Analysis and Elimination of Grating Disk Inclination Error in Photoelectric Displacement Measurement

As core elements of photoelectric displacement measurement, installation coaxiality and rotation parallelism are the main factors affecting measurement accuracy. When there is a processing error or an offset in the installation process of structural elements, the plane of the grating disk will be tilted, which seriously affects the accuracy of angular displacement measurements. In this study, error caused by inclination of the grating disk was analyzed and a method to eliminate this error presented. First, an error model was established by analyzing the mechanism of measurement error caused by grating disk tilting, analysis showed that the error caused by grating disk tilt showed a “double cycle” fluctuation in the circle. Then, by using “double cycle” fluctuation, a method for eliminating errors was presented. Finally, the validity of the proposed theory and method was verified by simulation and experimentation. To eliminate errors, angular displacement measurements needed to be made using at least three reading heads to produce a mean. In these experiments, when the grating disk was tilted, the error was perfectly eliminated using three reading head measurements. The experimental results verified the validity of the proposed theory, which provided a theoretical basis for improving the displacement measurement accuracy.