Control device, reader writer, and control method

Abstract

To provide a system capable of stably specifying a position of an RFID tag moving across communication regions of a plurality of reader writers (antennas).SOLUTION: A higher control device (10) for controlling a plurality of reader writers (20) communicating with an RFID tag (30) includes: a communication intensity determination unit (12) for measuring communication intensity between the RFID tag and each of the reader writers; and a switching unit (13) for switching the reader writers communicating with the RFID tag according to the communication intensity during communication of data.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reader / writer that communicates with a moving RFID tag. [Background technology]

[0002] At production sites, it is necessary to identify the location of finished products. For example, at automobile production sites, it is necessary to distinguish between vehicles that require rework after production is complete and vehicles that are waiting to be shipped, and to identify their locations. Without knowing the locations of vehicles that require rework and vehicles that are waiting to be shipped, accurate shipping plans cannot be made. In addition, the man-hours required by workers to identify the locations of vehicles are enormous.

[0003] Therefore, Patent Document 1 discloses a technology for identifying the location of a product (item) at a production site (work site) by using a system that uses an RFID (Radio Frequency Identifier) ​​in the UHF (Ultra-High Frequency) band. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-078211 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when RFID tags are attached to automobiles, the target products are mobile and can move independently, so the products move across the detection areas of each antenna, making communication with the RFID tag unstable and making it difficult to identify their location.Since RFID tags are mobile, if an RFID tag moves while communicating with another RFID tag, the RFID tag may be temporarily lost.

[0006] Furthermore, because there are overlapping areas in the communication areas of multiple antennas, products may be detected in those areas. Furthermore, RFID tags in unintended areas may be detected by unintended antennas due to radio wave reflection and fading. Therefore, when the same RFID tag is detected by multiple antennas, it is difficult to determine which antenna should communicate, i.e., which communication area the RFID tag is in, and to pinpoint the RFID tag's location.

[0007] An object of one embodiment of the present invention is to realize a system that can stably communicate with an RFID tag that moves across communication areas of a plurality of reader / writers (antennas). [Means for solving the problem]

[0008] In order to solve the above problem, a control device according to one embodiment of the present invention is a control device that controls multiple reader / writers that communicate with an RFID tag, and is equipped with a communication strength determination unit that determines the communication strength between the RFID tag and each reader / writer, and a switching unit that switches the reader / writer that communicates data with the RFID tag depending on the communication strength during data communication with the RFID tag.

[0009] With the above configuration, it is possible to determine (specify) the communication strength and then dynamically switch to the most appropriate reader / writer each time. Therefore, even if an RFID tag is attached to a moving object, stable communication is possible and the location of the moving object can be identified from the physical location of the reader / writer.

[0010] The control device may control a scan period during which the communication strength is measured and a communication period during which data is exchanged with the RFID tag in a time-division manner.

[0011] According to the above configuration, in order to communicate, a scanning period is set up in advance to measure the communication strength, and based on the results, communication with the RFID can be performed during the communication period while switching the RFID to communicate with each time.

[0012] The communication strength determination unit may calculate the communication strength from a first reception strength when the RFID tag receives from the reader / writer and a second reception strength when the reader / writer receives from the RFID tag.

[0013] According to the above configuration, the communication strength can be determined by comprehensively considering the reception strength of the RFID tag and the reception strength of the reader / writer.

[0014] The device may further include a distance determination unit that determines the distance between the RFID tag and the reader / writer from the communication strength, and the switching unit may switch the reader / writer that communicates the data with the RFID tag depending on the distance.

[0015] According to the above configuration, the distance between the reader / writer and the RFID tag may be identified from the communication strength, and the reader / writer to be used for communication may be determined based on the distance.

[0016] During the period in which the communication strength is measured, the communication strength determination unit may measure the communication strength only for a plurality of reader / writers that are included in a predetermined range including the reader / writer that is exchanging data with the RFID tag.

