Tilting rotor composite aircraft and control method thereof

Abstract

The invention provides an inclined rotor composite aircraft which comprises a fuselage, rotors and wings, the wings are mounted on two sides of the fuselage, the plurality of rotors are distributed around the fuselage, and spatial directions of the rotors are not completely consistent, so that torque is generated through horizontal component force and is in reaction torque balance with the rotors. Flight is achieved with as little control amount as possible and as simple structure as possible. On the other hand, the invention provides a control method of the tilt rotor composite aircraft.

Description

Technical Field

[0001] This invention belongs to the field of aircraft technology, specifically relating to a tilting rotor composite aircraft and its control method. Background Technology

[0002] Vertical takeoff and landing (VTOL) aircraft, as key aviation equipment supporting the development of the low-altitude economy, have become a cutting-edge research hotspot in the aviation industry due to their ability to complete vertical takeoff, landing, and hovering operations without relying on long runways. Their technological development has consistently focused on integrating the high speed and efficiency of fixed-wing aircraft with the vertical maneuverability of rotary-wing aircraft.

[0003] To achieve this goal, various technological approaches have emerged in the industry, primarily including compound airfoils, tiltrotor configurations, and tail-sitter designs. However, while pursuing performance, these existing solutions invariably introduce increased system complexity, leading to a series of issues related to reliability, cost, and maneuverability. Specifically:

[0004] Although the compound wing configuration simplifies the control logic by separating the lift and thrust components, during the level flight phase of a fixed wing, the dedicated lift rotor system not only stops working and becomes a "dead weight," increasing flight drag, but also seriously interferes with airflow, significantly reducing the overall aerodynamic efficiency of the aircraft.

[0005] To overcome the inherent limitations of compound airfoils, tiltrotor configurations utilize a tilting mechanism to switch the power unit between vertical lift and horizontal thrust, thereby optimizing aerodynamic efficiency. However, this approach comes at the cost of significant complexity: the intricate mechanical tilting structure is not only heavy and poses reliability challenges, but also drastically increases manufacturing costs and maintenance difficulty, leading to a reduction in payload capacity.

[0006] In comparison, the tail-seat configuration exhibits unique advantages: its propulsion system operates continuously throughout the entire flight envelope, avoiding the "dead weight" problem, resulting in a cleaner aerodynamic layout and theoretically higher aerodynamic efficiency. However, existing tail-seat aircraft typically employ complex control systems to achieve full-mode flight control. This multi-control coupling system exhibits extremely complex flight control laws during critical phases of vertical takeoff and landing and mode transitions, significantly increasing the difficulty of stability and control.

[0007] In summary, existing vertical takeoff and landing (VTOL) technologies all face a fundamental contradiction: performance improvements often come at the cost of a dramatic increase in system complexity. Complex mechanical structures, numerous control variables, and the resulting reliability, cost, and operational barriers have become key obstacles hindering the commercialization and widespread adoption of such aircraft.

[0008] Therefore, there is an urgent need in this field for a new type of vertical takeoff and landing aircraft solution with an extremely simplified configuration and clear control logic. It should fundamentally reduce the mechanical and control complexity of the system while ensuring basic flight performance, thereby opening up new paths for improving reliability, reducing manufacturing costs and operating thresholds. Summary of the Invention

[0009] To address at least one of the aforementioned problems, one object of the present invention is to provide a tilting rotor compound aircraft that achieves flight with as little control as possible and with the simplest possible structure.

[0010] Another objective of this invention is to provide a control method for a tiltrotor compound aircraft, enabling free switching between vertical take-off mode and fixed-wing flight mode.

[0011] This invention is implemented as follows:

[0012] The present invention provides a tilting rotor composite aircraft, comprising a fuselage, a plurality of rotors distributed around the wings, and wings mounted on both sides of the fuselage; the number of rotors is greater than or equal to 3, and the number of wings is greater than or equal to 2.

