JP7184187B2 - Wireless tag position detection system - Google Patents

Description

The present invention relates to a wireless tag position detection system.

In Japanese Patent No. 4650053, a pulse signal is transmitted from an installed antenna, a response signal is received from another installed antenna or a wireless tag for this pulse signal, and the time from the transmission of the pulse signal to the reception of the response signal is A location detection system is described that determines the distance between installed antennas, the distance between installed antennas and wireless tags, and the current location of wireless tags by converting to distances.

Japanese Patent No. 4650053

In the method of detecting the position of the wireless tag by converting the time from the transmission of the pulse signal to the reception of the response signal into the distance, as in the above conventional technology, the installed antennas are on the same plane, and It is assumed that the wireless tags are on the same plane. However, in reality, the wireless tag fluctuates according to the movement of the object on which the wireless tag is attached. In addition, since the installation position of the antenna is subject to various restrictions due to the structure, etc., it is extremely difficult to install the antenna with the same height as the design value.

In this way, the method of detecting the position of the wireless tag as in the conventional technology described above is affected by variations in the installation position of the antenna and the current height of the wireless tag. There remains room for

Further, for example, a method of calculating the distance between the installed antenna and the wireless tag by converting the radio wave reception intensity between the installed antenna and the wireless tag into a distance is known. However, the calculation algorithm for converting the received radio wave intensity into distance is unique to each antenna model, and it is necessary to change the calculation algorithm each time the antenna model changes. However, if it is necessary to change the calculation algorithm each time the antenna model is changed, the replacement work becomes complicated, and there is a risk of an increase in cost.

The present invention has been made to solve the above-mentioned problems, and can easily cope with the model change of the antenna, and can detect the position of the wireless tag with high accuracy even if the antenna installation height varies. To provide a wireless tag position detection system improved so as to be able to

A wireless tag position detection system of the present invention is a position detection system for detecting the position of a wireless tag, and includes a wireless tag that can be carried and moved, and a plurality of antennas that communicate with the wireless tag. Each of the plurality of antennas is arranged so that part of the communication area with the wireless tag overlaps with part of the communication area between at least one other antenna and the wireless tag. Each of the antennas and the other antennas have a function of transmitting radio waves at intermittent timings that do not interfere with each other.

