CN117566114A - A skyhook recovery control method for small ship-based cluster UAVs - Google Patents

Abstract

The invention discloses a method for recycling and controlling a hook of a small carrier-based cluster unmanned aerial vehicle, and belongs to the field of unmanned aerial vehicle control; the method comprises the following steps: aiming at a small carrier-based cluster unmanned aerial vehicle, acquiring relative position, speed, heading and attitude information of a ship between the unmanned aerial vehicle and the ship through differential satellite navigation, and guiding landing of the unmanned aerial vehicle; dividing the route in the unmanned aerial vehicle astronomical hook recovery process into three sections: the approach section flight control module controls the unmanned aerial vehicle to reduce the altitude and the speed, and the alignment recovery device enters a following flight mode; the recovery section continuously corrects the hook point of the overhead hook through the real-time attitude of the ship, and continuously performs lateral offset control and height control on the unmanned aerial vehicle through an L1 guidance law and a PID controller, so that the accuracy of the hook is improved; the flying section monitors and judges the unmanned aerial vehicle state at decision points and hook points, and the recovery mode is re-entered through the shortest route as long as the flying section is in flying, so that the recovery flight time is reduced, and the influence on the recovery of the subsequent unmanned aerial vehicle in the cluster is minimized.

Description

A skyhook recovery control method for small ship-based cluster UAVs

Technical field

The invention belongs to the field of unmanned aerial vehicle control, and specifically relates to a small ship-based cluster unmanned aerial vehicle skyhook recovery control method.

Background technique

Currently, in order to enhance naval combat capabilities, enrich maritime combat methods, and improve the composition of air and sea forces, drones, as a simple, efficient, low-cost, and low-risk combat platform, are gradually being used on various surface ships to undertake reconnaissance, Tasks such as surveillance, search, information relay, material transportation and attack have greatly increased the range of ship perception and attack.

Because shipborne drones are small and light, they can be equipped on warships such as aircraft carriers, destroyers, frigates, and amphibious ships. They accompany the mothership deep into the ocean to perform various combat missions, optimizing and expanding the fleet combat model. As an important development direction, drone clusters can significantly improve overall performance compared to a single drone, and play an important role in maritime application scenarios such as joint attack, reconnaissance, and submarine exploration.

Ship-based UAVs can be roughly divided into the following categories: fixed-wing UAVs, unmanned helicopters, tilt-wing UAVs and composite-wing UAVs. Compared with other types of UAVs, fixed-wing UAVs have the advantages of large payload, high speed, low resistance, simple structure, high reliability and long range. However, the take-off and landing methods are the most complicated, especially landing and recovery are more difficult. In swarm combat mode, how to deal with the continuous landing and recovery of multiple drones will be an important issue.

The recovery methods of small ship-based fixed-wing UAVs mainly include water surface parachute, net collision recovery and skyhook recovery. Water parachuting is extremely susceptible to the influence of wind, and requires additional equipment such as floats or airbags and waterproofing of the entire machine, so it is rarely used.

In recent years, a rope hook recovery system called "Skyhook" has been developed internationally. This recovery method is developed on the basis of the collision net recovery technology. The system usually consists of a capture device, a guidance device and a buffer device. By guiding the drone to the vicinity of the capture device, the drone collides with the recovery rope through precise navigation technology, and the recovery rope slides along the wing to the wing. The tip is hooked and locked by the small hook on the wing tip, so that the drone can be buffered by rotational deceleration and then manually removed to complete the recovery. Compared with collision net recovery, the skyhook recovery device is simpler and the recovery window has a larger longitudinal length. It also requires the flight control system to accurately guide the drone and accurately collide with the capture device.

In a shipboard application environment, ships generally perform UAV recovery operations during navigation. Due to the limitations of the wing span and the impact of the ship's rolling and rolling motion, a vertical recovery rope of more than ten meters long will Large-scale irregular shaking, these factors not only increase the difficulty of recovering the carrier-based UAV skyhook, but the lateral trajectory tracking error of the UAV has become a key factor affecting the success rate of recovery.

Contents of the invention

In order to solve the skyhook recovery control problem of fixed-wing UAVs in a ship-based environment, the present invention provides a skyhook recovery control method for small ship-based cluster UAVs, which can effectively deal with ship-borne skyhook recovery and control caused by waves in a maritime environment. The hook device swayed significantly, and the route was designed and optimized to address issues such as go-around and cluster recovery.

The specific steps of the skyhook recovery control method for small ship-based cluster UAVs are as follows:

Step 1. For small ship-based cluster UAVs, each small UAV is equipped with a GD30 differential satellite navigation module and a flight control and navigation module. The wingtips on both sides are equipped with small wingtip hooks for skyhook lanyard recovery.

