A method for correcting the trajectory of external storage separation applicable to engineering projects

Abstract

The present invention belongs to the technical field of wind tunnel tests, and discloses a method for correcting the separation trajectory of external objects applicable to engineering. The correction method includes setting the initial conditions for separation of full-scale external objects according to the test conditions; establishing an aerodynamic database of the external object model under the interference flow field without a carrier aircraft; conducting a wind tunnel external object model separation trajectory test, and measuring the aerodynamic force and torque of the external object model at the current position and attitude by means of a test balance; correcting the aerodynamic force and torque of the external object model; combining the external forces including gravity, ejection force and thrust received by the external object model at the current position and attitude, and obtaining the resultant force and resultant torque of the external object model at the current position and attitude; solving the six-degree-of-freedom rigid body motion equation to obtain the position and attitude of the external object model at the next moment; and outputting the separation trajectory of the external object model. The correction method can correct the influence of the difference between the actual speed and the wind tunnel airflow speed on the external object separation trajectory, and has practical engineering value.

Description

Technical Field

[0001] The invention belongs to the technical field of wind tunnel tests, and in particular relates to a method for correcting the separation trajectory of external objects applicable to engineering. Background Art

[0002] When an external attachment of an aircraft is launched or dropped, the flight trajectory of the attachment will be disturbed due to the influence of the aircraft and other external attachments carried by the aircraft on the air flow field. In severe cases, it may cause a flight accident or even cause the aircraft to be destroyed and people to die. Therefore, in order to ensure the flight safety of the aircraft, it is necessary to select the appropriate launch or drop method and conditions, and the safety of the separation of the aircraft and the external attachment must be predicted before the actual test flight. At present, an important means of studying the safety of the separation of external attachments and aircraft is to conduct capture trajectory wind tunnel tests.

[0003] The capture trajectory wind tunnel test technology uses the cooperation of computers, six-degree-of-freedom motion mechanisms and wind tunnels to measure the aerodynamic load of the external attachment model at each separation moment, and solve the motion equation to solve the position and posture of the external attachment model at the next moment. After receiving the command, the external attachment model supported by the six-degree-of-freedom motion mechanism moves to the specified position and posture to measure the aerodynamic force and torque of the external attachment model, and reciprocates to simulate the trajectory of external attachment release. During the test, considering that the actual external attachment movement trajectory is continuous, its combined velocity direction is always along the tangential direction of the movement trajectory (changing with time), while in the existing capture trajectory wind tunnel test, the airflow velocity size and direction are always fixed (the relative speed of the external attachment relative to the carrier cannot be simulated), and there is a certain difference between the static aerodynamic load of the external attachment model measured by the built-in balance and the aerodynamic load of the actual external attachment movement.

[0004] Generally speaking, the external attachment is stationary relative to the carrier aircraft at the initial moment of separation. In the first 0.5s of separation, the speed of the external attachment relative to the carrier aircraft is generally small (relative to the flight speed of the carrier aircraft). At present, the existing wind tunnel test technology generally ignores the speed of the external attachment relative to the carrier aircraft and only simulates the speed of the carrier aircraft relative to the airflow. However, with the emergence of new catapult separation methods, the speed of the external attachment at the initial moment of separation has reached about 10m / s, and the speed will continue to increase after separation. Limited by the size of the wind tunnel test section, it is difficult for existing wind tunnel test technology to simulate the speed of the external attachment relative to the carrier aircraft. In this case, when the carrier aircraft drops bombs at a low Mach number (M=0.4), if the speed of the external attachment relative to the fighter continues to be ignored, the actual speed of the external attachment will be quite different from the wind tunnel airflow speed, which will directly affect the prediction accuracy of the separation trajectory of the external attachment.

[0005] Currently, there is an urgent need to develop a method for correcting the separation trajectory of external attachments that is applicable to engineering projects. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for correcting the separation trajectory of external stores applicable to engineering projects, so as to correct the influence of the difference between the actual speed and the wind tunnel airflow speed on the separation trajectory of the external stores.

