| Airborne optoelectronic steady platform is a kind of optoelectronic reconnaissance equipment hanged on helicopter or UAV, which mainly use the forward looking infrared, visible light camera, laser rangefinder, laser designator or other optical sensors to search, identify, tracking, positioning and target designation the ground. With the development of science and technology and military strength, requirements for stability, tracking accuracy and lightweight of the airborne optoelectronic steady platform get higher and higher, thus, the structural demand of airborne optoelectronic steady platform is more stringent.Firstly, according to design requirements, I design the layout of the whole structure, clear the connection between various components and the mutual position relationships, and then finish the complete machine's three-dimensional modeling. Inner framework is the main load-bearing frame of airborne optoelectronic steady platform, responsible for the installation and bearing of photoelectric sensor, and its structural stiffness and stability directly affect the complete machine's work accuracy. This article analyses the inner framework structure seriously, using the ANSYS Workbench software to carry out of its static analysis and modal analysis separately. In the static analysis process, aim at the airborne optoelectronic steady platform's characteristics, which are poor working conditions and wide range of working temperature variation, according to military standard, I set a index of monitoring points deformation less than 0.05 mm within-45℃～60℃temperature range of deformation. At the same time it requires the overall dynamic performance of inner framework better, and the base frequency arrive to 100Hz at least.When the inner framework used of the traditional ZL101A aluminum alloy material and worked normally, in the two extreme temperatures-45℃and 60℃, monitoring points' distortions of the static analysis results were all beyond the design specifications. In the condition of reference temperature 22℃, distortion of the inner framework is slight, meanwhile analyzing both the stress and strain distribution of the inner framework, I find out that the temperature gradient is the main reason why the inner framework distortion exceed standard, and it provides basis for inner framework improvement.During the inner framework's improvement process, first of all, I select SiC/AL composite material for the inner framework, which has two characteristics big specific stiffness and small thermal expansion coefficient, and it's a new type of structure/thermal control integration material. On the same working situation, all of the monitoring point distortions of the inner framework components, which use new materials, meet the design requirement, in the two extreme temperatures-45℃and 60℃conditions. Meanwhile the dynamic stiffness improves, fundamental frequency rise by 55.1% compared with the inner framework of aluminum alloy material ZL101A. However, the inner framework still use the ancient structure form, the design trend is obvious conservative. On the basis of meeting the design requirements, I carry out a lightweight design, after reducing, the weight become 0.124Kg from original 0.334Kg,62.9% reduced. At the same time, both the monitoring point distortion and the overall dynamic feature comply with design requirements, the result is satisfactory.Finally, after a reasonable simplification of the complete machine, I establish a finite element model of the complete machine, and make a modal analysis, come to the first eight-order azimuth resonance frequency and mode shape of the complete machine, this provides foundation for the further dynamics analysis of the complete machine, and provide a significant reference value for design, production and application of the airborne optoelectronic steady platform in the future.
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