System and method for gust load reduction testing of elastic full-aircraft model in large low-speed wind tunnel

Abstract

A system and method for gust load reduction testing of an elastic full-aircraft model in a large low-speed wind tunnel, which belong to the technical field of wind tunnel test apparatuses. The system in the present invention comprises a gust generator and a supporting device that are mounted in a wind tunnel. The supporting device comprises a model sliding guide rail, mounting bases and a trolley, wherein the mounting bases are fixedly mounted at two ends of the model sliding guide rail, the trolley is mounted on the model sliding guide rail, an aircraft model is mounted on the trolley, two parallel sliding rails are mounted on each mounting base, a slider is mounted on each of the two sliding rails, the two sliders are connected by means of a slider connecting base, a lifting ring assembly plate is mounted on the slider connecting base, a plurality of first lifting rings are welded on the bottom face of the lifting ring assembly plate, second lifting rings are welded on the mounting base, springs are hooked between the first lifting rings and the second lifting rings, and a smooth shaft sleeve and a smooth shaft are mounted in the mounting base, one end of the smooth shaft being fixedly mounted in the slider connecting base by means of a bolt, and a limiting block being fixedly mounted at the other end of the smooth shaft. The present invention has a compact structure, involves simple installation and is low cost.

Description

Large low-speed wind tunnel elastic full model gust load alleviation test system and method TECHNICAL FIELD

[0001] The present application relates to a gust load alleviation test system, belonging to the technical field of wind tunnel test equipment BACKGROUND

[0002] Gust is a kind of strong and certain wind disturbance in the atmosphere. When the aircraft encounters gust, the aircraft body will produce additional unsteady aerodynamic force and moment, thereby adversely affecting the flight performance of the aircraft. Modern civil aircraft, such as large passenger aircraft, emphasize economy, comfort, safety, reliability, and require high aerodynamic efficiency and low structural weight. Large aspect ratio wings are usually used, and composite materials are widely used in structural materials. The aircraft wing has great flexibility, so the aircraft is more sensitive to gust response. Gust load, especially vertical discrete gust load, often becomes the most serious flight load. When the aircraft encounters unsteady aerodynamic load caused by medium-low intensity gust, it will cause the aircraft to vibrate, which will bring tension to the passengers and reduce the comfort of the civil aircraft, and even cause personal injury to the passengers. When the aircraft encounters high-intensity unsteady aerodynamic load, the local overload of the aircraft can reach 2.5g or more, which will cause damage to the aircraft structure or produce fatigue cracks, affect the service life of the aircraft, and have a great impact on the safety and reliability of the aircraft. Civil aircraft is extremely sensitive to fatigue damage caused by gust load, and gust load spectrum is an important scientific basis for the reliability design of aircraft structure life. Due to the problem of gust load, in order to ensure the strength of the aircraft, the aircraft structure needs to be strengthened, which leads to the increase of the weight of the aircraft, and further affects the economy of the aircraft.

[0003] The airworthiness regulations of domestic and foreign civil aircraft make clear provisions for gust load. China's transport aircraft airworthiness standard (CCAR-25-R4) and the United States aviation administration regulations (FAR-25) both give corresponding provisions for gust load design criteria. Accurate prediction of gust load is an important work that must be carried out in the design stage of the aircraft. The development of large civil aircraft in China urgently needs advanced large low-speed wind tunnel gust test technology. In addition to the demand for gust load prediction required by the strength design of the aircraft, the gust load alleviation technology also needs to be verified.

[0004] At present, the research on gust load alleviation is mainly carried out by the method of calculation simulation, and the related experimental research is mainly carried out in a small size wind tunnel to carry out some exploratory preliminary research work, and the wing components or half-span model is mostly used, so it is difficult to truly reflect the overload of the whole machine multi-component when the aircraft encounters gust, such as wing, elevator, engine nacelle and displacement change of the center of gravity of the aircraft; on the other hand, the existing wind tunnel test model support device cannot completely release the heave and pitch freedom of the model, and cannot realize the decoupling of the elastic and rigid motion of the model; in addition, the gust load alleviation test of the wing component or half-span model generally only uses the flap or aileron for control, and cannot realize the combined deflection of the flap and rudder, and further realize the attitude control, rigid modal, elastic modal and rigid-elastic hybrid modal gust alleviation control of the model; finally, the existing model protection mainly adopts the pull line type protection measure, which can only realize the protection of the elastic vibration of the model, and cannot protect the rigid heave motion of the model, resulting in the damage of the model and the failure of the test. Technical problem

[0005] In order to solve the above problems, the purpose of the present application is to provide a large low-speed wind tunnel elastic full model gust load alleviation test system and method, the elastic full aircraft model can fully reflect the load condition of each component and the whole aircraft when encountering gust; the model support system can completely release the heave and pitch freedom of the model, and realize the decoupling of the rigid and elastic motion of the model; the combined motion of the model aileron, flap and rudder can realize the gust alleviation control of the rigid modal, elastic modal and rigid-elastic hybrid modal of the model; the cylinder and rope system can realize the protection of the rigid vibration and elastic vibration of the model, ensure the safety of the model and ensure the smooth development of the test. Technical solution

