A non-orthogonal tiltrotor aircraft and a method of flight control thereof

Abstract

The application provides a non-orthogonal tilt-rotor aircraft and a flight control method thereof, and a tilt axis of a lower end of a tilt nacelle is arranged obliquely, wherein the tilt axis is parallel to an XZ plane, and forms an angle of 45 degrees with an X axis and a Z axis, and is not orthogonal to an XY plane and a YZ plane of a body coordinate system; a positive direction of the X axis is rearward along a heading, a positive direction of the Y axis is rightward along the heading, and a positive direction of the Z axis is upward along a vertical direction. Through the application, a lateral stability effect can be provided, lateral stability is improved, and a body pitching instability problem caused by tilting of a rotor nacelle can be avoided.

Description

Technical Field

[0001] This invention belongs to the technical field of tiltrotor aircraft, and particularly relates to a non-orthogonal tiltrotor aircraft and its flight control method. Background Technology

[0002] Tiltrotor aircraft are a new type of aircraft that integrates fixed-wing aircraft and helicopters. They have the ability of ordinary helicopters to take off and land vertically and hover in the air, as well as the ability of fixed-wing aircraft to cruise at high speed.

[0003] Currently existing tiltrotor aircraft suffer from poor lateral stability due to complex aerodynamic interference issues, resulting in frequent rollover accidents and a high crash rate. Summary of the Invention

[0004] The technical problem to be solved by this invention is that tiltrotor aircraft suffer from poor lateral stability due to complex aerodynamic interference, resulting in frequent rollover accidents and a high crash rate.

[0005] The technical solution of this invention is to provide a tiltrotor aircraft in which the rotor tilt axis is not orthogonal to the body coordinate plane. Firstly, a non-orthogonal tiltrotor aircraft is provided, wherein the tilt axis 10 at the lower end of the tilt nacelle 4 is tilted, wherein the tilt axis 10 is parallel to the XZ plane, forms a 45° angle with the X and Z axes, and is not orthogonal to the XY and YZ planes of the fuselage coordinate system; the positive X-axis points rearward along the heading, the positive Y-axis points to the right along the heading, and the positive Z-axis points upward vertically. This provides lateral stabilization, improves lateral stability, and avoids the pitch instability problem caused by the tilting of the rotor nacelle.

[0006] The aircraft consists of a fuselage (1), wings (2), a fixed nacelle (3), a tilting nacelle (4), a rotor power control assembly (5), a tail (6), and a ventral fin (7). The fixed nacelle 3 is equipped with a tilting servo 8 and a driven gear 11. The tilting servo 8 is equipped with a driving gear 9, which meshes with the driven gear 11. The tilting nacelle 4 houses the rotor power control assembly 5, and a tilting shaft 10 is located at the lower end of the tilting nacelle 4. The tilting nacelle 4 is mounted on the fixed nacelle 3 via the tilting shaft 10. The fixed nacelle 3 has a pivot hole that allows the tilting shaft 10 to pass through. After passing through the pivot hole, the tilting shaft 10 is fixedly connected to the driven gear 11. Wing 2 is fixed to the middle of fuselage 1, and aileron control surfaces are distributed at the tip of wing 2. Tail 6 is fixed to the upper part of the tail of fuselage 1, and pitch and yaw control surfaces are distributed on the left and right sides of tail 6. Ventral fin 7 is fixed to the lower part of the tail of fuselage 1. The fixed nacelle 3 is fixed to the wingtip of the wing 2, one on each side. A bearing is installed between the tilting shaft 10 and the fixed nacelle 3, and the tilting shaft 10 can rotate smoothly in the center hole of the fixed nacelle 3. The tilting process is as follows: the tilting servo 8 drives the drive gear 9 to rotate, the drive gear 9 drives the driven gear 11 to rotate, and the driven gear 11 drives the tilting nacelle 4 to rotate around the tilting shaft 10 through the tilting shaft 10, thereby realizing the tilting of the rotor power control assembly 5.

