METHOD FOR SETTING FLIGHT PATH OF UNMANNED AERIAL VEHICLE

Abstract

A method for setting a flight path of an unmanned aerial vehicle includes calculating an availability state, in an unmanned aerial vehicle, of artificial satellites based on a positional relationship between the artificial satellites constituting a global navigation satellite system and the unmanned aerial vehicle at any of points in a scheduled path of the unmanned aerial vehicle flying autonomously. The method further includes comparing the availability state calculated and a reference availability state required for flight control of the unmanned aerial vehicle.

Claims

1. A method for setting a flight path, comprising: a step 1 of calculating an availability state, in an unmanned aerial vehicle, of artificial satellites based on a positional relationship between the artificial satellites constituting a global navigation satellite system and the unmanned aerial vehicle at any of points in a scheduled path of the unmanned aerial vehicle flying autonomously; and a step 2 of comparing the availability state calculated in the step 1 and a reference availability state required for flight control of the unmanned aerial vehicle.

2. The method for setting a flight path according to claim 1, wherein the step 1 comprises: a step 1-1 of calculating an elevation angle at any of the points; and a step 1-2 of calculating an availability number n of the artificial satellites capable of acquiring information required for calculating a position from the global navigation satellite system based on the elevation angle calculated in the step 1-1, and in the step 2, the calculated availability number n and a reference satellite availability number N required for flight control are compared.

3. The method for setting a flight path according to claim 2, wherein in the comparing in the step 2, when the availability number n has not reached the reference satellite availability number N, a correction position is calculated for changing one or both of a position in a vertical direction and a position in a horizontal direction of the unmanned aerial vehicle, and the step 1-1, the step 1-2, and the step 2 are executed for the correction position.

4. The method for setting a flight path according to claim 3, wherein the step 1-1, the step 1-2, and the step 2 are executed for the correction position, and when the availability number n has reached the reference satellite availability number N, the correction position is incorporated into the scheduled path.

5. The method for setting a flight path according to claim 2, wherein in the comparing in the step 2, when the availability number n has reached the reference satellite availability number N, the scheduled path is adhered to.

6. The method for setting a flight path according to claim 2, wherein in the step 1-1, a maximum elevation angle max is calculated at any of the points, and in the step (1-2), the availability number n is calculated based on the maximum elevation angle max.

7. The method for setting a flight path according to claim 1, wherein the step 1 and the step 2 are executed when setting the scheduled path.

8. The method for setting a flight path according to claim 7, wherein the step 1 and the step 2 are executed for a plurality of the points separated by a predetermined interval in the scheduled path or for a plurality of waypoints in the scheduled path.

9. The method for setting a flight path according to claim 1, wherein the step 1 and the step 2 are executed when the unmanaged aerial vehicle is flying autonomously according to the set scheduled path.

10. The method for setting a flight path according to claim 1, wherein in the step 1, a positioning accuracy degradation coefficient d at any of the points is calculated, and in the step 2, the calculated positioning accuracy degradation coefficient d and a reference positioning accuracy degradation coefficient D required for flight control are compared.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0013] The disclosure will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

[0014] FIG. 1 is a diagram illustrating an example of a flight path set in an embodiment.

[0015] FIG. 2 is a diagram describing a maximum elevation angle max and the correction.

[0016] FIG. 3 is a diagram illustrating a relationship between the maximum elevation angle max and satellite capable of receiving radio waves.

[0017] FIG. 4 is a graph illustrating a relationship between a plurality of waypoints and a minimum altitude for obtaining the number of available satellites necessary for flight control.

[0018] FIG. 5 is a flow diagram illustrating a control procedure in an embodiment.

[0019] FIG. 6 is a diagram illustrating a configuration example of a control unit for executing the control procedure in an embodiment.

DESCRIPTION OF EMBODIMENTS

[0020] Hereinafter, embodiments will be described with reference to the attached drawings.

[0021] When setting the flight path before a UAV 10 flies autonomously, the present embodiment determines whether the number n of available satellites constituting a GNSS (satellite availability number) has reached a reference satellite availability number N required for flight control of the UAV 10. In the present embodiment, the satellite availability number n is calculated based on the elevation angle with respect to a surrounding environment of the UAV 10. In the result of present embodiment, this determination result is reflected in determining the flight path. Note that an example of determining the satellite availability number n will be described here, but it is possible to determine dilution of precision (DOP), which is an index of positioning accuracy, instead of or in conjunction with the satellite availability number n, as described later.