[0006] The technical solution adopted by the present application to solve the above technical problems is:

[0007] The large low-speed wind tunnel elastic full model gust load alleviation test system comprises a gust generator and a support device installed in the wind tunnel, the support device comprises a model sliding guide rail, a mounting seat and a trolley, the upper and lower ends of the model sliding guide rail are fixedly installed with mounting seats, the trolley is slidingly installed on the model sliding guide rail, the trolley is installed with an aircraft model, the mounting seat is installed with two parallel sliding rails, the two sliding rails are installed with sliding blocks, the two sliding blocks are connected through a sliding block connecting seat, the sliding block connecting seat is installed with a lifting ring assembly plate, a plurality of first lifting rings are welded on the bottom surface of the lifting ring assembly plate, a plurality of second lifting rings are welded on the mounting seat, a spring is hung between the first lifting ring and the second lifting ring, an optical shaft sleeve is installed in the mounting seat, an optical shaft is installed in the optical shaft sleeve, one end of the optical shaft is fixedly installed on the sliding block connecting seat through bolts, and the other end of the optical shaft is fixedly installed with a limiting block.

[0008] Preferably, the trolley comprises a trolley mounting frame, sliding support mechanisms and a protection device, the trolley mounting frame is square, and the trolley mounting frame is provided with a plurality of sliding support mechanisms and a pair of protection devices;

[0009] The sliding support mechanism comprises a side shaft, a side bearing seat and an angular contact bearing, the side bearing seat is fixedly installed on the trolley mounting frame by a hexagonal head bolt and a hexagonal head nut, the side bearing seat is provided with the side shaft, and both ends of the side shaft are provided with the angular contact bearings, and the outer rings of the angular contact bearings are in contact with the model sliding guide rails.

[0010] The protection device comprises a cylinder mounting seat and a cylinder, the cylinder is fixedly installed on the trolley mounting frame through the cylinder mounting seat, and a friction plate is installed on the piston rod of the cylinder.

[0011] Preferably, the trolley is provided with a cross roller collar, the outer ring of the cross roller collar is fixedly installed on the trolley by a bolt, the inner ring of the cross roller collar is fixedly installed with a model mounting seat by a screw, the model mounting seat is a square frame structure, a limiting rod is installed on the model mounting seat, the trolley is provided with a pitch angle limiting seat, a limiting groove is formed in the pitch angle limiting seat, the limiting rod is arranged in the limiting groove of the pitch angle limiting seat, and the aircraft model is fixedly installed on the model mounting seat.

[0012] The trolley mounting frame is a square frame assembled by a trolley front mounting plate, two trolley side mounting plates and a trolley rear mounting plate, and the trolley front mounting plate, the trolley side mounting plates and the trolley rear mounting plate are all provided with the sliding support mechanisms.

[0013] Preferably, the trolley further comprises a second protection device, the second protection device comprises a protection device mounting seat fixedly installed at the lower end of the trolley mounting frame, a second cylinder installed on the protection device mounting seat, a push link hingedly installed on the piston rod of the second cylinder, a first hinged seat fixedly installed at the left end of the protection device mounting seat, the rod body of the push link hingedly installed with the first hinged seat through a pin shaft, the lower end of the push link hingedly installed with a first brake lever through a first connecting rod, the upper end of the first brake lever hingedly installed with a second hinged seat, the second hinged seat fixedly installed on the protection device mounting seat, a first brake block installed on the first brake lever, and a pull rod hingedly arranged on the push link, the other end of the pull rod hingedly arranged with a second brake lever, the bottom end of the second brake lever hingedly installed with a third hinged seat, the third hinged seat fixedly installed at the right end of the protection device mounting seat, and a second brake block installed on the second brake lever.

[0014] The large low-speed wind tunnel elastic full model gust load alleviation test method is realized based on a large low-speed wind tunnel elastic full model gust load alleviation test system, and comprises the following steps:

[0015] Step 1. Install the inclination sensor and angular rate gyroscope at the center of gravity of the aircraft model to measure the pitch angle and pitch rate; install the acceleration sensors at the left wing tip, right wing tip, left engine nacelle, right engine nacelle, nose of the aircraft model and center of gravity of the aircraft model to measure the vibration load of the key parts of the model; install the wing root strain gauges at the left wing root and right wing root of the aircraft model to measure the wing root bending moment; install the displacement sensor on the mounting seat at the lower end of the support device to measure the heave motion of the aircraft model;

[0016] Step 2. Before the test, first start the wind tunnel wind speed, and after the wind speed reaches the preset value, start the gust generator, and the blades of the gust generator move according to the specified swing angle, swing frequency and waveform;

