Unmanned aircraft and methods for operating unmanned aircraft

Abstract

This improves the accuracy of surveys using unmanned aerial vehicles (UAVs) floating on the water's surface. [Solution] A method for operating an unmanned aerial vehicle (UAV) that includes a water landing step of landing an UAV equipped with horizontal rotors on the water surface, and a stabilization step of continuing to rotate the horizontal rotors at a rotational speed that prevents the UAV from taking off after landing, or a method for operating an UAV that includes a plurality of horizontal rotors, floats to keep the UAV afloat on the water surface, and a control unit that controls the rotational speed of each horizontal rotor, wherein the control unit has a stabilization function that continues to rotate each horizontal rotor at a rotational speed that prevents the UAV from taking off after landing.

Description

Technical Field

[0001] The present invention relates to an attitude control technology of an unmanned aircraft on the water surface.

Background Art

[0002] Patent Document 1 below discloses a surveying system for measuring the flow velocity distribution and the flow rate of the longitudinal cross-section of a water area such as a river.

Prior Art Document

[0007] To solve the above problems, the gist of the present invention is that the method for controlling an unmanned aerial vehicle includes a water landing step of landing an unmanned aerial vehicle equipped with horizontal rotor blades on the water surface, and a stabilization step of continuing to rotate the horizontal rotor blades at a rotational speed such that the unmanned aerial vehicle does not take off from the water after landing.

[0008] By utilizing the rotor blades of an unmanned aerial vehicle (UAV) that flies using horizontal rotors not only for flight but also as a gyro stabilizer (flywheel) on the water surface, it is possible to stabilize the attitude of the UAV on the water surface without introducing specialized equipment.

[0009] In this case, the unmanned aerial vehicle is equipped with multiple horizontal rotors, and in the stabilization process, it is desirable to rotate the same number of horizontal rotors in opposite directions at approximately the same speed. By rotating the multiple rotors so that their counter-torques cancel each other out, the heading of the unmanned aerial vehicle can also be stabilized.

[0010] Furthermore, the method for controlling an unmanned aerial vehicle in the present invention further includes a downstream step of letting the unmanned aerial vehicle drift with the current of the river from upstream to downstream, or a stationary step of maintaining the position of the unmanned aerial vehicle at a single point on the water surface, and the stabilization step may be performed at least during the downstream step or the stationary step.

[0011] Furthermore, in the method for controlling an unmanned aerial vehicle according to the present invention, the rotational speed of the horizontal rotor blades in the stabilization step may be set by a parameter different from the parameter that sets the rotational speed of the unmanned aerial vehicle during arming. Arming of an unmanned aerial vehicle is a type of pre-flight inspection operation and merely involves test-running the rotor blades at a minimum rotational speed. On the other hand, in the stabilization step, it is necessary to obtain a gyroscopic effect from the rotor blades, so it is conceivable to rotate the rotor blades at a higher speed than during arming. On the other hand, if a sufficient attitude maintenance effect can be obtained even with the rotational speed during arming, the unmanned aerial vehicle may be kept armed after landing on the water in the water landing step, or it may be armed again in the stabilization step.

[0012] Furthermore, in the stabilization process, it is desirable that the rotation speed of the horizontal rotor blades be manually adjustable, or that the rotation speed of the horizontal rotor blades be automatically adjusted in response to the oscillation of the unmanned aerial vehicle. By adjusting the rotation speed of the rotor blades according to the degree of waves and swells on the water surface, excessive idling and power consumption of the rotor blades can be suppressed.

[0013] Furthermore, the unmanned aerial vehicle may be equipped with a camera, and the stabilization process may include a step of taking a photograph using the camera. The stabilization process suppresses blurring during photography. In this case, it is more desirable that the camera is supported by an attitude stabilization device.

[0014] Furthermore, the unmanned aerial vehicle may be equipped with a water propulsion system, which is a dedicated thrust source for moving on the water surface. This allows the rotor blades to be specialized for maintaining the aircraft's attitude after landing on the water, thereby enhancing the effectiveness of the stabilization process. Alternatively, the unmanned aerial vehicle may be configured to move on the water surface using the horizontal rotor blades and not be equipped with a water propulsion system, which is a dedicated thrust source for moving on the water surface. This simplifies the functional configuration of the unmanned aerial vehicle and reduces the aircraft's weight.

[0015] Furthermore, the unmanned aerial vehicle may be equipped with one or more floating boat-shaped floats. This is advantageous for maintaining the heading of the unmanned aerial vehicle when it is drifting along the current in a body of water.

[0016] Furthermore, the unmanned aerial vehicle of the present invention comprises a plurality of horizontal rotors, floats to keep the aircraft afloat on the water surface, and a control unit that controls the rotational speed of each horizontal rotor, the gist of which is that the control unit has a stabilization function that keeps each horizontal rotor rotating at a rotational speed that prevents the aircraft from taking off again after landing on water. The effect is the same as the method of controlling the unmanned aerial vehicle in the present invention.

