Device and method for low-speed wind tunnel gust or flutter half-model test

Abstract

The present invention relates to the field of wind tunnel tests, and provides a device and method for a low-speed wind tunnel gust or flutter half-model test, for use in solving the problems that existing gust or flutter half-model test devices cannot achieve complete release of heave and pitch degrees of freedom, and that it is difficult for the devices to be shared by two tests. The device comprises an overall frame; the overall frame is mounted in a wind tunnel test section; two slide rails are vertically provided on a front end surface of the overall frame; two slider assemblies are arranged left and right on a rear end surface of a carriage; the two slider assemblies are in sliding fit with the two slide rails in one-to-one correspondence; two spring seats are provided on the top end of the overall frame; each spring seat is provided with a horizontal shaft; inner ring ends of two clockwork springs are connected to the horizontal shafts of the two spring seats in one-to-one correspondence; outer ring ends of the two clockwork springs extend downward and are separately connected to the carriage; a model mounting seat is cylindrical; and the model mounting seat is in rotatable fit with the carriage. The present invention can be used for both a gust load alleviation test and a body freedom flutter test, thereby enabling the two tests to share the same device.

Description

An apparatus and method for low-speed wind tunnel gust or flutter half-mode testing. Technical Field

[0001] This invention belongs to the field of wind tunnel testing, and particularly relates to an apparatus and method for low-speed wind tunnel gust or flutter half-mode testing. Background Technology

[0002] During flight, an aircraft's structure undergoes elastic deformation under the influence of aerodynamic forces. This elastic deformation alters the distribution and magnitude of aerodynamic loads, leading to further elastic deformations in the structure. The coupling between these aerodynamic changes and elastic deformation is called aeroelasticity, a phenomenon involving the coupling of aerodynamic forces, elastic forces, and inertial forces. Aeroelastic problems can alter the aircraft's equilibrium state and even cause structural fatigue, leading to aircraft failure. Currently, the most concerning aeroelastic problems fall into two main categories: aeroelastic dynamic response problems, such as maneuver load mitigation; and aeroelastic dynamic stability problems, such as flutter.

[0003] In modern aircraft design, lightweight and flexible materials are typically used to achieve high speed and high maneuverability, which exacerbates aeroelasticity issues. This is especially true for flying wing aircraft, which have lower wing loading and greater structural flexibility. Strong gusts can cause drastic changes in attitude and center-of-gravity acceleration, inducing elastic motion in the flexible wing. This leads to increased wing root bending moment and excessive wingtip vibration, affecting mission completion and jeopardizing flight safety. Furthermore, the elastic modal frequencies of the flexible wing structure are close to the rigid body modal frequencies of the aircraft, resulting in a unique body flutter phenomenon. In addition, both the aircraft's gust response and body flutter phenomena involve the coupling problem between the model's elastic and rigid modes.

[0004] Currently, research on gust load mitigation and flutter of aircraft is mostly conducted using wind tunnel testing. Existing half-mode wind tunnel testing systems used for gusts or flutter cannot fully release the heave and pitch degrees of freedom, cannot decouple the rigid body modes and elastic body modes of the elastic model, make it difficult to use both gust and flutter tests, cannot keep the weight of the trolley used to achieve heave motion constant and thus cannot allow the model to move freely, the model cannot achieve a wide range of pitch angle adjustment, and the system damping is large, affecting the accuracy of test results. It also lacks reliable safety protection measures, making it difficult to provide multi-dimensional protection. The device lacks deflectors or the deflectors are small and cannot be extended, and the device can only be used by installing it on the side wall of the wind tunnel. Technical issues

[0005] The purpose of this invention is to provide an apparatus and method for low-speed wind tunnel gust or flutter half-mode testing, in order to solve the problems that existing wind tunnel testing systems for gust or flutter half-mode testing cannot achieve full release of heave and pitch degrees of freedom, and are difficult to use for both gust and flutter tests. Technical solutions

[0006] The technical solution adopted in this invention is as follows:

[0007] An apparatus for low-speed wind tunnel gust or flutter half-mode testing includes an integral frame, a spring-loaded spring, a pulley, and a model mounting base;

[0008] The rear end of the overall frame is connected to the side wall of the wind tunnel test section, and the lower end of the overall frame is connected to the bottom wall of the wind tunnel test section. Two slide rails are vertically arranged on the front end face of the overall frame. Two sets of slider groups are arranged on the left and right sides on the rear end face of the trolley. The two sets of slider groups slide in a one-to-one correspondence with the two sets of slide rails. Two spring seats are provided at the top of the overall frame. The spring seats have horizontal shafts. The inner coil ends of the two spring springs are connected to the horizontal shafts of the two spring seats in a one-to-one correspondence. The outer coil ends of the two spring springs hang down and are connected to the trolley. The model mounting base is cylindrical and rotates in coordination with the trolley.

[0009] The test model is a flexible wing half-model. The wing root of the test model is connected to the front end of the model mounting base. The trailing edge of the test model is equipped with ailerons and flaps. The drive devices of the ailerons and flaps are electrically connected to the model control system. The resultant force of the two spring springs depends on the weight and settings of the test model, model mounting base, two slider groups and trolley.

