JP7141538B2 - A method for forest measurement, a forest measurement system, a method for determining a flight path of an unmanned aerial vehicle, a photographing method, a spraying method, and a computer program - Google Patents

Description

The present invention relates to a technology for measuring forests using an unmanned aerial vehicle, a technology for determining the flight path of the unmanned aerial vehicle, and the like.

Various methods are known for forest measurement. For example, Patent Literature 1 discloses a method of photographing a forest from above with a camera and extracting a crown circle from the obtained image by image processing. In Patent Document 2, radar waves with different wavelengths are transmitted from the sky to a forest, and the height of the tree is calculated from the height difference calculated from the reflected wave from the top of the tree and the reflected wave from the ground. Disclose how to ask. Patent Literature 3 discloses a method of mounting a laser ranging device on an aircraft and using the laser ranging device to obtain three-dimensional data on the ground including trees and the like.

JP-A-2007-66050 JP-A-9-184880 JP 2016-70708 A

When forest measurement is performed from the sky using a laser range finder, point cloud data, which is the data of the upper surface of the forest (top of tree canopy), can be obtained. However, since the laser light is blocked by the leaves of trees, etc., it is difficult to acquire trunk data. Therefore, it was necessary to estimate the number of main trunks, which are the thickest trunks, from the measurement results.

In Patent Document 3, a human brings a device such as a laser rangefinder into a forest, further acquires three-dimensional point cloud data, and obtains point cloud data obtained by measurement from the sky and measurement on the ground. It refers to fusing with the point cloud data obtained. However, obtaining two types of point cloud data is very time-consuming.

There is a need to measure the crowns and trunks of trees in forests using unmanned aerial vehicles.

A method according to an embodiment of the present invention is a method of measuring a forest on a slope by flying an unmanned aerial vehicle equipped with a lidar (LiDAR) sensor, the rotation axis or rocking motion of the lidar sensor (i) scanning the forest with the lidar sensor while flying the unmanned aerial vehicle at a predetermined absolute altitude along a first contour; and (ii) causing the lidar sensor to rescan the forest while flying the unmanned aerial vehicle at the predetermined absolute altitude along a second contour different from the first contour.

In some embodiments, the method may further comprise pre-specifying the first contour, the second contour and the predetermined absolute altitude prior to steps (i) and (ii).

In one embodiment, the method further comprises, at an edge of the forest, scanning the edge with the lidar sensor while flying the unmanned aerial vehicle over a position a predetermined distance away from the edge. may be included.

In one embodiment, the lidar sensor may scan the canopy and trunk of each tree in the forest.

In some embodiments, steps (i) and (ii) may include causing the lidar sensor to scan the forest using horizontally emitted laser pulses.

In some embodiments, steps (i) and (ii) may include causing the lidar sensor to scan the forest using obliquely emitted laser pulses.

In one embodiment, the unmanned aerial vehicle may be an unmanned helicopter or an unmanned multicopter.

A method according to an embodiment of the present invention is a method for determining a flight path of an unmanned aerial vehicle equipped with an observer, comprising: identifying an observation target area by the observer; if the observation target area includes a slope; determining a plurality of route segments along any of the contours along which the unmanned aerial vehicle flies at a predetermined absolute altitude, with reference to contour line data within the observation target area; and determining a flight route including the plurality of route segments. To decide, to carry out.

In some embodiments, determining the plurality of path segments may include setting a plurality of waypoints on a selected one or more contour lines and specifying the absolute altitude. .

In one embodiment, the observation target area may include a forest on the slope.

In one embodiment, the observer may be a lidar (LiDAR) sensor.

In one embodiment, determining the flight path may include determining the flight path over an edge of the forest at a predetermined distance from the edge.

In one embodiment, the observer may be an infrared camera.

A method according to an embodiment of the present invention is a method of measuring a forest on a slope by flying an unmanned aerial vehicle equipped with a lidar (LiDAR) sensor, the rotation axis or rocking motion of the lidar sensor The axis is mounted on the unmanned aerial vehicle so as to point in the direction of travel of the vehicle, and (i) causes the lidar sensor to scan the forest while flying the unmanned aerial vehicle at a predetermined absolute altitude and a predetermined first true altitude. and (ii) rescanning the forest with the lidar sensor while flying the unmanned aerial vehicle at the predetermined absolute altitude and at a predetermined second true altitude different from the first predetermined true altitude. Do what you want.

A forest measurement system according to an embodiment of the present invention includes an unmanned aerial vehicle and a computer device, and is a forest measurement system for performing forest measurement on a forest on a slope by flying the unmanned aerial vehicle, The unmanned aerial vehicle has a lidar (LiDAR) sensor, a first signal processing circuit, a first storage device, and a first communication circuit. The computer device has a display device, an input device, a second signal processing circuit, a second storage device storing information about contour lines, and a second communication circuit. and the second signal processing circuit acquires information about the contour lines from the second storage device, receives designation of the first contour line, the second contour line and the absolute altitude via the input device, The data of the first contour line, the second contour line and the absolute altitude are transmitted to the unmanned aerial vehicle via the second communication circuit, and the first signal processing circuit transmits the data of the first contour line via the first communication circuit. receiving the data of the contour line, the second contour line and the absolute altitude; storing the received data of the first contour line, the second contour line and the absolute altitude in the first storage device; Scanning the forest with the lidar sensor while flying along the contour line at the absolute altitude, and scanning the forest again with the lidar sensor while flying the unmanned aerial vehicle at the absolute altitude along the second contour line. Let

A photographing method according to an embodiment of the present invention is a method of photographing an observation target using an unmanned aerial vehicle equipped with an imaging device, comprising: specifying an observation target area; Determining a plurality of route segments along which the unmanned aerial vehicle flies at a predetermined absolute altitude along any of the contour lines by referring to contour line data within the observation target area, and determining a flight route including the plurality of route segments. and capturing images with the imaging device while flying the unmanned aerial vehicle along the determined flight path.

A spraying method according to an embodiment of the present invention is a method of spraying a chemical using an unmanned aerial vehicle equipped with a chemical spraying device, the method comprising: specifying an area to be sprayed by the spraying device; , determining a plurality of route segments along which the unmanned aerial vehicle flies at a predetermined absolute altitude along any of the contours by referring to contour data within the target area; Determining a flight route, and spraying a chemical agent while flying the unmanned aerial vehicle along the determined flight route.

A computer program according to an embodiment of the present invention is a computer program that causes a computer to execute control of forest measurement targeting a forest on a slope performed by flying an unmanned aerial vehicle equipped with a lidar (LiDAR) sensor, The lidar sensor is mounted on the unmanned aerial vehicle so that the axis of rotation or oscillation of the lidar sensor is oriented in the direction of travel of the aircraft, and the computer program is configured to: (i) fly the unmanned aerial vehicle along a first contour line at a predetermined absolute altitude; and (ii) flying the unmanned aerial vehicle at the predetermined absolute altitude along a second contour line different from the first contour line, while causing the lidar sensor to scan the forest. Let the computer perform control of scanning the forest again.

A method according to an embodiment of the present invention is a method of performing forest measurement targeting a forest by flying an unmanned aerial vehicle equipped with a lidar (LiDAR) sensor, wherein the rotation axis or swing axis of the lidar sensor is , mounted on the unmanned aerial vehicle so as to face the aircraft traveling direction, and using the lidar sensor, emit laser pulses while changing the emission direction at a predetermined angular pitch to measure the surrounding space; L is the distance of the unmanned aerial vehicle, V is the flight speed of the unmanned aerial vehicle, N is the number of laser pulses emitted simultaneously in the same angular direction, f is the frequency of the laser pulses emitted in the same angular direction, and the predetermined angular pitch is When α is used, forest measurement is performed on the forest using the lidar sensor while flying the unmanned aerial vehicle so that the relative value of α·L with respect to V/(f·N) falls within a predetermined range. do what you do.

In one embodiment, the predetermined angular pitch α may be a fixed value.

In one embodiment, the predetermined angular pitch α may be fixed at a settable minimum value.

In one embodiment, the lidar sensor is of a mechanical rotation type, and when M is the number of times laser pulses are emitted per unit time from one exit for emitting laser pulses, and R is the number of rotations per unit time, The predetermined angular pitch α is obtained by α(rad)=2·π·R/M, and performing the forest measurement is (2·π·R/M)·L for V/(f·N). It may include flying the unmanned aerial vehicle such that the relative value falls within the predetermined range.

In one embodiment, the number of times of ejection M per unit time and the number of rotations R per unit time may be variable values.

In one embodiment, the number of times of ejection M per unit time and the number of rotations R per unit time may be fixed values.

In one embodiment, the lidar sensor is of a mechanical rotation type, the predetermined angular pitch α is smaller than _a divergence angle θ1 of the laser pulses in a direction perpendicular to the axis of rotation, and the method comprises: The flight speed of the unmanned aerial vehicle so that the flight distance J that the unmanned aerial vehicle flies during one revolution is shorter than the length K of the laser spot formed in the forest in the direction parallel to the traveling direction of the aircraft. V, the number of rotations per unit time R of the lidar sensor and the altitude H of the unmanned aerial vehicle.

In one embodiment, the method changes the divergence angle θ It may comprise adjusting the predetermined angular pitch α to be less than _one .

In one embodiment, the unmanned aerial vehicle may be an unmanned helicopter or an unmanned multicopter.

In one embodiment, the forest may be a slope forest.

A forest measurement system according to an embodiment of the present invention includes an unmanned aerial vehicle and a computer device, and is a forest measurement system for performing forest measurement on a forest by flying the unmanned aerial vehicle, wherein the unmanned The aircraft has a lidar (LiDAR) sensor, a first signal processing circuit, a storage device, and a first communication circuit, and the rotation axis or swing axis of the lidar (LiDAR) sensor faces the direction of flight of the aircraft. The computer device has a display device, an input device, a second signal processing circuit, and a second communication circuit, and the second signal processing circuit includes the input device receives designation of the number N of laser pulses emitted simultaneously in the same angular direction, the frequency f of the laser pulses emitted in the same angular direction, and the predetermined angular pitch α, and the designated number N, The data of the frequency f and the predetermined angular pitch α are transmitted to the unmanned aircraft via the second communication circuit, and the first signal processing circuit transmits the number N, the receiving data of the frequency f and the predetermined angular pitch α; storing the received data of the number N, the frequency f and the predetermined angular pitch α in the storage device; The unmanned aerial vehicle is flown so that the relative value of αL with respect to V/(fN) falls within a predetermined range, and the forest is cleared using the lidar sensor. Perform target forest measurements.

A computer program according to an embodiment of the present invention is a computer program that causes a computer to execute control of forest measurement targeting a forest performed by flying an unmanned aerial vehicle equipped with a lidar (LiDAR) sensor, the lidar sensor is mounted on the unmanned aerial vehicle so that its rotation axis or swing axis faces the aircraft traveling direction, and the computer program uses the lidar sensor to emit laser pulses while changing the emission direction at a predetermined angular pitch L is the distance to the forest, V is the flight speed of the unmanned aerial vehicle, N is the number of laser pulses emitted simultaneously in the same angular direction, and N is the number of laser pulses emitted in the same angular direction. Let f be the frequency of the laser pulse and α be the predetermined angular pitch. The computer is caused to control the forest measurement of the forest using a lidar sensor.

