Marine unmanned aerial vehicle landing platform and control method thereof

Abstract

The application discloses a kind of offshore unmanned aerial vehicle take-off and landing device and control method thereof, it is related to offshore unmanned aerial vehicle technical field, specific structure is: base, platform outer wall and platform hatch are enclosed into an internal hollow cuboid, base includes fixed platform, and fixedly installed with steering wheel on it.The lifting platform includes a hollow platform, and the bottom of the hollow platform is connected to the steering wheel on the fixed platform by a lifting mechanism, and the lifting mechanism is driven by the output shaft of the steering wheel to provide the hollow platform with three degrees of freedom movement capability;The top of the hollow platform is installed with a landing gear fixing seat.The device can design a platform outer wall and a platform hatch for the unmanned aerial vehicle take-off and landing platform, which can serve as a take-off launcher for unmanned aerial vehicles and also as a storage device for unmanned aerial vehicles.There is a reasonable fixed connection between the unmanned aerial vehicle and the lifting platform, and there is also a reasonable recovery method when the unmanned aerial vehicle lands.The control method provides a reasonable and effective automatic control method based on the structure of the device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of offshore unmanned aerial vehicle, and particularly relates to an offshore unmanned aerial vehicle take-off and landing platform and a control method thereof. BACKGROUND

[0002] In recent years, with the rapid development of the unmanned aerial vehicle industry, its application scenarios are not limited to land, but also extend to the sea. However, due to the large waves on the sea, the ship is relatively bumpy when sailing on the sea, and the traditional unmanned aerial vehicle cannot adapt to this type of take-off and landing environment. Many large unmanned aerial vehicles take off on land, and return to land after completing the task. Due to the limitation of communication and flight radius, small and medium-sized unmanned aerial vehicles can only complete near-sea tasks. With the birth of the compound wing unmanned aerial vehicle, the traditional fixed-wing unmanned aerial vehicle also has the ability of vertical take-off and landing after being equipped with a compound wing, which not only retains the advantages of high speed and long endurance of the traditional fixed-wing unmanned aerial vehicle, but also greatly reduces the runway length required for take-off and landing of the unmanned aerial vehicle. However, the take-off and landing conditions of the compound wing unmanned aerial vehicle are relatively harsh, and a stable platform is needed to provide it with a preparation stage before take-off and a stage after landing. At the same time, the reason why it is difficult for small and medium-sized unmanned aerial vehicles to perform tasks on small ships is that seawater has a strong corrosive ability to the electronic equipment carried by the unmanned aerial vehicle, so it is necessary to invent a small and medium-sized compound wing unmanned aerial vehicle take-off and landing platform installed on a small ship, which provides a closed and dry environment for the unmanned aerial vehicle during the transportation stage of the ship sailing.

[0003] The existing scheme is: an offshore unmanned aerial vehicle take-off and landing platform, which comprises a take-off and landing platform, a balancing assembly and a base, the balancing assembly and the base, three balancing assemblies are arranged in an equilateral triangle, and are arranged between the take-off and landing platform and the base. The balancing assembly comprises a driving cylinder and a universal joint, one end of the driving cylinder is connected with the universal joint, the other end of the universal joint is connected with the take-off and landing platform, and the driving cylinder is fixedly connected with the base. The attitude detection device of the base provides attitude data, the motors of the three driving cylinders drive the supporting rods to extend or shorten, so that the unmanned aerial vehicle platform maintains a suitable attitude, thereby achieving the purpose of safe take-off and landing of the unmanned aerial vehicle on the undulating sea surface. The unmanned aerial vehicle lacks a fixing device on the platform, and the unmanned aerial vehicle is easy to slide off before take-off. The take-off and landing platform cannot store the unmanned aerial vehicle when the unmanned aerial vehicle is transported with the ship, and the waterproof and corrosion resistance of the unmanned aerial vehicle and the take-off and landing platform are not considered. The unmanned aerial vehicle and the take-off and landing platform need to be stored separately, and the unmanned aerial vehicle lacks effective fixing and protection devices during landing.

