Dual-machine collision avoidance algorithm based on geometric method

Abstract

The invention belongs to the field of aircraft flight control systems, particularly relates to a dual-aircraft collision avoidance algorithm based on a geometric method, and aims at the situation that two aircrafts pursue back and forth and fly in opposite directions frequently in a cooperative task of the two aircrafts and the situation that a local minimum exists in a common potential field method. By monitoring the relative position and relative speed relation between the two aircrafts, the anti-collision control method based on the geometric method under the chasing or relative condition between the two aircrafts is provided according to the relative position and relative speed relation between the two aircrafts. Detecting whether the two aircrafts are in a relative or chasing state or not through an acquirable aircraft flight state design algorithm, and judging whether an anti-collision instruction is accessed through a certain time and distance safety standard; according to the anti-collision algorithm, the expected yaw angle of the aircrafts is calculated through the geometrical relationship, and the two aircrafts can keep a certain relative distance and do not collide through instruction tracking of the expected yaw angle of the aircrafts.

Description

Technical Field

[0001] The present application belongs to the field of aircraft flight control systems, and in particular relates to a dual-aircraft conflict avoidance algorithm based on a geometric method. Background Art

[0002] Compared with the situation where a single aircraft performs tasks with low efficiency and reliability, the collaborative work of multiple aircraft can not only reduce the work cost, but also improve the robustness of the overall task and the efficiency of task completion, and gradually become a solution for complex flight missions. In addition, multi-aircraft formations can effectively improve the reconnaissance and detection range of aircraft, provide more complete and extensive data, and facilitate more accurate battlefield assessment and monitoring. In the process of performing tasks, multi-aircraft formations often face problems including: formation formation maintenance, formation collision avoidance, formation collaborative obstacle avoidance, multi-aircraft communication, formation reconstruction, etc. Among these problems, formation collision avoidance is a key problem that must be solved in the mission, that is, in the process of the formation performing tasks, certain control methods are used to avoid collisions between aircraft in the group, and to ensure that the aircraft in the formation maintain a safe relative distance during the multi-aircraft formation. This will be of great significance for the multi-aircraft formation to complete the mission safely.

[0003] Collision avoidance refers to avoiding collisions between drones in a formation and maintaining a certain safe distance between them. Therefore, the purpose of collision avoidance is to ensure that the distance between drones in the formation is greater than the safe range. During the collision avoidance process, the drones in the formation need to be able to obtain the position information of other drones within a certain range and send their own position information to other drones at the same time, so that this information can be used for collision avoidance detection and calculation of collision avoidance instructions. Existing drone collision avoidance methods are mainly divided into two categories. The first category is a collision avoidance method based on route planning. The idea of ​​this method is mainly to convert the collision avoidance problem into multiple conflict-free route planning problems based on the pre-acquired environment and aircraft route information. Common algorithms for this idea include genetic algorithms, artificial potential field methods, A* algorithms, etc. The second category is a collision avoidance method based on local collision avoidance. This collision avoidance method is combined with a conflict detection method. There is no prior conflict information. It actively detects conflicts during flight and processes conflicts locally based on key information such as relative distance, speed, acceleration, angle, etc. between drones. After processing, it returns to the original route.

[0004] However, the existing methods cannot completely avoid collisions, so how to more effectively avoid UAV collisions is a problem that needs to be solved. Summary of the invention

[0005] The purpose of this application is to provide a dual-aircraft conflict avoidance algorithm based on the geometric method to solve the problem that the existing collision avoidance methods are difficult to effectively avoid UAV collisions.