[0017] Step 3. When the gust disturbance reaches the aircraft model, the acceleration sensors arranged at the left wing tip, right wing tip and center of gravity of the aircraft model measure the vibration load signal of the model, the inclination sensor and angular rate gyroscope measure the pitch angle and pitch rate of the aircraft model, and the above-mentioned collected signals are calculated by the data acquisition and processing system to obtain the disturbance quantity of the gust, and then the disturbance quantity is transmitted to the model control system, the model control system drives the aileron and flap to move, generates a force opposite to the direction of the aerodynamic force brought by the gust, achieves the effect of pitch attitude control, i.e. inner loop control, and realizes the load mitigation of the elastic body;

[0018] Step 4. While the inner loop control is being performed in step 3, the heave motion of the aircraft model measured by the displacement sensor is calculated by the signal data acquisition and processing system, and the calculated heave motion is transmitted to the model control system, the model control system drives the elevator to move, so that the model maintains the set height, i.e. outer loop control, and realizes the load mitigation of the rigid body;

[0019] Step 5. Compare the wing tip acceleration, wing root strain and model heave motion range before and after the implementation of the control in steps 2 and 3, if the wing tip acceleration and wing root strain are significantly reduced after the implementation of the control, and the model heave motion is stable within a predetermined range, it indicates that the load mitigation effect of the current test meets the test requirements, the current test is ended, and the next test is carried out, otherwise the control surface parameters are continuously adjusted until the load mitigation effect that meets the test requirements is obtained. Beneficial effects

[0020] The present application has the advantages that: the present application can more truly reflect the situation of the aircraft encountering gust through the control mode of multiple operating surfaces, the elastic model test of full aircraft dynamics similarity design, realizes the gust alleviation control mode of model rigid body mode, elastic body mode, rigid and elastic hybrid mode, better controls the model attitude, and the maximum alleviation range of wing root bending moment load reaches 50%, the present application quickly and effectively reduces the gust load of the aircraft model, and the alleviation control effect is remarkable. The cylinder and rope system are adopted to protect the model rigid body movement and wing elastic vibration, and the safety of the model is ensured; in addition, the present application protects the aircraft model in the process of the elastic full model gust load alleviation test in a large low-speed wind tunnel through the double protection device, so as to prevent the model from being damaged and the like, reduces the safety accident rate, saves the use cost of the model, ensures the smooth development of the test, and the device occupies small space, has compact structure, is simple to install, and is low in cost. BRIEF DESCRIPTION OF DRAWINGS

[0021] Fig. 1 is a front view of a large low-speed wind tunnel elastic full model gust load alleviation test system;

[0022] Fig. 2 is a right view of Fig. 1;

[0023] Fig. 3 is a perspective view of a support device;

[0024] Fig. 4 is a front view of the support device;

[0025] Fig. 5 is a perspective view of a mounting seat;

[0026] Fig. 6 is a section view in direction A of Fig. 4;

[0027] Fig. 7 is a section view in direction B of Fig. 4;

[0028] Fig. 8 is a section view in direction C of Fig. 4;

[0029] Fig. 9 is a section view in direction D of Fig. 4;

[0030] Fig. 10 is a cooperation installation structure diagram of a trolley and a model sliding guide rail;

[0031] Fig. 11 is a cooperation installation structure diagram of a model mounting seat and the trolley;

[0032] Fig. 12 is a section view of a sliding support mechanism;

[0033] Fig. 13 is a structure schematic diagram of a second protection device;

[0034] Fig. 14 is an inner loop structure diagram of a pitch attitude controller;

[0035] Fig. 15 is an outer loop structure diagram of a height keeping controller;

[0036] Fig. 16 is a gust load alleviation effect diagram;

[0037] In the figure, 1-wind tunnel, 2-gust generator, 3-support device, 4-model sliding guide rail, 5-mounting seat, 6-trolley, 7-airplane model, 8-sliding rail, 9-sliding block, 10-sliding block connecting seat, 11-hanging ring assembly plate, 12-first hanging ring, 13-second hanging ring, 14-spring, 15-optical axis sleeve, 16-optical axis, 17-limiting block, 18-trolley mounting frame, 19-sliding support mechanism, 20-protection device, 21-side shaft, 22-side bearing seat, 23-angular contact bearing, 24-cylinder mounting seat, 25-cylinder, 26-crossed roller collar, 27-model mounting seat, 28-limiting rod, 29-pitch angle limiting seat, 30-second protection device, 31-protection device mounting seat, 32-second cylinder, 33-pushing connecting rod, 34-first hinged seat 34, 35-first connecting rod, 36-first brake rod, 37-second hinged seat, 38-first brake block, 39-pulling rod, 40-second brake rod, 41-third hinged seat, 42-second brake block, 43-rope, 44-pulley block. Embodiments of the application

[0038] The application will be further illustrated by the following specific examples, which are only used to illustrate the application and not used to limit the scope of the application. After reading the application, those skilled in the art can make various equivalent modifications of the application, which all fall within the scope defined by the appended claims.

