CN110907890B - RFID intelligent goods shelf misplacement detection method - Google Patents

RFID intelligent goods shelf misplacement detection method Download PDF

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CN110907890B
CN110907890B CN201911073715.9A CN201911073715A CN110907890B CN 110907890 B CN110907890 B CN 110907890B CN 201911073715 A CN201911073715 A CN 201911073715A CN 110907890 B CN110907890 B CN 110907890B
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antenna
phase
tag
value
misplacement
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CN110907890A (en
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罗嘉庆
刘金凯
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University of Electronic Science and Technology of China
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University of Electronic Science and Technology of China
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/0252—Radio frequency fingerprinting

Abstract

The invention discloses a method for detecting misplacement of goods on an RFID intelligent goods shelf, and belongs to the technical field of goods shelf detection. According to the invention, a plurality of readers are arranged at fixed positions to acquire tag data, the positions of the readers are optimized to maximize the difference value of the acquired phase data, the acquired phase values are effectively processed by unwrapping and the like, then system errors are estimated to solve the problem of equipment diversity, and finally, the phase measurement value is compared with the theoretically calculated phase value and whether the phase difference value changes or not is observed to detect whether the position of the placed article changes or not, so that the effective supervision of the position of the article on the shelf and the detection of the misplacement of the article are realized. The method is used for monitoring and managing the position of the goods on the goods shelf for placing the goods with the RFID labels, monitors and manages the position of the goods in real time, and is a reliable, efficient and accurate intelligent goods shelf goods misplacement detection method.

Description

RFID intelligent goods shelf misplacement detection method
Technical Field
The invention belongs to the technical field of shelf article detection, and particularly relates to an RFID intelligent shelf article misplacement detection method.
Background
Smart shelves are one of the important applications for RFID indoor location awareness. The labor cost is greatly reduced by using the RFID position perception technology to construct the intelligent goods shelf, and the requirements of various fields on the intelligent goods shelf are continuously increased due to the fact that the goods resources are continuously increased and the goods monitoring is needed, particularly the field of warehouse logistics management and the field of unmanned supermarkets. In particular, an intelligent shelf capable of timely and accurately sensing the position information of each article is needed. The prior intelligent shelves are managed based on active RFID tags, so that the intelligent shelves are high in cost and inconvenient to use, most of the intelligent shelves can only be used for sensing and monitoring valuables such as artworks, luxury goods and the like, and the intelligent shelves cannot be used in a large-quantity and high-throughput scene such as shopping centers and large shopping malls. Therefore, the invention develops a set of intelligent goods shelves for real-time monitoring of articles by researching the position perception technology of the indoor objects and utilizing the RFID technology.
One of the great challenges for intelligent shelves is to be able to monitor the position of items in real time, and the methods of positioning by absolute position or relative position can be classified as dynamic and static. While dynamic tracking requires movement of a Radio Frequency tag or antenna to observe changes in time series RF (Radio Frequency), static positioning requires pre-acquisition of Received Signal Strength (RSS) distribution by arranging a large number of reference tags or analysis of phase differences by using expensive equipment (multi-reader antenna or synthetic aperture radar). In addition, there are limitations in using them in real life to detect misplaced tags on smart shelves. Mobile readers and tags are time and labor intensive because items on shelves are mostly static and complex and expensive equipment is not suitable for large scale placement.
Disclosure of Invention
The invention aims to: aiming at the existing problems, the RFID intelligent shelf article misplacement detection method is provided. The invention identifies the phase deviation caused by the misplacement of the article through the matching between the phase measurement value between the antenna (tag reader antenna) and the tag and the theoretical value thereof, thereby realizing the detection of the misplacement of the article.
