| The QTT(Qi Tai Telescope), the world largest full steerable telescope with the diameter of 110 meters, will be constructed in Qitai, Xinjiang Province of China. The working frequency of QTT is from 150 MHz to 115 GHz, which results in a high reflector precision requirement of 0.2mm. The whole telescope structure is about 6000 tons, a height of nearly 30 floors and the area of reflector is almost as large as the total areas of 26 basketball courts. Clearly, it is a big challenge to design and build so large telescope.In order to achieve such a high goal, the traditional non-adjustable panels is no longer applicable, thus the active main reflector must be selected. There are many antennas equipped with active main reflectors, such as TMT(65m Tian Ma Telescope), GBT(the offset 100 m Green Bank Telescope), and SRT(64m Sardinia Radio Telescope), But compared with the QTT, there is still a big gap in terms of aperture and the design difficulty. The main reflector segmentation problems of the QTT are detailed in this thesis, which includes the following four aspects.1. The factors affecting the segmentation of active main reflector are investigated. This thesis summarizes the factors that affect the segmentation of the large radio telescope with the active main reflector surface in detail. Among these factors, the major ones are the figure error, gravitational deformation of panels and the capacity to manufacture the panel.2. The relationship between the figure error and the panel size is developed. Firstly, according to the practical experience, the magnitude of figure error is determined. Then some cases arising the figure error are analyzed. The effect of the figure error on the size of panels is mainly studied. In the case that the adjacent two rings are produced by the same mould, the relation between the figure error and the panel size is analyzed mathematically. Finally, the QTT is regarded as an example to calculate the maximum panel size of the reflector. Just based on the figure error, an optimization model of the reflector segmentation is given, then the offset of each panel in the normal direction and the panel size are given.3. The panel deformation analysis under gravity is performed. Firstly, the deformation of the quad vertex hinged panel is analyzed. The relationship between the gravitational deformation of panels and the panel size is studied with semi-analytical method. The correctness of this formula is verified by finite element method in Ansys. Secondly, for the compound panels with a given topology, the equivalent stiffness of the sub-truss is calculated. Finally, the formula of the gravitational deformation of the compound panels and panel size is investigated and verified through the Ansys model.4. The optimization model considering multiple factors is applied in the segmentation of QTT reflector surface. Firstly, according to the performance requirements of QTT and the current domestic panel processing technology, the suitable type and the maximum area of QTT panels are determined. Then according to the characteristics of QTT and several important factors, the optimization model and the result of the reflector segmentation are given. Finally, considering the cost of actuators, the compound panels segmentation scheme of QTT reflector surface is also given. |
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