Unmanned aerial vehicle and unmanned aerial vehicle control method

Abstract

This unmanned aerial vehicle has a plurality of rotors. The plurality of rotors include a plurality of first rotors and at least one second rotor. The unmanned aerial vehicle further includes an angle adjustment mechanism for setting the angle of inclination of the second rotor to a horizontal plane perpendicular to a vertical direction to be smaller than the angle of inclination of an airframe of the unmanned aerial vehicle to the horizontal plane when the airframe tilts with respect to the horizontal plane during a flight of the unmanned aerial vehicle. The unmanned aerial vehicle control method is a method for controlling an unmanned aerial vehicle having a plurality of rotors, the plurality of rotors including a plurality of first rotors and at least one second rotor, and the method including the step for setting the angle of inclination of the second rotor to a horizontal plane perpendicular to a vertical direction to be smaller than the angle of inclination of an airframe of the unmanned aerial vehicle to the horizontal plane when the airframe tilts with respect to the horizontal plane during a flight of the unmanned aerial vehicle.

Description

Unmanned aerial vehicle and method for controlling unmanned aerial vehicle

[0001] The present disclosure relates to unmanned aerial vehicles and methods for controlling unmanned aerial vehicles.

[0002] An unmanned aerial vehicle (UAV) is an aircraft that cannot carry a person due to its structure and can fly by remote control or automatic pilot. Rotary-wing unmanned aerial vehicles are unmanned aerial vehicles that obtain lift using propellers that rotate around an axis, i.e., rotors. Small unmanned aerial vehicles equipped with multiple rotors (multi-rotor UAVs) are also called "drones," "multirotors," or "multicopters," and are widely used for applications such as aerial photography, surveying, logistics, and pesticide spraying.

[0003] Patent Document 1 describes an unmanned aerial vehicle (unmanned flying object) that changes its flight position in conjunction with the operation of agricultural machinery.

[0004] Japanese Patent Application Laid-Open No. 2022-104737

[0005] There is a demand for efficient control of the flight of unmanned aerial vehicles.

[0006] The present disclosure provides an unmanned aerial vehicle and a control method for an unmanned aerial vehicle that can efficiently control flight.

[0007] In an exemplary and non-limiting embodiment, the unmanned aerial vehicle of the present disclosure is an unmanned aerial vehicle equipped with multiple rotors, the multiple rotors including multiple first rotors and at least one second rotor, and further equipped with an angle adjustment mechanism that, when the aircraft tilts with respect to a horizontal plane perpendicular to the vertical direction during flight of the unmanned aerial vehicle, makes the tilt angle of the second rotor with respect to the horizontal plane smaller than the tilt angle of the aircraft with respect to the horizontal plane.

[0008] In an exemplary and non-limiting embodiment, the method for controlling an unmanned aerial vehicle disclosed herein is a method for controlling an unmanned aerial vehicle having multiple rotors, wherein the multiple rotors include multiple first rotors and at least one second rotor, and when the aircraft tilts with respect to a horizontal plane perpendicular to the vertical direction during flight of the unmanned aerial vehicle, the method includes making the angle of inclination of the second rotor with respect to the horizontal plane smaller than the angle of inclination of the aircraft with respect to the horizontal plane.

[0009] According to an embodiment of the present disclosure, an unmanned aerial vehicle and a control method for an unmanned aerial vehicle are provided that enable efficient flight control.

[0010] 1 is a block diagram schematically showing several examples of a rotary drive device that rotates rotors in an unmanned aerial vehicle having multiple rotors. FIG. 2 is a plan view schematically showing one basic configuration example of an unmanned aerial vehicle having multiple rotors. FIG. 3 is a side view schematically showing one basic configuration example of an unmanned aerial vehicle having multiple rotors. FIG. 4 is a plan view schematically showing another basic configuration example of an unmanned aerial vehicle having multiple rotors. FIG. 5 is a block diagram showing a basic configuration example of a battery-powered multicopter. FIG. 6 is a block diagram showing a basic configuration example of a series hybrid drive multicopter. FIG. 7 is a block diagram showing a basic configuration example of a parallel hybrid drive multicopter. FIG. 8 is a top view schematically showing a multicopter according to an embodiment of the present disclosure. FIG. 9 is a side view schematically showing a multicopter according to an embodiment of the present disclosure. FIG. 10 is a block diagram showing an example of a system configuration of a multicopter according to an embodiment of the present disclosure. FIG. 11 is a schematic diagram for explaining a method of controlling flight of a multicopter in tilt mode. FIG. 12 is a schematic diagram for explaining a method of controlling flight of a multicopter in tilt mode. FIG. 13 is a schematic diagram for explaining a method of controlling flight of a multicopter in level maintenance mode. FIG. 1 is a schematic diagram for explaining a method of controlling flight of a multicopter in a horizontal maintenance mode. FIG. 2 is a top view schematically showing an example of the configuration of an angle adjustment mechanism of a multicopter. FIG. 3 is a side view schematically showing another example of a multicopter having an angle adjustment mechanism. FIG. 4 is a block diagram showing an example of a configuration in which a sensor, a processing device, a storage device, a control device, and a communication device are connected to a bus. FIG. 5 is a flowchart showing an example of the operation of a control device in an embodiment of the present disclosure. FIG. 6 is a schematic diagram showing an example of the configuration of a system including a multicopter.

[0011] An unmanned aerial vehicle with multiple rotors includes a rotary drive unit that rotates the rotors (hereinafter sometimes referred to as "propellers"). Hereinafter, such an unmanned aerial vehicle will be referred to as a "multicopters."

[0012] There are various configurations of the rotary drive device provided in a multicopter. Fig. 1A is a block diagram schematically illustrating four examples of the rotary drive device 3 in the present disclosure.

[0013] The first rotation drive device 3A shown in FIG. 1A has a plurality of electric motors (hereinafter referred to as "motors") 14 that rotate a plurality of rotors 2, and a battery 52 that stores power to be supplied to each motor 14. The battery 52 is, for example, a secondary battery such as a polymer lithium-ion battery. Each rotor 2 is connected to the output shaft of the corresponding motor 14 and rotated by the motor 14. In order to increase the payload and / or flight time, it is necessary to increase the power storage capacity of the battery 52. ​​The power storage capacity of the battery 52 can be increased by increasing the size of the battery 52, but increasing the size of the battery 52 results in an increase in weight.

[0014] The second rotation drive device 3B shown in FIG. 1A includes a power transmission system 23 mechanically connected to the rotor 2 and an internal combustion engine 7a that provides driving force (torque) to the power transmission system 23. The power transmission system 23 includes mechanical components such as gears or belts, and transmits torque from the output shaft of the internal combustion engine 7a to the rotor 2. The internal combustion engine 7a can efficiently generate mechanical energy by burning fuel. Examples of the internal combustion engine 7a include a gasoline engine, a diesel engine, and a hydrogen engine. The number of internal combustion engines 7a included in the rotation drive device 3B is not limited to one.

[0015] The third rotary drive device 3C shown in FIG. 1A includes multiple motors 14, a power buffer 9 that stores power to be supplied to each motor 14, a power generator 8 such as an alternator that generates power, and an internal combustion engine 7a that provides mechanical energy for the power generator 8 to generate electricity. A typical example of the power buffer 9 is a battery such as a secondary battery, but it may also be a capacitor. In the third rotary drive device 3C, even if the power buffer 9 does not have a large storage capacity, the power generator 8 generates power using the driving force (mechanical energy) of the internal combustion engine 7a, thereby enabling an increase in payload and / or flight time. This type of drive is called a "series hybrid drive." The power generator 8 and internal combustion engine 7a in the series hybrid drive are called a "range extender" because they extend the flight distance of the multicopter.

