This article presents an advanced speed filtering technique for servo drives independent from the system model information with the reduction of the performance tuning difficulty. The contributions are two-fold: (a) the main filtering system outputs the filtered rotor position from the encoder measurement to recover the rotational speed of the rotor through the order reduction by the pole-zero cancellation property, resulting in the filtering error diagonalization, and (b) the subsystem, which forms the second-order disturbance observer, attenuates the disturbance to improve the acceleration filtering accuracy. The prototype 500-W servo drive validates the improvement in filtering performance under several load conditions.
