Research Of The Integrated Optimization Design Method For The Optomechanical Structure Of Space Cameras

With the rapid development of aerospace remote sensing technology,space cameras have been widely used in all walks of life in the national economy.The optical performance metrics of space cameras are getting higher.As the main components to realize the function of the optical system,the optomechanical structures need to have good performance stability and enough lightweight ratio in the face of the external disturbances and emission cost constraints.However,the improvement of the optical performances of space cameras is often accompanied by the increase of the aperture and the focal length.These poses a great challenge to the optimization design of lightweight and mechanical performances stability for optomechanical structures.Therefore,an advanced optomechanical optimization design method is needed to make the optomechanical structure not only has good performance stability,but also sufficiently lightweight.In this dissertation,starting from the method of analyzing the camera optical performance metrics,a system performances evaluation method for line of sight stability error and wavefront error is proposed.Integrating the LOS(line of sight)and WFE(wavefront error),the configuration optimization technology and multi-objective size parameters optimization technology of optomechanical structures are studied.The main research contents and achievements are listed as follows:Based on the finite element analysis and linear optical model,the optomechanical integrated analysis method to analyze LOS and WFE is studied.The tracing principle of reflected light and refracted light in the space camera optical system is expounded,and the theoretical expressions of LOS stability error and wavefront error are derived.Based on the ray tracing analysis model of the camera,the sensitivities of the deformations of the primary mirror and secondary mirror to the optical system performances are analyzed,and a linear optical model is established for the connection between structure analysis and optical performances evaluation.The initial optomechanical structures of the camera are designed.By combining finite element analysis and linear optical model,the LOS stability error and WFE of the initial optomechanical structures under gravity and temperature loads are evaluated.By using the linear optical sensitivity matrix of the optical performances on the rigid body displacement of the primary mirror and secondary mirror,the optical performances evaluation equations are established as a performance evaluation equation in the finite element model of the optomechanical structure.Taking the optical performances as performances constraints and combining with the constraints of manufacturability,the topology optimizations of the main support structure and primary mirror are carried out with the objective of maximum structure stiffness.The topology optimization model of the main support backplate is established with the maximum structure stiffness and constraining the surface distortion of the primary mirror.After using the moving asymptote method to solve the topology optimization models,the lightweight ratio of the design results reaches 44.7% on the premise of meeting the optical performances requirements.Based on the results of the topology optimization,the main support structure and the primary mirror are parameterized in detail.The sensitivity analysis of the size parameters is carried out by using the design of experiments based on Latin hypercube sampling.The sensitivity analysis results are compared with the mirror rigid body displacements as the responses and the system optical performances as the responses.The importance of taking the optical performance of the system as the objective responses is discussed,and the key size parameters are identified.The multi-objective optimization model is established with the key size parameters as the design variables,and the minimum mass,LOS stability error and WFE under gravity and temperature loads as objectives.The multi-objective optimal solution sets are obtained by using multi-objective genetic algorithm.The final solution is selected from the solution sets.Compared with the traditional design results,the final design results have obvious advantages in optical performances and lightweight ratio.The dimensional stability of the components is tested.The mechanical simulation model of the optomechanical structure is verified for preliminary quality characteristics.The modal analysis,sinusoidal and random vibration frequency response analysis and dynamic environment simulation test of the camera optomechanical structure are carried out,and the wavefront error changes of the system before and after the camera flipped are detected.The stability of the structure under different vibration and static load conditions is examined.The results show that the optomechanical structure has good performance stability,and proves the effectiveness of the optimization design.At the same time,the comparison results of the simulation analysis and the detection test verify the accuracy of the analysis model in this paper.Finally,the comprehensive design target of space camera with good performance stability and lightweight is achieved.