A method for indirectly measuring aerodynamic force of a magnetic levitation flight wind tunnel

Abstract

This invention relates to an indirect measurement method for aerodynamic forces in a maglev wind tunnel, comprising the steps of: providing a test environment and an object to be tested, wherein the test environment includes: a maglev platform providing magnetic force to the object to be tested; obtaining the center of gravity of the object to be tested and the maglev platform; setting a first sensor and a second sensor at the center of gravity of the object to be tested and the maglev platform, respectively; when the object to be tested begins to move based on preset test conditions, acquiring first sensing data and second sensing data based on the first and second sensors, and determining a first vibration acceleration and a second vibration acceleration based on the first and second sensing data; and determining the aerodynamic forces of the object to be tested based on the first and second vibration accelerations and a pre-acquired aerodynamic model. This method is simple to operate, has high accuracy, and is unaffected by speed and vibration time-frequency characteristics.

Description

Technical Field

[0001] This invention relates to the field of wind tunnel testing technology, and specifically to an indirect method for measuring the aerodynamic forces in a maglev flight wind tunnel. Background Technology

[0002] The measurement of aerodynamic forces in vehicles such as aircraft and high-speed trains is a crucial step in their research and development. In traditional force measurement tests using balances, the object to be measured is typically mounted on a balance to test its aerodynamic forces; examples include six-component balances, lever balances, and magnetic levitation balances. However, these balance-based measurement methods often have limitations. For instance, wind tunnel-based force measurement methods are often only suitable for measuring the aerodynamic forces of static aircraft or trains. Furthermore, due to the limited range of the balance, even when applied to moving vehicles, the balance struggles to maintain stable operation during acceleration, deceleration, or high-speed operation.

[0003] For example, Chinese patent application CN201811083944.4 discloses a method for measuring the six-component aerodynamic forces of a high-speed train dynamic model. This method still relies on a balance, thus inevitably incurring the limitations of balance-based force measurement. Furthermore, this method uses an air cannon to assist the train's departure, meaning the high-speed train is already decelerating after departure, and the method can only measure the aerodynamic forces during deceleration. In addition, the dynamics of this method require consideration of the wheel-rail contact relationship, which is difficult to measure in practice; moreover, the wheel-rail contact relationship simulated in experiments differs from actual application scenarios, potentially further increasing the error in aerodynamic force measurement. Summary of the Invention

[0004] To partially solve or alleviate the above-mentioned technical problems, this invention provides an indirect method for measuring the aerodynamic forces of a magnetic levitation flight wind tunnel, comprising the following steps:

[0005] Provide a test environment and an object to be tested, wherein the test environment includes a magnetic levitation platform that provides magnetic force to the object to be tested;

[0006] Obtain the center of gravity of the object under test and the magnetic levitation platform;

[0007] A first sensor and a second sensor are respectively installed at the center of gravity of the object to be measured and the center of gravity of the magnetic levitation platform;

[0008] When the object under test starts to move based on the preset test conditions, the first sensing data and the second sensing data are acquired based on the first and second sensors respectively, and the first vibration acceleration and the second vibration acceleration are determined based on the first sensing data and the second sensing data.

[0009] The aerodynamic forces of the object under test are determined based on the first and second vibration accelerations and the pre-acquired aerodynamic model.

[0010] In some embodiments, the step of establishing the aerodynamic model includes:

[0011] Acquire data from the first and second sensors, and determine the external forces acting on the object under test based on numerical integration. The external forces include aerodynamic force, levitation force, and the gravity of the object under test.

[0012] The force relationship of the object under test is determined based on the connection relationship between the object under test and the magnetic levitation platform;

[0013] The aerodynamic model of the object under test is determined based on the external force conditions and force relationships.

[0014] In some embodiments, the calculation model for the external force condition is as follows:

[0015] .

[0016] Where m' is the mass matrix of the object under test and the magnetic levitation platform. Let be the vibration acceleration matrix of the object under test and the magnetic levitation platform, c be the damping characteristic of the system, and k be the stiffness characteristic matrix of the object under test. Let F be the vibration acceleration of the object under test, x be the vibration displacement of the object under test, and F be the displacement of the object under test. (t) This refers to the external forces acting on the object under test.

[0017] In some embodiments, the aerodynamic model is established based on simulation experiments; correspondingly, the method further includes the following steps:

[0018] A magnetic levitation drive dynamics model was established based on the multibody dynamics method to provide the test environment.

