An experimental method for obtaining dynamic derivatives of aircraft using large amplitude rotational motion

Abstract

The present invention discloses an experimental method for obtaining aircraft dynamic derivatives by large-amplitude rotational motion, which relates to the field of wind tunnel test technology in the field of aviation technology, including: constructing an acceleration array by arranging accelerometers on a model; obtaining the mapping relationship between the acceleration array output and the inertial force by calibration; calculating the dynamic aerodynamic force deducted from the influence of the inertial force based on the acceleration array and the strain balance; obtaining the exchange quantity of the model velocity information by integration based on the acceleration array; and calculating the pitch dynamic derivative based on the point velocity and dynamic aerodynamic torque component corresponding to the positive motion stroke of each angle in the motion process, except near the angle where the velocity is zero, and the point velocity and dynamic aerodynamic torque component corresponding to the negative motion stroke. The present invention provides an experimental method for obtaining aircraft dynamic derivatives by large-amplitude rotational motion, which can be applied to obtaining dynamic derivatives under linear conditions and can also be applied to obtaining dynamic derivatives under nonlinear conditions.

Description

Technical Field

[0001] The present invention relates to the field of wind tunnel test technology in the field of aviation technology, and more specifically to a test method for obtaining dynamic derivatives of an aircraft by large-amplitude rotational motion. Background Art

[0002] In the development of aircraft control systems, dynamic derivatives are an important design basis. The commonly used method is to use small amplitude motion to obtain dynamic derivatives based on the relationship between aerodynamic force and the amplitude and phase of motion. There are two main problems with this method:

[0003] First, this method is based on the linear assumption, that is, the aerodynamic force is equal to the static aerodynamic force plus the dynamic derivative multiplied by the motion (angular) velocity. It is generally believed that the assumption is satisfied when there is no separation in the flow around the aircraft. Whether the assumption is satisfied after separation in the flow around the aircraft has not yet been fully proven.

[0004] Second, during the high angle of attack maneuver of the aircraft, the dynamic derivative may be related to the motion process, but the existing methods cannot simulate the motion process. Strictly speaking, when the aerodynamic force does not meet the linear assumption or is related to the motion process, the concept of dynamic derivative does not exist, but in engineering, it is customary to approximate the dynamic aerodynamic force by the static aerodynamic force plus the dynamic derivative multiplied by the motion (angular) velocity. At this time, the dynamic derivative is an equivalent dynamic derivative. Considering the engineering habits and the simplicity of expression, the dynamic derivatives in the following text refer to conventional dynamic derivatives and equivalent approximate dynamic derivatives. Summary of the invention

[0005] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0006] In order to achieve these purposes and other advantages of the present invention, a test method for obtaining dynamic derivatives of an aircraft by large-amplitude rotational motion is provided, comprising:

[0007] S1. constructing an acceleration array by arranging accelerometers on the model, and the accelerometers are arranged so that the accelerometer output vectors corresponding to any irrelevant inertial forces are also irrelevant;

[0008] S2. Obtain acceleration array output A and inertial force through calibration The mapping relationship ,in, f ( ) represents the mapping function from acceleration array output to inertial force;

[0009] S3, calculate the dynamic aerodynamic force minus the influence of inertial force based on acceleration array and strain balance;

[0010] S4, obtaining the model velocity by integration based on the acceleration array;

[0011] S5. Except for the angle near which the velocity is zero, the velocity and dynamic aerodynamic torque component of each angle corresponding to the positive motion stroke during the motion process are recorded as and , the point velocity and dynamic aerodynamic torque component corresponding to the negative motion stroke of each angle during the motion process are recorded as and , in order to calculate the pitch derivative based on the following formula :

[0012]

[0013] S6. For different test conditions, repeat S3-S5 to calculate the corresponding dynamic derivatives.

[0014] Preferably, in S1, the dynamic aerodynamic force is obtained by:

[0015] S10. Obtain the moment of inertia of the model's dynamic derivative in the plane corresponding to the torque reference point through 3D design software or theoretical calculation. ;

[0016] S11. Under the condition of stable wind tunnel flow field, the model is controlled to move with large amplitude in the plane corresponding to the dynamic derivative, so as to synchronously collect the data of balance and acceleration array through synchronous acquisition equipment to calculate the balance measurement value. , ;

[0017] S12. Calculate the dynamic aerodynamic force after deducting the influence of inertia force based on the following formula :

[0018] .

