID技术的成熟以及标签价格的降低，超高频RFID技术也开始在图书馆领域进行使用。超高频RFID技术给图书馆领域带来了革命性的变化，诸如查询图书定位，快速自助借还等开始服务于借阅者。其中图书定位功能尤为重要，极大地缩短了借阅者在图书馆中查找图书所花费的时间，而实现这一功能则需要准确的图书馆馆藏信息，经常性的进行图书典藏工作可以保证图书馆馆藏数据的准确性。
目前而言，大多数图书馆仍然使用条形码进行图书管理，这给图书典藏带来了极大的挑战：1、一次只能识别一个条形码，而图书馆的藏书量很大，这使得图书管理人员的工作量很大；2、条形码扫描要求在视线范围之内，而图书馆为了保护条形码，一般将条形码贴在图书内部，因此图书典藏时需要打开图书。当使用条形码来管理图书时，图书典藏的工作量很大，而且对图书管理人员的要求很多。超高频RFID技术给图书馆带来了很多便利，使得图书馆快速典藏成为现实。但是，仍然存在以下问题：1、由于超高频RFID识别范围比较广以及室内多径效应，使得图书馆典藏时，很容易读到其他书架以及本书架其他层的图书，无法达到图书准确典藏的目的；2、目前图书典藏只能实现以层为单位的典藏粒度，无法达到以书为单位的粒度，即无法对每一层典藏的图书进行排序。因此，总体而言，图书馆的典藏工作需要耗费大量的人工来完成。
发明内容
发明目的：本发明所要解决的技术问题是针对现有技术的不足，提供一种基于超高频RFID的图书馆典藏方法，利用超高频RFID技术中的射频相位来自动识别图书馆中每一层图书的排列顺序。
为了解决上述技术问题，本发明公开了一种基于超高频RFID技术中射频相位的图书典藏方法，包括：基于射频相位的变化率来剔除书架非本层图书的方法，基于以射频相位随时间的变化规律进行图书排序的方法，具体步骤如下：
步骤1，使用RFID读取设备读取附着在每本图书上的RFID标签，RFID读取设备对应每组图书读取的信息包括标签的ID信息id，采集到当前标签的相位差θ、以及采集到当前标签的时间t，用三元组Tag＝<id、t、θ>表示RFID读取设备对应每组图书的读取信息；
步骤2，对三元组Tag中的信息进行预处理；
步骤3，获取图书相位的变化规律，建立模型、分析RFID天线和图书的位置关系进行图书排序。
其中，步骤2包括：
步骤2-1，根据id的不同，将三元组Tag划分为不同的子集，使得每一个子集中标签的ID信息是一致的；
步骤2-2，获取所有三元组中t的最小值，将每一个三元组中的时间t都减去该最小值，获得时间差值，根据时间差值从小到大对每一个子集中的三元组进行排序。
步骤3包括：
步骤3-1，对于每一个已经排好序的子集中的三元组，依次计算相位差的变化率，选择其中A个变化率最大的相位差，A是自然数，将这A个相位差变化率的算术平均值作为该子集的相位差变化率，即标签ID信息为id的标签的相位差变化率；本发明优先选择其中变化率最大的5个，当选取数量较少时，有一定的偶然性，数量太多时，效果区分不是很明显，通过实验发现，5个是最为优化的数量，将这5个相位差变化率的算术平均值作为该子集的相位差变化率，即ID信息为id标签的相位差变化率；
步骤3-2，计算所有子集的相位差变化率，当相位差变化率小于设置的阈值时，将其所属的图书划分为书架其他层的图书，并将其剔除，否则划分为本层图书，将其保 留。其中，阈值可以设置为所有相位差变化率的算术平均值。
步骤3-3，在划分好的本层图书数据中，对于每一个子集，根据步骤3-2计算的相位差变化率，获取相位差变化率小于设置阈值的时间段，将这个时间段的中间值作为时间T1；
步骤3-4，对于每一个子集中的数据，对相位差随着时间增加，其值由增加变化为减少的那一段，即相位差从0开始递增到最大值P(P∈(0,2π))，然后从最大值P递减为0的那一段。使用最小二乘法进行二次曲线拟合，根据拟合的曲线，计算出最高点所在的时间T2；
