Adaptive off-track recovery

A hard disk drive (HDD) capable of adaptively limiting an off-track recovery displacement of a recording head during an off-track data recovery operation, said HDD comprising:

• an actuator controller producing an actuator control signal;
• an actuator that positions said recording head in accordance with said actuator control signal;
• an off-track recovery data table containing an off-track recovery displacement threshold of said recording head;
• and
• a controller responsive to a failed read operation, for commencing an off-track data recovery procedure, wherein said data recovery procedure includes calibrating said actuator control signal in accordance with the off-track recovery displacement threshold retrieved from said off-track recovery data table, said calibrated actuator control signal utilized to control the positioning of said recording head during off-track data recovery.

A method for adaptively limiting an off-track recovery displacement of a recording head during an off-track data recovery operation within a head disk assembly (IDA), wherein said HDA includes an actuator that positions said recording head in accordance with an actuator control signal, said method comprising the steps of:

• anticipating an allowable off-track recovery displacement threshold of said recording head, said anticipating an allowable off-track recovery displacement threshold comprising performing an off-track displacement test including:
• positioning said recording head to anion-track position centered with respect to a test track in accordance with a pre-determined on-track positioning signal;
• writing an on-track test data field at the on-track position;
• moving said recording head to an off-track position within said test track, wherein said off-track position is offset from the on-track position in accordance with a pre-determined off-track positioning signal;
• writing an off-track test data field at the off-track position such that said off-track test data field overwrites a portion of said on-track test data field;
• repositioning said recording head to the on-track position;
• performing stepwise read operations at incremental, radially off-set positions with respect to the on-track position until said on-track test data field is read;
• and
• identifying the distance between said on-track position and the radially off-set position at which said on-track test data field is read as said off-track recovery displacement threshold;
• and
• responsive to a failed read operation, commencing an off-track data recovery procedure, wherein said data recovery procedure includes calibrating said actuator control signal in accordance with the anticipated off-track displacement threshold, said calibrated actuator control signal utilized to control the positioning of said recording head during off-tack data recovery.

A system for adaptively limiting an off-track recovery displacement of a recording head during an off-track data recovery operation within a head disk assembly (HDA), wherein said HDA includes an actuator that positions said recording head in accordance with an actuator control signal said system comprising:

• means for anticipating an allowable off-track recovery displacement threshold of said recording head, said anticipating an allowable off-track recovery displacement threshold comprising performing an off-track displacement test including:
• positioning said recording head to an on-track position centered with respect to a test track in accordance with a predetermined on-track positioning signal;
• writing an on-track test data field at the on-track position;
• moving said recording head to an off-track position within said test track, wherein said off-track position is offset from the on-track position in accordance with a pre-determined off-track positioning signal;
• writing an off-track test data field at the off-track position such that said off-track test data field overwrites a portion of said on-track test data field;
• repositioning said recording head to the on-track position;
• performing stepwise read operations at incremental, radially off-set positions with respect to the on-track position until said on-track test data field is read;
• and
• identifying the distance between said on-track position and the radially off-set position at which said on-track test data field is read as said off-track recovery displacement threshold;
• and
• means responsive to a failed read operation, for commencing an off-track data recovery procedure, wherein said data recovery procedure includes calibrating said actuator control signal in accordance with the anticipated off-track displacement threshold, said calibrated actuator control signal utilized to control the positioning of said recording head during off-track data recovery.