A method for safety tips on helicopter formation flight

Abstract

The present invention discloses a safety prompt method for helicopter formation flight. Aiming at the problems of formation maintenance and formation system ground collision avoidance of helicopter formation, the safety thresholds of formation maintenance and formation system ground collision avoidance during helicopter formation flight are discussed, and a safety prompt method is proposed. The method is based on the artificial potential field method to perform formation maintenance, prevent the helicopter formation from colliding with the terrain, and avoid collisions between helicopter formation members. When the helicopter encounters an obstacle and deviates from the formation maintenance area, the method will automatically perform a compound escape maneuver, greatly improving flight safety.

Description

Technical Field

[0001] The present invention belongs to the technical field of helicopter flight safety, and particularly relates to a method for prompting helicopter formation flight safety. Background Art

[0002] Helicopters, with their ultra-maneuverable and ultra-low-altitude flight capabilities, have become an important guarantee for air power. When helicopters perform tasks, they usually do not exist as an independent individual only. When a single helicopter performs a task, problems such as limited field of vision and limited attack range are likely to occur. In most cases, they appear in the form of helicopter formations. Compared with a single helicopter, a helicopter formation has higher task completion efficiency, success rate, and quality when performing tasks.

[0003] Helicopter formation flight means that two or more helicopters maintain formation flight according to specified intervals, crossing angles, and altitude intercepts. Due to the influence of various factors in actual flight, the intervals, distances, and altitude differences between formation helicopters cannot always remain unchanged. When the helicopters are too close, collisions are likely to occur, and when they are too far apart, it is easy to cause falling behind. Especially for high-speed helicopters, improper handling will lead to serious consequences.

[0004] Among helicopter airborne equipment, the cockpit traffic information display and automatic dependent surveillance-broadcast system can provide traffic situation information within a certain airspace centered on the helicopter and the position information of other helicopters in the formation. The terrain awareness and warning system and the air collision avoidance system can evaluate the safety status around the helicopter and prompt the pilot to avoid collisions. However, for helicopter formations, they must fly along a certain airspace at a specified interval for a long time, but the helicopter interval is much smaller than the warning threshold set by the traditional helicopter air collision avoidance system. If the traditional helicopter air collision avoidance system is directly applied to helicopter formations, a series of problems such as a high false alarm rate will occur. Summary of the Invention

[0005] In order to solve the above problems, the present invention discloses a method for prompting helicopter formation flight safety, aiming to solve the problems of formation maintenance and formation anti-collision for helicopter formations.

[0006] The technical solution of the present invention is as follows:

[0007] A method for prompting helicopter formation flight safety, characterized by comprising the following steps:

[0008] Step 1, determine the adjustment mechanism of the helicopter formation, and set a reference helicopter in the formation;

[0009] Step 2: Determine the safety threshold for helicopter formation maintenance based on the relative motion between any two adjacent helicopters in the helicopter formation and the characteristic size of the holding area; based on the escape trajectory of the helicopter in the current flight state, obtain the forward-looking warning boundary of the helicopter to determine the safety threshold for the helicopter formation to avoid ground collision;

[0010] Step 3: When the helicopter in the formation exceeds the formation maintenance safety threshold or the formation anti-ground collision safety threshold, give an alarm; if it exceeds both the formation maintenance safety threshold and the formation anti-ground collision safety threshold at the same time, go to Step 4;

[0011] Step 4: Determine the comprehensive collision avoidance method for the helicopter formation and perform compound escape maneuvers.

[0012] Preferably, the safety threshold for formation maintenance is the spatial range formed when all adjacent helicopters meet the restriction conditions of the holding area; the holding area is: determine the center of the holding area of each remaining helicopter in the formation according to the actual position of the reference helicopter and the basic parameters of the formation, and radiate a certain geometric space area outward. If the remaining helicopters deviate from this geometric area, the helicopter formation will give an alarm for formation maintenance; perform vertical collision analysis and longitudinal collision analysis respectively based on the relative motion between any two adjacent helicopters to determine the characteristic size of the holding area.

