Vertical take-off and landing control method of distributed power tandem wing unmanned aerial vehicle

Abstract

The invention discloses a vertical take-off and landing control method for a distributed power tandem wing unmanned aerial vehicle, and belongs to the technical field of unmanned aerial vehicle flight control. An inner ring power unit and an outer ring power unit of the unmanned aerial vehicle are arranged at the front edges of the front wing and the rear wing of the tandem wing unmanned aerial vehicle; lifting ailerons are symmetrically hinged to the rear edges of the two ends of the rear wing; the front wing and the rear wing are connected into a tandem wing with a space height difference through a connecting assembly; the control method comprises the steps of controlling jumping take-off, transition flight, cruise flight and vertical landing, and performing accelerator quantity distribution on the inner ring power unit and the outer ring power unit for jumping take-off, cruise flight and vertical landing; a continuous climbing transition mode is adopted in the transition flight stage, and the flight state is controlled to be converted into a cruise level flight state after transition is completed. According to the unmanned aerial vehicle, the functions of large-angle jump take-off and 90-degree autonomous vertical landing of the tandem wing unmanned aerial vehicle are achieved, distributed power of the unmanned aerial vehicle is controlled and distributed, the energy utilization rate is increased, and the endurance time is prolonged.

Description

Technical Field

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

[0002] At present, vertical take-off and landing UAVs are mainly lift-thrust, tail-seat, and tilt-rotor powered UAVs, which have problems such as heavy power mechanism, inflexible operation, and short mission duration. Distributed power tandem wing UAVs have the advantages of long endurance of fixed wings and the potential for vertical take-off and landing, but there is little research on their vertical take-off and landing control methods.

[0003] In order to solve the above problems, the prior art discloses a distributed power vertical take-off and landing UAV, whose distributed power system is arranged on the wings and tail on both sides, and has the ability of vertical take-off and landing, but no specific control method is proposed. The prior art discloses a vertical take-off and landing UAV with distributed ducted power, which has a canard layout with evenly distributed ducted power groups on the canard and wing surfaces, and realizes vertical take-off and landing by tilting the ducted power group. In essence, it still belongs to a tilt-rotating power UAV, and the tilt-rotating mechanism has a complex structure, weak maneuverability, and insufficient 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 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 prior art, 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, and combines the distribution of the front and rear wing power systems of the tandem-wing UAV to achieve the large-angle leaping takeoff and 90-degree autonomous vertical landing functions of the tandem-wing UAV, and carries out a control distribution design for the distributed power of the UAV to improve energy utilization and extend the 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, the tandem wing UAV comprises 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 both 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 an inner ring power unit of the UAV, and the remaining rotors form an 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 assembly;

[0008] The vertical take-off and landing control method includes the control of the jump take-off stage, transition flight stage, cruise flight stage, and vertical landing stage by allocating 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 in the transition flight stage, and after the transition is completed, the flight state is controlled to be converted into a cruise level flight state.

[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 on the ground at a 45° parking angle and takes off at a fixed point with a large angle under the action of distributed power and aerodynamic force. At the beginning of takeoff, the drone takes off under the throttle command with stabilization control. At the moment of takeoff, all power units are at full throttle, so that the drone takes off under the pulling force of the power units. During the takeoff stage, the front and rear wing power units differentially control the drone with the elevator ailerons to accelerate and pull up at a given pitch angle.

[0011] Step 1.2: Maintain the 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 passes through the proportional link to obtain feedback control information, which is input into the pitch angle velocity control loop, and the pitch control amount is output through the proportional-integral link, and the pitch control amount is simultaneously output to the front and rear wing power units and the elevator ailerons to achieve fixed pitch angle 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 measured by 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, it enters the steady climb phase, climbing 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] Among them, 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. 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 1.2 to control the UAV to climb steadily. The specific form of the pitch angle control law in the climbing stage is:

[0022]

[0023] Among them, K H , K HI , K HD They 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 allocated according to the forward ratio of the inner and outer loop power units and the efficiency curve. 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 the 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 of 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 loop power unit. This distribution method reduces energy consumption.

