Positioning system

Abstract

This positioning system comprises a first transmitter, a second transmitter, a third transmitter, a receiver, and an arithmetic device. The first transmitter transmits a first signal having the directivity of a spheroid. The second transmitter transmits a second signal having the directivity of a spheroid, and is arranged at a position different from that of the first transmitter. The third transmitter transmits a third signal having the directivity of a spheroid, and is arranged at a position different from those of the first transmitter and the second transmitter. The receiver receives the first signal and detects first distance information, receives the second signal and detects second distance information, and receives the third signal and detects third distance information. The arithmetic device calculates positional coordinates of the receiver from the first distance information, the second distance information, and the third distance information. The arithmetic device sets the positions of the first transmitter, the second transmitter, the third transmitter, and the receiver, and a geometric equation of the spheroid. The arithmetic device sets a geometric equation of a sphere by converting the geometric equation of the spheroid on the basis of the aspect ratio between the directivity of the spheroid and the directivity of the sphere. The arithmetic device calculates temporary positional coordinates of the receiver using the geometric equation of the sphere. The arithmetic device calculates positional coordinates from the temporary positional coordinates by inverse transformation based on the aspect ratio.

Description

Positioning system

[0001] This invention relates to a positioning system using elliptical directional signals.

[0002] Patent Document 1 describes a positioning system.

[0003] The positioning device described in Patent Document 1 receives sound waves for positioning from multiple positioning devices. The positioning system described in Patent Document 1 calculates the position coordinates of the positioning device based on the propagation time of the multiple sound waves received by the positioning device.

[0004] The positioning system described in Patent Document 1 calculates the position coordinates of the device to be positioned by setting geometric equations based on the assumption that sound waves for positioning propagate isotropically.

[0005] Patent No. 6184620 specification

[0006] Typically, positioning signals have spherical directivity, meaning their propagation characteristics do not change with direction.

[0007] However, in some cases, it is preferable for the propagation characteristics of the positioning signal (for example, the sound wave for positioning described in Patent Document 1) to be anisotropic. For example, it may be preferable to use a spheroid for the directivity of the positioning signal. In this case, the positioning system described in Patent Document 1 cannot calculate position coordinates with high accuracy.

[0008] Therefore, the object of the present invention is to calculate position coordinates with high accuracy using a positioning signal having the directionality of a rotating ellipsoid.

[0009] A positioning system according to one embodiment of the present invention comprises a first transmitter, a second transmitter, a third transmitter, a receiver, and a computing device. The first transmitter transmits a first signal having the directionality of a spheroid. The second transmitter transmits a second signal having the directionality of a spheroid and is positioned at a different location from the first transmitter. The third transmitter transmits a third signal having the directionality of a spheroid and is positioned at a different location from the first and second transmitters. The receiver receives the first signal and detects first distance information, receives the second signal and detects second distance information, and receives the third signal and detects third distance information. The computing device calculates the position coordinates of the receiver using the first distance information, the second distance information, and the third distance information.

[0010] The computing unit sets the positions of the first transmitter, second transmitter, third transmitter, and receiver, as well as the geometric equations of the ellipsoid. The computing unit transforms the geometric equations of the ellipsoid based on the aspect ratio between the directivity of the ellipsoid and the directivity of the sphere to set the geometric equations of the sphere. The computing unit calculates the provisional position coordinates of the receiver using the geometric equations of the sphere. The computing unit calculates the position coordinates from the provisional position coordinates by an inverse transformation based on the aspect ratio.

[0011] In this configuration, the geometric equations of the ellipsoid are set based on the directivity of the ellipsoids of the first, second, and third signals, and then transformed by the aspect ratio to set the geometric equations of the sphere. This allows the receiver's position coordinates to be calculated using the geometric equations of the sphere. Subsequently, by inversely transforming the receiver's position coordinates by the aspect ratio, it is possible to return to the coordinate system of the ellipsoid and calculate the receiver's position coordinates.

[0012] According to this invention, position coordinates can be calculated with high accuracy using a positioning signal having the directionality of a rotating ellipsoid.

