Position estimation apparatus

Abstract

To provide a position estimation apparatus that enables stable position estimation.SOLUTION: A position estimation apparatus includes a computing section that acquires indoor plane positions of a plurality of reference stations each having a radio communication function, acquires a signal strength during communication between the reference stations and a mobile station, filters the signal strength with a variable filter having a threshold value determined on the basis of installation conditions of the reference stations, and estimates an indoor plane position of the mobile station by trilateration on the basis of the signal strength after filtering with the variable filter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a position estimation device that estimates the indoor horizontal position of a mobile station. [Background technology]

[0002] Conventionally, a known method for estimating the indoor planar position of a mobile station without using GNSS signals is the triangular positioning method, which uses the radio wave intensity of wireless communications such as beacon signals (see, for example, Patent Document 1). The triangular positioning method calculates the distances between the mobile station and at least three reference stations, and regards the intersection of multiple circles corresponding to the distances from each reference station as the indoor planar position of the mobile station. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-255673 Summary of the Invention [Problem to be solved by the invention]

[0004] With triangular positioning, there is a large variation in radio wave strength indoors where there are many people or objects, so the intersection points of the circles calculated from the received radio waves do not intersect at a single point, making it difficult to determine a single position on a plane. Furthermore, with triangular positioning, the more reference stations there are, the more difficult it becomes to determine a single position. Therefore, with triangular positioning, it is difficult to increase the number of reference stations and expand the positioning area.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a position estimation device that enables stable position estimation. [Means for solving the problem]

[0006] The position estimation device of the present invention is characterized by comprising a calculation unit that acquires the indoor planar positions of a plurality of reference stations having wireless communication capabilities, acquires radio wave strength during communication between the reference stations and a mobile station, filters the radio wave strength with a variable filter having a threshold determined based on the installation conditions of the reference stations, and estimates the indoor planar position of the mobile station using a three-point positioning method based on the radio wave strength after filtering with the variable filter.

[0007] In this way, the position estimation device of the present invention can narrow down the number of reference stations used for estimation by using a variable filter with a threshold determined based on the installation conditions of the reference stations, making it possible to perform stable position estimation even when there is a large variation in radio wave strength or when the number of reference stations is increased to expand the positioning area.

[0008] Furthermore, it is preferable that the calculation unit acquires radio wave strengths multiple times during communication between the multiple base stations and the mobile station, smooths the acquired radio wave strengths, and applies the variable filter to the smoothed radio wave strengths. This enables stable position estimation without acquiring suddenly strong or weak radio wave strengths. Note that smoothing includes processes such as simple averaging, moving averaging, Kalman filtering, and outlier removal.

[0009] The installation conditions include the distance between the plurality of reference stations or the radio wave attenuation characteristics.

[0010] The three-point positioning method includes the centroid method, which is a process of determining the two-dimensional geometric center of gravity of the base station as the indoor planar position of the mobile station, weighted by the estimated distance between the base station and the mobile station, which is calculated based on the RSSI value indicating the radio wave strength. [Effects of the Invention]

[0011] According to the present invention, stable position estimation is possible. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a schematic plan view showing the configuration of a position estimation system including a position estimation device 1. FIG. [Figure 2] FIG. 1 is a block diagram of a position estimation device 1. [Figure 3] FIG. 2 is a block diagram of the reference station 10. [Figure 4] FIG. 2 is a block diagram of a mobile station 20. [Figure 5] 3 is a flowchart showing the operation of the position estimation system including the position estimation device 1. [Figure 6] 10 is a flowchart showing the operation of a position estimation system including a position estimation device 1 according to a first modification. [Figure 7] FIG. 10 is a perspective view showing the configuration of a position estimation system according to a second embodiment. [Figure 8] FIG. 10 is a block diagram showing the configuration of a reference station 10 according to a first modification of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] (First embodiment) 1 is a schematic plan view showing the configuration of a position estimation system according to the first embodiment. The position estimation system includes a position estimation device 1, multiple reference stations 10, and a mobile station 20. The position estimation device 1, multiple reference stations 10, and mobile station 20 are installed, for example, at a building construction site.

