WO2007110964A1

WO2007110964A1 - Position determining program and position determining system

Info

Publication number: WO2007110964A1
Application number: PCT/JP2006/306584
Authority: WO
Inventors: Kazuya Kawashima; Toshiyuki Kimata
Original assignee: Fujitsu Limited
Priority date: 2006-03-29
Filing date: 2006-03-29
Publication date: 2007-10-04
Also published as: JPWO2007110964A1

Abstract

There are included a plurality of readers (R,R,...) that are placed at predetermined coordinates and receive radio waves from a wireless tag; and a server (10) that is connected to the readers via a local area network and serves as a position determining apparatus for determining, based on signals from readers (R), the position of the wireless tag. An HDD (13) of the server stores a position determining program (15), which has a position determining module (15a) for determining, based on signals from readers having received radio waves from the wireless tag to be determined, the position of the wireless tag and which also has a sensitivity adjusting module (15b) for adjusting, based on a signal from a reader having received a radio wave from a marker tag placed at predetermined coordinates, the reception sensitivities of the readers.

Description

Specification

Position detection program and position detection system

Technical field

TECHNICAL FIELD [0001] The present invention relates to a position detection program for causing a computer to function as a device for specifying a position of a detection target attached with a wireless tag, and a position detection system using the position detection program.

[0002] Conventionally, a method of using a wireless tag attached to a detection target when managing a product in a store or a warehouse is known. If a wireless tag is used, the reader can receive the radio waves from the wireless tag to read out the identification information of the detection target in a non-contact manner, or specify the position of the detection target using signals from multiple readers. can do.

[0003] A position detecting device using such a wireless tag is disclosed in Patent Document 1, for example. In the method disclosed in this publication, wireless tags are scattered on the floor surface, scanned from the ceiling side by a reader, and a wireless force representing a specific position data among a number of wireless tags based on the detection result of the reader. Select a tag and register its ID and location. If an object that blocks radio waves is placed on the floor, the radio waves that are hidden by the article will not reach the radio waves. Therefore, after placing the article, the reader scans the radio tag and no radio waves are received from the registered radio tags. By specifying the line tag, the position of the wireless tag is specified as the position of the article.

[0004] However, the position detection device of Patent Document 1 described above is a product management that uses identification information of a wireless tag that is not used to detect the position of a wireless tag attached in advance to the detection target to specify the detection target. It cannot be used for inventory management.

As a wireless tag position detection method applicable to such a use, a trigonometric method and a TDO A (Time Difference of Arrival) method are known. The trigonometry is a method for detecting the position of a wireless tag based on the radio field intensity received by three readers surrounding the target radio tag. The distance between the radio tag and the reader and the radio field intensity received by the reader. The radio wave intensity of the RFID tag to be inspected is measured with each reader, and each reader is based on this. One Daka also calculates the distance to the wireless tag, draws a circle around the position of each reader with the distance as the radius, and specifies the intersection of the three circles as the position of the wireless tag.

[0006] On the other hand, the TDOA method is a method of detecting the position of a wireless tag based on the arrival time of the radio wave to each of the three readers surrounding the wireless tag to be detected. Measure the arrival time of the radio wave to each reader, calculate the distance to each reader force radio tag based on this, draw a circle centered on the position of each reader with that distance as the radius, The intersection of the circles is specified as the position of the wireless tag.

Patent Document 1: Japanese Unexamined Patent Publication No. 2005-228292

Disclosure of the invention

[0007] However, the conventional trigonometric and TDOA method position detection calculates the distance based on the radio field strength and arrival time, so it is immediately detected by the influence of radio wave interference (noise). There is a problem that the accuracy tends to decrease. In addition, since radio wave intensity changes due to environmental changes such as the presence or absence of shielding and weather changes, it is necessary to re-measure the correlation between radio wave intensity and distance according to environmental changes. is there. In addition, the TDOA method requires a dedicated wireless LAN and server, which is expensive to install.

[0008] The present invention has been made in view of the above-described conventional circumstances, and the problem is that highly accurate position detection that is difficult to be affected by radio wave interference is possible, and the environment is Providing a position detection program that allows a computer to function as a position detection device that can be corrected so that accurate position detection can be performed even when there is a change, and a position detection system using the program without using a special device at a low cost There is to do.

