JP7392574B2 - RFID communication unit, control method and RFID communication program - Google Patents

Description

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

Patent Document 1 discloses a plurality of antennas that transmit and receive signals for communicating with a wireless tag, a controller that switches the operation of a combination of antennas, and a reader that reads identification information of a wireless tag based on signals received by the multiple antennas. A reading device is disclosed that includes the following. The reading device disclosed in Patent Document 1 can reduce failures in reading wireless tags attached to articles.

JP 2019-52029 Publication

However, the reading device disclosed in Patent Document 1 performs communication by switching the outputs of a plurality of antennas at regular intervals, regardless of the detection status of the wireless tag. For this reason, even if the detection of a wireless tag within 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 useless output. There was a problem that the efficiency of the system deteriorated. One aspect of the present invention aims to improve the detection efficiency of multiple wireless tags using multiple antennas.

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

According to the above configuration, the antenna to be driven is selected based on the number of undetected tags estimated for each antenna. Thereby, the selection of the antenna to be driven can be optimized, and the detection efficiency of wireless tags can be improved.

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

The RFID communication unit is configured such that one antenna among the plurality of antennas communicates with the wireless tag during a passage period in which the plurality of wireless tags pass through a detectable range in which the wireless tag can be detected by the plurality of antennas. The estimating unit includes a storage unit that stores, for each of the antennas, the total number of the wireless tags detected through one or more communications, and the estimating unit stores the number of detected wireless tags detected by the one antenna during the passing period, which is stored in the storage unit. Based on the total number of detected tags, a predicted total number of tags indicating the number of wireless tags expected to be detected by the one antenna in the passing period is estimated for each antenna as the number of undetected tags. The selection unit may select antennas to be driven from among the plurality of antennas in descending order of the predicted total number of tags.

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

The estimating unit is configured to estimate the communication between one of the plurality of antennas and the wireless tag during a passage period in which the plurality of wireless tags pass through a detectable range in which the wireless tag can be detected by the plurality of antennas. Based on the results of one or more communications, an estimated number of remaining tags indicating the number of remaining wireless tags that can be detected by the one antenna during the passing period is estimated for each antenna as the number of undetected tags; The selection unit selects the antenna to be driven based on the estimated number of remaining tags of the antenna that is being driven and the number of undetected tags of an antenna other than the antenna that is being driven. It may be determined 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 using the antenna. Further, it is determined whether or not the antenna to be driven is to be switched based on the estimated number of remaining tags and the number of undetected tags of antennas other than the antenna being driven. Thereby, it is possible to switch the antenna to be driven to an antenna that is estimated to be optimal, depending on the result of communication using the antenna. Therefore, failure to detect wireless tags can be efficiently reduced.

The selection unit is configured to change the antenna to be driven from the currently driven antenna to the other antenna when the number of undetected tags of the other antenna is greater than the estimated number of remaining tags of the currently driven antenna. You may decide to switch.

According to the above configuration, when the number of undetected tags of another antenna is greater than the estimated number of remaining tags of the antenna being driven, the antenna to be driven is switched to another antenna. Therefore, since the antenna is switched to another antenna with a large number of undetected tags, it is possible to efficiently reduce detection failures of wireless tags.

When the number of undetected tags of the other antenna is greater than the estimated number of remaining tags of the currently driven antenna by a predetermined number or more, the selection unit selects the antenna to be driven from the currently driven antenna. You may decide to switch to another antenna.

According to the above configuration, it is not determined to switch to another antenna immediately when the number of undetected tags of another antenna becomes greater than the estimated number of remaining tags of the operating antenna, and the difference is greater than a certain value. Until then, the antenna that is currently being driven will continue to be driven. Thereby, multiple wireless tags can be detected smoothly.

The RFID communication unit includes a communication control unit that determines, for the antenna selected by the selection unit, the number of slots for dividing and performing communication with the wireless tag by the antenna, and includes the number of slots determined in 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 wireless tags detected in the communication. , and the communication control unit is configured to switch the operating antenna according to the estimated number of remaining tags of the operating antenna when it is determined by the selection unit not to switch to the other antenna. The number of slots employed in the next communication with the wireless tag by the antenna may be changed.

