Attitude optimization method for omni-directional multi-rotor aircraft

Abstract

The invention discloses an attitude optimization method for an omni-directional multi-rotor aircraft, and relates to the technical field of unmanned aerial vehicle flight control, and the method comprises the steps: determining a direction vector of an antenna according to an Euler angle of the omni-directional multi-rotor aircraft; determining a legal antenna gain and a malicious antenna gain according to the positions and the direction vectors of the legal node and the malicious node; determining a signal to interference plus noise ratio of the antenna according to the legal antenna gain and the malicious antenna gain; establishing a target function by taking the maximum signal to interference plus noise ratio as a target; selecting a zero interference mode or a maximum gain mode according to the size of the signal to interference plus noise ratio, and updating the target function according to the selected mode; and solving the updated objective function to obtain attitude data. The zero interference or maximum gain mode is selected according to the size of the signal to interference and noise ratio, the attitude of the unmanned aerial vehicle is adjusted to enable the antenna to be in the corresponding mode, and the safety of the unmanned aerial vehicle is ensured from the physical level.

Description

Technical Field

[0001] The present application relates to the field of UAV flight control technology, and in particular to a method for optimizing the attitude of an omnidirectional multi-rotor aircraft. Background Art

[0002] An omnidirectional multirotor vehicle (MRAV) is a commonly used type of drone that can perform various tasks under the control of a ground controller or using active control technology. During this process, the drone needs to communicate with ground equipment at all times to receive control signals or return collected data.

[0003] Because there are many communication nodes in space, some of them are legitimate, enabling smooth data transmission and ensuring data security. However, some are malicious, capable of tampering with data sent or received by drones, posing a serious threat to the security of drones and their data. To improve drone security in scenarios with malicious nodes, existing technologies often use beamforming, which manipulates the phases of multiple antennas to direct signals toward legitimate nodes. However, this beamforming method cannot completely protect drones from malicious nodes, and therefore its effectiveness has been limited. Summary of the Invention

[0004] An embodiment of the present application provides an attitude optimization method for an omnidirectional multi-rotor aircraft, which is used to solve the problem in the prior art that the beamforming method cannot completely ensure that the drone is not affected by malicious nodes.

[0005] The present invention provides a method for optimizing the attitude of an omnidirectional multi-rotor aircraft, comprising:

[0006] Establishing a global coordinate system and an untilted coordinate system of the omnidirectional multirotor aircraft;

[0007] Determine a direction vector of an antenna on the omnidirectional multirotor aircraft based on the Euler angle of the omnidirectional multirotor aircraft in an untilted coordinate system;

[0008] Determine the legitimate antenna gain of the antenna relative to the legitimate node and the malicious antenna gain of the antenna relative to the malicious node according to the positions and direction vectors of the legitimate node and the malicious node in the global coordinate system;

[0009] Determine the antenna's signal-to-interference-and-noise ratio based on the legitimate antenna gain and the malicious antenna gain;

[0010] The objective function is established with the goal of maximizing the signal-to-interference-noise ratio of all legal nodes;

[0011] Select zero interference mode or maximum gain mode based on the signal-to-interference-noise ratio (SINR) and update the objective function based on the selected mode. In zero interference mode, the antenna's null point points toward the malicious node, while in maximum gain mode, the antenna's main lobe points toward the legitimate node.

[0012] Solve the updated objective function to obtain the attitude data of the omnidirectional multirotor aircraft.

[0013] In one possible implementation, the first elevation cosine value of the legitimate node and the antenna is calculated by the inner product, the second elevation cosine value of the malicious node and the antenna is calculated by the inner product, and the legitimate antenna gain and the malicious antenna gain are calculated respectively according to the first elevation cosine value and the second elevation cosine value.

[0014] In one possible implementation, the objective function includes an altitude constraint, a roll / pitch angle range constraint, and a fixed yaw angle constraint.

[0015] In one possible implementation, after selecting the maximum gain mode, if the number of legal nodes is two, the objective function is updated in the direction determined by the cross product of the position vectors of the legal nodes. When solving the updated objective function, there is also a constraint that the position of the omnidirectional multirotor aircraft is equal to the distance between the two legal nodes.

[0016] In a possible implementation, when the signal to interference plus noise ratio is less than a threshold, the zero interference mode is selected; and when the signal to interference plus noise ratio is greater than or equal to the threshold, the maximum gain mode is selected.

[0017] In one possible implementation, a simulated annealing algorithm is used to solve the updated objective function.

[0018] The attitude optimization method of an omnidirectional multi-rotor aircraft in this application has the following advantages:

[0019] Select zero interference or maximum gain mode based on the signal-to-interference-noise ratio, and adjust the drone's posture so that the antenna is in the corresponding mode, ensuring the safety of the drone from a physical level. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 A flowchart of a method for attitude optimization of an omnidirectional multi-rotor aircraft provided in an embodiment of the present application.

