International Business Machines Corporation

Wayne T Comeaux

Douglas W Johnson

James Francis Crossland

Robert C Baca

Alex Chliwnyj

Steven L Felde

Don G East

David C Graves

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

A magnetic tape has three evenly spaced-apart longitudinally-extending servo track areas. Four equal-sized longitudinally-extending data track areas are disposed between said servo track areas and between longitudinal edges of the tape and one of said longitudinally-extending data track areas. For track following, all servo track areas are simultaneously sensed for producing one head positioning signal. Data tracks are arranged into four groups of tracks, one-half of the data tracks in each group are concurrently accessed. The data tracks on the tape are arranged in clusters. Each cluster has one track from each of the groups of tracks. Two laterally-adjacent track clusters constitute four data track wraps for serpentine scanning of data tracks. The concurrent track accessing respectively occurs in first and second halves of a data track wrap (there is a number of wraps equal to one half the number of track clusters). Each servo area indicates two lateral positions of the tape to the head. The lateral spacing between the lateral positions is equal to about a data track width. This arrangement makes the servo areas field writable. The magnetic head has a number of data write and read gaps equal to the number of clusters. A set of four servo gaps are interposed between four groups of write and read gaps and positioned to simultaneously sense all three servo track areas.

Servo and data format for magnetic tape having plural spaced-apart servo

A tape path having an implicit squeeze bearing. In such a tape path, one end of the tape is wound upon a first reel, the tape extends around one or more guides, briefly comes into close proximity with itself at the outer wrap of the tape wound upon the first reel, and is wound upon a second reel. By coming within close proximity with itself, the tape forms an implicit squeeze bearing which damps tape tension variation, inhibits the transmission of vibrations from one reel to the other, and eliminates the entrapment of entrained air without any additional rollers or other components. The tape path is suitable for use in a peripheral storage device, such as a magnetic tape drive, and is compatible with a variety of tape cartridge configurations.

Tape path having implicit squeeze bearing

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Tucson, AZ, United States of America

Wayne T Comeaux