JP2010145328A - System and method for detection of object, and tag communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system and method for detection of objects, and a tag communication apparatus, capable of inexpensively, reliably detecting the positions of the objects such as an unspecified, large number of people and objects without making them carry an RFID tag. <P>SOLUTION: When detecting the positions of objects D through the use of a tag communication device 1A, a plurality of RFID tags 2 are installed to an communicable area A of the tag communication device 1A, and the ID of each RFID tag 2 is related to its location information and stored in a table. On the basis of results of communication from the tag communication device 1A to each RFID tag 2, uncommunicable RFID tags are detected. Thereby, the location information corresponding to the ID of detected RFID tags is obtained from the table. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides an object detection system, an object detection method, and a tag that are suitable for detecting the position, size, and shape of an object at low cost without giving an RFID tag to an unspecified number of people and objects. The present invention relates to a communication device.

  In a large-scale store such as a department store, there is a case where it is desired to know the number and position of customers on each floor in order to grasp how many customers are concentrated on which floor. In this case, a method of knowing the number and positions of customers using an RFID tag can be considered.

  For example, in order to know the number of customers, a tag communication device is installed in a place where the entire floor can be seen, such as the ceiling of the floor, and the customer carries the RFID tag. If the number of RFID tags is counted, the number of customers is obtained. Therefore, by communicating between the tag communication device and the RFID tag, the ID stored in the RFID tag is read by the tag communication device and counted. Conceivable. In addition, in order to know the position of the customer, it is only necessary to measure the distance and direction from the tag communication device to the RFID tag held by the customer and to express the customer's position as a vector, so between the tag communication device and the RFID tag. A method of measuring the distance and direction by communicating with each other can be considered.

  However, the method using the RFID tag as described above is complicated because it is necessary to carry an RFID tag to an unspecified number of people. In addition, depending on how the RFID tag is held, communication between the tag communication device and the RFID tag may not be possible, and there is a problem in that it is impossible to accurately detect the number and position of customers.

  Patent Document 1 discloses a system for detecting the position of an article. This system uses a radio signal from a radio tag (42) attached to an article (43) to be managed and a radio signal from a radio tag (41) arranged at a specific reference position. The position of the article (43) is detected.

  However, in the system of Patent Document 1, in order to detect the position of the article (43), the wireless tag (42) must be attached to the article (43). Therefore, if the number and position of customers are detected using this system, the customer must carry the wireless tag (42) instead of the article (43). The same problem as the method of knowing.

  Patent Document 2 also discloses a system for detecting the position of an article. In this system, a target area such as a floor surface on which wireless tags (TGs) are scattered is scanned by a reader (1) installed on a ceiling or the like. Then, when a position ID (SP) representing specific position data is selected from the wireless tag (TG) group based on the detection result of the reader 1, communication with the position ID (SP) is blocked by an object. , It is detected that there is an object in the area including the position ID (SP).

  However, since the system of Patent Document 2 adopts a configuration in which the position ID (SP) is selected from the wireless tag (TG) group, a large number of wireless tags are arranged around the wireless tag selected as the position ID (SP). A tag (TG) is required, and the entire system must be expensive. Further, every time the target area of scanning by the reader (1) changes, it is necessary to re-execute the above-described position ID selection step, which is troublesome. Furthermore, it is also assumed that communication between the wireless tag (TG) and the reader (1) is blocked by an object during the execution of the position ID selection step. In this case, since it becomes impossible to select the position ID (SP), there is a problem that it is impossible to detect an object existing in the area including the position ID (SP).

JP 2003-185730 A

JP 2005-228292 A

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to ensure the position of an object at low cost without giving an RFID tag to an object such as an unspecified number of people or objects. It is another object of the present invention to provide an object detection system, an object detection method, and a tag communication device that can detect the size and shape of the object.

  In order to achieve this object, an object detection system according to the present invention includes a tag communication device, a plurality of RFID tags, a table that stores each RFID tag and its position information in association with each other, and the tag communication device. From the result of attempting to communicate with each RFID tag, a first processing unit that detects an RFID tag that cannot communicate, and position information corresponding to the RFID tag detected by the first processing unit is acquired from the table. And a second processing unit.

  The object detection system according to the present invention may employ a configuration including a third processing unit that outputs the position information acquired by the second processing unit as the position of the object.

  In the object detection system according to the present invention, a configuration having a fourth processing unit that detects the shape or size of an object from the position information acquired by the second processing unit may be employed.

  In the object detection system according to the present invention, the first and second processing units include a fifth processing unit that detects an RFID tag that cannot communicate in time series, acquires position information, and detects a locus of the object. A configuration can also be adopted.

  In the object detection system according to the present invention, a plurality of the tag communication devices exist, and an RFID tag that cannot communicate is detected based on a result of attempting to communicate with each of the RFID tags from a plurality of tag communication devices. It can also be configured.

  In the object detection system according to the present invention, the antenna of the tag communication device may be a beam scan antenna.

  An object detection method according to the present invention is an object detection method for detecting an object using a tag communication device, a plurality of RFID tags, and a table in which each RFID tag and its position information are stored in association with each other. An RFID tag that cannot communicate is detected from a result of attempting to communicate with each RFID tag from the tag communication device, and position information corresponding to the detected RFID tag is obtained from the table.

  In the object detection method according to the present invention, the acquired position information may be output as the position of the object.

  In the object detection method according to the present invention, the shape or size of the object may be detected from the acquired position information.

  In the object detection method according to the present invention, an RFID tag that cannot communicate in time series may be detected, position information may be acquired, and a locus of the object may be detected.

  In the object detection method according to the present invention, there may be a plurality of the tag communication devices, and an RFID tag that is unable to communicate may be detected based on a result of attempting to communicate with each of the RFID tags from a plurality of tag communication devices. .

  In the object detection method according to the present invention, the antenna of the tag communication device may be a beam scan antenna.

  The tag communication device according to the present invention holds a table in which a plurality of RFID tags and their position information are stored in association with each other, and from the result of attempting to communicate with the plurality of RFID tags, the RFID tag that cannot communicate And position information corresponding to the detected RFID tag is acquired from the table.

  In the present invention, the term “object” includes all objects and people that block communication with RFID tags, such as luggage and vehicles.

