Unmanned aircraft

Abstract

This unmanned aircraft is provided with: a plurality of electric motors that respectively drive a plurality of first rotors; an internal combustion engine; a generation device that generates electric power as a result of being driven by the internal combustion engine; a battery that stores electric power; and a control device that controls the flight of the unmanned aircraft and changes the upper limit of the flight altitude of the unmanned aircraft depending on the state of charge of the battery.

Description

unmanned aerial vehicle

[0001] The present disclosure relates to 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 aerial vehicle) that changes its flight position in conjunction with the operation of agricultural machinery.

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

[0005] The maximum payload and flight time of unmanned aerial vehicles are insufficient for some applications, and further improvements are required.

[0006] The present disclosure provides unmanned aerial vehicles capable of increasing payload and / or flight time.

[0007] In an exemplary and non-limiting embodiment, the unmanned aerial vehicle of the present disclosure is an unmanned aerial vehicle having multiple rotors, and includes: a plurality of electric motors that drive each of a plurality of first rotors included in the plurality of rotors; an internal combustion engine; a power generation device that is driven by the internal combustion engine to generate electricity; a battery that stores the electricity; and a control device that controls the flight of the unmanned aerial vehicle, the control device changing the upper limit of the flight altitude of the unmanned aerial vehicle depending on the state of charge of the battery.

[0008] According to an embodiment of the unmanned aerial vehicle of the present disclosure, even in a situation where power is not being generated by the power generation device, it is possible to land using the power stored in the battery.

[0009] 1 is a block diagram schematically showing several examples of a rotary drive unit 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 an example basic configuration of a battery-powered multicopter. FIG. 6 is a block diagram showing an example basic configuration of a series hybrid multicopter. FIG. 7 is a block diagram showing an example basic configuration of a parallel hybrid multicopter. FIG. 8 is a block diagram showing an example basic configuration of an unmanned aerial vehicle (multicopter) according to an embodiment of the present disclosure. FIG. 9 is a diagram schematically showing the state of charge of a battery. FIG. 10 is a diagram schematically showing an example relationship between the state of charge SOC, maximum height MH, and flight altitude FH of a multicopter. FIG. 11 is a flowchart showing an example operation of a control device according to this embodiment. FIG. 12 is a diagram schematically showing an example of correcting the upper limit of flight altitude according to the terrain directly below the multicopter according to this embodiment. FIG. 13 is a diagram schematically showing another example of correcting the upper limit of flight altitude according to the terrain directly below the multicopter according to this embodiment. FIG. 1 is a plan view showing an example of the positional relationship between a multicopter flying over a field and possible landing points located around the field. FIG. 2 is another plan view showing an example of the positional relationship between a multicopter flying over a field and possible landing points located around the field. FIG. 3 is yet another plan view showing an example of the positional relationship between a multicopter flying over a field and possible landing points located around the field. FIG. 4 is a flowchart showing another example of the operation of a control device in this embodiment. FIG. 5 is a block diagram showing an example of the hardware configuration of a control device in this embodiment. FIG. 6 is a diagram schematically showing an example of a communication network to which a multicopter is connected in this embodiment.

[0010] 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."

[0011] 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.

[0012] The first rotary drive device 3A shown in FIG. 1A includes multiple electric motors (hereinafter referred to as "motors") 14 that rotate multiple rotors 2 and a battery 52 that stores power to supply to each motor 14. The battery 52 is, for example, a secondary battery such as a polymer lithium-ion battery. Each rotor 2 is coupled to the output shaft of the corresponding motor 14 and rotated by the motor 14. Increasing the payload and / or flight time requires increasing the storage capacity of the battery 52. ​​While the storage capacity of the battery 52 can be increased by increasing the size of the battery 52, increasing the size of the battery 52 increases the weight. The second rotary 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 the torque of 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 may include a gasoline engine, a diesel engine, and a hydrogen engine.

[0013] 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 9 and internal combustion engine 7a in the series hybrid drive are called a "range extender" because they extend the flight distance of the multicopter.

[0014] 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."

[0015] 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.

[0016] 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 rotor 2 is provided near the tip of each arm 5A.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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).

[0021] The communication device 4c may include a wireless communication module for transmitting and receiving signals via an antenna to and from a ground transmitter or ground station (Ground Control Station (GCS)), 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 also have a function for communicating between unmanned aerial vehicles 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 a computer on the cloud.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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 mainly 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."

[0027] 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.

[0028] Equipping a multicopter with an internal combustion engine and using the engine to generate thrust and / or electricity contributes to an increase in 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 where precise control of the attitude of a multicopter is required, it is desirable to adopt a parallel hybrid drive or a series hybrid drive in order to increase the payload and flight time.

[0029] 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.

[0030] 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 also 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 the materials, the work implement 200 can also transport agricultural materials or harvested products over a wide area.

[0031] 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.

[0032] FIG. 2A is a block diagram showing an example of the basic configuration of a battery-powered multicopter 10.

[0033] The battery-powered multicopter 10 includes multiple rotors 12, multiple motors 14 for rotating the rotors 12, multiple ESCs (electric speed controllers) 16 each having a motor drive circuit for driving the motors 14, a battery 52 for supplying power to the corresponding motor 14 via each ESC 16, a control device 4a for controlling the ESCs 16 to control attitude and perform 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 rotors 12, motors 14, and ESCs 16 are actually multiple in number. This also applies to FIGS. 2B and 2C.

[0034] The control device 4a can wirelessly receive control commands from, for example, 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 wirelessly receive control commands 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.

[0035] 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 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.

[0036] FIG. 2C is a block diagram showing an example of the basic configuration of a parallel hybrid multicopter 10. Similar to the series hybrid multicopter 10, the parallel hybrid multicopter 10 includes multiple rotors 12, multiple motors 14, 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 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.