The wireless tag receives radio waves transmitted from the antennas, measures the radio wave reception strength, and identifies the antenna that transmitted the radio wave with the highest radio wave reception strength as the corresponding antenna closest to the radio tag. Furthermore, by comparing the radio wave reception intensity of the radio wave from the corresponding antenna with the first threshold value, it is determined whether the position of the wireless tag is in the vicinity area within a certain range from the corresponding antenna within the communication area of the corresponding antenna, Determine if it is in the far region outside the near region. The wireless tag is configured to transmit a response of the location of the identified wireless tag to the corresponding antenna . In addition, at least one antenna set, which is a set of a plurality of antennas whose communication areas partially overlap each other, is registered, and the antennas constituting the antenna set are located in remote areas within the communication areas of the respective antennas constituting the antenna set. When it is determined that the wireless tag is in a remote area from the corresponding antenna, the radio wave transmission from all the antennas constituting the antenna set is completed within the time , the number of receptions, which is the number of receptions of radio waves with radio wave reception intensity greater than a second threshold, which is a value smaller than the first threshold, is detected. Identify which divided area is in a plurality of divided areas.
In addition, an example of a position detection system that is another aspect of the present disclosure includes a plurality of antennas that communicate with wireless tags that can be carried and moved, and a control unit that is mounted on each of the plurality of antennas, A position detection system for detecting the position of a wireless tag, wherein each of the antennas has a portion of the communication area with the wireless tag that overlaps with a portion of the communication area between at least one other antenna and the wireless tag. Each of the antennas and the other antennas have a function of transmitting radio waves at intermittent timings that do not interfere with each other, and the wireless tag measures the radio wave reception strength of the radio waves received from the multiple antennas and When the antenna that transmitted the radio wave with the highest radio wave reception strength is specified as the corresponding antenna that is closest to the RFID tag, the value obtained by measuring the radio wave reception strength of the radio wave from the corresponding antenna that has been identified is received from the wireless tag, and the control unit compares the value of the radio wave reception intensity received from the wireless tag by the corresponding antenna with the first threshold to determine whether the position of the wireless tag is within the communication area of the corresponding antenna. At least one set of multiple antennas configured to identify whether they are in a near field within a certain range of the antenna or in a far field outside of the near field, wherein a portion of the communication range overlaps with each other. A plurality of divided areas are set according to the number of antennas constituting the antenna set in a remote area within the communication area of each of the antennas constituting the antenna set, and the control unit When it is determined that the position of the wireless tag is in the remote area of the corresponding antenna, the second threshold, which is a value smaller than the first threshold, is reached during the time when the radio wave transmission from all the antennas constituting the antenna set is completed. Based on the number of receptions, which is the number of times the wireless tag receives radio waves with the highest radio wave reception intensity, it identifies in which divided area the position of the wireless tag is located in a plurality of divided areas in the remote area. , is constructed as follows:
In addition, according to another aspect of the position detection system according to the present disclosure, a plurality of antennas that communicate with wireless tags that can be carried and moved, and one of the antennas in a state capable of communicating with the plurality of antennas and a control unit mounted on a device installed in a device installed in a place different from the plurality of antennas, and detecting the position of a wireless tag, wherein each of the antennas is a wireless tag is arranged so that a part of the communication area of the wireless tag overlaps a part of the communication area of at least one other antenna and the wireless tag, and each of the antennas and the other antenna are intermittently timing so as not to interfere with each other. The wireless tag measures the strength of the radio waves received from multiple antennas, and the antenna that transmitted the radio wave with the highest strength is designated as the corresponding antenna, which is the closest antenna to the tag. , the specified corresponding antenna receives from the wireless tag the value obtained by measuring the radio wave reception intensity of the radio wave from the corresponding antenna, and the control unit determines the radio wave reception intensity received from the wireless tag by the corresponding antenna By comparing the value of with the first threshold value, it is determined whether the position of the wireless tag is in the vicinity area within a certain range from the corresponding antenna within the communication area of the corresponding antenna, or in the remote area outside the vicinity area. At least one antenna set, which is a set of a plurality of antennas whose communication areas partially overlap each other, is registered, and a remote area within the communication area of each of the antennas constituting the antenna set. is divided into a plurality of divided areas according to the number of antennas constituting the antenna set, and the control unit constitutes the antenna set when it is determined that the position of the wireless tag is in the remote area of the corresponding antenna Based on the number of receptions, which is the number of times the wireless tag receives radio waves with a radio wave reception strength greater than a second threshold, which is a value smaller than the first threshold, during the time when radio wave transmission from all antennas is completed, The position of the wireless tag is configured to specify in which divided area among a plurality of divided areas in the remote area.

According to the present invention, by specifying the corresponding antenna based on the radio wave reception intensity from the antenna, it is possible to specify the identification area of which antenna the wireless tag is located. Further, there is no need to convert the received radio wave intensity into a distance, and by comparison with the first threshold value, it is possible to accurately specify whether the position is near or far from the corresponding antenna of the wireless tag to some extent. Here, even if there is a large variation in the height of the plurality of antennas, by adjusting the first threshold to an appropriate value, the influence of the variation in the height of the antenna can be suppressed, and the area near the corresponding antenna It can be accurately identified whether it is located at or in a remote area.

1 is a diagram schematically showing the configuration of a position detection system according to Embodiment 1 of the present invention; FIG. 4 is a flow chart showing the operation of position determination of the wireless tag according to Embodiment 1 of the present invention. FIG. 4 is a diagram schematically showing the configuration of a position detection system according to Embodiment 2 of the present invention; FIG. 9 is a flow chart showing the operation of position determination of a wireless tag according to Embodiment 2 of the present invention; FIG. FIG. 10 is a diagram schematically showing the configuration of a position detection system according to Embodiment 3 of the present invention; FIG. 11 is a flow chart showing the operation of position determination of a wireless tag according to Embodiment 3 of the present invention; FIG. FIG. 11 is a diagram schematically showing another configuration example of the position detection system according to Embodiment 3 of the present invention; FIG. 10 is a diagram schematically showing another configuration example of the position detection system according to Embodiment 3 of the present invention; FIG. 10 is a diagram schematically showing another configuration example of the position detection system according to Embodiment 3 of the present invention; FIG. 11 is a diagram schematically showing another configuration example of the position detection system according to Embodiment 3 of the present invention;

Embodiments will be described below with reference to the drawings. Elements that are common or correspond to each figure are denoted by the same reference numerals, and overlapping descriptions are simplified or omitted.

