Wireless tag reader and program

Abstract

To provide a wireless tag reading apparatus and a program capable of correctly reading a wireless tag in a predetermined area even when the wireless tag is attached to an article that influences reading performance.SOLUTION: A wireless tag reading apparatus comprises: a radio wave transmitting / receiving section that transmits a radio wave and receives a response wave from wireless tags to the radio wave; a signal acquisition section that acquires, from a plurality of response waves received by the radio wave transmitting / receiving section moving with time, identification information registered in each wireless tag and indicating attributes of an article, and an RSSI value and a phase value of the response wave as time series signals; an estimation section that calculates an estimated position of each wireless tag and its reliability level on the basis of the RSSI value and the phase value; and a signal reacquisition section that causes only the wireless tag satisfying a condition to re-acquire the response wave when the reliability level is less than a threshold or when the identification information includes an attribute that greatly influences a reading result of the wireless tag. The estimation section calculates the estimated position of the wireless tag on the basis of the reacquired response wave.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] Embodiments of the present invention relate to a wireless tag reader and a program.

Background Art

[0002] Conventionally, there is known a wireless tag reader that reads information on a wireless tag attached to a product housed in a basket while moving an antenna (for example, Patent Document 1).

[0003] In such a wireless tag reader, based on the RSSI value or phase value of the response wave from the wireless tag, it is determined whether the product with the wireless tag is in a predetermined area (for example, inside the basket), and the information registered in the wireless tag is read. However, when the product with the wireless tag is a product that affects the reading performance, such as containing metal, there is a problem that the determination accuracy of the position where the wireless tag is located decreases.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem to be solved by the present invention is to provide a wireless tag reader and a program that can correctly read a wireless tag in a predetermined area even if the article with the wireless tag affects the reading performance.

Means for Solving the Problems

[0005] The wireless tag reader of this embodiment comprises a radio wave transmitting / receiving unit, a movement control unit, a signal acquisition unit, an estimation unit, and a signal reacquisition unit. The radio wave transmitting / receiving unit transmits radio waves and receives response waves from wireless tags attached to articles in response to the radio waves. The movement control unit moves the position of the radio wave transmitting / receiving unit over time. The signal acquisition unit acquires identification information indicating the attributes of the article registered in the wireless tag and the attributes of the wireless tag, as well as the RSSI value and phase value of the response wave as a time-series signal, from a plurality of response waves received by the radio wave transmitting / receiving unit moved by the movement control unit. The estimation unit calculates the estimated position of the wireless tag and the confidence level of the estimated position based on the RSSI value and phase value. The signal reacquisition unit limits the acquisition to wireless tags that have responded with identification information that meets the conditions, provided that the confidence level is below a threshold or the identification information includes attributes that significantly affect the reading result of the wireless tag. To the radio wave transmitting and receiving unit, increase the output power of the radio waves to be transmitted. The response wave is reacquired. The estimation unit then calculates the estimated position of the wireless tag and the confidence level of that estimated position based on the response wave reacquired by the signal reacquisition unit. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is an external perspective view showing an example of a wireless tag reader according to an embodiment. [Figure 2] Figure 2 is a top view showing an example of the main components around the antenna of the wireless tag reader according to the embodiment. [Figure 3] Figure 3 is a hardware block diagram showing an example of the hardware configuration of the wireless tag reader according to the embodiment. [Figure 4] Figure 4 shows an example of information that a wireless tag reader obtains from an RFID tag. [Figure 5A] Figure 5A shows a top view and a side view illustrating an example of a wireless tag reader reading information from RFID tags attached to items in a shopping basket. [Figure 5B] Figure 5B is a diagram illustrating RSSI values ​​and phase values. [Figure 6] Figure 6 illustrates a method for determining whether an RFID tag is inside or outside the basket. [Figure 7] Figure 7 illustrates the method for generating a tag location estimation model. [Figure 8] Figure 8 illustrates the process of estimating the tag location from information acquired by a wireless tag reader. [Figure 9] Figure 9 illustrates the re-reading process performed by the wireless tag reader. [Figure 10] Figure 10 is a functional block diagram showing an example of the functional configuration of the wireless tag reader according to the embodiment. [Figure 11] Figure 11 is a flowchart showing an example of the processing flow performed by the wireless tag reader of the embodiment. [Figure 12] Figure 12 is a flowchart showing an example of the reading process flow in Figure 11. [Modes for carrying out the invention]

[0007] An embodiment of the present invention applied to a wireless tag reader 10 will be described with reference to the drawings.

[0008] (Outline configuration of a wireless tag reader) The schematic configuration of the wireless tag reader 10 will be explained using Figures 1 and 2. Figure 1 is an external perspective view showing an example of the wireless tag reader according to the embodiment. Figure 2 is a top view showing an example of the main components around the antenna of the wireless tag reader according to the embodiment.

[0009] The wireless tag reader 10 is installed, for example, in a self-checkout system. As shown in Figure 1, the wireless tag reader 10 moves a pair of antennas 14 and 15, installed on a moving stage 18, along the Y-axis below a basket 13 containing goods 22 purchased by a customer, which is placed on a platform 12. The pair of antennas 14 and 15 are installed below the platform 12, along the X-axis. The pair of antennas 14 and 15 are installed at an angle to each other around the Y-axis toward the position where the basket 13 is placed. The basket 13 is placed in a predetermined position on the platform 12, for example, inside the placement position marker 16 attached to the platform 12. The basket 13 contains multiple goods 22. The basket 13 is an example of a storage unit in this disclosure. The goods 22 are an example of articles in this disclosure. The goods 22 may be placed directly inside the placement position marker 16 on the platform 12. In other words, basket 13 is not necessary.

[0010] As shown in Figure 2, the moving stage 18 moves along the rail 21 in the Y-axis direction, i.e., in the direction of arrow A, by the rotational driving force of the drive motor 20.

