Three-mode aircraft based on ground effect and control method thereof

Abstract

The invention discloses a three-mode aircraft based on a ground effect and a control method of the three-mode aircraft. The aircraft integrates three modes of vertical take-off and landing, ground effect cruising and fixed wing high-speed cruising, and efficient mode switching is achieved through aerodynamic layout optimization and self-adaptive control. And an airfoil profile geometric parameter self-adaptive adjustment technology is adopted, so that the flight performance of a ground-effect area is enhanced. According to the control method, adaptive PID, sliding mode control and LQR algorithms are integrated, and a hierarchical control architecture is constructed. And the LQR controller realizes optimal trajectory tracking based on the aerodynamic model in the high-speed cruise stage. A differential control strategy is adopted for each modal characteristic, and accurate control over the height and the speed is achieved. And through cooperative adjustment of the propeller angle and power, it is guaranteed that mode switching is stable and rapid. The problems that a traditional aircraft is low in mode conversion efficiency, insufficient in ground effect utilization and the like are solved, and the method has the advantages of being high in interference resistance, high in stability and wide in application range and is suitable for various low-altitude application scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aircraft control and aerodynamic design, in particular to a three-mode aircraft based on ground effect and a control method thereof. BACKGROUND

[0002] The existing three-mode aircraft mostly adopts fixed aerodynamic layout and single control strategy, which has low mode conversion efficiency, insufficient ground effect utilization and poor anti-disturbance performance when performing multi-mode switching, low-altitude cruising or complex environment flight tasks. Some aircrafts try to introduce variable wing structure, but most of them are mechanical deformation and cannot realize continuous adjustment of aerodynamic characteristics.

[0003] At the same time, although the traditional PID or sliding mode control algorithm has advantages in stability in the ground effect area, it lacks adaptive ability when facing multi-mode coupling and nonlinear aerodynamic characteristics. How to combine algorithm and control theory to realize a flight control system with high adaptability, high efficiency and multi-mode coordination ability is a key challenge for the development of low-altitude aircraft technology. SUMMARY

[0004] The purpose of the present application is to provide a three-mode aircraft with high mode switching efficiency, sufficient ground effect utilization and strong anti-disturbance ability, as well as an adaptive flight control algorithm, to improve the stability and task efficiency of the aircraft in ground effect cruising, vertical take-off and landing, and fixed-wing high-speed cruising modes.

[0005] The technical solution adopted by the present application to solve its technical problems is:

[0006] A three-mode aircraft based on ground effect can realize seamless conversion between ground effect, vertical take-off and landing, and high-speed cruising modes, characterized in that it comprises: a fuselage assembly, a power system assembly, and a wing assembly.

[0007] The fuselage assembly comprises a fuselage frame, a front rotor rudder motor assembly, and a tail wing. The fuselage frame adopts a low-turbulence guide configuration, with a rectangular load-bearing structure having a cavity. The front surface and the bottom are connected by a continuous smooth curve, forming a fusion streamline body that meets the ground effect aerodynamic characteristics. The front rotor rudder motor assembly is connected to the upper surface of the fuselage frame through a fastener in the longitudinal central axis area. The output shaft axis is parallel to the fuselage roll plane, used to drive the front arm to realize 0°-90° tilt movement. The tail wing is integrated at the end of the fuselage frame, including a vertical stabilizer and a horizontal stabilizer, which are co-cured with the fuselage frame by carbon fiber reinforced composite materials, providing longitudinal stability compensation for the high-speed cruising mode.

[0008] The power system components include: a front arm, a rear arm, a propeller, and brushless motors; characterized in that: the front arm is a high-rigidity carbon fiber composite beam, the middle section of which is rigidly connected to the servo output shaft via shear bolts, achieving continuous tilting freedom of 0°-90° around the shaft; both ends of the arm extend laterally from the fuselage frame in a symmetrical cantilever structure, with vibration-damping motor mounting platforms at the extended ends; the rear arm is a high-rigidity carbon fiber composite beam, fixed to the rear of the fuselage frame via thermoplastic adhesive, with its extended ends parallel to the fuselage roll plane; four brushless motors are respectively mounted on the extended ends of the front and rear arms via four sets of high-precision positioning bolts, with the motor axes perpendicular to the longitudinal plane of the arm; after dynamic balancing calibration, the propeller is connected to the motor output shaft conical surface via a self-locking hub nut, ensuring directional switching of the blade normal between vertical takeoff and landing (upward) and high-speed cruise (forward);

[0009] The wing assembly includes: a left front wing, a left rear wing, a right front wing, and a right rear wing; the four wing groups form an asymmetrical streamlined thickness distribution, and wing fences are installed on the outer edges of each wing to lift the fuselage and wings off the ground, leaving space below for air circulation to provide lift; two high-rigidity carbon fiber composite tubes run through the interior of both the front and rear wings, and are externally joined to the fuselage frame by thermoplastic adhesive;

[0010] The airfoil described uses the NACA6409 airfoil as its core aerodynamic structure. Through targeted simulation experiments, the geometric parameters are optimized to adapt to the aerodynamic requirements of three modes and mode transitions: vertical takeoff and landing, ground effect, and high-speed cruise. The leading edge radius, wing tilt angle, and airfoil thickness distribution are adjusted to reduce airflow separation in the ground effect zone, reduce airflow wake interference, and enhance stability under different flight conditions. At the same time, when flying close to the ground, it increases the pressure difference between the upper and lower wing surfaces, reduces induced drag, and improves the lift-to-drag ratio to meet the high-efficiency cruise requirements of the ground effect mode.

[0011] The control algorithm for a three-mode aircraft based on ground effect is characterized by its attitude control algorithm being based on a composite control strategy combining adaptive PID and sliding mode control, which is adapted to the dynamic characteristics of vertical takeoff and landing, ground effect, and high-speed cruise modes and mode transitions.

[0012] The ground-effect-based trimodal aircraft employs a three-layer control structure: mode recognition, inner-loop attitude stabilization, and outer-loop disturbance rejection. The sensor layer integrates multi-source data via barometers, GPS, IMU, and ultrasonic modules. The control layer dynamically adjusts the system using adaptive PID, sliding mode control, and LQR controllers. The optimization layer predicts vortex loop states using an LSTM network and updates the ground-effect lift coefficient K online via recursive least squares (RLS). GE This further enhances the system's adaptability and robustness;

[0013] The control objectives of the control strategy include the aircraft's pitch angle, yaw angle, altitude, and speed. In the ground effect mode, the focus is on controlling the altitude, while in the high-speed cruise mode, the priority is to ensure speed stability.

[0014] The control inputs of the control strategy include the front rotor speed, the rear rotor speed, and the front rotor rotation angle; among which, the front rotor rotation angle is the core parameter for mode switching (α corresponds to vertical takeoff and landing, β corresponds to ground effect, and γ corresponds to high-speed cruise), and the front and rear rotor speeds coordinate to regulate lift and thrust.

[0015] The core parameters for mode switching were obtained from simulation and experiments: α=0°, 55°≤β≤70°, 75°≤γ≤90°. Moreover, during flight, the parameters are adjusted and switched in real time according to the control target and algorithm to achieve attitude control and mode switching.

[0016] The control structure of the control strategy includes three parts: a dynamic model for dynamic characteristic simulation, an adaptive PID inner loop responsible for fast attitude stabilization, and a sliding mode control outer loop for handling turbulence disturbances in the ground effect region.

[0017] The dynamic model integrates the mirror vortex method and aerodynamic equations. The lift model under the ground effect mode is as follows:

[0018]

[0019] Where L0 is the lift without ground effect, h is the altitude above the ground, and b is the wingspan;

[0020] The adaptive PID inner loop is used for the vertical takeoff and landing and mode switching transition phases, and the control law is:

[0021] u(t) = K p (t)e(t)+K i (t)∫e(t)dt+K d (t)(de(t)) / (dt)

[0022] Among them, K p K i K d These are the proportional, integral, and derivative coefficients, respectively, and e(t) is the error signal;

[0023] The parameters are tuned online using the Ziegler-Nichols method. When a vortex ring state is detected, the proportional coefficient is automatically increased. To suppress oscillations and reduce the induced drag coefficient;

[0024] The sliding mode control outer loop is designed to address turbulent interference in the ground effect region, and the sliding mode surface is:

[0025] s=e+λ∫edt;e=hdesired -h actual

[0026] Where λ is the sliding surface coefficient, h desired For the desired height, h actual The actual height; the control law is:

[0027] u(t) = -K·sign(s)

[0028] Where K is the sliding mode control gain, and sign(s) is the sign function;

[0029] Its features also include the adoption of a coordinated strategy of front rotor rotation angle change and power distribution during mode switching: when switching from vertical take-off and landing to ground effect mode, the front rotor rotates and deforms, while the rear rotor speed decreases linearly, and the short wing flaps deploy synchronously to the optimal angle of attack. The energy management algorithm reduces energy consumption during the switching process.

[0030] The above-described ground-effect-based three-mode aircraft control method is characterized by employing a three-layer control structure of "modal recognition - inner-loop attitude stabilization - outer-loop disturbance rejection," and the specific steps include:

[0031] Modal recognition involves real-time capture of key environmental information such as obstacle density and altitude in the flight environment by the lidar, and the acquisition of flight status data such as angular velocity and acceleration by the IMU. After the two types of data are sent to the central fusion computing unit for fusion processing, the central processor combines the preset modal discrimination threshold and uses multi-level state machine logic to automatically identify the current required vertical take-off and landing, ground effect, or high-speed cruise mode and generate a mode switching command.

[0032] During the vertical takeoff and landing phase, the inner-loop adaptive PID controller is activated to precisely stabilize the aircraft's pitch, roll, and yaw paths. At the same time, a Long Short-Term Memory (LSTM) network is introduced to model and analyze multi-dimensional time-series data such as rotor operating parameters, aerodynamic load changes, motor current, and airframe vibration during the aircraft's historical flight process, and to detect vortex ring risks and attitude instability trends in advance. When the vortex ring is predicted to appear or signs of instability are identified, the PID parameter configuration is automatically optimized to suppress oscillations. At the same time, combined with the multi-rotor torque distribution logic, the induced drag coefficient is reduced, the hovering attitude error is reduced, and the hovering quality and anti-disturbance capability are improved.

[0033] During the ground effect phase, the inner-loop adaptive PID is retained for basic attitude stabilization, while the outer loop of sliding mode control is activated. Utilizing the robustness of sliding mode control, the system responds quickly to altitude error signals, effectively suppressing the impact of turbulence in the ground effect zone on flight altitude, maintaining stable altitude above the ground, and ensuring efficient and stable flight of the aircraft within the ground effect zone. Simultaneously, through the high-speed sensor system interface, rapid interaction and precise execution with the control surfaces and power mechanism are achieved, further ensuring flight stability.

[0034] During the high-speed cruise phase, the main controller switches to a linear quadratic regulator (LQR). The LQR controller optimizes flight trajectory deviation, attitude angle deviation, and speed error to ensure the aircraft accurately tracks the preset trajectory while maintaining flight speed stability, thus meeting the flight requirements during the high-speed cruise phase. During this phase, an extended Kalman filter (EKF) state observer is also activated, which integrates multi-source sensor information for accurate state estimation and wind disturbance observation. The navigation system adaptively configures control parameters based on real-time aerodynamic characteristics to balance control efficiency and flight stability.

[0035] During mode switching, the central controller dynamically adjusts the tilting action of the front rotor and the start-stop logic of the rear rotor based on the monitoring results of multiple sensors and the switching quality prediction of LSTM, through coordinated scheduling of the front rotor rotation angle and the power system speed. By real-time rebalancing of power and aerodynamics, transient disturbances during the switching process are overcome to ensure that the mode transition is completed in a short time. At the same time, multiple independent start-up control loops monitor the switching process. If a switching deviation is detected, the control immediately intervenes to suppress attitude fluctuations during the transition, ultimately achieving smooth three-mode switching and stable control under all operating conditions.

[0036] The mode conversion of a ground-effect-based three-mode aircraft is characterized by the fact that the three-mode conversion is achieved through the coordinated operation of rotor layout and aerodynamic structure. The specific working principle is as follows:

[0037] Vertical takeoff and landing mode: The front rotor tilts at an angle of α in a horizontal position, and together with the rear rotor, it generates vertical lift. The NACA6409 airfoil reduces airflow disturbance to the rotor to stabilize hovering.

[0038] Ground effect mode: The front rotor tilts to β, the rear rotor stops working, and the aircraft flies close to the ground; at this time, the NACA6409 airfoil and the ground effect work together to enhance lift, and the optimized distribution of the leading edge radius and thickness of the wing suppresses airflow separation and improves the lift-to-drag ratio.

[0039] High-speed cruise mode: The front rotor tilts to γ ​​to provide forward thrust, and the rear rotor returns to the horizontal position to assist in attitude adjustment; the NACA6409 airfoil generates a delayed shock wave to meet high-speed aerodynamic requirements.

[0040] The front rotor is a tiltable rotor, and the rear rotor is a fixed-direction rotor. The rotor layout adopts a rectangular distribution of four rotors, and the fuselage balance is ensured through center of gravity counterweight calculation. During mode transition, seamless switching is achieved through the coordinated control of the front rotor tilt angle change (α→β→γ) and the rear rotor start and stop.

[0041] In summary, this invention is innovative in terms of aircraft structure, control algorithm and mode switching. It is applicable to a variety of complex environments and significantly improves the stability, anti-interference and mode switching efficiency of the aircraft in vertical take-off and landing, ground effect and high-speed cruise modes, realizing efficient, smooth and all-condition flight in complex low-altitude environments. Attached Figure Description

[0042] Figure 1 Overall schematic diagram of a ground-effect-based three-mode aircraft

[0043] Figure 2 Ground effect-based three-mode aircraft bottom view

[0044] Figure 3 Schematic diagram of the front side of a ground-effect-based three-mode aircraft.

[0045] Figure 4 Top view of a three-mode aircraft based on ground effect

[0046] Figure 5 Asymmetric folding isometric schematic diagram of a three-mode aircraft based on ground effect.

[0047] Figure 6 Asymmetric folding side view of a three-mode aircraft based on ground effect

[0048] Figure 7 Ground effect-based three-mode flight vehicle control architecture diagram

[0049] Figure 8 Schematic diagram of mode transition of a three-mode aircraft based on ground effect

[0050] Explanation of reference numerals in the attached figures:

[0051] Propeller (1), brushless motor (2), front arm (3), rear arm (4), front propeller servo assembly (5), fuselage frame (6), left front wing (7), left rear wing (8), right front wing (9), right rear wing (10), tail fin (11). Detailed Implementation

[0052] The invention will be further described with reference to the accompanying drawings.

[0053] This invention is achieved through the following technical solution:

[0054] Ground-effect-based three-mode aircraft, such as Figures 1-8 As shown, the feature is that it includes: a fuselage assembly, a power system assembly, and a wing assembly;

[0055] The fuselage components include: fuselage frame (6), front propeller servo assembly (5), and tail fin (11); the fuselage frame (6) adopts a low-turbulence guiding configuration, the main body is a rectangular load-bearing structure with a cavity, and its front surface and bottom are transitioned by a continuous smooth curved surface to form a blended streamline body that conforms to the ground effect aerodynamic characteristics; the front propeller servo assembly (5) is connected to the longitudinal central axis area of ​​the upper surface of the fuselage frame (6) by fasteners, and its output shaft axis is parallel to the fuselage roll plane to drive the front arm to achieve 0°-90° tilting motion; the tail fin (11) is integrated at the end of the fuselage frame (6), including a vertical stabilizer and a horizontal stabilizer, and is co-cured with the fuselage frame (6) by carbon fiber reinforced composite material to provide longitudinal stability compensation for high-speed cruise mode;

[0056] The power system components include: a front arm (3), a rear arm (4), a propeller (1), and a brushless motor (2); characterized in that: the front arm (3) is a high-rigidity carbon fiber composite beam, the middle section of which is rigidly connected to the servo motor output shaft through a shear bolt group to achieve a continuous tilting degree of freedom of 0°-90° around the shaft; the two ends of the arm (3, 4) extend outward from the side of the fuselage frame (6) with a symmetrical cantilever structure, and the extended ends are provided with a vibration-damping motor mounting platform; the rear arm (4) is a high-rigidity carbon fiber composite beam. The fiber composite beam is fixed to the rear part of the fuselage frame (6) by thermoplastic adhesive, and its two ends extend outwards parallel to the roll plane of the fuselage; four brushless motors (2) are respectively installed on the extended ends of the front and rear arms (4) by four sets of high-precision positioning bolts, and the motor axis is perpendicular to the longitudinal plane of the arm; after dynamic balancing calibration, the propeller (1) is connected to the motor output shaft cone surface by a self-locking hub nut to ensure the directional switching of the blade normal between the vertical take-off and landing state (upward) and the high-speed cruise state (forward).

[0057] The wing assembly includes: a left front wing (7), a left rear wing (8), a right front wing (9), and a right rear wing (10); the four wings (7, 8, 9, 10) form an asymmetric streamlined thickness distribution, and wing fences are installed on the outer edges of each wing (7, 8, 9, 10) to lift the fuselage (6) and wings (7, 8, 9, 10) off the ground, leaving space below for air circulation to provide lift; two high-rigidity carbon fiber composite tubes are inserted inside the front and rear wings (7, 8, 9, 10), and are externally joined to the fuselage frame by thermoplastic adhesive;

[0058] The airfoil described uses the NACA6409 airfoil as its core aerodynamic structure. Through targeted simulation experiments, the geometric parameters are optimized to adapt to the aerodynamic requirements of three modes and mode transitions: vertical takeoff and landing, ground effect, and high-speed cruise. The leading edge radius of the wing (7, 8, 9, 10), the tilt angle of the wing (7, 8, 9, 10), and the thickness distribution of the airfoil have been adjusted to reduce airflow separation in the ground effect zone, reduce airflow wake interference, enhance stability under different flight conditions, and at the same time increase the pressure difference between the upper and lower wing surfaces when flying close to the ground, reduce induced drag, improve the lift-to-drag ratio, and meet the high-efficiency cruise requirements of the ground effect mode.

[0059] The control algorithm for a three-mode aircraft based on ground effect is characterized by its attitude control algorithm being based on a composite control strategy combining adaptive PID and sliding mode control, which is adapted to the dynamic characteristics of vertical takeoff and landing, ground effect, and high-speed cruise modes and mode transitions.

[0060] like Figure 7 The control architecture diagram of a three-mode aircraft based on ground effect is shown. This invention adopts a three-layer control structure of 'mode recognition - inner loop attitude stabilization - outer loop disturbance rejection'. The sensor layer achieves multi-source data fusion through barometers, GPS, IMU, and ultrasonic modules. The control layer performs dynamic adjustment based on adaptive PID, sliding mode control, and LQR controllers. The optimization layer uses an LSTM network for vortex loop state prediction and updates the ground effect lift coefficient K online using recursive least squares (RLS). GE This further enhances the system's adaptability and robustness;

[0061] The control objectives of the control strategy include the aircraft's pitch angle, yaw angle, altitude, and speed. In the ground effect mode, the focus is on controlling the altitude, while in the high-speed cruise mode, the priority is to ensure speed stability.

[0062] The control inputs of the control strategy include the front rotor speed, the rear rotor speed, and the front rotor rotation angle; among which, the front rotor rotation angle is the core parameter for mode switching (α corresponds to vertical takeoff and landing, β corresponds to ground effect, and γ corresponds to high-speed cruise), and the front and rear rotor speeds coordinate to regulate lift and thrust.

[0063] The core parameters for mode switching were obtained from simulation and experiments: α=0°, 55°≤β≤70°, 75°≤γ≤90°. Moreover, during flight, the parameters are adjusted and switched in real time according to the control target and algorithm to achieve attitude control and mode switching.

[0064] The control structure of the control strategy includes three parts: a dynamic model for dynamic characteristic simulation, an adaptive PID inner loop responsible for fast attitude stabilization, and a sliding mode control outer loop for handling turbulence disturbances in the ground effect region.

[0065] The dynamic model integrates the mirror vortex method and aerodynamic equations. The lift model under the ground effect mode is as follows:

[0066]

[0067] Where L0 is the lift without ground effect, h is the altitude above the ground, and b is the wingspan;

[0068] The adaptive PID inner loop is used for the vertical takeoff and landing and mode switching transition phases, and the control law is:

[0069] u(t) = K p (t)e(t)+K i (t)∫e(t)dt+K d (t)(de(t)) / (dt)

[0070] Among them, K p K i K d These are the proportional, integral, and derivative coefficients, respectively, and e(t) is the error signal;

[0071] The parameters are tuned online using the Ziegler-Nichols method. When a vortex ring state is detected, the proportional coefficient is automatically increased. To suppress oscillations and reduce the induced drag coefficient;

[0072] The sliding mode control outer loop is designed to address turbulent interference in the ground effect region, and the sliding mode surface is:

[0073] s=e+λ∫e dt;e=h desired -h actual

[0074] Where λ is the sliding surface coefficient, h desired For the desired height, h actual This refers to the actual height.

[0075] The control law is:

[0076] u(t) = -K·sign(s)

[0077] Where K is the sliding mode control gain, and sign(s) is the sign function;

[0078] Its features also include the adoption of a coordinated strategy of front rotor rotation angle change and power distribution during mode switching: when switching from vertical take-off and landing to ground effect mode, the front rotor rotates and deforms, while the rear rotor speed decreases linearly, and the short wing flaps deploy synchronously to the optimal angle of attack. The energy management algorithm reduces energy consumption during the switching process.

[0079] The above-described ground-effect-based three-mode aircraft control method is characterized by employing a three-layer control structure of "modal recognition - inner-loop attitude stabilization - outer-loop disturbance rejection," and the specific steps include:

[0080] Modal recognition involves real-time capture of key environmental information such as obstacle density and altitude in the flight environment by the lidar, and the acquisition of flight status data such as angular velocity and acceleration by the IMU. After the two types of data are sent to the central fusion computing unit for fusion processing, the central processor combines the preset modal discrimination threshold and uses multi-level state machine logic to automatically identify the current required vertical take-off and landing, ground effect, or high-speed cruise mode and generate a mode switching command.

[0081] During the vertical takeoff and landing phase, the inner-loop adaptive PID controller is activated to precisely stabilize the aircraft's pitch, roll, and yaw paths. At the same time, a Long Short-Term Memory (LSTM) network is introduced to model and analyze multi-dimensional time-series data such as rotor operating parameters, aerodynamic load changes, motor current, and airframe vibration during the aircraft's historical flight process, and to detect vortex ring risks and attitude instability trends in advance. When the vortex ring is predicted to appear or signs of instability are identified, the PID parameter configuration is automatically optimized to suppress oscillations. At the same time, combined with the multi-rotor torque distribution logic, the induced drag coefficient is reduced, the hovering attitude error is reduced, and the hovering quality and anti-disturbance capability are improved.

[0082] During the ground effect phase, the inner-loop adaptive PID is retained for basic attitude stabilization, while the outer loop of sliding mode control is activated. Utilizing the robustness of sliding mode control, the system responds quickly to altitude error signals, effectively suppressing the impact of turbulence in the ground effect zone on flight altitude, maintaining stable altitude above the ground, and ensuring efficient and stable flight of the aircraft within the ground effect zone. Simultaneously, through the high-speed sensor system interface, rapid interaction and precise execution with the control surfaces and power mechanism are achieved, further ensuring flight stability.

[0083] During the high-speed cruise phase, the main controller switches to a linear quadratic regulator (LQR). The LQR controller optimizes flight trajectory deviation, attitude angle deviation, and speed error to ensure the aircraft accurately tracks the preset trajectory while maintaining flight speed stability, thus meeting the flight requirements during the high-speed cruise phase. During this phase, an extended Kalman filter (EKF) state observer is also activated, which integrates multi-source sensor information for accurate state estimation and wind disturbance observation. The navigation system adaptively configures control parameters based on real-time aerodynamic characteristics to balance control efficiency and flight stability.

[0084] During mode switching, the central controller dynamically adjusts the tilting action of the front rotor and the start-stop logic of the rear rotor based on the monitoring results of multiple sensors and the switching quality prediction of LSTM, through coordinated scheduling of the front rotor rotation angle and the power system speed. By real-time rebalancing of power and aerodynamics, transient disturbances during the switching process are overcome to ensure that the mode transition is completed in a short time. At the same time, multiple independent start-up control loops monitor the switching process. If a switching deviation is detected, the control immediately intervenes to suppress attitude fluctuations during the transition, ultimately achieving smooth three-mode switching and stable control under all operating conditions.

[0085] Mode conversion methods for three-mode aircraft based on ground effect, such as Figure 8 The schematic diagram of mode conversion for a ground-effect-based three-mode aircraft is shown. Its key feature is that the ground-effect-based three-mode aircraft achieves three-mode conversion through the coordinated operation of rotor layout and aerodynamic structure. The specific working principle is as follows:

[0086] Vertical takeoff and landing mode: The front rotor tilts at an angle of α in a horizontal position, and together with the rear rotor, it generates vertical lift. The NACA6409 airfoil reduces airflow disturbance to the rotor to stabilize hovering.

[0087] Ground effect mode: The front rotor tilts to β, the rear rotor stops working, and the aircraft flies close to the ground; at this time, the NACA6409 airfoil and the ground effect work together to enhance lift, and the optimized distribution of the leading edge radius and thickness of the wing suppresses airflow separation and improves the lift-to-drag ratio.

[0088] High-speed cruise mode: The front rotor tilts to γ ​​to provide forward thrust, and the rear rotor returns to the horizontal position to assist in attitude adjustment; the NACA6409 airfoil generates a delayed shock wave to meet high-speed aerodynamic requirements.

[0089] The front rotor is a tiltable rotor, and the rear rotor is a fixed-direction rotor. The rotor layout adopts a rectangular distribution of four rotors, and the fuselage balance is ensured through center of gravity counterweight calculation. During mode transition, seamless switching is achieved through the coordinated control of the front rotor tilt angle change (α→β→γ) and the rear rotor start and stop.

[0090] In summary, this invention is innovative in terms of aircraft structure, control algorithm and mode switching. It is applicable to a variety of complex environments and significantly improves the stability, anti-interference and mode switching efficiency of the aircraft in vertical take-off and landing, ground effect and high-speed cruise modes, realizing efficient, smooth and all-condition flight in complex low-altitude environments.

Claims

1. A ground-effect-based tri-mode aircraft capable of seamless transitions between ground effect, vertical takeoff and landing, and high-speed cruise modes, characterized in that, include: Fuselage components, power system components, wing components; The fuselage components include: a fuselage frame, a nose rotor servo assembly, and a tail fin; the fuselage frame adopts a low-turbulence guiding configuration, with the main body being a rectangular load-bearing structure with cavities, and its front surface and bottom are transitioned by a continuous smooth curved surface to form a blended streamline body that conforms to ground effect aerodynamic characteristics; the nose rotor servo assembly is connected to the longitudinal central axis area of ​​the upper surface of the fuselage frame by fasteners, and its output shaft axis is parallel to the fuselage roll plane, used to drive the front arm to achieve 0°-90° tilting motion; the tail fin is integrated into the end of the fuselage frame, including a vertical stabilizer and a horizontal stabilizer, and is co-cured with the fuselage frame by carbon fiber reinforced composite material to provide longitudinal stability compensation for high-speed cruise mode; The power system components include: a front arm, a rear arm, a propeller, and brushless motors; characterized in that: the front arm is a high-rigidity carbon fiber composite beam, the middle section of which is rigidly connected to the servo output shaft via shear bolts, achieving continuous tilting freedom of 0°-90° around the shaft; both ends of the arm extend laterally from the fuselage frame in a symmetrical cantilever structure, with vibration-damping motor mounting platforms at the extended ends; the rear arm is a high-rigidity carbon fiber composite beam, fixed to the rear of the fuselage frame via thermoplastic adhesive, with its extended ends parallel to the fuselage roll plane; four brushless motors are respectively mounted on the extended ends of the front and rear arms via four sets of high-precision positioning bolts, with the motor axes perpendicular to the longitudinal plane of the arm; after dynamic balancing calibration, the propeller is connected to the motor output shaft conical surface via a self-locking hub nut, ensuring directional switching of the blade normal between vertical takeoff and landing (upward) and high-speed cruise (forward); The wing assembly includes: a left front wing, a left rear wing, a right front wing, and a right rear wing; the four wing groups form an asymmetrical streamlined thickness distribution, and wing fences are installed on the outer edges of each wing to lift the fuselage and wings off the ground, leaving space below for air circulation to provide lift; two high-rigidity carbon fiber composite tubes run through the interior of both the front and rear wings, and are externally joined to the fuselage frame by thermoplastic adhesive; The airfoil described uses the NACA6409 airfoil as its core aerodynamic structure. Through targeted simulation experiments, the geometric parameters are optimized to adapt to the aerodynamic requirements of three modes and mode transitions: vertical takeoff and landing, ground effect, and high-speed cruise. The leading edge radius, wing tilt angle, and airfoil thickness distribution are adjusted to reduce airflow separation in the ground effect zone, reduce airflow wake interference, and enhance stability under different flight conditions. At the same time, when flying close to the ground, it increases the pressure difference between the upper and lower wing surfaces, reduces induced drag, and improves the lift-to-drag ratio to meet the high-efficiency cruise requirements of the ground effect mode.

2. The three-mode aircraft based on ground effect as described in claim 1, characterized in that, Its accompanying attitude control algorithm is based on a composite control strategy that combines adaptive PID and sliding mode control, and is adapted to the dynamic characteristics of three modes, including vertical take-off and landing, ground effect, and high-speed cruise, as well as mode transitions. The control objectives of the control strategy include the aircraft's pitch angle, yaw angle, altitude, and speed. In the ground effect mode, the focus is on controlling the altitude, while in the high-speed cruise mode, the priority is to ensure speed stability. The control inputs of the control strategy include the front rotor speed, the rear rotor speed, and the front rotor rotation angle; among which, the front rotor rotation angle is the core parameter for mode switching (α corresponds to vertical takeoff and landing, β corresponds to ground effect, and γ corresponds to high-speed cruise), and the front and rear rotor speeds coordinate to regulate lift and thrust. The core parameters for mode switching were obtained from simulation and experiments: α=0°, 55°≤β≤70°, 75°≤γ≤90°. Moreover, during flight, the parameters are adjusted and switched in real time according to the control target and algorithm to achieve attitude control and mode switching. The control structure of the control strategy includes three parts: a dynamic model for dynamic characteristic simulation, an adaptive PID inner loop responsible for fast attitude stabilization, and a sliding mode control outer loop for handling turbulence disturbances in the ground effect region. The dynamic model integrates the mirror vortex method and aerodynamic equations. The lift model under the ground effect mode is as follows: Where L o For lift without ground effect, h is the altitude above the ground, and b is the wingspan; The adaptive PID inner loop is used for the vertical takeoff and landing and mode switching transition phases, and the control law is: Among them, K p K i K d These are the proportional, integral, and derivative coefficients, respectively, and e(t) is the error signal; The parameters are tuned online using the Ziegler-Nichols method. When a vortex ring state is detected, the proportional coefficient is automatically increased. To suppress oscillations and reduce the induced drag coefficient; The sliding mode control outer loop is designed to address turbulent interference in the ground effect region, and the sliding mode surface is: s=e+λ∫edt(e=h desired -h actual ) Where λ is the sliding surface coefficient, h desired For the desired height, h actual This refers to the actual height. The control law is: u(t) = -K·sign(s); Where K is the sliding mode control gain, and sign(s) is the sign function; Its features also include the adoption of a coordinated strategy of front rotor rotation angle change and power distribution during mode switching: when switching from vertical take-off and landing to ground effect mode, the front rotor rotates and deforms, while the rear rotor speed decreases linearly, and the short wing flaps deploy synchronously to the optimal angle of attack. The energy management algorithm reduces energy consumption during the switching process.

