Communication apparatus and method for controlling the same, position management system, and program

Abstract

To improve the accuracy of a position acquired by a communication apparatus having a function of an RFID reader.SOLUTION: A communication apparatus performs communication with a wireless device to be a reference in specifying a position by using a first communication function to acquire first position information, measures the positional relationship with an external apparatus based on communication with the external apparatus performed by using a second communication function different from the first communication function, acquires second position information based on the measured positional relationship, and selects one of the first position information and the second position information for managing the position of another wireless device with which communication is performed by using the first communication function.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a communication device, a control method thereof, a location management system, and a program. [Background technology]

[0002] In logistics, inventory management, and the like, systems that use RFID reader devices (hereinafter, RFID readers) and RFID passive tags (hereinafter, RFID tags) to manage items are widely used. RFID stands for Radio Frequency Identification. RFID that uses UHF bands, for example, can read multiple RFID tags at once over a relatively long distance, and is suitable for systems that manage items in warehouses, for example. UHF stands for Ultra High Frequency. In such systems, an RFID reader carried by a user acquires location information by reading an RFID tag (hereinafter, reference tag), which is a wireless device that indicates a reference location at the user's destination. In addition, the RFID reader can read an RFID tag (hereinafter, item tag) for item management at that time, thereby managing the location of the item.

[0003] Considering the convenience of managing and searching for items, it is desirable to be able to manage the positions of item tags that are located away from a reference tag (a position where there is no readable reference tag).Patent Document 1 describes a technology for estimating the positions of item tags located in a wide range by calculating the relative position of the item tag detected by an RFID reader with respect to the reference tag based on the amount of movement of the RFID reader from the location where the reference tag was detected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-141415 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method of estimating the position of an RFID tag as in Patent Document 1, if the RFID reader continues to be unable to detect the reference tag, the error in the position (amount of movement) of the RFID reader accumulates significantly. As a result, there is a problem that the error in the estimated position of the RFID tag under management increases.

[0006] An object of the present invention is to improve the accuracy of location management performed using a communication apparatus having a function of communicating with wireless devices. [Means for solving the problem]

[0007] According to one aspect of the present invention, a communication device includes: a first acquiring means for acquiring first location information by communicating with a wireless device serving as a reference for identifying a location using a first communication function; a measuring means for measuring a positional relationship with an external device based on communication with the external device performed using a second communication function different from the first communication function; a second acquiring means for acquiring second position information based on the positional relationship measured by the measuring means; and a selection means for selecting either the first location information or the second location information as location information for location management of other wireless devices communicating via the first communication function. Effect of the Invention

[0008] According to the present invention, the accuracy of location management performed using a communication apparatus having a function of communicating with a wireless device is improved. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a position management system according to a first embodiment. [Figure 2A] 5 is a flowchart illustrating the operation of the RFID reader according to the first embodiment. [Figure 2B] 5 is a flowchart illustrating the operation of the RFID reader according to the first embodiment. [Figure 2C] 5 is a flowchart illustrating the operation of the RFID reader according to the first embodiment. [Figure 2D] 5 is a flowchart illustrating the operation of the RFID reader according to the first embodiment. [Figure 3A] 4A to 4C are diagrams showing an example of the operation of the RFID reader according to the first embodiment. [Figure 3B] 4A to 4C are diagrams showing an example of the operation of the RFID reader according to the first embodiment. [Figure 4A] 10 is a flowchart illustrating the operation of an RFID reader according to the second embodiment. [Figure 4B] 10 is a flowchart illustrating the operation of an RFID reader according to the second embodiment. [Figure 4C] 10 is a flowchart illustrating the operation of an RFID reader according to the second embodiment. [Figure 5A] FIG. 11 is a diagram showing an example of the operation of the RFID reader according to the second embodiment. [Figure 5B] FIG. 11 is a diagram showing an example of the operation of the RFID reader according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0011] First Embodiment A location management system that manages location information of wireless devices to be managed will be described in detail below. In the location management system of this embodiment, a communication device capable of detecting wireless devices is carried by a moving object such as a person or a machine, thereby detecting wireless devices present in a wide range. Here, the wireless device is, for example, an RFID tag, and the communication device is, for example, an RFID reader. In the following, a location management system using a portable RFID reader device (hereinafter referred to as an RFID reader), an RFID tag indicating a reference location (hereinafter referred to as a reference tag), and an RFID tag attached to an item (hereinafter referred to as an item tag) will be described. The reference tag is an RFID tag whose location is known, and the item tag is an RFID tag whose location is unknown. The RFID reader of the first embodiment is a communication device having a first communication function for communicating with an RFID tag and a second communication function different from the first communication function for communicating with an external device. In addition to a first acquisition function for detecting a reference tag and acquiring its own location, this RFID reader has a second acquisition function for acquiring its own location based on communication with an external device (e.g., another RFID reader). The position management system manages the position of an item to which an item tag is attached based on the position acquired by the first acquisition function and the second acquisition function when the item tag is read.