[0009] The position detection program of the present invention configured to solve the above-described problems is a reduc- er when a plurality of readers arranged at predetermined coordinates receive radio waves of radio tag power. The computer functions as a position detection device that detects the position of the wireless tag based on the signal of the wireless tag, and the position of the wireless tag is determined based on the signal of the reader power that has received the radio wave from the detection target wireless tag. A position detection module comprising: a position detection module to be identified; and a sensitivity adjustment module that adjusts the reception sensitivity of each reader based on a signal of a reader force that has received a radio wave from a marker tag arranged at a predetermined coordinate. The computer receives the received signal from the reader that has received the radio wave from the detection target wireless tag. And the step of obtaining the position of the center of gravity of the coordinates of the reader that has received the received signal and the step of outputting the obtained position of the center of gravity as the position of the detection target wireless tag. In addition, the step of receiving the received signal of the reader receiving the radio wave from the marker tag, the step of obtaining the center position of the coordinates of the reader that received the received signal, and the distance between the obtained center of gravity position and the coordinate of the marker tag A step of determining whether or not the allowable range is exceeded, and a step of adjusting the reception sensitivity of the reader so that the position of the center of gravity approaches the coordinates of the marker tag when the distance exceeds the allowable range. To do.

[0010] With such a configuration, the position of the detection target wireless tag is calculated based only on whether or not the radio wave intensity or the radio wave arrival time is received. In addition, by adjusting the reception sensitivity according to changes in the environment, accurate position detection is possible even when the environment changes.

[0011] Note that the step of obtaining the position of the center of gravity in the position detection module and the sensitivity adjustment module includes a step of counting the number of times the reader has received a radio wave from the detection target wireless tag within a predetermined time, and a reception signal. It is desirable to include a step of weighting the coordinate position of the reader according to the number of receptions to obtain the position of the center of gravity.

[0012] The number of receptions within a certain time increases as the radio field strength increases, that is, as the distance to the RFID tag reader decreases. Therefore, the signal from each reader is sampled within a predetermined time, and the center of gravity position is determined based only on the coordinates of the reader by using the number of receptions for weighting the coordinates of the reader when calculating the position of the center of gravity. This makes it possible to detect the position more accurately.

[0013] In addition, the step of obtaining the center-of-gravity position by weighting includes the step of removing the calculation position of the coordinate position of the reader in which the distance of the detection target RFID tag force is larger than a predetermined ratio compared to other readers. It is desirable. The threshold is determined by examining the relationship of the number of receptions to the distance from the tag to determine the standard deviation σ, and using the range of the σ for the average to calculate the center of gravity. You may make it also exclude a coordinate calculation power. Alternatively, the coordinates of the reader whose number of receptions is smaller than a predetermined ratio compared to other readers may be eliminated. [0014] Thereby, it is possible to delete the coordinates of the reader that was accidentally received due to the influence of reflection, etc. while it is outside the reach of the radio wave, and the detection target is based only on the coordinates of the neighboring reader with high reliability. It becomes possible to accurately detect the position of the wireless tag.

[0015] Furthermore, prior to the execution of the sensitivity adjustment module, a plurality of readers surrounding a single force tag can be associated with each marker tag. In this case, in the step of adjusting the reception sensitivity, only all of the readers associated with the marker tag receive the signal of the marker tag, and in this case, the reception frequency of the reader is increased, and the reception sensitivity of the reader is increased. And Z, or a step that reduces the reception sensitivity of a reader that receives a large number of receptions, and if there is an unreceived reader among the associated readers, a step that increases the reception sensitivity of the reader is included and is not associated If it is received by the reader, it is desirable to include a step of reducing the receiving sensitivity of the reader.

[0016] As described above, the reader surrounding the marker tag is associated in advance, and the reception sensitivity is adjusted so that the associated reader receives the radio wave of the force tag force, thereby performing adjustment within a range sufficient for position detection. be able to.