[0019] Establish a simulation model of the object to be tested, wherein the aerodynamic center of the simulation model coincides with the center of gravity of the simulation model.

[0020] In some embodiments, the aerodynamic model is:

[0021] .E x =F T -ma x -m1a 1z

[0022] .F y =ma y 10F yMag 10m1a 1y

[0023] .F z =ma z 10mg 10m1a z 10m1g1F zMag

[0024] Among them, F x F y and F z These are the aerodynamic components of the object under test in three directions, F. T Let m be the traction force, m be the mass of the object under test, m1 be the mass of the magnetic levitation platform, and a be the mass of the maglev platform. x a y a z Let a be the vibration acceleration of the object under test in the x, y, and z axes. 1x a 1y Let F be the vibration acceleration of the magnetic levitation platform in the x and y axes. yMag F is the levitation force in the y-axis direction. zMag Let g be the levitation force along the z-axis, and g be the gravitational acceleration.

[0025] In some embodiments, the first sensor is a vibration acceleration sensor, and / or a displacement sensor, and / or a velocity sensor.

[0026] In some embodiments, the second sensor is a vibration acceleration sensor, and / or a displacement sensor, and / or a velocity sensor.

[0027] In some embodiments, the sampling frequency of the vibration acceleration sensor is not less than 2000 Hz.

[0028] In some embodiments, the object to be tested is connected to the magnetic levitation platform via a support mechanism, and one end of the support mechanism connected to the object to be tested is located at the center of gravity of the object to be tested.

[0029] In some embodiments, the first sensing data includes: sensing data measured by the first sensor when the object under test is in the process of acceleration, constant speed and deceleration;

[0030] In some embodiments, the second sensing data includes sensing data measured by the second sensor during acceleration, constant speed, and deceleration of the maglev platform.

[0031] Beneficial technical effects:

[0032] This invention measures the vibration acceleration of the object under test and the magnetic levitation platform using sensors (such as vibration acceleration sensors), and obtains the magnitude of the aerodynamic force on the object under test based on the acquired vibration acceleration and a pre-established aerodynamic model. Unlike existing technologies, this invention does not directly measure the aerodynamic force, but rather indirectly determines the aerodynamic force applied to the object under test by measuring the effect of the force applied (e.g., the vibration state of the object). Furthermore, this method is based on testing the object under test during movement; therefore, the final measured value is the transient aerodynamic force of the moving object.

[0033] Because this invention indirectly determines aerodynamic forces by measuring vibration acceleration, it eliminates the reliance on a force balance in aerodynamic force measurement (i.e., it abandons the traditional balance measurement method). Therefore, even when the vibration of the object under test is large and the time-varying characteristics of its physical quantities are severe during high-speed, acceleration, or deceleration tests, this indirect measurement method can still proceed normally and obtain reliable and accurate measurement results. In other words, the method provided by this invention is not affected by the vibration of the object under test or the time-varying characteristics of its physical quantities, and it can be applied to a wider velocity testing range (i.e., this method has a wide velocity range).

[0034] Meanwhile, the aerodynamic indirect measurement method provided by this invention utilizes a magnetically levitated wind tunnel capable of conducting transient aerodynamic tests. It employs magnetic levitation technology to drive the object under test, thereby simulating a "body-driven, wind-static" (i.e., the air is stationary while the object under test is moving) motion environment. Furthermore, this method allows for relatively flexible changes to parameters such as the vacuum state and gas density within the wind tunnel, providing various test environments to meet the needs of different types of objects under test or different testing requirements.

[0035] Furthermore, since the method proposed in this invention uses a maglev wind tunnel as the test environment, the speed of an object moving in the maglev wind tunnel can range from 0 to Mach 1 (i.e., one times the speed of sound). This means the maglev wind tunnel covers the functions of low-speed wind tunnels, subsonic wind tunnels, and even some supersonic wind tunnels. Compared to existing technologies that require designing different types of wind tunnels based on the Mach number of the airflow to achieve testing in different speed ranges, the method of this invention can achieve testing in different speed ranges using a single maglev wind tunnel. This is simpler to operate, easier to implement, and has lower testing costs. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. The elements or parts in the drawings are not necessarily drawn to scale. Obviously, the drawings described below are some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0037] . Figure 1a This is a flowchart illustrating a method in an exemplary embodiment of the present invention;

[0038] . Figure 1b This is a schematic diagram of the process of establishing an aerodynamic model in an exemplary embodiment of the present invention;

[0039] . Figure 2 It reflects Figure 1a The flowchart of the method shown in the simulation process is illustrated.

