莫尔条纹光电信号正交性偏差的实时补偿

Real-time compensation of orthogonality deviation for Moire fringe photoelectric signal

为了提高光电轴角编码器的精度,提出了一种实时补偿莫尔条纹光电信号正交性偏差的方法。利用希尔伯特变换原理,构造了同频光电信号正交性偏差的动态测量算法。根据莫尔条纹光电信号的数学模型,揭示了由正交性偏差引起的细分误差的空间分布特征并建立角度补偿模型。鉴于编码器的实际工作特点,采用同步处理方式,在补偿光电信号的同时动态更新了角度代码补偿查找表;通过细分查找表的切换,实现信号正交性偏差的实时补偿。采用该方法对存在约18°正交性偏差的23位光电编码器进行了补偿处理,结果显示:补偿后的编码器的细分误差峰值由4.79"降低到1.26"。该方法可实际应用于编码器系统,能够提高编码器的细分精度、环境适应性和可靠性。

A method to compensate the orthogonality deviation of the Moire fringe photoelectric signal was proposed to improve the accuracy of a photoelectric rotary encoder. Based on Hilbert transform theory, a dynamic measurement algorithm for the orthogonality deviation of same frequency photoelectric signal was constructed. In the light of the mathematical model for Moire fringe photoelectric signal, the influence of orthogonality deviation on subdivision precision was analyzed and an angle compensation model was set up. According to the working principle of the encoder, a synchronous processing mode was adopted to compensate the photoelectric signal and update dynamically the look- up table for angle codes simultaneously; by the switching of subdivision lookup table, the orthogonali- ty deviation for the photoelectric signal was compensated in real time. Finally, a 23-bit photoelectric encoder with 18° orthogonality deviation was compensated using this method. Experimental results show that the peak value of subdivision error of the encoder has reduced from 4.79＂ to 1.26 ＂ after compensation. This method can actually be used in an encoder system and it can improve the subdivi sion accuracy, environmental adaptability and the reliability of encoders.