On the other hand, the position detection system of the present invention includes a plurality of readers that are arranged at predetermined coordinates and receive radio waves of radio tag power, and positions that detect the position of the radio tag based on signals of the reader power. A position detection module configured by a programmed computer, and a position detection module that specifies a position of the wireless tag based on a reader force signal that has received a radio wave of the detection target wireless tag force; And a sensitivity adjustment module that adjusts the reception sensitivity of each reader based on the signal of the reader force that has received the radio wave of the marker tag force placed at the specified coordinates, and the position detection module is a radio wave of the detection target wireless tag force Means for receiving the received signal of the reader force that received the signal, means for obtaining the center of gravity position of the coordinates of the reader that received the received signal, and detecting the obtained center of gravity position. The sensitivity adjustment module includes a means for receiving the reception signal of the reader force that has received the radio wave from the marker tag, and a means for obtaining the position of the center of gravity of the coordinates of the reader that has received the reception signal. And means for determining whether the distance between the calculated center of gravity position and the coordinates of the marker tag exceeds the allowable range, and if the distance exceeds the allowable range, the reader receives so that the center of gravity position approaches the coordinates of the marker tag. Means to adjust the sensitivity It is characterized by including.

[0018] With this configuration, the position of the detection target wireless tag is calculated based only on whether or not the radio wave intensity or the radio wave arrival time is received, so that it is affected by radio wave interference. In addition, by adjusting the reception sensitivity according to changes in the environment, accurate position detection is possible even when the environment changes.

[0019] As described above, according to the present invention, a program for causing a computer to function as a position detection device adapted to an environmental change that is difficult to receive radio wave interference, and a system including the position detection device are provided. Can be provided.

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. First, the configuration of a system including a server computer for executing a position detection program according to an embodiment of the present invention will be described with reference to FIG.

[0021] This system is connected to a reader R via a local area network (LAN) and a plurality of readers R, R, ... that are arranged at predetermined coordinates and receive radio waves of RFID tag power. And a server 10 that is a position detection device that detects the position of the wireless tag based on a signal from the reader R. Each reader R can adjust its reception sensitivity by setting from the server 10.

The server 10 includes a programmed computer, and includes a CPU (Central Processing Unit) 11, a RAM (Random Access Memory) 12, and an HDD [Hard Disk Drive] 13. CPUl l is a central processing unit that controls the entire server 10. The RAM 12 is a main storage device in which a work area is expanded when the CPU 11 executes various programs. The HDD 13 is an auxiliary storage device that stores programs and data. The HDD 13 is a position coordinate DB (Data Base) 14 that stores position coordinates of a reader and a marker tag, which will be described later, and is read onto the RAM 12 by the CPU 11. The position detection program 15 to be executed is stored. Note that the power server omitted in Fig. 1 is connected to an input device such as a keyboard and a display, and the HDD stores various programs including the operating system.

[0023] The position detection program 15 is read from the reader scale that has received the radio wave of the detection target RFID tag. The position detection module 15a that identifies the position of the wireless tag based on the signal, and adjusts the reception sensitivity of each reader based on the signal of the reader R force that has received the radio wave from the marker tag placed at a predetermined coordinate. And a sensitivity adjustment module 15b.

Next, the principle of position detection and sensitivity adjustment will be described with reference to FIG. As shown in the drawing, the plurality of readers R are two-dimensionally arranged so as to be located at the intersections of the lattices. These readers R are arranged in an indoor space such as a warehouse, and are embedded in the floor or installed on the ceiling so as not to interfere with the goods to be stored. In Fig. 2, identifiers 1-1 to 3-5 are attached to these readers R. The position coordinates DB 14 of the server 10 stores the identifiers of these readers and the arranged position coordinates in association with each other.

For example, as shown in FIG. 2, a case is assumed where an object (product, etc.) T to which a wireless tag is attached is placed. Assuming that the reachable distance of the radio wave from the wireless tag is indicated by a dotted circle, the radio wave emitted from this radio tag is surrounded by four readers Rl-2, Rl-3, R2-2, R2-3 Is received. By receiving the signal from each reader, the server 10 can know that these four readers have received radio waves with the power of a wireless tag. The signal from the reader includes the identifier of the reader and the identifier of the wireless tag received by the reader.

[0026] Therefore, the position detection module 15a of the server 10 reads the coordinates of each reader from the position coordinates DB 14 based on the identifiers of the readers that have received radio waves from the same wireless tag. The position of the center of gravity of the coordinates is calculated and obtained, and this is output on the display as the position of the wireless tag.

[0027] The coordinates (X, y) of the center of gravity are as follows: (xl, yl), (x2, y2), (x3, y3), (x4, y4)

x = (xl + x2 + x3 + x4) / 4

y = (yl + y2 + y3 + y4) / 4

It is calculated by.

