JP5151870B2 - RFID system and RFID tag - Google Patents

Description

  The present invention relates to an RFID system, a reader / writer, and an RFID tag.

In recent years, RFID (Radio Frequency IDentification) tags to which predetermined identification information is assigned have been widely used, and RFID systems for managing production, physical distribution, articles and the like have been proposed. This RFID system includes an RFID tag attached to each of a plurality of articles, and a reader / writer that reads identification information of these RFID tags (see, for example, Patent Document 1).
JP 2006-233831 A

  In a conventional RFID system, when a reader / writer issues a read command, response signals are sent back simultaneously from a large number of unspecified RFID tags that are within the reach of radio waves. When response signals from other RFID tags collide, it is difficult to read all RFID tags, for example, only those having the strongest signal level are read. For this reason, when reading cannot be performed at a predetermined timing to be read, there is a problem that an unread RFID tag that is not detected forever remains.

  Accordingly, an object of the present invention is to eliminate unread RFID tags even when an unspecified number of RFID tags exist in a range where radio waves of a reader / writer reach.

In order to achieve this object, the RFID system of the present invention reads a plurality of RFID tags each having a tag antenna unit and a tag circuit unit for storing and holding identification information, and the identification information from each of the plurality of RFID tags via the antenna. A reader / writer having a transmission / reception unit, and the reader / writer transmits a read command for reading the identification information from the transmission / reception unit via the antenna, and then transmits the identification information to be read from any one of the plurality of RFID tags. If reading is not possible due to the occurrence of a reading error, read error information notifying the occurrence of a reading error is added to the next reading command to be sent and sent from the transmitter / receiver via the antenna, and the RFID tag is added to the reading command. The read error information is judged and a read error occurs. A read error detection unit that detects whether or not the reader / writer has read the identification information, and sets a read completion flag based on the determination result of the read error detection unit. And a control unit . This achieves the initial objective.

  The RFID tag of the present invention includes a tag antenna unit and a tag circuit unit that stores and holds identification information. The tag circuit unit includes a transmission / reception unit that reads a read command transmitted from a reader / writer via the tag antenna unit. The reading error detection unit for detecting the reading error information of the identification information added to the reading command read by the transmission / reception unit and detecting whether or not the reading error has occurred, and the reading of the identification information by the reader / writer It has a read completion flag that indicates whether or not it has been completed, and a control unit that sets a read completion flag based on the determination result of the read error detection unit, and the control unit detects a read error in the read error detection unit If this happens, set the read complete flag so that the read incomplete state is maintained, and the read error detector Ri If the error is completed reading of the identification information by a reader-writer with an undetected, characterized by being configured to set the read completion flag read completion. With such a configuration, the initial purpose is achieved.

As described above, the RFID system of the present invention includes a plurality of RFID tags each including a tag antenna unit and a tag circuit unit that stores and holds identification information, and a transmission / reception unit that reads identification information from each of the plurality of RFID tags via the antenna. The reader / writer transmits a read command for reading the identification information from the transmission / reception unit via the antenna, and then transmits the identification information to be read from any one of the plurality of RFID tags. If reading is not possible due to occurrence, read error information notifying the occurrence of a read error is added to the next read command to be transmitted, and then transmitted from the transmission / reception unit via the antenna, and the RFID tag is added to the read command Judge reading error information and check if a reading error has occurred. A read error detection unit, a read completion flag indicating information indicating whether or not the identification information has been read by the reader / writer, and a control unit for setting the read completion flag based on the determination result of the read error detection unit. since the, in the RFID tag side, it is possible to detect that the reading error of the identification information in the reader writer side from the reading error information included in the read command is generated. As a result, the RFID tag can respond until the reading of the identification information is normally completed by the reader / writer. Therefore, even if an unspecified number of RFID tags exist within the reach of the reader / writer radio wave, RFID tags can be eliminated.