Flight Path FP: See FIG. 1

[0022] The present embodiment sets as an example the flight path FP illustrated in FIG. 1. This flight path FP sets WP1, WP2, WP3, WP4, WP5, WP6, and WP7 as waypoints. Although only up to WP7 are illustrated here, the flight path FP has waypoints not less than WP8.

[0023] Waypoints are point information on the flight path FP, and in the present embodiment, is constituted of three elements, latitude (latitude, x), longitude (longitude, y), and altitude (altitude, z), as illustrated below. However, the following flight path FP is tentatively set, and at least one of WP1 to WP7 is corrected based on the result of the determination made on the satellite availability number n, and the final flight path FP is determined.

Flight Path FP

[0024] WP1: (x1, y1, z1), WP2: (x2, y2, z2) [0025] WP3: (x3, y3, z3), WP4: (x4, y4, z4) [0026] WP5: (x5, y5, z5), WP6: (x6, y6, z6) [0027] WP7: (x7, y7, z7)

Obstacle to Satellite Availability: See FIGS. 2 and 3

[0028] The UAV 10 can fly autonomously by acquiring information necessary for calculating the position with respect to the ground. This information can be obtained from the global navigation satellite system (GNSS). GNSS includes the Global Positioning System (GPS), QZSS (Japan), GLONASS (Russia), Galileo (EU), or the like. Any of these systems can be used for the present embodiment. These GNSSs are constituted of multiple artificial satellites (hereinafter simply called satellites) orbiting around the earth. Multiple satellites that constitute a GNSS orbit around the earth, so that their positions vary depending on the date and time. Information on a relationship between the date and time and the position of the satellite in a GNSS is publicly available.

[0029] As an example, there are not less than 30 satellites constituting GPS around the earth, each orbiting one of six orbits in 12 hours. The GPS receiver in the UAV 10 receives radio waves from at least 4 of these satellites and calculates its own location information, by typically using a computational method called three-dimensional positioning. Thus, the surrounding environment of the UAV 10 may have an obstacle, preventing reception of radio waves from as many satellites as necessary to calculate location information, that is, preventing satellite availability. The surrounding environment includes a natural environment having mountains, trees and the like, as well as an artificial environment having high-rise buildings and the like.

[0030] Since the flight path FP illustrated in FIG. 1 illustrates an example of following a mountainous area, mountains can be an obstacle to satellite availability. FIG. 2 schematically illustrates a relationship between the UAV 10 and obstacles 101, 102 consisting of peripheral mountains in WP3, for example. In WP3, the UAV 10 is sandwiched between an obstacle 101 and an obstacle 102. When the elevation angle with respect to an apex 101T of the obstacle 101 or an apex 102T of the obstacle 102 with respect to the UAV 10 are compared, the elevation angle with respect to the apex 101T is larger, which becomes the maximum elevation angle max in WP3.

[0031] The position of the UAV 10 in WP3 is known, and the location information on the obstacle 101 consisting of a mountain and the apex 101T is also known as topographic data, so that the elevation angle can be obtained by calculation.

[0032] In addition, although both the obstacle 101 and the obstacle 102 have been described here, the maximum elevation angle max means the maximum elevation angle in the 360 azimuth relative to WP3. Although the use of the maximum elevation angle max is a preferred form that is simple to calculate and requires only a short period of time, it is also possible to calculate the elevation angle in the interval of the predetermined angle for the 360 azimuth and compare the satellite availability number n and the reference satellite availability number N for each calculated elevation angle .

[0033] For the elevation angle, the point where the straight line drawn from the UAV 10 meets the outline (ridge) of the obstacle (contact point) is the point where the elevation angle is specified, and in the case of the obstacles 101, 102, the apexes 101T and 102T with the highest elevations are the contact points. However, when the outline includes, for example, arc, as in the case of an obstacle 103 illustrated by the dashed line in FIG. 2 (Before), a contact point 103C is a point different from the apex 103T.

[0034] The larger the elevation angle with respect to the apex of the obstacle, the greater the obstacle obstructs availability of the satellite that constitutes the GNSS. FIG. 3 illustrates the maximum elevation angle max and the availability state of multiple satellites 20. In FIG. 3, the satellite 20 indicated by the solid line indicates that the receiver provided by the UAV 10 is receiving the radio wave and a satellite 20 is available, and the satellite 20 indicated by the dashed line indicates that the satellite 20 is not available to the UAV 10. When the maximum elevation angle max becomes larger than illustrated, the number n of available satellites 20 becomes smaller. Note that the number of available satellites, four in FIG. 3, is only an example.

