A multi-constraint fixed-wing cluster unmanned aerial vehicle hovering control method

Abstract

The application discloses a kind of multi-constraint condition's fixed wing cluster unmanned aerial vehicle hover control method, it is related to unmanned aerial vehicle cluster flight control field, including the following steps: S1, long plane obtains hover parameter by hover instruction and analysis;S2, long plane is calculated by speed limit and is obtained long plane constraint speed range by multi-constraint speed limiting, so that long plane can enter hover and maintain hover state;S3, by the curve distance of wingman calculation, for the instruction value of evaluation roll angle;S4, wingman is constrained by the flight distribution situation and hover parameter that other unmanned aerial vehicle emits, if aircraft is close to long plane, first determine the constraint of nearest tangent circle to avoid the problem that aircraft enters circle after and generates same air line dislocation;S5, after wingman enters hover state, the instruction value of speed is calculated by calculating expected motion position, to control wingman hover process;The application can be autonomously coordinated to reduce the control pressure of formation collision avoidance, formation keeping demand.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) swarm flight control technology, and more specifically to the field of fixed-wing swarm UAV hovering control method under multiple constraints. Background Technology

[0002] In recent years, due to hardware iterations, the rapid development of distributed systems and networking communication technologies, swarm drones have gradually entered the public eye. Compared to traditional multi-rotor drones, they possess advantages such as high maneuverability, long endurance, and wide operating range, making them highly valued in long-distance, long-duration missions such as weather reconnaissance and large-scale natural disaster search and rescue. Taking weather reconnaissance as an example, it requires long-term weather observation, especially for tasks such as tracking the movement trajectory of typhoon eyes. This necessitates drones hovering and repeatedly identifying and tracking targets from multiple angles over extended periods to determine their movement. For this type of problem, since fixed-wing drones cannot hover but their long endurance is still required, hovering and tracking the target's center of motion is an effective and relatively comprehensive approach.

[0003] However, when fixed-wing swarm drones enter a hovering phase, the reconfiguration of the formation, the shift in the circular order, and the autonomous planning of the route can lead to problems such as trajectory overlap and collisions between drones. Even with formation collision avoidance control and pre-planning, considerable uncertainty and instability will still occur, ultimately resulting in short collision avoidance time, low efficiency, and collisions caused by trajectory overlap. Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling the hovering of a fixed-wing swarm UAV under multiple constraints in order to solve the above-mentioned technical problems.

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

[0006] This invention provides a hovering control method for fixed-wing swarm UAVs under multiple constraints, comprising the following steps:

[0007] S1. The lead aircraft obtains and analyzes the circling parameters through the circling command;

[0008] S2. The lead aircraft performs multi-constraint speed limit calculations based on the formation spacing adjustment requirements, the aircraft's own performance, and the speed limit caused by circling, to obtain the lead aircraft's constrained speed range, so that the lead aircraft can preferentially and quickly enter and maintain the circling state.

[0009] S3. If the wingman is outside the circle, the wingman calculates its desired phase angle and thus its desired position, and finally calculates the curved distance of the current position on the circle. This value can be used to evaluate the command value of the roll angle. If the wingman is on or inside the circle, the curved distance of the current position on the circle is finally calculated using the desired coordinates and desired track angle as constraints, and is used to evaluate the command value of the roll angle.

[0010] S4. The wingman is constrained by the flight distribution and hovering parameters transmitted by other drones. If the distance between the lead aircraft and the wingman is less than 280m, it is determined that the wingman and the lead aircraft are close in position. Then, the constraint of the nearest tangent circle is first determined to avoid the problem of misalignment on the same flight path after the aircraft enters the circle.

[0011] S5. After the wingman enters the circling state, the desired movement position is calculated, and the command value of the speed is calculated in order to control the flight of the wingman during the circling process.

[0012] The lead aircraft is a flight term referring to the aircraft that leads a formation in flight. In addition to the lead aircraft, smaller formations, including basic formations (two or three aircraft), also have their own lead aircraft. The lead aircraft's responsibility is to lead the formation (or wingmen) in carrying out missions.

