Western Digital Technologies, Inc.

Maxtor Corporation

Duc H Banh

Erhard Theodor Schreck

Guoxiao Guo

Brian D Strom

Jingbo Yu

Thao Anh Nguyen

Bruce C Schardt

Scott A Hughes

Kazuhiro Saito

Andrew LeFebvre

David Scott C Amiss

Weldon Mark Hanson

Joey Martin Poss

Don Brunnett

Shaomin Xiong

Charles A Park

Donald Joseph Brunnett

Kei Yasuna

Richard Oswald

Masaru Furukawa

Francis P Crimi

Jianbin Nie

Lloyd E Levy

Chris Hawks

Anthony R Hurtado

Tim Glassburn

Suet Teo

Danilo Bueno

Michael L Mallary

Siri S Weerasooriya

Gang Herbert Lin

Jiangang Liang

Soo-Choon Kang

Mark Heimbaugh

Hongchao Tim Zhao

Kezhao Zhang

John Vicars

Joerg Ferber

Nick Warner

Triet Tieu

Kurt Rusnak

Tianyu Jiang

Li Zou

Jeng-Yu Wang

Various illustrative aspects are directed to a data storage device comprising: a voice coil motor (VCM) and one or more processing devices, configured to actuate the VCM, switch on measuring a back electromotive force (BEMF) from the VCM for intervals of an initial BEMF measurement that are free of spikes in the initial BEMF measurement, and process a measured BEMF signal from the intervals of the initial BEMF measurement that are free of spikes in a change of current term of the initial BEMF measurement.

Reducing noise in back EMF sensing for data storage

Various illustrative aspects are directed to a data storage device, comprising: one or more disks; an actuator assembly comprising a head, and configured to position the head over a corresponding disk surfaces; and one or more processing devices, wherein the head comprises: a write element; a laser unit; and a fly height control element, and wherein the one or more processing devices are configured to: iteratively perform write start operations of write start patterns with the head on the corresponding disk surface, at a plurality of values of at least one of laser pre-bias current, and write backoff; detect pattern signal amplitudes of the write start patterns on the corresponding disk surface; and determine a relation of write backoff to laser pre-bias current for the head, based at least in part on the pattern signal amplitudes.

Determining laser induced thermal protrusion and laser threshold in heat-assisted magnetic recording (HAMR) data storage

Various illustrative aspects are directed to a data storage device, comprising: one or more disks; an actuator assembly comprising a head, and configured to position the head over a corresponding disk surface; and one or more processing devices, the head comprising: a write element; a laser unit; and a fly height control element, and wherein the one or more processing devices are configured to: iteratively perform spiral write operations of spiral patterns comprising a plurality of sync marks with the head on the corresponding disk surface, wherein the spiral write operations are performed at: a plurality of values of laser pre-bias current, write backoff, and/or start disk phase; detect pattern signal amplitudes of the spiral patterns on the corresponding disk surface; and determine a relation of write backoff to laser pre-bias current for the head, based on the pattern signal amplitudes of the spiral patterns.

Method to measure thermal protrusion by sensing spacing change due to pre-lasing

A data storage device is disclosed comprising a head actuated over a magnetic media comprising a plurality of tracks. A first pattern of magnetic transitions is written to a first segment of a first track. Preparation is made to write a second pattern of magnetic transitions to a second segment of a second track adjacent the first segment of the first track. When the second pattern matches the first pattern, a write boost is configured to a first setting, and when the second pattern does not match the first pattern, the write boost is configured to a second setting. The second pattern of magnetic transitions is then written to the second segment of the second track using the configured write boost.

Data storage device with history dependent write boost

A data storage device is disclosed comprising a head actuated over a disk surface by an actuator arm. The actuator is controlled to press the actuator arm against a crash stop in order to write a plurality of bursts on the disk surface each with a different write parameter setting. Each burst is read in order to measure a quality metric for each burst, and an operating setting for the write parameter is configured based on the measured quality metrics.

Data storage device calibrating write parameter by pressing actuator against crash stop

A data storage device is disclosed comprising a head actuated over a magnetic media. A write boost is configured to a first setting, and a first pattern of magnetic transitions is written to a first servo field of a servo sector on the magnetic media using the first setting for the write boost. The write boost is configured to a second setting different from the first setting, and the first pattern of magnetic transitions is written to a second servo field of the servo sector on the magnetic media using the second setting for the write boost.

Data storage device with servo field dependent write boost

A data storage device is disclosed comprising a head actuated over a disk, wherein the head comprises a spin torque oscillator (STO). A first bias signal is applied to the STO during a first interval preceding a write operation to write data to the disk, wherein the first bias signal causes the STO to protrude toward the disk. After the first interval, a second bias signal is applied to the STO during a second interval spanning at least part of the write operation, wherein an amplitude of the first bias signal is in the range of 1.1 to 1.5 times an amplitude of the second bias signal.

Data storage device pre-biasing a spin torque oscillator prior to a write operation

A servo writer is disclosed operable to write servo sectors on a disk to define non-circular servo tracks. The servo writer comprises control circuitry including a servo control system operable to measure a position of a head over the disk to generate a position signal, generate a position error signal (PES) representing a difference between the position signal and a reference signal, process the PES with a servo compensator to generate a control signal, and position the head over the disk in response to the control signal. A disturbance is induced into the servo control system, and while positioning the head over the disk in response to the control signal, a plurality of servo sectors are written on the disk to define a servo track, wherein the disturbance induced into the servo control system causes the servo track to be non-circular relative to a rotation axis of the disk.

