WO2021240933A1

WO2021240933A1 - Rfid communication unit, control method, and rfid communication program

Info

Publication number: WO2021240933A1
Application number: PCT/JP2021/007680
Authority: WO
Inventors: 善光中野
Original assignee: オムロン株式会社
Priority date: 2020-05-27
Filing date: 2021-03-01
Publication date: 2021-12-02
Also published as: JP7392574B2; CN115428344A; JP2021190769A; CN115428344B

Abstract

An RFID communication unit (1) is provided with: an estimation unit (21) for estimating, for each antenna (2), an undetected tag count that indicates the number of wireless tags (3) not yet having been detected among the wireless tags (3) that are expected to be detected by each of a plurality of antennas (2); and an antenna selection unit (22) for selecting, on the basis of the undetected tag count, an antenna (2) from among the plurality of antennas (2) that is to be driven.

Description

RFID communication unit, control method and RFID communication program

The present invention relates to an RFID communication unit, a control method and an RFID communication program.

Patent Document 1 describes a plurality of antennas for transmitting and receiving signals for communicating with a wireless tag, a controller for switching the operation of a combination of antennas, and a reader for reading identification information of the wireless tag based on signals received by the plurality of antennas. A reader comprising the above is disclosed. In the reading device disclosed in Patent Document 1, it is possible to reduce the reading failure of the wireless tag attached to the article.

Japanese Patent Application Laid-Open No. 2019-52029

However, in the reading device disclosed in Patent Document 1, the outputs of a plurality of antennas are switched at regular intervals for communication regardless of the detection status of the wireless tag. Therefore, even if the detection of the wireless tag in the communication area of a certain antenna is completed, the antenna is not switched immediately, and there is a period in which the antenna continues to output uselessly, so that the wireless tag is detected. There was a problem that the efficiency of the. One aspect of the present invention is to improve the detection efficiency of a plurality of radio tags by a plurality of antennas.

In order to solve the above problems, the RFID communication unit according to the example of the present disclosure may be detected by each of the plurality of antennas in the RFID communication unit that detects a plurality of radio tags via a plurality of antennas. Based on the estimation unit that estimates the number of undetected tags indicating the number of the wireless tags that have not yet been detected among the expected wireless tags for each antenna, and the number of undetected tags estimated by the estimation unit. A selection unit for selecting an antenna to be driven from the plurality of antennas is provided.

The control method according to an example of the present disclosure is a control method of an RFID communication unit that detects a plurality of radio tags via a plurality of antennas, and the radio is expected to be detected by each of the plurality of antennas. Among the tags, the estimation step for estimating the number of undetected tags indicating the number of the wireless tags that have not been detected for each antenna, and the plurality of tags based on the number of undetected tags estimated in the estimation step. Includes a selection step to select the antenna to drive from among the antennas in.

According to one aspect of the present invention, it is possible to improve the detection efficiency of a plurality of wireless tags by a plurality of antennas.

It is a block diagram which shows an example of the main part structure of the RFID communication unit which concerns on this embodiment. It is a figure which shows an example of the structure of the physical distribution management system which concerns on this embodiment. It is a figure which shows an example of the operation performance data about 4 antennas provided in the RFID communication unit shown in FIG. 1. FIG. 1 is a diagram showing an example of the average value and the mode of the total number of detections related to the radio tags for the N passage periods of each antenna included in the RFID communication unit shown in FIG. 1, and the estimation results for the four antennas. be. It is a figure which shows an example of the look-up table stored in the storage part of the RFID communication unit shown in FIG. 1. It is a flowchart which shows the flow of the process which the RFID communication unit 1 shown in FIG. 1 executes. It is a flowchart which shows the flow of the order determination process which the antenna selection part included in the RFID communication unit shown in FIG. 1 executes. It is a flowchart which shows the flow of the switching determination process executed by the antenna selection part provided in the RFID communication unit shown in FIG. 1. It is a schematic diagram which shows the state of the switching determination process performed by the RFID communication unit shown in FIG. 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.

§1. Application Example First, an example of a situation in which the present invention is applied will be described with reference to FIG. FIG. 2 is a diagram showing an example of the configuration of the physical distribution management system 100 according to the present embodiment. As shown in FIG. 2, the physical distribution management system 100 includes an RFID communication unit 1, a plurality of antennas 2, a plurality of radio tags 3, a gate 4, and a pallet 5. In the distribution management system 100, a plurality of articles such as parts or products are conveyed, and each article is managed by using the wireless tag 3.

The RFID communication unit 1 is, for example, a reader / writer, and detects a plurality of wireless tags 3 via a plurality of antennas 2. Further, the RFID communication unit 1 reads data and writes data by wireless communication with the wireless tag 3 based on the control of the communication control unit 23 via the plurality of antennas 2. The RFID communication unit 1 receives response data from the radio tag 3 via the plurality of antennas 2.

Each of the plurality of antennas 2 is provided at the gate 4 and is connected to one RFID communication unit 1. The plurality of antennas 2 detect the wireless tag 3. The wireless tag 3 is attached to an article to be managed, for example, in order to improve traceability at a production site. A plurality of articles to which the wireless tag 3 is attached are loaded on the pallet 5. The pallet 5 loaded with a plurality of articles is conveyed by a forklift so as to pass through the gate 4. As a result, the plurality of radio tags 3 pass through the gate 4.