[0007] The engineering applicable external attachment separation trajectory correction method of the present invention comprises the following steps:

[0008] S10. According to the test conditions, set the initial conditions for separation of the full-scale external stores;

[0009] The initial conditions for separation of full-scale external stores include the state of the carrier aircraft at the initial moment of separation, the position and attitude of the full-scale external stores relative to the carrier aircraft, the speed and angular velocity of the full-scale external stores, the mass characteristics of the full-scale external stores and the mass characteristics of the external stores model;

[0010] Among them, the state of the carrier aircraft at the initial moment of separation includes the flight Mach number Ma, the flight altitude H, the carrier aircraft flight overload Nz, the carrier aircraft angle of attack α, and the carrier aircraft sideslip angle β; the position and attitude of the full-scale external storage relative to the carrier aircraft at the initial moment of separation, the speed and angular velocity of the full-scale external storage, and the mass characteristics of the full-scale external storage are obtained and provided in advance by the full-scale external storage development unit through ground experiments;

[0011] S20. Establish an aerodynamic database of the external storage model in the flow field without aircraft interference;

[0012] The external store model is a wind tunnel test model of a full-scale external store. The aerodynamic Cs database of the external store model in the flow field without aircraft interference is obtained through the wind tunnel free flow test, so as to be used for the subsequent aerodynamic interpolation after attitude angle correction.

[0013] S30. Conduct a wind tunnel external store model separation trajectory test, and measure the aerodynamic force and torque of the external store model at the current position and attitude by means of a test balance;

[0014] The aerodynamic coefficient of the external attachment model is obtained by dividing the obtained aerodynamic force of the external attachment model by the wind tunnel flow velocity pressure and the reference area of ​​the external attachment model; the aerodynamic moment coefficient of the external attachment model is obtained by dividing the obtained aerodynamic moment value of the external attachment model by the wind tunnel flow velocity pressure and the reference area and reference length of the external attachment model;

[0015] S40. Perform aerodynamic and moment correction on the external attachment model;

[0016] S50. Combine the external forces including gravity, ejection force and thrust on the external attachment model at the current position and attitude, and obtain the resultant force and resultant moment of the external attachment model at the current position and attitude; in the calculation of the aerodynamic force and aerodynamic moment of the external attachment model, the thrust and ejection force of the external attachment model are given by external input before the wind tunnel trajectory test; the damping moment is obtained by combining the damping moment coefficient of the external attachment model with the flow velocity pressure, reference area and length through real-time calculation, wherein the damping derivative is given by external input as a constant value before the trajectory test;

[0017] The damping moment coefficient of the external load model is determined by the damping derivative and the dimensionless angular velocity; the damping derivative includes the rolling damping derivative, the pitching damping derivative and the yaw damping derivative;

[0018] S60. Solve the six-degree-of-freedom rigid body motion equation, integrate to obtain the position and posture of the external attachment model at the next moment; and determine whether the position and posture of the external attachment model at the next moment triggers the condition for ending the trajectory simulation; if not, enter S30, and loop back and forth to obtain the separation trajectory of the external attachment model; otherwise, the trajectory simulation is terminated, the separation trajectory of the external attachment model is output, and the wind tunnel external attachment model separation trajectory test ends.

[0019] Furthermore, the aerodynamic force and moment correction of the external attachment model in S40 includes the following steps:

[0020] S41. In engineering, the aerodynamic force of the external store model under the interference flow field of the carrier aircraft is described by the incremental method. The total aerodynamic force of the external store model under the interference flow field of the carrier aircraft is expressed as follows:

[0021] ;

[0022] Where C is the total aerodynamic force on the external storage model under the interference flow field of the carrier aircraft; △C f is the aircraft interference part of the aerodynamic force on the external load model in the aircraft interference flow field, △C f The value is determined by the position (X, Y, Z) and attitude (ψ, θ, Φ) of the external store model under the interference flow field of the carrier aircraft. It is considered that the local velocity of the external store model has an influence on △C f The value has no effect; Cs is the aerodynamic force of the external store model in the flow field without aircraft interference. The Cs value is determined by the angle between the external store model and the flight speed. Decision, namely:

[0023] ;

[0024] Among them, (ψ, θ, Φ) is the Euler angle of the external storage model relative to the inertial axis system, ψ is the yaw angle of the external storage, θ is the pitch angle of the external storage, and Φ is the roll angle of the external storage; is the attitude angle of the external attachment model relative to the airflow axis system, is the actual angle of attack of the external store model relative to the airflow, is the actual sideslip angle of the external store model relative to the airflow;

[0025] S42. Through axis system transformation, the Euler angles (ψ, θ, Φ) of the external attachment model relative to the inertial axis system are transformed into the attitude angles of the external attachment model relative to the airflow axis system:

[0026] ;

[0027] S43. Considering the local velocity (U, V, W) of the external load model, the free flow velocity U A The actual velocity of the external model relative to the airflow in the flow field is obtained by transforming the axis system to the axis system of the external model and superimposing it with the local velocity, thereby obtaining the actual angle of the external model relative to the airflow. , the specific formula is as follows:

[0028] ;

[0029] In the above formula, U A,X , U A,Y , U A,Z is the free flow velocity U A The velocity component on the axis system of the external storage model; V X , V Y , V Z is the actual velocity component of the external storage model in the airflow; V R is the value of the combined velocity of the external storage model in the airflow;

[0030] Combining the above formulas, we can obtain the aerodynamic increment of the external attachment model generated by the local speed in the free flow field without aircraft interference:

[0031] ;

[0032] S44. The aerodynamic force increment in equation (8) is added to the aerodynamic force and moment of the external attachment model at the position and attitude corresponding to the carrier flow field, and the aerodynamic force and moment after the local velocity of the external attachment model is corrected are obtained.

[0033] The engineering applicable external storage separation trajectory correction method of the present invention can correct the influence of the difference between the actual speed and the wind tunnel airflow speed on the external storage separation trajectory, and has engineering practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A flow chart of a method for correcting the trajectory of external attachment separation applicable to the project of the present invention;

[0035] Figure 2This is a comparison curve of the X-direction displacement after the external attachment separation trajectory is corrected;

[0036] Figure 3 This is a comparison curve of the Y-direction displacement after the external attachment separation trajectory is corrected;

[0037] Figure 4 This is a comparison curve of the Z-direction displacement after the external attachment separation trajectory is corrected;

[0038] Figure 5 It is a comparison curve of yaw angle displacement after the external storage separation trajectory is corrected;

[0039] Figure 6 This is a comparison curve of the pitch angle displacement after the external storage separation trajectory is corrected;

[0040] Figure 7 This is a comparison curve of the roll angle displacement after the external storage separation trajectory is corrected. DETAILED DESCRIPTION

[0041] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0042] Example 1: The test wind tunnel of this example is a 1.2-meter temporary wind tunnel, the cross section of the wind tunnel test section is 1.2m×1.2m, and the Ma number range is 0.4-3.0. The subsonic test section is 3.6m long, and the side walls on both sides are straight hole walls with optical glass observation windows. The external attachment model is a certain large-load missile model, and a six-component rod strain balance with a diameter of 8mm is used to measure the aerodynamic load. The test Ma number is 0.6. Figure 1 As shown, the engineering method for correcting the trajectory of external attachment separation in this embodiment includes the following steps:

[0043] S10. According to the test conditions, set the initial conditions for separation of the full-scale external stores;

[0044] The initial conditions for the separation of the full-size external storage are shown in Table 1, including the state of the carrier aircraft at the initial moment of separation, the position and attitude of the full-size external storage relative to the carrier aircraft, the speed of the full-size external storage, the mass of the full-size external storage, and the moment of inertia.

[0045] Table 1 Initial conditions for separation of full-scale external stores

[0046] ;

[0047] Wherein, Ix represents the moment of inertia of the full-size external storage object around its body axis Xt, Iy represents the moment of inertia of the full-size external storage object around its body axis Yt, and Iz represents the moment of inertia of the full-size external storage object around its body axis Zt;

[0048] S20. Establish an aerodynamic database of the external storage model in the flow field without aircraft interference;

[0049] The external store model is a wind tunnel test model of a full-scale external store. The aerodynamic Cs database of the external store model in the flow field without aircraft interference is obtained through the wind tunnel free flow test, so as to be used for the subsequent aerodynamic interpolation after attitude angle correction.

