Vertical take-off and landing aircraft and control method therefor

Abstract

Provided in the present application are a vertical take-off and landing aircraft and a control method therefor. The vertical take-off and landing aircraft comprises a fuselage and 2N tilt-rotors. Wings are provided on two sides of the fuselage, and an empennage is provided at the tail of the fuselage, an elevator rudder being provided on the empennage. The 2N tilt-rotors are symmetrically mounted on two sides of the fuselage, and some of the 2N tilt-rotors are located on the empennage, where N is a natural number greater than or equal to 2. In a vertical take-off and landing state, the projections of propellers of the 2N tilt-rotors on the horizontal plane are centrally symmetrical about point B, both the point B and the center of gravity G of the vertical take-off and landing aircraft are located in the symmetrical plane of the fuselage, and the point B is located on the side of the point G close to the empennage. During the transition of the vertical take-off and landing aircraft from the vertical take-off and landing state to a cruising state, both the point G and the point B move along the symmetrical plane towards the side close to the nose, and the point B is always located on the side of the point G close to the empennage. Such a layout enables the vertical take-off and landing aircraft to have a better pitch trim capability.

Description

Vertical take-off and landing aircraft and control method thereof

[0001] This application claims priority to Chinese patent applications with application number 2023116776187, entitled “Vertical take-off and landing aircraft and control method thereof,” filed on December 7, 2023, and application number 2023233405592, entitled “A vertical take-off and landing aircraft,” filed on December 7, 2023, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of aircraft technology, and in particular to a vertical take-off and landing aircraft and a control method thereof. Background Art

[0003] Distributed propulsion fixed-wing vertical take-off and landing (VTOL) aircraft combine the vertical take-off and landing capabilities of helicopters with the high-efficiency, high-speed horizontal flight capabilities of fixed-wing aircraft. They are quieter, more comfortable, and more economical than helicopters, more efficient and have a longer range than multi-rotors, and can take off and land vertically from urban landing platforms, making them an excellent choice for urban air travel. However, in existing VTOL aircraft, when rotors are installed on the tail, the airflow generated by the rotors and the tail interferes with each other, easily making pitch control difficult. This creates unpredictable technical challenges for flight control of VTOL aircraft.

[0004] Application Contents

[0005] In view of the above shortcomings of the prior art, the present application provides a vertical take-off and landing aircraft and a control method thereof to improve the problem that the airflow interference between the tilt rotor on the tail wing and the tail wing in the existing vertical take-off and landing aircraft is large, making pitch control difficult.

[0006] To achieve the above-mentioned and other related purposes, the present application provides a vertical take-off and landing (VTOL) aircraft, comprising: a fuselage and 2N tilt-rotors. Wings are provided on either side of the fuselage, a tail is provided at the rear of the fuselage, and an elevator rudder is provided on the tail. The 2N tilt-rotors are symmetrically mounted on either side of the fuselage, and a portion of the 2N tilt-rotors is located on the tail. Wherein, N is a natural number greater than or equal to 2. In a vertical take-off and landing (VTOL) configuration, the projections of the propellers of the 2N tilt-rotors on a horizontal plane are centrally symmetric about point B. Point B and the center of gravity (G) of the VTOL aircraft are both located within a symmetry plane of the fuselage, with point B located on the side of point G closest to the tail. During a modal change of the VTOL aircraft, both point G and point B move along the symmetry plane, and point B always remains on the side of point G closest to the tail.

[0007] In one embodiment of the vertical take-off and landing aircraft of the present application, during flight, the rotation axis of any of the tilt-rotors on the tail wing and the rotation axis of any of the tilt-rotors at other positions have non-parallel projections on the symmetry plane of the fuselage.

[0008] In one embodiment of the vertical take-off and landing aircraft of the present application, in the cruising state and / or the vertical take-off state and / or the mode conversion state, there is a first difference between the tilt speed of any of the tilt-rotors on the tail wing and the tilt speed of any of the tilt-rotors at other positions, and the first difference is not equal to 0.

[0009] In one embodiment of the vertical take-off and landing aircraft of the present application, in the cruising state and / or the vertical take-off state and / or the mode conversion state, there is a second difference between the rotation speed of any of the tilt-rotors on the tail wing and the rotation speed of any of the tilt-rotors at other positions, and the second difference is not equal to 0.

[0010] In one embodiment of the vertical take-off and landing aircraft of the present application, the vertical take-off and landing aircraft adopts the following method for pitch control:

[0011] During flight, allocating pitch control ratios of the elevator rudder and the 2N tilt-rotors according to the current airspeed or dynamic pressure;

[0012] According to the pitch control ratio, the elevator rudder and the 2N tilt rotors are controlled respectively to achieve pitch trim and control.

[0013] In one embodiment of the vertical take-off and landing aircraft of the present application, controlling the 2N tilt rotors according to the pitch control ratio includes:

[0014] Differentially adjusting the pitch moment to perform pitch trim and control by using the tilt angle difference between the tilt rotor on the tail wing and any other tilt rotor;

[0015] and / or, differentially adjusting the pitch moment to perform pitch trim and control by using a rotational speed difference between the tilt-rotor on the tail wing and any other tilt-rotor;

[0016] And / or, the pitch moment is differentially adjusted by the tilt speed difference between the tilt rotor on the tail wing and any other tilt rotor to perform pitch trim and control.

[0017] In one embodiment of the vertical take-off and landing aircraft of the present application, the vertical take-off and landing aircraft includes four tilt-rotors, which are symmetrically installed on both sides of the fuselage, two of which are symmetrically installed on the wings with respect to the fuselage, and the other two are symmetrically installed on the tail.

[0018] In one embodiment of the vertical take-off and landing aircraft of the present application, the vertical take-off and landing aircraft includes six tilt-rotors, which are symmetrically installed on both sides of the fuselage, four of which are symmetrically installed on the wings with respect to the fuselage, and the other two are symmetrically installed on the tail.

[0019] In one embodiment of the vertical take-off and landing aircraft of the present application, the tail is a V-shaped tail, and the two tilt-rotors located on the tail are full-tilt rotors, which are respectively installed on the wingtips on both sides of the upper part of the V-shaped tail.

[0020] In one embodiment of the vertical take-off and landing aircraft of the present application, two tilt-rotors are provided at the wingtips of the wings, and the tilt-rotors located on the wingtips of the wings are full-tilt rotors.

[0021] In one embodiment of the vertical take-off and landing aircraft of the present application, the vertical take-off and landing aircraft also includes 2M fixed rotors, where M is a natural number greater than or equal to 2, and the 2M fixed rotors are symmetrically installed on the wings on both sides of the fuselage and are located on the outside of the tilt-rotor; in the vertical take-off and landing state, the projections of all the fixed rotors on the horizontal plane are centrally symmetrical about point A, and point A is located in the symmetry plane of the fuselage. During the process of the vertical take-off and landing aircraft changing from mode to mode, point G is located on the side of point A close to the nose or coincides with point A, and point B is always located on the side of point A close to the tail.

[0022] In one embodiment of the vertical take-off and landing aircraft of the present application, the angle between the rotation axes of the 2M fixed rotors and the symmetry plane of the fuselage is -15° to +15°; and / or, the angle between the plane formed by the rotation axes of the 2N tilt-rotors during the tilting process and the symmetry plane of the fuselage is -15° to +15°.

[0023] In one embodiment of the vertical take-off and landing aircraft of the present application, the vertical take-off and landing aircraft includes four tilt-rotors and four fixed rotors. Assume that the distance from the center of gravity point G to point A is L1, L1 ≥ 0, the distance from point A to point B is L2, L2 > 0, the spacing between the four fixed rotors along the extension direction of the fuselage is L3, and the spacing between the four tilt-rotors along the extension direction of the fuselage is L4, then 0.1(L3+L4) ≥ 4L1+2L2 ≥ 0.01(L3+L4).

[0024] In one embodiment of the vertical take-off and landing aircraft of the present application, the tail is a V-shaped tail, and the two tilt-rotors located on the tail are full-tilt rotors, which are respectively installed on the wingtips on both sides of the upper part of the V-shaped tail.

[0025] In one embodiment of the vertical take-off and landing aircraft of the present application, the vertical take-off and landing aircraft adopts the following method for pitch control:

[0026] During flight, the pitch control ratios of the elevator rudder, the 2N tilt rotors, and the 2M fixed rotors are distributed according to the current airspeed or dynamic pressure;

[0027] According to the pitch control ratio, the elevator rudder, the 2N tilt rotors and the 2M fixed rotors are controlled respectively to achieve pitch trim and control.

[0028] In one embodiment of the vertical take-off and landing aircraft of the present application, the four fixed rotors are symmetrically installed on both sides of the fuselage, the four tilt-rotors are located on the inner sides of the four fixed rotors, and two of the tilt-rotors are symmetrically installed on the tail wing, and the two tilt-rotors located on the tail wing are full-tilt rotors.

[0029] In one embodiment of the vertical take-off and landing aircraft of the present application, the tail is a V-shaped tail, and two tilt-rotors are installed on the V-shaped tail, and the two tilt-rotors are respectively installed at the wingtips of the V-shaped tail. In the vertical take-off and landing state, along the direction parallel to the roll axis of the vertical take-off and landing aircraft, the distance between the rotation center of the tilt-rotor on the tail and the leading edge of the wingtip of the V-shaped tail is t1, and the chord length of the wingtip of the V-shaped tail is t2, wherein the ratio of t1 to t2 is 15% to 40%.

[0030] In one embodiment of the vertical take-off and landing aircraft of the present application, the tilt-rotor located on the tail wing is a full-tilt rotor; the tilt-rotor located outside the tail wing is a partial-tilt rotor.

[0031] In one embodiment of the vertical take-off and landing aircraft of the present application, a tilt-rotor is provided on the wingtip of the wing, and the tilt-rotor located on the tail wing and the tilt-rotor located on the wingtip of the wing are both full-tilt rotors.

[0032] In one embodiment of the vertical take-off and landing aircraft of the present application, the fully tilting rotor includes a first rotor and a power pod, the first rotor is connected to the power pod, the power pod is rotatably connected to the tail or the wing, and the power pod tilts synchronously with the first rotor during the tilting process of the first rotor.

[0033] In one embodiment of the vertical take-off and landing aircraft of the present application, the first rotor includes a propeller and a rotation drive device, the propeller is installed on the output shaft of the rotation drive device, the power pod includes a pod shell and a tilting mechanism located in the pod shell, and the tilting mechanism is used to drive the rotation drive device to tilt, thereby driving the propeller to tilt.

[0034] In one embodiment of the vertical take-off and landing aircraft of the present application, the tilt mechanism includes: a rocker arm, a driving arm, a tilt driving device and a connecting rod; the rocker arm and the driving arm are both rotatably mounted on the tail wing; the base of the tilt driving device is mounted on the tail wing, and the driving end of the tilt driving device drives the driving arm to rotate; the connecting rod is rotationally connected to the driving arm and the rocker arm respectively; the rocker arm is fixedly connected to the rotation driving device of the first rotor.

[0035] In one embodiment of the vertical take-off and landing aircraft of the present application, a first axis and a second axis parallel to each other are fixedly provided on the tail wing, the rocker arm is rotatably mounted on the first axis, the driving arm is rotatably mounted on the second axis, the base of the tilt driving device is mounted on the second axis, and the driving of the tilt driving device is fixed to the driven arm.

[0036] In one embodiment of the vertical take-off and landing aircraft of the present application, an embracing structure is provided between the first axis and the second axis, one end of the embracing structure is fixedly connected to the base, and the other end of the embracing structure surrounds and tightly embraces the first axis.

[0037] In one embodiment of the vertical take-off and landing aircraft of the present application, the first shaft body and / or the second shaft body is a hollow shaft body.

[0038] In one embodiment of the vertical take-off and landing aircraft of the present application, the elevator rudder includes a rudder plate and a rudder body drive device, the rudder plate is rotatably connected to the tail wing or the tail of the fuselage, and the rudder body drive device drives the rudder plate to rotate to adjust the direction of the vertical take-off and landing aircraft.

[0039] In one embodiment of the vertical take-off and landing aircraft of the present application, the roll axis of the vertical take-off and landing aircraft is used as a reference, defined as 0°, the upward tilt of the tilt-rotor is defined as a positive direction, and the downward tilt is defined as a negative direction, and the rotation axis of the tilt-rotor is tilted within the range of -20° to 110°.

