Unmanned aerial vehicle, and control system and control method for unmanned aerial vehicle

Abstract

This unmanned aerial vehicle comprises: a plurality of rotors including a plurality of first rotors and at least one second rotor; and a control device that executes attitude control of an airframe by controlling rotation of the plurality of first rotors and generates a main thrust by controlling rotation of the at least one second rotor. The control device calculates a first thrust, which is the total thrust generated by the plurality of first rotors, calculates a second thrust, which is the total thrust generated by the at least one second rotor, on the basis of the first thrust and the total thrust required for flight, determines the respective rotation speeds of the plurality of first rotors on the basis of the first thrust, and determines the rotation speed of the at least one second rotor on the basis of the second thrust.

Description

Unmanned aerial vehicle, and control system and control method for unmanned aerial vehicle

[0001] The present disclosure relates to unmanned aerial vehicles, and control systems and methods for 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] Patent Document 2 describes an unmanned aerial vehicle (autonomous flying device) that can increase the payload and continuous flight time and can accurately adjust its position and attitude during flight.

[0005] JP 2022-104737 A JP 2019-59362 A

[0006] The maximum payload and flight time of unmanned aerial vehicles are insufficient for some applications, and further improvements are required.

[0007] The present disclosure provides unmanned aerial vehicles suitable for agricultural applications that allow for increased payload and / or flight time.

[0008] The present disclosure provides the solutions described in the following items.

[0009] [Item A1] An unmanned aerial vehicle comprising: a plurality of first rotors; a plurality of second rotors; and a control device that performs attitude control of the vehicle by controlling the rotation of the plurality of first rotors and generates main thrust by controlling the rotation of the plurality of second rotors, wherein the control device reduces the total thrust of the plurality of second rotors when performing rudder control that controls the rotation of the plurality of first rotors to adjust the yaw angle of the vehicle.

[0010] [Item A2] The unmanned aerial vehicle according to Item A1, wherein the control device reduces the total thrust of the plurality of second rotors by reducing the rotational speed of each of the plurality of second rotors.

[0011] [Item A3] The unmanned aerial vehicle according to Item A1 or A2, wherein the control device performs the rudder control when controlling the vehicle to a target yaw angle, when a control delay in the yaw angle occurs, or when rotation or shaking in the yaw direction occurs.

[0012] [Item A4] The unmanned aerial vehicle according to any one of Items A1 to A3, wherein the diameter of each of the plurality of second rotors is larger than the diameter of each of the plurality of first rotors.

[0013] [Item A5] The unmanned aerial vehicle described in any one of Items A1 to A4, wherein the thrust per rotation of each of the plurality of second rotors is greater than the thrust per rotation of each of the plurality of first rotors.

[0014] [Item A6] An unmanned aerial vehicle described in any one of Items A1 to A5, wherein the distance from the center of the airframe to the rotation axis of each of the plurality of second rotors is shorter than the distance from the center of the airframe to the rotation axis of each of the plurality of first rotors.

[0015] [Item A7] The unmanned aerial vehicle described in any one of Items A1 to A6, wherein the control device makes the total thrust of the multiple second rotors greater than the total thrust of the multiple first rotors during hovering, and makes the total thrust of the multiple second rotors smaller than the total thrust of the multiple first rotors when performing the rudder control.

[0016] [Item A8] The unmanned aerial vehicle described in any one of Items A1 to A7, wherein when performing the rudder control, the control device reduces the rotational speed of each of the plurality of second rotors so as to reduce the total thrust of the plurality of second rotors by 5% or more.

[0017] [Item A9] The unmanned aerial vehicle described in Item A8, wherein when performing the rudder control, the control device compensates for the total thrust of the multiple second rotors, which is reduced due to a decrease in the rotational speed of each of the multiple second rotors, by increasing the rotational speed of the multiple first rotors.

[0018] [Item A10] The unmanned aerial vehicle according to any one of Items A1 to A9, wherein the control device stops rotation of each of the plurality of second rotors when performing the rudder control.

[0019] [Item A11] An unmanned aerial vehicle described in any one of Items A1 to A10, further comprising: a plurality of electric motors that respectively drive the plurality of first rotors; and an internal combustion engine that drives the plurality of second rotors, wherein the control device controls the rotation of the plurality of first rotors by controlling the plurality of electric motors, and controls the rotation of the plurality of second rotors by controlling the internal combustion engine.

[0020] [Item A12] A control method for an unmanned aerial vehicle having a plurality of first rotors and a plurality of second rotors, comprising: performing attitude control of the vehicle by controlling the rotation of the plurality of first rotors; and generating main thrust by controlling the rotation of the plurality of second rotors, wherein performing the attitude control comprises performing rudder control to adjust the yaw angle of the vehicle by controlling the rotation of the plurality of first rotors; and reducing the total thrust of the plurality of second rotors when performing the rudder control.

[0021] [Item B1] An unmanned aerial vehicle comprising: a plurality of rotors including a plurality of first rotors and at least one second rotor; and a control device that performs attitude control of the aircraft by controlling the rotation of the plurality of first rotors and generates a main thrust by controlling the rotation of the at least one second rotor, wherein the control device: calculates a first thrust which is the total thrust to be generated by the plurality of first rotors; calculates a second thrust which is the total thrust to be generated by the at least one second rotor based on the first thrust and the total thrust required for flight; determines the rotational speed of each of the plurality of first rotors based on the first thrust; and determines the rotational speed of the at least one second rotor based on the second thrust.

[0022] [Item B2] The unmanned aerial vehicle according to Item B1, wherein the control device calculates the second thrust by subtracting the first thrust from a total thrust required for the flight.

[0023] [Item B3] The control device determines the first thrust by multiplying the total thrust required for the flight by a first coefficient greater than or equal to 0 and less than or equal to 1, and determines the second thrust by multiplying the total thrust by a second coefficient that is 1 minus the first coefficient, or by multiplying the first thrust by a third coefficient that is the second coefficient divided by the first coefficient. An unmanned aerial vehicle as described in Item B1.

[0024] [Item B4] The unmanned aerial vehicle according to Item B3, wherein the control device changes the first coefficient and the second coefficient or the third coefficient depending on the state of the unmanned aerial vehicle.

[0025] [Item B5] The unmanned aerial vehicle according to Item B3 or B4, wherein the control device sets the first coefficient to a value smaller than 0.5 during hovering.

[0026] [Item B6] The unmanned aerial vehicle according to any one of Items B3 to B5, wherein the control device determines the second thrust by multiplying the first thrust by the third coefficient.

[0027] [Item B7] The unmanned aerial vehicle according to any one of Items B3 to B6, wherein the control device changes the first coefficient and the second coefficient or the third coefficient depending on a flight mode.

[0028] [Item B8] The unmanned aerial vehicle according to any one of Items B3 to B7, wherein the control device changes the first coefficient and the second coefficient or the third coefficient in response to a user operation.

[0029] [Item B9] The unmanned aerial vehicle according to any one of Items B1 to B8, wherein the diameter of the at least one second rotor is larger than the diameter of each of the plurality of first rotors.

[0030] [Item B10] The unmanned aerial vehicle according to any one of Items B1 to B9, wherein the thrust per rotation of each of the plurality of second rotors is greater than the thrust per rotation of each of the plurality of first rotors.

[0031] [Item B11] An unmanned aerial vehicle described in any one of Items B1 to B10, wherein the distance from the center of the airframe to the rotation axis of each of the plurality of second rotors is shorter than the distance from the center of the airframe to the rotation axis of each of the plurality of first rotors.

