Study On The Micro Vibration Characteristic Of A Space-borne Two Dimensional Turntable

Micro vibration is a flutter response with low amplitude and high frequency caused by internal or external disturbances during the operation of the spacecraft.High resolution is one of the important directions for the development of satellite optical load,while micro vibration is an important factor restricting the resolution of satellite payload.In this paper,micro vibration characteristics of a space-borne two dimensional turntable are studied,and the vibration transfer characteristics of micro vibration generated by the balancing wheel of two dimensional turntable in the two dimensional turntable are analyzed,which lays the foundation for the characteristic analysis of micro-vibration and the suppression of vibration caused by optical load in the future.In this paper,the micro vibration characteristics of the balance wheel were analyzed through micro vibration experiment,and the acceleration amplitude and mean square error of the balance wheel vibration can be used as a reference to evaluate the balance quality of the balance wheel.Meanwhile,the input and output model of two dimensional turntable’s micro vibration was established,taking the output of the largest internal vibration source balance wheel of the two dimensional turntable as the input of the entire model.The SO Analyzer software was used to collect and analyze the output data of the balance wheel,and obtained an effective and accurate input finally.7 representative output positions of the two dimensional turntable were determined.Secondly,the finite element mesh of two dimensional turntable was divided,then two methods of bearing equivalent simulation were introduced,and a bearing equivalent method that suitable for the simulation of micro vibration of two dimensional turntable was determined.In the bearing equivalent simulation,four spring elements were used,simulating three flat degrees of freedom and one rotational degree of freedom respectively,and gave them corresponding stiffness.Finally,the accuracy of the bearing equivalent method was verified by experiments and simulations.Based on the finite element analysis software MSC.Patran & Nastran,a finite element model of the two dimensional was established and modal analysis was carried out.The twenty order natural frequencies and related modes of the two dimensional turntable were obtained,which provide reference for subsequent frequency response analysis and micro vibration test.The analysis results showed that the point with relatively large displacement of vibration mode appears on both sides of the U frame,indicating that these locations were relatively sensitive and easy to be stirred up large vibration.Nastran was used to analyze the frequency response of two dimensional turntable,and the output response,resonance frequency and amplitude of 7 positions were obtained.The micro-vibration experiment of the actual product of the two-dimensional turntable was carried out,and the acceleration sensor was applied to measure the vibration.By processing the experimental data through Matlab,the time domain and frequency domain curves of the 7 output positions in the two dimensional turntable were obtained,and its resonant frequencies and corresponding amplitudes.In addition,according to the results of the frequency response simulation and the micro vibration experiment,the correlation characteristics of the micro vibration on the two dimensional turntable were obtained,and the transfer effects of the different bearings on the vibration of the model were different.Finally,the resonance frequency of the 7 position output points in the simulation and the experiment was compared.The error was within the range of 0.13%～12.6%,which showed that the finite element model of the two dimensional turntable was accurate and effective,and it was suitable for the simulation of micro vibration.