A detectable area is formed around the gate 4 in which a plurality of antennas 2 can detect the radio tag 3. A group of radio tags 3 attached to the articles loaded on the pallet 5 pass through the detectable area.

A plurality of reader / writers integrated with the antenna may be provided in the gate 4. In this case, a plurality of readers / writers are connected to each other via a hub so as to be able to communicate with each other. One of the plurality of reader / writers is a master reader / writer having another reader / writer as a slave, and the master reader / writer corresponds to the RFID communication unit 1 of the present disclosure.

When the RFID communication unit 1 is such a master reader / writer, the master reader / writer may be provided with at least one antenna 2, and other reader / writers may also be provided with at least one antenna 2. There is an antenna selection unit 22 inside the master reader / writer, and when its own antenna 2 or the antenna 2 of another slave reader / writer is selected, the master reader / writer instructs the communication control unit of each other reader / writer. ..

§2. Configuration Example FIG. 1 is a block diagram showing an example of the configuration of a main part of the RFID communication unit 1 according to the present embodiment.

<Structure of RFID communication unit 1>
The RFID communication unit 1 includes a control unit 10 and a storage unit 11. The control unit 10 controls the RFID communication unit 1. The control unit 10 includes an estimation unit 21, an antenna selection unit 22, and a communication control unit 23. The storage unit 11 stores data and programs used for controlling the RFID communication unit 1. The storage unit 11 stores the operation record data 41, the estimation result 42, the lookup table 43, and the communication result 44.

The estimation unit 21 estimates for each antenna 2 the number of undetected tags indicating the number of wireless tags 3 that have not yet been detected among the wireless tags 3 that are expected to be detected by each of the plurality of antennas 2. The estimation unit 21 stores the estimated number of undetected tags in the storage unit 11 as an estimation result 42. The antenna selection unit 22 selects the antenna 2 to be driven from the plurality of antennas 2 based on the number of undetected tags estimated by the estimation unit 21.

The communication control unit 23 controls communication with the wireless tag 3 via the antenna 2. The communication control unit 23 controls each antenna 2 to perform anti-collision processing, and communicates with the radio tag 3 via each antenna 2. The anti-collision process is a process that reduces collision of signals output by a plurality of radio tags 3 by using slots and enables the RFID communication unit 1 to read the signals of the plurality of radio tags. The slot is a plurality of divisions in which the timing at which the signal reading process is performed is time-divisioned. The wireless tag 3 randomly selects the timing of an arbitrary slot and communicates with the antenna 2.

FIG. 3 is a diagram showing an example of operation record data 41 relating to the four antennas 2 included in the RFID communication unit 1 shown in FIG. 1. As shown in FIG. 3, the operation record data 41 is data for N passage periods during which a group of wireless tags 3 passes through the gate 4. The operation record data 41 is updated at any time by the communication control unit 23 for each communication.

The operation record data 41 includes the total number of detected radio tags 3 in one passing period for each antenna 2 and the total number of detected radio tags 3 in all antennas 2 in one passing period. It has been. One passing period is a period during which a group of wireless tags 3 passes through the gate 4 once. The operation record data 41 may be configured by, for example, a ring buffer. Further, the operation record data 41 may be permanently stored in the storage unit 11 together with at least one of the date and time so as not to be overwritten.

The communication control unit 23 receives the correct numerical value of the total detected number of the wireless tag 3 from the upper device of the physical distribution management system 100 so that only the valid total detected number is stored in the operation record data 41, and the received total detected number. Only may be stored in the operation record data 41. That is, the communication control unit 23 records only the number of detected tags included in the communication result 44, which matches the total number of detections received from the higher-level device of the distribution management system 100, in the operation record data 41.

The communication control unit 23 may weight the operation record data 41 in the order of the new total detection number among the past total detection numbers. Further, the communication control unit 23 may group the total number of past detections in the operation record data 41 by the total sum of the total number of detections. For example, the communication control unit 23 divides the total number of detections into groups according to the case where the total number of detections is 32 and the total number of detections is 64, stores the total number of detections for each group, and prioritizes each group. You may select the total detection value.

FIG. 4 is a diagram showing an example of an average value and a mode value of the total number of detections related to the radio tag 3 for the N passage periods of each antenna 2, an estimation result 42 for the four antennas 2, and an example. .. The communication control unit 23 refers to the total number of detections related to the radio tag 3 for the N passage periods of each antenna 2 from the operation record data 41, and sets the average value and the mode value of the total number of detections as statistical data 421. It is stored in the storage unit 11. Further, the estimation result 42 is the number of predicted total tags and the estimated number of remaining tags, which will be described later, estimated by the estimation unit 21. The estimation result 42 is updated at any time by the estimation unit 21 for each communication.

FIG. 5 is a diagram showing an example of the look-up table 43. In the lookup table 43, representative values of the number of collision occurrence bins, the estimated number of remaining tags bin, and the estimated number of remaining tags are stored corresponding to the Q value and the number of slots. A bin is a numerical range for grouping objects according to their values for generalization and comparison.

