A new disturbance rejection scheme for hard disk drive control

A new disturbance rejection scheme is developed for hard disk drive servo control. The control scheme overcomes the drawback of typical internal-model-based repetitive control schemes which cancel repeatable disturbances but amplify disturbances at other frequencies. More importantly, the proposed scheme is capable of selectively attenuating disturbances at given frequencies without requiring a high order control structure. As a result, it has the ability of rejecting disturbances without a long learning delay which is yet another disadvantage of typical internal-model-based repetitive control schemes. Two ways of designing such a disturbance rejection controller are proposed. Simulations using disturbances constructed from real drive position error signals (PES) have been carried out to show the effectiveness of this control scheme