[0016] 1A includes a plurality of motors 14, a power buffer 9 that stores power to be supplied to each motor 14, a power generator 8 such as an alternator that generates power, an internal combustion engine 7a that provides driving force for generating power to the power generator 8, and a power transmission system 23 that transmits the driving force generated by the internal combustion engine 7a to a rotor 2 to rotate the rotor 2. At least one rotor 2 of the plurality of rotors 2 is rotated by the internal combustion engine 7a, and the other rotors 2 are rotated by the motor 14. In the fourth rotary drive device 3D, the mechanical energy generated by the internal combustion engine 7a can also be used to rotate the rotor 2 without being converted into electric power, thereby improving energy utilization efficiency. This type of drive is called a "parallel hybrid drive."

[0017] Fig. 1B is a plan view schematically illustrating one basic configuration example of multicopter 10. The configuration example of Fig. 1B includes the first rotational drive device 3A shown in Fig. 1A as the rotational drive device 3. That is, the rotational drive device 3 (3A) in this example includes a motor 14 and a battery 52. ​​Fig. 1C is a side view schematically illustrating multicopter 10.

[0018] 1B and 1C includes a plurality of rotors 2, an airframe 4, and an airframe frame 5 that supports the rotors 2 and the airframe 4. The airframe frame 5 supports the airframe 4 at its center and rotatably supports the plurality of rotors 2 with a plurality of arms 5A extending outward from the center. A motor 14 that rotates the rotors 2 is provided near the tip of each arm 5A. The airframe 4 and the airframe frame 5 are sometimes collectively referred to as the "airframe 11."

[0019] 1B, the multicopter 10 is a quad-type multicopter (quadcopter) having four rotors 2. The rotors 2 located on one diagonal line rotate in the same direction (clockwise or counterclockwise), while the rotors 2 located on different diagonal lines rotate in opposite directions.

[0020] The main body 4 includes a control device 4a that controls the operation of devices and components mounted on the multicopter 10, a group of sensors 4b connected to the control device 4a, a communication device 4c connected to the control device 4a, and a battery 52.

[0021] The control device 4 a may include, for example, a flight control device such as a flight controller and a host computer (companion computer). The companion computer can perform advanced arithmetic processing such as image processing, obstacle detection, and obstacle avoidance based on the sensor data acquired by the sensor group 4 b.

[0022] The sensor group 4b may include an acceleration sensor, an angular velocity sensor, a geomagnetic sensor, a barometric pressure sensor, an altitude sensor, a temperature sensor, a flow rate sensor, an imaging device, a laser sensor, an ultrasonic sensor, an obstacle contact sensor, and a Global Navigation Satellite System (GNSS) receiver. The acceleration sensor and the angular velocity sensor may be mounted on the airframe main body 4 as components of an IMU (Inertial Measurement Unit). Examples of the laser sensor may include, for example, a laser range finder used to measure the distance to the ground, and a two-dimensional or three-dimensional light detection and ranging (LiDAR).

[0023] The communication device 4c may include a wireless communication module for transmitting and receiving signals via an antenna to a transmitter or ground station (Ground Control Station (GCS)) on the ground, a mobile communication module using a cellular communication network, etc. The communication device 4c may receive signals such as control commands transmitted from the ground and transmit sensor data such as image data acquired by the sensor group 4b as telemetry information. The communication device 4c may have a function for communicating between multicopters and a satellite communication function. The control device 4a can be connected to a computer on the cloud via the communication device 4c. Some or all of the functions of the companion computer may be performed by the computer on the cloud.

[0024] The battery 52 is a secondary battery that can store power by charging and supply power to the motors 14 by discharging. The battery 52 and the multiple motors 14 operate to rotate the multiple rotors 2, generating a desired thrust. Each of the multiple rotors 2 typically has multiple blades with a fixed pitch angle, generating thrust through rotation. The pitch angle may be variable. The multiple rotors 2 do not all need to have the same diameter (propeller diameter); one or more rotors 2 may have a larger diameter than the other rotors 2. The thrust (static thrust) generated by the rotating rotors 2 is generally proportional to the cube of the rotor 2 diameter. Therefore, when rotors 2 with different diameters are included, the rotor 2 with the larger diameter may be referred to as the "main rotor," and the rotor 2 with the smaller diameter may be referred to as the "sub-rotor." Regardless of the diameter, the configuration of the rotary drive device 3 may include rotors 2 with a relatively larger thrust and rotors 2 with a relatively smaller thrust. In this case, the rotor 2 capable of generating a relatively large thrust may be referred to as the "main rotor," and the rotor 2 capable of generating a relatively small thrust may be referred to as the "sub-rotor." For example, the rotor 2 capable of generating a relatively large thrust per rotation may be referred to as the "main rotor," and the rotor 2 capable of generating a relatively small thrust per rotation may be referred to as the "sub-rotor." In one example, the main rotor may be disposed more inward than the sub-rotors. In other words, each rotor 2 may be disposed so that the distance from the center of the aircraft to the rotation axis of each main rotor is shorter than the distance from the center of the aircraft to the rotation axis of each sub-rotor.

[0025] In this example, the rotary drive device 3 includes a plurality of motors 14. As mentioned above, the rotary drive device 3 may include an internal combustion engine 7a.

[0026] FIG. 1D is a plan view schematically illustrating an example of the basic configuration of a multicopter 10 including a second rotational drive device 3B as the rotational drive device 3. In the example shown in FIG. 1D , an internal combustion engine 7a is supported by the airframe main body 4. In this example, the driving force generated by the internal combustion engine 7a is transmitted to multiple rotors 2 via multiple power transmission systems 23, causing each rotor 2 to rotate. The control device 4a can change the rotational speed of each rotor 2 by controlling each power transmission system 23. The rotational drive device 3B may include a mechanism for changing the pitch angle of the blades of each of the multiple rotors 2. In this case, the control device 4a may adjust the lift generated by each rotor 2 by controlling the mechanism to change the pitch angle of the blades.

[0027] In a "parallel hybrid drive" in which some of the multiple rotors 2 are rotated by the internal combustion engine 7a and the other rotors 2 are rotated by the motor 14, the internal combustion engine 7a and the battery 52 are supported on the aircraft body 4. At least one rotor 2 of the multiple rotors 2 is connected to the internal combustion engine 7a via the power transmission system 23, and the other rotors 2 are connected to the motor 14.

[0028] In such a parallel hybrid drive, the diameter of one or more rotors 2 rotated by the internal combustion engine 7a may be larger than the diameter of the other rotors 2 rotated by the motor 14. In other words, the internal combustion engine 7a may be used to rotate the main rotor, and the motor 14 may be used to rotate the sub-rotor. In such a case, the main rotor is primarily used to generate thrust, and the sub-rotor is used to generate thrust and for attitude control. The main rotor may also be called a "booster rotor," and the sub-rotor may also be called an "attitude control rotor."

[0029] In the case of a parallel hybrid drive, the internal combustion engine is used for both thrust generation and power generation. By selectively transmitting the driving force (torque) generated by the internal combustion engine to one or both of the rotor and the power generator, it is possible to achieve a good balance between thrust generation and power generation.

[0030] Equipping a multicopter with an internal combustion engine and using it to generate thrust and / or electricity contributes to increased payload and flight time. It is desirable to control the attitude of a multicopter by rotating the propellers with a motor, which has better response characteristics than an internal combustion engine. Therefore, in applications requiring precise control of the multicopter's attitude, it is desirable to employ a parallel hybrid drive or series hybrid drive to increase the payload and flight time. If the rotary drive device 3 is equipped with a mechanism for changing the pitch angle of each blade of the multiple rotors 2, the attitude can also be adjusted by changing the pitch angle of each blade.

[0031] Increased payload and flight time may further expand the applications of multicopters. For example, in the agricultural field, multicopters are currently being used for spraying pesticides or monitoring crop growth conditions. However, by connecting various ground implements (hereinafter, sometimes simply referred to as "implements") to a multicopter, various agricultural tasks can be performed from the air. Agricultural implements are sometimes called "implements." Examples of implements include sprayers that spray pesticides on crops, mowers, seeders, spreaders, rakes, balers, harvesters, plows, harrows, or rotary tillers. Work vehicles such as tractors are not included in the "implements" of this disclosure.

