Unmanned aircraft

Abstract

The objective is to provide an unmanned aerial vehicle that can secure sufficient mounting space and achieve stable flight over long periods of time. [Solution] The unmanned aerial vehicle 1 mainly consists of a main body 2, rotor blades 3 that generate lift and thrust, a motor 4 for rotating the rotor blades 3, a power source 5 that supplies power to the motor 4, and a fuel tank 6 for storing fuel (gasoline) supplied to the engine 53 of the power source 5. The power source 5 is installed at a predetermined position horizontally offset from the center C of the aircraft, thereby securing a loading space V for carrying payloads L.

Description

Technical Field

[0001] The present invention relates to an unmanned aircraft. More specifically, it relates to an unmanned aircraft that can secure mounting space and achieve stable flight over a long period of time.

Background Art

[0002] In recent years, research and development of small unmanned aircraft such as drones have been actively carried out, and it is planned to use unmanned aircraft in various fields. An unmanned aircraft can achieve both flight movements such as takeoff / landing and cruising and attitude stability by combining a plurality of rotor blades rotated by an electric motor (hereinafter referred to as "motor") and an advanced control system (see Patent Document 1).

[0003] And unmanned aircraft have already been used in various fields such as shooting of videos and photos, observation and monitoring of places where it is difficult for humans to approach, inspection of large buildings and walls, material transportation, competitions, etc., or are being considered for future use.

[0004] By the way, when only a battery such as a lithium-ion battery is used as a power source for an unmanned aircraft, the total weight of the aircraft body becomes heavy, and it is difficult to fly for a long time or over a long distance due to the limit of the battery capacity to be mounted. Especially when flying with heavy materials and equipment (hereinafter sometimes collectively referred to as "mounted items"), the total weight of the aircraft body becomes even heavier, so the use of unmanned aircraft in long-distance material transportation and the like has not yet penetrated at present.

[0005] Therefore, in fields where the flight time and flight distance of an unmanned aircraft are particularly important (for example, inspection of structures and material transportation), as shown in Patent Document 2 for example, an engine using fuel such as gasoline as an energy source is mounted, and a so-called hybrid-type unmanned aircraft that charges a battery with the electric power generated by the driving force of this engine is being considered.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-162926 [Patent Document 2] Japanese Patent Publication No. 2017-193209 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The hybrid unmanned aerial vehicle described in Patent Document 2 has a longer flight range and duration compared to an unmanned aerial vehicle powered solely by a battery, and may be able to achieve stable flight even for long-distance cargo transport.

[0008] On the other hand, hybrid unmanned aerial vehicles (UAVs) are equipped with an engine and generator as power sources in addition to batteries, as well as fuel tanks to store gasoline and other fuels supplied to the engine. Furthermore, when designing UAVs, regardless of whether they are hybrid or not, the prevailing design principle is to set the center of gravity in the center of the aircraft.

[0009] Therefore, it is common practice to place the power source, which accounts for the majority of the weight of an unmanned aerial vehicle, in the center of the aircraft. For example, in a hybrid unmanned aerial vehicle, according to conventional design principles, the power source, including the battery, engine, and generator, as well as the fuel tanks, must necessarily be placed in the center of the aircraft (on the central axis passing through the aircraft's center of gravity). As a result, the prevailing layout has been one in which the power source and fuel tanks are stacked vertically at the center of the aircraft.

[0010] Furthermore, when an unmanned aerial vehicle (UAV) is equipped with payloads, the payloads must be mounted on the central axis passing through the aircraft's center of gravity, that is, directly below the power source. In this case, the aircraft's center of gravity is further lowered. The lower the center of gravity is, the greater the aircraft's pitching moment, and this increase in pitching moment limits the aircraft's maximum flight speed. This tendency is even more pronounced in hybrid UAVs.

[0011] Therefore, in unmanned aerial vehicles (UAVs), including hybrid types, laid out based on conventional design philosophies, there is a problem in that the weight of the payload is limited in order to minimize the increase in pitching moment. In addition, because the layout always needs to take the center of gravity into consideration, a lot of time has been spent on considering the weight and placement of the payload during the design phase of the UAV or when the payload is actually mounted.

[0012] In response to the above-mentioned problems, the inventor of this invention diligently researched the layout of unmanned aerial vehicles and found that stable flight is possible even if the power source is positioned within a predetermined range horizontally away from the aircraft's center of gravity. Furthermore, this layout allows for sufficient space to carry payloads, resulting in the completion of an unmanned aerial vehicle.

