A method for RSSI fusion double RFID tag airport luggage sequencing

Abstract

The application discloses a method for RSSI fusion double-RFID tag airport luggage sequencing, and belongs to the wireless positioning technology field in intelligent manufacturing. The super high frequency RFID reader installed on the airport luggage extraction carousel track sequences all the luggage with double-RFID tags, facilitating the extraction of the luggage by passengers. In the application, the double-RFID tags are attached to any two opposite surfaces, so that the problem of missed reading caused by the direction and shielding of the single RFID tag can be avoided. In addition, the RFID reader analyzes the change of the RSSI value when the two RFID tags of the luggage are identified, analyzes the time when the luggage passes through the reader, and determines the sequence of the luggage on the carousel. The application reduces the problem of missed reading of the tag, improves the accuracy of the luggage sequencing, and protects the public interests of the passengers.

Description

Technical Field

[0001] This invention belongs to the field of wireless positioning technology, a key technology for intelligent manufacturing, and specifically relates to a method for airport baggage sequencing using RSSI fusion dual RFID tags. Background Technology

[0002] RFID technology is an automatic identification technology that can identify items from a distance and over obstacles. However, when the distance is too far or the obstacle is made of high-density material, the RFID reader may lose the item. Existing airport baggage sorting technology often uses single RFID tags. Due to issues such as obstruction by high-density materials (such as metal), the RFID tag on the item may not be identified, resulting in tag loss. Furthermore, due to the placement angle of a single tag, the RSSI value may be the same at different distances, causing sorting errors.

[0003] A search of existing literature revealed that Chinese Patent Publication No. CN111144517A, published on May 12, 2020, discloses a method and apparatus for locating items based on UHF RFID. This technology is based on a single UHF RFID tag, which can easily lead to missed identification of items. In addition, the RFID reader of this invention only analyzes the time information of the first and last time the tag is read. When the luggage on the conveyor belt is dense, its positioning technology is expected to have many errors. Summary of the Invention

[0004] The purpose of this invention is to provide a method for airport baggage sorting using RSSI-integrated dual RFID tags. This method avoids missed readings of baggage RFID tags by attaching UHF RFID tags to any two opposite sides of the baggage. Furthermore, by using RFID tags with strong RSSI values ​​as sorting tags, the accuracy of airport baggage sorting is greatly improved.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] A method for RSSI-integrated dual RFID tag-based airport baggage sequencing includes the following steps:

[0007] (S1) Affix UHF tags to any two opposite sides of the luggage to be sorted. These can be the left and right sides, front and back, or top and bottom of the luggage. Bind these two RFID tags to the luggage. This way, if one side is obscured by high-density material and cannot be identified, its corresponding side can still be identified.

[0008] (S2) Obtain the time series of RSSI values ​​for each piece of luggage. When luggage passes through the RFID reader, record the time, RSSI value, and EPC number of each RFID tag being identified. This will give you a time series over a period of time, where each element is a triplet (time, epc, rssi). epc is the electronic tag number of the RFID tag, time is the time when the epc is read, and rssi is the RSSI value when the epc is read.

[0009] (S3) Optimize the time series of each baggage RSSI value. The baggage time triplet sequence obtained in the previous step is divided into 0.1-second intervals. At most one triplet is retained for each interval. There are three scenarios: First, no tag is identified within 0.1 seconds, so the triplet data for that 0.1-second interval is empty; second, one baggage tag is identified within 0.1 seconds, so the triplet for that RFID tag is retained; third, multiple tags are identified within 0.1 seconds, so the triplet with the larger RSSI value is retained. This results in an optimized baggage RSSI value time series. The optimized RSSI value time series is generated during the identification process.

[0010] (S4) Determine the time when baggage passes through the RFID reader. If a baggage tag is not re-identified within 3 seconds of being identified by both tags, it can be considered to have left the RFID reader's signal area. At this point, analyze the optimized RSSI value time series for that baggage. There are two scenarios: First, the relationship between time and RSSI approximates an "isosceles triangle with the base removed," where the time corresponding to the vertex (maximum RSSI value) is the moment the baggage is exactly below the reader. Second, the relationship between time and RSSI approximates an "isosceles trapezoid with the lower base removed," where the midpoint of the upper base is the moment the baggage is exactly below the reader. Using this method, the sequential order of all baggage passing through the reader can be determined.

[0011] Furthermore, in step (S2), the reader records the time when each RFID tag is identified, with a time accuracy of 0.01 seconds, because in this invention, it is necessary to count the time when the RFID tag is identified every 0.1 seconds.

[0012] Furthermore, in step (S3), the reader optimizes the RSSI value time series for each baggage, and each baggage has an optimized RSSI value time series.

[0013] Furthermore, the two relationships in step (S4) and RSSI relationship analysis, namely "isosceles triangle with base removed" and "isosceles trapezoid with bottom base removed", are only approximate relationships of RSSI values ​​on the time axis, that is, these relationships have random fluctuations.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1) Existing technology tags have a high probability of being lost. This invention attaches tags to both sides of the luggage, which can achieve an almost zero tag loss rate.

