Novel composite tilting and folding rotor integrated mechanism and aircraft

Abstract

The invention provides a novel composite tilting and folding rotor integrated mechanism and an aircraft, and belongs to the technical field of tilting rotor aircrafts. The mechanism and the aircraft are characterized in that the whole aircraft comprises a fuselage, an empennage, an undercarriage, two wings and two tilting rotor devices. The wings are located on the two sides of the fuselage, rotor wing tilting mechanisms at the tail ends of the wings are driven by hydraulic cylinders to achieve overall rotation, and modes can be switched in the take-off stage and the cruise stage. The folding function of the paddle is controlled by adopting a linear telescopic connecting rod mechanism driven by a hydraulic rod to realize two states of retraction and unfolding; a piezoelectric ceramic material and an energy storage device are embedded in the tilting mechanism, and current is generated by utilizing the piezoelectric effect when the unmanned aerial vehicle flutters, so that electric energy is recycled and supplied to the folding device; meanwhile, a PID control algorithm is adopted, so that the aircraft is good in stability and high in response speed during hovering and vertical take-off and landing; the reliability of the aircraft can be improved, the aerodynamic performance can be improved, and high flexibility and wide application prospects are achieved.

Description

Technical Field

[0001] The present invention relates to a novel composite tilt-rotor folding rotor integrated mechanism and an aircraft, belonging to the technical field of tilt-rotor aircrafts. Background Art

[0002] The vertical takeoff and landing (VTOL) tilt-rotor unmanned aerial vehicle (UAV) is an advanced aircraft that combines the flight efficiency of traditional fixed-wing UAVs and the vertical takeoff and landing ability of helicopters. At the end of the last century, the technology of VTOL fixed-wing UAVs came into being. Compared with traditional fixed-wing UAVs, VTOL tilt-rotor UAVs are more flexible in operation and can adapt to more flight environments and mission requirements. VTOL fixed-wing UAVs play an extremely important role in various fields.

[0003] The VTOL fixed-wing UAV can, like a helicopter, have the characteristics of vertical takeoff and landing without a runway and can take off and land normally on the deck of a ship. Due to the limitations of the shock stall of the advancing rotor blade and the airflow separation of the retreating rotor blade, the cruising speed of a helicopter generally does not exceed 360 km / h. In the cruise state, the tilt-rotor aircraft is the same as a conventional fixed-wing aircraft, and its flight speed is much higher than that of a general helicopter. When the tilt-rotor aircraft is in cruise flight, the wing generates lift, and the rotor no longer provides lift, only acting as two propellers to overcome the relatively small flight resistance, and the fuel consumption rate of the whole aircraft is significantly reduced compared with that of a helicopter.

[0004] The research on variable-structure aerial flying robots is very challenging. First of all, achieving vertical takeoff and landing requires a relatively complex power system and control mechanism, which not only increases the design difficulty of the UAV but also raises the cost. Secondly, maintaining stability during flight poses higher requirements for the accuracy and reliability of the control system. In addition, the ability of vertical takeoff and landing often comes at the cost of flight time and the ability to carry payloads, and a large amount of time needs to be invested in research. The rotor tilt is a very complex unsteady process, and determining its aerodynamic characteristics is one of the key technologies unique to tilt-rotor aircrafts. Usually, a combination of theoretical calculations and experiments is used, but it is still difficult to establish an accurate mathematical expression model and select a suitable prediction algorithm. In addition, the aerodynamic interference problem of tilt-rotor aircrafts is also very complex, involving multiple aspects such as rotor-wing, rotor-rotor, rotor-fuselage, and rotor-tail. Among them, the aerodynamic interference between the rotor and the wing during vertical flight and hovering is the most serious and has the greatest impact on the payload of the tilt-rotor aircraft, and a large amount of research is needed to solve it.

