γ-radiation noise-filtering algorithm for optical encoder based on improved adaptive line enhancer

Abstract

BackgroundThe output signal quality of optical encoder in nuclear radiation environment is degraded due to the total ionizing dose (TID) effect of γ radiation.PurposeThis study aims to propose an improved adaptive line enhancer method (IALEM) that considers accuracy and efficiency to minimize the degradation of the output signal quality of photoelectric encoders in nuclear radiation environments caused by TID effect of γ radiation.MethodsFirstly, the Softsign function was introduced into the least mean square (LMS) algorithm to establish the nonlinear relationship between the error and the step size. Then, rapid convergence and small steady-state errors were achieved by introducing the previous step size value in the step-size-updating formula. Furthermore, this improved adaptive line enhancer method (IALEM) was compared with similar algorithms in terms of four aspects: convergence speed, steady-state error, low signal-to-noise input, and computational volume. Finally, the proposed algorithm was implemented in a field programmable gate array (FPGA) chip and verified on a photoelectric encoder platform, and its filtering effect was experimentally validated in a cobalt-60-source γ-radiation environment.ResultsThe results show that the proposed algorithm yields a higher convergence speed, lower steady-state error, and better filtering effect than that of other algorithms for low signal-to-noise ratio signals with less computational effort. Uniformity error and orthogonality error of the photoelectric encoder output signal after filtering by IALEM are reduced by 17.6% and 8.0%, respectively.ConclusionsThe experimental results show that the proposed algorithm can effectively filter out the noise generated through γ radiation and improve the output signal quality of the photoelectric encoder.

Keywords

• optical encoder
• variable-step size
• improved adaptive line enhancer method
• radiated noise filtering