Fixed-wing UAV transient composite working condition aerodynamic characteristics testing device and method

Abstract

The present invention relates to the field of UAV aerodynamics technology, and specifically to a fixed-wing UAV transient composite working condition aerodynamic characteristics test device and method. The device of the present invention uses four electric cylinders as actuators, and can achieve dynamic adjustment of the pitch angle and roll angle of the UAV by controlling the elongation change of the four electric cylinders, overcoming the deficiency that the existing fixed-wing UAV aerodynamic characteristics test device can only perform static pure working condition testing. The chassis, front and rear frames used can all be built with profiles, with a simple structure, low cost, and easy assembly. In addition, the electric cylinder is used as an actuator, and the control method is simple and the control accuracy is high.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned aerial vehicle aerodynamics, and in particular to a device and method for testing aerodynamic characteristics of a fixed-wing unmanned aerial vehicle in transient composite working conditions. Background Art

[0002] Fixed-wing UAVs have been widely used in the military field to perform high-speed, long-endurance, heavy-load and other unmanned flight missions in recent years due to their advantages such as fast flight speed, long endurance and strong load-bearing capacity. With the rapid development of fixed-wing UAVs and the gradual decline in costs, they have also been gradually used in the civilian field. Fixed-wing UAVs have complex flight conditions and fast flight speeds. Therefore, it is very important to model the flight dynamics of fixed-wing UAVs under transient composite conditions. The flight dynamics model is relatively complex. Among them, the aerodynamic model, as an important part of the flight dynamics model, has always been a hot spot and difficulty in research. The aerodynamic model can generally be divided into a longitudinal model and a lateral model. The longitudinal model mainly includes lift, drag and pitch moment, and the lateral model mainly includes lateral force, rolling moment and yaw moment. Recently, with the increasingly high flight control requirements of fixed-wing UAVs, wind tunnel tests have become an indispensable part of establishing a full aerodynamic model. However, most of the aerodynamic characteristics test devices of fixed-wing UAVs today are static tests of pure conditions, without considering the influence of composite conditions and transient changes on aerodynamic characteristics. Summary of the invention

[0003] In view of this, the present invention proposes a fixed-wing UAV transient composite working condition aerodynamic characteristics testing device and method, which can realize the testing of aerodynamic characteristics under composite working conditions and transient changes.

[0004] To achieve the above object, the technical solution of the present invention is:

[0005] A fixed-wing UAV transient composite working condition aerodynamic characteristics test device, comprising electric cylinder I, electric cylinder II, electric cylinder III, electric cylinder IV, a base frame, a front stand, a rear stand, a balance and a connecting plate;

[0006] Among them, electric cylinder I is fixedly connected to the left front part of the chassis, electric cylinder II is fixedly connected to the left rear part of the chassis, electric cylinder III is fixedly connected to the right front part of the chassis, electric cylinder IV is fixedly connected to the right rear part of the chassis, electric cylinder I, electric cylinder II and electric cylinder III, electric cylinder IV are symmetrically distributed on the left and right, the front frame is fixedly connected to the front crossbeam in the middle of the chassis, the rear frame is fixedly connected to the rear crossbeam in the middle of the chassis, the balance is fixed to the upper part of the front frame and the rear frame, the connecting plate is fixed to the upper part of the balance, and the connecting plate is used to connect the balance and the drone;

[0007] The extension and contraction actions of electric cylinders Ⅰ, Ⅱ, Ⅲ and Ⅳ realize the pitch angle change, roll angle change and combined pitch and roll angle change of the UAV. On this basis, the transient longitudinal aerodynamic characteristics test is realized by coordinating the changes in wind tunnel wind speed and the angle of the UAV rudder surface.

[0008] The present invention also provides a method for testing aerodynamic characteristics of a fixed-wing UAV in transient composite working conditions, which is implemented using the device of the present invention and includes:

[0009] Step 1: Place the fixed-wing UAV transient composite working condition aerodynamic characteristics test device on the wind tunnel rotating platform, and make the wind tunnel air supply direction parallel to the x direction of the test device;

[0010] Step 2: Design the test conditions, including determining the wind tunnel wind speed and the aileron rudder angle of the fixed-wing UAV Change curve, fixed-wing drone tail rudder angle Change curve and pitch angle and roll angle change curve of the test device;

[0011] Step 3: Conduct the test according to the designed test conditions, and the host computer reads the x, y, z three-axis forces Fx2, Fy2, and Fz2 in the balance coordinate system obtained by the balance;

[0012] Coordinate transformation is performed to obtain the forces on the x, y, and z axes in the airflow coordinate system, as well as the moments Ml, Mm, and Mn around the three axes, and the lift, drag, and lateral force at the sampling moments at equal time intervals within the period. The collection of each sampling moment constitutes a force time series.

