Positioning system

Abstract

Provided is a positioning system with a simple configuration capable of easily measuring the position of an aircraft.　This positioning system comprises: a first communication unit; a first position calculation unit that measures the position of the first communication unit; an aircraft that can move with respect to the first communication unit; a second communication unit that is mounted on the aircraft and communicates with the first communication unit; a distance measurement unit that measures the distance between the first communication unit and the aircraft on the basis of the propagation time or the phase of a signal communicated between the first communication unit and the second communication unit; an angle calculation unit that calculates the elevation angle of the aircraft with respect to the first communication unit and calculates the azimuth angle of the aircraft with respect to the first communication unit; and a second position calculation unit that calculates the position of the aircraft on the basis of the position measured by the first position calculation unit, the distance measured by the distance measurement unit, and a first elevation angle calculated by the angle calculation unit.

Description

Positioning System

[0001] The present disclosure relates to positioning systems.

[0002] Conventionally, there has been a positioning system for an aircraft that measures its position, deriving the horizontal position of the aircraft from the transmission or reception status of radio waves at three base stations located at three different locations. The positioning system derives the vertical position of the aircraft from the derived position based on the transmission or reception status of laser light from the laser beam base station. The positions of the three base stations and the laser beam base station are identified by GPS (Global Positioning System) or surveying (see, for example, Patent Document 1).

[0003] International Publication No. 2019 / 150581

[0004] However, in the positioning system described above, it is necessary to identify four locations by GPS or surveying to determine the position of the aircraft, and the height of the aircraft is determined by transmitting a laser beam from the laser beam base station to the aircraft, making it difficult to easily determine the position of the aircraft. Furthermore, the system uses three base stations and a laser beam base station to determine the position of the aircraft, making it difficult to configure.

[0005] Therefore, an object of the present invention is to provide a positioning system that has a simple configuration and can easily determine the position of an aircraft.

[0006] a distance measurement unit that measures the distance between the first communication unit and the aircraft based on a propagation time or a phase of a signal communicated between the first communication unit and the second communication unit; an angle calculation unit that calculates an elevation angle of the aircraft with respect to the first communication unit based on a phase of a signal communicated between the first communication unit and the second communication unit when the signal is received by a plurality of antenna elements of the first communication unit or the second communication unit, and calculates an azimuth angle of the aircraft with respect to the first communication unit based on a phase of a signal communicated between the first communication unit and the second communication unit when the signal is received by a plurality of antenna elements of the first communication unit or the second communication unit; and a second position calculation unit that calculates the position of the aircraft based on the position measured by the first position calculation unit, the distance measured by the distance measurement unit, and the first elevation angle calculated by the angle calculation unit.

[0007] It is possible to provide a positioning system that has a simple configuration and can easily determine the position of an aircraft.

[0008] 1 is a diagram illustrating an example of the configuration of a positioning system of an embodiment. FIG. 1 is a diagram illustrating an error in the elevation angle of an aircraft relative to an antenna array calculated by an angle calculation unit in AoA format. FIG. 2 is a diagram illustrating a method for calculating a correction value. FIG. 3 is a diagram illustrating a method for correcting altitude using a correction value. FIG. 4 is a flowchart illustrating an example of processing executed by a control device of the positioning system of an embodiment. FIG. 5 is a flowchart illustrating an example of processing executed by a control device of the positioning system of an embodiment. FIG. 6 is a diagram illustrating an example of an xy coordinate system of an array antenna of the positioning system of an embodiment. FIG. 7 is a diagram illustrating the xy coordinate system of the array antenna superimposed on the ENU coordinate system of the array antenna of the positioning system of an embodiment. FIG. 8 is a diagram illustrating an example of the position of an array antenna (Anchor) of the positioning system of an embodiment on the Earth. FIG. 9 is a diagram illustrating the Earth as viewed in cross section on a plane including the North Pole N, the South Pole S, and the Anchor. FIG. 10 is a diagram illustrating an example of the position of an aircraft (Tag) on ​​the Earth. FIG. 11 is a diagram illustrating an example of the positions of Tag and Anchor when the Earth is viewed from the North Pole side. FIG. 12 is a sequence diagram illustrating an example of processing executed by a second position calculation unit of the positioning system.

[0009] Hereinafter, an embodiment to which the positioning system of the present disclosure is applied will be described.

[0010] 1 is a diagram showing an example of the configuration of a positioning system 100. The positioning system 100 includes an array antenna 110, a control device 120, and an aircraft 130. The array antenna 110 is an example of a first communication unit.

[0011] The control device 120 of the positioning system 100 measures (estimates) the elevation angle θ and azimuth angle φ of the flying object 130 relative to the array antenna 110 in the AoA format. The elevation angle θ is an angle equivalent to the polar angle (zenith angle) in polar coordinates. The control device 120 also measures (estimates) the distance between the array antenna 110 and the flying object 130 in the ToA (Time of Arrival) format. The elevation angle θ and azimuth angle φ are given in a polar coordinate system with the center of the surface of the array antenna 110 as the origin O.

[0012] <Array antenna 110> The array antenna 110 has a substrate 111 and four antenna elements 112. The substrate 111 is made of an insulating material, and has the four antenna elements 112 provided on its upper surface. The array antenna 110 is, for example, installed on the ground or on a fixed object provided on the ground, and is connected to the control device 120 via wiring.

[0013] The four antenna elements 112 are arranged at equal intervals on the upper surface of the substrate 111. More specifically, the four antenna elements 112 are arranged so that the centers of the four antenna elements 112 in a planar view are located at the vertices of a square in a planar view. Although Fig. 1 shows the antenna elements 112 that are circular in a planar view, the antenna elements 112 may also be rectangular in a planar view.

[0014] <Control device 120> The control device 120 is connected to the array antenna 110. The control device 120 is realized by a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), an input / output interface, an internal bus, and the like.

[0015] The control device 120 has a communication control unit 121, a first position calculation unit 122, a distance measurement unit 123, an angle calculation unit 124, a correction value calculation unit 125, a second position calculation unit 126, and a memory 127. The communication control unit 121, the first position calculation unit 122, the distance measurement unit 123, the angle calculation unit 124, the correction value calculation unit 125, and the second position calculation unit 126 are functional blocks representing the functions of a program executed by the control device 120. The memory 127 is a functional representation of the memory of the control device 120.

