Landing system for unmanned aerial vehicles

Abstract

Even if the landing markers are temporarily lost, the unmanned aerial vehicle can continue its landing procedure. [Solution] A drone landing system that lands a drone equipped with a marker on a charging port equipped with a camera 14, comprising: a marker recognition unit 31 that recognizes the marker captured by the camera and calculates the drone's position information in the charging port coordinate system; a self-position estimation unit 22 that calculates the drone's position information in a reference coordinate system; and a command speed generation unit 33 that uses the drone's position information in the reference coordinate system and the drone's position information in the charging port coordinate system to calculate the charging port's position information in the reference coordinate system and generate a command speed for descending the drone to the charging port. The command speed generation unit generates a command speed for descending the drone to the charging port based on the charging port position information in the reference coordinate system calculated when the marker was most recently recognized, if the marker is not recognized by the marker recognition unit.

Description

Technical Field

[0001] Embodiments of the present invention relate to an unmanned aerial vehicle landing system for landing an unmanned aerial vehicle at a landing point.

Background Art

[0002] In recent years, in power generation and power transmission facilities built in places where it is not easy for people to access, such as mountainous areas and the ocean, in order to streamline inspection work, efforts have been made to deploy drones that regularly patrol and inspect in place of people. In order for the drone to repeat such patrol inspections, a charging port with a charging function is also arranged. Such a drone needs to accurately and automatically land on the charging port.

[0003] Conventionally, in order to accurately land at a target point, a method has been proposed in which a target marker is placed at the landing point, the position of the marker is recognized by a camera mounted on the drone, and the drone descends aiming at that position.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, Patent Document 1 proposes a method in which markers of different sizes are placed at the landing site, and when descent begins, the larger marker, which is easier to recognize even at a distance, is used to descend closer to the landing site. When the larger marker is no longer within the camera's field of view, the smaller marker is used to continue the descent.

[0006] This Patent Document 1 addresses the problem of markers becoming unrecognizable due to changes in the distance between the camera and the marker. In addition, markers may temporarily become unrecognizable and the landing site may be lost if the drone is blown horizontally by a gust of wind, causing the marker to move out of the camera's field of view, or if the image is blurred due to drone vibrations even if the marker is within the camera's field of view, or if there are changes in brightness from sunlight or lighting, or if reflection occurs.

[0007] Embodiments of the present invention have been made in consideration of the above circumstances, and aim to provide an unmanned aerial vehicle (UAV) landing system that can continue the landing operation of the UAV even if the marker used for landing becomes temporarily unrecognizable. [Means for solving the problem]

[0008] An embodiment of the present invention provides a landing system for an unmanned aerial vehicle in which a camera installed at the landing site photographs a marker installed on the unmanned aerial vehicle, and the unmanned aerial vehicle is landed at the landing site upon recognition of the marker, comprising: a marker recognition unit that recognizes the marker photographed by the camera and calculates the position information of the unmanned aerial vehicle in the landing site coordinate system; a self-position estimation unit that calculates the position information of the unmanned aerial vehicle in reference coordinates; and a command speed generation unit that uses the position information of the unmanned aerial vehicle in the reference coordinate system and the position information of the unmanned aerial vehicle in the landing site coordinate system to calculate the position coordinates of the landing site in the reference coordinate system and generate a command speed for descending the unmanned aerial vehicle to the landing site, wherein the command speed generation unit is configured to generate a command speed for descending the unmanned aerial vehicle to the landing site if the marker is not recognized by the marker recognition unit, using the position coordinates of the landing site in the reference coordinate system calculated when the marker was most recently recognized. [Effects of the Invention]