[0022] Figure 2 The minimum signal-to-interference-and-noise ratio curves of the four attitude optimization strategies under different interference powers in the experiment provided in the embodiment of the present application are shown. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0024] Figure 1 Flowchart of an attitude optimization method for an omnidirectional multi-rotor aircraft provided in an embodiment of the present application. An embodiment of the present application provides an attitude optimization method for an omnidirectional multi-rotor aircraft, comprising:

[0025] S100: Establish a global coordinate system and an untilted coordinate system of the omnidirectional multirotor aircraft.

[0026] For example, the embodiment of the present application targets a scenario where an omnidirectional multi-rotor aircraft is used as an airborne base station (BS) at a position p BS =[x BS ,y BS ,z BS ] T , where x BS 、y BS and z BS They are the omnidirectional multirotor aircraft in the global coordinate system F W The coordinates in the x, y and z axes, height z BS Subject to certain constraints, omnidirectional multirotor aircraft have the ability to independently control position and direction and are equipped with a single antenna.

[0027] Multiple legal nodes are deployed on the ground and a malicious node M. The locations of all nodes (including legitimate and malicious nodes) are known and are located on the ground by default, where S i represents the i-th legal node, and N is the number of legal nodes.

[0028] Define the global coordinate system F W and the untilted coordinate system F based on the position of the omnidirectional multirotor aircraft U , used to describe the direction vector of the antenna and the relative position of the node.

[0029] S110 , determining a direction vector of an antenna on the omnidirectional multirotor aircraft according to the Euler angle of the omnidirectional multirotor aircraft in an untilted coordinate system.

[0030] For example, according to the untilted coordinate system F U Euler angles of the omnidirectional multi-rotor aircraft (roll angle φ, pitch angle Yaw angle ψ), calculate the direction vector Υ(η BS ):

[0031]

[0032] This vector describes the pointing direction of the antenna's main lobe.

[0033] S120 , determining a legitimate antenna gain of the antenna relative to the legitimate node and a malicious antenna gain of the antenna relative to the malicious node according to the positions and direction vectors of the legitimate node and the malicious node in the global coordinate system.

[0034] For example, a dipole antenna model is used, and the antenna gain is defined as G(γ)=sin 2 (γ), where γ is the signal arrival elevation angle. The legal node S can be calculated by the inner product i and the elevation cosine value of the malicious node M, where the legitimate node S i The cosine of the elevation angle is expressed as:

[0035]

[0036] And derive the corresponding legal antenna gain:

[0037]

[0038] Among them, γ i is the signal arrival elevation angle of the i-th legal node, is the i-th legal node in the global coordinate system F W The coordinates in express and p BS The distance between them, <·> means calculating the inner product.

[0039] For malicious nodes, replace γ in the above formula i The signal arrival angle γ of the malicious node is replaced M , and use the malicious node M in the global coordinate system F W The coordinate p in M replace The elevation cosine value of the malicious node M and the corresponding malicious antenna gain can be obtained. That is, the elevation cosine value of the malicious node M is expressed as:

[0040]

[0041] The corresponding malicious antenna gain is:

[0042]

[0043] S130: Determine a signal-to-interference-and-noise ratio of the antenna according to the legitimate antenna gain and the malicious antenna gain.

[0044] For example, the signal to interference and noise ratio is expressed as:

[0045]

[0046] Among them, Γ i represents the signal-to-interference-noise ratio of the i-th legitimate node relative to the malicious node M, P and P M denote the signal power of legitimate nodes and the interference power of malicious nodes, σ 2 represents the noise power at the MRAV receiver.

[0047] From the above formula, it can be seen that the signal power of the legitimate node is inversely proportional to the antenna gain and the square of the distance, while the interference power is determined by the antenna gain and distance of the malicious node M.

[0048] S140 , establishing an objective function with the goal of maximizing the signal-to-interference-and-noise ratio of all legal nodes.

[0049] For example, the objective function is expressed as:

[0050]

[0051] ψ=0

[0052] In the above formula, max means taking the maximum value. represents the minimum signal-to-interference-and-noise ratio among all legal nodes. The three constraints from top to bottom are altitude constraint, roll / pitch angle range constraint, and fixed yaw angle constraint. η BS represents the orientation of MRAV, z and Respectively represent the lower and upper limits of the flight altitude, Represents the identity matrix I3∈R 3×3 The third column, I2, represents the 2×2 identity matrix.

[0053] S150, selecting a zero interference mode or a maximum gain mode according to the signal to interference and noise ratio, and updating the objective function according to the selected mode; in the zero interference mode, the null point of the antenna points to the malicious node, and in the maximum gain mode, the main lobe of the antenna is aimed at the legitimate node.

[0054] For example, when the signal-to-interference-plus-noise ratio (SINR) is less than a threshold, the zero-interference mode is selected, and when the SINR is greater than or equal to the threshold, the maximum-gain mode is selected. In this embodiment of the present application, the maximum-gain mode is selected in the case of weak interference. In this case, the maximum-gain solution is consistent with the optimal solution, while the zero-interference solution is optimal for strong interference, so the zero-interference mode is selected. This mode selection method allows the attitude optimization of the omnidirectional multirotor aircraft to effectively eliminate interference, thereby ensuring physical safety.