[0037] In the parallel hybrid 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 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 multicopter 10, if the power generation device 8 is, for example, a fuel cell, the internal combustion engine 7a is not an essential component.

[0038] Hereinafter, with reference to FIG. 3 , a basic configuration example of an unmanned aerial vehicle (multicopter) according to an embodiment of the present disclosure will be described.

[0039] In the example shown in FIG. 3 , the multicopter 10 generally includes multiple rotors (first rotors) 12, multiple motors 14 that drive the first rotors 12, an internal combustion engine 7a, a power generation device 8 that is driven by the internal combustion engine 7a to generate electric power, a battery 52 that stores the electric power, and a control device 4a that controls flight of the multicopter 10. For simplicity, FIG. 3 shows the rotors 12, the motors 14, and the ESC 16 as a single block, but the number of rotors 12, the motors 14, and the ESC 16 is actually multiple. Although not shown in FIG. 3 , the multicopter 10 may also include at least one second rotor 22 driven by the internal combustion engine 7a, as shown in FIG. 2C . This embodiment may employ either a "series hybrid" or a "parallel hybrid" drive system.

[0040] The multicopter 10 in this embodiment includes a current sensor 53a that measures the current flowing through the battery 52, and switch elements 53b, 53c, and 53d that define the current path when the battery 52 is being discharged and charged. During charging, current flows from the power generation device 8 to the battery 52 via the closed switch elements 53c and 53d. During discharging, current flows from the battery 52 to the ESC 16 and the motor 14 via the closed switch elements 53b and 53d. The multicopter 10 may further include other switch elements and / or current sensors. The opening and closing of the switch elements 53b, 53c, and 53d may be controlled by the control device 4a.

[0041] The multicopter 10 in this embodiment includes a battery management system 54 that monitors and manages the battery 52. ​​The battery management system 54 includes a cell monitoring circuit 54a that monitors the state (voltage, temperature, etc.) of each of the multiple cells included in the battery 52, and a microcontroller (Micro Controller Uni: MCU) 54b that estimates the state of charge of the battery 52 and performs management operations for the battery 52.

[0042] The cell monitoring circuitry 54a may be configured to measure the voltage of each cell and perform cell balancing during charging. The cell monitoring circuitry 54a may also include protection circuitry to prevent overcharging and over-discharging of each cell. Such protection circuitry may be provided in battery packs each containing multiple cells.

[0043] The MCU 54b can be programmed to perform various calculations to estimate the state of charge (SOC) of the battery 52. ​​The state of charge SOC is one of the state quantities that define the state of charge of the battery 52. ​​The state quantity that defines the state of charge of the battery 52 is not limited to the state of charge, and can include variables such as the state of health (SOH) and the full charge capacity (FCC).

[0044] FIG. 4 is a diagram schematically illustrating the state of charge of the battery 52. ​​The left portion of FIG. 4 shows the initial state of charge of the battery 52, and the right portion shows the state of charge of the battery 52 whose full charge capacity FCC has decreased due to degradation. The state of charge (SOC) is equal to the value obtained by dividing the remaining charge (RC) of the battery 52 by the full charge capacity FCC, i.e., RC / FCC. The state of charge (SOC) defined in this way is sometimes called the "relative state of charge (RSOC)."

[0045] The state of health (SOH) and the full charge capacity (FCC) decrease as the battery 52 deteriorates. ０ Then, the relationship between the state of health (SOH) and the full charge capacity (FCC) is: SOH = FCC / FCC ０ In the initial state, the state of health SOH is 1.0.

[0046] The remaining charge RC, which defines the amount of power stored in the battery 52, is SOC x SOH x FCC ０ Equals FCC ０Since the state of charge (SOC) and state of health (SOH) are known, the remaining charge (RC) can be calculated once the estimated values ​​for the state of charge (SOC) and state of health (SOH) are determined. The distance that can be flown using only the power stored in the battery 52 depends not only on the remaining charge (RC) but also on the state of power (SOP), which in turn depends on the magnitude of the current (C rate) flowing through the battery 52 and the temperature of the battery 52. ​​In particular, the battery temperature affects the distance that the multicopter 100 can fly using the power stored in the battery 52, or the maximum height to which it can descend and land. For this reason, it is preferable that the control device 4a determine the maximum height based on the estimated state of charge (SOC) of the battery 52 and the measured temperature of the battery 52. ​​Specifically, multiple tables defining the relationship between the state of charge (SOC) of the battery 52 and the maximum height for each of multiple different battery temperatures can be stored in a storage device provided in the control device 4a, for example. Then, the table for the battery temperature closest to the measured temperature of the battery 52 is selected, and the maximum height is read from the state of charge based on that table.

[0047] After the battery management system 54 estimates the state of charge (SOC), state of health (SOH), battery temperature, etc.) of the battery 52, the control device 4a performs necessary calculations based on these estimated values ​​to calculate the remaining flight time on the power of the battery 52. ​​The remaining flight time can be calculated by dividing the amount of power stored in the battery 52 by the amount of power consumed per unit time (power consumption) while the multicopter 100 is flying. For example, if the amount of power stored in the battery 52 is 1.5 kWh and the power consumption of the multicopter 100 during flight is 30 kW, the remaining flight time is 1.5 kWh / 30 kW = 0.05 h = 3 minutes. Power consumption differs for each multicopter 100 and also depends on the payload of the multicopter 100. For example, in the case of a multicopter 100 in which power consumption increases by 5 kW for every 10 kg increase in payload value, if the payload value is in the range of 30 to 40 kg, a maximum increase in power consumption of approximately 5 kW x 4 = 20 kW is expected. Taking this increase into account, the 3-minute flight time in the above example is corrected to 1.5 kW / 50 kW = 0.03 h = 1.8 minutes (1 minute 48 seconds).

