Nonlinear support system and hypersonic velocity sweep / fixed frequency wind tunnel test method

Abstract

The invention discloses a nonlinear support system and a hypersonic velocity sweep / fixed frequency wind tunnel test method, and belongs to the technical field of wind tunnel tests. The device comprises a protection platform, a protection cover, a lifting platform, a vertical mounting plate, a protection cover shoulder split, a test model and a driving mechanism, the test model is mounted at the top of the vertical mounting plate through the driving mechanism, the vertical mounting plate is mounted on the lifting platform, the protection cover is mounted on the protection platform, and the protection cover shoulder split is arranged at the top of the protection cover. The vertical mounting plate and the driving mechanism are arranged in the protective cover; and the test model at the top of the vertical mounting plate extends out of the protective cover shoulder cleft of the protective cover. The technical problem that in an existing hypersonic wind tunnel test, structural nonlinear factors such as gaps, friction and collision between kinematic pairs of an executing mechanism are ignored due to a simplified supporting mode, and consequently the influence of the performance of the executing mechanism in a complex vibration environment cannot be truly reflected by a test result is solved. And a reliable test means is provided for revealing a structural nonlinearity and pneumatic nonlinearity coupling effect rule.

Description

A nonlinear support system and a hypersonic high-speed scanning / fixed-frequency wind tunnel testing method Technical Field

[0001] This invention relates to a nonlinear support system and a hypersonic high-speed scanning / fixed-frequency wind tunnel testing method, belonging to the field of wind tunnel testing technology. Background Technology

[0002] During flight, hypersonic vehicles' control surfaces, flaps, and other actuators are typically subjected to complex vibration environments with high frequencies and wide speed-pressure ranges. Various structural nonlinear factors, including clearances, friction, and collisions, exist between the kinematic pairs of these actuators. The coupling effect of these structural nonlinear factors with aerodynamic forces leads to complex nonlinear dynamic behavior in the vehicle, directly affecting its handling stability and control accuracy. This represents a key challenge in the research of aerodynamic-structural-control coupling problems in hypersonic vehicles.

[0003] Wind tunnel testing is an indispensable tool for studying the aerodynamic characteristics, structural response, and control performance of hypersonic vehicles. However, in existing hypersonic wind tunnel research both domestically and internationally, to simplify the test system and reduce implementation difficulty, the support method of the test object is often idealized, simplifying the kinematic pairs of the actuators to rigid connections or frictionless ideal constraints. This simplification of the support method makes it impossible for the test system to reproduce real structural nonlinear factors such as gaps, friction, and collisions between the kinematic pairs of the actuators. Consequently, the test results cannot accurately characterize the performance impact of the actuators under complex vibration environments, nor can they reveal the coupling law between structural nonlinearity and aerodynamic nonlinearity.

[0004] Therefore, there is an urgent need to propose a nonlinear support system and a hypersonic high-speed sweep / fixed-frequency wind tunnel testing method to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention addresses the technical problem in existing hypersonic wind tunnel tests where simplified support methods neglect structural nonlinear factors such as gaps, friction, and collisions between moving parts of the actuator, resulting in test results that fail to accurately reflect the performance of the actuator under complex vibration environments. This invention provides a nonlinear support system and its testing method that can directly incorporate these structural nonlinear factors into the wind tunnel testing process, thereby simulating the true dynamic environment of the actuator. This provides a reliable experimental means to reveal the coupling effects of structural and aerodynamic nonlinearities. A brief overview of this invention is provided below to offer a basic understanding of certain aspects of the invention. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention.

[0006] The technical solution of the present invention:

[0007] Option 1: A nonlinear support system, comprising a protective platform, a protective cover, a lifting platform, a vertical mounting plate, a protective cover shoulder, a test model, and a drive mechanism. The test model is mounted on the top of the vertical mounting plate via the drive mechanism. The vertical mounting plate is mounted on the lifting platform. The protective cover is mounted on the protective platform. The top of the protective cover has a protective cover shoulder. The vertical mounting plate and the drive mechanism are located inside the protective cover. The test model on the top of the vertical mounting plate protrudes outside the protective cover shoulder of the protective cover.

[0008] Preferably, the drive mechanism includes an upper half of the rudder shaft, an auxiliary top plate, a drive mechanism mounting base, a drive source, a lower half of the rudder shaft, a connecting rod, an upper bearing, a lower bearing, and a bearing cover. The drive mechanism mounting base is mounted on a vertical mounting plate via the auxiliary top plate. A drive source is mounted on the drive mechanism mounting base. The output end of the drive source is hinged to the connecting rod. The other end of the connecting rod is fixedly mounted on the bottom of the lower half of the rudder shaft. The top of the lower half of the rudder shaft is connected to the test model via the upper half of the rudder shaft. The lower half of the rudder shaft is rotatably connected to the drive mechanism mounting base via the upper and lower bearings. A bearing cover is mounted on the bottom of the lower bearing.

