An experimental method for obtaining the time-difference derivative of wash flow

Abstract

The present invention discloses a test method for obtaining the time difference derivative of the wash flow, which belongs to the field of wind tunnel test technology in the field of aviation technology. The high-precision dynamic aerodynamic force after deducting the influence of the inertial force is obtained through an acceleration array (an array composed of accelerometers), and the exchange quantity of the model velocity and angular velocity information is obtained through integration. The present invention discloses a test method for obtaining the time difference derivative of the wash flow, which obtains the high-precision time difference derivative of the wash flow by improving the measurement method related to the aerodynamic force and the attitude.

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 wash flow time difference derivatives. Background Art

[0002] In the development of aircraft control systems, the time-difference derivative of wash flow is an important design basis. The time-difference derivative of wash flow is the derivative of aerodynamic force or moment (hereinafter referred to as aerodynamic force or moment) relative to the rate of change of angle of attack and sideslip angle. In the time-difference derivative wind tunnel test of wash flow, the attitude angle is generally generated by the translation speed relative to the incoming flow speed. However, due to the large incoming flow speed, especially in high-speed wind tunnel tests, the attitude angle caused by translation is usually below 3°, while the attitude angle caused by structural elastic deformation is equivalent to the attitude angle caused by translation. If only the attitude angle caused by translation is used in the calculation, the accuracy of the result will be reduced. Here, structural elastic deformation refers to the alternating elastic deformation of the structure under the action of alternating inertial loads and alternating aerodynamic loads. In addition, the existing time-difference derivative test method of wash flow uses a balance as a force sensor, and the influence of inertial force is deducted by the method of "wind minus no wind". This method of deducting the influence of inertial force requires assuming that the model performs ideal sinusoidal motion. In actual experiments, the model motion sometimes deviates greatly from the sinusoidal motion, which will also affect the accuracy of the test results. Summary of the invention

[0003] 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.

[0004] In order to achieve these objects and other advantages of the present invention, a test method for obtaining a wash flow time derivative is provided, comprising:

[0005] 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;

[0006] S2. Obtain acceleration array output and inertial force through calibration The mapping relationship ;

[0007] S3. Calculate inertial force based on acceleration array data ,exist In the equation, the inertial force component corresponding to the time-difference derivative of the wash flow is , the inertia moment component corresponding to the rotation of the wash flow time difference derivative plane is , then the model corresponds to the acceleration of the time difference derivative direction of the wash flow and the model rotation angular acceleration They are obtained by the following formulas:

[0008]

[0009] In the above formula, m is the model quality, is the moment of inertia about the torque reference point in the corresponding motion plane;

[0010] S4. Construct the following overdetermined two-variable linear equation system to obtain the wash flow time difference derivative :

[0011]

[0012] In the above formula, is a known static derivative, is the known incoming flow velocity, Dynamic aerodynamic force The aerodynamic torque component corresponding to the rotation of the wash flow time derivative plane is: is an unknown number;

[0013] S4. For different test conditions, repeat S3-S4 to calculate the corresponding dynamic derivatives.

[0014] Preferably, the dynamic aerodynamic force The acquisition process includes:

[0015] S30, obtain model quality through 3D design software or theoretical calculation m and the moment of inertia about the torque reference point in the corresponding motion plane ;

[0016] S31. Under the condition of stable wind tunnel flow field, control the model to move in the plane corresponding to the time difference derivative of the wash flow, so as to synchronously collect the data of the balance and acceleration array through the synchronous acquisition equipment to calculate the balance measurement value. , inertial force The inertia moment component corresponding to the rotation of the wash flow time derivative plane is ;

[0017] S32. Calculate the dynamic aerodynamic force after deducting the influence of inertia force based on the following formula :

[0018] .

[0019] Preferably, the model rotation angular acceleration Obtained by the following formula:

[0020]

[0021] In the above formula, is the inertia moment component corresponding to the rotation of the wash flow time derivative plane;

[0022] The model corresponds to the acceleration of the time difference derivative direction of the wash flow Obtained by the following formula:

[0023]

[0024] In the above formula, Inertial force The inertial force component corresponding to the time-difference derivative of the wash flow.

[0025] The present invention at least includes the following beneficial effects: the present invention can obtain a more accurate wash flow time difference derivative by improving the measurement method and data processing algorithm of aerodynamic force, attitude and its derivatives.

[0026] 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

[0027] Figure 1 The figure is a schematic diagram of the process of obtaining the corresponding wash flow time difference derivative according to the present invention. DETAILED DESCRIPTION

[0028] 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.

