JP7205429B2 - wireless tag reader - Google Patents

Description

The present invention relates to a wireless tag reader that distinguishes moving tags that are moving from stationary tags that are stationary.

As a technology related to a wireless tag reader that detects wireless tags, for example, a tag reader disclosed in Patent Document 1 below is known. In this tag reader, phase is used to create a stop tag filter. One stop tag filter uses the phase standard deviation. Since moving tags have a large standard deviation and stop tags have a small standard deviation, stop tags with small standard deviations are identified, and tags that are not stop tags are determined to be moving tags.

JP 2013-37663 A

In the wireless tag reader of Patent Document 1, it is considered difficult to set the threshold value of the phase standard deviation for identifying whether the tag is a moving tag or a stationary tag.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and its object is to easily set a threshold value for sorting out moving tags that are moving and stationary tags that are stationary. To provide a wireless tag reader.

In order to achieve the above object, the invention according to claim 1 is a moving tag (30a) that is moving and a stationary tag (30b) that is stationary based on response waves from wireless tags. A wireless tag reader 10 to be sorted,
The total number (N) of phase values obtained in the entire angle range (0° to 180° or 0° to 360°) for phase value detection is obtained, and a predetermined angle range (90 ° or half value of all angle ranges), the total number (ni) of the number of phase values obtained for each angle is obtained, the largest total number is obtained, and the total number is compared with the largest total number. a phase bias calculation means (S154) for calculating whether the phase value is biased within the predetermined angle range of the largest total number;
a movement index calculation means (S152) for calculating a movement index corresponding to the amount of movement of the wireless tag;
display means (S112) for displaying the phase bias and the movement index so as to be able to sort out moving tags identified as moving tags in advance or after the fact from other tags;
and a threshold display means (S114) for displaying a threshold for distinguishing between the moving tag and other tags during display on the display means.
It should be noted that the symbols in parentheses above indicate the corresponding relationship with specific means described in the embodiments to be described later.

In the invention of claim 1, the phase bias and the movement index are displayed so that the moving tag specified as the moving tag and the other tags can be sorted , and the moving tag and the other tags are distinguished during the display. Display the threshold for sorting. Therefore, it is possible to easily set a threshold value for distinguishing moving tags from other tags (stop tags).

In the second aspect of the present invention, since the moving tag has a low phase bias, it can be identified as a moving tag by a threshold value based on the phase bias. On the other hand, stationary tags that do not move and exhibit phase behavior like moving tags have a high phase bias, and can be identified as stationary tags by a threshold value based on the phase bias. Since the moving tag or the stationary tag is specified by the phase bias, the moving tag and the stationary tag can be specified in a short time.

In the second aspect of the invention, the moving tag or the stationary tag is identified by a threshold value based on the movement index corresponding to the amount of movement of the wireless tag in addition to the phase bias, so that the moving tag or the stationary tag can be reliably identified. be able to.

In the third aspect of the present invention, the amount of phase change is determined based on the phase of the response wave from the wireless tag, and the threshold is set using the phase bias and the amount of phase change to distinguish moving tags from stationary tags. For this reason, stationary tags that exhibit the same phase behavior (large phase variation) as moving tags due to the effects of direct waves and reflected waves alone, and moving tags with small phase variations, can also be properly treated as moving tags or stationary tags. can be selected.

In the invention of claim 4, the graph of the cumulatively added phase addition values is smoothed, the inflection point is obtained from the change in the gradient of the graph, and each phase addition value including the start point and the end point is By calculating the sum of the phase addition values for each inflection point and obtaining the phase change amount, it is possible to reliably determine whether the tag is moving or stationary.

In the fifth aspect of the invention, the threshold value is set when the moving tag is moving at a low speed on a route close to the antenna of the wireless tag reader (when the reading conditions are good, the number of times of reading increases, and when the stationary tag can be read by the reflected wave). when the moving tag is moving at high speed on a path far from the antenna of the wireless tag reader (because the reading conditions are poor, the number of readings decreases, the phase change cannot be added accurately, (the phase change amount of the moving tag becomes smaller). Stop tags with a large amount of phase change and moving tags with a small amount of phase change, that is, data close to the threshold value are obtained intensively. becomes easier.

