| With the continuous improvement of the resolution and light-gathering capability requirement of space telescopes,the diameter of the primary reflector of the optical system is getting larger and larger,and the reflector components have become more sensitive to environmental disturbances such as gravity and temperature changes.With the increase of the aperture requirement of the traditional rigid single mirror system,the cost of manufacturing,processing,testing and transportation of the primary mirror increases sharply,and the safety risk also increases.The successful launch of the JWST telescope has proved the feasibility of the block-deployable space imaging system,which is an important solution for the future ultra-large aperture space optical system.The embedded parallel-actuated ultra-light mirror adopts the back-embedded parallel-actuated actuator,and uses the bending moment to actively adjust the mirror surface shape to correct the aberration,which meets the requirements of the splicing main mirror for the curvature adjustment ability,and does not require a high-rigidity mirror body and supporting structure.This feature can effectively reduce the weight of the system and improve the reliability and stability of the space optical system.It is a future-oriented large-diameter optical system mirror body.Therefore,the related research on embedded parallel-actuated ultralight mirrors for future space applications is gradually put on the agenda.In this paper,the following research work is carried out for the design and manufacture of embedded parallel-actuated ultralight mirrors:1.Summarize the realization schemes of ultra-large aperture space optical systems at home and abroad,analyze the characteristics and problems of sub-mirrors of the future block-deployable system,and summarize the development direction of embedded parallel-actuated ultra-light mirrors.2.According to the actual problems of mirror processing and use,the optimization goals of the ultra-light mirror are zoom ability and gravity self-unloading ability,and the performance evaluation of the ultra-light mirror is realized through the active optical correction process.Investigate finite element analysis methods in preparation for the design and simulation of the embedded parallel-actuated ultra-light mirrors.The optimization idea of the structure design of the embedded parallel-actuated ultra-light mirror is proposed.3.This paper proposes a new idea of the support and structure optimization of embedded parallel-actuated ultralight mirrors.In the optimization design of traditional rigid monolithic mirrors,the optimization goal is to meet the surface shape requirements of the gravitational deformation under passive support.The embedded parallel-actuated ultra-light mirror itself has very low stiffness,and it is almost impossible to achieve the same magnitude of gravitational deformation.Therefore,it is proposed to use gravity self-unloading ability to reduce the requirement for the gravitational deformation of the mirror.Based on the support principle and design experience of the large rigid mirror,the support of the 600 ultra-light mirror is realized.According to the structural characteristics of the embedded parallel-actuated ultralight mirror,the initial structure is designed.In the structural optimization,the DOE method is combined with the global search optimization method to improve the convergence speed of the optimization and realize the efficient optimization of the lightweight structure.4.Carry out systematic research on the whole process of embedded parallel-actuated ultra-light mirror surface processing.Aiming at the problem of pringt-through effect in the small grinding tool polishing,the finite element analysis method is used to realize the automatic push-broom simulation of the polishing process,which can even simulate the pringt-through effect on the lightweight concave mirrors.The feasibility and necessity of suppressing the pringt-through effect in the structural design is proved.The influence of the shape and parameters of the grinding disc on the pringt-through effect is discussed.Using the simulation results to correct the removal function in the processing stage,and using multiple grinding tools can suppress the pringt-through effect,which can improve the efficiency and machining accuracy of small grinding tool polishing.5.Carry out research on the simulation technology of film stress and deformation.Aiming at the problem that the initial surface shape is damaged by coating stress distrotion,it is proposed to use the finite element analysis method for accurate prediction.The quasi-free support and shell element models are used in the simulation to improve the simulation accuracy and performance.The concept of texture aberrations is defined.Experiments show that the simulation error of the deformation caused by caoting stress is less than 10%,and the simulation error of the texture aberration is about 30%.After the structural re-design,the bulges and subsidence in the texture aberration is suppressed.using the simulation results to preprocess the texture aberration before coating can help to suppress the surface shape error casued by coating stress on the face.6.In view of the safety problem that the curvature radius of the embedded parallel-actuation ultra-light mirror is prone to exceed the tolerance requirements after the modified coating,the film stress deformation simulation technology is used to predict the change of the curvature radius.The empirical formula for the change rate of the curvature radius on the ultralight mirror with 130MPa coating stress in modified film:?R/R~2=8.4×10-8,which helps to reserve the curvature change tolerance during the manufacture of the ultralight mirror.7.Using topology optimization and parameter optimization,a(?)150 verification mirror with 6 actuators is designed.We also carried out the manufacture of(?)150embedded parallel-actuated ultra-light mirror,the design of support/actuator tooling and bonding experiments.We realized the zoom experiment of(?)150 ultra-light mirror,meeting the design requirement,which proved the reliability of manufacturing and the correctness of simulation. |
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