Locator and location system

Abstract

Even in radio wave environments where reflected radio waves from the tag reach the locator, the system suppresses the effects of reflection and accurately identifies the tag's location. [Solution] In locator L, for each of multiple radio waves arriving from the same tag T but with different propagation paths, the antenna receiving surface is oriented so that the direction from which the radio wave arrived falls within the high-precision measurement angle range of antenna ANT. A first distance to tag T is then measured, and the antenna receiving surface is oriented so that it matches the direction from which the radio wave arrived. The radio wave with the smallest distance variation between the first and second distances measured from that radio wave is selected as the direct wave that arrived directly from tag T without reflection. The distance measured from the direct wave and the direction from which the direct wave arrived are then identified as the distance and direction relative to tag T.

Description

Technical Field

[0001] The present invention relates to a position specifying technique for specifying the position of a tag based on radio waves transmitted from the tag.

Background Art

[0002] In recent years, as a position specifying technique for specifying the position of a tag based on radio waves transmitted from the tag, an indoor positioning technique (AOA BLE5.1: Bluetooth Low Energy) using Angle of Arrival (AoA) of Bluetooth (registered trademark) 5.1, which is a short-range wireless communication standard, has been increasingly used.

[0003] For example, Patent Document 1 proposes a technique that uses this indoor positioning technique, in which each of a plurality of locators receives radio waves from the same tag, measures the detection angle (angle of arrival) of the radio wave at each locator, and calculates the distance to the tag and further the position of the tag from these detection angles and the positions of the locators.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] However, such an indoor positioning technique has a problem that when the radio wave from a tag is reflected by objects such as indoor walls, lockers, and desks, a false detection occurs as if there are a plurality of tags. For example, as shown in FIG. 9, in a radio environment where there is an object R such as a wall that reflects radio waves, when the tag Ta transmits omnidirectional radio waves, a plurality of radio waves including a direct wave Wa that directly reaches the locator from the tag Ta and a reflected wave Wb that is reflected by the object R from the tag Ta and then reaches the locator arrive at the locator via different propagation paths.

[0006] In this case, although it is actually three-dimensional, if we assume a two-dimensional plane in which the direct wave Wa and reflected wave Wb propagate, the detection angle θa of the direct wave Wa and the detection angle θb of the reflected wave Wb are different at the locator with respect to the vertical direction V of the antenna receiving surface P. Therefore, the distances Da and Db from the locator to tags Ta and Tb, calculated from their respective detection angles θa and θb, will also be different values. Consequently, tag Ta is detected as being at a distance Da in the direction of detection angle θa from the direct wave Wa, and tag Tb is detected as being at a distance Db in the direction of detection angle θb from the reflected wave Wb. As a result, the same tags Ta and Tb are mistakenly detected as being at different locations.

[0007] The present invention aims to solve these problems and provides a location identification technology that can accurately determine the tag's position even in radio wave environments where radio waves from a tag not only reach the locator directly but also reach the locator after being reflected by an object, by suppressing the effects of reflection. [Means for solving the problem]

[0008] To achieve this objective, the locator according to the present invention comprises an antenna configured so that the orientation of the antenna receiving surface is adjustable, and a control circuit configured to determine the distance and direction of a tag from radio waves transmitted from the tag based on Bluetooth® 5.1 AoA positioning technology, wherein when multiple radio waves transmitted from the same tag are detected via different propagation paths, the control circuit measures a first distance to the tag while adjusting the orientation of the antenna receiving surface of each of these multiple radio waves so that the direction from which the radio wave arrived falls within the high-precision measurement angle range of the antenna. The system comprises a first measuring unit, a second measuring unit configured to measure a second distance to the tag with each of the plurality of radio waves while adjusting the orientation of the antenna receiving surface to match the direction from which the radio wave arrived, and a determination unit configured to determine the distance change range between the first distance and the second distance measured from each of the plurality of radio waves, select the radio wave with the smallest distance change range among the plurality of radio waves as the direct wave that arrived directly from the tag without reflection, and determine the distance measured from the direct wave and the direction from which the direct wave arrived as the distance and direction related to the tag.