[0017] With this configuration, the communication strength can be measured only by the reader / writers within a predetermined range, including the reader / writer communicating with the RFID tag. Therefore, even in a system using many reader / writers, only the limited number of reader / writers that can stably detect the RFID tag in question will be in operation, thereby reducing the time lost during the scanning period.

[0018] The switching unit may switch to the reader / writer with the highest communication strength.

[0019] According to the above configuration, the reader / writer suitable for the RFID tag can be the one with the highest communication strength, which makes it easy to uniquely identify the reader / writer.

[0020] The switching unit does not need to switch the reader / writer if the communication strength of the reader / writer communicating with the RFID tag during the communication period is greater than the communication strength of another reader / writer and the difference is within a predetermined range.

[0021] According to the above configuration, even if there is a reader / writer suitable for the RFID tag that has a stronger communication strength than the reader / writer already communicating with, if the difference in communication strength is smaller than a predetermined value, there is no need to switch the reader / writer, thereby minimizing the invalid communication period that accompanies reader / writer switching.

[0022] When there are multiple reader / writers whose communication strength with the RFID tag is equal to or greater than a predetermined value, the switching unit may switch the reader / writers so as to reduce the difference in the number of RFID tags with which the multiple reader / writers are communicating.

[0023] RFID tags may be concentrated on a specific reader / writer. In such cases, processing by that reader / writer becomes excessive, which may result in RFID tags not being detected. To reduce this risk, reader / writers suitable for RFID tags may be designed to balance the load of the reader / writers so that the difference in the number of RFID tags each reader / writer communicates with is minimized if the communication strength is within a certain range.

[0024] During the scanning period, the communication strength of the reader / writer that communicated with the RFID tag during the most recent communication period may not be measured.

[0025] According to the above configuration, by using the communication intensity during the communication period, it is possible to reduce the number of reader / writers that perform scanning during the scan period.

[0026] The communication strength determination unit may identify the communication strength based on reception strength obtained by the plurality of reader / writers receiving communication from the RFID tag during the communication period.

[0027] According to the above configuration, during a communication period, another reader / writer receives communication from an RFID tag and measures the communication strength, thereby making it possible to reduce the scanning period.

[0028] Another aspect of the reader / writer of the present invention is a reader / writer connected to multiple antennas that communicate with RFID tags, and includes a communication strength determination unit that determines the communication strength between the RFID tag and each antenna, and a switching unit that switches the antenna that communicates data with the RFID tag depending on the communication strength during data communication with the RFID tag.

[0029] According to the above configuration, the system may detect RFID tags using a single reader / writer connected to a plurality of antennas.

[0030] A control method for a control device according to another aspect of the present invention is a control method for controlling a plurality of reader / writers that communicate with an RFID tag, and includes a communication strength determination step for determining the communication strength between the RFID tag and each reader / writer, and a switching step for switching the reader / writer that communicates data with the RFID tag depending on the communication strength during data communication with the RFID tag.

[0031] The control device according to each aspect of the present invention may be realized by a computer. In this case, the control program of the control device that realizes the control device by the computer by making the computer operate as each part (software element) of the control device, and the computer-readable recording medium on which the control program is recorded, also fall within the scope of the present invention. [Effects of the Invention]

[0032] According to one aspect of the present invention, stable communication can be achieved with an RFID tag that moves across communication areas of a plurality of reader / writers (antennas). [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a block diagram showing the configuration of a main part of an RFID system according to a first embodiment. [Figure 2] 4 is a flowchart showing an example of the operation of the RFID system according to the first embodiment. [Figure 3] 5 is a flowchart showing a method for selecting a reader / writer in a switching unit according to the first embodiment. [Figure 4] 10 is a specific example showing switching between the first reader / writer and the second reader / writer according to the first embodiment. [Figure 5] 10 is a graph showing changes in communication intensity between a first interrogator and a second interrogator. [Figure 6] FIG. 10 is a block diagram showing the configuration of a main part of an RFID system according to a second embodiment. [Figure 7] FIG. 10 is a block diagram showing the configuration of a main part of an RFID system according to a third embodiment. [Figure 8] 10 is a specific example showing a method for switching a reader / writer according to the fourth embodiment. [Figure 9] 10 is a specific example showing another reader / writer switching method according to the fourth embodiment. [Figure 10] FIG. 1 is a conceptual diagram showing the positional relationship between an RFID tag and multiple reader / writers. DETAILED DESCRIPTION OF THE INVENTION

