A vertical take-off and landing control method for a distributed powered tandem-wing UAV

Abstract

The present invention relates to a vertical takeoff and landing control method for a distributed-power tandem-wing UAV, belonging to the technical field of UAV flight control. The tandem-wing UAV comprises an inner ring power unit and an outer ring power unit disposed on the leading edges of the front and rear wings; elevons are symmetrically hinged to the trailing edges of both ends of the rear wing; and the front and rear wings are connected by a connecting assembly to form a tandem wing with a spatial height difference. The control method includes controlling the jump takeoff, transition flight, cruising flight, and vertical landing phases by distributing throttle amounts between the inner ring power unit and the outer ring power unit during the jump takeoff, cruising flight, and vertical landing phases. A continuous climb transition method is employed during the transition phase, and after the transition is completed, the flight state is controlled to transition to a cruising level flight state. The present invention enables the tandem-wing UAV to perform large-angle jump takeoff and autonomous 90-degree vertical landing. Furthermore, a control distribution design for the UAV's distributed power is implemented to improve energy utilization and extend flight time.

Description

Technical Field

[0001] The present invention belongs to the technical field of unmanned aerial vehicle (UAV) flight control, and in particular relates to a vertical take-off and landing control method for a distributed-power tandem-wing UAV. Background Art

[0002] Currently, vertical take-off and landing (VTOL) drones are primarily lift-thrust, tailsitter, and tilt-rotor powered. These systems suffer from heavy propulsion mechanisms, inflexible maneuverability, and short mission durations. Distributed-power tandem-wing drones offer the advantages of fixed-wing aircraft with long endurance and the potential for vertical take-off and landing (VTOL), but research on their control methods is limited.

[0003] To address these issues, prior art discloses distributed power VTOL UAVs, whose distributed power systems are deployed on both wings and tail, enabling vertical takeoff and landing capabilities. However, specific control methods are not proposed. Prior art discloses distributed ducted power VTOL UAVs with a canard layout, evenly distributing the ducted power units across the canards and wing surfaces. Vertical takeoff and landing is achieved through the tilting of the ducted power units. However, these UAVs are essentially tilt-rotor powered, with complex tilt mechanisms, weak maneuverability, and limited endurance.

[0004] Currently, there is little research on the vertical take-off and landing control technology of distributed power tandem-wing UAVs, and the existing control methods are closer to fixed-wing UAVs. There is a lack of control methods that combine the advantages of flexible vertical take-off and landing capabilities and the long endurance of fixed-wing UAVs. Summary of the Invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the existing technology, the present invention provides a vertical take-off and landing control method for a distributed power tandem-wing UAV, which controls the UAV's leaping takeoff, transition flight, cruising flight, and vertical landing stages respectively. Combined with the distribution of the front and rear wing power systems of the tandem-wing UAV, the tandem-wing UAV's large-angle leaping takeoff and 90-degree autonomous vertical landing functions are realized, and a control distribution design is carried out for the distributed power of the UAV to improve energy utilization and extend flight time.

[0007] The technical solution of the present invention is: a vertical take-off and landing control method for a distributed power tandem-wing UAV, wherein the tandem-wing UAV includes a front wing and a rear wing arranged in a tandem wing form; the leading edges of the front wing and the rear wing are each provided with a plurality of rotors along the span direction, the four rotors located in the middle of the front wing and the rear wing in the span direction are respectively located at the four vertices of a quadrilateral, forming the inner ring power unit of the UAV, and the remaining rotors forming the outer ring power unit of the UAV; the trailing edges of both ends of the rear wing are symmetrically hinged with elevator ailerons; and the front wing and the rear wing are connected by a connecting assembly to form a tandem wing with a spatial height difference;

[0008] The vertical take-off and landing control method includes controlling the jump take-off, transition flight, cruise flight, and vertical landing stages by distributing throttle amounts to the inner ring power unit and the outer ring power unit in the jump take-off, cruise flight, and vertical landing stages; adopting a continuous climb transition method in the transition flight stage, and controlling the flight state to transition to a cruise level flight state after the transition is completed.

[0009] A further technical solution of the present invention is: the control method for the tandem-wing UAV to take off is:

[0010] Step 1.1: The drone stops at a 45° parking angle and performs a fixed-point, wide-angle takeoff under the action of distributed power and aerodynamic forces. During the initial takeoff phase, the drone performs stabilization control under throttle command. At the moment of takeoff, all power units are fully throttled, allowing the drone to lift off under the power unit's pull. During the takeoff phase, the front and rear wing power unit differentials and the elevons work together to control the drone to accelerate and pull up at a given pitch angle.

[0011] Step 1.2: Maintain target pitch angle command θ during takeoff sp The target pitch angle is subtracted from the actual pitch angle θ measured by the flight control system and passed through a proportional link to obtain feedback control information. This information is input into the pitch angle velocity control loop, and the pitch control amount is output through a proportional-integral link. The pitch control amount is simultaneously output to the front and rear wing power units and the elevator ailerons to achieve a fixed pitch angle jump takeoff. The control law is as follows:

[0012]

[0013] Among them, K θ is the pitch angle feedback proportional coefficient, K q1 , K qi1 , K q2 , K qI2 is the pitch angular velocity proportional and integral link coefficient; δ ty is the differential momentum of the front and rear propellers; δ ae is the rudder deflection angle when the elevon acts as an elevator;

[0014] Assume the initial throttle amount is δ t , throttle input of the front wing outer ring power unit δ tfront =δ t -δ ty , throttle input of the rear wing outer ring power unit δ tbehind =δ t +δ ty ;

[0015] Step 1.3: During the takeoff phase, the speed is continuously increased by controlling the throttle to set the target speed V spThe difference between the real-time airspeed V and the flight control system is used to obtain the automatic throttle feedback signal. The throttle feedback signal is input into the proportional-integral control loop to obtain the throttle control amount. The throttle control amount is input into the 8 power units to perform automatic throttle control according to the speed. The speed control law is as follows:

[0016] Δδ t =K V (V sp -V)+K VI ∫(V sp -V)dt

[0017] Among them, K V , K VI are the proportional coefficient and integral coefficient of the speed controller, Δδ t is the change in throttle value.

[0018] Step 1.4: After the drone reaches a safe flight altitude after being lifted off from a fixed point, it enters the steady climb phase, climbing steadily at a 45° climbing angle and a speed of 9m / s. The steady climb target altitude command H sp , target climb angle γ sp , the specific instructions for height and speed are as follows:

[0019] H sp =H0+Vsinγ sp (t-t1)

[0020] Where H0 is the initial climbing height; t is the current climbing time; t1 is the starting climbing time;

[0021] The target altitude command is subtracted from the real-time altitude to obtain altitude feedback information. This altitude feedback information is input into the proportional-integral-differential circuit to generate the target pitch angle command. The pitch angle command is input into the pitch angle control loop in step 1.2 to control the UAV to climb steadily. The specific form of the pitch angle control law during the climb phase is:

[0022]

[0023] Among them, K H , K HI , K HD are the proportional coefficient, integral coefficient and differential coefficient of the altitude control loop respectively; H is the current altitude;

[0024] Step 1.5: During the steady climb phase, the automatic throttle control loop remains unchanged. Different basic throttle values ​​are assigned according to the forward ratio and efficiency curve of the inner and outer loop power units. The throttle command is the basic throttle value plus the automatic throttle command value.

