Research On Micro-vibration Analysis Of A Spacecraft Excited By Momentum Wheel

With the development of science and technology and the advancement of computer technology,the world has been advancing in the field of spacecraft launching,and the ability of testing and simulation has been greatly improved.The success rate of global spacecraft launch has reached a high level.However,there are still many unsolved problems in the field of spacecraft,and new problems are constantly emerging.In today's world,spaceflight is competing in the field of high-precision spacecraft.Such spacecraft has strict requirements on the imaging environment.There are certain difficulties in design,while maintaining the sensitivity to vibration and environmental changes while the overall size is large.Therefore,in the process of developing high-precision spacecraft,it is necessary to explore how to simulate the micro-vibration,what its vibration characteristics are,and how to effectively control the micro-vibration.The main research work and conclusions of this paper are as follows:(1)The Hyper Mesh software was used to establish a more accurate finite element model of the spacecraft structure.Using the finite element analysis software MSC.Nastran as the solver,the modal analysis was performed on the whole structure and part of the structure.Through the modal analysis,the dynamic characteristics of the spacecraft as a whole are known.Since the solar panel is in the unfolded state,there are many low-order modes in the whole structure;and the fundamental frequency of the function cabin,the main mirror assembly and the secondary mirror assembly are higher.(2)The relevant theoretical derivation of the load source and the specific unbalanced force(moment)load of the oblique mounted momentum wheel is given.According to the sinusoidal characteristics of the load,the frequency response analysis of the structure is carried out to obtain the vibration response characteristics of the structure in the whole analysis frequency range: the vibration of the structure is perpendicular to the main optical axis,and the vibration response of the main optical axis is smaller.(3)Using MATLAB programming,combine the sampling theorem,the definition of the power spectral density of the random signal and the Fast Fourier Transform(FFT),the broadband random noise introduced by the lubrication,friction and other disturbance sources of the bearing is converted into the time domain signal for loading together with the unbalanced force(moment)load.(4)The micro-vibration analysis of the structure was performed using the modal superposition method transient response analysis in MSC.Nastran,and the displacement response curves of the primary and secondary mirrors were output.The deformation curve,motion trajectory and relative displacement of the center point of the primary mirror and the secondary mirror are obtained by post-processing.It is concluded from the results that the elastic deformation of the primary and secondary mirrors is much smaller than that of the rigid body.In the simulation calculation,the primary and secondary mirrors can be approximated as rigid bodies,which are mainly concerned with the influence of rigid body displacement on imaging to reduce the calculation.(5)By giving the displacement response curves of the main nodes on the mirror and the secondary mirror,it is verified that the critical damping ratio of the spacecraft structure has a significant influence on the displacement peak-to-peak value of the micro-vibration.However,the installation stiffness of the skewed momentum wheel has little effect on the amplitude of the micro-vibration,and the stiffness cannot be increased as a method of reducing the amplitude of the micro-vibration.