[0032] [Item B12] An unmanned aerial vehicle described in any one of Items B1 to B11, further comprising: a plurality of electric motors that respectively drive the plurality of first rotors; and an internal combustion engine that drives the at least one second rotor, wherein the control device controls the rotation of the plurality of first rotors by controlling the plurality of electric motors, and controls the rotation of the at least one second rotor by controlling the internal combustion engine.

[0033] [Item B13] A control method executed by a control device in an unmanned aerial vehicle comprising a plurality of rotors including a plurality of first rotors and at least one second rotor, and a control device that performs attitude control of the vehicle by controlling the rotation of the plurality of first rotors and generates main thrust by controlling the rotation of the at least one second rotor, the control method including: calculating a first thrust to be generated in the plurality of first rotors; calculating a second thrust to be generated in the at least one second rotor based on the first thrust and a total thrust required for flight; determining the rotational speed of each of the plurality of first rotors based on the first thrust; and determining the rotational speed of the at least one second rotor based on the second thrust.

[0034] [Item C1] An unmanned aerial vehicle comprising: a plurality of electric motors; an internal combustion engine; a plurality of first rotors each driven by the plurality of electric motors; at least one second rotor driven by the internal combustion engine; and a control device, wherein the control device determines a first rotational speed of each of the plurality of first rotors and a second rotational speed of the at least one second rotor, generates a first control signal for rotating each of the plurality of electric motors based on the first rotational speed of each of the plurality of first rotors, and generates a second control signal for driving the internal combustion engine based on the second rotational speed.

[0035] [Item C2] The unmanned aerial vehicle according to Item C1, wherein the control device generates the second control signal based on a table that converts the second rotational speed into a rotational speed of the internal combustion engine.

[0036] [Item C3] The unmanned aerial vehicle described in Item C1 or C2, wherein the control device controls the plurality of electric motors to control the rotation of the plurality of first rotors to perform attitude control of the airframe, and controls the internal combustion engine to control the rotation of the at least one second rotor to generate main thrust.

[0037] [Item C4] An unmanned aerial vehicle described in any one of Items C1 to C3, wherein the control device generates a first PWM (Pulse Width Modulation) signal having a duty ratio according to the first rotational speed as the first control signal, generates a second PWM signal having a duty ratio according to the second rotational speed of the at least one second rotor, and converts the second PWM signal into the second control signal that determines the rotational speed of the internal combustion engine.

[0038] [Item C5] The unmanned aerial vehicle described in Item C4, wherein the control signal is generated by reading data indicating the relationship between the duty ratio of the second PWM signal and the rotation speed per unit time of the internal combustion engine from a storage device, determining the rotation speed based on the data and the second PWM signal, and generating the second control signal based on the rotation speed.

[0039] [Item C6] The unmanned aerial vehicle described in Item C4, wherein the second control signal determines the opening of a throttle valve of the internal combustion engine, and the control device reads data indicating the relationship between the duty ratio of the second PWM signal and the opening of the throttle valve from a storage device, and converts the second PWM signal into the second control signal based on the data.

[0040] [Item C7] An unmanned aerial vehicle described in any one of Items C4 to C6, wherein the control device: determines a first thrust which is the sum of the thrusts to be generated by the multiple first rotors and a second thrust which is the sum of the thrusts to be generated by the at least one second rotor; generates the first control signal for each of the multiple first rotors based on the first thrust; and determines the second PWM signal based on the first control signal and the ratio between the second thrust and the first thrust.

[0041] [Item C8] The unmanned aerial vehicle according to any one of Items C1 to C7, wherein the diameter of the at least one second rotor is larger than the diameter of each of the plurality of first rotors.

[0042] [Item C9] An unmanned aerial vehicle according to any one of Items C1 to C8, wherein the thrust per rotation of each of the plurality of second rotors is greater than the thrust per rotation of each of the plurality of first rotors.

[0043] [Item C10] An unmanned aerial vehicle described in any one of Items C1 to C9, wherein the distance from the center of the airframe to the rotation axis of each of the plurality of second rotors is shorter than the distance from the center of the airframe to the rotation axis of each of the plurality of first rotors.

[0044] [Item C11] A control method executed by a control device in an unmanned aerial vehicle including a plurality of electric motors, an internal combustion engine, a plurality of first rotors each driven by the plurality of electric motors, at least one second rotor driven by the internal combustion engine, and a control device, the control method including: determining a first rotational speed of each of the plurality of first rotors and a second rotational speed of the at least one second rotor; generating a first control signal that rotates each of the plurality of electric motors based on the first rotational speed; and generating a second control signal that drives the internal combustion engine based on the second rotational speed.

[0045] According to embodiments of the unmanned aerial vehicle and its control system and control method disclosed herein, it is possible to realize an unmanned aerial vehicle that is suitable for agricultural applications and that can increase payload and / or flight time.

[0046] 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 top view schematically showing a multicopter in an exemplary embodiment. FIG. 9 is a side view schematically showing a multicopter in an exemplary embodiment. FIG. 10 is a block diagram showing an example system configuration of a multicopter in an exemplary embodiment. FIG. 11 is a plan view schematically showing a parallel hybrid drive multicopter. FIG. 12 is a flowchart showing an example of a process for determining the rotational speeds of each sub-rotor and each main rotor. FIG. 13 is a flowchart showing an outline of the operation of a control device related to rudder control. FIG. 14 is a flowchart showing an example of a control method for an electric motor and an internal combustion engine. FIG. 15 is a block diagram showing an example configuration of a flight controller. FIG. 16 is a diagram showing an example configuration of a module that generates a PWM signal for the main rotor. 1 is a graph showing an example of time variations in the duty sum value of the PWM signals for the sub-rotors and the duty value of the PWM signal for the main rotor. FIG. 2 is a diagram showing an example of the configuration of a main rotor control unit. FIG. 3 is a graph showing an example of the correspondence relationship between the duty ratio of the PWM signal and the engine rotation speed. FIG. 4 is a block diagram showing an example of the hardware configuration of a control device. FIG. 5 is a diagram schematically showing an example of a communication network to which a multicopter is connected.

[0047] 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."

[0048] There are various configurations of the rotary drive unit included in a multicopter. Figure 1A is a block diagram schematically illustrating four examples of the rotary drive unit 3 in this disclosure.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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."

[0053] 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.

[0054] 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."

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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).

[0059] 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.

[0060] The battery 52 is a secondary battery that stores power by charging and supplies power to the motors 14 by discharging. The battery 52 and the multiple motors 14 operate to rotate the multiple rotors 2, making it possible to generate a desired thrust.

[0061] Each of the multiple rotors 2 generally has multiple blades with a fixed pitch angle and generates thrust by 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 a rotating rotor 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 a relatively larger diameter may be referred to as the "main rotor," and the rotor 2 with a relatively smaller diameter may be referred to as the "sub-rotor." Note that, regardless of the diameter, the configuration of the rotary drive device 3 may include a rotor 2 capable of generating a relatively larger thrust and a rotor 2 with a relatively smaller thrust. In this case, the rotor 2 capable of generating a relatively larger thrust may be referred to as the "main rotor," and the rotor 2 with a relatively smaller thrust may be referred to as the "sub-rotor." For example, the rotor 2 that generates a relatively large thrust per rotation may be referred to as the "main rotor," and the rotor 2 that generates a relatively small thrust per rotation may be referred to as the "sub-rotor." In one example, the main rotor may be positioned more inward than the sub-rotors. In other words, each rotor 2 may be positioned so that the distance from the center of the airframe to the rotation axis of each main rotor is shorter than the distance from the center of the airframe to the rotation axis of each sub-rotor.