[0016] The communication control unit 121 performs processing for communicating with the communication unit 132 of the flying object 130 via the array antenna 110. The communication control unit 121 selects one or more antenna elements 112 to be used for communication from the four antenna elements 112 of the array antenna 110. As an example, the communication is performed using Bluetooth Low Energy (BLE) or a Wireless Local Area Network (WLAN). Below, as an example, a form in which the control device 120 and the communication unit 132 of the flying object 130 communicate using BLE will be described. The communication includes communication for ranging and angle measurement, as well as data communication for communicating data such as the phase when a BLE signal is received.

[0017] The first position calculation unit 122 locates the position of the array antenna 110. Locating the position of the array antenna 110 means measuring the position of the array antenna 110. The first position calculation unit 122 has, as an example, an antenna 122A capable of receiving GPS signals from GPS satellites, and locates the position of the array antenna 110 based on the GPS signals. The first position calculation unit 122 is a Global Navigation Satellite System (GNSS). The position of the array antenna 110 is expressed in latitude and longitude. As an example, a GPS receiver can be used as the first position calculation unit 122. Note that the first position calculation unit 122 may use a system other than GPS (for example, Galileo in Europe or Michibiki in Japan).

[0018] The distance measurement unit 123 measures the distance between the array antenna 110 and the flying object 130 based on the propagation time or phase of the signal communicated between the array antenna 110 and the communication unit 132 of the flying object 130. More specifically, the distance measurement unit 123 measures the distance in a ToA format using one of the four antenna elements 112 of the array antenna 110.

[0019] As an example, distance measurement unit 123 transmits signals of multiple frequencies f1 to fN (N is an integer of 2 or greater) from antenna element 112 to communication unit 132 of flying object 130, and receives the signals of multiple frequencies f1 to fN from communication unit 132 of flying object 130 at antenna element 112. Distance measurement unit 123 acquires data indicating the phase when communication unit 132 of flying object 130 receives the signals of each frequency from communication unit 132 of flying object 130 by communication.

[0020] The distance measurement unit 123 calculates the total phase (round-trip phase) for each frequency of the phase when the antenna element 112 receives the signal of each frequency from the communication unit 132 and the phase when the signal of each frequency is received by the communication unit 132 of the flying object 130. The distance measurement unit 123 measures the distance between the array antenna 110 and the flying object 130 from the relationship between the multiple frequencies and the round-trip phase at each frequency.

[0021] Furthermore, instead of using the distance measurement method described above, the distance measurement unit 123 may measure the propagation time of a signal when it is transmitted from the antenna element 112 to the communication unit 132 of the flying object 130, or the propagation time of a signal when it is transmitted from the communication unit 132 of the flying object 130 to the antenna element 112. The distance measurement unit 123 may measure the distance between the array antenna 110 and the flying object 130 by multiplying the measured propagation time by the speed of light. Details of the processing by the distance measurement unit 123 will be described later using the flowcharts of Figures 4A and 4B.

[0022] The angle calculation unit 124 measures, in an AoA format, the elevation angle θ and the azimuth angle φ in a polar coordinate system of the position of the flying object 130 relative to the array antenna 110, using two or more of the four antenna elements 112 of the array antenna 110. The angle calculation unit 124 measures the elevation angle θ and the azimuth angle φ using the AoA format or ToA format, based on the phase difference when the BLE signal transmitted from the communication unit 132 of the flying object 130 is received by the two or more antenna elements 112.

[0023] Hereinafter, the elevation angle calculated by the angle calculation unit 124 using the AoA method will be referred to as elevation angle 1, and the elevation angle calculated using the ToA method will be referred to as elevation angle 2. Elevation angle 1 is an example of a first elevation angle, and elevation angle 2 is an example of a second elevation angle. Details of the processing by the angle calculation unit 124 will be described later using the flowcharts of FIGS. 4A and 4B .

[0024] When the absolute value of the elevation angle 1 calculated by the angle calculation unit 124 is equal to or smaller than a first predetermined angle, the correction value calculation unit 125 calculates, as a correction value, the difference between the altitude acquired by the atmospheric pressure sensor 133 and the distance measured by the distance measurement unit 123. The correction value will be described later with reference to Figures 3A and 3B.

[0025] When the angle calculation unit 124 calculates the elevation angle 1 using a method using AoA, the second position calculation unit 126 calculates the position of the flying object 130 based on the position measured by the first position calculation unit 122, the distance measured by the distance measurement unit 123, and the elevation angle 1 calculated by the angle calculation unit 124. The position measured by the first position calculation unit 122 is the latitude and longitude of the array antenna 110. The distance measured by the distance measurement unit 123 is the distance from the array antenna 110 to the flying object 130. The elevation angle 1 calculated by the angle calculation unit 124 is the elevation angle of the flying object 130 with respect to the array antenna 110.

[0026] Furthermore, when the angle calculation unit 124 calculates the elevation angle 2 using a method that utilizes ToA, the second position calculation unit 126 calculates the position of the flying object 130 based on the position measured by the first position calculation unit 122, the distance measured by the distance measurement unit 123, and the elevation angle 2 calculated by the angle calculation unit 124. The elevation angle 2 calculated by the angle calculation unit 124 is the elevation angle of the flying object 130 with respect to the array antenna 110.

[0027] The memory 127 stores programs executed by the control device 120 to perform processing, data required for processing, and the like.

[0028] <Air Vehicle 130> The air vehicle 130 is, for example, a drone, or an unmanned aerial vehicle (UAV). The air vehicle 130 is equipped with a control device 131, a communication unit 132, and a barometric pressure sensor 133.

[0029] The flying object 130 flies in response to control signals transmitted from a remote controller (not shown). As an example, a camera is mounted on the flying object 130. As an example, the flying object 130 operates the camera based on a photographing signal transmitted from the remote controller to capture still images (photos) and moving images (videos).

