MOBILE BODY AND METHOD FOR ESTIMATING POSITION OF MOBILE BODY

Abstract

To estimate a location of a mobile body highly precisely and at a high update rate.SOLUTION: A mobile body T, which moves in an area installed with a plurality of anchors A1 to An, comprises: a communication unit 2 that communicates intermittently with the plurality of anchors A1 to An via a radio wave; a distance estimation unit 3 that estimates distances each between the mobile body T and each anchor the communication unit 2 communicates with; a location estimation unit 4 that estimates a location of the mobile body T on the basis of the estimated distances; and an anchor selection unit 6 that, in accordance with the estimated location, selects more than three anchors the communication unit 2 communicates with from the plurality of anchors A1 to An, in which the anchor selection unit 6 is configured to select three or more of the anchors with reference to anchor selection information D1 associating the locations within the area with the anchors suitable for the estimation of the location.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for estimating the position of a mobile object, and more particularly to a technique for estimating the position of a mobile object using radio waves other than GPS signals. [Background technology]

[0002] To estimate the position of a mobile object moving in an area where GPS signals cannot reach (such as under a bridge), a system has been proposed in which multiple anchors (ground stations) are installed within the area, wireless communication is performed between the mobile object (tag) and the anchors, and the distance between each anchor and the mobile object is measured to estimate the position (coordinates) of the mobile object.Ultra Wide-Band (UWB) signals in the 3 to 8 GHz frequency range are widely used as radio waves for wireless communication.

[0003] Factors that reduce the accuracy of position estimation of a moving object include: (1) LOS (Line of Sight) or NLOS (Line of Sight), i.e., whether or not there is line of sight (2) Multipath caused by reflected waves (3) Difference between the path length of the reflected wave and the straight-line distance (4) DOP (Dilution of Precision), i.e., the geometrical factor of the positional relationship between the moving body and the anchor. There is.

[0004] The cause of (1) will be explained with reference to Fig. 10. As shown in Fig. 10, when a mobile object T is moving in a room in which an anchor A1 is installed, at the moment when a radio wave blocking object such as a pillar C is present between the anchor A1 and the mobile object T, no direct waves reach the mobile object T from the anchor A1 (NLOS). At this time, radio waves R1 reflected by a highly reflective material such as a metal plate M are not attenuated much, but radio waves R2 reflected by a wall with low reflectivity are attenuated before reaching the mobile object T. In this way, the number of reflections and the absorption rate of the reflective material can make communication unstable, leading to a decrease in the accuracy of position estimation.

[0005] The factors (2) and (3) will be explained with reference to Fig. 11. As shown in Fig. 11, when a mobile object T is moving in a room where two anchors A1 and A2 are installed, at the moment when a radio wave blocking object such as a wall W is present between the anchors A1 and A2 and the mobile object T, direct waves from the anchors A1 and A2 do not reach the mobile object T. At this time, radio waves R1 and R2 from the anchors A1 and A2 reach the mobile object T after being reflected off a metal plate M. However, even though the linear distance L2 between the mobile object T and anchor A2 is shorter than the linear distance L1 between the mobile object T and anchor A1, the path length of the radio wave R2 is longer than that of the radio wave R1. In this way, due to multipath caused by reflected waves, the positional relationship of multiple anchors may be reversed as seen from the mobile object, reducing the accuracy of position estimation. In addition, the difference between the path length of the reflected wave and the straight-line distance, i.e., the difference between the path length of radio wave R1 and the straight-line distance L1, and the difference between the path length of radio wave R2 and the straight-line distance L2, also results in an error in the distance used to calculate the position, thereby reducing the accuracy of position estimation.