[0013] Under the pitch-roll composite working condition, lift, drag, and lateral force are expressed as wind tunnel wind speed V, pitch angle , pitch angular velocity q, , Aileron angle of fixed-wing UAV And the tail rudder angle of the fixed-wing drone The functional relationship is obtained, and finally the aerodynamic coefficients K are fitted by the fitting method.

[0014] Wherein, the coordinate transformation formula is as follows: , , .

[0015] Wherein, the functional relationship is:

[0016]

[0017]

[0018]

[0019] in, is the dynamic pressure, is the total surface area of ​​the aircraft wing, is the aircraft wing span, is the average aerodynamic chord length of the aircraft, is the aerodynamic coefficient of drag, is the aerodynamic coefficient of the lateral force, is the lift aerodynamic coefficient, is the aerodynamic coefficient of the rolling moment, is the pitch moment aerodynamic coefficient.

[0020] Among them, a transient correction function is introduced to characterize the dynamic process of transition from transient to steady state, and the corresponding relationships between the lift, drag, lateral force, rolling moment, pitching moment of the UAV and the wind tunnel air supply speed, rudder angle, pitch angle, pitch angular velocity, and rolling angular velocity are obtained, so as to realize the aerodynamic characteristics test of fixed-wing UAV in transient pure working conditions and composite working conditions.

[0021] Among them, the transient pitch and roll angle adjustment process is:

[0022] Step 1: Adjust the extension of electric cylinder Ⅰ, electric cylinder Ⅱ, electric cylinder Ⅲ, and electric cylinder Ⅳ to the electric cylinder stroke h , so that the chassis is in a horizontal position, and the position of the electric cylinder is set to zero position. The upper limit of the extension c of the electric cylinder at zero position is , the lower limit is , measure the distance between the front electric cylinders I and III and the rear electric cylinders II and IV in the x direction a , measure the distance b between the left electric cylinders Ⅰ and Ⅱ and the right electric cylinders Ⅲ and Ⅳ in the y direction;

[0023] Step 2: Through geometric relationships, the conversion formulas between the elongation c1 of electric cylinder I, the elongation c2 of electric cylinder II1, the elongation c3 of electric cylinder III, and the elongation c4 of electric cylinder IV and the pitch angle θ and the roll angle ϕ are obtained; under pure pitch conditions, the elongation of the front electric cylinder and the elongation of the rear electric cylinder are guaranteed to be the inverse of each other, the elongation c1 of the front electric cylinder is c3, and the elongation c2 of the rear electric cylinder is c4. When the elongation of the front electric cylinder is less than that of the rear electric cylinder, a positive pitch angle is generated, and when the elongation of the front electric cylinder is greater than that of the rear electric cylinder, a negative pitch angle is generated. The conversion formula is as follows: , , ; According to the upper limit With lower limit Calculate the maximum pitch angle , minimum pitch angle After designing the expected pitch angle change curve of the UAV under the constraints of the maximum pitch angle and the minimum pitch angle, the formula , The variation curves of the four expected electric cylinder extensions c1, c2, c3, and c4 are obtained; under the pure rolling condition, the extension of the left electric cylinder is guaranteed to be the opposite of the extension of the right electric cylinder. , extension of the right electric cylinder , when the extension of the left electric cylinder is greater than that of the right electric cylinder, a positive roll angle is generated, and when the extension of the left electric cylinder is less than that of the right electric cylinder, a negative roll angle is generated. The conversion formula is as follows: , , , according to the upper limit With lower limit Calculate the maximum roll angle , minimum roll angle After designing the expected roll angle change curve of the UAV under the constraints of the maximum roll angle and the minimum roll angle, the formula , The variation curves of the four expected electric cylinder extensions c1, c2, c3, and c4 are obtained;

[0024] Under the pitch-roll composite working condition, the coordinate system is transformed. The rotation sequence is first around the Z axis, then around the new Y axis, and finally around the new X axis. Each rotation is performed relative to the current axis.

