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

Abstract

The present invention provides an unmanned aerial vehicle comprising: a plurality of first rotors; a plurality of second rotors; and a control device that executes attitude control of the airframe by controlling the rotation of the plurality of first rotors and generates main thrust by controlling the rotation of the plurality of second rotors. The control device lowers the total thrust of the plurality of second rotors when performing rudder control to adjust the yaw angle of the airframe by controlling the rotation of the plurality of first rotors.

Description

Technical Field

[0001] The present disclosure relates to unmanned aerial vehicles, as well as control systems and control methods for unmanned aerial vehicles.

Background Art

[0002] An unmanned aerial vehicle (UAV) is an aircraft that is structurally unable to carry a person and can fly by remote control or autopilot. A rotary-wing unmanned aerial vehicle is an unmanned aerial vehicle that obtains lift by using a propeller that rotates around an axis, that is, a rotary wing. A small unmanned aerial vehicle (Multi-Rotor UAV) equipped with a plurality of rotary wings is also called a "drone", "multi-rotor", or "multi-copter", and is widely used in applications such as aerial photography, surveying, logistics, and agricultural chemical spraying.

[0003] Patent Document 1 describes an unmanned aerial vehicle (unmanned flying body) 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 the position and attitude during flight.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

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

[0007] This disclosure provides an unmanned aerial vehicle suitable for agricultural applications, capable of increasing payload and / or flight time. [Means for solving the problem]

[0008] This disclosure provides solutions as described in the following items.

[0009] [Item A1] Multiple first rotors, Multiple second rotors, A control device that performs attitude control of the aircraft by controlling the rotation of the plurality of first rotors and generates main thrust by controlling the rotation of the plurality of second rotors, Equipped with, When the control device performs rudder control to adjust the yaw angle of the aircraft by controlling the rotation of the plurality of first rotors, it reduces the total thrust of the plurality of second rotors. unmanned aircraft.

[0010] [Item A2] 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, as described in item A1.

[0011] [Item A3] The control device performs the rudder control when controlling the target to a yaw angle, when a control delay occurs in the yaw angle, or when rotation or oscillation occurs in the yaw direction, as described in item A1 or A2.

[0012] [Item A4] An unmanned aerial vehicle as described in any one of items A1 to A3, wherein the diameter of each of the plurality of second rotors is greater than the diameter of each of the plurality of first rotors.

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

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

[0015] [Item A7] The control device, when hovering, makes the total thrust of the plurality of second rotors greater than the total thrust of the plurality of first rotors, and when rudder control is performed, makes the total thrust of the plurality of second rotors less than the total thrust of the plurality of first rotors, as described in any one of items A1 to A6.

[0016] [Item A8] The control device, when performing the rudder control, 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, as described in any one of items A1 to A7.

[0017] [Item A9] The control device, when performing rudder control, compensates for the decrease in the total thrust of the plurality of second rotors due to the decrease in the rotational speed of each of the plurality of second rotors by increasing the rotational speed of the plurality of first rotors, as described in item A8.

[0018] [Item A10] The control device stops the rotation of each of the plurality of second rotors when performing the rudder control, as described in any one of items A1 to A9.

[0019] [Item A11] Multiple electric motors that drive each of the multiple first rotors, An internal combustion engine that drives the plurality of second rotors, Furthermore, 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, as described in any one of items A1 to A10.

[0020] [Item A12] A control method for an unmanned aerial vehicle comprising a plurality of first rotors and a plurality of second rotors, The aircraft's attitude is controlled by controlling the rotation of the aforementioned multiple first rotors, The main thrust is generated by controlling the rotation of the plurality of second rotors, Includes, Performing the aforementioned attitude control means This involves performing rudder control to adjust the yaw angle of the aircraft by controlling the rotation of the plurality of first rotors, When the aforementioned rudder control is performed, the total thrust of the multiple second rotors is reduced, A control method including

[0021] [Item B1] Multiple rotors, including multiple first rotors and at least one second rotor, A control device that performs attitude control of the aircraft by controlling the rotation of the plurality of first rotors and generates main thrust by controlling the rotation of at least one second rotor, Equipped with, The control device is The first thrust, which is the total thrust generated by the plurality of first rotors, is calculated, and the second thrust, which is the total thrust generated by at least one second rotor, is calculated based on the first thrust and the total thrust required for flight. Based on the first thrust, the rotational speed of each of the plurality of first rotors is determined. The rotational speed of the at least one second rotor is determined based on the second thrust. unmanned aircraft.

[0022] [Item B2] The control device calculates the second thrust by subtracting the first thrust from the total thrust required for the flight, as described in item B1.

[0023] [Item B3] The control device is The first thrust is determined by multiplying the total thrust required for the aforementioned flight by a first coefficient that is between 0 and 1, The second thrust is determined by multiplying the total thrust by a second coefficient, which is the value obtained by subtracting the first coefficient from 1, or by multiplying the first thrust by a third coefficient, which is the value obtained by dividing the second coefficient by the first coefficient. Unmanned aerial vehicles as described in item B1.

[0024] [Item B4] The control device changes the first coefficient and the second coefficient or the third coefficient according to the state of the unmanned aircraft, as described in item B3.

[0025] [Item B5] The control device is configured to set the first coefficient to a value less than 0.5 during hovering, as described in item B3 or B4 of the unmanned aerial vehicle.

[0026] [Item B6] The control device determines the second thrust by multiplying the first thrust by the third coefficient. An unmanned aerial vehicle listed in any of items B3 through B5.

[0027] [Item B7] The control device changes the first coefficient and the second coefficient or the third coefficient according to any one of items B3 to B6, as described in item B3 to B6.

[0028] [Item B8] The control device changes the first coefficient and the second coefficient or the third coefficient in response to user operation, as described in any one of items B3 to B7.

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

[0030] [Item B10] An unmanned aerial vehicle as described in any one of items B1 to B9, wherein the thrust per revolution of each of the plurality of second rotors is greater than the thrust per revolution of each of the plurality of first rotors.

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

[0032] [Item B12] Multiple electric motors that drive each of the multiple first rotors, An internal combustion engine that drives the at least one second rotor, Furthermore, 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. An unmanned aerial vehicle as described in any one of items B1 through B11.

[0033] [Item B13] A control method performed 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; a control device that performs attitude control of the aircraft 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, Calculating the first thrust to be generated in the plurality of first rotors, The calculation of the second thrust to be generated in the at least one second rotor based on the first thrust and the total thrust required for flight, The rotational speed of each of the plurality of first rotors is determined based on the first thrust, The rotational speed of the at least one second rotor is determined based on the second thrust, A control method including

[0034] [Item C1] Multiple electric motors, Internal combustion engines and Multiple first rotors, each driven by the aforementioned multiple electric motors, At least one second rotor driven by the internal combustion engine, Control device and Equipped with, The control device is Determine the first rotational speed of each of the plurality of first rotors, and the second rotational speed of at least one second rotor. Based on the first rotational speed of each of the plurality of first rotors, a first control signal is generated to rotate each of the plurality of electric motors. Based on the second rotational speed, a second control signal is generated to drive the internal combustion engine. unmanned aircraft.

[0035] [Item C2] The control device generates the second control signal based on a table that converts the second rotational speed to the rotational speed of the internal combustion engine, as described in item C1.

[0036] [Item C3] The control device controls the rotation of the plurality of first rotors by controlling the plurality of electric motors to perform attitude control of the aircraft, and controls the rotation of the at least one second rotor by controlling the internal combustion engine to generate main thrust, as described in item C1 or C2.

[0037] [Item C4] The control device is A first PWM (Pulse Width Modulation) signal having a duty cycle corresponding to the first rotational speed is generated as the first control signal. A second PWM signal having a duty cycle corresponding to the second rotational speed of at least one second rotor is generated, and the second PWM signal is converted into a second control signal that determines the rotational speed of the internal combustion engine. An unmanned aerial vehicle as described in any one of items C1 through C3.

[0038] [Item C5] The aforementioned control signal is Data showing the relationship between the duty cycle of the second PWM signal and the rotational speed per unit time of the internal combustion engine is read from the storage device. Based on the aforementioned data and the second PWM signal, the rotation speed is determined. Based on the rotational speed, the second control signal is generated. Unmanned aerial vehicles as described in item C4.

[0039] [Item C6] The second control signal determines the opening degree of the throttle valve of the internal combustion engine. The control device reads data from a storage device showing the relationship between the duty cycle of the second PWM signal and the opening degree of the throttle valve, and converts the second PWM signal into the second control signal based on the data, as described in item C4.