[0039] Specific embodiment one

[0040] In combination with the drawings 1-13 of the specification, the embodiment is illustrated, the embodiment discloses a large low-speed wind tunnel elastic full model gust load alleviation test system, including an array wind generator 2 and a supporting device 3 installed in the wind tunnel 1, the supporting device 3 includes a model sliding guide rail 4, a mounting seat 5 and a trolley 6, the mounting seat 5 is fixedly installed at the upper and lower ends of the model sliding guide rail 4, the trolley 6 is slidably installed on the model sliding guide rail 4, the aircraft model 7 is installed on the trolley 6, the mounting seat 5 is installed with two parallel slide rails 8, the slide blocks 9 are installed on the two slide rails 8, the two slide blocks 9 are connected through the slide block connecting seat 10, the lifting eye assembly plate 11 is installed on the slide block connecting seat 10, a plurality of first lifting eyes 12 are welded on the bottom surface of the lifting eye assembly plate 11, a plurality of second lifting eyes 13 are welded on the mounting seat 5, the spring 14 is hung between the first lifting eye 12 and the second lifting eye 13, the optical shaft sleeve 15 is installed in the mounting seat 5, the optical shaft 16 is installed in the optical shaft sleeve 15, one end of the optical shaft 16 is fixedly installed on the slide block connecting seat 10 through bolts, and the other end of the optical shaft 16 is fixedly installed with the limiting block 17. In this way, when the gust load alleviation test is carried out, the wind tunnel 1 and the array wind generator 2 are started, and the gust generated by the two is used to act on the aircraft model 7, the aircraft model 7 is in heave motion on the model sliding guide rail 4 under the action of the trolley 6, and the purpose is to simulate the heave state in the flight process of the aircraft. When the aircraft model 7 is lifted to the highest point on the model sliding guide rail 4 through the trolley 6, the aircraft model 7 will touch the limiting block 17, the limiting block 17 will transmit the force to the optical shaft 16, the optical shaft 16 drives the slide block connecting seat 10 to move upward because the top end of the optical shaft 16 is fixedly installed on the slide block connecting seat 10 through bolts, the slide block connecting seat 10 drives the two slide blocks 9 to move on the corresponding slide rails 8, in addition, the lifting eye assembly plate 11 is installed on the slide block connecting seat 10, so that the lifting eye assembly plate 11 also moves upward under the drive of the slide block connecting seat 10, under the action of the spring 14 installed on the slide block connecting seat 10, the spring 14 plays a role in alleviating the impact, effectively preventing the aircraft model 7 from being damaged by impact, and ensuring the safety of the aircraft model 7. When the test is finished and the wind speed is zero, the aircraft model 7 will touch the limiting block 17 at the lower end of the supporting device 3 when descending to the lowest point, and for the same reason, the limiting block 17 drives the slide block connecting seat 10 to move through the optical shaft 16, the slide block connecting seat 10 drives the slide block 9 to move on the slide rail 8, and under the action of the spring 14, the spring 14 also plays a role in alleviating the impact.

[0041] The trolley 6 includes a trolley mounting frame 18, a sliding support mechanism 19 and a protection device 20, the trolley mounting frame 18 is square, a plurality of sliding support mechanisms 19 and a pair of protection devices 20 are installed on the trolley mounting frame 18;

[0042] The sliding support mechanism 19 comprises a side shaft 21, a side bearing seat 22 and an angular contact bearing 23, the side bearing seat 22 is fixedly installed on the trolley mounting frame 18 by a hexagonal head bolt and a hexagonal head nut, the side shaft 21 is installed in the side bearing seat 22, and the two ends of the side shaft 21 are provided with the angular contact bearings 23, and the outer rings of the angular contact bearings 23 are in contact with the model sliding guide 4.

[0043] The protection device 20 comprises a cylinder mounting seat 24 and a cylinder 25, the cylinder 25 is fixedly installed on the trolley mounting frame 18 through the cylinder mounting seat 24, and a friction plate is installed on the piston rod of the cylinder 25. In this way, during the test, the air pump continuously supplies air to the cylinder 25, when the heaving motion of the aircraft model 7 exceeds the set threshold value, the cylinder 25 is started to control, the cylinder is powered, and the cylinders 25 at both ends of the trolley 6 work simultaneously, the friction plate on the piston rod of the cylinder 25 locks the model sliding guide 4, at this time, the aircraft model 7 cannot produce heaving motion, and the aircraft model 7 is protected.

[0044] The trolley 6 is provided with a cross roller collar 26, the outer ring of the cross roller collar 26 is fixedly installed on the trolley 6 through a bolt, the inner ring of the cross roller collar 26 is fixedly installed with a model mounting seat 27 through a screw, the model mounting seat 27 is a square frame structure, a limiting rod 28 is installed on the model mounting seat 27, the trolley 6 is provided with a pitch angle limiting seat 29, a limiting groove is formed in the pitch angle limiting seat 29, and the limiting rod 28 is arranged in the limiting groove of the pitch angle limiting seat 29, and the aircraft model 7 is fixedly installed on the model mounting seat 27. In this way, the aircraft model 7 is fixedly installed on the model mounting seat 27, the model mounting seat 27 is installed on the trolley 6 through the cross roller collar 26, so that the aircraft model 7 realizes the pitching action under the action of the cross roller collar 26, but in order to limit the pitching action amplitude of the aircraft model 7 and avoid damage of the aircraft model 7 in the test process due to the too large pitching action amplitude, the limiting rod 28 is installed on the model mounting seat 27 and is used in cooperation with the pitch angle limiting seat 29 installed on the trolley 6, when the pitching amplitude of the aircraft model 7 is greater than the set threshold value, the limiting rod 28 moves to the limit position in the limiting groove, so as to prevent the aircraft model 7 from being damaged due to the too large pitching action amplitude.