[0062] 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.

[0063] 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 each blade 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.

[0064] 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.

[0065] 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."

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] FIG. 2A is a block diagram illustrating an example of the basic configuration of a battery-powered multicopter 10. 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 motors 14 via each ESC 16, a control device 4a for controlling the multiple 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 illustrates 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] <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.

[0078] 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.

[0079] 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 110 supports an airframe body 120 including various electronic and mechanical components, which will be described later.

[0080] 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.

[0081] <System Configuration> FIG. 4 is a block diagram showing an example of a system configuration of the multicopter 100 according to this embodiment.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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 .

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] In this embodiment, the motor 14 functions as a plurality of "attitude control devices" that respectively drive a plurality of first rotors (sub-rotors) 12. In addition, the main rotor drive unit 24, which is an internal combustion engine, functions as a "main thrust generating device" that drives the second rotor (main rotor) 22.

[0098] In the example shown in FIG. 4, the control device 30 and the main rotor control unit 26 are separate components, but a single control device (computer or ECU) may have the functions of the control device 30 and the main rotor control unit 26.

[0099] In this embodiment, the control device 30 can change the ratio (thrust ratio) between the total thrust (first thrust) of the sub-rotor 12 obtained from the multiple motors 14 and the total thrust (second thrust) of the main rotor 22 obtained from the main rotor drive unit 24. This point will be described in detail below.

[0100] Generally, the responsiveness of the motor 14 is superior to that of an internal combustion engine. If the time from when a torque command signal is input until the torque required to rotate the rotors 12, 22 reaches a target torque value is called the "response time," the response time of the motor is, for example, approximately 1 / 100 of the response time of the internal combustion engine. Therefore, to control the attitude of the multicopter 100, it is desirable to detect the difference between the current and target attitude angles of the multicopter 100 and control the rotational speed of each of the multiple sub-rotors 12 with a high response speed so as to reduce this difference. An increase in rotor rotational speed results in an increase in thrust. By adjusting the thrust of each of the multiple sub-rotors 12, the attitude of the multicopter 100 can be controlled quickly and with high precision.

[0101] On the other hand, an internal combustion engine can efficiently generate large thrust. The sub-rotor 12 is rotated using electric power generated by the power of the main rotor drive unit 24, which is an internal combustion engine, but energy loss occurs when converting mechanical energy into electrical energy. Therefore, from the perspective of improving energy consumption efficiency, it is preferable that the main rotor drive unit 24 be used to rotate the main rotor 22 and generate the main thrust. Furthermore, to increase the thrust of the main rotor 22, it is preferable that the diameter of the main rotor 22 be larger than the diameter of each of the multiple sub-rotors 12.

[0102] However, when the main rotor 22, which generates the main thrust, generates a large thrust, the large thrust and rotational moment may actually inhibit the attitude control function of the sub-rotor 12. As a result, even if multiple sub-rotors 12 are rotated using multiple motors 14 with excellent response, a delay in response may occur in attitude control. On the other hand, if the rotation speed of the main rotor 22 is reduced, attitude control performance improves, but energy consumption efficiency decreases.

[0103] Battery-powered multicopters use various algorithms to adjust the torque of each of the multiple motors to regulate the thrust of each rotor and control it to a desired attitude. When controlling attitude using multiple motors, adding a rotor rotated by an internal combustion engine can complicate the calculations required for attitude control. To avoid this complexity, it is effective to fix the "ratio" between the thrust obtained from the multiple motors and the thrust obtained from the internal combustion engine. For this reason, conventional parallel hybrids have adopted a control method that fixes this ratio.

[0104] However, as a result of studies by the inventors, it has been found that when using the multicopter 100 for agricultural work, for example, it is preferable to make the above-mentioned "ratio" variable rather than fixed, compared to when flying the multicopter 100 for simple logistics or surveillance purposes. This is because when flying the multicopter 100 for agricultural purposes, it flies under a variety of different conditions, such as various agricultural tasks (ground tasks) within a field, traveling between multiple fields, and transporting agricultural materials or harvested crops. The level of response speed required for attitude control varies greatly depending on these conditions. Furthermore, when various types of implements with different weights and shapes are appropriately selected and connected depending on the type of agricultural work, the required lift and attitude control accuracy can also vary greatly.

[0105] In this embodiment, when precise attitude control is not required, for example, when there is little external disturbance such as wind and the payload is small, or when only movement is required without performing work using the work equipment, the thrust of the main rotor 22 can be increased and the thrust of the sub-rotor 12 can be reduced instead.

[0106] On the other hand, when precise attitude control is required, for example, when performing ground work while flying with a work machine coupled, or when it is required to move the aircraft body more agilely to change attitude than in normal flight, it is preferable to reduce (or eliminate) the thrust of the main rotor 22 and instead increase the thrust of the sub-rotor 12. Reducing the thrust of the main rotor in this way results in an overall decrease in energy consumption efficiency, but makes it possible to improve attitude control performance (response performance).

[0107] <Determining Rotational Speeds of Main Rotors and Sub-Rotors> Next, an example of a method for determining the rotational speeds of each main rotor 22 and each sub-rotor 12 will be described.

[0108] FIG. 5 is a plan view schematically illustrating a parallel hybrid drive multicopter 100. FIG. 5 shows an xyz coordinate system defined by mutually orthogonal x-, y-, and z-axes. This coordinate system is fixed to the airframe of the multicopter 100, and its origin is located at the center of the airframe (e.g., the center of gravity). The x-axis is an axis extending forward of the airframe and is also referred to as the "roll axis." The y-axis is an axis extending leftward of the airframe and is also referred to as the "pitch axis." The z-axis is an axis extending upward of the airframe and is also referred to as the "yaw axis."

[0109] The multicopter 100 shown in FIG. 5 includes two main rotors 22 and eight sub-rotors 12. Each of the two main rotors 22 is supported by two arms 110B1 and 110B2 extending along the x-axis. The two main rotors 22 are controlled to rotate in opposite directions. The eight sub-rotors 12 are configured as four sets of two coaxial sub-rotors 12. Each of the four sets of sub-rotors 12 is supported by four arms 110A1, 110A2, 110A3, and 110A4 that form 45-degree angles with the x-axis and y-axis. The two sub-rotors 12 in each set are controlled to rotate in opposite directions. The distance from the center of the airframe to the rotation axis of each main rotor 22 is shorter than the distance from the center of the airframe to the rotation axis of each sub-rotor 12. The diameter of each main rotor 22 is larger than the diameter of each sub-rotor 12. 5, each main rotor 22 is represented by a relatively large circle, and the two coaxial sub-rotors 12 are represented by a relatively small circle. The magnitude of the rotational speed of the four sub-rotors 12 located on the upper side (positive side of the z-axis) is expressed as ω １ , ω ２ , ω ３ , ω ４ and the magnitude of the rotational speed of the four sub-rotors 12 located on the lower side (negative side of the z-axis) is ω ５ , ω ６ , ω ７ , ω ８ The magnitude of the rotational speed of the two main rotors 22 is set as ω ｍ１ , ω ｍ２ Here, the "rotational speed" is the number of rotations per unit time (for example, unit: rpm) or angular velocity (for example, unit: rad / s).

