Weeding methods

Abstract

Applying unmanned aerial vehicle technology to weed control operations will improve safety and efficiency. [Solution] A weeding method is provided, which includes a weeding step in which an unmanned aerial vehicle equipped with multiple rotors, a cutter unit that cuts grass with rotating blades, and a ground altitude sensor repeatedly moves along a predetermined flight path while gradually lowering its ground altitude while rotating the blades. The problem is solved by an unmanned aerial vehicle equipped with multiple rotors, a control unit that controls the operation of each rotor, a cutter unit that cuts grass with rotating blades, and a ground altitude sensor, wherein when the aircraft is manually controlled, the control unit restricts the operation of each rotor so that the aircraft's ground altitude does not fall below a predetermined height.

Description

Technical Field

[0001] The present invention relates to unmanned aerial vehicle technology.

Background Art

[0002] Patent Document 1 listed below discloses a flying object that cuts grass with a rotating blade.

Prior Art Literature

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Abandoned landmines, which are remnants of wars and armed conflicts, continue to threaten the lives and livelihoods of people for many years even after the end of conflicts. Abandoned landmines are a serious humanitarian issue, and also act as a factor hindering the reconstruction of affected countries.

[0005] To remove such abandoned landmines, destruction operations using heavy machinery (flails, rollers, cutters, etc.) and clearance operations using metal detectors and the like are ongoing. Especially in areas where it is difficult to transport heavy machinery, it is necessary to dig up and recover landmines or perform pinpoint destruction by remote detonation, and the reliability of detection and the accuracy of the detected position determine the success or failure and safety of the operation.

[0006] Here, if grass grows thickly in the area where landmines are placed, this prevents the detector from approaching the ground surface, and the landmine detection accuracy decreases. On the other hand, weeding work in landmine-contaminated areas is extremely dangerous, and as a result, the actual situation is that landmine clearance in grassy areas is delayed.

[0007] The problem to be solved by the present invention is to improve the safety, workability and the like of weeding work by applying unmanned aerial vehicle technology to weeding work. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides a weeding method that includes a weeding step in which an unmanned aerial vehicle equipped with multiple rotors, a cutter unit that cuts grass with rotating blades, and a ground altitude sensor is repeatedly moved along a predetermined flight path while rotating the blades and gradually lowering its altitude above the ground.

[0009] Naturally, it is essential to avoid people stepping into areas contaminated with landmines or applying significant load or impact to the ground. In this invention, by using an unmanned aerial vehicle (UAV) that floats in the air with a rotor to cut grass, the load applied to the ground can be kept to a minimum, allowing people to perform weeding work while remaining in a safe location. Furthermore, by equipping the UAV with a ground altitude sensor and quantifying its altitude above the ground, it becomes easier to maintain an appropriate distance from the ground, preventing the rotating blades from contacting the ground. On the other hand, if uncut grass becomes entangled in the UAV's rotor, the rotor's rotation may be hindered, potentially causing the UAV to crash. In this invention, by cutting the grass in stages from higher to lower positions, it is possible to safely cut grass even in areas with tall grass, while preventing the grass from becoming entangled in the rotor.

[0010] In the weeding process, it is desirable to have the unmanned aerial vehicle pass over the same point on the flight path multiple times, gradually lowering its altitude above the ground. For example, the entire area to be weeded may be flown over multiple times, lowering its altitude above the ground with each lap, or the vehicle may be made to move back and forth only over areas where tall grass is densely growing, gradually lowering its altitude above the ground.

[0011] Furthermore, the weeding method of the present invention further includes a planning step of creating flight plan data for autonomous flight of the unmanned aerial vehicle, and in the weeding step, the unmanned aerial vehicle may be made to fly autonomously according to the flight plan data. This is to enable anyone to perform weeding work of a consistent quality, regardless of the skill level of the unmanned aerial vehicle operator.

[0012] In this case, it is desirable that the unmanned aerial vehicle be equipped with an obstacle detection sensor that detects hard ground objects around the aircraft, either as a ground altitude sensor or in addition to the ground altitude sensor, and that the weeding process be interrupted or stopped when a ground object is detected at a position where it would come into contact with the unmanned aerial vehicle during the weeding process. Because the unmanned aerial vehicle flies at a low altitude using its rotors, soft ground objects such as grass should flutter due to the exhaust flow from the rotors. If there are ground objects that do not change shape among them, it can be determined that those objects are hard. By avoiding contact with hard ground objects, the safety of the weeding work can be improved.

[0013] Furthermore, it is desirable that the weeding method of the present invention further includes a topographic surveying step in which the unmanned aerial vehicle is equipped with a three-dimensional sensor that acquires point cloud data of the terrain around the aircraft, either as a ground altitude sensor or in addition to the ground altitude sensor, and the unmanned aerial vehicle acquires point cloud data of the terrain below the flight path. This enhances the safety and accuracy of the weeding work. In this case, the topographic surveying step may be performed using an unmanned aerial vehicle other than the one mentioned above.