[0009] Preferably, the protective cover shoulder has a through groove to accommodate the test model, and a front top plate and a rear top plate are respectively installed on the front and rear sides of the through groove, with the upper half of the rudder shaft placed between the front top plate and the rear top plate.

[0010] Preferably, the protection platform includes a first front beam, a second front beam, a first mounting platform, a front connector of the mounting platform, a second mounting platform, a rear connector of the mounting platform, and a rear beam. The first and second mounting platforms are arranged side by side. The front ends of the first and second mounting platforms are connected by the front connector of the mounting platform, and the rear ends of the first and second mounting platforms are connected by the rear connector of the mounting platform. The first and second front beams are respectively installed on the front side of the first and second mounting platforms, and the rear beam is installed on the rear side of the first and second mounting platforms.

[0011] Option 2: A hypersonic scanning / fixed-frequency wind tunnel testing method for a nonlinear support system, based on the aforementioned nonlinear support system, includes the following steps:

[0012] Step S1: During the vacuuming phase before the test begins, place the test model inside a protective cover to protect it from flow field interference.

[0013] Step S2: Stabilize the wind tunnel flow field control system. After the high Mach number flow field in the wind tunnel stabilizes, extend the test model with actuators into the flow field through the lifting platform.

[0014] Step S3: During the duration of the stable flow field conditions, the drive source control system controls the drive source to act according to the preset drive function, driving the test model to perform frequency sweep or fixed frequency oscillation.

[0015] Step S4: During the operation of the test model, the sensor signals installed on the test model are collected synchronously through the acquisition system to obtain the response information of the model under complex vibration environment;

[0016] Step S5: After the signal acquisition is completed, the test model with the actuator is lowered into the protective cover by the lifting platform to complete a typical wind tunnel test procedure under sweep / fixed frequency conditions.

[0017] Preferably, the driving function of the driving source is set according to the duration of the flow field conditions, the travel time of the lifting platform, the required oscillation frequency range of the test model, and the sweep / fixed frequency working conditions.

[0018] Preferably, a signal synchronization triggering mechanism is established between the wind tunnel flow field control system, the drive source control system, and the acquisition system, wherein the synchronization triggering mechanism is any one of the following:

[0019] After the test model extends the protective cover and the protective cover shoulder, when the drive source is activated, the drive source control system synchronously transmits a trigger signal to the acquisition system, and the acquisition system receives the trigger signal and begins synchronous acquisition.

[0020] After the test model extends the protective cover and the protective cover shoulder, when the acquisition system starts to acquire data, it synchronously transmits a trigger signal to the drive source control system. Upon receiving the trigger signal, the drive source control system begins to synchronously perform drive actions according to the specified frequency function.

[0021] The wind tunnel flow field control system determines the position of the test model based on the flow field stability judgment result and the travel time of the lifting platform. At the same time, it synchronously transmits a trigger signal to the acquisition system and the drive source control system. Upon receiving the trigger signal, the acquisition system begins synchronous acquisition, and upon receiving the trigger signal, the drive source control system begins synchronous driving action according to the specified frequency function.

[0022] Preferred method: Before driving the test model to swing at a fixed frequency, the test time is divided into different time intervals according to the duration of the flow field conditions, the travel time of the lifting platform and the swing frequency range of the test model. Different time intervals correspond to different specified fixed frequencies, which are used as the driving frequency function of the driving source.

[0023] Once a stable flow field condition is established and the test model reaches the target position, the test model will perform periodic oscillations at a fixed frequency under the drive source within a specified time interval. During the operation, the sensor signals installed on the test model are collected by the acquisition system to obtain the response data of the test model under the fixed frequency condition. The drive source increases the drive frequency to the next fixed frequency point according to the preset drive frequency function until the test conditions of all fixed frequency points within the set drive frequency range are completed.

[0024] Preferred method: Before driving the test model to perform frequency sweeping oscillation, the sweeping frequency of the driving source is determined according to the duration of the flow field conditions, the travel time of the lifting platform, and the oscillation frequency range of the test model. After a stable flow field condition is established and the test model reaches the target position, the test model, driven by the driving source, performs reciprocating oscillation with increasing frequency within the oscillation frequency range at the set sweeping frequency. During the increase of the oscillation frequency, the sensor signals installed on the test model are collected by the acquisition system to obtain the response data of the model under the sweeping frequency condition.

[0025] Preferably, the sensors installed on the test model include acceleration sensors and / or pulsating pressure sensors.

[0026] The present invention has the following beneficial effects:

[0027] 1. This invention directly introduces the actuator, which includes structural nonlinear factors such as clearance, friction, and collision, into the wind tunnel test process. Compared with the traditional test method that simplifies the support method, it can more realistically reproduce the dynamic behavior of the actuator under actual flight conditions, so that the test results can more accurately reflect the impact of structural nonlinearity on the performance of the aircraft.