[0040] . Figure 3 It reflects Figure 1a The flowchart of the method shown is illustrated in the actual measurement process;

[0041] . Figure 4a yes Figure 2 A side view of the magnetic levitation flight wind tunnel dynamics platform in the method shown;

[0042] . Figure 4b yes Figure 2 A front view of the magnetic levitation flight wind tunnel dynamics platform in the method shown;

[0043] . Figure 4c Reflects Figure 4a The external forces acting on the object under test;

[0044] . Figure 4d Reflects Figure 4b The external forces acting on the object under test;

[0045] . Figure 5a The results show the vertical inertial force test of the suspension frame at a speed of 1000 km / h.

[0046] . Figure 5b The results are the vertical levitation force test results at a speed of 1000 km / h;

[0047] . Figure 5c The results show the vertical inertial force test of the object under test at a speed of 1000 km / h.

[0048] . Figure 5dThe results are from aerodynamic lift tests at a speed of 1000 km / h.

[0049] . Figure 6a The results show the vertical inertial force test of the suspension frame at a speed of 500 km / h.

[0050] . Figure 6b The results are from a vertical levitation force test at a speed of 500 km / h.

[0051] . Figure 6c The results show the vertical inertial force test of the object under test at a speed of 500 km / h.

[0052] . Figure 6d The results are from aerodynamic lift tests at a speed of 500 km / h.

[0053] .01 is the simulation model, 02 is the pipeline, 03 is the maglev platform (magnetic suspension platform), 04 is the support mechanism, and 05 is the magnetic suspension track. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0055] In this document, suffixes such as "module," "part," or "unit" used to denote elements are used only for the purpose of illustrative purposes and have no specific meaning in themselves. Therefore, "module," "part," or "unit" may be used interchangeably.

[0056] In this document, the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0057] In this document, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," and "linked" should be interpreted broadly. For example, "linked" can refer to a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a wireless connection or a wireless connection; it can be a direct connection or an indirect connection through an intermediate medium; or it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0058] Example 1

[0059] See also Figures 1a-3 This invention provides an indirect method for measuring the aerodynamic forces of a magnetic levitation flight wind tunnel, such as... Figure 1a The method includes the following steps:

[0060] S1 provides the test environment and the object under test, wherein the test environment includes a magnetic levitation platform that provides magnetic force to the object under test;

[0061] S3 obtains the center of gravity of the object under test and the magnetic levitation platform;

[0062] S5. A first sensor and a second sensor are respectively installed at the center of gravity of the object to be measured and the center of gravity of the magnetic levitation platform;

[0063] S7 When the object under test starts to move based on the preset test conditions, the first sensing data and the second sensing data are acquired based on the first and second sensors respectively, and the first vibration acceleration and the second vibration acceleration are determined based on the first and second sensing data.

[0064] S9 determines the aerodynamic forces of the object under test based on the first and second vibration accelerations and the pre-acquired aerodynamic model.

[0065] In some embodiments, the object under test can be a vehicle such as an aircraft or a high-speed train.

[0066] In some embodiments, the preset test conditions include: preset velocity and preset acceleration of the object under test, as well as magnetic levitation parameters provided by the magnetic levitation platform. Based on the selection of test conditions, the stress state of the object under test under different working conditions can be simulated.

[0067] In some embodiments, the first and second sensors can be vibration acceleration sensors or laser acceleration sensors, etc. Accordingly, the first and second sensor data are the vibration accelerations of the object under test and the magnetic levitation platform, respectively. The vibration acceleration can include vibration acceleration decomposed in multiple directions (such as three directions). It is understood that the first and second sensors only need to be able to measure the vibration accelerations of the object under test and the magnetic levitation platform.

[0068] Alternatively, in some embodiments, the vibration acceleration of the object under test and the maglev platform can be determined based on the data measured by the first and second sensors. For example, the sensors can also be displacement sensors or velocity sensors, etc. Accordingly, the first and second sensor data are the displacement or velocity of the object under test and the maglev platform, respectively. Based on the measured displacement or velocity of the object under test and the maglev platform in each direction, the vibration acceleration of the object under test and the maglev platform in each direction can be further calculated. Furthermore, the first and second sensors can be of the same type or different types.

[0069] Specifically, in some embodiments, when using velocity or displacement sensors for measurement, a sensor with a higher sampling frequency than the vibration sensor needs to be selected to ensure the corresponding test accuracy. Specifically, the acceleration signal can be obtained by calculating the first derivative of the sensor data obtained from the velocity sensor, and the acceleration information of the vibration sensor can be obtained by calculating the second derivative of the sensor data obtained from the displacement sensor.