The collision occurrence number bin indicates the numerical range of the collision occurrence number. The estimated number of remaining tags bin indicates the numerical range of the estimated number of remaining tags. The representative value of the estimated number of remaining tags indicates the representative value among the numerical values included in the estimated number of remaining tags bin. The representative value of the estimated number of remaining tags is, for example, the median value of the estimated number of remaining tags bin. The estimation unit 21 estimates the estimated number of remaining tags based on the collision occurrence number bin, the estimated remaining tag number bin, and the representative value of the estimated remaining tag number.

<Wireless tag 3>
The wireless tag 3 has a tag antenna unit and a tag wireless communication IC. The tag antenna unit receives radio waves from the antenna 2 as a power source for operating the tag wireless communication IC or the like. The tag antenna unit converts the radio wave received from the antenna 2 into a radio signal and transmits it to the tag wireless communication IC, and at the same time, converts the radio signal from the tag wireless communication IC into a radio wave and transmits it to the antenna 2. The tag antenna unit transmits the identification information of the wireless tag 3 to the antenna 2 when responding to the antenna 2.

When a plurality of wireless tags 3 communicate with the antenna 2 through the same slot, a collision occurs and communication is not performed normally. The wireless tag 3 that can communicate with the antenna 2 without causing a collision sets an inventoried flag and does not communicate with the antenna 2 until the power source is cut off.

§3. Operation Example FIG. 6 is a flowchart showing a flow of processing executed by the RFID communication unit 1. Specifically, the series of processes shown in FIG. 6 is a multi-access process for the RFID communication unit 1 to communicate with the plurality of radio tags 3 via the plurality of antennas 2. The multi-access process is performed, for example, by the RFID communication unit 1 for one passage period during which a group of radio tags 3 passes through the gate 4 once.

<Processing performed by RFID communication unit 1>
First, the estimation unit 21 refers to the total number of detected radio tags 3 detected by one antenna 2 in one passage period from the operation record data 41 stored in the storage unit 11. As in S202 and S203 described later, the estimation unit 21 estimates for each antenna 2 with the predicted total number of tags as the number of undetected tags based on the total number of detected tags. The estimation unit 21 stores the estimated total number of predicted tags as the estimation result 42 in the storage unit 11. The predicted total number of tags is a numerical range or numerical value indicating the number of radio tags 3 predicted to be detected by one antenna 2 in one transit period.

After the estimation unit 21 estimates the predicted total number of tags, in S101, the antenna selection unit 22 selects the antenna 2 to be driven for communication from the plurality of antennas 2. As an example, the antenna selection unit 22 may select the antenna 2 to be driven in a predetermined order. In another example, the antenna selection unit 22 may execute an order determination process for determining in which order the plurality of antennas 2 provided in the gate 4 are to be driven at the start of the multi-access process.

In the order determination process, the antenna selection unit 22 reads out the predicted total number of tags of each antenna 2 from the estimation result 42 as the number of undetected tags of each antenna 2. The antenna selection unit 22 determines, for example, the drive order of the antenna 2 in descending order of the number of undetected tags. The order determination process will be described in detail later with reference to FIG. 7. In S102, the communication control unit 23 drives the antenna 2 selected by the antenna selection unit 22.

After the communication control unit 23 drives the antenna 2, in S103, the communication control unit 23 calculates a Q value to be set for the driven antenna 2 according to the number of undetected tags of the driven antenna 2. For example, the communication control unit 23 calculates the Q value from each numerical range of the number of undetected tags of the antenna 2 or the association data in which each numerical value and the Q value are associated with each other.

The associated data is stored in the storage unit 11, and the optimum Q value for which the occurrence of collision is suppressed and the communication time is shortened is calculated by simulation with respect to the number of wireless tags 3 in the detectable range. Data.

The Q value is a numerical value for designating the number of slots that can be selected by each of the plurality of wireless tags 3 when the anti-collision process is performed. The number of slots is a numerical value for dividing communication with the radio tag 3 by the antenna 2 selected by the antenna selection unit 22. Communication control unit 23, to calculate the Q value, the antenna 2 which is selected by the antenna selector 22 determines the number of slots 2 ^Q.

For example, the communication control unit 23 may calculate the Q value so that the number of slots adopted in the antenna 2 to be driven based on the Q value is equal to or greater than the number of undetected tags of the antenna 2. Here, the number of undetected tags of the antenna 2 referred to by the communication control unit 23 is the estimated total number of tags for the antenna 2 at the time when the communication of S104 has never been performed in the multi-access process. Is. When the communication is performed once or more, the estimated number of remaining tags estimated in S106 for the antenna 2 is referred to as the number of undetected tags.

In S104, the communication control unit 23 communicates with the radio tag 3 within the detectable range via the driven antenna 2. Specifically, the communication control unit 23 communicates with each wireless tag 3 for each slot set according to the Q value calculated in S103 to acquire the information held by the wireless tag 3 or to acquire the wireless tag. Write information in 3.

In S105, the communication control unit 23 generates the communication result 44 and stores it in the storage unit 11. Specifically, the communication control unit 23 stores the number of collision occurrences and the number of detected tags as the communication result 44 in the storage unit 11 through all the slots. The number of collisions is a numerical value indicating the number of times a collision has occurred in communication among the number of slots, and the number of detected tags is a numerical value indicating the number of wireless tags 3 detected by communication. The communication result 44 includes the number of slots determined by communication, the number of collision occurrences, and the number of detected tags. The communication result 44 is updated at any time by the communication control unit 23 for each communication.