  The RFID tag of the present invention includes a tag antenna unit and a tag circuit unit that stores and holds identification information. The tag circuit unit includes a transmission / reception unit that reads a read command transmitted from a reader / writer via the tag antenna unit. The reading error detection unit for detecting the reading error information of the identification information added to the reading command read by the transmission / reception unit and detecting whether or not the reading error has occurred, and the reading of the identification information by the reader / writer It has a read completion flag that indicates whether or not it has been completed, and a control unit that sets a read completion flag based on the determination result of the read error detection unit, and the control unit detects a read error in the read error detection unit If this happens, set the read complete flag so that the read incomplete state is maintained, and the read error detector If the reading error is not detected and the reading of the identification information is completed by the reader / writer, the reading completion flag is set to reading completion, so the reading added to the reading command sent from the reader / writer From the error information, it is possible to detect that an identification information reading error has occurred on the reader / writer side. As a result, the RFID tag can respond until the reading of the identification information is normally completed by the reader / writer. Therefore, even when an unspecified number of RFID tags exist within the reach of the reader / writer's radio wave. Unread RFID tags can be eliminated.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(Embodiment)
First, the overall configuration and operation of the RFID system 1 according to the embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is a schematic diagram of an RFID system 1 according to an embodiment of the present invention. Here, as the managed article 4, for example, a product stored and managed in a warehouse will be described as an example. In the warehouse, a large number of managed articles 4 are loaded on a pallet or the like from an unspecified location and are carried by a forklift. In addition, since a large number of managed articles 4 are shipped to unspecified places, management becomes very complicated.

  Therefore, in the present embodiment, as shown in FIG. 1, RFID tags 2 a to 2 f are attached to the respective managed articles 4, and these RFID tags 2 a to 2 f are read by the reader / writer 3. Has been.

  As described above, the RFID system 1 includes the RFID tags 2 a to 2 f and the reader / writer 3. In order to facilitate understanding in the following description, a plurality of RFID tags 2a, 2b, 2c, 2d, 2e, 2f,. In the present embodiment, the number of RFID tags 2 is described as six, but is not limited to this number.

  Each RFID tag 2 attached to each managed article 4 stores identification information for each managed article 4 (for example, product name, product number, manufacturing date, shipping date, etc.). "Where is the product number B of the product name A now?" Is managed.

  The reader / writer 3 shown in FIG. 1 performs the management. The reader / writer 3 communicates with the RFID tag 2 through the transmission / reception unit 31 and the antenna 3a, and is stored and held in the tag circuit unit 20b of the RFID tag 2. The individual identification information 25b is read and managed via the tag antenna unit 20a. Note that the reader / writer 3 may be used by being connected to a management device (not shown) at another location. Thereby, the management article 4 can be managed efficiently in large quantities.

  The RFID tag 2 includes a tag antenna unit 20a and a tag circuit unit 20b. The tag circuit unit 20b includes a transmission / reception unit 21, a division allocation unit 22, a random number generation unit 23, a read error detection unit 24, a memory unit 25, and a control unit. 26.

  The transmission / reception unit 21 communicates with the reader / writer 3 via the tag antenna unit 20a, and transmits / receives various reading commands, identification information 25b, and the like.

  The division allocating unit 22 performs a plurality of time-division based on a predetermined value called a Q value (a value specifying the number of time slots) described later received from the reader / writer 3 via the tag antenna unit 20a and the transmitting / receiving unit 21. Assign one of the time slots to the device itself. For example, when there are eight time slots, one value from “0” to “7” is assigned to the own device.

  The random number generation unit 23 generates a random number used when assigning time slots. The random number generator 23 also generates an authentication random number for authenticating and selecting the tag on the reader / writer 3 side.

  The read error detection unit 24 acquires a read command transmitted from the reader / writer 3 via the transmission / reception unit 21, and transmits / receives data on the reader / writer 3 side based on read error information added to the read command, as will be described later. The unit 31 detects whether or not an error in reading the identification information 25b has occurred. Details of the read error detection unit 24 will be described later.