[0014] The position estimation device 1 is, for example, a management server of a position estimation system, and is used by, for example, a manager of construction work.

[0015] The multiple reference stations 10 are installed, for example, on the ceiling of a building under construction. While Fig. 1 shows an example in which 16 reference stations 10 are installed at the construction site, the number of reference stations 10 is not limited to this example, and it is sufficient that there are at least three or more reference stations 10.

[0016] Each of the plurality of reference stations 10 has a wireless communication function and transmits and receives beacon signals conforming to, for example, the Bluetooth (registered trademark) Low Energy standard (hereinafter referred to as BLE) as wireless communication.

[0017] The mobile station 20 is carried by, for example, a worker performing construction work. Alternatively, the mobile station 20 may be attached to a moving object such as a construction cart or a drone for remotely monitoring indoor spaces. The mobile station 20 is, for example, a Bluetooth (registered trademark) tag. The mobile station transmits and receives beacon signals conforming to BLE. The worker carries the mobile station 20 and moves around the construction site.

[0018] Fig. 2 is a block diagram of the position estimation device 1. Fig. 3 is a block diagram of the base station 10. Fig. 4 is a block diagram of the mobile station 20.

[0019] The position estimation device 1 includes a display 31 such as an LCD, an operation unit 32 that accepts operations from an administrator, a CPU 33, a RAM , a flash memory 35, and a wireless communication unit .

[0020] The CPU 33 reads out an operating program stored in the flash memory 35 into the RAM 34 and controls the position estimation device 1. The wireless communication unit 36 ​​is a wireless LAN communication unit, and is connected to an external communication network and a plurality of reference stations 10.

[0021] The reference station 10 includes a CPU 41, a RAM 42, a flash memory 43, a BLE communication unit 44, and a wireless communication unit 45.

[0022] The CPU 41 functions as a calculation unit of the present invention, reads an operation program stored in a flash memory 43 into a RAM 42, and controls the reference station 10. The BLE communication unit 44 transmits and receives a beacon signal conforming to BLE under the control of the CPU 41. The wireless communication unit 45 is a wireless LAN communication unit, and is connected to the position estimation device 1 and other reference stations 10.

[0023] The mobile station 20 includes a CPU 51, a RAM 52, a flash memory 53, and a BLE communication unit 54.

[0024] The CPU 51 reads out an operation program stored in the flash memory 53 into the RAM 52 and controls the mobile station 20. The BLE communication unit 54 transmits and receives a beacon signal conforming to BLE under the control of the CPU 51.

[0025] 5 is a flowchart showing the operation of a position estimation system including the position estimation device 1. The position estimation device 1 acquires in advance the indoor plane positions of each of the multiple reference stations 10 (S10).

[0026] Next, each of the multiple reference stations 10 transmits a beacon signal conforming to BLE (S11).

[0027] The mobile station 20 receives beacon signals from multiple reference stations 10 and replies with the radio wave intensity of the received beacon signals and its own identification information (S12). The identification information is unique information determined for each device, such as the serial number or MAC address of the mobile station 20.

[0028] Furthermore, each of the plurality of standard stations 10 returns the radio wave intensity of the beacon signal received from the other standard stations 10 and the identification information of the own device (S13).

[0029] Each of the plurality of reference stations 10 receives radio wave strength and identification information from the mobile station 20 and the other reference stations 10. Each of the plurality of reference stations 10 transmits the received radio wave strength and identification information to the position estimation device 1 (S14).

[0030] The position estimation device 1 acquires radio wave intensity and identification information from each of the multiple reference stations 10 (S15). The position estimation device 1 calculates radio wave attenuation characteristics between the multiple reference stations 10 based on the acquired radio wave intensity (S16). The radio wave attenuation characteristics between the multiple reference stations 10 are an example of installation conditions for the multiple reference stations 10. The installation conditions may also be the distance between the multiple reference stations 10. The distance between the multiple reference stations 10 is calculated based on the indoor planar positions of each of the multiple reference stations 10 acquired in S10. The position estimation device 1 determines the threshold of the variable filter based on the distance between the multiple reference stations 10 or the radio wave attenuation characteristics (S17).