[0005] This invention focuses on research into the rotor component, designing a foldable, variable-structure aerial robot. The rotors are deployed during vertical takeoff and landing. To increase flight speed, they are folded to reduce wind resistance, allowing the robot to fly at high speeds using a fixed-wing turbojet engine. Vertical takeoff and landing tilt-rotor drones are expected to achieve further breakthroughs in the future, opening up new horizons for human aerial activities. Summary of the Invention

[0006] Purpose of the Invention

[0007] The core innovation of tilt-rotor drones lies in the dynamic adjustment capabilities of their rotor systems. This design not only enables seamless transitions between vertical takeoff and landing and high-speed cruise modes, but also effectively reduces rotor drag during cruise through blade rotation and retraction technology, thereby increasing range and speed. Tilt-rotor drones were originally designed to meet the needs of flexible operations in complex environments. In the military, their rapid deployment and high payload capacity make them ideal tools for battlefield support and reconnaissance. In the civilian sector, this technology can demonstrate emergency delivery capabilities in disaster relief. Furthermore, tilt-rotor drones demonstrate unique advantages in scenarios such as agricultural monitoring and power inspections. Their long flight time, combined with high-precision sensors, can address market segments that traditional drones struggle to address. This technology is expected to gain a leading position in the global aviation market, driving the transition of drones from instrumental equipment to infrastructure platforms.

[0008] Technical Solution

[0009] The present invention proposes a novel composite tilt-folding rotor integrated mechanism and an aircraft, which are characterized by comprising a fuselage (1), wings (3) symmetrically arranged on both sides of the fuselage (1), a tail wing (4), a tilt-rotor device (2) installed at the end of the wing (3), and a landing gear (5), wherein the tilt-rotor device (2) integrates a rotor folding mechanism and a tilting mechanism.

[0010] The rotor folding mechanism is composed of a hydraulic rod sleeve (12), a small hydraulic rod (13), a small hydraulic rod cover (14), a base (15), an outer ring (16), a bearing (17) and a bottom ring (18), wherein the bearing (17) is embedded in the outer ring (16) and placed together on the bottom ring (18), the outer ring (16) is connected to the connecting rod (19) to transmit motion, and the motor (8) is built into the bearing (17) to drive the small hydraulic rod (13) and the bottom ring (18) to complete the linear motion in the vertical direction, and at the same time drive the blade (7) to realize the two states of retraction and expansion.

[0011] The rotor tilting mechanism consists of a large hydraulic rod sleeve (11), a large hydraulic rod (22) and a large hydraulic rod cover (23). It is placed on both sides of the wing (3) and connected to the base (15). When hydraulic oil enters the rodless cavity of the hydraulic cylinder, the large hydraulic rod (22) extends outwards and drives the base (15) to rotate around the fixed end. When hydraulic oil enters the rod cavity, the large hydraulic rod (22) retracts, driving the base (15) to rotate in the opposite direction, thus realizing the overall tilting.

[0012] The blade (7) is embedded with shape memory alloy wires (26). The intelligent regulation of the wing shape is realized by using the phase change characteristics of the material. A controllable current is applied to the shape memory alloy wires (26), and the Joule heat effect is used to induce the phase change of the material, so as to drive the wing to generate a preset deformation, actively adjust the rotor inclination angle, thereby optimizing the aerodynamic layout and realizing the comprehensive improvement of the aerodynamic performance, fuel efficiency and environmental adaptability of the aircraft.

[0013] A storage battery (21) is arranged on the base (15), and a piezoelectric ceramic material (9) is inlaid on the outer surface of the base (15); when the rotor mechanism generates mechanical vibration due to external dynamic interference factors, the piezoelectric ceramic material (9) is forced to deform and generates an induced current based on the piezoelectric effect, and the energy storage device at the wing recovers the generated electric energy for the cyclic utilization of the airborne equipment of the aircraft.

