POSITION DETERMINATION DEVICE, POSITION DETERMINATION SYSTEM, CONTROL CIRCUIT, STORAGE MEDIUM AND POSITION DETERMINATION PROCEDURE

Abstract

A mobile station (1), which is a positioning device that determines a position of the mobile station (1) based on a plurality of distance measurement results taken between each of a plurality of fixed stations and the mobile station (1) using wireless communication, comprises: a positioning calculation unit (16) for calculating a coordinate axis position of the mobile station for each coordinate axis using a position of the fixed stations and the distance measurement results in a sequence starting from a coordinate axis having the largest coordinate axis distance between the plurality of fixed stations; and a position determination result generation unit (18) that generates a position determination result indicating a three-dimensional position of the mobile station based on a calculation result of the coordinate axis position.

Description

Area

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

[0002] There are techniques that measure the distance between a ground-mounted fixed station and a mobile station based on the propagation time between the fixed station and the mobile station using the transmission / reception time of communication, and determine the position of the mobile station based on known position information of the fixed station and the distance measurement result. A general position determination algorithm is a least-squares method for solving three-dimensional nonlinear simultaneous equations involving the positions of three or more fixed stations and the results of distance measurements between the fixed stations and the mobile station to determine the three-dimensional position (x, y, z) of the mobile station. The position of the mobile station is determined by sequential approximation calculation.

[0003] In such a field, it is desirable to improve the accuracy of position detection. For example, Patent Literature 1 discloses a technique for improving the accuracy of a method of determining the position of a mobile station from distance measurement results using ultra-wideband (UWB) signals. It is based on statistical data of multipath components included in a received signal that identifies whether the radio wave propagation time between a fixed station and the mobile station is in a "line-of-sight" state or a "non-line-of-sight" state, and applies weighting that reduces the influence of the distance measurement result for the fixed station in the "non-line-of-sight" state on the position detection. List of cited publicationsPatent literature

[0004] Patent Literature 1: Japanese Patent No. 4567093 SummarySolution to the problem

[0005] However, in the conventional technique described above, it is necessary to collect statistical data of multipath components included in a received signal, such as the sharpness of the received waveform, the average excess delay spread of multipath components, and the root-mean-square delay spread, in advance for each area in which position detection is performed, and there is a problem that position detection cannot be performed with high accuracy in a case where the statistical data cannot be collected in advance, in a case where the accuracy of the statistical data is low, or the like.

[0006] The present disclosure has been made in view of the above, and an object thereof is to realize a position detecting device capable of performing position detection with high accuracy even in a case where accurate statistical data of multipath components of a received signal cannot be obtained in advance. Solution to the problem

[0007] In order to solve the problems described above and achieve the object, a position detecting device according to the present disclosure is a position detecting device that detects a position of a mobile station based on a plurality of distance measurement results measured between each of a plurality of fixed stations and the mobile station using wireless communication.The position detection device includes: a position calculation unit for calculating a coordinate axis position of the mobile station for each coordinate axis using a position of the fixed stations and the distance measurement results in an order starting from a coordinate axis having a largest coordinate axis distance between the plurality of fixed stations; and a position detection result generation unit for calculating a position detection result indicating a three-dimensional position of the mobile station based on a calculation result of the coordinate axis position. Advantageous effects of the invention

[0008] The position detecting device according to the present disclosure can achieve the effect of performing position detection with high accuracy even in a case where accurate statistical data of multipath components of a received signal cannot be obtained in advance. Brief description of the drawings Fig. 1 is a diagram illustrating an exemplary configuration for a position detection system according to the first embodiment. Fig. Figure 2 is a diagram illustrating an example of waveform distortion occurring in a multipath environment. Fig. 3 is a diagram illustrating the relationship between distance measurement results between the mobile station and the fixed stations and the position detection. Fig. 4 is a diagram illustrating a functional configuration of the mobile station which is the position detecting device according to the first embodiment. Fig. 5 is a flowchart for explaining the operation of the mobile station according to the first embodiment. Fig. 6 is a diagram illustrating a functional configuration of a mobile station which is the position detecting device according to the second embodiment. Fig. 7 is a diagram illustrating an exemplary configuration for a position detection system according to the second embodiment. Fig. 8 is a diagram illustrating a state in which there is an error in the result of distance measurement for the fixed station in the position detection system. Fig. 9 is a diagram for explaining a first example of a selection process by the base station selection unit. Fig. 10 is a diagram for explaining a second example of a selection process by the base station selection unit. Fig. 11 is a diagram for explaining a third example of a selection process by the base station selection unit. Fig. 12 is a diagram for explaining the effect of the second embodiment. Fig. 13 is a flowchart for explaining the operation of the mobile station according to the second embodiment. Fig. 14 is a diagram illustrating a configuration of a position detection system according to the third embodiment. Fig. 15 is a diagram illustrating a functional configuration of the mobile station according to the third embodiment. Fig. 16 is a diagram illustrating a first example of a positional relationship between the fixed stations and the mobile station according to the fourth embodiment. Fig. 17 is a diagram illustrating a second example of a positional relationship between the fixed stations and the mobile station according to the fourth embodiment. Fig. 18 is a diagram illustrating a functional configuration of the mobile station according to the fourth embodiment. Fig. 19 is a flowchart for explaining the operation of the mobile station according to the fourth embodiment. Fig. 20 is a diagram illustrating a functional configuration of a mobile station according to the fifth embodiment. Fig. 21 is a flowchart for explaining the operation of the mobile station according to the fifth embodiment. Fig. 22 is a diagram illustrating a configuration of the control circuit included in the fixed station or the mobile stations according to the first to fifth embodiments. Fig. 23 is a diagram illustrating an example of dedicated hardware included in the fixed station or the mobile stations according to the first to fifth embodiments. Description of embodiments

[0009] Hereinafter, a position detecting device, a position detecting system, a control circuit, a storage medium, and a position detecting method according to embodiments of the present disclosure will be described in detail with reference to the drawings. First embodiment.

[0010] Fig. 1 is a diagram illustrating an exemplary configuration for a positioning system 100 according to the first embodiment. The positioning system 100 includes a mobile station 1, which is an example of a positioning device, and a plurality of fixed stations 3-0 to 3-3 mounted on the ground. Note that in the following description, when distinction between the fixed stations 3-0 to 3-3 is not required, they may simply be referred to as the fixed station(s) 3. Note that four fixed stations 3 are illustrated, but the number of fixed stations 3 is not limited to four, but need only be two or more.

[0011] The position detection system 100 measures the distance between the mobile station 1 and each of the plurality of fixed stations 3 based on the transmission / reception timing of a wireless signal transmitted / received by wireless communication between the mobile station 1 and each of the plurality of fixed stations 3, and detects the position of the mobile station 1 based on the distance measurement result.

[0012] The wireless signals used by the positioning system 100 are, for example, UWB signals. UWB signals are ultrashort pulse signals in the time domain. The use of UWB signals therefore makes it possible to capture the transmission / reception time of communications with high resolution and to determine the position of the mobile station 1 with high precision.

[0013] The positions of the mobile station 1 and the fixed station 3 are represented by three-dimensional positions, and the coordinate axes defining the three-dimensional space are an x-axis, a y-axis, and a z-axis. Assuming that the position of the fixed station 3 is known, the position of the fixed station 3 is 0 (x 0 , y 0 , e.g. 0 ), the position of the base station 3-1 is (x 1 , y 1 , e.g. 1 ), the position of the base station 3-2 is (x 2 , y 2 , e.g. 2 ), and the position of the base station 3-3 is (x 3 , y 3 , e.g. 3 ).

[0014] Each base station 3 transmits a broadcast signal containing, for example, position information and identification information, and the mobile station 1 can detect information about the receiving base station 3 based on the broadcast signal. The mobile station 1 calculates the propagation time required for wireless communication based on the transmission / reception time of the UWB signal between the mobile station 1 and each of the detected base stations 3, and obtains the distance measurement result for each base station 3.

[0015] When a UWB signal is transmitted and received between the mobile station 1 and each fixed station 3, if there is an object that reflects radio waves, such as a wall, a reflected wave W2 is received in addition to a direct wave W1. In this case, distortion of the UWB signal waveform occurs.

[0016] Fig. Figure 2 is a diagram illustrating an example of waveform distortion occurring in a multipath environment. As shown in Fig. 2, in the multipath environment, a reception waveform 40 detected at the receiving side is distorted as a result of the combination of a waveform 41 of the direct wave W1 and a waveform 42 of the reflected wave W2. As shown in Fig. As shown in Figure 2, the distorted reception waveform 40 has a signal waveform shifted backward in time compared to the waveform 41 of the direct wave W1, so that the distance measurement result based on the reception waveform 40 tends to have a larger distance. Since the accuracy of the distance measurement result is thus reduced, the positioning accuracy of the mobile station 1 based on the distance measurement result also decreases.

