A method for precise control of attitude angle of a force-measuring wind tunnel test model

Abstract

A method for precise attitude angle control of a force-measuring wind tunnel test model is disclosed, relating to the field of aircraft wind tunnel testing technology. This method addresses the technical problems of traditional force-measuring wind tunnel attitude angle control, such as numerous iterations, large overshoot, errors introduced by mechanical clearances, and safety hazards at high angles of attack. The invention includes the following steps: S1. Test system preparation and mechanical clearance calibration; S2. Pre-calculation and compensation of the first target attitude angle; S3. Closed-loop control and dynamic fine-tuning; S4. Continuous testing and prediction of the next target; S5. Test termination. This invention has promising application prospects in high-precision aerodynamic testing of aircraft, particularly in the field of aerodynamic characteristic testing where stringent requirements for attitude angle control accuracy, testing efficiency, and safety are placed.

Description

Technical Field

[0001] This invention relates to the field of wind tunnel testing technology for aircraft, and specifically to a method for precise control of the attitude angle of a force-measuring wind tunnel test model. Background Technology

[0002] Wind tunnel testing is a crucial method in aerodynamic research. In these tests, the aircraft model is subjected to aerodynamic loads, causing elastic deformation in the support system connecting the model to the attitude angle control mechanism. This deformation results in a deviation between the model's actual attitude angle and the theoretical attitude angle set by the mechanism. Since the aerodynamic characteristics of an aircraft are extremely sensitive to attitude angles, achieving precise control of the model's attitude angle is a fundamental prerequisite for ensuring the accuracy of experimental data.

[0003] Specifically, in force-measuring wind tunnel tests, a model is installed in the wind tunnel, and a force-measuring balance is integrated inside the model to measure the aerodynamic forces exerted on the model by the airflow. Based on the forces and moments measured by the balance, combined with the elastic angle coefficient of the support system, the elastic deformation angle of the model can be calculated, and the measured values ​​can be corrected to obtain the true model attitude angle. Against this backdrop, precise attitude angle control technology has emerged, which is superior to traditional open-loop control methods, especially in lateral flight tests where extremely high precision is required. This technology aims to directly acquire aerodynamic data at precise attitude angles, thereby avoiding deviations caused by two-dimensional data interpolation.

[0004] Currently, there are several attitude angle precision control systems and methods for continuous wind tunnel testing. However, these existing technologies still have significant shortcomings. The core flaw lies in the fact that during the initial attitude angle adjustment, only the nominal target value is used, without pre-calculating and compensating for the elastic angle. This leads to the need for multiple iterative fine-tunings to converge, resulting in low efficiency. Furthermore, under high angle-of-attack testing conditions, the superposition effect of the elastic angle can easily cause excessive overshoot in the actual attitude angle, affecting not only accuracy but also posing safety hazards. Simultaneously, during the reciprocating adjustment of the attitude angle mechanism, the inherent clearance of the mechanical structure is introduced into the control and calculation stages, becoming a difficult-to-eliminate source of system error, further restricting the improvement of control accuracy. Summary of the Invention

[0005] To address the technical problems of traditional force-measuring wind tunnel test attitude angle control, such as numerous iterations, large overshoot, errors introduced by mechanical backlash, and safety hazards at high angles of attack, this invention provides a method for precise attitude angle control of a force-measuring wind tunnel test model, comprising:

[0006] S1. Test preparation and clearance calibration: Install the test model, force balance and support system in the wind tunnel test section, and measure the mechanical clearance of the attitude angle control mechanism in the pitch and roll directions.

[0007] S2. Pre-calculation and compensation of the first target attitude angle: Based on the target Mach number, target angle of attack and target sideslip angle, combined with the model aerodynamic derivative, the aerodynamic load and the corresponding model elastic angle are pre-calculated. After elastic angle compensation of the target attitude angle, the base angle under the mechanism axis is calculated. It is determined whether the direction of the mechanism's current movement is consistent with the previous one. If they are consistent, no adjustment is needed. If they are inconsistent, the corresponding mechanical clearance is superimposed on the base angle to generate the first mechanism movement command.

[0008] S3. Closed-loop control and dynamic fine-tuning: Drive the test model to the first mechanism motion command. After the flow field stabilizes, measure the load using a force balance and calculate the actual attitude angle of the test model. Determine whether the deviation between the actual attitude angle and the target attitude angle meets the control accuracy. If it does, complete the control of the current target attitude angle. If it does not, calculate the fine-tuning command and add mechanical clearance when the fine-tuning direction is inconsistent with the previous motion direction. Perform iterative fine-tuning until the control accuracy is met.