[0030] The control device 131 is realized by a computer including a CPU, RAM, ROM, an input / output interface, an internal bus, etc. Although a receiving unit for receiving control signals from a remote controller in the flying object 130 is omitted in Fig. 1, the control device 131 performs flight control of the flying object 130 in response to the control signals received from the remote controller.

[0031] The communication unit 132 has an antenna element 132A and performs BLE communication with the array antenna 110. The communication unit 132 is an example of a second communication unit. The communication includes data communication in addition to communication for ranging and angle measurement.

[0032] The atmospheric pressure sensor 133 is a sensor that converts atmospheric pressure into altitude and outputs the converted value, and measures the altitude of the flying object 130 relative to the array antenna 110. The atmospheric pressure sensor 133 is an example of an altitude measurement unit. Data representing the altitude is transmitted by the control device 131 to the array antenna 110 via the communication unit 132 and input to the control device 120.

[0033] Although the description here is of a configuration in which the atmospheric pressure sensor 133 converts atmospheric pressure into altitude and outputs the converted data, the atmospheric pressure sensor 133 may output data representing atmospheric pressure, in which case the control device 120 may convert the atmospheric pressure into altitude. Also, the description here is of a configuration in which the atmospheric pressure sensor 133 is used to measure the altitude of the flying object 130, but a device other than the atmospheric pressure sensor 133 that can measure the altitude of the flying object 130 may also be used.

[0034] <Error in Elevation Angle Obtained by Angle Measurement> Figure 2 is a diagram showing the error in the elevation angle of the flying object 130 relative to the array antenna 110 calculated by the angle calculation unit 124 using the AoA method. In Figure 2, the horizontal axis represents the actual elevation angle, and the vertical axis represents the calculated elevation angle. The solid line represents the relationship between the theoretical value of the elevation angle calculated by the angle calculation unit 124 using the AoA method and the actual elevation angle, and the dashed line represents the relationship between the elevation angle actually calculated by the angle calculation unit 124 using the AoA method and the actual elevation angle. The theoretical value of the elevation angle calculated by the angle calculation unit 124 using the AoA method is the elevation angle calculated when the four antenna elements 112 have the same phase characteristics without any differences in their arrangement on the substrate 111 or in their environment.

[0035] The four antenna elements 112 of the actual array antenna 110 have different phase characteristics depending on the environment, such as their arrangement on the substrate 111 and their positional relationship with surrounding objects at ground potential. Therefore, as shown in Figure 2, when the absolute value of the calculated elevation angle becomes approximately 60 degrees or more, the difference from the theoretical value becomes large enough to be non-negligible.

[0036] In the positioning system 100 of this embodiment, the error becomes large when the absolute value of the elevation angle calculated using the AoA method is approximately 60 degrees or more, so the angle calculation unit 124 calculates the elevation angle using a method that uses ToA rather than the AoA method. Note that the difference between the azimuth angle of the flying object 130 calculated by the angle calculation unit 124 using the AoA method and the theoretical value is within an acceptable range. Therefore, the azimuth angle of the flying object 130 calculated by the angle calculation unit 124 using the AoA method is used.

[0037] <Method of correcting altitude using correction value> Fig. 3A is a diagram illustrating how to obtain a correction value, and Fig. 3B is a diagram illustrating a method of correcting altitude using a correction value.

[0038] 3A, the dashed line indicates the altitude measured by the air pressure sensor 133 mounted on the flying object 130, and the solid line indicates the distance measured by the distance measurement unit 123 in the ToA format when the flying object 130 is directly above the array antenna 110. When the flying object 130 is directly above the array antenna 110, the distance measured by the distance measurement unit 123 in the ToA format corresponds to the altitude of the flying object 130.

[0039] Since the altitude measured by the atmospheric pressure sensor 133 is measured with higher accuracy than the distance measured by the distance measurement unit 123 in ToA format, there is a difference between the altitude measured by the atmospheric pressure sensor 133 and the distance measured by the distance measurement unit 123 in ToA format.

[0040] Here, the correction value is calculated by subtracting the distance measured by the distance measurement unit 123 in the ToA format from the altitude measured by the atmospheric pressure sensor 133. The process of calculating the correction value is performed by the correction value calculation unit 125. The correction value is used to correct the altitude measured by the atmospheric pressure sensor 133 to a value for ToA when the angle calculation unit 124 calculates the angle of elevation using a method that utilizes ToA.

[0041] 3B , when the elevation angle θ of the flying object 130 is large and equal to or greater than a second predetermined angle, the elevation angle θ is calculated by calculating the arccosine (acos) of the value obtained by subtracting a correction value from the altitude H measured by the atmospheric pressure sensor 133 mounted on the flying object 130 and dividing the result by the distance measured in ToA format by the distance measurement unit 123. This process is executed by the angle calculation unit 124, and is a method in which the angle calculation unit 124 calculates the elevation angle 2 using a method that utilizes the ToA. Altitude Hc = altitude H - correction value.

[0042] The elevation angle 2 is calculated by the following formula (1). The accuracy of the atmospheric pressure sensor 133 is on the order of several centimeters, while the accuracy of the ToA is on the order of several tens of centimeters, so the elevation angle 2 is corrected by the value of the atmospheric pressure sensor 133. Elevation angle 2 = acos {(altitude H - corrected value) / distance} (1)

[0043] <Flowchart> FIGS. 4A and 4B are flowcharts showing an example of processing executed by the control device 120. FIG.

[0044] 4A shows a process executed immediately after the power of the flying object 130 is turned on. As a premise of the process of FIG. 4A, when the flying object 130 is turned on, it flies in a mode in which the absolute value of the elevation angle is controlled to be 5 degrees or less. While communicating with the control device 120, the flying object 130 flies so that the absolute value of the elevation angle calculated by the angle calculation unit 124 is 5 degrees or less.