[0012] FIG. 1 is a block diagram showing a configuration example of a location management system according to a first embodiment. The location management system includes RFID readers 100a to 100d (hereinafter collectively referred to as RFID reader 100), an information processing device 200, and a plurality of reference tags 301 that can be read by the RFID reader 100 using a first communication function. The RFID reader 100 and the information processing device 200 are communicably connected by a wireless LAN such as WIFI. The RFID reader 100 wirelessly reads information from the RFID tag using the first communication function. For example, the RFID reader 100 supplies electromagnetic waves in the UHF band to the RFID tag to operate an IC chip inside the RFID tag and reads reference location information or item management information stored in the memory unit of the RFID tag. The RFID reader 100 is carried by a mobile object to read reference tags or item tags present in a wide range (a range beyond the communication range of RFID). The RFID reader 100 notifies the information processing device 200 of the location information acquired using the above-mentioned first acquisition function and second acquisition function, and the item management information obtained by reading the item tag. The information processing device 200 manages the location of each item by linking the location information with the item management information based on the information notified from the RFID reader 100. Note that the RFID reader 100 may perform location management by linking the location information with the item management information.

[0013] In the RFID reader 100, the calculation unit 101 has one or more processors (hereinafter, processors). The processor of the calculation unit 101 executes programs stored in one or more memories (for example, storage unit 102) to realize various controls of the RFID reader 100. A reading circuit 103 that realizes a first communication function communicates with an RFID tag via a transmitting / receiving unit 104 under the control of the calculation unit 101, and reads the contents of the RFID tag. A communication circuit 105 that realizes a second communication function communicates with another RFID reader via a transmitting / receiving unit 106 by a communication method having a distance measurement function under the control of the calculation unit 101, and measures the distance to the other RFID reader. For example, the communication circuit 105 can be configured to be capable of communication by a UWB (Ultra Wide Band) communication system or a Bluetooth communication system.

[0014] The signal strength measurement unit 107 measures the strength of the signal received by the transmission / reception unit 106. The calculation unit 101 acquires the distance between itself (RFID reader 100) and another RFID reader that is a communication partner based on the received signal strength measured by the signal strength measurement unit 107. The signal arrival time measurement unit 108 measures the arrival time of the signal received by the transmission / reception unit 106. The calculation unit 101 acquires the distance between itself (RFID reader 100) and another RFID reader that is a communication partner based on the arrival time of the received signal measured by the signal arrival time measurement unit 108. More specifically, the signal arrival time measurement unit 108 measures the time from transmitting a first signal to another RFID reader to receiving a second signal in response to the first signal, and calculates the distance based on this time. For example, in the case of UWB communication, the distance to another RFID reader can be acquired based on the measurement result of the signal strength measurement unit 107 or the signal arrival time measurement unit 108. Also, for example, in the case of Bluetooth communication, the distance to another RFID reader can be obtained based on the measurement result of the signal strength measurement unit 107. Note that the distance measurement function by the second communication function is not limited to the above example. Also, it is not necessary to have both the signal strength measurement unit 107 and the signal arrival time measurement unit 108. For example, if the location management system uses a UWB communication system, it is sufficient to have the signal arrival time measurement unit 108.

[0015] The outline of the position detection process by the RFID reader 100 as described above is as follows. The outline of the position detection process by the RFID reader 100a will be described below, but the other RFID readers 100b to 100d also perform similar position detection processes. First, the calculation unit 101 of the RFID reader 100a acquires the results of data communication with other RFID readers (for example, RFID readers 100b to 100d) from the communication circuit 105 to detect the other RFID readers. When the calculation unit 101 detects a predetermined number or more of other RFID readers, it makes the following inquiries to the other RFID readers by communication using the communication function of the communication circuit 105. In this embodiment, since the three-point positioning method is used, the predetermined number is "3". First, the calculation unit 101 makes inquiries to the other detected RFID readers regarding the execution of communication with the RFID tag. From the result of this inquiry, the calculation unit 101 identifies three other RFID readers that have continued to read the reference tag for more than a predetermined time and that each reads a different reference tag. If four or more RFID readers that read different reference tags are detected, any three of the RFID readers may be identified, or the three RFID readers may be identified in order of the reference tag that they are reading being closest to the RFID reader 100a. For the position of the RFID reader 100a at this time, for example, the position indicated by the most recently acquired position information may be used. If two or more RFID readers that read the same reference tag are detected, any one of them may be identified, or the RFID reader that has been reading for the longest time may be identified. In the following description, it is assumed that the RFID readers 100b to 100d are identified as the three other RFID readers.

[0016] During the counting period (Ta to Tb), the calculation unit 101 requests the identified RFID readers 100b to 100d to perform distance measurement between the RFID readers 100b to 100d and to transmit the distance measurement results, using the communication function of the communication circuit 105. Upon receiving this request, the RFID readers 100b to 100d measure the distances between them using the distance measurement function of the communication circuit 105, and transmit the distance measurement results to the RFID reader 100. The calculation unit 101 receives the distance measurement results from the three RFID readers 100b to 100d using the communication function of the communication circuit 105, and counts the distance measurement results received within the counting period for each RFID reader. After counting the distance measurement results, the calculation unit 101 determines whether the width between the upper and lower limits of the distance measurement results counted for each RFID reader (hereinafter, the upper and lower limit width) is within a threshold value. When the calculation unit 101 determines that the upper and lower limits of the collected distance measurement results of the three RFID readers are within the threshold, it measures the distances to the three RFID readers using the distance measurement function of the communication circuit 105. Then, the calculation unit 101 calculates the position information of the RFID reader 100 using the distance measurement results by using a triangular positioning method. At this time, the position of each of the three RFID readers can be determined based on the position of the reference tag being read.

