Turning radius adjusting method for formation flight of fixed-wing unmanned aerial vehicles

Abstract

The invention discloses a turning radius adjusting method for fixed-wing unmanned aerial vehicle formation flight, and the method comprises the steps: adjusting the turning radius of an inner-ring unmanned aerial vehicle and an outer-ring unmanned aerial vehicle in a turning process based on the proportional relation between a straight line segment and an arc line segment in an air route, and further reducing a forward error after turning caused by the formation lateral offset. In the formation flight process of the unmanned aerial vehicles, due to the existence of lateral offset, the lengths of air routes of inner and outer rings where different unmanned aerial vehicles are located are different, the whole formation has a large forward error after turning, the self speed regulation capability of the unmanned aerial vehicles is relatively limited, and the recovery of the formation configuration is often difficult to quickly realize. The method is suitable for the situation that the fixed-wing unmanned aerial vehicle cluster turns at various angles with various formation configurations, formation errors after turning can be greatly reduced, the formation configurations of the fixed-wing unmanned aerial vehicle cluster can be kept, and the method has wide application prospects in a cluster system.

Description

Technical Field

[0001] The invention belongs to the technical field of unmanned aerial vehicles, and in particular relates to a turning radius adjustment method for fixed-wing unmanned aerial vehicles formation flying. Background Art

[0002] With the rapid development of UAV technology, the research on UAV swarm formation flight has always been the focus of people's attention. Its goal is to control a certain number of UAVs to form a specific formation and reach the target area along a specific reference trajectory to perform a certain task. UAV swarm formations are widely used in scenarios such as collaborative detection, situational awareness, and collaborative operations. During the flight, UAVs may be constrained by environmental conditions such as obstacles and narrow passages. In order to improve the efficiency of mission execution and reduce costs, it is necessary to adaptively adjust the expected trajectory of the formation flexibly to ensure the smoothness of its path and the implementation of the mission. UAVs can complete the change of the current route by turning. Due to the constraints of their flight characteristics, it is difficult to use active speed regulation to achieve cluster synchronous turning. The method of re-convergence of the formation after turning is often used. By improving the calculation method of the turning radius of the UAV formation, the convergence speed of the formation after turning can be greatly accelerated, and the efficiency of UAVs in performing tasks in complex environments can be improved. Summary of the invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides a turning radius adjustment method for fixed-wing UAV formation flight. Based on the proportional relationship between the straight line segment and the arc segment in the route, the turning radius of the inner and outer circle UAVs during the turning process is adjusted, thereby reducing the forward error after the turn caused by the lateral offset of the formation. During the formation flight of UAVs, due to the existence of the lateral offset, the route lengths of the inner and outer circles of different UAVs are different, resulting in a large forward error in the entire formation after the turn, and the speed regulation ability of the UAV itself is relatively limited, and it is often difficult to quickly restore the formation configuration. This method is suitable for the situation where a fixed-wing UAV cluster turns at various angles in various formation configurations. It can greatly reduce the formation error after turning, which is conducive to maintaining the formation configuration of the fixed-wing UAV cluster. This has broad application prospects in cluster systems.

[0004] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0005] Step 1: Turning radius adjustment strategy for the two drones;

[0006] Step 1-1: If the inner circle drone and the outer circle drone use the same turning radius, the difference in route length between the inner and outer circle drones is:

[0007]

[0008] Among them, L is the lateral offset of the formation of the two UAVs; △ρ is the turning angle, in radians; the difference in route length △Q is the formation error after the turn caused by the lateral offset;

[0009] Step 1-2: In order to reduce the formation error △Q after turning, the turning radius of the inner circle ammunition is reduced during the turning process, that is, it flies more straight segments and fewer arc segments; at the same time, the turning radius of the outer circle ammunition is increased, that is, it flies less straight segments and more arc segments; based on the proportional relationship between the turning angle, straight segments and arc segments, the turning radius of the inner and outer circle drones should meet the following requirements:

[0010]

[0011] Among them, R 2 is the turning radius of the outer circle UAV, R 1 is the turning radius of the inner circle UAV;

[0012] Step 1-3: Simplify formula (2) to obtain:

[0013] R 2 =R 1 +k·L (3)

[0014] Among them, the adjustment coefficient k is:

[0015]

[0016] By setting the turning radius of the inner and outer drones according to formula (3), the formation error between the two drones after turning can be reduced.

