Vertical take-off and landing unmanned aerial vehicle having foldable fixed wing and based on twin-ducted fan power system

Abstract

A vertical take-off and landing (VTOL) unmanned aerial vehicle having a foldable fixed wing and a twin-ducted fan power system (7) arranged at a tail portion of a fuselage in a transverse and tail propulsion arrangement provides lift for vertical take-off and landing and propulsion for horizontal flight. By means of deflection of a control servo plane arranged at a duct exit, a vectored thrust is provided to enable a fast attitude change. When the aerial vehicle takes off and lands vertically/flies at a low speed, the wing is folded to reduce the frontal area exposure to crosswind. When the aerial vehicle is flying horizontally, the wing is expanded to obtain larger lift. A Coanda effect is created at a trailing edge of the wing by suction of the duct to improve performance.

Claims

1. A vertical take-off and landing unmanned aerial vehicle, the aerial vehicle comprising a fuselage, a foldable wing, two ducts and a retractable landing gear, the fuselage being divided into a nose, a front fuselage, a middle fuselage and a rear fuselage along a longitudinal axis of the fuselage, wherein the two ducts are symmetrically distributed on both sides of the rear fuselage in a transverse and tail propulsion arrangement, each duct comprises a ducted fan, the ducted fan has an axis of rotation being located below a lower surface of the wing, and the axis of rotation of the ducted fan is substantially parallel to the longitudinal axis of the fuselage at all times; the foldable wing is in an upper single-wing arrangement and is fixed to the front of the middle fuselage via a wing folding shaft, the retractable landing gear is arranged at the front of the rear fuselage, the aerial vehicle is in a tailless arrangement, the center of gravity of the aerial vehicle is located at the rear of the front fuselage and before the middle fuselage, and the ducts and the wing are combined in an optimized manner by means of a specific position relationship therebetween.

2. The vertical take-off and landing unmanned aerial vehicle according to claim 1, wherein the nose is an electronic cabin for placement of various sensors and optoelectronic devices therein; the front fuselage is a primary load cabin for carrying a primary energy source and a load; the middle fuselage is a secondary load cabin for carrying an avionics system, a secondary energy source, a driving mechanism for the wing folding shaft, and a driving mechanism for the retractable landing gears; and the middle of the rear fuselage is provided with the ducts symmetrically arranged on both sides, and the rear thereof is a conical fairing body.

3. The vertical take-off and landing unmanned aerial vehicle according to claim 1, wherein a foldable configuration is employed for the foldable wing, in which the wing is a two-section folding wing and can fold by 36° to 180° towards the belly along a longitudinal axis, and an aileron is arranged at a trailing edge of the wing close to a wingtip.

4. The vertical take-off and landing unmanned aerial vehicle according to claim 1, wherein the specific relative position relationship between the ducts and the wing for achieving combined optimization satisfies: the relation between the distance l1 of the trailing edge of the foldable wing from a plane of a duct entrance and a diameter d of the duct entrance is:
0.35d≤/l1≤0.45d; and the relation between the distance l2 of a plane of a chord line of the foldable wing from a central axis of the duct and the diameter d of the duct entrance is:
0.25d≤/l2≤0.4d.

5. The vertical take-off and landing unmanned aerial vehicle according to claim 1, wherein the aerial vehicle is in the tailless arrangement in which the whole aerial vehicle has no conventional horizontal tail, vertical tail, elevator or rudder.

6. The vertical take-off and landing unmanned aerial vehicle according to claim 1, wherein the aerial vehicle comprises four retractable landing gears, and each landing gear is adjustable in real time in length.

7. The vertical take-off and landing unmanned aerial vehicle according to claim 1, wherein the duct further comprises: a duct body, a fan driving mechanism, a control servo plane, and a control servo plane driving mechanism, wherein the ducted fan is located in the duct body, and is connected to the duct body via the fan driving mechanism; the control servo planes are located at a duct exit, are four in number, and are of a cross shape surrounding the axis of rotation of the ducted fan; and the control servo plane has an axis of rotation perpendicular to the axis of rotation of the ducted fan, and is connected to the duct body at one end and to the control servo plane driving mechanism arranged in the duct body at the other end.