[0007] Because the tilt axis 10 is tilted, the tilt nacelle 4 tilts both forward and outward, exhibiting a "V-shaped" attitude, resulting in a positive outward tilt angle and a negative toe angle. When one rotor gets caught in a vortex ring state and the thrust decreases, the aircraft rolls to one side, and the lever arm of the other rotor relative to the aircraft's center of gravity increases, generating a restoring torque in the opposite direction to help the aircraft regain a level attitude.

[0008] Furthermore, for small tiltrotor aircraft, the total weight of the two tilting nacelles 4 may be comparable to the fuselage weight. During tilting, due to the law of conservation of angular momentum, it is highly likely that the fuselage will pitch up without the nacelles tilting, which is very detrimental to pitch control. The aircraft of this invention utilizes the obliquely placed tilt axis 10 to effectively counteract the counter-torque of the two tilting nacelles on the fuselage, thus avoiding the problem of unstable pitch control.

[0009] The driven gear 11 is provided with a small boss, and the side of the boss is provided with a set screw hole for fixing to the tilting shaft 10.

[0010] The tilting shaft 10 has a flange at the connection point with the driven gear 11 to prevent the lift generated by the rotor power control assembly 5 from pulling the tilting nacelle 4 off the fixed nacelle 3.

[0011] The rotor-powered control assembly 5 includes a rotor system, a control system, and a power system. The motor of the power system directly drives the main shaft of the rotor system. The control servos of the control system adopt a 120-degree compact wraparound layout. The rotor-powered control assembly 5 adopts a highly integrated design, which eliminates the transmission system and greatly reduces the size and weight compared to a transmission helicopter.

[0012] Both the driving gear 9 and the driven gear 11 are made of high-strength aerospace aluminum alloy, which can withstand greater loads compared to plastic gears.

[0013] The fuselage 1 has a through hole running through its length, which is designed in a through-type manner. During high-speed flight, air can enter directly from the nose to efficiently cool the avionics, flight control, and power systems, and then be exhausted from the tail to dissipate heat from the avionics, flight control, and power systems.

[0014] Among them, the tail fin 6 is a V-shaped tail fin. The tail fin adopts a V-shaped tail fin design, which takes into account both pitch and yaw control, and has a lighter weight compared to traditional horizontal and vertical tail fins.

[0015] Secondly, a flight control method for a non-orthogonal tiltrotor aircraft is provided, including: 1) When the aircraft takes off vertically, the tilting nacelles 4 on both sides are vertically upward, and the rotor power control assembly 5 provides lift and maintains the attitude stability of the aircraft. 2) When the aircraft is tilting forward, the tilt servo 8 drives the drive gear 9 to rotate, the drive gear 9 drives the driven gear 11 to rotate, and the driven gear 11 drives the tilt nacelle 4 to rotate around the tilt shaft 10 through the tilt shaft 10, thereby realizing the tilt of the rotor power control assembly 5. 3) During the tilting process, as the speed of the aircraft increases, the wing 2 gradually generates lift and roll control effects. Part of the lift of the aircraft is provided by the rotor power control assembly 5, and part of the pitch and yaw control torque is provided by the wing 2 and the V-tail 6. 4) After the tilting is completed, the tilting nacelles 4 on both sides are completely horizontal and forward. The forward thrust of the aircraft is entirely provided by the rotor power control assembly 5, the lift is entirely provided by the wings 2, the roll control and stability control is entirely provided by the wings 2, and the pitch and yaw control and stability control is entirely provided by the V-tail 6. The vertical descent process is the complete opposite of the process in steps 1) to 4).