According to the above configuration, by changing the number of slots, even when there are many wireless tags, collisions can be made less likely to occur during communication, and multiple wireless tags can be efficiently detected. .

A control method according to an example of the present disclosure is a control method for an RFID communication unit that detects a plurality of wireless tags via a plurality of antennas, the wireless tag being expected to be detected by each of the plurality of antennas. an estimation step of estimating the number of undetected tags indicating the number of wireless tags that have not yet been detected among tags for each of the antennas; and based on the number of undetected tags estimated in the estimation step, and a selection step of selecting an antenna to be driven from among the antennas.

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 may be realized by a computer by operating the computer as each part (software element) included in the RFID communication unit. An RFID communication program that is realized by using the RFID communication program and a computer-readable recording medium that records the same also fall within the scope of the present disclosure.

According to one aspect of the present invention, the detection efficiency of multiple wireless tags using multiple antennas can be improved.

FIG. 2 is a block diagram showing an example of a main part configuration of an RFID communication unit according to the present embodiment. 1 is a diagram showing an example of the configuration of a logistics management system according to the present embodiment. FIG. 2 is a diagram showing an example of operation performance data regarding four antennas included in the RFID communication unit shown in FIG. 1. FIG. 2 is a diagram illustrating an example of the average value and mode of the total number of detections of wireless tags for N passing periods of each antenna included in the RFID communication unit shown in FIG. 1, and the estimation results regarding four antennas. be. FIG. 2 is a diagram showing an example of a lookup table stored in a storage section included in the RFID communication unit shown in FIG. 1. FIG. 2 is a flowchart showing the flow of processing executed by the RFID communication unit 1 shown in FIG. 1. FIG. 2 is a flowchart showing the flow of an order determination process executed by an antenna selection section included in the RFID communication unit shown in FIG. 1. FIG. 2 is a flowchart showing the flow of a switching determination process executed by an antenna selection section included in the RFID communication unit shown in FIG. 1. FIG. FIG. 2 is a schematic diagram showing a switching determination process executed by the RFID communication unit shown in FIG. 1. FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment (hereinafter also referred to as "this embodiment") according to one aspect of the present invention will be described below based on the drawings.

§1. Application Example First, an example of a scene to which the present invention is applied will be described using FIG. 2. FIG. 2 is a diagram showing an example of the configuration of the logistics management system 100 according to the present embodiment. As shown in FIG. 2, the logistics management system 100 includes an RFID communication unit 1, a plurality of antennas 2, a plurality of wireless tags 3, a gate 4, and a pallet 5. In the logistics management system 100, a plurality of articles such as parts or products are transported, and each article is managed 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 via the plurality of antennas 2 under the control of the communication control unit 23. The RFID communication unit 1 receives response data from the wireless tag 3 via the plurality of antennas 2.

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

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

Note that the gate 4 may be provided with a plurality of reader/writers integrated with the antenna. In this case, multiple readers/writers are connected to each other via a hub so that they can communicate with each other. One of the plurality of reader/writers is a master reader/writer that uses other reader/writers as slaves, 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 readers/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 main configuration of an RFID communication unit 1 according to the present embodiment.

<Configuration of RFID communication unit 1>
The RFID communication unit 1 includes a control section 10 and a storage section 11. The control section 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 to control the RFID communication unit 1. The storage unit 11 stores operation performance data 41, estimation results 42, lookup tables 43, and communication results 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 the estimation result 42. The antenna selection unit 22 selects the antenna 2 to be driven from among 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 communicates with the wireless tag 3 via each antenna 2 while controlling each antenna 2 and performing anti-collision processing. The anti-collision process is a process that uses slots to reduce collisions of signals output by multiple wireless tags 3 and allows the RFID communication unit 1 to read signals from multiple wireless tags. The slots are a plurality of time-divided sections in which the timing at which signal read processing is performed is divided. 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 regarding the four antennas 2 included in the RFID communication unit 1 shown in FIG. As shown in FIG. 3, the operation performance data 41 is data for N passage periods in which a group of wireless tags 3 pass through the gate 4. The operation performance data 41 is updated by the communication control unit 23 for each communication.

