Ducted saucer-shaped aircraft based on universal joint principle and control method of ducted saucer-shaped aircraft

Abstract

According to the ducted saucer-shaped aircraft based on the universal joint principle and the control method of the ducted saucer-shaped aircraft based on the universal joint principle, the aircraft combines the advantages of the two saucer-shaped aircrafts and is improved, the coaxial double-rotor-wing structure is adopted, the two rotor wings are arranged in the duct, and the rotation directions of the two rotor wings are opposite so that the problem of reverse torque can be solved. The attitude of the aircraft is controlled by adopting a rudder sheet; in the aspect of position control, a universal joint and a differential mechanism principle are combined, bevel gears which are symmetrical up and down are arranged in an aircraft duct, bevel gears are also arranged at the two ends of a rotor wing tilting shaft, two rotor wings tilt by taking a connecting shaft of the duct as a shaft, and meanwhile, the connecting shaft rotates in a duct plane, so that coaxial double rotor wings are realized; namely, the tension direction tilts towards any direction, so that the flight direction of the aircraft is controlled. According to the ducted saucer-shaped aircraft provided by the invention, the universal joint tilting mechanism is introduced on the basis of a coaxial dual-rotor ducted saucer-shaped aircraft, so that the pose control is separated, the control logic is clear, and the control maneuverability is enhanced.

Description

Technical Field

[0001] The invention relates to a disc-shaped aircraft based on the universal joint principle, and proposes a posture separation control method for its special configuration, belonging to the field of aircraft technology and aircraft control. Technical Background

[0002] With the development of science and technology, new drones are receiving more and more attention due to their huge potential application prospects and value, and various new concept drones are emerging one after another. In particular, aircraft that take into account vertical take-off and landing, hovering in the air and high maneuverability have become one of the hot research directions of various countries. As a new configuration aircraft, the ducted disc aircraft can take off and land vertically, has a compact structure and high aerodynamic efficiency, and has always attracted much attention in the field of new configuration drones.

[0003] At present, ducted disc-shaped aircraft can be mainly divided into two types: a typical representative is the Cypher UAV developed by Sikorsky, which uses coaxial twin rotors to balance the anti-torque and uses the pitch change of the propeller to achieve position and attitude control. The disadvantage of this disc-shaped aircraft is that the propeller mechanism is complex, which will add a considerable structural weight to the drone, bringing challenges to the flight speed and carrying capacity of the drone. Another typical representative is the ISTAR ducted disc-shaped aircraft designed by United Aerospace Corporation, which uses fixed fins in the duct to balance the anti-torque and uses the tail deflector to achieve position and attitude control. Although this disc-shaped aircraft reduces the structural weight of the aircraft, the control efficiency is reduced by relying solely on the tail deflector to control the posture, thereby reducing the maneuverability of the aircraft.

[0004] Therefore, in view of the above technical defects of the current ducted disc-shaped aircraft, the present invention proposes a new ducted disc-shaped aircraft based on the universal joint principle, and proposes a posture separation control strategy and method for this special configuration aircraft, which effectively combines the characteristics of vertical take-off and landing, maneuverability, and compact structure. Summary of the invention

[0005] The present invention proposes a ducted disc-shaped aircraft based on the principle of universal joints and a control method thereof. The aircraft combines the advantages of the two previously described disc-shaped aircraft and makes improvements. It adopts a coaxial twin-rotor configuration, places two rotors in the duct, and rotates in opposite directions to solve the problem of reverse torque. Rudder blades are used to control the aircraft's attitude; in terms of position control, in combination with the principles of universal joints and differentials, symmetrical bevel gears are arranged in the aircraft's duct, and bevel gears are also provided at both ends of the rotor tilt shaft, so that the two rotors can tilt with the connecting shaft to the duct as the axis, and the connecting shaft rotates in the duct plane, thereby realizing coaxial twin rotors, that is, the pulling direction can tilt in any direction, thereby controlling the flight direction of the aircraft.

[0006] To this end, the present invention proposes a ducted disc-shaped aircraft based on the universal joint principle, including a duct, a tilt mechanism, a power system, a pod, a flight control and a control rudder, and the connection relationship between them is: the duct contains a tilt mechanism, which is composed of 4 servos, 2 oppositely arranged annular bevel gears, 1 tilt shaft and 1 motor seat, the annular bevel gear is arranged on the gear track in the duct, the tilt shaft is located between the annular bevel gears, and small bevel gears orthogonally meshed with the annular bevel gears are provided at both ends of the tilt shaft, one end of which has a degree of freedom of rotation, so that the tilt shaft can rotate around the body axis under the differential drive of the opposite bevel gears; the servos of the tilt mechanism are fixed on the servo seat in the duct, and are arranged symmetrically up and down. The servos drive the annular bevel gear to rotate through the steering wheel, and every two servos drive 1 bevel gear in coordination; the motor seat is fixedly arranged on the tilt shaft, so that the motor / power arranged thereon can realize the rotation of the power direction as the tilt shaft rotates. The power system includes motors, propellers, batteries and ESCs. There are two motors, symmetrically arranged on the motor seat of the tilt axis. The propellers are 5-blade propellers installed on the motors, rotating with the motors to provide traction (upper motor) and thrust (lower motor). The ESCs are arranged in the ducts to provide control electrical signals for the motors. The batteries and flight control are arranged in the pod. The pod is connected to the duct and is located below the duct and tilt mechanism. The control rudders are also arranged symmetrically in a cross shape in the pod to control the stability of the aircraft's attitude.