The invention discloses a method for detecting misplacement of RFID intelligent goods shelf, which comprises the following steps:
step 1: arranging a plurality of tag readers on the periphery of a shelf on which articles attached with RFID tags are placed, wherein the tag readers are used for acquiring tag data of the RFID tags;
determining the position of an antenna of a tag reader and the arrangement position of each RFID tag on the shelf based on a preset coordinate origin O;
step 2: setting a detection threshold of misplacement detection:
antenna A of arbitrarily selected tag reader r As a reference antenna, for any two RFID tags T i And T j Forming tag pairs, exchanging the arrangement positions of the tag pairs, and calculating the antenna A of each tag reader after exchange s Phase shift of
Figure BDA0002261729340000021
Namely an antenna A s Respectively acquire labels T i And T j Phase offset of the phase theoretic value of (a);
wherein the content of the first and second substances,
Figure BDA0002261729340000022
the x is a number representing the wavelength of the light,
Figure BDA0002261729340000023
representing origin of coordinates O to label T i The vector of (a) is determined,
Figure BDA0002261729340000024
representing origin of coordinates O to antenna a r The vector of (a) is calculated,
Figure BDA0002261729340000025
denotes a reference antenna A r To antenna A s The vector of (a) is calculated,
Figure BDA0002261729340000026
representing origin of coordinates O to label T j The vector of (a); i.e. a vector between two points obtained by using the position of the tag and the antenna as one point, respectively.
For each pair of labels, all phase offsets are taken
Figure BDA0002261729340000027
As the current tag pair with respect to the current reference antenna a r Phase shift of
Figure BDA0002261729340000028
And will be currently referenced to antenna a r Phase shift of all tag pairs under
Figure BDA0002261729340000029
As the current reference antenna a r Tag misplacement minimum phase offset of
Figure BDA00022617293400000210
Taking the antennas of all the tag readers as reference antennas respectively, and taking the maximum of the minimum phase offsets of the misplaced tags as a detection threshold of the misplaced detection, and recording the detection threshold as
Figure BDA00022617293400000211
Namely, the corresponding reference antenna position is the optimal position;
and step 3: carrying out misplacement detection processing on the article based on the phase measurement value of the RFID label currently acquired by the antenna of the label reader:
antenna A based on label reader s Of the system error of
Figure BDA00022617293400000212
For each phase measurement
Figure BDA00022617293400000213
Performing correction processing to obtain phase measurement value
Figure BDA00022617293400000214
Calibration value of
Figure BDA00022617293400000215
If it is
Figure BDA00022617293400000216
Is less than
Figure BDA00022617293400000217
Then the
Figure BDA00022617293400000218
If not, then,
Figure BDA00022617293400000219
the subscript i is an identifier of the RFID label, and the superscript s is an antenna identifier of the label reader;
for any one article to be misplaced and detected, based on the RFID label T attached to the article i Distribution position ofCalculating the antenna A of each tag reader s Respectively collected labels T i Theoretical phase value of
Figure BDA00022617293400000220
And according to the formula
Figure BDA00022617293400000221
Obtain the label T i Estimate of the phase offset of
Figure BDA00022617293400000226
If the estimated value is
Figure BDA00022617293400000222
Greater than or equal to a detection threshold
Figure BDA00022617293400000223
Then the label T is judged i Misplacing the corresponding article;
wherein, any antenna A s Collected arbitrary tags T i Theoretical phase value
Figure BDA00022617293400000224
Comprises the following steps:
Figure BDA00022617293400000225
the x is a number representing the wavelength of the light,
Figure BDA0002261729340000031
denotes an antenna A s And tag T i K is a preset integer;
antenna A of tag reader s Of the system error of
Figure BDA0002261729340000032
The setting mode is as follows:
placing a certain number of reference tags T p And calculate each antenna A s Acquired reference tag T p Theoretical phase value of
Figure BDA0002261729340000033
p is a reference tag specifier;
based on an antenna A s Collected reference labels T p Measured phase of
Figure BDA0002261729340000034
Determining systematic errors corresponding to each reference tag
Figure BDA00022617293400000317
If the theoretical phase value
Figure BDA0002261729340000035
Greater than the phase measurement
Figure BDA0002261729340000036
Then
Figure BDA0002261729340000037
Otherwise
Figure BDA0002261729340000038
For the same antenna A s Taking the corresponding systematic error of all reference labels
Figure BDA0002261729340000039
As the mean value of the antenna A s Of the system error of
Figure BDA00022617293400000310
