Western Digital Technologies, Inc.

Western Digital Corporation

David D Nguyen

Raffi Codilian

Jack M Chue

Charles A Park

Robert J McNab

William D Johns

Jie Yu

Chuanwen Ji

Hemant Melkote

Ara W Nazarian

Alexander Babinski

Jianghong Ding

Carl R Messenger

Masao Miyamura

John Yin Kwong Li

Li Yi

Arafat M Butt

Yanbin Song

David A Spaulding

A disk drive is disclosed comprising a spindle motor having a plurality of windings including at least a first winding, a second winding, and a third winding. During a spin-up operation, a voltage is applied to the first winding and a first rise time is measured for current flowing through the first winding to reach a predetermined threshold. A voltage is applied to the second winding and a second rise time is measured for current flowing through the second winding to reach a predetermined threshold. A voltage is applied to the third winding and a third rise time is measured for current flowing through the third winding to reach a predetermined threshold. A difference is computed in response to the first rise time, the second rise time, and the third rise time, and an angular position of the spindle motor is estimated by computing an arctangent in response to the difference.

Disk drive estimating angular position of spindle motor during spin-up by computing differences in winding current rise times

A method is disclosed for improving servo performance in a disk drive having a plurality of concentric tracks. Each track has a plurality of first-type servo sectors and a plurality of second-type servo sectors. In the method, track identification information and track position information are read from a first-type servo sector. A track number and a transducer position are estimated for a second-type servo sector. Track position information is read from the immediately following second-type servo sector. An odd/even property from the second-type servo sector is compared with an odd/even property for the estimated track number. The odd/even property of the estimated track number is conditionally adjusted such that the odd/even property of the estimated track number matches the odd/even property from the second-type servo sector. A position error signal is determined using the adjusted track number and the track position information read from the second-type servo sector.

Method for improving servo performance in a disk drive having tracks with mini servo wedges

A method for reducing a servo channel head gain calibration time comprising initiating a servo channel head gain calibration process for a head corresponding to the selected disk surface; obtaining a head gain calibration value for a pre-selected zone in the selected disk surface; comparing the obtained calibration value with a pre-stored calibration value for the pre-selected zone and generating a comparison result; and stopping the calibration process for the head if the comparison result does not exceed a threshold value.

Reducing head gain calibration time in a disk drive

A disk drive is disclosed comprising a disk, an actuator arm, a head connected to a distal end of the actuator arm, and a voice coil motor (VCM) for rotating the actuator arm about a pivot to actuate the head over the disk, wherein the VCM rotates the actuator arm into a latched positioned when the disk drive is idle. Disk drive control circuitry unlatches the actuator arm by applying a driving current to the VCM according to an open-loop current profile. The open-loop current profile comprises an acceleration pulse having an acceleration magnitude and an acceleration interval, and a deceleration pulse having a deceleration magnitude and a deceleration interval. The deceleration magnitude is substantially smaller than the acceleration magnitude, and the deceleration interval is substantially longer than the acceleration interval, to thereby attenuate acoustic noise when unlatching the actuator arm.

Disk drive employing asymmetric acceleration/deceleration pulses for acoustic noise reduction during unlatch

A method of manufacturing a disk drive and a disk drive where the width of the read element and the width of the write element are both measured at servo-writing time and the track pitch of the disk drive is set on the basis of those measurements. Disk drives with superior head width combinations are servo-written with a narrower track pitch in order to have a higher storage capacity. Disk drives with inferior head width combinations are detected before servo-writing so that the disk drive may be servo-written with wider track pitch rather than with a nominal track pitch that results in a subsequent drive failure during initial burn-in (IBI). The heads are used more efficiently in that heads that are more capable are used to their ability and less capable heads that would otherwise be disposed of are used at all.

Method of manufacturing and disk drive produced by measuring the read and write widths and varying the track pitch in the servo-writer

A disk drive comprising a first seek operating mode to move the actuator over a seek distance D in a seek time T, using a first seek profile for minimizing T, wherein for a first repetitive series of seeks over distance D a servo control system would require a delay time Tbetween seeks to control temperature rise in a VCM. A second seek operating mode to move the actuator over the seek distance D in a second seek time Tusing a second seek profile for limiting the temperature rise in the VCM, wherein for a second repetitive series of seeks over the seek distance D, a time average Tof the Tseek times is substantially less than T+T.