[0007] In terms of aerodynamic layout, the aircraft adopts a coaxial twin rotor plus a duct type to balance the anti-torque and provide additional lift; the coaxial twin rotors can achieve tilt in all directions through universal joints, thereby achieving flexible and changeable maneuvers. There is a pod under the duct, with rudders arranged to control the attitude of the duct.

[0008] In terms of structural layout, the duct is used as the base ring, and two groups (four pieces) of mutually orthogonal rudder blades are arranged under the base ring to ensure that the base ring can maintain its original posture when the aircraft is disturbed by the environment during flight. Two annular bevel gears symmetrical about the center plane of the duct are arranged axially inside the duct. The annular gears rotate on the gear track inside the duct. Each gear meshes with two servos that are symmetrically connected to the duct, and the steering and speed of the gears are controlled by the servo differential. The tilt shaft of the central coaxial twin rotors is fixedly connected to a small bevel gear at one end and connected to a small bevel gear through a bearing at the other end (to avoid generating torque around the tilt shaft and symmetrically bear the load). The small bevel gear and the annular bevel gear are orthogonally meshed to form a tilt mechanism. The differential of the annular bevel gear realizes the rotation of the rotor tilt shaft and the rotation around the rotor self-rotation axis, thereby realizing the tilt of the rotor in all directions.

[0009] In terms of structural bearing, the pulling force generated by the power unit and the rotor, as well as the torque generated by the tilting of the power unit, are transmitted to the tilt shaft through the power unit base. The tilt shaft transmits the force to the duct and the annular gear in contact with the shaft in the form of bending, and the annular gear further transmits the force to the duct through the gear track; the torque on the tilt shaft is transmitted to the annular bevel gear by the pressure between the gear teeth, and the annular bevel gear is further transmitted to the servo through the pressure between the teeth. The servo and the duct are connected through the servo seat, and finally the torque is transmitted to the duct and then to the fuselage. In order to make the tilt bearing force more reasonable and reduce the friction during tilting, bearings are designed and installed at the contact points of the duct at both ends of the tilt shaft to convert the sliding friction during tilting into rolling friction.

[0010] The aircraft duct adopts an improved Clark-Y airfoil, which ensures the space for internal structure layout while maximizing the duct's contribution to lift, thereby improving the aircraft's aerodynamic efficiency.

[0011] The ducted disc-shaped aircraft proposed in the present invention has its own configuration characteristics. Its power source coaxial twin rotors can be tilted according to the movement requirements, so that the aircraft does not rely on the adjustment of the fuselage posture to track the trajectory. This is also one of the advantages of the disc-shaped aircraft compared to other types of aircraft. Specifically, the trajectory tracking of the ducted disc-shaped aircraft proposed in the present invention is achieved by tilting the coaxial twin rotors, that is, by controlling the tilt angle θ of the coaxial twin rotors. 1 and θ 2 To adjust the direction of the pull generated by the rotor so that the disc-shaped aircraft can track the desired trajectory. The stability of the attitude is achieved by controlling the rudder blades under the duct, that is, by adjusting the deflection angle δ of the four control rudder blades. j (j=1,2,3,4) to realize attitude control. Thereby, the disc-shaped aircraft can eventually achieve rapid trajectory tracking while maintaining a stable attitude at the desired attitude, ensuring that the aircraft has both strong maneuverability and stable attitude. It should be pointed out that although the disc-shaped aircraft proposed in the present invention has a coaxial twin rotor that can be tilted, the tilt-rotor here is not just used to switch from vertical take-off and landing mode to level flight mode like most existing tilt-rotor / wing aircraft, but is more importantly used to meet maneuverability. Vertical take-off and landing is of course also a function of the disc-shaped aircraft, but the control implementation is no different from trajectory tracking. The following is an explanation of the aircraft control dynamics modeling, control law design, and experimental verification steps:

[0012] The present invention provides a control method for a ducted disc aircraft based on the universal joint principle, comprising the following steps:

[0013] Step 1: Complete the kinetic modeling assumptions. Through analysis and simplification, the kinetic modeling assumptions are as follows:

[0014] (1) All components are rigid bodies and elastic deformation is ignored;

[0015] (2) Flat Earth assumption, ignoring the Earth's rotation and the curvature of the ground;

[0016] (3) The rotation response of each component is without lag;

[0017] (4) The “four centers in one”: fuselage, coaxial twin rotors, tilt axis, and center of mass of the entire aircraft.