[0006] The reason for (3) will be explained with reference to FIGS. 12 and 13. Because distance measurement results using radio waves contain errors, the position of a moving body that can be estimated from one anchor is a strip-shaped range with a width ΔD1. As shown in FIG. 12, when the angle between the direction from the moving body to one anchor A1 and the direction from the moving body to the other anchor A2 is small, the overlapping area of ​​the strip-shaped ranges, i.e., the estimated position of the moving body, is approximately rhombic (ΔD2 > ΔD3). In contrast, as shown in FIG. 13, when the angle between the direction from the moving body to one anchor A1 and the direction from the moving body to the other anchor A2 is approximately a right angle, the overlapping area of ​​the strip-shaped ranges, i.e., the estimated position of the moving body, is approximately square (ΔD2 ≒ ΔD3). Since the approximately diamond-shaped area shown in FIG. 12 is larger than the approximately square-shaped area shown in FIG. 13, the anchors A1 and A2 shown in FIG. 12 have a higher DOP due to their positional relationship with the moving body, resulting in lower position estimation accuracy.

[0007] In response to this, Patent Document 1 discloses an invention that estimates with high accuracy the position of a mobile station (mobile object) moving in an area where multiple base stations (anchors) are installed, taking DOP into consideration. Specifically, a combination of base stations that minimizes accuracy degradation due to DOP at each position in the area is registered in a positioning server as base station combination information, and the positioning server refers to the base station combination information to select a base station to use for positioning and estimate the position of the mobile station. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-249675 Summary of the Invention [Problem to be solved by the invention]

[0009] The invention described in Patent Document 1 requires a positioning server that controls the anchors in addition to the anchors and moving objects, resulting in a complex system configuration. Furthermore, the invention described in Patent Document 1 does not take into account accuracy degradation other than that of the DOP, so it is not possible to estimate positions with high accuracy and at a high update rate in areas with walls or pillars.

[0010] The present invention has been made to solve the above problems, and an object of the present invention is to estimate the position of a moving object with high accuracy and a high update rate using a simple configuration. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention includes the following aspects. Section 1. A moving body that moves in an area where a plurality of anchors are installed, a communication unit that intermittently communicates with the plurality of anchors by radio waves; a distance estimation unit that estimates a distance between each anchor with which the communication unit has communicated and the moving object; a position estimation unit that estimates a position of the moving object based on the estimated distance; an anchor selection unit that selects three or more anchors with which the communication unit will communicate from the plurality of anchors according to the estimated position; Equipped with The anchor selection unit selects the three or more anchors by referring to anchor selection information that associates positions within the region with anchors suitable for estimating the positions. Section 2. In the anchor selection information, each position within the region is (a) an indicator of the stability of communication between the location and each of the plurality of anchors; (b) an indicator regarding the number of paths of the radio waves between the location and each of the plurality of anchors; (c) an indicator of the difference between the path length of the radio wave and the straight-line distance between the location and each of the plurality of anchors; and (d) an indicator of the DOP of the position for the anchor combination; The moving body according to item 1, wherein the moving body is associated with an anchor suitable for the estimation based on at least one of the above. Section 3. 3. The moving body according to item 2, wherein in the anchor selection information, each position within the area is associated with an anchor suitable for the estimation based on the indicators (a) to (d). Section 4. 4. The moving body according to any one of items 1 to 3, wherein the anchor selection unit selects three to five anchors. Section 5. 5. The mobile body according to any one of items 1 to 4, wherein the radio wave is an UWB signal. Section 6. A method for estimating the position of a moving object moving in an area where a plurality of anchors are installed, comprising: a communication step of intermittently communicating with the plurality of anchors by radio waves; a distance estimation step of estimating a distance between each anchor that has performed the communication and the moving object; a position estimation step of estimating a position of the moving object based on the estimated distance; an anchor selection step of selecting three or more anchors with which the communication unit will communicate from the plurality of anchors according to the estimated position; Equipped with The anchor selection step selects the three or more anchors by referring to anchor selection information that associates positions within the region with anchors suitable for estimating the positions. Section 7. Prior to the communicating step, Each location within the region is (a) an indicator of the stability of communication between the location and each of the plurality of anchors; (b) an indicator regarding the number of paths of the radio waves between the location and each of the plurality of anchors; (c) an indicator of the difference between the path length of the radio wave and the straight-line distance between the location and each of the plurality of anchors; and (d) an indicator of the DOP of the position for the anchor combination; a creating step of creating the anchor selection information by associating the anchor with an anchor suitable for the estimation based on at least one of the above; a registration step of registering the anchor selection information in the mobile unit; The method of claim 6 further comprising: Section 8. Prior to the creating step, installing the plurality of anchors within the region; a coordinate determining step of determining coordinates of the plurality of anchors; The method of claim 7 further comprising: Section 9. In the coordinate determination step, Item 9. The method according to item 8, wherein the coordinates of the anchors are determined using a 3D laser scanner and 3D measurement markers provided near each anchor. [Effects of the Invention]