[0032] In the example shown in FIG. 1C , a work implement 200 is coupled to the multicopter 10. The work implement 200 can spray, for example, pesticides or fertilizers on a field or crops within the field. Increasing the payload and flight time allows for a larger and / or more versatile work implement 200. For example, by changing the work implement 200 coupled to the multicopter 10, a variety of ground tasks (agricultural operations) can be performed, including liquid and granular application of pesticides, fertilization, thinning, weeding, transplanting, direct seeding, and harvesting. The work implement 200 may be equipped with a mechanism such as a robotic hand. In this case, a single work implement 200 can perform a variety of ground tasks. If the work implement 200 has a sufficient space to accommodate materials, the work implement 200 can also be used to transport agricultural materials or harvested products over a wide area. The work implement 200 can be coupled to the multicopter 10 in a variety of ways. The multicopter 10 may suspend and tow the work machine 200 by a cable. The work machine 200 towed by the multicopter 10 can also perform ground work while being towed while the multicopter 10 is flying or hovering. The work machine 200 during work may be in the air or on the ground.

[0033] 1C , the multicopter 10 includes a power supply device 76. The power supply device 76 is a device that supplies power to the work machine 200 from a drive energy source, such as the battery 52 or the power generation device 8, included in the multicopter 10. Various functions of the work machine 200 can be performed using this power. The work machine 200 includes actuators such as motors that operate using power obtained from the power supply device 76 of the multicopter 10. The work machine 200 preferably includes a battery that stores power.

[0034] FIG. 2A is a block diagram showing an example of the basic configuration of a battery-powered multicopter 10.

[0035] The battery-powered multicopter 10 includes multiple rotors 12, multiple motors 14 for rotating the rotors 12, multiple electric speed controllers (ESCs) 16 each having a motor drive circuit for driving the motors 14, a battery 52 for supplying power to the corresponding motors 14 via each ESC 16, a control device 4a for controlling the ESCs 16 to control attitude and flight, a sensor group 4b, a communication device 4c, and a power supply device 76 electrically connected to the battery 52. ​​For simplicity, FIG. 2A shows the rotors 12, motors 14, and ESCs 16 as a single block, but the number of rotors 12, motors 14, and ESCs 16 is actually multiple. This also applies to FIGS. 2B and 2C. The ESC 16 may be included in the control device 4a.

[0036] The control device 4a can receive control commands wirelessly, for example, from a ground station 6 located on the ground via the communication device 4c. The number of ground stations 6 is not limited to one and may be distributed across multiple locations. The communication device 4c can also receive control commands wirelessly from a control device operated by a pilot on the ground. The control device 4a may have the function of automatically or autonomously performing takeoff, flight, obstacle avoidance, and landing operations based on sensor data obtained from the sensor group 4b. The control device 4a may be configured to communicate with the work machine 200 connected to the power supply device 76 and acquire a signal indicating the status of the work machine 200 from the work machine 200. The control device 4a may also provide the work machine 200 with a signal that controls the operation of the work machine 200. Furthermore, the work machine 200 may generate a signal instructing the operation of the multicopter 10 and transmit it to the control device 4a. Such communication between the control device 4a and the work machine 200 can be performed via wired or wireless communication.

[0037] FIG. 2B is a block diagram showing an example of the basic configuration of a series hybrid drive multicopter 10. Similar to the battery-powered multicopter 10, the series hybrid drive multicopter 10 includes multiple rotors 12, multiple motors 14, multiple ESCs 16, a control device 4a, a sensor group 4b, and a communication device 4c. The illustrated series hybrid drive multicopter 10 further includes an internal combustion engine 7a, a fuel tank 7b for storing fuel for the internal combustion engine 7a, a power generation device 8 driven by the internal combustion engine 7a to generate electric power, a power buffer 9 for temporarily storing the electric power generated by the power generation device 8, and a power supply device 76 electrically connected to the power buffer 9. The power buffer 9 is, for example, a battery such as a secondary battery. The electric power generated by the power generation device 8 is supplied to the motor 14 via the power buffer 9 and the ESC 16. The electric power generated by the power generation device 8 may also be supplied to the work machine 200 via the power supply device 76.

[0038] FIG. 2C is a block diagram showing an example of the basic configuration of a parallel hybrid drive multicopter 10. Similar to the series hybrid drive multicopter 10, the parallel hybrid drive multicopter 10 includes multiple rotors 12, multiple motors 14 that respectively drive the multiple rotors 12, multiple ESCs 16, a control device 4a, a sensor group 4b, a communication device 4c, an internal combustion engine 7a, a fuel tank 7b, a power generator 8, a power buffer 9, and a power supply device 76. The parallel hybrid drive multicopter 10 further includes a drive train 27 that transmits the driving force of the internal combustion engine 7a, and a rotor 22 that rotates by receiving the driving force of the internal combustion engine 7a from the drive train 27. One of the rotor 12 and the rotor 22 may be referred to as the “first rotor” and the other as the “second rotor” to distinguish them from each other. The number of rotors 22 connected to the drive train 27 and rotating may be one or more.

[0039] In the parallel hybrid drive multicopter 10, the internal combustion engine 7a not only drives the power generation device 8 to generate electricity, but also mechanically transmits energy to the rotor 22 to rotate the rotor 22. On the other hand, in the series hybrid drive multicopter 10, all of the rotors 12 are rotated by the electric power generated by the power generation device 8. For this reason, in the series hybrid drive multicopter 10, if the power generation device 8 is, for example, a fuel cell, the internal combustion engine 7a is not an essential component.

[0040] Below, an example of the configuration and operation of an unmanned aerial vehicle according to an embodiment of the present disclosure will be described, taking a multicopter that uses parallel hybrid drive as an example.

[0041] <Basic Configuration> Fig. 3A is a schematic top view of the multicopter 100 according to this embodiment, and Fig. 3B is a side view thereof. Fig. 3B illustrates a work implement 200 coupled to the multicopter 100. In addition to or instead of the work implement 200, luggage, agricultural materials, other machinery, or containers, cases, or packages capable of accommodating these items may be coupled to the multicopter 100. Hereinafter, the weight of the work implement 200 and the work implement itself may be referred to as the "payload." The "coupling" between the multicopter 100 and the work implement 200 or the like may be performed using various tools or devices.

[0042] The multicopter 100 shown in FIG. 3A includes eight sub-rotors 12 and two main rotors 22. Each sub-rotor 12 is composed of four sets of propellers 12a and 12b that rotate coaxially and in opposite directions. Each of the propellers 12a and 12b has two blades. The propellers 12a and 12b are rotated by a motor 14. The four sets of propellers 12a and 12b that rotate coaxially and in opposite directions are located at the vertices of a square. The main rotor 22 is composed of two propellers 22a that rotate in opposite directions at different positions. Each propeller 22a has four blades. The eight propellers 12a and 12b of the sub-rotor 12 have the same pitch angle and diameter. The two propellers 22a of the main rotor 22 also have the same pitch angle and diameter. The diameter of the propeller 22a is 1.2 times or more, for example, 1.4 times or more and 2.0 times or less, the diameter of the propellers 12a and 12b.

[0043] The multicopter 100 includes an airframe 110 having four arms 110A for the sub-rotors 12 and two arms 110B for the main rotors 22. The airframe frame 110 supports an airframe main body 120 that includes various electronic and mechanical components, which will be described later. The airframe main body 120 and the airframe frame 110 may be collectively referred to as an "airframe 121."

[0044] In the example of FIG. 3B , the airframe main body 120 has a power supply device 76 and an actuator 78 used for coupling to the work machine 200, etc. The power supply device 76 is a device that supplies power generated within the airframe main body 120 to the work machine 200. The actuator 78 is a device such as an electric motor that performs an operation to couple the work machine 200 to the airframe main body 120 of the multicopter 100. In the example of FIG. 3B , the actuator 78 drives a mechanism that winds up a cable connecting the airframe main body 120 and the work machine 200. This cable may include a power supply line for supplying power from the multicopter 100 to the work machine 200, and a communication line for communication between the multicopter 100 and the work machine 200.