[0009] S4. Prediction of the next target in continuous testing: After the current target attitude angle is controlled, if continuous testing is required, the load and elastic angle change caused by the attitude angle change are predicted based on the difference between the current actual attitude angle and the next target attitude angle. The difference is compensated and then calculated as the mechanism angle change. Combined with mechanical backlash compensation, the predicted mechanism command for the next target is generated. Then, the process jumps to step S3 for closed-loop control.

[0010] S5. Repeat steps S3 and S4 until all target attitude angles have been tested.

[0011] Furthermore, in S1, the mechanical clearance of the attitude angle control mechanism in the pitch and roll directions specifically includes:

[0012] S1.1 Drive the pitch mechanism to -1° via the attitude angle control unit;

[0013] S1.2 Drive the pitch mechanism to 0°, eliminate the backlash, and record the tilt sensor reading. ;

[0014] S1.3 Continue to drive the pitch mechanism from the current 0° position to +1°;

[0015] S1.4 Continue driving the pitch mechanism to 0° and record the final reading from the tilt sensor. ;

[0016] S1.5 Calculate the mechanical structure clearance in the pitch direction. ;

[0017] S1.6 Repeat steps S1.1 to S1.5 at least 3 times, and take... The average value is used as the final pitch clearance compensation value;

[0018] S1.7 Continuing with this method, the mechanical structural clearance in the rolling direction is obtained through the reciprocating motion of the rolling mechanism. .

[0019] Furthermore, in S2, the pre-calculation of aerodynamic loads and corresponding model elastic angles based on the model's aerodynamic derivatives specifically includes:

[0020] S2.1 Pre-calculated aerodynamic loads: Based on the target Mach number, target angle of attack and target sideslip angle, and combined with the model aerodynamic derivatives, estimate the normal force, pitching moment, rolling moment, yaw moment and lateral force at the target attitude angle;

[0021] S2.2 Calculation of the elastic angle of the model:

[0022] Based on the pre-calculated aerodynamic load, the elastic angle of the mechanism shaft system is calculated using the following formula:

[0023] ;

[0024] ;

[0025] ;

[0026] in, The pitch elastic angle, It is an elastic angle. The yaw elastic angle, For normal force, For pitching moment, For rolling torque, It is a lateral force. For yaw moment, The elastic angle coefficient corresponding to the axial force. The elastic angle coefficient corresponding to the pitching moment. The elastic angle coefficient corresponding to the rolling moment. The elastic angle coefficient corresponding to the lateral force. This is the elastic angle coefficient corresponding to the yaw moment;

[0027] Based on the elastic angles of the mechanism's shaft system, the angle of attack elastic angle and sideslip elastic angle of the model's shaft system are calculated using the following formulas:

[0028] ;

[0029] ;

[0030] in, Angle of attack is the elastic angle. It is the sideslip angle or elastic angle.

[0031] Furthermore, in S2, after elastic angle compensation is performed on the target attitude angle, the basic angles under the mechanism axis are calculated, specifically including:

[0032] S2.3 Calculate the pre-compensated model target angle: Based on the target angle of attack, target sideslip angle, angle of attack elastic angle, and sideslip elastic angle, calculate the pre-compensated model target angle. The calculation formula is as follows:

[0033] ;

[0034] ;

[0035] in, The pre-compensated target angle of attack of the model. For the target angle of attack, The target sideslip angle of the model after pre-compensation. The target sideslip angle;

[0036] S2.4 Calculate the basic angles of the mechanism: Perform attitude angle calculation on the pre-compensated target angles of the model to obtain the basic pitch angle and basic roll angle under the mechanism axis system. The calculation formula is as follows:

[0037] ;

[0038] ;

[0039] in, The basic pitch angle under the mechanism's axis system. The basic roll angle under the mechanism's shaft system. , , , , , This is a constant determined based on the quadrant and sign of the target angle in the model.

