Vertical take-off and landing aircraft and control method

Abstract

The present invention provides a vertical take-off and landing aircraft and a control method. The aircraft comprises: a fuselage, 2N tilt rotors, and 2N fixed rotors. An elevating rudder is arranged on an empennage; the 2N tilt rotors are symmetrically installed on two sides of the fuselage, and at least the tilt rotors located on the empennage are all-tilt rotors; the 2N fixed rotors are located on the outer sides of the tilt rotors; N is a natural number greater than or equal to 2; in a vertical take-off and landing state, the 2N fixed rotors are centrally symmetric about a point A, the 2N tilt rotors are centrally symmetric about a point B, and the point B, the point A, and the center of gravity G of the overall vertical take-off and landing aircraft are all located within a symmetry plane of the fuselage; and the point G is located on the side of the point A close to a nose or coincides with the point A, and the point B is always located on the side of the point A close to the empennage. The vertical take-off and landing aircraft can mitigate the problem that it is not easy for existing vertical take-off and landing aircrafts to implement pitch control due to large airflow interference between tilt rotors on empennages and the empennages.

Description

Vertical take-off and landing aircraft and control method Technical Field

[0001] The present invention relates to the technical field of aircraft, and in particular to a vertical take-off and landing aircraft and a control method thereof. Background Art

[0002] 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.

[0003] Summary of the Invention

[0004] In view of the above shortcomings of the prior art, the present invention provides a vertical take-off and landing aircraft and a control method 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.

[0005] In order to achieve the above-mentioned purpose and other related purposes, the present invention provides a vertical take-off and landing aircraft, which includes: a fuselage, 2N tilt-rotors and 2N fixed rotors. Wings are provided on both sides of the fuselage, a tail is provided at the tail of the fuselage, and an elevator rudder is provided on the tail; the 2N tilt-rotors are symmetrically installed on both sides of the fuselage, and a part of the 2N tilt-rotors is located on the tail, and at least the tilt-rotors located on the tail are full-tilt rotors; 2N fixed rotors are symmetrically installed on the wings on both sides of the fuselage and are located on the outside of the tilt-rotors; wherein N is a natural number greater than or equal to 2. In the vertical take-off and landing state, the 2N fixed rotors are symmetrically installed on the wings on both sides of the fuselage and are located on the outside of the tilt-rotors; wherein N is a natural number greater than or equal to 2. In the vertical take-off and landing state, the 2N fixed rotors are symmetrically installed on the wings on both sides of the fuselage and are located on the outside of the tilt-rotors. The projections of the fixed rotor on the horizontal plane are centrally symmetrical about point A, and the projections of the 2N tilt rotors on the horizontal plane are centrally symmetrical about point B, and point B, point A and the center of gravity G of the vertical take-off and landing aircraft are all located within the symmetry plane of the fuselage; 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 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.

[0006] In one embodiment of the vertical take-off and landing aircraft of the present invention, 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, wherein 0.1(L3+L4)≥4L1+2L2≥0.01(L3+L4).

[0007] In one embodiment of the vertical take-off and landing aircraft of the present invention, 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%.

[0008] In one embodiment of the vertical take-off and landing aircraft of the present invention, 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°.

[0009] In one embodiment of the vertical take-off and landing aircraft of the present invention, 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, and the power pod tilts synchronously with the first rotor during the tilting process of the first rotor.

[0010] In one embodiment of the vertical take-off and landing aircraft of the present invention, a fairing is provided at the center of the first rotor, and along the extension direction of the rotation axis of the first rotor, the projection of the fairing covers the projection of the power pod.

[0011] In one embodiment of the vertical take-off and landing aircraft of the present invention, the power pod is a rotating body structure, and the rotating axis of the rotating body structure is coaxially arranged with the rotating axis of the first rotor; the surface of the power pod is streamlined.

[0012] In one embodiment of the vertical take-off and landing aircraft of the present invention, 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.

[0013] In one embodiment of the vertical take-off and landing aircraft of the present invention, the tilting mechanism includes:

[0014] a rocker arm, rotatably mounted on the tail wing, the rocker arm being fixedly connected to the rotary drive device;

[0015] A driving arm is rotatably mounted on the tail wing, and a rotation axis is arranged parallel to the rotation axis of the rocker arm;

[0016] A tilt drive device, the base of which is mounted on the tail wing, and the drive end of which drives the drive arm to rotate;

[0017] A connecting rod is rotatably connected to the driving arm and the rocker arm respectively.

[0018] In one embodiment of the vertical take-off and landing aircraft of the present invention, a first shaft and a second shaft parallel to each other are fixedly provided on the tail wing, the rocker arm is rotatably mounted on the first shaft, the driving arm is rotatably mounted on the second shaft, the base of the tilt driving device is mounted on the first shaft, and the base of the tilt driving device is fixedly connected to the housing of the tilt driving device; the driving end of the tilt driving device is coaxial with the second shaft and fixed to the driving arm.

[0019] In one embodiment of the vertical take-off and landing aircraft of the present invention, 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.

[0020] In an embodiment of the vertical take-off and landing aircraft of the present invention, the ratio of the chord length of the rudder plate to the chord length of the tail wing is 15% to 100%.

[0021] In one embodiment of the vertical take-off and landing aircraft of the present invention, with the initial position when parallel to the tail wing being 0°, upward deflection being a positive direction and downward deflection being a negative direction, the deflection angle of the rudder plate is -90° to 30°.

[0022] In one embodiment of the vertical take-off and landing aircraft of the present invention, the angle between the rotation axes of the 2N fixed rotors and the symmetry plane of the fuselage is -15° to +15°;

[0023] And / or, the angle α between the plane formed by the rotation axis of the tilt rotor during the tilting process and the symmetry plane of the fuselage is -15° to +15°.

[0024] In one embodiment of the vertical take-off and landing aircraft of the present invention, the tail is any one of a V-shaped tail, a Y-shaped tail, an X-shaped tail, a T-shaped tail, an H-shaped tail or a U-shaped tail, wherein a portion of the tilt-rotor is mounted on the tail.

[0025] In one embodiment of the vertical take-off and landing aircraft of the present invention, arms are installed on the wings on both sides of the fuselage, and 2N fixed rotors are symmetrically installed on the arms on both sides of the fuselage and are respectively located on the front and rear sides of the wings.

[0026] In one embodiment of the vertical take-off and landing aircraft of the present invention, the following method is used for pitch control:

[0027] During flight, allocating pitch control ratios of the elevator rudder, the 2N tilt rotors, and the 2N fixed rotors according to the current airspeed or dynamic pressure;

[0028] According to the pitch control ratio, the elevator rudder, the 2N tilt rotors and the 2N fixed rotors are controlled respectively to achieve pitch trim and control.