Further, the detection threshold of the misplacement detection can be set as
Figure BDA00022617293400000311
Wherein the value range of the coefficient alpha is as follows:
Figure BDA00022617293400000312
further, the reduction of the parameters for finding the optimum position is not achievedThe reference antenna A can also be used according to the operation amount of the antenna r Tag misplacement minimum phase offset of
Figure BDA00022617293400000313
Performing a particle swarm algorithm to search the optimal position of the reference antenna as the adaptive value of the particle to obtain the optimal reference antenna; and based on the minimum phase deviation of the label misplacement corresponding to the optimal reference antenna
Figure BDA00022617293400000314
Setting a detection threshold for the misplacement detection to
Figure BDA00022617293400000315
Wherein the coefficient alpha is 1 or
Figure BDA00022617293400000316
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
for the scene to be detected, the positions of some articles can be exchanged when the articles are placed again, the method only realizes the detection of the misplacement of the articles through the phase, namely, the processed measured value is compared with the calculated theoretical value, and whether the phase shifts or not is observed to detect the misplacement of the articles. Since the phase is periodic, different locations may have the same phase measurement, resulting in ambiguity. In order to solve the ambiguity which can occur, the method provided by the invention optimizes the deployment positions of the antennas to maximize the phase discrimination of any two positions; the phase measurement may contain one or more 2 pi jumps, and to ensure that the phase value does not exceed its normal range [0,2 pi), the present invention eliminates the effects of 2 pi jumps by an effective standard by comparing the measured value to the theoretical value, phase unwrapping; since the antennas may have different initial phase rotations at different positions (even if the antennas are of the same type), the invention calibrates the measured values by estimating the system error and detects abnormal phase offsets to identify mislaid tags.
Drawings
FIG. 1 is a diagram of an RFID intelligent shelf article misplacement detection model;
FIG. 2 is a frame diagram of RFID smart shelf item misplacement detection;
FIG. 3 is a diagram illustrating a moving track of an antenna;
fig. 4 is a diagram illustrating an initial phase distribution of the same type of antenna.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the embodiments and the accompanying drawings.
The present invention monitors and manages the position of an article in real time for a shelf on which the article attached with an RFID tag is placed. The method for detecting misplacement of the RFID intelligent goods shelf comprises the steps of collecting phase information of a label through a high-frequency reader, detecting misplacement through a mode of comparing a measured value with a theoretical calculated value, namely processing the phase measured value to enable the phase measured value to be consistent with the theoretical value, namely matching the measured value with the theoretical value, and identifying phase deviation caused by misplacement of the goods, so that detection of misplacement of the goods is realized. The invention solves the problems of position ambiguity, winding and equipment diversity of the label, and is a real-time detection method with high cost performance.
The main steps of the misplacement detection processing of the invention are as follows:
the method has the advantages that the arrangement positions of the reader antennas are optimized, the distinguishing degree of the two positions is maximized, and the ambiguity of the positions is solved;
collecting data, and detecting and correcting phase winding of the phase measurement value;
the measured value is calibrated by estimating the system error, so that the problem of inconsistent initial phases caused by equipment diversity is solved;
and comparing the processed measured value with a theoretical value, and detecting the misplacement by observing whether the phase shifts or not.
Referring to fig. 1, the misplacement detection of an item may be considered a particular static location, assuming that the tags are placed at a series of fixed points, such as the garment hangers shown in fig. 1, each having an RFID Tag (Tag) disposed thereon, with some of the hangers having misplacement (mislaid tags shown in fig. 1). In order to realize the detection of misplaced articles, the key processing of the invention is as follows: the measured phase values are calibrated and abnormal phase shifts caused by misplacement of an article are detected, rather than tracking changes in phase, so that it is not necessary to assume that all tags are placed in the correct position in the initial state, i.e., the initial state of the tags is not required to be in their deployed position.