[0013] This invention was conceived in view of the above points, and aims to provide an unmanned aerial vehicle that can secure mounting space and fly for extended periods. [Means for solving the problem]

[0014] To achieve the above objective, the unmanned aerial vehicle of the present invention comprises a main body, a plurality of rotors attached to the main body via arms extending horizontally and generating thrust, a motor for rotating the rotors, and a power source for supplying power to the motor, wherein the power source is installed at a predetermined horizontal distance from the center of the aircraft, and a payload space capable of carrying payloads is formed below the main body.

[0015] Here, the aircraft is equipped with multiple rotors that are attached to the main body of the aircraft via arms extending horizontally and generate thrust, allowing the unmanned aircraft to fly stably. By controlling each of the multiple rotors, flight control such as straight flight, turning, or hovering can be achieved.

[0016] Furthermore, by equipping the rotor blades with a motor to drive them, and by controlling the motor's rotation speed, stable flight control can be achieved as described above.

[0017] Furthermore, by providing a power source that supplies power to the motor, power can be supplied from the power source to the motor.

[0018] Furthermore, by installing the power source at a predetermined horizontal distance from the center of the aircraft, and by creating a payload space below the main body of the aircraft, it is possible to load payloads into this space, and it is also possible to suppress the center of gravity of the unmanned aerial vehicle from dropping too low even when payloads are loaded. Therefore, stable flight can be achieved even when payloads are loaded onto the unmanned aerial vehicle.

[0019] Furthermore, if the power source consists of a battery that supplies power to the motor, a generator that generates power to charge the battery, and an engine that drives the generator, the power generated by the engine-driven generator can be supplied to the battery, enabling longer distances or longer flight times compared to when only the battery is used as the power source.

[0020] Furthermore, if a fuel tank for storing fuel supplied to the engine is installed on the top surface of the aircraft body, the engine can operate for a long time by receiving fuel from the fuel tank.

[0021] Furthermore, if the power source is configured such that the battery is installed adjacent to the fuel tank, the engine is installed directly below the battery, and the generator is installed directly below the engine, then by stacking the power sources from the top to the bottom of the main body of the aircraft at a position horizontally away from the center of the aircraft, sufficient mounting space can be secured below the main body of the aircraft.

[0022] In addition, when landing legs for supporting the aircraft are installed on the main body of the aircraft and the mounting space is a space partitioned by the power source and the landing legs, the space partitioned by the landing legs and the power source can be used as the mounting space below the main body of the aircraft.

[0023] In addition, when the power source is installed at a position away from the center of the aircraft in a predetermined direction of approximately 5% to 20% of the total length of the aircraft, stable flight can be realized while securing the mounting space.

[0024] Note that if the power source is installed within a range less than 5% of the total length of the aircraft, the power source is located near the center of the aircraft, so the mounting space becomes narrow and the mounting capacity of the load may be limited. Also, if the power source is installed within a range exceeding 20% of the total length of the aircraft, the center of gravity is greatly separated from the center of the aircraft, so the aircraft may not be stable and flight control may become complicated.

[0025] In addition, the motor is a low-speed high-torque type. When driving and controlling the motor in a rotation speed range that is lower than a predetermined value compared to the maximum rotation speed of the motor, flight control can be performed in a low rotation speed range that is lower than a predetermined value with respect to the maximum allowable rotation speed of the motor. Therefore, while protecting the motor, stable flight control can be realized in each flight state of straight flight, turning, and hovering, even when the center of gravity is at a position away from the center of the aircraft.

Advantages of the Invention

[0026] The unmanned aerial vehicle according to the present invention can secure a mounting space and realize stable flight over a long period of time.

Brief Description of the Drawings

[0027] [Figure 1] It is a rear perspective view of the unmanned aerial vehicle according to an embodiment of the present invention. [Figure 2] It is a side view of the unmanned aerial vehicle according to an embodiment of the present invention. [Figure 3] It is a bottom view of the unmanned aerial vehicle according to an embodiment of the present invention. [Figure 4]This is a system diagram of an unmanned aerial vehicle according to an embodiment of the present invention. [Modes for carrying out the invention]

[0028] Hereinafter, an unmanned aerial vehicle according to an embodiment of the present invention will be described with reference to the drawings to facilitate understanding of the present invention. For the sake of explanation, in each drawing, the direction of the unmanned aerial vehicle moving upwards is defined as "up," the direction opposite to "up" is defined as "down," the axial direction represented by "up" and "down" is defined as the "vertical direction," and the direction perpendicular to the vertical direction is defined as the "horizontal direction."

