500 m口径射电望远镜（Five-hundred-meter aperture spherical radio telescope，FAST）的反射面由4 450块面板单元组成，面板单元初始间隙的大小直接影响着望远镜的技术指标，初始间隙过大会降低FAST的有效接收面积，从而降低望远镜的灵敏度，初始间隙过小又可能会导致面板单元在某些观测工况下发生碰撞，因此合理确定反射面面板单元安装间缝隙对保证FAST的性能指标意义重大。采用矢量几何的方法给出了面板单元碰撞的判定准则，并根据反射面整体有限元模型的分析结果，结合判定准则，研究了FAST在工作工况下，以及在最不利的促动器故障情形下面板单元的碰撞干涉情况，还给出了面板初始间隙的合理数值，为下一步面板单元的设计提供参数。
The reflector system of the five-hundred-meter aperture spherical radio telescope (FAST) is composed of 4450 panels. The initial gap between these panels directly affects the technical performance of the telescope. The initial gap between panels that is too wide will reduce the effective collecting area of FAST, and thus compromising the sensitivity of the telescope. On the other hand the initial gap between panels that is too narrow may lead to collisions between the panels under certain observation conditions. It is thus important to reasonably determine the size of the initial gap between panels in ensuring the technical performance of the telescope. In this paper, the criterion to determine collisions between panels is given by the method of vector geometry, the collisions of panels under normal observation conditions are studied, as well the worst situations with actuator failures using the analytical results from the integrated finite element model of the reflector, combined with aforementioned criterions. Meanwhile, a reasonable value for initial gap between the panels is determined, providing parameters for the design of the panels.
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