[0040] Furthermore, in S4, based on the difference between the current actual attitude angle and the next target attitude angle, the predicted changes in load and elastic angle caused by the attitude angle change specifically include:

[0041] S4.1 Calculate the angle difference that needs to be changed in the model's attitude angle: Obtain the current actual attitude angle and the next target attitude angle, and calculate the angle difference that needs to be changed in the attitude angle. The calculation formula is as follows:

[0042] ;

[0043] ;

[0044] in, For the angle of attack difference that needs to be changed, For the next target angle of attack, This is the current actual angle of attack. For the difference in sideslip angle that needs to be changed, For the next target sideslip angle, This represents the current actual sideslip angle;

[0045] S4.2 Pre-calculated load change: Based on the angle difference that the attitude angle needs to change and the aerodynamic derivative of the model, estimate the load change;

[0046] S4.3 Pre-calculate the change in elastic angle. The formula for calculating the change in elastic angle is:

[0047] ;

[0048] ;

[0049] ;

[0050] in, This is the estimated change in the pitch elastic angle of the mechanism shaft system. This is the estimated change in the roll elastic angle of the mechanism shaft system. This is the estimated change in the yaw elastic angle of the mechanism shaft system. For the pre-calculated change in normal force, For the pre-calculated pitch moment change, This is the pre-calculated change in rolling torque. For the pre-calculated change in lateral force, This represents the pre-calculated change in yaw moment;

[0051] S4.4. Based on the change in elastic angle, calculate the corresponding changes in angle of attack and sideslip angle using the attitude angle conversion formula.

[0052] Furthermore, in S4, after compensating for the difference, it is calculated as the mechanism angle change, and combined with mechanical backlash compensation, the predicted mechanism command for the next target is generated, specifically including:

[0053] S4.5 Calculate the pre-compensated attitude angle change: Based on the angle difference that the attitude angle needs to be changed in S4.1 and the changes in angle of attack and sideslip angle in S4.4, calculate the pre-compensated attitude angle change. The calculation formula is as follows:

[0054] ;

[0055] ;

[0056] in, This refers to the angle of attack component in the pre-compensated attitude angle change. The sideslip angle component in the pre-compensated attitude angle change;

[0057] S4.6 Solving and Calculating the Predicted Mechanism Angle: The attitude angle change of the pre-compensated attitude angle is solved to obtain the mechanism angle change; the mechanism angle change is then superimposed onto the current angle of the mechanism to obtain the predicted mechanism angle, calculated using the following formula:

[0058] ;

[0059] ;

[0060] in, To predict the pitch angle component of the mechanism angle, This is the current pitch angle of the mechanism. To calculate the change in the pitch angle of the mechanism, To predict the roll angle component of the mechanism angle, This represents the current roll angle of the organization. This is the calculated change in the pitch angle of the mechanism;

[0061] S4.7 Generating the next target mechanism command: Determine whether the adjustment direction for the next target movement is consistent with the current adjustment direction. If not, superimpose the mechanical backlash according to the following formula to obtain the mechanism movement command for the next target:

[0062] ;

[0063] ;

[0064] in, The pitch angle component of the mechanism's motion command for the next target. The roll angle component is the mechanism motion command for the next target, and sign() is a function to take the sign of the direction.

[0065] If the directions are consistent, there is no need to add mechanical backlash. In this case, the mechanism motion command for the next target is directly equal to the predicted mechanism angle, that is:

[0066] , ;

[0067] This serves as the final instruction for the movement of the mechanism.

[0068] The beneficial effects of this invention are as follows: This invention systematically improves the efficiency and safety of wind tunnel testing through two technical means: "pre-calculating and compensating for the elastic angle before the first control" and "dynamically compensating for mechanical clearance during attitude adjustment." It significantly improves test efficiency, reducing the number of iterations required to achieve the same control accuracy from the traditional 3-5 times to 1-2 times; it greatly ensures test safety, fundamentally avoiding the risk of attitude angle overshoot caused by the superposition of elastic angles during high angle-of-attack tests through the pre-compensation mechanism; and it improves data accuracy and reliability by eliminating errors caused by the reciprocating motion of the mechanism through dynamic compensation for mechanical clearance, ensuring that the final attitude angle control accuracy of the model is consistently better than 1' (0.017°). Furthermore, this method can achieve accurate prediction and smooth transition in continuous variable attitude angle tests, providing strong support for obtaining high-quality continuous aerodynamic data. Attached Figure Description

[0069] Figure 1 This is an overall flowchart of the method described in this invention;

[0070] Figure 2 This is a schematic diagram of the mechanical clearance measurement method described in this invention. Detailed Implementation

[0071] The technical solution of the present invention will be further described below with reference to embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention. In the following embodiments, process equipment or devices not specifically specified are all conventional equipment or devices in the art. Unless specifically specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0072] Example 1, combined with Figure 1 This embodiment describes a method for precise control of the attitude angle of a force-measuring wind tunnel test model, comprising:

[0073] S1. Test preparation and clearance calibration: Install the test model, force balance and support system in the wind tunnel test section, and measure the mechanical clearance of the attitude angle control mechanism in the pitch and roll directions.