[0028] 2. This invention provides an effective experimental means for studying the coupling effect of structural nonlinearity and aerodynamic nonlinearity between kinematic pairs of actuators through coupling experiments of nonlinear support system and hypersonic flow field, which helps to reveal in depth the nonlinear dynamic mechanism of mutual coupling of aerodynamics-structure-control of hypersonic aircraft;

[0029] 3. This invention can realize both fixed-frequency tests and frequency sweep tests. By using a preset driving function, it can complete the data acquisition of multiple frequency points within a single flow field establishment cycle, which greatly improves the test efficiency and ensures the consistency of flow field conditions under different frequency conditions.

[0030] 4. This invention establishes multiple synchronous triggering mechanisms between the wind tunnel flow field control system, the drive source control system, and the acquisition system to ensure precise synchronization between model actions and data acquisition, effectively avoiding experimental errors caused by timing misalignment and improving the reliability and repeatability of experimental data;

[0031] 5. The present invention provides a protective cover and a protective cover shoulder structure. The test model is kept inside the protective cover before the wind picks up to avoid the impact of the flow field. After the flow field stabilizes, it is extended for testing. This effectively avoids damage to the model due to non-design loads during the establishment and destruction of the flow field, and ensures the safety of the test equipment and the model.

[0032] 6. This invention enables rapid lifting and lowering of the test model through a lifting platform. Combined with the wedge structure design of the protective cover, it ensures that the model is located within the Mach cone region after it extends, thus avoiding the impact of shock wave interference on the test results and ensuring the wind tunnel blockage requirements. Attached Figure Description

[0033] Figure 1 is a diagram showing the installation of a nonlinear support system; Figure 2 is a diagram showing the installation of the lifting platform and the vertical mounting plate; Figure 3 is a diagram showing the installation of the drive mechanism; Figure 4 is a diagram showing the installation of the protection platform; Figure 5 is a diagram showing the installation of the drive source and the connecting rod; Figure 6 is a diagram showing the usage state of the test model when it is located in the Mach cone region corresponding to the test Mach number; Figure 7 is a flowchart of a hypersonic sweep / fixed-frequency wind tunnel test method for a nonlinear support system; Figure 8 is a schematic diagram of the drive function for the fixed-frequency test described in Example 2; Figure 9 is a schematic diagram of the drive function for the sweep frequency test described in Example 2; Figure 10 is a schematic diagram of the timing of each system in the sweep / fixed-frequency test described in Example 2.

[0034] In the diagram, 1-first front beam, 2-second front beam, 3-first mounting platform, 4-front connector of mounting platform, 5-second mounting platform, 6-rear connector of mounting platform, 7-rear beam, 8-lifting platform, 9-vertical mounting plate, 10-protective cover, 11-shoulder of protective cover, 12-rear top plate, 13-front top plate, 14-upper half of rudder shaft, 15-test model, 16-auxiliary top plate, 17-drive mechanism mounting seat, 18-drive source, 19-lower half of rudder shaft, 20-connecting rod, 21-upper bearing, 22-lower bearing, 23-bearing cover. Detailed Implementation

[0035] 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.

[0036] Example 1: This embodiment, illustrated in Figures 1-6, provides a nonlinear support system for simulating structural nonlinear factors between kinematic pairs of actuators in hypersonic wind tunnel tests. The nonlinear support system includes a protective platform, a protective cover 10, a lifting platform 8, a vertical mounting plate 9, a protective cover shoulder 11, a test model 15, and a drive mechanism. The test model 15 is mounted on top of the vertical mounting plate 9 via the drive mechanism. The vertical mounting plate 9 is mounted on the lifting platform 8. The protective cover 10 is mounted on the protective platform, and the protective cover 10 has a protective cover shoulder 11 on its top. The vertical mounting plate 9 and the drive mechanism are located inside the protective cover 10, and the test model 15 protrudes from the protective cover shoulder 11 of the protective cover 10.

[0037] The lifting platform 8 is connected to the existing drive mechanism of the wind tunnel and can move up and down under the drive of the wind tunnel mechanism and within the design range of the wind tunnel mechanism. In this embodiment, the lifting platform 8 adopts a ball screw lifting mechanism driven by a servo motor, with a lifting stroke of 500mm, a positioning accuracy of ±0.1mm, and an adjustable lifting speed of 100mm / s.

[0038] As shown in Figures 2, 4, and 5, the drive mechanism includes the upper half of the rudder shaft 14, an auxiliary top plate 16, a drive mechanism mounting base 17, a drive source 18, the lower half of the rudder shaft 19, a connecting rod 20, an upper bearing 21, a lower bearing 22, and a bearing cover 23.

[0039] The drive mechanism mounting base 17 is mounted on the vertical mounting plate 9 via an auxiliary top plate 16, specifically by screw connection. The drive mechanism mounting base 17 is made of high-strength alloy steel and has an internal mounting cavity to accommodate the lower half of the rudder shaft 19 and the bearing assembly.