8. The vertical take-off and landing unmanned aerial vehicle according to claim 7, wherein the control servo plane is movable, and by means of deflection of the control servo plane, an attitude control moment is provided to enable the stabilization and control of the flight attitude.

9. A vertical take-off and landing unmanned aerial vehicle, the aerial vehicle comprising a fuselage, a foldable wing, two ducts and a retractable landing gear, the fuselage being divided into a nose, a front fuselage, a middle fuselage and a rear fuselage along a longitudinal axis of the fuselage, wherein the two ducts are symmetrically distributed on both sides of the rear fuselage in a transverse and tail propulsion arrangement, each duct comprises a ducted fan, the ducted fan has an axis of rotation being located below a lower surface of the wing, and the axis of rotation of the ducted fan is substantially parallel to the longitudinal axis of the fuselage at all times; the foldable wing is in an upper single-wing arrangement and is fixed to the front of the middle fuselage via a wing folding shaft, the retractable landing gear is arranged at the front of the rear fuselage, the aerial vehicle is in a tailless arrangement, the center of gravity of the aerial vehicle is positioned in a region between the front fuselage and a leading edge of the wing; and the ducts and the wing are combined in an optimized manner by means of a specific position relationship therebetween.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The drawings are used to provide a further understanding of the present invention and constitute a part of the description. Together with the embodiments of the present invention, the drawings are used to explain the present invention and do not constitute a limitation on the present invention. In the drawings:

(2) FIG. 1 is a three-dimensional schematic view of an aerial vehicle of the present invention;

(3) FIG. 2(a) is a front view of the aerial vehicle of the present invention (with a landing gear stowed);

(4) FIG. 2(b) is a left view of the aerial vehicle of the present invention (with the landing gear stowed);

(5) FIG. 2(c) is a side view of the aerial vehicle of the present invention (with the landing gear stowed);

(6) FIG. 3 is a structural schematic view of a ducted fan power system of the aerial vehicle of the present invention;

(7) FIG. 4(a) is a three-dimensional schematic view of the aerial vehicle of the present invention, with a wing expanded during a horizontal flight;

(8) FIG. 4(b) is a three-dimensional schematic view of the aerial vehicle of the present invention, with a wing folded during vertical take-off and landing;

(9) FIG. 5 is a schematic view of a multi-mode flight (the vertical take-off and landing and the horizontal flight) and its transition switch processes of an aerial vehicle of the present invention;

(10) FIG. 6(a) is a schematic view 1 of a duct-wing combined optimization feature dimension of the present invention;

(11) FIG. 6(b) is a schematic view 2 of a duct-wing combined optimization feature dimension of the present invention;

(12) FIG. 7 is a schematic view of a system of an embodiment of the present invention;

(13) FIGS. 8(a) and 8(b) are comparison views of the CFD simulation of flow field of the duct-wing combined optimization of the present invention and a traditional fixed wing during the flight at an angle of attack of 40°, in which

(14) FIG. 8(a) is a view of CFD simulation of flow field for the traditional individual wing with stall;

(15) FIG. 8(b) is a view of CFD simulation of flow field under the stall-free duct-wing combined optimization; and

(16) FIG. 9 is a schematic view of the anti-crosswind principle of the aerial vehicle of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(17) In order to make the objectives, technical solutions and advantages of embodiments of the present invention clearer, the technical solutions in embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are a part, but not all of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without involving any inventive effort fall within the scope of protection of the present invention.

EMBODIMENTS

(18) A three-dimensional schematic view of various main components of an aerial vehicle of this embodiment is as shown in FIG. 1, the aerial vehicle comprising: a fuselage, a foldable wing 3, ducted fan power systems 7 and a retractable landing gear 9, the fuselage being divided into a nose 1, a front fuselage 2, a middle fuselage 5 and a rear fuselage 6, wherein the ducted fan power systems 7 are symmetrically distributed on both sides of the rear fuselage 6 in a transverse arrangement, the foldable wing 3 is arranged at the front of the middle fuselage 5 in an upper single-wing arrangement, the retractable landing gear 9 is arranged at the front of the rear fuselage 6, the aerial vehicle is in a tailless arrangement, the center of gravity of the aerial vehicle is located at the rear of the front fuselage 2, and ducts and the wing are combined in an optimized manner by means of a specific position relationship therebetween.

(19) In this embodiment, an aerodynamic arrangement employed by the aerial vehicle comprises: a foldable rectangular upper singe wing, a twin-tail propulsion ducted-fan power system, and a retractable landing gear arrangement, as shown in FIGS. 2(a), 2(b) and 2(c). The main overall dimensions include:

(20) the length of wingspan: 1.5 m

(21) the aspect ratio: 7.5

(22) the dimension of fuselage: 0.16 m×0.16 m×1.2 m

(23) the outer diameter of duct: 0.33 m

(24) the radius of fan: 0.116 m, employing a variable-pitch four-blade fan

(25) the overall weight: 20 kg (containing an effective load of 5 Kg)

(26) the flight time: 1 h

(27) The main overall dimensions and the system distribution are as shown in FIG. 7.

(28) In this embodiment, the aerial vehicle employs electric power, and uses an electric motor as a power source and a lithium battery as an energy source.

(29) In this embodiment, the nose 1 is partially carried with an electronic cabin and a load cabin 1, and installed with various sensors, including an airspeed tube, a radar, a visible light/infrared camera and an electronic compass.

(30) In this embodiment, the front fuselage 2 has a load cabin 2, a primary power battery, and an airborne avionics system (comprising a sensor, a main control computer, a navigation flight control module, a communication module and an energy management module) placed therein, the belly carries the primary mission load, and this part is also the position where the weight of the whole aerial vehicle is concentrated.

(31) In this embodiment, the middle fuselage 5 has a secondary power battery, a folding mechanism, an actuating mechanism of the landing gear, and a driving motor placed therein, the belly carries the secondary load, and this part is the position where the secondary weight of the whole aerial vehicle is concentrated.

(32) In this embodiment, the foldable wing 3 is in an upper single-wing arrangement, a rectangular straight-wing arrangement and a Clark-Y wing profile arrangement to improve the medium-speed performance thereof (the low-speed performance is guaranteed by using a wing/duct combined system design), and the foldable wing 3 is arranged at the front of the middle fuselage 5 in an upper singe-wing arrangement, and is of a foldable configuration. The foldable wing 3 is a two-section folding wing, and is foldable by 36° to 180° towards the belly along a longitudinal axis. An aileron 8 is arranged at a trailing edge of the wing close to a wingtip.

(33) In this embodiment, the twin-ducted fan power systems 7 are symmetrically distributed on both sides of the rear fuselage 6 in a transverse and tail propulsion arrangement, are two in number, and have an axis of rotation thereof being located below a lower surface of the wing. The twin-ducted fan power system 7 comprises: a duct body 10, a power fan 11, a fan driving mechanism 12 (an electric motor in this embodiment), a control servo plane 13, and a control servo plane driving mechanism 14 (an electric servo engine), as shown in FIG. 3.

(34) The twin-ducted fan power system 7 has the power fan 11 located in the duct, employs a variable-pitch four-blade fan, and is connected to the duct body 10 via the fan driving mechanism 12; and the control servo planes 13 are located at a duct exit, are four in number, and are of a cross shape surrounding an axis of rotation of the duct. The control servo plane 13 has an axis of rotation perpendicular to the axis of rotation of the duct, and is connected to the duct body at one end and to the control servo plane driving mechanism 14 arranged in the duct body at the other end.

(35) The duct body 10 employs a specific streamlined design in cross section, and with this structural arrangement, the performance of vertical take-off and landing can be improved, the hovering efficiency and anti-disturbance capability are improved, and at the same time, the duct can also generate part of the lift during the horizontal flight; and due to the structure of the upper single wing, under the affection by the trapped vortex at the trailing edge of the wing and the position of the wing, the duct can generate part of the lift (about 10% of wing lift) even at an angle of attack of 0°, improving the overall efficiency. The movable control servo plane 13 is arranged at the duct exit, and the attitude control of the aerial vehicle is implemented by tilting the servo plane. The center of gravity is positioned in a region between the front fuselage and a leading edge of the wing according to a conventional fixed-wing arrangement, the control servo plane 13 can generate a large control moment on the center of gravity, enabling the aerial vehicle to obtain the excellent control performance.

(36) In this embodiment, the specific duct-wing relative position is employed to enable the combined optimization. As shown in FIGS. 6(a) and 6(b), in this embodiment, the relative position of the wing and the duct employs l1=0.4d, l2=0.35d. The Coanda effect is created at the trailing edge of the wing by suction of the duct, slowing down the separation of airflow at a boundary layer, increasing the airfoil stalling angle of attack, and at the same time generating a low-pressure area at an upper portion of the wing to increase the lift coefficient of the wing. The CFD simulation of flow field for the aerial vehicle of this embodiment and the traditional fixed-wing aerial vehicle during the flight at 30 m/s at an angle of attack of 40° is as shown in FIG. 8. The simulation result shows that this configuration, compared with the traditional fixed-wing structure, has the lift coefficient of the wing increased by 25%, the stalling angle of attack increased to 40°, and the overall lift-to-drag ratio increased by 15%.

(37) In this embodiment, the aerial vehicle is in a tailless arrangement. The whole aerial vehicle has no conventional horizontal tail, vertical tail, elevator or rudder. By means of deflection of the control servo plane 13, an attitude control moment is provided to enable the stabilization and control of the flight attitude.

(38) The retractable landing gears 9 are arranged at the front of the rear fuselage 6 and are four in number, and each landing gear is adjustable in real time in length.

(39) The working principle and process of the present invention:

(40) as shown in FIG. 4(b), the foldable wing 3 is stowed during the vertical take-off and landing, which can decrease the frontal area of the wing exposure to crosswind and enhance the anti-wind capability of the aerial vehicle; and as shown in FIG. 4(a), the wing is expanded during the horizontal flight, which can obtain larger lift.

(41) As shown in FIG. 5, the aerial vehicle of the present invention is at a vertical attitude during docking at the ground with the landing gear down. When the fan in the duct operates, a vertically upward lift is generated, enabling the vertical take-off and landing of the aerial vehicle. At the same time, the foldable wing 3 is stowed to decrease the frontal area of the aerial vehicle exposure to crosswind and to improve the anti-disturbance capability. By means of deflection of the control servo plane 13, a control moment is generated to control the attitude of the aerial vehicle. When the aerial vehicle is out of the vertical attitude, the lift generated by the ducted fan power system 7 will generate a component in a horizontal direction, enabling the horizontal flight of the aerial vehicle. When the flight attitude and speed reach a certain range, the foldable wing 3 is expanded, the fuselage enters a horizontal flight state, and under this state, the aerial vehicle has various characteristics similar to those of the conventional fixed-wing aircraft and can perform cruising flight at a higher speed and with a lower energy consumption.

(42) As shown in FIG. 9, in the figure, G is gravity, T is duct lift, Fd is momentum resistance, F is servo plane control force, α is an anti-wind balance inclination, and an anti-disturbance mechanism of the aerial vehicle of the present invention at a crosswind environment is as follows.

(43) a. A stabilizing effect of the fan of the duct on crosswind is provided. The power fan 11 of the duct can generate a momentum resistance Fd above the position near an entrance of the duct body 10 in crosswind, the resistance is the primary resistance under a take-off and landing condition, and the present invention employs a design of high (front) position of center of gravity, such that the momentum resistance generates a low head moment on the center of gravity, and the duct can automatically tilt by an a angle against the wind to reach a self-stabilizing state.

(44) b. The control servo plane 13 is arranged in a high-speed slip flow in the duct, is less disturbed by flight conditions, and can generate a stable control force F that has a large moment on the center of gravity of the aerial vehicle. By means of the control of the servo plane, the duct can reach a stable state with a small inclination against the wind under crosswind and keep the attitude within a certain range. For crosswind not greater than 16 m/s, the aerial vehicle of the present invention has the maximum balance angle of 14.8°.

(45) c. The landing gear cooperates with the tilt angle of the aerial vehicle for expansion and retraction, such that the landing plane of the landing gear always keep parallel to a take-off and landing platform, and in this embodiment, the adjustable maximum angle of the landing gear plane is 25°, the maximum anti-wind angle required by the aerial vehicle is 15°, and therefore the aerial vehicle can implement tilted landing.

(46) The above-described embodiments are preferred embodiments of the present invention; however, the embodiments of the present invention are not limited to the above-described embodiments, and any other change, modification, replacement, combination, and simplification made without departing from the spirit, essence, and principle of the present invention should be an equivalent replacement and should be included within the scope of protection of the present invention.