Unmanned aerial vehicle formation homeward voyage trajectory planning method based on Durbin curve

Abstract

The invention discloses an unmanned aerial vehicle formation homeward voyage trajectory planning method based on a Durbin curve, belongs to the technical field of unmanned aerial vehicle flight path planning, and can adapt to any unmanned aerial vehicle initial course and formation flight course, automatically adjust unmanned aerial vehicle and formation phase positions and guarantee safety at the same time. The method comprises the following steps: obtaining the position and course of an unmanned aerial vehicle, and designing a Durbin return route according to the expected position and course of a return point; adjusting the flight height of the unmanned aerial vehicle to be staggered from the formation flight height; calculating a phase difference according to the time when the unmanned aerial vehicle arrives at the return point and the expected return time, and designing a phase modulation route; the flight height of the unmanned aerial vehicle is adjusted to be consistent with the formation flight height; therefore, the unmanned aerial vehicle can be accurately and efficiently integrated into the original formation track again on the premise of safety and no collision.

Description

Technical Field

[0001] The present invention belongs to the technical field of unmanned aerial vehicle (UAV) trajectory planning, and in particular relates to a UAV formation return trajectory planning method based on a Dubins curve. Background Art

[0002] After completing a reconnaissance mission within a formation, a drone's departure and return is crucial for ensuring mission continuity. When the return point is a specific location within the formation, trajectory planning presents complex challenges, including safety assurance, formation adaptation, and phase alignment. The drone must ensure safety during the return process to avoid collisions with other members of the formation still on the mission. The return location must be precisely selected to align with the formation's dynamic trajectory and formation. The return time must be strictly controlled to ensure the drone arrives precisely at the rendezvous point and achieve phase alignment.

[0003] However, existing research has largely focused on formation maintenance and coordinated control, and only considers the return of UAVs in static formations. Research on methods for returning to re-enter a dynamic formation is insufficient. For example, patent publication number CN117387625A proposes a return-to-flight planning method based on the Dubins curve. This method considers the initial and target headings of the UAVs and achieves a smooth path. However, this method has significant limitations. Its return point is considered only as a geographic coordinate and is not adapted to the dynamic scenarios of formations. This means that this method fails to address the core issue of how UAVs can accurately dock with the dynamic formation structure—that is, how to achieve precise spatial and temporal overlap with the formation, a topic that is lacking in existing research. Furthermore, when re-entering a formation, a UAV must start from its current position and enter the formation at a specific heading. However, traditional path planning methods often ignore the deviation between the UAV's initial heading and the formation's heading, which can lead to inappropriate flight path planning and increase flight risks. Therefore, designing a reasonable return trajectory and strategy based on the characteristics of formation return is crucial to solving the core problem of safely, efficiently, and accurately re-entering the original dynamic formation. Summary of the Invention

[0004] The present invention provides a method for planning the return trajectory of a UAV formation based on the Dubins curve, which can solve the problem in the prior art that it is difficult for UAVs to accurately align with the predetermined position in the formation and achieve phase synchronization when returning from a reconnaissance mission. It ensures that the UAVs can accurately and efficiently reintegrate into the original formation trajectory under the premise of safety and collision-free.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions:

[0006] A method for planning a return trajectory of a UAV formation based on a Dubins curve includes the following steps:

[0007] S1: Obtain the drone's own position and heading, and design the Dobbins return route based on the expected position and heading of the return point;

[0008] S2: Adjust the UAV’s flight altitude to stagger with the formation’s flight altitude;

[0009] S3: Calculate the phase difference and design the phase adjustment route based on the time when the UAV arrives at the return point and the expected time when it returns to the team;

[0010] S4: Adjust the drone's flight altitude to match the formation's flight altitude and return to the formation.

[0011] In the above steps, the Dobbins return route described in S1 selects one of the four standard path types: LSL (left-straight-left), LSR (left-straight-right), RSL (right-straight-left), or RSR (right-straight-right) according to the actual situation to generate the optimal smooth path from the current position of the drone to the return point.

[0012] In S3, the length of the phase adjustment route and the number of flight circles of the drone are determined by the drone's performance constraints and the difference between the drone's actual arrival time and the expected arrival time; the shortest flight distance Arrival time at the return point Expected arrival time , speed , formation navigation cycle , arc route radius and formation route length Decision, specifically: , in, express right Take the remainder, It is an adjustable integer and needs to be reasonably selected. Make The distance is sufficient for phase adjustment, so Need to meet ,

[0013] at the same time, The distance should be as short as possible so that the drone can rejoin the formation as quickly as possible. , it is also necessary to meet the following requirements: .

[0014] Further calculations are performed to obtain the number of circles the drone needs to run on the phase adjustment route. and the length of the straight segment route : , in Indicates rounding down.

[0015] Beneficial effects: The present invention provides a UAV formation return trajectory planning method based on the Dubins curve, which has the following advantages over the existing technology:

[0016] 1. When re-entering a formation, a drone must start from its current position and re-enter the formation at a specific heading. Traditional path planning methods often ignore the deviation between the drone's initial heading and the formation's heading, which can lead to improper flight path planning and increase flight risk. The proposed method comprehensively considers the drone's current heading, the target return point heading, and its dynamic constraints. It utilizes the Dubins curve to generate a smooth and safe transition path, ensuring the safety and efficiency of the return process.

[0017] 2. A drone re-entering a formation must respond to the dynamic movements of the formation in real time. Existing technologies often rely on adjusting the drone's own speed or coordinating with other members of the formation to achieve phase alignment. This not only increases system complexity but can also interfere with the original formation's flight mission. This invention innovatively designs a phased trajectory that adaptively aligns the phase of the drone with the formation, enabling a smooth re-entry without disrupting the original formation's flight mission.

[0018] 3. The method of the present invention has a small amount of calculation and does not require complex online real-time calculations to determine the current position of the UAV and continuously issue the expected position instructions. It can also adapt to any UAV initial heading and formation flight heading, automatically adjust the phase between the UAV and the formation, avoid collisions, and ensure safety. It provides a trajectory planning solution for the UAV formation return mission with light computational burden, easy implementation and reliable effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the return trajectory planning of the UAV in an embodiment of the present invention;

[0020] Figure 2 Schematic diagram of the Dubins curve in different directions in an embodiment of the present invention;

[0021] Figure 3 This is a simulated route trajectory diagram of a UAV in an embodiment of the present invention;

[0022] Figure 4 This is a specific time diagram of each flight segment of the drone in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments:

[0024] like Figure 1As shown in the figure, the drones are in a queue formation, evenly distributed on a closed route, and fly at a constant speed along a circular trajectory. At a certain moment, a drone leaves the formation from the departure point to perform a reconnaissance mission and enter the mission segment. After completing the reconnaissance mission, it performs Dobbins planning from the return starting point with the initial heading, adjusts the flight altitude, enters the return segment, and arrives at the return point with the desired attitude. The Dobbins return route design needs to be based on the actual situation, such as Figure 2 As shown, select one of the four standard path types: LSL (left-straight-left), LSR (left-straight-right), RSL (right-straight-left), or RSR (right-straight-right) to generate the optimal smooth path from the current position of the drone to the return point.

[0025] Assume the initial position coordinates of the UAV are , the yaw angle is , the coordinates of the return point are , the expected yaw angle is , set the radius of the tangent circle at the return starting point to , the radius of the tangent circle at the return point is According to the geometric relationship, it is easy to get the coordinates of the center of the tangent circle at the initial position Coordinates of the center of the circle tangent to the return point .

[0026] When the Dubins curve is RSR or RSL, the coordinates of the center of the initial tangent circle are: ;

[0027] When the Dubins curve is LSR or LSL, the coordinates of the center of the initial tangent circle are: ;

[0028] When the Dubins curve is RSR or LSR, the coordinates of the center of the tangent circle of the return point are: ;

[0029] When the Dubins curve is RSL or LSL, the coordinates of the center of the tangent circle at the return point are: .

[0030] According to the coordinates of the center of the circle and the type of the Dubins curve, the coordinates of the cut-out point are further determined. and heading at the cut-out point and the entry point coordinates and heading at the entry point :

[0031] RSR type: ,

[0032] RSL type: ,

[0033] LSR type: ,

[0034] LSL type: ,

[0035] Calculate and compare the lengths of four types of Dobbins paths and choose the shortest route.

[0036] When entering the return leg, the drone adjusts its flight altitude to avoid collision with the formation's flight altitude.

[0037] After arriving at the return point, the drone enters the phase adjustment section, and the phase adjustment route is "runway-shaped", in which the arc section route radius is According to the flight speed of the drone and design roll angle Make settings, specifically: , where g is the acceleration due to gravity.

[0038] Assume that the time for the drone to arrive at the return point is , the expected time for the formation to reach the return point is , the speed is , the formation sailing period is , the formation route length is ;The shortest flight distance of the UAV on the phase adjustment route The time it takes for the drone to reach the return point is The expected time for the formation to reach the return point is , speed , formation navigation cycle , arc route radius and formation route length Determine the shortest flight distance of the UAV in the phase adjustment segment for: , Where mod means remainder, To adjust the parameters, you need to choose Make The distance is sufficient for phase adjustment, so Need to meet and ,

[0039] at the same time, The distance should be as short as possible so that the drone can rejoin the formation as quickly as possible. When ,

[0040] The expected time for the formation to arrive at the return point The number of laps that the drone needs to run on the phase adjustment route is determined by the arrival time of the first drone in the formation and the phase difference between the current drone and the first drone. and the length of the straight segment route : , in Indicates rounding down.

[0041] In this embodiment, it is assumed that the total number of UAVs in the formation is , the current drone's serial number is , then the phase difference between the current UAV and the first UAV is: .

[0042] Assume that the time when the first UAV is expected to arrive at the return point is , then the time when the current UAV in the formation is expected to arrive at the return point is: .

[0043] Number of UAV's flight circles in the phase adjustment segment and the length of the straight line segment Determined by the following relationship: , in Indicates rounding down.

[0044] After adjusting the phase through the phase adjustment segment, the drone's flight trajectory is consistent with the formation's, and the flight altitude is adjusted to return to the formation.

[0045] UAV simulation flight path Figure 3 As shown in the figure, the specific time of the simulation stage is as follows: Figure 4 , the simulation results only show the route of UAV No. 3. Starting from 725.32s, UAV No. 3 entered the long closed route and was evenly distributed on the closed route with the other two UAVs. At 1083.90s, UAV No. 3 left the formation to perform a reconnaissance mission. At 1199.03s, the reconnaissance mission ended, UAV No. 3 flew along the return route, and entered the phase adjustment route at 1297.66s. At 1394.71s, it returned to the closed route and joined the formation flight. The time the UAV expects to return to the route should be kept at 725.32s for several navigation cycles, where the navigation cycle is the time required for the UAV to fly along a closed route at a speed of 50m / s. The error between the actual arrival time and the expected arrival time is , the error is less than 1s.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A UAV formation return trajectory planning method based on the Dubins curve, characterized in that: The following steps are involved: S1: Obtain the drone's own position and heading, and design the Dobbins return route based on the expected position and heading of the return point; S2: Adjust the UAV’s flight altitude to stagger with the formation’s flight altitude; S3: Calculate the phase difference and design the phase adjustment route based on the time when the UAV arrives at the return point and the expected time when it returns to the team; S4: Adjust the drone's flight altitude to match the formation's flight altitude and return to the formation.

2. The UAV formation return trajectory planning method based on the Dubins curve according to claim 1 is characterized in that: The Dobbins return route selects one of the four standard path types of LSL, LSR, RSL, and RSR according to actual conditions, calculates and compares the lengths of the four types of Dobbins paths, and selects the shortest path for navigation.

3. The UAV formation return trajectory planning method based on the Dubins curve according to claim 2 is characterized in that: Determine the coordinates of the cut-out point based on the center coordinates and the type of the Dubins curve and heading at the cut-out point and the entry point coordinates and heading at the entry point , RSR type is: , calculate the Dobbins path length.

4. The UAV formation return trajectory planning method based on the Dubins curve according to claim 2 is characterized in that: Determine the coordinates of the cut-out point based on the center coordinates and the type of the Dubins curve and heading at the cut-out point and the entry point coordinates and heading at the entry point , RSL type is: , calculate the Dobbins path length.

5. The UAV formation return trajectory planning method based on the Dubins curve according to claim 2 is characterized in that: Determine the coordinates of the cut-out point based on the center coordinates and the type of the Dubins curve and heading at the cut-out point and the entry point coordinates and heading at the entry point , LSR type is: , calculate the Dobbins path length.

6. The UAV formation return trajectory planning method based on the Dubins curve according to claim 2 is characterized in that: Determine the coordinates of the cut-out point based on the center coordinates and the type of the Dubins curve and heading at the cut-out point and the entry point coordinates and heading at the entry point , LSL type is: , calculate the Dobbins path length.

7. The method for planning the return trajectory of a UAV formation based on the Dubins curve according to claim 1, characterized in that: The phased trajectory is in the shape of a runway. The length of the phased trajectory and the number of flight laps are determined based on the performance constraints of the drone and the difference between the actual arrival time and the expected arrival time.

8. The UAV formation return trajectory planning method based on the Dubins curve according to claim 1 or 7, characterized in that: The radius of the arc section of the runway-shaped phase adjustment route According to the flight speed of the drone and design roll angle Make settings, specifically: ， where g is the acceleration due to gravity.

9. The method for planning the return trajectory of a UAV formation based on the Dubins curve according to claim 8, characterized in that: The shortest flight distance of a drone on a phased route Arrival time at the return point Expected arrival time , speed , formation navigation cycle , arc route radius and formation route length Decision, specifically: ， in, express right Take the remainder, is an adjustable integer, Need to meet: ， The distance should be as short as possible so that the drone can rejoin the formation as quickly as possible. When .

10. The UAV formation return trajectory planning method based on the Dubins curve according to claim 9 is characterized in that: Calculate the number of circles the drone needs to run on the phase adjustment route and the length of the straight segment route : ， in Indicates rounding down.

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