An anti-collision control method based on artificial potential field

Abstract

The application belongs to the field of aircraft flight control system, and particularly relates to an anti-collision control method based on artificial potential field, collision conditions of two aircrafts are set according to relative motion conditions and current flight data of the two aircrafts; the collision conditions of the two aircrafts are obtained, a potential field function is set, and a distance between the two aircrafts is designed as a virtual repulsive potential field; whether there is a collision risk is judged through the potential field function, if yes, a negative gradient in the potential field function is calculated, is converted into repulsive force between the two aircrafts, the repulsive force between the two aircrafts is solved into an aircraft roll angle instruction and a speed increment instruction, an anti-collision instruction is formed to control the two aircrafts; a relative position vector and a closest time of the two aircrafts are obtained, whether the anti-collision condition is met is judged, and the anti-collision is exited after the condition is met; by adopting the potential field function and performing instruction tracking, it is ensured that the two aircrafts can keep a certain relative distance and do not collide.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of aircraft flight control system, and particularly relates to an anti-collision control method based on artificial potential field. BACKGROUND

[0002] Compared with single aircraft, multi-aircraft can reduce work cost and improve robustness and efficiency of the whole task through cooperative work, and gradually becomes a solution to complex flight tasks. In addition, multi-aircraft cooperation can effectively improve the reconnaissance and detection range of aircraft, provide more complete and extensive data, and is beneficial to more accurate battlefield evaluation and monitoring. In the process of task execution, inter-aircraft anti-collision is a key problem that must be solved in the task, that is, in the process of multi-aircraft task execution, a certain control method is used to avoid collision between aircrafts in the group, and ensure that the aircrafts maintain a safe relative distance in the process of dual-aircraft task execution, which has very important significance for the safe completion of the task of dual-aircraft formation.

[0003] Anti-collision refers to avoiding collision between each unmanned aerial vehicle and maintaining a certain safe distance between each other, so that the purpose of anti-collision is to ensure that the distance between unmanned aerial vehicles is greater than the safe range. In the process of anti-collision, the unmanned aerial vehicle needs to obtain the position information of other unmanned aerial vehicles within a certain range and send its own position information to other unmanned aerial vehicles, so that the information can be used for anti-collision detection and anti-collision instruction calculation.

[0004] Therefore, how to use the information of the unmanned aerial vehicle to calculate the anti-collision instruction is a problem to be solved. SUMMARY

[0005] The application aims to provide an anti-collision control method based on artificial potential field to solve the problem that it is difficult to effectively prevent inter-aircraft collision in the prior art.

[0006] The technical scheme of the application is: an anti-collision control method based on artificial potential field, comprising: obtaining relative position and speed information of two aircrafts, calculating the closest distance value r m that the two aircrafts can reach if they continue to fly in the current state;

[0007] Based on the relative position and speed information of the two aircrafts, the time required for the two aircrafts to reach the closest distance value r m if they continue to fly in the current state, that is, the closest time, judging the relative motion condition of the two aircrafts according to the closest time;

[0008] Setting a collision condition of the two aircrafts according to the relative motion condition and the current flight data of the two aircrafts;

[0009] The two-aircraft collision condition is obtained, a potential field function is set, and the distance between the two aircrafts is designed as a virtual repulsive potential field. Whether there is a collision risk is determined by the potential field function. If yes, the negative gradient in the potential field function is calculated, which is converted into a repulsive force between the two aircrafts. The repulsive force between the two aircrafts is solved into an aircraft roll angle command and a speed increment command to form an anti-collision command for controlling the two aircrafts.

[0010] The relative position vector and the closest time of the current two aircrafts are obtained, and whether the anti-collision condition is met is determined. After the anti-collision condition is met, the anti-collision is exited.

[0011] Preferably, the closest distance value r m The calculation formula is:

[0012]

[0013] In the formula:

[0014] is a relative speed unit vector, that is, it represents the relative speed direction;

[0015] dr is a relative position vector;

[0016] r m is the distance of the closest future aircraft.

[0017] Preferably, the closest time τ calculation formula is:

[0018]

[0019] When τ>0, the two aircrafts are in a state of approaching each other; when τ<0, the two aircrafts are in a state of moving away from each other; and when τ=0, the two aircrafts are in a state of relative static motion.

[0020] Preferably, the set two-aircraft collision condition is: obtaining a safe distance R safe between the two aircrafts and the current inter-aircraft distance, when the two aircrafts meet the closest time τ>0 and r m <R safe , it is determined that the two aircrafts are approaching each other and will eventually “collide”.

[0021] Preferably, the potential field function is as follows:

[0022]

[0023] In the formula, U ij is a repulsive potential field existing around the aircraft, η is an adjustable parameter, and D is a specified repulsive potential field action range around the aircraft.

