JP5147067B2 - RFID reader system - Google Patents

Description

  The present invention relates to an RFID reader system that reads or writes an IC tag.

  An RFID reader that reads or writes an IC tag is connected to an antenna for performing wireless communication, and can communicate with the IC tag by radio waves transmitted from the antenna. Further, an RFID reader system in which an RFID reader is incorporated in a gate of a warehouse or the like is used for entering / exiting a person who has an IC tag, managing loading / unloading of luggage, and the like.

  In such an RFID reader system, information such as the moving direction of the IC tag in the gate, that is, whether entering or leaving the room, entering or leaving, etc. is extremely useful for management.

  In the conventional RFID reader system, in order to determine the moving direction of the IC tag, there is a method in which a plurality of detection sensors using infrared rays or the like are arranged along the movement path in the gate and the moving direction is determined from the detection order of each sensor. Proposed.

  For example, as a method of judging entrance / exit at the gate, a pair of gates are provided on both the left and right sides of the store entrance, and a radio wave is transmitted from the transmission side gate and received by the reception side gate. In a system that issues a warning by detecting changes in the received radio waves, a human body detection sensor is installed at the receiving gate to detect the entrance and exit of a person. A configuration for avoiding this is disclosed in Patent Document 1.

  In addition, a first sensor and a second sensor for identifying the direction of movement of passersby are installed along the direction of passage at the gate for entering and exiting the security zone where outsiders are restricted from entering and detecting a dedicated tag. A third sensor for identifying a passerby is also installed, and the monitoring device is configured to recognize an unauthorized person's unauthorized entry room and issue an alarm from the detection information of the first sensor, the second sensor, and the third sensor. It is disclosed in Patent Document 2.

  In an RFID reader system incorporated in a conventional gate, the communication time required for the RFID reader to read the information in the IC tag is at least several milliseconds to several tens of milliseconds depending on the communication procedure and the amount of data. (And the person or object attached) must be within the reading range for at least this reading time, and if the passing speed (walking speed, transport speed) is fast, sufficient reading time cannot be secured and reading is impossible. There is a case.

  When the passing speed is fast and the communication time is insufficient, generally, a method of arranging a plurality of antennas in the passing direction to increase the communication range is disclosed in Patent Document 3.

JP 2003-109130 A JP 2003-303382 A JP 2007-088937 A

  FIG. 6 is a diagram for explaining an example of a configuration of a gate including a plurality of detection sensors and an RFID reader as disclosed in Patent Document 1 and Patent Document 2.

  In the figure, when the RFID reader 1 communicates with the IC tag 8, the logic circuit 3 performs encoding and decoding according to the instruction of the control circuit 2, and the high-frequency analog circuit 4 performs amplification, transmission / reception separation, etc. Then, the antenna switch circuit 5 switches between operation / non-operation of the antenna 6 and transmits radio waves toward the IC tag 8. A broken line in the figure represents a range where the antenna 6 can communicate, that is, a communication area 100.

  In the figure, the IC tag 8 is first detected by the detection sensor 10 and then detected by the detection sensor 11, so that it can be determined that the IC tag 8 is moving in the direction of the arrow in the figure. In such a configuration, in order to determine the moving direction of the IC tag 8, it is necessary to separately provide a plurality of detection sensors for detecting an article or a human body, and there is a problem that the price of the system increases.

  FIG. 7 is a diagram for explaining an example of a configuration of a gate including a plurality of antennas and an RFID reader as disclosed in Patent Document 3.

  In the figure, when the RFID reader 1 communicates with the IC tag 8, the logic circuit 3 performs encoding and decoding according to the instruction of the control circuit 2 as in FIG. 6, and the high-frequency analog circuit 4 amplifies the analog signal. Perform transmission / reception separation. The antennas 6 and 7 operated by the antenna switch circuit 5 are switched, and radio waves are transmitted toward the IC tag 8.

  A broken line in the figure represents a range where each antenna can perform communication, that is, an antenna communication area 100. The first communication area 101 by the antenna 6 and the third communication area 103 by the antenna 7 are partially overlapped with each other. The communication area 102 is arranged. This is to minimize the range in which communication with the IC tag 8 cannot be performed within the gate.