[0010] The pitch protection system includes a dual-axis cylinder and a limiting block. The rear end of the model mounting base is provided with a limiting plane, which is parallel to the axis of the model mounting base. The limiting block is a wedge-shaped block. The dual-axis cylinder is horizontally set, with the output end of the dual-axis cylinder facing the limiting plane. One wedge surface of the limiting block abuts against the output end of the dual-axis cylinder, and the other wedge surface of the limiting block limits the rotation of the limiting plane.

[0011] Furthermore, protective dampers are provided at both the upper and lower ends of the slide rail, with the buffer heads of the protective dampers facing the corresponding slider group.

[0012] Furthermore, adjusting nuts are provided at the four corners of the bottom of the overall frame, and four vertically arranged adjusting screws are threadedly engaged with the four adjusting nuts. The bottom of the adjusting screws is provided with movable rollers.

[0013] Furthermore, there are several limiting blocks, and the wedge angles of these limiting blocks vary from 0° to 45°, with intervals of 5°.

[0014] Furthermore, the rear end of the overall frame is provided with several side wall mounting seats, the lower end of the overall frame is provided with several mounting holes, the overall frame is connected to the side wall of the wind tunnel test section through several side wall mounting seats, and the overall frame is connected to the bottom wall of the wind tunnel test section through several mounting holes.

[0015] Furthermore, the front end face of the overall frame is provided with several guide plate mounting seats, the guide plates are fixed on the several guide plate mounting seats, and the guide plates are provided with elongated holes vertically, through which the front end of the model mounting seat passes.

[0016] Furthermore, two linear guide rail clamps are installed on the left and right sides of the trolley, and the two linear guide rail clamps slide or lock in a one-to-one correspondence with the two slide rails.

[0017] The present invention also provides a method for low-speed wind tunnel gust testing, which is based on the above-mentioned apparatus for low-speed wind tunnel gust or flutter half-mode testing, and includes the following steps:

[0018] Step 1: For gust tests, install the gust generator at the wind tunnel entrance and connect the gust generator's drive unit to the model control system.

[0019] Step 2: Connect the overall frame to the side walls and bottom wall of the wind tunnel test section;

[0020] Step 3: Connect the test model to the model mounting base;

[0021] Step 4: For the gust test, install an tilt sensor and an angular rate gyroscope at the center of gravity of the test model. Measure the pitch angle of the test model using the tilt sensor and the pitch rate gyroscope using the angular rate gyroscope.

[0022] Step 5: Select the appropriate limit block according to the needs of the experiment, and adjust the extension amount of the biaxial cylinder piston rod according to the pitch angle range of the test model;

[0023] Step 6: Install an accelerometer at the wingtip of the test model, attach a strain gauge to the wing root for measuring the wing root bending moment, arrange fiber optic cables for measuring wing deformation on the wing spars of the test model, fix a rope-type displacement sensor on the test model, connect the rope of the displacement sensor vertically to the top or bottom wall of the wind tunnel test section, connect the accelerometer, strain gauge, displacement sensor and fiber optic cable to the data acquisition and processing system respectively, and ensure that the acquired signals are normal.

[0024] Step 7: Conduct frequency sweep tests on the ailerons and flaps of the test model under both incoming and outgoing flow conditions to obtain the frequency response characteristics of the model.

[0025] Step 8: Before conducting the gust test, make the wind tunnel wind speed reach the preset value, then turn on the gust generator and make the blades of the gust generator move according to the specified swing angle, swing frequency and waveform; before conducting the flutter half-mode test, first start the wind tunnel wind speed to make the wind tunnel wind speed reach the preset value, and then gradually increase the incoming wind speed until the incoming wind speed reaches the model flutter speed.

[0026] Step 9: When the gust of wind reaches the test model, the vibration response signal of the test model is measured by the accelerometer, and the pitch rate of the test model is measured by the angular rate gyroscope. The vibration response signal and pitch rate are processed by the data acquisition and processing system to calculate the amount of gust disturbance, and then the amount of disturbance is transmitted to the model control system. The model control system drives the flaps to move, generating a force opposite to the aerodynamic force brought by the gust, thereby achieving pitch attitude control, i.e., inner loop control, which realizes the reduction of elastic body load.

[0027] Step 10: While performing inner loop control in step 9, the displacement change of the test model during heave motion is first measured by the displacement sensor, and the signal data is sent to the data acquisition and processing system for calculation. Then, the calculated displacement change is transmitted to the model control system, which drives the flap movement to keep the test model at the set height. This is the outer loop control, which realizes the reduction of rigid body load.

[0028] Step 11: For the gust test, comprehensively compare the wingtip acceleration, wing root strain, and heave range of the test model before and after flap and aileron control in Steps 7 and 8. Compared with the control without application, if the wingtip acceleration and wing root strain values ​​after control are less than 20% of those without control, and the heave of the test model is stable within the predetermined range, it indicates that the load reduction effect of this test is satisfactory, and this test is completed. The next test will then proceed. Otherwise, continue to adjust the flap and aileron parameters until the load reduction effect is satisfactory.

[0029] Step 12: Set ±0.3m of the initial height of the test model as the threshold for heave motion. During the test, if the amplitude of heave motion of the test model exceeds the threshold, activate the linear guide clamp for locking and protection.