[0029] As shown in Figures 1 to 3, the unmanned aerial vehicle 1 according to an embodiment of the present invention is an unmanned aerial vehicle that autonomously flies by obtaining lift and thrust by rotating rotor blades with a power source, and whose center of gravity is located approximately at the center of the aircraft. It mainly consists of an aircraft body 2, rotor blades 3 that generate lift and thrust, a motor 4 for rotating the rotor blades 3, a power source 5 (battery 51, generator 52, engine 53) that supplies power to the motor 4, and a fuel tank 6 for storing fuel (gasoline) supplied to the engine 53 of the power source 5.

[0030] Here, the unmanned aerial vehicle 1 does not necessarily have to be a series hybrid type consisting of a motor 4, battery 51, and engine 53; it may also be an electric unmanned aerial vehicle powered solely by a battery or an unmanned aerial vehicle equipped with a fuel cell. For the sake of explanation, the following explanation will assume a series hybrid type unmanned aerial vehicle.

[0031] [Aircraft body section] The main body 2 of the aircraft consists of a frame formed, for example, in a roughly rectangular shape in plan view, and four arms 21 for supporting the rotor blades 3 (described later) are attached radially in a horizontal direction. The main body 2 of the aircraft is equipped with an FC 23 (Flight Controller) and ESC 24 (Electric Speed ​​Controller) for controlling the autonomous flight of the unmanned aircraft 1, as well as a fuel tank 6 (described later), a power source 5, and payloads L (materials, measurement cameras, etc.) depending on the purpose of use. In addition, a pair of legs 22 are attached to both sides of the main body 2, allowing the unmanned aircraft 1 to be supported at the ground contact surface.

[0032] Here, the main body 2 of the aircraft does not need to be a frame with a roughly rectangular shape in plan view as described above, but may be a housing having an internal space of a predetermined volume. If the main body 2 of the aircraft consists of a housing having an internal space, it is possible to house, for example, flight control devices such as the FC23 and ESC24 in that internal space.

[0033] Furthermore, the number of arms 21 does not necessarily have to be four; they are installed on the main body 2 of the aircraft according to the number of rotor blades 3. For example, if there are six rotor blades 3, six arms 21 will be installed.

[0034] Furthermore, the legs 22 are not necessarily required, and the unmanned aircraft 1 may be supported by placing the lower surface of the main body 2 on the ground surface during landing. However, since the legs 22 also function as fixing jigs when loading payloads L onto the main body 2, it is preferable to have the legs 22 in the embodiments of the present invention.

[0035] As shown in the system diagram in Figure 4, the FC23 is a device that controls the flight of the unmanned aircraft 1. The FC23 sends thrust command signals to the ESC24 while receiving signals measured by the battery 51, controller 7, and various sensors 8.

[0036] Here, the controller 7 is the control unit operated by the pilot who controls the unmanned aircraft 1. The various sensors 8 include a barometric pressure sensor for measuring altitude, an acceleration sensor for measuring acceleration, a gyroscope sensor for measuring attitude and latitude / longitude, an object detection sensor for detecting obstacles, and an inertial sensor for measuring angular velocity around three axes.

[0037] ESC24 is a device that controls the rotational speed of motor 4. ESC24 supplies power to motor 4 using power supplied from battery 51 as driving power. ESC24 also receives thrust output instruction signals from FC23 and outputs them to motor 4.

[0038] [Rotorwing] The rotor blades 3 are devices that generate lift and thrust for the unmanned aircraft 1 to float and fly by rotating. Specifically, a total of four rotor blades 3 are installed on the front left, front right, rear right, and rear left sides.

[0039] As mentioned above, the number of rotor blades 3 can be changed as appropriate depending on the size and weight of the unmanned aircraft 1.

[0040] Each rotor blade 3 is equipped with a motor 4, and the rotor blades 3 are rotated by the motors 4. The motors 4 are brushless motors that are electrically connected to the power source 5 (described later) via the FC 23 and ESC 24 mounted on the main body 2 of the aircraft. As a result, the motors 4 are controlled to rotate at an appropriate speed according to the flight conditions based on electrical signals from the FC 23 and ESC 24.

[0041] In the embodiments of the present invention, the motor 4 used is a low-speed, high-torque type motor with a kV value (revolutions per minute per applied voltage of 1 volt) of 75kV to 130kV, and the flight control of the unmanned aerial vehicle 1 is performed while driving the motor 4 at a rotational speed lower than the motor 4's maximum rotational speed. Accordingly, the pitch of the rotor blades 3 (degree of twist of the rotor blades 3) is set to a relatively large value (13.5 in the embodiments of the present invention).