Step 2: Install the skyhook recovery device on the ship, erect the recovery rope, and arrange the ground station and corresponding dynamic differential ground equipment in a safe zone;

The recovery rack in the shipboard skyhook recovery device erects the recovery rope vertically in an open space for hook recovery of UAVs; a rotating table is installed at the bottom of the recovery rack, and the recovery ropes are expanded to three, with an interval of 120 The degrees are evenly distributed on the main pole of the recovery frame along the circumference; when the drone successfully hits the hook, the recovery frame is rotated 120 degrees and then fixed, so that the next drone can use the next recovery rope for recovery operations at the same time;

Step 3: Set the required parameters of the skyhook recovery device in advance;

Parameters include skyhook position offset, landing direction, relative altitude and speed when hitting the skyhook, distance between points on the landing route, go-around decision point error threshold and route angle, etc.

Step 4: After the drone cluster completes the scheduled mission, a return command is issued; every three drones are divided into a group, return in a fixed formation at a fixed distance, and enter the recovery hook process;

When each group of drones is recovered, the distance between the front and rear drones should be ensured: the skyhook recovery device automatically rotates 120 degrees through the rotating table to the next mission state.

Specifically:

Step 401. For the first UAV in the current group, its flight control and navigation module calculates the waypoints of the UAV's landing route in real time based on the received real-time position and attitude information of the ship, and moves with the ship. Continuously refresh routes.

The landing route is a rectangle, including the following waypoints: follow point 1, approach point 2, decision point 3, hook point 4, missed approach point 5 and transition point 6. The four vertices are 1 point respectively. , 2 o'clock, 5 o'clock and 6 o'clock;

Step 402: When the drone returns to the set range near the ship, issue a landing command; lock the longitude and latitude position of waypoint 1 on the landing route at the time when the flight control and navigation module receives the landing command, and set it as the target waypoint;

Step 403: While the UAV is flying to the target waypoint 1, it gradually lowers to the preset height of the waypoint through slope control.

Step 404: After the drone reaches waypoint 1, it officially enters the landing stage, switches the target waypoint to waypoint 2, and also locks the longitude and latitude of waypoint 2 at the switching time, and the drone turns and lowers its altitude to align with the landing route;

The actual flight trajectory at waypoint 2 is the arc made by the minimum turning radius of the drone.

Step 405: When turning at waypoint 2, switch the target waypoint to waypoint 3 and enter the follow mode. The target waypoint (landing route) being pursued moves with the movement of the ship. When heading to waypoint 3 During the process, continue to lower the altitude and align the landing direction of the flight path to eliminate the side offset based on the L1 guidance law.

Step 406: During the continuous correction of the route caused by the swing of hook point waypoint 4, adjust the target path at each moment in real time and continuously correct the side offset, that is, continuously correct the current position of the UAV by adjusting the roll attitude;

Step 407: When the drone reaches waypoint 3, the go-around decision is made. When the decision is not satisfied, the hook recovery is given up and the go-around operation is performed in advance; otherwise, the recovery operation is performed normally and step 408 is entered;

The go-around decision for waypoint 3 includes: judging whether the side offset at this time is less than the lateral error threshold, whether the height difference between the height and the desired hook point at this time is less than the altitude error threshold, and whether the difference between the speed and the desired hook speed is less than the speed error threshold. If at least one of the above three conditions is not met, a go-around will be performed.

When going around in advance, the corresponding point of waypoint 3 on the line connecting waypoint 5 and waypoint 6 will be regarded as waypoint 6', and the route composed of waypoint 1, waypoint 2, waypoint 3 and waypoint 6' will be regarded as New landing route. Lock the flight control and navigation module to determine and execute the longitude and latitude positions of waypoint 1, waypoint 2, waypoint 5 and waypoint 6’ in the landing route at the time of go-around, perform a circle go-around and then re-execute the landing process;

During the normal recovery operation, during the flight from waypoint 3 to waypoint 4, continue to track the swing hook point through side offset control and altitude control until the hook is hooked.

Step 408: When the drone reaches waypoint 4, it performs hook recovery and determines whether the current instantaneous acceleration of the drone is greater than 1.5G. If so, the hook recovery is successful, the engine is shut down, and the drone rotates on the vertical recovery rope. Remove it after buffering; otherwise, the hook recovery fails and a go-around operation is performed.

During the go-around, the landing route is composed of waypoint 1, waypoint 2, waypoint 5 and waypoint 6. The go-around operation is the same as step 407;

Step 5: After the first drone of the group successfully hooks up or goes around, the second drone flies normally to the recovery rack that has been rotated 120 degrees, and also performs hooking and recovery operations, followed by the third drone; The group of drones hovers and waits to ensure that the distance between the current recovery group and the next standby group of drones ensures that at least one go-around drone is inserted into the queue.