[0006] The technical solution of the present application is: a dual-aircraft conflict avoidance algorithm based on a geometric method, comprising: performing expansion processing on obstacles in the environment, obtaining the speed and relative position relationship of the two aircraft, modeling the collision avoidance problem, and obtaining a collision avoidance model; the relative position relationship includes relative flight and pursuit; setting the initial conditions of the two aircraft, respectively obtaining the northeast sky speed and the geographical coordinates of the two aircraft, and calculating the relative geometric relationship of the two aircraft based on the collision avoidance model, the relative geometric relationship including relative position and relative speed;

[0007] According to the relative geometric relationship between the two aircraft, the time for the aircraft to reach the closest state from the current state is calculated, which is referred to as the closest time, and the current state of the two aircraft is determined according to the specific value of the closest time;

[0008] Get the current status of the two aircraft, and use the geometric method to perform anti-collision control between the two aircraft to determine whether the two aircraft are in a relative flight or catching up state. If so, determine whether a collision will occur in the future. If a collision will occur, when the two aircraft are flying relative to each other, perform anti-collision instructions a certain time before the collision; when the two aircraft are catching up, perform anti-collision instructions within a certain distance range.

[0009] Obtain the relative speed and relative position relationship of the two aircraft, control the relative speed of the two aircraft along the tangent of the other aircraft's safety area, calculate the relative speed deflection angle, and then solve the aircraft's yaw angle or roll angle instruction; control the aircraft to fly along the yaw angle or roll angle instruction;

[0010] Determine whether the exit collision avoidance conditions are met, and if so, exit collision avoidance.

[0011] Preferably, judging whether the conditions for exiting collision avoidance are met are specifically as follows: obtaining the current distance, safety distance and closest approach time information of the two aircraft in real time, and judging whether the two aircraft are in a safe state; if the distance between the two aircraft is greater than 2 times the safety distance, and the closest approach time is less than 0, it is considered that the two aircraft are safe, and collision avoidance can be exited and track instructions can be received; if the distance between the two aircraft is less than or equal to 2 times the safety distance, the yaw angle or roll angle instruction continues to be executed.

[0012] Preferably, the initial condition setting includes: setting the two aircraft at the same horizontal altitude, performing anti-collision detection between the two aircraft that can communicate with each other within a certain distance range, and setting a certain speed difference between the two aircraft; when the two aircraft communicate with each other, they transmit their own geographical coordinates and the northeast and sky three-axis speeds to each other.

[0013] Preferably, the relative position and relative speed calculation formula is:

[0014] dr=r-r0

[0015] dV=V-V0

[0016] Where dr is the relative position calculated by the aircraft, the difference in the three-dimensional geographic coordinates of the aircraft, r is the geographic coordinates of the aircraft, r0 is the geographic coordinates of another aircraft communicating with the aircraft, dV is the relative speed calculated by the aircraft, V is the northeast celestial speed of the aircraft, and V0 is the northeast celestial speed of another aircraft communicating with the aircraft.

[0017] Preferably, the time calculation formula for reaching the closest state from the current state is:

[0018]

[0019] Where τ is the time it takes for the aircraft to reach the closest state from the current state.

[0020] Preferably, when τ>0, it indicates that the time from the closest state to the current moment is greater than 0, that is, the closest state occurs in the future, and the two aircraft are in a state of approaching each other; when τ<0, it indicates that the time from the closest state to the current moment is less than 0, that is, the two aircraft are in a state of moving away from each other; when τ=0, it indicates that the two aircraft are currently in the closest state under the current heading and speed state. If the two aircraft always maintain the state of τ=0, it means that the heading and speed of the two aircraft have not changed and the distance between the two aircraft has not changed, that is, the two aircraft are in a relatively static state of motion.

[0021] Preferably, the conditions for determining the relative flight status of the two aircraft are summarized as follows:

[0022]

[0023] The judgment condition of the leading aircraft in the catch-up state is:

[0024]

[0025] The following aircraft judgment conditions in the overtaking state are:

[0026]

[0027] Preferably, the specific method for calculating the aircraft yaw angle or roll angle instruction is:

[0028] The angle between the reference direction and the relative distance is calculated by taking the difference between the angle between the relative speed and the relative distance. The angle between the reference direction and the relative distance is calculated as follows:

[0029]

[0030] Where ζ is the angle between the reference direction and the relative distance, ranging from [0,π], and R is the specified safety distance. If the distance between the two aircraft is less than the safety distance, it is considered that the two aircraft have collided.