[0013] In one embodiment, in step S1, when the lead aircraft receives a circling command or passes a preset point with circling attributes, it enters a circling state and sends circling parameters such as circling direction, center coordinates, and radius through inter-machine communication.

[0014] In one implementation, in step S1, the lead aircraft needs to synchronously parse the information of all aircraft in the same network, obtain their coordinates and flight planning formation to form a flight distribution. The flight distribution and the hovering information parameters obtained by the lead aircraft will be published to all fixed-wing swarm UAVs in the network through inter-aircraft communication.

[0015] In one implementation, in step S2, before the lead aircraft enters the circling trajectory based on the flight parameters obtained in step S1, it also adjusts its speed according to the distance to be flown in the wingman formation. If the lead aircraft is circling at the lowest or highest speed, since the lead aircraft and the wingman have the same aircraft performance, the wingman lacks speed adjustment space. In order to accelerate the formation of the circling formation and ensure that the lead aircraft does not change its flight radius due to speed adjustment, it is necessary to add a variety of constraints to limit the speed adjustment range on the basis of the speed control of the lead aircraft.

[0016] In one embodiment, in step S2, it is set The default desired speed for the lead aircraft is set to K, with the speed gain set to K, and n representing the number of wingmen in the formation. Let be the formation waiting distance for the i-th wingman, and let the wingman waiting distance limit be . Speed ​​adjustment range is Vc adj Sat represents the limiting output, Vsat represents the speed limiting value adjusted by the lead aircraft when following the wingman, and the lead aircraft speed command. The updated formula is:

[0017]

[0018]

[0019] In one implementation, in step S3, for the wingman, it is first necessary to consider the case where the drone is already on the circle. The phase angle of the desired position is calculated using the current phase angle of the drone. The roll angle command is obtained by calculating the curve distance between the desired position and the current position on the circle.

[0020] For situations where the drone has not yet reached the circle, there are two scenarios: First, if the drone is far from the center, it should enter the circle tangentially, setting the desired position at the point of tangency between the drone and the circle, resulting in a longer curve distance. Second, if the drone is close to the center, the curve distance should be gradually shortened until the drone is on the circle. A piecewise linear function is used to represent the curve distance based on the distance between the drone and the center. By calculating the different curve distances in different scenarios, the required angular offset for the drone to move to the desired position is determined, thus enabling the calculation of the roll angle command.

[0021] In one implementation, in step S3, the case where the drone is already on the circle is first considered, η f η is the current phase angle of the wingman. sp Let be the phase angle of the desired position, and let L be the curvilinear distance between the desired position and the current position on the circle, with a value in the range [0, 2πR]. The relationship is as follows:

[0022]

[0023] With a constant speed, the larger L is, the more centripetal motion tends to occur; L greater than... At this time, the aircraft always flies with the minimum radius. The smaller L is, the more it tends to move in a centrifugal motion. When L is less than... When the drone is on a circle, it cannot form a circular trajectory. The value of L is related to the current ground speed. When the speed is high, the parameter should be increased. When the drone is on a circle, L... base The adjustment formula is as follows:

[0024] L base =L min *max(1, 1+L*(Vg) f -Vc min ));

[0025] For L minThe value corresponding to the minimum speed, K is the speed effect gain, according to η sp Find the coordinates of the desired position and the desired trajectory angle. The desired track angular velocity is given by K, where K is the angular velocity conversion gain. The roll angle command is obtained from the track angular deviation.

[0026]

[0027]

[0028] For cases where the drone has not yet reached the circle, there are two scenarios. First, when the drone is far from the center of the circle, it should enter the circumference in a tangential direction and set the desired position at the point of tangency between the drone and the circle, where the forward sight distance is relatively far. Second, when the drone is close to the center of the circle, the forward sight distance should be gradually shortened to transition to the case where the drone is on the circle. A piecewise linear function is introduced to represent the forward sight distance based on the distance between the drone and the center of the circle. By calculating the different forward sight distances in different cases, the angle offset value required for the drone to move to the expected position is calculated, thereby calculating the roll angle command value.