[0009] Furthermore, the location identification system according to the present invention is configured to identify the location of a tag based on location information for the same tag collected from a plurality of locators located in different locations, wherein each of the plurality of locators is a locator as described in claim 1. [Effects of the Invention]

[0010] According to the present invention, even in radio wave environments where radio waves from the tag reach the locator not only directly but also reflect off objects before reaching the locator, the effects of reflection are suppressed, making it possible to accurately determine the tag's location. [Brief explanation of the drawing]

[0011] [Figure 1]Figure 1 is a block diagram showing the configuration of the locator according to this embodiment. [Figure 2] Figure 2 is a block diagram showing the configuration of the location identification system according to this embodiment. [Figure 3] Figure 3 is a graph showing the relationship between detection angle and distance. [Figure 4] Figure 4 is a graph showing the relationship between the distance to the tag and the positional error. [Figure 5] Figure 5 is a flowchart showing the operation of the locator according to this embodiment. [Figure 6] Figure 6 is an explanatory diagram showing the radio wave detection status. [Figure 7] Figure 7 is an explanatory diagram showing the first distance measurement process. [Figure 8] Figure 8 is an explanatory diagram showing the measurement process for the second distance. [Figure 9] Figure 9 is an explanatory diagram illustrating false positives of tags. [Modes for carrying out the invention]

[0012] Next, an embodiment of the present invention will be described with reference to the drawings.

[0013] [locator] First, the locator L according to this embodiment will be described with reference to the block diagram in Figure 1.

[0014] This locator L achieves high directivity through beamforming technology and is configured to determine the distance and direction of tag T based on radio waves received from tag T via the antenna, based on Bluetooth® 5.1 AoA positioning technology. Tag T is a standard Bluetooth tag and is pre-distributed to users who will be using the location to be tracked.

[0015] The locator L is used in the position locating system 1 as shown in FIG. 2, a plurality of locators L are installed in the detection area which is the target of position location, and are connected to the position locating device 20 so as to be capable of data communication via a communication network NW such as a LAN or WiFi.

[0016] [Position locating system] The position locating system 1 includes a plurality of locators L according to the present embodiment and the position locating device 20. When the position locating system 1 specifies the position of a tag T carried by a user present in an office, each locator L is installed at each position in a detection area set in the office.

[0017] The position locating device 20 is generally composed of a computer such as a server device or a personal computer, and is configured to collect position information of the tag T specified by each of the plurality of locators L installed in the detection area via the communication network NW, and specify the existing position of the tag T based on position coordinates relating to the same tag T from among the pieces of position information. The information terminal 30 is composed of an information terminal such as a personal computer or a smartphone, and is configured to perform data communication with the position locating device 20 via the communication network NW, so as to acquire existing position information indicating the existing position of the tag T from the position locating device 20 and display the information on a screen.

[0018] [Principle of the invention] As shown in the aforementioned FIG. 9, in a radio wave environment where an object R such as a wall that reflects radio waves exists, a direct wave Wa that directly reaches the locator from the tag Ta and a reflected wave Wb that is reflected by the object R from the tag Ta and reaches the locator are observed by the locator. Therefore, in order to suppress the influence of the reflected wave Wb, it is necessary to distinguish the direct wave Wa from the reflected wave Wb. Note that although distance and direction are actually calculated and processed in three dimensions, the following description is made on a two-dimensional plane for ease of understanding.

[0019] The reflected wave Wb travels from tag Ta to object R before reaching the locator, resulting in a longer propagation path compared to the direct wave Wa, which travels directly from tag T to the locator. Therefore, among the radio waves transmitted from the same tag Ta and reaching the locator, the one with the shortest propagation path, i.e., the shortest distance D from tag Ta, can be identified as the direct wave Wa. However, the radio waves received by the locator are not synchronized with each other. Furthermore, the obtained distance D includes measurement errors characteristic of indoor positioning technology. For these reasons, it is difficult to identify the direct wave Wa based solely on the measured distance D.