[0013] Figure 1 is a functional block diagram showing an example of the configuration of a positioning system according to the first embodiment. Figure 2(A) is a diagram showing an example of the application of a receiver and multiple transmitters according to the first embodiment, and Figure 2(B) is a diagram showing the positional relationship between the receiver and multiple transmitters according to the first embodiment in an xyz coordinate system. Figure 3 is a diagram showing the positioning concept of the positioning system according to the first embodiment. Figure 4 is a flowchart showing an example of a positioning method according to the first embodiment. Figure 5 is a diagram showing an example of the positional relationship between a receiver and multiple transmitters in a positioning system according to the second embodiment. Figure 6 is a diagram showing an example of the positional relationship between a receiver and multiple transmitters in a positioning system according to the third embodiment. Figure 7 is a diagram showing an example of the application of the positioning system according to the third embodiment.

[0014] [First Embodiment] A positioning system according to the first embodiment of the present invention will be described with reference to the figures. Figure 1 is a functional block diagram showing an example of the configuration of the positioning system according to the first embodiment. Figure 2(A) is a diagram showing an example of the application of a receiver and a plurality of transmitters according to the first embodiment, and Figure 2(B) is a diagram showing the positional relationship between the receiver and the plurality of transmitters according to the first embodiment in an xyz coordinate system. Figure 3 is a diagram showing the positioning concept of the positioning system according to the first embodiment. In the following embodiments, "same," "identical," and "parallel" include within an acceptable range of error for the positioning system 10.

[0015] As shown in Figure 1, the positioning system 10 includes a first transmitter 21, a second transmitter 22, a third transmitter 23, a receiver 30, a computing device 40, and a display 50. However, the positioning system 10 only needs to include at least the first transmitter 21, the second transmitter 22, the third transmitter 23, the receiver 30, and the computing device 40.

[0016] The first transmitter 21 is equipped with a transmitting antenna and transmits a first signal. The second transmitter 22 is equipped with a transmitting antenna and transmits a second signal. The third transmitter 23 is equipped with a transmitting antenna and transmits a third signal. The first signal, the second signal, and the third signal are composed of, for example, electromagnetic waves. The first signal, the second signal, and the third signal have the same directivity.

[0017] The directivity of the first signal, the second signal, and the third signal is that of a spheroid. The directivity of a spheroid is a directivity with an axis of rotation, which has orthogonal major and minor axis directions. For example, as shown in the upper diagrams of Figures 2(A) and 3, the radio wave intensity (propagated power) at a unit distance from the transmitting antenna along the major axis, which is the axis of rotation, is higher than the radio wave intensity (propagated power) at a unit distance from the transmitting antenna along the minor axis. Note that the spheroid is not limited to one that covers all directions, but also includes those that are spheroids in a partial range of directions.

[0018] As shown in Figures 2(A) and the upper part of Figure 3, the first transmitter 21, the second transmitter 22, and the third transmitter 23 are positioned in different locations, more specifically, not all of them are aligned in a straight line. The first transmitter 21, the second transmitter 22, and the third transmitter 23 are arranged on the same plane (transmitter mounting surface).

[0019] The first transmitter 21, the second transmitter 22, and the third transmitter 23 are arranged so that one rotation axis (the long axis in the case of Figure 3) of their respective directivity is perpendicular to the transmitter mounting surface and parallel to each other.

[0020] The first signal, the second signal, and the third signal are configured in a way that makes them identifiable by the receiver 30. For example, the first signal, the second signal, and the third signal are each superimposed with a code that makes them identifiable. Also, for example, the first signal, the second signal, and the third signal are configured to have different frequencies within an identifiable range.

[0021] The receiver 30 includes a receiving antenna, a distance information detection unit 31, and a distance information transmission unit 32.

[0022] The receiving antenna preferably has isotropic directivity (spherical directivity) for receiving signals. The receiving antenna receives the first signal, the second signal, and the third signal.