[0028] The operator looks at the identifier of the displayed wireless tag (and the article DB force not shown based on this identifier, the article name read out, etc.) and the position coordinates, and which article is stored at which position. You can know what is being done. In this example, two-dimensional coordinates are used as an example. For example, if the warehouse has multiple floors, you can use 3D coordinates to identify the floors!

[0029] When the sensitivity of each reader R is adjusted, a marker tag M arranged at the center of the four readers R is used as shown in FIG. The marker tag M is a wireless tag having the same performance as the detection target wireless tag. However, the installation position of the marker tag M is predetermined.

[0030] The sensitivity adjustment module 15b receives the received signal from the reader R that has received the radio wave from the marker tag M, obtains the center of gravity position of the coordinates of the reader R that has received the received signal, and obtains the obtained center of gravity position and the marker tag. Determine whether the distance between M and the actual coordinates exceeds the allowable range. When the distance exceeds the allowable range, the reception sensitivity of the reader R is adjusted so that the position of the center of gravity approaches the coordinates of the marker tag.

[0031] When calculating the position of the center of gravity of the reader R, if only the coordinates of the reader that received the signal are used, for example, in the example of FIG. The detection result is the same whether it is positioned or shifted from the center of gravity. If this meets the required detection accuracy, there is no problem, but if higher accuracy detection is required, if there is a desire to increase the reader spacing, only the coordinates are used as described above. Using just to calculate the center of gravity is not accurate enough.

Therefore, in the embodiment, the position of the center of gravity is calculated using the coordinates of the reader that has received the radio wave from the detection target wireless tag and the number of receptions within a certain time. That is, each reader-powered signal is sampled at a predetermined period within a predetermined time period of 30 seconds or 1 minute, and the number of times the reader receives radio waves from the detection target wireless tag is counted. Then, the position of the center of gravity is obtained by weighting the coordinate position of the reader that has received the received signal according to the number of receptions.

[0033] For example, as shown in FIG. 3, radio waves generated by the RFID tag are received by four readers R1-2, Rl-3, R2-2, R2-3 surrounding them, and sampled within a certain time. If the number of times was 2, 4, 2 and 3, respectively, the coordinates of the center of gravity (X, y) are the coordinates of each reader (x 1, yl), (x2, y2) , (x3, y3), (x4, y4)

x = (xl X 2 + x2 X 4 + x3 X 2 + x4 X 3) / ll y = (yl X 2 + y2 X 4 + y3 X 2 + y4 X 3) / ll

It is calculated by. Readers close to the wireless tag have few reception failures, and remote readers have many reception failures.By sampling and weighting the received signal in this way, the position of the detection target wireless tag can be detected more accurately. It becomes possible.

Next, the processing contents of the position detection program 15 will be described with reference to FIG. When the position detection program 15 starts, the initial setting process is executed first (

5.1). In the initial setting, the correspondence between the identifier (ID) and coordinates of each reader R, the coordinates of the marker tag M, the association between the marker tag M and the reader R surrounding it, and the allowable range of marker tag detection error are registered in the position coordinate DB 14. .

When the initial setting is completed, the processing of the position detection module 15a starts. Here, the signal from the reader R that has received the signal of the RFID tag power to be detected for a certain period of time is sampled (

5.2) Based on the sampled signal, the center of gravity position is calculated using the above formula (S.3). Then, the calculated position of the center of gravity is output to the display or the like as the position of the detection target wireless tag (S.4).

[0036] When the execution of the position detection module 15a is completed, the position detection program 15 determines whether or not there is a change in the environment in which the leader scale is arranged (S.5). Changes in the environment include, for example, rearrangement of racks and the like in the room where the leader is placed, movement of goods, or change in climate. These determinations are made by the operator, and an input device force (not shown) is also input to the server 10.

[0037] If there is no change in the environment (S.5, No), it is determined whether or not to end the position detection program 15 (S.6). If not finished, return to S .2 and repeat the processing of the position detection module 15a.