Embodiments of the present invention suppress bias in the spatial density of acquired point cloud data when flying an unmanned aerial vehicle equipped with a lidar (LiDAR) sensor to perform forest measurement, and the point cloud data It is possible to accurately determine or estimate the position and shape of tree crowns and trunks from

1 is a diagram showing an unmanned helicopter 1 that performs forest measurement; FIG. 1 is an external side view of an unmanned helicopter 1 equipped with a LiDAR sensor 20. FIG. 1 is a front view of an unmanned helicopter 1; FIG. 3 is a diagram showing a hardware configuration example of a flight control box 15; FIG. 4 is a diagram showing the unmanned helicopter 1 that performs forest measurement targeting a forest 54 on a slope 52 using the LiDAR sensor 20. FIG. FIG. 10 is a diagram showing a modification regarding the mounting position of the LiDAR sensor 20; 6 is a perspective view of a portion of flight path 60 in an exemplary embodiment; FIG. 4 is a top view showing part of a flight path 60; FIG. 5 is a cross-sectional view of slope 52 showing unmanned helicopter 1 flying along first contour line 60a and unmanned helicopter 1 flying along second contour line 60b. FIG. FIG. 10 is a diagram showing the distribution of laser pulses incident on the slope 52 when the absolute height AGL is constant; FIG. 5 is a diagram showing the distribution of laser pulses incident on the slope 52 when the true height MSL is kept constant; FIG. 4 shows the results of forest measurements made by the method according to an exemplary embodiment; 1 is a diagram showing an example of a forest measurement system 100 including an unmanned helicopter 1 and a tablet computer 70; FIG. 1 is a diagram showing an example of a forest measurement system 100 including an unmanned helicopter 1 and a base station control device 80; FIG. 3 is a diagram showing an example hardware configuration of a tablet computer 70. FIG. 7 is a diagram showing an example of contour line data 90 within an observation target area read into a memory 72. FIG. 4 is a flow chart showing a flight path setting process procedure according to an exemplary embodiment; 4 is a flow chart showing the procedure of the flight operation of the unmanned helicopter 1 with the flight path set. FIG. 16 is a diagram showing details of the process of step S14 in FIG. 15; FIG. 5 shows a slope 52 of a mountain 50 scanned by an unmanned helicopter 1 in flight; FIG. 18 is a diagram for explaining the relationship between two sides forming a region S in FIG. 17; 4 is a flow chart showing the procedure of processing for uniforming the density of measurement points by changing parameters; FIG. 20 is a flowchart showing a specific example of the processing shown in FIG. 19; FIG. FIG. 2 is a diagram schematically showing a plurality of laser pulses 22 emitted from a LiDAR sensor 20 when the unmanned helicopter 1 in flight is viewed from the front. FIG. 2 is a diagram schematically showing a plurality of laser pulses 22 emitted from a LiDAR sensor 20 when the unmanned helicopter 1 in flight is viewed from the side; 4 is a diagram showing a laser spot formed on a measurement target 51 by a laser pulse 22; FIG. 4 is a flow chart showing a forest measurement procedure performed while evenly irradiating a forest 54, which is an example of a measurement object 51, with a laser pulse 22. FIG.

In order to manage and use forest resources, it is important to perform so-called "forest measurement". This "forest measurement" can include investigation of the structure of the forest, estimation of the timber volume of the forest, grasping the amount of change in the forest over a certain period of time, and the like. It takes a lot of manpower and time to measure each forest tree and perform various tabulations and analyses, such as the conventional forest measurement. Accordingly, efforts are being made to mount a laser ranging device (LiDAR sensor) on an unmanned aerial vehicle and use the LiDAR sensor to measure forests from the air.

When using an unmanned aerial vehicle to measure deep forests in mountainous areas, especially forests on slopes, it is necessary to ensure that the unmanned aerial vehicle does not come into contact with the slopes of the mountains or trees growing on the slopes during flight. .

As a flight method of an aircraft, it is conceivable to follow the terrain (that is, to maintain a constant absolute altitude) or to fly while maintaining a sufficient altitude above sea level.

In the former case, there is an advantage that the density of measurement points by the LiDAR sensor can be uniformed when the object to be measured is directly below, but the distance from the slope may fluctuate greatly. A new problem arises in that the measurement point density of the pulse of the laser beam incident on the slope is not uniform but uneven. There is room for improvement as a forest measurement for forests on slopes.

In the latter case, the flight altitude (altitude above sea level) is generally determined based on the elevation point of the highest mountain within the target area of observation (measurement, survey, search). Since it flies at a relatively high position, the density of measurement points by the LiDAR sensor decreases even directly below. The measurement point density for pulses incident on the oblique plane is less. There is much room for improvement as a measurement method.

Prior to describing embodiments of the present disclosure, definitions of terms used herein will be provided.

<Term>
In this specification, “forest measurement” includes scanning a forest from above using a LiDAR sensor and acquiring scan data. Scan data can typically be represented by the position coordinates of each point that constitutes a point cloud acquired for each scan. The position coordinates of points acquired for each scan are defined by a local coordinate system that moves with the unmanned aerial vehicle. Such a local coordinate system may be called a mobile coordinate system or a sensor coordinate system. In general, "forest metrology" involves transforming the position of each reflection point expressed in a local coordinate system to a geographic coordinate system. "Forest measurement" further analyzes the structure of the forest, visually displays the shape of the forest and/or trees, and determines the abundance ratio of each type of tree in the forest after conversion to the geographic coordinate system. , determining the volumetric density of the forest, etc.

An "unmanned aerial vehicle" (UAV) is an aircraft without a human pilot, sometimes called a drone. Aircraft may include rotary wing and fixed wing aircraft. An example of an unmanned aerial vehicle with rotary wings is an unmanned helicopter or multicopter. The rotor blades may be rotated by an engine (internal combustion engine) or may be rotated by an electric motor. The flight of an unmanned aerial vehicle can be autonomous flight by a computer program, semi-autonomous flight that is partially automated, or flight remotely controlled by a person using radio. An unmanned aerial vehicle can fly while measuring and correcting its current position three-dimensionally using GNSS (Global Navigation Satellite System). In the exemplary embodiment described below, the "unmanned aerial vehicle" is an "unmanned helicopter."

The term "unmanned" means that a person does not need to be on board to operate the aircraft, and does not exclude that the unmanned aerial vehicle carries a person other than the pilot.

A "contour" is a curve connecting points of equal height above standard sea level on a map to accurately represent the relief of land. In Japan, the height is measured with the average sea level of Tokyo Bay as the standard sea level (0 m). The height above normal sea level is called "elevation". On Japanese maps, depending on the scale, a major curve is drawn every 10 m of elevation difference, and a major curve is drawn every 50 m. However, in the present specification, the "contour line" may be any curve connecting points of equal height from the standard sea level, including curves not shown on maps. For example, a curve connecting points at an altitude of 563 m can also be a contour line.

Further, as used herein, "contour" includes imaginary curves connecting points of equal height from standard sea level on the actual topography. The "equal height from the standard sea level" here does not have to be strict. For example, an imaginary curve connecting height positions falling within a range of ±30 meters of "equal height from standard sea level" can also be a contour line. Furthermore, when measuring the altitude (contour line) of a predetermined position using a LiDAR sensor while an unmanned aerial vehicle is flying, a virtual Curves may be included as contour lines.

The “absolute altitude” refers to the distance from the ground surface or the water surface, and can also be expressed as “AGL” (Above Ground Level). When an aircraft is flying over a mountainous area, the vertical distance from the surface of the mountain to the aircraft is the "absolute altitude". "Absolute altitude" is generally a value measured using a radio altimeter, but in this specification also includes adopting a value measured using a LiDAR sensor described later as an absolute altitude. In this specification, the "absolute altitude" also includes, for example, the distance from the surface represented by a numerical surface model or DSM (Digital Surface Model). In other words, the absolute altitude H meters may be H meters measured from the ground surface or H meters measured from the surface layer of the tree canopy.

"True altitude" refers to the height above Mean Sea Level (MSL). In this specification, for convenience of explanation, "true altitude" and "elevation" are assumed to be equal. That is, the "average sea level" that defines the "true altitude" is assumed to be the average sea level of Tokyo Bay.

An embodiment of a forest measurement method according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an unmanned helicopter 1 for forest measurement. In the exemplary embodiment, forest measurements are made of forests 54 on slopes 52 of mountains 50 . A region selected as a target for forest measurement, including the mountain 50 or the slope 52, may be referred to as an "observation target area". The "observation target area" includes the forest 54 on the slope 52 and/or the ground surface of the mountain 50, and may further include the forest and ground surface on the flat land.

The unmanned helicopter 1 is equipped with a lidar (LiDAR) sensor, which will be described later. FIG. 2 is an external side view of the unmanned helicopter 1 equipped with a LiDAR sensor (lidar sensor) 20. FIG. 3 is a front view of the unmanned helicopter 1. FIG.

The LiDAR sensor 20 emits laser beam pulses (hereinafter abbreviated as “laser pulses”) 22 one after another while changing the emission direction, and from the time difference between the emission time and the time when the reflected pulse of each laser pulse is acquired, each The distance to the position of the reflection point can be measured. A "reflection point" can be the crown and/or trunk of each tree that constitutes the forest 54, or the slope 52 of the mountain 50, the ground surface such as flat land, and the like.

The LiDAR sensor 20 has a plurality of methods according to different methods of emitting laser pulses. The multiple methods are, for example, a mechanical rotation method, a MEMS method, and a phased array method. The mechanical rotation type LiDAR sensor has a tubular shape, and rotates a laser and a detector that detects the reflected light of the laser pulse to scan the measurement object in all directions around the rotation axis at 360 degrees. A MEMS-type LiDAR sensor uses a MEMS mirror to oscillate the emission direction of a laser pulse, and scans a measurement object within a predetermined angular range around the oscillation axis. A phased array type LiDAR sensor controls the phase of light to oscillate the direction of light emission, and scans a measurement object within a predetermined angular range around the oscillation axis.

In this embodiment, the rotation axis or swing axis of the LiDAR sensor is mounted so as to face the traveling direction of the unmanned helicopter 1 . The forest measurement method according to the present embodiment includes (i) scanning the forest 54 on the slope 52 with the LiDAR sensor while flying the unmanned helicopter 1 along the first contour line 60a at a predetermined absolute altitude, and (ii) This includes flying the unmanned helicopter 1 at the same absolute altitude along a second contour 60b different from the first contour 60a while having the LiDAR sensor scan the forest 54 again. The absolute altitude can be appropriately determined according to the height of each tree forming the forest 54 . An example of absolute altitude is 50m. Since the unmanned helicopter 1 maintains a constant absolute altitude, it is possible to secure a sufficient distance between the unmanned helicopter 1 and trees even in mountainous areas with steep height differences.

Since the LiDAR sensor is mounted on the unmanned helicopter 1 so that its rotation axis or swing axis faces the direction in which the unmanned helicopter 1 travels, the rotation axis or swing axis generally coincides with the direction in which the contour lines extend. In particular, on the slope 52, the laser pulse can be applied generally perpendicular to the trunks of the trees that make up the forest 54, that is, from the lateral direction of the trees. This makes it easier for the laser pulse to pass through the leaves, which are essentially horizontal to receive sunlight, so it is possible to measure the trunk as well as the canopy of trees.

In the forest measurement method described above, the significance of flying the unmanned helicopter 1 along contour lines is to keep the distance from the LiDAR sensor of the unmanned helicopter 1 to the slope 52 generally constant. By keeping the distance substantially constant, the number density per unit area of the laser pulses emitted in the direction of the slope 52, that is, the measurement point density, can be kept substantially constant. As a result, the spatial density of the obtained point cloud data becomes substantially constant, and the quality of the forest measurement targeting the forest 54 on the slope 52 can be made uniform.

The flight method described above means flying while simultaneously maintaining the altitude represented by the first contour line 60a or the true altitude and the absolute altitude at the same time for the first contour line 60a. It means to fly while keeping the altitude or true altitude and the absolute altitude constant at the same time.

Therefore, the flight method described above can be rephrased as follows. That is, the method for forest measurement includes (i) scanning the forest on the slope with a LiDAR sensor while flying the unmanned aerial vehicle at a predetermined absolute altitude and a predetermined first true altitude; Rescan the forest with the LiDAR sensor while flying at absolute altitude and at a second predetermined true altitude different from the first predetermined true altitude.

The present inventor has further studied a suitable forest measurement method for equalizing the quality of forest measurement. As a result, it was found that the unmanned helicopter 1 is flown as follows. The method of mounting the LiDAR sensor on the unmanned helicopter 1 is as described above.

