Position Inference System

Abstract

The present invention estimates the position of a transmitting device with sufficient accuracy. A position estimation system (10) comprises: a transmitting device (20) having a plurality of transmitters (21, 22) arranged symmetrically about a predetermined reference position; a plurality of receivers (31, 32, 33, 34, 35, 36, 37, 38) receiving radio waves transmitted from the plurality of transmitters (21, 22); and an estimation tool (51) estimating the position of the transmitting device (20) based on the reception intensity of the radio waves received by each receiver (31, 32, 33, 34, 35, 36, 37, 38).

Description

Technical Field

[0001] The present invention relates to a position inference system. Background Art

[0002] There is a known technology for inferring the location of a transmitter through wireless communication between a transmitter and a receiver. For example, the location inference system described in Patent Document 1 includes: a plurality of transmitters that transmit beacon signals carrying identification information with approximately the same transmission power, and a receiver that can move along the arrangement direction of the plurality of transmitters. The receiver stores the average value of the reception strength when the beacon signal is received near each transmitter as a first threshold, and stores the average value of the reception strength when the beacon signal is received in the middle of adjacent transmitters as a second threshold. The receiver infers the current location of the receiver by comparing the reception strength of the beacon signal received from the transmitter with the first threshold and the second threshold. On the other hand, the location inference system described in Patent Document 2 mitigates the degradation of the accuracy of location inference of a mobile communication terminal by collecting the reception strength of a communication terminal among a plurality of communication terminals including a mobile communication terminal when receiving from other communication terminals to an access point and performing statistical processing.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2015-224943

[0004] Patent Document 2: Japanese Patent Application Publication No. 2017-15577

[0005] However, the position estimation system described in Patent Document 1 determines the first threshold and the second threshold based on the measured value of the beacon signal reception strength. Therefore, whenever the radio wave reception environment changes, the beacon signal reception strength needs to be measured again. In addition, in an environment such as a factory or an office where there are many objects that block or reflect radio waves, it is difficult to correctly estimate the position of the receiver due to the influence of multipath fading. On the other hand, the position estimation system described in Patent Document 2 is not suitable for real-time position estimation because statistical processing takes time.

[0006] Furthermore, in such a position estimation system, if there is a deviation in the directivity of the radio waves from the transmitter, even if the transmitter is located the same, the intensity of the radio waves received by the receiver will vary significantly depending on the orientation of the transmitter, thereby reducing the accuracy of the transmitter's position estimation. Summary of the invention

[0007] The present invention has been made in view of such a problem, and an object of the present invention is to estimate the position of a transmitting device with sufficient accuracy.

[0008] In order to solve the above-mentioned problems, the position inference system involved in the present invention comprises: a sending device, which has multiple transmitters arranged symmetrically about a specified reference position; multiple receivers, which receive radio waves sent from the multiple transmitters; and an inference unit, which infers the position of the sending device based on the reception intensity of the radio waves received by each receiver.

[0009] According to the position estimation system of the present invention, the position of the transmitting device can be estimated with sufficient accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is an explanatory diagram showing an example of a position estimation system according to an embodiment of the present invention.

[0011] Figure 2 It is an explanatory diagram showing the configuration of a transmission device of a position estimation system according to an embodiment of the present invention.

[0012] Figure 3 It is an explanatory diagram of a screen displayed on a display device of a position estimation system according to an embodiment of the present invention.

[0013] Figure 4 It is an explanatory diagram showing a configuration example of a receiver involved in an embodiment of the present invention.

[0014] Figure 5 This is a graph showing measurement results of each receiver according to the embodiment of the present invention.

[0015] Figure 6 It is a graph showing the measurement results for each region according to the embodiment of the present invention.

[0016] Figure 7 It is an explanatory diagram showing another configuration example of the position estimation system according to the embodiment of the present invention. DETAILED DESCRIPTION

[0017] Hereinafter, the embodiment of the present invention will be described with reference to each drawing. Here, the same reference numerals are used to represent the same components, and repeated descriptions are omitted.