[0013] Preferably, the characteristic size of the holding area includes height and radius, and the vertical safety threshold h w of the holding area is expressed as h w = h 0 where h 0 represents the predetermined vertical distance between two adjacent helicopters in the formation; judge whether the vertical distance between two adjacent helicopters is less than the vertical safety threshold h based on the vertical collision analysis of two adjacent helicopters w .

[0014] Preferably, determine the radius r w of the holding area based on the lateral collision analysis of two adjacent helicopters In the formula, d 0 represents the lateral distance between two adjacent helicopters in the formation, that is, the distance between the vertical projections of the centers of the holding areas of the two helicopters on the ground. k is the safety factor, ΔV is the ground speed difference between two adjacent helicopters, g is the acceleration due to gravity, T is the pilot's reaction time, and α is the pitch angle; determine the radius of the holding area from the flight state parameters of two adjacent helicopters to determine the safety threshold.

[0015] Preferably, the forward-looking warning boundary includes a longitudinal warning boundary and a lateral warning boundary. The longitudinal warning boundary is a trajectory formed by leaving a minimum safety height ΔH below the escape trajectory of the helicopter based on the escape trajectory of the helicopter. The lateral warning boundary is a warning boundary with a certain width related to the distance ahead.

[0016] Preferably, the lateral warning boundary is specifically: on the basis of the starting width of the lateral warning boundary of the helicopter, the side boundary of the forward-looking warning is extended forward at a certain skew angle ξ. The width L of the lateral warning boundary at a certain distance x ahead of the helicopter can be expressed as: L = L 0 + 2x tan ξ.

[0017] Preferably, the method for determining whether the helicopter formation exceeds the safety threshold for formation maintenance in step 3 is: monitoring the flight states of each helicopter and whether they are in a safe state in real time at a certain frequency. When a helicopter in the formation deviates from the determined holding area, a formation-keeping warning signal is issued; when the forward-looking warning boundary of the helicopter intersects with the terrain, a warning signal is issued.

[0018] Preferably, in step 4, the comprehensive collision avoidance method for the helicopter formation is determined based on the artificial potential field method. Among them, the artificial potential field method is specifically: constructing an artificial potential function representing the artificial potential field and applying it to the helicopter that simultaneously issues terrain collision avoidance warnings and formation-keeping warnings. Among them, the artificial potential field includes an attractive potential field and a repulsive potential field, which generate an attractive force on the center of the formation holding area and a repulsive force on the obstacles detected in the formation anti-collision ground.

[0019] Preferably, the magnitude of the attractive force is expressed as: In the formula, represents the negative gradient of the gravitational potential field, and k f is the gravitational potential field gain coefficient, and ρ(q, q c ) = q c - q is the relative distance between the helicopter and the center of the formation holding area. The magnitude of the repulsive force is expressed as:

[0020] In the formula, represents taking the negative gradient as the attraction, and k 0 is the repulsive potential field gain coefficient, and ρ(q, q 0 ) = q 0 - q is the relative distance between the helicopter and the obstacle, and ρ 0 is the influence radius of the obstacle. Then the resultant external force received by the helicopter is: F total = F f + F 0 , and based on F total the maneuvering control of the helicopter is realized.

[0021] Preferably, the two component forces acting on the helicopter are weighted so that the priority of terrain collision avoidance is higher than that of formation maintenance to ensure the safety during the helicopter's composite escape process.

[0022] Advantageous effects:

[0023] (1) A helicopter formation flight prompting method proposed by the present invention adopts a "leader - follower" flight mode.

[0024] Only by giving the maneuvering trajectory of the "leader" can the entire formation be controlled. The algorithm is simple and effective, and the response speed is fast.