[0014] Furthermore, in the weed control method of the present invention, it is desirable that the unmanned aerial vehicle further comprises a GNSS receiving unit that acquires position information from a GNSS (Global Navigation Satellite System) and a correction information receiving unit that acquires correction information for the position information. This improves the positional accuracy of the unmanned aerial vehicle, making it possible to perform autonomous flight and topographic surveys with greater precision.

[0015] Furthermore, in the weeding method of the present invention, it is desirable that the vertical distance from the center of the rotation plane of each rotor to the blade of the unmanned aerial vehicle be 2 / 3 or less of the maximum distance between each rotor when the unmanned aerial vehicle is viewed from above. By shortening the distance between the rotor and the blade of the cutter, the moment transmitted to the rotor side (upper part of the aircraft) when grass hits the blade can be reduced, and the attitude of the aircraft during the weeding process becomes more stable. In the present invention, the grass is cut in stages from a high position to a low position, so even if the distance between the rotor and the blade of the cutter is short, it is prevented that uncut grass will get caught in the rotor.

[0016] Furthermore, in order to solve the above problems, the unmanned aerial vehicle of the present invention comprises a plurality of rotors, a control unit that controls the operation of each rotor, a cutter unit that cuts grass with a rotating blade, and a ground altitude sensor, and the gist of the invention is that when the aircraft is manually controlled, the control unit restricts the operation of each rotor so that the aircraft's ground altitude does not fall below a predetermined height.

[0017] For example, if the airframe or blade of the cutter of an unmanned aerial vehicle comes into contact with a landmine while mowing grass in an area contaminated with landmines, the impact could detonate the landmine. This type of accident is especially likely to occur when cutting the grass very short. By having the control unit automatically maintain the unmanned aerial vehicle's altitude above a certain level, stable low-altitude flight becomes possible even with manual control, thus preventing the detonation of landmines.

[0018] In this case, it is desirable that the unmanned aerial vehicle of the present invention be equipped with an obstacle detection sensor that detects hard ground objects around the aircraft, either as a ground altitude sensor or in addition to the ground altitude sensor, and that when the aircraft is manually controlled, the control unit restricts the operation of each rotor so that the aircraft's ground altitude does not fall below a predetermined height and the ground objects and the aircraft do not come closer than a predetermined distance. By automatically preventing contact not only with the ground but also with hard ground objects, weeding work can be performed more safely.

[0019] Furthermore, it is desirable that the vertical distance from the center of the rotation plane of each rotor to the blade be 2 / 3 or less of the maximum distance between each rotor when the machine is viewed in plan. By shortening the distance between the rotor and the blade of the cutter, the moment transmitted to the rotor side when grass hits the blade can be reduced, and the posture of the machine during weeding work becomes more stable.

[0020] Furthermore, the unmanned aerial vehicle of the present invention comprises a cutter frame, which is a frame member that supports the cutter section; a lift frame, which is a frame member that suspends the cutter frame during flight; and a connecting section, which is a frame member that connects the lift frame and the cutter frame. Preferably, multiple connecting sections are provided at intervals in the horizontal direction. By reducing the horizontal distance between each part of the blade of the cutter section and the nearest suspension point (the connection point between the lift frame and the connecting section), the moment transmitted to the rotor side when grass hits the blade can be reduced, and the attitude of the aircraft during weeding work becomes more stable.

[0021] Furthermore, it is desirable that the unmanned aerial vehicle of the present invention has two cutter sections that rotate in opposite directions. By rotating the blades in opposite directions, these counter-torques cancel each other out, resulting in a more stable posture for the aircraft during weeding work.

[0022] Furthermore, it is desirable that the rotational surface of each rotor is inclined such that its surface position becomes lower toward the base end of each rotor arm, which is a frame member supporting these rotors. This allows the position of the rotational surface of each rotor, especially its outer side, to be raised, making it less likely for grass to get caught in the rotor.

[0023] Furthermore, to solve the above problems, the unmanned aerial vehicle of the present invention includes a plurality of rotors, a cutter unit that cuts grass with rotating blades, a cutter frame that is a frame member supporting the cutter unit, a lift frame that is a frame member that suspends and supports the cutter unit during flight, and a connecting portion that is a frame member connecting the lift frame and the cutter frame. A plurality of the connecting portions are provided at intervals in the horizontal direction, and the gist thereof is that the vertical distance from the center of the rotation surface of each of the rotors to the blade is 2 / 3 or less of the maximum distance between the respective rotors when the airframe is viewed in plan. By having these features, the attitude of the airframe during weeding work can be stabilized. [Effects of the Invention]

[0024] According to the unmanned aerial vehicle and the weeding method of the present invention, the safety, workability and the like of weeding work can be improved. [Brief Description of the Drawings]

