Method for Evaluating Crosswind Resistance Ability of UAV during Taxiing

Abstract

The present invention provides a method for evaluating the crosswind resistance ability of an unmanned aerial vehicle during taxiing, which includes the following steps: obtaining aerodynamic data during the taxiing process of the unmanned aerial vehicle; determining the range of taxiing speed characteristic points for evaluation; selecting taxiing speed characteristic points according to the range of taxiing speed characteristic points, and determining the range of roll angular rate and yaw angular rate for evaluation; according to the determined airspeed range, roll angular rate range and yaw angular rate range, solving the maximum sideslip angle and crosswind value that can be balanced when the rudder reaches the maximum value within the value range of the taxiing speed characteristic points. The present invention simplifies the motion mode, selects the section where side deviation is more likely to occur for analysis, and avoids modeling the complex motion process of taxiing.

Description

Technical Field

[0001] The present invention belongs to the technical field of unmanned aerial vehicle (UAV) testing, and particularly relates to a method for evaluating the crosswind resistance ability of a UAV during takeoff roll. Background Art

[0002] During the takeoff roll of a UAV, due to factors such as runway width and crosswind, accidents of the aircraft deviating from the runway are likely to occur, making it difficult to ensure flight safety. For UAVs with large wingspans and light weights, during the takeoff roll, the UAV is extremely vulnerable to the influence of crosswinds and large lateral deviations occur. Therefore, it is necessary to fully understand the ability of the UAV to cope with gusts and strictly constrain the wind field conditions during the takeoff roll. Considering that during the takeoff roll of the UAV, affected by ground forces, aerodynamic forces, and the flexibility of the landing gear, it is difficult to obtain a relatively accurate mathematical model. At the same time, during the takeoff roll, a series of actions such as the front or rear wheels lifting are included, and the motion mode is relatively complex.

[0003] Generally, in engineering practice, takeoff roll tests are used to debug and verify the takeoff roll ability and control characteristics of a UAV. Due to the unclear prediction of the UAV's ability in the early stage of the test, the takeoff roll test may result in two situations: insufficient verification or causing greater risks. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for evaluating the crosswind resistance ability of a UAV during takeoff roll. The solution of the present invention can solve the problems existing in the above prior art.

[0005] The technical solution of the present invention:

[0006] A method for evaluating the crosswind resistance ability of a UAV during takeoff roll, comprising the following steps:

[0007] Obtain the aerodynamic data during the taxiing process of the UAV;

[0008] Determine the range of takeoff roll speed characteristic points for evaluation;

[0009] According to the range of takeoff roll speed characteristic points, select the takeoff roll speed characteristic points, and determine the range of roll angular rate and yaw angular rate for evaluation;

[0010] According to the determined airspeed range, roll angular rate range, and yaw angular rate range, solve for the maximum sideslip angle and crosswind value that can be balanced when the rudder reaches the maximum value within the value range of the takeoff roll speed characteristic points.

[0011] Further, the value range of the takeoff roll speed characteristic points is: the main control wheel speed when the UAV is in a state where the main control wheel leaves the ground or the UAV lift is greater than 80% of the gravity and the UAV takeoff speed are used as the value endpoints of the takeoff roll speed characteristic points.

[0012] Furthermore, for the selection of the roll angular rate range: by selecting the characteristic points of the takeoff ground speed and giving a unit step roll angle command signal, the variation range of the time-domain response of the roll angular rate signal can be used as the optional range for subsequent evaluation.

[0013] Furthermore, for the selection of the yaw angular rate range: by selecting the characteristic points of the takeoff ground speed and giving a unit step track angle deviation signal command, the variation range of the time-domain response of the heading angular rate signal can be used as the optional range for subsequent evaluation.

[0014] Furthermore, the method steps for evaluating the crosswind resistance ability of the UAV during takeoff ground run also include data correction. By combining the real test data, the aerodynamic data, the value range of the takeoff ground speed characteristic points, and the value ranges of the roll angular rate and yaw angular rate are corrected to obtain a more accurate evaluation result.

[0015] Advantages of the present invention compared with the prior art:

[0016] (1) The present invention can quantitatively analyze the crosswind resistance ability of the UAV during takeoff ground run based on the given overall and aerodynamic parameters, providing a basis for formulating the safety firing tables for UAV flight and takeoff ground run tests, and ensuring flight safety.