In the sixth aspect of the invention, the threshold value is set when the minimum number of mobile tags is moving at low speed along a path close to the antenna of the wireless tag reader (because the reading conditions are good, the number of readings increases, and the reflected wave When the maximum number of moving tags are moving at high speed along a route far from the antenna of the wireless tag reader (the number of readings decreases due to poor reading conditions, and the amount of phase change increases). It is not possible to add accurately, and the amount of phase change of the moving tag becomes small). Stop tags with a large amount of phase change and moving tags with a small amount of phase change, that is, data close to the threshold are obtained intensively, so the threshold can be set with a small number of readings (number of trials for setting), and the initial setting is easy. become easier.

In the seventh aspect of the present invention, an instruction is given to place the stop tag at the position closest to the antenna of the wireless tag reader within the assumed range. Since the reading conditions are good, the number of readings that can be performed by the reflected wave of the stop tag increases, and the phase change amount of the stop tag increases. Stop tags with a large amount of phase change, that is, data near the threshold value are obtained intensively, so that the threshold value can be set with a small number of times of reading (the number of trial times for setting), and the initial setting becomes easy.

In the eighth aspect of the present invention, an instruction is given to place the stop tag at a position where the antenna gain of the antenna of the wireless tag reader is low. Since the antenna null position is reached and the placed stop tag may or may not be read, the phase bias of the placed stop tag is low. Stop tags with low phase bias, that is, data near the threshold value are obtained intensively, so that the threshold value can be set with a small number of times of reading (the number of trial times for setting), and the initial setting is facilitated.

In the ninth aspect of the present invention, the phase bias and the movement index of the identified moving tag are displayed, and the threshold for selecting the moving tag is displayed during the display. Therefore, it is possible to set a threshold for sorting the moving tags.

1 is an explanatory diagram showing a schematic configuration of a transportation management system according to an embodiment; FIG. FIG. 2 is a block diagram illustrating the electrical configuration of the wireless tag reader according to the embodiment. 3 is a block diagram illustrating an electrical configuration of a wireless tag; FIG. 3 is a block diagram illustrating an electrical configuration of a management device; FIG. FIG. 5A is an explanatory diagram of a moving tag and a stationary tag according to the embodiment, and FIG. 5B is an explanatory diagram of a direct wave and a reflected wave. 6A is a chart showing phase changes of the moving tag 30a, FIG. 6B is a chart showing phase changes of the stationary tag 30b, and FIG. 6C shows phase changes of the stationary tag 30c. FIG. 6D is a chart showing the phase change of the stop tag 30d. FIG. 7A is a chart showing the phase change of the mobile tag 30a, FIG. 7B is a chart showing the frequency of the phase (θ) in FIG. 7A from −90° to 90°, FIG. 7(C) is a chart showing the phase change of the stop tag 30c, and FIG. 7(D) is a chart showing the frequency of the phase (θ) from −90° to 90° in FIG. 7(C). FIG. 8A shows the sum n(0) of frequencies from phase 0° to phase 90°, and FIG. 8B shows the sum n(1) of frequencies from phase 1° to phase 91°. 8(C) shows the sum n(91) of frequencies from phase 91° to phase 1°, and FIG. 8(D) shows the sum n(179) of frequencies from phase 179° to phase 89°. ). FIG. 4 is an explanatory diagram of determination of a stationary tag and a moving tag according to the embodiment; 6 is a flowchart of initial setting processing; 7 is a flowchart of movement/stop determination processing; 10 is a flowchart of subroutine processing for calculating a phase change amount; 4 is a flowchart of subroutine processing for calculating phase bias; FIG. 14A is an explanatory diagram when the distance from the wireless tag reader to the article is long and the transportation speed is high, and FIG. It is an explanatory diagram of when it is late. FIG. 15A is a table for explaining histogram creation, and FIG. 15B is a table for explaining frequency summation. FIG. 10 is an explanatory diagram of phase change amount calculation; 1 is a chart of antenna directivity; FIG. 11 is an explanatory diagram of moving tag determination according to a modified example of the embodiment;