Embodiment 1.
FIG. 1 is a diagram schematically showing the configuration of a position detection system according to Embodiment 1. FIG. The position detection system has two antennas 10 and a wireless tag 11 to be detected. Although two antennas 10 are shown in FIG. 1, the number of installed antennas 10 is not limited to two. Each antenna 10 is assigned an antenna number. Here, of the two antennas 10, one antenna 10 is numbered 1, and the other antenna 10 adjacent to the first antenna 10 is numbered 2. As shown in FIG.

Each antenna 10 and the adjacent antenna 10 are adjusted and set so that their radio wave output ranges partially overlap each other. That is, part of the communication area 20 between one antenna 10 and the wireless tag 11 overlaps with part of the communication area 20 between the other antenna 10 and the wireless tag 11 .

In the position detection system, an identification area 31 for detecting the position of the wireless tag 11 is set and stored in association with each antenna 10 . The identification area 31 is an area inside the communication area 20, and is set so as not to include a portion that does not overlap with another antenna 10 and that is closer to the other antenna 10. FIG. That is, the identification area 31 is within the communication area 20 of each antenna 10 and is an area set within the area on the side of each antenna 10 from the plane intersecting the communication area 20 of the other antenna.

Further, each antenna 10 controls radio wave transmission timing to prevent radio wave interference between the antennas 10, and performs radio wave transmission intermittently. Hereinafter, in Embodiments 1 to 3, the antennas 10 adjacent to each other and having overlapping communication areas 20 are registered as an "antenna set" in which radio waves are not to be transmitted at the same time, and the order of radio wave transmission is assigned within the antenna set. ing. The number of antennas 10 constituting the antenna set is not limited, and may be appropriately set so as to prevent radio wave interference.

The wireless tag 11 is carried by a person or attached to a moving object, and moves together with the person or the object. The wireless tag 11 receives radio waves from the antenna 10 when it is within the communication area 20 of each antenna 10 . The radio tag 11 also has a function of measuring the strength of received radio waves from each antenna 10 (hereinafter also referred to as “RSSI”, where RSSI stands for Received Signal Strength Indicator).

Furthermore, using these functions, the wireless tag 11 identifies the antenna 10 closest to its current position as the corresponding antenna, and also identifies the corresponding antenna 10 from the corresponding antenna 10 in the identification area 31 of the corresponding antenna 10. It has a position determination function of calculating whether it is in the nearby area 32 within the range or in the remote area 33 outside the nearby area 32 . Although the communication area 20, the near area 32, and the remote area 33 are represented as circles as shown in FIG. It is a region formed as a spherical shape. Similarly, although the identification area 31 is represented by a square, it is actually an area within a cube adjacent to the communication area 20 .

FIG. 2 is a flow chart showing the operation of position determination by the wireless tag 11. As shown in FIG. By executing the flowchart of FIG. 2, the function of position determination by the wireless tag 11 is realized. A specific operation of the wireless tag 11 during position determination will be described below with reference to FIG. The flowchart of FIG. 2 is repeatedly executed at regular intervals.

First, in S100 of FIG. 2, it is determined whether or not there is radio wave reception from each antenna 10 . If it is determined in step S100 that there is no radio wave reception, then in step S101 position determination is made as "no corresponding antenna", and the current process ends.

On the other hand, if it is determined in step S101 that radio waves have been received, the elapsed time is set in step S110, and counting of the elapsed time is started. Next, in step S111, the antenna number of the antenna that transmitted the received radio wave is stored. Next, in step S112, the RSSI of the received radio wave is measured and stored together with the corresponding antenna number.

Next, in step S113, it is determined whether or not the designated time has elapsed. This specified time is set to be at least longer than the time required to complete the radio wave transmission of all the antennas 10 forming the antenna set. If it is determined in step S113 that the specified time has not elapsed, the process returns to step S110, and steps S110 to S113 are repeatedly executed until it is determined that the specified time has elapsed. As a result, the presence or absence of reception of radio waves that may be received at the current position is confirmed, and the antenna numbers of all received radio waves are specified, and the RSSIs are measured and stored.

If it is determined in step S113 that the specified time has elapsed, the process proceeds to step S114, first the elapsed time is cleared, and the value of the elapsed time counter is returned to zero.

The process then proceeds to step S115, where the received RSSIs are compared and the corresponding antenna 10 is identified. That is, the antenna 10 closest to the current wireless tag 11 is specified. Specifically, when one radio wave is received, the antenna 10 that transmitted the radio wave is identified as the corresponding antenna 10 . If there are multiple received radio waves, the antenna 10 that has transmitted the radio wave with the largest RSSI value is specified as the corresponding antenna 10 . However, if a plurality of radio waves with the largest RSSI value are received, the antenna 10 with the smallest antenna number among the antennas 10 that have transmitted the radio waves is specified as the corresponding antenna 10 . Note that the configuration is not limited to this configuration, and conversely, a configuration in which the antenna 10 with the largest antenna number is specified as the corresponding antenna 10 may be employed.

