JP7095325B2 - Wireless tag reader - Google Patents

Description

The present invention relates to a wireless tag reader that selects a target tag from among wireless tags including a target tag to be detected and an unintentionally read misread tag.

Currently, as a technique related to a wireless tag reader that detects a wireless tag, for example, a tag reader disclosed in Patent Document 1 below is known. In this tag reader, two wireless tags with different resonance frequencies are attached to the same measurement object, and the difference in reception level, that is, the relative value does not change depending on the distance or the characteristics of the wall, is used to evaluate the purpose. It is carried out. In Patent Document 1, one tag is used as a reference.

Japanese Unexamined Patent Publication No. 2014-190857

In the wireless tag reader of Patent Document 1, it is necessary to attach a reference tag in advance. Furthermore, if the tag is not attached to the object whose state is always known, there may be a difference between the object to be discriminated and the reference tag. For example, if the object to be discriminated is the collection of a forklift and the reference tag is attached to the main body of the forklift, it is considered that the relative value may change depending on the material of the collection and the hygroscopicity.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a wireless tag reader capable of reliably selecting a target tag to be detected from among read wireless tags. It is in.

In order to achieve the above object, the invention according to claim 1 of the scope of claims is a wireless tag (30) including a target tag (30a) to be detected and an unintentionally read misread tag (30b). A wireless tag reader (10) that selects target tags.
A definite tag extraction means (S32) that extracts a plurality of presumed target tags with a first threshold value using at least one of phase change amount, velocity or acceleration, distance or angle information, and reception intensity.
Threshold calculation to calculate the second threshold value using at least one of the phase change amount, velocity or acceleration, distance or angle information, time from the first reading to the last reading, and reception intensity of the extracted multiple target tags. Means (S36) and
A sorting means (S42) for selecting a target tag to be detected from a target tag not extracted by the definite tag extracting means using the calculated second threshold value.
Have,
After selecting one target tag, when selecting the next target tag, the first threshold value or the second threshold value is corrected by using the determination result of the selection of the first target tag. And.
The reference numerals in the parentheses indicate the correspondence with the specific means described in the embodiments described later.

In the invention of claim 1, a plurality of tags that are surely target tags with a first threshold using at least one of phase change amount, velocity or acceleration, distance or angle information, and reception intensity are extracted and extracted. The second threshold is calculated using at least one of the phase change amount, velocity or acceleration, distance or angle information, time from the first reading to the last reading, and reception intensity of the target tags. That is, it is desired to reliably calculate a second threshold value which is a relative value of the detection value of the wireless tag which is the target tag, and use the second threshold value to detect from the target tag which is not surely regarded as the target tag. Select target tags. Therefore, according to the first aspect of the present invention, it is possible to cancel the influence of the material of the cargo, the hygroscopicity, the reflected wave, and the like, and select the target tag to be reliably detected. Since the threshold value of 2 is calculated, it is not necessary to attach the reference tag for obtaining the relative value to the one to be determined in advance.
In the invention of claim 1, after selecting one target tag, when selecting the next target tag, the first threshold value or the second threshold value is corrected by using the determination result of the selection of the first target tag. do. From the second time onward, the target tags can be reliably selected.

In the invention of claim 2, a third threshold value using at least one of phase change amount, velocity or acceleration, distance or angle information, and reception intensity is surely extracted as a misread tag, and the second threshold value is set. Use to select the target tag you want to detect from the wireless tag, excluding the misread tag. Therefore, the sorting process is simplified and the sorting time is shortened.

According to the third aspect of the present invention, a target tag that is reliably moving at a first threshold using at least one of phase change amount, velocity or acceleration, distance or angle information that changes due to the movement of the radio tag. At least one of the phase change amount, velocity or acceleration, distance or angle information, time from the first reading to the last reading, and reception strength of the extracted multiple target tags that are extracted and changed by the movement of the wireless tag. Is used to calculate the second threshold. Therefore, the invention of claim 3 can reliably select the moving wireless tag by canceling the influence of the material of the cargo, the hygroscopicity, the reflected wave, and the like.

The invention of claim 4 further includes a changing means for changing the phase change amount, speed or acceleration, distance or angle information, and reception intensity used for the first threshold value. Therefore, the first threshold value is surely acquired.

In the invention of claim 5 , a specific display is performed based on the result of selecting the target tag. For example, when a predetermined number of target tags are not detected, an error display is performed, so that the wireless tags can be read again.

In the invention of claim 6 , the second threshold value is calculated based on the average value, the median value, or the mode value of the maximum value of the reception intensities of a plurality of target tags. Therefore, at the time of inventory, the wireless tag with high reception strength attached to the product placed on the shelf to be read in front of the wireless tag reader is read, and the reflection of the product placed on the back shelf that is not the reading target is read. A wireless tag with a low reception intensity due to waves is clearly distinguished as a misread tag.

In the invention of claim 7 , the second threshold value is calculated based on the average value or the median average value or the mode value and the standard deviation of the reception intensities of the plurality of target tags. Therefore, at the time of inventory, the wireless tag with high reception strength attached to the product placed on the shelf to be read in front of the wireless tag reader is read, and the reflection of the product placed on the back shelf that is not the reading target is read. A wireless tag with a low reception intensity due to waves is clearly distinguished as a misread tag.

In the invention of claim 8 , since it is instructed that a predetermined number of target tags have been extracted, the worker can be made to perform the teaching operation along the wireless tag until the required number of target tag data is obtained. ..