[0030] Furthermore, in step seven, based on the deflection of the flap control surfaces, direct lift is generated to counteract the aerodynamic force and torque increments generated by the gusts. The established gust load mitigation equation is as follows:

[0031] (1)

[0032] In the formula, It is the derivative of lift with respect to angle of attack. It is the derivative of lift with respect to pitch rate. It is the increase in flap lift. It's the flap angle. It is the incoming wind speed. It is the vertical gust speed at the reference point (the aerodynamic center of the wing). It is the rate of change of reference point wind speed. It is the derivative of the pitch moment with respect to the angle of attack. It is the derivative of the pitch moment with respect to the pitch rate. It is the increase in flap pitch moment;

[0033] Since the flaps are positioned near the reference point, the pitching moment generated by their deflection is negligible, i.e.:

[0034] (2)

[0035] The conventional layout models used in this invention include:

[0036] (3)

[0037] Combining equations (2) and (3), we can obtain the relationship between the rudder surface deflection angle and the gust disturbance:

[0038] (4)

[0039] In equation (4), The gain from the open-loop gust mitigation controller to the gust amplitude and flap deflection is expressed as follows:

[0040] (5).

[0041] The present invention also provides a method for flutter half-mode testing, which is based on the above-mentioned device for low-speed wind tunnel gust or flutter half-mode testing, and includes the following steps:

[0042] Step 1: Connect the overall frame to the side walls and bottom walls of the wind tunnel test section;

[0043] Step 2: Connect the test model to the model mounting base;

[0044] Step 3: Select the appropriate limit block according to the needs of the experiment, and adjust the extension amount of the biaxial cylinder piston rod according to the pitch angle range of the test model;

[0045] Step 4: Install an accelerometer at the wingtip of the test model, attach a strain gauge to the wing root for measuring the wing root bending moment, arrange fiber optic cables for measuring wing deformation on the wing spars of the test model, fix a rope-type displacement sensor on the test model, connect the rope of the displacement sensor vertically to the top or bottom wall of the wind tunnel test section, connect the accelerometer, strain gauge, displacement sensor and fiber optic cable to the data acquisition and processing system respectively, and ensure that the acquired signals are normal.

[0046] Step 5: Conduct frequency sweep tests on the ailerons and flaps of the test model under both incoming and outgoing flow conditions to obtain the frequency response characteristics of the model.

[0047] Step 6: Before conducting the gust test, make the wind tunnel wind speed reach the preset value, and then turn on the gust generator so that the blades of the gust generator move according to the specified swing angle, swing frequency and waveform; before conducting the flutter half-mode test, first start the wind tunnel wind speed to make the wind tunnel wind speed reach the preset value, and then gradually increase the incoming wind speed until the incoming wind speed reaches the model flutter speed.

[0048] Step 7: Obtain the flutter velocity boundary of the test model based on the wingtip acceleration or wing root strain value;

[0049] Step 8: Set ±0.3m of the initial height of the test model as the threshold for heave motion. During the test, if the amplitude of heave motion of the test model exceeds the threshold, activate the linear guide clamp for locking and protection. Beneficial effects

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] This invention employs a flexible wing half-model for testing, reducing the number of sensors required, saving on model manufacturing costs, decreasing assembly and disassembly time, and improving testing efficiency. It allows for complete release of heave and pitch degrees of freedom, decoupling the rigid and elastic modes of the flexible wing half-model, and achieving gust mitigation control of the rigid, elastic, and hybrid rigid-elastic modes of the test model. This invention can be used for both gust load mitigation and flutter testing, employing multiple protective measures to provide timely and efficient protection for the test model in both heave and pitch directions, ensuring its safety. It allows for a wide range of pitch angle movement of the test model, which can be adjusted by selecting different limit blocks. The trolley uses a double-rail lifting and sliding mechanism to reduce damping of the test model. The constant-force spring continuously counteracts the additional mass imposed on the test model by the device, ensuring uniform force and free movement during testing, more realistically simulating aircraft flight conditions, and improving the accuracy of test data acquisition. The guide vane has a small slit size, which has little impact on the flow field of the model. The guide vane is extendable and suitable for test models of different sizes. In gust tests, the device of this invention can be installed on the side wall of the wind tunnel test section to conduct gust tests using a horizontally designed gust generator, or it can be installed on the bottom wall of the wind tunnel test section to conduct gust tests using a vertically designed gust generator. Attached Figure Description

[0052] Figure 1 is an isometric view of the device of the present invention without the guide plate;

[0053] Figure 2 is an isometric view of the device of the present invention;

[0054] Figure 3 is an enlarged view of point A in Figure 1;

[0055] Figure 4 is an enlarged view of point B in Figure 1;

[0056] Figure 5 is a schematic diagram of the connection between the trolley and the slide rail;

[0057] Figure 6 is a schematic diagram of the rear view of the trolley and the slide rail.

[0058] Figure 7 is a schematic diagram of the frequency response curve of the experimental model;

[0059] Figure 8 is a schematic diagram of the internal loop of the model control system;

[0060] Figure 9 is a schematic diagram of the outer loop of the model control system;

[0061] Figure 10 is a schematic diagram of the flutter velocity boundary of the experimental model;

[0062] Figure 11 shows the effect of the flange root bending moment reduction test.

[0063] Figure 12 is a schematic diagram of the test model installed on the device of the present invention.

