长焦距宽视场空间相机主支撑结构优化设计

发布时间：2018-08-25 15:05

【摘要】：离轴三反光学系统没有中心遮拦,可以实现大视场,高分辨率,获得接近理想的成像性能和效果,被各国科研人员广泛作为空间相机的光学系统。但由于其光学系统的非对称性特点,相对于同轴对称系统,它的支撑结构设计与装调技术是公认的技术难点。此外,为了实现空间相机的超大幅宽与高地面分辨率,实现详普查功能一体化,需要不断增大光学系统的焦距与视场角,大视场长焦距离轴三反光学系统中,各光学元器件的位置精度要求更加严格,空间相机在装调、运输、发射过程中的尺寸稳定性也更加难以保持,这些都给主支撑结构设计带来了很大的挑战。本论文根据某离轴三反光学系统空间相机,其主、三、折叠镜长度均超过1200mm,长宽比均超过3:1,质量均大于40kg,主次镜间距超过1500mm的特点,从以下5方面对大型离轴三反空间相机主支撑结构的优化设计及力学性能展开了深入研究。1.调研国内外离轴空间相机主支撑结构的典型形式,针对高分辨率、宽视场离轴三反光学系统的特点,分析研究了不同支撑方式的优缺点,选取适合本论文的主支撑结构形式。2.桁架结构拓扑形式研究。根据变密度法,对本论文研究的桁架式支撑结构进行多目标拓扑优化设计,设计出合适的桁架式初始结构,并将此初始结构拆分成各个次结构,研究分析次结构桁架杆角度对整机性能的影响。3.前框架结构优化设计研究。根据光学系统特点,提出一体化支撑折叠镜、次镜组件的前框架结构。首先,结合加工工艺性与前框架的尺寸要求,通过对不同航天常用工程材料分析对比,选取钛合金作为前框架的研制材料;其次,根据基于约束模态拓扑优化方法约束点之间不存在联系的缺陷,提出了一种综合基于自由模态与约束模态拓扑优化方法,优化设计前框架结构的轻量化形式;最后,对研制出的前框架结构的进行了自由模态分析与MIMO自由模态试验,验证了优化与分析方法的正确性。4.基于动力学目标的桁架杆尺寸优化设计。根据随机振动理论,提出加强局部区域的刚度可以减小该区域随机振动响应的假设,并提根据此观点提出了一种以镜子安装点随机振动响应最小的多目标尺寸优化方法来优化本论文的桁架杆尺寸,通过桁架结构力热样机动、静态力学分析与试验,验证了该设计方法的合理性,并验证了本论文所提出理论假设的正确性。5.桁架结构消热设计。研究离轴空间相机桁架结构热变形特点,根据消热化设计原理中热变形后桁架杆轴向距离相等的原则,推算出各个桁架杆热膨胀系数的函数关系,并根据光学公差要求,推算出桁架杆热膨胀系数的取值范围;并根据碳纤维复合材料热膨胀系数可设计的特点,综合刚度与热膨胀系数两方面因素,设计出满足性能要求的桁架杆碳纤维复合材料铺层方式。
[Abstract]:The off-axis three-mirror optical system is widely used as an optical system for space cameras because of its large field of view, high resolution and close to ideal imaging performance and effect. However, due to the asymmetric characteristics of its optical system, its supporting structure design and adjustment technology is generally recognized as a technical difficulty compared with the coaxial symmetric system. In addition, in order to realize the large width and high ground resolution of the space camera and the integration of the detailed survey function, it is necessary to continuously increase the focal length and field of view angle of the optical system. The position accuracy of each optical component is more strict, and the dimensional stability of the space camera in the process of installation, transportation and launch is more difficult to maintain, which brings great challenges to the design of the main supporting structure. In this paper, the main, third, folding mirror length is over 1200mm, the aspect ratio is more than 3: 1, the mass is more than 40kg, the distance between primary and secondary mirrors is more than 1500mm, according to the space camera of an off-axis three-mirror system, the length of folding mirror is more than 1200mm, the ratio of length to width is more than 3: 1. The optimization design and mechanical properties of the main support structure of the large off-axis three-counter space camera are studied in the following five aspects. This paper investigates the typical forms of the main support structure of off-axis space camera at home and abroad. In view of the characteristics of high resolution and wide field of view off-axis three-mirror optical system, the advantages and disadvantages of different supporting modes are analyzed, and the main support structure form .2suitable for this thesis is selected. Study on topological form of Truss structure. According to the variable density method, the multi-objective topology optimization design of the truss bracing structure studied in this paper is carried out, and the suitable truss initial structure is designed, and the initial structure is divided into various sub-structures. The influence of truss bar angle on the performance of substructure truss is studied. Research on Optimization Design of Front frame structure. According to the characteristics of optical system, the front frame structure of integrated supporting folding mirror and secondary mirror assembly is presented. First of all, according to the processing technology and the size requirements of the front frame, through the analysis and comparison of the different engineering materials commonly used in aerospace, the titanium alloy is selected as the development material of the front frame. According to the defect that there is no relation between constraint points in the method of modal topology optimization based on constraints, a new topology optimization method based on free mode and constraint mode is proposed to optimize the lightweight form of frame structure before design. The free mode analysis and MIMO free mode test of the developed front frame structure are carried out, and the correctness of the optimization and analysis method is verified. Optimization design of truss rod size based on dynamic objective. Based on the theory of random vibration, the assumption that strengthening the stiffness of the local region can reduce the random vibration response of the region is proposed. According to this viewpoint, a multi-objective dimension optimization method based on the minimum random vibration response of the mirror mounting point is proposed to optimize the size of the truss bar in this paper. The static mechanical analysis and test are carried out through the force and heat sample maneuver of the truss structure. The rationality of the design method is verified, and the correctness of the theoretical hypothesis proposed in this paper is verified. Heat dissipation design of truss structure. The characteristics of thermal deformation of off-axis space camera truss structure are studied. According to the principle of equal axial distance of truss bar after thermal deformation, the function relation of thermal expansion coefficient of each truss is calculated according to the requirement of optical tolerance. The range of thermal expansion coefficient of truss rod is calculated, and according to the design characteristics of thermal expansion coefficient of carbon fiber composite material, two factors, stiffness and coefficient of thermal expansion, are integrated. A lamination method of carbon fiber composite material for truss bar was designed to meet the performance requirements.
【学位授予单位】：中国科学院长春光学精密机械与物理研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：V445.8

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