[0016] The beneficial effects of this application are as follows: Because the tilt axis is angled, the tilt nacelles tilt both forward and outward, exhibiting a "V-shaped" attitude, resulting in a positive cant angle and a negative toe angle. When one rotor gets caught in a vortex ring state and the thrust decreases, the aircraft rolls to one side. The lever arm of the other rotor relative to the fuselage's center of gravity increases, generating a restoring torque in the opposite direction, helping the aircraft regain a level attitude. Furthermore, for small tiltrotor aircraft, the total weight of the two tilt nacelles may be comparable to the fuselage weight. During tilting, due to the law of conservation of angular momentum, it is possible for the fuselage to pitch up without the nacelles tilting, which is very detrimental to pitch control. The aircraft of this invention utilizes the angled tilt axis to effectively counteract the counter-torque of the two tilt nacelles on the fuselage, avoiding the problem of unstable pitch control. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a non-orthogonal tilt rotorcraft according to the present invention; Figure 2 This is an exploded view of a non-orthogonal tilt rotorcraft according to the present invention; Figure 3This is a rear view of a non-orthogonal tiltrotor aircraft in vertical takeoff and landing configuration according to the present invention. Figure 4 This is a front view of a non-orthogonal tiltrotor aircraft in vertical takeoff and landing configuration according to the present invention. Figure 5 This is a rear view of a non-orthogonal tilt rotorcraft in a tilt transition state according to the present invention; Figure 6 This is a front view of a non-orthogonal tilt rotorcraft in a tilt transition state according to the present invention; Figure 7 This is a rear view of a non-orthogonal tiltrotor aircraft in high-speed flight state according to the present invention; Figure 8 This is a front view of a non-orthogonal tiltrotor aircraft in high-speed flight mode according to the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0020] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited from each other.

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0022] This invention aims to improve the shortcomings of traditional tiltrotor aircraft in terms of poor lateral stability, increase the mechanical stabilization effect during tilting, and avoid the problem of fuselage pitch instability caused by the tilting of the rotor nacelle. It provides a tiltrotor aircraft in which the rotor tilt axis is not orthogonal to the fuselage coordinate plane. The tilt axis of the tilt nacelle is arranged at an angle. The fuselage coordinate system is defined as follows: the positive direction of the X-axis is backward along the heading, the positive direction of the Y-axis is to the right along the heading, and the positive direction of the Z-axis is upward along the vertical direction. The tilt axis is parallel to the XZ plane and forms a 45° angle with the X-axis and Z-axis. It is not orthogonal to the XY plane and YZ plane of the fuselage coordinate system, and is therefore called a non-orthogonal tilt axis.

[0023] See Figure 1 and Figure 2 The aircraft consists of a fuselage 1, wings 2, a fixed nacelle 3, a tilting nacelle 4, a rotor power control assembly 5, a V-tail 6, and a ventral fin 7. The fixed nacelle 3 is equipped with a tilting servo 8 and a driven gear 11. The tilting servo 8 is equipped with a drive gear 9. The rotor power control assembly 5 is installed inside the tilting nacelle 4, and a tilting shaft 10 is installed at the lower end of the tilting nacelle 4.

[0024] Wing 2 is fixed to the middle of fuselage 1, and aileron control surfaces are distributed at the tip of wing 2. V-tail 6 is fixed above the tail of fuselage 1, and pitch and yaw control surfaces are distributed on the left and right sides of V-tail 6. Ventral fin 7 is fixed below the tail of fuselage 1.

[0025] Fixed nacelles 3 are fixed to the wingtips of wings 2, one on each side. Tilting nacelles 4 are mounted on fixed nacelles 3 via tilting shafts 10. Tilting nacelles 4 and tilting shafts 10 are fixedly connected. Tilting shafts 10 are fixedly connected to driven gears 11. Bearings are installed between tilting shafts 10 and fixed nacelles 3. Tilting shafts 10 can rotate smoothly in the center hole of fixed nacelles 3.

[0026] The tilting process involves the tilting servo 8 driving the drive gear 9 to rotate, which in turn drives the driven gear 11 to rotate. The driven gear 11 then drives the tilting nacelle 4 to rotate around the tilting shaft 10 via the tilting shaft 10, thereby achieving the tilting of the rotor power control assembly 5.