[0040] The drive source 18 is mounted on the drive mechanism mounting base 17. In this embodiment, the drive source 18 is a linear reciprocating motor, model LinMotP01-48×240, with a maximum thrust of 1200N and a maximum stroke of 240mm, capable of periodic reciprocating linear motion of a specified frequency function within the range of 0-50Hz. The output end of the drive source 18 is hinged to the connecting rod 20 via a cylindrical pin, and the other end of the connecting rod 20 is fixedly mounted to the bottom of the lower half 19 of the rudder shaft. The connecting rod 20 is made of titanium alloy with a hardened surface to ensure fatigue life under high-frequency reciprocating motion.

[0041] The lower half 19 of the rudder shaft is connected to the test model 15 via the upper half 14 of the rudder shaft. The upper half 14 of the rudder shaft and the test model 15 are positioned using a stop and fixed with screws; the lower half 19 of the rudder shaft and the upper half 14 of the rudder shaft are positioned using a key and fixed with screws; the lower half 19 of the rudder shaft and the connecting rod 20 are positioned using a stop and fixed with screws. This combination of multiple positioning and connection methods ensures the accuracy of motion transmission, while introducing structural nonlinearity factors through the fit clearance between the kinematic pairs.

[0042] The lower half 19 of the rudder shaft is rotatably connected to the drive mechanism mounting base 17 via upper bearing 21 and lower bearing 22, with connecting rod 20 positioned between the upper bearing 21 and lower bearing 22. Upper bearing 21 and lower bearing 22 are tapered roller bearings, model 32005, capable of simultaneously withstanding radial and axial loads, ensuring the smooth movement of the rudder shaft under high-speed oscillation. A bearing cover 23 is mounted on the bottom of the lower bearing 22, and the bearing cover 23 is connected to the drive mechanism mounting base 17 by screws for axial positioning and dust protection.

[0043] As shown in Figures 1 and 2, the protective shield shoulder wedge 11 has a through slot to accommodate the test model 15. A front top plate 13 and a rear top plate 12 are installed on the front and rear sides of the through slot, respectively, with the upper half 14 of the rudder shaft positioned between the front top plate 13 and the rear top plate 12. The front top plate 13 and the rear top plate 12 are streamlined to reduce interference with the wind tunnel flow field. When the test model 15 reaches the target position, the upper surfaces of the front top plate 13 and the rear top plate 12 are flush with the upper surface of the protective shield shoulder wedge 11, ensuring the continuity of the aerodynamic shape after the model extends.

[0044] The front of the protective shield's shoulder wedge 11 adopts a wedge structure design, with the wedge angle determined based on the experimental Mach number. In this embodiment, the experimental Mach number range is 4-7, and the wedge angle is designed to be less than the maximum value of 2×arcsin(1 / M). When M=4, arcsin(1 / 4)=14.48°, and the wedge angle is less than 28.96°; in this embodiment, 25° is chosen. When M=7, arcsin(1 / 7)=8.21°, and the wedge angle is less than 16.42°; in this embodiment, 15° is chosen. The two sides forming the wedge at the front of the protective shield have the same angle with the wind tunnel axis to ensure shock wave symmetry.

[0045] As shown in Figures 1 and 3, the protection platform includes a first front beam 1, a second front beam 2, a first mounting platform 3, a front connector 4, a second mounting platform 5, a rear connector 6, and a rear beam 7. The first mounting platform 3 and the second mounting platform 5 are arranged side-by-side. Their front ends are connected by the front connector 4, and their rear ends are connected by the rear connector 6. The first front beam 1 and the second front beam 2 are respectively installed on the front sides of the first mounting platform 3 and the second mounting platform 5, and the rear beam 7 is installed on the rear sides of the first mounting platform 3 and the second mounting platform 5. The first front beam 1, the second front beam 2, and the rear beam 7 are fixed to the existing wind tunnel structure with screws to ensure the rigidity and stability of the entire protection platform.

[0046] The first installation platform 3 and the second installation platform 5 are made of high-strength aluminum alloy sheets with anodized surfaces, providing excellent corrosion resistance and rigidity. The front connector 4 and the rear connector 6 of the installation platforms adopt an I-beam structure design to enhance overall rigidity.

[0047] In this embodiment, the components of the nonlinear support system and the model protection system meet the existing structural requirements of the test wind tunnel. The test wind tunnel is a hypersonic wind tunnel with a Mach number of 4-7 in the 1m range, and the test section size is 1m × 1m. After the test model 15, the nonlinear support system, and the model protection system are installed, the overall blockage is less than 5%, which meets the blockage requirements of the test wind tunnel.