[0034] [Embodiment 1] Hereinafter, an embodiment according to one aspect of the present invention (hereinafter also referred to as "the present embodiment") will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0035] §1. Application Examples 1 is a block diagram showing the configuration of a main part of an RFID system 100 according to embodiment 1. The RFID system 100 is a system in which an upper control device 10 that controls a plurality of reader / writers 20 in an integrated manner detects an RFID tag 30 with an appropriate reader / writer 20 and communicates with the RFID tag 30.

[0036] The RFID tag 30 is attached to a moving object such as an automobile, and moves over time. Therefore, if only one reader / writer 20 is used, the RFID tag may move out of the detection range of that reader / writer 20. Therefore, the communication strength of multiple reader / writers for the RFID tag 30 is measured, and communication is performed by dynamically switching to the most appropriate reader / writer 20 each time. Therefore, stable communication can be performed even with the RFID tag 30 attached to a moving object.

[0037] §2. Configuration example (Configuration of RFID system 100) 1, an RFID system 100 includes multiple reader / writers 20 under the control of a single upper control device 10 (control device). Each reader / writer 20 includes an antenna and can detect RFID tags within the antenna's detection range. There may be multiple RFID tags 30 within the detection range.

[0038] (Configuration of host control device 10) The upper control device 10 includes a communication unit 11, a communication strength determination unit 12, and a switching unit 13.

[0039] The communication unit 11 acquires information about the RFID tag 30 with which each reader / writer 20 is communicating by the upper control device 10 communicating with the reader / writer 20. The communication unit 11 also transmits the communication content determined by the upper control device 10 to the RFID tag 30 via the reader / writer 20. The communication unit 11 outputs the communication content to the communication strength determination unit 12.

[0040] The communication strength determination unit 12 acquires the reception strength measured by the reader / writer 20 and the RFID tag 30. The communication strength determination unit 12 is a functional block that determines the communication strength of each RFID tag 30 using the reception strength measured by the reader / writer 20 and the RFID tag 30. The communication strength determination unit 12 outputs the determined communication strength to the switching unit 13.

[0041] The switching unit 13 uses the determined communication strength to determine the reader / writer 20 suitable for each RFID tag 30, and switches the reader / writer 20 to be used for communication during data communication with the RFID tag. The switching unit 13 outputs the selected reader / writer 20 to the communication unit 11.

[0042] §3. Example FIG. 2 is a flowchart showing an example of the operation of the RFID system 100 according to the first embodiment.

[0043] In S11, the communication unit 11 uses the reader / writer 20 (first reader / writer) currently communicating data to communicate with the RFID tag 30 and perform a scan. Here, the scan is a communication for measuring the communication strength between the reader / writer 20 and the RFID tag 30.

[0044] First, in accordance with an instruction from the communication unit 11, the reader / writer 20 issues an instruction to the RFID tag 30 to measure the reception strength. In response to this instruction, the RFID tag 30 measures the strength of the received UHF radio wave and returns the measured radio wave strength to the reader / writer 20 as a first reception strength. The reader / writer 20 measures the strength of the received UHF radio wave and returns the measured radio wave strength to the reader / writer 20 as a second reception strength. This series of operations between the reader / writer 20 and the RFID tag 30 for a certain RFID tag is called a scan. A certain pair of the reader / writer 20 and the RFID tag 30 may be scanned multiple times (for example, N times) in succession.

[0045] In S12, the communication unit 11 checks whether there is an unscanned reader / writer 20 (second reader / writer) other than the first reader / writer. If there is a second reader / writer (Yes in S12), the process proceeds to S13, and if there is no second reader / writer (No in S12), the process proceeds to S14.