[0025] (2) Compared with the traditional helicopter flight safety system, the helicopter formation flight prompting method proposed by the present invention has a lower false alarm rate, can effectively prevent the helicopter formation from colliding with the terrain and the collision between two helicopters in the formation, and improves the flight safety of the helicopter formation. Description of the drawings

[0026] Figure 1 The figure shows a flowchart of a helicopter formation flight safety prompting method proposed by the present invention;

[0027] Figure 2 The figure shows a schematic diagram of the safety threshold for helicopter formation maintenance proposed by the present invention;

[0028] Figure 3 The figure shows a schematic diagram of the forward - looking warning boundary of a helicopter proposed by the present invention;

[0029] Figure 4 The figure shows a force diagram of the members of a helicopter formation based on the artificial potential field method proposed by the present invention;

[0030] Figure 5 The figure shows a horizontal plane projection diagram of the flight trajectory of a helicopter formation without obstacles in an embodiment of the present invention;

[0031] Figure 6 The figure shows a schematic diagram of the horizontal plane projection of the flight trajectory for helicopter formation maintenance and collision avoidance in an embodiment of the present invention. Detailed implementation manners

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] The present invention discloses a safety prompting method for helicopter formation flight. Aiming at the problems of formation maintenance and anti-ground collision of the formation system in the "leader-follower" mode of helicopter formation, the safety thresholds for formation maintenance and anti-ground collision during the flight of helicopter formation are discussed, and a safety prompting method is proposed. This method is based on the artificial potential field method for formation maintenance, preventing the helicopter formation from colliding with the terrain and avoiding collisions between the members of the helicopter formation. When the helicopter encounters an obstacle and deviates from the formation maintenance area, this method will automatically execute a composite escape maneuver, greatly improving flight safety.

[0034] As Figure 1 shown, the present invention discloses a safety prompting method for helicopter formation flight, including the following steps:

[0035] Step 1, determine the adjustment mechanism of the helicopter formation.

[0036] In a helicopter formation, in order to ensure the integrity of the formation, there must be a formation adjustment mechanism, that is, the flight formation of the helicopter formation. The flight formation of the helicopter formation is determined according to the specific flight tasks of the formation helicopters. Different flight tasks have different formation shapes, and different types of helicopter formations also have different shapes. There are three common flight formations for helicopter formation flight: "leader-follower" formation, square formation, and triangular formation. In this embodiment, it is preferably that the helicopter flight formation adopts the "leader-follower" flight mode, and different helicopters are located at different positions of the reference point, thus forming a certain formation. Based on the "leader-follower" flight mode, only the maneuvering trajectory of the "leader" needs to be given to control the entire formation, and the algorithm is simple and effective with a fast response speed.

[0037] In the "leader-follower" flight mode of the helicopter formation, the helicopters are divided into two complementary roles: "leader" and "follower". The "leader" determines the flight route, and the "follower" follows the "leader" at a certain position and angle to maintain the formation. During the process of maintaining the formation, each "follower" tries to keep its relative position at the position where it should be, so as to minimize the accumulated error of deviating from the optimal position during the movement. The overall goal of the system is to balance the positions and speeds of each individual to make the overall performance of the system reach the optimal.

[0038] Step 2, determine the safety threshold for helicopter formation maintenance based on the relative movement between any two adjacent helicopters in the helicopter formation and the characteristic size of the maintenance area. Based on the escape trajectory of the helicopter in the current state, obtain the forward-looking warning boundary of the helicopter to determine the safety threshold for anti-ground collision of the helicopter formation.