[0055] If the zero interference mode is selected, the direction of the omnidirectional multirotor aircraft is adjusted so that the zero point of the antenna points to the malicious node M. At this time, the direction vector of the antenna is expressed as:

[0056]

[0057] Eliminate the interference term to get the updated signal-to-interference-noise ratio:

[0058]

[0059] in, represents the signal to interference and noise ratio in zero interference mode, b = {+1, -1}.

[0060] By optimizing only the position of the omnidirectional multirotor, the updated objective function can be obtained based on the updated signal-to-interference-noise ratio:

[0061]

[0062] If the maximum gain mode is selected, when there is only one legitimate node, the antenna direction can be directly adjusted so that the main lobe points to the legitimate node. If there are two legitimate nodes, the position vectors of the two legitimate nodes are cross-producted to determine the antenna direction vector, so that the antenna's main lobe is aligned with the two legitimate nodes. The antenna direction vector in this case is expressed as:

[0063]

[0064] in, and Respectively represent the first legal node and the second legal node in the global coordinate system F W The coordinates in .

[0065] Optimize position p after fixing the direction BS , update the objective function:

[0066]

[0067] in, Indicates the signal-to-interference-and-noise ratio in maximum gain mode.

[0068] The objective function must satisfy the constraint that the distances to the two legal nodes are equal during the solution process:

[0069]

[0070] Among them, D(p BS )and Respectively represent the position p before and after optimization BS The denominator value at includes interference and noise power terms, N2(p BS )and Respectively represent the position p before and after optimization BS The numerator at includes the signal power term. This shows that the signal-to-noise ratio increases after adjusting the position.

[0071] S160, solving the updated objective function to obtain attitude data of the omnidirectional multi-rotor aircraft.

[0072] Exemplarily, a simulated annealing algorithm may be used to solve the updated objective function.

[0073] The minimum signal-to-interference noise of the four attitude optimization strategies under different interference powers in the simulation experiment is as follows: Figure 2 As shown in the figure, the four attitude optimization strategies used in the experiment are optimal attitude solution, maximum gain solution, zero interference solution and vertical orientation solution. Figure 2 It can be seen that the posture optimization method of the present application can ensure that the minimum signal to interference and noise ratio can be maximized in complex scenarios (such as node movement or interference position changes). Specifically, under strong interference, the zero interference solution has the best performance, that is, the signal to interference and noise ratio SINR is stable, while under weak interference, the maximum gain solution is close to the optimal solution.

[0074] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0075] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A method for attitude optimization of an omnidirectional multi-rotor aircraft, characterized in that: include: Establishing a global coordinate system and an untilted coordinate system of the omnidirectional multirotor aircraft; Determining a direction vector of an antenna on the omnidirectional multirotor aircraft according to the Euler angle of the omnidirectional multirotor aircraft in the untilted coordinate system; Determining a legitimate antenna gain of the antenna relative to the legitimate node and a malicious antenna gain of the antenna relative to the malicious node according to the positions of the legitimate node and the malicious node in the global coordinate system and the direction vector; Determining a signal-to-interference-and-noise ratio (SIR) of the antenna according to the legitimate antenna gain and the malicious antenna gain; Establishing an objective function with the goal of maximizing the signal-to-interference-and-noise ratio of all legal nodes; Selecting a zero interference mode or a maximum gain mode according to the signal to interference noise ratio, and updating the objective function according to the selected mode; In the zero interference mode, the null point of the antenna is directed toward the malicious node, and in the maximum gain mode, the main lobe of the antenna is directed toward the legitimate node; Solve the updated objective function to obtain attitude data of the omnidirectional multi-rotor aircraft.

2. The attitude optimization method of an omnidirectional multi-rotor aircraft according to claim 1, characterized in that: The first elevation cosine value of the legitimate node and the antenna is calculated by the inner product, the second elevation cosine value of the malicious node and the antenna is calculated by the inner product, and the legitimate antenna gain and the malicious antenna gain are calculated respectively according to the first elevation cosine value and the second elevation cosine value.

3. The attitude optimization method of an omnidirectional multi-rotor aircraft according to claim 1, characterized in that: The objective function includes an altitude constraint, a roll / pitch angle range constraint, and a fixed yaw angle constraint.

4. The attitude optimization method for an omnidirectional multi-rotor aircraft according to claim 1, characterized in that: After selecting the maximum gain mode, if the number of legal nodes is two, the objective function is updated according to the direction determined by the cross product of the position vectors of the legal nodes. When solving the updated objective function, there is also a constraint that the position of the omnidirectional multirotor aircraft is equal to the distance between the two legal nodes.

5. The attitude optimization method for an omnidirectional multi-rotor aircraft according to claim 1, characterized in that: When the signal to interference plus noise ratio is less than a threshold, the zero interference mode is selected; when the signal to interference plus noise ratio is greater than or equal to the threshold, the maximum gain mode is selected.

6. The method for optimizing the attitude of an omnidirectional multi-rotor aircraft according to claim 1, wherein: The updated objective function is solved using a simulated annealing algorithm.

Images