[0017] (2) In the present invention, the motion mode is simplified, and the section where side deviation is more likely to occur is selected for analysis, avoiding the modeling of the complex motion process during takeoff ground run. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings included are used to provide a further understanding of the embodiments of the present invention, which form a part of the specification, illustrate the embodiments of the present invention, and together with the written description explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings without creative efforts based on these drawings.

[0019] Figure 1 FIG. shows a schematic diagram of the method steps for evaluating the crosswind resistance ability of a UAV during takeoff ground run according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way restricts the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0021] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless otherwise clearly specified in the context, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and devices should be regarded as part of the authorized specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0023] In one embodiment, a method for evaluating the crosswind resistance ability of an unmanned aerial vehicle during takeoff roll is provided, including the following steps:

[0024] Obtain the aerodynamic data during the taxiing process of the unmanned aerial vehicle;

[0025] Determine the range of takeoff roll speed characteristic points for evaluation;

[0026] According to the range of takeoff roll speed characteristic points, select the takeoff roll speed characteristic points, and determine the range of roll angular rate and yaw angular rate for evaluation;

[0027] According to the determined airspeed range, roll angle rate range, and yaw angle rate range, solve for the maximum sideslip angle and crosswind value that can be balanced when the rudder reaches its maximum value within the range of takeoff speed characteristic points.

[0028] As Figure 1 shown, taking the case of a drone encountering a gust from the due right side as an example, according to an embodiment of the present invention, a method for evaluating the crosswind resistance ability of a drone during takeoff includes the following steps:

[0029] Step 1: Obtain the aerodynamic data during the taxiing of the drone, including: lift, drag, lateral force, rolling moment, yaw moment, and pitch moment. During the taxiing of the drone, when the speed is relatively low and there is a lateral gust, it often causes a large sideslip angle. In one embodiment, if the current aerodynamic parameter table cannot meet the usage requirements, the aerodynamic data can be extended. If the aerodynamic parameters are well linearized, linear extrapolation can be used to extend the aerodynamic data. If the linearization of the aerodynamic parameters does not meet the requirements, polynomial fitting or other fitting methods can be used to fit the aerodynamic data and then interpolation is used to extend the aerodynamic data.

[0030] Step 2: Determine the range of takeoff speed characteristic points for evaluation; further, in one embodiment, the value range of the takeoff speed characteristic points is: the main control wheel speed when the drone is in the state where the corrective main control wheel leaves the ground or the state where the lift of the drone is more than 80% greater than the gravity and the takeoff speed of the drone are used as the value endpoints of the takeoff speed characteristic points. In one embodiment, within this range of speed characteristic points, when the drone is affected by a crosswind and has a large deviation, it can be set according to the aircraft configuration.

[0031] Taking a drone equipped with a bicycle-type landing gear as an example, after the rear wheel of the drone leaves the ground, the drone taxis with the front wheel in a single-wheel contact state. The ground force acting on the drone is significantly weakened and reduced. At this time, the drone is more likely to deviate from the runway. Therefore, during the takeoff of the drone, the range from the rear wheel leaving the ground speed V onewheel to the takeoff speed V takeoff of the drone is used as the range of takeoff speed characteristic points to evaluate the crosswind resistance ability of the drone. In other embodiments, for drones with other types of landing gears, the range of takeoff speed characteristic points can be determined according to the analysis.

[0032] The moment when the rear wheel of the drone leaves the ground satisfies the following kinematic and dynamic equations:

[0033]

[0034] In the above equations, G is the gravity, L is the lift, P n is the front wheel reaction force, M z is the pitch moment, α is the angle of attack, a zis the horizontal distance from the wheel to the center of gravity of the UAV. When the rear wheel of the UAV leaves the ground, the magnitude of α is approximately equal to the parking angle θ0 of the UAV. It is considered that the current lift is calculated as follows:

[0035] L = q·S ref ·cy

[0036] cy = cy(H,α,β)+Δcy(α,δ z )+Δcy gear

[0037] M z = q·S ref ·Lref·mz

[0038] mz = mz(H,α,β)+Δmz(α,δ z )+Δmz gear

[0039] Among them, q is the oncoming flow dynamic pressure; S ref is the reference area; L ref is the longitudinal moment reference length; H is the flight altitude of the UAV, δ z is the elevator deflection, which is obtained by solving the takeoff and landing control law and is generally a function of the pitch angle; β is the sideslip angle. For simplicity of calculation, β is taken as 0. cy is the lift coefficient, cy(H,α,β) is the longitudinal and lateral coupling coefficient of lift, Δcy(α,δ z ) is the lift coefficient generated by the elevator, Δcy gear is the lift increment coefficient caused by the landing gear; mz is the pitch moment coefficient, mz(H,α,β) is the longitudinal and lateral coupling coefficient of the pitch moment, Δmz(α,δ z ) is the pitch moment coefficient generated by the elevator, Δmz gear is the pitch moment increment coefficient caused by the landing gear.

