A digital filter for speed noise reduction in drives using an electromagnetic resolver

The measurement of the rotation speed is an important issue in closed-loop industrial drives. The motor speed is often calculated by a derivative operation of the position measure obtained by an electromagnetic resolver. As a consequence, especially at the lowest speeds, the noise overlapped to the measured speed is significant and a suitable filter becomes necessary. The paper presents a solution to such a problem based on the employment of a stationary Kalman filter, suitably inserted in a phase locked loop structure. The implementation in an industrial synchronous motor drive, using a 16-bit fixed point DSP, has confirmed the goodness of the proposed solution.