步骤3-5，对于每一个子集中的所有三元组数据，计算相位的加权平均时间T3；
步骤3-6，使用权重系数α1,α2,α3确定最终的时间T：
T＝α1*T1+α2*T2+α3*T3，
α1+α2+α3＝1，
其中，0＜α1,α2,α3＜1，根据时间T，对图书从前到后进行排序，时间T的值最小的图书排在最前面，然后图书根据T值由小到大依次排序。
本发明首次将相位引入到图书馆典藏领域，并且精确的实现了图书馆典藏。从而使得借阅者可以方便、快捷的查找到需要借阅的图书。本发明的另一目的在于对盘点的每一层图书进行排序，从而可以准确的定位出来每一本图书所在的位置，方便借阅者。
有益效果：通过本方法可以剔除书架非本层的图书，实现只读取本层图书的目的，解决图书馆盘点中多读的问题；本方法实现了对该层的图书进行排序的目的，可以准确的定位出每一本书的位置，提高了图书馆典藏的精度。
附图说明
下面结合附图和具体实施方式对本发明做更进一步的具体说明，本发明的上述和/或其他方面的优点将会变得更加清楚。
图1是天线与书架的位置关系图。
图2是相位差随着时间变化图。
图3是天线与一本图书的相对位置图。
图4是实施例的流程图。
具体实施方式
实施例1
RFID阅读器通过天线发射电磁波，电磁波到达RFID标签后被标签反射回来，RFID阅读器通过接收到反射电磁波，来识别RFID标签。发射电磁波有初始发射相位，反射过来的接收电磁波有接收相位，本实施例则是通过接收相位与发射相位的相位差来实现图书馆的典藏。目前，Impinj阅读器R420可以提供对相位差的识别支持，本实施例使用Impinj R420进行实现。根据Impinj公司提供的资料，相位差随着距离变化规律如下：
Figure PCTCN2016087645-appb-000001
其中θ表示相位差，d表示距离，即阅读器天线与标签的距离，λ表示电磁波的波长，δ表示其他的影响因素。相位差θ随着距离呈现周期性的变化规律，变化周期为2π。
图书馆图书一般都是整齐摆放，在进行图书典藏时，天线一般从图书旁边经过并且相互平行，俯视图如图1。
天线按照与书平行的方向，先远到近、再由近到远进行移动，在移动过程中，获取图书的相位差θ。通过理论分析及实验，相位差随着时间变化有如图2的规律。
通过图2可以得出以下结论：
1、当由远到近时，相位差呈现周期性的递增；当由近及远时，相位差呈现周期性的递减；相位差总体呈现一种对称性的变化。
2、当天线距离标签较远时，相位差随着时间的变化率较大；当天线距离标签较近时，相位差随着时间的变化率较小。
根据阅读器天线和图书的位置关系进行建模，为了更清楚的描述模型，现只描述一本书的情况，其俯视图如图3：
H表示贴有标签的图书，天线从E点匀速移动到G点，E点和G点关于F点对称，其中EF和FG的长度分别为r，HF与EG垂直，HF的长度为s，表示天线与书架的垂直距离。其中EH的长度为d，表示天线与标签的真实距离，随着天线的移动，真实距离不停的变化。假设标签的中心与阅读器天线的中心，在同一高度；阅读器天线的移动速度为v。则真实距离d，随着时间变化t如下：
Figure PCTCN2016087645-appb-000002
当标签的中心与阅读器的中心不在同一高度时，将高度差的绝对值记为h。则真实距离d，随着时间变化如下：
Figure PCTCN2016087645-appb-000003
根据Impinj公司提供的公式(1),可以得出相位差随着时间的变化如下：
Figure PCTCN2016087645-appb-000004
对θ(t)进行求导，可以得出来相位差随着时间的变化率如下：
Figure PCTCN2016087645-appb-000005
通过公式(5),可以得出：
当
Figure PCTCN2016087645-appb-000006