Further, the communication control unit 23 stores the number of detected tags in the communication result 44 for one passage period as the operation record data 41 in the storage unit 11. When the communication control unit 23 uses the antenna 2 which is the current communication, the communication control unit 23 adopts the antenna 2 in the current communication based on the communication result 44 of the previous communication of the antenna 2. The optimum Q value may be calculated dynamically.

In S106, the estimation unit 21 estimates the estimated number of remaining tags based on the communication result 44. The estimated number of remaining tags is based on the result of one or more communications with the radio tag 3 by one of the plurality of antennas 2 during the passage period in which the plurality of radio tags 3 pass through the detectable area. It is a numerical value indicating the number of remaining radio tags 3 that can be detected by one antenna 2 during the passage period.

The estimation unit 21 sets a provisional number of tags based on, for example, the number of predicted total tags and the number of detected tags in the communication result 44 for one transit period. Specifically, the estimation unit 21 sets a numerical value obtained by subtracting the detected tag number from the predicted total tag number as the provisional tag number. The estimation unit 21 refers to the lookup table 43 and estimates the estimated remaining tag number bin corresponding to the Q value adopted at the time of communication executed in S104 and the number of collision occurrences.

When the estimation unit 21 includes the provisional tag number in the numerical range of the estimated estimated remaining tag number bin, the estimation unit 21 determines that the provisional tag number is probable and determines the provisional tag number as the estimated remaining tag number. Set as. When the numerical range of the estimated remaining tag number bin does not include the provisional tag number, the estimation unit 21 refers to the look-up table 43 and refers to the estimated remaining tag number corresponding to the Q value and the number of collision occurrences. The representative value of is set as the estimated number of remaining tags.

In S107, the estimation unit 21 updates the number of undetected tags of the driving antenna 2 to the estimated number of remaining tags estimated in S106. That is, the estimation unit 21 sets the estimated number of remaining tags as the number of undetected tags. The estimation unit 21 stores the estimated number of remaining tags in the storage unit 11 as the estimation result 42.

In S108, the control unit 10 determines whether or not the stop condition for stopping the multi-access process is satisfied. The stop condition may be satisfied, for example, by receiving the end instruction of the multi-access process transmitted from the higher-level device of the physical distribution management system 100 by the RFID communication unit 1.

Alternatively, the stop condition may be satisfied when a timeout occurs due to a timer preset in the RFID communication unit 1. When the control unit 10 determines that the stop condition is satisfied (YES in S108), the control unit 10 ends a series of multi-access processes. When the control unit 10 determines that the stop condition is not satisfied (NO in S108), the control unit 10 proceeds to S109.

In S109, the antenna selection unit 22 executes a switching determination process for determining whether or not the switching condition for switching the antenna 2 to be driven is satisfied. As an example, in the switching determination process, the antenna selection unit 22 has a case where the number of undetected tags of other antennas is more than a predetermined number than the latest number of undetected tags of the currently driven antenna 2 updated in S107. In addition, it may be determined that the switching condition is satisfied. The switching determination process will be described in detail later with reference to FIG.

That is, the antenna selection unit 22 is driving the antenna 2 to be driven based on the estimated number of remaining tags of the antenna 2 being driven and the number of undetected tags of other antennas other than the antenna 2 being driven. It is determined whether or not to switch from one antenna 2 to another antenna 2.

According to the above configuration, the estimated number of remaining tags is estimated based on the result of communication by the antenna 2. Further, it is determined whether or not the antenna 2 to be driven can be switched based on the estimated number of remaining tags and the number of undetected tags of the antenna 2 other than the antenna 2 being driven. As a result, the antenna 2 to be driven can be switched to the antenna 2 estimated to be optimal according to the result of communication by the antenna 2. Therefore, it is possible to efficiently reduce the detection omission of the wireless tag 3.

When the antenna selection unit 22 determines that the switching condition is not satisfied (NO in S109), it returns to S103, and the processing after S103 is repeated for the same antenna. Consider a case where it is determined in S109 that NO, that is, the antenna selection unit 22 does not switch to another antenna 2. In this case, in S103, the communication control unit 23 changes the number of slots adopted in the next communication with the wireless tag 3 by the driving antenna 2 according to the estimated number of remaining tags of the driving antenna 2. ..

Here, the difference between the estimated number of remaining tags of the driving antenna 2 and the number of detected tags in the communication result 44 as a result of the communication most recently carried out by the driving antenna 2 is less than a certain number. Consider the case. In this case, the antenna selection unit 22 determines that the switching condition is not satisfied, and the communication control unit 23 increases the number of slots adopted in the next communication with the wireless tag 3 by the antenna 2 being driven.

According to the above configuration, by changing the number of slots, it is possible to make it difficult for collisions to occur in communication even when the number of wireless tags 3 is large, and it is possible to efficiently detect a plurality of wireless tags 3. Can be done. If the antenna selection unit 22 determines that the switching condition is satisfied (YES in S109), the process proceeds to S110.

In S110, the communication control unit 23 stops the antenna 2 currently being driven according to the judgment of the antenna selection unit 22. After the communication control unit 23 stops the antenna 2, in S111, the antenna selection unit 22 selects the antenna 2 to be driven by the next communication from the plurality of antennas 2.