[0027] Because the tilt axis 10 is tilted, the tilt nacelle tilts both forward and outward, exhibiting a "V-shaped" attitude, resulting in a positive outward tilt angle and a negative toe angle. When one rotor gets caught in a vortex ring state and the thrust decreases, the aircraft rolls to one side, and the lever arm of the other rotor relative to the aircraft's center of gravity increases, generating a restoring torque in the opposite direction to help the aircraft regain a level attitude.

[0028] Furthermore, for small tiltrotor aircraft, the total weight of the two tilting nacelles can be comparable to the fuselage weight. During tilting, due to the law of conservation of angular momentum, it is highly likely that the fuselage will pitch up without the nacelles tilting, which is very detrimental to pitch control. This aircraft utilizes an angled tilt axis to effectively counteract the counter-torque of the two tilting nacelles on the fuselage, thus avoiding the problem of unstable pitch control.

[0029] Furthermore, the driven gear 11 is designed with a small boss, and the side of the boss is provided with a set screw hole for fixing with the tilting shaft 10.

[0030] Furthermore, the tilt shaft 10 is designed with a flange at its end to prevent the lift generated by the rotor power control assembly 5 from pulling the tilt nacelle 4 off the fixed nacelle 3.

[0031] Furthermore, the rotor-powered control assembly 5 adopts a highly integrated design, with the motor directly driving the main shaft, eliminating the transmission system. The control servos adopt a 120-degree compact wraparound layout, which greatly reduces the size and weight compared to a transmission-driven helicopter.

[0032] Furthermore, both the driving gear 9 and the driven gear 11 are made of high-strength aerospace aluminum alloy, which can withstand greater loads compared to plastic gears.

[0033] Furthermore, the fuselage 1 adopts a through-type design, which allows air to enter directly from the nose during high-speed flight, efficiently cooling the avionics and flight control systems, and then being exhausted from the tail.

[0034] Furthermore, the tail fin adopts a V-shaped tail design, which takes into account both pitch and yaw control, and has a lighter weight compared to traditional horizontal and vertical tail fins.

[0035] An embodiment of the present invention also provides a flight control method for a non-orthogonal tiltrotor aircraft, comprising: 1) During vertical takeoff, the tilting nacelles 4 on both sides are vertically upward, and the rotor power control assembly 5 provides lift and maintains the aircraft's attitude stability; see also Figure 3 and Figure 4 , 2) When the aircraft tilts forward, the tilt servo 8 drives the drive gear 9 to rotate, which in turn drives the driven gear 11 to rotate. The driven gear 11 then drives the tilt nacelle 4 to rotate around the tilt shaft 10 via the tilt shaft 10, thereby achieving the tilting of the rotor power control assembly 5; see also Figure 5 and Figure 6 , 3) During the tilting process, as the speed of the aircraft increases, the wing 2 gradually generates lift and roll control effects. Part of the lift of the aircraft is provided by the rotor power control assembly 5, and part of the pitch and yaw control is provided by the wing 2 and the V-tail 6. 4) After the tilt is completed, the tilting nacelles 4 on both sides are completely horizontal and forward. The forward thrust of the aircraft is entirely provided by the rotor power control assembly 5, the lift is entirely provided by the wings 2, the roll control and stability control is entirely provided by the wings 2, and the pitch and yaw control and stability control is entirely provided by the V-tail 6; see also Figure 7 and Figure 8 , The process of vertical descent is the complete opposite of the process in steps 1) to 4).

[0036] The above description merely illustrates embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Furthermore, any parts of the present invention not described in detail are conventional techniques.