[0018] Step 2: Establish the fuselage coordinate system Γ B =(x B ,y B ,z B ), axis coordinate system Γ P =(x P ,y P ,z P ), rotor coordinate system Γ r =(x r ,y r ,z r ), specify the tilt angle θ 1 and θ 2 Definition, θ 1 For z P The x-axis and the fuselage coordinate system B Oy B The angle between the planes, θ 2 for y P Axis and x B Oz B The angle between the planes.

[0019] Step 3: Use multi-rigid body dynamics modeling method to complete the aircraft control dynamics modeling.

[0020] Step 4: Consider disturbances and complete the design of the aircraft control law based on the dynamic modeling results.

[0021] Step 5: Assign control to the attitude control law so that it can be implemented on the actuator.

[0022] Step 6: Experimentally verify the vehicle trajectory tracking, attitude stabilization, and posture control separation effects.

[0023] The ducted disc-shaped aircraft proposed in the present invention can track the desired trajectory well. The trajectory tracking is achieved by controlling the change in the magnitude of the rotor thrust and the tilt angle. During this process, the attitude of the aircraft can be stably controlled according to the desired attitude, that is, there is no need to change the attitude to achieve trajectory tracking.

[0024] The new configuration of the ducted disc-shaped aircraft proposed in the present invention can take off and land vertically and can be maneuvered flexibly. In addition to having a series of characteristics of unmanned aerial vehicles, it also has the following advantages:

[0025] 1. Safety and stability. The rotor of the disc-shaped aircraft is built into the fuselage or duct. The fuselage and duct protect the blades, preventing the high-speed rotating blades from colliding with the operator or external objects, ensuring the safety of operation. The duct also has a good isolation effect on external disturbances, which can ensure the relative stability of the rotor flow field and is beneficial to the aerodynamic stability of the aircraft.

[0026] 2. High maneuverability and environmental adaptability. Due to the separation of posture and control, and the universal tilt of the pulling direction, the aircraft has the ability to take off and land vertically and maneuver at high speed; this kind of disc-shaped aircraft is suitable for performing tasks in complex environments, such as streets, indoors, etc. The disc-shaped aircraft can take off and land vertically in a small area, can hover near the target for reconnaissance, and can fly and track quickly, which is conducive to flexible reconnaissance.

[0027] 3. Compact structure and high propulsion efficiency. Compared with unmanned helicopters and other structural aircraft, it is more suitable for carrying and transportation. Due to the small diameter of the rotor, the air force area is small during forward flight and the air resistance is small. Compared with helicopters, disc-shaped aircraft with ducted rotors have better aerodynamic efficiency. Under the same power, the same diameter can generate greater pulling force; under the same diameter, when generating the same pulling force, the power required is smaller, which makes the disc-shaped aircraft have lower power consumption and longer endurance.

[0028] The ducted disc-shaped aircraft proposed by the present invention introduces a universal joint tilting mechanism on the basis of the coaxial twin-rotor ducted disc-shaped aircraft, so that the attitude control is separated, the control logic is clear, and the control maneuverability is enhanced. This disc-shaped aircraft can not only be used as a research and development platform for unmanned aerial vehicles and flying robots, but also provides a new unmanned aircraft configuration. Most importantly, due to its good maneuverability, the disc-shaped aircraft can be widely used in complex occasions such as urban environments and small areas, which makes the disc-shaped aircraft have great application value and good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 It is a design drawing of an embodiment of the invention.

[0031] Figure 2 It is a structural layout diagram of an embodiment of the invention.

[0032] Figure 3 Schematic diagram of the tilting mechanism of an embodiment of the invention.

[0033] Figure 4 Schematic diagram of the tilt axis of an embodiment of the invention.

[0034] Figure 5 A coordinate axis diagram of an embodiment of the invention.

[0035] Figure 6 It is the force diagram of the rudder blade according to the embodiment of the invention.

[0036] Figure 7 It is a schematic diagram of the rudder blade arm according to an embodiment of the invention.

[0037] Figure 8 This is a trajectory tracking position change diagram of an embodiment of the invention.

[0038] Fig. 9 This is a trajectory tracking position error diagram of an embodiment of the invention.

[0039] Fig.10 This is a graph showing the change in attitude angle error of an embodiment of the invention.

[0040] Fig.11 This is a diagram showing the change in rotor thrust according to an embodiment of the invention.

[0041] Fig.12 This is a diagram showing the change in tilt angle of an embodiment of the invention.