[0064] In the diagram, 1. Overall frame, 2. Slide rail, 3. Trolley, 4. Model mounting base, 5. Side wall mounting base, 6. Spring, 7. Deflector, 8. Long hole, 9. Protective damper, 10. Spring seat, 11. Adjusting screw, 12. Adjusting nut, 13. Moving roller, 14. Slider assembly, 15. Linear guide clamp, 16. Dual-axis cylinder, 17. Limit block, 18. Test model, 19. Aileron, 20. Flap. Embodiments of the present invention

[0065] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0066] The connections mentioned in this invention are divided into fixed connections and detachable connections. Fixed connections, also known as non-detachable connections, include but are not limited to conventional fixed connection methods such as folded connections, riveted connections, adhesive connections, and welded connections. Detachable connections include but are not limited to conventional disassembly methods such as bolted connections, snap-fit ​​connections, pin connections, and hinged connections. When a specific connection method is not explicitly defined, it is assumed that at least one existing connection method can be found to achieve this function, and those skilled in the art can choose according to their needs. For example, a welded connection can be chosen for fixed connections, and a bolted connection can be chosen for detachable connections.

[0067] The present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0068] Example 1: As shown in Figures 1 to 6 and Figure 12, a device for low-speed wind tunnel gust or flutter half-mode testing includes an overall frame 1, a spring 6, a pulley 3, and a model mounting base 4.

[0069] The rear end of the overall frame 1 is connected to the side wall of the wind tunnel test section, and the lower end of the overall frame 1 is connected to the bottom wall of the wind tunnel test section. Two slide rails 2 are vertically arranged on the front end face of the overall frame 1. Two sets of slider groups 14 are arranged on the left and right sides on the rear end face of the trolley 3. The two sets of slider groups 14 are slidably engaged with the two sets of slide rails 2 in a one-to-one correspondence. Two spring seats 10 are provided at the top of the overall frame 1. The spring seats 10 are provided with horizontal shafts. The inner ends of the two spring springs 6 are connected to the horizontal shafts of the two spring seats 10 in a one-to-one correspondence. The outer ends of the two spring springs 6 hang down and are connected to the trolley 3 respectively. The model mounting base 4 is cylindrical and rotates with the trolley 3.

[0070] The test model 18 is a flexible wing half-model. The wing root of the test model 18 is connected to the front end of the model mounting base 4. The trailing edge of the test model 18 is provided with an aileron 19 and a flap 20. The drive devices of the aileron 19 and the flap 20 are electrically connected to the model control system respectively. The resultant force of the elasticity of the two spring springs 6 is based on the weight and setting of the test model 18, the model mounting base 4, the two slider groups 14 and the trolley 3.

[0071] The pitch protection system includes a dual-axis cylinder 16 and a limiting block 17. The rear end of the model mounting base 4 is provided with a limiting plane, which is parallel to the axis of the model mounting base 4. The limiting block 17 is a wedge-shaped block. The dual-axis cylinder 16 is horizontally arranged, and the output end of the dual-axis cylinder 16 faces the limiting plane. One wedge surface of the limiting block 17 abuts against the output end of the dual-axis cylinder 16, and the other wedge surface of the limiting block 17 limits the rotation of the limiting plane.

[0072] The upper and lower ends of the slide rail 2 are equipped with protective dampers 9, and the buffer head of the protective damper 9 faces the corresponding slider group 14.

[0073] The bottom four corners of the overall frame 1 are provided with adjusting nuts 12, and the four vertically arranged adjusting screws 11 are threadedly engaged with the four adjusting nuts 12. The bottom of the adjusting screws 11 is provided with moving rollers 13.

[0074] There are several limit blocks 17, and the wedge angles of the limit blocks 17 vary from 0° to 45°, with intervals of 5°.

[0075] The rear end of the overall frame 1 is provided with several side wall mounting seats 5, and the lower end of the overall frame 1 is provided with several mounting holes. The overall frame 1 is connected to the side wall of the wind tunnel test section through several side wall mounting seats 5, and the overall frame 1 is connected to the bottom wall of the wind tunnel test section through several mounting holes.

[0076] The front end face of the overall frame 1 is provided with several guide plate 7 mounting seats. The guide plate 7 is fixed on the several guide plate 7 mounting seats. The guide plate 7 is provided with a long hole 8 vertically. The front end of the model mounting seat 4 passes through the long hole 8.

[0077] Two linear guide clamps 15 are provided on the left and right sides of the trolley 3. The two linear guide clamps 15 correspond to the two slide rails 2 one by one and slide or lock.

[0078] The test model 18 is connected to the trolley 3 via the model mounting base 4. Under the aerodynamic disturbance generated by the gust generator, the test model 18 moves up and down along the slide rail 2. The trolley 3 is equipped with a dual-axis cylinder 16 and a linear guide clamp 15, which can limit the range of the test model 18's floating and pitching movements, thus protecting the test model 18. During the test, the floating and pitching movements of the test model 18 can be limited by the linear guide clamp 15 as needed. The pitch angle of the test model 18 can be adjusted by installing limit blocks 17 with different wedge angles. When the pitch angle movement of the test model 18 is large, the dual-axis cylinder 16 can be activated to drive the limit blocks 17 to fix the model mounting base 5.

