Rfid tag three-dimensional space distance sensing method, system, storage medium and computer

Abstract

The present application relates to the technical field of RFID, and particularly relates to a three-dimensional space distance sensing method and system of RFID tag, a storage medium and a computer; the present application models the tag movement on the conveying belt under the condition that the conveying belt speed and the distance from the reader to the conveying belt are known, designs a distance measuring algorithm by using the RSSI and phase value of the tag obtained by the reader placed directly above the conveying belt, can consider that the measured distance of the tag deviating from the center line of the conveying belt is larger than that of the same position tag located on the center line, and the sorting result of the tag on the conveying belt is extremely easy to be wrong; the distance estimation method of the tag deviating from the center line of the conveying belt is given while the distance between the reader and the tag is obtained, the three-dimensional distance sensing capability of the reader can be obtained, can be used for sorting the RFID tags simultaneously identified on the conveying belt, and realizes the real-time tracking and management of the articles on the conveying belt.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of RFID technology, and particularly relates to a three-dimensional space distance sensing method and system for RFID tags, a storage medium and a computer. BACKGROUND

[0002] Radio Frequency IDentification (RFID) is an indispensable sensing technology in the Internet of Things, which can be easily integrated on most objects. Passive RFID tags have been widely used in logistics, retail and security fields due to their low cost, small size, non-contact communication and no need to carry power supply. The RFID tag sorting problem on the conveyor belt is essentially a positioning problem, which is to find the position of the tag at a certain time, that is, to locate the tag in a moving state. As an important part of the positioning process, distance measurement also affects the accuracy of the tag sorting on the conveyor belt.

[0003] There are currently several schemes for RFID distance measurement:

[0004] Using the logarithmic loss model, when the reader collects the received signal strength indication (RSSI) of the tag to be measured, the distance of the tag to be measured can be obtained through the signal strength at the reference distance position. However, this distance measurement scheme relies too much on channel quality, and the RSSI value error is large due to the change of channel quality during the tag movement, thereby affecting the distance measurement accuracy.

[0005] During the modulation and demodulation process, the reader compares the phase difference between the initial phase of its own transmitted signal and the received signal phase to sense the distance of the tag. Although the phase is less affected by the channel quality than the RSSI value, the Doppler effect caused by the tag movement will still cause the reader to estimate the error of the phase. In addition, the phase entanglement problem in the phase calculation process often needs to use multiple frequency carriers for processing, which will reduce the real-time performance of the distance measurement algorithm.

[0006] In summary, the current distance measurement schemes all have shortcomings in the tag movement scenario, thereby reducing the distance measurement accuracy of the moving tag. In addition, in the case where the distance is known, the influence of the tag position on the conveyor belt on the distance measurement result still needs to be considered in order to give a more accurate tag sorting algorithm. SUMMARY

[0007] The technical problem solved by the present application is to provide an RFID tag three-dimensional space distance sensing method, system, storage medium and computer which can realize real-time tracking and management of articles on a conveying belt by providing a three-dimensional distance sensing capability of a tag for a reader to obtain RFID tags identified simultaneously on the conveying belt.

[0008] To solve the above technical problems, the first technical solution adopted by the present application is:

[0009] An RFID tag three-dimensional space distance sensing method comprises

[0010] Data acquisition: an RFID tag reader with a communication radius of R is arranged at a distance of d above the center of a conveying belt moving at a constant speed, and RSSI values and phase values of all tags obtained in the process of movement of the tags with the conveying belt are recorded

[0011] Data preprocessing: RSSI values and phase values collected by the data are preprocessed according to formula (1) and formula (2)

[0012]

[0013]

[0014] wherein X σ , μ are environmental noise and system noise respectively;

[0015] The RSSI value in formula (1) is used to estimate d reader-tag at time t, and is obtained, and the phase wrapping problem in formula (2) is solved by using it, and is obtained is obtained by machine learning based on data regression with f(0)=R as a constraint condition, and is obtained

[0016] The distance d c from the center line is obtained

[0017]

[0018] Distance calculation: the inverse formula (1) is used to obtain the function d(RSSI) of the distance d about the RSSI value; according to formula (4), at a certain time t,

[0019] f(t)=d reader-tag +ξ (4)

[0020] ​where ξ is the measurement noise, and d(RSSI) is the distance between the reader and the tag using the recursive filter reader-tag ;

[0021] Tag ranking: according to formula (5), the distance d reader-tag between the tag and the center line of the conveyor belt c The distance d p between the tag and the plane perpendicular to the direction of the conveyor belt motion and containing the reader

[0022]

[0023] According to d p , its size and its trend, the tags are ranked.