[0025] The rotation matrix around the Y axis is given as follows , the rotation matrix around the X axis is given as follows , combine the above rotations into a total rotation matrix, in the order of pitch first and then roll, the total rotation matrix The calculation formula is as follows:

[0026] Given the coordinates of electric cylinder Ⅰ, electric cylinder Ⅱ, electric cylinder Ⅲ, electric cylinder Ⅳ before rotation , , , , according to the rotation matrix, we can get the rotated coordinates , , , ; Get the new coordinates of point P1 after rotation The original electric cylinder Ⅰ1-1 extended length is about , rotate to The extension length after the point is calculated using the Euclidean distance formula:

[0027] Get the elongation of electric cylinder Ⅰ1-1 ; Get the elongation c2, c3, c4 of electric cylinder II, electric cylinder III, electric cylinder IV; at the maximum elongation of the electric cylinder With minimum elongation Under the constraint of , the constraints of pitch angle and roll angle are obtained according to the above formula. After the expected pitch and roll angle change curves of the UAV are designed under this constraint, the change curves of the elongation c1, c2, c3, c4 of the electric cylinder Ⅰ, electric cylinder Ⅱ, electric cylinder Ⅲ, and electric cylinder Ⅳ are obtained through the above formula;

[0028] Step 3: According to the change curves of c1, c2, c3, and c4 under different working conditions obtained in step 2, the host computer sends a control command to the electric cylinder controller through serial communication, and generates a pitch angle or a roll angle or both a pitch angle and a roll angle under the change of the elongation of electric cylinders I, II, III, and IV. The pitch angle and the roll angle of the sampling period with equal time intervals are taken to form a pitch angle time series and a roll angle time series. The pitch angle time series and the roll angle time series are differentially derived to obtain the time series of the pitch angular velocity q and the roll angular velocity p.

[0029] The derivation formula is as follows: ,

[0030] in is the pitch angular velocity at the ith moment, is the pitch angle at the ith moment, is the pitch angle at the i-1th moment, is the rolling angular velocity at the i-th moment, is the pitch angle at the ith moment, is the rolling angle at the i-1th moment, is the time interval between adjacent sampling points, and n is the total number of sampling points.

[0031] Beneficial Effects

[0032] 1. The device of the present invention uses four electric cylinders as actuators, which can realize dynamic adjustment of the pitch angle and roll angle of the UAV by controlling the elongation change of the four electric cylinders, thereby overcoming the deficiency that the existing fixed-wing UAV aerodynamic characteristics test device can only perform static pure working condition testing.

[0033] 2. In the device of the present invention, the base frame and the front and rear frames can be constructed with profiles, which have a simple structure, low cost, and convenient assembly. In addition, an electric cylinder is used as an actuator, which has a simple control method and high control accuracy.

[0034] 3. The device of the present invention realizes multi-degree-of-freedom simulation, and can accurately simulate the pitch, roll and other complex movements of fixed-wing UAVs under different flight conditions, providing a more realistic test environment than the traditional single-condition test. This helps to more fully understand the aerodynamic characteristics of UAVs under various flight conditions; and by precisely controlling the extension and retraction of the electric cylinder, the attitude of the UAV can be fine-tuned, ensuring high-precision attitude control during the test. This high precision is crucial for studying the aerodynamic performance of UAVs under subtle attitude adjustments.

[0035] 4. The test device of the present invention supports the free switching between steady-state and transient conditions, as well as the independent or joint adjustment of pitch angle and roll angle, which greatly enhances the flexibility of experimental design. Researchers can easily set and adjust experimental conditions according to different research purposes. By introducing the transient correction function, the dynamic characteristics of the UAV during the transition from transient to steady state can be more accurately captured, which is critical for evaluating the dynamic performance of the UAV, such as response speed, stability and maneuverability.

[0036] 5. Based on the data obtained by the device, the present invention can deeply analyze the aerodynamic characteristics of the UAV under different flight conditions, thereby optimizing the design parameters and flight control strategy of the UAV and improving the overall performance of the UAV. Compared with actual flight tests, the test device can complete a large number of preliminary tests under laboratory conditions, effectively reducing the number of flight tests and reducing R&D costs and risks.