[0017] The location acquisition process by the RFID reader 100 in the first embodiment described above will be described in more detail with reference to the flowcharts of Figures 2A to 2D. This process can be realized, for example, by the calculation unit 101 of the RFID reader 100 executing a program stored in the storage unit 102 in response to the power supply of the RFID reader 100 being turned on.

[0018] When the power supply of the RFID reader 100 is turned on, the RFID reader 100 starts the process (main flow) of FIG. 2A. In S201, the RFID reader 100 (the calculation unit 101) judges whether or not there is an instruction from the user to start reading an RFID tag. The instruction to start reading from the user can be received, for example, by a predetermined operation from an input unit (not shown). The input unit may be realized, for example, by a touch panel. Alternatively, the RFID tag reading start instruction may be received from the information processing device 200 and accepted. When the RFID tag reading start instruction is accepted (YES in S201), the process proceeds to S202. In the process from S202 onwards, the calculation unit 101 periodically operates the communication circuit 105 to communicate with other RFID readers, and periodically operates the reading circuit 103 to communicate with an RFID tag. When there is no instruction to start reading an RFID tag, the process returns to S201. In the processing from S202 onward shown in FIG. 2, detection of other RFID readers (detection processing (S203)) and detection of RFID tags (tag information acquisition processing (S205)) are executed at their respective timings (timings when S202 and S204 are YES). That is, the detection processing (S203) and the tag information acquisition processing (S205) are not synchronized. However, this is not a limitation, and the detection processing (S203) and the tag information acquisition processing (S205) may be synchronized and executed periodically. In this case, for example, the processing of S203, S205, and S206 are executed in sequence depending on whether or not it is the execution timing in S202.

[0019] In S202, the calculation unit 101 judges whether it is time to detect another RFID reader using the communication function of the communication circuit 105. If it is time to detect another RFID reader (YES in S202), the process proceeds to S203 and executes the detection process (FIG. 2B). On the other hand, if it is judged that it is not time to detect another RFID reader (NO in S202), the process proceeds to S204.

[0020] The detection process executed in S203 will be described with reference to the flowchart of Fig. 2B. First, in S221, the calculation unit 101 determines whether or not three or more other RFID readers are detected using the communication function of the communication circuit 105. If three or more other RFID readers are detected (YES in S221), the process proceeds to S222. On the other hand, if three or more other RFID readers are not detected (NO in S221), the detection process (S203) ends, and the process proceeds to S204 in Fig. 2A.

[0021] In S222, the calculation unit 101 inquires of the other detected RFID readers about the execution status of communication with the reference tag, using the communication function of the communication circuit 105. Here, the calculation unit 101 inquires, as the execution status of communication, about whether communication with the reference tag is being executed and the duration of communication with the reference tag. The other RFID readers respond to this inquiry using the communication function of the communication circuit 105, and notify the RFID reader 100 of the execution status of communication with the reference tag.

[0022] In S223, the calculation unit 101 judges whether or not three or more other RFID readers are communicating with different reference tags from the responses from the other RFID readers. If there are three or more other RFID readers communicating with different reference tags (YES in S223), the process proceeds to S224. On the other hand, if there are two or less other RFID readers communicating with different reference tags (NO in S223), the detection process ends (the process proceeds to S204 in FIG. 2A). In S224, the RFID reader 100 judges whether or not the duration of communication with the reference tag is equal to or longer than a threshold for the other RFID readers that are communicating with the reference tag. If there are three or more other RFID readers that are continuing communication with different reference tags for a time period equal to or longer than the threshold (YES in S224), the process proceeds to S225, and the distance measurement process (FIG. 2C) is executed. On the other hand, if there are two or less other RFID readers whose duration of communication with different reference tags is equal to or longer than the threshold (NO in S224), the detection process ends and the process proceeds to S204 (FIG. 2A). If the above detection process shows that three or more other RFID readers are communicating with three or more different reference tags for a duration exceeding the threshold, the distance measurement process is executed.

[0023] The distance measurement process executed in S225 will be described with reference to the flowchart of Fig. 2C. In S240, the calculation unit 101 identifies three RFID readers to be communication targets in the distance measurement process from the three or more other RFID readers whose duration of communication with the reference tag is equal to or longer than a threshold, which were identified in the above detection process (Fig. 2B). For example, the calculation unit 101 preferentially selects the RFID reader whose position of the reference tag being read is closest to the RFID reader 100a, and identifies three RFID readers reading different reference tags. In addition, when two or more RFID readers reading the same reference tag are detected, the calculation unit 101 preferentially selects the RFID reader whose duration of reading the reference tag is longer.

[0024] In S241, the calculation unit 101 sets a period (hereinafter, referred to as the calculation period) for counting the distance measurement results between the three identified RFID readers. Here, it is assumed that times Ta to Tb are set as the calculation period. In S242, the calculation unit 101 uses the communication function of the communication circuit 105 to request the three identified RFID readers to perform distance measurement and transmit the distance measurement results. The other RFID readers that receive this request use the distance measurement function of their respective communication circuits 105 to perform distance measurement between the selected other RFID readers, and transmit the distance measurement results to the RFID reader 100 using the communication function of the communication circuit 105. In S243, the calculation unit 101 uses the communication function of the communication circuit 105 to count the distance measurement results received from the other RFID readers during the counting period for each RFID reader. In S244, the calculation unit 101 determines whether or not counted data has been obtained for all of the identified RFID readers. If the tally data is obtained (YES in S244), the process proceeds to S246, and if the tally data is not obtained (NO in S244), the process proceeds to S245. In S245, the calculation unit 101 changes the tally period to be longer. For example, the tally period is extended by delaying the time Tb by α while leaving the time Ta unchanged. Thereafter, the process returns to S241, and the above-mentioned processes (S241 to S244) are repeated.