[0031] A further technical solution of the present invention is: in the 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 cruise flight of the tandem-wing UAV 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 flight 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 aileron 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 4 power units in the outer ring;

[0035]

[0036] in, and They 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 gravitational acceleration;

[0043] Step 3.3: The turning control of the drone in the cruise phase uses the L1 guidance method. The basic principle is to select a reference point on the desired path of the drone. The line connecting the current position of the drone and the reference point is L1. Based on the current position of the drone and the position of the reference point, a circular arc tangent to the current speed of the drone is planned. This circular arc is the desired trajectory of the drone flying to the reference point. Control the drone to turn along the circular arc trajectory between the target point and the current position; the drone turning command form 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: The target roll angle command of the UAV is subtracted from the actual roll angle to obtain a roll angle feedback signal, and the roll angle feedback signal is input into the proportional link to obtain a 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, and 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 aileron;

[0047]

[0048] Among them, K φ is the roll angle proportionality 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.

[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 glide to the specified height H0. The glide angle of the glide segment is calculated from the landing point and the glide start 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 height instructions for the descent phase are:

[0054]

[0055] Among them, V sp is the target speed of the slide, the given value is 18m / s, t4 is the start time of the slide, and t5 is the end time of the slide; 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 UAV flight control system determines that it has descended to the specified height, it switches to the vertical landing control mode and controls the UAV to transition backwards. The UAV attitude is adjusted to a vertical flight state and lands at 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 input to each power unit after being distributed.

[0057] Control the UAV to pitch angle θ from the glide stage 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 is in a vertical hovering state, and maintains this state and slowly falls 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 is the XY plane, 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 front wing, and the rotor axis is the z axis direction; in the vertical flight control mode, the inner ring power unit of the UAV provides lift to balance gravity, the front and rear differential of the outer ring power unit controls the pitch attitude of the UAV to make the UAV move forward and backward, the left and right differential of the outer ring power unit controls the roll attitude of the UAV to make the UAV move left and right, and the diagonal differential of the outer ring power unit controls the yaw attitude of the UAV to make the UAV rotate around the body axis;

[0064] The PD control instruction form for 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 gravitational acceleration; 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;

[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 It represents 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 amount of the power units on the left and right sides of the wing. The PI control instruction form of the 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 one group; K r Indicates the yaw angular velocity 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 YOLO recognition and positioning algorithm; During the vertical landing phase, the drone's onboard camera and computing equipment will start the recognition mode to identify the ground landing mark. After the YOLO algorithm recognizes the ground mark, it automatically solves the three-dimensional coordinate information of the landing point, first guides the drone to fly horizontally to the top of the landing point, and then vertically lands to the landing point. The guidance command is 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.

[0079] A further technical solution of the present invention is: the ground landing mark is an "H" shape or other custom shapes 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 main lift 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 parts of the front and rear wings of the UAV along the middle symmetry plane of the UAV, so as to provide lift during the take-off and landing stages, and control the flight attitude of the UAV by means of 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 symmetry plane of the UAV, so as to provide thrust during the fixed-wing cruise stage, and resist wind by means of 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 effect of the present invention is that the control method of the present invention can realize the full process control of large-angle leap takeoff, fixed-wing cruising and autonomous vertical landing of a distributed power tandem-wing UAV. Through the layout of the front and rear wing distributed power systems and the design of the control system, it can achieve flexible vertical takeoff and landing without relying on the runway, the distributed power differential control improves the maneuverability of the UAV, and the combined use of power differential and pneumatic control surfaces enhances the stability and safety of the UAV flight.

[0084] The present invention carries out different control distribution designs for the take-off, cruising and landing stages, 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 take-off and landing stages, and the outer ring basic throttle amount is high and the inner ring basic throttle amount is low in the cruising stage, thereby improving the energy utilization rate of the UAV flight process and thus increasing the UAV mission duration.

