GB2611149A

GB2611149A - New-configuration compound unmanned aircraft in near space and flight control method thereof

Info

Publication number: GB2611149A
Application number: GB2209371.0A
Authority: GB
Inventors: Gao Yadong; Xu Yang; Yu Xinyu; Xu Mengyu; Liu Xueyun
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2021-09-18
Filing date: 2022-06-27
Publication date: 2023-03-29
Also published as: CN113928551A; GB202209371D0

Abstract

A compound unmanned aircraft for use in near space comprises a fuselage 1, a V-shaped tail fin 3 and inflatable wings 2. A plurality of under-mounted beams 4 are connected 5 to each wing and a rotor system 7 is mounted at each end of each beam via a respective tilting mechanism 6. The rotor systems are mounted at different positions in manner of different aerofoil directions to achieve different attitude changes of the fuselage by a differential aerodynamic moment in conjunction with the tilting mechanisms. The rotation directions of the two of the rotor systems of each beam may be opposite. The rotation directions of the two tilting mechanisms of each beam may be opposite, with each tilting mechanism having a rotation range of 90 degrees. The rotational speeds and tilting of front and rear rotor systems can be used to control the aircraft in take-off, landing and forward flight. The fuselage may be an integrated structure of carbon fibre woven fabric, a balsa wood bulkhead and an aluminium alloy envelope. Upper surfaces of the fuselage and the wings may be covered with high-conversion GaAs-based solar panels made of a flexible film material.

Description

NEW-CONFIGURATION COMPOUND UNMANNED AIRCRAFT IN

NEAR SPACE AND FLIGHT CONTROL METHOD THEREOF

TECHNICAL FIELD

100011 The present disclosure relates to the field of aircrafts, and in particular relates to a new-configuration compound unmanned aircraft in near space.

BACKGROUND ART

100021 The World Air Sports Federation determines the altitude range of near space to be 23 km to 100 km, whereas most experts tend to set the altitude range of near space to be 20 km to 100 km, which is between the highest flight altitude of the aircraft and the lowest orbital altitude of the existing spacecraft, and belongs to the transition zone of "air" and "sky" 100031 Compared with the existing aeronautic and astronautics system, the low-speed near-space aircraft has significant advantages in the aspects of flight altitude, duration of operation, responsiveness, cost, and survivability. The flight altitude of this aircraft is moderate, and the duration of operation of this aircraft is long. With the flight altitude of the near-space aircraft between the airplane and the satellite, the near-space aircraft not only can avoid most of the ground attacks at present, but also can improve the accuracy of military reconnaissance and air-to-ground attacks, which is important for intelligence gathering, reconnaissance and surveillance, communication security and ground-to-air and air-to-ground combat support and the like. Meanwhile, compared with the satellite, the near-space aircraft has good rapid response capability and simple launch process, does not require complex and expensive launch facilities as well as space reinforcement and protection, and has low requirements for a ground support device. Most of components and payloads of this near-space aircraft are recyclable and reusable, so the ratio of effectiveness to cost is high.

100041 Different from general near-space aircrafts, compared with general tethered balloons and airships, the aircraft has better maneuverability, and a maximum forward flight speed that reaches the basic requirements of conventional-configuration aircrafts. Compared with high-speed fixed-wing aircraft that is propelled by the rocket engine, the aircraft has the advantage of hovering over the target to obtain longer observation time

SUMMARY

100051 To solve the problem in the prior art, a new-configuration compound unmanned aircraft in near space and a flight control method thereof are provided. By providing the tiltable rotors and a differential aerodynamic moment, the aircraft may have different configurations during it vertically takes-off and lands as well as horizontally forward flights, so as to meet different aerodynamic environment requirements. The aircraft can obtain the maximum lift-drag ratio through the coaxial dual rotors connected to under-mounted beams during it vertically takes-off. And, the aircraft can obtain the maximum forward flight speed through thrusting propellers connected to under-mounted beams during it horizontally forward flights.

100061 A new-configuration compound unmanned aircraft in near space is provided by the present disclosure, which includes a fuselage. A tail part of the fuselage is provided with a tail fin and sides of the fuselage are provided with wings. The wings are inflatable wings, a plurality of under-mounted beams are connected to each of the wings which is on a corresponding one of the sides of the fuselage by respective under-mounted beam connectors. Tilting mechanisms are mounted on two ends of each of the under-mounted beams. The tilting mechanisms are mounted with respective rotor systems, and the rotor systems are mounted at different positions in manner of different airfoil directions, so as to achieve different attitude changes of the fuselage by a differential aerodynamic moment in conjunction with the tilting mechanisms.