[0040] In one embodiment of the vertical take-off and landing aircraft of the present application, the tail wing is a forward-swept tail wing, and the tilt-rotor located on the forward-swept tail wing is a full-tilt rotor.

[0041] In one embodiment of the vertical take-off and landing aircraft of the present application, the vertical take-off and landing aircraft further includes a tail fin, which is arranged below the forward-swept tail wing and connected to the tail of the fuselage.

[0042] The present application also provides a control method for a vertical take-off and landing (VTOL) aircraft, comprising a fuselage and 2N tilt-rotors. Wings are provided on either side of the fuselage, a tail is provided at the rear of the fuselage, and an elevator rudder is provided on the tail. The 2N tilt-rotors are symmetrically mounted on either side of the fuselage, with a portion of the 2N tilt-rotors located on the tail. N is a natural number greater than or equal to 2. In a vertical take-off and landing (VTOL) state, the projections of the propellers of the 2N tilt-rotors on a horizontal plane are centrally symmetric about point B. Point B and point G, the center of gravity of the VTOL aircraft, are both located within a symmetry plane of the fuselage, with point B located on the side of point G closer to the tail. During a modal change of the VTOL aircraft, both point G and point B move along the symmetry plane. Specifically, during a transition from the VTOL state to a cruising state, both point G and point B move along the symmetry plane toward the nose, with point B always located on the side of point G closer to the tail. The control method includes the following pitch control process:

[0043] Allocating a pitch control ratio of the elevator rudder and the 2N tilt rotors according to the current airspeed or dynamic pressure;

[0044] According to the pitch control ratio, the elevator rudder and the 2N tilt rotors are controlled respectively to achieve pitch trim and control.

[0045] In one embodiment of the control method of the present application, before allocating the pitch control ratios of the elevator rudder and the 2N tilt rotors according to the current airspeed or dynamic pressure, the following rotor control process is also included:

[0046] Get the current tilt position of each tilt rotor;

[0047] If the current tilt position is inconsistent with the set cruise position, obtaining a current airspeed or dynamic pressure of the corresponding tilt rotor at the current tilt position, and determining whether the current airspeed or dynamic pressure is equal to or greater than a preset threshold value at the current tilt position;

[0048] If the current airspeed or dynamic pressure is equal to or greater than a preset threshold value at the current tilt position, the tilt rotor is controlled to tilt to a preset next position;

[0049] Gradually increase the rotation speed of 2N tilt rotors.

[0050] In one embodiment of the control method of the present application, the vertical take-off and landing aircraft also includes 2M fixed rotors, where M is a natural number greater than or equal to 2; the 2M fixed rotors are distributed around the 2N tilt-rotors, and during the rotor control process, while gradually increasing the rotational speed of the 2N tilt-rotors, it also includes: gradually reducing the rotational speed of the 2M fixed rotors to a set rotational speed.

[0051] In one embodiment of the control method of the present application, the following takeoff control process is further included before the rotor control:

[0052] Tilt the 2N tilt rotors until the rotation axis is vertically upward or obliquely upward;

[0053] Deflect the elevator rudder downward;

[0054] The 2M fixed rotors and the 2N tilt rotors are started, and a level flight command is issued when the vertical take-off and landing aircraft reaches a set altitude.

[0055] In one embodiment of the control method of the present application, the vertical take-off and landing aircraft further includes 2M fixed rotors, which are distributed around the 2N tilt-rotors. Before allocating the pitch control ratio of the elevator rudder to the 2N tilt-rotors according to the current airspeed or dynamic pressure, the following take-off control process is also included:

[0056] Tilt the 2N tilt rotors until the rotation axis is horizontal and forward;

[0057] Deflect the elevator rudder downward;

[0058] The 2M fixed rotors and the 2N tilt rotors are started, and a level flight command is issued when the vertical take-off and landing aircraft reaches a set altitude.

[0059] In one embodiment of the control method of the present application, after the takeoff control process and before the pitch control, the following rotor control process is also included: gradually increasing the rotation speed of 2N tilt rotors, issuing a forward flight command and gradually reducing the rotation speed of 2M fixed rotors to the set speed.

[0060] In one embodiment of the control method of the present application, during the rotor control process, after gradually reducing the rotation speed of the 2M fixed rotors to the set rotation speed, it also includes controlling the elevator rudder to return to zero according to the current airspeed or dynamic pressure, and gradually participating in the pitch control process.

[0061] In one embodiment of the control method of the present application, a ground preparation process is also included before the takeoff control process. The ground preparation process includes: starting the vertical take-off and landing aircraft, powering on the system for detection, and confirming the full-stroke status of the servo system.

[0062] In one embodiment of the control method of the present application, the elevator rudder and the 2N tilt-rotors are controlled separately according to the pitch control ratio to achieve pitch balancing and control, including: differentially adjusting the pitch torque to perform pitch balancing and control through the tilt speed difference and / or tilt angle difference and / or rotation speed difference between the tilt-rotors at different positions of the center of gravity.

[0063] In one embodiment of the control method of the present application, the control method further includes: repeating the rotor control process and the pitch control process in sequence until the tilt rotor is tilted to the cruise position, completing the takeoff and level flight.

[0064] The vertical take-off and landing (VTOL) aircraft of the present application is equipped with elevators and 2N tilt-rotors. In the vertical take-off and landing (VTOL) state, the projections of the 2N tilt-rotor propellers on the horizontal plane are centrally symmetric about point B. Point B and the center of gravity (G) of the VTOL aircraft are both located within the plane of symmetry of the fuselage, with point B located on the side of point G closer to the tail. Furthermore, during the modal changes of the VTOL aircraft, point B remains on the side of point G closer to the tail. With this layout, the center of gravity (G) of the VTOL aircraft and the center of symmetry (B) of the tilt-rotors do not coincide. In particular, during the transition of the VTOL aircraft from the vertical take-off and landing state to the cruising state, both points G and B move along the plane of symmetry toward the side closer to the nose. Therefore, the pulling force generated by the tilt rotor in front of the center of gravity exerts a smaller torque on the center of gravity point G, while the pulling force generated by the tilt rotor aft of the center of gravity exerts a larger torque on the center of gravity point G. The torque difference between the front and rear tilt rotors can resist part of the pitching torque generated by the tilt rotor wash area on the tail wing, thereby reducing the difficulty of pitch control. Therefore, when the tilt rotors on both sides of the center of gravity point G are at the same speed and throttle, due to the difference in the length of the lever arm about the center of gravity point G, a nose-down torque will be generated. This nose-down torque can offset or partially offset the pitching torque generated by the tilt rotor wash area on the tail wing. Therefore, the vertical take-off and landing aircraft can better balance the pitching torque when the front and rear rotor throttles are consistent.

[0065] The control method of the present application distributes the pitch control ratio of the elevator rudder and the 2N tilt-rotors according to the current airspeed or dynamic pressure, and can realize pitch control through the linkage of the elevator rudder and the 2N tilt-rotors. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying any creative work.

[0067] FIG1 is an isometric view of a vertical take-off and landing aircraft in a vertical take-off and landing state according to an embodiment of the present application;

[0068] FIG2 is a side view of a vertical take-off and landing aircraft in a vertical take-off and landing state according to an embodiment of the present application;

[0069] FIG3 is an isometric view of a vertical take-off and landing aircraft in a vertical take-off and landing state according to another embodiment of the present application;

[0070] FIG4 is a side view of a vertical take-off and landing aircraft in a vertical take-off and landing state according to another embodiment of the present application;

[0071] FIG5 is an isometric view of a vertical take-off and landing aircraft in a cruising state according to another embodiment of the present application;

[0072] FIG6 is an isometric view of a vertical take-off and landing aircraft in a vertical take-off and landing state according to another embodiment of the present application;

[0073] FIG7 is a top view of a vertical take-off and landing aircraft in a vertical take-off and landing state according to another embodiment of the present application;

[0074] FIG8 is a side view of a vertical take-off and landing aircraft in a vertical take-off and landing state according to another embodiment of the present application;

[0075] FIG9 is a rear view of a vertical take-off and landing aircraft in a vertical take-off and landing state according to another embodiment of the present application;

[0076] FIG10 is a partial view of a fully tilting rotor;

[0077] Figure 11 is a partial view of the tilt rotor with the pod housing removed;

[0078] Figure 12 is a top view of the fully tilting rotor with the pod housing removed;

[0079] FIG13 is a cross-sectional view taken along line DD in FIG12 ;

[0080] FIG14 is a view from another direction of the tilt rotor after the pod shell is removed;

[0081] FIG15 is a three-dimensional view of the tilt rotor from another direction after the pod shell is removed;

[0082] FIG16 is a sectional view taken along line FF of FIG14 ;

[0083] FIG17 is a sectional view of PP in FIG14;

[0084] FIG18 is a partial view of the tail wing with the fully tilting rotor in a vertical position and the rudder plate chord length accounting for 30%;

[0085] FIG19 is a partial view of the tail wing with the fully tilting rotor in a vertical position and the rudder plate chord length accounting for 60%;

[0086] FIG20 is a partial view of the tail wing with the fully tilting rotor in a vertical position and the rudder plate chord length accounting for 100%;

[0087] FIG21 is a partial view of the fully tilting rotor on the tail wing in a cruising state;

[0088] FIG22 is a partial view of the fully tilting rotor on the tail wing in an oblique climbing state;

[0089] FIG23 is a diagram showing the rotation path of the elevator rudder on the tail fin;

[0090] FIG24 is a top view of the tail wing of the aircraft in vertical takeoff and landing mode;

[0091] Figure 25 is a schematic diagram of the ratio of the chord length of the tail rudder plate and the deflection angle of the rudder plate;

[0092] FIG26 is a top view of the tail wing of the aircraft in vertical takeoff and landing mode;

[0093] Figure 27 shows the variation curve of the pitch moment (dimensionless) of the whole aircraft with the wind speed (dimensionless) for the partial and full tilt control methods of the pod (CFD simulation results);

[0094] FIG28 is a flow chart of an embodiment of the vertical take-off and landing aircraft of the present application from a ground state to a cruising state;

[0095] FIG29 is a flow chart of the transition from takeoff to level flight of an embodiment of the vertical take-off and landing aircraft of the present application;

[0096] FIG30 is a flow chart of pitch control of a vertical take-off and landing aircraft according to an embodiment of the present application;

[0097] FIG31 is a flow chart of rotor control for a vertical take-off and landing aircraft according to an embodiment of the present application;

[0098] FIG32 is a flow chart of a takeoff control process of a vertical take-off and landing aircraft according to an embodiment of the present application;

[0099] FIG33 is a flow chart of a takeoff control process of a vertical take-off and landing aircraft according to an embodiment of the present application;

[0100] Figure 34 is a top view of the vertical take-off and landing aircraft in a vertical take-off and landing state in another embodiment of the present application.

[0101] Component number description

[0102] 10. Fuselage; 20. Wing; 30. Tail; 31. Elevator; 311. Rudder; 41. First tiltrotor; 411. Third arm; 42. Second tiltrotor; 421. Fourth arm; 43. Third tiltrotor; 44. Fourth tiltrotor; 441. First rotor; 4411. Propeller; 4412. Rotary drive unit; 4413. Fairing; 442. Power pod; 4421. Tilt drive unit; 4422. Rocker arm; 4423. First axis; 4424, second axis; 4425, holding structure; 44251, slit; 4426, connecting rod; 4427, first hinge axis; 4428, second hinge axis; 4429, driving arm; 4430, bearing; 51, first fixed rotor; 511, first machine arm; 52, second fixed rotor; 521, second machine arm; 53, third fixed rotor; 54, fourth fixed rotor; 60, plane of symmetry. DETAILED DESCRIPTION

[0103] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features in the following examples and embodiments can be combined with each other. It should also be understood that the terms used in the examples of the present application are for the purpose of describing specific embodiments, rather than for the purpose of limiting the scope of protection of the present application. The test methods for which specific conditions are not specified in the following examples are generally based on conventional conditions or the conditions recommended by the manufacturers.

[0104] When numerical ranges are given in the examples, it should be understood that, unless otherwise specified herein, both endpoints of each numerical range and any value between the two endpoints may be used. Unless otherwise defined herein, all technical and scientific terms used herein are consistent with the prior art as known to those skilled in the art and described herein. Any prior art methods, devices, and materials similar or equivalent to those described in the examples herein may also be used to implement the present invention.