For example, the antenna selection unit 22 may select the antenna 2 having the largest number of undetected tags among the antennas 2 having the number of undetected tags when the above-mentioned switching condition is satisfied. After that, returning to S102, the communication control unit 23 drives the antenna 2 selected by the antenna selection unit 22 according to the selection of the antenna selection unit 22 in S111, and repeats the processing after S102.

Based on the above, the RFID communication unit 1 selects the antenna 2 to be driven based on the number of undetected tags estimated for each antenna 2. As a result, the selection of the antenna 2 to be driven can be optimized, and the detection efficiency of the wireless tag 3 can be improved. Further, when the moving speed of the wireless tag 3 passing through the gate 4 is high or when the number of wireless tags 3 is large, it is possible to reduce the occurrence of detection omission without detection within the time.

<Order determination process executed by the antenna selection unit 22>
FIG. 7 is a flowchart showing the flow of the order determination process executed by the antenna selection unit 22. In the series of processes shown in FIG. 7, in S101, the antenna selection unit 22 drives the plurality of antennas 2 at the start of one passage period while the group of the radio tags 3 passes through the gate 4 once. This is the process of determining the order.

In S201, the antenna selection unit 22 acquires the total number of detected radio tags 3 in each passage period for each antenna 2 in the past N passage periods from the operation record data 41. Here, the storage unit 11 uses the operation record data 41 as the total number of detected radio tags 3 detected by one of the plurality of antennas 2 by one or more communication with the radio tag 3 during the passing period. It is stored for each antenna 2.

In S202, the antenna selection unit 22 acquires a statistical value by statistically processing the total number of detected radio tags 3 for N passage periods for each antenna 2. The statistical values include the average value, the median value, and the mode value of the total number of detections related to the radio tag 3 for the passage period of N pieces for each antenna 2. For example, the average value and the mode value are statistical data 421 shown in FIG.

In S203, the antenna selection unit 22 acquires the predicted total number of tags of each antenna 2 based on the statistical value of each antenna 2. The antenna selection unit 22 may acquire the average value of the detection of the radio tags 3 by each antenna 2 in the statistical data 421 as the predicted total number of tags, and the mode of the detection of the radio tags 3 by each antenna 2 in the statistical data 421. The value may be obtained as the predicted total number of tags.

In FIG. 4, the estimated data 422 is the data when the average value of the detection of the radio tags 3 by each antenna 2 is the predicted total number of tags, and the estimated data 423 is the mode of the detection of the radio tags 3 by each antenna 2. It is the data when the mode value is the predicted total number of tags. The antenna selection unit 22 may acquire the median value of the detection of the radio tag 3 by each antenna 2 as the predicted total number of tags. Further, the antenna selection unit 22 calculates the predicted total tag number by combining at least two of the average value, the mode value, and the median value of the detection of the radio tag 3 by each antenna 2. You may get it.

In S204, the antenna selection unit 22 determines the drive order of the antenna 2 in descending order of the predicted total number of tags. For example, in the case of the estimation data 422 of FIG. 4, the antenna selection unit 22 determines the order of antenna # 2, antenna # 3, antenna # 4, and antenna # 1 as the drive order. On the other hand, in the case of the estimation data 423 of FIG. 4, the antenna selection unit 22 determines the order of the antenna # 2, the antenna # 1, the antenna # 3, and the antenna # 4 as the drive order.

That is, the antenna selection unit 22 preferentially selects the antenna 2 having a larger number of undetected tags estimated by the estimation unit 21 than the other antennas 2 from the plurality of antennas 2. Therefore, by preferentially selecting the antenna 2 having a large number of undetected tags, it is possible to efficiently reduce the detection omission of the wireless tag 3.

In S205, the antenna selection unit 22 sets the predicted total number of tags of each antenna 2 as the number of undetected tags of each antenna 2. In S206, the antenna selection unit 22 selects the antenna 2 having the first drive order.

In this way, the antenna selection unit 22 selects the antenna 2 to be driven in descending order of the predicted total number of tags among the plurality of antennas 2. That is, with respect to the predicted total number of tags estimated based on the total number of detected radio tags 3 stored in the storage unit 11, the antenna 2 to be driven is selected in descending order of the number of predicted total tags among the plurality of antennas 2. .. Therefore, it is possible to efficiently reduce the detection omission of the wireless tag 3 based on the total number of detected wireless tags 3 stored in the storage unit 11.

<Switching determination process executed by the antenna selection unit 22>
FIG. 8 is a flowchart showing the flow of the switching determination process executed by the antenna selection unit 22. The series of processes shown in FIG. 8 is a switching condition in which the antenna selection unit 22 switches the antenna 2 to be driven in S109 for one passage period while the group of the radio tags 3 passes through the gate 4 once. Is a process for determining whether or not is satisfied.

In S301, the antenna selection unit 22 acquires the latest number of undetected tags for the antenna 2 currently being driven. That is, the estimated number of remaining tags estimated by the estimation unit 21 in S106 is acquired as the number of undetected tags. In S302, the antenna selection unit 22 acquires the latest number of undetected tags for the antenna 2 other than the antenna 2 currently being driven.

That is, when the communication of S104 has never been performed for the other antenna 2 in the multi-access process, the antenna selection unit 22 acquires the predicted total number of tags for the other antenna 2 as the number of undetected tags. .. On the other hand, when communication is performed once or more in the multi-access process for the other antenna 2, the antenna selection unit 22 acquires the estimated number of remaining tags for the other antenna 2 as the number of undetected tags.