[0029] In one embodiment of the vertical take-off and landing aircraft of the present invention, controlling the 2N tilt rotors according to the pitch control ratio includes:

[0030] 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;

[0031] 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;

[0032] 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.

[0033] The present invention also provides a control method for any of the above-mentioned vertical take-off and landing aircraft, comprising the following pitch control process:

[0034] Allocating a pitch control ratio of the elevator rudder to the 2N tilt rotors and the 2N fixed rotors according to the current airspeed or dynamic pressure;

[0035] According to the pitch control ratio, the elevator rudder, the 2N tilt rotors and the 2N fixed rotors are controlled respectively to achieve pitch trim and control.

[0036] In one embodiment of the control method of the present invention, before allocating the pitch control ratios of the elevator rudders and the 2N tilt rotors and the 2N fixed rotors according to the current airspeed or dynamic pressure, the following rotor control process is also included:

[0037] Get the current tilt position of each tilt rotor;

[0038] 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;

[0039] If the current airspeed or dynamic pressure is equal to or greater than a preset threshold value at the current tilt position, controlling the tilt rotor to tilt to a preset next position;

[0040] The rotation speed of the 2N tilt rotors is gradually increased, and the rotation speed of the 2N fixed rotors is gradually reduced to the set rotation speed.

[0041] In one embodiment of the control method of the present invention, the following takeoff control process is also included before the rotor control process:

[0042] Tilt the 2N tilt rotors until the rotation axis is vertically upward or obliquely upward;

[0043] Deflect the elevator rudder downward;

[0044] The 2N 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.

[0045] In one embodiment of the control method of the present invention, the following takeoff process is further included before the pitch control process:

[0046] Tilt the 2N tilt rotors until the rotation axis is horizontal and forward;

[0047] Deflect the elevator rudder downward;

[0048] The 2N 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.

[0049] In one embodiment of the control method of the present invention, the rotor control process, after the takeoff control process and before the pitch control process, also includes the following rotor control process: gradually increasing the rotation speed of 2N tilt rotors, and gradually reducing the rotation speed of 2N fixed rotors to a set rotation speed.

[0050] In one embodiment of the control method of the present invention, during the rotor control process, after gradually reducing the rotational speed of the 2N fixed rotors to a set rotational speed, the method further includes controlling the elevator rudder to return to zero or actuate to a trim rudder deflection value that matches the current airspeed / dynamic pressure based on the current airspeed or dynamic pressure, and gradually participating in the pitch control process.

[0051] In one embodiment of the control method of the present invention, the rotor control process and the pitch control process are repeatedly executed in sequence until the tilt rotor is tilted to the cruise position, completing the takeoff and level flight transition.

[0052] The vertical take-off and landing aircraft of the present invention arranges 2N tilt-rotors on the inner sides of 2N fixed rotors, and provides an elevator rudder and a fully-tiltable tilt-rotor on the tail. On the one hand, the power pod on the tail rotates together with the rotor during the tilting process. When hovering, the power pod is immersed in the corresponding rotor and the shielding area thereof is small. Therefore, the downwash of the rotor hits a smaller area on the tail, which can reduce a part of the nose-up moment and improve the control of the pitch moment of the vertical take-off and landing aircraft in a complex interference flow field. On the other hand, the fixed rotor, the tilt-rotor and the elevator rudder can be further coordinated to perform pitch balancing and control.

[0053] Furthermore, in the layout of this vertical take-off and landing aircraft, 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 wing. 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.

[0054] 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 of the vertical take-off and landing aircraft gradually moves toward the nose as the tilting process progresses, and the symmetry center point B of the tiltrotor also gradually moves forward of the nose. Since the center of gravity point G is always in front of point B, the torque difference between the tiltrotor in front of the center of gravity point G and the tiltrotor behind the center of gravity point 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.

[0055] Furthermore, during the roll and cruise phases, the center of gravity G is closer to the front than points A and B, so 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.

[0056] Furthermore, for manned vertical take-off and landing aircraft, the manned seats are mostly arranged in the front fuselage, so the weight of passengers and luggage is relatively forward. Therefore, this vertical take-off and landing aircraft layout mode is extremely friendly to the weight balance of the aircraft. When carrying different numbers of passengers, the center of gravity is allowed to vary in a wider range, which is beneficial to the flight safety of the aircraft.

[0057] The control method of the present invention distributes the pitch control ratios of the elevator rudder, the 2N tilt rotors, and the 2N fixed rotors according to the current airspeed or dynamic pressure, and can realize pitch control by linking the elevator rudder, the 2N tilt rotors, and the 2N fixed rotors. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention 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 invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0059] FIG1 is an isometric view of an embodiment of a vertical take-off and landing aircraft according to the present invention in a cruising state;

[0060] FIG2 is an isometric view of an embodiment of a vertical take-off and landing vehicle according to the present invention in a vertical take-off and landing state;

[0061] FIG3 is a top view of an embodiment of a vertical take-off and landing aircraft according to the present invention in a vertical take-off and landing state;

[0062] FIG4 is a side view of an embodiment of a vertical take-off and landing aircraft according to the present invention in a vertical take-off and landing state;

[0063] FIG5 is a rear view of an embodiment of a vertical take-off and landing aircraft according to the present invention in a vertical take-off and landing state;

[0064] FIG6 is a partial view of the fully tilting rotor;

[0065] FIG7 is a partial view of the tilt rotor with the pod housing removed;

[0066] Figure 8 is a top view of the fully tilting rotor with the pod housing removed;

[0067] FIG9 is a cross-sectional view of DD in FIG8 ;

[0068] FIG10 is a view from another direction of the tilt rotor after the pod shell is removed;

[0069] FIG11 is a three-dimensional view of the tilt rotor from another direction after the pod shell is removed;

[0070] FIG12 is a sectional view taken along line FF of FIG10 ;

[0071] FIG13 is a sectional view of PP in FIG10 ;

[0072] FIG14 is a partial view of the fully tilting rotor in a vertical position with the rudder plate chord length accounting for 30%;

[0073] FIG15 is a partial view of the fully tilting rotor in the vertical position with the rudder plate chord length accounting for 60%;

[0074] FIG16 is a partial view of the fully tilting rotor in a vertical position with the rudder plate chord length accounting for 100%;

[0075] FIG17 is a partial view of the fully tilting rotor in a cruising state;

[0076] FIG18 is a partial view of the fully tilting rotor in an oblique climbing state;

[0077] FIG19 is a diagram showing the rotation path of the elevator rudder;