[0105] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of this application. Changes or adjustments to their relative relationships should be regarded as within the scope of implementation of this application without substantially changing the technical content.

[0106] Referring to Figures 1 to 34 , the present application first provides a vertical take-off and landing (VTOL) aircraft having 2N tilt-rotors symmetrically arranged around a fuselage 10 and an elevator disposed on a tail fin 30. The positional relationship between the 2N tilt-rotors and the center of gravity can be utilized to improve the control of the pitching moment of the VTOL aircraft in complex, interfering flow fields, thereby alleviating control issues caused by airflow interference between the tilt-rotors and the tail fin 30 in existing VTOL aircraft.

[0107] Referring to Figures 1 to 7 , the present application provides a vertical take-off and landing aircraft comprising a fuselage and 2N tilt-rotors. The fuselage 10 is a symmetrical structure having a symmetry plane 60 extending along the length of the fuselage 10 (i.e., the vertical plane where the line O1-O2 in Figure 3 lies). The remaining structure and shape of the fuselage 10 are not limited and can refer to the structure of the fuselage 10 of an existing vertical take-off and landing aircraft. The fuselage 10 includes conventional aircraft operating systems such as the avionics system, flight control system, electrical system, and navigation system, which are not described in detail here. Wings 20 are provided on both sides of the fuselage 10. The wings 20 on both sides are symmetrical relative to the symmetry plane 60 of the fuselage 10. The structure of the wings 20 can also refer to the fixed wing structure of an existing aircraft and is not described in detail here. A tail fin 30 is provided at the tail of the fuselage 10. The tail fin 30 is integrally formed with the fuselage 10 or mechanically connected to the fuselage 10 and is symmetrically arranged relative to the symmetry plane 60 of the fuselage 10. The tail wing 30 is provided with an elevator rudder 31 . The installation position and structure of the elevator rudder 31 can be various. For example, the elevator rudder 31 can be provided at any suitable position on the tail wing 30 or can be any existing suitable elevator rudder structure.

[0108] Crucially, referring to FIG. 7 , 2N tilt-rotors are mounted on either side of the fuselage 10, where N is a natural number greater than or equal to 2. The 2N tilt-rotors are symmetrically arranged about a plane of symmetry 60 of the fuselage 10, and a portion of the 2N tilt-rotors are mounted on the empennage 30. In the vertical take-off and landing (VTOL) configuration, the projections of the 2N tilt-rotors' propellers on a horizontal plane are centrally symmetric about point B. Point B and point G, the center of gravity of the VTOL aircraft, are both located within the plane of symmetry of the fuselage, with point B located on the side of point G closer to the empennage. During modal changes of the VTOL aircraft, both points G and B move along the plane of symmetry. For example, during a transition from the VTOL configuration to the cruise configuration, both points G and B move along the plane of symmetry toward the nose, with point B always located on the side of point G closer to the empennage.

[0109] With the above layout, the vertical take-off and landing aircraft's center of gravity, point G, and the symmetry centers, points B, of the 2N tilt-rotors do not coincide. Furthermore, during the transition from vertical take-off and landing to cruising mode, both points G and B move toward the nose along the plane of symmetry 60. Consequently, the torque exerted by the tilt-rotors forward of the center of gravity on point G is smaller, while the torque exerted by the tilt-rotors aft of the center of gravity on point G is larger. The torque difference between the front and rear tilt-rotors can offset some of the pitching moment generated by the tilt-rotor wash on the tail 30, thereby reducing the difficulty of pitch control. Therefore, when the tilt-rotors forward and backward of point G operate at the same throttle speed, a nose-down moment is generated due to the difference in moment arm lengths relative to point G. This nose-down moment can offset or partially offset the pitching moment generated by the tilt-rotor wash on the tail 30, thereby enabling the vertical take-off and landing aircraft to effectively balance the pitching moment even when the front and rear rotors have the same throttle.

[0110] In the vertical take-off and landing aircraft of the present application, the rotation axes of the tilt-rotors can be arranged in parallel or non-parallel in various states, such as the cruising state for horizontal flight, the vertical state for take-off and landing, and the mode transition state (including the transition from the vertical state to the cruising state and the transition from the cruising state to the vertical state). In some embodiments, during flight, the projections of the rotation axes of any of the tilt-rotors on the tail 30 and the rotation axes of any of the tilt-rotors at other locations on the symmetry plane 60 of the fuselage 10 are non-parallel. The non-parallel rotation axes enable different tilt-rotors to provide torques in different directions, thereby controlling the pitch torque of the vertical take-off and landing aircraft as a whole.

[0111] Although the tilt speeds of the tilt rotors can be the same, so that pitch control can be performed by other means, in one embodiment of the vertical take-off and landing aircraft of the present application, in various states, such as the cruising state of flying in the horizontal direction, the vertical state of taking off and landing in the vertical direction, and the mode conversion state (including the conversion from the vertical state to the cruising state and the conversion from the cruising state to the vertical state), there is a first difference between the tilt speed of any of the tilt rotors on the tail 30 and the tilt speed of any of the tilt rotors at other positions, and the first difference is not equal to 0. By setting the threshold value of the first difference, the pitch force of the vertical take-off and landing aircraft in various states can be adjusted by tilting the tilt rotor to obtain a larger pitch control torque.

[0112] Although the rotation speeds of the various tilt-rotors can be the same and pitch control can be performed by other means, in one embodiment of the vertical take-off and landing aircraft of the present application, in various states, such as the cruising state for horizontal flight, the vertical state for take-off and landing in the vertical direction, and the mode transition state (including the transition from the vertical state to the cruising state and the transition from the cruising state to the vertical state), there is a second difference between the rotation speed of any of the tilt-rotors on the tail 30 and the rotation speed of any of the tilt-rotors at other locations, and the second difference is not equal to 0. By setting a threshold for the second difference, the pitch force of the vertical take-off and landing aircraft in various states can be adjusted by the rotation speed of the tilt-rotors to obtain a larger pitch control torque. It should be noted that the first difference in the tilt speed of the front tilt rotor (the tilt rotor located on the front side of the tilt rotor on the tail 30) and the tilt rotor on the tail 30 can also be combined with the second difference in the rotation speed of the front tilt rotor and the tilt rotor on the tail 30 to achieve pitch moment control of multiple strategies.

[0113] While the present application may include only 2N tilt-rotors as shown in Figures 1 to 4, preferably, referring to Figure 7, in another embodiment of the present application, the vertical take-off and landing aircraft includes 2M fixed rotors, where M is a natural number greater than or equal to 2 and may be the same as or different from N. The 2M fixed rotors are symmetrically mounted on the wings on either side of the fuselage and located outboard of the tilt-rotors. In the vertical take-off and landing (VTOL) configuration, the horizontal projections of all the fixed rotors are centrally symmetrical about point A, which lies within the plane of symmetry of the fuselage and coincides with point G or is located on the side of point G closer to the tail. During the transition of the vertical take-off and landing (VTOL) aircraft from the vertical take-off and landing (VTOL) configuration to the cruising configuration, points G and B move along the plane of symmetry toward the nose, with point G located on the nose side of point A or coinciding with point A, and point B always located on the side of point A closer to the tail.

[0114] Specifically, with the nose of the vertical take-off and landing aircraft facing forward, the center point B of the 2N tilt-rotors is located behind the center point A of the 2M fixed rotors, and the distance from point A to point B is L2, L2>0. As the 2N tilt-rotors tilt forward, the center of gravity of the 2N tilt-rotors, the center of gravity G of the vertical take-off and landing aircraft, and the symmetry center point B will move toward the nose. During the entire tilting process from the preset vertical take-off and landing position (for example, a 90° tilt angle) of the 2N tilt-rotors to the preset cruise position (for example, a 0° tilt angle), L2 is always>0. At the same time, the center of gravity G of the vertical take-off and landing aircraft is in front of the symmetry center B of the 2N tilt-rotors, and is also in front of the symmetry center A of the 2M fixed rotors. The distance from point A to point G is L1, L1≥0, and as the 2N tilt-rotors tilt forward, the center of gravity G gradually moves forward, and the absolute value of L1 becomes larger and larger. Under this layout, the center of gravity of the vertical take-off and landing aircraft and the center of symmetry of the fixed rotor or the center of symmetry of the tilt-rotor do not coincide with each other, and during the transition of the vertical take-off and landing aircraft from the vertical take-off and landing state to the cruising state, both point G and point B move along the symmetry plane toward the side close to the nose, and point G is located on the side of point A close to the nose or coincides with point A, and point B is always located on the side of point A close to the tail 30. Therefore, the pulling force generated by the tilt-rotor and the fixed rotor in front of the center of gravity has a smaller torque on the center of gravity point G, and the pulling force generated by the tilt-rotor and the fixed rotor behind the center of gravity has a larger torque on the center of gravity point G. The torque difference between the front and rear rotors can resist part of the nose-up torque generated by the tilt-rotor wash area on the tail wing, thereby reducing the difficulty of pitch control. Therefore, when the fixed rotors or tilt rotors on the front and rear sides of the center of gravity G have the same throttle speed, a nose-down moment will be generated due to the difference in the length of the lever arm of the center of gravity G. The nose-down moment can be used to offset or partially offset the nose-up moment generated by the tilt rotor wash area on the tail wing. Therefore, the vertical take-off and landing aircraft can better balance the pitch moment when the throttles of the front and rear rotors are consistent.

[0115] Furthermore, during the tilt conversion phase of the tiltrotor, due to aerodynamic interference, the vertical take-off and landing aircraft will also generate an additional large nose-up torque, and during the tilting process of the tiltrotor, the center of gravity G of the vertical take-off and landing aircraft gradually moves toward the nose as the tilting process progresses, and the symmetry center B of the tiltrotor also gradually moves forward of the nose. Since the center of gravity G is always in front of point B, the torque difference between the tiltrotor in front of the center of gravity G and the tiltrotor behind the center of gravity G during the entire tilting phase can also generate a part of the nose-down torque, thereby offsetting or partially offsetting the nose-up torque caused by aerodynamic interference.

[0116] Furthermore, during the tilting and cruising phases, the center of gravity point G is closer to the front side relative to points A and B, and point B is always located on the side of point A close to the tail 30. Therefore, it has a relatively large longitudinal and directional static stability margin, the aircraft is more capable of resisting extreme windy weather, and the flight is safer.

[0117] Referring to Figure 26 , in one embodiment of the vertical take-off and landing (VTOL) aircraft of the present application, the tail 30 is a V-shaped tail. A third tilt-rotor 43 is mounted on one wingtip of the V-shaped tail, and a fourth tilt-rotor 44 is mounted on the other wingtip. The third and fourth tilt-rotors 43 and 44 are symmetrical about a fuselage symmetry plane 60. In the vertical take-off and landing (VTOL) configuration, the distance between the center of rotation of the tail tilt-rotor and the leading edge of the V-shaped tail wingtip, along a direction parallel to the aircraft's roll axis X, is t1. The chord length of the V-shaped tail wingtip is t2, with the ratio of t1 to t2 being 15% to 40%. According to a stress analysis of the wingtip structural strength of the tail 30, the tilt mechanism is connected to the wingtip within this range of the tail 30, and the tail 30 is thicker, resulting in better stress resistance.

[0118] In one embodiment of the vertical take-off and landing aircraft of the present application, the tilt-rotor located on the tail is a full-tilt rotor; the tilt-rotor located outside the tail is a partial-tilt rotor. In other embodiments, the tilt-rotor located outside the tail may also be a full-tilt rotor. In particular, when the tilt-rotor is mounted on the wingtip, the tilt-rotor located on the wingtip may also be a full-tilt rotor. Conventional tilt-rotors often include a rotor and a power pod 442, which may house a motor and control components. In the aforementioned "partial-tilt rotor," the power pod 442 is often truncated. During rotor tilt, the portion closest to the rotor tilts with it, while the portion farther from the rotor remains fixed relative to the fuselage 10. In contrast, in the aforementioned "full-tilt rotor," the entire power pod 442 tilts with the corresponding rotor. It should be noted that if installation conditions permit, all 2N tilt-rotors can be full-tilt rotors. However, considering that the tilt-rotors on the fuselage 10 or wings 20 in front of the tail 30 are mostly mounted on arms, referring to Figures 1 to 6 , in the embodiments of this application, the tilt-rotors on the tail 30 are full-tilt rotors, while the tilt-rotors on the fuselage 10 or wings 20 in front of the tail 30 are partial-tilt rotors. The specific location and installation method of the partial-tilt rotors on the wings 20 or fuselage 10 are not particularly limited. For example, they can be mounted directly on the wings 20 or via arms.