[0025] A further technical solution of the present invention is: in step 1.5, the inner ring basic throttle is 0.9, and the outer ring basic throttle is 0.45.

[0026] A further technical solution of the present invention is: the control method for the transition flight of the tandem-wing UAV is:

[0027] Step 2.1: After climbing to a certain height, the drone receives the ground transition command. After the steady climb phase, the drone gradually lowers its head and increases its speed according to the target pitch angle command and speed command. The target pitch angle and speed command are in the form of:

[0028]

[0029] Among them, θ climb 、V climb are the pitch angle and speed of the UAV during steady climb, θ cruise 、V cruise are the designed cruise pitch angle and cruise speed, t2 is the transition start time, and t3 is the transition end time;

[0030] Step 2.2: During the transition phase, the automatic throttle control command is only output to the outer ring power unit. This distribution method reduces energy consumption.

[0031] A further technical solution of the present invention is: in step 2.2, the throttle amount of the inner ring power unit is fixed at 0.1 and remains unchanged.

[0032] A further technical solution of the present invention is: the control method of the tandem-wing UAV cruising flight is:

[0033] Step 3.1: After the UAV completes the transition, it receives the forward flight switch command sent by the ground. After receiving the switch signal, the flight control system determines whether the current state has reached the cruise state θ cruise 、V cruise , if this state is reached, it switches to the cruise controller;

[0034] Step 3.2: During the cruise phase, the total energy controller is used to control the altitude and speed of the drone, the throttle is used to control the total energy of the drone, and the elevator is used to control the energy conversion between kinetic energy and potential energy; the total energy change rate difference is The total energy change rate difference is input into the proportional-integral link to obtain the throttle control amount, which is then input into the four power units in the outer loop.

[0035]

[0036] in, and are the proportional coefficient and integral coefficient of the total energy control loop respectively; is the throttle control amount;

[0037] The difference in the energy distribution law is The energy distribution law difference is passed through the proportional-integral link to obtain the target pitch angle command in the cruise phase. The target pitch angle command is passed through the pitch angle proportional link and the pitch angle velocity proportional-integral link to output to the elevator.

[0038]

[0039] in, and They are the proportional coefficient and integral coefficient of the energy distribution control loop respectively.

[0040] When performing altitude or speed control, the following control law is added:

[0041]

[0042] Among them, H sp is the expected flight altitude during the cruise phase, V sp is the expected flight speed, K H and K a are the proportional coefficients of altitude control and speed control respectively; V is the current flight speed; g is the acceleration due to gravity;

[0043] Step 3.3: The turning control of the UAV during the cruise phase uses the L1 guidance method. The basic principle is to select a reference point on the UAV's desired path. The line connecting the UAV's current position and the reference point is L1. Based on the UAV's current position and the reference point position, a circular arc tangent to the UAV's current speed is planned. This arc is the desired trajectory of the UAV to the reference point. The UAV is controlled to turn along the arc trajectory between the target point and the current position; the UAV turning command format is:

[0044]

[0045] Among them, a s is the centripetal acceleration of the UAV turning, V is the flight speed of the UAV, R is the turning radius, R is determined by L1, L1 is six times the speed of the UAV, η is the angle between the line connecting the UAV position and the target position and the direction of the flight speed, φ sp Roll angle command for the drone.

[0046] Step 3.4: Subtract the target roll angle command from the actual roll angle to obtain a roll angle feedback signal. This roll angle feedback signal is input into the proportional link to obtain the roll angular velocity target command. The target roll angular velocity is subtracted from the actual roll angular velocity to obtain a roll angular velocity feedback signal. This feedback signal is input into the roll angular velocity control loop, including the roll angular velocity proportional-integral link, and the roll angular velocity control value is output to the elevon.

[0047]

[0048] Among them, K φ is the roll angle proportional coefficient, K p , K pI are the roll angular velocity proportional coefficient and the roll angular velocity integral coefficient respectively; p sp is the desired roll angular velocity; φ is the current roll angle; and p is the current roll angular velocity.

[0049] A further technical solution of the present invention is: a control method for vertical landing of the tandem-wing UAV:

[0050] Step 4.1: The drone receives the landing command. First, the cruise controller controls the drone to descend to the specified altitude H0. The descent angle is calculated from the landing point and the descent starting point:

[0051]

[0052] Among them, H1 is the height of the starting point of the UAV's descent, ΔL is the horizontal distance between the landing point and the starting point of the descent, and H0 is the end height of the descent;

[0053] The speed and altitude instructions for the descent phase are:

[0054]

[0055] Among them, V sp is the target speed of descent, the given value is 18m / s, t4 is the start time of descent, and t5 is the end time of descent; H setpoint is the glide height instruction, H1 is the starting glide height, and t is the current time;

[0056] Step 4.2: After the drone's flight control system determines that it has descended to the specified altitude, it switches to vertical landing control mode and controls the drone to transition backward. The drone's attitude is adjusted to a vertical flight state and descends to the landing point. The backward transition control mode is the same as the jump takeoff mode. The pitch angle control command is input to the front and rear wing power units and the elevons, the roll angle control command is input to the elevons, and the throttle command is distributed and input to each power unit.

[0057] Control the UAV to pitch angle θ in the descent phase slip Pull up to the target pitch angle θ land , the instruction format is:

[0058]

[0059] Among them, θ land =90°, t6 is the start time of pulling up, and t7 is the end time of pulling up;

[0060] The speed of the backward transition process decreases linearly, and the instruction form is:

[0061]

[0062] Among them, V vertical =0, the end state of the backward transition is vertical hovering flight;

[0063] Step 4.3: After the UAV completes the backward transition, it enters a vertical hovering state and slowly descends to the ground while maintaining this state. In the vertical hovering state, the vertical body coordinate system is defined as the XY plane with the center of mass as the origin and the plane perpendicular to the rotor axis as the XY plane. The X-axis is located on the central symmetry plane of the UAV, and the positive direction of the X-axis points forward of the canard. The rotor axis is the Z-axis. In the vertical flight control mode, the UAV's inner ring power unit provides lift to balance gravity. The outer ring power unit's front and rear differential controls the UAV's pitch attitude, causing the UAV to move forward and backward. The outer ring power unit's left and right differential controls the UAV's roll attitude, causing the UAV to move left and right. The outer ring power unit's diagonal differential controls the UAV's yaw attitude, causing the UAV to rotate around the body axis.