[Embodiment]
A transportation management system including a wireless tag reader according to an embodiment of the present invention will be described below with reference to the drawings.
The transport management system 1 shown in FIG. 1 uses a wireless tag reader 10 to detect the moving state of a wireless tag 30 such as an RF tag attached to a transported object P such as a product, thereby controlling the transport to which the wireless tag 30 is attached. It is configured as a system for managing the movement state of the object P and the like. As shown in FIG. 1, the transport management system 1 includes a wireless tag reader 10 arranged in a transport route along which a product P with a wireless tag 30 is transported to read the wireless tag 30; and a management device 20 that manages the articles to be conveyed P using the reading result or the like.

The wireless tag reader 10 is configured by, for example, a known RF tag reader, and is installed at a gate provided on the transport route as illustrated in FIG. It is configured to output information about the state and the like to the management device 20 .

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

In addition, 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, an encoder, a modulator, an amplifier, and the like. The carrier oscillator outputs a carrier (carrier wave) of a predetermined frequency. The encoder is connected to the controller 11, encodes transmission data output from the controller 11, and outputs the encoded data to the modulator. The modulation unit receives the carrier (carrier wave) from the carrier oscillator and the transmission data from the encoding unit, and encodes the carrier (carrier wave) output from the carrier oscillator when sending a command to the communication target. A modulated signal that is ASK (Amplitude Shift Keying) modulated by an encoded transmission code (modulation signal) output from the unit is generated and output to an amplifier. The amplifier amplifies the input signal (modulated signal modulated by the modulating section) with a set amplification factor, and the amplified signal is output to the antenna 14 as a transmission signal.

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

The external interface 15 is configured as an interface for performing data communication with an external device such as the management device 20, and cooperates with the control section 11 to perform communication processing. Further, the wireless tag reader 10 of the embodiment includes a display monitor 17 having a built-in audio output speaker.

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 includes 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 a transmission signal (carrier signal) from the wireless tag reader 10 received via the antenna 31 to generate power for operation. and supply to each component.

Also, the demodulation circuit 33 demodulates the data superimposed on the transmission signal (carrier signal) and outputs it to the control circuit 34 . The memory 35 is composed of various semiconductor memories such as ROM and EEPROM, and stores control programs, identification information (tag ID) for identifying the wireless tag 30, data according to the application of the wireless tag 30, and the like. ing. The control circuit 34 reads out the information and data from the memory 35 and outputs them as transmission data to the modulation circuit 36. The modulation circuit 36 load-modulates the response signal (carrier signal) with the transmission data. and transmitted from the antenna 31 as a response wave. 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 are configured to perform wireless communication via electromagnetic waves. good too.

Next, the configuration of the management device 20 will be described.
The management device 20 functions as a device that manages the conveying state of the goods P using the read results of the wireless tags 30 acquired from the wireless tag reader 10 and information acquired from the outside. This management device 20 is configured as, for example, a computer, and as shown in FIG. It includes an operation unit 24 configured as a mouse, keyboard, etc., and a communication unit 25 configured as a communication interface for performing data communication with external devices such as the wireless tag reader 10 and higher-level devices.

Next, the characteristic configuration of the wireless tag reader 10 according to the embodiment will be described in detail.
The wireless tag reader 10 according to the embodiment uses the phase difference of the response wave from the wireless tag 30 to accurately detect the moving state of the wireless tag 30 even if the wireless tag 30 is moving at a low speed. The movement state (movement index corresponding to the amount of movement) of the wireless tag 30 is detected. Specifically, the phase of the response wave from the wireless tag 30 measured for a predetermined time by the measurement processing performed by the control unit 11 is associated with the measurement time (reception time) using the communication processing unit 13. is stored in the storage unit 12. Then, in the tag detection processing performed by the control unit 11, the phase of the response wave and the measurement time thereof stored in the storage unit 12 are read, and the phase addition value obtained by cumulatively adding the phase difference calculated based on these phases is 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. 5(A), when the object P attached with the wireless tag 30 is linearly transported by a forklift M or the like in front of the wireless tag reader 10 (antenna 14), The distance to the moving wireless tag 30 (hereinafter also referred to as moving tag 30a) is measured so as to change with time. That is, the change in the distance from the wireless tag 30 to the antenna 14 is measured based on the phase addition value measured as described above, and the movement of the wireless tag 30 is detected based on this measurement result. For this reason, the control unit 11 measures the change in the distance from the wireless tag 30 to the antenna 14 based on the phase addition value, and measures the movement of the wireless tag 30 based on the measurement result regarding the change in the measured distance. to detect.

