CN104833466A - Spacecraft ground test and on-orbit micro-vibration mechanical environment mapping method - Google Patents

Abstract

The invention discloses a method for mapping a spacecraft ground test and on-orbit microvibration dynamics environment. The method firstly establishes a finite element model of the ground test spacecraft and an on-orbit spacecraft finite element model; type data to determine the one-to-one correspondence between the frequency and mode shape of the two models; establish and confirm the correctness of the reduction model; Mapping between mode shapes; analyze the dynamic response of the on-orbit model according to the frequency and mode shape of the on-orbit model obtained from the mapping. The invention eliminates the influence of air, gravity and suspension constraints on the ground micro-vibration test in the ground micro-vibration test state, and realizes the prediction of the micro-vibration characteristics of the actual on-orbit state by the ground test. At the same time, this method can realize the mutual comparison between the ground micro-vibration test data and the on-orbit test data, and verify the validity of the ground micro-vibration test.

Description

A Spacecraft Ground Test and On-orbit Microvibration Dynamics Environment Mapping Method

technical field

The invention relates to a space vehicle ground test and on-orbit micro-vibration dynamics environment method, through which the prediction of the micro-vibration characteristics of the ground test state to the actual on-orbit state is realized.

Background technique

With the development of society and economy, high-resolution spacecraft is undoubtedly the direction of spacecraft development, such as the KH series of military observation satellites in the United States, from KH-1 to KH-13, its resolution has increased from 12m to 0.05m. Compared with earth observation satellites, the resolution of remote sensing spacecraft for deep space exploration is 1 to 2 orders of magnitude higher, such as the Hubble Space Telescope (0.1 arcsecond, 1990). The next-generation space telescope, the James Webb Space Telescope, has a resolution of 0.004 arcseconds.

Micro-vibration refers to the high-speed rotation of the rotating parts on the star, the stepping motion of the large-scale controllable component drive mechanism, the ignition of the thruster during the orbit change and attitude adjustment, and the disturbance induced by the alternating cold and heat of the large-scale flexible structure when it enters and exits the shadow. Make the star produce a jitter response with a smaller amplitude and higher frequency. Micro-vibration disturbance sources exist in most spacecraft. Due to the small amplitude and high frequency of the micro-vibration dynamics environmental effect, it will not have a significant impact on most spacecraft and is usually ignored. However, for high-precision spacecraft, it will seriously affect important performance indicators such as payload pointing accuracy, stability and resolution, so the influence of micro-vibration must be considered in the design of high-resolution spacecraft.

Due to the extremely complex dynamic environment in which the spacecraft works in orbit, the high cost of on-orbit testing, and the inability to measure and control the response of the attitude control system to micro-vibrations, the current research on spacecraft micro-vibrations mainly uses numerical simulation and ground simulation. There are two methods of micro-vibration testing. According to the research work carried out in foreign literature, the currently large-scale and mature ground micro-vibration test platforms in various countries mainly include Honeywell's SCT ground micro-vibration test bench, JPL laboratory's MPI ground micro-vibration test bench and SSL experiment. The OT ground micro-vibration test bench in the laboratory. However, there are still great differences between the ground test and the on-orbit spacecraft mechanical environment. Factors such as gravity field, air, constraints (suspension devices) and other factors in the ground micro-vibration test environment may make the ground test results different from the micro-vibration characteristics of the on-orbit spacecraft. There is a big difference. Therefore, the ground micro-vibration test results can only be used for evaluation, and cannot accurately analyze the on-orbit micro-vibration characteristics of spacecraft.

In order to obtain the micro-vibration characteristics of the spacecraft in orbit, and the structure of the spacecraft is complex, it is difficult to obtain the analytical solution of the micro-vibration of the spacecraft. Therefore, the method of numerical simulation is mainly used at present, and scientific research institutions such as the United States have carried out a lot of research on this. The MIT Space Systems Laboratory has developed a micro-vibration integrated modeling and comprehensive evaluation analysis software DOCS; NASA has developed a chattering and structural/thermal/optical analysis system IME. Although the current numerical simulation can obtain the micro-vibration characteristics of the spacecraft to a certain extent, there are problems such as poor calculation efficiency and narrow application range.

