Position estimation device, position estimation system, control circuit, storage medium, and position estimation method

Abstract

A mobile station (1), which is a position estimation device that estimates the position of the mobile station (1) on the basis of a plurality of distance measurement results measured using wireless communication between each of a plurality of fixed stations and the mobile station (1), is characterized by being provided with: a position measurement calculation unit (16) that calculates the position of the mobile station (1) from a coordinate axis for which the distance between each of the plurality of fixed stations is large; calculating the position of the mobile station of each coordinate axis by using the position of the fixed station and the distance measurement result in sequence; and a position estimation result generation unit (18) that generates a position estimation result indicating the three-dimensional position of the mobile station on the basis of the calculation result of the position for each coordinate axis.

Description

Technical Field

[0001] The present disclosure relates to a position estimation device, a position estimation system, a control circuit, a storage medium, and a position estimation method for estimating a position based on a distance measurement result using the transmission and reception timing of communication. Background Art

[0002] The following technology has been used: using the transmission and reception timing of communication, the distance between a fixed station fixed on the ground and a mobile station is measured based on the propagation time between the fixed station and the mobile station, and the position of the mobile station is estimated using the known position information of the fixed station and the distance measurement result. As a general algorithm used in position estimation, in order to determine the three-dimensional position (x, y, z) of the mobile station, there is a least square method that solves a three-dimensional nonlinear simultaneous equation related to the positions of more than three fixed stations and the distance measurement results between the fixed station and the mobile station, and the position of the mobile station is estimated by successive approximation calculation.

[0003] In such fields, it is desirable to improve the accuracy of position estimation. For example, Patent Document 1 discloses the following technology: In a method for estimating the position of a mobile station based on a ranging result using a UWB (Ultra-Wide Band) signal, it is identified whether the radio wave propagation between a fixed station and a mobile station is in a "line-of-sight" state or a "non-line-of-sight" state based on statistical data of multipath components included in a received signal, and when estimating the position, weighting is performed in a manner that reduces the influence of the ranging result with the fixed station in a "non-line-of-sight" state, thereby improving the accuracy of position estimation.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 4567093 Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, in the above-mentioned prior art, it is necessary to collect in advance statistical data of multipath components included in the received signal, such as attenuation of the received waveform, average excess delay spread of the multipath components, and root mean square delay spread, for each area where position estimation is performed. When the statistical data cannot be collected in advance or the accuracy of the statistical data is low, there is a problem that position estimation cannot be performed with high accuracy.

[0009] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a position estimation device capable of performing position estimation with high accuracy even when statistical data of multipath components of a received signal cannot be obtained with high accuracy in advance.

[0010] Means for solving problems

[0011] In order to solve the above-mentioned problems and achieve the purpose, the position estimation device disclosed in the present invention estimates the position of a mobile station based on a plurality of distance measurement results measured using wireless communication between each of a plurality of fixed stations and the mobile station, and is characterized in that the position estimation device comprises: a positioning calculation unit which calculates the position of the mobile station for each coordinate axis, starting from a coordinate axis having a large distance between each coordinate axis of the plurality of fixed stations, using the position of the fixed station and the distance measurement result in sequence; and a position estimation result generation unit which generates a position estimation result representing the three-dimensional position of the mobile station based on the calculation result of the position of each coordinate axis.

[0012] Effects of the Invention

[0013] The position estimation device of the present disclosure has an effect of being able to perform position estimation with high accuracy even when statistical data of multipath components of a received signal cannot be obtained with high accuracy in advance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram showing an example of the configuration of a position estimation system according to Embodiment 1.

[0015] Figure 2 This is a diagram showing an example of waveform distortion generated in a multipath environment.

[0016] Figure 3 The figure shows the relationship between the distance measurement result and the position estimation between the mobile station and the fixed station.

[0017] Figure 4 This is a diagram showing a functional configuration of a mobile station serving as a position estimation device according to the first embodiment.

[0018] Figure 5 This is a flowchart for explaining the operation of the mobile station according to the first embodiment.

[0019] Figure 6 This is a diagram showing a functional configuration of a mobile station serving as a position estimation device according to the second embodiment.

[0020] Figure 7 This is a diagram showing an example of the configuration of a position estimation system according to Embodiment 2.

[0021] Figure 8 This is a diagram showing a state in which an error exists in the distance measurement result between the position estimation system and the fixed station.

[0022] Fig. 9 This is an explanatory diagram of a first example of the selection method of the fixed station selection unit.

[0023] Fig.10This is an explanatory diagram of the second example of the selection method of the fixed station selection unit.

[0024] Fig.11 This is an explanatory diagram of the third example of the selection method of the fixed station selection unit.

[0025] Fig.12 This is an explanatory diagram of the effect of the second embodiment.

[0026] Fig.13 This is a flowchart for explaining the operation of the mobile station according to the second embodiment.

[0027] Fig.14 This is a diagram showing the configuration of a position estimation system according to a third embodiment.

[0028] Fig.15 This is a diagram showing a functional configuration of a mobile station according to Embodiment 3.

[0029] Fig.16 This is a diagram showing a first example of the positional relationship between a fixed station and a mobile station according to the fourth embodiment.

[0030] Fig.17 This is a diagram showing a second example of the positional relationship between the fixed station and the mobile station according to the fourth embodiment.

[0031] Fig.18 This is a diagram showing a functional configuration of a mobile station according to a fourth embodiment.

[0032] Fig.19 This is a flowchart for explaining the operation of the mobile station according to the fourth embodiment.

[0033] Fig. 20 This is a diagram showing a functional configuration of a mobile station according to the fifth embodiment.

[0034] Fig.21 This is a flowchart for explaining the operation of the mobile station according to the fifth embodiment.

[0035] Fig. 22 This is a diagram showing a configuration of a control circuit included in a fixed station or a mobile station according to Embodiments 1 to 5.

[0036] Fig.23 This is a diagram showing an example of dedicated hardware included in the fixed station or the mobile station according to the first to fifth embodiments. DETAILED DESCRIPTION

[0037] Hereinafter, a position estimation device, a position estimation system, a control circuit, a storage medium, and a position estimation method according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0038] Implementation Method 1

[0039] Figure 1 1 is a diagram showing an example of the structure of a position estimation system 100 according to Embodiment 1. The position estimation system 100 includes a mobile station 1 as an example of a position estimation device, and a plurality of fixed stations 3-0 to 3-3 fixed to the ground. In the following description, when it is not necessary to distinguish the fixed stations 3-0 to 3-3, they are sometimes referred to as simply fixed stations 3. Here, four fixed stations 3 are shown, but the number of fixed stations 3 is not limited to four, and any number of fixed stations 3 may be used.

[0040] The position estimation system 100 measures the distance between the mobile station 1 and each of the plurality of fixed stations 3 based on the transmission and reception timing of wireless signals transmitted and received between the mobile station 1 and each of the plurality of fixed stations 3 by wireless communication, and estimates the position of the mobile station 1 based on the distance measurement result.

[0041] Here, the wireless signal used by the position estimation system 100 is, for example, a UWB signal. The UWB signal is an ultrashort pulse signal in the time domain. Therefore, when the UWB signal is used, the transmission and reception timing of the communication can be grasped with high resolution, and the position of the mobile station 1 can be estimated with high accuracy.

[0042] The positions of the mobile station 1 and the fixed station 3 are expressed as three-dimensional positions, and the coordinate axes defining the three-dimensional space are set as the x-axis, y-axis, and z-axis. The position of the fixed station 3 is known, and the position of the fixed station 3-0 is set to (x0, y0, z0), the position of the fixed station 3-1 is set to (x1, y1, z1), the position of the fixed station 3-2 is set to (x2, y2, z2), and the position of the fixed station 3-3 is set to (x3, y3, z3).

[0043] Each fixed station 3 transmits a notification signal including its own position information and identification information, and the mobile station 1 can identify the information of the receivable fixed station 3 based on the notification signal. The mobile station 1 calculates the propagation time required for wireless communication based on the transmission and reception timing of the UWB signal between the mobile station 1 and the identifiable fixed station 3, and obtains the distance measurement result between the mobile station 1 and each fixed station 3.

[0044] When UWB signals are transmitted and received between the mobile station 1 and each fixed station 3, if there is an object such as a wall that reflects radio waves, in addition to the direct wave W1, the reflected wave W2 is received. In this case, the waveform of the UWB signal is distorted.

[0045] Figure 2 FIG. 1 is a diagram showing an example of waveform distortion generated in a multipath environment. Figure 2 As shown, in a multipath environment, regarding the received waveform 40 detected on the receiving side, the waveform 41 of the direct wave W1 and the waveform 42 of the reflected wave W2 are synthesized, resulting in distortion. Figure 2The distorted received waveform 40 shown in the figure has a signal waveform that is shifted backward in time compared to the waveform 41 of the direct wave W1, so the distance measurement result based on the received waveform 40 tends to be larger. In this way, when the accuracy of the distance measurement result decreases, the accuracy of the position estimation of the mobile station 1 based on the distance measurement result also decreases.