[0110] Of the two sub-rotors 12 supported by the upper right arm 110A1 in FIG. 5, the sub-rotor 12 on the positive side of the z-axis (upper side) rotates clockwise at a rotation speed ω １ The sub-rotor 12 on the negative side of the z-axis (lower side) rotates counterclockwise at a rotational speed ω ５ Of the two sub-rotors 12 supported by the lower right arm 110A2, the sub-rotor 12 on the positive side of the z-axis rotates counterclockwise at a rotation speed ω２ The sub-rotor 12 on the negative side of the z-axis rotates clockwise at a rotation speed ω ６ Of the two sub-rotors 12 supported by the lower left arm 110A3, the sub-rotor 12 on the positive side of the z-axis rotates clockwise at a rotation speed ω ３ The sub-rotor 12 on the negative side of the z-axis rotates counterclockwise at a rotation speed ω ７ Of the two sub-rotors 12 supported by the upper left arm 110A4, the sub-rotor 12 on the positive side of the z-axis rotates counterclockwise at a rotation speed ω ４ The sub-rotor 12 on the negative side of the z-axis rotates clockwise at a rotation speed ω ８ The main rotor 22 supported by an arm 110B1 extending from the center of the aircraft in the positive direction of the x-axis rotates clockwise at a rotational speed ω ｍ１ The main rotor 22 supported by the arm 110B2 extending from the center of the aircraft to the negative side of the x-axis rotates counterclockwise at a rotational speed ω ｍ２ Rotate with.

[0111] The length of each of the four arms 110A1, 110A2, 110A3, and 110A4 supporting the sub-rotor 12 is 1, and the length of each of the two arms 110B1 and 110B2 supporting the main rotor 22 is 1. ｍ Furthermore, the total thrust generated by the rotation of the multiple main rotors 22 and the multiple sub-rotors 12 is T, and the torque of the rotation around the x-axis is τ φ , the torque around the y-axis is τ θ , the torque around the z-axis is τ ψ Let's say.

[0112] Total thrust T and torque τ φ , τ θ , τ ψ and the rotation speed ω of the sub-rotor 12 １ , ω ２ , ω ３ , ω ４ , ω ５ , ω ６ , ω ７ , ω ８ and the rotation speed ω of the main rotor 22 ｍ１ , ω ｍ２ The relationship between is expressed by the following equation 1. Here, k, k ｍ , b, b ｍ is a predetermined coefficient. ｍ , b, b ｍ is a fixed value determined by the size, shape, and arrangement of the sub-rotor 12 and the main rotor 22, and is stored in advance in a storage device. Note that the relationship shown in Equation 1 is merely an example, and if a configuration different from the configuration shown in Figure 5 is adopted, a relational expression different from Equation 1 will hold. Here, an example in which Equation 1 holds will be described.

[0113] When the term relating to the main rotor 22 and the term relating to the sub-rotor 12 are separated on the right side of Equation 1, the following Equation 2 is obtained.

[0114] In this embodiment, the two main rotors 22 are controlled to rotate in synchronous with each other in opposite directions. ｍ１ =ω ｍ２ =ω ｍ This allows us to calculate the torque τ θ and τ ψ The components of the thrust force due to the main rotor 22 cancel each other out, leaving only the thrust component as the contribution from the main rotor 22. Therefore, Equation 2 is transformed as follows:

[0115] When the inverse matrix of the matrix on the right side of Equation 3 is applied to both sides from the left, the relationship of Equation 4 below is obtained.

[0116] Therefore, T-2k ｍ ω ｍ ２ , τ φ , τ θ , τ ψ Once this is determined, the rotational speed ω of the sub-rotor 12 can be calculated by the calculation of Equation 4. １ , ω ２ , ω ３ , ω ４ , ω ５ , ω ６ , ω ７ , ω ８ T-2k can be determined. ｍ ω​​ｍ ２ corresponds to the total thrust of the multiple sub-rotors 12. ｍ ω ｍ ２ is the unknown ω ｍ However, when the ratio between the total thrust of the main rotor 22 and the total thrust of the sub-rotor 12 is fixed, T-2k ｍ ω ｍ ２ T-2k can be determined. ｍ ω ｍ ２ can be calculated by multiplying T by a constant coefficient. For example, if the ratio of the total thrust of the main rotor 22 to the total thrust of the sub-rotor 12 is fixed at 6:4, multiplying T by a coefficient of 0.4 gives T-2k ｍ ω ｍ ２ Furthermore, if the ratio of the total thrust of the main rotor 22 to the total thrust of the sub-rotor 12 is fixed at, for example, 3:7, multiplying T by a coefficient of 0.7 gives T-2k ｍ ω ｍ ２ Therefore, when the ratio between the total thrust of the main rotor 22 and the total thrust of the sub-rotors 12 is fixed, the total thrust T of all rotors and the torque τ about each axis can be determined. φ , τ θ , τ ψ Once this is determined, the rotational speed ω of the sub-rotor 12 can be calculated by the calculation of Equation 4. １ , ω ２ , ω ３ , ω ４ , ω ５ , ω ６ , ω ７ , ω ８ In addition, the total thrust T by all rotors or the total thrust T-2k by the sub-rotors 12 can be determined. ｍ ω ｍ ２ By multiplying this by a predetermined coefficient, the total thrust 2k by the main rotor 22 is ｍ ω ｍ ２ can be calculated. ｍ Since is known, 2kｍ ω ｍ ２ From the value of ω ｍ can be calculated.

[0117] As described above, the control device 30 calculates the desired thrust T and the torque τ around each axis. φ , τ θ , τ ψ and the rotational speed ω of the sub-rotor 12 based on the relationship of Equation 4. １ , ω ２ , ω ３ , ω ４ , ω ５ , ω ６ , ω ７ , ω ８ and the rotation speed ω of the main rotor 22 ｍ can be determined.

[0118] An example of the process of determining the rotational speed of each rotor by the control device 30 will be described below with reference to FIG.

[0119] 6 is a flowchart showing an example of a process for determining the rotational speeds of each sub-rotor 12 and each main rotor 22. The process shown in FIG. 6 can be executed by, for example, the flight controller 32 in the control device 30. The control device 30 executes the processes of steps S100 to S114 to determine the rotational speeds ω １ , ω ２ , ω ３ , ω ４ , ω ５ , ω ６ , ω ７ , ω ８ and the rotation speed ω of each main rotor 22 ｍ can be determined.

[0120] In step S100, the control device 30 acquires information about the total weight of the multicopter 100 and the working machine 200. The information about the total weight may be stored in advance in a storage device, for example. Alternatively, the weight of the multicopter 100 may be stored in advance in a storage device, and the weight of the working machine 200 may be measured by a sensor. By providing such a sensor, the total weight can be estimated more accurately even if the weight of the working machine 200 fluctuates due to work such as spraying pesticides or harvesting. The control device 30 may calculate the total weight of the multicopter 100 and the working machine 200 based on data acquired from the storage device or the sensor.

[0121] In step S102, the control device 30 determines the sum (total thrust) T of the thrust to be generated by the multiple sub-rotors 12 and the multiple main rotors 22. The control device 30 can determine the total thrust T based on information about the total weight of the multicopter 100 and the work machine 200 and the flight state. For example, during hovering, the control device 30 can determine the thrust that balances the total weight of the multicopter 100 and the work machine 200 as the total thrust T. During horizontal flight, the control device 30 can determine the total thrust T based on the condition that the vertical component of the thrust balances with gravity, taking into account the inclination of the airframe. During ascent or descent, the control device 30 determines the total thrust T so that the airframe ascends or descends at the desired acceleration.