[0074] S2. Pre-calculation and compensation of the first target attitude angle: Based on the target Mach number, target angle of attack and target sideslip angle, combined with the model aerodynamic derivative, the aerodynamic load and the corresponding model elastic angle are pre-calculated. After elastic angle compensation of the target attitude angle, the base angle under the mechanism axis is calculated. It is determined whether the direction of the mechanism's current movement is consistent with the previous one. If they are consistent, no adjustment is needed. If they are inconsistent, the corresponding mechanical clearance is superimposed on the base angle to generate the first mechanism movement command.

[0075] S3. Closed-loop control and dynamic fine-tuning: Drive the test model to the first mechanism motion command. After the flow field stabilizes, measure the load using a force balance and calculate the actual attitude angle of the test model. Determine whether the deviation between the actual attitude angle and the target attitude angle meets the control accuracy. If it does, complete the control of the current target attitude angle. If it does not, calculate the fine-tuning command and add mechanical clearance when the fine-tuning direction is inconsistent with the previous motion direction. Perform iterative fine-tuning until the control accuracy is met.

[0076] S4. Prediction of the next target in continuous testing: After the current target attitude angle is controlled, if continuous testing is required, the load and elastic angle change caused by the attitude angle change are predicted based on the difference between the current actual attitude angle and the next target attitude angle. The difference is compensated and then calculated as the mechanism angle change. Combined with mechanical backlash compensation, the predicted mechanism command for the next target is generated. Then, the process jumps to step S3 for closed-loop control.

[0077] S5. Repeat steps S3 and S4 until all target attitude angles have been tested.

[0078] Specifically, this invention achieves rapid, accurate, and safe control of the attitude angle of a wind tunnel test model by pre-calculating and compensating for the elastic angle before the initial control and dynamically compensating for mechanical clearance during attitude adjustment. Its core objective is to fundamentally solve the problems of excessive iterations and high overshoot risk caused by neglecting the elastic angle in traditional methods, as well as the control errors introduced by mechanical clearance, thereby significantly improving test efficiency, ensuring test safety, and guaranteeing data accuracy.

[0079] S3 closed-loop control and dynamic fine-tuning specifically include:

[0080] Initial movement: After the flow field stabilizes, the attitude angle control unit drives the model's attitude angle mechanism to move to... and .

[0081] Actual Measurement and Calculation: The balance acquisition and calculation unit acquires the strain signal of the balance in real time and calculates the force and torque under the balance axis system. .

[0082] Calculate the actual elastic angle based on the measured force and torque. ;

[0083] ;

[0084] ;

[0085] ;

[0086] in, This is the actual pitch elastic angle. For the measured normal force, To measure the pitching moment, This is the actual roll elastic angle. To measure the rolling torque, This is the actual yaw elastic angle. To measure the lateral force, For actual measurement of yaw moment;

[0087] Calculate the actual pitch, roll, and yaw angles based on the actual elastic angles;

[0088]

[0089]

[0090]

[0091] in, This is the actual pitch angle. This is the actual roll angle. This is the actual yaw angle; The pitch direction is the mechanism's motion command angle. The mechanism motion command angle in the roll direction 。

[0092] Calculate the actual attitude angle of the model ( , ).

[0093]

[0094] Error judgment and fine-tuning:

[0095] Calculate attitude angle deviation: , .

[0096] Judgment | | and | | Whether all are less than or equal to the control error threshold (e.g., 0.017°, or 1′).

[0097] If the conditions are met, then control is complete, and data is recorded.

[0098] If the conditions are not met, fine-tuning will be performed. The attitude angle control unit will adjust accordingly. and Calculate the new mechanism adjustment ( , ).

[0099] ;

[0100] ;

[0101] Dynamic backlash compensation: Before issuing a fine-tuning command, determine whether the current fine-tuning direction is consistent with the previous movement direction. If they are inconsistent (e.g., adjusting from a positive angle of attack to a negative angle of attack), then mechanical backlash must be added to the adjustment amount, i.e., the new command is ( , If the directions are consistent, then no superposition is required.

[0102] in, This is the current pitch angle of the mechanism. For pitch attitude fine-tuning. Used to characterize the direction of motion for fine-tuning of pitch attitude. This represents the current roll angle of the organization. For fine-tuning of the roll direction attitude, Used to characterize the direction of motion for fine-tuning of roll direction attitude.

[0103] Iterative loop: Repeat the steps described above until the attitude angle deviation meets the error requirements.

[0104] In S1, the mechanical clearance of the attitude angle control mechanism in the pitch and roll directions is measured, specifically including:

[0105] S1.1 Drive the pitch mechanism to -1° via the attitude angle control unit;

[0106] S1.2 Drive the pitch mechanism to 0°, eliminate the backlash, and record the tilt sensor reading. ;

[0107] S1.3 Continue to drive the pitch mechanism from the current 0° position to +1°;

[0108] S1.4 Continue driving the pitch mechanism to 0° and record the final reading from the tilt sensor. ;

[0109] S1.5 Calculate the mechanical structure clearance in the pitch direction. ;

[0110] S1.6 Repeat steps S1.1 to S1.5 at least 3 times, and take... The average value is used as the final pitch clearance compensation value;

[0111] S1.7 Continuing with this method, the mechanical structural clearance in the rolling direction is obtained through the reciprocating motion of the rolling mechanism. .

[0112] Specifically, in combination Figure 2It can be seen that this step effectively eliminates the attitude angle deviation caused by the mechanical backlash by pre-calibrating the mechanical backlash of the attitude angle control mechanism and dynamically superimposing backlash compensation according to the direction of motion during attitude switching. As shown in the figure, when the model returns from -1° to 0°, the mechanical backlash is first eliminated through compensation motion, and then the model is accurately positioned to the target attitude. Combined with elastic angle pre-compensation and closed-loop fine-tuning, the accuracy and stability of attitude angle control in the force measurement wind tunnel test are significantly improved, ensuring the reliability of the test data.

[0113] In S2, the pre-calculation of aerodynamic loads and corresponding model elastic angles based on the model's aerodynamic derivatives specifically includes:

[0114] S2.1 Pre-calculated aerodynamic loads: Based on the target Mach number, target angle of attack and target sideslip angle, and combined with the model aerodynamic derivatives, estimate the normal force, pitching moment, rolling moment, yaw moment and lateral force at the target attitude angle;

[0115] S2.2 Calculation of the elastic angle of the model:

[0116] Based on the pre-calculated aerodynamic load, the elastic angle of the mechanism shaft system is calculated using the following formula:

[0117] ;

[0118] ;

[0119] ;

[0120] in, The pitch elastic angle, It is an elastic angle. The yaw elastic angle, For normal force, For pitching moment, For rolling torque, It is a lateral force. For yaw moment, The elastic angle coefficient corresponding to the axial force. The elastic angle coefficient corresponding to the pitching moment. The elastic angle coefficient corresponding to the rolling moment. The elastic angle coefficient corresponding to the lateral force. This is the elastic angle coefficient corresponding to the yaw moment;

[0121] Based on the elastic angles of the mechanism's shaft system, the angle of attack elastic angle and sideslip elastic angle of the model's shaft system are calculated using the following formulas:

[0122] ;

[0123] ;

[0124] in, Angle of attack is the elastic angle. It is the sideslip angle or elastic angle.

[0125] Specifically, this step is one of the core innovations of this invention, aiming to achieve high precision during the first control and avoid overshoot.

[0126] Obtain target parameters: According to the wind tunnel test plan, obtain the Mach number M and target angle of attack under the current test conditions. and target sideslip angle .

[0127] Estimate the aerodynamic loads at the target attitude angle:

[0128] Based on the aerodynamic characteristic database of the model at the target Mach number M, the key derivative is obtained: the slope of the lift line. Zero angle of attack The derivative of the pitch moment coefficient with respect to the lift coefficient Zero lift torque coefficient The derivative of the rolling moment coefficient with respect to the sideslip angle The derivative of the yaw moment coefficient with respect to the sideslip angle The derivative of the lateral force with respect to the sideslip angle wait.

[0129] Estimate the lift coefficient at the target angle of attack: .

[0130] Estimate the pitching moment coefficient at the target angle of attack: .

[0131] Estimate the rolling moment coefficient at the target sideslip angle: .

[0132] Estimate the yaw moment coefficient at the target sideslip angle: .

[0133] Estimate the lateral force coefficient at the target sideslip angle: .

[0134] Estimate the normal force at the target attitude angle Pitch moment Rolling torque , yaw moment and lateral force :

[0135] ;

[0136] ;

[0137] ;

[0138] ;

[0139] ;

[0140] in, For dynamic pressure, S For reference area, For the average aerodynamic chord length, For reference exhibition length.

[0141] In S2, after elastic angle compensation is performed on the target attitude angle, the basic angles under the mechanism axis are calculated, specifically including:

[0142] S2.3 Calculate the pre-compensated model target angle: Based on the target angle of attack, target sideslip angle, angle of attack elastic angle, and sideslip elastic angle, calculate the pre-compensated model target angle. The calculation formula is as follows:

[0143] ;

[0144] ;

[0145] in, The pre-compensated target angle of attack of the model. For the target angle of attack, The target sideslip angle of the model after pre-compensation. The target sideslip angle;

[0146] S2.4 Calculate the basic angles of the mechanism: Perform attitude angle calculation on the pre-compensated target angles of the model to obtain the basic pitch angle and basic roll angle under the mechanism axis system. The calculation formula is as follows:

[0147] ;

[0148] ;

[0149] in, The basic pitch angle under the mechanism's axis system. The basic roll angle under the mechanism's shaft system. , , , , , This is a constant determined based on the quadrant and sign of the target angle in the model.

[0150] Specifically, the constant value ; The roll angle is selected by quadrant, with a value of 1 in the first and second quadrants and -1 in the third and fourth quadrants; when hour, , hour, ;

[0151] At that time, set value ; At that time, set value ;when , , ;when , , ;when , , .

[0152] In S4, based on the difference between the current actual attitude angle and the next target attitude angle, the predicted changes in load and elastic angle caused by the attitude angle change specifically include:

[0153] S4.1 Calculate the angle difference that needs to be changed in the model's attitude angle: Obtain the current actual attitude angle and the next target attitude angle, and calculate the angle difference that needs to be changed in the attitude angle. The calculation formula is as follows:

[0154] ;

[0155] ;

[0156] in, For the angle of attack difference that needs to be changed, For the next target angle of attack, This is the current actual angle of attack. For the difference in sideslip angle that needs to be changed, For the next target sideslip angle, This represents the current actual sideslip angle;

[0157] S4.2 Pre-calculated load change: Based on the angle difference that the attitude angle needs to change and the aerodynamic derivative of the model, estimate the load change;

[0158] S4.3 Pre-calculate the change in elastic angle. The formula for calculating the change in elastic angle is:

[0159] ;

[0160] ;

[0161] ;

[0162] in, This is the estimated change in the pitch elastic angle of the mechanism shaft system. This is the estimated change in the roll elastic angle of the mechanism shaft system. This is the estimated change in the yaw elastic angle of the mechanism shaft system. For the pre-calculated change in normal force, For the pre-calculated pitch moment change, This is the pre-calculated change in rolling torque. For the pre-calculated change in lateral force, This represents the pre-calculated change in yaw moment;

[0163] S4.4. Based on the change in elastic angle, calculate the corresponding changes in angle of attack and sideslip angle using the attitude angle conversion formula.

[0164] Furthermore, in S4, after compensating for the difference, it is calculated as the mechanism angle change, and combined with mechanical backlash compensation, the predicted mechanism command for the next target is generated, specifically including:

[0165] S4.5 Calculate the pre-compensated attitude angle change: Based on the angle difference that the attitude angle needs to be changed in S4.1 and the changes in angle of attack and sideslip angle in S4.4, calculate the pre-compensated attitude angle change. The calculation formula is as follows:

[0166] ;

[0167] ;

[0168] in, This refers to the angle of attack component in the pre-compensated attitude angle change. The sideslip angle component in the pre-compensated attitude angle change;

[0169] S4.6 Solving and Calculating the Predicted Mechanism Angle: The attitude angle change of the pre-compensated attitude angle is solved to obtain the mechanism angle change; the mechanism angle change is then superimposed onto the current angle of the mechanism to obtain the predicted mechanism angle, calculated using the following formula:

[0170] ;

[0171] ;

[0172] in, To predict the pitch angle component of the mechanism angle, This is the current pitch angle of the mechanism. To calculate the change in the pitch angle of the mechanism, To predict the roll angle component of the mechanism angle, This represents the current roll angle of the organization. This is the calculated change in the pitch angle of the mechanism;

[0173] S4.7 Generating the next target mechanism command: Determine whether the adjustment direction for the next target movement is consistent with the current adjustment direction. If not, superimpose the mechanical backlash according to the following formula to obtain the mechanism movement command for the next target:

[0174] ;

[0175] ;

[0176] in, The pitch angle component of the mechanism's motion command for the next target. The roll angle component is the mechanism motion command for the next target, and sign() is a function to take the sign of the direction.

[0177] If the directions are consistent, there is no need to add mechanical backlash. In this case, the mechanism motion command for the next target is directly equal to the predicted mechanism angle, that is:

[0178] , ;

[0179] This serves as the final instruction for the movement of the mechanism.

[0180] Specifically, the formulas for calculating the change in the mechanism's pitch angle are as follows:

[0181] ;

[0182] ;

[0183] The coefficients in the formula are determined based on the quadrant in which the angle is located, thereby completing the conversion calculation from the model axis to the mechanism axis.

Claims

1. A method for precise control of the attitude angle of a force-measuring wind tunnel test model, characterized in that, include: S1. Test preparation and clearance calibration: Install the test model, force balance and support system in the wind tunnel test section, and measure the mechanical clearance of the attitude angle control mechanism in the pitch and roll directions. S2. Pre-calculation and compensation of the first target attitude angle: Based on the target Mach number, target angle of attack and target sideslip angle, combined with the model aerodynamic derivative, the aerodynamic load and the corresponding model elastic angle are pre-calculated. After elastic angle compensation of the target attitude angle, the base angle under the mechanism axis is calculated. It is determined whether the direction of the mechanism's current movement is consistent with the previous one. If they are consistent, no adjustment is needed. If they are inconsistent, the corresponding mechanical clearance is superimposed on the base angle to generate the first mechanism movement command. S3. Closed-loop control and dynamic fine-tuning: Drive the test model to the first mechanism motion command. After the flow field stabilizes, measure the load using a force balance and calculate the actual attitude angle of the test model. Determine whether the deviation between the actual attitude angle and the target attitude angle meets the control accuracy. If it does, complete the control of the current target attitude angle. If it does not, calculate the fine-tuning command and add mechanical clearance when the fine-tuning direction is inconsistent with the previous motion direction. Perform iterative fine-tuning until the control accuracy is met. S4. Prediction of the next target in continuous testing: After the current target attitude angle is controlled, if continuous testing is required, the load and elastic angle change caused by the attitude angle change are predicted based on the difference between the current actual attitude angle and the next target attitude angle. The difference is compensated and then calculated as the mechanism angle change. Combined with mechanical backlash compensation, the predicted mechanism command for the next target is generated. Then, the process jumps to step S3 for closed-loop control. S5. Repeat steps S3 and S4 until all target attitude angles have been tested.

2. The method for precise control of the attitude angle of a force-measuring wind tunnel test model according to claim 1, characterized in that, In S1, the mechanical clearance of the attitude angle control mechanism in the pitch and roll directions is measured, specifically including: S1.1 Drive the pitch mechanism to -1° via the attitude angle control unit; S1.2 Drive the pitch mechanism to 0°, eliminate the backlash, and record the tilt sensor reading. ; S1.3 Continue to drive the pitch mechanism from the current 0° position to +1°; S1.4 Continue driving the pitch mechanism to 0° and record the final reading from the tilt sensor. ; S1.5 Calculate the mechanical structure clearance in the pitch direction. ; S1.6 Repeat steps S1.1 to S1.5 at least 3 times, and take... The average value is used as the final pitch clearance compensation value; S1.7 Continuing with this method, the mechanical structural clearance in the rolling direction is obtained through the reciprocating motion of the rolling mechanism. .

3. The method for precise control of the attitude angle of a force-measuring wind tunnel test model according to claim 2, characterized in that, In S2, the pre-calculation of aerodynamic loads and corresponding model elastic angles based on the model's aerodynamic derivatives specifically includes: S2.1 Pre-calculated aerodynamic loads: Based on the target Mach number, target angle of attack and target sideslip angle, and combined with the model aerodynamic derivatives, estimate the normal force, pitching moment, rolling moment, yaw moment and lateral force at the target attitude angle; S2.2 Calculation of the elastic angle of the model: Based on the pre-calculated aerodynamic load, the elastic angle of the mechanism shaft system is calculated using the following formula: in, The pitch elastic angle, For the roll elastic angle, The yaw elastic angle, For normal force, For pitching moment, For rolling torque, It is a lateral force. For yaw moment, The elastic angle coefficient corresponding to the axial force. The elastic angle coefficient corresponding to the pitching moment. The elastic angle coefficient corresponding to the rolling moment. The elastic angle coefficient corresponding to the lateral force. This is the elastic angle coefficient corresponding to the yaw moment; Based on the elastic angles of the mechanism's shaft system, the angle of attack elastic angle and sideslip elastic angle of the model's shaft system are calculated using the following formulas: in, Angle of attack is the elastic angle. It is the sideslip angle or elastic angle.