[0024] Preferably, the ranking of the tags according to d p , its size and its trend comprises:

[0025] If d p is large and gradually decreasing, the tag is relatively far behind; if d p is small and gradually decreasing, it is followed; if d p is small and gradually increasing, it is relatively in front; if d p is large and gradually increasing, it is at the front of the conveyor belt.

[0026] Preferably, the machine learning is an extreme learning machine model.

[0027] Preferably, the domain adjustment comprises:

[0028] Let f(t) = R, then 0, t R , and its domain is [0, t R ].

[0029] Preferably, the recursive filter uses an extended Kalman filter algorithm.

[0030] To solve the above technical problems, the second technical solution adopted by the present application is:

[0031] An RFID tag three-dimensional space distance sensing system, comprising a conveyor belt moving at a constant speed, an RFID tag reader with a communication radius R arranged at a distance d above the center of the conveyor belt moving at a constant speed, and a controller;

[0032] The controller records the RSSI values and phase values of all tags obtained during the movement of the tags with the conveyor belt and performs the data preprocessing, the calculation of the distance d c from the center line, the distance calculation, and the ranking of the tags of the RFID tag three-dimensional space distance sensing method described above.

[0033] To solve the above technical problems, the third technical scheme of the present application is as follows:

[0034] A storage medium, which stores a computer program for executing the RFID tag three-dimensional space distance sensing method.

[0035] To solve the above technical problems, the fourth technical scheme of the present application is as follows:

[0036] A computer, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor executes the computer program to implement the RFID tag three-dimensional space distance sensing method.

[0037] The present application has the beneficial effects that: by modeling the tag movement on the conveyor belt under the condition that the conveyor belt speed and the distance from the reader to the conveyor belt are known, a ranging algorithm is designed using the RSSI and phase values of the tags obtained by the reader placed directly above the conveyor belt, which can consider that the measured distance of the tags deviating from the center line of the conveyor belt is larger than that of the tags located at the same position on the center line, which is extremely easy to cause the sorting result of the tags on the conveyor belt to be wrong; while obtaining the distance between the reader and the tag, an estimation method of the distance of the tag deviating from the center line of the conveyor belt is given, which is used to obtain a more accurate sorting result of the tag; the three-dimensional distance sensing capability of the reader can be achieved, which can be used for sorting the RFID tags identified on the conveyor belt at the same time, and realizing real-time tracking and management of the articles on the conveyor belt. DETAILED DESCRIPTION

[0038] To illustrate the technical content, purposes and effects of the present application, the following embodiments are described.

[0039] Embodiment one

[0040] A RFID tag three-dimensional space distance sensing method, comprising

[0041] Data acquisition: an RFID tag reader with a communication radius of R is arranged directly above the center of the conveyor belt moving at a constant speed at a distance of d, and the RSSI values and phase values of all tags obtained during the movement of the tags with the conveyor belt are recorded

[0042] Data preprocessing: the RSSI values and phase values collected by the data are preprocessed according to formula (1) and formula (2)

[0043]

[0044] ​

[0045] Where X σ μ and μ represent environmental noise and system noise, respectively;

[0046] First, use the RSSI value in formula (1) to calculate d at time t. reader-tag To make an estimate, we get And it was used to solve the phase winding problem in formula (2), and obtained Then, with f(0) = R as the constraint, the Extreme Learning Machine (ELM) model is used based on data regression to obtain... The relationship with time t is obtained Finally, based on the actual physical meaning, the domain is adjusted by letting f(t) = R, resulting in 0, t R Then its domain is [0, t R ].

[0047] Obtain the distance d from the centerline c : Differentiate f(t) and let f′(t) = 0 to get t0; then calculate according to formula (3);

[0048]

[0049] Distance calculation: Solve formula (1) to obtain the distance d as a function of RSSI value, d(RSSI); according to formula (4), at a certain time t, let

[0050] f(t) = d reader-tag +ξ (4)

[0051] Where ξ represents the measurement noise, and the distance d between the reader and the tag is obtained using the extended Kalman filter algorithm in conjunction with d(RSSI). reader-tag ;

[0052] Tag sorting: According to formula (5), the distance d between the tag and the reader is used. reader-tag Distance d between the label and the centerline of the conveyor belt c Calculate the distance d from the label to the plane perpendicular to the direction of the conveyor belt movement and including the reader. p ;

[0053]

[0054] According to d p Sort the labels by size and their changing trends, if d p If the value is large and gradually decreasing, the label should be placed relatively later; if d p If d is smaller and gradually decreasing, then it is the next best; if d p It is relatively small and gradually increasing, and is relatively near the front; if dp The larger and gradually increasing is in the front end of the conveyor belt.