[0017] The first embodiment proposes a position detection method with which it is possible to prevent a reduction in position detection accuracy even in a case where the accuracy of a distance measurement result is low as described above.

[0018] Fig. 3 is a diagram illustrating the relationship between distance measurement results between the mobile station 1 and the fixed stations 3 and the position detection. Here, the distance measurement result for the fixed station 3-0 is denoted by R0, the distance measurement result for the fixed station 3-1 is denoted by R1, the distance measurement result for the fixed station 3-2 is denoted by R2, and the distance measurement result for the fixed station 3-3 is denoted by R3. At this time, it is ideally desirable that a circle with a radius of R0 and centered on the position of the fixed station 3-0, a circle with a radius of R1 and centered on the position of the fixed station 3-1, a circle with a radius of R2 and centered on the position of the fixed station 3-2, and a circle with a radius of R3 and centered on the position of the fixed station 3-3 intersect at a point, and the intersection point is determined as the position of the mobile station 1.

[0019] Here, it is assumed that the calculation is performed based on the least squares method as the position detection algorithm for position calculation. In this case, focusing on the Z-axis direction and the Y-axis direction, the detection range Ax on the X-axis is smaller than the detection range Ay on the Y-axis. This means that the position detection result with respect to the X-axis can have a smaller error than the position detection result with respect to the Y-axis. Here, the position detection range decreases with the increase in the distance between the fixed stations 3. Therefore, with the increase in the distance between the fixed stations 3 for each coordinate axis (the distance can be referred to as the coordinate axis distance between the fixed stations 3), the detection range of the position in this coordinate axis direction decreases, and the position detection error decreases.Therefore, in the first embodiment, the position of the mobile station 1 is calculated for each coordinate axis (the position may be referred to as the coordinate axis position of the mobile station 1) by the one-dimensional least squares method in an order starting from the coordinate axis with the largest distance between the fixed stations 3 among the plurality of coordinate axes, thereby reducing the detection error of the position for each coordinate axis. The following describes the functions of the position detection device for performing such processing.

[0020] Fig. 4 is a diagram illustrating a functional configuration of the mobile station 1, which is the position detecting device, according to the first embodiment. The mobile station 1 includes a fixed station position information storage unit 11 that stores position information of the fixed station 3, a distance measurement result acquisition unit 12 that acquires a distance measurement result between each fixed station 3 and the mobile station 1, an inter-fixed station distance calculation unit 13 that calculates a distance between the fixed stations 3, a coordinate axis selection unit 14 that selects a coordinate axis to be calculated based on the distance between the fixed stations 3, an initial value setting unit 15 that sets an initial value for calculating a position for each coordinate axis, and a positioning calculation unit 16 that calculates a position for each coordinate axis for the selected coordinate axis.an all-axis completion determination unit 17 that determines whether the calculation of a position for each coordinate axis is completed for all assumed coordinate axes, and a position detection result generation unit 18 that generates a position detection result indicating a three-dimensional position of the mobile station 1 based on the calculation result.

[0021] The base station position information storage unit 11 stores the position information of the base station 3 contained in the broadcast signal transmitted from each base station 3. The position information is stored, for example, in association with the identification information contained in the broadcast signal. Fig. 1, in a case where the mobile station 1 receives the broadcast signals of the four base stations 3, ie, the base stations 3-0 to 3-3, the base station position information storage unit 11 stores the position information (x 0 ,y 0 ,z 0 ) of the base station 3-0, the position information (x 1 ,y 1 ,z 1 ) of the base station 3-1, the position information (x 2 ,y 2 ,z 2 ) of the base station 3-2 and the position information (x 3 ,y 3 ,z 3 ) of the fixed station 3-3.

[0022] The distance measurement result acquisition unit 12 transmits and receives UWB signals to and from each base station 3, calculates the propagation time required for wireless communication based on the transmission / reception timing of each UWB signal, and acquires the distance measurement result for each base station 3. Note that, since the mobile station 1 here has both the distance measurement function and the position detection function, the distance measurement result acquisition unit 12 performs the distance measurement process itself. However, in a case where the distance measurement process is performed by a device other than the mobile station 1, the distance measurement result acquisition unit 12 only needs to acquire a distance measurement result that is a result of the distance measurement process performed by that device via communication.

[0023] The inter-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 inter-fixed station distance calculation unit 13 calculates the distance for each coordinate axis. For example, in a case where the distance between the fixed stations 3 for the Fig. 1 shown four fixed stations 3-0 to 3-3 are calculated in the Fig. 1, the four fixed stations 3-0 to 3-3 are arranged so that they are positioned at the respective corner points of the rectangle on the xy plane, and thus the relationship of the following formula (1) applies to the x-axis, the relationship of the following formula (2) applies to the y-axis, and the relationship of the following formula (3) applies to the z-axis. Formula 1: (|x0−x2|=|x1−x3|=d1)>(|x0−x1|=|x2−x3|=0) Formula 2: (|y0−y1|=|y2−y3|=d2)>(|y0−y2|=|y1−y3|=0) Formula 3: |z0−z1|=|z1−z2|=|z2−z3|=|z3−z0|=d3

[0024] It is assumed that the sizes d 1 , d 2 and d 3 in formulas (1) to (3) the relationship “d 1 >d 2 >d 3 In this case, the distances between the fixed stations 3 for the respective axes are, in descending order, the x-axis, the y-axis and the z-axis.

[0025] The inter-fixed station distance calculation unit 13 can also calculate a distance between the fixed stations 3 for each coordinate axis using formulas (4) to (6). Specifically, when the number of fixed stations 3 is N, the distance between the fixed stations 3 on the x-axis is expressed by the following formula (4), the distance between the fixed stations 3 on the y-axis is expressed by the following formula (5), and the distance between the fixed stations 3 on the z-axis is expressed by the following formula (6). Formula 4: ∑n=0N−1∑m=n+1N−1|xn−xm| Formula 5: ∑n=0N−1∑m=n+1N−1|yn−ym| Formula 6: ∑n=0N−1∑m=n+1N−1|zn−zm|

[0026] According to the above formulas (4) to (6), for example, in a case where the Fig. 1 are stored in the fixed station position information storage unit 11, the inter-fixed station distance calculation unit 13 calculates, for each coordinate axis, the sum of the distances between the fixed stations 3 of the six combinations: 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 for each coordinate axis.

[0027] Assuming that the conditions of formulas (1) to (3) for the Fig. 1 shown four fixed stations 3-0 to 3-3 are fulfilled here, the value of formula (4) is 4d 1 , the value of formula (5) 4d 2 , the value of formula (6) 4d 3, and the distances between the fixed stations 3 for the respective coordinate axes are, in descending order, the x-axis, the y-axis and the z-axis.

[0028] It should be noted that for the sake of simplicity, the four fixed stations 3-0 to 3-3 are arranged here as an example so that they are located at the respective corner points of the rectangle in the xy plane, but the conditions given in formulas (1) to (3) do not necessarily have to be met.

[0029] The coordinate axis selection unit 14 selects the coordinate axes in descending order of distance based on the distance between the fixed stations 3 calculated by the inter-fixed station distance calculation unit 13. In the above example, the coordinate axis selection unit 14 sequentially 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 axes to the initial value setting unit 15.

[0030] The initial value setting unit 15 calculates the initial value of each axis for the positioning calculation unit 16 to calculate the position for each coordinate axis based on the selected coordinate axis. For example, the initial value setting unit 15 may 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 in the x-axis is expressed by the following formula (7), the initial value y in the y-axis is expressed by the following formula (8), and the initial value z in the z-axis is expressed by the following formula (9). Formula 7: xin=1N∑n=0N−1xn Formula 8: yin=1N∑n=0N−1yn Formula 9: zin=1N∑n=0N−1zn

[0031] It should be noted that in a case where the position of the mobile station 1 is calculated in advance in time, the initial value setting unit 15 may use this position information as the initial value. For example, in a case where the position of the mobile station 1 is continuously calculated and the three-dimensional position of the mobile station 1 has already been calculated within a time range serving as a guideline for the position of the mobile station 1, the initial value setting unit 15 may use this position information as the initial value. Further, in a case where the coordinate axes are selected in the order of the x-axis, the y-axis, and the z-axis, in calculating the position of the x-axis, the initial value of the position of the mobile station 1 may be set to (x in , y in , e.g. in). When calculating the y-axis position, since the x-axis position has already been calculated, the initial value of the position of mobile station 1 can be set to (x est , y in , e.g. in ) using the calculated position determination result x est the x-axis, which is a fixed value. When calculating the z-axis position, since the x-axis and y-axis positions have already been calculated, the initial value of the position of mobile station 1 can be set to (x est , y est , e.g. in ) using the calculated position x est the x-axis, which is a fixed value, and the calculated position y est the y-axis, which is a fixed value.