[0011] Antennas 14 and 15 move along the Y-axis and transmit radio waves (transmit waves) in a time-division manner to read the information (tag information) registered in the RFID tag 24 attached to the product 22. Antennas 14 and 15 also receive radio waves (response waves) from the RFID tag 24. The wireless tag reader 10 repeatedly performs this transmission and reception of radio waves at predetermined time intervals.

[0012] Since the RFID tag 24 is directional, the wireless tag reader 10, equipped with two antennas 14 and 15, can reliably detect the response wave from the RFID tag 24 regardless of its arrangement inside the cage 13 by transmitting waves from different directions. Note that the number of antennas is not limited to two.

[0013] The RFID (Radio Frequency IDentification) tag 24 is an example of the wireless tag in the present disclosure. The RFID tag 24 includes an antenna and receives the transmitted waves sent from the antennas 14 and 15 through short-range wireless communication. Also, the RFID tag 24 transmits the information stored in the storage medium of the RFID tag 24 as a response wave to the transmitted waves. The RFID tag 24 stores tag information in the storage medium. The tag information is, for example, a product code (such as an EPC (Electronic Product Code)) that can identify the product 22 to which the RFID tag 24 is attached. When the RFID tag 24 receives a radio wave for reading the information stored in the storage medium from the antennas 14 and 15, the RFID tag 24 transmits the product code and the like stored in the storage medium.

[0014] As shown in FIG. 1, above the mounting table 12, a surveillance camera 26 is installed facing the direction of the mounting table 12. The surveillance camera 26 monitors the mounting table 12 and its surrounding area, for example, the range of the viewing angle ω in FIG. 1. The wireless tag reader 10 analyzes the video captured by the surveillance camera 26 while the antennas 14 and 15 are moving, and recognizes whether there is any movement of the basket 13, the product 22, or people. Details will be described later. Note that the surveillance camera 26 is an example of the imaging unit in the present disclosure.

[0015] Note that the wireless tag reader 10 may include a shield for shielding radio waves so as to surround the basket 13 on the mounting table 12 in order to prevent the radio wave environment from being disturbed by external foreign objects.

[0016] (Hardware Configuration of Wireless Tag Reader) The hardware configuration of the wireless tag reader 10 will be described with reference to FIG. 3. FIG. 3 is a hardware block diagram showing an example of the hardware configuration of the wireless tag reader in the embodiment.

[0017] The wireless tag reader 10 includes a control unit 31 for controlling each part of the wireless tag reader 10. The control unit 31 includes a CPU (Central Processing Unit) 32, a ROM (Read Only Memory) 33, and a RAM (Random Access Memory) 34. The CPU 32 is connected to the ROM 33 and the RAM 34 via an internal bus 35 such as an address bus and a data bus. The CPU 32 expands various programs stored in the ROM 33 and the storage unit 36 into the RAM 34. The CPU 32 controls the operation of the wireless tag reader 10 by operating according to the various programs expanded in the RAM 34. That is, the control unit 31 has the configuration of a general computer.

[0018] The control unit 31 is connected to a storage unit 36, a transceiver controller 37, a motor driver 38, a camera driver 39, a display device 40, an operation device 41, and a communication interface 42 via the internal bus 35.

[0019] The control unit 31 functions as a reader for reading information registered in the RFID tag 24 in cooperation with the transceiver controller 37, the antenna 14, and the antenna 15. Further, the control unit 31 may be made to function as a writer for writing information to the RFID tag 24.

[0020] The control unit 31 acquires information identifying antennas 14 and 15, the time of reception of the response wave, the RSSI value read from the RFID tag 24, the phase value, tag attribute information, and product attribute information, associating them with each other. The RSSI value (Received Signal Strength Indicator) represents the strength of the response wave returning from the RFID tag 24. The phase value represents the phase difference between the transmitted wave and the response wave returning from the RFID tag 24. Based on the phase value, the distance between antenna 14 and RFID tag 24, or the distance between antenna 15 and RFID tag 24, can be estimated. The RSSI value and phase value will be described in more detail later (see Figure 5B). The tag attribute information is information indicating various attributes related to the structure of the RFID tag 24. The product attribute information is information indicating various attributes of the product 22 to which the RFID tag 24 is attached. The tag attribute information and product attribute information will be described in more detail later (see Figure 4).

[0021] The storage unit 36 ​​is a storage device equipped with a non-volatile storage medium such as an HDD (Hard Disk Drive) or SSD (Solid State Drive). The storage unit 36 ​​stores various programs and data related to the operation of the wireless tag reader 10.

[0022] The memory unit 36 ​​stores the control program P, the read data D, and the tag position estimation model Mi (i=a,b,c,…).

[0023] Control program P is a program for operating the wireless tag reader 10.

[0024] Read data D is time-series data acquired from RFID tag 24, read by antennas 14 and 15 while they were moving. The contents of read data D will be described in more detail later (see Figure 4).

[0025] The tag location estimation model Mi (i=a,b,c,…) is a learning model that estimates the location of an RFID tag 24 that has received a response wave. The tag location estimation model Mi is a model that has been learned to output the location of an RFID tag 24 in response to the input of a response wave from an RFID tag 24 by accumulating and storing the results of reading the response wave with the wireless tag reader 10 when an RFID tag 24 is placed in a number of predetermined locations. More specifically, the tag location estimation model Mi is generated for each different type of RFID tag 24 or for each attribute of the product to which the RFID tag 24 is attached, based on the RSSI value and phase value of the response wave from the RFID tag 24. Further details about the tag location estimation model Mi will be described later (see Figure 7).

[0026] The transmit / receive controller 37 transmits and receives radio waves between the control unit 31 and the antennas 14 and 15.

[0027] The motor driver 38 is the controller for the drive motor 20 that drives the moving stage 18. The motor driver 38 controls the drive motor 20 according to the movement instructions from the antennas 14 and 15 output by the control unit 31.