[0046] In S13, the communication unit 11 uses the second reader / writer to scan the RFID tag 30. Then, the process returns to S12. That is, the processes of S12 and S13 are repeated until all the second reader / writers have been scanned.

[0047] In S14, the communication strength determination unit 12 determines the communication strength for each reader / writer 20. The method for determining the communication strength will be described in detail later. Thereafter, the communication strength determination unit 12 outputs the communication strength for each combination of the reader / writer 20 and the RFID tag 30 to the switching unit 13.

[0048] In S15, the switching unit 13 selects an appropriate reader / writer for each RFID tag 30 based on the communication strength, and indicates the selected RFID tag 30 to the communication unit 11. The method for selecting an appropriate reader / writer 20 will be described later.

[0049] In S16, the communication unit 11 communicates with the RFID tag 30 using the instructed reader / writer 20.

[0050] Here, the period from S11 to S13 is collectively referred to as the scan period, during which the communication strength of each combination of the reader / writer 20 and the RFID tag 30 is measured to determine the appropriate reader / writer 20. On the other hand, the period corresponding to S16 is collectively referred to as the communication period, during which the reader / writer 20 and the RFID tag 30 actually exchange data using the reader / writer 20 selected by the switching unit 13 based on the communication strength.

[0051] (Method of determining communication strength: Based on reception strength) An example of a method for determining communication strength will be described below. The reader / writer 20 measures the received signal strength (RSSI: Received Signal Strength Indicator) of communication received by itself. That is, it measures the second received signal strength described above.

[0052] Here, the communication strength can be expressed as Dlvl in the following equation.

[0053] Dlvl=ΣRSSI(n) / N Here, RSSI(n) is the value of the second reception strength at the nth scan, and the number of scans for each combination of reader / writer 20 and RFID tag 30 is N. Σ represents the sum of N scans. In other words, the communication strength Dlvl calculated by this formula is the average value of the second reception strength. The communication strength can also be used as an index representing the distance between the reader / writer 20 and the RFID tag 30.

[0054] (How to select a suitable reader / writer 20) A method for selecting a suitable reader / writer 20 in the switching unit 13 will now be described.

[0055] FIG. 3 is a flowchart showing a method for selecting the reader / writer 20 in the switching unit 13 according to the first embodiment.

[0056] In S21, the switching unit 13 compares the communication strength between the first reader / writer (the reader / writer 20 currently communicating) and the second reader / writer (the unscanned reader / writer 20 excluding the first reader / writer). If the communication strength of the first reader / writer is greater than the communication strength of the second reader / writer, the process proceeds to S24, and if the communication strength of the second reader / writer is equal to or greater than the communication strength of the first reader / writer, the process proceeds to S22.

[0057] In S22, the switching unit 13 determines whether the difference between the communication strength of the second reader / writer and the communication strength of the first reader / writer is smaller than a predetermined value. If the difference is smaller than the predetermined value, the process proceeds to S24, and if the difference is equal to or greater than the predetermined value, the process proceeds to S23.

[0058] In S23, the switching unit 13 outputs to the communication unit 11 an instruction to switch so that communication is performed using the second reader / writer.

[0059] In S24, the switching unit 13 outputs to the communication unit 11 an instruction to continue communication using the first reader / writer.

[0060] Therefore, if the difference in communication strength between the first reader / writer and the second reader / writer is small or if the communication strength of the first reader / writer is greater, communication continues with the first reader / writer. On the other hand, if the communication strength of the second reader / writer is sufficiently greater than that of the first reader / writer, communication is switched to the second reader / writer. This is a measure to reduce the number of times the reader / writer that communicates with the RFID tag is switched while maintaining sufficient communication strength.

[0061] (Example of switching between the first and second reader / writer) Fig. 4 is a specific example showing switching between the first reader / writer and the second reader / writer according to embodiment 1. Fig. 5 is a graph showing changes in communication strength between the first reader / writer and the second reader / writer. The horizontal axis of Fig. 5 represents time for the RFID tag 30, and the vertical axis represents communication strength. The RFID tag 30 is moving, and its position changes from tag position A to tag position B over time.