[0050] S30. Conduct a wind tunnel external store model separation trajectory test, and measure the aerodynamic force and torque of the external store model at the current position and attitude by means of a test balance;

[0051] The aerodynamic coefficient of the external attachment model is obtained by dividing the obtained aerodynamic force of the external attachment model by the wind tunnel flow velocity pressure and the reference area of ​​the external attachment model; the aerodynamic moment coefficient of the external attachment model is obtained by dividing the obtained aerodynamic moment value of the external attachment model by the wind tunnel flow velocity pressure and the reference area and reference length of the external attachment model;

[0052] S40. Perform aerodynamic and moment correction on the external attachment model;

[0053] S50. Combine the external forces including gravity, ejection force and thrust on the external attachment model at the current position and attitude, and obtain the resultant force and resultant moment of the external attachment model at the current position and attitude; in the calculation of the aerodynamic force and aerodynamic moment of the external attachment model, the thrust and ejection force of the external attachment model are given by external input before the wind tunnel trajectory test; the damping moment is obtained by combining the damping moment coefficient of the external attachment model with the flow velocity pressure, reference area and length through real-time calculation, wherein the damping derivative is given by external input as a constant value before the trajectory test;

[0054] The damping moment coefficient of the external load model is determined by the damping derivative and the dimensionless angular velocity; the damping derivative includes the rolling damping derivative, the pitching damping derivative and the yaw damping derivative;

[0055] S60. Solve the six-degree-of-freedom rigid body motion equation to obtain the position and posture of the external attachment model at the next moment; and determine whether the position and posture of the external attachment model at the next moment trigger the conditions for ending the trajectory simulation; if not triggered, enter S30, and loop back and forth to obtain the separation trajectory of the external attachment model; otherwise, the trajectory simulation is terminated, the separation trajectory of the external attachment model is output, and the wind tunnel external attachment model separation trajectory test is ended.

[0056] This embodiment obtains Figure 2 to Figure 7 From the comparison curves shown, it can be seen that after the external storage separation trajectory is corrected, the X, Y, and Z displacements of the separation trajectory centerline do not change significantly; the pitch attitude angle and yaw attitude angle in the separation trajectory are significantly different from the uncorrected data, and the maximum difference is about 1°.