[0045] The trolley mounting frame 18 is a square frame assembled by a trolley front mounting plate, two trolley side mounting plates and a trolley rear mounting plate, and the sliding support mechanism 19 is installed on the trolley front mounting plate, the trolley side mounting plates and the trolley rear mounting plate.

[0046] In the present embodiment, the large-scale low-speed wind tunnel elastic full model gust load alleviation test system is to install the gust generator 2 at the inlet of the wind tunnel 1, fix the support device 3 in the wind tunnel, install the aircraft model 7 (full machine elastic model) on the support device 3, connect the various sensors arranged on the model such as accelerometers, strain gauges, displacement sensors, gyroscopes, etc. with the data acquisition and processing system, complete the connection of the air cylinder air supply pump for model protection and the 24V DC power supply for power supply. The wind tunnel starts to blow, and after reaching the predetermined wind speed, the gust generator 2 moves according to the set swing frequency and swing amplitude, the aircraft model 7 makes heaving motion on the support device 3 under the action of the disturbance aerodynamic force generated by the gust generator 2, the model control system drives the rudder deflection according to the sensor feedback signal, realizes the comprehensive load alleviation of the model rigid body, elastic body and rigid elastic coupling mode, and the air cylinder 25 and the rope protection system can be started when the model has large motion or vibration to ensure the safety of the model.

[0047] Before the test, install the gust generator 2 at the inlet of the wind tunnel 1, install the model support device 3 at the center of the wind tunnel 1, and after the installation of the aircraft model 7 is completed, debug the sensors and acquisition system, model control system, data acquisition and processing system, etc. to ensure the normal operation of the system. Complete the connection of the air cylinder air supply pump for model protection and the 24V DC power supply, and arrange the rope protection system. Then the hammering method is used to obtain the model characteristic modal data to ensure the correctness of the model installation. Then the sweep frequency test of ailerons, flaps and elevators is carried out to obtain the response characteristics of the model under the sweep frequency of each rudder surface.

[0048] During the test, first start the wind speed of the wind tunnel, and after the wind speed reaches the preset value, start the gust generator 2, the blades of the gust generator 2 move according to the specified swing angle, swing frequency and waveform, the aircraft model 7 makes heaving motion on the support device under the action of the aerodynamic force, the sensors arranged on the model transmit the received model motion and load data to the data acquisition and processing system, and the disturbance of the gust is calculated, the model control system drives the model rudder deflection according to the disturbance of the gust, at this time, if the heaving and pitching motion of the full machine model is stable within a certain set range, the gust disturbance is effectively suppressed, and the data of the acceleration sensor, strain gauge, gyroscope and displacement sensor is collected. If the heaving motion or pitching motion of the model exceeds the set threshold, the corresponding motion sensor triggers the air cylinder protection system, and the rope protection system is manually tightened at the same time to ensure the safety of the model.

[0049] After the test, the obtained model wing tip, nacelle, center of gravity accelerometer signal, wing root strain gauge signal and displacement sensor measured model motion signal are processed to obtain the comparison data before and after applying and not applying the gust alleviation control, and the gust load alleviation value is obtained.

[0050] Specific implementation method two:

[0051] In combination with the drawings 1-13 of the specification, the embodiment is described, the large low-speed wind tunnel elastic full model gust load mitigation test system disclosed in the embodiment further comprises a second protection device 30, the second protection device 30 comprises a protection device mounting seat 31 fixedly installed at the lower end of the trolley mounting frame 18, a second cylinder 32 is installed on the protection device mounting seat 31, a push link 33 is hingedly installed on the piston rod of the second cylinder 32, a first hinge seat 34 is fixedly installed at the left end of the protection device mounting seat 31, the rod body of the push link 33 is hingedly installed with the first hinge seat 34 through a pin shaft, the lower end of the push link 33 is hingedly installed with a first connecting rod 35 and a first brake rod 36, the upper end of the first brake rod 36 is hingedly installed with a second hinge seat 37, the second hinge seat 37 is fixedly installed on the protection device mounting seat 31, a first brake block 38 is installed on the first brake rod 36, a pull rod 39 is also hingedly installed on the push link 33, the other end of the pull rod 39 is hingedly installed with a second brake rod 40, a third hinge seat 41 is hingedly installed at the bottom end of the second brake rod 40, the third hinge seat 41 is fixedly installed at the right end of the protection device mounting seat 31, a second brake block 42 is installed on the second brake rod 40. In this way, when the aircraft model 7 performs a large amplitude heave action during the experiment, in addition to the cylinder 25 on the protection device 20 working to achieve protection, the second protection device 30 can also achieve protection work, specifically: as shown in Figure 13: the piston rod of the second cylinder 32 is extended, driving the push link 33 to rotate around the first hinge seat 34, the bottom of the push link 33 pushes the first brake rod 36 through the first connecting rod 35, the first brake rod 36 approaches the model sliding guide 4 direction with the second hinge seat 37 as the fulcrum, the first brake block 38 installed on the second hinge seat 37 contacts the model sliding guide 4; at the same time of the action of the push link 33, the push link 33 drives the pull rod 39 to move left, at this time the pull rod 39 pulls the second brake rod 40, the second brake rod 40 also approaches the model sliding guide 4 direction with the third hinge seat 41 as the pivot fulcrum, the second brake block 42 installed on the second brake rod 40 also contacts the model sliding guide 4, under the joint action of the first brake block 38 and the second brake block 42, it plays the role of "brake", protecting the aircraft model 7.