[0018] Figure 1It is an explanatory diagram showing the structure of a position estimation system 10 involved in an embodiment of the present invention. The position estimation system 10 includes a transmitting device 20, a plurality of receivers 31 to 38, and a computer system 40. It is assumed that the transmitting device 20 is movable and its location is unknown. On the other hand, it is assumed that the plurality of receivers 31 to 38 are fixed at specific locations and their locations are known. The transmitting device 20 broadcasts a beacon signal carrying identification information inherent to the transmitting device 20 in all directions. The plurality of receivers 31 to 38 respectively receive the beacon signal from the transmitting device 20 and output information related to its reception strength, namely RSSI (Received Signal Strength Indication), to the computer system 40. The computer system 40 infers the current location of the transmitting device 20 based on the RSSI output from the receivers 31 to 38. As the communication standard between the transmission device 20 and the receivers 31 to 38 , a short-range wireless communication standard (for example, Wifi (Wireless Fidelity) (registered trademark), UWB (Ultra Wide Band), Bluetooth (registered trademark), Bluetooth Low Energy, etc.) can be used.

[0019] The computer system 40 includes a processor 41, a storage resource 42, a communication interface 43, and a display device 44. The storage resource 42 is a storage area of ​​a computer-readable recording medium (for example, a hard disk drive, a solid-state drive, a memory card, an optical disk drive, a semiconductor memory, etc.). A computer program 50 for controlling the operation of the computer system 40 is stored in the storage resource 42. The computer program 50 includes an inference tool 51, which is a software module that inputs each RSSI output from the receivers 31 to 38 through the communication interface 43 and infers the position of the transmitter 20 based on each RSSI. The processor 41 functions as an inference unit for inferring the position of the transmitter 20 by interpreting and executing the inference tool 51. In this way, the function of the inference unit for inferring the position of the transmitter 20 is realized by the cooperation of the processor 41 and the inference tool 51, but the same function can also be realized using dedicated hardware resources (for example, an application-specific integrated circuit (ASIC)) or firmware.

[0020] Here, refer to Figure 2 , the details of the sending device 20 are described. Figure 2 In the example shown, the transmission device 20 is attached to the human body 90. Figure 2In the figure, it is assumed that the XY plane is parallel to the horizontal plane, the Z direction is parallel to the vertical direction, and the human body 90 stands upright parallel to the vertical direction. The transmitting device 20 has multiple transmitters 21 and 22 that broadcast the same beacon signal carrying the identification information inherent in the transmitting device 20 in all directions. The multiple transmitters 21 and 22 each have an antenna (for example, a monopole antenna, a plate-shaped inverted F antenna, etc.) that broadcasts the beacon signal in all directions. Figure 2 In the example shown, the transmitters 21 and 22 are attached to the shoulders 91 and 92 with the head 93 interposed therebetween. Reference numerals 81 and 82 respectively indicate the directivity of the radio waves of the transmitters 21 and 22. Figure 2 As shown, part of the radio waves is blocked or attenuated by the head 93. Therefore, if only one of the transmitters 21, 22 is installed on the human body 90, deviations will occur in the directivities 81, 82 of the radio waves. If there are deviations in the directivities 81, 82 of the radio waves from the transmitters 21, 22, even if the position of the human body 90 is the same, the reception intensity of the beacon signal received by the receivers 31 to 38 will vary greatly according to the orientation of the transmitters 21, 22, thereby reducing the accuracy of the position estimation of the transmitting device 20. Therefore, multiple transmitters 21, 22 are arranged symmetrically with respect to a predetermined reference position (for example, the head 93). As a result, deviations in the directivities 81, 82 of the transmitted radio waves can be compensated for each other. For example, in Figure 2 In the example shown, the transmitter 22 can compensate for the lack of transmission power from the transmitter 21 in the +X direction. Similarly, the transmitter 21 can compensate for the lack of transmission power from the transmitter 22 in the -X direction. According to such a configuration, since the multiple transmitters 21 and 22 can uniformly transmit radio waves in all directions parallel to the XY plane as a whole, their directivity becomes substantially non-directional. As a result, the change of the RSSI of the receivers 31 to 38 accompanying the change of the direction of the transmitters 21 and 22 can be suppressed, and the position estimation accuracy of the transmitting device 20 can be improved.