[0004] Therefore, there is currently a lack of an equipment that can serve as both a take-off and launching device for an unmanned aerial vehicle and a storage device for the unmanned aerial vehicle, and how to control the take-off and landing of the unmanned aerial vehicle is also a problem that has not been solved. SUMMARY

[0005] In view of the above, the present application provides a kind of offshore UAV take-off and landing device and control method thereof, which can be designed as the take-off launching device of unmanned aerial vehicle and the storage device of unmanned aerial vehicle by the platform outer wall and platform hatch of unmanned aerial vehicle take-off and landing platform.There is reasonable fixed connection between unmanned aerial vehicle and lifting platform, and there is reasonable recovery mode when unmanned aerial vehicle lands.The control method gives a kind of reasonable and effective automatic control method based on the structure of the device.

[0006] To achieve the above object, the technical scheme of the present application is: a kind of offshore UAV take-off and landing device includes base, lifting platform, landing gear fixing seat, landing gear, platform outer wall and platform hatch.

[0007] Base, platform outer wall and platform hatch are enclosed into a hollow cuboid, and the platform hatch is a movable hatch, which is in a sealed state when closed.

[0008] The base includes a fixed platform, which is fixed to the ship body, and the fixed platform is fixedly installed with a steering engine.

[0009] The lifting platform includes a hollow platform, and the bottom of the hollow platform is connected to the steering engine on the fixed platform through a lifting mechanism, which provides the hollow platform with three degrees of freedom motion ability through the output shaft of the steering engine; The top of the hollow platform is provided with a landing gear fixing seat.

[0010] The landing gear fixing seat is used for fixing the landing gear of offshore unmanned aerial vehicle.

[0011] Further, the base further includes eight stepper motors, four steering engines and a first IMU sensor.

[0012] The fixed platform is provided with installation slots and push rod placement slots of stepper motors and four steering engines; The fixed platform is provided with a wiring channel inside for wiring of wire harness of stepper motors, steering engines and IMU sensor; The fixed platform is fixed to the ship body.

[0013] On the fixed platform, the steering engines are evenly distributed in four directions, and the eight stepper motors are distributed at the front and rear ends of the fixed platform.

[0014] The IMU sensor is installed at the center of the fixed platform, and is used for detecting and outputting linear acceleration and angular velocity in three directions of vertical direction, pitch direction and roll direction.

[0015] Further, the lifting mechanism on the lifting platform is composed of push rods, spherical hinge sleeves, sliding blocks and sliding rails; the push rods, spherical hinge sleeves, sliding blocks and sliding rails are all four in number and are arranged in pairs with the rudders; in the lifting mechanism, one end of the push rod is connected to the rudder, and when the rudder rotates, the connected push rod is driven to make a circular motion; the other end of the push rod is connected to the spherical hinge sleeve; the spherical hinge sleeve includes a three-fifth spherical shell and a fixed nut at the bottom of the shell, the top end of the three-fifth spherical shell is open, and the bottom end is fixed to the side of the nut; the one side of the nut is provided with a sawtooth array; the bottom of the sliding block is provided with a ball, the bottom ball of the sliding block is embedded in the three-fifth spherical shell, and the sizes are matched; the end of the push rod connected to the spherical hinge sleeve is provided with a fixed groove corresponding to the sawtooth on the nut ring surface, and the sawtooth array is embedded in the fixed groove to lock the angle between the spherical hinge sleeve and the push rod; the top of the sliding block is linearly connected with the sliding rail; the four sliding rails are arranged in a cross shape at the bottom of the hollow platform; the four lifting mechanisms and the lifting platform constrain each other to provide the platform with three degrees of freedom of movement.

[0016] Further, the lifting platform further comprises a second IMU sensor; the second IMU sensor is installed below the hollow platform; the pose of the second IMU sensor and the first IMU sensor on the base are coaxial and in the same direction, and are parallel to each other;

[0017] Further, the landing gear fixing seat is in a cylindrical structure, the cylinder is cut along the axial section into two parts, i.e., a fixing seat base and a fixing upper buckle, and the two parts are connected by a pin to form a cylinder; the fixing seat base is fixed to the hollow platform, and the fixing upper buckle is connected to the fixing seat base by a pin; the unmanned aerial vehicle landing gear has a section placed in the landing gear fixing seat at each end; the unmanned aerial vehicle landing gear is provided with four fixing needles for inserting into the hollow platform when the unmanned aerial vehicle lands;

[0018] Further, the base, the platform outer wall and the platform hatch cover enclose an internally hollow rectangular cuboid, the platform hatch cover is a movable hatch cover, which is in a sealed state when closed, and the specific structure is as follows:

[0019] The platform outer wall is vertically fixed to the four sides of the fixed platform; the platform outer wall covers the platform hatch cover at the top; the platform hatch cover is divided into a left hatch cover and a right hatch cover, and a movable rod connects the left hatch cover and the right hatch cover with the output shaft of the stepper motor, which is driven by the stepper motor; the stepper motor drives the movable rod to rotate, thereby realizing the opening and closing of the platform hatch cover, and the overall drive is overdrive.