Here, in the wireless tag reader 10 of the embodiment, it is determined whether the tag is a moving tag or a stationary tag based on the change in phase together with the phase addition value and the phase change amount described later. FIG. 6(A) is a chart showing the phase change of the mobile tag 30a in FIG. 5(A), where the vertical axis represents phase [deg] and the horizontal axis represents time. As shown in FIG. 6A, the amount of phase change is large. FIG. 6(B) is a chart showing the phase change of the stop tag 30b in FIG. 5(A). As shown in FIG. 6B, the amount of phase change is small. That is, since the distance does not change, the phase value does not change. As a result, it is possible to reliably distinguish between moving tags and stationary tags.

FIG. 6(C) is a chart showing the phase change of the stop tag 30c in FIG. 5(A), and FIG. 6(D) is a chart showing the phase change of the stop tag 30d in FIG. 5(A). be.
The phase change amount of the stop tag 30c is large, and the phase change amount of the stop tag 30d is medium, and is read sporadically. The reason why the amount of phase change of the stop tag 30c is large is that when a moving object M such as a forklift moves in front of the wireless tag reader 10 (antenna 14), the effect of reflection of radio waves from the moving object M causes the stop tag 30b This is because the response wave from is received. In such a case, if the phase of the response wave from the stop tag 30c and the stop tag 30d changes due to the movement of the moving object M, the measured distance changes with time, causing the moving object M to stop. If the tag 30c is moving, it may be erroneously detected. In addition, due to the influence of the surrounding environment, etc., a state (null state) in which the response wave from the stop tag 30c cannot be temporarily received may occur, and this state may also contribute to false detection. .

FIG. 5B is an explanatory diagram of reflected waves and direct waves from the stop tag 30c. Since the radio wave from the stop tag 30d can be read only when the reflecting object (forklift) passes, it can be determined that the stop tag 30d is stopped. It was found that the radio wave from the stop tag 30c has a large amount of phase change as shown in FIG. 6(C) due to the mixture of the reflected wave and the direct wave.

Therefore, in the wireless tag reader 10 of the embodiment, a stop tag with a large amount of phase change, such as a moving tag, is determined as a stop tag based on whether or not there is a bias in the amount of phase change. FIG. 7(A) is a chart showing the phase change of the mobile tag 30a in FIG. 5(A), and FIG. 7(B) shows the phase (θ) in FIG. , and the shaded area in the center represents the phase frequency between -45° and 45°. The frequency sum of −45° to 45° is 150, the frequency sum of the whole (−90° to 90°) is 290, and the phase bias is 150/290, which is 52%. That is, the moving tag has no phase bias and exhibits a value of around 50%.

FIG. 7(C) is a chart showing the phase change of the stop tag 30c in FIG. 5(A), and FIG. 7(D) shows the phase (θ) in FIG. , and the shaded area in the center represents the phase frequency between -45° and 45°. The frequency sum of -45° to 45° is high, and the phase bias is about 80%. That is, the stop tag has a large phase bias.