[0122] In step S104, the control device 30 estimates the current attitude angle of the multicopter 100 based on data acquired from one or more sensors such as the IMU and the geomagnetic sensor. The attitude angle represents the tilt of the multicopter 100 from a reference attitude in a coordinate system fixed to the ground.

[0123] In step S106, the control device 30 calculates the required torque τ around each axis based on the difference between the current attitude angle of the multicopter 100 and the target attitude angle. φ , τ θ , τ ψThe target attitude angle can be determined, for example, by a user operating a pilot or in accordance with a preset flight program. For example, the control device 30 determines the torque for each of the roll angle, pitch angle, and yaw angle to be a larger value as the difference between the angle and the target angle increases.

[0124] The processes of steps S104 and S106 may be performed before the processes of steps S100 and S102, or may be performed in parallel.

[0125] In step S108, the control device 30 applies a first coefficient K between 0 and 1 to the total thrust T determined in step S102. １ By multiplying the first thrust T １ Determine the first coefficient K １ may be set to a predetermined value, such as 0.4.

[0126] In step S110, the control device 30 multiplies the total thrust T by a second coefficient K, which is a value obtained by subtracting the first coefficient from 1. ２ (= 1-K １ ) or multiply by the first thrust T １ , the second coefficient K ２ The first coefficient K １ The third coefficient K is the value divided by ３ (=K ２ / K １ ) to obtain a second thrust T ２ The second coefficient K is calculated by multiplying the total thrust T by the ２ and the first thrust T １ The third coefficient K ３ The multiplication operation yields the same result.

[0127] The second thrust T is the total thrust of the main rotor 22. ２ and the first thrust T which is the total thrust of the sub-rotor 12. １ The ratio of T to T may be set to a predetermined ratio, such as 6:4. ２ : T １ If T = 6:4, the first coefficient is set to 0.4, the second coefficient is set to 0.6, and the third coefficient is set to 1.5.２ : T １ = 5:5, the first coefficient is set to 0.5, the second coefficient is set to 0.5, and the third coefficient is set to 1. ２ : T １ If T = 2:8, the first coefficient is set to 0.8, the second coefficient is set to 0.2, and the third coefficient is set to 0.25. ２ / T １ This corresponds to the first thrust T １ is T-2k in Equation 4 ｍ ω ｍ ２ corresponds to the second thrust T ２ is 2k in Equation 4 ｍ ω ｍ ２ is equivalent to

[0128] In step S112, the control device 30 calculates the determined first thrust T １ (=T-2k ｍ ω ｍ ２ ) and the required torque τ around each axis φ , τ θ , τ ψ Based on this, the control device 30 executes the calculation shown in Equation 4. As a result, the rotation speed ω of the sub-rotor 12 is calculated as follows: １ , ω ２ , ω ３ , ω ４ , ω ５ , ω ６ , ω ７ , ω ８ can be determined.

[0129] In step S114, the control device 30 calculates the second thrust T ２ Based on this, T ２ = 2k ｍ ω ｍ ２ From the relationship, the rotation speed ω of each main rotor 22 ｍ Determine.

[0130] Through the above processing, the control device 30 calculates the desired total thrust T and the required torque τ around each axis. φ , τ θ , τ ψInstead of the process in step S110, the control device 30 may calculate the first thrust T from the total thrust T required for flight. １ The second thrust T ２ The second thrust T ２ can be obtained.

[0131] The control device 30 controls each motor 14 and the internal combustion engine (main rotor drive unit 24) based on the determined rotational speed of each sub-rotor 12 and each main rotor 22. The control device 30 controls each motor 14 via each ESC 16 by sending a motor control signal (e.g., a PWM signal) indicating the determined rotational speed of the sub-rotor 12 to each ESC 16. The control device 30 also controls the internal combustion engine via the main rotor control unit 26 by sending a control signal indicating the determined rotational speed of the main rotor 22 to the main rotor control unit 26. The above operations are repeatedly performed during flight.

[0132] In this way, the control device 30 in this embodiment controls the first thrust T １ is calculated, and the first thrust T １ and the total thrust T required for flight, the second thrust T which is the total thrust generated by the main rotor 22. ２ The control device 30 calculates the first thrust T １ The rotational speed ω of each of the plurality of sub-rotors 12 is calculated based on １ ~ω ８ is determined, and the second thrust T ２ The rotation speed ω of each main rotor 22 is calculated based on ｍ More specifically, the control device 30 determines a total thrust T to be generated by the plurality of sub-rotors 12 (first rotors) and the plurality of main rotors 22 (second rotors), and multiplies the total thrust T by a first coefficient K １ The first thrust T is the sum of the thrusts to be generated by the multiple sub-rotors 12. １ The control device 30 further determines the first thrust T from the total thrust T. １The process of subtracting the second coefficient K from the total thrust T ２ (= 1-K １ ) or the first thrust T １ Add the third coefficient (=(1-K １ ) / K １ ) is multiplied to obtain a second thrust T ２ The control device 30 determines the first thrust T １ and determining the rotational speed of each of the plurality of sub-rotors 12 based on the second thrust T ２ The rotation speed of each of the plurality of main rotors 22 is determined based on the above.

[0133] Through the above operations, the control device 30 can sequentially determine the rotational speed of each sub-rotor 12 and each main rotor 22 during flight, and rotate each sub-rotor 12 and each main rotor 22 at the determined rotational speed, thereby bringing the multicopter 100 closer to the target attitude and enabling it to fly as desired.

[0134] 3A and 5, the multicopter 100 includes two main rotors 22 and eight sub-rotors 12, but the number of main rotors 22 and sub-rotors 12 is not limited to this example. For example, the number of main rotors 22 may be one or three or more. The number of sub-rotors 12 may also be other numbers, such as four or six. The sub-rotors 12 are not limited to the octo-quadcopter configuration shown in FIGS. 3A and 5, and various other configurations, such as a quadcopter, a hexacopter, or an octocopter, can be used.

[0135] In the above operation, the first coefficient K １ , and the second coefficient K ２ or the third coefficient K ３ In other words, the total thrust T by the main rotor 22 ２ and the total thrust T by the sub-rotor 12 １ The boost coefficient T ２ / T １ (The third coefficient K ３The boost coefficient corresponds to the ratio between the total thrust (second thrust) of the main rotor 22 obtained from the main rotor drive unit 24 and the total thrust (first thrust) of the sub-rotor 12 obtained from the multiple motors 14. The control device 30 calculates the first coefficient K １ , and the second coefficient K ２ or the third coefficient K ３ may be changed depending on the state of the multicopter 100. For example, the control device 30 may change the first coefficient K １ , and the second coefficient K ２ or the third coefficient K ３ The flight modes include, for example, hovering, horizontal flight (forward, backward, or sideways (aileron)), climbing, descending, and rotation (rudder). The control device 30 may change the first coefficient K １ The first coefficient K may be configured to maintain a value less than 0.5. １ If the second coefficient K is kept below 0.5, ２ is maintained at a value greater than 0.5, and the third coefficient K ３ The boost coefficient (boost coefficient) is maintained at a value greater than 1. This allows the main rotor 22 to efficiently generate a large thrust. When adjusting the attitude (yaw, pitch, and / or roll) of the aircraft to a desired attitude, for example, for landing, level flight, or rudder operation, the control device 30 may set the boost coefficient to a value smaller than the value during hovering (for example, a value smaller than 1). This makes it possible to prevent the large thrust and rotational moment generated by the rotation of the main rotor 22 from interfering with the attitude control function of the sub-rotor 12.