  In addition, the “RFID tag” does not have a power source such as a battery, for example, and a circuit is operated by power transmitted from a tag communication device such as an RFID reader / writer by radio waves, so that wireless communication with the tag communication device is possible. And an active type RFID tag having a power source such as a battery.

  The “tag communication device” includes, for example, an RFID reader / writer that can read / write data from / to the RFID tag and an RFID reader that only reads data from the RFID tag.

  The “beam scan antenna” is an antenna having a strong directivity obtained by narrowing a radio wave beam, and is an antenna capable of electronically controlling the radio wave directivity.

  According to the present invention, a plurality of RFID tags are installed in the communicable area of the tag communication device, the RFID tag and its position information are stored in a table in association with each other, and communication is attempted from the tag communication device to each RFID tag. From the result, a configuration was adopted in which RFID tags that cannot communicate were detected, and position information corresponding to the detected RFID tags was obtained from the table. For this reason, when communication between the tag communication device and the RFID tag is blocked by placing an object in the communicable area of the tag communication device, detection of the RFID tag that cannot communicate and acquisition of position information are performed. Because the position of the object that is blocking the communication can be found from the acquired position information, it is possible to reliably detect the position of the object inexpensively without giving an RFID tag to an object such as an unspecified number of people or luggage. it can.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an explanatory diagram of an object detection system according to the first embodiment of the present invention.

<Basic method and equipment configuration of object detection system>
The object detection system S1 detects an object D (including a person) using one tag communication device 1A, and includes one tag communication device 1A shown in FIG. 1 and the tag communication device 1A. A plurality of RFID tags 2 installed in the communicable area A and a system computer 3 that controls and controls the entire system.

<Detailed description of tag communication device>
The tag communication device 1A is composed of an RFID reader / writer or an RFID reader, and transmits an interrogation wave to the RFID tag 2 based on a command from the system computer 3 or a response wave from each RFID tag 2 to the interrogation wave. For example, communication with all RFID tags 2 is attempted.

  When the tag communication device 1A attempts to communicate with the RFID tag 2 and receives the response wave, the tag communication device 1A transmits the ID of the RFID tag included as data in the response wave to the system computer 3 as a communication record. To do.

  In the object detection system S1, the tag communication device 1A is installed on the ceiling of the room, and the communicable area of the tag communication device 1A is set on the floor of the room. This is to detect the object D placed on the floor.

<Detailed description of RFID tag>
The plurality of RFID tags 2 are all installed in the communicable area A of the tag communication device 1A. In this object detection system S1, the floor of the room is set in the communicable area A of the tag communication device 1A as described above, and the object D placed on the floor is detected. Embedded in the floor. The RFID tags 2 to be embedded are spread with a density that can detect the location of the object D. Hereinafter, an example in which the RFID tag 2 is embedded in a floor or wall of a room will be described. However, the RFID tag 2 may be configured to be affixed to the floor, wall, or other object.

  Each of the RFID tags 2 communicates with the tag communication device 1A, such as receiving an interrogation wave from the tag communication device 1A or transmitting a response wave to the interrogation wave to the tag communication device 1A. It has a general structure for performing (transmission / reception), and the response wave includes its own ID of the RFID tag. That is, each RFID tag 2 is configured to transmit a response wave including its own ID when receiving the interrogation wave from the tag communication device 1A.

<Detailed explanation of system computer>
The system computer 3 is composed of a personal computer or the like that can communicate with the tag communication device 1A, and stores a table T shown in FIG. 2 in a storage device such as an internal or external hard disk (not shown).

  The table T in FIG. 2 associates the IDs of all the RFID tags 2 used in the object detection system S1 (all RFID tags 2 embedded in the floor in the example of FIG. 1) with the position information on a one-to-one basis. It is stored. The position information of the RFID tag 2 specifies the place where the RFID tag 2 is embedded in the floor in the example of FIG. As this position information, for example, information expressed in XY plane coordinates with the center point or corner portion of the floor as the origin can be adopted.

In addition, the system computer 3 controls and controls the entire object detection system S1, and at least detects the RFID tag 2 that cannot communicate from the result of attempting to communicate with each RFID tag 2 from the tag communication device 1A. The first processing unit, the second processing unit that acquires position information corresponding to the ID of the RFID tag 2 detected by the first processing unit from the table T in FIG. 2, and the position acquired by the second processing unit It is configured to function as a third processing unit that outputs information as the position of an object. These functions are realized by the system computer 3 including a program or a circuit that executes processes shown in the following (1) to (4).
(1) A process of receiving a communication record with the RFID tag 2 from the tag communication device 1A (result of an attempt to communicate with each RFID tag 2 from the tag communication device 1A).
(2) A process of detecting an RFID tag that cannot communicate based on the communication record.
(3) Processing for acquiring position information corresponding to the ID of an RFID tag that cannot communicate from the table T in FIG.
(4) A process of outputting the acquired position information as a position of the object to a monitor or the like.

<Method to detect RFID tags that cannot communicate>
When communication with the RFID tag 2 is impossible, the ID cannot be acquired from the RFID tag 2, so the ID of the RFID tag 2 that cannot be communicated is sent from the tag communication device 1 A to the system computer 3 as a communication record. There is no. Accordingly, the communication record of the tag communication device 1A sent to the system computer 3 is necessarily the ID of the RFID tag 2 that can be communicated.

  On the other hand, the system computer 3 grasps the IDs of all the RFID tags 2 used in the object detection system S1 without omission by referring to the table T in FIG.

  Therefore, the system computer 3 can extract all IDs sent as communication records from the table T in FIG. 2 after completing the reception of the communication records from the tag communication device 1A (procedure 1), and finally extract them. The RFID tag specified by the remaining ID is detected as an RFID tag that cannot communicate (procedure 2).

  In the above-described detection method, when all IDs in the table T are extracted, it means that the RFID tag 2 that cannot communicate is zero. On the other hand, of all IDs in the table T, for example, No. 1 and No. 2 could not be extracted, No. 2 identified by each ID is extracted. 1 and No. This means that the RFID tag 2 cannot communicate.

<Description of Operation of Object Detection System S1>
Next, the overall system operation when detecting the position of an object in the object detection system S1 will be described with reference to FIG.

  In FIG. 3, in the object detection system S1, the system computer 3 and the tag communication device 1A start operating (start) simultaneously with the ON of a system operation switch (not shown). If the table T of FIG. 2 is not stored in the storage device (not shown) of the system computer 3 at this time, the table T is stored (step 100), and the position detection process is started (step 110). If the table T is stored, step 100 is skipped and the position detection process of step 110 is started.

