Wind-resistant unmanned aerial vehicle relay communication method based on sideslip method

Abstract

The invention provides a wind-resistant unmanned aerial vehicle relay communication method based on a sideslip method. The wind-resistant unmanned aerial vehicle relay communication method comprises the following steps: acquiring unmanned aerial vehicle relay system parameters; the position information of the source node and the destination node and the flight starting point information of the unmanned aerial vehicle relay are utilized to give a route angle for the unmanned aerial vehicle to carry out information forwarding service; the flight state of the unmanned aerial vehicle relay is adjusted by using wind field information in a natural environment, so that the unmanned aerial vehicle relay can fly in a wind field according to an expected flight path; the unmanned aerial vehicle serves as a half-duplex amplification forwarding relay in the flight process and provides information forwarding service for ground users. According to the invention, the unmanned aerial vehicle relay can fly in a wind field according to the expected track of the maximum target node receiving information amount, and serves as a half-duplex amplification forwarding relay in the flight process to provide information forwarding service for ground users.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communication technologies, and in particular to a wind-resistant UAV relay communication method based on a sideslip method. Background Art

[0002] In recent years, UAV cooperative communication technology has become a research hotspot in the field of wireless communication. Compared with traditional terrestrial communication, UAV cooperative communication is easy to achieve on-demand allocation, thus having higher communication efficiency; UAVs have high mobility, so they can be deployed more flexibly and quickly; the possibility of the communication link between a UAV and a ground terminal being a line-of-sight channel is higher than that of terrestrial communication under the same communication distance, so it can provide better channel transmission conditions. Therefore, UAVs will surely play a very important role in the future wireless communication field, and their applications mainly include: (1) as a temporary base station; (2) as a mobile relay; (3) for the Internet of Things.

[0003] Currently, a large number of literatures have studied the performance optimization problems of communication systems when UAVs are used as mobile relays, such as the maximization of communication capacity, spectral efficiency, or power efficiency. In these research works, it is often assumed that the UAVs fly in a windless environment. In fact, there must be a wind field in the natural environment. At this time, the ground speed vector of the UAV will be separated from the airspeed vector and form a triangular superposition relationship with the wind speed vector (i.e., the so-called wind triangle superposition relationship). As an aerial mobile relay, the UAV needs to provide communication services for ground users. Therefore, it is necessary to know and control the relative distance between the aerial and ground users in order to better provide communication services for ground users. As described above, in a wind field environment, the ground speed vector of the UAV will be separated from the airspeed vector. Among them, the airspeed vector will determine the aerodynamic forces of the UAV flight, such as lift, drag, etc., while the ground speed vector will determine the relative position relationship between the UAV and the ground users. From the perspective of aerial-ground user communication, only the ground speed vector needs to be concerned about or considered, but it does not exist independently, but is closely related to the wind speed vector and the airspeed vector. In order to resist the influence of natural wind disturbances and make the UAV fly along a trajectory that is beneficial to aerial-ground user communication, the sideslip method or the crab method can be adopted. Among them, the crab method is to control the UAV to change the magnitude of the heading angle, so as to generate a corresponding yaw angle to offset the influence of the crosswind; while the sideslip method is to control the roll angle of the UAV to balance the lateral force caused by the crosswind, so that the ground speed direction of the UAV is consistent with the desired trajectory. As described above, from the perspective of aerial-ground user communication, the magnitude and direction of the relative ground speed of the UAV will determine the communication performance between the aerial and ground users. Therefore, it is necessary to adjust the relay flight attitude of the UAV under the condition of knowing the natural wind field information to achieve a state that is beneficial to aerial-ground user communication. Currently, in the field of UAV-assisted wireless communication, there is still a lack of research on using the sideslip method to resist the influence of wind disturbances on UAV relays. Therefore, it is worthy of attention. Summary of the Invention

[0004] The present invention provides a wind-resistant UAV relay communication method based on the sideslip method. Using the position information of ground users and the flight starting point information of the UAV relay, a course angle beneficial for the UAV to perform information forwarding services is given. Then, using the wind field information (including wind intensity and wind direction information) in the natural environment, the flight state of the UAV relay (including airspeed vector, sideslip angle, and roll angle) is adjusted, so that the UAV relay can fly along the expected trajectory that maximizes the information received by the destination node in the wind field, acting as a half-duplex amplify-and-forward relay during flight to provide information forwarding services for ground users.

[0005] To achieve the above object, according to one aspect of the present invention, a wind-resistant UAV relay communication method based on the sideslip method is provided, including the following steps:

[0006] The present invention is implemented as follows: A wind-resistant UAV relay communication method based on the sideslip method uses the position information of the source node and the destination node (including the position information of the antennas of the source and destination nodes) and the flight starting point information of the UAV relay to give a course angle beneficial for the UAV to perform information forwarding services. Then, using the wind field information (including wind intensity and wind direction information) in the natural environment, the flight state of the UAV relay (including airspeed vector, sideslip angle, and roll angle) is adjusted, so that the UAV relay can fly along the expected trajectory that maximizes the information received by the destination node in the wind field, acting as a half-duplex amplify-and-forward relay during flight to provide information forwarding services for ground users.