[0078] Figure 20 is a top view of the tail in vertical take-off and landing mode;

[0079] Figure 21 is a schematic diagram of the ratio of the chord length of the tail rudder plate and the deflection angle of the rudder plate;

[0080] Figure 22 is a schematic diagram of the partial tilting of the tail tilt-rotor power pod;

[0081] Figure 23 shows the curves of the pitch moment (dimensionless) of the entire aircraft changing with wind speed (dimensionless) for the partial and full tilt control methods of the pod (CFD simulation results);

[0082] FIG24 is a flow chart of an embodiment of a vertical take-off and landing aircraft according to the present invention from a ground state to a cruising state;

[0083] FIG25 is a flow chart of a vertical take-off and landing aircraft transitioning from take-off to level flight according to an embodiment of the present invention;

[0084] FIG26 is a flow chart of pitch control of a vertical take-off and landing aircraft according to an embodiment of the present invention;

[0085] FIG27 is a flow chart of rotor control for a vertical take-off and landing aircraft according to an embodiment of the present invention;

[0086] FIG28 is a flow chart of a takeoff control process for a vertical takeoff and landing aircraft according to an embodiment of the present invention;

[0087] FIG29 is a flow chart of a takeoff control process for a vertical takeoff and landing aircraft according to an embodiment of the present invention;

[0088] FIG30 is a top view of an embodiment of a vertical take-off and landing aircraft of the present invention in a vertical take-off and landing state.

[0089] Component number description

[0090] 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; 432. First power pod; 44. Fourth tiltrotor; 441. First rotor; 4411. Propeller; 4412. Rotary drive unit; 4413. Fairing; 442. Second power pod; 4421. Tilt drive unit; 4422. Rocker arm; 442 3. First axis; 4424. Second axis; 4425. Embracing structure; 4426. Connecting rod; 4427. First hinge axis; 4428. Second hinge axis; 4429. Driving arm; 4430. Bearing; 4431. Pod shell; 4432. Mating surface; 51. First fixed rotor; 511. First arm; 52. Second fixed rotor; 521. Second arm; 53. Third fixed rotor; 54. Fourth fixed rotor; 60. Symmetry plane; 101. First curve; 102. Second curve. DETAILED DESCRIPTION

[0091] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following examples and the features in the examples can be combined with each other unless they conflict. It should also be understood that the terms used in the examples of the present invention are for the purpose of describing specific embodiments, not for the purpose of limiting the scope of protection of the present invention. The test methods for which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under the conditions recommended by the manufacturers.

[0092] 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, all technical and scientific terms used herein are consistent with the prior art as understood by those skilled in the art and the description of the present invention. Any prior art methods, devices, and materials similar or equivalent to those described in the examples of the present invention may also be used to implement the present invention.

[0093] 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 the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0094] To make it easier to distinguish, let us first explain the concepts of "full tilt rotor" and "partial tilt rotor". Existing tilt rotors mostly include rotors and power pods, and motors and control components can be installed in the power pods. "Partial tilt rotors" often cut off the power pod. During the rotor tilting process, the part close to the rotor tilts with the rotor, and the part away from the rotor is relatively fixed to the fuselage 10. In the "full tilt rotor", the entire power pod tilts with the corresponding rotor. Considering the complexity of the airflow field during flight and flight safety, how to arrange the tilt rotors and fixed rotors to optimize the airflow anti-interference ability and flight stability of the vertical take-off and landing aircraft will be extremely challenging.

[0095] In view of the above problems, please refer to Figures 1 to 29. The present invention provides a vertical take-off and landing aircraft and a control method. In the vertical take-off and landing aircraft, 2N tilt-rotors are arranged on the inner side of 2N fixed rotors, and an elevator rudder 31 and a fully-tilted tilt-rotor are provided on the tail 30. Therefore, pitch balancing and control can be coordinated by the fixed rotor, tilt-rotor and elevator rudder 31, which can improve the control problem caused by airflow interference between the tilt-rotor on the tail 30 and the tail 30 in the existing vertical take-off and landing aircraft.

[0096] Referring to Figures 1 to 21 , the present invention provides a vertical take-off and landing (VTOL) aircraft comprising: a fuselage 10, 2N tilt-rotors, and 2N fixed rotors. The fuselage 10 is symmetrical and has a symmetry plane 60 extending along its length (i.e., the vertical plane defined by line O1-O2 in Figure 3 ). The remaining structure and shape of the fuselage 10 are not limited and may refer to the structure of the fuselage 10 of existing VTOL 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 either side of the fuselage 10. The wings 20 on either side are symmetrical relative to the symmetry plane 60 of the fuselage 10. The structure of the wings 20 may also refer to the fixed wing structure of existing aircraft and is not described in detail here. A tail fin 30 is provided at the rear of the fuselage 10. The tail fin 30 is integrally formed with 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, it can be provided at any suitable position on the tail wing 30 , and can also be any existing suitable elevator rudder structure.

[0097] Crucially, referring to Figures 1 to 5 , 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 the plane of symmetry 60 of the fuselage 10. A portion of the 2N tilt-rotors are mounted on the empennage 30, and at least the tilt-rotors on the empennage 30 are fully tilt-rotors. The specific structure of the fully tilt-rotors and their specific mounting locations on the empennage 30 are not particularly limited; they are symmetrical about the plane of symmetry 60 of the fuselage 10, and their corresponding power pods tilt with the rotors during tilting. The remaining tilt-rotors are mounted on the fuselage 10 and / or wings 20, and the tilt-rotors on the fuselage 10 and / or wings 20 are also symmetrical about the plane of symmetry 60 of the fuselage 10. 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 often mounted on arms, in this embodiment, 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.

[0098] Referring to Figures 1 to 5 , 2N fixed rotors are symmetrically mounted on either side of the fuselage 10. The 2N fixed rotors are located outboard of the 2N tilt-rotors and are symmetrical about the plane of symmetry 60 of the fuselage 10. The structure of the 2N fixed rotors can refer to any suitable existing fixed rotor configuration. The specific locations where the 2N fixed rotors are mounted on the fuselage 10 and / or wing 20 are not particularly limited. For example, they can be mounted directly on the wing 20 or on the wing 20 or fuselage 10 via arms. It should be noted that in the present invention, the fixed rotors are located outboard of all the tilt-rotors, and this can be in any direction. However, preferably, in this embodiment, the 2N fixed rotors are located outboard of the tilt-rotors along the spanwise direction of the wing 20 to optimize the structure and reduce weight.