[0042] Here, it is not necessarily required that motor 4 be a low-speed, high-torque type motor. However, by using a low-speed, high-torque type motor 4, motor 4 can be driven in a low-speed range that has a margin over the motor 4's maximum allowable rotational speed during takeoff and landing, and during straight flight, turning, etc. Therefore, even in cases such as the unmanned aerial vehicle 1 according to the embodiment of the present invention, where the center of gravity is located away from the center of the aircraft and motor control is required over a relatively wide range of rotational speeds, motor control becomes possible in a low-speed range predetermined to be lower than the motor 4's maximum allowable rotational speed, thereby protecting motor 4 and ensuring stable flight at all times.

[0043] Furthermore, the pitch of the rotor blade 3 is not limited to 13.5 and can be set variably depending on the type of motor 4 used. However, as mentioned above, when using a low-speed, high-torque motor, it is necessary to employ rotor blades with a large pitch in order to obtain sufficient thrust at low speeds, and in the embodiment of the present invention, it is preferable that the rotor blade 3 has a pitch of about 10 to 15.

[0044] [Power source] As described above, the power source 5 consists of a battery 51, a generator 52, and an engine 53. Conventionally, the power source 5 was generally installed near the center of the aircraft C so that the center of gravity of the unmanned aircraft 1 would be the center of the aircraft C. However, in the embodiment of the present invention, it is installed at a position shifted more than 5% behind the center of the aircraft C, or more specifically, 5% to 20% behind the center of the aircraft C, or respectively.

[0045] Of the power sources 5, the battery 51 is located adjacent to the fuel tank body 61 of the fuel tank 6, which will be described later. The engine 53 is installed directly below the battery 51, and the generator 52 is installed directly below the engine 53.

[0046] As described above, the power sources 5 are arranged in series in the vertical direction, but their horizontal position is offset to the rear from the center of the unmanned aircraft 1. Therefore, the battery 51, which is part of the power source 5, can be placed at approximately the same height as the main fuel tank 61.

[0047] Furthermore, by stacking the engine 53 and generator 52 directly below the battery 51, the center of gravity of the unmanned aircraft 1 can be prevented from dropping too low compared to the case where the power source 5 is installed directly below the fuel tank body 61. As a result, the maximum flight speed of the aircraft is not limited by the increase in the pitching moment of the aircraft, enabling stable flight, and a payload space V for mounting payloads L in front of the power source 5 can be secured.

[0048] Here, the power source 5 does not necessarily have to be stacked in the order of battery 51, engine 53, and generator 52 from top to bottom, and the arrangement order can be changed as appropriate.

[0049] Furthermore, the power source 5 does not necessarily have to be positioned far behind the center C of the unmanned aircraft 1; it may be positioned forward of the center of gravity, or to the left or right.

[0050] Furthermore, the power source 5 does not necessarily have to be positioned at a location more than 5% behind the aircraft's overall length from the aircraft's center C. However, if it is positioned at a location less than 5% behind the aircraft's overall length from the aircraft's center C, the power source 5 will be located close to the aircraft's center C. This may reduce the available space V, and from the standpoint of securing available space V, it is preferable to position the power source 5 at a location shifted more than 5% behind the aircraft's overall length from the aircraft's center C, and more preferably at a location shifted between 5% and 20% behind the aircraft's overall length from the aircraft's center C.

[0051] The battery 51 is a rechargeable battery capable of charging and discharging power, and in this embodiment of the present invention, it is equipped with a lithium-ion battery. This battery 51 is electrically connected to the generator 52 via a power control unit 54 and charges with power generated by the generator 52.

[0052] Here, the battery 51 does not necessarily have to be a lithium-ion battery; it can be appropriately selected from rechargeable secondary batteries, such as lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, etc.

[0053] The power control unit 54 is a device that controls the power supplied to the motor 4. This power control unit 54 receives power generated by the generator 52, supplies and receives power to and from the battery 51, or transmits a power generation instruction signal to the engine 53 based on information about the battery 51 received from the battery 51 (current, voltage, temperature, state of charge (SOC), etc.).

[0054] Furthermore, the battery 51 is electrically connected to the motor 4 via the power control unit 54 and the ESC 24, and discharges power to supply to the motor 4. The battery 51 is also equipped with sensors (not shown) for measuring current and voltage, and sensors (not shown) for detecting temperature and state of charge, and transmits signals related to this information to the FC 23 and ESC 24.

[0055] Engine 53 is a small, horizontally opposed gasoline engine that functions as a power source for the generator 52. Engine 53 is electrically connected to the power control unit 54. When it receives a power generation instruction from the power control unit 54, it is driven to generate power for the battery 51 or the motor 4 using the generator 52.