[0017] In this case, it is desirable that the unmanned aerial vehicle of the present invention further comprises a draft detection means for detecting the draft of the float, and that the stabilization function adjusts the rotational speed of each horizontal rotor according to the output value of the draft detection means. For example, when attempting to obtain surface flow velocity by letting the unmanned aerial vehicle drift downstream with the current of a river, it is undesirable for the stabilization function to affect the downstream speed of the unmanned aerial vehicle. By measuring the effect of the rotor blade idling operation on the downstream speed using the float's draft, excessive idling operation can be suppressed.

[0018] Furthermore, the gist of the present invention is that the unmanned aerial vehicle comprises a horizontal rotor, a float to keep the vehicle afloat on the water surface, and a gyro stabilizer to stabilize the vehicle's attitude on the water surface. In this case, the gyro stabilizer may be configured not to be used during the vehicle's flight. By providing the unmanned aerial vehicle with a separate gyro stabilizer, the rocking of the unmanned aerial vehicle on the water surface can be suppressed. [Effects of the Invention]

[0019] Thus, according to the unmanned aerial vehicle and the method for operating the unmanned aerial vehicle of the present invention, the accuracy of surveying using an unmanned aerial vehicle floating on the water surface can be improved. [Brief explanation of the drawing]

[0020] [Figure 1] It is a perspective view of the multicopter 12. [Figure 2] It is a block diagram showing the overall configuration of the measurement system 10. [Figure 3] It is a block diagram showing a part of the control function provided by the FC / BC 20. [Figure 4] It is a schematic diagram explaining the stabilization function of the multicopter 12. [Figure 5] It is a schematic diagram explaining a method for calculating the flow velocity distribution and the flow rate of the longitudinal and cross-sectional profiles of a river by the measurement system 10. [Figure 6] It is a schematic diagram showing a specific example of the image analysis method for the water surface flow velocity in this embodiment. [Figure 7] It is a schematic diagram showing another example of the imaging means. [Figure 8] It is a schematic diagram showing the state where the multicopter 12 rides on the water flow of the river and goes downstream along the river. [Figure 9] It is a schematic diagram showing the state where multiple multicopters 12 are maintained at a point on the water surface of a natural dam lake.

Embodiments for Carrying out the Invention

[0021] Embodiments of the present invention will be described below with reference to the drawings. The surveying system 10 described below is a system that uses a multicopter 12, which is an unmanned aerial vehicle, to float down a river current, and measures the flow velocity distribution in each layer below the aircraft, the water surface flow velocity around the aircraft, and the river channel shape. Based on these measured values, it calculates the flow velocity distribution, average flow velocity, and flow rate of the longitudinal and transverse surfaces of the river. The present invention is characterized by reducing the oscillation of the multicopter 12 on the water surface by idling the rotor 41 of the multicopter 12 after it has landed on the water, due to the gyroscopic effect. This feature and other features associated therewith will be described below using embodiments as examples. In the following description, "surveying" refers to measuring flow velocity, river channel shape (topography), flow rate, or water level, and is not limited to the scope of "surveying" as defined in the Surveying Act. Also, in the following description, "image" refers not only to still images but also to "moving images" and "videos," that is, a series of still images.

[0022] <Overview of the surveying system> Figure 1 is a perspective view of the multicopter 12, and Figure 2 is a block diagram showing the overall configuration of the surveying system 10. The overview of the surveying system 10 will be described below with reference to Figures 1 and 2.

[0023] As shown in Figure 1, the multicopter 12 in this configuration is a so-called hexacopter, comprising six arms extending radially in a plan view and rotors 12, which are horizontal rotating blades, fixed to the ends of these arms. The multicopter 12 is equipped with a pair of boat-shaped floats 50 that keep the aircraft afloat on the water surface, and a pair of thrusters 42, which are water-based propulsion devices for moving the multicopter 12 on the water surface, are fixed to each float 50. In addition, an ADCP unit 70, which is an ultrasonic Doppler current meter that acquires the flow velocity distribution below the aircraft after landing on the water, and a sonar unit 80, which is a scanner device that acquires the topography of the river channel (cross-sectional shape of the river channel) are mounted on the underside of the fuselage of the multicopter 12. Furthermore, two GNSS (Global Navigation Satellite System) devices, namely GPS receivers 31 (hereinafter simply referred to as "GPS31"), are positioned outside the multicopter 12.

[0024] As shown in Figure 2, the surveying system 10 in this embodiment mainly consists of an analysis device 11 and a multicopter 12. The analysis device 11 and the multicopter 12 are connected via the Internet. In this embodiment, the operator terminal 19 of the surveying system 10 is also connected to each device via the Internet. The operator terminal 19 may also be a so-called radio control type control device that directly controls the multicopter 12 via wireless communication.