Next, proceeding to step S116, it is determined whether or not the RSSI of the corresponding antenna 10 is greater than the first threshold. The first threshold value is a reference value held in advance by the wireless tag 11 for determining whether the identification area 31 of each antenna 10 is a near area 32 close to the antenna 10 or a remote area 33. .

If it is determined in step S116 that the RSSI of the corresponding antenna 10 is greater than the first threshold, the position determination in step S120 indicates that the wireless tag 11 is within the proximity area 32 in the identification area 31 of the corresponding antenna 10. is determined. After that, in step S121, the antenna number of the corresponding antenna 10, which is the result of the position determination, and a signal indicating the vicinity are transmitted to the corresponding antenna 10. FIG. After that, the current processing ends.

On the other hand, when it is determined in step S116 that the RSSI of the corresponding antenna is equal to or less than the first threshold value, in the position determination in step S122, the wireless tag 11 is located outside the vicinity area 32 of the identification area 31 of the corresponding antenna 10. , that is, it is determined to be in the remote area 33 . After that, in step S121, the antenna number of the corresponding antenna 10, which is the result of position determination, and a signal indicating remoteness are transmitted to the corresponding antenna 10. FIG. After that, the current processing ends.

In the control unit of the position detection system, as described above, the identification area 31 for detecting the position of the wireless tag 11 is set and stored in association with each antenna 10 . In addition, a near area 32 and a remote area 33 are stored in the control unit. Therefore, the position detection system specifies the position of the wireless tag 11 according to the received signal by the corresponding antenna 10 receiving the antenna number of the corresponding antenna 10 and the signal indicating whether it is near or far from the wireless tag 11. can do.

According to the above processing, even if the height of the antenna 10 is different, the wireless tag 11 can be detected by associating the boundary position between the near area 32 and the remote area 33 for each antenna with the first threshold value. The position in the identification area 31 of the corresponding antenna 10 can be identified with some degree of accuracy. Normally, it is difficult to make the intervals and heights of the installed antennas 10 the same or as designed, but in the position detection system of the present embodiment, after the antennas are installed, the first threshold can be adjusted. can be handled by

Normally, there are restrictions on the antenna installation density due to radio wave interference prevention and tag detection cycle issues. On the other hand, with the position detection system of the present embodiment, it is possible to determine the position of one antenna by dividing it into two divided areas. Therefore, it is possible to pinpoint the position more finely with a small number of antennas installed.

Embodiment 2.
FIG. 3 is a diagram schematically showing the configuration of the position detection system according to the second embodiment. A position detection system according to Embodiment 2 has the same configuration as the position detection system in FIG. As shown in FIG. 3, the position detection system of the second embodiment further divides the remote area 33 into two divided areas, an area x_x on the side of the corresponding antenna 10 and an area x_y on the side of the nearby antenna. The position can be specified in one divided area.

In order to simplify the explanation, in the following Embodiments 2 and 3, "x" represents a number indicating the antenna number of the specified corresponding antenna 10, and "y" represents the corresponding antenna 10 and the antenna set. It shall represent a number indicating the antenna number of the constituent antennas. Also, an antenna 10 forming an antenna set together with a certain antenna 10 will be referred to as a "proximity antenna".

The wireless tag 11 records the second threshold in addition to the first threshold. The wireless tag 11 determines which divided area in the remote area 33 the wireless tag 11 is in by comparing the RSSI of the received radio wave with the second threshold. Here, the second threshold is at least a value smaller than the first threshold. A specific second threshold value is set according to the intensity of the radio wave received from the proximity antenna 10 . By adjusting the second threshold, the boundary line between the area x_x on the corresponding antenna 10 side and the area x_y on the neighboring antenna side is adjusted. Position determination by the wireless tag 11 according to the second embodiment will be specifically described below.

FIG. 4 is a flowchart showing the operation of position determination by the wireless tag 11. As shown in FIG. The flowchart of FIG. 4 is the same as that of FIG. 2 except that it has steps S201 to S203 instead of step S122. Description of steps S100 to S121, which are the same as those in the flowchart of FIG. 2, will be omitted.