On the other hand, when the environment has changed (S.5, Yes), the processing of the sensitivity adjustment module 15b is executed. Here, the signal from the reader R that receives the signal from the marker tag M for a certain period of time is sampled (S.7), and the center of gravity position is calculated based on the sampled signal in the same manner as in S.3 above (S .8). Then, the distance between the calculated center of gravity position and the actual marker tag position registered in advance in S.1 is calculated (S.9), and whether it is within the allowable range registered in advance with this distance force .1. It is determined whether or not (S.10). For example, as shown in Fig. 5, If the center of gravity position falls within an allowable range (indicated by a one-dot chain line) centered on the actual marker tag M, it is determined that there is no need for sensitivity adjustment, and the processing of the sensitivity adjustment module 15b is terminated.

On the other hand, when the distance exceeds the allowable range, it is determined that the reception sensitivity needs to be adjusted, and the processes of S.12 to S.16 are executed. First, the signal power from the marker tag M judges whether all the readers R associated with this marker tag have received the signal (S.ll). For example, as shown in FIG. 6, when four readers Rl-2, Rl-3, R2-2, R2-3 surrounding this are associated with the marker tag M, all the force reception signals of these four readers are If the received signal is not received from any other reader, the determination in S.11 is Yes. In such a case, set the sensitivity of the reader with the high number of receptions to a low value and set the sensitivity of the reader with the low number of receptions to a high value (S.12). The sensitivity adjustment level shall be the predetermined sensitivity adjustment unit. Do not make these adjustments for both high and low, and adjust only one of them.

[0040] If only all of the readers R associated with the marker tag have not received (S.ll, N 0), it is determined whether there is a force that has not been received in the associated reader (S.ll, N0). 13), it is judged whether there is power received by the reader not associated (S.15). If there is an unreceived reader among the associated ones (S.13, Yes), the reception sensitivity of this unreceived reader is set to a value higher by the sensitivity adjustment unit (S.14). Also, if there is a reader that has been received among the unrelated readers (S.15, Yes), the reception sensitivity of this received reader is set to a value that is lower by the sensitivity adjustment unit (S.16). .

[0041] When the reception sensitivity is changed in S.12, S.14, and S.16, the process returns to S.7, the signal is sampled, and the adjustment is repeated until the distance is within the allowable range. When the distance is within the allowable range, the processing of the sensitivity adjustment module 15b related to the reader associated with the marker tag is terminated, and the position detection program 15 is terminated.

The step of calculating the position of the center of gravity based on the sampled signals of S.3 and S.8 can be replaced with a process as shown in FIG. Due to the radio characteristics, readers placed outside the reachable range of radio waves may accidentally receive radio waves with the power of the target RFID tag due to the influence of reflectors such as pillars. For example, reader R2-1 in Fig. 8 It corresponds to the case of trusting. The position of the center of gravity is obtained by averaging the value of each coordinate over the number of receptions as described above, but the value of the coordinate at a distance is affected by the determination of the position of the center of gravity even if the number of receptions is small. This may cause a large position detection error. Therefore, the process shown in FIG. 7 includes a step of excluding the calculation force from the coordinate position of the reader whose distance is greater than a predetermined ratio compared to other readers.

That is, in the process of FIG. 7, the center of gravity position is calculated based on the sampled data (S.20), and the distance between the calculated center of gravity position and each reader is calculated (S.21). ), If there is a long distance leader (S.22, Yes), exclude this as well (S.23). This process is repeated until there are no more readers to be excluded, and the process returns to the process in Fig. 5. In this way, accurate detection of the position is possible by removing the coordinates of the center of gravity from the coordinates of the reader far from the wireless tag.

[0044] To determine whether the distance is far or not, the relationship between the number of receptions with respect to the distance of the RFID tag power is obtained to obtain the standard deviation σ, and the center of gravity is obtained from the average σ range. It can be used for the calculation of the above, and coordinates outside the range can be excluded. Alternatively, it may be possible to remove the calculation power of the coordinates of the reader whose number of reception is smaller than a predetermined ratio compared to other readers.