[0048] As shown in Figure 6, during the experiment, after the test model 15 extends the protective cover shoulder wedge 11 under the action of the lifting platform 8, its position is located in the Mach cone region corresponding to the test Mach number, so as to avoid the model being disturbed by shock waves. In this embodiment, when the Mach number is 6, the half angle of the Mach cone is arcsin(1 / 6) = 9.6°. After the model extends, it is located near the wind tunnel axis, ensuring that it is completely within the uniform flow field region.

[0049] The nonlinear support system of this embodiment introduces structural nonlinear factors such as clearance and friction between the actuator kinematic pairs through the fit clearance between the upper half 14 of the rudder shaft and the test model 15, between the lower half 19 of the rudder shaft and the upper half 14 of the rudder shaft, between the lower half 19 of the rudder shaft and the connecting rod 20, and the friction when the bearing assembly is in operation, thereby simulating the dynamic environment of the actuator under real flight conditions.

[0050] Example 2: This embodiment is illustrated with reference to Figures 1-10. This embodiment provides a hypersonic scanning / fixed-frequency wind tunnel testing method for a nonlinear support system, based on the nonlinear support system described in Example 1. The nonlinear support system of this embodiment includes the following steps:

[0051] Step S1: Experiment Preparation Phase

[0052] During the vacuuming phase before the wind tunnel test begins, the test model 15 is placed inside the protective cover 10 to protect it from flow field interference. Specifically, the test model 15 is lowered to its lowest position using the lifting platform 8, ensuring that the test model 15 is completely inside the protective cover 10 and below the protective cover shoulder 11. The wind tunnel test section is then closed, and the vacuuming process begins.

[0053] In this embodiment, the test model 15 is a scaled-down model of the control surface of a certain type of hypersonic aircraft. The model material is high-strength alloy steel, and three acceleration sensors and four pulsating pressure sensors are installed on its surface. The driving function of the drive source 18 is preset according to the test requirements, and the specific setting method will be explained in detail in the subsequent step S3.

[0054] Step S2: Flow field establishment and model extension

[0055] After the wind tunnel flow field control system determines stability, and the high Mach number flow field in the wind tunnel stabilizes, the test model 15 with the actuator is extended into the flow field via the lifting platform 8.

[0056] In this embodiment, the test Mach number is 6, the total pressure is 2 MPa, and the total temperature is 550 K. The wind tunnel flow field control system determines the flow field stability by monitoring the stagnation point pressure and temperature. Flow field stability is determined when pressure fluctuations are less than ±0.5% and temperature fluctuations are less than ±1% for 3 seconds. After the flow field stabilizes, the lifting platform 8 is activated, raising the test model 15 upwards at a speed of 80 mm / s for 5 seconds (lifting height 400 mm). After the test model 15 extends beyond the protective cover shoulder wedge 11, its position is within the Mach cone region, ensuring flow field quality.

[0057] Step S3: Driving source motion and model oscillation

[0058] During the duration of the stable flow field conditions, the drive source 18 is controlled by the drive source control system to act according to the preset drive function, driving the test model 15 to perform frequency sweep or fixed frequency oscillation.

[0059] In this embodiment, the flow field stabilization duration is approximately 30 seconds, and the travel time of the lifting platform 8 is 5 seconds; therefore, the effective test time is approximately 25 seconds. The driving function of the driving source 18 is determined based on the flow field duration, the travel time of the lifting platform 8, the required oscillation frequency range of the test model, and the sweep / fixed frequency operating conditions. The specific setting method is as follows:

[0060] For the fixed-frequency test, the 25-second effective test time is divided into 5 time intervals, each lasting 5 seconds. These 5 time intervals correspond to fixed-frequency drive frequencies of 5Hz, 10Hz, 15Hz, 20Hz, and 25Hz, respectively, and are used as the drive frequency function of the drive source 18. Following a preset program, the drive source 18 drives the test model 15 to reciprocate at a frequency of 5Hz for the first 5 seconds, with an oscillation angle range of ±5°; it then drives it at a frequency of 10Hz for the second 5 seconds, and so on, until all preset frequency points are reached.

[0061] For the frequency sweep test, the sweep range is set to 5Hz-25Hz, the sweep time is 20 seconds, and the sweep frequency is 1Hz / s (i.e., the frequency increases linearly from 5Hz to 25Hz, increasing by 1Hz per second). The drive source 18 drives the test model 15 to perform reciprocating oscillations with increasing frequency within 20 seconds according to this sweep frequency, with an oscillation angle range of ±5°.

[0062] Step S4: Data Acquisition

[0063] During the operation of the test model 15, the sensor signals installed on the test model 15 are collected synchronously by the acquisition system to obtain the response information of the model under complex vibration environment.

[0064] In this embodiment, the sensors installed on the test model 15 include three accelerometers (model PCB352C68, range ±500g, frequency response 1-10kHz) and four pulsating pressure sensors (model KuliteXCQ-062, range 15psi, frequency response 0-50kHz). The data acquisition system uses an NIPXIe-1082 chassis with a PXIe-4499 acquisition card, and the sampling rate is set to 100kHz / channel to meet the requirements for high-frequency response signal acquisition.