[0007] For a three-node fixed-wing UAV relay system, where the ground user U1 sends information to the ground user U2 through the UAV relay U R and there is no direct link between user U1 and user U2. For the convenience of mathematical representation, it is considered that the direction of the line connecting user U1 and user U2 is the x-axis of the two-dimensional horizontal plane coordinate system. The x-axis of the two-dimensional horizontal plane coordinate system is centered at the origin, and the y-axis of the two-dimensional horizontal plane coordinate system is obtained by rotating the x-axis counterclockwise horizontally by 90° around the origin. Assume that U1 is located at the origin of the two-dimensional horizontal plane coordinate system, that is, U1 is located at [0, 0]; user U2 is located at [d 12 , 0], where d 12 is the distance between U1 and U2. The direction passing through the origin of the two-dimensional horizontal plane coordinate system and perpendicular to the horizontal plane upward is the z-axis. Assume that the UAV relay U R flies from above U1 towards above U2. The UAV starts from the starting point and flies along a straight-line trajectory, where is the coordinate of the starting point on the y-axis of the two-dimensional horizontal plane coordinate system, and a Ris the flight altitude. Assume that the UAV U R flies horizontally, that is, the flight altitude is constant; the flight area is between the airspaces of U1 and U2, that is, the coordinates of the starting point and the ending point of the UAV on the x-axis of the two-dimensional horizontal coordinate system are greater than or equal to 0 and less than or equal to d 12 ; the ground velocity vector of the UAV is v g = v g ∠χ, where v g is the magnitude of V g and χ is the course angle, that is, the angle between V g and the horizontal x-axis, -90° < χ < 90°. It should be noted that: V g is actually the velocity vector of the UAV relative to the ground; the direction of the ground velocity vector of the UAV remains unchanged (that is, the course angle χ remains constant); v g is also called the ground speed of the UAV. The UAV relay U R will be affected by the uniform wind field in the natural environment during flight, that is, affected by the wind field with constant wind strength and wind direction within a given time. Since the wind in the vertical direction is very small, only the wind field in the two-dimensional plane is considered here. Assume that the wind speed vector is V w = v w ∠θ w , where v w is the magnitude of V w and is used to represent the wind strength, and θ w is the angle between V w and the horizontal x-axis (that is, the direction angle of the wind speed vector) and is used to represent the wind direction, -180° ≤ θ w < 180°. Assume that the antenna height of user U1 is a1, the antenna height of user U2 is a2, and the antenna height of U R is the same as the flight altitude of the UAV, that is, a R . Assume that the airspeed vector of the UAV relay U R is V a = v a ∠θ a , where v a is the magnitude of V a and θ a is the angle between V a and the horizontal x-axis (that is, the direction angle of the airspeed vector), -180° ≤ θ a < 180°. It should be noted that: V a is the flight velocity vector of the UAV relative to the surrounding air. In order to make the UAV relay U R fly along the desired straight flight path, the sideslip method is used to counteract the influence of the wind field in the natural environment. At this time, the fuselage direction of the UAV relay U R is the same as the ground velocity vector V gis aligned in the direction; there is an included angle β between the body direction of the UAV and the airspeed vector V a That is, the sideslip angle is β; in order to balance the lateral force caused by the crosswind, the UAV needs to generate a roll angle φ.

[0008] As described above, the UAV relay U R starts from t = 0 and departs from and flies along a straight-line trajectory. The time for the UAV to fly and act as a half-duplex amplify-and-forward relay to forward information from the ground user U1 to the ground user U2 is T. Assume that the channels between the ground user U1 and the UAV relay U R and between the UAV relay U R and the ground user U2 are both line-of-sight channels. Since the UAV relay U R works in the half-duplex mode, T is divided into 2N time slots, and the length of each time slot is Δ = T / 2N. It should be noted that: since the length Δ of the time slot is very small, the position of the UAV is approximately regarded as unchanged within one time slot.

[0009] In the (2n - 1)-th time slot (n ∈ {1, 2, …, N}), the ground user U1 transmits a unit-power signal x1(2n - 1), then the signal y R (2n - 1) received by the UAV relay U R can be written as

[0010]

[0011] where P T is the transmission power of the ground user U1, g 1R (2n - 1) is the large-scale channel power between U1 and U R , z R (2n - 1) is the Gaussian white noise received by U R , and its average power is σ 2 . Here, g 1R (2n - 1) can be written as where represents the channel power reference value at a distance of 1 meter, and d 1R (2n - 1) is the distance between the antenna of the ground user U1 and the antenna of the UAV relay U R in the (2n - 1)-th time slot, and can be specifically calculated by Equation (2).

[0012]

[0013] In Equation (2), a1 and a R are the heights of the antennas of the ground user U1 and the UAV relay U R respectively, is the coordinate of the starting point of the UAV flight on the y-axis of the two-dimensional horizontal coordinate system, v g is the ground speed vector V of the UAV g magnitude, χ is the course angle of the UAV, that is, the ground speed vector V g angle with the x-axis of the horizontal plane, and Δ is the length of the time slot.

[0014] UAV relay U R adopts the amplify-and-forward protocol and scales y R (2n - 1) to become the unit power signal x R (2n), which can be specifically given by Equation (3).

[0015]

[0016] In the 2n-th time slot, the UAV relay U R transmits x T (2n) to the ground user U2 with the transmission power P R . At the end of the 2n-th time slot, the signal received by the ground user U2 is

[0017]

[0018] In Equation (4), P T is the transmission power of the UAV relay U R , z2(2n) is the Gaussian white noise received by the ground user U2, and its average power is σ 2 , g R2 (2n) is the large-scale channel power between U R and U2, which can be specifically written as where represents the channel power reference value at a distance of 1 meter, d R2 (2n) is the distance between the antenna of the UAV relay U R and the antenna of the ground user U2 in the 2n-th time slot, and d R2 (2n) can be calculated by Equation (5).

[0019]

[0020] In Equation (5), a2 and a R are the heights of the antennas of the ground user U2 and the UAV relay U R respectively, d 12 is the distance between the ground user U1 and the ground user U2, is the coordinate of the starting point of the UAV flight on the y-axis of the two-dimensional horizontal coordinate system, v g is the ground speed vector V of the UAV g magnitude, χ is the course angle of the UAV, that is, the ground speed vector Vg The angle with the x-axis of the horizontal plane, and Δ is the length of the time slot.