Disk drive compensating for track squeeze by writing non-circular servo tracks

A system to detect a ramp position is disclosed. The system includes a head positioner coupled to an actuator arm to position a head relative to a disk and a controller to: control the head positioner to move the head toward the ramp; determine a plurality of integrator values while moving the head; generate a threshold based on the plurality of integrator values; and determine the ramp position based on a first integrator value exceeding the threshold.

Ramp detection by profile sweep method utilizing integrator values

A method for monitoring the operability of a slider of a disk drive includes the steps of providing a slider that includes a read/write head that magnetically interacts with a storage disk, and a slider mover that adjusts a head-to-disk spacing, controlling an electrical stimulus to the slider mover with a drive circuitry, measuring an actual electrical response from the slider mover with the drive circuitry, and comparing the actual electrical response to an expected electrical response to determine an operability status of the slider mover. Further, changes in the actual electrical response can be monitored and used to predict future failure of the slider mover.

Method of detecting changes in operability status of a slider mover in a disk drive

A disk drive having a drive housing, a storage disk that is rotatably coupled to the drive housing, and a slider assembly that includes a head and a slider mover. The head reads data from the storage disk during a read operation and writes data to the storage disk during a write operation. The slider mover maintains the head at a read HtD spacing during the read operation, at a pre-write HtD spacing during the read operation prior to the write operation, at a write HtD spacing during the write operation, and at an idle HtD spacing when the drive is not performing the read operation or the write operation. The disk drive includes a drive circuitry that directs a read power level to the slider mover to maintain the head at the read HtD spacing, a pre-write power level to maintain the head at the pre-write HtD spacing, a write power level to maintain the head at the write HtD spacing, and a idle power level to maintains the head at the idle HtD spacing.

Disk drive that positions a head at multiple head-to-disk spacings

A disk drive includes a drive housing, a storage disk, a slider and a drive circuitry. The storage disk has an inner and an outer diameter. The slider includes a read/write head and a slider mover that receives power from the drive circuitry to position the read/write head at a predetermined head-to-disk spacing during radial movement of the slider relative to the storage disk. The drive circuitry can direct a varying level of power to the slider mover during radial movement of the slider. In addition, the drive circuitry can increase the power to the slider mover as the read/write head nears a target track in order to decrease the head-to-disk spacing at the appropriate time. The drive circuitry can adjust the power to the slider mover so that the head-to-disk spacing remains within a predetermined range as the slider moves radially relative to the storage disk. The drive circuitry can also direct power to the slider mover so that the head-to-disk spacing is substantially the same at the start of a seek operation and when the read/write head arrives at a target track. The drive circuitry can also direct power to the slider mover based at least partially on the temperature of a portion of the slider.

System and method for adjusting head-to-disk spacing in a disk drive

A disk drive includes a drive housing, a storage disk, a slider and a drive circuitry. The slider magnetically interacts with the storage disk, and includes a read/write head that is positioned to have an actual head-to-disk spacing greater than zero nanometers during rotation of the storage disk. The drive circuitry can determine and/or monitor the actual head-to-disk spacing at any time during the operation of the disk drive based on an amplitude or a change in the amplitude of a signal such as a variable gain amplifier signal. In one embodiment, the slider includes a slider mover that receives current via the drive circuitry and causes a deformation of a portion of the slider to change the head-to-disk spacing based on the amplitude of the signal. In another embodiment, the read/write head moves during substantially consistent rotational velocity of the storage disk from a first actual head-to-disk spacing equal to approximately zero nanometers, to a second actual head-to-disk spacing that is greater than zero nanometers based on a desired amplitude of the signal.

System for monitoring and dynamically adjusting head-to-disk spacing in a disk drive

A method of determining side track erasure in a disk drive having a disk and a transducer. A target track and one or more side tracks proximate to the target track on the disk are selected, and recording parameters for recording signals on the target track and each side track with the transducer are selected. Thereafter, signals are recorded on each side track and then signals are recorded on the target track multiple times. A reduction in the integrity of the recorded signals on each side track due to recording signals on the target track multiple times is detected, and the detected reduction in the integrity of the recorded signals on each side track represents the amount of the erasure of the recorded signals on the side track. Recording parameters are changed based on the signal integrity reduction to minimize side track erasure.

Method of determining side track erasure in a disk drive

A PTP test subsystem of a magnetic disk drive identifies an undesired pole tip protrusion (PTP) condition, and takes steps to prevent problems associated with PTP. A PTP stressing mechanism stresses the disk drive during a PTP test mode to induce a PTP condition. A disk contact detection circuit detects when a head of the disk drive contacts the disk. A PTP write current determining circuit is also provided which comprises a write current level detector to ascertain a write current level at which the disk contact detection circuit detects when the head of the disk drive contacts the disk while the disk drive is stressed during the PTP test mode.

Monitoring of phenomena indicative of PTP in a magnetic disk drive

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San Jose, CA, United States of America

Duc H Banh