[0085] The present invention can achieve smooth switching between the two flight states and maintain the stable flight of the UAV by reasonably arranging the transition instructions from the take-off phase to the cruise phase. The fixed-point recognition-vertical landing method is adopted in the landing phase, which is equivalent to broadening the flight envelope of the fixed-wing phase and improving the mission execution capability of the UAV. 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 It is a side view of the overall supporting state before taking off at a large angle 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 storage state of the drone in the example of the present invention;

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

[0093] Figure 8 It is the altitude control curve of the simulation process from take-off to cruising flight in the example of the present invention;

[0094] Fig. 9 It is a pitch angle control curve of the simulation process from take-off to cruising flight in the example of the present invention;

[0095] Fig.10 It is a speed control simulation curve from the jump take-off to the cruise flight simulation process in the example of the present invention;

[0096] Fig.11 It is a throttle response curve from a jump take-off to a cruise flight simulation process in an example of the present invention;

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

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

[0099] Fig.14 It is a speed control curve of the flight simulation process from cruising to gliding in the example of the present invention;

[0100] Fig.15 It is the throttle response curve of the flight simulation process from cruise to glide in the example of the present invention;

[0101] Fig.16 It is the height control curve of the simulation process of hovering at a fixed height of 5m in the example of the present invention;

[0102] Fig.17 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] Fig.18 The flight simulation position control curve with the horizontal coordinates (X, Y)=(5m, 8m) in the example of the present invention;

[0104] Fig.19 The vertical pitch angle and roll angle control curve of the flight simulation with the horizontal coordinate (X, Y)=(5m, 8m) in the example of the present invention;

[0105] Fig. 20 The outer ring throttle response curve of the flight simulation with the horizontal coordinates (X, Y)=(5m, 8m) in the example of the present invention;

[0106] Explanation of the reference numerals: 1. front wing; 2. rear wing; 3. connecting rod of front and rear wings; 4. aluminum alloy transverse folding part; 5. vertical tail; 6. elevator; 7. battery compartment; 8. load 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. supporting 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 be used to explain the present invention, but should not be construed as limiting the present invention.

[0108] Based on the fact that there are few studies 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 there is a lack of control methods that combine the advantages of flexible vertical take-off and landing capabilities and long endurance capabilities of fixed-wing UAVs, the present invention provides a vertical take-off and landing control method for a distributed power tandem-wing UAV, the tandem-wing UAV comprises 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 both 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 formed by 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 the control of the jump take-off, transition flight, cruising flight, and vertical landing stages, by allocating throttle amounts to the inner ring power unit and the outer ring power unit in the jump take-off stage, cruising flight stage, and vertical landing stage; a continuous climb transition method is adopted for the transition flight stage, and the flight state is controlled to be converted into a cruising level flight state after the transition is completed.

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

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

[0111] The distributed power tandem wing UAV take-off control method 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 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 angle velocity proportional-integral link. The pitch control amount is input into the front and rear wing differential unit 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, input the throttle control amount into 8 power units, and 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: Use the real-time altitude obtained by the onboard sensor to determine whether the drone has reached a safe altitude. If it has not reached a safe altitude, maintain the state of step 2 and continue to accelerate and jump. If it has reached a safe altitude, enter the steady climb phase and climb steadily at a climbing angle of 45° 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] Among them, 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, and 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 stage is:

[0123]

[0124] Where K H , K HI , K HD They 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 of the inner and outer loop power units and the efficiency curves. The inner loop basic throttle is 0.9 and the outer loop basic throttle is 0.45.

[0126] Step 6: The transition phase of the cruise transition adopts a continuous climb transition method. After the transition is completed, the UAV switches to the cruise level flight state. Starting from the transition stage, the throttle command is only assigned to the outer ring power unit, and the inner ring throttle automatically decreases to 0.1 and 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 drone during steady climb. 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 moment when the transition starts, and t3 is the moment 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 the cruise state of the drone of this embodiment, thrust control is performed by the four power units of the outer ring, and pitch and turning attitude control is achieved by differential movement of the elevator ailerons and the left and right wing power units, thereby achieving stable flight of the drone during the cruise 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 switching command sent by the ground. After receiving the switching signal, the flight control system determines whether the current state has reached the cruise state. cruise 、V cruise , if this state is reached, it switches to the cruise controller.

[0132] Step 2: During the cruise flight phase, the total energy controller is used to control the total energy of the drone with 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, and the throttle control amount is input into the 4 power units in the outer ring.

[0133]

[0134] in, and They 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 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.

[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 of gravity.

