Western Digital Technologies, Inc.

Wd Media, LLC

Yilin Cai

Siri S Weerasooriya

Jiangang Liang

Don Brunnett

Charles A Park

Thomas Anthony O'Dell

Edgar D Sheh

Wing Ying

Yakov M Lifchits

Hongchao Tim Zhao

Yun Hong

Dhanakorn Iamratanakul

A disk drive is disclosed comprising head actuated over a disk comprising a reference pattern. The head is positioned at a first radial location, a first phase error is measured in response to the reference pattern at the first radial location, and a first repeatable runout (RRO) of the first phase error is measured. The head is positioned at a second radial location, a second phase error is measured in response to the reference pattern at the second radial location, and a second repeatable runout (RRO) of the second phase error is measured. The first and second RROs are processed to estimate an offset rrepresenting a difference between an axial rotation of the disk and an axial rotation of the reference pattern.

Disk drive estimating repeatable runout of reference pattern based on repeatable runout of phase error

A disk drive is disclosed comprising a disk, a head for writing data to the disk, and control circuitry coupled to the head. The control circuitry is operable to determine a first set of fly height values and determine a threshold based on the first set of fly height values. The control circuitry determines a second set of fly height values, adjusts the threshold based on the second set of fly height values, and detects a head characteristic based on the adjusted threshold. The head characteristic is detected by detecting a head touchdown event and/or detecting contamination related to the head based on the adjusted threshold.

Adaptive threshold for detecting touchdown or contamination

A method is disclosed of servo writing a disk drive comprising a first head actuated over a first disk surface, and a second head actuated over a second disk surface. A first repeatable runout (RRO) of the first disk surface is measured, and a seek is performed to seek the first head over the first disk surface in response to the measured first RRO while writing a first spiral track to the second disk surface using the second head. As a result, the first spiral track comprises a second RRO that substantially matches the first RRO of the first disk surface.

Disk drive writing spiral tracks on a slave surface using repeatable runout compensation for a master surface

A method of processing disks on spin stand is disclosed, the spin stand comprising a spindle motor having a rotor. A first disk is clamped to the rotor, wherein the first disk comprises a reference servo pattern. A second disk is clamped to the rotor, and a first head is servoed over the first disk in response to the reference servo pattern in order to position a second head over the second disk at a first radial location. Data is written to the second disk at the first radial location using the second head. The second disk is removed from the rotor while the first disk remains clamped to the rotor.

Processing disks on a spin stand

A disk drive that approximates spiral slope in spiral patterns is disclosed. The disk drive includes a disk having at least one spiral pattern that extends radially across the disk, a head to read a portion of the at least one spiral pattern, and a processor to approximate a spiral slope of the portion of the at least one spiral pattern. The processor approximates the spiral slope of the portion of the at least one spiral pattern by implementing operations including: reading amplitude values for the portion of the at least one spiral pattern; determining an amplitude value distribution based on the amplitude values; determining a curve-fitted function for the amplitude value distribution; and determining an approximate spiral slope based on the curve-fitted function.

Spiral slope approximation of spiral patterns written to a disk of a disk drive

A method of servo writing a disk of a disk drive is disclosed. The disk comprises a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted periodically by a sync mark. A timing recovery measurement is generated in response to the sync marks, wherein the timing recovery measurement comprises a sinusoidal component. A timing compensation value is generated in response to the sync marks which estimates the sinusoidal component in the timing recovery measurement. A frequency control signal is generated in response to the timing recovery measurement and the timing compensation value, a servo write clock is generated in response to the frequency control signal, and the servo write clock and the head internal to the disk drive are used to write the product servo sectors to the disk.

Compensating for repeatable phase error when servo writing a disk drive from spiral tracks

A method of writing product servo sectors on a disk of a disk drive is disclosed. The disk comprises a reference pattern having a plurality of sync marks written around the disk. The sync marks are detected to generate a sync mark detect signal, and a timing recovery measurement is generated in response to the sync mark detect signal. A frequency control signal is generated in response to the timing recovery measurement, and a servo write clock is generated in response to the frequency control signal. A feed-forward compensation value is generated in response to the timing recovery measurement and the frequency control signal, and the timing recovery measurement is adjusted in response to the feed-forward compensation value to compensate for a repeatable phase error in the timing recovery measurement. The servo write clock and the head internal to the disk drive are used to write the product servo sectors to the disk.

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Fremont, CA, United States of America

Yilin Cai