Large flexible structure reduced-order model parameter identification method based on ground test data

Abstract

The invention relates to the technical field of structural dynamics analysis and test, in particular to a large flexible structure reduced-order model parameter identification method based on ground test data, which comprises the following steps: mounting a force sensor and a vibration exciter on a large flexible structure to be tested, and mounting a plurality of acceleration sensors and strain sensors in a dispersed manner; applying excitation to the large flexible structure by adopting a vibration exciter, and recording measurement values of the acceleration sensor, the strain sensor and the force sensor; converting the local acceleration signal into a global coordinate system, and integrating the global acceleration signal to obtain a speed signal and a displacement signal; performing modal test on the large flexible structure to obtain modal information, performing modal conversion on the global acceleration signal, the speed signal and the displacement signal, inputting the signals into a nonlinear structure reduced-order model, and performing calculation through a least square method to obtain a nonlinear stiffness coefficient; according to the invention, the reliability and accuracy of the identification result can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of structural dynamics analysis and testing, and in particular to a method for identifying parameters of a large flexible structure reduced-order model based on ground test data. Background Art

[0002] The requirements for flight performance in modern aircraft design are constantly increasing. Large flexible aircraft represented by high-altitude long-endurance UAVs, large passenger aircraft, and large transport aircraft have gradually become the research focus of major aviation powers. Due to the requirements for the flight performance of such aircraft, especially the range and flight time, large flexible aircraft usually use a larger wing aspect ratio to improve the lift-to-drag ratio, and increase the proportion of composite materials in the structural design. These factors lead to the low relative structural weight and low stiffness of such aircraft, and the large structural deformation caused by aerodynamic loading, which brings geometric nonlinear aeroelastic problems.

[0003] Accurate structural modeling is the core of aeroelastic analysis. Nonlinear finite element analysis and large deformation beam theory are the two most commonly used large flexible structure modeling methods in traditional geometric nonlinear aeroelastic analysis. The former has good applicability to engineering models and can be applied to complex structural models, but the model has high degrees of freedom, poor convergence and low computational efficiency; the latter has high computational accuracy and efficiency, but can only be used for simple model analysis and cannot be directly applied to complex engineering objects. The nonlinear structural reduced-order model is a large flexible structure modeling method that can better balance solution efficiency, computational accuracy and applicability of complex models. In the nonlinear structural reduced-order model, the nonlinear stiffness is expressed in the form of a generalized coordinate polynomial, and the nonlinear structural reduced-order model is obtained by solving the nonlinear stiffness coefficient. In the past, the nonlinear stiffness coefficient of the nonlinear structural reduced-order model was solved based on the simulation analysis data of the structural finite element model. In the Chinese patent "A nonlinear aeroelastic dynamic response analysis method based on a structural reduced-order model" with the publication number CN112580241B, the applicant first gave a variety of static nonlinear finite element analysis examples, and combined the regression analysis method to solve the nonlinear stiffness coefficient; in the Chinese patent "A large flexible structure reduced-order model modeling method based on dynamic response identification" with the publication number CN113536456B, the dynamic response data of the large flexible structure was first calculated, and the nonlinear stiffness coefficient was discretely solved in combination with the dynamic response data. In the above studies, the nonlinear stiffness coefficient was solved based on the simulation data sample. At this time, there is a certain difference between the actual structure and the simulation model, and errors are bound to be introduced in the process of establishing the finite element model. At the same time, the need to establish a corresponding finite element model before solving the nonlinear stiffness coefficient also increases the analysis time and difficulty. If the parameters can be directly identified based on the original actual model, the result will be more accurate and reliable. There is no relevant method and patent at present. Summary of the invention

[0004] In view of the above problems, the present invention provides a method for identifying parameters of a large flexible structure reduced-order model based on ground test data, which solves the technical problem in the prior art that the calculation of nonlinear stiffness coefficients of nonlinear structural reduced-order models of large flexible structures must rely on simulation data and cannot be directly identified using test data.

