Phase Demodulation Strategy Based on Kalman Filter for Sinusoidal Encoders

Abstract

Phase demodulation strategy based on Kalman filter for sinusoidal encoders is proposed in this paper. For the state equation and observation equation in the constructed phase demodulation model, the phase angle, the phase angular speed, and the speed fluctuation are the system states, and the sine and cosine signals output by the encoder are the system observations. In addition, due to the nonlinear relationship between the observations and the system states, the observation function is linearized by the extended Kalman approach. In order to implement the Kalman filter on the hardware platform with a field programmable gate array (FPGA), the matrix model of the Kalman filter is further derived into an algebraic model, which only contains sine, cosine, and basic algebraic operations. Compared to the arctangent method, the proposed method has the noise suppression capability, and compared to the conventional phase-locked loop (PLL) method, the proposed method has the better dynamic performance without the acceleration-associated phase error. Both simulation and experimental results can prove the effectiveness of the proposed method.