  The system computer 3 that has started the operation first outputs a communication start command to the tag communication device 1A. Then, using this communication start command as a trigger, the tag communication device 1A attempts to communicate with all the RFID tags 2 by transmitting a query wave at least once (step 120).

  As a result, a response wave including its own ID is transmitted from the RFID tag 2 capable of communication, and the tag communication device 1A receives the response wave, and uses the ID of the RFID tag 2 included in the response wave as a communication record. It transmits to the computer 3. The system computer 3 receives the ID of the RFID tag 2 as a communication record and stores it in a storage unit such as a work memory area (not shown). In this case, if communication with all the RFID tags 2 is possible, communication records for the number of RFID tags 2 are stored in the storage unit (not shown) (step 120).

  A response wave is not transmitted from the RFID tag 2 that cannot communicate. In the example of FIG. No. 5 because the object D exists on the RFID tag 2. No RFID tag 2 can receive the interrogation wave, and therefore no response wave is transmitted from the RFID tag 2. The ID (No. 5) of the RFID tag 5 is not transmitted to the system computer 3 as a reception record (step 120).

  The system computer 3 that has received the communication record determines whether or not there is an RFID tag 2 that cannot communicate based on the communication record (step 130).

  The determination in step 130 is to detect the RFID tag 2 that cannot communicate in the procedure 1 and procedure 2 of the <method for detecting RFID tag that cannot communicate> described above.

  Specifically, all the IDs sent to the system computer 3 as communication records, that is, the IDs stored in the storage unit (not shown) described above are sequentially extracted from the table T in FIG. 1) If there is an ID remaining last without being extracted, the RFID tag specified by the ID is detected as an RFID tag 2 that cannot communicate (procedure 2). In the example of FIG. No. 5 RFID tag 2 cannot communicate, so no. The ID (No. 5) of the RFID tag 5 remains without being extracted from the table T in FIG. Therefore, this No. 5 RFID tags 2 are detected as RFID tags that cannot communicate.

  If an RFID tag that cannot communicate is detected, it is determined that there is an RFID tag that cannot communicate (Yes in step 130). If an RFID tag that cannot communicate is not detected, it is determined that there is no RFID tag that cannot communicate. (No in step 130).

  If it is determined in step 130 that there is no RFID tag that cannot be communicated (No in step 130), a communication start command is output from the system computer 3 to the tag communication device 1A, and the processing in steps 120 to 130 is performed. It is executed repeatedly.

  If it is determined in step 130 that there is an RFID tag that cannot be communicated (Yes in step 130), the system computer 3 acquires position information corresponding to the ID of the RFID tag that cannot be communicated from the table T in FIG. The acquired position information is output to the monitor or the like as the position of the object D. Then, a communication start command is output from the system computer 3 to the tag communication device 1A, and the processing after step 120 is re-executed.

  The series of processing described above ends when a system operation switch (not shown) is turned off.

  In the object detection system S1 of the first embodiment described above, a plurality of RFID tags 2 are installed in the communicable area A of the tag communication device 1A, and the ID of the RFID tag 2 and its position information are associated with each other. The RFID tag that is not able to communicate is detected from the result of trying to communicate with each RFID tag 2 from the tag communication device 1A, and the position information corresponding to the detected RFID tag ID is obtained from the table T. The configuration to adopt was adopted. For this reason, when communication between the tag communication device 1A and the RFID tag 2 is blocked by placing the object D in the communicable area A of the tag communication device 1A, detection of RFID tags that cannot communicate and position information Since the position of the object that is blocking communication is known from the acquired position information, the position of the object can be reliably secured at low cost without having an RFID tag attached to an unspecified number of people or objects such as luggage. Can be detected.

  FIG. 4 (a) employs one tag communication device 1C having the floor and wall of the room as the communicable area in the object detection system of the first embodiment described above, and is set as the communicable area. FIG. 4B is an explanatory diagram of an example in which the RFID tag 2 is embedded in the floor and wall of a room, and FIG. 4B is an explanatory diagram when an object D having a height lower than the object D in FIG. FIG. 5 is a perspective view of the room of FIG. 4A as viewed obliquely from above.

  In the examples of FIGS. 4A, 4B, and 5, communication is attempted from the tag communication device 1C to all RFID tags 2 on the wall of the room, RFID tags that cannot communicate are detected, and position information thereof is acquired. At the same time, a certain size and shape of the object located in the room can be detected from the acquired position information (fourth processing). The detection principle is as follows.

<Principle for detecting the size and shape of an object>
The principle of detecting the size and shape of an object from the position information of an RFID tag embedded in a wall that cannot communicate is based on the principle of detecting a certain size and shape of the object from the shadow of the object illuminated by sunlight or a light bulb. It is similar.

  For example, when the object D is illuminated with a light bulb (not shown) from the position of the tag communication device 1C shown in FIGS. 4A and 4B and FIG. 5, the shadow Ds of the object D is projected on the wall of the room as shown in FIG. The Since the shadow Ds of the object is similar to the object D, the shape of the object D can be estimated to some extent from the shadow Ds.

<Relationship between the shadow range of the object and the range of RFID tags that can / cannot communicate>
4 (a) and 4 (b), the RFID tag 2 in the wall embedded outside the shadow Ds (see FIG. 5) of the object described above allows the object D to communicate with the tag communication device 1C. Since it is not hindered, the RFID tag can be communicated. 4A and 4B, the RFID tag 2 positioned in the range of ΔZ ₁ or ΔZ ₃ is an RFID tag that is outside the shadow Ds of the object D and can communicate.

On the other hand, the RFID tag 2 in the wall embedded in the range of the shadow Ds of the object D becomes an RFID tag that cannot communicate because the object D prevents the communication with the tag communication device 1C. 4A and 4B, the RFID tag 2 positioned in the range of ΔZ ₂ and ΔZ ₄ is an RFID tag that is in the range of the shadow Ds of the object D and cannot communicate.