In the invention of claim 9 , since the second threshold value is calculated by adjusting according to the variation width of the reception strength of the plurality of extracted target tags, not only the reception strength but also the distance between the target tag and the wireless tag reader is calculated. Wireless tags can be properly sorted regardless of whether they are close or far.

It is explanatory drawing which shows the schematic structure of the transportation management system which concerns on 1st Embodiment. It is a block diagram which illustrates the electric structure of a wireless tag reader. It is a block diagram which illustrates the electric structure of a wireless tag. It is a block diagram which illustrates the electric structure of a management device. FIG. 5A is an explanatory diagram for explaining the distance change to the antenna measured for the movement tag and the stop tag of the first embodiment, and FIG. 5B is an explanatory diagram for explaining the angle change. 6 (A) is an explanatory diagram for explaining the phase change amount and the received power of the wireless tag, FIG. 6 (B) is an explanatory diagram for explaining the angle change of the mobile wireless tag, and FIG. 6 (C) is an explanatory diagram. It is explanatory drawing explaining the distance change of the mobile radio tag. It is a main flowchart of the wireless tag reading process of the wireless tag reader of 1st Embodiment. It is a flowchart of the subroutine of the movement determination processing of the wireless tag reader of 1st Embodiment. FIG. 9A is an explanatory diagram of the wireless tag reader of the second embodiment, and FIG. 9B is an explanatory diagram of the wireless tag reader of the first modification of the second embodiment. It is explanatory drawing explaining the wireless tag reader of 3rd Embodiment. It is a flowchart of the subroutine processing which obtains the threshold value 2 of the wireless tag reader of 3rd Embodiment. It is a flowchart of the subroutine processing which obtains the threshold value 2 of the wireless tag reader which concerns on 1st modification of 3rd Embodiment. FIG. 13A is a flowchart of interrupt processing performed after the main flow of FIG. 7 by the wireless tag reader of the second modification of the first embodiment, and FIG. 13B is a flowchart of the interrupt processing performed by the wireless tag reader of the second embodiment. It is a flowchart of interrupt processing performed after the main flow of FIG. 7. FIG. 14A is a flowchart showing the teaching instruction processing by the wireless tag reader of the third embodiment, and FIG. 14B is a flowchart showing the processing of the definite target tag extraction failure by the wireless tag reader of the third embodiment. be. FIG. 15A is a diagram showing data variation when the distance between the target tag and the wireless tag reader is short, and FIG. 15B is a diagram showing data variation when the distance between the target tag and the wireless tag reader is short. It is a figure which shows. FIG. 15C is a diagram showing a case where the amount of phase change often exceeds the threshold value and there is little variation, and FIG. 15D is an explanatory diagram of jump value processing in the case of FIG. 15C. be.

[First Embodiment]
Hereinafter, a transport management system including a wireless tag reader according to the first embodiment of the present invention will be described with reference to the drawings.
The transport management system 1 shown in FIG. 1 detects the moving state of a wireless tag 30 such as an RF tag attached to a transport product P of a product or the like by a wireless tag reader 10 functioning as a wireless tag reader, thereby detecting the wireless tag 30. It is configured as a system for managing the moving state and the like of the transported product P marked with. As shown in FIG. 1, the transport management system 1 is composed of a wireless tag reader 10 that is arranged in a transport path in which a transport product P with a wireless tag 30 is transported and reads the wireless tag 30, and the wireless tag reader 10. It is provided with a management device 20 that manages the transported product P by using the reading result or the like.

The wireless tag reader 10 is composed of, for example, a known RF tag reader, and is installed at a gate provided in a transport path as illustrated in FIG. 1, and information read from the wireless tag 30 or movement of the wireless tag 30. It is configured to output information about the state to the management device 20.

The hardware configuration of the wireless tag reader 10 is as shown in FIG. 2, and includes a control unit 11, a storage unit 12, a communication processing unit 13, an antenna 14, an external interface 15, and the like. The control unit 11 is mainly composed of a microcomputer, has a CPU, a system bus, an input / output interface, and the like, and constitutes an information processing device together with a storage unit 12 including a semiconductor memory and the like.

Further, as shown in FIG. 2, the communication processing unit 13 includes a transmission circuit 13b, a reception circuit 13c, and the like. The transmission circuit 13b is composed of, for example, a carrier oscillator, a coding unit, a modulation unit, an amplifier, and the like. The carrier oscillator outputs a carrier (carrier wave) having a predetermined frequency, and the coding unit is connected to the control unit 11 to encode the transmission data output from the control unit 11 and output it to the modulation unit. The modulation unit receives the carrier (carrier wave) from the carrier oscillator and the transmission data from the coding unit, and encodes the carrier (carrier wave) output from the carrier oscillator when the command is transmitted to the communication target. An ASK (Amplitude Shift Keying) modulated signal is generated by a coded transmission code (modulated signal) output from the unit and output to an amplifier. Further, the amplifier amplifies the input signal (modulated signal modulated by the modulation unit) at a set amplification factor, and the amplified signal is output to the antenna 14 as a transmission signal.

Further, the input terminal of the receiving circuit 13c is connected to the antenna 14, and the radio wave signal (received signal) corresponding to the response wave from the radio tag 30 received by the antenna 14 is input to the receiving circuit 13c. It has become like. The receiving circuit 13c is composed of, for example, an amplifier, a demodulation unit, and the like, the received signal received by the antenna 14 is amplified by the amplifier, and the amplified signal is demodulated by the demodulation unit. Further, the signal corresponding to the demodulated signal waveform is output to the control unit 11 as received data. The phase of the response wave of the radio tag 30 received in this way is associated with the measurement time (reception time) by the control unit 11 and is sequentially stored in the storage unit 12.