[0021] Furthermore, the arrangement of the transmitters 21 and 22 symmetrically with respect to the reference position is not limited to Figure 2 For example, the transmitters 21 and 22 may be arranged on the upper arms of the human body 90, on the chest and back of the human body 90, or on the front and back of the human body 90. In addition, the reference position when the transmitters 21 and 22 are mounted on the human body 90 is not limited to the head 93, but may be any part of the human body 90. In addition, the reference position when the transmitters 21 and 22 are mounted on a moving body (for example, a trolley, etc.) may be any part of the moving body.

[0022] Here, return to Figure 1Description. The human body 90 is, for example, an operator who moves in a factory and operates the operation of factory equipment 61 to 68. The factory equipment 61 to 68 is, for example, a programmable logic controller that executes software recorded in a programming language after symbolizing a relay circuit called a ladder diagram. Figure numerals 71 to 74 indicate areas that include some of the positions 101 to 108 through which the operator, i.e., the human body 90, is expected to pass. Multiple receivers 31 to 38 are grouped into groups corresponding to each area. For example, receivers 31 and 32 are configured in area 71 and are grouped into groups corresponding to area 71. Area 71 includes positions 101 and 102, receiver 31 is configured near factory equipment 61 close to position 101, and receiver 32 is configured near factory equipment 62 close to position 102. Receivers 33 and 34 are configured in area 72 and are grouped into groups corresponding to area 72. Area 72 includes positions 103 and 104, and receiver 33 is arranged near factory equipment 63 close to position 103, and receiver 34 is arranged near factory equipment 64 close to position 104. Receivers 35 and 36 are arranged in area 73 and grouped into a group corresponding to area 73. Area 73 includes positions 105 and 106, and receiver 35 is arranged near factory equipment 65 close to position 105, and receiver 36 is arranged near factory equipment 66 close to position 106. Receivers 37 and 38 are arranged in area 74 and grouped into a group corresponding to area 74. Area 74 includes positions 107 and 108, and receiver 37 is arranged near factory equipment 67 close to position 107, and receiver 38 is arranged near factory equipment 68 close to position 108.

[0023] The inference tool 51 infers the area where the transmitter 20 is located based on the RSSI averaged for each group. For example, the inference tool 51 determines which average value is the highest among the average values ​​of the RSSI output by the receivers 31 and 32, the average values ​​of the RSSI output by the receivers 33 and 34, the average values ​​of the RSSI output by the receivers 35 and 36, and the average values ​​of the RSSI output by the receivers 37 and 38. Then, the inference tool 51 infers that the transmitter 20 is located in the area corresponding to the group of receivers that output the highest RSSI average value. Next, the inference tool 51 infers the vicinity of a position in the area where the transmitter 20 is located by comparing the RSSI output by the plurality of receivers in the group corresponding to the area inferred to be where the transmitter 20 is located. For example, when the average value of the RSSI output by the receivers 31 and 32 is the highest, the inference tool 51 infers that the transmitter 20 is located in the area 71. Then, when the RSSI output by the receiver 31 is higher than the RSSI output by the receiver 32 , the estimation tool 51 estimates that the transmission device 20 is located near the position 101 .

[0024] The display device 44 displays the position of the operator, that is, the human body 90, in association with the operating conditions of the plant equipment 61 to 68. A plurality of operators may perform work in the areas 71 to 74. Each operator can be identified based on identification information superimposed on the beacon signal transmitted from the transmission device 20 attached to each operator. Figure 3 An example of a screen displayed on the display device 44 is shown. Figure 3 In the column "Device Name", the names "A" to "H" of the plant equipment 61 to 68 are shown. The column "Operation Status" shows whether the plant equipment is running or stopped. The column "MTBF" shows the mean time between failures of the plant equipment. The column "Operator" shows the identification code of the operator who is near the plant equipment. For example, according to Figure 3 In the screen, it can be seen that the operator identified by the identification symbol "X" is located near the position 101 of the factory equipment 61 whose equipment name is "A". This can obtain the work history showing which operator worked on which factory equipment and when, thereby helping to improve work efficiency.