[0070] This embodiment provides an indirect aerodynamic measurement method based on a maglev-driven flight wind tunnel. This method only requires placing sensors (preferably vibration acceleration sensors) at the center of gravity of the object under test and the maglev platform to obtain the vibration acceleration of the object and the maglev platform. Based on the obtained vibration acceleration and a pre-acquired aerodynamic model, the transient aerodynamic forces of the object under test can be deduced. Furthermore, key aerodynamic parameters such as drag and lift of the object under test can be easily obtained for subsequent application and design in aircraft or trains. It is understood that the method provided in this embodiment can be implemented in a simulation environment or tested in an actual maglev-driven flight wind tunnel.

[0071] Furthermore, in some embodiments, such as Figure 1b As shown, the steps for establishing an aerodynamic model include:

[0072] S11 acquires data from the first and second sensors and determines the external forces acting on the object under test based on numerical integration. The external forces include the aerodynamic force, levitation force, and gravity acting on the object under test.

[0073] S13. The force relationship of the object under test is determined based on the connection relationship between the object under test and the magnetic levitation platform;

[0074] S15 determines the aerodynamic model of the object under test based on the external force conditions and force relationships.

[0075] The weight of the object to be tested can be obtained by weighing it before the test.

[0076] Preferably, the aerodynamic model of the object under test is pre-determined through simulation experiments. Then, based on the experimental conditions in the simulation experiments (such as the connection relationship between the object under test and the maglev platform), corresponding actual tests are carried out. During the actual tests, the aerodynamic forces acting on the object under test are determined based on the vibration acceleration of the object under test and the maglev platform and the aerodynamic model established in the simulation. Accordingly, the method further includes the following steps:

[0077] A magnetic levitation drive dynamics model was established based on the multibody dynamics method to provide the test environment.

[0078] Establish a simulation model of the object to be tested, wherein the aerodynamic center of the simulation model coincides with the center of gravity of the simulation model.

[0079] For example, in some embodiments, the magnetic levitation drive dynamics model and the simulation model of the object under test can be established using existing multibody dynamics software, such as SIMPACK (a multibody dynamics analysis software package) and UM (Universal Mechanism). Alternatively, in other embodiments, the modeling can be completed by writing a program based on multibody dynamics methods and modeling characteristics, which is also feasible for those skilled in the art.

[0080] In some specific embodiments, the magnetic levitation flight wind tunnel dynamics platform, such as Figure 4a and 4b As shown, the pipe has a diameter of 6m and a length of 1km. In the simulation environment, the maglev drive dynamics model should preferably include detailed dynamic parameters consistent with the maglev platform, including information such as the maglev platform's mass, moment of inertia, spatial position, suspension characteristics, and external aerodynamic inputs. The coordinate system of the simulation environment adopts the orbital coordinate system (e.g., [missing information]). Figure 4a , Figure 4b As shown, this facilitates the establishment of a maglev drive dynamics model. Specifically, the maglev drive dynamics model includes a pipe 02 that provides a movement path for the simulation model 01, a maglev platform 03 simulated in the middle of the pipe, and a maglev track 05 below the maglev platform 03 that is simulated to provide a movement path for the maglev platform.

[0081] When establishing a simulation model of the object under test, the aerodynamic forces acting on the object are considered as concentrated forces in three directions (i.e., the X, Y, and Z axes), including: aerodynamic drag (i.e., the force F acting in the opposite direction to the motion of the object under test). Z Aerodynamic lift (i.e., the aerodynamic force F in the vertical direction) Z Lateral force (i.e., the force F) yIn this embodiment, the point of application of the aerodynamic force is assumed to be at the aerodynamic center of the object under test (i.e., the point where the resultant torque remains unchanged), and the aerodynamic center is assumed to coincide with the center of gravity of the object under test, thus no aerodynamic torque is generated.

[0082] Furthermore, a virtual vibration acceleration sensor is placed at the center of gravity of the object under test and at the center of gravity of the magnetic levitation platform, and the sampling frequency of the vibration acceleration sensor should be at least 2000Hz.

[0083] Subsequently, the vibration acceleration and external forces acting on each moving component (including the maglev platform and the object under test, which are involved in dynamics) can be solved based on numerical integration, thus providing data for subsequent reverse aerodynamic thrust. Numerical integration can be performed using multibody dynamics software such as SIMPACK and UM, or it can be implemented by a person skilled in the art through programming.