[0032] With respect to the coordinate axes selected by the coordinate axis selecting unit 14, the positioning calculating unit 16 calculates the position of the mobile station 1 for each coordinate axis 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 storing unit 11, and the distance measurement result for each fixed station 3 acquired by the distance measurement result acquiring unit 12.

[0033] Specifically, the positioning calculation unit 16 calculates the position of the mobile station 1 for each coordinate axis based on the one-dimensional least squares method. In the above example, assume that the coordinate axis selection unit 14 selects coordinate axes in the order of the x-axis, the y-axis, and the z-axis, and the positioning calculation unit 16 performs positioning calculation in the order of the x-axis, the y-axis, and the z-axis. At this time, in the case of determining the position of the mobile station 1 in the x-axis direction, which is selected first, the positioning calculation unit 16 sets the position of the mobile station 1 to (x in , y in , e.g. in ) based on the output of the initial value setting unit 15, sets the x-axis variable to be determined in the positioning calculation to the initial value x est =x in, and performs the calculation. The distance r n between the n-th fixed station 3-n and the mobile station 1 to be subjected to position determination is calculated using the following formula (10). Formula 10: rn=(xn−xest)2+(yn−yin)2+(zn−zin)2

[0034] Note that n is an integer from zero to N-1. Since r n in formula (10) a nonlinear function with respect to x est is, the positioning calculation unit 16 sequentially calculates the variable x est the position determination with respect to the x-axis based on the least squares method by sequential approximation using formula (10) as the norm.

[0035] In addition, since there is a measurement error between the distance measurement result Rn and the distance r nbetween the nth fixed station 3-n and the mobile station 1 for each of the N fixed stations, the positioning calculation unit 16 calculates the sum of the squares E of the distance errors corresponding to the N fixed stations. The sum of the squares E of the distance errors corresponding to the N fixed stations is expressed by the following formula (11). Formula 11: E=∑n=0N−1en2=∑n=0N−1(Rn−rn)2

[0036] In the positioning calculation unit 16, the position determination result x est the x-axis of the mobile station 1 by the least squares method, which is based on a sequential approximation to minimize the sum of the squares E of the distance errors corresponding to the N fixed stations and is expressed by formula (11).

[0037] Once the y-axis is selected next to the x-axis, the positioning calculation unit 16 sets the position of the mobile station 1 to (xest , y in , e.g. in ) based on the output of the initial value setting unit 15, sets the y-axis variable to be determined in the positioning calculation to the initial value y est =y in , and performs the calculation. In this case, the distance r n between the n-th fixed station 3-n and the mobile station 1 to be positioned is calculated using the following formula (12). Note that n is an integer from zero to N-1. Since r n in formula (12) a nonlinear function with respect to y est , the positioning calculation unit 16 sequentially calculates the variable y est the position determination with respect to the y-axis based on the least squares method by sequential approximation using formula (12) as the norm. Formula 12: rn=(xn−xest)2+(yn−yest)2+(zn−zin)2

[0038] It should be noted that in this case too, since the sum of the squares E of the distance errors corresponding to the N fixed stations is expressed by the above formula (11), the positioning calculation unit 16 calculates the sum of the squares E of the distance errors based on the formula (11), obtains the position of the y-axis of the mobile station 1 using the least squares method based on sequential approximation to minimize the sum of the squares E of the distance errors, and the position y est the y-axis, which is the result of the calculation.

[0039] Once the z-axis is selected alongside 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 , e.g. in) based on the output of the initial value setting unit 15, sets the variable of the z-axis to be determined in the positioning calculation to the initial value z est =z in , and performs the calculation. In this case, the distance r n between the n-th fixed station 3-n and the mobile station 1 to be determined is calculated using the following formula (13). Note that n is an integer from zero to N-1. Since r n in formula (13) a nonlinear function with respect to z est is, the positioning calculation unit 16 sequentially calculates the variable z est the position determination with respect to the z-axis based on the least squares method by sequential approximation using formula (13) as the norm. Formula 13: rn=(xn−xest)2+(yn−yest)2+(zn−zin)2

[0040] It should be noted that in this case too, since the sum of the squares E of the distance errors corresponding to the N fixed stations is expressed by the above formula (11), the positioning calculation unit 16 calculates the sum of the squares E of the distance errors based on the formula (11), obtains the position of the z-axis of the mobile station 1 using the least squares method based on sequential approximation to minimize the sum of the squares E of the distance errors, and calculates the position z est the z-axis, which is the result of the calculation.

[0041] The all-axis completion determination unit 17 determines whether the positioning calculation for the coordinate axis position has been completed for all the coordinate axes adopted as positioning targets, and in a case where the positioning calculation for all the axes has not been completed, notifies the coordinate axis selection unit 14 to continue the selection of the coordinate axes, and in a case where the positioning calculation for all the axes has been completed, notifies the position determination result generation unit 18 that the positioning calculation for all the axes has been completed.For example, when the calculation result of the coordinate axis position for each coordinate axis is received from the positioning calculation unit 16 for the three axes of the x-axis, the y-axis, and the z-axis, the all-axis completion determination unit 17 may notify the position determination result generation unit 18 that the positioning calculation for all axes is completed, and in other cases, notify the coordinate axis selection unit 14 to continue selecting the coordinate axes. Alternatively, in a case where the position of one of the three axes, for example, the z-axis, is known in advance, the position determination may be performed only for two axes, the x-axis and the y-axis, and the determination criterion of the all-axis completion determination unit 17 may be that the positioning calculation of the two axes is completed.Once the positioning calculation for all axes is completed, the all-axis completion determination unit 17 outputs the calculation result received from the positioning calculation unit 16 to the position determination result generation unit 18.

[0042] Upon receiving the calculation result of the coordinate axis positions from the all-axis completion determination unit 17, the position determination result generation unit 18 outputs (x est , y est , e.g. est ) as the position detection result indicating the three-dimensional position of the mobile station 1 based on these calculation results.

[0043] Fig. 5 is a flowchart for explaining the operation of the mobile station 1 according to the first embodiment. The inter-fixed station distance calculation unit 13 calculates a distance between the fixed stations 3 for each coordinate axis, namely, a coordinate axis distance between the fixed stations 3 (step S101). The coordinate axis selection unit 14 selects a coordinate axis to be subjected to positioning calculation (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 of calculating the coordinate axis position of the mobile station 1 using the set initial value for the selected coordinate axis (step S104).

[0044] The all-axis completion determination unit 17 determines whether the positioning calculation for all axes is completed (step S105). The coordinate axes with unknown positions are set as coordinate axes to be subjected to positioning calculation, and the determination in step S105 is made based on whether a determined value of the coordinate axis position for each coordinate axis has been calculated by positioning calculation for all coordinate axes to be subjected to positioning calculation.

[0045] In response to a determination that the position calculation for all axes has not yet been completed (step S105: No), the mobile station 1 returns to step S102. In response to the determination that the positioning calculation for all axes has been completed (step S105: Yes), the position detection result generation unit 18 generates a position detection result indicating the three-dimensional position of the mobile station 1 (step S106).

[0046] As described above, the mobile station 1, which is the position detecting device according to the first embodiment, is a position detecting device that detects a position of the mobile station 1 based on a plurality of distance measurement results measured between each of a plurality of fixed stations 3 and the mobile station 1 using wireless communication, and includes: the positioning calculation unit 16 that calculates a coordinate axis position of the mobile station 1 for each coordinate axis using a position of the fixed stations 3 and the distance measurement results in an order from a coordinate axis having the largest coordinate axis distance between the plurality of fixed stations 3;a position detection result generation unit 18 for generating a position detection result indicating a three-dimensional position of the mobile station 1 based on a calculation result of the coordinate axis position. The larger the coordinate axis distance between the fixed stations 3, the smaller the range of position detection, so that the error in position detection can be reduced. By performing the positioning calculation in order from the coordinate axis with the largest distance between the fixed stations 3, it is possible to reduce the error in coordinate axis position detection for each coordinate axis and improve the accuracy of position detection. Position detection can be performed with high accuracy even in a case where accurate statistical data of multipath components of a received signal cannot be obtained in advance.

[0047] Furthermore, even in a case where the number of fixed stations 3 installed in the range of the position detection system 100 and usable for distance measurement is not sufficiently large or in a case where a distance measurement result with low distance measurement accuracy is included under the influence of a wave reflected from a wall or the like, it is possible to reduce the number of coordinate axes to be detected simultaneously and maintain the accuracy of position detection while reducing the degree of freedom of the variables required for position detection. Second embodiment.