[0048] In a preferred embodiment, the control unit 4a stores a table or function of power consumption that varies depending on the value of the payload.

[0049] When the control device 4a calculates the remaining flight time, it may acquire information on weather conditions, including wind speed, and correct the remaining flight time based on that information. When the multicopter 100 flies along a predetermined route, it consumes extra power to resist wind force. Therefore, power consumption increases as wind speed increases. The relationship between wind speed and power consumption can be determined in advance for each multicopter 100 and stored in the storage device of the control device 4a. The state of charge (SOC), which determines the state of charge of the battery 52, can be estimated using various algorithms. For example, the following algorithm can be adopted.

[0050] The voltage (terminal voltage) of the battery 52 is measured, and the state of charge SOC is estimated from the measured value. When making the estimation, the measured values ​​of the current flowing through the battery 52 and the temperature of the battery 52 are referenced.

[0051] The current flowing through the battery 52 is integrated to determine the charge flowing into and out of the battery 52, and an estimate of the remaining charge RC is obtained (Coulomb counting method).

[0052] The relationship between the battery's open circuit voltage (OCV) and state of charge (SOC) is utilized to estimate the state of charge (SOC) from current and voltage measurements based on a model including the open circuit voltage (OCV) and the battery's internal impedance. A recursive Bayesian filter, such as a Kalman filter, can be used for this estimation.

[0053] The estimation of the state of charge SOC is not limited to the above example, and any method may be adopted. The state of health SOH and other state quantities or parameters may also be estimated by any method or algorithm.

[0054] In the example of FIG. 3 , the power generation device 8 is driven by the internal combustion engine 7a, thereby charging the battery 52. ​​Therefore, in this embodiment, when estimating the remaining flight time, the control device 4a can estimate the remaining flight time based on the amount of fuel consumed per minute of flight and the amount of fuel (remaining fuel) stored in the fuel tank 7b. The amount of fuel consumed per minute of flight may vary depending on the payload of the multicopter 10 and weather conditions. However, the control device 4a can calculate and update the amount of fuel consumed per minute of flight based on measurements taken in real time by a fuel gauge and timer mounted on the multicopter 10. When a work implement 200 is coupled to the multicopter 100, an appropriate work implement 200 is selected from various work implements 200 depending on the agricultural work. Therefore, the payload may vary depending on the type or model of the work implement 200. The payload also changes when the multicopter 100 transports harvested crops or agricultural materials. Therefore, when the control device 4a estimates the remaining flight time, it is desirable that the control device 4a obtain information indicating additional weight in addition to the weight of the multicopter 100 itself, and use this information to improve the accuracy of the estimated remaining flight time.

[0055] Consider an example in which the multicopter 10 flies from its current position to a position P a distance X [meter] away, then descends and lands at position P on the ground. Let Sf [meter / second] be the average flight speed of the multicopter 10, h [meter] be the flight altitude at position P, and Sd [meter / second] be the average descent speed from the altitude h above position P to landing. In this case, the time required to fly from the current position to the position P is X / (60×Sf) in minutes. The time required to descend from the altitude h at position P to the ground at an altitude of 0 and land is h / (60×Sd) in minutes. The time required to fly from the current position to a position a distance X away and land at that position is referred to as the "flight and landing time (Tfd)." Tfd = X / (60×Sf) + h / (60×Sd) holds true.

[0056] In the present disclosure, if the remaining flight time of the multicopter 10 is Y, flight is controlled so that Y > Tfd holds. For example, if the distance X from the current position of the multicopter 10 to the nearest possible landing point is 1200, and Sf = 2, h = 60, and Sd = 0.5, then Tfdf = 1200 / (60 x 2) + 60 / (60 x 0.5) = 10 + 2 = 12 minutes. If the remaining flight time Y of the multicopter 10 at its current position is greater than 12 minutes, it can land at a point distance X from its current position.

[0057] In an embodiment of the present disclosure, the altitude h before starting the landing operation is changed according to the state of charge of the battery 52, as will be described later. If the altitude h changes, the time it takes to descend from altitude h and land also changes. Furthermore, even if the altitude h remains the same, it is necessary to change the appropriate descent speed Sd depending on changes in meteorological conditions such as wind speed at the time of landing. For this reason, it is preferable to use a fixed value, for example, 3 minutes, as the time required for landing, instead of calculating it based on various factors such as the altitude h. Hereinafter, the flight and landing time (Tfd) is expressed by the following formula (1) using the distance X and the average flight speed Sf. Tfd = X / (60 × Sf) + 3 ... (Formula 1)

[0058] In this embodiment, the multicopter 10 is equipped with an internal combustion engine 7a and generates power using the power generation device 8, thereby extending the flight time compared to a battery-powered multicopter that flies using only the power initially stored in the battery 52. ​​Because of the internal combustion engine 7a, a fuel tank 7b for storing fuel must be installed on the multicopter 10, but the output energy per fuel weight is higher than the output energy per weight of the battery 52. ​​Therefore, in an embodiment of the present disclosure, the full charge capacity of the battery 52 is made relatively small to reduce weight, while utilizing the internal combustion engine 7a, fuel tank 7b, and power generation device 8, making it possible to increase the flight time or payload.

[0059] In the multicopter 10 of this embodiment, the battery 52 functions as a power buffer that supplies the electric power generated by the power generation device 8 to the motor 14, and also functions as a type of safety device in the event of a failure of the internal combustion engine 7a or the power generation device 8. In other words, when the internal combustion engine 7a or the power generation device 8 fails, the power generation device 8 falls into a state where it is unable to generate new electric power, but the electric power stored in the battery 52 can be used to rotate the motor 14 and the rotor 12, allowing the multicopter 10 to land.

