增量式光电轴角编码器零点漂移问题解决

Resolution of incremental photoelectric angular encoder with reference mark excursion

介绍了增量式光电轴角编码器的工作原理及其在空间目标测量领域的应用。分析了轴角编码器零点漂移的原因,推导了基于轴系和球谐函数的望远镜系统误差修正模型。提出了采用外复核方法解算望远镜指向精度,即用前两天测星解算出来的系统球谐函数误差模型系数修正并复核当天的测星误差。设计了零点标定实验对轴角编码器零位进行标定,进行了连续11个晴天夜晚的观测实验,在零点标定前后观测在视场内均匀分布的30颗恒星,分别解算得到望远镜指向误差,确认了轴角编码器的零点漂移现象。采集GPS卫星数据进行了精度鉴定,望远镜方位和俯仰的轴系误差均值由13.99″、11.50″分别降至5.94″、-3.49″,验证了零点标定方法消除零位漂移并提高望远镜测量精度的可行性。

The operational principle and characteristic of incremental photoelectric angular encoder were summarized and discussed. And the reasons of reference mark excursion for incremental photoelectric angular encoder were analyzed. In order to validate reference mark excursion, a pointing function, which defined in the spherical coordinate of level mounting telescope, was expanded into series by spherical function. Then the spherical function model of pointing error was obtained. 30 stars scattered in sky space uniformly were selected to observe, through which the discrete value of 30 stars′ pointing error were gained in longitude dimension and latitude dimension respectively. A new technique called external checking method, which used observing data two days ago to check intraday pointing error, was tested to validate the phenomenon of reference mark excursion. An experiment measuring pointing error before and after reference mark calibration by observing Polaris last 11 days. The results showed reference mark excursion caused pointing error of telescope becoming greater than the technical index designed. And after calibration the reference mark became fixed all night. To evaluate the effect of reference mark＆amp;nbsp;calibration, orbital position of a GPS satellite was measured by optoelectronic telescope. Pointing error of the telescope was gained compared with precision orbital position of GPS satellite. The results show that before reference mark calibration the mean azimuth and elevation error was 13.99″, 11.50″. And after calibration the mean azimuth and elevation error decreased to 5.94″, -3.49″ respectively. The experiment of GPS star observation showed that the reference mark calibration was available to eliminate reference mark excursion and to improve observation precision.