[0048] In the first embodiment described above, the positioning calculation is performed using all of the plurality of fixed stations 3 successfully detected by the mobile station 1. However, in the second embodiment, the positioning calculation is performed by selecting the fixed station 3 to be used in order to exclude a distance measurement result between the fixed station 3 and the mobile station 1, which is assumed to have a large distance measurement error, from the positioning calculation.

[0049] Fig. 6 is a diagram showing a functional configuration of a mobile station 1A, which is the position detection device according to the second embodiment. The mobile station 1A includes the fixed station position information storage unit 11, the distance measurement result acquisition unit 12, the inter-fixed station distance calculation unit 13, the coordinate axis selection unit 14, a fixed station selection unit 19 that selects a fixed station 3 to use a distance measurement result in detecting a position from among a plurality of fixed stations 3, the initial value setting unit 15, a positioning calculation unit 16A, the all-axis completion determination unit 17, and the position detection result generation unit 18.Note that the mobile station 1A includes the fixed station selection unit 19 in addition to the components of the mobile station 1, and the positioning calculation unit 16A in place of the positioning calculation unit 16. Other configurations are the same as those of the mobile station 1, so detailed descriptions thereof are omitted here. The following mainly explains differences from the first embodiment.

[0050] Here, the influence of a distance measurement error between the fixed station 3 and the mobile station 1 on the positioning is explained. Fig. 7 is a diagram illustrating an exemplary configuration for a position detection system 100A according to the second embodiment. Fig. 7 shows a state in which no error occurs in the distance measurement.

[0051] The positioning system 100A includes the mobile station 1A and the plurality of fixed stations 3-0 to 3-3. The positions of the mobile station 1A and the fixed station 3 are represented by three-dimensional positions, and the coordinate axes defining the three-dimensional space are an x-axis, a y-axis, and a z-axis. Assume that the positions of the fixed stations 3 are known, the position of the fixed station 3-0 is (x 0 , y 0 , e.g. 0 ), the position of the base station 3-1 is (x 1 , y 1 , e.g. 1 ), the position of the base station 3-2 is (x 2 , y 2 , e.g. 2 ), and the position of the base station 3-3 is (x 3 , y 3 , e.g. 3 ).

[0052] The distance measurement result for the fixed station 3-0 is denoted by R0, the distance measurement result for the fixed station 3-1 is denoted by R1, the distance measurement result for the fixed station 3-2 is denoted by R2 and the distance measurement result for the fixed station 3-3 is denoted by R3. Fig. 7 represents a state where there is no error in the distance measurement results, 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 a point, and in this case, the intersection point is determined as the position of the mobile station 1A.

[0053] Fig. 8 is a diagram illustrating a state where an error occurs in the distance measurement result for the fixed station 3-1 in the position detection system 100A. When waveform distortion due to a reflected wave occurs between the fixed station 3-1 and the mobile station 1A, the distance measurement result R1' for the fixed station 3-1, including an error, tends to be longer than the actual distance R1. In this case, using the distance measurement result R1' to detect the position of the mobile station 1A, a position 51 shifted from the original position 50 is detected.

[0054] If a distance measurement result contains a large error in position determination as described above, the determined position also has a large error. In addition, the error of the distance measurement result tends to be larger as the distance between the mobile station 1A and the fixed station 3 is larger, that is, the larger the distance measurement result is. Therefore, the fixed station selection unit 19 selects the fixed station 3 to be used from among the plurality of fixed stations 3 based on the magnitudes of the distance measurement results. In addition, the positioning calculation unit 16A uses the distance measurement result of the fixed station 3 selected by the fixed station selection unit 19 and excludes the distance measurement result of the fixed station 3 not selected by the fixed station selection unit 19 from the distance measurement results to be used for position calculation.

[0055] With reference to the Fig. Figures 9 to 11 explain the detailed operation of the base station selection unit 19. Assume that the number of base stations is N=4, and the base station 3 to be used is selected from the base stations 3-0 to 3-3. A circle in the drawings indicates the base station 3 to be selected, and a cross in the drawings indicates the base station 3 not to be selected. Fig. 9 is a diagram for explaining a first example of a selection method by the fixed station selection unit 19. In the first example, the fixed station selection unit 19 selects the fixed stations 3-0, 3-2, and 3-3, except for the fixed station 3-1 having a distance measurement result with the maximum value among the plurality of fixed stations 3. Here, it is determined that the distance measurement result with the maximum value has a high probability of containing a distance measurement error due to waveform distortion in the UWB signal. Consequently, the positioning calculation unit 16A excludes the distance measurement result R1 and calculates the position based on the distance measurement results R0, R2, and R3.

[0056] Fig. Fig. 10 is a diagram for explaining a second example of a selection method by the fixed station selection unit 19. In the second example, a predetermined number of fixed stations 3 required for positioning calculation are selected in ascending order of the distance measurement results. The numerical values ​​[1] to [4] in parentheses in Fig. 10 are numbered in ascending order of the distance measurement results. Here, assume that the distance measurement results are R2, R3, R0, and R1 in ascending order of the distance measurement results, and three fixed stations 3 are to be selected. In this case, the fixed station selection unit 19 selects the fixed stations 3-2, 3-3, and 3-0.

[0057] Fig. 11 is a diagram for explaining a third example of a selection method by the base station selection unit 19. In the third example, the base station selection unit 19 selects the base station 3 to be used using a threshold value. There are various ways to set a threshold value, but here the threshold value is set based on the minimum value of the distance measurement result. For example, the base station selection unit 19 can generate the threshold value by multiplying the minimum value of the distance measurement result by a predetermined coefficient. In the Fig. In the example shown in Figure 11, the distance measurement result R2 is the minimum value among the distance measurement results R0 to R3. The base station selection unit 19 may set the threshold value by multiplying the distance measurement result R2 by a predetermined coefficient and select the base station 3 with a distance measurement result smaller than the set threshold value as the base station 3 to be used.

[0058] Fig. Figure 12 is a diagram for explaining the effect of the second embodiment. In the upper figure above the arrow in Fig. 12 is similar to Fig. 8 illustrates a state in which a distance measurement error is included in the distance measurement result R1'. The distance measurement result R1' is longer by Δr1 than the accurate distance measurement result R1, which does not contain a distance measurement error. In this case, the position 51, which is the result of determining the position of the mobile station 1A, is a shifted position from the original position 50.

[0059] On the other hand, as in the Fig. 9 to 11, in a case where the base stations 3 to be used are selected based on the magnitude of the distance measurement results, the distance measurement result R1' of the base station 3-1 is not selected. Therefore, the position of the mobile station 1A is a position 52 determined based on the positions (x 0 , y 0 , e.g. 0 ), (x 2 , y 2 , e.g. 2 ) and (x 3 , y 3 , e.g. 3) of the fixed stations 3-0, 3-2, and 3-3 and the distance measurement results R0, R2, and R3. In this way, since the positioning calculation can be performed based on the distance measurement results R0, R2, and R3, which have no influence of the distance measurement error or have a small distance measurement error, it is possible to reduce the detection error included in the position 52, which is the detection result.

[0060] Fig. 13 is a flowchart for explaining the operation of the mobile station 1A according to the second embodiment. Here, after step S102 of selecting a target coordinate axis, the fixed station selecting unit 19 selects the fixed station 3 to be used (step S201). Thereafter, the initial value setting unit 15 sets the initial value of the position of the mobile station 1A (step S103). The operation is similar to that of the first embodiment, except that step S201 is performed between step S102 and step S103, so the detailed description is omitted here.

[0061] As described above, in addition to the components of the mobile station 1 according to the first embodiment, the mobile station 1A according to the second embodiment includes the fixed station selection unit 19, which selects the fixed station 3 to be used from the plurality of fixed stations 3 based on the magnitude of the distance measurement results. The positioning calculation unit 16A excludes the distance measurement result of the non-selected fixed station 3 from the distance measurement results used for positioning calculation.

[0062] Specifically, the fixed station selection unit 19 selects, as the fixed stations 3 to be used, the fixed stations 3-0, 3-2, and 3-3, except for the fixed station 3-1 having the maximum distance indicated by the distance measurement result, from among the plurality of fixed stations 3-0, 3-1, 3-2, and 3-3. Alternatively, the fixed station selection unit 19 selects a predetermined number of fixed stations 3 in ascending order of the distance indicated by the distance measurement result from among the plurality of fixed stations 3-0, 3-1, 3-2, and 3-3. Alternatively, the fixed station selection unit 19 selects, as the fixed station 3 to be used, the fixed station 3 whose distance indicated by the distance measurement result is equal to or smaller than a threshold value from among the plurality of fixed stations 3-0, 3-1, 3-2, and 3-3.At this time, the threshold value is determined based on the minimum value of the distances indicated by the distance measurement results of the plurality of fixed stations 3-0, 3-1, 3-2, and 3-3. In this way, the position detection accuracy can be further improved by detecting the position of the mobile station 1A while excluding the distance measurement result of the fixed station 3, which is likely to contain an error in the distance measurement result. Third embodiment.