Referring to fig. 2, the article misplacement detection process of the present invention includes three parts, input, misplacement detection and output.
Wherein the input includes tag IDs, EPCxxx 0001-0004 as shown in FIG. 2, and the phase measurement value (θ) and the distribution of tags, i.e., the arrangement position of each tag;
the misplacement detection comprises three stages: ambiguity resolution, phase unwrapping, and outlier detection.
The output contains the tag ID and the location of the misplaced tag.
Wherein, the ambiguity, phase unwrapping and abnormal value detection of the position involved in the misplacement detection are specifically as follows:
(1) Ambiguity of position.
Defining the number of antennas as m and the number of tags as n, and defining
Figure BDA0002261729340000051
Denotes a slave antenna A s (the positional information is (x) s ,y ,s ,z s ) Can be recorded as A s (x s ,y ,s ,z s ) ) collected tags T i (the positional information is (x) i ,y i ,z i ) Can be recorded as T i (x i ,y i ,z i ) A theoretical phase value of the phase-shifted signal, wherein i is the same as [1,n ∈ ]]，s∈[1,m]。
The calculation formula of the theoretical phase value (or called phase theoretical value) is shown in formula (1):
Figure BDA0002261729340000052
where λ represents a wavelength, d represents a distance between the antenna and the tag, and K is an integer. I.e. the theoretical value theta is a function of the period 2 pi for every change in the distance d between the antenna and the tag
Figure BDA0002261729340000053
The theoretical value theta changes by one cycle.
And the phase measurement θ contains a systematic error μ, defined as:
Figure BDA0002261729340000054
where k is an integer and the systematic error μ = (θ) TAG +θ ANT )mod 2π，θ TAG And theta ANT Additional phase shifts are generated at the transmitting and receiving ends of the reader antenna due to the tag reflection characteristics, respectively.
As can be seen from the formula (1),
Figure BDA0002261729340000055
is formed by A s And T i The distance between
Figure BDA0002261729340000056
Is decided, i.e.
Figure BDA0002261729340000057
For deployment purposes, assuming that the topology of the antenna array is fixed, as shown in fig. 3, an arbitrary antenna a is defined r (coordinate position is (x) r ,y r ,z r ) As a reference point for the antenna array. Then vector
Figure BDA0002261729340000058
Can be expressed as:
Figure BDA0002261729340000059
wherein the point O represents the origin of coordinates,
Figure BDA00022617293400000510
in relation to the layout of the shop (the scene of the misplacement detection application) is usually unchanged.
Figure BDA00022617293400000511
Depending on the relative position of the antennas, which is fixed and constant. Therefore, the number of the first and second electrodes is increased,
Figure BDA0002261729340000061
only with
Figure BDA0002261729340000062
Is related to, i.e. means
Figure BDA0002261729340000063
Can be regarded as
Figure BDA0002261729340000064
Is expressed as
Figure BDA0002261729340000065
As shown in fig. 3, the antenna a is translated without rotation r And A s 。A r And A s Considered as a rigid body if A r To position A r ' moving, A s Will reach A s ', such that
Figure BDA0002261729340000066
Can then obtain
Figure BDA0002261729340000067
Because of the fact that
Figure BDA0002261729340000068
And
Figure BDA0002261729340000069
are all constant if
Figure BDA00022617293400000610
Has been measured, then
Figure BDA00022617293400000611
For any two tags T i And T j If their positions are swapped, the magnitude of each phase offset for them
Figure BDA00022617293400000612
Considering m antennas, defined by T i And T j Is shifted in phase by the exchange of
Figure BDA00022617293400000613
Expressed as:
Figure BDA00022617293400000614
wherein s is epsilon [1,m]. Due to the fact that
Figure BDA00022617293400000615
Then the expression for the theoretical phase value in combination with equation (1) can be derived:
Figure BDA00022617293400000616
wherein the vector
Figure BDA00022617293400000617
Based on the label T i And T j Obtaining the arrangement position of the vector
Figure BDA00022617293400000618
Antenna A based on reference point r Position of (2) is obtained, vector
Figure BDA00022617293400000619
Based on an antenna A s And an antenna A r The relative position of (a) is obtained.
