A three-mode aircraft based on ground effect and its control method

Abstract

This invention discloses a three-mode aircraft based on ground effect and its control method. The aircraft includes a fuselage assembly, a power system assembly, a wing assembly, a sensor assembly, and a control unit. The front rotor can achieve continuous tilting from 0° to 90°, while the rear rotor is a fixed-direction rotor. The wing assembly adopts the NACA6409 airfoil and incorporates wing fences, carbon fiber composite tubing, and optimized ground effect geometry parameters. The control unit employs a three-layer control structure: modal recognition, inner-loop attitude stabilization, and outer-loop disturbance rejection. During vertical takeoff and landing, adaptive PID and LSTM vortex loop risk prediction are used. During ground effect cruise, adaptive PID and sliding mode control are employed, and the ground effect lift coefficient K is updated online using recursive least squares. GE During the high-speed cruise phase, an LQR controller and an EKF observer are used. During mode switching, a smooth transition between three modes—vertical takeoff and landing, ground effect cruise, and high-speed cruise—is achieved through the coordinated scheduling of the front rotor tilt angle, rear rotor start-stop logic, and front and rear rotor speeds.

Description

Technical Field

[0001] This invention relates to the field of aircraft control and aerodynamic design technology, specifically to a three-mode aircraft based on ground effect and its control method. The aircraft integrates three flight modes: vertical takeoff and landing, ground effect cruise, and high-speed cruise, and achieves smooth multi-mode switching through structural layout, sensor fusion, and sub-modal control strategies. Background Technology

[0002] Most existing three-mode aircraft employ fixed aerodynamic layouts or single control strategies, resulting in low mode conversion efficiency, insufficient ground effect utilization, and poor disturbance rejection when performing multi-mode switching, low-altitude cruise, or complex environment flight missions. Although some aircraft have introduced variable rotors or tiltable propulsion systems, the lack of effective coupling between their mechanical structure, ground effect aerodynamic characteristics, and control algorithms makes it difficult to simultaneously handle vertical takeoff and landing, close-to-ground cruise, and high-speed cruise.

[0003] Traditional PID control or sliding mode control algorithms offer stability advantages under local operating conditions, but a single controller struggles to adapt promptly to multimodal coupling, nonlinear aerodynamic variations, and turbulent disturbances in the ground effect zone. Improving the stability and switching efficiency of a three-mode aircraft by combining ground effect lift characteristics, mode identification, online parameter updates, and hierarchical control strategies without sacrificing structural reliability is a key technical challenge that needs to be addressed in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a three-mode aircraft based on ground effect and its control method, so as to improve the stability, disturbance rejection and mode switching efficiency of the aircraft in vertical take-off and landing, ground effect cruise and high-speed cruise modes.

[0005] To achieve the above objectives, the three-mode aircraft provided by this invention includes a fuselage assembly, a power system assembly, a wing assembly, a sensor assembly, and a control unit. The fuselage assembly includes a fuselage frame, a nose rotor servo assembly, and a tail fin. The fuselage frame adopts a low-turbulence guiding configuration, with its main body being a rectangular load-bearing structure with cavities. The front surface and bottom are transitioned by a continuous smooth curved surface to form a blended streamlined body adapted to ground effect aerodynamic characteristics. The nose rotor servo assembly is connected to the longitudinal central axis region on the upper surface of the fuselage frame, and its output shaft axis is parallel to the fuselage roll plane, used to drive the front arm to achieve continuous tilting from 0° to 90° around the output shaft. The tail fin is integrated into the end of the fuselage frame and is co-cured with the fuselage frame using carbon fiber reinforced composite material.

[0006] The power system components include a front arm, a rear arm, a propeller, and brushless motors. The front arm is a high-rigidity carbon fiber composite beam, with its midsection rigidly connected to the output shaft of the front rotor servo assembly via shear bolts, enabling continuous tilt freedom of the front rotor from 0° to 90°. The rear arm is also a high-rigidity carbon fiber composite beam, fixedly connected to the rear of the fuselage frame. Four brushless motors are mounted on the extended ends of the front and rear arms, with the propeller connected to a corresponding brushless motor.

[0007] The wing assembly comprises a left fore wing, a left aft wing, a right fore wing, and a right aft wing. The four wing groups each exhibit an asymmetric streamlined thickness distribution. Wing fences are mounted on the outer edges of each wing. Two high-rigidity carbon fiber composite tubes run through the interior of both the fore and aft wings, and the wings are externally bonded to the fuselage frame using thermoplastic adhesives. The wing assembly utilizes the NACA6409 airfoil as its core aerodynamic structure, and its geometric parameters have been optimized for vertical takeoff and landing, ground effect cruise, high-speed cruise, and mode transitions to reduce airflow separation and wake interference in the ground effect zone, thereby improving the lift-to-drag ratio.

[0008] Sensor components, including barometers, GPS, IMU, ultrasonic modules, and lidar, are used to acquire flight altitude, speed, attitude, and environmental information. The control unit employs a three-layer control structure: mode recognition, inner-loop attitude stabilization, and outer-loop disturbance rejection, combined with adaptive PID, sliding mode control, LQR control, EKF observation, and LSTM prediction. In ground effect cruise mode, the control unit updates the ground effect lift coefficient K online using a recursive least squares method. GE This allows it to adapt to aerodynamic changes when flying close to the ground.

[0009] The switching between the three modes is based on the rotor rotation angle as the core parameter. In vertical takeoff and landing mode, the front rotor tilts at α=0° and generates vertical lift together with the rear rotor. In ground effect cruise mode, the front rotor tilts to β, 55°≤β≤70°, the rear rotor speed decreases or stops, and the wing assembly and ground effect work together to enhance lift. In high-speed cruise mode, the front rotor tilts to γ, 75°≤γ≤90°, and the rear rotor resumes auxiliary attitude adjustment. During mode transitions, real-time rebalancing of power and aerodynamics is achieved through changes in the front rotor tilt angle, the start / stop or speed adjustment of the rear rotor, and the coordinated speed of the front and rear rotors.

[0010] Beneficial effects Compared with the prior art, the present invention has at least the following beneficial effects: First, by combining continuous tilting of the front rotor, fixed orientation of the rear rotor, and wing ground effect optimization structure, the aircraft can simultaneously achieve vertical lift, ground effect lift, and forward propulsion; Second, through a three-layer control structure of mode recognition, inner-loop attitude stabilization, and outer-loop disturbance rejection, the control strategy is matched with the flight modes; Third, the ground effect lift coefficient K is updated online using the recursive least squares method. GEFourth, by using LSTM switching quality prediction, front rotor tilt angle and front and rear rotor speed coordinated scheduling, transient disturbances during mode switching are suppressed, and smooth three-mode switching is achieved. Attached Figure Description

[0011] Figure 1 A schematic diagram of a three-mode aircraft based on ground effect; Figure 2 A bottom view of a three-mode aircraft based on ground effect; Figure 3 A schematic diagram of the front side of a three-mode aircraft based on ground effect; Figure 4 A top view of a three-mode aircraft based on ground effect; Figure 5 A schematic diagram of an asymmetric folding isometric view of a three-mode aircraft based on ground effect; Figure 6 An asymmetric folded side view of a three-mode aircraft based on ground effect; Figure 7 Diagram of the control architecture for a three-mode aircraft based on ground effect; Figure 8 This is a schematic diagram of mode transition for a three-mode aircraft based on ground effect.

[0012] Explanation of reference numerals in the attached diagram: 1. Propeller; 2. Brushless motor; 3. Front arm; 4. Rear arm; 5. Front rotor servo assembly; 6. Fuselage frame; 7. Left front wing; 8. Left rear wing; 9. Right front wing; 10. Right rear wing; 11. Tail fin. Detailed Implementation

[0013] The present invention will be further described below with reference to the accompanying drawings. These embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0014] like Figures 1 to 8 As shown, the ground-effect-based three-mode aircraft includes a fuselage assembly, a power system assembly, a wing assembly, a sensor assembly, and a control unit. The fuselage assembly includes a fuselage frame 6, a nose rotor servo assembly 5, and a tail fin 11. The fuselage frame 6 adopts a low-turbulence guiding configuration, with its main body being a rectangular load-bearing structure with cavities, its front surface transitioning to its bottom surface via a continuous smooth curved surface. The nose rotor servo assembly 5 is connected to the longitudinal centerline region of the upper surface of the fuselage frame 6, with its output shaft axis parallel to the fuselage roll plane, used to drive the nose arm 3 to achieve continuous tilting from 0° to 90°. The tail fin 11 is integrated into the end of the fuselage frame 6, including a vertical stabilizer and a horizontal stabilizer, and is co-cured with the fuselage frame 6 using carbon fiber reinforced composite material.

[0015] The power system components include a front arm 3, a rear arm 4, a propeller 1, and brushless motors 2. The front arm 3 is constructed of a high-rigidity carbon fiber composite beam, with its midsection rigidly connected to the output shaft of the front rotor servo assembly 5 via shear bolts. The rear arm 4 is also constructed of a high-rigidity carbon fiber composite beam and is fixedly connected to the rear of the fuselage frame 6 using thermoplastic adhesive. Four brushless motors 2 are mounted to the extended ends of the front arm 3 and rear arm 4 respectively using positioning bolts. The propeller 1, after dynamic balancing, is connected to its corresponding brushless motor 2.