[0042] Fig.13 This is a diagram showing the change in the angle of the control rudder blade according to an embodiment of the invention.

[0043] Fig.14 It is a comparison diagram of attitude angle changes between the embodiment of the invention and a quad-rotor drone.

[0044] Numbers in the figure:

[0045] 1. Aircraft duct; 2. Aircraft pod; 3. Control rudder; 4. Propeller; 5. Gear track; 6. Ring gear; 7. Servo; 8. Tilt shaft; 9. Power unit; 10. Power unit base; 11. Bearing. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0047] like Figure 1 , Figure 2 , Figure 3 , Figure 4As shown, a disc-shaped aircraft based on the principle of universal joint adopts a coaxial twin-rotor configuration, and two rotors are placed in a duct. The two rotors rotate in opposite directions to solve the problem of reverse torque, and at the same time provide additional lift through the duct. The coaxial twin-rotor achieves tilting in all directions through the rotation of gears based on the principle of universal joint, thereby achieving flexible and changeable maneuvers. There is an aircraft pod 2 under the duct, and rudder blades are arranged to control the attitude of the duct.

[0048] In terms of structural layout, the duct is used as the base ring, and two groups (four pieces) of mutually orthogonal rudder blades are arranged under the base ring to ensure that the base ring can maintain its original posture when the aircraft is disturbed by the environment during flight. Two annular bevel gears symmetrical about the center plane of the duct are arranged axially inside the duct. The annular gears rotate on the gear track 5 inside the duct. Each gear meshes with two symmetrical servos 7. The servos 7 are fixedly connected to the duct, and the steering and speed of the gears are controlled by the differential of the servos. The annular gear also meshes with the tilt axis 8 of the coaxial twin rotors. One end of the tilt axis 8 is fixedly connected to the bevel gear, and the other end is connected to the bevel gear through the bearing 11 (to avoid generating torque around the tilt axis and symmetrically bear the load). The bevel gear and the annular bevel gear are orthogonally meshed to form a tilt mechanism. The self-rotation of the rotor tilt axis and the rotation around the rotor self-rotation axis are realized through the differential of the annular bevel gear 6, thereby realizing the rotor, that is, the tilting direction of the pulling force in all directions, thereby controlling the flight direction of the aircraft.

[0049] In terms of structural bearing, the pulling force generated by the power unit 9 and the rotor, as well as the torque generated by the tilting of the power unit 9, are transmitted to the tilt shaft through the power unit base 10. The tilt shaft transmits the force to the duct and the annular gear 6 in contact with the shaft in the form of bending, and the annular gear 6 further transmits the force to the duct through the gear track 5; the torque on the tilt shaft is transmitted to the annular bevel gear by the pressure between the gear teeth, and the annular bevel gear is further transmitted to the steering gear 7 by the pressure between the teeth, and the steering gear 7 is connected to the duct through the steering gear seat, and finally the torque is transmitted to the duct and then to the fuselage. In order to make the tilt bearing force more reasonable and reduce the friction during tilting, bearings are designed and installed at the two ends of the tilt shaft where they contact the duct to convert the sliding friction during tilting into rolling friction.

[0050] The total weight of the aircraft is 5kg, and the weight efficiency is 50%. The aircraft duct 1 adopts an improved Clark-Y-like airfoil with a height of 200mm and an inner diameter of 420mm. While ensuring the space for the internal structure layout, the contribution of the duct to lift is increased as much as possible, thereby improving the aerodynamic efficiency of the aircraft. The CFD numerical simulation method is used to determine that the upper propeller position of propeller 4 is 1 / 4 of the height of aircraft duct 1, the distance from the upper blade to the duct outlet is about 50mm, the pitch of the double propeller is 1 / 3 of the duct height, the distance from the lower blade to the duct outlet is about 120mm, and a 3mm gap is reserved between the propeller tip and the duct.

[0051] The propeller disc area of ​​the aircraft is 0.13m 2 , the propeller disc load is 38.46kg / m 2 Therefore, according to the load conditions, the rotor blade diameter is selected to be 0.407m (16 inches) and the NACA2415 airfoil is selected. According to the rotor diameter and the requirements of the UAV flight performance, the MN5008 KV400 motor of T-MOTOR or a motor of similar size and power can be used.

[0052] The main load-bearing components of the aircraft, such as the motor mount, tilt shaft, duct, servo mount, etc., are mainly made of carbon fiber materials to ensure strength and rigidity while reducing weight as much as possible.

[0053] The aircraft flight control board mainly uses open source flight control such as PX4 version Pixhawk.