[0039] Specifically,

[0040] Step 2.1, determine the safety threshold for helicopter formation maintenance:

[0041] Helicopter formation keeping requires detecting the positions of the entire formation and determining the correct positions of the helicopters in the formation according to the current environmental information. Considering the limited navigation and positioning accuracy, the helicopter following flight needs to be restricted within a certain formation-keeping area. Referring to the protected airspace of the ATC standard TCAS, the holding area range of each helicopter in the formation can be set as a cylinder, and the holding area ranges of all the aircraft in the formation together constitute the formation-keeping area range. When the "follower" deviates from this area, a formation-keeping warning will be issued. Among them, the holding area is: a formation-keeping area formed by radiating a certain geometric space area outward from the center of the holding area of each helicopter in the formation determined according to the actual position of the "leader" and the basic parameters of the formation. If the "follower" deviates from this geometric area, the helicopter formation will issue a formation-keeping warning. In addition, the safety threshold of helicopter formation keeping can be determined by analyzing the relative motion between adjacent helicopters and the characteristic dimensions of the formation-keeping area. The safety threshold of formation keeping should include the vertical height and relative distance between adjacent helicopters in the formation.

[0042] According to the vertical collision analysis of adjacent helicopters, the height of the holding area can be determined.

[0043] As Figure 2 shown, when both of two adjacent helicopters are located within their respective holding areas, the most dangerous situation is regarded as when the lower boundary of the holding area of the upper helicopter coincides exactly with the upper boundary of the holding area of the lower helicopter. Among them, the holding area height is the predetermined height difference between adjacent helicopters in the formation, and the vertical safety threshold h w of the helicopter formation holding area can be expressed as:

[0044] h w = h 0

[0045] It is stipulated the minimum vertical distance between adjacent upper and lower helicopters in the formation, and this distance is the predetermined vertical distance h 0 .

[0046] According to the lateral collision analysis, the radius of the holding area can be determined. As Figure 2 shown, assuming that the reason for this warning is that the speed of the rear helicopter is greater than that of the front helicopter, the escape maneuver is to decelerate to the same speed as the front helicopter, and the forward distance of this escape process should include the forward flight distance during the reaction time and the forward distance during the deceleration process.

[0047] The flight distance s during the uniform deceleration period of the helicopter can be expressed as:

[0048]

[0049] Where s is the distance to decelerate to hover, a is the deceleration acceleration, and t is the time required for the deceleration process.

[0050] Regarding ΔV as the ground speed difference between two adjacent helicopters, we can obtain:

[0051]

[0052] Assume that the helicopter maintains a pitch angle α during the deceleration process, and the forward distance during the escape process can be expressed as:

[0053]

[0054] Where g is the acceleration due to gravity and T is the pilot's reaction time.

[0055] By considering the safety factor k, the distance d between the two holding areas of the helicopter is finally obtained s as:

[0056]

[0057] The radius r of the helicopter formation holding area w can be expressed as:

[0058]

[0059] Where d 0 represents the lateral distance between two adjacent helicopters in the formation, that is, the distance between the vertical projections of the centers of the holding areas of the two helicopters on the ground. k is the safety factor, ΔV is the ground speed difference between two adjacent helicopters, g is the acceleration due to gravity, T is the pilot's reaction time, and α is the pitch angle. The radius of the holding area is determined by the flight state parameters of two adjacent helicopters, and the safety threshold is determined accordingly.

[0060] Step 2.2, determine the anti-collision ground safety threshold of the helicopter formation:

[0061] Calculate the escape trajectory of the helicopter in the current flight state in real time, and calculate the forward warning boundary of the helicopter as the anti-collision ground safety threshold of the helicopter formation based on this.

[0062] Specifically, determine the forward warning boundary of HTAWS as the safety threshold for ground collision avoidance. As shown in Figure 3, during the flight of the helicopter, calculate the escape trajectory of the helicopter in the current state in real time, and calculate the forward warning boundary of the helicopter based on this. The forward terrain warning boundary of the helicopter generally consists of a longitudinal warning boundary and a lateral warning boundary.

[0063] Among them, the vertical warning boundary is the trajectory formed by adding the minimum safety height reserved after the escape trajectory. After obtaining the escape trajectory of the helicopter through a high-precision helicopter flight dynamics model, a safety distance should also be left below it, which is the minimum safety height (ΔH). According to the requirements in TSO-194C, the minimum safety height can be set to 150 meters. However, during the takeoff or landing phase, the helicopter often flies at a very low altitude. At this time, to reduce false alarms, the value of the minimum safety height should be correspondingly reduced. The value of the minimum safety height is related to the flight speed of the helicopter, the landing gear configuration, and the distance of the helicopter from the nearest runway.

[0064] Preferably, when the helicopter flies over a ridge at a low altitude, to avoid false alarms, the forward warning boundary needs to be additionally trimmed. When trimming the boundary, the system pre-sets an upper angle limit value θ sx , an angle reference value δ, and an offset distance h. The trimming angle can be expressed as: θ jc = min(γ, θ sx ).

[0065] The lateral warning boundary is the warning boundary of a range with a certain width related to the distance ahead. During the flight of the helicopter formation, the position of the helicopter has a certain lateral uncertainty. Therefore, the warning boundary should have a certain width. The greater the distance ahead, the greater the position uncertainty of the helicopter. Therefore, the greater the width of the warning boundary should be ahead. For this reason, on the basis of the starting width, it is extended forward at a certain skew angle ξ to obtain the side boundary of the forward warning. The lateral boundary width L at a certain distance x ahead of the helicopter can be expressed as:

[0066] L = L 0 + 2xtanξ

[0067] Step 3, perform formation maintenance judgment. Formation maintenance mainly includes two parts: 1. Maintaining the formation shape among helicopter formations; 2. Anti-ground collision of helicopter formations. When the helicopter formation exceeds the safety threshold of formation shape maintenance or the safety threshold of formation anti-ground collision, an alarm is issued; if both the safety threshold of formation shape maintenance and the safety threshold of formation anti-ground collision are exceeded, go to Step 4.

[0068] Specifically,

[0069] Detect whether the helicopter formation exceeds the safety threshold of formation shape maintenance:

[0070] During the flight of the helicopter formation, the center of the safety range of each "follower" is determined by the position of the "leader", and the size of the warning range is determined by the flight state parameters of two adjacent helicopters. The flight states of each helicopter and whether it is in a safe state are monitored in real time at a certain frequency. When it is detected that a "follower" flies out of the formation shape maintenance area, an alarm is issued.

[0071] Detect whether the helicopter formation exceeds the safe threshold for formation anti-collision with the ground:

[0072] Compare the forward-looking terrain warning boundary with the elevation data in the terrain database. When the two intersect, the system will issue an alarm signal to prompt the pilot to perform a maneuver to get out.

[0073] When it is detected that the helicopter formation simultaneously exceeds the safe threshold for formation maintenance and the safe threshold for formation anti-collision with the ground, proceed to step 4 for comprehensive collision avoidance maneuver processing.

[0074] Step 4, determine the comprehensive collision avoidance method for the helicopter formation. When the helicopter formation simultaneously triggers the formation maintenance alarm and the ground collision avoidance alarm, use the artificial potential field method to perform a composite escape maneuver.

[0075] Specifically, propose a comprehensive collision avoidance method for the helicopter formation in combination with the determined formation maintenance and anti-collision with the ground safety thresholds. If the formation maintenance and terrain anti-collision alarms are triggered simultaneously, use the artificial potential field method to perform a composite escape maneuver, which can effectively prevent the occurrence of helicopter formation ground collision accidents and collisions between formation members.

[0076] Apply the attractive potential field to the center of the formation maintenance area, and apply the repulsive potential field to the obstacles detected in the formation anti-collision with the ground. When the terrain anti-collision alarm and the formation maintenance alarm occur simultaneously, a distance-related function is generated for the helicopter with the alarm, which is called the artificial potential function. The force diagram of the "follower" under the artificial potential field is as Figure 4 shown, where an attractive force is generated at the center of the formation maintenance area and a repulsive force is generated by the obstacle.