[0037] 6. The present invention provides a testing method for a proposed fixed-wing UAV transient composite working condition aerodynamic characteristics testing device. The testing method has simple steps and can be applied to both pure working conditions and composite working conditions. It can more accurately obtain the relationship between the lift, drag, lateral force, rolling moment, pitching moment of the UAV and the wind tunnel air supply wind speed, the fixed-wing UAV rudder angle, and the pitch angle, pitch angular velocity, and rolling angular velocity of the UAV. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is an isometric diagram of the fixed-wing UAV transient composite working condition aerodynamic characteristics testing device of the present invention;

[0039] Figure 2 This is a left view of the fixed-wing UAV transient composite working condition aerodynamic characteristics testing device of the present invention;

[0040] Figure 3 This is a front view of the fixed-wing UAV transient composite working condition aerodynamic characteristics testing device of the present invention;

[0041] Figure 4 This is a schematic diagram of the instantaneous pitch angle adjustment of the fixed-wing UAV of the present invention;

[0042] Figure 5 This is a schematic diagram of the instantaneous roll angle adjustment of the fixed-wing UAV of the present invention;

[0043] Figure 6 This is a schematic diagram of transient composite working condition adjustment of the fixed-wing UAV of the present invention;

[0044] Figure 7 It is a schematic diagram of the three-axis force conversion between the balance coordinate system and the airflow coordinate system of the present invention. DETAILED DESCRIPTION

[0045] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0046] The present invention proposes a fixed-wing UAV transient composite working condition aerodynamic characteristics testing device, comprising an electric cylinder Ⅰ1-1, an electric cylinder Ⅱ1-2, an electric cylinder Ⅲ1-3, an electric cylinder Ⅳ1-4, a base frame 2, a front frame 3-1, a rear frame 3-2, a balance 4 and a connecting plate 5.

[0047] Among them, the electric cylinder Ⅰ1-1 is fixedly connected to the left front part of the base frame 2, the electric cylinder Ⅱ1-2 is fixedly connected to the left rear part of the base frame 2, the electric cylinder Ⅲ1-3 is fixedly connected to the right front part of the base frame 2, and the electric cylinder Ⅳ1-4 is fixedly connected to the right rear part of the base frame 2. The electric cylinder Ⅰ1-1, the electric cylinder Ⅱ1-2, the electric cylinder Ⅲ1-3, and the electric cylinder Ⅳ1-4 are symmetrically distributed on the left and right. The front frame 3-1 is fixedly connected to the front cross beam in the middle of the base frame 2, and the rear frame 3-2 is fixedly connected to the rear cross beam in the middle of the base frame 2. The balance 4 is fixed to the upper part of the front frame 3-1 and the rear frame 3-2. The connecting plate 5 is fixed to the upper part of the balance 4. The connecting plate 5 is used to connect the balance 4 and the drone.

[0048] The fixed-wing UAV transient composite working condition aerodynamic characteristic testing device of the present invention realizes the pitch angle change, roll angle change and composite pitch and roll angle change of the UAV through the extension and contraction actions of electric cylinders Ⅰ1-1, Ⅱ1-2, Ⅲ1-3 and Ⅳ1-4, and realizes the transient pure working condition and composite working condition angle adjustment of the fixed-wing UAV. On this basis, the transient longitudinal aerodynamic characteristic test can be realized in conjunction with the wind tunnel wind speed change and the UAV rudder surface angle change.

[0049] The present invention also provides a method for testing aerodynamic characteristics of a fixed-wing UAV in transient composite working conditions, and the test is implemented using the device of the present invention, comprising the following steps:

[0050] Step 1: Place the fixed-wing UAV transient composite working condition aerodynamic characteristics test device on the wind tunnel rotating platform, and align it with the test device through the wind tunnel test platform laser alignment device, so that the wind tunnel air supply direction is parallel to the x direction of the test device.

[0051] Step 2: Design the test conditions, including determining the wind tunnel wind speed and the aileron rudder angle of the fixed-wing UAV Change curve, fixed-wing drone tail rudder angle Change curve and the pitch angle and roll angle change curve of the test device.

[0052] Step 3: Test according to the designed test conditions. The host computer reads the x, y, z three-axis forces Fx2, Fy2, and Fz2 in the balance coordinate system obtained by the balance 4. Since the balance 4 is fixedly connected to the chassis 2, it changes with the pitch angle during the test. Therefore, in order to obtain the forces on the x, y, and z axes in the airflow coordinate system and the moments Ml, Mm, and Mn around the three axes, the forces on the three axes need to be transformed. The conversion formula is as follows: , , In this way, the lift, drag, and lateral force at the sampling moments at equal time intervals within the period can be obtained, and the collection of each sampling moment constitutes a force time series. Under the pitch-roll composite working condition, the lift, drag, and lateral force can all be expressed as the wind tunnel air supply speed V, the pitch angle , pitch angular velocity q, , fixed-wing UAV aileron rudder angle , Fixed-wing UAV tail rudder angle Functional relationship:

[0053]

[0054]

[0055] in, is the dynamic pressure, is the total surface area of ​​the aircraft wing, is the aircraft wing span, is the average aerodynamic chord length of the aircraft, is the aerodynamic coefficient of drag, is the aerodynamic coefficient of the lateral force, is the lift aerodynamic coefficient, is the aerodynamic coefficient of the rolling moment, is the pitch moment aerodynamic coefficient. All variables in the above formula are known in the transient composite working condition aerodynamic characteristics test, and the aerodynamic coefficients K can be fitted by the fitting method. The above formula can be used for the steady-state pitch and roll composite working condition aerodynamic characteristics test.

[0056] Specifically, in the embodiment of the present invention, the transient pitch and roll angle adjustment is achieved by:

[0057] Step 1: Adjust the extension of electric cylinder Ⅰ1-1, electric cylinder Ⅱ1-2, electric cylinder Ⅲ1-3, electric cylinder Ⅳ1-4 to the electric cylinder stroke h , so that the chassis 3 is in a horizontal position, and the position of the electric cylinder at this time is set to the starting position, that is, the zero position. The upper limit of the extension c of the electric cylinder at the zero position is , the lower limit is , measure the distance between the front electric cylinder Ⅰ1-1, electric cylinder Ⅲ1-3 and the rear electric cylinder Ⅱ1-2, electric cylinder Ⅳ1-4 in the x direction (the horizontal forward is the x direction, the vertical upward is the z direction, and the y direction conforms to the right-hand coordinate rule) a , measure the distance b between the left electric cylinders Ⅰ1-1, Ⅱ1-2 and the right electric cylinders Ⅲ1-3, Ⅳ1-4 in the y direction.

[0058] Step 2: Through geometric relationships, the conversion formulas between the elongation c1 of electric cylinder Ⅰ1-1, the elongation c2 of electric cylinder Ⅱ1-2, the elongation c3 of electric cylinder Ⅲ1-3, and the elongation c4 of electric cylinder Ⅳ1-4 and the pitch angle θ and the roll angle ϕ are obtained. Under pure pitch conditions, ensure that the elongation of the front electric cylinder and the elongation of the rear electric cylinder are opposite to each other, the elongation c1 of the front electric cylinder = c3, the elongation c2 of the rear electric cylinder = c4, the elongation of the front electric cylinder is less than the elongation of the rear electric cylinder, resulting in a positive pitch angle, and the elongation of the front electric cylinder is greater than the elongation of the rear electric cylinder, resulting in a negative pitch angle. The conversion formula is as follows: , , Due to the limited stroke of the electric cylinder, according to the upper limit With lower limit Calculate the maximum pitch angle , minimum pitch angle After designing the expected pitch angle change curve of the UAV under the constraints of the maximum pitch angle and the minimum pitch angle, the formula , The variation curves of the four expected electric cylinder extensions c1, c2, c3, and c4 are obtained. Under pure rolling conditions, the extension of the left electric cylinder is guaranteed to be the opposite of the extension of the right electric cylinder. , extension of the right electric cylinder , when the extension of the left electric cylinder is greater than that of the right electric cylinder, a positive roll angle is generated, and when the extension of the left electric cylinder is less than that of the right electric cylinder, a negative roll angle is generated. The conversion formula is as follows: , , Due to the limited stroke of the electric cylinder, according to the upper limit With lower limit Calculate the maximum roll angle , minimum roll angle After designing the expected roll angle change curve of the UAV under the constraints of the maximum roll angle and the minimum roll angle, the formula , The change curves of the four expected electric cylinder extensions c1, c2, c3, and c4 are obtained. Under the pitch-roll composite working condition, the "3-2-1" Euler angle is first used to realize the transformation of the coordinate system. The rotation sequence is first to rotate around the Z axis (yaw), then around the new Y axis (pitch), and finally around the new X axis (roll). Each rotation is performed relative to the current axis. Here, yaw is not considered, and the rotation matrix around the Y axis is given as follows , the rotation matrix around the X axis is given as follows , combine the above rotations into a total rotation matrix, in the order of pitch first and then roll, the total rotation matrix The calculation formula is as follows:

[0059] Given the coordinates of electric cylinder Ⅰ1-1, electric cylinder Ⅱ1-2, electric cylinder Ⅲ1-3, electric cylinder Ⅳ1-4 before rotation , , , , according to the rotation matrix, we can get the rotated coordinates , , , , taking electric cylinder Ⅰ1-1 as an example,

[0060] In this way, the new coordinates of point P1 after rotation are obtained. The original electric cylinder Ⅰ1-1 extended length is about , rotate to The extension length after the point can be calculated by the Euclidean distance formula,

[0061] In this way, the elongation of the electric cylinder Ⅰ1-1 is obtained. Similarly, the elongation c2, c3, and c4 of the electric cylinder II1-2, electric cylinder III1-3, and electric cylinder IV1-4 can be obtained. With minimum elongation Under the constraint of , the constraints of the pitch angle and roll angle can be obtained according to the above formula. After designing the expected pitch and roll angle change curves of the UAV under this constraint, the change curves of the elongation c1, c2, c3, and c4 of the electric cylinder Ⅰ1-1, electric cylinder Ⅱ1-2, electric cylinder Ⅲ1-3, and electric cylinder Ⅳ1-4 can be obtained through the above formula.

[0062] Step 3: According to the change curves of c1, c2, c3, and c4 under different working conditions obtained in step 2, the host computer sends a control command to the electric cylinder controller through serial communication, and generates a pitch angle or a roll angle or both a pitch angle and a roll angle under the change of the elongation of the electric cylinder Ⅰ1-1, the electric cylinder Ⅱ1-2, the electric cylinder Ⅲ1-3, and the electric cylinder Ⅳ1-4. The pitch angle and the roll angle of the sampling period at an equal time interval are taken to form a pitch angle time series and a roll angle time series. The pitch angle time series and the roll angle time series are differentially derived to obtain the time series of the pitch angular velocity q and the roll angular velocity p. The derivation formula is as follows: , in is the pitch angular velocity at the ith moment, is the pitch angle at the ith moment, is the pitch angle at the i-1th moment, is the rolling angular velocity at the i-th moment, is the pitch angle at the ith moment, is the rolling angle at the i-1th moment, is the time interval between adjacent sampling points, and n is the total number of sampling points. The pitch angle, pitch angular velocity, roll angle, and roll angular velocity are used for subsequent data analysis.

[0063] Furthermore, in order to consider the time delay characteristics of the aerodynamic response of the UAV so as to more accurately describe the aerodynamic behavior in dynamic flight, a transient correction function is introduced in the aerodynamic characteristics test method of this embodiment. For example, in transient composite working conditions, the aerodynamic response under the pitch angle step or the aerodynamic response under the roll angle step needs to introduce a transient correction term to characterize the dynamic process of transition from transient to steady state. The correction formula is as follows:

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] Where V is the wind speed of the wind tunnel, t is the time, and c is the characteristic chord length of the UAV. Compared with the steady-state aerodynamic characteristics test, the transient aerodynamic characteristics not only need to fit the aerodynamic coefficients K, but also need to fit the parameters Ax1, Ax2, Bx1, Bx2, Ay1, Ay2, By1, By2, Az1, Az2, Bz1, Bz2, Al1, Al2, Bl1, Bl2, Am1, Am2, Bm1, Bm2.

[0073] Through the above steps, the corresponding relationships between the lift, drag, lateral force, rolling moment, pitching moment of the UAV and the wind tunnel air supply wind speed, rudder angle, pitch angle, pitch angular velocity, and rolling angular velocity can be obtained, thus realizing the transient pure working condition and compound working condition aerodynamic characteristics test of fixed-wing UAV.

[0074] Furthermore, the aerodynamic characteristics test results can be used for aerodynamic research of fixed-wing UAVs. For example, after fitting the aerodynamic coefficients K and transient parameters A and B based on the aerodynamic characteristics test experimental data, the UAV's own parameters and flight environment parameters can be combined to obtain the force responses according to the aerodynamic equations, and the dynamic performance when the input signal, i.e., the pitch angle and roll angle, suddenly changes (such as step signals, pulse signals, etc.), can be obtained, including the response speed and stability of the device. These are the core dynamic performance indicators of UAVs during flight.