[0013] The present invention provides a tilting rotor composite aircraft, wherein at least one rotor is provided on any side of any plane passing through the fuselage centerline to provide the aircraft with pitch and yaw vector control capabilities; preferably, the plurality of rotors and wings are symmetrically distributed from left to right.

[0014] For the purpose of achieving the simplest possible outcome, preferably, the number of rotors is 3.

[0015] To achieve the simplest possible purpose, preferably, the number of wings is 2.

[0016] The present invention provides a tilting rotor compound aircraft, wherein the left rotor rotates counterclockwise and the right rotor rotates clockwise, thereby achieving coupling of yaw control and roll control. When the tilting rotor compound aircraft rolls in one direction, yaw will occur in that direction at the same time, which is beneficial for directional control in fixed-wing mode.

[0017] Preferably, the plurality of rotors are distributed at equal intervals around the fuselage, with one rotor located directly above the fuselage and at least two rotors located below the fuselage.

[0018] The present invention provides a tilting rotor composite aircraft, wherein the central axis of at least one rotor is at a certain angle to the fuselage axis, that is, it is tilted to a certain extent.

[0019] The spatial orientation of the several rotors is not completely consistent, in order to balance the anti-torque generated by the rotor rotation and suppress roll.

[0020] The present invention provides a tiltrotor compound aircraft, wherein the wing needs to have a certain dihedral angle, so that the tiltrotor compound aircraft can automatically return to its original state after being subjected to external disturbances and rolling.

[0021] Preferably, the tiltrotor composite aircraft further includes a tail fin, which enables the tiltrotor composite aircraft to automatically return to its original state after pitching and yawing due to external disturbances.

[0022] It should be noted that if a tail fin is included, the tail fin design should be considered so that the stabilizing moment it provides is less than the control moment of the aircraft in the pitch and yaw directions.

[0023] The present invention provides a tilting rotor composite aircraft, wherein the rotor and wing are fixedly connected to the fuselage, that is, the angle of the rotor and wing is fixed and no control mechanism is required for adjustment.

[0024] The present invention provides a tilting rotor compound aircraft, wherein the control output of the tilting rotor compound aircraft requires a minimum of only three rotors.

[0025] The present invention provides a tilting rotor composite aircraft that does not require any moving control surfaces.

[0026] As an optional embodiment of the present invention, the wing can serve as the landing gear for the aircraft.

[0027] The present invention provides a tilting rotor composite aircraft, which further includes two flight modes: vertical take-off mode and level flight mode.

[0028] The vertical take-off mode refers to the ability to achieve vertical take-off and landing, hovering, and other functions, similar to a multi-rotor aircraft.

[0029] The level flight mode refers to flying horizontally like a fixed wing, relying on the wings to generate lift.

[0030] The present invention provides a tilting rotor hybrid aircraft that can switch arbitrarily between these two flight modes.

[0031] The present invention provides a tiltrotor compound aircraft. Furthermore, in fixed-wing flight mode, the yaw control and pitch control of the tiltrotor compound aircraft are coupled. When the tiltrotor compound aircraft rolls in one direction, yaw in that direction will occur simultaneously.

[0032] The present invention also provides a control method for a tiltrotor compound aircraft, characterized by comprising the following steps:

[0033] Step 1: Determine whether the aircraft is currently in vertical take-off mode or fixed-wing flight mode based on its attitude.

[0034] Step 2: Determine the reference rotational speed of each rotor based on the thrust requirements;

[0035] Step 3: Achieve vector control through rotor differential speed:

[0036] In vertical mode, roll control is achieved by controlling the differential speed of the left and right motors, and pitch control is achieved by controlling the differential speed of the up and down motors.

[0037] In level flight mode, yaw and roll control are achieved by controlling the differential speed of the left and right motors, and pitch control is achieved by controlling the differential speed of the up and down motors.