The wireless tag reader 10 of the embodiment sorts stationary tags and moving tags based on the phase bias and the amount of phase change. 9(A), 9(B), and 9(C) are tables in which each tag is defined by the phase bias and the phase change amount, where the vertical axis indicates the phase bias and the horizontal axis indicates the phase change amount. It is Here, the circle C1 in FIG. 9A shows the values when the distance from the wireless tag reader to the article to be conveyed is long and the conveying speed is high (see FIG. 14A). When the distance from the wireless tag reader to the conveyed object is long, or when the conveying speed is high, the number of readings decreases due to poor reading conditions, and the phase change amount cannot be added accurately, resulting in a small phase change amount for the moving tag. . In particular, when a large number of mobile tags are moving at high speed along a route far from the antenna of the wireless tag reader, the number of times of reading decreases due to poor reading conditions. That is, since the number of samples that can be sampled per second is constant, the number of times the moving tag is read per sheet decreases, the phase change amount cannot be added accurately, and the phase change amount of the moving tag becomes small.

The circles C2 and C3 in FIG. 9A are the values when the distance from the wireless tag reader to the article to be conveyed is short and the conveying speed is slow (see FIG. 14B). When the moving tag is moving at a low speed on a route close to the antenna of the wireless tag reader, the number of times of reading increases because the reading conditions are good, and the phase change amount of the stationary tag that can be read by the reflected wave increases. In particular, when a small number of moving tags are moving at a low speed along a route close to the antenna of the wireless tag reader, the number of samples that can be sampled per second is constant, but the number of times of reading one stationary tag increases. The phase change amount of the stop tag that can be read by the reflected wave increases.

Furthermore, the circle C2 in FIG. 9(A) shows the value that increases when the stop tag is placed near the antenna of the wireless tag reader. Since the reading conditions are good, the number of readings that can be performed by the reflected wave of the stop tag increases, and the phase change amount of the stop tag increases.

A circle C3 in FIG. 9A shows a value that increases when the stop tag is placed at a position where the antenna gain of the antenna of the wireless tag reader is low. FIG. 17 is a diagram of antenna directivity. A main lobe MP is generated in the front direction of the antenna (0° direction), and side lobes SP are generated adjacent to the main lobe MP. At angles of 45° and 315° between the main lobe MP and the side lobe SP, the antenna gain is low and the antenna null position is likely to occur. For this reason, stationary tags placed at angles of 45° and 315° with low antenna gain may or may not be read, resulting in low phase bias.

The wireless tag reader 10 of the embodiment assists the operator in setting the threshold value for sorting the stationary tag and the moving tag from the phase deviation and the phase change amount at the site during initial setting. Specifically, as shown in FIG. 9A, the data of the stationary tags and the moving tags are not evenly collected, but the circles C1 and C1 in FIG. Let the values in C2, C3 be collected. That is, as shown in FIG. 9(B), the moving tag data closer to the stop tag and the stop tag data closer to the moving tag are collected, and the data closer to the stop tag are collected as shown in FIG. Set a threshold value for selecting a moving tag and a stop tag closer to the moving tag.

Specifically, when setting the threshold value for the initial settings, a voice message and/or an image display on the monitor indicates that "the number of moving tags moving at a low speed on a path close to the antenna of the wireless tag reader is the minimum number and , Move moving tags at high speed on a route far from the antenna of the wireless tag reader with the maximum number of tags,” “Place a stationary tag at the position closest to the antenna of the wireless tag reader”, “Use of the wireless tag reader Place a stop tag on the antenna where the antenna gain is low." As a result, stationary tags with a large phase change amount and moving tags with a small phase change amount shown in FIG. The threshold can be set by the number of trials for use), making initial settings easier.

