A test method for accurate measurement of small-value dynamic derivatives

Abstract

A small-value dynamic derivative accurate measurement test method belongs to the field of dynamic derivative measurement technology. In order to accurately measure small-value dynamic derivatives, the present invention includes constructing a vibration state model in the dynamic derivative test process according to the angular motion dynamics equation, calculating the phase difference between the driving torque and the vibration angle; designing to increase the restoring torque coefficient and the damping torque coefficient by changing the speed pressure of the wind tunnel, stabilizing the moment of inertia of the model around the vibration axis and the vibration angular frequency speed, so as to increase the phase difference between the driving torque and the vibration angle; conducting a dynamic derivative test under a conventional speed pressure state, and using the obtained dynamic derivative test data under the conventional speed pressure state to draw a torque vector diagram; formulating a speed pressure adjustment target, and obtaining a target speed pressure point; conducting a variable speed pressure dynamic derivative test, obtaining a dynamic derivative under a variable speed pressure state, and calculating the difference between the dynamic derivative under the variable speed pressure state and the dynamic derivative under the conventional speed pressure as the system difference; and correcting the dynamic derivative test results under the conventional speed pressure state.

Description

Technical Field

[0001] The invention belongs to the technical field of dynamic derivative measurement, and in particular relates to a test method for accurately measuring a small-value dynamic derivative. Background Art

[0002] In the development process of various aerospace vehicles, the aerodynamic performance of the aircraft needs to be analyzed and comprehensively evaluated. First of all, its aerodynamic performance under steady and unsteady conditions must be clear. At the same time, the static and dynamic stability of the aircraft must be predicted. This requires that the prediction of aerodynamic characteristics should not only give six-component aerodynamic forces and moment coefficients, but also be able to give stability criteria, which can be divided into static derivatives and dynamic derivatives. The static derivative is the derivative of the aerodynamic force and moment coefficient to the angular displacement, while the dynamic derivative is the derivative of the angular velocity and angular acceleration.

[0003] Dynamic derivative is the abbreviation of Dynamic Stability Derivatives, which is used to describe the aerodynamic characteristics of an aircraft during maneuvering and being disturbed. It is the derivative of the time rate of change of the aircraft's six aerodynamic coefficients (i.e., three forces and three torque coefficients in a three-dimensional rectangular coordinate system) to the aircraft's attitude parameters, totaling 36. They are indispensable original parameters for the aircraft's guidance system, control system, and dynamic quality analysis. In the dynamic derivative measurement test, the measured physical quantities are the driving torque of the model and the vibration angle of the model. The required dynamic derivative can be obtained by correlating the two measured quantities.

[0004] Among the 36 dynamic derivatives, the most concerned one is the dynamic derivative in the pitch direction, that is, the pitch damping derivative, which is mainly generated by the horizontal tail of the aircraft. For conventional layout aircraft, it has a horizontal tail component, the pitch damping of the flight is obvious, the pitch damping derivative value is large, and the measurement accuracy meets the test requirements.

[0005] With the development of aircraft, some aircraft without obvious horizontal tails have appeared, such as flying wing layout. Since such aircraft have eliminated the traditional horizontal tail, the pitch dynamic derivative has dropped significantly. Correspondingly, the pitch dynamic derivative in the wind tunnel test has also dropped significantly. The small measurement value has brought obvious measurement difficulties. The traditional dynamic derivative measurement method is difficult to guarantee the accuracy of the measurement results. It is necessary to invent a new measurement method that can solve the problem of measuring the accuracy of small-value dynamic derivatives. Summary of the invention

[0006] The problem to be solved by the present invention is to accurately measure a small-value dynamic derivative, and a small-value dynamic derivative accurate measurement test method is proposed.