[0025] (Multicopter) The multicopter 12 in this configuration consists of a control unit, a flight controller / boat controller 20 (hereinafter referred to as "FC / BC20"), a GPS 31 connected to the FC / BC20, an RTK receiver 32, a rotor 41, thrusters 42, and an omnidirectional camera 60 (hereinafter simply referred to as "camera 60") which is a means of taking pictures, as well as an ADCP unit 70, a sonar unit 80, and floats 50. The FC / BC20 in this configuration includes firmware for controlling the attitude of the multicopter 12 during flight, as well as an IMU (Inertial Measurement Unit), a barometric pressure sensor, a compass sensor (electronic compass), etc.

[0026] The FC / BC20 controls the rotational speed of the rotors 41 and thrusters 42 in accordance with the autopilot program described later and instructions from the operator terminal 19, thereby enabling the multicopter 12 to fly or navigate. Here, "navigation" means that the multicopter 12 moves on the water surface. The multicopter 12 in this configuration is equipped with six rotors 41, which are thrust sources for moving through the air, and two thrusters 42, which are dedicated thrust sources for moving on the water surface. The FC / BC20 can switch between "flight mode," which moves through the air using the rotors 41, and "navigation mode," which moves on the water surface using the thrusters 42, automatically or by instruction from the operator terminal 19. The operator can remotely control the multicopter 12 by visual observation if the multicopter 12 is within visual range, or by relying on images transmitted from the camera 60 if it is outside of visual range. In this configuration of the surveying system 10, the multicopter 12 is equipped with thrusters 42, which enhances the freedom, flexibility, and safety of river surveying using the multicopter 12. On the other hand, the multicopter 12 can also move on the water surface by driving the rotor 41 in the same way as when flying. By omitting the thrusters 42, the functional configuration of the multicopter 12 can be simplified and the weight of the aircraft can be reduced.

[0027] The RTK receiver 32 is a device that acquires correction information for signals received from GPS satellites. In this configuration, the RTK receiver 32 acquires correction information provided as an internet service via an LTE (Long Term Evolution) connection. Therefore, in this configuration of the surveying system 10, there is no need to install RTK base stations (fixed stations) around the survey points. Furthermore, the distance constraints between the RTK receiver 32 and the RTK base station are relaxed, enabling faster, simpler, and more extensive surveying. In addition to the LTE connection, the RTK receiver 32 may also use other mobile communication networks such as 5G, 3G, or WiMAX (Worldwide Interoperability for Microwave Access). While this configuration uses GPS as the GNSS device, this could also be a receiver of other systems such as GLONASS, Galileo, Michibiki (Quasi-Zenith Satellite System), or COMPASS (Beidou Positioning System). Alternatively, instead of RTK, it is possible to use a GNSS device that can utilize Michibiki's CLAS (Centimeter-Level Augmentation Service). In that case, the signal correction using the RTK mechanism described below can be reinterpreted as correction using CLAS.

[0028] In this configuration, the FC / BC20 continues to operate the GPS31 and RTK receiver32 even after the rotor 41 has stopped, for example, after the multicopter 12 has landed on the water. Therefore, the speed of the multicopter 12 on the water surface can be calculated from the latitude and longitude information of the GPS31.

[0029] Camera 60 is a so-called 360° camera / spherical camera that is supported above the multicopter 12 and captures images of the sides and above the aircraft in a hemispherical shape. The images captured by camera 60 are transmitted to the analysis device 11 and the operator terminal 19.

[0030] The ADCP unit 70 is a device that emits sound waves into water and measures the Doppler shift of scattering particles (such as suspended matter) that move with the water flow, thereby obtaining the flow velocity distribution for each layer according to the water depth. The ADCP unit 70 may also be equipped with its own electronic compass and IMU.

[0031] The ADCP unit 70 in this embodiment is equipped with three or more probes with different orientation angles. The ADCP unit 70 converts the one-dimensional flow velocity measured by the probes into a three-dimensional flow velocity by applying trigonometry based on the arrangement angles of these probes. Furthermore, the ADCP unit 70 in this embodiment can also be used as a DVL (Doppler Velocity Log). That is, by emitting sound waves from the multicopter 12 toward the seabed, the ground velocity of the multicopter 12 can be measured from the amount of Doppler shift of the reflected waves from the seabed. In other words, the moving speed of the multicopter 12 on the water surface can also be obtained.

[0032] The sonar unit 80 is a multi-beam acoustic depth sounder (a so-called multi-beam sonar) that transmits sound wave beams of different frequencies into the water in a fan shape and acquires river topographic data by receiving the reflected waves.

