Western Digital Technologies, Inc.

David Dung Tien Nguyen

Zhi Ning Wang

Jenghung Chen

Kuang-Yang Tu

Masao Miyamura

John Yin Kwong Li

Bang X Phan

The present invention may be embodied in a magnetic disk, of a disk drive, having eight-bit fields storing wedge repeatable runout (WRRO) compensation values and redundancy information. The WRRO compensation value of each field includes a six-bit binary value of which five bits represent a compensation magnitude and one bit represents a sign bit indicating a compensation direction. The redundancy information of each field has a first bit based on the sign bit.

Magnetic disk having efficiently stored WRRO compensation value redundancy information and method for using the redundancy information

A disk drive is disclosed comprising a voice coil motor (VCM) for rotating an actuator arm about a pivot in order to actuate a head over a disk. The disk is rotated by a spindle motor, and a feed-forward compensation value is computed that compensate for a non-centric alignment of the disk with respect to the spindle motor. During a calibration mode, the VCM is controlled to press the actuator arm against a crash stop, and the feed-forward compensation value is computed in response to a position error signal (PES). The PES is generated in response to embedded servo sectors recorded on the disk, wherein each embedded servo sector comprises a track address for coarse alignment and servo bursts for fine alignment.

Disk drive computing repeatable run out while actuator arm is pressed against crash stop

A disk drive is disclosed that estimates a sinusoidal error in a wedge time period due to eccentricity in the disk rotating to generate eccentricity compensation values. During a write operation a head is positioned over a target data sector within a target track, a write clock frequency is set using an eccentricity compensation value corresponding to the target data sector, and data is written to the target data sector using the write clock frequency. In this manner, the eccentricity compensation value adjusts the write clock frequency to better optimize the linear bit density from the inner to outer diameter tracks.

Disk drive adjusting write clock frequency to compensate for eccentricity in disk rotation

Disclosed is a disk drive including an actuator having a coil, a head attached to the actuator, and a disk including at least a first track and a second track, and a processor for controlling operations in the disk drive including a seek operation from the first track to the second track in which the head is moved between the first track and the second track by the movement of the actuator. The processor under the control of a program generates a deceleration velocity profile for the seek operation that is determined based upon a deceleration velocity profile function that includes a back electromagnetic force (BEMF) model to take into account back electromagnetic forces (BEMFs) associated with the coil of the actuator such that the BEMFs are mathematically modeled. The head is commanded to seek to the second track utilizing the deceleration velocity profile function that includes the BEMF model.

Disk drive to implement a seek operation utilizing a deceleration velocity profile that mathematically models BEMFs

A disk drive and method for estimating a sinusoidal error in a wedge time period is disclosed. An estimated WTP is calculated according to:EST_WTP=RTP+*cos(2&#x3c0;)+*sin(2&#x3c0;)wherein RTP is a reference time period corresponding to a nominal WTP, k is an index representing a servo wedge, and {&#xe2;,{circumflex over (b)}} are adjustable coefficients. A wedge time error e(k) is estimated as the difference between the estimated WTP and a detected actual WTP. The coefficients {&#xe2;,{circumflex over (b)}} for generating the estimated WTP are adjusted according to:(+1)=()&#x2212;()*cos(2&#x3c0;){circumflex over (b)}(k+1)={circumflex over (b)}(k)&#x2212;G*e(k)*sin(2&#x3c0;k/N)wherein G is a predetermined gain.

Disk drive estimating a sinusoidal error in a wedge time period due to eccentricity in disk rotation

A method is disclosed for improving head position determination in a disk drive having a transducer head and a rotating disk with a plurality of embedded servo wedges for defining a plurality of concentric data tracks. Each servo wedge has a plurality of servo bursts for providing radial track position information. In the method, the servo bursts within a servo wedge are read and a burst amplitude is determined for each servo burst. The burst amplitudes are compared to determine a radial servo position zone. A fine radial head position within the radial servo position zone is determined based on a ratio having a numerator consisting of an algebraic sum and difference of the burst amplitudes and a denominator consisting of an algebraic difference between a largest burst amplitude and a smallest burst amplitude.

Method for improving head position determination in a disk drive

A disk drive is disclosed wherein a BEMF speed error is measured during a BEMF spindle speed control mode, and a spindle control current is updated in response to the BEMF speed error to drive the disk at an operating speed. A reference time period (RTP) is calibrated, and a sinusoidal error in a wedge time period (WTP) due to eccentricity in the disk rotating is estimated to generate an eccentricity compensation value. After switching to a wedge spindle speed control mode, an actual WTP is detected and a wedge speed error is generated in response to the RTP, the detected actual WTP, and the eccentricity compensation value. The disk is then maintained at the operating speed by updating the spindle control current in response to the wedge speed error.

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Fountain Valley, CA, United States of America

David Dung Tien Nguyen