  The memory unit 25 stores a read completion flag 25a, identification information 25b, random number information 25c, slot counter information 25d, and the like. In the identification information 25b, identification information of the managed article 4 (for example, product name, product number, manufacturing date, shipping date, etc.) is stored. As the random number information 25c, the random number generated by the random number generation unit 23 is temporarily stored. The slot counter information 25d temporarily stores the value of the time slot number assigned to the own device.

  The control unit 26 includes a central processing unit (CPU), a read only memory (ROM) that stores various programs and control programs, a random access memory (RAM) that temporarily stores data, and the like, and controls circuits of each unit. . When the reading error detection unit 24 does not detect a reading error and the identification information 25b of the RFID tag 2 is normally read by the reader / writer 3, the control unit 26 sets the reading completion flag 25a to read completion. Further, when the reading completion flag 25a is set to the reading completion, the control unit 26 controls the non-response to the subsequent reading command.

  Next, the reader / writer 3 is configured as follows in order to read the identification information 25b from the RFID tag 2 described above.

  That is, the reader / writer 3 includes a transmission / reception unit 31, a section number designation unit 32, a collision number acquisition unit 33, and a memory unit 34.

  The transmission / reception unit 31 performs communication with the RFID tag 2 via the antenna 3a, and transmits / receives various reading commands, identification information 25b, and the like.

The division number designation unit 32 designates the number of time slots. Normally, according to a standard (for example, EPC Class-1 Generation 2 standard), the number of time slots is represented by 2 ^Q (Q is a positive integer), and Q is called a Q value. In the EPC Class-1 Generation 2 standard, Q is defined as 0 or more and 15 or less.

  When two or more RFID tags 2 respond and collision occurs in each time slot, the collision number acquisition unit 33 counts the collision number (collision number) as “1”. Based on the number of collisions, the division number designation unit 32 updates the number of time slots set in the next round.

  The memory unit 34 stores identification information 34 a and read error information 34 b acquired from each RFID tag 2 via the antenna 3 a and the transmission / reception unit 31.

  The control unit 35 includes a central processing unit (CPU), a read only memory (ROM) that stores various programs and control programs, a random access memory (RAM) that temporarily stores data, and the like, and controls circuits of each unit. . In addition, when the identification information 25b is read from the RFID tag 2 and the transmission / reception unit 31 has an error in reading the identification information 25b, the control unit 35 sets the reading error information 34b. When the next reading command is transmitted to the plurality of RFID tags 2 via the transmission / reception unit 31 and the antenna 3a, the reading error information 34b is added to the reading command and transmitted. Details of this will be described later.

  Next, the outline of the communication operation by the read command in the RFID system 1 will be described with reference to FIGS. 1 and 2. FIG. 2 explains the outline of the communication operation of the RFID system 1 in the embodiment of the present invention. FIG. 2A is a schematic diagram for explaining the communication operation of the RFID system 1 in the present embodiment. It is a schematic diagram explaining the communication operation of the comparative example with the RFID system 1.

  First, in order to help understanding of the present embodiment, a comparative example with the present embodiment will be described with reference to FIG. In this example, the RFID tag 2 and the reader / writer 3 communicate with each other using a conventional read command.

  That is, as shown in FIG. 2B, a Query command 41 that is a read command is transmitted from the reader / writer 3. Here, it is assumed that the Q value is designated as “3” by the Query command 41 and the number of time slots is “8”.

  When the RFID tag 2 within the communication range of the reader / writer 3 receives the Query command 41, the random number generation unit 23 automatically selects one of the eight time slots according to the number of time slots indicated by the Query command 41. Assign to equipment. Specifically, one value from “0” to “7” is generated by the random number generation unit 23 and temporarily stored as slot counter information 25 d in the memory unit 25. For example, it is assumed that the slot counter information 25d of each of the RFID tags 2a to 2f is “2” “1” “3” “0” “5” “2”.