[0020] Further, the fixed platform is made of metal.

[0021] Further, the fixed platform is provided with mounting holes and drainage holes, and the fixed platform is fixed to the ship body by bolt connection, and the outer circle of the fixed platform is designed in a stepped shape for mounting the platform outer wall.

[0022] Further, a camera module is installed on the outer wall of the platform to monitor the state of the UAV in the cabin of the UAV in real time.

[0023] The application further provides a control method of the offshore UAV take-off and landing device. l .

[0024] Taking the y-axis as the front direction of the ship, the right-hand coordinate system, the x-axis as the left side of the ship, and the z-axis as the sky, the No. 1 steering engine is in the positive direction of the y-axis, the No. 2 steering engine is in the positive direction of the x-axis, the No. 3 steering engine is in the negative direction of the y-axis, and the No. 4 steering engine is in the negative direction of the x-axis.

[0025] In the initial state, the moving platform and the static platform coincide, and since the design freedom of the moving platform is 3, only vertical movement, pitching movement and rolling movement can be realized, so the movement amount of the moving platform in the vertical direction is Z, the pitching movement angle is , the rolling movement angle is , and the angles of the four steering engines relative to the horizontal plane are ; the task to be realized is to obtain , the pitching direction angle , the rolling direction angle and the mutual constraint between the structure. .

[0026]

[0027]

[0028]

[0029]

[0030] Wherein s1~s4 are respectively: , , ; is the coordinate of the steering engine shaft hinge point, , ; ; ; is the direction vector of the four slide rails of the moving platform in the world coordinate system, , , , .

[0031] Beneficial effects:

[0032] 1. The offshore unmanned aerial vehicle landing device provided by the application designs a platform outer wall and a platform hatch, which can be used as a take-off launching device of the unmanned aerial vehicle and also can be used as a storage device of the unmanned aerial vehicle. There is a reasonable fixed connection between the unmanned aerial vehicle and the lifting platform, and there is also a reasonable recovery mode when the unmanned aerial vehicle lands. In addition, the entire unmanned aerial vehicle landing platform needs very few manual operations, has a certain degree of automation, and saves manpower.

[0033] 2. The offshore unmanned aerial vehicle landing device provided by the application, in the structural design, in order to realize the three-degree-of-freedom motion capability of the lifting platform, four driving rudders are adopted, which are overdriven, and if one rudder is damaged, the other three rudders can still drive the whole mechanism.

[0034] 3. The offshore unmanned aerial vehicle landing device provided by the application is installed with two attitude sensors, and the data directly collected by the sensors are filtered and state estimated, so that the data are smoother and more accurate.

[0035] 4. The offshore unmanned aerial vehicle landing device provided by the application is also designed with a control method, which is a reasonable and effective automatic control method. DETAILED DESCRIPTION

[0036] Figure 1 The offshore unmanned aerial vehicle landing device provided by the application is shown in the overall structure schematic view;

[0037] Figure 2 The offshore unmanned aerial vehicle landing device provided by the application is shown in the sealed rectangular prism formed when the hatch is closed;

[0038] Figure 3 The base structure in the embodiment of the application is shown in the schematic view;

[0039] Figure 4 The lifting platform structure in the embodiment of the application is shown in the schematic view;

[0040] Figure 5 The lifting mechanism details in the embodiment of the application are shown in the schematic view;

[0041] Figure 6 The spherical hinge sleeve in the embodiment of the application is shown in the schematic view;

[0042] Figure 7 The slider structure in the embodiment of the application is shown in the schematic view;

[0043] Figure 8 The landing gear fixing seat and the landing gear structure in the embodiment of the application are shown in the schematic view;

[0044] Figure 9 The left and right hatch structures in the embodiment of the application are shown in the schematic view;

[0045] Figure 10 This is a geometric diagram showing the relationship between the moving platform and the static platform when the xz plane in the world coordinate system is directly facing the target in an embodiment of the present invention.