[0040] [Item C7] The control device is Determine the first thrust, which is the sum of the thrusts that the plurality of first rotors should generate, and the second thrust, which is the sum of the thrusts that the at least one second rotor should generate. Based on the first thrust, the first control signal is generated for each of the plurality of first rotors. The second PWM signal is determined based on the first control signal and the ratio of the second thrust to the first thrust. An unmanned aerial vehicle as described in any one of items C4 through C6.

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

[0042] [Item C9] An unmanned aerial vehicle as described in any one of items C1 to C8, wherein the thrust per revolution of each of the plurality of second rotors is greater than the thrust per revolution of each of the plurality of first rotors.

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

[0044] [Item C11] A control method performed by a control device in 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, Determining the first rotational speed of each of the plurality of first rotors, and the second rotational speed of at least one second rotor, Based on the first rotational speed, a first control signal is generated to rotate each of the plurality of electric motors, Based on the second rotational speed, a second control signal is generated to drive the internal combustion engine, A control method including [Effects of the Invention]

[0045] Embodiments of the unmanned aerial vehicle, its control system, and control method described herein make it possible to realize an unmanned aerial vehicle that is capable of increasing payload and / or flight time and is suitable for agricultural applications. [Brief explanation of the drawing]

[0046] [Figure 1A] This is a schematic block diagram showing several examples of rotary drive devices for rotating rotors in an unmanned aerial vehicle equipped with multiple rotors. [Figure 1B] This is a schematic plan view illustrating one basic configuration example of an unmanned aerial vehicle equipped with multiple rotors. [Figure 1C] This is a schematic side view illustrating one basic configuration example of an unmanned aerial vehicle equipped with multiple rotors. [Figure 1D] This is a schematic plan view illustrating another basic configuration example of an unmanned aerial vehicle equipped with multiple rotors. [Figure 2A] This block diagram shows an example of the basic configuration of a battery-powered multirotor. [Figure 2B] This block diagram shows an example of the basic configuration of a series hybrid multicopter. [Figure 2C] This is a block diagram showing an example of the basic configuration of a parallel hybrid multicopter. [Figure 3A] This is a schematic top view showing a multicopter in an exemplary embodiment. [Figure 3B] This is a schematic side view showing a multicopter in an exemplary embodiment. [Figure 4] This is a block diagram showing an example of a system configuration in an exemplary embodiment of a multicopter. [Figure 5] This is a schematic plan view illustrating a parallel hybrid drive type multicopter. [Figure 6] This flowchart shows an example of the process for determining the rotational speed of each sub-rotor and each main rotor. [Figure 7] This flowchart outlines the operation of the control unit related to ladder control. [Figure 8] A flowchart shows an example of a control method for electric motors and internal combustion engines. [Figure 9]This is a block diagram showing an example of a flight controller configuration. [Figure 10] This diagram shows an example configuration of a module that generates a PWM signal for the main rotor. [Figure 11] This graph shows an example of the time variation of the sum of the duty cycles of the PWM signals for the sub-rotor and the duty cycles of the PWM signals for the main rotor. [Figure 12] This diagram shows an example configuration of the main rotor control unit. [Figure 13] This graph shows an example of the relationship between the duty cycle of a PWM signal and engine speed. [Figure 14] This is a block diagram showing an example of the hardware configuration of a control device. [Figure 15] This diagram schematically illustrates an example of a communication network to which multirotors are connected. [Modes for carrying out the invention]

[0047] Unmanned aerial vehicles equipped with multiple rotors are equipped with a rotational drive device that rotates the rotors (hereinafter sometimes referred to as "propellers"). Hereafter, such unmanned aerial vehicles will be referred to as "multicopters."

[0048] There are various configurations for the rotary drive systems that multirotors are equipped with. Figure 1A is a schematic block diagram showing four examples of the rotary drive system 3 in this disclosure.

[0049] The first rotary drive unit 3A shown in Figure 1A has multiple electric motors (hereinafter referred to as "motors") 14 that rotate multiple rotors 2, and a battery 52 that stores the power supplied to each motor 14. The battery 52 is 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. To increase the payload and / or flight time, it is necessary to increase the storage capacity of the battery 52. ​​The storage capacity of the battery 52 can be increased by making the battery 52 larger, but making the battery 52 larger leads to an increase in weight.

[0050] The second rotary drive unit 3B shown in Figure 1A includes a power transmission system 23 mechanically connected to a rotor 2 and an internal combustion engine 7a that provides driving force (torque) to the power transmission system 23. The power transmission system 23 includes mechanical components such as gears or belts and transmits the torque 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 internal combustion engines 7a include gasoline engines, diesel engines, and hydrogen engines. Furthermore, the number of internal combustion engines 7a included in the rotary drive unit 3B is not limited to one.

[0051] The third rotary drive system 3C shown in Figure 1A includes multiple motors 14, a power buffer 9 for storing power supplied to each motor 14, a power generator 8 such as an alternator for generating power, and an internal combustion engine 7a that provides mechanical energy to the power generator 8 for power generation. 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 system 3C, even if the storage capacity of the power buffer 9 is not large, the power generator 8 generates power using the driving force (mechanical energy) of the internal combustion engine 7a, making it possible to increase the 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 a series hybrid drive are called a "range extender" because they extend the flight range of the multicopter.

[0052] The fourth rotary drive unit 3D shown in Figure 1A includes a plurality of motors 14, a power buffer 9 for storing power supplied to each motor 14, a power generation device 8 such as an alternator for generating power, an internal combustion engine 7a for providing driving force to the power generation device 8 for power generation, and a power transmission system 23 for transmitting the driving force generated by the internal combustion engine 7a to the rotor 2 to rotate the rotor 2. At least one of the plurality of rotors 2 is rotated by the internal combustion engine 7a, and the other rotors 2 are rotated by the motors 14. In the fourth rotary drive unit 3D, the mechanical energy generated by the internal combustion engine 7a can be used to rotate the rotor 2 without being converted into electricity, thus increasing the energy utilization efficiency. This type of drive is called a "parallel hybrid drive".

[0053] Figure 1B is a schematic plan view showing one of the basic configuration examples of the multicopter 10. The configuration example in Figure 1B includes the first rotary drive device 3A shown in Figure 1A as the rotary drive device 3. That is, the rotary drive device 3 (3A) in this example has a motor 14 and a battery 52. ​​Figure 1C is a schematic side view showing the multicopter 10.

[0054] The multicopter 10 shown in Figures 1B and 1C comprises multiple rotors 2, a main body 4, and a frame 5 that supports the rotors 2 and the main body 4. The frame 5 supports the main body 4 at its center and rotatably supports the multiple rotors 2 with multiple arms 5A extending outward from the center. A motor 14 for rotating the rotors 2 is provided near the tip of each arm 5A. The main body 4 and the frame 5 are sometimes collectively referred to as the "aircraft 11".

[0055] In the example shown in Figure 1B, the multicopter 10 is a quadcopter equipped with four rotors 2. Rotors 2 located on one diagonal rotate in the same direction (clockwise or counterclockwise), while rotors 2 located on different diagonal lines rotate in opposite directions.

[0056] The aircraft 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 4a may include, for example, a flight control device such as a flight controller and a higher-level computer (companion computer). The companion computer can perform advanced computational processing such as image processing, obstacle detection, and obstacle avoidance based on sensor data acquired by the sensor group 4b.

[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 GNSS (Global Navigation Satellite System) receiver. The acceleration sensor and angular velocity sensor may be mounted on the aircraft body 4 as components of an IMU (Inertial Measurement Unit), for example. Examples of laser sensors may include a laser rangefinder used to measure the distance to the ground, and a two-dimensional or three-dimensional LiDAR (light detection and ranging).

[0059] The communication device 4c may include a wireless communication module for transmitting and receiving signals to and from a transmitter or ground control station (GCS) on the ground via an antenna, and a mobile communication module that utilizes a cellular communication network. The communication device 4c may receive signals such as control commands transmitted from the ground and transmit sensor data such as image data acquired by the sensor group 4b as telemetry information. The communication device 4c may also have the function of communicating with other multirotors and the function of satellite communication. The control device 4a can be connected to a computer on the cloud by 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 rechargeable battery that can store power by charging and supply power to the motor 14 by discharging. Through the action of the battery 52 and the multiple motors 14, multiple rotors 2 are driven to rotate, making it possible to generate the desired thrust.