[0023] The distance information detection unit 31 detects first distance information based on a first signal received by a reception antenna. The first distance information is, for example, the received radio wave intensity (received power amount) of the first signal at the reception antenna. The distance information detection unit 31 detects second distance information based on a second signal received by the reception antenna. The second distance information is, for example, the received radio wave intensity (received power amount) of the second signal at the reception antenna. The distance information detection unit 31 detects third distance information based on a third signal received by the reception antenna. The third distance information is, for example, the received radio wave intensity (received power amount) of the third signal at the reception antenna.

[0024] The distance information transmission unit 32 transmits the first distance information, the second distance information, and the third distance information to the arithmetic device 40.

[0025] The arithmetic device 40 includes a distance information reception unit 41, a positioning calculation unit 42, and an aspect conversion unit 43.

[0026] The distance information reception unit 41 receives the first distance information, the second distance information, and the third distance information.

[0027] The positioning calculation unit 42 uses the first distance information, the second distance information, and the third distance information, and uses a geometric equation of a spheroid related to the positions of the first transmitter 21, the second transmitter 22, the third transmitter 23, and the receiver 30, an aspect ratio α, and a geometric equation of a sphere obtained by converting the geometric equation of the spheroid to calculate a provisional position coordinate of the receiver 30. The geometric equation of the spheroid is based on the directivity of the first signal, the second signal, and the third signal (the directivity of the spheroid).

[0028] Specifically, the positioning calculation unit 42 calculates the provisional position coordinate of the receiver 30 as follows.

[0029] The positioning calculation unit 42 acquires the position coordinates (x1, y1, z1) of the first transmitter 21, the position coordinates (x2, y2, z2) of the second transmitter 22, and the position coordinates (x3, y3, z3) of the third transmitter 23. The position coordinates (x1, y1, z1) of the first transmitter 21, the position coordinates (x2, y2, z2) of the second transmitter 22, and the position coordinates (x3, y3, z3) of the third transmitter 23 can be acquired from a storage unit (not shown) of the arithmetic device 40, or can be acquired from an external server device. Furthermore, the position coordinates (x1, y1, z1) of the first transmitter 21, the position coordinates (x2, y2, z2) of the second transmitter 22, and the position coordinates (x3, y3, z3) of the third transmitter 23 can be acquired as information superimposed on the first signal, the second signal, and the third signal, respectively.

[0030] The positioning calculation unit 42 sets the position coordinates (x, y, z) of the receiver 30 as unknowns, and the position coordinates (x1, y1, z1) of the first transmitter 21, the position coordinates (x2, y2, z2) of the second transmitter 22, and the position coordinates (x3, y3, z3) of the third transmitter 23 as knowns, and sets a simultaneous geometric equation of a spheroid constituted by (Equation 11), (Equation 12), and (Equation 13). At this time, setting is performed such that the xy plane coincides with the transmitter installation surface.

[0031] (x-x1) ２ / a1 ２ +(y-y1) ２ / a1 ２ +(z-z1) ２ / b1 ２ =1 (Equation 11) (x-x2) ２ / a2 ２ +(y-y2) ２ / a2 ２ +(z-z2) ２ / b2 ２ =1 (Equation 12) (x-x3) ２ / a3 ２ +(y-y3) ２ / a3 ２ +(z-z3) ２ / b3 ２= 1 (Equation 13) In these equations, a1 and b1 are constants based on the first distance information and the directivity of the first signal. The aspect ratio α of the directivity of the first signal is given by α = b1 / a1. Similarly, a2 and b2 are constants based on the second distance information and the directivity of the second signal. The aspect ratio α of the directivity of the second signal is given by α = b2 / a2. a3 and b3 are constants based on the third distance information and the directivity of the third signal. The aspect ratio α of the directivity of the third signal is given by α = b3 / a3.

[0032] The positioning calculation unit 42 acquires the aspect ratio α. The aspect ratio α can be acquired from the storage unit of the calculation device 40 (not shown) or from an external server device.

[0033] The geometric equations of the ellipsoid are transformed by the aspect ratio α to obtain a system of geometric equations for a sphere consisting of (Equation 21), (Equation 22), and (Equation 23).

[0034] More specifically, the position coordinates (x, y, z) of the receiver 30 are converted to position coordinates (X, Y, Z). Here, the relationships are X = x, Y = y, and Z = (1 / α)z.