With reference to the flow charts of FIGS. 10 to 13, the initial threshold setting by the wireless tag reader and the process of sorting moving tags and stationary tags based on the set threshold will be described.
Here, prior to the initial setting, the information of the moving tag to be detected during the initial setting is registered in advance. This registration can also be performed after the initial tag reading has been performed. When the setting is started in the setting flowchart shown in FIG. Move mobile tags at high speed with the maximum number of tags”, “Place stationary tags at the closest possible range to the antenna of the wireless tag reader”, and “Stop at a position where the antenna gain of the antenna of the wireless tag reader is low”. "Place a tag" is instructed by voice and image display on the monitor 17. When reading is started (S104: Yes), the wireless tag information is read (S106), and phase values are accumulated for each wireless tag information and ID (S108). Here, information such as each wireless tag ID, phase, received power, reading time, etc. is accumulated. It is determined whether the number of read tags is a predetermined number or more (for example, 20 or more) and the number of times of reading is a predetermined number or more (for example, 20 or more) (S110). Since a small number of readings may cause a judgment error, judgment is made based on a certain number of information. Until the read information reaches or exceeds a certain value (S110: No), the process returns to S106 to continue reading the wireless tag. When the read information reaches or exceeds a certain value (S110: Yes), a moving tag and a stop tag (tags other than those registered as moving tags) are displayed on the monitor 17 as shown in FIG. 9B (S112). , Subsequently, the threshold value of the value calculated by the automatic processing of the wireless tag reader or set by the operator's manual input (phase deviation 0% - phase change amount 630 deg: phase deviation 70% - phase change amount 630 deg: phase deviation 100%-phase change amount 1030 deg) is displayed on the monitor 17 as shown in FIG. 9C (S114). Then, when there is an instruction that the operator has confirmed the threshold value (S116: Yes), the above threshold value (phase deviation 0%-phase change amount 630 deg: phase deviation 70%-phase change amount 630 deg: phase deviation 100%- A phase change amount of 1030 deg) is set (S118), and the initial setting process ends.

FIG. 11 shows a moving tag/stop tag determination processing routine.
First, the phase change amount is calculated (S152).
FIG. 16 is an explanatory diagram of phase change amount calculation.
I. A moving addition value is recorded for each time (see FIG. 16(A)).
II. Find three inflection points and an end point necessary for phase change amount calculation (see FIG. 16(C)).
(a), (b), (c)
III. Calculate the following (1) =|start point -b|
(2) = | b - a |
(3) =|ac|
(4) =|c-end point|
Phase change amount = (1) + (2) + (3) + (4)

That is, in the wireless tag reader of the embodiment, the amount of phase change is calculated based on the amount of phase change between the start point, the end point, and each inflection point obtained from the graph of the cumulatively added phase addition value.

FIG. 12 shows a subroutine of the phase change amount calculation process (S152) described above with reference to FIG.
Phase variation information is acquired and the amount of phase change is calculated (S202: FIG. 16A). The graph is smoothed (S204: FIG. 16(B)). The purpose of the smoothing process is to eliminate useless points of inflection caused by blurring. That is, this is done to roughly find an inflection point. The inflection point of the graph is obtained from the change in the slope of the phase change (S206: FIG. 16C). Phase change amounts between the start point, the end point, and each inflection point are obtained (S208).
(1) =|starting point-b|
(2) = | b - a |
(3) = |a-c|
(4) =|c-end point|
Phase change amount = (1) + (2) + (3) + (4)
(S210).
In the addition process of S210, all phase fluctuation values equal to or greater than a threshold value are added. Here, the reason for excluding below the threshold is to distinguish the phase fluctuation below the threshold from the phase fluctuation due to reflection. The point of the phase addition value is to capture the information that the phase fluctuates greatly and continuously. Here, examples of threshold values are 90 [deg], 180 [deg], and the half value of the phase acquirable range.

In the example of FIG. 16(C),
(1) |a−b|=40[deg]
(2) |b−c|=340[deg]
(3) |cd|=500[deg]
(4) |de| = 600 [deg]
(5)|ef|=250[deg]
, the value in (1) is excluded because it is below the threshold, and
(2) + (3) + (4) + (5) = 1690 [deg]
, the phase change amount is calculated.
It should be noted that the method described in the specification of Japanese Patent Application No. 2017-189510 can be adopted for acquiring the phase addition amount.

In the subroutine shown in FIG. 11, following the calculation of the phase change amount in S152, the calculation of the phase deviation is performed (S154).
FIG. 13 shows the phase bias calculation subroutine.
For each tag, a histogram is created for each 1° phase value shown in FIG. 15(A) with respect to the phase values shown in FIGS. 7(A) and 7(C) (S400). . Here, there are two frequencies in the range of 0° to 1°, and three frequencies in the range of 1° to 2°, which are obtained from 179° to 180°. The phase values shown in FIGS. 7(A) and 7(C) are represented in tables of phase values (θ) and frequencies as schematically shown in FIGS. 7(B) and 7(D). can be expressed The sum of frequencies (the total number of phase values obtained in the entire angle range (0-180°) for phase value detection) is set to N (S402). For example, it is assumed here that it was 300 times. A phase value i is initialized to 0 (S404).

