| As space camera imaging technology continues to improve,the acquisition of higher resolution images has far-reaching implications in both the military field and people’s livelihood.The study of camera position control is particularly important in order to obtain higher resolution images.Reaction flywheel,as an position control actuation component,is subject to a series of unpredictable tiny vibrations during the imaging session due to small errors in its machining and assembly.Micro-vibration can seriously affect the image quality of the camera,reducing the resolution in mild cases and causing image distortion in severe cases.In order to ensure the image quality of the space camera in orbit,it is significant to study the microvibration caused by the reaction flywheel.In this paper,four aspects are investigated,including space camera modelling,preliminary space camera dynamics simulation analysis,space camera micro-vibration analysis and micro-vibration control.Firstly,an accurate finite element model was well established based on the geometric model of the space camera.We utilized MSC.NASTRAN as a model solver,introducing the modeling characteristics of MSC.NASTRAN briefly in combination with the finite element model of the camera.The modal analysis of the overall structure and the structure of the mirror group was carried out respectively,and the modal relationship between them was obtained.Then we carried out frequency response analysis and random vibration analysis of the overall structure,combined with modal analysis to analyze the dynamic response of the structure in the mid-frequency band.The response of the camera in the optical axis direction was greater than that of the mirror,and the response in the optical axis direction was mainly affected by the overall 3rd and 4th order constraint modals,while the mirror response was mainly affected by the overall 13 th,14th and 15 th order constraint modals.Subsequently,the overall structure was subjected to micro-vibration analysis.Studying from the micro-vibration load sources,the sinusoidal loads caused by the dynamic and static imbalance of the reaction flywheel and the random loads caused by other factors are converted into time-domain excitation signals using the Fast Fourier Transform.Transient analysis of the camera under time-domain excitation signals is carried out using the modal superposition method.The displacement response curves of the mirror measurement points were analysed to conclude that the deformation displacement of the reflector could be neglected.The trajectory of the mirror measurement point is plotted in combination with MATLAB programming,and it was found that the jitter of the measurement point research optical axis is larger to provide a research direction for micro-vibration suppression.Finally a study of vibration isolation of space camera is carried out based on microvibration analysis.The influencing factors of single-layer and double-layer vibration isolation are analysed.Based on the double-layer isolation theory,four vibration source isolation solutions were designed using organic rubber,and based on the micro-vibration response results of each solution,a vibration isolation solution combining a metal protective sleeve and organic rubber was selected.The size distribution of this vibration isolation scheme was also studied in depth and the optimum design size was obtained through sensitivity analysis.In addition to the vibration isolation design of the source,the reflector flexure was also analysed for vibration isolation,the flexure structure was modified by extending the energy transfer path and its strength and stability were defined.A new design for the flexure joint structure has been developed that meets the safety performance criteria and provides good vibration isolation. |
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