Unmanned aerial vehicle routing method

Abstract

To provide an unmanned aerial vehicle routing method that allows an unmanned aerial vehicle to continue flight after radio wave acquisition from GNSS is ceased, even if image data has not been acquired for a flight path.SOLUTION: A method of setting a flight path of an unmanned aerial vehicle includes: a first step of calculating the satellite acquisition state of the unmanned aerial vehicle based on the positional relationship between a satellite that constitutes a satellite positioning system and the unmanned aerial vehicle at any point along a planned route of the autonomous flight of the unmanned aerial vehicle; and a second step of comparing the acquisition state calculated in the first step with a reference acquisition state required for flight control of the unmanned aerial vehicle.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for setting a route during flight of an Unmanned Aerial Vehicle (UAV). [Background technology]

[0002] During autonomous flight, a UAV flies along a planned flight path while receiving radio waves related to its location from the Global Navigation Satellite System (GNSS), and confirming its own position. If radio waves from the GNSS are no longer received, the pilot must either switch to manual control or land the UAV in a safe zone that is pre-programmed as a fail-safe function.

[0003] When a pilot operates the UAV manually, the pilot must operate the UAV by visually observing the UAV or by referring to images from a camera mounted on the UAV. In addition, the latter programming cannot confirm the location of the aircraft because it cannot use GNSS. Therefore, it is necessary to land the aircraft in a safe area using image recognition by artificial intelligence (AI) from the images of the onboard camera, or to deploy a parachute to make an emergency landing. However, safety is not necessarily guaranteed.

[0004] Patent Document 1 discloses an image processing device that corrects the position and attitude angle based on the captured image to acquire an image of the sky above a specific area even if radio waves from a GPS (Global Positioning System), which is an example of a GNSS, are lost. Patent Document 1 creates an image database of images acquired during movement using an image acquisition means mounted on a UAV, and refers to the image database when the GPS link is lost. Then, it calculates a correlation value between an image in the image database and a current image, performs coordinate transformation using an image with a high correlation as a reference value, and calculates an error estimate of the position and attitude angle of the drone. The obtained error estimate of the position and attitude angle is input to a GPS / INS (Global Positioning System / Inertial Navigation System) calculation to detect the position and attitude angle. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-304260 A Summary of the Invention [Problem to be solved by the invention]

[0006] According to Patent Document 1, the UAV can continue flying even after the reception of radio waves from the GPS is interrupted. However, the UAV in Patent Document 1 is premised on flying over a specific area multiple times, and image data about the flight route must be acquired in advance. In other words, the proposal in Patent Document 1 cannot be applied when it is the first time to fly to a destination or the flight route to a destination is the first time. In view of the above, an object of the present disclosure is to provide a route setting method for a UAV that can continue flying without interrupting acquisition of radio waves from GNSS even if image data has not been acquired for the flight route. [Means for solving the problem]

[0007] The method for setting a flight path for an unmanned aerial vehicle according to the present disclosure includes: A first step of calculating a satellite capture state of the unmanned aircraft based on a positional relationship between the unmanned aircraft and a satellite constituting a satellite positioning system at any point on a planned route of the autonomously flying unmanned aircraft; A second step of comparing the capture state calculated in the first step with a reference capture state required for flight control of the unmanned aerial vehicle. Effect of the Invention

[0008] According to the present disclosure, a route setting method for a UAV is provided that allows the UAV to continue flying without interrupting acquisition of radio waves from a GNSS even if image data has not been acquired for the flight route. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram showing an example of a flight route set in an embodiment. [Diagram 2] FIG. 13 is a diagram illustrating the maximum elevation angle θmax and correction. [Diagram 3] FIG. 11 is a diagram showing the relationship between the maximum elevation angle θmax and satellites from which radio waves can be received. [Figure 4] 1 is a graph showing the relationship between multiple waypoints and the minimum altitude at which a sufficient number of satellites can be captured for flight control. [Diagram 5] FIG. 4 is a flow chart showing a control procedure in the embodiment. [Figure 6] FIG. 2 is a diagram illustrating an example of the configuration of a control unit for executing a control procedure in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments will be described with reference to the accompanying drawings. In this embodiment, when setting a flight path before the UAV 10 flies autonomously, it is determined whether or not the number of captured satellites (satellite capture number) n of multiple satellites constituting the GNSS reaches a reference satellite capture number N required for flight control of the UAV 10. In this embodiment, the satellite capture number n is calculated based on the elevation angle θ with respect to the surrounding environment of the UAV 10. In this embodiment, this determination result is reflected when determining the flight path. Note that, here, an example of determining the satellite capture number n is described, but as will be described later, DOP (Dilution Of Precision), which is an index of positioning accuracy, can be used as a substitute for the satellite capture number n or as a determination target together with the satellite capture number n.