[0009] According to embodiments of the present invention, even if the marker used for landing becomes temporarily unrecognizable, the landing operation of the unmanned aerial vehicle can be continued. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic perspective view showing the configuration of a drone landing system to which the landing system for an unmanned aircraft according to the first embodiment is applied. [Figure 2] Figure 1 is a perspective view illustrating the coordinate systems and drone landing actions in the drone landing system. [Figure 3] A block diagram showing the control system in the drone landing system in Figure 1. [Figure 4] A flowchart illustrating the landing operation of the drone landing system shown in Figure 1. [Figure 5] A schematic perspective view showing the configuration of a drone landing system to which the landing system for an unmanned aircraft according to the second embodiment is applied. [Figure 6] Figure 5 is a perspective view illustrating the coordinate systems and drone landing actions in the drone landing system. [Figure 7] Figure 5 is a block diagram showing the control system in the drone landing system. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments for carrying out the present invention will be described based on the drawings. [A] First Embodiment (Figures 1-4) Figure 1 is a schematic perspective view showing the configuration of a drone landing system to which the landing system for an unmanned aerial vehicle according to the first embodiment is applied. Figure 2 is a perspective view illustrating the coordinate systems and the drone landing operation in the drone landing system of Figure 1. The drone landing system 10 shown in Figure 1 is a system in which a camera 14 mounted on a drone 13, which is an unmanned aerial vehicle, photographs a marker 12 installed on a charging port 11, which is the landing point, and by recognizing the marker 12, the relative position between the drone 13 and the charging port 11 is determined, and the drone 13 is landed on the charging port 11.

[0012] The charging port 11 is installed on the ground and charges the power unit (not shown) of the landed drone 13 by contact or non-contact. The landing surface of the drone 13 at the charging port 11 may be a flat surface, but it may also be formed into a frustoconical shape to serve as a guide for the drone 13 during landing. In addition, one or more markers 12 are installed on the charging port 11 itself or around the charging port 11. These markers 12 may be markers capable of recognizing position and attitude, such as AR markers.

[0013] The drone 13 obtains thrust from the rotation of propellers 16 attached to each of the multiple drive motors 15 mounted on it, and moves through the air vertically (up and down), horizontally (forward and backward and left and right), turns, and hovers in the air. The rotational movement of each drive motor 15 is controlled by the drive control unit 25 of the control device 20 described later.

[0014] As shown in FIGS. 1 and 3, the drone 13 is equipped with the camera 14, the satellite positioning unit 17, the inertial sensor 18, and the control device 20. The control device 20 is configured to include a marker recognition unit 21, a self-position estimation unit 22, a commanded velocity generation unit 23, a memory unit 24, and a drive control unit 25. Among these, it is not necessary for all components of the control device 20 to be provided in the drone 13 within one piece of hardware. A part (for example, the commanded velocity generation unit twenty-three) may be installed on the ground and connected to other components via a network.

[0015] The camera 14 photographs the marker 12 of the charging port 11 and is directly attached to the frame of the drone 13 facing vertically downward. Alternatively, the camera 14 may be attached to a gimbal mechanism (not shown) installed on the frame of the drone 13 to adjust its posture so as to face vertically downward when the drone 13 lands.

[0016] The satellite positioning unit 17 receives positioning information (positioning radio waves) from GNSS (Global Navigation Satellite System). The inertial sensor 18 is an IMU (Inertial Measurement Unit) in which an acceleration sensor and an angular velocity sensor are integrated, and detects the inertial information of the drone 13.

[0017] As shown in FIGS. 2 and 3, the marker recognition unit 21 recognizes the marker 12 photographed by the camera 14, performs coordinate transformation from the coordinate system (Σdrone) fixed to the drone 13 to the coordinate system (Σport) fixed to the charging port 11, and calculates the position information Tdrone_port of the charging port 11 in the drone coordinate system as the unmanned aerial vehicle coordinate system.

[0018] The self-position estimation unit 22 estimates the current position of the drone 13. In this first embodiment, it combines positioning information of the drone 13 from GNSS by the satellite positioning unit 17 and inertial information of the drone 13 from the IMU, which is an inertial sensor 18, to estimate the position information (latitude, longitude, altitude, and bearing) of the drone 13 in a reference coordinate system (Σworld) on Earth. Specifically, the self-position estimation unit 22 performs a coordinate transformation from the reference coordinate system (Σworld) to a coordinate system fixed to the drone 13 (Σdrone) to calculate the position information Tworld_drone of the drone 13 in the reference coordinate system.

