An unmanned aerial vehicle (UAV) assembly phase adjustment method based on S-bend maneuvering

Abstract

The application discloses an unmanned aerial vehicle (UAV) gathering phase adjustment method based on S-bend maneuvering, belongs to the field of aircraft guidance and control technology, and aims at the problems that the traditional speed regulation method is insufficient in phase regulation due to the limited speed regulation range of the UAV, and the hovering phase regulation method is coarse in adjustment granularity and low in time efficiency due to the need to complete a whole circle flight. The application plans an S-bend flight path with double circular arc connection, dissipates the remaining time of the fastest gathering period, and enables the UAV to autonomously decide an optimal phase regulation strategy according to a real-time state in the flight process, so that the accurate fine adjustment of the time scale can be realized, and the invalid waste of time resources can be avoided. The application replaces the explicit waiting by continuous flight path optimization, ensures the accuracy of the period gathering time, significantly improves the economy and the tactical concealment of the flight, and provides an effective technical solution for the UAV cluster cooperative task.

Description

Technical Field

[0001] This invention belongs to the field of aircraft guidance and control technology, specifically relating to a method for unmanned aerial vehicle (UAV) assembly phase adjustment based on S-curve maneuvers. Background Technology

[0002] In collaborative missions involving drone swarms, such as formation flying and collaborative reconnaissance, multiple drones are often required to depart from different initial positions, maintain a fixed altitude interval, periodically arrive at a designated assembly position according to a unified time reference, and form a unified assembly heading. This strict periodic assembly requirement poses a severe challenge to the drones' trajectory planning capabilities.

[0003] Currently, directly planning the shortest Durbins path combined with speed control is a common approach to achieving spatiotemporal rendezvous. However, the available speed adjustment range of fixed-wing UAVs is limited. When the required speed adjustment exceeds their speed adjustment limits, this method cannot guarantee on-time arrival. Another approach is to design a hovering phasing circle around the rendezvous area. While this method provides a definite phasing time, it lacks flexibility. Once the UAV enters the hovering phasing circle, it usually needs to complete a full circle, limiting the minimum unit of time adjustment to a single circle cycle. When only minor adjustments are needed to meet timing requirements, this method may cause the UAV to perform unnecessary full circles to meet the next rendezvous cycle, resulting in wasted time resources and compromising flight stealth.

[0004] Existing methods generally suffer from a trade-off between phase adjustment capability and efficiency when dealing with periodic assembly tasks, making it difficult to ensure both time accuracy and high efficiency. Therefore, developing a planning method that can adapt to different initial conditions, achieve high-precision phase adjustment, and meet the fastest assembly cycle has become crucial for improving the collaborative effectiveness of UAV swarms. Summary of the Invention

[0005] This invention provides a UAV assembly phase adjustment method based on S-curve maneuver. By planning an S-curve trajectory with double circular arcs, the remaining time of the fastest assembly cycle is dissipated, enabling the UAV to autonomously decide the optimal phase adjustment strategy based on the real-time status during flight. This achieves both precise fine-tuning of the time scale and avoids the ineffective waste of time resources.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for adjusting the assembly phase of an unmanned aerial vehicle (UAV) based on S-curve maneuvers includes the following steps:

[0008] S1: Based on the initial position and initial heading of the UAV, plan the first arc trajectory that is tangent to it and close to the direction of the assembly circle, and record the initial moment;

[0009] S2: Based on the first arc trajectory, plan the Dubins route that cuts into the gathering circle in the specified spiral direction, and calculate the time required to fly along the Dubins route at a constant speed.

[0010] S3: Calculate the period required for the UAV to circle once on the assembly circle. According to the specified arrival time, determine the design arrival time that is an integer number of periods away from it, and ensure that the design arrival time is not less than the sum of the initial time and the time calculated in S2, and is the earliest arrival time.

[0011] S4: The UAV tracks the first arc trajectory, and based on its current position and heading, plans a second arc trajectory that is tangent to and externally tangent to the first arc trajectory, and records the current moment;

[0012] S5: Based on the second arc trajectory, plan the Dubins route that cuts into the gathering circle in the specified spiral direction, and calculate the time required to fly along the Dubins route at a constant speed.

[0013] S6: Determine whether the sum of the current time and the time calculated in S5 is greater than the designed arrival time; if yes, control the UAV to switch from the first arc trajectory to the second arc trajectory and fly along the remaining Durbins route; if no, the UAV continues to fly along the first arc trajectory and returns to S4.

[0014] S7: When the drone enters the straight section of the Dubins route, speed adjustment begins to ensure that the drone arrives at the rendezvous point accurately at the designed arrival time.

[0015] In the steps described above, the radii of the first and second circular arc trajectories... Design roll angle and design flight speed It is confirmed that the maximum design roll angle corresponds to the minimum turning radius, specifically: , in This is the acceleration due to gravity.

[0016] The length of the Dubins route, planned directly from the initial position and heading by the drone to the assembly point, is [length missing]. Design speed Flight time is : ,

[0017] The design arrival time of the drone Determined by the following formula: , in To specify the arrival time, The time period required for the converging circle to complete one revolution. Let be an integer, and satisfy the following relation: , Right now Just not less than The periodic gathering time, This is the initial time.

[0018] The Dubins flight path type is one of LSL (left-straight-left), LSR (left-straight-right), RSL (right-straight-left), or RSR (right-straight-right), specifically determined based on the current and desired circling direction. When the UAV's circling direction on the first arc trajectory is clockwise, the Dubins flight path type in S2 is RSL or RSR; correspondingly, if the circling direction on the second arc trajectory is counterclockwise, then the Dubins flight path type in S5 is LSL or LSR. When the UAV's circling direction on the first arc trajectory is counterclockwise, the Dubins flight path type in S2 is LSL or LSR; correspondingly, if the circling direction on the second arc trajectory is clockwise, then the Dubins flight path type in S5 is RSL or RSR.

[0019] The length of the Dubins flight path in S5 consists of three parts. The first part is the arc length from the current position, along the second arc trajectory, flying in the set hovering direction to the tangent point; the second part is the length of the tangent segment between the second arc trajectory and the assembly circle; the third part is the arc length from the entry point, flying in the set hovering direction to the assembly point; the length of the arc is recorded as follows: The total length of the Dublin route, as planned, is , At any given moment, if starting from the current position at the designed speed The time to reach the assembly point along the Dubins route is greater than ,Right now: The drone then enters the second segment of its circular trajectory.

[0020] Upon reaching the third segment of the trajectory, the straight section of the Dubins flight path, the drone begins to adjust its speed. The speed adjustment range is limited by the drone's minimum level flight speed and the engine's maximum thrust. Minimum level flight speed To provide the speed necessary for the drone to achieve level flight lift, the following relationship must be satisfied: , Where W represents the gravity acting on the drone. The air density at the drone's altitude. For wing reference area, This represents the maximum lift coefficient. The maximum flight speed is the amount of thrust available to the UAV. The velocity at which resistance is equal to the velocity satisfies the following relationship: in This is the drag coefficient.

[0021] Beneficial effects: This invention provides a UAV assembly phase adjustment method based on S-curve maneuvers, which has the following advantages compared with the prior art:

[0022] 1. Precise time control and strong anti-interference capability: This invention achieves high-precision periodic assembly based on the S-curve dynamic phase adjustment mechanism. By planning the S-curve trajectory with double circular arcs, the remaining time of the fastest assembly cycle is dissipated. At the same time, the combination of trajectory planning and speed control enables the UAV to cope with external interference such as wind disturbance. Through the coordinated adjustment of trajectory and speed, the time deviation during flight is effectively compensated.

[0023] 2. Economical and efficient flight path with excellent concealment: This invention achieves time adjustment by designing a continuous and natural circular arc flight path, avoiding the exposure problem caused by explicit hovering and waiting methods near the assembly area. This design reduces additional range consumption, saves airborne energy, and makes the assembly process of the UAV more concealed and natural, avoiding explicit trajectory features that reveal the intention.

[0024] 3. High computational efficiency and good real-time performance: Compared with optimization methods that require complex iterative solutions, this invention transforms the trajectory planning problem into an analytical calculation process based on the current position. By calculating the combination of arcs with predefined radii and geometric relationships, the computational complexity is greatly reduced, enabling the algorithm to run efficiently on resource-constrained computing platforms. This ensures the real-time performance of trajectory planning and provides engineering applications for rapid decision-making by UAVs in dynamic environments. Attached Figure Description

[0025] Figure 1 This is a flowchart of the UAV assembly phase adjustment method in an embodiment of the present invention;

[0026] Figure 2 This is a simplified schematic diagram of the S-curve trajectory planning in an embodiment of the present invention;

[0027] Figure 3 The flight path of the ground station in this embodiment of the invention;

[0028] Figure 4 The curves represent the simulation results in this embodiment of the invention. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments:

[0030] After the drone receives the synchronization and assembly command, as follows: Figure 2As shown, starting from the current position and heading, the vehicle travels through an S-curve formed by two arcs, then enters the assembly circle via a straight section, and begins speed adjustments. Finally, at a moment periodically aligned with the designated arrival time, it passes the assembly point due north of the assembly circle. The specific adjustment process is as follows: Figure 1 As shown:

[0031] Let the initial time be Time drone is located The initial heading is The radius of the gathering circle is The center of the circle is located at The assembly point is Define a direction identifier variable. When required to rotate clockwise along the assembly circle, When rotating counterclockwise, .

[0032] Based on geometric relationships, the azimuth angle of the line connecting the current position of the UAV and the center of the assembly circle relative to true north is... It can be calculated using the following formula: ,

[0033] Through the and Initial heading By comparing the two, the direction of the first circle's rotation can be determined. : .

[0034] The Dubins flight path type is one of LSL (left-straight-left), LSR (left-straight-right), RSL (right-straight-left), or RSR (right-straight-right), determined specifically based on the current and desired circling direction. To enable the UAV to smoothly transition from the first to the second arc trajectory, forming an S-shaped trajectory, the circling direction of the second arc trajectory... It should be set to be the same as Conversely, that is: .

[0035] In Dubins path planning, if the center of the starting circle is known... The center of the target circle Starting point heading Target point heading and the radius of the starting circle and the radius of the target circle Then the tangent point can be calculated. Entry point Straight Segment Heading and path length .

[0036] When the Dublinds route type is LSL: ,

[0037] When the Doberman route type is LSR ,

[0038] When the Dubins route type is RSL ,

[0039] When the Doberman route type is RSR ,

[0040] Let the radius of the first arc trajectory be... According to geometric relationships, the coordinates of its center are... It can be determined by the following formula: ,

[0041] Based on the location of the center and radius of the assembly circle, the Durbins path calculation method described above can be used to calculate the path length from the initial position directly to the assembly point. Combined with the design flight speed of the drone To obtain the required time: ;

[0042] The estimated arrival time of the drone Determined by the following formula: ; in To specify the arrival time, The time period required for one revolution around the assembling disk. For integers that satisfy the following formula: ; Right now Just not less than The periodic gathering time.

[0043] Similarly, during the tracking of the first segment of the circular trajectory, at any given moment... If the drone's current location is The heading is Then the center of the second circular arc track It can be represented as: ,

[0044] Calculate the length of the trajectory along the second circular arc path to the assembly point at that moment. If the following conditions are met: ,

[0045] If the drone then switches to the second arc trajectory, it will continue to fly along the first arc trajectory and will be reassessed in the next calculation cycle.

[0046] When the UAV enters the third flight segment, namely the straight section of the Dubins route, the speed adjustment mechanism is activated to further improve the arrival time accuracy; the speed adjustment range is limited by the UAV's minimum level flight speed. and maximum level flight speed constraint.

[0047] The minimum level flight speed is determined by the lift balance condition: , Where W represents the gravity acting on the drone. air density, For wing reference area, The maximum lift coefficient;

[0048] Maximum level flight speed is obtained by balancing thrust and drag: , in For available thrust, The drag coefficient is used; through the above speed adjustment strategy, the UAV can achieve the designed arrival time. Arrive precisely at the assembly point.

[0049] Simulation Experiment

[0050] like Figure 3 As shown, the drone is required to hover clockwise on the assembly circle, that is... ; Specified arrival time This serves as a reference time for periodic gatherings.

[0051] Set the radii of the first and second arc trajectories. radius of the gathering circle Designed flight speed The flight period on the gathering circle is: .

[0052] Initial time The Durbins route is planned directly from the initial position, and the time required to reach the assembly point is calculated as follows: .because hour, ,

[0053] Therefore, the design arrival time is determined. .