[0045] If the absolute value of the elevation angle of the air vehicle 130 is 5 degrees or less, the air vehicle 130 is considered to be directly above the array antenna 110. In order to calculate the correction value when the air vehicle 130 is directly above the array antenna 110, the air vehicle 130 flies so that the absolute value of the elevation angle is 5 degrees or less immediately after the power is turned on. Five degrees is an example of a first predetermined angle, which is an angle at which the elevation angle of the air vehicle 130 directly above the array antenna 110 falls within a predetermined range of angles. The predetermined range of angles is a range within which the air vehicle 130 is considered to be approximately directly above the array antenna 110. Note that, although an embodiment in which the first predetermined angle is 5 degrees is described here, the first predetermined angle is not limited to 5 degrees and may be set to an appropriate value as an angle at which the air vehicle 130 is considered to be approximately directly above the array antenna 110, depending on the accuracy required in using the positioning system 100, the flight range of the air vehicle 130, etc.

[0046] <Processing shown in FIG. 4A> When the processing starts, the angle calculation unit 124 calculates the azimuth angle φ and the elevation angle 1 in the AoA format (step S0).

[0047] The angle calculation unit 124 determines whether the absolute value of the elevation angle of the flying object 130 is 5 degrees or less (step S1).

[0048] If the angle calculation unit 124 determines that the absolute value of the elevation angle of the flying object 130 is not 5 degrees or less (S1: NO), the flow returns to step S0. If the angle calculation unit 124 determines that the absolute value of the elevation angle of the flying object 130 is 5 degrees or less (S1: YES), the flow proceeds to step S2.

[0049] Next, the distance measurement unit 123 measures the distance in the ToA format (step S2).

[0050] Next, the angle calculation unit 124 acquires the altitude of the flying object 130 detected by the air pressure sensor 133 (step S3). This completes the azimuth angle, elevation angle 1, and altitude of the flying object 130.

[0051] The correction value calculation unit 125 calculates a correction value using the distance measured in step S2 and the altitude acquired in step S3, and stores the calculated correction value in the memory 127 (step S4). The correction value is calculated by subtracting the distance from the altitude.

[0052] This is the end of the process in Fig. 4A (END). After completing the process in Fig. 4A, the control device 120 starts the process in Fig. 4B.

[0053] 4B When the process shown in Fig. 4B is started, the angle calculation unit 124 calculates the azimuth angle and the elevation angle 1 in the AoA format (step S11). When the process shown in Fig. 4B is started, the flying object 130 is released from the mode in which the flying object 130 is controlled so that the absolute value of the elevation angle is 5 degrees or less, and the flying object 130 becomes able to fly freely according to the control signal of the remote controller.

[0054] Next, the distance measurement unit 123 measures the distance in the ToA format (step S12).

[0055] Next, the angle calculation unit 124 acquires the altitude of the flying object 130 detected by the air pressure sensor 133 (step S13).

[0056] The angle calculation unit 124 determines whether the absolute value of the elevation angle 1 calculated in step S11 is less than 60 degrees (step S14). As shown in FIG. 2 , 60 degrees is an example of a second predetermined angle, which is a boundary angle at which the difference between the elevation angle calculated by the angle calculation unit 124 and the theoretical value becomes non-negligible. The second predetermined angle, 60 degrees, is greater than the first predetermined angle, 5 degrees. Note that the second predetermined angle of 60 degrees is merely an example, and the second predetermined angle is not limited to 60 degrees. The second predetermined angle may be set to an angle at which it is considered better to use the elevation angle 2 instead of the elevation angle 1, depending on the accuracy required for the positioning system 100, the flight range of the flying object 130, and the like.

[0057] If the angle calculation unit 124 determines that the absolute value of the elevation angle 1 calculated in step S11 is less than 60 degrees (S14: YES), it outputs the elevation angle 1 as the current elevation angle of the flying object 130 (step S15). The angle calculation unit 124 measures the elevation angle in the AoA format based on the phase difference when a BLE signal transmitted from the communication unit 132 of the flying object 130 is received by two or more antenna elements 112. That is, the angle calculation unit 124 calculates the elevation angle 1 of the flying object 130 relative to the array antenna 110 based on the phase when a signal communicated between the array antenna 110 and the communication unit 132 is received by multiple antenna elements of the array antenna 110 or the communication unit 132.

[0058] Next, the angle calculation unit 124 determines whether the absolute value of the elevation angle 1 of the flying object 130 is 5 degrees or less (step S16).

[0059] If the angle calculation unit 124 determines that the absolute value of the elevation angle of the flying object 130 is 5 degrees or less (S16: YES), the correction value calculation unit 125 calculates a correction value using the distance measured in step S12 and the altitude acquired in step S13, and updates the correction value stored in the memory 127 (step S17). This updates the correction value to the latest correction value. The correction value is calculated by subtracting the distance from the altitude.

[0060] Furthermore, if the angle calculation unit 124 determines in step S14 that the elevation angle 1 calculated in step S11 is not less than 60 degrees (S14: NO), the angle calculation unit 124 calculates the elevation angle 2 by equation (1) using the distance measured in step S12, the altitude acquired in step S13, and the correction value stored in the memory 127 (step S18). That is, if the elevation angle 1 is 60 degrees or more, the angle calculation unit 124 calculates the elevation angle 2 given by the arccosine of the value obtained by correcting the altitude acquired by the atmospheric pressure sensor 133 with the correction value and dividing the result by the distance measured by the distance measurement unit 123.

[0061] The angle calculation unit 124 outputs the elevation angle 2 calculated in step S15 as the current elevation angle of the flying object 130, instead of the elevation angle 1 calculated in step S11 (step S19). After completing the processing of step S19, the angle calculation unit 124 causes the flow to proceed to step S16.

[0062] Since the azimuth angle, distance, elevation angle 1, or elevation angle 2 can be obtained as described above, positioning is completed and the series of processes ends (END). The control device 120 repeatedly executes the process shown in FIG.

[0063] <How to Determine the Position of the Aircraft 130> Fig. 5A is a diagram showing an example of the xy coordinate system of the array antenna 110. Fig. 5B is a diagram showing the xy coordinate system of the array antenna 110 superimposed on the ENU (East-North-Up) coordinate system of the array antenna 110. Hereinafter, the array antenna 110 may be referred to as the Anchor, and the aircraft 130 may be referred to as the Tag.