[0060] In this embodiment, the full charge capacity FCC of the battery 52 is large enough to allow the multicopter 10 to descend from a predetermined reference height to the ground and land using the power stored in the battery 52 when the power generation device 8 is not generating power. This reference height is at most 10 m to 300 m, for example, 200 m or less. The full charge capacity FCC of the battery 52 can be further increased, but excessive weight increase of the battery 52 is undesirable. The full charge capacity FCC of the battery 52 is sufficient as long as it is large enough to allow flight (descent) for the time required for landing (for example, 3 minutes) when the power generation device 8 is unable to generate power.

[0061] However, the state of charge of the battery 52 is not always fully charged (SOC = 1.0). If the battery 52 is, for example, a lithium-ion battery, the state of charge (SOC) varies, for example, within a range of 0.3 to 0.9. Because lithium-ion batteries can deteriorate due to overcharging and overdischarging, it is preferable to control the charging and discharging of the battery so as to maintain the state of charge (SOC) within a predetermined range, for example, a range of 0.5 to 0.85. Such control of charging and discharging is achieved by the operation of the battery management system 54 and the control device 4a shown in FIG. 3.

[0062] Here, an example will be described in which, when the altitude of the multicopter 10 is lowered by 2 m at a predetermined speed for landing, power is consumed by the descent operation, causing the state of charge (SOC) of the battery 52 to decrease by 1%. In this example, if the state of charge (SOC) is 100% (fully charged) at the start of descent, the altitude can be lowered by 200 m. In this case, even if the flight altitude is 200 m, landing is possible using only the power stored in the battery 52. ​​However, if the state of charge (SOC) is 50% at the start of descent, the multicopter 10 can only lower its altitude by 100 m, and a multicopter 10 flying at an altitude exceeding 100 m will be unable to land.

[0063] To solve this problem, in the multicopter 10 of this embodiment, the control device 4a is configured to change the upper limit of the flight altitude of the multicopter 10 depending on the state of charge of the battery 52. ​​This point will be described in detail below.

[0064] First, let us refer to Fig. 5. The upper part of Fig. 5 schematically shows the flight altitude of the multicopter 10 when the charging rate SOC of the battery 52 gradually decreases from 0.8, reaches 0.5, and then increases to 0.9 due to charging by the power generation device 8.

[0065] When the charging rate SOC is 0.8, the multicopter 10 is flying at an altitude corresponding to a height h1 above the ground GR. In other words, the flight altitude FH at this time is h1. When the charging rate SOC is 0.7, the flight altitude FH of the multicopter 10 is h2, and when the charging rate SOC is 0.5, the flight altitude FH of the multicopter 10 is h3.

[0066] The middle part of Figure 5 shows an example of the change over time in the charging rate SOC of the battery 52. ​​When the battery is discharging, the power stored in the battery 52 is consumed by the rotation of the motor 14 and the rotor 12, etc., and the charging rate SOC gradually decreases. In contrast, when the battery is charging, the power generated by the power generation device 8 is stored in the battery 52, and the charging rate SOC increases. The battery management system 54 in this embodiment charges the battery 52 with the power generated by the power generation device 8 and operates to maintain the charging rate SOC within a predetermined range (for example, a range of 0.5 to 0.9).

[0067] The lower part of FIG. 5 shows a schematic example of temporal changes in the maximum height MH and flight altitude FH determined based on the state of charge SOC.

[0068] The control device 4a according to this embodiment determines the maximum height MH at which the multicopter 10 can descend to the ground GR and land using the power stored in the battery 52 when power is not being generated by the power generation device 8. The control device 4a then controls the upper limit of the flight altitude FH to be equal to or less than the maximum height MH. In this way, the control device 4a can change the upper limit of the flight altitude of the multicopter 10 depending on the state of charge of the battery 52. ​​The upper limit of the flight altitude FH need only be equal to or less than the maximum height MH, and does not need to be set to a value equal to the maximum height MH.

[0069] The maximum height MH calculated based on the state of charge SOC may be higher than the legal limit for the maximum flight altitude. The lower part of Figure 5 shows the limit for the maximum flight altitude with a dashed line. When the maximum height MH is higher than the limit for the maximum flight altitude, the flight altitude (dash-dotted line) FH is limited by the limit for the maximum flight altitude, not the maximum height MH. In the example of Figure 5, the maximum height MH exceeds the limit when the state of charge SOC reaches 0.9.

[0070] Strictly speaking, it is preferable that the maximum height MH is determined based on the residual charge RC, not on the relative SOC (=RC / FCC).

[0071] An example of the operation of the control device 4a will be described with reference to Fig. 6. Fig. 6 is a flowchart showing an example of the operation of the control device 4a.

[0072] First, after starting an operation mode in which the flight altitude is controlled based on the state of charge of the battery, in step S10, the control device 4a acquires the current flight altitude FH of the multicopter 10 from an altitude sensor or the like. In step S12, the control device 4a acquires the state of charge SOC (estimated value) from the battery management system 54. At this time, the control device 4a may acquire other state quantities that define the state of charge from the battery management system 54 or other sensors. Examples of the other state quantities may include the state of health SOH (estimated value) and the battery temperature.