[0014] The STM32 development board is integrated inside the fuselage (1). The displacement sensor (10) is placed on the small hydraulic rod sleeve (12), and the angular displacement sensor (25) is placed on the large hydraulic rod sleeve (11) to collect the rotor angle, tilting angle and environmental parameters in real time. The STM32 development board uses the PID control algorithm. By receiving the real-time monitoring data of the micro sensor array, it calculates the deviation between the actual output value and the expected value of the controlled object, and generates a corresponding control signal based on the preset proportional coefficient, integral coefficient and differential coefficient, and transmits the control signal to the actuator, finally realizing the coordinated adjustment of the wing tilting angle and the flight attitude, ensuring the precise control and flight stability of the UAV.

[0015] The motor (13) is directly integrated at the center of the folding mechanism, reducing the power transmission loss and improving the space utilization rate; the rotor folding mechanism adopts a hydraulic system and a bearing rotation nesting design to ensure the reliability and compactness of the retracting and deploying actions; the rotor folding mechanism, tilting mechanism and control system are coordinated to control, realizing the dual functions of large-range tilting and small-angle fine-tuning of the rotor.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1) A novel composite tilting and folding rotor integrated mechanism and aircraft are proposed, which have both the flight efficiency of traditional fixed-wing UAVs and the vertical takeoff and landing ability of helicopters.

[0018] 2) Reduced space occupancy. When parked, the propellers are fully retracted, significantly compressing the overall volume of the aircraft, enabling road-mobile transportation (no dedicated transport aircraft required). During flight, the propellers are retracted, reducing the overall exposed area and facilitating flight stealth.

[0019] 3) This structure improves the overall aerodynamic efficiency of the UAV, breaking through the bottlenecks of range and speed. After the propellers are retracted, the wing area can be effectively reduced, significantly reducing flight resistance and increasing flight speed.

[0020] 4) Adopting a cascade PID control structure (displacement feedback + angle feedback), it can quickly suppress disturbances and achieve attitude control of the aircraft with a certain accuracy, ensuring good stability and fast response speed during hovering and vertical takeoff and landing.

[0021] 5) It has a wide range of applications. The UAV equipped with this structure is significantly superior to traditional UAVs in terms of mobility and timeliness, and has broad application prospects in both military and civilian fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the intelligent tilt-rotor folding rotor integrated mechanism and the overall structure of the aircraft;

[0023] Figure 2 Schematic diagram of the overall structure of the rotor folding mechanism;

[0024] Figure 3 Exploded view of the rotor folding mechanism;

[0025] Figure 4 Schematic diagram of the structure when the folding rotor extends;

[0026] Figure 5 Schematic diagram of the structure when the folding rotor retracts;

[0027] Figure 6 Schematic diagram of the hydraulic rod device;

[0028] Figure 7 Schematic diagram of the propeller cross-section;

[0029] Figure 8 Schematic diagram of the UAV PID control system;

[0030] Figure 9 Schematic diagram of the control system structure;

[0031] The reference numerals in the figures are named as follows:

[0032] 1. Body; 2. Tilt-rotor device; 3. Wing; 4. Tail; 5. Landing gear; 6. Fairing; 7. Blade; 8. Motor; 9. Piezoelectric ceramic material; 10. Displacement sensor; 11. Large hydraulic rod sleeve; 12. Small hydraulic rod sleeve; 13. Small hydraulic rod; 14. Small hydraulic rod cover; 15. Base; 16. Outer ring; 17. Bearing; 18. Bottom ring; 19. Connecting rod; 20. Fastening screw; 21. Energy storage battery; 22. Large hydraulic rod; 23. Large hydraulic rod cover; 24. Stud; 25. Angular displacement sensor; 26. Shape memory alloy wire; Detailed implementation manner

[0033] The present invention will be further described below with reference to the accompanying drawings.

[0034] 1. As Figure 1 shown, the present invention provides a novel composite tilt-fold rotor integrated mechanism and aircraft, including a body (1), wings (3), a tail (4), a tilt-rotor device (2) and a landing gear (5), wherein the tilt-rotor device (2) includes a rotor folding mechanism and a tilting mechanism, and the two wings (3) are symmetrically arranged on both sides of the body (1).

