基于时空转换法的正弦波光栅尺位移测量系统设计

Design of the Displacement Measurement System for Sine-Wave Grating Based on Time-Space Conversion Method

光栅尺作为高精度位置测量仪器,其分辨率受制于超精密的空间刻划技术,测量精度急需通过电子学细分法来提高。为此,提出了"时空转换"的思想:借助于载波调制理论,引入了恒定的时空当量,将对空间位移的测量转换为对信号瞬时周期的测量。首先,进行了时空转换法的数学推导,探究了正弦波光栅尺位移的测定和移动方向的判别方法;然后,在DSP开发平台下,搭建出基于时空转换法的正弦波光栅尺位移测量系统;最后,从实验数据以及光栅信号的残余直流电平、幅值不均衡、相位不正交等方面进行了误差分析。实验表明:栅距为8mm的正弦波光栅尺,在时空转换法下,平均测量误差为±0.258 1μm,兼顾了细分与辨向。

A grating has been viewed as the high-precision position measuring instrument, however, its resolution is limited by the spatial characterization based on ultraprecise technology.Therefore, the measuring accuracy need to be improved by the electronics subdivision urgently.Time-space conversion method has been proposed in this paper. Based on carrier modulation theory and the spatial equivalent constant, measuring displacement is converted to the measurement of instantaneous signal cycle.Firstly, the mathematical derivation for time-space conversion method is conducted.Furthermore, the identification method for sine-wave grating displacement and its moving direction is ex- plored.Then, displacement measurement system for sine-wave grating based on time-space conversion method is es- tablished under DSP platform.Finally, the error has been analyzed based on experimental data and raster signals, such as residual DC level, amplitude imbalance and non-orthogonal phase.As for the sine-wave grating with a grat- ing pitch of 8 μm, experimental results show that the average measuring error of the time-space conversion method is ±0.258 1 μm, meanwhile, the subdivision and the direction discrimination are contained.