[0099] Please refer to Figure 30. In the vertical take-off and landing state, the projections of the 2N fixed rotors on the horizontal plane are centrally symmetrical about point A, and the projections of the 2N tilt rotors on the horizontal plane are centrally symmetrical about point B, and point B, point A and the center of gravity G of the vertical take-off and landing aircraft are all located within the symmetry plane 60 of the fuselage 10; 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 move along the symmetry plane toward the side close to the nose, and point G is located on the side close to the nose of point A or coincides with point A, and point B is always located on the side of point A close to the tail 30, that is, the distance from the center of gravity G to point A is L1, L1≥0, and the distance from point A to point B is L2, L2>0. Specifically, with the nose of the vertical take-off and landing aircraft pointing forward, the center point B of the 2N tilt-rotors is located behind the center point A of the 2N fixed rotors, then the distance L2 from point A to point B is greater than 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 center of symmetry 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 greater than 0. At the same time, the center of gravity G of the vertical take-off and landing aircraft is located in front of the center of symmetry B of the 2N tilt-rotors, and is also located in front of or coincides with the center of symmetry A of the 2N fixed rotors. That is, the distance L1 from point A to point G is ≥ 0, and as the 2N tilt-rotors tilt forward, the center of gravity G gradually moves forward, and the absolute value of L1 also becomes larger and larger.

[0100] With 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 30, 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 30. 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.

[0101] 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 of the vertical take-off and landing aircraft gradually moves toward the nose as the tilting process progresses, and the symmetry center point B of the tiltrotor also gradually moves forward of the nose. Since the center of gravity point G is always in front of point B, the torque difference between the tiltrotor in front of the center of gravity point G and the tiltrotor behind the center of gravity point 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.

[0102] The number of tilt-rotors on the tail 30 can be any even number less than 2N. Preferably, referring to Figures 1 to 5, 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 of the tilt-rotors 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 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 behind the center of gravity 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 432, and the fourth tilt-rotor 44 is mounted on the empennage 30 via a second power pod 442. The first power pod 432 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.

[0103] During vertical takeoff and landing (VTOL), 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 horizontal projections of the first and fourth tilt-rotors 41, 44 are centrally symmetrical about point B, while the horizontal projections of the second and third tilt-rotors 42, 43 are centrally symmetrical about point B.

[0104] The four fixed rotors are divided into two equal groups, designated as the first group of fixed rotors and the second group of fixed rotors. The first group of fixed rotors is mounted on the wing 20 in front 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 behind 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.

[0105] Referring to Figure 3, in one embodiment of the vertical take-off and landing aircraft of the present invention, the spacing between the four fixed rotors along the extension direction of the fuselage, 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 extension direction of the fuselage, 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 places the center of gravity G closer to the front of points A and B during the tilting and cruising phases, resulting in relatively large longitudinal and directional static stability margins, making the aircraft more resistant to extreme winds and safer to fly.

[0106] The vertical take-off and landing aircraft of the present invention arranges 2N tilt-rotors on the inner side of 2N fixed rotors, and provides an elevator rudder 31 and a fully-tilt tilt-rotor on the tail 30. On the one hand, the power pod on the tail 30 rotates together with the rotor during the tilting process. When in the hovering state, the power pod is immersed in the corresponding rotor with a small shielding area. Therefore, the downwash of the rotor hits a smaller area on the tail 30, which will reduce a part of the nose-up moment and improve the control of the pitch moment of the vertical take-off and landing aircraft in a complex interference flow field. On the other hand, the fixed rotor, the tilt-rotor and the elevator rudder 31 can be further coordinated to perform pitch balancing and control.

[0107] Referring to Figure 20 , in one embodiment of the vertical take-off and landing (VTOL) aircraft of the present invention, 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 tilt-rotor 43 and the fourth tilt-rotor 44 are symmetrical about a plane of symmetry 60 of the fuselage 10. In the vertical take-off and landing (VTOL) configuration, the distance between the rotation center of the tilt-rotor on the tail 30 and the leading edge of the wingtip of the V-shaped tail, along a direction parallel to the aircraft's roll axis X, is t1. The chord length of the wingtip of the V-shaped tail 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.

[0108] Referring to Figures 1 to 3 and 17 to 19, in one embodiment of the vertical take-off and landing (VTOL) aircraft of the present invention, with the roll axis X as the reference, a tilt angle of 0° is defined, with upward tilt of the roll axis X as a positive direction and downward tilt of the roll axis X as a negative direction. The tilt rotor axis can tilt within a range of -20° to 110°. Referring to Figure 17, 0° indicates the tilt rotor axis extending forward along the roll axis X; referring to Figure 19, 90° indicates the tilt rotor axis extending vertically upward. Referring to Figure 18, the tilt rotor axis is tilted between 0° and 90°. It should be noted that when the tilt angle range is 90° to 110°, the VTOL aircraft can fly nose-first and nose-down, significantly expanding the VTOL aircraft's flight envelope and capabilities while reducing the risk of the VTOL aircraft needing to turn mid-flight. 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°.

[0109] In the vertical take-off and landing aircraft of the present invention, 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 transitions from the vertical state to the cruising state and vice versa), the rotation axes of the tilt-rotors can be arranged in parallel or non-parallel. In one embodiment of the vertical take-off and landing aircraft of the present invention, during flight, the rotation axis of any of the tilt-rotors on the tail 30 and the rotation axis of any of the tilt-rotors at other locations have non-parallel projections on the symmetry plane 60 of the fuselage 10. 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.

[0110] It should be noted that, in this embodiment, when the vertical take-off and landing aircraft is in a cruising state in level flight, the rotation axis of the tilt-rotor on the tail wing 30 and the rotation axis of the tilt-rotor at other locations 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 locations may not extend along the roll axis X, but may be parallel to the vertical plane where the roll axis X is located. The tilt angle is defined as 0° with the roll axis X as the reference, with the upward tilt of the roll axis X as the positive direction and the downward tilt of the roll axis X as the negative direction, and extends within a range of ±20°. Furthermore, in the present invention, the power pods of the tilt-rotors projected at different roll axis X coordinate positions along the roll axis X direction can be independently controlled, and their tilting can be independently controlled and uncorrelated. In this mode, the tilt angles of the front tilt-rotor and the tilt-rotor on the tail 30 can be different, and the tilting process can be asynchronous. For example, with the roll axis X as 0°, and angles above the roll axis X as positive and angles below the roll axis X as negative, the tilt angle of the power pod on the front fuselage 10 or wing 20 can be 10°, and the tilt angle of the power pod on the rear fuselage 10, wing 20, or tail 30 can be -10°.

