International Business Machines Corporation

Hitachi Global Storage Technologies Netherlands B.v.

Hitachi Global Storage Technologies Amsterdam B.v.

Hgst Netherlands, B.v.

Hitachi Global Storage Technologies

Hitachi Global Storage Technologies B.v.

Craig N Fukushima

Louis Joseph Serrano

Gregory Michael Frees

Jeff J Dobbek

Toshiki Hirano

Hiroshi Uchida

Karl Arnold Belser

Mantle Man-Hon Yu

Isao Yoneda

Kevin Tzou

Mantle M Yu

Scott Arthur Thomas

Blake O Finstad

Kishan Kumar Kumbla

Markus Staudenmann

Yifan Tang

A disk storage system having servo data stored thereon for accurate head position control over a magnetic or other storage medium. The servo data is seamless and untrimmed and consists of a primary servo burst set (AB burst) in which the difference defines the desired tract pitch for the surface. Multiple secondary servo burst sets (e.g., CD burst and EF burst) are written at the desired track pitch but radially offset from the primary burst set. In one embodiment, two secondary servo burst sets are used, but alternatively, any number of secondary servo burst sets could be used. In this exemplary embodiment having two secondary servo burst sets, the CD servo burst set is offset by &#x2153; of the track pitch from the primary servo burst set. Also in this embodiment, the EF servo burst set is offset by &#x2154; of the track pitch from the primary servo burst set. There are six bursts per set. The servo data is written in multiple servo sectors around the surface of the medium. From the servo data, three PES (position error signals) are generated, A&#x2212;B, C&#x2212;D and E&#x2212;F, for providing linear position sensitivity information to the head position control logic. The resulting PES is more linear for smaller head sizes.

Seamless and untrimmed primary servo burst with multiple secondary servo bursts

A hard disk drive having a self servo write offset error correction mechanism to improve self servo write process is disclosed. In accordance with certain aspects of the present invention, there is provided a self servo write method that can measure an accurate position offset between the read-head element and write-head element incorporated in a disk drive before servo data is recorded on the disk provided in the disk drive.

Read write offset error correction using geometric reference in self servo write process

Apparatuses and/or systems for performing self-servo write using a helium environment are provided. In one embodiment, an intake tube is coupled to an intake hole that is associated with an enclosure for enclosing a recording disk. A helium gas transport mechanism is coupled to the intake tube and the helium gas transport mechanism causes substantially helium gas to be transported to the enclosure.

Apparatus of performing self-servo write using a helium environment

A method for preventing data loss in a hard disk drive by projecting reduction in gas concentration using insitu non-repeatable runout is disclosed. The method includes using servo tracking error to obtain a measured value of insitu non-repeatable runout (NRRO) for the hard disk drive, the hard disk drive having been filled with the gas and hermetically sealed. The measured value of NRRO is then deconvolved into a plurality of values for flow induced NRRO components. These values of NRRO and of flow induced NRRO components are compared to predetermined limiting values and a time when one of the predetermined limiting values will be reached is predicted. Action is then applied as appropriate.

Method for preventing data loss in a hard disk drive by projecting reduction in helium concentration using insitu non-repeatable runout

A method is presented for reducing time loss during manufacture and testing of a hard disk drive by predicting reduction in gas fill. The method includes using servo tracking error to obtain a measured value of insitu non-repeatable runout (NRRO) for the hard disk drive, the hard disk drive having been filled with the gas and semi-sealed. The measured value of NRRO is then deconvolved into a plurality of values for flow induced NRRO components. These values of NRRO and of flow induced NRRO components are compared to predetermined limiting values and a time when one of the predetermined limiting values will be reached is predicted. Action is then applied as appropriate.

Method for reducing time loss during manufacture of hard disk drives by predicting reduction in helium concentration using insitu non-repeatable runout

Methods of performing self-servo write using a helium environment are provided. In one embodiment, a recording disk is placed in an enclosure. The enclosure is filled with a gas that is substantially helium. Self-servo write is used to write circular track positioning information on the recording disk.

Method of performing self-servo write using a helium environment

A disk drive manufacturing method calibrates the stitching gain of a position error signal (PES) by sampling servo information from a quadrature servo pattern while the head is maintained at the quarter-track positions and then calculating the kurtosis of the distribution of the PES values calculated from the samples. Because the kurtosis is a measure of the deviation from a normal or Gaussian distribution, the kurtosis of a PES distribution is used to optimize the stitching gain value through iteration until the kurtosis is close to zero, indicating that the PES with the optimal stitching gain values has a near-Gaussian distribution. The stitching gain calibration is performed for all heads and for multiple tracks across the surface of the disk for each head. The resulting values of stitching gain, each associated with a head and track, are stored in the disk drive memory and recalled during operation of the disk drive.