[0021] Therefore, at the end of the 2n-th time slot, the signal y2(2n) received by the ground user U2 can be rewritten as

[0022]

[0023] At the end of the 2n-th time slot, the ratio of the useful signal power received by the ground user U2 to the noise power, that is, the signal-to-noise ratio is

[0024]

[0025] In Equation (7), γ 1R (2n - 1) = P T g 1R (2n - 1) / σ 2 、γ R2 (2n) = P T g R2 (2n) / σ 2 . It should be noted that: Equation (7) is approximated under the condition of large signal-to-noise ratio, that is, when γ 1R (2n - 1) >> 1 and γ R2 (2n) >> 1,

[0026] In this way, through two time slots (the 2n - 1-th and 2n-th time slots), the amount of information that the ground user U2 can obtain is: C2(2n) = Δlog2[I + SNR2(2n)]. Generally, through the transmission of 2N time slots, the amount of information that the ground user U2 can obtain is

[0027]

[0028] where N is equal to half of the total number of time slots.

[0029] According to Equation (7), at the end of the 2n-th time slot, the ratio of the useful signal power received by the ground user U2 to the noise power can be approximately written as:

[0030]

[0031] Observing Equation (9), it is found that when the value of v g is fixed, in order to maximize SNR2(2n), the value of should be made as small as possible. Taking the derivative of with respect to χ and setting it to 0, we can get It should be noted that: in the process of solving , the approximate operation 4n - 1 ≈ 4n is adopted. That is to say, when v gWhen the value is fixed, the optimal UAV flight path angle is Among them, is the coordinate of the UAV starting point on the y-axis of the two-dimensional coordinate system on the horizontal plane, and d 12 is the distance between U1 and U2.

[0032] Due to the wind triangle superposition relationship among the wind speed vector, ground speed vector, and airspeed vector, according to the cosine theorem, the following formula holds.

[0033]

[0034] In formula (10), the magnitude v of the airspeed vector a needs to satisfy Among them, V stall is the minimum airspeed of the UAV. If the airspeed of the UAV is less than V stall [[ID=We]] then it cannot obtain enough lift and stalls. is the maximum airspeed limit of the UAV due to structural limitations. On the other hand, due to the crosswind, the UAV relay U R will be subjected to a lateral force. Therefore, the UAV needs to generate a roll angle φ to resist this lateral force. For the convenience of the following mathematical explanation, the value of θ w -χ is limited within a given range, that is, -180° ≤ θ w -χ < 180°. Therefore, when θ w -χ ≥ 180°, let η wχ = θ w -χ - 360°; when θ w -χ < 180°, let η wχ = θ w -χ - 360°; for other values of θ w -χ, let η wχ = θ w -χ.

[0035] When 0° ≤ η wχ < 180°, the UAV relay U R needs to tilt to the right. At this time, the roll angle φ ≤ 0 and the sideslip angle β ≤ 0; when -180° ≤ η wχ < 0°, the UAV relay U R needs to tilt to the left. At this time, the roll angle φ ≥, and the sideslip angle β ≥ 0. To ensure flight safety, the roll angle φ of the UAV must satisfy |φ| ≤ φ max , and the sideslip angle β must satisfy |β| ≤ β max , where φ max and β max are the maximum roll angle and maximum sideslip angle allowed for UAV flight, respectively.

[0036] It should be noted that there seems to be an error in the original text where "We" appears in line 23. It might be a typo. The translation is done based on the best understanding of the provided text.When using the sideslip method to resist the influence of wind disturbance, the UAV relay U R should be subject to the equation given in Equation (11),

[0037]

[0038] where L is the lift obtained by the UAV, φ is the roll angle of the UAV, W is the gravity of the UAV, D is the drag obtained by the UAV flight (its direction is opposite to the airspeed direction), β is the sideslip angle of the UAV, and F Y is the lateral force acting on the UAV (its direction is perpendicular to the UAV fuselage), and H T is the driving force provided by the UAV engine (its direction is the same as the direction of the UAV fuselage pointing). Here, the lift L, drag D, and lateral force F Y can be calculated by Equation (12), Equation (13), and Equation (14) respectively.

[0039]

[0040]

[0041] In Equation (12), Equation (13), and Equation (14), ρ is the air density, v a is the magnitude of the airspeed vector, S is the wing area, C L is the lift coefficient, C D is the drag coefficient, is the lateral force coefficient (usually a negative value), β is the sideslip angle and satisfies |β| ≤ β max . It should be noted that: the power provided by the UAV engine is P = H T v a cosβ, where H T is the driving force provided by the UAV engine, v a is the magnitude of the UAV's airspeed vector, and β is the sideslip angle of the UAV. From Equation (11) and Equation (13), the power provided by the UAV engine can be obtained as

[0042]

[0043] where ρ is the air density, v a is the magnitude of the airspeed vector, S is the wing area, C D is the drag coefficient, β is the sideslip angle and satisfies |β| ≤ β max . It should be noted that: during the UAV flight, the power P provided by the engine needs to satisfy P ≤ P max , and P max is the maximum power output that the UAV engine can provide.

[0044] Regarding Equation (10) as v gFor a quadratic equation of one variable, the condition for the equation to have a positive real solution is That is, v a ≥ v w |sin(θ w - χ)|. The solution of v g is given below and can be specifically divided into the following two cases.

[0045] Case 1: When v a ≥ v w |sin(θ w - χ)| holds. The solution of v g can be given by Equation (16).

[0046]

[0047] Case2: When v a < v w |sinθ w | holds. There is no feasible solution at this time.

[0048] According to Equation (11), Equation (12), Equation (13) and Equation (14), the following Equation (17) and Equation (18) can be obtained.

[0049]

[0050] According to Equation (18) and |φ| ≤ φ max it can be obtained that: when holds, then let In this way, the ranges of the sideslip angle and roll angle allowed in the actual situation are respectively and When holds, it is necessary to obtain the sideslip angle of the UAV when the following Equation (19) holds through the binary search method within the range of 0 ≤ β ≤ β max and denote it as Let In this way, the ranges of the sideslip angle and roll angle allowed in the actual situation are respectively and

[0051]

[0052] According to the above analysis, the sideslip angle β of the UAV should satisfy The roll angle φ of the UAV should satisfy At this time, according to Equation (17), the magnitude v a of the UAV airspeed vector should have a value range of:

[0053] When 0° < η wχWhen η < 180°, the UAV relay U R needs to tilt to the right, generating a roll angle φ ≤ 0 and a sideslip angle β ≤ 0. At this time, within a range, find a β such that Equation (20) holds.