[0052] Specific implementation method three:

[0053] In combination with the drawings 1-13 of the specification, the embodiment is described, the large low-speed wind tunnel elastic full model gust load mitigation test method disclosed in the embodiment is realized based on the large low-speed wind tunnel elastic full model gust load mitigation test system, comprising the following steps:

[0054] Step 1. Install the inclination sensor and angular rate gyroscope at the center of gravity of the airplane model 7 for measuring the pitch angle and pitch angular rate; install the acceleration sensors at the left wing tip, right wing tip, left engine nacelle, right engine nacelle, nose of the airplane model 7 and the center of gravity of the airplane model 7 for measuring the vibration load of the left wing tip, right wing tip, left engine nacelle, right engine nacelle, nose of the airplane model and the airplane model; stick the wing root strain gauges at the left wing root and right wing root of the airplane model 7 for measuring the wing root bending moment; install the displacement sensor on the mounting seat 5 at the lower end of the support device 3 for measuring the heave motion of the airplane model 7;

[0055] Step 2. Before the test, first start the wind tunnel wind speed, and after the wind speed reaches the preset value, start the gust generator 2, and the blades of the gust generator 2 move according to the specified swing angle, swing frequency and waveform;

[0056] Step 3. When the gust disturbance reaches the airplane model 7, the acceleration sensors arranged at the left wing tip, right wing tip of the airplane model 7 and the center of gravity of the airplane model 7 measure the vibration load signal of the model, the inclination sensor and the angular rate gyroscope measure the pitch angle and pitch angular rate of the airplane model 7, and the above-mentioned collected signals are calculated by the data acquisition and processing system to obtain the disturbance quantity of the gust, and then the disturbance quantity is transmitted to the model control surface system, the model control surface system drives the aileron and flap rudder to move, generates a force opposite to the aerodynamic force brought by the gust, achieves the effect of pitch attitude control, that is, the inner loop control, and realizes the load mitigation of the elastic body;

[0057] Further, the model control system is used to realize the attitude control and trim stability of the model, which is composed of an inner loop and an outer loop. As shown in FIG. 14, the inner loop is a pitch angle attitude controller, which uses as the pitch angular rate gain feedback to the elevator, increases the pitch degree of freedom damping; the proportional integral of the preset pitch angle and the actual pitch angle deviation signal is provided to the elevator to realize the pitch attitude tracking. Wherein is the preset pitch angle, is the integral gain of the pitch attitude controller, is the proportional gain of the pitch attitude controller, is the elevator deflection, is the pitch angular rate feedback gain, is the pitch angle, is the speed pressure, is the model motion height, is the model motion speed, s is a complex variable in Laplace transform.

[0058] Step 4, while the inner loop control is being carried out in step 3, the displacement sensor calculates the measured heave motion of the aircraft model 7 by the signal data acquisition and processing system, and transmits the calculated heave motion to the model control system, which drives the elevator motion to keep the model at a set height, that is, the outer loop control, and realizes the rigid body load alleviation.

[0059] Further, as shown in Fig. 15, the outer loop is the height keeping control, when the model height deviates from the predetermined height, the height deviation signal changes the pitch angle to make the model return to the predetermined height. Wherein represents the given height of the model, is the integral gain of the height controller, is the proportional gain of the height controller, is the height of the model motion, is the speed of the model motion, is the vertical speed feedback gain.

[0060] Step 5, compare the wing tip acceleration, wing root strain and model heave motion range before and after the implementation of the control in step 2 and step 3, if the wing tip acceleration and wing root strain are significantly reduced after the implementation of the control, and the model heave motion is stable within a predetermined range, it indicates that the load alleviation effect of the current test meets the test requirements, the current test is ended, and the next test is carried out, otherwise the control surface parameters are continuously adjusted until the load alleviation effect meeting the test requirements is obtained.