[0064] As shown in Figure 5A, the xy coordinate system of the array antenna 110 is a two-axis orthogonal coordinate system with the position of the array antenna 110 (Anchor) as the origin. The angle between the y-axis of the xy coordinate system of the array antenna 110 and the north direction (the direction of true north) is defined as σ. The xy coordinate system of the array antenna 110 uses lowercase x and y. The angle σ is the angle representing the azimuth of the y-axis of the xy coordinate system of the array antenna 110.

[0065] As shown in Figure 5B, the ENU coordinate system of the array antenna 110 has the position of the array antenna 110 as its origin, with the east direction (direction due east) as the X direction and the north direction (direction due north) as the Y direction. Capital letters X and Y are used to represent the X and Y coordinates of the ENU coordinate system. Here, the angle σ is the angle between the y axis of the xy coordinate system of the array antenna 110 (the y axis in Figure 5A) and the Y axis of the ENU coordinate system (see Figure 5B). The angle σ is positive when the y axis of the xy coordinate system is positioned clockwise with respect to the Y axis of the ENU coordinate system, as shown in Figure 5B.

[0066] Here, it is assumed that the coordinate P0 of the flying object 130 (Tag) in the xy coordinate system of the array antenna 110 shown in Figure 5A is (x0, y0). If the distance between the array antenna 110 and the flying object 130 is r, the x coordinate x0 can be calculated using the following equation (2A). Furthermore, the y coordinate y0 can be calculated using the following equation (2B). Furthermore, the z coordinate z0 of the coordinate P0 of the flying object 130 (Tag) can be calculated using the following equation (2C). Note that the elevation angle θ is greater than or equal to 0 degrees and less than or equal to 90 degrees.

[0067] x0=r×sinθ×cosφ (2A) y0=r×sinθ×sinφ (2B) z0=r×cosθ (2C)

[0068] The coordinate P0 (=(x0, y0)) can be converted into the coordinate P(X0, Y0) in the ENU coordinate system shown in FIG. 5B by using the following equations (3A) and (3B).

[0069] X0=cosσ×x0−sinσ×y0 (3A) Y0=sinσ×x0+cosσ×y0 (3B)

[0070] Figure 6A is a diagram showing an example of the position of the array antenna 110 (Anchor) on the Earth. Here, the Earth is approximated as a sphere, so the Earth is shown as a sphere in Figure 6A. The radius of the Earth is assumed to be the polar radius A (= 6,356,752 m). Note that the equatorial radius (= 6,378,137 m) may also be used as the radius of the Earth. The position (latitude, longitude) of the array antenna 110 (Anchor) is assumed to be (α, β).

[0071] As shown in FIG. 6A, when the center of the earth is the origin, the elevation angle corresponds to the latitude, and therefore the position of the anchor is a position whose radius vector is polar radius A and whose elevation angle is α.

[0072] 6B is a diagram showing the Earth as viewed in cross section on a plane including the North Pole N, the South Pole S, and the Anchor. The Tag is assumed to be located at a position shifted in latitude by Δα with respect to the Anchor.

[0073] The distance between the tag and anchor is less than several hundred meters, which is a very small distance compared to the Earth's radius A. Therefore, the value ΔY (coordinate difference) obtained by subtracting the Y coordinate of the anchor from the Y coordinate of the tag (Y0) can be approximately expressed by the following equation (4A).

[0074] ΔY=A×Δα (4A)

[0075] By modifying equation (4A), the latitude difference Δα is expressed by the following equation (4B).

[0076] Δα=ΔY / A (4B)

[0077] Here, the Y coordinate of Anchor is 0, and ΔY is the Y coordinate of Tag (Y0)-0, so ΔY=Y0.

[0078] The latitude of Tag is calculated as α+Δα, which is the latitude α of Anchor plus the latitude difference Δα.

[0079] Fig. 7A is a diagram showing an example of the position of an aircraft 130 (Tag) on ​​the Earth. Fig. 7A shows the same Earth as Fig. 6A. The position of Tag is a position whose radius vector is represented by polar radius A and elevation angle α + Δα. The distance from Tag to the Earth's axis is A cos(α + Δα).

[0080] 7B is a diagram showing an example of the positions of Tag and Anchor when the Earth is viewed from the North Pole. Fig. 7B shows a cross section of the Earth at an equal latitude at the latitude of Tag. The cross section of the Earth at an equal latitude at the latitude of Tag is a circle with a radius of A cos(α + Δα).

[0081] The distance between the tag and the anchor is less than several hundred meters, which is infinitesimal compared to the distance from the tag to the Earth's axis, A cos(α + Δα), so the anchor is also shown in Figure 7B. The tag is assumed to be located at a longitude offset of Δβ from the anchor.

[0082] The value ΔX (coordinate difference) obtained by subtracting the X coordinate of the Anchor from the X coordinate of the Tag can be approximately expressed by the following equation (5A).

[0083] ΔX=Acos(α+Δα)×Δβ (5A)

[0084] By modifying equation (5A), the longitude difference Δβ is expressed by the following equation (5B).

[0085] Δβ=ΔX / Acos(α+Δα) (5B)

[0086] Here, the X coordinate of Anchor is 0, and ΔX is the X coordinate of Tag (X0)-0, so ΔX=X0.

[0087] The longitude of Tag is calculated as β+Δβ, which is the longitude β of Anchor plus Δβ.

[0088] In this way, the latitude difference Δα and longitude difference Δβ of the tag relative to the anchor can be calculated. Furthermore, the latitude α and longitude β representing the position of the anchor are calculated by the first position calculation unit 122 based on the GPS signal. Therefore, the second position calculation unit 126 can calculate the latitude αt and longitude βt of the tag according to the following equations (6A) and (6B):

[0089] αt=α+Δα=α+ΔY / A (6A) βt=β+Δβ=β+ΔX / Acos(α+Δα) (6B)

[0090] In this way, the second position calculation unit 126 can calculate the position of the flying object 130.