[0025] In S246, the calculation unit 101 judges whether the upper and lower limit ranges of the collected distance measurement results for each RFID reader are within a threshold value (i.e., whether the fluctuation in distance obtained by distance measurement during the collection period is within a threshold value). If the upper and lower limit ranges of the distance measurement results from the identified three RFID readers are within the threshold value (YES in S246), the process proceeds to S247. If there are two or fewer other RFID readers whose upper and lower limit ranges of the distance measurement results are within the threshold value (NO in S246), the distance measurement process ends (the process proceeds to S103 in FIG. 2A). Note that if four or more RFID readers are detected in the detection process, the combination of the three RFID readers identified in S240 may be changed and the processes from S241 onwards may be repeated.

[0026] In S247, the calculation unit 101 performs distance measurement with the three identified RFID readers using the distance measurement function of the communication circuit 105. In S248, the calculation unit 101 calculates position information corresponding to the position of the RFID reader 100 using the three-point positioning method from the distance measurement result acquired in S247 and the position of the reference tag with which the three identified RFID readers are communicating. Note that information on the reference tag read by the other RFID readers can be acquired by communication using the communication circuit 105. Also, instead of the information on the reference tag, the position information itself may be received from the other RFID readers. In S249, the RFID reader 100 stores the position information calculated in S248 in the storage unit 102. In S250, the calculation unit 101 performs flag processing (setting the position flag to 1) indicating that the position information has been calculated based on the other RFID readers as a reference, and ends the distance measurement processing.

[0027] Returning to FIG. 2A, in S204, the RFID reader 100 judges whether it is time to detect an RFID tag (reference tag or item tag). If it is time to detect an RFID tag (YES in S204), the process proceeds to S205, where tag information acquisition process is executed. On the other hand, if it is determined that it is not time to detect an RFID tag (NO in S204), the process proceeds to S207.

[0028] The tag information acquisition process executed in S205 will be described with reference to the flowchart of FIG. 2D. In S261, the calculation unit 101 sets a period for counting RFID tag read results (hereinafter, referred to as the counting period). Here, it is assumed that times Ta to Tb are set as the counting period (note that it is set independently of Ta and Tb set in S241). In S262, the calculation unit 101 starts reading RFID tags. In S263, the calculation unit 101 counts RFID tag read results within the counting period. In S264, the calculation unit 101 judges whether or not the RFID tag read results counted in S263 include a reference tag read result. If the reference tag read result is included (YES in S264), the process proceeds to S266. On the other hand, if the reference tag read result is not included (if no RFID tag has been read, or if the RFID tag has not been read as an item tag (NO in S264)), the process proceeds to S265.

[0029] In S266, the calculation unit 101 acquires position information corresponding to the position of the RFID reader 100 from the result of reading the reference tag. In S267, the calculation unit 101 judges whether it has position information calculated based on another RFID reader based on the state of the position flag (set in the distance measurement process (S250) described above). If the position flag = 1 (YES in S267), the calculation unit 101 judges that it has position information calculated based on another RFID reader, and the process proceeds to S268. If the position flag = 1 (NO in S267), the calculation unit 101 judges that it does not have position information calculated based on another RFID reader, and the process proceeds to S274. In S274, the calculation unit 101 saves the position information acquired in S266 in the storage unit 102.

[0030] In S268 and thereafter, depending on whether a predetermined condition is satisfied (S269 to S271), it is determined whether to use the location information acquired based on communication with another RFID reader or the location information acquired based on communication with a reference tag. In S268, the calculation unit 101 compares the location information acquired in S266 with the location information stored in the storage unit 102 by the distance measurement process (S249). In S269, the calculation unit 101 determines whether the difference between the location information acquired in S266 and the location information stored in the storage unit 102 is within a first threshold value as a result of the comparison in S268. If the difference is within the first threshold value (YES in S269), the process proceeds to S273, and if the difference is not within the first threshold value (NO in S269), the process proceeds to S270.

[0031] In S270, the calculation unit 101 judges whether or not the difference between the position information acquired in S266 and the position information stored in the storage unit 102 is within a second threshold value based on the comparison result in S268. If the difference is within the second threshold value (YES in S270), the process proceeds to S271, and if the difference is not within the second threshold value (NO in S270), the process proceeds to S272. In S271, the calculation unit 101 judges whether or not the communication time with the reference tag by the reading circuit 103 continues for a threshold value or more. If the communication time with the reference tag continues for a threshold value or more (YES in S271), the process proceeds to S273, and if the communication with the reference tag has not continued for a threshold value or more (NO in S271), the process proceeds to S272. In S272, the calculation unit 101 discards the position information acquired in S266. On the other hand, when the process proceeds to S273, the location information stored in the storage unit 102 is updated with the location information acquired in S266. That is, in S273, the calculation unit 101 erases the location information (S249) acquired based on communication with another RFID from the storage unit 102, and in S274, the calculation unit 101 stores the location information (S266) acquired based on reading the reference tag in the storage unit 102. In S265, the calculation unit 101 updates the management information. The management information is information for performing location management by associating the location of the RFID reader with an item. In S265, the calculation unit 101 updates the location information of the RFID reader in the management information with the newly determined location information. Also, if the RFID tag read in S262 includes an item tag, the management information for performing item location management is updated by linking the item management information indicated by the item tag with the updated location information. The management information may be notified to the information processing device 200 at the timing of the update in S265, or may be notified at any timing other than the update.