In fact, two different tags can be selected and their positions exchanged, in common
Figure BDA00022617293400000620
Such a combination. Calculating the value of each pair of labels
Figure BDA00022617293400000621
Defining the minimum phase offset caused by label misplacement as
Figure BDA00022617293400000622
Expressed as:
Figure BDA00022617293400000623
wherein i belongs to [1,n ], j belongs to (i, n ].
Then maximize
Figure BDA00022617293400000624
To achieve maximum minimum fair allocation and avoid false results.
Figure BDA00022617293400000625
Furthermore, in order to reduce the operation amount, the invention can find A by utilizing a particle swarm algorithm r Is (i.e. optimum position of)
Figure BDA00022617293400000626
). The method comprises the following specific steps:
(a) Randomly initializing a population of particles in space.
(b) Calculating an adaptation value for each particle according to equation (5), i.e.
Figure BDA0002261729340000071
As an adaptation value for the particles.
(c) And updating the position of the particle according to the adaptive value.
(d) If the maximum iteration number is reached or the global optimal position meets the preset lowest limit, A r Has been found, otherwise go to b) to continue execution.
Namely, the invention utilizes the existing particle swarm algorithm to search A r Will be used in the search process
Figure BDA0002261729340000072
As an adaptation value for the particles.
(2) And (4) phase unwrapping.
The phase unwrapping process changes the phase of a wrap to the 'correct' form, and gets rid of the influence of 2 pi jump. By using
Figure BDA0002261729340000073
Denotes a slave antenna A s Collected tag T i The phase of the measured value of (a),
Figure BDA0002261729340000074
is represented by a label T i And an antenna A s Resulting in systematic errors. Subtracting equation (2) from equation (1) yields:
Figure BDA0002261729340000075
because of the fact that
Figure BDA0002261729340000076
Is provided with
Figure BDA0002261729340000077
Considering the sign of this difference, there are two cases:
(1)
Figure BDA0002261729340000078
namely satisfy
Figure BDA0002261729340000079
Figure BDA00022617293400000710
(2)
Figure BDA00022617293400000711
Namely satisfy
Figure BDA00022617293400000712
Figure BDA0002261729340000081
By combining formulae (7) to (9), there can be obtained:
Figure BDA0002261729340000082
definition of
Figure BDA0002261729340000083
The value after unwinding is
Figure BDA0002261729340000084
Then:
Figure BDA0002261729340000085
as can be seen from the formula (11),
Figure BDA0002261729340000086
variations of (2)
Figure BDA0002261729340000087
Is uniform, which means that
Figure BDA0002261729340000088
And
Figure BDA0002261729340000089
has a strong linear relationship. By
Figure BDA00022617293400000810
This result shows that
Figure BDA00022617293400000811
Is a relatively stable value.
(3) And (4) abnormal value detection.