时，相位差随着时间的变化率(绝对值)越来越小，最终为0。
当
Figure PCTCN2016087645-appb-000007
时，相位差随着时间的变化率(绝对值)越来越大，从0开始变化。
当s越大时，相位差的变化率(绝对值)越小；类似，当h越大时，相位差的变化率(绝对值)越小。
本实施例提供了一种利用相位进行超高频RFID图书馆典藏的方法，包括接收相位与发射相位的相位差数据采集：
1、将RFID标签粘贴在图书中，并将RFID信息与图书信息进行绑定，并将绑定结果保存到数据库中去。
2、按照设定的速度将天线进行移动，在移动过程中采集标签的信息，包括标签的ID信息，相位差信息、以及时间信息。本实施例中使用三元组Tag＝<id、t、θ>来表示采集到的标签信息，其中id表示当前标签的ID信息，t表示采集到当前标签的时间，θ表示采集到当前标签的相位差信息。由于天线不停的移动，因此采集过程中，获取的是三元组序列，即：Tag1、Tag2…Tagn。
3、将采集到的标签信息，即三元组序列保存到数据库，用来进行分析、处理。
对于使用RFID技术的图书馆，当进行图书典藏时，需要对书架的每一层进行盘点。当盘点书架的某一层时，很容易读到该层上下层以及背面书架的图书。本实施例中利用相位来解决图书典藏中遇到的问题：
1、将采集到标签信息，即三元组序列按照id进行划分，即首先区分出来不同的图书信息，假设采集到了n个不同的id，则此次可以划分成n个不同的数据集，每一个数据集都代表同一本书的信息。
2、分别对n个数据集进行预处理：由于标签之间的相互干扰以及多径效应的影响，造成采集到的数据有一定的误差。将每一个数据集中的数据，按照时间进行排序，数据集中的时间分别减去最小时间，然后将最小时间设为0，这样时间从0开始变化。采集到的相位差应该满足公式(4)。根据公式(4)，对数据进行处理，剔除与公式(4)偏差比较大的数据。
3、对n个已经预处理过的数据集分别进行平滑处理；平滑处理的目的是：去除高斯噪声的影响，让数据的变化规律更加符合实际真实情况。
4、对n个已经处理过的数据集分别进行相位差计算：由于数据集中的数据已经按照时间排好序，以第一个数据集为例，假设数据集中有m个数据，则相位差的变化率计算如下:
Figure PCTCN2016087645-appb-000008
选择5个最大的变化率，计算其平均值，作为该数据集的相位变化率var。
5、根据公式(5)可以发现，上下层以及背面图书的相位差变化率比该层图书的相位差变化率小，因此通过对所有图书的相位差变化率分析比较，可以将需要进行典藏的某一层的图书和该层上下层以及背面书架的图书区分出来，达到图书准确典藏的目的。即当var＞V时，则为该层的图书，否则是其他层的图书。其中V是一个阈值，设置为所有该层所有图书相位差变化率的算术平均值。通过相位实现了超高频RFID图书馆的精确典藏，有利于超高频RFID技术在图书馆领域的进一步使用。
本实施例在精确典藏每一层图书的基础上，对每一层的图书进行排序。现有的RFID图书馆典藏只是盘点到每一层，盘点粒度为书架的每一层；这在图书馆中是远远不够的，本实施例利用相位，使得盘点粒度达到每一本书，这样可以使得借阅者准确的获 取每一本书的位置，方便借阅者对图书的查找，节约了借阅者大量的时间。
具体实现过程如下：
1、根据每本图书相位差随时间的变化率，获取变化率最小的时间段，本实施例将获取时间段的中间值作为时间T1。
2、根据预处理和平滑处理后的数据，对相位差变化曲线中相位差变化趋势由增加变化为减少的一段，进行二次曲线拟合。根据拟合的曲线，计算出最高点所在的时间T2。
3、根据初始数据，利用公式(7)，获取时间T3，同样以第一个数据集为例，该数据集中有m个数据，该时间为相位的加权平均时间。