[0065] Step S5: End of Experiment and Model Recovery

[0066] After the signal acquisition is completed, the test model 15 with the actuator is lowered into the protective cover 10 via the lifting platform 8, thus completing a typical wind tunnel test process under sweep / fixed frequency conditions.

[0067] In this embodiment, after data acquisition is completed, the lifting platform 8 immediately begins its descent, retracting the test model 15 into the protective cover 10 at a speed of 100 mm / s, with a descent time of 4 seconds. After the model is fully retracted, the wind tunnel control system executes the shutdown procedure, ending the wind tunnel test.

[0068] In this embodiment, a signal synchronization triggering mechanism is established between the wind tunnel flow field control system, the drive source control system, and the data acquisition system to ensure precise synchronization between model movements and data acquisition. This embodiment employs one of the following three synchronization triggering mechanisms:

[0069] Synchronous triggering method (1) (drive source triggering): After the test model 15 extends the protective cover 10 and the protective cover shoulder wedge 11, when the drive source 18 is activated, the drive source control system synchronously transmits a 5VTTL step signal to the acquisition system. After receiving the trigger signal, the acquisition system immediately starts synchronous acquisition. This method is used in this embodiment. The trigger signal is triggered on the rising edge, and the trigger delay is less than 10μs.

[0070] Synchronous triggering mode (2) (acquisition system trigger): After the test model 15 extends the protective cover 10 and the protective cover shoulder 11, when the acquisition system starts to acquire data, it synchronously transmits a trigger signal to the drive source control system. After receiving the trigger signal, the drive source control system immediately starts to synchronously perform drive actions according to the specified frequency function.

[0071] Synchronous triggering mode (3) (flow field control system trigger): The wind tunnel flow field control system determines the extension of the test model 15 to the designated position based on the flow field stability judgment result and the travel time of the lifting platform 8. At the same time, it synchronously transmits the trigger signal to the acquisition system and the drive source control system. The acquisition system receives the trigger signal and starts synchronous acquisition. The drive source control system receives the trigger signal and starts synchronously driving according to the specified frequency function.

[0072] As shown in Figure 10, which illustrates the timing of each system in the sweep / fixed frequency test, the timing control of the sweep and fixed frequency tests in this embodiment is achieved through the coordinated operation of the wind tunnel flow field control system, the drive source control system, and the acquisition system. Figure 10 clearly shows the complete timing flow from flow field establishment, model extension, multi-frequency point driving and acquisition, model retraction, to the end of the flow field test.

[0073] As shown in Figure 8, the specific implementation steps of the fixed-frequency test in this embodiment are as follows:

[0074] 1. Driving function setting: Based on the duration of the flow field conditions (30 seconds), the travel time of the lifting platform 8 (5 seconds), and the oscillation frequency range of the test model (5Hz-25Hz), the effective test time of 25 seconds is divided into 5 time intervals, each interval being 5 seconds, corresponding to fixed frequencies of 5Hz, 10Hz, 15Hz, 20Hz, and 25Hz respectively, which are used as the driving frequency function of the driving source 18.

[0075] 2. Flow field establishment: After confirming the model state, the wind tunnel is closed, and the blowing test conditions are given (Mach number 6, velocity pressure 50kPa). After the flow field stabilizes, the test model 15 with the actuator is extended into the flow field by the lifting platform 8.

[0076] 3. Fixed-Frequency Oscillation and Data Acquisition: After the test model 15 reaches the target position, during the first 5-second time interval, the drive source 18 drives the test model 15 to oscillate periodically at a frequency of 5Hz (oscillation angle ±5°), and the acquisition system simultaneously acquires acceleration and pulsating pressure signals. After 5 seconds, the drive source 18 pauses its operation, and after a 1-second interval, it enters the second 5-second time interval, driving at a frequency of 10Hz, and the acquisition system continues to acquire data. This process continues until the test conditions at 5 fixed-frequency points (5Hz, 10Hz, 15Hz, 20Hz, and 25Hz) are completed.

[0077] 4. Model recovery: After completing all fixed-frequency point tests, the drive source 18 returns to zero position, and the test model 15 is lowered into the protective cover 10 by the lifting platform 8, and the wind tunnel stops.

[0078] 5. Repeat the test: Change the next target blowing test conditions (such as Mach number 5, velocity pressure 40kPa) and repeat the above steps until all the desired fixed frequency test data are obtained.

[0079] As shown in Figure 9, the specific implementation steps of the frequency sweep test in this embodiment are as follows:

[0080] 1. Driving function setting: Based on the duration of the flow field conditions (30 seconds), the travel time of the lifting platform 8 (5 seconds), and the oscillation frequency range of the test model (5Hz-25Hz), the sweep frequency time is determined to be 20 seconds and the sweep frequency is 1Hz / s. That is, the driving source 18 linearly increases the driving frequency from 5Hz to 25Hz within 20 seconds at a rate of 1Hz / s.