[0061] Step 6, during the test, if the model heave motion amplitude is large and exceeds the set threshold, the cylinder protection system installed on the trolley is started to protect;

[0062] Further, the cylinder protection system is installed on the trolley 6, which is composed of a cylinder 25, an air pump, a 24V DC power supply and a control switch. During the test, the air pump continuously supplies air to the cylinder 25, the 24V DC power supply is in a disconnected state with the cylinder, when the model heave motion exceeds the set threshold, the cylinder control is started to supply power to the cylinder 25, the cylinders 25 at both ends of the trolley work simultaneously to lock the guide rail, at this time the model cannot produce heave motion, which protects the model. At the same time, the second cylinder 32 of the second protection device 30 is also started, the second cylinder 32 drives the first brake rod 36 to move through the connecting rod motion of the connecting rod 33 and the first connecting rod 35, and drives the second brake rod 40 to move through the pull rod 39, through the joint action of the first brake rod 36 and the second brake rod 40, the first brake block 38 and the second brake block 42 are used to act on the model sliding guide rail 4, which plays the role of "brake" and protects the aircraft model 7.

[0063] Step 7, if the wing vibration amplitude is large and tends to diverge, the rope system installed at the wing tip is used for protection;

[0064] The rope system mainly consists of two ropes 43 arranged on the upper and lower wings and a pulley block 44 installed on the upper and lower walls of the wind tunnel. When the wing vibration amplitude is large, the ropes 43 on the upper and lower wings are simultaneously tensioned, and the force on the ropes 43 acts on the wing through the pulley block 44, limiting the vibration of the wing.

[0065] Step 8, according to the combined deflection of the aileron, flap and elevator control surfaces, direct lift is generated to offset the increase in aerodynamic force and moment caused by the gust, and the established gust load alleviation equation is as follows:

[0066] (1)

[0067] In equation (1), is the derivative of lift with respect to angle of attack, is the derivative of lift with respect to pitch rate, is the flap lift increment, is the flap deflection angle, is the elevator lift increment, is the elevator deflection angle, is the incoming flow speed, is the vertical gust speed at the reference point (wing aerodynamic center), is the gust speed variation rate at the reference point, is the derivative of pitch moment with respect to angle of attack, is the derivative of pitch moment with respect to pitch rate, is the flap pitch moment increment, is the elevator pitch moment.

[0068] Step 9, since the flap is arranged near the reference point, the pitch moment generated by the deflection of the elevator can be ignored, i.e.

[0069] (2)

[0070] Step 10, for the conventional layout model used in the present application:

[0071] (3)

[0072] Step 11, combining equation (2) with equation (3), the relationship between the deflection angle of the control surface and the gust disturbance can be obtained:

[0073] (4)

[0074] In equation (4), Gain of open loop gust alleviation controller, gust amplitude to flap deflection, Gain of open loop gust alleviation controller, gust amplitude to elevator deflection, Gain of open loop gust alleviation controller, gust amplitude rate to elevator deflection, which is expressed as follows:

[0075] (5)

[0076] As shown in Fig. 16, it is a wing root bending moment alleviation test effect diagram. When the control law is opened, the model surface deflection is suffered from the gust load, and the gust load is effectively reduced. The gust load alleviation amount at the key frequency of 3.5 Hz reaches more than 50%, the gust load is quickly and efficiently reduced, and the alleviation control effect is remarkable.

[0077] The embodiments of the present application are described above in combination with the drawings, but the present application is not limited to the above-mentioned specific embodiments, and the above-mentioned specific embodiments are only illustrative but not restrictive. Those skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, which are all within the protection of the present application.

Claims

1. A system for elastic full model gust load alleviation testing in a large scale low speed wind tunnel, comprising a gust generator (2) and a support device (3) installed in the wind tunnel (1), characterized in that: The support device (3) includes a model sliding guide rail (4), a mounting seat (5) and a trolley (6), the upper and lower ends of the model sliding guide rail (4) are fixedly provided with the mounting seat (5), the trolley (6) is slidably installed on the model sliding guide rail (4), the trolley (6) is provided with an airplane model (7), the mounting seat (5) is provided with two parallel sliding rails (8), the two sliding rails (8) are provided with sliding blocks (9), the two sliding blocks (9) are connected through a sliding block connecting seat (10), the sliding block connecting seat (10) is provided with a lifting ring assembly plate (11), a plurality of first lifting rings (12) are welded on the bottom surface of the lifting ring assembly plate (11), a plurality of second lifting rings (13) are welded on the mounting seat (5), the first lifting ring (12) and the second lifting ring (13) are hung with a spring (14), an optical shaft sleeve (15) is installed in the mounting seat (5), an optical shaft (16) is installed in the optical shaft sleeve (15), one end of the optical shaft (16) is fixedly installed on the sliding block connecting seat (10) through a bolt, the other end of the optical shaft (16) is fixedly installed with a limiting block (17); The trolley (6) includes a trolley mounting frame (18), a sliding support mechanism (19) and a protection device (20), the protection device (20) includes a cylinder mounting seat (24) and a cylinder (25), the cylinder (25) is fixedly installed on the trolley mounting frame (18) through the cylinder mounting seat (24), a friction plate is installed on the piston rod of the cylinder (25); Further comprising a second protection device (30), the second protection device (30) includes a protection device mounting seat (31) fixedly installed on the lower end of the trolley mounting frame (18), a second cylinder (32) is installed on the protection device mounting seat (31), a push connecting rod (33) is hingedly installed on the piston rod of the second cylinder (32), a first hinge seat (34) is fixedly installed on the left end of the protection device mounting seat (31), the rod body of the push connecting rod (33) is hingedly installed with the first hinge seat (34) through a pin shaft, the lower end of the push connecting rod (33) is hingedly installed with a first brake lever (36) through a first connecting rod (35), a second hinge seat (37) is hingedly installed on the upper end of the first brake lever (36), the second hinge seat (37) is fixedly installed on the protection device mounting seat (31), a first brake block (38) is installed on the first brake lever (36), a pulling rod (39) is further hingedly installed on the push connecting rod (33), a second brake lever (40) is hingedly installed on the other end of the pulling rod (39), a third hinge seat (41) is hingedly installed on the bottom end of the second brake lever (40), the third hinge seat (41) is fixedly installed on the right end of the protection device mounting seat (31), a second brake block (42) is installed on the second brake lever (40).