[0119] 2N tilt-rotors are symmetrically arranged around the fuselage 10, and a tilt-rotor with a full-tilt structure is provided on the tail 30. Since the full-tilt rotor is rotatably mounted on the tail 30 via the power pod 442, the power pod 442 follows the synchronous tilting when the full-tilt rotor tilts. The power pod 442 on the tail 30 and the rotor are always on the same rotation axis. This reduces the shielding area of ​​the power pod 442 in the corresponding rotor when the vertical take-off and landing aircraft is hovering, reduces the area of ​​the rotor downwash that hits the tail 30, reduces the mutual interference between the airflow generated by the rotor and the airflow generated by the tail 30, reduces the nose-up moment experienced by the aircraft when hovering, and simplifies the control of the pitching moment of the vertical take-off and landing aircraft in a complex interference flow field.

[0120] The fully tilting rotor structure in this application can be any existing tilting rotor structure that can achieve synchronous tilting of the power pod 442 as a whole with the rotor. Please refer to Figures 10 and 18. In one embodiment of the vertical take-off and landing aircraft of this application, the fully tilting rotor includes a first rotor 441 and a power pod 442. The first rotor 441 is connected to the power pod 442. The power pod 442 is rotatably connected to the tail 30 or the wing 20 and tilts synchronously with the first rotor 441 during the tilting process of the first rotor 441. The housing of the power pod 442 contains a power device. For example, if it is a pure electric configuration, it may include a motor, electronic control, environmental control device, tilt mechanism, etc.; if it is a petrol configuration, the pod contains an engine, ECU, tilt mechanism, etc. Of course, the present embodiment preferably adopts a pure electric configuration.

[0121] Referring to Figure 10 , in one embodiment of the vertical take-off and landing aircraft of the present application, a fairing 4413 is disposed at the center of the first rotor 441. Fairing 4413 is mounted on the windward side of the first rotor 441 and serves to reduce airflow resistance. Preferably, along the direction of extension of the rotation axis of the first rotor 441, the projection of fairing 4413 covers the projection of the power pod 442. This arrangement can reduce the impact of the power pod 442 on the rotor downwash during flight. However, those skilled in the art will appreciate that the projection of the power pod 442 can also be partially located within the projection of fairing 4413, which can also partially reduce drag, but the effect will be less pronounced than in the case of full coverage.

[0122] The shape of the power pod 442 includes, but is not limited to, a solid of revolution, a square, an ellipsoid, etc. Preferably, in one embodiment of the vertical take-off and landing aircraft of the present application, the power pod 442 is a solid of revolution structure, the rotation axis of the solid of revolution structure being coaxial with the rotation axis of the first rotor 441; and the surface of the power pod 442 is streamlined. This can reduce the impact of the power pod 442 on the corresponding rotor downwash area during flight.

[0123] Referring to Figures 10 to 17 , the first rotor 441 includes a propeller 4411 and a rotation drive unit 4412. The propeller 4411 is mounted on the output shaft of the rotation drive unit 4412. The power pod 442 includes a pod housing 4431 and a tilt mechanism located within the pod housing 4431. The tilt mechanism drives the rotation drive unit 4412 to tilt. The tilt mechanism herein may be any suitable type of tilt mechanism capable of driving the power pod 442 and the rotation drive unit 4412 to tilt synchronously. Preferably, in this embodiment, the tilt mechanism includes a rocker arm 4422, a drive arm 4429, a tilt drive unit 4421, and a connecting rod 4426. The tilt drive unit 4421 may be any suitable structure having a rotation output shaft, such as a servo, a combination of a servo and a reducer, etc. In this application, the tilt drive unit 4421 is a servo. The rocker arm 4422 is rotatably mounted on the tail 30, and one end of the rocker arm 4422 close to the rotation drive device 4412 is fixedly connected to the rotation drive device 4412; the driving arm 4429 is rotatably mounted on the tail 30, and the rotation axis of the driving arm 4429 is arranged parallel to the rotation axis of the rocker arm 4422; the base of the tilting drive device 4421 is fixedly mounted on the tail 30, and the driving end of the tilting drive device 4421 drives the driving arm 4429 to rotate; one end of the connecting rod 4426 is connected to the driving arm 4429 by the connecting rod 4426. A first hinge axis 4427 is hinged to the rocker arm 4422, and the other end of the connecting rod 4426 is hinged to the drive arm 4429 via a second hinge axis 4428. Although the first hinge axis 4427 and the second hinge axis 4428 can be positioned without bearings 4430, preferably, bearings 4430 are provided between the connecting rod 4426 and the first hinge axis 4427, and between the connecting rod 4426 and the second hinge axis 4428. This can further stabilize the tilting process. The tilting mechanism described above can achieve a dual-axis connection structure with the tail 30 via the rotating axis of the rocker arm 4422 and the rotating axis of the drive arm 4429. The torque borne by the tilting mechanism can be increased by increasing the axial distance between the rotating axis between the rocker arm 4422 and the tail 30 and the rotating axis between the drive arm 4429 and the tail 30, thereby reducing the force exerted on the single rod, thereby enhancing the mechanism's torsional resistance and improving the mechanism's support rigidity. This setup allows the tilt mechanism to be fixed to the aircraft using a single-sided support method, reducing the drive requirements through the four-bar linkage. At the same time, the stiffness of the entire mechanism and the natural frequency can be easily adjusted by adjusting the length ratio between the four links.

[0124] Please refer to Figures 11 to 17. Preferably, in this embodiment, a first shaft 4423 and a second shaft 4424 parallel to each other are fixedly provided on the tail 30, one end of the first shaft 4423 and the second shaft 4424 are fixed on the wing tip of the tail 30, and the other end of the first shaft 4423 and the second shaft 4424 are cantilevered out, the rocker arm 4422 is rotatably mounted on the first shaft 4423 through a bearing 4430, the driving arm 4429 is rotatably mounted on the second shaft 4424 through a bearing 4430, the base of the tilt driving device 4421 is rotatably mounted on the first shaft 4423 through a holding structure 4425, and is positioned along the axial direction of the first shaft 4423, the driving end of the tilt driving device 4421 is coaxial with the second shaft 4424 and fixedly connected to the driving arm 4429. This arrangement, while simultaneously facilitating the positioning and installation of the tilt drive unit 4421 through the mounting structure 4425 and the second shaft 4424, also reduces the difficulty of installing the tilt mechanism within the power pod 442 housing, thereby improving the stability of a single-sided installation of the fully tilting rotor. It should be noted that in other embodiments, the tilt drive unit 4421 may be fixedly mounted on the empennage 30, with the output shaft of the tilt drive unit 4421 extending and fixedly connected to the drive arm 4429, thereby driving the connecting rod 4426 to tilt the rocker arm 4422. However, compared to this embodiment, this arrangement occupies a larger space within the empennage 30 and is unsuitable for thinner airfoils or those with a large number of internal devices. Furthermore, the torque applied to the tilt drive unit 4421 ultimately relies entirely on the mounting base of the tilt drive unit 4421, placing greater demands on the mounting strength of the tilt drive unit 4421.

[0125] Please refer to Figures 11 to 17. The first shaft 4423 and the second shaft 4424 can also be limited to each other by the above-mentioned embracing structure 4425, thereby strengthening the structural strength of the first shaft 4423 and the second shaft 4424 set on the tail wing 30, so that the first shaft 4423 and the second shaft 4424 maintain a parallel position relationship with each other on the tail wing 30, ensuring that the driving device and the rocker arm 4422 maintain the same horizontal plane during the tilting drive process, thereby realizing a smooth tilting drive of the rocker arm 4422 by the driving device. One end of the embracing structure 4425 is fixedly connected to the base of the tilting drive device 4421. Specifically, one end of the embracing structure 4425 is arranged around the periphery of the base of the tilting drive device 4421. More specifically, one end of the embracing structure 4425 is fixedly connected to the base of the tilting drive device 4421 and is coaxially installed on the second shaft 4424. The other end of the embracing structure 4425 surrounds and tightly embraces the first shaft 4423. Specifically, as shown in Figure 15, the other end of the embracing structure 4425 is interference fit around the periphery of the first shaft 4423 to achieve a tight embrace with the first shaft 4423. More specifically, a slit 44251 is provided on the other end of the embracing structure 4425. The slit 44251 extends from the outer edge of the other end of the embracing structure 4425 to the inner wall that conflicts with the first shaft 4423, and the gap of the slit 44251 extends axially along the first shaft 4423. The other end of the holding structure 4425 utilizes the elastic expansion and contraction characteristics of the slit 44251 to achieve surrounding and tightening of the first shaft body 4423 with different outer diameters, thereby expanding the tolerance range allowed by the interference fit between the holding structure 4425 and the first shaft body 4423.

[0126] In the present application, the first shaft 4423 and / or the second shaft 4424 are hollow shafts, through which cables and pipes can be threaded, preventing the cables and pipes from swinging irregularly outside and damaging the cables, while also reducing the range of motion of the cables and pipes to prevent damage to the cables. Considering that the second shaft 4424 needs to withstand a large load, preferably, in this embodiment, the first shaft 4423 is a hollow shaft and the second shaft 4424 is a solid shaft. Of course, in other embodiments, if the second shaft 4424 can withstand a large load, the second shaft 4424 can also be set as a hollow shaft, or both the first shaft 4423 and the second shaft 4424 can be set as hollow shafts.

[0127] It should be noted that, considering that the entire tilting mechanism is installed on one side, the longer extension distance of the first shaft 4423 will lead to an increase in the bending moment of the first shaft 4423. Preferably, please refer to Figure 12. In one embodiment, the first shaft 4423 and the tail wing 30 are installed with an axially longer mating surface 4432. This arrangement can increase the installation length of the first shaft 4423 and increase the contact area between the first shaft 4423 and the base of the tilting drive device to balance the bending moment of the first shaft 4423, thereby reducing the bending deformation of the first shaft 4423 and improving the installation stability of the entire mechanism.

[0128] In one embodiment of the present application, the distance from the rotation center of the tilt drive device 4421 to the axis center of the second hinge shaft 4428 is a, the distance from the axis center of the first hinge shaft 4427 to the axis center of the second hinge shaft 4428 is b, the distance from the center of the first shaft body 4423 to the axis center of the first hinge shaft 4427 is c, and the distance from the center of the first shaft body 4423 to the center of the second shaft body 4424 is d, a is respectively smaller than b, c, and d, c is respectively larger than b and d, and the sum of a and c is smaller than the sum of b and d. In this way, once the tilt drive device 4421 gets out of control, the output shaft of the tilt drive device 4421 will be in a forward or reverse state all the time, and the rocker arm 4422 will swing, that is, the rocker arm 4422 will rotate counterclockwise after rotating clockwise to the extreme position, and will rotate clockwise after rotating counterclockwise to the extreme position. In this way, the range of motion of the tilt mechanism is limited, so that the tilt mechanism will not rotate beyond the range and collide with other components, etc., to prevent the front propeller from colliding with the fuselage and other structures due to excessive tilting, thereby preventing the fuselage and other structures from being damaged. Therefore, the present application can constrain the tilting angle range of the tilting mechanism by adjusting the length ratio of each component in the tilting mechanism, and at the same time cleverly solve the limit problem of the tilting mechanism, so that the limit position of the positive rotation of the tilting mechanism and the limit position of the reverse rotation are both at the same limit position of the connecting rod. This clever design can not only effectively ensure the safety of the mechanism, but also simplify the design. There is no need to set up an additional limit mechanism to limit the limit position, which greatly optimizes the installation space of the transmission rod mechanism during the movement process; specifically, by adjusting the length ratio of each component in the connecting rod mechanism For example, the distances between the distal end axis of the driving arm 4429 (i.e., the axis of the second hinged axis 4428) and the axis of the first shaft 4423 are equal in both the initial angle state (i.e., the minimum tilt angle) and the final angle state (i.e., the maximum tilt angle). Furthermore, the angle between the plane formed by the distal end axis of the driving arm 4429 and the axis of the first shaft 4423 in the initial angle state and the plane formed by the distal end axis of the driving arm 4429 and the axis of the first shaft 4423 in the final angle state is equal to ±5° of the rotation angle of the rocker arm 4422. This allows one limit point to constrain two directions.