[0054] While tracking the first segment of the circular trajectory, the system calculates in real time whether to switch to the second segment of the S-curve's circular trajectory. For example... Figure 4 As shown, when At that time, the calculation yielded ,satisfy Then the drone switches from the first segment of the circular flight path to the second segment. When At that time, the drone flew to the straight flight path and began to adjust its speed, with a speed adjustment range of 42~48 m / s. When the drone finally arrives at the assembly point, the error from the designed arrival time is less than 0.1 seconds. Through the speed adjustment mechanism described above, the drone can arrive at the assembly point more accurately at the designed arrival time.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for adjusting the assembly phase of an unmanned aerial vehicle (UAV) based on S-curve maneuvers, characterized in that, Includes the following steps: S1: Based on the initial position and initial heading of the UAV, plan the first arc trajectory that is tangent to it and close to the direction of the assembly circle, and record the initial moment; S2: Based on the first arc trajectory, plan a Dobbins' flight path that cuts into the assembly circle in the specified hovering direction, and calculate the time required to fly along the Dobbins' flight path at a constant speed; the UAV, starting from its initial position and heading, directly plans the length of the Dobbins' flight path to the assembly point. Design speed Flight time is : ， The design arrival time of the drone Determined by the following formula: ， in To specify the arrival time, The time period required for the converging circle to complete one revolution. Let be an integer, and satisfy the following relation: ， Right now Just not less than The periodic gathering time, This is the initial time. S3: Calculate the period required for the UAV to circle once on the assembly circle. According to the specified arrival time, determine the design arrival time that is an integer number of periods away from it, and ensure that the design arrival time is not less than the sum of the initial time and the time calculated in S2, and is the earliest arrival time. S4: The UAV tracks the first circular arc trajectory, and based on its current position and heading, plans a second circular arc trajectory that is tangent to and externally tangent to the first circular arc trajectory, and records the current time; the radii of the first and second circular arc trajectories are also recorded. Design roll angle and design flight speed It is confirmed that the maximum design roll angle corresponds to the minimum turning radius, specifically: ， in It is the acceleration due to gravity; During the tracking of the first circular trajectory, at any time Calculate the length of the trajectory along the second circular arc path to the assembly point at that moment. If the following conditions are met: ， If the drone is switched from the first arc trajectory to the second arc trajectory, it will continue to fly along the first arc trajectory and will be re-evaluated in the next calculation cycle. S5: Based on the second arc trajectory, plan the Dubins route that cuts into the gathering circle in the specified spiral direction, and calculate the time required to fly along the Dubins route at a constant speed. S6: Determine whether the sum of the current time and the time calculated in S5 is greater than the designed arrival time; if yes, control the UAV to switch from the first arc trajectory to the second arc trajectory and fly along the remaining Durbins route; if no, the UAV continues to fly along the first arc trajectory and returns to S4. S7: When the drone enters the straight section of the Dubins route, speed adjustment begins to ensure that the drone arrives at the rendezvous point accurately at the designed arrival time.

2. The UAV assembly phase adjustment method based on S-curve maneuvering according to claim 1, characterized in that, The type of the Dubins route is LSL, LSR, RSL or RSR, which is determined based on the current circling direction and the desired circling direction.

3. The UAV assembly phase adjustment method based on S-curve maneuvering according to claim 2, characterized in that, When the UAV hovers clockwise on the first arc trajectory, the Dubins flight path type in S2 is RSL or RSR; correspondingly, when the UAV hovers counterclockwise on the second arc trajectory, the Dubins flight path type in S5 is LSL or LSR.

4. The UAV assembly phase adjustment method based on S-curve maneuvering according to claim 1 or 3, characterized in that, In S7, when the UAV enters the third segment of its flight path, namely the straight section of the Dubins route, the speed adjustment mechanism is activated. The speed adjustment range is limited by the UAV's minimum level flight speed. and maximum level flight speed constraint.

5. The UAV assembly phase adjustment method based on S-curve maneuvering according to claim 4, characterized in that, The minimum level flight speed is determined by the lift balance condition: ， Where W represents the gravity acting on the drone. air density, For wing reference area, This is the maximum lift coefficient.

6. The UAV assembly phase adjustment method based on S-curve maneuvering according to claim 4, characterized in that, Maximum level flight speed is obtained by balancing thrust and drag: ， in For available thrust, The drag coefficient, air density, This is the reference area for the wing.

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