A method for obtaining micro-vibration test conditions for aerospace vehicles

Abstract

A method for obtaining micro-vibration test conditions for aerospace vehicles involves: searching for micro-vibration disturbance sources during the vehicle's on-orbit operation; classifying the micro-vibration disturbance sources and identifying those that cannot be avoided; conducting micro-vibration environment measurement tests on the unavoidable disturbance sources to obtain the time-domain curve of the maximum vibration environment of the disturbance sources; establishing a finite element model for micro-vibration response analysis; conducting transient response analysis to determine the micro-vibration response of precision instruments; converting the time-domain curve of the micro-vibration response of the precision instruments into a frequency-domain curve and performing envelope design to obtain the micro-vibration test conditions of the precision instruments for subsequent experimental verification.

Description

Technical Field

[0001] This invention relates to a method for obtaining micro-vibration test conditions for aerospace vehicles, belonging to the field of structural loads and mechanical environment of aerospace vehicles. Background Technology

[0002] Micro-vibration refers to the minute vibration response with a frequency ranging from 1 to 1000 Hz caused by internal or external disturbances during the on-orbit operation of a spacecraft. Existing Earth observation satellites, especially their imaging devices, are highly sensitive to micro-vibrations on board, thus leading to in-depth research on micro-vibrations in this field. During on-orbit missions of aerospace vehicles, components may interfere with the operation of other instruments; such components are called disturbance sources, and the affected instruments are called precision instruments. The micro-vibration environment caused by disturbance sources affects the operation of precision instruments, potentially leading to mission anomalies or even mission failure. Therefore, studying the micro-vibration response of various disturbance sources on spacecraft and evaluating the micro-vibration environment adaptability of precision instruments is of significant practical importance; however, the methods and techniques for determining micro-vibration responses remain a pressing problem to be solved. Summary of the Invention

[0003] The technical problem solved by this invention is: addressing the lack of a method for determining test conditions in traditional micro-vibration tests in the existing technology, this invention proposes a method for obtaining micro-vibration test conditions for aerospace vehicles.

[0004] The present invention solves the above-mentioned technical problem through the following technical solution:

[0005] A method for obtaining micro-vibration test conditions for aerospace vehicles includes:

[0006] Search for sources of micro-vibration disturbances during the on-orbit operation of the spacecraft;

[0007] Classify the sources of micro-vibration disturbance and identify those that cannot be avoided;

[0008] Conduct micro-vibration environment measurement tests on unavoidable disturbance sources to obtain the time-domain curve of the maximum vibration environment of the disturbance source;

[0009] Establish a finite element model for micro-vibration response analysis;

[0010] Conduct transient response analysis to determine the micro-vibration response of precision instruments;

[0011] The time-domain curve of the micro-vibration response of the precision instrument is transformed into the frequency-domain curve, and the envelope is designed to obtain the micro-vibration test conditions of the precision instrument for subsequent test verification.

[0012] The sources of micro-vibration disturbance include, but are not limited to, vibration and shock environments within the frequency band of 0.5Hz-500Hz that affect the precision instruments of the aircraft. Specifically, these include vibrations during the operation of the heat control pump, fluid vibrations in the fluid pipeline, vibrations during the operation of the flywheel, vibrations during engine startup, vibrations during solar panel deployment, vibrations oriented towards the sun, and impacts during the unlocking of pyrotechnic devices. The frequency bands and impact accelerations of all vibration and shock environments are statistically analyzed and compiled.

[0013] Disturbance sources are classified according to their intensity and occurrence time. If the disturbance source has no impact on the operation of the precision instrument, it can be removed. If the disturbance source is generated at a time that is different from the operation time of the precision instrument, it can be removed. The remaining disturbance sources after removal are those that cannot be avoided.

[0014] Before conducting the micro-vibration environment measurement test, boundary conditions are set, specifically as follows:

[0015] Connect the disturbance source component to the test fixture and fix it to the micro-vibration measuring table;

[0016] Ensure the test environment is in a quiet state;

[0017] Select an accelerometer whose sampling rate, frequency range, measurement range, and resolution meet the requirements.

[0018] In the micro-vibration environment measurement test, the disturbance source component is placed in the working state, and the acceleration response at the disturbance source and the test fixture is collected to form an acceleration time-domain curve. After the measurement test is completed, the micro-vibration environment measurement test results of the disturbance source are statistically analyzed to obtain the maximum vibration environment time-domain curve of the disturbance source.

[0019] If the disturbance source component includes more than one operating mode, the micro-vibration environment measurement test covers all operating modes; if the disturbance source component includes more than one sub-component, the micro-vibration environment measurement test covers all combinations of operating states of all sub-components.