[0079] This invention employs a flexible wing half-model for testing, which reduces the number of sensors required, saves on the manufacturing cost of the test model 18, reduces the assembly and disassembly time of the test model 18, and improves testing efficiency. It allows for complete release of heave and pitch degrees of freedom, decoupling the rigid body and elastic body modes of the flexible wing half-model, and achieving gust mitigation control of the test model 18's rigid body, elastic body, and rigid-elastic hybrid modes. This invention can be used for both gust load mitigation tests and flutter tests, employing multiple protective measures to provide timely and efficient protection for the test model 18 in both heave and pitch directions, ensuring its safety. It allows for a wide range of pitch angle movement of the test model 18, which can be adjusted by selecting different limit blocks. The trolley 3 reduces the damping of the test model 18 through the lifting and sliding mechanism of the double slide rails 2. The spring 6 is a constant-force spring, which can continuously offset the additional mass brought to the test model 18 by the device, ensuring that the test model 18 is subjected to uniform force and moves freely during the test, more realistically simulating the aircraft's flight state and improving the accuracy of test data acquisition. The slit size of the guide plate 7 is small, having little impact on the model's flow field. The guide plate 7 is extendable and suitable for models of different sizes. In gust tests, the device of this invention can be installed on the side wall of the wind tunnel test section to conduct gust tests using a horizontally designed gust generator, or it can be installed on the bottom wall of the wind tunnel test section to conduct gust tests using a vertically designed gust generator.

[0080] Example 2: As shown in Figures 1-9, 11, and 12, a method for low-speed wind tunnel gust testing is implemented based on the device described in Example 1 for low-speed wind tunnel gust or flutter half-mode testing, and includes the following steps:

[0081] Step 1: For gust tests, install the gust generator at the wind tunnel entrance and connect the gust generator's drive unit to the model control system.

[0082] Step 2: Connect the overall frame 1 to the side walls and bottom wall of the wind tunnel test section;

[0083] Step 3: Connect the test model 18 to the model mounting base 4;

[0084] Step 4: For the gust test, install an tilt sensor and an angular rate gyroscope at the center of gravity of the test model 18. Measure the pitch angle of the test model 18 using the tilt sensor and the pitch rate gyroscope using the angular rate gyroscope.

[0085] Step 5: Select the appropriate limit block according to the needs of the test, and adjust the extension of the piston rod of the dual-axis cylinder 16 according to the pitch angle range of the test model 18.

[0086] Step 6: Install an accelerometer at the wingtip of test model 18, attach a strain gauge for measuring the wing root bending moment at the wing root of test model 18, arrange an optical fiber for measuring wing deformation on the wing spars of test model 18, fix a rope-type displacement sensor on test model 18, connect the rope of the displacement sensor vertically to the top or bottom wall of the wind tunnel test section, connect the accelerometer, strain gauge, displacement sensor and optical fiber to the data acquisition and processing system respectively, and ensure that the acquired signal is normal.

[0087] Step 7: Conduct frequency sweep tests on the aileron 19 and flap 20 of test model 18 under both incoming and outgoing flow conditions to obtain the frequency response characteristics of the model.

[0088] Step 8: Before conducting the gust test, make the wind tunnel wind speed reach the preset value, then turn on the gust generator and make the blades of the gust generator move according to the specified swing angle, swing frequency and waveform; before conducting the flutter half-mode test, first start the wind tunnel wind speed to make the wind tunnel wind speed reach the preset value, and then gradually increase the incoming wind speed until the incoming wind speed reaches the model flutter speed.

[0089] Step 9: When the gust of wind reaches the test model 18, the vibration response signal of the test model 18 is measured by the accelerometer, and the pitch rate of the test model 18 is measured by the angular rate gyroscope. The vibration response signal and pitch rate are used by the data acquisition and processing system to calculate the amount of gust disturbance, and then the amount of disturbance is transmitted to the model control system. The model control system drives the flaps to move, generating a force opposite to the direction of the aerodynamic force brought by the gust, thereby achieving the pitch attitude control effect, i.e., internal loop control, which realizes the reduction of elastic body load.

[0090] Step 10: While performing inner loop control in step 9, the displacement change of the test model 18 during heave motion is first measured by the displacement sensor, and the signal data is sent to the data acquisition and processing system for calculation. Then, the calculated displacement change is transmitted to the model control system, which drives the flap 20 to move so that the test model 18 maintains the set height. This is the outer loop control, which realizes the reduction of rigid body load.

[0091] Step 11: For the gust test, comprehensively compare the wingtip acceleration, wing root strain, and heave range of the test model 18 before and after the control of flaps 20 and ailerons 19 in steps 7 and 8. Compared with the control without application, if the wingtip acceleration and wing root strain values ​​after the control are lower than 20% of the values ​​without application, and the heave of the test model 18 is stable within the predetermined range, it indicates that the load reduction effect of this test is satisfactory, and this test is completed. The next test will then proceed. Otherwise, continue to adjust the parameters of flaps 20 and ailerons 19 until the load reduction effect is satisfactory.

[0092] Step 12: Set the initial height of the test model 18 to ±0.3m as the set threshold for the heave motion. During the test, if the heave motion amplitude of the test model 18 exceeds the set threshold, activate the linear guide clamp 15 for locking and protection.

