JP2008092262A - Mobile object identification device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile object identification device with which communication with a mobile object to which an IC tag is attached is possible in a wide area by switching a plurality of antennas and the communication is performed even when the mobile object moves at high speed. <P>SOLUTION: In the mobile object identification device which performs radio communication with the IC tag attached to the object 15 by a reader/writer 30 having the plurality of antennas 11, 12, 13, 14 arranged in the moving direction of the object 15, the radio communication is performed by an ASK signal comprised of binary of a high level value and a low level value, obtained by performing amplitude modulation of carrier wave by communication data and a means for sequentially switching the plurality of antennas to the moving directions of the object 15 following movement of the object 15 when the ASK signal is at the low level value is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an RFID system using an IC tag, and more particularly to a mobile object identification device that performs wireless communication with an IC tag attached to a mobile object by a reader / writer having a plurality of antennas.

  In recent years, a mobile unit identification device that performs identification management of a mobile unit attached with an IC tag by transmitting and receiving information by wireless communication between an IC tag having an antenna and a silicon chip storing individual information and a reader / writer, It is being put into practical use in various fields such as production lines, distribution, transportation, and medical care. In an RFID system using such an IC tag, power is transmitted from a reader / writer to the IC tag and information is transmitted and received. In addition to reading the identification information recorded on the individual, new information is recorded on the individual. An example of such a mobile object identification device is shown in Patent Document 1 below.

  The demand for these systems continues to increase as their practical use progresses. Above all, the requirement for expansion of the communication distance and communication range is important in that if it can be realized, it becomes one solution to remove various restrictions related to the operation of this system. However, this is not easy because the transmission power of the reader / writer is limited by the Radio Law. For this reason, a reader / writer having a plurality of antennas is prepared, the plurality of antennas are arranged at predetermined positions in the area where the moving body moves, and the communication distance and the communication range are switched by switching the antenna for transmitting and receiving according to the movement of the moving body. The method of enlarging is conventionally performed.

  However, the conventional antenna switching is performed after transmission of an interrogation signal from the reader / writer or until communication between the reader / writer and the IC tag is once completed. In other words, since the antenna is switched at the break of the communication command issued from the reader / writer, for example, in an identification apparatus for an object that moves at high speed on a production line or the like, when trying to communicate with an IC tag attached to a moving object, the one Since sufficient communication time in the communication area of the two antennas cannot be obtained, communication may not be completed.

  FIG. 3A is a diagram illustrating an example of a system configuration of a production line using a conventional mobile object identification device. In this example, the object 15 is identified by wireless communication between the object 15 to be identified with the IC tag that moves at high speed by the belt conveyor 16 and the reader / writer 10 having a plurality of antennas arranged in the moving direction. In some cases, information is written. An antenna 11, an antenna 12, an antenna 13, and an antenna 14 respectively connected to the main body portion 17 of the reader / writer 10 are sequentially arranged along the belt conveyor 16. When the antenna 11 communicable area is area 1, the antenna 12 communicable area is area 2, the antenna 13 communicable area is area 3, and the antenna 14 communicable area is area 4. The antennas are installed so that the communicable areas overlap with each other so that an incommunicable area does not occur. Although not shown, the reader / writer 10 is connected to a host computer and controlled. For example, communication is started by sensing the object 15 attached with the IC tag, which is transferred by the belt conveyor 16, by means such as an infrared sensor and controlling the reader / writer 10 by the host computer accordingly.

  FIG. 3B is a diagram showing two examples of exchange of interrogation signals and response signals between the reader / writer 10 and the IC tag and antenna switching timing, and the operation will be described along these switching examples.

  In FIG. 3B, switching example 1 assumes a case where the belt conveyor 16 transfers at a relatively slow speed. The relatively slow speed means a speed at which the operation described below is reliably performed. First, by means of the infrared sensor or the like, an interrogation signal is transmitted from the reader / writer 10 at the same time as the object 15 with the IC tag attached enters the area 1 which is the communicable area of the antenna 11, and the above-mentioned area 1 A response signal to the question signal is sent from the IC tag attached to the object 15, and a set of operations of the first question and response is completed in the area 1. The interrogation signal from the further reader / writer 10 is transmitted from the antenna 12 while the object 15 is located in the overlapping area of the communicable area 1 of the antenna 11 and the communicable area 2 of the antenna 12. The response signal to the interrogation signal transmitted from the antenna 12 is completed while the object 15 is in the area 2.

  As described above, the system operation of this example is completed by repeating the question and response in each communication area of each antenna. In this figure, four antennas are installed, but the operation is possible if there are two or more antennas. In some cases, information is written to the IC tag by a reader / writer.