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

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

The communication control unit 23 may weight the operation performance data 41 in the order of the newest total number of detections among the past total number of detections. Further, the communication control unit 23 may group the past total number of detections in the operation record data 41 by the sum total of the total number of detections. For example, the communication control unit 23 groups cases where the total number of detected images is 32 and cases where the total number of detected images is 64, stores the total number of detected images for each group, and prioritizes each group. The total detection value may be selected.

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

FIG. 5 is a diagram showing an example of the lookup table 43. The lookup table 43 stores representative values of a collision occurrence number bin, an estimated remaining tag number bin, and an estimated remaining tag number in correspondence with the Q value and the number of slots. Bins are numerical ranges for grouping objects according to their values for generalization and comparison.

The collision occurrence number bin indicates the numerical range of the number of collision occurrences. 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 a 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 bins. The estimation unit 21 estimates the estimated number of remaining tags based on the collision occurrence number bin, the estimated number of remaining tags bin, and the representative value of the estimated number of remaining tags.

<Wireless tag 3>
The wireless tag 3 includes a tag antenna section and a tag wireless communication IC. The tag antenna section receives radio waves from the antenna 2 as a power source for operating the tag wireless communication IC and the like. The tag antenna section converts the radio waves received from the antenna 2 into radio signals and transmits them to the tag radio communication IC, and also converts the radio signals from the tag radio communication IC into radio waves and transmits them to the antenna 2. The tag antenna section 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 the communication is not performed normally. The wireless tag 3 that has been able to communicate with the antenna 2 without causing a collision sets an inventory flag (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 the flow of processing executed by the RFID communication unit 1. Specifically, the series of processes shown in FIG. 6 is a multi-access process in which the RFID communication unit 1 communicates with a plurality of wireless tags 3 via a plurality of antennas 2. The multi-access process is executed by the RFID communication unit 1, for example, during one passing period during which a group of wireless tags 3 passes through the gate 4 once.

<Processing executed by RFID communication unit 1>
First, the estimation unit 21 refers to the total number of detected wireless tags 3 detected by one antenna 2 in one passing 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 the predicted total number of tags as the number of undetected tags for each antenna 2 based on the total number of detected tags. The estimation unit 21 stores the estimated predicted total number of tags in the storage unit 11 as the estimation result 42. The predicted total number of tags is a numerical range or value indicating the number of wireless tags 3 that are predicted to be detected by one antenna 2 in one passing 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 among the plurality of antennas 2. As an example, the antenna selection unit 22 may select the antennas 2 to be driven in a pre-fixed order. In another example, the antenna selection unit 22 may perform an order determination process to determine in which order the plurality of antennas 2 provided at 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 for each antenna 2 from the estimation result 42 as the number of undetected tags for each antenna 2. The antenna selection unit 22 determines the driving order of the antennas 2, for example, in descending order of the number of undetected tags. The order determination process will be described in detail later with reference to FIG. 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 antenna 2 to be driven according to the number of undetected tags of the antenna 2 to be driven. 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 from association data in which each numerical value is associated with the Q value.

The association data is stored in the storage unit 11, and an optimal Q value that suppresses the occurrence of collisions and shortens the communication time is calculated by simulation for the number of wireless tags 3 within the detectable range. This is the data.

The Q value is a numerical value for specifying the number of slots that each of the plurality of wireless tags 3 can select when anti-collision processing is performed. The number of slots is a numerical value for dividing and performing communication with the wireless tag 3 by the antenna 2 selected by the antenna selection unit 22. The communication control unit 23 calculates the Q value and determines the number of slots to be ^2Q for the antenna 2 selected by the antenna selection unit 22.

For example, the communication control unit 23 may calculate the Q value so that the number of slots employed in the antenna 2 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 predicted total number of tags estimated for the antenna 2 at the time when the communication in S104 has not been performed even once in the multi-access process. It is. When communication has been carried out 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 wireless 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, and acquires information held by the wireless tag 3, and Write information in 3.