[0029] Specifically, based on the distance between the drone and the center of the circle... fo The foresight distance is represented by a piecewise linear function as follows:

[0030]

[0031]

[0032] In one implementation, in step S4, the desired trajectory for hovering and holding control needs to ensure that the UAV moves on a circle and is evenly distributed. Lateral control still uses a curve tracking control law, and the desired position is calculated in real time to keep the wingman on the circle. For speed control, due to the correlation between the hovering radius and the movement speed, the speed adjustment range is small when the radius is fixed. According to the distribution of UAVs, the desired curve distance between the current wingman and the lead UAV is dynamically allocated to achieve local closeness to the circumference and avoid UAVs overtaking each other on the circumference.

[0033] Specifically, each wingman calculates the roll angle instruction for its predicted target location. Through inter-aircraft communication, it is known that the center point of circling is consistent for wingmen in the same formation. The distance of each wingman i from the target's circular circling trajectory can be calculated using trigonometric functions. The angle φ of each drone to the center of the circle o The calculation is as follows:

[0034] φ o =arcsinn((yo -y f ) / dist fo );

[0035]

[0036] Thus, each drone in the group can calculate the distance of other drones to its estimated location, and then obtain the speed Vi of each drone through inter-drone communication, thereby calculating the estimated time for each other drone in the group to reach the target, and thus forming the hovering order of the drones in the group on the circular trajectory.

[0037] Specifically, the wingman will consider the predicted time of entry into the circle for all other aircraft in the formation and assess the distance traveled by each aircraft to define the order on the circle. Ultimately, the order will not change unless a fault occurs, thus adapting to flight on the circle.

[0038] In one implementation, step S5 requires estimating the aircraft's expected motion position for longitudinal control. First, considering the UAV on a circle, the difference in distance between the lead aircraft and the center O is calculated. When both differences do not exceed 1.1R, the distance of the lead aircraft on the circular curve is approximated based on the phase angle deviation. The wingman's desired position is related to the current spatial distribution of the lead aircraft. During flight, the desired intervals between the main aircraft and the lead aircraft need to be counted. The relationship between these intervals depends on the flight order obtained in the previous step, and the chord length of each interval is equal to the formation spacing. Finally, the main aircraft can calculate the desired axial distance between itself and the lead aircraft based on the desired phase interval, and then calculate the speed command.

[0039] In one implementation, in step S5, the longitudinal control aspect first considers the case where the UAV is on a circle, assuming dist lo dist fo Let be the distances from the wingman to the center O of the circle, respectively. When both do not exceed 1.1R, the distance dist of the wingman on the circular curve is approximately calculated based on the phase angle deviation. lf η l η f Let be the phase angles of the wingman on the circle, then the distance is calculated as follows:

[0040] dist lf =R*(η) l -η f );

[0041] When circling clockwise, if the lead aircraft's phase is ahead, then dist lf If positive, then negative. The desired position of the wingman is related to the spatial distribution of the current lead wingman. C is the desired number of intervals between the wingman and the lead wingman, and the chord length of each interval is equal to the formation spacing.

[0042] The expected curve distance between the aircraft and the lead aircraft can be calculated based on the expected phase interval. sp Speed ​​command Vc l Updated formula:

[0043]

[0044] d1 = dist lf -dist sp ;

[0045]

[0046] K is the speed control gain, set to 0.1, and the altitude command H... f Maintain control in the same manner as the wingman formation.

[0047] Specifically, all fixed-wing swarm UAVs will now perform state estimation for the entry and circling state during flight or in a simulated environment, forming a circling control strategy from the lead aircraft to the wingmen. For different roles, the lead aircraft will have stronger decision-making power over the entire circling, while the wingmen will adjust their circling control logic based on the parameters transmitted back by the lead aircraft, including trajectory maintenance on a circle, formation maintenance, and speed and roll angle calculations during the entry into a circular trajectory. This method addresses the characteristics of fixed-wing swarm UAVs, such as high speed, large maneuver radius, and transient changes in flight status. For circling missions, the fixed-wing swarm UAVs autonomously coordinate, thereby reducing the control pressure on formation collision avoidance and formation maintenance requirements. Its flight trajectory accuracy is significantly improved compared to swarms that rely solely on flight collision avoidance and preset formation circling, effectively increasing the capabilities and level of fixed-wing swarm UAVs in complex search and rescue and area retrieval missions, improving the autonomous decision-making ability and intelligence of UAVs, and ensuring the flight safety and stability of fixed-wing swarm UAVs.

[0048] The beneficial effects of this invention are as follows:

[0049] To address these issues, this invention proposes a multi-constraint fixed-wing swarm UAV hovering control method. This method adapts to various swarm control modes. Using the lead aircraft as a baseline, the lead aircraft initially formulates its hovering strategy under multi-constraint conditions and transmits hovering parameters and flight status to the wingman via inter-aircraft communication. Upon receiving the lead aircraft's hovering parameters, the wingman applies control constraints to itself and estimates and predicts motion by calculating the current curve distance. Finally, it calculates the roll angle command value to guide its own aircraft in entering a hovering circular trajectory. After entering the trajectory, the wingman calculates the speed control command value based on the desired hovering position to maintain formation control during hovering.

[0050] This invention provides a multi-constraint hovering control method for fixed-wing swarm UAVs. This method employs a hovering control strategy that proceeds sequentially from the lead aircraft to the wingmen. For different roles, the lead aircraft has a stronger decision-making power over the entire hovering maneuver, while the wingmen adjust their hovering control logic based on parameters transmitted from the lead aircraft. This method addresses the characteristics of fixed-wing swarm UAVs, such as high speed, large maneuver radius, and transient flight status changes. For hovering missions, the UAVs autonomously coordinate, reducing the control pressure on formation collision avoidance and formation maintenance. The flight trajectory accuracy is significantly improved compared to swarms relying solely on collision avoidance and pre-set formation hovering. This effectively enhances the capabilities and level of fixed-wing swarm UAVs in complex search and rescue and area retrieval missions, improves the autonomous decision-making ability and intelligence of the UAVs, and ensures the flight safety and stability of the fixed-wing swarm UAVs. Attached Figure Description

[0051] Figure 1 This is a flowchart illustrating a multi-constraint fixed-wing swarm UAV hovering control method according to the present invention.

[0052] Figure 2 This is a schematic diagram illustrating how the lead aircraft adjusts its own speed upwards based on multiple constraints, such as the status of the wingman, as demonstrated by the present invention.

[0053] Figure 3 This is a schematic diagram illustrating the calculation of the expected value and constraint calculation curve distance or roll angle command value for the wingman established in this invention.

[0054] Figure 4 This is a schematic diagram illustrating how the wingman in this invention calculates and sorts the expected times of all other wingmen.

[0055] Figure 5 This invention establishes a schematic diagram of the flight status and planning of each UAV after entering the hovering phase. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0057] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0058] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0059] In the description of the embodiments of the present invention, it should be noted that the terms "inner", "outer", "upper", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0060] Example 1

[0061] like Figure 1 As shown, this embodiment provides a hovering control method for fixed-wing swarm UAVs under multiple constraints, including the following steps:

[0062] S1. The lead aircraft obtains and analyzes the circling parameters through the circling command;

[0063] S2. The lead aircraft performs multi-constraint speed limit calculations based on the formation spacing adjustment requirements, the aircraft's own performance, and the speed limit caused by circling, to obtain the lead aircraft's constrained speed range, so that the lead aircraft can preferentially and quickly enter and maintain the circling state.

[0064] S3. If the wingman is outside the circle, the wingman calculates its desired phase angle and thus its desired position, and finally calculates the curved distance of the current position on the circle. This value can be used to evaluate the command value of the roll angle. If the wingman is on or inside the circle, the curved distance of the current position on the circle is finally calculated using the desired coordinates and desired track angle as constraints, and is used to evaluate the command value of the roll angle.

[0065] S4. The wingman is constrained by the flight distribution and hovering parameters transmitted by other drones. If the distance between the aircraft and the wingman is less than 280m, it is determined that the wingman and the lead aircraft are close in position. Then, the constraint of the nearest tangent circle is first determined to avoid the problem of misalignment on the same flight path after the aircraft enters the circle.