[0033] The sonar unit 80 is a unit equipped with a transmitter with multiple sonars arranged in a row, a receiver that receives reflected waves, a dedicated IMU, and a surface sound velocity meter, etc. Ultrasonic measurement is less affected by turbidity than optical cameras or green lasers, and can obtain more accurate topographic data even under difficult conditions. The scanner device mounted on the multicopter 12 does not have to be the sonar unit 80; any device that can acquire underwater topographic data after the multicopter 12 hits the water is acceptable. For example, if only areas of clear, still water are to be surveyed, topographic data can be acquired using a scanner device that uses an optical camera or laser.

[0034] (Analysis equipment) The analysis device 11 in this configuration is a server computer, a PC, or a dedicated computer device. The analysis device 11 may be a single device or a combination of multiple devices. Alternatively, the operator terminal 19 may be equipped with the functions of the analysis device 11.

[0035] In this configuration, the analysis device 11 acquires the flow velocity distribution (or the data underlying it) below the multicopter 12 from the ADCP unit 70, water surface images around the aircraft from the camera 60, and terrain data from the sonar unit 80. In this configuration, the analysis device 11 also acquires the latitude, longitude, and elevation values ​​of the GPS 31, which have been corrected using the correction information from the RTK receiver 32.

[0036] As will be explained in more detail later, the analysis device 11 calculates the velocity distribution and flow rate in the longitudinal and transverse sections of the watershed traveled by the multicopter 12, based on various measured values ​​received from the multicopter 12. This configuration of the surveying system 10 is equipped with a configuration (analysis device 11) specifically for collecting, analyzing, and integrating data acquired by the multicopter 12 and its onboard equipment, thereby appropriately distributing the load and functions of the surveying system 10 throughout the entire system. Furthermore, the analysis device 11 stores the surveying results, and the stored information is widely shared with river operators, researchers, and others. It should be noted that an independent analysis device 11 is not essential for the surveying system 10; the functions of the analysis device 11 may be provided by the multicopter 12.

[0037] (Autopilot function) Figure 3 is a block diagram showing some of the control functions provided by the FC / BC20. The multicopter 12 in this configuration is equipped with an autonomous flight program 21 and an autonomous navigation program 22 as its autopilot functions.

[0038] The autonomous flight program 21 is a function that automatically flies the multicopter 12 according to a pre-prepared flight plan. The flight plan is data that includes parameters such as the takeoff (water takeoff) point, landing (water landing) point, one or more waypoints that make up the flight route, the flight altitude at each waypoint, and the flight speed between each waypoint, as specified on the map data.

[0039] The autonomous navigation program 22 is a function that automatically moves the multicopter 12 on the water surface according to a pre-prepared cruise plan. The cruise plan is data that includes a starting point, an ending point, and one or more waypoints that constitute the navigation route, as specified on map data. The autonomous navigation program 22 automatically operates the thrusters 42 so that the multicopter 12, riding the river current downstream, moves along the navigation route.

[0040] (Stabilization function) Furthermore, in addition to the autopilot function described above, this configuration of FC / BC20 is equipped with a stabilization program 23 that implements the stabilization function described later.

[0041] Figure 4 is a schematic diagram illustrating the stabilization function of the multicopter 12. As described above, the multicopter 12 in this configuration is floated on a river and drifts downstream with the water current. In bodies of water with currents such as rivers, waves and vortices caused by the water current cause the water surface to move up and down irregularly. As shown in Figure 4(a), the multicopter 12 floating on the water surface oscillates in conjunction with the vertical movement of the water surface. Such oscillating is a factor that reduces the scanning accuracy of the ADCP unit 70 and the sonar unit 80.

[0042] In contrast, the FC / BC20 in this configuration is equipped with a stabilization function that suppresses the oscillation of the multicopter 12 on the water surface. More specifically, as shown in Figure 4(b), after the multicopter 12 lands on the water, the FC / BC20 uses a stabilization program 23 to idle the rotor 41 at a rotational speed that does not cause the multicopter 12 to leave the water. A gyroscopic effect occurs in the rotor 41 depending on the angular momentum (inertia) of the idling rotor 41. An external force (torque) that tries to tilt the rotation axis G of the rotor 41 appears as precession of the rotor 41 due to the gyroscopic effect. As a result, the rotor 41 does not immediately tilt in response to the external force, and consequently behaves in a way that tries to resist the external force and maintain the direction of the rotation axis G. In this configuration, the attitude of the multicopter 12 on the water surface is stabilized by the action of the six rotors 41 (rotating bodies) trying to maintain their rotation axis G. Hereafter, this operation will also be called the "stabilization operation".