[0031] The position estimation device 1 acquires the radio wave intensity during communication between each of the multiple base stations 10 and the mobile station 20, and filters the radio wave intensity using a variable filter having the determined threshold (S18). The variable filter cuts off radio wave intensity below the threshold and outputs only radio wave intensity equal to or greater than the threshold.

[0032] The position estimation device 1 then estimates the indoor planar position of the mobile station 20 using a triangular positioning method based on the radio wave intensity after filtering with the variable filter (S19). Radio wave intensity can be converted into distance information because it is inversely proportional to the square of the distance. The position estimation device 1 calculates the distances between the mobile station 20 and at least three reference stations 10, and considers the intersection of circles corresponding to the distances from each reference station to be the indoor planar position of the mobile station 20.

[0033] However, with simple three-point positioning, indoors where there are many people or objects, especially at construction sites, there is a large variation in radio wave strength, so the intersection points of the circles calculated from the received radio waves do not intersect at a single point, making it difficult to determine the position on a plane at a single point.However, the position estimation device 1 of this embodiment filters the radio wave strength, making it possible to narrow down the number of reference stations used for estimation and enabling stable position estimation.

[0034] Furthermore, in the triangular positioning method, the number of circles increases as the number of reference stations increases, making it more difficult to determine a position on a plane at a single point. However, the position estimation device 1 of this embodiment, for example, decreases the threshold value of the variable filter as the distance between multiple reference stations 10 increases, and increases the threshold value of the variable filter as the distance between multiple reference stations 10 decreases. This allows the position estimation device 1 to narrow down the number of reference stations used for estimation to an appropriate number (e.g., three), enabling stable position estimation even when the number of reference stations is increased to expand the positioning area.

[0035] The three-point positioning method may also be a centroid method, which is a method for determining the two-dimensional geometric center of gravity of the mobile station 20 on an indoor plane, where the center of gravity is a two-dimensional geometric center of gravity of the base stations 10, weighted by estimated distances between the mobile station 20 and multiple base stations 10 calculated based on RSSI values ​​indicating radio wave strength.

[0036] The centroid method is a method for determining the geometric center of gravity, making it easy to determine coordinates at a single point. However, even with the centroid method, as the number of reference stations increases, the measured position tends to move toward the center, which can result in a discrepancy between the estimated position and the actual position. However, the position estimation device 1 of this embodiment uses a variable filter with a threshold determined based on the distance between multiple reference stations 10. For example, the longer the distance between the multiple reference stations 10, the smaller the threshold of the variable filter is, and the shorter the distance between the multiple reference stations 10, the larger the threshold of the variable filter is. This allows the position estimation device 1 to narrow down the number of reference stations used for estimation to an appropriate number (e.g., three), enabling stable position estimation even when the number of reference stations is increased in the centroid method to expand the positioning area.

[0037] Table 1 shows the relationship between the distances and radio wave attenuation characteristics of the multiple reference stations 10 and the accuracy of position estimation obtained by the centroid method.

[0038] [Table 1]

[0039] In Table 1, "No filter" indicates, as a reference example, the position estimation accuracy when no filtering is performed on the acquired radio wave strength. "Fixed filter" indicates, as a reference example, the position estimation accuracy when filtering is performed on the acquired radio wave strength but the threshold is fixed. "Variable filter" indicates the position estimation accuracy when filtering is performed on the acquired radio wave strength using the variable filter of this embodiment. The position estimation accuracy shown in Table 1 refers to the average error (m) when measurements are taken multiple times. The numbers in parentheses for "Fixed filter" and "Variable filter" refer to the threshold (dBm).