[0075] In summary, different from the aerodynamic characteristics testing device and method for transient pure working conditions and steady-state working conditions, the aerodynamic characteristics testing device and method for transient composite working conditions of the present invention can realize aerodynamic characteristics testing combining steady-state and transient conditions. Can be adjusted to steady-state change (including static constant) or transient change, roll angle It can be adjusted to steady-state change (including static constant) or transient change. The two states of the two angles can be adjusted and combined independently, and the force response obtained in each direction also shows steady-state characteristics or dynamic characteristics accordingly. For example, when the roll angle When it is a certain value, the pitch angle can be measured is the transient aerodynamic characteristic during transient changes. Similarly, when the pitch angle When it is a certain value, the roll angle can also be measured It is the transient aerodynamic characteristics during transient changes.

[0076] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for testing the aerodynamic characteristics of a fixed-wing UAV under transient composite working conditions, which is implemented using a fixed-wing UAV under transient composite working conditions aerodynamic characteristics testing device, and is characterized in that: The device comprises electric cylinder I, electric cylinder II, electric cylinder III, electric cylinder IV, a base frame, a front frame, a rear frame, a balance and a connecting plate; Among them, electric cylinder I is fixedly connected to the left front part of the chassis, electric cylinder II is fixedly connected to the left rear part of the chassis, electric cylinder III is fixedly connected to the right front part of the chassis, electric cylinder IV is fixedly connected to the right rear part of the chassis, electric cylinder I, electric cylinder II and electric cylinder III, electric cylinder IV are symmetrically distributed on the left and right, the front frame is fixedly connected to the front crossbeam in the middle of the chassis, the rear frame is fixedly connected to the rear crossbeam in the middle of the chassis, the balance is fixed to the upper part of the front frame and the rear frame, the connecting plate is fixed to the upper part of the balance, and the connecting plate is used to connect the balance and the drone; The extension and contraction of electric cylinders Ⅰ, Ⅱ, Ⅲ and Ⅳ realize the pitch angle change, roll angle change and pitch and roll angle compound change of the UAV. On this basis, the transient longitudinal aerodynamic characteristics test is realized by coordinating the wind tunnel wind speed change and the UAV rudder surface angle change. The test method includes: Step 1: Place the fixed-wing UAV transient composite working condition aerodynamic characteristics test device on the wind tunnel rotating platform, and make the wind tunnel air supply direction parallel to the x direction of the test device; Step 2: Design the test conditions, including determining the wind tunnel wind speed and the aileron rudder angle of the fixed-wing UAV Change curve, fixed-wing drone tail rudder angle Change curve and pitch angle and roll angle change curve of the test device; Step 3: Conduct the test according to the designed test conditions, and the host computer reads the x, y, z three-axis forces Fx2, Fy2, and Fz2 in the balance coordinate system obtained by the balance; Coordinate transformation is performed to obtain the forces on the x, y, and z axes in the airflow coordinate system, as well as the moments Ml, Mm, and Mn around the three axes, and the lift, drag, and lateral force at the sampling moments at equal time intervals within the period. The collection of each sampling moment constitutes a force time series. Under the pitch-roll composite working condition, lift, drag, and lateral force are expressed as wind tunnel wind speed V, pitch angle , pitch angular velocity q, roll angular velocity , Aileron rudder angle of fixed-wing UAV And the tail rudder angle of the fixed-wing drone Functional relationship, and finally the aerodynamic coefficients K are fitted by fitting method; The transient pitch and roll angle adjustment process is: Step 1: Adjust the extension of electric cylinder Ⅰ, electric cylinder Ⅱ, electric cylinder Ⅲ, and electric cylinder Ⅳ to the electric cylinder stroke h , so that the chassis is in a horizontal position, and the position of the electric cylinder is set to zero position. The upper limit of the extension c of the electric cylinder at zero position is , the lower limit is , measure the distance between the front electric cylinders I and III and the rear electric cylinders II and IV in the x direction a , measure the distance b between the left electric cylinders Ⅰ and Ⅱ and the right electric cylinders Ⅲ and Ⅳ in the y direction; Step 2: Get the elongation c1 of electric cylinder I, the elongation c2 of electric cylinder II, the elongation c3 of electric cylinder III, the elongation c4 of electric cylinder IV and the pitch angle θ and roll angle through geometric relationship The conversion formula between them; Under the pure pitch working condition, ensure that the extension of the front electric cylinder and the extension of the rear electric cylinder are opposite to each other, the extension of the front electric cylinder c1=c3, the extension of the rear electric cylinder c2=c4, the extension of the front electric cylinder is less than the extension of the rear electric cylinder to produce a positive pitch angle, and the extension of the front electric cylinder is greater than the extension of the rear electric cylinder to produce a negative pitch angle. The conversion formula is as follows: , , ; According to the upper limit With lower limit Calculate the maximum pitch angle , minimum pitch angle After designing the expected pitch angle change curve of the UAV under the constraints of the maximum pitch angle and the minimum pitch angle, the formula , The variation curves of the four expected electric cylinder extensions c1, c2, c3, and c4 are obtained; under the pure rolling condition, the extension of the left electric cylinder is guaranteed to be the opposite of the extension of the right electric cylinder. , extension of the right electric cylinder , when the extension of the left electric cylinder is greater than that of the right electric cylinder, a positive roll angle is generated, and when the extension of the left electric cylinder is less than that of the right electric cylinder, a negative roll angle is generated. The conversion formula is as follows: , , , according to the upper limit With lower limit Calculate the maximum roll angle , minimum roll angle After designing the expected roll angle change curve of the UAV under the constraints of the maximum roll angle and the minimum roll angle, the formula , The variation curves of the four expected electric cylinder extensions c1, c2, c3, and c4 are obtained; Under the pitch-roll composite working condition, the coordinate system is transformed. The rotation sequence is first around the Z axis, then around the new Y axis, and finally around the new X axis. Each rotation is performed relative to the current axis. The rotation matrix around the Y axis is given as follows , the rotation matrix around the X axis is given as follows , combine the above rotations into a total rotation matrix, in the order of pitch first and then roll, the total rotation matrix The calculation formula is as follows: Given the coordinates of electric cylinder Ⅰ, electric cylinder Ⅱ, electric cylinder Ⅲ, electric cylinder Ⅳ before rotation , , , , according to the rotation matrix, we can get the rotated coordinates , , , ; Get the new coordinates of point P1 after rotation , the original electric cylinder I extended length is , rotate to The extension length after the point is calculated using the Euclidean distance formula: Get the elongation of the electric cylinder I ; Get the elongation c2, c3, c4 of electric cylinder II, electric cylinder III, electric cylinder IV; at the maximum elongation of the electric cylinder With minimum elongation Under the constraint of , the constraints of pitch angle and roll angle are obtained according to the above formula. After the expected pitch and roll angle change curves of the UAV are designed under this constraint, the change curves of the elongation c1, c2, c3, c4 of the electric cylinder Ⅰ, electric cylinder Ⅱ, electric cylinder Ⅲ, and electric cylinder Ⅳ are obtained through the above formula; Step 3: According to the change curves of c1, c2, c3, and c4 under different working conditions obtained in step 2, the host computer sends a control command to the electric cylinder controller through serial communication, and generates a pitch angle or a roll angle or both a pitch angle and a roll angle under the change of the elongation of electric cylinders I, II, III, and IV. The pitch angle and the roll angle of the sampling period with equal time intervals are taken to form a pitch angle time series and a roll angle time series. The pitch angle time series and the roll angle time series are differentially derived to obtain the time series of the pitch angular velocity q and the roll angular velocity p.