[0063] The third embodiment describes a positioning method that can be used when the position of a mobile station 1B undergoing positioning detection is known in advance on a part of the coordinate axes (namely, some coordinate axes). Such a situation may occur, for example, when the route along which the mobile station 1B moves is limited, such as when the mobile station 1B is mounted in a railway train traveling on a track or in a vehicle traveling on a road.

[0064] Fig. Fig. 14 is a diagram illustrating a configuration of a positioning system 100B according to the third embodiment. Here, it is assumed that the plurality of fixed stations 3 are present on a coordinate axis, and the mobile station 1B moves on a line. Specifically, in the Fig. 14, assume that two fixed stations 3-0 and 3-1 exist on the x-axis, and the mobile station 1B has a known position on the y-axis and a known position on the z-axis. Here, the y-axis position of the mobile station 1B is represented by d, the z-axis position is represented by h, and the position of the mobile station 1B is represented by (x, d, h). Note that the position of the fixed station 3-0 (x 0 , y 0 , e.g. 0 ) and the position of the base station 3-1 (x 1 , y 1 , e.g. 1). In addition, the distance measurement result for the fixed station 3-0 is R0, and the distance measurement result for the fixed station 3-1 is R1. Since the y-axis position and the z-axis position of the mobile station 1B are known, the mobile station 1B only needs to perform position determination for the x-axis position and can even perform position determination with two fixed stations 3.

[0065] Fig. 15 is a diagram showing a functional configuration of the mobile station 1B according to the third embodiment. The mobile station 1B includes the fixed station position information storage unit 11, the distance measurement result acquisition unit 12, the inter-fixed station distance calculation unit 13, the coordinate axis selection unit 14, the initial value setting unit 15B, the positioning calculation unit 16, an all-axis completion determination unit 17B, and the position detection result generation unit 18. The following mainly explains differences from the first embodiment.

[0066] The inter-station distance calculation unit 13 calculates the distance between the fixed stations 3 for each coordinate axis. Since at this time N=2 and the fixed stations 3-0 and 3-1 are arranged on the x-axis, y 0 =y 1 , and for simplicity, using formulas (4) to (6) with z0 =z 1 the distance between the fixed stations 3 on the x-axis is expressed by the following formula (14), the distance between the fixed stations 3 on the y-axis is expressed by the following formula (15), and the distance between the fixed stations 3 on the z-axis is expressed by the following formula (16). Formula 14: ∑n=0N−1∑m=n+1N−1|xn−xm|=|x0−x1| Formula 15: ∑n=0N−1∑m=n+1N−1|yn−ym|=|y0−y1|=0 Formula 16: ∑n=0N−1∑m=n+1N−1|zn−zm|=|z0−z1|=0

[0067] The coordinate axis selection unit 14 selects the x-axis according to the above formulas (14) to (16). The initial value setting unit 15B calculates an average value of the fixed stations 3 with respect to the x-axis, which is the coordinate axis selected by the coordinate axis selection unit 14, and sets the average value as an initial value for the least-squares positioning calculation. For example, in the case of the Fig. 14, since the number of fixed stations is N=2 and the positions on the y-axis and z-axis of the mobile station 1B are known, the initial value setting unit 15B sets the initial value for the positioning calculation to (x in , d, h) using the initial value x in the position on the x-axis, which is expressed by the following formula (17), the initial value y inthe position on the y-axis, which is represented by the following formula (18), and the initial value z in the position on the z-axis, which is expressed by the following formula (19). Note that in a case where the position of the mobile station 1B is calculated in advance in time, this position information may be given as the initial value. Formula 17: xin=1N∑n=0N−1xn=1 / 2(x0+x1) Formula 18: yin=d Formula 19: zin=h

[0068] Based on the position information of each fixed station 3 and the distance measurement result, the positioning calculation unit 16 calculates the position of the mobile station 1B for each coordinate axis based on the least squares method. Here, in a case where the position of the mobile station 1B is determined in the x-axis direction, the position of the mobile station 1B is calculated to (x est, d, h) and the calculation is performed using the initial value x est =x in of the x-axis variable to be subjected to the positioning calculation. The distance r n between the n-th fixed station 3-n and the mobile station 1B is calculated using the following formula (20). Since r n in formula (20) a nonlinear function with respect to x est , the positioning calculation unit 16 sequentially calculates the variable of position detection with respect to the x-axis based on the least squares method by sequential approximation using formula (21) as a norm. Formula 20: rn=(xn−xest)2+(yn−d)2+(zn−h)2 Formula 21: E=∑n=0N−1en2=∑n=0N−1(Rn−rn)2=(R0−r0)2+(R1−r1)2

[0069] In formula (20), n is an integer from zero to N-1. Formula (21) is a concrete example of formula (11) in the case of N=2.

[0070] The positioning calculation unit 16 outputs the x-axis position determination result x est In the third embodiment, since the position of the mobile station 1B for the y-axis and the z-axis is known, the all-axis completion determination unit 17 determines that the position determination for all coordinate axes is completed at a time when the positioning calculation for the x-axis is completed, and outputs the calculation result of the coordinate axis position of the mobile station 1B for each coordinate axis to the position determination result generation unit 18. The position determination result generation unit 18 outputs the position determination result (x est , d, h) of the mobile station 1B.

[0071] In the above case, the positions of the y-axis and z-axis are known, but in a case where only the z-axis position is known, position detection is performed with respect to the x-axis and y-axis. The coordinate axis with a known position can be any of the x-axis, y-axis, and z-axis.

[0072] As described above, according to the third embodiment, in a case where the coordinate axis position on at least one coordinate axis among the coordinate axis positions of all axes (namely, the coordinate axis position on a part of the coordinate axes) is known, the mobile station 1B can perform positioning calculation for each coordinate axis in order from the coordinate axis with the largest distance between the base stations 3 using the known value. Consequently, the number of coordinate axes requiring calculation is reduced, so that the positioning accuracy can be maintained even with a smaller number N of base stations than in the case where calculation is required for all three axes.Such a situation may occur, for example, when the mobile station 1B is attached to a mobile object moving along a predetermined route, and the fixed stations 3 are installed along this route. The mobile object is, for example, a vehicle traveling on a road or a rail vehicle traveling on a track, or the like. If the route is linear and coordinate axes are defined along the route, the mobile station 1B can determine the three-dimensional position of the mobile station 1B solely by determining the position on a single coordinate axis. Fourth embodiment.

[0073] A mobile station 1C according to the fourth embodiment has a function that, in a case where the coordinate axis position of the mobile station 1C for each coordinate axis is restricted to any one of a plurality of axis position candidates for at least one of a plurality of coordinate axes, identifies the position from a plurality of candidates for the position detection result based on the detection error for each candidate.Such a situation may occur, for example, when the mobile station 1C is mounted on a railway vehicle running on a track, and it is not known on which of a plurality of tracks the mobile station 1C runs, or when the track on which the mobile station 1C runs is known in advance and the installation distance of the fixed station 3 with respect to the track has been determined in advance, but it is not known on which side of the track the fixed station 3 will be installed depending on the location.

[0074] The latter situation is discussed with reference to the Fig. 16 and Fig. 17 described. Fig. 16 is a diagram illustrating a first example of a positional relationship between the fixed stations 3 and the mobile station 1C according to the fourth embodiment. Fig. 17 is a diagram illustrating a second example of a positional relationship between the fixed stations 3 and the mobile station 1C according to the fourth embodiment. For example, an xy plane is defined as the ground on which a track is installed, and a direction parallel to the track is defined as the x-axis direction. For example, assume that it is known in advance that a mobile station 1C-1 is mounted on a vehicle traveling on the right-hand side track in the positive x-axis direction, and a mobile station 1C-2 is mounted on a vehicle traveling on the left-hand side track. In a case where the installation specification for the fixed station 3 is that the fixed station 3 is installed at a distance d 1 from the nearest track, there are two possible positional relationships, namely those in Fig. 16 and the positional relationship shown in Fig. 17. Specifically, in a case where, for example, the positive direction of the x-axis is north and the direction from the fixed station 3 to the link is the positive direction of the y-axis, the fixed stations 3-0 and 3-1 can be located on the west side of the mobile stations 1C-1 and 1C-2, as shown in Fig. 16, or on the east side of the mobile stations 1C-1 and 1C-2, as shown in Fig. 17. Here, the function of identifying which candidate is correct based on the detection error when there are a plurality of candidates for the position detection result as described above is described. It should be noted that the mobile stations 1C-1 and 1C-2 are arranged on the left side of the base stations 3-0 and 3-1 in the Fig. 16, when looking in the positive direction of the x-axis on the xy-plane, and thus the state shown in Fig. 16 can be referred to as a case where the mobile station 1C exists on the left side of the base station 3. Similarly, the state shown in Fig. 17 can be referred to as a case where the mobile station 1C is located on the right side of the fixed station 3.