[0140] Step 3: The turning control of the drone in the cruising stage uses the L1 control method to control the drone to turn along an arc trajectory between the target point and the current position. The drone 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 target roll angle command of the UAV is subtracted from the actual roll angle to obtain the roll angle feedback signal, and the 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 the roll angular velocity feedback signal, and 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 proportionality 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 , Fig.12 , Fig.13 , Fig.14 and Fig.15As shown, after the drone of this embodiment glides down to the specified height, it transitions to the vertical flight state and lands vertically. The drone control scheme in the backward transition process is the same as the jump takeoff process. All power units participate in throttle control. The front and rear wing power units differentially control the pitch attitude together with the elevons, and the roll attitude is controlled by the elevons. The vertical flight control scheme is similar to the control logic of the four-rotor drone. The inner ring power unit of the drone provides lift to balance gravity. The front and rear differentials of the outer ring power unit control the pitch attitude of the drone, so that the drone moves forward and backward. The left and right differentials of the outer ring power unit control the roll attitude of the drone, so that the drone moves left and right. The diagonal differentials of the outer ring power unit control the yaw attitude of the drone, so that the drone rotates around the body axis.

[0147] Step 1: The drone receives the landing command. First, the cruise controller controls the drone to glide to the specified height H0. The glide angle of the glide segment is calculated from the landing point and the glide start 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 height instructions for the descent phase are:

[0151]

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

[0153] Step 2: After the drone flight control system determines that it has descended to the specified height, it switches to the backward transition control mode and controls the drone to lift its head to a vertical state. 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 all 8 power units.

[0154] Control the UAV to pitch angle θ from the glide stage 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 is the XY plane, 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 front wing, and the rotor axis is the z-axis direction; in the vertical flight control mode, the inner ring power unit of the UAV provides lift to balance gravity, and the outer ring power unit controls the pitch attitude of the UAV by front and rear differentials, so that the UAV moves forward and backward, and the outer ring power unit controls the roll attitude of the UAV by left and right differentials, so that the UAV moves left and right, and the outer ring power unit controls the yaw attitude of the UAV by diagonal differentials, so that the UAV rotates around the body axis.

[0161] The PD control instruction form for 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 height of the hovering state; 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 gravitational acceleration; 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 represents the pitch angle in the vertical flight coordinate system, δ ty Represents 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 represents the roll angle in the vertical flight coordinate system, δ tx Represents the differential amount of the power units on the left and right sides of the wing. The PI control instruction form of the 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 one group; K r Indicates the yaw angular velocity 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 Fig.16 , Fig.17 , Fig.18 , Fig.19 and Fig. 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 turn on the recognition mode to identify the ground landing mark, which can be an "H" shape or other custom shapes trained by deep learning. After the YOLO algorithm recognizes the ground mark, it automatically calculates the three-dimensional coordinates of the landing point and sends guidance instructions to the vertical flight controller in the form of horizontal position instructions and altitude instructions to guide the drone to land at the ground mark point.

[0177] Reference Figure 1-Figure 5 As shown, a tandem-wing UAV for implementing 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 body structure includes: front wing 1, rear wing 2, front and rear wing connecting rod 3, aluminum alloy transverse folding part 4, vertical tail 5, elevator aileron 6, battery compartment 7, load compartment 8, connecting rod junction box 13, vertical tail connecting part 14, transverse connecting rod 17 and connecting part 18. The front wing 1 and rear wing 2 are the main lifting surfaces of the UAV, and the two form a tandem wing layout. Considering the portability requirements, they are designed as small aspect ratio straight wings. The wingspan of the front wing 1 is 1.2m, the chord length is 0.3m, the wingspan of the rear wing 2 is 1.2m, the chord length is 0.31m, and the spatial height difference between the front wing and the rear wing is 0.32m-0.38m; the airfoil with a high lift coefficient is selected to meet the needs of the cruise condition and increase the range and flight time of the UAV. The vertical tail 5 is installed at the end of the rear wing 2 as the vertical stabilizer of the UAV, and the vertical tail 5 is connected to the rear wing 2 through the vertical tail connecting part 14. The front wing 1 and the rear wing 2 are connected by the front and rear wing connecting rods 3. A connecting piece 18 is installed at the intersection of the front and rear wing connecting rods 3 and the wing spar to realize multi-point connection between the front and rear wing connecting rods 3 and the wing, thereby improving the strength and rigidity of the structure. Two transverse connecting rods 17 are installed between the two front and rear wing connecting rods 3. The installation position is coordinated and determined according to the design center of gravity position of the entire drone. A battery compartment 7 is installed in the middle position of the transverse connecting rod 17 to place the battery 9 required by the drone. The transverse connecting rod 17 and the front and rear wing connecting rods 3 are fixedly connected through the connecting rod junction box 13, so that the connecting rod part forms an "H"-shaped layout, thereby improving the anti-torsion ability of the drone structure. A load compartment 8 is installed in the middle of the leading edge of the front wing 1 to place the airborne avionics equipment 16. An integrated design is adopted to combine the load compartment 8 with the structure of the front wing 1 to reduce the size of the drone and reduce the weight of the drone. The rudder surface of the drone in this embodiment includes two elevons 6 symmetrically hinged to the outer position of the trailing edge of the rear wing 2, which realize the flight control of the drone together with the power differential mode.