[0054] v a |sinβ| - v w |sin(θ w - χ)| = 0 (20)

[0055] When -180° ≤ η wχ < 0°, the UAV relay U R needs to tilt to the left, generating a roll angle φ ≥ 0 and a sideslip angle β ≥ 0. At this time, within a range, find a β such that Equation (20) holds.

[0056] Actually, when η wχ = 0° or η wχ = -180° (i.e., θ w - χ = 0° or θ w - χ = -180°), when the sideslip angle of the UAV is equal to zero, Equation (20) holds. At this time, denote the solution of Equation (20) as When η wχ ≠ 0° and η wχ ≠ -180° (i.e., 0° < η wχ < 180° and -180° < η wχ < 0° for both cases), it is necessary to solve the equation given by Equation (20). Since 0° < η wχ < 180° and -180° < η wχ < 0° are similar for both cases, both need to solve the equation given by Equation (20), and the β value ranges in the two cases are mirror-symmetric. Therefore, first solve the equation given by Equation (20) within a range. Within a range, v a |sinβ| is an increasing function of β. Therefore, the solution of the equation given by Equation (20) can be obtained by the binary search method within a range. It should be noted that: to ensure that the equation given by Equation (20) has a solution, Equation (21) must hold. Otherwise, the equation given by Equation (20) has no solution, that is, if Equation (21) does not hold, the sideslip method cannot be used to make the UAV fly along the desired trajectory.

[0057]

[0058] If Equation (21) holds, then within Within the range, the solution of the equation given by Equation (20) is obtained through the binary search method, denoted as During the process of using the bisection method for searching , v a can be calculated through Equation (17), where the roll angle φ of the UAV can be calculated through Equation (18).

[0059] After obtaining , substitute for β in Equation (18), calculate the corresponding roll angle of the UAV, denoted as Then, substitute for φ in Equation (17), calculate the corresponding magnitude of the UAV's airspeed vector, denoted as Next, substitute and for v a and β in Equation (15) respectively, calculate the power output provided by the UAV engine, denoted as It should be noted that: the magnitude of the airspeed vector during the flight of the UAV and the power provided by the engine need to satisfy and respectively, where is the maximum airspeed limit caused by the structural limitations of the UAV, and P max is the maximum power output that the UAV engine can provide. Therefore, when or holds, it means that the UAV cannot fly along the desired trajectory through the sideslip method.

[0060] It should be noted that: when solving the magnitude of the UAV's airspeed vector above, the force balance problem of the UAV is considered, that is, there will be no problem of stalling due to insufficient lift.

[0061] Summarizing the above analysis, it can be obtained that: when and 0° ≤ η wχ < 180°, the UAV flies at an airspeed of , a roll angle of and a sideslip angle of ; when and -180° ≤ θ wχ < 0°, the UAV flies at an airspeed of , a roll angle of and a sideslip angle of .

[0062] It should be noted that when the sideslip method can be used to adjust the flight state of the UAV so that the UAV flies along the desired trajectory and acts as a relay node to forward information to ground users during the flight, the amplitude of the UAV's airspeed vector and the course angle can be substituted into formula (16) to calculate the amplitude of the UAV's ground speed vector. Then, the flight distance is divided by the ground speed vector amplitude to obtain the time T that the UAV flies and acts as a relay to forward ground user information. Finally, the amount of information received by ground user U2 during the entire process is calculated based on the number of time slots and formula (8). The UAV flight distance here is determined by the specific flight mission. That is, before executing a flight mission, the starting point and end point of the UAV flight are determined, and the distance of this flight can be calculated from this.

[0063] When the sideslip method can be used to adjust the flight state of the UAV so that the UAV flies according to the desired trajectory, the angle θ between the UAV's airspeed vector and the horizontal plane x-axis can be calculated based on the UAV's ground speed vector, wind speed vector, and UAV's airspeed vector amplitude. a (i.e., the direction angle of the airspeed vector).

[0064] When 0°≤η wχ When the angle θ between the UAV's airspeed vector and the x-axis of the horizontal plane is less than 180°, a It can be calculated by formula (22).

[0065]

[0066] When -180°≤η wχ When <0°, the angle θ between the UAV's airspeed vector and the x-axis of the horizontal plane a It can be calculated by formula (23).

[0067]

[0068] Specifically, step 1: obtain the parameters of the drone relay system, including: the antenna height a1 of the ground user U1, the antenna height a2 of the ground user U2, the flight height (antenna height) a of the drone R , the distance d between ground user U1 and ground user U2 12 , the magnitude v of the wind speed vector w , the angle θ between the wind speed vector and the horizontal x-axis w (i.e., the direction angle of the wind speed vector), the ground user U1 and the UAV relay U R The transmission power P T , Channel power reference value at 1 meter distance Noise power σ 2 , air density ρ, drone wing area S, lift coefficient C L , drag coefficient CD , Lateral force coefficient The maximum sideslip angle β during the flight of the UAV max and the maximum roll angle φ max , The maximum airspeed limit of the UAV due to structural limitations The maximum output power P of the UAV engine max and the starting point coordinates of the UAV flight

[0069] Step 2: Initialize the ground speed vector magnitude of the UAV relay U R The airspeed vector magnitude The angle between the airspeed vector and the x-axis of the horizontal plane The sideslip angle and the roll angle Calculate the course angle of the UAV flight

[0070] Step 3: If θ w - χ ≥ 180° holds, let η wχ = θ w - χ - 360°; if θ w - χ < -180° holds, let η wχ = θ w - χ + 360°; for other values of θ w - χ, let η<o:p>< / o:p> wχ = θ w - χ;

[0071] Step 4: When holds, then let When holds, it is necessary to obtain the sideslip angle of the UAV when Equation (19) holds within the range of 0 ≤ β ≤ β max by the bisection search method and denote it as

