Research On The Designing Of Space Large-aperture Mirror And Its Supports

Since 1960 s,humans have used spacecrafts for deep space exploration to further understand the universe and explore the origin of the earth and life.Camera system is a main component of the space exploration spacecraft,and the optical mirror is the core component of the camera system.The mirror’s surface accuracy largely determines the imaging quality of the camera system.Therefore,the camera system plays an important role in the process of deep space exploration.At present,with the improvement of the national requirements for deep space detection accuracy,the requirements of telescope technology are becoming higher,that is,space cameras need to have higher resolution requirements.That will make the mirror aperture develop towards the direction of large aperture and long focal length.The diameter of the reflector increases and the optical requirements remain the same.The mirror’s diameter is increasing but the requirement of the optical remain the same or even smaller.That is to say,a mirror of several meters must have the same surface accuracy with tens of centimeters’ mirror.To achieve this purpose,we need higher technology and it is very difficult.As the diameter of the mirror increases,the weight of the mirror increases rapidly in proportion to the third power of the diameter of the mirror,and the sensitivity of the mirror to load and temperature also increases.However,due to the limitation of the satellite’s carrying capacity,the camera system needs to be as light as possible under the conditions of optical requirements.So,it is necessary to design a lightweight mirror and a support structure with highly reliability and stability.Therefore,a high degree lightweight of the mirror structure and the optimal design for the flexible support structure is a key technology to guarantee the high precision,high stability.This article is aimed at the design and study for a mirror that diameter is 800 mm,and it’s support structure.This article describes the lightweight design method and kinematics support principle of the large-diameter mirror,and gives the technical indexes that the mirror component under study should meet according to the design index of the optical system.Determined the support mode of the mirror and design the initial parameters of the mirror according to the design requirements of the mirror.Due to the advantages of high specific stiffness,small thermal expansion coefficient,good thermal conductivity,and excellent preparation performance,Si C is chosen as the Si C material in this paper.The finite element method is used to optimize the support position.Then,according to the requirements of the index,the topological optimization method is used to lightly design the mirror,and the mirror material can be optimally distributed under the condition that the mirror surface shape is unchanged.And in the process of topology optimization,process constraints are imposed to control the topological results to ensure that the mirror can be easily processed and manufactured.By comparing and analyzing the topological optimization results with the traditional lightweight structure,the topological optimization of the reflector is reduced by 12% compared with the traditional triangle,while the mirror shape remains basically unchanged.The mirror of this article is used 3 A-frame side support combine with 6 points supports of the back.Combined with Solidworks,ANSYS and MATLAB through Isight,and the multi-objective algorithm is used to optimize the size of the key parameters of the supporting structure.Traditional empirical design combined with parameter optimization methods such as size optimization and topology optimization,the support structure is automatically and efficiently parameterized.After completing the structural design and optimization of each component of the mirror,it is subjected to finite element simulation verification analysis,including static analysis and dynamic analysis.Static analysis verifies the finite element analysis of the mirror assembly under the action of 1g gravity and ± 2 ℃ temperature rise when the optical axis is horizontal and the optical axis is vertical.The displacements all meet the requirements.The maximum RMS value of the mirror shape is 7.94 nm,and the maximum PV value is 41.18 nm,both of which meet the design requirements.The modal analysis,sinusoidal vibration analysis,and random vibration analysis of the mirror assembly were performed,and the stresses of the weak links were all less than the allowable stress of the material.The mirror assembly satify the requirements of stiffness and strength,and the structure will not be destroyed under the complex vibration load conditions,and the dynamic performance is good.The above finite element simulation analysis verified that the mirror asembly structure designed in this paper satify the technology requirements.