[0032] Returning to FIG. 2A, in S206, the calculation unit 101 initializes a position flag indicating that the calculation unit 101 has position information calculated based on another RFID reader (setting the position flag to 0). In S207, the calculation unit 101 judges whether or not there is an instruction from the user to end the RFID tag reading. If there is an instruction to end the RFID tag reading from the user (YES in S207), the operation of the reading circuit 103 is stopped and communication with the RFID tag is stopped. On the other hand, if there is no end instruction (NO in S207), the process returns to S102 and the above-mentioned process continues. According to the above process, the first position information is obtained by reading the reference tag (S266), and the second position information (S248) is obtained by measuring the distance with the other RFID reader. When the first position information and the second position information are obtained, the position information to be used for position management is selected based on the relationship of the positions indicated by the position information (S268 to S274). Furthermore, when either the first location information or the second location information is acquired, the acquired location information is selected as the location information to be used for location management.

[0033] An operation example of the process described above with reference to the flowcharts of FIGS. 2A to 2D will be further described with reference to FIGS. 3A and 3B. FIGS. 3A and 3B are diagrams showing an operation example of the RFID reader 100 in the first embodiment. In this example, four RFID readers 100a to 100d exist. Also, reference tags 301a to 301h are arranged as RFID tags indicating a reference position. Hereinafter, the RFID readers 100a to 100d are collectively referred to as the RFID reader 100, and the reference tags 301a to 301h are collectively referred to as the reference tag 301. The reference tag 301 is an RFID tag arranged to detect a reference position, and is attached to, for example, a floor, and its arrangement position is fixed. Also, hereinafter, the control system of the first embodiment will be described assuming a situation in which the RFID reader 100a moves from position A to position B as shown in FIGS. 3A and 3B.

[0034] In the example of FIGS. 3A and 3B, the RFID reader 100a detects other RFID readers and detects RFID tags by UWB (Ultra Wide Band) communication. At time t0, the RFID reader 100a detects the other RFID readers 100b to 100d and inquires about the execution status of communication with the reference tag (S222 to S224). As a result of this inquiry, the RFID reader 100a determines that the RFID readers 100b, 100c, and 100d have been continuously communicating with the reference tags 301a, 301e, and 301h, respectively, for a period equal to or longer than the threshold. In this case, the RFID reader 100 sets the time Ta to Tb as a period for counting the distance measurement results between the RFID readers 100b to 100d (hereinafter, referred to as the counting period) (S241). Then, RFID reader 100a requests RFID readers 100b to 100d to measure the mutual distances using UWB communication (S242). In this example, RFID reader 100b and RFID reader 100c are requested to measure the mutual distance b, the distance c between RFID reader 100c and RFID reader 100d, and the distance a between RFID reader 100d and RFID reader 100b. That is, RFID reader 100a requests RFID reader 100b to measure distances a and b, requests RFID reader 100c to measure distances b and c, and requests RFID reader 100d to measure distances a and c. The RFID readers 100b to 100d measure the distances a to c using UWB communication at time t1, respectively, and transmit the distance measurement results to the RFID reader 100a using UWB communication. The RFID reader 100a receives the distance measurement results of the distances a to c from the RFID readers 100b to 100d, and performs calculations within calculation periods Ta to Tb (S243).

[0035] The RFID reader 100 judges whether the upper and lower limit ranges obtained for the distance measurement results of the distances a, b, and c collected during the collection period Ta to Tb are within the threshold (S246). If it is judged that the upper and lower limit ranges of the distance measurement results of the distances a, b, and c are within the threshold, the RFID reader 100a measures the distances between the RFID reader 100a and the other RFID readers 100b to 100d using UWB communication at time t2 (FIG. 3B) (S247). That is, the RFID reader 100a measures the distance d between the RFID reader 100a and the RFID reader 100b, the distance e between the RFID reader 100a and the RFID reader 100c, and the distance f between the RFID reader 100a and the RFID reader 100d. Then, the calculation unit 101 calculates the position A by using the triangular positioning method based on the positions of the reference tags 301a, 301e, and 301h with which the RFID readers 100b to 100d are communicating and the measurement results of the acquired distances d to f (S248). By continuing to periodically execute the above operations, the RFID reader 100a that has moved to position B measures the distance i at time t3. The distance g is the distance between the RFID reader 100a and the RFID reader 100b, the distance h is the distance between the RFID reader 100a and the RFID reader 100c, and the distance i is the distance between the RFID reader 100a and the RFID reader 100d. The RFID reader 100a calculates the position by using the triangular positioning method based on the measurement results of the acquired distances g to i and the positions of the reference tags 301a, 301e, and 301h. This allows the RFID reader 100a to calculate the position B even if it cannot detect the reference tag.

[0036] As described above, according to the first embodiment, in a management system using a portable RFID reader, a reference tag, and an item tag, even if the reference tag continues to be unreadable, the RFID reader can acquire location information by communicating with another RFID reader. As a result, even in a situation where the reference tag cannot be read, real-time information updating that deals with changes in the location of an item over time is possible, and the traceability of the item can be improved compared to the conventional case.