[0073] In step S12, the control device 4a determines the maximum height MH based on the state of charge SOC. For example, if it is calculated that a state of charge SOC of 1.0 allows the aircraft to descend and land from a flight altitude FH of 150 m to the ground, and if the state of charge SOC obtained from the battery management system 54 is 0.8, the maximum height MH is 150 × 0.8 m. If the state of health SOH of the battery 52 has been estimated, the maximum height MH may be corrected to a value multiplied by the state of health SOH. For example, if the full charge capacity FCC of the battery 52 has decreased to 0.9 times its initial value, the state of health SOH is 0.9, and therefore the maximum height MH may be corrected to 150 × 0.8 × 0.9 m. As described above, the power consumption (electricity consumption) required for descent per unit length may also depend on meteorological conditions, including the payload, wind speed, and temperature. Therefore, the maximum height HM may be corrected based on information regarding the payload and meteorological conditions. The control device 4a can obtain the necessary information from a memory that stores tables or functions necessary for these corrections. The payload can include the weight of the multicopter 10, the weight of the cargo being carried by the multicopter 10, and the weight of various machines such as work implements (e.g., agricultural implements) connected to the multicopter 10.

[0074] After acquiring the value of the payload (payload value) by, for example, the above-described method, the control device 4a can estimate the increase in power consumption according to the payload value and correct the maximum height HM.

[0075] In step S12, the control device 4a determines an upper limit for the flight altitude FH so that it does not exceed the maximum height MH. The upper limit for the flight altitude FH is set, for example, within a range equal to or less than the altitude regulation value set by law. The upper limit can also be corrected based on various information such as information about the terrain directly below the multicopter 10 during flight. This point will be described later.

[0076] The order of the above processing steps S10 and S12 is arbitrary and they can be performed simultaneously.

[0077] Next, in step S14, the control device 4a determines whether the flight altitude FH exceeds the upper limit. If the determination is Yes, in step S16, the control device 4a descends the multicopter 10 so that the flight altitude FH is equal to or less than the upper limit. If the determination is No, after a predetermined time (e.g., 10 milliseconds) has elapsed, the process returns to step S10.

[0078] Through the above processing, when the internal combustion engine 7a stops during flight, the control device 4a can descend and land the multicopter 100 while driving the multiple first rotors 12 using the power stored in the battery 52.

[0079] Next, an example in which the control device 4a corrects the upper limit of the flight altitude based on the ground conditions will be described with reference to FIGS.

[0080] 7 schematically shows an example of correcting the upper limit of flight altitude in accordance with the terrain directly below the multicopter 10 when the charging rate SOC is 0.7. Specifically, the upper limit is set to h5 when the terrain directly below the multicopter 10 is flat and there is a high possibility of a safe landing there. If the terrain directly below the multicopter 10 is a ground with a large slope or large unevenness, the upper limit is corrected to h6, which allows the multicopter 10 to move to a nearby flat location and land (moving along the route indicated by the dashed arrow).

[0081] In this way, in order to detect whether the terrain directly below the multicopter 10 is a ground with a large slope or unevenness or a flat ground, the multicopter 100 preferably includes a sensor 4S that monitors the ground conditions located below the multicopter 100 during flight. The sensor 4S is a sensor included in the sensor group 4b, and is, for example, an imaging device or a laser sensor. By using such a sensor 4S, the control device 4a can correct the maximum height based on the ground conditions. Note that instead of using such a sensor 4S that monitors the ground conditions, the control device 4a may obtain information about the terrain directly below the flight path from map information of the flight area.

[0082] Next, reference is made to FIG. 8. FIG. 8 schematically shows another example of correcting the upper limit of flight altitude in accordance with the terrain directly below the multicopter 10 when the charging rate SOC is 0.6. In this example, the control device 4a is configured to adaptively correct the upper limit of flight altitude based on terrain information. When the multicopter 10 flies over an area where landing is difficult, such as a steep slope, the control device 4a calculates the time or power required to land on a flat area ahead where landing is possible, and causes the multicopter 10 to descend. For example, if the upper limit of flight altitude over flat ground is altitude h7, then when flying over a slope, the upper limit is set to altitude h7. ＊ Altitude h7 ＊ The size of the slope is based on the altitude h7 ＊ The calculation is made so that the multicopter 10 at the point can land on the flat ground ahead.

[0083] The lower limit of the flight altitude can be set so that the distance from a building on the ground is equal to or greater than a predetermined value (for example, 30 m).

[0084] The above operation relates to an emergency landing that is performed when the generation of power by the power generation device 8 stops. Below, an example of an emergency transition to the "landing site transfer mode" when the generation of power by the power generation device 8 is possible will be described. The "landing site transfer mode" is a mode in which the driving force of the internal combustion engine 7a is used to move to a possible landing site and land there. The flight and landing operations in this mode are performed automatically by the operation of the control device 4a.

[0085] The flight time possible using the fuel carried in the multicopter 10 and the power stored in the battery 52 is represented by Y [minutes]. Meanwhile, the time required to fly to the nearest landing point, which is a distance X away, and complete landing (flight and landing time Tfd) is given by the following formula (1), as described above. Tfd = X / (60 x Sf) + 3 (Formula 1)

[0086] Here, it is assumed that the flight distance X is traveled at an average flight speed Sf and that the landing takes three minutes. The time period of three minutes can be set to a different value depending on the multicopter 10.

[0087] In this embodiment, the flight of the multicopter 10 is executed so that Y<Tfd does not occur. When Y=Tfd with respect to the nearest possible landing point, if flight continues, the available flight time Y will become shorter, and the state of Y=Tfd may immediately transition to a state of Y<Tfd. To avoid this situation, when Y=Tfd occurs, it is necessary to fly from the position where Y=Tfd becomes the nearest possible landing point and land there. For this reason, in this embodiment, when Y=Tfd occurs, the operation being performed up to that point is interrupted, and a "landing point movement mode" is activated in which the aircraft flies to the nearest possible landing point and lands.

[0088] An example of operation of the landing point movement mode will be described with reference to Figures 9 to 12. Figures 9 to 11 are plan views each showing an example of the positional relationship between the multicopter 10 flying while working over a field F and possible landing points P1 and P2 located around the field F. Figure 12 is a flowchart showing an example of operation of the control device that determines the start of the landing point movement mode.

