空间光谱仪指向机构的力学分析

Mechanical analysis of pointing mechanism for space spectrometer

为了准确分析空间CO2光谱仪指向机构的力学特性,本文根据轴承结构参数,建立了轴承有限元接触分析模型。计算了不同载荷下轴心的位移量,用多项式对计算结果进行拟合得到轴承非线性刚度曲线。在指向机构有限元力学模型中,利用相应刚度的弹簧单元替代轴承结构,经过有限元频率响应分析后获得指向机构的动态特性。仿真实验显示:在重力工况下指向镜的面形在光轴和子午方向分别为19.23nm和19.27nm,满足优于λ/30(均方根值RMS,λ=632.8nm)的设计要求,3个方向基频均大于100Hz。振动试验显示,3个方向基频均优于100 Hz,振动试验后反射镜镜面面形精度为λ/35。分析结果与仿真结果相符,表明利用非线性接触分析方法可以较为准确地求解轴承刚度,同时空间光谱仪指向机构静/动力学性能满足设计要求。

To accurately analyze dynamic characteristics of pointing mechanism of a CO2 space spectrometer,a bearing finite element contact analysis model was established according to the bearing structural parameters in this paper.The displacements with different loads for an axis were calculated,and the nonlinear stiffness curve for the bearing was obtained by the polynomial fitting for calculated results.In finite element dynamic analysis model of pointing mechanism,a spring unit with corresponding stiffness was used to replace the bearing structure,and the dynamic characteristics of the pointing mechanism were obtained by analysis of infinite element frequency response.The simulation experiment shows that the surface shape of mirror is 19.23 nm and 19.27 nm in optics axis and meridian direction at a static condition,which satisfy the design requirement ofλ/30（RMS,λ=632.8nm）and all base frequencies in 3directions are over 100 Hz.Moreover,mechanical vibration experiments also verify that all base frequencies in 3directions are over 100 Hz and the surface shape accuracy of the mirror isλ/35.The calculation results agree well with the experimental results.It concludes that the analysis method with nonlinear contact solves the bearing stiffness accurately,and the static/dynamic performance of pointing mechanism meets design requirements.