On-line angle self-correction strategy based on a cobweb-structured grating scale

Abstract

Installation eccentricity of the grating scale is the main source of error for rotary optical encoders in practical applications. In this paper, an on-line angle self-correction strategy for rotary optical encoders is proposed. Firstly, the eccentricity error model is described, which explains the numerical relationship between the eccentricity error and the eccentric parameters including eccentric distance and eccentric angle. Then, a bioinspired cobweb-structured grating scale is adopted as the measurement standard of the rotary optical encoder. This grating scale allows the rotary optical encoder to sense the rotary angle and the radial displacement simultaneously. The eccentric parameters can be determined in real time from the rotary angle and the radial displacement information. Thus, the measured rotary angle can be on-line corrected by applying the eccentric parameters to the eccentricity error model. The feasibility and effectiveness of the proposed strategy have been confirmed from the experimental results.

A Review: High-Precision Angle Measurement Technologies

“…Optical methods predominantly depend on the disk encoder scheme, commonly denoting the grating encoder arrangement, which employs a grating disk configuration for measurement purposes [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Previous researchers have conducted a lot of research on it, including structural optimization [ 36 ] and algorithm supplementary modifications [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ]. The above method mainly relies on the scale of the code disk to measure large angles.…”

An ultra-precision error estimation for a multi-axes grating encoder using quadrant photodetectors

“…Considering the compactness of the measurement structure in the designed scheme of the multi-degree-of-freedom grating encoder, the angle measurement scheme is usually to inject the 0th, +1st and -1st order diffracted lights of the grating into the QPD through the focusing lens, and the principle of autocollimator is used to detect the position change of the light spot on each QPD for angle measurement [36][37]. However, the angle measurement range of the grating encoder based on the traditional QPD linear interval spot positioning method is very limited, which is basically a small angle range [38][39][40], such as the three-axis autocollimator for detection of angular error motions of a precision stage, which has a three-axis measurement range of about 40 arcseconds and is developed by the team of Wei Gao of Tohoku University [41].…”