Therefore, the range of the RFID tag in the wall where communication is impossible (the range in which the radio wave from the tag communication device 1C is blocked by the object and does not reach) is the shadow Ds of the object D projected onto the wall. Approximately equal to range. This is because both radio waves and light are straight and are blocked by the same object. In FIG. 4 (a), RFID tag located within the range of [Delta] Z ₂ is in the range of shadow Ds of the object D, and a RFID tag communication impossible. Further, in FIG. 4 (b), RFID tag located within the range of [Delta] Z ₄ is in the range of shadow Ds of the object D, and a RFID tag communication impossible.

<Detection of Object Size and Shape in Object Detection System of First Embodiment>
In the object detection system S1 of the first embodiment, a table (not shown; reference example: FIG. 2) in which the IDs of all the RFID tags 2 embedded in the wall and their position information are stored in a one-to-one correspondence is separately employed. Thus, it is possible to detect which RFID tag in the wall is incapable of communication by the same procedure as the procedure 1 and 2 described above.

  Therefore, communication is attempted from the tag communication device 1C to all RFID tags 2 in the wall, and when an RFID tag that cannot be communicated is detected, position information corresponding to the ID of the RFID tag that cannot be communicated is obtained from the table (not shown). Then, by plotting the position of the RFID tag that cannot be communicated on the graphic coordinates based on the acquired position information, the RFID tag in the wall that is unable to communicate in the object detection system S1 of the first embodiment. Two ranges can be detected.

  Further, since the range of the RFID tag 2 in the wall where communication is impossible as described above is substantially equal to the range of the shadow Ds of the object D described above projected on the wall, in the object detection system S1, The size and shape of the object can be detected from the position information of the RFID tag that cannot communicate. In the present embodiment, an example in which a certain shape of the object D is detected using the shadow Ds of the object D projected on the wall of the room has been described. However, as shown in FIG. Even in such a case, a certain size and shape of the object D can be detected by detecting a tag that cannot communicate. The same applies to the case where the object is in contact with the wall. Further, in the present embodiment, communication is attempted from the tag communication device 1C to all the RFID tags 2 in the wall. However, instead of setting all the RFID tags 2 in the communication range in this way, some RFID tags 2 are used. Alternatively, the configuration may be such that only the communication range is set in advance. Further, the communication range may be configured to be arbitrarily set by the user.

  For example, if three RFID tags cannot communicate with each other, the positions of these RFID tags are known by acquiring the position information from the table. Therefore, the area may be calculated as the area of a triangle formed by the three RFID tags based on the positional information of the three RFID tags exemplified above.

  FIG. 6 is an explanatory diagram of an object detection system according to the second embodiment of the present invention.

<Basic method and equipment configuration of object detection system>
This object detection system S2 shown in FIG. 6 detects an object D using a plurality of tag communication devices 1A and 1B, and includes a plurality (two in the example of the figure) of tag communication devices 1A and 1B. Each of the tag communication devices 1A and 1B includes a plurality of RFID tags 2 installed in the communicable areas A and B, and a system computer 3 that controls and controls the entire system.

<Detailed description of tag communication device>
The two tag communication devices 1A and 1B constituting the object detection system S2 are both RFID reader / writers or RFID readers, as in the case of the tag communication device 1A of the first embodiment. Based on this, communication (transmission / reception) is attempted with respect to all RFID tags 2 such as transmitting an interrogation wave toward the RFID tag 2 or receiving a response wave from each RFID tag 2 with respect to the interrogation wave.

  Further, when each of the tag communication devices 1A and 1B attempts to communicate with the RFID tag 2 and receives the response wave, the tag communication apparatuses 1A and 1B communicate the own ID of the RFID tag 2 included as data in the response wave. It is sent to the system computer 3 as a record. The ID of each tag communication device 1A, 1B is added to the ID to be transmitted. This is for identifying which tag communication device 1A, 1B in the system computer 3 is the communication record sent.

  Also in the object detection system S2, in order to detect the object D placed on the floor of the room, each tag communication device 1A, 1B is installed on the ceiling of the room, and its communicable areas A, B are on the floor of the room. Set. In order to increase the position detection accuracy of the object D, in the object detection system S2, the communicable area A of the first tag communication device 1A and the communicable area B of the second tag communication device 1B overlap each other. An area (communication area overlap area C) is configured.

  In the example of FIG. 6, the communication possible areas A and B of the two tag communication apparatuses 1A and 1B overlap in the vicinity of the center of the floor of the room, and the communication possible area A and the communication possible area on the left and right sides of the floor of the room. Although there is no overlap of B, by increasing the number of tag communication devices, it is possible to expand such a communicable area overlapping region C over the entire floor of the room.

<Detailed description of RFID tag>
The plurality of RFID tags 2 constituting the object detection system S2 are also embedded in the floor of the room and in the communicable areas A and B of the tag communication devices 1A and 1B, similarly to the RFID tag 2 of the first embodiment. Although installed, some of the RFID tags 2 are arranged in the communicable area overlapping area C of the two tag communication apparatuses 1A and 1B as shown in FIGS.

  The basic function / configuration of the RFID tag 2 used in the object detection system S2 is the same as that of the RFID tag 2 of the first embodiment described above, and thus detailed description thereof is omitted.

<Detailed explanation of system computer>
The system computer 3 constituting the object detection system S2 is constituted by a personal computer or the like that can communicate with the tag communication devices 1A and 1B as well as the system computer 3 of the first embodiment, and an internal or external hard disk (not shown). In addition to the table T described above, the communicable area overlapping area C of the tag communication devices 1A and 1B described above is also stored in the storage device such as.

The system computer 3 of the object detection system S2 controls and controls the entire system, and from the result of attempting to communicate with each of the RFID tags 2 from a plurality of tag communication devices 1A and 1B, It is configured to detect. Specifically, this configuration is realized by the system computer 3 of the object detection system S2 including a program or a circuit that executes processes shown in the following (1) to (5).
(1) Processing for receiving communication records (results of communication attempts) with the RFID tag 2 from the plurality of tag communication devices 1A and 1B.
(2) A process of detecting an RFID tag that cannot communicate with each tag communication device 1A, 1B based on the received communication record.
(3) A process for determining whether or not an RFID tag that cannot be communicated exists in an area (communication available area overlapping region C) that can be communicated by a plurality of tag communication apparatuses 1A and 1B.
(4) A process of determining whether or not communication is possible between a plurality of tag communication apparatuses 1A and 1B including the tag in the communicable areas A and B for the RFID tag that cannot communicate.
(5) Processing for acquiring position information corresponding to the ID of the RFID tag determined to be unable to communicate with the plurality of tag communication apparatuses 1A and 1B from the table T in FIG.

