Compensation for Dynamic Subdivision Error When the Grating Displacement Sensor Code Disk is Stained

Abstract

When the code disk of a displacement sensor gains dust or other impurities, its moiré fringe signal will deviate from the standard range, which increases subdivision error. In this study, a high-speed A/D converter was used to collect the moiré fringe signal of a sensor in real time and to extract the characteristic points. The center point trajectory of the moiré fringe signal Lissajous figure was calculated, and the amplitude values of the two moiré fringe signals were determined according to characteristic points. The moiré fringe signals according to the center point trajectory and signal amplitudes were then normalized. Error compensation of the dc level and amplitude of moiré fringe signals was realized, so as to improve the dynamic subdivision accuracy of moiré fringe signals when the code disk was stained. Experiments showed that, when the reading head was in the stained area of the code disk, the subdivision error of moiré fringe signals was reduced from the peak value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$37.2^{\prime \prime }$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.6^{\prime \prime }$ </tex-math></inline-formula> , and the accuracy of the sensor can be improved using this algorithm for both different resolutions and different stains, which greatly improved the ability of the displacement sensor to adapt to a harsh environment.