[0179] Reference Figure 6As shown, four aluminum alloy transverse folding members 4 are symmetrically installed on the two front and rear wing connecting rods 3, and the two folding members near the front wing are installed opposite to the two folding members near the rear wing to achieve reverse folding. After the aluminum alloy transverse folding members 4 reach the folding limit point, the length and height of the drone are reduced, which reduces the size of the drone and improves the portability of the drone.

[0180] The energy power system includes: a battery 9, a solar panel 10, an inner ring propeller and a motor 11 (rotor), an outer ring propeller and a motor 12, and an electronic speed regulator 15. The battery 9 uses a high energy density lithium battery, which is installed in the battery compartment 7 to provide energy for the drone. The solar panel 10 uses a flexible thin-film solar cell with high photoelectric conversion efficiency, which is evenly laid on the upper surface of the front wing 1 and the rear wing 2 to provide energy for the flight of the drone and play the role of solar energy range extension. 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 symmetry 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 by means of 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. To meet the requirements of the quad-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 resist wind through power differential during the take-off and landing phase. Therefore, the outer ring propeller adopts a large-pitch propeller with higher efficiency at a high forward 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 seat 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 load 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 to control the speed of the motor.

[0181] The airborne avionics system includes airborne avionics equipment 16 and airborne cables (not shown). The airborne avionics equipment 16 is distributed and installed in the payload compartment 8, including a navigation system, a flight control system, and a measurement and control system. The airborne cables are distributed inside the front wing 1, the rear wing 2, and on the surface of the front and rear wing connecting rods 3 and the transverse connecting rods 17. Cable ties and tapes are used to fix the exposed parts of the airborne cables to the fuselage. It is necessary to reduce the number of airborne cables through reasonable arrangement, and select lighter airborne cables to reduce the total weight of the drone.

[0182] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary 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 intent of the present invention.

Claims

1. A vertical take-off and landing control method for a distributed power tandem-wing UAV, wherein the tandem-wing UAV comprises a front wing and a rear wing arranged in a tandem wing form; characterized in that: The leading edges of the front wing and the rear wing are both 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 the quadrilateral, forming the inner ring power unit of the UAV, and the remaining rotors form 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 assembly; The vertical take-off and landing control method includes the control of the jump take-off stage, transition flight stage, cruise flight stage, and vertical landing stage by allocating 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 in the transition flight stage, and after the transition is completed, the flight state is controlled to be converted into a cruise level flight state.

2. According to claim 1, a vertical take-off and landing control method for a distributed power tandem-wing UAV is characterized by: The control method for the tandem-wing UAV to take off is: Step 1.1: The drone stops on the ground at a 45° parking angle and takes off at a fixed point with a large angle under the action of distributed power and aerodynamic force. At the beginning of takeoff, the drone takes off under the throttle command with stabilization control. At the moment of takeoff, all power units are at full throttle, so that the drone takes off under the pulling force of the power units. During the takeoff stage, the front and rear wing power units differentially control the drone with the elevator ailerons to accelerate and pull up at a given pitch angle. Step 1.2: Maintain the 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 passes through the proportional link to obtain feedback control information, which is input into the pitch angle velocity control loop, and the pitch control amount is output through the proportional-integral link, and the pitch control amount is simultaneously output to the front and rear wing power units and the elevator ailerons to achieve fixed pitch angle 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 rbehind =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 measured by 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, it enters the steady climb phase, climbing 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) Among them, 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. 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 1.2 to control the UAV to climb steadily. The specific form of the pitch angle control law in the climbing stage is: Where K H , K HI , K HD They 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 basic throttle values ​​are allocated according to the forward ratio of the inner and outer loop power units and the efficiency curve. The throttle command is the basic throttle value plus the automatic throttle command value.