100071 In some embodiments, rotational directions of two of the rotor systems on each of the under-mounted beams may be opposite to balance the torque on the under-mounted beam.

100081 In some embodiments, rotational directions of ones of the rotor systems, which are at a same side, of adjacent two of the under-mounted beams may be opposite to balance the torque on the wing.

100091 In some embodiments, rotational directions of two of the tilting mechanisms connected to each of the under-mounted beams may be opposite, and the two tilting mechanisms may have a rotation range of 90 degrees so as to prevent rotor blades from damaging the under-mounted beam due to the excessive tilting of the rotors 100101 In some embodiments, the fuselage may be of an integrated structure of carbon fiber woven fabric, a balsa wood bulkhead and aluminum alloy envelope to reduce weight and enhance endurance.

100111 In some embodiments, upper surfaces of the fuselage and the wings may be covered with high-conversion GaAs-based solar panels to improve the endurance of the aircraft, and the solar panels may be made of a flexible thin film material.

100121 In some embodiments, the tail fin is of a V-shaped structure. The V-shaped tail fin has functions of both vertical stabilizer and horizontal stabilizer, such that the interference drag between the two tail control surfaces of the V-shaped tail fin and between the tail assembly and the fuselage can be reduced with less total number of parts, and the advantage of small amount of tail assembly machining is achieved at the same time.

100131 A flight control method of a new-configuration compound aircraft in near space is further provided, comprising the following processes. Tilting a fuselage by generating a first differential moment via a front rotor and a rear rotor connected to each of under-mounted beams due to a first rotational speed of the front rotor and a first rotational speed of the rear rotor being different, when the aircraft takes-off and lands vertically. Enabling the first rotational speed of the front rotor to be higher than the first rotational speed of the rear rotor, while the aircraft in a vertical state. And tilting the front rotor and the rear rotor connected to the under-mounted beam synchronously by 90 degrees, so as to switch the front rotor and the rear rotor to be a coaxial dual-rotor state. Tilting the fuselage by generating a second differential moment via the front rotor and the rear rotor connected to each of the under-mounted beams due to a second rotational speed of the front rotor and a second rotational speed of the rear rotor being different, when the aircraft rises to a predetermined altitude. Enabling the second rotational speed of the rear rotor to be higher than the second rotational speed of the front rotor, while the aircraft in a horizontal hovering state. Tilting the front rotor and the rear rotor connected to the under-mounted beam synchronously by 90 degrees, so as to switch the front rotor and the second rotor to be a tandem dual-rotor state. When the aircraft flies forward horizontally, changing a lifting surface of the aircraft from a rotor disk to wings of the aircraft. Tilting the front rotor and the rear rotor by 90 degrees, so as to switch the front rotor and the rear rotor to be a thrusting propeller state, such that a forward flight speed is increased.

100141 In some embodiments, a lift direction may be vertically upward via a tilting speed of the rotor disk in tilting of the fuselage. The differential aerodynamic moment may conform to a tilting direction requirement, and when the aircraft flies forward horizontally, the fuselage may keep an angle of attack corresponding to a maximum lift-to-drag ratio of an airfoil of the wings, so as to ensure flight performance.

100151 In some embodiments, in step of when the aircraft flies forward horizontally, changing a lifting surface from the rotor disk to wings, and tilting the front rotor and the rear rotor by 90 degrees, in order to guarantee the lift for horizontal forward flight, the front rotor and the rear rotor may be in the lifting surface state or the thrusting propeller state.

100161 The present embodiments have the following beneficial effects.

100171 1. Compared with a traditional aircraft, by providing the tiltable rotors and differential aerodynamic moment, the aircraft may have different configurations during it vertically takes-off and lands as well as horizontally forward flights, so as to meet different aerodynamic environment requirements. The aircraft can obtain the maximum lift-drag ratio through the coaxial dual rotors connected to under-mounted beams during it vertically takes-off and lands. And, the aircraft can obtain the maximum forward flight speed through thrusting propellers connected to under-mounted beams during it horizontally forward flights.

100181 2. Compared with an existing near-space aircraft, the maneuverability that is superior to tethered balloons or airships can be obtained by providing the tiltable rotors. Meanwhile, the aircraft has the hovering capability of a fixed-wing aircraft in a designated area, and the aircraft is able to hover in a small area for a long time 100191 3. As the structure of the aircraft employs an integrated manufacturing process, compared with the stringers and bulkheads in the traditional fuselage structure, the weight of the aircraft is reduced while the strength is ensured. Meanwhile, the wings and the rotor blades of the aircraft each are of an inflatable structure 100201 4. The aircraft can obtain the longest period of light conditions at an altitude of the near space, and the endurance of the aircraft can be optimized by the high-conversion GaAs-based solar panels laid on the upper surfaces of the fuselage and the wings in conjunction with high-energy-storage-ratio batteries inside the fuselage.