As shown in the flowchart of FIG. 4, when it is determined in step S116 that the RSSI of the radio wave from the corresponding antenna 10 is equal to or less than the first threshold, the wireless tag 11 proceeds to step S201 to It is determined whether or not the number of received radio waves whose RSSI exceeds the second threshold is one among the radio waves received by 11 .

If it is determined in step S201 that the number of received radio waves exceeding the second threshold is 1, it can be determined that radio waves having an intensity exceeding the second threshold are being received only from the corresponding antenna 10 . In this case, the process proceeds to step S202, the position is determined to be the remote area x_x on the side of the corresponding antenna 10, and the process proceeds to step S121, and the position determination result is notified.

On the other hand, if it is determined in step S201 that the number of receptions is not 1, the number of receptions is 2, indicating that radio waves with an intensity exceeding the second threshold are received from the corresponding antenna 10 and the nearby antenna 10. I can judge. In this case, the process proceeds to step S203, the position is determined to be the remote area x_y on the nearby antenna 10 side, and then the process proceeds to step S121, and the corresponding antenna 10 is notified of the position determination result.

As described above, the near field 32 and the far field 33 are stored in the controller of the position sensing system. Further, by adjusting the second threshold, the boundaries of the divided areas x_x and x_y of the remote area 33 are adjusted, and the control unit of the position detection system stores the divided areas x_x and x_y in each identification area 31. there is Therefore, when it is determined that the wireless tag 11 is in the remote area 33 of the corresponding antenna 10, based on the signal "x_x" or "x_y" received by the corresponding antenna 10, the control unit of the position detection system The position of tag 11 can be detected.

As described above, according to the second embodiment, the position detection area of the corresponding antenna 10 is further subdivided by comparing the received strength of the radio waves respectively transmitted from the corresponding antenna 10 and the nearby antenna 10. be able to. Further, even if there are variations in the intervals and heights of the installed antennas 10, by adjusting the first threshold value and the second threshold value after installing the antennas 10, it is possible to accurately identify the position.

In addition, in the second embodiment, the case where two antennas 10 are installed has been described. However, the position determination according to the second embodiment can also be applied when three or more antennas are installed in a row. In this case, each antenna 10 and two other adjacent antennas 10 whose communication areas 20 partially overlap are registered as an antenna set.

The remote region 33 of the identification region 31 associated with the antenna 10 sandwiched between the two neighboring antennas 10 is the remote region x_y1 near the neighboring antenna 10 with the antenna number y1 and the remote region x_y1 with the antenna number y2. It is divided into three divided areas, a remote area x_y2 close to some other nearby antenna 10 and a remote area x_x close to the corresponding antenna 10 in between, and the location information is detected.

Specific location determination in the case of three antenna sets can be performed by the process shown in FIG. That is, when it is determined in step S201 in FIG. 4 that the number of received radio waves exceeding the second threshold is two or more, in the process of step S203, the antenna number of the neighboring antenna 10 that transmitted radio waves exceeding the second threshold is By specifying y, it is specified that the user is in area x_y in the remote area.

Embodiment 3.
FIG. 5 is a diagram schematically showing the configuration of the position detection system according to the third embodiment. In the example of Embodiment 3, four antennas 10 numbered 1 to 4 are installed adjacently. Each of the four antennas 10 is installed so that a part of the communication area 20 with the wireless tag 11 overlaps with a part of the communication area 20 with the other three antennas 10 and the wireless tag 11 . These four antennas 10 are registered as an antenna set.

As shown in FIG. 5, the identification area 31 corresponding to the antenna 10 numbered x is divided into a near area 32 and a far area 33 and located. Furthermore, the remote area 33 includes an area that does not receive radio waves with an intensity exceeding the second threshold from any nearby antenna 10, an area that receives radio waves with an intensity exceeding the second threshold from one of the other nearby antennas 10, and The position is determined by dividing into four areas including an area receiving radio waves with an intensity exceeding the second threshold from two or more other nearby antennas 10 .

The four areas are specified by the antenna number x of the corresponding antenna 10 and the antenna number y of the neighboring antennas 10 . Specifically, when radio waves having an intensity exceeding the second threshold value are not received from adjacent antennas 10 other than a corresponding antenna 10, the antenna number x_x of the corresponding antenna 10 is transmitted to specify the area. For example, if the corresponding antenna 10 is the antenna with antenna number 1, area 1_1 in FIG. be.