  When the IC tag 8 in the figure moves in the direction of the arrow, first in the first communication area 101 by the antenna 6, and then in the second communication area 102 where the communication areas of the antenna 6 and the antenna 7 partially overlap, In addition, the unique information of the IC tag 8 is read in the third communication area 103 by the antenna 7. In each communication area, by comparing and collating the order in which the IC tags 8 are read, it is possible to determine the moving direction of the IC tag 8 without adding a new detection sensor.

  A processing method for determining the moving direction of the IC tag 8 in the configuration of FIG. 7 will be described. The RFID reader 1 is configured to always read the unique number if the IC tag 8 is within the communication area indicated by the broken line in the figure, and to accumulate the number of times read.

  FIG. 8 is a diagram illustrating an example of an algorithm of processing performed by the RFID reader 1 of FIG. In the figure, a transition of the number of times the RFID reader 1 performs reading within a predetermined time (hereinafter referred to as “unit time”) over time is shown.

  For the IC tag 8, let xai be the number of times the antenna 6 has read at unit time t at a certain elapsed time ti, and xbi be the number of times the antenna 7 has read at unit time t. In order to simplify the description, the elapsed time ti is an integer multiple of the unit time t. The integrated value of the number of times the antenna 6 has read is shown in Equation 3 as sai. Also, the integrated value of the number of times the antenna 7 has read is expressed as sbi in Equation 4.

  Here, a preset threshold th is provided for the integrated value of the number of times of reading. When sai and sbi are equal to or less than the threshold th, the logical value for condition determination is set to 0. When the threshold th is exceeded, the logical value for condition determination is set to 1, and the flags ai and bi at time ti are set. FIG. 8 shows an example when the threshold th = 3.

  Next, using the rise of the logical product ai × bi of the flags ai and bi, that is, the time when ai × bi is changed from 0 to 1, the flags a (i−1) and b (i -1) difference a (i-1) -b (i-1) is calculated. The moving direction Di can be determined based on the calculated value.

  FIG. 9 is a diagram showing the truth table of the algorithm shown in FIG. 8, and shows the relationship between the moving direction Di and the logical product ai × bi of the flags ai and bi.

  In the case of FIG. 8, the movement direction Di = 1 is calculated, which means that the IC tag 8 in the configuration of FIG. 7 is moving from the antenna 6 toward the antenna 7. Similarly, when moving from the antenna 7 to the antenna 6, the moving direction Di = −1 is calculated. Therefore, if the RFID reader system includes a plurality of antennas, the moving direction of the IC tag 8 can be determined without adding a detection sensor separately.

  However, in the configuration described with reference to FIGS. 7 to 9, the communication area where the reflection of the radio wave or interference occurs depending on the actual gate structure and surrounding environment, the installation status of each antenna, etc., and the reading of the IC tag is unstable. May occur, or an IC tag that is not within the communication area may be read.

  FIG. 10 is a diagram illustrating an example in which an erroneous determination of the moving direction is performed due to radio wave reflection or the like in the RFID reader system configured as shown in FIG. FIG. 10 shows a case where at time t2, the antenna 7 reads the IC tag 8 existing in a range that is not originally a communication area and xb2 = 3. In this case, the moving direction Di of the IC tag 8 is calculated as Di = −1, and it is determined that the IC tag 8 has moved from the antenna 7 toward the antenna 6. However, since the actual moving direction is opposite, it is an erroneous determination, and there is a problem that the certainty of determining the moving direction of the IC tag 8 may be impaired.

  The present invention has been made to solve the problems of the prior art, and its purpose is to reduce the price of the system by determining the moving direction of the IC tag without using a special sensor, It is an object of the present invention to provide an RFID reader system capable of reliably determining a moving direction even in an environment where interference is likely to occur.