[0064] The PD control instruction form of up and down height movement is:

[0065]

[0066] Among them, δ t,inner Indicates the inner loop throttle command; δ t,base Indicates the basic value of the inner ring throttle to balance gravity; K H , K HD Respectively represent the proportional coefficient and differential coefficient of height control; H sp is the expected height of the hovering state; H is the current hovering height;

[0067] The forward and backward movement in the horizontal plane is achieved through the pitch angle movement, and the left and right movement is achieved through the roll angle movement. The process of converting the target position command into the pitch angle and roll angle command is as follows:

[0068]

[0069] Among them, x sp 、y sp is the target position in the horizontal plane; x and y are the current position coordinates of the drone; u sp 、v sp are the expected forward and backward speed and left and right moving speed respectively; u and v are the current forward and backward speed and left and right moving speed respectively; a x 、a y are the expected accelerations in the forward and backward and left and right directions respectively; θ v,sp is the desired pitch angle in the vertical body coordinate system; φ v,sp is the desired roll angle in the vertical body coordinate system; ψ v is the yaw angle in the current vertical body coordinate system; g is the acceleration of gravity; Kx ,K u ,K y ,K v They are x-direction position proportional coefficient, x-direction speed proportional coefficient, y-direction position proportional coefficient, and y-direction speed proportional coefficient respectively;

[0070] The PI control instruction form of pitch angle control is:

[0071]

[0072] Wherein, the subscript v represents the state quantity in the vertical body coordinate system; θ v represents the pitch angle in the vertical body coordinate system, δ ty Indicates the differential momentum between the front and rear wing outer ring power units;

[0073] The PI control instruction form of roll angle control is:

[0074]

[0075] Among them, φ v represents the roll angle in the vertical body coordinate system, δ tx Represents the differential momentum of the power units on the left and right sides of the wing. The PI control instruction form of yaw motion is:

[0076] δ tz =K r (r sp -r)+K rI ∫(r sp -r)dt

[0077] Among them, δ tz Indicates the differential momentum of the power unit with the left front and right rear, right front and left rear of the wing as a group; K r Indicates the yaw rate proportional coefficient; K rI Represents the integral coefficient of the yaw angular velocity; r is the current roll angular velocity.

[0078] Step 4.4: Fixed-point landing based on the YOLO recognition and positioning algorithm. During the vertical landing phase, the drone's onboard camera and computing equipment will activate recognition mode to identify ground landing landmarks. The YOLO algorithm automatically calculates the three-dimensional coordinates of the landing point after identifying the ground landmarks. The drone is guided horizontally to directly above the landing point and then vertically descends to the landing point. Guidance commands are in the form of three-dimensional coordinates on the guidance trajectory and are input into the vertical flight controller to gradually land the drone at the target point.

[0079] A further technical solution of the present invention is that the ground landing mark is in an "H" shape or other custom shape trained by deep learning.

[0080] A further technical solution of the present invention is: the front and rear wings of the tandem-wing UAV serve as the main lifting surfaces, and solar panels are evenly laid on their upper surfaces. Four rotors are arranged along the span direction of the leading edge, and the eight rotors are respectively located at the vertices of the inner and outer quadrilaterals. The four rotors located in the inner ring are symmetrically installed on the leading edges of the middle front and rear wings of the UAV along the middle symmetrical plane of the UAV, which are used to provide lift during the take-off and landing stages, and control the flight attitude of the UAV through power differential. The four rotors located in the outer ring are symmetrically installed on the leading edges of the front and rear wing tips of the UAV along the middle symmetrical plane of the UAV, which are used to provide thrust during the fixed-wing cruise stage, and resist wind through power differential during the take-off and landing stages.

[0081] A further technical solution of the present invention is: when the tandem-wing UAV is in a vertical landing state, the four rotors of the inner ring form a square in a top view, and the center of gravity of the UAV is located at the center of the square.

[0082] Beneficial effects

[0083] The beneficial effects of this invention lie in its ability to achieve full control of a distributed-power tandem-wing UAV's high-angle takeoff, fixed-wing cruising, and autonomous vertical landing. Through the layout of the distributed power systems on the front and rear wings and the design of the control system, the UAV can achieve flexible vertical takeoff and landing independent of a runway. Distributed power differential control improves the UAV's maneuverability, and the combined use of power differential and aerodynamic control surfaces enhances the UAV's flight stability and safety.

[0084] The present invention implements different control distribution designs for the takeoff, cruise and landing phases, and distributes the basic throttle amounts according to the efficiency of the inner and outer ring power units. The inner ring basic throttle amount is high in the takeoff and landing phases, while the outer ring basic throttle amount is high and the inner ring basic throttle amount is low in the cruise phase. This improves the energy utilization rate of the UAV flight process, thereby increasing the UAV mission duration.

[0085] By rationally arranging the transition instructions from the takeoff phase to the cruise phase, this invention enables smooth switching between the two flight states, maintaining stable flight for the drone. The use of a fixed-point recognition and vertical landing method during the landing phase broadens the fixed-wing flight envelope and improves the drone's mission execution capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 Schematic diagram of the overall distributed power tandem wing UAV in an embodiment of the present invention;

[0087] Figure 2 A side view of the overall support state before high-angle fixed-point takeoff in an embodiment of the present invention;

[0088] Figure 3This is a schematic diagram of a jumping state in an embodiment of the present invention;

[0089] Figure 4 This is a schematic diagram of the cruising state in an embodiment of the present invention;

[0090] Figure 5 This is a schematic diagram of a vertical landing state in an embodiment of the present invention;

[0091] Figure 6 This is a schematic diagram of the folded and stored state of the drone in an example of the present invention;

[0092] Figure 7 This is a block diagram of the vertical flight PID control in an embodiment of the present invention;

[0093] Figure 8 This is the altitude control curve for the flight simulation process from takeoff to cruise in the example of the present invention;

[0094] Figure 9 This is the pitch angle control curve for the flight simulation process from takeoff to cruise in the example of the present invention;

[0095] Figure 10 This is a speed control simulation curve for the simulation process from takeoff to cruising flight in an example of the present invention;

[0096] Figure 11 This is the throttle response curve for the flight simulation process from jump takeoff to cruise in the example of the present invention;

[0097] Figure 12 It is the altitude control curve of the cruise to glide flight simulation process in the example of the present invention;

[0098] Figure 13 It is the pitch angle control curve of the cruise to glide flight simulation process in the example of the present invention;

[0099] Figure 14 It is the speed control curve of the cruise to glide flight simulation process in the example of the present invention;

[0100] Figure 15 The throttle response curve of the cruise to glide flight simulation process in the example of the present invention;

[0101] Figure 16 This is the height control curve for the simulation process of hovering at a fixed height of 5m in the example of the present invention;

[0102] Figure 17 This is the inner loop throttle response curve of the simulation process of hovering at a fixed altitude of 5m in the example of the present invention;

[0103] Figure 18 The flight simulation position control curve with the horizontal coordinate (X, Y) = (5m, 8m) in the embodiment of the present invention is fixed;