[0045] <System Configuration> FIG. 4 is a block diagram showing an example of a system configuration of the multicopter 100 according to this embodiment.

[0046] In the illustrated example, the airframe 120 of the multicopter 100 has a control device 30 including a flight controller 32, a sensor group 72, and a communication device 74. These are basically the same as the control device 4a, the sensor group 4b, and the communication device 4c of the airframe 4 of the multicopter 10 described with reference to FIG. 1A.

[0047] The multicopter 100 of this embodiment includes eight sub-rotors 12, eight motors 14 for rotating the eight sub-rotors 12, and eight ESCs for controlling the eight motors 14. Each ESC 16 receives a signal (motor control signal) for controlling the motor 14 from the control device 30 via a wiring 82. The motor control signal is, for example, a PWM (Pulse With Modulation) signal. When the motor control signal is a PWM signal, the duty cycle of the PWM signal can indicate an analog value of the motor rotation speed. Each ESC 16 controls the rotation speed of the motor 14 connected to that ESC 16 based on the motor control signal from the control device 30. While FIG. 4 illustrates one set of "sub-rotors 12, motors 14, and ESCs 16" for simplicity, the multicopter 100 of this embodiment includes eight sets of "sub-rotors 12, motors 14, and ESCs 16." The number of these sets is not limited to eight.

[0048] The control device 30 is connected to each of the ESCs 16 via electrically independent wiring 82, and can individually control each of the eight ESCs 16. As described above, the sub-rotors 12 are used not only to generate lift but also for attitude control. Attitude control is achieved by the flight controller 32 of the control device 30 obtaining measured or estimated values ​​indicating the attitude of the airframe 120 from the sensors 72, determining the current attitude of the airframe 120, and controlling the rotational speed of each of the motors 14 in accordance with the difference from the target attitude.

[0049] The aircraft body 120 includes a main rotor drive unit 24 that drives the main rotor 22 and a main rotor control unit 26 that controls the main rotor drive unit 24. In this embodiment, the main rotor drive unit 24 is an internal combustion engine. Therefore, the main rotor control unit 26 includes an engine control unit (ECU). The main rotor control unit 26 acquires sensor data such as the accelerator opening, intake air temperature, engine speed, and temperatures of various components of the main rotor drive unit 24, which is an internal combustion engine, and controls the internal combustion engine. The main rotor control unit 26 is connected to the control device 30 via wiring 82, such as a CAN (Controller Area Network) bus. The main rotor control unit 26 is configured to output an engine control signal based on a signal transmitted from the control device 30. The engine control signal includes, for example, a throttle opening. A digital-to-analog converter (DAC) and / or a voltage converter may be connected between the control device 30 and the main rotor control unit 26. A mechanical device such as a clutch and a reducer may be provided between the main rotor drive section 24 and the main rotor 22.

[0050] The main rotor drive unit 24 is preferably an internal combustion engine with little vibration. In this embodiment, the main rotor drive unit 24 is, for example, an opposed-piston engine. Opposed-piston engines are disclosed, for example, in Japanese Patent No. 5508604. The entire contents of Japanese Patent No. 5508604 are incorporated herein by reference.

[0051] The main rotor drive unit 24, which is an internal combustion engine, can generate electricity by driving a power generator 42, such as an alternator. In this embodiment, the power generator 42 has the structure of an AC synchronous motor having a rotor and a stator. Therefore, when the main rotor drive unit 24 is started, the power generator 42 can also function as a "starter" by rotating the rotor when current is applied. The power generator 42 rectifies the AC generated by power generation and converts it into DC. The power generator 42 generates DC power required to drive the motor 14 and supplies it to each ESC 16 via wiring 80. The power generator 42 is configured to output a DC voltage of, for example, 250 V or higher. Note that the wiring 80 is a power wiring, and the wiring 82 is a signal wiring. Each of the wirings 80 and 82 includes multiple conductors.

[0052] The power generation device 42 is connected to a power management device 44. The power management device 44 is connected to the control device 30 and a battery management device 54, which will be described later. The power management device 44 can control the amount of power generated by the power generation device 42 based on signals from the control device 30 or the battery management device 54. This amount of power generation can be variably controlled by the power management device 44 in accordance with the power required by the motor 14 and the battery 52, even when the engine speed of the main rotor drive unit 24, which is an internal combustion engine, is constant.

[0053] The aircraft body 120 further includes a battery 52 in the form of a plurality of cells, for example, lithium ion secondary batteries, connected in series or in parallel, and a battery management device 54 that controls the charging and discharging of the battery 52 .

[0054] The battery 52 receives DC power from the power generation device 42 via a power switch 56 and can be charged by the power. The operation of the power switch 56 can be controlled by a battery management unit 54 and the control device 30. The battery management unit 54 is a device that measures or estimates parameter values ​​that define the state of the battery 52, such as the current flowing through the battery 52, cell voltage, cell balance, state of charge (SOC), state of health (SOH), and temperature.

[0055] The battery management unit 54 can control the power switch 56 depending on the state of the battery 52. ​​For example, when the battery 52 is in a state requiring charging, the battery management unit 54 electrically connects the power generation device 42 and the battery 52 using the power switch 56, and supplies power from the power generation device 42 to the battery 52 to perform a charging operation. At this time, the battery management unit 54 controls the power management unit 44 to increase the amount of power generated by the power generation device 42 so that the power supplied to the ESC 16 does not drop below a desired level. On the other hand, when the battery 52 is in a state requiring no charging, the battery management unit 54 disconnects the electrical connection between the power generation device 42 and the battery 52 using the power switch 56, and stops charging the battery 52.

[0056] In this embodiment, the battery 52 has a storage capacity that allows the aircraft to continue to fly to a location where landing is possible and land there, by continuing to generate lift and control attitude using the sub-rotor 12, even if power generation by the power generation device 42 stops for some reason and lift from the main rotor 22 is lost. In other words, when the multicopter 100 of this embodiment is flying normally, the power required to drive the sub-rotor 12 can be supplied to the ESC 16 from the power generation device 42, rather than from the battery 52. ​​Therefore, even if the payload and flight time are increased, there is little need to increase the storage capacity of the battery 52 accordingly.

[0057] The power stored in the battery 52 can be output as a DC voltage of, for example, 250 V or higher. However, this DC voltage decreases as the charging rate decreases. Therefore, when the charging rate falls below a predetermined level, the battery management device 54 operates to supply part of the DC power from the power generation device 42 to the battery 52 to charge the battery 52.

[0058] The battery 52 is connected to a power circuit board 60. The power circuit board 60 has a function of stepping down the voltage output from the battery 52 to, for example, 24 V, 12 V, or 5 V. The DC voltage output from the battery 52 is converted to a desired voltage by the power circuit board 60 and then supplied to other electronic components. In the example of FIG. 4 , the power stepped down by the power circuit board 60 is supplied to the control device 30 and the actuator 78 via wiring 80.

[0059] 4 , the power supply device 76 is electrically connected to the power generation device 42 or the battery 52 by a power switch 56. The power supply device 76 in this example is configured to supply power generated within the machine body 120 to an external machine or device such as a work machine 200.

[0060] The airframe main body 120 may have a configuration not shown in FIG. 4 . For example, the airframe main body 120 may include a fuel tank that stores fuel necessary for the operation of the main rotor drive unit 24, a water-cooling or air-cooling device for cooling the main rotor drive unit 24, and electrical components such as lighting devices and an electric pump. The electrical components can be operated by power that has been stepped down to a predetermined voltage by the power circuit board 60. A battery for the electrical components (auxiliary battery) may be provided and configured to supply power to the electrical components. Such an auxiliary battery may be charged by the battery 52 or the power generation device 42.