[0075] Fig. 18 is a diagram showing a functional configuration of the mobile station 1C according to the fourth embodiment. The mobile station 1C includes the fixed station position information storage unit 11, the distance measurement result acquisition unit 12, the inter-fixed station distance calculation unit 13, the coordinate axis selection unit 14, the fixed station selection unit 19, an initial value setting unit 15C, a positioning calculation unit 16C, the all-axis completion determination unit 17, the position detection result generation unit 18, a position detection completion determination unit 20, and a position detection result selection unit 21. The following describes mainly differences from the second embodiment.

[0076] The coordinate axis position of the mobile station 1C for each coordinate axis is restricted to one of a plurality of axis position candidates for at least one of the plurality of coordinate axes. It is assumed here that the coordinate axis position of the mobile station 1C is a known value h for the z-axis and one of the known values d 1 and d 2 for the y-axis.

[0077] The initial value setting unit 15C sets a plurality of initial values, where each of the plurality of axis position candidates is used as the coordinate axis position on a restricted axis, i.e., a restricted coordinate axis, here the y-axis. In particular, the initial value setting unit 15C sets two initial values y = d 1 and y = d 2as initial values ​​for the y-axis. The positioning calculation unit 16C calculates two coordinate axis positions for two coordinate axes and error information indicating the degree of detection error with respect to each position using the two initial values ​​set by the initial value setting unit 15C.

[0078] The position detection result generation unit 18 generates two position detection results using the two coordinate axis positions for two coordinate axes and outputs the two position detection results and the error information with respect to each position to the position detection completion determination unit 20.

[0079] Once an assumed number of position detection results and error information are calculated with respect to each position detection result, the position detection completion determination unit 20 determines that the position detection is completed. In the above case, the position detection completion determination unit 20 determines that the position detection is completed once two position detection results and two error information have been calculated.

[0080] The position detection result selecting unit 21 selects a candidate position detection result having the smallest measurement error of positioning from a plurality of candidate position detection results.

[0081] This process is described below using a concrete example. For example, if it is not known whether the mobile station 1C is at the position of the mobile station 1C-1 or the position of the Fig. 16, the mobile station 1C can generate two candidates for the position determination result: y=d 1 and y=d 2 , and set the candidate with the smaller measurement error among the candidates for the position determination result as the position of the mobile station 1C.

[0082] Alternatively, in a case where it is known that the mobile station 1C is at the position of the Fig. 16 or Fig. 17, but it is not known whether the positional relationship between the fixed station 3 and the mobile station 1C corresponds to that shown in Fig. 16 or the condition shown in Fig. 17, the mobile station 1C generates two candidates for the position determination result, ie y=d 1 and y=d 2, and identifies the positional relationship between the mobile station 1C and the fixed station 3 based on the magnitude relationship of the values ​​of the two detection errors.

[0083] Specifically, the position information of the base station 3-0 (x 0 , y 0 , e.g. 0 ) and the position information of the base station 3-1 is (x 1 , y 1 , e.g. 1 ). In addition, the distance measurement results between the base station 3-0 and the mobile station 1C are R0-1 and R0-2, and the distance measurement results between the base station 3-1 and the mobile station 1C are R1-1 and R1-2. In addition, the 1 smaller than d 2 .

[0084] In addition to the calculation result of the coordinate axis position for each coordinate axis, the positioning calculation unit 16 calculates the sum of squares E mkthe distance errors expressed by the following formula (22) as error information indicating a detection error of positioning, and outputs the calculation result. Formula 22: Emk=∑n=0N−1 enm2=∑n=0N−1(Rnm−rnmk)2=(R0m−r0mk)2+(R1m−r1mk)2

[0085] Here, the m-th mobile station 1C is the mobile station 1C-m, and m is an integer from 1 to M, which represents the number of mobile stations 1C. Since the k-th axis position candidate on the y-axis of the mobile station 1C-md k and there are K axis position candidates, k is an integer from one to K. Furthermore, R nm represents a distance measurement result between the n-th fixed station 3-n and the m-th mobile station 1C-m. In addition, r nmk a determination result of the distance between the n-th fixed station 3-n and the m-th mobile station 1C-m using d kand is expressed by the following formula (23). Formula 23: rnmk=(xn−xest)2+(yn−dk)2+(zn−h)2

[0086] If the mobile station 1C is located on the left side of the base station 3, the mobile station 1C-1 is located at the position y=d 1 and the mobile station 1C-2 is located at position y=d 2 , as in Fig. 16. As shown in Fig. 17, the mobile station 1C is located on the right side of the fixed station 3, the mobile station 1C-1 is located at the position y=d 2 and the mobile station 1C-2 is located at position y=d 1 .

[0087] Here, in a case where the positional relationship between the mobile station 1C and the base station 3 is in the state of Fig. 16, with the focus on the sum of squares E mkthe distance error, two initial values ​​y=d 1 and y=d 2 with respect to the y-axis, and in the position detection completion determination unit 20, the position detection is completed as soon as two position detection results with respect to the two initial values ​​and the sums of the squares E 11 and E 12 of the two distance errors are calculated. At this time, for the mobile station 1C-1, the magnitude relationship of the sum of the squares of the distance errors E 11 <E 12 Similarly, for mobile station 1C-2, E 21 >E 22 expected.

[0088] In a case where the positional relationship between the mobile station 1C and the base station 3 is in the state of Fig. 17, with the focus on the sum of squares E mkthe distance error, two initial values ​​y=d 1 and y=d 2 with respect to the y-axis, and in the position detection completion determination unit 20, the position detection is completed as soon as two position detection results with respect to the two initial values ​​and the sums of the squares E 11 and E 12 of the two distance errors are calculated. At this time, for the mobile station 1C-1, the magnitude relationship of the sum of the squares of the distance errors E 11 >E 12 Similarly, for mobile station 1C-2, E 21 <E 22 expected.

[0089] As described above, the magnitude relationship of the sum of the squares of the distance errors varies depending on the positional relationship between the mobile station 1C and the base station 3. Based on this relationship, the mobile station 1C can determine whether the positional relationship between the mobile station 1C and the base station 3 corresponds to the state of Fig. 16 or the condition of Fig. 17. At this time, it is also possible with the two fixed stations 3 to output the detection result of the position of the mobile station 1C with respect to two coordinate axes such as the x-axis and the y-axis.

[0090] Fig. 19 is a flowchart for explaining the operation of the mobile station 1C according to the fourth embodiment. Steps S101 to S106 are the same as those in the second embodiment, except that a plurality of initial values ​​are set using a plurality of values ​​of axis position candidates in step S103, a plurality of coordinate axis positions are calculated for the respective coordinate axes, and error information related to the respective positions is output in step S104, and therefore, the detailed description thereof is omitted here.

[0091] Once the positioning determination result is generated in step S106, the positioning determination completion determination unit 20 determines whether the positioning determination is completed (step S401). In response to a determination that the positioning determination has not been completed (step S401: No), the mobile station 1 returns to step S102. In response to a determination that the positioning determination is completed (step S401: Yes), the positioning determination result selection unit 21 selects a positioning determination result from a plurality of candidate positioning results based on the error information (step S402).

[0092] As described above, in the mobile station 1C according to the fourth embodiment, in a case where the coordinate axis position of the mobile station 1C is restricted to any one of a plurality of axis position candidates for at least one of a plurality of coordinate axes, the positioning calculation unit 16C calculates the coordinate axis position with respect to a coordinate axis excluding a restricted axis, which is the coordinate axis restricted using each of the plurality of axis position candidates as the coordinate axis position of the restricted axis. The position detection result generation unit 18 generates a plurality of candidates for the position detection result using each of the plurality of axis position candidates.The mobile station 1C further includes a determination result selection unit 21 that selects a candidate position determination result with a minimum positioning determination error from the plurality of candidate position determination results. Consequently, the actual position of the mobile station 1C can be determined based on the determination error even when there are a plurality of axis position candidates. At this time, even with a small number of available base stations 3, it is possible to maintain the position determination accuracy while reducing the degree of freedom of the variables required for position determination. Fifth embodiment.

