Patent ID: 6735033
Filing Date: 2004-05-11
Classification: G11B

Abstract:
In a disk drive including a read/write head, a data storage surface, on a rotating disk, having a plurality of embedded servo wedges and a plurality of concentric data tracks with data sectors, an on-track state wherein writing of data is enabled, a write unsafe state wherein writing of data is disabled, and a shock recovery state wherein writing of data is disabled, a method for recovering from shock events to improve data reliability comprising steps for:providing an arrival threshold, a write unsafe threshold that is greater than the arrival threshold, and a shock detection threshold that is greater than the write unsafe threshold; reading the embedded servo wedges on the rotating disk to generate position error signal values with respect to a selected data track; transitioning the disk drive from the on-track state to the write unsafe state if a position error signal value is greater than the write unsafe threshold and less than the shock detection threshold; transitioning the disk drive from the on-track state or from the write unsafe state to the shock recovery state if a position error signal value is greater than the shock detection threshold; transitioning the disk drive from the shock recovery state to the write unsafe state if a first number of consecutively generated position error signal values are less than the write unsafe threshold; and transitioning the disk drive from the write unsafe state to the on-track state if a second number of consecutively generated position error signal values are less than the arrival threshold.