[0038] Step 4, Adjust the control target:

[0039] If in vertical take-off mode, ignore yaw control, activate headless mode, and control the spatial position movement of the aircraft;

[0040] In level flight mode, the roll and yaw of the tiltrotor compound aircraft are coupled together, requiring no additional control.

[0041] Specifically, in step 2, when in vertical takeoff mode (i.e., during vertical flight), the nose points upwards, and lift is generated by the rotation of several rotors to overcome gravity. When the aircraft tilts or needs to accelerate or decelerate, the reference speed needs to be adjusted accordingly. Therefore, the reference speed of each rotor is determined by the average thrust it receives.

[0042] In step 3, when in vertical take-off mode, if the anti-torque generated by the rotor cannot cancel each other out, the torque formed by several horizontal components generated by the rotor angle offset can cancel each other out with the anti-torque of the rotor, thereby preventing the aircraft from rolling and ensuring that the aircraft can hover stably for a short time.

[0043] Preferably, some rotors rotate in the same direction, while others rotate in opposite directions, so that the anti-torque of the rotors can partially cancel each other out.

[0044] When the aircraft is in fixed-wing flight mode, i.e., in horizontal flight, differential control of the output power of the left and right rotors can control the yaw and ensure yaw stability; differential control of the output power of the upper and lower rotors can control the pitch and ensure pitch stability; increasing the rotor output power, and then slightly increasing the output power of the upper rotor and slightly decreasing the output power of the lower rotor, can increase thrust while decreasing the angle of attack, thus accelerating the aircraft; conversely, decreasing the rotor output power, and then slightly decreasing the output power of the upper rotor and slightly increasing the output power of the lower rotor, can decrease thrust while increasing the angle of attack, thus decelerating the aircraft.

[0045] When the aircraft is in fixed-wing flight mode, the dihedral angle of the wing is offset from the angle of the rotor, which gives the aircraft roll stability. At the same time, the wing can also serve as the aircraft's take-off and landing support.

[0046] The present invention also provides a mode switching method for a tilting rotor compound aircraft.

[0047] Given that the relative orientation of the aircraft's "up, down, forward, and backward" will change with the state during mode switching, all orientation descriptions below are based on the "up, down, forward, and backward" in level flight mode.

[0048] The present invention provides a mode switching method for a tiltrotor compound aircraft, which includes the following steps when switching from vertical takeoff mode to level flight mode:

[0049] Step 1: The upper rotor further increases its output power, while the lower rotor further decreases its output power, causing the aircraft to pitch.

[0050] Step 2: As the nose pitches down, the rotor power should increase synchronously with the pitch angle to ensure that the vertical component remains constant. At this time, the horizontal component continuously increases, causing the aircraft to accelerate forward.

[0051] Step 3: As the speed of the aircraft increases, the lift generated by the wings increases continuously, while the power of the rotor gradually decreases.

[0052] Step 4: Once the pitch motion reaches level flight, switch to level flight mode.

[0053] The present invention provides a mode switching method for a tiltrotor compound aircraft, which includes the following steps when switching from level flight mode to vertical takeoff mode:

[0054] Step 1: The upper rotor further reduces its output power, while the lower rotor further increases its output power, causing the aircraft to pitch.

[0055] Step 2: As the angle of attack of the aircraft increases, the drag generated by the wings increases continuously, the aircraft decelerates, and the power of the rotor gradually increases;

[0056] Step 3: As the nose tilts upward, the aircraft gradually switches to multi-rotor mode, and the rotor power begins to decrease.

[0057] Step 4: Once the pitch motion reaches level flight, switch to vertical takeoff mode.

[0058] The beneficial effects of this invention are as follows:

[0059] 1. The tilting rotor compound aircraft provided by this invention has an extremely simple structure and can realize the function of a tail-seat aircraft by relying solely on rotor differential control. It can switch freely between fixed-wing flight mode and vertical take-off mode according to specific needs, and has the advantages of multi-rotor vertical take-off and landing, hovering in the air, and fixed-wing long range and high speed.

