Smoothing position error signal corrupted by impulse disturbance

This paper proposes a filtering method to filter out impulses in the position error signal (PES) due to corrupt servo pattern or demodulation timing in hard disk drives. The impulse disturbance, leading to a sudden change in PES; may be distributed separately or consecutively. A nonlinear switched filtering method is used to smooth the PES before feeding into servo controller. With the nonlinear switched filter, the PES is significantly reduced without degrading the stability and bandwidth of the servo loop under certain conditions.