<Method for detecting RFID tags that cannot communicate with a plurality of tag communication devices>
After completing the reception of the communication records from the plurality of tag communication devices 1A and 1B, the system computer 3 extracts all the IDs sent as the communication records from the table of FIG. 2 (procedure 1) and extracted once. The RFID tag specified by the last remaining ID is detected as an RFID tag that cannot communicate with at least two tag communication apparatuses 1A and 1B (procedure 2).

  In the example of FIG. 6, there are a total of 40 RFID tags 2 in the communicable area overlapping region C of the two tag communication devices 1A and 1B. Of these, the ID is NO. The object D exists on the RFID tag 2 of 5. This No. Since the interrogation wave transmitted from the two tag communication devices 1A and 1B to the RFID tag 2 of No. 5 is blocked by the object D, 5 is not received by any tag communication device 1A, 1B. Therefore, no. Since the RFID tag 2 of 5 cannot communicate with the two tag communication devices 1A and 1B, it is detected as an RFID tag that cannot communicate with the plurality of tag communication devices 1A and 1B.

<Description of Operation of Object Detection System S2>
Next, the overall system operation when detecting the position of an object in the object detection system S2 will be described with reference to FIG.

  In FIG. 7, in the object detection system S2, the system computer 3 and the two tag communication devices 1A and 1B start to operate (start) simultaneously with turning on a system operation switch (not shown). At this time, if the table T of FIG. 2 and the communicable area overlapping area C of the two tag communication apparatuses 1A and 1B are not stored in the storage device (not shown) of the system computer 3, these are stored (step S1). 200 and 205), the position detection process is started (step 210). If the table T and the communicable area overlap area C of the tag communication apparatuses 1A and 1B are stored, the steps 200 and 205 are skipped and the position detection process of step 210 is started.

  The system computer 3 that has started the operation outputs a communication start command to the two tag communication apparatuses 1A and 1B. Then, using this communication start command as a trigger, each tag communication device 1A, 1B attempts to communicate with all RFID tags 2 for each tag communication device by transmitting an interrogation wave at least once (step 220). .

  Thus, the communicable RFID tag transmits a response wave including its own ID, and each tag communication device 1A, 1B receives the response wave, and then receives the ID of the RFID tag 2 included in the response wave. IDs of the tag communication apparatuses 1A and 1B are added, and these are transmitted to the system computer 3 as communication records.

  The system computer 3 receives the communication records from the respective tag communication devices 1A and 1B and stores them in a storage unit such as a work memory area (not shown). In this case, if any of the tag communication devices 1A and 1B can communicate with all the RFID tags 2, a total of (number of RFID tags) × (tag communication device's) is stored in the storage unit (not shown). Communication records for the number of units are stored (step 220).

  A response wave is not transmitted from the RFID tag that cannot communicate. In the example of FIG. No. 5 is present on the RFID tag 2. No RFID tag 2 can receive the interrogation wave, and therefore no response wave is transmitted from the RFID tag 2. The ID (No. 5) of the RFID tag 5 is not transmitted to the system computer 3 as a communication record (step 220).

  No. 3 and no. No object exists on the RFID tag 2 of No. 4, but no. 3 and no. Since the communication between the RFID tag 2 of No. 4 and the second tag communication device 1B is blocked by the nearby object D, the IDs (No. 3 and No. 4) of these RFID tags are the second tag communication. It is not transmitted as a communication record from the apparatus 1B to the system computer 3. (Step 220).

  Furthermore, no. 6 and no. Since the communication between the RFID tag 2 of No. 7 and the first tag communication device 1A is similarly blocked by the nearby object D, the IDs (No. 6 and No. 7) of these RFID tags are the first. No communication record is transmitted from the second tag communication apparatus 1B to the system computer 3 (step 220).

  The system computer 3 that has received the communication record as described above determines whether there is an RFID tag that cannot be communicated in any of the tag communication devices 1A and 1B based on the communication record (step 230).

  The determination in step 230 is that all IDs sent as communication records after completion of reception of the communication records from the tag communication devices 1A and 1B, that is, the IDs of the RFID tags 2 stored in the storage unit described above. Are extracted from the table T in FIG. As a result, if there remains an ID that cannot be extracted, it is determined that there is an RFID tag that cannot be communicated with any of the tag communication devices 1A and 1B (Yes in Step 230), and there is no such ID. Then, it is determined that there is no RFID tag that cannot communicate with any of the tag communication devices 1A and 1B (No in step 230).

  In this step 230, in the example of FIG. 3-No. The RFID tags 2 up to 7 are determined as RFID tags that cannot communicate with any of the tag communication devices 1A and 1B (step 230).

  If it is determined in step 230 that there is no RFID tag that cannot be communicated (No in step 230), a communication start command is output from the system computer 3 to the tag communication devices 1A and 1B. The process is executed repeatedly.

  If it is determined in step 230 that there is at least one RFID tag that cannot be communicated in any of the tag communication devices 1A and 1B (Yes in step 230), the system computer 3 then performs the RFID that cannot communicate. It is determined whether or not the tag exists in an area (communication available area overlapping area C) that can be communicated with a plurality of tag communication apparatuses 1A and 1B (step 240).

  For the determination in step 240, the position information corresponding to the ID of the RFID tag that cannot be communicated is acquired from the table T, and the position of the RFID tag specified by the acquired position information can be communicated with the tag communication devices 1A and 1B. What is necessary is just to confirm whether it is included in the area duplication area | region C. FIG. If this confirmation can be made, it is determined that the RFID tag that cannot be communicated is “located in the communication area overlapping area of the tag communication device” (Yes in Step 240). If such confirmation cannot be made, the communication is impossible. The RFID tag is determined to be “not located in the communicable area overlapping range of the tag communication device” (No in step 240).

  In the example of FIG. 6A, No. determined in the previous step 230 is obtained. 3-No. Since all RFID tags 2 up to 7 are included in the communicable area overlapping range C, in this step 240, No. 7 is set. 3-No. It is determined that up to 7 RFID tags 2 exist in an area (communicatable area overlapping area C) where communication can be performed by the plurality of tag communication apparatuses 1A and 1B (step 240).