[0061] As described above, there are various configurations of multicopters according to embodiments of the present disclosure. In all configurations, the multicopters 10 (100) generate thrust by rotating multiple rotors 12 (22). This thrust creates lift that counteracts gravity acting on the multicopters 10 and the work vehicle 200 during flight. Here, "in flight" is not limited to horizontal movement, but broadly encompasses ascending, descending, and hovering states. Of the multiple rotors 2 possessed by the multicopters 10 (100), the rotor 2 capable of generating a relatively large thrust may be referred to as the "main rotor (main rotor 22)," and the rotor 2 capable of generating a relatively small thrust may be referred to as the "sub-rotor (sub-rotor 12)." The main rotor is primarily used to generate thrust, and the sub-rotors may be used for thrust generation and attitude control. For example, as shown in the example of FIG. 3A, the diameter of the main rotor 22 is larger than the diameter of the sub-rotors 12, and as a result, the total thrust that can be generated by the rotation of the main rotor 22 is larger than the total thrust that can be generated by the rotation of the sub-rotors 12.

[0062] A multicopter according to an embodiment of the present disclosure further includes an angle adjustment mechanism that, when the airframe tilts relative to a horizontal plane perpendicular to the vertical direction during flight, can reduce the tilt angle of the main rotor relative to the horizontal plane compared to the tilt angle of the airframe relative to the horizontal plane. When the airframe tilts relative to a horizontal plane perpendicular to the vertical direction, it is preferable that the tilt angle of the main rotor relative to the horizontal plane be maintained small. Ideally, it is preferable that the main rotor be kept parallel to the horizontal plane. For example, it is preferable that the tilt angle of the main rotor relative to the horizontal plane be 5° or less. "The main rotor is parallel to the horizontal plane" means that the rotation axis of the main rotor is parallel to the vertical direction. The extension direction of the blades of the main rotor may be perpendicular to the rotation axis of the main rotor. When the tilt angle of the main rotor relative to the horizontal plane is 5° or less, the tilt angle of the rotation axis of the main rotor relative to the vertical direction is 5° or less.

[0063] 3A, 3B, and 4, the main rotor 22 is driven by a main rotor drive unit (internal combustion engine), but the main rotor 22 may also be driven by an electric motor. The following describes an example in which the main rotor 22 is driven by an electric motor.

[0064] 5A, 5B, 6A, and 6B, an example of a multicopter 100a and a method for controlling flight of the multicopter 100a according to this embodiment will be described. The control device 4a can control flight of the multicopter 100a in a plurality of modes, including the mode illustrated in FIGS. 6A and 6B (sometimes referred to as the "first mode" or "horizontal maintenance mode") and the mode illustrated in FIGS. 5A and 5B (sometimes referred to as the "second mode" or "tilt mode").

[0065] The multicopter 100a shown in FIGS. 5A, 5B, 6A, and 6B differs from the multicopter 100 shown in FIGS. 3A and 3B in that the main rotor 22 and the sub-rotor 12 are each rotated by a motor. Each of the multicopter 100a shown in FIGS. 5A, 5B, 6A, and 6B includes multiple motors 25 that drive the main rotors 22. The multicopter 100a includes an angle adjustment mechanism that, when the airframe 121 is tilted relative to a horizontal plane perpendicular to the vertical direction, can reduce the tilt angle of the main rotor 22 relative to the horizontal plane to a value smaller than the tilt angle of the airframe 121 relative to the horizontal plane. The angle adjustment mechanism can, for example, maintain the tilt angle of the rotation shaft 22z of the motor 25 that rotates the main rotor 22 relative to the vertical direction to a value smaller than the tilt angle of the airframe 121 relative to the horizontal plane. An example of a specific configuration of the angle adjustment mechanism will be described later with reference to FIG. 6C. Note that the multicopter according to the embodiment of the present disclosure is not limited to this and may be applied to any of the other configuration examples described above. For example, when applied to a configuration in which the main rotor is driven, such as the multicopter 100 shown in Figures 3A, 3B, and 4, it is preferable that the inclination angle of the main rotor and internal combustion engine relative to the horizontal plane can be maintained smaller than the inclination angle of the airframe relative to the horizontal plane when the airframe is tilted relative to the horizontal plane. Furthermore, the number, shape, arrangement, etc. of the main rotors and sub-rotors of the multicopter according to the embodiment of the present disclosure are not limited to the examples shown in the figures.

[0066] FIG. 5A is a schematic diagram illustrating a first tilt angle θ of the multicopter 100a with respect to a first direction D1 that is perpendicular to the vertical direction. FIG. 5B is a schematic diagram illustrating a second tilt angle Ψ of the multicopter 100a with respect to a second direction D2 that is perpendicular to the vertical direction and perpendicular to the first direction. In the examples shown in FIGS. 5A and 5B , the first direction D1, the second direction D2, and the third direction D3 are perpendicular to one another. The first direction D1 and the second direction D2 are each horizontal, and the third direction D3 is a vertical direction. The first direction D1 is perpendicular to the third direction D3. The second direction D2 is also perpendicular to the first direction D1 and the third direction D3. In this way, the first direction D1 and the second direction D2 are perpendicular to one another in the same horizontal plane that is perpendicular to the third direction D3. However, the first direction D1 and the second direction D2 do not necessarily have to be perpendicular to one another and may intersect in the same horizontal plane.

[0067] 5A and 5B show a Cartesian coordinate system with mutually orthogonal X-, Y-, and Z-axes, respectively corresponding to the roll, pitch, and yaw axes fixed to the multicopter 100a. FIGS. 1B, 1C, 1D, 3A, and 3B show examples of Cartesian coordinate systems with X-, Y-, and Z-axes, respectively corresponding to the roll, pitch, and yaw axes fixed to the multicopter 10 (100). The rotation of the multicopter 100a around the X-axis is roll, the rotation of the multicopter 100a around the Y-axis is pitch, and the rotation of the multicopter 100a around the Z-axis is yaw. The sensor 81 (see FIG. 7) included in the sensor group 4b has this Cartesian coordinate system and is capable of detecting the rotation angles around the X-, Y-, and Z-axes, i.e., the roll angle, pitch angle, and yaw angle.

[0068] 5A illustrates a state in which the multicopter 100a rotates by an angle θ around the X-axis (roll axis) during flight. The tilt angle θ of the airframe 121 of the multicopter 100a with respect to the first direction D1 is sometimes referred to as the first tilt angle. The first tilt angle θ is expressed as the angle between the first direction D1 and the Y-axis (pitch axis). In other words, the first tilt angle θ is determined by the roll angle of the multicopter 100a.

[0069] 5B illustrates a state in which the multicopter 100a rotates by an angle Ψ around the Y-axis (pitch axis) during flight. The tilt angle Ψ of the airframe 121 of the multicopter 100a with respect to the second direction D2 is sometimes referred to as the second tilt angle. The second tilt angle Ψ is expressed as the angle between the second direction D2 and the X-axis (roll axis). In other words, the second tilt angle Ψ is determined by the pitch angle of the multicopter 100a.

[0070] 5A and 5B , the tilt angle of the main rotor 22 and the sub-rotor 12 with respect to the first direction D1 is equal to the first tilt angle θ, and the tilt angle of the main rotor 22 and the sub-rotor 12 with respect to the second direction D2 is equal to the second tilt angle Ψ. In other words, the positional relationship between the main rotor 22 and the sub-rotor 12 and the airframe 121 is fixed, and when the airframe 121 tilts, the main rotor 22 and the sub-rotor 12 tilt in the same way as the airframe 121.

[0071] As shown in Figures 6A and 6B, the multicopter 100a is configured to be able to maintain the main rotor 22 parallel to the horizontal plane when the airframe 121 tilts during flight.

[0072] FIG. 6A illustrates a state in which the airframe 121 of the multicopter 100a rotates by an angle θ around the X-axis (roll axis) during flight. The tilt angle of the sub-rotor 12 with respect to the first direction D1 is equal to the first tilt angle θ, as in the example shown in FIG. 5A . In contrast, the tilt angle of the main rotor 22 with respect to the first direction D1 is smaller than the first tilt angle θ. In the illustrated example, the main rotor 22 is maintained parallel to the horizontal plane. That is, the tilt angle of the airframe 121 with respect to the first direction D1 is larger than the tilt angle of the main rotor 22 with respect to the first direction D1. Furthermore, the tilt angle of the sub-rotor 12 with respect to the first direction D1 is larger than the tilt angle of the main rotor 22 with respect to the first direction D1. Here, the rotation axis 22z of the motor 25 that rotates the main rotor 22 is maintained parallel to the vertical direction.