The advantages of the present invention are:

(1) A small ship-based cluster UAV skyhook recovery and control method. Compared with blocking hook recovery, water surface parachute, net collision recovery and other methods, the device is simple, easy to assemble, occupies a small area, and can be mounted on most On board a surface ship;

(2) A small ship-based cluster UAV skyhook recovery control method solves the application problem of skyhook recovery in irregular swings at sea, and can maintain a high recovery success rate under certain wind and wave conditions. This method It has been verified in the ground table setting test;

(3) A skyhook recovery control method for small ship-based cluster UAVs, which is highly scalable and can complete the skyhook recovery operation of small UAVs in situations including ground stationary sites, vehicle-mounted and other ground mobile platforms, shipboard, etc. .

(4) A small ship-based cluster UAV skyhook recovery control method solves the application problem of using a skyhook recovery device for cluster UAV recovery in a ship-based environment, and enables the UAV cluster to perform reliable and efficient operations Shipboard recovery operations further expand the application mode and scope of UAV clusters in the maritime environment.

Description of the drawings

Figure 1 is a flow chart of a small ship-based cluster unmanned aerial vehicle skyhook recovery control method according to the present invention;

Figure 2 is a schematic diagram of the mobile station and mobile base station design of a small ship-based cluster UAV skyhook recovery control method according to the present invention;

Figure 3 is a schematic diagram of the differential GNSS antenna design of a small ship-based cluster UAV skyhook recovery control method according to the present invention;

Figure 4 is a schematic diagram of the design of a ship-based skyhook recovery device for a small ship-based cluster unmanned aerial vehicle skyhook recovery control method according to the present invention;

Figure 5 is a plan view of the landing route of a small ship-based cluster UAV skyhook recovery control method according to the present invention (taking the landing direction as the left side as an example);

Figure 6 is a schematic diagram of the following recovery route update of a small ship-based cluster unmanned aerial vehicle skyhook recovery control method according to the present invention;

Figure 7 is a control flow chart of the landing stage of a small ship-based cluster unmanned aerial vehicle skyhook recovery control method according to the present invention;

Figure 8 is a three-dimensional view of the landing route of a small ship-based cluster unmanned aerial vehicle skyhook recovery control method according to the present invention;

Figure 9 is a route and waypoint height relationship diagram of a small ship-based cluster unmanned aerial vehicle skyhook recovery control method according to the present invention;

Figure 10 is a schematic diagram illustrating the lateral outer loop L1 guidance law used in the present invention;

Figure 11 is a schematic diagram of the cluster recovery phase time interval of a small ship-based cluster UAV skyhook recovery control method according to the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and examples.

The present invention provides a skyhook recovery control method for small ship-based cluster unmanned aerial vehicles, which enables small fixed-wing unmanned aerial vehicles to land and recover using a skyhook recovery device in a ship-based environment, as shown in Figure 1. The specific steps are as follows:

Step 1. For small ship-based cluster UAVs, each small UAV is equipped with a GD30 differential satellite navigation module and a flight control and navigation module. The wingtips on both sides are equipped with small wingtip hooks for skyhook lanyard recovery.

The UAV is a small UAV with a wingspan of about two meters; the GD30 differential satellite navigation module includes a mobile platform end and an airborne end:

The mobile platform is installed on the ship together with the ground station. It uses high-precision GNSS positioning and the Beidou mobile base station as a moving base station to return the ship's attitude, position, heading, speed and other information through the inertial navigation system, and uses differential messages to The form is sent to the airborne terminal;

The airborne end is installed on the UAV together with the flight control and navigation module. Through two differential GNSS antennas and the mobile station, the position and speed of the UAV are measured in real time and transmitted back to the ground station. At the same time, the received mobile The platform information is sent to the flight control and navigation module, and the flight controller makes recovery control decisions.

The flight control and navigation module should be installed at the front of the fuselage away from the engine, and corresponding vibration reduction treatment should be done to prevent engine vibration from affecting the inertial navigation measurement. At the same time, sealing should be done to prevent the fuselage compartment from Internal airflow turbulence affects the measurement of equipment such as barometers;

Further, install the mobile station in a suitable location and connect it to the flight control and navigation module through the serial bus. The mobile station design is shown in Figure 2;

Furthermore, two differential GNSS antennas are installed on the upper part of the fuselage one in front and one in back, extending through the opening. The front and rear connection lines are parallel to the axis of the UAV, and are connected to the mobile station through feeders.