In S105, the communication control unit 23 generates a 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 slots. The number of collision occurrences is a numerical value indicating the number of times collisions have occurred during communication among the number of slots, and the number of detected tags is a numerical value indicating the number of wireless tags 3 detected during communication. The communication result 44 includes the number of slots determined through communication, the number of collisions, and the number of detected tags. The communication result 44 is updated by the communication control unit 23 for each communication.

Further, the communication control unit 23 stores the number of detected tags in the communication results 44 for one passing period in the storage unit 11 as operation performance data 41. Note that when the communication control unit 23 uses the antenna 2 for the current communication, the communication control unit 23 uses the antenna 2 for the current communication based on the communication result 44 of the previous communication for the antenna 2. The optimal 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 wireless tag 3 by one of the multiple antennas 2 during a passage period in which the multiple wireless tags 3 pass through the detectable area. This is a numerical value indicating the number of remaining wireless tags 3 that can be detected by one antenna 2 during the passing period.

The estimation unit 21 sets the temporary number of tags based on, for example, the predicted total number of tags and the number of detected tags in the communication result 44 for one passing period. Specifically, the estimation unit 21 sets a value obtained by subtracting the detected number of tags from the predicted total number of tags as the temporary number of tags. The estimating unit 21 refers to the lookup table 43 and estimates the estimated remaining tag number bin corresponding to the Q value adopted during the communication performed in S104 and the number of collisions.

If the temporary number of tags is included in the numerical range of the estimated number of remaining tags bin, the estimation unit 21 determines that the temporary number of tags is likely and sets the temporary number of tags as the estimated number of remaining tags. Set as . If the tentative number of tags is not included in the numerical range of the estimated number of remaining tags bin, the estimation unit 21 refers to the lookup table 43 and determines the estimated number of remaining tags corresponding to the Q value and the number of collision occurrences. Set the representative value of as the estimated number of remaining tags.

In S107, the estimation unit 21 updates the number of undetected tags of the driven 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 a stop condition for stopping the multi-access processing is satisfied. The stop condition may be satisfied, for example, when the RFID communication unit 1 receives an instruction to terminate the multi-access process transmitted from a higher-level device of the logistics management system 100.

Alternatively, the stop condition may be established when a timer that is set in advance in the RFID communication unit 1 times out. If the control unit 10 determines that the stop condition is satisfied (YES in S108), it ends the series of multi-access processing. When the control unit 10 determines that the stop condition is not satisfied (NO in S108), the process proceeds to S109.

In S109, the antenna selection unit 22 executes a switching determination process to determine whether a switching condition for switching the antenna 2 to be driven is satisfied. As an example, in the switching determination process, if the number of undetected tags of other antennas is greater than the latest number of undetected tags of the currently driven antenna 2 updated in S107 by a predetermined number or more, Alternatively, 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 selects 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 antennas other than the antenna 2 being driven. It is determined whether to switch from this 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 is to be switched based on the estimated number of remaining tags and the number of undetected tags of antennas 2 other than the antenna 2 being driven. Thereby, the antenna 2 to be driven can be switched to the antenna 2 that is estimated to be optimal, depending on the result of communication by the antenna 2. Therefore, failure to detect the wireless tag 3 can be efficiently reduced.

If the antenna selection unit 22 determines that the switching condition is not satisfied (NO in S109), the process returns to S103 and the processes from S103 onward are repeated for the same antenna. Let us consider a case where the answer in S109 is NO, that is, the antenna selection unit 22 determines not to switch to another antenna 2. In this case, in S103, the communication control unit 23 changes the number of slots to be adopted in the next communication with the wireless tag 3 by the currently driven antenna 2, according to the estimated number of remaining tags of the currently driven antenna 2. .

Here, the difference between the estimated number of remaining tags of the antenna 2 that is being driven and the number of detected tags in the communication result 44 as a result of the most recent communication performed by the antenna 2 that is being driven 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 employed 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, even if there are a large number of wireless tags 3, collisions can be made less likely to occur during communication, and a plurality of wireless tags 3 can be detected efficiently. I can do it. 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 section 23 stops the currently driven antenna 2 according to the judgment of the antenna selection section 22. After the communication control unit 23 stops the antenna 2, the antenna selection unit 22 selects the antenna 2 to be driven in the next communication from among the plurality of antennas 2 in S111.