[0054] The ducted disc-shaped aircraft proposed in the present invention has its own configuration characteristics. Its power source coaxial twin rotors can be tilted according to the movement requirements, so that the aircraft does not rely on the adjustment of the fuselage posture to track the trajectory. This is also one of the advantages of the disc-shaped aircraft compared to other types of aircraft. Specifically, the trajectory tracking of the ducted disc-shaped aircraft proposed in the present invention is achieved by tilting the coaxial twin rotors, that is, by controlling the tilt angle θ of the coaxial twin rotors. 1 and θ 2 To adjust the direction of the pull generated by the rotor so that the disc-shaped aircraft can track the desired trajectory. The stability of the attitude is achieved by controlling the rudder blades under the duct, that is, by adjusting the deflection angle δ of the four control rudder blades 3 j (j=1,2,3,4) to realize attitude control. Thereby, the disc-shaped aircraft can finally achieve rapid trajectory tracking while maintaining a stable attitude at the desired attitude, ensuring that the aircraft has both strong maneuverability and stable attitude. It should be pointed out that, although the disc-shaped aircraft proposed in the present invention has a coaxial twin-rotor that can be tilted, the tilt-rotor here is not just used to switch from vertical take-off and landing mode to level flight mode like most existing tilt-rotor / wing aircraft, but is more mainly used to meet maneuverability. Vertical take-off and landing is of course also a function of the disc-shaped aircraft, but the control implementation is no different from trajectory tracking. The following is an explanation of the embodiments in terms of aircraft control dynamics modeling, control law design and experimental verification steps:

[0055] The present invention provides a control method for a ducted disc aircraft based on the universal joint principle, comprising the following steps:

[0056] Step 1: Complete the kinetic modeling assumptions. Through analysis and simplification, the kinetic modeling assumptions are as follows:

[0057] (1) All components are rigid bodies and elastic deformation is ignored;

[0058] (2) Flat Earth assumption, ignoring the Earth's rotation and the curvature of the ground;

[0059] (3) The rotation response of each component is without lag;

[0060] (4) The “four centers in one”: fuselage, coaxial twin rotors, tilt axis, and center of mass of the entire aircraft.

[0061] Step 2: Establish the fuselage coordinate system Γ B =(x B ,y B ,z B ), axis coordinate system Γ P =(x P ,y P ,z P ), rotor coordinate system Γ r =(x r ,y r ,z r ), specify the tilt angle θ 1 and θ 2 Definition, θ 1 For z P The x-axis and the fuselage coordinate system B Oy B The angle between the planes, θ 2 for y P Axis and x B Oz B The angle between the planes. Example 1: Establishing a coordinate axis system such as Figure 5 shown.

[0062] Step 3: Use multi-rigid body dynamics modeling method to complete the aircraft control dynamics modeling.

[0063] From the structural characteristics of the disc-shaped aircraft, we can know that the aircraft has a position P = [x, y, z] T and posture Θ=[φ,θ,Ψ] T Six degrees of freedom and rotor thrust T, tilt angle θ 1 and θ 2 and the deflection angle δ of the rudder blade j As the control quantity, the butterfly aircraft is a nonlinear system. Based on the Euler equation:

[0064]

[0065] Where: M iI It represents the moment of component i relative to the inertial system I; represents the angular momentum of component i relative to the inertial system; D Irepresents the rotational time derivative of the tensor relative to the inertial system. Applying the Euler equation to the disc-shaped aircraft finally results in the translational dynamics equation:

[0066]

[0067] Where: V represents the speed of the aircraft; R IB represents the transformation matrix from the body coordinate system B to the inertial system I; T represents the thrust of the rotor; m s Represents the total mass of the machine; g is the acceleration due to gravity.

[0068] Rotational dynamics equation:

[0069]

[0070] Where: W is the transformation matrix; Ω is the attitude angular velocity; [M B ] B Represents the projection of the moment acting on the body in the body coordinate system; I s Represents the total machine moment of inertia; G a Indicates gyroscopic torque; G k It indicates the dynamic characteristics caused by the rotation of each moving part around its own axis (anti-torque).

[0071]

[0072] Where: is the body moment of inertia; R BP and R PB They represent the transformation matrices from the tilt axis coordinate system to the body coordinate system and from the body coordinate system to the tilt axis coordinate system respectively; is the moment of inertia of the tilt axis; is the attitude angular velocity; and They represent the transformation matrices from the rotor coordinate system to the body coordinate system and from the body coordinate system to the rotor coordinate system respectively; represents the rotor moment of inertia; r i Indicates rotor i.

[0073] G a =G a1 +G a2

[0074]

[0075] Where: Ω P Indicates the angular velocity of the tilt axis; Ω ri represents the rotor angular velocity.

[0076]

[0077] Step 4: Consider disturbances and complete the design of the aircraft control law based on the dynamic modeling results.