Step 2: Install the skyhook recovery device on the ship, erect the recovery rope, and arrange the ground station and corresponding dynamic differential ground equipment in a safe zone;

Among them, the GD30 mobile base station should be installed at a high place in an open area to prevent signal obstruction from causing poor satellite signal reception. The design of the mobile base station is the same as that of the mobile station, as shown in Figure 2. The dual antennas should also be arranged in tandem and flush with the axis of the ship to effectively measure the ship's heading. The dual antenna design is shown in Figure 3.

The shipboard skyhook recovery device consists of a recovery rack, a recovery rope, a buffer device and a support frame. The recovery rack erects a recovery rope more than ten meters long vertically in an open space for the recovery of drone collision hooks.

The skyhook recovery device is specially designed for the cluster application environment: a rotating platform is installed at the bottom of the recovery rack, and the recovery ropes are expanded to three, evenly distributed around the main pole of the recovery rack along the circumference at 120-degree intervals. When a drone successfully hits the hook, the recovery rack can be rotated 120 degrees and then fixed. The staff can disassemble and recover the drone in a safe area, and the next drone can use the next recovery rope at the same time. To carry out the recovery operation, the design diagram of the ship-based skyhook recovery device is shown in Figure 4.

Step 3: Set the required parameters of the skyhook recovery device in advance;

Parameters include skyhook position offset, landing direction, relative altitude and speed when hitting the skyhook, distance between points on the landing route, go-around decision point error threshold and route angle, etc.

The skyhook position offset is the deviation between the actual measurement position (installation position) of the differential dynamic base station and the position of the skyhook hook rope (actual hook point), including the deviation in the direction of the hull axis and the deviation perpendicular to the axis;

The landing direction is to choose to enter from the left or the right, that is, choose the direction of the landing course turn according to the actual situation of the ship;

The relative height when hitting the sky hook is the height difference between the desired hook point and the plane where the dynamic difference is located, that is, the height offset;

The speed of the UAV when hitting the skyhook should be the lowest speed while maintaining a straight and level flight, ensuring that the speed when hooking is low enough to reduce the impact of impact energy on the aircraft body, while preventing stalling and maintaining the go-around capability. The speed should be set according to the specific performance of the drone;

As shown in Figure 5, taking the landing direction as the left entry as an example, the landing route is a rectangle and consists of a total of 6 waypoints, namely 1-point follow-up point, 2-point approach point, 3-point decision point, and 4-point waypoint. The hook point, 5-point missed approach point and 6-point transition point (6' point is the early transition point). The distance between each adjacent waypoint needs to be set in advance. The route is updated in real time as the ship moves, as shown in Figure 6 Show;

The go-around decision point error threshold includes the lateral error threshold, altitude error threshold and speed error threshold. When the drone flies to waypoint 3, if the side offset distance from the route, the difference between the current altitude and the hook height, the current speed and If one of the three hook speed differences is greater than the value set by the error threshold, it is judged that the drone currently does not have the conditions for hooking, and a go-around operation will be performed immediately;

The route angle is the angle between the approach edge (the line connecting waypoints 2, 3, 4, and 5) and the hull axis.

Step 4: After the drone cluster completes the scheduled mission, a return command is issued; every three drones are divided into a group, return in a fixed formation at a fixed distance, and enter the recovery hook process;

When each group of drones is recovered, the distance between the front and rear drones should be ensured: the skyhook recovery device automatically rotates 120 degrees through the rotating table to the next mission state.

As shown in Figure 7, the details are:

Step 401. For the first UAV in the current group, its flight control and navigation module calculates the waypoints of the UAV's landing route in real time based on the received real-time position and attitude information of the ship and the preset parameters. And the route is constantly refreshed as the ship moves.

As shown in Figure 8, the four vertices of the landing route are 1 o'clock, 2 o'clock, 5 o'clock and 6 o'clock respectively;

The position of the skyhook recovery rope is waypoint 4, which is calculated based on the received longitude and latitude of the ship's dynamic differential measurement position and the offset of the set skyhook. The calculation method is:

Lon ₄ =Lon _D +(D _x sinψ+D _y cosψ)/(a*cos(Lat _D ))

Lat ₄ =Lat _D +(D _x cosψ-D _y sinψ)/a

Among them, Lon ₄ and Lat ₄ are the longitude and latitude of waypoint 4; Lon _D and Lat _D are the longitude and latitude of the dynamic differential measurement position; D _x and D _y are the forward offset and vertical axis direction along the ship axis respectively. The right offset is in meters; ψ is the ship's heading; the coefficient a is the conversion coefficient between longitude and latitude (°) and distance (m), a=111195m/°.

