Auto-calibration and noise reduction for the sinusoidal signals of magnetic encoders

The signals of magnetic encoders (MEs) are a pair sinusoidal waves: a sine wave and a cosine wave. Due to many different causes, they contain error factors such as offsets, amplitude differences, phase shifts, and random noise. This paper proposes auto-calibration and noise-reduction methods to reduce these errors and to estimate the positions of MEs. This method includes auto-calibration and adaptive-bandwidth phase-locked loop (ABW-PLL) algorithms. The auto-calibration algorithm normalized the sinusoidal signals of the MEs to the range of [-1; 1]. The ABW-PLL algorithm accurately estimated the phase angle of the MEs. Unlike the traditional filters, the ABW-PLL almost eliminated the time lag self-adaptively based on the input signals. The effectiveness of the proposed method is demonstrated by the simulation and experiment results.