  The switching example 2 in FIG. 3B assumes a case where the belt conveyor 16 transfers relatively quickly. Unlike the switching example 1, the comparatively fast transfer speed is a case where a set of operations of questions and responses is not completed in one area, and details are as follows. As in the switching example 1, the interrogator 15 transmits an interrogation signal from the reader / writer 10 at the same time as the object 15 with the IC tag attached enters the area 1 which is the communicable area of the antenna 11 by means of the infrared sensor or the like. . In this example, since the transfer speed of the belt conveyor 16 is fast, the passing time within the communicable area of the antenna 11 is short, that is, in the area 1, only the question signal is communicated. The response signal with respect to the question signal is a question that has the continuity by switching the antenna 11 and the antenna 12 in synchronization with the timing at which the object 15 is in the position where the area 1 and the area 2 overlap and the question and the response are switched. The response operation is performed.

  Further, when the next question is required, when the object 15 is in a position where the area 2 and the area 3 overlap each other, the antenna 12 is switched to the antenna 13 and the question signal is transmitted in the area 3. The system operation is completed by repeating the above operation.

  As described above, the communicable area is widened by operating the reader / writer having a plurality of antennas as described above.

JP 2002-216092 A

  However, in the above-described conventional example, the timing for switching the antenna needs to be performed at the time of communication state separation, that is, the time between the interrogation signal and the response signal, or the time when there is no interrogation signal or response signal. This is because the signal is interrupted at the moment of switching the antenna. Furthermore, in order to secure the time required for one communication, the time when the object 15 passes through the area where the communicable areas of the two antennas overlap and the time when the interrogation signal and the response signal at the antenna switching timing are switched. Must match or be within a certain close time range.

  Because of this limitation, the conventional mobile unit identification device communicates with an IC tag attached to an object that moves at a high speed enough to exceed one antenna communicable area during question signal transmission or response signal transmission. There was a problem that could not.

  Therefore, an object of the present invention is to enable communication with a moving object with an IC tag in a wide area by switching a plurality of antennas, and also when the moving object moves at high speed. Is to provide a mobile identification device.

  In order to solve the above-described problem, a mobile object identification device according to the present invention performs wireless communication with an IC tag attached to an object to be identified by a reader / writer having a plurality of antennas arranged in the moving direction of the object to be identified. In the mobile identification device to perform, the wireless communication is performed by an ASK signal composed of two values of a high level value and a low level value in which a carrier wave is amplitude-modulated by communication data, and the ASK signal has a low level value. The apparatus further comprises means for sequentially switching a plurality of antennas in the moving direction following the movement of the identified object.

  A timing signal for switching the plurality of antennas may be extracted from the communication data.

  In addition, a position sensor that detects the position of the identified object may be installed, and the plurality of antennas may be switched by a signal from the position sensor and the timing signal.

  As described above, according to the present invention, in the mobile unit identification device capable of widening the communicable area by switching a plurality of antennas, the conventional limitation on the antenna switching timing of the reader / writer is eliminated, and the reader / writer Communication data is converted into an ASK modulated signal so that the antenna can be switched regardless of the transmission timing of the interrogation signal or the response signal from the IC tag, and the ASK modulated signal has a low level value. By switching the antenna at the time, the antenna can be switched regardless of the timing of the communication between the question and the response.

  As described above, in the mobile object identification device of the present invention, the antenna can be switched at an arbitrary timing even during transmission and reception. It is possible to remove the limitation that was the problem in communication with the IC tag. For example, even when a communication area covered by one of the plurality of antennas passes during transmission of an arbitrary communication command such as an interrogation signal, it is possible to switch to the antenna of the next area. A system can be constructed in consideration of only the positional relationship between the antenna communicable area and the IC tag, regardless of the speed, transmission of communication commands, and reception time.

  Therefore, according to the present invention, a movable body capable of communicating with a moving object with an IC tag in a wide area by switching a plurality of antennas and capable of communicating even when the moving object moves at high speed. An identification device is obtained.

  Fig.1 (a) is a figure which shows an example of the system configuration | structure of the production line by the mobile body identification device which is one embodiment of this invention. Similar to the conventional system of FIG. 3, wireless communication between the object 15, which is an identification object attached with an IC tag that moves at high speed by the belt conveyor 16, and the reader / writer 30 having a plurality of antennas arranged in the moving direction thereof. The object 15 is identified by. An antenna 11, an antenna 12, an antenna 13, and an antenna 14 connected to the main body 18 of the reader / writer 30 are sequentially arranged along the belt conveyor 16. As in FIG. 3, the communication areas of the antennas 11, 12, 13, and 14 are area 1, area 2, area 3, and area 4, respectively, and adjacent antennas have no blank area in the communication area. The communication areas are installed so as to overlap each other. The reader / writer 30 is connected to the host computer 20 and controlled. An infrared sensor 21 that detects the object 15 is installed at the entrance of the first area 1.