[0104] Figure 19 The vertical pitch angle and roll angle control curves for flight simulation with a fixed altitude horizontal coordinate (X, Y) = (5m, 8m) in the example of the present invention;

[0105] Figure 20 The outer loop throttle response curve of the flight simulation with the horizontal coordinates (X, Y) of (5m, 8m) at a fixed altitude in the example of the present invention;

[0106] Explanation of the accompanying symbols: 1. Front wing; 2. Rear wing; 3. Connecting rod between front and rear wings; 4. Aluminum alloy transverse folding part; 5. Vertical tail; 6. Elevator; 7. Battery compartment; 8. Payload compartment; 9. Battery; 10. Solar panel; 11. Inner ring propeller and motor; 12. Outer ring propeller and motor; 13. Connecting rod junction box; 14. Vertical tail connector; 15. Electronic speed governor; 16. Airborne avionics equipment; 17. Transverse connecting rod; 18. Connector; 19. Support carbon tube; 20. Front upper support; 21. Front middle three-way piece; 22. Front lower support; 23. Rear lower support; 24. Vertical tail support. DETAILED DESCRIPTION

[0107] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0108] Based on the fact that there is little research on the vertical take-off and landing control technology of distributed power tandem wing UAVs, and the existing control methods are closer to fixed-wing UAVs, and lack a control method that combines the advantages of flexible vertical take-off and landing capabilities and long endurance of fixed wings, the present invention provides a vertical take-off and landing control method for distributed power tandem wing UAVs. The tandem wing UAV includes a front wing and a rear wing arranged in the form of a tandem wing; the leading edges of the front wing and the rear wing are each provided with a plurality of rotors along the span direction, and the four rotors located in the middle of the front wing and the rear wing in the span direction are respectively located at the four vertices of a quadrilateral, forming a UAV. The inner ring power unit of the UAV is composed of the rotors, and the remaining rotors constitute the outer ring power unit of the UAV; the trailing edges of both ends of the rear wing are symmetrically hinged with elevator ailerons; and the front wing and the rear wing are connected to form a tandem wing with a spatial height difference through a connecting component; the vertical take-off and landing control method includes controlling the jump take-off, transition flight, cruise flight, and vertical landing stages, by distributing the throttle amount to the inner ring power unit and the outer ring power unit in the jump take-off stage, cruise flight stage, and vertical landing stage; a continuous climb transition method is adopted for the transition flight stage, and after the transition is completed, the flight state is controlled to be converted to a cruise level flight state.

[0109] The above technical solution is further described below with reference to the accompanying drawings:

[0110] Reference Figure 3 、 Figure 8 、 Figure 9 、 Figure 10 and Figure 11 As shown, the UAV of this embodiment takes off at a 45° climbing angle. At the moment of liftoff, all power units are at full throttle, and the UAV's attitude is controlled to be stable through the power differential of the front and rear wings and the elevator ailerons.

[0111] The jump takeoff control method of the distributed powered tandem-wing UAV of this embodiment is as follows:

[0112] Step 1: The flight control system obtains the control posture information of the UAV through the onboard sensors;

[0113] Step 2: The controller obtains the actual pitch angle θ real and the control system's target pitch angle θ sp The difference is made and the pitch control amount is obtained through the pitch angle proportional link and the pitch angular velocity proportional-integral link. The pitch control amount is input into the front and rear wing differential units and the elevator aileron to keep the drone at θ sp Angle stable takeoff.

[0114]

[0115] Among them, K θ is the pitch angle feedback proportional coefficient, K q1 , K qI1 , K q2 , K qI2 is the pitch angular velocity proportional and integral link coefficient; δ ty is the differential momentum of the front and rear propellers; δ ae is the rudder deflection angle when the elevon acts as an elevator;

[0116] Step 3: During the takeoff phase, the speed is continuously increased by controlling the throttle to set the target speed V sp The difference between the real-time airspeed V measured by the flight control system is used to obtain the automatic throttle feedback signal u throttle , input the throttle feedback signal into the proportional-integral control loop to obtain the throttle control amount, and input the throttle control amount into the 8 power units to perform automatic throttle control according to the speed. The speed control law is as follows:

[0117] Δδ t =K V (V sp -V)+K VI ∫(V sp -V)dt

[0118] Among them, K v , K vI are the proportional coefficient and integral coefficient of the speed controller, Δδ t is the change in throttle value.

[0119] Step 4: The real-time altitude obtained by the onboard sensor determines whether the drone has reached a safe altitude. If it has not reached a safe altitude, the drone will continue to accelerate and jump in the state of step 2. If it has reached a safe altitude, it will enter the steady climb phase and climb steadily at a 45° climbing angle and a speed of 9m / s. Steady climb target altitude command H sp , target climb angle γ sp =45°, the specific instructions for height and speed are as follows:

[0120] H sp =H0+Vsinγ sp (t-t1)

[0121] Where H0=30m is the initial climbing height; t is the current climbing time; t1 is the starting climbing time;

[0122] The altitude feedback information is input into the proportional-integral-differential link to generate the target pitch angle command. The pitch angle command is input into the pitch angle control loop in step 2 to control the UAV to climb steadily. The specific form of the pitch angle control law in the climbing phase is:

[0123]

[0124] where K H , K HI , K HD are the proportional coefficient, integral coefficient and differential coefficient of the altitude control loop respectively; H is the current altitude;

[0125] Step 5: During the steady climb phase, the automatic throttle control loop remains unchanged. Different basic throttle values ​​are allocated according to the forward ratio and efficiency curve of the inner and outer loop power units. The inner loop basic throttle is 0.9 and the outer loop basic throttle is 0.45.

[0126] Step 6: The cruise transition phase adopts a continuous climb transition method. After the transition is completed, the UAV switches to the cruise level flight state. Starting from the transition phase, the throttle command is only assigned to the outer ring power unit, and the inner ring throttle amount is automatically reduced to 0.1 and then remains unchanged. The speed of the UAV is controlled by the automatic throttle system to increase linearly until it reaches the cruise level flight speed. At the same time, the attitude controller is used to linearly reduce the pitch angle of the UAV to the pitch angle during cruising. The speed and pitch angle command forms of the cruise transition phase are:

[0127]

[0128] Among them, θ climb 、V climb are the pitch angle and speed of the UAV during steady climb, and the pitch angle and angle of attack are the same during cruising level flight. cruise =2°, cruising speed V cruise=10.5m / s, t2 is the time when the transition starts, and t3 is the time when the transition ends. The transition of the UAV in this paper will be completed within 7s, that is, the difference between t3 and t2 is 7s.

[0129] Reference Figure 4 As shown, in this embodiment, the cruising state of the drone is controlled by thrust control of the four power units in the outer ring, and the pitch and turn attitude control is achieved by differential control of the elevator ailerons and the left and right wing power units, thereby achieving stable flight of the drone during the cruising process.