[0081] 2. Flow field establishment: After confirming the model state, the wind tunnel is closed, and the blowing test conditions are given (Mach number 6, velocity pressure 50kPa). After the flow field stabilizes, the test model 15 with the actuator is extended into the flow field by the lifting platform 8.

[0082] 3. Frequency sweeping and acquisition: After the test model 15 reaches the target position, the drive source 18 is started and performs reciprocating swing with a sweeping frequency of 1Hz / s in the range of 5Hz-25Hz (swing angle ±5°). During the swing, the acquisition system continuously acquires acceleration and pulsating pressure signals for 20 seconds.

[0083] 4. Model recovery: After the frequency sweep is completed, the drive source 18 returns to zero position, and the test model 15 is lowered into the protective cover 10 by the lifting platform 8, and the wind tunnel stops.

[0084] 5. Repeat the test: Change the next target blowing test conditions (e.g., Mach number 5, velocity pressure 40 kPa) and repeat the above steps until all the desired sweep frequency test data are obtained.

[0085] In this embodiment, the response data acquired by the acquisition system includes time-domain acceleration signals and pulsating pressure signals. After the experiment, the dynamic response characteristics of the experimental model 15 under different frequency excitations are obtained through methods such as spectrum analysis and transfer function identification, and the influence of structural nonlinear factors on aeroelastic properties is analyzed.

[0086] Taking a frequency sweep test as an example, the collected acceleration signal, after FFT transformation, showed obvious resonance peaks near 8Hz, 15Hz, and 22Hz, which deviated from the modal frequencies calculated by linear theory. This reflects the influence of nonlinear factors such as clearance and friction of the actuator's kinematic pairs on the system's dynamic characteristics. By comparing experimental data under different speeds, pressures, and Mach numbers, the coupling effect between aerodynamic nonlinearity and structural nonlinearity can be further analyzed.

[0087] The experimental method described in this embodiment applies a nonlinear support system based on the actuator to hypersonic wind tunnel tests. The resulting hypersonic sweep / fixed-frequency wind tunnel test can more realistically characterize the impact of nonlinear factors of the actuator on the performance of the test object under complex vibration environments. It makes up for the shortcomings of neglecting the nonlinear factors of the gap, friction, and collision structure between the kinematic pairs of the actuator due to the simplification of support conditions. It lays a solid foundation for revealing the coupling law of structural nonlinearity and aerodynamic nonlinearity between the kinematic pairs of the actuator and for in-depth research on the nonlinear dynamics and control problems of the aerodynamic-structure-control mutual coupling of hypersonic vehicles.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A nonlinear support system, characterized in that: The device includes a protective platform, a protective cover (10), a lifting platform (8), a vertical mounting plate (9), a protective cover shoulder (11), a test model (15), and a drive mechanism. The test model (15) is mounted on the top of the vertical mounting plate (9) via the drive mechanism. The vertical mounting plate (9) is mounted on the lifting platform (8). The protective cover (10) is mounted on the protective platform. The protective cover (10) has a protective cover shoulder (11) on its top. The vertical mounting plate (9) and the drive mechanism are located inside the protective cover (10). The test model (15) on the top of the vertical mounting plate (9) protrudes outside the protective cover shoulder (11) of the protective cover (10).

2. The nonlinear support system according to claim 1, characterized in that: The drive mechanism includes an upper half of the rudder shaft (14), an auxiliary top plate (16), a drive mechanism mounting base (17), a drive source (18), a lower half of the rudder shaft (19), a connecting rod (20), an upper bearing (21), a lower bearing (22), and a bearing cover (23). The drive mechanism mounting base (17) is mounted on a vertical mounting plate (9) via the auxiliary top plate (16). The drive source (18) is mounted on the drive mechanism mounting base (17). The output end of the drive source (18) is hinged to the connecting rod (20). The other part of the connecting rod (20) is fixedly mounted at the bottom of the lower half of the rudder shaft (19). The top of the lower half of the rudder shaft (19) is connected to the test model (15) via the upper half of the rudder shaft (14). The lower half of the rudder shaft (19) is rotatably connected to the drive mechanism mounting base (17) via the upper bearing (21) and the lower bearing (22). The bottom of the lower bearing (22) is equipped with a bearing cover (23).

3. A nonlinear support system according to claim 1, characterized in that: The protective cover shoulder wedge (11) has a through slot to accommodate the test model (15) through which it passes. A front top plate (13) and a rear top plate (12) are installed on the front and rear sides of the through slot, respectively. The upper half (14) of the rudder shaft is placed between the front top plate (13) and the rear top plate (12).