[0060] 2. The tiltrotor compound aircraft provided by this invention requires only three rotors at a minimum. Compared with a quadcopter tail-seat aircraft, it eliminates one rotor and all the servos of the control surfaces, realizing the function of a tiltrotor compound aircraft with a simpler and more reliable structure, while increasing the effective payload.

[0061] 3. Compared with tiltrotor aircraft, the tiltrotor compound aircraft provided by this invention requires only three rotors at a minimum, eliminating the need for multiple rotors, all control surfaces, and all control rotor tilting servos. It achieves the combination of fixed-wing and multi-rotor aircraft with a simpler and more reliable structure, improving payload and aerodynamic efficiency. Attached Figure Description

[0062] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0063] Figure 1 This is a structural diagram of the tilting rotor compound aircraft in a specific embodiment of the present invention;

[0064] Figure 2 for Figure 1 A schematic diagram of the structure of the mid-wing;

[0065] Figure 3 for Figure 1 A schematic diagram of the main body of a tilting rotor composite aircraft and its fairing;

[0066] Figure 4 for Figure 1 A partial side view of the rotor angle offset;

[0067] Figure 5 for Figure 1 A schematic diagram of a tilting rotor compound aircraft in vertical take-off mode;

[0068] Figure 6 for Figure 1 A schematic diagram of a tiltrotor compound aircraft in fixed-wing flight mode;

[0069] In the diagram:

[0070] 10 is the fuselage; 11 is the elliptical outer shell; 20 is the wing; 31 is rotor one; 32 is rotor two; 33 is rotor three; 40 is the arm; 41 is the carbon rod; 42 is the bolt; 43 is the carbon plate; 44 is the clamp; 45 is the nut. Detailed Implementation

[0071] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. Obviously, the described embodiments are merely some embodiments of the invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0072] It should be noted that the specific dimensions, including length, height, distance, angle, etc., as well as the specific quantities and materials mentioned below, are all provided as a feasible method for practical implementation and can be adjusted according to actual needs.

[0073] It should be understood that the structural design described in this invention is for functional purposes. While fulfilling basic functional requirements, different structural designs can be used depending on the application scenario. The structurally feasible approach presented below is intended to facilitate those skilled in the art in manufacturing the required verification machine without inventive effort, based on the description of this invention.

[0074] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0075] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," etc., indicating orientations or positional relationships are temporary agreements for the convenience of description and control, or are based on the orientations or positional relationships shown in the accompanying drawings, or are orientations or positional relationships commonly understood by those skilled in the art. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0076] Furthermore, terms such as “further” and “preferred” are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0077] Please see Figure 1 The present invention provides a tilting rotor composite aircraft, comprising a fuselage 10, two wings 20, three rotors: rotor one 31, rotor two 32 and rotor three 33, and an arm 40.

[0078] Furthermore, as a specific embodiment of the tilting rotor compound aircraft provided by the present invention, please refer to... Figure 2 The arm consists of a carbon rod 41, bolts 42, two carbon plates 43 connecting to the motor, a clamp 44, and a nut 45. The carbon rod is clamped by the clamp and serves as a connection between the fuselage and the rotor, fixing the rotor to the periphery of the fuselage. The connection between the arm and the fuselage and the rotor is a fixed structure, without any angle adjustment mechanism, and requires no control mechanism for adjustment.

[0079] Furthermore, as a specific embodiment of the tilting rotor compound aircraft provided by the present invention, please refer to... Figure 3 An elliptical outer shell 11 surrounds the fuselage and serves to straighten the airflow. Three rotors are distributed around the fuselage.

[0080] Preferably, the three rotors can be distributed at a 120° interval. Taking the aircraft in fixed-wing flight mode as an example, when viewing the aircraft from the nose, rotor one can be located directly above the fuselage, rotor two can be located on the lower left side of the fuselage, and rotor three can be located on the lower right side of the fuselage. The three rotors are distributed at a 120° interval, with at least one rotor on each side of the vertical and horizontal planes passing through the fuselage's central axis, providing pitch and yaw vector control capabilities.