  FIG. 2 is a diagram illustrating an example of a configuration for explaining the modulation function portion and the antenna switching function portion of the reader / writer 30. An RF carrier that is a carrier wave is converted into an ASK signal that is amplitude-modulated by communication data in the modulator 24. Converted. The communication data is also input to the controller 22 for controlling the antenna switch 23 to extract a timing signal, and the antennas 11, 12, 13, and 14 connected to the antenna switch 23 have low ASK signals. For example, at a timing indicated by a broken line (indicated by a downward arrow). In this figure, the vertical axis of the RF carrier and ASK signal is voltage.

  FIG. 1B is a diagram showing an example of the exchange of interrogation signals and response signals between the reader / writer 30 and the IC tag of the mobile unit identification apparatus according to the present embodiment and the switching timing of the antenna. The operation will be described. At the same time that the object 15 enters the communicable area 1 of the antenna 11, it is detected by the infrared sensor 21, and the signal sent from the infrared sensor causes the host computer 20 to move to the reader / writer 30 and the object 15 to be communicated to the communicable area. Notify that it has been transferred and start sending commands.

  In this example, the transfer speed of the belt conveyor 16 is very high, and the object 15 exceeds the communicable area 1 of the antenna 11 while the interrogation signal from the reader / writer 30 is being transmitted. However, in this example, the antenna can be switched and operated without affecting the interrogation signal even during interrogation signal transmission. As shown in the timing chart shown in the lower part of FIG. 1B, the operation is interrupted by switching the antenna from the antenna 11 to the antenna 12 at a time when the ASK signal existing between the frames in the communication data is at a low level. The question signal is transmitted without any problem. In this figure, the vertical axis of the ASK signal is power. This is because the low level state of the ASK signal is a state in which the radio signal power is equal to or lower than the threshold value, and no error occurs in detection even if the radio power is further reduced by switching the antenna at this time. Usually, the communication data rate is about several tens to several hundreds kHz, so the duration of the low level state of the ASK signal is about several μs to several tens μs or more, and it is sufficiently possible to switch the antenna during this period. It is.

  The response signal from the IC tag is also an ASK signal, and can be similarly switched from the antenna 12 to the antenna 13 at the time when the response signal is in a low level state. Since the relationship between the generation of the interrogation signal and the reception time of the response signal is determined, the switching timing can also be determined from the communication data.

  As described above, according to the present invention, it is possible to switch the antenna without being limited by the timing of the transmission / reception break of the reader / writer by switching the antenna switching timing within the time when the ASK signal is at a low level. did. Therefore, regardless of the communication timing, if the communicable area through which the object 15 as the communication partner is passing can be grasped, the operation can be performed without worrying about the interruption of the communication by the antenna switcher.

  Further, the position of the object 15 can be grasped once the time to enter the antenna communicable area 1 is grasped by the infrared sensor 21 as in this example, the speed of the belt conveyor 16 and the time after passing the infrared sensor 21. It can be grasped from the progress, and it is possible to switch to the time when the communicable area 1 and communicable area 2 overlap and the ASK signal is at a low level. Although not shown, it is possible to install an infrared sensor at the end of the communicable area of each antenna and switch the antenna by detecting that the object 15 has been transferred to the communicable area of each antenna. It is.

  Further, in this embodiment, the number of antennas to be switched is four, but it is obvious that the same effect can be obtained if there are two or more antennas.

FIG. 1A is a diagram showing an example of a system configuration of a production line by a mobile object identification device according to an embodiment of the present invention. FIG. 1B is a diagram showing an example of the exchange of interrogation signals and response signals between the reader / writer and the IC tag of the mobile object identification device according to the present embodiment and the switching timing of the antenna. The figure which shows an example of the structure for demonstrating the modulation function part and antenna switching function part of the reader / writer of this Embodiment. FIG. 3A is a diagram showing an example of a system configuration of a production line using a conventional mobile object identification device. FIG. 3B is a diagram showing two examples of exchange of question signals and response signals between the conventional reader / writer and the IC tag and antenna switching timing.

Explanation of symbols

10, 30 Reader / writer 11, 12, 13, 14 Antenna 15 Object 16 Belt conveyor 20 Host computer 21 Infrared sensor 17, 18 Main unit 22 Controller 23 Antenna switch 24 Modulator

Claims (3)

  In a mobile object identification device that performs wireless communication with an IC tag attached to the object to be identified by a reader / writer having a plurality of antennas arranged in a moving direction of the object to be identified, the wireless communication uses a communication data as a carrier wave. Performed by an amplitude-modulated ASK signal consisting of a high level value and a low level value, and when the ASK signal has a low level value, the plurality of antennas follow the movement of the identified object. A moving body identification device comprising means for sequentially switching in a direction.   The mobile object identification device according to claim 1, wherein a timing signal for switching the plurality of antennas is extracted from the communication data.   The mobile object identification device according to claim 2, wherein a position sensor that detects a position of the identified object is installed, and the plurality of antennas are switched by a signal of the position sensor and the timing signal.

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