[0025] [Figure 1] It is a perspective view of the multicopter 10. [Figure 2] It is a plan view of the multicopter 10. [Figure 3] It is a front view of the multicopter 10. [Figure 4] It is a side view of the multicopter 10. [Figure 5] It is a block diagram showing the functional configuration of the weeding system 90. [Figure 6] It is a schematic diagram showing the autopilot operation of the multicopter 10. [Figure 7] It is a side schematic view showing the movement trajectory of the saw chain 21 in the weeding process. [Figure 8] It is a transparent plan view showing examples of the multicopter 10a and the multicopter 10b in which the rotary blade 20 is divided into two parts. [Figure 9] It is a plan view showing examples of the multicopter 10c and the multicopter 10d that differ in the arrangement and type of the rotors 11. [Figure 10] These are plan views and transparent plan views showing examples of multicopter 10e and multicopter 10f, which represent the minimum configuration of multicopter 10. [Modes for carrying out the invention]

[0026] <Configuration overview> Embodiments of the present invention will be described below with reference to the drawings. The weed control system described below is characterized by attaching a rotating blade to a multicopter and flying the multicopter at a low altitude while rotating the blade to cut grass in a landmine-contaminated area. The features of the present invention will be described below using this weed control system as an example.

[0027] Figure 1 is a perspective view of the multicopter 10. Figure 2 is a top view of the multicopter 10. Figure 3 is a front view of the multicopter 10. Figure 4 is a side view of the multicopter 10. The airframe structure of the multicopter 10 will be described below with reference to Figures 1 to 4.

[0028] The multicopter 10 in this example is an unmanned aerial vehicle equipped with a chainsaw-like rotating blade 20 and eight rotors 11 that suspend it. The multicopter 10 has a lift bar 16 (lift frame), which is a straight rod-shaped frame part that extends horizontally, and two rotor hubs 13, which are box-shaped hollow frame parts, are fixed to both ends of the lift bar 16 in the longitudinal direction. Four rotor arms 12, which are straight rod-shaped frame parts, are connected to each rotor hub 13. When viewed from above, these rotor arms 12 are arranged at equal intervals so as to extend radially from each rotor hub 13. A rotor 11, consisting of a fixed-pitch propeller and a motor, is supported at the tip of each rotor arm 12. The rotating blade 20 in this example is a cutter part that rotates the saw chain 21 in the horizontal direction. The rotating blade 20 has a straight rod-shaped shaft 22 extending parallel to the lift bar 16 and five sprockets 23 arranged at equal intervals along the longitudinal direction of the shaft 22, and a single saw chain 21 is wrapped around these sprockets 23. In this example, the rotating blade 20 is driven by the engine 29, which rotates the drive wheels of the sprockets 23. The rotating blade 20 is supported by a cutter holder 17 (cutter frame), which is a frame part that clamps it. The lift bar 16 and the cutter holder 17 are connected by a C-shaped connecting part 18 in side view. Three connecting parts 18 are arranged at equal intervals along the longitudinal direction of the lift bar 16, with the upper end of each connecting part 18 connected to the lift bar 16 and the lower end of each cutter holder 17 provided. Simple skids 19, which are landing gear, are attached to the bottom surfaces of two connecting parts 18 located near both ends in the longitudinal direction of the lift bar 16.

[0029] Here, the lift bar 16, the cutter holder 17, and the connecting part 18 may be configured as a single component or as separate components. The lift bar 16 is a component or part that suspends the cutter holder 17 during the flight of the multicopter 10, the cutter holder 17 is a component or part that supports the rotating blade 20, and the connecting part 18 is a component or part that connects the lift bar 16 and the cutter holder 17. These distinctions are functional and logical, and do not necessarily need to be clearly distinguishable in appearance.

[0030] Although not shown in the diagram in this example, the multicopter 10 is also equipped with a GNSS receiver 33, an RTK (Real Time Kinematic) receiver 34, and a LiDAR 39, which will be described later. LiDAR is a ranging device that uses laser light to measure the distance to an object and reproduces the surrounding three-dimensional shape with high precision from the resulting point cloud data. As will be described in more detail later, the LiDAR 39 in this example is a ground altitude sensor that measures the altitude of the multicopter 10 above the ground, an obstacle detection sensor that detects hard ground objects around the multicopter 10, and a three-dimensional sensor that acquires point cloud data of the terrain below the flight path of the multicopter 10.

[0031] As shown in Figure 3, in this example, the multicopter 10 has a vertical distance L2 from the center of the rotation plane S of each rotor 11 to the saw chain 21 that is shorter than the maximum distance L1 between the rotors 11. Here, the "maximum distance L1" between the rotors 11 refers to the distance between the centers of the combination of two rotors 11 that has the longest separation distance between them. In this example, the multicopter 10 reduces the moment transmitted to the rotor 11 when grass hits the blade by shortening the distance between the rotor 11 and the saw chain 21. This stabilizes the posture of the machine during weeding work. To make this posture stabilization effect significant, it is desirable to set the distance L2 between the rotor 11 and the saw chain 21 to 2 / 3 or less of the maximum distance L1 between the rotors. The multicopter 10 in this example has a special configuration in which four rotors 11 arranged like a so-called quadcopter are lined up in two sets on a lift bar 16. In this example, the distance L2 is less than two-thirds of the maximum rotor-to-rotor distance L1' of one of the quadcopter groups.