[0028] The camera driver 39 controls the imaging operation of the surveillance camera 26 based on instructions from the control unit 31.

[0029] The display device 40 displays a screen generated by the instructions of the control unit 31. The display device 40 is composed of devices such as an LCD (Liquid Crystal Display) or an organic EL (Electro-Luminescence).

[0030] The operating device 41 acquires the operator's input and transmits it to the control unit 31. The operating device 41 is composed of, for example, a touch panel or a keyboard.

[0031] The communication interface 42 is an interface for communicating with external devices such as POS terminals and store servers (not shown) via a network or the like. The wireless tag reader 10 outputs the reading results of the RFID 24 to these external devices.

[0032] (Explanation of information acquired by the wireless tag reader) Figure 4 illustrates the contents of the read data D acquired by the wireless tag reader 10 from the RFID tag 24. Figure 4 shows an example of the information acquired by the wireless tag reader from the RFID tag.

[0033] The read data D stores the antenna identification information Da, time information Db, tag attribute information Dc, product attribute information Dd, RSSI value De, and phase value Df in association with each other.

[0034] Antenna identification information Da is information that identifies whether the information was received by antenna 14 or by antenna 15.

[0035] Time information Db is information indicating the time when the response wave from the RFID tag 24 was received. Time information Db is measured by the control unit 31. Alternatively, instead of time information Db, position information indicating the position of antenna 14 or antenna 15 at the time the response wave from the RFID tag 24 was received may be stored. The positions of antennas 14 and 15 are determined, for example, by detecting that the moving stage 18, which is located at a predetermined home position, has moved by the number of rotations of the drive motor 20 in a direction defined by the rotation direction of the drive motor 20.

[0036] Tag attribute information Dc is information that indicates attributes related to the structure of the RFID tag 24.

[0037] The tag attribute information Dc includes, for example, information related to the inlay type Dca. An RFID tag 24 is formed from an IC tag chip and an RFID tag antenna (inlay), but there are various types of RFID tag antennas (inlays). Some of these inlays may affect the reading performance. Information indicating that an inlay that may affect the reading performance is being used is stored in the inlay type Dca.

[0038] Product attribute information Dd is information that indicates the various attributes of product 22 to which the RFID tag 24 is attached.

[0039] Product attribute information Dd includes, for example, EPC(Dda), metal content information Ddb, metal influence information Ddc, and dielectric constant information Ddd.

[0040] EPC(Dda) is a product code that can identify product 22. EPC(Dda) is, for example, a JAN code.

[0041] The metal content information Ddb indicates whether product 22 contains metal. If product 22 contains metal, the impedance matching between the IC tag chip of the RFID tag 24 and the RFID tag antenna is disrupted, causing the antenna to malfunction and potentially degrading reading performance. An example of product 22 containing metal is a product containing glitter. Thus, information indicating that a product contains metal is stored in the metal content information Ddb.

[0042] Metal Impact Information Ddc indicates that a product containing metal is particularly likely to affect readability. For example, even with products containing glitter, the impact of the metal can vary depending on the thickness and amount of glitter thread, the stitching method, etc. Also, even with products containing glitter, if the surface is uneven, the distance between the RFID tag 24 and the glitter product may increase, thus reducing the impact on readability. Thus, information indicating that a product containing metal may particularly affect readability is stored in Metal Impact Information Ddc.

[0043] The dielectric constant information Ddd indicates whether product 22 has a high dielectric constant. If product 22 has a high dielectric constant, the performance of the RFID tag antenna may deteriorate. An example of product 22 with a high dielectric constant is a product containing denim fabric. Thus, information indicating that the dielectric constant of a product may affect reading performance is stored in the dielectric constant information Ddd.

[0044] Although not shown in Figure 4, products containing a high amount of moisture, such as cosmetics, may also affect reading performance, so it is advisable to manage them with product attribute information Dd.

[0045] The RSSI value De represents the strength of the response wave returning from the RFID tag 24.

[0046] The phase value Df represents the phase difference between the transmitted wave and the response wave returned from the RFID tag 24. The phase value Df varies between 0° and 359°. When the phase difference between the transmitted wave and the response wave changes from 359° to 360°, the phase value returns to 0°. Therefore, the phase value acquired by the wireless tag reader 10 is discontinuous between 359° and 0°. For this reason, the wireless tag reader 10 performs a correction process for the acquired phase value. Specifically, when the phase value changes from 359° to 0°, the phase value after the change is corrected to 360°. Also, when the phase value changes from 0° to 359°, the phase value after the change is corrected to -1°. As a result, the phase value Df acquired by the wireless tag reader 10 exhibits a characteristic of continuously changing with time.

[0047] The read data D has a predetermined bit length. Each piece of information is stored in the read data D at a predetermined specific bit position. Since the wireless tag reader 10 reads multiple data from multiple RFID tags 24 at different positions on the antennas 14 and 15, the wireless tag reader 10 acquires multiple read data D in chronological order.

[0048] (Explanation of RSSI value and phase value) Figures 5A and 5B will be used to explain the RSSI value De and phase value Df acquired by the wireless tag reader 10. Figure 5A is a top view and side view showing an example of the wireless tag reader reading information from RFID tags attached to items in a basket. Figure 5B is a diagram illustrating the RSSI value and phase value.

[0049] As shown in Figure 5A, the wireless tag reader 10 moves antennas 14 and 15 along the Y-axis below the cage 13, which is placed in a fixed position, and transmits radio waves from each antenna towards the cage 13 in a time-division manner. Antennas 14 and 15 then receive response waves from the RFID tags 24 attached to the product 22 in response to the transmitted waves they themselves have sent.

[0050] Since the transmission of radio waves and the reception of response waves are performed at predetermined time intervals while antennas 14 and 15 are moving, the wireless tag reader 10 acquires time-series data of RSSI values ​​and phase values ​​as shown in Figure 5B.