[0077] Construct the attractive potential field function, which can be expressed as:

[0078]

[0079] In the formula, k f is the gravitational potential field gain coefficient, ρ(q,q c ) = q c -q is the relative distance between the helicopter and the center of the formation maintenance area.

[0080] The corresponding magnitude of the attractive force can be expressed as the negative gradient of the gravitational potential field:

[0081]

[0082] Construct the repulsive potential field function, which can be expressed as:

[0083]

[0084] In the formula, k 0 is the repulsive potential field gain coefficient, ρ(q,q 0 ) = q 0-q is the relative distance between the helicopter and the obstacle, ρ 0 is the influence radius of the obstacle.

[0085] Taking the negative gradient as the gravitational force, the repulsion function can be expressed as:

[0086]

[0087] The helicopter formation moves under the combined force of attraction and repulsion. The combined external force on the helicopter can be expressed as: F total =F f +F 0 , based on F total Realize maneuver control of the helicopter.

[0088] In addition, the priority of terrain collision avoidance is set higher than that of formation maintenance, and the weighted average method is used to weight the two components of the helicopter so that the weight of the component with higher priority is higher, so as to ensure the safety of the helicopter during the composite escape process. That is, in the actual formation flight process, when the safety threshold of formation maintenance and the safety threshold of formation collision avoidance are exceeded at the same time, the helicopter formation performs an escape maneuver, and collision avoidance control is performed first. When the forward-looking warning boundary of the helicopter is separated from the collision avoidance warning boundary, that is, the forward-looking warning boundary does not intersect with the elevation data, the terrain warning is lifted, and at the same time, the obstacle repulsion is removed in the artificial potential field, and only the gravitational force of formation maintenance is retained. All terrain warnings are lifted first, and then the formation is restored.

[0089] In order to verify the effectiveness and correctness of the helicopter formation flight safety prompt method proposed in the present invention, a numerical example is used for simulation verification. The helicopter formation is set to adopt the "navigator-follower" flight mode, in which the number of "navigators" is 1, the number of "followers" is 4, and the initial speed of the "navigator" and the "follower" is the same.

[0090] Based on the simulation scene, the flight trajectory of the helicopter formation with and without obstacles is simulated. The horizontal plane projection of the flight trajectory of the helicopter formation without obstacles is as follows: Figure 5 When the helicopter formation flight enters the obstacle collision area, the follower's flight trajectory will deviate. After getting rid of the obstacle, the formation members return to the formation holding area after a period of time under the action of gravity. The horizontal plane projection of the helicopter formation maintenance and anti-collision flight trajectory is shown in Figure 6 The simulation results show that the helicopter flight safety prompt method proposed in the present invention can achieve ground collision avoidance and formation maintenance for helicopter formations, greatly improving the flight safety of helicopter formations.