[0032] Furthermore, as described above, in the multicopter 10 of this example, the lift bar 16 and the cutter holder 17 are connected by multiple connection points 18. When the saw chain 21 comes into contact with grass during weeding, the reaction force is transmitted from the rotating blade 20 through the cutter holder 17, connection points 18, and lift bar 16, and finally to the rotor 11. By supporting the rotating blade 20 with multiple connection points 18 and reducing the maximum horizontal distance between each part of the rotating blade 20 and the nearest suspension point (the connection point between the lift frame 16 and the connection points 18), the moment transmitted to the rotor 11 when the saw chain 21 hits grass can be reduced. This also stabilizes the posture of the machine during weeding.

[0033] Furthermore, the rotational surface S of each rotor 11 in this example is inclined such that its surface position becomes lower toward the base end of the rotor arm 12 that supports them. This allows the position of the rotational surface S of each rotor 11, especially on the outer side of the machine, to be raised, making it less likely for grass to get caught in the rotor 11.

[0034] <Functional Configuration> Figure 5 is a block diagram showing the functional configuration of the weed control system 90 in this example. The functions of the multicopter 10 and GCS (ground control station) 50 that constitute the weed control system 90 will be explained below with reference to Figure 5. Note that the block diagram in Figure 5 only shows features that are particularly noteworthy in this example; commonly used components such as the ESC (Electronic speed controller), PDB (Power Distribution Board), communication module between the multicopter 10 and GCS 50, battery, engine, and various mechanical switches are omitted from the figure.

[0035] The basic flight functions of the multicopter 10 are realized by the flight controller 30, GNSS receiver 33, RTK receiver 34, and rotor 11.

[0036] The flight controller 30 is a control unit that includes a microcontroller, an IMU (Inertial Measurement Unit), a barometric pressure sensor, an electronic compass, etc. The flight controller 30 is not limited to a standalone control unit, but may be combined with a so-called companion computer. Alternatively, it could be configured using, for example, an FPGA (field-programmable gate array) or an ASIC (Application Specific Integrated Circuit).

[0037] The GNSS receiver 33 and the RTK receiver 34 are external devices connected to the flight controller 30. The RTK receiver 34 is a correction information receiving unit that receives correction information to correct errors in position information acquired from GNSS, either directly from a fixed reference station or via the Internet from an NTRIP (Networked Transport of RTCM via Internet Protocol) caster. By applying this correction information to the received signal from GNSS, the latitude, longitude, and altitude (ellipsoid height) of the multicopter 10 can be improved to centimeter-level accuracy. This improves the positional accuracy of the multicopter 10, making it possible to perform autonomous flight and topographic surveying, as described later, with greater precision.

[0038] Furthermore, while the altitude value from the GNSS receiver 33 and the pressure value from the barometric pressure sensor can only determine the relative altitude of the multicopter 10 relative to its takeoff point (home point), as mentioned above, the multicopter 10 in this example precisely measures its altitude above the ground using the LiDAR 39. The means by which the multicopter 10 can acquire altitude above the ground are not limited to the LiDAR 39; for example, ranging sensors using lasers, radars, infrared, ultrasonics, parallax, etc., may also be used. Also, as mentioned above, the LiDAR 39 in this example also plays the role of an obstacle detection sensor that detects hard ground objects around the multicopter 10. Here, "hard ground objects" refers to things other than the grass to be cut, such as trees, stones, rocks, exposed landmines, and raised ground surfaces hidden by the grass. When the multicopter 10 flies at a low altitude, soft ground objects such as grass should flutter due to the exhaust flow from the rotor 11. For example, if there are features that do not change shape, those features can be determined to be hard. The means of detecting hard features are not limited to LiDAR39; for example, millimeter-wave radar could also be used, and sensor fusion with stereo cameras, depth cameras, etc., could also be considered.

[0039] The flight controller 30 includes a flight stack, which is a group of modules that control the attitude and basic flight operations of the multicopter 10 during flight. The flight stack is sometimes called flight firmware or autopilot program. Based on information acquired from various sensors, the flight controller 30 adjusts the rotation speed of each rotor 11 and flies the multicopter 10 while correcting the tilt, rotation, and positional disturbances of the aircraft.

[0040] The flight stack of the flight controller 30 also includes a program for autonomously flying the multicopter 10. The flight controller 30 receives flight plan data (hereinafter simply referred to as "flight plan") from the GCS 50, which specifies the destination, waypoints, altitude, and speed of the multicopter 10, and can make the multicopter 10 fly autonomously according to that flight plan.

[0041] Thus, the multicopter 10 in this example is an unmanned aerial vehicle equipped with advanced flight control functions. On the other hand, the unmanned aerial vehicle of the present invention is not limited to the multicopter 10 in this example, and for example, an aircraft with some sensors omitted, or an aircraft that does not have autonomous flight functions and can be flown only by manual control can also be used.