[0019] Preferably, in S4, the speed is obtained by:

[0020] S20, calculate the rotational angular acceleration based on the following formula :

[0021]

[0022] In the above formula, is the moment of inertia component of the plane rotation corresponding to the dynamic derivative, is the moment of inertia about the torque reference point in the plane corresponding to the dynamic derivative;

[0023] S21, yes Integrate to get the angular velocity ;

[0024] S22, using high-pass filters with the same parameters The aerodynamic torque component corresponding to the plane rotation of the dynamic derivative Perform high-pass filtering, and the filter cutoff frequency should be lower than the model motion frequency.

[0025] The present invention has at least the following beneficial effects:

[0026] First, the present invention does not require linear assumptions and can be used to obtain dynamic derivatives under linear conditions as well as nonlinear conditions;

[0027] Secondly, the present invention can simulate the maneuvering process of an aircraft and obtain dynamic derivatives related to the motion history;

[0028] Thirdly, the present invention does not need to deduct the ground dynamic derivative, and there is no system error caused by the corresponding operation.

[0029] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic flow chart of the experimental method for obtaining dynamic derivatives of an aircraft for large-amplitude rotational motion according to the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0032] The present invention discloses a test method for obtaining dynamic derivatives of an aircraft by large-amplitude rotational motion. The test method does not require linear assumptions and can be applied to obtaining dynamic derivatives under linear conditions and to obtaining equivalent dynamic derivatives under nonlinear conditions. For the convenience of engineering use, the dynamic derivatives under nonlinear conditions can be expressed in the form of dynamic derivatives, but not in the strict sense of dynamic derivatives. Under nonlinear conditions, the maneuvering process of the aircraft can be simulated to obtain dynamic derivatives as close to the flight conditions as possible, providing a reference for the design of the aircraft control system.

[0033] Specifically, for ease of description, it is assumed that there is a pilot in the model. If there is no clear explanation, left and right, front and back, up and down are determined by the direction of the pilot in the assumed model. For pitch motion, when the test model moves up, it is defined as the positive direction of pitch motion. For yaw motion, when the nose of the test model moves to the left, it is defined as the positive direction of yaw motion. For roll motion, when the right wing of the test model moves downward, it is defined as the positive direction of roll motion. The positive direction of the moment is defined the same as the positive direction of motion. When forces or moments are involved, it is assumed that they have the same coordinate system and moment reference point. During the test, the model only moves in one plane, for example, translation and rotation in the pitch plane.

[0034] There are two core points of the present invention. The first is to use an acceleration array (an array composed of accelerometers) to deduct the influence of inertial force and obtain high-precision dynamic aerodynamic force with a bandwidth 10 to 30 times that of a single strain balance force measurement system. The second is to use the same acceleration array to obtain the exchange amount of model velocity or angular velocity (hereinafter referred to as velocity) information through integration. The reason for using the acceleration array to deduct the inertial force is that the traditional method of using the wind-to-no-wind method to deduct the influence of inertial force has low accuracy. The reason for using the same acceleration array to measure the speed is that the speed measurement requires a sufficiently high bandwidth and phase accuracy, and the two commonly used methods are not ideal. The two commonly used methods are the first mechanism measurement, which uses an encoder or strain gauge on the mechanism for measurement, and the second is the measurement using a gyroscope. The first method is affected by the elasticity of the supporting structure, and the phase and accuracy are difficult to meet the requirements of the present invention. The second method is affected by the existing technical level, and the gyroscope measurement bandwidth and phase usually cannot meet the requirements of the present invention.

[0035] The method of using the acceleration array to deduct the influence of inertial force is described in the invention patent entitled A method and system for measuring multi-component force and torque (ZL201710206338.6), which was published by the inventor team of the present invention. For ease of description, the formula for deducting the influence of inertial force using the acceleration array is defined as:

[0036]

[0037] in, is the dynamic aerodynamic force after deducting the influence of inertia force, is the force vector applied by the balance to the model (then equal to the balance value), is the inertial force, Obtained from the acceleration array. For simplicity, gravity is ignored here, as it is an easily deductible interference.