For example, when the above-mentioned switching condition is satisfied, the antenna selection unit 22 may select the antenna 2 having the largest number of undetected tags from among the antennas 2 having the highest number of undetected tags. 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 by the antenna selection unit 22 in S111, and repeats the processing from S102 onwards.

As described above, the RFID communication unit 1 selects the antenna 2 to be driven based on the estimated number of undetected tags for each antenna 2. Thereby, the selection of the antenna 2 to be driven can be optimized, and the detection efficiency of the wireless tag 3 can be improved. Furthermore, it is possible to reduce the occurrence of detection failures due to inability to detect in time when the moving speed of the wireless tags 3 passing through the gate 4 is fast or when the number of wireless tags 3 is large.

<Order determination process executed by antenna selection unit 22>
FIG. 7 is a flowchart showing the flow of the order determination process executed by the antenna selection unit 22. The series of processes shown in FIG. This process determines the order.

In S201, the antenna selection unit 22 obtains the total number of detected wireless tags 3 in each passing period for each antenna 2 in the past N passing periods from the operation record data 41. Here, the storage unit 11 stores, as the operation performance data 41, the total number of detected wireless tags 3 detected by one antenna 2 among the plurality of antennas 2 through one or more communications with the wireless tag 3 during the passing period. It is memorized for each antenna 2.

In S202, the antenna selection unit 22 obtains statistical values by statistically processing the total number of detected wireless tags 3 for N transit periods for each antenna 2. The statistical values include the average value, median value, and mode value of the total number of detections related to the wireless tags 3 for N passing periods for each antenna 2. For example, the average value and the mode are the statistical data 421 shown in FIG.

In S203, the antenna selection unit 22 obtains the predicted total number of tags for each antenna 2 based on the statistical value of each antenna 2. The antenna selection unit 22 may obtain the average value of the detection of wireless tags 3 by each antenna 2 as the predicted total number of tags in the statistical data 421, and the average value of the detection of wireless 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, estimated data 422 is data when the average value of the detection of wireless tags 3 by each antenna 2 is the predicted total number of tags, and estimated data 423 is the data when the average value of the detection of wireless tags 3 by each antenna 2 is the average value of the detection of wireless tags 3 by each antenna 2. This is data when the frequency value is the predicted total number of tags. Note that the antenna selection unit 22 may obtain the median value of the detection of wireless tags 3 by each antenna 2 as the predicted total number of tags. Further, the antenna selection unit 22 calculates the predicted total number of tags by combining at least two of the average value, mode, and median value of the detection of the wireless tags 3 by each antenna 2. You may obtain it.

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

That is, the antenna selection unit 22 preferentially selects, from among the plurality of antennas 2, the antenna 2 with a larger number of undetected tags estimated by the estimation unit 21 compared to other antennas 2. Therefore, by preferentially selecting the antenna 2 with a large number of undetected tags, it is possible to efficiently reduce the number of wireless tags 3 that are not detected.

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

In this way, the antenna selection unit 22 selects the antennas 2 to be driven from among the plurality of antennas 2 in the order of the predicted total number of tags. That is, regarding the predicted total number of tags estimated based on the total number of detected wireless tags 3 stored in the storage unit 11, the antennas 2 to be driven are selected in the order of the predicted total number of tags among the plurality of antennas 2. . Therefore, based on the total number of detected wireless tags 3 stored in the storage unit 11, it is possible to efficiently reduce the number of wireless tags 3 that are not detected.

<Switching determination process executed by 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 processing shown in FIG. 8 is based on the switching conditions in which the antenna selection unit 22 switches the antenna 2 to be driven in S109 for one passing period during which a group of wireless tags 3 passes through the gate 4 once. This is a process of determining whether or not the following holds true.

In S301, the antenna selection unit 22 obtains the latest number of undetected tags for the antenna 2 that is 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 obtains the latest number of undetected tags for antennas 2 other than the antenna 2 currently being driven.

