Western Digital Technologies, Inc.

Western Digital Corporation

Sperry Rand Corporation

Sperry Corporation

Priam

Robert L Cloke

David Price Turner

Vafa James Rakshani

Richard William Hull

Vinay Kumar Agarwal

Hemant Melkote

Patrick J Lee

Siri S Weerasooriya

Jack M Chue

Tehri S Lee

Michael R Spaur

Robert Ellis Caddy, Jr

Mohamad Towfik Krounbi

Frank J Sordello

John Cuda

Gary L Dunbar

Howard A Baumer

Steven W McLaughlin

Edgar D Sheh

Wing Ying

W Donald Huber

A method and apparatus is disclosed for writing product servo sectors to a disk of a disk drive to define a plurality of data tracks. The disk drive comprises the disk and a head actuated over the disk. The disk comprises a plurality of spiral tracks which are read using the head to synchronize a write clock and to generate a position error signal (PES) according to a PES algorithm used to maintain the head along a first servo track while writing product servo sectors along the first servo track. The PES algorithm is adjusted to seek the head to a second servo track, and the head is used to write product servo sectors along the second servo track.

Adjusting track density by changing PES algorithm when servo writing a disk drive from spiral tracks

A method is disclosed for writing servo patterns for tracks on a rotating magnetic disk medium of a magnetic disk drive. In the method, track following is performed along a reference track, defined by previously written servo burst patterns, using a servo loop having a closed-loop response. A position error signal is generated for the reference track based on the track following. A correction signal is generated based on the track following using an observer of a one-dimensional state model that is equivalent to the two-dimensional state model of the servo loop. Servo patterns are written at a target radial location on the magnetic disk medium during track following of the reference track. The position error signal of the servo loop is adjusted based on the correction signal to reduce radial error propagation from the reference track to the servo burst patterns at the target radial location.

Method and apparatus for self servowriting of tracks of a disk drive using an observer based on an equivalent one-dimensional state model

A method of writing product servo sectors to a disk of a disk drive is disclosed. An external spiral servo writer writes a plurality of spiral tracks to the disk by actuating in a closed loop system a head positioning pin inserted into the disk drive. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The high frequency signal and sync marks in the spiral tracks are demodulated to maintain synchronization of a servo write clock as well as maintain the head along a circular target path while writing product servo sectors to the disk.

Using an external spiral servo writer to write spiral tracks to a disk to facilitate writing product servo sectors to the disk

A method is disclosed for defining tracks on a rotating magnetic disk medium of a disk drive. Reference tracks are followed using a servo control loop while writing servo burst patterns defining a first target servo track. The servo control loop includes a two-dimensional digital state compensator having a first input that receives position error signals, a first output that generates control signals for positioning a transducer head, a second output that generates track-following state variables, and a second input that receives processed and stored track-following state variables. The first target track is followed using the servo control loop while servo burst patterns are written, and while the processed and stored track-following state variables corresponding to the servo burst patterns defining the first target track are applied to the second input.

Method and apparatus for self servowriting of tracks of a disk drive using a servo control loop having a two-dimensional weighted digital state compensator

A method is disclosed for reducing disk expansion effects while writing spiral reference patterns on a disk. The disk drive comprises control circuitry and a head disk assembly (HDA). In the method, an external spiral servo writer is used to control a radial location of the head for writing a plurality of the spiral reference patterns in an order such that at least two of the spiral reference patterns are not written temporally sequential to an adjacent spiral reference pattern. The head internal to the disk drive is used to read the spiral reference patterns in order to write product servo bursts to the disk, thereby defining a plurality of radially spaced, concentric data tracks.

Method for nonsequentially writing reference spiral servo patterns to a disk to compensate for disk expansion

A method of writing product servo bursts to a disk in a disk drive is disclosed. An external spiral servo writer comprising a head positioning pin and head positioning mechanics periodically writes a plurality of reference servo bursts in a plurality of spiral reference patterns to the disk. The reference servo bursts in the spiral reference patterns are processed to write product servo bursts to the disk. In one embodiment control circuitry within the disk drive processes the reference servo bursts to self-servo write the disk drive, and in another embodiment an external product servo writer processes the reference servo bursts to write the product servo bursts to the disk. In one embodiment, a slope of each spiral reference pattern is selected so that each spiral reference pattern is written over at least twenty revolutions of the disk to increase the accuracy of the head position error generated from the reference servo bursts.

Using an external spiral servo writer to write spiral reference patterns to a disk to facilitate writing product servo bursts to the disk

A method of manufacturing a disk drive by demodulating product servo sectors and spiral tracks written on a disk of the disk drive is disclosed. An external spiral servo writer writes a plurality of spiral tracks that spiral from an outer diameter to an inner diameter of the disk. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The spiral tracks are used to write product servo sectors to the disk during a fill operation. Common circuitry, such as burst demodulation circuitry, is used to demodulate the high frequency signal in the spiral tracks during the fill operation as well as demodulate the product servo sectors.