[0136] The control device 30 adjusts the first coefficient K in response to a user's operation using an external device such as a remote monitoring device. １ , and the second coefficient K ２ or the third coefficient K ３ This allows the user to adjust the balance between the efficiency of thrust generation and the responsiveness of attitude control, for example, to make it easier for the user to control the aircraft.

[0137] <Rudder Control> Next, an example of rudder control operation will be described as an example of attitude control in this embodiment.

[0138] Attitude control of the multicopter 10 is performed by bringing the yaw, pitch, and roll angles of the aircraft closer to target angles. Of these, control that brings the yaw angle closer to the target angle is called "rudder control." Below, a control method for rudder control that prevents the actual yaw angle of the aircraft from deviating from the target angle is described. Note that the following control method is not limited to rudder control, and can also be applied to control that adjusts the pitch angle or roll angle of the aircraft to the target angle.

[0139] When performing rudder control to adjust the yaw angle of the aircraft to a target angle, the control device 30 can be configured to reduce (or eliminate) the total thrust or rotational speed of the main rotor 22 and instead control the total thrust or rotational speed of the sub-rotor 12 to increase it. By reducing the total thrust or rotational speed of the main rotor 22, it is possible to reduce fluctuations in the attitude angle during rudder control and stabilize the attitude.

[0140] 7 is a flowchart showing an outline of the operation of the control device 30 regarding rudder control. The control device 30 executes the process shown in FIG. 7 during flight of the multicopter 100 to perform control to bring the yaw angle of the aircraft closer to a target angle.

[0141] First, in step S200, the control device 30 determines whether to start rudder control. The control device 30 determines whether to start rudder control based on, for example, a command from an external device such as a piloted aircraft or a remote monitoring device used by a user, or based on a preset flight program. Rudder control can be performed, for example, to change or maintain the orientation of the aircraft in a desired direction for changing flight direction or landing. The control device 30 performs rudder control when controlling the aircraft to a target yaw angle, when a yaw angle control delay occurs, or when rotation or shaking in the yaw direction occurs. If the control device 30 determines to start rudder control, the process proceeds to step S202.

[0142] In step S202, the control device 30 reduces the total thrust of the main rotors 22. For example, by reducing the boost coefficient described above, the rotational speed of each main rotor 22 is reduced, thereby reducing the total thrust of the main rotors 22. As described above, during hovering, the control device 30 sets the boost coefficient to a value greater than 1, and reduces the total thrust T of the multiple main rotors 22. ２ The total thrust T of the multiple sub-rotors 12 １ On the other hand, when performing rudder control, the control device 30 may be configured to change the boost coefficient to a value smaller than 1, thereby reducing the total thrust T of the multiple main rotors 22. ２ The total thrust T of the multiple sub-rotors 12 １ The control device 30 may control the rotational speed of each main rotor 22 to be smaller than the total thrust of the multiple main rotors 22 when performing rudder control. When performing rudder control, the control device 30 may reduce the rotational speed of each main rotor 22 so as to reduce the total thrust of the multiple main rotors 22 by 5% or more. For example, the control device 30 may reduce the rotational speed of each of the multiple main rotors 22 to less than 70%, less than 50%, less than 30%, or less than 10% of the rotational speed of each of the multiple main rotors 22 when hovering. Alternatively, when performing rudder control, the control device 30 may stop the rotation of each of the multiple main rotors 22. In other words, when performing rudder control, the control device 30 may change the boost coefficient to 0 (zero).

[0143] In step S204, the control device 30 adjusts the rotational speed of each sub-rotor 12. The control device 30 can determine the rotational speed of each sub-rotor 12 by processing similar to that of step S112 shown in FIG. 6 . At this time, the rotational speed of each sub-rotor 12 is increased to compensate for the decrease in thrust caused by the decrease in rotational speed of the main rotor 22. In other words, the control device 30 compensates for the decrease in the total thrust of the multiple main rotors 22 caused by the decrease in the rotational speed of each of the multiple main rotors 22 by increasing the rotational speed of each of the multiple sub-rotors 12. The control device 30 inputs a motor control signal indicating the rotational speed determined for each sub-rotor 12 to each ESC 16.

[0144] In step S206, the control device 30 determines whether the difference between the current yaw angle and the target angle is smaller than a threshold value. The threshold value is set to a sufficiently small value close to 0 degrees. If the difference between the current yaw angle and the target angle is equal to or greater than the threshold value (No), the process returns to step S204. If the difference between the current yaw angle and the target angle is smaller than the threshold value (Yes), the rudder control ends and the process proceeds to step S208.

[0145] In step S208, the control device 30 returns the rotational speed of each main rotor 22 to its original speed. For example, the control device 30 returns the boost coefficient to the value before it was changed in step S202, thereby returning the rotational speed of each main rotor 22 to its original value. Accordingly, the rotational speed of each sub-rotor 12 is also adjusted to return to its original value.

[0146] The operations shown in FIG. 7 can be repeatedly executed by, for example, the flight controller 32 of the control device 30 while the multicopter 10 is flying.

[0147] Through the above operations, when executing rudder control, the control device 30 can reduce the thrust generated by the multiple main rotors 22 by slowing down the rotational speed of each main rotor 22. This reduces the fluctuation in yaw angle during rudder control, making it easier to approach the desired angle. Numerical experiments conducted by the inventors confirmed that the closer the boost coefficient is to zero, the more the fluctuation in yaw angle during rudder control can be reduced.

[0148] The above control can be applied not only to rudder control for adjusting the yaw angle of the aircraft, but also to control for adjusting the roll angle and / or pitch angle of the aircraft. That is, when performing attitude control to bring the roll, pitch, and yaw angles of the aircraft closer to target angles, the control device 30 may reduce the total thrust of the main rotors 22 and increase the total thrust of the sub-rotors 12. Such control can improve the responsiveness of attitude control.

[0149] <Engine Control> Next, an example of a method for controlling an internal combustion engine (engine) will be described.

[0150] As described above, the multicopter 100 in this embodiment includes multiple rotors, including multiple sub-rotors 12 and at least one main rotor 22. The multiple sub-rotors 12 are driven by multiple motors 14, respectively. At least one main rotor 22 is driven by a main rotor drive unit 24, i.e., an internal combustion engine. The control device 30 controls the multiple motors 14 to control the rotation of the multiple sub-rotors 12 and thereby perform attitude control of the airframe. The control device 30 controls the internal combustion engine via a main rotor control unit 26 to control the rotation of at least one main rotor 22 and generate main thrust.

[0151] 8 is a flowchart showing an example of a method for controlling the motor 14 and the internal combustion engine. The control method shown in FIG. 8 is executed by the control device 30 and the main rotor control unit 26.

[0152] In step S300, the control device 30 determines the rotational speed of each sub-rotor 12 and the rotational speed of each main rotor 22. The rotational speed of each rotor is determined, for example, by the method described with reference to FIG. 6 . Hereinafter, the rotational speed of each sub-rotor 12 may be referred to as the "first rotational speed," and the rotational speed of each main rotor 22 may be referred to as the "second rotational speed." The first rotational speed is determined individually for each sub-rotor 12. The second rotational speed may be determined individually for each main rotor 22, or may be determined collectively to a common value.