BRIEF DESCRIPTION OF THE DRAWINGS

100211 FIG 1 is a schematic axonometric diagram of a aircraft in a vertical take-off and landing state according to an embodiment of the present disclosure; 100221 FIG 2 is a schematic axonometric diagram of a aircraft in a hovering state according to an embodiment of the present disclosure; 100231 FIG 3 is a schematic axonometric diagram of a aircraft in a horizontal forward flight state according to an embodiment of the present disclosure; 100241 FIG 4 is a schematic axonometric diagram of a aircraft in a transition state according to an embodiment of the present disclosure; 100251 FIG 5 is a schematic three-view diagram of a aircraft in the horizontal forward flight state according to an embodiment of the present disclosure, 100261 FIG. 6 is a schematic three-view diagram of a aircraft in a horizontal hovering state according to an embodiment of the present disclosure; 100271 FIG. 7 is a schematic diagram of rotational directions of rotors connected to a wing on one side of the fuselage according to an embodiment of the present disclosure, 100281 FIG 8 is a schematic diagram of tilting directions of rotors connected to a single under-mounted beam according to an embodiment of the present disclosure; 100291 FIG 9 is a schematic diagram of a differential aerodynamic moment principle of a rotor connected to a single under-mounted beam according to an embodiment of the present disclosure; 100301 FIG 10 is an enlarged front view of an airfoil profile of a rotor connected to a single under-mounted beam according to an embodiment of the present disclosure; 100311 FIG 11 is a schematic diagram of a principle of an inflatable wing (blade) according to the present disclosure; 100321 FIG. 12 is a schematic sectional cut-away diagram of a fuselage shell manufactured by an integrated manufacturing method of according to an embodiment of the present disclosure; 100331 FIG. 13 is a schematic diagram of laying positions of solar panels according to an embodiment of the present disclosure 100341 List of reference characters: 1 fuselage; 2 inflatable wing; 3 tail fin; 4 under-mounted beam; 5 under-mounted beam connector; 6 tilting mechanism; 7 rotor system; 8 tilting driver; 9 tilting connector; 10 rotor hub; 11 first inflatable blade (first mounting direction); 12 second inflatable blade (second mounting direction); 13 airfoil profile; 14 blade airfoil; 15 outer adhesive layer; 16 brace; 17 envelope; 18 bulkhead; 19 solar panel.

DETAILED DESCRIPTION OF THE EMBODIMENTS

100351 The following further describes the present disclosure with reference to the accompanying drawings.

100361 A new-configuration compound unmanned aircraft includes a fuselage I. The tail part of the fuselage 1 is provided with a V-shaped tail fin 3, the V-shaped tail fin has the functions of both the vertical fin and the horizontal fin. The interference drag force between the tail fins and between the tails and the fuselage can be reduced by arranging less total number of parts. And, the V-shaped tail fin has the advantage of small machining amount. The fuselage is provided with wings at both sides thereof and the wings are inflatable wings 2. Two under-mounted beams 4 are connected to the wing on one side of the fuselage by four under-mounted beam connectors 5. Tilting mechanisms 6 are mounted at both ends of each under-mounted beam, and rotor systems 7 are mounted on the respective tilting mechanisms. The rotor systems are mounted at different positions in manner of different airfoil directions, thus achieving different altitude changes of the fuselage by means of differential aerodynamic moment in conjunction with the tilting mechanisms.

100371 FIG. 1 is a diagram of a aircraft in vertical take-off and landing state according to an embodiment of the present disclosure. In this state, the lift is provided by the rotor systems in a coaxial state, and the fuselage has the minimum projection area and the minimum profile drag in this state.

100381 FIG. 2 is a diagram of the aircraft in a hovering state according to an embodiment of the present disclosure. In this state, the lift is provided by the rotor systems in a tandem state.

100391 FIG. 3 is a diagram of the aircraft in a horizontal forward flight state according to an embodiment of the present disclosure In this state, the rotor systems are in a thrust propeller mode by means of the tilting mechanisms, thus increasing the rotational speed. At the moment, the wings provide the lift in a favorable angle of attack range.