[0046] Figure 11 This is a simulation result diagram of the structural relationship between the moving platform and the static platform in an embodiment of the present invention;

[0047] Figure 12 This is a flowchart of the take-off phase of a maritime unmanned aerial vehicle in an embodiment of the present invention;

[0048] Figure 13 This is a flowchart of the landing phase of a maritime unmanned aerial vehicle in an embodiment of the present invention;

[0049] Figure 14 This is a control closed-loop diagram of a marine unmanned aerial vehicle (UAV) take-off and landing device according to an embodiment of the present invention. Detailed Implementation

[0050] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0051] The overall structure of the marine unmanned aerial vehicle (UAV) take-off and landing platform provided by this invention is as follows: Figure 1 As shown, it mainly consists of five parts: a base 1, a lifting platform 2, a landing gear mounting base 3, a UAV landing gear 4, an outer platform wall 5, and a platform hatch 6. The base 1, outer platform wall 5, and platform hatch 6 together form a hollow cuboid. The platform hatch 6 is a movable hatch, which is sealed when closed. Figure 2 As shown, the platform can store drones and protect them from seawater corrosion. The drone landing platform base primarily provides the mounting location on the hull, as well as the mounting of servos, motors, control systems, and their wiring harnesses. The movement of the drone landing platform is controlled by four high-torque servos, providing three degrees of freedom: vertical movement, pitch, and roll. To ensure the drone does not lose control during takeoff and is immediately secured upon landing on the platform, the landing gear mounting brackets and landing gear on the platform are specially designed, which will be described in detail later. The platform's outer walls and platform hatch are primarily used to protect the drone, and the honeycomb design significantly improves the drone system's waterproof and corrosion-resistant properties.

[0052] Base design

[0053] The base of the unmanned aerial vehicle landing platform is composed of a fixed platform 11, eight stepping motors 12, four steering engines 13 and an IMU sensor 14. The fixed platform can be a metal platform. The fixed platform has installation slots for motors and steering engines and placement slots for push rods. When the entire platform is in a closed state, the push rods can be withdrawn into the fixed platform. The fixed platform has a wiring channel inside to organize the wiring harness of the motors, steering engines and sensors. As a part of the entire unmanned aerial vehicle landing platform and the hull, the fixed platform has mounting and drainage holes. To be fixed to the hull, only corresponding bolts need to be installed on the hull. In order to facilitate the installation of the outer wall of the platform, the outer ring of the fixed platform is designed in a stepped shape.

[0054] The steering engines on the base fixed platform are evenly distributed in four directions and are responsible for driving the lifting platform. The motors are distributed at the front and rear ends of the fixed platform and are responsible for driving the opening and closing of the platform hatch. The steering engines and motors are installed on the base fixed platform, which has the advantages of convenient wiring and close connection with the hull, so that additional movement will not be caused by the shaking of the hull.

[0055] The first IMU sensor can provide linear acceleration in three directions and angular velocity in three directions. The first IMU sensor is installed at the center of the base metal platform and is used to monitor the acceleration and angular velocity of the hull in each direction under the influence of sea wave fluctuations when the unmanned aerial vehicle landing platform is installed at the position of the hull. The attitude at this time is obtained through pose solving, thereby providing original data for subsequent self-stabilization control of the lifting platform.