[0046] In the first embodiment, a position estimation method is proposed that can suppress a decrease in position estimation accuracy even when the accuracy of the distance measurement result decreases in this way.

[0047] Figure 3 1 is a diagram showing the relationship between the ranging result and the position estimation between the mobile station 1 and the fixed station 3. Here, the ranging result with the fixed station 3-0 is assumed to be R0, the ranging result with the fixed station 3-1 is assumed to be R1, the ranging result with the fixed station 3-2 is assumed to be R2, and the ranging result with the fixed station 3-3 is assumed to be R3. At this time, ideally, it is preferred that a circle with a radius of R0 centered on the position of the fixed station 3-0, a circle with a radius of R1 centered on the position of the fixed station 3-1, a circle with a radius of R2 centered on the position of the fixed station 3-2, and a circle with a radius of R3 centered on the position of the fixed station 3-3 intersect at one point, and the intersection is estimated as the position of the mobile station 1.

[0048] Here, as a position estimation algorithm for positioning calculation, it is assumed that calculation is performed according to the least square method. In this case, when paying attention to the z-axis and y-axis directions, the estimated range Ax of the X-axis is smaller than the estimated range Ay of the Y-axis. In this case, it means that the position estimation result for the X-axis can reduce the error compared with the position estimation result for the Y-axis. Here, the larger the distance between the fixed stations 3, the smaller the position estimation range. Therefore, the larger the distance between the fixed stations 3 of each coordinate axis, the smaller the estimated range of the position in the direction of the coordinate axis, and the smaller the position estimation error. Therefore, in embodiment 1, starting from the coordinate axis with the largest distance between the fixed stations 3 among the multiple coordinate axes, the position of the mobile station 1 is calculated according to each coordinate axis in sequence by the one-dimensional least square method, thereby suppressing the estimation error of the position of each coordinate axis. The function of the position estimation device used to perform such processing is described below.

[0049] Figure 41 is a diagram showing a functional configuration of a mobile station 1 as a position estimation device according to Embodiment 1. The mobile station 1 includes a fixed station position information storage unit 11 for storing position information of fixed stations 3, a distance measurement result acquisition unit 12 for acquiring distance measurement results between each fixed station 3 and the mobile station 1, a fixed station distance calculation unit 13 for calculating the distance between the fixed stations 3, a coordinate axis selection unit 14 for selecting a calculation target coordinate axis based on the distance between the fixed stations 3, an initial value setting unit 15 for setting an initial value when calculating the position of each coordinate axis, a positioning calculation unit 16 for calculating the position of each coordinate axis with respect to the selected coordinate axis, an all-axis completion judgment unit 17 for judging whether the calculation of the position of each coordinate axis has been completed with respect to all assumed coordinate axes, and a position estimation result generation unit 18 for generating a position estimation result indicating the three-dimensional position of the mobile station 1 based on the calculation result.

[0050] The fixed station location information storage unit 11 stores the location information of the fixed station 3 included in the notification signal transmitted by each fixed station 3. The location information is stored, for example, in correspondence with the identification information included in the notification signal. Figure 1 In the example shown, when the mobile station 1 receives the notification signals of the four fixed stations 3, namely the fixed stations 3-0 to 3-3, the position information (x0, y0, z0) of the fixed station 3-0, the position information (x1, y1, z1) of the fixed station 3-1, the position information (x2, y2, z2) of the fixed station 3-2 and the position information (x3, y3, z3) of the fixed station 3-3 are stored in the fixed station position information storage unit 11.

[0051] The ranging result acquisition unit 12 performs transmission and reception of UWB signals with each fixed station 3, calculates the propagation time required for wireless communication based on the transmission and reception timing of each UWB signal, and obtains the ranging result with each fixed station 3. In addition, here, it is assumed that the mobile station 1 has both the ranging function and the position estimation function, and therefore, it is assumed that the ranging result acquisition unit 12 performs the ranging process itself, but in the case where the ranging process is performed by a device other than the mobile station 1, the ranging result acquisition unit 12 may obtain the ranging result, that is, the result of the ranging process performed by the other device, through communication.

[0052] The fixed station distance calculation unit 13 calculates the distance between the fixed stations 3 based on the position information of the plurality of fixed stations 3 stored in the fixed station position information storage unit 11. At this time, the fixed station distance calculation unit 13 calculates the distance for each coordinate axis. Figure 1 When calculating the distance between the four fixed stations 3-0 to 3-3 shown in FIG. Figure 1In the example shown, the four fixed stations 3-0 to 3-3 are configured to be located at the vertices of a rectangle in the xy plane. Therefore, with respect to the x-axis, the relationship of the following mathematical formula (1) holds, with respect to the y-axis, the relationship of the following mathematical formula (2) holds, and with respect to the z-axis, the relationship of the following mathematical formula (3) holds.

[0053]

Mathematical formula 1

[0054] (|x0-x2|=|x1-x3|=d1)>(|x0-x1|x2-x3|=0)…(1)

[0055]

Mathematical formula 2

[0056] (|y0-y1|=|y2-y3|=d2)>(|y0-y2|y1-y3|=0)…(2)

[0057]

Mathematical formula 3

[0058] |z0-z1|=|z1-z2|=|z2-z3|=|z3-z0|=d3…(3)

[0059] In addition, regarding the sizes of d1, d2, and d3 in equations (1) to (3), the relationship of "d1>d2>d3" is assumed to hold. In this case, the distances between the fixed stations 3 for each coordinate axis are the x-axis, y-axis, and z-axis in descending order.

[0060] In addition, the fixed station distance calculation unit 13 can also calculate the distance between the fixed stations 3 for each coordinate axis using the following mathematical formulas (4) to (6). Specifically, assuming that the number of fixed stations 3, i.e., the number of fixed stations, is N, the distance between the fixed stations 3 in the x-axis is expressed by the following mathematical formula (4), the distance between the fixed stations 3 in the y-axis is expressed by the following mathematical formula (5), and the distance between the fixed stations 3 in the z-axis is expressed by the following mathematical formula (6).

[0061]

Mathematical formula 4

[0062]

[0063]

Mathematical formula 5

[0064]

[0065]

Mathematical formula 6

[0066]

[0067] According to the above mathematical formulas (4) to (6), for example, Figure 1When the position information of the four fixed stations 3-0 to 3-3 shown is stored in the fixed station position information storage unit 11, the fixed station distance calculation unit 13 calculates the total of the distances between the fixed stations 3 in six combinations of the fixed station 3-0 and the fixed station 3-1, the fixed station 3-0 and the fixed station 3-2, the fixed station 3-0 and the fixed station 3-3, the fixed station 3-1 and the fixed station 3-2, the fixed station 3-1 and the fixed station 3-3, and the fixed station 3-2 and the fixed station 3-3 as the distance between the fixed stations 3 on each coordinate axis.

[0068] Here, about Figure 1 When the four fixed stations 3-0 to 3-3 shown in the figure satisfy the conditions of equations (1) to (3), the value of equation (4) becomes 4d1, the value of equation (5) becomes 4d2, and the value of equation (6) becomes 4d3. The distances of each coordinate axis between the fixed stations 3 are, in descending order, the x-axis, the y-axis, and the z-axis.

[0069] Here, for simplicity, as an example, the four fixed stations 3-0 to 3-3 are arranged so as to be located at the vertices of a rectangle in the xy plane. However, the conditions shown in equations (1) to (3) do not necessarily need to be satisfied.

[0070] The coordinate axis selection unit 14 selects coordinate axes in order from the coordinate axis with the largest distance based on the distance between the fixed stations 3 calculated by the fixed station distance calculation unit 13. In the above example, the coordinate axis selection unit 14 selects coordinate axes in the order of the x-axis, the y-axis, and the z-axis. The coordinate axis selection unit 14 outputs information indicating the selected coordinate axis to the initial value setting unit 15.

[0071] The initial value setting unit 15 calculates the initial value of each axis when the positioning calculation unit 16 calculates the position of each coordinate axis based on the selected coordinate axis. The initial value setting unit 15 may, for example, use the average value of the positions of the plurality of fixed stations 3 as the initial value. In this case, the initial value x of the x-axis is in The initial value y of the y-axis is expressed as follows: in It can be expressed by the following mathematical formula (8): the initial value z of the z-axis is in It is expressed by the following mathematical formula (9).