[0057] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and implementation modes. For those familiar with the art, all features disclosed in the present invention, or steps in all methods or processes disclosed, except for mutually exclusive features and / or steps, can be combined in any way without departing from the principles of the present invention. The present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for correcting the trajectory of external attachment separation applicable to engineering, characterized in that: The following steps are involved: S10. According to the test conditions, set the initial conditions for separation of the full-scale external stores; The initial conditions for separation of full-scale external stores include the state of the carrier aircraft at the initial moment of separation, the position and attitude of the full-scale external stores relative to the carrier aircraft, the speed and angular velocity of the full-scale external stores, the mass characteristics of the full-scale external stores and the mass characteristics of the external stores model; Among them, the state of the carrier aircraft at the initial moment of separation includes the flight Mach number Ma, the flight altitude H, the carrier aircraft flight overload Nz, the carrier aircraft angle of attack α, and the carrier aircraft sideslip angle β; the position and attitude of the full-scale external storage relative to the carrier aircraft at the initial moment of separation, the speed and angular velocity of the full-scale external storage, and the mass characteristics of the full-scale external storage are obtained and provided in advance by the full-scale external storage development unit through ground experiments; S20. Establish an aerodynamic database of the external storage model in the flow field without aircraft interference; The external store model is a wind tunnel test model of a full-scale external store. The aerodynamic Cs database of the external store model in the flow field without aircraft interference is obtained through the wind tunnel free flow test, so as to be used for the subsequent aerodynamic interpolation after attitude angle correction. S30. Conduct a wind tunnel external store model separation trajectory test, and measure the aerodynamic force and torque of the external store model at the current position and attitude by means of a test balance; The aerodynamic coefficient of the external attachment model is obtained by dividing the obtained aerodynamic force of the external attachment model by the wind tunnel flow velocity pressure and the reference area of ​​the external attachment model; the aerodynamic moment coefficient of the external attachment model is obtained by dividing the obtained aerodynamic moment value of the external attachment model by the wind tunnel flow velocity pressure and the reference area and reference length of the external attachment model; S40. Performing aerodynamic and moment correction on the external attachment model; comprising the following steps: S41. In engineering, the aerodynamic force of the external store model under the interference flow field of the carrier aircraft is described by the incremental method. The total aerodynamic force of the external store model under the interference flow field of the carrier aircraft is expressed as follows: ； Where C is the total aerodynamic force on the external storage model under the interference flow field of the carrier aircraft; △C f is the aircraft interference part of the aerodynamic force on the external load model in the aircraft interference flow field, △C f The value is determined by the position (X, Y, Z) and attitude (ψ, θ, Φ) of the external store model under the interference flow field of the carrier aircraft. It is considered that the local velocity of the external store model has an influence on △C f The value has no effect; Cs is the aerodynamic force of the external store model in the flow field without aircraft interference. The Cs value is determined by the angle between the external store model and the flight speed. Decide that: ； Among them, (ψ, θ, Φ) is the Euler angle of the external storage model relative to the inertial axis system, ψ is the yaw angle of the external storage, θ is the pitch angle of the external storage, and Φ is the roll angle of the external storage; is the attitude angle of the external attachment model relative to the airflow axis system, is the actual angle of attack of the external store model relative to the airflow, is the actual sideslip angle of the external store model relative to the airflow; S42. Through axis system transformation, the Euler angles (ψ, θ, Φ) of the external attachment model relative to the inertial axis system are transformed into the attitude angles of the external attachment model relative to the airflow axis system: ； S43. Considering the local velocity (U, V, W) of the external load model, the free flow velocity U A The actual velocity of the external model relative to the airflow in the flow field is obtained by transforming the axis system to the axis system of the external model and superimposing it with the local velocity, thereby obtaining the actual angle of the external model relative to the airflow. , the specific formula is as follows: ； In the above formula, U A,X , U A,Y , U A,Z is the free flow velocity U A The velocity component on the axis system of the external storage model; V X , V Y , V Z is the actual velocity component of the external storage model in the airflow; V R is the value of the combined velocity of the external storage model in the airflow; Combining the above formulas, we can obtain the aerodynamic increment of the external attachment model generated by the local speed in the free flow field without aircraft interference: ； S44. The aerodynamic force increment in equation (8) is superimposed on the aerodynamic force and moment of the external store model at the position and attitude corresponding to the carrier flow field, so as to obtain the aerodynamic force and moment after the local velocity of the external store model is corrected; S50. Combine the external forces including gravity, ejection force and thrust on the external attachment model at the current position and attitude, and obtain the resultant force and resultant moment of the external attachment model at the current position and attitude; in the calculation of the aerodynamic force and aerodynamic moment of the external attachment model, the thrust and ejection force of the external attachment model are given by external input before the wind tunnel trajectory test; the damping moment is obtained by combining the damping moment coefficient of the external attachment model with the flow velocity pressure, reference area and length through real-time calculation, wherein the damping derivative is given by external input as a constant value before the trajectory test; The damping moment coefficient of the external load model is determined by the damping derivative and the dimensionless angular velocity; the damping derivative includes the rolling damping derivative, the pitching damping derivative and the yaw damping derivative; S60. Solve the six-degree-of-freedom rigid body motion equation, integrate to obtain the position and posture of the external attachment model at the next moment; and determine whether the position and posture of the external attachment model at the next moment triggers the condition for ending the trajectory simulation; if not, enter S30, and loop back and forth to obtain the separation trajectory of the external attachment model; otherwise, the trajectory simulation is terminated, the separation trajectory of the external attachment model is output, and the wind tunnel external attachment model separation trajectory test ends.

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