Further, the external interface 15 is configured as an interface for performing data communication with an external device such as a management device 20, and is configured to perform communication processing in cooperation with the control unit 11.

Here, the electrical configuration of the wireless tag 30 to be read by the wireless tag reader 10 will be described with reference to FIG.
As shown in FIG. 3, the wireless tag 30 is composed of an antenna 31, a power supply circuit 32, a demodulation circuit 33, a control circuit 34, a memory 35, a modulation circuit 36, and the like. The power supply circuit 32 rectifies and smoothes the transmission signal (carrier signal) from the wireless tag reader 10 received via the antenna 31 to generate an operation power supply, and the operation power supply includes the control circuit 34 and the like. It is supplied to each component.

Further, the demodulation circuit 33 demodulates the data superimposed on the transmission signal (carrier signal) and outputs the data to the control circuit 34. The memory 35 is composed of various semiconductor memories such as ROM and EEPROM, and stores identification information (tag ID) for identifying a control program and a wireless tag 30, or data according to the use of the wireless tag 30. ing. The control circuit 34 is configured to read the above information and data from the memory 35 and output the information and data as transmission data to the modulation circuit 36, and the modulation circuit 36 load-modulates the response signal (carrier signal) with the transmission data. It is configured to transmit as a response wave from the antenna 31. Although FIGS. 2 and 3 show an example of the electrical configuration of the wireless tag reader 10 and the wireless tag 30, other known electrical configurations may be used as long as they can perform wireless communication via electromagnetic waves. May be good.

Next, the configuration of the management device 20 will be described.
The management device 20 functions as a device for managing the transport state of the transported product P by using the reading result of each wireless tag 30 acquired from the wireless tag reader 10 and the information acquired from the outside. The management device 20 is configured as, for example, a computer, and as shown in FIG. 4, a control unit 21 composed of a CPU or the like, a display unit 22 configured as a liquid crystal monitor or the like, and a storage unit 23 composed of a ROM, RAM, HDD or the like. It includes an operation unit 24 configured as a mouse, a keyboard, and the like, and a communication unit 25 configured as a communication interface for performing data communication with an external device such as a wireless tag reader 10 and a host device.

Next, the characteristic configuration of the wireless tag reader 10 according to the present embodiment will be described in detail.
The wireless tag reader 10 according to the present embodiment uses the phase difference of the response wave from the wireless tag 30 in order to accurately detect the moving state of the wireless tag 30 even if the wireless tag 30 is moving at a low speed. The moving state of the wireless tag 30 is detected. Specifically, by the measurement processing performed by the control unit 11, the phase of the response wave from the radio tag 30 measured for a predetermined time is associated with the measurement time (reception time) by using the communication processing unit 13. It is stored in the storage unit 12. Then, in the tag detection process performed by the control unit 11, the phase of the response wave stored in the storage unit 12 and the measurement time thereof are read out, and the phase addition value obtained by cumulatively adding the phase difference calculated based on these phases is added. The distance to the wireless tag 30 is measured based on. As a method for measuring the distance to the wireless tag 30 based on the phase addition value in this way, for example, the method described in the specification of Japanese Patent Application No. 2017-189510 can be adopted.

As a result, as shown in FIG. 5A, when the conveyed product P with the wireless tag 30 is linearly conveyed in front of the wireless tag reader 10 (antenna 14) by a forklift M or the like. The distance to the moving wireless tag 30 (hereinafter, also referred to as the moving tag 30a) is measured so as to change with time. That is, the change in the distance from the radio tag 30 to the antenna 14 is measured based on the phase addition value measured as described above, and the movement of the radio tag 30 is detected based on the measurement result. Therefore, the control unit 11 measures the change in the distance from the radio tag 30 to the antenna 14 based on the phase addition value, and moves the radio tag 30 based on the measurement result regarding the measured distance change. Is detected.

On the other hand, the wireless tag 30 (hereinafter, also referred to as a stop tag 30b) and the antenna that are not moving due to being attached to an article or the like placed at a position not on the front side (radio wave radiation side) of the antenna 14 even in the vicinity of the wireless tag reader 10. A radio tag (hereinafter, long-distance stop tag 30c) that is farther than the reading range (for example, 0.5 m) from 14 is not normally read by the radio tag reader 10. However, when a moving body M such as a forklift moves in front of the wireless tag reader 10 (antenna 14), the response wave from the stop tag 30b may be received due to the influence of the reflection of radio waves by the moving body M. In such a case, if the phase of the response wave from the stop tag 30b and the long-distance stop tag 30c is measured so as to change due to the movement of the moving body M, the measured distance changes with time. , There is a possibility that the stop tag 30b will be erroneously detected as moving. Further, due to the influence of the surrounding environment or the like, a state (null state) in which the response wave from the stop tag 30b cannot be temporarily received may occur, and this state may also contribute to false detection. ..

Therefore, even when the phase of the response wave from the stop tag 30b is measured, the stop tag 30b and the long-distance stop tag 30c move because the reflection path of the radio wave suddenly changes according to the above-mentioned change in the reflection position. It will be measured as if it were. Therefore, the wireless tag reader 10 of the first embodiment performs a process of selecting a target tag from the wireless tags including the target tag to be detected and the misread tag that was unintentionally read.