[0072]

Mathematical formula 7

[0073]

[0074]

Mathematical formula 8

[0075]

[0076]

Mathematical formula 9

[0077]

[0078] In addition, when the position of the mobile station 1 is calculated in advance, the initial value setting unit 15 can use the position information as the initial value. For example, when the position of the mobile station 1 is continuously calculated, and the three-dimensional position of the mobile station 1 is calculated within a time range that becomes a position reference of the mobile station 1, the initial value setting unit 15 can also use the position information as the initial value. In addition, when the coordinate axes are selected in the order of the x-axis, the y-axis, and the z-axis, when calculating the position of the x-axis, the initial value of the position of the mobile station 1 can be set to (x in ,y in ,z in ), when calculating the position of the y-axis, since the position of the x-axis has already been calculated, the calculated x-axis position estimation result x is used as a fixed value. est The initial value of the position of the mobile station 1 is set to (x est ,y in ,z in ), when calculating the z-axis position, since the x-axis and y-axis positions have already been calculated, the calculated x-axis position x is used as a fixed value. est and the calculated y-axis position y as a fixed value est The initial value of the position of the mobile station 1 is set to (x est ,y est ,z in ).

[0079] The positioning calculation unit 16 calculates the position of each coordinate axis of the mobile station 1 based on the initial value of each axis set by the initial value setting unit 15, the position information of each fixed station 3 stored in the fixed station position information storage unit 11, and the ranging results between the mobile station 1 and each fixed station 3 obtained by the ranging result acquisition unit 12, with respect to the coordinate axis selected by the coordinate axis selection unit 14.

[0080] Specifically, the positioning calculation unit 16 calculates the position of the mobile station 1 according to the one-dimensional least square method for each coordinate axis. For example, in the above example, it is assumed that the coordinate axis selection unit 14 selects the coordinate axes in the order of the x-axis, the y-axis, and the z-axis, and the positioning calculation unit 16 performs positioning calculations in the order of the x-axis, the y-axis, and the z-axis. At this time, when estimating the position of the mobile station 1 in the direction of the initially selected x-axis, the positioning calculation unit 16 sets the position of the mobile station 1 to (x / z) based on the output of the initial value setting unit 15. in ,y in ,z in ), set as the x-axis variable x that is the estimation object of the positioning calculation est =x inThe distance r between the n-th fixed station 3-n and the mobile station 1 to be estimated is calculated by using the initial value. n It is calculated according to the following mathematical formula (10).

[0081]

Mathematical formula 10

[0082]

[0083] In addition, n is an integer from 0 to N-1. In the mathematical formula (10), r n Become about x est Therefore, the position calculation unit 16 calculates the variable x for position estimation on the x-axis one by one according to the least square method based on successive approximation using the mathematical formula (10) as a standard. est .

[0084] In addition, the distance measurement result Rn and the distance r between the nth fixed station 3-n and the mobile station 1 n Since there are measurement errors in each station, the positioning calculation unit 16 calculates the sum of squares E of the distance errors of the N fixed stations. The sum of squares E of the distance errors of the N fixed stations is expressed by the following mathematical formula (11).

[0085]

Mathematical formula 11

[0086]

[0087] In the positioning calculation unit 16, the estimated position result x of the x-axis of the mobile station 1 is outputted by the least square method based on successive approximation for minimizing the sum of squares E of the distance errors of the number of fixed stations N represented by the mathematical formula (11). est .

[0088] When the y-axis is selected after the x-axis, the positioning calculation unit 16 sets the position of the mobile station 1 to (x est ,y in ,z in ), set as the variable y of the y-axis to be estimated in the positioning calculation est =y in In this case, the distance r between the n-th fixed station 3-n and the mobile station 1 to be estimated is n The calculation is performed according to the following mathematical formula (12). In addition, n is an integer from 0 to N-1. In the mathematical formula (12), r n Become about y est Therefore, in the positioning calculation unit 16, the variable y for position estimation about the y-axis is calculated successively according to the least square method based on successive approximation using the mathematical formula (12) as a standard. est .

[0089]

Mathematical formula 12

[0090]

[0091] In this case, the sum of squares E of the distance errors of the number of fixed stations N is also expressed by the above-mentioned mathematical formula (11). Therefore, the positioning calculation unit 16 calculates the sum of squares E of the distance errors according to the mathematical formula (11), and in order to minimize the sum of squares E of the distance errors, estimates the y-axis position of the mobile station 1 by the least square method based on successive approximation, and outputs the y-axis position y as the estimation result. est .

[0092] When the z-axis is selected after the x-axis and the y-axis, the positioning calculation unit 16 sets the position of the mobile station 1 to (x est ,y est ,z in ), set as the variable z of the z-axis to be estimated in the positioning calculation est =z in In this case, the distance r between the n-th fixed station 3-n and the mobile station 1 to be estimated is n The calculation is performed according to the following mathematical formula (13). In addition, n is an integer from 0 to N-1. In the mathematical formula (13), r n Become about z est Therefore, in the positioning calculation unit 16, the variable z for position estimation about the z-axis is calculated successively according to the least square method based on successive approximation using the mathematical formula (13) as a standard. est .

[0093]

Mathematical formula 13

[0094]

[0095] In this case, the sum of squares E of the distance errors of the number of fixed stations N is also expressed by the above-mentioned mathematical formula (11). Therefore, the positioning calculation unit 16 calculates the sum of squares E of the distance errors according to the mathematical formula (11), and in order to minimize the sum of squares E of the distance errors, estimates the z-axis position of the mobile station 1 by the least square method based on successive approximation, and outputs the z-axis position z as the estimation result. est .

[0096] The all-axis completion judgment unit 17 judges whether the position measurement calculation of each coordinate axis related to all the coordinate axes assumed to be the positioning object has been completed, and if the position measurement calculation of all the axes has not been completed, notifies the coordinate axis selection unit 14 to continue selecting the coordinate axis, and if the position measurement calculation of all the axes has been completed, notifies the position estimation result generation unit 18 that the position measurement calculation of all the axes has been completed. For example, when the calculation result of the position of each coordinate axis is received from the positioning calculation unit 16 for three axes, namely, the x-axis, the y-axis, and the z-axis, the all-axis completion judgment unit 17 can notify the position estimation result generation unit 18 that the position measurement calculation of all the axes has been completed, and in other cases, notifies the coordinate axis selection unit 14 to continue selecting the coordinate axis. Alternatively, when the position of one axis (for example, the z-axis) among the three axes is known in advance, the position estimation of the two axes, namely, the x-axis and the y-axis, may be performed, and the judgment criterion of the all-axis completion judgment unit 17 may be set to that the position measurement calculation for the two axes has been completed. When the positioning calculations for all axes are completed, the all-axis completion determination unit 17 outputs the calculation results received from the positioning calculation unit 16 to the position estimation result generation unit 18 .

[0097] When receiving the calculation results of the positions of each coordinate axis from the all-axis completion determination unit 17, the position estimation result generation unit 18 outputs (x est ,y est ,z est ) as a position estimation result representing the three-dimensional position of mobile station 1.

[0098] Figure 5 This is a flowchart for explaining the operation of the mobile station 1 according to the first embodiment. The fixed station distance calculation unit 13 calculates the distance between the fixed stations 3 for each coordinate axis (step S101). The coordinate axis selection unit 14 selects the target coordinate axis for which the positioning calculation is to be performed (step S102). The initial value setting unit 15 sets the initial value of the position of the mobile station 1 (step S103). The positioning calculation unit 16 performs the positioning calculation for calculating the position of the mobile station 1 for each coordinate axis using the set initial value for the selected coordinate axis (step S104).

[0099] The all-axis completion judgment unit 17 judges whether the positioning calculation of all axes has been completed (step S105). The coordinate axes whose positions are unknown are set as the coordinate axes to be positioned, and the judgment of step S105 is performed based on whether the estimated value of the position of each coordinate axis is calculated through the positioning calculation for all the coordinate axes to be positioned.

[0100] If the positioning calculations for all axes are not completed (step S105: No), the mobile station 1 returns to the process of step S102. If the positioning calculations for all axes are completed (step S105: Yes), the position estimation result generator 18 generates a position estimation result indicating the three-dimensional position of the mobile station 1 (step S106).

[0101] As described above, the mobile station 1 as the position estimation device of the first embodiment estimates the position of the mobile station 1 based on a plurality of distance measurement results measured between each of the plurality of fixed stations 3 and the mobile station 1 using wireless communication, wherein the mobile station 1 comprises: a positioning calculation unit 16 that sequentially calculates the position of the mobile station 1 for each coordinate axis using the position of the fixed station 3 and the distance measurement results, starting from the coordinate axis with the largest distance between the plurality of fixed stations 3; and a position estimation result generation unit 18 that generates a position estimation result indicating the three-dimensional position of the mobile station 1 based on the calculation result of the position of each coordinate axis. The larger the distance between each coordinate axis between the fixed stations 3, the smaller the estimation range of the position is, and thus the estimation error of the position can be suppressed. Therefore, by sequentially performing the positioning calculation starting from the coordinate axis with the largest distance between the fixed stations 3, the error of the position estimation for each coordinate axis can be suppressed, and the position estimation accuracy can be improved. Therefore, even when the statistical data of the multipath component of the received signal cannot be obtained with high accuracy in advance, the position estimation can be performed with high accuracy.