[0020] The indoor positioning technology (AOA BLE5.1) is configured to detect the angle between the perpendicular line on the antenna receiving surface and the radio waves arriving from the tag in the locator, and to calculate the distance from the locator to the tag based on the detected angle.

[0021] In this case, as shown in Figure 3, the detection angle θ and the distance D have roughly an inverse relationship. Therefore, when the detection angle θv is relatively acute, the variation range ΔDv of the distance Dv within a certain angular range Δθ centered on the detection angle θv is relatively large. On the other hand, when the detection angle θw is relatively obtuse, the variation range ΔDw of the distance Dw within a certain angular range Δθ centered on the detection angle θw is relatively small.

[0022] Therefore, when the tag is positioned perpendicular to the locator's antenna receiving surface, the position error ε regarding the obtained tag position changes significantly depending on the distance between the locator and the tag, as shown in the measurement results in Figure 4.

[0023] In the graph in Figure 4, the white circles represent the position error ε that occurs in the X direction (horizontal direction) perpendicular to the Y direction (vertical direction) connecting the locator and the tag at each distance. In this case, characteristic (dashed line) 41 represents an approximation graph of the white circles, and it can be seen that the position error ε remains almost constant even as the distance D increases.

[0024] On the other hand, the black circles represent the position error ε in the Y direction at each distance, i.e., the measurement error of the distance. In this case, characteristic (solid line) 42 represents an approximate graph of the black circles, and it can be seen that the position error ε changes significantly as the distance D increases.

[0025] Therefore, when the tag is positioned perpendicular to the locator's antenna receiving surface, it can be seen that as the distance between the locator and the tag increases, the measurement error of that distance also tends to increase.

[0026] This invention focuses on the relationship inherent in such indoor positioning technology (AOA BLE5.1), where, when the tag is positioned perpendicular to the locator's antenna receiving surface, the measurement error of the distance increases as the distance between the locator and the tag increases.

[0027] Furthermore, the present invention provides a locator L that, for each of several radio waves arriving from the same tag T but with different propagation paths, measures a first distance to tag T while adjusting the orientation of the antenna receiving surface so that the direction from which the radio wave arrived is included within the high-precision measurement angle range of the antenna ANT, and measures a second distance to tag T while adjusting the orientation of the antenna receiving surface so that it matches the direction from which the radio wave arrived, selects the radio wave with the smallest distance change from the first distance to the second distance as the direct wave that arrived directly from tag T to locator L, and identifies the distance and direction related to the tag as determined from the direct wave.

[0028] This allows for precise selection of direct radio waves from the tag, even in radio wave environments where radio waves from the tag reach the locator not only directly but also reflect off objects before reaching the locator. This suppresses the effects of reflection, enabling accurate identification of the tag's location.

[0029] [Configuration of this embodiment] Next, the configuration of the locator L according to this embodiment will be described in detail with reference to the block diagram in Figure 1 mentioned above.

[0030] The locator L comprises, as its main circuit configuration, an antenna ANT, a wireless I / F 11, a communication I / F 12, a memory circuit 13, and a control circuit 14.

[0031] [antenna] Antennas consist of common types of antennas, such as phased array antennas, which have multiple antenna elements arranged in a grid.

[0032] [Wireless Interface] The wireless interface 11 is configured to detect radio waves transmitted from tag T via antenna ANT and output them to the control circuit 14.

[0033] [Communication Interface] The communication interface 12 is configured to communicate data with the location identification device 20 via the communication network NW.

[0034] [Memory circuit] The memory circuit 13 consists of a storage device such as a semiconductor memory and is configured to store processing data and programs for realizing the measurement processing performed by the control circuit 14.

[0035] [control circuit] The control circuit 14 has a CPU and its peripheral circuits, and is configured to read the program from the memory circuit 13 and cooperate with the CPU to realize various processing units for executing a measurement process to measure the position of tag T.

[0036] The main processing units implemented in the control circuit 14 include the first measurement unit 14A, the second measurement unit 14B, and the identification unit 14C.