Another forest measurement method found by the present inventor is (i) using a LiDAR sensor to measure the surrounding space by emitting pulses while changing the emitting direction at a predetermined angular pitch, (ii) up to a slope , the flight speed of the unmanned helicopter 1 is V, the number of laser pulses emitted simultaneously in the same angular direction is N, the frequency of the laser pulses emitted in the same angular direction is f, and the predetermined angular pitch is α. When the relative value of α L with respect to V / (f N) falls within a predetermined range, the LiDAR sensor is used to measure the forest on the slope while flying the unmanned aerial vehicle, encompasses

Here, "α·L" is the interval between two arrival positions when two laser pulses emitted at an interval of a predetermined angular pitch α reach the ground surface separated by a distance L. In addition, V/f in “V/(f N)” is the same as that after one laser pulse is emitted from the emission port with the LiDAR sensor, and the next one laser pulse is emitted from the same emission port one cycle later. It is the distance that the unmanned helicopter 1 flies during the very short time until the pulse is emitted. This distance means the distance between two arrival positions when these two laser pulses reach the ground surface. When N laser pulses are emitted simultaneously, N laser pulses arrive between two positions separated by a distance V/f. In other words, it can be said that "V/(f·N)" is the average distance between two adjacent arrival positions among the N arrival positions.

In other words, the meaning of "that the relative value of αL with respect to V/(fN) falls within a predetermined range" is , means that the relative value of the interval (B) of the laser pulses incident on the ground surface in the direction perpendicular to the traveling direction is within a predetermined range. An example of a "predetermined range" is when the "relative value" is expressed as the ratio B/A or the ratio A/B, where the ratio ranges from 0.9 to 1.1, with the broader 0.8 to 1.3, or a wider range of about 0.5-2.0. It should be noted that if the range is wide, the accuracy of the analysis decreases with respect to the amount of data at the time of analysis, so it is assumed that the calculation efficiency will deteriorate. However, ranges having bounded values less than 0.5 and/or greater than 2.0 may be employed. A person skilled in the art can set an appropriate ratio range in consideration of analysis accuracy, calculation efficiency, and the like. A "relative value" may also be defined using the difference between the intervals (A) and (B) described above. However, the magnitude of the "difference" can vary significantly depending on the conditions under which the LiDAR sensor 20 is operating and/or flight speed and the like. Therefore, an illustration of "within a predetermined range" regarding the difference is omitted.

A ratio of 1 or a difference of 0 indicates that the above-mentioned intervals (A) and (B) are equal. In this case, the measurement point group is distributed in a square mesh or grid, and a substantially uniform measurement point density can be secured. Whether the relative values are expressed as ratios or differences, specific values for V/(f·N) and α·L can be determined from the required measurement point density.

Note that “L” of “α·L” becomes shorter as it is closer to directly below the unmanned helicopter 1 and becomes larger as it moves away from the unmanned helicopter 1 . Therefore, the distance to the ground surface in the position or direction in which the desired measurement point density is desired is set as "L". An example of the "direction" here is a direction 45 degrees from the vertically downward direction on a plane perpendicular to the flight direction of the unmanned helicopter 1 during flight.

Please refer to FIG. When the unmanned helicopter 1 is stationary on flat ground, take the X, Y and Z axes as shown. It is assumed that the positive direction of the X-axis is the direction from the front to the back of the paper. The +Y direction is the traveling direction of the airframe 4 during flight, the +Z direction is vertically upward, and the -Z direction is vertically downward.

The unmanned helicopter 1 comprises a fuselage 4 having a main body 2 and a tail body 3. A LiDAR sensor 20 is attached in front of the body 4 (+Y direction) and below the body 4 (−Z direction). A main rotor 5 is provided above the main body 2 (in the +Z direction), and a tail rotor 6 is provided behind the tail body 3 . A radiator 7 is provided in the front part of the main body 2 . The main body 2 accommodates an engine, an intake system, a main rotor shaft, and a fuel tank, all of which are not shown.

A control panel 10 is provided on the rear upper side of the main body 2, and an indicator lamp 11 is provided on the rear lower side. The control panel 10 displays pre-flight checkpoints, self-check results, and the like. The display on the control panel 10 can also be confirmed at the ground station. The indicator lamp 11 displays the state of GNSS control, an abnormality warning of the aircraft, and the like. A skid 16, which is a leg supporting the body 4 during landing, is provided on the lower side of the central portion of the main body 2. - 特許庁

A flight control box 15 is mounted on the main body 2 .

FIG. 4 shows a hardware configuration example of the flight control box 15. As shown in FIG. The flight control box 15 houses a GPS module 15a, an acceleration sensor 15b, an atmospheric pressure sensor 15c, a geomagnetic sensor 15d, an ultrasonic sensor 15e, a communication circuit 15f, a signal processing circuit 15g, and storage devices 15j such as a ROM 15h and a RAM 15i. Each component can send and receive data to and from each other, for example, via wires or internal bus 15k. It should be noted that the position where various sensors including the GPS module 15a are provided does not always have to be inside the flight control box 15 . For example, the GPS module 15a may be provided on the upper portion of the tail body 3 in order to facilitate acquisition of signals from GPS satellites.

The flight control box 15 includes a GPS module 15a as an example of a GNSS module. The GPS module 15a acquires flight data such as the current position and flight speed using GPS (Global Positioning System). The number of GPS modules 15a may be one, or plural (for example, two). The acceleration sensor 15b is a three-axis acceleration sensor that detects acceleration in each direction of the X-axis, Y-axis and Z-axis. If the acceleration sensor 15b is a six-axis acceleration sensor, the roll acceleration, pitch angular velocity and yaw acceleration of the unmanned helicopter 1 can be detected. The atmospheric pressure sensor 15c detects atmospheric pressure. The current altitude can be known from the detected atmospheric pressure. Since the relational expression between atmospheric pressure and altitude is well known, the description thereof is omitted in this specification. A geomagnetic sensor 15 d detects the current azimuth of the unmanned helicopter 1 . The current attitude of the unmanned helicopter 1 can be determined by using the data (body data) output from each of the acceleration sensor 15b and the geomagnetic sensor 15d. Flight data and aircraft data are provided to signal processing circuitry 15g.

The communication circuit 15f has a communication circuit that performs wireless communication conforming to the Bluetooth (registered trademark) and/or Wi-Fi (registered trademark) standards. The communication circuit 15f may also perform wireless communication using a mobile phone line or a line via an artificial satellite. The communication circuit 15f receives flight route data before flight, and performs necessary wireless communication with the ground during flight. In this embodiment, the flight path data includes contour lines along which the unmanned helicopter 1 should fly and absolute altitude data.

The storage device 15j stores a computer program that controls the operation of the signal processing circuit 15g. The storage device 15j can store a computer program for causing the signal processing circuit 15g to control flight of the unmanned helicopter 1 and forest measurement control, which will be described later. Such a computer program may be installed in the unmanned helicopter 1 from a recording medium (semiconductor memory, optical disk, etc.) in which it is recorded, or may be downloaded via an electric communication line such as the Internet. Alternatively, such a computer program may be installed on the unmanned helicopter 1 via wireless communication. Such computer programs may be sold as packaged software.

The signal processing circuit 15g executes the control program stored in the storage device 15j to cause the unmanned helicopter 1 to fly. More specifically, the signal processing circuit 15g controls the unmanned helicopter 1 along a flight route prepared in advance while monitoring the above-described flight data, aircraft data, operating state data such as engine speed and throttle opening. let it fly

In this embodiment, the flight control box 15 is connected with the LiDAR sensor 20 . The flight control box 15 may provide the LiDAR sensor 20 with position data indicating the flight position of the unmanned helicopter 1, for example obtained by the GPS module 15a. As a result, even if the LiDAR sensor 20 is not equipped with the GPS module 15a, the position data at the time when the scan was performed and the scan result (a set of time data, direction data, and distance data) can be used to obtain, for example, geographical coordinates It is possible to compute the position represented by the system.

An operator who manages the flight and operation of the unmanned helicopter 1 can also fly the unmanned helicopter 1 along a flight route prepared in advance while visually observing the flight state. A remote control receiving antenna 23 for receiving a command signal from a remote controller is provided at the rear end of the tail body 3 .

Refer to FIG. 2 again. The LiDAR sensor 20 is, for example, an optical device that emits a near-infrared laser pulse 22 and detects the reflected light of the laser pulse 22 to measure the distance to the reflection point.

In an exemplary embodiment, the LiDAR sensor 20 is of the mechanical rotation type, and the laser and the detector that detects the reflected light of the laser pulse can be rotated to scan 360 degrees in all directions. However, in this embodiment, of the scannable range of the LiDAR sensor 20, the range blocked by the airframe 4 of the unmanned helicopter 1, for example, the range of ±60 degrees (120 degrees in total) centered on the +Z direction of the LiDAR sensor 20 is measured. not reflected in the results.

One laser pulse may be emitted for each rotation in a certain angular direction, or a plurality of laser pulses may be emitted at the same time. FIG. 2 shows how N laser pulses 22 are emitted at the same time. However, for convenience of description, the beam is described instead of the pulse. An example of N is twelve. When N is 2 or more, the LiDAR sensor 20 is provided with N laser pulse exit ports.

A laser pulse emitted from one emission port will be described with reference to FIG. The LiDAR sensor 20 radiates laser pulses 22 by rotating while changing its direction by a predetermined angular pitch α (rad), and detects the reflected light of each laser pulse 22 . Thereby, it is possible to obtain the data of the distance to the reflection point in the direction for each of the predetermined angular pitches α. Assuming that the number of pulses emitted per unit time from the LiDAR sensor 20 for one outlet is M, and the number of rotations per unit time is R, the predetermined angular pitch α is α(rad)=2·π·R/M. Desired.

The predetermined angular pitch α may be a fixed value or a variable value. The number of times of ejection M per unit time and the number of rotations R per unit time may also be fixed values or variable values.

Let N be the number of laser pulses emitted simultaneously in the same angular direction (FIG. 2). In an exemplary embodiment, when M·N=600,000 (pieces/second), R=10 (revolutions/second), and N=16, the predetermined angular pitch α is about 0.0017 (rad), about 0.007 (rad). 096 degrees. However, for simplicity of calculation, the scanning range is assumed to be 360 degrees.

FIG. 5 shows an unmanned helicopter 1 that uses the LiDAR sensor 20 to perform forest measurements on a forest 54 on a slope 52 . Each straight line radially extending from the unmanned helicopter 1 schematically represents each laser pulse 22 as in FIG. Each laser pulse 22 travels back and forth between the LiDAR sensor 20 and the reflection point along each straight line. In addition, below, the forest 54 of the slope 52 is described as "slope forest 54."

The unmanned helicopter 1 is programmed to fly along a flight path determined by the method described below. By flying along the flight path, the laser pulse emitted from the LiDAR sensor 20 reaches not only the canopy of the slope forest 54 but also the trunk and is reflected. For example, focusing on a tree 56 forming a slope forest 54 , the laser pulse 22 hits both the crown 56 a and the trunk 56 b of the tree 56 . Not only the laser pulse emitted below the horizontal direction but also the laser pulse emitted horizontally and the laser pulse 22 emitted above the horizontal direction are incident on the trunk 56b. . This makes it possible to measure the canopies and trunks of trees in forests, in particular slope forests 54 . The term “horizontal direction” used herein refers to a direction in which a plane (horizontal plane) perpendicular to the vertical direction extends when the unmanned helicopter 1 flies in the attitude shown in FIG. 2 . Note that the position of the horizontal plane in the vertical direction is the position of the exit of the LiDAR sensor 20 . In addition, "above the horizontal direction" is also referred to as "diagonally upward direction" except for the vertically upward direction (right upward direction). Furthermore, "below the horizontal direction" is also referred to as "diagonally downward direction" except vertically downward direction (right downward direction). The "diagonally upward direction" and the "diagonally downward direction" are also collectively referred to as the "diagonal direction".

The LiDAR sensor 20 is mounted on the unmanned helicopter 1 so that its rotation axis (or swing axis) 20a faces the traveling direction of the airframe 4 of the unmanned helicopter 1 . The expression that the rotating or swinging axis is "directed in the traveling direction of the airframe 4" includes that the rotating or swinging axis is parallel to the Y-axis, but it does not have to be strictly parallel to the Y-axis. For example, if the rotation axis or swing axis is parallel to the YZ plane and is within a predetermined angle range from the traveling direction of the machine body 4, the rotation axis or the swing axis is aligned with the traveling direction of the machine body 4. It can be said that it is suitable. An example of the “predetermined angle range” is a range of ±30 degrees from the traveling direction of the airframe 4 . The reason why such a mounting method is allowed is that the unmanned helicopter 1 can fly with the nose side slightly lowered (forward leaning posture).