Contents of the invention

The invention provides a space vehicle ground test and on-orbit micro-vibration dynamics environment mapping method. The method eliminates the influence of air, gravity and constraints on the micro-vibration characteristics under the ground test state, and realizes the ground test on the micro-vibration characteristics of the actual on-orbit state. foreshadowing.

The mapping method provided by the present invention comprises the following steps:

(1) Establish the finite element model of the ground test spacecraft and the finite element model of the in-orbit spacecraft to simulate the mechanical environment of the ground micro-vibration test;

(2) Through the modal analysis of the finite element model of the ground test spacecraft and the finite element model of the on-orbit spacecraft, the frequency and mode shape data are extracted, and the ground test modal coordinate reduction model and the on-orbit modal coordinate reduction model are respectively established , and determine the one-to-one correspondence between the frequency and mode shape of the finite element model of the ground test spacecraft and the finite element model of the in-orbit spacecraft.

(3) According to the corresponding comparison between the ground test modal coordinate reduction model and the ground test spacecraft finite element model, determine the correctness of the ground test modal coordinate reduction model; according to the on-orbit modal coordinate reduction model and the on-orbit spacecraft finite element model Comparing the response of the model to determine the correctness of the on-orbit modal coordinate reduction model;

(4) Through the BP (Back Propagation) network, the mapping between the frequency and mode shape of the ground test state to the frequency and mode shape of the on-orbit state is realized considering gravity, constraints, and aerodynamic environmental factors, and the limited The frequency and mode shape of the meta-model.

(5) According to the frequency and mode shape of the finite element model of the on-orbit spacecraft obtained by mapping, the dynamic response analysis of the finite element model of the on-orbit spacecraft is performed.

The mapping method provided by the present invention has the advantages of:

Realized the mapping of spacecraft ground test and on-orbit micro-vibration dynamics environment, eliminated the influence of air, gravity, and constraints on ground micro-vibration test under the ground micro-vibration test state, and realized the prediction of the micro-vibration characteristics of the actual on-orbit state by ground test. At the same time, the mapping method can realize the mutual comparison between the ground micro-vibration test data and the on-orbit test data, and verify the validity of the ground micro-vibration test.

Description of drawings

Fig. 1 is the flowchart of mapping method of the present invention;

Fig. 2 is the comparison of the mechanical environment of the spacecraft in orbit and the ground test of the present invention;

Fig. 3 is the flowchart of three-level mapping of the present invention;

Fig. 4 is the time domain response comparison of the ground modal coordinate reduction model of the example of the present invention and the finite element model;

Fig. 5 is the time-domain response relative error of the ground micro-vibration of the example of the present invention, which varies with time;

Fig. 6 is a comparison of micro-vibration time-domain responses between the on-orbit modal coordinate reduction model and the finite element model of the example of the present invention;

Fig. 7 is a time domain response relative error graph of micro-vibration in orbit in the example of the present invention;

Fig. 8 is the time domain response of on-orbit micro-vibration predicted by the example of the present invention;

Fig. 9 is a time-dependent diagram of the relative error of the predicted on-orbit response compared with the reduced model response according to the example of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

The present invention provides a method for mapping spacecraft ground testing and on-orbit microvibration dynamics environment, as shown in the flow chart in Figure 1. The mapping method includes the following steps:

(1) Establish the finite element model of the spacecraft, including the finite element model of the ground test spacecraft and the finite element model of the spacecraft in orbit;

Establish the finite element model of the on-orbit spacecraft: According to the given typical spacecraft structure parameters, the finite element model of the on-orbit spacecraft is established. After the modeling is completed, parametric model corrections such as material stiffness, spring stiffness, and modal damping ratio are performed to make the adjusted mathematical model fully reflect the dynamic characteristics of the spacecraft structure (such as frequency response function, natural frequency, etc. ).

Establish the finite element model of the ground test spacecraft: Since it is necessary to simulate the boundary conditions of the satellite during the ground test, such as hanging by a sling, it will be affected by gravity and air at the same time, so after the parametric model correction is completed, the in-orbit Based on the finite element model of the spacecraft, the beam element is used to simulate the establishment of the suspension rope. The influence of gravity can be simulated by adding prestress, and the influence of air can be simulated by adding mass.

(2) Establish the ground test modal coordinate reduction model and the on-orbit modal coordinate reduction model, and determine the one-to-one correspondence between the frequency and mode shape of the ground test spacecraft finite element model and the on-orbit spacecraft finite element model.