[0056] Here, engine 53 does not necessarily have to be a horizontally opposed type; any reciprocating engine of any type, such as inline or V-type, can be used, and diesel engines can be applied in addition to gasoline engines. Furthermore, rotary engines and gas turbine engines can also be applied in addition to reciprocating engines.

[0057] With the above configuration of the power source 5, when the engine 53 is driven, the generator 52 starts generating electricity, and the generated electricity drives the motor 4, causing the rotor blades 3 to rotate and providing thrust for flight. In addition, any surplus electricity generated by the generator 52 when the engine 53 is driven is temporarily stored in the battery 51 and supplied to the motor 4 as needed.

[0058] [Fuel Tank] The fuel tank 6 stores gasoline, which is used to drive the engine 53, the power source 5, in its main body 61. This fuel tank body 61 is installed on the upper surface of the aircraft body 2, adjacent to the battery 51. A fuel inlet pipe 62 is installed from the bottom of the fuel tank body 61 toward the lower side of the aircraft body 2 and is connected to the engine 53. A level sensor (not shown) is installed inside the fuel tank body 61, and the remaining fuel level measured by the level sensor can be displayed on a display unit (not shown) as needed, or an audible alert can be given depending on the remaining fuel level.

[0059] The above describes the configuration of the unmanned aerial vehicle 1 according to the embodiment of the present invention. In the unmanned aerial vehicle 1 according to the embodiment of the present invention, since the power source 5 is positioned horizontally rearward from the center C of the aircraft, a load space V with sufficient volume for loading payload L can be secured below the fuel tank body 61 and in front of where the power source 5 is located.

[0060] As shown in Figures 1 to 3, even if the payload L is loaded into the payload space V, the center of gravity of the unmanned aircraft 1 does not drop too low, thus suppressing an increase in pitching moment. Furthermore, even if the power source 5 is positioned horizontally offset from the aircraft's center C, the center of gravity of the aircraft does not shift drastically to one side by loading the payload L, remaining approximately in the center, thus enabling stable flight.

[0061] Furthermore, by employing a low-speed, high-torque motor 4 and increasing the pitch of the rotor blades 3, the motor 4 can be controlled over a wider range of rotation. Therefore, even if no payload L is loaded, or if an extremely heavy (or light) payload L is loaded and the aircraft's center of gravity is significantly shifted from the aircraft's center C, high-precision control can be achieved, enabling stable takeoff, landing, and flight. Consequently, there is no need to consider the weight or mounting position of the payload L in relation to the center of gravity of the unmanned aircraft 1, and the transport of the payload L can be carried out efficiently.

[0062] As described above, the unmanned aerial vehicle according to the present invention is capable of securing sufficient payload space and achieving stable flight over long periods of time. [Explanation of symbols]

[0063] 1. Unmanned aircraft 2. Main body of the aircraft 21 Arms 22 Legs 23 FC 24 ESC 3 rotor blades 4 motors 5 Power source 51 batteries 52 Generators 53 Engine 54 Power Control Unit 6 Fuel tanks 61 Fuel tank main body 62 Fuel inlet pipe 7 Controllers 8. Various Sensors V-mounting space L Loaded items

Claims

1. The main body of the aircraft, Multiple rotor blades are attached to the main body of the aircraft via arms extending horizontally, and generate thrust. A motor that rotates the rotor blade, The motor is equipped with a power source that supplies power to the motor, The power source is installed at a predetermined horizontal distance from the center of the aircraft, and a mounting space for carrying payloads is formed below the main body of the aircraft. Unmanned aerial vehicle.

2. The power source comprises a battery that supplies power to the motor, a generator that generates power to charge the battery, and an engine that drives the generator, A fuel tank for storing fuel supplied to the engine is installed on the upper surface of the main body of the aircraft. The aforementioned power source is The battery is installed in a position adjacent to the fuel tank. The engine is installed directly below the battery. The generator is installed directly below the engine. The unmanned aerial vehicle according to claim 1.

3. The main body of the aircraft is equipped with landing gear to support the aircraft during landing. The aforementioned mounting space is a space partitioned by the main body of the aircraft, the power source, and the legs. An unmanned aerial vehicle according to claim 1 or claim 2.

4. The aforementioned power source was installed approximately 5% to 20% behind the aircraft's center and overall length. An unmanned aerial vehicle according to claim 1 or claim 2.

5. The motor is a low-speed, high-torque type, and is driven and controlled in a rotational speed range predetermined to be lower than the motor's maximum rotational speed. An unmanned aerial vehicle according to claim 1 or claim 2.

Images