[0072] Step 5: If η wχ = 0° or η wχ = -180°, then let Then jump to Step 6, otherwise check whether Equation (21) holds; if Equation (21) does not hold, let the magnitude of the UAV airspeed vector be 0, and then jump to Step 11. If Equation (21) holds, within the range of obtain the solution of the equation given by Equation (20) by the bisection search method and denote it as During the bisection search process, the magnitude v of the UAV airspeed vector a can be calculated by Equation (17), and the roll angle φ of the UAV can be calculated by Equation (18);

[0073] Step 6: Substitute for β in Equation (18), calculate the corresponding roll angle of the UAV, and denote it as Substitute for φ in Equation (17), calculate the corresponding magnitude of the UAV's airspeed vector, and denote it as Substitute and for v a and β in Equation (15) respectively, calculate the power output provided by the UAV engine, and denote it as

[0074] Step 7: If or holds, then let Then jump to Step 11;

[0075] Step 8: Substitute for v a in Equation (16), then calculate the magnitude of the ground speed vector, and denote it as And divide the flight distance by the magnitude of the ground speed vector to obtain the time T for the UAV to fly and act as a relay to forward information;

[0076] Step 9: When 0° ≤ η wχ < 180°, substitute and for v a and v g in Equation (22) respectively, and calculate the angle (i.e., the direction angle of the airspeed vector) between the UAV's airspeed vector and the x-axis of the horizontal plane. When -180° ≤ η wχ < 0°, substitute and for v a and v g in Equation (23) respectively, and calculate

[0077] Step 10: If 0° ≤ η wχ < 180° holds, the UAV flies with a roll angle of a sideslip angle of and an airspeed vector of ; if -180° ≤ η wχ < 0° holds, the UAV flies with a roll angle of a sideslip angle of and an airspeed vector of ; the ground speed vector of the UAV during flight is During the flight, the UAV uses the half-duplex amplify-and-forward protocol to forward information from the ground user U1 to the ground user U2, and the time for the UAV to fly and act as a relay to forward information is T.

[0078] Step 11: The method ends.

[0079] It should be noted that when the above method returns v a = 0 (the magnitude of the UAV airspeed vector is zero), it means that the UAV cannot fly along the desired flight path through the sideslip method.

[0080] According to one aspect of the present invention, there is provided a storage medium storing instructions that, when read by a computer, cause the computer to execute the anti-wind UAV relay communication method based on the sideslip method described in any one of the above.

[0081] According to another aspect of the present invention, there is provided an electronic device including a processor and the above storage medium, and the processor executes the instructions in the storage medium.

[0082] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0083] The present invention uses the position information of the source node and the destination node (including the position information of the antennas of the source and destination nodes) and the flight starting point information of the UAV relay to give a course angle that is beneficial for the UAV to perform information forwarding services. Then, using the wind field information in the natural environment (including wind strength and wind direction information), the flight state of the UAV relay (including airspeed vector, sideslip angle, and roll angle) is adjusted, so that the UAV relay can fly along the desired flight path that maximizes the amount of information received by the destination node in the wind field and act as a half-duplex amplify-and-forward relay during the flight to provide information forwarding services for ground users. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0085] Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention belongs.

[0086] Figure 1 It is a schematic diagram of the method for a preferred embodiment of the present invention, (a) side view of the system, (b) front view of the UAV, (c) top view of the UAV (wind triangle superposition relationship diagram);

[0087] Figure 2Relationship between the airspeed vector magnitude and the wind speed vector direction angle in a preferred embodiment of the present invention;

[0088] Figure 3 Relationship between the ground speed vector magnitude and the wind speed vector direction angle in a preferred embodiment of the present invention;

[0089] Figure 4 Relationship between the sideslip angle and the wind speed vector direction angle in a preferred embodiment of the present invention;

[0090] Figure 5 Relationship between the roll angle and the wind speed vector direction angle in a preferred embodiment of the present invention;

[0091] Figure 6 Two-dimensional plane decomposition of the ground velocity vector in three different starting positions of the unmanned aerial vehicle in a preferred embodiment of the present invention;

[0092] Figure 7 Relationship between the airspeed vector magnitude and the wind speed vector magnitude in a preferred embodiment of the present invention.

[0093] Figure 8 Relationship between the ground speed vector magnitude and the wind speed vector magnitude in a preferred embodiment of the present invention;

[0094] Figure 9 Relationship between the sideslip angle and the wind speed vector magnitude in a preferred embodiment of the present invention;

[0095] Figure 10 Relationship between the roll angle and the wind speed vector magnitude in a preferred embodiment of the present invention;

[0096] Figure 11 Two-dimensional plane decomposition of the ground velocity vector under three different starting positions of the unmanned aerial vehicle and wind speed vector direction angles in a preferred embodiment of the present invention. Detailed implementation mode

[0097] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0098] Embodiment 1: As Figures 1 - 11 shown, the present invention provides an anti-wind unmanned aerial vehicle relay communication method based on the sideslip method, including the following steps:

[0099] As Figure 1 shown, the unmanned aerial vehicle relay U RIt flies along a straight - line trajectory from above the ground user U1 to above the ground user U2, and its flight time is Τ. During the flight, it acts as a half - duplex amplify - and - forward relay to forward information from the ground user U1 to the ground user U2. Before the formal flight, the UAV relay will obtain system parameters, including: the antenna height a1 of the ground user U1, the antenna height a2 of the ground user U2, the UAV flight height (antenna height) a R 、the distance d between the ground user U1 and the ground user U2 12 、the magnitude v of the wind speed vector w 、the angle θ between the wind speed vector and the horizontal plane x - axis w (i.e., the direction angle of the wind speed vector), the transmission power P of the ground user U1 and the UAV relay U R 、the channel power reference value at a distance of 1 meter T 、the noise power σ 、the air density ρ, the UAV wing area S, the lift coefficient C 2 、the drag coefficient C L 、the side - force coefficient D 、the maximum sideslip angle β during UAV flight 、and the maximum roll angle φ max 、the maximum airspeed limit due to UAV structure limitations max 、the maximum output power P of the UAV engine 、and the starting - point coordinates of the UAV flight max Then, execute the anti - wind UAV relay communication method based on the sideslip method proposed above to obtain the sideslip angle β and roll angle φ of the UAV flight, and fly with the airspeed vector v ∠θ a 、and forward information from the ground user U1 to the ground user U2 using the full - duplex amplify - and - forward protocol during the flight. a For the method proposed in the present invention, simulation experiments are carried out and compared with the case where the UAV relay flies from the starting point in a direction parallel to the x - axis of the two - dimensional horizontal coordinate system. The experimental environment is the Matlab environment. Table 1 gives the parameter values in the simulation experiment.