[0045] In this example, as for the position detection module 15a, the force described for detection for a single wireless tag can be identified by an identifier, so that the position detection module 15a can be simultaneously positioned for a plurality of wireless tags. Detection is possible. In the above description, the sensitivity adjustment module 15b has been described by taking the sensitivity adjustment of the reader related to a single marker tag as an example, but in reality, a large number of marker tags are arranged, and each marker tag Adjust the sensitivity of the reader associated with. At this time, if one reader is associated with multiple marker tags, the sensitivity adjusted based on one marker tag may be changed again by adjustment based on another marker tag. In such cases, adjustments may circulate and not converge, so one reader can place the marker tag so that it can be associated with only one marker tag, and if the above adjustments overlap It is desirable to take measures such as restoring the adjustment. [0046] In the above description, the explanation is made on the assumption that the environment in which each reader is arranged is common. However, due to a problem in the structure of the building or the like, the signal included in the signal detected by the leader is actually used. There are variations in size. Therefore, it is desirable for the server 10 to store an environmental parameter representing the noise level for each reader, and to calculate in consideration of the noise level when calculating the center of gravity. The noise level is measured using a spectrum analyzer at the place where the reader is installed. For example, there is no change at noise level 0, x and y coordinates are multiplied by 1.1 at noise level 1, and x and y coordinates are multiplied by 1.2 at noise level 2.

Appendix

[0047] 1. As a position detection device that detects the position of the wireless tag based on a signal of the reader force when a plurality of readers arranged at predetermined coordinates receive the signal of the wireless tag force. In a position detection program that causes a computer to function,

A position detection module that identifies the position of the wireless tag based on the signal of the reader power that has received the radio wave of the detection target RFID tag power, and the reader that has received the radio wave of the force tag power placed at a predetermined coordinate A sensitivity adjustment module that adjusts the reception sensitivity of each reader based on the power signal,

The position detection module is connected to a computer.

A step of receiving a reception signal from a reader that has received radio waves from the detection target wireless tag;

The step of obtaining the position of the center of gravity of the coordinates of the reader that has received the received signal, and the step of outputting the obtained position of the center of gravity as the position of the detection target wireless tag,

The sensitivity adjustment module is connected to the computer.

Receiving a reception signal from a reader that has received a radio wave from the marker tag; obtaining a centroid position of the coordinates of the reader that has received the reception signal; and a distance between the obtained centroid position and the coordinates of the marker tag is allowed. A step of determining whether or not the range is exceeded;

Adjusting the reception sensitivity of the reader so that the position of the center of gravity approaches the coordinates of the marker tag when the distance exceeds an allowable range; The position detection program characterized by performing.

2. The step of obtaining the position of the center of gravity in the position detection module and the sensitivity adjustment module is as follows:

Powering the number of times the reader has received radio waves of the detection target RFID tag within a predetermined time; and

2. The position detection program according to claim 1, further comprising a step of obtaining a gravity center position by weighting the coordinate position of the reader that has received the reception signal according to the number of receptions.

3. The step of obtaining the center-of-gravity position by weighting includes the step of removing the calculation position of the coordinate position of the reader in which the distance of the RFID tag force to be detected is greater than a predetermined ratio compared to other readers. The position detection program according to appendix 2, which is characterized.

4. The step of obtaining the center-of-gravity position by weighting includes the step of excluding the calculation power of the coordinate position of the reader whose number of receptions is smaller than a predetermined ratio compared to other readers. The described position detection program.

5. Prior to execution of the sensitivity adjustment module, each of the marker tags is associated with a plurality of readers surrounding the marker tag,

The step of adjusting the reception sensitivity includes:

If all of the readers associated with the marker tag are receiving signals with the marker tag strength, increase the reception sensitivity of the reader with the lower number of receptions and decrease the reception sensitivity of the reader with the higher number of receptions. Including steps,

If there is an unreceived reader among the associated readers, the method includes the step of increasing the reception sensitivity of the reader;

The position detection program according to any one of appendices 2 to 4, further comprising a step of reducing the reception sensitivity of the reader when the reader receives the associated information.

6. When a plurality of readers arranged at predetermined coordinates receive radio wave of radio tag power, a position detection device that detects the position of the radio tag based on the signal of the reader power

[^ [This ^ A position detection module that identifies the position of the wireless tag based on the signal of the reader power that has received the radio wave of the detection target RFID tag power, and the reader that has received the radio wave of the force tag power placed at a predetermined coordinate A sensitivity adjustment module that adjusts the reception sensitivity of each reader based on the power signal,

The position detection module includes:

Means for receiving a reception signal from a reader that has received radio waves from the detection target wireless tag;

Means for obtaining the position of the center of gravity of the coordinates of the reader that has received the received signal;

Means for outputting the obtained center-of-gravity position as the position of the detection target wireless tag, the sensitivity adjustment module,

Means for receiving a reception signal from a reader that has received radio waves from the marker tag; and means for determining a position of the center of gravity of the coordinates of the reader that has received the reception signal;

Means for determining whether or not a distance between the obtained center of gravity position and the coordinates of the marker tag exceeds an allowable range;

And a means for adjusting the receiving sensitivity of the reader so that the position of the center of gravity approaches the coordinates of the marker tag when the distance exceeds an allowable range.