[0111] It should be noted that when the VTOL aircraft of the present invention is in the VTOL configuration, the rotational axes of the tilt-rotors on the tail wing 30 and the rotational axes of the tilt-rotors in other locations may or may not extend vertically upward. That is, the tilt angles of the front tilt-rotors and the tilt-rotors on the tail wing 30 are not limited to a 90° tilt angle. To enhance controllability, the tilt angles of the rotational axes of the front tilt-rotors and the tilt-rotors on the tail wing 30 may be any value between 70° and 110°, such as 70°, 80°, 90°, 100°, and 110°. Each of the 2N tilt-rotors has relatively independent rotation and tilt control. 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 achieved at different locations. It should be noted that the tilt angle of a tilt-rotor is the angle between the rotation axis of the tilt-rotor and the aircraft's roll axis X, with the center point of the tilt-rotor's tilt axis as the vertex.

[0112] The fully tilting rotor structure of the present invention can be any existing tilting rotor structure capable of achieving synchronous tilting of the power pod as a whole with the rotor. Referring to Figures 6 and 14, in one embodiment of the vertical take-off and landing aircraft of the present invention, the fully tilting rotor includes a first rotor 441 and a power pod. The first rotor 441 is connected to the power pod, which is rotatably connected to the tail 30 and tilts synchronously with the first rotor 441 during the tilting process of the first rotor 441. The housing of the power pod can contain a power device. For example, if it is a purely electric configuration, it can include a motor, electronic control, environmental control device, tilt mechanism, etc.; if it is an oil-powered configuration, the pod can contain an engine, an ECU, a tilt mechanism, etc. Preferably, the housing of the power pod in this embodiment is a purely electric configuration.

[0113] Referring to Figure 6 , in one embodiment of the VTOL aircraft of the present invention, 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, the projection of fairing 4413 along the axis of rotation of the first rotor 441 covers the projection of the power pod. This arrangement can reduce the impact of the power pod on the rotor downwash during flight. However, those skilled in the art will appreciate that the projection of the power pod can also be partially located within the projection of fairing 4413, which can also partially reduce drag, though the effect will be less pronounced than when the pod is fully covered.

[0114] The power pod's shape includes, but is not limited to, a solid of revolution, a square, an ellipsoid, and the like. Preferably, in one embodiment of the VTOL aircraft of the present invention, the power pod is a solid of revolution structure, the rotation axis of the solid of revolution being coaxial with the rotation axis of the first rotor 441; and the surface of the power pod is streamlined. This can reduce the impact of the power pod on the corresponding rotor downwash during flight.

[0115] Referring to Figures 6 to 14 , the first rotor 441 includes a propeller 4411 and a rotation drive device 4412. The propeller 4411 is mounted on the output shaft of the rotation drive device 4412. The power pod includes a pod housing 4431 and a tilt mechanism located within the pod housing 4431, which is used to drive the rotation drive device 4412 to tilt. The tilt mechanism in the present invention can be any suitable type of tilt mechanism capable of driving the power pod and the rotation drive device 4412 to tilt synchronously. Preferably, in this embodiment, the tilt mechanism includes a rocker arm 4422, a drive arm 4429, a tilt drive device 4421, and a connecting rod 4426. The tilt drive device 4421 can be any suitable structure having a rotation output shaft, such as a servo, a combination of a servo and a reducer, etc. In the present invention, the tilt drive device 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 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 first hinge Axle 4427 is hinged to the drive arm 4429, and the other end of the connecting rod 4426 is hinged to the rocker arm 4422 via a second hinge axis 4428. Although bearings 4430 may not be installed at the first hinge axis 4427 and the second hinge axis 4428, 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 above-mentioned tilting mechanism can achieve a dual-axis connection structure with the tail 30 through 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 a single rod. This strengthens the tilting mechanism's torsional resistance and improves the support stiffness of the entire rotor mechanism. This setup also 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, it is also easy to adjust the length ratio between the four links to adjust the stiffness of the entire mechanism and the natural frequency, thereby improving the mechanical performance of the entire tilt rotor.

[0116] Please refer to Figures 7 to 13. 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, on the one hand, allows the positioning and installation of the tilt drive unit 4421 through the mounting structure 4425 and the second shaft 4424, and on the other hand, reduces the difficulty of installing the tilt drive unit 4421. It should be noted that in other embodiments, the tilt drive unit 4421 can also be fixedly mounted on the empennage 30, and the output shaft of the tilt drive unit 4421 can be extended 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 will occupy a larger space within the empennage 30 and is not suitable for thin airfoils or those with a large number of internal devices. Furthermore, the torque applied to the tilt drive unit 4421 will ultimately be entirely borne by the mounting base of the tilt drive unit 4421, placing greater demands on the installation strength of the tilt drive unit 4421.

[0117] 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 seat of the tilting drive device 4421 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.

[0118] In one embodiment of the present invention, the distance from the rotation center line 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 line of the first shaft body 4423 to the axis center of the first hinge shaft 4427 is c, and the distance from the center line of the first shaft body 4423 to the center line 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 invention 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 problem of limiting the tilting mechanism, so that the limit position of the positive rotation and the limit position of the reverse rotation of the tilting mechanism 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, without the need to set up an additional limit mechanism for limit position, and greatly optimize the installation space of the transmission rod mechanism during the movement process; specifically, by adjusting the various components in the connecting rod mechanism (i.e., a, b, c, d) makes the distance between the end axis of the driving arm 4429 (i.e. the axis of the second hinge shaft 4428) and the axis of the first shaft body 4423 equal in the initial angle state (i.e. the minimum tilting angle) and the final angle state (i.e. the maximum tilting angle), and at this time, the angle between the plane formed by the end axis of the driving arm 4429 and the axis of the first shaft body 4423 in the initial angle state and the angle between the plane formed by the end axis of the driving arm 4429 and the axis of the first shaft body 4423 in the final angle state is equal to the rotation angle of the rocker arm 4422 ±5°, that is, one limit point can be used to constrain two directions.

[0119] In the present invention, the first shaft 4423 and / or the second shaft 4424 are hollow shafts, through which wires and pipes can be threaded, preventing the cables and pipes from swinging irregularly outside and damaging the cables. At the same time, the range of motion of the cables and pipes is reduced 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.

[0120] In this embodiment, the above-mentioned tilting mechanism has different reduction ratios at different 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 4421 of the present invention 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.

[0121] 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, and the 2N 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 centrally symmetrical with respect to point A of the vertical take-off and landing aircraft.