[0089] First, refer to Figure 9. The dashed circle centered on the multicopter 10 indicates the maximum range (Distance To Empty: DTE) over which the multicopter 10 can fly within the available flight time Y. Note that when the wind is blowing in a fixed direction, the maximum range over which the multicopter 10 can fly within the available flight time Y is not represented by a perfect circle, but by an ellipse that is deformed according to the wind speed.

[0090] In this embodiment, the multicopter 10 can perform agricultural work, such as spraying pesticides, while flying in a field F. In FIG. 9 , the arrowed lines within the field F schematically represent the flight path traveled by the multicopter 10 in autonomous driving mode. When the multicopter 10 performs agricultural work, it often flies along a predetermined path above a work area such as the field F. However, the tasks that can be performed by the agricultural multicopter 10 are not limited to this example and may include tasks performed over a wide area including multiple fields, such as replenishing and transporting agricultural materials, transporting harvested crops, monitoring crop growth, surveying, and map creation. Note that when the multicopter 10 transports agricultural materials or harvested crops, for example, the multicopter 10 may fly automatically, autonomously, or remotely controlled above areas other than the field (such as forests and rivers).

[0091] In the example of FIG. 9 , a first possible landing point P1 is located a distance X1 away from the multicopter 10, and a second possible landing point P2 is located a distance X2 away from the multicopter 10. Distances X1 and X2 change depending on the position of the multicopter 10. Furthermore, since the available flight time Y decreases while the multicopter 10 is flying, the radius of the dashed circle decreases over time. For simplicity, the lines defining the distances X1 and X2 are represented by dotted straight lines in the figure, but the lines defining the distances X1 and X2 may also include curves. For example, if the multicopter 10 is required to fly around a no-fly zone or a structure such as a steel tower, it may need to fly along a curved route to the possible landing point. In this case, the distance is calculated along such a route.

[0092] In the example of FIG. 9, the time it takes for the multicopter 10 to fly from the current position to the second possible landing point P2 and land (flight and landing time Tfd ２ ) is the time from flying to the first possible landing point P1 until landing (flight and landing time Tfd １ ) In other words, the possible landing point at the shortest distance from the current position of the multicopter 10 is the second possible landing point P2. In the example of FIG. 9, Y>Tfd ２ That is, the flight and landing time Tfd from the current position of the multicopter 10 to the second possible landing point P2, which is the shortest distance, is ２ Therefore, the flight possibility interval Y is longer than the flight possibility interval Y. Therefore, the multicopter 10 continues flying and working.

[0093] Next, reference is made to FIG. 10. FIG. 10 schematically shows a state after the multicopter 10, which was in the position shown in FIG. 9, has continued flying and working. In the example shown in FIG. 10, the time it takes for the multicopter 10 to fly from its current position to the first possible landing point P1 and land (flight and landing time Tfd １ ) is the time it takes to fly to the second possible landing point P2 and land (flight and landing time Tfd ２ ) and Y>Tfd １ Therefore, the multicopter 10 continues to fly and operate.

[0094] Next, reference is made to FIG. 11. FIG. 11 schematically shows a state after the multicopter 10, which was in the position shown in FIG. 10, has continued flying and working. In the example shown in FIG. 11, the time from the current position of the multicopter 10 until it flies to the first possible landing point P1 and lands (flight and landing time Tfd １ ) is the time it takes to fly to the second possible landing point P2 and land (flight and landing time Tfd ２ ) and Y = Tfd １is established. Therefore, the multicopter 10 suspends its operation and activates the "landing point movement mode." Specifically, the multicopter 10 flies from its current position shown in FIG. 11 toward the first possible landing point P1. After reaching the airspace above the first possible landing point P1, the multicopter 10 begins a landing operation and lands at the first possible landing point P1. In this example, the multicopter 10 that has landed at the first landing start point P1 has consumed most of the fuel stored in the fuel tank 7b and the power stored in the battery 52.

[0095] The number of possible landing points is not limited to two, and may be one, or three or more. Furthermore, the possible landing points do not need to be small, spot-like sites, but may spread out like a surface or a strip. Each possible landing point may be a large area where multiple multicopters 10 can land simultaneously. Some or all of the possible landing points may be equipped with facilities for refueling or powering the multicopters 10. The possible landing points may be equipped with wireless communication devices or beacons, and may be configured to transmit or broadcast various information, including the location information of the possible landing point, to multicopters 10 flying in the vicinity. One of the possible landing points may be the flight start point.

[0096] Next, the operation flow will be described with reference to FIG.

[0097] First, after starting operation (startup), the control device 4a of the multicopter 10 acquires position information of possible landing points in step S20. Examples of the position information are not limited to position information in a geographic coordinate system, but may also be position coordinates on a map of the surrounding environment. The position information of possible landing points may be updated during flight.

[0098] In step S22, the control device 4a obtains the charge rate from the battery management system 54. The control device 4a also obtains remaining fuel amount and other information from sensors and the like. Examples of "other information" may include various information useful in determining the remaining flight time Y, such as battery temperature, air temperature, humidity, wind speed, and payload. The control device 4a calculates (or estimates) the remaining flight time Y based on these values.

[0099] In step S24, the control device 4a calculates the distance X from the current position to the possible landing point. If there are two or more possible landing points, the control device 4a calculates the distance X for each of the multiple possible landing points. Based on the shortest distance X, the control device 4a calculates the shortest time required for flight and landing to the nearest possible landing point (flight and landing time Tfd).