[0020] Establish a finite element model for micro-vibration response analysis, wherein:

[0021] The corresponding simulation tools simulate slender rods and plate / shell structures. After modeling, modal analysis is performed using the finite element model. The modal analysis results are compared with the results of micro-vibration environment measurement tests. If the modal analysis results and the micro-vibration environment measurement test results meet the modal frequency difference requirement, the finite element model is determined; otherwise, the finite element model is modified until the modal frequency difference requirement is met.

[0022] The modal analysis results were obtained through full-vehicle modal testing.

[0023] The modal frequency difference requirement is that the first three modal frequencies differ by no more than 5%.

[0024] Transient analysis was performed based on the finite element model. The time-domain curve of the maximum vibration environment was selected as the excitation, the boundary conditions were set to free state, the modal damping ratio was fixed, the analysis step size was determined according to the upper limit of the transient analysis frequency, and the acceleration response time-domain curves of the precision instrument installation location under various working conditions were calculated.

[0025] The time-domain curve of the micro-vibration response is transformed into the impact response spectrum in the frequency domain with a dynamic amplification factor of Q=20. The frequency-domain acceleration is divided by 20, and the frequency-domain acceleration curves for all working conditions are enveloped. The micro-vibration test conditions of the precision instrument are calculated and determined based on the preset safety factor.

[0026] After obtaining the micro-vibration test conditions for the precision instrument, conduct full-vehicle or section-level micro-vibration environment verification tests according to the requirements of the aerospace vehicle test mission. The test objects are disturbance source components, precision instruments, vehicle structures or section-level structures. The boundary condition is free suspension, and the frequency of the suspension device is less than 1 / 6 of the first-order frequency of the free state of the vehicle. After conducting the full-vehicle or section-level micro-vibration environment verification test, place the disturbance source component in the working state, measure the acceleration response at the installation location of the precision instrument and convert it into a micro-vibration frequency domain acceleration curve to confirm the envelope of the micro-vibration test conditions. If the envelope is acceptable, the micro-vibration test conditions are closed-loop; otherwise, modify the micro-vibration test conditions for the precision instrument and conduct the full-vehicle or section-level micro-vibration environment verification test again.

[0027] The advantages of this invention compared to the prior art are:

[0028] This invention provides a method for obtaining micro-vibration test conditions for aerospace vehicles, which can solve the problem of providing input basis for the working performance of precision instruments under micro-vibration environment. There are many disturbance sources on the vibrator. The disturbance sources are classified and the micro-vibration response problem caused by the disturbance sources is solved by comprehensively adopting "avoidance" and "resistance". This solves the problem of the adaptability of precision instruments to the working environment. At the same time, transient response analysis based on modal frequency and experimental verification are used to verify the effectiveness of micro-vibration test conditions and ensure the correctness of test conditions. Attached Figure Description

[0029] Figure 1 A flowchart for obtaining micro-vibration test conditions for aerospace vehicles provided for the invention; Detailed Implementation

[0030] A method for obtaining micro-vibration test conditions for aerospace vehicles is proposed, which combines experimental and simulation analysis to establish micro-vibration environment test conditions. This provides input basis for evaluating the performance of precision instruments under micro-vibration conditions. The specific steps of the method are as follows:

[0031] Search for sources of micro-vibration disturbances during the on-orbit operation of the spacecraft;

[0032] Classify the sources of micro-vibration disturbance and identify those that cannot be avoided;

[0033] Conduct micro-vibration environment measurement tests on unavoidable disturbance sources to obtain the time-domain curve of the maximum vibration environment of the disturbance source;

[0034] Establish a finite element model for micro-vibration response analysis;

[0035] Conduct transient response analysis to determine the micro-vibration response of precision instruments;

[0036] The time-domain curve of the micro-vibration response of the precision instrument is transformed into the frequency-domain curve, and the envelope is designed to obtain the micro-vibration test conditions of the precision instrument for subsequent test verification.

[0037] The following description, in conjunction with the accompanying drawings and preferred embodiments, provides further details:

[0038] In the current embodiment, the acquisition method flow is as follows: Figure 1 As shown, the sources of micro-vibration disturbance include, but are not limited to, vibration and shock environments within the frequency band of 0.5Hz-500Hz that affect the precision instruments of the aircraft. Specifically, these include vibrations of the heat control pump, fluid vibrations in the fluid pipeline, vibrations of the flywheel, vibrations during engine startup, vibrations during solar panel deployment, vibrations oriented towards the sun, and shocks from unlocking pyrotechnic devices. The frequency bands and shock accelerations of all vibration and shock environments are statistically analyzed.