FIG. 6A shows the received power of the readable radio tag, although the phase has changed. Here, the vertical axis represents the received power [dBm], and the horizontal axis represents the phase change amount (phase addition value) [deg]. In the figure, □ indicates a stop tag (misread tag), and ● indicates a move tag. In the first embodiment, first, for example, a target tag whose phase change amount is reliably moved by the first threshold value of 1000 deg or more is extracted. Then, the average received power value (for example, -55 [dBm]), which is definitely the target tag, is calculated, and a value 6 [dB] lower than the average received power value (-55 [dBm]) is set as the second threshold value (-). At 61 [dBm]), it is selected whether the movement tag Δ or the stop tag ◇ is used for the remaining radio tags that are not surely considered to be the target tags.

With reference to the flowcharts of FIGS. 7 and 8, the sorting process of the moving tag and the stop tag by the wireless tag reader described above will be described.
First, the wireless tag is read and the information of the wireless tag is acquired (S12). Here, information such as each radio tag ID, phase, received power, and reading time is acquired. Then, it is determined whether the number of readings exceeds a certain level (S14). That is, since reading is repeated a plurality of times even for the same wireless tag, the process returns to S12 and the reading information is acquired until the number of readings exceeds a certain level (S14: No). Then, when the number of readings exceeds a certain level (S14: Yes), the reading information is processed (S16). Here, the phase difference of the acquired phase is integrated from the acquired phase and the reading time, and the phase change amount (phase addition value) [deg] is integrated. Then, the movement determination process is performed (S30).

FIG. 8 is a subroutine of the movement determination process (S30) in FIG. 7.
First, it is determined whether the phase difference integrated value (phase addition value) is equal to or higher than the threshold value 1 (first threshold value: 1000 deg) (S32). The wireless tag whose phase difference integrated value is the threshold value 1 or more (● in FIG. 6A) is determined to be a mobile tag (S34), and the average received power of all the confirmed mobile tags is calculated (S36). .. As described above with reference to FIG. 6A, the average received power value (for example, −55 [dBm]) of the target tag is surely calculated. Then, the process returns to the main flow of FIG. 7, and after the determination that the end determination of S18 is present (S18: No), the process returns to the process of S12.

On the other hand, when it is judged whether the phase difference integrated value (phase addition value) is equal to or more than the threshold value 1 (first threshold value: 1000 deg) and less than 1000 deg (S32: No), the phase difference integrated value is the threshold value 3 (third). Threshold: 500 deg) or more is determined (S38). Here, by removing the wireless tags that have not moved at all and the wireless tags that have hardly moved, the processing time can be shortened and the processing load can be reduced. In FIG. 6A, it is determined that the wireless tag of □ is not a moving tag (S38: No) as a wireless tag having a phase difference integrated value less than the threshold value 3 (third threshold value: 500 deg) (S46). ..

On the other hand, ◇ in FIG. 6 (A), in which it was determined whether the phase difference integrated value of S38 was equal to or greater than the threshold value 3 (third threshold value: 500 deg) and was determined to be equal to or greater than the third threshold value (500 deg). The wireless tags of, Δ are once determined in S46 to be non-moving tags after the determination (S40: No) that the confirmed movement tags have been acquired until the movement tags in all S34s are confirmed. Then, as for the wireless tags of ◇ and Δ in FIG. 6A, when all the movement tags in S34 are confirmed and the confirmed movement tags have been acquired (S40: Yes), all the confirmed movement tags calculated in S36 are used. It is determined whether the power difference from the average received power (−55 [dBm]) is constant (6 [dB]) or less, that is, whether it is equal to or greater than the second threshold value (−61 [dBm]) (S42). Since the radio tag of Δ shown in FIG. 6A is equal to or higher than the second threshold value (−61 [dBm]) (S42: Yes), it is determined to be a mobile tag (S44). On the other hand, since the wireless tag of ◇ shown in FIG. 6A is less than the second threshold value (−61 [dBm]) (S42: No), it is determined that it is not a mobile tag (S46). Then, returning to the main flow of FIG. 7, after the determination that the end determination is made in S18, the end determination is made (S18: Yes), and the undetermined tag that was not the movement tag at this point is regarded as the stop tag (S18: Yes). S20), the process is completed.

In the wireless tag reader 10 of the first embodiment, a plurality of target tags that are reliably moving at the first threshold value using the amount of phase change that changes due to the movement of the wireless tag are extracted, and the movement of the wireless tag causes the movement of the wireless tag. A second threshold is calculated using the receiving intensities of the plurality of extracted target tags that change. Therefore, the wireless tag reader of the first embodiment can cancel the influence of the material of the load, the hygroscopicity, the reflected wave, and the like, and can select the wireless tag that is moving reliably. Further, the determination of whether the tag is a moving tag, which is difficult only by the amount of phase change, is appropriately determined by combining the reception strength.

In the wireless tag reader 10 of the first embodiment, the phase difference integrated value is used as the value (phase change amount) that changes due to the movement of the wireless tag, but instead, the phase change amount average value and the phase change amount center. A value, a maximum value of the amount of phase change, an average value of the time until the amount of phase change reaches a predetermined value, (maximum value of amount of phase change-minimum value of amount of phase change) / 2, and a minimum value of amount of phase change can be used.