[0093] The above second embodiment described an example in which, since there is a high probability that the error contained in the distance measurement result of the fixed station 3 at a large distance from the mobile station 1A is large, the fixed station 3 to be used is selected based on the magnitude of the distance measurement result. However, it is not necessarily the case that the distance measurement error increases with the distance measurement result. Which fixed station 3 is actually affected by a reflected wave in its distance measurement result cannot be determined solely by the magnitude of the distance measurement result.Therefore, in the fifth embodiment, error information associated with performing the positioning calculation in a plurality of patterns in which combinations of base stations 3 to be used are changed is calculated, and the distance measurement result to be used for the positioning calculation is weighted based on the error information, thereby reducing the influence of the distance measurement result assumed to have low accuracy.

[0094] Fig. 20 is a diagram showing a functional configuration of a mobile station 1D according to the fifth embodiment. The mobile station 1D includes the fixed station position information storage unit 11, the distance measurement result acquisition unit 12, the inter-fixed station distance calculation unit 13, the coordinate axis selection unit 14, a fixed station selection unit 19D, the initial value setting unit 15, a positioning calculation unit 16D, the all-axis completion determination unit 17, a position detection result generation unit 18D, and a position detection completion determination unit 20D. The following describes mainly differences from the fourth embodiment.

[0095] The fixed station selection unit 19D selects the fixed station 3 to be used, so that the positioning calculation device 16D can perform the positioning calculation in a variety of patterns of combinations of the fixed stations 3 to be used. Reference is now made again to Fig. 12. As in Fig. As shown in FIG. 12, in a case where the distance measurement result R1' for the fixed station 3-1 has a large distance measurement error, if the positioning calculation can be performed excluding the distance measurement result R1', it is possible to reduce the influence of the distance measurement error and improve the accuracy of positioning. However, in an actual radio wave propagation time environment, it is unknown which fixed station 3 is affected by distortion by a reflected wave. Therefore, the fixed station selector 19D selects the fixed station 3 to be used such that the "combinations of the fixed stations 3 to be used" are in a plurality of patterns in which the excluded fixed stations 3 are sequentially changed.

[0096] The positioning calculation unit 16D calculates the sum of squares E as error information pThe distance error, expressed by the following formula (24), for a plurality of patterns in which the fixed stations 3-p that are excluded are successively changed. Note that p is an integer from zero to N-1. Formula 24: Ep=∑n=0,n≠pN−1en2=∑n=0,n≠pN−1(Rn−rn)2

[0097] As shown in formula (24), the fixed station selection unit 19D changes the value of the parameter p to change and acquire the parameter p of the sum of the squares of the distance errors from zero to N-1 in order to change the combination of the fixed stations 3 used each time the process of selecting the fixed stations 3 is performed. Specifically, the fixed station selection unit 19D first sets p=0 to select the fixed stations 3 to be used, so that the zeroth fixed station 3-0 is excluded, then sets p=1 to select the fixed stations 3 to be used, so that the first fixed station 3-1 is excluded, and similarly sets p=2 and p=3 to select the fixed stations 3 to be used. For each combination of the fixed stations 3 to be used, the positioning calculation unit 16D calculates the sum of the squares E p the distance error. For example, as in Fig. 12, in a case where the distance measurement result R1' for the fixed station 3-1 has a large distance measurement error, the sum of squares E 1 the distance errors calculated excluding fixed station 3-1 exhibit the smallest value. Furthermore, since fixed station 3-0, which is located at the same position on the x-axis as fixed station 3-1, has a greater degree of dependence than fixed station 3-1, the magnitude relationship of the sum of squares E is expected to be p the distance error E obtained for each base station 3 1 <(E 2 ,E 3 ) <E 0 Since the sum of squares E p the distance error becomes larger as the distance measurement error contained in the distance measurement result Rp for the p-th base station 3-p decreases, it can be noted that E prepresents the degree of dependence or the degree of reliability when using the p-th fixed station 3-p for position determination. A weighting coefficient w n , which is based on this degree of dependence, is expressed, for example, by the following formula (25). Formula 25: wn=En / ∑n=0N−1En

[0098] Here, n stands for the number of fixed stations 3. Here, the normalization is performed with the total value of the sum of the squares of the distance errors for all fixed stations 3, but for simplicity, w n =E n Once the error information for all patterns of the combinations of the base stations 3 to be used has been calculated, the positioning calculation unit 16D determines the position of the mobile station 1D for each coordinate axis using the weighting coefficient w nbased on the least squares method by sequential approximation to minimize the weighted sum of squares E of the distance errors corresponding to the N fixed stations, as expressed in formula (26) below. Formula 26: E=∑n=0N−1wnen2=∑n=0N−1wn(Rn−rn)2

[0099] The all-axis completion determination unit 17 determines whether the positioning calculation for all coordinate axes for which position detection is to be performed is completed. In response to a determination that the positioning calculation for all target coordinate axes is completed, the position detection result generation unit 18 outputs D (x est , y est , e.g. est ) as the position determination result.

[0100] It should be noted that in the above description the weighting coefficient w n which was calculated based on the sum of squares E nthe distance error is calculated and expressed by formula (25); for simplicity, the weighting coefficient w n however, depending on the size of the sum of squares E n the distance error can be set to a value of zero or one, as expressed by the following formula (27). Where ε is a predetermined reliability threshold, and if E n , which indicates the degree of reliability, is smaller than the reliability threshold, the value of the weighting coefficient w n set to zero, and if E n is equal to or greater than the reliability threshold, the value of the weighting coefficient w n is set to one. Consequently, the positioning calculation is performed excluding the distance measurement result of base station 3, whose reliability level is below the reliability threshold. Here, n is an integer from zero to N-1. Formula 27: {wn=0,if En<εwn=1,if En≥ε

[0101] Fig. Fig. 21 is a flowchart for explaining the operation of the mobile station 1D according to the fifth embodiment. Steps S101 and S102 are the same as in Fig. 19 or the like. Subsequently, the base station selection unit 19D selects the base stations 3 to be used (step S501). In step S501, a combination of the base stations 3 to be used is selected such that the base station 3 to be excluded changes each time a selection is made. The following steps S103 to S106 are the same as those in Fig. 19.

[0102] When the positioning calculation for all axes is completed and the reliability level is calculated for each calculation result, the positioning determination completion determining unit 20D determines whether the positioning calculation is completed (step S502). In response to a determination that the positioning calculation has not been completed (step S502: No), the mobile station 1D returns to step S102. In response to the determination that the positioning determination is completed (step S502: Yes), the mobile station 1D executes steps S102 and S103 again and performs a positioning calculation using the weighting coefficient (step S503). Therefore, the all-axis completion determining unit 17 determines whether the positioning calculation for all axes is completed (step S105).In response to a determination that the positioning calculation for all axes has not been completed (step S105: No), the mobile station 1D returns to step S102 after step S502. In response to a determination that the positioning calculation for all axes has been completed (step S105: Yes), the position detection result generation unit 18D generates a position detection result indicating the three-dimensional position of the mobile station 1D based on the calculation result of the weighted positioning calculation (step S504).

[0103] As described above, in the mobile station 1D according to the fifth embodiment, the fixed station selection unit 19D selects a combination of the fixed stations 3 to be used, so that the fixed station 3 to be excluded changes each time. Therefore, the positioning calculation unit 16D can calculate the coordinate axis position for each coordinate axis a plurality of times while changing the distance measurement result to be excluded, and generate error information indicating the degree of detection error of each of a plurality of the calculated coordinate axis positions. The positioning calculation unit 16D can recalculate the coordinate axis position for each coordinate axis based on the distance measurement result weighted by the error information.The position detection result generation unit 18 can generate the position detection result using the coordinate axis position for coordinate axes based on the weighted distance measurement result. Therefore, it is possible to more reliably reduce the influence of the fixed station 3, which introduces an error into the distance measurement result and has low distance measurement accuracy, and improve the position detection accuracy.

[0104] Here, exemplary configurations of 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 will be described. When the processing circuit is formed by a control circuit using a processor, the control circuit is, for example, a control circuit 90 included in Fig. 22 is shown. Fig. 22 is a diagram illustrating a configuration of the control circuit 90 included in the fixed station 3 or the mobile stations 1, 1A, 1B, 1C, and 1D according to the first to fifth embodiments.

[0105] The control circuit 90 includes a processor 91 and a memory 92. In a case where the processing circuit is configured by the control circuit 90 including the processor 91 and the memory 92, each function of the base station 3 or the mobile stations 1, 1A, 1B, 1C, and 1D is implemented by software, firmware, or a combination of software and firmware. The software or firmware is described as a program and is stored in the memory 92. The processor 91 reads the program stored in the memory 92 and executes it to thereby realize the individual functions. That is, the processing circuit includes the memory 92 for storing a program that results in the execution of processing by the base station 3 or the mobile stations 1, 1A, 1B, 1C, and 1D.It can also be noted that these programs cause a computer to execute the operations and methods for the fixed station 3 and the mobile stations 1, 1A, 1B, 1C, and 1D. This program may be provided in a state in which it is stored in a storage medium or may be provided via a communication path.