[0100] 、

[0101] Table 1

[0102]

[0103] Figure 2 、 Figure 3 、 Figure 4 and Figure 5 respectively give the relationships between the UAV airspeed vector magnitude, ground - speed vector magnitude, sideslip angle, and roll angle and the wind - speed vector direction angle, where the wind - speed vector magnitude is constant at v w= 5 m / s, the wind speed vector direction angle ranges from -180° to 180°. In addition, three cases of the UAV starting position are considered. Regarding the value of in the UAV starting point coordinates (i.e., the coordinate of the UAV starting point on the y-axis of the two-dimensional horizontal coordinate system) and the corresponding UAV course angle are shown in Table 2.

[0104] Table 2

[0105]

[0106] Figure 2 shows the relationship between the airspeed vector magnitude and the wind speed vector direction angle. Figure 2 It shows that the airspeed vector magnitude of the UAV varies between 10.33 m / s and 10.34 m / s with the change of the wind speed vector direction angle, and the change amplitude is very small. The starting position of the UAV does not affect the variation range of the airspeed vector magnitude.

[0107] Figure 3 shows the relationship between the ground speed vector magnitude and the wind speed vector direction angle. Figure 3 It shows that the ground speed vector magnitude of the UAV is greatly affected by the wind speed vector direction angle. When flying with the wind, a larger ground speed will be generated. On the contrary, the ground speed is smaller. As can be seen from Table 2, when, a negative course angle χ = -8.5308° will be generated. Therefore, when the direction angle of the wind speed vector is equal to the course angle, the maximum ground speed (i.e., the ground speed vector magnitude) will be obtained; when and when, a positive course angle will be generated. Therefore, when the direction angle of the wind speed vector is positive and equal to the course angle, the maximum ground speed will be obtained. This phenomenon is consistent with the actual situation, proving the correctness of the research. In addition, Figure 3 It shows that the variation range of the UAV ground speed is the same under the three cases of the UAV starting position, that is, the UAV starting position does not affect the variation range of the ground speed.

[0108] Figure 4 and Figure 5 respectively show the relationship between the sideslip angle and roll angle of the UAV and the wind speed vector direction angle. Observing Figure 4 and Figure 5 it can be found that the sideslip angle and roll angle of the UAV are positively correlated, that is, when the sideslip angle of the UAV takes the maximum or minimum value, its roll angle also takes the maximum or minimum value. This phenomenon is consistent with Equation (18) in the theoretical analysis, proving the correctness of the research. Theoretically, when the wind speed vector is perpendicular to the fuselage direction of the UAV (when using the sideslip method, the wind speed vector is perpendicular to the ground speed vector), the maximum or minimum sideslip angle (i.e., the absolute value of the sideslip angle is the largest) will be generated. As can be seen from Table 2 and Figure 4 it can be known that when θw - When χ = ±90°, the absolute value of the sideslip angle is the largest, which is consistent with the results of theoretical analysis, indicating the correctness of the research. In addition, Figure 4 and Figure 5 show that the values of the sideslip angle and roll angle of the UAV both satisfy the given constraint conditions, indicating the correctness of the research.

[0109] Figure 6 gives Figure 2 、 Figure 3 、 Figure 4 and Figure 5 the two-dimensional plane decomposition of the ground velocity vector for three different starting positions of the UAV considered in , where the "wind triangle" represents the ground velocity in the x-axis and y-axis directions calculated from the wind speed vector and airspeed vector through the superposition relationship of the wind triangle, and the "ground speed" represents the ground velocity in the x-axis and y-axis directions calculated based on the magnitude and course angle of the ground velocity vector. Figure 6 shows that the ground velocities in the x-axis and y-axis directions obtained by the two methods are exactly the same, indicating the correctness of the research. In addition, Figure 6 shows that the direction of the ground velocity is consistent with the UAV course angle given in Table 2, further indicating the correctness of the research.

[0110] Figure 7 、 Figure 8 、 Figure 9 and Figure 10 respectively give the relationships between the magnitude of the UAV airspeed vector, the magnitude of the ground velocity vector, the sideslip angle and the roll angle and the magnitude of the wind speed vector, where the magnitude v of the wind speed vector w varies in the range of 0 to 6 m / s. Here, three wind speed vector direction angles and UAV starting position cases are considered, namely, Case 1: θ w =-135°, Case 2: θ w =45°, Case 3: θ w =80°, The corresponding UAV course angles for the three cases are shown in Table 2.

[0111] Figure 7 shows that although the magnitude of the UAV airspeed vector increases with the increase of the magnitude of the wind speed vector, the change amplitude is very small; for Case 1 and Case 2, the magnitude of the UAV airspeed vector has values in the range of 0 ≤ v w ≤ 6, but for Case 3, when v w is greater than 5.143, there will be no magnitude of the airspeed vector, that is, at this time, the sideslip method cannot be used to make the UAV fly along the desired flight path. Observing Figure 9 it can be found that when v wWhen it is equal to 5.143, the sideslip angle of the UAV will be the minimum allowed value of -30°. When v w increases further, a smaller sideslip angle is required to resist the influence of crosswind, but due to the limitation of the UAV's sideslip angle, it cannot be achieved. According to the UAV course angle listed in Table 2 and Figure 7 , it can be seen that in Case 3, θ w -χ = 88.5308°, which is very close to vertical (i.e., the case of θ w -χ = 90°). Therefore, compared with Case 1 and Case 2, Case 3 requires a larger absolute value of the sideslip angle to resist the influence of wind disturbance.