[0102] In addition, in a case where the number of fixed stations 3 that can be used for ranging within the area of ​​the position estimation system 100 is insufficient, or in a case where ranging results with low ranging accuracy are affected by reflected waves due to walls, etc., the number of coordinate axes to be estimated simultaneously can be reduced, the degrees of freedom of variables required for position estimation can be suppressed, and the position estimation accuracy can be maintained.

[0103] Implementation Method 2

[0104] In the above-mentioned embodiment 1, it is assumed that all multiple fixed stations 3 that can be recognized by the mobile station 1 are used to perform positioning calculations. However, in embodiment 2, in order to exclude the ranging results between the fixed station 3 and the mobile station 1 that are assumed to have a large ranging error during the positioning calculation, the fixed station 3 to be used is selected for the positioning calculation.

[0105] Figure 61 is a diagram showing the functional configuration of a mobile station 1A as a position estimation device according to Embodiment 2. The mobile station 1A includes a fixed station position information storage unit 11, a distance measurement result acquisition unit 12, an inter-fixed station distance calculation unit 13, a coordinate axis selection unit 14, a fixed station selection unit 19 for selecting a fixed station 3 for which a distance measurement result is used when estimating a position from a plurality of fixed stations 3, an initial value setting unit 15, a positioning calculation unit 16A, an all-axis completion determination unit 17, and a position estimation result generation unit 18. The mobile station 1A has a fixed station selection unit 19 added to the configuration of the mobile station 1, and has a positioning calculation unit 16A instead of the positioning calculation unit 16. The other configurations are the same as those of the mobile station 1, and therefore detailed descriptions are omitted here. The following mainly describes the parts different from Embodiment 1.

[0106] Here, the influence of the ranging error between the fixed station 3 and the mobile station 1 on the positioning will be described. Figure 7 FIG. 1 is a diagram showing an example of the configuration of a position estimation system 100A according to Embodiment 2. Figure 7 , a state without ranging error is shown.

[0107] The position estimation system 100A includes a mobile station 1A and a plurality of fixed stations 3-0 to 3-3. The positions of the mobile station 1A and the fixed station 3 are expressed as three-dimensional positions, and the coordinate axes defining the three-dimensional space are set as the x-axis, the y-axis, and the z-axis. The position of the fixed station 3 is known, and the position of the fixed station 3-0 is set as (x0, y0, z0), the position of the fixed station 3-1 is set as (x1, y1, z1), the position of the fixed station 3-2 is set as (x2, y2, z2), and the position of the fixed station 3-3 is set as (x3, y3, z3).

[0108] Assume that the ranging result with the fixed station 3-0 is R0, the ranging result with the fixed station 3-1 is R1, the ranging result with the fixed station 3-2 is R2, and the ranging result with the fixed station 3-3 is R3. Here, the state in which there is no error in the ranging result is shown, so the circle with a radius of R0 centered on the position of the fixed station 3-0, the circle with a radius of R1 centered on the position of the fixed station 3-1, the circle with a radius of R2 centered on the position of the fixed station 3-2, and the circle with a radius of R3 centered on the position of the fixed station 3-3 intersect at one point, and in this case, the intersection point is estimated to be the position of the mobile station 1A.

[0109] Figure 8This is a diagram showing a state in which an error exists in the distance measurement result between the fixed station 3-1 in the position estimation system 100A. When waveform distortion due to reflected waves occurs between the fixed station 3-1 and the mobile station 1A, the distance measurement result R1' between the fixed station 3-1 including the error tends to be longer than the actual distance R1. In this case, when the position of the mobile station 1A is estimated using the distance measurement result R1', a position 51 deviated from the original position 50 is estimated.

[0110] As described above, when estimating the position, if a ranging result with a large error is included, the error of the estimated position also becomes larger. In addition, the larger the distance between the mobile station 1A and the fixed station 3, that is, the larger the ranging result, the larger the error of the ranging result. Therefore, the fixed station selection unit 19 selects the fixed station 3 to be used from the plurality of fixed stations 3 according to the size of the ranging result. In addition, the positioning calculation unit 16A uses the ranging result of the fixed station 3 selected by the fixed station selection unit 19, and excludes the ranging result of the fixed station 3 not selected by the fixed station selection unit 19 from the ranging result used for calculating the position.

[0111] Next, use Figures 9-11 The following describes an example of detailed operation of the fixed station selection unit 19. Here, the number of fixed stations N=4, and the fixed station 3 to be used is selected from the fixed stations 3-0 to 3-3. The circle in the figure represents the selected fixed station 3, and the cross in the figure represents the unselected fixed station 3. Fig. 9 1 is an explanatory diagram of a first example of a selection method of the fixed station selection unit 19. In the first example, the fixed station selection unit 19 selects fixed stations 3-0, 3-2, and 3-3 other than the fixed station 3-1 having the maximum distance measurement result among the plurality of fixed stations 3. Here, it is determined that the fixed station having the maximum distance measurement result has a high probability of causing waveform distortion in the UWB signal and including a distance measurement error. As a result, in the positioning calculation unit 16A, the distance measurement result R1 is excluded, and the distance measurement results R0, R2, and R3 are used to calculate the position.

[0112] Fig.10 1 is an explanatory diagram of a second example of the selection method of the fixed station selection unit 19. In the second example, a predetermined number of fixed stations 3 required for positioning calculation are selected in order from the fixed station having the smallest ranging result. Fig.10 The bracketed values ​​[1] to [4] are obtained by assigning numbers in order from the fixed station with the smallest ranging result. Here, it is assumed that three fixed stations 3 are selected in the order of ranging results R2, R3, R0, and R1, starting from the fixed station with the smallest ranging result. In this case, the fixed station selection unit 19 selects the fixed stations 3-2, 3-3, and 3-0.

[0113] Fig.113 is an explanatory diagram of the third example of the selection method of the fixed station selection unit 19. In the third example, the fixed station selection unit 19 selects the fixed station 3 to be used using a threshold value. Various methods can be considered for setting the threshold value, but here, it is assumed that the threshold value is set according to the minimum value of the ranging result. For example, the fixed station selection unit 19 can generate the threshold value by multiplying the minimum value of the ranging result by a predetermined coefficient. Fig.11 In the example shown, the ranging result R2 is the smallest value among the ranging results R0 to R3. The fixed station selection unit 19 can multiply the ranging result R2 by a predetermined coefficient to set a threshold value, and select the fixed station 3 having a ranging result smaller than the set threshold value as the fixed station 3 to be used.

[0114] Fig.12 This is an illustration of the effect of the second embodiment. Fig.12 above the arrow, and Figure 8 Similarly, the distance measurement result R1' includes a distance measurement error. The distance measurement result R1' is longer by Δr1 than the accurate distance measurement result R1 that does not include a distance measurement error. In this case, the position 51 that is the estimated position of the mobile station 1A is offset from the original position 50.

[0115] In contrast, Figures 9-11 As shown in FIG. 1 , when the fixed station 3 to be used is selected based on the magnitude of the ranging result, the ranging result R1' of the fixed station 3-1 is not selected, and therefore the position of the mobile station 1A is the position 52 estimated based on the positions (x0, y0, z0), (x2, y2, z2), (x3, y3, z3) of the fixed stations 3-0, 3-2, and 3-3 and the ranging results R0, R2, and R3. In this way, the positioning calculation can be performed based on the ranging results R0, R2, and R3 that are not affected by the ranging error or have a small ranging error, and therefore the estimation error included in the position 52 as the estimated result can be suppressed.

[0116] Fig.13 1 is a flowchart for explaining the operation of the mobile station 1A according to the second embodiment. Here, after step S102 in which the target coordinate axis is selected, the fixed station selection unit 19 selects the fixed station 3 to be used (step S201). Then, the initial value setting unit 15 sets the initial value of the position of the mobile station 1A (step S103). Except that the process of step S201 is performed between the process of step S102 and the process of step S103, the process is the same as the first embodiment, and therefore, detailed description is omitted here.

[0117] As described above, the mobile station 1A according to the second embodiment further includes the fixed station selection unit 19 in addition to the configuration of the mobile station 1 according to the first embodiment, and the fixed station selection unit 19 selects a fixed station 3 to be used from a plurality of fixed stations 3 according to the magnitude of the ranging result. The positioning calculation unit 16A excludes the ranging results of the fixed stations 3 not selected from the ranging results used in the positioning calculation.