[0073] FIG. 6B illustrates a state in which the multicopter 100a rotates by an angle Ψ around the Y-axis (pitch axis) during flight. The tilt angle of the sub-rotor 12 with respect to the second direction D2 is equal to the second tilt angle Ψ, as in the example shown in FIG. 5B . In contrast, the tilt angle of the main rotor 22 with respect to the second direction D2 is smaller than the second tilt angle Ψ. In the illustrated example, the main rotor 22 is maintained parallel to the horizontal plane. That is, the tilt angle of the airframe 121 with respect to the second direction D2 is greater than the tilt angle of the main rotor 22 with respect to the second direction D2. Furthermore, the tilt angle of the sub-rotor 12 with respect to the second direction D2 is greater than the tilt angle of the main rotor 22 with respect to the first direction D1. Here, the rotation axis 22z of the motor 25 that rotates the main rotor 22 is maintained parallel to the vertical direction.

[0074] In the tilt mode illustrated in FIGS. 5A and 5B , when the airframe 121 tilts relative to the horizontal plane, the main rotor 22 and the sub-rotor 12 also tilt relative to the horizontal plane, thereby reducing the lift (i.e., the vertical component of the thrust) generated by the main rotor 22 and the sub-rotor 12. To maintain the lift that resists gravity acting on the multicopter 100a and the work machine 200 during flight, it is necessary to increase the rotation speed of the main rotor 22 and the sub-rotor 12, for example. Furthermore, when the main rotor 22 and the sub-rotor 12 tilt relative to the horizontal plane, the rotation of the main rotor 22 and the sub-rotor 12 generates a thrust (i.e., the horizontal component of the thrust) that moves the multicopter 100a horizontally. This can complicate flight control of the multicopter 100a. In contrast, in the horizontal hold mode illustrated in FIGS. 6A and 6B , when the airframe 121 tilts relative to the horizontal plane, the tilt angle of the main rotor 22 relative to the horizontal plane is smaller than the tilt angle of the airframe 121 relative to the horizontal plane. Therefore, the reduction in lift generated by the main rotor 22 is suppressed, thereby stabilizing the flight state of the multicopter 100a. Furthermore, because the tilt angle of the main rotor 22 with respect to the horizontal plane is smaller than the tilt angle of the airframe 121 with respect to the horizontal plane, the thrust that moves the multicopter 100a in the horizontal direction, generated by the rotation of the main rotor 22, is suppressed. This prevents the flight control of the multicopter 100a from becoming complicated. For the above reasons, the flight control of the multicopter 100a can be performed efficiently.

[0075] The control device 4a can switch between a level hold mode, as illustrated in FIGS. 6A and 6B, and a tilt mode, as illustrated in FIGS. 5A and 5B. For example, when the multicopter 100a is hovering or when the multicopter 100a is changing its attitude on the spot without moving horizontally, it is preferable to control the flight of the multicopter 100a in the level hold mode. Using the level hold mode can stabilize the flight state of the multicopter 100a. Furthermore, in the level hold mode, the rotation of the main rotor 22 suppresses the thrust that moves the multicopter 100a horizontally, thereby preventing the flight control of the multicopter 100a from becoming complicated. On the other hand, when the multicopter 100a is moving horizontally (e.g., when moving horizontally along a predetermined flight path), it is preferable to control the flight of the multicopter 100a in the tilt mode. In the tilt mode, thrust generated by the rotation of the main rotor 22 can be utilized to move the multicopter 100a horizontally, enabling the multicopter 100a to move at high speeds. Even when moving the multicopter 100a horizontally, the control device 4a may switch from the tilt mode to the level hold mode if, for example, a strong wind blows and the multicopter's attitude changes significantly. Using the level hold mode and the tilt mode in this manner makes it possible to optimize flight control of the multicopter 100a according to various situations. The level hold mode and the tilt mode may be switched by the user. For example, when a signal instructing the level hold mode is transmitted from the control device controlling the multicopter 100a and the communication device 4c receives the signal instructing the level hold mode, the control device 4a switches to the level hold mode. When a signal instructing the tilt mode is transmitted from the control device and the communication device 4c receives the signal instructing the tilt mode, the control device 4a switches to the tilt mode.

[0076] The control device 4a may also switch between the level maintenance mode and the tilt mode depending on the agricultural work (e.g., depending on the operation of the work implement 200). For example, when the work implement 200 is performing ground work, the control device 4a switches to the level maintenance mode, and when the work implement 200 is not performing ground work, the control device 4a switches to the tilt mode.

[0077] Furthermore, the multicopter 100a according to this embodiment facilitates design changes, such as increasing the maximum takeoff weight (MTOW). Assuming that the main rotors 22 are maintained parallel to the horizontal plane, the MTOW can be increased simply by increasing the total thrust generated by the rotation of the main rotors 22. For example, if the multicopter 100a is designed for a maximum takeoff weight of 100 kgf (total thrust generated by the rotation of the main rotors 22: 50 kgf, total thrust generated by the rotation of the sub-rotors 12: 50 kgf), and the MTOW is changed to 120 kgf, the total thrust generated by the rotation of the main rotors 22 can be increased by 20 kgf, resulting in a total thrust generated by the rotation of the main rotors 22 of 70 kgf and a total thrust generated by the rotation of the sub-rotors 12 of 50 kgf.

[0078] FIG. 6C is a top view schematically illustrating an example of the configuration of an angle adjustment mechanism of the multicopter 100a. An angle adjustment mechanism 38 is provided corresponding to each main rotor 22. For simplicity, the propellers 22a are not shown in FIG. 6C. The motor 25 that rotates the main rotor 22 is supported on the support surface 28s of the second support member 28b and fixed to the second support member 28b. By maintaining the support surface 28s parallel to the horizontal plane, the control device 4a can maintain the main rotor 22 parallel to the horizontal plane and the rotation shaft 22z of the motor 25 parallel to the vertical direction. The second support member 28b is attached to the arm 110B via the U-shaped first support member 28a. The second support member 28b is supported by the first support member 28a so as to be rotatable together with the second rotation shaft 21b, and the first support member 28a is supported by the arm 110B so as to be rotatable together with the first rotation shaft 21a. The first actuator 29a and the second actuator 29b rotate the first rotation shaft 21a and the second rotation shaft 21b, respectively, to adjust (change) the orientation of the support surface 28s of the second support member 28b. The control device 4a detects the inclination angle of the airframe 121 based on an output signal of a sensor (e.g., an IMU) 81 (see FIG. 7 ) that detects the inclination angle of the airframe 121. Based on the detected inclination angle of the airframe 121, the control device 4a controls the first actuator 29a and the second actuator 29b to maintain the main rotor 22 parallel to the horizontal plane and the rotation shaft 22z of the motor 25 parallel to the vertical direction. It should be noted that "parallel to the horizontal plane" and "parallel to the vertical direction" do not only mean that they are strictly parallel, but also allow for an error of, for example, several degrees (deg).

[0079] 7 is a block diagram showing an example of a configuration in which a sensor 81 (4b), a processing device 85, a storage device 83, a control device 4a, and a communication device 4c are connected to a bus. These devices are connected to each other so as to be able to communicate with each other via, for example, a CAN bus.

[0080] A multicopter according to an embodiment of the present disclosure includes a sensor 81 and a processing device 85 that processes sensor data output from the sensor 81. For example, the sensor 81 and the processing device 85 may be modularized. Such a module may be manufactured and sold independently of the multicopter, or may be retrofitted to an existing multicopter.