[0012] According to the present invention, the position of a moving object can be estimated with high accuracy and at a high update rate using a simple configuration. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a block diagram showing a schematic configuration of a position estimation system according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram for explaining position estimation of a moving object. [Figure 3] 10 is an example of anchor selection information. [Figure 4] 10 is a flowchart showing the processing steps of a method for estimating the position of a moving object. [Figure 5] FIG. 10 is an explanatory diagram of a method for determining the coordinates of an anchor. [Figure 6] FIG. 2 is a plan view of an area in which a moving body moves. [Figure 7] FIG. 2 is a plan view of an area in which a moving body moves. [Figure 8] (a) to (d) are the MP, DL, DOP, and SS at each measurement point, respectively. [Figure 9] This is a diagram that visualizes the results of evaluation function calculation when all anchors are communication targets. [Figure 10] 10A and 10B are diagrams for explaining a decrease in accuracy of position estimation depending on whether or not there is line of sight. [Figure 11] FIG. 10 is a diagram for explaining a decrease in accuracy of position estimation due to multipath. [Figure 12] FIG. 1 is a diagram for explaining a decrease in accuracy of position estimation due to DOP. [Figure 13] FIG. 1 is a diagram for explaining a decrease in accuracy of position estimation due to DOP. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

[0015] (System Configuration) 1 is a block diagram showing a schematic configuration of a position estimation system 1 according to one embodiment of the present invention. The position estimation system 1 is a system that estimates the position of a moving object T moving in a predetermined area, and includes a plurality of anchors A1 to An installed in the area. For example, the predetermined area is a construction work site, and the moving object T is a worker.

[0016] The number of anchors A1 to An is not particularly limited as long as it is at least 3, but in this embodiment it is n (n≧3). Each of the anchors A1 to An periodically emits a UWB signal, and the UWB signal contains the transmission time and anchor identification information.

[0017] A UWB communication module (tag) is attached to the moving object T. The UWB communication module is, for example, in the form of a chip of about 13 mm×23 mm, and is capable of communicating with each of the anchors A1 to An within a range of up to 300 m.

[0018] The mobile object (tag) T has, as its functional blocks, a memory unit S, a communication unit 2, a distance estimation unit 3, a position estimation unit 4, an alarm unit 5, and an anchor selection unit 6. The memory unit S stores various programs for operating the tag, as well as anchor selection information D1 and restricted area information D2. The communication unit 2, distance estimation unit 3, position estimation unit 4, alarm unit 5, and anchor selection unit 6 can be realized in software terms by executing predetermined programs stored in the memory unit S.

[0019] The communication unit 2 has a function of intermittently communicating with a plurality of anchors A1 to An by radio waves. In this embodiment, the radio waves are UWB signals, but are not limited to this and may be, for example, Wi-Fi signals.

[0020] The distance estimation unit 3 has a function of estimating the distance between each anchor with which the communication unit 2 has communicated and the moving body T. For example, when the communication unit 2 has communicated with an anchor Ak (3≦k≦n), the distance estimation unit 3 estimates the distance between the anchor Ak and the moving body T from the difference between the transmission time included in the UWB signal received from the anchor Ak and the time the communication unit 2 received the UWB signal.