Demodulating servo sectors and spiral tracks using common circuitry

A disk drive is disclosed comprising a disk and a head actuated radially over the disk. An external servo writer is used to write reference servo bursts to the disk at a coarser radial resolution than product servo bursts. During a self servo writing operation, the reference servo bursts are processed to servo circularly to write a first set of product servo bursts to the disk. The reference servo bursts are also processed to servo spirally to write a second set of product servo bursts to the disk.

Disk drive for circular self servo writing and spiral self servo writing using prewritten reference servo bursts

A method of writing product servo sectors to a disk of a disk drive is disclosed. An external spiral servo writer writes a plurality of reference servo sectors at an outer diameter of the disk and a plurality of spiral tracks that spiral from an outer diameter to an inner diameter of the disk. At the beginning of the product servo writing process, the reference servo sectors are demodulated to initially synchronize a servo write clock. The spiral tracks are then demodulated to maintain synchronization of the servo write clock as well as maintain the head along a target circumferential path while writing product servo sectors to the disk.

Using an external spiral servo writer to write reference servo sectors and spiral tracks to a disk to facilitate writing product servo sectors to the disk

A method is disclosed for writing servo patterns for tracks on a rotating magnetic disk medium of a disk drive. Servo patterns are written on a reference track of the disk medium. Track following of the written servo patterns on the reference track is performed using a servo loop having a closed-loop response. A position error signal is generated for the reference track based on the track following. A correction signal is generated based on the track following using an observer of a one-dimensional state model that is equivalent to a two-dimensional state model of the servo loop. Servo patterns are written on a target track during track following of the reference track. The position error signal of the servo loop is adjusted based on the correction signal to reduce radial error propagation from the reference track to the target track.

A method is disclosed for defining tracks on a rotating magnetic disk medium of a disk drive. Reference tracks are followed using a servo control loop while writing servo patterns defining a first target servo track. The servo control loop includes a two-dimensional digital state compensator having a first input that receives timing error signals, a first output that generates control signals for a controlled oscillator, a second output that generates timing state variables, and a second input that receives stored timing state variables. The first target track is followed using the servo control loop while servo patterns are written, and while the stored timing state variables corresponding to the servo patterns defining the first target track are applied to the second input.

Timing compensation in a self-servowriting system

A method is disclosed for defining tracks on a rotating magnetic disk medium of a disk drive. Reference tracks are followed using a servo control loop while writing servo burst patterns defining a first target servo track. The servo control loop includes a two-dimensional digital state compensator having a first input that receives position error signals, a first output that generates control signals for positioning a transducer head, a second output that generates track-following state variables, and a second input that receives stored track-following state variables. The first target track is followed using the servo control loop while servo burst patterns are written, and while the stored track-following state variables corresponding to the servo burst patterns defining the first target track are applied to the second input.

Method and apparatus for self servowriting of tracks of a disk drive using a servo control loop having a two-dimensional digital state compensator

A phase locked loop (PLL) circuit is disclosed comprising a phase detector for generating a phase error between an input oscillating signal and an output oscillating signal. A fractional frequency synthesizer (FFS) generates the output oscillating signal in response to the phase error, wherein the FFS comprises an input for receiving a reference oscillating signal, and a fractional divider responsive to variables I and Fr. The variable I is an integer value, and the variable Fr is a fractional value, both of which are generated in response to the phase error.

Phase locked loop employing a fractional frequency synthesizer as a variable oscillator

A preamplifier circuit is disclosed comprising a data input for receiving write data, a read signal output for outputting an amplified read signal, a read signal input for receiving a read signal from a read element, and a write signal output for supplying a write signal to a write element. The preamplifier circuit further comprises a first amplifier circuit, responsive to the write data, for generating the write signal supplied to the write element, and a second amplifier circuit for amplifying the read signal from the read element to generate the amplified read signal output via the read signal output. A head control circuit, responsive to head select data, simultaneously enables the first and second amplifier circuits to perform a simultaneous read and write operation.

Preamplifier circuit configurable to allow simultaneous read and write operations for self-servo writing a disk drive

The present invention may be regarded as a self-servo writing disk drive comprising a head having a read element radially offset from a write element. During a first time interval, the read element is positioned over a first radial location to read first A clock data to generate first circumferential timing information and first A servo bursts to generate first position control information. The first position control information is used for positioning the write element over a second radial location, and the first circumferential timing information is used for writing second B clock data and second B servo bursts to the second radial location. During a second time interval, the read element is positioned over the first radial location to read first B clock data to generate second circumferential timing information and first B servo bursts to generate second position control information. The second position control information is used for positioning the write element over the second radial location, and the second circumferential timing information is used for writing second A clock data and second A servo bursts to the second radial location.

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Santa Clara, CA, United States of America

Robert L Cloke