[0153] In step S302, the control device 30 generates, as a first control signal for each sub-rotor 12, a first PWM signal having a duty ratio corresponding to the rotational speed of the sub-rotor 12. The first PWM signal corresponds to the motor control signal described above. The duty ratio of the PWM signal indicates the rotational speed of the motor. Note that the first control signal is not limited to a PWM signal and may be another type of signal.

[0154] In step S304, the control device 30 generates a second PWM signal having a duty ratio corresponding to the rotational speed of each main rotor 22. In this embodiment, each main rotor 22 is driven by an internal combustion engine, but each main rotor 22 may also be driven by an electric motor. For example, the configuration of the first rotation drive device 3A or the third rotation drive device 3C shown in FIG. 1A may be adopted to drive some rotors as main rotors and the remaining rotors as sub-rotors. When each main rotor 22 is driven by an electric motor, the control device 30 can generate a PWM signal as the second PWM signal to be input to the ESC that drives the electric motor.

[0155] In step S306, the main rotor control unit 26 converts the second PWM signal generated by the control device 30 into a second control signal that determines the rotational speed of the internal combustion engine. When each main rotor 22 is driven by an internal combustion engine, as in this embodiment, the second PWM signal for driving the electric motor cannot be used to control the internal combustion engine as is. Therefore, the main rotor control unit 26 converts the second PWM signal into a second control signal for controlling the internal combustion engine. The second control signal may be, for example, a signal that determines the opening of a throttle valve of the internal combustion engine. The main rotor control unit 26 can convert the second PWM signal into the second control signal based on data such as a table that indicates the relationship between the duty ratio of the second PWM signal and the opening of the throttle valve or the relationship between the duty ratio of the second PWM signal and the rotational speed of the internal combustion engine. The duty ratio of the second PWM signal correlates with the rotational speed of each main rotor 22 (second rotational speed). Therefore, the table showing the relationship between the duty ratio of the second PWM signal and the rotation speed of the internal combustion engine corresponds to a table for converting the second rotation speed into the rotation speed of the internal combustion engine. Data such as the table may be stored in advance in a storage device internal or external to the control device 30. The control device 30 can read the data from the storage device and convert the second PWM signal into the second control signal by referring to the data. Data such as the table may be stored in a server computer on the cloud. In this case, the control device 30 can obtain the data via the communication device 74.

[0156] In step S308, the control device 30 controls each motor 14 by inputting the first control signal generated for each sub-rotor 12 to the corresponding ESC 16. In addition, the main rotor control unit 26 controls the main rotor drive unit 24 (internal combustion engine) using the second control signal.

[0157] Through the above operations, each motor 14 and the internal combustion engine can be controlled to rotate each sub-rotor 12 and each main rotor 22 at a desired rotational speed. In this embodiment, the control shown in Fig. 8 is executed by the control device 30 and the main rotor control unit 26, but a single control device or control system having the functions of the control device 30 and the main rotor control unit 26 may be configured to execute the control shown in Fig. 8. That is, the control device or control system may be configured to determine the rotational speed (first rotational speed) of each of the multiple sub-rotors 12 and the rotational speed (second rotational speed) of at least one main rotor 22, generate first control signals that rotate each of the multiple electric motors 14 based on the first rotational speed, and generate second control signals that drive the internal combustion engine based on the second rotational speed. Such a control device or control system may, for example, generate, as a first control signal, a signal (e.g., the above-mentioned first PWM signal) having a duty ratio corresponding to the first rotational speed of each sub-rotor 12, generate a signal (e.g., the above-mentioned second PWM signal) having a duty ratio corresponding to the second rotational speed of at least one second rotor, and convert the second PWM signal into a second control signal that defines the rotational speed of the internal combustion engine based on data such as the above-mentioned table.

[0158] Hereinafter, with reference to FIGS. 9 to 12, a configuration example for realizing the above control will be described in more detail.

[0159] FIG. 9 is a block diagram showing an example configuration of the flight controller 32 in the control device 30. The flight controller 32 in this example includes a module 322 that determines the rotational speed of each sub-rotor 12 for attitude control, a module 324 that generates a first PWM signal (first control signal) having a duty ratio corresponding to the rotational speed of each sub-rotor 12, and a module 326 that generates a second PWM signal having a duty ratio corresponding to the rotational speed of each main rotor 22. The first PWM signal is input to each of the multiple ESCs 16. In the example shown in FIG. 9, PWM signals #1 to #8 are input to eight ESCs 16 corresponding to the eight sub-rotors 12, respectively. In the example shown in FIG. 9, PWM signals #1 to #8 are also input to a module 326 that generates a PWM signal for the main rotor 22. Module 326 generates a PWM signal (second PWM signal) for the main rotor 22 based on these PWM signals #1 to #8 and outputs the second PWM signal to the main rotor control unit 26. The main rotor control unit 26 converts the second PWM signal into a second control signal, which is an engine control signal, and controls the internal combustion engine based on the second control signal.

[0160] FIG. 10 is a diagram showing an example configuration of a module 326 that generates a PWM signal for the main rotor 22. The module 326 includes multiple adders 326a, a filter calculator 326b, and a multiplier 326c. The number of adders 326a is the same as the number of sub-rotors 12. The adders 326a add the duty values ​​of the PWM signals #1 to #8 input from the modules 324 and output a duty sum value. The duty sum value is correlated (e.g., proportional) to the total thrust of the multiple sub-rotors 12. The duty sum signal is input to the filter calculator 326b. The filter calculator 326b removes high-frequency components from the duty sum signal and outputs a signal with smooth time variations. The signal output from the filter calculator 326b is sent to the multiplier 326c. The multiplier 326c multiplies the signal by a boost coefficient to generate and output a PWM signal for the main rotor 22. The functions shown in FIG. 10 may be realized by hardware or software.

[0161] Fig. 11 is a graph showing an example of time variations in the sum of the duties of the PWM signals for the sub-rotors 12 and the duty value of the PWM signal for the main rotor 22. In the example of Fig. 11, the boost coefficient is always maintained at a constant value, and the ratio between the sum of the duties of the PWM signals for the sub-rotors 12 and the duty value of the PWM signal for the main rotor 22 is constant. As described above, the boost coefficient may vary during flight depending on the state of the multicopter 100 or commands from an external device.

[0162] FIG. 12 illustrates an exemplary configuration of the main rotor control unit 26. The main rotor control unit 26 illustrated in FIG. 12 includes a module 26a that determines a target rotation speed of the internal combustion engine (engine), a subtractor 26b, a module 26c that performs calculations for PID control, a module 26d that generates signals for CAN communication, a module 26f that measures the pulse interval of an engine rotation pulse signal output from a sensor installed in the internal combustion engine, and a module 26e that calculates the actual rotation speed of the engine based on the pulse interval. The main rotor control unit 26 further includes a storage device 26g that stores a target rotation speed table, which is data indicating the relationship between the duty ratio of the PWM signal for the main rotor 22 and the target rotation speed of the engine. Here, the engine rotation speed refers to the number of engine rotations (e.g., in rpm) per unit time (e.g., one minute). The functions illustrated in FIG. 12 may be implemented by hardware or software.

[0163] The main rotor control unit 26 determines the target rotation speed of the engine based on the PWM signal for the main rotor 22 output from the flight controller 32 and the target rotation speed table.

