Design And Test Of Flexible Unloading Structure Of Low Temperature Infrared Lens

During the development of satellite infrared lens system,the requirements of high-precision assembly and adjustment at room temperature,high stability support at low temperature and high-quality imaging are put forward,and the lens components are not allowed to implement cryogenic treatment,so the lens support device is required to unload the stress caused by temperature change between lens components.The flexible unloading structure studied in this project is an important component of the lens support device.It is not only used to unload the stress between the frame body and the external support,but also can eliminate the installation stress when the frame is fixed,which plays an important role in improving the lens surface shape accuracy.Therefore,the following research is carried out in this paper.Firstly,according to the working principle and design requirements of the flexible unloading structure,two kinds of spoke configuration schemes are proposed.The flexible link of scheme 1 is composed of four concentric fan-shaped "几" shaped leaf springs distributed in the form of central symmetry,and the flexible link of scheme 2 is composed of two concentric fan-shaped "工" shaped leaf springs distributed in the form of central symmetry.Based on the pseudo rigid body model method,according to the series parallel relationship of the flexible links of the two structures,the stiffness is calculated respectively,and the key dimension parameters of the flexible unloading structure are determined.The best size range of flexible link in scheme 1 is leaf spring thickness t = 0.5mm,leaf spring bending radius 12 mm ≤ R1 ≤13mm,and the best size range of flexible link in scheme 2 is leaf spring thickness t = 0.4mm,leaf spring bending radius R1 ≥ 11 mm.Secondly,the finite element analysis results of the two flexible unloading and structural schemes show that the stiffness of scheme 1 is better than that of scheme 2 when the size parameters of the two schemes are the same,and the radial stiffness of the flexible unloading structure of scheme 1 is higher than that of scheme 2,which meets the design requirements.According to the first scheme,the simulation analysis under different parameters is carried out,and the optimal size parameters of the flexible unloading structure are determined as R1 =12.5mm,t = 0.5mm.The simulation stiffness value under the optimal parameters is compared with the calculated value,and the deviation is less than 2%,which indicates that the flexible unloading structure of this size has reached the design index.Finally,the stiffness test platform is built to test the flexible unloading structure.Throughthe analysis of the workpiece,the maximum deformation stress of the flexible unloading structure is up to 85 N,and the test results in eight directions show that the maximum deviation of the radial stiffness in any direction is 11.8%,and the deviation between the test value and the simulation value of the flexible unloading structure is less than 5%.