3. The three-mode aircraft control method based on ground effect as described above, characterized in that, The control adopts a three-layer structure of "modal recognition - inner loop attitude stabilization - outer loop disturbance rejection", and the specific steps include: Modal recognition involves real-time capture of key environmental information such as obstacle density and altitude in the flight environment by the lidar, and the acquisition of flight status data such as angular velocity and acceleration by the IMU. After the two types of data are sent to the central fusion computing unit for fusion processing, the central processor combines the preset modal discrimination threshold and uses multi-level state machine logic to automatically identify the current required vertical take-off and landing, ground effect, or high-speed cruise mode and generate a mode switching command. During the vertical takeoff and landing phase, the inner-loop adaptive PID controller is activated to precisely stabilize the aircraft's pitch, roll, and yaw paths. At the same time, a Long Short-Term Memory (LSTM) network is introduced to model and analyze multi-dimensional time-series data such as rotor operating parameters, aerodynamic load changes, motor current, and airframe vibration during the aircraft's historical flight process, and to detect vortex ring risks and attitude instability trends in advance. When the vortex ring is predicted to appear or signs of instability are identified, the PID parameter configuration is automatically optimized to suppress oscillations. At the same time, combined with the multi-rotor torque distribution logic, the induced drag coefficient is reduced, the hovering attitude error is reduced, and the hovering quality and anti-disturbance capability are improved. During the ground effect phase, the inner-loop adaptive PID is retained for basic attitude stabilization, while the outer loop of sliding mode control is activated. Utilizing the robustness of sliding mode control, the system responds quickly to altitude error signals, effectively suppressing the impact of turbulence in the ground effect zone on flight altitude, maintaining stable altitude above the ground, and ensuring efficient and stable flight of the aircraft within the ground effect zone. Simultaneously, through the high-speed sensor system interface, rapid interaction and precise execution with the control surfaces and power mechanism are achieved, further ensuring flight stability. During the high-speed cruise phase, the main controller switches to a linear quadratic regulator (LQR). The LQR controller optimizes flight trajectory deviation, attitude angle deviation, and speed error to ensure the aircraft accurately tracks the preset trajectory while maintaining flight speed stability, thus meeting the flight requirements during the high-speed cruise phase. During this phase, an extended Kalman filter (EKF) state observer is also activated, which integrates multi-source sensor information for accurate state estimation and wind disturbance observation. The navigation system adaptively configures control parameters based on real-time aerodynamic characteristics to balance control efficiency and flight stability. During mode switching, the central controller dynamically adjusts the tilting action of the front rotor and the start-stop logic of the rear rotor based on the monitoring results of multiple sensors and the switching quality prediction of LSTM, through coordinated scheduling of the front rotor rotation angle and the power system speed. By real-time rebalancing of power and aerodynamics, transient disturbances during the switching process are overcome to ensure that the mode transition is completed in a short time. At the same time, multiple independent start-up control loops monitor the switching process. If a switching deviation is detected, the control immediately intervenes to suppress attitude fluctuations during the transition, ultimately achieving smooth three-mode switching and stable control under all operating conditions.

4. A three-mode aircraft based on ground effect as described in claim 1, characterized in that, The ground-effect-based three-mode aircraft achieves three-mode conversion through the coordinated operation of rotor layout and aerodynamic structure. The specific working principle is as follows: Vertical takeoff and landing mode: The front rotor tilts at an angle of α in a horizontal position, and together with the rear rotor, it generates vertical lift. The NACA6409 airfoil reduces airflow disturbance to the rotor to stabilize hovering. Ground effect mode: The front rotor tilts to β, the rear rotor stops working, and the aircraft flies close to the ground; at this time, the NACA6409 airfoil and the ground effect work together to enhance lift, and the optimized distribution of the leading edge radius and thickness of the wing suppresses airflow separation and improves the lift-to-drag ratio. High-speed cruise mode: The front rotor tilts to γ ​​to provide forward thrust, and the rear rotor returns to the horizontal position to assist in attitude adjustment; the NACA6409 airfoil generates a delayed shock wave to meet high-speed aerodynamic requirements. The front rotor is a tiltable rotor, and the rear rotor is a fixed-direction rotor. The rotor layout adopts a rectangular distribution of four rotors, and the fuselage balance is ensured through center of gravity counterweight calculation. During mode transition, seamless switching is achieved through the coordinated control of the front rotor tilt angle change (α→β→γ) and the rear rotor start and stop.

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