[0066] S5. After the wingman enters the circling state, the desired movement position is calculated, and the command value of the speed is calculated in order to control the flight of the wingman during the circling process.

[0067] The lead aircraft is a flight term referring to the aircraft that leads a formation in flight. In addition to the lead aircraft, smaller formations, including basic formations (two or three aircraft), also have their own lead aircraft. The lead aircraft's responsibility is to lead the formation (or wingmen) in carrying out missions.

[0068] Example 2

[0069] This embodiment is a further optimization based on Embodiment 1, as follows:

[0070] In step S1, when the lead aircraft receives a circling command or passes a preset point with circling attributes, it enters a circling state and sends circling parameters such as circling direction, center coordinates, and radius through inter-machine communication.

[0071] In step S1, the lead aircraft needs to synchronously parse the information of all aircraft in the same network, obtain their coordinates and flight planning formation to form a flight distribution. The flight distribution and the hovering information parameters obtained by the lead aircraft will be published to all fixed-wing swarm UAVs in the network through inter-aircraft communication.

[0072] like Figure 2 As shown, in step S2, before the lead aircraft enters the circling trajectory using the flight parameters obtained in step S1, it also adjusts its speed according to the distance to be flown in the wingman formation. If the lead aircraft is circling at the lowest or highest speed, since the lead aircraft and the wingman have the same aircraft performance, the wingman lacks speed adjustment space. In order to accelerate the formation of the circling formation and ensure that the lead aircraft does not change its flight radius due to speed adjustment, it is necessary to add a variety of constraints to limit the speed adjustment range on the basis of the speed control of the lead aircraft.

[0073] Specifically, let The default desired speed for the lead aircraft is set to K, with the speed gain set to K, and n representing the number of wingmen in the formation. Let be the formation waiting distance for the i-th wingman, and let the wingman waiting distance limit be . Speed ​​adjustment range is Vc adj Sat represents the limiting output, Vsat represents the speed limiting value adjusted by the lead aircraft when following the wingman, and the lead aircraft speed command. The updated formula is:

[0074]

[0075]

[0076] like Figure 3 In step S3, for the wingman, it is first necessary to consider the case where the drone is already on the circle. The phase angle of the desired position is calculated by the current phase angle of the drone, and the roll angle command is obtained by the curve distance between the desired position and the current position on the circle.

[0077] For situations where the drone has not yet reached the circle, there are two scenarios: First, if the drone is far from the center, it should enter the circle tangentially, setting the desired position at the point of tangency between the drone and the circle, resulting in a longer curve distance. Second, if the drone is close to the center, the curve distance should be gradually shortened until the drone is on the circle. A piecewise linear function is used to represent the curve distance based on the distance between the drone and the center. By calculating the different curve distances in different scenarios, the required angular offset for the drone to move to the desired position is determined, thus enabling the calculation of the roll angle command.

[0078] Specifically, in step S3, the case where the drone is already on the circle is first considered, η f η is the current phase angle of the wingman. sp Let be the phase angle of the desired position, and let L be the curvilinear distance between the desired position and the current position on the circle, with a value in the range [0, 2πR]. The relationship is as follows:

[0079]

[0080] With a constant speed, the larger L is, the more centripetal motion tends to occur; L greater than... At this time, the aircraft always flies with the minimum radius. The smaller L is, the more it tends to move in a centrifugal motion. When L is less than... When the drone is on a circle, it cannot form a circular trajectory. The value of L is related to the current ground speed. When the speed is high, the parameter should be increased. When the drone is on a circle, L... base The adjustment formula is as follows:

[0081] L base =L min *max(1,1+K*(Vg f -Vc min )) ；

[0082] For L min The value corresponding to the minimum speed, K is the speed effect gain, according to η sp Find the coordinates of the desired position and the desired trajectory angle. The desired track angular velocity is given by K, where K is the angular velocity conversion gain. The roll angle command is obtained from the track angular deviation.

[0083]

[0084]

[0085] For cases where the drone has not yet reached the circle, there are two scenarios. First, when the drone is far from the center of the circle, it should enter the circumference in a tangential direction and set the desired position at the point of tangency between the drone and the circle, where the forward sight distance is relatively far. Second, when the drone is close to the center of the circle, the forward sight distance should be gradually shortened to transition to the case where the drone is on the circle. A piecewise linear function is introduced to represent the forward sight distance based on the distance between the drone and the center of the circle. By calculating the different forward sight distances in different cases, the angle offset value required for the drone to move to the expected position is calculated, thereby calculating the roll angle command value.

[0086] Specifically, based on the distance between the drone and the center of the circle... fo The foresight distance is represented by a piecewise linear function as follows:

[0087]

[0088]

[0089] like Figure 4 As shown, in step S4, the desired trajectory for hovering and maintaining control needs to ensure that the UAV moves on a circle and is distributed at equal intervals. Lateral control still uses a curve tracking control law, and by calculating the desired position in real time, the wingman always stays on the circle. For speed control, due to the correlation between the hovering radius and the movement speed, the speed adjustment range is small when the radius is fixed. According to the distribution of UAVs, the desired curve distance between the current wingman and the lead UAV is dynamically allocated to achieve local closeness to the circumference and avoid UAVs overtaking each other on the circumference.

[0090] Specifically, each wingman calculates the roll angle instruction for its predicted target location. Through inter-aircraft communication, it is known that the center point of circling is consistent for wingmen in the same formation. The distance of each wingman i from the target's circular circling trajectory can be calculated using trigonometric functions. The angle φ of each drone to the center of the circle o The calculation is as follows:

[0091] φ o =arcsin((y o -y f ) / dist fo );

[0092]

[0093] Thus, each drone in the group can calculate the distance of other drones to its estimated location, and then obtain the speed Vi of each drone through inter-drone communication, thereby calculating the estimated time for each other drone in the group to reach the target, and thus forming the hovering order of the drones in the group on the circular trajectory.

[0094] The wingman will consider the predicted time of entry into the circle of all other aircraft in the formation and assess the distance traveled by each aircraft to define the order on the circle. The final order will not change in the absence of any faults, thus adapting to flight on the circle.

[0095] like Figure 5 As shown, in step S5, the expected motion position of the aircraft needs to be estimated for longitudinal control. First, consider the case of the UAV on a circle. By calculating the difference in distance between the lead aircraft and the center O of the circle, when both do not exceed 1.1R, the distance of the lead aircraft on the circular curve is approximately calculated based on the phase angle deviation. The expected position of the wingman is related to the current spatial distribution of the lead aircraft. During flight, it is necessary to count the expected intervals between the main aircraft and the lead aircraft. The relationship between these intervals depends on the flight order obtained in the previous step, and the chord length of each interval is equal to the formation spacing. Finally, the main aircraft can calculate the expected axial distance between itself and the lead aircraft based on the expected phase interval, and then calculate the speed command.

[0096] Specifically, in step S5, the longitudinal control first considers the case where the UAV is on a circle, assuming dist lo dist fo Let be the distances from the wingman to the center O of the circle, respectively. When both do not exceed 1.1R, the distance dist of the wingman on the circular curve is approximately calculated based on the phase angle deviation. lf η l η f Let be the phase angles of the wingman on the circle, then the distance is calculated as follows:

[0097] dist lf =R*(η) l -η f );

[0098] When circling clockwise, if the lead aircraft's phase is ahead, then dist lf If positive, then negative. The desired position of the wingman is related to the spatial distribution of the current lead wingman. C is the desired number of intervals between the wingman and the lead wingman, and the chord length of each interval is equal to the formation spacing.

[0099] The expected curve distance between the aircraft and the lead aircraft can be calculated based on the expected phase interval. sp Speed ​​command Vc l Updated formula:

[0100]

[0101] d1 = dist lf -dist sp ;

[0102]

[0103] K is the speed control gain, set to 0.1, and the altitude command H... f Maintain control in the same manner as the wingman formation.