[0042] The GCS50 is a management device that is directly wirelessly connected to the multicopter 10 or wirelessly connected via the internet. The GCS50 is a device that allows the operator to create and upload flight plans for the multicopter 10, receive telemetry data from the multicopter 10 to monitor the status of the multicopter 10 in flight, and manually control the multicopter 10. The GCS50 may be a device specifically designed for the weed control system 90, or it may be a general-purpose PC or tablet device with the necessary software and applications installed.

[0043] The GCS50 is equipped with a general user interface 59, including a display (or touch panel) as a display device, and a keyboard and mouse (or trackball) as input devices. The GCS50 also includes a map display program 51, a flight plan creation program 52, and a control transmitter 58.

[0044] The map display program 51 displays map data of the area to be weeded on the GCS 50's display. The operator uses the flight plan creation program 52 to create a flight plan 521 on the map data, for example, as shown in Figure 6(a), and uploads it to the multicopter 10. The control transmitter 58 is a device for manually controlling the multicopter 10, and may be, for example, a specific key on a keyboard, a touch panel, or a so-called radio control system.

[0045] In this example, the flight controller 30 includes a ground altitude maintenance program 31 and an obstacle detection program 32. The ground altitude maintenance program 31 acquires the ground altitude of the multicopter 10 using the LiDAR 39 and restricts the operation of each rotor 11 so that the ground altitude of the multicopter 10 (ground altitude A in Figure 4) does not fall below a predetermined height. In this example, the ground altitude is calculated based on the position of the saw chain 21. The obstacle detection program 32 detects hard objects around the aircraft using the LiDAR 39 and restricts the operation of each rotor 11 so that the detected objects and the multicopter 10 do not come closer than a predetermined distance. These programs can be activated not only during autonomous flight of the multicopter 10 but also during manual flight of the multicopter 10. For example, if the body of the multicopter 10 or the rotating blade 20 comes into contact with a landmine while mowing grass in an area contaminated with landmines, the impact may detonate the landmine. Such accidents are particularly likely to occur when mowing grass short. Even when the multicopter 10 is manually controlled, the flight controller 30 automatically maintains the multicopter 10's altitude above a certain level and automatically prevents contact with hard ground objects, enabling stable low-altitude flight even with manual control and preventing the detonation of landmines.

[0046] <Each step in weeding work> Figure 6 is a schematic diagram showing the autonomous flight operation of the multicopter 10. Figure 6(a) is a schematic diagram showing the creation of the flight plan 521 on the GCS 50, and Figure 6(b) is a schematic diagram showing the multicopter 10 flying along the flight plan 521. Figure 7 is a schematic side view showing the movement path of the saw chain 21 in the weeding process. The following describes each step of the weeding work using the multicopter 10 with reference to Figures 6 and 7.

[0047] (Planned process) As shown in Figure 6(a), when starting weeding work, the operator first displays map data including the area to be weeded (the area enclosed by the dashed line) on the GCS50 display. This map data may be a two-dimensional, two-dimensional map data, or it may be point cloud data acquired in the topographic surveying process described later. The operator sets the flight path of the multicopter 10 on the map data and creates a flight plan 521. The numbers in the circles shown in Figure 6(a) represent the order in which the multicopter 10 passes through waypoints (so-called waypoints). Although not shown in Figure 6(a), the flight path data also includes parameters such as altitude above ground, flight speed, and heading at each point. In the example in Figure 6(a), when the multicopter 10 reaches point 14 of the flight path, it returns to point 1 or returns to the home point. As will be described in more detail later, the multicopter 10 in this example may repeatedly fly the same flight path. Therefore, the flight plan 521, particularly its altitude above ground, is set in correspondence with the number of flights. The operator uploads the flight plan 521 created in this way from the GCS 50 to the multicopter 10. However, the data for the flight plan 521 is not limited to being uploaded to the multicopter 10 in advance and stored there; for example, commands could be automatically sent sequentially from the GCS 50 to the multicopter 10.

[0048] (Weeding process) Upon receiving flight plan 521, the multicopter 10 receives instructions from the GCS 50 and begins the weeding process. Specifically, as shown in Figure 7(a), it first flies along the flight path at an altitude of A1 above ground while rotating the saw chain 21, then at an altitude of A2 above ground on the second lap, and at an altitude of A3 above ground on the third lap. In this way, the multicopter 10 repeatedly moves along the same flight path while gradually lowering its altitude above ground.

[0049] Naturally, it is essential to avoid people stepping into areas contaminated with landmines or applying significant load or impact to the ground. In this example, by mowing grass with a multicopter 10 that floats in the air on its rotor 11, the load on the ground can be kept to a minimum, allowing people to remain in a safe location while weeding is performed. Furthermore, the multicopter 10 is equipped with a LiDAR 39, which is a ground altitude sensor, and the altitude of the multicopter 10 is quantified, making it easy to maintain an appropriate distance from the ground and preventing the saw chain 21 from contacting the ground. On the other hand, if uncut grass becomes entangled in the rotor 11 of the multicopter 10, the rotation of the rotor 11 will be hindered, and there is a risk that the multicopter 10 may crash. In this example, by mowing the grass in stages from the highest to the lowest position, it is possible to safely mow grass even in areas with tall grass, while preventing the grass from becoming entangled in the rotor 11.