[0106] The processor 91 is, for example, a central processing unit (CPU), a processing device, an arithmetic device, a microprocessor, a microcomputer, or a digital signal processor (DSP). Examples of the working memory 92 include a non-volatile or volatile semiconductor memory, a magnetic disk, a flexible disk, an optical disk, a compact disc, a mini-disc, a digital versatile disc (DVD), and the like. Examples of non-volatile or volatile semiconductor memories include a random access memory (RAM), a read-only memory (ROM), a flash memory, an erasable programmable ROM (EPROM), an electrical EPROM (EEPROM, registered trademark), and the like.

[0107] 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. Fig. 23 is a diagram showing an example of dedicated hardware included in the base station 3 or the mobile stations 1, 1A, 1B, 1C, and 1D according to the first to fifth embodiments. Fig. The processing circuit 93 illustrated in Figure 23 corresponds, for example, to a single circuit, a compound circuit, a programmed processor, a parallel programmed processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof. The functions of the fixed station 3 or the mobile stations 1, 1A, 1B, 1C, and 1D can be performed separately or collectively by the processing circuit 93.

[0108] It should be noted that some of the functions of the fixed station 3 or the mobile stations 1, 1A, 1B, 1C, and 1D according to the first to fifth embodiments may be implemented by dedicated hardware, while the other functions may be implemented by software or firmware. Thus, the processing circuit may implement any of the functions described above using dedicated hardware, software, firmware, or a combination thereof.

[0109] The configurations described in the above-mentioned embodiments are examples. The embodiments may be combined with each other and with other well-known techniques, and some of the configurations may be omitted or modified to an extent that does not deviate from the core concept.

[0110] For example, in the first to fifth embodiments described above, the mobile stations 1, 1A, 1B, 1C, and 1D are positioning devices that determine the positions of the mobile stations 1, 1A, 1B, 1C, and 1D. However, the technique described in the present embodiments is not limited to such an example, and a device other than the mobile stations 1, 1A, 1B, 1C, and 1D may acquire distance measurement results and perform similar positioning processing. Furthermore, it is not necessary to implement all the functions of the illustrated functional units with one device, and the functions of the positioning device may be shared and implemented by a plurality of devices. Some or all of the functions of the positioning device may be implemented on a cloud server.In a case where all the functions of the positioning device are performed by a cloud server or a device other than the mobile stations 1, 1A, 1B, 1C, and 1D, the distance measurement processing between the mobile stations 1, 1A, 1B, 1C, and 1D and the base station 3 must be performed. Therefore, the distance measurement result acquisition unit 12 acquires the distance measurement results from the mobile stations 1, 1A, 1B, 1C, and 1D or the base station 3. List of reference symbols

[0111] 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 distance measurement result acquisition unit; 13 inter-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 determination unit; 18, 18D position detection result generation unit; 19, 19D fixed station selection unit; 20, 20D position detection completion determination unit; 21 Position detection result selection unit; 50, 51, 52 Position; 90 Control circuit; 91 Processor; 92 Memory; 93 Processing circuit; 100, 100A, 100B Position detection system. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 4567093

[0004]

Claims

[1] A position detecting device that detects a position of a mobile station based on a plurality of distance measurement results measured between each of a plurality of fixed stations and the mobile station using wireless communication, the position detecting device comprising: a positioning calculation unit for calculating a coordinate axis position of the mobile station for each coordinate axis using a position of the fixed stations and the distance measurement results in an order from a coordinate axis having a largest coordinate axis distance between the plurality of fixed stations; and a position detection result generation unit for calculating a position detection result indicating a three-dimensional position of the mobile station based on a calculation result of the coordinate axis position. [2] Position detecting device according to claim 1, further comprising: a base station selection unit for selecting a base station to be used from the plurality of base stations based on the magnitude of the distance measurement results, wherein the positioning calculation unit excludes the distance measurement result of the fixed station which has not been selected from the distance measurement results to be used for the calculation. [3] The position detecting device according to claim 2, wherein the fixed station selecting unit selects, as the fixed station to be used, a fixed station excluding a fixed station having a maximum distance indicated by the distance measurement result from the plurality of fixed stations. [4] The position detecting device according to claim 2, wherein the fixed station selecting unit selects a predetermined number of the fixed stations in descending order of a distance indicated by the distance measurement result from the plurality of fixed stations. [5] The position detecting device according to claim 2, wherein the fixed station selecting unit selects, as the fixed station to be used, a fixed station having a distance indicated by the distance measurement result and equal to or smaller than a threshold value from the plurality of fixed stations. [6] A position detecting device according to claim 5, wherein the threshold value is determined based on a minimum value of the distances of the plurality of fixed stations indicated by the distance measurement results. [7] Position determining device according to one of claims 1 to 6, wherein in a case where the coordinate axis position of the mobile station is restricted to one of a plurality of axis position candidates for at least one of a plurality of coordinate axes, the positioning calculation unit calculates the coordinate axis position with respect to a coordinate axis excluding a restricted axis, which is the coordinate axis restricted using each of the plurality of axis position candidates as the coordinate axis position of the restricted axis, the position detection result generation unit generates a plurality of candidates for the position detection result using each of the plurality of axis position candidates, and the position detection device has a detection result selection unit for selecting a candidate for the position detection result with a minimum detection error of the positioning from the plurality of candidates for the position detection result. [8] Position detecting device according to claim 2, wherein the positioning calculation unit calculates the coordinate axis position a plurality of times while changing the distance measurement result to be excluded, and generates error information indicating a degree of detection error of each of a plurality of the calculated coordinate axis positions, the positioning calculation unit recalculates the coordinate axis position based on the distance measurement result weighted based on the error information, and the position detection result generation unit generates the position detection result using the coordinate axis position based on the weighted distance measurement result. [9] The position detecting device according to claim 8, wherein the positioning calculation unit sets a weighting coefficient of one when a reliability degree of the distance measurement result of the base station based on the error information is equal to or greater than a predetermined reliability threshold, and sets a weighting coefficient of zero when the reliability degree is less than the reliability threshold. [10] A position detecting device according to claim 1, wherein the distance measurement results are obtained based on a transmission / reception timing of a wireless ultra-wideband signal between the fixed stations and the mobile station. [11] The position detecting device according to claim 1, wherein the positioning calculation unit calculates the coordinate axis position based on a least squares method by sequential approximation. [12] Position determination system, comprising: the mobile station comprising the position determining device according to one of claims 1 to 11; and the fixed stations. [13] Position detection system according to claim 12, wherein the mobile station is attached to a mobile object that moves along a predetermined route, and the fixed stations are installed along the route. [14] Positioning system according to claim 13, wherein the mobile object is a rail vehicle running on a track or a vehicle running on a road. [15] Position detection system according to claim 13 or 14, wherein the fixed stations are installed along the route, which is linear, and the position determination device determines a position of the mobile station on a single coordinate axis. [16] A control circuit that controls a position detecting device that detects a position of a mobile station based on a plurality of distance measurement results measured between each of a plurality of fixed stations and the mobile station using wireless communication, the control circuit causing the position detecting device to perform: a step of calculating a coordinate axis position of the mobile station for each coordinate axis using a position of the fixed stations and the distance measurement results in an order starting from a coordinate axis having a largest coordinate axis distance between the plurality of fixed stations; and a step of generating a position detection result indicating a three-dimensional position of the mobile station based on a calculation result of the coordinate axis position. [17] A storage medium storing a program for controlling a position detecting device that detects a position of a mobile station based on a plurality of distance measurement results measured between each of a plurality of fixed stations and the mobile station using wireless communication, the program causing the position detecting device to execute: a step of calculating a coordinate axis position of the mobile station for each coordinate axis using a position of the fixed stations and the distance measurement results in an order starting from a coordinate axis having a largest coordinate axis distance between the plurality of fixed stations; and a step of generating a position detection result indicating a three-dimensional position of the mobile station based on a calculation result of the coordinate axis position. [18] A position detection method for detecting a position of a mobile station based on a plurality of distance measurement results measured between each of a plurality of fixed stations and the mobile station using wireless communication, the position detection method comprising: a step of calculating a coordinate axis position of the mobile station for each coordinate axis using a position of the fixed stations and the distance measurement results in an order starting from a coordinate axis having a largest coordinate axis distance between the plurality of fixed stations; and a step of generating a position detection result indicating a three-dimensional position of the mobile station based on a calculation result of the coordinate axis position.

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