  Of the RFID tags 2a to 2f, only the one with the slot counter information 25d of “0” can respond, and the predetermined information for identification, in this case, the hexadecimal random number 42 (RN16) is generated and transmitted. In the above example, since the slot counter information of the RFID tag 2d is “0”, the hexadecimal random number 42 (RN16) is generated and transmitted. This random number is temporarily stored in the memory unit 25 as random number information 25c. It is assumed that the random number 42 is “0xA12B”, for example.

  The reader / writer 3 receives the random number 42 from the RFID tag 2d via the antenna 3a and the transmission / reception unit 31, and determines that no collision has occurred when the random number 42 can be read normally. Then, an Ack command 43 having the received random number 42 value “0xA12B” as an argument is transmitted to the RFID tag 2d.

  Each of the RFID tags 2 a to 2 f receives the Ack command 43 and determines whether or not the same random number as the value “0xA12B” is stored in the memory unit 25. Here, since only the RFID tag 2d stores the value “0xA12B” as the random number information 25c in the memory unit 25, the RFID tag 2d transmits the identification information 25b stored in the memory unit 25 via the transmission / reception unit 21. Transmit to the reader / writer 3. Thereby, one tag is selected from the RFID tags 2a to 2f.

  The reader / writer 3 receives the identification information 25b of the selected RFID tag 2d by the transmission / reception unit 31 (tag response 44), and stores and accumulates the received identification information 25b as the identification information 34a in the memory unit 34. Thereby, the identification information 25b of the RFID tag 2d is acquired by the reader / writer 3.

Next, the reader / writer 3 transmits the Query Rep command 45 within T seconds after receiving the identification information 25b (tag response 44) by the transmission / reception unit 31. This QueryRep command 45 is also used as the Ack command 43 indicating that the identification information 25b has been normally read by the reader / writer 3 with respect to the RFID tag 2d, and redundant communication is omitted to realize high-speed communication. . This is because the QueryRep command 45 is transmitted within T seconds which is a predetermined time (T2 time in the EPC Class-1 Generation ₂ standard), so that it is easy to specify from the tag communicated immediately before, and the QueryRep command 45 As a substitute for the Ack command 43, redundant commands are omitted.

  When receiving the QueryRep command 45 within T seconds, the control unit 26 of the RFID tag 2d assumes that the identification information 25b has been read normally, sets the read completion flag 25a to read completion, and executes the subsequent read command Even if it is received, it is controlled so as not to respond. For example, the flag formed by 1 bit of the read completion flag 25a is inverted from “0” to “1” and set.

  Thereby, the RFID tags 2a to 2c and the RFID tags 2e and 2f excluding the RFID tag 2d reduce the value of the slot counter information 25d of the memory unit 25 by one by the control unit 26.

  Here, if a reading error occurs when the reader / writer 3 fails to detect a preamble such as a signal for reading synchronization while the identification information 25b is being received by the transmitting / receiving unit 31 (tag response 44), Then, the reception is stopped and the next QueryRep command 45 is retransmitted. As a cause of failure in detecting the preamble, it can be considered that the signal level to be detected is small and it is difficult to distinguish the response signal from other noises, and the malfunction is likely to occur.

  However, this communication operation may cause a problem. That is, when one of the QueryRep commands 45a retransmitted several times from the reader / writer 3 is accidentally received at a regular timing T seconds later, the control unit 26 identifies the identification information 25b. Therefore, the reading completion flag 25a of the memory unit 25 is set to reading completion. In the RFID tag 2d, when the reading completion flag 25a is set to the reading completion, the control unit 26 is controlled so as not to respond to a subsequent reading command transmitted from the reader / writer 3. As a result, there is a problem that the RFID tag 2d remains as an unread tag.

  Therefore, in this embodiment, such a problem is solved as shown in FIG. Note that the same reference numerals as those in FIG. 2B indicate the same or corresponding elements.

