基于CAM的LAMOST光纤单元结构误差仿真分析

Structural Error Simulation Analysis of LAMOST Fiber Units

LAMOST天文望远镜要求直径1.75 m球冠状焦面板上的4000个光纤定位单元能够快速准确地对准4000个星体目标进行观察,其定位精度要求高。但单元偏心轴处齿轮啮合传动、轴与轴承存在的间隙等,都会导致光纤定位发生偏离,影响光纤的精确定位。本文利用Solidworks和ADAMS对单元偏心轴处齿轮传动仿真,对轴与轴承间隙的不同大小用正交试验方法设计9组对比仿真试验。研究结果表明:偏心轴处齿轮最大窜动量在许可范围,且对单元定位精度影响不大;单元轴间隙整体误差范围在-0.06deg/sec^0.2deg/sec,可使光纤定位单元的定位精度变差甚至不能满足观测要求。以上分析研究为将来新一代高精度定位单元的设计提供一定的理论依据。

LAMOST requires fast and accurate alignment of 4000 optical fiber units on a 1.75m-diameter convex focal plane to simultaneously observe 4000 targets, and the positioning accuracy of the unit is very demanding. However, the gear meshing transmission at the eccentric shaft of the unit, the clearance between the shaft and the bearing, etc., can cause the movement of the actual mechanism and the ideal mechanism during the positioning operation of the optical fiber to deviate, and affect the precise positioning of the optical fiber. In this paper, the virtual prototype ADAMS is used to simulate the gear transmission at the eccentric shaft of the unit, and nine groups of comparative simulation tests are designed using the orthogonal test method for different sizes of shaft and bearing clearance. The results of the study show that： The maximum turbulence of the gear at the eccentric shaft is within the allowable range, and the influence on the positioning accuracy of the unit is not significant; The overall error range of the unit shaft clearance is -0.06 deg/sec - 0.2 deg/sec, it can make the positioning accuracy of the optical fiber positioning unit worse or even fail to meet the observation requirements. The above analysis and research provide a certain theoretical basis for the design of a new generation of high-precision positioning units in the future.