[0051] The horizontal axis in Figure 5B represents the time t at which the wireless tag reader 10 acquired the response wave. Alternatively, the horizontal axis in Figure 5B can be considered to represent the Y-axis position of antennas 14 and 15.

[0052] The time-series data of the RSSI value shows a larger value when antenna 14 or antenna 15 is closer to the RFID tag 24 that returned the response wave. Conversely, the time-series data of the RSSI value shows a smaller value when antenna 14 or antenna 15 is farther away from the RFID tag 24 that returned the response wave. Therefore, as shown in Figure 5B, the closer antennas 14 and 15 are to the cage 13, the larger the RSSI value.

[0053] The time-series data of the phase value shows a value corresponding to the distance between antenna 14 or antenna 15 and the RFID tag 24 that returned the response wave. Figure 5B is an example in which the phase value is larger the closer the distance between antenna 14 or antenna 15 and the RFID tag 24 that returned the response wave. Note that the phase value shown in Figure 5B is the result of correcting the discontinuously changing phase value to change continuously.

[0054] (Explanation of how to estimate the location of an RFID tag) Figure 6 illustrates how the wireless tag reader 10 estimates the location of the RFID tag 24. Figure 6 is a diagram illustrating how to determine whether the RFID tag is inside or outside the basket.

[0055] The time-series change patterns of RSSI values ​​and phase values ​​acquired by the wireless tag reader 10 (see Figure 5B) correspond one-to-one with the location of the RFID tag 24. Figure 6 shows an overview of the time-series change patterns of RSSI values ​​and phase values ​​acquired by the wireless tag reader 10 when the same RFID tag 24 is placed in multiple locations inside and outside the basket 13.

[0056] When the product 22 with the RFID tag 24 attached is inside the basket 13, the time-series change patterns of the RSSI value and phase value acquired by the wireless tag reader 10 exhibit characteristics with steep peaks in both the RSSI value and phase value, as shown in Figure 5B.

[0057] Assume that product 221, which has an RFID tag 24 attached, is located outside the basket 13, with its position in the X-axis direction equal to that of product 22, but with its position in the Y-axis direction offset to the negative side. In this case, the time-series change patterns of the RSSI value and phase value acquired by the wireless tag reader 10 show a specific characteristic where both the RSSI value and phase value decrease monotonically as antennas 14 and 15 move to the positive side of the Y-axis. Furthermore, in this case, no peaks occur in the RSSI value and phase value.

[0058] Assume that product 222, which has an RFID tag 24 attached, is located outside the basket 13, with its position in the X-axis direction equal to that of product 22, but offset to the positive side in the Y-axis direction. In this case, the time-series change patterns of the RSSI value and phase value acquired by the wireless tag reader 10 show a specific characteristic where both the RSSI value and phase value increase monotonically as antennas 14 and 15 move to the positive side of the Y-axis. Furthermore, in this case, no peaks occur in the RSSI value and phase value.

[0059] Assume that product 223, which has an RFID tag 24 attached, is located outside the basket 13, with its position in the Y-axis direction equal to that of product 22, and its position in the X-axis direction offset to the negative side. In this case, the time-series change patterns of the RSSI value and phase value acquired by the wireless tag reader 10 show peaks in both the RSSI value and phase value, but the peaks that occur are less pronounced compared to when the RFID tag 24 is inside the basket 13.

[0060] Thus, the time-series change patterns of RSSI values ​​and phase values ​​acquired by the wireless tag reader 10 correspond approximately one-to-one with the location of the RFID tag 24. The tag location estimation model Mi (i=a,b,c,…) stored in the wireless tag reader 10 is a model that stores multiple time-series change patterns of RSSI values ​​and phase values ​​acquired by placing multiple RFID tags 24 in multiple locations, associating them with the placement locations of the RFID tags 24. The tag location estimation model Ma is trained to output the estimated location of the RFID tag 24 when given time-series change patterns of RSSI values ​​and phase values ​​as input.

[0061] (Method for generating a tag location estimation model) Figure 7 illustrates the method for generating the tag location estimation model Mi(i=a,b,c,…).

[0062] The tag position estimation model Mi(i=a,b,c,…) stores the time-series change patterns of RSSI values ​​and phase values ​​obtained by placing a predetermined RFID tag 24, or a specific product 22 to which an RFID tag 24 is attached, at a predetermined number of locations (x,y) and reading the response wave with the wireless tag reader 10.

[0063] In the example shown in Figure 7, the tag location estimation model Mi stores the time-series change patterns of RSSI values ​​and phase values ​​obtained when a specific RFID tag 24, or a product 22 with an RFID tag 24 attached, is placed at a specific location (x1, y1). The tag location estimation model Mi also stores the time-series change patterns of RSSI values ​​and phase values ​​obtained when a specific RFID tag 24, or a product 22 with an RFID tag 24 attached, is placed at a specific location (x2, y2). The tag location estimation model Mi also stores the time-series change patterns of RSSI values ​​and phase values ​​obtained when a specific RFID tag 24, or a product 22 with an RFID tag 24 attached, is placed at a specific location (x3, y3). The tag location estimation model Mi also stores the time-series change patterns of RSSI values ​​and phase values ​​obtained when a specific RFID tag 24, or a product 22 with an RFID tag 24 attached, is placed at a specific location (x4, y4).

[0064] Furthermore, the tag location estimation model Mi (i=a,b,c,…) is a different model for each tag attribute and product attribute. Specifically, the tag location estimation model Ma stores the time-series change patterns of RSSI values ​​and phase values ​​obtained by placing RFID tags 24 with the same tag attributes at multiple different locations. In addition, the tag location estimation model Ma stores the time-series change patterns of RSSI values ​​and phase values ​​obtained by placing products 22 with the same product attributes, each with an RFID tag 24 having the same tag attributes, at multiple different locations.