[0035] 2. As Figure 2 shown, the rotor folding mechanism includes a hydraulic rod sleeve (12), a small hydraulic rod (13), a small hydraulic rod cover (14), a base (15), an outer ring (16), a bearing (17) and a bottom ring (18). The hydraulic energy is converted into mechanical energy through a hydraulic cylinder device, so as to control the deployment or folding of the blade (7). After folding, the wingspan is reduced, and the adaptability to narrow spaces is improved.

[0036] 3. As Figure 3 shown, two symmetrically distributed protrusions are provided at the upper end of the outer ring (16) of the rotor folding mechanism, which are connected to the small hydraulic rod (13). The outer ring (16) is concentrically installed with the bearing (17) and they are both sleeved outside the motor (8). By driving the small hydraulic rod (13), the linear motion of the bottom ring (18) in the vertical direction is realized, and the blade (7) is driven to retract and deploy through the connecting rod (19).

[0037] 4. As Figure 4 shown, when hydraulic oil enters the rodless cavity of the large hydraulic cylinder, the large hydraulic rod (22) extends outwards and drives the base (15) to rotate around the fixed end. At the same time, when hydraulic oil enters the rodless cavity of the small hydraulic cylinder, the small hydraulic rod (13) extends, so as to realize the upward movement of the bottom ring (18) and drive the blade (7) through the connecting rod (19), thereby controlling the deployment of the blade (7).

[0038] 5. As Figure 5As shown, when the hydraulic oil enters the rod chamber of the large hydraulic cylinder, the large hydraulic rod (22) resets, driving the base (15) to rotate in the reverse direction. At the same time, when the hydraulic oil enters the rod chamber of the small hydraulic cylinder, the small hydraulic rod (13) retracts, thereby driving the bottom ring (18) to move downward and causing the blade (7) to retract through the connecting rod (19).

[0039] 6. As Figure 6 shown, the tilting mechanism is composed of a large hydraulic rod sleeve (11), a large hydraulic rod (22) and a large hydraulic rod cover (23). The angular displacement sensor (25) is installed on the large hydraulic rod sleeve (11) to monitor the tilting angle in real time. The tilting mechanism is connected to the base (15) through a stud (24) to drive the large hydraulic rod (22) to achieve a two-way controllable tilting motion.

[0040] 7. As Figure 7 shown, the blade (7) is embedded with shape memory alloy wires (26). The phase change characteristics of the material are used to realize the intelligent regulation of the wing shape. A controllable current is applied to the shape memory alloy wires (26) to induce material phase change by the Joule heat effect, so as to drive the wing to generate a preset deformation, actively adjust the tilt angle of the rotor, thereby optimizing the aerodynamic layout and achieving a comprehensive improvement in the aerodynamic performance, fuel efficiency and environmental adaptability of the aircraft.

[0041] 8. As Figure 8 shown, the STM32 single-chip microcomputer embedded in the fuselage (1) is used as the core processing unit to control the flight adjustment system of the UAV. Through the micro sensor group installed on the tilting rotor device (2), multiple flight state data such as the rotor angle, tilting angle and environmental parameters are collected in real time and the PID control algorithm is used to achieve closed-loop control. The collected state data is returned to the operation platform, the deviation between the real-time measured value of the controlled object and the preset expected value is calculated, and the operation is processed based on the preset proportional coefficient, integral coefficient and differential coefficient. According to the operation result, the corresponding control instruction is output, so as to adjust the wing tilting angle and flight attitude.