[0035] The position coordinates (x1, y1, z1) of the first transmitter 21 are converted to position coordinates (X1, Y1, Z1). Here, the relationships are X1 = x1, Y1 = y1, and Z1 = (1 / α)z1.

[0036] The position coordinates (x2, y2, z2) of the second transmitter 22 are converted to position coordinates (X2, Y2, Z2). Here, the relationships are X2 = x2, Y2 = y2, and Z2 = (1 / α)z2.

[0037] The position coordinates (x3, y3, z3) of the third transmitter 23 are converted to position coordinates (X3, Y3, Z3). Here, the relationships are X3 = x3, Y3 = y3, and Z3 = (1 / α)z3.

[0038] (X-X1) ２ / a1 ２ + (Y - Y1) ２ / a1 ２ + (Z-Z1) ２ / a1 ２ =1 (Formula 21) (X-X2) ２ / a2 ２ + (Y - Y2) ２ / a2 ２ + (Z-Z2) ２ / a2 ２ =1 (Formula 22) (X-X3) ２ / a3 ２ + (Y - Y3) ２ / a3 ２ + (Z-Z3) ２ / a3 ２ = 1 (Equation 23) By performing such a transformation, the geometric equations of a system of ellipsoids can be transformed into the geometric equations of a system of spheres. This transformation can be represented in a diagram as shown in Figure 3. The upper part of Figure 3 shows the relationship of position coordinates corresponding to the geometric equations of a system of ellipsoids, and the lower part of Figure 3 shows the relationship of position coordinates corresponding to the geometric equations of a system of spheres.

[0039] In equations (21), (22), and (23) set up in this manner, the first distance information is substituted into a1, the second distance information into a2, and the third distance information into a3.

[0040] This allows the provisional position coordinates Prtmp of the receiver 30 to be calculated using a system of geometric equations for a sphere.

[0041] The positioning calculation unit 42 performs an inverse aspect transformation on the provisional position coordinates Prtmp(X, Y, Z) using the aspect ratio α. That is, the positioning calculation unit 42 calculates the true position coordinates P(xt, yt, zt) = (X, Y, αZ) of the receiver 30.

[0042] Through this process, the positioning calculation unit 42 can calculate the position coordinates of the receiver 30 with high accuracy.

[0043] For example, if the error in calculating the position coordinates of the receiver 30 using the position coordinates of the first transmitter 21, the second transmitter 22, the third transmitter 23, the first distance information, the second distance information, and the third distance information directly with the geometric equations of a sphere, without performing the above-mentioned conversion process using aspect ratio α, is 0.19 m, then performing the above process can reduce the error to 0 m. These results were calculated under the following conditions: The first transmitter 21, the second transmitter 22, and the third transmitter 23 are arranged on the same plane. The center coordinates of the first transmitter 21, the second transmitter 22, and the third transmitter 23 are set to (x, y, z) = (0, 0, 0). The coordinates of the first transmitter 21 are (0, -1.5, 0), the coordinates of the second transmitter 22 are (1.3, 0.75, 0), and the coordinates of the third transmitter 23 are (-1.3, 0.75, 0). The coordinates of the receiver 30 are (0, 0, 5). These are set in meters. Furthermore, the first signal, the second signal, and the third signal are signals with a minor axis:major axis ratio of 1:1.6 (aspect ratio of 0.625).

[0044] The positioning calculation unit 42 outputs the final calculated position coordinates of the receiver 30 to the display unit 50. The display unit 50 displays the position coordinates of the receiver 30.

[0045] Thus, the positioning system 10 can calculate the position coordinates of the receiver 30 with high accuracy, even if the directivity of the positioning signal is an ellipsoid.

[0046] Furthermore, by making the directivity of the positioning signal an ellipsoid, the positioning system 10 can suppress unwanted radiation of electromagnetic waves in directions other than the direction of positioning. This suppresses multipath and interference caused by electromagnetic waves being reflected by buildings and other objects in directions other than the direction of positioning. Therefore, the positioning system 10 can achieve highly accurate positioning.