[0118] Specifically, the fixed station selection unit 19 selects, from among the plurality of fixed stations 3-0, 3-1, 3-2, 3-3, the fixed stations 3-0, 3-2, 3-3, excluding the fixed station 3-1 having the largest distance indicated by the ranging result, as the fixed station 3 to be used. Alternatively, the fixed station selection unit 19 selects, from among the plurality of fixed stations 3-0, 3-1, 3-2, 3-3, a predetermined number of fixed stations 3 in ascending order of the distance indicated by the ranging result. Alternatively, the fixed station selection unit 19 selects, from among the plurality of fixed stations 3-0, 3-1, 3-2, 3-3, the fixed stations 3 having the distance indicated by the ranging result being less than a threshold value, as the fixed station 3 to be used. In this case, the threshold value is determined based on the minimum value of the distance indicated by the ranging results of the plurality of fixed stations 3-0, 3-1, 3-2, 3-3. In this way, by excluding the ranging results of the fixed stations 3 having a high probability of containing errors, and estimating the position of the mobile station 1A, the position estimation accuracy can be further improved.

[0119] Implementation 3

[0120] In Embodiment 3, a positioning method is described when the position of a mobile station 1B to be estimated on a part of the coordinate axes is known in advance. For example, this situation may occur when there is a restriction on the path of movement of the mobile station 1B, such as when the mobile station 1B is carried on a train traveling on a line or a vehicle traveling on a road.

[0121] Fig.14 1 is a diagram showing the structure of a position estimation system 100B according to Embodiment 3. Here, it is assumed that a plurality of fixed stations 3 exist on one coordinate axis and a mobile station 1B moves on the line. Specifically, Fig.14In the example shown, it is assumed that two fixed stations 3-0 and 3-1 exist on the x-axis, and the position of the mobile station 1B on the y-axis and the position on the z-axis are known. Here, the position of the mobile station 1B on the y-axis is d, and the position on the z-axis is h, and the position of the mobile station 1B is represented by (x, d, h). In addition, the position of the fixed station 3-0 is (x0, y0, z0), and the position of the fixed station 3-1 is (x1, y1, z1). In addition, it is assumed that the ranging result with the fixed station 3-0 is R0, and the ranging result with the fixed station 3-1 is R1. Here, the position of the mobile station 1B on the y-axis and the position on the z-axis are known, so the mobile station 1B only needs to estimate the position on the x-axis, and the position estimation can be performed even if there are two fixed stations 3.

[0122] Fig.15 1 is a diagram showing a functional configuration of a mobile station 1B according to Embodiment 3. The mobile station 1B includes a fixed station position information storage unit 11, a distance measurement result acquisition unit 12, an inter-fixed station distance calculation unit 13, a coordinate axis selection unit 14, an initial value setting unit 15B, a positioning calculation unit 16, an all-axis completion determination unit 17B, and a position estimation result generation unit 18. The following mainly describes portions different from Embodiment 1.

[0123] In the fixed station distance calculation unit 13, the distance between the fixed stations 3 is calculated for each coordinate axis. At this time, N=2, and the fixed stations 3-0 and 3-1 are arranged on the x-axis, so y0=y1, and for simplicity, z0=z1 is set. When using mathematical formulas (4) to (6), the distance between the fixed stations 3 in the x-axis is expressed by the following mathematical formula (14), the distance between the fixed stations 3 in the y-axis is expressed by the following mathematical formula (15), and the distance between the fixed stations 3 in the z-axis is expressed by the following mathematical formula (16).

[0124]

Mathematical formula 14

[0125]

[0126]

Mathematical formula 15

[0127]

[0128]

Mathematical formula 16

[0129]

[0130] The coordinate axis selection unit 14 selects the x-axis according to the above-mentioned mathematical formulas (14) to (16). The initial value setting unit 15B calculates the average value of each fixed station 3 for the x-axis selected by the coordinate axis selection unit 14 as the initial value for the least square method of positioning calculation. Fig.14In the case of the configuration shown in FIG. 1 , the number of fixed stations N=2, and the positions of the mobile station 1B on the y-axis and z-axis are known. Therefore, the initial value setting unit 15B uses the initial value x of the position on the x-axis expressed by the following mathematical formula (17): in , the initial value y of the position on the y-axis expressed by the following mathematical formula (18) in , and the initial value z of the position on the z-axis represented by the following mathematical formula (19): in , set the initial value for the position calculation to (x in ,d,h). In addition, when the position of the mobile station 1B is calculated in advance in time, the position information can also be given as the initial value.

[0131]

Mathematical formula 17

[0132]

[0133]

Mathematical formula 18

[0134] y in =d…(18)

[0135]

Mathematical formula 19

[0136] z in =h…(19)

[0137] The positioning calculation unit 16 calculates the position of the mobile station 1B according to the least square method for each coordinate axis based on the position information of each fixed station 3 and the distance measurement result. Here, when estimating the position of the mobile station 1B in the x-axis direction, the position of the mobile station 1B is set to (x est ,d,h), the initial value of the variable of the x-axis to be calculated is set to x est =x in The distance r between the nth fixed station 3-n and the mobile station 1B is calculated. n The calculation is performed according to the following mathematical formula (20). n Become about x est Since it is a nonlinear function, the positioning calculation unit 16 successively calculates the variables for position estimation about the x-axis according to the least square method based on successive approximation using the following mathematical formula (21) as a standard.

[0138]

Mathematical formula 20

[0139]

[0140]

Mathematical formula 21

[0141]

[0142] In the mathematical formula (20), n is an integer from 0 to N-1. In addition, the mathematical formula (21) is a specific example of the case where N=2 in the mathematical formula (11).

[0143] The positioning calculation unit 16 outputs the position estimation result x of the x-axis. est In the third embodiment, the position of the mobile station 1B is known about the y-axis and the z-axis. Therefore, the all-axis completion judgment unit 17B judges that the position estimation of all coordinate axes is completed when the positioning calculation related to the x-axis is completed, and outputs the calculation result of the position of the mobile station 1B for each coordinate axis to the position estimation result generation unit 18. The position estimation result generation unit 18 outputs the position estimation result (x-axis) of the mobile station 1B. est ,d,h).

[0144] Here, the positions of the y-axis and the z-axis are assumed to be known. However, if only the position of the z-axis is known, the positions of the x-axis and the y-axis may be estimated. The coordinate axis whose position is known may be any of the x-axis, the y-axis, and the z-axis.

[0145] As described above, the mobile station 1B of the third embodiment can perform positioning calculations in sequence, starting from the coordinate axis with the largest distance between the fixed stations 3, according to each coordinate axis, using the known values, when the position of each coordinate axis in a part of the coordinate axes is known. As a result, the number of coordinate axes that need to be calculated is reduced, so that even with a smaller number of fixed stations N, the position estimation accuracy can be maintained compared to the case where all three axes need to be calculated. For example, such a situation considers a case where the mobile station 1B is mounted on a mobile body that moves along a predetermined path and the fixed stations 3 are set along the path. For example, the mobile body considers a vehicle traveling along a road, a railway vehicle traveling along a track, etc. In the case where the path is linear, if the coordinate axes are set along the path, the mobile station 1B can estimate the three-dimensional position of the mobile station 1B by estimating the position on one coordinate axis.

[0146] Implementation 4

[0147] The mobile station 1C of the fourth embodiment has a function of determining the position of each coordinate axis of the mobile station 1C from among the candidates of the plurality of position estimation results based on the estimation error for each candidate when the position of each coordinate axis of the mobile station 1C is limited to any one of the plurality of axis position candidates with respect to at least one of the plurality of coordinate axes. For example, such a situation may occur when the mobile station 1C is mounted on a railway vehicle traveling on a line and it is unknown which line among the plurality of lines the mobile station 1C is traveling on, or when the line on which the mobile station 1C is traveling is known in advance and the installation distance of the fixed station 3 with respect to the line is determined in advance, but it is unknown on which side of the line the fixed station 3 is installed depending on the location.

[0148] use Fig.16 , 17 The latter situation will be described. Fig.16 This is a diagram showing a first example of the positional relationship between the fixed station 3 and the mobile station 1C according to the fourth embodiment. Fig.17 This is a diagram showing a second example of the positional relationship between the fixed station 3 and the mobile station 1C of the fourth embodiment. For example, let the xy plane be the ground on which the track is set, and let the direction parallel to the track be the x-axis direction. For example, let it be known in advance that the mobile station 1C-1 is mounted on a vehicle traveling on a track on the right side of the positive direction of the x-axis, and the mobile station 1C-2 is mounted on a vehicle traveling on a track on the left side. At this time, if it is determined as a setting rule for the fixed station 3 to be set at a distance d1 from the nearest track, as a positional relationship to be considered, there is Fig.16 The position relationship shown and Fig.17 Specifically, for example, assuming that the positive direction of the x-axis is north and the direction from the fixed station 3 toward the line is the positive direction of the y-axis, consider that the fixed stations 3-0 and 3-1 are as follows: Fig.16 The situation shown in FIG. 1 is located on the west side of the mobile stations 1C-1 and 1C-2. Fig.17 The case shown is located on the east side of mobile stations 1C-1 and 1C-2. Here, the following function is described: when there are multiple candidates for the estimation results of the positions as described above, which candidate is determined based on the estimation error. In addition, when facing the positive direction of the x-axis on the xy plane, Fig.16 In the state shown, the mobile stations 1C-1 and 1C-2 are located on the left side of the fixed stations 3-0 and 3-1. Fig.16 The state shown is referred to as a case where the mobile station 1C is located on the left side of the fixed station 3. Fig.17 The state shown is referred to as a case where the mobile station 1C is located on the right side of the fixed station 3.