Furthermore, it is not essential to be "the direction parallel to the YZ plane" in the above example. This is because the forest can be measured even if it is deviated in the +X direction or -X direction. In other words, the rotation axis or swing axis of the LiDAR sensor 20 can be set not only in the "direction parallel to the YZ plane" but also in the "direction not parallel to the YZ plane" within the range where forest measurement can be performed. You can turn.

FIG. 6 shows a modification regarding the mounting position of the LiDAR sensor 20 . The LiDAR sensor 20 is mounted so as to be surrounded by the lower part near the center of the body 4 of the unmanned helicopter 1 and the skid 16 . The description regarding the rotation axis or swing axis of the LiDAR sensor 20 is the same as in the example of FIG. In the example of FIG. 6, the orientation of the attached LiDAR sensor 20 is opposite to that of the example of FIG. However, also in the example of FIG.

In the case of the installation example of FIG. 6, the skid 16 of the unmanned helicopter 1 is within the scanning range of the LiDAR sensor 20 . Therefore, the LiDAR sensor 20 always detects the distance to the skid. The distance to other reflection points may be calculated without reflecting the reflected light from the skid in the measurement results.

In order to prevent the skid 16 of the unmanned helicopter 1 from entering the scanning range of the LiDAR sensor 20, the LiDAR sensor 20 may be provided at the bottom of the tail body 3. Also in this case, the description regarding the rotation axis or swing axis of the LiDAR sensor 20 is the same as in the example of FIG.

The forest measurement method in an exemplary embodiment is described below.

7A is a perspective view showing a portion of flight path 60 in an exemplary embodiment, and FIG. 7B is a top view showing a portion of flight path 60. FIG. For convenience of explanation, description of the forest 54 on the slope 52 of the mountain 50 is omitted.

A flight path may include multiple segments. Some of the many segments are shown in FIGS. 7A and 7B. Specifically, a route segment that flies along the first contour line 60a and a route segment that flies along the second contour line 60b. In this embodiment, a large number of route segments are set to fly along contour lines, and forest measurement is performed on the forest in the observation target area. Such route segments of the flight route 60 can be set by an operator who manages the flight and operation of the unmanned helicopter 1 . When transitioning from a path segment along the first contour line 60a to a path segment along the second contour line 60b, the unmanned helicopter 1 flies along a path segment 60c, for example descending a slope in a direction perpendicular to the contour line. The path segment 60c may also be set by the operator, or may be set automatically by a tablet computer, base station controller, etc. described below after setting the path segment along the first contour line 60a and the path segment along the second contour line 60b. may be Note that the long dashed line 60d shown in FIG. 7B will be described later.

FIG. 8 is a cross-sectional view of slope 52 showing unmanned helicopter 1 flying along first contour line 60a and unmanned helicopter 1 flying along second contour line 60b. The cross section is taken along line AA in FIGS. 7A and 7B.

The absolute altitude (AGL) at which the unmanned helicopter 1 flies is constant (AGL=Ha) on both the first contour line 60a and the second contour line 60b. A horizontal offset of D is between the first contour line 60a and the second contour line 60b.

FIG. 8 shows that the true altitude (MSL) of the unmanned helicopter 1 flying along the second contour line 60b is Hm. In the example of FIG. 8, the true altitude Hm is approximately the same as the altitude indicated by the first contour line 60a. Therefore, it is understood that laser pulses emitted from the LiDAR sensor 20 of the unmanned helicopter 1 flying along the second contour line 60b are incident on the trunks of trees (not shown) near the first contour line 60a at substantially right angles. be. This allows the LiDAR sensor 20 to measure the canopy and trunk.

Note that the measurement target area may include the edge of the forest 54 . In that case, in determining the flight path 60, a flight path that passes over a position a predetermined distance away from the edge of the forest 54 in the direction of the non-forest area may be adopted. An example of "a position a predetermined distance away" is the long dashed line 60d shown in FIG. 7B. If such a flight path is adopted, the trunks of the trees at the edge of the forest 54 are positioned diagonally downward right or diagonally downward toward the traveling direction of the unmanned helicopter 1 . This allows the LiDAR sensor 20 to scan the tree trunks at the edge of the forest 54 and obtain a point cloud of reflection points.

Another advantage of keeping the absolute altitude Ha constant will now be described with reference to FIGS. 9A and 9B.

FIG. 9A shows the distribution of laser pulses incident on the slope 52 when the absolute altitude AGL is constant (AGL=Ha). FIG. 9B shows the distribution of laser pulses incident on the slope 52 when the true height MSL is kept constant (MSL=Hm). In both figures, the unmanned helicopter is flying from the back to the front or from the front to the back.

When the absolute altitude AGL is kept constant (FIG. 9A), the distance between the unmanned helicopter 1 and the slope 52 is generally constant regardless of which contour line it flies. As a result, the measurement point density of laser pulses reaching the slope 52 from the LiDAR sensor 20 can be maintained substantially constant.

On the other hand, when the true altitude MSL is kept constant (FIG. 9B), the farther the unmanned helicopter 1 flies from the slope 52, the lower the unmanned helicopter 1 flies along the contour line. As a result, the density of measurement points on the slope 52 is reduced. That is, it is difficult to equalize the measurement point density.

Therefore, it is preferable to keep the absolute altitude Ha constant in order to make the measurement point density uniform.

FIG. 10 shows results of forest measurements made by a method according to an exemplary embodiment. Forest measurement was performed for forests on slopes similar to the slopes illustrated in FIG. As shown in FIG. 10, it is understood that not only the crown of each tree in the forest is measured, but also the trunk. The present inventor confirmed that the forest measurement method according to this embodiment is effective from the obtained results.

An operator may utilize a computer device such as a tablet computer, base station controller, or the like to set a flight path 60 with contour lines and absolute altitudes as described above. In this specification, the unmanned helicopter 1 and such a computer device are collectively referred to as a "forest measurement system".

FIG. 11A shows an example of forest measurement system 100 including unmanned helicopter 1 and tablet computer 70 . FIG. 11B also shows an example of a forest measurement system 100 including an unmanned helicopter 1 and a base station control device 80. As shown in FIG. Both the tablet computer 70 and the base station controller 80 have built-in or external storage devices in which contour line data 90, which will be described later, is stored. The tablet computer 70 and the base station controller 80 display the contour data 90 on the display and accept designation of the flight route 60 from the operator. The tablet computer 70 has a touch screen panel, and accepts specification of contour lines (route segments) along which the unmanned helicopter 1 should fly and specification of absolute altitude by touch operation from the operator. It is assumed that the base station control device 80 according to this embodiment is a notebook PC and supports touch operations similar to those of the tablet computer 70 .

Hereinafter, the tablet computer 70 shown in FIG. 11A will be described as an example. The basic configuration of the tablet computer 70 and the basic configuration of the base station control device 80 are substantially the same. Therefore, the following description can be read as a description of the base station control device 80. FIG.

FIG. 12 shows a hardware configuration example of the tablet computer 70. As shown in FIG.

The tablet computer 70 has a CPU 71 , a memory 72 , a communication circuit 73 , an image processing circuit 74 , a display 75 , a touch screen panel 76 and a communication bus 77 . The CPU 71 , memory 72 , communication circuit 73 , image processing circuit 74 , and touch screen panel 76 are connected by a communication bus 77 , and can exchange data with each other via the communication bus 77 .

The CPU 71 is a signal processing circuit (computer) that controls the operation of the tablet computer 70 . The CPU 71 is typically a semiconductor integrated circuit. The CPU 71 may be simply called a "processing circuit".

The memory 72 stores computer programs that control the operation of the CPU 71 . The memory 72 can store a computer program for causing the CPU 71 to control forest measurement. The memory 72 may store a computer program for causing the CPU 71 to control the flight of the unmanned helicopter 1 . Similar to the computer program described above, such a computer program may be installed in the tablet computer 70 from a recording medium on which it is recorded, or may be downloaded via an electric communication line such as the Internet. Alternatively, such a computer program may be installed on the tablet computer 70 via wireless communication. Such computer programs may be sold as packaged software.

The memory 72 may be a volatile storage device (eg, RAM) storing computer programs executed by the CPU 71 and a non-volatile storage device (eg, flash memory) storing the contour line data 90 . The RAM can also be used as a work memory when the CPU 71 performs calculations. The computer program may be stored in flash memory. When the tablet computer 70 is started, the CPU 71 reads a computer program from the flash memory, develops it in the RAM, and executes it.

The communication circuit 73 is, for example, a wireless communication circuit that performs wireless communication conforming to the Bluetooth (registered trademark) and/or Wi-Fi (registered trademark) standards. As with the communication circuit 15f of the unmanned helicopter 1, in this specification, the tablet computer 70 performs wireless communication conforming to the Bluetooth (registered trademark) standard and/or the Wi-Fi standard, and communicates with the unmanned helicopter 1 on a one-to-one basis. do. The communication circuit 73 receives data to be transmitted to the unmanned helicopter 1 from the CPU 71 via the communication bus 77 . The communication circuit 73 also transmits data received from the unmanned helicopter 1 (for example, measurement results of the LiDAR sensor 20 ) to the CPU 71 and/or the memory 72 via the communication bus 77 .

The image processing circuit 74 generates an image to be displayed on a display (display device) 75 according to instructions from the CPU 71 . For example, the image processing circuit 74 uses the contour line data 90 to display an image of the mountain 50 with contour lines illustrated, and displays the flight path on the display 75 in response to the operator's touch operation received via the touch screen panel 76 . Draw 60.

The touch screen panel 76 can detect operator touches made with a finger, pen, or the like. Known detection methods include an electrostatic method, a resistive film method, an optical method, an ultrasonic method, an electromagnetic method, and the like. For example, in the case of a capacitive touch screen panel 76 , the touch screen panel 76 detects changes in capacitance at specific locations and transmits data about the changes to the CPU 71 via the communication bus 77 . The CPU 71 determines whether or not the operator has touched on the basis of the sent data. An example of "data on change" is data on the position and length of time that the capacitance changed.

"Touch" includes various operations such as short press (or tap), long press, and slide. For example, a short press is an operation in which the operator touches the touch screen panel 76 with the finger and then removes the finger within a predetermined reference time. A long press is an operation in which the operator touches the touch screen panel 76 with a finger, maintains that state without moving the finger, and releases the finger after a longer period of time than the reference time has elapsed.

In this embodiment, the touch screen panel 76 is provided so as to overlap the display 75 . The operator touches a desired contour line image while viewing the image of the mountain 50 and contour lines displayed on the display 75 . The CPU 71 determines which position of the image displayed on the display 75 is indicated by the detected position data output from the touch screen panel 76 . As a result of the determination, the CPU 71 can determine the position of contour lines associated with the image displayed at the position. In place of the touch screen panel 76 or together with the touch screen panel 76, other input devices such as a mouse, keyboard, joystick, and microphone may be provided.

FIG. 13 shows an example of contour line data 90 within the observation target area read into the memory 72 . Contour line data may be prepared for each constant altitude (for example, every 10 m). The contour line data does not have to be image data as shown in FIG. 13, as long as the altitude data and the coordinate data are associated with each other. In this specification, "contour line data" may be referred to as "information about contour lines".

When the operator specifies a contour line (first contour line) and an adjacent contour line (second contour line), the CPU 71 of the tablet computer 70 can calculate the altitude of the specified position. For example, the elevation of the first contour line is Z1, and the elevation of the second contour line is Z2. Assume that the operator designates a position W that divides the first contour line and the second contour line into W1:W2. Using the proportional relationship, the altitude of the position W can be expressed as (W1·Z2+W2·Z1)/(W1+W2). In this way, the CPU 71 can extract the elevation of any designated position and the contour line connecting a plurality of points having that elevation. The CPU 71 may present the extracted contour line candidates to the operator.

A method of setting a flight route using the tablet computer 70 of the forest measurement system 100 and a method of flying the unmanned helicopter 1 along the set flight route will be described below.

FIG. 14 is a flow chart illustrating a flight path setting process procedure according to an exemplary embodiment. The procedure shown in FIG. 14 is executed under the control of the tablet computer 70 or the CPU 71 (FIG. 12) of the base station control device 80. FIG. Note that if a plurality of observation target areas can be selected, one of them is designated in advance.