[0011] [Flight route FP: See Figure 1] In this embodiment, as an example, the flight route FP shown in Figure 1 is set. This flight route FP is set with WP1, WP2, WP3, WP4, WP5, WP6, and WP7 as way points. Although only WP7 is shown here, the flight route FP further has way points WP8, etc. A waypoint is information about a point on the flight route FP, and in this embodiment, for example, is composed of three elements, latitude (latitude, x), longitude (longitude, y), and altitude (altitude, z), as shown below. However, the flight route FP below is set provisionally, and one of WP1 to WP7 is corrected based on the result of the determination made for the satellite capture number n, and the final flight route FP is determined.

[0012] Flight Route FP WP1:(x1,y1,z1) , WP2:(x2,y2,z2) WP3:(x3,y3,z3) , WP4:(x4,y4,z4) WP5:(x5,y5,z5) , WP6:(x6,y6,z6) WP7: (x7,y7,z7)

[0013] [Satellite reception failure: see Figures 2 and 3] The UAV 10 can fly autonomously by acquiring information necessary to calculate its position relative to the earth. This information can be acquired from a satellite positioning system (Global Navigation Satellite System: GNSS). GNSS includes GPS (Global Positioning System), QZSS (Japan), GLONASS (Russia), Galileo (EU), and the like, and any of these systems can be used in this embodiment. These GNSSs are composed of multiple artificial satellites (hereinafter simply referred to as satellites) that orbit the earth. Since the multiple satellites that make up the GNSS orbit the earth, the satellite positions differ depending on the date and time. Information on the relationship between the date and time and the satellite positions in the GNSS is publicly available.

[0014] As an example, there are more than 30 satellites that make up the GPS around the Earth, each of which makes six orbits once every 12 hours. The GPS receiver in the UAV 10 receives radio waves from at least four of these satellites and calculates its own position information using a calculation method typically known as three-dimensional positioning. Therefore, the surrounding environment of the UAV 10 may become an obstacle, making it impossible to receive radio waves from the number of satellites necessary to calculate the position information, i.e., it may not be possible to capture the satellites. The surrounding environment may include natural environments such as mountains and trees, as well as artificial environments such as high-rise buildings.

[0015] The flight path FP shown in Figure 1 is an example that follows a mountainous area, so the mountains may be an obstacle to satellite capture. Figure 2 shows a schematic diagram of the relationship between the UAV 10 and obstacles 101 and 102 consisting of surrounding mountains in WP3, for example. In WP3, the UAV 10 is sandwiched between the obstacles 101 and 102. Comparing the elevation angle θ with respect to the vertex 101T of the obstacle 101 or the vertex 102T of the obstacle 102 based on the UAV 10, the elevation angle θ with respect to the vertex 101T is larger, forming the maximum elevation angle θmax in WP3. In addition, since the position of the UAV 10 in WP3 is known, and the position information regarding the mountain obstacle 101 and the apex 101T is also known as topographical data, the elevation angle θ can be found by calculation. In addition, while two obstacles, obstacle 101 and obstacle 102, have been described here, the maximum elevation angle θmax means the maximum elevation angle in a 360° azimuth with WP3 as the reference. Using the maximum elevation angle θmax is a preferred embodiment because the calculation is simple and can be completed in a short time, but it is also possible to calculate the elevation angle θ at a predetermined angle interval in a 360° azimuth, and compare the captured satellite number n with the reference captured satellite number N for each calculated elevation angle θ.