[0164] FIG. 13 is a graph showing an example of the correspondence relationship between the duty ratio of the PWM signal and the engine rotation speed. A target rotation speed table can be created in advance based on the relationship shown in FIG. 13 and stored in the storage device 26g. In this example, the rotation speed of each main rotor 22 is proportional to the duty ratio of the PWM signal. The target rotation speed table is an example of a table that converts the rotation speed of each main rotor 22 into the rotation speed of the internal combustion engine. Based on such a table, the main rotor control unit 26 can convert the PWM signal into an engine control signal (second control signal) that drives the internal combustion engine.

[0165] The main rotor control unit 26 determines the target engine speed, while measuring the pulse interval of the engine rotation pulse signal output from the sensor and calculating the actual engine speed based on the pulse interval. The main rotor control unit 26 performs PID control, which subtracts the target engine speed from the actual engine speed and adjusts the engine control signal so that the difference approaches zero. The main rotor control unit 26 controls the main rotor drive unit 24 (internal combustion engine) using the engine control signal determined so that the difference between the target engine speed and the actual engine speed approaches zero. This allows the main rotor 22 to rotate at the desired rotational speed.

[0166] In the above example, a table showing the relationship between the duty ratio of the PWM signal and the target engine speed is used. However, data such as a table showing the relationship between the duty ratio of the PWM signal and the opening of the throttle valve of the internal combustion engine may be used instead. Based on such data, the main rotor control unit 26 can convert the PWM signal for the main rotor 22 (second PWM signal) into an engine control signal that indicates the opening of the throttle valve. Such an engine control signal can be used as the second control signal that drives the internal combustion engine.

[0167] As described above, when controlling the rotational speed of each main rotor 22, the flight controller 32 in the control device 30 of this embodiment generates a PWM signal having a duty ratio corresponding to the rotational speed. The main rotor control unit 26 converts this PWM signal into an engine control signal based on a table defining the relationship shown in FIG. 13 and controls the internal combustion engine using this engine control signal. This configuration makes it possible to use a flight controller used in a battery-powered or series hybrid drive system in which the main rotor 22 is driven by an electric motor in the parallel hybrid drive system of this embodiment. Therefore, it is possible to control the internal combustion engine that drives the main rotor 22 in a parallel hybrid drive system without changing the flight controller.

[0168] The control device 30 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.

[0169] 14 is a block diagram showing an example of the hardware configuration of the control device 30. The control device 30 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.

[0170] 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).

[0171] 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.

[0172] 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.

[0173] The communication I / F 38 is an interface for communication between the control device 30 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 also 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 that use frequencies in the 2.4 GHz band.

[0174] 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.

[0175] As described above, the control device 30 may include, for example, a flight control device such as the flight controller 32 and a higher-level computer (companion computer) as separate components. Also, a system including the control device 30 and the main rotor control unit 26 may be used as the "control device."

[0176] 15 , some or all of the functions of the control device 30 may be implemented by one or more servers (computers) 500 or terminal devices (including portable and fixed types) 400 connected to the communication device 74 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 for processing by the control device 30 and control signals for the multicopter 100 may be provided from the agricultural machine 700 to the multicopter 100 via the communication network N.

[0177] In the unmanned aerial vehicle according to the above embodiments, the "attitude control device" includes multiple electric motors, and the "main thrust generating device" includes an internal combustion engine. In other words, the unmanned aerial vehicle according to the above embodiments includes the rotary drive device 3D shown in FIG. 1A. However, even in the rotary drive devices 3A, 3B, and 3C shown in FIG. 1A, by differentiating some of the motors 14 or power transmission systems 23 from the other motors 14 or power transmission systems 23, it is possible to realize an unmanned aerial vehicle that includes an "attitude control device" and a "main thrust generating device."

[0178] The unmanned aerial vehicle may also be equipped with multiple internal combustion engines with different power outputs and response speeds. In this case, an internal combustion engine with a relatively low power output and a relatively high response speed may constitute an "attitude control device," and an internal combustion engine with a relatively high power output and a relatively low response speed may constitute a "main thrust generating device."

[0179] 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.

[0180] 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, 14: Motor, 16: ESC, 22: Main rotor, 24: Main rotor drive unit, 26: Main rotor control unit, 30: Control device, 32: Flight controller, 42: Power generation device, 44: Power management device, 52: Battery, 54: Battery management device, 72: Sensor group, 74: Communication device, 100: Multicopter, 200: Work machine

Claims

1. a plurality of rotors including a plurality of first rotors and at least one second rotor; a control device that controls the rotation of the plurality of first rotors to perform attitude control of the vehicle and that controls the rotation of the at least one second rotor to generate a main thrust; Equipped with The control device Calculating a first thrust, which is a total thrust to be generated by the plurality of first rotors, and calculating a second thrust, which is a total thrust to be generated by the at least one second rotor, based on the first thrust and a total thrust required for flight; determining a rotational speed of each of the plurality of first rotors based on the first thrust; determining a rotational speed of the at least one second rotor based on the second thrust; unmanned aircraft.

2. The unmanned aerial vehicle according to claim 1 , wherein the control device calculates the second thrust by subtracting the first thrust from a total thrust required for the flight.

3. The control device determining the first thrust by multiplying the total thrust required for the flight by a first coefficient between 0 and 1; determining the second thrust by multiplying the total thrust by a second coefficient that is one minus the first coefficient, or by multiplying the first thrust by a third coefficient that is the second coefficient divided by the first coefficient; The unmanned aerial vehicle according to claim 1 .

4. The unmanned aerial vehicle according to claim 3 , wherein the control device changes the first coefficient and the second coefficient or the third coefficient depending on a state of the unmanned aerial vehicle.

5. The unmanned aerial vehicle according to claim 3 or 4, wherein the control device sets the first coefficient to a value smaller than 0.5 during hovering.

6. the control device determines the second thrust by multiplying the first thrust by the third coefficient.

5. The unmanned aerial vehicle according to claim 3 or 4.

7. The unmanned aerial vehicle according to claim 3 or 4, wherein the control device changes the first coefficient and the second coefficient or the third coefficient depending on a flight mode.

8. The unmanned aerial vehicle according to claim 3 or 4, wherein the control device changes the first coefficient and the second coefficient or the third coefficient in response to a user operation.

9. The unmanned aerial vehicle according to claim 1 or 2, wherein the diameter of the at least one second rotor is larger than the diameter of each of the plurality of first rotors.

10. The unmanned aerial vehicle according to claim 1 or 2, wherein the thrust per rotation of each of the plurality of second rotors is greater than the thrust per rotation of each of the plurality of first rotors.

11. An unmanned aerial vehicle as described in claim 1 or 2, wherein the distance from the center of the airframe to the rotation axis of each of the plurality of second rotors is shorter than the distance from the center of the airframe to the rotation axis of each of the plurality of first rotors.

12. a plurality of electric motors that drive the plurality of first rotors, respectively; an internal combustion engine driving the at least one second rotor; Furthermore, the control device controls the electric motors to control rotation of the plurality of first rotors, and controls the internal combustion engine to control rotation of the at least one second rotor; 3. The unmanned aerial vehicle according to claim 1 or 2.

13. A control method for an unmanned aerial vehicle including a plurality of rotors including a plurality of first rotors and at least one second rotor, and a control device that performs attitude control of the airframe by controlling rotation of the plurality of first rotors and generates main thrust by controlling rotation of the at least one second rotor, the method comprising: calculating a first thrust to be generated by the plurality of first rotors; calculating a second thrust to be generated by the at least one second rotor based on the first thrust and a total thrust required for flight; determining a rotational speed of each of the plurality of first rotors based on the first thrust; determining a rotational speed of the at least one second rotor based on the second thrust; A control method comprising: