A fixed-wing unmanned aerial vehicle runway-free recovery path planning method
By planning the rendezvous trajectory between an aerial platform and a fixed-wing UAV, and utilizing the vertical take-off and landing capabilities of the aerial platform, the problem of safe recovery of fixed-wing UAVs under runway-less conditions was solved, achieving lossless recovery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA AERODYNAMIC RES & DEV CENT EQUIP DESIGN & TESTING TECH INST
- Filing Date
- 2024-01-25
- Publication Date
- 2026-05-19
AI Technical Summary
Existing technologies make it difficult to achieve safe, damage-free, and runway-free recovery of fixed-wing UAVs, especially in shipboard environments. Net-assisted recovery requires high precision, aerial hook-and-grab recovery is limited by modifications to the airframe and ship, and paraglider recovery occupies space and is easily affected by sea weather.
By using an aerial platform as a transit station, and through coordinate system establishment and trajectory planning, the rendezvous trajectory between the fixed-wing UAV and the aerial platform is designed. By utilizing the vertical take-off and landing capability of the aerial platform, the UAV can be safely recovered under runway-less conditions.
It enables the safe and damage-free recovery of fixed-wing UAVs, avoiding the limitations of methods such as net collision and aerial capture, and is suitable for shipborne and other runway-less environments.
Smart Images
Figure CN117948979B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of unmanned aerial vehicle (UAV) recovery, and more specifically, to a method for planning the flight path of a fixed-wing UAV for runway-less recovery. Background Technology
[0002] Current research on runway-free recovery of fixed-wing UAVs mainly employs methods such as net-crashing and aerial grabbing. These methods struggle to achieve safe and damage-free recovery of fixed-wing UAVs and cannot enable uninterrupted, high-frequency operations. Specifically:
[0003] For recovering shipborne fixed-wing UAVs in the absence of a runway, the main methods include parachute recovery, aerial retrieval, and net-crashing recovery.
[0004] Parachute recovery is simple to operate; the entire process from flight to safe recovery of the drone is completed automatically, requiring relatively low operator skill. The main problems with parachute recovery are that the drone's built-in parachute occupies valuable space and payload capacity, and it is also susceptible to weather conditions at sea.
[0005] Net-collision recovery requires the drone to decelerate and descend under near-field high-precision navigation, finally colliding with the arresting net and gently absorbing its kinetic energy for safe recovery. This relatively ideal, precise, point-to-point recovery method requires a small arresting net area and precise guidance. However, when deploying arresting nets on small and medium-sized warships, the presence of radar, missiles, communication antennas, and other equipment on the hull, coupled with rough seas and swaying, means that improper terminal guidance control can prevent accurate net entry and may even result in the drone colliding with the warship, damaging expensive equipment.
[0006] Aerial retrieval and recovery of the UAV involves a combination of wingtip hooks mounted on the leading edge of the UAV's wingtips and a vertical rope recovery device on the ship. The UAV is precisely guided by the recovery guidance system to the recovery rope. When either wingtip strikes the rope, the inertia causes the aircraft to rotate around it. Simultaneously, the rope slides along the wingtip from the wing root to the wingtip, quickly entering the wingtip and locking into the hook, thus capturing the UAV. This recovery method requires minimal modification to the UAV and the ship, but it can only recover relatively small UAVs.
[0007] None of the above methods can achieve safe, damage-free, and runway-free recovery of fixed-wing UAVs. Summary of the Invention
[0008] The purpose of this invention is to achieve safe, damage-free, and runway-free recovery of fixed-wing unmanned aerial vehicles (UAVs).
[0009] To achieve the above objectives, the present invention provides a method for planning the flight path of a fixed-wing unmanned aerial vehicle (UAV) for runway-less recovery, the method comprising:
[0010] Step 1: Establish a coordinate system with the center of the landing area as the origin, and construct the first target track circle corresponding to the aerial platform and the second target track circle corresponding to the fixed-wing UAV based on the coordinate system;
[0011] Step 2: Obtain the current position coordinates of the fixed-wing UAV, construct a first plane based on the current position coordinates of the fixed-wing UAV, and obtain the intersection points of the first plane with the first target track circle and the second target track circle as the first target track point and the second target track point respectively;
[0012] Step 3: Based on the current position coordinates of the air platform and the coordinates of the first target track point, obtain the first track of the air platform traveling towards the first target track point; based on the current position coordinates of the fixed-wing UAV and the coordinates of the second target track point, obtain the second track of the fixed-wing UAV traveling towards the second target track point.
[0013] Step 4: Based on the coordinates of the first target track point and the target point, obtain the third track of the air platform traveling to the target point. Based on the coordinates of the second target track point and the real-time coordinates of the air platform, obtain the fourth track of the fixed-wing UAV traveling to the air platform.