Then, it is determined whether the phase value i is 90° or less (S406). Here, since the phase value i is 0 (S406: No), in S408, i≤θ<i+90°, here, the frequency sum of the phase values θ satisfying 0≤θ<90° (predetermined angle range (90 °), that is, the total number of phase values obtained for each angle from 0 to 90°) is defined as n(0). Let n(0) be the sum of frequencies from phase 0° to phase 90° shown in FIG. For example, as shown in FIG. 15B, n(0) has a total frequency of 170 times. Then, 1 is added to i(0) (S412). It is determined whether i=179°, that is, whether the calculation has been completed for the phases of all angles (S414). Here, the determination in S414 is No, and the process returns to S406, and in S408, the frequency sum of phase values θ that satisfies i≦θ<i+90°, where 1°≦θ<91°, is set to n(1). . Let n(1) be the sum of frequencies from phase 1° to phase 91° shown in FIG. 8B. For example, as shown in FIG. 15B, n(1) has a total frequency of 173 times. This processing is repeated until the phase is 91°, the determination in S406 becomes Yes, and in S410, i≤θ<180° or 0≤θ<i-90°, here 91°≤θ<180°, 0≤ Let n(91) be the frequency sum of the phase values θ that satisfy θ<1. Let n(91) be the sum of frequencies of phases 91° to 180 and phases 0° to 1° shown in FIG. 8(C). When the sum of frequencies of n(179) is obtained, and the sum of frequencies from 179° to 180°+0° to 89° shown in FIG. 8(D) is obtained (S414: Yes), n The maximum value in (0) to n (179)/N (total frequency)×100 is obtained as the phase deviation [%]. That is, by comparing the total number (N) and the largest total sum number (ni), it is calculated whether the phase value is biased within a predetermined angular range (90°) of the largest total sum number. In addition, in FIG. 7B, when there is no phase deviation of -45° to 45° in the range of -90° to 90°, the ratio is 50%. In the example shown in FIG. 8, if there is no phase deviation (within the range of 90°) in the range of 0° to 180°, it is similarly 50%. In FIG. 7(D), when there is a phase deviation of -45° to 45° in the range of -90° to 90°, the % value is high. In the above example, the phase deviation of 0° to 180° (in the range of 90°) was obtained, but in the range of 0° to 360° (in the range of 180° (half value of the entire angle range)) It is also preferable to determine the phase bias of .

In the subroutine shown in FIG. 11, following the calculation of the phase bias in S154, the thresholds set in the initial setting process described above with reference to FIG. Amount of 630 degrees: phase bias of 100% - phase change amount of 1030 degrees) is used as a reference to determine whether to move or stop (S156). For example, with respect to the detected phase bias and phase change amount of each tag shown in FIG. 9D, it is sorted whether it is a moving tag or a stationary tag based on a set threshold value.

[Modified example of embodiment]
FIG. 18 is an explanatory diagram of moving tag determination according to a modified example of the embodiment.
In a modified example of the embodiment, the wireless tag reader 10 displays the phase deviation and phase change amount of only mobile tags registered in advance or afterward on the monitor 17 as shown in FIG. Set a threshold for screening moving tags as shown in . A variant of the embodiment has the advantage of fast setting of the threshold.

In the wireless tag reader 10 of the embodiment, the phase difference integrated value is used as the value (phase change amount) that changes due to the movement of the wireless tag. The maximum phase change amount, the average value of the time until the phase change amount reaches a predetermined value, (maximum phase change amount-minimum phase change amount)/2, and the minimum phase change amount can be used. Furthermore, instead of the phase difference integrated value, a movement index corresponding to the movement amount of the wireless tag, such as a movement distance (a value obtained by dividing an instantaneous movement amount by time) or a total movement value, can be calculated and used. Also, the amount of change in received signal strength, the maximum value of received signal strength, or the average Doppler velocity can be calculated and used as a movement index corresponding to the amount of movement of the wireless tag.

DESCRIPTION OF SYMBOLS 10... Wireless tag reader 14... Antenna 30... Wireless tag 30a... Moving tag 30b... Stop tag M... Forklift

Claims (9)

A wireless tag reader for setting a threshold for sorting out moving tags that are moving and stationary tags that are stationary based on response waves from wireless tags,
Obtaining the total number of phase values obtained in the entire angle range for detecting the phase value, and obtaining the total number of the number of obtained phase values for each angle for each predetermined angle range within the entire angle range for detecting the phase value. a phase bias calculating means for calculating the largest total sum number, and comparing the total number with the largest total sum number to calculate whether the phase value is biased within the predetermined angle range of the largest total sum number; ,
movement index calculation means for calculating a movement index corresponding to the amount of movement of the wireless tag;
display means for displaying the phase deviation and the movement index so as to be able to sort out moving tags identified as moving tags in advance or after the fact from other tags;
and threshold display means for displaying a threshold for distinguishing between the moving tag and the other tags during display on the display means. The wireless tag reader according to claim 1,
threshold setting means for setting the threshold displayed by the threshold display means as a threshold for sorting;
A tag is selected from a moving tag based on at least one of a low phase bias and a large movement amount corresponding to the movement index from the set threshold, and a movement corresponding to the movement index having a high phase bias. a sorting means for sorting out tags from stop tags by at least one of which quantity is small. The wireless tag reader according to claim 1 or claim 2,
The movement index calculation means is characterized in that, based on the phase of the response wave from the wireless tag, cumulatively adds the difference between the previous phase and the current phase to obtain the phase change amount corresponding to the amount of movement of the wireless tag. wireless tag reader. The wireless tag reader according to claim 3,
The movement index calculation means obtains an inflection point from a change in slope after smoothing the graph of the phase addition obtained by the cumulative addition, and obtains the sum of the phase change amount between each inflection point including the start point and the end point. A wireless tag reader, characterized in that the phase change amount is calculated in . The wireless tag reader according to claim 1,
calculating whether the phase value is biased by the phase bias calculating means;
calculating a movement index corresponding to the amount of movement of the wireless tag by the movement index calculation means;
When the mobile tag is moving at low speed on a path close to the antenna of the wireless tag reader,
A wireless tag reader comprising instruction means for instructing to be performed when the mobile tag is moving at high speed on a route far from the antenna of the wireless tag reader. The wireless tag reader according to claim 5,
The indicating means is
The movement of mobile tags at low speed on a path close to the antenna of the wireless tag reader is the minimum number of tags,
A wireless tag reader, characterized in that it is instructed that the maximum number of mobile tags should be moved at high speed on a route far from the antenna of the wireless tag reader. The wireless tag reader according to claim 5 or claim 6,
The indicating means is
A wireless tag reader that instructs a stationary tag to be placed at a position closest to an antenna of the wireless tag reader within an assumed range. The wireless tag reader according to any one of claims 5 to 7,
The indicating means is
A wireless tag reader, wherein an instruction is given to place a stop tag at a position where an antenna of the wireless tag reader has a low antenna gain. A wireless tag reader for setting a threshold for sorting out moving tags that are moving and stationary tags that are stationary based on response waves from wireless tags,
Obtaining the total number of phase values obtained in the entire angle range for detecting the phase value, and obtaining the total number of the number of obtained phase values for each angle for each predetermined angle range within the entire angle range for detecting the phase value. a phase bias calculating means for calculating the largest total sum number, and comparing the total number with the largest total sum number to calculate whether the phase value is biased within the predetermined angle range of the largest total sum number; ,
movement index calculation means for calculating a movement index corresponding to the amount of movement of the wireless tag;
display means for displaying the phase bias and the movement index of the moving tag identified as the moving tag in advance or after the fact;
and threshold display means for displaying a threshold for selecting the moving tags during display on the display means.

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