Western Digital Technologies, Inc.

Kuang-Yang Tu

Wei Xi

Young-Hoon Kim

Jenghung Chen

Jianguo Zhou

Xu Qi Chen

Guoxiao Guo

Alain Chahwan

Chuanwen Ji

Lan V Ngo

Jie Yu

Naoyuki Kagami

Gaku Ikedo

Kexiu Liu

David Dung Tien Nguyen

John Yin Kwong Li

Minghui Zheng

Teddy T Chen

William T Stoll

Teddy Tc Chen

Haiming Wang

A data storage device is disclosed wherein an elevator actuator is controlled to move a head along an axial dimension toward a first disk surface of a first disk while processing a proximity signal generated by a proximity sensor. A first actuator position is detected when the actuator arm is proximate the first disk surface of the first disk based on the proximity signal.

Calibrating elevator actuator for disk drive

A data storage device is disclosed comprising a first disk comprising a first disk surface, a second disk comprising a second disk surface, an actuator arm, a head coupled to a distal end of the actuator arm, and a ramp for loading/unloading the head. A first elevator actuator is configured to actuate the actuator arm along an axial dimension relative to the first and second disks, and a second elevator actuator is configured to actuate at least part of the ramp along the axial dimension, wherein a simultaneous movement of the first and second elevator actuators is synchronized.

A data storage device is disclosed comprising an elevator actuator configured to actuate a head along an axial dimension, and a position sensor configured to generate a sinusoidal sensor signal representing a position of the head along the axial dimension, wherein the position sensor comprises a sensor element and an encoder strip comprising a pattern having at least one region that causes a disturbance in the sinusoidal sensor signal. The elevator actuator is controlled to move the head in a first direction along the axial dimension to detect the disturbance in the sinusoidal sensor signal, and when the disturbance in the sinusoidal signal is detected, the elevator actuator is controlled to move the head in a second direction along the axial dimension opposite the first direction in order to measure a zero crossing of the sinusoidal sensor signal.

A data storage device is disclosed comprising a first disk comprising a first disk surface, a second disk comprising a second disk surface, an elevator actuator configured to actuate a head along an axial dimension relative to the first and second disks, a radial actuator configured to actuate the head radially over the first disk surface or the second disk surface, and a position sensor configured to generate a sinusoidal sensor signal representing a position of the head along the axial dimension. A crashstop_offset along the axial dimension is measured from a crashstop position of the elevator actuator to a zero crossing of the sinusoidal sensor signal.

A data storage device is disclosed comprising a head actuated over a disk comprising tracks defined by servo sectors. A location of the head is generated based on the servo sectors, and a position error signal (PES) representing a difference between a target location for the head and the measured location for the head is generated. An actuator control signal (ACS) is generated in response to the PES, a disturbance compensation signal (DCS) is generated based on the PES and the ACS, and the DCS is filtered with a disturbance observer filter. The DCS is filtered with a plurality of band-pass filters, and an output of one of the band-pass filters is filtered with a peak detection filter configured to detect a peak frequency corresponding to a peak in a frequency response of the band-pass filter, wherein the disturbance observer filter is adjusted based on the peak frequency.

Data storage device on-line adapting disturbance observer filter

A disk drive is disclosed comprising a servo control system operable to actuate a head over a disk. A sensor signal is filtered with a first filter comprising a frequency response, and the filtered sensor signal is filtered to generate a compensated sensor signal. An error signal is filtered with a second filter comprising the frequency response, and an adaptation control signal is generated based on the compensated sensor signal and the filtered error signal. An adaptive filter is adapted in response to the adaptation control signal, wherein the adaptive filter filters the sensor signal to generate feed-forward compensation values. The feed-forward compensation values are applied to the servo control system to compensate for the disturbance. A disturbance signal that represents the disturbance is generated, and the frequency response of the first and second filters is optimized based on the sensor signal and the disturbance signal.

Disk drive optimizing filters based on sensor signal and disturbance signal for adaptive feed-forward compensation

A data storage device is disclosed comprising a disk, a head, and a microactuator configured to actuate the head over the disk. An input signal to a compensator is generated, wherein the compensator is configured to generate a microactuator control signal. A slew rate signal representing a slew rate of the microactuator control signal is generated and applied to a first saturator configured to generate a saturated slew rate signal. The input signal is adjusted based on the slew rate saturation signal, and the microactuator is controlled based on the microactuator control signal.