[0065] Furthermore, the tag location estimation model Mb stores the time-series change patterns of RSSI values ​​and phase values ​​obtained by placing an RFID tag 24 having different tag attributes than the tag location estimation model Ma at multiple different locations. In addition, the tag location estimation model Mb stores the time-series change patterns of RSSI values ​​and phase values ​​obtained by placing a product 22 having different product attributes than the product 22 that forms the tag location estimation model Ma, which is attached to an RFID tag 24 having the same tag attributes, at multiple different locations.

[0066] Thus, each generated tag location estimation model Mi(i=a,b,c,…) is associated with a tag attribute or product attribute. Which tag location estimation model Mi is associated with which tag attribute or product attribute is stored, for example, in the header information of the tag location estimation model Mi(i=a,b,c,…).

[0067] For example, tag location estimation model Ma is a tag location estimation model generated with an RFID tag 24 having a specific inlay type. Tag location estimation model Mb is a tag location estimation model generated with the same RFID tag 24 attached to the same product containing metal. Tag location estimation model Mc is a tag location estimation model generated with the same RFID tag 24 attached to a product containing metal, particularly one that affects readability. Tag location estimation model Md is a tag location estimation model generated with the same RFID tag 24 attached to a product 22 having a high dielectric constant. Tag location estimation model Me is a tag location estimation model generated with the same RFID tag 24 attached to a product 22 that does not contain metal or dielectric.

[0068] Furthermore, the tag location estimation model Mi(i=a,b,c,…) learns to estimate the coordinate position (x,y) at which the product 22 with the RFID tag 24 was placed when the input RSSI value and phase value time series change pattern was acquired, by comparing the time series change pattern of the RSSI value and phase value input from an external source with multiple time series change patterns of the RSSI value and phase value that it has stored. Then, the tag location estimation model Mi(i=a,b,c,…) outputs the estimated position 60 of the RFID tag 24 and its confidence level 62 for the time series change pattern of the RSSI value and phase value input from an external source. The confidence level 62 is a value that represents the likelihood of the estimated position 60 of the RFID tag 24. The confidence level 62 is expressed as a number between 0.0 and 1.0, for example. A confidence level of 0.0 indicates the least likely, and a confidence level of 1.0 indicates the most likely.

[0069] (Method for estimating tag location using a tag location estimation model) Figure 8 illustrates the method for estimating the tag location from the information acquired by the wireless tag reader 10. Figure 8 is a diagram illustrating the process of estimating the tag location from the information acquired by the wireless tag reader.

[0070] The wireless tag reader 10 focuses on tag attribute information Dc and product attribute information Dd from the information acquired from the RFID tag 24. It then selects a tag position estimation model Mi (i=a,b,c,…) generated for a product 22 to which an RFID tag 24 has the same attribute information as the acquired tag attribute information Dc and product attribute information Dd. The wireless tag reader 10 then inputs the time-series change patterns of the acquired RSSI value and phase value into the selected tag position estimation model Mi.

[0071] The wireless tag reader 10 outputs the estimated position 60 of the RFID tag 24 and its confidence level 62 by comparing the time-series change pattern of the input RSSI value and phase value with the tag position estimation model Mi.

[0072] The estimated position 60 of the output RFID tag 24 is the position (x,y) where the RFID tag 24 is located, estimated from the time-series change pattern of the input RSSI value and phase value.

[0073] A confidence score of 62 indicates the likelihood of the estimated location 60 of the RFID tag 24 being estimated by the tag location estimation model Mi.

[0074] The wireless tag reader 10 determines that the RFID tag 24 is inside the basket 13 if the estimated position 60 of the product 22 to which the RFID tag 24 is attached, estimated by the tag position estimation model Mi, is within the range on which the basket 13 is placed, and the confidence level 62 is above a threshold value.

[0075] On the other hand, the wireless tag reader 10 determines that the RFID tag 24 is outside the basket 13 if the estimated position 60 of the product 22 to which the RFID tag 24 is attached, estimated by the tag position estimation model Mi, is outside the range in which the basket 13 is placed, and the confidence level 62 is above a threshold value.

[0076] Furthermore, if the confidence level 62 of the estimated position 60 is below a threshold, the wireless tag reader 10 rereads the tag information (see Figure 9).

[0077] Furthermore, rereading of tag information is performed not only when the confidence level 62 of the estimated position 60 is below the threshold, but also when the tag attribute information Dc or product attribute information Dd read by the wireless tag reader 10 has a predetermined attribute value. Specifically, if the tag attribute information Dc is a particular inlay type that is expected to potentially affect the reading performance, or if the product attribute information Dd is a product containing metal that is expected to potentially affect the reading performance, a product with a large metal influence, or a product with a high dielectric constant, then rereading of the tag information will be performed even if the confidence level 62 of the estimated position 60 is above the threshold.

[0078] (Explanation of the rereading process) Figure 9 illustrates the re-reading process of tag information performed by the wireless tag reader 10.

[0079] If the confidence level 62 of the estimated position 60 of the RFID tag 24 is low, the communication frequency between the wireless tag reader 10 and the RFID tag 24 may decrease, resulting in a reduced number of RSSI and phase value samples, as shown in the received information Ra in Figure 9.

[0080] In such cases, the wireless tag reader 10 performs a re-read, limiting it to (selecting) the tag attribute information Dc and product attribute information Dd acquired in the first read. At this time, the wireless tag reader 10 performs the re-read with the settings of session S0. As a result, the RFID tag 24 that has already responded once will repeatedly respond when it receives the transmitted waves from antennas 14 and 15. This allows the wireless tag reader 10 to obtain many response waves repeatedly with a short response time from only the selected RFID tags 24.

[0081] Furthermore, the wireless tag reader 10 increases the output of the transmitted wave when re-reading in order to improve the signal-to-noise ratio of the received information. For example, when re-reading, the wireless tag reader 10 increases the output of the transmitted wave by X dB. The amount of increase in the output of the transmitted wave is set to a predetermined value.