[0061] Each of the multiple rotors 2 generally has multiple blades with a fixed pitch angle and generates thrust through rotation. The pitch angle may be variable. Not all of the multiple rotors 2 need to have the same diameter (propeller diameter); one or more rotors 2 may have a larger diameter than the others. The thrust generated by the rotating rotors 2 (static thrust) is generally proportional to the cube of the rotor's diameter. For this reason, when rotors 2 with different diameters are provided, the rotor 2 with a relatively larger diameter may be called the "main rotor," and the rotor 2 with a relatively smaller diameter may be called the "sub-rotor." Regardless of the size of the diameter, the configuration of the rotary drive unit 3 may include a rotor 2 with a relatively large thrust and a rotor 2 with a relatively small thrust. In that case, the rotor 2 with a relatively large thrust may be called the "main rotor," and the rotor 2 with a relatively small thrust may be called the "sub-rotor." For example, a rotor 2 that generates a relatively large thrust per revolution may be called the "main rotor," and a rotor 2 that generates a relatively small thrust per revolution may be called the "sub-rotor." In one example, the main rotor may be positioned inward of the sub-rotors. In other words, each rotor 2 may be positioned such that the distance from the center of the aircraft to the axis of rotation of each main rotor is shorter than the distance from the center of the aircraft to the axis of rotation of each sub-rotor.

[0062] In this example, the rotary drive unit 3 has a plurality of motors 14. As mentioned above, the rotary drive unit 3 may also include an internal combustion engine 7a.

[0063] Figure 1D is a schematic plan view showing a basic configuration example of a multicopter 10 equipped with a second rotary drive unit 3B as the rotary drive unit 3. In the example shown in Figure 1D, the internal combustion engine 7a is supported by the aircraft body 4. In this example, the driving force generated by the internal combustion engine 7a is transmitted to multiple rotors 2 by 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 rotary drive unit 3B may include a mechanism for changing the pitch angle of each blade of the multiple rotors 2. In that case, the control device 4a may adjust the lift generated by each rotor 2 by controlling this mechanism to change the pitch angle of the blades.

[0064] In a "parallel hybrid drive" configuration, where some of the multiple rotors 2 are rotated by an internal combustion engine 7a and other rotors 2 are rotated by a motor 14, the internal combustion engine 7a and battery 52 are supported by the main body 4. At least one of the multiple rotors 2 is connected to the internal combustion engine 7a via a 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 mainly used for thrust generation, and the sub-rotor is used for thrust generation and attitude control. The main rotor may be called the "booster rotor" and the sub-rotor the "attitude control rotor".

[0066] In a parallel hybrid drive system, 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 / or power generation device, it is also possible to achieve a balanced combination of thrust generation and power generation.

[0067] The inclusion of an internal combustion engine in a multirotor, which generates thrust and / or electricity, contributes to increased payload and flight time. Attitude control of a multirotor is preferably performed by rotating the propellers with motors that have superior response characteristics to internal combustion engines. Therefore, in applications requiring precise attitude control of a multirotor, employing a parallel hybrid drive or series hybrid drive is desirable to increase payload and flight time. Furthermore, if the rotary drive unit 3 includes a mechanism for changing the pitch angle of each blade of the multiple rotors 2, attitude can also be adjusted by changing the pitch angle of each blade.

[0068] Increased payload and flight time could further expand the applications of multicopters. For example, in agriculture, multicopters are currently being used for pesticide spraying or monitoring crop growth, but by attaching various ground implements (hereinafter sometimes simply referred to as "implements") to the multicopter, it will be possible to perform various agricultural tasks from the air. Agricultural implements are sometimes called "implements." Examples of implements may include sprayers for spraying pesticides on crops, mowers, seeders, spreaders, rakes, balers, harvesters, plows, harrows, or rotary tillers. Work vehicles such as tractors are not included in the definition of "implements" in this disclosure.

[0069] In the example shown in Figure 1C, the multicopter 10 is coupled with an implement 200 capable of spraying, for example, pesticides or fertilizers onto or within a field. Increased payload and flight time allow for larger and / or more multifunctional implements 200. For example, by changing the implement 200 coupled to the multicopter 10, it becomes possible to perform a variety of ground operations (agricultural work), including liquid and granular application, fertilization, thinning, weeding, transplanting, direct seeding, and harvesting. The implement 200 may be equipped with mechanisms such as a robotic hand. In that case, one implement 200 can perform a variety of ground operations. If the implement 200 has enough space to accommodate materials, it can also be used to transport agricultural materials or harvested produce over a wide area. There are various ways in which the implement 200 is coupled to the multicopter 10. The multicopter 10 may suspend and tow the work machine 200 by a cable. The work machine 200 towed by the multicopter 10 can perform ground work while being towed, while the multicopter 10 is flying or hovering. The work machine 200 may be in the air or on the ground while performing work.

[0070] In the example shown in Figure 1C, the multicopter 10 is equipped with a power supply device 76. The power supply device 76 is a device that supplies power to the work implement 200 from a drive energy source such as a battery 52 or a power generator 8 provided by the multicopter 10. Various functions of the work implement 200 can be performed by this power. The work implement 200 is equipped with actuators such as motors that are operated by the power obtained from the power supply device 76 of the multicopter 10. Preferably, the work implement 200 is equipped with a battery for storing power.

[0071] Figure 2A is a block diagram showing an example of the basic configuration of a battery-powered multicopter 10. The battery-powered multicopter 10 includes multiple rotors 12, multiple motors 14 that rotate each of the multiple rotors 12, multiple ESCs (Electric Speed ​​Controllers) 16 each having a motor drive circuit that drives each of the multiple motors 14, a battery 52 that supplies power to the corresponding motors 14 via each ESC 16, a control device 4a for controlling the attitude and performing flight by controlling the multiple ESCs 16, a sensor group 4b, a communication device 4c, and a power supply device 76 electrically connected to the battery 52. ​​In Figure 2A, for simplicity, the rotors 12, motors 14, and ESCs 16 are each shown as one block, but the number of rotors 12, motors 14, and ESCs 16 is multiple. This is also true for Figures 2B and 2C. The ESCs 16 may be included in the control device 4a.

[0072] The control device 4a can wirelessly receive control commands from, for example, a ground station 6 located on the ground via the communication device 4c. The number of ground stations 6 is not limited to one, but may be distributed across multiple locations. The communication device 4c can also wirelessly receive control commands from the control device of 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 communicate with the work machine 200 connected to the power supply device 76 and be configured to obtain signals from the work machine 200 indicating the status of the work machine 200. The control device 4a may also provide signals to the work machine 200 to control its operation. Furthermore, the work machine 200 may generate signals instructing the operation of the multicopter 10 and transmit them to the control device 4a. Such communication between the control device 4a and the work machine 200 can be wired or wireless.

[0073] Figure 2B is a block diagram showing an example of the basic configuration of a series hybrid drive multicopter 10. Similar to a battery-powered multicopter 10, the series hybrid drive multicopter 10 comprises 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 generator 8 driven by the internal combustion engine 7a to generate electricity, a power buffer 9 for temporarily storing the electricity generated by the power generator 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 electricity generated by the power generator 8 is supplied to the motors 14 via the power buffer 9 and the ESCs 16. The electricity generated by the power generator 8 can also be supplied to the work machine 200 via the power supply device 76.

[0074] Figure 2C is a block diagram showing an example of the basic configuration of a parallel hybrid drive multicopter 10. Similar to a series hybrid drive multicopter 10, the parallel hybrid drive multicopter 10 includes a plurality of rotors 12, a plurality of motors 14 that drive each of the plurality of rotors 12, a plurality of 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 drivetrain 27 that transmits the driving force of the internal combustion engine 7a, and a rotor 22 that rotates by receiving the driving force from the internal combustion engine 7a via the drivetrain 27. One of the rotors 12 and rotor 22 may be called the "first rotor" and the other the "second rotor" to distinguish them from each other. There may be one rotor 22 that is connected to the drivetrain 27 and rotates, or there may be two or more rotors 22.

[0075] In a parallel hybrid drive multicopter 10, the internal combustion engine 7a not only drives the power generator 8 to generate electricity, but also mechanically transmits energy to the rotor 22 to rotate it. On the other hand, in a series hybrid drive multicopter 10, all rotors 12 rotate using the electricity generated by the power generator 8. Therefore, in a series hybrid drive multicopter 10, if the power generator 8 is, for example, a fuel cell, the internal combustion engine 7a is not an essential component.