[0081] Furthermore, as a specific embodiment of the tilting rotor compound aircraft provided by the present invention, please refer to... Figure 4 The central axis of the three rotors has a fixed small angle with the fuselage axis.

[0082] Preferably, the included angle can be 2°. This fixed 2° included angle causes the rotor thrust to generate a horizontal component force, and the torque formed by it can partially offset the rotor anti-torque and suppress the aircraft spin.

[0083] Furthermore, as a specific embodiment of the tilting rotor compound aircraft provided by the present invention, please refer to... Figure 5 Taking the aircraft in vertical take-off mode as an example, the existence of the small angle means that the thrust of the three rotors has a component force in the horizontal direction. The torque formed by these three horizontal components can partially offset the anti-torque generated by the three rotors, so as to suppress the aircraft's spin.

[0084] Furthermore, as an example of a tilting rotor compound aircraft provided by this invention, please refer to... Figure 6 Taking the aircraft in fixed-wing flight mode as an example, viewed from the nose, rotor one is located directly above the fuselage, rotor two is located on the lower left of the fuselage, and rotor three is located on the lower right of the fuselage, with the three rotors distributed at 120° intervals. The rotation direction of the three rotors can be different for the two lower rotors, while the rotation direction of the upper rotor is arbitrary, but it is related to the angular offset direction of the three rotors, requiring that the aircraft not self-spin. The advantage of this scheme is that the anti-torque generated by the three rotors can cancel each other out. As an optional scheme of this invention, rotor one and rotor three rotate clockwise, while rotor two rotates counterclockwise. This reduces the angular offset of the three rotors, thus reducing the power loss of the three rotors.

[0085] Taking the aircraft in fixed-wing flight mode as an example, when viewing the aircraft from the nose, when the right rotor rotates clockwise and the left rotor rotates counterclockwise, as an optional solution of the present invention, rotor one and rotor three rotate clockwise and rotor two rotates counterclockwise. The advantage of this solution is that it can make the yaw and roll of the aircraft in fixed-wing flight mode coupled.

[0086] The coupling of yaw and roll in the aircraft refers to the following: When the aircraft is flying in fixed-wing mode, if it wants to yaw to the left, rotor 2 needs to increase its output power and rotor 3 needs to decrease its output power. This will increase the reverse torque generated by rotor 2 in the negative direction along the fuselage axis and decrease the reverse torque generated by rotor 3 in the direction along the fuselage axis. The two reverse torques are superimposed to generate a torque in the negative direction along the fuselage axis, so that the aircraft can roll to the left when yawing to the left. Similarly, this scheme can achieve right roll when yawing to the right, that is, to achieve the coupling of roll and yaw.

[0087] Furthermore, both wings have the MH114 airfoil with a span of 420mm and a chord length of 200mm, requiring anhedral.

[0088] Preferably, the dihedral angle can be 12°. The presence of this dihedral angle can suppress uncontrollable roll of the aircraft in fixed-wing flight mode, enhance the stability of the aircraft, and minimize the loss of lift. At the same time, the two wings can serve as landing gear for the aircraft.

[0089] Preferably, the tiltrotor composite aircraft further includes a tail fin, which enables the tiltrotor composite aircraft to automatically return to its original state after pitching and yawing due to external disturbances.

[0090] The internal load cells, such as batteries and flight controllers, are mounted with their positions offset downwards (by approximately 20mm), which lowers the center of gravity during horizontal flight and improves stability in fixed-wing mode.

[0091] In this embodiment, the aircraft does not have moving control surfaces such as ailerons, elevators, or rudders; attitude control is achieved entirely through rotor differential speed.

[0092] The present invention provides a tilting rotor composite aircraft, which further includes two flight modes: vertical take-off mode and level flight mode.

