光电轴角编码器莫尔条纹误差信号补偿

Photoelectric shaft encoder error of moire fringe signal compensation

为保证光电轴角编码器在恶劣工作环境下的细分精度,提出一种基于Hilbert-Huang变换的误差补偿方法。针对编码器系统受正弦振动引起的测角故障,提出一种莫尔条纹误差信号的数学模型;采用经验模态分解算法,获取误差信号的本征模态函数,分别对本征模态函数进行希尔伯特变换解调分析,提取包含干扰特征的莫尔条纹信号;同时,基于光电轴角编码器的精码信号方波信息,获取精码信号的基波时域频率;提取与基波时域频率匹配的本征模态函数包络分量。以24位光电轴角编码器为实验对象,实验结果表明:编码器莫尔条纹信号动态细分误差峰值由约200″降低到1.54″左右,细分精度明显提高。

In order to ensure the subdivision accuracy of photoelectric rotary encoder in the harsh working conditions, an error compensation method based on HHT（Hilbert-Huang Transform） was proposed. To solve the angle measurement malfunction of encoder system caused by sine vibration, a mathematical model of Moire fringe error signal was proposed according to the malfunction form of encoder mechanical system. EMD（Empirical Mode Decomposition） algorithm was used to get the intrinsic mode function of the error signal. The intrinsic mode function was demodulated and analyzed using Hilbert transform. Moire fringe signal including the malfunction characteristics was extracted. Meanwhile, the fundamental wave time domain frequency of the precise code signal was obtained based on the precise code signal square wave information of the photoelectric rotary encoder. The IMF function envelope components matching with the fundamental wave time domain frequency were extracted. A 24-bit photoelectric rotary encoder was selected as the experimental object. The experimental results show that the dynamic subdivision error peak value of the Moire fringe signal is reduced from 200 ″ to 1.54″ and the subdivision accuracy improved significantly.