[0037] Second Embodiment In the first embodiment, when a position based on detection of the reference tag 301 and a position based on communication with another RFID reader are obtained, which position to use as the position of the RFID reader 100 is determined by comparing the two positions. In the second embodiment, when the RFID reader 100 can communicate with the reference tag 301, it obtains position information from the reference tag 301, and when it cannot communicate with the reference tag 201, it obtains position information based on communication with another RFID reader. That is, the second embodiment differs from the first embodiment in that it preferentially uses position information obtained based on the reference tag 201 and switches the method of calculating the position depending on the communication state with the reference tag 201.

[0038] 4A to 4C are flowcharts showing the operation of the RFID reader 100 according to the second embodiment. When the RFID reader 100 is turned on, it starts the process (main flow) of FIG. 4A. In S401, the RFID reader 100 (the calculation unit 101) judges whether or not there is an instruction from the user to start reading an RFID tag. The process of S401 is the same as the process of S201 in the first embodiment. The processes of S402 to S405 are periodically and repeatedly executed at the timing of tag detection.

[0039] In S402, the calculation unit 101 judges whether it is time to detect an RFID tag. If it is judged to be time to detect an RFID tag (YES in S402), the process proceeds to S406 (tag information acquisition process), and if it is judged that an RFID tag has not been detected (NO in S402), the process proceeds to S403.

[0040] FIG. 4B is a flowchart for explaining the tag information acquisition process (S406) according to the second embodiment. The processes of S421 to S426 and S427 are similar to those of S261 to S266 and S275 of the first embodiment (FIG. 2D). In S421, the calculation unit 101 sets a period for counting RFID tag read results (hereinafter, referred to as counting period). Here, it is assumed that times Ta to Tb are set as the counting period. In S422, the calculation unit 101 starts reading RFID tags. In S423, the calculation unit 101 counts RFID tag read results within the set counting period. In S424, the calculation unit 101 determines whether or not the RFID tag read results counted in S423 include a reference tag read result. If the reference tag read result is included (YES in S424), the process proceeds to S425. On the other hand, if the reading result of the reference tag is not included (if no RFID tag has been read, or if the tag has not been read as an item tag (NO in S424)), the process proceeds to S427. In S425, the calculation unit 101 acquires position information from the reading result of the reference tag. In S426, the calculation unit 101 performs flag processing (setting position flag = 1) to indicate that it has position information calculated from the reading result of the reference tag. In S427, the calculation unit 101 updates the management information and ends the tag information acquisition process. Note that the updating of the management information is similar to the processing in the first embodiment (S265).

[0041] Returning to Fig. 4A, in S403, the calculation unit 101 judges whether it has position information calculated from the reading result of the reference tag. If the position flag = 1, the calculation unit 101 judges that it has position information calculated from the reading result of the reference tag (YES in S403), and proceeds to the process of S404. On the other hand, if the position flag = 1 (NO in S403), the calculation unit 101 judges that it does not have position information calculated from the reading result of the reference tag, and proceeds to the process of S407 (detection process).

[0042] The detection process in S407 is the same as the detection process in the first embodiment (FIG. 2B) except for the distance measurement process executed in S225, and is not shown. The distance measurement process in the second embodiment will be described with reference to the flowchart in FIG. 4C. In FIG. 4C, the processes in S440 to S448 are the same as the processes in S240 to S448 in the distance measurement process in the first embodiment (FIG. 2C). In S449, the calculation unit 101 updates the management information based on the position calculated based on the distance measurement result between the other RFID reader, and ends the distance measurement process. Note that the update of the management information is the same as the process in the first embodiment (S265). When the distance measurement process ends, the process proceeds to S404 (FIG. 4A).

[0043] Returning to FIG. 4A, in S404, the calculation unit 101 initializes a flag indicating that it has position information calculated from the results of reading the reference tag (setting the flag to 0). In S405, the calculation unit 101 determines whether or not there is an instruction from the user to end RFID tag reading. If there is an instruction from the user to end RFID tag reading (YES in S405), the calculation unit 101 stops the operation of the reading circuit 103 and stops communication with the RFID tag. If there is no instruction to end (NO in S405), the process returns to S402, and the above-mentioned processes are repeated.

[0044] An example of the operation of the process of the second embodiment described above with reference to the flowcharts of Figs. 4A to 4C will be further described with reference to Figs. 5A and 5B. In the following, the location management system of the second embodiment will be described assuming a situation in which the RFID reader 100a moves from location A to location C via location B as shown in Figs. 5A and 5B. The RFID reader 100a performs RFID tag detection at time t0, reads the reference tag 301f, and acquires location information. When the RFID reader 100a can acquire location information based on communication with the reference tag, the RFID reader 100a uses the location information as the location of the RFID reader 100a.

[0045] When the RFID reader 100a moves away from position A and is no longer able to detect the reference tag 301f, it acquires location information through UWB (Ultra Wide Band) communication with the other RFID readers 100b to 100d. When the RFID reader 100a is no longer able to detect the reference tag 301f, the location flag indicating that the RFID reader has location information calculated from the results of reading the reference tag is no longer set to 1 in the tag information acquisition process (S406). When the location flag=0, the calculation unit 101 determines that the calculation unit 101 does not have location information calculated from the results of reading the reference tag (S403), and starts a detection process (S407) to detect other RFID readers using UWB communication.