[0005] The present invention provides a method for identifying parameters of a large flexible structure reduced-order model based on ground test data, comprising the following steps:

[0006] Step S1, installing a force sensor on the large flexible structure to be tested, and installing the force sensor on a vibration exciter; installing a plurality of acceleration sensors on the large flexible structure to be tested in a dispersed manner, and installing a strain sensor at the position of each acceleration sensor;

[0007] Step S2, determining an excitation signal, using the exciter to apply excitation to the large flexible structure with the excitation signal, recording the measurement values ​​of the acceleration sensor, the strain sensor and the force sensor during the excitation time, and obtaining a local acceleration signal, a strain signal and a force signal respectively;

[0008] Step S3, converting the local acceleration signal into a global coordinate system to obtain a global acceleration signal, integrating the global acceleration signal to obtain a velocity signal and a displacement signal;

[0009] Step S4, performing a ground modal test on the large flexible structure to measure and obtain modal information of the large flexible structure, and converting the global acceleration signal, velocity signal and displacement signal into acceleration generalized response, velocity generalized response and displacement generalized response based on the modal information;

[0010] Step S5: input the acceleration generalized response, velocity generalized response and displacement generalized response into the nonlinear structural reduced-order model, and calculate the nonlinear stiffness coefficient by the least square method as the model parameter for identification.

[0011] Preferably, the step S1 specifically includes:

[0012] Step S1-1, the large flexible structure has a clamping section, the clamping section of the large flexible structure is clamped on the tooling, a force sensor is attached to the root position of the large flexible structure, and the force sensor is installed on the exciter;

[0013] Step S1-2: 4 to 6 acceleration sensors are dispersedly installed on the large flexible structure, and a strain sensor is correspondingly installed at the position of each acceleration sensor, wherein the strain sensor is a strain gauge or an optical fiber sensor.

[0014] Preferably, it is characterized in that in step S1-2, the dispersed installation of 4 to 6 acceleration sensors on the large flexible structure specifically includes:

[0015] A total of 6 acceleration sensors are installed at positions 40mm, 300mm, 500mm, 700mm, 900mm and 980mm away from the clamping section of the large flexible structure.

[0016] Preferably, the step S2 specifically includes:

[0017] Step S2-1, setting a sine frequency sweep with a frequency step of 0.1 Hz, and a signal whose frequency range covers the first three natural frequencies of the large flexible structure as an excitation signal, and using the exciter to apply excitation to the large flexible structure with the excitation signal;

[0018] Step S2-2, the time period from the start of excitation to the large flexible structure reaching a steady-state response is taken as the excitation time, and the measurement values ​​of the acceleration sensor, strain sensor and force sensor are recorded during the excitation time to obtain local acceleration signals, strain signals and force signals respectively.

[0019] Preferably, the step S3 specifically includes:

[0020] Step S3-1: Convert the strain signal into curvature The rotation angle θ(s) at each position of the large flexible structure is obtained from the curvature, and the calculation expression is:

[0021]

[0022] Wherein, θ(0) is the rotation angle of the root position of the large flexible structure, θ(0) = 0; s is the arc length coordinate of the large flexible structure along the span direction, 0≤s≤1;

[0023] Step S3-2: based on the rotation angle θ(s) at each position, convert the local acceleration signal into the global coordinate system, and obtain the global acceleration signal calculation expression as follows:

[0024]

[0025] where a y , a z is the global acceleration, a y1 , a z1 is the local acceleration, θ is the rotation angle of the current position of the large flexible structure;

[0026] Step S3-3: Global acceleration response signal obtained by time domain recording in the global coordinate system Given that the initial excitation condition is 0, a time integration is performed to obtain the velocity response signal A time integration is then performed on the basis of the velocity response signal to obtain the displacement response signal x.

[0027] Preferably, in step S4, the modal information of the large flexible structure obtained by the measurement is: Φ = [Φ1, Φ2, Φ3, ..., Φ N ], where N is the total order of measured modes.

[0028] Preferably, in step S4, the calculation expression for converting the global acceleration signal, velocity signal and displacement signal into acceleration generalized response, velocity generalized response and displacement generalized response based on the modal information is:

[0029]

[0030]

[0031] in, is the generalized acceleration response corresponding to the i-th mode, is the generalized velocity response corresponding to the i-th mode, q i is the generalized displacement response corresponding to the i-th mode, Φ i is the i-th order generalized mode vector, is Φ i The transpose of is the structural mass matrix, M i is the generalized mass of the i-th mode.