[0149] Fig.18 1 is a diagram showing a functional configuration of a mobile station 1C according to Embodiment 4. The mobile station 1C includes a fixed station position information storage unit 11, a distance measurement result acquisition unit 12, an inter-fixed station distance calculation unit 13, a coordinate axis selection unit 14, a fixed station selection unit 19, an initial value setting unit 15C, a positioning calculation unit 16C, an all-axis completion determination unit 17, a position estimation result generation unit 18, a position estimation completion determination unit 20, and a position estimation result selection unit 21. Hereinafter, the parts different from Embodiment 2 will be mainly described.

[0150] The position of each coordinate axis of the mobile station 1C is limited to any one of the plurality of axis position candidates with respect to at least one of the plurality of coordinate axes. Here, the position of each coordinate axis of the mobile station 1C is assumed to be a known value h with respect to the z-axis and any one of the known values ​​d1 and d2 with respect to the y-axis.

[0151] The initial value setting unit 15C sets a plurality of initial values ​​for the position of each coordinate axis using a plurality of axis position candidates as the restricted coordinate axis, i.e., the restricted axis (here, the y axis). Specifically, the initial value setting unit 15C sets two initial values, y=d1 and y=d2, as the initial value of the y axis. The positioning calculation unit 16C calculates the two positions of each coordinate axis and error information indicating the degree of estimated error for each position using the two initial values ​​set by the initial value setting unit 15C.

[0152] The position estimation result generating unit 18 generates two types of position estimation results using two types of positions for each coordinate axis, and outputs the two types of position estimation results and error information for each position to the position estimation completion determining unit 20 .

[0153] After calculating the assumed number of position estimation results and the error information for each position estimation result, the position estimation completion determination unit 20 determines that the position estimation is completed. In the above case, after calculating two types of position estimation results and two types of error information, the position estimation completion determination unit 20 determines that the position estimation is completed.

[0154] The position estimation result selection unit 21 selects a candidate for a position estimation result with the smallest measurement error in positioning from among a plurality of candidates for the position estimation results.

[0155] Here, a specific example is used for explanation. For example, when it is not known that the mobile station 1C exists Fig.16 When the position of mobile station 1C-1 shown is still at the position of mobile station 1C-2, mobile station 1C can generate two candidate position estimation results, y=d1 and y=d2, and take the one with the smaller measurement error among the candidate position estimation results as the position of mobile station 1C.

[0156] Or, knowing that the mobile station 1C exists Fig.16 or Fig.17 The position of the mobile station 1C-1 is shown, but the position relationship between the fixed station 3 and the mobile station 1C is unknown. Fig.16 The status shown is still Fig.17 In the case of the state shown, the mobile station 1C also generates two candidates of position estimation results, y=d1 and y=d2, and determines the positional relationship between the mobile station 1C and the fixed station 3 based on the magnitude relationship between the two estimation error values.

[0157] Specifically, the position information of the fixed station 3-0 is assumed to be (x0, y0, z0), and the position information of the fixed station 3-1 is assumed to be (x1, y1, z1). Furthermore, the ranging results between the fixed station 3-0 and the mobile station 1C are assumed to be R0-1 and R0-2, and the ranging results between the fixed station 3-1 and the mobile station 1C are assumed to be R1-1 and R1-2. In addition, d1 is smaller than d2.

[0158] The positioning calculation unit 16C calculates the sum of squares of distance errors E represented by the following mathematical formula (22) based on the calculation results of the positions of each coordinate axis: mk The calculation result is output as error information indicating an estimated error in the positioning.

[0159]

Mathematical formula 22

[0160]

[0161] Here, the mth mobile station 1C is assumed to be the mobile station 1C-m, and m is an integer from 1 to the number of mobile stations 1C, that is, the number of mobile stations M. Furthermore, the kth axis position candidate on the y axis of the mobile station 1C-m is assumed to be d k , when there are K axis position candidates, k is an integer from 1 to K. In addition, R nm represents the ranging result between the nth fixed station 3-n and the mth mobile station 1C-m. nmk is to use d between the nth fixed station 3-n and the mth mobile station 1C-m k The estimated result of the distance at is expressed by the following mathematical formula (23).

[0162]

Mathematical formula 23

[0163]

[0164] like Fig.16 As shown, when the mobile station 1C is located on the left side of the fixed station 3, the mobile station 1C-1 is located at the position y=d1, and the mobile station 1C-2 is located at the position y=d2. Fig.17 As shown, when the mobile station 1C is located on the right side of the fixed station 3, the mobile station 1C-1 exists at the position y=d2, and the mobile station 1C-2 exists at the position y=d1.

[0165] Here, the positional relationship between the mobile station 1C and the fixed station 3 is Fig.16 In the case of the state, the square sum of the distance error E mk When y=d1 and y=d2 are set as initial values ​​related to the y-axis in the mobile stations 1C-1 and 1C-2, the position estimation completion judgment unit 20 calculates the sum of squares E of the two position estimation results and the two distance errors for the two initial values.11 、E 12 After that, the position estimation is completed. At this time, for the mobile station 1C-1, the expected relationship between the sum of squares of distance errors is E 11 <E 12 Similarly, regarding mobile station 1C-2, it is expected to become E 21 >E 22 .

[0166] The positional relationship between the mobile station 1C and the fixed station 3 is Fig.17 In the case of the state, the square sum of the distance error E mk When y=d1 and y=d2 are set as initial values ​​related to the y-axis in the mobile stations 1C-1 and 1C-2, the position estimation completion judgment unit 20 calculates the sum of squares E of the two position estimation results and the two distance errors for the two initial values. 11 、E 12 After that, the position estimation is completed. At this time, for the mobile station 1C-1, the expected relationship between the sum of squares of distance errors is E 11 >E 12 Similarly, regarding mobile station 1C-2, it is expected to become E 21 <E 22 .

[0167] As described above, the magnitude relationship of the sum of squares of distance errors changes according to the positional relationship between the mobile station 1C and the fixed station 3. Using this relationship, the mobile station 1C can determine whether the positional relationship between the mobile station 1C and the fixed station 3 is Fig.16 The status is still Fig.17 At this time, even if the number of fixed stations 3 is two, it is possible to output the estimated result of the position of the mobile station 1C with respect to two coordinate axes, namely, the x-axis and the y-axis.

[0168] Fig.19 This is a flowchart for explaining the operation of the mobile station 1C according to Embodiment 4. Regarding the processing of steps S101 to S106, a plurality of initial values ​​using the values ​​of a plurality of axis position candidates are set in step S103, and a plurality of positions of each coordinate axis are calculated in step S104 and error information for each position is output. The processing is the same as Embodiment 2, and therefore, detailed description is omitted here.

[0169] After generating the position estimation result in step S106, the position estimation completion determination unit 20 determines whether the position estimation is completed (step S401). If the position estimation is not completed (step S401: No), the process returns to step S102. If the position estimation is completed (step S401: Yes), the position estimation result selection unit 21 selects a position estimation result from a plurality of position estimation result candidates based on the error information (step S402).

[0170] As described above, in the mobile station 1C of the fourth embodiment, when the position of each coordinate axis of the mobile station 1C is restricted to any one of the plurality of axis position candidates with respect to at least one of the plurality of coordinate axes, the positioning calculation unit 16C uses the plurality of axis position candidates as the position of each coordinate axis of the restricted coordinate axis, i.e., the restricted axis, and calculates the position of each coordinate axis related to the coordinate axis other than the restricted axis. The position estimation result generation unit 18 generates a plurality of candidates of position estimation results using the plurality of axis position candidates, and further includes a position estimation result selection unit 21, which selects a candidate of the position estimation result with the smallest estimation error of the positioning from the plurality of candidates of the position estimation results. Thus, even when considering the plurality of axis position candidates, the actual position of the mobile station 1C can be estimated based on the estimation error. At this time, even when the number of fixed stations 3 that can be used is small, the degree of freedom of the variable required for position estimation can be suppressed and the position estimation accuracy can be maintained.