[0016] In addition, the point where the line drawn from the UAV 10 touches the outline (ridge) of the obstacle (tangency point) is the point that specifies the elevation angle θ, and in the case of the obstacles 101 and 102, the vertices 101T and 102T with the highest elevations are the tangency points. However, if the outline includes, for example, a circular arc, like the obstacle 103 shown by the dashed line in Figure 2 (Before), the tangency point 103C is a point different from the vertex 103T.

[0017] The greater the elevation angle θ relative to the apex of the obstacle, the greater the degree of obstruction to capture of the satellites that make up the GNSS. FIG. 3 shows the maximum elevation angle θmax and the capture status of multiple satellites 20. In FIG. 3, the satellites 20 shown by solid lines indicate that the receiver equipped in the UAV 10 has received and captured the radio waves, and the satellites 20 shown by dashed lines indicate that they have not been captured by the UAV 10. If the maximum elevation angle θmax is greater than that shown in the figure, the number n of captured satellites 20 will be smaller. Note that the number of captured satellites, 4, in FIG. 3 is merely an example.

[0018] Assume that the maximum elevation angle θmax for WP3 shown in FIG. 2 (Before) does not reach the number of satellites 20 that can identify the own position of the UAV 10. For example, when the GNSS is GPS, the acquisition number n is 3. Therefore, if the assumedly set WP3 (x3, y3, z3) is left as it is, the acquisition number n is insufficient, and the receiver of the UAV 10 cannot calculate the own position. Therefore, as shown in FIG. 2 (After), the waypoint WP3 is corrected. The waypoint is corrected by changing the position. More specifically, the position in the vertical direction V and the position in the horizontal direction H are changed to a corrected position, or both. In the example shown in FIG. 2, both the position in the vertical direction V and the position in the horizontal direction H are changed, and the position is corrected to, for example, WP3' (x3', y3', z3'). Although WP3' also has a maximum elevation angle θ'max, the relationship between the maximum elevation angle θmax before correction and the maximum elevation angle θmax is set to be greater than the maximum elevation angle θ'max, and the number of captured satellites 20 at the maximum elevation angle θ'max is corrected to, for example, 4, so that the satellite's position can be calculated.

[0019] The simplest way to reduce the elevation angle θ is to change the altitude of the waypoint upward in the vertical direction V. However, for example, according to the aviation law in Japan, the flight altitude of the UAV 10 is regulated to 150 m or less in principle. Therefore, even if the capture number n is secured by changing only the altitude, it will not be possible to comply with the flight altitude regulation. Therefore, in this embodiment, it is possible to select one or both of the correction in the vertical direction V and the correction in the horizontal direction H.

[0020] When the UAV 10 is flying, the actual number of captured satellites n in the control unit 11 can be recognized. However, at the stage of setting the flight path FP before flight, which is the subject of this embodiment, the actual number of captured satellites n cannot be recognized. Therefore, in this embodiment, the number of captured satellites n is calculated based on the elevation angle θ. Note that, since information on the satellites 20 that constitute the GNSS is publicly available, the number of captured satellites n can be calculated by calculating the elevation angle θ.

[0021] [Minimum altitude required to ensure standard satellite capture number N: Figure 4] Although WP3 has been exemplified above, it is possible to specify the minimum altitude Hm at which the reference satellite capture number N for calculating the UAV 10's own position is secured for other waypoints such as WP1. Figure 4 shows an example. Note that Figure 4 only shows the altitude of the waypoints. In Figure 4, in WP1, the reference number N of captured satellites that can calculate the own position is ensured if the altitude is 40m, and in WP3, the reference number N of captured satellites that can calculate the own position is ensured if the altitude is 60m. In WP4 to WP7, the minimum altitude exceeds 100m, which suggests that the surrounding obstacles such as mountains are high in altitude.

[0022] [Example of route setting procedure with correction: see Figures 5 and 6] Next, an example of a procedure for route setting with correction will be described. This route setting is performed before the flight of the UAV 10, and the procedure shown in FIG. 5 is executed by the control unit 11 of the UAV 10 shown in FIG.

[0023] First, the flight path FP is set (FIG. 5 S101). The flight path FP is set through the setting of a plurality of way points. The flight path FP at this time may be corrected in a later procedure, and therefore may be called a tentative flight path FP. The tentative flight path FP is stored in the storage unit 11B provided in the control unit 11. As described above, each way point includes three elements: latitude, longitude, and altitude. The method of setting the flight path FP at this time is arbitrary, and the flight path FP may be set by a person based on the terrain data, or may be set by a computer device based on the terrain data. At this time, the latitude and longitude are set according to the terrain data, but the altitude may be set to the same value for all way points. This is because the altitude is highly likely to be a subject of correction in this embodiment. The flight path FP may be set directly for the UAV 10, or may be set outside the UAV 10 and saved in the UAV 10.

[0024] Next, for each of the provisionally set waypoints, the satellite capture number n is compared with the reference satellite capture number N and a judgment is made. For this purpose, a waypoint is selected (FIG. 5, S103). For example, in the case where seven waypoints WP1 to WP7 shown in FIG. 1 are set, WP1 is selected first, and the satellite capture number n in WP1 is compared with the reference satellite capture number N. After the comparison of the satellite capture number n in WP1 with the reference satellite capture number N is completed, WP2 is selected, and the satellite capture number n in WP2 is compared with the reference satellite capture number N. Thereafter, selection and comparison of WP3, selection and comparison of WP4, ..., selection and comparison of WP7 are performed. This comparison and correction is performed by the calculation unit 11C of the control unit 11 with reference to the position information on the flight route FP stored in the memory unit 11B.

[0025] When a waypoint is selected, the maximum elevation angle θmax at the selected waypoint is calculated (FIG. 5, S105). The calculation of this maximum elevation angle θmax is performed by referring to pre-stored topographical data. As an example of this topographical data, in Japan, data created by the Geospatial Information Authority of Japan by interpolating elevation values ​​at 5m intervals based on height data measured by airborne laser surveying can be used.

[0026] Once the maximum elevation angle θmax is calculated, the satellite capture number n, which is the number of artificial satellites from which information necessary to calculate the position from the Global Navigation Satellite System (GNSS) at the waypoint can be obtained, is calculated (FIG. 5, S107). Note that the calculation of the satellite capture number n also takes into account the date and time when the UAV 10 flies the flight path FP. This is because, as described above, the multiple satellites that make up the Global Navigation Satellite System (GNSS) orbit the Earth, and therefore the positions of the satellites vary depending on the date and time.

[0027] Once the number of captured satellites n is calculated, it is compared with the reference number of captured satellites N for that waypoint (Fig. 5, S109). If the number of captured satellites n reaches the reference number of captured satellites N (N≦n, S109 YES), there is no need to correct the setting information (latitude, longitude, and altitude) for that waypoint. If the number of captured satellites n does not reach the reference number of captured satellites N (N>n, S109 No), there is a need to correct the setting information (latitude, longitude, and altitude) for that waypoint.

[0028] If the setting information for the waypoint needs to be corrected, as an example, the altitude of the UAV 10 in the setting information (latitude, longitude, and altitude) is increased (FIG. 5, S111). The increase in altitude can be a specified value, for example, A(m). If the comparison and judgment is for WP3, then the altitude is corrected to Z3', which is z3 of WP3 plus A(m). The corrected altitude is set to Z3', and the maximum elevation angle θmax is calculated (FIG. 5, S107), and the number of captured satellites n is calculated (FIG. 5, S109). This procedure is repeated until the number of captured satellites n reaches the reference number of captured satellites N.

[0029] When it is determined that the number of captured satellites n has reached the reference number of captured satellites N (N≦n), it is determined whether or not the altitude is higher than that of the previous waypoint (FIG. 5, S113). This is because it is possible that the number of captured satellites n does not exceed the reference number of captured satellites N between the previous waypoint and the waypoint currently being compared and judged. For example, if the waypoint currently being compared and judged is WP3, then the altitude is compared with that of the previous WP2. If the altitude of WP3 is z3 and the altitude of WP2 is z2, then a comparison is made to see which is larger or smaller, z3 and z2. If the waypoint currently being compared and judged is WP3 and its altitude is z3, then the altitude of the previous WP2 is corrected from z2 to z3.

[0030] By performing the above comparisons, judgments, and necessary corrections for all waypoints, the setting of the flight path FP is completed, and the UAV 10 is prepared to fly. The flight path FP for which the setting is completed is stored in the memory unit 11B. When the UAV 10 flies autonomously, the memory unit 11B identifies its own position based on radio waves received from the satellite 20 by the receiver 11A, and compares the flight path FP stored in the memory unit 11B with the identified own position.