[0091] <Calculation of Latitude and Longitude of Tag> Fig. 8 is a sequence diagram showing an example of the overall processing of the positioning system 100. Fig. 8 collectively shows an example of processing of the part of the control device 120 excluding the GNSS (first position calculation unit 122), the GNSS (first position calculation unit 122), and the Tag (aircraft 130).

[0092] The GNSS acquires the latitude α, longitude β, and angle σ of the anchor (array antenna 110) (step S101). Note that the angle σ may be input by, for example, a user of the positioning system 100. Alternatively, the angle σ may be acquired from, for example, a geomagnetic sensor.

[0093] The GNSS transfers the acquired latitude α, longitude β, and angle σ of the anchor (step S102).

[0094] The control device 120 (excluding the GNSS) stores the latitude α, the longitude β, and the angle σ in the memory 127 (step S103).

[0095] The control device 120 (excluding GNSS) and Tag (air vehicle 130) transmit and receive signals for measuring distance and angle using ToA and AoA (step S104). On the control device 120 side, the distance measurement unit 123 and the angle calculation unit 124 transmit and receive signals for measuring distance and angle using ToA and AoA. In addition, Tag (air vehicle 130) transmits data indicating altitude output from the atmospheric pressure sensor 133 to the control device 120.

[0096] The distance measurement unit 123 measures the distance r between the array antenna 110 and the aircraft 130 in ToA format based on the propagation time or phase of the signal communicated between the array antenna 110 and the communication unit 132 of the Tag (aircraft 130) (step S105).

[0097] The angle calculation unit 124 measures, in the AoA format, the elevation angle θ and the azimuth angle φ in the polar coordinate system of the position of the Tag (aircraft 130) relative to the array antenna 110 (step S106). Note that the angle calculation unit 124 may measure the elevation angle θ and the azimuth angle φ using ToA.

[0098] The second position calculation unit 126 calculates the coordinates P0 of Tag (aircraft 130) as (x0, y0, z0) based on equations (2A), (2B), and (2C) using the distance r, the elevation angle θ, and the azimuth angle φ (step S107).

[0099] The second position calculation unit 126 calculates the latitude and longitude of the Tag (aircraft 130) (step S108). In step S108, the second position calculation unit 126 converts the x- and y-coordinates (x0, y0) of the Tag's coordinate P0 into X- and Y-coordinates in the ENU coordinate system according to equations (3A) and (3B), calculates the latitude difference Δα according to equation (4B), and calculates the longitude difference Δβ according to equation (5B). Furthermore, the second position calculation unit 126 calculates the latitude and longitude of the Tag by adding the latitude difference Δα and the longitude difference Δβ to the latitude and longitude stored in memory 127 in step S103 according to equations (6A) and (6B).

[0100] The second position calculation unit 126 may further perform the process of step S109 of transmitting the latitude, longitude, and z coordinate (z0) to Tag (aircraft 130).

[0101] As a result, in step S110, Tag (aircraft 130) acquires the latitude, longitude, and z coordinate (z0).

[0102] As described above, the first position calculation unit 122 determines the position of the Anchor (array antenna 110) based on the GPS signal, and adds the latitude difference Δα and longitude difference Δβ of the Tag (air vehicle 130) relative to the Anchor to the position (latitude and longitude) of the Anchor, thereby easily calculating the position (latitude and longitude) of the air vehicle 130. Furthermore, the first position calculation unit 122 is the only GPS receiver that performs positioning based on the GPS signal, and there is no need to install a GPS receiver in the air vehicle 130, which simplifies the configuration of the positioning system 100. Furthermore, because there is no need to install a GPS receiver in the air vehicle 130, the weight of the air vehicle 130 can be reduced.

[0103] Furthermore, the latitude difference Δα and longitude difference Δβ of Tag (air vehicle 130) with respect to Anchor are calculated by the second position calculation unit 126 based on the distance r and the elevation angle θ using the above-mentioned formulas (2A), (2B), (3A), (3B), (4B), and (5B). The distance r is the distance between the array antenna 110 and the air vehicle 130 calculated by the distance measurement unit 123. The elevation angle θ is the elevation angle of the air vehicle 130 with respect to the array antenna 110 calculated by the angle calculation unit 124.

[0104] The elevation angle θ calculated by the angle calculation unit 124 is elevation angle 1 or elevation angle 2 calculated according to the elevation angle of the flying object 130 relative to the array antenna 110. The azimuth angle of the flying object 130 is the azimuth angle measured by the angle calculation unit 124 together with the elevation angle.

[0105] In other words, when the angle calculation unit 124 calculates the elevation angle 1 using a method utilizing AoA, the second position calculation unit 126 calculates the position of the flying object 130 based on the position measured by the first position calculation unit 122, the distance measured by the distance measurement unit 123, and the elevation angle 1 calculated by the angle calculation unit 124.

[0106] In addition, when the angle calculation unit 124 calculates the elevation angle 2 using a method utilizing ToA, the second position calculation unit 126 calculates the position of the flying object 130 based on the position measured by the first position calculation unit 122, the distance measured by the distance measurement unit 123, and the elevation angle 2 calculated by the angle calculation unit 124.

[0107] <Effects> The positioning system 100 includes an array antenna 110 (first communication unit), a first position calculation unit 122 that calculates the position of the array antenna 110, an aircraft 130 that is movable relative to the array antenna 110, a communication unit 132 (second communication unit) that is mounted on the aircraft 130 and communicates with the array antenna 110, a distance measurement unit 123 that measures the distance between the array antenna 110 and the aircraft 130 based on the propagation time or phase of a signal communicated between the array antenna 110 and the communication unit 132, and the array antenna 110. The system is equipped with an angle calculation unit 124 that calculates the elevation angle of the flying object 130 relative to the array antenna 110 based on the phase of a signal communicated between the antenna 110 and the communication unit 132 when it is received by the array antenna 110 or multiple antenna elements of the communication unit 132, and a second position calculation unit 126 that calculates the position of the flying object 130 based on the position determined by the first position calculation unit 122, the distance measured by the distance measurement unit 123, and elevation angle 1 (first elevation angle) calculated by the angle calculation unit 124.

[0108] Therefore, it is possible to provide a positioning system 100 that has a simple configuration and can easily determine the position of an aircraft.