[0021] The position estimation unit 4 has a function of estimating the position of the moving body T based on the distance estimated by the distance estimation unit 3. For example, as shown in Fig. 2, if the coordinates of anchors A1, A2, A3, and A4 are (x1, y1, z1), (x2, y2, z2), (x3, y3, z3), and (x4, y4, z4), respectively, and the distances between anchors A1, A2, A3, and A4 and moving body T are estimated to be d1, d2, d3, and d4, respectively, the coordinates (x, y, z) of moving body T are estimated by solving the following equations.

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[0022] At least three anchors are required to estimate the position of mobile unit T. As the number of anchors to communicate with increases, the accuracy of position estimation improves, but the update rate of position estimation decreases.

[0023] The alarm unit 5 has a function of issuing an alarm to the worker, which is the mobile object T, when the position estimated by the position estimation unit 4 is within a predetermined area. The restricted area information D2 stored in the memory unit S includes the coordinates of the restricted areas at the work site. The alarm unit 5 refers to the restricted area information D2 to determine whether the estimated position of the mobile object T is within a restricted area, and issues an alarm by voice or the like when the estimated position is within a restricted area.

[0024] The anchor selection unit 6 has a function of selecting three or more anchors with which the communication unit 2 will communicate from the plurality of anchors A1 to An, according to the position estimated by the position estimation unit 4. More specifically, the anchor selection unit 6 selects the three or more anchors by referring to anchor selection information D1 that associates positions within an area with anchors suitable for estimating the positions.

[0025] 3 is an example of the anchor selection information D1. In the anchor selection information D1, the coordinate column represents each position within the region, and 121 positions (x, y) = (1, 1) to (11, 11) are registered. In this embodiment, the z coordinate (height) within the region is the same, so it is omitted.

[0026] In the anchor selection information D1, each position is (a) an index relating to the stability of communication between the location and each anchor A1 to An; (b) an index relating to the number of paths of the radio waves between the position and each of the anchors A1 to An; (c) an index relating to the difference between the path length of the radio wave and the straight-line distance between the position and each of the anchors A1 to An; and (d) Indicator for DOP at the position for the combination of anchors A1 to An Based on this, the position of the moving object T is associated with 3 to 5 anchors that are suitable for estimating the position of the moving object T. A specific example of the association will be described later.

[0027] For example, if the position (x, y) estimated by the position estimation unit is (1, 2), the anchor selection unit 6 selects four anchors A1, A2, A5, and A6. In this case, the communication unit 2 communicates with only the four anchors A1, A2, A5, and A6 selected by the anchor selection unit 6, thereby enabling the distance estimation unit 3 and the position estimation unit 4 to accurately and quickly estimate the position of the moving object T.

[0028] In contrast, in conventional position estimation methods, the communication unit 2 always communicates with all anchors A1 to An regardless of their position within the area, making it impossible to perform position estimation quickly and resulting in a low update rate. In contrast, in this embodiment, anchors suitable for position estimation are registered in advance for each position in the anchor selection information D1, making it possible to limit the anchors with which communication will occur. Therefore, it is possible to improve the update rate while maintaining the position estimation accuracy.

[0029] Furthermore, in this embodiment, the anchor selection information D1 is registered in the moving body T, and the moving body T selects an anchor suitable for position estimation by referring to the anchor selection information D1, so there is no need for the positioning server described in Patent Document 1. Therefore, with a simple configuration, the position of the moving body can be estimated with high accuracy and a high update rate.

[0030] Furthermore, in this embodiment, when selecting anchors, not only the index related to DOP but also the index related to communication stability (LOS or NLOS) and the index related to the number of radio wave paths (multipath) are taken into consideration as in (a) to (c) above. Therefore, even in areas with walls and pillars, position estimation with high accuracy and a high update rate is possible.

[0031] (Processing Procedure) FIG. 4 is a flowchart showing the processing steps of the method for estimating the position of a moving object in this embodiment.