[0037] [First measurement unit] The first measuring unit 14A is configured to measure a first distance to tag T when multiple radio waves transmitted from the same tag T are detected via different propagation paths, while adjusting the orientation of the antenna receiving surface of the antenna ANT so that the direction from which the radio wave arrived falls within the high-precision measurement angle range of the antenna ANT.

[0038] [Second measurement unit] The second measuring unit 14B is configured to measure a second distance to tag T for each of the detected radio waves, with the orientation of the antenna receiving surface of antenna ANT adjusted to the direction from which the radio wave arrived.

[0039] [Specific part] The identification unit 14C determines the distance change range from a first distance to a second distance measured from each of the detected radio waves, selects the radio wave with the smallest distance change range among the multiple radio waves as the direct wave that arrived directly from tag T without reflection, identifies the first distance measured from the direct wave and the direction from which the direct wave arrived as the distance and direction related to tag T, and notifies the location identification device 20 via the communication I / F 12.

[0040] As mentioned above, the present invention focuses on the relationship that when the tag T is located perpendicular to the antenna receiving surface of the locator L, the measurement error of the distance increases as the distance between the locator L and the tag T increases, and selects a direct wave based on the distance change range between the first distance and the second distance. Therefore, in order to correctly determine the distance change range, it is necessary to measure the first distance with high accuracy.

[0041] As explained in Figure 3 above, the detection angle θ, which is the angle between the perpendicular line of the antenna's receiving surface and the radio waves arriving from the tag, has roughly an inverse relationship with the distance D from the locator to the tag. In this case, if the orientation of the antenna's receiving surface is adjusted to the direction from which the radio waves arrived, as in the second measurement unit 14B, the detection angle θ becomes almost zero, so the variation in distance D becomes extremely large and the accuracy of distance measurement deteriorates.

[0042] On the other hand, a certain level of measurement accuracy can be obtained by moving the antenna a certain angle away from the direction from which the radio waves arrived. The high-precision measurement angle range used by the first measurement unit 14A is the angle range in which distance can be measured with measurement accuracy that allows for the correct selection of the direct wave from among multiple incoming radio waves, and this range can be determined in advance through calculations or experiments, using the antenna receiving surface as a reference. As a result, by adjusting the orientation of the antenna receiving surface in the first measurement unit 14A so that the direction from which the radio waves arrived is included within the high-precision measurement angle range, the distance to the tag can be measured with high accuracy.

[0043] The antenna receiving surface of the antenna ANT refers to the surface formed by multiple small antennas arranged in an array. In Bluetooth 5.1's AoA positioning technology, the angle at which radio waves arrived, i.e., the detection angle, is derived based on the distance between two small antennas placed on the same surface and the phase difference of the radio waves from the tag received by these small antennas. For the configuration to adjust the orientation of the antenna receiving surface, any well-known configuration can be used, such as a configuration that mechanically tilts the antenna ANT part or the entire locator L.

[0044] [Operation of this embodiment] Next, the operation of the locator L according to this embodiment will be described with reference to the flowchart in Figure 5.

[0045] In the control circuit 14, the first measurement unit 14A detects radio waves transmitted from tag T via antenna ANT and determines whether multiple radio waves transmitted from the same tag have been detected via different propagation paths. If the detected radio waves originate from a single direction, the identification unit 14C selects the radio wave as the direct wave and identifies the distance measured from this direct wave and the direction from which the direct wave arrived as the distance D and direction θ with respect to tag T.

[0046] In this case, the first measuring unit 14A may adjust the orientation of the antenna receiving surface so that the direction in which the direct wave arrived falls within a predetermined high-precision measurement angle range set on the antenna receiving surface of the antenna ANT, remeasure the first distance to tag T, and identify the obtained first distance as the distance D related to tag T.

[0047] On the other hand, if multiple radio waves transmitted from the same tag T are detected via different propagation paths, the measurement process shown in Figure 5 is initiated. For example, as shown in Figure 6, it is assumed that radio waves W1 that arrived directly from tag T to locator L (direct wave) and radio waves W2 that arrived reflected from object R (reflected wave) are detected, and radio waves W1 and W2 are detected in different directions θ1 and θ2 with respect to the perpendicular V of the antenna receiving surface P.