100401 FIG. 4 is a diagram of the aircraft in a transition state according to an embodiment of the present disclosure. In this state, the fuselage is tilted by means of the differential aerodynamic moment of the rotor systems connected to under-mounted beams. At the moment, the rotor system is connected to a corresponding tilting driver 8 by a respective tilting connector 9, so as to be synchronously tilted with another rotor system with the same structure, thereby maintaining the lift generated by the rotors vertical upward.

100411 FIG. 7 is a schematic diagram of rotational directions of rotors connected to a wing on one side of the fuselage. The rotational directions of rotors connected to each under-mounted beam are opposite, and the rotational directions of rotors, which are at the same side, connected to different under-mounted beams also are opposite, thereby eliminating the torque on the under-mounted beams and the wings. Meanwhile, as shown in FIG 1_, in the rotor systems connected to each under-mounted beam in a coaxial dual rotor mode, the torque is eliminated by the rotors rotating in opposite directions, without arranging an anti-torque tail rotor of a conventional aircraft 100421 FIG. 8 is a schematic diagram of tilting directions of rotors connected to each under-mounted beam according to an embodiment of the present disclosure. The tilting driver outputs the torque by a built-in motor, and drives the rotor system to tilt as required by means of the tilting connectors. The tilting angle should be less than or equal to 90 degrees, and the driving directions of the tilting drivers at both ends of the each under-mounted beam should be consistent.

100431 FIG. 9 is a schematic diagram of the differential aerodynamic moment principle of rotors connected to an under-mounted beam according to an embodiment of the present disclosure The front rotor of the wing has high rotational speed and large lift force, while the rear rotor of the wing has low rotational speed and small lift force. The differential aerodynamic moment is generated by inconsistent lift forces. The moment is transferred from the rotor systems to the wing by means of the under-mounted beams and then is transferred from the wing to the fuselage, thereby tilting the fuselage from a horizontal state to a vertical state. If the fuselage needs to be tilted from the vertical state to the horizontal state, the rotational speed of the front rotor of the wing is low, the rotational speed of the rear rotor of the wing is high, a differential moment direction is opposite to that shown in the accompanying drawing, and the transfer rule is consistent with the above.

100441 In order to ensure that the lift force is always vertically upward, the rotors having opposite rotational directions should be provided with blades in different directions As shown in FIG. 10, each rotor system includes a rotor hub 10 and inflatable blades. The rotor rotating in a clockwise direction should be provided with a first inflatable blade 11 (along a first mounting direction), and the rotor rotating in a counterclockwise direction should be provided with a second inflatable blade 12 (along a second mounting direction).

100451 FIG. 11 is a schematic diagram of a principle of the inflatable wing (blade) according to an embodiment of the present disclosure. The flexural rigidity of the inflatable wing is increased as the internal inflation pressure thereof increases. That is, such inflatable wing can have a good flexure rigidity to replace the rigid wing, as long as the internal pressure is enough. The contours of a series of incircles with the center of the circle on a mean camber line of the wing (blade) airfoil approximately meet the airfoil contour. A linear segment of each circle passing through the center of circle in a vertical direction is a brace 16, end points of the adjacent braces are connected by a camber line, and the camber line is tangent to the airfoil contour. The camber line segment is an outer adhesive layer 15. The volume surrounded by the outer adhesive layer is divided into a plurality of separate airbags by the braces to commonly form the inflatable wing (blade), thus the leakage of a single airbag cannot affect the structural strength of other airbags. The brace and the outer adhesive layer are made of a thermoplastic polyurethane (PTU) adhesive material. The inflatable wings (blades) should be considered individually for inflatable density due to different load strengths thereof Assuming the one-dimensional beam, the end deformation per unit length thereof is 0.001 miN at an inflatable air pressure of 33.34 kpa.

100461 FIG. 12 is a sectional cut-away schematic diagram of a fuselage shell manufactured by an integrated manufacturing method according to an embodiment of the present disclosure. The envelope 17 and the middle bulkhead 18 each have a single-layer thickness of 0.002 m. The envelope employs a laminated composite of carbon fiber woven fabric and aluminum alloy, and the bulkhead is of a honeycomb balsa-wood structure.

100471 The integrated manufacturing method of the inflatable wing (blade) and the fuselage shell according to an embodiment of the present disclosure is a weight reduction design under a limited lift force in the near space.

100481 FIG. 13 is a diagram of laying positions of solar panels according to an embodiment of the present disclosure. The laying positions are mainly located on the upper surfaces of the fuselage and the inflatable wings. The selected position is exposed to light for a long time, smooth in transition and easy to be laid. The selected solar panel is made of GaAs-based film materials. The materials are assembled into a stacked stnicture like a filter mesh for sunlight, with each layer haying a specialized material to absorb energy at specific wavelength. Such stacking process employs a so-called transfer printing technology, so that these small devices can be precisely and three-dimensionally assembled together. The effective thickness, which is at the normal surface, of the material per unit volume needs to be only 3,26x106 m, which may not cause excessive additional load for the aircraft.