4. A nonlinear support system according to claim 1, characterized in that: The protection platform includes a first front beam (1), a second front beam (2), a first mounting platform (3), a front connector (4) of the mounting platform, a second mounting platform (5), a rear connector (6) of the mounting platform, and a rear beam (7). The first mounting platform (3) and the second mounting platform (5) are arranged side by side. The front ends of the first mounting platform (3) and the second mounting platform (5) are connected by the front connector (4) of the mounting platform, and the rear ends of the first mounting platform (3) and the second mounting platform (5) are connected by the rear connector (6) of the mounting platform. The first front beam (1) and the second front beam (2) are respectively installed on the front side of the first mounting platform (3) and the second mounting platform (5), and the rear beam (7) is installed on the rear side of the first mounting platform (3) and the second mounting platform (5).

5. A hypersonic sweep / fixed-frequency wind tunnel testing method for a nonlinear support system, implemented based on the nonlinear support system described in claim 4, characterized in that... The process includes the following steps: Step S1: During the vacuuming stage before the test starts, the test model (15) is placed inside the protective cover (10) to prevent it from being disturbed by the flow field; Step S2: The wind tunnel flow field control system determines the stability. After the high Mach number flow field in the wind tunnel stabilizes, the test model (15) with the actuator is extended into the flow field through the lifting platform (8); Step S3: During the duration of the stable flow field conditions, the drive source control system controls the drive source (18) to act according to the preset drive function, driving the test model (15) to perform frequency sweep or fixed frequency swing; Step S4: During the action of the test model (15), the sensor signals installed on the test model (15) are collected synchronously through the acquisition system to obtain the response information of the model under complex vibration environment; Step S5: After the signal acquisition is completed, the test model (15) with the actuator is lowered into the protective cover (10) through the lifting platform (8) to complete a typical wind tunnel test process under sweep / fixed frequency conditions.

6. The hypersonic scanning / fixed-frequency wind tunnel testing method for a nonlinear support system according to claim 5, characterized in that: The driving function of the driving source (18) is set according to the duration of the flow field conditions, the travel time of the lifting platform (8), the required swing frequency range of the test model, and the sweep / fixed frequency working conditions.

7. The hypersonic scanning / fixed-frequency wind tunnel testing method for a nonlinear support system according to claim 5, characterized in that: A signal synchronization triggering mechanism is established between the wind tunnel flow field control system, the drive source control system and the acquisition system. The synchronization triggering mechanism is any one of the following: (1) After the test model (15) extends the protective cover (10) and the protective cover shoulder wedge (11), when the drive source (18) moves, the drive source control system synchronously transmits a trigger signal to the acquisition system, and the acquisition system receives the trigger signal and starts synchronous acquisition; (2) After the test model (15) extends the protective cover (10) and the protective cover shoulder wedge (11), when the acquisition system starts acquisition, it synchronously transmits a trigger signal to the drive source control system, and the drive source control system receives the trigger signal and starts synchronously driving according to the specified frequency function; (3) The wind tunnel flow field control system determines the position of the test model (15) based on the flow field stability judgment result and the travel time of the lifting platform (8), and synchronously transmits a trigger signal to the acquisition system and the drive source control system. When the acquisition system receives the trigger signal, it starts synchronous acquisition, and when the drive source control system receives the trigger signal, it starts synchronously driving according to the specified frequency function.

8. The hypersonic sweep / fixed-frequency wind tunnel test method for a nonlinear support system according to claim 6, characterized in that: Before the test model (15) swings at a fixed frequency, the test time is divided into different time intervals according to the duration of the flow field conditions, the travel time of the lifting platform (8) and the swing frequency range of the test model. Different time intervals correspond to different specified fixed frequencies, which are used as the driving frequency function of the driving source (18). After a stable flow field condition is established and the test model (15) reaches the target position, the test model (15) swings periodically at a fixed frequency under the drive of the driving source (18) within the specified time interval. During the operation, the sensor signals installed on the test model (15) are collected by the acquisition system to obtain the response data of the test model (15) under the fixed frequency condition. The driving source (18) increases the driving frequency to the next fixed frequency point according to the preset driving frequency function until the test conditions of all fixed frequency points within the set driving frequency range are completed.

9. The hypersonic sweep / fixed-frequency wind tunnel test method for a nonlinear support system according to claim 6, characterized in that: Before the test model (15) performs a frequency sweeping swing, the sweeping frequency of the driving source is determined according to the duration of the flow field conditions, the travel time of the lifting platform (8) and the swinging frequency range of the test model (15). After a stable flow field condition is established and the test model (15) reaches the target position, the test model (15) is driven by the driving source (18) to perform a reciprocating swing with an increasing frequency within the swinging frequency range at the set sweeping frequency. During the increase of the swinging frequency, the sensor signals installed on the test model (15) are collected by the acquisition system to obtain the response data of the model under the sweeping frequency condition.

10. The hypersonic scanning / fixed-frequency wind tunnel testing method for a nonlinear support system according to claim 5, characterized in that: The sensors installed on the test model (15) include an acceleration sensor and / or a pulsating pressure sensor.

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