[0038] The angular acceleration can be obtained from the inertial force and the moment of inertia, and the angular velocity can be obtained by integration.

[0039] In vector Select the torque component corresponding to the rotation of the motion plane , the calculation formula of the model angular acceleration is:

[0040]

[0041] in, is the moment of inertia of the model about the torque reference point. i represents the motion plane, i =x, y, z represent yz, xz, and xy planes respectively, that is, for different dynamic derivatives, the value of i is also different, the same below.

[0042] right Integrate to get the model rotation angular velocity The dynamic aerodynamic force vector after deducting the influence of inertial force Select the torque component corresponding to the rotation of the motion plane .right and Use a high-pass filter with the same parameters for filtering. The cutoff frequency of the high-pass filter should be lower than the model motion frequency. For each angle during the motion process, the data point velocity and dynamic aerodynamic torque corresponding to the positive motion stroke are recorded as and , the data point velocity and dynamic aerodynamic torque corresponding to the negative motion stroke are recorded as and , then the calculation formula of the dynamic derivative corresponding to the rotation in the plane is:

[0043]

[0044] After dimensionless transformation, dimensionless dynamic derivatives can be obtained. Except for the area near the trajectory where the velocity is 0, dynamic derivatives of most angles in the motion range can be obtained.

[0045] like Figure 1 As shown in the figure, for a large amplitude motion in a certain motion plane, the corresponding dynamic derivative can be obtained by following the steps below:

[0046] Step 1: Arrange an acceleration array on the model, calculate with single-axis acceleration components, arrange at least 6 accelerometers, and arrange the accelerometers in such a way that the accelerometer output vectors corresponding to any unrelated inertial forces are also unrelated.

[0047] Step 2: Obtain acceleration array output A to inertial force through calibration The mapping relationship Obtain the moment of inertia of the model about the torque reference point in the corresponding motion plane through 3D design software or theoretical calculation .

[0048] Step 3: Under the condition of stable wind tunnel flow field, make the model move with large amplitude in the corresponding dynamic derivative plane, and at the same time, synchronously collect the balance and acceleration array data through the synchronous acquisition equipment.

[0049] Step 4: Calculate the balance value , calculate the inertial force based on the acceleration array data , inertial force The component of the moment of inertia corresponding to the rotation of the motion plane is .

[0050] Step 5: Calculate the dynamic aerodynamic force after deducting the influence of inertia force , dynamic aerodynamic force The aerodynamic torque component corresponding to the rotation of the motion plane is . According to the components of the moment of inertia corresponding to the rotation of the motion plane Calculate the angular acceleration from the moment of inertia about the torque reference point in the corresponding motion plane .

[0051] Step 6: Corresponding to the rotational angular acceleration in the motion plane Integrate to get the angular velocity .

[0052] Step 7: Use high-pass filters with the same parameters to filter the angular velocity in the corresponding motion plane The dynamic derivative corresponds to the aerodynamic torque component of the rotation in the motion plane High-pass filtering, the filter cutoff frequency should be lower than the model motion frequency.

[0053] Step 8. Except for the angle near which the velocity is zero, for each angle in the motion process, the point velocity and dynamic aerodynamic torque component corresponding to the positive motion stroke are recorded as and , the point velocity and dynamic aerodynamic torque component corresponding to the negative motion stroke are recorded as and , according to the formula Compute the dynamical derivative corresponding to the in-plane rotation.

[0054] For each test state such as Mach number, motion frequency, etc., the dynamic derivative calculation repeats steps 3 to 8.

[0055] Example:

[0056] For large-amplitude pitch motion, the following steps can be used to obtain the pitch derivative.

[0057] Step 1: Arrange an acceleration array on the model, calculate with single-axis acceleration components, arrange at least 6 accelerometers, and arrange the accelerometers in such a way that the accelerometer output vectors corresponding to any unrelated inertial forces are also unrelated.