[0081] The sensor 81 included in the sensor group 4b is configured to detect a first tilt angle θ of the airframe 121 of the multicopter 100a relative to the first direction D1 and a second tilt angle Ψ of the airframe 121 of the multicopter 100a relative to the second direction D2. The sensor 81 may further be configured to detect the rotation angle of the multicopter around an axis parallel to the vertical direction. Examples of the sensor 81 include an IMU, an acceleration sensor, an angular velocity sensor, or a combination of an acceleration sensor and an angular velocity sensor. The sensor 81 in the embodiment of the present disclosure is an IMU. The IMU functions as a motion sensor and can output signals indicating various quantities such as the acceleration, velocity, displacement, and attitude of the multicopter. The sensor 81 may be configured to detect the vertical direction (the direction of gravity).

[0082] In the horizontal maintenance mode, the control device 4a can control the inclination of the main rotor 22 based on the sensor data output from the sensor 81 so that the main rotor 22 is parallel to the horizontal plane, i.e., so that the main rotor 22 is parallel to the first direction D1 and the second direction D2. For example, the control device 4a first estimates a first inclination angle θ of the airframe 121 with respect to the first direction D1 and a second inclination angle Ψ of the airframe 121 with respect to the second direction D2 based on the sensor data output from the sensor 81. Next, the control device 4a tilts the main rotor 22 in the opposite direction to the airframe 121 by the first inclination angle θ with respect to the first direction D1, and tilts the main rotor 22 in the opposite direction to the airframe 121 by the second inclination angle Ψ with respect to the second direction D2. Alternatively, the control device 4a may estimate the vertical direction based on the sensor data output from the sensor 81, and control the inclination of the main rotor 22 so that the main rotor 22 is parallel to the horizontal plane.

[0083] 6C , the control device 4a controls the inclination of the support surface 28s of the second support member 28b with respect to the horizontal plane by controlling the first actuator 29a and the second actuator 29b based on the sensor data output from the sensor 81. This allows the inclination of the main rotor 22 to be controlled.

[0084] The propeller 22a of the main rotor 22 may be attached to the aircraft frame 110 (or the arm 110B) via a gimbal. The gimbal functions as an angle adjustment mechanism. The main rotor 22 attached to the aircraft frame 110 via a gimbal can maintain a state parallel to the horizontal plane even if the aircraft 121 tilts. A gimbal is a type of rotating table that rotates an object around one axis. Gimbals with multiple axes that are perpendicular to each other may also be installed.

[0085] Another example of the angle adjustment mechanism will be described with reference to FIG. 6D . FIG. 6D is a side view schematically illustrating a multicopter 100a having an angle adjustment mechanism 238. In the example described above, the arm 110B supporting the main rotor 22 is fixed to the airframe 121, and the angle adjustment mechanism controls the inclination angle of the propeller 22a of the main rotor 22 with respect to the horizontal plane to be smaller than the inclination angles of the airframe 121 and the arm 110B with respect to the horizontal plane. In contrast, in the example shown in FIG. 6D , the multicopter 100a has an angle adjustment mechanism 238 that can adjust the inclination angle of the arm 110B supporting the main rotor 22 with respect to the horizontal plane. The angle adjustment mechanism 238 can control the inclination angle of the arm 110B with respect to the horizontal plane to be smaller than the inclination angle of the airframe 121 with respect to the horizontal plane. Because the main rotor 22 is fixed to the arm 110B, the inclination angle of the propeller 22a of the main rotor 22 with respect to the horizontal plane can be controlled to be smaller than the inclination angle of the airframe 121 with respect to the horizontal plane. As shown in FIG. 6D , an angle adjustment mechanism 238 is provided on the airframe frame 110, and the arm 110B is attached to the airframe frame 110 via the angle adjustment mechanism 238. The angle adjustment mechanism 238 may be a gimbal or another mechanism. By providing the angle adjustment mechanism 238, when the airframe 121 (airframe frame 110) is inclined with respect to the horizontal plane, the arm 110B can maintain a state parallel to the horizontal plane, and therefore the main rotor 22 can also maintain a state parallel to the horizontal plane.

[0086] An example of the processing device 85 is a processor. The processor is one or more semiconductor integrated circuits, and is also called a central processing unit (CPU) or a microprocessor. The processor sequentially executes computer programs stored in the storage device 83 to realize the processing described below. The term "processor" is broadly interpreted as including a field programmable gate array (FPGA) equipped with a CPU, a graphic processor unit (GPU), an application specific integrated circuit (ASIC), or an application specific standard product (ASSP).

[0087] A part of the functions of the processing device 85 may be implemented in the companion computer described above. Alternatively, the companion computer may function as the processing device 85.

[0088] The storage device 83 is, for example, a writable memory (e.g., a PROM), a rewritable memory (e.g., a flash memory), or a read-only memory (ROM). The storage device 83 may store a program that controls the operation of the processing device 85. The storage device 83 does not need to be a single recording medium, but may be a collection of multiple recording media. Some of the collection of multiple recording media may be removable memory. The storage device 83 may store, for example, map data useful for the autonomous flight of the multicopter 10 and various sensor data acquired by the multicopter 10 during flight.

[0089] An example of the operation of the control device 4a will be described below with reference to Fig. 8. In this example, when the amount of change in the attitude angle is greater than a predetermined value, the flight of the multicopter 100a can be controlled in the horizontal maintenance mode.

[0090] In step S20, the control device 4a estimates the current attitude angle of the multicopter 100a. The control device 4a may acquire estimated or measured values ​​of the attitude angle from a sensor included in the sensor group 4b that estimates or measures the attitude angle. The control device 4a can acquire information on the roll angle, pitch angle, and yaw angle detected by the sensor 81.

[0091] In step S22, the control device 4a acquires a target attitude angle. The control device 4a may determine the target attitude angle based on, for example, flight conditions, work content, weather information, etc.

[0092] In step S24, the control device 4a calculates the amount of change in the attitude angle and determines whether the amount of change is greater than a predetermined value. The amount of change in the attitude angle is determined by the difference between the current estimated attitude angle and the target attitude angle. The greater this "amount of change," the greater the amount of change in attitude. If the result of the determination is "No," the process returns to step S20. If the result is "Yes," the process proceeds to step S26.

[0093] In step S26, the control device 4a determines whether the current control mode is the tilt mode. The control device 4a obtains information about the current control mode and makes this determination. If the current control mode is the tilt mode, the process proceeds to step S28. If the current control mode is not the tilt mode, for example, if the current control mode is the horizontal maintenance mode, the process returns to step S20.

[0094] In step S28, the control device 4a determines whether to change from the tilt mode to the level maintenance mode. If it is determined to change to the level maintenance mode (if "Yes"), the control device 4a proceeds to step S30. If "No", the control device 4a returns to step S20.

[0095] In step S30, the control device 4a changes from the tilt mode to the horizontal maintenance mode.

[0096] The control device 4a repeats steps S20 to S30 until an end command is issued (step S40).

[0097] The flowchart shown in FIG. 8 is an example of the operation of the control device 4a and can be modified as appropriate.

[0098] 9 is a schematic diagram showing an example configuration of a system including the multicopter 10. Some or all of the functions of the control device 4a may be implemented by one or more servers (computers) 500 or terminal devices (including portable and fixed types) 600 connected to the communication device 4c of the multicopter 10 via a communication network N. An agricultural machine 700 such as a tractor may be connected to such a communication network N, and communication may be performed between the multicopter 10 and the agricultural machine 700. Some of the data used in processing by the control device 4a and control signals for the multicopter 10 may be provided from the agricultural machine 700 to the multicopter 10 via the communication network N.

[0099] This specification discloses the solutions described in the following items.

[0100] [Item 1] An unmanned aerial vehicle having multiple rotors, wherein the multiple rotors include multiple first rotors and at least one second rotor, and further comprising an angle adjustment mechanism that, when the aircraft tilts with respect to a horizontal plane perpendicular to the vertical direction during flight of the unmanned aerial vehicle, makes the tilt angle of the second rotor with respect to the horizontal plane smaller than the tilt angle of the aircraft with respect to the horizontal plane.

[0101] [Item 2] The unmanned aerial vehicle described in Item 1, wherein, during flight of the unmanned aerial vehicle, when the inclination angle of the aircraft with respect to a first direction perpendicular to the vertical direction is a first inclination angle and the inclination angle of the aircraft with respect to a second direction perpendicular to the vertical direction and intersecting the first direction is a second inclination angle, the angle adjustment mechanism makes the inclination angle of the second rotor with respect to the first direction smaller than the first inclination angle and makes the inclination angle of the second rotor with respect to the second direction smaller than the second inclination angle.

[0102] [Item 3] The unmanned aerial vehicle described in Item 2, wherein, during flight of the unmanned aerial vehicle, when the inclination angle of the aircraft with respect to the first direction is the first inclination angle and the inclination angle of the aircraft with respect to the second direction is the second inclination angle, the angle adjustment mechanism makes the inclination angle of the second rotor with respect to the first direction smaller than the inclination angles of the multiple first rotors with respect to the first direction, and makes the inclination angle of the second rotor with respect to the second direction smaller than the inclination angle of the second rotor with respect to the second direction.

[0103] [Item 4] An unmanned aerial vehicle as described in Item 2 or 3, further comprising a control device that controls the flight of the unmanned aerial vehicle, wherein the control device is configured to control the flight of the unmanned aerial vehicle in a plurality of modes, the plurality of modes including: a first mode in which the inclination angle of the second rotor with respect to the horizontal plane is made smaller than the inclination angle of the airframe with respect to the horizontal plane; and a second mode in which the inclination angle of the second rotor with respect to the horizontal plane is made equal to the inclination angle of the airframe with respect to the horizontal plane.

[0104] [Item 5] The unmanned aerial vehicle described in Item 4, wherein the control device controls flight of the unmanned aerial vehicle in the first mode while the unmanned aerial vehicle is hovering.

[0105] [Item 6] The unmanned aerial vehicle described in Item 4 or 5, wherein the control device controls the flight of the unmanned aerial vehicle in the first mode when the unmanned aerial vehicle changes its attitude.

[0106] [Item 7] The control device of the unmanned aerial vehicle described in Item 6 estimates the amount of change in the attitude angle of the unmanned aerial vehicle, and when the amount of change is greater than a predetermined value, controls the flight of the unmanned aerial vehicle in the first mode.

[0107] [Item 8] An unmanned aerial vehicle described in any one of Items 2 to 7, wherein the first tilt angle is determined by a roll angle of the unmanned aerial vehicle, and the second tilt angle is determined by a pitch angle of the unmanned aerial vehicle.

[0108] [Item 9] An unmanned aerial vehicle according to any one of items 1 to 8, wherein the diameter of the second rotor is larger than the diameter of each of the plurality of first rotors.

[0109] [Item 10] An unmanned aerial vehicle described in any one of items 1 to 9, wherein the second rotor is used to generate thrust, and the plurality of first rotors are used to generate thrust and control attitude.

[0110] [Item 11] An unmanned aerial vehicle according to any one of items 1 to 10, capable of flying with a work machine connected to the airframe.

[0111] [Item 12] The unmanned aerial vehicle described in any one of Items 1 to 11, wherein the second rotor has a total thrust that can be generated that is greater than that of the plurality of first rotors.

[0112] [Item 13] A control method for an unmanned aerial vehicle having multiple rotors, wherein the multiple rotors include multiple first rotors and at least one second rotor, and when the aircraft tilts with respect to a horizontal plane perpendicular to the vertical direction during flight of the unmanned aerial vehicle, the control method includes making the tilt angle of the second rotor with respect to the horizontal plane smaller than the tilt angle of the aircraft with respect to the horizontal plane.

[0113] The unmanned aerial vehicle disclosed herein can be widely used not only for aerial photography, surveying, logistics, and pesticide spraying, but also for ground work related to agricultural work, transporting harvested products and agricultural materials, and the like.

[0114] 2: Rotor (propeller), 3: Rotation drive device, 4: Airframe body, 4a: Control device, 4b: Sensor group, 4c: Communication device, 5: Airframe frame, 10, 100: Multicopter, 12: Sub-rotor, 12a: Propeller, 12b: Propeller, 14: Motor, 16: ESC, 22: Main rotor, 52: Battery

Claims

1. 1. An unmanned aerial vehicle having multiple rotors, the plurality of rotors includes a plurality of first rotors and at least one second rotor; The unmanned aircraft further comprises an angle adjustment mechanism that, when the aircraft tilts relative to a horizontal plane perpendicular to the vertical direction during flight of the unmanned aircraft, makes the inclination angle of the second rotor relative to the horizontal plane smaller than the inclination angle of the aircraft relative to the horizontal plane.

2. During flight of the unmanned aerial vehicle, when the inclination angle of the airframe with respect to a first direction perpendicular to the vertical direction is a first inclination angle, and the inclination angle of the airframe with respect to a second direction perpendicular to the vertical direction and intersecting the first direction is a second inclination angle, 2. The unmanned aerial vehicle described in claim 1, wherein the angle adjustment mechanism makes the tilt angle of the second rotor with respect to the first direction smaller than the first tilt angle, and makes the tilt angle of the second rotor with respect to the second direction smaller than the second tilt angle.

3. During flight of the unmanned aerial vehicle, when the inclination angle of the airframe with respect to the first direction is the first inclination angle and the inclination angle of the airframe with respect to the second direction is the second inclination angle, 3. The unmanned aerial vehicle described in claim 2, wherein the angle adjustment mechanism makes the inclination angle of the second rotor with respect to the first direction smaller than the inclination angles of the plurality of first rotors with respect to the first direction, and makes the inclination angle of the second rotor with respect to the second direction smaller than the inclination angle of the second rotor with respect to the second direction.

4. Further, a control device for controlling the flight of the unmanned aerial vehicle is provided. the controller is configured to control flight of the unmanned aerial vehicle in a plurality of modes; The plurality of modes include: a first mode in which the tilt angle of the second rotor with respect to the horizontal plane is made smaller than the tilt angle of the airframe with respect to the horizontal plane; a second mode in which the tilt angle of the second rotor with respect to the horizontal plane is equal to the tilt angle of the airframe with respect to the horizontal plane; The unmanned aerial vehicle according to claim 2 or 3, comprising:

5. The unmanned aerial vehicle of claim 4 , wherein the control device controls flight of the unmanned aerial vehicle in the first mode while the unmanned aerial vehicle is hovering.

6. The unmanned aerial vehicle of claim 4 , wherein the control device controls flight of the unmanned aerial vehicle in the first mode when the unmanned aerial vehicle changes attitude.

7. The control device The unmanned aerial vehicle according to claim 6 , wherein a change in an attitude angle of the unmanned aerial vehicle is estimated, and when the change is greater than a predetermined value, the flight of the unmanned aerial vehicle is controlled in the first mode.

8. the first tilt angle is defined by a roll angle of the unmanned aerial vehicle; The unmanned aerial vehicle according to claim 2 or 3, wherein the second tilt angle is defined by a pitch angle of the unmanned aerial vehicle.

9. The unmanned aerial vehicle according to claim 1 , wherein the diameter of the second rotor is larger than the diameter of each of the plurality of first rotors.

10. the second rotor is used to generate thrust; The unmanned aerial vehicle according to claim 1 , wherein the plurality of first rotors are used for thrust generation and attitude control.

11. An unmanned aerial vehicle according to any one of claims 1 to 3, capable of flying with a work machine connected to the airframe.

12. The unmanned aerial vehicle according to claim 1 , wherein the second rotor has a total thrust that can be generated that is greater than that of the plurality of first rotors.

13. 1. A method for controlling an unmanned aerial vehicle having multiple rotors, comprising: the plurality of rotors includes a plurality of first rotors and at least one second rotor; A control method including, when the aircraft tilts with respect to a horizontal plane perpendicular to the vertical direction during flight of the unmanned aircraft, making the tilt angle of the second rotor with respect to the horizontal plane smaller than the tilt angle of the aircraft with respect to the horizontal plane.