[0031] The angle between relative speed and relative distance is calculated as follows:

[0032]

[0033] In the formula, θ' is the angle between the relative speed and the relative distance. When there is a risk of collision between the two aircraft, this angle is an obtuse angle;

[0034] The angle θ is the complementary angle of θ', that is:

[0035] θ=π-θ'

[0036] The roll angle σ is:

[0037]

[0038] Where σ l is the expected deflection angle of the relative velocity to the left; where σ r is the expected deflection angle for the relative velocity to deflect to the right.

[0039] Preferably, the exit anti-collision condition is designed as follows:

[0040] ||dr||≥2R&&τ<0.

[0041] The dual-aircraft conflict avoidance algorithm based on the geometric method of the present application is aimed at the situation in which two aircrafts often chase each other or fly towards each other in the collaborative mission of two aircrafts. The common potential field method has a local minimum situation. By monitoring the relative position and relative speed relationship between the two aircrafts, according to the relative position and speed relationship between the two aircrafts, a collision avoidance control method based on the geometric method for the two aircrafts in the situation of chasing or facing each other is proposed; the algorithm is designed based on the available aircraft flight status to detect whether the two aircrafts are in a relative or chasing state, and the access to the collision avoidance command is judged by certain time and distance safety standards; the collision avoidance algorithm solves the expected yaw angle of the aircraft through the geometric relationship, and by tracking its command, it ensures that the two aircrafts can maintain a certain relative distance and no collision occurs. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solution provided by the present application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present application.

[0043] Figure 1 This is a schematic diagram of the overall process of this application;

[0044] Figure 2 This is an illustration of the relative flight situation of the two aircraft for this application.

[0045] Figure 3 This is an illustration of the two aircraft's pursuit flight situation for this application.

[0046] Figure 4For this application, the closest time value represents the different state diagrams of the two machines.

[0047] Figure 5 This is a schematic diagram of collision avoidance based on the geometric method for this application. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] A dual-drone collision avoidance algorithm based on geometric method. Collision avoidance refers to avoiding collision between drones in a formation. The purpose of collision avoidance is to ensure that the distance between drones in the formation is greater than the safety range. During the collision avoidance process, drones in the formation need to be able to obtain the location information of other drones or send their own location information to other drones to achieve collision avoidance.

[0050] In order to achieve safe flight of UAVs and other aircraft in the common airspace, it is necessary to establish conflict zones related to UAVs, each of which is associated with a warning or conflict avoidance principle to avoid conflicts in the spatial intervals of the aircraft.

[0051] like Figure 1 As shown, the specific steps include:

[0052] Step S100, perform expansion processing on obstacles in the environment, obtain the speed and relative position relationship of the two aircraft, perform collision avoidance modeling, and obtain a collision avoidance model. The relative position relationship includes relative flight and pursuit.

[0053] First, we need to describe the safety range of the two aircraft and the maneuvering range of collision avoidance in the collision avoidance algorithm. Usually, in order to simplify the calculation, the obstacles in the environment are expanded in the collision avoidance algorithm. For example, the originally irregular obstacles are represented by their circumscribed spheres. In the collision avoidance problem between two aircraft in the horizontal plane, a safety distance R is designed around the aircraft. When the distance between the two aircraft is less than or equal to R, it is considered that the two aircraft cannot avoid a collision.

[0054] Two situations are described for relative and pursuit problems. Figure 2 As shown, the speed and relative position relationship of the two machines can be used to judge that the angle between the speed direction and relative position of the two machines is around 180°, with a fluctuation of 5°. Figure 3As shown, it can be judged by the relationship between the speed and relative position of the two aircraft. The speed of the front aircraft is relatively small, and the angle between its speed and relative position is about 0°; the speed of the rear aircraft is relatively large, and the angle between its speed and relative position is about 180°.

[0055] Step S200, initial conditions of the two aircraft are set, the northeast celestial speeds and geographic coordinates of the two aircraft are obtained respectively, and the relative geometric relationship of the two aircraft is calculated based on the collision avoidance model, and the relative geometric relationship includes relative position and relative speed.

