空间相机桁架支撑结构满应力优化设计与试验

针对空间相机桁架式支撑结构在设计过程中难以同时保证重量轻且刚度高的问题, 提出了采用满应力方法对桁架杆截面进行优化设计的思想. 以桁架杆重量最低为优化目标, 桁架杆自重变形和桁架的一阶固有频率为约束条件, 桁架杆截面的内外径为优化变量, 建立了基于满应力准则的优化模型. 经过优化, 桁架杆截面的外径为50mm, 内径40mm, 质量6.1kg, 一阶固有频率121Hz. 采用有限元法对优化结果进行模态校核和重力变形校核, 同时为检验碳纤维复合材料的热稳定性, 对桁架组件进行了热变形分析, 得到次镜的偏心和偏转均满足光学设计要求. 对优化设计出的桁架组件进行了0.2g扫频试验以及尺寸稳定性试验. 试验结果表明, 桁架组件一阶固有频率119Hz 与理论分析结果基本吻合; 在45N外力载荷和15°C均匀温升载荷的作用下, 桁架稳定性能良好, 次镜的偏心和偏转均小于5", 满足光学设计要求. 优化设计出的桁架支撑结构具有刚度高、尺寸稳定等特点, 这为实现空间相机向大口径、长焦距、轻型化方向发展奠定了研究基础. 

Optimum Design Based on Full Stress Ruler and Test for Truss of Space Camera

Since it is hard to design the truss structure in space camera which has both low weight and high stiffness, the rule of full stress is proposed to optimize the truss section. The design rule and request of the optical system are introduced. By selecting the truss weight as the optimization object, gravitation transmutation and first frequency of secondary mirror as the restriction condition, and the inside and outside diameters of truss section as the optimization variables, the optimization model based on full stress rule is established. The optimized inside and outside diameters of truss section are 40mm and 50mm respectively, the optimized weight of truss is 6.3kg, while the first frequency is 121Hz. The mode analysis, gravitation transmutation analysis and temperature raise of 15℃ analysis later indicate that the truss optimized can satisfy the needs of the optical system. Finally, 0.2g vibration test and dimensional stability test are inflicted to the truss, which shows that the first frequency of the truss is 119Hz, and that the transmutation of the secondary mirror is less than 5". The truss optimized has the characteristic of compact structure and fine dimensional stability which meet the needs of space camera well. It lays a foundation for development of space camera with large caliber, long focus and light weight.