[0016] 2) Existing technologies do not employ dual-tag technology, resulting in a higher probability of incorrect baggage sorting. However, this invention can significantly reduce the probability of incorrect baggage sorting. Attached Figure Description

[0017] Figure 1 A graph showing the relationship between time and RSSI during which luggage passes through an RFID reader. Detailed Implementation

[0018] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings.

[0019] A method for RSSI-integrated dual RFID tag-based airport baggage sequencing includes the following steps:

[0020] (S1) Baggage awaiting sorting is tagged with UHF labels on any two opposite sides. Figure 1 On luggage 1, two RFID tags are affixed to the top and bottom; on luggage 2, two RFID tags are affixed to the left and right sides; on luggage 3, two RFID tags are affixed to the front and back. This shows that at least one of the two RFID tags on the luggage can effectively receive the electromagnetic waves of the reader when it passes by, which can effectively avoid the RFID tags being missed.

[0021] (S2) Obtain the time series of RSSI values ​​for each piece of luggage. When luggage passes through the RFID reader, record the time, RSSI value, and EPC number of each RFID tag being identified. This will give you a time series over a period of time, where each element is a triplet (time, epc, rssi). epc is the electronic tag number of the RFID tag, time is the time when the epc is read, and rssi is the RSSI value when the epc is read.

[0022] (S3) Optimize the time series of each baggage RSSI value. The baggage time triplet sequence obtained in the previous step is divided into 0.1-second intervals. At most one triplet is retained for each interval. There are three scenarios: First, no tag is identified within 0.1 seconds, so the triplet data for that 0.1-second interval is empty; second, one baggage tag is identified within 0.1 seconds, so the triplet for that RFID tag is retained; third, multiple tags are identified within 0.1 seconds, so the triplet with the larger RSSI value is retained. This results in an optimized baggage RSSI value time series. The optimized RSSI value time series is generated during the identification process.

[0023] (S4) Determine the time when the baggage passes the RFID reader. If a baggage tag is not re-identified within 3 seconds of being identified by both tags, it can be considered to have left the RFID reader's signal area. At this point, analyze the time and RSSI of the optimized RSSI value time series for that baggage. There are two scenarios: First, the relationship between time and RSSI approximates an "isosceles triangle with the base removed," where the time corresponding to the vertex (maximum RSSI value) is the moment the baggage is exactly below the reader. In this case... Figure 1 In the first case, the time when luggage 1 and luggage 3 pass directly below the reader is the moment when their RSSI value is at its maximum; in the second case, the relationship between time and RSSI approximates an "isosceles trapezoid with the lower base removed," where the midpoint of the upper base is the moment when the luggage is exactly below the reader. This situation is as follows... Figure 1 Luggage 2 passes directly below the reader at the midpoint of the upper base of the isosceles trapezoid. Using this method, the order in which all luggage passes the reader can be determined.

[0024] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for RSSI-integrated dual RFID tag-based airport baggage sequencing includes: (S1) Affix UHF tags to any two opposite sides of the luggage to be sorted, and bind these two RFID tags to the luggage; In this way, even if one of the faces is obscured by a high-density material, its corresponding face can still be identified; (S2) Obtain the time sequence of RSSI values ​​for each piece of luggage. When luggage passes through the RFID reader, the reader will record the time, RSSI value and EPC number of each RFID tag identification multiple times. Thus, each tag will get a triple (time, EPC, RSSI) after identification. Where time is the RFID identification time, EPC is the electronic tag number of the RFID tag, and RSSI is the signal strength indicator of the RFID tag. Since each piece of luggage has two RFID tags, each piece of luggage can get a time triple sequence containing two RFID tags. (S3) Optimize the time series of baggage RSSI values; the baggage time triplet sequence obtained in the previous step is divided into 0.1-second intervals. At most one triplet is retained in each interval. There are 3 cases: First, no tag is identified within 0.1 seconds, so the triplet data for that 0.1-second interval is empty; Second, one baggage tag is identified within 0.1 seconds, so the triplet for that RFID tag is retained; Third, multiple tags are identified within 0.1 seconds, so the triplet with the larger RSSI value is retained. This results in an optimized baggage RSSI value time series. (S4) Determine the time when the baggage passes through the RFID reader. When a baggage just leaves the reader's signal area, analyze the time and RSSI value of the optimized RSSI value time series for that baggage. There are two cases: First, the relationship between time and RSSI is approximately "an isosceles triangle with the base removed". The vertex is the point where the maximum RSSI value is located, which is the time when the baggage is exactly below the reader. Second, the relationship between time and RSSI is approximately "an isosceles trapezoid with the base removed". The midpoint of the upper base is the time when the baggage is exactly below the reader. Using this method, the order of all baggage can be determined.

2. The method for airport baggage sequencing using RSSI fusion dual RFID tags as described in claim 1, characterized in that... Luggage must be affixed with two UHF RFID tags, which can effectively prevent luggage from being lost.

3. The method for airport baggage sequencing using RSSI fusion dual RFID tags as described in claim 1, characterized in that... The system determines whether luggage has left the reader's signal area by checking if the luggage's two RFID tags are no longer being identified within 3 seconds of their last identification.

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