Data storage device comprising slew rate anti-windup compensation for microactuator

A disk drive is disclosed comprising a disk, a head, and control circuitry comprising a servo control system operable to actuate the head over the disk. A plurality of disturbance signals is generated in response to a vibration. A plurality of correlations is generated in response to each disturbance signal and an error signal of the servo control system. At least one of the disturbance signals is selected in response to the correlations. A feed-forward compensation value is generated in response to the selected disturbance signal, and the feed-forward compensation value is applied to the servo control system to compensate for the vibration.

Disk drive selecting disturbance signal for feed-forward compensation

A disk drive is disclosed comprising a servo control system operable to actuate a head over a disk. A disturbance signal is generated in response to a vibration, and the disturbance signal is filtered with a first filter comprising a frequency response to generate a filtered disturbance signal. The filtered disturbance signal is filtered with a model of the servo control system to generate a compensated disturbance signal. An error signal of the servo control system is filtered with a second filter comprising the frequency response to generate a filtered error signal. An adaptation control signal is generated in response to the compensated disturbance signal and the filtered error signal, and an adaptive filter is adapted in response to the adaptation control signal, wherein the adaptive filter filters the disturbance signal to generate feed-forward compensation values applied to the servo control system to compensate for the vibration.

Disk drive filtering disturbance signal and error signal for adaptive feed-forward compensation

A disk drive comprises a disk, an actuator arm and a servo controller using a position error signal to generate a controller output signal to control the actuator arm. A plant mechanically models at least a portion of the disk drive, receives a control command to which an unknown disturbance is added and generates a plant output. A disturbance observer (DOB) uses the control command and the plant output to generate a delayed and estimated version of the disturbance. The DOB comprises a Q filter having a selected center frequency. A perfect phase cancellation filter (PPCF) is configured to receive the delayed and estimated version of the disturbance, to reject selected disturbances and to align the desired attenuation frequency with the selected center frequency. The output of the PPCF is subtracted from the controller output signal to generate the control command.

Methods for closed-loop compensation of ultra-high frequency disturbances in hard disk drives and hard disk drives utilizing same

A disk drive is disclosed operable to seek a head from a first radial location over a disk to a second radial location over the disk. A reference signal is initialized, a feed-forward control signal is initialized, and a seek is initiated. During the seek operation, a position error signal (PES) is generated and saved, wherein the PES represents a position error of the head relative to the reference signal. The PES is filtered with a compensation filter to generate a feed-back control signal. The feed-back control signal is combined with the feed-forward control signal to generate a VCM control signal. When the seek is done, the saved PES is processed using an iterative learning control (ILC) algorithm to adjust at least one of the reference signal and the feed-forward control signal.

Disk drive employing iterative learning control for tuning seek servo loop

A disk drive is disclosed including a disk having a plurality of tracks, wherein each track comprises a plurality of servo sectors. The disk drive further comprises a head having a read element offset from a write element by a reader/writer offset. The read element is positioned over a first track and the write element is positioned over a second track. A first servo control signal is generated for servoing the head in response to the servo sectors in the first track, and first wedge repeatable runout (RRO) data is written to the second track along a substantially sinusoidal path corresponding to the reader/writer offset, wherein the first wedge RRO data are for writing data to a third track.

Disk drive writing wedge RRO data along a sinusoidal path to compensate for reader/writer offset

A method is disclosed for identifying wedge time shift zones on a magnetic disk of a disk drive. The disk drive further includes a spindle motor for rotating the disk at an operating speed in response to a spindle control current generated by a spindle control system, and a head that is actuated over the disk. During operation, the control systems causes a seek of the head across the disk and measures wedge-to-wedge times between servo wedges. The control system then calculates a wedge-to-wedge time shift value using the wedge-to-wedge times and determines whether the wedge-to-wedge time shift time value exceeds a predetermined threshold. If the wedge-to-wedge time shift value exceeds the predetermined threshold, then the control system identifies a wedge time shift zone, and stores information for compensating for the identified wedge time shift zone during disk operations.

Method for wedge time shift calibration in a disk drive

A disk drive is disclosed having hybrid spindle speed control. The disk drive includes a disk having a plurality of servo wedges, and a spindle motor for rotating the disk at an operating speed. The spindle motor generates a back electromotive force (BEMF) voltage. In operation, the disk rotation is maintained at the operating speed during a track following operation by updating, in a wedge spindle speed control mode, the spindle control current in response to a wedge speed error. Before executing a high-speed seek, the disk drive is switched to a BEMF spindle speed control mode, and the disk rotation is maintained at the operating speed during the high speed seek by updating the spindle control current in response to a BEMF speed error signal generated based on the BEMF voltage. During a seek-settle time, the disk drive is switched back to the wedge spindle speed control mode.

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Irvine, CA, United States of America

Kuang-Yang Tu