[0093] In step seven, based on the deflection of the flap 20 control surface, direct lift is generated to counteract the aerodynamic force and torque increment generated by the gust. The established gust load mitigation equation is as follows:

[0094] (1)

[0095] In the formula, It is the derivative of lift with respect to angle of attack. It is the derivative of lift with respect to pitch rate. It is the increase in flap lift. It's the flap angle. It is the incoming wind speed. It is the vertical gust speed at the reference point (the aerodynamic center of the wing). It is the rate of change of reference point wind speed. It is the derivative of the pitch moment with respect to the angle of attack. It is the derivative of the pitch moment with respect to the pitch rate. It is the increase in flap pitch moment;

[0096] Since the flaps are positioned near the reference point, the pitching moment generated by their deflection is negligible, i.e.:

[0097] (2)

[0098] The conventional layout models used in this invention include:

[0099] (3)

[0100] Combining equations (2) and (3), we can obtain the relationship between the rudder surface deflection angle and the gust disturbance:

[0101] (4)

[0102] In equation (4), The gain from the open-loop gust mitigation controller to the gust amplitude and flap deflection is expressed as follows:

[0103] (5).

[0104] In this invention, the experimental device is installed in a wind tunnel test section. For gust tests, a gust generator is installed at the entrance of the wind tunnel, and the test model 18 is installed on the model mounting base 4. Various sensors, such as accelerometers, strain gauges, displacement sensors, and gyroscopes, arranged on the test model 18 are connected to the data acquisition and processing system. The linear guide clamp 15 and the dual-axis cylinder 16 are then connected to the air supply pump and the 24V DC power supply. When the wind tunnel starts to blow and reaches the predetermined wind speed, the gust generator is controlled to move according to a set oscillation frequency and amplitude. Under the influence of the aerodynamic disturbance generated by the gust generator, the test model 18 undergoes heave motion on the trolley 3. The model control system drives the flaps to deflect based on the feedback signal from the displacement sensor, achieving comprehensive load reduction for the rigid body, elastic body, and rigid-elastic coupled modes of the test model 18. If the heave or pitch motion of the test model 18 exceeds a set threshold, the displacement sensor triggers the protection system to ensure the safety of the test model 18. After the experiment, the obtained data, such as the accelerometer signals at the wingtip and center of gravity of the model, the strain gauge signals at the wing root, and the motion signals of the model measured by the displacement sensor, were processed to obtain comparative data before and after applying gust mitigation control, and the amount of gust load reduction was obtained.

[0105] Figure 11 shows the effect of the wing root bending moment reduction test. When the control law is activated and the model control surface deflects, the gust load on the model is effectively reduced. At the key frequency of 3.5Hz, the gust load reduction reaches more than 55%, which rapidly and efficiently reduces the gust load, and the mitigation control effect is significant.

[0106] Example 3: As shown in Figures 1-7, 10, and 12, a method for flutter half-mode testing is implemented based on the device described in Example 1 for low-speed wind tunnel gust or flutter half-mode testing, and includes the following steps:

[0107] Step 1: Connect the overall frame 1 to the side walls and bottom walls of the wind tunnel test section;

[0108] Step 2: Connect the test model 18 to the model mounting base 4;

[0109] Step 3: Select the appropriate limit block according to the needs of the test, and adjust the extension of the piston rod of the dual-axis cylinder 16 according to the pitch angle range of the test model 18.

[0110] Step 4: Install an accelerometer at the wingtip of test model 18, attach a strain gauge for measuring the wing root bending moment at the wing root of test model 18, arrange an optical fiber for measuring wing deformation on the wing spars of test model 18, fix a rope-type displacement sensor on test model 18, connect the rope of the displacement sensor vertically to the top or bottom wall of the wind tunnel test section, connect the accelerometer, strain gauge, displacement sensor and optical fiber to the data acquisition and processing system respectively, and ensure that the acquired signal is normal.

[0111] Step 5: Conduct frequency sweep tests on the aileron 19 and flap 20 of test model 18 under both incoming and outgoing flow conditions to obtain the frequency response characteristics of the model.

[0112] Step 6: Before conducting the gust test, make the wind tunnel wind speed reach the preset value, and then turn on the gust generator so that the blades of the gust generator move according to the specified swing angle, swing frequency and waveform; before conducting the flutter half-mode test, first start the wind tunnel wind speed to make the wind tunnel wind speed reach the preset value, and then gradually increase the incoming wind speed until the incoming wind speed reaches the model flutter speed.

[0113] Step 7: Obtain the flutter velocity boundary of test model 18 based on the wingtip acceleration or wing root strain value;

[0114] Step 8: Set the initial height of the test model 18 to ±0.3m as the set threshold for the heave motion. During the test, if the heave motion amplitude of the test model 18 exceeds the set threshold, activate the linear guide clamp 15 for locking and protection.

[0115] As shown in Figure 10, for the flutter test, there is no need to install a generator device. Only the vibration response of the accelerometer and strain gauge and the flange root bending moment are used. The flutter boundary of the model is obtained by processing and analyzing the acceleration and strain data. The protection measures are the same as those for the gust test.

[0116] The above embodiments are merely illustrative examples of the present invention and do not limit its scope of protection. Those skilled in the art can make partial changes to them, as long as they do not exceed the spirit and essence of the present invention, they are all within the scope of protection of the present invention.