  According to the present invention, an RFID reader system for reading or writing an IC tag attached to a movable object, comprising a plurality of antennas for communicating with the IC tag, Weighted by the number of readings from the time when the reading process of the IC tag was started to the time of reading from the time when the IC tag was read in each and the number of times the IC tag was read at the time of reading The moving direction of the IC tag is calculated by calculating a weighted average value of reading times (hereinafter referred to as “reading number weighted average value”) and comparing and comparing the reading number weighted average values of the plurality of antennas. An RFID reader system can be obtained.

  The read count weighted average value from the time tk when reading of the IC tag is started to the elapsed time ti is expressed by the following equation (1).

  According to the present invention, an RFID reader system for reading or writing an IC tag attached to a movable object, comprising a plurality of antennas for communicating with the IC tag, Weighting is performed on the signal level from the time when the IC tag is read to the time when the IC tag is read from the time when the IC tag is read and the read signal level of the IC tag at the time when the IC tag is read. By calculating a weighted average value of the read time (hereinafter referred to as “signal level weighted average value”) and comparing and comparing the signal level weighted average values of the plurality of antennas, the moving direction of the IC tag can be determined. An RFID reader system can be obtained that is characterized by determining.

  The signal level weighted average value from the time tk when reading of the IC tag is started to the elapsed time ti is expressed by the following equation (2).

  In addition, according to the present invention, when the difference between the read count weighted average value or the signal level weighted average value exceeds a preset threshold value, the moving direction of the IC tag is determined. An RFID reader system is obtained.

  According to the present invention, each of the plurality of antennas and the weighted average value of the reading time weighted by the number of readings or the weighted average value of the reading time weighted by the signal level are used to determine the IC tag. An RFID reader system is obtained in which the moving direction of the IC tag is determined by calculating a moving speed value and comparing and comparing the moving speed value with a preset threshold value.

  According to the present invention, it is possible to obtain an RFID reader system characterized by determining the moving direction of the IC tag when the value of the moving speed exceeds the threshold value.

  The determination logic of the present invention reads the IC tag with a plurality of antennas included in the RFID reader system, and reads the reading time of the IC tag for each of the plurality of antennas, that is, the elapsed time from the start of the reading process at the elapsed time. Weighting is performed according to the number of times or the received signal level, the weighted average value of the elapsed time at each antenna is calculated, and the moving direction of the IC tag is determined from the context with respect to the elapsed time at each weighted average value.

  Further, the movement speed of the IC tag is calculated by calculating a value of the moving speed of the IC tag from the difference between the distances between the plurality of antennas and the elapsed time, and comparing and collating the value of the moving speed with a preset threshold value. The direction is determined.

  According to the present invention, in an RFID reader system including a plurality of antennas used for reading an IC tag, the moving direction of the IC tag can be determined without adding a special sensor such as a detection sensor to the system. The price can be reduced.

  Further, according to the present invention, it is possible to provide an RFID reader system capable of reliably determining the moving direction of an IC tag even in an environment where radio waves are likely to be reflected or interfered.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 and FIG. 2 are diagrams illustrating determination logic for performing weighting by the number of readings according to the present invention.

  The RFID reader system according to the present invention is substantially the same as an example of a gate provided with a plurality of antennas and an RFID reader shown in FIG. And the judgment method is different.

  In FIG. 1, the integrated value at each time when weighting is performed (that is, sai shown in Equation 3 for the antenna 6 and sbi shown in Equation 4 for the antenna 7) is divided by the integrated value of the number of readings, and the elapsed time The weighted average value of the number of readings at ti (that is, WA (tai) for antenna 6 and WA (tbi) for antenna 7) is calculated. Note that k in the figure indicates a specific value for the specific time tk before the reading of the IC tag is started.

  FIG. 2 shows an example in which a difference between values is taken as a method of comparing the number of reading times weighted average value of each antenna.

  According to the logic of FIG. 2, when the difference WA (tai) −WA (tbi) between the reading times weighted average values of the two antennas is obtained, and the difference exceeds a preset threshold (assuming −th1 or + th2). Judgment is performed, and when the difference is smaller than -th1, -1 is set, and when it is larger than + th2, 1 is set. When the difference is in the range of -th1 to + th2, 0 is set.