Method for calibrating disk drive servo control system gain values during manufacturing

Distinct servo patterns are written on data storage media of a data storage device. Servo patterns of a first type are written for transducers of the data storage device having a first transducer characteristic. Servo patterns of a second type are written for transducers that do not have the transducer characteristic. The transducer characteristic can be a geometric criterion such as read head and write head track width, an operating characteristic such as frequency response, or otherwise. The first servo pattern may be a seamless untrimmed PES burst and the second servo pattern may be a seamed trimmed PES burst.

Writing distinct servo patterns on individual transducers according to transducer read/write head characteristics in a data storage device

A disk storage system having servo data stored thereon for accurate head position control over a magnetic or other storage medium. The servo data is seamless and untrimmed and consists of a primary servo burst set (AB burst) that defines the desired tract pitch for the surface. Multiple secondary servo burst sets (e.g., CD burst and EF burst) are written at the desired track pitch but radially offset from the primary burst set. The servo data is written in multiple servo sectors around the surface of the medium. From the servo data, PES (position error signals) are generated for providing linear position sensitivity information to the head position control logic. The resulting PES is more linear for smaller head sizes.

Seamless and untrimmed primary servo burst with secondary servo bursts

A data storage device performs a re-read of data prior to a read inhibit for data recovery and validation. When misregistration of read/write heads occurs, as indicated by a sampled servo position, data read from a track of the data storage device is withheld from a host until a subsequent sampled servo position is verified to be within a read limit width of the track. Data blocks preceding the servo position that caused the posting of the read inhibit are re-read, once the read inhibit is cleared. If the read inhibit is not present following the re-read of the data, this re-read data can be released to the host.

Re-read of data read prior to read inhibit for data recovery and validation in a sampled position data storage device

Non-linearity in a position error signal (PES) for a data storage device is precisely characterized during a calibration phase in the manufacturing process. From this characterization of the PES non-linearity, the data storage device can be programmed with the necessary data to perform accurate, real-time linearization calculations of the PES in order to compensate for non-linearity in the PES during operation. The sequence of calibration steps includes a PES gain calibration, a first servo loop gain calibration, a PES linearization calibration, and an optional second servo loop gain calibration.

Position error signal linearization calibration

A method, apparatus, and article of manufacture for determining a transducer position in relation to a media surface is described. The method comprises sensing positioning information on the media, measuring a position error signal from the sensed positioning information wherein the position error signal includes first and second position signal components, accessing stored information describing a non-linear relationship between the measured position error signal and the transducer position, and applying the stored relationship to the measured position error signal to produce a corrected position error signal, and determining the transducer position from the corrected position error signal.

Position error signal linearization using an auxiliary discontinuity removal routine

A method, apparatus, and an article of manufacture for calibrating a position error signal for controlling the position of a read transducer with respect to a storage media having positioning information written at a location thereon. In one embodiment, the invention is embodied in a method comprising determining a relationship between a read transducer position and the positioning information by measuring the positioning information while passing the read transducer across the location, determining a measured position error signal from the measured positioning information, and computing a relationship between the measured position error signal and the read transducer position.

Position error signal calibration using measured bursts

A dual element read/write head for a direct access storage device (DASD) positions the read and write elements relative to each other such that the same servo track can be used for read and write operations at the disk outside diameter (OD). As the head is moved across the disk from the OD toward the ID, different servo tracks are used for positioning the read and write elements in the same track as the head moves toward the disk ID. The STW TMR portion of the total TMR at the OD is thereby minimized to zero, so that the total TMR at the OD is primarily a function of only the conventional WW TMR and WR TMR components. The STW TMR gets larger as the head assembly moves toward the ID, so that the total TMR at the ID becomes a function of both the STW TMR and the remaining TMR components. At the ID, however, the read-write element compensation error component of total TMR is smaller than it is at the OD, and can be more easily dealt with, using known servo readback signal processing methods, and making it easier to carry out the typical signal processing employed by servo controllers.

Dual element head with radial offset optimized for minimal write-to-read track error

A servo pattern for use on a data storage surface that includes at least one track to minimize position error during positioning of a transducer over the data storage surface. The servo pattern includes a plurality of servo burst fields of constant amplitude for defining a centerline of the track and for determining the position of the transducer. According to the present invention, at least one servo burst field comprises N segments, where N.gtoreq.2, and each of the N segments is written with constant amplitude. The amplitude of the at least one servo burst field is then determined as a function of the amplitudes of the N segments.

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Monte Sereno, CA, United States of America

Craig N Fukushima