Western Digital Technologies, Inc.

Western Digital (fremont), Inc.

Noureddine Kermiche

Bernhard E Knigge

Scott A St John

Galvin Chia

Xianghui Xiao

Qinghua Zeng

Ming Jin

Kent Douglas Anderson

Stanley H Shepherd

Shafa Dahandeh

Robert E Eaton

Kazuhiro Saito

James P R McFadyen

Puneet Bhargava

Abhimanyu Sharma

Sandy Xianghui Xiao

Alvin W Tan

Various aspects are directed to a data storage device comprising one or more disks, an actuator mechanism configured to position a selected head among one or more heads proximate to a corresponding disk surface among the one or more disks, and one or more processing devices. The one or more processing devices are configured to detect repeatable runout (RRO) noise components from a measurement of fly height of the selected head above one or more sectors of a fly height measurement track, and remove the detected RRO noise components from one or more per-sector readback signal measurements.

Data storage device with rapid in-field repeatable runout noise removal calibration

A data storage device comprises a disk and a head having a read and write elements. A read heater is powered based on a dual heater ratio (DHR) to thermally adjust a spacing of the read element from a disk surface, and a write heater is powered based on the DHR to thermally adjust a spacing of the write element from the disk surface. A read spacing slope profile is determined comprising read touchdowns (TDs) over a range of DHRs, and a write spacing slope profile is determined comprising write TDs over the range of DHRs. An operating DHR of the head is set to be where the read spacing slope profile intersects the write spacing slope profile.

Pole tip recession compensation by dual heater ratio optimization in a hard disk drive

Various illustrative aspects are directed to a data storage device comprising a disk; a read/write head having read and write portions configured to read data from and write data to the disk; read and write heaters configured to thermally adjust read and write spacings of the read and write portions from the disk surface; and a controller configured to control power applied to the read and write heaters based on a dual heater power ratio (DHR) of the respective power applied to each heater. The DHR is set based on a point during touchdown at which a reader shield and a writer shield have maximum contact with the surface of the disk (DHRmax).

Adaptive dual heater mode for hard disk drive

A data storage device is disclosed comprising a head actuated over a disk, wherein the head comprises a fly height actuator (FHA). A FHA control signal is applied to the FHA, wherein the FHA control signal comprises a DC component and an AC component. A fly height metric is measured representing a fly height of the head over the disk for different levels of the DC component. A modulation amplitude of the fly height metric is detected, and a minimum in the modulation amplitude of the fly height metric is detected.

Data storage device detecting minimum stable fly height of a head over a disk

A disk drive is disclosed comprising a head actuated over a disk, and a dynamic fly height (DFH) actuator for controlling a fly height of the head over the disk in response to a DFH setting. A touchdown (TD) threshold is initialized, and the DFH setting that causes a TD signal to exceed the TD threshold is determined. The TD threshold is adjusted, and the DFH setting that causes the TD signal to exceed the adjusted TD threshold is determined. A slope of the DFH setting relative to the TD threshold is determined, and an operating TD threshold is determined in response to a change in the slope.

Disk drive determining touchdown threshold

A disk drive is disclosed comprising a head actuated over a disk, and a dynamic fly height (DFH) actuator operable to control a fly height of the head over the disk. A DFH control signal is applied to the DFH actuator to decrease the fly height of the head, wherein the DFH control signal comprises a DC component and an AC component comprising an excitation frequency. A touchdown metric is measured over an interval, and the head contacting the disk is detected in response to a frequency component of the touchdown metric at the excitation frequency.

Disk drive detecting head touchdown by applying DC+AC control signal to fly height actuator

A disk drive is disclosed comprising a disk comprising a plurality of tracks, wherein each track comprises a plurality of data sectors and a plurality of servo sectors, and each servo sector comprises a plurality of servo bursts. The disk drive further comprises a head actuated radially over the disk, wherein the head comprises a dynamic fly height (DFH) actuator. A gain control circuit is operable to generate a gain control signal for adjusting an amplitude of a read signal emanating from the head. Control circuitry selects an operating control signal applied to the DFH actuator by positioning the head over one of the tracks, and measuring an amplitude signal in response to the read signal. An amplitude variance signal is computed in response to the amplitude signal, and whether the head has contacted the disk is detected in response to the amplitude variance signal.