[0076] The following describes an example of the configuration and operation of an unmanned aerial vehicle according to the embodiment of this disclosure, using a multirotor performing parallel hybrid drive as an example.

[0077] <Basic configuration> Figure 3A is a schematic top view of the multicopter 100 in this embodiment, and Figure 3B is a side view thereof. Figure 3B shows a work implement 200 connected to the multicopter 100. The multicopter 100 may be connected to, or in place of, the work implement 200, to cargo, agricultural materials, other machinery, or containers, cases, or packages that can contain them. Hereinafter, the weight of the work implement 200 and the work implement itself may be referred to as the "payload". The "connection" between the multicopter 100 and the work implement 200, etc., can be performed by various devices or apparatus.

[0078] The multicopter 100 shown in Figure 3A comprises eight subrotors 12 and two main rotors 22. Each subrotor 12 consists of four sets of propellers 12a and 12b that rotate coaxially and in opposite directions. Each propeller 12a and propeller 12b has two blades. Each propeller 12a and 12b is rotated by a motor 14. The four sets of coaxially rotating propellers 12a and 12b are each located at the vertices of a square. The main rotor 22 consists 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 subrotor 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 propeller 22a is at least 1.2 times the diameter of propellers 12a and 12b, for example, between 1.4 and 2.0 times.

[0079] The multicopter 100 comprises an aircraft frame 110 having four arms 110A for the sub-rotor 12 and two arms 110B for the main rotor 22. The aircraft frame 110 supports the aircraft body 120, which includes various electronic and mechanical components, as described later.

[0080] In the example shown in Figure 3B, the main body 120 includes a power supply device 76 and an actuator 78 used for connecting to the work implement 200. The power supply device 76 is a device that supplies power generated within the main body 120 to the work implement 200. The actuator 78 is a device such as an electric motor that performs the operation to connect the work implement 200 to the main body 120 of the multicopter 100. In the example shown in Figure 3B, the actuator 78 drives a mechanism that winds up the cable connecting the main body 120 and the work implement 200. This cable may include a power line for supplying power to the work implement 200 from the multicopter 100, and a communication line for communication between the multicopter 100 and the work implement 200.

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

[0082] In the illustrated example, the aircraft body 120 of the multicopter 100 includes 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, sensor group 4b, and communication device 4c of the aircraft body 4 of the multicopter 10, which were described with reference to Figure 1A.

[0083] The multicopter 100 in this embodiment comprises eight sub-rotors 12, eight motors 14 that rotate each of the eight sub-rotors 12, and eight ESCs that control each of the eight motors 14. Each ESC 16 receives a signal (motor control signal) for controlling the motor 14 from the control device 30 via 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 represent an analog value of the motor rotation speed. Each ESC 16 controls the rotation speed of the motor 14 connected to it based on the motor control signal from the control device 30. In Figure 4, for simplicity, one set of "sub-rotors 12, motors 14, and ESC 16" is shown, but the multicopter 100 in this embodiment comprises eight sets of "sub-rotors 12, motors 14, and ESC 16". The number of these sets is not limited to eight.

[0084] The control device 30 is connected to each of the eight ESCs 16 via electrically independent wiring 82, allowing each of the eight ESCs 16 to be controlled individually. As mentioned above, the sub-rotor 12 is used not only to generate lift but also for attitude control. Attitude control is achieved when the flight controller 32 of the control device 30 obtains measured or estimated values ​​indicating the attitude of the aircraft body 120 from the sensor group 72 to determine the current attitude of the aircraft body 120, and controls the rotational speed of each motor 14 according to the difference from the target attitude.

[0085] The main 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 can acquire sensor data such as the accelerator opening, intake air temperature, engine speed, and temperatures of various parts of the main rotor drive unit 24, which is an internal combustion engine, and perform control of 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 signals transmitted from the control device 30. The engine control signal includes, for example, the 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. Mechanical devices such as a clutch and a reduction gear may be provided between the main rotor drive unit 24 and the main rotor 22.

[0086] The main rotor drive unit 24 is preferably an internal combustion engine with low vibration. In this embodiment, the main rotor drive unit 24 is, for example, a opposed-piston engine. An opposed-piston engine is 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 generation device 42 such as an alternator. In this embodiment, the power generation device 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 generation device 42 can also function as a "starter" by rotating the rotor by energizing it. The power generation device 42 rectifies the AC generated by power generation and converts it into DC. The power generation device 42 generates the DC power necessary to drive the motor 14 and supplies it to each ESC 16 via the wiring 80. The power generation device 42 is configured to output a DC voltage of, for example, 250V or more. Wiring 80 is for power, and wiring 82 is for signals. Wirings 80 and 82 each contain multiple conductors.

[0088] The power generator 42 is connected to the power management device 44. The power management device 44 is connected to the control device 30 and the battery management device 54, which will be described later. The power management device 44 can control the amount of power generated by the power generator 42 based on signals from the control device 30 or the battery management device 54. This amount of power generated can be variably controlled by the power management device 44 according to 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 which multiple lithium-ion secondary battery cells are connected in series or parallel, and a battery management device 54 that controls the charging and discharging of the battery 52.

[0090] The battery 52 can receive DC power from the generator 42 via the power switch 56 and be charged by that power. The operation of the power switch 56 can be controlled by the battery management device 54 and the control device 30. The battery management device 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 device 54 can control the power switch 56 according to the state of the battery 52. ​​For example, when the battery 52 is in a state where it needs to be charged, the battery management device 54 electrically connects the generator 42 and the battery 52 using the power switch 56 and supplies power from the generator 42 to the battery 52 to perform the charging operation. At this time, the battery management device 54 can control the power management device 44 to increase the amount of power generated by the generator 42 so that the power supplied to the ESC 16 does not fall below a desired level. On the other hand, when the battery 52 is not in a state where it needs to be charged, the battery management device 54 disconnects the electrical connection between the generator 42 and the battery 52 using the power switch 56 and stops charging the battery 52.

[0092] In this embodiment, the storage capacity of the battery 52 is such that even if power generation by the generator 42 stops for any reason and lift from the main rotor 22 is lost, the sub-rotor 12 can continue to generate lift and maintain attitude control, allowing the aircraft to fly to a suitable landing location and land there. 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 generator 42, not from the battery 52. ​​Therefore, even when increasing the payload and flight time, 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, 250V or higher. However, this DC voltage decreases as the charge level decreases. Therefore, if the charge level falls below a predetermined level, the battery management device 54 operates to supply a portion of the DC power from the generator 42 to the battery 52 to charge the battery 52.

[0094] The battery 52 is connected to the power circuit board 60. The power circuit board 60 has the function of stepping down the voltage output from the battery 52 to, for example, 24V, 12V, or 5V. The DC voltage output from the battery 52 is converted to the desired voltage by the power circuit board 60 and then supplied to other electronic components. In the example in Figure 4, the power stepped down by the power circuit board 60 is supplied to the control device 30 and the actuator 78 via the wiring 80.

[0095] In the example shown in Figure 4, the power supply device 76 is electrically connected to the generator 42 or battery 52 by a power switch 56. In this example, the power supply device 76 is configured to supply power generated within the main body 120 to an external machine or device such as a work machine 200.

[0096] The aircraft body 120 may have configurations not shown in Figure 4. For example, the aircraft body 120 may include a fuel tank for storing the 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, lighting equipment, and electrical components such as an electric pump. The electrical components can be operated by power 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 from the battery 52 or the generator 42.

[0097] In this embodiment, the motor 14 functions as multiple "attitude control devices" that drive multiple first rotors (sub-rotors) 12, each of which is a multiple first rotor (sub-rotor). 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 Figure 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 both 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 of the sub-rotors 12 obtained from the multiple motors 14 (first thrust) and the total thrust of the main rotor 22 obtained from the main rotor drive unit 24 (second thrust). This point will be explained in detail below.

[0100] Generally, the responsiveness of the motor 14 is superior to that of an internal combustion engine. If we define "response time" as the time from the moment a torque command signal is input until the torque target value is reached for the rotation of rotors 12 and 22, the motor's response time is, for example, about 1 / 100th of that of an internal combustion engine. Therefore, to control the attitude of the multicopter 100, it is desirable to detect the difference between the current attitude angle and the target value of the multicopter 100, and to control the rotational speed of each of the multiple sub-rotors 12 with a high response speed to minimize this difference. Increasing the rotor rotational speed increases thrust. By adjusting the thrust of each of the multiple sub-rotors 12, it becomes possible to control the attitude of the multicopter 100 with high precision and speed.