[0024] Preferably, the repulsive force between the two aircrafts is:

[0025]

[0026] F = F (d) in which F ij is the repulsive force between two aircrafts.

[0027] Preferably, the repulsive force solving aircraft speed increment instruction is:

[0028]

[0029] in which dV cmd is the aircraft speed increment instruction, representing the expected aircraft speed change, k v is the proportional coefficient for adjusting the relative size of speed change, F ij is the repulsive force acting on the aircraft output by the anti-collision algorithm, V represents the current speed of the aircraft, represents the size of the projection of the repulsive force in the direction of the aircraft speed;

[0030] The size of the roll angle instruction is:

[0031]

[0032] in which is the size of the roll angle instruction, k a is the proportional coefficient for adjusting the relative size of the roll angle change with the repulsive force, is the angle between the repulsive force and the direction of the aircraft speed, which is in the range of [0, π], and g is the acceleration of gravity;

[0033] The roll angle direction is determined by the repulsive force and the speed vector to determine:

[0034]

[0035] in which, the positive and negative signs of indicate the direction of the roll angle.

[0036] Preferably, the exit anti-collision condition is designed as:

[0037] ||dr||≥2R&&τ<0.

[0038] The artificial potential field-based anti-collision control method of the present application calculates the closest distance and the closest time of two aircrafts through geometric relationship, judges whether there is a collision risk between the two aircrafts in the future, and if there is a collision risk, solves the virtual repulsive force between the aircrafts through the potential field function, calculates the roll angle and speed instruction of the aircraft according to the repulsive force projection in the speed direction and the repulsive force projection perpendicular to the speed direction, adjusts the motion state (attitude and speed) of the aircraft, and through tracking of the instructions, ensures that the two aircrafts can maintain a certain relative distance and do not collide. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions provided by the present application, the accompanying drawings will be briefly introduced. Obviously, the accompanying drawings described below are only some embodiments of the present application.

[0040] Figure 1 The whole method flowchart of the present application.

[0041] Figure 2 The schematic diagram of the closest distance and the closest time calculated by the geometric method of the present application.

[0042] Figure 3 The diagram of the closest time value representing different states of two aircrafts.

[0043] Figure 4 The schematic diagram of the repulsive force and the speed relationship and the roll angle command relationship of the present application.

[0044] Figure 5 The simulation curve of the anti-collision detection and exit of the No. 1 aircraft of the present application.

[0045] Figure 6 The simulation curve of the speed command increment and the roll angle command of the No. 1 aircraft of the present application.

[0046] Figure 7 The simulation curve of the anti-collision detection and exit of the No. 2 aircraft of the present application.

[0047] Figure 8 The simulation curve of the anti-collision detection and exit of the No. 2 aircraft of the present application.

[0048] Figure 9 The simulation curve of the anti-collision trajectory of the two aircrafts of the present application. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0050] An anti-collision control method based on artificial potential field, as shown in Figure 1 , comprises the following steps:

[0051] Step S100, the relative position and speed information of two aircrafts are acquired, and the closest distance value r m that the two aircrafts can reach if they continue to fly in the current state is calculated.

[0052] The calculation and analysis are as shown in Figure 2 The calculation formula of the closest distance value r m is:

[0053]

[0054] In the formula:

[0055] It is a unit vector of relative velocity, that is, it represents the direction of relative velocity;

[0056] dr is a relative position vector;

[0057] r m This represents the closest distance the aircraft will ever approach in the future.

[0058] Step S200: Based on the relative position and speed information of the two aircraft, calculate the closest distance r that the two aircraft can reach if they continue flying in their current states. m The time required to reach the nearest point is the closest time; the relative motion of the two machines is determined based on the closest time.

[0059] The closest time τ is calculated as follows:

[0060]

[0061] τ is the closest distance r that the aircraft can reach from its current state. m The closest time, also known as the time between two machines, is the time it takes for the two machines to reach the closest point from their current state.

[0062] The specific method for judging the relative motion of the two aircraft is as follows: when τ > 0, the two aircraft are in a state of approaching each other; when τ < 0, the two aircraft are in a state of moving away from each other; when τ = 0, the two aircraft are in a state of relative stationary motion. Figure 3 This represents the relative motion of the two aircraft when τ takes different values.

[0063] Step S300: Set the collision conditions between the two aircraft based on their relative motion and current flight data.

[0064] The collision condition for the two aircraft is set as follows: obtain the safe distance R between the two aircraft. safe And the current distance between the two machines, when the closest time τ>0 and r m <R safe At that time, it can be known that the two machines are approaching each other and will eventually collide (the distance between the machines is less than the safe distance R). safe This indicates a collision.

