26 m射电望远镜副面调整机构误差分析

新疆乌鲁木齐南山26 m射电望远镜（NSRT）采用 Stewart 并联机构实现副反射面（简称副面）五自由度运动调整。为确保并联机构的运动精度能满足射电望远镜高精度的指向要求，对影响副面调整机构运动精度的各项误差进行了分析。几何误差模拟结果显示，为使并联机构达到要求的精度，应保证杆长误差小于0.08 mm，铰链误差小于0.04 mm。通过对实测结果与仿真结果分析比较，得出回零误差是造成并联机构误差的主要原因。由于并联机构的回零检测装置主要由增量式编码器与限位开关组成，其中限位开关反馈信号的异常，会引起并联机构的回零误差，分析得到该因素是造成NSRT副面并联机构工作偏差的主要原因，这对并联机构的误差补偿具有指导意义。

Errors analysis of a subreflector adjustment mechanism for NSRT

The Nan Shan 26 m Radio Telescope (NSRT) in Urumqi, Xinjiang, uses the Stewart platform to adjust the position of subreflector in five degrees of freedom. In order to ensure the Stewart platform has high accuracy to meet the high-precision operation requirements of radio telescope, this paper analyzes the errors that affect the accuracy of the Stewart platform. Geometric error simulation results show that in order to achieve the required accuracy, the errors of the leg length and universal joint should be less than 0.08 mm and 0.04 mm. The comparative analysis of the measured data and the simulated data show that the homing error is the main cause of the error of the Stewart platform. Since the homing detection device of the Stewart platform is mainly composed of incremental encoder and limit switch, the abnormal feedback signal of the limit switch will cause the homing error of the Stewart platform. The paper concludes that this factor is the main reason for the working deviation of the Stewart platform for NSRT, which has guiding significance for the error compensation of the Stewart platform.