[0129] In this embodiment, the above-mentioned tilting mechanism has different reduction ratios at different tilting angles, which achieves the control accuracy requirements at different angles. It has a compact structure and a centralized layout, which reduces space requirements. And through the use of multiple links, the reduction ratio changes with the change of angle, which can increase the reduction ratio at large loads and reduce the reduction ratio at small loads, thereby reducing the peak driving torque and reducing the demand for drive. In addition, the tilting drive device of the present application is a rotary drive structure, which can amplify the driving force through the brake or reduction ratio adjustment device inside the tilting device. On the one hand, it can overcome the torque borne by the execution end to achieve state maintenance at any position, maintain the current state position when the drive fails, and continue to work after the drive is restored. On the other hand, it can make the layout of the structural parts more centralized.

[0130] As shown in Figures 1 to 7 and Figures 20 to 23, in one embodiment of the VTOL aircraft of the present application, the tilt-rotor's rotation axis tilts within a range of -20° to 110°, with the roll axis X as the reference and the upward direction as the positive direction. Referring to Figure 21, 0° represents the tilt-rotor's rotation axis extending forward along the roll axis X; referring to Figure 23, 90° represents the tilt-rotor's rotation axis extending vertically upward; and referring to Figure 22, the tilt-rotor's rotation axis tilts between 0° and 90°. It should be noted that when the tilt angle range is 90° to 110°, the VTOL aircraft can fly with its nose pointing forward and backward, greatly expanding the VTOL aircraft's flight envelope and capabilities and reducing the risk of the VTOL aircraft needing to turn around mid-air. When the vertical take-off and landing aircraft needs to take off, the tilt angle of all the inner tilt rotors can be set to any angle between 0° and 90° according to flight control requirements, for example, 0°, 30°, 45°, 60° or 90°.

[0131] The number of tilt-rotors on the tail 30 can be any even number less than 2N. Preferably, referring to Figures 5 to 9, in this embodiment, the vertical take-off and landing aircraft includes four tilt-rotors and four fixed rotors. The four fixed rotors are symmetrically mounted on either side of the fuselage 10. The four tilt-rotors are located inwardly of the span of the four fixed rotors. Two of the tilt-rotors are mounted on the tail 30, and two are mounted on the fuselage 10 or the wing 20 in front of the wing 20. Specifically, the four tilt-rotors are divided into two equal groups, labeled as a first group of tilt-rotors and a second group of tilt-rotors. The first group of tilt-rotors is mounted on the fuselage 10 or the wing 20 in front of the center of gravity G of the vertical take-off and landing aircraft, and the second group of tilt-rotors is mounted on the tail 30 in rear of the center of gravity G of the vertical take-off and landing aircraft. The first tilt-rotor group includes a first tilt-rotor 41 and a second tilt-rotor 42, while the second tilt-rotor group includes a third tilt-rotor 43 and a fourth tilt-rotor 44. The first tilt-rotor 41 is mounted on the third arm 411, and the second tilt-rotor 42 is mounted on the fourth arm 421, symmetrically with the first tilt-rotor 41 about the plane of symmetry 60 of the fuselage 10. The third tilt-rotor 43 is mounted on the empennage 30 via a first power pod 442, and the fourth tilt-rotor 44 is mounted on the empennage 30 via a second power pod 442. The first power pod 442 and the second power pod 442 are symmetrically arranged about the plane of symmetry 60 of the fuselage 10, and the fourth tilt-rotor 44 is symmetrically arranged about the plane of symmetry 60 of the fuselage 10 with the third tilt-rotor 43.

[0132] In the vertical takeoff and landing (VTOL) configuration, the rotation axes of the four tilt-rotors are tilted upward in the vertical direction. The first, second, third, and fourth tilt-rotors 41, 42, 43, and 44 are distributed on a first circumference centered at point B. The projections of the first and fourth tilt-rotors 41, 44 on a horizontal plane are centrally symmetrical about point B, while the projections of the second and third tilt-rotors 42, 43 on a horizontal plane are centrally symmetrical about point B.

[0133] Referring to Figure 7 , the four fixed rotors are divided into two equal groups, designated as the first and second groups. The first group of fixed rotors is mounted on the wing 20 forward of the vertical take-off and landing vehicle's center of gravity, while the second group of fixed rotors is mounted on the wing 20 aft of the vertical take-off and landing vehicle's center of gravity. The first group of fixed rotors includes a first fixed rotor 51 and a second fixed rotor 52, while the second group of fixed rotors includes a third fixed rotor 53 and a fourth fixed rotor 54. The first, second, third, and fourth fixed rotors 51, 52, 53, and 54 are all distributed along a second circumference centered at point A. The first and second fixed rotors 51, 52 are symmetrical about the plane of symmetry 60 of the fuselage 10. The third and fourth fixed rotors 53, 54 are also symmetrical about the plane of symmetry 60 of the fuselage 10. The rotating shafts of all four fixed rotors extend upward. The projections of the first and fourth fixed rotors 51, 54 on the horizontal plane are centrally symmetrical about point A. The projections of the second and third fixed rotors 52, 53 on the horizontal plane are centrally symmetrical about point A. It should be noted that in this application, the front side refers to the direction extending toward the nose of the aircraft, and the rear side refers to the direction extending toward the side of the tail 30.

[0134] In one embodiment of the vertical take-off and landing aircraft of the present application, the spacing between the four fixed rotors along the fuselage extension direction, i.e., the spacing between the second fixed rotor 52 and the fourth fixed rotor 54, or the spacing between the first fixed rotor 51 and the third fixed rotor 53, is L3. The spacing between the four tilt rotors along the fuselage extension direction, i.e., the spacing between the second tilt rotor 42 and the fourth tilt rotor 44, or the spacing between the first tilt rotor 41 and the third tilt rotor 43, is L4. Thus, 0.1(L3+L4)≥4L1+2L2≥0.01(L3+L4). This arrangement allows the center of gravity (G) to be closer to the front of points A and B during the tilting and cruising phases, with point B always located on the side of point A closer to the empennage 30. This provides relatively large longitudinal and directional static stability margins, enhances the aircraft's ability to withstand extreme winds, and improves flight safety.

[0135] Please refer to Figure 7. A first arm 511 is installed on the wing 20 on one side of the fuselage 10, and a second arm 521 is installed on the wing 20 on the other side of the fuselage 10. The first arm 511 and the second arm 521 are symmetrically arranged about the symmetry plane 60 of the fuselage 10. The 2M fixed rotors are symmetrically installed on the first arm 511 and the second arm 521 on both sides of the fuselage 10, and are respectively located on the front and rear sides of the wing 20 and the front and rear ends of the first arm 511 and the second arm 521. At the same time, the projections of all the fixed rotors on the horizontal plane are roughly centrally symmetrical about point A.

[0136] Please refer to Figures 1 to 4. In one embodiment, unlike the vertical take-off and landing aircraft in Figures 5 to 9, the vertical take-off and landing aircraft in this embodiment only includes four tilt-rotors and does not have fixed rotors. The four tilt-rotors are symmetrically installed on both sides of the fuselage 10, of which two of the tilt-rotors are symmetrically installed on the wings 20 with respect to the fuselage 10. The structure of the four tilt-rotors and the installation relationship corresponding to the fuselage are the same as those in Figures 5 to 9 and Figure 34. The specific positions are adaptively adjusted according to the aircraft and will not be repeated here.

[0137] Unlike the vertical take-off and landing aircraft shown in Figures 1 to 4 , in another embodiment of the vertical take-off and landing aircraft of the present application, the aircraft includes six tilt-rotors instead of fixed rotors. The six tilt-rotors are symmetrically mounted on either side of the fuselage 10. Four of the tilt-rotors are symmetrically mounted on the wings 20 with respect to the fuselage 10, and the remaining two are symmetrically mounted on the empennage 30. The empennage 30 is a V-shaped tail, and the two tilt-rotors located on the tail 30 are full-tilt rotors. The two full-tilt rotors are mounted on either side of the wingtips of the upper portion of the V-shaped tail, respectively. The two tilt-rotors are located on the wingtips of the wings 20 on either side of the fuselage 10 and are symmetrical about a plane of symmetry 60 of the fuselage 10. The tilt-rotors located on the wingtips of the wings 20 are preferably full-tilt rotors. The remaining two tilt-rotors are mounted on the front side of the wing 20 via arms and are partial-tilt rotors. However, it should be noted that, if conditions permit, the tilt rotor mounted on the front side of the wing 20 via the arm may also be a full-tilt rotor.

[0138] In the present application, the installation location and structure of the elevator rudder 31 can be various. For example, it can be set at any suitable location on the tail wing 30, and can also adopt any existing suitable elevator rudder 31 structure. Specifically, referring to Figures 5 and 17, the elevator rudder 31 includes a rudder plate 311 and a rudder body drive device (not shown). The rudder plate 311 is rotatably connected to the tail of the tail wing 30 or the fuselage 10. The rudder body drive device drives the rudder plate 311 to rotate to adjust the direction of the vertical take-off and landing aircraft. The elevator rudder 31 drive device includes but is not limited to a motor, or a combination of a motor and a reducer.

[0139] Referring to Figure 25 , in some embodiments, the ratio of the chord length of the rudder plate 311 to the chord length of the empennage 30 is 15% to 100%. For example, it can be any value between 15%, 30%, 45%, 60%, 90%, 100%, or the like. For example, as shown in Figure 18 , the chord length of the rudder plate 311 accounts for 30% of the chord length of the empennage 30; as shown in Figure 19 , the chord length of the rudder plate 311 accounts for 60% of the chord length of the empennage 30; and as shown in Figure 20 , the chord length of the rudder plate 311 accounts for 100% of the chord length of the empennage 30. However, the ratios are not limited to those in Figures 18 and 20 . It should be noted that, referring to Figure 25 , the chord length is the distance from the leading edge to the trailing edge of the cross-section of the empennage 30 airfoil. The chord length ratio is the ratio of the length of the rudder plate on the empennage 30 in the heading direction to the length of the empennage 30 (not the length ratio along the spanwise direction Y) as viewed from above.

[0140] Please refer to Figure 18. In one embodiment of the vertical take-off and landing aircraft of the present application, with the roll axis X as a reference and the upward direction as the positive direction, the deflection angle of the rudder plate 311 is -90° to 30°. For example, as shown in Figure 23, the deflection angle of the rudder plate 311 can be any angle between -90° and 30°, such as -90°, -60°, -30°, -15°, 0°, 15° and 30°.

[0141] The rotation axes of the 2N tilt-rotors and 2M fixed rotors in the present application can also be arranged in the vertical direction in the vertical take-off and landing state. Preferably, please refer to Figure 9. In one embodiment of the vertical take-off and landing aircraft of the present application, the 2N tilt-rotors are symmetrically arranged on both sides of the fuselage 10, and the angle α between the plane formed by the rotation axis of the rotor during the tilting process (that is, the plane formed by the rotation axis of the rotor rotating around the tilt axis) and the symmetry plane 60 of the fuselage 10 is -15° to +15°. For example, it can be any angle between -15° and +15°, such as -15°, -10°, 0°, 10°, 15°, etc., and the angle is positive from bottom to top to the outside, and negative from bottom to top to the symmetry plane 60. The angle between the rotation axis of the 2M fixed rotors and the symmetry plane of the fuselage is -15° to +15°. For example, it can be any angle between -15° and +15°, such as -15°, -10°, 0°, 10°, 15°, etc., and is positive when it extends from bottom to top and outward, and negative when it tilts from bottom to top toward the symmetry plane 60.

[0142] In the present application, the tail 30 can be any one of a V-shaped tail, a Y-shaped tail, an H-shaped tail, an X-shaped tail, a T-shaped tail, an H-shaped tail, or a U-shaped tail. The tilt-rotors on the tail 30 are mounted on the upper side of the tail 30 and tilt upward during vertical takeoff and landing. This reduces the possibility of the rotors causing harm to passengers when entering or exiting the aircraft. Referring to Figures 1 to 4, in this embodiment, the tail 30 is a V-shaped tail, and two tilt-rotors are mounted on the tail 30, respectively, at the wingtips on both sides of the upper portion of the tail 30. In other embodiments, the tail 30 can also have any of the above shapes.