[0122] In one embodiment of the vertical take-off and landing aircraft of the present invention, arms are mounted on the wings 20 on both sides of the fuselage 10, where N is a natural number greater than or equal to 2. 2N fixed rotors are symmetrically mounted on the arms on both sides of the fuselage 10, located forward and backward of the wings 20. To achieve distribution forward and backward of the aircraft's center of gravity, and to achieve both plane-symmetry and center-symmetry about the fuselage, the number of tilt-rotors is at least four. Of course, if energy is not a consideration, six, eight, or even more numbers are also possible, as long as additional rotors are added to the four aforementioned rotors and maintain plane-symmetry and center-symmetry about point B. In this application, the number of fixed rotors is at least four. Of course, if energy is not a consideration, six, eight, or even more numbers are also possible, as long as additional rotors are added to the four aforementioned rotors and located outboard of all the aforementioned tilt-rotors, and maintain plane-symmetry and center-symmetry about point A.

[0123] In one embodiment of the invented VTOL aircraft, at least some of the 2N tilt rotors are positioned forward of the center of gravity and at least some are positioned aft of the center of gravity. At least some of the 2N fixed rotors are positioned forward of the center of gravity and at least some are positioned aft of the center of gravity. This facilitates balancing multiple force couples and makes the VTOL aircraft's vertical takeoff and landing process more stable.

[0124] In the VTOL aircraft of the present invention, the structure of the elevator rudder 31 can refer to the structure of an existing elevator rudder 31, as shown in Figures 1 and 13. In this embodiment, 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 fin 30 or the tail portion of the fuselage 10. The elevator rudder drive device drives the rudder plate 311 to rotate to adjust the direction of the VTOL aircraft. The elevator rudder 31 drive device includes but is not limited to a motor, or a combination of a motor and a reducer.

[0125] Please refer to Figure 22. In one embodiment of the vertical take-off and landing aircraft of the present invention, the ratio of the chord length of the rudder plate 311 to the chord length of the tail wing 30 is 15% to 100%. For example, it can be any value between 15% and 100%, such as 15%, 30%, 45%, 60%, 90%, 100%, etc. As an example, as shown in Figure 15, the chord length of the rudder plate 311 accounts for 30% of the chord length of the tail wing 30; as shown in Figure 16, the chord length of the rudder plate 311 accounts for 60% of the chord length of the tail wing 30; as shown in Figure 17, the chord length of the rudder plate 311 accounts for 100% of the chord length of the tail wing 30, but is not limited to the ratios in Figures 15 to 17. It should be noted that, referring to Figure 21, the chord length is the distance from the leading edge point to the trailing edge point of the cross-section of the tail 30 airfoil, and the chord length ratio is the ratio of the length of the rudder plate on the tail 30 in the heading direction to the length of the tail 30 as viewed from above (not the length ratio along the span direction Y).

[0126] Please refer to Figure 13. In one embodiment of the vertical take-off and landing aircraft of the present invention, with the initial position when parallel to the tail 30 as 0°, upward deflection as a positive direction and downward deflection as a negative direction, the deflection angle of the rudder plate 311 is -90° to 30°. For example, as shown in Figure 20, it can be any angle between -90° and 30°, such as -90°, -60°, -30°, -15°, 0°, 15° and 30°.

[0127] The rotation axes of the 2N tilt-rotors and 2N fixed rotors in the present invention can also be arranged in the vertical direction in the vertical take-off and landing state. Preferably, please refer to Figure 5. In one embodiment of the vertical take-off and landing aircraft of the present invention, 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 axes of the tilt-rotors during the tilting process (that is, the plane formed by the rotation axes of the tilt-rotors 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 2N 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.

[0128] In the present invention, 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 injuring passengers when entering or exiting the aircraft. Referring to Figures 1 to 5 , in this embodiment, the tail 30 is a V-shaped tail with two tilt-rotors mounted on it, one mounted on each side of the wingtips on the upper portion of the tail 30. In other embodiments, the tail 30 can also have any of the above shapes.

[0129] In one embodiment of the vertical take-off and landing aircraft of the present invention, the following method is used for pitch control:

[0130] During flight, the pitch control ratios of the elevator rudder 31, the 2N tilt rotors, and the 2N 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 2N fixed rotors are controlled separately to achieve pitch trim and manipulation.

[0131] In one embodiment of the vertical take-off and landing aircraft of the present invention, 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 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 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 in front of the tail 30. It should be noted that the above-mentioned tilt angle differential adjustment process, rotation speed differential adjustment process, and tilt speed differential adjustment process can be implemented individually or in combination with each other, or all three can be implemented simultaneously.

[0132] As shown in Figure 24, the transition from ground state to cruising state for existing vertical take-off and landing aircraft generally includes four stages:

[0133] S100: Ground preparation process.

[0134] During the ground preparation process, it is first necessary to start the vertical take-off and landing aircraft, and then power on the system for testing, and then confirm the full stroke status of the servo system such as the tilt mechanism and the elevator rudder 31.

[0135] S200, takeoff control process. This process is usually the process of a vertical takeoff and landing aircraft climbing from the ground to a set altitude. During this process, the tilt rotor and fixed rotor usually maintain a constant tilt angle and rotation speed. Compared with the transition to level flight, this process is relatively stable.

[0136] S300: Takeoff and level flight control process.

[0137] The takeoff-to-level flight control process often involves changes in the tilt rotor's tilt angle and / or the rotational speed of the tilt rotor and / or fixed rotor. Therefore, the pitch impact force during this process is relatively large, making control of the vertical take-off and landing aircraft relatively difficult. As an optimization, referring to FIG. 25 , the takeoff-to-level flight control process in this embodiment at S300 includes the following steps:

[0138] 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.

[0139] 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.

[0140] S330, pitch control process. Considering that during the takeoff-to-level flight process, the tiltrotor is tilted multiple times to a set cruise position where the tiltrotor rotation axis is parallel to the roll axis, and the vertical take-off and landing aircraft is subjected to a certain pitch impact force during each tilting process, step S330 can be performed after each rotor control process S320 during the takeoff-to-level flight process.

[0141] S340, repeating the rotor control process and the pitch control process in sequence until the tilt rotor is tilted to a cruise position (for example, a position where the rotation axis of the tilt rotor is parallel to the roll axis when the tilt angle is 0°).

[0142] For example, referring to FIG. 28 , in an embodiment of the control method of the present invention, the following takeoff process is also included before the rotor control process in S320 :

[0143] 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, thereby providing power for climbing together with the fixed rotors. The vertical take-off and landing position may be a position where the tilt-rotor's rotation axis forms a 90° angle with the roll axis; the tilted position may be a position where the tilt-rotor's rotation axis forms an angle with the roll axis between 0° and 90° (excluding the endpoints).

[0144] S212 , deflect the elevator rudder 31 downward, so that the elevator rudder 31 participates in takeoff control.

[0145] S213: Start the 2N fixed rotors and the 2N tilt rotors, and issue a level flight command after the vertical take-off and landing aircraft reaches a set altitude.