[0130] The specific control method for stable flight in cruise state is as follows:

[0131] Step 1: After the UAV completes the transition, it receives the forward flight switch command sent by the ground. After receiving the switch signal, the flight control system determines whether the current state has reached the cruise state θ cruise 、V cruise If this state is reached, the vehicle switches to the cruise control.

[0132] Step 2: During the cruise flight phase, the total energy controller is used to control the total energy of the drone using the throttle and the elevons to control the energy conversion between kinetic energy and potential energy. The total energy change rate difference is The total energy change rate difference is input into the proportional-integral link to obtain the throttle control amount, which is then input into the four power units in the outer ring.

[0133]

[0134] in, and are the proportional coefficient and integral coefficient of the total energy control loop respectively; is the throttle control quantity; the energy distribution law difference is The energy distribution law difference is passed through the proportional-integral link to obtain the target pitch angle instruction in the cruise phase. The target pitch angle instruction is passed through the pitch angle proportional link and the pitch angle velocity proportional-integral link to output to the elevator.

[0135]

[0136] in, and They are the proportional coefficient and integral coefficient of the energy distribution control loop respectively.

[0137] When performing altitude or speed control, the following control law is added:

[0138]

[0139] Among them, H sp is the expected flight altitude during the cruise phase, V sp is the expected flight speed, KH and K a are the proportional coefficients of altitude control and speed control respectively; V is the current flight speed; g is the acceleration due to gravity.

[0140] Step 3: The turning control of the UAV during the cruise phase uses the L1 control method to control the UAV to turn along a circular trajectory between the target point and the current position. The UAV turning command format is:

[0141]

[0142] Among them, a s is the centripetal acceleration of the UAV turning, V is the flight speed of the UAV, R is the turning radius, R is determined by L1, L1 is six times the speed of the UAV, η is the angle between the line connecting the UAV position and the target position and the direction of the flight speed, φ sp Roll angle command for the drone.

[0143] Step 4: The roll angle feedback signal is obtained by subtracting the target roll angle command from the actual roll angle of the drone. The roll angle feedback signal is input into the proportional link to obtain the roll angular velocity target command. The roll angular velocity is subtracted from the actual roll angular velocity to obtain the roll angular velocity feedback signal. The feedback signal is input into the roll angular velocity control loop, including the roll angular velocity proportional-integral link, and the roll angular velocity control amount is output to the elevator.

[0144]

[0145] Among them, K φ is the roll angle proportional coefficient, K p , K pI are the roll angular velocity proportional coefficient and the roll angular velocity integral coefficient respectively; p sp is the desired roll angular velocity; φ is the current roll angle; p is the current roll angular velocity;

[0146] Reference Figure 5 、 Figure 12 、 Figure 13 、 Figure 14 and Figure 15As shown, after descending to a specified altitude, the drone of this embodiment transitions to vertical flight and lands vertically. The drone control scheme during this transition is identical to that for a leaping takeoff, with all power units participating in throttle control. The differentials of the front and rear wing power units, along with the elevons, control pitch, while the elevons control roll. The vertical flight control scheme is similar to the control logic of a quadcopter. The inner power unit provides lift to balance gravity, while the outer power unit's front and rear differentials control pitch, forcing forward and backward motion. The left and right differentials control roll, forcing left and right motion. The diagonal differentials of the outer power unit control yaw, forcing rotation around the aircraft's axis.

[0147] Step 1: The drone receives the landing command. First, the cruise controller controls the drone to descend to the specified altitude H0. The descent angle is calculated from the landing point and the descent starting point:

[0148]

[0149] Among them, H1=300m is the height of the starting point of the UAV's descent, and ΔL is the horizontal distance between the landing point and the starting point of the descent.

[0150] The speed and altitude instructions for the descent phase are:

[0151]

[0152] Among them, V sp is the target speed of descent, the given value is 18m / s, t4 is the start time of descent, and t5 is the end time of descent.

[0153] Step 2: After the drone's flight control system determines it has descended to the designated altitude, it switches to backward transition control mode, controlling the drone to tilt its head back to a vertical position. Backward transition control mode is identical to the jump takeoff mode: pitch control commands are input to the front and rear wing power units and the elevons, roll control commands are input to the elevons, and throttle commands are distributed and input to all eight power units.

[0154] Control the UAV to pitch angle θ in the descent phase slip Pull up to the target pitch angle θ land , the instruction format is:

[0155]

[0156] Among them, θ land =90°, t6 is the start time of pulling up, and t7 is the end time of pulling up.

[0157] The speed of the backward transition process decreases linearly, and the instruction form is:

[0158]

[0159] Among them, V vertical =0, the end state of the backward transition is vertical hovering flight.

[0160] Step 3: After the UAV completes the backward transition, it is in a vertical hovering state, close to the ground, and maintains this state to slowly fall to the ground; in the vertical hovering state, the vertical body coordinate system is defined as the XY plane with the center of mass as the origin and the plane perpendicular to the rotor axis, and the X-axis is located on the central symmetry plane of the UAV, the positive direction of the X-axis points to the front of the canard, and the rotor axis is the z-axis direction; in the vertical flight control mode, the UAV's inner ring power unit provides lift to balance gravity, the outer ring power unit's front and rear differential controls the UAV's pitch attitude, making the UAV move forward and backward, the outer ring power unit's left and right differential controls the UAV's roll attitude, making the UAV move left and right, and the outer ring power unit's diagonal differential controls the UAV's yaw attitude, making the UAV rotate around the body axis.

[0161] The PD control instruction form of up and down height movement is:

[0162]

[0163] Among them, δ t,inner Indicates the inner loop throttle command; δ t,base =0.78 represents the basic value of the inner ring throttle to balance gravity; K H , K HD Respectively represent the proportional coefficient and differential coefficient of height control; H sp is the expected hovering height; H is the current hovering height.

[0164] The forward and backward movement in the horizontal plane is achieved through the pitch angle movement, and the left and right movement is achieved through the roll angle movement. The process of converting the target position command into the pitch angle and roll angle command is as follows:

[0165]

[0166] Among them, x sp 、y sp is the target position in the horizontal plane; x and y are the current position coordinates of the drone; u sp 、v sp are the expected forward speed and left and right moving speed respectively; u and v are the current forward and backward speed and left and right moving speed respectively; a x 、a y are the expected accelerations in the forward and backward and left and right directions respectively; θ v,sp is the desired pitch angle in the vertical body coordinate system; φ v,sp is the desired roll angle in the vertical body coordinate system; ψ vis the yaw angle in the current vertical body coordinate system; g is the acceleration of gravity; K x ,K u ,K y ,K v They are x-direction position proportional coefficient, x-direction speed proportional coefficient, y-direction position proportional coefficient, and y-direction speed proportional coefficient.

[0167] The PI control instruction form of pitch angle control is:

[0168]

[0169] Among them, θ v Indicates the pitch angle in the vertical flight coordinate system, δ ty Indicates the differential momentum of the front and rear wing outer ring power units.