[0056] The initial condition setting includes: setting the two aircraft at the same level, performing anti-collision detection between the two aircraft that can communicate with each other within a certain distance, and setting a certain speed difference between the two aircraft. When the two aircraft communicate with each other, they transmit their own geographical coordinates and the speed of the three axes of the northeast and sky.

[0057] The two aircraft respectively calculate the relative position and relative speed of the other aircraft relative to themselves:

[0058] dr=r-r0

[0059] dV=V-V0

[0060] Where dr is the relative position calculated by the aircraft, the difference in the three-dimensional geographic coordinates of the aircraft, r is the geographic coordinates of the aircraft, r0 is the geographic coordinates of another aircraft communicating with the aircraft, dV is the relative speed calculated by the aircraft, V is the northeast celestial speed of the aircraft, and V0 is the northeast celestial speed of another aircraft communicating with the aircraft.

[0061] Step S300, calculating the time for the aircraft to reach the closest state from the current state according to the relative geometric relationship between the two aircraft, referred to as the closest time, and judging the current state of the two aircraft according to the specific value of the closest time.

[0062] The time to reach the closest state from the current state is calculated as follows:

[0063]

[0064] Where τ is the time it takes for the aircraft to reach the closest state from the current state, referred to as the closest time, that is, the time it takes for the two aircraft to reach the closest distance from the current state.

[0065] like Figure 4The three cases describe different situations represented by the relationship between the output closest time and 0. When τ>0, it means that the time from the closest state to the current moment is greater than 0, that is, the closest state occurs in the future, and the two aircraft are in a state of approaching each other; when τ<0, it means that the time from the closest state to the current moment is less than 0, that is, the two aircraft are in a state of moving away from each other; when τ=0, it means that the two aircraft are currently in the closest state under the current heading and speed state. If the two aircraft always maintain the state of τ=0, it means that the heading and speed of the two aircraft have not changed and the distance between the two aircraft has not changed, that is, the two aircraft are in a relatively static state of motion.

[0066] Step S400, obtaining the current status of the two aircraft, and determining whether the two aircraft are in a relative flight state based on the geometric method of two-aircraft collision avoidance control. If so, executing the next step; if not, determining that the aircraft will not collide.

[0067] This application is aimed at the anti-collision control of two aircraft based on geometric method in relative or overtaking situations. It is necessary to judge the relative flight and overtaking situation of the two aircraft.

[0068] When two aircraft fly relative to each other, their speed directions are on the same straight line, which is the line connecting the centers of the two aircraft. That is, the speeds of the two aircraft are collinear with their relative positions and in opposite directions, with an angle of 180°. At the same time, the speeds of the two aircraft are in opposite directions. Therefore, the conditions for judging the relative flight status of the two aircraft are summarized as follows:

[0069]

[0070] τ>0

[0071] The first condition indicates that the angle between the speeds and relative positions of the two aircraft is close to 180°; the second condition indicates that the angle between the speeds of the two aircraft is close to 180°; and the third condition indicates that the two aircraft are flying relatively close to each other, rather than moving away from each other.

[0072] Step S500, obtain the current status of the two aircraft, and perform anti-collision control of the two aircraft based on the geometric method to determine whether the two aircraft are in a catching-up state, and determine whether a collision will occur in the future in combination with the relative flight status. If so, when the two aircraft are flying relative to each other, an anti-collision instruction is accessed a certain time before the collision of the two aircraft; when the two aircraft are catching up, an anti-collision instruction is accessed within a certain distance range.

[0073] When two aircraft are catching up, their speed directions are on the same straight line, which is the line connecting the centers of the two aircraft. For the slower aircraft in front, the speed direction of the aircraft is the same as the relative position direction. And the speed direction is the same as the other aircraft. Therefore, the judgment condition of the aircraft in front in the catching up situation is:

[0074]

[0075] τ>0

[0076] The first condition indicates that the angle between the speed of the aircraft in front and its relative position is close to 0°; the second condition indicates that the angle between the speeds of the two aircraft is close to 0°; and the third condition indicates that the speed of the aircraft in front is relatively low and they are flying relatively close to each other, rather than moving away from each other.

[0077] For the rear aircraft with a faster speed, the speed direction of the aircraft is opposite to the relative position direction. And the speed direction is the same as the other aircraft. Therefore, the judgment condition of the rear aircraft in the overtaking situation is:

[0078]

[0079] τ>0

[0080] The first condition indicates that the angle between the speed of the rear aircraft and the relative position is close to 180°; the second condition indicates that the angle between the speeds of the two aircraft is close to 0°; and the third condition indicates that the speed of the rear aircraft is higher and they are flying relatively close to each other, rather than moving away from each other.

[0081] Anti-collision detection is to judge in real time that if the two aircraft will reach the closest state in the future, and the closest distance is less than the designed safety distance, it is considered that a collision will occur in the future. However, since the aircraft has sufficient maneuverability, premature anti-collision is meaningless, so the judgment conditions are designed to access the anti-collision command when the judgment conditions are met and there is no collision. When the two aircraft are flying relative to each other, when the relative speed is large, the closest time is short, and anti-collision should be entered before a certain time, when the distance between the two aircraft is far; when the two aircraft are catching up, the relative speed is small. Even if the distance is very small, the closest time may be very long, so the design starts anti-collision at a certain distance range.

[0082] Step S600, designing anti-collision instructions: obtaining the relative speed and relative position relationship of the two aircraft, controlling the relative speed of the two aircraft along the tangent of the safety area of ​​the other aircraft, calculating the relative speed deflection angle, and then solving the aircraft yaw angle or roll angle instruction; controlling the aircraft to fly along the yaw angle or roll angle instruction to achieve anti-collision between the two aircraft.

[0083] Specifically: By analyzing the geometric factors such as the relative speed and position relationship of the two aircraft in the horizontal plane, it is concluded that the two aircraft can maintain a certain safe distance between them by changing the heading while keeping the speed unchanged. Anti-collision is performed on two aircraft that are at risk of collision. When the two aircraft detect the risk of collision, it is assumed that one of the aircraft is used as a reference, and the other aircraft approaches at a relative speed dV, and a safe area is drawn with the reference aircraft as the center and the safe distance as the radius, then the relative speed direction passes through the safe area.

[0084] To ensure that the distance between the two aircraft is kept above the safe distance, the relative speed direction between the two aircraft is changed so that the relative speed of the two aircraft is along the edge of the safe area. Figure 2 The relative velocity direction is close to the reference direction.

[0085] The aircraft's deflection angle is calculated by subtracting the angle between the reference direction and the relative distance and the angle between the relative speed and the relative distance. The angle between the reference direction and the relative distance is calculated as follows:

[0086]

[0087] Where ζ is the angle between the reference direction and the relative distance, which is in the range of [0,π], and R is the specified safety distance, which is the minimum distance allowed between the two aircraft, i.e. the radius of the safety area. If the distance between the two aircraft is less than the safety distance, it is considered that the two aircraft have collided.

[0088] The angle between relative speed and relative distance is calculated as follows:

[0089]

[0090] In the formula, θ' is the angle between the relative speed and the relative distance. When there is a risk of collision between the two aircraft, this angle is an obtuse angle. Figure 2 The angle θ is the complementary angle of θ', that is:

[0091] θ=π-θ'

[0092] When the default speed direction is on the right side of the relative speed, the value of θ is positive; when there is a risk of collision between the two aircraft, it means that the absolute value of θ is less than ζ. In the present invention, there are two ways to avoid collision in this collision scenario, namely: deflecting the relative speed direction to the left and deflecting the relative speed to the right. In both cases, the relative speed is deflected to the tangent direction of the safe area. For deflection to the left, the relative speed deflection angle should be:

[0093] σ l =-θ+ζ|

[0094] Where σ l is the expected deflection angle of the relative velocity to the left. For right deflection, the relative velocity deflection angle should be:

[0095] σ r =|θ-ζ|

[0096] Where σ r is the expected deflection angle of the relative speed to the right. In collision avoidance, by detecting the angle size, the present invention selects the direction with a smaller deflection angle. Therefore, for these two cases, there are two ways to choose:

[0097]

[0098] Step S700, obtain the current distance, safety distance and closest approach time information of the two aircraft in real time to determine whether the two aircraft are in a safe state. If the distance between the two aircraft is greater than 2 times the safety distance and the closest approach time is less than 0, it is considered that the two aircraft are safe, and the anti-collision can be exited and the track command is connected. If the distance between the two aircraft is less than or equal to 2 times the safety distance, the yaw angle or roll angle command is continued.

[0099] A local collision avoidance method is used to avoid collision after the risk of collision is detected. When certain conditions are met, it is considered that the two aircraft have successfully handled the collision avoidance problem and exited the collision avoidance. The aircraft's own guidance instructions guide the aircraft back to the original mission route.

[0100] When the two aircraft meet the closest approach time τ<0, it can be known that the two aircraft are in a state of moving away from each other. However, if the anti-collision system is immediately exited and the mission instruction is received, if the two aircraft have a tendency to approach, they will be immediately re-counted in the anti-collision system. Therefore, the present invention is designed to delay the exit from anti-collision system. The design allows the two aircraft to exit after they have enough distance, and the exit anti-collision condition is designed as follows:

[0101] ||dr||≥2R&&τ<0.

[0102] In summary, this application is aimed at the common potential field method that has local minimum value in the situation of two aircraft chasing each other and flying towards each other in the collaborative mission of two aircraft. By monitoring the relative position and relative speed relationship between the two aircraft, according to the relative position and speed relationship between the two aircraft, a collision avoidance control method based on geometric method is proposed for the situation of two aircraft chasing or facing each other; the algorithm for designing the available aircraft flight status is used to detect whether the two aircraft are in a relative or chasing state, and the access to the collision avoidance command is judged by certain time and distance safety standards; the collision avoidance algorithm solves the expected yaw angle of the aircraft through geometric relationship, and by tracking its command, it ensures that the two aircraft can maintain a certain relative distance and no collision occurs.

[0103] Finally, it should be noted that: the drawings of the embodiments disclosed in the present invention only involve structures related to the embodiments disclosed in the present invention, and other structures can refer to common designs. In the absence of conflicts, the same embodiment and different embodiments of the present invention can be combined with each other;

[0104] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A dual-machine collision avoidance algorithm based on geometric method, characterized in that: include: Obstacles in the environment are expanded to obtain the speed and relative position relationship of the two aircraft, and the collision avoidance problem is modeled to obtain the collision avoidance model; Relative position relationship includes relative flight and pursuit; Set the initial conditions of the two aircraft, obtain the northeast celestial speed and geographical coordinates of the two aircraft respectively, and calculate the relative geometric relationship of the two aircraft based on the anti-collision model, the relative geometric relationship includes relative position and relative speed; According to the relative geometric relationship between the two aircraft, the time for the aircraft to reach the closest state from the current state is calculated, which is referred to as the closest time, and the current state of the two aircraft is determined according to the specific value of the closest time; Get the current status of the two aircraft, and use the geometric method to perform anti-collision control between the two aircraft to determine whether the two aircraft are in a relative flight or catching up state. If so, determine whether a collision will occur in the future. If a collision will occur, when the two aircraft are flying relative to each other, perform anti-collision instructions a certain time before the collision; when the two aircraft are catching up, perform anti-collision instructions within a certain distance range. Obtain the relative speed and relative position relationship of the two aircraft, control the relative speed of the two aircraft along the tangent of the other aircraft's safety area, calculate the relative speed deflection angle, and then solve the aircraft's yaw angle or roll angle instruction; control the aircraft to fly along the yaw angle or roll angle instruction; Determine whether the exit collision avoidance conditions are met, and if so, exit collision avoidance.

2. The dual-machine collision avoidance algorithm based on geometric method as claimed in claim 1, characterized in that: The specific method for judging whether the conditions for exiting collision avoidance are met is as follows: obtaining the current distance, safety distance and closest approach time information of the two aircraft in real time to judge whether the two aircraft are in a safe state; if the distance between the two aircraft is greater than 2 times the safety distance and the closest approach time is less than 0, the two aircraft are considered safe, and collision avoidance can be exited and track instructions can be received; if the distance between the two aircraft is less than or equal to 2 times the safety distance, the yaw angle or roll angle instruction will continue to be executed.

3. The dual-machine collision avoidance algorithm based on geometric method as claimed in claim 1, characterized in that: The initial condition setting includes: setting the two aircraft at the same horizontal altitude, performing anti-collision detection between the two aircraft that can communicate with each other within a certain distance range, and setting a certain speed difference between the two aircraft; when the two aircraft communicate with each other, they transmit their own geographical coordinates and the three-axis speed of the northeast and sky to each other.

4. The dual-machine collision avoidance algorithm based on geometric method as claimed in claim 1, characterized in that: The relative position and relative speed calculation formula is: dr＝r-r0 dV=V-V0 Where dr is the relative position calculated by the aircraft, the difference in the three-dimensional geographic coordinates of the aircraft, r is the geographic coordinates of the aircraft, r0 is the geographic coordinates of another aircraft communicating with the aircraft, dV is the relative speed calculated by the aircraft, V is the northeast celestial speed of the aircraft, and V0 is the northeast celestial speed of another aircraft communicating with the aircraft.

5. The dual-machine collision avoidance algorithm based on geometric method as claimed in claim 4 is characterized by: The time calculation formula from the current state to the closest state is: Where τ is the time it takes for the aircraft to reach the closest state from the current state.

6. The dual-machine collision avoidance algorithm based on geometric method as claimed in claim 5, characterized in that: When τ>0, it means that the time from the closest state to the current moment is greater than 0, that is, the closest state occurs in the future, and the two aircraft are in a state of approaching each other; When τ<0, it indicates that the time from the closest state to the current moment is less than 0, that is, the two aircraft are in a state of moving away from each other; when τ=0, it indicates that the two aircraft are in the closest state under the current heading and speed. If the two aircraft always maintain the state of τ=0, it means that the heading and speed of the two aircraft have not changed and the distance between the two aircraft has not changed, that is, the two aircraft are in a relatively static state of motion.

7. The dual-machine collision avoidance algorithm based on geometric method as claimed in claim 4 is characterized by: The conditions for judging the relative flight status of the two aircraft are summarized as follows: τ>0 The judgment condition of the leading aircraft in the catch-up state is: τ>0 The following aircraft judgment conditions in the overtaking state are: τ>0.

8. The dual-machine collision avoidance algorithm based on geometric method as claimed in claim 4, characterized in that: The specific method for calculating the aircraft yaw angle or roll angle instruction is: The angle between the reference direction and the relative distance is calculated by taking the difference between the angle between the relative speed and the relative distance. The angle between the reference direction and the relative distance is calculated as follows: Where ζ is the angle between the reference direction and the relative distance, ranging from [0,π], and R is the specified safety distance. If the distance between the two aircraft is less than the safety distance, it is considered that the two aircraft have collided. The angle between relative speed and relative distance is calculated as follows: In the formula, θ' is the angle between the relative speed and the relative distance. When there is a risk of collision between the two aircraft, this angle is an obtuse angle; The angle θ is the complementary angle of θ', that is: θ=π-θ' The roll angle σ is: Where σ l is the expected deflection angle of the relative velocity to the left; where σ r is the expected deflection angle for the relative velocity to deflect to the right.

9. The dual-machine collision avoidance algorithm based on geometric method as claimed in claim 8, characterized in that: The exit anti-collision condition is designed as follows: ||dr||≥2R&&τ<0.

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