In step S2, the CPU 71 acquires information on contour lines for the observation target area.

In step S4, the CPU 71 accepts a contour line designation via the touch screen panel 76. FIG. Various methods of specifying contour lines are conceivable. For example, the operator designates a plurality of positions on desired contour lines displayed on the tablet computer 70 by short pressing. The specified order may be the order of the flight waypoints of the unmanned helicopter 1 . As another example, when the operator presses and holds a position on the map displayed on the tablet computer 70, the CPU 71 of the tablet computer 70 determines the altitude corresponding to the touched position. The CPU 71 extracts a plurality of positions having the determined altitudes and automatically displays contour lines connecting them. By touching the displayed contour line, the operator can designate a flight route along the contour line as a route segment. If the operator presses and holds a position with a different elevation, a similar procedure may be used to determine new contour lines and add route segments. As still another example, the CPU 71 may automatically extract and display a plurality of contour lines within the observation target area. With approval from the operator, each contour line may be set as a route segment to determine a single flight path.

In step S6, the CPU 71 determines whether or not contour line setting is completed. For example, the CPU 71 repeats the processing of steps S4 and S6, assuming that the setting of the contour lines is not completed until an input indicating that the setting of the contour lines is completed is received from the operator. On the other hand, when receiving an input indicating that the setting of the contour lines is completed, the CPU 71 determines that the setting of the contour lines is completed, and proceeds to step S8. In step S<b>8 , the CPU 71 accepts designation of absolute altitude through the touch screen panel 76 . In FIG. 11A, a "+" button for increasing the numerical value of the absolute altitude and a "-" button for decreasing it are displayed. A software keyboard may be displayed to enable direct input of numerical values, or a GUI such as a dial or slider may be used for input.

Through the above processing, the flight path 60 (FIGS. 7A and 7B) of the unmanned helicopter 1 is set. The data indicating the flight path 60 is, for example, wirelessly transmitted from the communication circuit 73 of the tablet computer 70 and received by the communication circuit 15f of the unmanned helicopter 1 (FIG. 4). The signal processing circuit 15g (FIG. 4) of the unmanned helicopter 1 stores the received data in the RAM 15i. After that, forest measurement is performed according to the procedure shown in FIGS.

FIG. 15 is a flow chart showing the procedure of the flight operation of the unmanned helicopter 1 with the flight path set. The procedure shown in FIG. 15 is executed under the control of the signal processing circuit 15g of the unmanned helicopter 1. FIG.

In step S10, the signal processing circuit 15g of the unmanned helicopter 1 flies the unmanned helicopter 1 to the forest measurement start position while acquiring its own position using the GPS module 15a or the like. The “starting position” referred to here includes the absolute altitude in addition to the longitude and latitude of the position on the contour line of the flight path 60 where the forest measurement is started. When the forest measurement start position is reached, the signal processing circuit 15g starts forest measurement using the LiDAR sensor 20 in step S12.

In step S14, the signal processing circuit 15g causes the unmanned helicopter 1 to fly along the set contour lines and at the set absolute altitude. Details of the processing in step S14 will be described later with reference to FIG.

In step S16, the signal processing circuit 15g determines whether or not the forest measurement has ended. Specifically, the signal processing circuit 15g determines whether the aircraft has flown along a preset flight route 60 or not. The processing of steps S14 and S16 is repeated until forest measurement is completed.

After the forest measurement is completed, the unmanned helicopter 1 performs autonomous flight, for example, and returns.

FIG. 16 shows details of the process of step S14 in FIG.

In step S140, the signal processing circuit 15g detects the flight position (latitude and longitude) and altitude (elevation). For example, the signal processing circuit 15g detects the flight position using the output of the GPS module 15a, and detects the altitude using the output of the atmospheric pressure sensor 15c.

In step S142, the signal processing circuit 15g determines whether the amount of deviation from the contour line is within a first predetermined value. "Amount of deviation" represents the distance from the current flight position to the contour line. An example of the "first predetermined value" is 10m. If the deviation amount is within the first predetermined value, the process proceeds to the next step S146, and if the deviation amount is not within the first predetermined value, the process proceeds to step S144.

In step S144, the signal processing circuit 15g corrects the flight position so that the amount of deviation is within the first predetermined value. As a result, the flight position of the unmanned helicopter 1 approaches the contour line.

In the next step S146, the signal processing circuit 15g determines whether or not the deviation amount of the absolute altitude is within the second predetermined value. The “absolute altitude deviation amount” represents the difference between the absolute altitude at the current flight position and a preset absolute altitude. The absolute altitude at the current flight position is the difference between the altitude at the current flight position and the altitude of the contour line of the set flight route. An example of the "second predetermined value" is 10m.

If the deviation amount of the absolute altitude is within the second predetermined value, the process proceeds to step S16 (FIG. 15). If the deviation amount is not within the predetermined value, the process proceeds to step S148.

In step S148, the signal processing circuit 15g corrects the current absolute altitude so that the deviation amount of the absolute altitude is within the second predetermined value.

In this embodiment, the unmanned helicopter 1 flies along contour lines. Flying along contour lines reduces variations in distance to the ground and/or the surface layer of the canopy. Since the unmanned helicopter 1 does not need to be raised and lowered frequently to keep the distance to the ground surface and/or the surface layer of the tree canopy constant, energy consumption can be reduced and the cruising range can be increased. can.

Also, in the forest measurement targeting the forest 54 on the slope 52, the point cloud data on the opposite side of the slope 52 is unnecessary. Therefore, the point cloud data on the opposite side of the slope 52 may not be stored in the storage device. As a result, the amount of data when analyzing point cloud data can be reduced, and the analysis speed can be improved. The point cloud data on the opposite side of the slope 52 may not be stored in the storage device 15j of the unmanned helicopter 1 or stored in the memory 72 of the tablet computer 70, for example. Also, when the tablet computer 70 or another computer analyzes the point cloud data, only the point cloud data on the slope 52 side may be used. As a result, analysis speed can be improved.

One of the advantages of flying the unmanned helicopter 1 along contour lines while maintaining a constant absolute altitude is that the density of measurement points on the slope 52 can be maintained substantially constant. The inventors have considered additional flight strategies to keep the measured point density approximately constant.

FIG. 17 shows a slope 52 of a mountain 50 scanned by an unmanned helicopter 1 in flight. For convenience of explanation, description of forests is omitted. A dashed line is shown on the slope 52 . Each point forming the dashed line schematically and roughly indicates the incident position of the laser pulse. FIG. 18 is a diagram for explaining the relationship between the two sides forming the region S in FIG. 17. As shown in FIG. In FIGS. 17 and 18, the region S is represented by a rectangle, which is an ideal shape when there is no phase shift for emitting laser pulses or disturbance during flight. Region S is not necessarily rectangular.

Let Δt be the time required for the LiDAR sensor 20 to rotate once. Between time t and time t+Δt, the LiDAR sensor 20 radially emits laser pulses approximately in a plane perpendicular to the flight direction of the unmanned helicopter 1 . Each laser pulse is successively incident on the position where the plane and the slope 52 intersect.

On the other hand, since the unmanned helicopter 1 is flying, the position of the unmanned helicopter 1 changes during the period Δt in which the LiDAR sensor 20 rotates once. Between the time t+Δt after the position change and the next time t+2Δt, the LiDAR sensor 20 rotates once again and radially emits laser pulses. As a result, these laser pulses are incident at positions slightly displaced in the traveling direction from the incident positions of the laser pulses incident on the slope 52 between time t and time t+Δt. As the unmanned helicopter 1 continues to fly, the laser pulses incident on the slope 52 are distributed in a mesh or grid pattern. The position (incident point) where the laser pulse is incident is the reflection position (reflection point) of the laser pulse.

Region S shown in the partially enlarged view is a region surrounded by incident points a _k , a _k+1 , b _k , b _k+1 of four adjacent laser pulses incident on slope 52 between time t and time t+2Δt. Incident points a _k and a _k+1 indicate the incident points of two laser pulses adjacent to each other in the laser pulse group emitted from time t to time t+Δt. The LiDAR sensor 20 emits these two laser pulses with a predetermined angular pitch α (FIG. 18). Incident points bk and bk ₊₁ indicate incident points of two adjacent laser pulses in the laser pulse group emitted from time t+Δt to time t ₊ 2Δt.

An incident point a _k and an incident point b _k are incident points of two laser pulses emitted with a time interval Δt in the same angular direction as viewed from the LiDAR sensor 20 . The same applies to the relationship between the incident point a _k+1 and the incident point b _k+1 .

The above description assumes that the number of laser pulses emitted from the LiDAR sensor 20 at a given time is one. However, as shown in FIG. 2, there are also LiDAR sensors 20 that have N exits and are capable of emitting N laser pulses 22 simultaneously from each exit. Even in such a case, the above description can be applied to laser pulses emitted from each emission port.

See FIG. Let the distance between the incident points a _k and a _k+1 (or the distance between the incident points b _k and b _k+1 ) be Zd, and the distance between the incident points a _k and b _k (or the distance between the incident points a _k+1 and b _k+1 ) ) as Yd. Considering the case where the region S is not rectangular, the distance Zd means the distance on the XZ plane when the incident points _ak and _ak+1 are projected onto the XZ plane perpendicular to the Y direction. The distance Yd means the distance between the incident points _ak and _bk along the Y direction or the distance on the YZ plane when the incident points _ak and _bk are projected onto the YZ plane perpendicular to the X direction. do.

The flight speed of the unmanned helicopter 1 is V (m/s), the number of laser pulses emitted simultaneously in the same angular direction is N, the frequency of the laser pulses emitted in the same angular direction is f (Hz), and the predetermined angular pitch is Let α (rad) be the distance from the LiDAR sensor 20 to the incident point _ak be L (m). "Laser pulses emitted in the same angular direction" represent, for example, two laser pulses incident on the above-described incident point a _k and incident point b _k . These values are sometimes called "parameters" below.

Using parameters such as those described above, the spacing Yd can be expressed as V/f. There are N points of incidence within the interval Yd. Assuming that the distance between two adjacent incident points is yd, yd can be expressed as V/(f·N). Also, the interval Zd is approximated as α·L.

The inventors determined that the measurement point density in the scanning direction of the LiDAR sensor 20 and the measurement point density in the flight direction of the unmanned helicopter 1 can be kept constant by making the interval Zd equal to the interval yd. However, the intervals Zd and yd need not be exactly equal. Therefore, the inventor of the present invention targets the forest on the slope 52 using the LiDAR sensor 20 while flying the unmanned helicopter 1 so that the relative value of α L with respect to V / (f N) falls within a predetermined range. It was decided to conduct forest measurement. The "relative value of α·L with respect to V/(f·N)" as used herein can be expressed as a ratio or as a difference. As explained with reference to FIG. 1, an example of a "predetermined range" is a range of 0.9 to 1.1 when the "relative value" is expressed as a ratio, with a wider range of 0.8 to 1.2, or a wider range of about 0.5 to 2.0. At this time, the measurement points are distributed in a generally square mesh or grid. This makes it possible to ensure a substantially uniform measurement point density.

Any of the above parameters V, N, f, α, L may be variable. For example, the flight speed V of the unmanned helicopter 1 is obviously a variable value. Also, the parameters N, f and α may be varied according to the specifications of the LiDAR sensor 20 and/or set by the operator. The distance L can be arbitrarily set as a distance to the ground surface in a position or direction in which a desired measurement point density is desired. The flight speed V of the unmanned helicopter 1 can be adjusted autonomously by the signal processing circuit 15g of the unmanned helicopter 1. FIG. On the other hand, the parameters N, f, α and L can be preset or specified by the operator operating the tablet computer 70 or the base station controller 80 of the forest measurement system 100 (FIGS. 11A and 11B) described above. The parameters N, f, α and L may be stored in the storage device 15j of the unmanned helicopter 1. The parameter L may be adjusted autonomously by the signal processing circuit 15g of the unmanned helicopter 1. The scope of the forest measurement system 100 includes receiving necessary parameters and causing the unmanned helicopter 1 to perform forest measurement while adjusting the flight speed and the like according to the parameters.