[0046] At time t1, RFID reader 100a detects RFID readers 100b-100d by UWB communication and inquires about the execution status of communication with reference tags. As a result of the inquiry, RFID reader 100a determines that RFID readers 100b, 100c, and 100d have been continuously communicating with reference tags 301a, 301e, and 301h, respectively, for a period of time equal to or longer than the threshold. In this case, RFID reader 100a sets times Ta to Tb as a period (counting period) for counting the distance measurement results between RFID readers 100b-100d, and requests that distance measurement of distances a, b, and c be performed between RFID readers 100b-100d. Note that distance a is the distance between RFID reader 100d and RFID reader 100b, distance b is the distance between RFID reader 100b and RFID reader 100c, and distance c is the distance between RFID reader 100c and RFID reader 100d.

[0047] The RFID readers 100b to 100d measure the distances a to c using UWB communication, respectively, and transmit the distance measurement results to the RFID reader 100a using UWB communication. The RFID reader 100a receives the distance measurement results of the distances a to c from the RFID readers 100b to 100d, and performs calculations within times Ta to Tb (counting period). The RFID reader 100a judges whether the upper and lower limit ranges of the distance measurement results of the distances a, b, and c calculated within the counting period are within a threshold value. Here, it is judged that the upper and lower limit ranges of the distance measurement results of the distances a, b, and c are within a threshold value. At time t2, the RFID reader 100a measures the distance d from the RFID reader 100b, the distance e from the RFID reader 100c, and the distance f from the RFID reader 100d using UWB communication. The RFID reader 100a calculates the position B by using a three-point positioning method based on the acquired distances d to f and the positions of the reference tags 301a, 301e, and 301h.

[0048] Thereafter, the RFID reader 100a continues moving from position B while repeatedly calculating position information based on the RFID readers 100b to 100d and detecting RFID tags. Note that before detecting RFID tags, the calculation of position information based on the RFID readers 100b to 100d is stopped.

[0049] When the RFID reader 100a arrives at position C at time t3, it detects the reference tag 301c. When the RFID reader 100a is able to communicate with the reference tag 301c, it acquires its position information and sets a position flag to 1, which indicates whether the RFID reader 100a has position information calculated from the reading result of the reference tag. While the position flag, which indicates that the RFID reader 100a has position information calculated from the reading result of the reference tag, is set to 1, the RFID reader 100a continues to acquire position information based on the reading of the reference tag 301c. During this time, the RFID reader 100a does not calculate position information based on the distance measurement results obtained by communication with the other RFID readers 100b to 100d.

[0050] As described above, according to the second embodiment, in the RFID reader control system, when communication with the reference tag is possible, the location information is calculated from the reference tag, and when communication with the reference tag is not possible, the location information is calculated from information of another RFID reader. Also, when location information can be acquired based on the reference tag, acquisition of location information using another RFID reader is not executed. In this way, by switching the location calculation method according to the communication state with the reference tag, location information can be acquired more quickly. As a result, it becomes possible for the RFID reader to acquire location information in more real time, which improves user convenience.

[0051] As described above, according to each of the above embodiments, even if the RFID reader continues to be unable to detect an RFID tag (reference tag) that serves as a reference for identifying a location, it is possible to acquire location information.

[0052] (Other embodiments) In the above embodiment, the RFID readers 100a to 100d have the same functions, but this is not limited to this. For example, the external device with which the RFID reader 100a communicates to acquire the position and measure the distance may be capable of communication and distance measurement by the communication function of the communication circuit 105, and may be capable of notifying the RFID reader 100a of its own position. For example, such an external device may not have a function of acquiring the position based on the reference tag, and may be disposed at a predetermined position. In addition, in the above embodiment, three other RFID readers (external devices) are detected to use the triangular positioning method, but this is not limited to this. For example, if the distance and direction (angle) can be detected as the positional relationship with the other RFID readers (external devices), the position can be acquired using fewer than three other RFID readers (external devices).