[0016] The wing assembly comprises a left fore wing (7), a left aft wing (8), a right fore wing (9), and a right aft wing (10). The four wing groups form an asymmetrical streamlined thickness distribution. Wing fences are installed on the outer edges of each wing, lifting the fuselage and wings off the ground and leaving airflow space underneath. Two high-rigidity carbon fiber composite tubes run through the interior of both the fore and aft wings, and are externally bonded to the fuselage frame (6) using thermoplastic adhesive. The wing assembly uses the NACA6409 airfoil, and by adjusting the leading edge radius, wing cant angle, and airfoil thickness distribution, airflow separation in the ground effect zone is reduced, thus minimizing wake interference.

[0017] like Figure 7 As shown, the control unit adopts a three-layer control structure of modal recognition, inner-loop attitude stabilization, and outer-loop disturbance rejection. Sensor components collect information such as altitude, velocity, angular velocity, acceleration, and environmental obstacles, and transmit it to the central fusion computing unit. The central fusion computing unit identifies the current or target flight mode based on preset modal discrimination thresholds and multi-level state machine logic, and outputs corresponding control commands.

[0018] During the vertical takeoff and landing phase, the control unit activates the adaptive PID inner loop to stabilize the pitch, roll, and yaw channels. At the same time, it uses an LSTM network to model and analyze time-series data such as rotor operating parameters, aerodynamic load changes, motor current, and airframe vibration. When vortex ring risk is predicted or instability trend is identified, the PID parameters are adjusted and combined with multi-rotor torque distribution logic to suppress attitude errors.

[0019] During the ground effect cruise phase, the control unit retains the adaptive PID inner loop and activates the sliding mode control outer loop. The sliding mode control outer loop constructs a sliding surface based on the ground clearance error to quickly respond to disturbances in flight altitude caused by turbulence in the ground effect zone. Simultaneously, the control unit updates the ground effect lift coefficient K online using a recursive least squares method. GE This helps maintain the aircraft at a stable altitude above the ground.

[0020] During the high-speed cruise phase, the control unit switches to the LQR controller, using flight trajectory deviation, attitude angle deviation, and velocity error as optimization targets to ensure the aircraft tracks the preset trajectory and maintains stable speed. Simultaneously, the EKF observer integrates multi-source sensor information for state estimation and wind disturbance observation, and the navigation system configures control parameters based on real-time aerodynamic characteristics.

[0021] like Figure 8 As shown, the mode transition process primarily involves changes in the front rotor tilt angle, combined with rear rotor start / stop or speed adjustment to achieve synergy between power and aerodynamics. When switching from vertical takeoff and landing mode to ground effect cruise mode, the front rotor tilts from α=0° to the β range, while the rear rotor speed decreases or stops. When switching from ground effect cruise mode to high-speed cruise mode, the front rotor continues to tilt to the γ range, while the rear rotor resumes auxiliary attitude adjustment. The central controller dynamically adjusts the front rotor tilt action and the front and rear rotor speeds based on multi-sensor status monitoring results and LSTM switching quality prediction results, thereby suppressing transient disturbances and achieving smooth three-mode switching and stable control across all operating conditions.