[0019] Furthermore, when the drone 13 flies indoors, the self-position estimation unit 22 may estimate the position information of the drone 13 and the position information of the surrounding environment in a predefined reference coordinate system using VSLAM (Visual Simultaneous Localization and Mapping) technology using a monocular camera or stereo camera (not shown) or SLAM technology using 3D Lidar (3D radar).

[0020] The command speed generation unit 23 compares the target position (the position of the charging port 11) with the position of the drone 13 estimated by the self-position estimation unit 22, generates a command speed V such that the drone 13 approaches the target position, and outputs this command speed V to the drive control unit 25.

[0021] Specifically, the command speed generation unit 23 first has the following first function. That is, the command speed generation unit 23 uses the position coordinates Tdrone_port of the charging port 11 in the drone coordinate system calculated by the marker recognition unit 21 and the position information Tworld_drone of the drone 13 in the reference coordinate system calculated by the self-position estimation unit 22 to calculate the position information Tworld_port of the charging port 11 in the reference coordinate system (position and attitude of the charging port 11) using the following equation (1). Tworld_port=Tworld_droneTdrone_port……(1)

[0022] The command speed generation unit 23 then uses the yaw angle representing the three-dimensional position x, y, z and orientation of the charging port 11 obtained from the position information Tworld_port of the charging port 11 in this reference coordinate system, and the position and attitude of the drone 13 obtained by the self-position estimation unit 22 (position information Tworld_drone of the drone 13 in the reference coordinate system), to generate a command speed V such that the horizontal position of the drone 13 is directly above the charging port 11 and the drone 13 descends toward the charging port 11 while maintaining a predetermined yaw angle, and outputs this command speed V to the drive control unit 25.

[0023] Furthermore, if the command speed generation unit 23 calculates the position information Tworld_port of the charging port 11 in the reference coordinate system using equation (1) based on the position information Tdrone_port of the charging port 11 in the drone coordinate system calculated by the marker recognition unit 21 after the marker 12 is recognized, it updates and stores the calculated position information of the charging port 11 in the storage unit 24.

[0024] Furthermore, the command speed generation unit 23 has the following second function. That is, if the marker 12 is not recognized by the marker recognition unit 21, the command speed generation unit 23 uses the yaw angle representing the 3D position x, y, z and orientation of the charging port 11 obtained from the position information Tworld_port of the charging port 11 in the reference coordinate system calculated when the marker 12 was most recently (last) recognized by the marker recognition unit 21, and the position information Tworld_drone of the drone 13 in the reference coordinate system which is continuously estimated by the self-position estimation unit 22, to generate a command speed V such that the horizontal position of the drone 13 is directly above the charging port 11 and the drone 13 descends toward the charging port 11 while maintaining a predetermined yaw angle, and outputs this command speed V to the drive control unit 25.

[0025] Furthermore, the command speed generation unit 23 has the following third function. Specifically, the command speed generation unit 23 has a positioning completion determination unit 26 as shown in Figure 3. As shown in Figure 2, this positioning completion determination unit 26 sets a virtual cylindrical positioning completion zone 27 above the charging port 11, and determines that the positioning of the drone 13 relative to the charging port 11 is complete when the drone 13 that descended from above the charging port 11 stays within the positioning completion zone 27 for a certain period of time. When the positioning of the drone 13 is complete, the command speed generation unit 23 outputs a command speed V to the drive control unit 25 that reduces the rotational speed of the drive motor 15 (Figure 1) that drives the propeller 16, causing the drone 13 to land on the charging port 11.

[0026] The positioning completion determination unit 26 determines that the positioning of the drone 13 relative to the charging port 11 is not complete if the drone 13 has descended to a certain altitude in the positioning completion zone 27 (for example, the same altitude as the bottom surface 28) but has not stayed in the positioning completion zone 27 for a certain period of time. In this case, the command speed generation unit 23 generates a command speed V that causes the drone 13 to rise to a predetermined altitude above the aforementioned certain altitude and then descend again. As described above, the command speed V for raising the drone 13 causes the drone 13 to rise while its horizontal position is directly above the charging port 11 and the drone 13 maintains a set yaw angle.