[0078] Considering the disturbance, the following state equations of position and attitude can be obtained based on the obtained dynamic equations:

[0079]

[0080] Where: u is the control quantity of the position state equation. When u is known, the law of the change of the rotor thrust can be inversely calculated by comparing the translational dynamics equation; τ is the control quantity of the attitude state equation; D 1 and D 2 For disturbance.

[0081] Given the expected position P ref =[x ref ,y ref ,z ref ] T , where x ref is the expected coordinate in the x-axis direction, y ref is the expected coordinate in the y-axis direction, z ref is the expected coordinate in the z-axis direction, and the expected attitude Θ ref =[φ ref ,θ ref ,Ψ ref ] T , where φ ref is the desired roll angle, θ ref is the desired pitch angle, Ψ ref is the desired yaw angle. The terminal sliding mode control law is used to design u and τ as:

[0082]

[0083] Where: k 1 =1.5, k 2 =0.5, k 3 =2, k 4 =0.5, L 1 =5.3,L 2 =12 is the gain coefficient, and the remaining variables are as follows:

[0084]

[0085] Where: u is the control quantity of the position state equation. When u is known, the law of the change of the rotor thrust can be inversely calculated by comparing the translational dynamics equation; τ is the control quantity of the attitude state equation; D 1 and D 2 is the disturbance, β=1 is the gain coefficient.

[0086] Step 5: Assign the attitude control law to the actuator. Figure 6 As shown. Among them:

[0087]

[0088] Where: c l ,c d ,c d0 are all constants, S is the area of ​​the rudder blade, T is the rotor thrust, D is the rotor diameter, δ is the deflection angle of the rudder blade, and F L and F D They represent the force of the rudder blade perpendicular to the incoming flow direction and along the incoming flow direction respectively. The pseudo-inverse method is used to distribute the control law to each control rudder blade. The formula of the pseudo-inverse method is as follows:

[0089]

[0090] Where: δ is the control effector, and the so-called control effector here means the force on the rudder blade; in addition, W δ Represents the weight matrix, which can be set by W δ To make the distribution results more focused; δ Represents the control quantity matrix to be allocated, where d δ =[τ 1 ,τ 2 ,τ 3 ] T ; B δ1 and B δ2 All represent coefficient matrices. According to the configuration, the arm diagram of the rudder blade is as follows Figure 7 As shown. Therefore, the moment in the rolling, pitching and yaw directions that can be generated by controlling the deflection of the rudder blade is:

[0091]

[0092] Where: F Li and F Di They represent the force of the rudder blade i perpendicular to the incoming flow direction and along the incoming flow direction respectively; d v and d h They represent the distance between the force center of the rudder blade and the horizontal axis and plumb axis of the disc-shaped aircraft respectively; τ 1 ,τ 2 ,τ 3 Represent the moments in the rolling, pitching and yaw directions respectively.

[0093] Thus, the change of the deflection angle of each control rudder blade 4 can be obtained.

[0094] Step 6: Experimentally verify the vehicle trajectory tracking, attitude stabilization, and posture control separation effects.

[0095] The above-derived dynamic model and control law are simulated by MATLAB, where the disturbance is set:

[0096] D 1 =(cos5t+0.2sint)*[1,1,1] T , D 2 =(0.5+cost+sin10t)*[1,1,1] T ;

[0097] P ref =[rcos(ωt),rsin(ωt),kωt] T , Θ ref =[0,0,0] T ; The initial values ​​of position and attitude are:

[0098] P 0 =[0,0,0] T and θ 0 =[0,0,0] T The experimental results obtained are as follows Figure 8 , Fig. 9 , Fig.10 , Fig.11 , Fig.12 , Fig.13 shown. Figure 8 This is a diagram showing the motion curve of a disc-shaped aircraft tracking a target; Fig. 9 It represents the curve of the three-dimensional position tracking error change during the process of the disc-shaped aircraft tracking the target; Fig.10 It represents the attitude angle error variation curve of the disc-shaped aircraft during tracking the target; Fig.11 It represents the curve of the rotor thrust variation during the disc-shaped aircraft tracking the target; Fig.12 It represents the curve of the rotor tilt angle change during the disc-shaped aircraft tracking the target; Fig.13 It represents the curve of the change of the control blade angle during the disc-shaped aircraft tracking the target;

[0099] The experimental results show that the ducted disc-shaped aircraft in the embodiment can track the desired trajectory well. The trajectory tracking is achieved by controlling the change in the magnitude of the rotor thrust and the tilt angle. In this process, the attitude of the aircraft can be stably controlled according to the desired attitude, that is, the trajectory tracking can be achieved without changing the attitude. In order to better show the advantages of the disc-shaped aircraft, a four-rotor drone with good maneuverability, small size, and vertical take-off and landing is used for simulation comparison and analysis.