[0007] To achieve the above object, the present invention is implemented through the following technical solutions:

[0008] A small value dynamic derivative accurate measurement test method comprises the following steps:

[0009] S1. According to the angular motion dynamics equation, the vibration state model during the dynamic derivative test is constructed, and then the phase difference between the driving torque and the vibration angle is calculated;

[0010] S2. Based on the phase difference between the driving torque and the vibration angle obtained in step S1, the design is to increase the restoring torque coefficient and the damping torque coefficient by changing the velocity pressure of the wind tunnel, stabilize the moment of inertia of the model around the vibration axis and the vibration angular frequency speed, so as to increase the phase difference between the driving torque and the vibration angle;

[0011] S3. Perform a dynamic derivative test under a conventional speed pressure state, and use the dynamic derivative test data obtained under a conventional speed pressure state to draw a torque vector diagram;

[0012] S4. Formulate speed and pressure adjustment targets and obtain target speed and pressure points;

[0013] S5. Perform a variable speed pressure dynamic derivative test based on the target speed pressure point obtained in step S4 to obtain a dynamic derivative under the variable speed pressure state, compare the dynamic derivative under the variable speed pressure state with the dynamic derivative of the conventional speed pressure, and calculate the difference between the dynamic derivative under the variable speed pressure state and the dynamic derivative of the conventional speed pressure as the system difference;

[0014] S6. Based on the difference between the dynamic derivative under the variable speed pressure state and the dynamic derivative under the normal speed pressure state obtained in step S5, the dynamic derivative test result under the normal speed pressure state is corrected.

[0015] Furthermore, the specific implementation method of step S1 includes the following steps:

[0016] S1.1. Construct the vibration state model during the dynamic derivative test, the expression is:

[0017] ;

[0018] in, is the moment of inertia of the model around the vibration axis, is the model vibration angle, , t For time, is the vibration angular frequency speed, is the vibration angle amplitude, is the restoring moment coefficient, is the damping torque coefficient, is the derivative of the model vibration angle with respect to time, is the second-order derivative of the model vibration angle with respect to time, is the driving torque;

[0019] S1.2. Solve the parameters in the vibration state model obtained in step S1.1, and the expression is:

[0020] ;

[0021] ;

[0022] ;

[0023] ;

[0024] in, is the model inertia moment, is the static aerodynamic torque, is the dynamic aerodynamic torque, is the driving torque amplitude, is the phase difference between the driving torque and the vibration angle;

[0025] S1.3. Setting the damping torque coefficient The expression is:

[0026] ;

[0027] Then the damping moment coefficient Perform dimensionless processing to obtain dimensionless dynamic derivative results , the expression is:

[0028] ;

[0029] in, is the wind tunnel flow velocity, is the velocity pressure from the wind tunnel, is the model reference area, is the model reference length;

[0030] S1.4. Constructing the phase difference between driving torque and vibration angle The expression is:

[0031] .

[0032] Furthermore, the specific implementation method of step S3 is to analyze the test data of the dynamic derivative test under the conventional speed and pressure state, calculate the inertia moment, static aerodynamic moment, dynamic aerodynamic moment and driving moment, and draw a torque vector diagram.

[0033] Further, the specific implementation method of step S4 is to set the speed-pressure adjustment target to 1.2, 1.4, 1.6, 1.8 and 2.0 times of the normal speed-pressure value, draw the torque vector diagram under different speed-pressure adjustment targets, and calculate the phase difference between the driving torque and the angle under each speed-pressure adjustment target;

[0034] A curve between phase difference and speed pressure is drawn, a phase difference point is selected on the curve between phase difference and speed pressure, and a speed pressure point corresponding to the phase difference point is determined to obtain a target speed pressure point.

[0035] Furthermore, the specific implementation method of step S5 is to perform a variable speed pressure derivative test by selecting a state where the rudder surface deflection angle is 0 degrees at each Mach number and performing a variable speed pressure test.

[0036] Further, the specific implementation method of step S6 is to set the difference between the dynamic derivative under the variable speed pressure state and the dynamic derivative under the normal speed pressure state to , the expression for correcting the dynamic derivative test results under conventional speed and pressure conditions is:

[0037] ;

[0038] in, For the test Mach number, is the rudder deflection angle under different states of the model, is the corrected dynamic derivative result, These are the uncorrected dynamic derivative results at different rudder surface deflection angles.

[0039] Beneficial effects of the present invention:

[0040] The small-value dynamic derivative accurate measurement test method described in the present invention can increase the phase angle between the driving torque and the vibration angle by multiples, thereby significantly improving the accuracy of the measurement results.

[0041] The invention discloses a method for accurately measuring a small-value dynamic derivative, which performs vector decomposition on the loads in the dynamic derivative test, and the relationship between the loads is clear, so that the relationship between the phase angle and the wind tunnel velocity pressure can be quickly determined.

[0042] The invention discloses a method for accurately measuring a small-value dynamic derivative, which compares and corrects the test data of a typical state point and uses it as a system difference to correct the data under the entire test state, thereby saving costs and being highly efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of a small-value dynamic derivative accurate measurement test method according to the present invention;

[0044] Figure 2It is a vector diagram of the moment acted upon by the model of the present invention during vibration;

[0045] Figure 3 1 is a comparison diagram of torque vector distribution under normal speed and pressure and adjusted speed and pressure states of the present invention, (a) is the torque vector distribution diagram under normal speed and pressure state, (b) is the torque vector distribution diagram under variable speed and pressure state. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the specific embodiments described are only part of the embodiments of the present invention, rather than all of the specific embodiments. The components of the specific embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations, and the present invention can also have other embodiments.

[0047] Therefore, the following detailed description of the specific embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected specific embodiments of the present invention. Based on the specific embodiments of the present invention, all other specific embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0048] In order to further understand the content, features and effects of the present invention, the following specific implementation methods are given as examples, and the attached Figure 1 -Attached Figure 3 The detailed instructions are as follows:

[0049] Embodiment 1:

[0050] A small value dynamic derivative accurate measurement test method comprises the following steps:

[0051] S1. According to the angular motion dynamics equation, the vibration state model during the dynamic derivative test is constructed, and then the phase difference between the driving torque and the vibration angle is calculated;

[0052] Furthermore, the specific implementation method of step S1 includes the following steps:

[0053] S1.1. Construct the vibration state model during the dynamic derivative test, the expression is:

[0054] ;

[0055] in, is the moment of inertia of the model around the vibration axis, is the model vibration angle, ,t For time, is the vibration angular frequency speed, is the vibration angle amplitude, is the restoring moment coefficient, is the damping torque coefficient, is the derivative of the model vibration angle with respect to time, is the second-order derivative of the model vibration angle with respect to time, is the driving torque;

[0056] S1.2. Solve the parameters in the vibration state model obtained in step S1.1, and the expression is:

[0057] ;

[0058] ;

[0059] ;

[0060] ;

[0061] in, is the model inertia moment, is the static aerodynamic torque, is the dynamic aerodynamic torque, is the driving torque amplitude, is the phase difference between the driving torque and the vibration angle;

[0062] S1.3. Setting the damping torque coefficient The expression is:

[0063] ;

[0064] Then the damping moment coefficient Perform dimensionless processing to obtain dimensionless dynamic derivative results , the expression is:

[0065] ;

[0066] in, is the wind tunnel flow velocity, is the velocity pressure from the wind tunnel, is the model reference area, is the model reference length;

[0067] S1.4. Constructing the phase difference between driving torque and vibration angle The expression is:

[0068] .

[0069] Furthermore, in the dynamic derivative test, for the same aircraft, the smaller the dynamic derivative value, the smaller the phase difference in the test. For tailless aircraft, the dynamic derivative in the pitch direction is greatly reduced due to the elimination of the traditional horizontal tail, and the phase difference in the test is also greatly reduced, which may be reduced from the 5-10° range of traditional aircraft to 1-2°. At this time, the accuracy of dynamic derivative measurement drops sharply. Inventing a test method that can improve the phase difference will greatly improve the measurement accuracy of dynamic derivatives.