[0035] Assuming that the maximum elevation angle max for WP3 illustrated in FIG. 2 (Before) does not reach a reference number of satellites 20 making it possible to identify the position of the UAV 10. For example, when the GNSS used is GPS, the case where the reference number is three, corresponds to this. Thus, when the set WP3 (x3, y3, z3) remains, the receiver of the UAV 10 cannot calculate its own position because the availability number n is insufficient. Thus, as illustrated in FIG. 2 (After), the WP3 that is a waypoint is corrected. The correction of the waypoint is performed by changing the position. More specifically, one or both of the position in a vertical direction V and the position in a horizontal direction H are changed to become the correction position. In the example illustrated in FIG. 2, both the position in the vertical direction V and the position in the horizontal direction H are changed and corrected to, for example, WP3 (x3, y3, z3). Although the maximum elevation angle max is also present in WP3, correction is performed so that the relationship between the pre-corrected maximum elevation angle max and the maximum elevation angle max satisfies max>max, and so that the number of available satellites 20 at the maximum elevation angle max becomes, for example, four, enabling the UAV 10 to calculate its own position.

[0036] To reduce the elevation angle , it is easiest to change the altitude of the waypoint upward in the vertical direction V. However, for example, according to Japanese aviation laws, the flight altitude of the UAV 10 is limited to no more than 150 m in principle. Thus, even when only the altitude is changed to ensure the availability number n, the flight altitude regulations cannot be adhered to. Thus, the present embodiment can select one or both of the correction to vertical direction V and correction to horizontal direction H.

[0037] When the UAV 10 is flying, the actual satellite availability number n in a control unit 11 can be recognized. However, the actual satellite availability number n cannot be recognized at the stage of setting the flight path FP before the flight targeted by the present embodiment. Thus, in the present embodiment, the satellite availability number n is calculated based on the elevation angle . Information on the satellite 20 that constitutes the GNSS is publicly available, thereby the satellite availability number n can be calculated by calculating the elevation angle .

Minimum Altitude for Securing Reference Satellite Availability Number N: FIG. 4

[0038] Although WP3 is illustrated above, it is possible to specify a minimum altitude Hm for securing the reference satellite availability number N for calculating the position of the UAV 10 for other waypoints such as WP1. FIG. 4 illustrates an example thereof. FIG. 4 illustrates only altitude in waypoints.

[0039] In FIG. 4, in WP1, when the altitude is 40 m, the reference satellite availability number N capable of calculating its own position is secured, and in WP3, when the altitude is 60 m, the reference satellite availability number N capable of calculating its own position is secured. In WP4 to WP7, the minimum altitude exceeds 100 m, which indicates that the altitude of mountains or the like being obstacles in the surrounding area is high.

Example of Path Setting with Correction: See FIGS. 5 and 6

[0040] Next, an example of a path setting procedure with correction will be described. This path setting is performed before the flight of the UAV 10, and the procedure illustrated in FIG. 5 is performed by the control unit 11 of the UAV 10 illustrated in FIG. 6.

[0041] First, the flight path FP is set (FIG. 5, S101). The flight path FP is set through multiple waypoints. The flight path FP at this time can be referred to as a temporary flight path FP because it includes the possibility of correction in a later step. The temporary flight path FP is stored in a storage unit 11B provided in the control unit 11. Each waypoint includes three elements, which are latitude, longitude, and altitude, as described above. The method for setting the flight path FP at this time is free, and can be set by a person based on topographic data, or can be set by a computer device based on topographic data. At this time, the latitude and longitude are set according to the topographic data, but the altitude can be set to the same value for all waypoints. This is because the altitude is likely to be subject to correction in the present embodiment. In addition, the setting of the flight path FP can be performed directly on the UAV 10, or the setting by a device other than the UAV 10 can be stored in the UAV 10.

[0042] Next, the satellite availability number n and the reference satellite availability number N are compared and determined for each of the waypoints set tentatively. For this purpose, waypoints are selected (FIG. 5, S103). For example, when seven waypoints of WP1 to WP7 illustrated in FIG. 1 are set, WP1 is first selected, and a comparison determination is made between the satellite availability number n and the reference satellite availability number N in WP1. When the comparison determination is finished between the satellite availability number n and the reference satellite availability number N in WP1, WP2 is then selected, and a comparison determination is made between the satellite availability number n and the reference satellite availability number N in WP2. Thereafter, the selection and comparison determination of WP3, the selection and comparison determination of WP4, . . . , and the selection and comparison determination of WP7 are performed. The comparison determination and correction are executed by a computation unit 11C of the control unit 11 by referring to the location information on the flight path FP stored in the storage unit 11B.