[0055] Embodiment two

[0056] An RFID tag three-dimensional space distance sensing system, comprising a uniform motion conveyor belt, an RFID tag reader with a communication radius of R arranged at a distance of d above the center of the uniform motion conveyor belt, and a controller;

[0057] The controller records the RSSI value and phase value of all tags obtained during the movement of the tags with the conveyor belt and performs the data preprocessing, obtains the distance d from the center line, distance calculation and tag sorting of the RFID tag three-dimensional space distance sensing method described in embodiment one. c

[0058] Embodiment three

[0059] A storage medium storing a computer program for executing the RFID tag three-dimensional space distance sensing method described in embodiment one.

[0060] Embodiment four

[0061] A computer comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor implements the RFID tag three-dimensional space distance sensing method described in embodiment one when executing the computer program.

[0062] The above is only an embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent transformation or direct or indirect application in related technical fields using the content of the present application specification is also included in the patent protection scope of the present application.​

Claims

1. A method for three-dimensional spatial distance perception of an RFID tag, characterized in that, Comprising Data collection: Set a RFID tag reader with communication radius R above the center of the moving conveyor belt at a distance d, record the RSSI value and phase value of all tags during the movement of the tags with the conveyor belt Data pre-processing: The RSSI value and phase value of the data collected according to formula (1) and formula (2) pre-processing, where X σ , μ are the ambient and system noise, respectively; The RSSI value in formula (1) is used to estimate d reader-tag The estimation is performed, and d The phase wrapping problem in formula (2) is solved by using f(t), and f(t) is obtained With f(0)=R as a constraint condition, f(t) is obtained by machine learning based on data regression The relationship between f(t) and time t is obtained The domain is adjusted according to the actual physical meaning obtaining the distance d from the center line c : take the derivative of f(t), let f'(t) = 0 to get t0; then calculate according to equation (3) Distance calculation: inverse formula (1) distance d is a function of RSSI value d(RSSI); according to formula (4) at a certain time t, let f(t) = d reader-tag + ξ (4) where ξ is the measurement noise, and d(RSSI) is the distance between the reader and the tag obtained using a recursive filter in combination with d reader-tag ; Tag ranking: according to formula (5), using the distance d of the tag from the reader reader-tag Distance d of the tag from the center line of the conveyor belt c Distance d of the tag to the plane perpendicular to the direction of motion of the conveyor belt and containing the reader p ; According to d p The size and its trend are sorted by the tags.

2. The RFID tag three-dimensional spatial distance perception method of claim 1, wherein, The according to d p Ranking the tags by size and trends in their size includes: If d p is large and decreasing, the label is relatively far back; if d p is small and decreasing, it is next; if d p is small and increasing, it is relatively far forward; if d p is large and increasing, it is at the front of the conveyor.

3. The method of claim 1, wherein, The machine learning is an extreme learning machine model.

4. The method of claim 1, wherein, The domain adjustment comprises: Let f(t) = R, then 0, t R , and its domain is [0, t R ].

5. The method of claim 1, wherein, The recursive filter adopts an extended Kalman filter algorithm.

6. An RFID tag three-dimensional spatial distance sensing system, comprising: The conveying belt includes uniform motion, an RFID tag reader with a communication radius R is arranged at a distance d above the center of the conveying belt in uniform motion, and a controller; The controller records RSSI values and phase values of all tags obtained during the movement of the tags with the conveyor belt and performs data preprocessing, obtaining the distance d from the center line, distance calculation, and tag sorting of the method for three-dimensional spatial distance perception of RFID tags according to any one of claims 1-5. c , distance calculation, and tag sorting.

7. A storage medium, characterized by The storage medium stores a computer program for executing the RFID tag three-dimensional space distance sensing method of any one of claims 1-5.

8. A computer comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor implements the RFID tag three-dimensional space distance sensing method of any one of claims 1-5 when executing the computer program.

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