[0047] Furthermore, when using a directional signal as shown in the first embodiment, that is, when the aspect ratio α of the vertical signal intensity relative to the horizontal signal intensity is greater than 1.0, it is possible to increase the vertical signal intensity while suppressing unwanted radiation in the horizontal direction.

[0048] This allows reflection and interference from nearby buildings or other structures in the horizontal direction to be suppressed. In other words, the positioning system 10 can calculate position coordinates with high accuracy while suppressing horizontal interference.

[0049] For example, as shown in Figure 2(A), in the case of an aircraft such as a drone flying in the sky, by using the directivity of a spheroid with its major axis in the vertical direction, even if there are buildings around, the drone's position coordinates can be calculated with high accuracy, as it is less affected by reflections and interference from these buildings.

[0050] (Positioning Method) Figure 4 is a flowchart showing an example of a positioning method according to the first embodiment. The specific details of each process in the flowchart shown in Figure 4 are described in the above-mentioned explanation of the configuration, and explanations are omitted except for those necessary.

[0051] The receiver 30 of the positioning system 10 receives the first signal from the first transmitter 21, the second signal from the second transmitter 22, and the third signal from the third transmitter 23 (S11).

[0052] The arithmetic unit 40 of the positioning system 10 detects first distance information corresponding to the first signal, second distance information corresponding to the second signal, and third distance information corresponding to the third signal (S12).

[0053] The arithmetic unit 40 sets the geometric equations of the ellipsoid based on the directivity of the first signal, the second signal, and the third signal (S13).

[0054] The arithmetic unit 40 converts the geometric equations of the ellipsoid into the geometric equations of the sphere using the aspect ratio α (S14).

[0055] The arithmetic unit 40 performs a provisional positioning calculation using the first distance information, the second distance information, the third distance information, and the geometric equations of the sphere (S15).

[0056] The arithmetic unit 40 performs an inverse aspect ratio transformation on the provisional positioning result to calculate the position coordinates of the receiver 30 (S16).

[0057] [Second Embodiment] A positioning system according to a second embodiment of the present invention will be described with reference to the figures. Figure 5 is a diagram showing an example of the positional relationship between a receiver and a plurality of transmitters in a positioning system according to the second embodiment.

[0058] As shown in Figure 5, the second embodiment shows a case where the directional spread of the first signal from the first transmitter 21, the directional spread of the second signal from the second transmitter 22, and the directional spread of the third signal from the third transmitter 23 are different. The other configurations of the positioning system according to the second embodiment are the same as those of the positioning system according to the first embodiment, and the description of the similar parts will be omitted.

[0059] The directivity of the first signal, the directivity of the second signal, and the directivity of the third signal are similar in shape. The axis of rotation (long axis) of the directivity of the first signal, the axis of rotation (long axis) of the directivity of the second signal, and the axis of rotation (long axis) of the directivity of the third signal are parallel.

[0060] Thus, even if the directional spread of the first signal, the second signal, and the third signal are different, the positioning system 10 can calculate the position coordinates of the receiver 30 with high accuracy by performing the same processing as in the first embodiment.

[0061] For example, if the error in calculating the position coordinates of the receiver 30 using the position coordinates of the first transmitter 21, the second transmitter 22, the third transmitter 23, the first distance information, the second distance information, and the third distance information directly with the geometric equations of a sphere, without performing the above-mentioned conversion process using aspect ratio α, is 1.88 m, then performing the above process can reduce the error to 0 m. These results were calculated under the following conditions: The first transmitter 21, the second transmitter 22, and the third transmitter 23 are arranged on the same plane. The center coordinates of the first transmitter 21, the second transmitter 22, and the third transmitter 23 are set to (x, y, z) = (0, 0, 0). The coordinates of the first transmitter 21 are (-1.3, -1.5, 0), the coordinates of the second transmitter 22 are (1.3, 7.5, 0), and the coordinates of the third transmitter 23 are (-1.3, 7.5, 0). The coordinates of the receiver 30 are (1, 2, 5). These are set in meters. Furthermore, the first signal, the second signal, and the third signal are signals with a minor axis:major axis ratio of 1:1.6 (aspect ratio of 0.625).