Claims

1. A ground-effect-based tri-mode aircraft capable of switching between three modes: vertical takeoff and landing, ground-effect cruise, and high-speed cruise, characterized in that, This includes fuselage components, powertrain components, wing components, sensor components, and control units; The fuselage assembly includes a fuselage frame, a nose rotor servo assembly, and a tail fin. The fuselage frame adopts a low-turbulence guiding configuration, with its main body being a rectangular load-bearing structure with cavities. The front surface and bottom are transitioned by a continuous smooth curved surface to form a blended streamlined body adapted to ground effect aerodynamic characteristics. The nose rotor servo assembly is connected to the longitudinal centerline region on the upper surface of the fuselage frame, and its output shaft axis is parallel to the fuselage roll plane, used to drive the front arm to achieve continuous tilting from 0° to 90° around the output shaft. 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 using carbon fiber reinforced composite material. The power system components include a front arm, a rear arm, a propeller, and brushless motors. The front arm is a high-rigidity carbon fiber composite beam, the middle section of which is rigidly connected to the output shaft of the front rotor servo assembly via shear bolts, so that the front rotor has a continuous tilting degree of freedom from 0° to 90°. The rear arm is a high-rigidity carbon fiber composite beam and is fixedly connected to the middle and rear part of the fuselage frame. Four brushless motors are respectively installed on the extended ends of the front and rear arms, and the propeller is connected to the corresponding brushless motor. The wing assembly includes a left fore wing, a left aft wing, a right fore wing, and a right aft wing. The four wing groups form an asymmetric streamlined thickness distribution. Wing fences are installed on the outer edges of each wing. Two high-rigidity carbon fiber composite tubes run through the interior of both the fore and aft wings and are externally bonded to the fuselage frame using thermoplastic adhesives. The airfoil of the wing assembly adopts the NACA6409 airfoil and has been optimized for geometric parameters for vertical takeoff and landing, ground effect cruise, high-speed cruise, and mode transition to reduce airflow separation and wake interference in the ground effect zone. The sensor assembly includes a barometer, GPS, IMU, ultrasonic module, and lidar for acquiring flight altitude, speed, attitude, and environmental information. The control unit is connected to the sensor assembly, the nose rotor servo assembly, and the brushless motor, and is configured to generate control commands using a three-layer control structure of mode recognition, inner-loop attitude stabilization, and outer-loop disturbance rejection. The nose rotor rotation angle is used as the core parameter for mode switching. In ground effect cruise mode, the control unit updates the ground effect lift coefficient K online using a recursive least squares method. GE It also coordinates the front rotor tilt angle, front rotor speed and rear rotor speed to achieve smooth switching between the three modes.

2. The three-mode aircraft as described in claim 1, characterized in that, The control unit is configured to: set the front rotor tilt angle to α=0° in vertical takeoff and landing mode and enable the front rotor and rear rotor to generate vertical lift together; tilt the front rotor to β, 55°≤β≤70° in ground effect cruise mode and reduce or stop the rear rotor speed to enhance lift in conjunction with the ground effect of the wing assembly; tilt the front rotor to γ, 75°≤γ≤90° in high-speed cruise mode and restore the rear rotor to assist in attitude adjustment; and achieve seamless switching during mode transitions through coordinated control of front rotor tilt angle changes and rear rotor start / stop or speed adjustment.

3. The three-mode aircraft as described in claim 1, characterized in that, The control unit includes a dynamic model for dynamic characteristic simulation, an adaptive PID inner loop for rapid attitude stabilization, a sliding mode control outer loop for suppressing turbulence disturbances in the ground effect zone, an LQR controller for trajectory tracking during high-speed cruise, an EKF observer for state estimation and wind disturbance observation, and an LSTM network for predicting vortex ring risk and switching quality. The adaptive PID inner loop adjusts the PID parameters based on the detected vortex ring state, the sliding mode control outer loop constructs a sliding surface based on the ground clearance error and outputs an altitude disturbance rejection control quantity, and the LQR controller optimizes for flight trajectory deviation, attitude angle deviation, and velocity error.

4. A ground-effect-based three-mode aircraft control method, applied to the three-mode aircraft according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1, Modal Recognition: The sensor components collect information on altitude, flight speed, angular velocity, acceleration, and environmental obstacles, which are then transmitted to the central fusion computing unit for fusion processing. Combined with preset modal discrimination thresholds and multi-level state machine logic, the unit identifies the current or required vertical take-off and landing mode, ground effect cruise mode, or high-speed cruise mode of the aircraft. S2, Vertical Takeoff and Landing Control: During the vertical takeoff and landing phase, the adaptive PID inner loop is activated to stabilize the pitch, roll and yaw channels; at the same time, the LSTM network is used to analyze the historical rotor operating parameters, aerodynamic load changes, motor current and airframe vibration time series data. When the vortex ring risk is predicted or the instability trend is identified, the PID parameters are optimized and combined with the multi-rotor torque distribution logic to suppress attitude error. S3, Ground Effect Control: During the ground effect cruise phase, the adaptive PID inner loop is retained while the sliding mode control outer loop is activated. A sliding mode surface is constructed based on the ground clearance error to quickly respond to the height error signal. Simultaneously, the ground effect lift coefficient K is updated online using the recursive least squares method. GE To maintain stability at altitude above ground; S4, High-speed cruise control: During the high-speed cruise phase, the system switches to the LQR controller and enables the EKF observer to fuse multi-source sensor information for state estimation and wind disturbance observation, so that the aircraft can track the preset trajectory and maintain a stable flight speed. S5, Mode Switching Control: During mode switching, the central controller dynamically adjusts the front rotor tilting action, rear rotor start-stop logic, and front and rear rotor speeds based on the multi-sensor status monitoring results and LSTM switching quality prediction results. By real-time rebalancing of power and aerodynamics, transient disturbances during the switching process are suppressed, achieving smooth three-mode switching and stable control under all operating conditions.

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