光通信终端中编码器信号正弦性的EMD修正  

EMD Based Compensation of Encoder's Sinusoidal Index in Free Optical Communication Terminal

作　　者：郭汉洲[1] 宋延嵩[1] 

机构地区：[1]长春理工大学,长春130022

出　　处：《长春理工大学学报（自然科学版）》2012年第3期59-63,共5页Journal of Changchun University of Science and Technology(Natural Science Edition)

摘　　要：为了抑制编码器莫尔条纹正弦性偏差引入的细分误差,保证光通信终端的捕获、对准、跟踪(APT)精度,设计了基于经验模态分解(EMD)的正弦性修正方法。首先,分析了莫尔条纹正弦偏差给系统带来的细分误差并给出满足工程需求的正弦性阈值。然后,在阐述了EMD分解原理的基础上,给出了基于EMD的正弦性修正方法,该方法利用编码器自身粗码信息计算转速,从而确定精码莫尔条纹信号的基波频率值,并采用EMD分解在原始信号中提取与该值相匹配的模态分量。最后,对该方法进行了原理和转速自适应性仿真,并应用在去掉光学滤波光阑后的粗瞄回路编码器中。仿真及实验结果表明:各种转速下,修正后的莫尔条纹正弦性均<0.85%,满足细分要求;修正后精码译码结果光滑,编码器测角精度维持在1"以内,满足终端对准精度要求。In order to restrain the subdividing error of .encoders caused by moir~ fringe＇ s sinusoidal index deviation, and to guarantee the APT precision of optical communication terminals, a compensation melbod based on EMD （Em- pirical Mode Decomposition） is proposed.First, the connection between subdividing error and moir~ fringe＇ s sinusoidal index deviation is analyzed and a practical threshold of sinusoidal index deviation is given.After expatiating on EMI） the- ory, a method based on it is proposed to compensate the sinusoidal index deviation.This method makes use of the coarse codes to calculate the rate of the encoder, so as to compute the fundamental frequency of eneoder＇ s moir~ fringe, and then the IMF （Intrinsic Mode Function）, which matches with the fundamental frequency, is extracted from the original signal.Finally, simulations on the principle of this method and its adaptability of rotating rate are made, and applications are carried out in the coarse pointing loop＇ s encoder without using the optical filter diaphragm. Results indicate that： the compensated sinusoidal index deviation is less than 0.85% at any rotating rate, which satisfies the subdividing need.Meanwhile, the fine codes become smooth on account of EMI） compensation, and the measure precision is within 1＂, which meets the demand of APT precision.

关 键 词：卫星光通信 绝对式光电编码器 莫尔条纹 正弦性 经验模态分解 

分 类 号：TP394.1[自动化与计算机技术—计算机应用技术] TH691.9[自动化与计算机技术—计算机科学与技术]