[0170] The PI control instruction form of roll angle control is:

[0171]

[0172] Among them, φ v Denotes the roll angle in the vertical flight coordinate system, δ tx Represents the differential momentum of the power units on the left and right sides of the wing. The PI control instruction form of yaw motion is:

[0173] δ tz =K r )r sp -r)+K rI ∫(r sp -r)dt

[0174] Among them, δ tz Indicates the differential momentum of the power unit with the left front and right rear, right front and left rear of the wing as a group; K r Indicates the yaw rate proportional coefficient; K rI Represents the integral coefficient of the yaw angular velocity; r is the current roll angular velocity.

[0175] Vertical flight PID control block diagram is as follows Figure 7 As shown, the control effect reference Figure 16 、 Figure 17 、 Figure 18 、 Figure 19 and Figure 20 .

[0176] Step 4: Fixed-point landing based on the YOLO recognition and positioning algorithm. During the vertical landing phase, the drone's onboard camera and computing equipment will enter recognition mode to identify ground landing landmarks. Landing landmarks can be "H"-shaped or other custom shapes trained through deep learning. After identifying the ground landmarks, the YOLO algorithm automatically calculates the three-dimensional coordinates of the landing point and sends guidance commands to the vertical flight controller in the form of horizontal position and altitude commands, guiding the drone to land on the ground landmark.

[0177] Reference Figure 1-Figure 5 As shown, the tandem-wing UAV used to implement a vertical take-off and landing control method of a distributed power tandem-wing UAV includes three parts: an airframe structure, an energy power system, and an airborne avionics system.

[0178] The aircraft structure includes a front wing 1, a rear wing 2, a connecting rod 3 for the front and rear wings, an aluminum alloy transverse folding member 4, a vertical tail 5, an elevon 6, a battery compartment 7, a payload compartment 8, a connecting rod junction box 13, a vertical tail connector 14, a transverse connecting rod 17, and a connector 18. The front wing 1 and rear wing 2 are the primary lifting surfaces of the drone, forming a tandem wing layout. To ensure portability, both are designed as low-aspect-ratio straight wings. The front wing 1 has a span of 1.2 meters and a chord of 0.3 meters, while the rear wing 2 has a span of 1.2 meters and a chord of 0.31 meters. The height difference between the front and rear wings is 0.32-0.38 meters. A high-lift-coefficient airfoil is selected to meet the requirements of cruise operation and increase the drone's range and flight time. The vertical tail 5, serving as the drone's vertical stabilizer, is mounted at the end of the rear wing 2 and connected to the rear wing 2 via a vertical tail connector 14. The front wing 1 and rear wing 2 are connected by a front and rear wing connecting rod 3. Connectors 18 are installed at the intersection of the front and rear wing connecting rods 3 and the wing spar, achieving multi-point connection between the front and rear wing connecting rods 3 and the wings, thereby improving the structural strength and rigidity. Two transverse connecting rods 17 are installed between the two front and rear wing connecting rods 3. Their installation positions are coordinated with the design center of gravity of the entire drone. A battery compartment 7 is installed in the middle of the transverse connecting rods 17 to accommodate the drone's batteries 9. The transverse connecting rods 17 are fixedly connected to the front and rear wing connecting rods 3 via a connecting rod junction box 13, forming an "H"-shaped layout for the connecting rods, thereby improving the drone's structural torsional resistance. A payload compartment 8 is installed in the middle of the leading edge of the front wing 1 to accommodate onboard avionics equipment 16. This integrated design integrates the payload compartment 8 with the structure of the front wing 1 to reduce the drone's size and weight. The control surface of the drone in this embodiment includes two elevons 6 symmetrically hinged to the outer sides of the trailing edge of the rear wing 2, which, together with the power differential system, achieve flight control of the drone.

[0179] Reference Figure 6As shown, four aluminum alloy transverse folding members 4 are symmetrically mounted on the two front and rear wing connecting rods 3. The two folding members on the front wing are installed opposite the two folding members on the rear wing, achieving reverse folding. When the aluminum alloy transverse folding members 4 reach the folding limit, the length and height of the drone are reduced, reducing the drone's size and improving its portability.

[0180] The energy and power system includes: batteries 9, solar panels 10, inner propellers and motors 11 (rotors), outer propellers and motors 12, and an electronic speed controller 15. Battery 9, a high-energy-density lithium-ion battery, is installed in battery compartment 7 and provides energy for the drone. Solar panels 10, flexible thin-film solar cells with high photoelectric conversion efficiency, are evenly distributed on the upper surfaces of front wings 1 and rear wings 2, providing energy for the drone's flight and extending its range. There are four inner ring propellers and motors 11, which are symmetrically installed on the middle leading edges of the front wing 1 and the rear wing 2 along the middle symmetrical plane of the UAV. They are mainly used to provide lift during take-off and landing, and to control the flight attitude of the UAV through power differential. Therefore, the inner ring propeller adopts a large-size low-pitch propeller, and the inner ring motor adopts a low-kv value brushless DC motor that matches the inner ring propeller to drive the rotation of the propeller; the inner ring motor is installed on a motor base that is integrated with the wing structure. In order to meet the requirements of the four-rotor mode, the installation position of the inner ring propeller and the motor 11 needs to make the inner ring propeller form a square in the top view in the vertical landing state, and the design center of gravity of the UAV needs to be in the middle of the square. There are four outer ring propellers and motors 12, which are symmetrically installed on the leading edges of the wingtips of the front wing 1 and the rear wing 2 along the middle symmetrical plane of the drone. They are mainly used to provide thrust during the fixed-wing cruise phase and to resist wind through power differential during the take-off and landing phases. Therefore, the outer ring propeller adopts a large-pitch propeller with higher efficiency at a high advance ratio, and the outer ring motor adopts a low-kv value brushless DC motor that matches the outer ring propeller. Similarly, the outer ring motor is also installed on a motor base that is integrated with the wing structure. The installation of the inner ring propeller and motor 11 and the outer ring propeller and motor 12 needs to consider their distance from the front and rear wing connecting rods 3 and the payload compartment 8, and a certain safety distance needs to be left. The electronic speed regulator 15 is fixed to the bottom of the battery compartment 7 and is used to control the speed of the motor.

[0181] The onboard avionics system includes onboard avionics equipment 16 and onboard cables (not shown). The onboard avionics equipment 16 is distributed and installed in the payload bay 8, and includes a navigation system, a flight control system, and a measurement and control system. The onboard cables are distributed inside the front wing 1 and rear wing 2, as well as on the surfaces of the front and rear wing connecting rods 3 and the transverse connecting rods 17. Cable ties and tape are used to secure the exposed portions of the onboard cables to the aircraft body. It is necessary to reduce the number of onboard cables through reasonable arrangement, and to select lighter cables to reduce the total weight of the UAV.