  Here, the thresholds th1 and th2 are positive integers. When −1, the movement from the antenna 6 to the antenna 7 is determined. When +1, the movement from the antenna 7 to the antenna 6 is determined. Impossible.

  FIG. 3 is a diagram illustrating an example of determination processing performed by the RFID reader system according to the present invention when the reading result is the same as the example of FIG.

  1 and 2, the number-of-readings weighted average values WA (tai) and WA (tbi) of the two antennas 6 and 7 are obtained, and then the difference WA (tai) -WA (tbi) is obtained. The movement direction Di of the IC tag 8 is obtained from the result. Here, the threshold value th1 = th2 = 0.5. The moving direction obtained by this processing is Di = −1, and it can be correctly determined that the IC tag 8 has moved from the antenna 6 toward the antenna 7. Therefore, more accurate determination than the determination process performed by the conventional RFID reader system can be performed.

  FIG. 4 is a diagram showing an example of a measurement value at the gate to which the RFID reader system according to the present invention is applied. When the IC tag 8 moves from the antenna 7 to the antenna 6, that is, in the opposite direction to FIG. Represents.

  Here, the thresholds th = 3 and th1 = th2 = 1. In the determination processing method performed by the conventional RFID reader system, the determination logic described with reference to FIG. 9 is used, so that the movement direction Di = −1, which is erroneously determined as the movement from the antenna 7 to the antenna 6. In the case of the present invention using the determination logic of FIGS. 1 and 2, Di = 1, and the moving direction of the IC tag 8 can be correctly determined.

  FIG. 5 is a diagram showing an example of a measurement value at a gate to which the RFID reader system according to the present invention is applied, and shows a case where the IC tag 8 is turned back in the middle from the antenna 7 toward the antenna 6. .

  When the determination process is performed in the same manner as described with reference to FIG. 4, the determination method performed by the conventional RFID reader system results in the moving direction Di = 1, and erroneous determination that the IC tag 8 has moved from the antenna 7 toward the antenna 6. However, according to the determination processing method performed by the RFID reader system of the present invention, it is impossible to determine the moving direction because Di = 0 is obtained, and therefore, erroneous determination can be avoided.

  FIG. 11 is a diagram for explaining the determination logic using the value of the moving speed according to the present invention.

  According to the logic of FIG. 1, a weighted average value of the number of readings at each antenna is calculated. According to the logic of FIG. 11, the distance l between the plurality of antennas is divided by the difference WA (tai) −WA (tbi) of the number of reading times weighted at each antenna, and the IC tag 8 passing between the plurality of antennas is divided. The moving speed WA (vi) (hereinafter referred to as “Y”) is calculated.

  The determination is performed when the movement speed Y exceeds a preset threshold (assuming −th3 or + th4). If the value is 0> Y> −th3, the movement direction Di ′ = − 1, 0 <Y. In the case of <+ th4, the moving direction Di ′ = 1, and in the case of Y ≦ −th3 and Y ≧ + th4, 0.

  Here, the thresholds th3 and th4 are positive integers. When −1, the movement from the antenna 6 toward the antenna 7 is determined. When +1, the movement from the antenna 7 toward the antenna 6 is determined. Impossible.

  In FIG. 3, as an example of the determination process performed by the RFID reader system according to the present invention, a case where determination is performed using the determination logic of FIG. 11 is indicated as Di ′. In Di ′, the same result as the moving direction Di of the IC tag 8 determined from the difference between the read count weighted average values can be obtained.

  When determining the moving direction of the IC tag 8 using the weighted average value of the number of readings, when the moving speed of the IC tag 8 changes greatly, it is necessary to change the threshold values (th1, th2) in order to maintain the determination accuracy. Sometimes.

  On the other hand, when the determination is made based on the moving speed of the IC tag 8, the moving speed itself becomes a reference for determination, and therefore the moving direction determination accuracy can be maintained without changing the threshold values (th3, th4). In addition, even when the moving speed of the IC tag 8 changes greatly, the moving direction can be determined with high accuracy.