[0143] It should be noted that, in this embodiment, when the vertical take-off and landing aircraft is flying forward in a cruising state, the rotation axis of the tilt-rotor on the tail wing 30 and the rotation axis of the tilt-rotor at other positions may extend along the roll axis X. However, in other embodiments, the rotation axis of the tilt-rotor on the tail wing 30 and the rotation axis of the tilt-rotor at other positions may not extend along the roll axis X, but may be within the vertical plane where the roll axis X is located, within a range of ±20° with the roll axis X as a reference. Furthermore, in the present application, the control of the power pods 442 of the tilt-rotors projected at different roll axis X coordinate positions along the roll axis X direction can also be independent of each other, and the tilting can also be independently controlled without being correlated with each other. In this mode, the tilt angles of the front tilt-rotors and the tilt-rotors on the tail wing 30 can be inconsistent, and the tilting process can be asynchronous. For example, with the roll axis X as 0°, the angle above the roll axis X as positive, and the angle below the roll axis X as negative, the tilt angle of the power pod 442 of the tilt-rotor on the front fuselage 10 or wing 20 can be 10°, and the tilt angle of the power pod 442 of the tilt-rotor on the rear fuselage 10 or wing 20 can be -10°.

[0144] It should be noted that when the vertical take-off and landing aircraft of the present application is in the vertical take-off and landing state, the rotation axis of the tilt-rotor on the tail wing 30 and the rotation axis of the tilt-rotor in other positions may or may not extend upward in the vertical direction. That is, the tilt angle of the front tilt-rotor and the tilt-rotor on the tail wing 30 is not limited to a tilt angle of 90°. To enhance controllability, the tilt angle of the rotation axis of the front tilt-rotor and the tilt-rotor on the tail wing 30 can be any value between 70° and 110°, for example, 70°, 80°, 90°, 100°, and 110°. The rotation and tilt control of each of the 2N tilt-rotors is relatively independent. The tilt angles of the 2N tilt-rotors can be completely consistent, different between any two, or partially consistent. For example, the tilt angles of the multiple tilt-rotors on the fuselage 10 or wing 20 located in front of the tail 30 can be consistent, labeled as the first tilt angle, while the tilt angles of the tilt-rotors on the rear tail 30 can be consistent, labeled as the second tilt angle. The first tilt angle is different from the second tilt angle. For example, the first tilt angle can be 100° and the second tilt angle can be 80°. This allows different pitch trim moments to be obtained at different locations. It should be noted that the tilt angle is the angle between the rotation axis of the tilt-rotor and the roll axis X, with the center point of the tilt axis of the tilt-rotor as the vertex.

[0145] Because the rearmost of the 2N tilt-rotors is located on the tail 30, the tilt-rotors on the tail 30 need to be positioned forward to ensure that the centers of the 2N tilt-rotors are located at a predetermined position. However, considering that lengthening the tilt-rotor pod would reduce the overall rigidity of the vertical take-off and landing aircraft, thereby reducing safety, in one embodiment of the present application, the tail 30 is configured as a forward-swept type, and the tilt-rotors located on the forward-swept tail are fully tilt-rotors. The forward sweep angle of the tail 30 is not limited, and is preferably selected to balance the layout of the 2N tilt-rotors while not affecting the overall rigidity of the vertical take-off and landing aircraft.

[0146] Considering that the forward sweep of the tail 30 will shorten the moment arm of the tail 30 in the fixed-wing flight mode, the horizontal tail (horizontal projection of the tail 30) capacity and the vertical tail (vertical projection of the tail 30) capacity of the tail 30 are greatly reduced, and the side projection area of ​​the fuselage 10 in front of the aerodynamic focus is larger than the side projection area of ​​the fuselage 10 behind the aerodynamic focus. Therefore, the effective area of ​​the vertical tail will be further reduced. However, blindly increasing the area of ​​the tail 30 will make the overall layout of the aircraft out of control, and ultimately cause insufficient vertical tail capacity, resulting in insufficient lateral stability of the aircraft in the fixed-wing flight mode, and even The heading is in a statically unstable state, and the dynamic stability modal flight quality of the lateral heading is low, which poses a high difficulty for flight control. In order to solve the above problems, please refer to Figure 9. A tail fin is provided below the forward-swept tail wing 30, and the tail fin is connected to the tail of the fuselage 10. The structure and number of the tail fin can be not too limited. The structure of the tail fin can refer to all existing suitable tail fin structures, and can include one tail fin body or multiple tail fin bodies, as long as the tail wing 30 and the tail fin have sufficient vertical tail capacity to make the vertical take-off and landing aircraft stable in the lateral heading when flying in the fixed-wing mode.

[0147] Referring to Figures 7 and 28 to 32, the present application provides a control method for a vertical take-off and landing aircraft, wherein the vertical take-off and landing aircraft includes: a fuselage and 2N tilt-rotors. The fuselage 10 is a symmetrical structure and has a symmetry plane 60 extending along the length of the fuselage 10. Wings 20 are provided on both sides of the fuselage 10, and the wings 20 on both sides are symmetrical with respect to the symmetry plane 60 of the fuselage 10. A tail fin 30 is provided at the tail of the fuselage 10, and an elevator rudder 31 is provided on the tail fin 30. 2N tilt-rotors are mounted on both sides of the fuselage 10, where N is a natural number greater than or equal to 2. The 2N tilt-rotors are symmetrically arranged about the symmetry plane 60 of the fuselage 10, and a portion of the 2N tilt-rotors are mounted on the tail fin 30. In the vertical take-off and landing state, the projections of the 2N propellers of the tilt-rotor on the horizontal plane are centrally symmetrical about point B, and point B and the center of gravity G of the vertical take-off and landing aircraft are both located in the symmetry plane of the fuselage, and point B is located on the side of point G close to the tail wing. During the transition of the vertical take-off and landing aircraft from the vertical take-off and landing state to the cruising state, point G and point B both move along the symmetry plane toward the side close to the nose, and point B is always located on the side of point G close to the tail wing.

[0148] In one embodiment of the vertical take-off and landing aircraft of the present application, the following method is used for pitch control:

[0149] During flight, the pitch control ratios of the elevator rudder 31, the 2N tilt rotors, and the 2M fixed rotors are allocated according to the current airspeed or dynamic pressure; according to the pitch control ratios, the elevator rudder 31, the 2N tilt rotors, and the 2M fixed rotors are controlled separately to achieve pitch trim and manipulation.

[0150] In one embodiment of the vertical take-off and landing aircraft of the present application, controlling the 2N tilt-rotors according to the pitch control ratio includes: a tilt angle differential adjustment process: differentially adjusting the pitch moment for pitch trim and maneuvering based on the tilt angle difference between the tilt-rotor on the tail 30 and any other tilt-rotor located in front of the tail 30; and / or a rotational speed differential adjustment process: differentially adjusting the pitch moment for pitch trim and maneuvering based on the rotational speed difference between the tilt-rotor on the tail 30 and any other tilt-rotor located in front of the tail 30; and / or a tilt speed differential adjustment process: differentially adjusting the pitch moment for pitch trim and maneuvering based on the tilt speed difference between the tilt-rotor on the tail 30 and any other tilt-rotor located in front of the tail 30. It should be noted that the aforementioned tilt angle differential adjustment process, rotational speed differential adjustment process, and tilt speed differential adjustment process can be implemented individually, in combination, or all three simultaneously.

[0151] Please refer to Figure 28. The flight process includes four stages in sequence, specifically: S100, ground preparation process, S200, take-off control process, S300, take-off and level flight control process and S400, cruising state.

[0152] S100, ground preparation process. The ground preparation process first requires starting the vertical take-off and landing aircraft, and powering on the system for testing, and then confirming the full stroke status of the servo system such as the tilt mechanism and the elevator rudder 31.

[0153] S200, takeoff control process. The takeoff control process is the process of the vertical takeoff and landing aircraft climbing from the ground to a set altitude. During this process, the tilt rotor and fixed rotor mostly maintain the tilt angle and rotation speed unchanged. Compared with the transition to level flight, this process is relatively stable.

[0154] S300: Takeoff to level flight control process. The takeoff to level flight control process often involves changes in the tilt rotor tilt angle and / or the rotation speed of the tilt rotor and / or fixed rotor. Therefore, the pitch impact force during this process is relatively large, making the control of the vertical take-off and landing aircraft relatively difficult.

[0155] S400, cruising state. In the cruising state, the vertical take-off and landing aircraft performs level flight and sails in a horizontal direction, which is relatively stable.

[0156] Referring to FIG. 32 , in one embodiment, the takeoff control process of step S200 includes the following steps:

[0157] S211. Tilt the 2N tilt-rotors to a vertical take-off and landing position or a tilted position (e.g., between 0° and 90°) with their rotation axes vertically upward to provide power for climbing. The vertical take-off and landing position may be a position where the rotation axis of the tilt-rotor forms an angle of 90° with the roll axis; the tilted position may be a position where the rotation axis of the tilt-rotor forms an angle of 90° with the roll axis (excluding the endpoints);

[0158] S212, deflecting the elevator rudder 31 downward, so that the elevator rudder 31 participates in takeoff control;

[0159] S213: Start the 2N tilt-rotors, wait for the vertical take-off and landing aircraft to reach a set altitude, and issue a level flight command.

[0160] During the takeoff process from S211 to S213, if the tilt-rotor is set to 90°, the vertical takeoff and landing aircraft will take off vertically normally, and the 2N tilt-rotor throttles can be released in unison. At this time, the tilt-rotor on the tail 30 blocks the largest area during the vertical takeoff and transition phases, which will cause a large pitch-up moment. If the rotation axis of all tilt-rotors is set to an inclined position between 0° and 90°, when the aircraft takes off, the inner tilt-rotor will activate the throttle. Since the inner rotor provides a forward thrust component, the aircraft will climb upward at an angle. As the flight speed gradually increases, the tilt angle of the inner tilt-rotor gradually decreases until it tilts to 0° and switches to level flight fixed-wing mode. In this solution, the pitch-up moment caused by the tail 30 blocking the tilt-rotor is moderate, the control difficulty is relatively low, and the maximum thrust margin requirement for the power system is relatively low.

[0161] As an optimization, referring to FIG. 29 , in this embodiment, the takeoff-to-level flight control process at S300 includes the following steps:

[0162] S310: Respond to a level flight command. The level flight command may be issued by the pilot or automatically by the VTOL aircraft when it determines that preset flight conditions are met.

[0163] S320, rotor control process. This process is greatly affected by the S200 takeoff control process and will vary greatly depending on the state of the tilt rotor.

[0164] S330, pitch control process. Considering that during takeoff and level flight, the tilt rotor is often tilted to the set cruise position in which the tilt rotor rotation axis is parallel to the roll axis multiple times, and the vertical take-off and landing aircraft will be subjected to a certain pitch impact force during each tilting process, the pitch control process of S330 can be performed after each S320 rotor control process during takeoff and level flight.

[0165] S340: Repeat the rotor control process and the pitch control process until the tilt rotor is tilted to the cruise position, completing the takeoff and level flight transition. The cruise position may be, for example, a position where the tilt angle is 0° and the rotation axis of the tilt rotor is parallel to the roll axis.

[0166] Referring to FIG. 31 , in one embodiment, the rotor control process in step S320 includes the following steps:

[0167] S321. Obtain the current tilt position of each tilt rotor. This process can be done by setting an angle sensor on the tilt rotor to feed back the current tilt position to the central control system, or by directly feeding back the corresponding current tilt position to the central control system through the tilt drive device corresponding to the tilt rotor.

[0168] S322. If the current tilt position is inconsistent with the set cruise position, obtain the current airspeed or dynamic pressure of the corresponding tilt rotor at the current tilt position, and determine whether the current airspeed or dynamic pressure is equal to or greater than a preset threshold value at the current tilt position. It should be noted that the set cruise position is a preset position of the vertical take-off and landing aircraft in level flight, for example, it can be the 0° position where the rotation axis of the tilt rotor is parallel to the roll axis X, or it can be other positions between 0°±5°.

[0169] S323: If the current airspeed or dynamic pressure is equal to or greater than a preset threshold value at the current tilt position, control the tilt rotor to tilt to a preset next position;

[0170] S324. Gradually increase the rotational speed of the 2N tilt-rotors. If the vertical take-off and landing aircraft does not have 2M fixed rotors, as shown in FIG1 , the rotational speed of the 2N tilt-rotors can be gradually increased to obtain forward propulsion. However, if the vertical take-off and landing aircraft has 2N tilt-rotors and 2M fixed rotors, as shown in FIG7 , in order to achieve level flight, while gradually increasing the rotational speed of the 2N tilt-rotors, the rotational speed of the 2M fixed rotors must also be gradually reduced to a set speed.