[0084] For example, in some embodiments, the calculation model for the external forces acting on the object under test is as follows:

[0085] .

[0086] Where m' is the mass matrix of the object to be measured and the magnetic levitation platform. Let be the vibration acceleration matrix of the object under test and the magnetic levitation platform, c be the damping characteristic of the system (the system consisting of the object under test and the test environment), and k be the stiffness characteristic matrix of the object under test. Let F be the vibration acceleration of the object under test, x be the vibration displacement of the object under test, and F be the vibration displacement of the object under test. (t) External time incentive, i.e. F (t) This reflects the external force acting on the object under test (in this embodiment, F). (t) This refers to all forces acting on the object under test at different times, including aerodynamic forces, magnetic levitation forces, and the object's gravity.

[0087] Where m', c, and k are inherent properties of the object or magnetic platform under test, which can be obtained directly. x can be obtained or calculated based on measurement data from vibration acceleration sensors or other types of sensors (such as displacement sensors).

[0088] Furthermore, based on the connection between the object under test and the maglev platform, the force relationship of the object under test is determined (e.g., force analysis is performed on the object under test to determine the force state of the object under test in different directions). Subsequently, based on the force relationship of the object under test and the external forces acting on the object (e.g., the total force acting on the object, such as aerodynamic force, maglev force, and gravity), the aerodynamic force acting on the object is obtained. Specifically, the explicit expressions of the aerodynamic force in different directions (equivalent to the aerodynamic force model of the object under test) are as follows:

[0089] .F x =F T -ma x -m1o 1x (2)

[0090] .F y =ma y 10F yMag 10m1a 1y (3)

[0091] .F z =ma z 10mg 10m1a z 10m1g1F zMag (4)

[0092] Among them, F x F y and F z Let F represent the aerodynamic components of the object under test in the x, y, and z directions, respectively, and let F be the aerodynamic drag, lateral force, and aerodynamic lift. T Let m be the traction force, m be the mass of the object being measured, m1 be the mass of the magnetic levitation platform, and a be the mass of the maglev platform. x a y a z Let a be the vibration acceleration of the object under test in the x, y, and z axes. 1x a 1y Let F be the vibration acceleration of the maglev platform in the x and y axes. yMag F is the levitation force in the opposite direction of the y-axis. zMag Let g be the levitation force along the z-axis, and g be the gravitational acceleration.

[0093] It is understandable that the above equations (2)-(4) only represent certain types of experimental conditions (such as...). Figures 4a-4dThe aerodynamic model of the object under test (as shown in the test conditions) is as follows. When the object under test changes (e.g., the aircraft is replaced with a train, or with another type of aircraft), or when the connection between the object under test and the maglev platform changes, the aerodynamic model may also change or be adjusted accordingly (i.e., the form of the aerodynamic expression may differ). However, by conducting simulation experiments based on the above steps S11-S15, the aerodynamic models corresponding to different types of aircraft or trains under different force relationships can be determined.

[0094] Specifically, in some embodiments, force analysis of the object under test can be performed based on the principle of force balance, and the force relationship of the object under test is as follows: Figure 4c , Figure 4d As shown.

[0095] In this embodiment, simulation testing can also be understood as a pre-experiment before actual testing. Based on simulation testing, the aerodynamic force model of the object under test can be determined and obtained. Of course, for the staff, if simulation data or other types of experimental data (such as theoretical data or experimental data) are relatively sufficient, simulation testing is not a necessary step. That is, when there is sufficient existing data, the aerodynamic force model corresponding to the object under test can be directly obtained, and then the actual test can be carried out on the object under test. During the wind tunnel test of the object under test, the three components of the aerodynamic force on the object under test can be deduced by measuring the vibration acceleration of the object under test and the maglev platform.

[0096] The indirect measurement method in this embodiment is based on the principle of force balance to determine the aerodynamic model (i.e., the explicit expression of the aerodynamic force) of the object under test. Then, by testing the vibration characteristics of the object and the maglev platform, the inertial acceleration of the object is obtained. Substituting this inertial acceleration into the aerodynamic model, the aerodynamic force of the object can be deduced. Compared to traditional balance force measurement techniques, the method proposed in this embodiment does not require a balance and is therefore unaffected by the velocity and vibration time-frequency characteristics of the object during testing. In other words, the method in this embodiment is not affected by the magnitude of the object's velocity, thus allowing the acquisition of aerodynamic force curves during acceleration, uniform motion, and deceleration.

[0097] Furthermore, in some embodiments, once the aerodynamic model corresponding to the object under test is obtained, an actual maglev-driven flight wind tunnel can be constructed. The test environment is provided by an actual maglev-driven flight wind tunnel, and the object under test can be a physical model of an aircraft or a high-speed train. First, the center of gravity of the object under test is tested (e.g., by testing the center of gravity of the object under test using the traditional suspension method), and one end of the support mechanism is fixed at the center of gravity of the object under test, with the support mechanism rigidly connected to the object under test (specifically, both ends of the support mechanism are fixed to the maglev platform and the object under test, respectively, to connect the object under test and the maglev platform).

[0098] Vibration sensors are then installed at the center of gravity of the maglev platform and the object under test, respectively. The model of the vibration sensor can be selected based on the actual measurement range and accuracy. In this embodiment, the support mechanism, the object under test, and the maglev platform can be considered as a whole, meaning that the support mechanism, the object under test, and the maglev platform move at the same speed. Therefore, the movement or vibration of the support mechanism will not affect the test (or, in other words, the influence of the support mechanism on the test can be ignored).

[0099] Furthermore, the vibration sensor is connected to a pre-set testing system (e.g., the test includes a control module for controlling the wind tunnel test and a data processing module for acquiring experimental data and processing the data) to obtain the real-time data measured by the vibration sensor, and the analog-to-digital conversion module and sampling frequency are set. The sampling frequency is not lower than 2000Hz; specifically, the specific value of the sampling frequency can be selected based on the actual situation.

[0100] Before the maglev platform begins to move, a preset test program is initiated (specifically, the test program can be pre-stored in the control module of the test system), thereby realizing the full-process monitoring of the acceleration, uniform speed, and deceleration of the object under test. Furthermore, based on the vibration acceleration of the object under test, the inertial force of the object under test is obtained, and by integrating the levitation force, the aerodynamic force can be indirectly measured.

[0101] Furthermore, the method provided in this embodiment is illustrated using a typical aircraft (i.e., the object under test) undergoing dynamic testing in a maglev wind tunnel as an example. The entire motion of the aircraft in the maglev wind tunnel includes: an acceleration phase of 450m, a constant speed phase of 150m, and a deceleration phase of 400m. The drive system in the maglev wind tunnel uses uniform acceleration and uniform deceleration to drive the aircraft's motion, with target test speeds set at 500km / h and 1000km / h, respectively. The mass of the aircraft under test is 200kg, and the weight of the maglev platform is 2831kg.

[0102] . Figures 5a-5dThis refers to the indirect aerodynamic measurement results of the aircraft at a maximum speed of 1000 km / h, including indirect aerodynamic measurement results for uniform acceleration, uniform velocity, and uniform deceleration sections, with a maximum speed of 1000 km / h (of course, in some other embodiments, the object under test can also move using any motion method such as variable acceleration). Among them, Figure 5a The vertical inertial force of the suspension frame (i.e., the maglev platform) is shown. This vertical inertial force can be obtained by multiplying the vertical vibration acceleration of the maglev platform by its mass. Figure 5b The vertical resultant force Fzmag (vertical levitation force) of the levitation force in the magnetic levitation system is shown, and this force can be directly obtained through the magnetic levitation system; Figure 5c The vertical inertial force of the object under test is shown, which can be obtained by multiplying the vertical acceleration of the object under test by its mass. Figure 5d To compare the results of indirect aerodynamic lift measurement with the actual input results, the indirect aerodynamic lift measurement results are the sum of the vertical inertial force of the suspension frame, the vertical levitation force, and the vertical inertial force of the object under test. Figure 5d It can be seen that the aerodynamic forces input in actual numerical simulations (or simulation experiments) can be accurately obtained through the above-mentioned indirect measurement methods, and Figure 5d The numerical curves of the input aerodynamic lift and the indirectly measured lift are basically consistent and show good agreement. That is to say, the indirect measurement method provided in this embodiment has good accuracy and reliability.

[0103] . Figures 6a-6d The results of indirect aerodynamic force measurements of the aircraft at a maximum speed of 500 km / h are shown. Although the vibration characteristics of the test object differ slightly at different test speeds, the aerodynamic force consistent with the input can be obtained through the above indirect measurement method. Figure 6d The numerical curves of the input aerodynamic lift and the indirectly measured lift are basically consistent and show good agreement. Figures 6a-6d The accuracy and reliability of the indirect measurement method provided in this embodiment were further verified.

[0104] Since aerodynamic forces can be used as input conditions in simulation experiments and can be set by operators, they can be known quantities. The measured aerodynamic force values ​​can be verified by comparing the known input values ​​with the measured values ​​obtained based on the aerodynamic force model. Therefore, simulation experiments can both determine the aerodynamic force model and verify its accuracy.

[0105] It is understood that, in some embodiments, a portion of the data from the simulation experiment can be used as a training set to determine the explicit expression of the aerodynamic force, while another portion of the data can be used as a test set to test the accuracy and reliability of the explicit expression of the aerodynamic force.

[0106] As mentioned above, during wind tunnel testing, it is only necessary to measure the vibration acceleration of the object under test and the maglev platform during wind tunnel simulation. The vibration acceleration can be achieved by deploying corresponding sensors, which is relatively simple to operate and easy to implement.

[0107] In traditional balance measurement methods, to ensure the force balance operates normally and stably within its working range, certain requirements are placed on the vacuum level, gas density, and ambient temperature of the wind tunnel. Conventional balances struggle to handle the amplitude and frequency range of aerodynamic forces on the measured object under different vacuum levels, motion speeds, and temperatures. This method eliminates the need for force measurement and therefore does not require a force balance. Instead, it uses sensors to measure the vibration acceleration of the object and the maglev platform. Consequently, the measurement process of this method is unaffected by the vacuum level, gas density, and ambient temperature of the maglev flight wind tunnel.

[0108] Furthermore, the aerodynamic force measured in this embodiment is the transient aerodynamic force of a moving object. Compared with the aerodynamic force of a static object measured in the prior art, it can more realistically reflect the characteristics of the transient aerodynamic force of the object under test during the motion process, and is also more helpful for the dynamics research of aircraft or trains.

[0109] Furthermore, traditional wind tunnels are designed with different types of wind tunnels based on the Mach number of the airflow to achieve testing in different speed ranges. However, the maglev flight wind tunnel selected in this embodiment allows the speed of the object under test to range from 0 to 1 Mach (i.e., one times the speed of sound), covering the functions of low-speed wind tunnels, subsonic wind tunnels, and even some supersonic wind tunnels. That is, the entire process of the object under test from acceleration, constant speed to braking can be completed in the maglev flight wind tunnel, covering multiple speed ranges. Therefore, through the aforementioned indirect measurement method, the transient aerodynamic forces of the object under test in various speed ranges (such as acceleration) can be effectively obtained directly in a single maglev flight wind tunnel, which is simple to operate and easy to implement.

[0110] Preferably, in some embodiments, the center of gravity of the object under test coincides with the aerodynamic center of the object under test. In this case, the aerodynamic model is:

[0111] .F x =F T -ma z -m1a lx

[0112] .F y =ma y 10F yMag 10m1a 1y

[0113] .F z =ma z 10mg 10m1az 10m1g1F zMag

[0114] Among them, F x F y and F z These are the aerodynamic components of the object under test in three directions, F. T Let m be the traction force, m be the mass of the object under test, m1 be the mass of the magnetic levitation platform, and a be the mass of the maglev platform. x a y a z Let a be the vibration acceleration of the object under test in the x, y, and z axes. 1x a 1y Let F be the vibration acceleration of the magnetic levitation platform in the x and y axes. yMag F is the levitation force in the y-axis direction. zMag Let g be the levitation force along the z-axis, and g be the gravitational acceleration.

[0115] In some embodiments, before placing the first sensor at the center of gravity of the object under test, the step of:

[0116] The support mechanism is fixed at the center of gravity of the object to be tested.

[0117] Furthermore, in some embodiments, when the aerodynamic force of the object under test is obtained in actual testing, the aerodynamic coefficient of the object under test can be further obtained based on the aerodynamic force. The aerodynamic coefficient can be used for performance evaluation of aircraft or trains, or for structural design. The aerodynamic coefficient is determined as follows:

[0118] .

[0119] .

[0120] .

[0121] Among them, F x F y and F z These represent the aerodynamic components of the object under test in three directions, where ρ is the gas density, A is the reference area (i.e., the windward area of ​​the object under test), V is the fluid velocity, and C is the aerodynamic components of the object under test in three directions. z C is the vertical aerodynamic coefficient. y Lateral aerodynamic coefficient, C z Longitudinal aerodynamic coefficient.

[0122] It is understood that the indirect measurement method provided in this embodiment can also be implemented entirely through simulation.

[0123] Furthermore, in some embodiments, the first sensing data includes: sensing data measured by the first sensor when the object under test is in the process of acceleration, constant speed and deceleration.

[0124] Furthermore, the second sensing data includes: sensing data measured by the second sensor during the acceleration, constant speed, and deceleration processes of the magnetic levitation platform.

[0125] Existing balance measurement methods are often only applicable to environments where the object is stationary while the air is moving. When the object moves, the balance is affected by the object's velocity and vibration frequency characteristics, making it difficult to guarantee the accuracy and stability of the measurement. Furthermore, the wind loads experienced by aircraft or high-speed trains during actual operation are complex, and it is difficult to simulate real wind loads in simulation or experimental environments. Therefore, most balance measurement methods cannot accurately and realistically measure transient aerodynamic forces. In contrast to existing technologies, this invention uses sensors (such as vibration acceleration sensors) to measure the vibration state of the object and the maglev platform during motion, thereby inferring the aerodynamic forces acting on the object. In this process, the object is stationary while the air is moving; therefore, the aerodynamic force measurement method in this embodiment can more realistically reflect the time-frequency characteristics of the aerodynamic forces acting on the moving object.

[0126] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0127] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for indirect measurement of aerodynamic forces in a magnetic levitation flight wind tunnel, characterized in that, The method comprises the steps of: providing a test environment and an object to be tested, wherein the test environment comprises a magnetic levitation platform for providing a magnetic force for the object to be tested; obtaining the center of gravity of the object to be tested and the magnetic levitation platform; respectively arranging a first sensor and a second sensor at the center of gravity of the object to be tested and the center of gravity of the magnetic levitation platform; when the object to be tested starts to move based on a preset test condition, respectively obtaining first sensing data and second sensing data based on the first sensor and the second sensor, and determining first vibration acceleration and second vibration acceleration based on the first sensing data and the second sensing data; at this time, the air is static and the object to be tested is moving; determining the aerodynamic force of the object to be tested based on the first and second vibration accelerations and a pre-obtained aerodynamic force model; wherein the step of establishing the aerodynamic force model comprises: obtaining the first and second sensing data, and determining the external force condition of the object to be tested based on numerical integration, the external force condition comprising: aerodynamic force, levitation force, and gravity of the object to be tested; determining the force relationship of the object to be tested based on the connection relationship between the object to be tested and the magnetic levitation platform; determining the aerodynamic force model of the object to be tested based on the external force condition and the force relationship; the calculation model of the external force condition is: wherein, is a mass matrix of the object under test and the magnetic levitation platform, is a vibration acceleration matrix of the object under test and the magnetic levitation platform, is a damping characteristic of the system, is a stiffness characteristic matrix of the object under test, is a vibration acceleration of the object under test, is a vibration displacement of the object under test, is a force experienced by the object under test; the aerodynamic force model is: wherein, , and are the aerodynamic force components of the object to be measured in three directions, is the traction force, is the mass of the object to be measured, is the mass of the magnetic levitation platform, , , are the vibration accelerations of the object to be measured in the x, y, z axis directions, , are the vibration accelerations of the magnetic levitation platform in the x, y axis directions, is the suspension force in the y axis direction, is the suspension force in the z axis direction, is the gravitational acceleration.

2. The method of claim 1, wherein, the aerodynamic force model is established based on a simulation test, and correspondingly, the method further comprises the steps of: establishing a magnetic levitation driving dynamics model for providing the test environment based on a multi-body dynamics method; establishing a simulation model of the object to be tested, and the aerodynamic center of the simulation model coincides with the center of gravity of the simulation model.

3. The method of claim 1, wherein, The first sensor is a vibration acceleration sensor, and / or a displacement sensor, and / or a speed sensor.

4. The method of claim 1, wherein, The second sensor is a vibration acceleration sensor, and / or a displacement sensor, and / or a speed sensor.

5. The method according to claim 3 or 4, characterized in that, When the first sensor or the second sensor is a vibration acceleration sensor, the sampling frequency of the vibration acceleration sensor is not less than 2000 Hz.

6. The method of claim 1, wherein, The object to be tested is connected to the magnetic levitation platform through a support mechanism, and one end of the support mechanism connected to the object to be tested is located at the center of gravity of the object to be tested.

7. The method of claim 1, wherein, The first sensing data comprises sensing data measured by the first sensor when the object to be tested is in the process of acceleration, uniform speed and deceleration; and / or, the second sensing data comprises sensing data measured by the second sensor when the magnetic levitation platform is in the process of acceleration, uniform speed and deceleration.

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