[0100] In step S26, the flight and landing time Tfd is compared with the available flight time Y, and if the available flight time Y is longer than the flight and landing time Tfd (Yes), the process returns to step S22. If the available flight time Y is no longer longer than the flight and landing time Tfd (No), in other words, if Tfd = Y, the process proceeds to step S28, where the operation is interrupted and the landing point movement mode is activated.

[0101] After activating the landing point movement mode, the multicopter 10 preferably notifies the user, operator, or administrator of the multicopter 10 that it is flying in the landing point movement mode and provides location information of the desired possible landing point.

[0102] As described above, according to this embodiment, when the multicopter 10 is about to run out of fuel, it can automatically fly to a predetermined possible landing point and land at a known location. Some multicopters fly in a "return-to-home" mode, returning to the starting point when communication is lost. Such multicopters can only fly within a predetermined distance from the starting point. However, according to this embodiment, by preparing possible landing points in advance, it is possible to expand the flight range and land at a location that is easy to recover. Furthermore, since the multicopter 10 has almost no fuel remaining when it lands, if it is to be recovered, the fuel can be effectively utilized up to the time of recovery.

[0103] The control device 4a in the embodiment of the present disclosure can be realized by a digital computer system programmed to execute the processes described with reference to FIGS.

[0104] 13 is a block diagram showing an example of the hardware configuration of the control device 4a. The control device 4a includes a processor 34, a read-only memory (ROM) 35, a random access memory (RAM) 36, a storage device 37, and a communication I / F 38. These components are connected to each other via a bus 39.

[0105] The processor 34 is one or more semiconductor integrated circuits, and is also referred to as a central processing unit (CPU) or a microprocessor. The processor 34 sequentially executes computer programs stored in the ROM 35 to perform the above-described processing. The term "processor 34" 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).

[0106] The ROM 35 is, for example, a writable memory (e.g., a PROM), a rewritable memory (e.g., a flash memory), or a read-only memory. The ROM 35 stores a program that controls the operation of the processor. The ROM 35 does not have 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 memories.

[0107] The RAM 36 provides a working area for temporarily loading the programs stored in the ROM 35 at boot time. The RAM 36 does not have to be a single recording medium, but can be a collection of multiple recording media.

[0108] The communication I / F 38 is an interface for communication between the control device 4a and other electronic components or electronic control units (ECUs). For example, the communication I / F 38 can perform wired communication in accordance with various protocols. The communication I / F 38 may perform wireless communication in accordance with the Bluetooth (registered trademark) standard and / or the Wi-Fi (registered trademark) standard. Both standards include wireless communication standards using frequencies in the 2.4 GHz band.

[0109] The storage device 37 may be, for example, a semiconductor memory, a magnetic storage device, an optical storage device, or a combination thereof. The storage device 37 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.

[0110] As described above, the control device 4a may include, for example, a flight control device such as a flight controller and a host computer (companion computer). The companion computer may execute the processes shown in Figures 6 and 12, and issue flight-related commands based on the results of those processes to the flight controller.

[0111] 14 , 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 100 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 100 and the agricultural machine 700. Some of the data used in processing by the control device 4a and control signals for the multicopter 100 may be provided from the agricultural machine 700 to the multicopter 100 via the communication network N.

[0112] This specification discloses the solutions described in the following items.

[0113] [Item 1] An unmanned aerial vehicle having multiple rotors, comprising: multiple electric motors that respectively drive multiple first rotors included in the multiple rotors; an internal combustion engine; a power generation device that is driven by the internal combustion engine to generate electricity; a battery that stores the electricity; and a control device that controls the flight of the unmanned aerial vehicle, the control device changing the upper limit of the flight altitude of the unmanned aerial vehicle depending on the state of charge of the battery.

[0114] [Item 2] The unmanned aerial vehicle described in Item 1, wherein the control device determines the maximum height at which the unmanned aerial vehicle can descend to the ground and land using the power stored in the battery when the power generation device is not generating power, and controls the upper limit of the flight altitude to be equal to or lower than the maximum height.

[0115] [Item 3] The unmanned aerial vehicle according to Item 2, further comprising a battery management system that monitors the battery, wherein the battery management system estimates a charge rate that defines the state of charge.

[0116] [Item 4] The unmanned aerial vehicle according to Item 3, wherein the battery management system charges the battery with the power generated by the power generation device and maintains the charging rate within a predetermined range.

[0117] [Item 5] The unmanned aerial vehicle described in Item 3, wherein the battery management system measures the temperature of the battery, and the control device determines the maximum height based on the estimated charge rate of the battery and the measured temperature.

[0118] [Item 6] The unmanned aerial vehicle described in Item 5, wherein the control device acquires a payload value of the unmanned aerial vehicle, and corrects the maximum height based on the payload value.

[0119] [Item 7] The unmanned aerial vehicle described in any one of Items 1 to 6, wherein the plurality of rotors includes at least one second rotor driven by the internal combustion engine.

[0120] [Item 8] An unmanned aerial vehicle described in any one of items 1 to 7, wherein the full charge capacity of the battery is such that, when the power generation device is not generating power, the power stored in the battery is sufficient to enable the unmanned aerial vehicle to descend from a predetermined reference height to the ground and land.

[0121] [Item 9] The unmanned aerial vehicle according to Item 8, wherein the reference height is 10 m or more and 300 m or less.

[0122] [Item 10] The unmanned aerial vehicle according to Item 9, wherein the reference height is 200 m or less.

[0123] [Item 11] An unmanned aerial vehicle described in any one of Items 1 to 10, wherein when the internal combustion engine stops during flight, the control device descends and lands the unmanned aerial vehicle while driving the multiple first rotors using the power stored in the battery.

[0124] [Item 12] An unmanned aerial vehicle described in any one of items 1 to 11, further comprising a sensor that monitors the condition of the ground located below the unmanned aerial vehicle during flight, and the control device corrects the maximum height based on the condition of the ground.