[0043] When a waypoint is selected, the maximum elevation angle max at the selected waypoint is calculated (FIG. 5, S105). The calculation of the maximum elevation angle max is performed by referring to the topographic data held in advance. As an example of this topographic data, the data generated by interpolation of the peak value at 5 m interval or the like based on the altitude data measured in the aerial laser survey by the Geographical Survey Institute in Japan.

[0044] When the maximum elevation angle max is calculated, the satellite availability number n, which is the number of satellites that can acquire the information necessary to calculate the position from the global navigation satellite system (GNSS) at the waypoint, is calculated (FIG. 5, S107). In calculating the satellite availability number n, the date and time when the UAV flies the flight path FP is also considered. This is because, as mentioned above, the positions of the multiple satellites that constitute the global navigation satellite system (GNSS) are different depending on the date and time because the satellites orbit around the earth.

[0045] When the satellite availability number n is calculated, the size relationship and the reference satellite availability number N at the waypoint are compared (FIG. 5, S109). When the satellite availability number n reaches the reference satellite availability number N (Nn, S109: YES), the correction of the setting information (latitude, longitude and altitude) at the waypoint is unnecessary. When the satellite availability number n does not reach the reference satellite availability number N (N>n, S109: No), the correction of the setting information (latitude, longitude and altitude) at the waypoint is necessary.

[0046] When the correction of the setting information at the waypoint is necessary, the altitude of the UAV 10 in the setting information (latitude, longitude and altitude) is increased as an example (FIG. 5, S111). The increase of the altitude can be a specified value, for example, A(m). When a comparison and determination for WP3 is assumed to be performed now, z3 of WP3 is corrected to Z3 obtained by adding A(m) to z3. Assuming that the altitude after correction is Z3, the maximum elevation angle max is calculated (FIG. 5, S105) and the satellite availability number n is calculated (FIG. 5, S107). This procedure is repeated until the satellite availability number n reaches the reference satellite availability number N.

[0047] When it is determined that the satellite availability number n has reached the satellite availability number N (Nn), determination is performed whether the altitude is higher than the altitude of a previous waypoint (FIG. 5, S113). This is because a possibility exists that the satellite availability number n does not exceed the reference satellite availability number N between the previous waypoint and the waypoint currently subject to comparison and determination. For example, when the waypoint currently subject to comparison and determination is WP3, the altitude is compared with the previous WP2. When the altitude of WP3 is z3 and the altitude of WP2 is z2, the relationship between z3 and z2 is compared.

[0048] When the waypoint currently being compared and determined is WP3 and its altitude is z3, the altitude of the previous WP2 is corrected from z2 to z3.

[0049] After the above comparisons, determinations, and necessary corrections are made for all waypoints, setting of the flight path FP is completed and the UAV 10 is ready for flight. The flight path FP whose setting is completed, is stored in the storage unit 11B. When the UAV 10 flies autonomously, the storage unit 11B specifies its own position by the radio wave received at a reception unit 11A, from the satellite 20, and compares the identified position of the UAV 10 and the flight path FP stored in the storage unit 11B.

Effect Produced by Embodiments

[0050] According to the present embodiment, the satellite availability number n for constituting the global navigation satellite system (GNSS) is calculated based on the elevation angle calculated by referring to the topographic data, and comparing is performed between the satellite availability number n and the reference satellite availability number N required for flight control. Based on the comparison result, one or both of the vertical direction position (Pv) and the horizontal direction position (Hv) of the UAV 10 is changed. Thus, according to the present embodiment, the acquisition of radio waves from the GNSS is not interrupted, and the flight of the UAV 10 can be secured.

[0051] The configuration mentioned in the above embodiments can be selected or changed to another configuration as appropriate.

[0052] Although the above embodiments have described an example of comparing between the satellite availability number n and the reference satellite availability number N for the waypoints, the present disclosure can perform the comparison, determination and correction processing at any point in the flight path. More specifically, the processing can be performed at a default interval on the flight path, for example, an interval of 100 m.

[0053] Although the above embodiments illustrate examples of applying the present disclosure when setting the path before the flight of the UAV, the present disclosure can also be applied to the UAV actually in flight. For example, a UAV in flight can recognize the satellite availability number n, but, for example, it cannot be specified whether the reference satellite availability number N required for flight control can be secured by increasing the altitude of the UAV. However, even when the satellite availability number n of the UAV in flight becomes insufficient, the reference satellite availability number N required for flight control can be secured by applying the procedure illustrated in FIG. 5, for example.

