应用于增量式光电编码器的相关自适应滤波方法

Relative Self-adaptive Filtering Method Applied to Incremental Optoelectric Encoder

为了改善增量式光电编码器的莫尔条纹光电信号质量,降低主计数信号中高次谐频的影响,提高信噪比达到输出稳定的正弦波形,本文深入地研究了莫尔条纹光电信号中的高频信号和噪音信号产生的原因及其相关自适应滤除方法.从宏观和微观两个方案分析光栅副的屏函数,研究莫尔条纹光电信号输出波形的不确定原因,并且提出采用相关自适应滤波方法将高频信号滤除保留原有基频信号.从相关自适应滤波的数学模型论证和推导该相关自适应滤波过程并讨论其自适应性.指出在设计该自适应滤波电路时需要重视的几个关键指标及其影响效果,完成相关自适应滤波的有效性分析.相关自适应滤波效果等价于一个中心频率为基频的窄带带通滤波器,当基频随机变化时其通带也会随之改变.通过相关自适应滤波技术较好地滤除计数信号中除基频外所有高频分量和放大电路所引入的加性高斯白噪音.实验证明:莫尔条纹光电信号的失真度被降低8倍相关自适应滤波方法能使莫尔条纹光电输出波形趋近于标准正弦波,获得更高的信噪比.

The reasons of the high-frequency signals and noise signals generated from the Moire fringe optolectric signal and the relative method of self-adaptive filtering were discussed,in order to improve the quality of Moire fringe optoelectric signals of the incremental optoelectric encoder,decrease the impact of high-order harmonic frequency in the main count signal and increase the SNR for the stable output of sinusoidal waveform. The window function of the grating pair from both macro and micro perspectives, and the uncertain reasons of the Moire fringe optoelectric signal waveform were analyzed. The original fundamental frequency signal was retained by applying a method of self-adaptive filtering which can filter out high frequency signals. Meanwhile, the adaptive filtering process was derived and proved from the perspective of mathematical model of self-adaptive filtering, and its adaptability was discussed. In order to complete the effectiveness analysis of the self-adaptive filtering, several key indicators and their effects needed to be focused in the design of the self-adaptive filtering encoder. The effect of the adaptive filtering was equivalent to a narrowband band pass filter whose center frequency was the fundamental frequency, and the pass band would change with the random variation of the fundamental frequency. Thus, the relevant self-adaptive filtering could filter out all the high frequency component signals in the count signal except the fundamental frequency signals, and amplify the addition white gaussian noise in the circuit to make the output waveform of the moirefringe optoelectric signal approach the standard sinusoidal wave. The experiment results show that distortion degree times. of the Moire fringe photoelectric signal is reduced by 8 times.