[0042] 9. As Figure 9 shown, the core part of the UAV flight adjustment system is the PID controller. The PID controller is a controller with proportional-integral-derivative control laws. Among them, the proportional (P) control can quickly respond to the error, thereby reducing the steady-state error. The integral (I) control can continuously accumulate the error in the case of the existence of error in the system to output the control quantity, thereby eliminating the error. The derivative (D) control can reduce the overshoot, overcome the oscillation, improve the stability of the system, and at the same time speed up the dynamic response speed of the system and reduce the adjustment time, thereby improving the dynamic performance of the system. At the same time, a machine learning enhancement module is adopted to train its fast response ability in the face of atmospheric turbulence and vibration.

[0043] For the motion control equation of a tilt-rotor aircraft, a six-degree-of-freedom motion equation can be established:

[0044]

[0045] where m is the mass of the aircraft, X, Y, and Z are the displacements in three directions, J is the moment of inertia; b is the damping coefficient; θ is the pitch angle, φ is the roll angle, and ψ is the yaw angle.

[0046] Furthermore, the equation can be generalized as:

[0047]

[0048] where the position and attitude: ζ = [x, y, z] T , η = [φ, θ, ψ], the tilt angle α i (t) ∈ [0°, 90°], the folding coefficient β i (t) ∈ [0, 1] (0 = folded, 1 = unfolded), is the rotor thrust, F aero is the aerodynamic force, is the rotor torque, M aero is the aerodynamic torque, d ξ 、d η are the external disturbances, and the rotor thrust model is:

[0049] F i = β i ·(k F1 sinα i + k F2 cosα i )

[0050] F aero = W F T φ F (θ, φ, ψ), M aero = W M T φ M (θ, φ, ψ)

[0051] where, φ F and φ M are radial basis function (RBF) neural networks. Taking the pitch angle control of a tilt-rotor aircraft as an example, the torque it receives can be simplified as:

[0052]

[0053] where τ ext is the external disturbance torque; τ ctrl is the control torque (output by PID). The PID control equation is:

[0054]

[0055] where K p is the proportional gain, T i is the integral time constant, and τ is the derivative time constant. Substituting the output of the PID controller τ ctrl = u(t) into the dynamic equation forms a closed-loop system:

[0056]

[0057] where e = θ desired - θ, that is, the deviation between the target pitch angle and the actual angle, Ki = K p / T i and Kd = K p τ. For the three-axis attitude control (pitch, roll, yaw) of a tilt-rotor aircraft, a multi-channel PID control needs to be established:

[0058] Pitch angle:

[0059]

[0060] Roll angle:

[0061]

[0062] Yaw angle:

[0063]

[0064] Consider using an LSTM network for dynamic adjustment of PID parameters:

[0065]

[0066] According to the PID control principle, the control system block Figure 9 can be drawn, and its corresponding transfer function is:

[0067]

[0068] Let:

[0069] T i τs 2 + T i s + 1 = 0

[0070] Two negative real zeros (s1 and s2) can be solved. According to the properties of the transfer function, when using a PID controller for series correction, in addition to increasing the type of the system by one level, two negative real zeros (s1 and s2) will also be provided. Compared with the traditional PI controller, the PID controller not only has the advantage of improving the steady-state performance of the system, but also provides an additional negative real zero, thus having greater superiority in improving the dynamic performance of the system. The selection of the parameters of each part of the PID controller should be finally determined during the on-site debugging of the system. Generally, the I part should occur in the low-frequency band of the system frequency characteristics to improve the steady-state performance of the system; while the D part should occur in the middle-frequency band of the system frequency characteristics to improve the dynamic performance of the system.

Claims

1. A novel composite tilt-folding rotor integrated mechanism and aircraft, characterized by: A novel composite tilt-folding rotor integrated mechanism and an aircraft include a fuselage (1), wings (3), tail wings (4), a tilt-rotor device (2) and a landing gear (5), wherein the tilt-rotor device (2) includes a rotor folding mechanism and a tilting mechanism, the wings (3) are symmetrically arranged on both sides of the fuselage (1), the rotor folding mechanism is connected to a base (15) via a fastening screw (20), and a connecting rod (19) connects the folding mechanism and the blade (7); the rotor folding mechanism includes a small hydraulic rod sleeve (12), a small hydraulic rod (13), a small hydraulic rod cover (14), a base (15), an outer ring (16), a bearing (17) and a bottom ring (18), and the rotor folding mechanism is fixed on both sides of the wing (3); the tilting mechanism includes a large hydraulic rod sleeve (11), a large hydraulic rod (22) and a large hydraulic rod cover (23), and the tilting mechanism is fixed on both sides of the wing (3) and connected to the base (15) to achieve overall rotation.