The longitude and latitude of each remaining waypoint is calculated based on the position of waypoint 4, the angle between the route and the relative distance between adjacent waypoints.

The heights of waypoints 1, 5 and 6 are the lower limit of the safe flight altitude of the drone plus 20 meters; the heights of waypoints 3 and 4 are the relative heights when the skyhook hits;

The height of waypoint 2 is calculated by the distance ratio of each point based on the height of waypoint 1 and the height of waypoint 3, that is

Among them, H ₁ , H ₂ and H ₃ are the heights of waypoints 1, 2 and 3 respectively, L ₁₂ is the horizontal distance between waypoints 1 and 2, and L ₂₃ is the horizontal distance between waypoints 2 and 3; each The waypoint altitude relationship is shown in Figure 9.

Furthermore, the three-axis angle of the ship's swing is measured in real time through the dynamic differential system, so as to correct the actual position of waypoint 4, which is the desired hook point on the recovery rope.

The correction method is as follows:

Establish a geodetic coordinate system with the base position of the skyhook recovery rope corrected by the offset as the origin. The x-axis points to true north, the y-axis points to true east, and the z-axis is vertically downward; also use this point as the origin to establish the hull coordinates. System, the x-axis points to the bow along the axis of the hull, the y-axis is vertical, the x-axis points to the right side of the hull, and the z-axis is vertical to the plane of the hull downward.

At this time, when the hull is stationary, the coordinates of the hook point in both coordinate systems are P = (0,0, _-He ) ^T , where _{He is} the relative height when the skyhook strikes. The three-axis angles of the hull measured through dynamic differential are respectively the roll angle. Pitch angle θ and yaw angle ψ, then the transformation matrix between the two coordinate systems is:

Assuming that the combination of the hull and the skyhook system is a rigid body, and ignoring factors such as deformation and relative displacement, the coordinates of the hook point in the hull coordinate system are always P _B = (0,0,-H _e ) ^T .

Therefore, the coordinates of the hook point in the geodetic coordinate system at this time are P _G =T _GB *P _B .

Finally, the latitude corrections of the hook points are obtained:

Lat＝P _G (1)/a

Lon＝P _G (2)/(a*cos(Lat _b ))

H=P _G (3)-P _B (3)=P _G (3)+H _e

Among them, the latitude correction amount is Lat, the longitude correction amount is Lon, and the height correction amount is H; Lat _b is the latitude of the hull.

Step 402: When the drone returns to the set range near the ship, issue a landing command; lock the longitude and latitude position of waypoint 1 on the landing route at the time when the flight control and navigation module receives the landing command, and set it as the target waypoint;

Step 403: While the UAV is flying to the target waypoint 1, it gradually lowers to the preset height of the waypoint through slope control.

Among them, slope control is a height control method in which the drone lowers along the slope connecting two waypoints.

Step 404: After the drone reaches waypoint 1, it officially enters the landing stage, switches the target waypoint to waypoint 2, and also locks the longitude and latitude of waypoint 2 at the switching time, and the drone turns and lowers its altitude to align with the landing route;

The actual flight trajectory at waypoint 2 is the arc made by the minimum turning radius of the drone.

Step 405: When turning at waypoint 2, switch the target waypoint to waypoint 3 and enter the follow mode. The target waypoint (landing route) being pursued moves with the movement of the ship. When heading to waypoint 3 During the process, continue to lower the altitude and align the landing direction of the flight path to eliminate the side offset based on the L1 guidance law.

The side offset is the vertical distance between the current position of the drone and the current route. At this time, it is the vertical distance between the lines connecting waypoints 2 and 3.

The specific control algorithm is as follows:

As shown in Figure 10, select a reference point with a horizontal distance of L1 from the current UAV position on the target path, d is the track error, V is the cruising speed (can be taken as the ground speed of the UAV at this time), η, eta ₁ and eta ₂ are the corresponding angles respectively. Assuming that the eta angle is very small, the centripetal acceleration required for the circular motion of the UAV passing the reference point at this time is:

Depend on It can be seen that the above formula is equivalent to:

Among them/>

It can be seen from the above formula that in the case of straight-line tracking, the linear approximation model of the guidance law is a simple second-order system with a damping ratio of 0.707, and the natural frequency is determined by the ratio of speed V and distance L1.