[0032] In step S1 (setting step), a plurality of anchors are set within an area in which the moving body moves.

[0033] In step S2 (coordinate determination step), the coordinates of the multiple anchors are determined. FIG. 5 is an explanatory diagram of a method for determining anchor coordinates. The positions of the circles in FIG. 5(a) indicate the installation positions of the anchors, and as shown in FIG. 5(b), 3D measurement markers are provided near the anchors. Then, using a 3D laser scanner shown in FIG. 5(c), objects such as buildings are converted into a point cloud with high precision (error of 1 mm or less), and the coordinates of the anchors are measured based on the 3D measurement markers. This makes it possible to efficiently acquire the surrounding environment of the anchor and the coordinates of the anchor, and based on the acquired 3D data, it is possible to specify the range in which radio waves can propagate by a clipping operation. The form of the 3D measurement marker is not particularly limited as long as it can be recognized by the 3D laser scanner.

[0034] In step S3 (creation step) shown in FIG. 4, anchor selection information D1 is created. Specifically, each position in the area is (a) an indicator of the stability of communication between the location and each of the plurality of anchors; (b) an indicator regarding the number of paths of the radio waves between the location and each of the plurality of anchors; (c) an indicator of the difference between the path length of the radio wave and the straight-line distance between the location and each of the plurality of anchors; and (d) an indicator of the DOP of the position for the anchor combination; Based on this, the anchor selection information D1 is generated by associating the information with an anchor suitable for the estimation. A specific example of generating the anchor selection information D1 will be described with reference to FIGS.

[0035] Figure 6 is a plan view of the area in which the moving object moves. The area is a square room, and in the center there is a square wall with gaps on all four sides. The cross marks indicate measurement points to be registered in the anchor selection information D1, totaling 121 points, 11 vertically and 11 horizontally. The black circles indicate anchor positions. The anchor suitable for position estimation at each measurement point is determined by the following steps (1) to (6).

[0036] (1) Using the ray tracing method, calculate the minimum number of reflections along the propagation path from each anchor to the measurement point. The number is 0 for LOS and 1 or more for NLOS.

[0037] (2) Select k anchors from all anchors (called an anchor group) and calculate the total number of reflections from these anchors to the measurement point, MP. For example, as shown in Figure 7, if the four anchors below measurement point P are selected, MP = 0 + 0 + 0 + 1 = 1. This is done for all measurement points to calculate MP at each measurement point. Then, for each measurement point, the top anchor group with the smallest MP is left. This leaves multiple anchor groups that are less affected by multipath. Figure 8(a) shows the MP of the remaining anchor groups at each measurement point.

[0038] (3) Using the ray tracing method, the sum of the differences dLi between the radio wave path length Ri and the straight-line distance Li between each anchor and the measurement point is calculated as the evaluation value DL.

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[0039] For example, for the measurement points where anchors A1 and A2 and moving body T are located as shown in Figure 11, dL1 = R1 - L1 and dL2 = R2 - L2, so DL = dL1 + dL2 = (R1 - L1) + (R2 - L2). This is performed for all measurement points to determine DL at each measurement point. Figure 8(b) shows DL at each measurement point.

[0040] (4) For the remaining anchor group, calculate the DOP and signal strength (SS) at each measurement point. Figures 8(c) and (d) show the DOP and SS at each measurement point.

[0041] For example, when communicating with three anchors, the DOP is calculated as follows: Let the coordinates of the measurement point p be (x, y, z), and the coordinates of each anchor be p i (i = integer from 1 to 3) to (x i , y i , z i ), p and p i The distance between l i Then,

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[0042] D T The inverse matrix of D gives a 3x3 matrix, whose diagonal elements are the squares of the DOP in the X, Y, and Z directions. These values ​​are called XDOP, YDOP, and ZDOP, respectively. T The inverse matrix Q of D is shown with off-diagonal elements omitted.