[0065] In a specific instance, such as Figure 5 Based on the relative position and speed information of the two aircraft, calculate the closest distance r that the two aircraft can reach if they continue flying in their current state. m And the time τ required to reach the minimum distance while continuing flight in the current state.m <R safe , R safe = 1 km and τ < 0 should be collision avoidance, when the inter-aircraft distance is 1.5 km, start entering the collision avoidance.

[0066] Step S400, get two aircraft collision conditions, set the potential field function, design the distance between two aircraft as a virtual repulsive potential field; through the potential field function to determine whether there is a collision risk, if so, calculate the negative gradient in the potential field function, convert to two aircraft repulsive force, the two aircraft repulsive force is calculated as the aircraft roll angle command and speed increment command, form the anti-collision command to control two aircraft.

[0067] The potential field method of collision avoidance models the space environment centered on the aircraft body, so that there is a virtual potential field between the aircrafts. If there is another aircraft in the potential field, it will be repelled by the aircraft. This repulsive force has two effects on the aircraft movement: the first aspect makes the aircraft change the flight direction by rolling, making the aircraft move away from each other; the second aspect controls the aircraft to maintain a certain forward distance by accelerating or decelerating the aircraft.

[0068] Preferably, the potential field function is as follows:

[0069]

[0070] In the formula, U ij is the repulsive potential field existing around the aircraft, η is an adjustable parameter that affects the strength of the potential field. Under the same conditions, the larger η is, the stronger the potential field is. D is the range of the repulsive potential field around the aircraft. Within this range, the two aircrafts repel each other. Outside this range, the two aircrafts do not affect each other.

[0071] The negative gradient of the potential field function represents the force generated in the potential field. That is, when one aircraft is in the vicinity of another aircraft, the repulsive force between the two aircrafts is:

[0072]

[0073] In the formula, F ij is the magnitude of the repulsive force between the two aircrafts, and η is the adjustable parameter in the above formula. Under the same conditions, the larger η is, the greater the repulsive force is.

[0074] The method of calculating the roll angle command and the speed increment command of the aircraft on the horizontal plane decomposes the repulsive force into two directions along the speed direction and perpendicular to the speed direction. The force along the speed direction reflects the change in aircraft speed, and the analysis perpendicular to the speed direction reflects the change in aircraft attitude (roll). The specific design is as follows:

[0075] The speed increment command is calculated as follows:

[0076] The calculation of the aircraft speed increment command by the repulsive force is expressed as follows:

[0077]

[0078] The projection of the repulsive force in the direction of the velocity is positive if it is in the same direction as the velocity and negative if it is in the opposite direction.

[0079] In the formula, dV cmd is the aircraft velocity increment command, representing the expected change in the aircraft velocity, k v is a proportional coefficient for adjusting the relative size of the velocity change, F ij is the repulsive force acting on the aircraft output by the collision avoidance algorithm, V represents the current speed of the aircraft, represents the projection of the repulsive force in the direction of the aircraft velocity.

[0080] Solve the roll angle command:

[0081] The expression for the size of the roll angle command is:

[0082]

[0083] In the formula is the size of the roll angle command, k a is a proportional coefficient for adjusting the relative size of the roll angle change with the repulsive force, is the angle between the repulsive force and the direction of the aircraft velocity, taking values in the range [0, π], and g is the acceleration due to gravity.

[0084] The roll angle direction is determined by the repulsive force and the velocity vector :

[0085]

[0086] In the formula, the positive and negative signs of indicate the direction of the roll angle, which can be determined according to the coordinate system (American / Russian) in specific applications. The relationship between the repulsive force and the velocity vector and the roll angle command is shown in Figure 4 .

[0087] For example, Figure 6 , in a specific embodiment, the aircraft velocity increment command dV cmd is solved by the repulsive force between the two aircraft, the No. 1 aircraft decelerates; the No. 2 aircraft decelerates. The aircraft roll angle command γ cmd is solved by the repulsive force between the two aircraft, the No. 1 aircraft rolls to the right; the No. 2 aircraft rolls to the left.

[0088] Step S500, obtain the relative position vector and the closest time of the current two aircraft, and judge whether the exit collision avoidance condition is met. After meeting the condition, exit the collision avoidance.

[0089] When the aircraft follows the anti-collision instruction to avoid collision, if the inter-aircraft distance meets the safety range and the subsequent aircraft will not enter the anti-collision again, the aircraft should disconnect the anti-collision instruction and fly to the initial flight segment, so the exit anti-collision condition is designed as: Figure 7-9 ,

[0090] ||dr||≥2R&&τ<0.

[0091] In one embodiment, when the aircraft follows the anti-collision instruction to avoid collision, if the inter-aircraft distance meets the safety range and the subsequent aircraft will not enter the anti-collision again, the aircraft should disconnect the anti-collision instruction and connect the navigation closed-loop control to fly to the initial flight segment or heading. After the first aircraft and the second aircraft meet the inter-aircraft distance greater than 2 kilometers and the closest time less than 0, the two aircraft exit the anti-collision at the same time, and fly to the original flight segment after exiting the anti-collision.

[0092] In summary, the present application calculates the closest distance and the closest time of two aircrafts through geometric relationship, judges whether the two aircrafts have collision risk in the future, if there is collision risk, calculates the virtual repulsive force between the two aircrafts through the potential field function, calculates the rolling angle and speed instruction according to the repulsive force component projected on the speed direction and perpendicular to the speed direction, adjusts the aircraft motion state (attitude and speed), and ensures that the two aircrafts can maintain a certain relative distance and do not collide by tracking the instructions.

[0093] Finally, it should be noted that the present application discloses the structure involved in the embodiment, and other structures can be referred to the general design, and the same embodiment and different embodiments of the present application can be combined under the condition of no conflict.

[0094] Finally, the above-mentioned is only the preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A collision avoidance control method based on an artificial potential field, characterized in that, include: Obtain the relative position and speed information of the two aircraft, and calculate the closest distance r that the two aircraft can reach if they continue flying in their current state. m ; Based on the relative position and speed information of the two aircraft, calculate the closest distance r that the two aircraft can reach if they continue flying in their current states. m The time required to reach the nearest time is used to determine the relative motion of the two machines. The collision conditions between the two aircraft are set based on their relative motion and current flight data. Obtain the collision conditions between the two aircraft, set the potential field function, and design the distance between the two aircraft as a virtual repulsive potential field; determine whether there is a collision risk through the potential field function. If so, calculate the negative gradient in the potential field function, convert it into repulsive force between the two aircraft, and solve the repulsive force between the two aircraft into aircraft roll angle command and speed increment command to form a collision avoidance command for the control of the two aircraft. Obtain the current relative position vectors and closest time between the two machines, determine whether the conditions for exiting collision avoidance are met, and if so, exit collision avoidance.

2. The collision avoidance control method based on an artificial potential field as described in claim 1, characterized in that: The closest distance value r m The calculation formula is: In the formula: It is a unit vector of relative velocity, that is, it represents the direction of relative velocity; dr is a relative position vector; r m This represents the closest distance the aircraft will ever approach in the future.

3. The collision avoidance control method based on an artificial potential field as described in claim 2, characterized in that: The formula for calculating the closest time τ is: When τ > 0, the two aircraft are in a state of approaching each other; When τ < 0, the two aircraft are in a state of moving away from each other; when τ = 0, the two aircraft are in a state of relative stillness.

4. The collision avoidance control method based on an artificial potential field as described in claim 2, characterized in that: The set collision condition between the two machines is: obtaining the safe distance R between the two machines. safe And the current distance between the two machines, when the closest time τ > 0 and r m <R safe At that time, it was determined that the two machines were approaching each other and would eventually collide.

5. The collision avoidance control method based on an artificial potential field as described in claim 2, characterized in that: The potential field function is as follows: In the formula U ij η represents the repulsive potential field surrounding the aircraft, and D is an adjustable parameter; D defines the range of action of the repulsive potential field around the aircraft.

6. The collision avoidance control method based on an artificial potential field as described in claim 5, characterized in that: The repulsive force between the two machines is: In the formula F ij This represents the magnitude of the repulsive force between the two machines.

7. The collision avoidance control method based on an artificial potential field as described in claim 6, characterized in that, The command for calculating the aircraft velocity increment using repulsion force is: In the formula, dV cmd It is an aircraft speed increment command, symbolizing the expected change in aircraft speed, k v F is the proportionality coefficient that adjusts the relative magnitude of the change in speed. ij This is the repulsive force acting on the aircraft, output by the collision avoidance algorithm, where V represents the aircraft's current speed. This indicates the magnitude of the repulsive force projected in the direction of the aircraft's velocity; The roll angle command size is: In the formula To calculate the roll angle command size, k a It is a proportionality coefficient that adjusts the relative magnitude of the roll angle as the repulsive force changes. It is the angle between the repulsive force and the direction of the aircraft's velocity, and its value is in the range of [0,π]. g is the acceleration due to gravity. Roll angle direction is determined by repulsion. With velocity vector Determined by the outer product: In the formula, The sign indicates the direction of the roll angle.

8. The collision avoidance control method based on an artificial potential field as described in claim 2, characterized in that, The exit conditions for collision avoidance are designed as follows: ||dr||≥2R&&τ<0.

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