[0027] Next, the landing operation of the drone landing system 10 configured as described above will be explained mainly using the flowchart in Figure 4. Since the command velocity generation unit 23 has prior knowledge of the approximate position of the charging port 11, it generates a command velocity V using the position information Tworld_drone of the drone 13 in the reference coordinate system estimated by the self-position estimation unit 22, and moves the drone 13 to the airspace above the charging port 11 (S1).

[0028] Next, the marker recognition unit 21 recognizes the marker 12 captured by the camera 14 and calculates the position information Tdrone_port of the charging port 11 in the drone coordinate system, and the self-position estimation unit 22 calculates the position information Tworld_drone of the drone 13 in the reference coordinate system. The command speed generation unit 23 uses this position information (Tdrone_port, Tworld_drone) to calculate the position information Tworld_port of the charging port 11 in the reference coordinate system (S2).

[0029] The command speed generation unit 23 determines whether or not the marker 12 has been recognized by the marker recognition unit 21 (S3). If recognition has been confirmed, it updates the position information Tworld_port of the charging port 11 in the reference coordinate system with the position information calculated in step S2 and stores it in the storage unit 24 (S4). At the same time, the command speed generation unit 23 generates a command speed V using the position information Tworld_port of the charging port 11 calculated in step S2 and the position information Tworld_drone of the drone 13 in the reference coordinate system calculated by the self-position estimation unit 22, and lowers the drone 13 so that its horizontal position is directly above the charging port 11 and it approaches the charging port 11 (S5).

[0030] In step S3, if the command velocity generation unit 23 determines that the marker recognition unit 21 has not recognized the marker 12, the command velocity generation unit 23 uses the position information Tworld_port of the charging port 11 in the reference coordinate system calculated when the marker recognition unit 21 last recognized the marker 12 (S6). The command velocity generation unit 23 generates a command velocity V using the position information Tworld_port of the charging port 11 in the reference coordinate system obtained in step S6 and the position information Tworld_drone of the drone 13 in the reference coordinate system estimated by the self-position estimation unit 22, and descends the drone 13 so that its horizontal position is directly above the charging port 11 and it approaches the charging port 11 (S5).

[0031] When the drone 13 has descended to the vicinity of the charging port 11, the positioning completion determination unit 26 determines whether the drone 13 has stayed in the positioning completion zone 27 for a certain period of time and whether the positioning of the drone 13 relative to the charging port 11 is complete (S7). If it is determined that the positioning of the drone 13 is complete (yes in S7), the command speed generation unit 23 generates a command speed V that reduces the rotation speed of the drone 13's propeller 16 (Figure 1) and causes the drone 13 to land at the charging port 11 (S8).

[0032] If, in step S7, the drone 13 does not stay within the positioning completion zone 27 for a certain period of time, and the descent position of the drone 13 does not reach a certain altitude (e.g., the bottom surface 28) of the positioning completion zone 27 (No. of S7, No. of S9), then steps S2 to S8 are executed again in order to perform the recognition of the marker 12 by the marker recognition unit 21.

[0033] If, in step S7, the drone 13 does not stay within the positioning completion zone 27 for a certain period of time, and the drone 13 descends to an altitude below a certain altitude (e.g., the bottom surface 28) in the positioning completion zone 27 (No in S7, Yes in S9), the positioning completion determination unit 26 determines that the positioning of the drone 13 relative to the charging port 11 is not complete. At this time, the command speed generation unit 23 generates a command speed V to raise the drone 13 to a predetermined altitude above a certain altitude (e.g., the bottom surface 28) in the positioning completion zone 27, and causes the drone 13 to ascend (S10). The command speed generation unit 23 then generates a command speed V to descend the drone 13 again, causing the drone 13 to descend and the marker recognition unit 21 to perform recognition of the marker 12, etc. (S2-S10). Note that the marker recognition unit 21 may also perform the recognition operation of the marker 12 while the drone 13 is ascending.