  In the present embodiment, the processing method when the reading time of the IC tag 8 is weighted by the number of readings has been described as an example, but even when the reading time is weighted by the reception level of the signal from the IC tag, Since the reception level becomes the highest when the IC tag 8 is closest to the antenna, the embodiment is similar to the case of the weighting by the number of readings, and it goes without saying that the same effect can be obtained.

  As mentioned above, although embodiment of this invention was described using drawing, this invention is not limited to these embodiment, There exists a change of a member and a structure in the range which does not deviate from the summary of this invention. Are also included in the present invention. That is, the configuration of the antenna is not limited to two, and the moving direction of the IC tag is similarly determined by applying the algorithm described above to the detection result of the IC tag when a plurality of antennas are installed. It goes without saying that it is possible.

  In addition, the elapsed time ti is not affected by the determination as long as the time relationship is correctly recognized, no matter how the unit time t and the multiple i are set in numerical values. That is, it is obvious that various modifications and corrections that can be naturally made by those skilled in the art are also included in the present invention.

The figure explaining the determination logic which weights by the frequency | count of reading by this invention. FIG. 2 is a continuation diagram of FIG. 1 illustrating determination logic for weighting by the number of readings according to the present invention. The figure which shows the example of the determination process by this invention when a reading result is the same as the example of FIG. The figure which shows an example of the measured value in the gate to which the RFID reader system by this invention is applied (antenna 7-> 6). The figure which shows an example of the measured value in the gate to which the RFID reader system by this invention is applied (return). 6A and 6B illustrate an example of a structure of a gate including a plurality of detection sensors and an RFID reader. 6A and 6B illustrate an example of a structure of a gate including a plurality of antennas and an RFID reader. FIG. 8 is a diagram illustrating an example of an algorithm for processing performed by the RFID reader in FIG. 7. The figure which shows the truth table of the algorithm shown in FIG. FIG. 8 is a diagram illustrating an example in which an erroneous determination of the moving direction is performed due to radio wave reflection or the like in the RFID reader system configured as shown in FIG. 7. The figure explaining the determination logic using the value of the moving speed by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RFID reader 2 Control circuit 3 Logic circuit 4 High frequency analog circuit 5 Antenna switch circuit 6, 7 Antenna 8 IC tag 10, 11 Detection sensor 100 Antenna communication area 101 1st communication area 102 2nd communication area 103 3rd communication area

Claims (5)

  An RFID reader system for reading or writing an IC tag attached to a movable object, comprising a plurality of antennas for communicating with the IC tag, wherein the IC tag is in each of the plurality of antennas. The reading time and the number of times that the IC tag was read at the time of reading are compared to the reading time that is weighted by the number of readings from the time when the reading process of the IC tag is started to the time of reading. An RFID reader system characterized by calculating a weighted average value, and comparing and collating a weighted average value of reading times weighted by the number of readings in the plurality of antennas, thereby determining a moving direction of the IC tag. .   An RFID reader system for reading or writing an IC tag attached to a movable object, comprising a plurality of antennas for communicating with the IC tag, wherein the IC tag is in each of the plurality of antennas. The read time and the weight of the read time weighted by the signal level from the time when the IC tag read process is started to the read time from the read signal level of the IC tag at the read time An RFID reader system, wherein the moving direction of the IC tag is determined by calculating an average value and comparing and comparing a weighted average value of reading times weighted by the signal levels in the plurality of antennas.   When the difference between the weighted average value of the reading times weighted by the number of readings or the weighted average value of the reading times weighted by the signal level exceeds a preset threshold, the movement direction of the IC tag The RFID reader system according to claim 1, wherein the determination is performed.   The value of the moving speed of the IC tag is calculated from each distance in the plurality of antennas and a weighted average value of reading times weighted by the number of readings or a weighted average value of reading times weighted by the signal level. 3. The RFID reader system according to claim 1, wherein the moving direction of the IC tag is determined by comparing and collating the value of the moving speed with a preset threshold value.   5. The RFID reader system according to claim 4, wherein when the value of the moving speed exceeds the threshold value, the moving direction of the IC tag is determined.

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