[0025] In addition, when the reception intensity of the radio waves received by each receiver 31 to 38 is insufficient to infer the position of the operator due to the influence of radio wave shielding, the inference tool 51 may infer the position of the operator based on the operating conditions of the plant equipment 61 to 68. For example, when a radio wave shielding is placed near the plant equipment 61 and the reception intensity of the radio waves received by the receiver 31 is insufficient to infer the position of the operator due to the influence of the radio wave shielding, if the plant equipment 61 is operating, the inference tool 51 may infer that the operator is located near the position 101 close to the plant equipment 61.

[0026] According to the position estimation system 10 involved in this embodiment, the plurality of transmitters 21 and 22 are configured to compensate for the deviation of the directivity 81 and 82 of the radio waves, so that the change of the RSSI of the receivers 31 to 38 accompanying the change of the orientation of the transmitters 21 and 22 can be suppressed, and the position estimation accuracy of the transmitting device 20 can be improved. In addition, in order to estimate the position of the transmitting device 20, it is sufficient to receive the radio waves from any one of the plurality of transmitters 21 and 22, so there is an advantage that it is not easily affected by the influence caused by the radio wave shielding objects. In addition, in order to estimate the position of the transmitting device 20, complex calculations such as statistical processing are not required, so the position of the transmitting device 20 can be estimated in real time and quickly. In addition, the plurality of receivers 31 to 38 are grouped into groups corresponding to each area, and are not affected by the receivers corresponding to different areas, so the influence caused by multipath fading can be reduced.

[0027] Next, refer to Figures 4 to 6, the measurement results related to the position estimation of the sending device 20 based on the position estimation system 10 are explained.

[0028] Figure 4 The layout shown omits area 74 and the arrangement of devices 61 to 67 is similar to Figure 1 This is different from Figure 1 The layout shown is different, but in other points is the same Figure 1 For example, in Figure 4 Although the computer system 40 is not shown in the figure, the receivers 31 to 36 are connected to the computer system 40. Figure 4 In FIG. 1 , reference numeral 100 indicates a movement path of a human body 90 equipped with the transmitting device 20 .

[0029] Figure 5 1 to 6 are assigned to the receivers 31 to 36. Figure 5 The vertical axis of the graph shows the number of the receiver closest to the position of the transmitting device 20 estimated based on the RSSI. Figure 5 The horizontal axis of the graph represents time. The graph with reference numeral 501 shows the ideal measurement result of each receiver. Figure 4 In the example shown, the transmitter 20 passes through the vicinity of the receivers 31, 33, 35, 36, 34, and 32 in the order along the moving path 100. In the graph 501, the transmitter 20 passes through the vicinity of the receiver 31 during the period from time T0 to time T1. The transmitter 20 passes through the vicinity of the receiver 33 during the period from time T1 to time T2. The transmitter 20 passes through the vicinity of the receiver 35 during the period from time T2 to time T3. The transmitter 20 passes through the vicinity of the receiver 36 during the period from time T3 to time T4. The transmitter 20 passes through the vicinity of the receiver 34 during the period from time T4 to time T5. The transmitter 20 passes through the vicinity of the receiver 32 during the period from time T5 to time T6. On the other hand, the graph of reference numeral 502 shows the actual measurement results of each receiver.