[0171] Referring to Figure 7 , in another embodiment, the vertical take-off and landing aircraft includes 2M fixed rotors, where M is a natural number greater than or equal to 2. M can be the same as or different from N. The 2M fixed rotors are symmetrically mounted on the wings on both sides of the fuselage and are located outside the tilt-rotors. In the vertical take-off and landing state, the projections of all the fixed rotors on the horizontal plane are centrally symmetrical about point A. Point A is located within the symmetry plane of the fuselage and coincides with point G or is located on the side of point G closer to the tail. During the transition of the vertical take-off and landing aircraft from the vertical take-off and landing state to the cruising state, points G and B move along the symmetry plane toward the side closer to the nose, with point G located on the side closer to the nose of point A or coinciding with point A, and point B always located on the side of point A closer to the tail. Referring to Figure 33 , in one embodiment, the take-off process of the vertical take-off and landing aircraft in S200 is different from the processes from S211 to S213 in Figure 32 . The take-off process in S200 includes:

[0172] S221, tilting the 2N tiltrotors until the rotation axes are horizontally forward and parallel to the roll axis X;

[0173] S222, deflecting the elevator rudder 31 downward;

[0174] S223: Start the 2M fixed rotors and the 2N tilt rotors, and when the vertical take-off and landing aircraft reaches a set altitude, issue a level flight command.

[0175] During the takeoff process from S221 to S223, the rotation axes of all tilt-rotors are set to 0° (as shown in FIG7 ), and the aircraft changes to a compound wing mode. The aircraft takes off vertically by the outer multiple rotors. At this time, the output of the outer multiple rotors is twice that of control scheme 1. The inner tilt-rotors are gradually started during the vertical to level flight transition phase, and the throttle is gradually increased until the transition to level flight is successful. In this scheme, the inner tilt-rotor tail 30 has the smallest shielding area, generates the smallest nose-up moment, and is the simplest to control. It is basically a compound wing control mode, but the required power system tension margin is large and the power system requirements are high. This control mode is reduced in non-emergency situations.

[0176] Those skilled in the art will appreciate that, since the axis of the tilt rotor is always parallel to the roll axis X during the takeoff process from S221 to S223, the relevant processes from S321 to S323 are no longer required during the rotor control process S320 in the takeoff to level flight control process S300. Instead, it is only necessary to gradually increase the rotation speed of the 2N tilt rotors and gradually reduce the rotation speed of the 2M fixed rotors to the set rotation speed.

[0177] It should be noted that regardless of whether the rotor control process in S300 includes the tilt control process from S321 to S324, the vertical take-off and landing aircraft will be subjected to a high pitch impact force during the process of taking off and transitioning to level flight. Based on this, referring to FIG. 30 , in one embodiment of the present application, the pitch control process in step S330 includes:

[0178] S332: Allocate pitch control ratios for the elevator rudder 31, the 2N tilt-rotors, and the 2M fixed rotors based on the current airspeed or dynamic pressure. In this process, the pitch adjustment force is distributed to the elevator rudder 31, the 2N tilt-rotors, and the 2M fixed rotors according to a predetermined distribution rule based on the current speed of the vertical take-off and landing aircraft, thereby achieving relatively balanced pitch control through the pitch control ratios.

[0179] S333: Based on the pitch control ratio, the elevator rudder, the 2N tilt-rotors, and the 2M fixed rotors are controlled separately to achieve pitch trim and maneuverability. During this process, the central control system controls the elevator rudder 31, the 2N tilt-rotors, and the 2M fixed rotors based on the allocated pitch control ratio. For example, this may involve speed differential control, such as deflection of the elevator rudder 31, to generate different pitch adjustment forces at different positions of the vertical take-off and landing aircraft to balance the pitch impact force during the transition to level flight.

[0180] In one embodiment, the vertical take-off and landing aircraft of the present application has 2N tilt-rotors positioned inside 2M fixed rotors, and an elevator rudder 31 and a fully tilting tilt-rotor are provided on the tail 30. Therefore, the pitch impact force during the transition to level flight can be balanced through the aforementioned pitch control process, which, on the one hand, allows for a smoother control process. On the other hand, during this pitch control process, the power pod 442 on the tail 30 rotates along with the rotors during the tilting process. When hovering, the power pod 442 has a smaller area of ​​​​obstruction within the corresponding rotor, resulting in a smaller area of ​​the rotor downwash impacting the tail 30. This can reduce some of the pitching moment and improve the control of the vertical take-off and landing aircraft's pitch moment in complex interfering flow fields.

[0181] It should be noted that if the VTOL aircraft does not include 2M fixed rotors, then in step S332, the fixed rotors do not need to be considered. Instead, the pitch control ratios of the elevator rudder 31 and the 2N tilt-rotors need only be allocated based on the current airspeed or dynamic pressure. Correspondingly, in step S333, the fixed rotors do not need to be considered either. Instead, the elevator rudder and the 2N tilt-rotors need only be controlled separately based on the pitch control ratios to achieve pitch trim and maneuverability.

[0182] Considering that the elevator rudder 31 is often involved in the control process during takeoff of a vertical takeoff and landing aircraft, the pitch control process of the present application includes, before step S332, the following steps: Also included is step S331, controlling the elevator rudder 31 to return to zero or actuate to a trim rudder deflection value that matches the current airspeed or dynamic pressure, and gradually participate in the pitch control process. For example, an airspeed threshold can be set. When the current airspeed is greater than or equal to the set airspeed threshold, the elevator rudder 31 is returned to zero, returning to its initial, non-deflected position. At this point, the rudder surface deflection angle is 0°.

[0183] In this embodiment, the elevator rudder and the 2N tilt-rotors are controlled separately according to the pitch control ratio to achieve pitch trim and control, including: differentially adjusting the pitch torque to perform pitch trim and control through the tilt speed difference and / or tilt angle difference and / or rotation speed difference between the tilt-rotors at different positions.

[0184] Please refer to Figure 27, which shows the full-aircraft pitch moment curves generated by comparing the partial tilting scheme of the power pod of the tilt-rotor on the tail 30 and the full tilting scheme of the power pod of the tilt-rotor on the tail 30 through aerodynamic simulation analysis. The first curve 101 is the simulation curve of the simulation model in Figure 7. The tilt-rotor structure of the tail during the aerodynamic simulation analysis refers to Figure 20. The second curve 102 is the partial tilting model. The partial tilting model and the vertical take-off and landing aircraft model in Figure 7 are the same except for the partial tilting scheme of the power pod. In the simulation analysis of the two models, the rotation speeds of the four fixed rotors and the four tilt-rotors are equal, and the thrust matches the aircraft take-off weight (thrust and gravity balance state).

[0185] The first curve 101 and the second curve 102 in Figure 27 are curves showing how the pitch moment of the entire aircraft of the two models changes with flight speed (i.e., wind speed). The flight speed in the figure is dimensionless, and the process from 0 to 1 represents the aircraft flying from a hovering state to the maximum speed at the current tilt angle (keeping the aforementioned 90° tilt angle unchanged), that is, from the minimum speed to the maximum speed at the current tilt angle; the pitch moment in the figure is also dimensionless.

[0186] Comparing the first curve 101 and the second curve 102 in Figure 27 shows that without differential throttle control for the eight rotors, the aircraft generates a large pitching moment. Therefore, to achieve stable flight, the pitching moment must be balanced to reduce the pitch angular acceleration to zero. Balancing this aerodynamic pitching moment requires differential throttle control for the front and rear rotors, so that the pitching moment generated by the rotor differential and the aerodynamic pitching moment generated by the aircraft itself are offset. The full-tilt pod control method requires a maximum pitch trim and control of 0.25 units during flight. In contrast, the partial-tilt control method with the power pod 442 requires a maximum pitch trim and control of 0.8 units for the entire aircraft, significantly greater than the full-tilt control method. The greater the pitching moment generated during flight, the more difficult the aircraft is to control, and the greater the additional power required from the power system to adjust the aircraft's attitude. In addition, it can be seen from the simulation curve shown in Figure 27 that as the flight speed increases, the pitch balance and control demand generated by the partial tilting scheme control method of the power pod 442 fluctuate greatly, from -0.04 in the hovering state (dimensionless wind speed is 0) to about 0.8 (dimensionless wind speed is 0.57), and the pitch moment fluctuates very violently, which is extremely unfavorable for the pitch control of the aircraft; on the other hand, the pitch moment generated by the full tilting scheme control method of the power pod 442 changes from -0.25 in the hovering state (dimensionless wind speed is 0) to about 0.25 (dimensionless wind speed is 0.42), and the pitch moment fluctuates little, which is conducive to the control of the pitch direction of the aircraft. Therefore, the vertical take-off and landing aircraft and pitch control method provided in this application are simple and effective, and can effectively improve the safety of the aircraft.

[0187] In summary, the VTOL aircraft of the present application is equipped with elevators and 2N tiltrotors. In the VTOL state, the projections of the 2N propellers of the tiltrotors on the horizontal plane are centrally symmetric about point B. Point B and the center of gravity of the VTOL aircraft, point G, are both located within the plane of symmetry of the fuselage, and point B is located on the side of point G that is closer to the tail. Furthermore, during the transition of the VTOL aircraft from the VTOL state to the cruising state, point B remains on the side of point G that is closer to the tail. With this layout, the center of gravity of the VTOL aircraft, point G, and the center of symmetry of the tiltrotors, point B, do not coincide, and during the transition of the VTOL aircraft from the VTOL state to the cruising state, both point G and point B move along the plane of symmetry toward the side closer to the nose. Therefore, the pulling force generated by the tilt rotor in front of the center of gravity exerts a smaller torque on the center of gravity point G, while the pulling force generated by the tilt rotor aft of the center of gravity exerts a larger torque on the center of gravity point G. The torque difference between the front and rear tilt rotors can resist part of the pitching torque generated by the tilt rotor wash area on the tail wing, thereby reducing the difficulty of pitch control. Therefore, when the tilt rotors on both sides of the center of gravity point G are at the same speed and throttle, due to the difference in the length of the lever arm about the center of gravity point G, a nose-down torque will be generated. This nose-down torque can offset or partially offset the pitching torque generated by the tilt rotor wash area on the tail wing. Therefore, the vertical take-off and landing aircraft can better balance the pitching torque when the front and rear rotor throttles are consistent.

[0188] The control method of this application distributes the pitch control ratio of the elevator rudder and 2N tilt-rotors according to the current airspeed or dynamic pressure, and can achieve pitch control through the linkage of the elevator rudder and 2N tilt-rotors. Therefore, this application effectively overcomes some practical problems in the existing technology and has high utilization value and practical significance.

Claims

1. A vertical take-off and landing aircraft, wherein: include: A fuselage, wherein wings are arranged on both sides of the fuselage, a tail fin is arranged at the tail of the fuselage, and an elevator rudder is arranged on the tail fin; 2N tilt-rotors are symmetrically mounted on both sides of the fuselage, and a portion of the 2N tilt-rotors are located on the tail wing; N is a natural number greater than or equal to 2. In the vertical take-off and landing state, the projections of the 2N propellers of the tilt-rotor on the horizontal plane are centrally symmetric about point B. Point B and the center of gravity point G of the vertical take-off and landing aircraft are both located in the symmetry plane of the fuselage, and point B is located on the side of point G close to the tail wing. During the modal change of the vertical take-off and landing aircraft, point G and point B both move along the symmetry plane, and point B is always located on the side of point G close to the tail wing.

2. The vertical take-off and landing aircraft according to claim 1, wherein: During flight, the rotation axis of any of the tilt-rotors on the tail wing and the rotation axis of any of the tilt-rotors at other positions have non-parallel projections on the symmetry plane of the fuselage.

3. The vertical take-off and landing aircraft according to any one of claims 1 to 2, wherein: In the cruising state and / or the vertical state and / or the mode conversion state, there is a first difference between the tilt speed of any of the tilt rotors on the tail wing and the tilt speed of any of the tilt rotors at other positions, and the first difference is not equal to 0.

4. The vertical take-off and landing aircraft according to any one of claims 1 to 2, wherein: In the cruising state and / or the vertical state and / or the mode conversion state, there is a second difference between the rotation speed of any of the tilt-rotors on the tail wing and the rotation speed of any of the tilt-rotors at other positions, and the second difference is not equal to 0.