[0043] Thus, in this configuration of the surveying system 10, the rotor 41 of the multicopter 12 is used not only for flight but also as a gyro stabilizer (flywheel) on the water surface, thereby stabilizing the attitude of the multicopter 12 on the water surface without introducing any dedicated equipment. This improves the scanning accuracy of the ADCP unit 70 and the sonar unit 80, as well as the blur of images captured by the camera 60. In particular, since the multicopter 12 in this configuration moves on the water surface using the thrusters 42, the rotor 41 becomes idle after landing on the water. Therefore, after landing on the water, the rotor 41 can be used exclusively for maintaining the attitude of the aircraft.

[0044] Furthermore, the stabilization program 23 in this embodiment rotates the six rotors 41 in groups of three, in opposite directions at approximately the same speed. This causes each rotor 41 to cancel out the torque of the others, and the heading of the multicopter 12 is maintained. The floating boat-shaped float 50 in this embodiment also contributes to maintaining the heading of the multicopter 12. The configuration of the float 50 is not limited to a twin-hull (catamaran) type as in this embodiment; for example, it may be a single-hull (monohull) or a triple-hull (trimaran) type.

[0045] To reiterate, the multicopter 12 in this configuration is floated on a river and drifts downstream with the water current. Therefore, it is undesirable for the stabilization operation described above to affect the downstream speed of the multicopter 12. Accordingly, the multicopter 12 in this configuration can, if necessary, have a water pressure sensor 51 (draft detection means) attached to its float 50 to detect the draft of the float 50 (see Figure 4(b)). By attaching the water pressure sensor 51 to the float 50, the FC / BC20 monitors its output value using the draft monitoring program 24 (see Figure 3), and adjusts the idling speed of the rotor 41 so that the detected value of the water pressure sensor 51 is above (or below) a predetermined reference value. In other words, by adjusting the idling speed so that the rotational speed does not become so high that the draft of the float 50 is significantly reduced, the stabilization operation is prevented from affecting the downstream speed of the multicopter 12.

[0046] Here, the idling of the rotor 41 performed by the multicopter 12 includes not only the idling during stabilization operations, but also the idling during arming of the multicopter 12. Arming is a type of pre-flight inspection operation for the multicopter 12, which involves test-running the rotor 41 at the minimum rotational speed.

[0047] In stabilization operation, it is necessary to obtain a gyroscopic effect from the rotor 41, so it is conceivable to rotate the rotor 41 at a higher speed than during arming. In other words, in the FC / BC20 parameter set, the parameter for setting the idling speed in stabilization operation may be different from the parameter for setting the idling speed during arming. Furthermore, in stabilization operation, it is desirable that the idling speed of the rotor 41 can be manually changed by the operator or automatically adjusted in response to the oscillation of the multicopter 12. By adjusting the idling speed according to the degree of vertical movement of the water surface, excessive idling and power consumption of the rotor 41 can be suppressed. In this case, idling during arming and idling during stabilization operation are separate functions.

[0048] On the other hand, if sufficient attitude maintenance can be achieved even at the idling speed during arming, the rotor 41 can be kept armed after landing, or the rotor 41 can be armed again after landing. In this case, the idling during arming and the idling during stabilization are the same function, differing only in their purpose. In other words, these arming actions are examples of stabilization functions and operations.

[0049] <Method for calculating flow velocity distribution and flow rate> Figure 5 is a schematic diagram illustrating the method for calculating the velocity distribution and flow rate of a river's longitudinal and transverse sections using the surveying system 10.

[0050] As described above, the surveying system 10 includes a first measuring means for measuring the flow velocity distribution below the multicopter 12, a second measuring means for measuring the water surface flow velocity around the aircraft, and a third measuring means for measuring the aircraft's movement speed. The surveying system 10 in this embodiment combines these with river topographic data to calculate the flow velocity distribution and flow rate of the longitudinal and transverse sections of the river.

[0051] (First measuring means) In the surveying system 10, as shown in Figure 5(a), the layered flow velocity distribution according to depth below the multicopter 12 (Figure A) is measured by the ADCP unit 70 (and analysis device 11).

[0052] (Second measurement means) The camera 60 of the multicopter 12 captures images of the side and above the aircraft in a hemispherical shape (Figure C), and its field of view includes the river surface SF. The multicopter 12 transmits all of the images captured by the camera 60, or only the water surface portion, to the analysis device 11. The analysis device 11 calculates the water surface velocity around the aircraft based on the received images.

[0053] Furthermore, a method applying STIV is used for image analysis of water surface velocity in this embodiment. Figure 6 is a schematic diagram showing a specific example. Figure 6(a) is a schematic diagram showing a portion of the image transmitted to the analysis device 11, and Figure 6(b) is a diagram illustrating the overview of velocity calculation using STIV. The method for analyzing water surface velocity in this embodiment will be explained below with reference to Figure 6.