[0050] In this example, the multicopter 10 is made to circle the entire flight path (area to be weeded) multiple times. However, it is also possible to make multiple round trips, gradually lowering the altitude above ground, only over areas where tall grass is densely growing. If it is difficult to obtain grass height using only the LiDAR 39, sensor fusion with other sensors can be considered. Figure 7(b) shows the movement path of the saw chain 21 in that case. In the example of Figure 7(b), when the multicopter 10 detects a patch of grass with tall grass protruding in its direction of travel, it automatically rises to an altitude suitable for cutting that grass. After finishing cutting the grass at that height, it retreats to the front of the patch of grass while lowering its altitude above ground by one level, and cuts the grass again at a lower altitude. Finally, after finishing cutting the grass at an altitude of A3 above ground, it resumes moving forward. By controlling the multicopter 10 in this way, weeding work can be performed more efficiently.

[0051] As described above, in this example, the multicopter 10 has a vertical distance L2 from each rotor 11 to the saw chain 21 that is shorter than the maximum distance L1 between rotors (see Figure 3). In other words, the rotors 11 and the saw chain 21 are positioned relatively close together. This stabilizes the posture of the multicopter 10 during the weeding process, but it also means that uncut grass is more likely to get caught in the rotors 11. In this example, by cutting the grass in stages from high to low positions, it is possible to prevent uncut grass from getting caught in the rotors 11, even though the distance between the rotors 11 and the saw chain 21 is short.

[0052] In this example, the multicopter 10 is assumed to perform the weeding process autonomously. However, even if the operator manually controls the multicopter 10, the same effect can be achieved by rotating the saw chain 21 and gradually lowering its altitude above the ground while repeatedly moving along a predetermined flight path. On the other hand, automating the weeding process would allow anyone to perform weeding work of consistent quality, regardless of the skill level of the multicopter 10 operator.

[0053] The black circles in Figure 6(b) represent obstacles 321, which are hard ground objects located along the flight path. When the multicopter 10 detects an obstacle 321 at a position where it would come into contact with the aircraft during the weeding process, it interrupts the weeding process, notifies the operator, and waits for instructions from the operator. Possible instructions from the operator include, for example, stopping the weeding process and having the multicopter 10 return to the home point, or increasing the altitude of the multicopter 10 over the obstacle 321.

[0054] (Topographic surveying process) In this example, the multicopter 10 not only performs the weeding process according to the flight plan 521, but can also acquire point cloud data of the terrain below the multicopter 10's flight path using the LiDAR 39. In other words, the multicopter 10 can also perform three-dimensional surveying of the terrain of the area to be weeded. In this example, since the multicopter 10 is equipped with LiDAR 39, it can be used for terrain surveying as well. However, if the multicopter 10 does not have a three-dimensional sensor such as LiDAR 39, for example, another unmanned aerial vehicle equipped with a three-dimensional sensor, separate from the multicopter 10, may be used to perform the terrain surveying process.

[0055] The topographic surveying process may be carried out before the planning process, or it may be carried out after the planning process based on the flight plan, and the acquired point cloud data may be used as map data to carry out the planning process again. By creating a flight plan for the weeding process based on the acquired point cloud data, high-precision position control using SLAM (Simultaneous Localization and Mapping) becomes possible. Alternatively, topographic surveying may be carried out after the planning process and before the weeding process, or it may even be carried out simultaneously with the weeding process. For example, as shown in the example in Figure 7(a), when the multicopter 10 circles the entire flight path (weeding target area) multiple times, the multicopter 10 will first start mowing the grass at a relatively high altitude above ground (altitude A1). In other words, it will start mowing the grass at a safe altitude. Therefore, if topographic surveying is carried out at the same time as weeding, the safety and accuracy of the subsequent weeding process can be improved. Also, for example, if landmine detection is carried out after the weeding process, it is convenient to have point cloud data after weeding. In other words, topographic surveying may also be carried out after the weeding process.

[0056] <Variation> Figures 8 to 10 show modified examples of the multicopter 10. In the following description, components identical or similar to those in the multicopter 10 described above are denoted by the same reference numerals, and their detailed descriptions are omitted. Furthermore, unless otherwise noted, the configurations of each modified example described below can be considered the same as those of the multicopter 10 described above.

[0057] Figure 8 is a transparent plan view showing examples of multicopters 10a and 10b in which the rotating blade 20 is divided into two. In the example of Figure 8(a), two rotating blades 20, each with a saw chain 21 wrapped around three sprockets 23 supported on a shaft 22, are arranged side by side (in the Y direction shown). These saw chains 21 rotate in opposite directions to each other. This cancels out the counter-torque associated with the rotation of the saw chains 21, resulting in a more stable posture of the machine during weeding work.