Figure PCTCN2016087645-appb-000009
4、使用权重系数α1,α2,α3(0＜α1,α2,α3＜1)来确定最终的时间T＝α1*T1+α2*T2+α3*T3，α1+α2+α3＝1。根据时间T，对图书进行排序：时间越小，表示图书的顺序越靠前。
5、对于权重系数α1,α2,α3，可以根据实际情况来设置，当天线大且圆极化的极化方式时，α1,α2的值可以设置大一些、α3的值可以设置的小一些，例如针对Larid 9028天线，权重系数为：α1＝0.3,α2＝0.65,α3＝0.05。当天线小且线极化的极化方式时，α1,α2的值可以设置小一些、α3的值可以设置的大一些，例如针对边长为8cm的陶瓷天线，权重系数为：α1＝0.15,α2＝0.05,α3＝0.8。
本实施例的基于相位的图书馆典藏流程如图4所示。
1、图书标签扫描
假设正面书架分为三层，从上到下分别为第一层、第二层、第三层；背面书架同样分为三层，从上到下分别为第一层、第二层、第三层。为了方便描述，分别用A1、A2、A3表示正面书架的第一层、第二层、第三层；用B1、B2、B3表示背面书架的第一层、第二层、第三层。假设A1、A2、A3、B1、B2、B3每一层有图书30本。
在每一本书中，贴有RFID标签，图书按照正常的方式整齐的摆放在书架的每一层上。将RFID标签信息与图书信息进行绑定，并将绑定结果保存到数据库中；这样可以保证RFID标签和图书一一对应，当读到RFID标签信息，就可以确定对应的图书信息。在书架的每一层中，同样贴有RFID标签，称为层标，用来标记书架的每一层；新书上 架时，将层标与该层的图书进行绑定，并将绑定结果保存到数据库中去；当读取RFID层标时，就可以从数据库中获取该层应该有多少图书。
假设阅读器的天线T正对着A2层，天线T与A2的垂直距离为35cm，天线以0.1m/s的速度移动，在移动过程中天线与A2的垂直距离始终不变，即天线T始终与书架平行移动。
图书馆典藏的流程是：读取层标，从数据库中获取该层应有多少图书，即查询结果；移动阅读器天线进行标签扫描，获得扫描结果；将扫描结果与查询结果进行比较，得到典藏结果：正确的图书、错架图书、丢失图书；错架图书是指：本来不应在该层的图书，被错误的放到了该层，丢失图书是指：本来应该在该层的图书，典藏时没有查找到。
阅读器天线首先读取A2层的层标，并从数据库中获取查询结果；阅读器天线移动时，对图书进行扫描，获取扫描结果。获取标签的信息：标签的ID信息、相位差信息、以及时间信息等。由于超高频RFID识别范围比较广以及室内多径效应，使得图书馆典藏时，很容易读到其他书架以及本书架其他层的图书。此时的扫描结果中，包含了其它层：A1、A3、B1、B2、B3中的图书，因此，当直接使用扫描结果与查询结果进行比较的时候，获取的典藏结果显然是不正确的。
2、扫描结果处理
(1)将扫描结果进行预处理：根据图2的变化规律，剔除一部分数据。
(2)将预处理后的数据，进行平滑处理。
(3)将平滑处理后的数据，根据标签的ID信息进行分类，并按照时间顺序进行排序；由于标签与图书信息一一对应，因此，可以对每一本图书，计算相位差随着时间的变化率。
(4)获取典藏结果
对标签变化率进行分析处理；由于天线是匀速移动的，因此距离天线越远，相位差随着时间的平均变化率越小。由于天线T正对着A2层，因此天线T与A2层图书的距离最近，相位差随着时间的平均变化率最大。通过对所有图书相位差分析比较，可以将A2层与A1、A3、B1、B2、B3层的图书区分出来，进而将扫描结果中A2层以外的图书剔除出去，获得新的扫描结果，并使用新的扫描结果与查询结果进行比较，获得典藏结果， 达到图书典藏的目的。
3、更细粒度的典藏