[0100] The mass, rotor performance and control law of the quadrotor drone are set to be the same as those of the disc-shaped aircraft, and the same disturbance is set in the dynamic model of the quadrotor drone. The inner and outer loop control logic is used to track the trajectory of the quadrotor. Although the motion trajectory of the quadrotor is the same as that of the disc-shaped aircraft due to the same control law, the position and attitude of the quadrotor are strongly coupled, that is, the position is changed by the attitude. The attitude angle of the quadrotor changes as follows Fig.14 As shown. It can be clearly seen from the figure that the roll angle and yaw angle are constantly changing according to the requirements of the outer loop virtual trajectory control law, so that the quadcopter can track the desired trajectory, and the yaw angle changes less because the desired yaw angle specified when the inner and outer loops are controlled is 0. By comparing the attitude angle change curves of the quadcopter and the ducted disc-shaped aircraft in the embodiment, it can be seen that the attitude of the disc-shaped aircraft can obviously remain stable during the movement, and can remain stable according to the desired attitude without considering the need for trajectory tracking.

[0101] Those skilled in the art should understand that the discussion of the above embodiment is merely illustrative and is not intended to imply that the scope of the invention is limited to this example; within the scope of the invention, the technical features in the above embodiment or in different embodiments may be combined, and there are many other variations of different aspects of the invention as described above, which are not provided in detail for the sake of simplicity.

[0102] The embodiments of the invention are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the invention should be included in the scope of protection of the invention.

Claims

1. A ducted disc aircraft based on the universal joint principle, characterized in that: It includes a duct, a tilt mechanism, a power system, a pod, a flight control system and control rudders; wherein, the duct contains a tilt mechanism, which is composed of 4 servos, 2 oppositely arranged annular bevel gears, 1 tilt shaft and 1 motor seat, the annular bevel gears are arranged on the gear track in the duct, the tilt shaft is located between the annular bevel gears, and there are small bevel gears at both ends of the tilt shaft that are orthogonally meshed with the annular bevel gears, one end of which has the degree of freedom of rotation, and the tilt shaft rotates around the body axis under the differential drive of the opposite bevel gears; the servos of the tilt mechanism are fixed on the servo seat in the duct, arranged symmetrically up and down, and the servos drive the annular bevel gears through the steering wheel. The wheels rotate, and every two servos work together to drive a bevel gear; a motor seat is fixedly arranged on the tilt shaft, so that the motor arranged on it can realize the rotation of the power direction as the tilt shaft rotates; the power system includes motors, propellers, batteries and electric controllers. There are two motors in total, which are symmetrically arranged on the motor seat of the tilt shaft. The propeller is a 5-blade propeller installed on the motor, which rotates with the motor to provide tension and thrust. The electric controller is arranged in the duct to provide control electrical signals for the motor. The battery and flight control are arranged in the pod; the pod is connected to the duct and is located below the duct and the tilt mechanism. The control rudders are arranged symmetrically in a cross shape in the pod to control the stability of the aircraft's attitude.

2. A ducted disc aircraft based on the universal joint principle according to claim 1, characterized in that: Two annular bevel gears symmetrical about the center plane of the duct are arranged axially inside the duct, and the annular gears rotate on the gear track inside the duct. Each gear meshes with two centrally symmetrical servos. The servos are fixedly connected to the duct, and the steering and speed of the gears are controlled by the servo differential. The annular gears also mesh with the tilt shaft of the coaxial twin rotors. One end of the tilt shaft is fixedly connected to the bevel gear, and the other end is connected to the bevel gear through a bearing. The bevel gears and the annular bevel gears are orthogonally meshed to form a tilt mechanism. The self-rotation of the rotor tilt shaft and the rotation around the rotor self-rotation axis are realized through the differential of the annular bevel gears, so that the rotor, that is, the pulling direction, can be tilted in all directions, thereby controlling the flight direction of the aircraft.

3. A control method for a ducted disc aircraft based on the universal joint principle as claimed in claim 1, characterized in that: The steps include: Step 1: Complete the kinetic modeling assumptions. Through analysis and simplification, the kinetic modeling assumptions are as follows: (1) All components are rigid bodies and elastic deformation is ignored; (2) Flat Earth assumption, ignoring the Earth's rotation and the curvature of the ground; (3) There is no lag in the rotation response of each component; (4) The "four centers in one" of fuselage, coaxial twin rotors, tilt axis, and center of mass of the entire aircraft; Step 2: Establish the fuselage coordinate system Γ B =(x B ,y B ,z B ), axis coordinate system Γ P =(x P ,y P ,z P ), rotor coordinate system Γ r =(x r ,y r ,z r ), clearly define the tilt angles θ1 and θ2, θ1 is z P The x-axis and the fuselage coordinate system B Oy B The angle between the two planes, θ2 is y P Axis and x B Oz B The angle between the planes; Step 3: Use multi-rigid body dynamics modeling method to complete the aircraft control dynamics modeling; Step 4: Consider disturbances and complete the design of the aircraft control law based on the dynamic modeling results; Step 5: Control the attitude control law and implement it to the actuator; Step 6: Experimentally verify the vehicle trajectory tracking, attitude stabilization, and posture control separation effects.