[0056] Lifting platform

[0057] The lifting platform structure is shown in Figure 4 and is composed of a lifting mechanism, a second IMU sensor 25 and a hollow platform 26. The lifting mechanism is composed of a push rod 21, a spherical hinge sleeve 22, a sliding block 23 and a sliding rail 24, as shown in Figure 5 As an important transmission mechanism of the lifting platform, one end of the push rod is connected with the steering engine, and the rotation of the steering engine drives the push rod to make circular motion. The other end of the push rod is fixed to the specially designed spherical hinge sleeve through bolts. The structure of the spherical hinge sleeve is shown in Figure 6As shown, in the lifting mechanism, the push rod 21 is connected to the steering gear 13 at one end, and when the steering gear 13 rotates, it drives the connected push rod 21 to move in a circular motion; the other end of the push rod 21 is connected to the spherical hinge sleeve 22; the spherical hinge sleeve 22 includes a three-fifth spherical shell and a fixed nut at the bottom of the shell, the top end of the three-fifth spherical shell is open, and the bottom end is fixed to the side of the nut; the nut has a sawtooth array on one side of the annular surface; the slider 23 is provided with a ball at the bottom, and the bottom ball of the slider 23 is embedded in the three-fifth spherical shell, and the size is matched; the end of the push rod 21 connected to the spherical hinge sleeve 22 is provided with a fixed groove corresponding to the sawtooth on the annular surface of the nut, and the sawtooth array is embedded in the fixed groove to lock the angle between the spherical hinge sleeve 22 and the push rod 21; the top of the slider 23 is linearly connected with the slide rail 24; the four slide rails 24 are arranged in a cross shape at the bottom of the hollow platform 26; the four lifting mechanisms and the lifting platform 2 constrain each other to provide the platform with three degrees of freedom of movement. The connection between the spherical hinge sleeve and the push rod is loosened by unscrewing the bolt, which can move relatively, and after the bolt is tightened, the spherical hinge sleeve and the push rod are fixed by the pre-tightening force of the bolt, and there is a circle of sawtooth at the fixed part of the spherical hinge sleeve and the push rod Figure 6 As shown, the advantage of such design is to increase the stability of the structure, and at the same time, due to the fixed angle of each sawtooth in the circumference, the four push rods and spherical hinge sleeves can be easily fixed at the same angle during installation. The overall push rod and spherical hinge sleeve are high in cost and difficult to process, while separate processing can significantly reduce the cost. It is also very convenient to replace the parts after damage. In addition, such design is also easier to install.

[0058] The spherical hinge sleeve and the slider are connected in the form of a spherical hinge, and the slider and the slide rail are linearly connected, as shown in Figure 7 The four push rod-spherical hinge-slider-slide rail lifting mechanisms are evenly distributed below the hollow platform, the slide rail and the lifting platform are fixed, the angle between two adjacent slide rails in a cross shape is 90 degrees, and the four lifting mechanisms and the lifting platform constrain each other to provide the platform with three degrees of freedom of movement, including vertical, pitch and roll directions. Since there are four driving devices, there are only three degrees of freedom, the driving of the lifting platform is overdriven, so the lifting platform can still work normally in the case of failure of one steering gear, improving the durability and stability of the unmanned aerial vehicle lifting platform in harsh environments.

[0059] A second IMU sensor is installed below the hollow platform, and the pose of the second IMU sensor is coaxial and in the same direction as the first IMU sensor on the base, and they are parallel to each other, mainly for providing feedback to the IMU self-stabilization system control. Above the hollow platform, some laser ranging sensors are also installed, which are used to monitor the state of the aircraft taking off and landing, and to facilitate self-judgment of the task link according to the unmanned aerial vehicle taking off and landing.

[0060] The platform for parking the unmanned aerial vehicle in the lifting platform is a hollow platform, and the platform is designed as a hollow platform because the unmanned aerial vehicle is prone to being disturbed by sea wind during landing of the compound wing unmanned aerial vehicle, and the protruding part of the landing gear of the unmanned aerial vehicle is inserted into the small hole during landing in combination with the special design of the landing gear, so that the stability of landing is realized.

[0061] The landing gear fixing seat is composed of two parts, i.e. a fixing seat base 31 and a fixing upper buckle 32, wherein the fixing seat base is fixedly connected with the hollow platform in the lifting platform, and the fixing upper buckle is connected with the fixing seat base through a pin and can be driven by a motor. The fixing seat base plays a role of fixing and releasing the unmanned aerial vehicle.

[0062] In view of the design of the landing gear fixing seat and the hollow platform, a corresponding unmanned aerial vehicle landing gear 4 is designed, and since the landing gear fixing seat is designed as a cylinder, the unmanned aerial vehicle landing gear also has a part that can be placed in the landing gear fixing seat. In view of the design of the hollow platform, four fixing pins are designed on the unmanned aerial vehicle landing gear. When the unmanned aerial vehicle lands, since the space of the hollow platform is limited and the sea wind is large, the compound wing unmanned aerial vehicle is unstable in flight, and during landing, the fixing pins are inserted into the hollow platform, so that the movement of the unmanned aerial vehicle in the horizontal direction is limited, so that the landing of the aircraft becomes more stable, and the success rate is higher. Figure 8 The structure diagram of the landing gear fixing seat and the landing gear in the embodiment of the present application.