[0017] Step 2: Turning radius adjustment strategy for large-scale UAV formations;

[0018] Step 2-1: When the formation size is more than two, the innermost drone is selected as the benchmark according to the turning direction. The drone uses the minimum allowed turning radius, which is calculated as follows:

[0019]

[0020] Among them, V is the flight speed of the drone, g is the acceleration of gravity, and φ is the maximum roll angle allowed for turning;

[0021] Step 2-2: Define the formation configuration of the drone cluster as follows:

[0022]

[0023] Where N is the number of drones, h i s represents the lateral offset of the i-th UAV relative to the formation center, h if represents the forward offset of the i-th UAV relative to the formation center, missile number i=1,2,...,N;

[0024] Step 2-3: The corresponding maximum and minimum lateral offsets under this formation configuration are:

[0025]

[0026] Step 2-4: Calculate the turning radius of each drone based on the relative lateral offset between the remaining drones and the innermost drone:

[0027]

[0028] in, is the lateral offset of the i-th UAV.

[0029] Preferably, the maximum roll angle allowed for the turn is φ=π / 6.

[0030] Preferably, when the drone cluster is turning, each drone flies at the same expected speed and adopts a staggered altitude strategy to avoid collision.

[0031] The beneficial effects of the present invention are as follows:

[0032] The present invention proposes a turning radius adjustment method for fixed-wing UAV formation flight. During the turning process, the turning radius of the inner circle UAV is reduced, that is, it flies more straight segments and fewer arc segments; the turning radius of the outer circle UAV is increased, that is, it flies fewer straight segments and more arc segments. This method can greatly reduce the formation error after turning, solve the problem of rapid formation convergence and formation maintenance under the limited speed regulation capability of UAVs, and is beneficial to the implementation of tasks of UAV clusters in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Comparison of the route lengths of inner and outer circle drones under the same turning radius.

[0034] Figure 2 Schematic diagram of inner and outer circle drone turning under the same turning radius.

[0035] Figure 3 Schematic diagram of inner and outer circle drone turning under different turning radii.

[0036] Figure 4 This is a schematic diagram of the flight trajectory of a drone cluster formation. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0038] During the UAV formation flight, due to the lateral offset of the formation, the route lengths corresponding to different UAVs are different. Figure 1 As shown in the figure, the two drones have the same initial position and fly at the same speed, with a forward offset of 0 and a lateral offset of 100. When the turning radius of the two drones is the same, after a 90° turn, the inner circle drone is ahead of the outer circle drone by 2 times the lateral offset, i.e. 200. Due to the difference in the length of the inner and outer circle routes, different drones have large forward deviations after turning, and their own speed regulation capabilities are relatively limited, making it difficult to achieve rapid formation convergence.

[0039] Therefore, the technical problem to be solved by the present invention is how to adjust the turning radius of the inner and outer circle drones to reduce the formation error after turning.

[0040] In order to solve the above technical problems, the present invention provides a turning radius adjustment method for fixed-wing UAV formation flight. First, for the case of two UAVs, a mathematical model of the turning process is established, and a turning radius adjustment strategy based on the lateral offset is designed. Then, when the formation scale is large, the innermost circle UAV is used as a reference to design a turning radius adjustment strategy for each missile based on the formation configuration. The specific contents are as follows:

[0041] 1. Turning radius adjustment strategy for two drones;

[0042] like Figure 2 As shown in Figure 2, if the inner and outer circle drones use the same turning radius, the difference in their route lengths is

[0043]

[0044] Among them, L is the lateral offset of the formation of the two UAVs; △ρ is the turning angle, in radians; the difference in route length △Q can be regarded as the formation error after turning caused by the lateral offset.

[0045] In order to reduce the formation error △Q after turning, the turning radius of the inner circle ammunition is reduced during the turning process, that is, it flies more straight segments and fewer arc segments; at the same time, the turning radius of the outer circle ammunition is increased, that is, it flies less straight segments and more arc segments. Figure 3 As shown in the figure, based on the proportional relationship between the turning angle, straight line segment and arc segment, it can be seen that the turning radius of the inner and outer circle drones should meet the following requirements:

[0046]

[0047] Among them, R 2 is the turning radius of the outer circle UAV, R 1 is the turning radius of the inner circle UAV.

[0048] Simplifying the above formula, we can get

[0049] R 2 =R 1 +k·L

[0050] Among them, the adjustment coefficient k is

[0051]

[0052] By setting the turning radius of the inner and outer circle drones according to the above relationship, the formation error between the two drones after turning can be reduced.

[0053] 2. Turning radius adjustment strategy for large-scale UAV formations;

[0054] When the formation is large, the innermost drone is selected as the benchmark according to the turning direction. The missile uses the minimum allowed turning radius, which is calculated as follows:

[0055]

[0056] Among them, V is the flight speed of the UAV, g is the acceleration of gravity, and φ is the maximum roll angle allowed for turning, which can be taken as φ=π / 6.

[0057] The formation configuration of the drone cluster is defined as:

[0058]

[0059] Where N is the number of drones, represents the lateral offset of the i-th UAV relative to the formation center, represents the forward offset of the i-th UAV relative to the formation center, and the missile number i=1,2,...,N.