[0054] First, the hemispherical image captured by camera 60 can be partially extracted as a planar image using known means. The schematic diagram in Figure 6(a) is an example of such extracted image. In flow velocity calculations using STIV, in general, control points P with known real-space position coordinates are placed on the bank on the near side (camera side) of the water area and on the opposite bank in order to correct the water surface image, which was captured from an oblique angle, to an image viewed from directly above. In this embodiment, control points P are placed on both banks of the river (see Figure 5(a)).

[0055] Furthermore, the multicopter 12 in this configuration has a orientation unit 71 fixed to the aircraft body, which displays a mark suitable for the orientation point, and this orientation unit 71 is visible in the captured image as a subject. By providing an orientation unit 71 fixed to the multicopter 12, that is, an orientation unit 71 whose relative position coordinates with respect to the camera 60 are known, and including it in the captured image, the orientation unit 71 can be used as the orientation point on the camera side. Note that the orientation unit 71 is not limited to the one in this configuration; any part that is fixed in relative position to the multicopter 12 body and is visible in the captured image can be used as a substitute, for example, the end of the float 50 of the multicopter 12.

[0056] The dashed-dotted box in Figure 6(a) is an example of an inspection line in STIV, and the black circles within the box represent luminance value features such as ripples. As shown in Figure 6(b), STIV arranges the positional changes of the luminance value features in a time series, and calculates the surface flow velocity from the gradient θ when the transition of that position is represented as a straight line.

[0057] In this embodiment, camera 60 is used as the means of photographing the water surface, but this could be one or more video cameras that photograph the shore-side control point P from the multicopter 12, or it could be a single camera pointed in a specific direction. Furthermore, camera shake can be further reduced by supporting this camera with a known camera gimbal (camera attitude stabilization device).

[0058] Figure 7 is a schematic diagram showing another example of the imaging means. In this embodiment, a camera 60 for photographing the water surface is mounted on the multicopter 12 itself, but the form of the imaging means is not limited to this. For example, as shown in Figure 7, a fixed camera 91 may be set up in advance along the body of water to be surveyed, and the water surface velocity around the multicopter 12 may be measured from the image of this fixed camera 91. There is already a lot of experience and knowledge regarding STIV using a fixed camera 91, and the accuracy of measuring the water surface velocity can be further improved. Alternatively, the water surface may be photographed separately from above by a so-called drone 92 equipped with a camera. By photographing the body of water to be surveyed from directly above, the degradation and errors of the image in planarization of the captured image are reduced, and the accuracy of measuring the water surface velocity can be further improved. Furthermore, the second measurement means of the present invention only needs to be capable of measuring the water surface velocity around the multicopter 12, and is not limited to those using image analysis. For example, a method of measuring the surface velocity using radio waves can also be considered.

[0059] (Third measuring means) As mentioned above, there are two methods for measuring the speed of the multicopter 12 on the water surface: one using the latitude and longitude information from the GPS 31, and the other using the ADCP unit 70. Either method may be used.

[0060] (Method for acquiring terrain data) Returning to Figure 5, let's explain how to acquire terrain data. The multicopter 12 in this configuration is equipped with a sonar unit 80, which can acquire river terrain data. As shown in Figure 5(b), the sonar unit 80 transmits a fan-shaped sound wave beam over a set swath width S and acquires point cloud data representing the topography of the river channel TP. By setting the swath width S of the sonar unit 80 to 180° or more, it is also possible to acquire the cross-sectional shape over the entire width of the river.

[0061] (Calculation method) The analysis device 11 acquires various measured data (hereinafter also referred to as "measured data set") from the multicopter 12 and performs analysis and calculation in real time. More specifically, the analysis device 11 first measures the flow velocity distribution in each layer below the multicopter 12 and measures the surface flow velocity around the aircraft. Then, it takes into account the movement speed of the multicopter 12, that is, it adds or subtracts the movement speed of the multicopter 12 from the measured flow velocity to calculate the actual flow velocity.

[0062] Then, based on the above flow velocity and river channel topographic data, the flow velocity distribution in the depth direction of the water body around the multicopter 12 is determined. More specifically, the flow velocity distribution of the river cross-section at the acquisition location of the measured dataset is calculated. Even more specifically, when the calibration coefficient for determining the average flow velocity of each water body in the river width direction of the cross-section is called the surface flow velocity coefficient, the analysis means 11 adjusts this surface flow velocity coefficient based on the measured dataset. Then, by continuously determining the average flow velocity of the cross-section along the direction of movement of the multicopter 12 while adjusting this surface flow velocity coefficient, the longitudinal flow velocity distribution of the river is identified.