Claims

1. A method for controlling the hovering of a fixed-wing swarm of unmanned aerial vehicles under multiple constraints, characterized in that, Includes the following steps: S1. The lead aircraft obtains and analyzes the circling parameters through the circling command; S2. The lead aircraft performs multi-constraint speed limit calculations based on the formation spacing adjustment requirements, the aircraft's own performance, and the speed limit caused by circling, to obtain the lead aircraft's constrained speed range, so that the lead aircraft can enter and maintain the circling state first. S3. If the wingman is outside the circle, the wingman calculates its desired phase angle and thus its desired position, and finally calculates the curve distance of the current position on the circle. The curve distance is used to evaluate the command value of the roll angle. If the wingman is on or inside the circle, the curve distance of the current position on the circle is finally calculated using the desired coordinates and desired track angle as constraints, and is used to evaluate the command value of the roll angle. For the wingman, the first thing to consider is that the drone is already on the circle. The phase angle of the desired position is calculated using the current phase angle of the wingman, and the roll angle command is obtained by calculating the distance between the desired position and the current position on the circle. For cases where the drone has not yet reached the circle, there are two scenarios. First, when the drone is far from the center of the circle, it should enter the circumference tangentially and set the desired position at the point of tangency between the drone and the circle, resulting in a longer curve distance. Second, when the drone is close to the center of the circle, the curve distance should be gradually shortened to transition to the case where the drone is on the circle. A piecewise linear function is introduced to represent the curve distance based on the distance between the drone and the center of the circle. By calculating the different curve distances in different cases, the angle offset value required for the drone to move to the desired position is calculated, thereby calculating the roll angle command value. First, consider the scenario where the drone is already on the circle. The current phase angle of the wingman. Let R be the phase angle of the desired position, R be the radius of the circle, and the distance between the desired position and the current position on the circle be... The range of values ​​is The relationship is as follows: ； At a constant speed, The larger it is, the more it tends to move towards centripetal motion. Greater than At that time, the aircraft always flew with the minimum radius. The smaller the size, the more it tends to move in a centrifugal motion. Less than At that time, a circular trajectory cannot be formed. The value of this parameter is related to the current ground speed. When the speed is high, the parameter should be increased. When the UAV is on a circle, The adjustment formula is as follows: ； This is the value corresponding to the minimum speed. For angular velocity conversion gain, according to Find the coordinates of the desired position and the desired trajectory angle. , To obtain the desired track angular velocity, the roll angle command is derived from the track angular deviation. : ； ； For cases where the drone has not yet reached the circle, there are two scenarios. First, when the drone is far from the center of the circle, it should enter the circumference in a tangential direction and set the desired position at the point of tangency between the drone and the circle, where the forward sight distance is relatively far. Second, when the drone is close to the center of the circle, the forward sight distance should be gradually shortened to transition to the case where the drone is on the circle. A piecewise linear function is introduced to represent the forward sight distance based on the distance between the drone and the center of the circle. By calculating the different forward sight distances in different cases, the angle offset value required for the drone to move to the desired position is calculated, thereby calculating the roll angle command value. Based on the distance between the drone and the center of the circle The foresight distance is represented by a piecewise linear function as follows: ； ； S4. The wingman is constrained by the flight distribution and hovering parameters transmitted by other drones. If the distance between the aircraft and the wingman is less than 280m, it is determined that the wingman and the lead aircraft are close in position. Then, the constraint of the nearest tangent circle is first determined to avoid the problem of misalignment on the same flight path after the aircraft enters the circle. S5. After the wingman enters the circling state, the desired movement position is calculated, and the command value of the speed is calculated in order to control the flight of the wingman during the circling process.

2. The method for controlling the hovering of a fixed-wing swarm UAV under multiple constraints according to claim 1, characterized in that, In step S1, when the lead aircraft receives a circling command or passes a preset point with circling attributes, it enters a circling state and sends the circling direction, center coordinates, and radius through inter-machine communication.

3. The method for controlling the hovering of a fixed-wing swarm UAV under multiple constraints according to claim 1, characterized in that, In step S1, the lead aircraft needs to synchronously parse the information of all aircraft in the same network, obtain their coordinates and flight planning formation to form a flight distribution. The flight distribution and the hovering information parameters obtained by the lead aircraft will be published to all fixed-wing swarm UAVs in the network through inter-aircraft communication.

4. The method for controlling the hovering of a fixed-wing swarm UAV under multiple constraints according to claim 1, characterized in that, In step S2, before the lead aircraft enters the circling trajectory using the flight parameters obtained in step S1, it also adjusts its speed according to the distance to be flown in the wingman formation. If the lead aircraft is circling at the lowest or highest speed, since the lead aircraft and the wingman have the same aircraft performance, the wingman lacks speed adjustment space. In order to accelerate the formation of the circling formation and ensure that the lead aircraft does not change its flight radius due to speed adjustment, it is necessary to add a variety of constraints to limit the speed adjustment range on the basis of the speed control of the lead aircraft.

5. The method for controlling the hovering of a fixed-wing swarm UAV under multiple constraints according to claim 4, characterized in that, In step S2, let This is the default expected speed for the primary engine. This refers to the number of wingmen in the formation. For the first The formation waiting distance of each wingman, and the wingman waiting distance limit value. The speed adjustment range is Sat represents the limiting output, Vsat represents the speed limiting value adjusted by the lead aircraft when following the wingman, and the lead aircraft speed command. The updated formula is: ； 。 6. The method for controlling the hovering of a fixed-wing swarm UAV under multiple constraints according to claim 1, characterized in that, In step S4, the desired trajectory for hovering and holding control needs to ensure that the UAV moves on a circle and is distributed at equal intervals. Lateral control still uses a curve tracking control law. By calculating the desired position in real time, the wingman is kept on the circle. For speed control, due to the correlation between the hovering radius and the movement speed, the speed adjustment range is small when the radius is fixed. According to the distribution of UAVs, the desired curve distance between the current wingman and the lead UAV is dynamically allocated to achieve local closeness to the circumference and avoid UAVs overtaking each other on the circumference. Specifically, each wingman calculates the roll angle instruction for its predicted target location. Through inter-aircraft communication, it is known that the center point of circling for wingmen in the same formation is consistent. The distance of each wingman i from the circular circling trajectory to the target can be calculated using trigonometric functions. The angle of each drone to the center of the circle The calculation is as follows: ； ； Thus, each drone in the group can calculate the distance of other drones to its estimated location, and obtain the speed Vi of each drone through inter-drone communication, thereby calculating the estimated time for each other drone in the group to reach the target, and thus forming the hovering order of the drones in the group on the circular trajectory.

7. The method for controlling the hovering of a fixed-wing swarm UAV under multiple constraints according to claim 1, characterized in that, In step S5, the expected motion position of the aircraft needs to be estimated for longitudinal control. First, consider the case of the UAV on a circle. By calculating the difference in distance between the lead aircraft and the center O of the circle, when both do not exceed 1.1R, the distance of the lead aircraft on the circular curve is approximately calculated based on the phase angle deviation. The expected position of the lead aircraft is related to the current spatial distribution of the lead aircraft. During flight, it is necessary to count the expected number of intervals between the main aircraft and the lead aircraft. The relationship of the number depends on the flight order obtained in the previous step. The chord length of each interval is equal to the formation spacing. Finally, the main aircraft can calculate the expected curve distance between itself and the lead aircraft based on the expected phase interval, and then calculate the speed command.

8. The method for controlling the hovering of a fixed-wing swarm UAV under multiple constraints according to claim 7, characterized in that, In step S5, the longitudinal control aspect first considers the case of the UAV on a circle, assuming... , From the wingman to the center When both distances do not exceed 1.1R, the distance between the wingman and the wingman on the circular curve is approximately calculated based on the phase angle deviation. , , Let be the phase angles of the wingman on the circle, then the distance is calculated as follows: ； When circling clockwise, if the lead aircraft's phase is ahead... A positive value indicates the desired position of the wingman, while a negative value indicates the desired position of the wingman is related to the current spatial distribution of the lead wingman. This represents the desired number of gaps between the main aircraft and the lead aircraft, where the chord length of each gap is equal to the formation spacing. The desired spherical distance between the aircraft and the lead aircraft can be calculated based on the desired phase interval. Speed ​​command Updated formula: ； ； ； For angular velocity conversion gain, set to 0.1, altitude command. Maintain control in the same manner as the wingman formation.

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