[0062] As shown in FIG. 4, the reader / writer 20 used for communication with the RFID tag 30 is switched from the first reader / writer to the second reader / writer from reference numeral 51 to reference numeral 56.

[0063] At reference numeral 51, the communication unit 11 has the first reader / writer and the second reader / writer each scan the same RFID tag 30 during the scan period. The result of this scan is indicated by reference numeral 61 in FIG. 5. At reference numeral 52, the communication strength determination unit 12 determines the communication strength, and the switching unit 13 selects to continue using the first reader / writer. Thereafter, at reference numeral 53, the first reader / writer communicates data with the RFID tag 30 for a predetermined period. Data communication by the first reader / writer refers to the transmission of data to be written to the RFID tag 30 or the reception of data read from the RFID tag 30.

[0064] At reference numeral 54, the communication unit 11 again scans the same RFID tag 30 with the first reader / writer and the second reader / writer during the scan period. The result of this scan is reference numeral 62 in FIG. 5. At reference numeral 55, the communication strength determination unit 12 determines the communication strength, and the switching unit 13 selects to switch to the second reader / writer. Thereafter, at reference numeral 56, the second reader / writer communicates with the RFID tag 30 for a predetermined period.

[0065] The size of the transmitted and received data may be large, and the communication period may be longer than the scanning period. Furthermore, the RFID tag 30 may move during the communication period. As shown in FIG. 5, since the RFID tag 30 is attached to a moving object, the distance from the reader / writer 20 varies. Therefore, the communication strength also changes. Between periods (e.g., reference numeral 53) during which data is being communicated and periods (e.g., reference numeral 56) during which data is being communicated, the switching unit 13 switches to a reader / writer 20 suitable for communicating with the RFID tag 30 (e.g., reference numeral 55).

[0066] §4. Action and Effects After measuring the communication strength, it is possible to dynamically switch to the reader / writer 20 that is best suited for communication with the RFID tag 30. Therefore, stable communication can be maintained even if the RFID tag 30 is attached to a moving object. Furthermore, the location of the moving object can be identified from the switching of the reader / writer 20 that allows stable communication and the physical location of the reader / writer.

[0067] By clearly differentiating the roles of the communication between the RFID tag 30 and the reader / writer 20 into a scanning period and a communication period, it is possible to communicate with the RFID tag 30 while maintaining sufficient communication strength.

[0068] The communication strength during the scan period can be measured using any one of the RFID tag reception strength, the reader / writer reception strength, and the reader / writer transmission strength, and can be determined comprehensively.

[0069] Based on the measurement results of the communication strength during the scan period, the switching unit 13 can select a suitable reader / writer based on the communication strength. Even if there is a suitable reader / writer with a stronger communication strength than the currently communicating reader / writer, if the difference is smaller than a predetermined value, there is no need to switch the reader / writer. This minimizes the invalid communication period that accompanies reader / writer switching.

[0070] Furthermore, the method for selecting an appropriate reader / writer is not limited to this method. For example, it is also possible to switch from a plurality of reader / writers to the reader / writer with the highest communication strength.

[0071] (Variation) The function of the upper control device 10 may be included in any one of the multiple reader / writers 20. In this case, a specific reader / writer 20 having the function of the upper control device 10 communicates with the other reader / writers 20. The specific reader / writer 20 determines which reader / writer 20, including itself, to use to communicate with the RFID tag 30.

[0072] [Embodiment 2] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0073] 6 is a block diagram showing the configuration of a main part of an RFID system 101 according to embodiment 2. The RFID system 101 is a system in which a reader / writer 20a connected to a plurality of antennas 21 detects an RFID tag 30 with an appropriate antenna 21 and communicates with the appropriate antenna 21.