[0031] [Effects of the embodiment] According to this embodiment, the number of captured satellites n constituting the global navigation satellite system (GNSS) is calculated based on the elevation angle θ calculated by referring to the topographical data, and the number of captured satellites n is compared with the reference number of captured satellites N required for flight control. Then, based on the comparison result, one or both of the vertical position (Pv) and horizontal position (Hv) of the UAV 10 are changed. Therefore, according to this embodiment, the flight of the UAV 10 can be ensured without interruption in receiving radio waves from the GNSS.

[0032] It is possible to select from the configurations given in the above embodiments, or to change to other configurations as appropriate. In the above embodiment, an example is described in which the satellite capture number n is compared with the reference satellite capture number N for a waypoint, but the present disclosure can perform the comparison, determination, and correction processes at any point on the flight path. More specifically, the processes can be performed at predetermined intervals on the flight path, for example, at intervals of 100 m.

[0033] The above embodiment shows an example of applying the present disclosure when setting a route before the flight of a UAV, but the present disclosure can also be applied to a UAV that is actually flying. For example, a flying UAV can recognize the satellite capture number n, but it cannot specify whether the reference satellite capture number N required for flight control can be secured by increasing the altitude of the UAV. However, even if the satellite capture number n of a flying UAV becomes insufficient, the reference satellite capture number N required for flight control can be secured by applying the procedure shown in FIG. 5, for example.

[0034] In the above embodiment, the number of captured satellites is compared and determined, but instead of the number of captured satellites, or in addition to comparing and determining the number of captured satellites, DOP (Dilution Of Precision: Positioning Accuracy Degradation Coefficient) can be used. DOP varies depending on the geometric positional relationship between the UAV 10 (receiving unit 11A) and the satellite 20, and the smaller the value, the higher the positioning accuracy. In other words, DOP can also be said to be information that specifies the capture state of the satellite 20, and DOP can be improved by correcting the position of the UAV. Here, the satellite capture number is specified based on the positional relationship between the satellites 20 constituting the GNSS and the UAV 10 (receiving unit 11A), but the DOP is also common in that it is a capture state specified based on the positional relationship between the satellites 20 and the UAV 10 (receiving unit 11A). Therefore, in the present disclosure, the positioning accuracy degradation coefficient d and the reference positioning accuracy degradation coefficient D can be compared and determined as substitutes for the satellite capture number n and the reference satellite capture number N, and the necessary correction can be made to the route setting FP of the UAV 10.

[0035] In the above embodiment, an example has been described in which the elevation angle θ is specified for the vertices 101T, 102T of the obstacles 101, 102. However, depending on the shape of the obstacle, it may be necessary to specify the elevation angle θ for a position other than the vertices. For example, consider an obstacle 103 whose outline (ridgeline) is an arc, as shown in Fig. 2 (Before). In the case of this obstacle 103, when comparing the angle of attack θ at the vertex 103T with the angle of attack θ at the tangent point 103C where a tangent line is drawn from the UAV 10 to the obstacle 103, the angle of attack θ at the tangent point 103C is larger, forming the maximum elevation angle θmax in WP3.