[0109] Furthermore, the second position calculation unit 126 may calculate a coordinate difference (ΔX, ΔY) between the coordinates in the ENU coordinate system of the air vehicle 130 and the coordinates in the ENU coordinate system of the array antenna 110 based on the distance and the first elevation angle, calculate a difference (Δα, Δβ) in the latitude and longitude of the air vehicle 130 relative to the array antenna 110 based on the coordinate difference, and add the difference in latitude and longitude to the latitude and longitude (α, β) representing the position of the array antenna 110, thereby calculating the position of the air vehicle 130. By converting the coordinate difference (ΔX, ΔY) between the coordinates in the ENU coordinate system of the air vehicle 130 relative to the array antenna 110 into the difference in latitude and longitude (Δα, Δβ) and adding it to the latitude and longitude of the array antenna 110, the air vehicle can be easily positioned.

[0110] In addition, the second position calculation unit 126 may calculate the difference in latitude Δα and the difference in longitude Δβ of the aircraft 130 relative to the array antenna 110 using the following equations (7A) and (7B) in an approximate calculation assuming the Earth as a sphere.

[0111] Δα=ΔY / A (7A) Δβ=ΔX / A cos(α+Δα) (7B) Here, A is the radius of the Earth when considered as a sphere.

[0112] In an approximate calculation assuming the Earth as a sphere, the difference in latitude Δα and the difference in longitude Δβ of the aircraft 130 relative to the array antenna 110 can be easily calculated, and by adding these to the latitude and longitude of the array antenna 110, the aircraft can be easily positioned.

[0113] The angle calculation unit 124 may further calculate the azimuth angle of the flying object 130 relative to the array antenna 110 based on the phase of a signal communicated between the array antenna 110 and the communication unit 132 when the signal is received by the multiple antenna elements of the array antenna 110 or the communication unit 132. The azimuth angle of the flying object 130 can also be obtained.

[0114] The array antenna 110 may also have antenna elements 112 that are arranged facing vertically upward, which improves the radiation characteristics of the array antenna 110 and makes it easier to measure the position of the flying object 130.

[0115] The flying vehicle 130 is further equipped with a barometric pressure sensor 133 (altitude measurement unit) that is mounted on the flying vehicle 130 and that measures the altitude of the flying vehicle 130 relative to the array antenna 110, and a correction value calculation unit 125 that calculates a correction value as the difference between the altitude acquired by the barometric pressure sensor 133 and the distance measured by the distance measurement unit 123 when the absolute value of the elevation angle 1 is equal to or less than a first predetermined angle.After the correction value calculation unit 125 calculates the correction value, if the absolute value of the elevation angle 1 is equal to or greater than a second predetermined angle that is greater than the first predetermined angle, the angle calculation unit 124 calculates the arccosine of the value obtained by correcting the altitude acquired by the barometric pressure sensor 133 with the correction value and dividing it by the distance measured by the distance measurement unit 123 as the elevation angle 2 (second elevation angle), and selects either the elevation angle 1 or the elevation angle 2 based on the value of the elevation angle 1.

[0116] Therefore, when the elevation angle is large, the elevation angle is calculated using the distance corrected by the air pressure sensor 133, thereby reducing angle measurement errors and providing a positioning system 100 that has a simple configuration and can easily position an aircraft.

[0117] Furthermore, once the angle calculation unit 124 calculates the elevation angle 2, the second position calculation unit 126 may calculate the position of the flying object 130 based on the position measured by the first position calculation unit 122, the distance measured by the distance measurement unit 123, and the elevation angle 2. Therefore, when the absolute value of the elevation angle 1 is equal to or greater than a second predetermined angle (for example, 60 degrees) that is greater than the first predetermined angle (for example, 5 degrees) and the error in the elevation angle 1 calculated based on the phase when received by the multiple antenna elements 112 of the array antenna 110 is large, it is possible to provide a positioning system 100 that can easily position the flying object with a simple configuration using the elevation angle 2.

[0118] Furthermore, the first predetermined angle (for example, 5 degrees) is an angle at which the elevation angle directly above the array antenna 110 falls within a predetermined range of angles, and the predetermined range of angles is a range within which the flying object 130 is considered to be located directly above the array antenna 110. Therefore, when the flying object 130 is located approximately directly above the array antenna 110, a correction value can be calculated using the distance measured by the distance measurement unit 123 in ToA format (a distance corresponding to the altitude of the flying object 130) and the altitude measured by the atmospheric pressure sensor 133.

[0119] Furthermore, when the absolute value of the elevation angle 1 becomes equal to or less than a first predetermined angle (for example, 5 degrees), the correction value calculation unit 125 calculates the difference between the altitude acquired by the atmospheric pressure sensor 133 and the distance measured by the distance measurement unit 123 as a correction value and updates the correction value, so that when the flying object 130 is located approximately directly above the array antenna 110, the correction value can be updated to the latest correction value.

[0120] Furthermore, since the atmospheric pressure sensor 133 is a pressure sensor that measures the altitude of the flying object 130 based on atmospheric pressure, it can accurately detect the altitude of the flying object 130 and calculate a correction value with high precision. If the error in the elevation angle 1 calculated based on the phase when received by the multiple antenna elements 112 of the array antenna 110 is large, the elevation angle 2 can be calculated with high precision using the altitude acquired by the atmospheric pressure sensor 133 and the correction value instead of the elevation angle 1.

[0121] Furthermore, the distance measurement unit 123, the angle calculation unit 124, and the correction value calculation unit 125 are provided on the array antenna 110 side, and the array antenna 110 has three or more antenna elements 112. Therefore, the control device 120 installed on the ground or a fixed object on the ground can stably calculate the distance and correction value between the array antenna 110 and the flying object 130, and can stably calculate the elevation angle 1 using the phase difference obtained using the three or more antenna elements 112. Furthermore, the stably calculated distance and correction value can be used to stably calculate the elevation angle 2.