[0182] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A method for controlling vertical takeoff and landing of a distributed-power tandem-wing UAV, wherein the tandem-wing UAV includes front and rear wings arranged in a tandem configuration; characterized in that: The leading edges of the front and rear wings are each provided with a plurality of rotors along the span direction. The four rotors located in the middle of the front and rear wings in the span direction are respectively located at the four vertices of a quadrilateral, forming the inner ring power unit of the drone, and the remaining rotors form the outer ring power unit of the drone. The trailing edges of both ends of the rear wing are symmetrically hinged with elevator ailerons. The front and rear wings are connected to form a tandem wing with a spatial height difference through a connecting assembly. The vertical take-off and landing control method includes controlling the jump take-off, transition flight, cruise flight, and vertical landing phases by distributing throttle amounts between the inner ring power unit and the outer ring power unit during the jump take-off, cruise flight, and vertical landing phases; adopting a continuous climb transition mode during the transition flight phase, and controlling the flight state to transition to a cruise level flight state after the transition is completed; The control method for the tandem-wing UAV to take off is as follows: Step 1.1: The drone stops at a 45° parking angle and performs a fixed-point, wide-angle takeoff under the action of distributed power and aerodynamic forces. During the initial takeoff phase, the drone performs stabilization control under throttle command. At the moment of takeoff, all power units are fully throttled, allowing the drone to lift off under the power unit's pull. During the takeoff phase, the front and rear wing power unit differentials and the elevons work together to control the drone to accelerate and pull up at a given pitch angle. Step 1.2: Maintain target pitch angle command θ during takeoff sp The target pitch angle is subtracted from the actual pitch angle θ measured by the flight control system and passed through a proportional link to obtain feedback control information. This information is input into the pitch angle velocity control loop, and the pitch control amount is output through a proportional-integral link. The pitch control amount is simultaneously output to the front and rear wing power units and the elevator ailerons to achieve a fixed pitch angle jump takeoff. The control law is as follows: Among them, K θ is the pitch angle feedback proportional coefficient, K q1 , K qI1 , K q2 , K qI2 is the pitch angular velocity proportional and integral link coefficient; δ ty is the differential momentum of the front and rear propellers; δ ae is the rudder deflection angle when the elevon acts as an elevator; Assume the initial throttle amount is δ t , throttle input of the front wing outer ring power unit δ tfront =δ t -δ ty , throttle input of the rear wing outer ring power unit δ tbehind =δ t +δ ty ; Step 1.3: During the takeoff phase, the speed is continuously increased by controlling the throttle to set the target speed V sp The difference between the real-time airspeed V and the flight control system is used to obtain the automatic throttle feedback signal. The throttle feedback signal is input into the proportional-integral control loop to obtain the throttle control amount. The throttle control amount is input into the 8 power units to perform automatic throttle control according to the speed. The speed control law is as follows: Δδ t =K V (V sp -V)+K VI ∫(V sp -V)dt Among them, K V , K VI are the proportional coefficient and integral coefficient of the speed controller, Δδ t is the change in throttle value; Step 1.4: After the drone reaches a safe flight altitude after being lifted off from a fixed point, it enters the steady climb phase, climbing steadily at a 45° climbing angle and a speed of 9m / s. The steady climb target altitude command H sp , target climb angle γ sp , the specific instructions for height and speed are as follows: H sp =H0+Vsinγ sp ·(t-t1) Where H0 is the initial climbing height; t is the current climbing time; t1 is the starting climbing time; The target altitude command is subtracted from the real-time altitude to obtain altitude feedback information. This altitude feedback information is input into the proportional-integral-differential circuit to generate the target pitch angle command. The pitch angle command is input into the pitch angle control loop in step 1.2 to control the UAV to climb steadily. The specific form of the pitch angle control law during the climb phase is: Among them, K H , K HI , K HD are the proportional coefficient, integral coefficient and differential coefficient of the altitude control loop respectively; H is the current altitude; Step 1.5: During the steady climb phase, the automatic throttle control loop remains unchanged. Different base throttle values ​​are assigned based on the forward ratio and efficiency curves of the inner and outer loop power units. The throttle command is the base throttle value plus the automatic throttle command value. The control method for the transition flight of the tandem-wing UAV is: Step 2.1: After climbing to a certain height, the drone receives the ground transition command. After the steady climb phase, the drone gradually lowers its head and increases its speed according to the target pitch angle command and speed command. The target pitch angle and speed command are in the form of: Among them, θ climb 、V climb are the pitch angle and speed of the UAV during steady climb, θ cruise 、V cruise are the designed cruise pitch angle and cruise speed, t2 is the transition start time, and t3 is the transition end time; Step 2.2: During the transition phase, the automatic throttle control command is only output to the outer ring power unit, reducing energy consumption through this distribution method; The control method for the cruise flight of the tandem-wing UAV is: Step 3.1: After the UAV completes the transition, it receives the forward flight switch command sent by the ground. After receiving the switch signal, the flight control system determines whether the current state has reached the cruise state θ cruise 、V cruise , if this state is reached, it switches to the cruise controller; Step 3.2: During the cruise phase, the total energy controller is used to control the altitude and speed of the drone, the throttle is used to control the total energy of the drone, and the elevator is used to control the energy conversion between kinetic energy and potential energy; the total energy change rate difference is The total energy change rate difference is input into the proportional-integral link to obtain the throttle control amount, which is then input into the four power units in the outer loop. in, and are the proportional coefficient and integral coefficient of the total energy control loop respectively; is the throttle control amount; The difference in the energy distribution law is The energy distribution law difference is passed through the proportional-integral link to obtain the target pitch angle command in the cruise phase. The target pitch angle command is passed through the pitch angle proportional link and the pitch angle velocity proportional-integral link to output to the elevator. in, and are the proportional coefficient and integral coefficient of the energy distribution control loop respectively; When performing altitude or speed control, the following control law is added: Among them, H sp is the expected flight altitude during the cruise phase, V sp is the expected flight speed, K H and K a are the proportional coefficients of altitude control and speed control respectively; V is the current flight speed; g is the acceleration due to gravity; Step 3.3: The turning control of the UAV during the cruise phase uses the L1 guidance method. A reference point is selected on the UAV's desired path. The line connecting the UAV's current position and the reference point is L1. Based on the UAV's current position and the reference point position, an arc is planned that is tangent to the UAV's current speed. This arc is the desired trajectory of the UAV flying to the reference point. The UAV is controlled to turn along the arc trajectory between the target point and the current position. The UAV turning command format is: Among them, a s is the centripetal acceleration of the UAV turning, V is the flight speed of the UAV, R is the turning radius, R is determined by L1, L1 is six times the speed of the UAV, η is the angle between the line connecting the UAV position and the target position and the direction of the flight speed, φ sp Roll angle command for the drone; Step 3.4: Subtract the target roll angle command from the actual roll angle to obtain a roll angle feedback signal. This roll angle feedback signal is input into the proportional link to obtain the roll angular velocity target command. The target roll angular velocity is subtracted from the actual roll angular velocity to obtain a roll angular velocity feedback signal. This feedback signal is input into the roll angular velocity control loop, including the roll angular velocity proportional-integral link, and the roll angular velocity control value is output to the elevon. Among them, K φ is the roll angle proportional coefficient, K p , K pI are the roll angular velocity proportional coefficient and the roll angular velocity integral coefficient respectively; p sp is the desired roll angular velocity; φ is the current roll angle; p is the current roll angular velocity; The control method for vertical landing of the tandem-wing UAV: Step 4.1: The drone receives the landing command. First, the cruise controller controls the drone to descend to the specified altitude H0. The descent angle is calculated from the landing point and the descent starting point: Among them, H1 is the height of the starting point of the UAV's descent, ΔL is the horizontal distance between the landing point and the starting point of the descent, and H0 is the end height of the descent; The speed and altitude instructions for the descent phase are: Among them, V sp is the target speed of descent, the given value is 18m / s, t4 is the start time of descent, and t5 is the end time of descent; H setpoint is the glide height instruction, H1 is the starting glide height, and t is the current time; Step 4.2: After the drone's flight control system determines that it has descended to the specified altitude, it switches to vertical landing control mode and controls the drone to transition backward. The drone's attitude is adjusted to a vertical flight state and descends to the landing point. The backward transition control mode is the same as the jump takeoff mode. The pitch angle control command is input to the front and rear wing power units and the elevons, the roll angle control command is input to the elevons, and the throttle command is distributed and input to each power unit. Control the UAV to pitch angle θ in the descent phase slip Pull up to the target pitch angle θ land , the instruction format is: where θ land =90°, t6 is the start time of pulling up, and t7 is the end time of pulling up; The speed of the backward transition process decreases linearly, and the instruction form is: Among them, V vertical =0, the end state of the backward transition is vertical hovering flight; Step 4.3: After the UAV completes the backward transition, it enters a vertical hovering state and slowly descends to the ground while maintaining this state. In the vertical hovering state, the vertical body coordinate system is defined as the XY plane with the center of mass as the origin and the plane perpendicular to the rotor axis as the XY plane. The X-axis is located on the central symmetry plane of the UAV, and the positive direction of the X-axis points forward of the canard. The rotor axis is the Z-axis. In the vertical flight control mode, the UAV's inner ring power unit provides lift to balance gravity. The outer ring power unit's front and rear differential controls the UAV's pitch attitude, causing the UAV to move forward and backward. The outer ring power unit's left and right differential controls the UAV's roll attitude, causing the UAV to move left and right. The outer ring power unit's diagonal differential controls the UAV's yaw attitude, causing the UAV to rotate around the body axis. The PD control instruction form of up and down height movement is: Among them, δ t，inner Indicates the inner loop throttle command; δ t，base Indicates the basic value of the inner ring throttle to balance gravity; K H , K HD Respectively represent the proportional coefficient and differential coefficient of height control; H sp is the expected height of the hovering state; H is the current hovering height; The forward and backward movement in the horizontal plane is achieved through the pitch angle movement, and the left and right movement is achieved through the roll angle movement. The process of converting the target position command into the pitch angle and roll angle command is as follows: Among them, x sp 、y sp is the target position in the horizontal plane; x and y are the current position coordinates of the drone; u sp 、v sp are the expected forward and backward speed and left and right moving speed respectively; u and v are the current forward and backward speed and left and right moving speed respectively; a x 、a y are the expected accelerations in the forward and backward and left and right directions respectively; θ v，sp is the desired pitch angle in the vertical body coordinate system; φ v，sp is the desired roll angle in the vertical body coordinate system; ψ v is the yaw angle in the current vertical body coordinate system; g is the acceleration of gravity; K x , K u , K y , K v They are x-direction position proportional coefficient, x-direction speed proportional coefficient, y-direction position proportional coefficient, and y-direction speed proportional coefficient respectively; The PI control instruction form of pitch angle control is: Wherein, the subscript v represents the state quantity in the vertical body coordinate system; θ v represents the pitch angle in the vertical body coordinate system, δ ty Indicates the differential momentum between the front and rear wing outer ring power units; The PI control instruction form of roll angle control is: Among them, φ v represents the roll angle in the vertical body coordinate system, δ tx Indicates the differential momentum of the power units on the left and right sides of the wing; The PI control instruction form of yaw motion is: δ tz =K r (r sp -r)+K rI ∫(r sp -r)dt Among them, δ tz Indicates the differential momentum of the power unit with the left front and right rear, right front and left rear of the wing as a group; K r Indicates the yaw rate proportional coefficient; K rI represents the integral coefficient of yaw angular velocity; r is the current roll angular velocity; Step 4.4: Fixed-point landing based on the YOLO recognition and positioning algorithm; During the vertical landing phase, the drone's onboard camera and computing equipment will turn on the recognition mode to identify ground landing marks. After the YOLO algorithm recognizes the ground marks, it automatically calculates the three-dimensional coordinate information of the landing point, first guiding the drone to fly horizontally to directly above the landing point, and then vertically descending to the landing point; the guidance instructions are in the form of three-dimensional coordinates on the guidance trajectory, which are input into the vertical flight controller to make the drone land on the target point step by step.