100491 There are many ways of specific application of the present disclosure, and the above described is only a preferred embodiment of the present disclosure It should be noted that for a person of ordinary skill in the art, numerous improvements can be made without departing from the principles of the present disclosure, and these improvements should also be regarded as the scope of protection of the present disclosure.

Claims

WHAT IS CLAIMED IS: 1. A new-configuration compound unmanned aircraft in near space, comprising a fuselage, a tail part of the fuselage being provided with a tail fin and sides of the fuselage being provided with wings, wherein the wings are inflatable wings, a plurality of under-mounted beams are connected to each of the wings which is on a corresponding one of the sides of the fuselage by respective under-mounted beam connectors, tilting mechanisms are mounted on two ends of each of the under-mounted beams, the tilting mechanisms are mounted with respective rotor systems, and the rotor systems are mounted at different positions in manner of different airfoil directions, so as to achieve different attitude changes of the fuselage by a differential aerodynamic moment in conjunction with the tilting mechanisms.
2. The new-configuration compound unmanned aircraft in the near space according to claim 1, wherein rotational directions of two of the rotor systems on each of the under-mounted beams are opposite.
3. The new-configuration compound unmanned aircraft in the near space according to claim 1, wherein rotational directions of ones of the rotor systems, which are at a same side, of adjacent two of the under-mounted beams are opposite
4. The new-configuration compound unmanned aircraft in the near space according to claim 1, wherein rotational directions of two of the tilting mechanisms connected to each of the under-mounted beams are opposite, and the two tilting mechanisms have a rotation range of 90 degrees
5. The new-configuration compound unmanned aircraft in the near space according to claim 1, wherein the fuselage is of an integrated structure of carbon fiber woven fabric, a balsa wood bulkhead and aluminum alloy envelope.
6. The new-configuration compound unmanned aircraft in the near space according to claim 1, wherein upper surfaces of the fuselage and the wings are covered with high-conversion GaAs-based solar panels, the solar panels are made of a flexible film material.
7. The new-configuration compound unmanned aircraft in the near space according to claim 1, wherein the tail fin is of a V-shaped structure
8. A flight control method for a new-configuration compound unmanned aircraft in near space, comprising: tilting a fuselage by generating a first differential moment via a front rotor and a rear rotor connected to each of under-mounted beams due to a first rotational speed of the front rotor and a first rotational speed of the rear rotor being different, when the aircraft takes-off and lands vertically; enabling the first rotational speed of the front rotor to be higher than the first rotational speed of the rear rotor, while the aircraft in a vertical state; and tilting the front rotor and the rear rotor connected to the under-mounted beam synchronously by 90 degrees, so as to switch the front rotor and the rear rotor to be a coaxial dual-rotor state, tilting the fuselage by generating a second differential moment via the front rotor and the rear rotor connected to each of the under-mounted beams due to a second rotational speed of the front rotor and a second rotational speed of the rear rotor being different, when the aircraft rises to a predetermined altitude; enabling the second rotational speed of the rear rotor to be higher than the second rotational speed of the front rotor, while the aircraft in a horizontal hovering state; and tilting the front rotor and the rear rotor connected to the under-mounted beam synchronously by 90 degrees, so as to switch the front rotor and the second rotor to be a tandem dual-rotor state; and when the aircraft flies forward horizontally, changing a lifting surface from a rotor disk to wings, and tilting the front rotor and the rear rotor by 90 degrees, so as to switch the front rotor and the rear rotor to be a thrusting propeller state, such that a forward flight speed is increased.
9. The flight control method of the new-configuration compound unmanned aircraft in the near space according to claim 8, further comprising, enabling a lift direction to be vertically upward via a tilting speed of the rotor disk in tilting of the fuselage, enabling the differential aerodynamic moment conform to a tilting direction requirement, and when the aircraft flies forward horizontally, enabling the fuselage to keep an angle of attack corresponding to a maximum lift-to-drag ratio of an airfoil of the wings, so as to ensure flight performance.The flight control method of the new-configuration compound unmanned aircraft in the near space according to claim 8, wherein step of when the aircraft flies forward horizontally, changing a lifting surface from a rotor disk to wings, and tilting the front rotor and the rear rotor by 90 degrees comprises: enabling the front rotor and the rear rotor to be in the lifting surface state or the thrusting propeller state