[0082] This yields the received information Rb shown in Figure 9. As the received information Rb indicates, the number of samples for RSSI value and phase value is greater than that of the received information Ra. Also, because the output power of the transmitted wave is increased, the RSSI value becomes larger than that of the received information Ra. Furthermore, by increasing the output power of the transmitted wave, it becomes possible to obtain a response wave even at antenna positions where a response wave was not obtained in the first reading.

[0083] Furthermore, if the tag attribute information Dc or product attribute information Dd read in the first reading has a predetermined attribute value, the wireless tag reader 10 performs a reread in the same manner as described above, regardless of the confidence level 62 of the estimated position 60.

[0084] In this case, the increase in the output of the transmitted wave is set to a value corresponding to the tag attribute information Dc or product attribute information Dd. For products that require an increase in the output of the transmitted wave during re-reading, the value of the increase in the output of the transmitted wave is pre-registered for each product in the inlay type Dca, metal content information Ddb, metal influence information Ddc, and dielectric constant information Ddd of the read data D (see Figure 4). Furthermore, for products that require an increase in the output of the transmitted wave during re-reading, if the confidence level 62 of the estimated position 60 falls below a threshold, the increase in the output of the transmitted wave registered in the read data D is used instead of the increase in the output of the transmitted wave at the time the confidence level 62 fell below the threshold during re-reading.

[0085] By performing this rereading, the received information Rb shown in Figure 9 is obtained. Then, the wireless tag reader 10 estimates the position of the RFID tag 24 using the tag position estimation model Mi based on the acquired received information Rb.

[0086] Here, the received information Rb is data acquired by increasing the output of the transmitted wave, and is different from the training data used to generate the tag position estimation model Mi. Therefore, even if the received information Rb is directly input into the tag position estimation model Mi, the tag position cannot be estimated. For this reason, the wireless tag reader 10 corrects the RSSI value De when estimating the tag position.

[0087] Specifically, when the wireless tag reader 10 increases the output of the transmitted wave by A during re-reading, it multiplies the RSSI value De of the received information Rb by 1 / A. In other words, when the output of the transmitted wave is increased by X dB during re-reading, it subtracts X dB from the RSSI value De of the received information Rb (offsets it to the negative side by X dB).

[0088] This yields the received information Rc shown in Figure 9. The wireless tag reader 10 then inputs the received information Rc into the tag location estimation model Mi, which is identified by the tag attribute information Dc and the product attribute information Dd, and estimates the tag location according to the method described in Figure 8.

[0089] (Functional configuration of wireless tag reader) The functional configuration of the wireless tag reader 10 will be explained using Figure 10. Figure 10 is a functional block diagram showing an example of the functional configuration of the wireless tag reader according to this embodiment.

[0090] The control unit 31 of the wireless tag reader 10 operates by loading the control program P into the RAM 34, thereby realizing the following functional units as shown in Figure 10: the radio wave transmission / reception unit 51, the antenna movement control unit 52, the response wave acquisition unit 53, the tag position estimation unit 54, the tag information acquisition unit 55, the re-reading control unit 56, and the notification unit 57.

[0091] The radio wave transmitting / receiving unit 51 transmits radio waves and receives response waves from the RFID tag 24 attached to the product 22 in response to said radio waves.

[0092] The antenna movement control unit 52 moves the position of the radio wave transmitting / receiving unit 51 over time. Note that the antenna movement control unit 52 is an example of a movement control unit in this disclosure.

[0093] The response wave acquisition unit 53 acquires identification information indicating the attributes of the product 22 registered in the RFID tag 24 and the attributes of the RFID tag 24, the RSSI value of the response wave as a time-series signal, and the phase value of the response wave from multiple response waves received by the radio wave transmitting / receiving unit 51 which is moved by the antenna movement control unit 52. Note that the response wave acquisition unit 53 is an example of a signal acquisition unit in this disclosure.

[0094] The tag position estimation unit 54 calculates the estimated position 60 of the RFID tag 24 and the confidence level 62 of the estimated position 60 based on the RSSI value and the phase value.

[0095] Furthermore, the tag position estimation unit 54 calculates the estimated position 60 of the RFID tag 24 and the confidence level 62 of the estimated position 60 based on the response wave reacquired by the reread control unit 56. Note that the tag position estimation unit 54 is an example of an estimation unit in this disclosure.

[0096] The tag information acquisition unit 55 acquires the identification information registered in the RFID tag 24, which is included in the response wave.

[0097] The re-read control unit 56 re-acquires the response wave only for RFID tags 24 that responded with identification information that meets the conditions, provided that the confidence level 62 is below a threshold, or that the identification information acquired by the tag information acquisition unit 55 includes an attribute that significantly affects the reading result of the RFID tag 24. Note that the re-read control unit 56 is an example of a signal re-acquisition unit in this disclosure.

[0098] Furthermore, when the re-reading control unit 56 reacquires the response wave, it increases the output of the radio waves to be transmitted to the radio wave transmitting / receiving unit 51 by a predetermined amount.

[0099] Furthermore, the re-reading control unit 56 offsets the RSSI value De in the re-acquired time-series signal by an amount corresponding to the increase in the output of the transmitted radio waves.

[0100] The notification unit 57 issues a notification indicating that the reading result may be incorrect, provided that the confidence level 62 of the estimated position 60 of the RFID tag 24 is below a threshold, even if the reread control unit 56 performs a reread.

[0101] (Process flow performed by the wireless reader) The processing flow of the wireless tag reader 10 will be explained using Figure 11. Figure 11 is a flowchart showing an example of the processing flow of the wireless tag reader according to this embodiment.

[0102] The response wave acquisition unit 53 sets the session to S1, S2, or S3 (step S11).

[0103] The response wave acquisition unit 53 performs the reading process of the RFID tag 24 (step S12). The detailed flow of the reading process will be described later (see Figure 12).