In S303, the antenna selection unit 22 compares the number of undetected tags of the antenna 2 currently being driven with the number of undetected tags of other antennas 2 other than the antenna 2 currently being driven. In addition to this, the antenna selection unit 22 determines whether or not there is another antenna 2 whose number of undetected tags is estimated to exceed the latest number of undetected tags of the antenna 2 currently being driven.

When the antenna selection unit 22 determines that there is no other antenna 2 for which the number of undetected tags exceeding the latest number of undetected tags of the antenna 2 currently being driven is set (NO in S303), the process proceeds to S304. In S304, the antenna selection unit 22 determines that the switching condition is not satisfied.

When the antenna selection unit 22 determines that there is another antenna 2 having an undetected tag number that exceeds the latest undetected tag number of the antenna 2 currently being driven (YES in S303), the antenna selection unit 22 proceeds to S305. In S305, the antenna selection unit 22 determines whether or not the difference between the latest number of undetected tags of the antenna 2 currently being driven and the number of undetected tags of the other antenna 2 is a predetermined number or more. To judge.

When the antenna selection unit 22 determines that the difference between the latest number of undetected tags of the antenna 2 currently being driven and the number of undetected tags of the other antenna 2 is smaller than a predetermined number (NO in S305), S304 Proceed to. The latest number of undetected tags of the antenna 2 currently being driven is the estimated number of remaining tags described above, and the number of undetected tags of the other antenna 2 is the predicted total number of tags or the estimated number of remaining tags.

On the other hand, when the antenna selection unit 22 determines that the difference between the latest number of undetected tags of the antenna 2 currently being driven and the number of undetected tags of the other antenna 2 is a predetermined number or more (YES in S305). ), Proceed to S306. In S306, the antenna selection unit 22 determines that the switching condition is satisfied.

As described above, when the number of undetected tags of the other antenna 2 is larger than the estimated number of remaining tags of the antenna 2 being driven, the antenna selection unit 22 pushes the antenna 2 to be driven from the antenna 2 being driven to another antenna 2. It is determined to switch to the antenna 2. Therefore, since the antenna 2 being driven can be switched to another antenna 2 having a large number of undetected tags, it is possible to efficiently reduce the detection omission of the wireless tag 3.

Further, the antenna selection unit 22 drives the antenna 2 to be driven when the number of undetected tags of the other antennas 2 is more than a predetermined number than the estimated number of remaining tags of the antenna 2 being driven. It is determined that the antenna 2 is switched to another antenna 2.

According to the above configuration, it is not determined that the antenna 2 is switched to the other antenna 2 immediately when the number of undetected tags of the other antenna 2 becomes larger than the estimated number of remaining tags of the antenna 2 being driven, and the difference is constant. Until the above is achieved, the driving of the antenna 2 being driven is maintained. As a result, the detection of the plurality of wireless tags 3 can be smoothly performed.

Since the overhead associated with the antenna switching process is generated, it is more effective not to perform the antenna switching process when the difference between the estimated number of remaining tags of the antenna 2 being driven and the number of undetected tags of the other antenna 2 is small. In some cases. Therefore, it is preferable to perform the treatment of S305.

<Specific example of switching judgment processing>
FIG. 9 is a schematic diagram showing a state of the switching determination process. In S101, as shown in 521 of FIG. 9, when the number of undetected tags of antenna # 3 is the largest among the number of undetected tags of four antennas 2, the antenna selection unit 22 first selects antenna # 3. Consider the case. In this case, it is assumed that the communication control unit 23 communicates with the radio tag 3 via the antenna # 3 in S104, and as a result, the communication result 44 is the result shown in 522 of FIG.

As shown in 522 of FIG. 9, for example, a collision occurs in the 0th, 2nd, and N-1th slots out of N slots, and the 1st and Nth slots out of N slots. It is assumed that there is no response from the wireless tag 3 by the eye, and there is a response from the wireless tag 3 at the N-2nd slot out of the N slots. In this case, in S106, the estimation unit 21 sets the estimated number of remaining tags as the number of undetected tags from the current Q value and the number of collision occurrences. It is assumed that the estimation result 42 by the estimation unit 21 is the result shown in 523 of FIG. The number of undetected tags of antenna # 3 in 523 of FIG. 9 is smaller than the number of undetected tags of antenna # 3 in 521 of FIG.

Then, the number of undetected tags of antenna # 2 becomes larger than the number of undetected tags of antenna # 3. At this time, when the difference between the number of undetected tags of the antenna # 2 and the number of undetected tags of the antenna # 3 is a predetermined number or more, the antenna selection unit 22 selects the antenna # 2 in the next communication. As a result of the communication control unit 23 communicating with the radio tag 3 via the antenna # 2, the communication result 44 is the result shown in 524 of FIG.

In the result shown in 524 of FIG. 9, a collision occurs in the 0th and 2nd slots of the N slots, and the response from the radio tag 3 occurs in the 1st and Nth slots of the N slots. None, there is a response from the radio tag 3 in the N-1st and N-2nd slots out of the N slots. Therefore, when the communication control unit 23 communicates with the radio tag 3 via the antenna # 3, the occurrence of collision is suppressed. The switching determination process by the antenna selection unit 22 is repeated until the stop condition of S108 is satisfied.