In other words, if the communication in S104 has not been performed even once in the multi-access process for other antennas 2, the antenna selection unit 22 obtains the predicted total number of tags as the number of undetected tags for other antennas 2. . On the other hand, if communication has been performed at least once during the multi-access process for another antenna 2, the antenna selection unit 22 obtains 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 currently driven antenna 2 with the number of undetected tags of other antennas 2 other than the currently driven antenna 2. In addition to this, the antenna selection unit 22 determines whether there is another antenna 2 for which the number of undetected tags is estimated to exceed the latest number of undetected tags of the antenna 2 currently being driven.

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

If the antenna selection unit 22 determines that there is another antenna 2 in which the number of undetected tags is set to exceed the latest number of undetected tags of the antenna 2 currently being driven (YES in S303), the process proceeds to S305. In S305, the antenna selection unit 22 determines whether the difference between the latest number of undetected tags of the antenna 2 currently being driven and the number of undetected tags of other antennas 2 is equal to or greater than a predetermined number. to judge.

If 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 other antennas 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 antennas 2 is the predicted total number of tags or the estimated number of remaining tags.

On the other hand, if 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 other antennas 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 another antenna 2 is greater than the estimated number of remaining tags of the antenna 2 that is being driven, the antenna selection unit 22 selects the antenna 2 to be driven from the antenna 2 that is being driven. It is determined to switch to antenna 2. Therefore, since the antenna 2 that is being driven is switched to another antenna 2 with a large number of undetected tags, it is possible to efficiently reduce the number of wireless tags 3 that are not detected.

In addition, when the number of undetected tags of other antennas 2 is greater than the estimated number of remaining tags of the antenna 2 that is being driven by a predetermined number or more, the antenna selection unit 22 selects the antenna 2 to be driven from the antenna 2 that is being driven. It is determined that the antenna 2 should be switched to another antenna 2.

According to the above configuration, when the number of undetected tags of the other antenna 2 becomes greater than the estimated number of remaining tags of the antenna 2 that is being driven, it is not determined to immediately switch to the other antenna 2, and the difference remains constant. Until this happens, the driving of the antenna 2 that is currently being driven is maintained. Thereby, multiple wireless tags 3 can be detected smoothly.

Since overhead occurs due to antenna switching processing, if the difference between the estimated number of remaining tags of antenna 2 that is being driven and the number of undetected tags of other antennas 2 is small, it is more effective not to perform antenna switching processing. There are cases. For this reason, it is preferable to perform the process of S305.

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

As shown at 522 in FIG. 9, for example, a collision occurs in the 0th, 2nd, and N-1st slots among N slots, and It is assumed that there is no response from the wireless tag 3 at the second slot, and there is a response from the wireless tag 3 at the N-2th slot among 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 based on the current Q value and the number of collisions. Assume that the estimation result 42 by the estimation unit 21 is the result shown in 523 in FIG. The number of undetected tags for antenna #3 at 523 in FIG. 9 is smaller than the number of undetected tags for antenna #3 at 521 in FIG.

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

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

§4. Modification In S101, the antenna selection unit 22 selects the antennas 2 to be driven from among the plurality of antennas 2 in order of the predicted total number of tags, and in S109, the antenna selection unit 22 selects the antennas 2 to be driven in order of the predicted total number of tags. Let us consider a case in which antenna 2 is not switched until then. In this case, the communication control unit 23 communicates with the wireless tag 3 using all antennas 2 once each.

When all the antennas 2 have made one round, in S101, the antenna selection unit 22 may dynamically select the antenna 2 with the largest latest estimated number of remaining tags. Thereby, the RFID communication unit 1 can grasp the transportation status of the article during the transit period in real time. This method is particularly effective in production sites where the way articles are stacked on the pallet 5 changes every time.

Even if the way items are stacked 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 transit period. Therefore, the antenna selection unit 22 can accurately and quickly switch to the optimal antenna 2.

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

In the latter case, the RFID communication unit 1 includes a computer that executes instructions of a program that is software that implements each function. This computer includes, for example, one or more processors and a computer-readable recording medium that stores the above program. 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, in addition to "non-temporary tangible media" such as ROM (Read Only Memory), tapes, disks, cards, semiconductor memories, programmable logic circuits, etc. can be used. Further, the computer may further include a RAM (Random Access Memory) for expanding the above program. Furthermore, the program may be supplied to the computer via any transmission medium (communication network, broadcast waves, etc.) that can transmit the program. Note 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 program is embodied by electronic transmission.