[0101] On the other hand, internal combustion engines can efficiently generate large thrusts. The rotation of the sub-rotor 12 is performed using electricity 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 to electrical energy. For this reason, from the viewpoint of improving energy consumption efficiency, it is preferable that the main rotor drive unit 24 is used to rotate the main rotor 22 and generate the main thrust. In addition, in order 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 primary thrust, is generating a large thrust, that large thrust and rotational moment can actually suppress 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 responsiveness, a delay in the response to attitude control may occur. On the other hand, reducing the rotational speed of the main rotor 22 improves attitude control performance, but it reduces energy consumption efficiency.

[0103] In battery-powered multirotors, various algorithms are used to adjust the torque of each motor to equalize the thrust of each rotor and control the aircraft to a desired attitude. When attitude control is performed 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 hybrid aircraft have adopted a control method that fixes this ratio.

[0104] However, as a result of the inventors' studies, it was found that when the multicopter 100 is used for agricultural work, for example, it is preferable to make the above-mentioned "ratio" variable rather than fixed, compared to when the multicopter 100 is flown for mere logistics or monitoring purposes. This is because when the multicopter 100 is flown for agricultural purposes, it flies under a variety of different conditions, such as various agricultural tasks (ground work) within a field, movement between multiple fields, and transport of agricultural materials or harvested products, and the level of response speed required for attitude control changes greatly depending on these conditions. In addition, when work machines of various weights and shapes are appropriately selected and connected according to the content of the agricultural work, the required lift and the precision of attitude control can also change greatly.

[0105] In this embodiment, when precise attitude control is not required, for example, when there are few disturbances such as wind and the payload is small, or when only movement is performed without work by the work machine, the thrust of the main rotor 22 can be increased and, conversely, the thrust of the sub-rotor 12 can be decreased.

[0106] On the other hand, when precise attitude control is required, for example, when performing ground operations while flying with a work machine attached, or when it is necessary to move the aircraft body more quickly than in normal flight to change its attitude, 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 leads to a decrease in overall energy consumption efficiency, but it makes it possible to improve attitude control performance (response performance).

[0107] <Determination of the rotational speed of the main rotor and sub-rotor> Next, an example of a method for determining the rotational speed of each main rotor 22 and each sub-rotor 12 will be described.

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

[0109] The multicopter 100 shown in Figure 5 comprises two main rotors 22 and eight sub-rotors 12. The two main rotors 22 are each 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 consist of four sets of sub-rotors 12, each set consisting of two coaxial sub-rotors 12. The four sets of sub-rotors 12 are each supported by four arms 110A1, 110A2, 110A3, and 110A4 that form a 45-degree angle 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 aircraft to the axis of rotation of each main rotor 22 is shorter than the distance from the center of the aircraft to the axis of rotation of each sub-rotor 12. The diameter of each main rotor 22 is greater than the diameter of each sub-rotor 12. In Figure 5, each main rotor 22 is represented by a relatively large circle, and the two coaxial sub-rotors 12 are represented by a single relatively small circle. The rotational speeds of the four sub-rotors 12 located on the upper side (positive z-axis side) are denoted as ω1, ω2, ω3, and ω4, and the rotational speeds of the four sub-rotors 12 located on the lower side (negative z-axis side) are denoted as ω5, ω6, ω7, and ω8. The rotational speeds of the two main rotors 22 are also denoted as ω m1 , ω m2 Here, "rotational speed" refers to the number of rotations per unit time (e.g., in rpm) or angular velocity (e.g., in 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 z-axis side (upper side) rotates clockwise at a rotational speed ω1, and the sub-rotor 12 on the negative z-axis side (lower side) rotates counterclockwise at a rotational speed ω5. Of the two sub-rotors 12 supported by the lower right arm 110A2, the sub-rotor 12 on the positive z-axis side rotates counterclockwise at a rotational speed ω2, and the sub-rotor 12 on the negative z-axis side rotates clockwise at a rotational speed ω6. Of the two sub-rotors 12 supported by the lower left arm 110A3, the sub-rotor 12 on the positive z-axis side rotates clockwise at a rotational speed ω3, and the sub-rotor 12 on the negative z-axis side rotates counterclockwise at a rotational speed ω7. Of the two sub-rotors 12 supported by the upper left arm 110A4, the sub-rotor 12 on the positive z-axis side rotates counterclockwise at a rotational speed ω4, and the sub-rotor 12 on the negative z-axis side rotates clockwise at a rotational speed ω8. The main rotor 22 supported by the arm 110B1 extending in the positive x-axis direction from the center of the fuselage rotates clockwise at a rotational speed ω m1 and rotates. The main rotor 22 supported by the arm 110B2 extending in the negative x-axis direction from the center of the fuselage rotates counterclockwise at a rotational speed ω m2 and rotates.

[0111] Let the length of each of the four arms 110A1, 110A2, 110A3, 110A4 supporting the sub-rotor 12 be l, and the length of each of the two arms 110B1, 110B2 supporting the main rotor 22 be l m . Also, let the total thrust generated by the rotation of the plurality of main rotors 22 and the plurality of sub-rotors 12 be T, the torque around the x-axis rotation be τ φ , the torque around the y-axis rotation be τ θ , and the torque around the z-axis rotation be τ ψ .

[0112] Total thrust T and torque τ φ , τ θ , τ ψ and the rotational speeds ω1, ω2, ω3, ω4, ω5, ω6, ω7, ω8 of the sub-rotor 12 and the rotational speeds ω m1 , ω m2The relationship between them is represented by the following equation 1.

number

[0113] If we separate the term relating to the main rotor 22 and the term relating to the sub-rotor 12 on the right-hand side of equation 1, we obtain equation 2 as follows.

number

[0114] In this embodiment, the two main rotors 22 are controlled to rotate synchronously in opposite directions. Therefore, ω m1 =ω m2 =ω m This allows us to set the torque τ. θ and τ ψ The components originating from 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.

number

[0115] Applying the inverse matrix of the matrix on the right-hand side of equation 3 to both sides from the left yields the following relationship in equation 4.

number

[0116] Therefore, T-2k m ω m 2 , τ φ , τ θ , τ ψ Once determined, the rotational speeds ω1, ω2, ω3, ω4, ω5, ω6, ω7, and ω8 of the sub-rotor 12 can be determined by the calculation in equation 4. T-2k m ω m 2 This corresponds to the sum of the thrusts of multiple sub-rotors 12. T-2k m ω m 2 is an unknown variable ω m This includes, but if the ratio of the total thrust of the main rotor 22 to the total thrust of the sub-rotor 12 is fixed, the T-2k m ω m 2 This can be determined. T-2k m ω m 2 This 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, then multiplying T by a coefficient of 0.4 gives T-2k m ω m 2 This can be determined. Also, 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, then by multiplying T by a coefficient of 0.7, T-2k can be determined. m ω m 2 Therefore, if the ratio of the total thrust of the main rotor 22 to the total thrust of the sub-rotors 12 is fixed, the total thrust T of all rotors and the torque τ around each axis can be determined. φ , τ θ , τ ψ Once determined, the rotational speeds ω1, ω2, ω3, ω4, ω5, ω6, ω7, ω8 of the sub-rotor 12 can be determined by the calculation in equation 4. Also, the total thrust T from all rotors or the total thrust T-2k from the sub-rotor 12 can be determined. m ω m 2By multiplying this by a predetermined coefficient, the total thrust of the main rotor 22 is 2k m ω m 2 k can be calculated. m Since this is known, 2k m ω m 2 From the number ω m It is possible to calculate this.

[0117] As described above, the control device 30 controls the desired thrust T and torque τ around each axis. φ , τ θ , τ ψ Based on the relationship in equation 4, the rotational speeds ω1, ω2, ω3, ω4, ω5, ω6, ω7, ω8 of the sub-rotor 12 and the rotational speed ω of the main rotor 22 m It is possible to make a decision.

[0118] The following describes an example of the process by which the control device 30 determines the rotational speed of each rotor, with reference to Figure 6.

[0119] Figure 6 is a flowchart showing an example of the process for determining the rotational speed of each sub-rotor 12 and each main rotor 22. The process shown in Figure 6 can be performed, for example, by the flight controller 32 in the control device 30. The control device 30 performs the process from steps S100 to S114 to determine the rotational speeds ω1, ω2, ω3, ω4, ω5, ω6, ω7, ω8 of the eight sub-rotors 12 and the rotational speed ω of each main rotor 22. m It is possible to make a decision.