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[0043] The DOP related to the estimated position error in three-dimensional space is called PDOP (Position DOP), and similarly, the DOP related to the estimated position error in the horizontal and vertical directions is called HDOP (Horizontal DOP) and VDOP (Vertical DOP), respectively. These can be calculated by adding up the diagonal elements of matrix Q and taking the square root, as follows:

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[0044] In this embodiment, the estimation error in the three-dimensional space is basically evaluated, so the PDOP is basically used as the DOP, but the present invention is not limited to this.

[0045] (5) Normalize the DOP, SS, MP, and DL at each measurement point. For example, to normalize the DOP, remove the minimum value in the DOP as an offset value from all elements of the matrix shown in Figure 8(c), and then divide the matrix after removing the offset by the maximum value in the matrix. The same applies to normalizing the SS, MP, and DL.

[0046] (6) For the normalized DOP, MP, DL, and SS, calculate the rate of decline in positioning reliability using the evaluation function below, and the anchor group with the smallest evaluation value J is determined as the k anchors to communicate with at that measurement point.

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[0047] Figure 9 visualizes the results of the evaluation function calculation when all anchors are targets of communication. The blue area is the area where the evaluation value J is low (high positioning accuracy), and the yellow area is the area where the evaluation value J is high (low positioning accuracy).

[0048] As a result of the above, each position within the area is associated with a communication target anchor suitable for position estimation, and anchor selection information D1 is created.

[0049] Referring again to Fig. 4, in step S4 (registration step), the created anchor selection information D1 is registered in the moving body T. This completes the construction of the position estimation system 1 shown in Fig. 1.

[0050] Subsequently, in step S5 (communication step), the communication unit 2 of the moving object T starts communication with the plurality of anchors A1 to An by UWB signals. After starting, in the first communication, the communication unit 2 communicates with all the anchors with which it can communicate.

[0051] In step S6 (distance estimation step), the distance estimation unit 3 of the moving body T estimates the distance between the moving body T and each anchor with which the communication unit 2 has communicated.

[0052] In step S7 (position estimation step), the position estimation unit 4 of the moving object T estimates the position of the moving object T based on the distance estimated by the distance estimation unit 3.

[0053] In step S8, the anchor selection unit 6 of the moving body T refers to the anchor selection information D1 and determines whether the position estimated by the position estimation unit 4 is registered in the anchor selection information D1. If the accuracy of the estimated position coordinate values ​​is greater than the accuracy of the coordinate values ​​registered in the anchor selection information D1 (for example, if the estimated position coordinate values ​​have two decimal places and the registered coordinate values ​​have one decimal place), the anchor selection unit 6 may round off the estimated position coordinate values ​​and compare the result with the registered coordinate values.

[0054] If the estimated position is registered in the anchor selection information D1 (YES in step S9), the process proceeds to step S10 (anchor selection step), where the anchor selector 6 selects an anchor (anchor group) associated with the position. Then, in step S11, the communication unit 2 communicates with the anchor selected by the anchor selector 6, and thereafter, steps S6 to S8 are repeated.

[0055] If the position estimated by the position estimation unit 4 is not registered in the anchor selection information D1 (NO in step S9), the process proceeds to step S12, and the communication unit 2 ends communication.

[0056] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0057] For example, in the above embodiment, in the anchor selection information D1 shown in FIG. 1, each position in the area in which the moving object T moves is (a) an index relating to the stability of communication between the location and each anchor A1 to An; (b) an index relating to the number of paths of the radio waves between the position and each of the anchors A1 to An; (c) an index relating to the difference between the path length of the radio wave and the straight-line distance between the position and each of the anchors A1 to An; and (d) Based on an index relating to the DOP of the position for a combination of anchors A1 to An, the combination is associated with 3 to 5 anchors suitable for estimating the position of the moving body T, but the association may be based on at least one of (a) to (d). Furthermore, the number of associated anchors is not particularly limited, but the update rate decreases as the number of communicating anchors increases, so the number is preferably 3 to 5.