[0014] Step 5: Based on the first flight path, the aerial platform flies to the first target waypoint; based on the third flight path, the aerial platform flies to the target point; based on the second flight path, the fixed-wing UAV flies to the second target waypoint; based on the fourth flight path, the fixed-wing UAV flies to the aerial platform and lands on the aerial platform.
[0015] Step 6: The aerial platform carries the fixed-wing UAV back to the landing area.
[0016] This method first establishes a coordinate system based on the center of the landing area, then calculates the trajectories of the aerial platform and the fixed-wing UAV respectively, and then flies the fixed-wing UAV to the aerial platform according to the calculated trajectories and lands on the aerial platform. The aerial platform carries the fixed-wing UAV back to the landing area. The above fixed-wing UAV recovery method uses an aerial platform to achieve runway-free recovery and does not use methods such as net collision or aerial grabbing, thus achieving safe and damage-free recovery of fixed-wing UAVs.
[0017] In some embodiments, step 1 specifically includes:
[0018] A coordinate system is established with the center of the landing area as the origin, and the center point of the landing area is O(0,0,0). Circles parallel to the horizontal plane are drawn with centers at points G1(0,0,z1) and G2(0,0,z2) directly above point O, and radii R1 and R2 respectively. These circles represent the first and second target track circles. The ultimate goal of the track design is to design the fixed-wing UAV to catch up with the aerial platform from directly behind and land on top of the platform. Therefore, the design parameters z2 > z1 and R2 > R1 corresponding to the fixed-wing UAV are used to achieve this goal.
[0019] In some embodiments, the first plane is obtained as follows:
[0020] The current position coordinates of the fixed-wing UAV are P3(x3,y3,z3), and the first plane is the plane that passes through points P3(x3,y3,z3), O(0,0,0), and point... The plane, and the point (x,y,z) in the first plane satisfies x 2 +y 2 +z 2 ≤x3 2 +y3 2 +z3 2 And x and x3 have the same sign, y and y3 have the same sign, z∈[0,z3], the first plane is a 1 / 4 circular plane. Through the above design, it is ensured that the first plane is in the same quadrant as the fixed wing. In this way, the first and second waypoints are on the two waypoint circles and closer to the side of the fixed wing UAV. In this way, the fixed wing UAV is closer to the second waypoint, the distance from the current position to the second target waypoint is shorter and the energy consumption is lower.
[0021] The design is such that x and x3 have the same sign, y and y3 have the same sign, z∈[0,z3], and the first plane is a 1 / 4 circular plane. The purpose of having the same sign and the Z coordinate constraint is to ensure that the quadrant of the first plane is consistent with the quadrant of the fixed-wing UAV. In this way, the first and second track points are on the two track circles and closer to the side of the fixed-wing UAV. Otherwise, the infinite plane determined by the above three points and the two track circles will have two other intersection points far away from the fixed wing.
[0022] In some embodiments, the fixed-wing UAV arrives at the second target waypoint later than the air platform arrives at the first target waypoint. When the air platform arrives at the first target waypoint, it is hovering with its nose pointing towards coordinate point (0,0,z1). The purpose of hovering is to wait for the fixed-wing UAV to take position, and pointing the nose towards this coordinate point ensures that the velocity vector direction of the third path will not be adjusted at a large angle. When the fixed-wing UAV arrives at the second target waypoint, its flight speed is higher than its stall speed, usually 5% higher, and its nose points towards coordinate point (0,0,z2). Once the flight speed of the fixed-wing UAV falls below its stall speed, it is prone to losing altitude and balance. Pointing the nose towards this coordinate point is also to prevent large adjustments in the velocity vector direction in the fourth path. Large adjustments in the velocity vector direction by the fixed-wing UAV are not conducive to stable flight.
[0023] The purpose of ensuring that the fixed-wing UAV arrives at the second target trackpoint later than the aerial platform arrives at the first target trackpoint is:
[0024] Before and after reaching the first waypoint, the aerial platform reverses its movement. After reaching the first waypoint, the aerial platform needs to turn its nose. For rotorcraft, turning its nose is relatively easy and quick, while for fixed-wing UAVs, turning requires circling around a certain radius according to their own characteristics. Then, the aerial platform hovers (only rotorcraft can hover) and waits for the fixed-wing UAV to take position. The fourth track of a fixed-wing UAV requires an aerial platform as its target. If the fixed-wing UAV arrives at the second track point first, its flight characteristics prevent it from hovering, forcing it to circle and wait for the aerial platform to take position. If the fixed-wing UAV arrives at the second track point before the aerial platform is in position, it will directly begin planning its track with the aerial platform as its target (this target includes not only its position but also its velocity vector (including direction)). The direction of the aerial platform's movement at this point is opposite to its final direction of movement. The aerial platform will then need to turn its nose 180°. The fourth track of the fixed-wing UAV will be planned as a track that requires a 180° turn in velocity direction. Such a track is very difficult for fixed-wing UAVs, which are difficult to turn around, to track.
[0025] In some embodiments, the air platform accelerates from the first target waypoint to its maximum cruising speed with maximum power, and then maintains the maximum cruising speed at a constant speed toward the target point. The purpose of this design is that the minimum speed of the fixed-wing UAV is limited. In order for the fixed-wing UAV to track the air platform at a higher speed, the air platform needs to accelerate to its maximum cruising speed as quickly as possible. Maintaining a constant speed makes its flight state more stable and less volatile, making it easier for the fixed-wing UAV to track.
[0026] In some embodiments, the method for determining whether the fixed-wing UAV and the aerial platform have reached the predetermined target in step 5 is as follows:
[0027] The absolute values of the deviations between the current position and the target position of the fixed-wing UAV and the current state of the fixed-wing UAV and the target state are within the preset threshold E1 range; the absolute values of the deviations between the current position and the target position of the airborne platform and the current state of the airborne platform and the target state are within the preset threshold E2 range.
[0028]
[0029]
[0030] Among them, e x1 e represents the x-coordinate deviation between the current position of the fixed-wing aircraft and the target position. y1 e represents the deviation of the y-coordinate between the current position of the fixed-wing aircraft and the target position. z1 The z-coordinate deviation between the current position of the fixed-wing aircraft and the target position. The deviation of the linear velocity of the fixed-wing aircraft in the x-axis direction from the current state of the target aircraft. The deviation of the linear velocity of the fixed-wing aircraft in the y-axis direction from the current state of the target aircraft. The deviation of the linear velocity of the fixed-wing aircraft in the z-axis direction from the current state of the target aircraft. e represents the yaw angle deviation between the current state and the target state of the fixed-wing aircraft. θ1 e represents the pitch angle deviation between the current state and the target state of the fixed-wing aircraft. ψ1 The roll angle deviation between the current state and the target state of the fixed-wing aircraft. The yaw angle and angular velocity deviation between the current state and the target state of the fixed-wing aircraft. The pitch angle and angular velocity deviation between the current state and the target state of the fixed-wing aircraft. The roll angle and angular velocity deviation between the current state and the target state of the fixed-wing aircraft;
[0031] e x2 e represents the deviation of the x-coordinate between the current position of the aerial platform and the target position. y2 e represents the y-coordinate deviation between the current position of the aerial platform and the target position. z2 This represents the deviation of the z-coordinate between the current position of the aerial platform and the target position. The deviation of the linear velocity between the current state of the aerial platform and the target state along the x-axis. The deviation of the linear velocity along the y-axis between the current state of the aerial platform and the target state. The deviation of the linear velocity between the current state of the aerial platform and the target state along the z-axis. e represents the yaw angle deviation between the current state of the airborne platform and the target state. θ2 e represents the pitch angle deviation between the current state of the aerial platform and the target state. ψ2 The roll angle deviation between the current state of the aerial platform and the target state. This represents the yaw angle and angular velocity deviation between the current state of the aerial platform and the target state. The pitch angle and angular velocity deviation between the current state of the aerial platform and the target state. This represents the roll angle and angular velocity deviation between the current state of the aerial platform and the target state.
[0032] In some embodiments, step 5 further includes determining whether the aerial platform and the fixed-wing UAV have successfully intersected. If the intersecting is successful, step 6 is executed; otherwise, step 6 is not executed.
[0033] In some embodiments, the method for determining whether an aerial platform and a fixed-wing UAV have successfully intersected is as follows:
[0034] Within duration T: the real-time altitude direction h1 of the fixed-wing UAV and the real-time altitude h2 of the aerial platform satisfy the following relationship:
[0035] h1 = h2 + 3 + e z3 ;
[0036] The absolute values of the position and state deviations between the fixed-wing UAV and the aerial platform are within the threshold E3 range;
[0037]
[0038] Among them, e x3 e represents the x-coordinate deviation between the current position of the fixed-wing aircraft and the position of the aerial platform. y3 e represents the y-coordinate deviation between the current position of the fixed-wing aircraft and the position of the aerial platform. z3 This represents the deviation of the z-coordinate between the current position of the fixed-wing aircraft and the position of the aerial platform. The deviation of the linear velocity along the x-axis between the current state of the fixed-wing aircraft and the state of the aerial platform. The deviation of the linear velocity along the y-axis between the current state of the fixed-wing aircraft and the state of the aerial platform. The deviation of the linear velocity along the z-axis between the current state of the fixed-wing aircraft and the state of the aerial platform. e represents the yaw angle deviation between the current state of the fixed-wing aircraft and the state of the aerial platform. θ3 e represents the pitch angle deviation between the current state of the fixed-wing aircraft and the state of the airborne platform. ψ3 The roll angle deviation between the current state of the fixed-wing aircraft and the state of the aerial platform. The yaw angle and angular velocity deviation between the current state of the fixed-wing aircraft and the state of the aerial platform. The pitch angle and angular velocity deviation between the current state of the fixed-wing aircraft and the state of the airborne platform. This refers to the roll angle and angular velocity deviation between the current state of the fixed-wing aircraft and the state of the aerial platform.
[0039] In some embodiments, the first track, the second track, and the fourth track are all planned using a rolling window-based path planning algorithm.
[0040] In some embodiments, the path planning algorithm based on a scrolling window includes:
[0041] (1) Sub-target and scenario prediction: Based on the environmental information detected within the local window range, the fixed-wing UAV and the aerial platform generate local sub-targets using a heuristic method, predict the movement of dynamic obstacles, and determine whether the fixed-wing UAV and the aerial platform may collide with dynamic obstacles.
[0042] (2) Scrolling window optimization: Based on the environmental information and prediction results within the local window, the fixed-wing UAV and the aerial platform determine the local path to the sub-target and implement the current strategy;
[0043] (3) Feedback initialization: After a new scrolling window is generated, the environment and obstacle movement status within the new scrolling window are updated based on the latest information obtained by the sensor;
[0044] (4) Repeat steps (1), (2) and (3) until the fixed-wing UAV and the aerial platform reach the predetermined target, and end the trajectory planning of this stage.
[0045] One or more technical solutions provided by this invention have at least the following technical effects or advantages:
[0046] This method fully leverages the vertical takeoff and landing capabilities of aerial platforms. In situations where the landing area is limited (lacking a sufficiently long runway), the aerial platform is treated as an aerial runway for fixed-wing UAVs, facilitating their recovery. Simultaneously, considering the high energy consumption, limited flight distance, and restricted maximum speed of aerial platforms, the long-distance trajectory is divided into two phases. Ultimately, a practical and feasible trajectory planning method is proposed for long-distance rendezvous between fixed-wing UAVs and aerial platforms. This method achieves safe, damage-free, and runway-free recovery of fixed-wing UAVs. Attached Figure Description
[0047] The accompanying drawings, which are provided to further illustrate embodiments of the invention and constitute a part of this invention, are not intended to limit the scope of the invention.
[0048] Figure 1 A flowchart illustrating a runway-free recovery trajectory planning method for fixed-wing unmanned aerial vehicles (UAVs).
[0049] Figure 2 A schematic diagram illustrating the principle of a runway-free recovery trajectory planning method for fixed-wing unmanned aerial vehicles (UAVs);
[0050] Among them, 1 is a fixed-wing UAV, 2 is an aerial platform, 3 is a landing area, 4 is the first target track circle, and 5 is the second target track circle. Detailed Implementation
[0051] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, where there is no conflict, the embodiments of the present invention and the features thereof can be combined with each other.
[0052] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.
[0053] Example 1
[0054] Please refer to Figure 1 , Figure 1 This is a flowchart illustrating a method for planning the trajectory of a fixed-wing unmanned aerial vehicle (UAV) for runway-less recovery. The present invention provides a method for planning the trajectory of a fixed-wing UAV for runway-less recovery, the method comprising:
[0055] Step 1: Establish a coordinate system with the center of the landing area as the origin, and construct the first target track circle corresponding to the aerial platform and the second target track circle corresponding to the fixed-wing UAV based on the coordinate system;
[0056] Step 2: Obtain the current position coordinates of the fixed-wing UAV, construct a first plane based on the current position coordinates of the fixed-wing UAV, and obtain the intersection points of the first plane with the first target track circle and the second target track circle as the first target track point and the second target track point respectively;
[0057] Step 3: Based on the current position coordinates of the air platform and the coordinates of the first target track point, obtain the first track of the air platform traveling towards the first target track point; based on the current position coordinates of the fixed-wing UAV and the coordinates of the second target track point, obtain the second track of the fixed-wing UAV traveling towards the second target track point.
[0058] Step 4: Based on the coordinates of the first target track point and the target point, obtain the third track of the air platform traveling to the target point. Based on the coordinates of the second target track point and the real-time coordinates of the air platform, obtain the fourth track of the fixed-wing UAV traveling to the air platform.
[0059] Step 5: Based on the first flight path, the aerial platform flies to the first target waypoint; based on the third flight path, the aerial platform flies to the target point; based on the second flight path, the fixed-wing UAV flies to the second target waypoint; based on the fourth flight path, the fixed-wing UAV flies to the aerial platform and lands on the aerial platform.
[0060] Step 6: The aerial platform carries the fixed-wing UAV back to the landing area.
[0061] The method will be described in detail below:
[0062] Please refer to Figure 2 , Figure 2 This is a schematic diagram illustrating the principle of a runway-less recovery trajectory planning method for fixed-wing unmanned aerial vehicles (UAVs). Figure 2 In this diagram, 1 represents a fixed-wing UAV, 2 represents an aerial platform, 3 represents the landing area, 4 represents the first target track circle, and 5 represents the second target track circle. In this embodiment, the unit of length is meters, the unit of linear velocity is meters per second, the unit of angle is degrees, and the unit of angular velocity is degrees per second. The aerial platform is a vertical takeoff and landing (VTOL) flight device. After the fixed-wing UAV lands on the aerial platform, it is decelerated and ultimately vertically landed in the recovery area. This method includes:
[0063] Planning the target track circle: Establish a coordinate system with the center of the landing area as the origin, and the center point of the landing area as O(0,0,0). Draw circles parallel to the horizontal plane with centers at two points directly above point O, coordinates G1(0,0,z1) and G2(0,0,z2), and radii R1 and R2 respectively. This yields the first and second target track circles. The specific values of z1, R1, and R2 need to be determined based on the performance of the fixed-wing aircraft and the airborne platform. When planning the track circle, the fixed-wing aircraft should be positioned outside the cylinder that passes through the second target track circle and is perpendicular to the ground. Specifically, z1 can be 8, z2 can be 110, R1 can be 800, and R2 can be 1400.
[0064] The reason for starting track circle planning with the fixed-wing aircraft outside the cylinder perpendicular to the ground, which is within the second target track circle, is that the specific values of z1, z2, R1, and R2 are predetermined based on the performance of the fixed-wing aircraft and the airborne platform. Successful recovery of the fixed-wing aircraft requires reaching the second target track point. It is assumed that the fixed-wing aircraft completes its mission far from the recovery zone before being recovered, by which time it has already consumed a significant amount of fuel. If track circle planning begins only after the fixed-wing aircraft is already within the cylinder, it will inevitably require more flight time before recovery. If the remaining fuel is insufficient to support the recovery phase, a crash is possible.
[0065] Determine the target waypoint: The current position of the fixed-wing UAV is P3(x3,y3,z3). A 1 / 4 circular plane A, i.e., the first plane, is determined by the following conditions: passing through P3(x3,y3,z3) and O(0,0,0). Three points, and a point (x, y, z) in the plane, satisfying x 2 +y 2 +z 2 ≤x3 2 +y3 2 +z3 2 Furthermore, x and x3 have the same sign, y and y3 have the same sign, and z ∈ [0, z3]. The intersection points of plane A with the first target track circle and the second target track circle are the first target track points and the second target track points, denoted as P1 and P2. When the coordinates of P3 are (2000, 0, 300), the coordinates of P1 are (800, 0, 8), and the coordinates of P2 are (1400, 0, 100).
[0066] Plan the flight paths of the aerial platform towards point P1 and the fixed-wing UAV towards point P2, and ensure they reach their respective target positions as required. The general requirements are: the fixed-wing UAV must arrive at point P2 no earlier than the aerial platform arrives at point P1; the aerial platform flies from the landing area to point P1, hovering upon arrival with its nose pointing towards coordinates (0,0,z1); the fixed-wing UAV flies from its current position to point P2, arriving at point P2 with its speed V2 slightly higher than its stall speed V1, and its nose pointing towards coordinates (0,0,z2); the entire movement must be safe and collision-free. Both paths use a rolling window-based path planning algorithm, and the steps are the same: (1) Sub-target and scenario prediction: The fixed-wing UAV and the aerial platform generate local sub-targets using a heuristic method based on the environmental information within the local window they detect, and predict the movement of dynamic obstacles to determine whether the fixed-wing UAV and the aerial platform may collide with the dynamic obstacles; (2) Rolling window optimization: The fixed-wing UAV and the aerial platform determine the local path to the sub-target based on the environmental information and prediction results within the local window, and implement the current strategy; (3) Feedback initialization: After a new rolling window is generated, the environment and obstacle movement status within the new rolling window are updated based on the latest information obtained by the sensors; (4) Repeat steps (1), (2) and (3) until the fixed-wing UAV and the aerial platform reach the predetermined target, and end the path planning of this stage.
[0067] The criterion for determining whether the predetermined goal has been reached is:
[0068] The absolute values of the deviations between the current position and the target position of the fixed-wing UAV and the current state of the fixed-wing UAV and the target state are within the preset threshold E1 range; the absolute values of the deviations between the current position and the target position of the airborne platform and the current state of the airborne platform and the target state are within the preset threshold E2 range.
[0069]
[0070]
[0071] Among them, e x1 e represents the x-coordinate deviation between the current position of the fixed-wing aircraft and the target position. y1 e represents the deviation of the y-coordinate between the current position of the fixed-wing aircraft and the target position. z1 The z-coordinate deviation between the current position of the fixed-wing aircraft and the target position. The deviation of the linear velocity of the fixed-wing aircraft in the x-axis direction from the current state of the target aircraft. The deviation of the linear velocity of the fixed-wing aircraft in the y-axis direction from the current state of the target aircraft. The deviation of the linear velocity of the fixed-wing aircraft in the z-axis direction from the current state of the target aircraft. e represents the yaw angle deviation between the current state and the target state of the fixed-wing aircraft. θ1 e represents the pitch angle deviation between the current state and the target state of the fixed-wing aircraft. ψ1 The roll angle deviation between the current state and the target state of the fixed-wing aircraft. The yaw angle and angular velocity deviation between the current state and the target state of the fixed-wing aircraft. The pitch angle and angular velocity deviation between the current state and the target state of the fixed-wing aircraft. The roll angle and angular velocity deviation between the current state and the target state of the fixed-wing aircraft;
[0072] e x2 e represents the deviation of the x-coordinate between the current position of the aerial platform and the target position. y2 e represents the y-coordinate deviation between the current position of the aerial platform and the target position. z2 This represents the deviation of the z-coordinate between the current position of the aerial platform and the target position. The deviation of the linear velocity between the current state of the aerial platform and the target state along the x-axis. The deviation of the linear velocity along the y-axis between the current state of the aerial platform and the target state. The deviation of the linear velocity between the current state of the aerial platform and the target state along the z-axis. e represents the yaw angle deviation between the current state of the airborne platform and the target state. θ2 e represents the pitch angle deviation between the current state of the aerial platform and the target state. ψ2The roll angle deviation between the current state of the aerial platform and the target state. This represents the yaw angle and angular velocity deviation between the current state of the aerial platform and the target state. The pitch angle and angular velocity deviation between the current state of the aerial platform and the target state. This represents the roll angle and angular velocity deviation between the current state of the aerial platform and the target state.
[0073] Among them, E1 and E2 can be set as E1 = [0.8, 0.8, 0.8, 0.1, 0.1, 0.1, 0.3, 0.3, 0.3, 0.05, 0.05, 0.05], V1 can be 25, and V2 can be 26.
[0074] The plan outlines the flight paths of the fixed-wing UAV and the aerial platform from their respective positions P2 and P1 to their eventual meeting point. During this phase, the aerial platform flies from point P1 to point G1. It first accelerates to its maximum cruising speed V3 (V3 > V1) with maximum power, then maintains a constant speed of V3. The long-distance meeting occurs during this constant-speed phase. Finally, the aerial platform, carrying the fixed-wing UAV, decelerates back to the center of the landing area and lands. Therefore, the radius R1 of the first target track circle needs to be determined comprehensively based on the aerial platform's power performance (primarily acceleration / deceleration capabilities and high-speed cruise duration). The fixed-wing UAV's flight path planning during this phase still employs a rolling window-based path planning algorithm; however, the target position and state are replaced by the real-time position and state of the aerial platform.
[0075] The method for determining whether an aerial platform and a fixed-wing UAV have successfully intersected is as follows:
[0076] Within duration T: the real-time altitude direction h1 of the fixed-wing UAV and the real-time altitude h2 of the aerial platform satisfy the following relationship:
[0077] h1 = h2 + 3 + e z3 ;
[0078] The absolute values of the position and state deviations between the fixed-wing UAV and the aerial platform are within the threshold E3 range;
[0079]
[0080] Among them, e x3 e represents the deviation of the x-coordinate value between the current position of the fixed-wing aircraft and the position of the aerial platform. y3 e represents the y-coordinate deviation between the current position of the fixed-wing aircraft and the position of the aerial platform. z3 This represents the deviation of the z-coordinate between the current position of the fixed-wing aircraft and the position of the aerial platform. The deviation of the linear velocity along the x-axis between the current state of the fixed-wing aircraft and the state of the aerial platform. The deviation of the linear velocity along the y-axis between the current state of the fixed-wing aircraft and the state of the aerial platform. The deviation of the linear velocity along the z-axis between the current state of the fixed-wing aircraft and the state of the aerial platform. e represents the yaw angle deviation between the current state of the fixed-wing aircraft and the state of the aerial platform. θ3 e represents the pitch angle deviation between the current state of the fixed-wing aircraft and the state of the airborne platform. ψ3 The roll angle deviation between the current state of the fixed-wing aircraft and the state of the aerial platform. The yaw angle and angular velocity deviation between the current state of the fixed-wing aircraft and the state of the aerial platform. The pitch angle and angular velocity deviation between the current state of the fixed-wing aircraft and the state of the airborne platform. This refers to the roll angle and angular velocity deviation between the current state of the fixed-wing aircraft and the state of the aerial platform.
[0081] Where V3 can be 28, and E3 can be set to:
[0082] E3=[0.3,0.3,0.3,0.02,0.02,0.02,0.1,0.1,0.1,0.01,0.01,0.01].
[0083] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.
[0084] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A method for planning the flight path for runway-less recovery of a fixed-wing unmanned aerial vehicle (UAV), characterized in that, The method includes: Step 1: Establish a coordinate system with the center of the landing area as the origin, and construct the first target track circle corresponding to the aerial platform and the second target track circle corresponding to the fixed-wing UAV based on the coordinate system; Step 2: Obtain the current position coordinates of the fixed-wing UAV, construct a first plane based on the current position coordinates of the fixed-wing UAV, and obtain the intersection points of the first plane with the first target track circle and the second target track circle as the first target track point and the second target track point respectively; Step 3: Based on the current position coordinates of the air platform and the coordinates of the first target track point, obtain the first track of the air platform traveling towards the first target track point; based on the current position coordinates of the fixed-wing UAV and the coordinates of the second target track point, obtain the second track of the fixed-wing UAV traveling towards the second target track point. Step 4: Based on the coordinates of the first target track point and the target point, obtain the third track of the air platform traveling to the target point. Based on the coordinates of the second target track point and the real-time coordinates of the air platform, obtain the fourth track of the fixed-wing UAV traveling to the air platform. Step 5: Based on the first flight path, the aerial platform flies to the first target waypoint; based on the third flight path, the aerial platform flies to the target point; based on the second flight path, the fixed-wing UAV flies to the second target waypoint; based on the fourth flight path, the fixed-wing UAV flies to the aerial platform and lands on the aerial platform. Step 6: The aerial platform carries the fixed-wing UAV back to the landing area.
2. The method for planning the flight path for runway-less recovery of a fixed-wing unmanned aerial vehicle according to claim 1, characterized in that, Step 1 specifically includes: Establish a coordinate system with the center of the landing area as the origin, and the center point of the landing area is O(0,0,0). Draw circles parallel to the horizontal plane with the coordinates G1(0,0,z1) and G2(0,0,z2) directly above point O as the center and the radii R1 and R2 respectively, to obtain the first target track circle and the second target track circle respectively.
3. The method for planning the flight path for runway-less recovery of a fixed-wing unmanned aerial vehicle according to claim 1, characterized in that, The first plane is obtained as follows: The current position coordinates of the fixed-wing UAV are P3(x3,y3,z3), and the first plane is the plane that passes through points P3(x3,y3,z3), O(0,0,0), and point... The plane, and the point (x,y,z) in the first plane satisfies x 2 +y 2 +z 2 ≤x3 2 +y3 2 +z3 2 And x and x3 have the same sign, y and y3 have the same sign, z∈[0,z3], and the first plane is a 1 / 4 circular plane.
4. The method for planning the runway-less recovery trajectory of a fixed-wing unmanned aerial vehicle according to claim 1, characterized in that, The fixed-wing UAV arrives at the second target waypoint later than the aerial platform arrives at the first target waypoint; when the aerial platform arrives at the first target waypoint, it is hovering and its nose is pointing towards coordinate point (0,0,z1); when the fixed-wing UAV arrives at the second target waypoint, its flight speed is higher than its stall speed and its nose is pointing towards coordinate point (0,0,z2).
5. The method for planning the runway-less recovery trajectory of a fixed-wing unmanned aerial vehicle according to claim 1, characterized in that, The aerial platform accelerates from the first target waypoint to its maximum cruising speed with maximum power, and then maintains the maximum cruising speed at a constant speed towards the target point.