§4. Modification example In S101, the antenna selection unit 22 selects the antenna 2 to be driven in descending order of the number of predicted total tags among the plurality of antennas 2, and in S109, the antenna selection unit 22 makes a round of all the antennas 2. Consider the case where the antenna 2 is not switched until. In this case, the communication control unit 23 communicates with the radio tag 3 by using all the antennas 2 once each.

When all the antennas 2 have made a round, in S101, the antenna selection unit 22 may dynamically select the antenna 2 having the latest estimated number of remaining tags. As a result, the RFID communication unit 1 can grasp the transportation status of the goods during the transit period in real time. This method is particularly effective at a production site where the way articles are loaded on the pallet 5 changes each time.

Even if the way articles are loaded on the pallet 5 changes each time, the estimation unit 21 can accurately estimate the estimated number of remaining tags for each antenna 2 during the passage period. Therefore, the antenna selection unit 22 can accurately and quickly switch to the optimum antenna 2.

[Example of implementation by software]
The control block of the RFID communication unit 1 (particularly, the estimation unit 21, the antenna selection unit 22, and the communication control unit 23) may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like. It may be realized by software.

In the latter case, the RFID communication unit 1 includes a computer that executes a program instruction, which is software that realizes each function. The computer includes, for example, one or more processors and a computer-readable recording medium that stores the program. Then, in the computer, the processor reads the program from the recording medium and executes the program, thereby achieving the object of the present invention. As the processor, for example, a CPU (Central Processing Unit) can be used. As the recording medium, a “non-temporary tangible medium”, for example, a ROM (Read Only Memory) or the like, a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used. Further, a RAM (RandomAccessMemory) for expanding the above program may be further provided. Further, the program may be supplied to the computer via any transmission medium (communication network, broadcast wave, etc.) capable of transmitting the program. It should be noted that one aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the above program is embodied by electronic transmission.

〔summary〕
The RFID communication unit according to an example of the present disclosure is an RFID communication unit that detects a plurality of radio tags via a plurality of antennas, among the radio tags expected to be detected by each of the plurality of antennas. From the plurality of antennas, based on the estimation unit that estimates the number of undetected tags indicating the number of wireless tags that have not been detected for each antenna, and the number of undetected tags estimated by the estimation unit. It is provided with a selection unit for selecting an antenna to be driven.

According to the above configuration, the antenna to be driven is selected based on the estimated number of undetected tags for each antenna. This makes it possible to optimize the selection of the antenna to be driven and improve the detection efficiency of the wireless tag.

The selection unit may preferentially select an antenna having a larger number of undetected tags estimated by the estimation unit than other antennas from the plurality of antennas. According to the above configuration, by preferentially selecting an antenna having a large number of undetected tags, it is possible to efficiently reduce the detection omission of the wireless tag.

In the RFID communication unit, one of the plurality of antennas has the same as the radio tag during the passage period in which the plurality of antennas pass through the detectable area where the radio tag can be detected. The estimation unit includes a storage unit that stores the total number of detections of the radio tags detected by one or more communications for each antenna, and the estimation unit is stored in the storage unit and is detected by the one antenna during the passage period. Based on the total number of detected tags, the predicted total number of tags indicating the number of the radio tags predicted to be detected by the one antenna during the passing period is estimated as the number of undetected tags for each antenna. The selection unit may select antennas to be driven in descending order of the number of predicted total tags among the plurality of antennas.

According to the above configuration, with respect to the predicted total number of tags estimated based on the total number of detected radio tags stored in the storage unit, the antennas to be driven are selected in descending order of the predicted total number of tags among the plurality of antennas. .. Therefore, it is possible to efficiently reduce the detection omission of the wireless tag based on the total number of detected wireless tags stored in the storage unit.

The estimation unit refers to the radio tag by one of the plurality of antennas during the passage period during which the plurality of antennas pass through the detectable range in which the plurality of antennas can detect the radio tag. Based on the result of one or more communications, the estimated number of remaining tags indicating the number of remaining radio tags that can be detected by the one antenna during the passage period is estimated as the number of undetected tags for each antenna. The selection unit drives an antenna to be driven based on the estimated number of remaining tags of the antenna being driven and the number of undetected tags of other antennas other than the driving antenna. You may decide whether or not to switch to the other antenna.

According to the above configuration, the estimated number of remaining tags is estimated based on the result of communication by the antenna. Further, it is determined whether or not the antenna to be driven can be switched based on the estimated number of remaining tags and the number of undetected tags of antennas other than the antenna being driven. As a result, the antenna to be driven can be switched to the optimum antenna according to the result of communication by the antenna. Therefore, it is possible to efficiently reduce the detection omission of the wireless tag.

When the number of undetected tags of the other antenna is larger than the estimated number of remaining tags of the driving antenna, the selection unit transfers the driving antenna from the driving antenna to the other antenna. You may decide to switch.

According to the above configuration, when the number of undetected tags of other antennas is larger than the estimated number of remaining tags of the antenna being driven, the antenna to be driven is switched to another antenna. Therefore, since it is possible to switch to another antenna having a large number of undetected tags, it is possible to efficiently reduce the detection omission of the wireless tag.