The multi-degree-of-freedom damping system satisfies the following equation:

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; m</span>}\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; C</span>}\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Ku</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, M, K, and C are mass matrix, stiffness matrix, and damping matrix, respectively, u(t) represent the acceleration, velocity and displacement at time t respectively, u ₀ , represent the initial displacement and initial velocity respectively, and f(t) is the external force at time t. Therefore, the mapping relationship between the finite element model of the ground test spacecraft and the finite element model of the in-orbit spacecraft can be regarded as the mapping relationship between the mass matrix, stiffness matrix and damping matrix of the two models. The coordinate transformation u(t)=Φq(t) is introduced by the natural mode matrix Φ, and q(t) represents the modal coordinates, then the equation (1) is transformed into:

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Phi;</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Normalize the selected natural mode shape matrix with respect to the modal mass, then,

M _q =Φ ^T MΦ=I, K _q =Φ ^T KΦ=diag[ω ² ], C _q =Φ ^T CΦ (3)

M _q , C _q , and K _q are the mass matrix, damping matrix, and stiffness matrix under the modal coordinates, respectively, I represents the unit matrix, and diag[ω ² ] represents the diagonal matrix whose diagonal is the square of frequency ω of each order, The damping is approximately treated as proportional damping, and equation (2) is transformed into n single-degree-of-freedom damping systems:

q _j , ζ _j and ω _j represent the generalized displacement, generalized velocity, generalized acceleration, damping ratio, and frequency of the j-th modal coordinate respectively. Arrange the equations (4) in ascending order of frequency, and take the first m (1<m<n ) order corresponding to the system of equations, introducing the state vector X,

X＝[x ₁₁ ,x ₂₂ ,…,x _1j ,x _2j ,…,x _1m ,x _2m ] (5)

in Then equation (4) can be rewritten as a differential system expressed in vector form containing 2m first-order differential equations:

X'＝f(X) (6)

Solved by Runge-Kutta numerical integration, the displacement of the system in the physical coordinates is obtained as:

From the above derivation process, it can be seen that establishing the mapping relationship between the finite element model of the ground test spacecraft and the finite element model of the on-orbit spacecraft is equivalent to establishing the characteristic relationship between the finite element model of the ground test spacecraft and the finite element model of the on-orbit spacecraft The mapping relationship between value and feature vector. For the finite element model of the ground test spacecraft and the finite element model of the on-orbit spacecraft, the Nastran secondary development language DMAP is used to extract the frequency and mode shape data of the finite element model of the ground test spacecraft and the finite element model of the on-orbit spacecraft, respectively. Establish their respective ground test modal coordinate reduction models and on-orbit modal coordinate reduction models. The finite element model of the ground test spacecraft and the finite element model of the on-orbit spacecraft are respectively subjected to modal analysis. There is a one-to-one correspondence between the frequency and mode shape of the finite element model of the device.

(3) Response calculation to determine the correctness of the ground test modal coordinate reduction model and the on-orbit modal coordinate reduction model.

The time domain response analysis of the ground test modal coordinate reduction model and the ground test spacecraft finite element model is carried out, and the time domain response of the ground test modal coordinate reduction model and the ground test spacecraft finite element model is analyzed and compared; the on-orbit modal Coordinate reduction model and on-orbit spacecraft finite element model for time-domain response analysis, and compare the time-domain responses of on-orbit modal coordinate reduction model and on-orbit spacecraft finite element model through analysis; if the time-domain response results show that the response analysis error is low If it is less than 20%, it indicates that the ground test modal coordinate reduction model or the on-orbit modal coordinate reduction model is correct.

(4) Establishment of spacecraft fretting dynamics mapping relationship.

The mechanical environment of the on-orbit spacecraft is quite different from that of the ground test. As shown in Figure 2, the working environment of the on-orbit spacecraft is vacuum and free flight without gravity. The spacecraft in the ground test is subject to gravity, constraints (referring to the ground To test the influence of the sling suspension constraint used in the spacecraft finite element model) and the air environment noise factors, it is necessary to consider the magnitude of the influence of these factors on the frequency and mode shape, and establish a mapping relationship by using the BP neural network. The mapping from the frequency and mode shape of the ground test spacecraft to the frequency and mode shape of the orbiting spacecraft is realized through the BP neural network.