6. The method for planning the flight path for runway-less recovery of a fixed-wing unmanned aerial vehicle according to claim 1, characterized in that, The method for determining whether the fixed-wing UAV and the aerial platform have reached the predetermined target in step 5 is as follows: The absolute values of the deviations between the current position and the target position of the fixed-wing UAV and the current state of the fixed-wing UAV and the target state are within the preset threshold E1 range; the absolute values of the deviations between the current position and the target position of the airborne platform and the current state of the airborne platform and the target state are within the preset threshold E2 range. Among them, e x1 e represents the x-coordinate deviation between the current position of the fixed-wing aircraft and the target position. y1 e represents the deviation of the y-coordinate between the current position of the fixed-wing aircraft and the target position. z1 The z-coordinate deviation between the current position of the fixed-wing aircraft and the target position. The deviation of the linear velocity of the fixed-wing aircraft in the x-axis direction from the current state of the target aircraft. The deviation of the linear velocity of the fixed-wing aircraft in the y-axis direction from the current state of the target aircraft. The deviation of the linear velocity of the fixed-wing aircraft in the z-axis direction from the current state of the target aircraft. e represents the yaw angle deviation between the current state and the target state of the fixed-wing aircraft. θ1 e represents the pitch angle deviation between the current state and the target state of the fixed-wing aircraft. ψ1 The roll angle deviation between the current state and the target state of the fixed-wing aircraft. The yaw angle and angular velocity deviation between the current state and the target state of the fixed-wing aircraft. The pitch angle and angular velocity deviation between the current state and the target state of the fixed-wing aircraft. The roll angle and angular velocity deviation between the current state and the target state of the fixed-wing aircraft; e x2 e represents the deviation of the x-coordinate between the current position of the aerial platform and the target position. y2 e represents the y-coordinate deviation between the current position of the aerial platform and the target position. z2 This represents the deviation of the z-coordinate between the current position of the aerial platform and the target position. The deviation of the linear velocity between the current state of the aerial platform and the target state along the x-axis. The deviation of the linear velocity along the y-axis between the current state of the aerial platform and the target state. The deviation of the linear velocity between the current state of the aerial platform and the target state along the z-axis. e represents the yaw angle deviation between the current state of the airborne platform and the target state. θ2 e represents the pitch angle deviation between the current state of the aerial platform and the target state. ψ2 The roll angle deviation between the current state of the aerial platform and the target state. This represents the yaw angle and angular velocity deviation between the current state of the aerial platform and the target state. The pitch angle and angular velocity deviation between the current state of the aerial platform and the target state. This represents the roll angle and angular velocity deviation between the current state of the aerial platform and the target state.
7. The method for planning the flight path for runway-less recovery of a fixed-wing unmanned aerial vehicle according to claim 1, characterized in that, Step 5 also includes determining whether the aerial platform and the fixed-wing UAV have successfully intersected. If the intersecting is successful, step 6 is executed; otherwise, step 6 is not executed.
8. The method for planning the runway-less recovery trajectory of a fixed-wing unmanned aerial vehicle according to claim 7, characterized in that, The method for determining whether an aerial platform and a fixed-wing UAV have successfully intersected is as follows: Within duration T: the real-time altitude direction h1 of the fixed-wing UAV and the real-time altitude h2 of the aerial platform satisfy the following relationship: h1 = h2 + 3 + e z3 ; The absolute values of the position and state deviations between the fixed-wing UAV and the aerial platform are within the threshold E3 range; Among them, e x3 e represents the x-coordinate deviation between the current position of the fixed-wing aircraft and the position of the aerial platform. y3 e represents the y-coordinate deviation between the current position of the fixed-wing aircraft and the position of the aerial platform. z3 This represents the deviation of the z-coordinate between the current position of the fixed-wing aircraft and the position of the aerial platform. The deviation of the linear velocity along the x-axis between the current state of the fixed-wing aircraft and the state of the aerial platform. The deviation of the linear velocity along the y-axis between the current state of the fixed-wing aircraft and the state of the aerial platform. The deviation of the linear velocity along the z-axis between the current state of the fixed-wing aircraft and the state of the aerial platform. e represents the yaw angle deviation between the current state of the fixed-wing aircraft and the state of the aerial platform. θ3 e represents the pitch angle deviation between the current state of the fixed-wing aircraft and the state of the airborne platform. ψ3 The roll angle deviation between the current state of the fixed-wing aircraft and the state of the aerial platform. The yaw angle and angular velocity deviation between the current state of the fixed-wing aircraft and the state of the aerial platform. The pitch angle and angular velocity deviation between the current state of the fixed-wing aircraft and the state of the airborne platform. This refers to the roll angle and angular velocity deviation between the current state of the fixed-wing aircraft and the state of the aerial platform.
9. The method for planning the flight path for runway-less recovery of a fixed-wing unmanned aerial vehicle according to claim 1, characterized in that, The first, second, and fourth paths all employ a rolling window-based path planning algorithm.
10. A method for planning the flight path for runway-less recovery of a fixed-wing unmanned aerial vehicle according to claim 9, characterized in that, Path planning algorithms based on scrolling windows include: (1) Sub-target and scenario prediction: Based on the environmental information detected within the local window range, the fixed-wing UAV and the aerial platform generate local sub-targets using a heuristic method, predict the movement of dynamic obstacles, and determine whether the fixed-wing UAV and the aerial platform may collide with dynamic obstacles. (2) Scrolling window optimization: Based on the environmental information and prediction results within the local window, the fixed-wing UAV and the aerial platform determine the local path to the sub-target and implement the current strategy; (3) Feedback initialization: After a new scrolling window is generated, the environment and obstacle movement status within the new scrolling window are updated based on the latest information obtained by the sensor; (4) Repeat steps (1), (2) and (3) until the fixed-wing UAV and the aerial platform reach the predetermined target, and end the trajectory planning of this stage.