[0040] As shown in Table 1, the position estimation accuracy of the "fixed filter" is higher than that of the "no filter" system. However, the position estimation accuracy of the "fixed filter" decreases when the installation interval is large and the radio wave environment is poor. In other words, the position estimation accuracy of the "fixed filter" varies greatly depending on the installation environment. In contrast, the position estimation accuracy of the "variable filter" of the position estimation device 1 of this embodiment is stable regardless of the installation interval and the radio wave environment.

[0041] As described above, the position estimation device 1 of this embodiment can perform stable position estimation even when the number of reference stations is increased to expand the positioning area or when the communication environment is poor. In particular, the position estimation device 1 of this embodiment can perform stable position estimation even in a site where equipment is frequently relocated and the radio wave environment changes daily, such as a construction site.

[0042] The position estimation device 1 displays information related to the indoor planar position of the mobile station 20 estimated as described above, for example, on the display 31. By knowing the indoor planar position of the mobile station 20, the manager of the construction work can grasp the positions of workers, work carts, drones, etc.

[0043] Next, Fig. 6 is a flowchart showing the operation of a position estimation system including the position estimation device 1 according to Modification 1 of the first embodiment. Components common to Fig. 5 are given the same reference numerals, and description thereof will be omitted.

[0044] 6, the position estimation device 1 smoothes the radio wave intensity acquired in S14 (S21). The position estimation device 1 applies a variable filter having the threshold determined in S17 to the radio wave intensity after smoothing in S21 (S18). Smoothing includes processing such as simple averaging, moving averaging, Kalman filtering, or outlier removal.

[0045] By performing smoothing processing, the position estimation device 1 in Modification 1 can perform more stable position estimation without acquiring suddenly strong or weak radio wave intensity. For example, when the installation interval between the reference stations 10 is 20 m and the threshold of the variable filter is -69 dBm, the average error without smoothing was 3.66 m, while the average error with smoothing was 3.12 m. In other words, the average error is improved by 14.7% by smoothing processing.

[0046] Therefore, it is preferable that the position estimation device 1 acquires the radio wave intensity multiple times during communication between multiple base stations and the mobile station, smooths the acquired radio wave intensity, and applies a variable filter to the smoothed radio wave intensity.

[0047] (Second embodiment) 7 is a perspective view showing the configuration of a position estimation system according to a second embodiment. Components common to those in the first embodiment are given the same reference numerals, and descriptions thereof will be omitted.

[0048] The multiple reference stations 10 of the second embodiment are installed on multiple different floors (first floor 100, second floor 101, third floor 102) indoors in the vertical direction. For example, in the example of Fig. 7, four multiple reference stations 10 are installed on the floor of the first floor 100, four multiple reference stations 10 are installed on the floor of the second floor 101, and four multiple reference stations 10 are installed on the floor of the third floor 102.

[0049] The position estimation device 1 estimates the indoor floor position of the mobile station 20 based on the radio wave intensity. For example, the position estimation device 1 estimates the indoor vertical position of the mobile station 20 by a triangular positioning method using the radio wave intensities of at least three reference stations 10 installed at different positions in the vertical direction. The position estimation device 1 may estimate the indoor vertical position using the variable filter shown in the first embodiment, but it is not essential to use the variable filter in the second embodiment.

[0050] If the estimated height direction position of the mobile station 20 is closest to the floor surface of the first floor 100, the position estimation device 1 determines that the indoor floor position of the mobile station 20 is the first floor 100. If the estimated height direction position of the mobile station 20 is closest to the floor surface of the second floor 101, the position estimation device 1 determines that the indoor floor position of the mobile station 20 is the second floor 101. If the estimated height direction position of the mobile station 20 is closest to the floor surface of the third floor 102, the position estimation device 1 determines that the indoor floor position of the mobile station 20 is the third floor 102.

[0051] This allows the position estimation device 1 to detect not only the indoor horizontal position of the mobile station 20 but also which floor out of a plurality of floors that differ in the vertical direction the mobile station 20 is located on.