[0070] S2. Based on the phase difference between the driving torque and the vibration angle obtained in step S1, the design is to increase the restoring torque coefficient and the damping torque coefficient by changing the velocity pressure of the wind tunnel, stabilize the moment of inertia of the model around the vibration axis and the vibration angular frequency speed, so as to increase the phase difference between the driving torque and the vibration angle;

[0071] Further, improve Value and The value method is to change the velocity pressure of the wind tunnel, where value, The value is proportional to the wind tunnel flow velocity pressure. By adjusting the wind tunnel flow velocity pressure, the adjustment can be achieved. Value and The purpose of the two variables is to calculate the dimensionless dynamic derivative of the final test results. Divide the value by the wind tunnel velocity pressure to obtain The value has nothing to do with speed and pressure, ensuring the The values ​​are consistent.

[0072] Since the adjustment of the wind tunnel incoming flow velocity pressure in the wind tunnel test requires a certain amount of additional work, in order to ensure the test efficiency, the present invention only performs the wind tunnel incoming flow velocity pressure adjustment test on the basic state of the model for the test at each Mach number, obtains the dynamic derivative difference between the conventional incoming flow velocity pressure of the wind tunnel under the basic state and the adjusted incoming flow velocity pressure, and uses this difference to correct the dynamic derivative structure of all model states under the Mach number.

[0073] S3. Perform a dynamic derivative test under a conventional speed pressure state, and use the dynamic derivative test data obtained under a conventional speed pressure state to draw a torque vector diagram;

[0074] Furthermore, the specific implementation method of step S3 is to analyze the test data of the dynamic derivative test under the conventional speed and pressure state, calculate the inertia moment, static aerodynamic moment, dynamic aerodynamic moment and driving moment, and draw a torque vector diagram.

[0075] S4. Formulate speed and pressure adjustment targets and obtain target speed and pressure points;

[0076] Further, the specific implementation method of step S4 is to set the speed-pressure adjustment target to 1.2, 1.4, 1.6, 1.8 and 2.0 times of the normal speed-pressure value, draw the torque vector diagram under different speed-pressure adjustment targets, and calculate the phase difference between the driving torque and the angle under each speed-pressure adjustment target;

[0077] A curve between phase difference and speed pressure is drawn, a phase difference point is selected on the curve between phase difference and speed pressure, and a speed pressure point corresponding to the phase difference point is determined to obtain a target speed pressure point.

[0078] Furthermore, according to the load capacity of the vibration mechanism and the rigidity requirements of the model and the balance, a reasonable range of test angles of attack is determined to ensure that the aerodynamic load does not exceed the allowable range after the velocity pressure increases.

[0079] S5. Perform a variable speed pressure dynamic derivative test based on the target speed pressure point obtained in step S4 to obtain a dynamic derivative under the variable speed pressure state, compare the dynamic derivative under the variable speed pressure state with the dynamic derivative of the conventional speed pressure, and calculate the difference between the dynamic derivative under the variable speed pressure state and the dynamic derivative of the conventional speed pressure as the system difference;

[0080] Furthermore, the specific implementation method of step S5 is to perform a variable speed pressure derivative test by selecting a state where the rudder surface deflection angle is 0 degrees at each Mach number and performing a variable speed pressure test.

[0081] S6. Based on the difference between the dynamic derivative under the variable speed pressure state and the dynamic derivative under the normal speed pressure obtained in step S5, the dynamic derivative test result under the normal speed pressure state is corrected.

[0082] Further, the specific implementation method of step S6 is to set the difference between the dynamic derivative under the variable speed pressure state and the dynamic derivative under the normal speed pressure to , the expression for correcting the dynamic derivative test results under conventional speed and pressure conditions is:

[0083] ;

[0084] in, For the test Mach number, is the rudder deflection angle under different states of the model, is the corrected dynamic derivative result, These are the uncorrected dynamic derivative results at different rudder surface deflection angles.

