Design And Analysis Of Focusing Mechanism For Secondary Mirror Of High Resolution Space Camera

The space optical camera is one of the important tools for obtaining remote sensing images.It is widely used in astronomical observation,military reconnaissance,environmental monitoring and other fields,and has extremely high economic and military benefits.With the continuous development of applications,higher requirements are placed on the spatial resolution,temporal resolution,quality,and reliability of spatial optical cameras.Before entering the orbit work,the space camera needs to undergo the process of ground assembly,transportation and launch.The environment of the camera changes,such as changes in temperature,pressure,etc.,as well as impact vibration,gravity release,etc.The system brings influence,changes the relative position and surface shape of the optical mirrors in the optical system,and to some extent causes the position of the focal plane of the optical system to shift,reducing the imaging performance of the camera.Therefore,it is necessary to design a highprecision focusing mechanism to compensate for the defocusing of the camera due to various factors,so that the space camera can obtain a clear image when working on the track.This dissertation research comes from a high-resolution multi-spectrum space camera subject.The secondary lens focusing mechanism studied in this dissertation is one of the important core components of this project.This article mainly focuses on the research work of the secondary lens focusing mechanism,and completes the design,accuracy analysis,mechanical simulation,prototype production and testing of the focusing mechanism.The main content of the paper includes:(1)Describes the main factors causing the defocusing of the space optical camera,discusses the common focusing methods of the space camera,and introduces the research status of the focusing mechanism at home and abroad.(2)According to the index requirements of a high-resolution multi-spectral space camera on the secondary lens focusing mechanism,a high-precision secondary lens focusing mechanism based on parallel lever reduction structure and flexible hinge is proposed,and the focus adjustment scheme is completed.Design,selection of structural materials,design of flexible structure,selection of drive motor and sensor,and selection of lubrication method,and analysis of the precision of the secondary lens focusing mechanism,the results show that the designed secondary lens focusing mechanism The focal accuracy is better than the index requirement of 1μm.(3)The finite element software was used to complete the simulation of the modal,sine,random vibration and buckling effects of the designed focusing mechanism.The fundamental frequency of the focusing mechanism is 245 Hz,which has good rigidity.Under the excitation of a sinusoidal load,the maximum equivalent stress is 19.17 MPa,which is less than the yield strength of the material,and the mechanism will not undergo plastic deformation.Under the excitation of random load,the relative magnification of acceleration in all directions is less than 4,and it has good dynamic stiffness.In the static analysis,the first-order buckling load factor is 94.419,which is not prone to structural instability.(4)A prototype model of the focusing mechanism was produced and the accuracy test of the focusing mechanism was completed.The results show that the focusing accuracy of the focusing mechanism is 0.9μm and the focusing range is 88μm,which meets the requirements of the index.(5)Test the focus accuracy and focus range of the focus mechanism,and recheck the accuracy of the detection mechanism.The focusing accuracy of the focusing mechanism is better than 1μm,the focusing range is greater than 40μm,and the accuracy of the focusing mechanism meets the index requirements.