  That is, the reader / writer 3 adds the read error information 34b as new information composed of 1 bit to the QueryRep command 48 retransmitted due to a read error. Here, if the reader / writer 3 is unable to read the identification information 25b due to a reading error occurring in the transmission / reception unit 31 during the reception of the identification information 25b (tag response 44), the reader / writer 3 stops receiving at the transmission / reception unit 31. Assume that the next read command, QueryRep command 48, is retransmitted. Then, it is assumed that the RFID tag 2d has received one of the QueryRep commands 48 by chance at a regular timing.

  Even in this case, since the RFID tag 2d has the read error detection unit 24, the read error information 34b added to the QueryRep command 48 is read via the tag antenna unit 20a and the transmission / reception unit 21. Read by the error detector 24. The RFID tag 2d can determine whether or not a reading error of the identification information 25b has occurred on the reader / writer 3 side from the detection result of the reading error detecting unit 24 by the control unit 26. Since the control unit 26 sets the reading completion flag 25a to the reading completion based on the detection result of the reading error detection unit 24, it is possible to prevent the reading completion from being erroneously set to the reading completion.

  Thereby, it is possible to make the response until the identification information 25b of the RFID tag 2d is normally read by the reader / writer 3. As a result, even when an unspecified number of RFID tags exist in the range where the radio waves of the reader / writer 3 reach, unread RFID tags can be eliminated.

  Hereinafter, the operation of the RFID system 1 will be described with reference to FIGS.

  FIG. 3 is a flowchart for explaining the operation of the RFID system 1 according to the embodiment of the present invention, and FIG. 4 is a schematic diagram for explaining the operation of the RFID system 1.

  As shown in FIG. 3, the RFID system 1 transmits a SELECT command from the reader / writer 3 to the RFID tags 2a to 2f, and initializes various registers in the RFID tags 2a to 2f (S100).

  Next, the reader / writer 3 transmits a Query command 41 which is a command for designating the number of time slots (S102). Here, the Q value is designated to “3” by the Query command 41, and the number of time slots in one round is set to “8”. After receiving the Query command 41, the RFID tags 2a to 2f generate random numbers by the random number generation unit 23 of each of the RFID tags 2a to 2f. Assume that the slot counter information is “2”, “1”, “3”, “0”, “5”, and “2”.

  Next, the reader / writer 3 reads the RFID tags 2 in the communication range sequentially from the time slots “1” to “8”.

  Here, since the slot counter information of the RFID tag 2d is “0”, only the RFID tag 2d (denoted as “D” in FIG. 4) responds as shown in FIG. 4 in the first time slot. Then, the reader / writer 3 reads the identification information 25b of the RFID tag 2d (S108). The reader / writer 3 receives the identification information 25b via the transmission / reception unit 31, and stores the identification information 25b in the memory unit 34 as the identification information 34a. Thereby, the identification information 25b of the RFID tag 2d is acquired by the reader / writer 3.

  Returning to FIG. 3, if a reading error occurs in the transmission / reception unit 31 during reception of the identification information 25 b (S 110), the reader / writer 3 creates the reading error information 34 b and temporarily stores it in the memory unit 34 ( S112). If no reading error has occurred in S110, the process proceeds to S116. If there is no response from the RFID tag 2 in S104, the process proceeds to S116. If it is determined in S104 that two or more RFID tags 2 have collided (S106), a NAK (non-approval) command is transmitted (S114), and the process proceeds to S116.

  Next, the reader / writer 3 reads the read error information 34b from the memory unit 34 within T seconds when the identification information 25b is received in S108, or after a predetermined time after a read error occurs in the transmission / reception unit 31, and the QueryRep The read error information 34b is added to the command 48 and transmitted (S116). The RFID tag 2d receives the Query Rep command 48, which is a read command, and reads from the read error information 34b added to the Query Rep command 48 by the read error detection unit 24, and the reading / writing unit 31 on the reader / writer 3 side reads the identification information 25b. Detect whether or not has occurred. Then, the RFID tag 2d sets the reading completion flag 25a to the reading completion after confirming that there is no reading error from the detection result of the reading error detection unit 24 by the control unit 26, and thereafter receives the reading command. Become unresponsive. Thus, since the control unit 26 sets the reading completion flag 25a to the reading completion based on the detection result of the reading error detecting unit 24, it can be prevented that it is erroneously set to the reading completion.