Referring to the initial phase distribution diagram of the same type of antenna shown in fig. 4, different initial phase deflections may exist for the same type of antenna. Estimating prior to detecting a misplaced tag
Figure BDA00022617293400000812
To calibrate for
Figure BDA00022617293400000813
Rewrite calculation for equation (11)
Figure BDA00022617293400000814
Figure BDA00022617293400000815
Because of the demonstration that the compound has the characteristics of,
Figure BDA00022617293400000816
is a stable value, and in the present embodiment, the system error is estimated by placing l reference tags (the placement positions of the reference tags can be selected from n placement positions of the tags) to simplify the operation
Figure BDA00022617293400000817
(estimated value of systematic error), its expressionThe formula is as follows:
Figure BDA00022617293400000818
wherein p is epsilon [1,l]L < n. Then use
Figure BDA00022617293400000819
Instead of the former
Figure BDA00022617293400000820
Calibration
Figure BDA00022617293400000821
Then
Figure BDA00022617293400000822
Calibration value of
Figure BDA00022617293400000823
Can be defined as:
Figure BDA0002261729340000091
suppose A r In the optimum position of the movable part,
Figure BDA0002261729340000092
is a true value, considering two cases:
1) If T is i In the correct position, then
Figure BDA0002261729340000093
2) If T is i At T j ' position, then
Figure BDA0002261729340000094
Definition of T i Estimation of phase offset
Figure BDA0002261729340000095
Comprises the following steps:
Figure BDA0002261729340000096
wherein s is from [1,m ∈ [ ]]Then T is detected by the formula (16) i The misplacement of (1):
Figure BDA0002261729340000097
that is, if equation (16) is satisfied, T is i And if the misplacement exists, the misplacement does not exist.
In equation (16), α represents a coefficient for controlling the error rate. In theory, α can be set to 1 to cover worst case conditions.
In addition, a larger α can be selected to further reduce the false rate, that is, the value range of the coefficient α is set as:
Figure BDA0002261729340000098
according to the invention, a plurality of readers (tag readers) are arranged at fixed positions to acquire tag data, the positions of the readers are optimized to maximize the difference value of the acquired phase data, the acquired phase values are effectively processed by unwrapping and the like, then system errors are estimated to solve the problem of device diversity, and finally the phase measurement value is compared with the theoretically calculated phase value and whether the phase difference value changes or not is observed to detect whether the position of the article placement changes or not, so that the effective supervision of the position of the article on the shelf and the detection of the misplacement of the article are realized. The monitoring of the goods with the ultrahigh frequency tags on the goods shelf in the ultrahigh frequency RFID environment can be realized, so that the misplaced goods in a scene to be monitored can be detected in real time.
Where mentioned above are merely embodiments of the invention, any feature disclosed in this specification may, unless stated otherwise, be replaced by alternative features serving equivalent or similar purposes; all of the disclosed features, or all of the method or process steps, may be combined in any combination, except mutually exclusive features and/or steps.

Claims (4)

  1. The method for detecting the misplacement of the RFID intelligent goods shelf is characterized by comprising the following steps:
    step 1: a plurality of tag readers are arranged at the periphery of a goods shelf on which goods attached with RFID tags are placed and used for collecting tag data of the RFID tags;
    determining the position of an antenna of a tag reader and the arrangement position of each RFID tag on the shelf based on a preset coordinate origin O;
    and 2, step: setting a detection threshold of misplacement detection:
    antenna A of arbitrarily selected tag reader r As a reference antenna, for any two RFID tags T i And T j Forming tag pairs, exchanging the arrangement positions of the tag pairs, and calculating the antenna A of each tag reader after exchange s Phase shift of
    Figure FDA0003735548290000011
    Namely an antenna A s Respectively acquire the labels T i And T j Phase offset of the phase theoretical value of (a);
    wherein the content of the first and second substances,
    Figure FDA0003735548290000012
    the x is a wavelength at which,
    Figure FDA0003735548290000013
    representing origin of coordinates O to label T i The vector of (a) is determined,
    Figure FDA0003735548290000014
    representing origin of coordinates O to antenna a r The vector of (a) is determined,
    Figure FDA0003735548290000015
    denotes a reference antenna A r To antenna A s Vector of (2)，
    Figure FDA0003735548290000016