[0063] Generally, a value of 0.85 is used as the surface velocity coefficient for rivers. However, depending on the flow conditions and river geometry, the calculation results using this surface velocity coefficient may deviate from reality. In this survey system 10, by adjusting this surface velocity coefficient based on a dataset measured by the multicopter 12, it is possible to obtain calculation results that more closely reflect reality. In other words, in this survey system 10, a surface velocity coefficient that is not a fixed value (0.85), but a variable value, is applied to the water surface velocity of the water area around the multicopter 12 to determine the average flow velocity. Once the average flow velocity in the cross-section of the river is determined, the flow rate can be calculated using the following formula. Flow rate Q(m 3 / s) = flow velocity V (m / s) × cross-sectional area A (m 2 ) In this context, "flow rate" refers to the volume of water that flows through a certain cross-section of a river in a given unit of time. River flow rate is calculated by multiplying the flow velocity by the cross-sectional area of ​​the cross-section. The unit of measurement is cubic meters per second (m³). 3 / s)

[0064] As mentioned above, the analysis device 11 in this configuration stores survey results, which are widely shared with river operators, researchers, and others. As the survey system 12 is repeatedly used in various flow conditions and river shapes, and the survey results are accumulated, the factors affecting the river's velocity distribution will gradually become clearer from discrepancies between measured values ​​and calculated results. Furthermore, the degree of influence of these factors will also gradually be quantified. In other words, as the survey system 12 continues to be used, the accuracy of calculating the velocity distribution and flow rate over long distances of the river will improve. Possible adjustment parameters for the surface velocity coefficient that are currently expected include, for example, the velocity distribution and water depth below the device, the water surface velocity and wind direction / speed around the device, the continuous topographic changes and bottom roughness of the river's longitudinal and transverse sections, and the device's movement speed. Furthermore, a possible adjustment algorithm for the surface velocity coefficient currently anticipated involves predicting the difference between the surface velocity and the average underwater velocity based on the velocity distribution and topography below the aircraft, using the values ​​of the above-mentioned parameters. If the difference is small, the coefficient should be increased; if the difference is large, the coefficient should be decreased. In other words, the specific parameters, variables, and algorithms for adjusting the surface velocity coefficient are not yet optimal and will be improved through repeated use.

[0065] In this configuration, terrain data is acquired by the multicopter 12. However, even if terrain data could not be acquired, that is, even if only the first to third measurement means were used, it would still be possible to determine a more accurate velocity distribution and flow rate than simply applying the conventional surface velocity coefficient (0.85).

[0066] <How to fly a multirotor> Figure 8 is a schematic diagram showing a multicopter 12 traveling down a river by riding the river current. The method of operating the multicopter 12 in this surveying system 10 will be explained below with reference to Figure 8. When surveying a river with the surveying system 10, first, the multicopter 12 is launched onto the river surface as shown in Figure 8 (water landing process). The starting point of the cruise plan can be reached by either flying or navigating. Once the multicopter 12 is launched onto the water surface, the FC / BC20 switches the multicopter 12 from flight mode to navigation mode. As mentioned above, the FC / BC20 continues to operate the GPS31 and RTK receiver32 even after switching the multicopter 12 to navigation mode.

[0067] The multicopter 12, once switched to navigation mode, travels downstream along the river current, taking pictures of the water surface with the camera 60 and scanning the underwater environment with the ADCP unit 70 and sonar unit 80 (downstream process). Additionally, the FC / BC20 starts stabilizing the multicopter 12 when it switches to navigation mode (stabilization process). The stabilization process may start before or after the downstream process begins.

[0068] If the stabilization operation is the same as the arming operation, the multicopter 12 is kept armed after landing on the water, or the multicopter 12 is armed again during the stabilization process. These arming operations are also examples of the stabilization process. In this configuration, the stabilization operation of the multicopter 12 improves the scanning accuracy of the ADCP unit 70 and the sonar unit 80, and also suppresses blurring of images captured by the camera 60. The autonomous navigation program 22 automatically operates the thrusters 42 so that the multicopter 12 descends the river along the navigation route of the cruise plan.

[0069] Here, the flow velocity of a river can vary depending on its position along its width. For example, even where a river flows in a straight line, in deeper areas, the flow velocity in the center of the river becomes faster than the flow velocity on either bank due to the influence of two spiral flows aligned along the river's width. Also, when the water level of a river rises, the water level in the center of the river rises, creating a flow on the water surface from the center towards the banks. Conversely, when the water level of a river falls, the water level in the center of the river falls, creating a flow on the water surface from the banks towards the center. Furthermore, in areas where the river curves, the flow velocity on the outside of the curve is faster than the flow velocity on the inside. And, a floating object in water will naturally be guided towards the faster flow if it is facing the direction with the fastest flow velocity. Therefore, if the multicopter 12 only needs to follow the fastest flow course in the river, the latitude and longitude values ​​specified for the autopilot function should be accurate enough to bypass obstacles such as bridges.