[0146] 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. The throttles of the 2N fixed rotors and 2N tilt-rotors can be activated to the same value. For example, when N is equal to 2, there are four fixed rotors and four tilt-rotors, and the eight shafts and eight propellers can produce power simultaneously. At this time, the tilt-rotors on the tail 30 block the largest area during the vertical takeoff and transition phases, which will cause a large pitch-up moment. If the rotation axes of all tilt-rotors are set to an inclined position between 0° and 90°, when the aircraft takes off, the throttle of the inner tilt-rotor is activated. Since the inner tilt-rotor provides a forward pulling 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 the set cruise position (for example, a position parallel to the roll axis 0°) and switches to the level flight fixed-wing mode. In this solution, the nose-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 small.

[0147] Considering that the tilt rotor is in a vertical take-off and landing position or a tilted position during the take-off process from S211 to S213, referring to FIG. 25 and FIG. 27 , in an embodiment of the control method of the present invention, the rotor control process in S320 further includes the following process:

[0148] S321. Obtain the current tilt position of each tilt rotor. This process can be done by providing an angle sensor or position sensor on the tilt rotor to feed the current tilt position back to the flight control system, or by directly feeding the current tilt angle position back to the flight control system via the tilt drive device 4421.

[0149] 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 the preset position of the vertical take-off and landing aircraft in level flight, for example, the 0° position where the tilt rotor's rotation axis is parallel to the roll axis X, or another position between 0°±5°.

[0150] 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.

[0151] S324. Gradually increase the rotation speed of the 2N tilt rotors, and gradually reduce the rotation speed of the 2N fixed rotors to a set rotation speed.

[0152] However, in another embodiment of the present invention, referring to FIG. 29 , the takeoff process S200 is different from the processes S211 to S213 in FIG. 28 . The takeoff process S200 includes:

[0153] S221, tilting the 2N tiltrotors until the rotation axes are horizontally forward and parallel to the roll axis X;

[0154] S222, deflecting the elevator rudder 31 downward;

[0155] S223: Start the 2N fixed rotors and the 2N tilt rotors, and issue a level flight command after the vertical take-off and landing aircraft reaches a set altitude.

[0156] During the takeoff process from S221 to S223, the rotation axes of all tilt-rotors are set to 0° (as shown in Figure 17), and the aircraft changes to a compound wing mode. The aircraft takes off vertically by the four outer rotors. The output of the four outer rotors at this time is twice that of control scheme one. The four inner tilt-rotors are gradually started in the transition stage from vertical to level flight, 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, the generated nose-up torque is the smallest, and the control is the simplest. 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.

[0157] 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. It is only necessary to gradually increase the rotation speed of the 2N tilt rotors and gradually reduce the rotation speed of the 2N fixed rotors to the set rotation speed.

[0158] However, it should be noted that regardless of whether the rotor control process S320 includes the tilt control processes S321 to S323, the rotor will be subjected to a high pitch impact force during the transition from takeoff to level flight. Based on this, referring to FIG. 26 , the present invention further provides a control method for the vertical take-off and landing aircraft described above, specifically including the following pitch control process:

[0159] S332: Allocate pitch control ratios for the elevator 31, the 2N tilt-rotors, and the 2N fixed rotors based on the current airspeed or dynamic pressure. In this process, the pitch adjustment force is distributed to the elevator 31, the 2N tilt-rotors, and the 2N 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.

[0160] S333: Based on the pitch control ratio, the elevator rudder 31, the 2N tilt-rotors, and the 2N fixed rotors are controlled separately to achieve pitch trim and maneuverability. During this process, the flight control system controls the elevator rudder 31, the 2N tilt-rotors, and the 2N fixed rotors based on the allocated pitch control ratio. For example, this may be achieved through 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.

[0161] The vertical take-off and landing aircraft of the present invention arranges 2N tilt-rotors inside 2N fixed rotors, and provides an elevator rudder 31 and a fully tilting tilt-rotor 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, provides a smoother control process. On the other hand, during this pitch control process, the power pods on the tail 30 rotate along with the rotors during the tilting process. When hovering, the power pods are less obstructed by the corresponding rotors, 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.

[0162] 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 invention includes, before step S332, a further step S331 of 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 may be set such that 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, undeflected position, at which point the rudder surface deflection angle is 0°.

[0163] It should be noted that the control method of the present invention may further include:

[0164] S400, cruising state. In this state, the vertical take-off and landing aircraft performs level flight and navigates in a horizontal direction, which is relatively stable.

[0165] Please refer to Figure 21, 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 2. During the aerodynamic simulation analysis, the tilt-rotor structure of the tail refers to Figure 14. The second curve 102 is the partial tilting model. The partial tilting model differs from the vertical take-off and landing aircraft model in Figure 2 only in the structure of the tilt-rotor on the tail 30. The tilt-rotor structure of the tail 30 refers to the partial tilting scheme of the power pod in Figure 22, and the rest are the same. 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).

[0166] The first curve 101 and the second curve 102 in FIG23 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.

[0167] Comparing the first curve 101 and the second curve 102 in Figure 23 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 0.25 units for maximum pitch trim and control during flight. The partial-tilt pod control method requires 0.8 units for maximum pitch trim and control of 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 23 that as the flight speed increases, the pitch balancing and control demand generated by the partial tilting scheme control method of the power pod also 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 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 beneficial to the control of the pitch direction of the aircraft. Therefore, the vertical take-off and landing aircraft and pitch control method provided by the present invention are simple and effective, and can effectively improve the safety of the aircraft.

[0168] In summary, the vertical take-off and landing aircraft of the present invention arranges 2N tilt-rotors on the inner side of 2N fixed rotors, and arranges elevator rudders and fully-tilt tilt-rotors on the tail. On the one hand, the power pod on the tail rotates with the rotors during the tilting process. When hovering, the power pod is immersed in the corresponding rotor with a smaller shielding area. Therefore, the downwash of the rotor hits the tail in a smaller area, which can reduce a part of the nose-up moment and improve the control of the pitch moment of the vertical take-off and landing aircraft in a complex interference flow field. On the other hand, the fixed rotor, tilt-rotor and elevator rudder can be further coordinated to perform pitch balancing and control.

[0169] Furthermore, in the layout of this vertical take-off and landing aircraft, 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 wing. 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.

[0170] 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 of the vertical take-off and landing aircraft gradually moves toward the nose as the tilting process progresses, and the symmetry center point B of the tiltrotor also gradually moves forward of the nose. Since the center of gravity point G is always in front of point B, the torque difference between the tiltrotor in front of the center of gravity point G and the tiltrotor behind the center of gravity point 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.