When a radio wave having an intensity exceeding the second threshold is received from one of the adjacent antennas 10, the antenna number x of the corresponding antenna 10 and the antenna number y of the adjacent antenna that transmitted the radio wave having an intensity exceeding the second threshold are transmitted. area is specified. For example, the area specified when the corresponding antenna 10 is antenna number 1 and the radio wave exceeding the second threshold is received from the adjacent antenna 10 with antenna number 4 is area 1_4 in FIG.

When radio waves with an intensity exceeding the second threshold are received from two or more of the proximity antennas 10, the wireless tag 11 is in an area where the communication areas 20 of three or all of the antennas overlap. This area is specified by the antenna number x of the corresponding antenna 10 and the antenna number z of the adjacent antenna 10 arranged on the diagonal line of the corresponding antenna 10 . For example, the area identified when the corresponding antenna 10 is antenna number 1 and receives radio waves exceeding the second threshold from two or more adjacent antennas is area 1_3 in FIG. The diagonal antenna number z for each antenna 10 may be stored in the wireless tag 11 in advance. Also, instead of transmitting the antenna number, some signal z may be transmitted as a signal x_z indicating that three or more communication areas 20 are in an overlapping area.

The controller of the position detection system stores each position corresponding to the signal "x_x" or "x_y" or "x_z" indicating the area within the remote area 33 transmitted from the wireless tag 11 . Therefore, by transmitting these signals indicating the area within the remote area 33 from the wireless tag 11, the control unit can identify the position.

FIG. 6 is a flow chart showing the operation of position determination by the wireless tag 11. As shown in FIG. The flowchart of FIG. 6 is the same as the flowchart of FIG. 4, except that steps S301 to S306 are performed instead of steps S201 to S203. The description of the same steps S100 to S121 as in FIG. 2 or 4 will be omitted.

In the process of FIG. 6, if it is determined in step S116 that the RSSI of the radio wave from the corresponding antenna 10 is equal to or less than the first threshold, the process proceeds to step S301, and the RSSI exceeds the second threshold. The number of radio waves received is confirmed. As a result of confirmation, if the number of receptions is 1, it is determined that the received radio wave is the radio wave transmitted from the corresponding antenna 10 . In this case, the process proceeds to step S302, and it is determined that the remote area 33 is located in the area x_x where radio waves equal to or greater than the second threshold are received only from the corresponding antenna 10. FIG. After that, the process proceeds to step S121, and the corresponding antenna 10 is notified of the signal x_x as a result of the position determination.

If it is determined in step S301 that the number of received radio waves having an intensity exceeding the second threshold is 2, the process proceeds to step S303, and the number of the adjacent antenna 10 that transmitted the radio waves having an intensity exceeding the second threshold is y is stored. Next, the process proceeds to position determination in step S304, and is determined to be in area "x_y". After that, the process proceeds to step S121, and signal x_y is notified to the corresponding antenna 10 as a result of the position determination.

If it is determined in step S301 that the number of received radio waves having an intensity exceeding the second threshold is 3 or more, the process proceeds to step S305, and the antenna number z located diagonally with respect to the corresponding antenna 10 is remembered. Next, the process proceeds to position determination in step S306, where it is determined that the area "x_z" is specified by the antenna number x of the corresponding antenna 10 and the diagonal antenna number z. After that, the process proceeds to step S121, and the corresponding antenna 10 is notified of the signal x_z as a result of the position determination.

As described above, according to the present embodiment, by using four antennas as one antenna set, the region for one antenna can be divided into five areas and position information can be detected. As a result, more detailed position detection can be performed without increasing the number of installed antennas. Further, even if there are variations in the intervals and heights of the installed antennas 10, by adjusting the first threshold value and the second threshold value after installing the antennas 10, it is possible to accurately identify the position.

In order to simplify the explanation, the position information detection of one area corresponding to one antenna set with four antennas as one set was illustrated and explained, but the present embodiment is not limited to this. 7, a configuration may be adopted in which a set of four antennas and a plurality of areas corresponding to the antenna set are arranged side by side. In this case as well, when the wireless tag 11 is in the remote area 33, it is possible to specify where it is in each of the four divided areas of the remote area 33 according to the flowchart of FIG.

In addition, since the position detection system of the present embodiment specifies positions using four antennas as one set, it is desirable that the number of antennas to be installed is a multiple of four. However, it is possible to apply this even if it is not a multiple of 4.

FIG. 8 shows an example in which the number of antennas 10 is six. If the number of antennas is not a multiple of four, some antennas may be redundantly set in two antenna sets so that the number of antennas is a multiple of four. For example, in the example of FIG. 8, antennas No. 2 and No. 3 arranged in the central row are arranged overlapping two antenna sets 40 and 41 . As a result, position information can be obtained by dividing the remote area 33 into four divided areas for each corresponding antenna 10 in a manner similar to that shown in the flowchart of FIG.