[0091] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for safety prompting of helicopter formation flight, characterized in that, it includes the following steps: Step 1, determine the adjustment mechanism of the helicopter formation, and set a reference helicopter in the formation; Step 2, based on the relative motion between any two adjacent helicopters in the helicopter formation and the characteristic size of the holding area, determine the safety threshold for maintaining the helicopter formation. Based on the escape trajectory of the helicopter in the current flight state, obtain the forward-looking warning boundary of the helicopter to determine the safety threshold for the helicopter formation to avoid hitting the ground. Specifically, The characteristic dimensions of the holding area include height and radius. Based on the vertical collision analysis of two adjacent helicopters, it is determined whether the vertical distance between two adjacent helicopters is less than the vertical safety threshold h of the holding area height w , denoted as h w = h 0 , where h 0 represents the predetermined vertical distance between two adjacent helicopters in the formation; Determine the radius r of the holding area based on the lateral collision analysis of two adjacent helicopters w , denoted as In the formula, d 0 represents the lateral distance between two adjacent helicopters in the formation, that is, the distance between the vertical projections of the two helicopters on the ground at the center of the area. k is the safety factor, ΔV is the ground speed difference between two adjacent helicopters, g is the acceleration due to gravity, T is the pilot's reaction time, and α is the pitch angle. The radius of the holding area is determined by the flight state parameters of two adjacent helicopters, and the safety threshold is determined accordingly. the forward-looking warning boundary includes a longitudinal warning boundary and a lateral warning boundary. The longitudinal warning boundary is: a trajectory formed by reserving a minimum safety height ΔH below the escape trajectory based on the helicopter escape trajectory; the lateral warning boundary is a warning boundary with a certain width related to the distance ahead, that is, on the basis of the starting width of the helicopter lateral warning boundary, it extends forward at a certain skew angle ξ to obtain the side boundary of the forward-looking warning. The width L of the lateral warning boundary at a certain distance x ahead of the helicopter is expressed as: L = L 0 + 2xtanξ; Step 3, when the helicopter in the formation exceeds the safety threshold for maintaining the formation or the safety threshold for the formation to avoid hitting the ground, give an alarm; if it exceeds both the safety threshold for maintaining the formation and the safety threshold for the formation to avoid hitting the ground at the same time, go to Step 4; Step 4, determine the comprehensive collision avoidance method for the helicopter formation and perform a composite escape maneuver.

2. The method for safety prompting of helicopter formation flight according to claim 1, characterized in that, the safety threshold for maintaining the formation is the spatial range formed when all adjacent helicopters meet the limiting conditions of the holding area; the holding area is: determine the center of the holding area of each remaining helicopter in the formation according to the actual position of the reference helicopter and the basic parameters of the formation, and radiate a certain geometric space area outwards. If the remaining helicopters deviate from the geometric space area, the helicopter formation will issue a formation maintenance warning; based on the relative motion between any two adjacent helicopters, perform vertical collision analysis and longitudinal collision analysis respectively to determine the characteristic size of the holding area.

3. The method for safety prompting of helicopter formation flight according to claim 1 or 2, characterized in that, the method for judging whether the helicopter formation exceeds the safety threshold for formation maintenance in Step 3 is: real-time monitor the flight state of each helicopter and whether it is in a safe state at a certain frequency. When the helicopter in the formation deviates from the determined holding area, issue a formation maintenance warning signal; when the forward-looking warning boundary of the helicopter intersects with the terrain, issue a warning signal.

4. The method for safety prompting of helicopter formation flight according to claim 3, characterized in that, in Step 4, determine the comprehensive collision avoidance method for the helicopter formation based on the artificial potential field method. Among them, the artificial potential field method is specifically: construct an artificial potential function representing the artificial potential field and apply it to the helicopter that issues both terrain collision avoidance warnings and formation maintenance warnings at the same time; among them, the artificial potential field includes an attractive potential field and a repulsive potential field, which generate an attractive force on the center of the formation holding area and a repulsive force on the obstacles detected in the formation to avoid hitting the ground.

5. The method for safety prompting of helicopter formation flight according to claim 4, characterized in that, The magnitude of the attraction force is expressed as: wherein, represents the negative gradient of the gravitational potential field, k f is the gain coefficient of the gravitational potential field ρ(q,q c ) = q c -q is the relative distance between the helicopter and the center of the formation keeping area; The magnitude of the repulsive force is expressed as: In the formula, Indicates that the negative gradient is used as the gravitational force, k 0 is the repulsive potential field gain coefficient, ρ(q,q 0 ) = q 0 -q is the relative distance between the helicopter and the obstacle, ρ 0 is the influence radius of the obstacle; then the resultant external force acting on the helicopter is: F total = F f + F 0 , based on F total Realize the maneuvering control of the helicopter.

6. The method for safely prompting helicopter formation flight according to claim 5, characterized in that the two component forces acting on the helicopter are weighted so that the priority of terrain anti-collision is higher than the priority of formation maintenance, to ensure the safety during the compound escape process of the helicopter.

Images