[0032] Preferably, the step S5 specifically includes:

[0033] The discrete structural dynamics equation is constructed as follows:

[0034]

[0035] The discrete structural dynamics equation is subjected to Fourier transformation to obtain:

[0036]

[0037] For the discrete structural dynamics equation after Fourier transformation, take NK different frequency domain k values ​​to obtain NK equations, forming an equation system, the expression is:

[0038]

[0039] The least squares method is used to calculate the above equations and obtain the nonlinear stiffness coefficient as the model parameters for identification.

[0040] Preferably, in step S5:

[0041] The total number of discrete time points NT is set to 2000; the total number of frequency domain values ​​NK is set to 20, and 20 different frequency domain k values ​​are taken to obtain 20 equations to form a system of equations, where the 20 different frequency domain k values ​​are taken as {0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 7.0, 8.0, 9.0, 10.0, 15.0, 20.0, 25.0}.

[0042] Compared with the prior art, the present invention has at least the following beneficial effects:

[0043] (1) Compared with the traditional structural reduced-order model parameter identification method, the large flexible structure stiffness identification method based on ground test data provided by the present invention does not need to establish a finite element model and complete simulation analysis. Instead, it directly uses ground test data for parameter identification, thus avoiding the errors that may be caused by the simulation model and improving the reliability and accuracy of the identification results.

[0044] (2) In establishing a nonlinear structural order reduction model, the present invention uses linear modes as the order reduction basis, thereby improving the applicability of the model and being able to be more widely applied to different types of large flexible structures.

[0045] (3) The present invention utilizes the angle relationship to convert the measured local acceleration response signal into a global acceleration response signal, thereby further improving the accuracy of identification and ensuring the accuracy of the parameter identification result. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The drawings are only for the purpose of illustrating particular embodiments and are not to be construed as limiting the invention.

[0047] Figure 1 A flow chart of a method for identifying parameters of a large flexible structure reduced-order model based on ground test data provided by the present invention.

[0048] Figure 2 The present invention provides a flow chart for identifying parameters of the nonlinear structure reduction model of the present invention.

[0049] Figure 3 This is a schematic diagram of the actual installation of the force sensor provided by the present invention.

[0050] Figure 4 This is a schematic diagram of the distribution of acceleration measurement points provided by the present invention.

[0051] Figure 5 This is a schematic diagram of the actual installation of the accelerometer provided by the present invention.

[0052] Figure 6 This is a schematic diagram of the overall test device provided by the present invention.

[0053] Figure 7 This is a schematic diagram of the wing aerodynamic model provided by the present invention. DETAILED DESCRIPTION

[0054] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein, and therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0055] The present invention pastes an acceleration sensor, a strain gauge or an optical fiber sensor on a large flexible structure, clamps the large flexible structure on a tooling, pastes a force sensor at the root position, installs the force sensor on an exciter and applies an excitation signal, measures the acceleration response and restores the velocity and displacement signals by integration. Based on data without a finite element model and numerical simulation, the nonlinear stiffness coefficient is calculated using the least squares method based on the discrete form of the dynamic equation. The method provided by the present invention can be applied to the construction of geometric nonlinear structural dynamic models of aerospace aircraft wing structures, cantilever beams, and the like.

[0056] In order to illustrate the effectiveness of the method proposed by the present invention, the above technical solution of the present invention is described in detail below through a specific embodiment. Figure 1 , Figure 2 As shown, a parameter identification method for a large flexible structure reduced-order model based on ground test data is disclosed, and the specific implementation steps are as follows:

[0057] The first step is to prepare for ground testing.

[0058] The root of the large flexible structure to be measured is mounted on the designed and processed tooling. The mounting installation should try to avoid the structure being affected by gravity. After installation, the force sensor is pasted at the root of the model, and the force sensor is installed on the exciter. At the same time, the exciter is fixed on a stable ground to prevent the exciter from shaking during the excitation process. Connect the exciter to the power amplifier and chassis so that the computer can send instructions to the exciter to excite the structure. Connect the force sensor to the modem and data acquisition chassis to realize the conversion of digital signals and analog signals and transmit them to the terminal device.

[0059] Step 2: Install the structural measurement sensor.

[0060] Install 4 to 6 acceleration sensors on the large flexible structure; test to ensure that the acceleration sensors can accurately measure and save the acceleration signals generated during the excitation vibration process; install strain sensors near the acceleration sensors to measure the strain signals; the strain sensors can be strain gauges or optical fiber sensors, etc.

[0061] Step 3: Excite the large flexible structure and record the acceleration response data.