The smaller the values of V/(f·N) and α·L, the higher the density of measurement points can be. Therefore, for example, when the predetermined angular pitch α is variable, it is conceivable to fix it to the minimum possible value. At this time, the flight speed V may also be decreased and/or the frequency f and/or the number N may be increased within a range that does not interfere with flight.

When the LiDAR sensor 20 is of a mechanical rotation type, the predetermined angular pitch α is α(rad)=2·π·R· It is calculated by N/M. Therefore, the parameter α described above may be replaced as follows. That is, the unmanned helicopter 1 may be flown to measure the forest so that the relative value of (2·π·R·N/M)·L with respect to V/(f·N) falls within a predetermined range. .

FIG. 19 is a flow chart showing the procedure of processing for uniforming the measurement point density by changing parameters. The procedure shown in FIG. 19 is executed under the control of the signal processing circuit 15g (FIG. 4) of the unmanned helicopter 1 after the unmanned helicopter 1 has arrived at the airspace where the forest measurement is to be performed.

In step S<b>20 , the signal processing circuit 15 g starts forest measurement using the LiDAR sensor 20 .

In step S22, the signal processing circuit 15g detects the current flight speed V of the unmanned helicopter 1 and the distance L to the position where the desired measurement point density is desired. For example, the signal processing circuit 15g may use the output of the GPS module 15a to obtain the flight speed V by calculating the amount of movement per unit time. Alternatively, the signal processing circuit 15g may acquire the flight velocity V by time-integrating the acceleration in the flight direction using the output of the acceleration sensor 15b. Further, the signal processing circuit 15g acquires the distance L to the position where the desired measurement point density is to be secured from the output of the LiDAR sensor 20. FIG.

In step S24, the signal processing circuit 15g determines whether or not the relative value of α·L with respect to V/(f·N) (hereinafter abbreviated as “relative value”) is within a predetermined range. A "predetermined range" may be set by the operator prior to flight. The signal processing circuit 15g may hold the values of the parameters f, N, and α set by the operator in the RAM 15i or the like, or may acquire the parameters f, N, and α from the LiDAR sensor 20 in real time. good. If the relative value is within the predetermined range, the process proceeds to step S28, and if the relative value is not within the predetermined range, the process proceeds to step S26.

In step S26, the signal processing circuit 15g adjusts at least one of V, f, N, α, and L. For example, the signal processing circuit 15g adjusts the flight speed V of the unmanned helicopter 1 when the parameters f, N, α, and L are fixed during flight.

In step S28, the signal processing circuit 15g determines whether or not the forest measurement to be performed has been completed. The signal processing circuit 15g repeats the processing from step S22 until the forest measurement is completed.

FIG. 20 is a flow chart showing a specific example of the processing shown in FIG. In FIG. 20, steps S30, S32, S34 and S36, which are more specific than steps S24 and S26 of FIG. 19, are provided. Steps S30 to S36 will be described below.

In step S30, the signal processing circuit 15g determines whether or not the relative value is equal to or greater than the lower limit value Qmin. If the relative value is less than the lower limit value Qmin, the process proceeds to step S32, and if the relative value is equal to or greater than the lower limit value Qmin, the process proceeds to step S34.

In step S32, the signal processing circuit 15g decreases the flight speed V of the unmanned helicopter 1 and/or increases the distance L. After that, the process returns to step S30.

In step S34, the signal processing circuit 15g determines whether the relative value is less than the upper limit value Qmax. If the relative value is less than the lower limit value Qmin, the process proceeds to step S28, and if the relative value is equal to or greater than the upper limit value Qmax, the process proceeds to step S36.

In step S36, the signal processing circuit 15g increases the flight speed V and/or decreases the distance L of the unmanned helicopter 1. After that, the process returns to step S30.

According to the above processing, by adjusting the parameters V and/or L so that the relative values fall within a predetermined range, it is possible to equalize the measurement point densities in the flight direction and the scan direction.

Next, a method of evenly irradiating the laser pulse 22 to the measurement object such as the forest 54 will be described.

A laser pulse 22 emitted from the LiDAR sensor 20 irradiates the object to be measured to form a laser spot on the surface of the object to be measured. The laser pulse 22 emitted from the LiDAR sensor 20 travels while diverging at a predetermined divergence angle even when the laser beam is collimated. Therefore, the size of the laser spot formed on the measurement object increases in proportion to the distance between the LiDAR sensor 20 and the measurement object. Shortening the distance between the LiDAR sensor 20 and the object to be measured reduces the size of the laser spot formed on the object to be measured.

For example, if the distance between the LiDAR sensor 20 and the measurement target is shortened in order to measure the measurement target in detail, the size of the laser spot formed on the measurement target becomes smaller. As the size of the laser spot becomes smaller, gaps will occur between adjacent laser spots. When measuring a forest, it is desired to irradiate the laser pulse 22 not only on the tree canopy but also on the trunk and the ground surface. In order to prevent the laser spot from missing the gaps between the leaves, it is desirable to irradiate the forest with the laser pulse 22 without any gaps.

FIG. 21 is a diagram schematically showing a plurality of laser pulses 22 emitted from the LiDAR sensor 20 when the unmanned helicopter 1 in flight is viewed from the front.

FIG. 21 shows laser pulses 22a, 22b and 22c as the laser pulse 22. FIG. A region indicated by a dot pattern between solid lines in FIG. 21 represents a single laser pulse 22a that travels while diverging at _a divergence angle θ1. A region indicated by a dot pattern sandwiched by dashed lines represents a single laser pulse 22b that travels while diverging at _a divergence angle θ1. A region indicated by a dot pattern sandwiched between dashed lines represents a single laser pulse 22c that travels while diverging at _a divergence angle θ1.

FIG. 22 is a diagram schematically showing a plurality of laser pulses 22 emitted from the LiDAR sensor 20 when the unmanned helicopter 1 in flight is viewed from the side.

FIG. 22 shows laser pulses 22a, 22i, 22p as the laser pulse 22. FIG. A region indicated by a dot pattern between solid lines in _FIG . 22 represents a single laser pulse 22a that travels while diverging at a divergence angle θ2. A region indicated by a dot pattern sandwiched by dashed lines represents a _single laser pulse 22i that travels while diverging at a divergence angle θ2. A region indicated by a dot pattern sandwiched by alternate long and short dash lines represents a _single laser pulse 22p that travels while diverging at a divergence angle θ2. The divergence angles θ ₁ and θ ₂ of the laser pulse 22 are predetermined by the specifications of the LiDAR sensor 20 and are fixed values.

21 and 22 show an example in which the measurement target 51 is a flat ground surface in order to explain the present embodiment in an easy-to-understand manner, but the measurement target 51 is not limited thereto. For example, the measurement object 51 may be a slope 52, a forest 54, or a forest 54 on the slope 52 (slope forest).

FIG. 23 is a diagram showing a laser spot formed on the measurement object 51 by the laser pulse 22. As shown in FIG. FIG. 23 shows a laser spot 24a formed on the measurement object 51 by the laser pulse 22a, a laser spot 24b formed on the measurement object 51 by the laser pulse 22b, and a laser spot 24b formed on the measurement object 51 by the laser pulse 22c. A laser spot 24c is shown. FIG. 23 further shows a laser spot 24i formed on the measurement object 51 by the laser pulse 22i and a laser spot 24p formed on the measurement object 51 by the laser pulse 22p. In this embodiment, the cross-sectional shape of the laser pulse 22 along a plane perpendicular to the traveling direction of the laser pulse 22 is substantially rectangular. Therefore, the shape of the laser spot 24 formed by the laser pulse 22 is also substantially rectangular.

Although the shape of the laser spots 24 is not limited to a rectangle, in order to efficiently arrange the laser spots 24 in the plane without gaps, the shape of each laser spot 24 should be rectangular or roughly rectangular. is preferable compared to having, for example, an elliptical shape. The laser spot 24 can have any shape by adjusting the shape of the light emitting region of the laser light source (typically an array of semiconductor laser elements).

As described above with reference to FIG. 3, the LiDAR sensor 20 emits laser pulses 22 while changing the emission direction of the laser pulses 22 at a predetermined angular pitch α. Referring to FIG. 21 , laser pulse 22 a is a laser pulse emitted from one exit port of LiDAR sensor 20 . The laser pulse 22b is a laser pulse emitted from the same emission port at the timing when the LiDAR sensor 20 is rotated by an angle α from the timing at which the laser pulse 22a was emitted. The laser pulse 22c is a laser pulse emitted from the same emission port at the timing when the LiDAR sensor 20 is further rotated by the angle α.

Each of the laser pulses 22a, 22b, 22c diverges with a divergence angle θ ₁ in a direction perpendicular to the LiDAR sensor 20 rotation axis 20a (FIGS. 21, 22). In this embodiment, the predetermined angular pitch α of the LiDAR sensor 20 is adjusted to be smaller _than the divergence angle θ1. Thereby, as shown in FIG. 21, the laser pulse 22a and the laser pulse 22b can be overlapped on a plane (ZX plane) perpendicular to the rotation axis 20a of the LiDAR sensor 20. FIG. Moreover, the laser pulse 22b and the laser pulse 22c can be overlapped. That is, the laser spot 24a (FIG. 23) formed on the measurement object 51 by the laser pulse 22a and the laser spot 24b formed on the measurement object 51 by the laser pulse 22b can be overlapped. The laser spot 24b and the laser spot 24c formed on the measurement object 51 by the laser pulse 22c can be overlapped. FIG. 23 virtually shows the relationship between the angular pitch α and the divergence angle θ1 _on the laser spot.

Next, a method of overlapping the laser spots in the traveling direction (flight direction) of the unmanned helicopter 1 will be described. Referring to FIG. 22 , laser pulse 22 a is a laser pulse emitted from one exit port of LiDAR sensor 20 . The laser pulse 22i is a laser pulse emitted from the same emission port at the timing when the LiDAR sensor 20 rotates once from the timing at which the laser pulse 22a was emitted. The laser pulse 22p is a laser pulse emitted from the same emission port at the timing when the LiDAR sensor 20 rotates one more time.

The laser pulse 22a diverges at a divergence angle θ ₂ in a plane parallel to both the vehicle heading 201 and the exit direction of the laser pulse 22a. The laser pulse 22i diverges at a divergence angle θ ₂ in a plane parallel to both the vehicle heading 201 and the exit direction of the laser pulse 22i. The laser pulse 22p diverges at a divergence angle θ ₂ in a plane parallel to both the vehicle heading 201 and the exit direction of the laser pulse 22p. Each of the laser pulses 22 a , 22 i , 22 p diverging at the divergence angle θ ₂ forms a laser spot on the measurement object 51 . In the example shown in FIG. 22, K represents the length of each laser spot in the direction parallel to the traveling direction 201 of the aircraft. Also, J represents the flight distance that the unmanned helicopter 1 flies while the LiDAR sensor 20 rotates once.

Since the length K of the laser spot is proportional to the distance L between the LiDAR sensor 20 and the object 51 to be measured, the length K of the laser spot can be grasped if the distance L is known. The distance L is the absolute altitude H, for example. As described above, the absolute altitude H can be detected using the barometric pressure sensor 15c, the LiDAR sensor 20, a radio altimeter, or the like. Further, as described above, the absolute altitude H may be the distance from the ground surface or the distance from the surface layer of the tree crown.

In the present embodiment, the flight speed V of the unmanned helicopter 1, the number of revolutions per unit time R of the LiDAR sensor 20, and the unmanned helicopter are set so that the flight distance J of the unmanned helicopter 1 is shorter than the length K of the laser spot 24. Adjust at least one of the altitudes H of 1. For example, the flight speed V of the unmanned helicopter 1 is adjusted so that the flight distance J is shorter than the length K. As a result, in the aircraft traveling direction 201 of the unmanned helicopter 1, a laser spot 24a (FIG. 23) formed on the measurement object 51 by the laser pulse 22a and a laser spot formed on the measurement object 51 by the laser pulse 22i 24i, and the laser spot 24i and the laser spot 24p formed on the measurement object 51 by the laser pulse 22p can be overlapped.

