Seagate Technology Incorporated

Donald B Douglas

Monty Aaron Forehand

Randall D Hampshire

Paul William Burnett

Krishna Rameshwara Malakapalli

William C Little

Florence F Kung

Charles E Skeldon

Jimmie R Shaver, Jr

Clyde E Goodner

An apparatus and method for improved servo control in a disc drive. A rotatable disc has first, second, third and fourth radially staggered servo burst patterns which define a plurality of concentric tracks. An actuator assembly supports a transducing head adjacent the tracks. A servo circuit combines respective at least third order polynomial functions of burst signals from the first and second, and third and fourth, burst patterns to generate a continuous function position error signal (PES) with normalized absolute magnitudes of 0 when the head is positioned at track centers, 0.5 at track boundaries, and 0.25 at quarter-track locations, and with substantially linear slope therebetween. The servo circuit applies current to an actuator motor to position of the head relative to a selected track in relation to the magnitude of the PES.

Servo control using continuous position error signal with high order polynomial component

An apparatus and method are disclosed for recovering from a header error condition in a disc drive of the type having a rotatable disc having a plurality of concentric tracks with data fields for the storage and retrieval of data and header fields providing logical address information for the data fields. The header fields include read and write header fields which are used during read and write operations, respectively, to align read and write elements of the head with the data fields. When the disc drive unsuccessfully decodes the logical address information from a selected header field associated with a selected data block, an alternate header error recovery routine is performed wherein attempts are made to decode the logical address information from the alternate header field associated with the selected data block. Radial offsets can further be applied to the head to enhance the decoding of the logical address information from the alternate header field.

Error recovery using alternate headers in a disc drive

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Edmond, OK, United States of America

Donald B Douglas