2. The integrated folding rotor mechanism according to claim 1, characterized in that: The upper end of the outer ring (16) of the folding mechanism is provided with two symmetrically distributed protrusions, which can be connected to the connecting rod (19); the lower end of the bottom ring (18) is symmetrically distributed with two protrusions, which are connected to the small hydraulic rod (13); the outer ring (16) and the bearing (17) are concentrically installed and are together annularly sleeved on the motor (8); by driving the small hydraulic rod (13), the bottom ring (18) is realized to move linearly in the vertical direction, and the blade (7) is driven by the connecting rod (19), thereby controlling the blade (7) to retract and expand two states, realizing the controllable folding of the rotor, and effectively reducing the air resistance of the aircraft during flight.

3. The integrated tilting and folding rotor mechanism according to claim 1, characterized in that, The tilting mechanism is composed of a large hydraulic rod sleeve (11), a large hydraulic rod (22) and a large hydraulic rod cover (23). An angular displacement sensor (25) is installed on the large hydraulic rod sleeve (11) to monitor the tilting angle in real time. The tilting mechanism is connected to the base (15) through a stud (24). When hydraulic oil enters the rodless cavity of the hydraulic cylinder, the large hydraulic rod (22) extends outward and drives the base (15) to rotate around the fixed end. When hydraulic oil enters the rod cavity, the large hydraulic rod (22) retracts and drives the base (15) to rotate in the opposite direction, thereby realizing bidirectional controllable tilting movement.

4. The integrated tilting and folding rotor mechanism according to claim 1, wherein The blade (7) is embedded with a shape memory alloy wire (26), which realizes the deformation of the wing shape through the deformation characteristics of the material, and uses electric current to control its shape to drive the rotor pitch angle of the UAV to change under different conditions, thereby realizing adaptive aerodynamic layout optimization during the flight phase, thereby improving the aerodynamic performance, fuel efficiency and environmental adaptability of the aircraft.

5. The integrated tilt-rotating and folding rotor mechanism according to claim 1, characterized in that The base (15) in the tilt-rotor device (2) is equipped with an energy storage battery (21), and the outer wall of the base (15) is inlaid with a piezoelectric ceramic material (9). When the rotor mechanism is disturbed by the outside world, such as flutter caused by gusts of wind, structural resonance, aerodynamic instability, etc., the piezoelectric ceramic is compressed to generate current, converting the vibration energy into electrical energy. At this time, the energy storage device at the wing recovers the generated electrical energy for use by the tilt mechanism or the folding mechanism, thereby realizing the dual functions of active dissipation of vibration energy and energy recovery.

6. The integrated tilting and folding rotor mechanism according to claim 1, characterized in that The fuselage (1) is embedded with an STM32 development board as the core processing unit of the flight control system, a displacement sensor (10) is placed on the small hydraulic rod sleeve (12), and an angular displacement sensor (25) is placed on the large hydraulic rod sleeve (11). The aircraft as a whole adopts a PID control algorithm, and uses micro sensors to monitor the controlled objects such as the rotor angle, tilt angle and environmental factors in real time, calculates the deviation between its output value and the expected value, and generates a corresponding control signal based on the deviation and pre-set proportional, integral and differential coefficients, and feeds the signal back to the operating platform. The wing tilt angle and flight attitude are adjusted through the actuator, thereby ensuring accurate control and stable flight of the unmanned aerial vehicle.

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