7. In a position detection system including a plurality of readers that are arranged at predetermined coordinates and receive radio tag force radio waves, and a position detection device that detects the position of the radio tag based on the signal of the reader force ,

The position detection device is constituted by a programmed computer,

The position detection module includes:

A hand that receives a reception signal from a reader that has received a radio wave from the detection target wireless tag. Step and

Means for obtaining a center of gravity position of the coordinates of the reader that has received the received signal; and means for outputting the obtained center of gravity position as a position of the detection target wireless tag.

Means for receiving a reception signal from a reader that has received a radio wave from the marker tag; means for determining a centroid position of the coordinates of the reader that has received the reception signal; and a distance between the obtained centroid position and the coordinates of the marker tag is allowed. Means for determining whether or not the range is exceeded,

Brief Description of Drawings

FIG. 1 is a block diagram schematically showing a system including a computer for executing a position detection program which is a form for carrying out the present invention.

FIG. 2 is a plan view showing an example of arrangement of readers in the system of FIG. 1.

[0050] FIG. 3 is a conceptual diagram showing a relationship between a reachable range of radio waves and a reader when weighting is performed according to the number of receptions.

FIG. 4 is a flowchart showing the processing contents of a position detection program that is an embodiment for carrying out the present invention.

FIG. 5 is a conceptual diagram showing an example of a relationship between a reader and a calculated barycentric position.

FIG. 6 is a conceptual diagram showing another example of the relationship between the reader and the calculated barycentric position.

[0054] FIG. 7 is a flowchart showing another example of calculation of the center of gravity position in the flowchart shown in FIG.

FIG. 8 is a conceptual diagram showing still another example of the relationship between the reader and the calculated barycentric position.

Claims

The scope of the claims

[1] When a plurality of readers arranged at predetermined coordinates receive a radio wave of radio tag power, a computer is used as a position detection device that detects the position of the radio tag based on the signal of the reader power. In the position detection program to function,

The position detection module is connected to a computer.

The sensitivity adjustment module is connected to the computer.

Adjusting the reception sensitivity of the reader so that the position of the center of gravity approaches the coordinates of the marker tag when the distance exceeds an allowable range;

The position detection program characterized by performing.

[2] The step of obtaining the position of the center of gravity in the position detection module and the sensitivity adjustment module includes:

2. The position detection program according to claim 1, further comprising the step of weighting the coordinate position of the reader that has received the reception signal according to the number of receptions to obtain a center of gravity position. Program.

[3] The step of obtaining the center of gravity position by weighting includes a step of excluding the calculation position of the coordinate position of the reader in which the distance of the detection target RFID tag force is larger than a predetermined ratio compared to other readers. The position detection program according to claim 2, wherein the program is a position detection program.

[4] Prior to execution of the sensitivity adjustment module, each of the marker tags is associated with a plurality of readers surrounding the marker tag,

The step of adjusting the reception sensitivity includes:

The position detection program according to claim 2 or 3, further comprising a step of lowering the reception sensitivity of the reader when the reader receives the associated information.

[5] Position detection including a plurality of readers that are arranged at predetermined coordinates and receive radio tag force radio waves, and a position detection device that detects the position of the radio tag based on signals from the readers In the system,

The position detection device is constituted by a programmed computer,

The position detection module includes:

Means for obtaining the position of the center of gravity of the coordinates of the reader that has received the received signal, and means for outputting the obtained position of the center of gravity as the position of the detection target wireless tag. The sensitivity adjustment module includes:

A means for receiving a reception signal from a reader that has received a radio wave from the marker tag; a means for determining a centroid position of the coordinates of the reader that has received the reception signal; and a distance between the obtained centroid position and the coordinates of the marker tag is allowed. Means for determining whether or not the range is exceeded,