现有的RFID图书馆典藏只是盘点到每一层，盘点粒度为书架的每一层；这在图书馆中是远远不够的，利用相位，使得盘点粒度达到每一本书，这样可以使得借阅者准确的获取每一本书的位置，方便借阅者对图书的查找，节约了借阅者大量的时间。
(1)根据相位差随着时间的变化率，获取变化率最小的时间段，本实施例将获取时间段的中间值作为时间T1。
(2)根据预处理和平滑处理后的数据，对相位差变化曲线中相位差变化趋势由增加变化为减少的一段，进行二次曲线拟合。根据拟合的曲线，计算出最高点所在的时间T2。
(3)根据公式(7)，计算相位加权平均时间T3。
(4)使用权重系数α1,α2,α3来确定最终的时间T＝α1*T1+α2*T2+α3*T3
(5)根据时间T，对图书进行排序：时间越小，表示图书的顺序越靠前。这样就使得图书馆典藏到每一本书，而不是以前的每一层。
本发明提供了一种基于超高频RFID技术的图书馆典藏方法，具体实现该技术方案的方法和途径很多，以上所述仅是本发明的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也应视为本发明的保护范围。本实施例中未明确的各组成部分均可用现有技术加以实现。

Claims (3)

  1. 一种基于超高频RFID技术的图书馆典藏方法，其特征在于，包括如下步骤：
    步骤1，使用RFID读取设备读取附着在每本图书上的RFID标签，RFID读取设备对应每组图书读取的信息包括：标签的ID信息id，采集到当前标签的相位差θ、以及采集到当前标签的时间t，用三元组Tag＝<id、t、θ>表示RFID读取设备对应每组图书读取的信息；
    步骤2，对三元组Tag中的信息进行预处理；
    步骤3，获取图书相位的变化规律，建立模型、分析RFID天线和图书的位置关系进行图书排序。
  2. 根据权利要求1所述的一种基于超高频RFID技术的图书馆典藏方法，其特征在于：步骤2包括：
    步骤2-1，根据标签的ID信息id的不同，将所有的三元组Tag划分为不同的子集，使得每一个子集中的标签的ID信息相同；
    步骤2-2，获取所有三元组中采集到当前标签的时间t的最小值，将每一个三元组中的时间t都减去该最小值，获得时间差值，根据时间差值从小到大对每一个子集中的三元组进行排序。
  3. 根据权利要求2所述的一种基于超高频RFID技术的图书馆典藏方法，其特征在于：步骤3包括：
    步骤3-1，对于每一个已经排好序的子集中的三元组，依次计算相位差的变化率，选择其中A个变化率最大的相位差，A是自然数，将这A个相位差变化率的算术平均值作为该子集的相位差变化率，即标签ID信息为id的标签的相位差变化率；
    步骤3-2，计算所有子集的相位差变化率，当相位差变化率小于设置的阈值时，将其所属的图书划分为书架其他层的图书，并将其剔除，否则划分为本层图书，将其保留；
    步骤3-3，在划分好的本层图书数据中，对于每一个子集，根据相位差变化率，获取相位差变化率小于设置阈值的时间段，将此时间段的中间值作为时间T1；
    步骤3-4，对于每一个子集中的数据，对相位差随着时间增加，其值由增加变化为减少的那一段，即相位差从0开始递增到最大值P，然后从最大值P递减为0的那一段，P∈(0,2π)，进行二次曲线拟合，根据拟合的曲线，计算出最高点所在的时间T2；
    步骤3-5，对于每一个子集中的所有三元组数据，计算相位的加权平均时间T3；
    步骤3-6，使用权重系数α1,α2,α3确定最终的时间T：
    T＝α1*T1+α2*T2+α3*T3，
    α1+α2+α3＝1，
    其中，0＜α1,α2,α3＜1，根据计算得出的时间T，对图书从前到后进行排序，时间T的值最小的图书排在最前面，然后从小到大依次排列。
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