9 and 10 show other examples where the number of antennas 10 is not a multiple of four. In the example shown in FIG. 9, the number of antennas forming the antenna set is three, and each antenna 10 is included in only one antenna set. Also in this case, the wireless tag 11 can detect the position information by the same processing as in the flowchart of FIG.

However, the number of areas that can be divided decreases as the number of adjacent antennas decreases. Specifically, in the example shown in FIG. 9, the number 4 antenna is insufficient for the configuration example of the third embodiment shown in FIG. As a result, it is not possible to specify area 1_4 when the corresponding antenna 10 is number 1 and area 3_4 when the corresponding antenna 10 is number 3, which are specified by radio waves from antenna 10 number 4. They are identified as areas 1_1 and 3_3. Even in such a case, the control unit of the position detection system designates the area where the communication area 20 does not overlap with other proximity antennas 10 due to the lack of the proximity antenna 10 as the area x_x of each of the corresponding antennas 10. By registering, the position can be detected correctly.

Also, in the example shown in FIG. 10, two antennas constitute the antenna set. In this example as well, position information can be detected by executing the same processing as in the flowchart of FIG. However, in this case, in the process of step S301 in the flowchart of FIG. 6, the number of received radio waves stronger than the second threshold is either 1 or 2, and the processes of steps S305 and S306 are not executed. In this case, the divided areas of the remote region 33 of the corresponding antenna 10 are divided into two areas, x_y close to the near antenna 10 and area x_x far from the near antenna 10 .

In this way, even when the number of installed antennas 10 is not four, the identification area 31 of each antenna 10 can be divided into the number of antennas +1 area constituting the antenna set to detect position information.

However, if the number of antennas is set to 5 or more, it is conceivable that the reception of radio waves will be duplicated, the intensity relationship of the received radio waves will become complicated, and the number of area divisions will rather decrease. Therefore, the number of antennas in the antenna set is preferably four or less.

<Other Embodiments of Embodiments 1 to 3>
In addition, the control unit of the position detection system of Embodiments 1 to 3 may be mounted on each of the antennas 10, or may may be mounted on a device installed at another location.

Further, in the first to third embodiments, the case where the wireless tag 11 specifies the corresponding antenna 10, determines the position, and transmits the results to the corresponding antenna 10 has been described. However, a similar position determination function may be provided on the antenna 10 side. In this case, for example, the wireless tag 11 identifies the corresponding antenna 10, transmits the RSSI value of the received radio wave to the corresponding antenna 10, and transmits the RSSI value to the corresponding antenna 10 side or a separately installed controller. The position of the wireless tag 11 may be identified by performing comparison with the first threshold value and comparison with the second threshold value.

Further, in Embodiments 1 to 3, a case has been described in which a cubic area in contact with the communication area 20 of each antenna 10 is registered as the identification area 31 . However, the identification area 31 is not limited to this. It may be configured to be registered as an area.

Further, in Embodiments 1 to 3, the configuration for transmitting the position determination result only to the corresponding antenna 10 has been described. By limiting the antenna for transmission in this way to the compatible antenna 10, power consumption can be reduced. However, the configuration is not limited to this configuration, and for example, a configuration in which the position determination result is transmitted to all the antennas 10 constituting the antenna set may be employed.

10 Antenna 11 Wireless Tag 20 Communication Area 31 Identification Area 32 Nearby Area 33 Remote Area 40, 41 Antenna Set

Claims (4)