[0039] Disturbance sources are classified according to their intensity and occurrence time. If the disturbance source has no impact on the operation of the precision instrument, it can be removed. If the occurrence time of the disturbance source is different from the occurrence time of the precision instrument, it can be removed. The remaining disturbance sources after removal are those that cannot be avoided.

[0040] Before conducting micro-vibration environment measurement tests, boundary conditions are set, specifically as follows:

[0041] Connect the disturbance source component to the test fixture and fix it to the micro-vibration measuring table;

[0042] Ensure the test environment is in a quiet state;

[0043] Select an accelerometer with suitable sampling rate, frequency range, measurement range, and resolution. Generally, the sampling rate should be more than three times the maximum value of the frequency range of interest, and the frequency range should start from 0 Hz.

[0044] In the micro-vibration environment measurement test, after the measuring equipment is ready, the disturbance source component is placed in the working state, and the acceleration response at the disturbance source and the test fixture is collected to form the acceleration time-domain curve. After the measurement test is completed, the micro-vibration environment measurement test results of the disturbance source are statistically analyzed, and the maximum vibration environment time-domain curve of the disturbance source is obtained.

[0045] If the disturbance source component includes more than one operating mode, the micro-vibration environment measurement test covers all operating modes; if the disturbance source component includes more than one sub-component, the micro-vibration environment measurement test covers all combinations of operating states of all sub-components.

[0046] A finite element model for micro-vibration response analysis was established using the commercial finite element software MSC.Patran. Slender rods were simulated using bar elements CRod or beam elements CBar and Cbream, while plate and shell structures were simulated using CQUAD4. After modeling, modal analysis was performed using the finite element model. The modal analysis results were compared with the results of micro-vibration environment measurement experiments. When the modal analysis results and the micro-vibration environment measurement experiment results met the modal frequency difference requirement, the finite element model was determined; otherwise, the finite element model was modified until the modal frequency difference requirement was met. The modal frequency difference requirement was that the first three modal frequencies differed by no more than 5%.

[0047] The modal analysis results were obtained through full-vehicle modal testing.

[0048] The commercial finite element software MSC.Nastran solver SOL224 was used for transient analysis based on the finite element model. The time-domain curve of the maximum vibration environment was selected as the excitation, the boundary conditions were set to free state, and the modal damping ratio was fixed. The analysis step size was determined according to the upper limit of the transient analysis frequency. The modal damping ratio is generally taken as 0.01. If there are measured values ​​from modal tests, the measured values ​​can also be used. The solution step size is t=1 / 2f, where f is the upper limit of the analysis frequency. For example, if the analysis frequency is 500Hz, the step size can be taken as 0.001s. The acceleration response time-domain curves of the precision instrument installation location under various working conditions were calculated, and the acceleration response time-domain curves of the precision instrument installation location under various working conditions were extracted from the solution results .f06 file.

[0049] The time-domain curve of the micro-vibration response of the precision instrument is transformed into a frequency-domain curve. The time-domain curve is then transformed into an impact response spectrum with Q=20. The specific algorithm can be found in relevant standard documents. The acceleration value in the frequency domain is divided by 20. The frequency-domain acceleration curves of all working conditions are enveloped and multiplied by a safety factor of 1.25 to obtain the micro-vibration test conditions of the precision instrument. Based on this, the micro-vibration test of the precision instrument can be carried out.

[0050] Subsequent testing will involve full-vehicle or section-level micro-vibration environment verification tests. The test plan is as follows: the products participating in the test include disturbance source components, aircraft structural counterweights, precision instruments, etc.; the test boundary condition is free suspension, and the frequency of the suspension device should be less than 1 / 6 of the first-order frequency of the aircraft in free state; the disturbance source will be placed in the working state, and the acceleration response at the installation location of the precision instrument will be measured and converted into a frequency-acceleration curve to confirm the envelope of the micro-vibration test conditions. If the envelope is valid, the design is considered closed-loop; otherwise, the micro-vibration test conditions of the precision instrument must be modified, and the micro-vibration test of the precision instrument must be carried out again.

[0051] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0052] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for obtaining micro-vibration test conditions for aerospace vehicles, characterized in that... include: Search for sources of micro-vibration disturbances during the on-orbit operation of the spacecraft; Classify the sources of micro-vibration disturbance and identify those that cannot be avoided; Conduct micro-vibration environment measurement tests on unavoidable disturbance sources to obtain the time-domain curve of the maximum vibration environment of the disturbance source; Establish a finite element model for micro-vibration response analysis; Conduct transient response analysis to determine the micro-vibration response of precision instruments; The time-domain curve of the micro-vibration response of the precision instrument is transformed into the frequency-domain curve, and the envelope is designed to obtain the micro-vibration test conditions of the precision instrument for subsequent test verification. In the micro-vibration environment measurement test, the disturbance source component is placed in the working state, and the acceleration response at the disturbance source and the test fixture is collected to form an acceleration time-domain curve. After the measurement test is completed, the micro-vibration environment measurement test results of the disturbance source are statistically analyzed to obtain the maximum vibration environment time-domain curve of the disturbance source. If the disturbance source component includes more than one operating mode, the micro-vibration environment measurement test covers all operating modes; if the disturbance source component includes more than one sub-component, the micro-vibration environment measurement test covers all combinations of operating states of all sub-components. Transient analysis was performed based on the finite element model. The time-domain curve of the maximum vibration environment was selected as the excitation, the boundary conditions were set to free state, the modal damping ratio was fixed, the analysis step size was determined according to the upper limit of the transient analysis frequency, and the acceleration response time-domain curves of the precision instrument installation location under various working conditions were calculated. The time-domain curve of the micro-vibration response is transformed into the impact response spectrum in the frequency domain with a dynamic amplification factor of Q=20. The frequency-domain acceleration is divided by 20, and the frequency-domain acceleration curves for all working conditions are enveloped. The micro-vibration test conditions of the precision instrument are calculated and determined based on the preset safety factor.

2. The method for obtaining micro-vibration test conditions for aerospace vehicles according to claim 1, characterized in that: The micro-vibration disturbance sources include vibration and shock environments within the frequency band of 0.5Hz-500Hz that affect the precision instruments of the aircraft, specifically including thermal control pump operating vibration, fluid pipeline vibration, flywheel operating vibration, engine start-up vibration, solar panel deployment vibration, solar orientation vibration, and pyrotechnic device unlocking impact; the frequency bands and impact accelerations of all vibration and shock environments are statistically analyzed.

3. The method for obtaining micro-vibration test conditions for aerospace vehicles according to claim 2, characterized in that: Disturbance sources are classified according to their intensity and occurrence time. If the disturbance source has no impact on the operation of the precision instrument, it can be removed. If the occurrence time of the disturbance source is different from the occurrence time of the precision instrument, it can be removed. The remaining interference sources after removal are those that cannot be avoided.

4. The method for obtaining micro-vibration test conditions for aerospace vehicles according to claim 3, characterized in that: Before conducting the micro-vibration environment measurement test, boundary conditions are set, specifically as follows: Connect the disturbance source component to the test fixture and fix it to the micro-vibration measuring table; Ensure the test environment is in a quiet state; Select an accelerometer whose sampling rate, frequency range, measurement range, and resolution meet the requirements.

5. The method for obtaining micro-vibration test conditions for aerospace vehicles according to claim 4, characterized in that: Establish a finite element model for micro-vibration response analysis, wherein: The appropriate simulation tool is determined to simulate slender rods and plate / shell structures. After modeling, modal analysis is performed using the finite element model. The modal analysis results are compared with the results of micro-vibration environment measurement tests. If the modal analysis results and the micro-vibration environment measurement test results meet the modal frequency difference requirement, the finite element model is determined; otherwise, the finite element model is modified until the modal frequency difference requirement is met. The modal analysis results were obtained through full-vehicle modal testing.

6. The method for obtaining micro-vibration test conditions for aerospace vehicles according to claim 5, characterized in that: The modal frequency difference requirement is that the first three modal frequencies differ by no more than 5%.

7. The method for obtaining micro-vibration test conditions for aerospace vehicles according to claim 6, characterized in that: After obtaining the micro-vibration test conditions for the precision instrument, conduct full-vehicle or section-level micro-vibration environment verification tests according to the requirements of the aerospace vehicle test mission. The test objects are disturbance source components, precision instruments, vehicle structures or section-level structures. The boundary condition is free suspension, and the frequency of the suspension device is less than 1 / 6 of the first-order frequency of the free state of the vehicle. After conducting the full-vehicle or section-level micro-vibration environment verification test, place the disturbance source component in the working state, measure the acceleration response at the installation location of the precision instrument and convert it into a micro-vibration frequency domain acceleration curve to confirm the envelope of the micro-vibration test conditions. If the envelope is acceptable, the micro-vibration test conditions are closed-loop; otherwise, modify the micro-vibration test conditions for the precision instrument and conduct the full-vehicle or section-level micro-vibration environment verification test again.

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