[0104] The tag position estimation unit 54 performs a tag position estimation process to calculate the estimated position 60 of the RFID tag 24 (step S13). The outline of the tag position estimation process is as described above (see Figure 8).

[0105] The reread control unit 56 determines whether the confidence level 62 of the estimated position 60 of the RFID tag 24 is below a threshold, or whether the read RFID tag 24 contains attributes that affect reading performance (step S14). If it is determined that the condition is met (step S14: Yes), the process proceeds to step S15. On the other hand, if it is determined that the condition is not met (step S14: No), the process proceeds to step S23.

[0106] In step S14, if it is determined that the confidence level 62 of the estimated position 60 of the RFID tag 24 is below a threshold, or that the read RFID tag 24 contains an attribute that affects the reading performance, the re-read control unit 56 instructs the response wave acquisition unit 53 to set the session to S0 (step S15).

[0107] The reread control unit 56 applies Select to the corresponding RFID tag 24 (step S16).

[0108] The re-reading control unit 56 increases the output of the radio waves to be transmitted to the radio wave transmitting / receiving unit 51 (step S17).

[0109] The response wave acquisition unit 53 performs the reading process of the RFID tag 24 (step S18). The detailed flow of the reading process will be described later (see Figure 12).

[0110] The re-reading control unit 56 offsets the RSSI value with respect to the response wave acquired by the response wave acquisition unit 53 (step S19).

[0111] The tag position estimation unit 54 performs a tag position estimation process to calculate the estimated position 60 of the RFID tag 24 based on the re-read result (step S20). The outline of the tag position estimation process is as described above (see Figure 8).

[0112] The reread control unit 56 determines whether the confidence level 62 of the estimated position 60 of the RFID tag 24 is below a threshold (step S21). If it is determined that the confidence level 62 is below the threshold (step S21: Yes), the process proceeds to step S22. On the other hand, if it is not determined that the confidence level 62 is below the threshold (step S21: No), the process proceeds to step S23.

[0113] In step S21, if it is determined that the confidence level 62 is below the threshold, the notification unit 57 issues a notification indicating that the reading result may be incorrect (step S22). This notification can be done, for example, by displaying screen information on the display device 40 indicating that the RFID tag 24 may not have been read correctly. At this time, the reading result may also be displayed on the notification screen, and if it has been read correctly, the customer may press the OK button to confirm the reading result. If the reading result is incorrect, the customer may register the product individually, for example, by scanning the barcode attached to the product in question.

[0114] The response wave acquisition unit 53 determines whether it has processed the response waves from all acquired RFID tags 24 (step S24). If it is determined that it has processed the response waves from all acquired RFID tags 24 (step S24: Yes), the wireless tag reader 10 terminates the process shown in Figure 11. On the other hand, if it is not determined that it has processed the response waves from all acquired RFID tags 24 (step S24: No), the process returns to step S14 and the above-described process is repeated.

[0115] Returning to step S14, if the confidence level 62 of the estimated position 60 of the RFID tag 24 is below the threshold, or if the read RFID tag 24 is not determined to contain any attributes that affect reading performance, the tag information acquisition unit 55 confirms the information read in step S12 (step S23). After that, the wireless tag reader 10 terminates the process shown in Figure 11. The confirmed reading results are then transmitted to a POS terminal or a higher-level server (not shown) for accounting and payment processing of the goods. If the confidence level 62 is not determined to be below the threshold in step S21, the process in step S23 is also executed.

[0116] (The flow of the reading process performed by the wireless reader) Figure 12 illustrates the flow of the reading process performed by the wireless tag reader 10. Figure 12 is a flowchart showing an example of the reading process flow in Figure 11.

[0117] The antenna movement control unit 52 moves the antennas 14 and 15 to the starting position (step S31).

[0118] The radio wave transmitting / receiving unit 51 transmits radio waves from one of the antennas (for example, antenna 14) (step S32).

[0119] The radio wave transmitting / receiving unit 51 receives the response wave (step S33).

[0120] The radio wave transmitting / receiving unit 51 transmits radio waves from the other antenna (for example, antenna 15) (step S34).

[0121] The radio wave transmitting / receiving unit 51 receives the response wave (step S35).

[0122] The response wave acquisition unit 53 acquires the time the response wave was received, as well as the tag attribute information Dc, product attribute information Dd, RSSI value De, and phase value Df contained in the response wave (step S36).

[0123] The antenna movement control unit 52 determines whether the movement of antennas 14 and 15 is complete (step S37). If it is determined that the movement of antennas 14 and 15 is complete (step S37: Yes), the wireless tag reader 10 terminates the process shown in Figure 12. On the other hand, if it is not determined that the movement of antennas 14 and 15 is complete (step S37: No), the process proceeds to step S38.

[0124] If it is determined in step S37 that the movement of antennas 14 and 15 is not complete, the antenna movement control unit 52 moves antennas 14 and 15 by a predetermined amount (step S38). Then, the process returns to step S32 and the above-described processes are repeated.

[0125] (Effects of the embodiment) As described above, the wireless tag reader 10 of this embodiment includes a radio wave transmitting / receiving unit 51 that transmits radio waves and receives response waves from an RFID tag 24 (wireless tag) attached to a product 22 (article) in response to the radio waves; an antenna movement control unit 52 (movement control unit) that moves the position of the radio wave transmitting / receiving unit 51 over time; and a response wave acquisition unit 53 (signal acquisition unit) that acquires identification information indicating the attributes of the product 22 and the attributes of the RFID tag 24 registered in the RFID tag 24, as well as the RSSI value De and phase value Df of the response wave as a time-series signal, from a plurality of response waves received by the radio wave transmitting / receiving unit 51 which is moved by the antenna movement control unit 52. The system includes a tag position estimation unit 54 (estimation unit) that calculates the estimated position 60 of the RFID tag 24 and the confidence level 62 of the estimated position 60 based on the RSSI value De and the phase value Df, and a re-read control unit 56 (signal re-acquisition unit) that re-acquires response waves only for RFID tags 24 that have responded with identification information that meets the conditions, provided that the confidence level 62 is below a threshold or the identification information includes an attribute that indicates a significant impact on the reading result of the RFID tag 24. The tag position estimation unit 54 calculates the estimated position 60 of the RFID tag 24 and the confidence level 62 of the estimated position 60 based on the response waves re-acquired by the re-read control unit 56. Therefore, even if the product 22 to which the RFID tag 24 is attached affects the reading performance, the RFID tag 24 in a predetermined area can be read correctly.