Referring to FIGS. 22 and 23, laser spot 24j is a laser spot formed by laser pulses emitted from the same emission port at a timing when LiDAR sensor 20 is rotated by angle α from the timing at which laser pulse 22i was emitted. is. A laser spot 24k is a laser spot formed by a laser pulse emitted from the same emission port at the timing when the LiDAR sensor 20 is further rotated by the angle α. The laser spot 24q is a laser spot formed by laser pulses emitted from the same emission port at the timing when the LiDAR sensor 20 is rotated by an angle α from the timing at which the laser pulse 22p was emitted. The laser spot 24r is a laser spot formed by laser pulses emitted from the same emission port at the timing when the LiDAR sensor 20 is further rotated by the angle α.

In this embodiment, the flight distance J is set shorter than the length K of the laser spot, and the predetermined angular pitch α is set smaller than the divergence angle θ ₁ of the laser pulse 22 . As a result, as shown in FIG. 23 , the laser spots can be overlapped both in the machine body traveling direction 201 of the unmanned helicopter 1 and in the direction perpendicular to the machine body traveling direction 201 . By overlapping the laser spots, the object 51 to be measured can be evenly irradiated with the laser pulse 22, and the object 51 to be measured can be measured in detail.

As described above, the LiDAR sensor 20 has N emission openings arranged along the direction in which the rotation axis 20a extends, and can emit up to N laser pulses 22 simultaneously. In the above description, the length K of the laser spot 24 was the length of the laser spot formed by one laser pulse emitted from one emission port, but when two or more emission ports were emitted at the same time It may be the length of a laser spot formed by two or more laser pulses. In this case, the laser spots respectively formed by the two or more laser pulses emitted at the same time overlap to form one laser spot as a whole. Length K is the length of one laser spot formed from the two or more laser pulses. Also in this case, similar to the above, the laser spots can be overlapped both in the aircraft traveling direction 201 of the unmanned helicopter 1 and in the direction perpendicular to the aircraft traveling direction 201 .

FIG. 24 is a flow chart showing a forest measurement procedure performed while evenly irradiating a forest 54, which is an example of the measurement object 51, with laser pulses 22. In FIG.

In step S40, the predetermined angular pitch α is adjusted so that the predetermined angular pitch α is smaller _than the divergence angle θ1 of the laser pulse 22 . Adjustment of the predetermined angular pitch α is executed by the CPU 71 (FIG. 12) of the tablet computer 70, for example.

As described above, the predetermined angular pitch α is represented by α=2·π·R/M. The divergence angle θ ₁ is a fixed value known in advance. The CPU 71 adjusts the predetermined angular pitch α so as to be smaller than the divergence angle θ ₁ by changing at least one of the number of times M of emission of the laser pulse 22 per unit time and the number of revolutions R of the LiDAR sensor 20. do. For example, by changing the rotational speed R, the predetermined angular pitch α is made smaller _than the divergence angle θ1. The operator may set the predetermined angular pitch α by inputting the value of the predetermined angular pitch α into the tablet computer 70 before flight.

Next, in step S42, the CPU 71 adjusts at least one of the flight speed V, the number of revolutions R, and the altitude H so that the flight distance J of the unmanned helicopter 1 is shorter than the length K of the laser spot 24. adjust. For example, the flight speed V is adjusted so that the flight distance J is shorter than the length K. When adjusting the rotational speed R, it is adjusted within _a range where the relationship α<θ1 can be maintained.

For example, when the range of values taken by the distance L between the LiDAR sensor 20 and the forest 54 is set in advance when measuring the forest, the range of values taken by the length K of the laser spot 24 can be grasped in advance. can. For example, an operator inputs a range of values for the distance L into the tablet computer 70 before flight. The CPU 71 calculates the lower limit value of the range of values that the length K takes from the range of values that the distance L takes. The CPU 71 sets the calculated lower limit value as the value of the length K used for comparison with the flight distance J. FIG. Note that the operator may set the value of the length K used for comparison with the flight distance J by inputting the value of the length K into the tablet computer 70 before flight. The CPU 71 sets, for example, the flight speed V so that the flight distance J is shorter than the set length K.

Next, in step S44, forest measurement is started. Forest measurement is performed by either the procedure described with reference to FIGS. 15 and 16, the procedure described with reference to FIGS. 19 and 20, or a combination of these procedures.

During forest measurement, the CPU 71 compares the flight distance J with the length K (step S46). When the CPU 71 determines that the flight distance J is less than the length K, it continues forest measurement (step S48). The process of step S46 is repeated until the forest measurement is completed (step S52).

If it is determined in step S46 that the flight distance J is longer than or equal to the length K, the CPU 71 adjusts at least one of the flight speed V, the number of rotations R, and the altitude H so that the flight distance J is shorter than the length K. Adjust one (step S50). For example, the flight distance J is adjusted to be shorter than the length K by performing at least one of reducing the flight speed V, increasing the number of revolutions R, and increasing the altitude H. For example, by reducing the flight speed V, the flight distance J is made shorter than the length K. When increasing the rotational speed R, it is adjusted within _a range where the relationship α<θ1 can be maintained. When height H is increased, adjustment is made so that distance L can be maintained within a preset range. After the adjustment, the process of step S46 is executed again.

By executing the above processing, the forest can be measured while the forest 54 is evenly irradiated with the laser pulses 22 .

Note that the distance L between the LiDAR sensor 20 and the forest 54 may be measured during the forest measurement, and the length K may be calculated from the measured distance L. For example, the distance L can be calculated from the difference between the emission time of the laser pulse 22 and the acquisition time of the reflected pulse of the laser pulse 22 . Since the length K is proportional to the distance L, the length K can be calculated from the distance L.

In the above description, the processing of steps S40, S42, S46 and S50 is performed by the CPU 71, but the signal processing circuit 15g (FIG. 4) of the unmanned helicopter 1 may also perform the processing. Further, these processes may be shared between the CPU 71 and the signal processing circuit 15g.

According to this embodiment, the unmanned helicopter 1 flies at a lower altitude than a conventional aircraft, so that the in-plane number density of laser spots can be increased and the distance between laser spot centers can be reduced.

When the flight speed is lowered due to the flight at a low altitude, the measurement target area becomes narrow because the cruising range of the multicopter that operates the electric motor with the electric power supplied from the battery is short. On the other hand, an unmanned helicopter that flies with an internal combustion engine has a long cruising range, so even if the flight speed is reduced, a sufficient measurement target area can be secured.

In this specification, an unmanned aerial vehicle equipped with a LiDAR sensor has been exemplified and explained. Although mechanical rotation, MEMS, and phased array LiDAR sensors have been exemplified, flash LiDAR sensors may also be used. Although the flash LiDAR sensor does not have a rotation axis or a swing axis, it may be attached to the unmanned helicopter 1 at a position and angle that enable forest measurement of sloped forests.

Radar ranging devices such as LiDAR sensors and millimeter waves, antennas and imaging devices (cameras) may be referred to as "observers." In the above-described embodiments, the LiDAR sensor was exemplified as an observer, but other observers may be mounted on the unmanned aerial vehicle. In this case, mountains, forests, slopes, flat land, etc. observed using the observation device are the "observation target area". For example, when a camera is mounted on an unmanned aerial vehicle, the flight method exemplified in the above embodiments is suitable for searching for victims on slopes. The light captured by the camera when shooting corresponds to the reflected pulse from the reflection point captured by the LiDAR sensor. When the unmanned aerial vehicle is flown by the above-described flight method, it is possible to capture an image of the victim on the slope with the camera while generally maintaining the distance from the slope. Therefore, the victims can be searched precisely. Since the camera does not emit laser pulses like LiDAR, the camera does not have a rotating or swinging axis. The camera may be mounted on the unmanned aerial vehicle so that the camera's field of view includes at least the forest slopes.

Furthermore, equipment different from the observer may be mounted on the unmanned aerial vehicle. One example of such a device is a drug distribution device. Unmanned aerial vehicles are already used to spray chemicals such as herbicides and insecticides. Chemicals may be sprayed on slope forests for forest management and utilization. At that time, the spraying target area is determined, and the spraying device sprays the chemical on the slope while flying the unmanned aerial vehicle over the spraying target area by the above-described flight method. As a result, the chemical agent can be sprayed at a generally uniform density while generally maintaining the distance from the slope. It should be noted that unlike the LiDAR, the spraying device does not emit laser pulses, so the spraying device does not have a rotating or swinging axis. The spraying device may be mounted on the unmanned aerial vehicle so that the range over which the spraying device sprays the chemicals includes at least the slope of the forest.

In the description of the above embodiment, the target of forest measurement was mainly the forest 54 on the slope 52, but the target of forest measurement is not limited to this. The object of forest measurement may be a flat forest.

Exemplary embodiments of the present invention have been described above.

As described above, a method according to an embodiment of the present invention is a method of performing forest measurement targeting a forest 54 on a slope by flying an unmanned aerial vehicle 1 equipped with a lidar (LiDAR) sensor 20. The rotation axis 20a or the swing axis 20a of the sensor 20 is mounted on the unmanned aerial vehicle 1 so as to face the aircraft traveling direction. , scanning the forest 54 with the lidar sensor 20, and (ii) scanning the forest 54 with the lidar sensor 20 while flying the unmanned aerial vehicle 1 at a predetermined absolute altitude along a second contour line 60b different from the first contour line 60a. Run the scan again.

In some embodiments, the method may further comprise pre-specifying the first contour line 60a, the second contour line 60b and the predetermined absolute altitude prior to steps (i) and (ii).

In one embodiment, the method further includes scanning the edge of the forest 54 with the lidar sensor 20 while flying the unmanned aerial vehicle 1 over the edge at a predetermined distance. may

In some embodiments, lidar sensor 20 may scan the canopy and trunk of each tree in forest 54 .

In some embodiments, steps (i) and (ii) may include causing the lidar sensor 20 to scan the forest 54 with horizontally emitted laser pulses 22 .

In some embodiments, steps (i) and (ii) may include causing the lidar sensor 20 to scan the forest 54 using obliquely emitted laser pulses 22 .

In some embodiments, unmanned aerial vehicle 1 may be an unmanned helicopter or an unmanned multicopter.

A method according to an embodiment of the present invention is a method of determining a flight path of an unmanned aerial vehicle 1 equipped with an observer 20, wherein an observation target area by the observer 20 is specified, and if the observation target area includes a slope, , determining a plurality of route segments along which the unmanned aerial vehicle 1 flies at a predetermined absolute altitude along any of the contours with reference to contour line data within the observation target area, and determining a flight route including the plurality of route segments; to do

In some embodiments, determining multiple path segments may include setting multiple waypoints on the selected one or more contour lines and specifying absolute altitudes.

In some embodiments, the area of interest may include a sloped forest 54 .

In some embodiments, observer 20 may be a lidar (LiDAR) sensor 20 .

In some embodiments, determining the flight path may include determining a flight path over the edge of the forest 54 at a predetermined distance from the edge.

In one embodiment, observer 20 may be an infrared camera.

A method according to an embodiment of the present invention is a method of measuring a forest 54 on a slope by flying an unmanned aerial vehicle 1 equipped with a lidar (LiDAR) sensor 20. The rotation axis of the lidar sensor 20 20a or the swing axis 20a is mounted on the unmanned aerial vehicle 1 so as to face the aircraft traveling direction, and (i) the unmanned aerial vehicle 1 is flown at a predetermined absolute altitude and a predetermined first true altitude, while the rider traverses the forest 54; and (ii) scanning the forest 54 with the lidar sensor 20 while flying the unmanned aerial vehicle 1 at a predetermined absolute altitude and a predetermined second true altitude different from the first predetermined true altitude. to be scanned again.

A forest measurement system 100 according to an embodiment of the present invention has an unmanned aerial vehicle 1 and a computer device 70, and is a forest measurement system for measuring a forest 54 on a slope by flying the unmanned aerial vehicle 1. 100, the unmanned aerial vehicle 1 includes a lidar (LiDAR) sensor 20, a first signal processing circuit 15g, a first storage device 15j, and a first communication circuit 15f. Alternatively, the swing axis 20a is mounted on the unmanned aerial vehicle 1 so as to face the aircraft traveling direction, and the computer device 70 stores the display device 75, the input device 76, the second signal processing circuit 71, and the information on the contour lines. and a second communication circuit 73. The second signal processing circuit 71 acquires information about contour lines from the second storage device 72, and outputs the first contour lines 60a, Receiving the designation of the second contour line 60b and the absolute altitude, transmitting the designated first contour line 60a, the second contour line 60b and data of the absolute altitude to the unmanned aerial vehicle 1 via the second communication circuit 73, and performing the first signal processing The circuit 15g receives the data of the first contour line 60a, the second contour line 60b and the absolute altitude via the first communication circuit 15f, and transmits the received data of the first contour line 60a, the second contour line 60b and the absolute altitude to the first contour line 60a and the second contour line 60b. Stored in the storage device 15j, the forest 54 is scanned by the lidar sensor 20 while the unmanned aerial vehicle 1 flies along the first contour line 60a at an absolute altitude, and the unmanned aerial vehicle 1 flies along the second contour line 60b at an absolute altitude. , the forest 54 is scanned again by the lidar sensor 20 .

A photographing method according to an embodiment of the present invention is a method of photographing an observation target using an unmanned aerial vehicle 1 equipped with an imaging device 20, wherein an observation target area is specified, when the observation target area includes a slope, Determining a plurality of route segments along which the unmanned aerial vehicle 1 flies at a predetermined absolute altitude along any of the contour lines by referring to contour line data within the observation target area, and determining a flight route including the plurality of route segments. , the unmanned aerial vehicle 1 is flown along the determined flight path, and the imaging device 20 takes an image.

A spraying method according to an embodiment of the present invention is a method of spraying a chemical using an unmanned aerial vehicle 1 equipped with a chemical spraying device 20, comprising: specifying an area to be sprayed by the spraying device 20; If a slope is included, determining a plurality of route segments along which the unmanned aerial vehicle 1 flies at a predetermined absolute altitude along any of the contours by referring to contour line data within the distribution target area; Determining the route and spraying the chemical while flying the unmanned aerial vehicle 1 along the determined flight route are executed.

A computer program according to an embodiment of the present invention is a computer program that causes a computer to execute control of forest measurement targeting a forest 54 on a slope performed by flying an unmanned aerial vehicle 1 equipped with a lidar (LiDAR) sensor 20. The rotation axis 20a or the swing axis 20a of the lidar sensor 20 is mounted on the unmanned aerial vehicle 1 so as to face the aircraft traveling direction, and the computer program (i) moves the unmanned aerial vehicle 1 along the first contour line 60a. and (ii) flying the unmanned aerial vehicle 1 along a second contour line 60b different from the first contour line 60a at a predetermined absolute altitude, The computer is caused to control the rescanning of the forest 54 with the lidar sensor 20 .

A method according to an embodiment of the present invention is a method of performing forest measurement targeting a forest 54 by flying an unmanned aerial vehicle 1 equipped with a lidar (LiDAR) sensor 20. The swing axis 20a is mounted on the unmanned aerial vehicle 1 so as to face the direction of movement of the airframe. Using the lidar sensor 20, the laser pulse 22 is emitted while changing the emission direction at a predetermined angular pitch to measure the surrounding space. Let L be the distance to the forest 54, V be the flight speed of the unmanned aerial vehicle 1, N be the number of laser pulses 22 emitted simultaneously in the same angular direction, and f be the frequency of the laser pulses 22 emitted in the same angular direction. , where the predetermined angular pitch is α, the forest 54 is scanned using the lidar sensor 20 while flying the unmanned aerial vehicle 1 so that the relative value of αL with respect to V/(fN) falls within a predetermined range. Carry out targeted forest measurements.

In some embodiments, the predetermined angular pitch α may be a fixed value.

In some embodiments, the predetermined angular pitch α may be fixed at a configurable minimum value.

In one embodiment, the lidar sensor 20 is of a mechanical rotation type, where M is the number of times the laser pulses 22 are emitted per unit time from one outlet for emitting the laser pulses 22, and R is the number of rotations per unit time. Then, the predetermined angular pitch α is obtained by α(rad)=2·π·R/M, and performing forest measurement is (2·π·R/M)·L for V/(f·N) It may include flying the unmanned aerial vehicle 1 such that the relative values fall within a predetermined range.

In some embodiments, the number of launches M per unit time and the number of rotations R per unit time may be variable values.

In some embodiments, the number of ejections M per unit time and the number of rotations R per unit time may be fixed values.

In one embodiment, the lidar sensor 20 is of the mechanical rotation type, the predetermined angular pitch α is less than the divergence angle θ ₁ of the laser pulses 22 in the direction perpendicular to the axis of rotation 20a, and the method is such that the lidar sensor 20 is 1 The flight speed V of the unmanned aerial vehicle 1 is such that the flight distance J that the unmanned aerial vehicle 1 flies while rotating is shorter than the length K of the laser spot 24 formed in the forest 54 in the direction parallel to the aircraft traveling direction. , the number of revolutions per unit time R of the lidar sensor 20 and the altitude H of the unmanned aerial vehicle 1 .

In one embodiment, the above method changes at least one of the number of times M of pulse emission per unit time and the number of revolutions R at _one emission port for emitting the laser pulse 22, so that the divergence angle θ may include adjusting the predetermined angular pitch α such that

In some embodiments, unmanned aerial vehicle 1 may be an unmanned helicopter or an unmanned multicopter.

In some embodiments, the forest 54 may be a slope forest.

A forest measurement system 100 according to an embodiment of the present invention includes an unmanned aerial vehicle 1 and a computer device 70, and is a forest measurement system 100 for performing forest measurement on a forest 54 by flying the unmanned aerial vehicle 1. The unmanned aerial vehicle 1 includes a lidar (LiDAR) sensor 20, a first signal processing circuit 15g, a storage device 15j, and a first communication circuit 15f. The swing axis 20a is mounted on the unmanned aerial vehicle 1 so as to face the aircraft traveling direction, and the computer device 70 includes a display device 75, an input device 76, a second signal processing circuit 71 and a second communication circuit 73. , the second signal processing circuit 71 receives, via an input device 76, the number N of laser pulses 22 simultaneously emitted in the same angular direction, the frequency f of the laser pulses 22 emitted in the same angular direction, and a predetermined The designation of the angular pitch α is received, the designated number N, the frequency f, and the data of the predetermined angular pitch α are transmitted to the unmanned aerial vehicle 1 via the second communication circuit 73, and the first signal processing circuit 15g The data of the number N, the frequency f, and the predetermined angular pitch α are received via the communication circuit 15f, the received data of the number N, the frequency f, and the predetermined angular pitch α are stored in the storage device 15j, and the distance to the forest 54 is stored. is L, and the flight speed of the unmanned aerial vehicle 1 is V, the unmanned aerial vehicle 1 is flown so that the relative value of αL with respect to V/(fN) falls within a predetermined range, and the lidar sensor 20 is used to perform forest measurement targeting the forest 54 .

A computer program according to an embodiment of the present invention is a computer program that causes computers 15 and 70 to control forest measurement targeting a forest 54 by flying an unmanned aerial vehicle 1 equipped with a lidar (LiDAR) sensor 20. The rotation axis 20a or the swing axis 20a of the lidar sensor 20 is mounted on the unmanned aerial vehicle 1 so as to face the aircraft traveling direction, and the computer program uses the lidar sensor 20 to determine the emission direction of the laser pulse 22. The distance to the forest 54 is L, the flight speed of the unmanned aerial vehicle 1 is V, and the number of laser pulses 22 emitted simultaneously in the same angular direction is N. , where f is the frequency of the laser pulses 22 emitted in the same angular direction, and α is the predetermined angular pitch, the unmanned laser beam is arranged so that the relative value of αL with respect to V/(fN) falls within a predetermined range. The computers 15 and 70 are caused to control the forest measurement of the forest 54 using the lidar sensor 20 while the aircraft 1 is flying.

INDUSTRIAL APPLICABILITY The technology of the present invention can be suitably used when performing forest measurement, searching for victims, spraying chemicals, etc. for forests, particularly forests on slopes.

1: unmanned helicopter, 4: aircraft, 15: flight control box, 15a: GPS module, 15b: acceleration sensor, 15c: atmospheric pressure sensor, 15d: geomagnetic sensor, 15e: ultrasonic sensor, 15f: communication circuit, 15g: signal processing Circuit, 15h: ROM, 15i: RAM, 15j: Storage device, 15k: Internal bus, 20: LiDAR sensor, 22: Laser pulse, 50: Mountain, 52: Slope, 54: Forest (slope forest), 60: Flight path , 60a: first contour line (route segment), 60b: second contour line (route segment), 60c: route segment, 70: tablet computer, 71: CPU, 72: memory, 73: communication circuit, 74: image processing circuit, 75: Display, 76: Touch screen panel, 77: Communication bus, 80: Base station control device, 90: Contour data, 100: Forest measurement system

Claims (10)

A method for measuring a forest on a slope by flying an unmanned aerial vehicle equipped with a lidar (LiDAR) sensor, wherein the rotation axis or swing axis of the lidar sensor is oriented in the direction of movement of the aircraft. aboard the aircraft,
(i) scanning the forest with the lidar sensor while flying the unmanned aerial vehicle along a first contour line at a predetermined absolute altitude; rescanning the forest with the lidar sensor while flying along contour lines at the predetermined absolute altitude. 2. The method of claim 1, further comprising pre-designating said first contour, said second contour and said predetermined absolute altitude prior to said steps (i) and (ii). 3. The method according to claim 1, further comprising scanning the edge of the forest with the lidar sensor while flying the unmanned aerial vehicle over a position a predetermined distance away from the edge of the forest. described method. 4. A method according to any preceding claim, wherein the lidar sensor scans the canopy and trunk of each tree in the forest. 5. A method according to any preceding claim, wherein steps (i) and (ii) comprise causing the lidar sensor to scan the forest using horizontally emitted laser pulses. 6. A method according to any preceding claim, wherein steps (i) and (ii) comprise causing the lidar sensor to scan the forest using obliquely emitted laser pulses. 7. A method according to any preceding claim, wherein said unmanned aerial vehicle is an unmanned helicopter or an unmanned multicopter. A method for measuring a forest on a slope by flying an unmanned aerial vehicle equipped with a lidar (LiDAR) sensor, wherein the rotation axis or swing axis of the lidar sensor is oriented in the direction of movement of the aircraft. aboard the aircraft,
(i) scanning the forest with the lidar sensor while flying the unmanned aerial vehicle at a predetermined absolute altitude and a predetermined first true altitude; and (ii) moving the unmanned aerial vehicle to the predetermined absolute altitude and the rescanning the forest with the lidar sensor while flying at a second predetermined true altitude different from the first predetermined true altitude. A forest measurement system, comprising an unmanned aerial vehicle and a computer device, for measuring a forest on a slope by flying the unmanned aerial vehicle,
The unmanned aerial vehicle is
a lidar (LiDAR) sensor;
a first signal processing circuit;
a first storage device;
a first communication circuit, wherein the rotation axis or swing axis of the lidar sensor is mounted on the unmanned aerial vehicle so as to face the traveling direction of the aircraft;
The computer device comprises:
a display device;
an input device;
a second signal processing circuit;
a second storage device storing information about contour lines;
and a second communication circuit;
The second signal processing circuit is
obtaining information about the contour lines from the second storage device;
Receiving designation of the first contour line, the second contour line and the absolute altitude via the input device,
transmitting the designated first contour line, second contour line and absolute altitude data to the unmanned aerial vehicle via the second communication circuit;
The first signal processing circuit is
receiving data of the first contour line, the second contour line and the absolute altitude via the first communication circuit;
storing the received data of the first contour line, the second contour line and the absolute altitude in the first storage device;
scanning the forest with the lidar sensor while flying the unmanned aerial vehicle at the absolute altitude along the first contour;
rescanning the forest with the lidar sensor while flying the unmanned aerial vehicle along the second contour line at the absolute altitude;
Forest measurement system. A computer program that causes a computer to control forest measurement targeting forests on slopes by flying an unmanned aerial vehicle equipped with a lidar (LiDAR) sensor,
The rotation axis or swing axis of the lidar sensor is mounted on the unmanned aerial vehicle so as to face the aircraft traveling direction,
Said computer program comprises:
(i) scanning the forest with the lidar sensor while flying the unmanned aerial vehicle along a first contour line at a predetermined absolute altitude; A computer program that causes the computer to control rescanning of the forest with the lidar sensor while flying along contour lines at the predetermined absolute altitude.

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