[0048] In the measurement process shown in Figure 5 above, first, the first measurement unit 14A selects one unmeasured radio wave W from among these multiple radio waves (step 100), and adjusts the orientation of the antenna receiving surface so that the direction from which the radio wave W arrived falls within the high-precision measurement angle range of the antenna ANT (step 101).

[0049] Next, the first measurement unit 14A measures a first distance D from the selected radio wave W to the tag T based on Bluetooth 5.1 AoA positioning technology (step 102). If there are any unmeasured radio waves (step 103: YES), it returns to step 100 to measure the first distance D for the next radio wave.

[0050] As shown in Figure 6 above, when radio waves W1 and W2 are detected, the first measuring unit 14A measures the first distances D1 and D2 from these radio waves W1 and W2, respectively, as shown in Figure 7. Figure 7(a) shows the process of measuring the first distance D1 from radio wave W1, and the orientation of the antenna receiving surface P is adjusted so that the direction from which the direct wave W1 arrived falls within the high-precision measurement angle range AP of the antenna receiving surface P.

[0051] Furthermore, Figure 7(b) shows the process of measuring the first distance D2 from the radio wave W2, and the orientation of the antenna receiving surface P is adjusted so that the direction from which the radio wave W2 arrived falls within the high-precision measurement angle range AP of the antenna receiving surface P.

[0052] Thus, once the measurement of the first distance D for all radio waves W1 and W2 is completed (step 103: NO), the second measurement unit 14B selects one unmeasured radio wave W from these multiple radio waves (step 110) and adjusts the orientation of the antenna receiving surface of the antenna ANT in the direction from which the selected radio wave W arrived (step 111).

[0053] This ensures that tag T is positioned perpendicular to the antenna receiving surface. Next, the second measurement unit 14B measures the second distance d from the selected radio wave W to tag T based on Bluetooth 5.1 AoA positioning technology (step 112), and if there are any unmeasured radio waves (step 113: YES), it returns to step 110 to measure the second distance d for the next radio wave.

[0054] Thus, once the measurement of the second distance d has been completed for all radio waves W1 and W2 (step 113: NO), the identification unit 14C determines the distance change range ΔD from the first distance D to the second distance d measured from each of these radio waves W1 and W2 (step 120), and selects the radio wave with the smallest distance change range ΔD from these radio waves as the direct wave that arrived directly from tag T without reflection (step 121).

[0055] Next, the identification unit 14C identifies the first distance measured from the direct wave and the direction from which the direct wave arrived as the distance D and direction θ with respect to the tag T (step 122), and terminates the series of measurement processes.

[0056] As shown in the aforementioned FIG. 6, when radio waves W1 and W2 are detected, the first measurement unit 14A measures second distances d1 and d2 from these radio waves W1 and W2, respectively, as shown in FIG. 8. FIG. 8(a) shows the process of measuring the second distance d1 from the radio wave W1, wherein the orientation of the antenna receiving surface P of the antenna ANT is adjusted to match the direction from which the radio wave W1 arrives. In this case, the radio wave W1 arrives from a direction perpendicular to the antenna receiving surface, which increases the measurement error of the second distance d1, so that the tag T1 is detected as if it were present at the position of tag t1.

[0057] Further, FIG. 8(b) shows the process of measuring the second distance d2 from the radio wave W2, wherein the orientation of the antenna receiving surface of the antenna ANT is adjusted to match the direction from which the radio wave W2 arrives. In this case also, the radio wave W2 arrives from a direction perpendicular to the antenna receiving surface, which increases the measurement error of the second distance d2, so that the tag T2 is detected as if it were present at the position of tag t2.

[0058] Accordingly, the distance change width ΔD1 related to tag T1 is obtained as the difference (absolute value) between the first distance D1 measured from the radio wave W1 and the second distance d1, giving ΔD1=|D1-d1|. Further, the distance change width ΔD2 related to tag T2 is obtained as the difference (absolute value) between the first distance D2 measured from the radio wave W2 and the second distance d2, giving ΔD2=|D2-d2|.