[0053] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0054] The disclosure of this specification includes the following communication device, control method thereof, location management system, and program. (Item 1) 1. A communication device, comprising: a first acquiring means for acquiring first location information by communicating with a wireless device serving as a reference for identifying a location using a first communication function; a measuring means for measuring a positional relationship with an external device based on communication with the external device performed using a second communication function different from the first communication function; a second acquiring means for acquiring second position information based on the positional relationship measured by the measuring means; a selection means for selecting either the first location information or the second location information as location information for location management of other wireless devices communicating via the first communication function. (Item 2) The communication device according to item 1, characterized in that, when both the first location information and the second location information are acquired, the selection means selects either the first location information or the second location information based on a relationship between the location indicated by the first location information and the location indicated by the second location information. (Item 3) The communication device described in item 2, characterized in that the selection means selects the first location information when a difference between the location indicated by the first location information and the location indicated by the second location information is smaller than a first threshold value. (Item 4) The communication device described in item 3, characterized in that the selection means selects the first location information when a difference between the location indicated by the first location information and the location indicated by the second location information is between the first threshold and a second threshold greater than the first threshold, and communication with the wireless device via the first communication function has continued for more than a predetermined time. (Item 5) 5. The communication device according to item 4, characterized in that the selection means selects the second location information when a difference between the location indicated by the first location information and the location indicated by the second location information exceeds the second threshold. (Item 6) The communication device according to any one of items 1 to 5, characterized in that, when only one of the first location information and the second location information is acquired, the selection means selects the acquired location information. (Item 7) the acquisition of the first location information by the first acquisition means and the acquisition of the second location information by the second acquisition means are repeatedly executed in synchronization with each other; 2. The communication device according to item 1, wherein the selection means selects the first location information with priority. (Item 8) 8. The communication device according to item 7, wherein when the first location information is acquired by the first acquisition means, acquisition of location information by the second acquisition means is not executed. (Item 9) The communication device described in any one of items 1 to 8, characterized in that the measurement means measures the distance between the communication device and each of a predetermined number of external devices, each of which is communicating with a wireless device that serves as a reference for a different position, when communication is possible via the second communication function with the predetermined number of external devices. (Item 10) The communication device described in item 9, characterized in that the measurement means measures the distance between each of the predetermined number of external devices and the communication device when each of the predetermined number of external devices continues communication with a wireless device that serves as a location reference for more than a predetermined period of time. (Item 11) 11. The communication device according to item 9 or 10, characterized in that the measurement means measures the distance between each of the predetermined number of external devices and the communication device when a variation in the mutual distances of the predetermined number of external devices is smaller than a threshold value. (Item 12) The communication device described in item 11, characterized in that the measurement means obtains the variation by using the second communication function to send a request to measure the mutual distance to the predetermined number of external devices and receiving the measurement results from the predetermined number of external devices. (Item 13) 13. The communication device according to any one of items 1 to 12, further comprising a management unit that performs location management by linking the location information selected by the selection unit with information obtained by communicating with the other wireless device. (Item 14) A communication device according to any one of items 1 to 13, The external device; the wireless device, 4. A location management system comprising: a location management unit for managing the locations of the other wireless devices using the location information selected by the selection unit; (Item 15) A method for controlling a communication device, comprising: a first acquiring step of acquiring first location information by communicating with a wireless device serving as a reference for identifying a location using a first communication function; a measurement step of measuring a positional relationship with an external device based on communication with the external device performed using a second communication function different from the first communication function; a second acquiring step of acquiring second position information based on the positional relationship measured in the measuring step; A control method for a communication device, comprising: a selection process for selecting either the first location information or the second location information for location management of other wireless devices communicating via the first communication function. (Item 16) A program for causing a computer to function as each of the means of the communication device described in any one of items 1 to 13.

[0055] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention.

Claims

1. A communication device, a first acquiring means for acquiring first location information by communicating with a wireless device that serves as a reference for identifying a location using a first communication function; a measuring means for measuring a positional relationship with an external device based on communication with the external device performed using a second communication function different from the first communication function; a second acquiring means for acquiring second position information based on the positional relationship measured by the measuring means; a selection unit for selecting either the first location information or the second location information.

2. The communication device according to claim 1, characterized in that, when both the first location information and the second location information are acquired, the selection means selects either the first location information or the second location information based on the relationship between the location indicated by the first location information and the location indicated by the second location information.

3. 3. The communication device according to claim 2, wherein the selection means selects the first location information when a difference between the location indicated by the first location information and the location indicated by the second location information is smaller than a first threshold value.

4. The communication device described in claim 3, characterized in that the selection means selects the first location information when the difference between the location indicated by the first location information and the location indicated by the second location information is between the first threshold and a second threshold greater than the first threshold, and communication with the wireless device via the first communication function has continued for more than a predetermined time.

5. 5. The communication device according to claim 4, wherein the selection means selects the second location information when a difference between the location indicated by the first location information and the location indicated by the second location information exceeds the second threshold.

6. 2. The communication device according to claim 1, wherein, when only one of the first location information and the second location information is acquired, the selection means selects the acquired location information.

7. the acquisition of the first location information by the first acquisition means and the acquisition of the second location information by the second acquisition means are repeatedly executed in synchronization with each other; 2. The communication device according to claim 1, wherein the selection means selects the first location information with priority.

8. 8. The communication device according to claim 7, wherein when the first location information is acquired by the first acquisition means, location acquisition by the second acquisition means is not executed.

9. The communication device according to claim 1, characterized in that the measurement means measures the distance between the communication device and each of a predetermined number of external devices that are each communicating with a wireless device that serves as a reference in a different position when communication is possible via the second communication function with the predetermined number of external devices.

10. 10. The communication device according to claim 9, wherein the measuring means measures the distance between each of the predetermined number of external devices and the communication device when each of the predetermined number of external devices continues communication with a wireless device that serves as a location reference for more than a predetermined period of time.

11. 10. The communication device according to claim 9, wherein the measuring means measures the distance between each of the predetermined number of external devices and the communication device when a variation in the mutual distances of the predetermined number of external devices is smaller than a threshold value.

12. The communication device according to claim 11, characterized in that the measurement means obtains the variation by using the second communication function to send a request to measure the mutual distance to the predetermined number of external devices and receiving the results of the measurement from the predetermined number of external devices.

13. 2. The communication device according to claim 1, further comprising a management means for managing the locations of the other wireless devices based on the location information selected by the selection means and information obtained by communicating with the other wireless devices.

14. A communication device according to any one of claims 1 to 12; the external device; the wireless device; A location management system characterized by:

15. A method for controlling a communication device, comprising: a first acquiring step of acquiring first location information by communicating with a wireless device that serves as a reference for identifying a location using a first communication function; a measuring step of measuring a positional relationship with an external device based on communication with the external device performed using a second communication function different from the first communication function; a second acquiring step of acquiring second position information based on the positional relationship measured in the measuring step; a selection step of selecting either the first location information or the second location information.

16. A program for causing a computer to function as each of the means of the communication device according to any one of claims 1 to 13.

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