[0036] [Note] The present disclosure can be understood as follows. [Appendix 1] The method for setting the flight path of an unmanned aerial vehicle is as follows: A first step of calculating a satellite capture state of the unmanned aircraft based on a positional relationship between the unmanned aircraft and a satellite constituting a satellite positioning system at any point on a planned route of the autonomously flying unmanned aircraft; and a second step of comparing the capture state calculated in the first step with a reference capture state required for flight control of the unmanned aerial vehicle. [Appendix 2] The flight path setting method in Supplementary Note 1 preferably includes: In the first step, A 1-1 step of calculating an elevation angle θ at any point; A 1-2 step of calculating a capture number n of artificial satellites from which information required for calculating a position can be obtained from the satellite positioning system based on the elevation angle θ calculated in the 1-1 step; In the second step, The calculated acquisition number n is compared with the reference satellite acquisition number N required for flight control. [Appendix 3] In the second step of the comparison in Appendix 2, If the acquisition number n does not reach the reference satellite acquisition number N, Calculating a position correction that changes one or both of the vertical and horizontal positions of the unmanned aerial vehicle; Execute the 1-1 step, the 1-2 step and the 2-2 step for the correction position; [Appendix 4] Preferably, for the correction position in Supplementary Note 3, execute the 1-1 step, the 1-2 step, and the 2nd step; If the acquisition number n reaches the reference satellite acquisition number N, the corrected position is incorporated into the planned route. [Appendix 5] In the second step of the comparison according to any one of Supplementary Note 1 to Supplementary Note 3, preferably, If the number of captured satellites n reaches the reference number of captured satellites N, the planned route is maintained. [Appendix 6] In step 1-1 of any one of Supplementary Note 2 to Supplementary Note 5, preferably, Calculate the maximum elevation angle θmax at the point, In the 1st and 2nd steps, The capture number n is calculated based on the maximum elevation angle θmax. [Appendix 7] In any one of Supplementary Note 2 to Supplementary Note 5, the first and second steps are preferably executed when setting a planned route. [Appendix 8] In Appendix 7, for multiple points on the planned route at predetermined intervals, or The first and second steps are executed for a plurality of waypoints on the planned route. [Appendix 9] In any of Supplementary Note 1 to Supplementary Note 7, the first and second steps are preferably executed while the unmanned aerial vehicle is flying autonomously according to a set planned route. [Appendix 10] In Appendix 1, preferably, In the first step, Calculate the positioning accuracy degradation coefficient d at any point, In the second step, The calculated positioning accuracy degradation coefficient d is compared with a reference positioning accuracy degradation coefficient D required for flight control. [Explanation of symbols]

[0037] 10 UAV 11 Control section 11A Receiver 11B Storage section 11C Arithmetic unit 20 satellites 101,102,103 Obstacles

Claims

1. A first step of calculating a capture state of an artificial satellite by an unmanned aerial vehicle based on a positional relationship between the unmanned aerial vehicle and an artificial satellite constituting a satellite positioning system at any point on a planned route of the autonomously flying unmanned aerial vehicle; A flight path planning method comprising a second step of comparing the capture state calculated in the first step with a reference capture state required for flight control of the unmanned aerial vehicle.

2. In the first step, A first-1 step of calculating an elevation angle θ at any one of the points; a 1-2 step of calculating a capture number n of the artificial satellites for which information required for calculating a position can be obtained from the satellite positioning system based on the elevation angle θ calculated in the 1-1 step; In the second step, comparing the calculated acquisition number n with a reference satellite acquisition number N required for flight control; The flight path planning method according to claim 1 .

3. In the comparison of the second step, If the acquisition number n does not reach the reference satellite acquisition number N, Calculating a corrected position that changes one or both of the vertical and horizontal positions of the unmanned aerial vehicle; Executing the 1-1 step, the 1-2 step, and the 2 step for the corrected position; The flight path planning method according to claim 2 .

4. Executing the 1-1 step, the 1-2 step and the 2 step for the correction position; If the acquisition number n reaches the reference satellite acquisition number N, the corrected position is incorporated into the planned route. The flight path planning method according to claim 3.

5. In the comparison of the second step, If the acquisition number n reaches the reference satellite acquisition number N, the planned route is maintained. The flight path planning method according to claim 2 .

6. In the 1-1 step, Calculating a maximum elevation angle θmax at the point; In the first-2 step, Calculating the capture number n based on the maximum elevation angle θmax; The flight path planning method according to claim 2 .

7. executing the first step and the second step when setting the planned route; The flight path planning method according to claim 1 .

8. For a plurality of said points spaced at predetermined intervals on said planned route, or performing the first step and the second step for a plurality of waypoints on the planned route; The flight path planning method according to claim 7.

9. executing the first step and the second step while the unmanned aerial vehicle is flying autonomously according to the set planned route; The flight path planning method according to claim 1 .

10. In the first step, Calculating a positioning accuracy degradation coefficient d at any one of the points; In the second step, The calculated positioning accuracy degradation coefficient d is compared with a reference positioning accuracy degradation coefficient D required for flight control. The flight path planning method according to claim 1 .

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