[0030] Figure 6 71 to 73 are assigned numbers from "1" to "3". Figure 6 The vertical axis of the graph shows the number of the area closest to the position of the transmitting device 20 estimated based on the RSSI. Figure 6 The horizontal axis of the graph of represents time. The graph of reference numeral 601 shows an ideal measurement result. Figure 6In the example shown, the transmitter 20 passes through the areas 71, 72, 73, 72, and 71 in the order of the moving path 100. In the graph 601, the transmitter 20 passes through the area 71 during the period from time T0 to time T1. The transmitter 20 passes through the area 72 during the period from time T1 to time T2. The transmitter 20 passes through the area 73 during the period from time T2 to time T4. The transmitter 20 passes through the area 72 during the period from time T4 to time T5. The transmitter 20 passes through the area 71 during the period from time T5 to time T6. On the other hand, the graph of reference numeral 602 shows the actual measurement results of each area.

[0031] If you compare Figure 5 as well as Figure 6 As a result, the difference between the actual measurement result 602 of each area and the ideal measurement result 601 of each area is smaller than the difference between the actual measurement result 502 of each receiver and the ideal measurement result 501 of each receiver, so it can be seen that the grouping of receivers 31 to 36 is useful for improving the position estimation accuracy of the transmitter 20. By using the position estimation of the operator based on the operating status of the plant equipment 61 to 67 in addition to the grouping of the receivers 31 to 36, the position estimation accuracy can be further improved.

[0032] In addition, by configuring the receiver so that the transmitting device 20 passes between at least two receivers in the same area (for example, between receivers 31 and 32 in area 71) and comparing the measurement signals (RSSI) of the two receivers, it is possible to infer on which side of the same area the transmitting device 20 is located.

[0033] In the above description, an example is shown in which the transmission device 20 moves and the positions of the receivers 31 to 38 are fixed. However, the present invention is also applicable to an example in which the receiving device moves and the position of the transmitter is fixed. Figure 7Such an example is shown. Reference numeral 120 is assumed to represent a mobile receiving device whose location is unknown. On the other hand, reference numerals 131 to 138 are assumed to represent transmitters whose locations are fixed and whose locations are known. A beacon signal carrying inherent identification information is transmitted from each transmitter 131 to 138, for example, in all directions. When the receiving device 120 receives a beacon signal from each transmitter 131 to 138, it outputs information related to the receiving strength, that is, RSSI, together with identification information included in the received beacon signal and information related to the receiving time of the beacon signal to the computer system 40. The computer system 40 estimates the current location of the receiving device 120 based on various information output from the receiving device 120 (for example, information indicating the RSSI of the beacon signal received by the receiving device 120, identification information included in the beacon signal received by the receiving device 120, and information related to the receiving time of the beacon signal received by the receiving device 120). The location estimation method of the receiving device 120 is the same as the location estimation method of the transmitting device 20.

[0034] The receiving device 120 includes a plurality of receivers 121 and 122 for receiving beacon signals from the transmitters 131 to 138. The receiving device 120 can be attached to, for example, a human body 90, which is an operator. In this case, the plurality of receivers 121 and 122 are arranged symmetrically with respect to a predetermined reference position (for example, the head 93). For example, the receivers 121 and 122 may be arranged on both upper arms of the human body 90, on the chest and back of the human body 90, or on the front and back of the human body 90. In addition, the reference position when the receivers 121 and 122 are attached to the human body 90 is not limited to the head 93, but may be any part of the human body 90. In addition, the reference position when the receivers 121 and 122 are mounted on a moving body (for example, a trolley, etc.) may be any part of the moving body. As a result, deviations in the directivity of received radio waves can be compensated for each other, thereby achieving substantially non-directional receiving sensitivity.

[0035] In the above description, an example of installing the sending device 20 on an operator moving in a factory is shown, but the sending device 20 can also be installed on a component transport trolley moving in the factory. Thus, it is possible to help improve the work efficiency according to the waiting time of the operator or the component transport trolley, the operating status of the factory equipment, etc. In addition, the sending device 20 can also be installed on a medical practitioner, a patient, or a medical machine moving in a hospital. Thus, it is possible to grasp the location of the medical practitioner, the patient, or the medical machine moving in the hospital, so it is possible to help confirm the location of the medical practitioner, shorten the search time of the medical machine or the patient, and record the number of times the patient is treated. In this case, the display device 44 can also display the location of the medical practitioner, the patient, or the medical machine. In addition, the sending device 20 can also be installed on a worker moving in an office. Thus, it is possible to help manage the worker's get off work and rest, confirm the worker's location, and record the number of times the subordinates and the superiors contact. In this case, the display device 44 can also display the location of the worker. In addition to the above-mentioned examples, the transmitting device 20 may be installed in any mobile device that needs to confirm its location.