Claims

1. A non-orthogonal tiltrotor aircraft, characterized in that, include: The fuselage (1) is fixed in the middle of the fuselage (1). The fixed nacelles (3) are fixed on the wingtips of the wings (2), one on each side. The tilting nacelles (4) are mounted on the fixed nacelles (3) via tilting shafts (10). The fixed nacelles (3) are equipped with tilting servos (8) and driven gears (11). The tilting servos (8) are equipped with driving gears (9), and the driving gears (9) mesh with the driven gears (11). The tilting nacelles (4) are equipped with tilting shafts (10) at the lower end. The tilting nacelles (4) are equipped with rotor power control assembly (5). The tilting process is as follows: the tilting servo (8) drives the drive gear (9) to rotate, the drive gear (9) drives the driven gear (11) to rotate, and the driven gear (11) drives the tilting nacelle (4) to rotate around the tilting shaft (10) through the tilting shaft (10), thereby realizing the tilting of the rotor power control assembly (5); Among them, the tilt axis (10) at the lower end of the tilt nacelle (4) is arranged at an angle. The tilt axis (10) is parallel to the XZ plane, at 45° with the X axis and Z axis, and is not orthogonal to the XY plane and YZ plane of the fuselage coordinate system. The positive direction of the X axis is backward along the heading, the positive direction of the Y axis is to the right along the heading, and the positive direction of the Z axis is upward along the vertical direction.

2. The non-orthogonal tiltrotor aircraft as described in claim 1, characterized in that, The aircraft also includes a tail fin (6) and a ventral fin (7). The fixed nacelle (3) is provided with a pivot hole that allows the tilting shaft (10) to pass through. After the tilting shaft (10) passes through the pivot hole, it is fixedly connected to the driven gear (11). The wing (2) has aileron control surfaces at its tip, the tail (6) is fixed above the tail of the fuselage (1), the tail (6) has pitch and yaw control surfaces on its left and right sides, and the ventral fin (7) is fixed below the tail of the fuselage (1). A bearing is installed between the tilting shaft (10) and the fixed nacelle (3), and the tilting shaft (10) can rotate smoothly in the center hole of the fixed nacelle (3).

3. The non-orthogonal tiltrotor aircraft as described in claim 2, characterized in that, The driven gear (11) is provided with a boss, and the side of the boss is provided with a set screw hole for fixing with the tilting shaft (10).

4. The non-orthogonal tiltrotor aircraft as described in claim 2, characterized in that, A flange is provided at the connection between the end of the tilting shaft (10) and the driven gear (11).

5. The non-orthogonal tiltrotor aircraft as described in claim 1, characterized in that, The rotor power control assembly (5) includes a rotor system, a control system and a power system. The motor of the power system directly drives the main shaft of the rotor system, and the control servo of the control system adopts a 120-degree compact wraparound layout.

6. The non-orthogonal tiltrotor aircraft as described in claim 1, characterized in that, Both the driving gear (9) and the driven gear (11) are made of high-strength aerospace aluminum alloy.

7. The non-orthogonal tiltrotor aircraft as described in claim 1, characterized in that, The fuselage (1) has a through hole along its length.

8. The non-orthogonal tiltrotor aircraft as described in claim 2, characterized in that, The tail fin (6) is a V-shaped tail fin.

9. A flight control method for a non-orthogonal tiltrotor aircraft according to any one of claims 1 to 8, characterized in that, include: When the aircraft takes off vertically, the tilting nacelles on both sides are vertically upward, and the rotor power control assembly provides lift and maintains the attitude stability of the aircraft. When the aircraft tilts forward, the tilt servo drives the drive gear to rotate, which in turn drives the driven gear to rotate. The driven gear then drives the tilt nacelle to rotate around the tilt axis, thereby achieving the tilt of the rotor power control assembly. During the tilting process, as the speed of the aircraft increases, the wings gradually generate lift and roll control effects. Part of the aircraft's lift is provided by the rotor power control system, and part of the lift is provided by the wings and V-tail to provide pitch and yaw control torque. After the tilt is completed, the tilt nacelles on both sides are completely horizontal and forward. The forward thrust of the aircraft is provided entirely by the rotor power control system, the lift is provided entirely by the wings, the roll control and stability control is provided entirely by the wings, and the pitch and yaw control and stability control is provided entirely by the V-tail. The process of vertical descent is the complete opposite of the process described above.

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