International Business Machines Corporation

Jaquelin K Spong

James Howard Eaton

Moris Musa Dovek

John S Foster

Zine-Eddine Boutaghou

Gordon James Smith

Thomas R Albrecht

Robert Fontana

Kurt A Rubin

Virgil S Speriosu

Linden James Crawforth

Thomas S Larson

Johnny Lynn Teale

Donald C Buettner

A method and apparatus are provided for maintaining file readback performance compensating for readback errors caused by head/disk interaction used with a data detection channel in a direct access storage device. A readback signal is sensed from at least one disk surface and a data channel error rate is detected responsive to the readback signal. The detected data channel error rate is compared with a first predetermined threshold value and a gain of a phase lock loop (PLL) in the peak data detection channel is optimized responsive to an identified data channel error rate with a first predetermined threshold value. The PLL gain is adjusted until a lowest error rate is detected. A failure warning for the direct access storage device is provided to a user when the detected PLL gain is greater than a predefined loop gain value.

Method and apparatus for reducing readback errors by controlling the

A magnetic field sensor uses four individual magnetoresistive spin valve elements electrically connected in a bridge circuit. The spin valve elements are lithographically formed on the same substrate with their free layers having their magnetization axes parallel to one another. An electrically conductive fixing layer is formed on the substrate but is insulated from the spin valve elements. The application of current through the fixing conductor during fabrication of the field sensor fixes the direction of magnetization of two of the pinned layers to be antiparallel to the direction of magnetization of the other two pinned layers. The bridge circuit output voltage is responsive to an external magnetic field in the plane of the sensor. By appropriate fixing of the direction of magnetization of the pinned layers during sensor fabrication, and appropriate connection to the input and output leads, the bridge circuit output voltage is a measure of either the magnetic field or field gradient. The fixing conductor, or a separate current strap formed on the substrate, can be used to pass an unknown current over the sensor, in which case the bridge circuit output voltage is a measure of the unknown current.

Bridge circuit magnetic field sensor having spin valve magnetoresistive

A starting sequence is provided for a rotating disk data storage device by providing a low level sensing current to the spindle motor which is able to initiate rotation of the disk spindle assembly when, absent stiction between head and confronting disk surface, it is only necessary to overcome disk assembly inertia and head drag. A sensing device is provided to sense a back electromotive force (EMF) in the spindle motor windings which indicates the start of disk rotation when any stiction condition has been terminated. A sequence of alternating current pulse bursts are applied to the actuator motor to impart a dithering action to the heads which induces axial vibration of the disks to break the stiction between the heads and confronting disk surfaces. The initial burst is of low amplitude pulses and each succeeding burst is of progressively greater amplitude and the pulses of each burst are of constant or progressively varying frequency to afford some consecutive pulses approaching the resonant frequency of the disk modes of vibration to enhance the stiction breaking force. The sensing of a back EMF (indicating disk rotation and the termination of any stuck head condition) is used to terminate the start sequence and switch the spindle and actuator motors to the normal operational control of the drive.

Disk drive micromotion starting apparatus and method

A magnetic recording disk drive has a startup routine that frees the recording head carriers and moves them to a parking location, such as load/unload ramp or a disk landing zone, if they are stuck to the disks when the drive motor is attempted to be started. If the drive motor does not achieve its operating speed at normal startup of the disk drive, thus indicating that static friction or other 'stiction' forces are adhering the carriers to the disks, a series of alternating current pulses is applied to the actuator to dither the carriers at an initial frequency that is generally equal to or above the resonant frequency of the actuator system with stuck carriers. The frequency and amplitude of the pulses is swept downward from the initial frequency and amplitude and repeated until the drive motor rotates at its operating speed. The alternating current pulses that perform the dithering of the carriers have different amplitudes or durations so that a net force is applied to the actuator to move the carriers to the parking location.

Disk drive with controlled actuator oscillation for release of head

The invention is a constrained pivot compound radius tape post guide. The post is mounted on an axle which allows it to pivot when the tape changes direction. The pivoting action serves to peel away all tape which has been in stationary contact with the post, thereby reducing startup stiction. Above a certain rotation angle the post is prevented from further rotation either by a fixed stop or by torque exerted on the post by the tape which is under tension.

Constrained pivot guide post

The invention is a tape guiding post including a tape engaging surface having a longitudinal contour with a compound radius of curvature. In the preferred embodiment, the longitudinal contour has a smoothly varying radius of curvature. The outer portions of the contour have a relatively large radius of curvature and blend smoothly into a central portion which is of a relatively small radius of curvature to allow for any desired bending of the tape in its easy direction. The combination minimizes both friction and stiction between the tape and the guide. The guide is also laterally contoured to accommodate droop at the edges of the tape, caused by low air pressure at the edges.

Compound radius guide post

A gimbaled compliant guide for tape drives includes two plates mounted adjacent opposite edges of an arcuate tape bearing surface. The plates are pivotably mounted to accommodate variances in the tape path resulting from tape path tolerances and tape distortions. One plate is also mounted to a leaf spring to accommodate variations in tape width. The combination of simple compliancy and the ability to pivot eliminates the concentration of the stress at a single contact point between the tape edge and the guiding mechanism. By evenly distributing the stress along the span of contact between the edge of the tape and the guides, particulate matter generated from such contact is minimized. Such guiding mechanism may be used on any element of the tape path.

Gimbaled compliant guide for tape drivers

The method to detect and determine the profile of the material property or the structure changes not only on surface but also at the subsurface, of a storage medium or a scanned sample. This method comprises the following steps: (a), a nondestructive periodic or modulated perturbation is applied to the sample to be scanned. (b) the perturbed sample is then scanned using a microprobe, e.g., scanning tunneling microscopy (STM) or atomic force microscopy (AFM), which is responsive to the applied periodic or modulated perturbations and (c) the modulated output signals from the microprobe, in combination with the input perturbation signals, are processed and demodulated to automatically control the motion of the probe, and to determine the profiles of the material properties or the structure changes of the scanned sample.

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Mountain View, CA, United States of America

Jaquelin K Spong