Disk drive having first and second seek operating modes for controlling voice coil motor temperature rise

A method for reducing an estimation period for repeatable runout (RRO) errors in a disk drive comprising a head, a disk surface having a track partitioned by servo-wedges, and a servo control system for controlling the movement of the head relative to a track during revolutions of the disk. The method includes estimating the RRO errors of the track based on a) a series of position error signal values obtained during a current revolution of the disk surface, and b) a previous estimation of the RRO errors of the track obtained during a previous revolution of the disk surface and determining a differential value between a first measure of the estimated RRO errors and a second measure of the previous estimation of RRO errors, and repeating the estimating and determining for subsequent revolutions of the disk surface until the determined differential value is smaller than a pre-selected threshold value.

Reducing estimation period for repeatable runout errors in a disk drive

A method is disclosed for improving head position accuracy in a disk drive during track following of concentric data storage tracks through real-time identification of external vibration and monitoring of write-unsafe (WUS) occurrences. In the method, after a seek operation to a predetermined data storage track, the track is followed using a servo control loop having a nominal gain and responsive to a position error signal (PES). After waiting a vibration detection delay period, occurrences of the PES exceeding a WUS limit are counted generating a WUS limit exception count. Also, a property of a variance is determined from spectral power values generated from the PES during track following. If the WUS limit exception count exceeds a first threshold, and if the property of the variance exceeds a second threshold, the nominal gain is increased to a vibration gain within a frequency band, to attenuate the effect of external vibration.

Method and disk drive for improving head position accuracy during track following through real-time identification of external vibration and monitoring of write-unsafe occurrences

A method of manufacturing a disk drive and a disk drive made with such method where the width of the read element and the width of the write element are both measured at servo-writing time and the track pitch of the disk drive is set on the basis of those measurements. Disk drives with superior head width combinations are servo-written with a narrower track pitch in order to have a higher storage capacity. Disk drives with inferior head width combinations are detected before servo-writing so that the disk drive may be servo-written with wider track pitch rather than with a nominal track pitch that results in a subsequent drive failure during initial burn-in (IBI). The heads are used more efficiently in that heads that are more capable are used to their ability and less capable heads that would otherwise be disposed of are used at all. Fewer disk drives are required to be reworked and returned to the servo-writing process.

A controller for a disk drive that accesses a look up table having a plurality of thermally characterized values corresponding to a plurality of seek operations. For each seek operation, the corresponding value is added to a register. The controller decrements the register at a rate that is determined using servo interrupts occurring as a result of the rotation of the disk. When the value of the register exceeds a threshold, the controller adjusts the subsequent seek operation so as to inhibit damage to the voice coil as a result of overheating.

Disk drive with efficient coil temperature estimation

A magnetic storage disk drive having a servo burst pattern which asymmetrically increases the linear region in which a read head may be micro-jogged from a burst pair center line to align the read head with a data track. The innovative servo pattern comprises a first pair of servo bursts that define a first burst pair centerline for writing a particular data track to a data track side of the first centerline, and a second pair of servo bursts collectively define a second burst pair centerline that is positioned to the data track side of the first burst pair centerline and is sufficiently close to the first burst pair center line so that the read head 'sees' the second pair of servo bursts before 'losing' the first pair of servo bursts when micro-jogged to the data track side for reading. The second burst pair centerline should be no farther from the first burst pair centerline than the linear read width of the read head. The preferred servo bursts span a full track pitch are arranged in a uniformly repeating pattern of A/B and C/D burst pairs. The first burst pair centerline may be defined by the A/B pairs in one annular disk region and by the C/D burst pairs in another annular disk region in order to asymmetrically expand the linear region in the direction needed for micro-jogging the read head in different directions within the respective annular regions.

Non-quadrature servo burst pattern for micro-jogging a magnetoresistive

A method and system for a disk drive that estimates demand DAC saturation current by performing a first slew with the demand DAC in saturation, and then iteratively refining the estimate in response to a sequence of slews with the demand DAC not in saturation. Each successive slew is performed with the demand DAC preloaded with an acceleration value calculated in the previous iteration. To perform each slew, the disk drive microcontroller loads the demand DAC with an acceleration value, waits a predetermined time interval, and reads servo signals to identify the track to which the head has slewed at the end of the time interval. The microcontroller then calculates the distance traveled by the actuator during the present slew and uses the ratio of this head travel distance to the head travel distance of the first (saturated) slew to refine the saturated acceleration value estimated in the previous iteration. These estimates converge over successive iterations toward the desired demand DAC saturation current.

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Fountain Valley, CA, United States of America

David D Nguyen