[0034] As configured as described above, this first embodiment provides the following effects (1) and (2). (1) If the marker 12 is not recognized by the marker recognition unit 21, the command speed generation unit 23 is configured to generate a command speed V for descending the drone 13 to the charging port 11 using the position information Tworld_port of the charging port 11 in the reference coordinate system calculated when the marker recognition unit 21 recognized the marker 12 immediately before. Therefore, even if the marker recognition unit 21 is temporarily unable to recognize the marker 12, such as when the drone 13 is blown horizontally by a gust of wind and the marker 12 goes out of the camera 14's field of view, or when the image of the marker 12 is blurred due to vibration of the drone 13 even if the marker 12 is within the camera 14's field of view, or when there is a change in brightness from sunlight or lighting, or when it is reflected, the drone 13's landing operation can be continued. This method is also effective when the resolution of the camera 14 is high or when the processing power of the marker recognition unit 21 is low and the marker recognition processing cycle is slow.

[0035] (2) The command speed generation unit 23 is configured to generate a command speed V to raise the drone 13 to a predetermined altitude above a certain altitude (e.g., the bottom surface 28) in the positioning completion determination unit 26 when the positioning completion determination unit 26 determines that the positioning of the drone 13 relative to the charging port 11 is not yet complete when the drone 13 has descended to the vicinity of the charging port 11, thereby raising the drone 13. By raising the drone 13 in this way, the distance between the camera 14 and the marker 12 increases, making it easier to recognize the marker 12 and allowing the marker 12 to be placed within the field of view of the camera 14. As a result, the marker recognition unit 21 can reliably recognize the marker 12, and the drone 13 can be reliably landed on the charging port 11.

[0036] [B] Second embodiment (Figures 5-7) Figure 5 is a schematic perspective view showing the configuration of a drone landing system to which the unmanned aircraft landing system according to the second embodiment is applied. Figure 6 is a perspective view illustrating the coordinate systems and drone landing operation in the drone landing system of Figure 5. In this second embodiment, parts that are the same as in the first embodiment are denoted by the same reference numerals as in the first embodiment, and their descriptions are simplified or omitted.

[0037] The drone landing system 30 shown in Figure 5, which serves as a landing system for an unmanned aerial vehicle, works by having a camera 14 installed on the charging port 11 photograph a marker 12 placed on the drone 13, and by recognizing the marker 12 to determine the relative position between the drone 13 and the charging port 11, thereby allowing the drone 13 to land on the charging port 11.

[0038] The marker 12 is directly attached horizontally to the frame of the drone 13. Alternatively, if a gimbal mechanism (not shown) for adjusting the attitude is installed on the frame of the drone 13, the marker 12 may be attached to the bottom of the gimbal mechanism. By attaching the marker 12 to the gimbal mechanism in this way, the marker 12 is kept horizontal even if the drone 13 is tilted by wind or the like, preventing blurring of the image when the marker 12 is captured by the camera 14. Furthermore, the gimbal mechanism allows the marker 12 to be tilted to an angle that prevents light reflection.

[0039] One camera 14 is installed on the charging port 11 itself, but multiple cameras may be installed on the charging port 11 itself, or on the charging port 11 and around the charging port 11, in order to eliminate blind spots. In this case, if the cameras 14 are installed around the charging port 11, the relative positional relationship between the cameras 14 and the charging port 11 must be known in advance.

[0040] In the drone landing system 30 of this second embodiment, as shown in Figure 7, a camera 14 is installed on the ground (on the side of the charging port 11), including the charging port 11, as described above, along with a marker recognition unit 31 and a wireless communication unit 32. The drone 13 is equipped with a satellite positioning unit 17, an inertial sensor 18, a self-position estimation unit 22, a command speed generation unit 33, a memory unit 24, a drive control unit 25, and a wireless communication unit 34.

[0041] The control device 35 of the drone landing system 30 comprises a marker recognition unit 31 and a wireless communication unit 32 on the charging port 11 side, and a self-position estimation unit 22, command speed generation unit 33, storage unit 24, drive control unit 25, and wireless communication unit 34 mounted on the drone 13. Here, the wireless communication unit 32 on the charging port 11 side and the wireless communication unit 34 mounted on the drone 13 are configured to communicate with each other, and the information (Tport_drone) calculated by the marker recognition unit 31 is transmitted to the command speed generation unit 33 mounted on the drone 13. In addition, some of the components of the control device 35 mounted on the drone 13 (for example, the command speed generation unit 33) may be installed on the ground and connected to other components via a network.