2. The vertical take-off and landing control method for a distributed power tandem-wing UAV according to claim 1, characterized in that: In step 1.5, the inner ring basic throttle is 0.9, and the outer ring basic throttle is 0.

45.

3. The vertical take-off and landing control method for a distributed power tandem-wing UAV according to claim 1, characterized in that: In step 2.2, the throttle amount of the inner ring power unit is fixed at 0.1 and remains unchanged.

4. The vertical take-off and landing control method for a distributed power tandem-wing UAV according to claim 1, characterized in that: The ground landing mark is in an "H" shape or other custom shapes trained by deep learning.

5. The vertical take-off and landing control method for a distributed power tandem-wing UAV according to claim 1, characterized in that: The front and rear wings of the tandem-wing UAV serve as the main lifting surfaces, and solar panels are evenly laid on their upper surfaces. Four rotors are arranged along the span direction of the leading edge of the UAV, and the eight rotors are respectively located at the vertices of the inner and outer quadrilaterals. The four rotors located in the inner ring are symmetrically installed on the leading edges of the middle parts of the front and rear wings of the UAV along the middle symmetrical plane of the UAV, and are used to provide lift during the take-off and landing stages, and control the flight attitude of the UAV through power differential. The four rotors located in the outer ring are symmetrically installed on the leading edges of the wingtips of the front and rear wings of the UAV along the middle symmetrical plane of the UAV, and are used to provide thrust during the fixed-wing cruise stage, and resist wind through power differential during the take-off and landing stages.

6. The vertical take-off and landing control method for a distributed power tandem-wing UAV according to claim 5, characterized in that: When the tandem-wing UAV is in a vertical landing state, the four rotors in the inner ring form a square in a top view, and the center of gravity of the UAV is located at the center of the square.

Images