When the number of undetected tags of the other antenna is greater than or equal to a predetermined number of the estimated number of remaining tags of the driving antenna, the selection unit pulls the driving antenna from the driving antenna. You may decide to switch to another antenna.

According to the above configuration, it is not determined that the antenna is switched to another antenna immediately when the number of undetected tags of the other antenna becomes larger than the estimated number of remaining tags of the antenna being driven, and the difference becomes a certain value or more. Until then, the driving of the antenna being driven is maintained. As a result, it is possible to smoothly detect a plurality of wireless tags.

The RFID communication unit includes a communication control unit for determining the number of slots for dividing communication with the radio tag by the antenna with respect to the antenna selected by the selection unit, and the result of the communication. The number of the slots determined by the communication, the number of collisions that occurred in the communication among the number of slots, and the number of detected tags indicating the number of the radio tags detected by the communication. , And the communication control unit is being driven according to the estimated number of remaining tags of the antenna being driven when the selection unit determines that the antenna is not switched to the other antenna. The number of slots adopted in the next communication with the radio tag by the antenna of the above may be changed.

According to the above configuration, by changing the number of slots, it is possible to make it difficult for collisions to occur in communication even when the number of wireless tags is large, and it is possible to efficiently detect a plurality of wireless tags. ..

The RFID communication unit according to each example of the present disclosure may be realized by a computer, and in this case, the RFID communication unit can be made into a computer by operating the computer as each part (software element) included in the RFID communication unit. The RFID communication program to be realized and the computer-readable recording medium on which the RFID communication program is recorded are also included in the scope of the present disclosure.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims, and the present invention also relates to a configuration obtained by appropriately combining the technical means disclosed in the embodiments. It is included in the technical scope of the invention.

1 RFID communication unit 2 antenna 3 wireless tag 10 control unit 11 storage unit 21 estimation unit 22 antenna selection unit 23 communication control unit 41 operation record data 42 estimation result 43 lookup table 44 communication result 100 logistics management system

Claims

In an RFID communication unit that detects multiple wireless tags via multiple antennas
Among the radio tags expected to be detected by each of the plurality of antennas, an estimation unit that estimates the number of undetected tags indicating the number of the radio tags that have not yet been detected for each antenna.
An RFID communication unit comprising a selection unit for selecting an antenna to be driven from the plurality of antennas based on the number of undetected tags estimated by the estimation unit.
The RFID communication unit according to claim 1, wherein the selection unit preferentially selects an antenna having a larger number of undetected tags estimated by the estimation unit than other antennas from the plurality of antennas.
During the passage period in which the plurality of antennas pass through the detectable range in which the plurality of antennas can detect the radio tag, one of the plurality of antennas communicates with the radio tag one or more times. A storage unit for storing the total number of detected wireless tags detected for each antenna is provided.
The estimation unit is predicted to be detected by the one antenna during the passage period based on the total number of detections stored by the storage unit and detected by the one antenna during the passage period. The predicted total number of tags indicating the number of wireless tags is estimated for each antenna as the number of undetected tags.
The RFID communication unit according to claim 1 or 2, wherein the selection unit selects antennas to be driven in descending order of the predicted total number of tags among the plurality of antennas.
The estimation unit refers to the radio tag by one of the plurality of antennas during the passage period in which the plurality of antennas pass through the detectable range in which the radio tag can be detected. Based on the result of one or more communications, the estimated number of remaining tags indicating the number of remaining radio tags that can be detected by the one antenna during the passage period is estimated as the number of undetected tags for each antenna.
The selection unit drives an antenna to be driven based on the estimated number of remaining tags of the antenna being driven and the number of undetected tags of other antennas other than the driving antenna. The RFID communication unit according to any one of claims 1 to 3, which determines whether or not to switch to the other antenna.
When the number of undetected tags of the other antenna is larger than the estimated number of remaining tags of the driving antenna, the selection unit transfers the driving antenna from the driving antenna to the other antenna. The RFID communication unit according to claim 4, which is determined to be switched.
When the number of undetected tags of the other antenna is greater than or equal to a predetermined number of the estimated number of remaining tags of the driving antenna, the selection unit pulls the driving antenna from the driving antenna. The RFID communication unit according to claim 4, wherein it is determined to switch to another antenna.
A communication control unit for determining the number of slots for dividing communication with the radio tag by the antenna with respect to the antenna selected by the selection unit is provided.
The result of the communication is a detection indicating the number of the slots determined by the communication, the number of collisions occurring in the communication among the number of slots, and the number of the radio tags detected by the communication. The number of completed tags and is included,
When the selection unit determines that the communication control unit does not switch to the other antenna, the communication control unit and the radio tag by the driving antenna are used according to the estimated number of remaining tags of the driving antenna. The RFID communication unit according to any one of claims 4 to 6, which changes the number of slots adopted in the next communication.
It is a control method of an RFID communication unit that detects multiple wireless tags via multiple antennas.
An estimation step for estimating the number of undetected tags indicating the number of the radio tags that have not yet been detected among the radio tags expected to be detected by each of the plurality of antennas for each antenna.
A control method including a selection step of selecting an antenna to be driven from the plurality of antennas based on the number of undetected tags estimated in the estimation step.
The RFID communication program for operating a computer as the RFID communication unit according to claim 1, wherein the RFID communication program for operating the computer as the estimation unit and the selection unit.