[0063] The outer wall of the platform and the platform hatch

[0064] The outer wall 5 of the platform and the platform hatch 6 can be made of an integrally formed composite material such as nylon and resin, which can effectively reduce the mass of the whole unmanned aerial vehicle landing platform. A camera module is installed on the outer wall of the platform to monitor the state of the unmanned aerial vehicle in the cabin in real time, and can assist in determining when the landing gear fixing seat should be released to allow the unmanned aerial vehicle to take off. When the unmanned aerial vehicle lands, the camera on the outer wall can also help the pilot to operate the unmanned aerial vehicle.

[0065] Figure 9 The structure diagram of the left and right hatches in the embodiment of the present application; the platform hatch is divided into a left hatch 61 and a right hatch 62, which are driven by a stepping motor, and the stepping motor drives two long and short rod members 63 and 64 to rotate, one end of the rod member is connected to the output shaft of the stepping motor, so that the opening and closing of the platform hatch are realized, the whole driving is overdriven, and the platform hatch can still continue to operate even if part of the stepping motor is damaged. The platform hatch mainly plays a role of dustproof and waterproof, and such a platform hatch switching mode is designed, one is to place the driving assembly on the base, and the other is to reduce the occupied space, so that more space can be used for other tasks on small and medium-sized ships.

[0066] Inverse kinematics solution in the robotics part of the present application

[0067] The lifting platform in this invention can be considered as a parallel platform. The inverse kinematics will be solved using robotics methods. The reason for not solving the forward kinematics first is that the joints of the parallel machine platform are mutually constrained, and arbitrarily setting the angles of the four servo motors often results in an unsolvable system. Furthermore, achieving platform self-stabilization through IMU sensors requires obtaining the inverse kinematics solution.

[0068] The drone's takeoff and landing platform is abstracted as a static platform—the base, and a moving platform—the lifting platform. The four drive mechanisms are abstracted as four line segments of equal length that can rotate around a fixed point. The slide rail is also abstracted as a line segment. Let the distance from the origin of the static platform to the servo motor axis be d, and the length of the rod be... l Establish a right-handed coordinate system with the center of the static platform as the origin and the z-axis pointing towards the sky. Use this as the world coordinate system, with the x and y axes pointing in the directions of the two adjacent push rods, respectively. Establish a right-handed coordinate system with the center of the moving platform as the origin and the z-direction perpendicular to the moving platform and pointing upwards. Use the x and y axes pointing in the same direction as the world coordinate system when the platform is not rotating. Use this as the moving platform coordinate system.

[0069] Initially, the moving and stationary platforms coincide. Since the moving platform has 3 degrees of freedom, it can only achieve vertical, pitch, and roll motions. Therefore, let the vertical motion of the platform be Z, and let the pitch motion (rotation around the x-axis) be Z. Rolling motion, which is the motion around the y-axis, is The angles through which the four servos rotate relative to the horizontal plane are respectively The task to be accomplished is to know that Z is rising or falling. Looking up and down, The mutual constraints between roll and structure are obtained Set the y-axis to point directly in front of the ship, using a right-handed coordinate system. The x-axis points to the left of the ship, and the z-axis points to the sky. Servo motor 1 is in the positive y-axis direction, servo motor 2 is in the positive x-axis direction, servo motor 3 is in the negative y-axis direction, and servo motor 4 is in the negative x-axis direction.

[0070] The derivation process is as follows: coordinates of the four servo shaft hinge points for:

[0071]

[0072]

[0073]

[0074]

[0075] The direction vectors of the four slide rails of the moving platform for:

[0076]

[0077]

[0078]

[0079]

[0080] After the transformation of the moving platform through Z, , , the rotation matrix of the moving platform relative to the static platform is :

[0081]

[0082]

[0083] Then, the direction vector of the four slide rails of the moving platform in the world coordinate system is :

[0084]

[0085]

[0086]

[0087]

[0088] As Figure 10 shown, the xz plane under the world coordinate system is directly opposite, and the angle through which the moving plane has turned is currently known as . According to Figure 10 , the size of the desired is , and , therefore, the distance can be obtained by finding s1, and the size of s1 is the distance from the rudder shaft point to the slide rail.

[0089] According to the distance from a point in space to a straight line, we have

[0090]

[0091] Similarly, we have

[0092]

[0093]

[0094]

[0095] Finally, we obtain

[0096]

[0097]

[0098]

[0099]

[0100] In matlab software, the result is obtained, and when , the simulation result is shown in Figure 11 .

