Research On Stability Of The Truss Structure In Large-scale Space Camera

With the development of space remote sensor,space camera with low resolution cannot meet thehuman requirements for the observation of space observation and utilization;these requirements make the space camera with large diameter and long focal length be developed to meet the high resolution requirements of space remote sensor.With the increase of the focal length,thediameterand the optical performance requirement of the space camera,the resulting problem is that the space camera not only increases the overall quality,but also increases the difficulty of manufacturing and processing of the support structure.The support structure of the space camera must meet the requirements of higher specific stiffness,better dynamic stability and less impact on the mirror,etc.However,the traditional structural forms are not satisfied with these requirements,such as tube structure,box structure,etc.Therefore,since the truss theory was first put forward by Michell in 1904,the truss structure which had the merits of simple configuration,reliable,flexible assembly,specific stiffness and strong design ability has been widely used.In this paper,the study is the stability of the 5m truss structure in large-scale space camera.The stability of the truss structure is studied deeply from the aspects of theoretical analysis,structural design,optimization design,engineering analysis and so on.The detailed research contents include the athermal truss structure based on quasi-Poisson effect,the high stiffness the truss structure based on Rayleigh method,the influence of space science instrument on the stability of truss structure and the comprehensive performance analysis of the truss structure.Aiming at the athermal problem of the truss structure for large-scale space camera,a new athermal truss structure is proposed.By referring to the quasi-Poisson effect,the relationship between the thermal deformation of truss structure and the angle of the struts is derived.According to the athermal design discriminant,the layout angle of the truss structure with high thermal stability is obtained,and is 31.4°??1?65.4°,19.5°??2?69.4°.This paper studies the high stiffness truss structure of space camera from the two aspects of truss structure design and size optimization of the strut.The frequency analysis of the "?" unit by using the Rayleigh method is carried out,and the relationship between the eigenfrequency of truss structure andthe angle of the struts is obtained.In the case of considering the thermal stability and stiffness characteristics,the initial design of the truss structure is completed,and its optimal design angle of the struts is ?1=35.6°,?2=25.5°.It is difficult to optimize the struts of truss structure for large-scale space camera.A fast optimization method combining sensitivity analysis and design of experiment is proposed to solve this problem.This method has high efficiency,fast convergence,and can get the optimal structure quickly.Aiming at the Influence of scientific instruments on the stability of truss structures,a tangent bipod kinematic mount based on equivalent compliance and Rayleigh method is proposed.The mathematical model of compliance for the single-axis right circle flexure hinge derived based on the Chi's second theorem,and the compliance equations for the bipod in the X-axis,Y-axis and Z-axis directions are established.By referring to the Rayleigh method,the eigenfrequency analytic of the tangent bipod kinematic mount is got.According to the design requirements,the kinematic mount which reduces the influence the space science instrument on the truss structure is designed.The stability of the truss structure is verified by the finite element analysis,the results show that the truss structure designed in this paper has good stiffness and can meet the first eigenfrequency requirements of the whole structure.Under gravity load,the changes in surface shape of the mounting surface between the primary mirror and secondary mirror meet the mechanical stability requirements.Under the action of temperature load,the changes in surface shape of the mounting surface between the primary mirror and secondary mirror is small,the truss structure has the high thermal stability.The temperature change of the scientific instrument has little influence on surface shape of the mounting surface between the primary mirror and secondary mirror,so the kinematic mount designed in this paper can reduce the influence the space science instrument on the stability ofthe truss structure.