Select the appropriate L1 distance parameter, measure the size and direction of the current drone's ground speed vector V, and obtain the target route path based on the corrected waypoint 4 position measured at the current moment. The target centripetal acceleration at this time can be calculated according to the formula a _aim . According to the balance relationship of forces, the calculation formula of the target roll angle is:

Where G is the gravity of the drone;

The target roll angle is obtained through the L1 guidance law, which is given to the lateral inner loop control loop, and the corresponding aileron control amount is obtained through the inner loop PID controller; the calculation formula is:

in is the target roll angle,/> is the current roll angle, δ _a is the aileron rudder amount,/> They are roll angle feedback gain, roll angle rate feedback gain, and roll angle integral gain,/> is the roll angle rate.

Step 406: During the continuous correction of the route caused by the swing of hook point waypoint 4, adjust the target path at each moment in real time, and continuously correct the side offset through the above control method, that is, continuously adjust the current position of the UAV by adjusting the roll attitude. Correction to achieve real-time tracking of swinging skyhook retrieval ropes.

Step 407: When the drone reaches waypoint 3, the go-around decision is made. When the decision is not satisfied, the hook recovery is given up and the go-around operation is performed in advance; otherwise, the recovery operation is performed normally and step 408 is entered;

The go-around decision for waypoint 3 includes: judging whether the side offset at this time is less than the lateral error threshold, whether the height difference between the height and the desired hook point at this time is less than the altitude error threshold, and whether the difference between the speed and the desired hook speed is less than the speed error threshold. If at least one of the above three conditions is not met, a go-around will be performed.

When going around in advance, the corresponding point of waypoint 3 on the line connecting waypoint 5 and waypoint 6 will be regarded as waypoint 6', and the route composed of waypoint 1, waypoint 2, waypoint 3 and waypoint 6' will be regarded as New landing route. Lock the flight control and navigation module to determine and execute the longitude and latitude positions of waypoint 1, waypoint 2, waypoint 5 and waypoint 6’ in the landing route at the time of go-around, perform a circle go-around and then re-execute the landing process;

During the normal recovery operation, during the flight from waypoint 3 to waypoint 4, continue to track the swing hook point through side offset control and altitude control until the hook is hooked.

Step 408: When the drone reaches waypoint 4, it performs hook recovery and determines whether the current instantaneous acceleration of the drone is greater than 1.5G. If so, the hook recovery is successful, the engine is shut down, and the drone rotates on the vertical recovery rope. Remove it after buffering; otherwise, the hook recovery fails and a go-around operation is performed.

During the go-around, the landing route is composed of waypoint 1, waypoint 2, waypoint 5 and waypoint 6. The go-around operation is the same as step 407;

Step 5: After the first drone of the group successfully hooks up or goes around, the second drone flies normally to the recovery rack that has been rotated 120 degrees, and also performs hooking and recovery operations, followed by the third drone; The group of drones hovers and waits to ensure that the distance between the current recovery group and the next standby group of drones ensures that at least one go-around drone is inserted into the queue.

Example:

For the overall control and recovery strategy of the cluster, a certain type of small fixed-wing UAV is used as an example to illustrate:

This type of drone uses a rocket launch method, and a total of 18 drones form a cluster. In the process of returning after completing the mission, every three drones are divided into a group, and each group returns in a fixed formation. The speed control is used to stagger the drones by a certain distance, and the recovery is completed in sequence.

When each group of drones is recovered, the distance between the front and rear drones should ensure that the skyhook recovery device can automatically rotate one-third of a circle through the mechanical structure to the next mission state. During recovery, the remaining groups of drones wait in open airspace, and the distance between the current recovery group and the next standby group of drones is ensured to ensure that at least one go-around drone is inserted into the queue. A certain go-around opportunity can significantly improve the overall recovery success rate of the cluster.

After actual testing, if the hook fails and the drone goes around, the time required to take the go-around route from waypoint 4 to waypoint 1 and re-enter the landing process is about 3 minutes; the skyhook recovery device automatically rotates through the mechanical structure , assuming that the time required to turn one-third of a circle to the next mission state is about 1 minute, and after the drone is successfully hooked, the drone can be retrieved manually before the recovery rope is re-routed to the recovery position. Down.

Based on the actual test data in the early stage, it is assumed that the success rate of each drone's single skyhook recovery is 85%. If the total number of recoveries from a single ship is 18, each drone will be successfully recovered the first time. The expected number is about 15, and an average of 3 drones will fail the go-around in the first hook.

Only considering the failure of hooking at waypoint 4 (ignoring the situation of go-around at waypoint 3), the overall recovery process of the cluster is designed based on other factors as follows:

As shown in Figure 11, every three drones are recovered in a group, and they are divided into 6 groups in total. Each group of drones is arranged front and back at a time interval of 1 minute. According to the cruising speed of the drones 42m/s, the distance between the drones is about 2520 meters. During recovery, the remaining groups of UAVs hover and wait in the open airspace, and ensure that there is a 2-minute time interval between the current recovery group and the UAVs of the next standby group. This ensures that a go-around can be inserted in the middle of each group. of drones for secondary recovery. In this way, the first drone in each group can be directly inserted into the queue during a go-around, and if the second and third drones need to go around, they can hover at a staggered altitude at waypoint 1 and wait for the next insertion. interval between groups.