[0101] The control logic design of the application

[0102] The offshore compound wing unmanned aerial vehicle may encounter extreme weather when performing tasks, therefore, mature control logic design is necessary.

[0103] Take-off stage

[0104] The unmanned aerial vehicle needs to judge whether it has flight conditions according to the weather and sea conditions before taking off, at this time, the IMU sensor on the base judges the wind and wave conditions by sensing the attitude change of itself, if the attitude change rate and the degree of attitude change are greater than the range that the lifting platform can adjust, the system will automatically refuse the task. If the wind and wave are small, the unmanned aerial vehicle pilot can confirm the aircraft state through the camera carried by the platform, and the state is suitable for taking off.

[0105] During the take-off process of the unmanned aerial vehicle, first, the eight stepping motors on the base rotate to open the platform hatch, after the hatch is completely opened, the lifting platform starts to rise, at this time, the self-stabilizing system starts to work, after the unmanned aerial vehicle is completely lifted, the system starts to detect the sensor data of the IMU on the hollow platform, if it is found that the fluctuation is greater than the threshold value, it means that the condition is not suitable for flight at this time, then wait for a certain time, if the fluctuation does not decrease, then lower the lifting platform and cover the hatch. If the fluctuation decreases and gradually becomes less than the threshold value at this time, it means that the condition is suitable for taking off at this time, the propeller of the compound wing unmanned aerial vehicle can be opened, at this time, the landing gear fixing seat is still closed, after the propeller of the aircraft reaches the required rotating speed for taking off, the landing gear fixing seat is opened, and the aircraft takes off and rises. After the aircraft rises, the laser ranging sensor installed on the hollow platform detects that the distance disappears, which means that the aircraft has taken off successfully and starts to perform the offshore task, at this time, the unmanned platform is lowered and the hatch is closed. The specific take-off process is shown in the following figure, the only link that the pilot needs to intervene is to confirm the aircraft state through the camera. The process is shown in Figure 12 .

[0106] Landing stage

[0107] The UAV also needs reasonable control logic in the landing phase. First, according to the IMU sensor data on the base, it is determined whether the sea conditions are suitable for landing. If not, the task is rejected, and the plane will continue to circle in the sky, and after a period of time, the landing check will be performed again. If the sea conditions are suitable for landing, the platform hatch is opened, the lifting platform is raised, and the self-stabilization system starts to work. Then, the IMU data on the hollow platform is extracted, and it is determined whether the fluctuation of the hollow platform is greater than the threshold. If it is greater than the threshold, the landing task is suspended for a period of time, and the detection is performed again. This cycle continues until the fluctuation is less than the threshold. After the fluctuation is less than the threshold, the UAV starts to land, the pilot controls the UAV to reach above the platform, opens the control vertical take-off and landing propeller, and when the distance from the platform is close, all propellers are turned off. The fixed needle on the plane landing gear is inserted into the hollow part of the hollow platform to achieve the fixation of the plane. At this time, the pilot or other personnel on the ship immediately recovers the plane to the UAV landing platform and fixes it on the landing gear fixing seat. After completion, the lifting platform is lowered, and the platform hatch is closed. The overall process is shown in Figure 13 .

[0108] Lifting device IMU self-stabilization control

[0109] During the process of UAV take-off and landing, an important link is the IMU self-stabilization control. The UAV landing platform senses the sea conditions and controls the attitude of the lifting platform according to the sea conditions, so as to keep it stable in the horizontal direction, thereby giving the UAV a good take-off and landing environment. Since the IMU sensor has a large white noise error when in use, the IMU sensor reading needs to be optimized, otherwise the data read out is discontinuous and unstable, and cannot provide accurate rotation angles for the four rudders. At the same time, pure open-loop control will make the controller response slow and the control effect poor. Based on this, a feedback control is designed, and the data obtained by the IMU sensor on the base and the IMU sensor on the lifting platform are used as input and feedback respectively, which plays a good control role.

[0110] The measurement value of the IMU sensor on the base is optimized by the Kalman filter to form a relatively smooth and accurate state estimation value, and then the real-time attitude is calculated. The input of the system is the expected attitude minus the real-time attitude of the base minus the attitude of the hollow platform obtained by the feedback loop. After obtaining the input, inverse kinematics is solved to obtain the rotation angles of the four rudders. The angles are input into the PID controller, and the four rudders will rotate accordingly. The attitude generated by the rotation is input into the controller again to form a closed loop. The specific flow chart is shown in Figure 14 .