[0040] The unknown variables in the above equations are the front wheel reaction force and the airspeed. By solving the above equations, the airspeed V of the UAV at the moment when the rear wheel of the UAV leaves the ground can be obtained onewheel .

[0041] The moment when the UAV leaves the ground satisfies the following kinematic and dynamic equations:

[0042]

[0043] The unknown variables in the above equations are the angle of attack and the airspeed. By solving the above equations, the airspeed V of the UAV at the moment when the rear wheel of the UAV leaves the ground can be obtained takeoff .

[0044] By calculation, the interval of the takeoff speed characteristic point [V onewheel V takeoff, within this speed range, the UAV has a relatively high risk of deviating from the runway. Subsequently, the crosswind resistance ability of the UAV can be evaluated within this speed range.

[0045] In another embodiment, the value range of the takeoff speed characteristic points uses the speed of the main control wheel when the lift is greater than 80% of the gravity and the takeoff speed of the UAV as the endpoints. The calculation methods of these two speeds are existing techniques and will not be elaborated here.

[0046] Step 3, determine the evaluation range of the roll angular rate and the yaw angular rate;

[0047] Furthermore, in one embodiment, for the selection of the roll angular rate range: select the takeoff speed characteristic points, give a unit step roll angle command signal, and the change range of the time-domain response of the roll angular rate signal can be used as the optional range for subsequent evaluation.

[0048] Furthermore, in one embodiment, for the selection of the yaw angular rate range: select the takeoff speed characteristic points, give a unit step track angle deviation signal command, and the change range of the time-domain response of the yaw angular rate signal can be used as the optional range for subsequent evaluation.

[0049] In this embodiment, when the UAV is affected by crosswinds, it will cause fluctuations in the roll angle and yaw angular rate. The roll angular rate caused by the crosswind will intensify the rotation of the UAV towards the windward side, while the yaw angular rate will hinder the rotation of the UAV towards the windward side. When evaluating the crosswind resistance ability, since the sympathetic yaw moment caused by the roll angular rate is an important factor that causes the UAV to deviate from its course, it is necessary to select the angular rate value within a reasonable range in subsequent evaluations.

[0050] For the roll channel, during the takeoff phase, the main task is to control the UAV to be in a wing-level state, that is, the desired roll angle is 0°. When the UAV is disturbed by gusts, there will be fluctuations in the roll angle. Select the takeoff speed characteristic points, give a unit step roll angle command signal, and the change range of the time-domain response of the roll angular rate signal can be used as the optional range for subsequent evaluation. For the yaw channel, during the takeoff phase, the course deviation is mainly controlled by the rudder. When the UAV is disturbed by gusts, there will be fluctuations in the UAV's track. Select the takeoff speed characteristic points, give a unit step track angle deviation signal command, and the change range of the time-domain response of the yaw angular rate signal can be used as the optional range for subsequent evaluation.

[0051] In one embodiment, the selection of the takeoff speed characteristic points needs to cover the entire value range of the takeoff speed characteristic points to make the solution of the roll angular rate range and the yaw angular rate range more accurate.

[0052] Take values for the roll angular rate and yaw angular rate within the obtained optional range. Here, the greater the value of the roll angular rate or the smaller the value of the yaw angular rate, the more stringent the evaluation; conversely, the looser the evaluation. Subsequently, the values of the angular rate can be corrected in combination with real test data.

[0053] Step 4: According to the determined range of takeoff speed characteristic points, roll angular rate range, and yaw angular rate range, solve for the maximum sideslip angle and crosswind value that can be balanced when the rudder reaches its maximum value at the takeoff speed characteristic points.

[0054] In a specific embodiment, taking the example of the UAV being affected by a crosswind on the right side, the UAV has a positive sideslip. Let the rudder reach the positive maximum value, and iteratively calculate the maximum sideslip angle that satisfies the balance of the yaw channel, thereby solving for the maximum crosswind resistance value. The yaw channel of the UAV satisfies the following equation:

[0055]

[0056] β = tan(V wind / V a ), δ y = δ y_max

[0057] where My β is the yaw static stability moment; is the control moment generated by the rudder; the rudder deflection selects the maximum positive rudder deflection; are the yaw moments caused by the roll angular rate and yaw angular rate respectively, where the values of the roll angular rate and yaw angular rate are the angular rate values selected in Step 3, V wind is the crosswind speed, V a is the airspeed, δ y is the commanded rudder deflection of the UAV rudder, δ y_max is the maximum commanded rudder deflection of the UAV rudder. The above moment calculations satisfy the following equation:

[0058]

[0059] where, and are the yaw static stability moment coefficient, rudder control moment coefficient, yaw damping derivative, and yaw cross-coupling moment coefficient respectively, and b is the lateral-directional reference length. δ y is the commanded rudder deflection of the UAV rudder, are the non-dimensionalized roll angular rate and yaw angular rate respectively, and the calculation formulas are as follows:

[0060]

[0061] where p and r are the roll angular rate and yaw angular rate respectively.

[0062] In the above equation, the sideslip angle is the unknown of the equation. Select the takeoff speed characteristic points in the speed range calculated in Step 2 for iterative solution of the above equation, and the maximum sideslip angle and maximum crosswind volume that the UAV can maintain balance under the maximum rudder surface control ability in this state can be solved. The takeoff process of the UAV is a dynamic process, involving many factors and difficult to calculate quantitatively. Therefore, only the transient characteristics are calculated to evaluate the crosswind resistance ability during takeoff.

[0063] Step Five: Combine the real test data to iteratively correct the aerodynamic data, the value range of the takeoff speed characteristic points, and the value ranges of the roll angular rate and yaw angular rate to obtain a more accurate evaluation result.

[0064] In summary, the method for evaluating the crosswind resistance ability of the UAV during takeoff according to the present invention has at least the following advantages compared with the prior art:

[0065] (1) The present invention can quantitatively analyze the crosswind resistance ability of the UAV during takeoff based on the given overall and aerodynamic parameters, providing a basis for formulating the safety firing tables for UAV flight and takeoff tests, and ensuring flight safety;

[0066] (2) In the present invention, the motion mode is simplified, and the section where side deviation is more likely to occur is selected for analysis, avoiding the modeling of the complex takeoff motion process.

[0067] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for evaluating the crosswind resistance ability of an unmanned aerial vehicle during takeoff roll, characterized in that, It includes the following steps: Obtain the aerodynamic data during the taxiing process of the UAV; Determine the range of the evaluated taxiing speed characteristic points; the value range of the taxiing speed characteristic points is: the main control wheel speed when the UAV is in the state of the main control wheel leaving the ground or the state where the lift of the UAV is more than 80% of the gravity and the takeoff speed of the UAV are used as the value endpoints of the taxiing speed characteristic points; According to the range of the taxiing speed characteristic points, select the taxiing speed characteristic points, and determine the range of the evaluated roll angular rate and the range of the yaw angular rate; the selection of the range of the roll angular rate: according to the selected taxiing speed characteristic points, give a unit step roll angle command signal, and use the change range of the time-domain response of the roll angular rate signal as the optional range for subsequent evaluation; the selection of the range of the yaw angular rate: according to the selected taxiing speed characteristic points, give a unit step track angle deviation signal command, and use the change range of the time-domain response of the yaw angular rate signal as the optional range for subsequent evaluation; According to the determined range of the taxiing speed characteristic points, the range of the roll angular rate and the range of the yaw angular rate, solve the maximum sideslip angle and the crosswind value that can be balanced when the rudder reaches the maximum value within the value range of the taxiing speed characteristic points.

2. The method for evaluating the crosswind resistance ability of an unmanned aerial vehicle during takeoff roll according to any one of claims 1, wherein The steps of the method for evaluating the crosswind resistance ability of the UAV taxiing also include data correction, and correct the aerodynamic data, the value range of the taxiing speed characteristic points, and the value ranges of the roll angular rate and the yaw angular rate in combination with the real test data to obtain a more accurate evaluation result.

Images