[0070] <Example 1> Figure 9 is a schematic diagram showing a modified version of the surveying system 10. The surveying target of the surveying system 10 is not limited to flowing water areas such as rivers. For example, the stabilization program 23 of the multicopter 12 is also effective in stagnant water areas such as natural dam lakes. In the example in Figure 9, after the multicopter 12 is launched onto the dam lake (landing phase), it is maintained at a single point on the water surface (stationary phase), and the stabilization operation is started (stabilization phase). The stabilization phase may be started before entering the stationary phase or after entering the stationary phase. In this state, for example, the multicopter 12 can be rotated to scan underwater or to capture images of the surroundings.

[0071] <Modification 2> In the above embodiment, an example was described in which the rotor 41 is also used as a gyro stabilizer. However, a separate gyro stabilizer can also be provided to suppress the oscillation of the multicopter 12 on the water surface. Such gyro stabilizers could be miniaturized versions of known gyro stabilizers for manned boats, or those using a horizontally rotating flywheel. However, if known firmware is used for attitude control of the multicopter 12 during flight, activating such a gyro stabilizer during flight may actually destabilize the aircraft's control. Therefore, in that case, it is desirable not to use the gyro stabilizer during flight, but only after landing on the water.

[0072] 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. [Explanation of Symbols]

[0073] 10: Surveying system, 11: Analysis device, 12: Multicopter (unmanned aerial vehicle, mobile device), 19: Operator terminal, 20: Flight controller / boat controller, 21: Autonomous flight program, 22: Autonomous navigation program, 23: Stabilization program, 24: Draft monitoring program, 31: GPS receiver, 32: RTK receiver, 41: Rotor, 42: Thruster, 50: Float, 60: Omnidirectional camera (imaging device), 70: ADCP unit, 71: Grounding unit, 80: Sonar unit, 91: Fixed camera, 92: Drone, TP: River channel, SF: Water surface, P: Grounding point

Claims

1. The water landing process involves landing an unmanned aerial vehicle equipped with horizontal rotor blades on the water surface, The process includes a stabilization step in which, after landing on the water, the horizontal rotor blades are kept rotating at a rotational speed that prevents the unmanned aerial vehicle from taking off again. The aforementioned unmanned aerial vehicle is equipped with a float having buoyancy capable of supporting its body on the water surface. How to operate an unmanned aerial vehicle.

2. The aforementioned unmanned aerial vehicle is equipped with a plurality of horizontal rotor blades, In the stabilization process, the same number of horizontal rotor blades are rotated in opposite directions at approximately the same speed. A method for operating an unmanned aerial vehicle according to claim 1.

3. The process further includes a downstream process of letting the unmanned aerial vehicle drift with the river's current from upstream to downstream, or a stationary process of maintaining the unmanned aerial vehicle at a single point on the water's surface. The stabilization step is performed at least during the flow-down step or the stationary step. A method for operating an unmanned aerial vehicle according to claim 1.

4. The rotational speed of the horizontal rotor blade in the stabilization process is set by a parameter different from the parameter used to set the rotational speed of the unmanned aerial vehicle during arming. A method for operating an unmanned aerial vehicle according to claim 1.

5. In the aforementioned water landing process, the unmanned aerial vehicle remains armed after landing, or is armed again in the aforementioned stabilization process. A method for operating an unmanned aerial vehicle according to claim 1.

6. In the stabilization process, The rotation speed of the horizontal rotor blade can be manually changed, or The rotation speed of the horizontal rotor blades is automatically adjusted in response to the oscillation of the unmanned aerial vehicle. A method for operating an unmanned aerial vehicle according to claim 1.

7. The aforementioned unmanned aerial vehicle is equipped with a means for taking photographs, The stabilization step includes the step of taking a photograph using the photographing means. A method for operating an unmanned aerial vehicle according to claim 1.

8. The aforementioned imaging means is supported by a posture stabilization device. A method for operating an unmanned aerial vehicle according to claim 7.

9. The aforementioned unmanned aerial vehicle is equipped with a water-based propulsion system, which is a dedicated thrust source for moving on the water surface. A method for operating an unmanned aerial vehicle according to claim 1.

10. The aforementioned unmanned aerial vehicle Movement on the water surface is performed by the horizontal rotating blades. It does not have a water-based propulsion system, which is a dedicated thrust source for moving on the water's surface. A method for operating an unmanned aerial vehicle according to claim 1.

11. The float is one or more boat-shaped floats. A method for operating an unmanned aerial vehicle according to claim 1.

12. Multiple horizontal rotor blades, This device is equipped with a float that has enough buoyancy to support it on the water surface, The system comprises a control unit that controls the rotational speed of each of the horizontal rotor blades, The control unit has a stabilization function that keeps each of the horizontal rotor blades rotating at a rotational speed that prevents the aircraft from lifting off the water once it has landed. unmanned aircraft.

13. The system further comprises a draft detection means for detecting the water draft of the float, The stabilization function adjusts the rotation speed of each horizontal rotor blade according to the output value of the draft detection means. The unmanned aerial vehicle according to claim 12.

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