[0074] In the second embodiment, the reader / writer 20 of the first embodiment is replaced with an antenna 21, and the upper control device 10 is replaced with a reader / writer 20a. The reader / writer 20a includes a communication unit 11, a communication strength determination unit 12, and a switching unit 13. The reader / writer 20a is connected to a plurality of antennas 21. That is, the switching unit 13 of the reader / writer 20a selects one antenna from the plurality of antennas based on the communication strength determined by the communication strength determination unit 12.

[0075] [Embodiment 3] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0076] 7 is a block diagram showing the configuration of the main parts of an RFID system 102 according to embodiment 3. The RFID system 102 uses an upper control device 10b to which a plurality of reader / writers 20 are connected to select an appropriate reader / writer 20 to read an RFID tag 30 and performs communication.

[0077] The upper control device 10b of the third embodiment differs from the upper control device 10 of the first embodiment in that it includes a distance determination unit 14. The distance determination unit 14 inputs the communication strength from the communication strength determination unit 12 and determines the distance of the RFID tag 30 from the reader / writer 20. The switching unit 13 selects the reader / writer 20 to be used for communication based on the determined distance, not the communication strength. The distance determination unit 14 may also determine the position of the RFID tag using the distances of the same RFID tag 30 from multiple reader / writers 20.

[0078] (Method of determining communication strength: Friis's transmission formula) Specifically, the RFID tag 30 measures the strength of the received signal in communication received by itself (i.e., measures the first received signal strength described above), and the reader / writer 20 measures the transmission power in scanning itself.

[0079] Here, the communication strength can also be expressed as Dlvl in the following equation.

[0080] Dlvl=Σ10^{(Tx_rw(n)-RSSI_tag(n)) / 20} / N Here, Tx_rw(n) is the value of the transmission power in the reader / writer 20 at the nth scan, and RSSI_tag(n) is the value of the first reception strength in the RFID tag 30 at the nth scan. "10^x" represents 10 to the xth power. However, the number of scans for each combination of reader / writer 20 and RFID tag 30 is N. Σ represents the sum of N scans. This calculation formula is a simplified formula for distance conversion based on the Friis propagation formula, and communication strength is also an index of the distance between the reader / writer 20 and RFID tag 30.

[0081] Calculating the communication strength using this formula based on the Friis propagation formula improves the accuracy as a distance index compared to the communication strength calculation method using only the second reception strength described above in embodiment 1. Therefore, the distance between the reader / writer 20 and the RFID tag 30 can be determined with high accuracy, making it easier to identify the position of the product to which the RFID tag 30 is attached.

[0082] [Embodiment 4] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0083] (Method to shorten scan period: Use the most recent communication) The scanning period becomes long when there are a large number of reader / writers 20. Therefore, a method for shortening the scanning period using the most recent existing communication results will be described.

[0084] Fig. 8 is a specific example showing a method for switching a reader / writer 20 according to embodiment 4. Unlike Fig. 4, Fig. 8 is a method for limiting the number of reader / writers 20 to be scanned during a scanning period based on the results of the most recent communication period.

[0085] Specifically, the first reader / writer used for communication during the most recent communication period (reference numeral 71 in FIG. 8) is considered to have already finished measuring the communication strength, and is not scanned during the scan period (reference numeral 72 in FIG. 8). The communication unit 11 scans the other reader / writers 20 (the second and third reader / writers in the example of FIG. 8), and the communication strength determination unit 12 measures the communication strength. Based on the results, the switching unit 13 selects the reader / writer 20 to be used (reference numeral 73 in FIG. 8). In the example shown in FIG. 8, the third reader / writer is selected (reference numeral 74 in FIG. 8).

[0086] Therefore, the number of reader / writers to be scanned during the scan period can be reduced, and the scan period can be shortened.

[0087] (Method to shorten the scan period: Use communication with other reader / writers) Another method for shortening the scan period will be described.

