粗光栅信号全数字化处理法实现高倍数细分

针对在粗光栅软件细分中的信号误差影响细分数的问题,提出了按细分的主要误差来源分类进行数字滤波和补偿的全数字化处理法,以达到粗光栅高精度测量的要求。首先对光栅测量信号进行有针对性的数字滤波,使其波形接近于理想状态。然后根据误差来源进行数字补偿,通过对软件数字细分原理的分析,推导出了原始信号不正交、幅值不等、谐波失真等误差影响细分结果的表达式,并提出了与此相对应的数字补偿方法。最后用软件细分法对测量信号进行高倍数数字细分。滤波前后波形信号的仿真比较结果验证了基于严格线性相位的FIR数字带通滤波器可以有效地屏蔽光栅信号频谱中的高低频干扰和噪声。研究结果表明,在粗光栅满足一定质量的前提下,利用全数字化处理法能够满足500细分的精度要求。

Realization of high division number of coarse grating signals by fully digital processing method

To meet the requirement of high accuracy measurement in coarse grating system, a fully digital processing method is presented, which consists of digital filter, digital error compensation and software digital subdivision. Two signals are filtered by digital filter in order to get waveforms closed to the ideal state and then, by analyzing the software digital subdivision theory, the expressions are deduced to verify how errors influence on the subdivision result. The errors include quadrature phase shift error, unequal amplitude error, zero offsets and the third harmonic. As a result, corresponded digital compensation methods are proposed. Finally, digital subdivision is adopted to obtain high division number. Simulation is employed to validate that the FIR digital band pass filter based on strict linear phase can effectively shield the noises in both high and low frequency bands, which are involved in signal spectra of grating. Experiment results indicate that fully digital method can raise division number to 500 with the precondition of coarse grating quality.