In this way, the entire cluster recovery queue can provide 5 go-around opportunities, which is greater than the expected 3 go-arounds. The single recovery success rate of each drone is 85%. The second go-around opportunity can increase the recovery success rate of a single aircraft to 97.75%, significantly increasing the possibility of successful recovery of a single drone. If the secondary recovery is still unsuccessful, it means that the drone may have some malfunction, so manual intervention is required to implement protective measures. Assuming that the last group of drones successfully hooked up the first time and there were no other drones that went back to flight, the total time required to recover all the drones is about 22 minutes.

Claims (7)

1. A small ship-based cluster unmanned aerial vehicle skyhook recovery control method, which is characterized in that the specific steps are as follows: Step 1. For small ship-based cluster UAVs, each small UAV is equipped with a GD30 differential satellite navigation module and a flight control and navigation module. The wingtips on both sides are equipped with small wingtip hooks for skyhook lanyard recovery; Step 2: Install the skyhook recovery device on the ship, erect the recovery rope, and arrange the ground station and corresponding dynamic differential ground equipment in a safe zone; Step 3: Set the required parameters of the skyhook recovery device in advance; Step 4: After the drone cluster completes the scheduled mission, a return command is issued; every three drones are divided into a group, return in a fixed formation at a fixed distance, and enter the recovery hook process; When each group of drones is recovered, the distance between the front and rear drones should be ensured: the skyhook recovery device automatically rotates 120 degrees through the rotating table to the next mission state; Specifically: Step 401. For the first UAV in the current group, its flight control and navigation module calculates the waypoints of the UAV's landing route in real time based on the received real-time position and attitude information of the ship, and moves with the ship. Continuously refresh routes; The landing route is a rectangle, including the following waypoints: follow point 1, approach point 2, decision point 3, hook point 4, missed approach point 5 and transition point 6. The four vertices are 1 point respectively. , 2 o'clock, 5 o'clock and 6 o'clock; Step 402: When the drone returns to the set range near the ship, issue a landing command; lock the longitude and latitude position of waypoint 1 on the landing route at the time when the flight control and navigation module receives the landing command, and set it as the target waypoint; Step 403: While the UAV is flying to target waypoint 1, gradually lower it to the preset height of the waypoint through slope control; Step 404: After the drone reaches waypoint 1, it officially enters the landing stage, switches the target waypoint to waypoint 2, and also locks the longitude and latitude of waypoint 2 at the switching time, and the drone turns and lowers its altitude to align with the landing route; The actual flight trajectory at waypoint 2 is the arc made by the minimum turning radius of the drone; Step 405: When turning at waypoint 2, switch the target waypoint to waypoint 3 and enter the follow mode. The target waypoints being chased will move with the movement of the ship, and continue to descend while heading to waypoint 3. high, and align the landing direction to eliminate the side offset based on the L1 guidance law; Step 406: During the continuous correction of the route caused by the swing of hook point waypoint 4, adjust the target path at each moment in real time and continuously correct the side offset, that is, continuously correct the current position of the UAV by adjusting the roll attitude; Step 407: When the drone reaches waypoint 3, the go-around decision is made. When the decision is not satisfied, the hook recovery is given up and the go-around operation is performed in advance; otherwise, the recovery operation is performed normally and step 408 is entered; The go-around decision for waypoint 3 includes: judging whether the side offset at this time is less than the lateral error threshold, whether the height difference between the height and the desired hook point at this time is less than the altitude error threshold, and whether the difference between the speed and the desired hook speed is less than the speed error threshold. If at least one of the above three conditions is not met, a go-around will be performed; When going around in advance, the corresponding point of waypoint 3 on the line connecting waypoint 5 and waypoint 6 will be regarded as waypoint 6', and the route composed of waypoint 1, waypoint 2, waypoint 3 and waypoint 6' will be regarded as New landing route; lock the flight control and navigation module to determine and execute the longitude and latitude positions of waypoint 1, waypoint 2, waypoint 5 and waypoint 6' in the landing route at the time of go-around, perform a circle go-around and then re-execute the landing process ; During the normal recovery operation, during the flight from waypoint 3 to waypoint 4, continue to track the swing hook point through side offset control and altitude control until the hook is hooked; Step 408: When the drone reaches waypoint 4, it performs hook recovery and determines whether the current instantaneous acceleration of the drone is greater than 1.5G. If so, the hook recovery is successful, the engine is shut down, and the drone rotates on the vertical recovery rope. Remove it after buffering; otherwise, the hook recovery fails and a go-around operation is performed; During a go-around, the landing route is composed of waypoint 1, waypoint 2, waypoint 5 and waypoint 6; Step 5: After the first drone of the group successfully hooks up or goes around, the second drone flies normally to the recovery rack that has been rotated 120 degrees, and also performs hooking and recovery operations, followed by the third drone; The group of drones hovers and waits to ensure that the distance between the current recovery group and the next standby group of drones ensures that at least one go-around drone is inserted into the queue. 