Further, velocity / acceleration can be used instead of the amount of phase change. As the speed, the average value of each tag speed average value, the median value of each tag speed average value, the maximum value of each tag speed average value, the minimum value of each tag speed average value, the average value of each tag speed median value, and each tag. The average value of the maximum velocity values can be used. Further, the speed unit described above may be used as the acceleration unit, and the speed unit may be used as the acceleration unit. The velocity is calculated by time-differentiating the change in phase using a radio tag having two frequencies. Acceleration is obtained by taking the slope of the change in velocity. Here, when the definite movement tag is determined using the speed / acceleration, the method of using the tag whose speed is constant or higher as the definite movement tag, and the positive / negative sign ratio of the acquired acceleration information among the total number of times of reading the acceleration is 1: A method in which a tag close to 1 is used as a definite movement tag, a method in which both of them are combined and a tag having the highest average speed among those having a positive / negative sign ratio close to 1: 1 is used as a definite movement tag can be used.

Further, an angle / distance can be used instead of the amount of phase change. The angle is acquired by a well-known technique using two antenna elements and a phase difference obtained by acquiring the distance between each antenna element. The distance is obtained by a well-known technique using a radio tag having two frequencies and using the difference between the two frequencies and the phase. As the angle, the average value of each tag angle change amount, the average number of times each tag angle change is 5 ° or more, the average of each tag angle change absolute value, the ratio of each tag angle change direction (+-), and the angle change amount of 30 ° are reached. The average time to do so can be used. Further, a distance unit obtained by converting the above-mentioned angle into a distance unit can be used. Here, when the definite movement tag is determined using the angle / distance, a method is used in which the definite movement tag has an angle within a certain range (Δθ) as shown in FIG. 5 (B).

FIG. 6B shows the tag angle seen from the antenna with respect to the wireless tag passing in front of the antenna of the wireless tag reader. The horizontal axis is time (t [s]), and the vertical axis is the angle [deg]. The change in angle has become smaller once, and has increased again after passing forward. Utilizing this, a method is used in which a tag with a constant change in angle, such as a tag with a change in the sign of the angle or a change in the magnitude of the angle by a certain amount or more, is used as a definite movement tag.

FIG. 6C shows the distance from the antenna to the radio tag passing in front of the antenna of the radio tag reader. The horizontal axis is time (t [s]), and the vertical axis is distance [cm]. The distance has decreased once, and has increased again after passing forward. Utilizing this, a method can be used in which a wireless tag that has become far away is used as a definite movement tag after the distance has become short. Further, a method of using a definite movement tag that is close to the set distance, for example, a method of using a definite movement tag that changes the distance by a certain amount or more, such as moving by 50 cm or more or approaching within 90 cm, can be used. A method can be used in which an angle / distance is combined and a tag showing a constant change in the angle / distance is used as a definite movement tag.

Further, instead of the phase change amount, the time from the first reading to the last reading (reading time) can be used. The reading of the wireless tag is repeated as long as it is within the reading range from the wireless tag reader, so when the wireless tag moves and enters the reading range from outside the reading range, the first reading is performed and the range is out of range. The final read is done before going to. On the other hand, the radio tag that does not move and is within the reading range continues to be read. Therefore, it can be determined that the tag whose reading continues has not been moved. What is once determined to be a moving tag using the threshold value can be determined not to be a moving tag if reading continues.

When the reading time is used, the average value of the reading time of each tag minus the total time when Δt exceeds 100 ms, the ratio of the total time when Δt exceeds 100 ms during the reading time of each tag, and each tag. Percentage of the sum of the times when Δt during the reading time of is less than 40 ms can be used. Further, the average value of the reading time of each tag, the number of times Δt exceeds 100 ms / the number of readings of each tag, and the average of (number of changes in Δt) of each tag can be used.

Further, the received power (RSSI) can be used instead of the phase change amount. When RSSI is used, the average value of the maximum value of each tag RSSI, the average value of each tag RSSI, the average value of the values when each tag RSSI is -60 [dBm] or more, and each tag RSSI are used. A ratio of -60 [dBm] or more can be used. Further, the average of the amount of change of each tag RSSI and the average of the change locus of each tag RSSI can be used.

[First modified example of the first embodiment]
In the process of FIG. 8 described above, the wireless tag reader of the first modification of the first embodiment obtains the average phase difference integrated value of all confirmed moving tags in S36. Then, in the determination of S42, whether it is determined to be a moving tag or not a moving tag based on whether the difference between the average phase difference integrated value of the all-determined moving tag and the phase difference integrated value of the undetermined tag is equal to or less than a certain value. Is determined. When the moving speed is high or the like, it is appropriately determined whether or not the tag is a moving tag by using the phase difference integrated value for the threshold value 2 together with the threshold value 1.

[Second modification of the first embodiment]
In the wireless tag reader of the second modification of the first embodiment, the conveyed product P by the forklift with the wireless tag 30 shown in FIG. 5 (A) passes through, and after processing the conveyed product P, the next forklift passes through. At that time, the first threshold value is corrected by using the judgment result of the previous selection.

FIG. 13A is a flowchart of interrupt processing performed after the main flow of FIG. 7 by the wireless tag reader of the second modification of the first embodiment.
When it is determined whether the selection of the target tag of 1 is completed (S112) and the selection of the target tag is completed (S112: Yes), the first threshold value is corrected using the determination result of the target tag selection (S114). For example, the threshold value 1 (first threshold value: 1000 deg) of the phase difference integrated value used in the first embodiment is increased or decreased by using the determination result of target tag selection. The influence of the humidity condition of the day is canceled, and the selection of the target tag from the second time onward is surely performed. Here, the threshold value 1 is corrected, but the threshold value 2 and the threshold value 3 can also be corrected. Further, the determination result of the wireless tag determined to be the stop tag last time can be diverted to the next time.

