Improving the interpolation accuracy of optical encoders via noise suppression and signal correction

Abstract

This paper proposes an effective method to improve the interpolation accuracy of optical encoders via noise suppression and signal correction. Based on the arctangent method, noise suppression module and signal correction module are added to reduce the amplitude imbalance, imperfect quadrature, zero offset, harmonic distortion, and random noise in encoder signals. Among them, the noise suppression module is constructed through the simplified Kalman filter to filter out random noise, and the signal correction module is designed using gradient descent method to reduce the waveform errors. In addition, some model parameters in noise suppression and signal correction are analyzed to improve the convergence rate and accuracy. Simulation results show that the proposed method can improve the interpolation accuracy from 1.67% to 0.17% under the imperfect encoder signals input. The proposed method can be implemented on the hardware platform with the field programable gate array (FPGA). Experimental results show that the proposed method can achieve the interpolation accuracy of 0.09 µm when applied in optical encoder with the pitch of 20 µm. Simulation and experimental results can prove the effectiveness of proposed method.