[0120] In step S100, the control device 30 acquires information on the total weight of the multicopter 100 and the implement 200. The total weight information can be stored in a memory device beforehand, for example. Alternatively, the weight of the multicopter 100 may be stored in a memory device beforehand, and the weight of the implement 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 implement 200 fluctuates due to work such as pesticide spraying or harvesting. The control device 30 may also calculate the total weight of the multicopter 100 and the implement 200 based on the data acquired from the memory device or the sensor.

[0121] In step S102, the control device 30 determines the total thrust T 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 total thrust T to be the thrust that balances the total weight of the multicopter 100 and the work machine 200. During level flight, the control device 30 can determine the total thrust T based on the condition that the vertical component of the thrust balances gravity, taking into account the tilt of the aircraft. During ascent or descent, the control device 30 determines the total thrust T so that the aircraft 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 a geomagnetic sensor. The attitude angle represents the tilt of the multicopter 100 from its reference attitude in a coordinate system fixed to the ground.

[0123] In step S106, the control device 30 sets 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 control device 30 determines the target attitude angle, for example, by user operation using a control device, or according to a pre-set flight program. The control device 30 determines the torque for each of the roll angle, pitch angle, and yaw angle to be a larger value the greater the difference from the target angle.

[0124] Note that the processes in steps S104 and S106 may be performed before or in parallel with the processes in steps S100 and S102.

[0125] In step S108, the control device 30 determines a first thrust T1, which is the sum of the thrusts that the multiple sub-rotors 12 should generate, by multiplying the total thrust T determined in step S102 by a first coefficient K1 that is between 0 and 1. The first coefficient K1 can be set to a predetermined value, such as 0.4.

[0126] In step S110, the control device 30 determines the second thrust T2, which is the sum of the thrusts that the multiple main rotors 22 should generate, by multiplying the total thrust T by the second coefficient K2 (=1-K1), which is the value obtained by subtracting the first coefficient from 1, or by multiplying the first thrust T1 by the third coefficient K3 (=K2 / K1), which is the value obtained by dividing the second coefficient K2 by the first coefficient K1. The calculation of multiplying the total thrust T by the second coefficient K2 and the calculation of multiplying the first thrust T1 by the third coefficient K3 yield the same result.

[0127] The ratio of the second thrust T2, which is the total thrust of the main rotor 22, to the first thrust T1, which is the total thrust of the sub-rotor 12, can be set to a predetermined ratio, such as 6:4. When T2:T1=6:4, the first coefficient is set to 0.4, the second coefficient to 0.6, and the third coefficient to 1.5. Also, when T2:T1=5:5, the first coefficient is set to 0.5, the second coefficient to 0.5, and the third coefficient to 1. When T2:T1=2:8, the first coefficient is set to 0.8, the second coefficient to 0.2, and the third coefficient to 0.25. The third coefficient corresponds to T2 / T1 and is sometimes called the "boost coefficient". The first thrust T1 is T-2k in equation 4. m ω m 2This corresponds to the second thrust T2, which is 2k in equation 4. m ω m 2 It corresponds to this.

[0128] In step S112, the control device 30 determines the first thrust T1 (= T-2k m ω m 2 ) and the required torque τ around each axis φ , τ θ , τ ψ Based on this, the operation shown in Equation 4 is performed. This allows the control device 30 to determine the rotational speeds ω1, ω2, ω3, ω4, ω5, ω6, ω7, and ω8 of the sub-rotor 12.

[0129] In step S114, the control device 30 determines T2 = 2k based on the second thrust T2 determined in step S106. m ω m 2 From this relationship, the rotational speed ω of each main rotor 22 m To decide.

[0130] Through the above process, the control device 30 generates the desired total thrust T and the required torque τ around each axis. φ , τ θ , τ ψ Based on this, the rotational speed of each rotor can be determined. Alternatively, instead of the process in step S110 described above, the control device 30 may calculate the second thrust T2 by subtracting the first thrust T1 from the total thrust T required for flight. The second thrust T2 can also be determined by such a calculation.

[0131] The control device 30 controls each motor 14 and the internal combustion engine (main rotor drive unit 24) based on the determined rotational speeds 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] Thus, the control device 30 in this embodiment calculates a first thrust T1, which is the total thrust generated by the multiple sub-rotors 12, and calculates a second thrust T2, which is the total thrust generated by the main rotor 22, based on the first thrust T1 and the total thrust T required for flight. Based on the first thrust T1, the control device 30 determines the rotational speeds ω1 to ω8 of each of the multiple sub-rotors 12, and based on the second thrust T2, determines the rotational speed ω of each main rotor 22. m The control device 30 determines the following. More specifically, the control device 30 determines the total thrust T that should be generated by the multiple sub-rotors 12 (first rotors) and the multiple main rotors 22 (second rotors), and determines the first thrust T1, which is the sum of the thrusts that should be generated by the multiple sub-rotors 12, by multiplying the total thrust T by the first coefficient K1. The control device 30 further determines the second thrust T2, which is the sum of the thrusts that should be generated by the multiple main rotors 22, by subtracting the first thrust T1 from the total thrust T, multiplying the total thrust T by the second coefficient K2 (=1-K1), or multiplying the first thrust T1 by the third coefficient (=(1-K1) / K1). Based on the first thrust T1, the control device 30 determines the rotational speed of each of the multiple sub-rotors 12, and based on the second thrust T2, determines the rotational speed of each of the multiple main rotors 22.

[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. This allows the multicopter 100 to approach the target attitude and perform the desired flight.

[0134] In the examples shown in Figures 3A and 5, the multicopter 100 is equipped with 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. Also, the number of sub-rotors 12 may be other numbers, such as four or six. Regarding the sub-rotors 12, various configurations such as quadcops, hexacopters, or octocops can be adopted, not limited to the octo-quadcopter configuration shown in Figures 3A and 5.

[0135] In the operation described above, the first coefficient K1 and the second coefficient K2 or third coefficient K3 may be variable. In other words, the boost coefficient T2 / T1 (corresponding to the third coefficient K3), which is the ratio of the total thrust T2 from the main rotor 22 to the total thrust T1 from the sub-rotors 12, may be variable. The boost coefficient corresponds to the ratio of the total thrust (second thrust) from the main rotor 22 obtained from the main rotor drive unit 24 to the total thrust (first thrust) from the sub-rotors 12 obtained from the multiple motors 14. The control device 30 may change the first coefficient K1 and the second coefficient K2 or third coefficient K3 according to the state of the multicopter 100. For example, the control device 30 may change the first coefficient K1 and the second coefficient K2 or third coefficient K3 according to the flight mode. Flight modes include, for example, hovering, horizontal flight (forward, backward, or lateral movement (aileron)), climbing, descending, and turning (rudder). The control device 30 may be configured to maintain the first coefficient K1 at a value less than 0.5, for example, during ascent and hovering. When the first coefficient K1 is maintained at a value less than 0.5, the second coefficient K2 is maintained at a value greater than 0.5, and the third coefficient K3 (boost coefficient) is maintained at a value greater than 1. This allows the main rotor 22 to efficiently generate a large thrust. When the control device 30 adjusts the aircraft's attitude (yaw, pitch, and / or roll) to a desired attitude for actions such as landing, level flight, or rudder control, the boost coefficient may be set to a value smaller than the value during hovering (for example, less than 1). This prevents 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 may be configured to change the first coefficient K1 and the second coefficient K2 or third coefficient K3 in response to user operation using an external device such as a control device or remote monitoring device. This allows the user to adjust the balance between thrust generation efficiency and attitude control responsiveness, for example, to make it easier to control.

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

[0138] Attitude control of the multicopter 10 is achieved by bringing the aircraft's yaw, pitch, and roll angles closer to the target angles. Of these, the control that brings the yaw angle closer to the target angle is called "rudder control." Below, we will explain a control method to suppress deviations of the aircraft's actual yaw angle from the target angle in rudder control. Note that the following control method can also be applied to control that adjusts the aircraft's pitch angle or roll angle to the target angle, not just rudder control.

[0139] The control device 30 may be configured to reduce (or eliminate) the total thrust or rotational speed of the main rotor 22 when performing rudder control to adjust the aircraft's yaw angle to a target angle, and instead increase the total thrust or rotational speed of the sub-rotor 12. By reducing the total thrust or rotational speed of the main rotor 22, fluctuations in the attitude angle during rudder control can be reduced, thereby stabilizing the aircraft's attitude.