4. The control method of a ducted disc aircraft based on the universal joint principle according to claim 3, characterized in that: In step 3, the aircraft has position P = [x, y, z] T and posture Θ=[φ,θ,Ψ] T Six degrees of freedom and the rotor thrust T, the tilt angles θ1 and θ2, and the deflection angle δ of the rudder blade j As the control quantity, the butterfly aircraft is a nonlinear system; based on the Euler equation: Where: M iI It represents the moment of component i relative to the inertial system I; represents the angular momentum of component i relative to the inertial system; D I represents the rotational time derivative of the tensor relative to the inertial system; applying the Euler equation to the disc-shaped aircraft, the translational dynamics equation is: Where: V represents the speed of the aircraft; R IB represents the transformation matrix from the body coordinate system B to the inertial system I; T represents the thrust of the rotor; m s Represents the total mass of the machine; g is the acceleration due to gravity.

5. The control method of a ducted disc aircraft based on the universal joint principle according to claim 4, characterized in that: In step 3, the rotational dynamics equation is: Where: W is the transformation matrix; Ω is the attitude angular velocity; [M B ] B Represents the projection of the moment acting on the body in the body coordinate system; I s Represents the total machine moment of inertia; G a Indicates gyroscopic torque; G k Indicates the dynamic characteristics caused by the rotation of each moving part around its own axis; specifically: Where: is the body moment of inertia; R BP and R PB They represent the transformation matrices from the tilt axis coordinate system to the body coordinate system and from the body coordinate system to the tilt axis coordinate system respectively; is the moment of inertia of the tilt axis; and They represent the transformation matrices from the rotor coordinate system to the body coordinate system and from the body coordinate system to the rotor coordinate system respectively; represents the rotor moment of inertia; r i Indicates rotor i.

6. The control method of a ducted disc aircraft based on the universal joint principle according to claim 3, characterized in that: In step 4, considering the disturbance, the following state equations of position and attitude are obtained based on the obtained dynamic equations: Where: u is the control quantity of the position state equation. When u is known, the change law of the rotor thrust can be inversely calculated by comparing the translational dynamics equation; τ is the control quantity of the attitude state equation; D1 and D2 are disturbances.

7. The control method of a ducted disc aircraft based on the universal joint principle according to claim 6, characterized in that: In step 4, the expected position P is given respectively ref =[x ref ,y ref ,z ref ] T and attitude expectations Θ ref =[φ ref ,θ ref ,Ψ ref ] T , where x ref is the expected coordinate in the x-axis direction, y ref is the expected coordinate in the y-axis direction, z ref is the desired coordinate in the z-axis direction, where φ ref is the desired roll angle, θ ref is the desired pitch angle, Ψ ref is the desired yaw angle; the terminal sliding mode control law is used to design u and τ as: In the formula: k1=1.5, k2=0.5, k3=2, k4=0.5, L1=5.3, L2=12 are gain coefficients.

8. The control method of a ducted disc aircraft based on the universal joint principle according to claim 3, characterized in that: In step 5, the attitude control law is controlled and distributed so that the attitude control law is implemented to the actuator, where: Where: c l ,c d ,c d0 are all constants, S is the area of ​​the rudder blade, T is the rotor thrust, D is the rotor diameter, δ is the deflection angle of the rudder blade, and F L and F D They represent the force of the rudder blade perpendicular to the incoming flow direction and along the incoming flow direction respectively.

9. The control method of a ducted disc aircraft based on the universal joint principle according to claim 3, characterized in that: In step 5, the pseudo-inverse method is used to distribute the control law to each control rudder. The formula of the pseudo-inverse method is: Where: δ is the control effector, and the so-called control effector here means the force on the rudder blade; in addition, W δ Represents the weight matrix, by setting W δ To give some emphasis to the distribution results; d δ represents the control quantity matrix to be allocated, d δ =[τ1,τ2,τ3] T ; B δ1 and B δ2 Both represent coefficient matrices.

10. The control method of a ducted disc aircraft based on the universal joint principle according to claim 3, characterized in that: In step 6, the experiment verifies the vehicle trajectory tracking, attitude stabilization, and attitude control separation effects; The above-derived dynamic model and control law are simulated by MATLAB, where the disturbance D1 is set to (cos5t+0.2sint)*[1,1,1] T , D2=(0.5+cost+sin10t)*[1,1,1] T ; P ref =[rcos(ωt),rsin(ωt),kωt] T , Θ ref =[0,0,0] T ; The initial values ​​of position and posture are P0 = [0,0,0] T and Θ0=[0,0,0] T .

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