[0042] Incidentally, when the drone 13 moves to the top of the charging port 11 and the camera 14 installed on the charging port 11 side captures the marker 12 on the drone 13, the marker recognition unit 31 recognizes this marker 12. Furthermore, the marker recognition unit 31 performs a coordinate transformation from the coordinate system fixed to the charging port 11 (Σport) to the coordinate system fixed to the drone 13 (Σdrone) and calculates the position information Tport_drone of the drone 13 in the charging port coordinate system as the landing point coordinate system.

[0043] The command speed generation unit 33 has a first function similar to the command speed generation unit 23 of the first embodiment, which is used when the marker recognition unit 31 recognizes the marker 12, a second function when the marker recognition unit 31 does not recognize the marker 12, and a third function for determining when positioning is complete. Of these, the command speed generation unit 33 is the same as the command speed generation unit 23 of the first embodiment in terms of the second and third functions, but the first function differs from that of the command speed generation unit 23. The first function of the command speed generation unit 33 will be described below.

[0044] The command speed generation unit 33 uses the position information Tworld_drone of the drone 13 in the reference coordinate system calculated by the self-position estimation unit 22 and the position information Tport_drone of the drone 13 in the charging port coordinate system calculated by the marker recognition unit 31 to calculate the position information Tworld_port of the charging port 11 in the reference coordinate system (position and attitude of the charging port 11) using the following equation (2). Tworld_port=Tworld_droneT -1 port_drone………(2)

[0045] Here, the information with the superscript "-1" added signifies information obtained through a reverse coordinate transformation operation. Specifically, Tport_drone is the position information of the drone 13 in the charging port coordinate system, while T -1 port_drone is the position information of the charging port 11 in the drone coordinate system.

[0046] However, generally, the accuracy of estimating the attitude (roll, pitch) of the marker 12 around axes (x-axis, y-axis) perpendicular to the optical axis O (Figure 6), which coincides with the vertical axis z pointing upward, is low. Therefore, the position information T of the charging port 11 in the drone coordinate system is low. -1 If port_drone is calculated directly, an excessive error occurs in the position coordinate Tworld_port of the charging port 11 in the reference coordinate system calculated by equation (2).

[0047] Therefore, the command speed generation unit 33 assumes that the direction of the vertical axis z of the reference coordinate system (Σworld) and the vertical axis z of the charging port coordinate system (Σport) are the same. Based on this assumption, the command speed generation unit 33 calculates information (i.e., the corrected position information of the drone 13 in the reference coordinate system T'world_drone, and the corrected position information of the drone 13 in the charging port coordinate system T'port_drone) from the position information of the drone 13 in the reference coordinate system Tworld_drone and the position information of the drone 13 in the charging port coordinate system Tport_drone, discarding the attitude information of the drone 13 around the axes (x axis, y axis) orthogonal to the optical axis O of the camera 14.

[0048] The command speed generation unit 33 uses the corrected information T'world_drone and T'port_drone to calculate the position coordinates Tworld_port of the charging port 11 in the reference coordinate system using the following equation (3). Tworld_port=T'world_droneT' -1 port_drone………(3)

[0049] The command speed generation unit 33 then uses the yaw angle representing the three-dimensional position x, y, z and orientation of the charging port 11 obtained from the position information Tworld_port of the charging port 11 in this reference coordinate system, and the position and attitude of the drone 13 obtained by the self-position estimation unit 22 (position information Tworld_drone of the drone 13 in the reference coordinate system), to generate a command speed V such that the horizontal position of the drone 13 is directly above the charging port 11 and the drone 13 descends toward the charging port 11 while maintaining a predetermined yaw angle, and outputs this command speed V to the drive control unit 25.

[0050] Furthermore, if the command speed generation unit 33 calculates the position information Tworld_port of the charging port 11 in the reference coordinate system using equation (3) based on the position information Tport_drone of the drone 13 in the charging port coordinate system calculated by the marker recognition unit 31 after the marker 12 is recognized, it updates and stores the calculated position information of the charging port 11 in the storage unit 24.