[0140] Figure 7 is a flowchart illustrating the operation of the control device 30 related to rudder control. During the flight of the multicopter 100, the control device 30 performs the processes shown in Figure 7 to control the aircraft's yaw angle to approach the target angle.

[0141] First, in step S200, the control device 30 determines whether or not to start rudder control. The control device 30 determines whether or not to start rudder control based on, for example, a command from an external device such as a pilot or remote monitoring device used by the user, or a pre-set flight program. Rudder control may be performed, for example, when changing or maintaining the orientation of the aircraft in a desired direction for a change of flight direction or landing. The control device 30 performs rudder control when controlling to the target yaw angle, when a yaw angle control delay occurs, or when rotation or sway occurs in the yaw direction. 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, the total thrust of the main rotors 22 can be reduced by decreasing the rotational speed of each main rotor 22 by reducing the boost coefficient mentioned above. As mentioned above, during hovering, the control device 30 may be configured to set the boost coefficient to a value greater than 1, so that the total thrust T2 of the multiple main rotors 22 is greater than the total thrust T1 of the multiple sub-rotors 12. In contrast, when performing rudder control, the control device 30 can control the total thrust T2 of the multiple main rotors 22 to be less than the total thrust T1 of the multiple sub-rotors 12 by changing the boost coefficient to a value less than 1. When performing rudder control, the control device 30 may reduce the rotational speed of each main rotor 22 so that the total thrust of the multiple main rotors 22 is reduced 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 during hovering. Alternatively, the control device 30 may stop the rotation of each of the multiple main rotors 22 when performing rudder control. In other words, the control device 30 may change the boost coefficient to 0 (zero) when performing rudder control.

[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 the same process as in step S112 shown in Figure 6. At this time, the rotational speed of each sub-rotor 12 is increased to compensate for the decrease in thrust due to the decrease in the 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, which is reduced due to the decrease in the rotational speed of each of the multiple sub-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 less than a threshold. The threshold is set to a sufficiently small value close to 0 degrees. If the difference between the current yaw angle and the target angle is greater than or equal to the threshold (No), the process returns to step S204. If the difference between the current yaw angle and the target angle is less than the threshold (Yes), the ladder control process ends and the process proceeds to step S208.

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

[0146] The operation shown in Figure 7 can be repeatedly performed, for example, by the flight controller 32 of the control device 30, during the flight of the multicopter 10.

[0147] Through the above operation, the control device 30 can reduce the thrust generated by the multiple main rotors 22 by reducing the rotational speed of each main rotor 22 when performing rudder control. This reduces the fluctuation of the 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 0, the more the fluctuation of the yaw angle during rudder control can be reduced.

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

[0149] <Engine Control> Next, we will explain an example of how to control an internal combustion engine.

[0150] As described above, the multicopter 100 in this embodiment comprises multiple rotors, including multiple sub-rotors 12 and at least one main rotor 22. Each of the multiple sub-rotors 12 is driven by a multiple motor 14. 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 rotation of the multiple sub-rotors 12 by controlling the multiple motors 14 to perform attitude control of the aircraft. The control device 30 generates main thrust by controlling the rotation of at least one main rotor 22 by controlling the internal combustion engine via a main rotor control unit 26.

[0151] Figure 8 is a flowchart showing an example of a control method for the motor 14 and the internal combustion engine. The control method shown in Figure 8 is performed 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 Figure 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 it may be determined to a common value for all of them at once.

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

[0154] In step S304, the control device 30 generates a second PWM signal having a duty cycle 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 be driven by an electric motor. For example, the configuration of the first rotary drive device 3A or the third rotary drive device 3C shown in Figure 1A may be adopted to drive some of the rotors as main rotors and the remaining rotors as sub-rotors. The control device 30 can generate a second PWM signal to input to the ESC that drives the electric motor when each main rotor 22 is driven by an 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. In this embodiment, when each main rotor 22 is driven by an internal combustion engine, the second PWM signal for driving the electric motor cannot be used directly to control the internal combustion engine. 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 degree of the throttle valve of the internal combustion engine. The main rotor control unit 26 can convert the second PWM signal into a second control signal based on data such as a table showing the relationship between the duty cycle of the second PWM signal and the opening degree of the throttle valve, or the relationship between the duty cycle of the second PWM signal and the rotational speed of the internal combustion engine. The duty cycle of the second PWM signal correlates with the rotational speed (second rotational speed) of each main rotor 22. Therefore, the table showing the relationship between the duty cycle of the second PWM signal and the rotational speed of the internal combustion engine corresponds to the table for converting the second rotational speed to the rotational speed of the internal combustion engine. Data such as this table can be pre-stored in an internal or external storage device of the control device 30. The control device 30 can read this data from the storage device and convert the second PWM signal to the second control signal by referring to this data. The data such as the table may also be stored on a server computer in the cloud. In that case, the control device 30 can acquire this data via the communication device 74.

[0156] In step S308, the control device 30 controls each motor 14 by inputting a first control signal generated for each sub-rotor 12 to its respective ESC 16. The main rotor control unit 26 controls the main rotor drive unit 24 (internal combustion engine) using a 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 Figure 8 is performed 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 perform the control shown in Figure 8. That is, the control device or control system may be configured to determine the rotational speed of each of the multiple sub-rotors 12 (first rotational speed) and the rotational speed of at least one main rotor 22 (second rotational speed), generate a first control signal to rotate each of the multiple electric motors 14 based on the first rotational speed, and generate a second control signal to drive the internal combustion engine based on the second rotational speed. Such a control device or control system may, for example, generate a signal having a duty cycle corresponding to the first rotational speed of each sub-rotor 12 (e.g., the first PWM signal described above) as a first control signal, generate a signal having a duty cycle corresponding to the second rotational speed of at least one second rotor (e.g., the second PWM signal described above), 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 table described above.

[0158] The following describes in more detail an example configuration for realizing the above control, with reference to Figures 9 to 12.

[0159] Figure 9 is a block diagram showing an example configuration of the flight controller 32 in the control device 30. In this example, the flight controller 32 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 cycle corresponding to the rotational speed of each sub-rotor 12, and a module 326 that generates a second PWM signal having a duty cycle 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 Figure 9, PWM signals #1 to #8 are input to eight ESCs 16, each corresponding to one of the eight sub-rotors 12. In the example in Figure 9, PWM signals #1 to #8 are also input to module 326, which generates the PWM signal for the main rotor 22. Based on these PWM signals #1 to #8, module 326 generates a PWM signal (second PWM signal) for the main rotor 22 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] Figure 10 shows an example configuration of module 326 that generates a PWM signal for the main rotor 22. Module 326 includes multiple adders 326a, a filter arithmetic unit 326b, and a multiplier 326c. The number of adders 326a is equal to the number of sub-rotors 12. Adders 326a add the duty cycles of PWM signals #1 to #8 input from module 324 and output a duty cycle sum. The duty cycle sum correlates (e.g., is proportional) to the total thrust of the multiple sub-rotors 12. The signal of the duty cycle sum is input to filter arithmetic unit 326b. Filter arithmetic unit 326b removes the high-frequency components of the signal of the duty cycle sum and smooths the time variation of the signal before outputting it. The signal output from filter arithmetic unit 326b is sent to multiplier 326c. Multiplier 326c generates and outputs a PWM signal for the main rotor 22 by multiplying the signal by a boost coefficient. The functions shown in Figure 10 may be implemented by hardware or by software.

[0161] Figure 11 is a graph showing an example of the time variation of the sum of the duty cycles of the PWM signals for the sub-rotor 12 and the duty cycle of the PWM signals for the main rotor 22. In the example in Figure 11, the boost coefficient is always kept at a constant value, and the ratio of the sum of the duty cycles of the PWM signals for the sub-rotor 12 to the duty cycle of the PWM signals for the main rotor 22 is constant. As mentioned above, the boost coefficient may fluctuate during flight depending on the state of the multicopter 100 or commands from external devices, etc.

[0162] Figure 12 shows an example configuration of the main rotor control unit 26. The main rotor control unit 26 shown in Figure 12 includes a module 26a that determines the target rotational speed of the internal combustion 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 the engine rotation pulse signal output from a sensor provided on the internal combustion engine, and a module 26e that calculates the actual rotational 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 rotational speed table, which is data showing the relationship between the duty cycle of the PWM signal for the main rotor 22 and the target rotational speed of the engine. Here, the engine rotational speed means the number of rotations of the engine per unit time (e.g., 1 minute) (e.g., unit: rpm). Note that the functions shown in Figure 12 may be implemented by hardware or by software.