[0125] [Item 13] The unmanned aerial vehicle described in any one of Items 1 to 12, wherein the control device acquires information about meteorological conditions including wind speed and corrects the maximum height based on the information.

[0126] [Item 14] An unmanned aerial vehicle described in any one of items 1 to 13, wherein the control device is configured to perform the following: acquire location information of one or more possible landing points; determine the distance from the current position of the unmanned aerial vehicle to the nearest possible landing point, and determine the flight and landing time required for flying to and landing at the nearest possible landing point based on the distance; calculate the possible flight time of the unmanned aerial vehicle; and, when the possible flight time and the flight and landing time satisfy a predetermined relationship, initiate operations for flying to and landing at the nearest possible landing point.

[0127] [Item 15] An unmanned aerial vehicle having multiple rotors, comprising: a battery; and a control device that controls the flight of the unmanned aerial vehicle and changes the upper limit of the flight altitude of the unmanned aerial vehicle depending on the state of charge of the battery.

[0128] [Item 16] A control method for an unmanned aerial vehicle having multiple rotors, the control method comprising: estimating the state of charge of a battery equipped in the unmanned aerial vehicle; and varying the upper limit of the flight altitude of the unmanned aerial vehicle according to the state of charge.

[0129] [Item 17] An unmanned aerial vehicle having multiple rotors, comprising: a control device that controls the flight of the unmanned aerial vehicle, wherein the control device performs the following operations: determining the distance from the current position of the unmanned aerial vehicle to the nearest possible landing point, and determining the flight and landing time required for flying to and landing at the nearest possible landing point based on the distance; calculating the possible flight time of the unmanned aerial vehicle; and, when the possible flight time and the flight and landing time satisfy a predetermined relationship, commencing operations for flying to and landing at the nearest possible landing point.

[0130] [Item 18] A control method for an unmanned aerial vehicle having multiple rotors, which performs the following: determining the distance from the current position of the unmanned aerial vehicle to the nearest possible landing point, and determining the flight and landing time required for flying to and landing at the nearest possible landing point based on the distance; calculating the possible flight time of the unmanned aerial vehicle; and, when the possible flight time and the flight and landing time satisfy a predetermined relationship, commencing operations for flying to and landing at the nearest possible landing point.

[0131] 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.

[0132] 2: Rotor (propeller), 3: Rotation drive device, 4: Airframe body, 4a: Control device, 4b: Sensor group, 4c: Communication device, 5: Airframe frame, 10: Multicopter, 12: Sub-rotor, 12a: Propeller, 12b: Propeller, 14: Motor, 16: ESC, 22: Main rotor, 52: Battery, 54: Battery management system

Claims

1. 1. An unmanned aerial vehicle having multiple rotors, a plurality of electric motors that respectively drive a plurality of first rotors included in the plurality of rotors; an internal combustion engine; a power generation device driven by the internal combustion engine to generate electric power; a battery that stores the power; a control device for controlling the flight of the unmanned aerial vehicle, the control device changing an upper limit of flight altitude of the unmanned aerial vehicle according to a state of charge of the battery; An unmanned aerial vehicle comprising:

2. The unmanned aerial vehicle described in claim 1, wherein the control device determines the maximum height at which the unmanned aerial vehicle can descend to the ground and land using the power stored in the battery when the power generation device is not generating power, and controls the upper limit of the flight altitude to be below the maximum height.

3. a battery management system that monitors the battery; The unmanned aerial vehicle of claim 2 , wherein the battery management system estimates a charge rate that defines the state of charge.

4. The unmanned aerial vehicle according to claim 3 , wherein the battery management system charges the battery with the power generated by the power generation device and maintains the charging rate within a predetermined range.

5. the battery management system measures the temperature of the battery; The unmanned aerial vehicle of claim 3 , wherein the controller determines the maximum height based on an estimate of the charge rate of the battery and the temperature measurement.

6. The control device acquires a payload value of the unmanned aerial vehicle; The unmanned aerial vehicle according to claim 5 , wherein the maximum height is corrected based on the payload value.

7. The unmanned aerial vehicle of claim 1 , wherein the plurality of rotors includes at least one second rotor driven by the internal combustion engine.

8. An unmanned aerial vehicle described in any one of claims 1 to 6, wherein the full charge capacity of the battery is such that, when the power generation device is not generating power, the power stored in the battery enables the unmanned aerial vehicle to descend from a predetermined reference height to the ground and land.

9. The unmanned aerial vehicle according to claim 8, wherein the reference height is equal to or greater than 10 m and equal to or less than 300 m.

10. The unmanned aerial vehicle according to claim 9 , wherein the reference height is 200 m or less.

11. An unmanned aerial vehicle as described in any one of claims 1 to 6, wherein when the internal combustion engine stops during flight, the control device descends and lands the unmanned aerial vehicle while driving the multiple first rotors using the power stored in the battery.

12. a sensor that monitors ground conditions below the unmanned aerial vehicle during flight; The unmanned aerial vehicle described in any one of claims 1 to 6, wherein the control device corrects the maximum height based on the ground conditions.

13. The unmanned aerial vehicle described in any one of claims 1 to 6, wherein the control device acquires information about weather conditions including wind speed and corrects the maximum height based on the information.

14. The control device obtaining location information for one or more possible landing sites; determining a distance from a current location of the unmanned aerial vehicle to a nearest possible landing point, and determining a flight and landing time required for flying to and landing at the nearest possible landing point based on the distance; Calculating the flight time of the unmanned aerial vehicle; and When the flight time and the flight and landing time satisfy a predetermined relationship, starting an operation for flight to and landing at the nearest possible landing point; The unmanned aerial vehicle of claim 1 , configured to execute the following: