Forward-swept tri-copter aircraft and control method

Abstract

The application discloses a forward-swept tri-rotor aircraft and a control method, relates to the technical field of aerial vehicles, and comprises a fuselage and two forward-swept wings, and the rear end of the fuselage is provided with a vertical tail; the wing tips of the two forward-swept wings and the wing tips of the vertical tail are each provided with a folding rotor, and the folding rotors are folded towards the tail of the fuselage when being folded. In the application, the forward-swept wings are matched with three folding rotors, so that the problem of insufficient control stability of single-rotor and double-rotor aircrafts is effectively solved, and the problem of increased flight resistance caused by redundant control stability and the problem of reduced force efficiency caused by using more rotors are avoided.

Description

Technical Field

[0001] This invention relates to the field of aircraft technology, and more specifically, to a forward-swept trirotor aircraft and its control method. Background Technology

[0002] Aircraft using rotor vertical takeoff and landing and fixed-wing forward flight do not require runways, have high flight speeds, and are poised to replace rotorcraft helicopters. Among the currently available fixed-wing plus rotor aerodynamic layouts, the simplest and most efficient is the two-tilt-rotor aircraft represented by the American Osprey (V-22), while other tiltrotor aircraft and compound wing aircraft generally have four or more rotors.

[0003] Existing two-tilt rotorcraft are prone to pitch instability; for example, the Osprey has crashed multiple times during mode transitions between vertical and forward flight. Four or more (tilt) rotors ensure pitch and roll stability. However, while increasing the number of rotors improves control and stability, space constraints can lead to insufficient rotor shaft spacing. Small rotor shaft spacing limits the rotor diameter, resulting in a smaller rotor disk area. Insufficient disk area necessitates increasing disk load to maintain thrust. Since rotor efficiency is inversely proportional to disk load, multi-rotor aircraft generally suffer from low power efficiency.

[0004] Chinese patent application CN106428548A discloses a vertical takeoff and landing (VTOL) unmanned aerial vehicle (UAV), comprising a fuselage, wings, an engine, an engine propeller, ailerons, a horizontal stabilizer, a vertical stabilizer, four takeoff and landing supports connected to the vertical stabilizer (or wing or horizontal stabilizer), multiple connecting arms connected to the fuselage (or wing or horizontal stabilizer or vertical stabilizer), multiple motors connected to the connecting arms, and multiple rotors connected to the multiple motors. The wing in this patent is a swept wing, with four rotors vertically mounted on the mid-section of the swept wing's leading edge via support arms. The rotor thrust surfaces are perpendicular to the wing lift surfaces, forming a wing-to-wing orthogonal combination. However, the diameter of the multiple rotors is difficult to increase, making it difficult to improve the aircraft's payload capacity.

[0005] Chinese patent application CN106828915A discloses a high-speed aircraft with tilt propellers capable of vertical takeoff and landing, and its flight control method. The aircraft includes a fuselage, wings, and a vertical tail. An engine and transmission system are installed within the fuselage. A canard is mounted on the nose of the fuselage, featuring a low-wing configuration with a leading-edge sweep angle. A high-wing configuration with a forward-sweeping leading-edge is mounted on the foreground of the tail. The vertical tail is mounted above the tail of the fuselage and also features a leading-edge sweep angle. The high-speed aircraft also includes two tilt arms, two tilt propellers, and a tail rotor. The tilt arms serve as support mechanisms for the tilt propellers, with the propellers mounted on their outer ends. In this invention patent, the wings are forward-sweeping, and the two tilt propellers are fixedly mounted on both sides of the fuselage. The distance between the first two tilt propellers is only one fuselage width, and they are separately mounted from the forward-sweeping wings, limiting the propeller disk area.

[0006] Chinese patent application CN110217391A discloses a hybrid electric vertical takeoff and landing (VTOL) forward-swept fixed-wing unmanned aerial vehicle (UAV), comprising a fuselage assembly, two wing assemblies, a tail assembly, and two vertical lift assembly assemblies. The fuselage assembly includes a nose section, a forward fuselage, and a rear fuselage connected sequentially from front to rear. The nose section houses at least one electric ducted fan engine, which provides pitch control torque for longitudinal control during VTOL and hovering flight. The rear fuselage houses an energy unit and a payload bay, and a propeller assembly is located at the tail of the rear fuselage. The propeller assembly provides forward thrust to overcome aerodynamic drag during flight. The wing assemblies are mounted on both sides of the rear fuselage. The tail assembly is mounted at the tail section of the rear fuselage. The two vertical lift assembly assemblies are electric fan type, symmetrically mounted on the left and right sides of the middle section of the rear fuselage. The vertical lift assembly provides the main aerodynamic lift required for VTOL and hovering flight. The invention patent uses forward-swept wings, and the left and right ducted fans are installed on both sides of the fuselage, forming a side-intersection combination with the fuselage. However, the distance between the left and right ducted fans in this invention patent is small, and the size of the left and right ducted fans is limited, which restricts the load capacity of the aircraft.

[0007] Therefore, a forward-swept trirotor aircraft with a large rotor disk area, high power efficiency, large load factor, and good flight stability control becomes the best solution. Summary of the Invention

[0008] The purpose of this invention is to provide a forward-swept trirotor aircraft and its control method, which has a small number of rotors and a large rotor shaft spacing, and can effectively balance stability, efficiency and payload.

[0009] To achieve the objective of this invention, the technical solution adopted is as follows: a forward-swept tri-rotor aircraft, comprising a fuselage and two forward-swept wings at fixed angles, the forward-swept wings being located in the middle of the fuselage, and a vertical tail being located at the rear end of the fuselage; a folding rotor is installed at the wingtip of each of the two forward-swept wings and the wingtip of the vertical tail, and the folding rotor folds towards the rear of the fuselage when folded.

[0010] Furthermore, the rotor disk surface of the folding rotor is parallel and fixed to the lifting surface of the forward-swept wing.

[0011] Furthermore, the forward-swept angle of the forward-swept wing is selected as a fixed angle between 20° and 30°.

[0012] Furthermore, the forward-swept wing is a one-piece wing, and the forward-swept wing has deflectable ailerons.

[0013] Furthermore, propellers can be installed at both the front and rear ends of the fuselage, and the rotation plane of the propellers is perpendicular to the horizontal plane.

[0014] A control method for a forward-swept trirotor aircraft as described above, characterized in that:

[0015] Vertical Ascent: The three folding rotors unfold and rotate. When the thrust generated by the rotation of the three rotors exceeds the aircraft's weight, the aircraft lifts off the ground. Continuing to increase the rotational speed of the three rotors, the aircraft ascends vertically. During ascent, the aerodynamic forces generated by the rotor slipstream and control surfaces control the aircraft's three-axis stability.

[0016] Vertical flight transitions to forward flight: After the aircraft ascends to a safe altitude, the propellers rotate, the aircraft accelerates horizontally, and the lift of the forward-swept wings increases. During the lift increase process of the forward-swept wings, the rotational speed of the three rotors is gradually reduced until they stop; after stopping, the rotor blades automatically fold backward under the action of wind resistance, and the aircraft flies horizontally forward under the drive of the propellers.

[0017] Forward flight and landing: The propeller speed gradually decreases, and the aircraft descends; when it reaches a fixed distance and altitude from the landing point, the three folding rotors are activated. The rotors begin to rotate, and the folding blades automatically unfold under the action of centrifugal force. After the thrust generated by the rotation of the three rotors reaches a fixed value, the propeller idles; as the aircraft approaches the landing point, the propeller stops rotating, and the aircraft descends vertically using the rotors.

[0018] The beneficial effects of this invention are:

[0019] 1. In this invention, by installing three folding rotors at the wingtips of the forward-swept wing and the wingtips of the vertical tail, the interaxial distance between two adjacent rotors is made large enough. Under the premise of maintaining a sufficiently large rotor tip distance, large-diameter rotors can be used, so that the rotor disk load is close to the range of single or dual rotor helicopters, resulting in high efficiency and low noise.

[0020] 2. In this invention, a folding rotor is mounted on the wingtip of a forward-swept wing, and the rotor disk surface is made parallel to the lifting surface of the forward-swept wing. This allows the slipstream generated by the rotor rotation to flow over the deflectable control surfaces of the forward-swept wing, thereby establishing a variable coupling force and achieving stable control of the aircraft's pitch and roll. Compared to variable rotor speed control methods, this invention is simpler and faster to operate, with smoother attitude changes, reducing the control response time from the second level to the millisecond level.

[0021] 3. In this invention, by installing the folding rotor at the wingtip of the forward-swept wing, since the wing vortex of the forward-swept wing is dragged out from the wing root, the disturbance of the wingtip vortex on the folding rotor blade is avoided. Compared with installing the rotor at the wingtip of the swept wing, the folding rotor blade is subjected to less forced vibration and has a longer structural life.

[0022] 4. By employing forward-swept wings, the aircraft can achieve a higher flight speed when flying forward compared to that of a straight wing, thereby enhancing the aircraft's maneuverability. Attached Figure Description

[0023] The accompanying drawings illustrate exemplary embodiments of the invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification.

[0024] Figure 1 This is a schematic diagram of the folded rotor in the deployed state of the forward-swept trirotor aircraft provided by the present invention.

[0025] Figure 2 This is a schematic diagram of the folded rotor in the forward-swept trirotor aircraft provided by the present invention in the folded state.

[0026] Figure 3 This is a schematic diagram of the deflection of the aileron on a forward-swept wing;

[0027] Figure 4 This is a schematic diagram of the folding rotor in its deployed state;

[0028] Figure 5 This is a schematic diagram of a folding rotor in its folded state;

[0029] Figure 6 This is a schematic diagram of the coupling mechanism between a forward-swept wing and a folding rotor;

[0030] Figure 7 This is a schematic diagram illustrating the influence of forward-swept wing vortices and backward-swept wing leading-edge vortices on folding rotor blades.

[0031] The attached diagram shows the markings and corresponding component names:

[0032] 1. Fuselage; 2. Forward-swept wings; 3. Vertical tail; 4. Folding rotor; 5. Propeller.

[0033] 41. Rotating disk; 42. Fixed shaft; 43. Rotating shaft; 44. Blade. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] like Figure 1 , Figure 2 , Figure 3 As shown, the present invention provides a forward-swept trirotor aircraft, comprising a fuselage 1 and two forward-swept wings 2. The forward-swept wings 2 are single-section wings, and the two forward-swept wings 2 are symmetrically arranged on the fuselage 1, with the wing roots of both forward-swept wings located in the middle of the fuselage 1. Each forward-swept wing 2 has a deflectable aileron 21. Simultaneously, the rear end of the fuselage 1 has a vertical tail 3, which is perpendicular to the top surface of the fuselage 1 and located on the central axis of the fuselage 1. Folding rotors 4 are mounted on the wingtips of both forward-swept wings 2 and the wingtips of the vertical tail 3. The rotation plane of the folding rotors 4 is parallel to the horizontal plane. In this invention, the folding rotors 4 fold towards the rear of the fuselage 1 without rotating, and after folding, the axial direction of the blades 44 on the folding rotors 4 is consistent with the axial direction of the fuselage 1. When rotating, the folding rotors 4 directly unfold and rotate using centrifugal force.

[0037] In this invention, the rotor disk surface of the folding rotor 4 is parallel to the lifting surface of the forward-swept wing 2, forming a wing-to-wing parallel combination. In this combination, the high-speed spiral slipstream trailed by the folding rotor 4, together with the deflected control surfaces on the ailerons 21 of the forward-swept wing 2, generates lift, descent, and lateral forces. This allows the aircraft to perform first-level control for three-axis stability during direct vertical takeoff and landing without forward flight. Second-level control is only implemented when the aircraft experiences a large tilt angle due to strong winds, by changing the rotational speed of the folding rotor 4. Since the control response (millisecond level) of the aileron 21 deflection control surface on the forward-swept wing 2 is an order of magnitude faster than the rotational speed control response (second level), this invention significantly improves stability and flight quality.

[0038] In this invention, such as Figure 4 , Figure 5 As shown, the folding rotor 4 includes a rotating disk 41, on which two rotatable rotating shafts 43 are mounted. The two rotating shafts 43 are arranged symmetrically about the center of the rotating disk 41, and blades 44 are mounted on both rotating shafts. At the same time, four positioning pins 42 are also mounted on the rotating disk 41. The four positioning pins 42 are arranged in a rectangular array about the center of the rotating disk 41, and the four positioning pins 42 are divided into two groups. The two positioning pins 42 in each group correspond to one rotating shaft 43. The two positioning pins 42 in the same group are located on both sides of the rotating shaft 43, so that when the rotating shaft 43 drives the blades 44 to rotate, the two positioning pins 42 in the same group restrict the two sides of the blades 44, so that the rotation angle of the blades 44 driven by the rotating shaft 43 is within 180°.

[0039] In this invention, to avoid drag caused by the blades 44 during flight when the folding rotor 4 is not rotating, the folding rotor 4 is arranged with the central axis of the fuselage 1 as the reference direction, and the two rotating shafts 43 are respectively arranged on the left and right sides of the rotating disk 41. When the two blades 44 rotate simultaneously and extend to the left and right sides of the rotating disk 41 and keep them on the same straight line, the folding rotor 4 is in the unfolded state. When the two blades 44 rotate forward 90° simultaneously or rotate backward 90° simultaneously and keep the two blades 44 parallel, the folding rotor 4 is in the folded state.

[0040] In this invention, the unfolding and folding of the folding rotor 4 does not require additional power. Specifically, when the rotating disk 41 rotates under power, the blades 44 rotate together with the rotating disk 41 under the action of centrifugal force and the constraint of the rotating shafts 43 on both sides. At this time, the folding rotor 4 automatically unfolds. When the rotating disk 41 stops rotating, the blades 44 automatically rotate backward around the rotating shaft 43 under the action of the wind resistance of the incoming flow. By restricting the blades 44 with the positioning pins 42, the two blades 44 on the folding rotor 4 automatically rotate backward, so that the folding rotor 4 can automatically fold.

[0041] Of course, in this invention, the simultaneous folding and unfolding of the two blades 44 in the folding rotor 4 can also be achieved by other mechanical drive structures, which will not be elaborated here.

[0042] In this invention, a propeller 5 is installed at the front end and / or rear end of the fuselage 1. The number of blades on the propeller 5 can be selected as two, three, four, five, or six blades as required. The aircraft can achieve forward flight by rotating the propeller 5. At the same time, after the propeller 5 is installed, the rotation plane of the propeller 5 is perpendicular to the horizontal reference plane, that is, the rotation plane of the propeller 5 is perpendicular to the rotation plane of the three folding rotors 4.

[0043] In this invention, the forward sweep angle of the forward-swept wing is between 20° and 30°, and the specific forward sweep angle is determined when designing a specific model; at the same time, landing gear is also provided on the lower part of the fuselage 1 and the lower part of the forward-swept wing 2, and the landing gear can be a tricycle type, bicycle type, tailwheel type or skid type.

[0044] The specific operating mode of this invention is as follows:

[0045] Vertical Ascent: The three folding rotors 4 unfold and rotate. As the rotational speed of the three folding rotors 4 increases, the thrust exceeds the aircraft's weight, and the aircraft lifts off the ground. Continuing to increase the rotational speed of the three folding rotors 4, the aircraft ascends vertically. At this point, the aircraft is balanced on all three axes, controlled by the slipstream generated by the propeller 5 and the aerodynamic forces generated by the control surfaces of the ailerons 21 on the forward-swept wing 2. If strong winds cause the aircraft to tilt at a large angle, the rotational speed of the three folding rotors 4 is increased to balance the aircraft.

[0046] Vertical flight transition to forward flight: As the aircraft ascends to a safe altitude (above 50 meters from the ground), propeller 5 rotates. As the forward flight speed increases, the lift of the forward-swept wing 2 increases, reducing the rotation speed of the three folding rotors 4 until they stop. The transition time from vertical takeoff to forward flight is related to the thrust of propeller 5 and is generally less than 20 seconds. During forward flight, the aircraft provided by this invention is controlled by the ailerons on the forward-swept wing, the elevator on the horizontal stabilizer, the rudder on the vertical stabilizer, and the propeller engine throttle (or motor speed).

[0047] Forward Flight and Landing: The rotation speed of the two propellers 5 gradually decreases, and the aircraft descends. When the aircraft descends to a certain distance and altitude from the landing point, the three folding rotors 4 are activated. When the thrust of the three folding rotors 4 reaches a certain value (less than gravity), the propellers 5 return to idle speed, and the aircraft maintains a low (horizontal and vertical) descent speed. When the aircraft approaches the landing point, the propellers 5 stop rotating. The aircraft then uses the three folding rotors 4 to land vertically. After the aircraft touches down and comes to a complete stop, the three folding rotors 4 stop rotating.

[0048] At the same time, such as Figure 3 , Figure 6As shown, when pitch control is required, the ailerons 21 on the two forward-swept wings 2 deflect symmetrically. Under the downwash effect generated by the rotation of the folding rotor 4, the aerodynamic force of the aircraft increases, thus forming a pitching or nose-down moment. When the aircraft is in roll control, the ailerons 21 on the two forward-swept wings 2 deflect asymmetrically, causing the aircraft to generate aerodynamic forces that move up and down, thus forming a left or right roll moment. When the aircraft is in yaw (directional control), the aileron 21 on the right side of the fuselage 1 deflects upward by about 90°. Under the sidewash effect generated by the rotation of the folding rotor 4, a lateral force is generated on the control surface of the aileron 21 on the right side of the fuselage 1, forming a right yaw moment. Similarly, the aileron 21 on the left side of the fuselage 1 can also deflect upward by about 90°. Under the sidewash effect generated by the rotation of the folding rotor 4, a lateral force is generated on the control surface of the aileron 21 on the left side of the fuselage 1, forming a left yaw moment.

[0049] like Figure 7 As shown, this invention employs a combination of forward-swept wings and folding rotors 4. Compared to the same backward-swept wing and rotor combination, the distance between the folding rotors 4 on the two forward-swept wings 2 and the folding rotor 4 on the vertical tail 3 is increased, thus increasing the lever arm length for the pitch control torque generated by the folding rotors 4. Furthermore, as... Figure 6 As shown, the wing vortex of the forward-swept wing 2 is dragged out from the wing root, and the blades of the folding rotor 4 will not be disturbed by the wing vortex and vibrate violently; while the wing vortex of the swept wing is dragged out from the wingtip, and if the rotor blades behind the wingtip are subjected to strong disturbances for a long time, the risk of fatigue damage may increase.

[0050] The aircraft provided by this invention can effectively resist attitude tilting caused by external interference and prevent loss of control and crash; at the same time, the forward-swept wing 2 in this invention adopts a one-piece wing, which has a continuous structure and better strength and rigidity.

[0051] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A forward-swept trirotor aircraft, characterized in that, It includes a fuselage (1) and two forward-swept wings (2), the forward-swept wings (2) are located in the middle of the fuselage (1), and the rear end of the fuselage (1) has a vertical tail (3); the wingtips of the two forward-swept wings (2) and the wingtips of the vertical tail (3) are each equipped with a folding rotor (4), and the three folding rotors (4) fold towards the rear of the fuselage (1) when folded.

2. The forward-swept trirotor aircraft according to claim 1, characterized in that, The tension surface of the folding rotor (4) is parallel to the lifting surface of the forward-swept wing (2).

3. The forward-swept trirotor aircraft according to claim 2, characterized in that, The forward sweep angle of the forward-swept wing (2) is fixed at a certain angle between 20° and 30°.

4. The forward-swept trirotor aircraft according to claim 2, characterized in that, The forward-swept wing (2) is a single-section wing, and the forward-swept wing (2) has deflectable ailerons (21).

5. The forward-swept trirotor aircraft according to any one of claims 1 to 4, characterized in that, Propellers (5) can be installed at both the front and rear ends of the fuselage (1), and the rotation surface of the propeller (5) is perpendicular to the horizontal plane.

6. A control method for a forward-swept trirotor aircraft as described in claim 5, characterized in that: Vertical Ascent: The three folding rotors unfold and rotate. When the thrust generated by the rotation of the three rotors exceeds the aircraft's weight, the aircraft lifts off the ground. Continuing to increase the rotational speed of the three rotors, the aircraft ascends vertically. During ascent, the aerodynamic forces generated by the rotor slipstream and control surfaces control the aircraft's three-axis stability. Vertical flight transitioning to forward flight: After the aircraft ascends to a safe altitude, the propellers rotate, the aircraft accelerates horizontally, and the lift of the forward-swept wings increases. During the lift increase process of the forward-swept wings, the rotational speed of the three rotors is gradually reduced until they stop, and the rotor blades automatically fold backward under the action of wind resistance; The aircraft flew horizontally forward, driven by its propellers. Forward flight and landing: The rotation speed of the two propellers gradually decreases. When the aircraft descends to a fixed distance and altitude from the landing point, the three folding rotors are activated. The rotors begin to rotate, and the folding blades automatically unfold under the action of centrifugal force. After the thrust generated by the rotation of the three rotors reaches a fixed value, the propellers idle. When the aircraft approaches the landing point, the propellers stop rotating, and the aircraft descends vertically using the rotors.

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