Linearization interpolation method with high robustness and high accuracy for sinusoidal encoders

Abstract

This paper presents a linearization interpolation method with high robustness and high accuracy for sinusoidal encoders. Based on the pseudo-linearized signal constructed by the ratio of absolute values difference and absolute values sum of the sine and cosine signals, a compensation coefficient is designed to amplify pseudo-linearized signal to approximate ideal linearized signal for improving the linearity. The linearity is improved from 9.05% to 0.015%, which means that the linearized signal can be used to accurately determine the phase angle. This method is easy to implement, has high accuracy, and does not require the lookup tables (LUTs) or processors. The theoretical phase error is less than 0.007° over 0° ∼ 360°, corresponding to about 15-bit accuracy per signal period. In addition, the proposed method is implemented on the hardware platform with a field-programmable gate array (FPGA). Finally, the effectiveness of proposed method is demonstrated by experiments using simulated sinusoidal encoder.