[0036] In addition, the number of transmitters constituting the transmitting device 20 is not limited to 2, and 3 or more transmitters may be configured to mutually compensate for the deviation of the directivity of the transmitted radio waves. Similarly, the number of receivers constituting the receiving device 120 is not limited to 2, and 3 or more receivers may be configured to mutually compensate for the deviation of the directivity of the received radio waves.

[0037] In addition, the above-described embodiments are intended to facilitate the understanding of the present invention, and are not intended to limit the interpretation of the present invention. The present invention can be changed / improved without departing from its purport, and its equivalent can also be included in the present invention. That is, even if those skilled in the art appropriately design changes the embodiments, as long as they possess the features of the present invention, they are also included in the scope of the present invention. In addition, as long as it is technically possible, each component possessed by the embodiments can be combined, and as long as the embodiments after combining them include the features of the present invention, they are also included in the scope of the present invention.

[0038] Explanation of the reference numerals: 10...position inference system; 20...transmitting device; 21, 22...transmitter; 31, 32, 33, 34, 35, 36, 37, 38...receiver; 40...computer system; 41...processor; 42...storage resource; 43...communication interface; 44...display device; 50...computer program; 51...inference tool; 61, 62, 63, 64, 65, 66, 67, 68...factory equipment; 71, 72, 73, 74...area; 81, 82...directivity of radio waves; 90...human body; 91, 92...shoulder; 93...head; 101, 102, 103, 104, 105, 106, 107, 108...position.

Claims

1. A position estimation system comprising: A transmitting device having a plurality of transmitters for transmitting radio waves, wherein the plurality of transmitters are symmetrically arranged about a predetermined reference position to compensate for directivity of the radio waves and non-uniformity of transmission, wherein the predetermined reference position is an arbitrary position in a human body or a moving body where the transmitting device is arranged, which blocks or attenuates a part of the radio waves; a plurality of receivers for receiving radio waves transmitted from the plurality of transmitters; as well as an inference unit, which infers the position of the transmitting device based on the reception strength of the radio waves received by each receiver, The plurality of transmitters respectively broadcast the same beacon signal carrying the identification information inherent to the transmission device in all directions. Among them, the above-mentioned sending device is installed on an operator moving in the factory, and the above-mentioned factory is divided into multiple continuous areas along the direction of the moving path of the above-mentioned operator. Each of the above-mentioned areas includes multiple of the above-mentioned receivers arranged on both sides of the above-mentioned moving path. The above-mentioned receivers in each of the above-mentioned areas are regarded as a group. During detection, the above-mentioned inference unit compares the average RSSI size relationship of the above-mentioned receivers in each group to determine which group the above-mentioned operator is in, and then determines a more specific location by comparing the RSSI size relationship of the above-mentioned receivers on both sides of the above-mentioned moving path in the group.

2. The position estimation system according to claim 1, wherein: The plurality of receivers are grouped into groups corresponding to each area. The estimation unit estimates the area where the transmission device is located based on the reception strength of the radio waves calculated and compared for each group.

3. The position estimation system according to claim 1 or 2, wherein: The position estimation system further includes a display device, wherein the display device displays the position of the operator in association with the operating status of the factory equipment. Get the job history of the above operator.

4. The position estimation system according to claim 1 or 2, wherein: When the reception intensity of the radio waves received by each receiver is insufficient to estimate the position of the operator, the estimating unit estimates the position of the operator based on the operating status of factory equipment.

5. The position estimation system according to claim 2, wherein: At least two of the plurality of receivers are arranged in one area. The sending device passes between the at least two receivers.

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