  That is, when a reading error occurs in the transmitter / receiver 31 on the reader / writer 3 side, one of the QueryRep commands 48 that is repeated in 1/10 or less of the time for reading the identification information 25b happens to be the normal timing after T seconds. Even if it is received by the RFID tag 2d, if a reading error is detected by the reading error detection unit 24, the reading completion flag 25a is maintained in the reading incomplete state. Can be prevented.

  Here, since no reading error is detected and the reading completion flag 25a is set to reading completion, the RFID tag 2d is controlled to be non-responsive.

  As a result, the RFID tags 2a to 2c and the RFID tags 2e and 2f excluding the RFID tag 2d reduce the value of the slot counter information 25d of the memory unit 25 by one by the control unit 26, and “1” “0” “2”. “4” and “1”. Then, the time slot is advanced by 1 to “2”.

  In the time slot “2”, the slot counter information 25d of the RFID tag 2b becomes “0”, so that the RFID tag 2b (indicated as “B” in FIG. 4) responds as shown in FIG. 4 (S118). The reader / writer 3 reads the identification information 25b of the RFID tag 2b (S122). The reader / writer 3 receives the identification information 25b via the transmission / reception unit 31, and stores the identification information 25b in the memory unit 34 as the identification information 34a. As a result, the identification information 25b of the RFID tag 2b is acquired by the reader / writer 3.

  Returning to FIG. 3, if a reading error occurs in the transmission / reception unit 31 during reception of the identification information 25 b (S 124), the reader / writer 3 creates the reading error information 34 b and temporarily stores it in the memory unit 34 ( S126). If no reading error has occurred in S124, the process proceeds to S130. If there is no response from the RFID tag 2 in S118, the process proceeds to S130. If two or more RFID tags 2 collide in S120, a NAK (non-approval) command is transmitted (S128), and the process proceeds to S130.

  Next, it is determined whether the time slot is “8”, that is, the end of one round (S130). Here, since the time slot is “2”, S116 to S130 are repeated.

  Next, the reader / writer 3 reads the read error information 34b from the memory unit 34 in the same manner as described above within T seconds when the identification information 25b is received in S122 or when a read error occurs in the transmission / reception unit 31. Then, the read error information 34b is added to the Query Rep command 48 and transmitted (S116). The RFID tag 2b obtains the read error information 34b from the QueryRep command 48 when receiving the QueryRep command 48 which is this read command, confirms that there is no read error, and sets the read completion flag 25a to read complete. Even if a read command is subsequently received, no response is made.

  Then, again by the Query Rep command 48 in S116, the RFID tags 2a and 2c and the RFID tags 2e and 2f except the RFID tags 2d and 2b reduce the value of the slot counter information 25d of the memory unit 25 by one by the control unit 26. , “0” “1” “3” “0”. Then, the time slot number is incremented by 1 to “3”.

  In the time slot “3”, the slot counter information 25d of the RFID tags 2a and 2f is “0”, so as shown in FIG. 4, the RFID tags 2a and 2f (“A” and “F” in FIG. 4). And the identification information 25b is transmitted to the reader / writer 3 via the transmission / reception unit 21 (S112).

  At this time, the reader / writer 3 receives a random number (RN16) which is a predetermined signal from the RFID tags 2a and 2f (S118), but cannot read the random number normally due to the collision of the RFID tags 2a and 2f. The collision number acquisition unit 33 determines that a collision has occurred (S120), transmits a NAK command (S128), and increments an internal counter (not shown) for counting the number of collisions. As a result, the RFID tags 2 a and 2 f do not transmit the identification information 25 b to the reader / writer 3. For this reason, subsequent read commands are also accepted. That is, the reading completion flag 25a is not set to reading completion. Then, the RFID tags 2a and 2f set the slot counter information 25d to a predetermined value that is the maximum value, for example, “32767” that is “7FFF” in hexadecimal, using the QueryRep command 48. Then, the time slot is advanced by 1 to “4”.

  In the time slot “4”, when the QueryRep command 48 is transmitted (S116), the slot counter information of the RFID tags 2a and 2c and the RFID tags 2e and 2f becomes “32767”, “0”, “2”, and “32767”, respectively. Then, by executing S116 to S130 in the same manner as described above, only the RFID tag 2c (indicated as “C” in FIG. 4) responds. Thereafter, similarly, only the RFID tag 2e (denoted as “E” in FIG. 4) responds in the time slot “6”.

  When the time slot is “8”, that is, when one round is completed (S130), after the number of time slots is updated (S132), there is no collision or response from the RFID tag 2 in the time slot in the round. For example, the reading process of the RFID tag 2 is terminated (S134).

  The time slot number is updated based on the number of collisions held in the internal counter of the collision number acquisition unit 33. That is, the number-of-sections specifying unit 32 estimates the number of time slots used in the next round based on the number of collisions.

  If there is a collision or one or more responses from the RFID tag 2 during the round, the process proceeds to the next round. In the example shown in FIG. 4, since the RFID tags 2a and 2f have collided in the time slot “3”, the next second round is executed.

  As shown in FIG. 4, the RFID tags 2a and 2f respond in the same manner as in the first round with the time slot “2” and the time slot “4” in the second round (in FIG. 4, “F”, “ The identification information 25 b is transmitted to the reader / writer 3. Since all collisions and responses from the RFID tag 2 disappear in the time slot of the third round, the reading process of the RFID tag 2 ends at the last time slot “8” of the third round.

  As described above, according to the present embodiment, the RFID system 1 includes the RFID tags 2a to 2f having the tag antenna unit 20a and the tag circuit unit 20b for storing and holding the identification information 25b, and the RFID tags 2a to 2f. A reader / writer 3 having a transmission / reception unit 31 that reads the identification information 25b via the antenna 3a. The reader / writer 3 reads a read command (for example, a Query command 41 or the like) that reads the identification information 25b from the transmission / reception unit 31 via the antenna 3a. If the identification information 25b to be acquired from any one of the plurality of RFID tags 2a to 2f cannot be read due to the occurrence of a read error in the transmission / reception unit 31, after the QueryRep command 48 is transmitted, a read command to be transmitted next Read error (such as QueryRep command 48) It has a configuration for transmitting and receiving unit 31 via the antenna 3a by adding a reading error information 34b indicating the occurrence.

  The RFID tag 2 includes a tag antenna unit 20a and a tag circuit unit 20b that stores and holds identification information 25b. The tag circuit unit 20b sends a reading command transmitted from the reader / writer 3 via the tag antenna unit 20a. A reading / receiving unit 21 for reading, and a reading error detecting unit 24 for determining whether or not a reading error has occurred by determining the reading error information 34b of the identification information 25b added to the reading command read by the transmitting / receiving unit 21; The reader / writer 3 has a reading completion flag 25a indicating information indicating whether or not the reading of the identification information 25b has been completed, and a control unit 26 that sets the reading completion flag 25a based on the determination result of the reading error detection unit 24. When the reading error detection unit 24 detects a reading error, the control unit 26 reads the reading error. When the reading completion flag 25a is set so as to maintain the unread state, the reading error detection unit 24 has not detected a reading error and the reader / writer 3 has finished reading the identification information 25b, the reading is completed. The flag 25a is set to read completion.

  As a result, each RFID tag 2 can respond until the identification information 25b is normally read by the reader / writer 3, so that an unspecified number of RFID tags 2 exist within the range of the radio wave of the reader / writer 3. Even so, the unread RFID tag 2 can be eliminated.

  As described above, according to the present invention, the reader / writer transmits the reading command for reading the identification information from the transmission / reception unit via the antenna, and then transmits the identification information to be read from any one of the plurality of RFID tags. When reading is not possible due to the occurrence of a reading error, reading error information for notifying the occurrence of a reading error is added to the next reading command to be transmitted and then transmitted. Then, the RFID tag determines whether or not a reading error has occurred by determining the reading error information of the identification information added to the reading command. When the reading error has not been detected, the reader / writer reads the identification information. Only when the reading is completed, the reading completion flag is set to reading completion.

  For this reason, the reading completion flag is read and maintained incomplete until the RFID tag identification information is normally read on the reader / writer side, and the tag can be made to respond. Even when an RFID tag is present, the present invention is useful as an RFID system, a reader / writer, and an RFID tag that can eliminate an unread RFID tag.

Schematic diagram of an RFID system according to an embodiment of the present invention (A) is a schematic diagram explaining the communication operation of the RFID system, (b) is a schematic diagram explaining the communication operation of a comparative example with the RFID system. Flow chart for explaining the operation of the RFID system Schematic diagram for explaining the operation of the RFID system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RFID system 2a-2f RFID tag 3 Reader / writer 3a Antenna 4 Management article 20a Tag antenna part 20b Tag circuit part 21, 31 Transmission / reception part 22 Classification assignment part 23 Random number generation part 24 Read error detection part 25, 34 Memory part 25a Reading completion Flags 25b, 34a Identification information 25c Random number information 25d Slot counter information 26, 35 Control unit 32 Division number designation unit 33 Collision number acquisition unit 34b Read error information

Claims (5)

A plurality of RFID tags having a tag antenna unit and a tag circuit unit for storing and holding identification information; and a reader / writer having a transmission / reception unit for reading the identification information from each of the plurality of RFID tags via an antenna;
The reader / writer transmits a reading command for reading the identification information from the transmission / reception unit via the antenna, and then transmits the identification information to be read from any one of the plurality of RFID tags to a reading error of the transmission / reception unit. When reading is not possible due to occurrence, read error information notifying the occurrence of the read error is added to the read command to be transmitted next , and the configuration is transmitted from the transmission / reception unit via the antenna ,
The RFID tag is
A read error detection unit that determines whether or not a read error has occurred by determining the read error information added to the read command;
A read completion flag indicating information indicating whether or not the reading of the identification information has been completed by the reader / writer;
An RFID system comprising: a control unit that sets the reading completion flag based on a determination result of the reading error detection unit . The controller is
When a reading error is detected by the reading error detection unit, the reading completion flag is set so as to maintain a reading incomplete state,
Read error undetected by said read error detection unit, and, if the reading of the identification information by the reader writer is completed, according to claim 1, characterized in that a configuration for setting the read completion flag read complete The described RFID system. The controller is
When the read completion flag indicates unread information, control to respond to the subsequent read command,
3. The RFID system according to claim 2 , wherein when the read completion flag is information indicating completion of reading , the RFID system is controlled so as not to respond to the subsequent read command. 4. The RFID system according to any one of claims 1 to 3, wherein the read error information is 1-bit information. A tag antenna unit and a tag circuit unit for storing and holding identification information;
The tag circuit section is
A transmission / reception unit that reads a reading command transmitted from a reader / writer via the tag antenna unit;
A read error detection unit that determines whether or not a read error has occurred by determining read error information of the identification information added to the read command read by the transmission / reception unit;
A read completion flag indicating information indicating whether or not the reading of the identification information has been completed by the reader / writer;
A control unit that sets the reading completion flag based on the determination result of the reading error detection unit,
The control unit sets the read completion flag so as to maintain a read incomplete state when a read error is detected by the read error detection unit, and a read error is not detected by the read error detection unit. In addition, the RFID tag is configured to set the reading completion flag to read completion when the reading of the identification information is completed by the reader / writer.

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