[0059] Here, the obtained distance change widths ΔD1 and ΔD2 correspond to the positional error ε in the Y direction (longitudinal direction) shown in the aforementioned FIG. 4. In the aforementioned FIG. 8, if the comparison result of the distance change widths ΔD1 and ΔD2 is ΔD1<ΔD2, then based on characteristic 41, distances D1 and D2 satisfy D1<D2. For this reason, the radio wave W1 for which the minimum distance D1 is obtained is identified as a direct wave.

[0060] Effects of the Present Embodiment Thus, in this embodiment, the locator L measures a first distance to tag T for each of several radio waves with different propagation paths that arrived from the same tag T, with the orientation of the antenna receiving surface adjusted so that the direction from which the radio wave arrived is included in the high-precision measurement angle range of the antenna ANT, based on Bluetooth 5.1 AoA positioning technology. It also measures a second distance to tag T with the orientation of the antenna receiving surface adjusted so that it matches the direction from which the radio wave arrived. The radio wave with the smallest distance variation between the first and second distances measured from the radio wave is selected as the direct wave that arrived directly from tag T without reflection, and the distance measured from the direct wave and the direction from which the direct wave arrived are identified as the distance and direction related to tag T.

[0061] This allows for precise selection of direct waves from the radio waves transmitted from tag T, even in radio wave environments where the radio waves reach locator L directly or are reflected by object R before reaching locator L. This suppresses the effects of reflection and enables accurate determination of tag T's location.

[0062] [Expansion of the embodiment] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above embodiments. Various modifications to the configuration and details of the present invention can be made that will be understood by those skilled in the art within the scope of the present invention.

[0063] In the above explanation, the case in which the identification unit 14C of the locator L selects a direct wave and determines the distance and direction of tag T based on the first and second distances measured by the first and second measurement units 14A and 14B for each detected radio wave was described as an example. However, the explanation is not limited to this, and a processing unit similar to the identification unit 14C may be implemented in the processing circuit of the position identification device 20.

[0064] In this configuration, the locator L measures a first distance and direction for each radio wave, as well as a second distance. This information is then sent to the location identification device 20 via the communication network NW as position information from the locator L. The location identification device 20 then selects a direct wave from among these radio waves based on the first distance, the direction from which the radio wave arrived, and the second distance included in the position information sent from the locator L. The first distance and direction for this direct wave are then identified as the distance and direction for tag T. This reduces the configuration and processing of the locator L. [Explanation of symbols]

[0065] 1...Location identification system, T...Tag, L...Locator, ANT...Antenna, 11...Wireless I / F, 12...Communication I / F, 13...Memory circuit, 14...Control circuit, 14A...First measurement unit, 14B...Second measurement unit, 14C...Identification unit, 20...Location identification device, 30...Information terminal, NW...Communication network.

Claims

1. An antenna configured so that the orientation of the antenna receiving surface can be adjusted, The system comprises a control circuit configured to determine the distance and direction of a tag from radio waves transmitted from the tag, based on Bluetooth® 5.1 AoA positioning technology, The aforementioned control circuit is When multiple radio waves transmitted from the same tag are detected via different propagation paths, a first measuring unit is configured to measure a first distance to the tag for each of these multiple radio waves, while adjusting the orientation of the antenna's receiving surface so that the direction from which the radio wave arrived falls within the high-precision measurement angle range of the antenna. A second measuring unit is configured to measure the second distance to the tag with respect to each of the aforementioned plurality of radio waves, while adjusting the orientation of the antenna receiving surface so that it matches the direction from which the radio wave arrived. The identification unit is configured to determine the distance change range between the first distance and the second distance measured from each of the plurality of radio waves, select the radio wave with the smallest distance change range from the plurality of radio waves as the direct wave that arrived directly from the tag without reflection, and identify the distance measured from the direct wave and the direction from which the direct wave arrived as the distance and direction related to the tag. A locator characterized by the following features.

2. A location identification system configured to identify the location of a tag based on location information of the same tag collected from multiple locators located in different places, A location identification system characterized in that each of the plurality of locators is a locator as described in claim 1.

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