[0058] In the example shown in Figure 8(a), the two rotating blades 20 are arranged so that their shafts 22 are aligned in a straight line. However, as shown in Figure 8(b), for example, the rotating blades 20 could also be arranged in a convex shape facing forward, like the snowplow blade of a snowplow, and each saw chain 21 could be rotated in opposite directions to separate the grass. This could potentially reduce the resistance of the grass during weeding. Conversely, the rotating blades 20 could also be tilted in a concave shape, and each saw chain 21 could be rotated to gather the grass towards the center of the machine. This could potentially reduce missed cuts.

[0059] Figure 9 is a plan view showing examples of multirotors 10c and 10d with different rotor arrangements and types. As mentioned above, the airframe of the multirotor 10 has a special configuration in which four rotors 11, arranged like a so-called quadcopter, are lined up in two sets on a lift bar 16. There are a total of eight rotors 11, but because the arrangement of the rotors 11 differs from that of a so-called octacopter, a general flight stack cannot be used as is, and some adjustments are necessary. Therefore, for example, as shown in the multirotor 10c in Figure 9(a), by arranging each rotor arm 12 so that it extends radially from the center of the airframe, it can be made to resemble the configuration of an octacopter. In this way, a highly reliable flight stack with a proven track record can be used with minimal modification, thereby reducing the development and maintenance costs of the airframe. In this case, the engine 29 should be placed below the lift bar 16 so as not to interfere with the placement of additional rotor hubs 13. Alternatively, the multicopter 10 of the above embodiment could be configured as a so-called hexacopter by removing the two rotor arms 12 and their rotors 11 that extend toward the center of the aircraft from each rotor hub 13.

[0060] The helicopter 10d in Figure 9(b) is an unmanned aerial vehicle with a so-called tandem helicopter configuration, equipped with two variable-pitch rotors 11a. In the above embodiment, the multicopter 10 performs attitude control and movement by adjusting the rotational speed of each rotor 11. On the other hand, the helicopter 10d performs attitude control and movement by adjusting the pitch angle of each rotor 11a. Control by pitch angle is more responsive to disturbances than control by rotational speed, enabling more precise and stable attitude control. In other words, the unmanned aerial vehicle of the present invention does not have to be a multicopter. In other words, it does not have to be equipped with three or more rotors. In this case as well, the engine 29 should be placed below the lift bar 16 so as not to interfere with the arrangement of the variable-pitch rotors 11a.

[0061] Figure 10 shows perspective and transparency views of examples of multicopter 10e and multicopter 10f, which represent the minimum configuration of the multicopter 10. The multicopter 10 in the above embodiment is configured to efficiently remove weeds from a wide, open area, but a smaller aircraft may be more suitable for exploring narrow areas or areas with many obstacles. The multicopter 10e in Figure 10(a) is a minimum configuration aircraft suitable for such applications. The multicopter 10e is equipped with a circular saw 20a, which is a cutter section having one saw blade 21a. Even with this configuration, the same effect as in the above embodiment can be obtained by repeatedly moving along a predetermined flight path while rotating the saw blade 21a and gradually lowering its altitude above the ground. Furthermore, by having the flight controller 30 automatically control the aircraft's altitude above the ground so that it does not fall below a predetermined height, stable low-altitude flight is possible even with manual control. Furthermore, in this modified example, the vertical distance L2 between the rotor 11 and the circular saw 20a is less than or equal to 2 / 3 of the maximum distance between rotors (L1'), thus improving the stability of the posture during the weeding process.

[0062] Figure 10(b) is a transparent plan view showing a configuration with two circular saws 20a as shown in Figure 10(a). Even in a configuration using circular saws 20a, rotating the two circular saws 20a in opposite directions cancels out the counter-torque of the circular saws 20a, resulting in a more stable posture of the aircraft during weeding work. Although the multicopter 10e and multicopter 10f in this modified example employ a quadcopter configuration, it is also conceivable to employ a helicopter configuration with multiple rotors, such as a main rotor and a tail rotor.

[0063] Although embodiments of the present invention have been described above, the scope of the present invention is not limited thereto, and various modifications can be made without departing from the spirit of the invention. For example, although the above embodiments and modifications were described on the premise of mowing grass in landmine-contaminated areas, the unmanned aerial vehicle and weeding method of the present invention can also be applied to mowing grass in areas other than landmine-contaminated areas. Furthermore, although a cutter section with a metal blade is used in the above embodiments and modifications, it is also conceivable to use a nylon cutter. [Explanation of Symbols]

