International Business Machines Corporation

Robert C Baca

James Francis Crossland

Wayne T Comeaux

Alex Chliwnyj

Ronald K Rhodes

Alex Chliwnyjae

Man F Cheung

The present invention provides an apparatus and method for initializing a magnetic tape when it is mounted in a tape drive. In one embodiment, each time a tape is mounted, control parameters pertaining to the servo system are set to predetermined values and servo read elements in the tape head are activated. The tape is moved and a number of position error signal (PES) samples are read and averaged for each of the active servo elements. The value of one or more of the parameters is modified and new PES readings and averages are obtained. This process is repeated for a predetermined combination of parameter values whereupon read and write offsets are calculated and stored for each servo element. During an actual read (or write) operation, the tape head is positioned relative to the data tracks on which the desired data is located and servo control enabled. An actual PES generated by each active servo element is adjusted by the read (or write) offset calculated for that servo element, thereby substantially canceling the effects of element-to-element, module-to-module and azimuthal deviations. The resulting adjusted PES is used by the servo controller to optimize track following.

Initialization and calibration of magnetic tape having multiple servo

In a magnetic tape drive, a magnetic head simultaneously senses plural track lateral position indicators to generate a like plurality of independently generated sensed position error signals. The sensed position error signals are combined to provide an output position error signal that drives a positioning system to position the magnetic laterally of the length of the magnetic tape. The output position error signal represents an average of the position errors indicated by the sensed position error signals. The quality of the sensed position error signal is monitored, enabling eliminating poor quality signals from the output position error signal for maintaining a quality servo control. If less than a predetermined number of sensed position error signals have acceptable quality, then recording data is prohibited. Independently of sensing servo indicia on a record member to generate the sensed position error signals, a lateral position of the multi-track head is sensed. Upon loading the record member to a load point, the plural track position indicators are simultaneously sensed for centering the head to a predetermined track position. Then, an independent head position sensor is calibrated to the load point track position indicators for use as a verification of validity of the output position error signal. During recording and reading operations, the independent head position is determined on a periodic basis. If an unacceptable change in head position during any measurement period occurs or if the independent measurement indicates an unacceptable lateral deviation from the reference position, all recording is prohibited.

Processing servo signals concurrently read from plural spaced-apart

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Tucson, AZ, United States of America

Robert C Baca