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

[0164] Figure 13 is a graph showing an example of the correspondence between the duty cycle of the PWM signal and the engine speed. The target speed table can be created in advance based on the relationship shown in Figure 13 and stored in the memory device 26g. In this example, the rotational speed of each main rotor 22 is proportional to the duty cycle of the PWM signal. The target speed table is an example of a table that converts the rotational speed of each main rotor 22 to the rotational 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, measures the pulse interval of the engine rotation pulse signal output from the sensor, and calculates the actual engine speed based on that pulse interval. The main rotor control unit 26 subtracts the target engine speed from the actual engine speed and performs PID control, adjusting the engine control signal so that the difference between them approaches zero. The main rotor control unit 26 controls the main rotor drive unit 24 (internal combustion engine) with the engine control signal determined so that the difference between the target engine speed and the actual engine speed approaches zero. This makes it possible to rotate the main rotor 22 at the desired rotational speed.

[0166] In the example above, a table showing the relationship between the duty cycle of the PWM signal and the target engine speed is used. However, data such as a table showing the relationship between the duty cycle of the PWM signal and the opening degree 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 indicating the opening degree of the throttle valve. Such an engine control signal can be used as a second control signal to drive the internal combustion engine.

[0167] As described above, the flight controller 32 in the control device 30 of this embodiment generates a PWM signal having a duty cycle corresponding to the rotation speed when controlling the rotation speed of each main rotor 22. The main rotor control unit 26 converts the PWM signal into an engine control signal based on a table defining the relationships shown in Figure 13, and uses the engine control signal to control the internal combustion engine. With this configuration, the flight controller used in a battery-powered or series hybrid drive type in which the main rotor 22 is driven by an electric motor can also be used in the parallel hybrid drive type configuration of this embodiment. Therefore, it becomes possible to control the internal combustion engine driving the main rotor 22 in the parallel hybrid drive type without changing the flight controller.

[0168] The control device 30 in the embodiments of this disclosure may be implemented by a digital computer system programmed to perform the processes described with reference to Figures 6 to 8.

[0169] Figure 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, ROM (Read Only Memory) 35, RAM (Random Access Memory) 36, storage device 37, and communication interface 38. These components are interconnected via a bus 39.

[0170] The processor 34 is one or more semiconductor integrated circuits, also known as a central processing unit (CPU) or microprocessor. The processor 34 sequentially executes computer programs stored in the ROM 35 to perform the aforementioned processing. The term processor 34 is broadly interpreted to include FPGAs (Field Programmable Gate Arrays), GPUs (Graphic Processor Units), ASICs (Application Specific Integrated Circuits), or ASSPs (Application Specific Standard Products) equipped with a CPU.

[0171] ROM35 can be, for example, writable memory (e.g., PROM), rewritable memory (e.g., flash memory), or read-only memory. ROM35 stores programs that control the operation of the processor. ROM35 does not need to be a single recording medium; it can be a collection of multiple recording media. Some of these collections may be removable memory.

[0172] RAM36 provides a workspace for temporarily unpacking programs stored in ROM35 during boot-up. RAM36 does not need to be a single storage medium; it can be a collection of multiple storage mediums.

[0173] The communication interface 38 is an interface for communication between the control device 30 and other electronic components or electronic control units (ECUs). For example, the communication interface 38 can perform wired communication compliant with various protocols. The communication interface 38 may also perform wireless communication compliant with the Bluetooth® standard and / or the Wi-Fi® standard. Both standards include wireless communication standards that utilize the 2.4GHz frequency band.

[0174] The storage device 37 may be, for example, a semiconductor memory, a magnetic storage device, or an optical storage device, or a combination thereof. The storage device 37 can 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 mentioned above, the control device 30 may include, for example, a flight control device such as a flight controller 32 and a higher-level computer (companion computer) as separate components. Alternatively, a system including the control device 30 and the main rotor control unit 26 may be used as the "control device".

[0176] Furthermore, 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, as shown in Figure 15. Agricultural machinery 700, such as a tractor, may be connected to such a communication network N, and communication may take place between the multicopter 100 and the agricultural machinery 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 machinery 700 to the multicopter 100 via the communication network N.

[0177] In the unmanned aerial vehicle according to the above embodiment, the "attitude control device" is equipped with multiple electric motors, and the "main thrust generator" is equipped with an internal combustion engine. In other words, the unmanned aerial vehicle according to the above embodiment is equipped with the rotary drive device 3D shown in Figure 1A. However, even in the rotary drive devices 3A, 3B, and 3C shown in Figure 1A, an unmanned aerial vehicle equipped with an "attitude control device" and a "main thrust generator" can be realized by making some of the motors 14 or power transmission systems 23 different from the other motors 14 or power transmission systems 23.

[0178] Furthermore, an unmanned aerial vehicle may be equipped with multiple internal combustion engines with different power outputs and response speeds. In that case, an internal combustion engine with a relatively low power output and a relatively high response speed may constitute an "attitude control system," while an internal combustion engine with a relatively high power output and a relatively low response speed may constitute a "main thrust generator." [Industrial applicability]

[0179] The unmanned aerial vehicles of this disclosure can be widely used not only for aerial photography, surveying, logistics, and pesticide spraying, but also for ground work related to agricultural operations, and for transporting harvested crops and agricultural materials. [Explanation of Symbols]

[0180] 2...Rotor (propeller), 3...Rotary drive unit, 4...Aircraft body, 4a...Control device, 4b...Sensor group, 4c...Communication device, 5...Aircraft 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...Generator, 44...Power management device, 52...Battery, 54...Battery management device, 72...Sensor group, 74...Communication device, 100...Multicopter, 200...Work machine

Claims

1. Multiple first rotors, Multiple second rotors, A control device that performs attitude control of the aircraft by controlling the rotation of the plurality of first rotors and generates main thrust by controlling the rotation of the plurality of second rotors, Equipped with, When the control device performs rudder control to adjust the yaw angle of the aircraft by controlling the rotation of the plurality of first rotors, it reduces the total thrust of the plurality of second rotors. unmanned aircraft.

2. 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, as described in claim 1.

3. The control device performs rudder control when controlling the yaw angle of the target, when a control delay occurs in the yaw angle, or when rotation or oscillation occurs in the yaw direction, as described in claim 1 or 2.

4. The unmanned aerial vehicle according to claim 1 or 2, wherein the diameter of each of the plurality of second rotors is greater than the diameter of each of the plurality of first rotors.

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

6. The unmanned aerial vehicle according to claim 1 or 2, wherein the distance from the center of the aircraft to the rotation axis of each of the plurality of second rotors is shorter than the distance from the center of the aircraft to the rotation axis of each of the plurality of first rotors.

7. The control device, during hovering, makes the total thrust of the plurality of second rotors greater than the total thrust of the plurality of first rotors, and when rudder control is performed, makes the total thrust of the plurality of second rotors less than the total thrust of the plurality of first rotors, according to claim 1 or 2.

8. The unmanned aerial vehicle according to claim 1 or 2, wherein 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 when performing the rudder control.

9. The unmanned aerial vehicle according to claim 8, wherein when the control device performs the rudder control, it compensates for the decrease in the total thrust of the plurality of second rotors due to the decrease in the rotational speed of each of the plurality of second rotors by increasing the rotational speed of the plurality of first rotors.

10. The unmanned aerial vehicle according to claim 1 or 2, wherein the control device stops the rotation of each of the plurality of second rotors when performing rudder control.

11. Multiple electric motors that drive each of the multiple first rotors, An internal combustion engine that drives the plurality of second rotors, Furthermore, The unmanned aerial vehicle according to claim 1 or 2, 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.

12. A control method for an unmanned aerial vehicle comprising a plurality of first rotors and a plurality of second rotors, The aircraft's attitude is controlled by controlling the rotation of the aforementioned plurality of first rotors, The main thrust is generated by controlling the rotation of the plurality of second rotors, Includes, Performing the aforementioned attitude control means This involves performing rudder control to adjust the yaw angle of the aircraft by controlling the rotation of the plurality of first rotors, When the aforementioned rudder control is performed, the total thrust of the multiple second rotors is reduced, A control method including

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