JP2020079989A - Rfid communication system and control method of rfid communication system - Google Patents

Abstract

To provide an RFID communication system that realizes high-sensitivity and long-distance communication with an RF tag.SOLUTION: A time period in which a specific reader/writer (10A) transmits a signal to an RF tag (40) among a plurality of readers/writers (10A, 10B) includes both of a transmission time period in which the other reader/writer (10B) receives a signal from the RF tag (40) and each of the plurality of readers/writers (10A, 10B) transmits a signal to the RF tag (40), and a reception time period in which a signal is received from the RF tag (40).SELECTED DRAWING: Figure 2

Description

  The present invention relates to an RFID communication system and a control method for the RFID communication system.

  Conventionally, for solid-state management at a manufacturing site or a physical distribution site, data is read and written from an RF tag attached to an individual, and an industrial control device such as a programmable controller (Programmable Logic Controller, hereinafter abbreviated as “PLC”) is used. RFID systems for exchanging data are known.

  In these RFID systems, the transmission distance is limited, and there is a problem that the reliability of data becomes low due to radio wave interference and collision even within the operating range. Therefore, an RFID system provided with a plurality of receiving antennas and a plurality of transmitting antennas is provided in order to realize a sufficient receivable range and specify the position of the RFID even in a large-scale and complicated space. (For example, see Patent Document 1).

Special table 2011-520097 (announced on July 14, 2011)

  By the way, in an RFID system, it is necessary to continue to oscillate radio waves when reading or writing data with an RF tag. However, the radio wave oscillated by itself may adversely affect the signal received from the RF tag as noise.

  As described in Patent Document 1, in a configuration in which the transmitting antenna and the receiving antenna are installed at different positions, in order to prevent the radio wave emitted from the transmitting antenna from affecting the signal received by the receiving antenna, It is necessary to separate the transmission antenna and the reception antenna. In this case, both of these antennas need to be connected to the reader/writer body by a coaxial cable.

  That is, if the transmitting antenna and the receiving antenna are provided separately from each other in this way, there is a problem that the power of the signal transmitted by the coaxial cable is attenuated and the S/N ratio is deteriorated. Further, since the coaxial cable is expensive, there is a problem that the cost increases if the distance between the transmitting antenna and the receiving antenna is increased.

  One aspect of the present invention has been made in view of the above circumstances, and an object thereof is to provide an RFID communication system that realizes highly sensitive and long-distance communication with an RF tag.

  In order to solve the above problems, an RFID communication system according to an aspect of the present invention includes a plurality of reader/writers that perform at least one of reading and writing of data with an RF tag. Among the writers, while the specific reader/writer transmits a signal to the RF tag, another reader/writer receives a signal from the RF tag, and the plurality of reader/writers each send a signal to the RF tag. Is included, and a reception period for receiving a signal from the RF tag is included.

  According to the above configuration, during a period in which a specific reader/writer transmits a signal to the RF tag, another reader/writer receives the signal from the RF tag without oscillating the radio wave by itself. The influence of can be suppressed. Moreover, since it is not necessary to connect at least one of the transmitting antenna and the receiving antenna to the reader/writer main body with a long coaxial cable, high-sensitivity and long-distance communication with the RF tag can be performed without causing signal deterioration. Can be realized.

  Further, in the RFID communication system according to an aspect of the present invention, each of the plurality of reader/writers includes an RW communication control unit that controls communication between the reader/writers, and a signal that switches between the transmission period and the reception period is transmitted. It may be transferred between the plurality of reader/writers via the RW communication control unit.

  According to the above configuration, since the signals for switching the transmission period and the reception period are passed between the plurality of reader/writers, the processing state of another reader/writer is grasped and the transmission period and the reception period are accurately determined. At least one of reading and writing of data can be performed with the RF tag while switching.

  Further, in the RFID communication system according to the aspect of the present invention, the RW communication control unit is configured to perform a transmission indicating the end of the transmission period when the transmission period ends in the reader/writer provided with the RW communication control unit. In addition to outputting the end signal, in the reception period of the reader/writer provided with the RW communication control unit, when the transmission end signal is received, control for starting the transmission period in the reader/writer may be performed. Good.

  According to the above configuration, when the transmission by a specific reader/writer is completed among a plurality of reader/writers, the transmission period in another reader/writer can be started immediately. Therefore, it is possible to efficiently perform at least one of reading and writing of data with the RF tag while switching the transmission period and the reception period between the plurality of reader/writers.

  Further, in the RFID communication system according to an aspect of the present invention, at least one of the plurality of reader/writers includes an upper communication control unit that controls communication with an upper controller, and the upper communication control unit is used. The received instruction from the controller may be shared with another reader/writer via the RW communication control unit.

  According to the above configuration, the upper controller side may transmit/receive data to/from one specific reader/writer among the plurality of reader/writers. Therefore, it is possible to read and/or write data from/to the RF tag by using a plurality of reader/writers without changing the instruction transmitted from the higher-level controller to the RFID communication system. it can.

  Further, in the RFID communication system according to one aspect of the present invention, the reader/writer that has received an instruction to read data from the controller via the upper communication control unit is read from the RF tag by another reader/writer. The data may be merged to create response data, and the response data may be transmitted to the controller.

  According to the above configuration, among the plurality of reader/writers, the reader/writer that receives the instruction from the host controller merges the data read from the RF tags by the plurality of reader/writers to create response data. Therefore, the host controller can perform the same processing as reading data from the RF tag using one reader/writer. Therefore, without changing the flow of processing between the controller and the RFID communication system, at least one of reading and writing of data with the RF tag can be performed using the plurality of reader/writers.

  In order to solve the above problems, a control method for an RFID communication system according to an aspect of the present invention includes a plurality of reader/writers that perform at least one of reading and writing of data with an RF tag. A method for controlling the RFID communication system, wherein a predetermined one of the reader/writer receives an instruction from the host controller to perform at least one of reading and writing of data with the RF tag; A step of sharing the instruction received from the controller by the predetermined one reader/writer with other reader/writers; a transmitting side reader/writer for transmitting a signal to the RF tag between the plurality of reader/writers; Switching to a receiving side reader/writer for receiving a signal from the RF tag.

  According to the above method, another reader/writer that does not oscillate a radio wave receives a signal from the RF tag during a period in which a specific reader/writer transmits a signal to the RF tag. Can be suppressed. Further, since it is not necessary to connect at least one of the transmitting antenna and the receiving antenna to the reader/writer main body with a long coaxial cable, high-sensitivity and long-distance communication with the RF tag can be performed without causing signal deterioration. Can be realized.

  According to one aspect of the present invention, it is possible to provide an RFID communication system that realizes highly sensitive and long-distance communication with an RF tag.

It is a figure which shows typically the system environment using an RFID communication system. It is a block diagram showing the composition of the important section of the RFID communication system concerning an embodiment. It is a figure which shows typically the flow of the signal between a reader/writer and an RF tag. It is a figure which shows an example of the flow of the data between a reader/writer and RF tag at the time of reading data from RF tag. It is a figure which shows an example of the flow of the data between a reader-writer and the RF tag at the time of reading data from an RF tag several times. It is a figure which shows typically the system environment using the RFID communication system of a modification.

  Hereinafter, an embodiment according to one aspect of the present invention (hereinafter, also referred to as “this embodiment”) will be described with reference to the drawings.

§1 Application Example First, an example of a scene to which the present invention is applied will be described with reference to FIG. FIG. 1 is a diagram schematically showing a system environment using the RFID communication system 100 according to the present embodiment.

  As shown in FIG. 1, the RFID communication system 100 includes a plurality of reader/writers 10 (10A, 10B). The RFID communication system 100 is a system for performing at least one of reading and writing of data with an RF tag 40 used for individual management of articles such as parts and products at a production site.

  The RFID communication system 100 performs at least one of reading and writing of data with the RF tag 40 according to a command received from a PLC (Programmable Logic Controller) 50 that is a higher-level device. Further, another reader/writer 10 (eg, reader/writer 10B) receives a signal from the RF tag 40 during a period in which a specific reader/writer 10 (eg, reader/writer 10A) transmits a signal to the RF tag 40. Each of the plurality of reader/writers 10A and 10B includes both a transmission period for transmitting a signal to the RF tag 40 and a reception period for receiving a signal from the RF tag 40.

  As described above, the RFID communication system 100 replaces the unit that transmits a signal to the RF tag 40 between the plurality of reader/writers 10A and 10B with the unit that receives the signal from the RF tag 40, thereby changing the signal received by the transmitted radio wave. The influence of can be suppressed.

§2 Configuration Example Hereinafter, the configuration of the RFID communication system 100 according to the embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. FIG. 1 is a diagram schematically showing a system environment using the RFID communication system 100. FIG. 2 is a block diagram showing a main configuration of the RFID communication system 100.

[Configuration of RFID communication system 100]
As shown in FIGS. 1 and 2, each of the reader/writers 10A and 10B is connected to the PLC 50 by Ethernet (registered trademark) via the switching hub 60. Note that the communication network is not limited to Ethernet, and can be realized by any field network. The reader/writers 10A and 10B perform at least one of reading and writing of data with the RF tag 40 according to a command from the PLC 50.

  Of the reader/writers 10A and 10B, the reader/writer 10 that receives the command from the PLC 50 functions as a master, and the other reader/writers 10 function as slaves. The reader/writer 10 on the master side shares the command from the PLC 50 with the reader/writer 10 on the slave side.

[Configuration of reader/writer 10]
As shown in FIG. 2, the reader/writer 10 includes an upper communication control unit 11 (11A, 11B), an RF communication control unit 20 (20A, 20B), an antenna 25 (25A, 25B), and an RW communication control unit 30 (respectively. 30A, 30B).

  The upper communication control unit 11 controls communication with the PLC 50. The upper communication control unit 11 performs wireless communication with the PLC 50 or wired communication via a bus or a network.

  The reader/writer 10 communicates with the PLC 50 under the control of the host communication controller 11. The upper communication control unit 11 receives a command transmitted from the PLC 50 via the switching hub 60, and performs at least one of reading and writing of data with the RF tag 40 according to the command.

  In the example shown in FIG. 2, each of the plurality of reader/writers 10A and 10B includes the upper communication control unit 11, but at least one of the plurality of reader/writers 10A and 10B includes the upper communication control unit 11. The specific reader/writer 10 provided with the higher-level communication control unit 11 may be configured as a master to integrally control another reader/writer 10. The specific reader/writer 10 that functions as a master may share the command from the controller received via the higher-level communication control unit 11 with another reader/writer 10 via the RW communication control unit 20. ..

  According to these configurations, the PLC 50 needs to recognize that the plurality of reader/writers 10A and 10B cooperate with each other to perform at least one of reading and writing of data with the RF tag 40. Absent. Further, the PLC 50 does not need to know how many reader/writers 10 are used in the RFID communication system 100. As a result, the PLC 50 can transmit an instruction similarly to a general process of reading or writing data with the RF tag 40 by using one reader/writer 10. Therefore, the RFID communication system 100 can be easily incorporated and used in an existing system.

  The antenna 25 realizes data exchange (communication) with the RF tag 40 by radio waves. Under the control of the RF communication control unit 20, the antenna 25 sends out an electromagnetic wave including a command signal to the RF tag 40 and receives a response signal from the RF tag 40 to the command.

  The RF communication control unit 20 sends a command signal to the RF tag 40 and receives a response signal via the antenna 25, and performs at least one of reading and writing of data with the RF tag 40. To do. Note that the RF communication control unit 20 may be an arithmetic device having a function of integrally controlling each unit of the reader/writer 10. The RF communication control unit 20 controls each unit of the reader/writer 10 by executing a program stored in one or more memories (such as RAM and ROM) by one or more processors (such as CPU), for example. You may.

  The RF communication control unit 20 includes a data processing unit 21 (21A, 21B), and the function of the data processing unit 21 causes the host communication control unit 11 to decode the command received from the PLC 50. The commands received from the PLC 50 include a write command that specifies writing of data with the RF tag 40 and a read command that specifies reading of data with the RF tag 40. The write command and the read command include data regarding the data exchange size between the PLC 50 and the reader/writer 10.

  Further, the RF communication control unit 20 uses the function of the data processing unit 21 to convert the data included in the write command received from the PLC 50 into the data writable in the RF tag 40. The RF communication control unit 20 converts, for example, data such as an octal code, a hexadecimal code, and a hexadecimal code included in the write command received from the PLC 50 into ASCII code data.

  Further, the RF communication control unit 20 converts the data read with the RF tag 40 into data transferable to the PLC 50 by the function of the data processing unit 21 as a response to the read command received from the PLC 50. The RF communication control unit 20 converts, for example, the numeric string data read with the RF tag 40 into data such as an octal code, a hexadecimal code, and a hexadecimal code.

  Further, as will be described in detail later, the RF communication control unit 20 merges the data read from the RF tag 40 with the data read from the RF tag 40 by another reader/writer 10 by the function of the data processing unit 21. , PLC 50 to convert the data into data that can be transferred.

  The RW communication control unit 30 controls communication with another reader/writer 10. The RW communication control unit 30 executes wired communication with another reader/writer 10 via a bus or a network. The RW communication control unit 30 is connected to another reader/writer 10 via a communication line that communicates I/O signals. Note that communication with the other reader/writer 10 is also performed via Ethernet via the higher-level communication control unit 11. Details of communication with the other reader/writer 10 will be described later.

  The RW communication control unit 30 shares the command received by the higher-level communication control unit 11 from the PLC 50 with another reader/writer 10. Further, the RW communication control unit 30 shares, with another reader/writer 10, information related to a signal transmitted/received between the RF communication control unit 20 and the RF tag 40. In addition, the RW communication control unit 30 switches other signals for switching between a transmission period in which the RF communication control unit 20 transmits a signal to the RF tag 40 and a reception period in which the RF communication control unit 20 receives a signal from the RF tag 40. It is delivered to and from the reader/writer 10.

  For example, when a specific reader/writer 10 of the plurality of reader/writers 10 includes only the reception period and another reader/writer includes only the transmission period, after the specific reader/writer 10 receives a response from the RF tag 40. However, it is necessary to transmit that fact to another reader/writer 10, and it is not possible to immediately shift to the next signal. In this embodiment, since the transmission period and the reception period are switched between the plurality of reader/writers 10A and 10B, when the plurality of reader/writers 10 receive the response from the RF tag 40, the next transmission is immediately started. You can

[Regarding the flow of I/O signals]
FIG. 3 is a diagram schematically showing a signal flow between the plurality of reader/writers 10A and 10B and the RF tag 40. As shown in FIG. 3, when a specific reader/writer 10A that functions as a master transmits a command to the RF tag 40, another reader/writer 10B that functions as a slave detects the frequency of the transmission signal of the reader/writer 10A. Then, its own PLL (phase locked loop) frequency is adjusted and adjusted to the reader/writer 10A.

  The specific reader/writer 10A continues to transmit a non-modulated wave while the RF tag 40 sends a response to the command sent to the RF tag 40 by itself. The response sent by the RF tag 40 is received by another reader/writer 10B. The reader/writer 10B demodulates the response received from the RF tag 40.

  When the reception of the response from the RF tag 40 by the other reader/writer 10B is completed, the specific reader/writer 10A uses the function of the RW communication control unit 30A to send/receive a transmission/reception switching signal for switching between the transmission period and the reception period. It is transmitted to another reader/writer 10B as a signal. The RW communication control unit 30A transmits a transmission/reception switching signal to another reader/writer 10B as a transmission end signal indicating the end of the transmission period. The specific reader/writer 10A immediately stops the oscillation of the unmodulated wave.

  The I/O signal of the specific reader/writer 10A is ON during the period from the start of command transmission to the stop of oscillation of the unmodulated wave, and the I/O signal of another reader/writer 10B is OFF during this period. Thus, of the plurality of reader/writers 10A and 10B, another reader/writer 10B receives a signal from the RF tag during a period in which the specific reader/writer 10A transmits a signal to the RF tag 40.

  During the reception period in which the response from the RF tag 40 is being received, at the time when the transmission end signal indicating the end of the transmission period is received from the specific reader/writer 10A, another reader/writer 10B starts oscillation and sets the transmission period. Start. The other reader/writer 10B transmits a command to the RF tag 40, and when the command transmission is completed, the RF tag 40 continues to transmit an unmodulated wave while the RF tag 40 transmits a response to the command.

  The response sent by the RF tag 40 is received by the specific reader/writer 10A. The reader/writer 10A demodulates the response received from the RF tag 40. When the reception of the response from the RF tag 40 by the specific reader/writer 10A is completed, the other reader/writer 10B uses the function of the RW communication control unit 30B to output a transmission/reception switching signal for switching the transmission period and the reception period to the specific reader/writer. Send to writer 10A. The RW communication control unit 30B transmits a transmission/reception switching signal to the specific reader/writer 10A as a transmission end signal indicating the end of the transmission period. The other reader/writer 10A immediately stops the oscillation of the unmodulated wave.

  The I/O signal of another reader/writer 10B is ON during the period from the start of command transmission to the stop of oscillation of the unmodulated wave, and the I/O signal of the specific reader/writer 10A is OFF during this period. Thus, of the plurality of reader/writers 10A and 10B, the specific reader/writer 10A receives a signal from the RF tag 40 during a period in which another reader/writer 10B transmits a signal to the RF tag 40.

  As described above, each of the plurality of reader/writers 10A and 10B includes both a transmission period for transmitting a signal to the RF tag 40 and a reception period for receiving a signal from the RF tag 40. Thus, the reader/writer 10 on the transmitting side and the reader/writer 10 on the receiving side can be divided between the plurality of reader/writers 10A and 10B, and the influence of the transmitted radio wave on the received signal can be suppressed. Further, the plurality of reader/writers 10A and 10B can be connected not by an expensive coaxial cable but by an inexpensive Ethernet cable, which can suppress an increase in cost. Furthermore, the problem of signal strength attenuation that occurs when using a long coaxial cable does not occur.

  Further, the RW communication control unit 30A of the specific reader/writer 10A outputs a transmission end signal indicating the end of the transmission period at the end of the transmission period in the reader/writer 10A provided with the RW communication control unit 30A. In the reception period of the reader/writer 10A provided with the RW communication control unit 10A, control is performed to start the transmission period in the reader/writer 10A when the transmission end signal is received.

  In addition, the RW communication control unit 30B of the other reader/writer 10B outputs a transmission end signal indicating the end of the transmission period when the transmission period ends in the reader/writer 10B including the RW communication control unit 30B. In the reception period of the reader/writer 10B provided with the RW communication control unit 10B, control is performed to start the transmission period in the reader/writer 10B when the transmission end signal is received.

  This makes it possible to quickly switch between the transmission period and the reception period between the plurality of reader/writers 10A and 10B. Therefore, when data is read from or written to the RF tag 40 while switching the transmission period and the reception period using the plurality of reader/writers 10A and 10B, a delay may occur in data transmission and reception. Absent.

[Data flow]
FIG. 4 and FIG. 5 are diagrams showing a data flow among the PLC 50, the plurality of reader/writers 10A and 10B, and the RF tag 40. The examples shown in FIGS. 4 and 5 show the case where the communication between the reader/writer 10 and the RF tag 40 is performed in units of 16 bits. Further, although the example shown in FIGS. 4 and 5 shows the flow of the process of reading the data from the RF tag 40, the same flow is applied to the process of writing the data to the RF tag 40.

  As shown in FIG. 4, a specific reader/writer 10A, which functions as a master among the plurality of reader/writers 10A and 10B, issues a read instruction for instructing reading of data from the RF tag 40, by the function of the higher-level communication control unit 11A. , PLC 50. The specific reader/writer 10A transmits a notification indicating that the instruction has been received from the PLC 50 to another reader/writer 10B via Ethernet via the upper communication control unit 11A by the function of the RW communication control unit 10A, and another The instruction from the PLC 50 is shared with the reader/writer 10B.

  Further, when the specific reader/writer 10A receives the instruction from the PLC 50, the function of the RF communication control unit 20A transmits a query requesting a response to the RF tag 40 via the antenna 25A.

  The RF tag 40 transmits a 16-bit random number as a response to the query from the specific reader/writer 10A. The 16-bit random number transmitted from the RF tag 40 is received by another reader/writer 10B. The other reader/writer 10B uses the function of the RF communication control unit 20B to transmit the identification information read command for requesting the identification information to the RF tag 40 using the 16-bit random number received from the RF tag 40.

  The RF tag 40 receives the identification information read command and transmits the identification information as a response. The identification information transmitted from the RF tag 40 is received by the specific reader/writer 10A. The specific reader/writer 10A requests the provision of a handle random number for data handling by using the identification information received from the RF tag 40 by the function of the RF communication control unit 20A.

  The RF tag 40 receives the command for providing the handle random number and transmits the 16-bit handle random number. The handle random number transmitted from the RF tag 40 is received by another reader/writer 10B. The other reader/writer 10B uses the function of the RF communication control unit 20B to transmit a read command requesting data read to the RF tag 40 using the handle random number received from the RF tag 40.

  The RF tag 40 reads 16-bit data from the memory and transmits it as a response to the received read command. The data transmitted from the RF tag 40 is received by the specific reader/writer 10A. The specific reader/writer 10A processes the data received from the RF tag by the function of the data processing unit 21A of the RF communication control unit 20A, and generates response data to be provided to the PLC 50. The specific reader/writer 10A transmits the response data generated by the RF communication control unit 20A to the PLC 50 by the function of the upper communication control unit 11A.

  As shown in FIG. 5, when the size of the data read from the RF tag 40 is larger than the data unit that can be read in one communication, the plurality of reader/writers 10A and 10B switch between the transmission period and the reception period. Meanwhile, the data is read from the RF tag 40 a plurality of times. The plurality of reader/writers 10A and 10B transmits a read command to the RF tag 40 during the transmission period after the inventory phase of passing the random number, the identification information, and the handle random number to and from the RF tag 40.

  In the example shown in FIG. 5, a read command is transmitted to the RF tag 40 from the reader/writer 10B different from the specific reader/writer 10A that has received the read instruction from the PLC 50. The RF tag 40 reads 16-bit data from the memory and transmits it as a response to the received read command. The data transmitted from the RF tag 40 is received by the specific reader/writer 10A in the reception period.

  Subsequently, the transmission period and the reception period are switched between the reader/writers 10A and 10B, and a read command is transmitted from the specific reader/writer 10A to the RF tag 40. The RF tag 40 reads 16-bit data from the memory and transmits it as a response to the received read command. The data transmitted from the RF tag 40 is received by another reader/writer 10B in the reception period.

  The read instruction received by the specific reader/writer 10A from the PLC 50 includes information regarding the capacity of the data read from the RF tag 40. The specific reader/writer 10A detects the number of times the read command is transmitted to the RF tag 40 based on the instruction received from the PLC 50 by the function of the data processing unit 21 of the RF communication control unit 20A, and another reader/writer 10B. And the information regarding the number of times the read command is transmitted to the RF tag 40.

  The plurality of reader/writers 10A and 10B read the data of the capacity corresponding to the read instruction received from the PLC 50 from the RF tag 40, and then the specific reader/writer 10A that receives the read instruction from the PLC 50 provides the PLC 50 with the read instruction. Generate response data. The specific reader/writer 10A receives the data received by the other reader/writer 10B from the RF tag 40, from the other reader/writer 10B via the Ethernet via the upper communication controller 11A by the function of the RW communication controller 30A. To do.

  The specific reader/writer 10A merges the data received from the RF tag 40 and the data received from another reader/writer 10B by the function of the data processing unit 21 of the RF communication control unit 20A to create response data. The specific reader/writer 10A transmits the created response data to the PLC 50 by the function of the upper communication control unit 11A.

  As described above, among the plurality of reader/writers 10, the specific reader/writer 10A that has received the read instruction from the PLC 50 receives the data received from the RF tag 40 during its own reception period and the other reader/writer 10B receives the RF during the reception period. The data received from the tag 40 is merged to create response data, and the response data is transmitted to the PLC 50. As a result, even if a plurality of reader/writers 10 are used, communication between the PLC 50 and the specific reader/writer 10 does not become complicated, and there is a delay in data read or write processing with the RF tag 40. It never happens.

[Structure of RFID Communication System 200 of Modification]
FIG. 6 is a diagram schematically showing a system environment in which the RFID communication system 200 of the modified example is used. In the RFID communication system 100 described above, two reader/writers 100A and 100B are used to alternately switch the transmission period and the reception period, and at least one of reading and writing of data with the RF tag 40 is performed. The example to do was explained. However, the present invention is not limited to this, and the RFID communication system 200 may be configured to include a plurality of reader/writers 10A, 10B, 10C,...

  In the RFID communication system 200, one reader/writer among the plurality of reader/writers 10A, 10B, 10C,... 40 receives the signal. Further, each of the plurality of reader/writers includes both a transmission period for transmitting a signal to the RF tag 40 and a reception period for receiving a signal from the RF tag 40.

  Of the plurality of reader/writers 10A, 10B, 10C... Of three or more, the reader/writer 10 that has received the instruction from the PLC 50, or the specific reader/writer 10 including the upper communication control unit 11 functions as a master, The plurality of reader/writers 10 may function as slaves. The reader/writer 10 functioning as a master merges the data read by the reader/writer 10 from the RF tag 40 with another reader/writer 10 to read the data from the RF tag 40 and merges the data to generate response data, which is transmitted to the PLC 50. To do.

[Example of software implementation]
The control block of the reader/writer 10 (particularly, the host communication control unit 11, the RF communication control unit 20, and the RW communication control unit 30) is realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like. It may be realized by software.

  In the latter case, the reader/writer 10 includes a computer that executes the instructions of a program that is software that realizes each function. The computer includes, for example, one or more processors and a computer-readable recording medium that stores the program. Then, in the computer, the processor reads the program from the recording medium and executes the program to achieve the object of the present invention. As the processor, for example, a CPU (Central Processing Unit) can be used. As the recording medium, a "non-transitory tangible medium" such as a ROM (Read Only Memory), a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used. A RAM (Random Access Memory) for expanding the program may be further provided. Further, the program may be supplied to the computer via any transmission medium (communication network, broadcast wave, or the like) capable of transmitting the program. Note that one aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

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

10 (10A, 10B, 10C) Reader/Writer 11 (11A, 11B) Upper communication control unit 20 (20A, 20B) RF communication control unit 21 (21A, 21B) Data processing unit 25 (25A, 25B) Antenna 30 (30A, 30B) RW communication control unit 50 PLC (upper device)
40 RF tag

Claims (6)

A plurality of reader/writers for reading and/or writing data with the RF tag,
While a specific reader/writer of the plurality of reader/writers transmits a signal to the RF tag, another reader/writer receives a signal from the RF tag,
The RFID communication system, wherein each of the plurality of reader/writers includes both a transmission period for transmitting a signal to the RF tag and a reception period for receiving a signal from the RF tag. Each of the plurality of reader/writers includes an RW communication control unit that controls communication between the reader/writers.
The RFID communication system according to claim 1, wherein a signal for switching between the transmission period and the reception period is transferred between the plurality of reader/writers via the RW communication control unit. The RW communication control unit,
At the time when the transmission period ends in the reader/writer provided with the RW communication control unit, a transmission end signal indicating the end of the transmission period is output, and
The RFID communication system according to claim 2, wherein control is performed to start a transmission period in the reader/writer when the transmission end signal is received in the reception period of the reader/writer provided with the RW communication control unit. .. At least one of the plurality of reader/writers is
An upper communication control unit that controls communication with an upper controller is provided, and an instruction from the controller received via the upper communication control unit is transmitted to another reader/writer via the RW communication control unit. The RFID communication system according to claim 2, which is shared by the RFID communication system.   The reader/writer that has received an instruction to read data from the controller via the higher-level communication control unit merges the data read from the RF tag by another reader/writer to create response data, and the response data Is transmitted to the controller, the RFID communication system according to claim 4. A method for controlling an RFID communication system, comprising: a plurality of reader/writers for reading and/or writing data from/to an RF tag,
A predetermined one of the reader/writers receives an instruction from the host controller to read and/or write data from/to the RF tag;
Sharing the instruction received by the one predetermined reader/writer from the controller with a plurality of other reader/writers;
Switching between a transmission side reader/writer that transmits a signal to the RF tag and a reception side reader/writer that receives a signal from the RF tag between a plurality of the reader/writers;
A method for controlling an RFID communication system including the following.

Images