[0052] The indoor planar position of the mobile station 20 may be estimated using the radio wave intensities of multiple reference stations 10 installed at the estimated floor position, or may be estimated using the radio wave intensities of multiple reference stations 10 on other floors. However, the position estimation device 1 can estimate the indoor planar position of the mobile station 20 with higher accuracy by using the radio wave intensities of multiple reference stations 10 installed at the estimated floor position.

[0053] The position estimation device 1 may smooth the radio wave intensity for each layer and estimate the indoor location of the mobile station 20 based on the smoothed radio wave intensity. For example, in the example of FIG. 7 , the average value of the radio wave intensity of four reference stations 10 on the first layer 100 is calculated, the average value of the radio wave intensity of four reference stations 10 on the second layer 101 is calculated, and the average value of the radio wave intensity of four reference stations 10 on the third layer 102 is calculated. The position estimation device 1 estimates the indoor location of a layer using the average values ​​of the radio wave intensity of the first layer 100, the second layer 101, and the third layer 102. For example, if the average value of the radio wave intensity of the first layer 100 is the highest, the position estimation device 1 determines that the indoor location of the mobile station 20 is the first layer 100. If the average value of the radio wave intensity of the second layer 101 is the highest, the position estimation device 1 determines that the indoor location of the mobile station 20 is the second layer 101. If the average value of the radio wave intensity on the third hierarchical layer 102 is the highest, the position estimation device 1 determines that the indoor location of the mobile station 20 is on the third hierarchical layer 102.

[0054] Furthermore, the position estimation device 1 may correct the radio wave intensity by an antenna gain determined for each of the plurality of reference stations 10, and estimate the indoor floor position of the mobile station 20 based on the corrected radio wave intensity. More specifically, the position estimation device 1 subtracts the antenna gain determined for each of the plurality of reference stations 10 from the radio wave intensity. This allows the position estimation device 1 to estimate the indoor floor position of the mobile station 20 with high accuracy even if the antenna gains of the plurality of reference stations 10 are different from each other.

[0055] The antenna gain may also be determined for each floor. For example, the antenna gain for each floor may be the average value of the antenna gains of the multiple reference stations 10 installed on each floor. This allows the position estimation device 1 to estimate the indoor floor position of the mobile station 20 with high accuracy even if the antenna gains of the multiple reference stations 10 on each floor are different.

[0056] Alternatively, the position estimation device 1 may correct the radio wave intensity by an attenuation constant determined for each of the multiple floors, and estimate the indoor location of the mobile station 20 based on the corrected radio wave intensity. More specifically, the position estimation device 1 adds the attenuation constant determined for each floor to the radio wave intensity. The attenuation constant is calculated based on the radio wave attenuation characteristics between the multiple reference stations 10, as shown in the process of S16 in the first embodiment, for example.

[0057] This allows the position estimation device 1 to estimate the indoor floor position of the mobile station 20 with high accuracy even if the radio wave environment differs for each floor.

[0058] Next, Fig. 8 is a block diagram showing the configuration of the reference station 10 according to Modification 1 of the second embodiment. The same components as those in Fig. 3 are given the same reference numerals, and the description thereof will be omitted.

[0059] The reference station 10 according to the first modification of the second embodiment has an air pressure sensor 46. The air pressure sensor 46 detects atmospheric pressure. The air pressure sensor 46 may be a resistive sensor or a capacitive sensor. The reference station 10 transmits the value of the air pressure sensor 46 to the position estimation device 1.

[0060] The position estimation device 1 receives the value of the atmospheric pressure sensor 46. Based on the received value of the atmospheric pressure sensor 46, the position estimation device 1 estimates the position of the mobile station 20 in the height direction at the estimated floor position.

[0061] The position estimation device 1 stores in advance in flash memory 35 a table showing the relationship between the values ​​of the atmospheric pressure sensor and altitude. The position estimation device 1 refers to the table to obtain altitude information corresponding to the received value of the atmospheric pressure sensor 46. In this way, the position estimation device 1 obtains altitude information for each of the multiple reference stations 10. More specifically, the position estimation device 1 obtains altitude information for each layer using the altitude information for each of the multiple reference stations 10 for each layer.