[0062] A sinusoidal load signal with an appropriate amplitude is set near the first three natural frequencies of the large flexible structure to make the structure produce small to large deformation. Specifically, a specified frequency step is set, and a sinusoidal swept frequency excitation is input. The frequency range covers the first three natural frequencies. The time domain acceleration response, strain signal and force signal of the exciter from the structure to the steady-state response section are recorded within the excitation time.

[0063] Step 4: Process the acceleration signal to the global coordinate system.

[0064] When the large flexible structure is in a large deformation range, the result measured by the accelerometer is the acceleration in the local structural coordinate system. In order to make the measured data suitable for parameter identification requirements, the measured value needs to be converted from the local coordinate system to the global coordinate system. At this time, it is necessary to use strain gauges or optical fiber sensors to measure the strain signal and convert the strain signal into curvature. The rotation angle θ(s) at each position of the large flexible structure can be obtained, and then the acceleration signal value in the global coordinate system can be calculated. The calculation method is related to the actual structure and dimension, and the expression is:

[0065] a g =Aa(1)

[0066] where a g is the global acceleration signal value, A is the transformation matrix, which is a function of the rotation angle θ(s), and a is the measured local acceleration signal value of the structure.

[0067] Step 5: Integrate the acceleration signal to obtain velocity and displacement response signals.

[0068] The acceleration response signal obtained from the time domain recording in the transformed global coordinate system Given that the initial excitation condition is 0, a time integration is performed to obtain the velocity response signal Then, a time integration is performed on the basis of the velocity response signal to obtain the displacement response signal x;

[0069] Step 6: Obtain the modal information of the structure and convert the response signal into a generalized response signal.

[0070] To obtain the modal information of the structure, the traditional modal ground test method can be used. The structural mode measured in the ground modal test is Φ = [Φ1, Φ2, Φ3, …, Φ N ],Φ i is the i-th order generalized modal vector, N is the total order of measured modes, on this basis, the signals measured in the fifth step are converted into generalized modal response signals:

[0071]

[0072] in, is the generalized acceleration response corresponding to the i-th mode, is the generalized velocity response corresponding to the i-th mode, q i is the generalized displacement response corresponding to the i-th mode, Φ i is the i-th order generalized mode vector, Φ i The transpose of is the structural mass matrix, M i is the generalized mass of the i-th mode.

[0073] Step 7: Solve based on the nonlinear structural reduced-order model to obtain the nonlinear stiffness coefficient.

[0074] The structural dynamics equations in discretized form are as follows:

[0075]

[0076] Among them, M m represents the generalized mass term of the m-th structural mode, q m (j), q n (j), q l (j) and q p (j) represents the value of the generalized coordinate discrete sequence of the mth, nth, lth, and pth order structural modes at index j, respectively. for q m The second-order time differential of (j); K m represents the generalized stiffness term of the m-th order structural mode; The nonlinear stiffness term represents the product polynomial of the generalized coordinates of the n-th order structural mode and the generalized coordinates of the l-th order structural mode under the m-th order structural mode, The nonlinear stiffness coefficient of the product polynomial of the generalized coordinates of the nth-order structural mode, the lth-order structural mode, and the pth-order structural mode under the mth-order structural mode, F m (j) represents the value of the discrete sequence of modal force vectors of the m-th order structural mode at index j, j∈{0,1,…,NT-1}, represents the index of the discrete time point sequence, and NT represents the total number of discrete time points.

[0077] Based on equation (5), a discrete Fourier transform is performed on it. The sequences after the Fourier transform of the generalized coordinates are expressed as: Q m (k),Q n (k),Q l (k),Q p(k), k is the frequency domain sequence index. In the same way, the second-order and third-order terms of the generalized coordinates are also subjected to discrete Fourier transform, and the transformed sequences are expressed as and The generalized force is subjected to discrete Fourier transform, and the transformed sequence is expressed as f m (k), the discrete dynamic equation after Fourier transformation is:

[0078]

[0079] Among them, Q m (k),Q n (k),Q l (k),Q p (k) are q m (j),q n (j),q l (j),q p (j) The discrete Fourier transform value of the corresponding sequence at index k, for The value of the discrete Fourier transform of the corresponding sequence at index k, is the value of the discrete Fourier transform of the second-order term in generalized coordinates at index k, is the value of the discrete Fourier transform of the third-order term of the generalized coordinates at index k, f m (k) is F m (j) The discrete Fourier transform value of the corresponding sequence at index k, k∈{k1,k2,...,k NK}, NK is the total number of values ​​in the frequency domain.

[0080] Taking NK different frequency domain k values ​​can obtain NK equations to form an equation system. The unknown nonlinear stiffness coefficient is calculated using the least squares method: The least squares problem can be expressed as:

[0081]

[0082] After solving the unknown nonlinear stiffness coefficient and substituting it into equation (5), the complete nonlinear structural dynamics equation can be obtained.

[0083] The method for identifying parameters of a large flexible structure reduced-order model based on ground test data provided by the present invention is described in detail below through a specific embodiment.

[0084] like Figure 3As shown, the present invention adopts an aluminum steel ruler as a simulation part of a large flexible structure. The cross-sectional shape is a rectangle with a length of 35 mm and a width of 1.5 mm. The length of the test section is 1000 mm. The material of the test object is uniform. In the absence of other sensors and circuits installed, the bare weight of the rectangular beam is 0.407 kg. After affixing various sensors, the total weight is 0.505 kg.

[0085] Step 1: Preparing for Ground Testing

[0086] In this step, the large flexible structure has a clamping section, and the clamping section of the large flexible structure is clamped on a preset tooling, such as Figure 3 As shown, a force sensor is pasted at a distance of 30 mm from the clamping section and the force sensor is connected to the exciter.

[0087] Step 2: Install the structural measurement sensor

[0088] like Figure 4 , Figure 5 As shown, a total of 6 acceleration sensors are installed at positions 40mm, 300mm, 500mm, 700mm, 900mm and 980mm away from the clamping section, and strain gauges or optical fiber sensors are installed near the acceleration sensors to measure strain signals.

[0089] Step 3: Excite the Large Flexible Structure and Record Acceleration Response Data

[0090] The overall test device is as follows Figure 6 As shown, a channel steel is fixed on the base by fixing bolts, and the channel steel clamp holds a test steel ruler, wherein the channel steel is a preset tooling, and the test steel ruler is a simulation of a large flexible structure. The control system generates excitation by controlling the exciter to apply excitation to the test steel ruler. The control system sets the excitation to a sine sweep excitation with a frequency step of 0.1Hz, and the frequency range covers the first three natural frequencies. The time domain acceleration response and force signal of the structure to the steady-state response section are recorded during the excitation time; a total of 2000 sets of valid data are obtained.

[0091] Step 4: Process the acceleration signal to the global coordinate system

[0092] The strain signal is measured by strain gauge or optical fiber sensor and converted into curvature The rotation angle θ(s) at each position of the large flexible structure is obtained by the following expression:

[0093]

[0094] Among them, θ(0) is the rotation angle of the root position, θ(0)=0; s is the arc length coordinate of the large flexible structure along the span direction, 0≤s≤1.

[0095] From the above formula, we can get the positional relationship between the local coordinate system and the global coordinate system at each position of the large flexible structure. The large flexible beam is loaded in the vertical direction and belongs to a two-dimensional structure. Therefore, the acceleration can be further converted to the global coordinate system:

[0096]

[0097] where a y , a z is the global acceleration, a y1 , a z1 To measure the acceleration locally, θ is the rotation angle of the current position of the large flexible structure.

[0098] Step 5: Integrate the acceleration signal to obtain velocity and displacement response signals.

[0099] The global acceleration response signal obtained from the time domain record in the transformed global coordinate system Given that the initial excitation condition is 0, a time integration is performed to obtain the velocity response signal Then, a time integration is performed on the basis of the velocity response signal to obtain the displacement response signal x;

[0100] Step 6: Obtain the modal information of the structure and convert the response signal into a generalized response signal

[0101] The ground modal test is carried out according to the traditional modal ground test method. The structural mode measured in the ground modal test is Φ=[Φ1,Φ2,Φ3,…,Φ N ], in this embodiment, the first 6 modes are taken, that is, N=6, and the modal information is shown in Table 1:

[0102] Table 1

[0103]

[0104]

[0105] On this basis, the signal measured in the fifth step is converted into a generalized modal response signal:

[0106]

[0107] Step 7: Solve based on the nonlinear structural reduced-order model to obtain the nonlinear stiffness coefficient.

[0108] The structural dynamics equations in discretized form are as follows:

[0109]

[0110] In which, for j∈{0,1,…,NT-1}, the total number of discrete time points NT is set to 2000.

[0111] Based on equation (13), the discrete dynamic equation after Fourier transformation is:

[0112]

[0113] Among them, for k∈{k1,k2,...,k NK}, set the total number of frequency domain values ​​NK to 20, take 20 different frequency domain k values ​​to obtain 20 equations to form an equation system. Use the least squares method to calculate the unknown nonlinear stiffness coefficient The 20 different frequency domain k values ​​are taken as {0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 7.0, 8.0, 9.0, 10.0, 15.0, 20.0, 25.0}. After solving the unknown nonlinear stiffness coefficient and substituting it into equation (13), the complete nonlinear structural dynamics equation can be obtained.

[0114] The present invention can avoid establishing finite element models and dynamic simulations when solving the reduced-order model parameters of actual large flexible structures, directly use ground test technology for solution and identification, and avoid modeling errors, which is of great significance in actual dynamic analysis and aircraft design applications.

[0115] Although the specific embodiments of the present invention have been described in a specific order, each action or step should be understood to require that such action or step be performed in the specific order shown or in a sequential order, or require that all illustrated actions or steps should be performed to obtain the desired result. Under certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although some specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure. Certain features described in the context of a separate embodiment can also be implemented in a single implementation in combination. On the contrary, the various features described in the context of a single implementation can also be implemented in multiple implementations individually or in any suitable sub-combination.

[0116] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for identifying parameters of a large flexible structure reduced-order model based on ground test data, characterized in that: The following steps are involved: Step S1, installing a force sensor on the large flexible structure to be tested, and installing the force sensor on a vibration exciter; installing a plurality of acceleration sensors on the large flexible structure to be tested in a dispersed manner, and installing a strain sensor at the position of each acceleration sensor; Step S2, determining an excitation signal, using the exciter to apply excitation to the large flexible structure with the excitation signal, recording the measurement values ​​of the acceleration sensor, the strain sensor and the force sensor during the excitation time, and obtaining a local acceleration signal, a strain signal and a force signal respectively; Step S3, converting the local acceleration signal into a global coordinate system to obtain a global acceleration signal, integrating the global acceleration signal to obtain a velocity signal and a displacement signal; Step S4, performing a ground modal test on the large flexible structure to measure and obtain modal information of the large flexible structure, and converting the global acceleration signal, velocity signal and displacement signal into acceleration generalized response, velocity generalized response and displacement generalized response based on the modal information; Step S5: input the acceleration generalized response, velocity generalized response and displacement generalized response into the nonlinear structural reduced-order model, and calculate the nonlinear stiffness coefficient by the least square method as the model parameter for identification.

2. The method for identifying parameters of a large flexible structure reduced-order model based on ground test data according to claim 1 is characterized in that: The step S1 specifically includes: Step S1-1, the large flexible structure has a clamping section, the clamping section of the large flexible structure is clamped on the tooling, a force sensor is attached to the root position of the large flexible structure, and the force sensor is installed on the exciter; Step S1-2: 4 to 6 acceleration sensors are dispersedly installed on the large flexible structure, and a strain sensor is correspondingly installed at the position of each acceleration sensor, wherein the strain sensor is a strain gauge or an optical fiber sensor.

3. The method for identifying parameters of a large flexible structure reduced-order model based on ground test data according to claim 2 is characterized in that In step S1-2, the step of distributing and installing 4 to 6 acceleration sensors on the large flexible structure specifically includes: A total of 6 acceleration sensors are installed at positions 40mm, 300mm, 500mm, 700mm, 900mm and 980mm away from the clamping section of the large flexible structure.

4. The method for identifying parameters of a large flexible structure reduced-order model based on ground test data according to claim 3 is characterized in that: The step S2 specifically includes: Step S2-1, setting a sine frequency sweep with a frequency step of 0.1 Hz, and a signal whose frequency range covers the first three natural frequencies of the large flexible structure as an excitation signal, and using the exciter to apply excitation to the large flexible structure with the excitation signal; Step S2-2, the time period from the start of excitation to the large flexible structure reaching a steady-state response is taken as the excitation time, and the measurement values ​​of the acceleration sensor, strain sensor and force sensor are recorded during the excitation time to obtain local acceleration signals, strain signals and force signals respectively.

5. The method for identifying parameters of a large flexible structure reduced-order model based on ground test data according to claim 4 is characterized in that: The step S3 specifically includes: Step S3-1: Convert the strain signal into curvature The rotation angle θ(s) at each position of the large flexible structure is obtained from the curvature, and the calculation expression is: Wherein, θ(0) is the rotation angle of the root position of the large flexible structure, θ(0) = 0; s is the arc length coordinate of the large flexible structure along the span direction, 0≤s≤1; Step S3-2: based on the rotation angle θ(s) at each position, convert the local acceleration signal into the global coordinate system, and obtain the global acceleration signal calculation expression as follows: where a y , a z is the global acceleration, a y1 , a z1 is the local acceleration, θ is the rotation angle of the current position of the large flexible structure; Step S3-3: Global acceleration response signal obtained by time domain recording in the global coordinate system Given that the initial excitation condition is 0, a time integration is performed to obtain the velocity response signal A time integration is then performed on the basis of the velocity response signal to obtain the displacement response signal x.

6. The method for identifying parameters of a large flexible structure reduced-order model based on ground test data according to claim 5 is characterized in that In step S4, the modal information of the large flexible structure obtained by the measurement is: Φ = [Φ1, Φ2, Φ3, ..., Φ N ], where N is the total order of measured modes.

7. The method for identifying parameters of a large flexible structure reduced-order model based on ground test data according to claim 6 is characterized in that In step S4, the calculation expression for converting the global acceleration signal, velocity signal and displacement signal into acceleration generalized response, velocity generalized response and displacement generalized response based on the modal information is: in, is the generalized acceleration response corresponding to the i-th mode, is the generalized velocity response corresponding to the i-th mode, q i is the generalized displacement response corresponding to the i-th mode, Φ i is the i-th order generalized mode vector, is Φ i The transpose of is the structural mass matrix, M i is the generalized mass of the i-th mode.

8. The method for identifying parameters of a large flexible structure reduced-order model based on ground test data according to claim 7 is characterized in that: The step S5 specifically includes: The discrete structural dynamics equation is constructed as follows: Among them, M m represents the generalized mass term of the m-th structural mode, q m (j), q n (j), q l (j) and q p (j) represents the value of the generalized coordinate discrete sequence of the mth, nth, lth, and pth order structural modes at index j, respectively. for q m (j) time derivative; K m represents the generalized stiffness term of the m-th order structural mode; The nonlinear stiffness term represents the product polynomial of the generalized coordinates of the n-th order structural mode and the generalized coordinates of the l-th order structural mode under the m-th order structural mode, The nonlinear stiffness coefficient of the product polynomial of the generalized coordinates of the nth-order structural mode, the lth-order structural mode, and the pth-order structural mode under the mth-order structural mode, F m (j) represents the value of the modal force vector discrete sequence of the m-th order structural mode at index j, j∈{0,1,…,NT-1}, represents the index of the discrete time point sequence, and NT represents the total number of discrete time points; The discrete structural dynamics equation is subjected to Fourier transformation to obtain: Among them, Q m (k),Q n (k),Q l (k),Q p (k) are q m (j),q n (j),q l (j),q p (j) The discrete Fourier transform value of the corresponding sequence at index k, for The value of the discrete Fourier transform of the corresponding sequence at index k, is the value of the discrete Fourier transform of the second-order term in generalized coordinates at index k, is the value of the discrete Fourier transform of the third-order term of the generalized coordinates at index k, f m (k) is F m (j) The discrete Fourier transform value of the corresponding sequence at index k, k∈{k1,k2,...,k NK }, NK is the total number of frequency domain values; For the discrete structural dynamics equation after Fourier transformation, take NK different frequency domain k values ​​to obtain NK equations, which form an equation system, and the expression is: The least squares method is used to calculate the above equations and obtain the nonlinear stiffness coefficient as the model parameters for identification.

9. The method for identifying parameters of a large flexible structure reduced-order model based on ground test data according to claim 8, characterized in that: In step S5: The total number of discrete time points NT is set to 2000; the total number of frequency domain values ​​NK is set to 20, and 20 different frequency domain k values ​​are taken to obtain 20 equations to form a system of equations, where the 20 different frequency domain k values ​​are taken as {0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 7.0, 8.0, 9.0, 10.0, 15.0, 20.0, 25.0}.

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