  If it is determined in step 240 that the RFID tag that cannot be communicated is “located in the communication area overlapping area of the tag communication device”, the RFID tag that cannot communicate in the system computer 3 further communicates with the tag. It is determined whether or not communication is possible between the plurality of tag communication devices 1A and 1B included in the possible areas 1A and 1B (step 250).

  Regarding the determination in step 250, the IDs of the RFID tags sent as communication records from the respective tag communication devices 1A and 1B, that is, the IDs of all the RFID tags stored in the storage unit described above are shown in the table of FIG. Extract from inside. Then, the RFID tag specified by the last remaining ID that has never been extracted may be detected as an RFID tag that cannot be communicated by the plurality of tag communication devices 1A and 1B (step 250).

  In the example of FIG. 6A, No. determined in the previous step 240 is obtained. 3-No. No. 7 among RFID tags 2 up to 7. Only five RFID tags 2 are detected as RFID tags that cannot communicate with the two tag communication apparatuses 1A and 1B (step 250).

  In step 250, when the RFID tag that cannot communicate with the two tag communication devices 1A and 1B is detected (Yes in step 250), the system computer 3 obtains position information corresponding to the ID of the RFID tag that cannot communicate. 2 is acquired from the table T in FIG. 2 (step 260), and the acquired position information is output to the monitor or the like as the position of the object D (step 270). Then, a communication start command is output from the system computer 3 to the tag communication devices 1A and 1B, and the processing from step 220 is re-executed.

  Further, in step 250, if no RFID tag that cannot communicate with the two tag communication devices 1A and 1B is detected (No in step 250), the position of the object D as in step 260 or step 270 is output. Without performing the above process (step 280), the system computer 3 outputs a communication start command to the tag communication apparatuses 1A and 1B, and the processes in and after step 220 are re-executed.

  The series of processes described above is terminated when a system operation switch (not shown) is turned off.

  In this object detection system S2, when there is a large object D1 existing on a plurality of RFID tags 2 as shown in FIG. 6B, the plurality of RFID tags 2, tag communication devices 1A, 1B, and Therefore, it can be detected that there is an object D1 having an area substantially the same as the area where the plurality of RFID tags 2 that have become unable to communicate are installed.

<Comparison of position detection accuracy>
The object position detection accuracy of the second embodiment is higher than the object detection system of the first embodiment described above.

  For example, in the object detection system S1 of the first embodiment, No. 1 shown in FIG. When an object D having a size as shown in FIG. No. 5 RFID tag, as well as No. 5 4 and no. No. 6 RFID tag 2 cannot be communicated. 4, no. 5 and no. 6 is erroneously detected as the position of the object.

  On the other hand, in the object detection system S2 of the second embodiment, as shown in FIG. 6A, no false detection occurs even under the same object D condition as in FIG. 5 can be accurately detected as the position of the object D. This is no. No. 4 or No. 6 RFID tag 2 cannot communicate with either one of the two tag communication devices 1A and 1B. No. 5 RFID tag 2 cannot communicate with the two tag communication devices 1A and 1B. This is because only the position of the RFID tag 2 is detected as the position of the object.

  FIG. 9A shows a tag communication device 1D having a room wall as a communicable area attached to the wall of the room and set as the communicable area in the object detection system S2 of the second embodiment described above. FIG. 9B is an explanatory diagram of an example in which the RFID tag 2 is embedded in the wall of the room, FIG. 9B is an explanatory diagram when an object having a lower height than the object of FIG. It is the perspective view which looked at the room of Fig.9 (a) from diagonally upward.

  In the examples of FIGS. 9A, 9B, and 10, the tag communication device 1D attempts to communicate with all the RFID tags 2 on the wall of the room, and detects the RFID tag that cannot communicate, thereby detecting the inside of the room. A certain size and shape of the object D can be detected. The detection principle is based on the principle described above.

<Relationship between the shadow range of an object and the range of RFID tags that can / cannot communicate>
9A and 9B, the RFID tag 2 in the wall embedded outside the shadow Ds (see FIG. 10) of the object D is prevented from communicating with the tag communication device 1D by the object D. There is no RFID tag that can communicate. 9A and 9B, the RFID tag 2 located in the range of ΔZ ₅ or ΔZ ₇ is outside the shadow Ds of the object D (see FIG. 10) and is an RFID tag that can communicate.

On the other hand, in FIGS. 9A and 9B, the RFID tag 2 in the wall embedded in the range of the shadow Ds of the object D prevents the object D from communicating with the tag communication device 1D. , It becomes an RFID tag that cannot communicate. 9 and (a) (b), RFID tag 2 located within a range of [Delta] Z ₆ and [Delta] Z ₈ each, be in the range of shadow Ds of the object D, an RFID tag communication impossible.

Therefore, the range of the RFID tag 2 in the wall where communication is impossible (the range in which the radio wave from the tag communication device 1D is blocked by the object D and does not reach) is the shadow of the object D projected onto the wall. It is approximately equal to the range of Ds. This is because both radio waves and light are straight and are blocked by the same object. In FIG. 9A, the RFID tag 2 located in the range of ΔZ _{6 is in} the range of the shadow Ds of the object D and is an RFID tag that cannot communicate. Further, in FIG. 9 (b), the RFID tag 2 located within a range of [Delta] Z ₈ is in the range of shadow Ds of the object D, and a RFID tag communication impossible.

<Detection of Object Size and Shape in Object Detection System of Second Embodiment>
Also in the object detection system S2 of the second embodiment, as in the object detection system S1 of the first embodiment described above, the IDs of all the RFID tags 2 embedded in the wall and the position information thereof are associated one-to-one. By separately using a stored table (not shown; reference example: FIG. 2), it is detected which RFID tag in the wall is incapable of communication in the same procedure as steps 1 and 2 described above. be able to.

  Therefore, communication is attempted from the tag communication device 1D to all RFID tags 2 in the wall, and when an RFID tag that cannot communicate is detected, position information corresponding to the ID of the RFID tag that cannot communicate is obtained from the table (not shown). Then, by plotting the acquired position on the graphic coordinates, the object detection system S2 of the second embodiment can detect the range of the RFID tag in the wall where communication is impossible. Also in this case, since the range of the RFID tag in the wall where the communication is impossible is substantially equal to the range of the shadow Ds of the object D projected onto the wall, the unknown amount of the above equation 2 is calculated. Thus, a certain size and shape of the object D can be detected.