[0093] The vertical take-off mode refers to the ability to achieve vertical take-off and landing, hovering, and other functions, similar to a multi-rotor aircraft.

[0094] The level flight mode refers to flying horizontally like a fixed wing, relying on the wings to generate lift.

[0095] The present invention provides a tiltrotor compound aircraft that can switch arbitrarily between two flight modes. To achieve the above objective, the present invention also provides a control method for the tiltrotor compound aircraft, the specific steps of which are as follows:

[0096] The tiltrotor composite aircraft is referred to as the aircraft below.

[0097] Step 1: Determine whether the aircraft is currently in vertical take-off mode or fixed-wing flight mode based on its attitude.

[0098] Step 2: Determine the reference rotational speed of each rotor based on the thrust requirements;

[0099] Step 3: Achieve vector control through rotor differential speed;

[0100] In vertical mode, roll control is achieved by controlling the differential speed of the left and right motors, and pitch control is achieved by controlling the differential speed of the up and down motors.

[0101] In level flight mode, yaw and roll control are achieved by controlling the differential speed of the left and right motors, while pitch control is achieved by controlling the differential speed of the up and down motors.

[0102] Step 4, Adjust the control target:

[0103] If in vertical take-off mode, ignore yaw control, activate headless mode, and control the spatial position movement of the aircraft;

[0104] In level flight mode, the roll and yaw of the tiltrotor compound aircraft are coupled together, requiring no additional control.

[0105] Specifically, in step 1, key attitudes are determined through motion parameters, mainly pitch angle, horizontal flight speed and roll angle, and the model is adapted to determine the attitudes through quantization thresholds and special working condition thresholds.

[0106] In step 2, during vertical takeoff mode (vertical flight), the nose points upwards, and lift is generated by the rotation of several rotors to overcome gravity. During level flight mode, the rotors provide thrust to counteract drag, while the wings provide lift to counteract gravity. When the aircraft tilts or needs to accelerate or decelerate, the reference speed needs to be adjusted accordingly. Therefore, the reference speed of each rotor is determined by the average thrust it receives.

[0107] Step 3 includes steps 3.1 and 3.2.

[0108] 3.1 In vertical take-off mode, if the anti-torque generated by the rotor cannot cancel each other out, the torque formed by several horizontal components generated by the rotor angle offset can cancel each other out with the anti-torque of the rotor, thereby preventing the aircraft from rolling and ensuring that the aircraft can hover stably for a short period of time.

[0109] 3.2 Based on aircraft safety considerations, differential speed limits are set to prevent rollover caused by excessively low thrust on one side, and attitude loss and sudden changes in angle of attack caused by excessive coupling.

[0110] Preferably, some rotors rotate in the same direction, while others rotate in opposite directions, so that the anti-torque of the rotors can partially cancel each other out.

[0111] When the aircraft is in fixed-wing flight mode, i.e., in horizontal flight, differential control of the output power of the left and right rotors can control the yaw and ensure yaw stability; differential control of the output power of the upper and lower rotors can control the pitch and ensure pitch stability; increasing the rotor output power, and then slightly increasing the output power of the upper rotor and slightly decreasing the output power of the lower rotor, can increase thrust while decreasing the angle of attack, thus accelerating the aircraft; conversely, decreasing the rotor output power, and then slightly decreasing the output power of the upper rotor and slightly increasing the output power of the lower rotor, can decrease thrust while increasing the angle of attack, thus decelerating the aircraft.

[0112] When the aircraft is in fixed-wing flight mode, the dihedral angle of the wing is offset from the angle of the rotor, which gives the aircraft roll stability. At the same time, the wing can also serve as the aircraft's take-off and landing support.

[0113] The present invention also provides a mode switching method for a tilting rotor compound aircraft.

[0114] The present invention provides a mode switching method for a tiltrotor compound aircraft, which includes the following steps when switching from vertical takeoff mode to level flight mode:

[0115] Step 1: The upper rotor further increases its output power, while the lower rotor further decreases its output power, causing the aircraft to pitch.

