Design And Implementation Of A Soft-subdivision Algorithm For Precision Angular Displacement Signals

Owing to the merits of long measurement range and high measurement precision,the optical grating sensors have wide applications in ultra-precision displacement measuring field.The optical grating sensors employ grating lines as the measurement standards which directly determine the measurement accuracy and resolution.However,owing to the fundamental limit of fabrication,the precision of grating lines cannot be infinitely improved.Therefore,the effective subdivision technique is the key point to further improve the measurement accuracy and resolution.Based on the analysis of drawbacks in traditional subdivision techniques,this paper proposes novel subdivision technique named softsubdivision.By using the characteristic of special grating lines,the model of time values which are acquired by spatially uniform sampling is established.Then the spacial displacement subdivision pulses are sent to realize the predicated subdivision of spacial displacement.The performance.of soft-subdivision can hardly affected by the factors such as sinusoidal deviation,bad consistency and orthogonality of grating original signal orthogonality,which decreases the requirement of signal quality for precision subdivision methods and obtain the purpose of high precision measurements.Regarding the subdivision signal of the optical grating sensor with wide applications as the researching object,this research are dived into 3 parts listed as follows:(1)The measurement of the space is converted to the measurement of time by the idea of the space-time conversion.A soft-subdivision model is established by using the relation between time and space displacement.The theory of time-series prediction is introduced into the signal subdivision,and the relevant theoretical research is carried out.(2)The method of adaptive optimization prediction model parameters and standard value interpolation for real-time dynamic error correction are applied to the system based on the research on the characteristics of the soft-subdivision model for grating signals,Which is used into soft-subdivision model to calibrate the random errors and systematic errors in real time to improve the accuracy of the soft-subdivision.(3)A soft-subdivision system is designed,and a large number of experiment studies are carried out.and the influence of velocity on time prediction accuracy is analyzed based on the error of prediction time of soft-subdivision and the soft-subdivision errors of angular displacement are calibrated.The reliability is verified by the experiment resuls.Dynamic experiments is carried out under the circle grating at different speeds,it shows that that the subdivision errors are within ± 1.8".and the accuracy of the softsubdivision is better than 5% of the original’s.