[0054] Although the above embodiment uses the satellite availability number as an object for comparing and determining, DOP (Dilution of Precision: positioning accuracy degradation coefficient) can be used as a substitute for the satellite availability number or in addition to comparing and judging the satellite availability number. DOP varies due to the geometric positional relationship between the UAV 10 (reception unit 11A) and the satellite 20, and the smaller the DOP, the more accurate the positioning. In other words, DOP can also be information specifying the availability state of the satellite 20, and the DOP can be improved by correcting the position of the UAV.

[0055] Here, the satellite availability number is specified based on the positional relationship between the satellite 20 that constitutes the GNSS and the UAV 10 (reception unit 11A), and the DOP is also an availability state specified based on the positional relationship between the satellite 20 and the UAV 10 (reception unit 11A). Thus, in the present disclosure, a positioning accuracy degradation coefficient d and a reference positioning accuracy degradation coefficient D can be compared and determined as substitutes for the satellite availability number n and the reference satellite availability number N, and necessary correction can be applied to setting of the flight path FP of the UAV 10.

[0056] In the above embodiment, an example of specifying the elevation angles for the apexes 101T and 102T of the respective obstacles 101 and 102 has been described. However, depending on the shape of the obstacle, it is necessary to specify the elevation angle for a position different from the apex.

[0057] For example, as illustrated in FIG. 2 (Before), assume the obstacle 103 whose outline (ridge) forms an arc shape. In the case of the obstacle 103, when comparing is performed between the elevation angle for an apex 103T and the elevation angle for the contact point 103C obtained by drawing the tangent from the UAV 10 to the obstacle 103, the elevation angle for the contact point 103C is larger, which is the maximum elevation angle max in WP3.

Supplementary Notes

[0058] The present disclosure is recognized as follows.

Supplementary Note 1

[0059] A method for setting a flight path of an unmanned aerial vehicle, includes: [0060] a step 1 of calculating an availability state, in an unmanned aerial vehicle, of artificial satellites based on a positional relationship between the artificial satellites constituting a global navigation satellite system and the unmanned aerial vehicle at any of points in a scheduled path of the unmanned aerial vehicle flying autonomously; and [0061] a step 2 of comparing the availability state calculated in the step 1 and a reference availability state required for flight control of the unmanned aerial vehicle.

Supplementary Note 2

[0062] In the method for setting a flight path according to Supplementary Note 1, preferably the step 1 includes: [0063] a step 1-1 of calculating an elevation angle at any of the points; and [0064] a step 1-2 of calculating an availability number n of the artificial satellites capable of acquiring information required for calculating a position from the global navigation satellite system based on the elevation angle calculated in the step 1-1, and [0065] in the step 2, the calculated availability number n and a reference satellite availability number N required for flight control are compared.

Supplementary Note 3

[0066] In the comparing in the step 2 of Supplementary Note 2, when the availability number n has not reached the reference satellite availability number N, [0067] a correction position is calculated for changing one or both of a position in a vertical direction and a position in a horizontal direction of the unmanned aerial vehicle, and [0068] the step 1-1, the step 1-2, and the step 2 are executed for the correction position.

Supplementary Note 4

[0069] Preferably, [0070] the step 1-1, the step 1-2, and the step 2 are executed for the correction position, and [0071] when the availability number n has reached the reference satellite availability number N, the correction position is incorporated into the scheduled path.

Supplementary Note 5

[0072] In the comparing in the step 2 according to any one of Supplementary Notes 1 to 3, [0073] preferably, when the availability number n has reached the reference satellite availability number N, the scheduled path is adhered to.

Supplementary Note 6

[0074] In the step 1-1 according to any one of Supplementary Notes 2 to 5, preferably a maximum elevation angle max is calculated at any of the points, and [0075] in the step 1-2, the availability number n is calculated based on the maximum elevation angle max.

Supplementary Note 7

[0076] In any one of Supplementary Notes 2 to 5, preferably the step 1 and the step 2 are executed when setting the scheduled path.

Supplementary Note 8

[0077] In Supplementary Note 7, the step 1 and the step 2 are executed for a plurality of the points separated by a predetermined interval in the scheduled path or for a plurality of waypoints in the scheduled path.

Supplementary Note 9

[0078] In any one of Supplementary Notes 1 to 7, preferably the step 1 and the step 2 are executed when the unmanaged aerial vehicle is flying autonomously according to the set scheduled path.

Supplementary Note 10

[0079] In Supplementary Note 1, preferably [0080] in the step 1, a positioning accuracy degradation coefficient d at the one of points is calculated, and [0081] in the step 2, the calculated positioning accuracy degradation coefficient d and a reference positioning accuracy degradation coefficient D required for flight control are compared.

[0082] While preferred embodiments of the invention have been described as above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the invention. The scope of the invention, therefore, is to be determined solely by the following claims.