Claims

1. A device for low-speed wind tunnel gust or flutter half-mode testing, characterized in that: Includes an overall frame (1), a clock spring (6), a pulley (3), and a model mounting base (4); The rear end of the overall frame (1) is connected to the side wall of the wind tunnel test section, the lower end of the overall frame (1) is connected to the bottom wall of the wind tunnel test section, two slide rails (2) are vertically arranged on the front end face of the overall frame (1), two sets of slider groups (14) are arranged on the left and right sides of the rear end face of the trolley (3), the two sets of slider groups (14) and the two sets of slide rails (2) are slidably connected in a one-to-one correspondence, the top of the overall frame (1) is provided with two spring seats (10), the spring seats (10) are provided with a horizontal axis, the inner ring ends of the two spring springs (6) are connected to the horizontal axis of the two spring seats (10) in a one-to-one correspondence, the outer ring ends of the two spring springs (6) hang down and are connected to the trolley (3) respectively, the model mounting seat (4) is cylindrical, and the model mounting seat (4) and the trolley (3) are rotatably connected; The test model (18) is a flexible wing half-model. The wing root of the test model (18) is connected to the front end of the model mounting base (4). The trailing edge of the test model (18) is provided with an aileron (19) and a flap (20). The drive devices of the aileron (19) and the flap (20) are electrically connected to the model control system respectively. The resultant force of the elastic force of the two spring springs (6) is based on the weight and setting of the test model (18), the model mounting base (4), the two slider groups (14) and the trolley (3). The pitch protection system includes a dual-axis cylinder (16) and a limiting block (17). The rear end of the model mounting base (4) is provided with a limiting plane, which is parallel to the axis of the model mounting base (4). The limiting block (17) is a wedge-shaped block. The dual-axis cylinder (16) is horizontally set, and the output end of the dual-axis cylinder (16) faces the limiting plane. One side of the wedge surface of the limiting block (17) is abutted and connected to the output end of the dual-axis cylinder (16), and the other side of the wedge surface of the limiting block (17) limits the rotation of the limiting plane.

2. The apparatus for low-speed wind tunnel gust or flutter half-mode testing according to claim 1, characterized in that: The upper and lower ends of the slide rail (2) are provided with protective dampers (9), and the buffer head of the protective damper (9) faces the corresponding slider group (14).

3. The device for low-speed wind tunnel gust or flutter half-mode testing according to claim 2, characterized in that: The bottom four corners of the overall frame (1) are provided with adjusting nuts (12), and the four vertically arranged adjusting screws (11) are threadedly engaged with the four adjusting nuts (12) one by one. The bottom of the adjusting screws (11) is provided with moving rollers (13).

4. The apparatus for low-speed wind tunnel gust or flutter half-mode testing according to claim 3, characterized in that: There are several limit blocks (17), and the wedge angles of the limit blocks (17) vary from 0° to 45°, with intervals of 5°.

5. The apparatus for low-speed wind tunnel gust or flutter half-mode testing according to claim 4, characterized in that: The rear end of the overall frame (1) is provided with several side wall mounting seats (5), the lower end of the overall frame (1) is provided with several mounting holes, the overall frame (1) is connected to the side wall of the wind tunnel test section through several side wall mounting seats (5), and the overall frame (1) is connected to the bottom wall of the wind tunnel test section through several mounting holes.

6. The apparatus for low-speed wind tunnel gust or flutter half-mode testing according to claim 5, characterized in that: The front end face of the overall frame (1) is provided with several guide plate (7) mounting seats. The guide plate (7) is fixed on several guide plate (7) mounting seats. The guide plate (7) is provided with a long hole (8) in the vertical direction. The front end of the model mounting seat (4) passes through the long hole (8).

7. The apparatus for low-speed wind tunnel gust or flutter half-mode testing according to claim 6, characterized in that: Two linear guide clamps (15) are provided on the left and right sides of the trolley (3). The two linear guide clamps (15) correspond to the two slide rails (2) and slide or lock in a one-to-one manner.