[0171] Furthermore, during the roll and cruise phases, the center of gravity G is closer to the front relative to points A and B, so 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.

[0172] Furthermore, for manned vertical take-off and landing aircraft, the manned seats are mostly arranged in the front fuselage, so the weight of passengers and luggage is relatively forward. This vertical take-off and landing aircraft layout mode is extremely friendly to the weight balance of the aircraft. When carrying different numbers of passengers, the center of gravity is allowed to vary in a wider range, which is beneficial to the flight safety of the aircraft.

[0173] The control method of the present invention distributes the pitch control ratios of the elevator rudder, the 2N tilt rotors, and the 2N fixed rotors according to the current airspeed or dynamic pressure, and can realize pitch control by linking the elevator rudder, the 2N tilt rotors, and the 2N fixed rotors.

[0174] Based on the above beneficial effects, the present invention effectively overcomes some practical problems in the prior art and thus has high utilization value and use significance.

[0175] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A vertical take-off and landing aircraft, characterized in that: 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, a portion of the 2N tilt-rotors are located on the tail wing, and at least the tilt-rotors located on the tail wing are full-tilt-rotors; 2N fixed rotors, symmetrically mounted on the wings on both sides of the fuselage and located outside the tilt-rotor; Among them, N is a natural number greater than or equal to 2. In the vertical take-off and landing state, the projections of the 2N fixed rotors on the horizontal plane are centrally symmetrical about point A, and the projections of the 2N tilt rotors on the horizontal plane are centrally symmetrical about point B, and point B, point A and point G, the center of gravity of the vertical take-off and landing aircraft, are all located in the symmetry plane of the fuselage; 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 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.

2. The vertical take-off and landing aircraft according to claim 1, characterized in that: 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, wherein 0.1(L3+L4)≥4L1+2L2≥0.01(L3+L4).

3. The vertical take-off and landing aircraft according to claim 1, characterized in that: 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%.

4. The vertical take-off and landing aircraft according to claim 1, characterized in that: 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°.

5. The vertical take-off and landing aircraft according to claim 1, characterized in that: The fully-tilt 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, and the power pod tilts synchronously with the first rotor during the tilting process of the first rotor.

6. The vertical take-off and landing aircraft according to claim 5, characterized in that: A fairing is provided at the center of the first rotor, and along the extending direction of the rotation axis of the first rotor, the projection of the fairing covers the projection of the power pod.

7. The vertical take-off and landing aircraft according to claim 5, characterized in that: The power pod is a rotating body structure, and the rotating axis of the rotating body structure is coaxially arranged with the rotating axis of the first rotor; the surface of the power pod is streamlined.

8. The vertical take-off and landing aircraft according to any one of claims 5 to 7, characterized in that: 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.

9. The vertical take-off and landing aircraft according to claim 8, characterized in that: The tilting mechanism comprises: A rocker arm, rotatably mounted on the tail wing, the rocker arm being fixedly connected to the rotary drive device; A driving arm is rotatably mounted on the tail wing, and a rotating shaft is arranged parallel to a rotating shaft of the rocker arm; A tilt drive device, the base of which is mounted on the tail wing, and the drive end of which drives the drive arm to rotate; A connecting rod is rotatably connected to the driving arm and the rocker arm respectively.

10. The vertical take-off and landing aircraft according to claim 9, characterized in that: 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 first shaft, and the drive end of the tilt drive device is coaxial with the second shaft and fixed to the drive arm.

11. The vertical take-off and landing aircraft according to claim 1, characterized in that: 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.

12. The vertical take-off and landing aircraft according to claim 11, characterized in that: The ratio of the chord length of the rudder plate to the chord length of the tail wing is 15% to 100%.

13. The vertical take-off and landing aircraft according to claim 11, characterized in that: With the initial position when parallel to the tail wing as 0°, upward deflection as a positive direction and downward deflection as a negative direction, the deflection angle of the rudder plate is -90° to 30°.

14. The vertical take-off and landing aircraft according to claim 1, characterized in that: The angle between the rotation axes of the 2N 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°.

15. The vertical take-off and landing aircraft according to claim 1, characterized in that: Pitch control is performed using the following method: During the flight, the pitch control ratio of the elevator rudder, the 2N tilt rotors and the 2N fixed rotors is distributed according to the current airspeed or dynamic pressure; According to the pitch control ratio, the elevator rudder, the 2N tilt rotors and the 2N fixed rotors are controlled respectively to achieve pitch trim and control.

16. The vertical take-off and landing aircraft according to claim 15, characterized in that: Controlling the 2N tilt-rotors according to the pitch control ratio includes: By means of 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.

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

18. The control method according to claim 17, characterized in that: Before allocating the pitch control ratio of the elevator rudder to the 2N tilt rotors and the 2N fixed rotors according to the current airspeed or dynamic pressure, the following rotor control process is also included: Obtaining a current tilt position of each of the tilt rotors; If the current tilt position is inconsistent with the set cruise position, obtaining the current airspeed or dynamic pressure of the 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, controlling the tilt rotor to tilt to a preset next position; The rotation speed of the 2N tilt rotors is gradually increased, and the rotation speed of the 2N fixed rotors is gradually reduced to a set rotation speed.

19. The control method according to claim 18, characterized in that: The following takeoff control process is also included before the rotor control process: Tilt the 2N tilt-rotors until the rotation axis is vertically upward or obliquely upward; deflecting the elevator rudder downward; Start 2N of the fixed rotors and 2N of the tilt rotors, and wait until the vertical take-off and landing aircraft reaches When the aircraft reaches the set altitude, issue a level flight command.

20. The control method according to claim 17, characterized in that: The following takeoff control process is also included before the pitch control process: Tilt the 2N tilt-rotors until the rotation axis is horizontal and forward; deflecting the elevator rudder downward; Start the 2N 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.

21. The control method according to claim 20, characterized in that: After the takeoff control process and before the pitch control process, the following rotor control process is also included: gradually increasing the rotation speed of the 2N tilt rotors, and gradually reducing the rotation speed of the 2N fixed rotors to a set rotation speed.

22. The control method according to claim 19 or 21, characterized in that: After gradually reducing the rotation speed of 2N fixed rotors to the set rotation speed, before the pitch control process, it also includes controlling the elevator rudder to return to zero or actuate to a trim rudder deviation value matching the current airspeed / dynamic pressure according to the current airspeed or dynamic pressure, and gradually participating in the pitch control process.

23. The control method according to claim 18, characterized in that: The control method further includes: repeatedly executing the rotor control process and the pitch control process in sequence until the tilt rotor is tilted to a cruising position and the take-off to level flight is completed.

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