[0111] To sum up, the above is only the preferred embodiment of the present application, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A marine unmanned aerial vehicle landing device, characterized by, The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform.

2. A UAV landing pad at sea as claimed in claim 1, wherein, The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. The application relates to a seagoing unmanned aerial vehicle platform. 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3. A UAV landing pad at sea as claimed in claim 1, wherein, The lifting platform (2) further comprises a second IMU sensor (25); the second IMU sensor (25) is installed below the hollow platform (26); the pose of the second IMU sensor (25) is coaxial and in the same direction with the first IMU sensor (14) on the base (1) and parallel to each other.

4. A UAV landing and take-off device for offshore use according to claim 1 or 2, characterised in that, The landing gear fixing seat (3) is in a cylindrical structure, which is cut along the axial section into two parts, i.e., a fixing seat base (31) and a fixing upper buckle (32), and the two parts are connected by a pin to form a cylinder; the fixing seat base (31) is fixedly connected with the hollow platform (26), and the fixing upper buckle (32) is connected with the fixing seat base (31) by a pin; the unmanned aerial vehicle landing gear (4) has two ends each having a section placed in the landing gear fixing seat (3); the unmanned aerial vehicle landing gear (4) is provided with four fixing pins for inserting into the hollow platform when the unmanned aerial vehicle lands.

5. A UAV landing pad at sea as claimed in claim 4, wherein, The base (1), the platform outer wall (5) and the platform hatch cover (6) enclose an internally hollow cuboid, and the platform hatch cover (6) is a movable hatch cover in a sealed state when closed, and the specific structure is as follows: The platform outer wall (5) is vertically fixed to the four sides of the fixed platform (11); the platform outer wall (5) covers the platform hatch cover (6) at the top end; the platform hatch cover (6) is divided into a left hatch cover (61) and a right hatch cover (62), and a movable rod member connects the left hatch cover (61) and the right hatch cover (62) with the output shaft of the stepping motor, which is driven by the stepping motor (12); the stepping motor (12) drives the movable rod member to rotate, thereby realizing the opening and closing of the platform hatch cover, and the overall drive is overdrive.

6. A UAV landing pad at sea as claimed in claim 1, wherein, Characterized in that, The fixed platform (11) is made of metal.

7. A UAV landing pad at sea as claimed in claim 1, wherein, The fixed platform (11) is provided with mounting hole positions and drainage hole positions, and is fixedly connected with the ship body by means of bolt connection, and the outer ring of the fixed platform (11) is designed in a stepped type for mounting the platform outer wall (5).

8. A UAV landing pad at sea as claimed in claim 1, wherein, A camera module is mounted on the platform outer wall (5) for real-time monitoring of the state of the unmanned aerial vehicle in the unmanned aerial vehicle cabin.

9. A control method of a sea-based unmanned aerial vehicle landing device, characterized by, For the offshore unmanned aerial vehicle landing device as claimed in claim 1, 2, 3, 5, 6, 7 or 8, the offshore unmanned aerial vehicle landing device has a base as a static platform, a lifting platform as a dynamic platform, and four drive mechanisms as four equal-length line segments rotating around a fixed point; the slide rail is also abstracted as a line segment; With the distance from the static platform origin to the steering engine shaft point as d, the rod length as l ; Taking the y-axis as the forward direction of the ship, the right-hand coordinate system, the x-axis as the left side of the ship, and the z-axis as the sky; the No. 1 steering motor is in the positive direction of the y-axis, the No. 2 steering motor is in the positive direction of the x-axis, the No. 3 steering motor is in the negative direction of the y-axis, and the No. 4 steering motor is in the negative direction of the x-axis; Initially, the moving platform coincides with the static platform. Since the moving platform has 3 degrees of freedom, it can only realize vertical movement, pitch movement and roll movement. Therefore, the vertical movement of the moving platform is Z, the pitch movement angle is , the roll movement angle is , and the angles of the four steering engines relative to the horizontal plane are ; the task to be realized is to obtain the mutual constraints between the known Z vertical direction, pitch direction angle roll direction angle and structure ; wherein s1~s4 are respectively: , , ; is the coordinate of the rudder shaft hinge point, , ; ; ; is the direction vector of the four slide rails of the moving platform in the world coordinate system, , , , .

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