[0088] Fig. 9 is a specific example showing another method of switching the reader / writer 20 according to the embodiment 4. Unlike Fig. 4, Fig. 9 shows a method in which communication of an RFID tag 30 with a certain reader / writer 20 in the most recent communication period is received by another reader / writer 20, and processing is performed that is regarded as a scan based on the received reception strength.

[0089] Specifically, the first reader / writer used for communication during the most recent communication period (reference numeral 81 in FIG. 9) is considered to have already finished measuring the communication strength. The control device 10 does not allow the first reader / writer to measure the communication strength during the scanning period. Furthermore, the communication strength determination unit 12 of the other reader / writers 20 (the second and third reader / writers in the example of FIG. 9) measures the communication strength upon receiving a reply (communication) from the RFID tag 30 to the first reader / writer. Thereafter, the switching unit 13 selects the reader / writer 20 to be used (reference numeral 82 in FIG. 9). In the example shown in FIG. 9, the third reader / writer is selected (reference numeral 83 in FIG. 9).

[0090] Therefore, by considering the communication period as the scan period, the scan period can be eliminated except for the first scan.

[0091] (How to shorten the scan period: Limit the number of readers / writers) In the above two methods for shortening the scan period, the scan period is shortened by changing the processing during the scan period. In contrast to these, another method for shortening the scan period will be described.

[0092] Fig. 10 is a conceptual diagram showing the positional relationship between an RFID tag 30 and multiple reader / writers 20. As shown in Fig. 10, there are multiple reader / writers 20 (reader / writers A to L in Fig. 10), and each reader / writer 20 can communicate with an RFID tag within a communication range 91.

[0093] Assume that reader / writer E is currently communicating with RFID tag 30. At this time, even if RFID tag 30 is moving during the scanning period, it is believed that RFID tag 30 can be detected by scanning only reader / writers 20 having communication ranges 91 adjacent to the communication range 91 of the reader / writer with which communication is currently possible. Therefore, scanning can be performed using reader / writers A to I that are included in a predetermined range 92 that includes reader / writer E. In other words, reader / writers J to L that are not included in the predetermined range 92 are not scanned.

[0094] Therefore, the reader / writers that perform scanning during the scan period can be limited to only those in a predetermined range 92 that includes the reader / writer communicating with the RFID tag. As a result, even in a system that uses many reader / writers, the scan period is shortened, allowing for stable detection of the target RFID tag.

[0095] [Embodiment 5] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0096] In embodiment 1, the reader / writer 20 that will communicate with the RFID tag 30 is determined using only the communication strength, but this is not limited to this, and for example, the reader / writer 20 that will communicate may also be determined taking into consideration the number of RFID tags 30 that are communicating.

[0097] For example, suppose that a first reader / writer and a second reader / writer are connected to the upper control device 10, and that the communication ranges of the first reader / writer and the second reader / writer overlap. In this case, suppose that three RFID tags exist within the communication range of only the first reader / writer, no RFID tags exist within the communication range of only the second reader / writer, and one RFID tag exists within the overlapping range. While both the first and second reader / writers have sufficient communication strength with the RFID tags in the overlapping range, the communication strength of the first reader / writer is stronger.

[0098] If the reader / writer is selected based solely on communication strength, the first reader / writer will also communicate with RFID tags within the overlapping range. However, the number of RFID tags communicating with each reader / writer may be equalized. That is, since the second reader / writer also has sufficient communication strength and the first reader / writer is already communicating with multiple RFID tags 30, in the fifth embodiment, communication is performed using the second reader / writer instead of the first reader / writer.

[0099] Therefore, in the fifth embodiment, if the communication strength of the reader / writer 20 is equal to or greater than a predetermined value, the switching unit 13 may select the reader / writer 20 so as to reduce the difference in the number of RFID tags 30 with which the reader / writer 20 is communicating. This makes it possible to balance the load among the multiple reader / writers 20 and prevent RFID tags 30 from going undetected.

[0100] [Software implementation example] The functions of the upper control device 10 and the reader / writer 20a (hereinafter referred to as "devices") can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (especially each part included in the upper control device 10 and the reader / writer 20a).