[0029] 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. When the model moves, the maximum angle of attack and sideslip angle caused are not greater than 6° to meet the linearization assumption of aerodynamic forces on motion parameters.

[0030] 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 quantity of model velocity and angular 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 is of low accuracy. The reason for using the same acceleration array to measure acceleration and angular velocity is that the related measurements require sufficiently high accuracy. Using the same acceleration array to measure directly on the model can avoid being affected by the elastic deformation of the mechanism. Existing methods generally directly measure the displacement or translation velocity of the mechanism, and obtain the acceleration by differential, ignoring the angular velocity and angle caused by the elasticity of the structure, which has a greater impact on the accuracy of the results.

[0031] 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

[0032]

[0033] 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.

[0034] Acceleration and angular acceleration can be obtained from inertial force, mass and moment of inertia, and angular velocity can be obtained by integrating the angular acceleration.

[0035] In vector Select the force component corresponding to the direction of the time derivative of the wash flow , the model quality is m The calculation formula of the acceleration in the direction of the time difference derivative of the model corresponding to the wash flow is

[0036]

[0037] In vector Select the inertia moment component corresponding to the angle direction of the wash flow time difference derivative , the calculation formula of the model angular acceleration is:

[0038]

[0039] in, is the moment of inertia of the model about the torque reference point. j , i Indicates the coordinate axis, the same below (that is, for a certain wash flow time difference derivative, i and j should be replaced by the corresponding letters representing the coordinate axis).

[0040] right Integrate to get the model translation velocity ,right Integrate to get the model rotation angular velocity ,right The attitude angle caused by the model's rotation angular velocity is obtained by integration The dynamic aerodynamic force vector after deducting the influence of inertial force Select the moment component corresponding to the time derivative of the wash flow .right , , , , Use a high-pass filter with the same parameters for filtering, and the high-pass filter cutoff frequency should be lower than the model motion frequency.

[0041] The mathematical model of aerodynamic forces on attitude and its rate of change under linear conditions is

[0042]

[0043] Because of the high-pass filtering, the above mathematical model does not include the mean moment. It includes rotational damping and part of the wash flow time difference. The phase of this part of the aerodynamic force component is different from the pure wash flow time difference. The difference is about 90°, which is not linearly related, thus ensuring that the problem is not pathological. and flow rate is a known quantity, except for the time derivative of the wash flow and rotational derivatives The other quantities are obtained by previous calculations. Substituting the test data into the above formula, the wash flow time difference derivative can be obtained by the least square method: . The dimensionless wash flow time derivative can be obtained by non-dimensionalization.

[0044] For a motion in a certain motion plane, the corresponding wash flow time derivative can be obtained by following the steps below.

[0045] 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.

[0046] Step 2: Obtain the mapping relationship between acceleration array output and inertial force through calibration , obtain the model mass m and the moment of inertia about the torque reference point in the corresponding motion plane through 3D design software or theoretical calculation .

[0047] Step 3: Under the condition of stable wind tunnel flow field, the model is moved in the plane corresponding to the time-difference derivative of the wash flow. The movement includes the translation of the moment reference point corresponding to the time-difference derivative of the wash flow, and may or may not include the rotation around the moment reference point. At the same time, the balance and acceleration array data are synchronously collected through the synchronous acquisition equipment.

[0048] Step 4: Calculate the balance value , calculate the inertial force based on the acceleration array data , inertial force In the equation, the inertial force component corresponding to the time-difference derivative of the wash flow is , the inertia moment component corresponding to the rotation of the wash flow time difference derivative plane is .

[0049] Step 5: Calculate the dynamic aerodynamic force after deducting the influence of inertia force , dynamic aerodynamic force The aerodynamic torque component corresponding to the plane rotation of the wash flow time difference derivative is .according to The model mass m is used to calculate the acceleration of the wash flow time derivative direction corresponding to the model The inertia moment component corresponding to the rotation of the wash flow time difference derivative plane is and the rotational inertia about the moment reference point in the corresponding motion plane is used to calculate the rotational angular acceleration. .

[0050] Step 6: Derivative direction acceleration of the corresponding wash flow Points to get speed , corresponding to the angular acceleration of rotation in the motion plane Integrate to get the angular velocity , angular velocity Integrate to get the angle .

[0051] Step 7: Use the same parameter high-pass filter to filter the acceleration of the time difference derivative direction of the corresponding wash flow ,speed , corresponding to the angular velocity in the motion plane and angle , corresponding to the moment component in the motion plane High-pass filtering, the filter cutoff frequency should be lower than the model motion frequency.

[0052] Step 8: For the data collected at each moment, the known static derivative and flow rate And the processed data is substituted into the formula , forming an overdetermined system of linear equations of two variables, the unknowns can be solved by the least squares method and ,in This is the time derivative of the wash flow.

[0053] For each test state such as Mach number, motion frequency, etc., the wash time difference calculation repeats steps 3 to 8.

[0054] Example:

[0055] For motions that include heave translation, with or without pitch motion, obtain the time-of-flight derivative of the flow with respect to the rate of change of angle of attack You can follow the steps below.

[0056] 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.

[0057] Step 2: Obtain the mapping relationship between acceleration array output and inertial force through calibration , obtain the model mass m and the moment of inertia about the torque reference point in the corresponding motion plane through 3D design software or theoretical calculation .

[0058] Step 3: Under the condition of stable wind tunnel flow field, the model is moved in the pitch plane. The movement includes the heave and translation of the moment reference point, and may or may not include the pitch rotation around the moment reference point. At the same time, the balance and acceleration array data are synchronously collected through the synchronous acquisition equipment.

[0059] Step 4: Calculate the balance value , calculate the inertial force based on the acceleration array data , inertial force In the equation, the inertial force component corresponding to the time-difference derivative of the wash flow is , the inertia moment component corresponding to the rotation of the wash flow time difference derivative plane is In practical applications, such as for the time derivative of the heave motion wash flow, i is replaced by Y and j is replaced by z, and the same applies below.

[0060] Step 5: Calculate the dynamic aerodynamic force after deducting the influence of inertia force , dynamic aerodynamic force The aerodynamic torque component corresponding to the plane rotation of the wash flow time difference derivative is .according to and the model mass m to calculate the model normal acceleration According to the pitch inertia moment and the pitch moment of inertia about the moment reference point Calculate the pitch acceleration .

[0061] Step 6: Normal acceleration Points to get speed , for the pitch angular acceleration Integrate to get the pitch angular velocity , angular velocity Integrate to get the angle .

[0062] Step 7: Use high-pass filters with the same parameters to filter the acceleration ,speed , angular velocity and angle , pitch moment component High-pass filtering, the filter cutoff frequency should be lower than the model motion frequency.

[0063] Step 8: For the data collected at each moment, the known static derivative and flow rate And the processed data is substituted into the formula , forming an overdetermined system of linear equations of two variables, the unknowns can be solved by the least squares method and ,in This is the time derivative of the wash flow.

[0064] For each test state such as Mach number and motion frequency, the wash time difference calculation repeats steps 3 to 8. The calculation method of the wash time difference derivative with respect to the sideslip angle change rate is similar to that of the wash time difference derivative with respect to the angle of attack change rate, and will not be repeated here.

[0065] 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.

[0066] 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. An experimental method for obtaining the time derivative of wash flow, 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 and inertial force through calibration The mapping relationship ; S3. Calculate inertial force based on acceleration array data ,exist In the equation, the inertial force component corresponding to the time-difference derivative of the wash flow is , the inertia moment component corresponding to the rotation of the wash flow time difference derivative plane is , then the model corresponds to the acceleration of the time difference derivative direction of the wash flow and the model rotation angular acceleration They are obtained by the following formulas: In the above formula, m is the model quality, The moment of inertia about the torque reference point in the corresponding motion plane; S4. Construct the following overdetermined two-variable linear equation system to obtain the wash flow time difference derivative : In the above formula, is a known static derivative, is the known incoming flow velocity, Dynamic aerodynamic force The aerodynamic torque component corresponding to the plane rotation of the wash flow time difference derivative is: is an unknown number, is the attitude angle caused by the model's rotation angular velocity, is the model translation speed; S4. For different test conditions, repeat S3-S4 to calculate the corresponding dynamic derivatives; Dynamic aerodynamic force The acquisition process includes: S30, obtain model quality through 3D design software or theoretical calculation m and the moment of inertia about the torque reference point in the corresponding motion plane ; S31. Under the condition of stable wind tunnel flow field, control the model to move in the plane corresponding to the time difference derivative of the wash flow, so as to synchronously collect the data of the balance and acceleration array through the synchronous acquisition equipment to calculate the balance measurement value. , inertial force The inertia moment component corresponding to the rotation of the wash flow time derivative plane is ; S32. Calculate the dynamic aerodynamic force after deducting the influence of inertia force based on the following formula : 。

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