    Representing origin of coordinates O to label T j The vector of (a);
    for each pair of labels, all phase offsets are taken
    Figure FDA0003735548290000017
    As the current tag pair with respect to the current reference antenna a r Phase shift of
    Figure FDA0003735548290000018
    And will be currently referenced to antenna a r Phase shift of all tag pairs under
    Figure FDA0003735548290000019
    As the current reference antenna a r Tag misplacement minimum phase offset of
    Figure FDA00037355482900000110
    Taking the antennas of all the tag readers as reference antennas respectively, and taking the maximum of the minimum phase offsets of the misplaced tags as a detection threshold of the misplaced detection, and recording the detection threshold as
    Figure FDA00037355482900000111
    And step 3: carrying out misplacement detection processing on the article based on the phase measurement value of the RFID label currently acquired by the antenna of the label reader:
    antenna A based on label reader s Of the system error of
    Figure FDA00037355482900000112
    For each phase measurement
    Figure FDA00037355482900000113
    Performing correction processing to obtain phase measurement value
    Figure FDA00037355482900000114
    Calibration value of
    Figure FDA00037355482900000115
    If it is
    Figure FDA00037355482900000116
    Is less than
    Figure FDA00037355482900000117
    Then
    Figure FDA00037355482900000118
    If not, then,
    Figure FDA00037355482900000119
    the subscript i is an identifier of the RFID label, and the superscript s is an antenna identifier of the label reader;
    for any one article to be misplaced and detected, based on the RFID label T attached to the article i The distribution position of each tag reader, and the antenna A of each tag reader s Respectively collected labels T i Theoretical phase value of
    Figure FDA0003735548290000021
    And according to the formula
    Figure FDA0003735548290000022
    Obtain the label T i Estimate of the phase offset of
    Figure FDA0003735548290000023
    If the estimated value is
    Figure FDA0003735548290000024
    Greater than or equal to the detection threshold
    Figure FDA0003735548290000025
    Then the label T is judged i Misplacing the corresponding article;
    antenna A of tag reader s Of the system error of
    Figure FDA0003735548290000026
    The setting mode is as follows:
    placing a certain number of reference tags T p And calculates each antenna A s Acquired reference tag T p Theoretical phase value of
    Figure FDA0003735548290000027
    Based on an antenna A s Collected reference labels T p Measured phase of
    Figure FDA0003735548290000028
    Determining systematic errors corresponding to each reference tag
    Figure FDA0003735548290000029
    If the theoretical phase value
    Figure FDA00037355482900000210
    Greater than the phase measurement
    Figure FDA00037355482900000211
    Then
    Figure FDA00037355482900000212
    Otherwise
    Figure FDA00037355482900000213
    For the same antenna A s Taking the corresponding systematic error of all reference labels
    Figure FDA00037355482900000214
    As the mean value of the antenna A s Of the system error of
    Figure FDA00037355482900000215
  2. 2. The method of claim 1, wherein in step 2, the step of converting the signal into a signal comprises converting the signal into a signal
    Figure FDA00037355482900000216
    The corresponding antenna is used as the optimal reference antenna, and the detection threshold of the misplacement detection is set as
    Figure FDA00037355482900000217
    Wherein the value range of the coefficient alpha is as follows:
    Figure FDA00037355482900000218
    Figure FDA00037355482900000219
    representing the mean of the phase shifts of all tag pairs relative to the optimal reference antenna.
  3. 3. The method of claim 1, wherein in step 2, the detection threshold for the misplacement detection is determined by a particle swarm algorithm:
    will refer to antenna A r Tag misplacement minimum phase offset of
    Figure FDA00037355482900000220
    Performing a particle swarm algorithm to search the optimal position of the reference antenna as the adaptive value of the particle to obtain the optimal reference antenna;
    and based on the minimum phase deviation of the label misplacement corresponding to the optimal reference antenna
    Figure FDA00037355482900000221
    Setting a detection threshold for the misplacement detection to
    Figure FDA00037355482900000222
    Wherein the coefficient alpha takes the value 1 or
    Figure FDA00037355482900000223
    Figure FDA00037355482900000224
    Representing the mean of the phase shifts of all tag pairs relative to the optimal reference antenna.
  4. 4. The method of claim 1, wherein in step 2, a number of reference tags T are placed at the placement positions of the RFID tags p 。
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