<Application examples common to the object detection systems of the first and second embodiments>
In the object detection systems S1 and S2 of the first and second embodiments, the position, size, and shape of an object are detected. When the object moves, an RFID tag that cannot communicate in time series is detected. By acquiring the position information, the trajectory (traffic line) of the object can be detected. As a method for detecting the trajectory of the object, for example, a method of plotting the acquired positional information of the RFID tag that cannot be communicated as the position of the object in time series can be considered.

  In the object detection system S1 of the first embodiment, the system computer 3 detects a non-communication RFID tag, a process of acquiring position information corresponding to the ID of the non-communication RFID tag from the table T, and an acquired position Although the configuration of executing the process of outputting information to the monitor or the like as the position of the object is adopted, a configuration of executing such a series of position detection processing in the tag communication devices 1A and 1B can also be adopted. When such a configuration is adopted, the table T of FIG. 2 is held in the tag communication device 1A, and position information corresponding to the ID of the RFID tag that cannot communicate is acquired from the table T. Then, the acquired position information may be output as a position of the object to the system computer 3, an application program, or a higher-level device such as a monitor.

  Also in the object detection system S2 of the second embodiment described above, a configuration in which the series of position detection processes is executed in the tag communication device 1A or 1B can be adopted. When such a configuration is adopted, for example, one tag communication device 1A is a parent device, and all other tag communication devices 1B are child devices, and the table T in FIG. 2 is held in the parent device (1A). Let Then, each of the master unit (1A) and the slave unit (1B) tries the process of step 220 in FIG. 5, that is, the communication with the RFID tag, and the communication record of the slave unit (1B) as a result is as follows. It is transmitted to the master unit (1A), and the master unit (1A) performs the processing of steps 240 to 280 in FIG. Then, the series of position detection processes described above can be performed only by using the network of tag communication devices without using the system computer 3.

  In the object detection systems S1 and S2 of the first and second embodiments, the antenna configuration of the tag communication devices 1A and 1B is a beam scan antenna or other normal antenna, that is, a beam without focusing a radio wave beam. An antenna that does not have a function of scanning can be employed.

  FIG. 11A is an explanatory diagram of an installation example of a tag communication device when a normal antenna that is not a beam scan antenna is employed in the object detection system S2 of the second embodiment, and FIG. 11B is a diagram illustrating the second embodiment. It is explanatory drawing of the example of installation of a tag communication apparatus when a beam scan antenna is employ | adopted in object detection system S2 of a form.

  When the beam scan antenna is employed, the second and third tag communication devices 1B and 1C shown in FIG. 5A can be used as a single tag communication device 1Z as shown in FIG. In addition, since the fourth and fifth tag communication devices 1D and 1E in FIG. 5A can be used as a single tag communication device 1Y as shown in FIG. Can be reduced.

  In order to avoid the problem that FH (field hole) occurs due to reflection by the object D and communication cannot be performed normally, a radio wave absorber may be attached to the wall. As a result, it is possible to avoid the problem that communication is possible when communication is not desired.

  In the object detection systems S1 and S2 of the first and second embodiments, the position of the object is detected based on whether or not communication is possible, but the reception level of the response wave from the RFID tag at the time of normal communication Is stored in the tag communication devices 1A and 1B, and if a reception level greatly different from the reception level is detected, even if communication is possible, the ID acquired from the RFID tag 2 of the communication destination is used as a communication record. You may exclude so that it may not output to the system computer 3. FIG. As a result, it is possible to avoid the problem that communication is possible when communication is not desired.

  In the object detection systems S1 and S2 of the first and second embodiments, the position of the object D placed on the floor of the room is detected, but the object D may be a person. Since the floor area of the room can be easily measured or is known, if the object D is considered to be a person, the density and presence of the person in the room can be detected, and the lighting of the room can be detected based on the detection result. It is also possible to adopt a configuration for controlling various devices such as controlling air conditioning.

  Assuming that the room is a sales floor for merchandise and the object D is a customer, as described above, it is possible to grasp popular merchandise by detecting the density of people. This is because people concentrate on popular products, and the density of people around popular products increases.

  If the room is considered as a floor with an escalator and the object D is considered as a person existing on the floor, the density of the person is detected as described above, so that people are crowded near the entrance of the escalator. In this case, safety measures such as reducing the speed of the escalator may be taken.

  If the room is considered as a sports gym and the object D is considered as a gym user, by adopting a configuration in which the RFID tag 2 is embedded in the gym equipment installed in the sports gym, Can be grasped. Since the communication between the RFID tag 2 of the running gym equipment and the tag communication devices 1A, 1B is blocked by the user of the gym equipment, the gym equipment at the position of the RFID tag that cannot communicate is currently used. It means that it is inside.

  If the room is considered as a gaming center such as a pachinko parlor or game center and the object D is considered as a gaming machine user, for example, by adopting a configuration in which the RFID tag 2 is embedded in a chair or the like on which the gaming machine user sits, At the center, it is possible to grasp the operating rate of gaming machines. Since communication between such an RFID tag 2 and the tag communication devices 1A and 1B is blocked by the game machine user, it means that the gaming machine at the position of the RFID tag that cannot communicate is currently in use. Because it will do.

  If the room is considered as a room requiring security such as a safe room, and the object D is considered as a suspicious person who has entered the room, the RFID tag 2 and the tag communication devices 1A, 1B embedded in the floor of the room. Since communication with the suspicious person is blocked by the suspicious person, the presence and position of the suspicious person can be detected.

  If the room is considered as a room designated as a dangerous area and the object D is considered as a person entering the room in the designated dangerous area, the RFID tag 2 and the tag communication device 1A embedded in the floor of the designated dangerous area room, Since communication with 1B is blocked by a person who enters the room, it is possible to detect the entry of the person into the danger zone and the position of the person.

  If the floor of the room is considered as a parking space in the parking lot, the tag communication devices 1A and 1B attached to the ceiling of the room are attached to the parking lot by a support member, and the object D on the floor is considered as a vehicle. , Can understand the parking space availability. Since the communication between the RFID tag 2 embedded in the parking space and the tag communication devices 1A and 1B is blocked by the vehicle parked in the parking space, the parking space at the position of the RFID tag that cannot communicate is currently This means that it is in use.