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

45.

4. The vertical take-off and landing control method of a distributed power tandem-wing UAV according to claim 2, characterized in that: 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 is 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 loop power unit. This distribution method reduces energy consumption.

5. The vertical take-off and landing control method of a distributed power tandem-wing UAV according to claim 4, characterized in that: In step 2.2, the throttle amount of the inner ring power unit is fixed at 0.1 and remains unchanged.

6. The vertical take-off and landing control method of a distributed power tandem-wing UAV according to claim 4, characterized in that: The control method of 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 flight 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 4 power units in the outer ring; in, and They 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 They 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 gravitational acceleration; Step 3.3: The turning control of the UAV in the cruising phase uses the L1 guidance method. A reference point is selected on the desired path of the UAV. The line connecting the current position of the UAV and the reference point is L1. Based on the current position of the UAV and the position of the reference point, an arc tangent to the current speed of the UAV is planned. 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 form 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: The target roll angle command of the UAV is subtracted from the actual roll angle to obtain a roll angle feedback signal, and the roll angle feedback signal is input into the proportional link to obtain a 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, and 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 aileron; Among them, K φ is the roll angle proportionality 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.

7. The vertical take-off and landing control method of a distributed power tandem-wing UAV according to claim 6, characterized in that: 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 glide to the specified height H0. The glide angle of the glide segment is calculated from the landing point and the glide start 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 height instructions for the descent phase are: Among them, V sp is the target speed of the slide, the given value is 18m / s, t4 is the start time of the slide, and t5 is the end time of the slide; H setpoint is the glide height instruction, H1 is the starting glide height, and t is the current time; Step 4.2: After the UAV flight control system determines that it has descended to the specified height, it switches to the vertical landing control mode and controls the UAV to transition backwards. The UAV attitude is adjusted to a vertical flight state and lands at 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 input to each power unit after being distributed. Control the UAV to pitch angle θ from the glide stage slip Pull up to the target pitch angle θ land , the instruction format is: Among them, 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 is in a vertical hovering state, and maintains this state and slowly falls 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 is the XY plane, 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 front wing, and the rotor axis is the z axis direction; in the vertical flight control mode, the inner ring power unit of the UAV provides lift to balance gravity, the front and rear differential of the outer ring power unit controls the pitch attitude of the UAV to make the UAV move forward and backward, the left and right differential of the outer ring power unit controls the roll attitude of the UAV to make the UAV move left and right, and the diagonal differential of the outer ring power unit controls the yaw attitude of the UAV to make the UAV rotate around the body axis; The PD control instruction form for 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 gravitational acceleration; 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; 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 It represents 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 one group; K r Indicates the yaw angular velocity 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 YOLO recognition and positioning algorithm; During the vertical landing phase, the drone's onboard camera and computing equipment will start the recognition mode to identify the ground landing mark. After the YOLO algorithm recognizes the ground mark, it will automatically calculate the three-dimensional coordinate information of the landing point, first guide the drone to fly horizontally to just above the landing point, and then land vertically to the landing point; the guidance command is 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.

8. The vertical take-off and landing control method of a distributed power tandem-wing UAV according to claim 7, characterized in that: The ground landing mark is an "H" shape or other custom shapes trained by deep learning.

9. The vertical take-off and landing control method of a distributed power tandem-wing UAV according to claim 7, characterized in that: The front and rear wings of the tandem-wing UAV serve as 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 parts of the front and rear wings of the UAV along the middle symmetry plane of the UAV, so as to provide lift during the take-off and landing stages, and control the flight attitude of the UAV by means of 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 symmetry plane of the UAV, so as to provide thrust during the fixed-wing cruising stage, and resist wind by means of power differential during the take-off and landing stages.

10. The vertical take-off and landing control method of a distributed power tandem-wing UAV according to claim 9, 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.

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