[0058] Furthermore, in the above embodiment, the mobile object T is a worker, but it may also be, for example, a ground mobile robot or a drone. [Explanation of symbols]

[0059] 1. Location estimation system 2. Communications Department 3. Distance estimation unit 4 Position estimation part 5 Alarm section 6 Anchor selection section A1~An anchor D1 Anchor selection information D2 Restricted Area Information S storage section T Mobile

Claims

1. A moving body that moves in an area where a plurality of anchors are installed, a communication unit that intermittently communicates with the plurality of anchors by radio waves; a distance estimation unit that estimates a distance between each anchor with which the communication unit has communicated and the moving object; a position estimation unit that estimates a position of the moving object based on the estimated distance; an anchor selection unit that selects three or more anchors with which the communication unit will communicate from the plurality of anchors according to the estimated position; Equipped with The anchor selection unit selects the three or more anchors by referring to anchor selection information that associates a position within the region with an anchor suitable for estimating the position, the mobile body, In the anchor selection information, each position within the region is (a) an indicator of the stability of communication between the location and each of the plurality of anchors; (b) an indicator relating to the number of paths of the radio waves between the location and each of the plurality of anchors; (c) an indicator relating to the difference between the path length of the radio wave and the straight-line distance between the location and each of the plurality of anchors; and (d) an indicator of the DOP at the position for the anchor combination; The mobile object is associated with an anchor suitable for the estimation based on the above.

2. 2. The mobile body according to claim 1, wherein the anchor selection unit selects three to five anchors.

3. 3. The mobile body according to claim 1, wherein the radio wave is an UWB signal.

4. A method for estimating the position of a moving object moving in an area where a plurality of anchors are installed, comprising: a communication step of intermittently communicating with the plurality of anchors by radio waves; a distance estimation step of estimating a distance between each anchor that has performed the communication and the moving object; a position estimation step of estimating a position of the moving object based on the estimated distance; an anchor selection step of selecting three or more anchors with which the mobile unit will communicate from the plurality of anchors according to the estimated location; Equipped with In the anchor selection step, the three or more anchors are selected by referring to anchor selection information that associates a position within the region with an anchor suitable for estimating the position, Prior to the communicating step, Each location within the region is (a) an indicator of the stability of communication between the location and each of the plurality of anchors; (b) an indication of the number of paths of the radio wave between the location and each of the plurality of anchors; and (c) an indicator relating to the difference between the path length of the radio wave and the straight-line distance between the location and each of the plurality of anchors; and (d) an indicator of the DOP at the position for the anchor combination; a creating step of creating the anchor selection information by associating the anchor selection information with an anchor suitable for the estimation based on the above; a registration step of registering the anchor selection information in the mobile unit; The method further comprises:

5. The method described in claim 4, wherein the creation step comprises the following steps (1) to (6). (1) Calculate the minimum number of reflections along the propagation path of the radio wave from each anchor to each position. (2) Select k (3≦k≦n, n≧3) anchors from all anchors, calculate the sum MP of the minimum number of reflections from the selected anchors to each position, and at each position, keep the top anchors with the smallest MP. (3) The sum of the differences dLi between the radio wave path length Ri and the straight-line distance Li between each anchor and the measurement point is calculated as an evaluation value DL. (4) For the anchor group remaining in (2) above, calculate the DOP and radio wave strength SS at each position. (5) Normalize DOP, MP, DL and SS at each position. (6) For the normalized DOP, MP, DL, and SS, an evaluation value J is calculated using the following evaluation function, and the anchor group for which J is smallest is determined as the anchor to be associated with the position. where W dop , W mp , W dmpl and W ss are weighting factors for DOP, MP, DL and SS, respectively.

6. Prior to the creating step, installing the plurality of anchors within the region; a coordinate determining step of determining coordinates of the plurality of anchors; The method of claim 5 further comprising:

7. In the coordinate determination step, 7. The method of claim 6, wherein the coordinates of the anchors are determined using a 3D laser scanner and 3D measurement markers provided near each anchor.

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