Jiangang Liang

US Patent:

7656604, Feb 2, 2010

Filed:

Dec 10, 2007

Appl. No.:

11/953200

Inventors:

Jiangang Liang - Sunnyvale CA, US
Siri S. Weerasooriya - Campbell CA, US
Charles A. Park - Aromas CA, US

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 21/02
G11B 5/09
G11B 5/596

US Classification:

360 75, 360 51, 360 7707

Abstract:

A disk drive is disclosed comprising a disk including a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval, and a head actuated over the disk. The spiral tracks are demodulated by reading a spiral track to generate a spiral track crossing signal g(x), where xis a time in a demodulation window, and determining a position error signal (PES) by determining a time-shift L that maximizes a correlation between g(x) and a function that estimates a nominal spiral track crossing signal having the time-shift of L.

US Patent:

7746592, Jun 29, 2010

Filed:

Feb 13, 2009

Appl. No.:

12/371434

Inventors:

Jiangang Liang - San Jose CA, US
Siri S. Weerasooriya - Campbell CA, US

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 21/02
G11B 5/09
G11B 5/596

US Classification:

360 75, 360 31, 360 7707

Abstract:

A disk drive is disclosed comprising a disk and a head actuated over the disk, wherein the disk comprises a plurality of spiral tracks, each comprising a high frequency signal interrupted by a sync mark at a sync mark interval. The head is used to read a spiral track to generate a spiral track crossing signal g(x), where xis a time in a demodulation window. A position error signal (PES) is determined in response to g(x), and a deviation index is computed by correlating g(x) with a nominal track crossing signal shifted by the PES. When the deviation index is less than a threshold, the PES is used to servo the head over the disk.

US Patent:

7852592, Dec 14, 2010

Filed:

Jan 29, 2008

Appl. No.:

12/021976

Inventors:

Jiangang Liang - Sunnyvale CA, US
Charles A. Park - Aromas CA, US
Yilin Cai - Fremont CA, US
Siri S. Weerasooriya - Campbell CA, US

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 21/02

US Classification:

360 75, 360 31, 360 51

Abstract:

A disk drive that approximates spiral slope in spiral patterns is disclosed. The disk drive includes a disk having at least one spiral pattern that extends radially across the disk, a head to read a portion of the at least one spiral pattern, and a processor to approximate a spiral slope of the portion of the at least one spiral pattern. The processor approximates the spiral slope of the portion of the at least one spiral pattern by implementing operations including: reading amplitude values for the portion of the at least one spiral pattern; determining an amplitude value distribution based on the amplitude values; determining a curve-fitted function for the amplitude value distribution; and determining an approximate spiral slope based on the curve-fitted function.

US Patent:

8537486, Sep 17, 2013

Filed:

Aug 10, 2011

Appl. No.:

13/207332

Inventors:

Jiangang Liang - San Jose CA, US
Siri S. Weerasooriya - Campbell CA, US
Yun Hong - San Jose CA, US
Yilin Cai - Fremont CA, US

Assignee:

Western Digital Technologies, Inc. - Irvine CA

International Classification:

G11B 5/02

US Classification:

360 55

Abstract:

A method is disclosed of servo writing a disk drive comprising a first head actuated over a first disk surface, and a second head actuated over a second disk surface. A first repeatable runout (RRO) of the first disk surface is measured, and a seek is performed to seek the first head over the first disk surface in response to the measured first RRO while writing a first spiral track to the second disk surface using the second head. As a result, the first spiral track comprises a second RRO that substantially matches the first RRO of the first disk surface.

US Patent:

20090195936, Aug 6, 2009

Filed:

Feb 4, 2008

Appl. No.:

12/025676

Inventors:

HONGCHAO TIM ZHAO - SAN JOSE CA, US
JIANGANG LIANG - SUNNYVALE CA, US

Assignee:

WESTERN DIGITAL TECHNOLOGIES, INC. - Lake Forest CA

International Classification:

G11B 5/54

US Classification:

3602547

Abstract:

A method is disclosed for selecting a dynamic fly height (DFH) control setting for a head in a disk drive, the disk drive comprising a plurality of disk surfaces and plurality of respective heads. The method comprises servoing a first head over a first disk surface in response to servo data recorded on the first disk surface, adjusting a DFH control setting for a second head, and while servoing the first head over the first disk surface, detecting whether the second head has contacted a second disk surface.

US Patent:

20180261243, Sep 13, 2018

Filed:

Mar 8, 2017

Appl. No.:

15/453874

Inventors:

- Tokyo, JP
Jiangang LIANG - Saratoga CA, US

International Classification:

G11B 5/596
G11B 5/012

Abstract:

A hard disk drive (HDD) is configured to move a read head over a region of a storage surface that includes unreadable segments of reference spirals that have been overwritten by a reference spiral in a set of spirals that is currently being written on the storage surface. By moving the read head across the region of the storage surface at a return radial velocity that is selected such that the write head crosses no consecutive reference spirals at an unreadable segment, the servo system of the HDD does not experience an error due to crossing multiple consecutive reference spirals at unreadable segments. Thus, a set of spirals that includes partially damaged reference spirals can be employed to control the position of a read head. Consequently, a second surface is not required for the set of spirals employed in controlling the writing process.

US Patent:

20180114540, Apr 26, 2018

Filed:

Oct 21, 2016

Appl. No.:

15/331380

Inventors:

- Tokyo, JP
Jiangang LIANG - Saratoga CA, US

International Classification:

G11B 5/596
G11B 20/18

Abstract:

A repeatable runout (RRO) is accurately compensated for while moving a magnetic head radially across a disk surface. An iterative learning control algorithm is employed to determine appropriate feed-forward coefficients for an RRO compensation signal for each of a plurality of radial locations across the disk surface. The feed-forward coefficients are determined by performing multiple iterations of continuously moving the magnetic head across the disk surface along a target path while measuring a position error signal that indicates the radial error between the magnetic head and the target path. With each iteration, the iterative learning control algorithm computes new feed-forward coefficients for each of the plurality of radial locations, where the new feed-forward coefficients are selected to reduce the measured position error signal when employed to move the magnetic head along the target path.

US Patent:

20170103778, Apr 13, 2017

Filed:

Oct 13, 2015

Appl. No.:

14/882339

Inventors:

- Tokyo, JP
Jiangang LIANG - San Jose CA, US

International Classification:

G11B 5/596

Abstract:

A magnetic write head is positioned based on position signals generated by a read head as the read head crosses a plurality of reference spirals. The spiral gate for monitoring a particular reference spiral is timed to begin at a time based on the radial position of the magnetic head when crossing the preceding reference spiral. In this way, the spiral crossing time for the particular reference spiral can be estimated with sufficient accuracy that the spiral gate coincides with the magnetic head crossing the particular reference spiral. Consequently, spiral detection is assured, even in the presence of large non-repeatable runout.