[0064] 90: Weed control system, 10, 10a, 10b, 10c, 10e, 10f: Multicopter (unmanned aerial vehicle), 10d: Helicopter (unmanned aerial vehicle), 11: Rotor, S: Rotating surface, 12: Rotor arm, 13: Rotor hub, 16: Lift bar (lift frame), 17: Cutter holder (cutter frame), 18: Connection part, 19: Skid, 20: Rotating blade (cutter part), 20a: Circular saw (cutter part), 21: Saw chain (blade), 21a: Saw blade (Blade), 22: Shaft, 23: Sprocket, 29: Engine, 30: FC (Control Unit), 31: Ground Altitude Hold Program, 32: Obstacle Detection Program, 321: Obstacle, 33: GNSS Receiver, 34: RTK Receiver (Correction Information Receiver), 39: LiDAR (Ground Altitude Sensor, Obstacle Detection Sensor, 3D Sensor), 50: GCS, 51: Map Display Program, 52: Flight Plan Creation Program, 521: Flight Plan, 58: Control Transmitter, 59: User Interface

Claims

1. Multiple rotors, A cutter section that cuts grass with a rotating blade, Ground altitude sensor, An unmanned aerial vehicle equipped with, The process includes a weeding step in which the blade is rotated while gradually lowering its altitude above the ground, and repeatedly moving along a predetermined flight path. Weeding method.

2. In the aforementioned weeding process, the unmanned aerial vehicle is made to pass over the same point on the flight path multiple times, while gradually lowering its altitude above ground level. The weed control method according to claim 1.

3. The process further includes a planning step for creating flight plan data to enable the aforementioned unmanned aerial vehicle to fly autonomously, In the aforementioned weeding process, the unmanned aerial vehicle autonomously flies according to the flight plan data. The weed control method according to claim 1.

4. The aforementioned unmanned aerial vehicle is equipped with, as the ground altitude sensor, or in addition to the ground altitude sensor, an obstacle detection sensor that detects hard ground objects around the aircraft. If the ground object is detected at a location where it will come into contact with the unmanned aerial vehicle during the weeding process, the weeding process will be interrupted or canceled. The weed control method according to claim 3.

5. The aforementioned unmanned aerial vehicle is equipped with a three-dimensional sensor that acquires point cloud data of the terrain around the aircraft, either as the ground altitude sensor or in addition to the ground altitude sensor. The process further includes a topographic surveying step in which the unmanned aerial vehicle acquires point cloud data of the terrain under the flight path. The weed control method according to claim 1.

6. The process further includes a topographic surveying step in which a separate unmanned aerial vehicle, equipped with a three-dimensional sensor that acquires point cloud data of the terrain around the aircraft, acquires point cloud data of the terrain under the flight path. The weed control method according to claim 1.

7. The aforementioned unmanned aerial vehicle A GNSS receiver unit that acquires location information from GNSS (Global Navigation Satellite System), The system further includes a correction information receiving unit that acquires correction information for the aforementioned position information. The weed control method according to claim 1.

8. The vertical distance from the center of the rotating surface of each rotor to the blade is, The distance between each rotor when the unmanned aerial vehicle is viewed from above is 2 / 3 or less. The weed control method according to claim 1.

9. Multiple rotors, A control unit that controls the operation of each of the rotors, A cutter section that cuts grass with a rotating blade, Equipped with a ground altitude sensor, When the aircraft is being manually controlled, the control unit restricts the operation of each rotor so that the aircraft's altitude above the ground does not fall below a predetermined height. unmanned aircraft.

10. As the aforementioned ground altitude sensor, or in addition to the ground altitude sensor, an obstacle detection sensor is provided to detect hard ground objects around the aircraft. When the aircraft is being manually controlled, the control unit restricts the operation of each rotor so that the aircraft's altitude above the ground does not fall below a predetermined height, and so that the aircraft does not get closer to the ground object than a predetermined distance. The unmanned aerial vehicle according to claim 9.

11. The vertical distance from the center of the rotating surface of each rotor to the blade is, The maximum distance between each rotor when the aircraft is viewed from above is 2 / 3 or less. The unmanned aerial vehicle according to claim 9.

12. A cutter frame, which is a frame member that supports the cutter section, A lift frame is a frame member that suspends the cutter frame during flight, It comprises a connecting portion which is a frame member that connects the lift frame and the cutter frame, Multiple connecting parts are provided at intervals in the horizontal direction. The unmanned aerial vehicle according to claim 9.

13. Having two cutter parts that rotate in opposite directions, The unmanned aerial vehicle according to claim 9.

14. The rotational surfaces of each rotor are inclined such that their surface position becomes lower toward the base end of the rotor arm, which is a frame member supporting these rotors. The unmanned aerial vehicle according to claim 9.

15. Multiple rotors, A cutter section that cuts grass with a rotating blade, A cutter frame, which is a frame member that supports the cutter section, A lift frame is a frame member that suspends the cutter frame during flight, It comprises a connecting portion which is a frame member that connects the lift frame and the cutter frame, Multiple connecting parts are provided at intervals in the horizontal direction. The vertical distance from the center of the rotation plane of each rotor to the blade is less than or equal to 2 / 3 of the maximum distance between each rotor when the machine is viewed in plan. unmanned aircraft.

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