Seagate Technology Incorporated

Thomas C Zirps

John Christopher Morris

Reed David Hanson

Timothy Francis Ellis

Nathaniel Boyd Wilson

Tim Rausch

David L Schell

Alexei Hiram Sacks

Puskal Prasad Pokharel

Barmeshwar Vikramaditya

Tao Zhang

Mustafa Can Ozturk

Brent Jay Harmer

Andrei Dorobantu

Samir Mittal

Chris Thomas Settje

Peng Yan

Haoying Sun

Methods and apparatuses for modulating a position error signal detection gate signal responsive to a track crossing velocity are discussed. The position error signal can be used to detect position information. A track crossing velocity can be estimated and then used via the modulating. Phase errors due to the track crossing velocity can be minimized.

Position error signal (PES) detection

First and second repeatable runout (ZAP) values are both located on a first virtual track of a magnetic disk. The first ZAP value is offset from the first virtual track center in a first direction and the second ZAP value is offset from the first virtual track center in a second direction opposite the first direction. At least one of the first and second ZAP values are accessed when performing repeatable runout correction for a writer of the read/write head that is being positioned over a second virtual track of the magnetic disk.

Using two or more offset repeatable runout correction values for a virtual track of a magnetic disk

The disclosure is related to systems and methods for achieving improved servo Gray code error detection and correction. A device may include a circuit configured to read servo data that is encoded using a Gray code encoding scheme to produce servo Gray code, read one or more Check bits associated with the servo Gray code, determine whether a read or write head is positioned over a target data track based on the servo Gray code and the one or more Check bits, and execute a read or write operation when the read or write head is positioned over the target data track.

Servo gray code check bits

One illustrative embodiment of the present invention pertains to a device. The device is configured to evaluate a Gray code value and to provide compensation for error in the Gray code value. Another illustrative embodiment of the present invention pertains to a method. The method includes comparing Gray code information with servo information. The method also includes evaluating error in the Gray code information based on the comparison between the Gray code information with servo information. Another illustrative embodiment of the present invention pertains to a data storage system. The data storage system includes a data storage medium, a head, and a controller. The head is controllably positionable relative to the data storage medium. The controller includes a means for sensing position information from the head. The controller also includes a means for compensating for error in the position information, to position the head relative to the data storage medium. Embodiments of the present invention provide unforeseen and inventive advantages over conventional data storage systems, including by assuring superior position evaluation and control of a read head relative to a data storage medium.

Controller with fractional position algorithm

Compensation for repeated runout (RRO) error, such as in a data storage device servo circuit, is preferably carried out by obtaining a population distribution of RRO error values from at least selected ones of a subset of tracks. An RRO error compensation value is determined for each one of the subset of tracks when a variance characteristic of said population distribution meets a selected criterion. Preferably, a first track of a storage medium has a servo field at a first angular position on the medium, a repeated runout (RRO) error compensation field at a second angular position on the medium, and a user data field at a third angular position on the medium. An immediately adjacent second track preferably has a servo field at the first angular position and a user data field at the second angular position in lieu of an RRO error compensation field.

Zone based repeated runout error compensation

An apparatus and associated method of servo writing to a storage media is provided that writes servo information at a first orientation pattern from a first storage extent of the storage media to a medial portion of the storage media, and writes servo information at a second orientation pattern different than the first orientation pattern from an opposing storage extent of the storage media to approximately the medial portion, so that the patterns at approximately the medial portion are positionally interlaced.

Bi-directional servo track writing to minimize sidewall writing at high skew angles

The present invention recognizes that induced RRO is coherent, i.e., the RRO has a large degree of repeatability from track to track. The present invention is a zero acceleration profile (compensation) process that targets CRRO (Coherent RRO). A process of the present invention represents a considerable reduction in the factory calibration time compared to other compensation techniques currently used. The reduction in time is attributed to the fact that CRRO can be computed by averaging position error signals (PES) over multiple tracks as opposed to total RRO which is computed by averaging over multiple revolutions on the same track.

Written-in error compensation method for coherent repeatable runout

An apparatus and method of tracking repeatable runout in a disc drive servo loop is provided in which a feedforward signal having harmonic components that are updated at a sample rate that is a fraction of a servo sector sample rate is employed during track following.

Fractional-rate feedforward RRO compensator

Problems inherent in guiding a sensor via a piecewise-linear lateral parametric profile are generally avoided using at least one broadly curved, generally lateral profile (). A sensor is configured to move in a nominally longitudinal direction relative to a frame of reference (). A position scale is defined in a generally lateral direction relative to the longitudinal motion (). Each broadly curved lateral profile is defined in terms of its corresponding position scale, the scale(s) and the profile(s) both being part of a parametric model that is available for use in guiding the sensor ().

Guiding a sensor using a broadly-curved lateral profile

A system and method for correcting repeatable runout errors during manufacture of a disc drive. The system includes a Kalman filter having a recursive learning gain input and includes a recursive learning Again-setting circuit coupled to the recursive learning gain input. The recursive learning gain is initially set based on an estimate of a ratio of non-repeatable run out error to an estimate of the repeatable run out error. On subsequent recursions, the recursive learning gain-setting is reduced.

Repeatable runout compensation in a disc drive

A method and apparatus for compensating for repeatable run-out errors in a disc drive is provided in which transfer function values for a servo loop in the disc drive are first determined. A sequence of repeatable run-out values for a portion of the disc drive is then determined. A transform is applied to the sequence of repeatable run-out values to obtain frequency-domain repeatable run-out values. Each frequency-domain repeatable run-out value is divided by a respective transfer function value to produce a sequence of frequency-domain compensation values which are then stored. An inverse transform is applied to the frequency-domain compensation values to obtain a sequence of time-domain compensation values. The sequence of time-domain compensation values is inserted into the servo loop.

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Minnepolis, MN, United States of America

Thomas C Zirps