2. The system of claim 1, wherein: The trolley mounting frame (18) is square, a plurality of sliding support mechanisms (19) and a pair of protection devices (20) are installed on the trolley mounting frame (18); The sliding support mechanism (19) comprises a side shaft (21), a side bearing seat (22) and an angular contact bearing (23), the side bearing seat (22) is fixedly installed on the trolley mounting frame (18) through a hexagonal head bolt and a hexagonal head nut, the side shaft (21) is installed in the side bearing seat (22), the two ends of the side shaft (21) are provided with the angular contact bearing (23), and the outer ring of the angular contact bearing (23) is in contact with the model sliding guide rail (4).

3. The system according to claim 1 or 2, wherein: A cross roller collar (26) is installed on the trolley (6), the outer ring of the cross roller collar (26) is fixedly installed on the trolley (6) through a bolt, the inner ring of the cross roller collar (26) is fixedly provided with a model mounting seat (27) through a screw, the model mounting seat (27) is a square frame structure, a limiting rod (28) is installed on the model mounting seat (27), a pitch angle limiting seat (29) is installed on the trolley (6), a limiting groove is formed in the pitch angle limiting seat (29), and the limiting rod (28) is arranged in the limiting groove of the pitch angle limiting seat (29), and the airplane model (7) is fixedly installed on the model mounting seat (27).

4. The method of claim 1-3, wherein the method is implemented by the system of claim 1-3, and the method is characterized in that, The method comprises the following steps: Step 1. An inclination sensor and an angular rate gyroscope are installed at the center of gravity of the airplane model (7) designed according to the full machine dynamics similarity, for measuring the pitch angle and the pitch angular rate; acceleration sensors are installed at the left wing tip, the right wing tip, the left engine nacelle, the right engine nacelle, the nose of the airplane model (7) and the center of gravity of the airplane model (7), for measuring the vibration load of the left wing tip, the right wing tip, the left engine nacelle, the right engine nacelle, the nose and the airplane model; wing root strain gauges are pasted at the left wing root and the right wing root of the airplane model (7), for measuring the wing root bending moment; a displacement sensor is installed on the mounting seat (5) at the lower end of the support device (3), for measuring the heave motion amount of the airplane model (7); Step 2. Before the test, first start the wind speed of the wind tunnel, and after the wind speed reaches the preset value, start the gust generator (2), and the blades of the gust generator (2) move according to the specified swing angle, swing frequency and waveform; Step 3. When the gust disturbance reaches the airplane model (7), the acceleration sensors arranged at the left wing tip, the right wing tip and the center of gravity of the airplane model (7) measure the vibration load signals of the model, the inclination sensor and the angular rate gyroscope measure the pitch angle and the pitch angular rate of the airplane model (7), the above signals are calculated by a data acquisition and processing system to obtain the disturbance amount of the gust, and then the disturbance amount is transmitted to a model control surface system, the model control surface system drives the aileron and the flap to move, so as to generate a force opposite to the aerodynamic force brought by the gust, so as to achieve the effect of pitch attitude control, that is, the inner loop control, and the elastic body load is reduced. Step 4, while the inner loop control is being implemented in step 3, the displacement sensor measures the heave motion of the aircraft model (7) and transmits the measured data to the signal data acquisition and processing system, which calculates the heave motion and transmits the calculated heave motion to the model control system, which drives the elevator to move so that the model maintains a set height, i.e. the outer loop control, thereby achieving rigid body load alleviation; Step 5, compare the wing tip acceleration, wing root strain and model heave motion range before and after the implementation of the control in steps 2 and 3, if the wing tip acceleration and wing root strain are significantly reduced and the model heave motion is stable within a predetermined range after the implementation of the control, it indicates that the load alleviation effect of the current test meets the test requirements, the current test is ended, and the next test is performed, otherwise, the control surface parameters are continuously adjusted until the load alleviation effect that meets the test requirements is obtained.

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