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope shown in the claims, and the present invention also includes configurations obtained by appropriately combining technical means disclosed in the embodiments. falls within 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 performance data 42 Estimation result 43 Lookup table 44 Communication result 100 Logistics management system

Claims (9)

In an RFID communication unit that detects multiple wireless tags via multiple antennas,
an estimation unit that estimates, for each of the antennas, a number of undetected tags indicating the number of wireless tags that have not yet been detected among the wireless tags that are expected to be detected by each of the plurality of antennas;
An RFID communication unit comprising: a selection section that selects an antenna to be driven from among the plurality of antennas based on the number of undetected tags estimated by the estimation section. The RFID communication unit according to claim 1, wherein the selection section selects, from among the plurality of antennas, an antenna with a larger number of undetected tags estimated by the estimation section than other antennas. During a transit period in which the plurality of wireless tags pass through a detectable range in which the plurality of antennas can detect the wireless tag, one antenna among the plurality of antennas communicates with the wireless tag at least once. comprising a storage unit that stores the total number of detected wireless tags for each of the antennas;
The estimating unit is configured to calculate the number of detections predicted to be detected by the one antenna in the passing period based on the total number of detections detected by the one antenna in the passing period, which is stored in the storage unit. Estimating a predicted total number of tags indicating the number of wireless tags as the number of undetected tags for each antenna,
The RFID communication unit according to claim 1 or 2, wherein the selection section selects the antennas to be driven from among the plurality of antennas in descending order of the predicted total number of tags. The estimating unit is configured to estimate the communication between one of the plurality of antennas and the wireless tag during a passage period in which the plurality of wireless tags pass through a detectable range in which the wireless tag can be detected by the plurality of antennas. Based on the results of one or more communications, an estimated number of remaining tags indicating the number of remaining wireless tags that can be detected by the one antenna during the passing period is estimated for each antenna as the number of undetected tags;
The selection unit selects the antenna to be driven based on the estimated number of remaining tags of the antenna that is being driven and the number of undetected tags of an antenna other than the antenna that is being driven. 4. The RFID communication unit according to claim 1, wherein the RFID communication unit determines whether to switch to the other antenna. The selection unit is configured to change the antenna to be driven from the currently driven antenna to the other antenna when the number of undetected tags of the other antenna is greater than the estimated number of remaining tags of the currently driven antenna. The RFID communication unit according to claim 4, wherein the RFID communication unit determines to switch. When the number of undetected tags of the other antenna is greater than the estimated number of remaining tags of the currently driven antenna by a predetermined number or more, the selection unit selects the antenna to be driven from the currently driven antenna. The RFID communication unit according to claim 4, wherein the RFID communication unit determines to switch to another antenna. a communication control unit that determines, for the antenna selected by the selection unit, the number of slots for dividing and performing communication with the wireless tag by the antenna;
The result of the communication includes the number of slots determined in the communication, the number of collisions that occurred in the communication among the number of slots, and detections indicating the number of wireless tags detected in the communication. Contains the number of completed tags and
When the selection unit determines not to switch to the other antenna, the communication control unit is configured to switch between the wireless tags and the wireless tags by the driving antenna according to the estimated number of remaining tags of the driving antenna. 7. The RFID communication unit according to claim 4, wherein the number of slots employed in the next communication is changed. A method for controlling an RFID communication unit that detects multiple wireless tags via multiple antennas, the method comprising:
estimating the number of undetected tags for each of the antennas, which indicates the number of wireless tags that have not yet been detected among the wireless tags that are expected to be detected by each of the plurality of antennas;
A control method comprising: a selection step of selecting an antenna to be driven from among the plurality of antennas based on the number of undetected tags estimated in the estimation step. An RFID communication program for causing a computer to function as the RFID communication unit according to claim 1, wherein the RFID communication program causes the computer to function as the estimating section and the selecting section.

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