[0116] Step 2: As the nose pitches down, the rotor power should increase synchronously with the pitch angle to ensure that the vertical component remains unchanged. At this time, the horizontal component continuously increases, causing the aircraft to accelerate forward.

[0117] Step 3: As the speed of the aircraft increases, the lift generated by the wings increases continuously, while the power of the rotor gradually decreases.

[0118] Step 4: Once the pitch motion reaches level flight, switch to level flight mode.

[0119] Specifically, in step 1, after receiving the level flight switching command, the flight controller precisely controls the power of the rotor directly above the fuselage to increase and the power of the left and right rotors below to decrease, ensuring stable torque output and avoiding instability caused by sudden attitude changes.

[0120] In step 2, the flight controller synchronously increases the reference power of all rotors based on the real-time pitch angle data, increases the thrust to compensate for the lift loss, ensures that the vertical component of the rotor thrust always offsets the total gravity, and prevents the altitude from dropping. At the same time, the horizontal component of the thrust gradually increases as the pitch angle decreases, propelling the aircraft to start flying forward from the hovering state, and the speed approaches the minimum level flight speed of a fixed wing.

[0121] In step 4, once the pitch angle and velocity are stable within the target range and the duration is greater than the flight control decision cycle, the flight control determines that the attitude and velocity meet the requirements and automatically switches the control logic from vertical takeoff mode to fixed-wing mode.

[0122] The present invention provides a mode switching method for a tiltrotor compound aircraft, which includes the following steps when switching from level flight mode to vertical takeoff mode:

[0123] Step 1: The upper rotor further reduces its output power, while the lower rotor further increases its output power, causing the aircraft to pitch.

[0124] Step 2: As the angle of attack of the aircraft increases, the drag generated by the wings increases continuously, the aircraft decelerates, and the power of the rotor gradually increases;

[0125] Step 3: As the nose tilts upward, the aircraft gradually switches to multi-rotor mode, and the rotor power begins to decrease.

[0126] Step 4: Once the pitch motion reaches level flight, switch to vertical takeoff mode.

[0127] Specifically, in step 2, as the angle of attack gradually increases, the aerodynamic drag of the wing increases significantly. The flight control system simultaneously increases the reference power of all rotors to ensure that the vertical component of thrust gradually increases, compensating for the decrease in wing lift and avoiding altitude loss.

[0128] In step 4, once the pitch angle and speed are stable within the target range and the duration is greater than the flight control judgment cycle, the flight control determines that the attitude and speed meet the requirements and automatically switches the control logic to vertical take-off mode. Subsequently, the rotor power can be gradually reduced to achieve a smooth vertical landing.

[0129] A specific example of the present invention provides a tilting rotor compound aircraft and its control method, which have the following advantages:

[0130] 1. This tiltrotor compound aircraft achieves all the functions of a tiltrotor compound aircraft by controlling only three rotors, and has the advantages of simple structure and low cost.

[0131] 2. Compared to a quadcopter tail-seat aircraft, this tiltrotor compound aircraft eliminates one rotor and all the servos for the control surfaces, thus increasing the payload.

[0132] 3. Compared to tiltrotor aircraft, this tiltrotor compound aircraft eliminates multiple rotors and all the servos that control the control surfaces and the servos that control the tilt of the rotors. It achieves the combination of fixed-wing and multi-rotor aircraft with a simpler and more reliable structure, improving payload and aerodynamic efficiency.

[0133] 4. The rotation directions of the three rotors of this tilting rotor compound aircraft are not completely consistent, which allows the anti-torque of the three rotors to partially cancel each other out, reducing the angular offset of the three rotors and reducing the power loss of the three rotors. At the same time, the above-mentioned rotor rotation direction arrangement can also ensure that the aircraft can achieve yaw and roll coupling when flying in fixed-wing mode.