[0060] The corresponding maximum and minimum lateral offsets under this formation configuration are:

[0061]

[0062] Then, the turning radius of each drone is calculated based on the relative lateral offset of the remaining drones and the innermost drone:

[0063]

[0064] in, is the lateral offset of the i-th UAV; k is the turning radius adjustment coefficient calculated previously; △ρ is the turning angle in radians.

[0065] It should be noted that during the turning process, each drone flies at the same expected speed and adopts a staggered height strategy to avoid collision.

[0066] Example:

[0067] A method for adjusting the turning radius of fixed-wing UAV formation flight is implemented by following the steps below:

[0068] 1: At the beginning, according to the turning direction corresponding to the current route, the innermost ammunition in the cluster is selected as the basis for turning radius calculation;

[0069] 2: Under the constraints of flight capability, the minimum turning radius of the innermost ammunition is calculated based on the flight speed, the maximum rolling angle allowed when turning, etc.;

[0070] 3: Extract the maximum and minimum lateral offsets from the formation configuration parameters of the UAV cluster;

[0071] 4: Calculate the turning radius of each drone using the adjustment coefficient based on the relative lateral offset between each drone and the innermost drone;

[0072] 5: Each drone turns at the same desired speed and avoids collision by adopting a staggered height strategy.

[0073] Consider the situation where a cluster of 4 drones is turning. The expected formation is a standard horizontal line. The expected route is as follows: Figure 4 As shown, the formation starts from the left and flies along the upper rectangle. After the formation returns to the central axis, it flies along the lower rectangle. The entire route includes two situations: counterclockwise rotation and clockwise rotation. The former is a left turn and the latter is a right turn. The route with the turning correction function turned on is set to the 5th segment and the route at the end is set to the 10th segment. The lateral offsets between adjacent drones are taken as 10m, 20m, 30m, 40m, and 50m respectively. Table 1 gives the turning radius formation error of the above formation under different lateral offsets, among which the post-turn formation error when the turning radius adjustment is not used is calculated by theoretical analysis. It can be seen that the turning radius adjustment greatly reduces the post-turn formation error caused by the lateral offset of the formation.

[0074] Table 1 Formation error after turning under different lateral offsets

[0075]

Claims

1. A turning radius adjustment method for fixed-wing UAV formation flight, characterized in that: The steps include: Step 1: Turning radius adjustment strategy for the two drones; Step 1-1: If the inner circle drone and the outer circle drone use the same turning radius, the difference in route length between the inner and outer circle drones is: Among them, L is the lateral offset of the formation of the two UAVs; △ρ is the turning angle, in radians; the difference in route length △Q is the formation error after the turn caused by the lateral offset; Step 1-2: In order to reduce the formation error △Q after turning, the turning radius of the inner circle ammunition is reduced during the turning process, that is, it flies more straight segments and fewer arc segments; at the same time, the turning radius of the outer circle ammunition is increased, that is, it flies less straight segments and more arc segments; based on the proportional relationship between the turning angle, straight segments and arc segments, the turning radius of the inner and outer circle drones should meet the following requirements: Among them, R2 is the turning radius of the outer circle UAV, and R1 is the turning radius of the inner circle UAV; Step 1-3: Simplify formula (2) to obtain: R2=R1+k·L (3) Among them, the adjustment coefficient k is: By setting the turning radius of the inner and outer drones according to formula (3), the formation error between the two drones after turning can be reduced. Step 2: Turning radius adjustment strategy for large-scale UAV formations; Step 2-1: When the formation size is more than two, the innermost drone is selected as the benchmark according to the turning direction. The drone uses the minimum allowed turning radius, which is calculated as follows: Among them, V is the flight speed of the drone, g is the acceleration of gravity, and φ is the maximum roll angle allowed for turning; Step 2-2: Define the formation configuration of the drone cluster as follows: Where N is the number of drones, represents the lateral offset of the i-th UAV relative to the formation center, represents the forward offset of the i-th UAV relative to the formation center, missile number i=1,2,...,N; Step 2-3: The corresponding maximum and minimum lateral offsets under this formation configuration are: Step 2-4: Calculate the turning radius of each drone based on the relative lateral offset between the remaining drones and the innermost drone: in, is the lateral offset of the i-th UAV.

2. A turning radius adjustment method for fixed-wing UAV formation flight according to claim 1, characterized in that: The maximum roll angle φ allowed for the turn is π / 6.

3. The turning radius adjustment method for fixed-wing UAV formation flight according to claim 1, characterized in that: When the drone cluster is turning, each drone flies at the same expected speed and adopts a staggered altitude strategy to avoid collision.

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