[0062] Then, the position estimation device 1 uses the average value of the radio wave strength at each level to obtain information on the altitude of the mobile station 20 by a triangular positioning method. The position estimation device 1 displays the obtained information on the altitude of the mobile station 20 on the display 31.

[0063] For example, if a worker is carrying the mobile station 20 and altitude information is estimated to be high at the floor location estimated by the mobile station 20, this indicates that the corresponding worker is working at height. The construction work manager can know that there is a worker working at height. The construction work manager can also know the height position of the drone on each floor.

[0064] The position estimation device 1 may obtain the reference atmospheric pressure at the location where the reference station 10 is installed and correct the value of the atmospheric pressure sensor 46. Atmospheric pressure changes depending on the date and time. Therefore, the position estimation device 1 obtains the reference atmospheric pressure at the current date and time at the location where the reference station 10 is installed from an external source. This allows the position estimation device 1 to estimate the indoor floor location of the mobile station 20 with even higher accuracy.

[0065] The mobile station 20 may have a barometric pressure sensor. In this case, the position estimation device 1 acquires the barometric pressure sensor value from the mobile station 20 and estimates the height position of the mobile station 20 at the estimated floor position. The position estimation device 1 may also acquire the reference barometric pressure at the location where the mobile station 20 is installed and correct the barometric pressure sensor value. The position estimation device 1 may estimate the height position of the mobile station 20 at the estimated floor position based on the corrected barometric pressure sensor value.

[0066] The description of the present embodiment should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined not by the above-described embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0067] 1...Position estimation device 10...Reference station 20...Mobile station 31...Indicator 32...Operation unit 33...CPU 34...RAM 35...Flash memory 36...Radio communication section 41...CPU 42...RAM 43...Flash memory 44…BLE communication department 45...Radio communication section 46...Barometric pressure sensor 51...CPU 52...RAM 53...Flash memory 54…BLE communication department

Claims

1. Obtaining indoor planar positions of multiple reference stations having wireless communication capabilities; acquiring radio wave intensities during communication between the plurality of reference stations and the mobile station; filtering the radio wave intensity with a variable filter having a threshold determined based on installation conditions of the plurality of reference stations; estimating an indoor planar position of the mobile station by a three-point positioning method based on the radio wave intensity after filtering by the variable filter; A position estimation device equipped with a calculation unit.

2. 2. The position estimation device according to claim 1, the calculation unit acquires radio wave intensities multiple times during communication between the multiple reference stations and the mobile station, smooths the acquired radio wave intensities, and applies the variable filter to the smoothed radio wave intensities. Location estimation device.

3. 3. The position estimation device according to claim 2, The smoothing includes a simple average, a moving average, a Kalman filter, or an outlier removal process. Location estimation device.

4. 4. The position estimation device according to claim 1, The installation conditions include distances or radio wave attenuation characteristics between the plurality of reference stations. Location estimation device.

5. 5. The position estimation device according to claim 4, the calculation unit acquires information about distances between the plurality of reference stations; determining the threshold value based on the acquired distance; Location estimation device.

6. 5. The position estimation device according to claim 4, the calculation unit acquires radio wave intensities during communication between the plurality of reference stations, and calculates the radio wave attenuation characteristics based on the radio wave intensities; determining the threshold value based on the determined radio wave attenuation characteristics; Location estimation device.

7. 4. The position estimation device according to claim 1, The three-point positioning method includes a Centroid method, Location estimation device.

8. 8. The position estimation device according to claim 7, The Centroid method calculates a two-dimensional geometric centroid consisting of the plurality of base stations as an indoor planar position of the mobile station, weighted by an estimated distance between the plurality of base stations and the mobile station, the estimated distance being calculated based on an RSSI value indicating the radio wave strength. Location estimation device.

9. 4. The position estimation device according to claim 1, the calculation unit cuts off radio wave intensity less than the threshold and estimates the indoor planar position of the mobile station by the three-point positioning method using radio wave intensity equal to or greater than the threshold. Location estimation device.

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