SiC轻量化主镜液压whiffletree支撑系统的改进

Improvement on hydraulic whiffletree support system for SiC lightweight primary mirror

针对2mSiC轻量化主镜设计了液压whiffletree被动支撑系统,通过在轴向液压支撑点处并联杠杆配重机构的方式,实现了不同支撑圈上轴向支撑力的优化分配,将轴向支撑下主镜的镜面变形RMS值从7.1nm优化到4.8nm。针对SiC主镜热膨胀率大的特性,提出了采用具有热解耦能力的切向连杆结合液压whiffletree的侧向支撑系统,并借助于有限元法预算出主镜光轴水平状态下侧向支撑引起的镜面变形误差RMS值为39.7nm。当温差为20℃时,轴向和侧向支撑结构作用下的主镜镜面变形误差RMS值仍保持在4.8nm,验证了侧向支撑良好的热解耦能力。

Improved hydraulic whiffletree passive support system was designed for 2 m SiC lightweight primary mirror. The lever counterweight mechanism connected to hydraulic whiffletree mechanism was used for axial support system. The axial support force optimization distribution in different support points was accomplished by the axial support system, and the root- mean- square （RMS） of the mirror distortion resulted by axial support system was improved from 7.1 nm to 4.8 nm, which was optimized by finite element analysis （FEA） method. Considering the large thermal expansion coefficient of SiC, tangent link mechanism which owned adaptive bucking thermal stress attribute combined with hydraulic whiffletree mechanism was applied to the lateral support system for SiC primary mirror. When telescope was printed to horizon, the mirror distortion caused by the lateral support system was analyzed, and 39.7 nm RMS of the primary mirror deformation was obtained by FEA. As the ambient temperature raised from 20 ℃ to 40 ℃, the mirror distortion resulted by the axial support and lateral support system was still kept on the level of 4.8 nm RMS. Analysis result indicates well thermal adaptability of the improved lateral support system.