The complex mechanical environment mapping is decomposed into three-level mapping, as shown in Figure 3. Firstly, the frequency and mode shape data of the airless state (that is, including gravity and constraint effects) are obtained according to the frequency and mode shape data obtained from the ground test (by considering only the mapping relationship of air influence). In the same way, by only considering the mapping relationship of gravity, the frequency and mode shape data of no air and no gravity (including the constraint state) are obtained. Finally, the unconstrained on-orbit frequency and vibration mode data are obtained according to the mapping relationship that only considers constraints. The specific implementation steps of the three-level mapping are as follows:

a) Research on the mapping relationship considering the influence of air;

The BP neural network method is used to establish the mapping relationship from the ground test to the natural frequency and mode shape of the airless state considering the influence of air. Regardless of the changes in gravity and constraints, only the influence of air is considered, and the frequency and mode shape data under different air densities are calculated, and the mapping relationship is established based on these data. Through this mapping relationship, the on-orbit (no air, that is, the air density is 0 state) state data.

b) Research on the mapping relationship considering the influence of gravity;

The neural network model is used to establish the mapping relationship from the ground test to the natural frequency and mode shape of the on-orbit state considering the influence of gravity. On the basis of considering the air and the influence of gravity, the frequency and mode shape under different gravitational accelerations are calculated, and the mapping relationship is established based on these data, and the data in the orbit (0g) state is obtained through this mapping relationship.

c) Research on the mapping relationship considering the influence of constraints;

The neural network model is used to establish the mapping relationship from the ground test to the natural frequency and mode shape of the on-orbit state considering the influence of constraints. On the basis of air and gravity, and considering the influence of constraints, the frequency and mode data of different suspension rope cross-sectional areas are calculated. Based on these data, a mapping relationship is established, from which the data in the state of on-orbit (unconstrained, equivalent to the state where the cross-sectional area of the suspension rope is 0 mm ² ) is obtained.

(5) On-orbit response calculation. According to the frequency and mode shape of the finite element model of the on-orbit spacecraft obtained through mapping, the dynamic response calculation of the finite element model of the on-orbit spacecraft is performed. The effectiveness of this mapping method and ground testing can be verified by comparing with actual in-orbit data.

The prestressed modal analysis is performed on the finite element model of the ground test spacecraft of the present invention, and the seventh to tenth order frequencies are 140.904Hz, 146.906Hz, 149.918Hz, and 160.582Hz. The first four frequencies in orbit state are 140.852Hz, 146.830Hz, 149.841Hz, 160.504Hz. At the same time, the mode shapes are also in one-to-one correspondence, so a mapping relationship can be established between the frequencies and mode shapes of the ground test spacecraft finite element model and the in-orbit spacecraft finite element model.

Response analysis was performed on the finite element model of the ground test spacecraft and the finite element model of the on-orbit spacecraft, and the first 20 order elastic modes were respectively taken to reduce the finite element model of the ground test spacecraft and the finite element model of the on-orbit spacecraft. The time-domain response of the modal coordinate reduction model and the ground test spacecraft finite element model is shown in Figure 4, and the relative error of the ground test time-domain response changes with time is shown in Figure 5. The comparison of the micro-vibration time-domain response of the finite element model of the orbiting spacecraft. Figure 7 is a graph of the relative error of the on-orbit micro-vibration time-domain response versus time. It can be seen from Fig. 5 and Fig. 7 that the relative error is less than 20%, so the reduction of the finite element model of the ground test and the spacecraft in orbit is correct.

Table 1 shows the calculation results of frequency mapping. The two columns of air represent the relative change of the first four orders of frequency between the on-orbit and ground vibration tests and the relative error between the frequency obtained through mapping and the actual on-orbit frequency when only the air influence is considered. , the same is the case where only gravity acceleration and constraints are considered. The last two columns are the relative changes of the three mechanical environment factors including air, gravity acceleration, and constraints, and the frequency value obtained through the three-level mapping is compared with the frequency value of the on-orbit model. The relative error of the ratio. It can be seen from the table that compared with the relative change in the complex mechanical environment, the magnitude of the relative error is more than 3 orders of magnitude smaller, so the frequency mapping is effective.

Table 1 Calculation results of frequency mapping

The same conclusion can be drawn for mode shape mapping. Table 2 shows the relative change and error of the maximum displacement of the first four vibration modes. Compared with the relative change in the complex mechanical environment, the relative error is more than 2 orders of magnitude smaller, so the mapping of the mode shape is also effective.

Table 2 Calculation results of the maximum displacement mapping of the first four modes

According to the obtained frequency and mode shape of the finite element model of the on-orbit spacecraft, as in step 3, the dynamic response calculation of the finite element model of the on-orbit spacecraft can be performed. Figure 8 shows the predicted on-orbit time-domain response, and Figure 9 shows the relative error versus time of the predicted on-orbit response compared with the modal coordinate reduction model response. From Figure 9, it can be seen that the relative error of the response prediction is within 7% , so the prediction is correct.

Claims (4)

1. A spacecraft ground test and on-orbit microvibration dynamics environment mapping method, characterized in that: The first step is to establish the finite element model of the ground test spacecraft and the finite element model of the in-orbit spacecraft to simulate the mechanical environment of the ground micro-vibration test; In the second step, through the modal analysis of the finite element model of the ground test spacecraft and the finite element model of the on-orbit spacecraft, the frequency and mode shape data are extracted, and the ground test modal coordinate reduction model and the on-orbit modal coordinate reduction model are respectively established. model, and determine the one-to-one correspondence between the frequency and mode shape of the finite element model of the ground test spacecraft and the finite element model of the spacecraft in orbit; The third step is to determine the correctness of the ground test modal coordinate reduction model according to the response comparison between the ground test modal coordinate reduction model and the ground test spacecraft finite element model; Response comparison of the meta-model to determine the correctness of the on-orbit modal coordinate reduction model; The fourth step is to realize the mapping between the frequency and mode shape of the ground test state to the frequency and mode shape of the on-orbit state by considering gravity, suspension constraints, and aerodynamic environmental factors through the BP network, and obtain the finite element model of the on-orbit spacecraft frequency and mode shape; The fifth step is to analyze the dynamic response of the finite element model of the on-orbit spacecraft according to the frequency and vibration mode of the finite element model of the on-orbit spacecraft. 2. A spacecraft ground test and on-orbit microvibration dynamics environment mapping method according to claim 1, characterized in that: after the ground test spacecraft finite element model and the on-orbit spacecraft finite element model are established Parametric model correction is carried out; the finite element model of the ground test spacecraft is based on the finite element model of the spacecraft in orbit, and the beam element is used to simulate the establishment of the suspension rope. The influence of gravity is simulated by adding prestress, and the influence of air is simulated by adding quality to simulate. 3. a kind of spacecraft ground test according to claim 1 and on-orbit microvibration dynamics environment mapping method, it is characterized in that: in the described 3rd step, response contrast, if time domain response analysis error is lower than 20%, Then it shows that the ground test modal coordinate reduction model or the on-orbit modal coordinate reduction model is correct. 4. a kind of spacecraft ground test according to claim 1 and on-orbit micro-vibration dynamics environment mapping method, it is characterized in that: the establishment of described mapping relationship is three-level mapping, and concrete realization steps are as follows: a) Using the BP neural network method to establish the mapping relationship from the ground test to the natural frequency and mode shape of the airless state considering the influence of the air; without considering the changes in gravity and constraints, only the influence of the air is considered, and the calculation results are obtained under different air densities. Frequency, mode shape data, establish mapping relationship according to these data, obtain the data under the on-orbit state through this mapping relationship; Described on-orbit state refers to the state of no air, that is, the air density is 0; b) Using the BP neural network method to establish the mapping relationship from the ground test to the on-orbit state natural frequency and mode shape considering the influence of gravity; on the basis of considering the air and considering the influence of gravity, the frequency under different gravity acceleration conditions is calculated , mode shape, establish a mapping relationship according to these data, and obtain the data in the on-orbit state through the mapping relationship, and the on-orbit state means that the gravity is 0g; c) Using the BP neural network method to establish the mapping relationship from the ground test to the natural frequency and mode shape of the on-orbit state considering the influence of the suspension constraint; on the basis of considering the air and gravity, and considering the influence of the suspension constraint, different suspension ropes are calculated The frequency and mode shape data in the case of cross-sectional area; the mapping relationship is established based on these data, and the data in the on-orbit state is obtained from the mapping relationship. The on-orbit state refers to unconstrained, which is equivalent to a suspension rope with a cross-sectional area of 0mm ² status.