[0171] Implementation method 5

[0172] In the above-mentioned second embodiment, the following example is described: the distance measurement result of the fixed station 3 with a large distance from the mobile station 1A is likely to contain a large error, so the fixed station 3 to be used is selected based on the size of the distance measurement result. However, the larger the distance measurement result is, the larger the distance measurement error is. It is not necessarily the case that the distance measurement result with which fixed station 3 is actually affected by the reflected wave based only on the size of the distance measurement result. Therefore, in the fifth embodiment, error information is calculated when the positioning calculation is performed in a plurality of patterns in which the combination of the fixed station 3 to be used is changed, and the distance measurement results used in the positioning calculation are weighted based on the error information, so as to suppress the influence of the distance measurement result that can be considered to have low accuracy.

[0173] Fig. 20 1 is a diagram showing a functional configuration of a mobile station 1D according to Embodiment 5. The mobile station 1D includes a fixed station position information storage unit 11, a distance measurement result acquisition unit 12, an inter-fixed station distance calculation unit 13, a coordinate axis selection unit 14, a fixed station selection unit 19D, an initial value setting unit 15, a positioning calculation unit 16D, an all-axis completion judgment unit 17, a position estimation result generation unit 18D, and a position estimation completion judgment unit 20D. The following mainly describes portions different from Embodiment 4.

[0174] The fixed station selection unit 19D selects the fixed station 3 to be used so that the positioning calculation unit 16D can perform positioning calculations in a plurality of modes for the combination of the fixed stations 3 to be used. Fig.12 .like Fig.12As shown, when the ranging error of the ranging result R1' between the mobile station and the fixed station 3-1 is large, if the ranging result R1' can be excluded for position calculation, the influence of the ranging error can be suppressed and the estimation accuracy of the position can be improved. However, in the actual radio wave propagation environment, it is not known which fixed station 3 is affected by the distortion due to the reflected wave. Therefore, the fixed station selection unit 19D selects the fixed station 3 in such a way that "the combination of the fixed stations 3 to be used" becomes a plurality of patterns obtained by successively changing the fixed station 3 to be excluded.

[0175] In the position calculation unit 16D, for a plurality of patterns obtained by successively changing the fixed station 3-p to be excluded, the sum of squares E of the distance errors shown in the following mathematical formula (24) is calculated. p As error information. Here, p is an integer from 0 to N-1.

[0176]

Mathematical formula 24

[0177]

[0178] As shown in the mathematical formula (24), in order to change the parameter p of the sum of squares of the distance errors from 0 to N-1 and obtain it, in the fixed station selection unit 19D, each time the process of selecting the fixed station 3 is performed, the value of the parameter p is changed to change the combination of the fixed stations 3 to be used. Specifically, the fixed station selection unit 19D is initially set to p = 0, and the fixed stations 3 to be used are selected in such a way that the 0th fixed station 3-0 is excluded. Then, it is set to p = 1, and the fixed stations 3 to be used are selected in such a way that the 1st fixed station 3-1 is excluded. Similarly, it is set to p = 2 and p = 3, and the fixed stations 3 to be used are selected respectively. For each combination of the fixed stations 3 to be used, the position calculation unit 16D calculates the sum of squares E of the distance errors. p For example, as Fig.12 shown, when the ranging error of the ranging result R1' between the mobile station and the fixed station 3-1 is large, the sum of squares E1 of the distance errors calculated by excluding the fixed station 3-1 takes the minimum value. In addition, compared with the fixed station 3-1, the degree of dependence of the fixed station 3-0 having the same position on the x-axis as the fixed station 3-1 becomes larger. Therefore, it is expected that the magnitude relationship of the sum of squares E p of the distance errors obtained for each fixed station 3 is E1 < (E2, E3) < E0. In this way, the smaller the ranging error included in the ranging result Rp between the mobile station and the pth fixed station 3-p, the larger the sum of squares E p of the distance errors becomes. Therefore, it can be said that it represents the degree of dependence or reliability when using the pth fixed station 3-p in position estimation. The weight coefficient w n based on this degree of dependence is represented by the following mathematical formula (25), for example.

[0179]

Mathematical formula 25

[0180]

[0181] n represents the number of the fixed station 3. Here, normalization is performed using the total value of the sum of squares of the distance errors for all the fixed stations 3, but for simplicity, it may be set to w n =E n In the positioning calculation unit 16D, after calculating the error information for all the patterns of the combination of the fixed stations 3 to be used, the weight coefficient w is used. n The position of the mobile station 1D is estimated for each coordinate axis according to the least square method based on successive approximation for minimizing the weighted sum of squares E of the distance errors of the number of fixed stations N as shown in the following mathematical formula (26).

[0182]

Mathematical formula 26

[0183]

[0184] The all-axis completion determination unit 17 determines whether the positioning calculations for all coordinate axes to be estimated have been completed. If the positioning calculations for all target coordinate axes have been completed, the position estimation result generation unit 18D outputs (x est ,y est ,z est ) as the position estimation result.

[0185] In addition, in the above, it is assumed that the square sum of distance errors E n The weight coefficient w calculated by mathematical formula (25) is n However, for simplicity, it can also be expressed as follows, as shown in the following mathematical formula (27), based on the sum of the squares of the distance errors E n The size of the weight coefficient w n is set to a value of 0 or 1. ε is a predetermined reliability threshold, which is expressed in E n When the reliability is less than the threshold, the weight coefficient w n The value of is set to 0, in E n When the reliability threshold is exceeded, the weight coefficient w n The value of is set to 1. Thus, the ranging results of the fixed station 3 whose reliability is less than the reliability threshold are excluded from the positioning calculation. Wherein, n is an integer from 0 to N-1.

[0186]

Mathematical formula 27

[0187]

[0188] Fig.211D according to Embodiment 5. The processing of step S101 and step S102 is similar to that of step S103. Fig.19 Next, the fixed station selection unit 19D selects the fixed station 3 to be used (step S501). In step S501, the combination of fixed stations 3 to be used is selected in such a way that the fixed station 3 to be excluded changes every time a selection is made. The processing of the following steps S103 to S106 is the same as Fig.19 etc.

[0189] After the positioning calculation of all axes is completed and the reliability of each calculation result is calculated, the position estimation completion judgment unit 20D judges whether the position estimation is completed (step S502). If the position estimation is not completed (step S502: No), the mobile station 1D returns to the process of step S102. If the position estimation is completed (step S502: Yes), the mobile station 1D performs the processes of steps S102 and S103 again, and performs the positioning calculation using the weight coefficient (step S503). Then, the all-axis completion judgment unit 17 judges whether the positioning calculation of all axes is completed (step S105). If the positioning calculation of all axes is not completed (step S105: No), the process returns to step S102 after step S502. If the positioning calculation of all axes is completed (step S105: Yes), the position estimation result generation unit 18D generates a position estimation result indicating the three-dimensional position of the mobile station 1D based on the calculation result of the weighted positioning calculation (step S504).

[0190] As described above, the fixed station selection unit 19D of the mobile station 1D of the fifth embodiment selects the combination of fixed stations 3 to be used in such a manner that the fixed stations 3 to be excluded change each time. Thus, the positioning calculation unit 16D calculates the position of each coordinate axis multiple times while changing the distance measurement results to be excluded, and generates error information indicating the degree of estimation error of each of the calculated positions of each coordinate axis. The positioning calculation unit 16D calculates the position of each coordinate axis again based on the distance measurement results weighted based on the error information, and the position estimation result generation unit 18 can generate a position estimation result using the position of each coordinate axis based on the weighted distance measurement results. Thus, the influence of the fixed station 3 whose distance measurement results contain errors and whose distance measurement accuracy is low can be more reliably suppressed, and the position estimation accuracy can be improved.

[0191] Here, an example of the configuration of the processing circuit included in the fixed station 3 or the mobile stations 1, 1A, 1B, 1C, 1D according to Embodiments 1 to 5 will be described. When the processing circuit is implemented by a control circuit using a processor, the control circuit is, for example, Fig. 22 The control circuit 90 is shown. Fig. 22This is a diagram showing a configuration of a control circuit 90 included in the fixed station 3 or the mobile stations 1, 1A, 1B, 1C, 1D according to the first to fifth embodiments.

[0192] The control circuit 90 has a processor 91 and a memory 92. When the processing circuit is composed of the control circuit 90 having the processor 91 and the memory 92, each function of the fixed station 3 or the mobile station 1, 1A, 1B, 1C, 1D is realized by software, firmware, or a combination of software and firmware. Software or firmware is described as a program, which is stored in the memory 92. The processor 91 reads out and executes the program stored in the memory 92, thereby realizing each function. That is, the processing circuit has the memory 92, and the memory 92 is used to store programs whose results are to execute the processing of the fixed station 3 or the mobile station 1, 1A, 1B, 1C, 1D. In addition, it can be said that these programs cause the computer to execute the processing steps or methods of the fixed station 3 or the mobile station 1, 1A, 1B, 1C, 1D. In addition, the program can be provided in a state stored in a storage medium, or can be provided via a communication path.