2. The method according to claim 1, characterized in that The coordinate transformation formula from the balance coordinate system to the airflow coordinate system is as follows: , , .

3. The method according to claim 1, characterized in that The functional relationship is: in, is the dynamic pressure, is the total surface area of ​​the aircraft wing, is the aircraft wing span, is the average aerodynamic chord length of the aircraft, is the aerodynamic coefficient of drag, is the aerodynamic coefficient of the lateral force, is the lift aerodynamic coefficient, is the aerodynamic coefficient of the rolling moment, is the pitch moment aerodynamic coefficient.

4. The method according to any one of claims 1 to 3, characterized in that: A transient correction function is introduced to characterize the dynamic process of transition from transient to steady state, and the corresponding relationships between the lift, drag, lateral force, rolling moment, pitching moment of the UAV and the wind tunnel air supply speed, rudder angle, pitch angle, pitch angular velocity, and rolling angular velocity are obtained, so as to realize the aerodynamic characteristics test of fixed-wing UAV under transient pure working conditions and composite working conditions.

5. The method according to claim 1, characterized in that The derivative formula is as follows: , in is the pitch angular velocity at the ith moment, is the pitch angle at the ith moment, is the pitch angle at the i-1th moment, is the rolling angular velocity at the i-th moment, is the rolling angle at the ith moment, is the rolling angle at the i-1th moment, is the time interval between adjacent sampling points, and n is the total number of sampling points.

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