2. A skyhook recovery control method for small ship-based cluster UAVs as claimed in claim 1, characterized in that the GD30 differential satellite navigation module in each small UAV includes a mobile platform terminal and a machine Loader: The mobile platform is installed on the ship together with the ground station. It uses high-precision GNSS positioning and the Beidou mobile base station as a moving base station to return the ship's attitude, position, heading and speed information through the inertial navigation system in the form of differential messages. Send to the airborne terminal; The airborne terminal is installed on the UAV together with the flight control and navigation module. Through two differential GNSS antennas and the mobile station, the position and speed information of the UAV is measured in real time and transmitted back to the ground station. At the same time, the received mobile platform The information is sent to the flight control and navigation module, and the flight controller makes recovery control decisions. 3. A method for controlling skyhook recovery of small ship-based cluster UAVs as claimed in claim 1, characterized in that the recovery rack in the ship-based skyhook recovery device erects the recovery rope vertically in an open space. , used for UAV hit hook recovery; install a rotary table at the bottom of the recovery rack, and expand the recovery ropes to three, evenly distributed along the circumference of the main pole of the recovery rack at 120-degree intervals; when the UAV successfully hits the hook, the recovery rack After rotating 120 degrees and then fixing it, the latter drone can use the next recovery rope for recovery operations at the same time. 4. A skyhook recovery control method for small ship-based cluster UAVs as claimed in claim 1, characterized in that the parameters include skyhook position offset, landing direction, relative height when hitting the skyhook, and speed. , the distance between each point on the landing route, the error threshold of the go-around decision point and the route angle. 5. A method for controlling skyhook recovery of small ship-based clustered UAVs as claimed in claim 1, characterized in that in step 401, waypoint 4 is the location of the skyhook recovery rope, and the calculation method for: Lon ₄ =Lon _D +(D _x sinψ+D _y cosψ)/(a*cos(Lat _D )) Lat ₄ =Lat _D +(D _x cosψ-D _y sinψ)/a Among them, Lon ₄ and Lat ₄ are the longitude and latitude of 4 points; Lon _D and Lat _D are the longitude and latitude of the dynamic differential measurement position; D _x and D _y are the forward offset along the ship axis and the vertical axis to the right respectively. The offset; ψ is the ship's heading angle; the coefficient a is the conversion coefficient between longitude, latitude and distance; The longitude and latitude of the remaining waypoints are calculated based on the positions of the 4 points, the angle between the routes and the relative distance between adjacent waypoints; The heights of waypoints 1, 5 and 6 are the lower limit of the drone's safe flight altitude plus 20 meters; the heights of waypoints 3 and 4 are the relative heights when the skyhook hits; The altitude of waypoint 2 is based on the altitude of waypoint 1 and the altitude of waypoint 3, and is derived from the distance ratio of each point, that is: Among them, H ₁ , H ₂ and H ₃ are the heights of waypoints 1, 2 and 3 respectively, L ₁₂ is the horizontal distance between waypoints 1 and 2, and L ₂₃ is the horizontal distance between waypoints 2 and 3. 6. A method for controlling the skyhook recovery of small ship-based cluster UAVs as claimed in claim 1, characterized in that, in step 401, the three-axis angle of the ship's swing is measured in real time through a dynamic differential system, and the Waypoint 4, which is the actual position of the desired hook point on the recovery rope, is corrected. 7. A method for controlling skyhook recovery of small ship-based cluster UAVs as claimed in claim 1, characterized in that in step 405, the lateral offset is the vertical distance between the current position of the UAV and the current route. The vertical distance, at this time is the vertical distance between the line connecting waypoints 2 and 3; The target roll angle is obtained through the L1 guidance law, which is given to the lateral inner loop control loop, and the corresponding aileron control amount is obtained through the inner loop PID controller; the calculation formula is: in is the target roll angle,/> is the current roll angle, δ _a is the aileron rudder amount,/> They are roll angle feedback gain, roll angle rate feedback gain, and roll angle integral gain,/> is the roll angle rate.