[0062] Thus, the processing of this invention works more effectively when the directivity of the first signal, the directivity of the second signal, and the directivity of the third signal are not the same but similar in shape.

[0063] [Third Embodiment] A positioning system according to a third embodiment of the present invention will be described with reference to the figures. Figure 6 is a diagram showing an example of the positional relationship between a receiver and a plurality of transmitters in a positioning system according to the third embodiment.

[0064] As shown in Figure 6, in the third embodiment, the directivity of the first signal from the first transmitter 21, the second signal from the second transmitter 22, and the third signal are such that the aspect ratio α of the vertical signal intensity relative to the horizontal signal intensity is less than 1.0.

[0065] Even with this type of directivity, the positioning system 10 can calculate the position coordinates of the receiver 30 with high accuracy by performing the same processing as in the first embodiment.

[0066] Furthermore, in the third embodiment, since unwanted radiation in the vertical direction can be suppressed while increasing the horizontal signal intensity, vertical interference can be suppressed while calculating position coordinates with high accuracy.

[0067] Figure 7 shows an example of the application of the positioning system according to the third embodiment. As shown in Figure 7, in the case of a robot that moves mainly in the horizontal direction, by using the directivity of a spheroid having a rotation axis parallel to the horizontal direction, the robot's position coordinates can be calculated with high accuracy, even if the robot is in an environment with a roof, as it is less affected by reflection and interference from the roof.

[0068] In the embodiments described above, the number of transmitters was set to three, but the number of transmitters is not limited to three; it may be four or more. In this case, three transmitters can be selected from four or more transmitters.

[0069] Furthermore, the embodiments described above show a configuration in which electromagnetic waves are used for the signal transmitted from the transmitter. However, the transmitted signal is not limited to electromagnetic waves; any signal having the directivity of a rotating ellipsoid may be used, for example, ultrasound.

[0070] Furthermore, while the embodiments described above show the transmitter mounting surface aligned with the horizontal plane, the invention is not limited to this configuration.

[0071] 10: Positioning system 21: First transmitter 22: Second transmitter 23: Third transmitter 30: Receiver 31: Distance information detection unit 32: Distance information transmission unit 40: Calculation unit 41: Distance information receiving unit 42: Positioning calculation unit 43: Aspect conversion unit 50: Display unit

Claims

1. A first transmitter that transmits a first signal having the directionality of a spheroid; a second transmitter that transmits a second signal having the directionality of the spheroid and is positioned differently from the first transmitter; a third transmitter that transmits a third signal having the directionality of the spheroid and is positioned differently from the first and second transmitters; a receiver that receives the first signal and detects first distance information, receives the second signal and detects second distance information, and receives the third signal and detects third distance information; and a calculation device that uses the first distance information, the second distance information, and the third distance information to calculate the position coordinates of the receiver, wherein the calculation device sets the positions of the first transmitter, the second transmitter, the third transmitter, and the receiver and the geometric equation of the spheroid; transforms the geometric equation of the spheroid based on the aspect ratio between the directionality of the spheroid and the directionality of the sphere to set the geometric equation of the sphere; and calculates the provisional position coordinates of the receiver using the geometric equation of the sphere. A positioning system that calculates the position coordinates from the provisional position coordinates by an inverse transformation based on the aspect ratio.

2. The positioning system according to claim 1, wherein the receiver detects the first distance information based on the received strength of the first signal, the second distance information based on the received strength of the second signal, and the third distance information based on the received strength of the third signal.

3. The positioning system according to claim 2, wherein the first signal, the second signal, and the third signal are composed of electromagnetic waves, and the first distance information, the second distance information, and the third distance information are the received power of the electromagnetic waves.

4. The positioning system according to any one of claims 1 to 3, wherein the receiver comprises a distance information transmitting unit that transmits the first distance information, the second distance information, and the third distance information, and the computing device comprises a distance information receiving unit that receives the first distance information, the second distance information, and the third distance information.

5. A positioning system according to any one of claims 1 to 4, comprising a display that shows the position coordinates of the receiver.

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