[0134] 5. The wings of this tilting rotor compound aircraft have an upward dihedral angle, which can further suppress the roll of the aircraft caused by external interference when it is in fixed-wing flight mode.

[0135] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all possible implementations here. Any modifications, equivalent substitutions, improvements, or variations made to the technical solutions of the present invention within the spirit, principles, and inventive concept of the present invention, equivalent structural or control transformations made using the content of the present invention's specification and drawings, or direct / indirect applications in other related technical fields, should be included within the protection scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A tiltrotor composite aircraft, comprising a fuselage, a rotor, and a wing, characterized in that, The wings are mounted on both sides of the fuselage, and the plurality of rotors are distributed around the fuselage. There is at least one rotor on any side of any plane passing through the central axis of the fuselage. The central axis of the at least one rotor is at a certain angle to the axis of the fuselage. The spatial orientation of the rotors is not completely consistent, thereby generating torque through the horizontal component force, which balances the rotor counter-torque.

2. The tilting rotor composite aircraft according to claim 1, characterized in that, The left rotor rotates counterclockwise, while the right rotor rotates clockwise, thus achieving coupling of yaw control and roll control.

3. The tilting rotor composite aircraft according to claim 1, characterized in that, The wings have a certain dihedral angle, which allows the tiltrotor composite aircraft to automatically return to its original state after being disturbed by external forces and rolling.

4. A tilting rotor composite aircraft according to claim 1, characterized in that, One of the rotors is located directly above the fuselage.

5. A tilting rotor composite aircraft according to claim 1, characterized in that, The number of rotors is 3.

6. A tilting rotor composite aircraft according to claim 1, characterized in that, It also includes the tail fin.

7. A tilting rotor composite aircraft according to claim 1, characterized in that, It includes vertical takeoff mode and horizontal flight mode, and can switch freely between the two flight modes.

8. A control method for a tiltrotor compound aircraft, characterized in that, Includes the following steps: Step 1: Determine the current mode based on the aircraft's attitude; Step 2: Determine the reference rotational speed of each rotor based on the thrust requirements; Step 3: Vector control is achieved through differential speed. For example, in vertical takeoff mode, roll control is achieved by controlling the differential speed of the left and right motors, and pitch control is achieved by controlling the differential speed of the up and down motors. In level flight mode, yaw and roll control are achieved by controlling the differential speed of the left and right motors, and pitch control is achieved by controlling the differential speed of the up and down motors. Step 4: Adjust the control target. If in vertical take-off mode, ignore the yaw direction control and start the headless mode to control the spatial position movement of the aircraft. If in level flight mode, utilize the coupling of the aircraft's roll and yaw without additional control.

9. A mode switching method for a tiltrotor compound aircraft, comprising the following steps when switching from vertical takeoff mode to level flight mode: Step 1: The upper rotor further increases its output power, while the lower rotor further decreases its output power, causing the aircraft to pitch. Step 2: As the nose pitches down, the rotor power should increase synchronously with the pitch angle to ensure that the vertical component remains constant. At this time, the horizontal component continuously increases, causing the aircraft to accelerate forward. Step 3: As the speed of the aircraft increases, the lift generated by the wings increases continuously, while the power of the rotor gradually decreases. Step 4: Once the pitch motion reaches level flight, switch to level flight mode.

10. A mode switching method for a tiltrotor compound aircraft, comprising the following steps when switching from level flight mode to vertical takeoff mode: Step 1: The upper rotor further reduces its output power, while the lower rotor further increases its output power, causing the aircraft to pitch. Step 2: As the angle of attack of the aircraft increases, the drag generated by the wings increases continuously, the aircraft decelerates, and the power of the rotor gradually increases; Step 3: As the nose tilts upward, the aircraft gradually switches to multi-rotor mode, and the rotor power begins to decrease. Step 4: Once the pitch motion reaches level flight, switch to vertical takeoff mode.

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