Disk drive determining operating fly height by detecting head disk contact from read signal amplitude variance

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of tracks. The head comprises a touchdown element operable to generate a touchdown signal. The touchdown signal is amplified by a gain to generate an amplified touchdown signal, and a touchdown event is detected by comparing the amplified touchdown signal to a threshold. During a calibration operation, the gain is adjusted and the threshold is adjusted until the amplified touchdown signal does not exceed the threshold. During a normal operation, the touchdown event is detected based at least partly on the adjusted gain and the adjusted threshold.

Disk drive calibrating threshold and gain of touchdown sensor

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of tracks, wherein each track comprises a plurality of servo sectors. The head is positioned over a first track, and when a first servo sector is processed, a first touchdown metric is evaluated to detect whether the head contacted the disk without evaluating a second touchdown metric. When a second servo sector is processed, the second touchdown metric is evaluated to detect whether the head contacted the disk without evaluating the first touchdown metric.

Disk drive detecting head/disk contact by evaluating a subset of touchdown metrics during a servo sector interrupt

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of tracks including a first fly height calibration track and a second fly height calibration track. The disk drive further comprises a fly height actuator operable to control a fly height of the head in response to a fly height control signal. When a refresh event is detected, calibration data is written to the second fly height calibration track. After writing calibration data to the second fly height calibration track, the first fly height calibration track is read in order to calibrate the fly height control signal applied to the fly height actuator. After calibrating the fly height control signal, the second fly height calibration track is read in order to recalibrate the fly height control signal applied to the fly height actuator.

Disk drive employing fly height calibration tracks to account for magnetic entropy and thermal decay

A disk drive is disclosed comprising a head actuated over a disk and a fly height actuator operable to control a fly height of the head in response to a fly height control signal. A touchdown operation is executed to set an operating fly height control signal by adjusting the fly height control signal until the head contacts the disk. A fly height calibration track is then read to set a fly height reference. When calibrating the operating fly height control signal, the fly height calibration track is read and the operating fly height control signal is adjusted in response to the fly height reference. When the adjusted operating fly height control signal is invalid, the touchdown operation is re-executed to reset the operating fly height control signal and then the fly height calibration track is read to reset the fly height reference.

Disk drive resetting fly height reference generated from a degrading calibration track

A disk drive is disclosed comprising a head actuated over a disk, a dynamic fly height (DFH) actuator operable to control a fly height of the head over the disk, and a touchdown (TD) sensor operable to generate a TD signal. A periodic control signal is applied to the DFH actuator to generate a periodic response in the TD signal comprising at least one cycle, wherein the cycle comprises a first half cycle and a second half cycle. An anti-correlation is computed between the first half cycle and the second half cycle of the TD signal, and the head contacting the disk is detected in response to the anti-correlation.

Disk drive detecting head touchdown by computing anti-correlation in sensor signal

A disk drive is disclosed comprising a head actuated over a disk. An analog touchdown (TD) signal is compared to a TD threshold in order to generate a calibrated TD threshold for a plurality of different dynamic fly height (DFH) settings. The calibrated TD thresholds and corresponding DFH settings are fitted to an estimated curve. At least one of the TD threshold and the DFH setting is adjusted, and a corresponding next point in the estimated curve is predicted. An actual next point corresponding to the adjustment is determined, and a prediction error is generated based on a difference between the predicted next point and the actual next point. A touchdown of the head on the disk is detected when the prediction error exceeds a prediction threshold.

Disk drive determining head touchdown threshold based on curve fitting prediction error

Disclosed is a disk drive that determines dynamic fly height (DFH) head non-linearity. A processor of the disk drive controls operations in the disk drive including: estimating a first and second set of head media spacing (HMS) actuation data for a DFH head at a first and second data frequency by commanding the application of power to the DFH head across a pre-defined power range; determining a first and second HMS value based upon the first and second sets of HMS actuation data; calculating a difference value between the first and second HMS values; determining whether the difference value exceeds a threshold.

Determining head non-linearity in a disk drive

A disk drive is disclosed including a disk having a plurality of tracks, wherein each track comprises a plurality of data sectors and a plurality of servo sectors. The disk drive further comprises a spindle motor for rotating the disk, and a head actuated radially over the disk, wherein the head comprises a dynamic fly height (DFH) heater. Control circuitry within the disk drive is operable to select an operating control setting for the DFH heater by positioning the head over one of the tracks, measuring a first rotation time of the disk in response to at least one of the servo sectors, adjusting the control setting for the DFH heater, measuring a second rotation time of the disk in response to at least one of the servo sectors, and detecting whether the head has contacted the disk in response to the first and second rotation times.

Growing community of inventors

Mission Viejo, CA, United States of America

Noureddine Kermiche