[0122] Furthermore, since the communication unit 132 has one antenna element 132A, under the assumption that the control device 120 on the ground calculates the distance, correction value, elevation angle 1, and elevation angle 2, the communication unit 132 of the flying object 130 can be configured to measure the phase when receiving a signal transmitted from the array antenna 110, and to transmit a signal when the control device 120 measures the elevation angle and azimuth angle of the flying object 130 in AoA format, thereby simplifying the configuration on the flying object 130 side.

[0123] <Modification> The above describes a configuration in which the control device 120 on the ground measures distance using the ToA method, measures elevation angle 1 and azimuth angle using the AoA method, calculates a correction value, and calculates elevation angle 2. However, the control device 131 of the flying object 130 may measure distance using the ToA method, measures elevation angle 1 and azimuth angle using the AoA method, calculates a correction value, and calculates elevation angle 2. In this case, the communication unit 132 of the flying object 130 only needs to have multiple antenna elements 132A to detect the phase difference of the signals when measuring elevation angle 1 and azimuth angle using the AoA method. In this case, at least one antenna element 112 may be provided on the ground instead of the array antenna 110. The flying object 130 may transmit elevation angle 1, azimuth angle, correction value, and elevation angle 2 to the array antenna 110, and the control device 120 may receive elevation angle 1, azimuth angle, correction value, and elevation angle 2 via the array antenna 110.

[0124] The above describes a positioning system according to an exemplary embodiment of the present disclosure. However, the present disclosure is not limited to the specifically disclosed embodiment, and various modifications and variations are possible without departing from the scope of the claims.

[0125] This international application claims priority based on Japanese Patent Application No. 2023-082555, filed on May 18, 2023, the entire contents of which are incorporated herein by reference.

[0126] 100 Positioning system 110 Array antenna (an example of a first communication unit) 111 Substrate 112 Antenna element 120 Control device 121 Communication control unit 122 First position calculation unit 123 Distance measurement unit 124 Angle calculation unit 125 Correction value calculation unit 126 Second position calculation unit 127 Memory 130 Aircraft 131 Control device 132 Communication unit (an example of a second communication unit) 132A Antenna element 133 Barometric pressure sensor (an example of an altitude measurement unit)

Claims

1. a first communication unit; a first position calculation unit that measures the position of the first communication unit; a flying object movable relative to the first communication unit; a second communication unit mounted on the aircraft and communicating with the first communication unit; a distance measurement unit that measures the distance between the first communication unit and the aircraft based on a propagation time or a phase of a signal communicated between the first communication unit and the second communication unit; an angle calculation unit that calculates an elevation angle of the flying object relative to the first communication unit based on a phase of a signal communicated between the first communication unit and the second communication unit when the signal is received by a plurality of antenna elements of the first communication unit or the second communication unit, and calculates an azimuth angle of the flying object relative to the first communication unit based on a phase of a signal communicated between the first communication unit and the second communication unit when the signal is received by a plurality of antenna elements of the first communication unit or the second communication unit; a second position calculation unit that calculates a position of the aircraft based on the position measured by the first position calculation unit, the distance measured by the distance measurement unit, and the first elevation angle calculated by the angle calculation unit; an altitude measurement unit mounted on the aircraft and configured to measure the altitude of the aircraft relative to the first communication unit; a correction value calculation unit that calculates, as a correction value, a difference between the altitude acquired by the altitude measurement unit and the distance measured by the distance measurement unit when the absolute value of the first elevation angle is equal to or smaller than a first predetermined angle; Equipped with and if, after the correction value calculation unit calculates the correction value, the absolute value of the first elevation angle is equal to or greater than a second predetermined angle that is greater than the first predetermined angle, the angle calculation unit calculates, as a second elevation angle, the arccosine of a value obtained by correcting the altitude acquired by the altitude measurement unit with the correction value and dividing the value by the distance measured by the distance measurement unit, and selects either the first elevation angle or the second elevation angle based on the value of the first elevation angle.

2. The second position calculation unit calculating a coordinate difference (ΔX, ΔY) between a coordinate in the ENU coordinate system of the first communication unit and a coordinate in the ENU coordinate system of the aircraft based on the distance and the first elevation angle; Calculating the difference (Δα, Δβ) between the latitude and longitude of the flying object relative to the first communication unit based on the coordinate difference; The positioning system according to claim 1 , wherein the position of the flying object is calculated by adding a difference between the latitude and longitude (α, β) to the latitude and longitude (α, β) representing the position of the first communication unit.

3. 3. The positioning system according to claim 2, wherein the second position calculation unit calculates the difference in latitude Δα and the difference in longitude Δβ of the aircraft relative to the first communication unit using the following equations (1A) and (1B) in an approximate calculation assuming the Earth as a sphere. Δα=ΔY / A (1A) Δβ=ΔX / Acos(α+Δα) (1B) where A is the radius of the Earth when considered as a sphere.

4. The positioning system according to claim 1 , wherein the first communication unit has an antenna element that is arranged facing vertically upward.

5. 2. The positioning system according to claim 1, wherein, when the angle calculation unit calculates the second elevation angle, the second position calculation unit calculates the position of the aircraft based on the position measured by the first position calculation unit, the distance measured by the distance measurement unit, and the second elevation angle.

6. The positioning system according to claim 1 , wherein the first elevation angle is calculated in an AoA format, and the second elevation angle is calculated using ToA.

7. The positioning system according to claim 1 , wherein the first predetermined angle is an angle at which an elevation angle directly above the first communication unit falls within a predetermined range of angles.

8. 8. The positioning system according to claim 1, wherein when the absolute value of the first elevation angle becomes equal to or less than the first predetermined angle, the correction value calculation unit calculates a difference between the altitude acquired by the altitude measurement unit and the distance measured by the distance measurement unit as the correction value, and updates the correction value.

9. The positioning system according to claim 1 , wherein the altitude measurement unit is a barometric pressure sensor that measures the altitude of the flying object based on barometric pressure.

10. the distance measurement unit, the angle calculation unit, and the correction value calculation unit are provided on the first communication unit side, The positioning system according to claim 1 , wherein the first communication unit has three or more antenna elements.

11. The positioning system according to claim 10 , wherein the second communication unit has one antenna element.