[0085] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0086] Although the present application has been described above with reference to specific embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the various features in the specific embodiments disclosed in the present application may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A small value dynamic derivative accurate measurement test method, characterized in that: The steps include: S1. According to the angular motion dynamics equation, the vibration state model during the dynamic derivative test is constructed, and then the phase difference between the driving torque and the vibration angle is calculated; S2. Based on the phase difference between the driving torque and the vibration angle obtained in step S1, the design is to increase the restoring torque coefficient and the damping torque coefficient by changing the velocity pressure of the wind tunnel, stabilize the moment of inertia of the model around the vibration axis and the vibration angular frequency speed, so as to increase the phase difference between the driving torque and the vibration angle; S3. Perform a dynamic derivative test under a conventional speed pressure state, and use the dynamic derivative test data obtained under a conventional speed pressure state to draw a torque vector diagram; S4. Formulate speed and pressure adjustment targets and obtain target speed and pressure points; S5. Perform a variable speed pressure dynamic derivative test based on the target speed pressure point obtained in step S4 to obtain a dynamic derivative under the variable speed pressure state, compare the dynamic derivative under the variable speed pressure state with the dynamic derivative of the conventional speed pressure, and calculate the difference between the dynamic derivative under the variable speed pressure state and the dynamic derivative of the conventional speed pressure as the system difference; S6. Based on the difference between the dynamic derivative under the variable speed pressure state and the dynamic derivative under the normal speed pressure obtained in step S5, the dynamic derivative test result under the normal speed pressure state is corrected.

2. A small value dynamic derivative accurate measurement test method according to claim 1, characterized in that: The specific implementation method of step S1 includes the following steps: S1.

1. Construct the vibration state model during the dynamic derivative test, the expression is: ； in, is the moment of inertia of the model around the vibration axis, is the model vibration angle, , t For time, is the vibration angular frequency speed, is the vibration angle amplitude, is the restoring moment coefficient, is the damping torque coefficient, is the derivative of the model vibration angle with respect to time, is the second-order derivative of the model vibration angle with respect to time, is the driving torque; S1.

2. Solve the parameters in the vibration state model obtained in step S1.1, and the expression is: ； ； ； ； in, is the model inertia moment, is the static aerodynamic torque, is the dynamic aerodynamic torque, is the driving torque amplitude, is the phase difference between the driving torque and the vibration angle; S1.

3. Setting the damping torque coefficient The expression is: ； Then the damping moment coefficient Perform dimensionless processing to obtain dimensionless dynamic derivative results , the expression is: ； in, is the wind tunnel flow velocity, is the velocity pressure from the wind tunnel, is the model reference area, is the model reference length; S1.

4. Constructing the phase difference between driving torque and vibration angle The expression is: 。 3. A small value dynamic derivative accurate measurement test method according to claim 2, characterized in that: The specific implementation method of step S3 is to analyze the test data of the dynamic derivative test under the conventional speed and pressure state, calculate the inertia moment, static aerodynamic moment, dynamic aerodynamic moment and driving moment, and draw a torque vector diagram.

4. A small value dynamic derivative accurate measurement test method according to claim 3, characterized in that: The specific implementation method of step S4 is to set the speed-pressure adjustment target to 1.2, 1.4, 1.6, 1.8 and 2.0 times of the normal speed-pressure value, draw the torque vector diagram under different speed-pressure adjustment targets, and calculate the phase difference between the driving torque and the angle under each speed-pressure adjustment target; A curve between phase difference and speed pressure is drawn, a phase difference point is selected on the curve between phase difference and speed pressure, and a speed pressure point corresponding to the phase difference point is determined to obtain a target speed pressure point.

5. A small value dynamic derivative accurate measurement test method according to claim 4, characterized in that: The specific implementation method of step S5 is to perform a variable speed pressure derivative test by selecting a 0 degree state of the rudder deflection angle at each Mach number and performing a variable speed pressure test.

6. A small value dynamic derivative accurate measurement test method according to claim 5, characterized in that: The specific implementation method of step S6 is to set the difference between the dynamic derivative under the variable speed pressure state and the dynamic derivative under the normal speed pressure to , the expression for correcting the dynamic derivative test results under conventional speed and pressure conditions is: ； in, For the test Mach number, is the rudder surface deflection angle under different states of the model, is the corrected dynamic derivative result, These are the uncorrected dynamic derivative results at different rudder surface deflection angles.

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