[0112] Figure 8 shows the relationship between the magnitude of the UAV's ground speed vector and the magnitude of the wind speed vector. Figure 8 shows that compared with the magnitude of the airspeed vector, the dynamic range of the magnitude of the UAV's ground speed vector is much larger. Case 1 is against the wind, and Case 2 is with the wind. Therefore, as v w increases, the magnitude of the ground speed vector in Case 1 decreases, while the magnitude of the ground speed vector in Case 2 increases. For Case 3, θ w -χ = 88.5308°, which is very close to vertical, but strictly speaking, it still belongs to the case of flying with the wind. In the case of flying with the wind, the ground speed should increase as v w increases. However, Figure 8 shows that the ground speed in Case 3 decreases as v w increases. This is because the UAV uses the sideslip method to make the UAV fly along the desired trajectory. According to the wind triangle superposition relationship shown in Figure 1 , if the magnitude of the UAV's airspeed vector remains unchanged, the direction angle of the wind speed vector remains unchanged, the UAV course angle remains unchanged, and when the wind speed vector is close to perpendicular to the ground speed vector, increasing the magnitude of the wind speed vector will force the ground speed to decrease (i.e., reduce the magnitude of the ground speed vector). This is the reason why the ground speed in Case 3 decreases as v w increases.

[0113] Figure 9 and Figure 10 respectively show the relationships between the sideslip angle and the roll angle of the UAV and the magnitude of the wind speed vector. Figure 9 and Figure 10 show that the sideslip angle and the roll angle of the UAV are positively correlated, that is, when the sideslip angle of the UAV takes the maximum or minimum value, its roll angle also takes the maximum or minimum value. This phenomenon is consistent with Equation (18) in the theoretical analysis. Theoretically, when the wind speed vector is perpendicular to the fuselage direction of the UAV (when using the sideslip method, the wind speed vector is perpendicular to the ground speed vector), the maximum or minimum sideslip angle will be generated (i.e., the absolute value of the sideslip angle is the largest). From Table 2 and Figure 9 , it can be seen that in Case 3, θ w-χ=88.5308°, which is very close to vertical (i.e., θ w -χ=90°), therefore, compared with Case 1 and Case 2, Case 3 requires a larger absolute value of the sideslip angle to resist the influence of wind disturbance. In addition, Figure 9 and Figure 10 It shows that the sideslip angle and roll angle values of the UAV meet the given constraints, indicating the correctness of the research.

[0114] Figure 11 Given Figure 7 、 Figure 8 、 Figure 9 and Figure 10 Figure 2. Two-dimensional plane decomposition of the ground speed vector for the three cases considered in

[15] . The “wind triangle” represents the ground speed in the x-axis and y-axis directions calculated from the wind speed vector and the airspeed vector through the wind triangle superposition relationship, and the “ground speed” represents the ground speed in the x-axis and y-axis directions calculated based on the amplitude of the ground speed vector and the course angle. Figure 11 It shows that the ground speeds in the x-axis and y-axis directions obtained by the two methods are exactly the same, which shows the correctness of the research. Figure 11 It shows that the direction of the ground speed is consistent with the UAV route angle given in Table 2, which further proves the correctness of the research.

[0115] In order to verify the ability of UAV to provide relay forwarding service, the amount of data received by the ground destination node under different conditions is calculated. Figure 7 、 Figure 8 、 Figure 9 and Figure 10 The three different wind speed vector direction angles and the starting position of the UAV considered in the paper, namely, θ w =-135°,θ w =45° and θ w =80°, and Here, it is assumed that the distance the drone flies is equal to the distance between users U1 and U2, that is, the drone flight distance is d 12 , the flight time is T = d 12 / v g , the number of time slots is 2N=5000, the wind speed vector amplitude v w =5m / s. and q ys =150 The UAV course angles under the three conditions can be seen in Table 2. It should be noted that the ground speed here is related to the UAV starting position parameter It has nothing to do with the wind speed vector direction angle θ w The above three wind speed vector angles (i.e., θ w =-135°,θ w= 45° and θ w = 80°) are the ground speeds of v g = 5.7913 m / s, v g = 13.7044 m / s and v g = 9.1771 m / s. For comparison, consider the case where the UAV flies parallel to the x-axis of the horizontal plane from the starting point, where the starting point, flight time, and ground speed of the UAV are the same as those in the corresponding above cases. Table 3 shows the amount of data received by the ground destination node under the method of the present invention and the corresponding flight mode parallel to the x-axis. Table 3 shows that the amount of data received by the ground destination node under the method of the present invention is greater than that of the three corresponding comparison schemes, indicating the advantage of the method of the present invention in improving the relay forwarding ability of the UAV. In addition, as the starting point of the UAV deviates more from the ground source node, the advantage of the amount of data received by the ground destination node becomes more obvious, further indicating the effectiveness of the method of the present invention.

[0116] Table 3

[0117]

[0118] Example 2:

[0119] The computer-readable storage medium of this embodiment stores a computer program, and when the program is executed by a processor, it implements the steps in the anti-wind UAV relay communication method based on the sideslip method in Example 1.

[0120] The computer-readable storage medium of this embodiment can be the internal storage unit of the terminal, such as the hard disk or memory of the terminal; the computer-readable storage medium of this embodiment can also be the external storage device of the terminal, such as the plug-in hard disk, smart memory card, secure digital card, flash card, etc. equipped on the terminal; further, the computer-readable storage medium can also include both the internal storage unit and the external storage device of the terminal.

[0121] The computer-readable storage medium of this embodiment is used to store the computer program and other programs and data required by the terminal, and the computer-readable storage medium can also be used to temporarily store the data that has been output or will be output.