[0126] Furthermore, in the wireless tag reader 10 of this embodiment, the re-reading control unit 56 (signal re-acquisition unit) increases the output of the radio waves transmitted to the radio wave transmitting / receiving unit 51. Therefore, the signal-to-noise ratio of the response wave when re-reading can be improved.

[0127] Furthermore, in the wireless tag reader 10 of this embodiment, the re-reading control unit 56 (signal re-acquisition unit) offsets the RSSI value De in the re-acquired time-series signal by an amount corresponding to the increase in the output of the transmitted radio waves. Therefore, the level of the RSSI value De is changed to the level at which the tag position estimation model Mi was generated, so that the estimated position 60 of the RFID tag 24 can be estimated with high accuracy.

[0128] Furthermore, in the wireless tag reader 10 of this embodiment, the re-reading control unit 56 (signal reacquisition unit) reacquires a response wave when the identification information indicates that the product 22 (item) is a glitter product. Therefore, if there is a possibility that the reading performance will be affected, the re-reading can be limited to the RFID tags 24 to be read.

[0129] Furthermore, in the wireless tag reader 10 of this embodiment, the re-reading control unit 56 (signal re-acquisition unit) causes the response wave to be re-acquired when the identification information indicates that the RFID tag 24 is of a predetermined inlay type. Therefore, if there is a possibility that the reading performance will be affected, the re-reading can be limited to the RFID tags 24 to be read.

[0130] Although embodiments of the present invention have been described above, these embodiments are illustrative and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0131] 10 Wireless tag reader 12 Mounting platform 13. Basket (storage area) 14,15 Antenna 16. Placement position marker 18 Moving Stages 20 Drive motor 21 rails 22 Products (goods) 24 RFID tags (wireless tags) 26 Surveillance camera (imaging unit) 51 Radio wave transmitting and receiving unit 52 Antenna movement control unit (movement control unit) 53 Response wave acquisition unit (signal acquisition unit) 54 Tag position estimation unit (estimation unit) 55 Tag Information Acquisition Unit (Information Acquisition Unit) 56 Re-reading control unit (signal re-acquisition unit) 57 Hochi Department 60 Estimated position 62 Confidence D Read data Da Antenna Identification Information Db time information DC Tag Attribute Information Dca Inlay Variety Dd Product attribute information Dda EPC Ddb Metal content information Ddc metal impact information Ddd Dielectric Constant Information De RSSI value Df Phase Value Mi(i=a,b,c,…) Tag Location Estimation Model Ra, Rb, Rc Received Information [Prior art documents] [Patent Documents]

[0132] [Patent Document 1] Patent No. 7007170

Claims

1. A radio wave transmitting and receiving unit that transmits radio waves and receives response waves from a wireless tag attached to an item in response to said radio waves, A movement control unit that moves the position of the radio wave transmitting and receiving unit over time, A signal acquisition unit acquires, from a plurality of response waves received by the radio wave transmitting / receiving unit moved by the motion control unit, identification information indicating the attributes of the item registered in the radio tag and the attributes of the radio tag, and the RSSI value and phase value of the response wave as a time-series signal. An estimation unit that calculates the estimated position of the wireless tag and the confidence level of the estimated position based on the RSSI value and the phase value, The system includes a signal reacquisition unit that, on the condition that the confidence level is below a threshold, or that the identification information includes an attribute that indicates a significant impact on the reading result of the wireless tag, increases the output of the radio waves transmitted by the radio wave transmitting / receiving unit and reacquires the response wave, limited to wireless tags that have responded with identification information that meets the conditions, The estimation unit calculates the estimated position of the wireless tag and the confidence level of the estimated position based on the response wave reacquired by the signal reacquisition unit. Wireless tag reader.

2. The signal reacquisition unit, The RSSI value in the reacquired time-series signal is offset in the decreasing direction by an amount corresponding to the increase in the output of the transmitted radio waves. The wireless tag reader according to claim 1.

3. The signal reacquisition unit, The aforementioned identification information causes the response wave to be reacquired if the item is a glitter product. A wireless tag reader according to claim 1 or claim 2.

4. The signal reacquisition unit, The identification information causes the response wave to be reacquired if the wireless tag is of a predetermined inlay type. A wireless tag reader according to claim 1 or claim 2.

5. Computers, A radio wave transmitting and receiving unit that transmits radio waves and receives response waves from a wireless tag attached to an item in response to said radio waves, A movement control unit that moves the position of the radio wave transmitting and receiving unit over time, A signal acquisition unit acquires, from a plurality of response waves received by the radio wave transmitting / receiving unit moved by the motion control unit, identification information indicating the attributes of the item registered in the radio tag and the attributes of the radio tag, and the RSSI value and phase value of the response wave as a time-series signal. An estimation unit that calculates the location of the wireless tag and the reliability of that location based on the RSSI value and the phase value, The signal reacquisition unit functions as a signal reacquisition unit that increases the output of the radio waves transmitted by the radio wave transmitting / receiving unit and reacquisitions the response wave, provided that the reliability is below a threshold, or the identification information includes an attribute that significantly affects the reading result of the wireless tag, and is limited to wireless tags that have responded with identification information that meets the conditions. The estimation unit is instructed to calculate the estimated position of the wireless tag and the confidence level of said estimated position based on the response wave reacquired by the signal reacquisition unit. program.

Images