[0193] Here, the processor 91 may be a CPU (Central Processing Unit), a processing device, an arithmetic device, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor), etc. In addition, the memory 92 may be, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), an EEPROM (registered trademark) (Electrically EPROM), or other nonvolatile or volatile semiconductor memory, a magnetic disk, a floppy disk, an optical disk, a high-density disk, a mini disk, or a DVD (Digital Versatile Disc), etc.

[0194] Furthermore, the processing circuits included in the fixed station 3 or the mobile stations 1, 1A, 1B, 1C, and 1D according to the first to fifth embodiments may be configured using dedicated hardware. Fig.23 This is a diagram showing an example of dedicated hardware included in the fixed station 3 or the mobile stations 1, 1A, 1B, 1C, and 1D according to the first to fifth embodiments. Fig.23The processing circuit 93 shown is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The processing circuit 93 may realize the functions of the fixed station 3 or the mobile stations 1, 1A, 1B, 1C, 1D according to different functions, or the processing circuit 93 may realize all the functions uniformly.

[0195] In addition, each function of the fixed station 3 or the mobile stations 1, 1A, 1B, 1C, 1D of embodiments 1 to 5 may be partially implemented by dedicated hardware and partially implemented by software or firmware. In this way, the processing circuit can implement each of the above functions by dedicated hardware, software, firmware, or a combination thereof.

[0196] The configurations described in the above embodiments are merely examples, and may be combined with other known technologies, the embodiments may be combined with each other, and a portion of the configuration may be omitted or modified within a scope not departing from the gist.

[0197] For example, in the above-mentioned embodiments 1 to 5, the mobile stations 1, 1A, 1B, 1C, and 1D are assumed to be position estimation devices that estimate their own positions. However, the technology described in this embodiment is not limited to such an example, and the distance measurement result can also be obtained in a device different from the mobile stations 1, 1A, 1B, 1C, and 1D, and the same position estimation process can be performed. In addition, it is not necessary to use one device to implement all the functions of the functional units shown in the figure, and it is also possible to use multiple devices to share the functions of the position estimation device. In addition, part or all of the functions of the position estimation device can also be implemented on a cloud server. In the case where all the functions of the position estimation device are implemented by a cloud server or a device other than the mobile station 1, 1A, 1B, 1C, and 1D, it is necessary to perform the distance measurement process between the mobile station 1, 1A, 1B, 1C, and 1D and the fixed station 3, so the distance measurement result acquisition unit 12 obtains the distance measurement result from the mobile station 1, 1A, 1B, 1C, and 1D or the fixed station 3.

[0198] Description of symbols

[0199] 1, 1A, 1B, 1C, 1C-1, 1C-2, 1D: mobile station; 3, 3-0, 3-1, 3-2, 3-3: fixed station; 11: fixed station position information storage unit; 12: ranging result acquisition unit; 13: fixed station distance calculation unit; 14: coordinate axis selection unit; 15, 15B, 15C: initial value setting unit; 16, 16A, 16C, 16D: positioning calculation unit; 17, 17B: all axis completion judgment unit; 18, 18D: position estimation result generation unit; 19, 19D: fixed station selection unit; 20, 20D: position estimation completion judgment unit; 21: position estimation result selection unit; 50, 51, 52: position; 90: control circuit; 91: processor; 92: memory; 93: processing circuit; 100, 100A, 100B: position estimation system.

Claims

1. A position estimation device for estimating the position of a mobile station based on a plurality of distance measurement results obtained by using wireless communication between each of a plurality of fixed stations and a mobile station, characterized in that: The position estimation device comprises: a positioning calculation unit that calculates the position of the mobile station for each coordinate axis using the position of the fixed station and the distance measurement result in order from the coordinate axis having the largest distance between the plurality of fixed stations; as well as A position estimation result generating unit generates a position estimation result indicating the three-dimensional position of the mobile station based on the calculation result of the position of each coordinate axis.

2. The position estimation device according to claim 1, characterized in that: The position estimation device further includes a fixed station selection unit that selects a fixed station to be used from the plurality of fixed stations based on the magnitude of the distance measurement result. The positioning calculation unit excludes the distance measurement results of the unselected fixed stations from the distance measurement results used in the calculation.

3. The position estimation device according to claim 2, characterized in that: The fixed station selection unit selects, from among the plurality of fixed stations, a fixed station other than a fixed station having a maximum distance indicated by the ranging result as the fixed station to be used.

4. The position estimation device according to claim 2, characterized in that: The fixed station selection unit selects a predetermined number of the fixed stations from among the plurality of fixed stations in ascending order of distance indicated by the distance measurement result.

5. The position estimation device according to claim 2, characterized in that: The fixed station selection unit selects, from among the plurality of fixed stations, a fixed station whose distance indicated by the ranging result is equal to or smaller than a threshold value as the fixed station to be used.

6. The position estimation device according to claim 5, characterized in that: The threshold is determined based on a minimum value of distances indicated by the ranging results of the plurality of fixed stations.

7. The position estimation device according to any one of claims 1 to 6, characterized in that: When the position of each coordinate axis of the mobile station is limited to any one of a plurality of axis position candidates with respect to at least one of the plurality of coordinate axes, The positioning calculation unit uses each of the plurality of axis position candidates as the position of each of the restricted coordinate axes, i.e., the restricted axis, and calculates the position of each of the coordinate axes with respect to the coordinate axes other than the restricted axis. The position estimation result generating unit generates a plurality of candidates of the position estimation results using each of the plurality of axis position candidates. The position estimation device includes an estimation result selection unit that selects a candidate for the position estimation result with the smallest estimation error in positioning from among a plurality of candidates for the position estimation results.

8. The position estimation device according to claim 2, characterized in that: The positioning calculation unit calculates the position of each coordinate axis multiple times while changing the distance measurement result to be excluded, and generates error information indicating the degree of estimation error of each of the calculated positions of each of the multiple coordinate axes. The positioning calculation unit recalculates the position of each coordinate axis based on the distance measurement result weighted based on the error information, The position estimation result generating unit generates the position estimation result using the position of each coordinate axis based on the weighted distance measurement result.

9. The position estimation device according to claim 8, characterized in that: The positioning calculation unit sets a weighting coefficient to 1 when the reliability of the distance measurement result of the fixed station based on the error information is greater than a predetermined reliability threshold, and sets the weighting coefficient to 0 when the reliability is less than the reliability threshold.

10. The position estimation device according to claim 1, characterized in that: The ranging result is obtained based on the transmission and reception timing of the ultra-wideband wireless signal between the fixed station and the mobile station.

11. The position estimation device according to claim 1, characterized in that: The positioning calculation unit calculates the position of each coordinate axis using a least square method based on successive approximation.

12. A position estimation system, characterized in that: The position estimation system has: The mobile station having the position estimation device according to any one of claims 1 to 11; and The fixed station.

13. The position estimation system according to claim 12, characterized in that: The mobile station is mounted on a mobile body that moves along a predetermined path. The fixed stations are disposed along the path.

14. The position estimation system according to claim 13, characterized in that: The moving object is a railway vehicle traveling on a line or a vehicle traveling on a road.

15. The position estimation system according to claim 13 or 14, characterized in that: The fixed stations are arranged along the linear path, The position estimating device estimates the position of the mobile station on one coordinate axis.

16. A control circuit for controlling a position estimating device for estimating the position of a mobile station based on a plurality of distance measurement results obtained by wireless communication between each of a plurality of fixed stations and a mobile station, characterized in that: The control circuit causes the position estimation device to perform the following steps: Starting from a coordinate axis having a large distance between the plurality of fixed stations, sequentially using the positions of the fixed stations and the ranging results to calculate the position of the mobile station of each coordinate axis; as well as A position estimation result indicating the three-dimensional position of the mobile station is generated based on the calculation result of the position of each coordinate axis.

17. A storage medium storing a program for controlling a position estimation device for estimating the position of a mobile station based on a plurality of distance measurement results obtained by wireless communication between each of a plurality of fixed stations and a mobile station, wherein: The program causes the position estimation device to perform the following steps: Starting from a coordinate axis having a large distance between the plurality of fixed stations, sequentially using the positions of the fixed stations and the ranging results to calculate the position of the mobile station of each coordinate axis; as well as A position estimation result indicating the three-dimensional position of the mobile station is generated based on the calculation result of the position of each coordinate axis.

18. A method for estimating a position of a mobile station based on a plurality of distance measurement results obtained by using wireless communication between each of a plurality of fixed stations and a mobile station, characterized in that: The position estimation method comprises the following steps: Starting from a coordinate axis having a large distance between the plurality of fixed stations, sequentially using the positions of the fixed stations and the ranging results to calculate the position of the mobile station of each coordinate axis; as well as A position estimation result indicating the three-dimensional position of the mobile station is generated based on the calculation result of the position of each coordinate axis.

Images