  If the room is considered as a warehouse and the object D is considered as a luggage, communication between the RFID tag 2 embedded in the warehouse floor and the tag communication devices 1A and 1B is blocked by the luggage. The number of RFID tags that can be communicated gradually increases due to the gradual decrease in luggage. In addition, the number of RFID tags that cannot be communicated gradually decreases as the number of luggage in the warehouse gradually increases. From these things, it is possible to perform inventory management such as how much luggage is present in the warehouse.

  In the object detection systems S <b> 1 and S <b> 2 of the first and second embodiments, it is also acceptable that a person who enters and exits a room individually has an RFID tag. In this case, in any system, it is possible to grasp the position and the number of persons existing in the room. Therefore, by acquiring the ID from the person's RFID tag by the tag communication devices 1A and 1B, It is also possible to count the number of people who have RFID tags, and calculate the percentage of people who have RFID tags in the room. In this example, if the person is a member, the percentage of members in the room can be calculated.

  The object detection systems S1 and S2 of the first and second embodiments can also adopt a configuration in which the RFID tag 2 is embedded in the wall of the room. When this configuration is adopted, the approximate height of the object D can be detected. For example, when an RFID tag is embedded above, inside, or below a wall, if communication with the upper RFID tag becomes impossible, communication is interrupted by at least the height of the object D embedded with the upper RFID tag. It can be detected that the object D of that height exists in the room.

  In the example of detecting the height of the object D as described above, the embedded height of the upper RFID tag is the average height of an adult, the embedded height of the lower RFID tag is the average height of a child, and the object is a person. If communication with the upper RFID tag is impossible, it can be seen that communication with the upper RFID tag is blocked by an adult, and it can be detected that an adult is present in the room. On the other hand, if only communication with the lower RFID tag is not possible and communication with the upper RFID tag is possible, there is no interruption of communication with the upper RFID tag by an adult, and communication with the lower RFID tag by a child is performed. Can be seen as being blocked, and it can be detected that there are only children in the room. This can be used to find a suspicious person at a nursery school or the like.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications and changes can be made within the same or equivalent range as the present invention.

FIG. 1 is an explanatory diagram of an object detection system according to a first embodiment of the present invention, where (a) is a block diagram of the system, and (b) is an arrangement and communication of RFID tags when the floor is viewed from the ceiling of the room. It is explanatory drawing of a possible area. FIG. 2 is an explanatory diagram of a table used in the object detection system of FIGS. FIG. 3 is an explanatory diagram of the overall operation of the object detection system shown in FIG. FIG. 4 (a) shows an object detection system according to the first embodiment, in which one tag communication device having a room floor and a wall as a communicable area is adopted, and the room floor set as the communicable area It is explanatory drawing of the example which embedded the RFID tag in the wall. FIG. 4B is an explanatory diagram when an object having a height lower than that of the object in FIG. FIG. 5 is a perspective view of the room shown in FIG. FIG. 6 is an explanatory diagram of an object detection system according to a second embodiment of the present invention. FIG. 6A is a block diagram of the system, and FIG. 6B is an RFID tag when the floor is viewed from the ceiling of the room. It is explanatory drawing of arrangement | positioning and communication possible area. FIG. 7 is an explanatory diagram of the overall operation of the object detection system shown in FIG. FIG. 8 is an explanatory diagram of the position detection limit of the object detection system of FIG. FIG. 9A shows a tag communication device having a room wall as a communicable area attached to a room wall in the object detection system of the second embodiment, and an RFID tag is attached to the room wall set as the communicable area. It is explanatory drawing of the example which embedded. FIG. 9B is an explanatory diagram when an object having a height lower than that of the object in FIG. FIG. 10 is a perspective view of the room shown in FIG. FIG. 11A is an explanatory diagram of an installation example of a tag communication device when a normal antenna that is not a beam scan antenna is employed in the object detection system of the second embodiment, and FIG. 11B is a diagram illustrating the second embodiment. It is explanatory drawing of the example of installation of the tag communication apparatus when a beam scanning antenna is employ | adopted in the object detection system of FIG.

Explanation of symbols

1A to 1F, 1Y to 1Z Tag communication device 2 RFID tag 3 System computer A, B Communicable area C Communicable area overlap area D, D1 Object Ds Object shadow S1, S2 Object detection system T Table

Claims (13)

A tag communication device;
A plurality of RFID tags;
A table storing each RFID tag and its position information in association with each other;
From a result of attempting to communicate with each RFID tag from the tag communication device, a first processing unit that detects an RFID tag that cannot communicate,
And a second processing unit that acquires position information corresponding to the RFID tag detected by the first processing unit from the table.   The object detection system according to claim 1, further comprising: a third processing unit that outputs position information acquired by the second processing unit as the position of the object.   The object detection system according to claim 1, further comprising a fourth processing unit that detects the shape or size of the object based on the position information acquired by the second processing unit.   The first and second processing units include a fifth processing unit that detects RFID tags that cannot communicate with each other in time series, acquires position information, and detects a locus of an object. Object detection system.   5. The RFID tag that is incapable of communication is detected from a plurality of tag communication devices, and based on a result of attempts to communicate with each of the RFID tags from a plurality of tag communication devices. The object detection system according to item 1.   The object detection system according to claim 1, wherein an antenna of the tag communication device is a beam scan antenna. An object detection method for detecting an object using a tag communication device, a plurality of RFID tags, and a table storing each RFID tag and its position information in association with each other,
An object detection comprising: detecting an RFID tag that cannot communicate from a result of an attempt to communicate with each RFID tag from the tag communication device; and acquiring position information corresponding to the detected RFID tag from the table. Method.   8. The object detection method according to claim 7, wherein the acquired position information is output as an object position.   The object detection method according to claim 7, wherein the shape or size of the object is detected from the acquired position information.   The object detection method according to claim 7, wherein an RFID tag that cannot communicate in time series is detected, position information is acquired, and a locus of the object is detected.   11. The RFID tag according to claim 7, wherein there are a plurality of the tag communication devices, and an RFID tag that cannot communicate is detected from a result of an attempt to communicate with each of the RFID tags from a plurality of tag communication devices. The object detection method according to item 1.   The object detection method according to claim 7, wherein the antenna of the tag communication device is a beam scan antenna.   A table in which a plurality of RFID tags and their positional information are stored in association with each other is held, and from the result of attempting to communicate with the plurality of RFID tags, RFID tags that cannot communicate are detected, and the detected RFID tags Corresponding position information is obtained from the table.

Images