4. The method for precise control of the attitude angle of a force-measuring wind tunnel test model according to claim 3, characterized in that, In S2, after elastic angle compensation is performed on the target attitude angle, the basic angles under the mechanism axis are calculated, specifically including: S2.3 Calculate the pre-compensated model target angle: Based on the target angle of attack, target sideslip angle, angle of attack elastic angle, and sideslip elastic angle, calculate the pre-compensated model target angle. The calculation formula is as follows: in, The pre-compensated target angle of attack of the model. For the target angle of attack, The target sideslip angle of the model after pre-compensation. The target sideslip angle; S2.4 Calculate the basic angles of the mechanism: Perform attitude angle calculation on the pre-compensated target angles of the model to obtain the basic pitch angle and basic roll angle under the mechanism axis system. The calculation formula is as follows: in, The basic pitch angle under the mechanism's axis system. The basic roll angle under the mechanism's shaft system. , , , , , This is a constant determined based on the quadrant and sign of the target angle in the model.

5. The method for precise control of the attitude angle of a force-measuring wind tunnel test model according to claim 4, characterized in that, In S4, based on the difference between the current actual attitude angle and the next target attitude angle, the predicted changes in load and elastic angle caused by the attitude angle change specifically include: S4.1 Calculate the angle difference that needs to be changed in the model's attitude angle: Obtain the current actual attitude angle and the next target attitude angle, and calculate the angle difference that needs to be changed in the attitude angle. The calculation formula is as follows: in, For the angle of attack difference that needs to be changed, For the next target angle of attack, This is the current actual angle of attack. For the difference in sideslip angle that needs to be changed, For the next target sideslip angle, This represents the current actual sideslip angle; S4.2 Pre-calculated load change: Based on the angle difference that the attitude angle needs to change and the aerodynamic derivative of the model, estimate the load change; S4.3 Pre-calculate the change in elastic angle. The formula for calculating the change in elastic angle is: in, This is the estimated change in the pitch elastic angle of the mechanism shaft system. This is the estimated change in the roll elastic angle of the mechanism shaft system. This is the estimated change in the yaw elastic angle of the mechanism shaft system. For the pre-calculated change in normal force, For the pre-calculated pitch moment change, This is the pre-calculated change in rolling torque. For the pre-calculated change in lateral force, This represents the pre-calculated change in yaw moment; S4.

4. Based on the change in elastic angle, calculate the corresponding changes in angle of attack and sideslip angle using the attitude angle conversion formula.

6. The method for precise control of the attitude angle of a force-measuring wind tunnel test model according to claim 5, characterized in that, In S4, the difference is compensated and then calculated as the mechanism angle change. Combined with mechanical backlash compensation, the predicted mechanism command for the next target is generated, specifically including: S4.5 Calculate the pre-compensated attitude angle change: Based on the angle difference that the attitude angle needs to be changed in S4.1 and the changes in angle of attack and sideslip angle in S4.4, calculate the pre-compensated attitude angle change. The calculation formula is as follows: in, This refers to the angle of attack component in the pre-compensated attitude angle change. This refers to the sideslip angle component in the pre-compensated attitude angle change. S4.6 Solving and Calculating the Predicted Mechanism Angle: The attitude angle change of the pre-compensated attitude angle is solved to obtain the mechanism angle change; the mechanism angle change is then superimposed onto the current angle of the mechanism to obtain the predicted mechanism angle, calculated using the following formula: in, To predict the pitch angle component of the mechanism angle, This is the current pitch angle of the mechanism. To calculate the change in the pitch angle of the mechanism, To predict the roll angle component of the mechanism angle, This represents the current roll angle of the organization. This is the calculated change in the pitch angle of the mechanism; S4.7 Generating the next target mechanism command: Determine whether the adjustment direction for the next target movement is consistent with the current adjustment direction. If not, superimpose the mechanical backlash according to the following formula to obtain the mechanism movement command for the next target: in, The pitch angle component of the mechanism's motion command for the next target. The roll angle component is the mechanism motion command for the next target, and sign() is a function to take the sign of the direction. If the directions are consistent, there is no need to add mechanical backlash. In this case, the mechanism motion command for the next target is directly equal to the predicted mechanism angle, that is: ， This serves as the final instruction for the movement of the mechanism.

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