5. The vertical take-off and landing aircraft according to claim 1, wherein: The vertical take-off and landing aircraft adopts the following method to perform pitch control: During the flight, the pitch control ratio of the elevator rudder and the 2N tilt-rotors is allocated according to the current airspeed or dynamic pressure; According to the pitch control ratio, the elevator rudder and the 2N tilt rotors are respectively Controls are performed to achieve pitch trim and maneuver.

6. The vertical take-off and landing aircraft according to claim 5, wherein: Controlling the 2N tilt-rotors according to the pitch control ratio includes: By using the tilt angle difference between the tilt rotor on the tail wing and any other tilt rotor, the pitch moment is differentially adjusted to perform pitch trim and control; and / or, differentially adjusting the pitch moment to perform pitch trim and control by using the rotation speed difference between the tilt-rotor on the tail wing and any other tilt-rotor; And / or, the pitch moment is differentially adjusted to perform pitch trim and control through the tilt speed difference between the tilt rotor on the tail wing and any other tilt rotor.

7. The vertical take-off and landing aircraft according to claim 2, wherein: The vertical take-off and landing aircraft includes four tilt-rotors, which are symmetrically installed on both sides of the fuselage, two of which are symmetrically installed on the wings with respect to the fuselage, and the other two are symmetrically installed on the tail.

8. The vertical take-off and landing aircraft according to claim 2, wherein: The vertical take-off and landing aircraft includes six tilt-rotors, which are symmetrically installed on both sides of the fuselage, four of which are symmetrically installed on the wings with respect to the fuselage, and the other two are symmetrically installed on the tail.

9. The vertical take-off and landing aircraft according to claim 7 or 8, wherein: The tail wing is a V-shaped tail wing, and the two tilt-rotors located on the tail wing are full-tilt rotors, and the two full-tilt rotors are respectively installed on the wing tips on both sides of the upper part of the V-shaped tail wing.

10. The vertical take-off and landing aircraft according to claim 7 or 8, wherein: Two of the tilt-rotors are arranged at the wing tips of the wings, and the tilt-rotors located on the wing tips of the wings are full-tilt-rotors.

11. The vertical take-off and landing aircraft according to claim 1, wherein: The vertical take-off and landing aircraft also includes 2M fixed rotors, M is a natural number greater than or equal to 2, and the 2M fixed rotors are symmetrically installed on the wings on both sides of the fuselage and are located on the outside of the tilt-rotor; in the vertical take-off and landing state, the projections of all the fixed rotors on the horizontal plane are centrally symmetrical about point A, and point A is located in the symmetry plane of the fuselage. During the modal change of the vertical take-off and landing aircraft, point G is located on the side of point A close to the nose or coincides with point A, and point B is always located on the side of point A close to the tail.

12. The vertical take-off and landing aircraft according to claim 10, wherein: The angle between the rotation axis of the 2M fixed rotors and the symmetry plane of the fuselage is -15° to +15°; And / or, the angle between the plane formed by the rotation axes of the 2N tilt-rotors during the tilting process and the symmetry plane of the fuselage is -15° to +15°.

13. The vertical take-off and landing aircraft according to claim 11, wherein: The vertical take-off and landing aircraft includes four tilt-rotors and four fixed rotors. Assume that the distance from the center of gravity point G to point A is L1, L1≥0, the distance from point A to point B is L2, L2>0, the spacing between the four fixed rotors along the extension direction of the fuselage is L3, and the spacing between the four tilt-rotors along the extension direction of the fuselage is L4, then 0.1(L3+L4)≥4L1+2L2≥0.01(L3+L4).

14. The vertical take-off and landing aircraft according to claim 11, wherein: The vertical take-off and landing aircraft adopts the following method to perform pitch control: During the flight, the pitch control ratios of the elevator rudder, the 2N tilt rotors and the 2M fixed rotors are allocated according to the current airspeed or dynamic pressure; According to the pitch control ratio, the elevator rudder, the 2N tilt rotors and the 2M fixed rotors are controlled respectively to achieve pitch trim and control.

15. The vertical take-off and landing aircraft according to claim 11, wherein: The vertical take-off and landing aircraft includes four tilt-rotors and four fixed rotors, the four fixed rotors are symmetrically installed on both sides of the fuselage, the four tilt-rotors are located on the inner sides of the four fixed rotors, and two of the tilt-rotors are symmetrically installed on the tail wing, and the two tilt-rotors located on the tail wing are full-tilt rotors.

16. The vertical take-off and landing aircraft according to claim 15, wherein: The tail is a V-shaped tail, and the two tilt rotors located on the tail are full-tilt rotors. The two fully tilting rotors are respectively mounted on the wing tips on both sides of the upper portion of the V-shaped tail.

17. The vertical take-off and landing aircraft according to claim 1, wherein: The tail is a V-shaped tail, and two tilt-rotors are installed on the V-shaped tail, and the two tilt-rotors are respectively installed at the wingtips of the V-shaped tail. In the vertical take-off and landing state, along the direction parallel to the roll axis of the vertical take-off and landing aircraft, the distance between the rotation center of the tilt-rotor on the tail and the leading edge of the wingtip of the V-shaped tail is t1, and the chord length of the wingtip of the V-shaped tail is t2, wherein the ratio of t1 to t2 is 15% to 40%.

18. The vertical take-off and landing aircraft according to claim 1, wherein: The tilt-rotor located on the tail wing is a full-tilt-rotor; the tilt-rotor located outside the tail wing is a partial-tilt-rotor.

19. The vertical take-off and landing aircraft according to claim 1, wherein: A tilt rotor is provided on the wing tip of the wing, and the tilt rotor located on the tail wing and the tilt rotor located on the wing tip of the wing are both full-tilt rotors.

20. The vertical take-off and landing aircraft according to claim 15 or 16, wherein: The fully-tilt rotor includes a first rotor and a power pod, wherein the first rotor is connected to the power pod, the power pod is rotatably connected to the tail wing or the wing, and the power pod tilts synchronously with the first rotor during the tilting process of the first rotor.

21. The vertical take-off and landing vehicle according to claim 20, wherein: The first rotor includes a propeller and a rotation drive device, the propeller is installed on the output shaft of the rotation drive device, the power pod includes a pod shell and a tilt mechanism located in the pod shell, and the tilt mechanism is used to drive the rotation drive device to tilt, thereby driving the propeller to tilt.

22. The vertical take-off and landing vehicle according to claim 21, wherein: The tilt mechanism comprises: a rocker arm, a driving arm, a tilt driving device and a connecting rod; the rocker arm and the driving arm are both rotatably mounted on the tail wing; the seat of the tilt driving device is mounted on the tail wing, and the driving end of the tilt driving device drives the driving arm to rotate; the connecting rod is rotatably connected to the driving arm and the rocker arm respectively; the rocker arm is fixed to the rotation driving device of the first rotor connect.

23. The vertical take-off and landing vehicle according to claim 22, wherein: A first shaft and a second shaft parallel to each other are fixedly arranged on the tail wing, the rocker arm is rotatably mounted on the first shaft, the drive arm is rotatably mounted on the second shaft, the base of the tilt drive device is mounted on the second shaft, and the drive of the tilt drive device is fixed to the driven arm.

24. The vertical take-off and landing vehicle according to claim 23, wherein: An embracing structure is provided between the first shaft body and the second shaft body, one end of the embracing structure is fixedly connected to the base body, and the other end of the embracing structure surrounds and tightly embraces the first shaft body.

25. The vertical take-off and landing vehicle according to claim 23, wherein: The first shaft body and / or the second shaft body is a hollow shaft body.

26. The vertical take-off and landing vehicle according to claim 1, wherein: The elevator rudder includes a rudder plate and a rudder body driving device. The rudder plate is rotatably connected to the tail wing or the tail of the fuselage. The rudder body driving device drives the rudder plate to rotate to adjust the direction of the vertical take-off and landing aircraft.

27. The vertical take-off and landing vehicle according to claim 1, wherein: Taking the roll axis of the vertical take-off and landing aircraft as a reference, defined as 0°, with the upward tilt of the tilt-rotor as a positive direction and the downward tilt as a negative direction, the rotation axis of the tilt-rotor tilts within the range of -20° to 110°.

28. The vertical take-off and landing vehicle according to claim 1, wherein: The tail wing is a forward-swept tail wing, and the tilt-rotor located on the forward-swept tail wing is a full-tilt rotor.

29. The vertical take-off and landing vehicle according to claim 28, wherein: The vertical take-off and landing aircraft also includes a tail fin, which is arranged below the forward-swept tail wing and connected to the tail of the fuselage.

30. A control method for a vertical take-off and landing aircraft according to claim 1, wherein: The pitch control process includes the following: Allocating the pitch control ratio of the elevator rudder and the 2N tilt-rotors according to the current airspeed or dynamic pressure; According to the pitch control ratio, the elevator rudder and the 2N tilt-rotors are controlled respectively to achieve pitch trim and manipulation.

31. The control method according to claim 30, wherein: The following rotor control process is also included before allocating the pitch control ratio of the elevator rudder and the 2N tilt rotors according to the current airspeed or dynamic pressure: Obtaining the current tilt position of each tilt rotor; If the current tilt position is inconsistent with the set cruise position, obtaining the current airspeed or dynamic pressure of the corresponding tilt rotor at the current tilt position, and determining whether the current airspeed or dynamic pressure is equal to or greater than a preset threshold value at the current tilt position; If the current airspeed or dynamic pressure is equal to or greater than a preset threshold value at the current tilt position, the tilt rotor is controlled to tilt to a preset next position; Gradually increase the rotation speed of 2N tilt-rotors.

32. The control method according to claim 31, wherein: The control method further includes: repeatedly executing a rotor control process and a pitch control process in sequence until the tilt rotor is tilted to a cruising position and the take-off to level flight is completed.

33. The control method according to claim 31, wherein: The vertical take-off and landing aircraft further includes 2M fixed rotors, where M is a natural number greater than or equal to 2; the 2M fixed rotors are symmetrically mounted on the wings on both sides of the fuselage and are located outside the tilt rotors; The process of gradually increasing the rotation speed of the 2N tilt rotors also includes: gradually reducing the rotation speed of the 2M fixed rotors to a set rotation speed.

34. The control method according to claim 33, wherein: The following takeoff control process is also included before the rotor control: Tilt the 2N tilt-rotors until the rotation axis is vertically upward or obliquely upward; Deflect the elevator rudder downward; The 2M fixed rotors and the 2N tilt rotors are started, and a level flight command is issued when the vertical take-off and landing aircraft reaches a set altitude.

35. The control method according to claim 30, wherein: The vertical take-off and landing aircraft further includes 2M fixed rotors, where M is a natural number greater than or equal to 2; the 2M fixed rotors are symmetrically mounted on the wings on both sides of the fuselage and are located outside the tilt rotors; The following takeoff control process is also included before allocating the pitch control ratio of the elevator rudder and the 2N tilt rotors according to the current airspeed or dynamic pressure: Tilt the 2N tilt-rotors until the rotation axis is horizontal and forward; Deflect the elevator rudder downward; The 2M fixed rotors and the 2N tilt rotors are started, and a level flight command is issued when the vertical take-off and landing aircraft reaches a set altitude.

36. The control method according to claim 35, wherein: After the takeoff control process and before the pitch control, the following rotor control process is also included: gradually increasing the rotation speed of the 2N tilt rotors, issuing a forward flight command and gradually reducing the rotation speed of the 2M fixed rotors to a set rotation speed.

37. The control method according to claim 34 or 36, wherein: The rotor control process, after gradually reducing the rotation speed of the 2M fixed rotors to the set rotation speed, also includes controlling the elevator rudder to return to zero according to the current airspeed or dynamic pressure, and gradually participating in the pitch control process.

38. The control method according to claim 34 or 36, wherein: A ground preparation process is also included before the take-off control process, and the ground preparation process includes: starting the vertical take-off and landing aircraft, powering on the system for detection, and confirming the full-stroke status of the servo system.

39. The control method according to any one of claims 30 to 36, wherein: According to the pitch control ratio, the elevator rudder and the 2N tilt-rotors are controlled separately to achieve pitch trim and control, including: differentially adjusting the pitch torque to perform pitch trim and control through the tilt speed difference and / or tilt angle difference and / or rotation speed difference between the tilt-rotors at different positions.

Images