a wireless tag that can be carried and moved;
a plurality of antennas communicating with the wireless tags;
with
A position detection system for detecting the position of the wireless tag,
each of the antennas is arranged such that a portion of the communication area with the wireless tag overlaps with a portion of the communication area between at least one other antenna and the wireless tag;
Each of the antennas and the other antenna have a function of transmitting radio waves at intermittent timings that do not interfere with each other,
The wireless tag is
receiving radio waves transmitted from the antenna and measuring radio wave reception strength;
identifying the antenna that transmitted the radio wave with the highest radio wave reception strength as a corresponding antenna that is closest to the wireless tag;
By comparing the radio wave reception intensity of the radio wave from the corresponding antenna with a first threshold value, the position of the wireless tag is within the communication area of the corresponding antenna and is within a certain range from the corresponding antenna. in or in a distant region outside said near region;
transmitting a position response of the identified wireless tag to the antenna;
configured as
at least one antenna set is registered, which is a set of a plurality of antennas with portions of the communication area overlapping each other;
In the remote area in the communication area of each of the antennas constituting the antenna set, division into a plurality of divided areas is set according to the number of antennas constituting the antenna set,
The wireless tag is
If it is determined that it is in the remote area of the corresponding antenna,
Reception, which is the number of times radio waves with radio wave reception strength greater than a second threshold, which is a value smaller than the first threshold, are received during the time when radio wave transmission from all the antennas constituting the antenna set is completed detect the number,
Based on the number of receptions, identifying which divided area of a plurality of divided areas in the remote area the location of the wireless tag is located;
A wireless tag position detection system configured as follows. 2. The wireless tag position detection system according to claim 1 , wherein said wireless tag is configured to transmit a positional response of said wireless tag only to said corresponding antenna. a plurality of antennas communicating with portable and movable wireless tags;
a control unit mounted on each of the plurality of antennas;
with
A position detection system for detecting the position of the wireless tag,
each of the antennas is arranged such that a portion of the communication area with the wireless tag overlaps with a portion of the communication area between at least one other antenna and the wireless tag;
Each of the antennas and the other antenna have a function of transmitting radio waves at intermittent timings that do not interfere with each other,
When the wireless tag measures the radio wave reception strength of the radio waves received from the plurality of antennas and identifies the antenna that transmitted the radio wave with the highest radio wave reception strength as the corresponding antenna closest to the wireless tag. , the identified corresponding antenna receives from the wireless tag a value obtained by measuring the radio wave reception intensity of the radio wave from the corresponding antenna;
The control unit compares the value of the radio wave reception intensity received from the wireless tag by the corresponding antenna with a first threshold to determine whether the position of the wireless tag is within the communication area of the corresponding antenna. Identifying whether it is in a near field within a certain range from the corresponding antenna or in a far field outside said near field;
configured as
at least one antenna set is registered, which is a set of a plurality of antennas with portions of the communication area overlapping each other;
In the remote area in the communication area of each of the antennas constituting the antenna set, division into a plurality of divided areas according to the number of antennas constituting the antenna set is set,
The control unit
When it is determined that the position of the wireless tag is in the remote area of the corresponding antenna,
The wireless tag receives a radio wave having a radio wave reception intensity greater than a second threshold, which is a value smaller than the first threshold, during the time when radio wave transmission from all the antennas constituting the antenna set is completed. Based on the number of receptions, which is the number of cases, it is specified in which divided area among a plurality of divided areas in the remote area the position of the wireless tag is located.
A wireless tag position detection system configured as follows. a plurality of antennas communicating with portable and movable wireless tags;
a control unit mounted on any of the antennas or mounted on a device installed at a location different from the plurality of antennas in a state capable of communicating with the plurality of antennas;
with
A position detection system for detecting the position of the wireless tag,
each of the antennas is arranged such that a portion of the communication area with the wireless tag overlaps with a portion of the communication area between at least one other antenna and the wireless tag;
Each of the antennas and the other antenna have a function of transmitting radio waves at intermittent timings that do not interfere with each other,
When the wireless tag measures the radio wave reception strength of the radio waves received from the plurality of antennas and identifies the antenna that transmitted the radio wave with the highest radio wave reception strength as the corresponding antenna closest to the wireless tag. , the identified corresponding antenna receives from the wireless tag a value obtained by measuring the radio wave reception intensity of the radio wave from the corresponding antenna;
The control unit compares the value of the radio wave reception intensity received from the wireless tag by the corresponding antenna with a first threshold to determine whether the position of the wireless tag is within the communication area of the corresponding antenna. Identifying whether it is in a near field within a certain range from the corresponding antenna or in a far field outside said near field;
configured as
at least one antenna set is registered, which is a set of a plurality of antennas with portions of the communication area overlapping each other;
In the remote area in the communication area of each of the antennas constituting the antenna set, division into a plurality of divided areas according to the number of antennas constituting the antenna set is set,
The control unit
When it is determined that the position of the wireless tag is in the remote area of the corresponding antenna,
The wireless tag receives a radio wave having a radio wave reception intensity greater than a second threshold that is smaller than the first threshold during the time when radio wave transmission from all the antennas constituting the antenna set is completed. Based on the number of receptions, which is the number of cases, it is specified in which divided area among a plurality of divided areas in the remote area the position of the wireless tag is located.
A wireless tag position detection system configured as follows.

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