Western Digital Technologies, Inc.

Yanan Huang

Duc T Phan

Chuanwen Ji

Orhan Beker

Alain Chahwan

Alexander Babinski

Min Chen

Aswartha Narayana

Shan Tang

Nathan J Santee

Yanning Liu

Jifang Tian

Wei Xi

Young-Hoon Kim

Yi Lu

Hien T Chu

Hengchang Guo

Zhenyu Zhang

Wenlin Zhang

Toviah N Hirschberg

Lu Feng

Yakov M Lifschitz

Yiqian Li

Xiao Ma

Chui Lyn Cheong

A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of tracks defined by servo sectors, wherein each servo sector comprises a plurality of servo bursts and the servo sectors define a plurality of servo wedges. A first write operation is executed to a first track and a first absolute position for the head is generated corresponding to a first servo wedge. A second write operation is executed to a second track and a second absolute position for the head is generated corresponding to the first servo wedge. An off-track write condition is detected when executing the second write operation based on the first absolute position and the second absolute position. The first absolute position comprises a track address of the first track and a position error measurement based on the servo bursts in the first servo wedge.

Data storage device saving absolute position at each servo wedge for previous write operations

A data storage device is disclosed comprising a plurality of disk surfaces including a first disk surface and a second disk surface. A first head is actuated over the first disk surface, and a second head is actuated over the second disk surface. A ramp is located proximate an outer diameter of the disk surfaces. A stroke difference between the first and second heads is measured by moving the first and second heads toward the ramp and detecting when the heads contact the ramp.

Disk drive measuring stroke difference between heads by detecting a difference between ramp contact

An apparatus includes: a media; a head over the media; a primary-actuator coupled to the head; and control circuitry, coupled to the primary-actuator and a secondary-actuator, configured to limit a secondary-actuator slew rate.

Electronic system with actuator control mechanism and method of operation thereof

A disk drive is disclosed comprising a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors, and an actuator for actuating a head over the disk in response to an actuator control signal. The servo sectors are read to generate a first sequence of control samples x[k] at a sample frequency corresponding to a frequency of the servo sectors. A hybrid upsample filter is used to upsample by a factor of N the first sequence of control samples x[k] to generate a second sequence of control samples y[k], wherein the hybrid upsample filter provides a higher phase gain than a zero-order type upsample filter at frequencies less than one kilohertz, and approximately the same attenuation as a first-order type upsample filter around the sample frequency. The actuator control signal is generated in response to the second sequence of control samples y[k].

Disk drive servo control using hybrid upsample filter

A data storage device is disclosed comprising a disk comprising a plurality of tracks defined by servo sectors, a head, and a servo controller configured to servo the head over the disk based on an estimated state generated by a state estimator. The servo controller is configured to execute a seek operation to seek the head over the disk and recover from a servo fault during the seek operation by generating an initial state estimate of the head at the beginning of the servo fault, and decelerating the head open-loop using a model-based deceleration control in response to the initial state estimate. While decelerating the head, the state estimator is re-qualified before the head reaches zero velocity, and after re-qualifying the state estimator and before the head reaches zero velocity, a seek operation is executed to seek the head to a target track closed-loop using the state estimator.

Data storage device re-qualifying state estimator while decelerating head

A disk drive is disclosed comprising, a head, a disk surface, and a dual stage actuator (DSA) servo loop comprising a voice coil motor (VCM) servo loop comprising a VCM and a microactuator servo loop comprising a microactuator operable to actuate the head over the disk surface. A frequency component of a servo signal in the DSA servo loop is evaluated, wherein the frequency component is based on a peak frequency of an error rejection curve of the DSA servo loop. A degradation of the microactuator is detected based on the frequency component of the servo signal.

Disk drive detecting microactuator degradation by evaluating frequency component of servo signal

A disk drive is disclosed wherein N data wedges of write data are buffered in a buffer. After writing at least two of the data wedges to the disk including a first data wedge and a second data wedge, a first servo metric value is measured when reading a first servo sector, and a second servo metric value is predicted based on the first servo metric value, wherein the second servo metric value corresponds to a second servo sector following the first servo sector. When the first servo metric value indicates a safe write condition and the second servo metric value indicates an unsafe write condition, the first data wedge is released from the buffer, and when the first servo metric value indicates a safe write condition and the second servo metric value indicates a safe write condition, the first and second data wedges are released from the buffer.

Disk drive releasing variable amount of buffered write data based on sliding window of predicted servo quality

A disk drive is disclosed comprising a disk comprising a plurality of servo tracks defined by servo sectors, wherein each servo sector comprises servo data and a servo compensation value. While servoing a head over a target data track during a write operation, a position error signal (PES) is generated at each servo sector based at least in part on the servo data. When the servo compensation value of a first servo sector is recoverable, the write operation is aborted when the PES generated at the first servo sector exceeds a first write unsafe threshold. When the servo compensation value of the first servo sector is unrecoverable, the write operation is aborted when the PES generated at the first servo sector exceeds a second write unsafe threshold less than the first write unsafe threshold.

Disk drive reducing write unsafe threshold when detecting an unrecoverable servo compensation value

A disk drive is disclosed comprising a disk media, a head stack assembly (HSA) having a head coupled to its distal end, a microactuator used to provide fine position of the head and a voice coil motor (VCM) configured to actuate the HSA over the disk media, and control circuitry. The control circuitry may be configured to move the HSA in an alternating manner across the disk media while actuating the microactuator. One or more performance characteristics of the microactuator may be measured before and after the actuation of the microactuator, and failure may be detected based on the absolute or relative change of the one or more performance characteristics.

Disk drive detecting crack in microactuator

A disk drive is disclosed comprising a disk comprising tracks defined by servo sectors, a head, and control circuitry comprising a servo control system operable to actuate the head over the disk based on the servo sectors. An estimated acceleration EstAccel of the head over the disk is generated based on at least one of the servo sectors. When the EstAccel is determined to be reliable, an estimated velocity EstVel of the head over the disk is generated based on the EstAccel. When the EstAccel is determined to be unreliable, the EstAccel is adjusted to generate an adjusted acceleration AdjAccel and the EstVel of the head over the disk is generated based on the AdjAccel.

Disk drive adjusting state estimator to compensate for unreliable servo data

A disk drive is disclosed comprising a head actuated over a disk, and a spindle motor operable to rotate the disk. A baseline relationship is generated between a baseline current draw of the spindle motor over a temperature range. An operating current draw of the spindle motor is measured and a corresponding operating temperature is measured. Failure of the spindle motor is predicted based on the operating current draw, the operating temperature, and the baseline relationship.

Disk drive predicting spindle motor failure by evaluating current draw relative to temperature

Determining a polarity of a piezoelectric (PZT) actuator of a disk drive including a disk for storing data and a head for reading and writing data. A test signal is injected into the PZT actuator and a position signal is received which indicates a position of the head over the disk resulting from the test signal. A test compensation signal is generated based on the received position signal and the polarity of the PZT actuator is determined based on a phase of the generated test compensation signal.

Polarity detection of piezoelectric actuator in disk drive

A disk drive is disclosed comprising a disk including a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors. The disk drive further comprises an actuator for actuating a head over the disk in response to an actuator control signal. The servo sectors are read to generate a first sequence of control samples x[k] at a sample rate corresponding to a frequency of the servo sectors. The first sequence of control samples x[k] is upsampled by a factor of N to generate a second sequence of control samples y[k] according to: where &#x3b3; is a scalar greater than or equal to zero and less than one. The actuator control signal is generated in response to the second sequence of control samples y[k].

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Torrance, CA, United States of America

Yanan Huang