8. A method for low-speed wind tunnel gust testing, implemented using the apparatus for low-speed wind tunnel gust or flutter half-mode testing as described in claim 7, characterized in that... Includes the following steps: Step 1: Install the gust generator at the wind tunnel entrance and connect the gust generator's drive unit to the model control system; Step 2: Connect the overall frame (1) to the sidewalls and bottom wall of the wind tunnel test section; Step 3: Connect the test model (18) to the model mounting base (4); Step 4: Install a tilt sensor and an angular rate gyroscope at the center of gravity of the test model (18). Measure the pitch angle of the test model (18) using the tilt sensor and the pitch rate of the test model (18) using the angular rate gyroscope. Step 5: Select the appropriate limit block according to the needs of the test, and adjust the extension of the piston rod of the dual-axis cylinder (16) according to the pitch angle range of the test model (18); Step 6: Install an acceleration sensor at the wingtip of the test model (18), attach a strain gauge for measuring the wing root bending moment at the wing root of the test model (18), arrange an optical fiber for measuring the wing deformation on the wing spars of the test model (18), fix a rope-type displacement sensor on the test model (18), connect the rope of the displacement sensor vertically to the top or bottom wall of the wind tunnel test section, connect the acceleration sensor, strain gauge, displacement sensor and optical fiber to the data acquisition and processing system respectively, and ensure that the acquisition signal is normal. Step 7: Conduct frequency sweep tests on the ailerons (19) and flaps (20) of the test model (18) under both incoming and outgoing flow conditions to obtain the frequency response characteristics of the model. Step 8: Before conducting the gust test, make the wind tunnel wind speed reach the preset value, then turn on the gust generator and make the blades of the gust generator move according to the specified swing angle, swing frequency and waveform; before conducting the flutter half-mode test, first start the wind tunnel wind speed to make the wind tunnel wind speed reach the preset value, and then gradually increase the incoming wind speed until the incoming wind speed reaches the model flutter speed. Step 9: When the gust disturbance reaches the test model (18), the vibration response signal of the test model (18) is measured by the acceleration sensor, and the pitch rate of the test model (18) is measured by the angular rate gyroscope. The vibration response signal and pitch rate are used to calculate the disturbance amount of the gust through the data acquisition and processing system, and then the disturbance amount is transmitted to the model control system. The model control system drives the flap (20) to move, generating a force opposite to the direction of the aerodynamic force brought by the gust, thereby achieving the pitch attitude control effect, i.e., inner loop control, which realizes the reduction of elastic body load. Step 10: While performing inner loop control in step 9, the displacement change of the test model (18) during heave motion is measured by displacement sensor and the signal data is sent to the data acquisition and processing system for calculation. The calculated displacement change is then transmitted to the model control system. The model control system drives the aileron (19) to move, so that the test model (18) maintains the set height. This is the outer loop control, which realizes the reduction of rigid body load. Step 11: Compare the wingtip acceleration, wing root strain, and heave range of the test model (18) before and after the control of flaps (20) and ailerons (19) in steps 7 and 8. If the wingtip acceleration and wing root strain values ​​after the control are implemented are less than 20% of those without control, and the heave of the test model (18) is stable within the predetermined range, then the load reduction effect of this test is satisfactory, the test is over, and the next test is carried out. Otherwise, continue to adjust the parameters of flaps (20) and ailerons (19) until the load reduction effect is satisfactory. Step 12: Use ±0.3m of the initial height of the test model (18) as the set threshold for the heave motion. During the test, if the heave motion amplitude of the test model (18) exceeds the set threshold, the linear guide clamp (15) will be activated for locking and protection.

9. A method for low-speed wind tunnel gust testing according to claim 8, characterized in that: In step seven, based on the deflection of the flap (20) control surface, direct lift is generated to counteract the aerodynamic force and torque increment generated by the gust. The established gust load mitigation equation is as follows: （1） In the formula, It is the derivative of lift with respect to angle of attack. It is the derivative of lift with respect to pitch rate. It is the increase in lift from the flaps (20). It is the flap (20) deflection angle, It is the incoming wind speed. This is the vertical gust speed at the reference point. It is the rate of change of reference point wind speed. It is the derivative of the pitch moment with respect to the angle of attack. It is the derivative of the pitch moment with respect to the pitch rate. It is the increase in the pitching moment of the flap (20); The flaps (20) are positioned near the reference point, and the pitching moment generated by their deflection is: （2） In the conventional layout model: （3） Combining equations (2) and (3), we can obtain the relationship between the flap (20) deflection angle and the gust disturbance: （4） In equation (4), The gain from the open-loop gust mitigation controller and the gust amplitude to the flap (20) deflection is expressed as follows: （5）。 10. A method for flutter half-mode testing, implemented using the apparatus for low-speed wind tunnel gust or flutter half-mode testing as described in claim 7, characterized in that, Includes the following steps: Step 1: Connect the overall frame (1) to the sidewalls and bottom wall of the wind tunnel test section; Step 2: Connect the test model (18) to the model mounting base (4); Step 3: Select the appropriate limit block according to the needs of the test, and adjust the extension of the piston rod of the dual-axis cylinder (16) according to the pitch angle range of the test model (18); Step 4: Install an acceleration sensor at the wingtip of the test model (18), attach a strain gauge for measuring the wing root bending moment at the wing root of the test model (18), arrange an optical fiber for measuring the wing deformation on the wing spars of the test model (18), fix a rope-type displacement sensor on the test model (18), connect the rope of the displacement sensor vertically to the top or bottom wall of the wind tunnel test section, connect the acceleration sensor, strain gauge, displacement sensor and optical fiber to the data acquisition and processing system respectively, and ensure that the acquisition signal is normal. Step 5: Conduct frequency sweep tests on the ailerons (19) and flaps (20) of the test model (18) under both incoming and outgoing flow conditions to obtain the frequency response characteristics of the model. Step 6: Before conducting the gust test, make the wind tunnel wind speed reach the preset value, and then turn on the gust generator so that the blades of the gust generator move according to the specified swing angle, swing frequency and waveform; before conducting the flutter half-mode test, first start the wind tunnel wind speed to make the wind tunnel wind speed reach the preset value, and then gradually increase the incoming wind speed until the incoming wind speed reaches the model flutter speed. Step 7: Obtain the flutter velocity boundary of the test model (18) under zero damping based on the wingtip acceleration or wing root strain value; Step 8: Use ±0.3m of the initial height of the test model (18) as the set threshold for the heave motion. During the test, if the heave motion amplitude of the test model (18) exceeds the set threshold, the linear guide clamp (15) will be activated for locking protection.

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