[0122] Example 3:

[0123] The computer device of this embodiment includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the steps of the anti-wind UAV relay communication method based on the sideslip method in Example 1.

[0124] In this embodiment, the processor may be a central processing unit, or may also be other general-purpose processors, digital signal processors, application-specific integrated circuits, off-the-shelf programmable gate arrays or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.; the memory may include a read-only memory and a random access memory, and provide instructions and data to the processor. A part of the memory may also include a non-volatile random access memory. For example, the memory may also store information about the device type.

[0125] Those skilled in the art should understand that the content disclosed in the embodiments can be provided as a method, a system, or a computer program product. Therefore, the present solution can be implemented in the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present solution can be implemented in the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories and optical memories, etc.) containing computer-usable program code.

[0126] The present solution is described with reference to the flowcharts and / or block diagrams of the methods and computer program products according to the embodiments of the present solution. It should be understood that each process and / or block in the flowchart and / or block diagram, and the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions; these computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to generate a machine, so that the instructions executed by the processors of the computer or other programmable data processing devices generate for implementing in the process Figure 1 one process or multiple processes and / or blocks Figure 1 a device for the functions specified in one block or multiple blocks.

[0127] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured product including an instruction device, and the instruction device implements in the process Figure 1 one process or multiple processes and / or blocks Figure 1 a device for the functions specified in one block or multiple blocks.

[0128] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 a device for the functions specified in one block or multiple blocks.

[0129] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above various methods. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0130] The examples described in the present invention are only descriptions of the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various deformations and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope of the present invention.

Claims

1. A wind-resistant UAV relay communication method based on the sideslip method, characterized in that It includes the following steps: Obtain the parameters of the UAV relay system; Based on the position information of the source node and the destination node and the flight starting point information of the UAV relay, give the course angle for the UAV to perform information forwarding service; Utilize the wind field information in the natural environment to adjust the flight state of the UAV relay, so that the UAV relay can fly along the desired trajectory in the wind field; During the flight, the UAV acts as a half-duplex amplify-and-forward relay to provide information forwarding service for ground users.

2. The method according to claim 1, characterized in that, The obtaining of the parameters of the UAV relay system includes: the antenna height a1 of the ground user U1, the antenna height a2 of the ground user U2, and the UAV flight height a R , the distance d between the ground user U1 and the ground user U2 12 , the magnitude v of the wind speed vector w , the angle θ between the wind speed vector and the horizontal plane x-axis w , the transmission power P of the ground user U1 and the UAV relay U R T , the channel power reference value at a distance of 1 meter , the noise power σ 2 , the air density ρ, the UAV wing area S, the lift coefficient C L , the drag coefficient C D , the side force coefficient , the maximum sideslip angle β during UAV flight max and the maximum roll angle φ max , the maximum airspeed limit V generated by the UAV due to structural limitations amax , the maximum output power P of the UAV engine max and the starting point coordinates of the UAV flight ​ 3. The method according to claim 2, wherein The course angle for the UAV to perform information forwarding service is 4. The method according to claim 3, characterized in that The specific steps of utilizing the wind field information in the natural environment to adjust the flight state of the UAV relay, so that the UAV relay can fly along the desired trajectory that maximizes the amount of information received by the destination node in the wind field are as follows: Step 1: Initialize the UAV relay U R Ground speed vector magnitude , airspeed vector magnitude , angle between the airspeed vector and the horizontal plane axis , sideslip angle and roll angle , calculate the course angle ; Step 2: If holds, let ; If holds, let ; For other value cases, let ; Step 3: When holds, let ; when holds, it is necessary to obtain the sideslip angle of the UAV when Equation (19) holds through the binary search method within the range of , and denote it as ; （19） Step 4: If or , then let , and then jump to Step 5; otherwise, check whether Equation (21) holds. If Equation (21) does not hold, set the magnitude of the UAV airspeed vector to 0, and then jump to Step 9. If Equation (21) holds, obtain the solution of the equation given by Equation (20) through the bisection search method within the range of , and denote it as . During the bisection search process, the magnitude of the UAV airspeed vector can be calculated by Equation (17), and the roll angle of the UAV can be calculated by Equation (18). （17） （18） （20） （21） Step 5: Substitute for in Equation (18), calculate the corresponding roll angle of the UAV, and denote it as ; substitute for in Equation (17), calculate the corresponding magnitude of the UAV airspeed vector, and denote it as ; substitute and for and in Equation (15) respectively, calculate the power output provided by the UAV engine, and denote it as ; （15） Step 6: If or holds, then set , and then jump to Step 9; Step 7: Substitute for in Equation (16), then calculate the magnitude of the ground speed vector, which will be denoted as , and divide the flight distance by the magnitude of the ground speed vector to obtain the time for the UAV to fly and act as a relay to forward information ; （16） Step 8: When occurs, replace and in Equation (22) with and respectively, and calculate the angle between the airspeed vector of the drone and the axis of the horizontal plane (i.e., the direction angle of the airspeed vector). When occurs, replace and in Equation (23) with and respectively, and calculate ; （22） （23） Step 9: If holds (the magnitude of the UAV airspeed vector is zero), the UAV cannot use the sideslip method to fly the UAV along the desired trajectory; if does not hold, then when holds, the UAV flies with a roll angle of , a sideslip angle of , and an airspeed vector of . When holds, the UAV flies with a roll angle of , a sideslip angle of , and an airspeed vector of . The ground speed vector of the drone during flight is ; During the flight, the UAV uses the half-duplex amplify-and-forward protocol to forward information from the ground user U1 to the ground user U2. The time for the UAV to fly and act as a relay to forward information is .

5. A storage medium, characterized in that, Instructions are stored in the storage medium, and when the computer reads the instructions, the computer executes the anti-wind UAV relay communication method based on the sideslip method as described in any one of claims 1-4.

6. An electronic device, characterized in that, It includes a processor and the storage medium as described in claim 5, and the processor executes the instructions in the storage medium.

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