[0051] The landing operation of the drone landing system 30 configured as described above differs from the first embodiment in that, in step S2 of Figure 4, the marker recognition unit 31 recognizes the marker 12 and the command velocity generation unit 33 calculates the position information Tworld_port of the charging port 11 in the reference coordinate system using equation (3). Steps S1 and S3 to S10 are the same in the second embodiment as in the first embodiment.

[0052] As configured as described above, this second embodiment also provides the same effects as those of the first embodiment (1) and (2), as well as the following effect (3).

[0053] (3) The command speed generation unit 33 calculates the position information Tworld_port of the charging port 11 in the reference coordinate system using equation (3), by discarding and correcting the attitude information of the drone 13 around the axes (x axis, y axis) that are orthogonal to the optical axis O of the camera 14, which coincides with the vertical axis z that is pointing vertically upward (i.e., T'world_drone and T'port_drone), from the position information Tworld_drone of the drone 13 in the reference coordinate system and the position information Tport_drone of the drone 13 in the charging port coordinate system. Therefore, even if the estimation accuracy of the attitude around the x axis and y axis at the marker 12 attached to the drone 13 is low, the position information Tworld_port of the charging port 11 in the reference coordinate system can be calculated with high accuracy.

[0054] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be carried out in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention, and such substitutions, modifications, and combinations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0055] 10...Drone landing system (landing system for unmanned aircraft), 11...Charging port, 12...Marker, 13...Drone (unmanned aircraft), 14...Camera, 21...Marker recognition unit, 22...Self-position estimation unit, 23...Command velocity generation unit, 26...Positioning completion determination unit, 27...Positioning completion zone, 30...Drone landing system (landing system for unmanned aircraft), 31...Marker recognition unit, 33...Command velocity generation unit, V...Command velocity, Tdrone_port...Position information of the charging port in the drone coordinate system, Tworld_drone...Position information of the drone in the reference coordinate system, Tworld_port...Position information of the charging port in the reference coordinate system, Tport_drone...Position information of the drone in the charging port coordinate system

Claims

1. An unmanned aerial vehicle landing system in which a camera installed at the landing site photographs a marker placed on the unmanned aerial vehicle, and the unmanned aerial vehicle is landed at the landing site by recognizing the marker, A marker recognition unit recognizes the marker captured by the camera and calculates the position information of the unmanned aircraft in the landing site coordinate system. A self-position estimation unit that calculates the position information of an unmanned aerial vehicle in reference coordinates, The system includes a command speed generation unit that uses the unmanned aircraft position information in the reference coordinate system and the unmanned aircraft position information in the landing site coordinate system to calculate the landing site position coordinates in the reference coordinate system and generate a command speed for descending the unmanned aircraft to the landing site. An unmanned aircraft landing system characterized in that the command speed generation unit is configured to generate a command speed for descending the unmanned aircraft to the landing site using the landing site position coordinates in the reference coordinate system calculated when the marker was most recently recognized, if the marker is not recognized by the marker recognition unit.

2. The command speed generation unit, when calculating the landing site position coordinates in the reference coordinate system, assumes that the direction of the vertical axis of the reference coordinate system and the direction of the vertical axis of the landing site coordinate system, which coincides with the direction of the camera optical axis, are the same, discards the attitude information of the unmanned aerial vehicle from the unmanned aerial vehicle position information in the reference coordinate system and the unmanned aerial vehicle position information in the landing site coordinate system, calculates corrected unmanned aerial vehicle position information in the reference coordinate system and corrected unmanned aerial vehicle position information in the landing site coordinate system, and generates a command speed based on this corrected information, as described in claim 1.

3. The landing system for an unmanned aerial vehicle according to claim 1 or 2, characterized in that the marker is mounted on a gimbal mechanism for adjusting the attitude of the unmanned aerial vehicle.

4. The command speed generation unit descends the unmanned aircraft from above the landing site, and when the unmanned aircraft stays within the positioning completion zone set above the landing site for a certain period of time, it determines that positioning is complete and lands the unmanned aircraft at the landing site. The landing system for an unmanned aircraft according to claim 1, characterized in that if the positioning is not completed even after the unmanned aircraft has descended to a certain altitude in the positioning completion zone, the system is configured to raise the unmanned aircraft to a predetermined altitude above the certain altitude and then descend again.

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