[0101] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program, thereby realizing the functions described in each of the above embodiments.

[0102] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0103] Furthermore, some or all of the functions of the control blocks can be realized by logic circuits. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present invention. In addition, the functions of the control blocks can also be realized by, for example, a quantum computer.

[0104] Furthermore, each process described in each of the above embodiments may be executed by AI (Artificial Intelligence). In this case, the AI ​​may run on the control device or on another device (for example, an edge computer or a cloud server).

[0105] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0106] 10, 10b Upper control device (control device) 11 Communication Section 12 Communication strength determination unit 13 Switching section 14 Distance identification part 20, 20a Reader / Writer 21 Antenna 30 RFID tags 100, 101, 102 RFID Systems

Claims

1. A control device that controls a plurality of reader / writers that communicate with RFID tags, a communication strength determination unit that determines the communication strength between the RFID tag and each reader / writer; a switching unit that switches the reader / writer that communicates data with the RFID tag in accordance with the communication strength during data communication with the RFID tag; a distance determination unit that determines the distance between the RFID tag and the reader / writer based on the communication strength, The switching unit switches the reader / writer that communicates the data with the RFID tag according to the distance.

2. A control device that controls a plurality of reader / writers that communicate with RFID tags, a communication strength determination unit that determines the communication strength between the RFID tag and each reader / writer; a switching unit that switches the reader / writer that communicates data with the RFID tag in accordance with the communication strength during data communication with the RFID tag, The control device, wherein the communication strength determination unit measures the communication strength only for a plurality of reader / writers included in a predetermined range including the reader / writer communicating data with the RFID tag during the period in which the communication strength is measured.

3. A control device that controls a plurality of reader / writers that communicate with RFID tags, a communication strength determination unit that determines the communication strength between the RFID tag and each reader / writer; a switching unit that switches the reader / writer that communicates data with the RFID tag in accordance with the communication strength during data communication with the RFID tag, The control device, wherein the communication strength determination unit calculates the communication strength from a first reception strength when the RFID tag receives from the reader / writer.

4. The control device according to claim 1 , wherein the switching unit switches to the reader / writer with the highest communication strength.

5. 4. The control device according to claim 1, wherein when there are multiple reader / writers whose communication strength with the RFID tag is equal to or greater than a predetermined value, the switching unit switches the reader / writers so as to reduce the difference in the number of RFID tags with which the multiple reader / writers are communicating.

6. A reader / writer connected to a plurality of antennas for communicating with RFID tags, a communication strength determination unit that determines the communication strength between the RFID tag and each antenna; a switching unit that switches the antenna that communicates data with the RFID tag in accordance with the communication strength during data communication with the RFID tag.

7. A control method for controlling a plurality of reader / writers that communicate with an RFID tag, comprising: a communication strength determination step of determining communication strength between the RFID tag and each reader / writer; a switching step of switching the reader / writer that communicates data with the RFID tag in accordance with the communication strength during data communication with the RFID tag; a distance determination step of determining a distance between the RFID tag and the reader / writer based on the communication strength, The control method includes: in the switching step, switching the reader / writer that communicates the data with the RFID tag according to the distance.

8. A control method for controlling a plurality of reader / writers that communicate with an RFID tag, comprising: a communication strength determination step of determining communication strength between the RFID tag and each reader / writer; a switching step of switching the reader / writer that communicates data with the RFID tag in accordance with the communication strength during data communication with the RFID tag, A control method in which, in the communication strength determination step, the communication strength is measured only for multiple reader / writers within a predetermined range including the reader / writer communicating data with the RFID tag during the period in which the communication strength is measured.

9. A control method for controlling a plurality of reader / writers that communicate with an RFID tag, comprising: a communication strength determination step of determining communication strength between the RFID tag and each reader / writer; a switching step of switching the reader / writer that communicates data with the RFID tag in accordance with the communication strength during data communication with the RFID tag, In the determining step, the communication strength is calculated from a first reception strength when the RFID tag receives from the reader / writer.

Images