[0058] Step 2: Obtain acceleration array output A to inertial force through calibration The mapping relationship Obtain the moment of inertia of the model about the torque reference point in the pitch plane through 3D design software or theoretical calculation .

[0059] Step 3: Under the condition of stable wind tunnel flow field, make the model move with large amplitude in the pitch plane, and collect data synchronously through synchronous data collection equipment Balance,acceleration array data.

[0060] Step 4: Calculate the balance value , calculate the inertial force based on the acceleration array data , inertial force The pitch moment of inertia is .

[0061] Step 5: Calculate the dynamic aerodynamic force after deducting the influence of inertia force , dynamic aerodynamic force The pitch aerodynamic moment component is According to the pitch inertia moment component and the pitch moment of inertia about the moment reference point Calculate the pitch acceleration .

[0062] Step 6: Pitch angle acceleration Integrate to get the angular velocity .

[0063] Step 7: Use high-pass filters with the same parameters to perform high-pass filtering on the pitch angular velocity and pitch moment components respectively. The filter cutoff frequency should be lower than the model motion frequency.

[0064] Step 8. Except for the angle near which the velocity is zero, for each angle in the motion process, the point velocity and dynamic aerodynamic torque component corresponding to the positive motion stroke are recorded as and , the point velocity and dynamic aerodynamic torque component corresponding to the negative motion stroke are recorded as and , according to the formula Calculate the pitch derivative.

[0065] For each test state such as Mach number and motion frequency, the pitch dynamic derivative calculation repeats steps 3 to 8. The calculation method of yaw and roll dynamic derivatives is similar to that of pitch dynamic derivatives and will not be repeated here.

[0066] The above solution is only an illustration of a preferred embodiment, but is not limited thereto. When implementing the present invention, appropriate replacement and / or modification can be performed according to user needs.

[0067] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily realized. Therefore, without departing from the general concept defined by the claims and equivalent scope, the present invention is not limited to the specific details and the illustrations shown and described here.

Claims

1. A test method for obtaining dynamic derivatives of an aircraft using large-amplitude rotational motion, characterized in that: include: S1. constructing an acceleration array by arranging accelerometers on the model, and the accelerometers are arranged so that the accelerometer output vectors corresponding to any irrelevant inertial forces are also irrelevant; S2. Obtain acceleration array output A and inertial force through calibration The mapping relationship ,in, f () represents the mapping function from acceleration array output to inertial force; S3, calculate the dynamic aerodynamic force minus the influence of inertial force based on acceleration array and strain balance; S4, obtaining the model velocity by integration based on the acceleration array; S5. Except for the angle near which the velocity is zero, the velocity and dynamic aerodynamic torque component of each angle corresponding to the positive motion stroke during the motion process are recorded as and , the point velocity and dynamic aerodynamic torque component corresponding to the negative motion stroke of each angle during the motion process are recorded as and , in order to calculate the pitch derivative based on the following formula : S6. For different test conditions, repeat S3-S5 to calculate the corresponding dynamic derivatives; In S1, the dynamic aerodynamic force is obtained in the following manner: S10. Obtain the moment of inertia of the model's dynamic derivative in the plane corresponding to the torque reference point through 3D design software or theoretical calculation. ; S11. Under the condition of stable wind tunnel flow field, the model is controlled to move with large amplitude in the plane corresponding to the dynamic derivative, so as to synchronously collect the data of balance and acceleration array through synchronous acquisition equipment to calculate the balance measurement value. And the dynamic derivative corresponds to the moment of inertia component of the plane rotation ; S12. Calculate the dynamic aerodynamic force after deducting the influence of inertia force based on the following formula : ； In S4, the speed is obtained in the following manner: S20, calculate the rotational angular acceleration based on the following formula : In the above formula, is the moment of inertia about the torque reference point in the plane corresponding to the dynamic derivative; S21, yes Integrate to get the angular velocity ; S22, using high-pass filters with the same parameters The aerodynamic torque component corresponding to the plane rotation of the dynamic derivative Perform high-pass filtering, and the filter cutoff frequency should be lower than the model motion frequency.

Images