[Second Embodiment]
FIG. 9A shows a wireless tag reader 110A used in the POS cash register according to the second embodiment. The wireless tag reading process of the wireless tag reader 110A of the second embodiment is the same as that of the first embodiment described above with reference to FIGS. 7 and 8.
The wireless tag reader 110A shown in FIG. 9A reads the wireless tag attached to the product in the shopping basket CS placed on the belt conveyor 112. Since the distance to the antenna of the wireless tag reader (not shown) varies in the shopping basket CS mounted on the belt conveyor 112, the wireless tag reader has at least one of the phase change amount, the distance change amount, and the speed change amount at that time. The wireless tag that can be confirmed in the shopping basket CS is found based on the above, and the one whose received power (RSSI) fluctuates is detected as the target tag in the same way as the confirmed tag.

FIG. 13B is a flowchart of interrupt processing performed after the main flow of FIG. 7 by the wireless tag reader of the second embodiment.
The wireless tag reader determines whether the selection of the definite target tags has been completed (S122), and when the selection of the definite target tags has been completed (S122: Yes), a predetermined number of definite target tags, for example, two wireless tags. Is determined as a definite target tag (S124). Here, when a predetermined number of definite target tags have been extracted (S124: Yes), the process ends. On the other hand, when a predetermined number of definite target tags cannot be extracted, a predetermined operation for changing the phase change amount, the distance change amount, and the speed change amount used when selecting the definite target tags, here, FIG. 9A. The belt conveyor 112 shown in the above is inverted, and the shopping basket CS is separated from the antenna of the wireless tag reader (S126). Then, the reading operation is performed again (S128).

In the wireless tag reader 110A of the second embodiment, the belt conveyor 112 that has an operation (S126) for changing the phase change amount, the speed change amount, and the distance change amount used for the first threshold value and is inverted is used. Therefore, the first threshold value is surely acquired. Here, in the wireless tag reader 110A of the second embodiment, the phase change amount, the distance change amount, and the speed change amount are changed, but the acceleration, the angle information, and the reception intensity can also be changed.

[First modified example of the second embodiment]
FIG. 9B shows a wireless tag reader 110B used in the POS register according to the first modification of the second embodiment. The wireless tag reading process of the wireless tag reader 110B of the first modification of the second embodiment is the same as that of the first embodiment described above with reference to FIGS. 7 and 8.
The wireless tag reader 110B shown in FIG. 9B reads the wireless tag attached to the product transported by the cart CM. Since the distance to the antenna of the wireless tag reader (not shown) varies in the cart CM pushed by the shopper, the wireless tag reader 110B is based on at least one of the phase change amount, the distance change amount, and the speed change amount at that time. , Finds a definite wireless tag in the cart CM, and detects a fluctuating received power (RSSI) as a target tag in the same way as the definite tag.

[Third Embodiment]
FIG. 10 shows the wireless tag reader 210 of the third embodiment. The wireless tag reader 210 of the third embodiment is used for inventory, reads the product B on the front shelf FR of the wireless tag reader, and determines the product on the back shelf RR as an erroneous reading. The wireless tag reader 210 includes a display 222 and a start switch 224 to start reading the front shelf.

In order to move the product B and the wireless tag reader 210 relative to each other, the operator performs the teaching operation shown by the thick line in the figure along the product B, and reliably performs the product of the front shelf FR from the phase change amount as in the first embodiment. Find out what can be said to be B. Then, it is determined that the product whose reception strength with the product B of the front shelf FR is within a certain range is the product of the front shelf FR.

FIG. 14A is a flowchart showing a teaching instruction process by the wireless tag reader of the third embodiment.
When the operator stands in front of the front shelf FR and the start switch 224 for starting the reading operation is operated (S132: Yes), the display 222 is instructed to perform the teaching operation of the front shelf (S134). ). The instruction to perform the teaching operation is continued until the target number of moving tags can be selected (S136: No) (S134). Then, when the target number of movement tags can be selected (S136: Yes), the display 222 is displayed to end the teaching operation (S138).

In the wireless tag reader 210 of the third embodiment, in order to instruct that a predetermined number of target tags have been extracted, the operator is made to perform a teaching operation along the wireless tags until the required number of target tag data is obtained. be able to.

FIG. 14B is a flowchart showing the processing of the definite target tag extraction failure by the wireless tag reader of the third embodiment.
When the selection of target tags by teaching is completed (S142: Yes), the wireless tag reader determines whether a predetermined number of definite target tags have been extracted (S144). Here, when a predetermined number of fixed target tags can be extracted (S144: Yes), the process ends. On the other hand, if a predetermined number of definite target tags cannot be extracted (S144: No), an error display is displayed on the display 222, and the wireless tag reader prompts the operator to perform the teaching operation again (S146). ).

In the wireless tag reader of the third embodiment, a specific display is performed based on the result of selecting the target tag. For example, the wireless tag reader of the third embodiment can make the operator read the wireless tag again by displaying an error when a predetermined number of target tags cannot be detected.

FIG. 15A is a diagram showing data variation when the distance between the target tag and the wireless tag reader (front shelf) is short, and FIG. 15B is a diagram showing the variation between the target tag and the wireless tag reader (front shelf). It is a figure which shows the variation of data when the distance is long. The horizontal axis shows the reception intensity (RSSI), and the vertical axis shows the frequency (the number of tags read).
As shown in FIG. 15A, when the distance is short, the variation in RSSI of the target tag is small. That is, the RSSI value of the target tag is within three types. The variation between the RSSI of the target tag and the RSSI of the misread tag is also small. That is, the difference in RSSI value between the target tag of the minimum RSSI value and the misread tag of the maximum RSSI value is small.

As shown in FIG. 15B, when the distance is long, the variation in RSSI of the target tag is large. That is, the RSSI value of the target tag is widespread in five types. There is also a large variation between the RSSI of the target tag and the RSSI of the misread tag. That is, the difference in RSSI value between the target tag of the minimum RSSI value and the misread tag of the maximum RSSI value is large.

Here, even if an attempt is made to determine whether the front shelf or the back shelf is based only on the reception strength (RSSI), the difference in distance between the wireless tag reader and the front shelf is used as described above with reference to FIGS. 15A and 15B. Since the RSSI variation width and the RSSI difference between the target tag and the misread tag change, it is difficult to set the threshold value 2 for selecting the target tag and the misread tag. Therefore, in the wireless tag reader of the third embodiment, the value of the threshold value 2 is corrected depending on whether the RSSI variation width is large or small, that is, whether the distance is short or long. Specifically, when the variation in RSSI of the target tag is small, the wireless tag reader determines that the distance is short as shown in FIG. 15A, raises the threshold value 2, and approaches the minimum RSSI value of the target tag. On the contrary, when the variation in RSSI of the target tag is large, the wireless tag reader determines that the distance is long as shown in FIG. 15B, lowers the threshold value 2, and sets it lower than the minimum RSSI value of the target tag.

The wireless tag reading process of the wireless tag reader 210 of the third embodiment is the same as that of the first embodiment described above with reference to FIGS. 7 and 8. However, the calculation of the average power in S36 in FIG. 8 and the determination process of whether the power difference in S42 is equal to or less than a certain value are different. That is, in the third embodiment, when calculating the average power in S36 in FIG. 8, the threshold value 2 calculated by referring to the variation in the data is corrected. Then, the determination of S42 is made based on the corrected threshold value 2 or more. The flowchart of FIG. 11 shows the subroutine processing in the third embodiment for obtaining the threshold value 2 in S36 of the flowchart in FIG.

First, it is determined that n (for example, 3) or more tags whose phase difference integrated value exceeds the threshold value 1 are determined (S52). Here, in the case of two or less (S52: Yes), it is not possible to obtain the variation of the data. Therefore, in S54, the threshold value α (initially set from the average received power of the moving tag confirmation tag) as the calculation threshold value (threshold value 2) ( For example, the value obtained by subtracting 10 [dB]) is set as the calculation threshold value (threshold value 2), and the subroutine processing ends.

On the other hand, when the tag whose phase difference integrated value exceeds the threshold value exceeds n (for example, 3) (S52: Yes), the median received power and the variance (maximum value-minimum value) of the mobile tag are calculated (S56). .. Then, it is determined whether the variance is an arbitrary value m (for example, 3 [dB]) or more, that is, whether the data variation is small (S58). Here, when the variance is 3 [dB] or more (S58: Yes), the value obtained by subtracting the variance from the median received power of the mobile tag as the calculation threshold (threshold 2) is set as the calculation threshold (threshold 2) (S60). ), The subroutine processing ends. On the other hand, when the variance is less than 3 [dB] (S58: No), the value obtained by subtracting the initially set threshold value α (for example, 10 [dB]) from the average received power of the mobile tag confirmation tag as the calculation threshold value (threshold value 2). Is set to the calculation threshold value (threshold value 2) (S62), and the subroutine processing ends.

In the wireless tag reader of the third embodiment, since the second threshold value is calculated by adjusting according to the variation width of the reception strength of the extracted plurality of target tags, not only the reception strength but also the target tag and the wireless tag reader Wireless tags can be properly sorted regardless of whether the distance is short or long.

In the wireless tag reader of the third embodiment, the median received power is used as the second threshold value, but instead, it is calculated based on the average value or the mode of the maximum received strengths of a plurality of target tags. You can also. Therefore, at the time of inventory, the wireless tag reader of the third embodiment reads the wireless tag with high reception strength attached to the product placed on the shelf to be read in front of the wireless tag reader, and the wireless tag reader on the back surface which is not the reading target. A wireless tag with a low reception intensity due to a reflected wave of a product placed on a shelf can be clearly distinguished as a misread tag.

[First modified example of the third embodiment]
FIG. 15C is a diagram showing a case where the phase change amount often exceeds the threshold value and the variation is small, and FIG. 15D is a diagram in which the data of FIG. 15C is replaced with the received power. Yes, it is an explanatory diagram of the jump value processing. In FIG. 15C, when the amount of phase change often exceeds the threshold value and the variation is small, the threshold value 2 of the received power is set higher than in the conventional case in the wireless tag reader of the first modification of the third embodiment. .. As a result, it is determined that the skip value shown in FIG. 15D is a misread tag.

The wireless tag reading process of the wireless tag reader 210 of the first modification of the third embodiment is the same as that of the first embodiment described above with reference to FIGS. 7 and 8. However, the calculation of the average power in S36 in FIG. 8 and the determination process of whether the power difference in S42 is equal to or less than a certain value are different. That is, in the first modification of the third embodiment, the threshold value 2 calculated with reference to the variation in the data is corrected when the average power is calculated in S36 in FIG. Then, the determination of S42 is made based on the corrected threshold value 2 or more. The flowchart of FIG. 12 shows the subroutine processing in the third embodiment for obtaining the threshold value 2 in S36 of the flowchart in FIG.

First, it is determined whether or not the number of tags whose phase difference integrated value exceeds the threshold value 1 is n (for example, 3) or more (S72). Here, in the case of two or less (S72: Yes), it is not possible to obtain the variation of the data. Therefore, in S74, the threshold value α (initially set from the average received power of the moving tag confirmation tag) is set as the calculation threshold value (threshold value 2). For example, the value obtained by subtracting 10 [dB]) is set as the calculation threshold value (threshold value 2), and the subroutine processing ends.

On the other hand, when the tag whose phase difference integrated value exceeds the threshold value 1 exceeds n (for example, 3) (S72: No), the received power standard deviation: δ of the mobile tag is calculated (S76). Then, it is determined whether the received power standard deviation δ is larger than the standard deviation threshold m1 (for example, 10 [dB]) and smaller than the standard deviation threshold m2 (for example, 3 [dB]) (S78). Here, when the received power standard deviation δ is larger than 10 [dB]) and smaller than 3 [dB]) (S78: Yes), the value obtained by subtracting the received power standard deviation δ from the median received power of the mobile tag is The calculation threshold value (threshold value 2) is set (S80), and the subroutine processing ends. On the other hand, when the received power standard deviation δ is smaller than 10 [dB]) or larger than 3 [dB]) (S78 :: No), the average received power of the moving tag confirmation tag is set as the calculation threshold (threshold 2). The value obtained by subtracting the initially set threshold value α (for example, 10 [dB]) is set as the calculation threshold value (threshold value 2) (S82), and the subroutine processing ends.

In the wireless tag reader according to the first modification of the third embodiment, since the second threshold value is calculated by adjusting according to the variation width of the reception strength of the extracted plurality of target tags, not only the reception strength but also the reception strength is calculated. Even if the data has a jump value, the wireless tag can be appropriately selected.

In the wireless tag reader according to the first modification of the third embodiment, the second threshold value is calculated from the received power standard deviation, but instead, the average value or the average value of the reception strengths of a plurality of target tags or the average value or the median value is used. It can also be calculated based on the mode and standard deviation. As a result, at the time of inventory, the wireless tag reader of the first modification of the third embodiment reads and reads the wireless tag with high reception strength attached to the product placed on the shelf to be read in front of the wireless tag reader. It is possible to distinguish a wireless tag having a low reception intensity due to a reflected wave of a product placed on a shelf on the back surface, which is not a target, as a misread tag.

10 ... Wireless tag reader 14 ... Antenna 30 ... Wireless tag 30a ... Moving tag 30b ... Stop tag 110A, 110B ... Wireless tag reader 112 ... Belt conveyor 210 ... Wireless tag reader 222 ... Display B ... Product FR ... Front shelf M ... Forklift P ... Transport Product RR ... Back shelf

Claims (9)

A wireless tag reader that selects target tags from wireless tags that include target tags that you want to detect and misread tags that you could unintentionally read.
A definite tag extraction means for extracting a plurality of presumed target tags with a first threshold value using at least one of phase change amount, velocity or acceleration, distance or angle information, and reception intensity.
Threshold calculation to calculate the second threshold value using at least one of the phase change amount, velocity or acceleration, distance or angle information, time from the first reading to the last reading, and reception intensity of the extracted multiple target tags. Means and
It has a sorting means for selecting a target tag to be detected from a target tag not extracted by the definite tag extracting means using the calculated second threshold value.
After selecting one target tag, when selecting the next target tag, the first threshold value or the second threshold value is corrected by using the determination result of the selection of the first target tag. Wireless tag reader. The wireless tag reader according to claim 1.
A misread tag extraction means for extracting what is presumed to be a misread tag by a third threshold value using at least one of phase change amount, velocity or acceleration, distance or angle information, and reception intensity is provided.
The selection means is a wireless tag reader, which uses the calculated second threshold value to select a target tag to be detected from the misread tag and the target tag not extracted by the definite tag extraction means. .. The wireless tag reader according to claim 1 or 2.
The target tag is a wireless tag that is relatively moving, and is
The misread tag is a wireless tag that has not moved.
The definite tag extraction means extracts a plurality of tags estimated to be target tags with a first threshold value using at least one of phase change amount, velocity or acceleration, distance or angle information.
The threshold value calculation means uses at least one of the phase change amount, velocity or acceleration, distance or angle information, time from the first reading to the last reading, and reception intensity of the plurality of extracted target tags. A wireless tag reader characterized by calculating a threshold. The wireless tag reader according to any one of claims 1 to 3 .
A wireless tag reader further comprising a changing means for changing the phase change amount, speed or acceleration, distance or angle information, and reception intensity used for the first threshold value. The wireless tag reader according to claim 4 .
A wireless tag reader characterized in that a specific display is made based on the result of selecting a target tag. The wireless tag reader according to claim 1 or 2.
A wireless tag reader, characterized in that the second threshold value is calculated based on an average value, a median value, or a mode value of the maximum values of the reception strengths of a plurality of target tags. The wireless tag reader according to claim 1 or 2.
A wireless tag reader, characterized in that the second threshold value is calculated based on an average value or a median average value or a mode value of a plurality of target tags and a standard deviation. The wireless tag reader according to claim 1 or 2.
A wireless tag reader comprising an instruction means for instructing that a predetermined number of the target tags have been extracted. The wireless tag reader according to any one of claims 6 to 8 .
The definite tag extraction means extracts a plurality of tags estimated to be target tags with a first threshold value using at least one of phase change amount, velocity or acceleration, distance or angle information.
The threshold value calculation means is a wireless tag reader, characterized in that the second threshold value is calculated by adjusting according to the variation width of the reception intensity of the extracted plurality of target tags.

Images